WorldWideScience

Sample records for group i-a metal

  1. Grouped exposed metal heaters

    Energy Technology Data Exchange (ETDEWEB)

    Vinegar, Harold J [Bellaire, TX; Coit, William George [Bellaire, TX; Griffin, Peter Terry [Brixham, GB; Hamilton, Paul Taylor [Houston, TX; Hsu, Chia-Fu [Granada Hills, CA; Mason, Stanley Leroy [Allen, TX; Samuel, Allan James [Kular Lumpar, ML; Watkins, Ronnie Wade [Cypress, TX

    2012-07-31

    A system for treating a hydrocarbon containing formation is described. The system includes two or more groups of elongated heaters. The group includes two or more heaters placed in two or more openings in the formation. The heaters in the group are electrically coupled below the surface of the formation. The openings include at least partially uncased wellbores in a hydrocarbon layer of the formation. The groups are electrically configured such that current flow through the formation between at least two groups is inhibited. The heaters are configured to provide heat to the formation.

  2. Grouped exposed metal heaters

    Energy Technology Data Exchange (ETDEWEB)

    Vinegar, Harold J. (Bellaire, TX); Coit, William George (Bellaire, TX); Griffin, Peter Terry (Brixham, GB); Hamilton, Paul Taylor (Houston, TX); Hsu, Chia-Fu (Granada Hills, CA); Mason, Stanley Leroy (Allen, TX); Samuel, Allan James (Kular Lumpar, MY); Watkins, Ronnie Wade (Cypress, TX)

    2010-11-09

    A system for treating a hydrocarbon containing formation is described. The system includes two or more groups of elongated heaters. The group includes two or more heaters placed in two or more openings in the formation. The heaters in the group are electrically coupled below the surface of the formation. The openings include at least partially uncased wellbores in a hydrocarbon layer of the formation. The groups are electrically configured such that current flow through the formation between at least two groups is inhibited. The heaters are configured to provide heat to the formation.

  3. Platinum Group Metals New Material

    Institute of Scientific and Technical Information of China (English)

    XIE Ming; ZHANG Jiankang; WANG Saibei; HU Jieqiong; LIU Manmen; CHEN Yongtai; ZHANG Jiming; YANG Youcai; YANG Yunfeng; ZHANG Guoquan

    2012-01-01

    Platinum group metals (PGM) include six elements,namely Pt,Pd,Rh,Ir,Os and Ru.PGM and their alloys are the important fundamental materials for modern industry and national defense construction,they have special physical and chemical properties,widely used in metallurgy,chemical,electric,electronic,information,energy,environmental protection,aviation,aerospace,navigation and other high technology industry.Platinum group metals and their alloys,which have good plasticity and processability,can be processed to electrical contact materials,resistance materials,solder,electronic paste,temperature-measurement materials,elastic materials,magnetic materials and high temperature structural materials.

  4. Homochiral helical metal-organic frameworks of group 1 metals.

    Science.gov (United States)

    Reger, Daniel L; Leitner, Andrew; Smith, Mark D; Tran, T Thao; Halasyamani, P Shiv

    2013-09-01

    The reactions of (S)-2-(1,8-naphthalimido)propanoic acid (HL(ala)) and (S)-2-(1,8-naphthalimido)-3-hydroxypropanoic acid (HL(ser)), protonated forms of ligands that contain a carboxylate donor group, an enantiopure chiral center, and a 1,8-naphthalimide π···π stacking supramolecular tecton and in the case of HL(ser) an alcohol functional group, with the appropriate alkali metal hydroxide followed by a variety of crystallization methods leads to the formation of crystalline K(L(ala))(MeOH) (1), K(L(ala))(H2O) (2), Na(L(ala))(H2O) (3), KL(ser) (4), CsL(ser) (5), and CsL(ala) (6). Each of these new complexes has a solid state structure based on six-coordinate metals linked into homochiral helical rod secondary building unit (SBU) central cores. In addition to the bonding of the carboxylate and solvent (in the case of L(ser) the ligand alcohol) to the metals, both oxygens on the 1,8-naphthalimide act as donor groups. One naphthalimide oxygen bonds to the same helical rod SBU as the carboxylate group of that ligand forming a chelate ring. The other naphthalimide oxygen bonds to adjacent SBUs. In complexes 1-3, this inter-rod link has a square arrangement bonding four other rods forming a three-dimensional enantiopure metal-organic framework (MOF) structure, whereas in 4-6 this link has a linear arrangement bonding two other rods forming a two-dimensional, sheet structure. In the latter case, the third dimension is supported exclusively by interdigitated π···π stacking interactions of the naphthalimide supramolecular tecton, forming enantiopure supramolecular MOF solids. Compounds 1-3 lose the coordinated solvent when heating above 100 °C. For 1, the polycrystalline powder reverts to 1 only by recrystallization from methanol, whereas compounds 2 and 3 undergo gas/solid, single-crystal to single-crystal transformations to form dehydrated compounds 2* and 3*, and rehydration occurs when crystals of these new complexes are left out in air. The reversible single

  5. Intrinsic thermoelectric power of group VB metals

    Directory of Open Access Journals (Sweden)

    Gunadhor Singh Okram

    2012-03-01

    Full Text Available We have reinvestigated the thermopower of group VB metals in polycrystalline forms in the temperature range of 6-300K, taking into account the critical nature of the sample surface and heat treatment especially for niobium. Strikingly small magnitude, negative sign, phonon drag dip and superconductivity not reported previously were observed in surface-cleaned single crystalline Nb. However, while thermopower magnitudes are small, mixed signs were found in the polycrystalline V, Nb and Ta samples. These properties were therefore interpreted as their intrinsic properties and were briefly discussed taking into account of the existing theory by fitting also the data that give the Fermi energies of 10.94 eV, 5.08 eV and 1.86eV, respectively.

  6. Selective laser extraction of the Pt group metals

    Energy Technology Data Exchange (ETDEWEB)

    Fadeeva, S.; Krynetsky, B.; Prokhorov, A.; Zhidkov, A. [General Physics Institute, Russian Academy of Science, Moscow (Russian Federation)

    1995-11-15

    The interest to the platinum-group metals extraction from solutions, especially industry waste, is stimulated by their extraordinary chemical inert. The traditional chemical methods of the extraction are uneffective. Have been investigated process of the extraction of metal Pt-group from acid solutions. Discussed processes reduction of noble metals by resonance laser action.

  7. Development of radioactive platinum group metal catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Chung, H.S.; Kim, Y.S.; Kim, Y.E. [and others

    1999-03-01

    The fission product nuclides generated during the irradiation of reactor fuel include many useful elements, among them platinum group metals such as ruthenium, rhodium and palladium which are of great industrial importance, occur rarely in nature and are highly valuable. In this research, the authors reviewed various PGM recovery methods. Recovery of palladium from seven-component simulated waste solutions was conducted by selective precipitation method. The recovery yield was more than 99.5% and the purity of the product was more than 99%. Wet-proof catalyst was prepared with the recovered palladium. The specific surface area of the catalyst support was more than 400m{sup 2}/g.The content of palladium impregnated on the support was 1 to 10 wt. %. Hydrogen isotope exchange efficiency of more than 93% to equilibrium with small amount of the catalyst was obtained. It was turned out possible to consider using such palladium or other very low active PGM materials in applications where its activity is unimportant as in nuclear industries. (author). 86 refs., 44 tabs., 88 figs.

  8. Development of radioactive platinum group metal catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Chung, H.S.; Kim, Y.S.; Kim, Y.E. [and others

    1999-03-01

    The fission product nuclides generated during the irradiation of reactor fuel include many useful elements, among them platinum group metals such as ruthenium, rhodium and palladium which are of great industrial importance, occur rarely in nature and are highly valuable. In this research, the authors reviewed various PGM recovery methods. Recovery of palladium from seven-component simulated waste solutions was conducted by selective precipitation method. The recovery yield was more than 99.5% and the purity of the product was more than 99%. Wet-proof catalyst was prepared with the recovered palladium. The specific surface area of the catalyst support was more than 400m{sup 2}/g.The content of palladium impregnated on the support was 1 to 10 wt. %. Hydrogen isotope exchange efficiency of more than 93% to equilibrium with small amount of the catalyst was obtained. It was turned out possible to consider using such palladium or other very low active PGM materials in applications where its activity is unimportant as in nuclear industries. (author). 86 refs., 44 tabs., 88 figs.

  9. Exhaust system having a gold-platinum group metal catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Ragle, Christie Susan [Havana, IL; Silver, Ronald G [Peoria, IL; Zemskova, Svetlana Mikhailovna [Edelstein, IL; Eckstein, Colleen J [Metamora, IL

    2011-12-06

    A method of providing an exhaust treatment device is disclosed. The method includes applying a catalyst including gold and a platinum group metal to a particulate filter. The concentration of the gold and the platinum group metal is sufficient to enable oxidation of carbon monoxide and nitric oxide.

  10. Choirs H I galaxy groups: The metallicity of dwarf galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Sweet, Sarah M.; Drinkwater, Michael J. [School of Mathematics and Physics, University of Queensland, Qld 4072 (Australia); Meurer, Gerhardt; Bekki, Kenji [School of Physics, University of Western Australia, 35 Stirling Highway, Crawley, WA 6009 (Australia); Dopita, Michael A.; Nicholls, David C. [Research School of Astronomy and Astrophysics, Australian National University, Cotter Road, Weston ACT 2611 (Australia); Kilborn, Virginia, E-mail: sarah@sarahsweet.com.au [Swinburne University of Technology, Mail number H30, PO Box 218, Hawthorn, Victoria 3122 (Australia)

    2014-02-10

    We present a recalibration of the luminosity-metallicity relation for gas-rich, star-forming dwarfs to magnitudes as faint as M{sub R} ∼ –13. We use the Dopita et al. metallicity calibrations to calibrate the relation for all the data in this analysis. In metallicity-luminosity space, we find two subpopulations within a sample of high-confidence Sloan Digital Sky Survey (SDSS) DR8 star-forming galaxies: 52% are metal-rich giants and 48% are metal-medium galaxies. Metal-rich dwarfs classified as tidal dwarf galaxy (TDG) candidates in the literature are typically of metallicity 12 + log(O/H) = 8.70 ± 0.05, while SDSS dwarfs fainter than M{sub R} = –16 have a mean metallicity of 12 + log(O/H) = 8.28 ± 0.10, regardless of their luminosity, indicating that there is an approximate floor to the metallicity of low-luminosity galaxies. Our hydrodynamical simulations predict that TDGs should have metallicities elevated above the normal luminosity-metallicity relation. Metallicity can therefore be a useful diagnostic for identifying TDG candidate populations in the absence of tidal tails. At magnitudes brighter than M{sub R} ∼ –16, our sample of 53 star-forming galaxies in 9 H I gas-rich groups is consistent with the normal relation defined by the SDSS sample. At fainter magnitudes, there is an increase in dispersion of the metallicity of our sample, suggestive of a wide range of H I content and environment. In our sample, we identify three (16% of dwarfs) strong TDG candidates (12 + log(O/H) > 8.6) and four (21%) very metal-poor dwarfs (12 + log(O/H) < 8.0), which are likely gas-rich dwarfs with recently ignited star formation.

  11. Decision Development in Small Groups I: A Comparison of Two Models.

    Science.gov (United States)

    Poole, Marshall Scott

    1981-01-01

    Studies the sequence of phases in group decision making. Compares the unitary sequence model, which assumes that all groups follow the same sequence of phases, and the multiple sequence model, which assumes that different groups follow different sequences. Results support the latter model and suggest revisions in current decision development. (PD)

  12. Recent strikes in South Africa’s platinum-group metal mines: effects upon world platinum-group metal supplies

    Science.gov (United States)

    Yager, Thomas R.; Soto-Viruet, Yadira; Barry, James J.

    2012-01-01

    The recent labor disputes over wages and working conditions that have affected South Africa’s three leading platinum-group metal (PGM) producers have affected an industry already plagued by market pressures and labor unrest and raised the specter of constraints in the world’s supply of these metals. Although low demand for these metals in 2011 and 2012 helped to offset production losses of recent years, and particularly those losses caused by the strikes in 2012, a prolonged resumption of strikes could cause severe shortages of iridium, platinum, rhodium, ruthenium, and, to a lesser extent, palladium.

  13. METALLICITY DISTRIBUTION FUNCTIONS OF FOUR LOCAL GROUP DWARF GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Ross, Teresa L.; Holtzman, Jon [Department of Astronomy, New Mexico State University, P.O. Box 30001, MSC 4500, Las Cruces, NM 88003-8001 (United States); Saha, Abhijit [NOAO, 950 Cherry Avenue, Tucson, AZ 85726-6732 (United States); Anthony-Twarog, Barbara J., E-mail: rosst@nmsu.edu, E-mail: holtz@nmsu.edu, E-mail: bjat@ku.edu [Department of Physics and Astronomy, University of Kansas, Lawrence, KS 66045-7582 (United States)

    2015-06-15

    We present stellar metallicities in Leo I, Leo II, IC 1613, and Phoenix dwarf galaxies derived from medium (F390M) and broad (F555W, F814W) band photometry using the Wide Field Camera 3 instrument on board the Hubble Space Telescope. We measured metallicity distribution functions (MDFs) in two ways, (1) matching stars to isochrones in color–color diagrams and (2) solving for the best linear combination of synthetic populations to match the observed color–color diagram. The synthetic technique reduces the effect of photometric scatter and produces MDFs 30%–50% narrower than the MDFs produced from individually matched stars. We fit the synthetic and individual MDFs to analytical chemical evolution models (CEMs) to quantify the enrichment and the effect of gas flows within the galaxies. Additionally, we measure stellar metallicity gradients in Leo I and II. For IC 1613 and Phoenix our data do not have the radial extent to confirm a metallicity gradient for either galaxy. We find the MDF of Leo I (dwarf spheroidal) to be very peaked with a steep metal-rich cutoff and an extended metal-poor tail, while Leo II (dwarf spheroidal), Phoenix (dwarf transition), and IC 1613 (dwarf irregular) have wider, less peaked MDFs than Leo I. A simple CEM is not the best fit for any of our galaxies; therefore we also fit the “Best Accretion Model” of Lynden-Bell. For Leo II, IC 1613, and Phoenix we find similar accretion parameters for the CEM even though they all have different effective yields, masses, star formation histories, and morphologies. We suggest that the dynamical history of a galaxy is reflected in the MDF, where broad MDFs are seen in galaxies that have chemically evolved in relative isolation and narrowly peaked MDFs are seen in galaxies that have experienced more complicated dynamical interactions concurrent with their chemical evolution.

  14. Dipicolinate complexes of main group metals with hydrazinium cation

    Indian Academy of Sciences (India)

    K Saravanan; S Govindarajan

    2002-02-01

    Some new coordination complexes of hydrazinium main group metal dipicolinate hydrates of formulae (N2H5)2M(dip)2.H2O (where, M =Ca, Sr, Ba or Pb and = 0, 2, 4 and 3 respectively and dip = dipicolinate), N2H5Bi(dip)2.3H2O and (N2H5)3Bi(dip)3.4H2O have been prepared and characterized by physico-chemical techniques. The infrared spectra of the complexes reveal the presence of tridentate dipicolinate dianions and non-coordinating hydrazinium cations. Conductance measurements show that the mono, di and trihydrazinium complexes behave as 1:1, 2:1 and 3:1 electrolytes respectively, in aqueous solution. Thermal decomposition studies show that these compounds lose water followed by endothermic decomposition of hydrazine to give respective metal hydrogendipicolinate intermediates, which further decompose exothermically to the final product of either metal carbonates (Ca, Sr, Ba and Pb) or metal oxycarbonates (Bi). The coordination numbers around the metal ions differ from compound to compound. The various coordination numbers exhibited by these metals are six (Ca), seven (Ba), eight (Sr) and nine (Pb and Bi). In all the complexes the above coordination number is attained by tridentate dipicolinate dianions and water molecules. The X-ray diffraction patterns of these compounds differ from one another suggesting that they are not isomorphous.

  15. Effect of Platinum Group Metal Doping in Magnesium Diboride Wires

    DEFF Research Database (Denmark)

    Grivel, Jean-Claude; Alexiou, Aikaterini; Namazkar, Shahla

    2016-01-01

    The effect of some platinum group metals(PGM = Rh, Pd, and Pt) on the microstructure and critical current density of Cu/Nb-sheathed MgB2 wires has been studied using Mg1-x PGMxB2 powders with low doping levels. It was found that Pt and Pd do not enter the MgB2 lattice and have only limited....... The results are discussed in comparison with previous investigations using other transition metals for doping on the Mg site....

  16. Metallicity of the Fossil Group NGC 1550 Observed with Suzaku

    Science.gov (United States)

    Sato, Kosuke; Kawaharada, Madoka; Nakazawa, Kazuhiro; Matsushita, Kyoko; Ishisaki, Yoshitaka; Yamasaki, Noriko Y.; Ohashi, Takaya

    2010-12-01

    We studied the temperature and metal abundance distributions of the intra-cluster medium (ICM) in a group of galaxies, NGC 1550, observed with Suzaku. NGC 1550 is classified as a fossil group, which has few bright member galaxies, except for the central galaxy. Thus, such a type of galaxy is important to investigate how metals are enriched to the ICM. With the Suzaku XIS instrument, we directly measured not only the Si, S, and Fe lines, but also the O and Mg lines, and obtained those abundances to an outer region of ˜0.5r180 for the first time, and confirmed that the metals in the ICM of such a fossil group are indeed extending to a large radius. We found steeper gradients for the Mg, Si, S, and Fe abundances, while O showed an almost flat abundance distribution. Abundance ratios of α-elements to Fe were similar to those of the other groups and poor clusters. We calculated the number ratio of type II to type Ia supernovae for the ICM enrichment to be 2.9±0.5 within 0.1r180; the value is consistent with those for the other groups and poor clusters observed with Suzaku. We also calculated the metal mass-to-light ratios (MLRs) for Fe, O, and Mg with the B-band and K-band luminosities of the member galaxies of NGC 1550. The derived MLRs are comparable to those of the NGC 5044 group in the r region, while those of NGC 1550 are slightly higher than those of NGC 5044 in the outer region.

  17. Outliers from the Mass--Metallicity Relation I: A Sample of Metal-Rich Dwarf Galaxies from SDSS

    CERN Document Server

    Peeples, Molly S; Stanek, K Z

    2008-01-01

    We have identified a sample of 41 low-mass high--oxygen abundance outliers from the mass--metallicity relation of star-forming galaxies measured by Tremonti et al (2004). These galaxies, which have 8.6 M_B > -19.1 and 7.4 < log M_*/M_solar < 10, are surprisingly non-pathological. They have typical specific star formation rates, they are fairly isolated and, with few exceptions, have no obvious companions. Morphologically, they are similar to dwarf spheroidal or dwarf elliptical galaxies. We predict that their observed high oxygen abundances are due to relatively low gas masses, concluding that these are transitional dwarf galaxies nearing the end of their star formation activity.

  18. Chemical Reactivity Perspective into the Group 2B Metals Halides.

    Science.gov (United States)

    Özen, Alimet Sema; Akdeniz, Zehra

    2016-06-30

    Chemical reactivity descriptors within the conceptual density functional theory can be used to understand the nature of the interactions between two monomers of the Group 2B metal halides. This information might be valuable in the development of adequate force law parameters for simulations in the liquid state. In this study, MX2 monomers and dimers, where M = Zn, Cd, Hg and X = F, Cl, Br, I, were investigated in terms of chemical reactivity descriptors. Relativistic effects were taken into account using the effective core potential (ECP) approach. Correlations were produced between global and local reactivity descriptors and dimerization energies. Results presented in this work represent the first systematic investigation of Group 2B metal halides in the literature from a combined point of view of both relativistic effects and chemical reactivity descriptors. Steric effects were found to be responsible for the deviation from the chemical reactivity principles. They were introduced into the chemical reactivity descriptors such as local softness.

  19. Platinum group metal nitrides and carbides: synthesis, properties and simulation

    Energy Technology Data Exchange (ETDEWEB)

    Ivanovskii, Alexander L [Institute of Solid State Chemistry, Urals Branch of the Russian Academy of Sciences, Ekaterinburg (Russian Federation)

    2009-04-30

    Experimental and theoretical data on new compounds, nitrides and carbides of the platinum group 4d and 5d metals (ruthenium, rhodium, palladium, osmium, iridium, platinum), published over the past five years are summarized. The extreme mechanical properties of platinoid nitrides and carbides, i.e., their high strength and low compressibility, are noted. The prospects of further studies and the scope of application of these compounds are discussed.

  20. Zwitterionic Group VIII transition metal initiators supported by olefin ligands

    Science.gov (United States)

    Bazan, Guillermo C.; Chen, Yaofeng

    2011-10-25

    A zwitterionic Group VIII transition metal complex containing the simple and relatively small 3-(arylimino)-but-1-en-2-olato ligand that catalyzes the formation of polypropylene and high molecular weight polyethylene. A novel feature of this catalyst is that the active species is stabilized by a chelated olefin adduct. The present invention also provides methods of polymerizing olefin monomers using zwitterionic catalysts, particularly polypropylene and high molecular weight polyethylene.

  1. Mineral resource of the month: platinum group metals

    Science.gov (United States)

    Loferski, Patricia J.

    2010-01-01

    The article focuses on platinum group metals (PGMs) and their properties. According to the author, PGMs, which include iridium, osmium, palladium, platinum, rhodium, and ruthenium, are among the rarest mineral commodities in the Earth's crust. PGMs are primarily used as catalytic converters that clean harmful exhaust from vehicle engines. They are also used in the chemical industry as catalysts in the production of nitric acid and in the petroleum refining industry.

  2. Modeling platinum group metal complexes in aqueous solution.

    Science.gov (United States)

    Lienke, A; Klatt, G; Robinson, D J; Koch, K R; Naidoo, K J

    2001-05-07

    We construct force fields suited for the study of three platinum group metals (PGM) as chloranions in aqueous solution from quantum chemical computations and report experimental data. Density functional theory (DFT) using the local density approximation (LDA), as well as extended basis sets that incorporate relativistic corrections for the transition metal atoms, has been used to obtain equilibrium geometries, harmonic vibrational frequencies, and atomic charges for the complexes. We found that DFT calculations of [PtCl(6)](2-).3H(2)O, [PdCl(4)](2-).2H(2)O, and [RhCl(6)](3-).3H(2)O water clusters compared well with molecular mechanics (MM) calculations using the specific force field developed here. The force field performed equally well in condensed phase simulations. A 500 ps molecular dynamics (MD) simulation of [PtCl(6)](2-) in water was used to study the structure of the solvation shell around the anion. The resulting data were compared to an experimental radial distribution function derived from X-ray diffraction experiments. We found the calculated pair correlation functions (PCF) for hexachloroplatinate to be in good agreement with experiment and were able to use the simulation results to identify and resolve two water-anion peaks in the experimental spectrum.

  3. Peruvian perovskite Between Transition-metal to PGM/PlatinumGroupMetal Catalytic Fusion

    Science.gov (United States)

    Maksoed, Wh-

    2016-11-01

    Strongly correlated electronic materials made of simple building blocks, such as a transition-metal ion in an octahedral oxygen cage forming a perovskite structure- Dagotto & Tokura for examples are the high-temperature superconductivity & the CMR/Colossal Magnetoresistance . Helium-4 denotes from LC Case,ScD: "Catalytic Fusion of Deuterium into Helium-4"- 1998 dealt with gaseous D2- "contacted with a supported metallic catalyst at superatmospheric pressure". The catalyst is a platinum-group metal, at about 0.5% - 1% by weight, on activated C. Accompanies Stephen J Geier, 2010 quotes "transition metal complexes", the Energy thus produced is enormous, and because the deuterium is very cheap in the form of heavy water (less than US 1/g), the fuel cost is very low (<<1 %/KwH). "The oceans contain enough deuterium to satisfy the Earth's energy needs for many millions of year" to keep "maria"/Latin name of seas &Deuteronomy to be eternally preserves. Heartfelt Gratitudes to HE. Mr. Prof. Ir. HANDOJO.

  4. X-ray characterization of platinum group metal catalysts

    Science.gov (United States)

    Peterson, Eric J.

    Platinum group metals (PGMs) are used extensively as catalysts, employed in several sectors of the world energy economy. Fuel cells employing PGM catalysts show promise as power sources in the proposed hydrogen economy, using alcohols as hydrogen storage media. Currently, the most economically important application for PGMs is for the mitigation of emissions from internal combustion engines via catalytic converters. In all applications, efficient use of these expensive metals to fabricate robust catalysts is of the utmost importance. Understanding the catalyst structure/property relationship is the key to the improvement of existing catalysts and the discovery of new catalysts. For example, catalyst particle size can have profound effects on catalyst activity, as in the case of gold nanoparticles. Catalyst particle size control and stability is also important for the efficient use of PGM metals and catalyst deactivation prevention. The challenge is to identify and characterize structural features and determine if and how these features may relate to catalytic properties. The ultimate goal is to simultaneously measure catalyst structural characteristics and catalytic properties under operando conditions, unambiguously establishing the structure/property link. X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) are important techniques used for the characterization of PGM catalysts. Microstructural information such as crystallite size, as small as ~ 1 nm, and microstrain can be obtained from Bragg diffraction peak shapes in X-ray diffraction patterns, and long range crystal structure information is found in the intensities and positions of these peaks. In contrast, X-ray absorption spectroscopy provides information about the chemical state and local structure of selected atoms. From the average nearest neighbor coordination numbers, crystallite sizes can also be inferred, with particularly high sensitivity in the sub-nm size range. Electron microscopy

  5. Molecular early main group metal hydrides : synthetic challenge, structures and applications

    NARCIS (Netherlands)

    Harder, Sjoerd

    2012-01-01

    Within the general area of early main group metal chemistry, the controlled synthesis of well-defined metal hydride complexes is a rapidly developing research field. As group 1 and 2 metal complexes are generally highly dynamic and lattice energies for their [MH](infinity) and [MH2](infinity) salts

  6. Molecular early main group metal hydrides : synthetic challenge, structures and applications

    NARCIS (Netherlands)

    Harder, Sjoerd

    2012-01-01

    Within the general area of early main group metal chemistry, the controlled synthesis of well-defined metal hydride complexes is a rapidly developing research field. As group 1 and 2 metal complexes are generally highly dynamic and lattice energies for their [MH](infinity) and [MH2](infinity) salts

  7. Pyrometallurgical Recovery of Platinum Group Metals from Spent Catalysts

    Science.gov (United States)

    Peng, Zhiwei; Li, Zhizhong; Lin, Xiaolong; Tang, Huimin; Ye, Lei; Ma, Yutian; Rao, Mingjun; Zhang, Yuanbo; Li, Guanghui; Jiang, Tao

    2017-09-01

    As an important secondary resource with abundant platinum group metals (PGMs), spent catalysts demand recycling for both economic and environmental benefits. This article reviews the main pyrometallurgical processes for PGM recovery from spent catalysts. Existing processes, including smelting, vaporization, and sintering processes, are discussed based in part on a review of the physiochemical characteristics of PGMs in spent catalysts. The smelting technology, which produces a PGM-containing alloy, is significantly influenced by the addition of various collectors, such as lead, copper, iron, matte, or printed circuit board (PCB), considering their chemical affinities for PGMs. The vaporization process can recover PGMs in vapor form at low temperatures (250-700°C), but it suffers high corrosion and potential environmental and health risks as a result of involvement of the hazardous gases, mainly Cl2 and CO. The sintering process serves as a reforming means for recycling of the spent catalysts by in situ reduction of their oxidized PGMs components. Among these processes, the smelting process seems more promising although its overall performance can be further improved by seeking a suitable target-oriented collector and flux, together with proper pretreatment and process intensification using an external field.

  8. Synthesis of Group IVB Metals Oxicarbides by Carboreduction Reactions

    Directory of Open Access Journals (Sweden)

    A.D. Mazzoni

    2002-10-01

    Full Text Available The metals of the group IV B (Ti, Zr, Hf present a series of carbides and oxicarbides with scientific and technological interest. Many of these compounds belong to the subsystem "MO - MC" of the pseudoternary "MO - MN - MC" system (where M = Ti, Zr or Hf. In this work carboreduction reactions of TiO2 and ZrO2 were performed in argon atmosphere, using temperatures from 1250° to 1650° and reaction times of 120 min. The oxicarbides obtained were in the range TiC0.16O0.84 to TiC0.73O0.27 and ZrC0.46O0.54 to ZrC0.90O0.10. respectively. The reaction products were characterized by X-ray diffraction (XRD, with the calculation of their cell constants by means of the Rietveld method. Scanning Electron Microscopy (SEM was used in the characterization of powdered materials. Additionally, the carborreduction reaction was followed by weight loss.

  9. Platinum group metal recovery and catalyst manufacturing process

    Energy Technology Data Exchange (ETDEWEB)

    Chung, H. S.; Kim, Y. S.; Yoo, J. H.; Lee, H. S.; Ahn, D. H.; Kim, K. R.; Lee, S. H.; Paek, S. W.; Kang, H. S.

    1998-03-01

    The fission product nuclides generated during the irradiation of reactor fuel include many useful elements, among them platinum group metal such as ruthenium, rhodium and palladium which are of great industrial importance, occur rarely in nature and are highly valuable. In this research, the authors reviewed various PGM recovery methods. Recovery of palladium from seven-component simulated waste solution was conducted by selective precipitation method. The recovery yield was more than 99.5% and the purity of the product was more than 99%. Wet-proof catalyst was prepared with the recovered palladium. The specific surface area of the catalyst support was more than 400 m{sup 2}/g. The content of palladium impregnated on the support was 10 wt.%. Hydrogen isotope exchange efficiency of 93 % to equilibrium with small amount of the catalyst was obtained. It was turned out possible to consider using such palladium or other very low active PGM materials in applications where its actively is unimportant as in nuclear industries. (author). 63 refs., 38 tabs., 36 figs.

  10. Molecular early main group metal hydrides: synthetic challenge, structures and applications.

    Science.gov (United States)

    Harder, Sjoerd

    2012-11-25

    Within the general area of early main group metal chemistry, the controlled synthesis of well-defined metal hydride complexes is a rapidly developing research field. As group 1 and 2 metal complexes are generally highly dynamic and lattice energies for their [MH](∞) and [MH(2)](∞) salts are high, the synthesis of well-defined soluble hydride complexes is an obvious challenge. Access to molecular early main group metal hydrides, however, is rewarding: these hydrocarbon-soluble metal hydrides are highly reactive, have found use in early main group metal catalysis and are potentially also valuable molecular model systems for polar metal hydrides as a hydrogen storage material. The article focusses specifically on alkali and alkaline-earth metal hydride complexes and discusses the synthetic challenge, molecular structures, reactivity and applications.

  11. Asymptomatic prospective and retrospective cohorts with metal-on-metal hip arthroplasty indicate acquired lymphocyte reactivity varies with metal ion levels on a group basis.

    Science.gov (United States)

    Hallab, Nadim J; Caicedo, Marco; McAllister, Kyron; Skipor, Anastasia; Amstutz, Harlan; Jacobs, Joshua J

    2013-02-01

    Some tissues from metal-on-metal (MoM) hip arthroplasty revisions have shown evidence of adaptive-immune reactivity (i.e., excessive peri-implant lymphocyte infiltration/activation). We hypothesized that, prior to symptoms, some people with MoM hip arthroplasty will develop quantifiable metal-induced lymphocyte reactivity responses related to peripheral metal ion levels. We tested three cohorts (Group 1: n = 21 prospective longitudinal MoM hip arthroplasty; Group 2: n = 17 retrospective MoM hip arthroplasty; and Group 3: n = 20 controls without implants). We compared implant position, metal-ion release, and immuno-reactivity. MoM cohorts had elevated (p Group 1:1.2 ppb Co, 1.5 ppb Cr; Group 2: 3.4 ppb Co, 5.4 ppb Cr; Group 3: 0.01 ppb Co, 0.1 ppb Cr). However, only after 1-4 years post-op did 56% of Group 1 develop metal-reactivity (vs. 5% pre-op, metal-LTT, SI > 2), compared with 76% of Group 2, and 15% of Group 3 controls (patch testing was a poor diagnostic indicator with only 1/21 Group 1 positive). Higher cup-abduction angles (50° vs. 40°) in Group 1 were associated with higher serum Cr (p Group-1 participants (p Group 1 participants. Our results showed that lymphocyte reactivity to metals can develop within the first 1-4 years after MoM arthroplasty in asymptomatic patients and lags increases in metal ion levels. This increased metal reactivity was more prevalent in those individuals with extreme cup angles and higher amounts of circulating metal. Copyright © 2012 Orthopaedic Research Society.

  12. Multinuclear group 4 catalysis: olefin polymerization pathways modified by strong metal-metal cooperative effects.

    Science.gov (United States)

    McInnis, Jennifer P; Delferro, Massimiliano; Marks, Tobin J

    2014-08-19

    homogeneous and heterogeneous systems, macromolecules with dramatically altered properties, and large-scale industrial processes. It is noteworthy that many metalloenzymes employ multiple active centers operating in close synergistic proximity to achieve high activity and selectivity. Such enzymes were the inspiration for the research discussed in this Account, focused on the properties of multimetallic olefin polymerization catalysts. Here we discuss how modifications in organic ligand architecture, metal···metal proximity, and cocatalyst can dramatically modify polyolefin molecular weight, branch structure, and selectively for olefinic comonomer enchainment. We first discuss bimetallic catalysts with identical group 4 metal centers and then heterobimetallic systems with either group 4 or groups 4 + 6 catalytic centers. We compare and contrast the polymerization properties of the bimetallic catalysts with their monometallic analogues, highlighting marked cooperative enchainment effects and unusual polymeric products possible via the proximate catalytic centers. Such multinuclear olefin polymerization catalysts exhibit the following distinctive features: (1) unprecedented levels of polyolefin branching; (2) enhanced enchainment selectivity for linear and encumbered α-olefin comonomers; (3) enhanced polyolefin tacticity and molecular weight; (4) unusual 1,2-insertion regiochemistry for styrenic monomers; (5) modified chain transfer kinetics, such as M-polymer β-hydride transfer to the metal or incoming monomer; (6) LLDPE synthesis with a single binuclear catalyst and ethylene.

  13. The platinum group metals in Younger Dryas Horizons are terrestrial

    Science.gov (United States)

    Wu, Y.; Wikes, E.; Kennett, J.; West, A.; Sharma, M.

    2009-12-01

    The Younger Dryas (YD) event, which began 12,900 years ago, was a period of abrupt and rapid cooling in the Northern Hemisphere whose primary cause remains unclear. The prevalent postulated mechanism is a temporary shutdown of the thermohaline circulation following the breakup of an ice dam in North America. Firestone et al. (2007) proposed that the cooling was triggered by multiple cometary airbursts and/or impacts that engendered enormous environmental changes and disrupted the thermohaline circulation. The evidence in support for this hypothesis is a black layer in North America and in Europe marking the YD boundary containing charcoal, soot, carbon spherules and glass-like carbon suggesting extensive and intense forest fires. This layer is also enriched in magnetic grains high in iridium, magnetic microspherules, fullerenes containing extraterrestrial He-3, and nanodiamonds. Whereas the nanodiamonds could be produced in an impact or arrive with the impactor, the cometary burst/impact hypothesis remains highly controversial as the YD horizon lacks important impact markers such as craters, breccias, tektites and shocked minerals. Firestone et al. (2007) contend that bulk of Ir found at the YD boundary is associated with magnetic grains. The key issue is whether this Ir is meteorite derived. We used Ir and Os concentrations and Os isotopes to investigate the provenance of the platinum group metals in the YD horizon. The bulk sediment samples from a number of North American YD sites (Blackwater Draw, Murray Springs, Gainey, Sheriden Cave, and Myrtle Beach) and a site in Europe (Lommel) do not show any traces of meteorite derived Os and Ir. The [Os] = 2 to 45 pg/g in these sediments and the 187Os/188Os ratios are similar to the upper continental crustal values (~1.3), much higher than those in meteorites (0.13). Higher [Os] is observed in Blackwater Draw (= 194 pg/g). However, the Os/Ir ratio in Blackwater Draw is 5 (not 1 as expected for a meteorite) and 187Os/188

  14. Metallicities and kinematics for dwarf spheroidals in the local group

    NARCIS (Netherlands)

    Battaglia, G.; Tolstoy, E.; Helmi, A.; Irwin, M.; Randich, S; Pasquini, L

    2006-01-01

    We present the first results of Call triplet observations from VLT/FLAMES for Sculptor, Fornax and Sextans dSphs. For each galaxy, we obtained accurate velocity and metallicity measurements for hundreds of stars out to and beyond the tidal radius. In each case, we find clear evidence for the presenc

  15. Metallicity Distribution Functions of Four Local Group dwarf galaxies

    CERN Document Server

    Ross, Teresa L; Saha, Abhijit; Anthony-Twarog, Barbara J

    2015-01-01

    We present stellar metallicities in Leo I, Leo II, IC 1613, and Phoenix dwarf galaxies derived from medium (F390M) and broad (F555W, F814W) band photometry using the Wide Field Camera 3 (WFC3) instrument aboard the Hubble Space Telescope. We measured metallicity distribution functions (MDFs) in two ways, 1) matching stars to isochrones in color-color diagrams, and 2) solving for the best linear combination of synthetic populations to match the observed color-color diagram. The synthetic technique reduces the effect of photometric scatter, and produces MDFs 30-50 % narrower than the MDFs produced from individually matched stars. We fit the synthetic and individual MDFs to analytical chemical evolution models (CEM) to quantify the enrichment and the effect of gas flows within the galaxies. Additionally, we measure stellar metallicity gradients in Leo I and II. For IC 1613 and Phoenix our data do not have the radial extent to confirm a metallicity gradient for either galaxy. We find the MDF of Leo I (dwarf spher...

  16. Coevolution of metallicity and star formation in galaxies to z=3.7: I. A fundamental plane

    CERN Document Server

    Hunt, Leslie; Magrini, Laura; Ferrara, Andrea

    2016-01-01

    With the aim of understanding the coevolution of star formation rate (SFR), stellar mass (M*), and oxygen abundance (O/H) in galaxies up to redshift z=3.7, we have compiled the largest available dataset for studying Metallicity Evolution and Galaxy Assembly (MEGA); it comprises roughly 1000 galaxies with a common O/H calibration and spans almost two orders of magnitude in metallicity, a factor of 10^6 in SFR, and a factor of 10^5 in stellar mass. From a Principal Component Analysis, we find that the 3-dimensional parameter space reduces to a Fundamental Plane of Metallicity (FPZ) given by 12+log(O/H) = -0.14 log (SFR) + 0.37 log (M*) + 4.82. The mean O/H FPZ residuals are small (0.16 dex) and consistent with trends found in smaller galaxy samples with more limited ranges in M*, SFR, and O/H. Importantly, the FPZ is found to be redshift-invariant within the uncertainties. In a companion paper, these results are interpreted with an updated version of the model presented by Dayal et al. (2013).

  17. Oxidation of Group 8 transition-Metal Hydrides and Ionic Hydrogenation of Ketones and Aldehydes

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Kjell-Tore

    1996-08-01

    Transition-metal hydrides have received considerable attention during the last decades because of their unusual reactivity and their potential as homogeneous catalysts for hydrogenation and other reactions of organic substrates. An important class of catalytic processes where transition-metal hydrides are involved is the homogeneous hydrogenation of alkenes, alkynes, ketones, aldehydes, arenes and nitro compounds. This thesis studies the oxidation of Group 8 transition-metal hydrides and the ionic hydrogenation of ketones and aldehydes.

  18. Arbuscular mycorrhizal fungal phylogenetic groups differ in affecting host plants along heavy metal levels.

    Science.gov (United States)

    He, Lei; Yang, Haishui; Yu, Zhenxing; Tang, Jianjun; Xu, Ligen; Chen, Xin

    2014-10-01

    Arbuscular mycorrhizal fungi (AMF) are important components of soil microbial communities, and play important role in plant growth. However, the effects of AMF phylogenetic groups (Glomeraceae and non-Glomeraceae) on host plant under various heavy metal levels are not clear. Here we conducted a meta-analysis to compare symbiotic relationship between AMF phylogenetic groups (Glomeraceae and non-Glomeraceae) and host plant functional groups (herbs vs. trees, and non-legumes vs. legumes) at three heavy metal levels. In the meta-analysis, we calculate the effect size (ln(RR)) by taking the natural logarithm of the response ratio of inoculated to non-inoculated shoot biomass from each study. We found that the effect size of Glomeraceae increased, but the effect size of non-Glomeraceae decreased under high level of heavy metal compared to low level. According to the effect size, both Glomeraceae and non-Glomeraceae promoted host plant growth, but had different effects under various heavy metal levels. Glomeraceae provided more benefit to host plants than non-Glomeraceae did under heavy metal condition, while non-Glomeraceae provided more benefit to host plants than Glomeraceae did under no heavy metal. AMF phylogenetic groups also differed in promoting plant functional groups under various heavy metal levels. Interacting with Glomeraceae, herbs and legumes grew better than trees and non-legumes did under high heavy metal level, while trees and legumes grew better than herbs and non-legumes did under medium heavy metal level. Interacting with non-Glomeraceae, herbs and legumes grew better than trees and non-legumes did under no heavy metal. We suggested that the combination of legume with Glomeraceae could be a useful way in the remediation of heavy metal polluted environment.

  19. SEARCHING FOR CFC’s AND HCFC’s ALTERNATIVES. Part I: A REFRIGERANT DESIGN STRATEGY USING GROUP CONTRIBUTION METHODS

    Directory of Open Access Journals (Sweden)

    Y KHETIB

    2000-12-01

    Full Text Available It is now well established that the chlorofluorocarbons (CFC’s, the hydrochlorofluorocarbons (HCFC’s and other chlororinated hydrocarbons which are compounds mostly used as refrigerants, are causing more damages than benefits to the environment and particularly to the ozone layer. Therefore one can see how important it is to search for substitutes to these compounds with desirable combination of physical properties to meet the needs of specific applications but, ultimately, with no harms to the environment. In this paper, although the bases of a computer-aided design of refrigerants (CADR method being developed are outlined, the main purpose still remains the demonstration of the great ability and importance of group contribution methods in the development of such techniques, particularly for predicting vapour-liquid equilibria and other thermodynamic properties like the enthalpy or entropy of generated systems, by the use of models like the UNIFAC.

  20. Near-Infrared Spectroscopy of Carbon-Enhanced Metal-Poor Stars. I. A SOAR/OSIRIS Pilot Study

    CERN Document Server

    Beers, T C; Marstellar, B; Lee, Y S; Rossi, S; Plez, B; Beers, Timothy C.; Sivarani, Thirupathi; Marstellar, Brian; Lee, YoungSun; Rossi, Silvia; Plez, Bertrand

    2006-01-01

    We report on an abundance analysis for a pilot study of seven Carbon-Enhanced Metal-Poor (CEMP) stars, based on medium-resolution optical and near-infrared spectroscopy. The optical spectra are used to estimate [Fe/H], [C/Fe], [N/Fe], and [Ba/Fe] for our program stars. The near-infrared spectra, obtained during a limited early science run with the new SOAR 4.1m telescope and the Ohio State Infrared Imager and Spectrograph (OSIRIS), are used to obtain estimates of [O/Fe] and 12C/13C. The chemical abundances of CEMP stars are of importance for understanding the origin of CNO in the early Galaxy, as well as for placing constraints on the operation of the astrophysical s-process in very low-metallicity Asymptotic Giant Branch (AGB) stars. This pilot study includes a few stars with previously measured [Fe/H], [C/Fe], [N/Fe],[O/Fe], 12C/13C, and [Ba/Fe], based on high-resolution optical spectra obtained with large-aperture telescopes. Our analysis demonstrates that we are able to achieve reasonably accurate determi...

  1. Supernova Remnants in the Local Group I: A model for the radio luminosity function and visibility times of supernova remnants

    CERN Document Server

    Sarbadhicary, Sumit K; Chomiuk, Laura; Caprioli, Damiano; Huizenga, Daniel

    2016-01-01

    Supernova remnants (SNRs) in Local Group galaxies offer unique insights into the origin of different types of supernovae. In order to take full advantage of these insights, one must understand the intrinsic and environmental diversity of SNRs in the context of their host galaxies. We introduce a semi-analytic model that reproduces the statistical properties of a radio continuum-selected SNR population, taking into account the detection limits of radio surveys, the range of SN kinetic energies, the measured ISM and stellar mass distribution in the host galaxy from multi-wavelength images and the current understanding of electron acceleration and field amplification in SNR shocks from first-principle kinetic simulations. Applying our model to the SNR population in M33, we reproduce the SNR radio luminosity function with a median SN rate of $\\sim 3.1 \\times 10^{-3}$ per year and an electron acceleration efficiency, $\\epsilon_{\\rm{e}} \\sim 4.2 \\times 10^{-3}$. We predict that the radio visibility times of $\\sim 7...

  2. Structurally defined allyl compounds of main group metals: coordination and reactivity.

    Science.gov (United States)

    Lichtenberg, Crispin; Okuda, Jun

    2013-05-10

    Organometallic allyl compounds are important as allylation reagents in organic synthesis, as polymerization catalysts, and as volatile metal precursors in material science. Whereas the allyl chemistry of synthetically relevant transition metals such as palladium and of the lanthanoids is well-established, that of main group metals has been lagging behind. Recent progress on allyl complexes of Groups 1, 2, and 12-16 now provides a more complete picture. This is based on a fundamental understanding of metal-allyl bonding interactions in solution and in the solid state. Furthermore, reactivity trends have been rationalized and new types of allyl-specific reactivity patterns have been uncovered. Key features include 1) the exploitation of the different types of metal-allyl bonding (highly ionic to predominantly covalent), 2) the use of synergistic effects in heterobimetallic compounds, and 3) the adjustment of Lewis acidity by variation of the charge of allyl compounds.

  3. Friction behavior of members of the platinum metals group with gold

    Science.gov (United States)

    Buckley, D. H.

    1975-01-01

    The adhesion and friction behavior of the platinum metals group was examined with clean surfaces and surfaces selectively contaminated with oxygen, vinyl chloride (C2H3Cl), and methyl mercaptan (CH3SH). A pin or disk specimen configuration was used with the pin being a single crystal of gold of the (111) orientation and with the platinum metal disks also being single crystals of the (111) or (0001) orientation. Loads applied ranged from 1 to 10 g and a sliding velocity of 0.7 mm/min was employed. Results indicate adhesion and transfer of gold to all of the platinum metals. Despite this observation friction differences existed among the metals in the group. These differences are related to surface chemical activity. Adsorption of various friction reducing species was selective. With some adsorbates present strong adhesive forces between metals were still observed.

  4. Hydrothermal synthesis of platinum-group-metal nanoparticles by using HEPES as a reductant and stabilizer.

    Science.gov (United States)

    So, Man-Ho; Ho, Chi-Ming; Chen, Rong; Che, Chi-Ming

    2010-06-01

    Platinum-group-metal (Ru, Os, Rh, Ir, Pd and Pt) nanoparticles are synthesized in an aqueous buffer solution of 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) (200 mM, pH 7.4) under hydrothermal conditions (180 degrees C). Monodispersed (monodispersity: 11-15%) metal nanoparticles were obtained with an average particle size of less than 5 nm (Ru: 1.8+/-0.2, Os: 1.6+/-0.2, Rh: 4.5+/-0.5, Ir: 2.0+/-0.3, Pd: 3.8+/-0.4, Pt: 1.9+/-0.2 nm). The size, monodispersity, and stability of the as-obtained metal nanoparticles were affected by the HEPES concentration, pH of the HEPES buffer solution, and reaction temperature. HEPES with two tertiary amines (piperazine groups) and terminal hydroxyl groups can act as a reductant and stabilizer. The HEPES molecules can bind to the surface of metal nanoparticles to prevent metal nanoparticles from aggregation. These platinum-group-metal nanoparticles could be deposited onto the surface of graphite, which catalyzed the aerobic oxidation of alcohols to aldehydes.

  5. The oldest and most metal-poor stars in the APOSTLE Local Group simulations

    Science.gov (United States)

    Starkenburg, Else; Oman, Kyle A.; Navarro, Julio F.; Crain, Robert A.; Fattahi, Azadeh; Frenk, Carlos S.; Sawala, Till; Schaye, Joop

    2017-02-01

    We examine the spatial distribution of the oldest and most metal-poor stellar populations of Milky Way-sized galaxies using the A Project Of Simulating The Local Environment (APOSTLE) cosmological hydrodynamical simulations of the Local Group. In agreement with earlier work, we find strong radial gradients in the fraction of the oldest (tform stars, both of which increase outwards. The most metal-poor stars form over an extended period of time; half of them form after z = 5.3, and the last 10 per cent after z = 2.8. The age of the metal-poor stellar population also shows significant variation with environment; a high fraction of them are old in the galaxy's central regions and an even higher fraction in some individual dwarf galaxies, with substantial scatter from dwarf to dwarf. We investigate the dependence of these results on the assumptions made for metal mixing. Overall, over half of the stars that belong to both the oldest and most metal-poor population are found outside the solar circle. Somewhat counter-intuitively, we find that dwarf galaxies with a large fraction of metal-poor stars that are very old are systems where metal-poor stars are relatively rare, but where a substantial old population is present. Our results provide guidance for interpreting the results of surveys designed to hunt for the earliest and most pristine stellar component of our Milky Way.

  6. Mechanical, thermal and laser damage threshold analyses of II group metal complexes of thiourea

    Energy Technology Data Exchange (ETDEWEB)

    Dhanuskodi, S., E-mail: dhanus2k3@yahoo.com [School of Physics, Bharathidasan University, Tiruchirappalli 620 024, Tamil Nadu (India); Sabari Girisun, T.C. [School of Physics, Bharathidasan University, Tiruchirappalli 620 024, Tamil Nadu (India); Department of Physics, Bishop Heber College, Tiruchirappalli 620 017, Tamil Nadu (India); Bhagavannarayana, G. [Material Characterization Division, National Physical laboratory, New Delhi 110 012 (India); Uma, S.; Phillip, J. [Sophisticated Test and Instrumentation Center, Cochin University of Science and Technology, Cochin 682 022 (India)

    2011-04-15

    Research highlights: {yields} The role of the Group II metal ions in improving the stability is discussed. {yields} BTCC has a higher heat capacity than BTZC. {yields} Elastic stiffness is found to be higher for BTCC than BTZC. {yields} Microscopy studies confirm the damage is due to thermo-chemical ablation. {yields} BTCC has a higher laser damage threshold than BTZC. - Abstract: Single crystals of thiourea metal complexes with selected Group II metal ions, Zinc and Cadmium, have been grown by solvent evaporation technique. The crystals grown are bisthiourea zinc chloride (BTZC) and bisthiourea cadmium chloride (BTCC). Following an improved photopyroelectric technique, the thermal transport properties have been determined. It is found that BTCC has a higher heat capacity (304.09 J kg{sup -1} K{sup -1}) than BTZC (255.24 J kg{sup -1} K{sup -1}), and hence BTCC has better thermal stability. Vicker's microhardness measurements reveal that these materials have reverse indentation size effect and belong to the category of soft materials. Elastic stiffness is found to be higher for BTCC (1.57 GPa) than BTZC (0.76 GPa). The roles of the Group II metal ions in improving the mechanical and thermal stability of the metal complexes are discussed. Multi-shot laser damage studies on these materials reveal that BTCC has a higher laser damage threshold (15 GW cm{sup -2}) than BTZC (6 GW cm{sup -2}).

  7. PREPARATION OF POLYMER MICROSPHERES WITH PYRIDYL GROUP AND THEIR STABILIZED GOLD METALLIC COLLOIDS

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Narrow disperse poly(ethyleneglycol dimethacrylate-co-4-vinylpyridine) (poly(EGDMA-co-4-VPy)) microspheres were prepared by distillation-precipitation copolymerization of ethyleneglycol dimethacrylate (EGDMA) and 4-vinylpyridine (4-VPy) with 2,2'-azobisisobutyronitrile (AIBN) as initiator in neat acetonitrile. The polymer microspheres containing pyridyl group were then utilized as stabilizer for gold metallic colloids with the diameter around 7 nm, which were prepared by the in situ reduction of gold chloride trihydrate with sodium borohydride through the coordination of the pyridyl group on the gel layer and surface of the microsphere with the gold metallic nano-particles. The catalytic properties of the pyridyl-functionalized microsphere-stabilized gold metallic colloids and the behavior of the stabilized-catalyst for the recycling were investigated with reduction of 4-nitrophenol to 4-aminophenol as a model reaction.

  8. Aromatic H/D Exchange Reaction Catalyzed by Groups 5 and 6 Metal Chlorides

    Institute of Scientific and Technical Information of China (English)

    郭巧霞; 申宝剑; 郭海卿; 高桥保

    2005-01-01

    Groups 5 and 6 metal chlorides such as MoCl5, WCI6, NbCl5 and TaCl5 were found to be simple and very efficientcatalysts for the aromatic H/D exchange reactions. Compared with other metal chlorides such as ZnCl2, SnCl4 and TiCl4, groups 5 and 6 metal chlorides showed better catalytic activity in the H/D exchange reaction of naphthalene with C6D6. Deuteration of anthracene using MoC15 as a catalyst proceeded within 24 h at room temperature. Other aromatic compounds such as toluene, diphenylmethane and 1,1,2-triphenylethane were also deuterated smoothly in C6D6 within 24 h at room temperature.

  9. Group 3 metal stilbene complexes: Synthesis, reactivity, and electronic structure studies

    OpenAIRE

    Huang, W.; Abukhalil, PM; Khan, SI; Diaconescu, PL

    2014-01-01

    Group 3 metal (E)-stilbene complexes supported by a ferrocene diamide ligand were synthesized and characterized. Reactivity studies showed that they behave similar to analogous naphthalene complexes. Experimental and computational results indicated that the double bond was reduced and not a phenyl ring, in contrast to a previously reported uranium (E)-stilbene complex. © the Partner Organisations 2014.

  10. Lattice-Inversion Embedded-Atom-Method Interatomic Potentials for Group-VA Transition Metals

    Institute of Scientific and Technical Information of China (English)

    袁晓俭; 陈难先; 申江

    2011-01-01

    The lattice-inversion embedded-atom-method (LI-EAM) interatomic potential we developed previously [J. Phys.: Condens. Matter 22 (2010) 375503] is extended to group- VA transition metals (V, Nb and Ta). It is found that considering interatomic interactions up to appropriate-distance-neighbor atoms is crucial to constructing accurate EAM potentials, especially for the prediction of surface energy. The LI-EAM interatomic potentials for group-VA transition metals are successfully built by considering interatomic interactions up to the fifth neighbor atoms. These angular-independent potentials drastically promote the accuracy of the predicted surface energies, which match the experimental resuits well.%The lattice-inversion embedded-atom-method(LI-EAM)interatomic potential we developed previously[J.Phys.:Condens.Matter 22(2010)375503]is extended to group-VA transition metals(V,Nb and Ta).It is found that considering interatomic interactions up to appropriate-distance-neighbor atoms is crucial to constructing accurate EAM potentials,especially for the prediction of surface energy.The LI-EAM interatomic potentials for group-VA transition metals are successfully built by considering interatomic interactions up to the fifth neighbor atoms.These angular-independent potentials drastically promote the accuracy of the predicted surface energies,which match the experimental results well.

  11. Using amino acids for the chromatofocusing of metal ions on silica with bonded tetraethylenepentamine groups

    Science.gov (United States)

    Ivanov, A. V.

    2014-09-01

    Amino acid-based eluents are used for the chromatofocusing of metal ions on Tetren-SiO2 chelating sorbent (silica with bonded tetraethylenepentamine groups) for the first time. The smoothest quasilinear pH gradients form for eluents based on glutamic and aspartic acids. The separation of Mn2+, Cr3+, Co2+, Ni2+, and Cu2+ is achieved.

  12. Xinjiang Nonferrous Metals Group Achieved Annual Sales Revenue of RMB 50 Billion

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    <正>Xinjiang Nonferrous Metals Group has officially presented the following ideas for development in the 12th Five-Year Plan period: "take effective measures such as resource integration, scale expansion, capital operation and technological innovation, etc. to boost the

  13. Coulombic amino group-metal bonding: adsorption of adenine on Cu110.

    Science.gov (United States)

    Preuss, M; Schmidt, W G; Bechstedt, F

    2005-06-17

    The interaction between molecular amino groups and metal surfaces is analyzed from first-principles calculations using the adsorption of adenine on Cu110 as a model case. The amino group nitrogens are found to adsorb on top of the surface copper atoms. However, the bonding clearly cannot be explained in terms of covalent interactions. Instead, we find it to be largely determined by mutual polarization and Coulomb interaction between substrate and adsorbate.

  14. Investigation of complexing ability of ionites with various groups to some heavy and transition metal ions

    Directory of Open Access Journals (Sweden)

    Yedil Yergozhin

    2013-05-01

    Full Text Available The physico-chemical and complexing properties of the sorbent based on chloromethylated styrene and divinylbenzene copolymer with nicotinamide groups and copolymers based on metacryloilaminobenzene acids with 2-methyl-5-vinylpyridineisomers are studied. By potentiometric titration method the constant of polyelectrolytes functional groups ionization, the composition and strength of the resulting complexes with ions of some heavy and transition metals are determined.

  15. The oldest and most metal poor stars in the APOSTLE Local Group simulations

    CERN Document Server

    Starkenburg, Else; Navarro, Julio F; Crain, Robert A; Fattahi, Azadeh; Frenk, Carlos S; Sawala, Till; Schaye, Joop

    2016-01-01

    We examine the spatial distribution of the oldest and most metal poor stellar populations of Milky Way-sized galaxies using the APOSTLE cosmological hydrodynamical simulations of the Local Group. In agreement with earlier work, we find strong radial gradients in the fraction of the oldest (tform < 0.8 Gyr) and most metal poor ([Fe/H]< -2.5) stars, both of which increase outwards. The most metal poor stars form over an extended period of time; half of them form after z = 5.3, and the last 10% after z = 2.8. The age of the metal poor stellar population also shows significant variation with environment; a high fraction of them are old in the galaxy's central regions and an even higher fraction in some individual dwarf galaxies, with substantial scatter from dwarf to dwarf. Overall, over half of the stars that belong to both the oldest and most metal-poor population are found outside the solar circle. Somewhat counter-intuitively, we find that dwarf galaxies with a large fraction of metal poor stars that ar...

  16. Effect of functionalization of boron nitride flakes by main group metal clusters on their optoelectronic properties

    Science.gov (United States)

    Chakraborty, Debdutta; Chattaraj, Pratim Kumar

    2017-10-01

    The possibility of functionalizing boron nitride flakes (BNFs) with some selected main group metal clusters, viz. OLi4, NLi5, CLi6, BLI7 and Al12Be, has been analyzed with the aid of density functional theory (DFT) based computations. Thermochemical as well as energetic considerations suggest that all the metal clusters interact with the BNF moiety in a favorable fashion. As a result of functionalization, the static (first) hyperpolarizability (β ) values of the metal cluster supported BNF moieties increase quite significantly as compared to that in the case of pristine BNF. Time dependent DFT analysis reveals that the metal clusters can lower the transition energies associated with the dominant electronic transitions quite significantly thereby enabling the metal cluster supported BNF moieties to exhibit significant non-linear optical activity. Moreover, the studied systems demonstrate broad band absorption capability spanning the UV–visible as well as infra-red domains. Energy decomposition analysis reveals that the electrostatic interactions principally stabilize the metal cluster supported BNF moieties.

  17. Unmetallated and metallated phthalocyanines bearing oxadiazole groups: Synthesis, photophysical and photochemical studies

    Energy Technology Data Exchange (ETDEWEB)

    Nas, Asiye [Department of Chemistry, Karadeniz Technical University, 61080 Trabzon (Turkey); Kantekin, Halit, E-mail: halit@ktu.edu.tr [Department of Chemistry, Karadeniz Technical University, 61080 Trabzon (Turkey); Durmuş, Mahmut [Gebze Institute of Technology, Department of Chemistry, PO Box 141, Gebze, 41400 Kocaeli (Turkey); Gümrükçüoğlu, Nurhan [Department of Chemistry, Karadeniz Technical University, 61080 Trabzon (Turkey)

    2014-10-15

    Unmetallated (4) and metallated (zinc(II), cobalt(II), lead(II)) phthalocyanines (5–7) carrying four 4-(4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenoxy) groups on the peripheral positions were synthesized by cyclotetramerization of 4-(4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenoxy)phthalonitrile (3) in the presence of corresponding metal salts (zinc(II) acetate, cobalt(II) chloride, lead(II) oxide) for metallated and without any metal for unmetallated phthalocyanines. The obtained organo-soluble phthalocyanines were characterized by infrared, electronic absorption, nuclear magnetic resonance and mass spectral techniques and elemental analysis as well. The photophysical and photochemical properties of newly synthesized tetra-substituted unmetallated (4), zinc(II) (5) and lead(II) (7) phthalocyanines were reported in N,N-dimetilformamid (DMF). The synthesized phthalocyanine compound 6 was not evaluated for photophysical and photochemical studies due to open shell and paramagnetic behavior of cobalt(II) metal ions in the phthalocyanine cavity. - Highlights: • Synthesis of unmetallated and metallated phthalocyanines. • Photophysical and photochemical properties of tetra-substituted phthalocyanines. • Characterization of organosoluble phthalocyanines by several spectral techniques.

  18. Main Group Lewis Acid-Mediated Transformations of Transition-Metal Hydride Complexes.

    Science.gov (United States)

    Maity, Ayan; Teets, Thomas S

    2016-08-10

    This Review highlights stoichiometric reactions and elementary steps of catalytic reactions involving cooperative participation of transition-metal hydrides and main group Lewis acids. Included are reactions where the transition-metal hydride acts as a reactant as well as transformations that form the metal hydride as a product. This Review is divided by reaction type, illustrating the diverse roles that Lewis acids can play in mediating transformations involving transition-metal hydrides as either reactants or products. We begin with a discussion of reactions where metal hydrides form direct adducts with Lewis acids, elaborating the structure and dynamics of the products of these reactions. The bulk of this Review focuses on reactions where the transition metal and Lewis acid act in cooperation, and includes sections on carbonyl reduction, H2 activation, and hydride elimination reactions, all of which can be promoted by Lewis acids. Also included is a section on Lewis acid-base secondary coordination sphere interactions, which can influence the reactivity of hydrides. Work from the past 50 years is included, but the majority of this Review focuses on research from the past decade, with the intent of showcasing the rapid emergence of this field and the potential for further development into the future.

  19. A 3D analysis of the metal distribution in the compact group of galaxies HCG 31

    Science.gov (United States)

    Torres-Flores, Sergio; Mendes de Oliveira, Claudia; Alfaro-Cuello, Mayte; Rodrigo Carrasco, Eleazar; de Mello, Duilia; Amram, Philippe

    2015-02-01

    We present new Gemini/GMOS integral field unit observations of the central region of the merging compact group of galaxies HCG 31. Using this data set, we derive the oxygen abundances for the merging galaxies HCG 31A and HCG 31C. We found a smooth metallicity gradient between the nuclei of these galaxies, suggesting a mixing of metals between these objects. These results are confirmed by high-resolution Fabry-Perot data, from which we infer that gas is flowing between HCG 31A and HCG 31C.

  20. Reviews of Metallurgical Technology to Recovery Platinum Group Metals from Secondary Resource in China

    Institute of Scientific and Technical Information of China (English)

    GUO Junmei; HE Xiaotang; WANG Huan; WU Xilong; ZHAO Yu; LI Yong; LI Kun; HAN Shouli

    2012-01-01

    China is extremely poor in mineral resources of Platinum Group Metals (PGMs),productive output of PGMs from mineral resource is 2.5 tons per year.At the same time,China is the biggest PGMs consumption country in the world,the mineral resource of PGMs is critical shortage,it shows the importance of recycling the secondary resource of PGMs.Sino-Platinum Metals Resource (Yimen) Co.,Ltd.is the leader in recycling of PGMs from secondary resource,and has made outstanding contributions to China PGMs secondary resources recycling.This article elucidates the current situation of secondary resources recovery and development of metallurgical technology for PGMs.

  1. NGC 6845: metallicity gradients and star formation in a complex compact group

    CERN Document Server

    Olave-Rojas, D; Carrasco, E R; de Oliveira, C Mendes; de Mello, D F; Scarano, S

    2015-01-01

    We have obtained Gemini/GMOS spectra of 28 regions located across the interacting group NGC 6845, spanning from the inner regions of the four major galaxies (NGC 6845A, B, C, D) to the tidal tails of NGC 6845A. All regions in the tails are star-forming objects with ages younger than 10 Myr. We derived the gas-phase metallicity gradients across NGC 6845A and its two tails and we find that these are shallower than those for isolated galaxies. NGC 6845A has a gas-phase oxygen central metallicity of \\mbox{12+log(O/H)$\\sim$8.5} and a flat gas-phase metallicity gradient ($\\beta$=0.002$\\pm$0.004 dex kpc$^{-1}$) out to $\\sim$4 $\\times$ R$_{25}$ (to the end of the longest tidal tail). Considering the mass-metallicity relation, the central region of NGC 6845A displays a lower oxygen abundance than the expected for its mass. Taking into account this fact and considering the flat oxygen distribution measured along the eastern tidal tail, we suggest that an interaction event has produced a dilution in the central metallic...

  2. Probing the bonding of CO to heteronuclear group 4 metal-nickel clusters by photoelectron spectroscopy.

    Science.gov (United States)

    Zou, Jinghan; Xie, Hua; Yuan, Qinqin; Zhang, Jumei; Dai, Dongxu; Fan, Hongjun; Tang, Zichao; Jiang, Ling

    2017-04-12

    A series of heterobinuclear group 4 metal-nickel carbonyls MNi(CO)n(-) (M = Ti, Zr, Hf; n = 3-7) has been generated via a laser vaporization supersonic cluster source and characterized by mass-selected photoelectron velocity-map imaging spectroscopy. Quantum chemical calculations have been carried out to elucidate the geometric and electronic structures and support the spectral assignments. The n = 3 cluster is determined to be capable of simultaneously accommodating three different types of CO bonds (i.e., side-on-bonded, bridging, and terminal modes), resulting in a MNi[η(2)(μ2-C, O)](μ-CO)(CO)(-) structure, which represents the smallest metal carbonyl with the involvement of all the main modes of metal-CO coordination to date. The building block of three bridging CO molecules is favored at n = 4, the structure of which persists up to n = 7. The additional CO ligands are bonded terminally to the metal atoms. The present findings provide important new insight into the structure and bonding mechanisms of CO molecules with heteronuclear transition metals, which would have important implications for understanding chemisorbed CO molecules on alloy surfaces.

  3. High-temperature mass spectrometry - Vaporization of group 4-B metal carbides. [using Knudsen effusion

    Science.gov (United States)

    Stearns, C. A.; Kohl, F. J.

    1974-01-01

    The high temperature vaporization of the metal-carbon systems TiC, ZrC, HfC, and ThC was studied by the Knudsen effusion - mass spectrometric method. For each system the metal dicarbide and tetracarbide molecular species were identified in the gas phase. Relative ion currents of the carbides and metals were measured as a function of temperature. Second- and third-law methods were used to determine enthalpies. Maximum values were established for the dissociation energies of the metal monocarbide molecules TiC, ZrC, HfC, and ThC. Thermodynamic functions used in the calculations are discussed in terms of assumed molecular structures and electronic contributions to the partition functions. The trends shown by the dissociation energies of the carbides of Group 4B are compared with those of neighboring groups and discussed in relation to the corresponding oxides and chemical bonding. The high temperature molecular beam inlet system and double focusing mass spectrometer are described.

  4. Xinjiang Nonferrous Metal Group is Developing on Low-cost Expanding

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    <正>Xinjiang Xinxin Mining Industry Co.,Ltd., whose shareholder is Xinjiang Nonferrous Metal Group,issued a report through the Stock Exchange of Hong Kong Limited,or SEHK, that the company had made a 542.25 million yuan takeover of Yakesi Resources Develop- ment Co.,Ltd.and Hami Jubao Resource De- velopment Co.,Ltd.,the biggest copper nickel exploitation company in Hami area.This is the largest scale takeover since Xinxin became a

  5. Retention of heavy metals by carboxyl functional groups of biochars in small arms range soil.

    Science.gov (United States)

    Uchimiya, Minori; Bannon, Desmond I; Wartelle, Lynda H

    2012-02-22

    Long-term effectiveness of biochar for heavy metal stabilization depends upon biochar's sorptive property and recalcitrance in soil. To understand the role of carboxyl functional groups on heavy metal stabilization, cottonseed hull biochar and flax shive steam-activated biochar having a low O/C ratio (0.04-0.06) and high fixed carbon content (~80% dry weight basis) were oxidized using concentrated H(2)SO(4)/HNO(3) and 30% HNO(3). Oxidized and unoxidized biochars were characterized for O/C ratio, total acidity, pH, moisture, ash, volatile matter, and fixed carbon contents, Brunauer-Emmett-Teller surface area, and attenuated total reflectance Fourier transform infrared spectral features. Characterized biochars were amended (2%, 5%, 10%, and 20% in grams of biochar per gram of soil) on a sandy, slightly acidic (pH 6.27) heavy metal contaminated small arms range soil fraction (carbon (0.518%) and low cation exchange capacity (0.95 cmol(c) kg(-1)). Oxidized biochars rich in carboxyl functional groups exhibited significantly greater Pb, Cu, and Zn stabilization ability compared to unoxidized biochars, especially in pH 4.9 acetate buffer (standard solution for the toxicity characteristic leaching procedure). Oppositely, only oxidized biochars caused desorption of Sb, indicating a counteracting impact of carboxyl functional groups on the solubility of anions and cations. The results suggested that appropriate selection of biochar oxidant will produce recalcitrant biochars rich in carboxyl functional groups for a long-term heavy metal stabilization strategy in contaminated soils.

  6. Dichlorostannylene complexes of group 10 metals, a unique bonding mode stabilized by bridging 2-pyridyldiphenylphosphine ligands

    NARCIS (Netherlands)

    Cabon, Y.; Kleijn, H.; Siegler, M. A.; Spek, A.L.; Klein Gebbink, R.J.M.; Deelman, B.J.

    2010-01-01

    The reaction of tin dichloride with catalytically-relevant group 10 metal precursors [M(Cl)(X)(2-PyPPh2)2] (M = Ni, Pd, Pt; 2-PyPPh2 = 2-pyridyldiphenylphosphine; X = Cl, Me) provides easy access to unprecedented cationic dichlorostannylene complexes [M(X)(2-PyPPh2)2(SnCl2)]+ where the M–Sn bond is

  7. Comparison between alkalimetal and group 11 transition metal halide and hydride tetramers: molecular structure and bonding.

    Science.gov (United States)

    El-Hamdi, Majid; Solà, Miquel; Frenking, Gernot; Poater, Jordi

    2013-08-22

    A comparison between alkalimetal (M = Li, Na, K, and Rb) and group 11 transition metal (M = Cu, Ag, and Au) (MX)4 tetramers with X = H, F, Cl, Br, and I has been carried out by means of the Amsterdam Density Functional software using density functional theory at the BP86/QZ4P level of theory and including relativistic effects through the ZORA approximation. We have obtained that, in the case of alkalimetals, the cubic isomer of Td geometry is more stable than the ring structure with D4h symmetry, whereas in the case of group 11 transition metal tetramers, the isomer with D4h symmetry (or D2d symmetry) is more stable than the Td form. To better understand the results obtained we have made energy decomposition analyses of the tetramerization energies. The results show that in alkalimetal halide and hydride tetramers, the cubic geometry is the most stable because the larger Pauli repulsion energies are compensated by the attractive electrostatic and orbital interaction terms. In the case of group 11 transition metal tetramers, the D4h/D2d geometry is more stable than the Td one due to the reduction of electrostatic stabilization and the dominant effect of the Pauli repulsion.

  8. Carbide-forming groups IVB-VIB metals: a new territory in the periodic table for CVD growth of graphene.

    Science.gov (United States)

    Zou, Zhiyu; Fu, Lei; Song, Xiuju; Zhang, Yanfeng; Liu, Zhongfan

    2014-07-09

    Early transition metals, especially groups IVB-VIB metals, can form stable carbides, which are known to exhibit excellent "noble-metal-like" catalytic activities. We demonstrate herein the applications of groups IVB-VIB metals in graphene growth using atmospheric pressure chemical vapor deposition technique. Similar to the extensively studied Cu, Ni, and noble metals, these transition-metal foils facilitate the catalytic growth of single- to few-layer graphene. The most attractive advantage over the existing catalysts is their perfect control of layer thickness and uniformity with highly flexible experimental conditions by in situ converting the dissolved carbons into stable carbides to fully suppress the upward segregation/precipitation effect. The growth performance of graphene on these transition metals can be well explained by the periodic physicochemical properties of elements. Our work has disclosed a new territory of catalysts in the periodic table for graphene growth and is expected to trigger more interest in graphene research.

  9. WITNESSING GAS MIXING IN THE METAL DISTRIBUTION OF THE HICKSON COMPACT GROUP HCG 31

    Energy Technology Data Exchange (ETDEWEB)

    Torres-Flores, S.; Alfaro-Cuello, M. [Departamento de Física, Universidad de La Serena, Av. Cisternas 1200, La Serena (Chile); De Oliveira, C. Mendes [Instituto de Astronomia, Geofísica e Ciências Atmosféricas da Universidade de São Paulo, Cidade Universitária, CEP:05508-900, São Paulo, SP (Brazil); Amram, P. [Aix Marseille Université, CNRS, LAM (Laboratoire d' Astrophysique de Marseille) UMR 7326, F-13388, Marseille (France); Carrasco, E. R. [Gemini Observatory/AURA, Southern Operations Center, Casilla 603, La Serena (Chile); De Mello, D. F., E-mail: storres@dfuls.cl [Catholic University of America, Washington, DC 20064 (United States)

    2015-01-01

    We present for the first time direct evidence that in a merger of disk galaxies, the pre-existing central metallicities will mix as a result of gas being transported in the merger interface region along the line that joins the two coalescing nuclei. This is shown using detailed two-dimensional kinematics as well as metallicity measurements for the nearby ongoing merger in the center of the compact group HCG 31. We focus on the emission line gas, which is extensive in the system. The two coalescing cores display similar oxygen abundances. While in between the two nuclei, the metallicity changes smoothly from one nucleus to the other indicating a mix of metals in this region, which is confirmed by the high-resolution Hα kinematics (R = 45,900). This nearby system is especially important because it involves the merging of two fairly low-mass and clumpy galaxies (LMC-like galaxies), making it an important system for comparison with high-redshift galaxies.

  10. Energetics of small clusters of group IB metals (Cu, Ag, and Au) adsorbed on graphene

    Science.gov (United States)

    Kaur, Gagandeep; Gupta, Shuchi; Dharamvir, Keya

    2013-06-01

    The 2D structure of graphene maximizes the interaction of adsorbate on the layer. Many experiments have been devised to form stable metallic clusters of different sizes. We study the structure and binding energies of group IB clusters Mn (M=Au, Ag, Cu n=1, 3) adsorbed on graphene using Gupta potential [1] (for M-M interaction) and Lennard-Jones potential [2] (for metal-carbon interaction). The total energy of the system has been obtained by placing each of Mn cluster a certain distance above the graphene sheet at various positions and in various orientations. The minimized energy configurations, for all Mn clusters, lie above the center of a hexagon and parallel to the graphene sheet. Binding energy per atom for Ag and Cu metal clusters are less than those of respective Au indicating the lower stability of Ag/Cu metal-graphene system. Using various energy barriers, we can calculate the energy required to move small cluster from one position of minimum energy to another on graphene.

  11. Cycloadditions to Epoxides Catalyzed by GroupIII-V Transition-Metal Complexes

    KAUST Repository

    D'Elia, Valerio

    2015-05-25

    Complexes of groupIII-V transition metals are gaining increasing importance as Lewis acid catalysts for the cycloaddition of dipolarophiles to epoxides. This review examines the latest reports, including homogeneous and heterogeneous applications. The pivotal step for the cycloaddition reactions is the ring opening of the epoxide following activation by the Lewis acid. Two modes of cleavage (C-C versus C-O) have been identified depending primarily on the substitution pattern of the epoxide, with lesser influence observed from the Lewis acid employed. The widely studied cycloaddition of CO2 to epoxides to afford cyclic carbonates (C-O bond cleavage) has been scrutinized in terms of catalytic efficiency and reaction mechanism, showing that unsophisticated complexes of groupIII-V transition metals are excellent molecular catalysts. These metals have been incorporated, as well, in highly performing, recyclable heterogeneous catalysts. Cycloadditions to epoxides with other dipolarophiles (alkynes, imines, indoles) have been conducted with scandium triflate with remarkable performances (C-C bond cleavage). © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Highly Fluorescent Group 13 Metal Complexes with Cyclic, Aromatic Hydroxamic Acid Ligands

    Energy Technology Data Exchange (ETDEWEB)

    Seitz, Michael; Moore, Evan G.; Raymond, Kenneth N.

    2008-02-11

    The neutral complexes of two ligands based on the 1-oxo-2-hydroxy-isoquinoline (1,2-HOIQO) motif with group 13 metals (Al, Ga, In) show bright blue-violet luminescence in organic solvents. The corresponding transition can be attributed to ligand-centered singlet emission, characterized by a small Stokes shifts of only a few nm combined with lifetimes in the range between 1-3 ns. The fluorescence efficiency is high, with quantum yields of up to 37% in benzene solution. The crystal structure of one of the indium(III) complexes (trigonal space group R-3, a = b = 13.0384(15) {angstrom}, c = 32.870(8) {angstrom}, ? = {beta} = 90{sup o}, {gamma} = 120{sup o}, V = 4839.3(14) {angstrom}{sup 3}, Z = 6) shows a six-coordinate geometry around the indium center which is close to trigonal-prismatic, with a twist angle between the two trigonal faces of 20.7{sup o}. Time-dependent density functional theory (TD-DFT) calculations (Al and Ga: B3LYP/6-31G(d)); In: B3LYP/LANL2DZ of the fac and mer isomers with one of the two ligands indicate that there is no clear preference for either one of the isomeric forms of the metal complexes. In addition, the metal centers do not have a significant influence on the electronic structure, and as a consequence, on the predominant intraligand optical transitions.

  13. ALLOYING-DRIVEN PHASE STABILITY IN GROUP-VB TRANSITION METALS UNDER COMPRESSION

    Energy Technology Data Exchange (ETDEWEB)

    Landa, A; Soderlind, P

    2011-04-11

    The change in phase stability of Group-VB (V, Nb, and Ta) transition metals due to pressure and alloying is explored by means of first-principles electronic-structure calculations. It is shown that under compression stabilization or destabilization of the ground-state body-centered cubic (bcc) phase of the metal is mainly dictated by the band-structure energy that correlates well with the position of the Kohn anomaly in the transverse acoustic phonon mode. The predicted position of the Kohn anomaly in V, Nb, and Ta is found to be in a good agreement with data from the inelastic x-ray or neutron scattering measurements. In the case of alloying the change in phase stability is defined by the interplay between the band-structure and Madelung energies. We show that band-structure effects determine phase stability when a particular Group-VB metal is alloyed with its nearest neighbors within the same d-transition series: the neighbor with less and more d electrons destabilize and stabilize the bcc phase, respectively. When V is alloyed with neighbors of a higher (4d- or 5d-) transition series, both electrostatic Madelung and band-structure energies stabilize the body-centered-cubic phase. The opposite effect (destabilization) happens when Nb or Ta is alloyed with neighbors of the 3d-transition series.

  14. The two metallicity groups of the globular cluster M22: a chemical perspective

    CERN Document Server

    Marino, A F; Kraft, R P; Wallerstein, G; Norris, J E; Da Costa, G; Milone, A P; Ivans, I I; Gonzalez, G; Fulbright, J P; Hilker, M; Piotto, G; Zoccali, M; Stetson, P B

    2011-01-01

    We present a detailed chemical composition analysis of 35 red giant stars in the globular cluster M22. High resolution spectra for this study were obtained at five observatories, and analyzed in a uniform manner. We have determined abundances of representative light proton-capture, alpha, Fe-peak and neutron-capture element groups. Our aim is to better understand the peculiar chemical enrichment history of this cluster, in which two stellar groups are characterized by a different content in iron, neutron capture elements Y, Zr and Ba, and alpha element Ca. The principal results of this study are: (i) substantial star-to-star metallicity scatter (-2.0<[Fe/H]<-1.6); (ii) enhancement of s-process/r-process neutron-capture abundance ratios in a fraction of giants, positively correlated with metallicity; (iii) sharp separation between the s-process rich and s-process poor groups by [La/Eu] ratio; (iv) possible increase of [Cu/Fe] ratios with increasing [Fe/H], suggesting that this element also has a signific...

  15. Understanding hydrogen sorption in a metal-organic framework with open-metal sites and amide functional groups

    KAUST Repository

    Pham, Tony T.

    2013-05-09

    Grand canonical Monte Carlo (GCMC) studies of the mechanism of hydrogen sorption in an rht-MOF known as Cu-TPBTM are presented. The MOF is a decorated/substituted isostructural analogue to the unembellished rht-MOF, PCN-61, that was studied previously [ Forrest, K. A.J. Phys. Chem. C 2012, 116, 15538-15549. ]. The simulations were performed using three different hydrogen potentials of increasing complexity. Simulated hydrogen sorption isotherms and calculated isosteric heat of adsorption, Qst, values were in excellent agreement with the reported experimental data for only a polarizable model in one of four experimentally observed crystal structure configurations. The study demonstrates the ability of modeling to distinguish the differential sorption of distinct strucures; one configuration is found to be dominant due to favorable interactions with substrates. In addition, it was discovered that the presence of polar amide groups had a significant effect on the electrostatics of the Cu2+ ions and directs the low-pressure physisorption of hydrogen in the MOF. This is in contrast to what was observed in PCN-61, where an exterior copper ion had a higher relative charge and was the favored loading site. This tunability of the electrostatics of the copper ions via chemical substitution on the MOF framework can be explained by the presence of the negatively charged oxygen atom of the amide group that causes the interior Cu2+ ion to exhibit a higher positive charge through an inductive effect. Further, control simulations, taking advantage of the flexibility afforded by theoretical modeling, include artificially modified charges for both Cu2+ ions chosen equal to or with a higher charge on the exterior Cu2+ ion. This choice resulted in distinctly different hydrogen sorption characteristics in Cu-TPBTM with no direct sorption on the open-metal sites. Thus, this study demonstrates both the tunable nature of MOF platforms and the possibility for rational design of sorption

  16. Leaching platinum-group metals in a sulfuric acid/chloride solution

    Science.gov (United States)

    Mahmoud, M. H. H.

    2003-04-01

    A leaching process was established based on the ability of platinum-group metals to form stable chloro-complexes in acidic chloride solutions. Industrial catalyst losses were examined for the recovery of platinum, palladium, and rhodium by leaching with a mixture of sulfuric acid and sodium chloride to avoid using aqua regia or autoclave conditions. Extraction of platinum and rhodium in 60% H2SO4 at 135°C steadily increased with increasing NaCl concentrations reaching 95% and 85%, respectively, at 0.1 M NaCl after two hours. By comparison, palladium was dissolved more quickly but also reached 85% under the same conditions. Extraction of each metal increased with temperatures up to 125°C but plateaued at higher temperatures. Similar behavior was observed with increasing H2SO4 concentrations up to 60%. More than 99% extraction of each metal was obtained after ten hours using 0.1 M NaCl and 60% H2SO4 at 125°C.

  17. Extrinsic Hardening of Superhard Tungsten Tetraboride Alloys with Group 4 Transition Metals.

    Science.gov (United States)

    Akopov, Georgiy; Yeung, Michael T; Turner, Christopher L; Mohammadi, Reza; Kaner, Richard B

    2016-05-04

    Alloys of tungsten tetraboride (WB4) with the group 4 transition metals, titanium (Ti), zirconium (Zr), and hafnium (Hf), of different concentrations (0-50 at. % on a metals basis) were synthesized by arc-melting in order to study their mechanical properties. The phase composition and purity of the as-synthesized samples were confirmed using powder X-ray diffraction (PXRD) and energy dispersive X-ray spectroscopy (EDS). The solubility limit as determined by PXRD is 20 at. % for Ti, 10 at. % for Zr, and 8 at. % for Hf. Vickers indentation measurements of WB4 alloys with 8 at. % Ti, 8 at. % Zr, and 6 at. % Hf gave hardness values, Hv, of 50.9 ± 2.2, 55.9 ± 2.7 and 51.6 ± 2.8 GPa, respectively, compared to 43.3 GPa for pure WB4 under an applied load of 0.49 N. Each of the aforementioned compositions are considered superhard (Hv > 40 GPa), likely due to extrinsic hardening that plays a key role in these superhard metal borides. Furthermore, these materials exhibit a significantly reduced indentation size effect, which can be seen in the plateauing hardness values for the W1-xZrxB4 alloy. In addition, W0.92Zr0.08B4, a product of spinoidal decomposition, possesses nanostructured grains and enhanced grain hardening. The hardness of W0.92Zr0.08B4 is 34.7 ± 0.65 GPa under an applied load of 4.9 N, the highest value obtained for any superhard metal at this relatively high loading. In addition, the WB4 alloys with Ti, Zr, and Hf showed a substantially increased oxidation resistance up to ∼460 °C, ∼510 °C, and ∼490 °C, respectively, compared to ∼400 °C for pure WB4.

  18. Witnessing Gas Mixing in the Metal Distribution of the Hickson Compact Group HCG 31

    Science.gov (United States)

    Torres-Flores, S.; Mendes de Oliveira, C.; Amram, P.; Alfaro-Cuello, M.; Carrasco, E. R.; de Mello, D. F.

    2015-01-01

    We present for the first time direct evidence that in a merger of disk galaxies, the pre-existing central metallicities will mix as a result of gas being transported in the merger interface region along the line that joins the two coalescing nuclei. This is shown using detailed two-dimensional kinematics as well as metallicity measurements for the nearby ongoing merger in the center of the compact group HCG 31. We focus on the emission line gas, which is extensive in the system. The two coalescing cores display similar oxygen abundances. While in between the two nuclei, the metallicity changes smoothly from one nucleus to the other indicating a mix of metals in this region, which is confirmed by the high-resolution Hα kinematics (R = 45,900). This nearby system is especially important because it involves the merging of two fairly low-mass and clumpy galaxies (LMC-like galaxies), making it an important system for comparison with high-redshift galaxies. Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the Science and Technology Facilities Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministério da Ciência e Tecnologia (Brazil) and Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina) - Observing run: GS-2012B-Q-60.

  19. Detailed Iron-Group Abundances in a Very Metal-Poor Main Sequence Turnoff Star

    Science.gov (United States)

    Sneden, Chris; Roederer, Ian U.; Boesgaard, Ann M.; Lawler, James E.; Den Hartog, Elizabeth; Cowan, John J.; Sobeck, Jennifer

    2017-01-01

    We have obtained Keck HIRES and HST STIS high resolution, high signal-to-noise spectra of the very metal-poor ([Fe/H] ~ -2.9) main-sequence turnoff star BD+03 740. A detailed chemical composition analysis based on synthetic spectrum computations has been conducted. Our initial focus has been on the iron-group elements in the Z = 21-28 range. This study takes advantage of recent improvements in neutral and ionzied species transition data for all of these elements except Sc (Z = 21) by the Wisconsin atomic physics group (see a companion presentation on Cr II at this meeting). Several metal-poor abundance surveys have concluded that there are large overabundances of Co and underabundances of Cr with respect to Fe for stars with [Fe/H] synthesis in the Galaxy.This work has been supported by HST STScI Program GO-14232; and NSF grants AST-1211585 and AST-1616040 to CS; AST-1516182 to JEL and EDH; NASA grant NNX16AE96G to JEL

  20. HIGHLY REFRACTORY CRUCIBLES OF STABILIZED ZIRCONIA FOR INDUCTION MELTING OF THE PLATINUM GROUP METALS, FABRICATED BY VIBROCASTING

    Directory of Open Access Journals (Sweden)

    V. V. Primachenko

    2012-01-01

    Full Text Available As the result of the studies at PJSC « UKRNIIO them. A.S.Berezhnogo» the technology and commercial production of crucibles from stabilized zirconia for the smelting of platinum group metals are develop

  1. Oxidative addition of disulfide/diselenide to group 10 metal(0) and in situ functionalization to form neutral thiasalen/selenasalen group 10 metal(II) complexes.

    Science.gov (United States)

    Dutta, Pradip Kr; Asatkar, Ashish K; Zade, Sanjio S; Panda, Snigdha

    2014-01-28

    Three components, one pot synthesis of thiasalen/selenasalen Ni(II), Pd(II) and Pt(II) complexes, 14-19, by the oxidative addition of S-S/Se-Se bond of bis(o-formylphenyl)disulfide/-diselenide to Ni(0), Pd(0) and Pt(0) followed by in situ Schiff base formation with ethylenediamine is reported. S-S or Se-Se bonds were cleaved and coordinated to the metal center as thiolate (ArS(-)) or selenolate (ArSe(-)) while the formal oxidation state of metal centers was changed from '0' to '+2'. The disulfide/diselenide reacted with zero-valent metals at room temperature to give only the monometallic complexes. All complexes (except Pd-thiolate complex 15) were studied by single crystal X-ray crystallography and revealed the square planar geometry around metal centers.

  2. Metallicity of M dwarfs I. A photometric calibration and impact on the mass-luminosity relation at the bottom of the main sequence

    CERN Document Server

    Bonfils, X; Udry, S; Santos, N C; Forveille, T; Ségransan, D

    2005-01-01

    We obtained high resolution ELODIE and CORALIE spectra for both components of 20 wide visual binaries composed of an F-, G- or K-dwarf primary and an M-dwarf secondary. We analyse the well understood spectra of the primaries to determine metallicities ([Fe/H]) for these 20 systems, and hence for their M dwarf components. We pool these metallicities with determinations from the literature to obtain a precise (+- 0.2 dex) photometric calibration of M dwarf metallicities. This calibration represents a breakthrough in a field where discussions have had to remain largely qualitative, and it helps us demonstrate that metallicity explains most of the large dispersion in the empirical V-band mass-luminosity relation. We examine the metallicity of the two known M-dwarf planet-host stars, Gl 876 (+0.02 dex) and Gl 436 (-0.03 dex), in the context of preferential planet formation around metal-rich stars. We finally determine the metallicity of the 47 brightest single M dwarfs in a volume limited sample, and compare the m...

  3. Thermal Balance of the Magneto-Hydro-Dynamic Pump for Recovery of Platinum Group Metals from Spent Auto Catalysts

    Directory of Open Access Journals (Sweden)

    Gil S.

    2016-03-01

    Full Text Available Every new car should be equipped with the catalyst, which limits the amount of harmful chemical compounds such as NOx, CH and CO emitted to the air. Auto catalyst consists of the ceramic or metallic carrier, on which is the layer with Platinum Group Metals playing catalytic role. There are many methods using for recovery those valuable metals from spent auto catalyst, however evry of those methods have some limitations. Proces described in the article is the modified method of metal collector, which used magnetohydrodynamic pump. Rotary electromagnetic field generates in the liquid metal rotary current, which as a consequence washing out the PGM metals from the ceramic carriers. Considering the possibilities of commercialization of the described method, the energy balance was made. From that balance the energetic efficiency of the unit was determined and the analysis of the temperature distribution was shown thermographycally.

  4. Tunable magneto-optical effects in hole-doped group-IIIA metal-monochalcogenide monolayers

    Science.gov (United States)

    Feng, Wanxiang; Guo, Guang-Yu; Yao, Yugui

    2017-03-01

    Because of unusual properties and fascinating prospects for next-generation device applications, two-dimensional (2D) materials have attracted enormous attention since graphene was discovered in 2004. Among the 2D materials beyond graphene, group-IIIA metal-monochalcogenide (MX) monolayers (MLs), are receiving increasing interests because their excellent applications on electronics and optoelectronics. Recently, ferromagnetism and half-metallicity have been predicted in hole-doped GaS and GaSe MLs, which promise exciting potentials for semiconductor spintronics. Detection and measurement of spontaneous magnetization in these 2D materials will be essential for their spintronic applications. The magneto-optical (MO) effects not only are a powerful probe of magnetism in 2D materials but also have valuable applications in high-density data-storage technology. Furthermore, anomalous Hall effect is not only an ideal transport probe of itinerant magnetism but also of considerable current interest because of its topological nature. Here we perform a systematic first-principles density functional study on the MO Kerr and Faraday effects as well as such important magnetic and transport properties as magneto-crystalline anisotropy energy (MAE) and anomalous Hall conductivity (AHC) of all hole-doped MX (M = Ga, In; X = S, Se, Te) MLs. In this paper, we report the following important findings: (a) gate-tunable MO effects in MX MLs in a broad range of hole concentration; (b) large Kerr and Faraday rotation angles with Kerr angles comparable to well-known MO 3d-transition-metal multilayers and Faraday angles being among the largest ones reported; (c) tunable MAE and large AHC, making MX MLs suitable for magnetic memory devices current-driven via spin-transfer torque and also promising materials for magnetic field nanosensors with high sensitivity. Superior MO characteristics, together with the other interesting properties, would make MX MLs an excellent family of 2D materials for

  5. Electron-energy-loss spectroscopy on group-III nitrides and transition- metal oxides

    CERN Document Server

    Niessner, W

    2000-01-01

    A main topic represent electron-energy-loss spectroscopy (EELS) studies of the group-III nitrides AlN, GaN, InN, as well as their mixing systems Al sub x Ga sub 1 sub - sub x N, In sub x Ga sub 1 sub - sub x N. In EELS measurements with excitation energies above 1 keV clear collective excitations in AlN at 21 eV and in GaN at 15 eV were observed. In the mixing system Al sub x Ga sub 1 sub - sub x M a 2-mode behaviour is observed. Up to x=0.2 a GaN-like excitation remains preserved, while from x=0.44 the eigenfrequency of a AlN-like resonance shifts continuously. With vanadium dioxide a d sup 1 transition metal oxide was studied, which passes at 68 C a semiconductor-metal transition. In the EELS valence band spectra beside band transitions from the O2p subsigma and O2p subpi band an intense signal with a loss energy of 1 eV occurs. EELS studies on W- and F-doped VO sub 2 show, that it deals with a band transition from the V3d into the pd subpi band. EELS studies were for the first time also performed at lead t...

  6. Stimuli-Responsive Metal-Organic Frameworks with Photoswitchable Azobenzene Side Groups.

    Science.gov (United States)

    Kanj, Anemar Bruno; Müller, Kai; Heinke, Lars

    2017-07-31

    Metal-organic frameworks (MOFs) are nanoporous, crystalline hybrid materials, which enable various functionalities by incorporating functional organic molecules. By using organic linker molecules that possess photoswitchable azobenzene side groups, the remote control over certain properties was introduced to MOFs. Different MOF materials in the form of powders and thin films have been used to demonstrate the photoswitching. The applications of these stimuli-responsive nanoporous solids range from switching the adsorption capacity of various gases over remote-controlled release of guest molecules to continuously tunable membrane separation of molecular mixtures. A particular focus of this review is the effect of the azobenzene photoswitching on the host-guest interaction, enabling smart applications of the material. Steric hindrance, which may suppress the photoswitching in some MOF structures, is also discussed. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. HM+ and HM+-He (M = Group 2 metal): Chemical or physical interactions?

    Science.gov (United States)

    Harris, Joe P.; Dodson, Hannah; Breckenridge, W. H.; Wright, Timothy G.

    2014-09-01

    We investigate the HM+-He complexes (M = Group 2 metal) using quantum chemistry. Equilibrium geometries are linear for M = Be and Mg, and bent for M = Ca-Ra; the explanation for this lies in the differing nature of the highest occupied molecular orbitals in the two sets of complexes. The difference primarily occurs as a result of the formation of the H-M+ bond, and so the HM+ diatomics are also studied as part of the present work. The position of the He atom in the complexes is largely determined by the form of the electron density. HM+…He binding energies are obtained and are surprisingly high for a helium complex. The HBe+…He value is almost 3000 cm-1, which is high enough to suspect contributions from chemical bonding. This is explored by examining the natural orbital density and by population analyses.

  8. Materials design by evolutionary optimization of functional groups in metal-organic frameworks.

    Science.gov (United States)

    Collins, Sean P; Daff, Thomas D; Piotrkowski, Sarah S; Woo, Tom K

    2016-11-01

    A genetic algorithm that efficiently optimizes a desired physical or functional property in metal-organic frameworks (MOFs) by evolving the functional groups within the pores has been developed. The approach has been used to optimize the CO2 uptake capacity of 141 experimentally characterized MOFs under conditions relevant for postcombustion CO2 capture. A total search space of 1.65 trillion structures was screened, and 1035 derivatives of 23 different parent MOFs were identified as having exceptional CO2 uptakes of >3.0 mmol/g (at 0.15 atm and 298 K). Many well-known MOF platforms were optimized, with some, such as MIL-47, having their CO2 adsorption increase by more than 400%. The structures of the high-performing MOFs are provided as potential targets for synthesis.

  9. Explorations of new selenites of the group IIIA and IVA metals

    Science.gov (United States)

    Kong, Fang; Li, Pei-Xin; Zhang, Su-Yun; Mao, Jiang-Gao

    2012-06-01

    Systematic explorations of new phases in the GaIII/InIII/GeIV-SeIV-O systems by hydrothermal syntheses or solid-state reactions at high-temperature led to six new ternary compounds, namely, M2Se2O7 (M=Ga 1, In 2), M(OH)(SeO3) (M=Ga 3, In 4), α-Ge(SeO3)25 and β-Ge(SeO3)26. Ga2Se2O71 displays a 3D open framework composed of 2D gallium oxide layers being further bridged and capped by SeO3 groups. In2Se2O72 features a 3D indium oxide framework formed by corner- and edge- sharing InO6 octahedra with SeO3 groups attached on the cavities and the 8-member ring tunnels of the structure. The isostructural of M(OH)(SeO3) (M=Ga 3, In 4) exhibit a 2D metal selenite layer composed of 1D edge-sharing MO6 octahedral chains that are interconnected by SeO3 groups. α-Ge(SeO3)2 (P21/n) 5 displays a 3D open framework with 1D 8-member ring tunnels along the a-axis while β-Ge(SeO3)2 (Pa-3) 6 exhibits a condensed 3D network.

  10. Multiconfiguration pair-density functional theory: barrier heights and main group and transition metal energetics.

    Science.gov (United States)

    Carlson, Rebecca K; Li Manni, Giovanni; Sonnenberger, Andrew L; Truhlar, Donald G; Gagliardi, Laura

    2015-01-13

    Kohn-Sham density functional theory, resting on the representation of the electronic density and kinetic energy by a single Slater determinant, has revolutionized chemistry, but for open-shell systems, the Kohn-Sham Slater determinant has the wrong symmetry properties as compared to an accurate wave function. We have recently proposed a theory, called multiconfiguration pair-density functional theory (MC-PDFT), in which the electronic kinetic energy and classical Coulomb energy are calculated from a multiconfiguration wave function with the correct symmetry properties, and the rest of the energy is calculated from a density functional, called the on-top density functional, that depends on the density and the on-top pair density calculated from this wave function. We also proposed a simple way to approximate the on-top density functional by translation of Kohn-Sham exchange-correlation functionals. The method is much less expensive than other post-SCF methods for calculating the dynamical correlation energy starting with a multiconfiguration self-consistent-field wave function as the reference wave function, and initial tests of the theory were quite encouraging. Here, we provide a broader test of the theory by applying it to bond energies of main-group molecules and transition metal complexes, barrier heights and reaction energies for diverse chemical reactions, proton affinities, and the water dimerization energy. Averaged over 56 data points, the mean unsigned error is 3.2 kcal/mol for MC-PDFT, as compared to 6.9 kcal/mol for Kohn-Sham theory with a comparable density functional. MC-PDFT is more accurate on average than complete active space second-order perturbation theory (CASPT2) for main-group small-molecule bond energies, alkyl bond dissociation energies, transition-metal-ligand bond energies, proton affinities, and the water dimerization energy.

  11. Surface chemistry of the atomic layer deposition of metals and group III oxides

    Science.gov (United States)

    Goldstein, David Nathan

    Atomic Layer Deposition (ALD) is a thin-film growth technique offering precise control of film thickness and the ability to coat high-aspect-ratio features such as trenches and nanopowders. Unlike other film growth techniques, ALD does not require harsh processing conditions and is not limited by line-of-sight deposition. Emerging applications for ALD materials include semiconductor devices, gas sensors, and water-diffusion barriers. The chemistry behind ALD involves understanding how the precursors interact with surfaces to deposit the desired material. All ALD precursors need to be stable on the substrate to ensure self-limiting behavior yet reactive enough to be easily removed with the second reagent. Recent precursor development has provided many volatile organometallic compounds for most of the periodic table. As the number of precursors increases, proper precursor choice becomes crucial. This is because the film properties, growth rates, and growth temperature vary widely between the precursors. Many of the above traits can be predicted with knowledge of the precursor reaction mechanisms. This thesis aims to link surface reaction mechanisms to observed growth and nucleation trends in metal and oxide ALD systems. The first portion of this thesis explores the mechanisms of two ALD oxide systems. First, I examine the mechanism of ALD alumina with ozone. Ozone is used as an oxidant in the semiconductor industry because the deposited Al 2O3 films possess better insulating properties and ozone is easier to purge from a vacuum system. FT-IR analysis reveals a complicated array of surface intermediates such as formate, carbonate, and methoxy groups that form during Al2O3 growth with ozone. Next, a new method to deposit thin films of Ga2O3 is introduced. Gallium oxide is a transparent conducting oxide that needs expensive solid precursors to be deposited by ALD. I show that trimethylgallium is a good high-temperature ALD precursor that deposits films of Ga2O 3 with

  12. Asymmetric partitioning of metals among cluster anions and cations generated via laser ablation of mixed aluminum/Group 6 transition metal targets.

    Science.gov (United States)

    Waller, Sarah E; Mann, Jennifer E; Jarrold, Caroline Chick

    2013-02-28

    While high-power laser ablation of metal alloys indiscriminately produces gas-phase atomic ions in proportion to the abundance of the various metals in the alloy, gas-phase ions produced by moderate-power laser ablation sources coupled with molecular beams are formed by more complicated mechanisms. A mass spectrometric study that directly compares the mass distributions of cluster anions and cations generated from laser ablation of pure aluminum, an aluminum/molybdenum mixed target, and an aluminum/tungsten mixed target is detailed. Mass spectra of anionic species generated from the mixed targets showed that both tungsten and molybdenum were in higher abundance in the negatively charged species than in the target material. Mass spectra of the cationic species showed primarily Al(+) and aluminum oxide and hydroxide cluster cations. No molybdenum- or tungsten-containing cluster cations were definitively assigned. The asymmetric distribution of aluminum and Group 6 transition metals in cation and anion cluster composition is attributed to the low ionization energy of atomic aluminum and aluminum suboxide clusters. In addition, the propensity of both molybdenum and tungsten to form metal oxide cluster anions under the same conditions that favor metallic aluminum cluster anions is attributed to differences in the optical properties of the surface oxide that is present in the metal powders used to prepare the ablation targets. Mechanisms of mixed metal oxide clusters are considered.

  13. Metal-free annulation of arenes with 2-aminopyridine derivatives: the methyl group as a traceless non-chelating directing group.

    Science.gov (United States)

    Manna, Srimanta; Matcha, Kiran; Antonchick, Andrey P

    2014-07-28

    A novel annulation reaction between 2-aminopyridine derivatives and arenes under metal-free conditions is described. The presented intermolecular transformation provided straightforward access to the important pyrido[1,2-a]benzimidazole scaffold under mild reaction conditions. The unprecedented application of the methyl group of methylbenzenes as a traceless, non-chelating, and highly regioselective directing group is reported. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Bibliography of the technical literature of the Materials Joining Group, Metals and Ceramics Division, 1951 through June 1987

    Energy Technology Data Exchange (ETDEWEB)

    David, S.A.; Goodwin, G.M.; Gardner, K. (comps.)

    1987-08-01

    This document contains a listing of the written scientific information originating in the Materials Joining Group (formerly the Welding and Brazing Group), Metals and Ceramics Division, Oak Ridge National Laboratory during 1951 through June 1987. It is a registry of about 400 documents as nearly as possible in the order in which they were issued.

  15. Functionalization of metal-organic frameworks through the postsynthetic transformation of olefin side groups.

    Science.gov (United States)

    Hindelang, Konrad; Kronast, Alexander; Vagin, Sergei I; Rieger, Bernhard

    2013-06-17

    For the first time, the adaptability of the C=C double bond as a versatile precursor for the postsynthetic modification (PSM) of microporous materials was extensively investigated and evaluated. Therefore, an olefin-tagged 4,4'-bipyridine linker was synthesized and successfully introduced as pillar linker within a 9,10-triptycenedicarboxylate (TDC) zinc paddle-wheel metal-organic framework (MOF) through microwave-assisted synthesis. Different reactions, predominately used in organic chemistry, were tested, leading to the development of new postsynthetic reactions for the functionalization of solid materials. The postsynthetic oxidation of the olefin side groups applying osmium tetroxide (OsO₄) as a catalyst led to the formation of a microporous material with free vicinal diol functionalities. The epoxidation with dimethyldioxirane (DMDO) enabled the synthesis of epoxy-functionalized MOFs. In addition to that, reaction procedures for a postsynthetic hydroboration with borane dimethyl sulfide as well as a photoinduced thiol-ene click reaction with ethyl mercaptan were developed. For all of these PSMs, yields of more than 90% were obtained, entirely maintaining the crystallinity of the MOFs. Since the direct introduction of the corresponding groups by means of pre-synthetic approaches is hardly possible, these new PSMs are useful tools for the functionalization of porous solids towards applications such as selective adsorption, separation, and catalysis.

  16. Comparison of the interactions in the rare gas hydride and Group 2 metal hydride anions.

    Science.gov (United States)

    Harris, Joe P; Manship, Daniel R; Breckenridge, W H; Wright, Timothy G

    2014-02-28

    We study both the rare gas hydride anions, RG-H(-) (RG = He-Rn) and Group 2 (Group IIa) metal hydride anions, MIIaH(-) (MIIa = Be-Ra), calculating potential energy curves at the CCSD(T) level with augmented quadruple and quintuple basis sets, and extrapolating the results to the basis set limit. We report spectroscopic parameters obtained from these curves; additionally, we study the Be-He complex. While the RG-H(-) and Be-He species are weakly bound, we show that, as with the previously studied BeH(-) and MgH(-) species, the other MIIaH(-) species are strongly bound, despite the interactions nominally also being between two closed shell species: M(ns(2)) and H(-)(1s(2)). We gain insight into the interactions using contour plots of the electron density changes and population analyses. For both series, the calculated dissociation energy is significantly less than the ion/induced-dipole attraction term, confirming that electron repulsion is important in these species; this effect is more dramatic for the MIIaH(-) species than for RG-H(-). Our analyses lead us to conclude that the stronger interaction in the case of the MIIaH(-) species arises from sp and spd hybridization, which allows electron density on the MIIa atom to move away from the incoming H(-).

  17. A search for metal-poor stars pre-enriched by pair-instability supernovae I.A pilot study for target selection from Sloan Digital Sky Survey

    Institute of Scientific and Technical Information of China (English)

    Jing Ren; Norbert Christlieb; Gang Zhao

    2012-01-01

    We report on a pilot study on identifying metal-poor stars pre-enriched by Pair-Instability Supernovae (PISNe).Very massive,first generation (Population Ⅲ) stars (140 M⊙ ≤ M ≤ 260 M⊙) end their lives as PISNe,which have been predicted by theories,but no relics of PISNe have been observed yet.Among the distinct characteristics of the yields of PISNe,as predicted by theoretical calculations,are a strong odd-even effect,and a strong overabundance of Ca with respect to iron and the solar ratio.We use the latter characteristic to identify metal-poor stars in the Galactic halo that have been pre-enriched by PISNe,by comparing metallicites derived from strong,co-added Fe lines detected in low-resolution (i.e.,R = λ/Δλ ~ 2000) spectra of the Sloan Digital Sky Survey (SDSS),with metallicities determined by the SDSS Stellar Parameters Pipeline (SSPP).The latter are based on the strength of the Ca Ⅱ K line and assumptions on the Ca/Fe abundance ratio.Stars are selected as candidates if their metallicity derived from Fe lines is significantly lower than the SSPP metallicities.In a sample of 12 300 stars for which SDSS spectroscopy is available,we have identified 18 candidate stars.Higher resolution and signal-to-noise ratio spectra of these candidates are being obtained with the Very Large Telescope of the European Southern Observatory and the XSHOOTER spectrograph,to determine their abundance patterns,and to verify our selection method.We plan to apply our method to the database of several million stellar spectra to be acquired with the Guo Shou Jing Telescope (LAMOST) in the next five years.

  18. Bibliography of the technical literature of the Materials Joining Group, Metals and Ceramics Division, 1951--June 1989

    Energy Technology Data Exchange (ETDEWEB)

    David, S.A.; Goodwin, G.M.; Gardner, K. (comps.)

    1989-10-01

    This document contains a listing of the written scientific information originating in the Materials Joining (formerly the Welding and Brazing Group), Metals and Ceramics Division, Oak Ridge National Laboratory during 1951 through June 1989. This registry of documents is as much as possible, in the order of issue date. A complete cross-referenced listing of the technical literature of the Metals and Ceramics Division is also available.

  19. Direct intermolecular force measurements between functional groups and individual metallic or semiconducting single-walled carbon nanotubes.

    Science.gov (United States)

    Thong, Ya Xuan; Poon, Yin Fun; Chen, Tzu-Yin; Li, Lain-Jong; Chan-Park, Mary B

    2014-02-26

    Many electronic applications of single-walled carbon nanotubes (SWNTs) require electronic homogeneity in order to maximally exploit their outstanding properties. Non-covalent separation is attractive as it is scalable and results in minimal alteration of nanotube properties. However, fundamental understanding of the metallicity-dependence of functional group interactions with nanotubes is still lacking; this lack is compounded by the absence of methods to directly measure these interactions. Herein, a novel technology platform based on a recently developed atomic force microscopy (AFM) mode is reported which directly quantifies the adhesion forces between a chosen functional group and individual nanotubes of known metallicity, permitting comparisons between different metallicity. These results unambiguously show that this technology platform is able to discriminate the subtle adhesion force differences of a chosen functional group with pure metallic as opposed to pure semiconducting nanotubes. This new method provides a route towards rapid advances in understanding of non-covalent interactions of large libraries of compounds with nanotubes of varying metallicity and diameter; presenting a superior tool to assist the discovery of more effective metallicity-based SWNT separation agents.

  20. Electronic spectra of 2- and 3-tolunitrile in the gas phase. I. A study of methyl group internal rotation via rovibronically resolved spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ruiz-Santoyo, José Arturo; Álvarez-Valtierra, Leonardo, E-mail: leoav@fisica.ugto.mx [División de Ciencias e Ingenierías, Universidad de Guanajuato, León, Guanajuato 37150, México (Mexico); Wilke, Josefin; Wilke, Martin; Schmitt, Michael [Institut für Physikalische Chemie, Heinrich-Heine-Universität, 40225 Düsseldorf (Germany); Yi, John T. [Department of Chemistry, Winston-Salem State University, Winston-Salem, North Carolina 27110 (United States); Pratt, David W. [Department of Chemistry, University of Vermont, Burlington, Vermont 05405 (United States)

    2016-01-28

    Rotationally resolved fluorescence excitation spectra of the origin bands in the S{sub 1}←S{sub 0} transition of 2-tolunitrile (2TN) and 3-tolunitrile (3TN) have been recorded in the collision-free environment of a molecular beam. Analyses of these data provide the rotational constants of each molecule and the potential energy curves governing the internal rotation of the attached methyl groups in both electronic states. 2TN exhibits much larger barriers along this coordinate than 3TN. Interestingly, the electronic transition dipole moment in both molecules is markedly influenced by the position of the attached methyl group rather than the position of the cyano group; possible reasons for this intriguing behavior are discussed.

  1. No Evidence of Genotoxic Damage in a Group of Patients with Titanium Dental Implants and Different Metal Restorations in the Oral Cavity.

    Science.gov (United States)

    Camacho-Alonso, Fabio; Sánchez-Siles, Mariano; Gilbel-del Águila, Osmundo

    2015-08-01

    Titanium is the most widely used metal in implant dentistry. In spite of its biocompatibility, when it is released into the oral environment, it can have local negative biological effects. The aims of this study were to detect the concentration of metal ions in patients with dental implants, to evaluate whether or not their release might be influenced by the presence of other metals, and to assay whether these ions might provoke genotoxic damage in oral mucosa cells. One hundred five patients with a total of 180 dental implants were included. The sample was divided into seven groups (n = 15 per group). Group 1 consisted of patients with metal-porcelain fixed crowns on dental implants; Group 2, patients with metal-porcelain fixed crowns on teeth; Group 3, patients with dental amalgams; Group 4, patients with metal-porcelain fixed crowns on dental implants and metal-porcelain fixed crowns on teeth; Group 5, patients with metal-porcelain fixed crowns on dental implants and dental amalgams; and Group 6, patients with metal-porcelain fixed crowns on dental implants, metal-porcelain fixed crowns on teeth, and dental amalgams. Group 7 was the control group, without any dental treatment. The concentration of metal ions was detected using inductively coupled plasma mass spectrometry; genotoxicity was measured using the buccal micronucleus cytome assay protocol. Group 5 displayed the highest concentration of metal ions in parts per billion (Ti, Co, Ni, Zn, Pd, Sn, and Pb). Group 6 was characterized by the highest presence of Hg. No signs of genotoxic damage were found in any of the study groups. Patients with titanium dental implants combined with other metal restorations presented higher concentrations of metal ions, but no genotoxic damage was observed in oral mucosal epithelial cells. © 2013 Wiley Periodicals, Inc.

  2. Synthesising carbo-nitrides of some d-group transition metals using a solar furnace at PSA

    OpenAIRE

    Shohoji, Nobumitsu; Oliveira, F. A. Costa; Rosa, Luís Guerra; Fernandes, Jorge Cruz; Magalhães, Teresa; Coelho, Manuel Caldeira; Rodriguez,José; Canadas, Inmaculada; Ramos, Carlos; Martinez, Diego

    2013-01-01

    Carbo-nitride synthesis was undertaken using a solar furnace at PSA in flowing N2/Ar gas mixture under total pressure 1 atm and processing temperature T = 1600ºC for some d-group transition elements (Ti; Zr, V, Nb, Mo, W) starting from 1.5G/M (graphite/metal powder mixture with mole ratio 1.5:1) compact to ensure co-presence of free carbon with the reaction product. Clear X-ray diffraction (XRD) evidence of formation of carbo-nitride was detected for Ti (IVa group metal) showing higher N cont...

  3. The roadmap for unification in galaxy group selection:. I. A search for extended X-ray emission in the CNOC2 survey

    CERN Document Server

    Finoguenov, A; Parker, L C; Wilman, D J; Mulchaey, J S; Saglia, R P; Balogh, M L; Bower, R G; McGee, S L

    2009-01-01

    X-ray properties of galaxy groups can unlock some of the most challenging research topics in modern extragalactic astronomy: the growth of structure and its influence on galaxy formation. Only with the advent of the Chandra and XMM facilities have X-ray observations reached the depths required to address these questions in a satisfactory manner. Here we present an X-ray imaging study of two patches from the CNOC2 spectroscopic galaxy survey using combined Chandra and XMM data. A state of the art extended source finding algorithm has been applied, and the resultant source catalog, including redshifts from a spectroscopic follow-up program, is presented. The total number of spectroscopically identified groups is 25 spanning a redshift range 0.04-0.79. Approximately 50% of CNOC2 spectroscopically selected groups in the deeper X-ray (RA14h) field are likely X-ray detections, compared to 20% in the shallower (RA21h) field. Statistical modeling shows that this is consistent with expectations, assuming an expected e...

  4. Activity targets for nanostructured platinum-group-metal-free catalysts in hydroxide exchange membrane fuel cells

    Science.gov (United States)

    Setzler, Brian P.; Zhuang, Zhongbin; Wittkopf, Jarrid A.; Yan, Yushan

    2016-12-01

    Fuel cells are the zero-emission automotive power source that best preserves the advantages of gasoline automobiles: low upfront cost, long driving range and fast refuelling. To make fuel-cell cars a reality, the US Department of Energy has set a fuel cell system cost target of US$30 kW-1 in the long-term, which equates to US$2,400 per vehicle, excluding several major powertrain components (in comparison, a basic, but complete, internal combustion engine system costs approximately US$3,000). To date, most research for automotive applications has focused on proton exchange membrane fuel cells (PEMFCs), because these systems have demonstrated the highest power density. Recently, however, an alternative technology, hydroxide exchange membrane fuel cells (HEMFCs), has gained significant attention, because of the possibility to use stable platinum-group-metal-free catalysts, with inherent, long-term cost advantages. In this Perspective, we discuss the cost profile of PEMFCs and the advantages offered by HEMFCs. In particular, we discuss catalyst development needs for HEMFCs and set catalyst activity targets to achieve performance parity with state-of-the-art automotive PEMFCs. Meeting these targets requires careful optimization of nanostructures to pack high surface areas into a small volume, while maintaining high area-specific activity and favourable pore-transport properties.

  5. Alkali Metal Cation Affinities of Anionic Main Group-Element Hydrides Across the Periodic Table.

    Science.gov (United States)

    Boughlala, Zakaria; Fonseca Guerra, Célia; Bickelhaupt, F Matthias

    2017-08-05

    We have carried out an extensive exploration of gas-phase alkali metal cation affinities (AMCA) of archetypal anionic bases across the periodic system using relativistic density functional theory at ZORA-BP86/QZ4P//ZORA-BP86/TZ2P. AMCA values of all bases were computed for the lithium, sodium, potassium, rubidium and cesium cations and compared with the corresponding proton affinities (PA). One purpose of this work is to provide an intrinsically consistent set of values of the 298 K AMCAs of all anionic (XHn-1(-) ) constituted by main group-element hydrides of groups 14-17 along the periods 2-6. In particular, we wish to establish the trend in affinity for a cation as the latter varies from proton to, and along, the alkali cations. Our main purpose is to understand these trends in terms of the underlying bonding mechanism using Kohn-Sham molecular orbital theory together with a quantitative bond energy decomposition analyses (EDA). © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Activity targets for nanostructured platinum-group-metal-free catalysts in hydroxide exchange membrane fuel cells.

    Science.gov (United States)

    Setzler, Brian P; Zhuang, Zhongbin; Wittkopf, Jarrid A; Yan, Yushan

    2016-12-06

    Fuel cells are the zero-emission automotive power source that best preserves the advantages of gasoline automobiles: low upfront cost, long driving range and fast refuelling. To make fuel-cell cars a reality, the US Department of Energy has set a fuel cell system cost target of US$30 kW(-1) in the long-term, which equates to US$2,400 per vehicle, excluding several major powertrain components (in comparison, a basic, but complete, internal combustion engine system costs approximately US$3,000). To date, most research for automotive applications has focused on proton exchange membrane fuel cells (PEMFCs), because these systems have demonstrated the highest power density. Recently, however, an alternative technology, hydroxide exchange membrane fuel cells (HEMFCs), has gained significant attention, because of the possibility to use stable platinum-group-metal-free catalysts, with inherent, long-term cost advantages. In this Perspective, we discuss the cost profile of PEMFCs and the advantages offered by HEMFCs. In particular, we discuss catalyst development needs for HEMFCs and set catalyst activity targets to achieve performance parity with state-of-the-art automotive PEMFCs. Meeting these targets requires careful optimization of nanostructures to pack high surface areas into a small volume, while maintaining high area-specific activity and favourable pore-transport properties.

  7. Iron-Group Abundances in the Metal-Poor Main Sequence Turnoff Star HD~84937

    CERN Document Server

    Sneden, Christopher; Kobayashi, Chiaki; Pignatari, Marco; Lawler, James E; Hartog, Elizabeth A Den; Wood, Michael P

    2015-01-01

    We have derived new very accurate abundances of the Fe-group elements Sc through Zn (Z = 21-30) in the bright main-sequence turnoff star HD 84937, based on high-resolution spectra covering the visible and ultraviolet spectral regions. New or recent laboratory transition data for 14 species of seven elements have been used. Abundances from more than 600 lines of non-Fe species have been combined with about 550 Fe lines in HD 84937 to yield abundance ratios of high precision. The abundances have been determined from both neutral and ionized transitions, which generally are in agreement with each other. We find no substantial departures from standard LTE Saha ionization balance in this [Fe/H] = -2.32 star. Noteworthy among the abundances are: [Co/Fe] = 0.14 and [Cu/Fe] = -0.83, in agreement with past studies abundance trends in this and other low metallicity stars; and = 0.31, which has not been noted previously. A detailed examination of scandium, titanium, and vanadium abundances in large-sample spectroscopic...

  8. The Utilization of Amide Groups To Expand and Functionalize Metal-Organic Frameworks Simultaneously.

    Science.gov (United States)

    Lu, Zhiyong; Bai, Junfeng; Hang, Cheng; Meng, Fei; Liu, Wenlong; Pan, Yi; You, Xiaozeng

    2016-04-25

    A new stepwise ligand-elongation strategy by amide spacers is utilized to prepare isoreticularly high-porous metal-organic frameworks (MOFs), namely, quasi-mesoporous [Cu2 (PDBAD)(H2 O)]n (H4 PDBAD=5,5'-((4,4'-((pyridine-3,5-dicarbonyl)bis(azanediyl))bis(benzoyl))bis(azanediyl))diisophthalic acid; NJU-Bai22: NJU-Bai for Nanjing University Bai's group), and mesoporous [Cu2 (PABAD)(H2 O)]n (H4 PABAD=5,5'-((4,4'-((4,4'-((pyridine-3,5-dicarbonyl)bis(azanediyl))bis(benzoyl))bis (azanediyl))bis(benzoyl))bis(azanediyl))diisophthalic acid; NJU-Bai23). Compared with the prototypical MOF of [Cu2 (PDAD)(H2 O)]n (H4 PDAD=5,5'-(pyridine-3,5-dicarbonyl)bis(azanediyl)diisophthalic acid; NJU-Bai21, also termed as PCN-124), both MOFs exhibit almost the same CO2 adsorption enthalpy and CO2 selectivity values, and better capacity for CO2 storage under high pressure; these results make them promising candidate materials for CO2 capture and sequestration. Interestingly, this new method, in comparison with traditional strategies of using phenyl or triple-bond spacers, is easier and cheaper, resulting in a better ability to retain high CO2 affinity and selectivity in MOFs with large pores and high CO2 storage capacity. Additionally, it may lead to the high thermal stability of the MOFs and also their tolerance to water, which is related to the balance between the density of functional groups and pore sizes. Therefore, this strategy could provide new opportunities to explore more functionalized mesoporous MOFs with high performance. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Defect-Induced Optoelectronic Response in Single-layer Group-VI Transition-Metal Dichalcogenides

    Science.gov (United States)

    Chow, Philippe K.

    The ever-evolving symbiosis between mankind and nanoelectronics-driven technology pushes the limits of its constituent materials, largely due to the dominance of undesirable hetero-interfacial physiochemical behavior at the few-nanometer length scale, which dominates over bulk material characteristics. Driven by such instabilities, research into two-dimensional (2D) van der Waals-layered materials (e.g. graphene, transition metal dichalcogenides (TMDCs), boron nitride), which have characteristically inert surface chemistry, has virtually exploded over the past few years. The discovery of an indirect- to direct-gap conversion in semiconducting group-VI TMDCs (e.g. MoS2) upon thinning to a single atomic layer provided the critical link between metallic and insulating 2D materials. While proof-of-concept demonstrations of single-layer TMDC-based devices for visible-range photodetection, light-emission and solar energy conversion have showed promising results, the exciting qualities are downplayed by poorly-understood defectinduced photocarrier traps, limiting the best-achieved external quantum efficiencies to approximately ~1%. This thesis explores the behavior of defects in atomically-thin TMDC layers in response to optical stimuli using a combination of steady-state photoluminescence, reflectance and Raman spectroscopy at room-temperature. By systematically varying the defect density using plasma-irradiation techniques, an unprecedented room-temperature defect-induced monolayer PL feature was discovered. High-resolution transmission electron microscopy correlated the defect-induced PL with plasma-generation of sulfur vacancy defects while reflectance measurements indicate defect-induced sub-bandgap light absorption. Excitation intensity-dependent PL measurements and exciton rate modeling further help elucidate the origin of the defect-induced PL response and highlights the role of non-radiative recombination on exciton conversion processes. The results in this

  10. Warm Ice Giant GJ 3470b. I. A Flat Transmission Spectrum Indicates a Hazy, Low-methane, and/or Metal-rich Atmosphere

    CERN Document Server

    Crossfield, Ian J M; Hansen, Brad M S; Howard, Andrew W

    2013-01-01

    We report our spectroscopic investigation of the transiting ice giant GJ 3470b's atmospheric transmission, and the first results of extrasolar planet observations from the new Keck/MOSFIRE spectrograph. We measure a planet/star radius ratio of Rp/Rs = 0.0789 +/- 0.0020 in a bandpass from 2.09-2.36 micron and in six narrower bands across this wavelength range. When combined with existing broadband photometry, these measurements rule out cloud-free atmospheres in chemical equilibrium assuming either solar abundances (5.4 sigma confidence) or a moderate level of metal enrichment (50x solar abundances, 3.8 sigma), confirming previous results that such models are not representative for cool, low-mass, externally irradiated extrasolar planets. Current measurements are consistent with a flat transmission spectrum, which suggests that the atmosphere is explained by high-altitude clouds and haze, disequilibrium chemistry, unexpected abundance patterns, or the atmosphere is extremely metal-rich (>200x solar). Because G...

  11. [Search of heavy metals biosorbents among yeasts of different taxonomic groups].

    Science.gov (United States)

    Lozovaia, O G; Kasatkina, T P; Podgorskiĭ, V S

    2004-01-01

    The use of microbial cells as heavy metal biosorbents is a potential alternative for the existing methods of the environment treatment for pollution by these metals. Yeast may be successfully used in the metals sorption. An agar-plate screening method was used for rapid isolation of metal-accumulating strains of yeast and preliminary estimation of their biosorption capacity. The capacity to accumulate heavy metals, such as copper, zinc, lead, chrome and cobalt was estimated in 68 pigmented and pigmentless yeast strains isolated from different sources. The best capacity of copper and zinc accumulation was shown by pink-coloured Rhodotorula mucilaginosa, Rhodotorula aurantiaca, Rhodotorula glutinis and pigmentless strains of the yeast Candida krusei, Williopsis california.

  12. Cubic nitrides of the sixth group of transition metals formed by nitrogen ion irradiation during metal condensation

    Energy Technology Data Exchange (ETDEWEB)

    Ensinger, W. [Augsburg Univ. (Germany). Inst. fuer Physik; Kiuchi, M. [Osaka National Research Institute, Midorigaoka 1-8-31, Ikeda, Osaka 563 (Japan)

    1996-10-01

    Nitrogen-containing phases of chromium, molybdenum and tungsten were formed by evaporation of the metal under simultaneous nitrogen ion irradiation. With gradually increasing ion irradiation intensity, chromium forms initially Cr and Cr{sub 2}N phase mixtures, then additionally CrN appears, and at the highest intensities pure CrN films are formed. Molybdenum also forms pure nitride MoN under intense ion bombardment. However, in this case two different crystal structures are found, the stable hexagonal phase and the metastable cubic high-temperature phase. The latter is favoured under intense ion irradiation. In the case of tungsten, even at the highest intensities, only phase mixtures of W and W{sub 2}N were formed. These observed differences can be explained by the low reactivity of these metals towards nitrogen and the low chemical stability of the nitrides, particularly of WN. The metastable high-temperature structure of MoN is formed under the particular conditions of ion bombardment with rapid energy dissipation. (orig.)

  13. Modifications of chemical functional groups of Pandanus amaryllifolius Roxb and its effect towards biosorption of heavy metals

    Science.gov (United States)

    Abdullah, Mohd. Zamri; Ismail, Siti Salwa

    2015-07-01

    The utilization of non-living biomass as an alternative biosorbent for heavy metal removal has gain a tremendous consideration through the years. Pandanus amaryllifolius Roxb or pandan leaves, which is widely used as food additives in the South East Asia region, has been selected for its viability in the said effort due to the presence of chemical functional groups on its cellular network that enables the sorption to occur. In order to elucidate the possible mechanisms participated during the heavy metal removal process, the biosorbent undergone a series of modification techniques to alter the chemical functional groups present on its constituent. From the outcome of the chemically-modified biosorbent being subjected to the contact with metal cations, nitrogen- and oxygen-containing groups present on the biosorbent are believed to be responsible for the metal uptake to occur through complexation mechanism. Modifying amine groups causes 14% reduction of Cu(II) uptake, whereas removing protein element increases the uptake to 26% as compared to the unmodified biosorbent. Also, scanning electron micrographs further suggested that the adsorption mechanism could perform in parallel, as attributed to the evidence of porous structure throughout the biosorbent fibrous nature.

  14. Modifications of chemical functional groups of Pandanus amaryllifolius Roxb and its effect towards biosorption of heavy metals

    Energy Technology Data Exchange (ETDEWEB)

    Abdullah, Mohd Zamri, E-mail: zamriab@petronas.com.my; Ismail, Siti Salwa [Chemical Engineering Department, Universiti Teknologi PETRONAS, 31750 Bandar Seri Iskandar, Perak (Malaysia)

    2015-07-22

    The utilization of non-living biomass as an alternative biosorbent for heavy metal removal has gain a tremendous consideration through the years. Pandanus amaryllifolius Roxb or pandan leaves, which is widely used as food additives in the South East Asia region, has been selected for its viability in the said effort due to the presence of chemical functional groups on its cellular network that enables the sorption to occur. In order to elucidate the possible mechanisms participated during the heavy metal removal process, the biosorbent undergone a series of modification techniques to alter the chemical functional groups present on its constituent. From the outcome of the chemically-modified biosorbent being subjected to the contact with metal cations, nitrogen- and oxygen-containing groups present on the biosorbent are believed to be responsible for the metal uptake to occur through complexation mechanism. Modifying amine groups causes 14% reduction of Cu(II) uptake, whereas removing protein element increases the uptake to 26% as compared to the unmodified biosorbent. Also, scanning electron micrographs further suggested that the adsorption mechanism could perform in parallel, as attributed to the evidence of porous structure throughout the biosorbent fibrous nature.

  15. Ionization of the group 3 metals La, Y and Sc in H2---O2---Ar flames

    Science.gov (United States)

    Patterson, Patricia M.; Goodings, John M.

    1995-09-01

    Four pairs of premixed, fuel-rich/fuel-lean (FR/FL; equivalence ratio [Phi] = 1.5/0.75). H2---O2---Ar flames at four temperatures in the range 1900-2425 K, all at atmospheric pressure, were doped with about 10-6 mole fraction of the group 3 metals La, Y and Sc using atomizer techniques. The metals produce solid particles in the flames and gaseous metallic species. The latter include free metallic atoms, A, near the flame reaction zone, but only the monoxide AO and the oxide-hydroxide OAOH further downstream at equilibrium; the [OAOH]/[AO] ratio varies in FR/FL flames. Metallic ions (produce AO+; further downstream, the ionization level is sustained by the thermal (collisional) ionization of AO to produce AO+ and/or the chemi-ionization of OAOH with H to produce A(OH)2+. The ions AO+, A(OH)2+ and higher hydrates are all rapidly equilibrated by three-body association reactions with water. Ions are lost by dissociative electron-ion recombination of A(OH)2+ and possibly higher hydrates. The chemical ionization of the metallic species by H3O+ was investigated by adding a small quantity of CH4 to the flames. The ion chemistry is discussed in detail. An estimate of the bond dissociation energy D0°(OLa---OH) = 408 ± 40 kJ mol-1 (4.23 ± 0.41 eV) was obtained.

  16. Capacitance of the double electrical layer on the copper-group metals in molten alkali metal halides

    Science.gov (United States)

    Kirillova, E. V.; Stepanov, V. P.

    2016-08-01

    The electrochemical impedance is measured to study the capacitance of the double electrical layer of metallic Au, Ag, and Cu as a function of potential and temperature in nine molten salts, namely, the chlorides, bromides, and iodides of sodium, potassium, and cesium. The C- E curve of a gold electrode has an additional minimum in the anodic branch. This minimum for silver is less pronounced and is only observed at low ac signal frequencies in cesium halides. The additional minimum is not detected for copper in any salt under study. This phenomenon is explained on the assumption that the adsorption of halide anions on a positively charged electrode surface has a predominantly chemical rather than an electrostatic character. The specific adsorption in this case is accompanied by charge transfer through the interface and the formation of an adsorbent-adsorbate covalent bond.

  17. Electrochemical sensors and devices for heavy metals assay in water: the French groups' contribution

    National Research Council Canada - National Science Library

    Pujol, Luca; Evrard, David; Groenen-Serrano, Karine; Freyssinier, Mathilde; Ruffien-Cizsak, Audrey; Gros, Pierre

    2014-01-01

    A great challenge in the area of heavy metal trace detection is the development of electrochemical techniques and devices which are user-friendly, robust, selective, with low detection limits and allowing fast analyses...

  18. Ion mobility studies of carbohydrates as group I adducts: isomer specific collisional cross section dependence on metal ion radius.

    Science.gov (United States)

    Huang, Yuting; Dodds, Eric D

    2013-10-15

    Carbohydrates play numerous critical roles in biological systems. Characterization of oligosaccharide structures is essential to a complete understanding of their functions in biological processes; nevertheless, their structural determination remains challenging in part due to isomerism. Ion mobility spectrometry provides the means to resolve gas phase ions on the basis of their shape-to-charge ratios, thus providing significant potential for separation and differentiation of carbohydrate isomers. Here, we report on the determination of collisional cross sections for four groups of isomeric carbohydrates (including five isomeric disaccharides, four isomeric trisaccharides, two isomeric pentasaccharides, and two isomeric hexasaccharides) as their group I metal ion adducts (i.e., [M + Li](+), [M + Na](+), [M + K](+), [M + Rb](+), and [M + Cs](+)). In all, 65 collisional cross sections were measured, the great majority of which have not been previously reported. As anticipated, the collisional cross sections of the carbohydrate metal ion adducts generally increase with increasing metal ion radius; however, the collisional cross sections were found to scale with the group I cation size in isomer specific manners. Such measurements are of substantial analytical value, as they illustrate how the selection of charge carrier influences carbohydrate ion mobility determinations. For example, certain pairs of isomeric carbohydrates assume unique collisional cross sections upon binding one metal ion, but not another. On the whole, these data suggest a role for the charge carrier as a probe of carbohydrate structure and thus have significant implications for the continued development and application of ion mobility spectrometry for the distinction and resolution of isomeric carbohydrates.

  19. Calculating the melting curves by the thermodynamic data matching method: Platinum-group refractory metals (Ru, Os, and Ir)

    Science.gov (United States)

    Kulyamina, E. Yu.; Zitserman, V. Yu.; Fokin, L. R.

    2017-01-01

    A technique for reconstructing thermal properties, including the melting curve, of refractory metals based on the use of experimental data on caloric properties available up to the melting point and some regularities of the Debye-Grüneisen theory has been proposed. The calculation result is the consistent system of high-temperature thermal data, including the thermal expansion coefficient, solid-phase density, and volume jump upon melting. This technique was tried-out on refractory platinum-group metals based on experimental data on the enthalpy of the metals and confirmed by consistency with a thermodynamic calculation using shock-wave experiments and results obtained by the quantum molecular dynamics method.

  20. Carbon-rich dust production in metal-poor galaxies in the Local Group

    CERN Document Server

    Sloan, G C; Lagadec, E; van Loon, J Th; Kraemer, K E; McDonald, I; Groenewegen, M A T; Wood, P R; Bernard-Salas, J; Zijlstra, A A

    2012-01-01

    We have observed a sample of 19 carbon stars in the Sculptor, Carina, Fornax, and Leo I dwarf spheroidal galaxies with the Infrared Spectrograph on the Spitzer Space Telescope. The spectra show significant quantities of dust around the carbon stars in Sculptor, Fornax, and Leo I, but little in Carina. Previous comparisons of carbon stars with similar pulsation properties in the Galaxy and the Magellanic Clouds revealed no evidence that metallicity affected the production of dust by carbon stars. However, the more metal-poor stars in the current sample appear to be generating less dust. These data extend two known trends to lower metallicities. In more metal-poor samples, the SiC dust emission weakens, while the acetylene absorption strengthens. The bolometric magnitudes and infrared spectral properties of the carbon stars in Fornax are consistent with metallicities more similar to carbon stars in the Magellanic Clouds than in the other dwarf spheroidals in our sample. A study of the carbon budget in these sta...

  1. Electrochemical sensors and devices for heavy metals assay in water: the French groups' contribution

    Directory of Open Access Journals (Sweden)

    Luca ePUJOL

    2014-04-01

    Full Text Available A great challenge in the area of heavy metal trace detection is the development of electrochemical techniques and devices which are user-friendly, robust, selective, with low detection limits and allowing fast analyses. This review presents the major contribution of the French scientific academic community in the field of electrochemical sensors and electroanalytical methods within the last 20 years. From the well-known polarography to the up-to-date generation of functionalized interfaces, the different strategies dedicated to analytical performances improvement are exposed: stripping voltammetry, solid mercury-free electrode, ion selective sensor, carbon based materials, chemically modified electrodes, nano-structured surfaces. The paper particularly emphasizes their advantages and limits face to the last Water Frame Directive devoted to the Environmental Quality Standards for heavy metals. Recent trends on trace metal speciation as well as on automatic on line monitoring devices are also evoked.

  2. Group 4 Metalloporphyrin diolato Complexes and Catalytic Application of Metalloporphyrins and Related Transition Metal Complexes

    Energy Technology Data Exchange (ETDEWEB)

    Du, Guodong [Iowa State Univ., Ames, IA (United States)

    2003-01-01

    In this work, the first examples of group 4 metalloporphyrin 1,2-diolato complexes were synthesized through a number of strategies. In general, treatment of imido metalloporphyrin complexes, (TTP)M=NR, (M = Ti, Zr, Hf), with vicinal diols led to the formation of a series of diolato complexes. Alternatively, the chelating pinacolate complexes could be prepared by metathesis of (TTP)MCl2 (M = Ti, Hf) with disodium pinacolate. These complexes were found to undergo C-C cleavage reactions to produce organic carbonyl compounds. For titanium porphyrins, treatment of a titanium(II) alkyne adduct, (TTP)Ti(η2-PhC≡CPh), with aromatic aldehydes or aryl ketones resulted in reductive coupling of the carbonyl groups to produce the corresponding diolato complexes. Aliphatic aldehydes or ketones were not reactive towards (TTP)Ti(η2-PhC≡CPh). However, these carbonyl compounds could be incorporated into a diolato complex on reaction with a reactive precursor, (TTP)Ti[O(Ph)2C(Ph)2O] to provide unsymmetrical diolato complexes via cross coupling reactions. In addition, an enediolato complex (TTP)Ti(OCPhCPhO) was obtained from the reaction of (TTP)Ti(η2-PhC≡CPh) with benzoin. Titanium porphyrin diolato complexes were found to be intermediates in the (TTP)Ti=O-catalyzed cleavage reactions of vicinal diols, in which atmospheric oxygen was the oxidant. Furthermore, (TTP)Ti=O was capable of catalyzing the oxidation of benzyl alcohol and α-hydroxy ketones to benzaldehyde and α-diketones, respectively. Other high valent metalloporphyrin complexes also can catalyze the oxidative diol cleavage and the benzyl alcohol oxidation reactions with dioxygen. A comparison of Ti(IV) and Sn(IV) porphyrin chemistry was undertaken. While chelated diolato complexes were invariably obtained for titanium porphyrins on treatment with 1,2-diols, the reaction of vicinal diols with tin porphyrins gave a number of products, including mono

  3. Group 4 Metalloporphyrin diolato Complexes and Catalytic Application of Metalloporphyrins and Related Transition Metal Complexes

    Energy Technology Data Exchange (ETDEWEB)

    Guodong Du

    2004-12-19

    In this work, the first examples of group 4 metalloporphyrin 1,2-diolato complexes were synthesized through a number of strategies. In general, treatment of imido metalloporphyrin complexes, (TTP)M=NR, (M = Ti, Zr, Hf), with vicinal diols led to the formation of a series of diolato complexes. Alternatively, the chelating pinacolate complexes could be prepared by metathesis of (TTP)MCl{sub 2} (M = Ti, Hf) with disodium pinacolate. These complexes were found to undergo C-C cleavage reactions to produce organic carbonyl compounds. For titanium porphyrins, treatment of a titanium(II) alkyne adduct, (TTP)Ti({eta}{sup 2}-PhC{triple_bond}CPh), with aromatic aldehydes or aryl ketones resulted in reductive coupling of the carbonyl groups to produce the corresponding diolato complexes. Aliphatic aldehydes or ketones were not reactive towards (TTP)Ti({eta}{sup 2}-PhC{triple_bond}CPh). However, these carbonyl compounds could be incorporated into a diolato complex on reaction with a reactive precursor, (TTP)Ti[O(Ph){sub 2}C(Ph){sub 2}O] to provide unsymmetrical diolato complexes via cross coupling reactions. In addition, an enediolato complex (TTP)Ti(OCPhCPhO) was obtained from the reaction of (TTP)Ti({eta}{sup 2}-PhC{triple_bond}CPh) with benzoin. Titanium porphyrin diolato complexes were found to be intermediates in the (TTP)Ti=O-catalyzed cleavage reactions of vicinal diols, in which atmospheric oxygen was the oxidant. Furthermore, (TTP)Ti=O was capable of catalyzing the oxidation of benzyl alcohol and {alpha}-hydroxy ketones to benzaldehyde and {alpha}-diketones, respectively. Other high valent metalloporphyrin complexes also can catalyze the oxidative diol cleavage and the benzyl alcohol oxidation reactions with dioxygen. A comparison of Ti(IV) and Sn(IV) porphyrin chemistry was undertaken. While chelated diolato complexes were invariably obtained for titanium porphyrins on treatment with 1,2-diols, the reaction of vicinal diols with tin porphyrins gave a number of

  4. Global exploration and production capacity for platinum-group metals from 1995 through 2015

    Science.gov (United States)

    Wilburn, David R.

    2012-01-01

    Platinum-group metals (PGMs) are required in a variety of commercial, industrial, and military applications for many existing and emerging technologies, yet the United States is highly dependent on foreign sources of PGMs. Information on global exploration for PGMs since 1995 has been used in this study as a basis for identifying locations where the industry has determined that exploration has provided data sufficient to warrant development of a new mine or expansion of an existing operation or where a significant increase in capacity for PGMs is anticipated by 2015. Discussions include an overview of the industry and the selected sites, factors affecting mineral supply, and circumstances leading to the development of mineral properties with the potential to affect mineral supply. Of the 52 sites or regional operations that were considered in this analysis, 16 sites were producing before 1995, 28 sites commenced production from 1995 through 2010, and 8 sites were expected to begin production from 2011 through 2015 if development plans came to fruition. The United States imports PGMs primarily from Canada, Russia, South Africa, and Zimbabwe to meet increasing demand for these materials in a variety of specialized and high-tech applications. Feed sources of PGMs are changing in South Africa and Russia, which together accounted for about 89 percent of platinum production and 82 percent of palladium production in 2009. A greater amount of South African PGM capacity is likely to come from deeper, higher cost Upper Group Reef seam 2 deposits and deposits in the Eastern Bushveld area. Future Russian PGM capacity is likely to come from ore zones with generally lower PGM content and different platinum-to-palladium ratios than the nickel-rich ore that dominated PGM supply in the 1990s. Because PGM supply from Canada and Russia is derived as a byproduct of copper and nickel mining, the PGM supply from these countries is influenced by economic, environmental, political, and

  5. Global exploration and production capacity for platinum-group metals from 1995 through 2015

    Science.gov (United States)

    Wilburn, David R.

    2012-01-01

    Platinum-group metals (PGMs) are required in a variety of commercial, industrial, and military applications for many existing and emerging technologies, yet the United States is highly dependent on foreign sources of PGMs. Information on global exploration for PGMs since 1995 has been used in this study as a basis for identifying locations where the industry has determined that exploration has provided data sufficient to warrant development of a new mine or expansion of an existing operation or where a significant increase in capacity for PGMs is anticipated by 2015. Discussions include an overview of the industry and the selected sites, factors affecting mineral supply, and circumstances leading to the development of mineral properties with the potential to affect mineral supply. Of the 52 sites or regional operations that were considered in this analysis, 16 sites were producing before 1995, 28 sites commenced production from 1995 through 2010, and 8 sites were expected to begin production from 2011 through 2015 if development plans came to fruition. The United States imports PGMs primarily from Canada, Russia, South Africa, and Zimbabwe to meet increasing demand for these materials in a variety of specialized and high-tech applications. Feed sources of PGMs are changing in South Africa and Russia, which together accounted for about 89 percent of platinum production and 82 percent of palladium production in 2009. A greater amount of South African PGM capacity is likely to come from deeper, higher cost Upper Group Reef seam 2 deposits and deposits in the Eastern Bushveld area. Future Russian PGM capacity is likely to come from ore zones with generally lower PGM content and different platinum-to-palladium ratios than the nickel-rich ore that dominated PGM supply in the 1990s. Because PGM supply from Canada and Russia is derived as a byproduct of copper and nickel mining, the PGM supply from these countries is influenced by economic, environmental, political, and

  6. Isotope exchange of indoles with D/sub 2/O over group VIII metals

    Energy Technology Data Exchange (ETDEWEB)

    Karakhanov, E.A.; Dedov, A.G.; Kurts, A.L.; Luzikov, Yu.N.

    1981-08-01

    Results of H - D exchange between indole and its methyl derivatives and D/sub 2/O over metallic Pt, Rh, and Pd are reported. The composition of the reaction mixture after the isotopic exchange was determined by mass spectrometry. The order of reactivity of the metals was Pt>Pd>Rh. It was determined that it was only the heterocycle ..pi..-electron system that interacts with the surface and mainly the hydrogens at C/sub 2/ and C/sub 3/ that undergo exchange and not those bonded to the N. (BLM)

  7. Group 4 Transition-Metal Complexes of an Aniline–Carbene–Phenol Ligand

    KAUST Repository

    Despagnet-Ayoub, Emmanuelle

    2013-05-24

    Attempts to install a tridentate aniline-NHC-phenol (NCO) ligand on titanium and zirconium led instead to complexes resulting from unexpected rearrangement pathways that illustrate common behavior in carbene-early- transition-metal chemistry. © 2013 American Chemical Society.

  8. Phosphine and phosphine oxide groups in metal-organic frameworks detected by P K-edge XAS.

    Science.gov (United States)

    Morel, F L; Pin, S; Huthwelker, T; Ranocchiari, M; van Bokhoven, J A

    2015-02-07

    Phosphine metal-organic frameworks (P-MOFs) are crystalline porous coordination polymers that contain phosphorus functional groups within their pores. We present the use of X-ray absorption spectroscopy (XAS) at the P K-edge to determine the phosphine to phosphine oxide ratio in two P-MOFs with MIL-101 topology. The phosphorus oxidation state is of particular interest as it strongly influences the coordination affinity of these materials for transition metals. This method can determine the oxidation state of phosphorus even when the material contains paramagnetic nuclei, differently from NMR spectroscopy. We observed that phosphine in LSK-15 accounts for 72 ± 4% of the total phosphorus groups and that LSK-12 contains only phosphine oxide.

  9. The synthesis and characterization of organometallic copolymers with Mn-Re binuclear transition-metal group in the side chain

    Institute of Scientific and Technical Information of China (English)

    XU; Zhi; FENG; Gang; BAI; Zhifeng; MA; Yongqiang; CHANG; Weixing; LI; Jing

    2006-01-01

    Novel organometallic copolymers with Mn-Re binuclear transition-metal groups in the side chain are synthesized and characterized. The structure and properties of the copolymers are characterized by GPC, DSC, TG, NMR, FT-IR, UV-Vis spectra and elemental analysis. The glass transition temperature and UV-Vis spectra properties of these three organometallic copolymers are found to be different from the normal polystyrene. New synthetic strategy for the synthesis of organometallic copolymer is developed.

  10. Competitive platinum-group-metal (PGM) supply from the Eastern Limb, Bushveld Complex: Geological, mining and mineral economic aspects

    CSIR Research Space (South Africa)

    McGill, JE

    2011-08-01

    Full Text Available -GROUP-METAL (PGM) SUPPLY FROM THE EASTERN LIMB, BUSHVELD COMPLEX: GEOLOGICAL, MINING, AND MINERAL ECONOMIC ASPECTS Dr. Jeannette E. McGill & Prof. Murray W. Hitzman ACKNOWLEDGEMENTS ? COUNCIL FOR SCIENTIFIC AND INDUSTRIAL RESEARCH (CSIR) ? Centre for Mining... Innovation ? Office of Graduate Studies, Fogarty Endowment ? Mr. VISHNU PILLAY (EXECUTIVE HEAD: JV?S ? Anglo Platinum) ? ACADEMIC ADVISORS Prof. Murray Hitzman (Economic Geology); Dr. Hugh Miller (Mining Engineering); Prof. Rodderick Eggert (Mineral...

  11. Development of Novel Non-Pt Group Metal Electrocatalysts for PEM Fuel Cell Applications

    Energy Technology Data Exchange (ETDEWEB)

    Mukerjee, Sanjeev [Northeastern Univ., Boston, MA (United States). Dept. of Chemistry and Chemical Biology; Atanassov, Plamen [Univ. of New Mexico, Albuquerque, NM (United States); Barton, Scott [Michigan State Univ., East Lansing, MI (United States); Dale, Nilesh [Nissan Technical Center North America (NTCNA), Farmington Hills, MI (United States); Halevi, Bar [Pajarito Powder LLC, Albuquerque, NM (United States)

    2016-01-04

    The objective of this multi-institutional effort was to comprehensively pursue the goal of eliminating noble metal (Pt group metals, PGM) from the cathodic oxygen reduction reaction (ORR) electrode thereby providing a quantum leap in lowering the overall PGM loading in a polymer electrolyte fuel cell (PEMFC). The overall project scope encompassed (a) comprehensive materials discovery effort, (b) a concomitant effort to scale up these materials with very high ( ±5%) reproducibility, both intra and inter, (c) understanding mass transport in porous medium both in gas diffusion and micro-porous layers for enhanced areal activity, (d) understanding mechanistic aspects of active site structure and ORR electrocatalytic pathway. Overall project milestones and metrics were (a) first phase effort based on performance in oxygen where the project’s Go/No-Go decision point milestone of 100 mA/cm2 at 0.8 V (internal resistance-free, iR-free) at 80°C, pure H2/O2, with 1.5 bar total pressure was met. Subsequently, the principle objectives were to (a) transition the project from H2/O2 to H2/Air with slated target of exceeding 30 mA/cm2 @ 0.8 V, 2.5 bar total pressure and an end of the project target of 1 A/cm2 @ 0.4 V (same total pressure), both under 100% relative humidity. The target for catalyst material scale up was to achieve 100 g batch size at the end of the program. This scale up target had a quality control milestone of less than 5% variation of activity measured with H2/Air (2.5 bar total pressure) at 0.8 V. In addition, the project also aimed at arriving at a unified understanding of the nature of active sites in these catalysts as well as some preliminary understanding of the mechanistic pathway. Also addressed is the development of an integrated method for determination of mass transport parameters using a combination of Helox experiments and modeling of the gas

  12. Metal Organic Frameworks as Solid Catalysts in Condensation Reactions of Carbonyl Groups

    OpenAIRE

    Dhakshina Moorthy, Amarajothi; Opanasenko, Maksym; Cejka, Jirí; García Gómez, Hermenegildo

    2013-01-01

    This review summarizes the use of metal organic frameworks (MOFs) as solid catalysts for condensation reactions. After an introductory section, in which condensation reactions are generally presented, a list of the MOFs employed as condensation catalyst is given. The main part of the present review is organized according to the use of MOFs as solid acids, solid bases or as bi-functional solids containing both acid and basic sites. Throughout the review, the emphasis has been made on discussin...

  13. Group III alcohol dehydrogenase from Pectobacterium atrosepticum: insights into enzymatic activity and organization of the metal ion-containing region.

    Science.gov (United States)

    Elleuche, Skander; Fodor, Krisztian; von der Heyde, Amélie; Klippel, Barbara; Wilmanns, Matthias; Antranikian, Garabed

    2014-05-01

    NAD(P)(+)-dependent alcohol dehydrogenases (ADH) are widely distributed in all phyla. These proteins can be assigned to three nonhomologous groups of isozymes, with group III being highly diverse with regards to catalytic activity and primary structure. Members of group III ADHs share a conserved stretch of amino acid residues important for cofactor binding and metal ion coordination, while sequence identities for complete proteins are highly diverse (90 %). A putative group III ADH PaYqhD has been identified in BLAST analysis from the plant pathogenic enterobacterium Pectobacterium atrosepticum. The PaYqhD gene was expressed in the heterologous host Escherichia coli, and the recombinant protein was purified in a two-step purification procedure to homogeneity indicating an obligate dimerization of monomers. Four conserved amino acid residues involved in metal ion coordination were substituted with alanine, and their importance for catalytic activity was confirmed by circular dichroism spectrum determination, in vitro, and growth experiments. PaYqhD exhibits optimal activity at 40 °C with short carbon chain aldehyde compounds and NADPH as cofactor indicating the enzyme to be an aldehyde reductase. No oxidative activities towards alcoholic compounds were detectable. EDTA completely inhibited catalytic activity and was fully restored by the addition of Co(2+). Activity measurements together with sequence alignments and structure analysis confirmed that PaYqhD belongs to the butanol dehydrogenase-like enzymes within group III of ADHs.

  14. The Oldest Stars of the Extremely Metal-Poor Local Group Dwarf Irregular Galaxy Leo A

    CERN Document Server

    Schulte-Ladbeck, R E; Drozdovsky, I O; Greggio, L; Crone, M M; Schulte-Ladbeck, Regina E.; Hopp, Ulrich; Drozdovsky, Igor O.; Greggio, Laura; Crone, Mary M.

    2002-01-01

    We present deep Hubble Space Telescope single-star photometry of Leo A in B, V, and I. Our new field of view is offset from the centrally located field observed by Tolstoy et al. (1998) in order to expose the halo population of this galaxy. We report the detection of metal-poor red horizontal branch stars, which demonstrate that Leo A is not a young galaxy. In fact, Leo A is as least as old as metal-poor Galactic Globular Clusters which exhibit red horizontal branches, and are considered to have a minimum age of about 9 Gyr. We discuss the distance to Leo A, and perform an extensive comparison of the data with stellar isochrones. For a distance modulus of 24.5, the data are better than 50% complete down to absolute magnitudes of 2 or more. We can easily identify stars with metallicities between 0.0001 and 0.0004, and ages between about 5 and 10 Gyr, in their post-main-sequence phases, but lack the detection of main-sequence turnoffs which would provide unambiguous proof of ancient (>10 Gyr) stellar generation...

  15. [Synthesis and luminescent spectral characteristics of porphyrin complexes with platinum group metals].

    Science.gov (United States)

    Rumiantseva, V D; Ivanovskaia, N P; Konovalenko, L I; Tsukanov, S V; Mironov, A F; Osin, N S

    2008-01-01

    The synthesis of natural and synthetic porphyrin complexes with Pt, Pd, Rh, and Ru is reported. Their electronic absorption spectra, phosphorescence spectra, and lifetimes at room temperature both in the presence and in the absence of oxygen were studied. It has been shown that the variation of the nature of the central metal atom and of the substituents in pyrrole and phenyl rings allows the obtaining of metalloporphyrins with various phosphorescence excitation and phosphorescing emission spectra at room temperature. The English version of the paper: Russian Journal of Bioorganic Chemistry, 2008, vol. 34, no. 2; see also http://www.maik.ru.

  16. Transition metal ferrocenyl dithiocarbamates functionalized dye-sensitized solar cells with hydroxy as an anchoring group

    Science.gov (United States)

    Yadav, Reena; Waghadkar, Yogesh; Kociok-Köhn, Gabriele; Kumar, Abhinav; Rane, Sunit B.; Chauhan, Ratna

    2016-12-01

    Three new transition-metal dithiocarbamates involving ferrocene (Fc), namely [Co(FcCH2EtOHdtc)3] (Co), [M(FcCH2EtOHdtc)2] M = Ni (Ni), Cu (Cu) (EtOHdtc = N-ethanol dithiocarbamate), have been synthesized and characterized by microanalyses, FTIR, 1H and 13C NMR spectroscopies and single crystal X-ray diffraction technique. The peak broadening in the 1H spectrum of the copper complex indicates the paramagnetic behavior of this compound. The observed single quasi-reversible cyclic voltammograms for the complexes indicate the stabilization of a metal center (except copper) other than Fe in their characteristic oxidation state. These complexes have been used as photo-sensitizer in dye-sensitized solar cells which indicates that Co displays the best photosensitization property with an overall conversion efficiency of 3.25 ± 0.04%. The low cell efficiency of Ni and Cu complexes may be due to slow regeneration of the dye by iodine/iodide redox couple followed by charge injection into TiO2.

  17. The Oldest Stars of the Extremely Metal-Poor Local Group Dwarf Irregular Galaxy Leo A

    Science.gov (United States)

    Schulte-Ladbeck, Regina E.; Hopp, Ulrich; Drozdovsky, Igor O.; Greggio, Laura; Crone, Mary M.

    2002-08-01

    We present deep Hubble Space Telescope (HST) single-star photometry of Leo A in B, V, and I. Our new field of view is offset from the centrally located field observed by Tolstoy et al. in order to expose the halo population of this galaxy. We report the detection of metal-poor red horizontal branch stars, which demonstrate that Leo A is not a young galaxy. In fact, Leo A is as least as old as metal-poor Galactic Globular Clusters that exhibit red horizontal branches and are considered to have a minimum age of about 9 Gyr. We discuss the distance to Leo A and perform an extensive comparison of the data with stellar isochrones. For a distance modulus of 24.5, the data are better than 50% complete down to absolute magnitudes of 2 or more. We can easily identify stars with metallicities between 0.0001 and 0.0004, and ages between about 5 and 10 Gyr, in their post-main-sequence phases, but we lack the detection of main-sequence turnoffs that would provide unambiguous proof of ancient (>10 Gyr) stellar generations. Blue horizontal branch stars are above the detection limits but difficult to distinguish from young stars with similar colors and magnitudes. Synthetic color-magnitude diagrams show it is possible to populate the blue horizontal branch in the halo of Leo A. The models also suggest ~50% of the total astrated mass in our pointing to be attributed to an ancient (>10 Gyr) stellar population. We conclude that Leo A started to form stars at least about 9 Gyr ago. Leo A exhibits an extremely low oxygen abundance, only 3% of solar, in its ionized interstellar medium. The existence of old stars in this very oxygen-deficient galaxy illustrates that a low oxygen abundance does not preclude a history of early star formation. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

  18. SYNTHESES, CHARACTERIZATION AND ETHYLENE POLYMERIZATION OF HALF-SANDWICH GROUP IV METAL COMPLEXES WITH TRIDENTATE [O,N,S] LIGANDS

    Institute of Scientific and Technical Information of China (English)

    Ya-lin Qiao; Ping Hu; Guo-xin Jin

    2013-01-01

    A series of half-sandwich groupmetal complexes with tridentate monoanionic phenoxy-imine arylsulfide[O-NS] ligand [2-But4-Me-6-((2-(SC6H5)C6H4N =CHC6H2O)]-(La) and dianionic phenoxy-amine arylsulfide [O-N-S]ligand [2-Bu'4-Me-6-((2-(SC6H5)C6H4N-CH2C6H2O)]2-(Lb) have been synthesized and characterized.Lb was obtained easily in high yield by reduction of ligand La with excess LiAlH4 in cool diethyl ether.Half-sandwich Groupmetal complexes CpTi[O-NS]C12 (1a),CpZr[O-NS]C12 (1b),CpTi[O-N-S]C1 (2a),CpZr[O-N-S]C1 (2b) and Cp*Zr[O-N-S]Cl (2c)were synthesized by the reactions of La and Lb with CpTiCl3,CpZrCl3 and Cp*ZrCl3,and characterized by IR,1H-NMR,13C-NMR and elemental analysis.In addition,an X-ray structure analysis was performed on ligand Lb.The title Group Ⅳ half-sandwich bearing tridentate [O,N,S] ligands show good catalytic activities for ethylene polymerization in the presence of methylaluminoxane (MAO) as co-catalyst up to 1.58 × 107 g-PE·mol-Zr-1·h-1.The good catalytic activities can be maintained even at high temperatures such as 100 ℃ exhibiting the excellent thermal stability for these half-sandwich metal pre-catalysts.

  19. A Robust Metal-Organic Framework Combining Open Metal Sites and Polar Groups for Methane Purification and CO2 /Fluorocarbon Capture.

    Science.gov (United States)

    Chen, Cheng-Xia; Zheng, Shao-Ping; Wei, Zhang-Wen; Cao, Chen-Chen; Wang, Hai-Ping; Wang, Dawei; Jiang, Ji-Jun; Fenske, Dieter; Su, Cheng-Yong

    2017-03-23

    A 3D porous perchlorinated metal-organic framework (MOF), LIFM-26, featuring dual functionality, that is, functional polar groups and open metal sites, has been synthesized using perchlorinated linear dicarboxylate to link trigonal prismatic Fe3 (μ3 -O) units. LIFM-26 exhibits good thermal and chemical stability, and possesses high porosity with a BET surface area of 1513 m(2)  g(-1) , compared with isoreticular MOF-235 and Fe3 O(F4 BDC)3 (H2 O)3 (F4 BDC=2,3,5,6-tetrafluorobenzene-1,4-dicarboxylate). Most strikingly, LIFM-26 features good gas sorption/separation performance at 298 K and 1 atm with IAST selectivity values reaching up to 36, 93, 23, 11, 46, and 202 for CO2 /CH4 , CO2 /N2 , C2 H4 /CH4 , C2 H6 /CH4 , C3 H8 /CH4 , and R22/N2 (R22=CHClF2 ), respectively, showing potential for use in biogas/natural gas purification and CO2 /R22 capture. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. IUPAC-NIST Solubility Data Series. 85. Transition and 12-14 Main Group Metals, Lanthanide, Actinide, and Ammonium Halates

    Science.gov (United States)

    Miyamoto, Hiroshi

    2008-06-01

    This paper is the fourth and final volume in the halate solubility series. The solubility data for halates of transition metals, lanthanides, actinides, ammonium, and metallic elements of the main groups 12-14 are reviewed. Where appropriate, binary, ternary, and multicomponent systems are critically evaluated. Most of the solubility results were obtained in water or aqueous solutions of electrolytes. The solubility in organic solvents and aqueous-organic solvent mixtures is also collected in this volume. All these data were critically examined for their reliability. The best values were selected on the basis of critical evaluations and presented in tabular form. Fitting equations and graphical plots are also provided. When numerical data were not reported in an original publication, they were read out from figures and digitized by the compilers. The quantities, units, and symbols used in this volume are in accord with IUPAC recommendations. We always reported the original data and, if necessary, transferred them into the IUPAC recommended units and symbols. The literature on the solubility data was researched through 2002. The halates of these metals play a role in industrial processes. For example, some halates are essential as catalysts, heat stabilizers, and blanching reagents for manufacturing polymer products such as textiles and resins. Some iodates are used in pyrotechnic compounds for weather modification and colored smoke generation. The nonlinear halate crystals are important in construction of optical devices.

  1. Catalysis by alkali and alkaline-earth metal ions in nucleophilic attack of methoxide ion on crown ethers bearing an intra-annular acetoxy group

    NARCIS (Netherlands)

    Cacciapaglia, Roberta; Lucente, Silvia; Mandolini, Luigi; Doorn, van Arie R.; Reinhoudt, David N.; Verboom, Willem

    1989-01-01

    Rates of reaction of methoxide ion with crown ethers bearing an intra-annular acetoxy group are markedly enhanced by alkali and alkaline-earth metal bromides as a result of much stronger interactions of the metal ions with transition states than with reactants. Rates of reactions of methoxide ion w

  2. Complexes of bis(cyclopentadienyl)hydridorhenium with group-II metal halides

    Energy Technology Data Exchange (ETDEWEB)

    Ishchenko, V.M.; Arkhireeva, T.M.; Bulychev, B.M.; Soloveichik, G.L.; Nikolaeva, S.N.

    1986-11-01

    It has been shown that the interaction of bis(cyclopentadienyl)hydridorhenium (Cp/sub 2/ReH, where Cp = eta/sup 5 -/C/sub 5/H/sub 5/) with the halides of zinc, cadmium, beryllium, and magnesium in diethyl ether results in the formation of complex compounds with the general formula Cp/sub 2/ReH MHal/sub 2/. The replacement of ether by tetrahydrofuran in the case of zinc derivatives gives monosolvates with the formula Cp/sub 2/ReH x ZnHal/sub 2/ x THF (Hal = Br, I). On the basis of data from IR and PMR spectroscopy it has been concluded that the bonding of the metal-containing fragments in these complexes is realized either as a result of an Re :..-->.. M donor-acceptor interaction (the complexes with ZnHal/sub 2/ and CdI/sub 2/) or as a result of the formation of a mixed bond (the complexes with BeCl/sub 2/ and MgHal/sub 2/).

  3. OB stars at the lowest Local Group metallicity: GTC-OSIRIS observations of Sextans A

    CERN Document Server

    Camacho, I; Herrero, A; Simón-Díaz, S

    2016-01-01

    Our aim is to find and classify OB stars in Sextans A, to later determine accurate stellar parameters of these blue massive stars in this low metallicity region $(Z \\sim 0.1 \\rm Z_{\\odot})$. Using UBV photometry, the reddening-free index Q and GALEX imaging, we built a list of blue massive star candidates in Sextans A. We obtained low resolution (R $\\sim$ 1000) GTC-OSIRIS spectra for a fraction of them and carried out spectral classification. For the confirmed O-stars we derive preliminary stellar parameters. The target selection criteria and observations were successful and have produced the first spectroscopic atlas of OB-type stars in Sextans A. From the whole sample of 18 observed stars, 12 were classified as early OB-types, including 5 O-stars. The radial velocities of all target stars are in agreement with their Sextans A membership, although three of them show significant deviations. We determined the stellar parameters of the O-type stars using the stellar atmosphere code FASTWIND, and revisited the s...

  4. First determination of the levels of platinum group metals in Manta birostris (manta ray) caught along the Ghanaian coastline.

    Science.gov (United States)

    Essumang, D K

    2010-06-01

    Tissues from Manta birostris caught by fishermen from Dixcove in the western part of Ghana were analyzed for their Platinum, palladium and rhodium concentrations (PGM). The use of chondrichthyan fish has permitted the study of trace levels of Platinum group metals (PGMs) which have travelled very far into the sea. The analysis showed that Ghana's coastline is fairly polluted with these platinum group metals (PGMs). PGM concentration in manta ray recorded a range of (0.15-0.85) microg/g for Pt, (0.033-0.67) microg/g for Pd and (0.007-0.145) microg/g for Rh. Comparing these values to the UK dietary intake of 0.2 microg/day for Pt and Rh and 1.0 microg/day for Pd, its indicates that the values obtained from the analysis for Pt was above the required level. This is the first study to show the accumulation of PGM in chondrichthyan fish, although the sources of this pollution are not clear as manta birostris is migratory and therefore need to be investigated further. The presence of the PGM is very significant, since manta ray meat is consumed in Ghana. This may presents a health risk, due to a possible accumulation of PGMs in humans.

  5. Catalytic co-pyrolysis of peat and polymeric wastes in the presence of iron sub-group metal chlorides

    Energy Technology Data Exchange (ETDEWEB)

    Sulman, E.M.; Kosivtsov, Y.Y.; Lugovoy, Y.V. [Tver Technical University, Tver (Russian Federation)

    2008-07-01

    The purpose of this investigation is the study of activity of iron sub-group metal chlorides in co-processing of peat and polymeric wastes by low-temperature catalytic pyrolysis method. Iron sub-group metal chlorides in concentration varied from 1 to 10% (wt) were used as the catalysts of pyrolysis. The process was conducted in fixed bed reactor in inert gaseous atmosphere at the temperature interval of 350-550{sup o}C. All the investigated catalysts were found to promote the increase of liquid fraction mass and the decrease of solid carbon-containing residue mass up to 10-30%. Cobalt catalyst revealed the highest selectivity with respect to liquid products formation. The use of the catalysts in low-temperature peat and polymeric wastes pyrolysis process was found to favour the increase gaseous products volume up to 20-50% as well as unsaturated hydrocarbons volume in 1.2 folds in comparison to uncatalysed process. 9 refs., 3 figs., 2 tabs.

  6. Strategic and tactical determinants for South African platinum-group-metals supply

    CSIR Research Space (South Africa)

    McGill, JE

    2011-11-01

    Full Text Available for competitive future supply being derived from the eastern limb. 1 Introduction The mineral resources sector displays a careful balancing act between operation specific tactics designed to maximize shareholder returns; and overarching industry...-related strategies employed by various entities including country governments, global interest groups, and multi-national head offices. This balancing act of short-term business tactics juxtaposed along-side long-run strategic intent of the extraction sector...

  7. Removal of transition metals from dilute aqueous solution by carboxylic acid group containing absorbent polymers

    Science.gov (United States)

    A new carboxylic acid group containing resin with cation exchange capacity, 12.67 meq/g has been used to remove Cu2+, Co2+ and Ni2+ ions from dilute aqueous solution. The resin has Cu2+, Co2+ and Ni2+ removal capacity, 216 mg/g, 154 mg/g and 180 mg/g, respectively. The selectivity of the resin to ...

  8. Lead-chromium carbonyl complexes incorporated with group 8 metals: synthesis, reactivity, and theoretical calculations.

    Science.gov (United States)

    Shieh, Minghuey; Chu, Yen-Yi; Hsu, Miao-Hsing; Ke, Wei-Ming; Lin, Chien-Nan

    2011-01-17

    The trichromium-lead complex [Pb{Cr(CO)5}3](2-) (1) was isolated from the reaction of PbCl2 and Cr(CO)6 in a KOH/MeOH solution, and the new mixed chromium-iron-lead complex [Pb{Cr(CO)5}{Fe(CO)4}2](2-) (3) was synthesized from the reaction of PbCl2 and Cr(CO)6 in a KOH/MeOH solution followed by the addition of Fe(CO)5. X-ray crystallography showed that 3 consisted of a central Pb atom bound in a trigonal-planar environment to two Fe(CO)4 and one Cr(CO)5 fragments. When complex 1 reacted with 1.5 equiv of Mn(CO)5Br, the Cr(CO)4-bridged dimeric lead-chromium carbonyl complex [Pb2Br2Cr4(CO)18](2-) (4) was produced. However, a similar reaction of 3 or the isostructural triiron-lead complex [Pb{Fe(CO)4}3](2-) (2) with Mn(CO)5Br in MeCN led to the formation of the Fe3Pb2-based trigonal-bipyramidal complexes [Fe3(CO)9{PbCr(CO)5}2](2-) (6) and [Fe3(CO)9{PbFe(CO)4}2](2-) (5), respectively. On the other hand, the Ru3Pb2-based trigonal-bipyramidal complex [Ru3(CO)9{PbCr(CO)5}2](2-) (7) was obtained directly from the reaction of PbCl2, Cr(CO)6, and Ru3(CO)12 in a KOH/MeOH solution. X-ray crystallography showed that 5 and 6 each had an Fe3Pb2 trigonal-bipyramidal core geometry, with three Fe(CO)3 groups occupying the equatorial positions and two PbFe(CO)4 or PbCr(CO)5 units in the axial positions, while 7 displayed a Ru3Pb2 trigonal-bipyramidal geometry with three equatorial Ru(CO)3 groups and two axial PbCr(CO)5 units. The complexes 3-7 were characterized spectroscopically, and their nature, formation, and electrochemistry were further examined by molecular orbital calculations at the B3LYP level of density functional theory.

  9. Planetary nebulae: the universal mass-metallicity relation for Local Group dwarf galaxies and the chemistry of NGC 205

    CERN Document Server

    Gonçalves, D R; Teodorescu, Ana M; Carneiro, Carolina M

    2014-01-01

    Here we study 16 planetary nebulae (PNe) in the dwarf irregular galaxy NGC 205 by using GMOS@Gemini spectra to derive their physical and chemical parameters. The chemical patterns and evolutionary tracks for 14 of our PNe suggest that there are no type I PNe among them. These PNe have an average oxygen abundance of 12+log(O/H)=8.08$\\pm$0.28, progenitor masses of 2-2.5M$_{\\odot}$ and thus were born ~1.0-1.7Gyr ago. Our results are in good agreement with previous PN studies in NGC 205. The present 12+log(O/H) is combined with our previous works and with the literature to study the PN metallicity trends of the Local Group (LG) dwarf galaxies, in an effort to establish the PN luminosity- and mass-metallicity relations (LZR and MZR) for the LG dwarf irregulars (dIrrs) and dwarf spheroidals (dSphs). Previous attempts to obtain such relations failed to provide correct conclusions because were based on limited samples (Richer & McCall 1995; Gon\\c{c}calves et al. 2007). As far as we are able to compare stellar wit...

  10. Assessing Economic Modulation of Future Critical Materials Use: The Case of Automotive-Related Platinum Group Metals.

    Science.gov (United States)

    Zhang, Jingshu; Everson, Mark P; Wallington, Timothy J; Field, Frank R; Roth, Richard; Kirchain, Randolph E

    2016-07-19

    Platinum-group metals (PGMs) are technological and economic enablers of many industrial processes. This important role, coupled with their limited geographic availability, has led to PGMs being labeled as "critical materials". Studies of future PGM flows have focused on trends within material flows or macroeconomic indicators. We complement the previous work by introducing a novel technoeconomic model of substitution among PGMs within the automotive sector (the largest user of PGMs) reflecting the rational response of firms to changing prices. The results from the model support previous conclusions that PGM use is likely to grow, in some cases strongly, by 2030 (approximately 45% for Pd and 5% for Pt), driven by the increasing sales of automobiles. The model also indicates that PGM-demand growth will be significantly influenced by the future Pt-to-Pd price ratio, with swings of Pt and Pd demand of as much as 25% if the future price ratio shifts higher or lower even if it stays within the historic range. Fortunately, automotive catalysts are one of the more effectively recycled metals. As such, with proper policy support, recycling can serve to meet some of this growing demand.

  11. Heavy main-group iodometallates hybridized by alkali metal via 1,10-Phenanthroline-5,6-dione

    Indian Academy of Sciences (India)

    Mengfan Yin; Gengxing Cai; Peng Wang; Xihui Chao; Jibo Liu; Haohong Li; Zhirong Chen

    2015-09-01

    Alkali metals were introduced into heavy main-group iodometallates to get two new IA/IVAheterometallic frameworks [PbI3K(pdon)(H2O)2] (1) and {[Pb3I9K2(pdon)2(H3O)]·H2O} (2) (pdon=1,10-phenanthroline-5,6-dione), which were obtained as single phases by hydrothermal method at different pH values. Compounds 1 and 2 are three-dimensional heterometallic frameworks constructed from the linkage of pdon ligand between iodometallate chains and potassium oxides/iodide clusters. Specially, these two heterometallic frameworks exhibit broadened absorption bands at 700 and 750 nm compared with those of bulk PbI2 and pdon ligand. The band gap of 2 is wider than that of 1, which is due to the absence of · · · interaction in 2. Their thermal stabilities are also discussed.

  12. Buried Volume Analysis for Propene Polymerization Catalysis Promoted by Group 4 Metals: a Tool for Molecular Mass Prediction

    KAUST Repository

    Falivene, Laura

    2015-10-02

    A comparison of the steric properties of homogeneous single site catalysts for propene polymerization using the percentage of buried volume (%VBur) as molecular descriptor is reported. The %VBur calculated on the neutral precursors of the active species seems to be a reliable tool to explain several experimental data related to the propene insertion and to the monomer chain transfer. Interestingly, a linear correlation between the buried volume calculated for a large set of neutral precursors and the energetic difference between propagation and termination steps calculated by DFT methods is found for Group 4 metal catalysts. The “master curves” derived for Ti, Zr and Hf confirm not only that the %VBur is an appropriate molecular descriptor for the systems considered but also that it could be used as tool for a large computational screening of new ligands.

  13. Electrochemically Smart Bimetallic Materials Featuring Group 11 Metals: In-situ Conductive Network Generation and Its Impact on Cell Capacity

    Energy Technology Data Exchange (ETDEWEB)

    Takeuchi, Esther [Stony Brook Univ., NY (United States)

    2016-11-30

    Our results for this program “Electrochemically smart bimetallic materials featuring Group 11 metals: in-situ conductive matrix generation and its impact on battery capacity, power and reversibility” have been highly successful: 1) we demonstrated material structures which generated in-situ conductive networks through electrochemical activation with increases in conductivity up to 10,000 fold, 2) we pioneered in situ analytical methodology to map the cathodes at several stages of discharge through the use of Energy Dispersive X-ray Diffraction (EDXRD) to elucidate the kinetic dependence of the conductive network formation, and 3) we successfully designed synthetic methodology for direct control of material properties including crystallite size and surface area which showed significant impact on electrochemical behavior.

  14. Dual Exchange in PCN-333: A Facile Strategy to Chemically Robust Mesoporous Chromium Metal-Organic Framework with Functional Groups.

    Science.gov (United States)

    Park, Jihye; Feng, Dawei; Zhou, Hong-Cai

    2015-09-16

    A facile preparation of a mesoporous Cr-MOF, PCN-333(Cr) with functional group, has been demonstrated through a dual exchange strategy, involving a sequential ligand exchange and metal metathesis process. After optimization of the exchange system, the functionalized PCN-333(Cr), N3-PCN-333(Cr) shows well maintained crystallinity, porosity, as well as much improved chemical stability. Because of the exceptionally large pores (∼5.5 nm) in PCN-333(Cr), a secondary functional moiety, Zn-TEPP with a size of 18 Å × 18 Å, has been successfully clicked into the framework. In this article, we have also analyzed kinetics and thermodynamics during dual exchange process, showing our attempts to interpret the exchange event in the PCN-333. Our findings not only provide a highly stable mesoporous Cr-MOF platform for expanding MOF-based applications, but also suggest a route to functionalized Cr-MOF which may have not been achievable through conventional approaches.

  15. Contamination from gold and platinum-group metals mining in the Gulf of Darién, Colombia

    Science.gov (United States)

    Vasquez-Bedoya, L.; Palacio Baena, J.

    2013-12-01

    Gulf of Darién, triangular southernmost extension of the Caribbean Sea, bounded by Panama on the southwest and by Colombia on the southeast and east. The Gulf is made up of 17 municipalities in the department of Choco and Antioquia. The Gulf of Darién is a geostrategic region, rich in biodiversity, known for its natural resources of minerals, oil, lumber as well as its water and fertile land. The Darién also acts as the bridge between South America and Central America and has access to the Pacific Ocean and the Caribbean Sea. The economy in the region is based mainly on agribusinesses, tourism and mining activities, mainly the 'mining of gold and platinum-group metals'. In our study we determined the degree of trace element contamination in estuarine sediment samples originated from mining activities and municipal waste water discharges of effluents on the gulf of Darién. . Surface samples were taken from 17 locations through the entire Gulf. Grain size, Corg, Ag, Al, Ca , Cr, Cu, Fe, Mg, Mn, Na, Ni, Pb and Zn concentrations were analyzed, and enrichment factors (EF) as well as geo-accumulation indices (Igeo) were calculated. Concentrations of Pb, Zn, Ni, Cu and Cr show levels that are consistent with those typically found in urbanized marine environments. EF and Igeo values revealed that the Gulf is extremely contaminated with Ag and moderately contaminated with Cr and Zn. The sources of Cr, Ag, Hg and Zn are associated with the development of mining activities in the Atrato River basin. The observed enrichment of Ag may be explained as a residue of the extraction of gold and platinum-group metals.

  16. Structure, bonding and energetics of N-heterocyclic carbene (NHC) stabilized low oxidation state group 2 (Be, Mg, Ca, Sr and Ba) metal complexes: A theoretical study

    Indian Academy of Sciences (India)

    Ashim Baishya; V Rao Mundlapati; Sharanappa Nembenna; Himansu S Biswal

    2014-11-01

    A series of N-heterocyclic carbene stabilized low oxidation state group 2 metal halide and hydrides with metal-metal bonds ([L(X) M-M(X) L]; L = NHC ((CHNH)2C:), M = Be, Mg, Ca, Sr and Ba, and X = Cl or H) has been studied by computational methods. The main objective of this study is to predict whether it is possible to stabilize neutral ligated low oxidation state alkaline-earth metal complexes with metal-metal bonds. The homolytic metal-metal Bond Dissociation Energy (BDE) calculation, Natural Bond Orbital (NBO) and Energy Decomposition Analyses (EDA) on density functional theory (DFT) optimized [L(X)M-M(X)L] complexes revealed that they are as stable as their -diketiminate, guanidinate and -diimine counterparts. The optimized structures of the complexes are in trans-linear geometries. The bond order analyses such as Wiberg Bond Indices (WBI) and Fuzzi Bond Order (FBO) confirm the existence of single bond between two metal atoms, and it is covalent in nature.

  17. Metal distributions out to 0.5 r {sub 180} in the intracluster medium of four galaxy groups observed with Suzaku

    Energy Technology Data Exchange (ETDEWEB)

    Sasaki, Toru; Matsushita, Kyoko; Sato, Kosuke, E-mail: j1213703@ed.tus.ac.jp, E-mail: matusita@rs.kagu.tus.ac.jp [Department of Physics, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601 (Japan)

    2014-01-20

    We studied the distributions of metal abundances and metal-mass-to-light ratios in the intracluster medium (ICM) of four galaxy groups, MKW 4, HCG 62, the NGC 1550 group, and the NGC 5044 group, out to ∼0.5 r {sub 180} observed with Suzaku. The iron abundance decreases with radius and is about 0.2-0.4 solar beyond 0.1 r {sub 180}. At a given radius in units of r {sub 180}, the iron abundance in the ICM of the four galaxy groups was consistent with or smaller than those of clusters of galaxies. The Mg/Fe and Si/Fe ratios in the ICM are nearly constant at the solar ratio out to 0.5 r {sub 180}. We also studied systematic uncertainties in the derived metal abundances, comparing the results from two versions of atomic data for astrophysicists (ATOMDB) and single- and two-temperature model fits. Since the metals have been synthesized in galaxies, we collected K-band luminosities of galaxies from the Two Micron All Sky Survey catalog and calculated the integrated iron-mass-to-light-ratios (IMLR), or the ratios of the iron mass in the ICM to light from stars in galaxies. The groups with smaller gas-mass-to-light ratios have smaller IMLR values and the IMLR is inversely correlated with the entropy excess. Based on these abundance features, we discussed the past history of metal enrichment processes in groups of galaxies.

  18. Synthesis and characterization of norfloxacin-transition metal complexes (group 11, IB): Spectroscopic, thermal, kinetic measurements and biological activity

    Science.gov (United States)

    Refat, Moamen S.

    2007-12-01

    The investigation of the new structures of Ag(I), Cu(II) and Au(III) complexes, [Ag 2(Nor) 2](NO 3) 2, [Cu(Nor) 2(H 2O) 2]SO 4·5H 2O and [Au(Nor) 2 (H 2O) 2]Cl 3 (where, Nor = norfloxacin) was done during the reaction of silver(I), copper(II) and gold(III) ions with norfloxacin drug ligand. Elemental analysis of CHN, infrared, electronic, 1H NMR and mass spectra, as well as thermo gravimetric analysis (TG and DTG) and conductivity measurements have been used to characterize the isolated complexes. The powder XRD studies confirm the amorphous nature of the complexes. The norfloxacin ligand is coordinated to Ag(I) and Au(III) ions as a neutral monodentate chelating through the N atom of piperidyl ring, but the copper(II) complex is coordinated through the carbonyl oxygen atom (quinolone group) and the oxygen atom of the carboxylic group. The norfloxacin and their metal complexes have been biologically tested, which resulted in norfloxacin complexes showing moderate activity against the gram positive and gram negative bacteria as well as against fungi.

  19. Novel relationship between hydroxyl radical initiation and surface group of ceramic honeycomb supported metals for the catalytic ozonation of nitrobenzene in aqueous solution.

    Science.gov (United States)

    Zhao, Lei; Sun, Zhizhong; Ma, Jun

    2009-06-01

    Comparative experiments have been performed to investigate the degradation efficiency of nitrobenzene and the removal efficiency of TOC in aqueous solution bythe processes of ceramic honeycomb supported different metals (Fe, Ni, and Zn) catalytic ozonation, indicating that the modification with metals can enhance the activity of ceramic honeycomb for the catalytic ozonation of nitrobenzene, and the loading percentage of metal and the metallicity respectively presents a positive influence on the degradation of nitrobenzene. The degradation efficiency of nitrobenzene is determined by the initiation of hydroxyl radical (*OH) according to a good linear correlation in all the processes of modified ceramic honeycomb catalytic ozonation at the different loading percentages of metals. The modification of ceramic honeycomb with metals results in the conversion of the pH at the point of zero charge (pHpzc) and the evolution of surface groups. Divergence from the conventional phenomenon, the enhancement mechanism of ozone decomposition on the modified ceramic honeycomb with metals is proposed due to the basic attractive forces of electrostatic forces or/and hydrogen bonding. Consequently, a novel relationship between the initiation of *OH and the surface-OH2+ group on the modified catalyst is established based on the synergetic effect between homogeneous and heterogeneous reaction systems.

  20. Unexpected metal ion-assisted transformations leading to unexplored bridging ligands in Ni(II) coordination chemistry: the case of PO3F(2-) group.

    Science.gov (United States)

    Dermitzaki, Despina; Raptopoulou, Catherine P; Psycharis, Vassilis; Escuer, Albert; Perlepes, Spyros P; Stamatatos, Theocharis C

    2014-10-21

    The initial 'accidental', metal ion-assisted hydrolysis of PF6(-) to PO3F(2-) has been evolved in a systematic investigation of the bridging affinity of the latter group in Ni(II)/oximate chemistry; mono-, di- and trinuclear complexes have been prepared and confirmed both the rich reactivity of PO3F(2-) and its potential for further use as bridging ligand in high-nuclearity 3d-metal cluster chemistry.

  1. High-performance ab initio density matrix renormalization group method: Applicability to large-scale multireference problems for metal compounds

    Science.gov (United States)

    Kurashige, Yuki; Yanai, Takeshi

    2009-06-01

    This article presents an efficient and parallelized implementation of the density matrix renormalization group (DMRG) algorithm for quantum chemistry calculations. The DMRG method as a large-scale multireference electronic structure model is by nature particularly efficient for one-dimensionally correlated systems, while the present development is oriented toward applications for polynuclear transition metal compounds, in which the macroscopic one-dimensional structure of electron correlation is absent. A straightforward extension of the DMRG algorithm is proposed with further improvements and aggressive optimizations to allow its application with large multireference active space, which is often demanded for metal compound calculations. Special efficiency is achieved by making better use of sparsity and symmetry in the operator and wave function representations. By accomplishing computationally intensive DMRG calculations, the authors have found that a large number of renormalized basis states are required to represent high entanglement of the electron correlation for metal compound applications, and it is crucial to adopt auxiliary perturbative correction to the projected density matrix during the DMRG sweep optimization in order to attain proper convergence to the solution. Potential energy curve calculations for the Cr2 molecule near the known equilibrium precisely predicted the full configuration interaction energies with a correlation space of 24 electrons in 30 orbitals [denoted by (24e,30o)]. The energies are demonstrated to be accurate to 0.6mEh (the error from the extrapolated best value) when as many as 10 000 renormalized basis states are employed for the left and right DMRG block representations. The relative energy curves for [Cu2O2]2+ along the isomerization coordinate were obtained from DMRG and other correlated calculations, for which a fairly large orbital space (32e,62o) is modeled as a full correlation space. The DMRG prediction nearly overlaps

  2. Dissociation potential curves of low-lying states in transition metal hydrides. 3. Hydrides of groups 6 and 7.

    Science.gov (United States)

    Koseki, Shiro; Matsushita, Takeshi; Gordon, Mark S

    2006-02-23

    The dissociation curves of low-lying spin-mixed states in monohydrides of groups 6 and 7 were calculated by using an effective core potential (ECP) approach. This approach is based on the multiconfiguration self-consistent field (MCSCF) method, followed by first-order configuration interaction (FOCI) calculations, in which the method employs an ECP basis set proposed by Stevens and co-workers (SBKJC) augmented by a set of polarization functions. Spin-orbit coupling (SOC) effects are estimated within the one-electron approximation by using effective nuclear charges, since SOC splittings obtained with the full Breit-Pauli Hamitonian are underestimated when ECP basis sets are used. The ground states of group 6 hydrides have Omega = (1)/(2)(X(6)Sigma(+)(1/2)), where Omega is the z component of the total angular momentum quantum number. Although the ground states of group 7 hydrides have Omega = 0(+), their main adiabatic components are different; the ground state in MnH originates from the lowest (7)Sigma(+), while in TcH and ReH the main component of the ground state is the lowest (5)Sigma(+). The present paper reports a comprehensive set of theoretical results including the dissociation energies, equilibrium distances, electronic transition energies, harmonic frequencies, anharmonicities, and rotational constants for several low-lying spin-mixed states in these hydrides. Transition dipole moments were also computed among the spin-mixed states and large peak positions of electronic transitions are suggested theoretically for these hydrides. The periodic trends of physical properties of metal hydrides are discussed, based on the results reported in this and other recent studies.

  3. DFT study on the mechanism of water-assisted dihydrogen elimination in group 6 octahedral metal hydride complexes.

    Science.gov (United States)

    Sandhya, K S; Suresh, Cherumuttathu H

    2012-08-28

    The reaction of water with octahedral bis-, tris- and tetrakis-(phosphine)tungsten, (phosphine)molybdenum and (phosphine)chromium complexes has been studied using B3LYP/def2-TZVPP level of DFT to elucidate dissociative, associative and hydride migratory insertion mechanisms for hydrogen elimination. In the dissociative mechanism, phosphine dissociation requires 19.3-28.5 kcal mol(-1) of energy. The phosphine-water ligand exchange is endergonic due to poor coordination ability of water to group 6 metals (binding energy 8.8-15.5 kcal mol(-1)). The ligand exchange leads to intermolecular M-H···H(2)O dihydrogen interaction and facilitates dihydrogen elimination (G(act) = 6.8-15.5 kcal mol(-1)). In the associative mechanism, a water molecule in the first solvation shell interacts with the M-H bond through a dihydrogen bond (interaction energy 2.7-4.0 kcal mol(-1)) and leads to the elimination of H(2) by forming a hydroxide complex. Compared to the dissociative mechanism, G(act) of associative mechanisms are ~22 kcal mol(-1) higher. In the hydride migratory insertion mechanism, the hydride ligand shifts to the CO ligand (G(act) = 25.4-30.4 kcal mol(-1)) to afford a formyl complex and subsequently the H-H bond coupling occurs between formyl and water ligand (G(act) = 2.8-4.4 kcal mol(-1)). In many cases, the migratory insertion mechanism can simultaneously operate with the dissociative mechanism as a minor pathway, whereas owing to high G(act) value, the associative mechanism can be described as inactive in the reaction. The general argument that dihydrogen elimination is preceded by the formation of a dihydrogen intermediate is not applicable for the systems studied herein as the most favoured dissociative mechanism does not pass through such an intermediate. On the other hand, irrespective of the mechanisms, dihydrogen elimination invariably occurs with the formation of a dihydrogen bonded transition state. Our results also suggest that group 6 octahedral metal

  4. First principles study of structural, electronic and elastic properties of group IB metal nitrides TMN{sub x} (TM = Cu, Ag and Au: x = 1, 2)

    Energy Technology Data Exchange (ETDEWEB)

    Rajeswarapalanichamy, R., E-mail: rrpalanichamy@gmail.com [Department of Physics, N.M.S.S.V.N College, Madurai, Tamil Nadu 625 019 (India); Priyanga, G. Sudha; Murugan, A.; Santhosh, M.; Cinthia, A. Jemmy [Department of Physics, N.M.S.S.V.N College, Madurai, Tamil Nadu 625 019 (India); Kanagaprabha, S. [Department of Physics, Kamaraj College, Tuticorin, Tamil Nadu 628 003 (India); Iyakutti, K. [Department of Physics and Nanotechnology, SRM University, Chennai, Tamil Nadu 603 203 (India)

    2013-12-15

    Highlights: •Electronic, structural and elastic properties of group IB nitrides are investigated. •A pressure induced structural phase transition is predicted under high pressure. •Electronic structure reveals that these materials exhibit metallic behavior. •Computed elastic moduli obey traditional mechanical stability condition. •The Debye temperature values are computed for Group IB metal mono and di-nitrides. -- Abstract: The structural, electronic and elastic properties of group IB transition metal nitrides (TMN{sub x}: TM = Cu, Ag, Au and x = 1, 2) are investigated by first principles calculation using the Vienna ab initio simulation package. The lattice constants, cohesive energy, bulk modulus, band structures and the density of states are obtained. The calculated lattice parameters are in good agreement with the available results. The electronic structure reveals that these materials exhibit metallic behaviour. A pressure-induced structural phase transition from NaCl to CsCl phase in AgN at 6 GPa, NaCl to ZB phase in AuN at 34.2 GPa and ZB to NaCl phase in CuN at 36.2 GPa is observed. In group IB metal di-nitrides, CaF{sub 2} to AlB{sub 2} phase transition is predicted. The computed elastic constants indicate that these nitrides are mechanically stable at ambient pressure. The calculated Debye temperature values are in good agreement with experimental and other theoretical results.

  5. Adsorption of group 1b metal ions on Galena: Effects on half-cell potential and photovoltage

    Science.gov (United States)

    Kunze, O. A.

    The conditions at the solid-liquid interface play a crucial role in the flotation of minerals. These conditions are susceptible to a variety of influences, a detailed knowledge of which is important in extractive metallurgy. In this study, effects on the electrode potential and the surface photovoltage of galena as a result of the adsorption of group 1b metal ions were investigated. Significant differences in the effects of copper, silver and gold could be observed. Copper, even at very low concentration, was found to affect the rest potential markedly (> 100 mV for 1 ppm Cu 2+) and to quench the surface photovoltage. These experimental observations led us to propose a qualitative electrostatic-electrochemical model of the galena-electrolyte interface during copper-ion adsorption. According to this model, copper ions on galena can be present and act in two different modes: (a) as surface states in conjunction with the galena surface and; (b) as a constituent of copper sulphide formed on that surface. Silver produced a similar change in potential but no quenching action on the photovoltage was observed. Gold was found to have less influence on the electrode potential. The appearance of a slow photovoltage of opposite polarity to the original surface photovoltage indicates the formation of a surface layer with high lying metastable acceptor levels.

  6. First-Principles Momentum Dependent Local Ansatz Approach to the Ground-State Properties of Iron-Group Transition Metals

    Science.gov (United States)

    Kakehashi, Yoshiro; Chandra, Sumal

    2016-08-01

    The ground-state properties of iron-group transition metals from Sc to Cu have been investigated on the basis of the first-principles momentum dependent local ansatz (MLA) theory. Correlation energy gain is found to show large values for Mn and Fe: 0.090 Ry (Mn) and 0.094 Ry (Fe). The Hund-rule coupling energies are found to be 3000 K (Fe), 1400 K (Co), and 300 K (Ni). It is suggested that these values can resolve the inconsistency in magnetic energy between the density functional theory and the first-principles dynamical coherent potential approximation theory at finite temperatures. Charge fluctuations are shown to be suppressed by the intra-orbital correlations and inter-orbital charge-charge correlations, so that they show nearly constant values from V to Fe: 1.57 (V and Cr), 1.52 (Mn), and 1.44 (Fe), which are roughly twice as large as those obtained by the d band model. The amplitudes of local moments are enhanced by the intra-orbital and inter-orbital spin-spin correlations and show large values for Mn and Fe: 2.87 (Mn) and 2.58 (Fe). These values are in good agreement with the experimental values estimated from the effective Bohr magneton number and the inner core photoemission data.

  7. First-Principles Momentum Dependent Local Ansatz Approach to the Momentum Distribution Function in Iron-Group Transition Metals

    Science.gov (United States)

    Kakehashi, Yoshiro; Chandra, Sumal

    2017-03-01

    The momentum distribution function (MDF) bands of iron-group transition metals from Sc to Cu have been investigated on the basis of the first-principles momentum dependent local ansatz wavefunction method. It is found that the MDF for d electrons show a strong momentum dependence and a large deviation from the Fermi-Dirac distribution function along high-symmetry lines of the first Brillouin zone, while the sp electrons behave as independent electrons. In particular, the deviation in bcc Fe (fcc Ni) is shown to be enhanced by the narrow eg (t2g) bands with flat dispersion in the vicinity of the Fermi level. Mass enhancement factors (MEF) calculated from the jump on the Fermi surface are also shown to be momentum dependent. Large mass enhancements of Mn and Fe are found to be caused by spin fluctuations due to d electrons, while that for Ni is mainly caused by charge fluctuations. Calculated MEF are consistent with electronic specific heat data as well as recent angle resolved photoemission spectroscopy data.

  8. Putting an ultrahigh concentration of amine groups into a metal-organic framework for CO2 capture at low pressures.

    Science.gov (United States)

    Liao, Pei-Qin; Chen, Xun-Wei; Liu, Si-Yang; Li, Xu-Yu; Xu, Yan-Tong; Tang, Minni; Rui, Zebao; Ji, Hongbing; Zhang, Jie-Peng; Chen, Xiao-Ming

    2016-10-19

    Tremendous efforts have been devoted to increasing the CO2 capture performance of porous materials, especially for low CO2 concentration environments. Here, we report that hydrazine can be used as a diamine short enough to functionalize the small-pore metal-organic framework [Mg2(dobdc)] (H4dobdc = 2,5-dihydroxyl-1,4-benzenedicarboxylic acid). By virtue of the ultrahigh concentration of free amine groups (6.01 mmol g(-1) or 7.08 mmol cm(-3)) capable of reversible carbamic acid formation, the new material [Mg2(dobdc)(N2H4)1.8] achieves a series of new records for CO2 capture, such as single-component isotherm uptakes of 3.89 mmol g(-1) or 4.58 mmol cm(-3) at the atmospheric CO2 concentration of 0.4 mbar at 298 K and 1.04 mmol g(-1) or 1.22 mmol cm(-3) at 328 K, as well as more than a 4.2 mmol g(-1) or 4.9 mmol cm(-3) adsorption/desorption working capacity under dynamic mixed-gas conditions with CO2 concentrations similar to those in flue gases and ambient air.

  9. Batch leaching tests of motherboards to assess environmental contamination by bromine, platinum group elements and other selected heavy metals.

    Science.gov (United States)

    Almeida, César; Grosselli, Melina; González, Patricia; Martínez, Dante; Gil, Raúl

    2016-02-01

    In this study, a batch leaching test was executed to evaluate the toxicity associated with chemicals contained in motherboards. The leaching solutions used were distilled water, nitric acid, acetic acid and synthetic acid rain solution. A total of 21 elements including Ag, As, Au, Br, Cd, Co, Cr, Cu, Hf, Ir, Mn, Ni, Os, Pb, Pd, Pt, Rd, Rh, Se, U and Zn were analyzed. In this study, the pH values of all the leachates fell within the range of 2.33-4.88. The highest concentrations of metals were obtained from the acid rain solution, whilst the maximum value of bromine was achieved with solution of acetic acid. Appreciable concentrations of platinum group elements were detected with concentrations around 3.45, 1.43, 1.21 and 22.19 µg L(-1) for Ir, Pd, Pt and Rh, respectively. The different leaching of the motherboards revealed the predominant presence of the toxic substances in the leached from the e-waste.

  10. Benchmark Calculations of Energetic Properties of Groups 4 and 6 Transition Metal Oxide Nanoclusters Including Comparison to Density Functional Theory

    Energy Technology Data Exchange (ETDEWEB)

    Fang, Zongtang; Both, Johan; Li, Shenggang; Yue, Shuwen; Aprà, Edoardo; Keçeli, Murat; Wagner, Albert F.; Dixon, David A.

    2016-08-09

    The heats of formation and the normalized clustering energies (NCEs) for the group 4 and group 6 transition metal oxide (TMO) trimers and tetramers have been calculated by the Feller-Peterson-Dixon (FPD) method. The heats of formation predicted by the FPD method do not differ much from those previously derived from the NCEs at the CCSD(T)/aT level except for the CrO3 nanoclusters. New and improved heats of formation for Cr3O9 and Cr4O12 were obtained using PW91 orbitals instead of Hartree-Fock (HF) orbitals. Diffuse functions are necessary to predict accurate heats of formation. The fluoride affinities (FAs) are calculated with the CCSD(T) method. The relative energies (REs) of different isomers, NCEs, electron affinities (EAs), and FAs of (MO2)n ( M = Ti, Zr, Hf, n = 1 – 4 ) and (MO3)n ( M = Cr, Mo, W, n = 1 – 3) clusters have been benchmarked with 55 exchange-correlation DFT functionals including both pure and hybrid types. The absolute errors of the DFT results are mostly less than ±10 kcal/mol for the NCEs and the EAs, and less than ±15 kcal/mol for the FAs. Hybrid functionals usually perform better than the pure functionals for the REs and NCEs. The performance of the two types of functionals in predicting EAs and FAs is comparable. The B1B95 and PBE1PBE functionals provide reliable energetic properties for most isomers. Long range corrected pure functionals usually give poor FAs. The standard deviation of the absolute error is always close to the mean errors and the probability distributions of the DFT errors are often not Gaussian (normal). The breadth of the distribution of errors and the maximum probability are dependent on the energy property and the isomer.

  11. Bridging the gap between ionic liquids and molten salts: group 1 metal salts of the bistriflamide anion in the gas phase.

    Science.gov (United States)

    Leal, João P; da Piedade, Manuel E Minas; Canongia Lopes, José N; Tomaszowska, Alina A; Esperança, José M S S; Rebelo, Luís Paulo N; Seddon, Kenneth R

    2009-03-19

    Fourier transform ion cyclotron resonance mass spectrometry experiments showed that liquid Group 1 metal salts of the bistriflamide anion undergoing reduced-pressure distillation exhibit a remarkable behavior that is in transition between that of the vapor-liquid equilibrium characteristics of aprotic ionic liquids and that of the Group 1 metal halides: the unperturbed vapors resemble those of aprotic ionic liquids, in the sense that they are essentially composed of discrete ion pairs. However, the formation of large aggregates through a succession of ion-molecule reactions is closer to what might be expected for Group 1 metal halides. Similar experiments were also carried out with bis{(trifluoromethyl)sulfonyl}amine to investigate the effect of H(+), which despite being the smallest Group 1 cation, is generally regarded as a nonmetal species. In this case, instead of the complex ion-molecule reaction pattern found for the vapors of Group 1 metal salts, an equilibrium similar to those observed for aprotic ionic liquids was observed.

  12. Probing Interaction Between Platinum Group Metal (PGM) and Non-PGM Support Through Surface Characterization and Device Performance

    Science.gov (United States)

    Saha, Shibely

    High cost and limited abundance of Platinum (Pt) have hindered effective commercialization of Proton Exchange Membrane Fuel Cell and Electrolyzer. Efforts have been undertaken to reduce precious group metal (PGM) requirement for these devices without compromising the activity of the catalyst by using transition metal carbides (TMC) as non-PGM support thanks to their similar electronic and geometric structures as Pt. In this work Mo2C was selected as non-PGM support and Pt was used as the PGM of interest. We hypothesize that the hollow nanotube morphology of Mo2C support combined with Pt nano particles deposited on it via atomic layer deposition (ALD) technique would allow increased interaction between them which may increase the activity of Pt and Mo2C as well as maximize the Pt active surface area. Specifically, a rotary ALD equipment was used to grow Pt particles from atomic level to 2--3 nanometers by simply adjusting number of ALD cycles in order to probe the interaction between the deposited Pt nanoparticles and Mo2C nanotube support. Interaction between the Pt and Mo2 C was analyzed via surface characterization and electrochemical characterization. Interaction between Pt and Mo2C arises due to the lattice mismatch between Pt and Mo2C as well as electron migration between them. Lattice spacing analysis using high resolution transmission electron microscopy (HRTEM) images, combined with Pt binding energy shift in XPS results, clearly showed strong bonding between Pt nanoparticles and the Mo2C nanotube support in all the resultant Pt/Mo2C samples. We postulate that this strong interaction is responsible for the significantly enhanced durability observed in our constant potential electrolysis (CPE) and accelerated degradation testing (ADT). Of the three samples from different ALD cycles (15, 50 and 100), Mo2C nanotubes modified by 50 (1.07 wt% Pt loading) and 100 cycles (4.4 wt% Pt) of Pt deposition, showed higher HER and HOR activity per Pt mass than commercial

  13. Group 1 and group 2 metal complexes supported by a bidentate bulky iminopyrrolyl ligand: synthesis, structural diversity, and ε-caprolactone polymerization study.

    Science.gov (United States)

    Kottalanka, Ravi K; Harinath, A; Rej, Supriya; Panda, Tarun K

    2015-12-14

    We report here a series of alkali and alkaline earth metal complexes, each with a bulky iminopyrrolyl ligand [2-(Ph3CN=CH)C4H3NH] (1-H) moiety in their coordination sphere, synthesized using either alkane elimination or silylamine elimination methods or the salt metathesis route. The lithium salt of molecular composition [Li(2-(Ph3CN=CH)C4H3N)(THF)2] (2) was prepared using the alkane elimination method, and the silylamine elimination method was used to synthesize the dimeric sodium and tetra-nuclear potassium salts of composition [(2-(Ph3CN=CH)C4H3N)Na(THF)]2 (3) and [(2-(Ph3CN=CH)C4H3N)K(THF)0.5]4 (4) respectively. The magnesium complex of composition [(THF)2Mg(CH2Ph){2-(Ph3CN=CH)C4H3N}] (5) was synthesized through the alkane elimination method, in which [Mg(CH2Ph)2(OEt2)2] was treated with the bulky iminopyrrole ligand 1-H in 1 : 1 molar ratio, whereas the bis(iminopyrrolyl)magnesium complex [(THF)2Mg{2-(Ph3CN=CH)C4H3N}2] (6) was isolated using the salt metathesis route. The heavier alkaline earth metal complexes of the general formula {(THF)nM(2-(Ph3CN=CH)C4H3N)2} [M = Ca (7), Sr (8), and n = 2; M = Ba (9), n = 3] were prepared in pure form using two synthetic methods: in the first method, the bulky iminopyrrole ligand 1-H was directly treated with the alkaline earth metal precursor [M{N(SiMe3)2}2(THF)n] (where M = Ca, Sr and Ba) in 2 : 1 molar ratio in THF solvent at ambient temperature. The complexes 7-9 were also obtained using the salt metathesis reaction, which involves the treatment of the potassium salt (4) with the corresponding metal diiodides MI2 (M = Ca, Sr and Ba) in 2 : 1 molar ratio in THF solvent. The molecular structures of all the metal complexes (1-H, 2-9) in the solid state were established through single-crystal X-ray diffraction analysis. The complexes 5-9 were tested as catalysts for the ring-opening polymerization of ε-caprolactone. High activity was observed in the heavier alkaline earth metal complexes 7-9, with a very

  14. Chiral Sulfur Functional Groups as Definers of the Chirality at the Metal in Ir- and Rh-Half Sandwich Complexes: A Combined CD-X-ray Study.

    Science.gov (United States)

    Sierra, Miguel A; de la Torre, Maria C; Fernandez de la Pradilla, Roberto; Viso, Alma; Frutos, Maria; Avello, Marta G; Velado, Marina; Gornitzka, Heinz; Hemmert, Catherine

    2017-07-27

    Mesoionic carbenes (MIC) derived from triazolium salts containing chiral sulfoxide or sulfoximine functional groups lead to enantiopure chiral-at-metal Ir(III) and Rh(III) half-sandwich complexes, through the sequence MIC complexation-C-H aromatic activation. The process is efficient and totally diastereoselective in the formation of enantiopure five membered metallacycles. The use of the enantiomers of the sulfur chiral groups allows to prepare complexes having opposite configurations at the metal. Complete retention of the configuration at the metal center is observed during the formation of cationic Ir(III) complexes and upon insertion of alkynes into the Ir(III)-C bond, as demonstrated by a combined Circular Dichroism (CD)-X-ray study. These results point to vicinal assisted SN-like processes. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. The Regularities of Phase and Structural Transformation in Binary Titanium Alloys with Metals of IV—VIII Groups of the Periodic Table

    National Research Council Canada - National Science Library

    Dobromyslov, A V

    2008-01-01

    Martensitic β→α′(α″) and β→ω transformation in a series of Ti-base alloys with transition metals of groups IV-VIII have been investigated using the techniques of X-ray diffraction, optical and transmission electron microscopy...

  16. Synthesis of group 10 metal complexes with a new unsymmetrical PN3P-pincer ligand through ligand post-modification: Structure and reactivity

    KAUST Repository

    Wang, Xiufang

    2017-01-01

    A post-modification strategy are used to synthesize a new class of diimine-amido PN3P-pincer group-10 transition metal complexes. The coordination chemistry and the thermal stabilities of their organometallic derivatives are characterized and investigated.

  17. The chemistry of the most metal-rich damped Lyman $\\alpha$ systems at z$\\sim2$ II. Context with the Local Group

    CERN Document Server

    Berg, Trystyn A M; Prochaska, J Xavier; Venn, Kim A; Dessauges-Zavadsky, Miroslava

    2015-01-01

    Using our sample of the most metal-rich damped Lyman $\\alpha$ systems (DLAs) at z$\\sim2$, and two literature compilations of chemical abundances in 341 DLAs and 2818 stars, we present an analysis of the chemical composition of DLAs in the context of the Local Group. The metal-rich sample of DLAs at z$\\sim2$ probes metallicities as high as the Galactic disc and the most metal-rich dwarf spheroidals (dSphs), permitting an analysis of many elements typically observed in DLAs (Fe, Zn, Cr, Mn, Si, and S) in comparison to stellar abundances observed in the Galaxy and its satellites (in particular dSphs). Our main conclusions are: (1) non-solar [Zn/Fe] abundances in metal-poor Galactic stars and in dSphs over the full metallicity range probed by DLAs, suggest that Zn is not a simple proxy for Fe in DLAs and therefore not a suitable indicator of dust depletion. After correcting for dust depletion, the majority of DLAs have subsolar [Zn/Fe] similar to dSphs; (2) at [Fe/H]$\\sim-0.5$, a constant [Mn/Fe]$\\sim-0.5$ and ne...

  18. Evaluation of status of trace and toxic metals in biological samples (scalp hair, blood, and urine) of normal and anemic children of two age groups.

    Science.gov (United States)

    Shah, Faheem; Kazi, Tasneem Gul; Afridi, Hassan Imran; Kazi, Naveed; Baig, Jameel Ahmed; Shah, Abdul Qadir; Khan, Sumaira; Kolachi, Nida Fatima; Wadhwa, Sham Kumar

    2011-06-01

    Anemia affects a substantial portion of the world's population, provoking severe health problems as well as important economic losses to the region in which this condition is found. This study was designed to compare the levels of essential trace and toxic elements in scalp hair, blood, and urine samples of anemic children (n = 132) with age range 1-5 and 6-10 years of both genders. For a comparative study, 134 non-anemic age- and sex-matched children as control subjects, residing in the same city, were selected. The metals in the biological samples were measured by flame atomic absorption spectrophotometry/electrothermal atomic absorption spectrometry prior to microwave-assisted acid digestion. The proposed method was validated using certified reference samples of hair, blood, and urine. The results indicated significantly lower levels of iron, copper, and zinc in the biological samples as compared to the control children of both genders (p = 0.01-0.008). The mean values of lead and cadmium were significantly high in all three biological samples of anemic children as compared to non-anemic children of both age groups (p = 0.005-0.001). The ratios of essential metal to toxic metals in the biological samples of anemic children of both age groups were significantly lower than that of controls. Deficiency of essential trace metals and high level of toxic metals may play a role in the development of anemia in the subjects under study.

  19. Synthesis and Molecular Structure of A Bimetallic Salen Complex Containing Zn and La: A Disordered Nitrate Group Dancing between Two Metal Centers

    Institute of Scientific and Technical Information of China (English)

    Leon Dyers Jr; Donald Van Derveer; Xiu R Bu

    2005-01-01

    A new bimetallic complex containing Zn and La was prepared from a salen ligand possessing methoxyl groups at the 3, 3'-positions. The structural feature is that one of nitrate groups is disordered and displaced between two metal centers. Crystal system: Triclinic space group:P-1, Z=2. a=0.82714(17) nm, b=1.3484(3) (1) nm, and c=1.3898(3) (1) nm, α=79.89(3)°, β=76.67(3)°, and γ=72.43(3)°. V=1.428.6(5) nm3, Dx=1.812 g·cm-3. (Δρ)max=1.510×10-3 enm3, (Δρ)min=-1.503×10-3 enm3. Accordingly, two water molecules occupy the metal centers in the apical positions via the syn-geometry.

  20. Evidence for a metal-thiolate intermediate in alkyl group transfer from epoxypropane to coenzyme M and cooperative metal ion binding in epoxyalkane:CoM transferase.

    Science.gov (United States)

    Boyd, Jeffrey M; Ensign, Scott A

    2005-10-04

    Epoxyalkane:coenzyme M transferase (EaCoMT) catalyzes the nucleophilic addition of coenzyme M (CoM, 2-mercaptoethanesulfonic acid) to epoxypropane forming 2-hydroxypropyl-CoM. The biochemical properties of EaCoMT suggest that the enzyme belongs to the family of alkyltransferase enzymes for which Zn plays a role in activating an organic thiol substrate for nucleophilic attack on an alkyl-donating substrate. The enzyme has a hexameric (alpha(6)) structure with one zinc atom per subunit. In the present work M(2+) binding and the role of Zn(2+) in EaCoMT have been established through a combination of biochemical, calorimetric, and spectroscopic techniques. A variety of metal ions, including Zn(2+), Co(2+), Cd(2+), and Ni(2+), were capable of activating a Zn-deficient "apo" form of EaCoMT, affording enzymes with various levels of activity. Titration of Co(2+) into apo-EaCoMT resulted in UV-visible spectroscopic changes consistent with the formation of a tetrahedral Co(2+) binding site, with coordination of bound Co(2+) to two thiolate ligands. Quantification of UV-visible spectral changes upon Co(2+) titration into apo-EaCoMT demonstrated that EaCoMT binds Co(2+) cooperatively at six interacting sites. Isothermal titration calorimetric studies of Co(2+) and Zn(2+) binding to EaCoMT also showed cooperativity for metal ion binding among six sites. The addition of CoM to Co(2+)-substituted EaCoMT resulted in UV-visible spectral changes indicative of formation of a new thiol-Co(2+) bond. Co(2+)-substituted EaCoMT exhibited a unique Co(2+) EPR spectrum, and this spectrum was perturbed significantly upon addition of CoM. The presence of a divalent metal ion was required for the release of protons from CoM upon binding to EaCoMT, with Zn(2+), Co(2+), and Cd(2+) each facilitating proton release. The divalent metal ion of EaCoMT is proposed to play a key role in the coordination and deprotonation of CoM, possibly through formation of a metal-thiolate that is activated for attack

  1. Tamm plasmon-polariton with negative group velocity induced by a negative index meta-material capping layer at metal-Bragg reflector interface.

    Science.gov (United States)

    Liu, Cunding; Kong, Mingdong; Li, Bincheng

    2014-05-05

    Influence of a negative refractive index meta-material (NIM) capping layer on properties of Tamm plasmon-polariton at the interface of metal-Bragg reflector structure is investigated. Conditions for excitation of the plasmon-polariton is determined from reflectivity mapping calculation and analyzed with cavity mode theory. For specific thicknesses of capping layers, Tamm plasmon-polariton with negative group velocity is revealed in a wide region of frequency. Different from backward optical propagation induced by negative effective-group-refractive-index in dispersive media, negative group velocity of Tamm plasmon-polariton results from opposite signs of cross-section-integrated field energy and Poynting vector.

  2. Effect of the ortho-hydroxy group of salicylaldehyde in the A3 coupling reaction: A metal-catalyst-free synthesis of propargylamine

    Directory of Open Access Journals (Sweden)

    Sujit Ghosh

    2017-03-01

    Full Text Available The synthesis of propargylamines via A3 coupling mostly under metal-catalyzed procedures is well known. This work invented an unprecedented effect of salicylaldehyde, one of the A3 coupling partners, which could lead to the formation of propargylamine, an important pharmaceutical building block, in the absence of any metal catalyst and under mild conditions. The role of the hydroxy group in ortho position of salicylaldehyde has been explored, which presumably activates the Csp–H bond of the terminal alkyne leading to the formation of propargylamines in good to excellent yields, thus negating the function of the metal catalyst. This observation is hitherto unknown, tested for a variety of salicylaldehyde, amine and acetylene, established as a general protocol, and is believed to be of interest for synthetic chemists from green chemistry.

  3. Encapsulation of hydride by molecular main group metal clusters: manipulating the source and coordination sphere of the interstitial ion.

    Science.gov (United States)

    Boss, Sally R; Coles, Martyn P; Eyre-Brook, Vicki; García, Felipe; Haigh, Robert; Hitchcock, Peter B; McPartlin, Mary; Morey, James V; Naka, Hiroshi; Raithby, Paul R; Sparkes, Hazel A; Tate, Christopher W; Wheatley, Andrew E H

    2006-12-21

    The sequential treatment of Lewis acids with N,N'-bidentate ligands and thereafter with ButLi has afforded a series of hydride-encapsulating alkali metal polyhedra. While the use of Me3Al in conjunction with Ph(2-C5H4N)NH gives Ph(2-C5H4N)NAlMe2 and this reacts with MeLi in thf to yield the simple 'ate complex Ph(2-C5H4N)NAlMe3Li.thf, the employment of an organolithium substrate capable of beta-hydride elimination redirects the reaction significantly. Whereas the use of ButLi has previously yielded a main group interstitial hydride in which H- exhibits micro6-coordination, it is shown here that variability in the coordination sphere of the encapsulated hydride may be induced by manipulation of the organic ligand. Reaction of (c-C6H11)(2-C5H4N)NH with Me3Al/ButLi yields [{(c-C6H11)(2-C5H4N)N}6HLi8]+[(But2AlMe2)2Li]-, which is best viewed as incorporating only linear di-coordination of the hydride ion. The guanidine 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine (hppH) in conjunction with Me2Zn/ButLi yields the micro8-hydride [(hpp)6HLi8]+[But3Zn]-.0.5PhMe. Formation of the micro8-hydride [(hpp)6HLi8]+[ButBEt3]- is revealed by employment of the system Et3B/ButLi. A new and potentially versatile route to interstitial hydrides of this class is revealed by synthesis of the mixed borohydride-lithium hydride species [(hpp)6HLi8]+[Et3BH]- and [(hpp)6HLi8]+[(Et3B)2H]- through the direct combination of hppLi with Et3BHLi.

  4. Protecting group and switchable pore-discriminating adsorption properties of a hydrophilic-hydrophobic metal-organic framework

    Science.gov (United States)

    Mohideen, M. Infas H.; Xiao, Bo; Wheatley, Paul S.; McKinlay, Alistair C.; Li, Yang; Slawin, Alexandra M. Z.; Aldous, David W.; Cessford, Naomi F.; Düren, Tina; Zhao, Xuebo; Gill, Rachel; Thomas, K. Mark; Griffin, John M.; Ashbrook, Sharon E.; Morris, Russell E.

    2011-04-01

    Formed by linking metals or metal clusters through organic linkers, metal-organic frameworks are a class of solids with structural and chemical properties that mark them out as candidates for many emerging gas storage, separation, catalysis and biomedical applications. Important features of these materials include their high porosity and their flexibility in response to chemical or physical stimuli. Here, a copper-based metal-organic framework has been prepared in which the starting linker (benzene-1,3,5-tricarboxylic acid) undergoes selective monoesterification during synthesis to produce a solid with two different channel systems, lined by hydrophilic and hydrophobic surfaces, respectively. The material reacts differently to gases or vapours of dissimilar chemistry, some stimulating subtle framework flexibility or showing kinetic adsorption effects. Adsorption can be switched between the two channels by judicious choice of the conditions. The monoesterified linker is recoverable in quantitative yield, demonstrating possible uses of metal-organic frameworks in molecular synthetic chemistry as ‘protecting groups’ to accomplish selective transformations that are difficult using standard chemistry techniques.

  5. Vibrational spectra of bis(dmit) complexes of main group metals: IR, Raman and ab initio calculations

    OpenAIRE

    Ferreira,Glaucio B.; Nadia M. Comerlato; Wardell, James L.; Hollauer,Eduardo

    2004-01-01

    This work reports a theoretical-experimental investigation of the infrared/Raman vibrational spectra of several metal 1,3-dithole-2-thione-4,5-dithiolate (dmit) complexes; [NEt4]2[Zn(dmit)2], [NEt4][Sb(dmit)2] and [NEt4][Bi(dmit)2]. IR/Raman spectra of all the solids and the solution IR spectrum of [NEt4]2[Zn(dmit)2] were recorded from 4000 to 100 cm-1. Two regions were clearly identified: below 380 cm-1, the modes presented significant metal-ligand contributions, and above, the modes indicat...

  6. Preparation of magnetic metal organic frameworks adsorbent modified with mercapto groups for the extraction and analysis of lead in food samples by flame atomic absorption spectrometry.

    Science.gov (United States)

    Wang, Yang; Chen, Huanhuan; Tang, Jie; Ye, Guiqin; Ge, Huali; Hu, Xiaoya

    2015-08-15

    A novel magnetic metal organic frameworks adsorbent modified with mercapto groups was synthesized and developed for extraction and spectrophotometric determination of trace lead. The adsorbent was characterized by Fourier transforms infrared spectrometer, X-ray diffraction, scanning electron microscopy and vibrating sample magnetometry. The results indicated the adsorbents exhibited high adsorption capacities for lead due to the chelation mechanism between metal cations and mercapto groups. Meanwhile, the lead sorption onto the adsorbents could be easily separated from aqueous solution using a magnetic separation method. Under the optimal conditions, a linear calibration curve in the range from 1 to 20 μg L(-1) was achieved with an enrichment factor of 100. The limits of detection and quantitation for lead were found to be 0.29 and 0.97 μg L(-1), respectively. The developed method was successfully applied to the determination of trace amounts of lead in food samples and certified reference material with satisfactory results.

  7. Versatile structures of group 13 metal halide complexes with 4,4'-bipy: from 1D coordination polymers to 2D and 3D metal-organic frameworks.

    Science.gov (United States)

    Sevastianova, Tatiana N; Bodensteiner, Michael; Maulieva, Albina F; Davydova, Elena I; Virovets, Alexander V; Peresypkina, Eugenia V; Balázs, Gábor; Graßl, Christian; Seidl, Michael; Scheer, Manfred; Frenking, Gernot; Berezovskaya, Ekaterina A; Kazakov, Igor V; Khoroshilova, Olesya V; Timoshkin, Alexey Y

    2015-12-21

    A systematic structural study of complexes formed by aluminium and gallium trihalides with 4,4'-bipyridine (bipy) in 2 : 1, 1 : 1, and 1 : 2 stoichiometric ratios has been performed. Molecular structures of 11 complexes in the solid state have been determined for the first time. Complexes of 2 : 1 composition are molecular, while complexes of 1 : 1 composition form metal-organic frameworks of different kinds: an ionic 3D network (three interpenetrated lvt nets for AlCl3bipy), an ionic 2D network for AlBr3bipy and GaBr3bipy and a 1D coordination polymer in the case of GaCl3bipy. Thus, the nature of the Lewis acid plays a critical role in the structural type of the complex in the solid state. Incorporation of excess bipy molecules into (GaCl3bipy)∞ (formation of crystallosolvate) leads to an unprecedented change of the molecular structure from a non-ionic 1D coordination polymer to an ionic 2D metal organic framework [GaCl2bipy2](+)[GaCl4](-)·2bipy. As indicated by the temperature-dependent XRD study, removal of bipy by heating in a vacuum restores the non-ionic 1D structure. Quantum chemical computations for simple cluster model systems (up to eight Al and Ga atoms) reveal that ionic forms are slightly favourable, although the energy differences between the ionic and non-ionic structures are not large. These theoretical predictions are in good agreement with experimental findings. Thus, even relatively simple cluster models may be used to indicate the structural preferences in the solid state. Both experimental and computational IR frequency shifts of the in-plane ring bending mode of bipy upon complexation correlate well with the M-N bond distances in the complexes.

  8. Half-sandwich pentamethylcyclopentadienyl group 9 metal complexes of 2-aminopyridyl ligands: Synthesis, spectral and molecular study

    Indian Academy of Sciences (India)

    Mahesh Kalidasan; Scott Forbes; Yurij Mozharivskyj; Mohan Rao Kollipara

    2015-06-01

    Thereaction of [Cp*M(-Cl)Cl]2 (M = Rh, Ir) with 2-aminopyridyl based ligands lead to the formation of mononuclear neutral complexes of general formula [Cp*MCl2(L)] {where L1= 2-aminopyridine, L2= 2-amino-3-picoline, L3= 2-amino-3-nirtopyridine, and L4= 2-amino-3-pyridine carboxyaldehyde}. The complexes have been characterized by FT-IR, UV-Vis, 1H-13C NMR and mass spectroscopic methods. X-ray crystallographic studies of the complexes have shown typical piano-stool geometry around the metal centre in which 2-aminopyridyl ligand acts as an N-monodentate ligand and the amino functionality is not involved in metal coordination. The intra/intermolecular arrangement is due to hydrogen bonding.

  9. Ferromagnetism in IV main group element (C and transition metal (Mn doped MgO: A density functional perspective

    Directory of Open Access Journals (Sweden)

    Vinit Sharma

    2011-09-01

    Full Text Available The formation of magnetic moment due to the dopants with p-orbital (d-orbital is named d0 (d − magnetism, where the ion without (with partially filled d states is found to be responsible for the observed magnetic properties. To study the origin of magnetism at a fundamental electronic level in such materials, as a representative case, we theoretically investigate ferromagnetism in MgO doped with transition metal (Mn and non-metal (C. The generalized gradient approximation based first-principles calculations are used to investigate substitutional doping of metal (Mn and non-metal (C, both with and without the presence of neighboring oxygen vacancy sites. Furthermore, the case of co-doping of (Mn, C in MgO system is also investigated. It is observed that the oxygen vacancies do not play a role in tuning the ferromagnetism in presence of Mn dopants, but have a significant influence on total magnetism of the C doped system. In fact, we find that in MgO the d0 magnetism through C doping is curtailed by pairing of the substitutional dopant with naturally occurring O vacancies. On the other hand, in case of (Mn, C co-doped MgO the strong hybridization between the C (2p and the Mn(3d states suggests that co-doping is a promising approach to enhance the ferromagnetic coupling between the nearest-neighboring dopant and host atoms. Therefore, (Mn,C co-doped MgO is expected to be a ferromagnetic semiconductor with long ranged ferromagnetism and high Curie temperature.

  10. Mesomorphism and Optical Properties of Peripherally Substituted Phthalocyanines: Influence of Chain Length, Linking Group and Central Metal Ion

    OpenAIRE

    Sleven, Jurgen

    2002-01-01

    Phthalocyanines form a colourful class of macrocyclic compounds, attracting the attention of many scientists. Some of these compounds – especially the metal containing phthalocyanines – play an important role in industrial activity and in society. Applications for phthalocyanines are found in the fields of non-linear optics, catalysis, electronic (bio)sensors, photovoltaic solar cells, optical data storage, lubricants, photo- and radiosensitizers for treatment of cancer, protein inhibitors … ...

  11. Stellar metallicities beyond the Local Group: the potential of J-band spectroscopy with extremely large telescopes

    CERN Document Server

    Evans, C J; Kudritzki, R -P; Puech, M; Yang, Y; Cuby, J -G; Figer, D F; Lehnert, M D; Morris, S L; Rousset, G

    2010-01-01

    We present simulated J-band spectroscopy of red giants and supergiants with a 42m European Extremely Large Telescope (E-ELT), using tools developed toward the EAGLE Phase A instrument study. The simulated spectra are used to demonstrate the validity of the 1.15-1.22 micron region to recover accurate stellar metallicities from Solar and metal-poor (one tenth Solar) spectral templates. From tests at spectral resolving powers of four and ten thousand, we require continuum signal-to-noise ratios in excess of 50 (per two-pixel resolution element) to recover the input metallicity to within 0.1 dex. We highlight the potential of direct estimates of stellar metallicites (over the range -1<[Fe/H]<0) of red giants with the E-ELT, reaching out to distances of ~5 Mpc for stars near the tip of the red giant branch. The same simulations are also used to illustrate the potential for quantitative spectroscopy of red supergiants beyond the Local Volume to tens of Mpc. Calcium triplet observations in the I-band are also ...

  12. Synthesis and Reactivity of Group 6 Metal Carbonyl Complexes with Bis(pyrazol-1-yl)methanes Modified by the Vinyltin Groups

    Institute of Scientific and Technical Information of China (English)

    WEN,Zhenkang; YANG,Zhi; SONG,Haibin; TANG,Liangfu

    2009-01-01

    Diphenyl(vinyl)stannylbis(3,5-dimethylpyrazol-1-yl)methane and diphenyl(vinyl)stannylbis(3,4,5-trimethyl-pyrazol-1-yl)methane have been synthesized by the reaction of bis(3,5-dimethylpyrazol-1-yl)methyl or bis(3,4,5-trimethylpyrazol-1-yl)methyllithium with diphenyl(vinyl)tin iodide. Treatment of these bis(pyrazol-l-yl)methanes modified by the vinyltin groups with M(CO)5THF (M=Mo and W) in refluxing THF resulted in new heterobimeto allic complexes R3SnCHPz2M(CO)3 (R3Sn represents trivinyltin or diphenyl(vinyl)tin, and Pz represents substituted pyrazol-1-yl), in which a vinyl group bonds to the molybdenum or tungsten atom in η2-fashion to lead to bis(pyrazol-1-yl)methanes acting as a tridentate κ3-(π,N,N) ligand. Reaction of (CH2 = CH)3SnCH(3,5-Me2Pz)2W(CO)3 and Ph2(CH2=CH)SnCH(3,5-Me2Pz)2W(CO)3 with I2 has been investigated. The former gave a complex CH2(3,5-Me2Pz)2W(CO)4, while the latter yielded a four-membered heterometallocyclic complex CH(3,5-Me2Pz)2W(CO)3 I with the loss of the organotin group. Treatment of this four-membered heterometallocyc-lic complex with PhSNa led to the iodide anion replaced by the thiophenolate anion to give a complex CH(3,5-Me2Pz)2W(CO)3SPh.

  13. Experimental observations on noble metal nanonuggets and Fe-Ti oxides, and the transport of platinum group elements in silicate melts

    Science.gov (United States)

    Anenburg, Michael; Mavrogenes, John A.

    2016-11-01

    Platinum group element (PGE) nanonuggets are a nuisance in experimental studies designed to measure solubility or partitioning of noble metals in silicate melts. Instead of treating nanonuggets as experimental artifacts, we studied their behaviour motivated by recent discoveries of PGE nanonuggets in a variety of natural settings. We used an experimental setup consisting of AgPd, Pt or AuPd capsules and Fe(-Ti) oxide-saturated hydrous peralkaline silicate melts to maximise nanonugget production. TABS (Te, As, Bi, Sb, Sn) commonly occur in PGM (platinum group minerals), prompting addition of Bi to our experiments to investigate its properties as well. Three-dimensional optical examination by 100× objective and immersion oil reveals variable colour which correlates with nanonugget size and shape due to plasmon resonance effects. We observe two textural types: (1) intermediate-sized nanonuggets dispersed in the glass and adhering to oxides, and (2) abundant fine nanonuggets dispersed in the glass with coarse euhedral crystals in contact with oxides. Slow cooling removes dispersed nanonuggets and greatly coarsens existing oxide-associated metal crystals. Nanonugget-free halos are commonly observed around oxide grains. All metal phases are composed of major (Ag, Pd) and trace (Pt, Ir, Au) capsule material. Our results show reduction processes, imposed by growing oxides, causing local metal saturation in the oxide rich zones with preferential nucleation on smaller oxide grains. The redox gradient then blocks additional metals from diffusing into oxide rich zones, forming halos. As the entire experimental charge is reduced throughout the run, nanonuggets form in the distal glass. Bismuth contents of metal phases do not depend on Bi2O3 amounts dissolved in the melt. Further PGM crystallisation consumes nanonuggets as feedstock. We conclude that the appearance of metallic PGE phases happens in two stages: first as nanonuggets and then as larger PGM. Once formed

  14. Molecular and ionic-scale chemical mechanisms behind the role of nitrocyl group in the electrochemical removal of heavy metals from sludge

    Science.gov (United States)

    Hasan, S. W.; Ahmed, I.; Housani, A. A.; Giwa, A.

    2016-08-01

    The chemical basis for improved removal rates of toxic heavy metals such as Zn and Cu from wastewater secondary sludge has been demonstrated in this study. Instead of using excess corrosive chemicals as the source of free nitrous acid (FNA) for improved solubility of heavy metals in the sludge (in order to enhance electrokinetics), an optimized use of aqua regia has been proposed as an alternative. Fragments of nitrocyl group originated from aqua regia are responsible for the disruption of biogenic mixed liquor volatile suspended solids (MLVSS) and this disruption resulted in enhanced removal of exposed and oxidized metal ions. A diversity of nitric oxide (NO), peroxy nitrous acid, and peroxy nitroso group are expected to be introduced in the mixed liquor by the aqua regia for enhanced electrochemical treatment. The effects of pectin as a post treatment on the Zn removal from sludge were also presented for the first time. Results revealed 63.6% Cu and 93.7% Zn removal efficiencies, as compared to 49% Cu and 74% Zn removal efficiencies reported in a recent study. Also, 93.3% reduction of time-to-filter (TTF), and 95 mL/g of sludge volume index (SVI) were reported. The total operating cost obtained was USD 1.972/wet ton.

  15. Synthesis of main group, rare-earth, and d{sup 0} metal complexes containing beta-hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Ka King [Iowa State Univ., Ames, IA (United States)

    2013-01-01

    A series of organometallic compounds containing the tris(dimethylsilyl)methyl ligand are described. The potassium carbanions KC(SiHMe2)3 and KC(SiHMe2})3TMEDA are synthesized by deprotonation of the hydrocarbon HC(SiHMe2)3 with potassium benzyl. KC(SiHMe2)3TMEDA crystallizes as a dimer with two types of three-center-two-electron KH- Si interactions. Homoleptic Ln(III) tris(silylalkyl) complexes containing β-SiH groups M{C(SiHMe2)3}3 (Ln = Y, Lu, La) are synthesized from salt elimination of the corresponding lanthanide halide and 3 equiv. of KC(SiHMe2)3. The related reactions with Sc yield bis(silylalkyl) ate-complexes containing either LiCl or KCl. The divalent calcium and ytterbium compounds M{C(SiHMe2)3}2L (M = Ca, Yb; L = THF2 or TMEDA) are prepared from MI2 and 2 equiv of KC(SiHMe2)3. The compounds M{C(SiHMe2)3}2L (M = Ca, Yb; L = THF2 or TMEDA) and La{C(SiHMe2)3}3 react with 1 equiv of B(C6F5)3 to give 1,3- disilacyclobutane {Me2Si-C(SiHMe2)2}2 and MC(SiHMe2)3HB(C6F5)3L, and La{C(SiHMe2)3}2HB(C6F5)3, respectively. The corresponding reactions of Ln{C(SiHMe2)3}3 (Ln = Y, Lu) give the β-SiH abstraction product [{(Me2HSi)3C}2LnC(SiHMe2)2SiMe2][HB(C6F5)3] (Ln = Y, Lu), but the silene remains associated with the Y or Lu center. The abstraction reactions of M{C(SiHMe2)3}2L (M = Ca, Yb; L = THF2or TMEDA) and Ln{C(SiHMe2)3}3 (Ln = Y, Lu, La) and 2 equiv of B(C6

  16. Synthesis of main group, rare-earth, and d{sup 0} metal complexes containing beta-hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Ka King [Iowa State Univ., Ames, IA (United States)

    2013-01-01

    A series of organometallic compounds containing the tris(dimethylsilyl)methyl ligand are described. The potassium carbanions KC(SiHMe2)3 and KC(SiHMe2})3TMEDA are synthesized by deprotonation of the hydrocarbon HC(SiHMe2)3 with potassium benzyl. KC(SiHMe2)3TMEDA crystallizes as a dimer with two types of three-center-two-electron KH- Si interactions. Homoleptic Ln(III) tris(silylalkyl) complexes containing β-SiH groups M{C(SiHMe2)3}3 (Ln = Y, Lu, La) are synthesized from salt elimination of the corresponding lanthanide halide and 3 equiv. of KC(SiHMe2)3. The related reactions with Sc yield bis(silylalkyl) ate-complexes containing either LiCl or KCl. The divalent calcium and ytterbium compounds M{C(SiHMe2)3}2L (M = Ca, Yb; L = THF2 or TMEDA) are prepared from MI2 and 2 equiv of KC(SiHMe2)3. The compounds M{C(SiHMe2)3}2L (M = Ca, Yb; L = THF2 or TMEDA) and La{C(SiHMe2)3}3 react with 1 equiv of B(C6F5)3 to give 1,3- disilacyclobutane {Me2Si-C(SiHMe2)2}2 and MC(SiHMe2)3HB(C6F5)3L, and La{C(SiHMe2)3}2HB(C6F5)3, respectively. The corresponding reactions of Ln{C(SiHMe2)3}3 (Ln = Y, Lu) give the β-SiH abstraction product [{(Me2HSi)3C}2LnC(SiHMe2)2SiMe2][HB(C6F5)3] (Ln = Y, Lu), but the silene remains associated with the Y or Lu center. The abstraction reactions of M{C(SiHMe2)3}2L (M = Ca, Yb; L = THF2or TMEDA) and Ln{C(SiHMe2)3}3 (Ln = Y, Lu, La) and 2 equiv of B(C6

  17. Synthesis and characterization of near-IR absorbing metal-free and zinc(II phthalocyanines modified with aromatic azo groups

    Directory of Open Access Journals (Sweden)

    Mukaddes Özçeşmeci

    2015-05-01

    Full Text Available Metal-free and zinc(II phthalocyanine complexes bearing peripheral (E-4-((2-hydroxynaphthalen-1-yldiazenyl units have been synthesized. Novel phthalonitrile derivative required for the preparation of phthalocyanine complexes was prepared by coupling 4-aminophthalonitrile and 2-naphthol. The structures of these new compounds were characterized by using elemental analyses, proton nuclear magnetic resonance, fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, fluorescence spectroscopy and mass spectrometry. In the UV-Vis spectra a broad absorption band appears for phthalocyanine complexes at around 450–500 nm resulting from azo-group introduced onto the phthalocyanine ring. The photophysical properties of metal-free and zinc(II phthalocyanines were studied in tetrahydrofuran.

  18. Stable two-channel Kondo fixed point of an SU(3) quantum defect in a metal: renormalization-group analysis and conductance spikes.

    Science.gov (United States)

    Arnold, Michael; Langenbruch, Tobias; Kroha, Johann

    2007-11-02

    We propose a physical realization of the two-channel Kondo (2CK) effect, where a dynamical defect in a metal has a unique ground state and twofold degenerate excited states. In a wide range of parameters the interactions with the electrons renormalize the excited doublet downward below the bare defect ground state, thus stabilizing the 2CK fixed point. In addition to the Kondo temperature T(K) the three-state defect exhibits another low-energy scale, associated with ground-to-excited-state transitions, which can be exponentially smaller than T(K). Using the perturbative nonequilibrium renormalization group we demonstrate that this can provide the long-sought explanation of the sharp conductance spikes observed by Ralph and Buhrman in ultrasmall metallic point contacts.

  19. I-PfoP3I: a novel nicking HNH homing endonuclease encoded in the group I intron of the DNA polymerase gene in Phormidium foveolarum phage Pf-WMP3.

    Directory of Open Access Journals (Sweden)

    Shuanglei Kong

    Full Text Available Homing endonucleases encoded in a group I self-splicing intron in a protein-coding gene in cyanophage genomes have not been reported, apart from some free-standing homing edonucleases. In this study, a nicking DNA endonuclease, I-PfoP3I, encoded in a group IA2 intron in the DNA polymerase gene of a T7-like cyanophage Pf-WMP3, which infects the freshwater cyanobacterium Phormidium foveolarum is described. The Pf-WMP3 intron splices efficiently in vivo and self-splices in vitro simultaneously during transcription. I-PfoP3I belongs to the HNH family with an unconventional C-terminal HNH motif. I-PfoP3I nicks the intron-minus Pf-WMP3 DNA polymerase gene more efficiently than the Pf-WMP4 DNA polymerase gene that lacks any intervening sequence in vitro, indicating the variable capacity of I-PfoP3I. I-PfoP3I cleaves 4 nt upstream of the intron insertion site on the coding strand of EXON 1 on both intron-minus Pf-WMP3 and Pf-WMP4 DNA polymerase genes. Using an in vitro cleavage assay and scanning deletion mutants of the intronless target site, the minimal recognition site was determined to be a 14 bp region downstream of the cut site. I-PfoP3I requires Mg(2+, Ca(2+ or Mn(2+ for nicking activity. Phylogenetic analysis suggests that the intron and homing endonuclease gene elements might be inserted in Pf-WMP3 genome individually after differentiation from Pf-WMP4. To our knowledge, this is the first report of the presence of a group I self-splicing intron encoding a functional homing endonuclease in a protein-coding gene in a cyanophage genome.

  20. Determination of Stability Constants of Triazole Ligand Carrying Naphthol Group with Heavy Metal Ions in Aqueous Solutions

    Directory of Open Access Journals (Sweden)

    Nurhan Gümrükçüoğlu

    2013-12-01

    Full Text Available Interaction of 4-(2-hydroxy-1-naphthylmethylamino-3-methyl-5-(4-tolyl-4H-1,2,4-triazole with heavy metal cations such as Cu2+, Co2+, Cd2+, Ni2+ and Pb2+ was investigated by using UV-visible spectrophotometric technique. The complex stability constants (Log β were determined in aqueous as well as in methanol: water (1:1 system at 25 ± 0.1°C by Buschmann’s method and Valeur’s methods, respectively. The ligand showed good sensitivity for Co2+ with a linear range of 210-6M to 310-5M.

  1. Doping anatase TIO_{2} with group V-b and VI-b transition metal atoms : a hybrid functional first-principles study

    OpenAIRE

    Matsubara, Masahiko; Saniz, Rolando; Partoens, Bart; Lamoen, Dirk

    2017-01-01

    Abstract: We investigate the role of transition metal atoms of group V-b (V, Nb, and Ta) and VI-b (Cr, Mo, and W) as n- or p-type dopants in anatase TiO2 using thermodynamic principles and density functional theory with the HeydScuseriaErnzerhof HSE06 hybrid functional. The HSE06 functional provides a realistic value for the band gap, which ensures a correct classification of dopants as shallow or deep donors or acceptors. Defect formation energies and thermodynamic transition levels are calc...

  2. Levels of Platinum Group Metals in Selected Species (Sarotherodon melanotheron, Chonophorus lateristriga, Macrobrachium vollenhovenii and Crassostrea tulipa in Some Estuaries and Lagoons Along the Coast of Ghana

    Directory of Open Access Journals (Sweden)

    D. K. Essumang

    2010-01-01

    Full Text Available The use of some biota as bioindicators of heavy metal pollution has been demonstrated as particularly adequate due to their capacity of bioconcentration. This study evaluated the levels of platinum group metals (PGMs in some selected species along the coastal belt of Ghana, using the neutron activation analysis (NAA method. The result was processed to evaluate pollution indices in order to map the distribution of the metals in those species in the lagoons and estuaries along the costal belt of Ghana. The analysis showed significant levels of all PGMs in blackchin tilapia (Sarotherodon melanotheron Cichlidae, brown goby (Chonophorus lateristriga Gobiidae, shrimp (Macrobrachium vollenhovenii Palaemonidae, and mangrove oysters (Crassostrea tulipa Ostreidae in the lagoons and river Pra estuary. However, the oysters showed an elevated mean concentration of 0.13 μ/g (dry weight Pd. From the pollution indices, most of the sampling sites registered mean contamination factor (CF values between 1.20 and 3.00 for Pt, Pd, and Rh. The pollution load index (PLI conducted also gave an average pollution index between 0.79 and 2.37, indicating progressive contamination levels. The results revealed that anthropogenic sources, industrial and hospital effluent, etc., together with vehicular emissions, could be the contributing factors to the deposition of PGMs along the Ghanaian coast.

  3. Chelation ion chromatography of alkaline earth and transition metals a using monolithic silica column with bonded N-hydroxyethyliminodiacetic acid functional groups.

    Science.gov (United States)

    McGillicuddy, Nicola; Nesterenko, Ekaterina P; Nesterenko, Pavel N; Jones, Phil; Paull, Brett

    2013-02-08

    A commercially available porous silica monolithic column (Onyx Monolithic Si, 100 mm×4.6 mm I.D.) was 'in-column' covalently functionalised with 2-hydroxyethyliminodiacetic acid (HEIDA) groups, and applied to the simultaneous and rapid separation of alkaline earth and transition metal ions, using high-performance chelation ion chromatography (HPCIC). With a 0.3mM dipicolinic acid (DPA) containing eluent, the baseline separation of various common transition and heavy metal ions and the four alkaline earth metal ions could be achieved in under 14 min with a flow rate of just 0.8 mL/min. Detection was achieved using spectrophotometric detection at 540 nm after post-column reaction (PCR) with 4-(2-pyridylazo)-resorcinol (PAR). Significant effects from variation of eluent nature, concentration and temperature upon selectivity and retention were demonstrated with the new monolithic silica chelating phase. Under optimised conditions (0.165 M LiNO(3) eluent, pH 2.5), peak efficiencies of 54,000, 60,000 and 64,000 N/m, for Zn(2+), Mn(2+) and Cd(2+), respectively, were recorded, far exceeding that previously reported for IDA based chelation ion exchange columns.

  4. Extraction equilibria of various metal picrates with 19-crown-6 between benzene and water. Effect of the extra methylene group on extraction ability and selectivity.

    Science.gov (United States)

    Katsuta, S; Kanazawa, M; Takeda, Y; Ouchi, M

    1999-07-12

    The overall extraction equilibrium constants (K(ex)) of picrates of Li(+), Na(+), K(+), Rb(+), Cs(+), Ag(+), Tl(+), and Sr(2+)with 19-crown-6 (19C6) were determined between benzene and water at 25 degrees C. The K(ex) values were analyzed into the constituent equilibrium constants, i.e. the extraction constant of picric acid, the distribution constant of the crown ether, the formation constant of the metal ion-crown ether complex in water, and the ion-pair extraction constant of the complex cation with the picrate anion. The effects of an extra methylene group of 19C6 on the extraction ability and selectivity are discussed in detail by comparing the constituent equilibrium constants of 19C6 with those of 18-crown-6 (18C6). The K(ex) value of 19C6 for each metal ion is lower than that of 18C6, which is mostly attributed to the higher lipophilicity of 19C6. The extraction ability of 19C6 for the univalent metal ions decreases in the order Tl(+)>K(+)>Rb(+)>Ag(+)>Cs(+)>Na(+)Li(+), which is the same as that observed for 18C6. The difference in logK(ex) between the univalent metals is generally smaller for 19C6 than for 18C6. The extraction selectivity of 19C6 is governed by the selectivity in the ion-pair extraction, whereas that of 18C6 depends on both the selectivities in the ion-pair extraction and in the complexation in water.

  5. Metathesis of carbon dioxide and phenyl isocyanate catalysed by group(IV) metal alkoxides: An experimental and computational study

    Indian Academy of Sciences (India)

    Akshai Kumar; Ashoka G Samuelson

    2011-01-01

    The insertion reactions of zirconium(IV) -butoxide and titanium(IV) -butoxide with a heterocumulene like carbodiimide, carbon dioxide or phenyl isocyanate are compared. Both give an intermediate which carries out metathesis at elevated temperatures by inserting a second heterocumulene in a head-to-head fashion. The intermediate metallacycle extrudes a new heterocumulene, different from the two that have inserted leading to metathesis. As the reaction is reversible, catalytic metathesis is feasible. In stoichiometric reactions heterocumulene insertion, metathesis and metathesis cum insertion products are observed. However, catalytic amounts of the metal alkoxide primarily led to metathesis products. It is shown that zirconium alkoxides promote catalytic metathesis (isocyanates, carbon dioxide) more efficiently than the corresponding titanium alkoxide. The difference in the metathetic activity of these alkoxides has been explained by a computational study using model complexes Ti(OMe)4 (1bTi) and Zr(OMe)4 (1bZr). The computation was carried out at the B3LYP/LANL2DZ level of theory.

  6. Catalytic transformations of fatty acids derivatives for food, oleochemicals and fuels over carbon supported platinum group metals

    Energy Technology Data Exchange (ETDEWEB)

    Simakova, I.

    2010-07-01

    prominent in linoleic acid deoxygenation giving only 3 % conversion of fatty acids in 330 min. The deactivation originated from the formation of C17 aromatic compounds and fatty acid dimers via Diels-Alder reaction. Thus hydrogenation of unsaturated fatty acids can be considered as preliminary chemical modification step in the green diesel production. In this work particular care was taken to strengthen the nano level understanding of the Pd role, in particular metal size effect, in the catalytic hydrogenation and deoxygenation. Pd/C catalysts were synthesized with the same Pd loading and systematically varied metal dispersion via the controllable formation of Pd particles over carbon support surface. The effect of metal dispersion on hydrogenation rate and trans/cis ratio was revealed. An optimum metal dispersion giving the highest decarboxylation reaction rate was observed. In addition to the particle size effect, the impact of mass transfer was elucidated and detail discussions on temperature programmed desorption of CO from the fresh and spent samples was provided. Hydrogenation of vegetable feedstocks was performed in batch and continuous modes, using powdered and granulated Pd/C catalysts correspondingly. One of the main focuses of the work was put on the scale-up of the hydrogenation process. There are several challenges attributed to the scale-up of a chemical process which have to be recognized before progressing to an industrial application. In terms of the high production volumes the logical step is to investigate the performance of hydrogenation as a continuous process. A laboratory study in a continuous fixed bed reactor was performed, giving crucial information about the catalyst long-term stability and catalyst deactivation. Furthermore, the impact of using free fatty acids or triglycerides feedstocks as well as the effect of catalyst particle size and Pd loading were investigated in continuous mode. Finally, the production capacities for different operation

  7. Improvement of oxygen-containing functional groups on olive stones activated carbon by ozone and nitric acid for heavy metals removal from aqueous phase.

    Science.gov (United States)

    Bohli, Thouraya; Ouederni, Abdelmottaleb

    2016-08-01

    Recently, modification of surface structure of activated carbons in order to improve their adsorption performance toward especial pollutants has gained great interest. Oxygen-containing functional groups have been devoted as the main responsible for heavy metal binding on the activated carbon surface; their introduction or enhancement needs specific modification and impregnation methods. In the present work, olive stones activated carbon (COSAC) undergoes surface modifications in gaseous phase using ozone (O3) and in liquid phase using nitric acid (HNO3). The activated carbon samples were characterized using N2 adsorption-desorption isotherm, SEM, pHpzc, FTIR, and Boehm titration. The activated carbon parent (COSAC) has a high surface area of 1194 m(2)/g and shows a predominantly microporous structure. Oxidation treatments with nitric acid and ozone show a decrease in both specific surface area and micropore volumes, whereas these acidic treatments have led to a fixation of high amount of surface oxygen functional groups, thus making the carbon surface more hydrophilic. Activated carbon samples were used as an adsorbent matrix for the removal of Co(II), Ni(II), and Cu(II) heavy metal ions from aqueous solutions. Adsorption isotherms were obtained at 30 °C, and the data are well fitted to the Redlich-Peterson and Langmuir equation. Results show that oxidized COSACs, especially COSAC(HNO3), are capable to remove more Co(II), Cu(II), and Ni(II) from aqueous solution. Nitric acid-oxidized olive stones activated carbon was tested in its ability to remove metal ions from binary systems and results show an important maximum adsorbed amount as compared to single systems.

  8. Synthesis of phosphinoferrocene amides and thioamides from carbamoyl chlorides and the structural chemistry of Group 11 metal complexes with these mixed-donor ligands.

    Science.gov (United States)

    Fernandes, Tiago A; Solařová, Hana; Císařová, Ivana; Uhlík, Filip; Štícha, Martin; Štěpnička, Petr

    2015-02-21

    The reaction of in situ generated 1'-(diphenylphosphino)-1-lithioferrocene with carbamoyl chlorides, ClC(E)NMe2, affords the corresponding (thio)amides, Ph2PfcC(E)NMe2 (E = O (), S (); fc = ferrocene-1,1'-diyl). These compounds as well as their analogues, Ph2PfcC(O)NHMe () and Ph2PfcC(O)NH2 (), prepared from 1'-(diphenylphosphino)ferrocene-1-carboxylic acid (Hdpf) were studied as ligands for the Group 11 metal ions. In the reactions with [Cu(MeCN)4][BF4], the amides give rise to bis-chelate complexes of the type [Cu(L-κ(2)O,P)2][BF4]. Similar products, [Ag(L-κ(2)O,P)2]ClO4, are obtained from silver(i) perchlorate and , or . In contrast, the reaction of AgClO4 with produces a unique molecular dimer [Ag()(ClO4-κO)]2, where the metal centres are bridged by the sulfur atoms of the P,S-chelating thioamides. The reactions of with [AuCl(tht)] (tht = tetrahydrothiophene) afford the expected gold(i)-phosphine complexes, [AuCl(L-κP)], containing uncoordinated (thio)amide moieties. Hemilabile coordination of the phosphinoamide ligands in complexes with the soft Group 11 metal ions is established by the crystal structure of a solvento complex, [Cu(-κ(2)O,P)(-κP)(CHCl3-κCl)][BF4], which was isolated serendipitously during an attempted crystallisation of [Cu(-κ(2)O,P)2][BF4]. All of the compounds are characterised by spectroscopic methods, and the structures of several representatives of both the free phosphinoamides and their complexes are determined by X-ray diffraction analysis and further studied by DFT calculations and cyclic voltammetry.

  9. Insertion of functional groups into a Nd3+ metal-organic framework via single-crystal-to-single-crystal coordinating solvent exchange.

    Science.gov (United States)

    Manos, Manolis J; Kyprianidou, Eleni J; Papaefstathiou, Giannis S; Tasiopoulos, Anastasios J

    2012-06-04

    Single-crystal-to-single-crystal (SCSC) transformations represent some of the most fascinating phenomena in chemistry. They are not only intriguing from a basic science point of view but also provide a means to modify or tune the properties of the materials via the postsynthetic introduction of suitable guest molecules or organic functional groups into their structures. Here, we describe UCY-2, a new flexible Nd(3+) metal-organic framework (MOF), which exhibits a unique capability to undergo a plethora of SCSC transformations with some of them being very uncommon. These structural alterations involve the replacement of coordinating solvent molecules of UCY-2 by terminally ligating solvents and organic ligands with multiple functional groups including -OH, -SH, -NH-, and -NH(2) or their combinations, chelating ligands, anions, and two different organic compounds. The SCSC coordinating solvent exchange is thus demonstrated as a powerful method for the functionalization of MOFs.

  10. Dynamical Mean-Field Theory Plus Numerical Renormalization-Group Study of Spin-Orbital Separation in a Three-Band Hund Metal.

    Science.gov (United States)

    Stadler, K M; Yin, Z P; von Delft, J; Kotliar, G; Weichselbaum, A

    2015-09-25

    We show that the numerical renormalization group is a viable multi-band impurity solver for dynamical mean-field theory (DMFT), offering unprecedented real-frequency spectral resolution at arbitrarily low energies and temperatures. We use it to obtain a numerically exact DMFT solution to the Hund metal problem for a three-band model on a Bethe lattice at 1/3 filling. The ground state is a Fermi liquid. The one-particle spectral function undergoes a coherence-incoherence crossover with increasing temperature, with spectral weight being transferred from low to high energies. Further, it exhibits a strong particle-hole asymmetry. In the incoherent regime, the self-energy displays approximate power-law behavior for positive frequencies only. The spin and orbital spectral functions show "spin-orbital separation": spin screening occurs at much lower energies than orbital screening. The renormalization group flows clearly reveal the relevant physics at all energy scales.

  11. Performance of the TPSS Functional on Predicting Core Level Binding Energies of Main Group Elements Containing Molecules: A Good Choice for Molecules Adsorbed on Metal Surfaces.

    Science.gov (United States)

    Pueyo Bellafont, Noèlia; Viñes, Francesc; Illas, Francesc

    2016-01-12

    Here we explored the performance of Hartree-Fock (HF), Perdew-Burke-Ernzerhof (PBE), and Tao-Perdew-Staroverov-Scuseria (TPSS) functionals in predicting core level 1s binding energies (BEs) and BE shifts (ΔBEs) for a large set of 68 molecules containing a wide variety of functional groups for main group elements B → F and considering up to 185 core levels. A statistical analysis comparing with X-ray photoelectron spectroscopy (XPS) experiments shows that BEs estimations are very accurate, TPSS exhibiting the best performance. Considering ΔBEs, the three methods yield very similar and excellent results, with mean absolute deviations of ∼0.25 eV. When considering relativistic effects, BEs deviations drop approaching experimental values. So, the largest mean percentage deviation is of 0.25% only. Linear trends among experimental and estimated values have been found, gaining offsets with respect to ideality. By adding relativistic effects to offsets, HF and TPSS methods underestimate experimental values by solely 0.11 and 0.05 eV, respectively, well within XPS chemical precision. TPSS is posed as an excellent choice for the characterization, by XPS, of molecules on metal solid substrates, given its suitability in describing metal substrates bonds and atomic and/or molecular orbitals.

  12. STUDENTS’ DECISION STEPS IN META-COGNITIVE LEARNING IN FREE ONLINE GROUPS (METAL-FROG: A Case Study

    Directory of Open Access Journals (Sweden)

    Kinsley Ng SEN FA

    2011-01-01

    Full Text Available What prompts the students to respond in online dialogic discussion? Why some students chose to fall out? This case study through the lens of phenomenography observation attempts to explain the five decision steps of students to respond in Meta-cognitive Learning in Free Online Groups (MetaL-FrOG discussion. It presents a part of a research project by the name of Triarchy Perspective on Meta-cognitive Learning in Free Online Groups. The research setting was online learner community on the platform of Free Online Group web intended for post-graduate students enrolled for the paper Psychology of Learning in Faculty of Education, University Malaya, Malaysia. Preliminary study revealed three factors contributed to MetaL-FrOG success: Motivation, Cognitive Resources and Pro-learning Behaviors. This paper only presents a part of the findings under the Pro-Learning Behaviors Sub-theory. We found striking similarities between the model proposed by Latane & Darley (1971, Five Essential Steps to a Pro-social Response in an Emergency, and our research subject. The model which explains the course of a pro-social decision was borrowed and modified as surrogate theory to explain the online discussion response of the students. The insights help educators to better understand what holds students back from fruitful online peer diologic discussion.

  13. Renormalization Group Approach to the X-Ray Absorption Problem and Application to the Vigman-Finkelshtein Model for Magnetic Impurities in Metals.

    Science.gov (United States)

    Nunes de Oliveira, Luiz

    The renormalization group techniques developed by Wilson for the Kondo problem are applied to three related problems: the absorption of x-rays by metals, the absorption of x-rays by impurities in metals, and the specific heat of dilute magnetic alloys. In the first problem considered, the x-ray absorption problem, the metal is represented by a half-filled conduction band and a deep level representing a core state. The absorption of an x-ray photon excites an electron from this core level to the conduction band creating a core hole whose positive charge interacts with the conduction electrons. The absorption spectrum is, for the first time, calculated in the energy range 10('-10)D ) (omega)(,T)) expression to seven decimal places; the prefactor (mu)(,o) is calculated for the first time. For (omega)-(omega)(,T) (TURNEQ) D, remarkably small deviations (e.g., deviations of 15% for (omega)-(omega)(,T) = .3D) from the Nozieres-De Dominicis power law are found. As a second application of the renormalization group techniques, the x-ray absorption spectrum for the resonant level model for impurities in metals is calculated. In this model, the metal is represented by a half-filled conduction band and the impurity by two levels: a core level from which an electron is excited to the conduction band by the absorption of an x-ray photon, and a resonant level, coupled to the conduction electrons, whose energy is lowered by the interaction with the core hole created by the absorption of the x-ray. In the x-ray absorption process, the resonant level is thus shifted to lower energy. The absorption spectrum approaches a power law in the energy range (omega)-(omega)(,T) >> (GAMMA), where (GAMMA) is the width of the resonant level, and a different power law in the range (omega)-(omega)(,T) body effect found in the spectrum of certain systems having a discrete level coupled to a continuum of energies) is elaborated. The problem of the specific heat of dilute magnetic alloys is attacked

  14. Low temperature hydrogenolysis of waxes to diesel range gasoline and light alkanes: Comparison of catalytic properties of group 4, 5 and 6 metal hydrides supported on silica-alumina

    KAUST Repository

    Norsic, Sébastien

    2012-01-01

    A series of metal hydrides (M = Zr, Hf, Ta, W) supported on silica-alumina were studied for the first time in hydrogenolysis of light alkanes in a continuous flow reactor. It was found that there is a difference in the reaction mechanism between d 0 metal hydrides of group 4 and d 0 ↔ d 2 metal hydrides of group 5 and group 6. Furthermore, the potential application of these catalysts has been demonstrated by the transformation of Fischer-Tropsch wax in a reactive distillation set-up into typical gasoline and diesel molecules in high selectivity (up to 86 wt%). Current results show that the group 4 metal hydrides have a promising yield toward liquid fuels.

  15. Influence of metal loading and humic acid functional groups on the complexation behavior of trivalent lanthanides analyzed by CE-ICP-MS

    Energy Technology Data Exchange (ETDEWEB)

    Kautenburger, Ralf, E-mail: r.kautenburger@mx.uni-saarland.de [Institute of Inorganic Solid State Chemistry, Saarland University, Campus Dudweiler, Am Markt Zeile 3-5, D-66125 Saarbrücken (Germany); Hein, Christina; Sander, Jonas M. [Institute of Inorganic Solid State Chemistry, Saarland University, Campus Dudweiler, Am Markt Zeile 3-5, D-66125 Saarbrücken (Germany); Beck, Horst P. [Institute of Inorganic and Analytical Chemistry and Radiochemistry, Saarland University, Campus Dudweiler, Am Markt Zeile 5, D-66125 Saarbrücken (Germany)

    2014-03-01

    Highlights: • Free and complexed HA-Ln species are separated by CE-ICP-MS. • Weaker and stronger HA-binding sites for Ln-complexation can be detected. • Complexation by original and modified humic acid (HA) with blocked phenolic hydroxyl- and carboxyl-groups is compared. • Stronger HA-binding sites for Ln³⁺ can be assumed as chelating complexes. • Chelates consist of trivalent Ln and a combination of both OH- and COOH-groups. Abstract: The complexation behavior of Aldrich humic acid (AHA) and a modified humic acid (AHA-PB) with blocked phenolic hydroxyl groups for trivalent lanthanides (Ln) is compared, and their influence on the mobility of Ln(III) in an aquifer is analyzed. As speciation technique, capillary electrophoresis (CE) was hyphenated with inductively coupled plasma mass spectrometry (ICP-MS). For metal loading experiments 25 mg L⁻¹ of AHA and different concentrations (c Ln(Eu+Gd)} = 100–6000 μg L⁻¹) of Eu(III) and Gd(III) in 10 mM NaClO₄ at pH 5 were applied. By CE-ICP-MS, three Ln-fractions, assumed to be uncomplexed, weakly and strongly AHA-complexed metal can be detected. For the used Ln/AHA-ratios conservative complex stability constants log βLnAHA decrease from 6.33 (100 μg L⁻¹ Ln³⁺) to 4.31 (6000 μg L⁻¹ Ln³⁺) with growing Ln-content. In order to verify the postulated weaker and stronger humic acid binding sites for trivalent Eu and Gd, a modified AHA with blocked functional groups was used. For these experiments 500 μg L⁻¹ Eu and 25 mg L⁻¹ AHA and AHA-PB in 10 mM NaClO₄ at pH-values ranging from 3 to 10 have been applied. With AHA-PB, where 84% of the phenolic OH-groups and 40% of the COOH-groups were blocked, Eu complexation was significantly lower, especially at the strong binding sites. The log β-values decrease from 6.11 (pH 10) to 5.61 at pH 3 (AHA) and for AHA-PB from 6.01 (pH 7) to 3.94 at pH 3. As a potential consequence, particularly humic acids with a high amount of

  16. Role of the metal cation types around VO4 groups on the nonlinear optical behavior of materials: experimental and theoretical analysis.

    Science.gov (United States)

    Su, Xin; Yang, Zhihua; Han, Guopeng; Wang, Ying; Wen, Ming; Pan, Shilie

    2016-09-28

    In order to explore new NLO crystals with superior performances, it is greatly desirable to understand the intrinsic relationship between the macroscopic optical properties and microscopic structural features in crystals. A novel mechanism for nonlinear optical (NLO) effects of vanadate crystals, Li3VO4, KCd4(VO4)3 and Ca3(VO4)2 with distorted (VO4)(3-) groups, has been investigated. Experiments related to the synthesis and structures were determined. In addition, infrared and UV-Vis-NIR diffuse reflectance spectroscopy, as well as electronic band structure calculations, were performed on the reported materials. A comprehensive analysis for the structure-property relationship is given by combining the experimental measurements, the electronic structure calculations and the SHG-weighted electron density to the linear and NLO properties. It was found that the contribution of the (VO4)(3-) anionic group to the second harmonic generation (SHG) response was the dominant anionic group, which plays a vital role to the SHG effects in Li3VO4, KCd4(VO4)3 and Ca3(VO4)2. It was also concluded that the metal cation types and coordination around VO4 groups, the distorted and parallel oriented VO4 tetrahedron decided the SHG coefficient values.

  17. Group 11 Metal Compounds with Tripodal Bis(imidazole Thioether Ligands. Applications as Catalysts in the Oxidation of Alkenes and as Antimicrobial Agents

    Directory of Open Access Journals (Sweden)

    Armando Varela-Ramírez

    2011-08-01

    Full Text Available New group 11 metal complexes have been prepared using the previously described tripodal bis(imidazole thioether ligand (N-methyl-4,5-diphenyl-2-imidazolyl2C(OMeC(CH32S(tert-Bu ({BITOMe,StBu}, 2. The pincer ligand offers a N2S donor atom set that can be used to coordinate the group 11 metals in different oxidation states [AuI, AuIII, AgI, CuI and CuII]. Thus the new compounds [Au{BITOMe,StBu}Cl][AuCl4]2 (3, [Au{BITOMe,StBu}Cl] (4, [Ag{BITOMe,StBu}X] (X = OSO2CF3- 5, PF6- 6 and [Cu{BITOMe,StBu}Cl2] (7 have been synthesized from reaction of 2 with the appropriate metal precursors, and characterized in solution. While attempting characterization in the solid state of 3, single crystals of the neutral dinuclear mixed AuIII-AuI species [Au2{BITOMe,S}Cl3] (8 were obtained and its crystal structure was determined by X-ray diffraction studies. The structure shows a AuIII center coordinated to the pincer ligand through one N and the S atom. The soft AuI center coordinates to the ligand through the same S atom that has lost the tert-butyl group, thus becoming a thiolate ligand. The short distance between the AuI-AuIII atoms (3.383 Å may indicate a weak metal-metal interaction. Complexes 2-7 and the previously described CuI compound [Cu{BITOMe,StBu}]PF6 (9 have been evaluated in the oxidation of biphenyl ethylene with tert-butyl hydrogen peroxide (TBHP as the oxidant. Results have shown that the AuI and AgI complexes 4 and 6 (at 10 mol % loading are the more active catalysts in this oxidative cleavage. The antimicrobial activity of compounds 2-5, 7 and 9 against Gram-positive and Gram-negative bacteria and yeast has also been evaluated. The new gold and silver compounds display moderate to high antibacterial activity, while the copper derivatives are mostly inactive. The gold and silver complexes were also potent against fungi. Their cytotoxic properties have been analyzed in vitro utilizing HeLa human cervical carcinoma cells. The compounds displayed a

  18. Group 11 Metal Compounds with Tripodal Bis(imidazole) Thioether Ligands. Applications as Catalysts in the Oxidation of Alkenes and as Antimicrobial Agents.

    Science.gov (United States)

    Liu, Fangwei; Anis, Reema; Hwang, Eunmi; Ovalle, Rafael; Varela-Ramírez, Armando; Aguilera, Renato J; Contel, María

    2011-08-08

    New group 11 metal complexes have been prepared using the previously described tripodal bis(imidazole) thioether ligand (N-methyl-4,5-diphenyl-2-imidazolyl)2C(OMe)C(CH3)2S(tert-Bu) ({BITOMe,StBu}, 2). The pincer ligand offers a N2S donor atom set that can be used to coordinate the group 11 metals in different oxidation states [AuI, AuIII, AgI, CuI and CuII]. Thus the new compounds [Au{BITOMe,StBu}Cl][AuCl4]2 (3), [Au{BITOMe,StBu}Cl] (4), [Ag{BITOMe,StBu}X] (X = OSO2CF3- 5, PF6- 6) and [Cu{BITOMe,StBu}Cl2] (7) have been synthesized from reaction of 2 with the appropriate metal precursors, and characterized in solution. While attempting characterization in the solid state of 3, single crystals of the neutral dinuclear mixed AuIII-AuI species [Au2{BITOMe,S}Cl3] (8) were obtained and its crystal structure was determined by X-ray diffraction studies. The structure shows a AuIII center coordinated to the pincer ligand through one N and the S atom. The soft AuI center coordinates to the ligand through the same S atom that has lost the tert-butyl group, thus becoming a thiolate ligand. The short distance between the AuI-AuIII atoms (3.383 Å) may indicate a weak metal-metal interaction. Complexes 2-7 and the previously described CuI compound [Cu{BITOMe,StBu}]PF6 (9) have been evaluated in the oxidation of biphenyl ethylene with tert-butyl hydrogen peroxide (TBHP) as the oxidant. Results have shown that the AuI and AgI complexes 4 and 6 (at 10 mol % loading) are the more active catalysts in this oxidative cleavage. The antimicrobial activity of compounds 2-5, 7 and 9 against Gram-positive and Gram-negative bacteria and yeast has also been evaluated. The new gold and silver compounds display moderate to high antibacterial activity, while the copper derivatives are mostly inactive. The gold and silver complexes were also potent against fungi. Their cytotoxic properties have been analyzed in vitro utilizing HeLa human cervical carcinoma cells. The compounds displayed a very

  19. Study on separation of platinum group metals from high level liquid waste using macroporous (MOTDGA-TOA)/SiO{sub 2}-P silica-based absorbent

    Energy Technology Data Exchange (ETDEWEB)

    Ito, Tatsuya [Department of Quantum Science and Energy Engineering, Graduate School of Engineering, Tohoku University, Aoba 6-6, Aramaki, Aoba-ku, Sendai, Miyagi 980-8579 (Japan); Japan Atomic Energy Agency, Tokai-mura Naka-gun, Ibarak319-1195 (Japan); Kim, Seong-Yun; Xu, Yuanlai; Hitomi, Keitaro [Cyclotron and Radioisotope Center, Tohoku University, Aoba 6-3, Aramaki, Aoba-ku, Sendai, Miyagi 980-8578 (Japan); Ishii, Keizo [Department of Quantum Science and Energy Engineering, Graduate School of Engineering, Tohoku University, Aoba 6-6, Aramaki, Aoba-ku, Sendai, Miyagi 980-8579 (Japan); Nagaishi, Ryuji; Kimura, Takaumi [Japan Atomic Energy Agency, Tokai-mura Naka-gun, Ibarak319-1195 (Japan)

    2013-07-01

    The recovery of platinum group metals (PGMs) from high level liquid waste (HLLW) by macroporous silica-based adsorbent, (MOTDGA-TOA)/SiO{sub 2}-P has been developed by impregnating two extractants of N,N'-dimethyl-N,N'-di-n-octyl-thio-diglycolamide (MOTDGA) and tri-n-octylamine (TOA) into a silica/polymer composite support (SiO{sub 2}-P). The adsorption of Ru(III), Rh(III) and Pd(II) have been investigated in simulated HLLW by batch method. The adsorbent has shown good uptake property for Pd(II). In addition, the combined use of MOTDGA and TOA improved the adsorption of Ru(III) and Rh(III) better than the individual use of them. The usability of adsorbent in radiation fields was further confirmed by irradiation experiments. The adsorbent remained to have the uptake capability for PGMs over the absorbed dose of 100 kGy, corresponding with one really adsorbed by the adsorbent, and showed good retention capability for Pd(II) even at the absorbed dose of 800 kGy. The chromatographic separation of metal ions was demonstrated with the adsorbent packed column, there is no influence of Re(VII) (instead of Tc) on the excellent separation behavior of Pd(II). (authors)

  20. Ab Initio Research on a New Type of Half-Metallic Double Perovskites, A2CrMO6 (A = IVA Group Elements; M = Mo, Re and W

    Directory of Open Access Journals (Sweden)

    Yun-Ping Liu

    2014-03-01

    Full Text Available The research based on density functional theory was carried out using generalized gradient approximation (GGA for full-structural optimization and the addition of the correlation effect (GGA + U (Coulomb parameter in a double perovskite structure, A2BB’O6. According to the similar valance electrons between IIA(s2 and IVA(p2, IVA group elements instead of alkaline-earth elements settled on the A-site ion position with fixed BB' combinations as CrM (M = Mo, Re and W. The ferrimagnetic half-metallic (HM-FiM properties can be attributed to the p-d hybridization between the Crd-Mp and the double exchange. All the compounds can be half-metallic (HM materials, except Si2CrMoO6, Ge2CrMo and Ge2CrReO6, because the strong-correlation correction should be considered. For M = W, only A = Sn and Pb are possible candidates as HM materials. Nevertheless, an examination of the structural stability is needed, because Si, Ge, Sn and Pb are quite different from Sr. All compounds are stable, except for the Si-based double perovskite structure.

  1. Enhanced Retention of Chelating Reagents in Octadecylsilyl Silica Phase by Interaction with Residual Silanol Groups in Solid Phase Extraction of Divalent Metal Ions.

    Science.gov (United States)

    Ohmuro, Satoshi; Fujii, Kan; Yasui, Takashi; Takada, Kazutake; Yuchi, Akio; Kokusen, Hisao

    2016-01-01

    Solid-phase extraction (SPE) of divalent metal ions with a lipophilic and potentially divalent hexadentate chelating reagent (H2L), with which octadecylsilyl silica (ODS), was impregnated with was studied to gain more insight into and develop the potential of this methodology. This is the first time to demonstrate that this reagent as well as other common nitrogen-containing reagents were retained both by adsorption due to hydrogen bonding between nitrogen atoms of the reagent and residual silanol groups in the ODS phase and by simple distribution into the hydrophobic space. An appreciably large amount of this reagent could be retained by the adsorption mechanism even with a relatively thin loading solution. The divalent metal ions of Mn(2+), Co(2+) and Zn(2+) were extracted as 1:1 neutral complexes ([ML]), while Ni(2+) and Cu(2+) as ion-pairs of 1:1 cationic complex ([MHL](+)) with anion in SPE with H2L. The extractability and selectivity were substantially the same as that in liquid-liquid extraction.

  2. Platinum-group elements in the Eastern Deccan volcanic province and a comparison with platinum metals of the western Deccan

    Indian Academy of Sciences (India)

    James Crocket; Dalim Paul; Trisha Lala

    2013-08-01

    This study is the first detailed investigation of the platinum-group elements (PGE) at the eastern margin of the Deccan volcanic province of India. One of the PGE, osmium, is not included largely because of analytical problems. The study is focused on mafic volcanics and dykes from four areas including Amarkantak, Umaria, Shahdol and Chirimiri. The first two localities represent two lava piles of about 170 and 400 m thickness respectively. In Umaria, 16 flows have been demarcated based on petrography and field studies. The Shahdol samples are basal lava formations overlying Gondwana sediments (Carboniferous) and the Chirimiri samples are dykes. In this study, the western Deccan province is defined as the Western Ghats plus Kutch. On average, the PGE are ∼20% higher in Amarkantak than Umaria and the flows are ∼13% higher in PGE than the dykes. A Zr vs. Pd scattergram found a strong positive correlation for these two elements except for one Umaria sample which indicated severe Pd loss. A comparison of west and east parts of the Deccan volcanic province using primitive mantle normalization showed that higher values prevailed in the western province suite in the Ni-Ir-Ru-Pt region. In contrast, eastern province values dominated in the Pd-Au-Cu region at the ‘Cu’ end of the profiles. A strong dominance of Pd in the eastern Deccan was also of interest. A number of factors, for example, percentage partial melting of the source rock and the temperature and pressure of partial melting strongly influence the character of these profiles. The observed PGE profile characteristics probably result in part from a long distance of subsurface transport of Deccan magma from the western to eastern regions.

  3. Effect of combining the metals of group VI supported on H-ZSM-5 zeolite as catalysts for non-oxidative conversion of natural gas to petrochemicals

    Institute of Scientific and Technical Information of China (English)

    A.K.Aboul-Gheit; A.E.Awadallah

    2009-01-01

    The most prestigious catalyst applied in natural gas (methane) non-oxidative conversion to petrochemicals is 6%Mo/H-ZSM-5.Chromium,molybdenum and tungsten are the group VI metals.Hence,in this work,6%Mo/H-ZSM-5 was correlated with 3%Cr+3%Mo/H-ZSM-5 and 3%W+3%Mo/H-ZSM-5 as catalysts to examine their promoting or inhibiting effects on the various reactions taking place during methane conversion.The catalytic activities of these catalysts were tested in a continuous flow fixed bed reactor at 700℃ and a GHSV of 1500 ml·g-1 ·h-1. Characterization of the catalysts using XRD,TGA and TPD were investigated.XRD and NH3-TPD showed greater interaction between the W-phase and the Bronsted acid sites in the channels of the zeolite than between Cr-phase and the acid sites in the zeolite.

  4. Phenyl Groups Result in the Highest Benzene Storage and Most Efficient Desulfurization in a Series of Isostructural Metal-Organic Frameworks.

    Science.gov (United States)

    He, Wen-Wen; Yang, Guang-Sheng; Tang, Yu-Jia; Li, Shun-Li; Zhang, Shu-Ran; Su, Zhong-Min; Lan, Ya-Qian

    2015-06-26

    A series of isoreticular metal-organic frameworks (MOFs; NENU-511-NENU-514), which all have high surface areas and strong adsorption capacities, have been successfully constructed by using mixed ligands. NENU-513 has the highest benzene capacity of 1687 mg g(-1) at 298 K, which ranks as the top MOF material among those reported up to now. This NENU series has been used for adsorptive desulfurization because of its permanent porosity. The results indicate that this series has a higher adsorptive efficiency in the removal of organosulfur compounds than other MOF materials, especially NENU-511, which has the highest adsorptive efficiency in the ambient atmosphere. This study proves that the design and synthesis of targeted MOFs with higher surface areas and with functional groups present is an efficient method to enhance benzene-storage capacity and the adsorption of organosulfur compounds. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. 阳离子树脂净化铂族金属溶液的研究%Purification of Platinum Group Metals Solution by Cation Exchange

    Institute of Scientific and Technical Information of China (English)

    毕向光; 余建民; 杨金富; 贺洪亮; 李权

    2015-01-01

    研究了阳离子交换树脂净化含大量贱金属的铂族金属溶液的工艺条件,结果表明,在pH=1~1.5时001×7阳离子交换树脂吸附贱金属的次序为:Ni>Cu>Co>Fe;Fe、Ni、Co、Cu的穿透容量分别为(g/kg):0.13,1.25,0.42,0.87;饱和容量分别为(g/kg):0.32,6.65,2.33,4.72,合计为14.02 g/kg;贱金属的分离效率主要取决于贵贱金属浓度及交换柱的数量;吸附在树脂上的贱金属极易被6 mol/L HCl洗脱,所有贱金属的最大洗脱均发生在洗脱液体积与床体积之比为1.0/1.7处,当洗脱液体积为床体积的2.0倍时贱金属被完全洗脱。实验结果为离子交换分离贱金属净化铂族金属溶液的工业化应用提供了强有力的理论依据。%The platimum group metals ( PGMs) solution containing a large amount of base metals purified with cation exchange resin had been investigated. The results showed that the adsorption of base metals by 001 × 7 cation ion exchange resin at pH=1~1.5 was in the order of Ni>Cu>Co>Fe. From the tests, the breakthrough capacities ( g/kg) of Fe, Ni, Co and Cu were 0.13, 1.25, 0.42 and 0.87, respectively, while the saturated capacities ( g/kg) were 0.32, 6.65, 2.33 and 4.72, respectively and 14.02 g/kg in total. It is shown that the separation efficiency of the base metals depends largely on the concentrations of the precious and base metals, as well as the number of exchange columns. The base metals absorbed on the resin could be easily eluted by adding HCl solution at the amount of 6 mol/L, with the elution reaching the maximum as the eluent volume and bed volume at the ratio of 1.0/1.7 and completely finished as the eluent volume being 2. 0 times the bed volume. The experimental results can definitely provide a theoretical basis favorably for the industrial application of PGMs solution purified by cation exchange resin.

  6. pipetas usadas para I. A.

    Directory of Open Access Journals (Sweden)

    J. Castañeda

    2004-01-01

    Full Text Available La vagina y cerviz de las cerdas son estimuladas físicamente durante la inseminación. Este contacto puede afectar características reproductivas tales como el transporte espermático y el proceso de ovulación. En el presente trabajo se evaluaron desde el punto de vista económico y reproductivo, tres tipos de pipetas utilizadas para I. A. de cerdas de diferente material y forma. Se utilizaron 120 animales multíparos asignados de acuerdo a su orden de entrada al celo, en forma sucesiva a uno de tres grupos experimentales: 1 I. A. mediante pipeta reusable de hule tipo Melrose ( Medata, 2 I. A. con pipeta desechable de punta plástica en espiral y 3 I. A. con pipeta desechable con punta de poliestireno redonda (Medi chimica. No se encontró diferencia (P>0.05 entre los porcentajes de gestación, parición y promedio de lechones nacidos vivos por parto, en el tiempo de aplicación del semen, ni en el volumen del mismo, arrojado por las cerdas en los 10 min. posteriores a la I. A. Los valores promedio fueron de: 91.7%, 86.7%, 10.4 ± 2.8, 7.8 ± 2.6 min. y 10.4 ± 11.3 ml, respectivamente. El análisis de regresión, no mostró significancia en cuanto a paridad en ninguna de las variables estudiadas (P>0.05. Se concluye que las pipetas evaluadas no difieren en su efecto sobre el desarrollo reproductivo de la piara. Sin embargo, la pipeta reusable tipo Melrose ofrece ventaja económica bajo las condiciones del presente estudio

  7. 30 CFR 57.22401 - Underground retorts (I-A and I-B mines).

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Underground retorts (I-A and I-B mines). 57... METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-UNDERGROUND METAL AND NONMETAL MINES Safety Standards for Methane in Metal and Nonmetal Mines Underground Retorts § 57.22401...

  8. Four-Component Damped Density Functional Response Theory Study of UV/Vis Absorption Spectra and Phosphorescence Parameters of Group 12 Metal-Substituted Porphyrins.

    Science.gov (United States)

    Fransson, Thomas; Saue, Trond; Norman, Patrick

    2016-05-10

    The influences of group 12 (Zn, Cd, Hg) metal-substitution on the valence spectra and phosphorescence parameters of porphyrins (P) have been investigated in a relativistic setting. In order to obtain valence spectra, this study reports the first application of the damped linear response function, or complex polarization propagator, in the four-component density functional theory framework [as formulated in Villaume et al. J. Chem. Phys. 2010 , 133 , 064105 ]. It is shown that the steep increase in the density of states as due to the inclusion of spin-orbit coupling yields only minor changes in overall computational costs involved with the solution of the set of linear response equations. Comparing single-frequency to multifrequency spectral calculations, it is noted that the number of iterations in the iterative linear equation solver per frequency grid-point decreases monotonously from 30 to 0.74 as the number of frequency points goes from one to 19. The main heavy-atom effect on the UV/vis-absorption spectra is indirect and attributed to the change of point group symmetry due to metal-substitution, and it is noted that substitutions using heavier atoms yield small red-shifts of the intense Soret-band. Concerning phosphorescence parameters, the adoption of a four-component relativistic setting enables the calculation of such properties at a linear order of response theory, and any higher-order response functions do not need to be considered-a real, conventional, form of linear response theory has been used for the calculation of these parameters. For the substituted porphyrins, electronic coupling between the lowest triplet states is strong and results in theoretical estimates of lifetimes that are sensitive to the wave function and electron density parametrization. With this in mind, we report our best estimates of the phosphorescence lifetimes to be 460, 13.8, 11.2, and 0.00155 s for H2P, ZnP, CdP, and HgP, respectively, with the corresponding transition

  9. Assessing the potential of group 13 and 14 metal/metalloid phthalocyanines as hole transport layers in organic light emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Plint, Trevor; Lessard, Benoît H. [Department of Chemical Engineering and Applied Chemistry, University of Toronto, 200 College Street, Toronto, Ontario M5S 3E5 (Canada); Bender, Timothy P. [Department of Chemical Engineering and Applied Chemistry, University of Toronto, 200 College Street, Toronto, Ontario M5S 3E5 (Canada); Department of Materials Science and Engineering, University of Toronto, 184 College Street, Toronto, Ontario M5S 3E4 (Canada); Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6 (Canada)

    2016-04-14

    In this study, we have assessed the potential application of group 13 and 14 metal and metalloid phthalocyanines ((X){sub n}-MPcs) and their axially substituted derivatives as hole-transporting layers in organic light emitting diodes (OLEDs). OLEDs studied herein have the generic structure of glass/ITO/(N,N′-di(1-naphthyl)-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine (NPB) or (X){sub n}-MPc)(50 nm)/Alq{sub 3} (60 nm)/LiF (1 nm)/Al (80 nm), where X is an axial substituent group. OLEDs using chloro aluminum phthalocyanine (Cl-AlPc) showed good peak luminance values of 2620 ± 113 cd/m{sup 2} at 11 V. To our knowledge, Cl-AlPc has not previously been shown to work as a hole transport material (HTL) in OLEDs. Conversely, the di-chlorides of silicon, germanium, and tin phthalocyanine (Cl{sub 2}-SiPc, Cl{sub 2}-GePc, and Cl{sub 2}-SnPc, respectively) showed poor performance compared to Cl-AlPc, having peak luminances of only 38 ± 4 cd/m{sup 2} (12 V), 23 ± 1 cd/m{sup 2} (8.5 V), and 59 ± 5 cd/m{sup 2} (13.5 V), respectively. However, by performing a simple axial substitution of the chloride groups of Cl{sub 2}-SiPc with pentafluorophenoxy groups, the resulting bis(pentafluorophenoxy) silicon phthalocyanine (F{sub 10}-SiPc) containing OLED had a peak luminance of 5141 ± 941 cd/m{sup 2} (10 V), a two order of magnitude increase over its chlorinated precursor. This material showed OLED characteristics approaching those of a baseline OLED based on the well-studied triarylamine NPB. Attempts to attach the pentafluorophenoxy axial group to both SnPc and GePc were hindered by synthetic difficulties and low thermal stability, respectively. In light of the performance improvements observed by simple axial substitution of SiPc in OLEDs, the use of axially substituted MPcs in organic electronic devices remains of continuing interest to us and potentially the field in general.

  10. Assessing the potential of group 13 and 14 metal/metalloid phthalocyanines as hole transport layers in organic light emitting diodes

    Science.gov (United States)

    Plint, Trevor; Lessard, Benoît H.; Bender, Timothy P.

    2016-04-01

    In this study, we have assessed the potential application of group 13 and 14 metal and metalloid phthalocyanines ((X)n-MPcs) and their axially substituted derivatives as hole-transporting layers in organic light emitting diodes (OLEDs). OLEDs studied herein have the generic structure of glass/ITO/(N,N'-di(1-naphthyl)-N,N'-diphenyl-(1,1'-biphenyl)-4,4'-diamine (NPB) or (X)n-MPc)(50 nm)/Alq3 (60 nm)/LiF (1 nm)/Al (80 nm), where X is an axial substituent group. OLEDs using chloro aluminum phthalocyanine (Cl-AlPc) showed good peak luminance values of 2620 ± 113 cd/m2 at 11 V. To our knowledge, Cl-AlPc has not previously been shown to work as a hole transport material (HTL) in OLEDs. Conversely, the di-chlorides of silicon, germanium, and tin phthalocyanine (Cl2-SiPc, Cl2-GePc, and Cl2-SnPc, respectively) showed poor performance compared to Cl-AlPc, having peak luminances of only 38 ± 4 cd/m2 (12 V), 23 ± 1 cd/m2 (8.5 V), and 59 ± 5 cd/m2 (13.5 V), respectively. However, by performing a simple axial substitution of the chloride groups of Cl2-SiPc with pentafluorophenoxy groups, the resulting bis(pentafluorophenoxy) silicon phthalocyanine (F10-SiPc) containing OLED had a peak luminance of 5141 ± 941 cd/m2 (10 V), a two order of magnitude increase over its chlorinated precursor. This material showed OLED characteristics approaching those of a baseline OLED based on the well-studied triarylamine NPB. Attempts to attach the pentafluorophenoxy axial group to both SnPc and GePc were hindered by synthetic difficulties and low thermal stability, respectively. In light of the performance improvements observed by simple axial substitution of SiPc in OLEDs, the use of axially substituted MPcs in organic electronic devices remains of continuing interest to us and potentially the field in general.

  11. Ages and sources of components of Zn-Pb, Cu, precious metal, and platinum group element deposits in the goodsprings district, clark county, Nevada

    Science.gov (United States)

    Vikre, P.; Browne, Q.J.; Fleck, R.; Hofstra, A.; Wooden, J.

    2011-01-01

    The Goodsprings district, Clark County, Nevada, includes zinc-dominant carbonate replacement deposits of probable late Paleozoic age, and lead-dominant carbonate replacement deposits, copper ?? precious metal-platinum group element (PGE) deposits, and gold ?? silver deposits that are spatially associated with Late Triassic porphyritic intrusions. The district encompasses ??500 km2 although the distribution of all deposits has been laterally condensed by late Mesozoic crustal contraction. Zinc, Pb, and Cu production from about 90 deposits was ??160,000 metric tons (t) (Zn > Pb >> Cu), 2.1 million ounces (Moz) Ag, 0.09 Moz Au, and small amounts of PGEs-Co, V, Hg, Sb, Ni, Mo, Mn, Ir, and U-were also recovered. Zinc-dominant carbonate replacement deposits (Zn > Pb; Ag ?? Cu) resemble Mississippi Valley Type (MVT) Zn-Pb deposits in that they occur in karst and fault breccias in Mississippian limestone where the southern margin of the regional late Paleozoic foreland basin adjoins Proterozoic crystalline rocks of the craton. They consist of calcite, dolomite, sphalerite, and galena with variably positive S isotope compositions (??34S values range from 2.5-13%), and highly radiogenic Pb isotope compositions (206Pb/204Pb >19), typical of MVT deposits above crystalline Precambrian basement. These deposits may have formed when southward flow of saline fluids, derived from basinal and older sedimentary rocks, encountered thinner strata and pinch-outs against the craton, forcing fluid mixing and mineral precipitation in karst and fault breccias. Lead-dominant carbonate replacement deposits (Pb > Zn, Ag ?? Cu ?? Au) occur among other deposit types, often near porphyritic intrusions. They generally contain higher concentrations of precious metals than zinc-dominant deposits and relatively abundant iron oxides after pyrite. They share characteristics with copper ?? precious metal- PGE and gold ?? silver deposits including fine-grained quartz replacement of carbonate minerals in

  12. Electrical and structural properties of group-4 transition-metal nitride (TiN, ZrN, and HfN) contacts on Ge

    Energy Technology Data Exchange (ETDEWEB)

    Yamamoto, Keisuke; Nakashima, Hiroshi, E-mail: nakasima@astec.kyushu-u.ac.jp [Art, Science and Technology Center for Cooperative Research, Kyushu University, 6-1 Kasuga-koen, Kasuga, Fukuoka 816-8580 (Japan); Noguchi, Ryutaro; Wang, Dong [Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, 6-1 Kasuga-koen, Kasuga, Fukuoka 816-8580 (Japan); Mitsuhara, Masatoshi; Nishida, Minoru [Department of Engineering Sciences for Electronics and Materials, Kyushu University, 6-1 Kasuga-koen, Kasuga, Fukuoka 816-8580 (Japan); Hara, Toru [National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan)

    2015-09-21

    Electrical and structural properties were investigated for group-4 transition-metal nitride contacts on Ge (TiN/Ge, ZrN/Ge, and HfN/Ge), which were prepared by direct sputter depositions using nitride targets. These contacts could alleviate the intrinsic Fermi-level pinning (FLP) position toward the conduction band edge. It was revealed that this phenomenon is induced by an amorphous interlayer (a-IL) containing nitrogen atoms at the nitride/Ge interfaces. The strength of FLP alleviation positively depended on the thickness of a-IL. TiN/Ge and ZrN/Ge contacts with ∼2 nm-thick a-ILs showed strong FLP alleviations with hole barrier heights (Φ{sub BP}) in the range of 0.52–56 eV, and a HfN/Ge contact with an ∼1 nm-thick a-IL showed a weaker one with a Φ{sub BP} of 0.39 eV. However, TaN/Ge contact without a-IL did not show such FLP alleviation. Based on the results of depth distributions for respective elements, we discussed the formation kinetics of a-ILs at TiN/Ge and ZrN/Ge interfaces. Finally, we proposed an interfacial dipole model to explain the FLP alleviation.

  13. Validation and Verification the Expanded Table for Transition Metal Carbonyl and Main Group Element Cluster Series which obey the 18-Electron and 8-Electron (octet Rules respectively

    Directory of Open Access Journals (Sweden)

    Enos Masheija Kiremire

    2014-12-01

    Full Text Available The transition metal carbonyl clusters and Main group element clusters belong to natural series based on the number theory. The number series of the cluster series have been generated using the empirical formula k = ½ (E-V where k represents the linkages or bonds that glue together the cluster elements which obey the eighteen electron rule or the octet rule and E is related to the sum of eighteen electrons or the eight electrons and V is the sum of the valence electrons. An expanded cluster table been constructed to accommodate the analysis of medium to relatively large clusters of high nuclearity. Using the knowledge of k-value and the cluster table it is possible for a given cluster formula to be categorized into its type of series and its geometry deduced. This is relatively easy for simple to medium clusters. It is hoped that this simple approach to be adapted to categorize and deduce structures of clusters with high nuclearity. This approach to clusters using number theory will complement the existing clusters theories such as Wade-Mingos rules1-7, Jemmismno rules8-9 and topology rules10.

  14. Platinum group metal-free electrocatalysts: Effects of synthesis on structure and performance in proton-exchange membrane fuel cell cathodes

    Science.gov (United States)

    Workman, Michael J.; Dzara, Michael; Ngo, Chilan; Pylypenko, Svitlana; Serov, Alexey; McKinney, Sam; Gordon, Jonathan; Atanassov, Plamen; Artyushkova, Kateryna

    2017-04-01

    Development of platinum group metal free catalysts for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs) requires understanding of the interactions between surface chemistry and performance, both of which are strongly dependent on synthesis conditions. To elucidate these complex relationships, a set of Fe-N-C catalysts derived from the same set of precursor materials is fabricated by varying several key synthetic parameters under controlled conditions. The results of physicochemical characterization are presented and compared with the results of rotating disk electrode (RDE) analysis and fuel cell testing. We find that electrochemical performance is strongly correlated with three key properties related to catalyst composition: concentrations of 1) atomically dispersed Fe species, 2) species in which N is bound to Fe, and 3) surface oxides. Not only are these factors related to performance, these types of chemical species are shown to correlate with each other. This study provides evidence supporting the role of iron coordinated with nitrogen as an active species for the ORR, and offers synthetic pathways to increase the density of atomically dispersed iron species and surface oxides for optimum performance.

  15. H{sub 2}/air alkaline membrane fuel cell performance and durability, using novel ionomer and non-platinum group metal cathode catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Piana, Michele; Boccia, Massimiliano; Filpi, Antonio; Flammia, Elisa; Miller, Hamish A.; Orsini, Marco; Salusti, Francesca; Santiccioli, Serena [Acta S.p.A., Fuel cell Technology, via di Lavoria 56/G, I-56042 Crespina (PI) (Italy); Ciardelli, Francesco; Pucci, Andrea [Department of Chemistry and Industrial Chemistry, University of Pisa, Via, Risorgimento 35, I-56126 Pisa (Italy)

    2010-09-15

    The development of H{sub 2}/air alkaline membrane fuel cells (AMFCs) enables the use of non-platinum group metal (PGM) catalysts which are intrinsically stable and have an activity similar to platinum in alkaline media for the oxygen reduction reaction (ORR). As opposed to PEMFCs, the research and development of these types of catalysts for AMFC has had little attention and even less has been given to the development of alkaline membranes and ionomers. Acta S.p.A. has developed recently new non-PGM ORR catalysts with activity higher than Pt in alkaline media. More importantly, a new anionic ionomer derived from cheap starting materials with optimum performance has been produced. In this paper we demonstrate the use of this new ionomer in H{sub 2}/air AMFCs showing the first polarization and durability data, with current densities higher than those recently reported in the literature. Furthermore, we report the effect of CO{sub 2} on AMFC performance, showing the possibility of use of such alkaline devices not only in outer-space applications, but also with atmospheric air for large scale devices. (author)

  16. Versatile cooperative ligand effects in group 9 transition metal catalysis: Applications in transfer hydrogenation & hydrogen autotransfer reactions, ketene & ketene imine synthesis and hydroformylation

    NARCIS (Netherlands)

    Tang, Z.

    2015-01-01

    Cooperative ligand effects of transition metal complexes have a profound impact on the reaction outcome of catalytic reactions, and development of (new) cooperative metal-ligand systems is a hot topic in current catalysis research. Conventional ligands with hydride-accepting/delivering activities ar

  17. Evaluating the abnormal ossification in tibiotarsi of developing chick embryos exposed to 1.0ppm doses of platinum group metals by spectroscopic techniques.

    Science.gov (United States)

    Stahler, Adam C; Monahan, Jennifer L; Dagher, Jessica M; Baker, Joshua D; Markopoulos, Marjorie M; Iragena, Diane B; NeJame, Britney M; Slaughter, Robert; Felker, Daniel; Burggraf, Larry W; Isaac, Leon A C; Grossie, David; Gagnon, Zofia E; Sizemore, Ioana E Pavel

    2013-04-01

    Platinum group metals (PGMs), i.e., palladium (Pd), platinum (Pt) and rhodium (Rh), are found at pollutant levels in the environment and are known to accumulate in plant and animal tissues. However, little is known about PGM toxicity. Our previous studies showed that chick embryos exposed to PGM concentrations of 1mL of 5.0ppm (LD50) and higher exhibited severe skeletal deformities. This work hypothesized that 1.0ppm doses of PGMs will negatively impact the mineralization process in tibiotarsi. One milliliter of 1.0ppm of Pd(II), Pt(IV), Rh(III) aqueous salt solutions and a PGM-mixture were injected into the air sac on the 7th and 14th day of incubation. Control groups with no-injection and vehicle injections were included. On the 20th day, embryos were sacrificed to analyze the PGM effects on tibiotarsi using four spectroscopic techniques. 1) Micro-Raman imaging: Hyperspectral Raman data were collected on paraffin embedded cross-sections of tibiotarsi, and processed using in-house-written MATLAB codes. Micro-Raman univariate images that were created from the ν1(PO4(3-)) integrated areas revealed anomalous mineral inclusions within the bone marrow for the PGM-mixture treatment. The age of the mineral crystals (ν(CO3(2-))/ν1(PO4(3-))) was statistically lower for all treatments when compared to controls (p≤0.05). 2) FAAS: The percent calcium content of the chemically digested tibiotarsi in the Pd and Pt groups changed by ~45% with respect to the no-injection control (16.1±0.2%). 3) Micro-XRF imaging: Abnormal calcium and phosphorus inclusions were found within the inner longitudinal sections of tibiotarsi for the PGM-mixture treatment. A clear increase in the mineral content was observed for the outer sections of the Pd treatment. 4) ICP-OES: PGM concentrations in tibiotarsi were undetectable (<5ppb). The spectroscopic techniques gave corroborating results, confirmed the hypothesis, and explained the observed pathological (skeletal developmental abnormalities

  18. Nitriding VI-group metals (Cr, Mo and W) in stream of NH3 gas under concentrated solar irradiation in a solar furnace at PSA (Plataforma Solar de Almería)

    OpenAIRE

    Oliveira, F. A. Costa; Rosa, Luís Guerra; Fernandes, Jorge Cruz; Rodriguez,José; Canadas, Inmaculada; Magalhães, Teresa; Shohoji, Nobumitsu

    2015-01-01

    Carbides and nitrides of d-group transition metals are classified as refractory hard material and their industrial importance has been recognized for long. In recent years, unique functionalities including catalytic function and superconductivity are discovered for this group of materials to raise serious attention of materials researchers and engineers to refractory carbides and nitrides as novel functional materials. Synthesis of refractory carbides and nitrides demands high temperature rea...

  19. Using extracellular polymeric substances (EPS)-producing cyanobacteria for the bioremediation of heavy metals: do cations compete for the EPS functional groups and also accumulate inside the cell?

    Science.gov (United States)

    Pereira, Sara; Micheletti, Ernesto; Zille, Andrea; Santos, Arlete; Moradas-Ferreira, Pedro; Tamagnini, Paula; De Philippis, Roberto

    2011-02-01

    Many cyanobacteria produce extracellular polymeric substances (EPS) mainly of polysaccharidic nature. These EPS can remain associated to the cell surface as sheaths, capsules and/or slimes, or be liberated into the surrounding environment as released polysaccharides (RPS). The ability of EPS-producing cyanobacteria to remove heavy metals from aqueous solutions has been widely reported in the literature, focusing mainly on the biotechnological potential. However, the knowledge of the effects of the metals in the cell's survival/growth is still scarce, particularly when they are simultaneously exposed to more than one metal. This work evaluated the effects of different concentrations of Cu(2+) and/or Pb(2+) in the growth/survival of Gloeothece sp. PCC 6909 and its sheathless mutant Gloeothece sp. CCY 9612. The results obtained clearly showed that both phenotypes are more severely affected by Cu(2+) than Pb(2+), and that the mutant is more sensitive to the former metal than the wild-type. Evident ultrastructural changes were also observed in the wild-type and mutant cells exposed to high levels (10 mg l(-1)) of Cu(2+). Moreover, in bi-metal systems, Pb(2+) was preferentially removed compared with Cu(2+), being the RPS of the mutant that is the most efficient polysaccharide fraction in metal removal. In these systems, the simultaneous presence of Cu(2+) and Pb(2+) caused a mutual inhibition in the adsorption of each metal.

  20. Specific metal-ion binding sites in a model of the P4-P6 triple-helical domain of a group I intron.

    Science.gov (United States)

    Lindqvist, M; Sandström, K; Liepins, V; Strömberg, R; Gräslund, A

    2001-08-01

    Divalent metal ions play a crucial role in RNA structure and catalysis. Phosphorothioate substitution and manganese rescue experiments can reveal phosphate oxygens interacting specifically with magnesium ions essential for structure and/or activity. In this study, phosphorothioate interference experiments in combination with structural sensitive circular dichroism spectroscopy have been used to probe molecular interactions underlying an important RNA structural motif. We have studied a synthetic model of the P4-P6 triple-helical domain in the bacteriophage T4 nrdB group I intron, which has a core sequence analogous to the Tetrahymena ribozyme. Rp and Sp sulfur substitutions were introduced into two adjacent nucleotides positioned at the 3' end of helix P6 (U452) and in the joining region J6/7 (U453). The effects of sulfur substitution on triple helix formation in the presence of different ratios of magnesium and manganese were studied by the use of difference circular dichroism spectroscopy. The results show that the pro-Sp oxygen of U452 acts as a ligand for a structurally important magnesium ion, whereas no such effect is seen for the pro-Rp oxygen of U452. The importance of the pro-Rp and pro-Sp oxygens of U453 is less clear, because addition of manganese could not significantly restore the triple-helical interactions within the isolated substituted model systems. The interpretation is that U453 is so sensitive to structural disturbance that any change at this position hinders the proper formation of the triple helix.

  1. Comparison between Base Metals and Platinum Group Metals in Nitrogen, M Codoped TiO2 (M = Fe, Cu, Pd, Os for Photocatalytic Removal of an Organic Dye in Water

    Directory of Open Access Journals (Sweden)

    Alex T. Kuvarega

    2014-01-01

    Full Text Available The photocatalytic performance of a number of nonmetal and metal codoped TiO2 for the degradation of eosin yellow under simulated solar radiation was investigated. The synthesised materials were characterised by FTIR, Raman spectroscopy, XRD, DRUV-Vis, SEM, and TEM. The N, metal codoped TiO2 containing 0.5 wt.% of the metal consisted mainly of the anatase phase, with a particle size range of 15–28 nm. The particles were largely spherical and shifted the absorption edge well into the visible region. Band gap reduction was more pronounced for the N, PGM codoped TiO2 compared to N, base metal codoped samples. Codoping led to an enhancement in the photocatalytic activity of the materials for the degradation of eosin yellow. N, Pd codoped TiO2 was the most effective photocatalyst (99.9% dye removal while N, Cu codoped TiO2 showed the least activity (25.5% removal. The mechanism for the photocatalytic enhancement was proposed on the basis of formation of an electron deficient Schottky barrier at the semiconductor-metal interface, which acts as an electron sink and thus retards electron-hole recombination. It was shown that the ability of the photocatalyst to degrade the dye depends on the nature and type of the metal dopant in the codoped TiO2 system.

  2. 30 CFR 57.22601 - Blasting from the surface (I-A mines).

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Blasting from the surface (I-A mines). 57.22601... Standards for Methane in Metal and Nonmetal Mines Explosives § 57.22601 Blasting from the surface (I-A mines... blast area and through at least one atmospheric monitoring sensor. (b) After blasting, if the...

  3. Synthesis, structure, and reactivity of tris(amidate) mono(amido) and tetrakis(amidate) complexes of group 4 transition metals.

    Science.gov (United States)

    Payne, Philippa R; Thomson, Robert K; Medeiros, Diane M; Wan, Geoff; Schafer, Laurel L

    2013-11-28

    The syntheses of a series of tris(amidate) mono(amido) titanium and zirconium complexes are reported. The binding motif of the amidate ligand has been determined to depend on the size of the metal centre for these sterically demanding N,O-chelating ligands; the larger zirconium metal centre supports three κ(2)-(N,O) bound amidate ligands while the titanium analogue has one ligand bound in a κ(1)-(O) fashion to alleviate steric strain. Reactivity studies indicate that, despite high steric crowding about the tris(amidate) mono(amido) zirconium metal centre, transamination of the reactive dimethylamido ligand can be achieved using aniline. This complex is also an active precatalyst for intramolecular alkene hydroamination, in which protonolysis of one amidate ligand in the presence of excess amine is observed as an initiation step prior to catalytic turnover. Eight-coordinate homoleptic κ(2)-amidate complexes of zirconium and hafnium have also been prepared.

  4. Surface structure determination of group 11 metals adsorbed on a rhenium(10 anti 10) surface by low-energy electron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Messahel, Lyria

    2012-11-12

    This thesis deals with the computational surface determination of various long-range ordered phases formed by thin films of copper, silver, and gold adsorbed on the rhenium- (10 anti 10) surface. It is based upon LEED-I,V curves for these phases that were recorded in the course of detailed experimental investigations of the respective films carried out in our group (using techniques such as LEED, MEED, and TPD). In order to solve the intricate puzzle of surface structural analysis, the electron elastic scattering behaviour of the investigated coinage metal phases was calculated using the Erlangen TensErLEED program package. Thereby first a set of theoretical LEED-I,V curves is derived for a guessed reference structure. Subsequently its structural input parameters are varied in a trial-and-error procedure until optimal agreement between experiment and theory is attained. The (1 x 1) phases formed by the deposited metals were tackled first to establish an absolute coverage calibration and to elucidate the respective growth modes on the Re(10 anti 10) surface. In all three cases the (1 x 1) structure is developed best at a coverage {Theta}{sub Cu,Ag,Au}=2 ML=1 BL. Extension of the investigation to experimental I,V curves for higher Cu coverages revealed that this element continues to grow bilayerwise, thereby retaining the Re hcp morphology. Ag, in contrast to Cu and Au, happens not to grow as homogeneously, and the TPD data suggest that Ag films exhibit the so-called simultaneous-multilayer (SM) growth mode. The following analysis of the sub-bilayer coverage range shows that the three systems exhibit considerable differences. While Cu, having a negative lattice misfit compared to Re, shows no long-range ordered superstructures, Ag and Au with a similar positive misfit form a couple of such phases. Ag features both a (1 x 4) phase, stable at ambient temperatures, that upon heating transforms into a c(2 x 2) phase that only exists at elevated temperatures. The

  5. M@B9 and M@B10 molecular wheels containing planar nona-and deca-coordinate heavy group 11, 12, and 13 metals (M=Ag, Au, Cd, Hg, In, Tl)

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    A density functional and ab initio theory investigation on M@B9 and M@B10 molecular wheels containing planar nona-and deca-coordinate heavy group 11, 12 and 13 metals (M=Ag, Au, Cd, Hg, In, Ti) has been performed. These unusual clusters all prove to be true minima on the potential energy surfaces of the systems and σ+π double aromatic in nature. The first two vertical one-electron detachment energies of M@B-10 (M=Ag, Au) anions and first two ionization potentials of M@B9 (M=Ag, Au) and M@B10 (M=Cd, Hg) neutrals were calculated to aid future experiments. The cluster complexes designed in this work may expend the domain of planar hyper-coordinate elements to include heavy group 11, 12, and 13 metals and serve as interesting candidates to be targeted in experiments.

  6. The effect of heavy metal concentration and soil pH on the abundance of selected microbial groups within ArcelorMittal Poland steelworks in Cracow.

    Science.gov (United States)

    Lenart, Anna; Wolny-Koładka, Katarzyna

    2013-01-01

    The present study aimed to identify the effect of heavy metal concentration and soil pH on the abundance of the selected soil microorganisms within ArcelorMittal Poland steelworks, Cracow. The analysis included 20 soil samples, where the concentration of Fe, Zn, Cd, Pb, Ni, Cu, Mn, Cr and soil pH were evaluated together with the number of mesophilic bacteria, fungi, Actinomycetes and Azotobacter spp. In the majority of samples soil pH was alkaline. The limits of heavy metals exceeded in eight samples and in one sample, the concentration of Zn exceeded 31-fold. Chromium was the element which most significantly limited the number of bacteria and Actinomycetes.

  7. X-ray and NMR study of the structural features of SCS-pincer metal complexes of the group 10 triad

    NARCIS (Netherlands)

    Kruithof, C.A.|info:eu-repo/dai/nl/311433871; Dijkstra, H.P.|info:eu-repo/dai/nl/241119952; Lutz, M.|info:eu-repo/dai/nl/304828971; Spek, A.L.|info:eu-repo/dai/nl/156517566; Klein Gebbink, R.J.M.|info:eu-repo/dai/nl/166032646; van Koten, G.|info:eu-repo/dai/nl/073839191

    2008-01-01

    SCS-pincer metal complexes [MX(SCS)] (SCS = [2,6-(RSCH2)2C6H3]−; R = Ph: PhSCS; R = Me: MeSCS; M = Pd, Pt, Ni) have been synthesized via mild and tolerant oxidative addition procedures. The complexes have been characterized by 1H and 13C NMR spectroscopy and X-ray crystal structure determination.

  8. The effect of temperature and pressure on the distribution of iron group elements between metal and olivine phases in the process of differentiation of protoplanetary material

    Science.gov (United States)

    Vinogradov, A. P.; Ilyin, N. P.; Kolomeytsava, L. N.

    1977-01-01

    The distribution patterns of Ni, Co, Mn, and Cr were studied in olivines of various origins: from meteorites (chondrites, achondrites, pallasites), which are likely analogs of the protoplanetary material, to peridotite inclusions in kimberlite pipes, which are analogs of mantle material. According to X-ray microanalysis data, nickel is concentrated in peridotite olivines, while manganese is concentrated in meteoritic olivines. The maximum chromium content was found in ureilites, which were formed under reducing conditions. Experiments at pressures of 20 to 70 kbar and temperatures of 1100 to 2000 C have shown that in a mixture of olivine and Ni metal or NiO, nickel enters the silicate phase, displacing Fe into the metallic phase. Equilibrium temperatures were estimated from the Fe, Ni distribution coefficients between the metal and olivine: 1500 K for pallasites, 1600 K for olivine-bronzite H6 chondrites, 1200 K for olivine-hypersthene L6, 900 K for LL6, and 1900 K for ureilites (at P = 1 atm). The equilibrium conditions of peridotites are close to T = 1800 K and P over 100 kbar. It is concluded that there is a sharp difference between the conditions of differentiation of the protoplanetary material at the time meteorites were formed and the conditions of differentiation of the planets into concentric layers.

  9. The use of new modified poly(acrylamide chelating resin with pendent benzothiazole groups containing donor atoms in the removal of heavy metal ions from aqueous solutions

    Directory of Open Access Journals (Sweden)

    Semmedu Selvaraj Kalaivani

    2014-03-01

    Full Text Available The adsorption studies of poly(6-(ethoxybenzothiazole acrylamide (PEBTA, for Cu(II and Zn(II metal ions removal from an aqueous solution have been investigated, as a function of solution pH, adsorbent dose, contact time, initial metal ion concentration and temperature. The chemical and structural characteristics of the adsorbent were determined by the FT-IR, 1H-NMR, TGA, SEM, and EDAX analysis. The maximum adsorption capacities of the adsorbent for Cu(II and Zn(II ions, as calculated from the Langmuir isotherm model, were 273.5 and 216.4 mg/g, respectively. The adsorption kinetic studies show that the adsorption of Cu(II and Zn(II ions onto PEBTA follows the pseudo second order kinetic model. Thermodynamic parameters such as ΔG°, ΔH° and ΔS° were also evaluated, and it has been found that the adsorption process is feasible, spontaneous and exothermic in nature. Desorption studies were carried out using 0.3 N HCl, and it revealed that the adsorbed Cu(II and Zn(II ions can be easily removed. The adsorption–desorption process is reversible, and this indicates that PEBTA is an effective adsorbent for the removal of heavy metal ions from an aqueous medium.

  10. Assessment of metallic mineral resources in the Humboldt River Basin, Northern Nevada, with a section on Platinum-Group-Element (PGE) Potential of the Humboldt Mafic Complex

    Science.gov (United States)

    Wallace, Alan R.; Ludington, Steve; Mihalasky, Mark J.; Peters, Stephen G.; Theodore, Ted G.; Ponce, David A.; John, David A.; and Berger, Byron R.; Zientek, Michael L.; Sidder, Gary B.; Zierenberg, Robert A.

    2004-01-01

    The Humboldt River Basin is an arid to semiarid, internally drained basin that covers approximately 43,000 km2 in northern Nevada. The basin contains a wide variety of metallic and nonmetallic mineral deposits and occurrences, and, at various times, the area has been one of the Nation's leading or important producers of gold, silver, copper, mercury, and tungsten. Nevada currently (2003) is the third largest producer of gold in the world and the largest producer of silver in the United States. Current exploration for additional mineral deposits focuses on many areas in northern Nevada, including the Humboldt River Basin.

  11. Interdiffusion behavior of tungsten or rhenium and group 5 and 6 elements and alloys of the periodic table, part 1. [at dissimilar metal joints

    Science.gov (United States)

    Arcella, F. G.

    1974-01-01

    Arc cast W, CVD W, CVD Re, and powder metallurgy Re materials were hot isostatically pressure welded to ten different refractory metals and alloys (Cb, Cb-1Zr, Ta, Ta-10W, T-111, ASTAR-811C, W-25Re, Mo-50Re, W-30Re-20Mo, ect.) and thermally aged at 10 to the minus 8th power torr at 1200, 1500, 1630, 1800, and 2000 C for 100 to 2000 hours. Electron beam microprobe analysis was used to characterize the interdiffusion zone width of each couple system as a function of age time and temperature. Extrapolations of interdiffusion zone thickness to 10,000 hours were made. Classic interdiffusion analysis was performed for several of the systems by Boltzmann-Matano analysis. A method of inhibiting Kirkendall voids from forming during thermal ageing of dissimilar metal junctions was devised and experimentally demonstrated. An electron beam weld study of Cb-1Zr to Re and W-25Re demonstrated the limited acceptability of these welds.

  12. Electroless metal plating of plastics

    Science.gov (United States)

    Krause, Lawrence J.

    1984-01-01

    Process for plating main group metals on aromatic polymers is carried out by the use of a nonaqueous solution of a salt of an alkali metal in a positive valence state and a main group metal in a negative valence state with contact between the solution and polymer providing a redox reaction causing the deposition of the main group metal and the reduction of the polymer. Products from the process exhibit useful decorative and electrical properties.

  13. Structure and catalytic activity of metal complexes immobilized on supports. Part 1. The synthesis of palladium complexes on silica gel, modified by aldiminopropylheteryl groups, and their properties

    Energy Technology Data Exchange (ETDEWEB)

    Nesterov, M.A.; Lafer, L.I.; Dykh, Z.L.; Sharf, V.Z.; Yakerson, V.I.

    1987-07-10

    Based on silica gel containing a ..gamma..-aminopropyl group and ..cap alpha..-, ..beta..-, and ..gamma..-aldehydes of the heterocyclic series, supports having graft aldimine groups and their stable complexes with palladium have been obtained. It has been established by IR spectroscopy that the hydroxyl coating of silica gel is almost completely replaced by functional groups of ligands combined with the surface through O atoms. The Pd atom is coordinated by the N atom of the aldimine group, the heteroatom of the pyridine ring, and in the case of furan by the ..pi..-electrons of the ring. The catalytic activity and selectivity of Pd complexes in the isomerization and hydrogenation of allylbenzene is determined by the nature of the grafted heterocyclic ligand.

  14. Deposition of Metal-Organic Frameworks by Liquid-Phase Epitaxy: The Influence of Substrate Functional Group Density on Film Orientation

    Science.gov (United States)

    Liu, Jinxuan; Shekhah, Osama; Stammer, Xia; Arslan, Hasan K.; Liu, Bo; Schüpbach, Björn; Terfort, Andreas; Wöll, Christof

    2012-01-01

    The liquid phase epitaxy (LPE) of the metal-organic framework (MOF) HKUST-1 has been studied for three different COOH-terminated templating organic surfaces prepared by the adsorption of self-assembled monolayers (SAMs) on gold substrates. Three different SAMs were used, mercaptohexadecanoic acid (MHDA), 4’-carboxyterphenyl-4-methanethiol (TPMTA) and 9-carboxy-10-(mercaptomethyl)triptycene (CMMT). The XRD data demonstrate that highly oriented HKUST-1 SURMOFs with an orientation along the (100) direction was obtained on MHDA-SAMs. In the case of the TPMTA-SAM, the quality of the deposited SURMOF films was found to be substantially inferior. Surprisingly, for the CMMT-SAMs, a different growth direction was obtained; XRD data reveal the deposition of highly oriented HKUST-1 SURMOFs grown along the (111) direction.

  15. Deposition of Metal-Organic Frameworks by Liquid-Phase Epitaxy: The Influence of Substrate Functional Group Density on Film Orientation

    Directory of Open Access Journals (Sweden)

    Christof Wöll

    2012-09-01

    Full Text Available The liquid phase epitaxy (LPE of the metal-organic framework (MOF HKUST-1 has been studied for three different COOH-terminated templating organic surfaces prepared by the adsorption of self-assembled monolayers (SAMs on gold substrates. Three different SAMs were used, mercaptohexadecanoic acid (MHDA, 4’-carboxyterphenyl-4-methanethiol (TPMTA and 9-carboxy-10-(mercaptomethyltriptycene (CMMT. The XRD data demonstrate that highly oriented HKUST-1 SURMOFs with an orientation along the (100 direction was obtained on MHDA-SAMs. In the case of the TPMTA-SAM, the quality of the deposited SURMOF films was found to be substantially inferior. Surprisingly, for the CMMT-SAMs, a different growth direction was obtained; XRD data reveal the deposition of highly oriented HKUST-1 SURMOFs grown along the (111 direction.

  16. Deposition of metal-organic frameworks by liquid-phase epitaxy: The influence of substrate functional group density on film orientation

    KAUST Repository

    Liu, J.

    2012-09-05

    The liquid phase epitaxy (LPE) of the metal-organic framework (MOF) HKUST-1 has been studied for three different COOH-terminated templating organic surfaces prepared by the adsorption of self-assembled monolayers (SAMs) on gold substrates. Three different SAMs were used, mercaptohexadecanoic acid (MHDA), 4\\'-carboxyterphenyl-4-methanethiol (TPMTA) and 9-carboxy-10-(mercaptomethyl)triptycene (CMMT). The XRD data demonstrate that highly oriented HKUST-1 SURMOFs with an orientation along the (100) direction was obtained on MHDA-SAMs. In the case of the TPMTA-SAM, the quality of the deposited SURMOF films was found to be substantially inferior. Surprisingly, for the CMMT-SAMs, a different growth direction was obtained; XRD data reveal the deposition of highly oriented HKUST-1 SURMOFs grown along the (111) direction.

  17. Synthesis of 1,3-diaryl-3-trifluoromethylcyclopropenes by transition-metal-free reaction of 2,2,2-trifluoroacetophenone tosylhydrazones with alkynes: the effect of the trifluoromethyl group.

    Science.gov (United States)

    Barroso, Raquel; Jiménez, Azucena; Pérez-Aguilar, M Carmen; Cabal, María-Paz; Valdés, Carlos

    2016-03-04

    1,3-Diaryl-3-trifluoromethylcyclopropenes and 2-aryl- or 2-alkyl-1,3-diaryl-3-trifluoromethylcyclopropenes are prepared in a very simple way by reaction between 1,1,1-trifluoroacetophenone tosylhydrazones and terminal or internal alkynes, respectively, in a base promoted process that does not require the presence of any metal catalyst. The essential role of the trifluoromethyl group, which enables the formation of the cyclopropenes instead of the expected pyrazoles, has been computationally investigated, suggesting the participation of a free carbene.

  18. Electrochemical, linear optical, and nonlinear optical properties and interpretation by density functional theory calculations of (4-N,N-dimethylaminostyryl)-pyridinium pendant group associated with polypyridinic ligands and respective multifunctional metal complexes (Ru(II) or Zn(II)).

    Science.gov (United States)

    Dumur, Frédéric; Mayer, Cédric R; Hoang-Thi, Khuyen; Ledoux-Rak, Isabelle; Miomandre, Fabien; Clavier, Gilles; Dumas, Eddy; Méallet-Renault, Rachel; Frigoli, Michel; Zyss, Joseph; Sécheresse, Francis

    2009-09-07

    The synthesis, linear optical and nonlinear optical properties, as well as the electrochemical behavior of a series of pro-ligands containing the 4-(4-N,N-dimethylaminostyryl)-1-methyl pyridinium (DASP(+)) group as a push-pull moiety covalently linked to terpyridine or bipyridine as chelating ligands are reported in this full paper. The corresponding multifunctional Ru(II) and Zn(II) complexes were prepared and investigated. The structural, electronic, and optical properties of the pro-ligands and the ruthenium complexes were investigated using density functional theory (DFT) and time-dependent (TD) DFT calculations. A fairly good agreement was observed between the experimental and the calculated electronic spectra of the pro-ligands and their corresponding ruthenium complexes. A quenching of luminescence was evidenced in all ruthenium complexes compared with the free pro-ligands but even the terpyridine-functionalized metal complexes exhibited detectable luminescence at room temperature. Second order nonlinear optical (NLO) measurements were performed by Harmonic Light Scattering and the contribution of the DASP(+) moieties (and their relative ordering) and the metal-polypyridyl core need to be considered to explain the nonlinear optical properties of the metal complexes.

  19. The effect of group IIIA metal ion dopants on the photocatalytic activities of nanocrystalline Sr0.25H1.5Ta2O6·H2O.

    Science.gov (United States)

    Liang, Shijing; Zhu, Shuying; Zhu, Jia; Chen, Yan; Zhang, Yongfan; Wu, Ling

    2012-01-21

    A series of group IIIA metal ion electron acceptors doped into Sr(0.25)H(1.5)Ta(2)O(6)·H(2)O (HST) samples have been prepared by an impregnation and calcination method for the first time. The samples are characterized by XRD, TEM, DRS and XPS. The variations in the electronic structure and photoelectric response after metal ion doping are investigated by theoretical calculations and photocurrent experiments, respectively. Results show that the metal ions can be efficiently incorporated into the HST crystal structure, which is reflected in the lattice contraction. Meanwhile, the photoabsorption edges of the metal-doped HST samples are red shifted to a longer wavelength. Taking into account the ionic radii and electronegativities of the dopants, as well as the XRD and XPS results, it is concluded that Ta(5+) ions may be partially substituted by the Al(3+) and Ga(3+) ions in the framework, while In(3+) ions are the favourable substitutes for Sr(2+) sites in the cavity. The first-principles DFT calculations confirm that the variation of the band structure is sensitive to the type of group IIIA metal ion. Introducing the dopant only at the Ta site induces an obvious variation in the band structure and the band gap becomes narrow. Meanwhile, an ''extra step'' appeared in the band gap, which can trap photogenerated electrons from the valance band (VB) and could enhance the charge mobility and the photocurrent. For the photocatalytic degradation of methyl orange in an aqueous solution and in benzene in the gas phase, the doped samples show superior photocatalytic activities compared with both undoped samples and TiO(2). The enhanced photocatalytic activities can be well explained by their electronic structure, photoabsorption performance, photoelectric response, and the concentration of the active species. Due to the fact that Ga ion doping can create an acceptor impurity level and change the electronic band, efficiently narrowing the band gap, the Ga-doped sample shows

  20. Enhancement of hydrogen adsorption in metal-organic frameworks by the incorporation of the sulfonate group and Li cations. A multiscale computational study.

    Science.gov (United States)

    Mavrandonakis, Andreas; Klontzas, Emmanouel; Tylianakis, Emmanuel; Froudakis, George E

    2009-09-23

    By means of ab initio methods, the effect on the H(2) storage ability of a newly proposed organic linker for IRMOF-14 has been studied. The linker comprises a negatively charged sulfonate (-SO(3)(-1)) group in combination with a Li cation. It is found that these two charged groups significantly increase the interaction energy between the hydrogen molecules and the new proposed organic linker of the MOF. The substituted group of the linker may host up to six hydrogen molecules with an average interaction energy of 1.5 kcal/mol per H(2) molecule. This value is three times larger than the binding energy over the bare linker that has been obtained from DFT calculations. GCMC atomistic simulations verified that the proposed material can be qualified among the highest adsorbing materials for volumetric capture of H(2), especially at ambient conditions. This functionalization strategy can be applied in many different MOF structures to enhance their storage abilities.

  1. 30 CFR 57.22211 - Air flow (I-A mines).

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Air flow (I-A mines). 57.22211 Section 57.22211... Methane in Metal and Nonmetal Mines Ventilation § 57.22211 Air flow (I-A mines). The average air velocity... openings nearest the face, shall be at least 40 feet per minute. The velocity of air ventilating each...

  2. Reactivity studies of group 15 Zintl ions towards homoleptic post-transition metal organometallics: a 'bottom-up' approach to bimetallic molecular clusters.

    Science.gov (United States)

    Knapp, Caroline; Zhou, Binbin; Denning, Mark S; Rees, Nicholas H; Goicoechea, Jose M

    2010-01-14

    Reactions between ethylenediamine (en) solutions of the intermetallic Zintl phases K(3)E(7) (E = P, As) and a series of homoleptic post-transition metal organometallics such as Cu(5)(Mes)(5), M(C(6)H(5))(2) (M = Zn, Cd) and In(C(6)H(5))(3) have yielded a family of novel bimetallic cluster anions. These new species were isolated as [K(2, 2,2-crypt)](+) salts in [K(2,2,2-crypt)](4)Cu(2)E(14) (E = P (1), As (2)), [K(2,2,2-crypt)](4)ZnE(14) (E = P (3), As (4)), [K(2,2,2-crypt)](4)CdP(14) x 6py (5) and [K(2,2,2-crypt)](2)E(7)InPh(2) (E = P (6), As (7)). Species 2, 3, 5 and 6 were crystallographically characterised by single-crystal X-ray diffraction. The stability of all of the cluster anions in solution was confirmed by electrospray mass-spectrometry and by (1)H, (13)C{(1)H} and (31)P{(1)H} NMR spectroscopy when possible.

  3. Synthesis and structural study of platinum group metal complexes containing pyrimidine bridged pyrazolyl-pyridine ligand and 5 and 6 - cyclic hydrocarbons

    Indian Academy of Sciences (India)

    Thirumala Prasad Kota; Mohan Rao Kollipara

    2014-07-01

    The mononuclear compounds [(6-arene)Ru(bppm)Cl]PF6{bppm = 4,6-bis3-(2-pyridyl)-1Hpyrazol-1-yl}pyrimidine; arene = C6H6, [1]; -$^i$PrC6H4Me, [2]; C6Me6, [3]}, [CpRu(bppm)(PPh3)]PF6{Cp = 5-C5H5, [4]; 5-C5Me5, [5]; 5-C9H7, [6]} and [Cp∗M(bppm)Cl]PF6 {M = Rh [7]; Ir [8]} have been synthesized from the reaction of 4,6-bis{3-(2-pyridyl)-1H-pyrazol-1-yl}pyrimidine (bppm) and the corresponding precursor metal complexes [(6-arene)Ru(-Cl)Cl]2, [CpRu(PPh3)2Cl] and [Cp∗M(-Cl)Cl]2, respectively, in the presence of NH4PF6. They were characterized by the following techniques viz. IR, NMR, mass spectrometry and UV-visible spectroscopy. The molecular structures of [2] and [7] have been established by single crystal X-ray structure analyses.

  4. O2 insertion into group 9 metal-hydride bonds: evidence for oxygen activation through the hydrogen-atom-abstraction mechanism.

    Science.gov (United States)

    Keith, Jason M; Teets, Thomas S; Nocera, Daniel G

    2012-09-03

    A detailed density functional study was performed to examine the reaction of mixed-valence dirhodium and diiridium species [M(2)(0,II)(tfepma)(2)(CN(t)Bu)(2)(Cl)(2) (1, tfepma = MeN[P(OCH(2)CF(3))(2)](2), CN(t)Bu = tert-butyl isocyaninde)] with HCl and oxygen with an interest in examining the pathways for oxygen insertion into the intermediate metal hydride to form hydroperoxo species. The O(2) hydrogen atom abstraction mechanism for both the Rh and Ir was found to be feasible. This is the first time this mechanism has been applied to a Rh system and only the second time it has been examined for a system other than Pd. The competing trans HCl reductive elimination pathway was also examined and found to be greatly dependent on the stereochemistry of the starting hydride primarily due to the intermediate formed upon the loss of Cl(-). As a result, the reductive elimination pathway was more favorable by 11.5 kcal/mol for the experimentally observed Ir stereoisomer, while the two pathways were isoenergetic for the other stereoisomer of the Rh complex. All findings are consistent with the kinetics study previously performed.

  5. 5 and 6 - cyclic -perimeter hydrocarbon platinum group metal complexes of 3-(2-pyridyl)pyrazole derived ligands with a pendant nitrile group: Syntheses, spectral and structural studies

    Indian Academy of Sciences (India)

    Gloria Sairem; Venkateswara Rao Anna; Peng Wang; Bbulal Das; Mohan Rao Kollipara

    2012-03-01

    Reaction of two equivalents 4-{(3-(pyridine-2-yl) 1H-pyrazole-1-yl}methyl benzonitrile (L1) and 3-{(3-(pyridine-2-yl)1H-pyrazole-1-yl}methyl benzonitrile (L2) with one equivalent of [(6-arene)Ru(- Cl)Cl]2 and [Cp∗M(-Cl)Cl]2 in methanol yielded mononuclear complexes of the formulae [(6-arene)Ru(L1/L2)Cl]BF4{arene =C6H6 (1, 6); C10H14 (2, 7); C6Me6 (3, 8)} and [Cp∗M(L1/L2)Cl]PF6/BF4 {Cp∗= 5-C5Me5, M=Rh (4, 8); Ir (5, 10)}. These complexes are characterized by IR, 1H NMR and identities of the structure are established by single crystal XRD studies of some of the representative complexes. It is confirmed from the spectral studies that the nitrile group is not taking part in complexation; instead it remains as a free pendant group only.

  6. Interaction between anions and cationic metal complexes containing tridentate ligands with exo-C-H groups: complex stability and hydrogen bonding.

    Science.gov (United States)

    Martínez-García, Héctor; Morales, Dolores; Pérez, Julio; Puerto, Marcos; del Río, Ignacio

    2014-05-05

    [Re(CO)3 ([9]aneS3 )][BAr'4 ] (1), prepared by reaction of ReBr(CO)5 , 1,4,7-trithiacyclononane ([9]aneS3 ) and NaBAr'4 , forms stable, soluble supramolecular adducts with chloride (2), bromide, methanosulfonate (3) and fluoride (4) anions. These new species were characterized by IR, NMR spectroscopy and, for 2 and 3, also by X-ray diffraction. The results of the solid state structure determinations indicate the formation of CH⋅⋅⋅X hydrogen bonds between the anion (X) and the exo-CH groups of the [9]aneS3 ligand, in accord with the relatively large shifts found by (1) H NMR spectroscopy in dichloromethane solution for those hydrogens. The stability of the chloride adduct contrasts with the lability of the [9]aneS3 ligand in allyldicarbonyl molybdenum complexes recently studied by us. With fluoride, in dichloromethane solution, a second, minor neutral dimeric species 5 is formed in addition to 4. In 4, the deprotonation of a CH group of the [9]aneS3 ligand, accompanied by CS bond cleavage and dimerization, afforded 5, featuring bridging thiolates. Compounds [Mo(η(3) -methallyl)(CO)2 (TpyN)][BAr'4 ] (6) and [Mo(η(3) -methallyl)(CO)2 (TpyCH)][BAr'4 ] (7) were synthesized by the reactions of [MoCl(η(3) -methallyl)(CO)2 (NCMe)2 ], NaBAr'4 and tris(2-pyridyl)amine (TpyN) or tris(2-pyridyl)methane (TpyCH) respectively, and characterized by IR and (1) H and (13) C NMR spectroscopy in solution, and by X-ray diffraction in the solid state. Compound 6 undergoes facile substitution of one of the 2-pyridyl groups by chloride, bromide, and methanosulfonate anions. Stable supramolecular adducts were formed between 7 and chloride, bromide, iodide, nitrate, and perrhenate anions. The solid state structures of these adducts (12-16) were determined by X-ray diffraction. Binding constants in dichloromethane were calculated from (1) H NMR titration data for all the new supramolecular adducts. The signal of the bridgehead CH group is the one that undergoes a

  7. Metallated metal-organic frameworks

    Energy Technology Data Exchange (ETDEWEB)

    Bury, Wojciech; Farha, Omar K.; Hupp, Joseph T.; Mondloch, Joseph E.

    2017-08-22

    Porous metal-organic frameworks (MOFs) and metallated porous MOFs are provided. Also provided are methods of metallating porous MOFs using atomic layer deposition and methods of using the metallated MOFs as catalysts and in remediation applications.

  8. Metallated metal-organic frameworks

    Energy Technology Data Exchange (ETDEWEB)

    Bury, Wojciech; Farha, Omar K.; Hupp, Joseph T.; Mondloch, Joseph E.

    2017-02-07

    Porous metal-organic frameworks (MOFs) and metallated porous MOFs are provided. Also provided are methods of metallating porous MOFs using atomic layer deposition and methods of using the metallated MOFs as catalysts and in remediation applications.

  9. New rht-Type Metal-Organic Frameworks Decorated with Acylamide Groups for Efficient Carbon Dioxide Capture and Chemical Fixation from Raw Power Plant Flue Gas.

    Science.gov (United States)

    Guo, Xiangyang; Zhou, Zhen; Chen, Cong; Bai, Junfeng; He, Cheng; Duan, Chunying

    2016-11-23

    The combination of carbon dioxide capture and chemical fixation in a one-pot process is attractive for both chemists and governments. The cycloaddition of carbon dioxide with epoxides to produce cyclic carbonates is an atomic economical reaction without any side products. By incorporating acylamide to enhance the binding affinity toward CO2, new rht-type metal-organic frameworks (MOFs) with (3, 28) and (3, 24) connected units were constructed. Zn-NTTA with two types of dinuclear paddlewheel building blocks-{Zn2(OOC(-))4} and {Zn2(OOC(-))3}. The high uptake of CO2 (115.6 cm(3)·g(-1)) and selectivity over N2 (30:1) at 273 K indicated that these MOFs are excellent candidates for postcombustion CO2 isolation and capture. The MOFs feature high catalytic activity, rapid dynamics of transformation and excellent stability with turnover number (TON) values up to 110 000 per paddlewheel unit after 5 × 6 rounds of recyclability, demonstrating that they are promising heterogeneous catalysts for CO2 cyclo-addition to value-added cyclic carbonates. The cycloaddition of epoxides with wet gases demonstrated that the catalyst activity was not affected by moisture, and the indices of the PXRD patterns of the bulk samples filtered from the catalytic reaction revealed that the crystallinities were maintained. The combination of the selective capture and catalytic transformation in one-pot enables the use of a negative-cost feedstock-raw power plant flue gas without any separation and purification-revealing the broad prospects of such MOFs for practical CO2 fixation in industry.

  10. Group 4 metal complexes of Trost's semi-crown ligand: synthesis, structural characterization and studies on the ring-opening polymerization of lactides and ε-caprolactone.

    Science.gov (United States)

    Rajashekhar, Bijja; Roymuhury, Sagnik K; Chakraborty, Debashis; Ramkumar, Venkatachalam

    2015-10-07

    The synthesis of titanium(IV), zirconium(IV) and hafnium(IV) complexes of Trost's semi-crown ligand is described. All complexes were fully characterized by 1H and 13C NMR and mass spectroscopy. The molecular structures of the representative complexes 2, 3 and 4 were determined by single-crystal X-ray diffraction studies. The X-ray diffraction studies reveal that complexes 2, 3 and 4 crystallized in an orthorhombic crystal system. Complexes 2 and 3 have a monomeric structure in the solid state with distorted octahedral geometry around the metal center, whereas complex 4 was found to crystallize in a trimeric structure bridging with an oxygen atom, where the geometry around the titanium is distorted trigonal bipyramidal. The activities and stereoselectivities of these complexes toward the ring-opening polymerization (ROP) of lactides (L-LA and rac-LA) and ε-caprolactone (CL) have been investigated. Complexes 1–4 were found to be efficient single-component initiators for the ring-opening polymerization of cyclic esters and yielded high molecular weight polymers (Mn) with narrow molecular weight distributions (MWD).The microstructure of the resultant polylactides (PLAs) from rac-LA was determined. Complexes 2 and 3 afforded isotactic-enriched PLA (Pm = 0.78–0.71) with narrow MWD (1.07–1.04), on the other hand complexes 1 and 4 produced atactic PLA. Kinetic and post polymerization studies confirm that the polymerization proceeds through the coordination–insertion mechanism.

  11. Interatomic potentials for van der Waals complexes of group 13 metal atoms: AlAr, AlKr, and AlXe

    Science.gov (United States)

    Callender, C. L.; Mitchell, S. A.; Hackett, P. A.

    1989-05-01

    Interatomic potential parameters for the ground X1,2 2Π1/2,3/2 and excited B 2Σ+1/2 states of jet-cooled van der Waals complexes of Al atoms with rare gases have been determined from fluorescence excitation and emission spectra. Vibrational numbering in the B states is established from isotopic and rotational broadening of fluorescence excitation line shapes. Bond distances are estimated by comparison with analogous states of alkali-rare gas molecules, and by modeling observed relative emission intensities with calculated Franck-Condon factors. Morse potentials are found to adequately describe the data for the ground states, but for the excited states there are indications of departures from Morse functions at large internuclear distances. Dissociation energies De are estimated from Birge-Sponer extrapolations. Multiplet splittings in Al-rare gas complexes are compared to those in In-rare gas complexes and are discussed in terms of an empirical treatment of spin-orbit coupling, which assumes that the spin-orbit coupling constant for the molecule is the same as that for the atom. The ground X1 state of each Al-rare gas molecule is more stable than that of the analogous In complex, whereas the spin-orbit excited X2 state is less stable. This is explained by the greater mixing between the X1 state and the dissociative A 2Σ+1/2 state for indium over aluminum, caused by the greater spin-orbit coupling constant for the heavier metal.

  12. Fabrication of Metallic Hollow Nanoparticles

    Science.gov (United States)

    Kim, Jae-Woo (Inventor); Choi, Sr., Sang H. (Inventor); Lillehei, Peter T. (Inventor); Chu, Sang-Hyon (Inventor); Park, Yeonjoon (Inventor); King, Glen C. (Inventor); Elliott, James R. (Inventor)

    2016-01-01

    Metal and semiconductor nanoshells, particularly transition metal nanoshells, are fabricated using dendrimer molecules. Metallic colloids, metallic ions or semiconductors are attached to amine groups on the dendrimer surface in stabilized solution for the surface seeding method and the surface seedless method, respectively. Subsequently, the process is repeated with additional metallic ions or semiconductor, a stabilizer, and NaBH.sub.4 to increase the wall thickness of the metallic or semiconductor lining on the dendrimer surface. Metallic or semiconductor ions are automatically reduced on the metallic or semiconductor nanoparticles causing the formation of hollow metallic or semiconductor nanoparticles. The void size of the formed hollow nanoparticles depends on the dendrimer generation. The thickness of the metallic or semiconductor thin film around the dendrimer depends on the repetition times and the size of initial metallic or semiconductor seeds.

  13. Synthesis and Exploratory Catalysis of 3d Metals: Group-Transfer Reactions, and the Activation and Functionalization of Small Molecules Including Greenhouse Gases

    Energy Technology Data Exchange (ETDEWEB)

    Mindiola, Daniel J.

    2014-05-07

    Our work over the past three years has resulted in the development of electron rich and low-coordinate vanadium fragments, molecular nitrides of vanadium and parent imide systems of titanium, and the synthesis of phosphorus containing molecules of the 3d transition metal series. Likewise, with financial support from BES Division in DOE (DE-FG02-07ER15893), we now completed the full characterization of the first single molecular magnet (SMM) of Fe(III). We demonstrated that this monomeric form of Fe(III) has an unusual slow relaxation of the magnetization under zero applied field. To make matters more interesting, this system also undergoes a rare example of an intermediate to high-spin transition (an S = 3/2 to S = 5/2 transition). In 2010 we reported the synthesis of the first neutral and low-coordinate vanadium complexes having the terminal nitride functionality. We have now completed a full study to understand formation of the nitride ligand from the metastable azide precursor, and have also explored the reactivity of the nitride ligand in the context of incomplete and complete N-atom transfer. During the 2010-2013 period we also discovered a facile approach to assemble low-coordinate and low-valent vanadium(II) complexes and exploit their multielectron chemistry ranging from 1-3 electrons. Consequently, we can now access 3d ligand frameworks such as cyclo-P3 (and its corresponding radical anion), nitride radical anions and cations, low-coordinate vanadium oxo’s, and the first example of a vanadium thionitrosyl complex. A cis-divacant iron(IV) imido having some ligand centered radical has been also discovered, and we are in the process of elucidating its electronic structure (in particular the sign of zero field splitting and the origin of its magnitude), bonding and reactivity. We have also revisited some paramagnetic and classic metallocene compounds with S >1/2 ground states in order to understand their reactivity patterns and electronic structure. Lastly

  14. Hard rock, heavy metal, metal

    OpenAIRE

    Hein, Fabien

    2011-01-01

    Le terme générique metal désigne une multitude de genres et de sous-genres musicaux issus de l’appariement du hard rock et du heavy metal. Il résulte d’une agrégation sémantique consécutive de l’érosion et de l’interpénétration de ces termes au cours des années 1980. Leurs modèles canoniques, respectivement représentés par les groupes Led Zeppelin et Black Sabbath, se sont progressivement dilués sous l’effet d’une filiation particulièrement effervescente et féconde : black, thrash, doom, prog...

  15. The Synthesis of π,n-Complexes of 1-Thio-1,3-dienes with Chromium Group Metals. The Inner-Sphere Hydrophosphorylation of α-Enethiones

    Directory of Open Access Journals (Sweden)

    Kuramshin A.I.

    2015-06-01

    Full Text Available New 1-thio-1,3-diene complexes of chromium(0, molybdenum(0, and tungsten(0 with the biden-tate bonding of unsaturated ligand to the metal’s core via the π-system of the C=C bond and sulfur lone electron pair of heterodiene are obtained. Quantum-chemical calculations reveal geometry, electron structure, and formation free energies of these complexes, as well as factors governing the coordination mode. Hydrophosphorylation of the complexes begins from the attack of H-dialkylphosphonate towards the thiocarbonyl group; the generated organometallic α-mercaptophosphonates subsequently undergo the mercaptophosphonate-thiolphospate and thiolphosphate-thionphosphate rearrangements with organ-ophosphorus compounds remaining bound to the metal’s core.

  16. Multi-elemental characterization of tunnel and road dusts in Houston, Texas using dynamic reaction cell-quadrupole-inductively coupled plasma-mass spectrometry: Evidence for the release of platinum group and anthropogenic metals from motor vehicles

    Energy Technology Data Exchange (ETDEWEB)

    Spada, Nicholas; Bozlaker, Ayse [Department of Civil and Environmental Engineering, University of Houston, Houston, TX 77204-4003 (United States); Chellam, Shankararaman, E-mail: chellam@uh.edu [Department of Civil and Environmental Engineering, University of Houston, Houston, TX 77204-4003 (United States); Department of Chemical and Biomolecular Engineering, University of Houston, Houston, TX 77204-4004 (United States)

    2012-07-20

    Highlights: Black-Right-Pointing-Pointer Analytical method for PGEs, main group, transition and rare earth metals developed. Black-Right-Pointing-Pointer Comprehensive characterization of road and tunnel dust samples was accomplished. Black-Right-Pointing-Pointer PGEs in dusts arise from autocatalyst attrition. Black-Right-Pointing-Pointer Mobile sources also contributed to Cu, Zn, Ga, As, Mo, Cd, Sn, Sb, Ba, W and Pb. Black-Right-Pointing-Pointer All other elements, including rare earths arose from crustal sources. - Abstract: Platinum group elements (PGEs) including Rh, Pd, and Pt are important tracers for vehicular emissions, though their measurement is often challenging and difficult to replicate in environmental campaigns. These challenges arise from sample preparation steps required for PGE quantitation, which often cause severe isobaric interferences and spectral overlaps from polyatomic species of other anthropogenically emitted metals. Consequently, most previous road dust studies have either only quantified PGEs or included a small number of anthropogenic elements. Therefore a novel analytical method was developed to simultaneously measure PGEs, lanthanoids, transition and main group elements to comprehensively characterize the elemental composition of urban road and tunnel dusts. Dust samples collected from the vicinity of high-traffic roadways and a busy underwater tunnel restricted to single-axle (predominantly gasoline-driven) vehicles in Houston, TX were analyzed for 45 metals with the newly developed method using dynamic reaction cell-quadrupole-inductively coupled plasma-mass spectrometry (DRC-q-ICP-MS). Average Rh, Pd and Pt concentrations were 152 {+-} 52, 770 {+-} 208 and 529 {+-} 130 ng g{sup -1} respectively in tunnel dusts while they varied between 6 and 8 ng g{sup -1}, 10 and 88 ng g{sup -1} and 35 and 131 ng g{sup -1} in surface road dusts. Elemental ratios and enrichment factors demonstrated that PGEs in dusts originated from autocatalyst

  17. METALS DEPOSITS

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    <正>20111705 An Junbo(Team 603,Bureau of Nonferrous Metals Geological Exploration of Jilin Province,Hunchun 133300,China);Xu Renjie Geological Features and Ore Genesis of Baishilazi Scheelite Deposit in Yanbian Area(Jilin Geology,ISSN1001-2427,CN22-1099/P,29(3),2010,p.39-43,2 illus.,2 tables,7 refs.)Key words:tungsten ores,Jilin ProvinceThe Baishilazi scheelite deposit is located in contacting zone between the marble of the Late Palaeozoic Qinglongcun Group and the Hercynian biotite granite.The vein and lenticular major ore body is obviously controlled by NE-extending faults and con

  18. In-situ Evaluation of Soil Organic Molecules: Functional Group Chemistry Aggregate Structures, Metal & Surface Complexation Using Soft X-Ray

    Energy Technology Data Exchange (ETDEWEB)

    Myneni, Satish, C

    2008-11-30

    Organic molecules are common in all Earth surface environments, and their composition and chemistry play an important role in a variety of biogeochemical reactions, such as mineral weathering, nutrient cycling and the solubility and transport of contaminants. However, most of what we know about the chemistry of these molecules comes from spectroscopy and microscopy studies of organic molecules extracted from different natural systems using either inorganic or organic solvents. Although all these methods gave us clues about the composition of these molecules, their composition and structure change with the extraction and the type of ex-situ analysis, their true behavior is less well understood. The goal of this project is to develop synchrotron instrumentation for studying natural organics, and to apply these recently developed synchrotron X-ray spectroscopy and microscopy techniques for understanding the: (1) functional group composition of naturally occurring organic molecules; (2) macromolecular structures of organic molecules; and (3) the nature of interactions of organic molecules with mineral surfaces in different environmental conditions.

  19. Metal-free protodeboronation of electron-rich arene boronic acids and its application to ortho-functionalization of electron-rich arenes using a boronic acid as a blocking group.

    Science.gov (United States)

    Ahn, Su-Jin; Lee, Chun-Young; Kim, Nak-Kyoon; Cheon, Cheol-Hong

    2014-08-15

    The metal-free thermal protodeboronation of various electron-rich arene boronic acids was studied. Several reaction parameters controlling this protodeboronation, such as solvent, temperature, and a proton source, have been investigated. On the basis of these studies, suitable reaction conditions for protodeboronation of several types of electron-rich arene boronic acids were provided. On the basis of this protodeboronation, a new protocol for the synthesis of ortho-functionalized electron-rich arenes from these boronic acids was developed using the boronic acid moiety as a blocking group in the electrophilic aromatic substitution reaction, followed by the removal of the boronic acid moiety via thermal protodeboronation. Mechanistic studies suggested that this protodeboronation might proceed via the complex formation of a boronic acid with a proton source, followed by the carbon-boron bond fission through σ-bond metathesis, to afford the corresponding arene compound and boric acid.

  20. Immunology of metal allergies.

    Science.gov (United States)

    Schmidt, Marc; Goebeler, Matthias

    2015-07-01

    Allergic contact hypersensitivity to metal allergens is a common health concern worldwide, greatly impacting affected individuals with regard to both quality of life and their ability to work. With an estimated 15-20 % of the Western population hypersensitive to at least one metal allergen, sensitization rates for metallic haptens by far outnumber those reported for other common triggers of allergic contact dermatitis such as fragrances and rubber. Unfortunately, the prevalence of metal-induced hypersensitivity remains high despite extensive legislative efforts to ban/reduce the content of allergy-causing metals in recreational and occupational products. Recently, much progress has been made regarding the perception mechanisms underlying the inflammatory responses to this unique group of contact allergens. This review summarizes recent advances in our understanding of this enigmatic disease. Particular emphasis is put on the mechanisms of innate immune activation and T cell activation by common metal allergens such as nickel, cobalt, palladium, and chromate.

  1. Degenerate doping of metallic anodes

    Science.gov (United States)

    Friesen, Cody A; Zeller, Robert A; Johnson, Paul B; Switzer, Elise E

    2015-05-12

    Embodiments of the invention relate to an electrochemical cell comprising: (i) a fuel electrode comprising a metal fuel, (ii) a positive electrode, (iii) an ionically conductive medium, and (iv) a dopant; the electrodes being operable in a discharge mode wherein the metal fuel is oxidized at the fuel electrode and the dopant increases the conductivity of the metal fuel oxidation product. In an embodiment, the oxidation product comprises an oxide of the metal fuel which is doped degenerately. In an embodiment, the positive electrode is an air electrode that absorbs gaseous oxygen, wherein during discharge mode, oxygen is reduced at the air electrode. Embodiments of the invention also relate to methods of producing an electrode comprising a metal and a doped metal oxidation product.

  2. Scalar relativistic calculations of hyperfine coupling constants using ab initio density matrix renormalization group method in combination with third-order Douglas-Kroll-Hess transformation: case studies on 4d transition metals.

    Science.gov (United States)

    Nguyen Lan, Tran; Kurashige, Yuki; Yanai, Takeshi

    2015-01-13

    We have developed a new computational scheme for high-accuracy prediction of the isotropic hyperfine coupling constant (HFCC) of heavy molecules, accounting for the high-level electron correlation effects, as well as the scalar-relativistic effects. For electron correlation, we employed the ab initio density matrix renormalization group (DMRG) method in conjunction with a complete active space model. The orbital-optimization procedure was employed to obtain the optimized orbitals required for accurately determining the isotropic HFCC. For the scalar-relativistic effects, we initially derived and implemented the Douglas-Kroll-Hess (DKH) hyperfine coupling operators up to the third order (DKH3) by using the direct transformation scheme. A set of 4d transition-metal radicals consisting of Ag atom, PdH, and RhH2 were chosen as test cases. Good agreement between the isotropic HFCC values obtained from DMRG/DKH3 and experiment was archived. Because there are no available gas-phase values for PdH and RhH2 radicals in the literature, the results from the present high-level theory may serve as benchmark data.

  3. Group 6 Layered Transition-Metal Dichalcogenides in Lab-on-a-Chip Devices: 1T-Phase WS2 for Microfluidics Non-Enzymatic Detection of Hydrogen Peroxide.

    Science.gov (United States)

    Toh, Rou Jun; Mayorga-Martinez, Carmen C; Han, Jongyoon; Sofer, Zdenek; Pumera, Martin

    2017-05-02

    Two-dimensional (2D) layered transition-metal dichalcogenides (TMDs) have been placed in the spotlight for their advantageous properties for catalytic and sensing applications. However, little work is done to explore and exploit them in enhancing the performance of analytical lab-on-a-chip (LOC) devices. In this work, we demonstrate a simple, sensitive, and low-cost fabrication of electrochemical LOC microfluidic devices to be used for enzymatic detection. We integrated four t-BuLi exfoliated, group 6 TMD materials (MoS2, MoSe2, WS2, and WSe2) within the LOC devices by the drop-casting method and compared their performance for H2O2 detection. The 1T-phase WS2-based LOC device outperformed the rest of the TMD materials and exhibited a wide range of linear response (20 nM to 20 μM and 100 μM to 2 mM), low detection limit (2.0 nM), and good selectivity for applications in real sample analysis. This work may facilitate the expanded use of electrochemical LOC microfluidics, with its easier integrability, for applications in the field of biodiagnostics and sensing.

  4. The Close Relationships between the Crystal Structures of MO and MSO 4 (M = Group 10, 11, or 12 Metal), and the Predicted Structures of AuO and PtSO 4

    KAUST Repository

    Derzsi, Mariana

    2013-08-21

    The structural relations of (and between) late transition metal monoxides, MO, and monosulfates, MSO4, are analyzed. We show that all of these late transition metal oxides, as well as 4d and 5d metal sulfates, crystallize in distorted rock salt lattices and argue that the distortions are driven by collective first- and/or second order Jahn-Teller effects. The collective Jahn-Teller deformations lead either to tetragonal contraction or (seldom) elongation of the rock salt lattice. On the basis of the rock salt representation of the oxides and sulfates, we show that PdO, CuO, and AgO are metrically related and that the 4d and 5d metal sulfates are close to isostructural with their oxides. These observations guide us towards as yet unknown AuO and PtSO4, for which we predict crystal structures from electronic structure calculations. The structural relations of (and between) late transition metal monoxides, MO, and monosulfates, MSO4, are analyzed. We show that all of these late transition metal oxides, as well as 4d and 5d metal sulfates, crystallize in distorted rock salt lattices and argue that the distortions are driven by collective first- and/or second order Jahn-Teller effects, as quantified by the c′/a′ ratio. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. GREAT I. A Position Paper of the PPIWG (Public Participation and Information Work Group) Executive Board.

    Science.gov (United States)

    1978-09-01

    furtraders in pirogues and bateau followed from 1730 to 1750. 1760: Keelboats transported early settlers and military parties followed by flatboats...result in a major reduction in sediment yields to the river. 6. Raw sand dredged material piles should be stabilized with vegetation. 7. Monitoring of

  6. Group X

    Energy Technology Data Exchange (ETDEWEB)

    Fields, Susannah

    2007-08-16

    This project is currently under contract for research through the Department of Homeland Security until 2011. The group I was responsible for studying has to remain confidential so as not to affect the current project. All dates, reference links and authors, and other distinguishing characteristics of the original group have been removed from this report. All references to the name of this group or the individual splinter groups has been changed to 'Group X'. I have been collecting texts from a variety of sources intended for the use of recruiting and radicalizing members for Group X splinter groups for the purpose of researching the motivation and intent of leaders of those groups and their influence over the likelihood of group radicalization. This work included visiting many Group X websites to find information on splinter group leaders and finding their statements to new and old members. This proved difficult because the splinter groups of Group X are united in beliefs, but differ in public opinion. They are eager to tear each other down, prove their superiority, and yet remain anonymous. After a few weeks of intense searching, a list of eight recruiting texts and eight radicalizing texts from a variety of Group X leaders were compiled.

  7. Triple Point Topological Metals

    Directory of Open Access Journals (Sweden)

    Ziming Zhu

    2016-07-01

    Full Text Available Topologically protected fermionic quasiparticles appear in metals, where band degeneracies occur at the Fermi level, dictated by the band structure topology. While in some metals these quasiparticles are direct analogues of elementary fermionic particles of the relativistic quantum field theory, other metals can have symmetries that give rise to quasiparticles, fundamentally different from those known in high-energy physics. Here, we report on a new type of topological quasiparticles—triple point fermions—realized in metals with symmorphic crystal structure, which host crossings of three bands in the vicinity of the Fermi level protected by point group symmetries. We find two topologically different types of triple point fermions, both distinct from any other topological quasiparticles reported to date. We provide examples of existing materials that host triple point fermions of both types and discuss a variety of physical phenomena associated with these quasiparticles, such as the occurrence of topological surface Fermi arcs, transport anomalies, and topological Lifshitz transitions.

  8. VLSI metallization

    CERN Document Server

    Einspruch, Norman G; Gildenblat, Gennady Sh

    1987-01-01

    VLSI Electronics Microstructure Science, Volume 15: VLSI Metallization discusses the various issues and problems related to VLSI metallization. It details the available solutions and presents emerging trends.This volume is comprised of 10 chapters. The two introductory chapters, Chapter 1 and 2 serve as general references for the electrical and metallurgical properties of thin conducting films. Subsequent chapters review the various aspects of VLSI metallization. The order of presentation has been chosen to follow the common processing sequence. In Chapter 3, some relevant metal deposition tec

  9. Group morphology

    NARCIS (Netherlands)

    Roerdink, Jos B.T.M.

    2000-01-01

    In its original form, mathematical morphology is a theory of binary image transformations which are invariant under the group of Euclidean translations. This paper surveys and extends constructions of morphological operators which are invariant under a more general group TT, such as the motion group

  10. Interplay of metal-allyl and metal-metal bonding in dimolybdenum allyl complexes

    Energy Technology Data Exchange (ETDEWEB)

    John, Kevin D [Los Alamos National Laboratory; Martin, Richard L [Los Alamos National Laboratory; Obrey, Steven J [Los Alamos National Laboratory; Scott, Brian L [Los Alamos National Laboratory

    2008-01-01

    Addition of PMe{sub 3} to Mo{sub 2}(allyl){sub 4} afforded Mo{sub 2}(allyl){sub 4}(PMe{sub 3}){sub 2}, in which two of the allyl groups adopt an unprecedented {mu}{sub 2{sup -}}{eta}{sup 1}, {eta}{sup 3} bonding mode; theoretical studies elucidate the role sof the {sigma}- and {pi}-donor ligands in the interplay of metal-allyl and metal-metal bonding.

  11. Metal Detectors.

    Science.gov (United States)

    Harrington-Lueker, Donna

    1992-01-01

    Schools that count on metal detectors to stem the flow of weapons into the schools create a false sense of security. Recommendations include investing in personnel rather than hardware, cultivating the confidence of law-abiding students, and enforcing discipline. Metal detectors can be quite effective at afterschool events. (MLF)

  12. The extragalactic origin of the Arcturus group

    NARCIS (Netherlands)

    Navarro, JF; Helmi, A; Freeman, KC

    2004-01-01

    We reanalyze the group of stars associated kinematically with Arcturus and confirm that they constitute a peculiar grouping of metal-poor stars with similar apocentric radius, common angular momentum, and distinct metal abundance patterns. These properties are consistent with those expected for a gr

  13. Group devaluation and group identification

    NARCIS (Netherlands)

    Leach, C.W.; Rodriguez Mosquera, P.M.; Vliek, M.L.W.; Hirt, E.

    2010-01-01

    In three studies, we showed that increased in-group identification after (perceived or actual) group devaluation is an assertion of a (preexisting) positive social identity that counters the negative social identity implied in societal devaluation. Two studies with real-world groups used order manip

  14. [Metal poisoning].

    Science.gov (United States)

    Ferrer, A

    2003-01-01

    Metals are amongst the oldest toxic substances known to man. In today's industrialized world the sources of exposure to metals are ubiquitous both in the field of work and from polluted water, foodstuffs and the environment. Their toxicity is characterized by the metallic element in question, but this is modified by the type of compound, whether organic or inorganic, and its characteristics of hydrosolubility and liposolubility, which determines its toxicokinetics and thus the possibilities of it reaching its targets. The biomolecules most affected by metals are the proteins with enzymatic activity, which is why their pathology is multisystemic. The principal systems affected are the gastrointestinal, central and peripheral neurological, haematic and renal. Some metallic compounds are carcinogenic. Metals's treatment is conditioned by their chemical reactivity. They can be deactivated and eliminated by the administering of chelating agents that produce complex molecules, which are non-toxic and can be excreted. The principal chelating agents are: BAL (British Anti-Lewisite or dimercaprol) DMPS (2,3-Dimercapto-1-propanesulfonic Acid) and DMSA (meso-2,3-Dimercaptosuccinic or Succimer), EDTA, Penicilamine (b,b-dimethylcysteine) and Deferoxamine. Toxicokinetic characteristics, mechanism of action, clinical picture and treatment of some of the most relevant metals and metalloids: lead, mercury and arsenic, are considered.

  15. Metals 2000

    Energy Technology Data Exchange (ETDEWEB)

    Allison, S.W.; Rogers, L.C.; Slaughter, G. [Oak Ridge National Lab., TN (United States); Boensch, F.D. [6025 Oak Hill Lane, Centerville, OH (United States); Claus, R.O.; de Vries, M. [Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States)

    1993-05-01

    This strategic planning exercise identified and characterized new and emerging advanced metallic technologies in the context of the drastic changes in global politics and decreasing fiscal resources. In consideration of a hierarchy of technology thrusts stated by various Department of Defense (DOD) spokesmen, and the need to find new and creative ways to acquire and organize programs within an evolving Wright Laboratory, five major candidate programs identified are: C-17 Flap, Transport Fuselage, Mach 5 Aircraft, 4.Fighter Structures, and 5. Missile Structures. These results were formed by extensive discussion with selected major contractors and other experts, and a survey of advanced metallic structure materials. Candidate structural applications with detailed metal structure descriptions bracket a wide variety of uses which warrant consideration for the suggested programs. An analysis on implementing smart skins and structures concepts is given from a metal structures perspective.

  16. ' HEAVY METALS

    African Journals Online (AJOL)

    exposed fish were about 3-5 times higher than the concentrations detected in control fish. ... The outcome effect 15 impairment of carbohydrate metabolism, which caused fish ..... of pesticides, heavy metal, detergent and petroleum.

  17. Algebraic Groups

    DEFF Research Database (Denmark)

    2007-01-01

    The workshop continued a series of Oberwolfach meetings on algebraic groups, started in 1971 by Tonny Springer and Jacques Tits who both attended the present conference. This time, the organizers were Michel Brion, Jens Carsten Jantzen, and Raphaël Rouquier. During the last years, the subject...... of algebraic groups (in a broad sense) has seen important developments in several directions, also related to representation theory and algebraic geometry. The workshop aimed at presenting some of these developments in order to make them accessible to a "general audience" of algebraic group......-theorists, and to stimulate contacts between participants. Each of the first four days was dedicated to one area of research that has recently seen decisive progress: \\begin{itemize} \\item structure and classification of wonderful varieties, \\item finite reductive groups and character sheaves, \\item quantum cohomology...

  18. Group Grammar

    Science.gov (United States)

    Adams, Karen

    2015-01-01

    In this article Karen Adams demonstrates how to incorporate group grammar techniques into a classroom activity. In the activity, students practice using the target grammar to do something they naturally enjoy: learning about each other.

  19. MUYANG GROUP

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    @@ With its headquarters in the historic city of Yangzhou,Jiangsu Muyang Group Co.,Ltd has since its founding in 1967 grown into a well-known group corporation whose activities cover research&development.project design,manufacturing,installation and services in a multitude of industries including feed machinery and engineering,storage engineering,grain machinery and engineering,environmental protection,conveying equipment and automatic control systems.

  20. Abelian groups

    CERN Document Server

    Fuchs, László

    2015-01-01

    Written by one of the subject’s foremost experts, this book focuses on the central developments and modern methods of the advanced theory of abelian groups, while remaining accessible, as an introduction and reference, to the non-specialist. It provides a coherent source for results scattered throughout the research literature with lots of new proofs. The presentation highlights major trends that have radically changed the modern character of the subject, in particular, the use of homological methods in the structure theory of various classes of abelian groups, and the use of advanced set-theoretical methods in the study of undecidability problems. The treatment of the latter trend includes Shelah’s seminal work on the undecidability in ZFC of Whitehead’s Problem; while the treatment of the former trend includes an extensive (but non-exhaustive) study of p-groups, torsion-free groups, mixed groups, and important classes of groups arising from ring theory. To prepare the reader to tackle these topics, th...

  1. Plasma metallization

    CERN Document Server

    Crowther, J M

    1997-01-01

    Many methods are currently used for the production of thin metal films. However, all of these have drawbacks associated with them, for example the need for UHV conditions, high temperatures, exotic metal precursors, or the inability to coat complex shaped objects. Reduction of supported metal salts by non-isothermal plasma treatment does not suffer from these drawbacks. In order to produce and analyse metal films before they become contaminated, a plasma chamber which could be attached directly to a UHV chamber with XPS capability was designed and built. This allowed plasma treatment of supported metal salts and surface analysis by XPS to be performed without exposure of the metal film to the atmosphere. Non-equilibrium plasma treatment of Nylon 66 supported gold(lll) chloride using hydrogen as the feed gas resulted in a 95% pure gold film, the remaining 5% of the film being carbon. If argon or helium were used as the feed gases during plasma treatment the resultant gold films were 100% pure. Some degree of s...

  2. Heavy Metal Fluoride Glasses.

    Science.gov (United States)

    1987-04-01

    i 2N E ihhhhh1112h MEmhhhhEEEohhhhE I.’....momo 111111111’-20 LA ’Ll2. AFWL-TR-86-37 AFWL-TR- 86-37 oT C ,l C ’-’ N HEAVY METAL FLUORIDE GLASSES 0nI...Secwrit CkasmfcationJ HEAVY METAL FLUORIDE GLASSES 12. PERSONAL AUTHOR(S) Reisfield, Renata; and Eyal, Mrek 13. TYPE OF REPORT 113b. TIME COVERED 114...glasses containing about 50 mole% of ZrF4 [which can be replaced by HfF 4 or TIF 4 (Refs. 1-3) or heavy metal fluorides based on PbF2 and on 3d-group

  3. Prevalence of pseudotumor in asymptomatic patients after metal-on-metal hip arthroplasty.

    Science.gov (United States)

    Williams, Daniel H; Greidanus, Nelson V; Masri, Bassam A; Duncan, Clive P; Garbuz, Donald S

    2011-12-07

    The cause of recently reported pseudotumor formation in patients with metal-on-metal hip replacements is unknown. It has been postulated that there is an association between elevated levels of serum metal ions and pseudotumor formation. The primary purpose of this study was to assess the prevalence of pseudotumor formation in asymptomatic patients with a metal-on-metal total hip replacement after a minimum duration of follow-up of two years. A secondary purpose was to assess whether a correlation exists between elevated serum metal ion levels and pseudotumor formation. In the present study, the prevalence of pseudotumor formation, as detected with ultrasound, was evaluated for thirty-one asymptomatic patients with a metal-on-metal total hip arthroplasty, twenty-four asymptomatic patients with a metal-on-polyethylene total hip arthroplasty, and twenty asymptomatic patients with a metal-on-metal hip resurfacing arthroplasty. Serum levels of cobalt and chromium were measured in the metal-on-metal total hip arthroplasty and hip resurfacing arthroplasty groups. Ten patients (32%) in the metal-on-metal total hip arthroplasty group had a solid or cystic mass, with another three patients (10%) having a substantial fluid collection. Five patients (25%) in the hip resurfacing arthroplasty group had a solid or cystic mass, with another patient (5%) having a fluid collection. Pseudotumor formation was significantly more frequent in the metal-on-metal total hip arthroplasty group compared with the metal-on-polyethylene total hip arthroplasty group (p = 0.015). We did not detect a significant correlation between the serum metal ion levels and the size of pseudotumor abnormality. The median serum metal ion level was greater in patients with pseudotumor formation than it was in those without pseudotumor formation, but the difference was not significant. We recommend high-resolution ultrasound surveillance of all asymptomatic patients with a metal-on-metal implant that is known to

  4. Metals and metal compounds in cancer treatment.

    Science.gov (United States)

    Desoize, Bernard

    2004-01-01

    Metals and metal compounds have been used in medicine for several thousands of years. In this review we summarized the anti-cancer activities of the ten most active metals: arsenic, antimony, bismuth, gold, vanadium, iron, rhodium, titanium, gallium and platinum. The first reviewed metal, arsenic, presents the anomaly of displaying anti-cancer and oncogenic properties simultaneously. Some antimony derivatives, such as Sb2O3, salt (tartrate) and organic compounds, show interesting results. Bismuth directly affects Helicobacter pylori and gastric lymphoma; the effects of bismuth complexes of 6-mercaptopurine are promising. Gold(I) and (III) compounds show anti-tumour activities, although toxicity remains high. Research into the potential use of gold derivatives is still ongoing. Several derivatives of vanadium show anti-proliferative activity, but their toxicity must be overcome. Several pieces of evidence indicate that iron deprivation could be an excellent therapeutic approach; furthermore, it is synergistic with classic anti-cancer drugs. Rhodium belongs to the same group as platinum and it also presents interesting activity, but with the same nephrotoxicity. Several rhodium compounds have entered phase I clinical trials. In contrast to the platinum complexes, titanium derivatives showed no evidence of nephrotoxicity or myelotoxicity; titanocene dichloride is undergoing clinical trial. The anti-proliferative effect of gallium could be related to its competition with the iron atom; in addition a derivative appears to reverse the multidrug resistance. The last metal reviewed, platinum, has given some of the very best anti-cancer drugs. Four derivatives are used today in the clinic; their mechanism of action and of resistance are described.

  5. Hydrogen dominant metallic alloys: high temperature superconductors?

    Science.gov (United States)

    Ashcroft, N W

    2004-05-07

    The arguments suggesting that metallic hydrogen, either as a monatomic or paired metal, should be a candidate for high temperature superconductivity are shown to apply with comparable weight to alloys of metallic hydrogen where hydrogen is a dominant constituent, for example, in the dense group IVa hydrides. The attainment of metallic states should be well within current capabilities of diamond anvil cells, but at pressures considerably lower than may be necessary for hydrogen.

  6. Metallic Hydrogen

    Science.gov (United States)

    Silvera, Isaac; Zaghoo, Mohamed; Salamat, Ashkan

    2015-03-01

    Hydrogen is the simplest and most abundant element in the Universe. At high pressure it is predicted to transform to a metal with remarkable properties: room temperature superconductivity, a metastable metal at ambient conditions, and a revolutionary rocket propellant. Both theory and experiment have been challenged for almost 80 years to determine its condensed matter phase diagram, in particular the insulator-metal transition. Hydrogen is predicted to dissociate to a liquid atomic metal at multi-megabar pressures and T =0 K, or at megabar pressures and very high temperatures. Thus, its predicted phase diagram has a broad field of liquid metallic hydrogen at high pressure, with temperatures ranging from thousands of degrees to zero Kelvin. In a bench top experiment using static compression in a diamond anvil cell and pulsed laser heating, we have conducted measurements on dense hydrogen in the region of 1.1-1.7 Mbar and up to 2200 K. We observe a first-order phase transition in the liquid phase, as well as sharp changes in optical transmission and reflectivity when this phase is entered. The optical signature is that of a metal. The mapping of the phase line of this transition is in excellent agreement with recent theoretical predictions for the long-sought plasma phase transition to metallic hydrogen. Research supported by the NSF, Grant DMR-1308641, the DOE Stockpile Stewardship Academic Alliance Program, Grant DE-FG52-10NA29656, and NASA Earth and Space Science Fellowship Program, Award NNX14AP17H.

  7. The metal to metal interface and its effect on adhesion and friction

    Science.gov (United States)

    Buckley, D. H.

    1976-01-01

    The paper considers the interface between two bulk metals and the effect of this interface on adhesive bonding, resistance to tangential displacements, friction and the interfacial transport from one surface to another. Using Auger emission spectroscopy, field ion microscopy, and low energy electron diffraction techniques, the influence of surface orientation, lattice registry, crystal lattice structure and defects, metal surface chemistry and alloying on the characteristics of the interface was studied for noble, platinum, transition, and Group 4B metals. With dissimilar metals in contact, epitaxial transfer of the cohesively weaker to the cohesively stronger metal has been observed. Surface chemical activity of the noble and platinum metals is shown to affect interfacial behavior as does a valence bonding in the transition metals, and the degree of metallic nature in the Group 4B elements. Alloying elements, e.g., Si and Fe, can alter interfacial behavior by segregation to the surface of metals or by altering bulk properties such as crystal transformation kinetics.

  8. Group Anonymity

    CERN Document Server

    Chertov, Oleg; 10.1007/978-3-642-14058-7_61

    2010-01-01

    In recent years the amount of digital data in the world has risen immensely. But, the more information exists, the greater is the possibility of its unwanted disclosure. Thus, the data privacy protection has become a pressing problem of the present time. The task of individual privacy-preserving is being thoroughly studied nowadays. At the same time, the problem of statistical disclosure control for collective (or group) data is still open. In this paper we propose an effective and relatively simple (wavelet-based) way to provide group anonymity in collective data. We also provide a real-life example to illustrate the method.

  9. Informal groups

    NARCIS (Netherlands)

    E. van den Berg; P. van Houwelingen; J. de Hart

    2011-01-01

    Original title: Informele groepen Going out running with a group of friends, rather than joining an official sports club. Individuals who decide to take action themselves rather than giving money to good causes. Maintaining contact with others not as a member of an association, but through an Inter

  10. Size of the Group IVA Iron Meteorite Parent Body

    Science.gov (United States)

    Moskovitz, N.; Walker, R.

    2011-10-01

    The group IVA fractionally crystallized iron meteorites display a diverse range of metallographic cooling rates, ranging from 100 - 6600 K/Myr [1]. These have been attributed to their formation in a metallic core, ˜150 km in radius that cooled to crystallization without any appreciable insulating mantle. Such an exposed core may have resulted from a hit-and-run collision [2] between two large (˜ 103 km) protoplanetary bodies. Here we build upon this formation scenario by incorporating several new constraints. These include (i) a recent U-Pb radiometric closure age of 4565.3 Mya (IVA iron Muonionalusta [3], (ii) new measurements and modeling of highly siderophile element compositions for a suite of IVAs, and (iii) consideration of the thermal effects of heating by the decay of the short-lived radionuclide 60Fe.

  11. COMMUNICATIONS GROUP

    CERN Multimedia

    L. Taylor

    2011-01-01

    The CMS Communications Group, established at the start of 2010, has been busy in all three areas of its responsibility: (1) Communications Infrastructure, (2) Information Systems, and (3) Outreach and Education. Communications Infrastructure There are now 55 CMS Centres worldwide that are well used by physicists working on remote CMS shifts, Computing operations, data quality monitoring, data analysis and outreach. The CMS Centre@CERN in Meyrin, is the centre of the CMS offline and computing operations, hosting dedicated analysis efforts such as during the CMS Heavy Ion lead-lead running. With a majority of CMS sub-detectors now operating in a “shifterless” mode, many monitoring operations are now routinely performed from there, rather than in the main Control Room at P5. The CMS Communications Group, CERN IT and the EVO team are providing excellent videoconferencing support for the rapidly-increasing number of CMS meetings. In parallel, CERN IT and ...

  12. Lego Group

    DEFF Research Database (Denmark)

    Møller Larsen, Marcus; Pedersen, Torben; Slepniov, Dmitrij

    2010-01-01

    The last years’ rather adventurous journey from 2004 to 2009 had taught the fifth-largest toy-maker in the world - the LEGO Group - the importance of managing the global supply chain effectively. In order to survive the largest internal financial crisis in its roughly 70 years of existence......, the management had, among many initiatives, decided to offshore and outsource a major chunk of its production to Flextronics. In this pursuit of rapid cost-cutting sourcing advantages, the LEGO Group planned to license out as much as 80 per cent of its production besides closing down major parts...... of the production in high cost countries. Confident with the prospects of the new partnership, the company signed a long-term contract with Flextronics. This decision eventually proved itself to have been too hasty, however. Merely three years after the contracts were signed, LEGO management announced that it would...

  13. Group play

    DEFF Research Database (Denmark)

    Tychsen, Anders; Hitchens, Michael; Brolund, Thea

    2008-01-01

    of group dynamics, the influence of the fictional game characters and the comparative play experience between the two formats. The results indicate that group dynamics and the relationship between the players and their digital characters, are integral to the quality of the gaming experience in multiplayer......Role-playing games (RPGs) are a well-known game form, existing in a number of formats, including tabletop, live action, and various digital forms. Despite their popularity, empirical studies of these games are relatively rare. In particular there have been few examinations of the effects...... of the various formats used by RPGs on the gaming experience. This article presents the results of an empirical study, examining how multi-player tabletop RPGs are affected as they are ported to the digital medium. Issues examined include the use of disposition assessments to predict play experience, the effect...

  14. Group Connections: Whole Group Teaching.

    Science.gov (United States)

    Griffiths, Dorothy

    2002-01-01

    A learner-centered approach to adult group instruction involved learners in investigating 20th-century events. The approach allowed learners to concentrate on different activities according to their abilities and gave them opportunities to develop basic skills and practice teamwork. (SK)

  15. Glycosylated Metal Phthalocyanines

    Directory of Open Access Journals (Sweden)

    Michael Hanack

    2015-11-01

    Full Text Available In the first part; the syntheses of mono-; di-; and tetra-glycosylated phthalonitriles is described; which are the most used starting materials for the preparation of the corresponding glycosylated metal (mostly zinc phthalocyanines. In the second section; the preparation of symmetric and unsymmetric mono-; tetra-; and octa- glycosylated zinc phthalocyanines are reviewed; in which the sugar is attached to the phthalocyanine macrocycle; either anomerically or via another one of its OH-groups.

  16. Crystal structures of meso-tetrakis(2′,6′/3′,5′-difluorophenyl)porphyrins and their metal complexes: Influence of position of the fluoro groups on their structural properties

    Indian Academy of Sciences (India)

    Bhyrappa Puttaiah; Karuppaiah Karunanithi

    2016-04-01

    Two series of non-solvated structures of 5,10,15,20-tetrakis(2′,6′/3′,5′-difluorophenyl)porphyrins, H2T(2′,6′/3′,5′-DFP)P and their metal (Cu(II) and Zn(II)) complexes were determined by single crystal XRD. H2(2′,6′-DFP)P, 1 and its metal (Cu(II), 2 and Zn(II), 3) complexes showed near planar geometry of the porphyrin ring with the maximum root-mean-square (r.m.s.) which is the average deviation of the 24 core atoms from their least-squares plane by 0.056(3) Å while MT(3′,5′-DFP)P (Cu(II), 4 and Zn(II), 5) structures feature significant distortion of the macrocycle (r.m.s. = 0.22(2) Å). Nearly planar structures 1-3 revealed more number of intermolecular short contacts than that observed in nonplanar structures 4 and 5. Normal coordinate structure decomposition analysis of the structures 1-3 revealed negligible wave distortion of the macrocycle but the corresponding nonplanar 4 and 5 structures feature mainly ruffled combined with minimal saddled distortions. The increased nonplanarity of the less sterically hindered derivatives 4 and 5 has been ascribed to intermolecular interactions and/or crystal packing forces.

  17. Methods of selectively incorporating metals onto substrates

    Energy Technology Data Exchange (ETDEWEB)

    Ernst; Richard D. (Salt Lake City, UT), Eyring; Edward M. (Salt Lake City, UT), Turpin; Gregory C. (Salt Lake City, UT), Dunn; Brian C. (Salt Lake City, UT)

    2008-09-30

    A method for forming multi-metallic sites on a substrate is disclosed and described. A substrate including active groups such as hydroxyl can be reacted with a pretarget metal complex. The target metal attached to the active group can then be reacted with a secondary metal complex such that an oxidation-reduction (redox) reaction occurs to form a multi-metallic species. The substrate can be a highly porous material such as aerogels, xerogels, zeolites, and similar materials. Additional metal complexes can be reacted to increase catalyst loading or control co-catalyst content. The resulting compounds can be oxidized to form oxides or reduced to form metals in the ground state which are suitable for practical use.

  18. Sensor for metal detection

    KAUST Repository

    Kodzius, Rimantas

    2014-06-26

    NOVELTY - The sensor has a microfluidic flow channel that is provided with an inlet port, an outlet port, and a detection chamber. The detection chamber is provided with a group of sensing electrodes (4) having a working electrode (8), a counter electrode (9), and a reference electrode (10). A flow sensor is configured to measure flow in the channel. A temperature sensor (6) is configured to measure temperature in the channel (3). An electrical connection is configured to connect the sensor to a sensing device. USE - Sensor for detecting metal such as toxic metal in sample such as clinical sample such as stool, saliva, sputum, bronchial lavage, urine, vaginal swab, nasal swab, biopsy, tissue, tears, breath, blood, serum, plasma, cerebrospinal fluid, peritoneal fluid, pleural fluid, pericardial fluid, joint fluid, and amniotic fluid, water sample, food sample, air sample, and soil sample (all claimed). ADVANTAGE - The sensor for use with the portable analytical instrument is configured for detection of metalsin samples. The sensor can provide the excellent solution for on-site metal detection, including heavy metal detection. The sensors can provide significant advantages in higher throughput, lower cost, at the same time being less labor intensive and less dependent on individual skills. The disposable design of the sensor, the enhanced reliability and repeatability of measurements can be obtained. The sensors can be widely applied in various industries. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following: (1) a system for detecting metal in sample; and (2) a method for using sensor for detecting metal in sample. DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of the sensor prototype. Channel (3) Sensing electrodes (4) Temperature sensor (6) Working electrode (8) Counter electrode (9) Reference electrode (10)

  19. COMMUNICATIONS GROUP

    CERN Multimedia

    L. Taylor

    2011-01-01

    The CMS Communications Group has been busy in all three areas of its responsibility: (1) Communications Infrastructure, (2) Information Systems, and (3) Outreach and Education. Communications Infrastructure The 55 CMS Centres worldwide are well used by physicists working on remote CMS shifts, Computing operations, data quality monitoring, data analysis and outreach. The CMS Centre@CERN in Meyrin, is the centre of the CMS Offline and Computing operations, and a number of subdetector shifts can now take place there, rather than in the main Control Room at P5. A new CMS meeting room has been equipped for videoconferencing in building 42, next to building 40. Our building 28 meeting room and the facilities at P5 will be refurbished soon and plans are underway to steadily upgrade the ageing equipment in all 15 CMS meeting rooms at CERN. The CMS evaluation of the Vidyo tool indicates that it is not yet ready to be considered as a potential replacement for EVO. The Communications Group provides the CMS-TV (web) cha...

  20. COMMUNICATIONS GROUP

    CERN Multimedia

    L. Taylor

    2010-01-01

    The CMS Communications Group, established at the start of 2010, has been strengthening the activities in all three areas of its responsibility: (1) Communications Infrastructure, (2) Information Systems, and (3) Outreach and Education. Communications Infrastructure The Communications Group has invested a lot of effort to support the operations needs of CMS. Hence, the CMS Centres where physicists work on remote CMS shifts, Data Quality Monitoring, and Data Analysis are running very smoothly. There are now 55 CMS Centres worldwide, up from just 16 at the start of CMS data-taking. The latest to join are Imperial College London, the University of Iowa, and the Università di Napoli. The CMS Centre@CERN in Meyrin, which is now full repaired after the major flooding at the beginning of the year, has been at the centre of CMS offline and computing operations, most recently hosting a large fraction of the CMS Heavy Ion community during the lead-lead run. A number of sub-detector shifts can now take pla...

  1. C-Cl activation by group IV metal oxides in solid argon matrixes: matrix isolation infrared spectroscopy and theoretical investigations of the reactions of MOx (M = Ti, Zr; x = 1, 2) with CH3Cl.

    Science.gov (United States)

    Zhao, Yanying

    2013-07-11

    Reactions of the ground-state titanium and zirconium monoxide and dioxide molecules with monochloromethane in excess argon matrixes have been investigated in solid argon by infrared absorption spectroscopy and density functional theoretical calculations. The results show that the ground-state MOx (M = Ti, Zr; x = 1, 2) molecules react with CH3Cl to first form the weakly bound MO(CH3Cl) and MO2(CH3Cl) complexes. The MO(CH3Cl) complexes can rearrange to the CH3M(O)Cl isomers with the Cl atom of CH3Cl coordination to the metal center of MO upon UV light irradiation (λ MOx mechanism was interpreted by the calculated potential energy profiles.

  2. COMMUNICATIONS GROUP

    CERN Multimedia

    L. Taylor

    2011-01-01

    Communications Infrastructure The 55 CMS Centres worldwide are well used by physicists working on remote CMS shifts, Computing operations, data quality monitoring, data analysis and outreach. The CMS Centre@CERN in Meyrin is particularly busy at the moment, hosting about 50 physicists taking part in the heavy-ion data-taking and analysis. Three new CMS meeting room will be equipped for videoconferencing in early 2012: 40/5B-08, 42/R-031, and 28/S-029. The CMS-TV service showing LHC Page 1, CMS Page 1, etc. (http://cmsdoc.cern.ch/cmscc/projector/index.jsp) is now also available for mobile devices: http://cern.ch/mcmstv. Figure 12: Screenshots of CMS-TV for mobile devices Information Systems CMS has a new web site: (http://cern.ch/cms) using a modern web Content Management System to ensure content and links are managed and updated easily and coherently. It covers all CMS sub-projects and groups, replacing the iCMS internal pages. It also incorporates the existing CMS public web site (http:/...

  3. COMMUNICATIONS GROUP

    CERN Multimedia

    L. Taylor

    2012-01-01

      Outreach and Education We are fortunate that our research has captured the public imagination, even though this inevitably puts us under the global media spotlight, as we saw with the Higgs seminar at CERN in December, which had 110,000 distinct webcast viewers. The media interest was huge with 71 media organisations registering to come to CERN to cover the Higgs seminar, which was followed by a press briefing with the DG and Spokespersons. This event resulted in about 2,000 generally positive stories in the global media. For this seminar, the CMS Communications Group prepared up-to-date news and public material, including links to the CMS results, animations and event displays [http://cern.ch/go/Ch8thttp://cern.ch/go/Ch8t]. There were 44,000 page-views on the CMS public website, with the Higgs news article being by far the most popular item. CMS event displays from iSpy are fast becoming the iconic media images, featuring on numerous major news outlets (BBC, CNN, MSN...) as well as in the sci...

  4. COMMUNICATIONS GROUP

    CERN Multimedia

    L. Taylor

    2010-01-01

    The recently established CMS Communications Group, led by Lucas Taylor, has been busy in all three of its main are areas of responsibility: Communications Infrastructure, Information Systems, and Outreach and Education Communications Infrastructure The damage caused by the flooding of the CMS Centre@CERN on 21st December has been completely repaired and all systems are back in operation. Major repairs were made to the roofs, ceilings and one third of the floor had to be completely replaced. Throughout these works, the CMS Centre was kept operating and even hosted a major press event for first 7 TeV collisions, as described below. Incremental work behind the scenes is steadily improving the quality of the CMS communications infrastructure, particularly Webcasting, video conferencing, and meeting rooms at CERN. CERN/IT is also deploying a pilot service of a new videoconference tool called Vidyo, to assess whether it might provide an enhanced service at a lower cost, compared to the EVO tool currently in w...

  5. New group 6 metal carbonyl complexes with 4,5-dimethyl-N,N-bis(pyridine-2-yl-methylene)benzene-1,2-diimine Schiff base: synthesis, spectral, cyclic voltammetry and biological activity studies.

    Science.gov (United States)

    Mohamed, Rania G; Elantabli, Fatma M; Helal, Nadia H; El-Medani, Samir M

    2015-04-15

    Thermal reaction of M(CO)6 (M=Cr, Mo or W) with a Schiff base (DMPA) derived from the condensation of 4,5-dimethyl-1,2-phenylenediamine and pyridine-2-carboxaldehyde in THF in absence and presence of a secondary ligand; 2-aminobenzimidazole (Abz), thiourea (Tu) or 2-(2'-pyridyl)benzimidazole (pybz) were studied. The reaction of Cr(CO)6 gave the four complexes Cr2(CO)2(DMPA)2; 1, Cr(DMPA)2(Abz)2; 2, Cr2(CO)4(DMPA)2(Tu)2; 3 and Cr(DMPA)2(Pybz); 4, while the thermal reaction of Mo(CO)6 resulted in the formation of the two complexes Mo2(O)6(DMPA)2; 5, and Mo2(O)2(CO)2(DMPA)2(Tu)2; 6. Thermal reaction of W(CO)6 and the Schiff base DMPA gave the complex W(O)2(DMPA)2; 7. The ligand DMPA and its metal complexes have been reported and characterized based on elemental analyses, IR, (1)H NMR, magnetic measurements, and thermal analysis. Cyclic voltammetry and biological activity were also investigated. Copyright © 2015 Elsevier B.V. All rights reserved.

  6. Focused fluorescent probe library for metal cations and biological anions.

    Science.gov (United States)

    Rhee, Hyun-Woo; Lee, Sang Wook; Lee, Jun-Seok; Chang, Young-Tae; Hong, Jong-In

    2013-09-09

    A focused fluorescent probe library for metal cations was developed by combining metal chelators and picolinium/quinolinium moieties as combinatorial blocks connected through a styryl group. Furthermore, metal complexes derived from metal chelators having high binding affinities for metal cations were used to construct a focused probe library for phosphorylated biomolecules. More than 250 fluorescent probes were screened for identifying an ultraselective probe for dTTP.

  7. Design, synthesis and characterization of metal organic frameworks

    KAUST Repository

    Eddaoudi, Mohamed

    2015-12-03

    A molecular building block composition can include a metal ion component; and a ligand component including a core including at least one functional group associated with the metal ion component and the core.

  8. Glassy metals

    CERN Document Server

    Russew, Krassimir

    2016-01-01

    The topics discussed in this book focus on fundamental problems concerning the structural relaxation of amorphous metallic alloys, above all the possibility of studying it on the basis of viscous flow behavior and its relation to rheological anomalies, such as bend stress relaxation, thermal expansion, specific heat, density changes, and crystallization. Most relaxation studies deal with the relaxation changes of a single definite material property, and not with a wider spectrum of physical properties integrated into a common framework. This book shows that it is possible to describe these property changes on the basis of a more comprehensive theoretical understanding of their mechanism.

  9. Photochemistry of Transition Metal Hydrides.

    Science.gov (United States)

    Perutz, Robin N; Procacci, Barbara

    2016-08-10

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

  10. Carbon Nanotube Patterning on a Metal Substrate

    Science.gov (United States)

    Nguyen, Cattien V. (Inventor)

    2016-01-01

    A CNT electron source, a method of manufacturing a CNT electron source, and a solar cell utilizing a CNT patterned sculptured substrate are disclosed. Embodiments utilize a metal substrate which enables CNTs to be grown directly from the substrate. An inhibitor may be applied to the metal substrate to inhibit growth of CNTs from the metal substrate. The inhibitor may be precisely applied to the metal substrate in any pattern, thereby enabling the positioning of the CNT groupings to be more precisely controlled. The surface roughness of the metal substrate may be varied to control the density of the CNTs within each CNT grouping. Further, an absorber layer and an acceptor layer may be applied to the CNT electron source to form a solar cell, where a voltage potential may be generated between the acceptor layer and the metal substrate in response to sunlight exposure.

  11. Biofilm susceptibility to metal toxicity.

    Science.gov (United States)

    Harrison, Joe J; Ceri, Howard; Stremick, Carol A; Turner, Raymond J

    2004-12-01

    This study compared bacterial biofilm and planktonic cell susceptibility to metal toxicity by evaluating the minimum inhibitory concentration (MIC), the planktonic minimum bactericidal concentration (MBC), and minimum biofilm eradication concentration (MBEC) using the MBEC device. In total, 17 metal cations and oxyanions, chosen to represent groups VIB to VIA of the periodic table, were each tested on biofilm and planktonic cultures of Escherichia coli JM109, Staphylococcus aureus ATCC 29213, and Pseudomonas aeruginosa ATCC 27853. In contrast to control antibiotic assays, where biofilm cultures were 2 to 64 times less susceptible to killing than logarithmically growing planktonic bacteria, metal compounds killed planktonic and biofilm cultures at the same concentration in the vast majority of combinations. Our data indicate that, under the conditions reported, growth in a biofilm does not provide resistance to bacteria against killing by metal cations or oxyanions.

  12. 41 CFR 101-42.1101 - Federal supply classification (FSC) groups and classes which contain hazardous materials.

    Science.gov (United States)

    2010-07-01

    ... device. 2520 Vehicular power transmission components Items containing asbestos. 2530 Vehicular brake... metallic sodium. Group 29 Engine accessories Engine valves containing metallic sodium. Group 30 Mechanical power transmission equipment Equipment containing hazardous hydraulic fluids including PCBs. Group...

  13. From mapping class groups to automorphism groups of free groups

    DEFF Research Database (Denmark)

    Wahl, Nathalie

    2005-01-01

    We show that the natural map from the mapping class groups of surfaces to the automorphism groups of free groups, induces an infinite loop map on the classifying spaces of the stable groups after plus construction. The proof uses automorphisms of free groups with boundaries which play the role...... of mapping class groups of surfaces with several boundary components....

  14. Main group multiple C-H/N-H bond activation of a diamine and isolation of a molecular dilithium zincate hydride: experimental and DFT evidence for alkali metal-zinc synergistic effects.

    Science.gov (United States)

    Campbell, Ross; Cannon, Daniel; García-Álvarez, Pablo; Kennedy, Alan R; Mulvey, Robert E; Robertson, Stuart D; Sassmannshausen, Jörg; Tuttle, Tell

    2011-08-31

    two distinct metals in the system are able to interact synergically to catalyze this otherwise challenging transformation.

  15. Metal ion trend may be more predictive for malfunctioning metal-on-metal implants than a single measurement

    NARCIS (Netherlands)

    Smolders, J.M.; Hol, A.; Susante, J.L.C. van

    2013-01-01

    Forty-eight unilateral hip resurfacing arthroplasty patients were evaluated for cobalt and chromium levels. The metal ion trend of 42 well-functioning patients was compared with six sub-optimal functioning patients. Median metal ion levels were significantly higher for the sub-optimal group. For the

  16. The Sounds of Metal

    DEFF Research Database (Denmark)

    Grund, Cynthia M.

    2015-01-01

    Two, I propose that this framework allows for at least a theoretical distinction between the way in which extreme metal – e.g. black metal, doom metal, funeral doom metal, death metal – relates to its sound as music and the way in which much other music may be conceived of as being constituted...

  17. Metal matrix Composites

    Directory of Open Access Journals (Sweden)

    Pradeep K. Rohatgi

    1993-10-01

    Full Text Available This paper reviews the world wide upsurge in metal matrix composite research and development activities with particular emphasis on cast metal-matrix particulate composites. Extensive applications of cast aluminium alloy MMCs in day-to-day use in transportation as well as durable good industries are expected to advance rapidly in the next decade. The potential for extensive application of cast composites is very large in India, especially in the areas of transportation, energy and electromechanical machinery; the extensive use of composites can lead to large savings in materials and energy, and in several instances, reduce environmental pollution. It is important that engineering education and short-term courses be organized to bring MMCs to the attention of students and engineering industry leaders. India already has excellent infrastructure for development of composites, and has a long track record of world class research in cast metal matrix particulate composites. It is now necessary to catalyze prototype and regular production of selected composite components, and get them used in different sectors, especially railways, cars, trucks, buses, scooters and other electromechanical machinery. This will require suitable policies backed up by funding to bring together the first rate talent in cast composites which already exists in India, to form viable development groups followed by setting up of production plants involving the process engineering capability already available within the country. On the longer term, cast composites should be developed for use in energy generation equipment, electronic packaging aerospace systems, and smart structures.

  18. Metals production

    Science.gov (United States)

    Beck, Theodore S.

    1992-02-01

    Existing procedures for design of electrochemical plants can be used for design of lunar processes taking into consideration the differences in environmental conditions. These differences include: 1/6 Earth gravity, high vacuum, solar electrical and heat source, space radiation heat sink, long days and nights, and different availability and economics of materials, energy, and labor. Techniques have already been developed for operation of relatively small scale hydrogen-oxygen fuel cell systems used in the U.S. lunar landing program. Design and operation of lunar aqueous electrolytic process plants appears to be within the state-of-the-art. Finding or developing compatible materials for construction and designing of fused-magma metal winning cells will present a real engineering challenge.

  19. Heavy metal biosorption by bacterial cells

    NARCIS (Netherlands)

    Vecchio, A; Finoli, C; Di Simine, D; Andreoni, [No Value

    1998-01-01

    Microbial biomass provides available ligand groups on which metal ions bind by different mechanisms. Biosorption of these elements from aqueous solutions represents a remediation technology suitable for the treatment of metal-contaminated effluents. The purpose of the present investigation was the a

  20. Effect of heavy metals on soil fungi

    Science.gov (United States)

    Sosak-Świderska, Bożena

    2010-05-01

    Fungi constitute a high proportion of the microbial biomass in soil.Being widespread in soil their large surface-to-volume ratio and high metabolic activity, fungi can contribute significantly to heavy metal dynamics in soil. At neutral pH heavy metals in soils tend to be immobilized to precipitation and/or absorption to cation exchange sites of clay minerals. In the acidic soils, metals are more mobile and enter food webs easier. Microbial production of acids and chelating agents can mobilize to toxic metals. Mobilization is often by uptake and intracellular accumulation of the heavy metlas, and in this way, the bioavailability of metals towards other organisms can be more reduced. Fungi were isolated from soils from Upper Silesia in Poland and belonged to widespread genera: Aspergillus, Cladosporium, Penicillium and Trichoderma. Fungi from different taxonomic groups differ greatly in their tolerance to heavy metals. This could be related to their wall structure and chemistry as well as biochemical and physiological characteristics of fungi. Localization of metals in fungal cells was studied using electron microscopy analysis. Metal biosorption in the cell wall can be complex as melanin granules. Fungal vacuoles have an important role in the regulation of the cytosolic concentration of metal ions, and may contribute to heavy metal tolerance.In polluted soils with heavy metals, fungal species composition can be changed and their physiological activity can be changed, too.

  1. Maailma kaunid aiad : Sissinghurst'i aed / Ann Tenno

    Index Scriptorium Estoniae

    Tenno, Ann, 1952-

    2004-01-01

    Inglismaa Sissinghurst'i aed oli Vita Sackville-Westi (suri 1962) ja tema abikaasa Harold Nicolson'i (suri 1968) ühislooming. Nad ostsid selle maakoha 1930. a. Aed läks 1967. a. National Trust'i valdusse. Aed kujundati eraldiseisvate ruumidena endisaegsete müüride ja hoonete vahele. Jugapuude ja pärnade käigust, vallikraavist, valgest, viljapuu-, cottage ja ürdiaiast. 39 ill

  2. Metal-phosphate binders

    Science.gov (United States)

    Howe, Beth Ann [Lewistown, IL; Chaps-Cabrera, Jesus Guadalupe [Coahuila, MX

    2009-05-12

    A metal-phosphate binder is provided. The binder may include an aqueous phosphoric acid solution, a metal-cation donor including a metal other than aluminum, an aluminum-cation donor, and a non-carbohydrate electron donor.

  3. The Effect of Donor Group Rigidification on the Electronic and Optical Properties of Arylamine-Based Metal-Free Dyes for Dye-Sensitized Solar Cells: A Computational Study.

    Science.gov (United States)

    Estrella, Liezel L; Balanay, Mannix P; Kim, Dong Hee

    2016-07-28

    One of the most significant aspects in the development of dye-sensitized solar cells is the exploration and design of high-efficiency and low-cost dyes. This paper reports the theoretical design of various triphenylamine analogues, wherein the central nitrogen moiety establishes an sp(2)-hybridization, which endows a significant participation in the charge-transfer properties. Density functional theory (DFT) and time-dependent DFT methodologies were utilized to investigate the geometry, electronic structure, photochemical properties, and electrochemical properties of these dyes. Different exchange-correlation functionals were initially evaluated to establish a proper methodology for calculating the excited-state energy of the reference dye, known as DIA3. Consequently, TD-LC-ωPBE with a damping parameter of 0.175 Bohr(-1) best correlates with the experimental value. Four new dyes, namely, Dhk1, Dhk2, Dhk3, and Dhk4, were designed by modifying the rigidity of the donor moiety. According to the results, altering the type and position of binding in the donor group leads to distinct planarity of the dyes, which significantly affects their properties. The designed Dhk4 dye showed more red-shifted and broadened absorption spectra owing to the enhanced coplanarity between its donor and π-bridge moiety, which brings an advantage for its potential use as sensitizer for photovoltaic applications.

  4. Transition-metal complexes [(PMe(3))(2)Cl(2)M(E)] and [(PMe(3))(2)(CO)(2)M(E)] with naked group 14 atoms (E=C-Sn) as ligands; part 1: parent compounds.

    Science.gov (United States)

    Parameswaran, Pattiyil; Frenking, Gernot

    2009-09-07

    The equilibrium geometries and bond dissociation energies of 16-valence-electron(VE) complexes [(PMe(3))(2)Cl(2)M(E)] and 18-VE complexes [(PMe(3))(2)(CO)(2)M(E)] with M=Fe, Ru, Os and E=C, Si, Ge, Sn were calculated by using density functional theory at the BP86/TZ2P level. The nature of the M--E bond was analyzed with the NBO charge decomposition analysis and the EDA energy-decomposition analysis. The theoretical results predict that the heavier Group 14 complexes [(PMe(3))(2)Cl(2)M(E)] and [(PMe(3))(2)(CO)(2)M(E)] with E=Si, Ge, Sn have C(2v) equilibrium geometries in which the PMe(3) ligands are in the axial positions. The complexes have strong M--E bonds which are slightly stronger in the 16-VE species 1ME than in the 18-VE complexes 2ME. The calculated bond dissociation energies show that the M--E bonds become weaker in both series in the order C>Si>Ge>Sn; the bond strength increases in the order FeE pi-acceptor bonds, which are not degenerate. The shape of the frontier orbitals reveals that the HOMO-2 sigma MO and the LUMO and LUMO+1 pi* MOs of 1ME are very similar to the frontier orbitals of CO.

  5. Metal RIE 2: Unaxis SHUTTLELINE ICP

    Data.gov (United States)

    Federal Laboratory Consortium — Description:CORAL Name: Unaxis ICP EtcherChlorine-based system utilizing Boron Trichloride and Chlorine to etch metals and III-V group materials on planar substrates...

  6. Battlefield-Acquired Immunogenicity to Metals Affects Orthopaedic Implant Outcome

    Science.gov (United States)

    2015-10-01

    subject compared to the normal populations. Figure 2. S ystemic levels of metal ions in subject groups in part per billion ( PPB ). 0.00...totaling 60mL) from soldiers exposed to metals in battle and compared with immune cell reactivity of 3 other groups of people (injured soldiers without...on an individual’s metal immune reactivity profile and systemic lead level. This study will involve 75 subjects divided into three groups of 25

  7. Recycling of Metals

    DEFF Research Database (Denmark)

    Damgaard, Anders; Christensen, Thomas Højlund

    2011-01-01

    appliances, vehicles and buildings, containing iron and aluminium metals, have long lifetimes before they end up in the waste stream. The recycling of production waste and postconsumer metals has a long history in the metal industry. Some metal smelters are today entirely based on scarp metals. This chapter...... describes briefly how iron and aluminium are produced and how scrap metal is recycled in the industry. Quality requirements and use of recycled products are discussed, as are the resource and environmental issues of metal recycling. Copper and other metals are also found in waste but in much smaller...

  8. Slow light in metal-insulator-metal waveguide by negative Goos-Hänchen shift

    Science.gov (United States)

    Oh, Geum-Yoon; Chheang, Vuthy; Kim, Doo-Gun; Kim, Tae-Ryong; Jun, Li; Kim, Hong-Seung; Choi, Young-Wan

    2014-12-01

    We demonstrated group velocity delay using a metal-insulator-metal structure for slow light that would be very simple to fabricate. A negative Goos-Hänchen shift of the surface plasmon resonance can be caused by incident radiation while reflecting, resulting in a general group delay. Using this phenomenon, we induced a group delay of 70 fs using a very simple 20-μm-long waveguide.

  9. Influence of gas environment on synthesis of silicon carbide and some carbides and carbonitrides of d-group transition metals through reaction between metal powders and amorphous carbon powders in a solar furnace at P.S.A. (plataforma solar de Almeria)

    Energy Technology Data Exchange (ETDEWEB)

    Martinez, D.; Rodriguez, J. [Plataforma Solar de Almeria, PSA, Centro Europeo de Ensayos de Energia Solar, Centro de Investigaciones Energeticas Medioambientales y Tecnologicas, Tabernas (Spain); Guerra Rosa, L.; Cruz Fernandes, J. [Instituto Superior Tecnico, IST, Dept. de Engenharia de Materiais, Lisboa (Portugal); Shohoji, N. [Instituto Nacional de Engenharia e Tecnologia Industrial, INETI, Instituto de Materiais e Tecnologias de Producao, Dept. de Tecnologias de Producao, Lisboa (Portugal)

    1999-03-01

    Refractory carbides and carbonitrides including silicon carbide SiC, tungsten carbide WC, titanium carbide TiC{sub x} (0.5metal powders and amorphous carbon powders through heating in a solar furnace under controlled atmosphere (Ar or N{sub 2}). Under irradiation of the solar energy flux 1,350 kW/m{sup 2} (ca. 1650 deg C in terms of measured temperature) for 30 min in Ar atmosphere, Si, W and Ti were converted to SiC, WC and TiC{sub x}, respectively. By the similar reaction undertaken in N{sub 2} atmosphere, Si and W were converted to SiC and WC, respectively, but carbonitride TiC{sub x}N{sub y} formed from Ti. No special influence of atmosphere was detected on the WC formation, but conversion to SiC from Si was somewhat retarded in N{sub 2} atmosphere. In either Ar or N{sub 2} atmosphere, progress of graphitization of amorphous carbon was not detectable by X-ray diffraction analysis in the reaction with Si and Ti but graphitization of amorphous carbon appeared to be significantly accelerated in the reaction with W. (authors)

  10. Quantum percolation in granular metals.

    Science.gov (United States)

    Feigel'man, M V; Ioselevich, A S; Skvortsov, M A

    2004-09-24

    Theory of quantum corrections to conductivity of granular metal films is developed for the realistic case of large randomly distributed tunnel conductances. Quantum fluctuations of intergrain voltages (at energies E much below the bare charging energy scale E(C)) suppress the mean conductance g (E) much more strongly than its standard deviation sigma(E). At sufficiently low energies E(*) any distribution becomes broad, with sigma(E(*)) approximately g (E(*)), leading to strong local fluctuations of the tunneling density of states. The percolative nature of the metal-insulator transition is established by a combination of analytic and numerical analysis of the matrix renormalization group equations.

  11. Football Pools and the Reactivity Series of Metals.

    Science.gov (United States)

    Heselden, Russ

    2001-01-01

    Describes an activity which presents the reactivity of metals series as a football pool with more reactive metals at the top of the table and unreactive metals at the bottom. Describes how the activity can be applied in different ways for different ability groups. (Author/MM)

  12. Nanocomposites Based on Metal and Metal Sulfide Clusters Embedded in Polystyrene

    Directory of Open Access Journals (Sweden)

    Gianfranco Carotenuto

    2011-08-01

    Full Text Available Transition-metal alkane-thiolates (i.e., organic salts with formula Me(SRx, where R is a linear aliphatic hydrocarbon group, –CnH2n+1 undergo a thermolysis reaction at moderately low temperatures (close to 200 °C, which produces metal atoms or metal sulfide species and an organic by-product, disulfide (RSSR or thioether (RSR molecules, respectively. Alkane-thiolates are non-polar chemical compounds that dissolve in most techno-polymers and the resulting solid solutions can be annealed to generate polymer-embedded metal or metal sulfide clusters. Here, the preparation of silver and gold clusters embedded into amorphous polystyrene by thermolysis of a dodecyl-thiolate precursor is described in detail. However, this chemical approach is quite universal and a large variety of polymer-embedded metals or metal sulfides could be similarly prepared.

  13. Possibilities Of Metals Extracton From Spent Metallic Automotive Catalytic Converters By Using Biometallurgical Method

    Directory of Open Access Journals (Sweden)

    Willner J.

    2015-09-01

    Full Text Available The main task of automotive catalytic converters is reducing the amount of harmful components of exhaust gases. Metallic catalytic converters are an alternative to standard ceramic catalytic converters. Metallic carriers are usually made from FeCrAl steel, which is covered by a layer of Precious Group Metals (PGMs acting as a catalyst. There are many methods used for recovery of platinum from ceramic carriers in the world, but the issue of platinum and other metals recovery from metallic carriers is poorly described. The article presents results of preliminary experiments of metals biooxidation (Fe, Cr and Al from spent catalytic converters with metallic carrier, using bacteria of the Acidithiobacillus genus.

  14. Symmetry foundations of a polymer model for close-packed metallic liquids and glasses

    Science.gov (United States)

    Kraposhin, V. S.; Talis, A. L.

    2016-02-01

    The atomic packing density of metallic melts and glasses is too high for their structures to be considered as chaotic. To remove this contradiction, we propose to describe the structures of metallic liquids and the glasses that form from them using (i) a base set of three spirals made of regular tetrahedra with specific noncrystallographic symmetry and (ii) combinatorial permutations of the vertices of a set of the coordination polyhedra that describe the polymorphic transformations in metals. The symmetry base of the proposed model of the structures of liquids and glasses is represented by projective linear groups PSL(2, p), where the order of the Galois field is p = 3, 7, and 11. These groups uniquely determine a tetrahedron, the 7-vertex joining of four tetrahedra along their faces (tetrablock), the 11-vertex joining of two tetrablocks into a spiral, and the throwing over of the diagonals in a rhombus from two triangular faces of neighboring tetrahedra. The throwing over of the diagonals in a rhombus is considered as a unit act of any structural transformation and ensures the melt-crystal, melt-glass, and glass-crystal transitions and the structural relaxation of metallic glasses. In terms of the proposed scheme, the high density of melts and glasses is caused by tetrahedral packing (up to 78%), and the absence of a diffraction pattern of melts and glasses is explained by the absence of translation along the spiral axis. The suggested polymer model also explains the collective effects (string vibrations) that were detected upon measuring the shear modulus relaxation of a metallic glass.

  15. Metal-binding silica materials for wastewater cleanup

    Energy Technology Data Exchange (ETDEWEB)

    Kroh, F.O. [TPL, Inc., Albuquerque, NM (United States)

    1997-10-01

    In this Phase I Small Business Innovation Research program, TPL, Inc. is developing two series of high-efficiency covalently modified silica materials for removing heavy metal ions from wastewater. These materials have metal ion capacities greatly exceeding those of commercial ion exchange resins. One series, containing thiol groups, has high capacity for {open_quotes}soft{close_quotes} heavy metal ions such as Hg, Pb, Ag, and Cd; the other, containing quaternary ammonium groups, has high capacity for anionic metal ions such as pertechnetate, arsenate, selenite, and chromate. These materials have high selectivity for the contaminant metals and will function well in harsh systems that inactivate other systems.

  16. Ceramic to metal seal

    Energy Technology Data Exchange (ETDEWEB)

    Snow, Gary S. (Albuquerque, NM); Wilcox, Paul D. (Albuquerque, NM)

    1976-01-01

    Providing a high strength, hermetic ceramic to metal seal by essentially heating a wire-like metal gasket and a ceramic member, which have been chemically cleaned, while simultaneously deforming from about 50 to 95 percent the metal gasket against the ceramic member at a temperature of about 30 to 75 percent of the melting temperature of the metal gasket.

  17. Heavy metal jako subkultura

    OpenAIRE

    KOUTNÁ, Daniela

    2016-01-01

    This bachelor thesis deals with heavy metal subculture. Its aim is to introduce the most important branches and to show broadness of heavy metal. This bachelor thesis describes development and history, briefly shows Czech heavy metal history alongside with the biggest and most popular Czech heavy metal festivals. It shows the most dressing concerns of society against this style.

  18. Integrated Groups and Smooth Distribution Groups

    Institute of Scientific and Technical Information of China (English)

    Pedro J. MIANA

    2007-01-01

    In this paper, we prove directly that α-times integrated groups define algebra homo-morphisms. We also give a theorem of equivalence between smooth distribution groups and α-times integrated groups.

  19. Effect of Metal Collar on Marginal Distortion of Base Metal Crowns

    Directory of Open Access Journals (Sweden)

    Grami Panah F

    2000-06-01

    Full Text Available It has been shown that noble alloys require metal collar to resist distortion when subjected to"nrepeat firing cycle of porcelain. Metal collar is undesirable due to esthetic concerns. Since base metal"nalloys have superior physical properties, it seems that metal collar would not be necessary for obtaining"nbetter marginal adaptation of base metal crowns. The Purpose of this study was to evaluate the effect of"nmetal collar on marginal distortion of base metal- ceramic crowns, Twenty base metal copings were"nconstructed and divided into two groups with and without collars. After surface preparation, porcelain"nwas applied onto the surface of specimens. Marginal gap was measured by scanning electron microscope"nduring three stages of crown fabrication: before degassing, after degassing and after glazing. The mean"nmeasurements in collarless group were; 21.4±13.4, 2I.4±14.9 and 21.9±11.9 u_m, respectively, and in-"ngroup with collar; 24.7±11.4, 24.0±! 1.5 and 26.6±11.7 urn, respectively. Two- way ANOVA revealed"nno significant difference in the mean values between two groups and among different stages of crown"nfabrication. The results of this study showed that base metal alloys did not distort during crown"nfabrication and metal collar had no effect on the amount of marginal opening (gap.

  20. Optimizing the fMRI data-processing pipeline using prediction and reproducibility performance metrics: I. A preliminary group analysis

    DEFF Research Database (Denmark)

    Strother, Stephen C.; Conte, Stephen La; Hansen, Lars Kai

    2004-01-01

    of baseline scans have constant, equal means, and this assumption was assessed with prediction metrics. Higher-order polynomial warps compared to affine alignment had only a minor impact on the performance metrics. We found that both prediction and reproducibility metrics were required for optimizing......We argue that published results demonstrate that new insights into human brain function may be obscured by poor and/or limited choices in the data-processing pipeline, and review the work on performance metrics for optimizing pipelines: prediction, reproducibility, and related empirical Receiver...... Operating Characteristic (ROC) curve metrics. Using the NPAIRS split-half resampling framework for estimating prediction/reproducibility metrics (Strother et al., 2002), we illustrate its use by testing the relative importance of selected pipeline components (interpolation, in-plane spatial smoothing...

  1. Fabrication of metal nanoshells

    Science.gov (United States)

    Kim, Jae-Woo (Inventor); Choi, Sang H. (Inventor); Lillehei, Peter T. (Inventor); Chu, Sang-Hyon (Inventor); Park, Yeonjoon (Inventor); King, Glen C. (Inventor); Elliott, Jr., James R. (Inventor)

    2012-01-01

    Metal nanoshells are fabricated by admixing an aqueous solution of metal ions with an aqueous solution of apoferritin protein molecules, followed by admixing an aqueous solution containing an excess of an oxidizing agent for the metal ions. The apoferritin molecules serve as bio-templates for the formation of metal nanoshells, which form on and are bonded to the inside walls of the hollow cores of the individual apoferritin molecules. Control of the number of metal atoms which enter the hollow core of each individual apoferritin molecule provides a hollow metal nonparticle, or nanoshell, instead of a solid spherical metal nanoparticle.

  2. Metalloproteins and metal sensing.

    Science.gov (United States)

    Waldron, Kevin J; Rutherford, Julian C; Ford, Dianne; Robinson, Nigel J

    2009-08-13

    Almost half of all enzymes must associate with a particular metal to function. An ambition is to understand why each metal-protein partnership arose and how it is maintained. Metal availability provides part of the explanation, and has changed over geological time and varies between habitats but is held within vital limits in cells. Such homeostasis needs metal sensors, and there is an ongoing search to discover the metal-sensing mechanisms. For metalloproteins to acquire the right metals, metal sensors must correctly distinguish between the inorganic elements.

  3. Group typicality, group loyalty and cognitive development.

    Science.gov (United States)

    Patterson, Meagan M

    2014-09-01

    Over the course of childhood, children's thinking about social groups changes in a variety of ways. Developmental Subjective Group Dynamics (DSGD) theory emphasizes children's understanding of the importance of conforming to group norms. Abrams et al.'s study, which uses DSGD theory as a framework, demonstrates the social cognitive skills underlying young elementary school children's thinking about group norms. Future research on children's thinking about groups and group norms should explore additional elements of this topic, including aspects of typicality beyond loyalty.

  4. Which finite simple groups are unit groups?

    DEFF Research Database (Denmark)

    Davis, Christopher James; Occhipinti, Tommy

    2014-01-01

    We prove that if G is a finite simple group which is the unit group of a ring, then G is isomorphic to either (a) a cyclic group of order 2; (b) a cyclic group of prime order 2^k −1 for some k; or (c) a projective special linear group PSLn(F2) for some n ≥ 3. Moreover, these groups do all occur...

  5. Multiple heavy metal removal using an entomopathogenic fungi Beauveria bassiana.

    Science.gov (United States)

    Gola, Deepak; Dey, Priyadarshini; Bhattacharya, Arghya; Mishra, Abhishek; Malik, Anushree; Namburath, Maneesh; Ahammad, Shaikh Ziauddin

    2016-10-01

    Towards the development of a potential remediation technology for multiple heavy metals [Zn(II), Cu(II), Cd(II), Cr(VI) and Ni(II)] from contaminated water, present study examined the growth kinetics and heavy metal removal ability of Beauveria bassiana in individual and multi metals. The specific growth rate of B. bassiana varied from 0.025h(-1) to 0.039h(-1) in presence of individual/multi heavy metals. FTIR analysis indicated the involvement of different surface functional groups in biosorption of different metals, while cellular changes in fungus was reflected by various microscopic (SEM, AFM and TEM) analysis. TEM studies proved removal of heavy metals via sorption and accumulation processes, whereas AFM studies revealed increase in cell surface roughness in fungal cells exposed to heavy metals. Present study delivers first report on the mechanism of bioremediation of heavy metals when present individually as well as multi metal mixture by entomopathogenic fungi.

  6. Metals and metal derivatives in medicine.

    Science.gov (United States)

    Colotti, Gianni; Ilari, Andrea; Boffi, Alberto; Morea, Veronica

    2013-02-01

    Several chemical elements are required by living organisms in addition to the four elements carbon, hydrogen, nitrogen and oxygen usually present in common organic molecules. Many metals (e.g. sodium, potassium, magnesium, calcium, iron, zinc, copper, manganese, chromium, molybdenum and selenium) are known to be required for normal biological functions in humans. Disorders of metal homeostasis and of metal bioavailability, or toxicity caused by metal excess, are responsible for a large number of human diseases. Metals are also extensively used in medicine as therapeutic and/or diagnostic agents. In the past 5000 years, metals such as arsenic, gold and iron have been used to treat a variety of human diseases. Nowadays, an ever-increasing number of metal-based drugs is available. These contain a broad spectrum of metals, many of which are not among those essential for humans, able to target proteins and/or DNA. This mini-review describes metal-containing compounds targeting DNA or proteins currently in use, or designed to be used, as therapeutics against cancer, arthritis, parasitic and other diseases, with a special focus on the available information, often provided by X-ray studies, about their mechanism of action at a molecular level. In addition, an overview of metal complexes used for diagnosing diseases is presented.

  7. MetalPDB: a database of metal sites in biological macromolecular structures.

    Science.gov (United States)

    Andreini, Claudia; Cavallaro, Gabriele; Lorenzini, Serena; Rosato, Antonio

    2013-01-01

    We present here MetalPDB (freely accessible at http://metalweb.cerm.unifi.it), a novel resource aimed at conveying the information available on the three-dimensional (3D) structures of metal-binding biological macromolecules in a consistent and effective manner. This is achieved through the systematic and automated representation of metal-binding sites in proteins and nucleic acids by way of Minimal Functional Sites (MFSs). MFSs are 3D templates that describe the local environment around the metal(s) independently of the larger context of the macromolecular structure embedding the site(s), and are the central objects of MetalPDB design. MFSs are grouped into equistructural (broadly defined as sites found in corresponding positions in similar structures) and equivalent sites (equistructural sites that contain the same metals), allowing users to easily analyse similarities and variations in metal-macromolecule interactions, and to link them to functional information. The web interface of MetalPDB allows access to a comprehensive overview of metal-containing biological structures, providing a basis to investigate the basic principles governing the properties of these systems. MetalPDB is updated monthly in an automated manner.

  8. Random Walker Ranking for NCAA Division I-A Football

    CERN Document Server

    Callaghan, T; Mucha, P J; Callaghan, Thomas; Porter, Mason A.; Mucha, Peter J.

    2003-01-01

    We develop a one-parameter family of ranking systems for NCAA Division I-A football teams based on a collection of voters, each with a single vote, executing independent random walks on a network defined by the teams (vertices) and the games played (edges). The virtue of this class of ranking systems lies in the simplicity of its explanation. We discuss the statistical properties of the randomly walking voters and relate them to the community structure of the underlying network. We compare the results of these rankings for recent seasons with Bowl Championship Series standings and component rankings. To better understand this ranking system, we also examine the asymptotic behaviors of the aggregate of walkers. Finally, we consider possible generalizations to this ranking algorithm.

  9. STUDY ON THE INTERACTION BETWEEN POLYVINYLPYRROLIDONE AND PLATINUM METALS DURING THE FORMATION OF THE COLLOIDAL METAL NANOPARTICLES

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Several PVP-stabilized colloidal platinum metals nanoparticles have been synthesized and characterized by FTIR and TEM.Comparing with the pure PVP,carbonyl groups of PVP in the mixture of PVP and the metal precursors or in the PVP-stabilized metal nanoparticles have obvious peak shifts in FTIR spectra.The peak shifts reveal the interaction between PVP and the metal species.The interaction between PVP and metal precursors has effect on the formation of the colloidal metal nanoparticles.Strength of the interaction between PVP and metal nanoparticles has direct influence on the stability and the size of the PVP-stabilized metal nanoparticles.Therein,species of the metal precursors and amount of the stabilizer are main factors on the strength of the interaction.

  10. Applications of Bis(1-R-imidazol-2-yl)disulfides and Diselenides as Ligands for Main Group and Transition Metals: κ2-[N,N] Coordination, S-S Bond Cleavage and S-S/E-E (E = S, Se) Bond Metathesis Reactions

    Science.gov (United States)

    Figueroa, Joshua S.; Yurkerwich, Kevin; Melnick, Jonathan; Buccella, Daniela; Parkin, Gerard

    2008-01-01

    Bis(1-R-imidazol-2-yl)disulfides, (mimR)2 (R = Ph, But), and diselenides, (seimMes)2, serve as bidentate [N,N]-donor ligands for main group and transition metals. For example, [κ2-(mimBut)2]MCl2 (M = Fe, Co, Ni, Zn), [κ2-(mimPh)2]MCl2 (M = Co, Zn), [κ2-(mimBut)2]CuX (X = Cl, I) and [κ2-(seimMes)2]MCl2 (M = Fe, Co, Ni) are obtained by treatment of (mimBut)2 or (seimMes)2 with the respective metal halide, and have been structurally characterized by X-ray diffraction. On the other hand, the zerovalent nickel complex Ni(PMe3)4 effects cleavage of the disulfide bond of (mimBut)2 to give square planar trans-Ni(PMe3)2(mimBut)2 in which the (mimBut) ligands coordinate via nitrogen rather than sulfur, a most uncommon coordination mode for this class of ligands. Although [κ2-(mimR)2]MCl2 (M = Fe, Co, Ni, Zn) are not subject to homolytic cleavage of the S-S bond because the tetravalent state is not readily accessible, the observation that [κ2-(mimPh)2]CoCl2 and [κ2-(mimBut)2]CoCl2 form an equilibrium mixture with the asymmetric disulfide [κ2-(mimPh)(mimBut)]CoCl2 indicates that S-S bond cleavage via another mechanism is possible. Likewise, metathesis between disulfide and diselenide ligands is observed in the formation of [κ2-(mimBut)(seimMes)]CoCl2 upon treatment of [κ2-(mimBut)2]CoCl2 with [κ2-(seimMes)2]CoCl2. PMID:17900186

  11. Group Cohesion in Experiential Growth Groups

    Science.gov (United States)

    Steen, Sam; Vasserman-Stokes, Elaina; Vannatta, Rachel

    2014-01-01

    This article explores the effect of web-based journaling on changes in group cohesion within experiential growth groups. Master's students were divided into 2 groups. Both used a web-based platform to journal after each session; however, only 1 of the groups was able to read each other's journals. Quantitative data collected before and…

  12. Domestic Production Issues in Chromium and Platinum-Group Metals

    Science.gov (United States)

    1988-09-01

    Protection Agency. OPA 87-005. Washington: Government Printing Office, May 1987. 16. Foley, Jeffrey Y. and James C. Barker . Chromite Deposits Along...Mining, Metallurgical, and Petroleum Engineers, 1976. 52. Stowe, Clive W. Evolution of Chromium Ore Fields. New York: Van Nostrand Reinhold Company

  13. Beyond the iron group: heavy metals in hot subdwarfs

    CERN Document Server

    O'Toole, S J

    2004-01-01

    We report the discovery of strong photospheric resonance lines of Ga III, Ge IV, Sn IV and Pb IV in the UV spectra of more than two dozen sdB and sdOB stars at temperatures ranging from 22000 K to 40000 K. Lines of other heavy elements are also detected, however in these cases more atomic data are needed. Based on these discoveries, we present a hypothesis to explain the apparent lack of silicon in sdB stars hotter than ~32000 K. The existence of triply ionised Ge, Sn, and Pb suggests that rather than silicon sinking deep into the photosphere, it is removed from the star in a fractionated stellar wind. This hypothesis provides a challenge to diffusion models of sdB stars.

  14. Platinum Group Metal Recycling Technology Development - Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Lawrence Shore

    2009-08-19

    BASF Catalysts LLC, formerly Engelhard Corporation, has completed a project to recover Pt from PEM fuel cell membrane electrode assemblies. The project, which began in 2003, has met the project objective of an environmentally-friendly, cost-effective method for recovery of platinum without release of hydrogen fluoride. This has been achieved using a combination of milling, dispersion and acid leaching. 99% recovery of Pt was achieved, and this high yield can be scaled up using one vessel for a single leach and rinse. Leaching was been successfully achieved using a 10% solids level, double the original target. At this solids content, the reagent and utility costs represent ~0.35% of the Pt value of a lot, using very conservative assumptions. The main cost of the process is capital depreciation, followed by labor.

  15. Chemical Cartography. I. A Carbonicity Map of the Galactic Halo

    Science.gov (United States)

    Lee, Young Sun; Beers, Timothy C.; Kim, Young Kwang; Placco, Vinicius; Yoon, Jinmi; Carollo, Daniela; Masseron, Thomas; Jung, Jaehun

    2017-02-01

    We present the first map of carbonicity, [C/Fe], for the halo system of the Milky Way, based on a sample of over 100,000 main-sequence turnoff stars with available spectroscopy from the Sloan Digital Sky Survey. This map, which explores distances up to 15 kpc from the Sun, reveals clear evidence for the dual nature of the Galactic halo, based on the spatial distribution of stellar carbonicity. The metallicity distribution functions of stars in the inner- and outer-halo regions of the carbonicity map reproduce those previously argued to arise from contributions of the inner- and outer-halo populations, with peaks at [Fe/H] = -1.5 and -2.2, respectively. From consideration of the absolute carbon abundances for our sample, A(C), we also confirm that the carbon-enhanced metal-poor (CEMP) stars in the outer-halo region exhibit a higher frequency of CEMP-no stars (those with no overabundances of heavy neutron-capture elements) than of CEMP-s stars (those with strong overabundances of elements associated with the s-process), whereas the stars in the inner-halo region exhibit a higher frequency of CEMP-s stars. We argue that the contrast in the behavior of the CEMP-no and CEMP-s fractions in these regions arises from differences in the mass distributions of the mini-halos from which the stars of the inner- and outer-halo populations formed, which gives rise in turn to the observed dichotomy of the Galactic halo.

  16. Group Work Publication-1991.

    Science.gov (United States)

    Zimpfer, David G.

    1992-01-01

    Lists 21 new publications in group work, of which 9 are reviewed. Those discussed include publications on group counseling and psychotherapy, structured groups, support groups, psychodrama, and social group work. (Author/NB)

  17. From Metal String Complexes to Metal Wires

    Institute of Scientific and Technical Information of China (English)

    PENG SheMing

    2001-01-01

    @@ Our efforts to extend the metal number from dinuclear metal complexes to linear oligonuclear metal complexes with all-syn form of oligo-( α-pyridyl)amido ligands are successful. The oligonuclear complexes are divided into two systems according their MM bond strength, one is the oligonickel( Ⅱ ) complexes without M-M bond, the other is the oligochromium(Ⅱ) and cobalt(H) complexes with a strong M-M bond. Their structures and magnetic behaviors for various metal complexes with specific metal numbers are summarized. The potential application of these metal complexes as a molecular metal wire is discussed by the band structures of hypothetical onedinensional metal strings based on the polynuclear Cr, Co and Ni complexes. Moreover, self-assembled monolayers of n-alkanethiols are employed as a two-dinensional matrix to isolate the metal string complexes, which exhibit protrusions under the measurements of scanning tunneling microscopy (STM) imaging. The topographic STM images reveal that the protruding features for tricobalt and trichromium complexes are, respectively, 0.3 nm and 0.6 nm higher than that of trinickel complex. The increasing trend in conductivity is consistent with their bond orders, obtained from qualitative EHMO calculations.

  18. From Metal String Complexes to Metal Wires

    Institute of Scientific and Technical Information of China (English)

    PENG; SheMing

    2001-01-01

    Our efforts to extend the metal number from dinuclear metal complexes to linear oligonuclear metal complexes with all-syn form of oligo-( α-pyridyl)amido ligands are successful. The oligonuclear complexes are divided into two systems according their MM bond strength, one is the oligonickel( Ⅱ ) complexes without M-M bond, the other is the oligochromium(Ⅱ) and cobalt(H) complexes with a strong M-M bond. Their structures and magnetic behaviors for various metal complexes with specific metal numbers are summarized. The potential application of these metal complexes as a molecular metal wire is discussed by the band structures of hypothetical onedinensional metal strings based on the polynuclear Cr, Co and Ni complexes. Moreover, self-assembled monolayers of n-alkanethiols are employed as a two-dinensional matrix to isolate the metal string complexes, which exhibit protrusions under the measurements of scanning tunneling microscopy (STM) imaging. The topographic STM images reveal that the protruding features for tricobalt and trichromium complexes are, respectively, 0.3 nm and 0.6 nm higher than that of trinickel complex. The increasing trend in conductivity is consistent with their bond orders, obtained from qualitative EHMO calculations.  ……

  19. Recycling of Metals

    DEFF Research Database (Denmark)

    Damgaard, Anders; Christensen, Thomas Højlund

    2011-01-01

    Metals like iron and aluminium are produced from mineral ore and used for a range of products, some of which have very short lifetimes and thus constitute a major fraction of municipal waste. Packaging in terms of cans, foils and containers are products with a short lifetime. Other products like...... appliances, vehicles and buildings, containing iron and aluminium metals, have long lifetimes before they end up in the waste stream. The recycling of production waste and postconsumer metals has a long history in the metal industry. Some metal smelters are today entirely based on scarp metals. This chapter...... describes briefly how iron and aluminium are produced and how scrap metal is recycled in the industry. Quality requirements and use of recycled products are discussed, as are the resource and environmental issues of metal recycling. Copper and other metals are also found in waste but in much smaller...

  20. Group theories: relevance to group safety studies.

    Science.gov (United States)

    Benevento, A L

    1998-01-01

    Promoting safety in the workplace has been attempted in a variety of ways. Increasingly, industries are using groups such as safety teams and quality circles to promote worker safety. Group influences on individual behavior and attitudes have long been studied in the social psychology literature, but the theories have not been commonly found outside the psychology arena. This paper describes the group theories of group polarization, risky shift, social loafing, groupthink and team think and attempts to apply these theories to existing studies that examine work group influences on safety. Interesting parallels were found but only one study examined group influences as their primary focus of research. Since groups are increasingly used for safety promotion, future research on safety that studies group influences with respect to current group theories is recommended.

  1. Trends in Ionization Energy of Transition-Metal Elements

    Science.gov (United States)

    Matsumoto, Paul S.

    2005-01-01

    A rationale for the difference in the periodic trends in the ionization energy of the transition-metal elements versus the main-group elements is presented. The difference is that in the transition-metal elements, the electrons enter an inner-shell electron orbital, while in the main-group elements, the electrons enter an outer-shell electron…

  2. Heavy Metal Biosorption Sites Studies of Laminaria japonica

    Institute of Scientific and Technical Information of China (English)

    QIAN Aihong; WANG Xian; DENG Yongzhi; CHEN Lidan

    2005-01-01

    The role played by the functional groups of Laminaria japonica treated by methanol and formaldehyde in biosorption of the heavy metals was investigated.Infrared spectroscopy analysis and biosorption experiments show that both carboxyl and amino groups join in the sorption; chemical treatment decreased the biosorption efficiency of the heavy metals.

  3. Metal-doped semiconductor nanoparticles and methods of synthesis thereof

    Science.gov (United States)

    Ren, Zhifeng (Inventor); Chen, Gang (Inventor); Poudel, Bed (Inventor); Kumar, Shankar (Inventor); Wang, Wenzhong (Inventor); Dresselhaus, Mildred (Inventor)

    2009-01-01

    The present invention generally relates to binary or higher order semiconductor nanoparticles doped with a metallic element, and thermoelectric compositions incorporating such nanoparticles. In one aspect, the present invention provides a thermoelectric composition comprising a plurality of nanoparticles each of which includes an alloy matrix formed of a Group IV element and Group VI element and a metallic dopant distributed within the matrix.

  4. 资源型企业组织转型的过程及绩效分析--以铜陵有色为例%Process and Performance Analysis of Resource-based Enterprise Organizational Transformation---Example of Tongling Nonferrous Metals Group

    Institute of Scientific and Technical Information of China (English)

    韦江宏

    2014-01-01

    After the organizational transformation of Tongling Nonferrous Metals Group was analyzed in terms of its background, process and method based on the organizational change model proposed by Tichy, an organizational transformation model was established for resource-based enterprise. It is found that since the organizational transformation strategy, consisting predominantly of “separation of main businesses and auxiliary business, as well as overall listing”, was implemented in Tongling Nonferrous Metals Group in 2007, its performance has increased greatly. The external environment is one of key factors to consider during organizational transformation, especially government policies and guidelines play an important role in the enterprise organizational transformation. Due to the particularity of resource-based enterprise, the stratge of progressive transformation should be adopted, starting from peripheral sectors rather than core sector of the corporation.%以铜陵有色为例,依据Tichy 提出的组织变革模型,在对铜陵有色的组织转型背景、转型历程、转型方式等进行深入分析的基础上,构建了资源型企业组织转型过程模型。研究表明:铜陵有色在2007年实施主辅分离、整体上市为主要内容的组织转型后,绩效大幅提升;外部环境是资源型企业转型必须考虑的一个重要因素,尤其是政府政策引导在企业组织转型中仍发挥重要作用;由于资源型企业的特殊性,应实施渐进式转型,并且转型突破口的选择上,应先从公司外围部门开始转型,而不应从公司核心部门开始。

  5. Application of Trianionic Pincer Ligands to Reactions Involving Group VI Alkylidynes, Metal-Metal Multiple Bonds, and Group IV Amides

    Science.gov (United States)

    2008-08-01

    azametallacyclobutadiene (VII). This complex showed promise for NACM but, 16 unfortunately, required an external electrophile, namely ClSi (CH3)3 or AlMe3, to...probability level; hydrogens are omitted for clarity. C1 C6 C5 C4 C3 C17 C18 C19 C22 C21 C20 O2 W1 O1 C25 C24 C23 C26 C7 C12 C11...2) 2730(7) 2108(3) 44(2) C21 2492(2) 2162(8) 2363(3) 50(3) C22 2389(2) 1266(8) 2564(3) 47(2) C23 1662(2) 3025(7) 1779(3) 45(2) C24 1829(3) 4038(7

  6. Interest in biology. Part I: A multidimensional construct

    Science.gov (United States)

    Gardner, Paul L.; Tamir, Pinchas

    Interest in a school subject (e.g., biology) is conceptualized in terms of three components: topics, activities, and motives, each of which has several dimensions. In this study, seven instruments were developed and administered to grade-10 biology students in Israel. Factor analysis provided support for the conceptualization which underlies the development of the instruments. Topic dimensions included biochemical processes, nonhuman organisms, human biology, personal hygiene, and practical applications; the activity dimensions were experiential learning, reception learning, writing/summarizing and group discussion; motives included environmental issues, moral issues, examination success, personal independence, problem solving, and four career dimensions (research, high-status professions, lower-status careers, woodsy-birdsy careers). In an analysis described in Part II of this paper, the students were classified into four groups on the basis of their grade-11 subject enrollment intentions: H (high-level biology), L (low-level biology), P (physical science), and N (no science). Zero-order and multiple correlations were found between interest and other variables and membership/nonmembership of the four groups. Students in Group H were characterized by higher achievement in year-10 biology, higher levels of enjoyment of biology, career orientations towards research or high-status biology-based professions, greater interest in various biology topics, especially reproduction/cell division/genetics, and a greater tendency to regard the Bagrut (grade-12) examination as interesting. Students in Group N displayed lower levels of interest in various topics (especially the microscope, plants, and reproduction), were less motivated to solve problems, had poorer grades in biology (and chemistry), were less likely to perceive biology as useful, were less likely to regard the Bagrut examination as fair, and were less likely to be interested in social modes of learning. There

  7. When are thin films of metals metallic?

    Science.gov (United States)

    Plummer, E. W.; Dowben, P. A.

    1993-04-01

    There is an increasing body of experimental information suggesting that very thin films of materials, normally considered to be metals, exhibit behavior characteristic of a nonmetal. In almost all cases, there is a nonmetal-to-metal transition as a function of film density or thickness, frequently accompanied by a structural transition. Amazingly, this behavior seems to occur for metal films on metal substrates, as well as for metals on semiconductors. The identification of this phenomena and the subsequent explanation has been slow in developing, due to the inability to directly measure the conductivity of a submonolayer film. This paper will discuss the evidence accumulated from variety of spectroscopic experimental techniques for three systems: a Mott-Hubbard transition, a Peierls-like distortion, and a Wilson transition.

  8. Magnetic translation groups as group extension

    OpenAIRE

    Florek, Wojciech

    1998-01-01

    Extensions of a direct product T of two cyclic groups Z_n1 and Z_n2 by an Abelian (gauge) group G with the trivial action of T on G are considered. All possible (nonequivalent) factor systems are determined using the Mac Lane method. Some of resulting groups describe magnetic translation groups. As examples extensions with G=U(1) and G=Z_n are considered and discussed.

  9. Metal release and metal allergy after total hip replacement with resurfacing versus conventional hybrid prosthesis

    DEFF Research Database (Denmark)

    Gustafson, Klas; Jakobsen, Stig Storgaard; Lorenzen, Nina D

    2014-01-01

    to an increased incidence of metal allergy. METHODS: 52 hips in 52 patients (median age 60 (51-64) years, 30 women) were randomized to either a MOM hip resurfacing system (ReCap) or a standard MOP total hip arthoplasty (Mallory Head/Exeter). Spot urine samples were collected preoperatively, postoperatively, after....... RESULTS: A statistically significant 10- to 20-fold increase in urinary levels of cobalt and chromium was observed throughout the entire follow-up in the MOM group. The prevalence of metal allergy was similar between groups. INTERPRETATION: While we observed significantly increased levels of metal ions...

  10. High surface area graphene-supported metal chalcogenide assembly

    Energy Technology Data Exchange (ETDEWEB)

    Worsley, Marcus A.; Kuntz, Joshua D.; Orme, Christine A.

    2017-04-25

    Disclosed here is a method for hydrocarbon conversion, comprising contacting at least one graphene-supported assembly with at least one hydrocarbon feedstock, wherein the graphene-supported assembly comprises (i) a three-dimensional network of graphene sheets crosslinked by covalent carbon bonds and (ii) at least one metal chalcogenide compound disposed on the graphene sheets, wherein the chalcogen of the metal chalcogenide compound is selected from S, Se and Te, and wherein the metal chalcogenide compound accounts for at least 20 wt. % of the graphene-supported assembly.

  11. Group Dynamic Processes in Email Groups

    Science.gov (United States)

    Alpay, Esat

    2005-01-01

    Discussion is given on the relevance of group dynamic processes in promoting decision-making in email discussion groups. General theories on social facilitation and social loafing are considered in the context of email groups, as well as the applicability of psychodynamic and interaction-based models. It is argued that such theories may indeed…

  12. Interagency mechanical operations group numerical systems group

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-09-01

    This report consists of the minutes of the May 20-21, 1971 meeting of the Interagency Mechanical Operations Group (IMOG) Numerical Systems Group. This group looks at issues related to numerical control in the machining industry. Items discussed related to the use of CAD and CAM, EIA standards, data links, and numerical control.

  13. AREVA group overview; Presentation du groupe AREVA

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2002-02-08

    This document presents the Group Areva, a world nuclear industry leader, from a financial holding company to an industrial group, operating in two businesses: the nuclear energy and the components. The structure and the market of the group are discussed, as the financial assets. (A.L.B.)

  14. Evolutionary population synthesis in stellar systems. I. A global approach

    Energy Technology Data Exchange (ETDEWEB)

    Buzzoni, A. (Osservatorio Astronomico di Brera, Milan (Italy))

    1989-12-01

    A new grid of 450 theoretical models for old simple stellar populations is presented. Evolutionary synthesis explores the influence of relevant parameters such as age, chemical composition, initial mass function, and stellar mass loss, on the integrated spectral energy distribution. Ages range between 4 and 18 Gyr, and the metallicity Z ranges from 0.0001 to 0.03, with helium content Y = 0.23 and 0.25, respectively. Three values are considered for the initial mass function, assumed as a power law, N(M) proportional to M exp-s; s = 1.35, 2.35, and 3.35. The computational code takes into account in a quantitative way the contributions from all the relevant stellar evolutionary phases according to the theory of the stellar evolution. Thus, late stage in the life of low- mass stars, such as the horizontal branch and the asymptotic and postasymptotic giant branches are accounted for. Furthermore, a simplified treatment for the evolution of the horizontal branch is developed, and the influence of different morphologies are investigated. 109 refs.

  15. Metal-on-metal hip joint tribology.

    Science.gov (United States)

    Dowson, D; Jin, Z M

    2006-02-01

    The basic tribological features of metal-on-metal total hip replacements have been reviewed to facilitate an understanding of the engineering science underpinning the renaissance of these hard-on-hard joints. Metal-on-polymer hip replacements operate in the boundary lubrication regime, thus leading to the design guidance to reduce the femoral head diameter as much as is feasible to minimize frictional torque and volumetric wear. This explains why the gold-standard implant of this form from the past half-century had a diameter of only 22.225 mm (7/8 in). Metal-on-metal implants can operate in the mild mixed lubrication regime in which much of the applied load is supported by elastohydrodynamic films. Correct tribological design leads to remarkably low steady state wear rates. Promotion of the most effective elastohydrodynamic films calls for the largest possible head diameters and the smallest clearances that can reasonably be adopted, consistent with fine surface finishes, good sphericity and minimal structural elastic deformation of the cup on its foundations. This guidance, which is opposite in form to that developed for metal-on-polymer joints, is equally valid for solid (monolithic) metallic heads on metallic femoral stems and surface replacement femoral shells. Laboratory measurements of friction and wear in metal-on-metal joints have confirmed their potential to achieve a very mild form of mixed lubrication. The key lies in the generation of effective elastohydrodynamic lubricating films of adequate thickness compared with the composite roughness of the head and cup. The calculation of the film thickness is by no means easy, but the full procedure is outlined and the use of an empirical formula that displays good agreement with calculations based upon the full numerical solutions is explained. The representation of the lambda ratio, lambda, embracing both film thickness and composite roughness, is described.

  16. Glassy metallic plastics

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    This paper reports a class of bulk metallic glass including Ce-, LaCe-, CaLi-, Yb-, and Sr-based metallic glasses, which are regarded as glassy metallic plastics because they combine some unique properties of both plastics and metallic alloys. These glassy metallic plastics have very low glass transition temperature (Tg~25oC to 150oC) and low Young’s modulus (~20 GPa to 35 GPa). Similar to glassy plastics, these metallic plastics show excellent plastic-like deformability on macro-, micro- and even nano-scale in their supercooled liquid range and can be processed, such as elongated, compressed, bent, and imprinted at low temperatures, in hot water for instance. Under ambient conditions, they display such metallic properties as high thermal and electric conductivities and excellent mechanical properties and other unique properties. The metallic plastics have potential applications and are also a model system for studying issues in glass physics.

  17. Economic Geology (Metals)

    Science.gov (United States)

    Gair, Jacob E.

    1972-01-01

    Reviews metalliferous ore-deposit research reported in 1971. Research was dominated by isotopic studies, and worldwide metals exploration was marked by announcements of important new discoveries of base metals, iron ore, nickel, titanium, and uranium. (Author/PR)

  18. Economic Geology (Metals)

    Science.gov (United States)

    Gair, Jacob E.

    1972-01-01

    Reviews metalliferous ore-deposit research reported in 1971. Research was dominated by isotopic studies, and worldwide metals exploration was marked by announcements of important new discoveries of base metals, iron ore, nickel, titanium, and uranium. (Author/PR)

  19. The Local Group: Inventory and History

    CERN Document Server

    Tolstoy, Eline

    2010-01-01

    My presentation was an overview of what we know about the Local Group of galaxies, primarily from optical imaging and spectroscopy. AGB stars are on the whole a very sparse and unrepresentative stellar population in most Local Group galaxies. However, more detailed studies of star formation histories and chemical evolution properties of populations, like Main Sequence dwarf stars and Red Giant Branch stars, allow a better understanding of the evolutionary context in which AGB stars can be observed. There are a variety of galaxy types in the Local Group which range from predominantly metal poor (e.g., Leo A) to metal-rich (e.g., M 32). Dwarf galaxies are the most numerous type of galaxy in the Local Group, and provide the opportunity to study a relatively simple, typically metal-poor, environment that is likely similar to the conditions in the early history of all galaxies. Hopefully the range of star formation histories, peak star formation rates and metallicities will provide enough information to properly c...

  20. Nanochemistry of metals

    Science.gov (United States)

    Sergeev, Gleb B.

    2001-10-01

    The results of studies on the nanochemistry of metals published in recent years are generalised. Primary attention is centred on the methods for the synthesis of nanoparticles and their chemical reactions. The means of stabilisation of nanoparticles which involve individual metals and incorporate atoms of several metals are considered as well as their physicochemical properties. Self-assembling processes of nanoparticles are described. The prospects of using metal nanoparticles in semiconductor devices, catalysis, biology and medicine are discussed. The bibliography includes 165 references.

  1. Marks of Metal Copenhell

    DEFF Research Database (Denmark)

    2015-01-01

    Planchebaseret udendørs udstilling på musikfestivalen Copenhell 18-20/6 2015. En mindre udgave af udstillingen Marks of Metal - Logodesign og visualitet i heavy metal. Udarbejdet i samarbejde med Mediemuseet.......Planchebaseret udendørs udstilling på musikfestivalen Copenhell 18-20/6 2015. En mindre udgave af udstillingen Marks of Metal - Logodesign og visualitet i heavy metal. Udarbejdet i samarbejde med Mediemuseet....

  2. Testing their metal.

    OpenAIRE

    Fisher, B. E.

    1999-01-01

    Metals continually rank at the top of the U.S. Environmental Protection Agency's annual list of agents that pose the greatest hazard to the people of the United States. Metals aren't going away, either. They do not biodegrade, and they often concentrate in human and animal cells and tissue. Many metals are known human and animal carcinogens, while many others are suspected to play a role in cancer. Little is known, however, about the mechanisms by which metals cause cancer.

  3. Phosphopeptide enrichment by immobilized metal affinity chromatography

    DEFF Research Database (Denmark)

    Thingholm, Tine E.; Larsen, Martin R.

    2016-01-01

    Immobilized metal affinity chromatography (IMAC) has been the method of choice for phosphopeptide enrichment prior to mass spectrometric analysis for many years and it is still used extensively in many laboratories. Using the affinity of negatively charged phosphate groups towards positively...... charged metal ions such as Fe3+, Ga3+, Al3+, Zr4+, and Ti4+ has made it possible to enrich phosphorylated peptides from peptide samples. However, the selectivity of most of the metal ions is limited, when working with highly complex samples, e.g., whole-cell extracts, resulting in contamination from...

  4. Band theory of metals the elements

    CERN Document Server

    Altmann, Simon L

    1970-01-01

    Band Theory of Metals: The Elements focuses on the band theory of solids. The book first discusses revision of quantum mechanics. Topics include Heisenberg's uncertainty principle, normalization, stationary states, wave and group velocities, mean values, and variational method. The text takes a look at the free-electron theory of metals, including heat capacities, density of states, Fermi energy, core and metal electrons, and eigenfunctions in three dimensions. The book also reviews the effects of crystal fields in one dimension. The eigenfunctions of the translations; symmetry operations of t

  5. Use of algae for removing heavy metal ions from wastewater: progress and prospects.

    Science.gov (United States)

    Mehta, S K; Gaur, J P

    2005-01-01

    Many algae have immense capability to sorb metals, and there is considerable potential for using them to treat wastewaters. Metal sorption involves binding on the cell surface and to intracellular ligands. The adsorbed metal is several times greater than intracellular metal. Carboxyl group is most important for metal binding. Concentration of metal and biomass in solution, pH, temperature, cations, anions and metabolic stage of the organism affect metal sorption. Algae can effectively remove metals from multi-metal solutions. Dead cells sorb more metal than live cells. Various pretreatments enhance metal sorption capacity of algae. CaCl2 pretreatment is the most suitable and economic method for activation of algal biomass. Algal periphyton has great potential for removing metals from wastewaters. An immobilized or granulated biomass-filled column can be used for several sorption/desorption cycles with unaltered or slightly decreased metal removal. Langmuir and Freundlich models, commonly used for fitting sorption data, cannot precisely describe metal sorption since they ignore the effect of pH, biomass concentration, etc. For commercial application of algal technology for metal removal from wastewaters, emphasis should be given to: (i) selection of strains with high metal sorption capacity, (ii) adequate understanding of sorption mechanisms, (iii) development of low-cost methods for cell immobilization, (iv) development of better models for predicting metal sorption, (v) genetic manipulation of algae for increased number of surface groups or over expression of metal binding proteins, and (vi) economic feasibility.

  6. About group digital signatures

    National Research Council Canada - National Science Library

    Adriana Cristina Enache

    2012-01-01

    ...).A group digital signature is a digital signature with enhanced privacy features that allows members of a given group to anonymously sign messages on behalf of the group, producing a group signature...

  7. Toxicity from Metals, Old Menaces and New Threats

    Directory of Open Access Journals (Sweden)

    Wayne Briner

    2010-12-01

    Full Text Available Metals make up the bulk of the periodic table and range from the very light (e.g., beryllium to the very heavy (e.g., the actinides. Metals are important constituents of life, drive economic activity and industry, but can also be a hazard to human health. The metals can be roughly divided into three groups. The first being those metals, such as iron and zinc, that are essential to human life and have a wide therapeutic dose range. The second group of metals, such as lead, mercury, and uranium, has no known biological role and are toxic even at low doses. The third group of metals, such as selenium and manganese, has a role in maintaining human health but has a very narrow dose range that, when exceeded, produces toxic effects. [...

  8. Introduction to Sporadic Groups

    Directory of Open Access Journals (Sweden)

    Luis J. Boya

    2011-01-01

    Full Text Available This is an introduction to finite simple groups, in particular sporadic groups, intended for physicists. After a short review of group theory, we enumerate the 1+1+16=18 families of finite simple groups, as an introduction to the sporadic groups. These are described next, in three levels of increasing complexity, plus the six isolated ''pariah'' groups. The (old five Mathieu groups make up the first, smallest order level. The seven groups related to the Leech lattice, including the three Conway groups, constitute the second level. The third and highest level contains the Monster group M, plus seven other related groups. Next a brief mention is made of the remaining six pariah groups, thus completing the 5+7+8+6=26 sporadic groups. The review ends up with a brief discussion of a few of physical applications of finite groups in physics, including a couple of recent examples which use sporadic groups.

  9. Molecular mechanisms of heavy metal hyperaccumulation and phytoremediation.

    Science.gov (United States)

    Yang, Xiaoe; Feng, Ying; He, Zhenli; Stoffella, Peter J

    2005-01-01

    A relatively small group of hyperaccumulator plants is capable of sequestering heavy metals in their shoot tissues at high concentrations. In recent years, major scientific progress has been made in understanding the physiological mechanisms of metal uptake and transport in these plants. However, relatively little is known about the molecular bases of hyperaccumulation. In this paper, current progresses on understanding cellular/molecular mechanisms of metal tolerance/hyperaccumulation by plants are reviewed. The major processes involved in hyperaccumulation of trace metals from the soil to the shoots by hyperaccumulators include: (a) bioactivation of metals in the rhizosphere through root-microbe interaction; (b) enhanced uptake by metal transporters in the plasma membranes; (c) detoxification of metals by distributing to the apoplasts like binding to cell walls and chelation of metals in the cytoplasm with various ligands, such as phytochelatins, metallothioneins, metal-binding proteins; (d) sequestration of metals into the vacuole by tonoplast-located transporters. The growing application of molecular-genetic technologies led to the well understanding of mechanisms of heavy metal tolerance/accumulation in plants, and subsequently many transgenic plants with increased resistance and uptake of heavy metals were developed for the purpose of phytoremediation. Once the rate-limiting steps for uptake, translocation, and detoxification of metals in hyperaccumulating plants are identified, more informed construction of transgenic plants would result in improved applicability of the phytoremediation technology.

  10. Metal Nitrides for Plasmonic Applications

    DEFF Research Database (Denmark)

    Naik, Gururaj V.; Schroeder, Jeremy; Guler, Urcan;

    2012-01-01

    Metal nitrides as alternatives to metals such as gold could offer many advantages when used as plasmonic material. We show that transition metal nitrides can replace metals providing equally good optical performance for many plasmonic applications.......Metal nitrides as alternatives to metals such as gold could offer many advantages when used as plasmonic material. We show that transition metal nitrides can replace metals providing equally good optical performance for many plasmonic applications....

  11. Metal Detecting in Denmark

    DEFF Research Database (Denmark)

    Dobat, A.S.

    2016-01-01

    Since the early 1980s, metal detector surveying conducted by non-professional volunteers (amateur archaeologists) has contributed significantly to archaeological research and heritage practice in Denmark. Metal detecting has always been legal in Denmark, and official stakeholders have from...... the beginning of metal detector archaeology pursued a liberal model, focusing on cooperation and inclusion rather than confrontation and criminalization. Like no other surveying method, the metal detector has contributed to increasing enormously the amount of data and sites from metal-rich periods. Virtually...... all of the spectacular and ground-breaking discoveries of the past decades are owed to metal detectors in the hands of amateur archaeologists. In order to serve as a contribution to the discussion on the upsides and downsides of liberal metal detector archaeology, this article addresses mainly three...

  12. Metals and breast cancer.

    Science.gov (United States)

    Byrne, Celia; Divekar, Shailaja D; Storchan, Geoffrey B; Parodi, Daniela A; Martin, Mary Beth

    2013-03-01

    Metalloestrogens are metals that activate the estrogen receptor in the absence of estradiol. The metalloestrogens fall into two subclasses: metal/metalloid anions and bivalent cationic metals. The metal/metalloid anions include compounds such as arsenite, nitrite, selenite, and vanadate while the bivalent cations include metals such as cadmium, calcium, cobalt, copper, nickel, chromium, lead, mercury, and tin. The best studied metalloestrogen is cadmium. It is a heavy metal and a prevalent environmental contaminant with no known physiological function. This review addresses our current understanding of the mechanism by which cadmium and the bivalent cationic metals activate estrogen receptor-α. The review also summarizes the in vitro and in vivo evidence that cadmium functions as an estrogen and the potential role of cadmium in breast cancer.

  13. Reaction phases and diffusion paths in SiC/metal systems

    Energy Technology Data Exchange (ETDEWEB)

    Naka, M.; Fukai, T. [Osaka Univ., Osaka (Japan); Schuster, J.C. [Vienna Univ., Vienna (Austria)

    2004-07-01

    The interface structures between SiC and metal are reviewed at SiC/metal systems. Metal groups are divided to carbide forming metals and non-carbide forming metals. Carbide forming metals form metal carbide granular or zone at metal side, and metal silicide zone at SiC side. The further diffusion of Si and C from SiC causes the formation of T ternary phase depending metal. Non-carbide forming metals form silicide zone containing graphite or the layered structure of metal silicide and metal silicide containing graphite. The diffusion path between SiC and metal are formed along tie-lines connecting SiC and metal on the corresponding ternary Si-C-M system. The reactivity of metals is dominated by the forming ability of carbide or silicide. Te reactivity tendency of elements are discussed on the periodical table of elements, and Ti among elements shows the highest reactivity among carbide forming metals. For non-carbide forming metals the reactivity sequence of metals is Fe>Ni>Co. (orig.)

  14. Metal pad instabilities in liquid metal batteries

    Science.gov (United States)

    Zikanov, Oleg

    2016-11-01

    Strong variations between the electrical conductivities of electrolyte and metal layers in a liquid metal battery indicate the possibility of 'metal pad' instabilities. Deformations of the electrolyte-metal interfaces cause strong perturbations of electric currents, which, hypothetically, can generate Lorentz forces enhancing the deformations. We investigate this possibility using two models: a mechanical analogy and a two-dimensional linearized approximation. It is found that the battery is prone to instabilities of two types. One is similar to the sloshing-wave instability observed in the Hall-Héroult aluminum reduction cells. Another is new and related to the interactions of current perturbations with the azimuthal magnetic field induced by the base current. Financial support was provided by the U.S. National Science Foundation (Grant CBET 1435269).

  15. Molecularly doped metals.

    Science.gov (United States)

    Avnir, David

    2014-02-18

    The many millions of organic, inorganic, and bioorganic molecules represent a very rich library of chemical, biological, and physical properties that do not show up among the approximately 100 metals. The ability to imbue metals with any of these molecular properties would open up tremendous potential for the development of new materials. In addition to their traditional features and their traditional applications, metals would have new traits, which would merge their classical virtues such as conductivity and catalytic activity with the diverse properties of these molecules. In this Account, we describe a new materials methodology, which enables, for the first time, the incorporation and entrapment of small organic molecules, polymers, and biomolecules within metals. These new materials are denoted dopant@metal. The creation of dopant@metal yields new properties that are more than or different from the sum of the individual properties of the two components. So far we have developed methods for the doping of silver, copper, gold, iron, palladium, platinum, and some of their alloys, as well as Hg-Ag amalgams. We have successfully altered classical metal properties (such as conductivity), induced unorthodox properties (such as rendering a metal acidic or basic), used metals as heterogeneous matrices for homogeneous catalysts, and formed new metallic catalysts such as metals doped with organometallic complexes. In addition, we have created materials that straddle the border between polymers and metals, we have entrapped enzymes to form bioactive metals, we have induced chirality within metals, we have made corrosion-resistant iron, we formed efficient biocidal materials, and we demonstrated a new concept for batteries. We have developed a variety of methods for synthesizing dopant@metals including aqueous homogeneous and heterogeneous reductions of the metal cations, reductions in DMF, electrochemical entrapments, thermal decompositions of zerovalent metal carbonyls

  16. Effects of tin plating on base metal alloy-ceramic bond strength.

    Science.gov (United States)

    Değer, S; Caniklioglu, M B

    1998-01-01

    This study investigated the metal-ceramic bonding of treated metal surfaces. The study was divided into two parts. In Part I, the depth of tin diffusion from a tin-plated bone metal alloy surface was measured using an energy-dispersive spectrometer. In Part II the metal-ceramic bond strength was determined using a shear test. The weakest bonding was observed in the directly tin-plated group, and the strongest metal-ceramic bonding was maintained in the tin-diffused group. A controlled oxidation produced the greatest bond strengths. With the base metal alloys tested, diffusion under the argon environment was conducive to a stronger metal-ceramic bond. The metal oxidation rate should approximate the ceramic vitrification rate, and the diffusion rate of the metal elements should be slower than the vitrification rate to obtain the strongest metal-ceramic bond.

  17. Thin Metallic Films from Solvated Metal Atoms.

    Science.gov (United States)

    1987-07-14

    research has developed over the past two decades that deals with the generation of atoms of metals (by metal evaporation, and the interaction of these...Departamento de Quimica , Universidad de Concepcion, Cassilla 3-:, c oncepcion, Chile. -I{ - ~ *~.’JS*~M 4 .~4\\ 821 19 the gold particles were negatively...flocculation were observed, as shown in table a Generally about 0.1 g In was Suspended in 100-200 nl solvent. Several approacies to characterization of

  18. Group Work: How to Use Groups Effectively

    Science.gov (United States)

    Burke, Alison

    2011-01-01

    Many students cringe and groan when told that they will need to work in a group. However, group work has been found to be good for students and good for teachers. Employers want college graduates to have developed teamwork skills. Additionally, students who participate in collaborative learning get better grades, are more satisfied with their…

  19. Metal Matrix Composite Solar Cell Metallization

    Directory of Open Access Journals (Sweden)

    Wilt David M.

    2017-01-01

    Full Text Available Advanced solar cells are moving to ever thinner formats in order to save mass and in some cases improve performance. As cells are thinned, the possibility that they may fracture or cleave due to mechanical stresses is increased. Fractures of the cell can degrade the overall device performance if the fracture propagates through the contact metallization, which frequently occurs. To address this problem, a novel semiconductor metallization system based on multi-walled carbon nanotube (CNT reinforcement, termed metal matrix composite (MMC metallization is under investigation. Electro-mechanical characterization of MMC films demonstrate their ability to provide electrical conductivity over >40 micron wide cracks in the underlying semiconductor, with the carbon nanotubes bridging the gap. In addition, these materials show a “self-healing” behaviour, electrically reconnecting at ~30 microns when strained past failure. Triple junction (TJ space cells with MMC metallization demonstrated no loss in Jsc after intentional fracture, whereas TJ cells with conventional metallization suffer up to 50% Jsc loss.

  20. Small Group Research

    Science.gov (United States)

    McGrath, Joseph E.

    1978-01-01

    Summarizes research on small group processes by giving a comprehensive account of the types of variables primarily studied in the laboratory. These include group structure, group composition, group size, and group relations. Considers effects of power, leadership, conformity to social norms, and role relationships. (Author/AV)

  1. Free Boolean Topological Groups

    Directory of Open Access Journals (Sweden)

    Ol’ga Sipacheva

    2015-11-01

    Full Text Available Known and new results on free Boolean topological groups are collected. An account of the properties that these groups share with free or free Abelian topological groups and properties specific to free Boolean groups is given. Special emphasis is placed on the application of set-theoretic methods to the study of Boolean topological groups.

  2. Metal-Phenolic Supramolecular Gelation.

    Science.gov (United States)

    Rahim, Md Arifur; Björnmalm, Mattias; Suma, Tomoya; Faria, Matthew; Ju, Yi; Kempe, Kristian; Müllner, Markus; Ejima, Hirotaka; Stickland, Anthony D; Caruso, Frank

    2016-10-24

    Materials assembled by coordination interactions between naturally abundant polyphenols and metals are of interest for a wide range of applications, including crystallization, catalysis, and drug delivery. Such an interest has led to the development of thin films with tunable, dynamic properties, however, creating bulk materials remains a challenge. Reported here is a class of metallogels formed by direct gelation between inexpensive, naturally abundant tannic acid and group(IV) metal ions. The metallogels exhibit diverse properties, including self-healing and transparency, and can be doped with various materials by in situ co-gelation. The robustness and flexibility, combined with the ease, low cost, and scalability of the coordination-driven assembly process make these metallogels potential candidates for chemical, biomedical, and environmental applications.

  3. Metal uptake and acute toxicity in zebrafish: Common mechanisms across multiple metals

    Energy Technology Data Exchange (ETDEWEB)

    Alsop, Derek, E-mail: alsopde@mcmaster.ca [Department of Biology, McMaster University, 1280 Main St. W., Hamilton, ON L8S 4K1 (Canada); Wood, Chris M. [Department of Biology, McMaster University, 1280 Main St. W., Hamilton, ON L8S 4K1 (Canada)

    2011-10-15

    All metals tested reduced calcium uptake in zebrafish larvae. However, it was whole body sodium loss that was functionally related to toxicity. The zebrafish larvae acute toxicity assay save time, space and resources. - Abstract: Zebrafish larvae (Danio rerio) were used to examine the mechanisms of action and acute toxicities of metals. Larvae had similar physiological responses and sensitivities to waterborne metals as adults. While cadmium and zinc have previously been shown to reduce Ca{sup 2+} uptake, copper and nickel also decreased Ca{sup 2+} uptake, suggesting that the epithelial transport of all these metals is through Ca{sup 2+} pathways. However, exposure to cadmium, copper or nickel for up to 48 h had little or no effect on total whole body Ca{sup 2+} levels, indicating that the reduction of Ca{sup 2+} uptake is not the acute toxic mechanism of these metals. Instead, mortalities were effectively related to whole body Na{sup +}, which decreased up to 39% after 48 h exposures to different metals around their respective 96 h LC50s. Decreases in whole body K{sup +} were also observed, although they were not as pronounced or frequent as Na{sup +} losses. None of the metals tested inhibited Na{sup +} uptake in zebrafish (Na{sup +} uptake was in fact increased with exposure) and the observed losses of Na{sup +}, K{sup +}, Ca{sup 2+} and Mg{sup 2+} were proportional to the ionic gradients between the plasma and water, indicating diffusive ion loss with metal exposure. This study has shown that there is a common pathway for metal uptake and a common mechanism of acute toxicity across groups of metals in zebrafish. The disruption of ion uptake accompanying metal exposure does not appear to be responsible for the acute toxicity of metals, as has been previously suggested, but rather the toxicity is instead due to total ion loss (predominantly Na{sup +}).

  4. FOOD ALLERGY AND ORAL ALLERGY SYNDROME. Part I. A review.

    Directory of Open Access Journals (Sweden)

    Miglena Balcheva

    2013-09-01

    Full Text Available Food allergy and intolerance are wide spread nowadays. However, the problem existed and was registered and described still by the ancients. It was fully understood and scientifically depicted in the 20th century after IgE and anaphylaxis were discovered, new diagnostic tests were initiated and the term “allergy” was introduced. There are some interesting aspects of the problem. Epidemiology is the first one – in the last two decades the number of people suffering from food allergy increased significantly and reached 4% of the population. Food allergy covers all ages, both sexes; atopic people and these with other allergic or digestive diseases are in the risk group also. There is certain influence of the eating habits as well. Etiology is rich and varied. It includes all foodstuffs of plant and animal origin, spices, honey, medicinal products - milk, eggs, meat, fish, nuts, fruits and vegetables, etc. Pathogenesis is complex.

  5. MSUD Family Support Group

    Science.gov (United States)

    ... Group The MSUD Family Support Group is a non-profit 501 (c)(3) organization for those with MSUD ... Family Support Group is a 501(c)(3) non-profit organization with no paid staff. Funds are needed ...

  6. Profinite graphs and groups

    CERN Document Server

    Ribes, Luis

    2017-01-01

    This book offers a detailed introduction to graph theoretic methods in profinite groups and applications to abstract groups. It is the first to provide a comprehensive treatment of the subject. The author begins by carefully developing relevant notions in topology, profinite groups and homology, including free products of profinite groups, cohomological methods in profinite groups, and fixed points of automorphisms of free pro-p groups. The final part of the book is dedicated to applications of the profinite theory to abstract groups, with sections on finitely generated subgroups of free groups, separability conditions in free and amalgamated products, and algorithms in free groups and finite monoids. Profinite Graphs and Groups will appeal to students and researchers interested in profinite groups, geometric group theory, graphs and connections with the theory of formal languages. A complete reference on the subject, the book includes historical and bibliographical notes as well as a discussion of open quest...

  7. Homomorphisms of quantum groups

    CERN Document Server

    Meyer, Ralf; Woronowicz, Stanisław Lech

    2010-01-01

    We introduce some equivalent notions of homomorphisms between quantum groups that behave well with respect to duality of quantum groups. Our equivalent definitions are based on bicharacters, coactions, and universal quantum groups, respectively.

  8. Food Groups Recipes

    OpenAIRE

    2012-01-01

    15 pages In 2011, My Plate replaced the Food Pyramid as a visual representation for the USDA Dietary Guidelines. This publication, a group of recipes based on this new division of food groups, reflects the effort of the USDA and other groups to translate science-based research into everyday practice for Americans. Fifteen recipes (3 from each food group) show ways to use foods from each food group. They are complete with basic nutritional analyses and food group amounts.

  9. Trace metal speciation and bioavailability in anaerobic digestion: A review.

    Science.gov (United States)

    Thanh, Pham Minh; Ketheesan, Balachandran; Yan, Zhou; Stuckey, David

    2016-01-01

    Trace metals are essential for the growth of anaerobic microorganisms, however, in practice they are often added to anaerobic digesters in excessive amounts, which can lead to inhibition. The concept of bioavailability of metals in anaerobic digestion has been poorly understood in the past, and a lack of deep understanding of the relationship between trace metal speciation and bioavailability can result in ineffective metal dosing strategies for anaerobic digesters. Sequential extraction schemes are useful for fractionating trace metals into their different forms, and metal sulfides can serve as a store and source for trace metals during anaerobic digestion, while natural/synthetic chelating agents (soluble microbial products-SMPs, extracellular polysaccharides-EPS, and EDTA/NTA) are capable of controlling trace metal bioavailability. Nevertheless, more work is needed to: investigate the speciation and bioavailability of Ca, Mg, Mn, W, and Se; compare the bioavailability of different forms of trace metals e.g. carbonates, sulfides, phosphates to different anaerobic trophic groups; determine what factors influence metal sulfide dissolution; investigate whether chelating agents can increase trace metal bioavailability; develop and adapt specialized analytical techniques, and; determine how trace metal dynamics change in an anaerobic membrane bioreactor (AnMBR).

  10. Locally minimal topological groups

    OpenAIRE

    Außenhofer, Lydia; Chasco, María Jesús; Dikranjan, Dikran; Domínguez, Xabier

    2009-01-01

    A Hausdorff topological group $(G,\\tau)$ is called locally minimal if there exists a neighborhood $U$ of 0 in $\\tau$ such that $U$ fails to be a neighborhood of zero in any Hausdorff group topology on $G$ which is strictly coarser than $\\tau.$ Examples of locally minimal groups are all subgroups of Banach-Lie groups, all locally compact groups and all minimal groups. Motivated by the fact that locally compact NSS groups are Lie groups, we study the connection between local minimality and the ...

  11. GROUP PROFILE Computer Technique

    Directory of Open Access Journals (Sweden)

    Andrey V. Sidorenkov

    2015-01-01

    Full Text Available This article contains a description of the structure, the software and functional capabilities, and the scope and purposes of application of the Group Profile (GP computer technique. This technique rests on a conceptual basis (the microgroup theory, includes 16 new and modified questionnaires, and a unique algorithm, tied to the questionnaires, for identification of informal groups. The GP yields a wide range of data about the group as a whole (47 indices, each informal group (43 indices, and each group member (16 indices. The GP technique can be used to study different types of groups: production (work groups, design teams, military units, etc., academic (school classes, student groups, and sports.

  12. Method of making controlled morphology metal-oxides

    Science.gov (United States)

    Ozcan, Soydan; Lu, Yuan

    2016-05-17

    A method of making metal oxides having a preselected morphology includes preparing a suspension that includes a solvent, polymeric nanostructures having multiplicities of hydroxyl surface groups and/or carboxyl surface groups, and a metal oxide precursor. The suspension has a preselected ratio of the polymeric nanostructures to the metal oxide precursor of at least 1:3, the preselected ratio corresponding to a preselected morphology. Subsequent steps include depositing the suspension onto a substrate, removing the solvent to form a film, removing the film from the substrate, and annealing the film to volatilize the polymeric nanostructures and convert the metal oxide precursor to metal oxide nanoparticles having the preselected morphology or to a metal oxide nanosheet including conjoined nanoparticles having the preselected morphology.

  13. Soil heavy metals

    Energy Technology Data Exchange (ETDEWEB)

    Sherameti, Irena [Jena Univ. (Germany). Inst. fuer Allgemeine Botanik und Pflanzenphysiologie; Varma, Ajit (eds.) [Amity Univ., Uttar Pradesh (India). Amity Inst. of Microbial Technology; Amity Science, Technology and Innovation Foundation, Noida, UP (India)

    2010-07-01

    Human activities have dramatically changed the composition and organisation of soils. Industrial and urban wastes, agricultural application and also mining activities resulted in an increased concentration of heavy metals in soils. How plants and soil microorganisms cope with this situation and the sophisticated techniques developed for survival in contaminated soils is discussed in this volume. The topics presented include: the general role of heavy metals in biological soil systems; the relation of inorganic and organic pollutions; heavy metal, salt tolerance and combined effects with salinity; effects on abuscular mycorrhizal and on saprophytic soil fungi; heavy metal resistance by streptomycetes; trace element determination of environmental samples; the use of microbiological communities as indicators; phytostabilization of lead polluted sites by native plants; effects of soil earthworms on removal of heavy metals and the remediation of heavy metal contaminated tropical land. (orig.)

  14. Light metal production

    Science.gov (United States)

    Fan, Qinbai

    2016-04-19

    An electrochemical process for the production of light metals, particularly aluminum. Such a process involves contacting a light metal source material with an inorganic acid to form a solution containing the light metal ions in high concentration. The solution is fed to an electrochemical reactor assembly having an anode side containing an anode and a cathode side containing a cathode, with anode side and the cathode side separated by a bipolar membrane, with the solution being fed to the anode side. Light metal ions are electrochemically transferred through the bipolar membrane to the cathode side. The process further involves reducing the light metal ions to light metal powder. An associated processing system is also provided.

  15. Removal of heavy metals through adsorption using sand

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The removal of four heavy metals i.e. Pb, Cr, Cu, and Zn from their aqueous solutions, using ordinary sand as an adsorbent, was studied at 20oC. The amount of metal adsorbed to form monolayer on sand(am), obtained from Langmuir isotherm, exhibited the preference of metals for sand in the order Pb>Cr>Cu>Zn. The heavy metal-sand adsorption phenomena can be illustrated on the basis of the interaction between surface functional group of silicates (sand) and the metal ions. It is deduced that sand can be used as a low cost adsorbent for the removal of heavy metal from wastewater (containing low conc. of metals), especially in the developing countries.

  16. Ordered groups and infinite permutation groups

    CERN Document Server

    1996-01-01

    The subjects of ordered groups and of infinite permutation groups have long en­ joyed a symbiotic relationship. Although the two subjects come from very different sources, they have in certain ways come together, and each has derived considerable benefit from the other. My own personal contact with this interaction began in 1961. I had done Ph. D. work on sequence convergence in totally ordered groups under the direction of Paul Conrad. In the process, I had encountered "pseudo-convergent" sequences in an ordered group G, which are like Cauchy sequences, except that the differences be­ tween terms of large index approach not 0 but a convex subgroup G of G. If G is normal, then such sequences are conveniently described as Cauchy sequences in the quotient ordered group GIG. If G is not normal, of course GIG has no group structure, though it is still a totally ordered set. The best that can be said is that the elements of G permute GIG in an order-preserving fashion. In independent investigations around that t...

  17. Computational Design of Metal Ion Sequestering Agents

    Energy Technology Data Exchange (ETDEWEB)

    Hay, Benjamin P.; Rapko, Brian M.

    2006-06-01

    Organic ligands that exhibit a high degree of metal ion recognition are essential precursors for developing separation processes and sensors for metal ions. Since the beginning of the nuclear era, much research has focused on discovering ligands that target specific radionuclides. Members of the Group 1A and 2A cations (e.g., Cs, Sr, Ra) and the f-block metals (actinides and lanthanides) are of primary concern to DOE. Although there has been some success in identifying ligand architectures that exhibit a degree of metal ion recognition, the ability to control binding affinity and selectivity remains a significant challenge. The traditional approach for discovering such ligands has involved lengthy programs of organic synthesis and testing that, in the absence of reliable methods for screening compounds before synthesis, have resulted in much wasted research effort.

  18. Optical resonance of metal-coated nanoshell

    Institute of Scientific and Technical Information of China (English)

    Diao Jia-Jie(刁佳杰); Chen Guang-De(陈光德); Xi Cong(席聪); Z Y Fan; Yuan Jin-She(苑进社)

    2003-01-01

    Metal-coated nanoshell, the nanoparticle consisting of a nanometre-scale dielectric core coated with a thin metallic shell, exhibits three distinct optical resonant forms, the sphere cavity resonance (SCR), plasmon resonance (PR), and concentric dielectric sphere resonance (CDSR). The SCR, PR and CDSR of the metal-coated nanoshell reveal a geometric tunability controlled by the core radius and by the ratio of the core radius to the total radius. Classical electrodynamics and Mie scattering theory are used to treat the resonant forms and the transition state between the resonant forms. Based on previous experimental research, we present a group of resonant equations for all the resonant forms, which depend on the geometric structure of the metal-coated nanoshell.

  19. Metal atomization spray nozzle

    Science.gov (United States)

    Huxford, Theodore J.

    1993-01-01

    A spray nozzle for a magnetohydrodynamic atomization apparatus has a feed passage for molten metal and a pair of spray electrodes mounted in the feed passage. The electrodes, diverging surfaces which define a nozzle throat and diverge at an acute angle from the throat. Current passes through molten metal when fed through the throat which creates the Lorentz force necessary to provide atomization of the molten metal.

  20. Metal oxides as photocatalysts

    Directory of Open Access Journals (Sweden)

    Mohammad Mansoob Khan

    2015-09-01

    Full Text Available Metal oxides are of great technological importance in environmental remediation and electronics because of their capability to generate charge carriers when stimulated with required amount of energy. The promising arrangement of electronic structure, light absorption properties, and charge transport characteristics of most of the metal oxides has made possible its application as photocatalyst. In this article definition of metal oxides as photocatalyst, structural characteristics, requirements of the photocatalyst, classification of photocatalysts and the mechanism of the photocatalytic process are discussed.

  1. Creep in amorphous metals

    Directory of Open Access Journals (Sweden)

    Michael E. Kassner

    2015-01-01

    Full Text Available This paper reviews the work on creep behavior of amorphous metals. There have been, over the past several years, a few reviews of the mechanical behavior of amorphous metals. Of these, the review of the creep properties of amorphous metals by Schuh et al. though oldest of the three, is particularly noteworthy and the reader is referred to this article published in 2007. The current review of creep of amorphous metals particularly focuses on those works since that review and places the work prior to 2007 in a different context where new developments warrant.

  2. Synthesis of aromatic nitriles using nonmetallic cyano-group sources.

    Science.gov (United States)

    Kim, Jinho; Kim, Hyun Jin; Chang, Sukbok

    2012-11-26

    Aromatic nitriles are prepared efficiently through transition-metal-mediated cyanation of aryl (pseudo)halides with metallic cyano-group sources, such as CuCN, KCN, NaCN, Zn(CN)(2), TMSCN, or K(4) [Fe(CN)(6)]. However, this approach often suffers from drawbacks, such as the formation of stoichiometric amounts of metal waste, the poisoning of the metal catalysts, or the generation of toxic HCN gas. As a result, a range of "nonmetallic" organic cyano-group sources have been explored for the cyanation of aryl halides and arene C-H bonds. This Minireview summarizes types of nonmetallic cyano-group sources and their applications in the preparation of aryl nitriles. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Leachability of protein and metals incorporated into aquatic invertebrates: are species and metals-exposure history important?

    Science.gov (United States)

    Meyer, J.S.; Suedkamp, M.J.; Morris, J.M.; Farag, A.M.

    2005-01-01

    To partially simulate conditions in fish intestinal tracts, we leached six groups of metals-contaminated invertebrates at pH 2 and pH 7, and analyzed the concentrations of four metals (Cd, Cu, Pb, and Zn) and total protein in the leachates. Four of the groups of invertebrates were benthic macroinvertebrates collected from metals-contaminated rivers (the Clark Fork River in Montana and the Coeur d’Alene River in Idaho, USA); the other two groups of invertebrates (one of which was exposed to metals in the laboratory) were laboratory-reared brine shrimp (Artemia sp.). Additionally, we fractionated the pH 2 leachates using size-exclusion chromatography (SEC). Protein content was 1.3 to 1.4× higher in Artemia than in the benthic macroinvertebrates, and leachability of metals and protein differed considerably among several of the groups of invertebrates. In SEC fractions of the pH 2 leachates from both groups of Artemia, Cu and protein co-eluted; however, Cu and protein did not co-elute in SEC fractions of the leachates from any of the benthic macroinvertebrate groups. Although none of the other three metals co-eluted with protein in any of the pH 2 leachates, one or more of the metals co-eluted with lower-molecular-weight molecules in the leachates from all of the groups of invertebrates. These results suggest fundamental differences in metal-binding properties and protein leachability among some invertebrates. Thus, different invertebrates and different histories of metals exposure might lead to different availability of metals and protein to predators.

  4. Communication in Organizational Groups

    OpenAIRE

    Monica RADU

    2007-01-01

    Organizational group can be defined as some persons between who exist interactive connections (functional, communication, affective, normative type). Classification of these groups can reflect the dimension, type of relationship or type of rules included. Organizational groups and their influence over the individual efficiency and the efficiency of the entire group are interconnected. Spontaneous roles in these groups sustain the structure of the relationship, and the personality of each indi...

  5. Large head metal-on-metal cementless total hip arthroplasty versus 28mm metal-on-polyethylene cementless total hip arthroplasty: design of a randomized controlled trial

    Directory of Open Access Journals (Sweden)

    van Raaij Jos JAM

    2008-10-01

    Full Text Available Abstract Background Osteoarthritis of the hip is successfully treated by total hip arthroplasty with metal-on-polyethylene articulation. Polyethylene wear debris can however lead to osteolysis, aseptic loosening and failure of the implant. Large head metal-on-metal total hip arthroplasty may overcome polyethylene wear induced prosthetic failure, but can increase systemic cobalt and chromium ion concentrations. The objective of this study is to compare two cementless total hip arthroplasties: a conventional 28 mm metal-on-polyethylene articulation and a large head metal-on-metal articulation. We hypothesize that the latter arthroplasties show less bone density loss and higher serum metal ion concentrations. We expect equal functional scores, greater range of motion, fewer dislocations, fewer periprosthetic radiolucencies and increased prosthetic survival with the metal-on-metal articulation. Methods A randomized controlled trial will be conducted. Patients to be included suffer from non-inflammatory degenerative joint disease of the hip, are aged between 18 and 80 and are admitted for primary cementless unilateral total hip arthroplasty. Patients in the metal-on-metal group will receive a cementless titanium alloy acetabular component with a cobalt-chromium liner and a cobalt-chromium femoral head varying from 38 to 60 mm. Patients in the metal-on-polyethylene group will receive a cementless titanium alloy acetabular component with a polyethylene liner and a 28 mm cobalt-chromium femoral head. We will assess acetabular bone mineral density by dual energy x-ray absorptiometry (DEXA, serum ion concentrations of cobalt, chromium and titanium, self reported functional status (Oxford hip score, physician reported functional status and range of motion (Harris hip score, number of dislocations and prosthetic survival. Measurements will take place preoperatively, perioperatively, and postoperatively (6 weeks, 1 year, 5 years and 10 years. Discussion

  6. Recovery of metal ions by microfungal filters.

    Science.gov (United States)

    Wales, D S; Sagar, B F

    1990-01-01

    Many microfungi contain chitin/chitosan as an integral part of the cell wall structure. The binding of toxic and heavy metal ions by chitosan or partly deacetylated chitin is a direct consequence of the base strength of the primary amine group and is most effective for those metals that form complexes with ammonia. Of the microfungi studied, hyphae from Mucor mucedo and Rhizomucor miehei, after treatment with hydroxide to expose the chitin/chitosan, were found to be most effective in the capture of metal ions. Chemically treated mycelia have so far been shown to bind silver, zinc, lead, copper, nickel, cobalt, cadmium, iron and chromium, with the efficiency of metal-ion binding apparently being inversely proportional to the valency state of the metal ions to be bound. Wet-laid papers produced from mixed slurries of treated mycelia and various conventional paper-making and textile fibres have exceptionally good tensile- and bursting-strength properties, particularly in the wet state. Papers containing 1 g treated mycelia removed up to 90% of various metal ions in solution (50 cm3, 1.5 mmol dm-3) with flow rates of 0.5 cm3 cm-2 min-1. However, the total metal-ion binding capacities of single-thickness microfungal papers are limited under constant flow conditions. The total volume flowing through the system before metal-ion breakthrough occurs increases in direct proportion to the number of sheets of microfungal paper but the concomitant reduction in flow rates becomes a limiting factor. Mycelia-containing structures that allow efficient metal-ion binding at commercially acceptable flow rates are currently being investigated.

  7. Metal and metal oxide nanoparticle synthesis from metal organic frameworks (MOFs): finding the border of metal and metal oxides

    Science.gov (United States)

    Das, Raja; Pachfule, Pradip; Banerjee, Rahul; Poddar, Pankaj

    2012-01-01

    Herein, for the first time, we report a generalized strategy for the successful synthesis of highly crystalline metal and metal oxide nanoparticles embedded in a carbon matrix by the controlled thermolysis of metal organic frameworks (MOFs). The rationalized synthesis strategy of a broad range of metal and metal oxides nanoparticles, such as Cu/CuO, Co/Co3O4, ZnO, Mn2O3, MgO and CdS/CdO, by thermolysis of MOFs demonstrates for the first time that metal ions with a reduction potential of -0.27 volts or higher present in MOFs always form pure metal nanoparticles during thermolysis in N2, whereas metal ions with a reduction potential lower than -0.27 volts form metal oxide nanoparticles during thermolysis in N2. Another point of interest is the fact that we have found a unique relationship between the nanoparticle size and the distance between the secondary building units inside the MOF precursors. Interestingly, the crystallinity of the carbon matrix was also found to be greatly influenced by the environment (N2 and air) during thermolysis. Moreover, these nanoparticles dispersed in a carbon matrix showed promising H2 and CO2 adsorption properties depending on the environment used for the thermolysis of MOFs.Herein, for the first time, we report a generalized strategy for the successful synthesis of highly crystalline metal and metal oxide nanoparticles embedded in a carbon matrix by the controlled thermolysis of metal organic frameworks (MOFs). The rationalized synthesis strategy of a broad range of metal and metal oxides nanoparticles, such as Cu/CuO, Co/Co3O4, ZnO, Mn2O3, MgO and CdS/CdO, by thermolysis of MOFs demonstrates for the first time that metal ions with a reduction potential of -0.27 volts or higher present in MOFs always form pure metal nanoparticles during thermolysis in N2, whereas metal ions with a reduction potential lower than -0.27 volts form metal oxide nanoparticles during thermolysis in N2. Another point of interest is the fact that we have

  8. Polymer-supported metals and metal oxide nanoparticles: synthesis, characterization, and applications

    Energy Technology Data Exchange (ETDEWEB)

    Sarkar, Sudipta [Thapar University, Department of Biotechnology and Environmental Sciences (India); Guibal, E. [Ecole des Mines d' Ales, Laboratoire Genie de l' Environnement Industriel, BPCI Group (France); Quignard, F. [Institut Charles Gerhardt Montpellier-UMR 5253-CNRS-UMII-ENSCM-UMI, Materiaux Avances pour la Catalyse et la Sante (France); SenGupta, A. K., E-mail: arup.sengupta@lehigh.edu [Lehigh University, Environmental Engineering Program (United States)

    2012-02-15

    Metal and metal oxide nanoparticles exhibit unique properties in regard to sorption behaviors, magnetic activity, chemical reduction, ligand sequestration among others. To this end, attempts are being continuously made to take advantage of them in multitude of applications including separation, catalysis, environmental remediation, sensing, biomedical applications and others. However, metal and metal oxide nanoparticles lack chemical stability and mechanical strength. They exhibit extremely high pressure drop or head loss in fixed-bed column operation and are not suitable for any flow-through systems. Also, nanoparticles tend to aggregate; this phenomenon reduces their high surface area to volume ratio and subsequently reduces effectiveness. By appropriately dispersing metal and metal oxide nanoparticles into synthetic and naturally occurring polymers, many of the shortcomings can be overcome without compromising the parent properties of the nanoparticles. Furthermore, the appropriate choice of the polymer host with specific functional groups may even lead to the enhancement of the properties of nanoparticles. The synthesis of hybrid materials involves two broad pathways: dispersing the nanoparticles (i) within pre-formed or commercially available polymers; and (ii) during the polymerization process. This review presents a broad coverage of nanoparticles and polymeric/biopolymeric host materials and the resulting properties of the hybrid composites. In addition, the review discusses the role of the Donnan membrane effect exerted by the host functionalized polymer in harnessing the desirable properties of metal and metal oxide nanoparticles for intended applications.

  9. Silicon metal-semiconductor-metal photodetector

    Science.gov (United States)

    Brueck, Steven R. J.; Myers, David R.; Sharma, Ashwani K.

    1997-01-01

    Silicon MSM photodiodes sensitive to radiation in the visible to near infrared spectral range are produced by altering the absorption characteristics of crystalline Si by ion implantation. The implantation produces a defected region below the surface of the silicon with the highest concentration of defects at its base which acts to reduce the contribution of charge carriers formed below the defected layer. The charge carriers generated by the radiation in the upper regions of the defected layer are very quickly collected between biased Schottky barrier electrodes which form a metal-semiconductor-metal structure for the photodiode.

  10. Metal pad instabilities in liquid metal batteries

    CERN Document Server

    Zikanov, Oleg

    2015-01-01

    A mechanical analogy is used to analyze the interaction between the magnetic field, electric current and deformation of interfaces in liquid metal batteries. It is found that, during charging or discharging, a sufficiently large battery is prone to instabilities of two types. One is similar to the metal pad instability known for aluminum reduction cells. Another type is new. It is related to the destabilizing effect of the Lorentz force formed by the azimuthal magnetic field induced by the base current and the current perturbations caused by the local variations of the thickness of the electrolyte layer.

  11. Defect-Tolerant Monolayer Transition Metal Dichalcogenides

    DEFF Research Database (Denmark)

    Pandey, Mohnish; Rasmussen, Filip Anselm; Kuhar, Korina;

    2016-01-01

    -principles investigation of defect tolerance in 29 monolayer transition metal dichalcogenides (TMDs) of interest for nanoscale optoelectronics. We find that the TMDs based on group VI and X metals form deep gap states upon creation of a chalcogen (S, Se, Te) vacancy, while the TMDs based on group IV metals form only...... shallow defect levels and are thus predicted to be defect-tolerant. Interestingly, all the defect sensitive TMDs have valence and conduction bands with a very similar orbital composition. This indicates a bonding/antibonding nature of the gap, which in turn suggests that dangling bonds will fall inside...... the gap. These ideas are made quantitative by introducing a descriptor that measures the degree of similarity of the conduction and valence band manifolds. Finally, the study is generalized to nonpolar nanoribbons of the TMDs where we find that only the defect sensitive materials form edge states within...

  12. Group Psychotherapy in Iceland.

    Science.gov (United States)

    Ívarsson, Ómar

    2015-10-01

    In this overview of group psychotherapy in Iceland, an attempt will be made to describe how it is practiced today, give some glimpses into its earlier history, and clarify seven issues: (1) the standing of group psychotherapy in Iceland, its previous history, and the theoretical orientation of dynamic group therapy in the country; (2) the role of group therapy in the health care system; (3) how training in group therapy is organized; (4) the relationship between group psychotherapy research and clinical practice; (5) which issues/processes can be identified as unique to therapy groups in Iceland; and (6) how important are group-related issues within the social background of the country; and (7) what group work holds for the future.

  13. Locally minimal topological groups

    CERN Document Server

    enhofer, Lydia Au\\ss; Dikranjan, Dikran; Domínguez, Xabier

    2009-01-01

    A Hausdorff topological group $(G,\\tau)$ is called locally minimal if there exists a neighborhood $U$ of 0 in $\\tau$ such that $U$ fails to be a neighborhood of zero in any Hausdorff group topology on $G$ which is strictly coarser than $\\tau.$ Examples of locally minimal groups are all subgroups of Banach-Lie groups, all locally compact groups and all minimal groups. Motivated by the fact that locally compact NSS groups are Lie groups, we study the connection between local minimality and the NSS property, establishing that under certain conditions, locally minimal NSS groups are metrizable. A symmetric subset of an abelian group containing zero is said to be a GTG set if it generates a group topology in an analogous way as convex and symmetric subsets are unit balls for pseudonorms on a vector space. We consider topological groups which have a neighborhood basis at zero consisting of GTG sets. Examples of these locally GTG groups are: locally pseudo--convex spaces, groups uniformly free from small subgroups (...

  14. REMOVAL OF CERTAIN FISSION PRODUCT METALS FROM LIQUID BISMUTH COMPOSITIONS

    Science.gov (United States)

    Dwyer, O.E.; Howe, H.E.; Avrutik, E.R.

    1959-11-24

    A method is described for purifying a solution of urarium in liquid bismuth containing at least one metal from the group consisting of selenium, tellurium, palladium, ruthenium, rhodium, niobium, and zirconium. The solution is contacted with zinc in an inert atmosphere to form a homogeneous melt, a solid zinc phase is formed, and the zinc phase containing the metal is separated from the melt.

  15. Synthesis of main-chain metal carbonyl organometallic macromolecules (MCMCOMs).

    Science.gov (United States)

    Cao, Kai; Murshid, Nimer; Wang, Xiaosong

    2015-04-01

    Synthesis of main-chain metal carbonyl organometallic macromolecules (MCMCOMs) is difficult, mainly due to the instability of metal carbonyl complexes. Despite its challenge a number of MCMCOMs has been prepared by strategically using organometallic, organic, and polymer synthetic chemistry. Main contributions to this research field were reported by the groups of Tyler, Pannell, and Wang and are briefly summarized in this article.

  16. Bioaccumulation of eight heavy metals in cave animals from Dashui ...

    African Journals Online (AJOL)

    ajl2

    Eight heavy metals content in the dominant animal groups, soil and water in Malang and Dashui caves ... Dashui cave is situated in the urban zone of Guiyang City, Guizhou, and Guizhou Aluminum ... cient of a metal in animal suggests higher absorption capacity of ... Pb, As, Cd and Hg, respectively, while the ranking of.

  17. Metal ion binding to peptides: Oxygen or nitrogen sites?

    NARCIS (Netherlands)

    Dunbar, R. C.; Polfer, N. C.; G. Berden,; Oomens, J.

    2012-01-01

    Infrared multiple-photon dissociation (IRMPD) spectroscopy was used to probe the conformations of gas-phase metal-ion complexes between a series of five metal ions and six small peptide ligands. This report is presented in recognition and tribute for the Armentrout group's long and hugely produ

  18. Metal ion binding to peptides: oxygen or nitrogen sites?

    NARCIS (Netherlands)

    R.C. Dunbar; N.C. Polfer; G. Berden; J. Oomens

    2012-01-01

    Infrared multiple-photon dissociation (IRMPD) spectroscopy was used to probe the conformations of gas-phase metal-ion complexes between a series of five metal ions and six small peptide ligands. This report is presented in recognition and tribute for the Armentrout group's long and hugely productive

  19. China Speeds up in Finding Metal Resources Overseas

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    <正>According to Luotao, general manager of China Nonferrous Metals Group (CNMG), the company is speeding up its efforts in the development for overseas nonferrous metals resources. Presently, the company has developed some projects with certain scale for overseas mineral resources and it has become a

  20. Metal ions affecting the pulmonary and cardiovascular systems.

    Science.gov (United States)

    Corradi, Massimo; Mutti, Antonio

    2011-01-01

    Some metals, such as copper and manganese, are essential to life and play irreplaceable roles in, e.g., the functioning of important enzyme systems. Other metals are xenobiotics, i.e., they have no useful role in human physiology and, even worse, as in the case of lead, may be toxic even at trace levels of exposure. Even those metals that are essential, however, have the potential to turn harmful at very high levels of exposure, a reflection of a very basic tenet of toxicology--"the dose makes the poison." Toxic metal exposure may lead to serious risks to human health. As a result of the extensive use of toxic metals and their compounds in industry and consumer products, these agents have been widely disseminated in the environment. Because metals are not biodegradable, they can persist in the environment and produce a variety of adverse effects. Exposure to metals can lead to damage in a variety of organ systems and, in some cases, metals also have the potential to be carcinogenic. Even though the importance of metals as environmental health hazards is now widely appreciated, the specific mechanisms by which metals produce their adverse effects have yet to be fully elucidated. The unifying factor in determining toxicity and carcinogenicity for most metals is the generation of reactive oxygen and nitrogen species. Metal-mediated formation of free radicals causes various modifications to nucleic acids, enhanced lipid peroxidation, and altered calcium and sulfhydryl homeostasis. Whilst copper, chromium, and cobalt undergo redox-cycling reactions, for metals such as cadmium and nickel the primary route for their toxicity is depletion of glutathione and bonding to sulfhydryl groups of proteins. This chapter attempts to show that the toxic effects of different metallic compounds may be manifested in the pulmonary and cardiovascular systems. The knowledge of health effects due to metal exposure is necessary for practising physicians, and should be assessed by inquiring

  1. Investigation of biologically-designed metal-specific chelators for potential metal recovery and waste remediation applications.

    Energy Technology Data Exchange (ETDEWEB)

    Criscenti, Louise Jacqueline; Ockwig, Nathan W.

    2009-01-01

    Bacteria, algae and plants produce metal-specific chelators to capture required nutrient or toxic trace metals. Biological systems are thought to be very efficient, honed by evolutionary forces over time. Understanding the approaches used by living organisms to select for specific metals in the environment may lead to design of cheaper and more effective approaches for metal recovery and contaminant-metal remediation. In this study, the binding of a common siderophore, desferrioxamine B (DFO-B), to three aqueous metal cations, Fe(II), Fe(III), and UO{sub 2}(VI) was investigated using classical molecular dynamics. DFO-B has three acetohydroxamate groups and a terminal amine group that all deprotonate with increasing pH. For all three metals, complexes with DFO-B (-2) are the most stable and favored under alkaline conditions. Under more acidic conditions, the metal-DFO complexes involve chelation with both acetohydroxamate and acetylamine groups. The approach taken here allows for detailed investigation of metal binding to biologically-designed organic ligands.

  2. Marks of Metal

    DEFF Research Database (Denmark)

    2015-01-01

    Udstilling på Mediemuseet med fokus på den visuelle side af heavy metal: Logoer, pladecovers og lignende.......Udstilling på Mediemuseet med fokus på den visuelle side af heavy metal: Logoer, pladecovers og lignende....

  3. Thermodynamics of liquid metal

    Energy Technology Data Exchange (ETDEWEB)

    Kushnirenko, A.N.

    1988-01-01

    The thermodynamics of a liquid metal based on quantum-mechanical models of the crystal, electronic, and nuclear structures of the metal are derived in this paper. The models are based on such formulations as the Bohr radius, the Boltzmann constant, the Planck Law, the Fermi surface, and the Pauli principle.

  4. Triad ''Metal - Enamel - Glass''

    Science.gov (United States)

    Mukhina, T.; Petrova, S.; Toporova, V.; Fedyaeva, T.

    2014-10-01

    This article shows how to change the color of metal and glass. Both these materials are self-sufficient, but sometimes used together. For example, enameling. In this case, the adhesion between metal substrate and stekloobraznae enamel layer, which was conducted on a stretching and a bend, was tested.

  5. Characterization of Metal Proteins

    Science.gov (United States)

    Unno, Masaki; Ikeda-Saito, Masao

    Some metals are essential for life. Most of these metals are associated with biological macromolecule like DNA (deoxyribonucleic acid), RNA (ribonucleic acid), and more often with proteins: metals bind or interact with them. A number of protein molecules intrinsically contain metals in their structure. Some of these proteins catalyze unique chemical reactions and perform specific physiological functions. In this chapter, we will shed light on the several metalcontaining proteins, termed metalloproteins, and other proteins interacting metals. We will also introduce several key techniques which have been used to characterize these proteins. Characterizing these proteins and to understand the relationships between their structures and functions shall continue to be one of the major avenues to solve the mysteries of life. At first, we introduce what are the protein structures and how these proteins interact with metals. In the next section, we discuss the physiological roles of some representative metals. Next, we show two examples of special metal cofactors those help the biological macromolecules to carry out their functions. Then we describe some functions of metalloproteins. Finally, we introduce some physical methods to characterize metalloproteins.

  6. Conducting metal dithiolate complexes

    DEFF Research Database (Denmark)

    Underhill, A. E.; Ahmad, M. M.; Turner, D. J.;

    1985-01-01

    Further work on the chemical composition of the one-dimensional metallic metal dithiolene complex Li-Pt(mnt) is reported. The electrical conduction and thermopower properties of the nickel and palladium complexes are reported and compared with those of the platinum compound...

  7. Higher arithmetic Chow groups

    CERN Document Server

    Gil, J I Burgos

    2009-01-01

    We give a new construction of higher arithmetic Chow groups for quasi-projective arithmetic varieties over a field. Our definition agrees with the higher arithmetic Chow groups defined by Goncharov for projective arithmetic varieties over a field. These groups are the analogue, in the Arakelov context, of the higher algebraic Chow groups defined by Bloch. The degree zero group agrees with the arithmetic Chow groups of Burgos. Our new construction is shown to be a contravariant functor and is endowed with a product structure, which is commutative and associative.

  8. Metal Borohydrides synthesized from metal borides and metal hydrides

    DEFF Research Database (Denmark)

    Sommer, Sanna

    2014-01-01

    and Ca(BH4)2, respectively [3,4]. An attempt to synthesize alkali and alkaline earth metal borohydrides from various borides by ball milling under high hydrogen pressure is presented here. MgB2, AlB2 and CaB6 have been milled with MHx (M = Li, Na, Mg, Ca) at p(H2) = 110 bar for 24 hours. All samples were...

  9. Stars at Low Metallicity in Dwarf Galaxies

    NARCIS (Netherlands)

    Tolstoy, Eline; Battaglia, Giuseppina; Cole, Andrew; Hunt, LK; Madden, S; Schneider, R

    2008-01-01

    Dwarf galaxies offer an opportunity to understand the properties of low metallicity star formation both today and at the earliest times at the, epoch of the formation of the first stars. Here we concentrate on two galaxies in the Local Group: the dwarf irregular galaxy Leo A, which has been the rece

  10. Phosphopeptide enrichment by immobilized metal affinity chromatography

    DEFF Research Database (Denmark)

    Thingholm, Tine E.; Larsen, Martin R.

    2016-01-01

    Immobilized metal affinity chromatography (IMAC) has been the method of choice for phosphopeptide enrichment prior to mass spectrometric analysis for many years and it is still used extensively in many laboratories. Using the affinity of negatively charged phosphate groups towards positively...

  11. Chelation in Metal Intoxication

    Directory of Open Access Journals (Sweden)

    Swaran J.S. Flora

    2010-06-01

    Full Text Available Chelation therapy is the preferred medical treatment for reducing the toxic effects of metals. Chelating agents are capable of binding to toxic metal ions to form complex structures which are easily excreted from the body removing them from intracellular or extracellular spaces. 2,3-Dimercaprol has long been the mainstay of chelation therapy for lead or arsenic poisoning, however its serious side effects have led researchers to develop less toxic analogues. Hydrophilic chelators like meso-2,3-dimercaptosuccinic acid effectively promote renal metal excretion, but their ability to access intracellular metals is weak. Newer strategies to address these drawbacks like combination therapy (use of structurally different chelating agents or co-administration of antioxidants have been reported recently. In this review we provide an update of the existing chelating agents and the various strategies available for the treatment of heavy metals and metalloid intoxications.

  12. Production of magnesium metal

    Science.gov (United States)

    Blencoe, James G [Harriman, TN; Anovitz, Lawrence M [Knoxville, TN; Palmer, Donald A [Oliver Springs, TN; Beard, James S [Martinsville, VA

    2010-02-23

    A process of producing magnesium metal includes providing magnesium carbonate, and reacting the magnesium carbonate to produce a magnesium-containing compound and carbon dioxide. The magnesium-containing compound is reacted to produce magnesium metal. The carbon dioxide is used as a reactant in a second process. In another embodiment of the process, a magnesium silicate is reacted with a caustic material to produce magnesium hydroxide. The magnesium hydroxide is reacted with a source of carbon dioxide to produce magnesium carbonate. The magnesium carbonate is reacted to produce a magnesium-containing compound and carbon dioxide. The magnesium-containing compound is reacted to produce magnesium metal. The invention further relates to a process for production of magnesium metal or a magnesium compound where an external source of carbon dioxide is not used in any of the reactions of the process. The invention also relates to the magnesium metal produced by the processes described herein.

  13. Metals and Neurodegeneration.

    Science.gov (United States)

    Chen, Pan; Miah, Mahfuzur Rahman; Aschner, Michael

    2016-01-01

    Metals play important roles in the human body, maintaining cell structure and regulating gene expression, neurotransmission, and antioxidant response, to name a few. However, excessive metal accumulation in the nervous system may be toxic, inducing oxidative stress, disrupting mitochondrial function, and impairing the activity of numerous enzymes. Damage caused by metal accumulation may result in permanent injuries, including severe neurological disorders. Epidemiological and clinical studies have shown a strong correlation between aberrant metal exposure and a number of neurological diseases, including Alzheimer's disease, amyotrophic lateral sclerosis, autism spectrum disorders, Guillain-Barré disease, Gulf War syndrome, Huntington's disease, multiple sclerosis, Parkinson's disease, and Wilson's disease. Here, we briefly survey the literature relating to the role of metals in neurodegeneration.

  14. Heavy metals in carabids (Coleoptera, Carabidae

    Directory of Open Access Journals (Sweden)

    Ruslan Butovsky

    2011-05-01

    Full Text Available Carabid beetles (Coleoptera, Carabidae are one of the most studied soil groups in relation to heavy metal (HM accumulation and use for bioindication of environmental pollution. Accumulation of Zn and Cu in carabid beetles was species-, sex- and trophic group-specific. No differences were found in HM contents between omnivorous and carnivorous species. The use of carabid beetles as indicators of HM accumulation appears to be rather limited.

  15. Platinum metals in the environment

    Energy Technology Data Exchange (ETDEWEB)

    Zereini, Fathi [Frankfurt Univ. (Germany). Dept. of Environmental Analytical Chemistry; Wiseman, Clare L.S. (ed.) [Toronto Univ. (Canada). School of the Environment

    2015-03-01

    This book contains the five chapters with the following topics: 1. SOURCES OF PGE EMISSIONS ELEMENTS: Sources of Platinum Group Elements (PGE) in the Environment; Impact of Platinum Group Element Emissions from Mining and Production Activities. 2. ANALYTICAL METHODS FOR THE DETERMINATION OF PGE IN BIOLOGICAL AND ENVIRONMENTAL MATRICES: Appraisal of Biosorption for Recovery, Separation and Determination of Platinum, Palladium and Rhodium in Environmental Samples; On the Underestimated Factors Influencing the Accuracy of Determination of Pt and Pd by Electrothermal Atomic Absorption Spectrometry in Road Dust Samples; Application of Solid Sorbents for Enrichment and Separation of Platinum Metal Ions; Voltammetric Analysis of Platinum in Environmental Matrices; Speciation Analysis of Chloroplatinates; Analysis of Platinum Group Elements in Environmental Samples: A Review. 3. OCCURRENCE, CHEMICAL BEHAVIOR AND FATE OF PGE IN THE ENVIRONMENT: Brazilian PGE Research Data Survey on Urban and Roadside Soils; Platinum, Palladium and Rhodium in a Bavarian Roadside Soil; Increase of Platinum Group Element Concentrations in Soils and Airborne Dust During the Period of Vehicular Exhaust Catalysts Introduction; Platinum-Group Elements in Urban Fluvial Bed Sediments-Hawaii; Long-Term Monitoring of Palladium and Platinum Contents in Road Dust of the City of Munich, Germany; Characterization of PGEs and Other Elements in Road Dusts and Airborne Particles in Houston, Texas; Accumulation and Distribution of Pt and Pd in Roadside Dust, Soil and Vegetation in Bulgaria; Increase of the Environmental Pt Concentration in the Metropolitan Area of Mexico City Associated to the Use of Automobile Catalytic Converters; Solubility of Emitted Platinum Group Elements (Pt, Pd and Rh) in Airborne Particulate Matter (PM10) in the Presence of Organic Complexing Agents; The Influence of Anionic Species (Cl{sup -}, NO{sub 3}{sup -}, SO{sub 4}{sup 2-}) on the Transformation and Solubility of Platinum in

  16. Working with Groups.

    Science.gov (United States)

    Morris, Joan, Ed.

    1984-01-01

    Describes nine Canadian programs for counseling groups of students. Topics include introducing computer-assisted guidance, future challenges for counselors, sociometry, sexuality, parent counseling, reluctant students, shyness, peer groups, education for living, and guidance advisory committees. (JAC)

  17. Gestalt Interactional Groups

    Science.gov (United States)

    Harman, Robert L.; Franklin, Richard W.

    1975-01-01

    Gestalt therapy in groups is not limited to individual work in the presence of an audience. Describes several ways to involve gestalt groups interactionally. Interactions described focus on learning by doing and discovering, and are noninterpretive. (Author/EJT)

  18. Group B streptococcus - pregnancy

    Science.gov (United States)

    ... page: //medlineplus.gov/ency/patientinstructions/000511.htm Group B streptococcus - pregnancy To use the sharing features on this page, please enable JavaScript. Group B streptococcus (GBS) is a type of bacteria that ...

  19. Group Decision Process Support

    DEFF Research Database (Denmark)

    Gøtze, John; Hijikata, Masao

    1997-01-01

    Introducing the notion of Group Decision Process Support Systems (GDPSS) to traditional decision-support theorists.......Introducing the notion of Group Decision Process Support Systems (GDPSS) to traditional decision-support theorists....

  20. About group digital signatures

    Directory of Open Access Journals (Sweden)

    Adriana Cristina Enache

    2012-09-01

    Full Text Available

    Group signatures try to combine security (no framing, no cheating and privacy(anonymity, unlinkability.A group digital signature is a digital signature with enhanced privacy features that allows members of a given group to anonymously sign messages on behalf of the group, producing a group signature. However, in the case of dispute the identity of the signature's originator can be revealed by a designated entity (group manager. The present paper describes the main concepts about group signatures, along with a brief state of the art and shows a personal cryptographic library implemented in Java that includes two group signatures.

  1. Fast Overlapping Group Lasso

    CERN Document Server

    Liu, Jun

    2010-01-01

    The group Lasso is an extension of the Lasso for feature selection on (predefined) non-overlapping groups of features. The non-overlapping group structure limits its applicability in practice. There have been several recent attempts to study a more general formulation, where groups of features are given, potentially with overlaps between the groups. The resulting optimization is, however, much more challenging to solve due to the group overlaps. In this paper, we consider the efficient optimization of the overlapping group Lasso penalized problem. We reveal several key properties of the proximal operator associated with the overlapping group Lasso, and compute the proximal operator by solving the smooth and convex dual problem, which allows the use of the gradient descent type of algorithms for the optimization. We have performed empirical evaluations using the breast cancer gene expression data set, which consists of 8,141 genes organized into (overlapping) gene sets. Experimental results demonstrate the eff...

  2. Half-metallicity in 2D organometallic honeycomb frameworks

    Science.gov (United States)

    Sun, Hao; Li, Bin; Zhao, Jin

    2016-10-01

    Half-metallic materials with a high Curie temperature (T C) have many potential applications in spintronics. Magnetic metal free two-dimensional (2D) half-metallic materials with a honeycomb structure contain graphene-like Dirac bands with π orbitals and show excellent aspects in transport properties. In this article, by investigating a series of 2D organometallic frameworks with a honeycomb structure using first principles calculations, we study the origin of forming half-metallicity in this kind of 2D organometallic framework. Our analysis shows that charge transfer and covalent bonding are two crucial factors in the formation of half-metallicity in organometallic frameworks. (i) Sufficient charge transfer from metal atoms to the molecules is essential to form the magnetic centers. (ii) These magnetic centers need to be connected through covalent bonding, which guarantee the strong ferromagnetic (FM) coupling. As examples, the organometallic frameworks composed by (1,3,5)-benzenetricarbonitrile (TCB) molecules with noble metals (Au, Ag, Cu) show half-metallic properties with T C as high as 325 K. In these organometallic frameworks, the strong electronegative cyano-groups (CN groups) drive the charge transfer from metal atoms to the TCB molecules, forming the local magnetic centers. These magnetic centers experience strong FM coupling through the d-p covalent bonding. We propose that most of the 2D organometallic frameworks composed by molecule—CN—noble metal honeycomb structures contain similar half metallicity. This is verified by replacing TCB molecules with other organic molecules. Although the TCB-noble metal organometallic framework has not yet been synthesized, we believe the development of synthesizing techniques and facility will enable the realization of them. Our study provides new insight into the 2D half-metallic material design for the potential applications in nanotechnology.

  3. Generalized Group Signature Scheme

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The concept of generalized group signature scheme will bepresent. Based on the generalized secret sharing scheme proposed by Lin and Ha rn, a non-interactive approach is designed for realizing such generalized group signature scheme. Using the new scheme, the authorized subsets of the group in w hich the group member can cooperate to produce the valid signature for any messa ge can be randomly specified

  4. Multicultural group work

    DEFF Research Database (Denmark)

    Hansen, Annette Skovsted

    2014-01-01

    Motivation for the activity I use this strategy for forming groups to ensure diverse/multicultural groups that combine a variety of different strengths and resources based on student's academic, disciplinary, linguistic, national, personal and work backgrounds.......Motivation for the activity I use this strategy for forming groups to ensure diverse/multicultural groups that combine a variety of different strengths and resources based on student's academic, disciplinary, linguistic, national, personal and work backgrounds....

  5. Framework for Metals Risk Assessment

    Science.gov (United States)

    The Framework for Metals Risk Assessment is a science-based document that addresses the special attributes and behaviors of metals and metal compounds to be considered when assessing their human health and ecological risks.

  6. Metal and metal oxide nanoparticle synthesis from metal organic frameworks (MOFs): finding the border of metal and metal oxides.

    Science.gov (United States)

    Das, Raja; Pachfule, Pradip; Banerjee, Rahul; Poddar, Pankaj

    2012-01-21

    Herein, for the first time, we report a generalized strategy for the successful synthesis of highly crystalline metal and metal oxide nanoparticles embedded in a carbon matrix by the controlled thermolysis of metal organic frameworks (MOFs). The rationalized synthesis strategy of a broad range of metal and metal oxides nanoparticles, such as Cu/CuO, Co/Co(3)O(4), ZnO, Mn(2)O(3), MgO and CdS/CdO, by thermolysis of MOFs demonstrates for the first time that metal ions with a reduction potential of -0.27 volts or higher present in MOFs always form pure metal nanoparticles during thermolysis in N(2), whereas metal ions with a reduction potential lower than -0.27 volts form metal oxide nanoparticles during thermolysis in N(2). Another point of interest is the fact that we have found a unique relationship between the nanoparticle size and the distance between the secondary building units inside the MOF precursors. Interestingly, the crystallinity of the carbon matrix was also found to be greatly influenced by the environment (N(2) and air) during thermolysis. Moreover, these nanoparticles dispersed in a carbon matrix showed promising H(2) and CO(2) adsorption properties depending on the environment used for the thermolysis of MOFs.

  7. Groups, combinatorics and geometry

    CERN Document Server

    Ivanov, A A; Saxl, J

    2003-01-01

    Over the past 20 years, the theory of groups in particular simplegroups, finite and algebraic has influenced a number of diverseareas of mathematics. Such areas include topics where groups have beentraditionally applied, such as algebraic combinatorics, finitegeometries, Galois theory and permutation groups, as well as severalmore recent developments.

  8. Asymmetry within social groups

    DEFF Research Database (Denmark)

    Barker, Jessie; Loope, Kevin J.; Reeve, H. Kern

    2016-01-01

    Social animals vary in their ability to compete with group members over shared resources and also vary in their cooperative efforts to produce these resources. Competition among groups can promote within-group cooperation, but many existing models of intergroup cooperation do not explicitly account...

  9. Higher arithmetic Chow groups

    DEFF Research Database (Denmark)

    Gil, J. I. Burgos; Feliu, Elisenda

    2012-01-01

    We give a new construction of higher arithmetic Chow groups for quasi-projective arithmetic varieties over a field. Our definition agrees with the higher arithmetic Chow groups defined by Goncharov for projective arithmetic varieties over a field. These groups are the analogue, in the Arakelov co...

  10. Quantum chemical treatments of metal clusters.

    Science.gov (United States)

    Weigend, Florian; Ahlrichs, Reinhart

    2010-03-28

    This work focuses on finding and rationalizing the building principles of clusters with approximately 300 atoms of different types of metals: main group elements (Al, Sn), alkaline earth metals (Mg), transition metals (Pd) and clusters consisting of two different elements (Ir and Pt). Two tools are inevitable for this purpose: (i) quantum chemical methods that are able to treat a given cluster with both sufficient accuracy and efficiency and (ii) algorithms that are able to systematically scan the (3n-6)-dimensional potential surface of an n-atomic cluster for promising isomers. Currently, the only quantum chemical method that can be applied to metal clusters is density functional theory (DFT). Other methods either do not account for the multi-reference character of metal clusters or are too expensive and thus can be applied only to clusters of very few atoms, which usually is not sufficient for studying the building principles. The accuracy of DFT is not known a priori, but extrapolations to bulk values from calculated series of data show satisfying agreement with experimental data. For scans of the potential surface, simulated annealing techniques or genetic algorithms were used for the smaller clusters (approx. 20-30 atoms), and for the larger clusters considerations were restricted to selected packings and shapes. For the mixed-metallic clusters, perturbation theory turned out to be efficient and successful for finding the most promising distributions of the two atom types at the different sites.

  11. COORDINATION OF CASSAVA STARCH TO METAL IONS AND ...

    African Journals Online (AJOL)

    a

    Soc. Ethiop. 2003, 17(2), 155-165. ISSN 1011-3924 ... Cassava starch formed Werner-type complexes with ions of metals from the transition groups. This was proven by conductivity and electron paramagnetic resonance measurements.

  12. Designer ligands: The search for metal ion selectivity

    Directory of Open Access Journals (Sweden)

    Perry T. Kaye

    2011-03-01

    Full Text Available The paper reviews research conducted at Rhodes University towards the development of metal-selective ligands. The research has focused on the rational design, synthesis and evaluation of novel ligands for use in the formation of copper complexes as biomimetic models of the metalloenzyme, tyrosinase, and for the selective extraction of silver, nickel and platinum group metal ions in the presence of contaminating metal ions. Attention has also been given to the development of efficient, metal-selective molecular imprinted polymers.

  13. Properties of structural materials in liquid metal environment. Proceedings

    Energy Technology Data Exchange (ETDEWEB)

    Borgstedt, H.U. [ed.

    1991-12-15

    The International Working Group on Fast Reactors (IWGFR) Specialists Meeting on Properties of Structural Materials in Liquid Metal Environment was held during June 18 to June 20, 1991, at the Nuclear Research Centre (Kernforschungszentrum) in Karlsruhe, Germany. The Specialists Meeting was divided into five technical sessions which addressed topics as follows: Creep-Rupture Behaviour of Structural Materials in Liquid Metal Environment; Behaviour of Materials in Liquid Metal Environments under Off-Normal Conditions;Fatigue and Creep-Fatigue of Structural Materials in Liquid Metal Environment; Crack Propagation in Liquid Sodium; and Conclusions and recommendations. Individual papers have been cataloged separately.

  14. Mechanisms of lichen resistance to metallic pollution

    Energy Technology Data Exchange (ETDEWEB)

    Sarret, C.; Manceau, A.; Eybert-Berard, L. [Univ. of Grenoble and CNRS (France). Environmental Geochemistry Group; Cuny, D.; Haluwyn, C. van [Lab. de Botanique et de Cryptogamie, Lille (France); Deruelle, S. [Institut d`Ecologie, Paris (France); Hazemann, J.L.; Menthonnex, J.J. [Univ. of Grenoble and CNRS (France). Environmental Geochemistry Group]|[CNRS, Grenoble (France). Lab. de Cristallographie; Soldo, Y. [CNRS, Grenoble (France). Lab. de Cristallographie

    1998-11-01

    Some lichens have a unique ability to grow in heavily contaminated areas due to the development of adaptative mechanisms allowing a high tolerance to metals. Here the authors report on the chemical forms of Pb and Zn in the metal hyperaccumulator Diploschistes muscorum and of Pb in the metal tolerant lichen Xanthoria parietina. The speciation of Zn and Pb has been investigated by powder X-ray diffraction (XRD) and extended X-ray absorption fine structure (EXAFS) spectroscopy using the advanced third-generation synchrotron radiation source of the European synchrotron radiation facility (ESRF in Grenoble). This study reveals that in both lichens cells are protected from toxicity by complexation of heavy metals, but the strategies differ: in D. muscorum, Pb and Zn are accumulated through an enhanced synthesis of oxalate, which precipitates toxic elements as insoluble salts, whereas in X. parietina, Pb is complexed to carboxylic groups of the fungal cell walls. The authors conclude that hyperaccumulation of metals results from a reactive mechanism of organic acid production, whereas metallo-tolerance is achieved by a passive complexation to existing functional groups.

  15. Work group diversity.

    Science.gov (United States)

    van Knippenberg, Daan; Schippers, Michaéla C

    2007-01-01

    Work group diversity, the degree to which there are differences between group members, may affect group process and performance positively as well as negatively. Much is still unclear about the effects of diversity, however. We review the 1997-2005 literature on work group diversity to assess the state of the art and to identify key issues for future research. This review points to the need for more complex conceptualizations of diversity, as well as to the need for more empirical attention to the processes that are assumed to underlie the effects of diversity on group process and performance and to the contingency factors of these processes.

  16. Groups of Circle Diffeomorphisms

    CERN Document Server

    Navas, Andrés

    2011-01-01

    In recent years scholars from a variety of branches of mathematics have made several significant developments in the theory of group actions. Groups of Circle Diffeomorphisms systematically explores group actions on the simplest closed manifold, the circle. As the group of circle diffeomorphisms is an important subject in modern mathematics, this book will be of interest to those doing research in group theory, dynamical systems, low dimensional geometry and topology, and foliation theory. The book is mostly self-contained and also includes numerous complementary exercises, making it an excell

  17. On -nilpotent abelian groups

    Indian Academy of Sciences (India)

    Mohammad Mehdi Nasrabadi; Ali Gholamian

    2014-11-01

    Let be a group and $A = \\text{Aut}(G)$ be the group of automorphisms of . Then, the element $[g, ] = g^{-1}(g)$ is an autocommutator of $g \\in G$ and $ \\in A$. Hence, for any natural number the -th autocommutator subgroup of is defined as $K_{m}(G)=\\langle [g,_{1},\\ldots,_{m}]|g\\in G,_{1},\\ldots,_{m}\\in A\\rangle$, where $[g, _{1}, _{2},\\ldots, _{m}] = [[g,_{1},\\ldots,_{m−1}], _{m}]$. In this paper, we introduce the new notion of -nilpotent groups and classify all abelian groups which are -nilpotent groups.

  18. CHAOTIC GROUP ACTIONS

    Institute of Scientific and Technical Information of China (English)

    ShiEnhui; ZhouLizhen; ZhouYoucheng

    2003-01-01

    It is proved that there is no chaotic group actions on any topological space with free arc.In this paper the chaotic actions of the group like G×F,where F is a finite group,are studied.In particular,under a suitable assumption ,if F is a cyclic group,then the topological space which admits a chaotic action of Z×F must admit a chatotic homeomorphism.A topological space which admits a chaotic group action but admits no chaotic horneomorphism is constructed.

  19. Group I intron ribozymes

    DEFF Research Database (Denmark)

    Nielsen, Henrik

    2012-01-01

    Group I intron ribozymes constitute one of the main classes of ribozymes and have been a particularly important model in the discovery of key concepts in RNA biology as well as in the development of new methods. Compared to other ribozyme classes, group I intron ribozymes display considerable......, the intronic products of these pathways have the potential to integrate into targets and to form various types of circular RNA molecules. Thus, group I intron ribozymes and associated elements found within group I introns is a rich source of biological phenomena. This chapter provides a strategy and protocols...... for initial characterization of new group I intron ribozymes....

  20. Group theory I essentials

    CERN Document Server

    Milewski, Emil G

    2012-01-01

    REA's Essentials provide quick and easy access to critical information in a variety of different fields, ranging from the most basic to the most advanced. As its name implies, these concise, comprehensive study guides summarize the essentials of the field covered. Essentials are helpful when preparing for exams, doing homework and will remain a lasting reference source for students, teachers, and professionals. Group Theory I includes sets and mapping, groupoids and semi-groups, groups, isomorphisms and homomorphisms, cyclic groups, the Sylow theorems, and finite p-groups.