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1

Experimental demonstration of efficient and selective population transfer and qubit distillation in a rare-earth-metal-ion-doped crystal  

E-print Network

in a rare-earth-metal-ion-doped crystal Lars Rippe, Mattias Nilsson, and Stefan Kröll Department of Physics on optical interactions in rare-earth- metal-ion-doped crystals. The optical transition lines of the rare-earth-metal out in preparation for two-qubit gate operations in the rare-earth-metal-ion-doped crystals

Suter, Dieter

2

Effects of Alkaline Earth Metal Ion Complexation on Amino Acid Zwitterion Stability: Results from Infrared Action  

E-print Network

for Plasma Physics "Rijnhuizen", Edisonbaan 14, 3439 MN Nieuwegein, The Netherlands Received December 21 but the smallest alkaline earth metal ion, University of California, Berkeley. FOM Institute for Plasma Physics

Cohen, Ronald C.

3

Rare Earth Metal Silicides Synthesized by High Current Metal Ion Implantation  

SciTech Connect

The YSi2, LaSi2, CeSi2, PrSi2, NdSi2, SmSi2, GdSi2, TbSi2, DySi2, and ErSi2 layers were formed on Si wafers by respective high current metal-ion implantation using a metal vacuum vapor arc (MEVVA) ion source and the formation temperature was considerable lower than the critical temperatures (300-350 deg. C) required for the rare earth metal silicides by solid-state reaction. It was found that the crystalline structures could be improved with increasing slightly the formation temperature as well as the implantation dose. Concerning the growth kinetics, in some cases, fractal patterns were observed on Si surfaces and the branches of the fractals consisted of the grains of respective precipitated silicides. Interestingly, the fractal dimension increased with formation temperature and eventually approached to a value of 2.0, corresponding to a continuous layer, which was required in practical application. The formation mechanism as well as the growth kinetics was discussed in terms of the far-from-equilibrium process involved in the MEVVA ion implantation.

Cheng, X.Q.; Wang, R.S.; Tang, X.J.; Liu, B.X. [Advanced Materials Laboratory, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China)

2003-08-26

4

Efficient qubit detection using alkaline-earth-metal ions and a double stimulated Raman adiabatic process  

SciTech Connect

We present a scheme for robust and efficient projection measurement of a qubit consisting of the two magnetic sublevels in the electronic ground state of alkaline-earth-metal ions. The scheme is based on two stimulated Raman adiabatic passages involving four partially coherent laser fields. We show how the efficiency depends on experimentally relevant parameters: Rabi frequencies, pulse widths, laser linewidths, one- and two-photon detunings, residual laser power, laser polarization, and ion motion.

Moeller, Ditte; Soerensen, Jens L.; Thomsen, Jakob B.; Drewsen, Michael [QUANTOP - Danish National Research Foundation Center for Quantum Optics, Department of Physics and Astronomy, University of Aarhus, DK-8000 (Denmark)

2007-12-15

5

Efficient qubit detection using alkali earth metal ions and a double STIRAP process  

E-print Network

We present a scheme for robust and efficient projection measurement of a qubit consisting of the two magnetic sublevels in the electronic ground state of alkali earth metal ions. The scheme is based on two stimulated Raman adiabatic passages (STIRAP) involving four partially coherent laser fields. We show how the efficiency depends on experimentally relevant parameters: Rabi frequencies, pulse widths, laser linewidths, one- and two-photon detunings, residual laser power, laser polarization and ion motion.

Ditte Møller; Jens L. Sørensen; Jakob B. Thomsen; Michael Drewsen

2007-10-10

6

Complex formation of p-nitrocalix[6]arene with rare earth metal ions.  

PubMed

p-Nitrocalix[6]arene (CALX-N6, L) formed a 1:1 metal complex, ML, with light rare earth metal ions (M3+), such as La3+, Pr3+ and Nd3+ except Ce3+, but formed a 1:2 (M(3+):L) complex, ML2 (the charge of the complex is omitted) with heavy rare earth metal ions, such as Sm(3+)-Lu3+ including Y3+. The conditional stability constants of these 1:1 and 1:2 complexes, KML and KML2, were measured by a ligand displacement method using absorption spectrophotometry in 4% (v/v) acetone aqueous solution at pH 9.65 +/- 0.15 and 25 degrees C. PMID:16733323

Kajiwara, Makiko; Koga, Masayoshi; Nishida, Masashi; Yoshida, Isao

2006-03-01

7

Multicomponent analysis of mixed rare-earth metal ion solutions by the electronic tongue sensor system  

SciTech Connect

Novel electrochemical sensors based on well-known extracting agents are developed. Sensors have shown high sensitivity towards a variety of rear earth metal ions in acidic media at pH=2. Multi-sensor system (electronic tongue) comprising newly developed sensors was successfully applied for the analysis of binary and ternary mixtures of Ce{sup 3+}, Nd{sup 3+}, Sm{sup 3+} and Gd{sup 3+} cations in different combinations. (authors)

Legin, A.; Kirsanov, D.; Rudnitskaya, A. [St. Petersburg University, Chemistry Department, Laboratory of Chemical Sensors, Universitetskaya nab. 7/9, St. Petersburg, 199034 (Russian Federation); Babain, V. [Khlopin Radium Institute, 28, 2nd Murinsky av., St. Petersburg, 194021 (Russian Federation); Rovny, S.; Logunov, M. [PA Mayak, Ozyorsk (Russian Federation)

2007-07-01

8

Coherent spectroscopy of rare-earth-metal-ion-doped whispering-gallery-mode resonators  

SciTech Connect

We perform an investigation into the properties of Pr{sup 3+}:Y{sub 2}SiO{sub 5} whispering-gallery-mode resonators as a first step toward achieving the strong coupling regime of cavity QED with rare-earth-metal-ion-doped crystals. Direct measurement of cavity QED parameters are made using photon echoes, giving good agreement with theoretical predictions. By comparing the ions at the surface of the resonator to those in the center, it is determined that the physical process of making the resonator does not negatively affect the properties of the ions. Coupling between the ions and resonator is analyzed through the observation of optical bistability and normal-mode splitting.

McAuslan, D. L.; Korystov, D.; Longdell, J. J. [Jack Dodd Centre for Photonics and Ultra-Cold Atoms, Department of Physics, University of Otago, Dunedin, New Zealand. (New Zealand)

2011-06-15

9

Temperature effects on alkaline earth metal ions adsorption on gibbsite: approaches from macroscopic sorption experiments and molecular dynamics simulations.  

PubMed

Two approaches, macroscopic adsorption experiments and molecular dynamics simulations, were employed to study the effect of temperature on alkaline earth metals adsorption on gibbsite surfaces. Increased reaction temperature enhanced the extent of metal ion adsorption for all of the alkaline earth metals studied. Whereas Mg(2+) and Sr(2+) adsorption displayed dependence on ionic strength, Sr(2+) adsorption exhibited less dependence on background ionic strength regardless of temperature. The ionic strength dependence was attributed to outer-sphere complexation reactions. The ionic strength effect on metal ion removal decreased with increasing temperature for both metals. Ba(2+) removal by gibbsite, on the other hand, was not affected by ionic strength. Results from molecular dynamics simulations were in agreement with the findings of the experimental study. The amount of thermal energy required to remove waters of hydration from the metal cation and the ratio of outer-sphere to inner-sphere complexation decreased with increasing ionic radii. It was observed from both macroscopic and molecular approaches that the tendency to form inner-sphere complexes on gibbsite decreased in the order: Ba(2+)>Sr(2+)>Mg(2+) and that the common assumption that alkaline earth metal ions form outer-sphere complexes appears to be dependent on ionic radius and temperature. PMID:23540825

Katz, Lynn E; Criscenti, Louise J; Chen, Chia-chen; Larentzos, James P; Liljestrand, Howard M

2013-06-01

10

Experimental demonstration of efficient and selective population transfer and qubit distillation in a rare-earth-metal-ion-doped crystal  

NASA Astrophysics Data System (ADS)

In optically controlled quantum computers it may be favorable to address different qubits using light with different frequencies, since the optical diffraction does not then limit the distance between qubits. Using qubits that are close to each other enables qubit-qubit interactions and gate operations that are strong and fast in comparison to qubit-environment interactions and decoherence rates. However, as qubits are addressed in frequency space, great care has to be taken when designing the laser pulses, so that they perform the desired operation on one qubit, without affecting other qubits. Complex hyperbolic secant pulses have theoretically been shown to be excellent for such frequency-addressed quantum computing [I. Roos and K. Molmer, Phys. Rev. A 69, 022321 (2004)]—e.g., for use in quantum computers based on optical interactions in rare-earth-metal-ion-doped crystals. The optical transition lines of the rare-earth-metal-ions are inhomogeneously broadened and therefore the frequency of the excitation pulses can be used to selectively address qubit ions that are spatially separated by a distance much less than a wavelength. Here, frequency-selective transfer of qubit ions between qubit states using complex hyperbolic secant pulses is experimentally demonstrated. Transfer efficiencies better than 90% were obtained. Using the complex hyperbolic secant pulses it was also possible to create two groups of ions, absorbing at specific frequencies, where 85% of the ions at one of the frequencies was shifted out of resonance with the field when ions in the other frequency group were excited. This procedure of selecting interacting ions, called qubit distillation, was carried out in preparation for two-qubit gate operations in the rare-earth-metal-ion-doped crystals. The techniques for frequency-selective state-to-state transfer developed here may be also useful also for other quantum optics and quantum information experiments in these long-coherence-time solid-state systems.

Rippe, Lars; Nilsson, Mattias; Kröll, Stefan; Klieber, Robert; Suter, Dieter

2005-06-01

11

Self-propelled droplets for extracting rare-earth metal ions.  

PubMed

We have developed self-propelled droplets having the abilities to detect a chemical gradient, to move toward a higher concentration of a specific metal ion (particularly the dysprosium ion), and to extract it. Such abilities rely on the high surface activity of di(2-ethylhexyl) phosphoric acid (DEHPA) in response to pH and the affinity of DEHPA for the dysprosium ion. We used two external stimuli as chemical signals to control droplet motion: a pH signal to induce motility and metal ions to induce directional sensing. The oil droplets loaded with DEHPA spontaneously move around beyond the threshold of pH even in a homogeneous pH field. In the presence of a gel block containing metal ions, the droplets show directional sensing and their motility is biased toward higher concentrations. The metal ions investigated can be arranged in decreasing order of directional sensing as Dy(3+)? Nd(3+) > Y(3+) > Gd(3+). Furthermore, the analysis of components by using an atomic absorption spectrophotometer reveals that the metal ions can be extracted from the environmental media to the interiors of the droplets. This system may offer alternative self-propelled nano/microscale machines to bubble thrust engines powered by asymmetrical catalysts. PMID:25029997

Ban, Takahiko; Tani, Kentaro; Nakata, Hiroki; Okano, Yasunori

2014-09-01

12

Rare-earth neutral metal injection into an electron beam ion trap plasma  

SciTech Connect

We have designed and implemented a neutral metal vapor injector on the SuperEBIT high-energy electron beam ion trap at the Lawrence Livermore National Laboratory. A horizontally directed vapor of a europium metal is created using a thermal evaporation technique. The metal vapor is then spatially collimated prior to injection into the trap. The source's form and quantity constraints are significantly reduced making plasmas out of metal with vapor pressures ?10{sup ?7} Torr at ?1000?°C more obtainable. A long pulsed or constant feed metal vapor injection method adds new flexibility by varying the timing of injection and rate of material being introduced into the trap.

Magee, E. W., E-mail: magee1@llnl.gov; Beiersdorfer, P.; Brown, G. V. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Hell, N. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Dr. Remeis-Sternwarte and ECAP, Universität Erlangen-Nürnberg, 96049 Bamberg (Germany)

2014-11-15

13

Rare-earth neutral metal injection into an electron beam ion trap plasmaa)  

NASA Astrophysics Data System (ADS)

We have designed and implemented a neutral metal vapor injector on the SuperEBIT high-energy electron beam ion trap at the Lawrence Livermore National Laboratory. A horizontally directed vapor of a europium metal is created using a thermal evaporation technique. The metal vapor is then spatially collimated prior to injection into the trap. The source's form and quantity constraints are significantly reduced making plasmas out of metal with vapor pressures ?10-7 Torr at ?1000 °C more obtainable. A long pulsed or constant feed metal vapor injection method adds new flexibility by varying the timing of injection and rate of material being introduced into the trap.

Magee, E. W.; Beiersdorfer, P.; Brown, G. V.; Hell, N.

2014-11-01

14

Selectivity Study of Alkaline Earth and Divalent Transition Metal Ions on [Al + Na]-Substituted Tobermorites  

Microsoft Academic Search

The ion-exchange selectivities of [Al + Na]-substituted tobermorites with 1–20 mol% substitution of aluminum for silicon at low loadings were investigated for Mg, Sr, Ba, and Ni. The selectivity order depended on the degree of substitution, exchanging medium, and loading of metal ions, reflecting different types of ion-exchange sites in the Al-substituted tobermorites which are an interesting group of calcium

Masamichi Tsuji; Sridhar Komarneni

1993-01-01

15

Interaction of alkali, alkaline earth and transition metal ions with a ketocyanine dye: A comparative electronic spectroscopic study  

NASA Astrophysics Data System (ADS)

Interaction of a dye which is structurally similar to a ketocyanine dye with metal ions (alkali, alkaline earth and transition metal) has been studied by monitoring the electronic absorption, steady state and time resolved fluorescence parameters of the dye. The dye (S0 state) forms a 1:1 complex with cations as indicated by the appearance of a new band at a longer wavelength. Equilibrium constant and other thermodynamic parameters for complexation have been determined. The interaction between the dye and the cation is mostly electrostatic in nature. Spectroscopic results have been supplemented by DFT calculation. For very low concentration of cations, where complexation is insignificant, the absorption band of the dye undergoes a slight blue shift. Enhancement of fluorescence intensity has been observed in the same concentration range. Both phenomena have been explained in terms of formation of a weak association complex where one/more cation replace equivalent solvent molecules in the cybotatic region around the dye. The binding constant of the weak association complex involving cation and the dye (S1 state) has been determined and has been found to depend on the charge-to-size ratio of the cations. Measurement of fluorescence lifetime of the dye indicates that the association complex is slowly decaying relative to solvated dye. At higher concentration of metal ions, however, fluorescence of the dye is quenched by the metal ions. A red shift of fluorescence maximum has also been observed in this concentration range.

Sardar, Sanjib Kr.; Srikanth, Kambalapalli; Mandal, Prasun K.; Bagchi, Sanjib

2012-12-01

16

Alkaline earth metal ion induced coil-helix-coil transition of lysine-coumarin-azacrown hybrid foldamers with OFF-OFF-ON fluorescence switching.  

PubMed

A new metal-ion-responsive and fluorescent foldamer, OPLM(8), composed of eight lysine-coumarin-azacrown units, has been designed and synthesized. The flexible OPLM(8) can be forced into a well-defined helix structure only upon the addition of alkaline earth metal ions. The structural change is based on the crown ether moieties being positioned in the requisite arrangement along the peptide chain, that is, at i, i+4 spacing, such that the alkaline earth metal ions can mediate the formation of four sandwich complexes between them. Moreover, varying the chelator-to-metal-ion ratio from 2:1 to 1:1 resulted in disassembly of the sandwich complexes leading to collapse of the helical structure to a random coil. These metal-ion-induced structural transitions could not only be monitored by the CD amplitude change but also easily probed by unique "OFF-OFF-ON" fluorescence intensity changes from 0.7-fold to 14-fold as the structure changed from the folded helix to a random coil. To further verify that the helix formation was indeed induced by metal-ion complexation, two kinds of control octamers with only four metal-ion chelators on the side chains were studied. One, which was capable of forming two sandwich complexes between the i and i+4 residues, displayed a negative Cotton couplet with the magnitude of its A value close to half that of OPLM(8), and the second had four metal-ion chelators positioned in the same turn, and hence was incapable of forming intramolecular metal complexes and showed different induced CD signals. Collectively, the photospectroscopic data and the results of the control studies suggest that alkaline earth metal ions can efficiently promote the flexible octamer OPLM(8) into a well-organized helix by the formation of sandwich complexes between substituents at an i, i+4 spacing. PMID:23193029

Lin, Yu-Chen; Chen, Chao-Tsen

2013-02-11

17

Properties of alkali-metal atoms and alkaline-earth-metal ions for an accurate estimate of their long-range interactions  

NASA Astrophysics Data System (ADS)

Accurate knowledge of interaction potentials among the alkali-metal atoms and alkaline-earth ions is very useful in the studies of cold atom physics. Here we carry out theoretical studies of the long-range interactions among the Li, Na, K, and Rb alkali-metal atoms with the Ca+, Ba+, Sr+, and Ra+ alkaline-earth ions systematically, which are largely motivated by their importance in a number of applications. These interactions are expressed as a power series in the inverse of the internuclear separation R . Both the dispersion and induction components of these interactions are determined accurately from the algebraic coefficients corresponding to each power combination in the series. Ultimately, these coefficients are expressed in terms of the electric multipole polarizabilities of the above-mentioned systems, which are calculated using the matrix elements obtained from a relativistic coupled-cluster method and core contributions to these quantities from the random-phase approximation. We also compare our estimated polarizabilities with the other available theoretical and experimental results to verify accuracies in our calculations. In addition, we also evaluate the lifetimes of the first two low-lying states of the ions using the above matrix elements. Graphical representations of the dispersion coefficients versus R are given among all the alkaline ions with Rb.

Kaur, Jasmeet; Nandy, D. K.; Arora, Bindiya; Sahoo, B. K.

2015-01-01

18

Spin-Orbit Qubits of Rare-Earth-Metal Ions in Axially Symmetric Crystal Fields  

NASA Astrophysics Data System (ADS)

Contrary to the well-known spin qubits, rare-earth-metal qubits are characterized by a strong influence of crystal field due to large spin-orbit coupling. At low temperature and in the presence of resonance microwaves, it is the magnetic moment of the crystal-field ground state which nutates (for several ?s) and the Rabi frequency ?R is anisotropic. Here, we present a study of the variations of ?R(H?0) with the magnitude and direction of the static magnetic field H?0 for the odd Er167 isotope in a single crystal CaWO4:Er3+. The hyperfine interactions split the ?R(H?0) curve into eight different curves which are fitted numerically and described analytically. These “spin-orbit qubits” should allow detailed studies of decoherence mechanisms which become relevant at high temperature and open new ways for qubit addressing using properly oriented magnetic fields.

Bertaina, S.; Shim, J. H.; Gambarelli, S.; Malkin, B. Z.; Barbara, B.

2009-11-01

19

A preorganized metalloreceptor for alkaline earth ions showing calcium versus magnesium selectivity in water: biological activity of selected metal complexes.  

PubMed

The N,N'-bis[(3-hydroxy-4-pyron-2-yl)methyl]-N,N'-dimethylethylendiamine (Malten = L) forms the highly stable [CuH(-2)L] species in water, in which the converging maltol oxygen atoms form an electron-rich area able to host hard metal ions. When considering the alkaline earth series (AE), the [Cu(H(-2)L)] species binds all metal ions, with the exception of Mg(2+), exhibiting the relevant property to discriminate Ca(2+) versus Mg(2+) at physiological pH?7.4; the binding of the AE metal is visible to the naked eye. The stability constant values of the trinuclear [AE{Cu(H(-2)L)}2](2+) species formed reach the maximum for Ca(2+) (log?K=7.7). Ca(2+) also forms a tetranuclear [Ca{Cu(H(-2)L)}]2(4+) species at a high Ca(2+) concentration. Tri- and tetranuclear calcium complexes show blue- and pink-colored crystals, respectively. [Cu(H(-2)L)] is the most active species in inducing DNA alterations. The DNA damages are compatible with its hydrolytic cleavages. PMID:25069710

Amatori, Stefano; Ambrosi, Gianluca; Fanelli, Mirco; Formica, Mauro; Fusi, Vieri; Giorgi, Luca; Macedi, Eleonora; Micheloni, Mauro; Paoli, Paola; Rossi, Patrizia

2014-08-25

20

Infrared and Raman spectroscopic and theoretical studies of nonaaqua complexes of trivalent rare earth metal ions.  

PubMed

Infrared (IR), far-infrared (far-IR) and Raman spectra have been recorded of the hydrated lanthanide(III) trifluoromethanesulfonates, [Ln(OH2)9](CF3SO3)3, (Ln=La, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu), and also for the deuterated [La(OD2)9](CF3SO3)3 compound. This has enabled complete assignments of all seven metal-oxygen stretching modes for the first time. Force constant calculations have been performed for an LnO9(3+) moiety, with a tricapped trigonal prismatic oxygen atom arrangement in D3h point group symmetry. The lanthanide contraction in reflected in continuously increasing trends for the averaged LnO stretching frequencies and force constants with increasing inverse of ionic radii. The stretching force constants increased from 0.81 to 1.16 Ncm-1 for the LnO6 prism in the series from La to Lu, while those for the capping LnO3 bonds increased from 0.49 to 0.65 Ncm-1. The LnO stretching force constants showed a smooth correlation with the LnO bond distances to the prism oxygen atoms, while the correlation to the LnO capping oxygen atoms has a different shape, reflecting the increased ligand-ligand repulsion with decreasing lanthanide ion size. PMID:15820897

Mink, János; Skripkin, Mikhail Yu; Hajba, László; Németh, Csaba; Abbasi, Alireza; Sandström, Magnus

2005-05-01

21

Rare earth metal borocarbides  

Microsoft Academic Search

A variety of structural types of solid-state rare earth metal borocarbide materials containing infinite two-dimensional layers, infinite one-dimensional chains, or finite groups of boron and carbon are reviewed. Although the solid-state language of Zintl–Klemm concept, band structures, and density of states is necessary to rationalize this kind of compound, they are governed by the laws that guide most molecular and

Josef Bauer; Jean-François Halet; Jean-Yves Saillard

1998-01-01

22

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

PubMed

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. PMID:23298846

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

2013-02-01

23

EXTRACTIVE PROPERTIES TOWARDS RARE-EARTH METAL IONS OF CALIX[ 4] ARENES SUBSTITUTED AT THE NARROW RIM BY PHOSPHORYL AND AMIDE GROUPS  

Microsoft Academic Search

The extractive properties of the cone and partial-cone isomers of 5,11,17,23-tetra-?ert-butyl-25,27-bis( diethylcarbamoylmethoxy)-26,28-bisi( diphenylphospninoylmethoxy) calyx[ 4] arene ( cone-1 and partial-cone -1) in 1,2-dichloroethane towards rare-earth metal ions in nitrate media at 25 ° C were investigated. The analysis of the extraction equilibrium obtained from a mixture of four rare-earths ( La, Eu, Er and Y) revealed that the extracted species

M. R. Yaftian; M. Burgard; C. Wieseir; C. B. Dieleman; D. Matt

1998-01-01

24

Structural diversity in binuclear complexes of alkaline earth metal ions with 4,6-diacetylresorcinol  

NASA Astrophysics Data System (ADS)

A new series of binuclear and mixed-ligand complexes with the general formula: [M 2(LO)yClz]; where M = Mg(II), Ca(II), Sr(II) and Ba(II); H2L = 4,6-diacetylresorcinol, the secondary ligand L' = acetylacetone (acac), 8-hydroxyquinoline (8-HQ) or 2,2'-bipyridyl (Bipy), n = 0-2, m = 1, 2, x = 0, 1, 2, 4, y = 0, 2, 4, 5 and z = 0-2; have been synthesized. They have been characterized by the analytical and spectral methods (IR, 1H NMR and mass) as well as TGA and molar conductivity measurements. The spectroscopic and conductance data suggested that the H2L ligand behaves as a neutral, monobasic or dibasic tetradentate ligand, depending on the basicity of the secondary ligand, through the two phenolic and two carbonyl groups. Binuclear octahedral geometry has been assigned to all of the prepared complexes in various molar ratios 2:2; 2:2:2; 1:2:1 and 1:2:4 (L:M:L'). Molecular orbital calculations were performed for the ligands and their complexes using Hyperchem 7.52 program on the bases of PM3 level and the results were correlated with the experimental data. The ligand and some of its alkaline metal(II) complexes showed antibacterial activity towards some of Gram-positive and Gram-negative bacteria, yeast (Candida albicans) and fungus (Aspergillus fumigatus).

Shebl, Magdy; Khalil, Saied M. E.; Taha, A.; Mahdi, M. A. N.

2012-11-01

25

Multilayer membranes of p-sulfonato-calix[8]arene and polyvinylamine and their use for selective enrichment of rare earth metal ions  

NASA Astrophysics Data System (ADS)

Using alternating electrostatic layer-by-layer assembly of p-octasulfonato-calix[8]arene and polyvinylamine, multilayer assemblies were built up on porous polymer supports. The resulting composite membranes with ultrathin separation layer were studied on their permeability for various metal chloride salts in aqueous solution. The membranes were permeable for sodium chloride, but much less permeable for divalent metal chlorides such as magnesium and zinc chloride, the theoretical separation factors ? (NaCl/MgCl 2) and ? (NaCl/ZnCl 2) being 43 and 20. Rare earth metal chlorides LnCl 3 with Ln being La, Ce, Pr and Sm and the related YCl 3 were strongly rejected from the membrane, the theoretical separation factors ? (NaCl/LaCl 3) and ? (NaCl/YCl 3) being 138 and 160, for example. Possible origins for the selective ion transport are discussed in terms of Donnan rejection of the highly charged ions and complex formation of the rare earth metal ions with the p-sulfonato-calixarene units in the membrane.

Toutianoush, Ali; El-Hashani, Ashraf; Schnepf, Judit; Tieke, Bernd

2005-06-01

26

Rare-earth metal-ion separation using a supported liquid membrane mediated by a narrow rim phosphorylated calix[4]arene  

Microsoft Academic Search

The transport of rare-earth metal ions through a supported liquid membrane mediated by 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrakis(diphenylphosphinoylmethoxy)calix[4]arene (1) (cone conformation) in o-nitrophenyl hexyl ether (NPHE) has been investigated. The effect of the initial metal concentration, salting-out agent concentration in the feed phase and temperature as well as the carrier concentration on the flux was studied. The separation ability of ligand 1 was tested

M. R Yaftian; M Burgard; C. B Dieleman; D Matt

1998-01-01

27

Investigations on the electrical and mechanical properties of triglycine sulphate single crystals modified with some rare earth metal ions  

Microsoft Academic Search

Single crystals of triglycine sulphate (TGS) modified with La3+, Ce3+ and Nd3+ have been grown from aqueous solutions by low-temperature solution growth method. The effect of rare earth ion dopants (La, Ce and Nd) on the ferroelectric properties of TGS is reported. Dielectric constant and dielectric loss have been measured for different frequencies. Dielectric measurements revealed that the dielectric constant

R Muralidharan; R Mohankumar; R Dhanasekaran; A. K Tirupathi; R Jayavel; P Ramasamy

2003-01-01

28

Strong-coupling cavity QED using rare-earth-metal-ion dopants in monolithic resonators: What you can do with a weak oscillator  

SciTech Connect

We investigate the possibility of achieving the strong coupling regime of cavity quantum electrodynamics using rare-earth-metal-ions as impurities in monolithic optical resonators. We conclude that due to the weak oscillator strengths of the rare-earth-metals, it may be possible but difficult to reach the regime where the single photon Rabi frequency is large compared to both the cavity and atom decay rates. However, reaching the regime where the saturation photon and atom numbers are less than one should be much more achievable. We show that in this 'bad cavity' regime, transfer of quantum states and an optical phase shift conditional on the state of the atom is still possible and suggest a method for coherent detection of single dopants.

McAuslan, D. L.; Longdell, J. J.; Sellars, M. J. [Jack Dodd Centre for Photonics and Ultra-Cold Atoms, Department of Physics, University of Otago, Dunedin (New Zealand); Laser Physics Centre, Research School of Physical Sciences and Engineering, Australian National University, Canberra, ACT 0200 (Australia)

2009-12-15

29

Effect of sodium ions on the extraction of rare earth metals by liquid surfactant membranes containing a calix[4]arene carboxyl derivative  

Microsoft Academic Search

A novel host compound calixarene has been applied as a mobile carrier for the separation and concentration of rare earth metals by liquid surfactant membranes (LSMs). Using the novel carrier, extraction of rare earth metals (Ho, Er and Y) by LSMs was systematically studied in a stirred cell. Extraction behavior of rare earth metals by the carboxyl derivative of calix[4]arene

Takahiko Kakoi; Tatsuya Oshima; Takayuki Nishiyori; Fukiko Kubota; Masahiro Goto; Seiji Shinkai; Fumiyuki Nakashio

1998-01-01

30

Thermophysical properties of liquid rare earth metals  

NASA Astrophysics Data System (ADS)

The thermodynamical properties like long wavelength limit S(0), iso-thermal compressibility (?T), thermal expansion coefficient (?V), thermal pressure coefficient (?V), specific heat at constant volume (CV) and specific heat at constant pressure (CP) are calculated for liquid rare earth metals. Our newly constructed parameter free model potential is used to describe the electron ion interaction due to Sarkar et al (S) local field correction function. Lastly, we conclude that our newly constructed model potential is capable to explain the thermophysical properties of liquid rare earth metals.

Thakor, P. B.; Sonvane, Y. A.; Patel, H. P.; Jani, A. R.

2013-06-01

31

Hydration Energies and Structures of Alkaline Earth Metal Ions, M2+ (H2O)n, n = 5–7, M = Mg, Ca, Sr, and Ba  

PubMed Central

The evaporation of water from hydrated alkaline earth metal ions, produced by electrospray ionization, was studied in a Fourier transform mass spectrometer. Zero-pressure-limit dissociation rate constants for loss of a single water molecule from the hydrated divalent metal ions, M2+(H2O)n (M = Mg, Ca, and Sr for n = 5–7, and M = Ba for n = 4–7), are measured as a function of temperature using blackbody infrared radiative dissociation. From these values, zero-pressure-limit Arrhenius parameters are obtained. By modeling the dissociation kinetics using a master equation formalism, threshold dissociation energies (Eo) are determined. These reactions should have a negligible reverse activation barrier; therefore, Eo values should be approximately equal to the binding energy or hydration enthalpy at 0 K. For the hepta- and hexahydrated ions at low temperature, binding energies follow the trend expected on the basis of ionic radii: Mg > Ca > Sr > Ba. For the hexahydrated ions at high temperature, binding energies follow the order Ca > Mg > Sr > Ba. The same order is observed for the pentahydrated ions. Collisional dissociation experiments on the tetrahydrated species result in relative dissociation rates that directly correlate with the size of the metals. These results indicate the presence of two isomers for hexahydrated magnesium ions: a low-temperature isomer in which the six water molecules are located in the first solvation shell, and a high-temperature isomer with the most likely structure corresponding to four water molecules in the inner shell and two water molecules in the second shell. These results also indicate that the pentahydrated magnesium ions have a structure with four water molecules in the first solvation shell and one in the outer shell. The dissociation kinetics for the hexa- and pentahydrated clusters of Ca2+, Sr2+, and Ba2+ are consistent with structures in which all the water molecules are located in the first solvation shell. PMID:16429612

Rodriguez-Cruz, Sandra E.; Jockusch, Rebecca A.

2005-01-01

32

The rare-earth metals  

Microsoft Academic Search

A brief survey is given of the physical properties of the rare earth metals. In doing this their characteristic structural and magnetic behaviour is described first and this is then followed by an examination of the ways in which these features affect the other properties.

K. N. R. Taylor

1970-01-01

33

Imestigation ol" Maenons in Rare Earth Metals  

E-print Network

Imestigation ol" Maenons in Rare Earth Metals b\\ Inelastic Neutron Scattering tL Bjerrum Moiler #12;BLANK PAGE #12;Riso Report No. 178 Investigation of Magnons in Rare Earth Metals by Inelastic NeutronN LANGF h. a. dec. #12;Contents Page PREFACE 7 I. INTRODUCTION *> 1. Magnetism of Rare Earth Metals 10 2

34

Metal ion release from metal implants  

Microsoft Academic Search

Metal ion release from metallic materials, e.g. stainless steel, cobalt–chromium alloy, titanium, and titanium alloys, implanted into human body was reviewed in this paper. Surface oxide films on metallic materials play an important role as an inhibitor of ion release and they change with the release in vivo. Low concentration of dissolved oxygen, inorganic ions, proteins, and cells may accelerate

T. Hanawa

2004-01-01

35

Nuclear magnetic resonance in rare earth metals  

Microsoft Academic Search

This article describes the study, by nuclear magnetic resonance, of both static and dynamical aspects of the hyperfine interaction in rare earth metals, and illustrates the categories of information that can be obtained by using nuclei as microscopic probes in metallic media. The systems discussed include not only the pure rare earth metals but also their alloys and their metallic

M. A. H. McCausland; I. S. Mackenzie

1979-01-01

36

Dialing in color with rare earth metals: facile photoluminescent production of true white light  

E-print Network

Dialing in color with rare earth metals: facile photoluminescent production of true white light of lanthanide ions which is the focus of this report. Rare earth metal complexes have relatively good Combining polymeric architectures with metal ions produces hybrid materials with extremely rich properties

Tew, Gregory N.

37

The electric field gradient in heavy rare earth metals  

Microsoft Academic Search

Estimates of the electric field gradient in heavy rare earth metals have been evaluated from experimental hyperfine interaction data. In addition, the magnetic hyperfine fields are analyzed. In the metals the effective radial integrals r-3>4f of the magnetic and quadrupole hyperfine interaction are reduced at most by 10% compared with the free ion values. The electric field gradients due to

J. Pelzl; Fachbereich Physik

1972-01-01

38

RARE-EARTH METALS--1997 61.1 RARE-EARTH METALS  

E-print Network

RARE-EARTH METALS--1997 61.1 RARE-EARTH METALS By James B. Hedrick The rare earths are a relatively million, to thulium and lutetium, the least abundant rare-earth elements at about 0.5 parts per million. Scandium, atomic number 21, is the lightest rare-earth element. It is the 31st most abundant element

39

SOLVENT EXTRACTION OF THE RARE-EARTH METAL IONS BY A CONE-SHAPED CALDC[4]ARENE SUBSTITUTED AT THE LOWER RTM BY FOUR CH2P(O)Ph2 LIGANDS  

Microsoft Academic Search

The extraction properties of cone-5,11,17,23-tetra-t-butyl-25,26,27,28-tetrakis(diphenylphosphinoylmethoxy)calix[4]arene (1) in 1,2-dichloroethane towards rare-earth metal ions at 25 °C have been investigated. The slope analysis showed a 1:1 metal\\/ligand ratio for the extracted species (La, Eu, Er and Y). The distribution coefficients increase with the polarity of the diluents : chloroform ? dichioromethane ? 1,2-dichloroethane ? nitrobenzene. In the competitive extraction of 11 rare-earth

M. R. Yaftian; M. Burgard; D. Matt; C. B. Dieleman; F. Rastegar

1997-01-01

40

Ecotoxicity of rare earth elements Rare earth elements (REEs) or rare earth metals is the  

E-print Network

Ecotoxicity of rare earth elements Info Sheet Rare earth elements (REEs) or rare earth metals isolated. Actually, most rare earth elements exist in the Earth's crust in higher concentrations than though most people have never heard of rare earth elements, sev- eral of them govern mankind's modern

Wehrli, Bernhard

41

Dosimetric studies of YAlO3: Mn co-doped with transition (Co, Cu, Fe) and rare earth (Yb, Ce) metal ions  

NASA Astrophysics Data System (ADS)

Dosimetric studies on single crystals of YAlO3:Mn co-doped with transition (Co, Cu, Fe) and rare earth (Yb, Ce) metal ions using UV radiation exposure for the duration 5-30 min have been studied. A single well resolved thermoluminescence glow peak was observed at 183 °C in Co and Cu co-doped single crystals. In Fe co-doped single crystals, two well resolved glow peaks at 196 °C and 238 °C were observed. A well resolved glow peak at 215 °C in Yb and 176 °C in Ce co-doped single crystals was observed. Variations of thermoluminescent (TL) glow peaks intensity in all the co-doped crystals with different UV-exposures were studied. TL glow peak intensity increases sublinearly in Co, Cu co-doped crystals, whereas in Fe co-doped crystals glow peaks at 196 °C and 238 °C increase linearly. Fading effect was studied at different intervals up to 30 d for all co-doped crystals exposed to UV source for 10 min. Strong fading was observed initially and stabilized after 15 d. Fe co-doped YAlO3:Mn2+ records 40% fading, whereas other samples of YAlO3:Mn2+ co-doped with Cu, Co, Yb and Ce show 60% fading. The kinetic parameters (E, b, s) were estimated using glow peak shape method for UV irradiated samples and results are discussed in detail.

Premkumar, H. B.; Nagabhushana, H.; Sharma, S. C.; Prashantha, S. C.; Nagabhushana, B. M.; Nagaswarupa, H. P.; Zhao, Guangjun; Chen, Jianyu

2014-04-01

42

{sup 1}H and {sup 23}Na MAS NMR spectroscopy of cationic species in CO{sub 2} selective alkaline earth metal porous silicoaluminophosphates prepared via liquid and solid state ion exchange  

SciTech Connect

The location of extraframework cations in Sr{sup 2+} and Ba{sup 2+} ion-exchanged SAPO-34 was estimated by means of {sup 1}H and {sup 23}Na MAS NMR spectroscopy and spectral deconvolution. Incorporation of the alkaline earth metal cations onto the SAPO framework was achieved via liquid state ion exchange, coupled partial detemplation/solid-state ion exchange, and combination of both techniques. MAS NMR revealed that the level of ion exchange was limited by the presence of protons and sodium cations near hexagonal prisms (site SI), which are relatively difficult to exchange with the alkaline earth metal due to steric and charge repulsion criteria. In addition, the presence of ammonium cations in the supercages facilitated the exchange of otherwise tenacious hydrogen as corroborated by unit cell compositional data as well as enhanced CO{sub 2} adsorption at low partial pressures. The extraframework ammonium species were produced from partial detemplation of the structure-directing agent employed for the SAPO-34 synthesis, tetraethylammonium. - Graphical abstract: MAS NMR was used to elucidate the position the cationic species in alkaline earth metal exchanged silicoaluminophosphates. These species played a significant role during the ion exchange process and, therefore, the materials ultimate CO{sub 2} adsorption performance. Highlights: Black-Right-Pointing-Pointer Location of extraframework Sr{sup 2+} or Ba{sup 2+} cations was estimated by means of {sup 1}H and {sup 23}Na MAS NMR. Black-Right-Pointing-Pointer Level of Sr{sup 2+} or Ba{sup 2+} ion exchange was limited by the presence of protons and sodium cations. Black-Right-Pointing-Pointer Presence of ammonium cations in the supercages facilitated the exchange. Black-Right-Pointing-Pointer Sr{sup 2+} and Ba{sup 2+} ion exchanged SAPOs are outstanding CO{sub 2} adsorbents.

Arevalo-Hidalgo, Ana G. [Department of Chemical Engineering, University of Puerto Rico-Mayagueez Campus, Mayagueez, PR 00681-9000 (Puerto Rico); Dugar, Sneha; Fu, Riqiang [National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310 (United States); Hernandez-Maldonado, Arturo J., E-mail: arturoj.hernandez@upr.edu [Department of Chemical Engineering, University of Puerto Rico-Mayagueez Campus, Mayagueez, PR 00681-9000 (Puerto Rico)

2012-07-15

43

Rare earth metals for automotive exhaust catalysts  

Microsoft Academic Search

The usage of rare earth metals for automotive exhaust catalysts is demonstrated in this paper. Rare earth metals have been widely used in automotive catalysts. In particular, three-way catalysts require the use of ceria compounds as oxygen storage materials, and lanthana as both a stabilizer of alumina and a promoter. The application for diesel catalysts is also illustrated. Effects of

Hirohumi Shinjoh

2006-01-01

44

Rare Earth Metals: Resourcefulness and Recovery  

NASA Astrophysics Data System (ADS)

When we appreciate the digital revolution carried over from the twentieth century with mobile communication and the Internet, and when we enjoy our high-tech lifestyle filled with iDevices, hybrid cars, wind turbines, and solar cells in this new century, we should also appreciate that all of these advanced products depend on rare earth metals to function. Although there are only 136,000 tons of annual worldwide demand, (Cho, Rare Earth Metals, Will We Have Enough?)1 rare earth metals are becoming such hot commodities on international markets, due to not only to their increasing uses, including in most critical military hardware, but also to Chinese growth, which accounts for 95% of global rare earth metal production. Hence, the 2013 technical calendar topic, planned by the TMS/Hydrometallurgy and Electrometallurgy Committee, is particularly relevant, with four articles (including this commentary) contributed to the JOM October Issue discussing rare earth metals' resourcefulness and recovery.

Wang, Shijie

2013-10-01

45

Recycling of rare earth metals from rare earth-transition metal alloy scrap by liquid metal extraction  

DOEpatents

Method of treating rare earth metal-bearing scrap, waste or other material (e.g. Nd--Fe--B or Dy--Tb--Fe scrap) to recover the rare earth metal comprising melting the rare earth metal-bearing material, melting a Group IIA metal extractant, such as Mg, Ca, or Ba, in which the rare earth is soluble in the molten state, and contacting the melted material and melted extractant at a temperature and for a time effective to extract the rare earth from the melted material into the melted extractant. The rare earth metal is separated from the extractant metal by vacuum sublimation or distillation.

Ellis, Timothy W. (Ames, IA); Schmidt, Frederick A. (Ames, IA)

1995-08-01

46

Recycling of rare earth metals from rare earth-transition metal alloy scrap by liquid metal extraction  

DOEpatents

A method is described for treating rare earth metal-bearing scrap, waste or other material (e.g. Nd--Fe--B or Dy--Tb--Fe scrap) to recover the rare earth metal comprising melting the rare earth metal-bearing material, melting a Group IIA metal extractant, such as Mg, Ca, or Ba, in which the rare earth is soluble in the molten state, and contacting the melted material and melted extractant at a temperature and for a time effective to extract the rare earth from the melted material into the melted extractant. The rare earth metal is separated from the extractant metal by vacuum sublimation or distillation. 2 figs.

Ellis, T.W.; Schmidt, F.A.

1995-08-01

47

Adsorption of Ni(II) and Cd(II) from water by novel chelating sponge and the effect of alkali-earth metal ions on the adsorption.  

PubMed

Novel chelating sponge (PVA-M-H) was prepared with polyvinyl alcohol by graft polymerization and nucleophilic substitution. E.A, SEM, FT-IR, (13)CNMR, and XPS analyses were used to characterize PVA-M-H. The equilibrium adsorption capacities of PVA-M-H for Ni(II) and Cd(II) were 65.39 and 125.11mgg(-1), respectively. Within the range of 278-308K, the adsorption enthalpy changes of Ni(II) and Cd(II) on PVA-M-H were about 36.39-37.72kJmol(-1), and the free energy were about -13.27 to -1.7kJmol(-1). Both pseudo-first- and -second-order equations fit the adsorption kinetic curves well, and the initial adsorption rates of Ni(II) and Cd(II) onto PVA-M-H were 17.83 and 34.81mg (gmin)(-1), respectively. Although the presence of alkali-earth metal ions in solution decreased Ni(II) and Cd(II) removal, PVA-M-H still retained more than 60 and 80% of its adsorption capacity even as the concentration of Ca(2+) and Mg(2+) was up to 10mmolL(-1), respectively. Both 0.1M HCl and 0.1M EDTA solution could desorb Ni(II) and Cd(II) from PVA-M-H effectively, and the adsorption capacity of PVA-M-H for Ni(II) and Cd(II) could still maintain more than 90% level without any obvious decrease at the fifth cycle. PMID:24316805

Cheng, Cheng; Wang, Jinnan; Yang, Xin; Li, Aimin; Philippe, Corvini

2014-01-15

48

Rare earth ions in magnetically ordered crystals  

NASA Astrophysics Data System (ADS)

Theoretical methods for studying the physical properties of rare earth magnetic materials are presented in a systematic manner. Particular attention is given to the properties of the rare earth ion in a magnetically ordered crystal and its interaction with the crystal's and external magnetic fields as well as exchange, dipole, quadrupole, and magnetoelastic interactions. The nature of magnetic ordering and magnetic phase transitions in a wide class of rare earth crystals are also discussed.

Zvezdin, A. K.; Matveev, V. M.; Mukhin, A. A.; Popov, A. I.

49

Luminescent properties of rare-earth-metal ion-doped KLaNb{sub 2}O{sub 7} with layered perovskite structures  

SciTech Connect

The photochemical properties of layered materials has been extensively studied, but the photochemical properties of two-dimensional oxides of layered compounds has not. This study examined the photoluminescence and thermoluminescence of lanthanide-metal-ion-doped KLaNb{sub 2}O{sub 7} with a layered perovskite structure. 16 refs., 5 figs.

Kudo, Akihiko [Science Univ. of Tokyo (Japan)] [Science Univ. of Tokyo (Japan)

1997-03-01

50

Rare Earth Metal Silicides and exotic Nuclei  

NASA Astrophysics Data System (ADS)

The use of Rare Earth Metal Silicides has been seen in thermal detection since World War II. What results can be expected when Rare Earths are used with certain isotopes? More to the point can exotic isotopes of Rare Earths be made from what is known more recently about Hadrons and their construction? What if anything can be gained from manipulating isotopes with a more recent theory than that known around World War II?

Kriske, Richard

2009-11-01

51

Alkaline earth metal catalysts for asymmetric reactions.  

PubMed

The group 2 alkaline earth metals calcium (Ca), strontium (Sr), and barium (Ba) are among the most common elements on Earth, abundant in both the sea and the Earth's crust. Although they are familiar in our daily lives, their application to organic synthesis has, so far, been limited. Some particularly useful properties of these elements include (i) low electronegativity, (ii) a stable oxidation state of +2, meaning that they can potentially form two covalent bonds with anions, and (iii) the ability to occupy a variety of coordination sites due to their large ionic radius. Furthermore, the alkaline earth metals, found between the group 1 and group 3 elements, show mild but significant Lewis acidity, which can be harnessed to control coordinative molecules via a Lewis acid-base interaction. Taken together, these characteristics make the metals Ca, Sr, and Ba very promising components of highly functionalized acid-base catalysts. In this Account, we describe the development of chiral alkaline earth metal catalysts for asymmetric carbon-carbon bond-forming reactions. Recently prepared chiral alkaline earth metal complexes have shown high diastereo- and enantioselectivities in fundamental and important chemical transformations. We chose chiral bisoxazoline (Box) derivatives bearing a methylene tether as a ligand for chiral modification. These molecules are very useful because they can covalently coordinate to alkaline earth metals in a bidentate fashion through deprotonation of the tether portion. It was found that chiral calcium-Box complexes could successfully promote catalytic asymmetric 1,4-addition and [3 + 2] cycloaddition reactions with high diastereo- and enantioselectivities. Both the calcium-Box complexes and chiral strontium-bis-sulfonamide and chiral barium-BINOLate complexes could catalyze asymmetric 1,4-addition reactions with high enantioselectivities. Furthermore, we designed a calcium-neutral coordinative ligand complex as a new type of chiral alkaline earth metal catalyst. We found that pyridinebisoxazolines (Pybox) worked well: they served as excellent ligands for calcium compounds in 1,4-addition reactions and Mannich reactions. Moreover, they were successful in 1,4-additions in concert with enantioselective protonation, affording the desired products in good to high enantioselectivities. Our results demonstrate that alkaline earth metals are very useful and attractive catalysts in organic synthesis. Moreover, their ubiquity in the environment is a distinct advantage over rare metals for large-scale processes, and their minimal toxicity is beneficial in both handling and disposal. PMID:20979379

Kobayashi, Sh?; Yamashita, Yasuhiro

2011-01-18

52

Laser spectroscopy of rare earth ions  

Microsoft Academic Search

The main part of this thesis reports on the study of a wide range of EuVO4 samples grown from different starting flux materials, and doped with different rare earth ions. Conventional optical absorption and emission spectroscopy was used to measure the energies of the 5D and 7F levels of the Eu(3+) ion in the different growths. Related optical absorption work

Peter C. Hansen

1990-01-01

53

Synthesis, structure and reactivity of rare-earth metal complexes containing anionic phosphorus ligands.  

PubMed

A comprehensive review of structurally characterized rare-earth metal complexes containing anionic phosphorus ligands is presented. Since rare-earth elements form hard ions and phosphorus is considered as a soft ligand, the rare-earth metal phosphorus coordination is regarded as a less favorite combination. Three classes of phosphorus ligands, (1) the monoanionic organophosphide ligands (PR2(-)) bearing one negative charge on the phosphorus atom; (2) the dianionic phosphinidene (PR(2-)) and P(3-) ligands; and (3) the pure inorganic polyphosphide ligands (Pn(x-)), are included here. Particular attention has been paid to the synthesis, structure, and reactivity of the rare-earth metal phosphides. PMID:23945727

Li, Tianshu; Kaercher, Sabrina; Roesky, Peter W

2014-01-01

54

Pressure-Induced Electronic Phase Transitions Transition Metal Oxides and Rare Earth Metals  

E-print Network

Pressure-Induced Electronic Phase Transitions in Transition Metal Oxides and Rare Earth Metals Metal Oxides and Rare Earth Metals by Brian Ross Maddox Electron correlation can affect profound changes transition in a transition metal monoxide. iv #12;The lanthanides (the 4f metals also known as rare-earths

Islam, M. Saif

55

Catalysis using hydrous metal oxide ion exchanges  

DOEpatents

In a process which is catalyzed by a catalyst comprising an active metal on a carrier, said metal being active as a catalyst for the process, an improvement is provided wherein the catalyst is a hydrous, alkali metal or alkaline earth metal titanate, zirconate, niobate or tantalate wherein alkali or alkaline earth metal cations have been exchanged with a catalytically effective amount of cations of said metal.

Dosch, Robert G. (Albuquerque, NM); Stephens, Howard P. (Albuquerque, NM); Stohl, Frances V. (Albuquerque, NM)

1985-01-01

56

Catalysis using hydrous metal oxide ion exchangers  

DOEpatents

In a process which is catalyzed by a catalyst comprising an active metal on a carrier, said metal being active as a catalyst for the process, an improvement is provided wherein the catalyst is a hydrous, alkali metal or alkaline earth metal titanate, zirconate, niobate or tantalate wherein alkali or alkaline earth metal cations have been exchanged with a catalytically effective amount of cations of said metal.

Dosch, R.G.; Stephens, H.P.; Stohl, F.V.

1983-07-21

57

METAL-NON METAL TRANSITIONS /N RARE EARTH COMPOUNDS. EXPERIMENT AND THEORK /.  

E-print Network

METAL-NON METAL TRANSITIONS /N RARE EARTH COMPOUNDS. EXPERIMENT AND THEORK /. VALENCE INSTABILITIES, superconductivity, electron-phonon and band theory, to name a few. 2. Properties of normal rare earth metals. - Before discussing rare earth valence instabilities, three relevant general features of rare earth metals

Paris-Sud XI, Université de

58

Upconversion Processes in Transition Metal and Rare Earth Metal Systems  

Microsoft Academic Search

The design and characterization of new luminescent materials is an active area of research. Here we present several current\\u000a topics in the area of upconversion by transition-metal and rare-earth-metal doped halide lattices. Following introduction\\u000a to the necessary background material related to upconversion mechanisms and kinetics, a series of topics are discussed which\\u000a illustrate some key areas of developing interest in

Daniel R. Gamelin; Hans U. Güdel

59

ONDES DE SPIN MAGNETISM IN THE LIGHT RARE EARTH 'METALS  

E-print Network

ONDES DE SPIN MAGNETISM IN THE LIGHT RARE EARTH 'METALS A. R. MACKINTOSH H. C. Mrsted Institute terres rares Ikgeres. Abstract. -The magnetic properties of the light rare earth metals are reviewed the last decade, the magnetism of the heavy rare earth metals is now rather well understood. The magnetic

Boyer, Edmond

60

Mechanistic Enzyme Models: Pyridoxal and Metal Ions.  

ERIC Educational Resources Information Center

Background information, procedures, and results are presented for experiments on the pyridoxal/metal ion model system. These experiments illustrate catalysis through Schiff's base formation between aldehydes/ketones and primary amines, catalysis by metal ions, and the predictable manner in which metal ions inhibit or catalyze reactions. (JN)

Hamilton, S. E.; And Others

1984-01-01

61

Reversible photodeposition and dissolution of metal ions  

DOEpatents

A cyclic photocatalytic process for treating waste water containing metal and organic contaminants. In one embodiment of the method, metal ions are photoreduced onto the photocatalyst and the metal concentrated by resolubilization in a smaller volume. In another embodiment of the method, contaminant organics are first oxidized, then metal ions removed by photoreductive deposition. The present invention allows the photocatalyst to be recycled until nearly complete removal of metal ions and organic contaminants is achieved.

Foster, Nancy S. (Boulder, CO); Koval, Carl A. (Golden, CO); Noble, Richard D. (Boulder, CO)

1994-01-01

62

Metallic ions in the equatorial ionosphere  

NASA Technical Reports Server (NTRS)

Four positive ion composition measurements of the equatorial E region made at Thumba, India, are presented. During the day, the major ions between 90 and 125 km are NO(+) and O2(+). A metallic ion layer centered at 92 km is observed, and found to contain Mg(+), Fe(+), Ca(+), K(+), Al(+), and Na(+) ions. The layer is explained in terms of a similarly shaped latitude distribution of neutral atoms which are photoionized and charge-exchanged with NO(+) and O2(+). Three body reactions form molecular metallic ions which are rapidly lost by dissociative ion-electron recombination. Nighttime observations show downward drifting of the metallic ion layer caused by equatorial dynamo effects. These ions react and form neutral metals which exchange charges with NO(+) and O2(+) to produce an observed depletion of those ions within the metallic ion region.

Aikin, A. C.; Goldberg, R. A.

1972-01-01

63

Characteristics of thermal decomposition products of rare earth, alkali earth metal and transition metal p -toluenesulfonates  

Microsoft Academic Search

Summary A series of alkali earth (Ca, Ba), lanthanide (La, Ce, Pr, Nd,) and transition metal (Fe, Mn, Co, Ni, Cu, Zn, Cd) p-toluenesulfonates were synthesized. Thermal analysis, infrared spectrophotometry, and XRD powder diffraction patterns were employed to characterize the final thermal decomposition products. By heating in dynamic air atmosphere at 30-850°C, it has been found that the alkali earth

Z.-L. Sun

2005-01-01

64

Ion Acceleration at the Earth's Bow Shock  

NASA Astrophysics Data System (ADS)

The Earth's bow shock is the most studied example of a collisionless shock in the solar system. It is also widely used to model or predict the behaviour at other astrophysical shock systems. Spacecraft observations, theoretical modelling and numerical simulations have led to a detailed understanding of the bow shock structure, the spatial organization of the components making up the shock interaction system, as well as fundamental shock processes such as particle heating and acceleration. In this paper we review the observations of accelerated ions at and upstream of the terrestrial bow shock and discuss the models and theories used to explain them. We describe the global morphology of the quasi-perpendicular and quasi-parallel shock regions and the foreshock. The acceleration processes for field-aligned beams and diffuse ion distribution types are discussed with connection to foreshock morphology and shock structure. The different possible mechanisms for extracting solar wind ions into the acceleration processes are also described. Despite several decades of study, there still remain some unsolved problems concerning ion acceleration at the bow shock, and we summarize these challenges.

Burgess, D.; Möbius, E.; Scholer, M.

2012-11-01

65

ZnS nanocrystals co-activated by transition metals and rare-earth metals—a new class of luminescent materials  

Microsoft Academic Search

We report on the unique luminescent properties of ZnS nanoparticles co-activated by Cu2+ and rare-earth metallic ions. The co-activated ZnS nanocrystals with varying sizes from 20 to 30Å have been prepared by using a chemical coprecipitation at room temperature. The nanoparticles can be co-doped with copper and rare-earth metallic ions during synthesis without altering X-ray diffraction patterns. However, the doping

Ping Yang; Mengkai Lü; Dong Xü; Duolong Yuan; Guangjun Zhou

2001-01-01

66

Metal enhanced fluorescence in rare earth doped plasmonic core-shell nanoparticles  

E-print Network

We theoretically and numerically investigate metal enhanced fluorescence of plasmonic core-shell nanoparticles doped with rare earth (RE) ions. Particle shape and size are engineered to maximize the average enhancement factor (AEF) of the overall doped shell. We show that the highest enhancement (11 in the visible and 7 in the near-infrared) are achieved by tuning either the dipolar or quadrupolar particle resonance to the rare earth ions excitation wavelength. Additionally, the calculated AEFs are compared to experimental data reported in the literature, obtained in similar conditions (plasmon mediated enhancement) or when a metal-RE energy transfer mechanism is involved.

Derom, S; Pillonnet, A; Benamara, O; Jurdyc, A M; Girard, C; Francs, G Colas des

2013-01-01

67

A set of alkali and alkaline-earth coordination polymers based on the ligand 2-(1H-benzotriazol-1-yl) acetic acid: Effects the radius of metal ions on structures and properties  

NASA Astrophysics Data System (ADS)

Four new metal coordination complexes, namely, [Na(BTA)]n (1), [K2(BTA)2(?2-H2O)]n (2), and [M(BTA)2(H2O)2]n (M=Ca(II) and Sr(II) for 3 and 4, respectively) [BTA=2-(1H-benzotriazol-1-yl) acetic anion], have been obtained under hydrothermal condition, by reacting the different alkali and alkaline-earth metal hydroxides with HBTA. Complexes 1-4 were structurally characterized by X-ray single-crystal diffraction, EA, IR, PXRD, and thermogravimetry analysis (TGA). These complexes display low-dimensional features displaying various two-dimensional (2D) and one-dimensional (1D) coordination motifs. Complex 1 displays a 2D layer with the thickness of 1.5 nm and possesses a topologic structure of a 11 nodal net with Schläfli symbol of {318}. Complex 2 also shows a thick 2D sheet and its topologic structure is a 9 nodes with Schläfli symbol of {311×42}. Complexes 3 and 4 possess a 1D linear chain and further stack via hydrogen bonding interactions to generate a three-dimensional supramolecular architecture. These results suggest that both the coordination preferences of the metal ions and the versatile nature of this flexible ligand play a critical role in the final structures. The luminescent spectra show strong emission intensities in complexes 1-4, which display violet photoluminescence. Additionally, ferroelectric, dielectric and nonlinear optic (NLO) second-harmonic generation (SHG) properties of 2 are discussed in detail.

Wang, Jin-Hua; Tang, Gui-Mei; Qin, Ting-Xiao; Yan, Shi-Chen; Wang, Yong-Tao; Cui, Yue-Zhi; Weng Ng, Seik

2014-11-01

68

DNA-bound metal ions: recent developments.  

PubMed

The affinity of metal ions for DNA is logical considering that the structure of DNA includes a phosphate backbone with a net-negative charge, a deoxyribose sugar with O atoms, and purine and pyrimidine bases that contain O and N atoms. DNA-metal ion interactions encompass a large area of research that ranges from the most fundamental characterization of DNA-metal ion binding to the role of DNA-bound metal ions in disease and human health. Alternative DNA base pairing mediated by metal binding is also being investigated and manipulated for applications in logic gates, molecular machines, and nanotechnology. This review highlights recent work aimed at understanding interactions of redox-active metal ions with DNA that provides a better understanding of the mechanisms by which various types of oxidative DNA damage (strand breakage and base modifications) occur. Antioxidants that mitigate oxidative DNA damage by coordinating metal ions that produce reactive oxygen species are addressed, as well as recent work on the effect of DNA-metal ion interactions and the efficacy of quinolone-based antibacterial drugs. Recent advances in metal-mediated base pairing that triggers conformational changes in DNA structure for use as selective metal ion sensors and novel nanotechnology applications are also included. PMID:25367620

Morris, Daniel L

2014-10-01

69

Liquid metal ion source and alloy  

DOEpatents

A liquid metal ion source and alloy, wherein the species to be emitted from the ion source is contained in a congruently vaporizing alloy. In one embodiment, the liquid metal ion source acts as a source of arsenic, and in a source alloy the arsenic is combined with palladium, preferably in a liquid alloy having a range of compositions from about 24 to about 33 atomic percent arsenic. Such an alloy may be readily prepared by a combustion synthesis technique. Liquid metal ion sources thus prepared produce arsenic ions for implantation, have long lifetimes, and are highly stable in operation.

Clark, Jr., William M. (Thousand Oaks, CA); Utlaut, Mark W. (Saugus, CA); Behrens, Robert G. (Los Alamos, NM); Szklarz, Eugene G. (Los Alamos, NM); Storms, Edmund K. (Los Alamos, NM); Santandrea, Robert P. (Santa Fe, NM); Swanson, Lynwood W. (McMinnville, OR)

1988-10-04

70

Low specificity of metal ion binding in the metal ion core of a folded RNA  

PubMed Central

The structure and activity of nucleic acids depend on their interactions with metal ions. Fundamental to these interactions is the degree of specificity observed between the metal ions and nucleic acids, and a complete description of nucleic acid folding requires that we understand the nature of the interactions with metal ions, including specificity. The prior demonstration that high concentrations of monovalent cations prevent nonspecific association of divalent ions with nucleic acids provides a novel and powerful means to examine site-specific metal ion binding isolated from complicating effects of the ion atmosphere. Using these high monovalent cation solution conditions we have monitored the affinity of a series of divalent metal ions for two site-specific metal ion binding sites in the P4-P6 domain of the Tetrahymena group I intron ribozyme. The metal ion core of this highly structured RNA binds two divalent metal ions under these conditions. Despite multiple metal ion–RNA interactions observed in the X-ray crystallographic structure of P4-P6 RNA at the metal ion binding sites, these sites exhibit low specificity among Mn2+, Mg2+, Ca2+, Ni2+, and Zn2+. Nevertheless, the largest divalent metal ions tested, Sr2+ and Ba2+, were excluded from binding, exhibiting affinities at least two orders of magnitude weaker than observed for the other metal ions. Thus, a picture emerges of two metal ion binding sites, each with a high tolerance for metal ions with different properties but also with limits to accommodation. These limits presumably arise from steric or electrostatic features of the metal ion binding sites. PMID:17616553

Travers, Kevin J.; Boyd, Nathan; Herschlag, Daniel

2007-01-01

71

ChemTeacher: Alkaline Earth Metals = Group 2 (IIA)  

NSDL National Science Digital Library

ChemTeacher compiles background information, videos, articles, demonstrations, worksheets and activities for high school teachers to use in their classrooms. The Alkaline Earth Metals page includes resources for teaching students about the discovery, properties, and uses of the alkaline earth metals.

2011-01-01

72

Laser spectroscopy of rare earth ions  

NASA Astrophysics Data System (ADS)

The main part of this thesis reports on the study of a wide range of EuVO4 samples grown from different starting flux materials, and doped with different rare earth ions. Conventional optical absorption and emission spectroscopy was used to measure the energies of the 5D and 7F levels of the Eu(3+) ion in the different growths. Related optical absorption work was carried out on the Ho(3+) ion, in the two cases 1 percent Ho:EuVO4 (one of the doped EuVO4 growths) and 10 percent Ho:YVO4 (as a aid to understanding HoVO4). The absorption spectrum of Eu(3+) in the immediate vicinity of the forbidden 7F(sub 0)-5D(sub 0) transition was recorded by low resolution laser spectroscopy for all the sample growths. Samples from each growth revealed up to fifty different absorption lines, believed due to the presence of Eu(3+) at defect sites. The behavior of the forbidden intrinsic line, which is allowed when magnetic fields is applied, was examined in the different growth. This was compared with the predictions of perturbation theory. A search was made for Eu(3+) ions at defect sites that were inequivalent with respect to the application of magnetic field along the a and a' axes in the basal plane. Optical holeburning was applied in zero-field to determine the nuclear quadrupole parameters for the 5D(sub 0) excited state of all the defect sites in all the growth. In this thesis, a detailed recalculation of the predicted values for the nuclear quadrupole parameter P and the dependence of (P,eta) upon energy, based upon the nuclear quadrupole Hamiltonian, is put forward. Radio frequency optically detected nuclear quadrupole resonance (ODNQR) experiments were carried out on certain selected Eu(3+) defect sites in some of the sample growth. High precision measurements of the nuclear parameters (P,eta) for the 7F(sub 0) ground state of Eu(3+) was made. A brief report is made of some experimental and theoretical work on the compound HoF3.

Hansen, Peter C.

73

Laser Spectroscopy of Rare Earth Ions.  

NASA Astrophysics Data System (ADS)

Available from UMI in association with The British Library. Requires signed TDF. The main part of this thesis reports on the study of a wide range of EuVO_4 samples grown from different starting flux materials, and doped with different rare earth ions. Conventional optical absorption and emission spectroscopy has been used to measure the energies of the ^5D and ^7F energy levels of the Eu^ {3+} ion in the different growths. Related optical absorption work has been carried out on the Ho^{3+} ion, in the two cases 1%Ho:EuVO_4 (one of the doped EuVO_4 growths) and 10%Ho:YVO_4 (as an aid to understanding HoVO_4).. The absorption spectrum of Eu^ {3+} in the immediate vicinity of the forbidden ^7F_0 -^5D_0 transition has been recorded by low resolution laser spectroscopy for all the sample growths. Samples from each growth revealed up to fifty different absorption lines, believed due to the presence of Eu^{3+} at defect sites. The behaviour of the forbidden intrinsic line, which is allowed when magnetic field is applied, has been examined in the different growths. This has been compared with the predictions of perturbation theory. A search has been made for Eu^{3+} ions at defect sites that were inequivalent with respect to the application of magnetic field along the a and a ^' axes in the basal plane. Optical holeburning has been applied in zero-field to determine the nuclear quadrupole parameters for the ^5D_0 excited state of all the defect sites in all the growths. In this thesis, a detailed recalculation of the predicted values for the nuclear quadrupole parameter P and the dependence of (P,eta) upon energy, based upon the nuclear quadrupole Hamiltonian, is put forward. Radio frequency optically detected nuclear quadrupole resonance (ODNQR) experiments have been carried out on certain selected Eu^{3+} defect sites in some of the sample growths. High precision measurements of the nuclear parameters (P,eta) for the ^7F_0 ground state of Eu^{3+} have been made. A brief report is made of some experimental and theoretical work on the compound HoF_3. (Abstract shortened by UMI.).

Hansen, Peter C.

1990-01-01

74

COMPUTATIONAL DESIGN OF METAL ION SEQUESTERING AGENTS  

EPA Science Inventory

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...

75

N-(4-amino-7-nitrobenzaoxa-1,3-diazole)-substituted aza crown ethers: complexation with alkali, alkaline earth metal ions and ammonium  

PubMed Central

Three novel aza-crown ether derivatives incorporating 4-amino-7-nitrobenzaoxa-1,3-diazole (NBD) chromophore were synthesized and their structure confirmed by 1H-NMR, IR and elemental analysis. The influence of the solvent polarity and protonation on the photophysical properties of NBD-15-crown-5 was studied by UV/Vis and fluorescence methods. The influence of the investigated cations on the absorption spectra of the ligands was negligible, however emission was strongly affected. Complexation and binding stability of NBD-aza-15-crown-5 and NBD-aza-18-crown-6 were studied using fluorescence spectroscopy. NBD-aza-18-crown-6 exhibits strong selectivity toward Ca2+ and Sr2+ ions with formation constants about 103 times higher than the formation constants with the other ions included in the study. PMID:21461179

Deiab, Shihab D.; Archibong, Edikan E.; Jackson, Mercedes; Mochona, Bereket; Gangapuram, Madhavi; Redda, Kinfe K.

2011-01-01

76

Pseudo ribbon metal ion beam source  

SciTech Connect

The paper describes high broad metal ion source based on dc macroparticle filtered vacuum arc plasma generation with the dc ion-beam extraction. The possibility of formation of pseudo ribbon beam of metal ions with the parameters: ion beam length 0.6 m, ion current up to 0.2 A, accelerating voltage 40 kV, and ion energy up to 160 kV has been demonstrated. The pseudo ribbon ion beam is formed from dc vacuum arc plasma. The results of investigation of the vacuum arc evaporator ion-emission properties are presented. The influence of magnetic field strength near the cathode surface on the arc spot movement and ion-emission properties of vacuum-arc discharge for different cathode materials are determined. It was shown that vacuum-arc discharge stability can be reached when the magnetic field strength ranges from 40 to 70 G on the cathode surface.

Stepanov, Igor B., E-mail: stepanovib@tpu.ru; Ryabchikov, Alexander I.; Sivin, Denis O.; Verigin, Dan A. [Tomsk Polytechnic University, 30 Lenina Avenue, Tomsk 634050 (Russian Federation)] [Tomsk Polytechnic University, 30 Lenina Avenue, Tomsk 634050 (Russian Federation)

2014-02-15

77

Pseudo ribbon metal ion beam source.  

PubMed

The paper describes high broad metal ion source based on dc macroparticle filtered vacuum arc plasma generation with the dc ion-beam extraction. The possibility of formation of pseudo ribbon beam of metal ions with the parameters: ion beam length 0.6 m, ion current up to 0.2 A, accelerating voltage 40 kV, and ion energy up to 160 kV has been demonstrated. The pseudo ribbon ion beam is formed from dc vacuum arc plasma. The results of investigation of the vacuum arc evaporator ion-emission properties are presented. The influence of magnetic field strength near the cathode surface on the arc spot movement and ion-emission properties of vacuum-arc discharge for different cathode materials are determined. It was shown that vacuum-arc discharge stability can be reached when the magnetic field strength ranges from 40 to 70 G on the cathode surface. PMID:24593634

Stepanov, Igor B; Ryabchikov, Alexander I; Sivin, Denis O; Verigin, Dan A

2014-02-01

78

Pseudo ribbon metal ion beam source  

NASA Astrophysics Data System (ADS)

The paper describes high broad metal ion source based on dc macroparticle filtered vacuum arc plasma generation with the dc ion-beam extraction. The possibility of formation of pseudo ribbon beam of metal ions with the parameters: ion beam length 0.6 m, ion current up to 0.2 A, accelerating voltage 40 kV, and ion energy up to 160 kV has been demonstrated. The pseudo ribbon ion beam is formed from dc vacuum arc plasma. The results of investigation of the vacuum arc evaporator ion-emission properties are presented. The influence of magnetic field strength near the cathode surface on the arc spot movement and ion-emission properties of vacuum-arc discharge for different cathode materials are determined. It was shown that vacuum-arc discharge stability can be reached when the magnetic field strength ranges from 40 to 70 G on the cathode surface.

Stepanov, Igor B.; Ryabchikov, Alexander I.; Sivin, Denis O.; Verigin, Dan A.

2014-02-01

79

Heavy metal ions removal by chelating resin  

Microsoft Academic Search

Purpose – Preparation of chelating resin to be used in the removal of heavy metal ions from solutions. Design\\/methodology\\/approach – Chelating resin based on poly (glycidyl-methacrylate-co-N, N-methylene-bis-acrylamide) containing ethylenediamine was synthesised and used in removal of heavy metals from solutions. Findings – The optimal pH values for adsorption of different metal ions occur in the range 4.0-10.0 depending on the

N. M. Abd El-Moniem; M. R. El-Sourougy; D. A. F. Shaaban

2005-01-01

80

40 CFR 721.4668 - Hydrated alkaline earth metal salts of metalloid oxyanions.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Hydrated alkaline earth metal salts of metalloid oxyanions. ...Substances § 721.4668 Hydrated alkaline earth metal salts of metalloid oxyanions. ...substance identified as hydrated alkaline earth metal salts of metalloid...

2013-07-01

81

40 CFR 421.270 - Applicability: Description of the primary rare earth metals subcategory.  

Code of Federal Regulations, 2012 CFR

...Applicability: Description of the primary rare earth metals subcategory. 421.270 Section...MANUFACTURING POINT SOURCE CATEGORY Primary Rare Earth Metals Subcategory § 421.270 Applicability: Description of the primary rare earth metals subcategory. The...

2012-07-01

82

40 CFR 421.270 - Applicability: Description of the primary rare earth metals subcategory.  

Code of Federal Regulations, 2010 CFR

...Applicability: Description of the primary rare earth metals subcategory. 421.270 Section...MANUFACTURING POINT SOURCE CATEGORY Primary Rare Earth Metals Subcategory § 421.270 Applicability: Description of the primary rare earth metals subcategory. The...

2010-07-01

83

40 CFR 721.4668 - Hydrated alkaline earth metal salts of metalloid oxyanions.  

Code of Federal Regulations, 2012 CFR

...2012-07-01 false Hydrated alkaline earth metal salts of metalloid oxyanions. ...Substances § 721.4668 Hydrated alkaline earth metal salts of metalloid oxyanions. ...substance identified as hydrated alkaline earth metal salts of metalloid...

2012-07-01

84

40 CFR 421.270 - Applicability: Description of the primary rare earth metals subcategory.  

Code of Federal Regulations, 2013 CFR

...Applicability: Description of the primary rare earth metals subcategory. 421.270 Section...MANUFACTURING POINT SOURCE CATEGORY Primary Rare Earth Metals Subcategory § 421.270 Applicability: Description of the primary rare earth metals subcategory. The...

2013-07-01

85

40 CFR 721.4668 - Hydrated alkaline earth metal salts of metalloid oxyanions.  

Code of Federal Regulations, 2011 CFR

...2011-07-01 false Hydrated alkaline earth metal salts of metalloid oxyanions. ...Substances § 721.4668 Hydrated alkaline earth metal salts of metalloid oxyanions. ...substance identified as hydrated alkaline earth metal salts of metalloid...

2011-07-01

86

40 CFR 421.270 - Applicability: Description of the primary rare earth metals subcategory.  

Code of Federal Regulations, 2011 CFR

...Applicability: Description of the primary rare earth metals subcategory. 421.270 Section...MANUFACTURING POINT SOURCE CATEGORY Primary Rare Earth Metals Subcategory § 421.270 Applicability: Description of the primary rare earth metals subcategory. The...

2011-07-01

87

40 CFR 421.270 - Applicability: Description of the primary rare earth metals subcategory.  

...Applicability: Description of the primary rare earth metals subcategory. 421.270 Section...MANUFACTURING POINT SOURCE CATEGORY Primary Rare Earth Metals Subcategory § 421.270 Applicability: Description of the primary rare earth metals subcategory. The...

2014-07-01

88

40 CFR 721.4668 - Hydrated alkaline earth metal salts of metalloid oxyanions.  

...2014-07-01 false Hydrated alkaline earth metal salts of metalloid oxyanions. ...Substances § 721.4668 Hydrated alkaline earth metal salts of metalloid oxyanions. ...substance identified as hydrated alkaline earth metal salts of metalloid...

2014-07-01

89

40 CFR 721.4668 - Hydrated alkaline earth metal salts of metalloid oxyanions.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 false Hydrated alkaline earth metal salts of metalloid oxyanions. ...Substances § 721.4668 Hydrated alkaline earth metal salts of metalloid oxyanions. ...substance identified as hydrated alkaline earth metal salts of metalloid...

2010-07-01

90

Different Adsorption Behavior of Rare Earth and Metallic Ion Complexes on Langmuir Mono layers Probed by Sum-Frequency Generation Spectroscopy  

SciTech Connect

Adsorption behavior of counterions under a Langmuir monolayer was investigated by sum-frequency generation (SFG) spectroscopy. By comparing SFG spectra of arachidic acid (AA) Langmuir monolayer/water interface with and without added salt, it was found that the simple trivalent cation La3+ adsorbed on AA monolayer only when the carboxylic headgroups are charged (deprotonated), implying that counterion adsorption is induced by Coulomb interaction. On the other hand, metal hydroxide complex Fe(OH)3 adsorbed even on a charge-neutral AA monolayer, indicating that the adsorption of iron hydroxide is due to chemical interaction such as covalent or hydrogen bonding to the headgroup of the molecules at the monolayer.

Song, Woongmo [Sogang University, Seoul; Vaknin, David [Ames Laboratory; Kim, Doseok [Sogang University, Seoul

2013-02-25

91

Metal ion coordination, conditional stability constants, and solution behavior of chelating surfactant metal complexes.  

PubMed

Coordination complexes of some divalent metal ions with the DTPA (diethylenetriaminepentaacetic acid)-based chelating surfactant 2-dodecyldiethylenetriaminepentaacetic acid (4-C12-DTPA) have been examined in terms of chelation and solution behavior. The headgroup of 4-C12-DTPA contains eight donor atoms that can participate in the coordination of a metal ion. Conditional stability constants for five transition metal complexes with 4-C12-DTPA were determined by competition measurements between 4-C12-DTPA and DTPA, using electrospray ionization mass spectrometry (ESI-MS). Small differences in the relative strength between the coordination complexes of DTPA and 4-C12-DTPA indicated that the hydrocarbon tail only affected the chelating ability of the headgroup to a limited extent. The coordination of Cu(2+) ions was investigated in particular, using UV-visible spectroscopy. By constructing Job's plots, it was found that 4-C12-DTPA could coordinate up to two Cu(2+) ions. Surface tension measurements and NMR diffusometry showed that the coordination of metal ions affected the solution behavior of 4-C12-DTPA, but there were no specific trends between the studied divalent metal complexes. Generally, the effects of the metal ion coordination could be linked to the neutralization of the headgroup charge of 4-C12-DTPA, and the resulting reduced electrostatic repulsions between adjacent surfactants in micelles and monolayers. The pH vs concentration plots, on the other hand, showed a distinct difference between 4-C12-DTPA complexes of the alkaline earth metals and the transition metals. This was explained by the difference in coordination between the two groups of metal ions, as predicted by the hard and soft acid and base (HSAB) theory. PMID:24702119

Svanedal, Ida; Boija, Susanne; Almesåker, Ann; Persson, Gerd; Andersson, Fredrik; Hedenström, Erik; Bylund, Dan; Norgren, Magnus; Edlund, Håkan

2014-04-29

92

Sorption of metal ions on alumina  

SciTech Connect

The adsorption of metal ions on aluminas is of great interest in different fields such as geochemistry, oceanography, limnology, and pollution control. Precipitation and adsorption of metal ions (Co(II), Ni(II), Cu(II), and Cr(III)) on {gamma}-alumina were investigated experimentally. A surface chemical reaction model to calculate concentrations of aluminum ions, metal ions, and pH as variables depending on amount of alumina, volume of liquid and gas phase, initial metal concentration, and amount of acid or base added is presented. In the case of Co(II) the pH dependence of rest concentrations with and without alumina is equal; adsorption may be disregarded. For the other ions adsorption is important. Considering the charge of the surface does not improve the fit. In the pH region, where adsorption leads to lower rest concentrations than precipitation, adsorption may be described by a Henry isotherm.

Baumgarten, E.; Kirchhausen-Duesing, U. [Heinrich-Heine Univ. Duesseldorf (Germany). Inst. fuer Physikalische Chemie und Elektrochemie] [Heinrich-Heine Univ. Duesseldorf (Germany). Inst. fuer Physikalische Chemie und Elektrochemie

1997-10-01

93

Valence state at the surface of rare-earth metals  

Microsoft Academic Search

The valence state of a rare-earth metal surface is investigated by using general properties of the surface tension of metals. Thereby it is concluded that samarium is likely to have a divalent or partly divalent surface on top of its trivalent bulk phase, which agrees with recent spectroscopic observations. Also californium metal is discussed from this point of view. Finally,

Börje Johansson

1979-01-01

94

Near-Earth asteroids: Metals occurrence, extraction, and fabrication  

NASA Technical Reports Server (NTRS)

Near-earth asteroids occur in three principle types of orbits: Amor, Apollo, and Aten. Amor asteroids make relatively close (within 0.3 AU) approaches to the earth's orbit, but do not actually overlap it. Apollo asteroids spend most of their time outside the earth's orbital path, but at some point of close approach to the sun, they cross the orbit of the earth. Aten asteroids are those whose orbits remain inside the earth's path for the majority of their time, with semi-major axes less than 0.1 AU. Near-earth orbit asteroids include: stones, stony-irons, irons, carbonaceous, and super-carbonaceous. Metals within these asteroids include: iron, nickel, cobalt, the platinum group, aluminum, titanium, and others. Focus is on the extraction of ferrous and platinum group metals from the stony-iron asteroids, and the iron asteroids. Extraction of the metal fraction can be accomplished through the use of tunnel-boring-machines (TBM) in the case of the stony-irons. The metals within the story-iron asteroids occur as dispersed granules, which can be separated from the stony fraction through magnetic and gaseous digestion separation techniques. The metal asteroids are processes by drilling and gaseous digestion or by gaseous digestion alone. Manufacturing of structures, housings, framing networks, pressure vessels, mirrors, and other products is accomplished through the chemical vapor deposition (CVD) of metal coating on advanced composites and on the inside of contour-defining inflatables (CDI). Metal coatings on advanced composites provide: resistance to degradation in the hostile environments of space; superior optical properties; superior heat dissipation; service as wear coatings; and service as evidential coatings. Metal coatings on the inside of CDI produce metal load-bearing products. Fibers such as graphite, kevlar, glass, ceramic, metal, etc., can be incorporated in the metal coatings on the inside of CDI producing metal matrix products which exhibit high strength and resist crack propagation.

Westfall, Richard

1991-01-01

95

Near-Earth asteroids: Metals occurrence, extraction, and fabrication  

NASA Astrophysics Data System (ADS)

Near-earth asteroids occur in three principle types of orbits: Amor, Apollo, and Aten. Amor asteroids make relatively close (within 0.3 AU) approaches to the earth's orbit, but do not actually overlap it. Apollo asteroids spend most of their time outside the earth's orbital path, but at some point of close approach to the sun, they cross the orbit of the earth. Aten asteroids are those whose orbits remain inside the earth's path for the majority of their time, with semi-major axes less than 0.1 AU. Near-earth orbit asteroids include: stones, stony-irons, irons, carbonaceous, and super-carbonaceous. Metals within these asteroids include: iron, nickel, cobalt, the platinum group, aluminum, titanium, and others. Focus is on the extraction of ferrous and platinum group metals from the stony-iron asteroids, and the iron asteroids. Extraction of the metal fraction can be accomplished through the use of tunnel-boring-machines (TBM) in the case of the stony-irons. The metals within the story-iron asteroids occur as dispersed granules, which can be separated from the stony fraction through magnetic and gaseous digestion separation techniques. The metal asteroids are processes by drilling and gaseous digestion or by gaseous digestion alone. Manufacturing of structures, housings, framing networks, pressure vessels, mirrors, and other products is accomplished through the chemical vapor deposition (CVD) of metal coating on advanced composites and on the inside of contour-defining inflatables (CDI). Metal coatings on advanced composites provide: resistance to degradation in the hostile environments of space; superior optical properties; superior heat dissipation; service as wear coatings; and service as evidential coatings. Metal coatings on the inside of CDI produce metal load-bearing products. Fibers such as graphite, kevlar, glass, ceramic, metal, etc., can be incorporated in the metal coatings on the inside of CDI producing metal matrix products which exhibit high strength and resist crack propagation.

Westfall, Richard

96

Site of transition metal ions in ion-exchanged metal-doped glasses  

Microsoft Academic Search

Metal-for-alkali ion-exchange is largely used to dope surface layer of glass with metal ions so inducing a modification of the optical properties of the doped layer, useful to fabricate low-loss optical waveguides. X-ray absorption spectroscopy is a particularly important technique used to investigate the site of the metal ions introduced into the matrix, in specific cases also singling out the

C. Maurizio; F. D’Acapito; C. Sada; E. Cattaruzza; F. Gonella; G. Battaglin

2008-01-01

97

IONS OF EXTRATERRESTRIAL ORIGIN IN THE EARTH'S IONOSPHERE  

Microsoft Academic Search

Two of the tasks of the third Russian satellite were to determine the ; chemical composition of the main ion components in the earth's daytime ionosphere ; and to study the variation in composition in the main components with altitude in ; the E, Fâ, and Fâ regions of the ionosphere. In some of the ; measurements, ions were discovered

V ISTOMIN

1963-01-01

98

ION EXCHANGE SOFTENING: EFFECTS ON METAL CONCENTRATIONS  

EPA Science Inventory

A corrosion control pipe loop study to evaluate the effect of ion exchange water softening on metal leaching from household plumbing materials was conducted on two different water qualities having different pH's and hardness levels. The results showed that removing hardness ions ...

99

Detection of Heavy Metal Ions Based on Quantum Point Contacts  

E-print Network

Detection of Heavy Metal Ions Based on Quantum Point Contacts Vasanth Rajagopalan, Salah Boussaad. The ability to detect trace amounts of metal ions is important because of the toxicity of heavy metal ions on many living organisms and the consequence of heavy metal ions not being biodegradable. To date, heavy

Zhang, Yanchao

100

Reactions of fulvic acid with metal ions  

Microsoft Academic Search

Fulvic acid is a water-soluble humic material that occurs widely in soils and waters and that tends to form water-soluble and water-insoluble complexes with a variety of metal ions, some of which are toxic. This paper presents information on the conditions under which the different types of FA-metal complexes are formed.

M. Schnitzer; H. Kerndorff

1981-01-01

101

Metal-ion rescue revisited: Biochemical detection of site-bound metal ions important for RNA folding  

E-print Network

Metal-ion rescue revisited: Biochemical detection of site-bound metal ions important for RNA-dimensional architectures of RNA molecules, divalent metal ions populate specific locations, shedding their water molecules make essential contributions to function. Defining the locations of these site-bound metal ions remains

Das, Rhiju

102

Selective extraction and recovery of rare earth metals from phosphor powders in waste fluorescent lamps using an ionic liquid system.  

PubMed

The recycling of rare earth metals from phosphor powders in waste fluorescent lamps by solvent extraction using ionic liquids was studied. Acid leaching of rare earth metals from the waste phosphor powder was examined first. Yttrium (Y) and europium (Eu) dissolved readily in the acid solution; however, the leaching of other rare earth metals required substantial energy input. Ionization of target rare earth metals from the waste phosphor powders into the leach solution was critical for their successful recovery. As a high temperature was required for the complete leaching of all rare earth metals, ionic liquids, for which vapor pressure is negligible, were used as an alternative extracting phase to the conventional organic diluent. An extractant, N, N-dioctyldiglycol amic acid (DODGAA), which was recently developed, showed a high affinity for rare earth metal ions in liquid-liquid extraction although a conventional commercial phosphonic extractant did not. An effective recovery of the rare earth metals, Y, Eu, La and Ce, from the metal impurities, Fe, Al and Zn, was achieved from the acidic leach solution of phosphor powders using an ionic liquid containing DODGAA as novel extractant system. PMID:23587931

Yang, Fan; Kubota, Fukiko; Baba, Yuzo; Kamiya, Noriho; Goto, Masahiro

2013-06-15

103

Study of a liquid metal ion source for external ion injection into electron-beam ion source  

E-print Network

Study of a liquid metal ion source for external ion injection into electron-beam ion source A York 11973 Presented on 13 September 2005; published online 22 March 2006 A liquid metal ion source LMIS has several attractive features as an external injector of primary ions mostly metallic ions

104

New Proton-Ionizable, Calixarene-Based Ligands for Selective Metal Ion Separations  

SciTech Connect

The project objective was the discovery of new ligands for performing metal ion separations. The research effort entailed the preparation of new metal ion complexing agents and polymers and their evaluation in metal ion separation processes of solvent extraction, synthetic liquid membrane transport, and sorption. Structural variations in acyclic, cyclic, and bicyclic organic ligands were used to probe their influence upon the efficiency and selectivity with which metal ion separations can be performed. A unifying feature of the ligand structures is the presence of one (or more) side arm with a pendent acidic function. When a metal ion is complexed within the central cavity of the ligand, ionization of the side arm(s) produces the requisite anion(s) for formation of an overall electroneutral complex. This markedly enhances extraction/transport efficiency for separations in which movement of aqueous phase anions of chloride, nitrate, or sulfate into an organic medium would be required. Through systematic structural variations, new ligands have been developed for efficient and selective separations of monovalent metal ions (e.g., alkali metal, silver, and thallium cations) and of divalent metal ion species (e.g., alkaline earth metal, lead, and mercury cations). Research results obtained in these fundamental investigations provide important insight for the design and development of ligands suitable for practical metal ion separation applications.

Bartsch, Richard A.

2012-06-04

105

Correlation of metal ion toxicities to mice.  

PubMed

Recently reported correlations of acute ip LD50 metal ion toxicities to mice by Turner et al. (1983), have been re-investigated using the ion-specific parameters reported by Kaiser (1980) for sublethal metal ion toxicities to Daphnia magna. For the 15 ions with partially or completely filled d-shells, Rh(III), Fe(III), Cr(III), Mn(II), Co(II), Pd(II), Ni(II), Au(III), Zn(II), Pt(II), Ag(I), Cu(II), In(III), Hg(II), and Cd(II), a correlation coefficient of r2 = 0.76 is found. This is a significant improvement over the value of r2 = 0.36 observed for the 14 divalent metal ions by Turner et al. with the softness parameter sigma as the independent variable. This re-investigation proves the applicability of the ionization potential and redox potential derived parameters for the quantitative correlation of metal ion toxicities to both aquatic and terrestrial biota. PMID:4081779

Kaiser, K L

1985-11-01

106

Distribution of thermal oxygen ions in the near earth magnetosphere  

NASA Astrophysics Data System (ADS)

Based on eleven years of Cluster particle observations, we investigate the distribution of thermal oxygen ions in the near earth magnetosphere with full spatial coverage between 4 to 20 Re. Averaged oxygen ion fluxes are calculated for three energy ranges (E1: 25-136eV; E2: 136eV-3keV; E3 3-35keV) based on measurements from CIS instrument. In a preliminary analysis, we found that oxygen ions of E1 energy are observed mostly in the Polar Regions flowing toward the nightside with average speed of ~20 km/s at 5 Re. They are accelerated to E2 energy range before they arrive at plasmasheet. Clear dawn-dusk asymmetry is observed in the plasmasheet for oxygen ions of the E1 and E2 energy that they are distributed beyond 10 Re on the duskside and beyond 15 Re on the dawnside, suggesting the transportation from ionosphere to plasmasheet is asymmetric for dawn and dusk sides. These oxygen ions are further accelerated in the plasmasheet to E3 energy range and are transported toward the Earth, while they drift westward. These oxygen ions finally reach the dayside, and then either return to the ionosphere or escape from the dayside magnetopause to magnetosheeth. This study provides background knowledge on complete distribution of thermal oxygen ions in the near earth magnetosphere for the modelling and simulation studies on ionosphere-magnetosphere coupling.

Liu, W.; Cao, J.

2013-12-01

107

Fluorescent ion indicators for detecting heavy metals  

NASA Astrophysics Data System (ADS)

A series of fluorescent ion indicators were tested for their spectral response to submicromolar levels of 13 divalent and trivalent metal ions in aqueous solution. Upon binding their target ions, these fluorescent compounds exhibit changes in fluorescence emission intensity that are easily detectable, making them useful for direct the detection of soluble heavy metal ions including Hg2+, Cu2+, Ni2+ and Cd2+. The fluorescence response of these indicators to ion binding results from photoinduced electron transfer effects, fluorophore/quencher interactions, fluorescence quenching by heavy metal ions or a combination of these processes. The majority of the indicators we tested bind their target ions reversibly with dissociation constants (Kd) near 1 (mu) M (approximately 1 ppm) and detection limits near 100 nM (approximately 100 ppb) at pH 7. However, several indicators exhibit very high affinity for their target ion; for example, Magnesium GreenTM binds Zn2+ with a Kd near 20 nM. All the indicators synthesized and tested are based on water-soluble fluorophores that have high fluorescence quantum yields (from 0.3 to 0.7) and can be excited with an Ar laser, fluorometer or hand- held UV lamp. Furthermore, the excitation and emission spectra of these indicators are insensitive to pH changes over the range of 5 to 10, as well as to high concentrations of K+, Na+, Ca2+ and Mg2+. These properties make the indicators useful for the direct measurement of metal ions in solutions, such as biological fluids, sea water and waste streams, that contain high concentrations of salts.

Kuhn, Michael A.; Hoyland, Brian; Carter, Scott; Zhang, Cailan; Haugland, Richard P.

1995-05-01

108

Separation and microdetermination of rare earth metals with N-phenylbenzohydroxamic acid and Xylenol Orange  

Microsoft Academic Search

A simple, sensitive and selective method for solvent extraction and spectrophotometric determination of lanthanum(III), praseodymium(III), neodymium(III) and samarium(III) is described. The rare earth metals are extractable into chloroform solution of N-phenylbenzohydroxamic acid (PBHA) at pH9–10. Various parameters are studied to optimize the extraction conditions. Stoichiometry of the complexes and the effect of various ions is discussed. The molar absorptivity is

P. T. Thomaskutty; Y. K. Agrawal

1987-01-01

109

Method for treating rare earth-transition metal scrap  

DOEpatents

Rare earth-transition metal (e.g., iron) scrap (e.g., Nd-Fe-B scrap) is flux (slag) remelted to reduce tramp non-metallic impurities, such as oxygen and nitrogen, and metallic impurities, such as Li, Na, Al, etc., picked up by the scrap from previous fabrication operations. The tramp impurities are reduced to concentrations acceptable for reuse of the treated alloy in the manufacture of end-use articles, such as permanent magnets. The scrap is electroslag or inductoslag melted using a prefused, rare earth fluoride-bearing flux of CaF.sub.2, CaCl.sub.2 or mixtures thereof or the slag resulting from practice of the thermite reduction process to make a rare earth-iron alloy.

Schmidt, Frederick A. (Ames, IA); Peterson, David T. (Ames, IA); Wheelock, John T. (Nevada, IA); Jones, Lawrence L. (Des Moines, IA)

1992-12-29

110

Method for treating rare earth-transition metal scrap  

DOEpatents

Rare earth-transition metal (e.g., iron) scrap (e.g., Nd-Fe-B scrap) is flux (slag) remelted to reduce tramp non-metallic impurities, such as oxygen and nitrogen, and metallic impurities, such as Li, Na, Al, etc., picked up by the scrap from previous fabrication operations. The tramp impurities are reduced to concentrations acceptable for reuse of the treated alloy in the manufacture of end-use articles, such as permanent magnets. The scrap is electroslag or inductoslag melted using a rare earth fluoride-bearing flux of CaF[sub 2], CaCl[sub 2] or mixtures thereof or the slag resulting from practice of the thermite reduction process to make a rare earth-iron alloy. 3 figs.

Schmidt, F.A.; Peterson, D.T.; Wheelock, J.T.; Jones, L.L.

1992-12-29

111

Diffraction studies of rare earth metals and superlattices  

Microsoft Academic Search

We review the results of X-ray scattering studies of the rare earth metals and present related new results for superlattices and thin slabs. In rare earth crystals we have observed weak structural modulations which accompany the magnetic ordering. The wave length of this modulation can be derived from a spin-slip model in accordance with symmetry considerations. X-ray scattering of both

J. Bohr; Doon Gibbs; J. D. Axe; D. E. Moncton; K. L. D'Amico; C. F. Majkrzak; J. Kwo; M. Hong; C. L. Chien; J. Jensen

1989-01-01

112

MAGNETISM AND SUPERCONDUCTIVITY OF ANOMALOUS RARE-EARTH METALS AND ALLOYS  

E-print Network

MAGNETISM AND SUPERCONDUCTIVITY OF ANOMALOUS RARE-EARTH METALS AND ALLOYS B. COQBLIN Laboratoire de impurities. 1. Introduction. -The rare-earth metals can be divided in two groups : - The (( normal )) rare-earths lantha- num are (( anomalous )) rare-earths metals. The same duality exists in alloys with rareearth

Boyer, Edmond

113

Symmetric charge-transfer cross sections of IIIa rare-earth-metal elements  

SciTech Connect

Symmetric charge-transfer cross sections of IIIa rare-earth-metal elements (Sc, Y, and Gd) in the impact energy range of 30 to 1000 eV were measured for the first time. The experiments were performed with a crossed-beam apparatus that featured primary ion production by photoionization with a tunable dye laser. Comparing the cross sections of IIIa rare-earth-metal elements ({sigma}{sub Sc}, {sigma}{sub Y}, and {sigma}{sub Gd}) with those of alkali metals or helium {sigma}{sub 0}, we found that {sigma}{sub 0{approx_equal}{sigma}Sc}<{sigma}{sub Y}<{sigma}{sub Gd{approx_equal}}2{sigma}{sub 0}at an impact energy of 1000 eV.

Hashida, Masaki; Sakabe, Shuji; Izawa, Yasukazu [ARCBS, Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan) and Department of Physics, Graduate School of Science, Kyoto University, Kitashirakawa, Sakyo, Kyoto 606-8502 (Japan); Institute of Laser Engineering, Osaka University, Suita, Osaka 565-0871 (Japan) and Institute for Laser Technology, 2-6 Yamadaoka, Suita, Osaka 565-0871 (Japan)

2011-03-15

114

Magnetic and Electronic Properties of Rare-Earth - Metallic Glasses.  

NASA Astrophysics Data System (ADS)

Results of magnetic measurements are presented on the new metallic glass systems (R(,80)G(,20))(,100-x)Fe(,x) and (R(,80)Ga(,20))(,90)B(,10), where R is a rare-earth (i.e., La, Pr, Nd, Sm, Gd, Tb and Er) and G is Ga or Au for 0 (LESSTHEQ) x (LESSTHEQ) 30. High-field magnetization (to 80 kOe) and A.C. and D.C. susceptibility measurements were made from 1.4 K to 300 K. High-field magnetization data are analyzed by an Arrott plot technique and some Gd-based glasses show results consistent with the presence of the recently predicted infinite susceptibility phase of Aharony and Pytte. The magnetic hardness properties of most of these glasses (not containing S-state ions) are discussed in terms of the 'microdomain' model of Callen et al. In many glasses the magnetization reversal seems consistent with a coherent rotation mechanism as is suggested from the thermal variation of the coercivity. The glasses (R(,80)Ga(,20))(,70)Fe(,30) where R is Er and Tb are more complex and show behavior consistent with the presence of domain walls. Magnetic saturation was not obtained (at 80 kOe) on any glass containing an anisotropic rare -earth while glasses based on S-state rare-earths were fairly easily saturated. Giant intrinsic magnetic hardness is observed in the glasses (R(,80)G(,20))(,100-x)Fe(,x) where R is Nd or Pr and G is Ga or Au for 15 (LESSTHEQ) x (LESSTHEQ) 30. An unusual thermal variation of the coercive field is observed showing peaks at intermediate temperatures ((DBLTURN) 90 K). A phase separation into different amorphous stoichiometries is shown to exist by Fe('57) Mossbauer effect and other measurements. These results are consistent with a recent theory by Paul predicting that magnetic hardness can result from the presence of site-to-site variations in magnetic properties. Electrical resistivity measurements were made on the above glasses as well as the series (Pr(,80)Ga(,20))(,80)T(,20), where T = Cr, Mn, Co, Ni, Cu and Ga. These show negative temperature coefficients of resistivity at higher temperatures in most cases as well as structure in the resistivity below magnetic ordering temperatures. These results are shown to be consistent with some recent theories (for instance the extended Ziman theory) predicting negative slopes of the resistivity as well as to some theories predicting a magnetic contribution to the resistivity from coherent exchange scattering.

Cornelison, Steven G.

1982-03-01

115

Influence of metal ion complexation on the metastable fragmentation of DNA hexamers  

NASA Astrophysics Data System (ADS)

Here, we study the metastable decay of 5'-d(TTGCTT) in the presence of 0-6 alkaline metal ions (Li+, Na+, K+, Rb+) and 0-3 alkaline earth metal ions (Mg2+ and Ca2 +), which replace the corresponding number of protons in the oligonucleotide. We find that all ions studied here stabilize the oligonucleotide with respect to simple 3'-C-O backbone cleavage, but at the same time these metal ions promote a central oligonucleotide deletion accompanied by a concomitant recombination of the terminal d(TT) groups. We find that the quenching of the 3'-C-O backbone cleavage is not ion specific, since it is due to the removal of the phosphate protons upon replacement with the respective metal ions. The central nucleotide deletion competes with the 3'-C-O backbone cleavage channels and is thus promoted through the replacement of the exchangeable protons against metal ions. However, with increasing positive charge density of the metal ions the yield of the central nucleotide deletion further increases. We attribute this effect to the necessity of sufficient proximity of the terminal d(TT) group to allow for their recombination on this reaction path. Hence, the formation of a reactive conformer is mediated by the metal ions.

Piekarczyk, Andreas; Bald, Ilko; Flosadóttir, Helga D.; Ómarsson, Benedikt; Lafosse, Anne; Ingólfsson, Oddur

2014-06-01

116

Structure of liquid transition and rare earth metals S. N. Khanna and F. Cyrot-Lackmann  

E-print Network

L-45 Structure of liquid transition and rare earth metals S. N. Khanna and F. Cyrot-Lackmann Groupe It is shown that the observed structure factors of transition and rare earth liquid metals can be reaso- nably. The difference is particularly large for V, Ti, and rare earth metals which are precisely the metals where

Boyer, Edmond

117

Metal ions and human sperm mannose receptors.  

PubMed

Zinc and lead concentrations were measured in seminal plasma from fertile donors, infertile men with varicocoele and men undergoing work-ups for in vitro fertilization. Ejaculated spermatozoa from these subjects were incubated in vitro with various metal ions and/or dibromoethane and dibromochloropropane. Mannose receptor expression was correlated with metal and toxicant levels. Sperm distributions of potassium channels were compared with lead ions and calcium channels with zinc ions. Mannose receptor expression by capacitated spermatozoa increased linearly with seminal plasma zinc levels, and correlated inversely with lead levels. Cobalt had no effect on mannose receptor expression, but nickel had a concentration-dependent biphasic effect. Mannose receptor expression was not affected by dibromoethane and dibromochloropropane if the cholesterol content of the sperm membrane was high, but mannose receptor expression was decreased in low cholesterol spermatozoa by exposures below estimated permissive exposure limits. Potassium channels and lead ions co-localized over the entire head of human spermatozoa, while both calcium channels and zinc ions were confined to the equatorial segment of the head. Mannose receptor expression on the external surface of the human sperm plasma membrane is a biomarker for the effects of transition and heavy metals and organic toxicants on sperm fertility potential. PMID:11021525

Benoff, S; Cooper, G W; Centola, G M; Jacob, A; Hershlag, A; Hurley, I R

2000-09-01

118

Material Removes Heavy Metal Ions From Water  

NASA Technical Reports Server (NTRS)

New high capacity ion-exchange polymer material removes toxic metal cations from contaminated water. Offers several advantages. High sensitivities for such heavy metals as lead, cadmium, and copper and capable of reducing concentrations in aqueous solutions to parts-per-billion range. Removes cations even when calcium present. Material made into variety of forms, such as thin films, coatings, pellets, and fibers. As result, adapted to many applications to purify contaminated water, usually hard wherever found, whether in wastewater-treatment systems, lakes, ponds, industrial plants, or homes. Another important feature that adsorbed metals easily reclaimed by either destructive or nondestructive process. Other tests show ion-exchange polymer made inexpensively; easy to use; strong, flexible, not easily torn; and chemically stable in storage, in aqueous solutions, and in acidic or basic solution.

Philipp, Warren H., Jr.; Street, Kenneth W.; Hill, Carol; Savino, Joseph M.

1995-01-01

119

Polymer nanocomposites based on transition metal ion modified organoclays  

E-print Network

Polymer nanocomposites based on transition metal ion modified organoclays Pranav Nawani a , Priya: Transition metal ion; Organoclay; Nanocomposite 1. Introduction Thermoplastic nanocomposites with improved; accepted 4 December 2006 Available online 3 January 2007 Abstract A unique class of nanocomposites

Frenkel, Anatoly

120

Rare earth transition metal magnesium compounds—An overview  

NASA Astrophysics Data System (ADS)

Intermetallic rare earth-transition metal-magnesium compounds play an important role as precipitations in modern light weight alloys and as host materials for hydrogen storage applications. Recent results on the crystal chemistry, the chemical bonding peculiarities, physical properties, and hydrogenation behavior of these materials are reviewed.

Rodewald, Ute Ch.; Chevalier, Bernard; Pöttgen, Rainer

2007-05-01

121

Induced transition metal moments in rare-earth (yttrium) compounds  

NASA Astrophysics Data System (ADS)

The exchange interactions were analysed in rare-earth (yttrium) transition metal compounds. A transition from nonmagnetic to magnetic state was shown for Co and Ni at ? 70 T and ? 35 T, respectively. The temperature dependences of the magnetic susceptibilities, for the exchange enhanced paramagnets, which change from a T2 dependence to a Curie-Weiss behaviour, as temperature increases, is also analysed.

Burzo, E.

2007-04-01

122

The structure of rare earth metals in the liquid state  

Microsoft Academic Search

The structure of liquid rare earth metals (So, La, Ce, Pr, Eu, Gd, Tb and Yb) have been systematically examined by X-ray diffraction at temperatures above their melting points. The structure factors of liquid La, Ce, Pr, Eu and Yb were temperature insensitive in the presently available experimental temperature range. In terms of the usual Fourier analysis, the atomic radial

Y. Waseda; S. Tamaki

1977-01-01

123

Developments of rare earth metal catalysts for olefin polymerization  

Microsoft Academic Search

This review article describes recent developments in rare earth metal complexes as polymerization catalysts, focusing on the polymerization of ethylene and ?-olefins. Most of this kind of catalysts had been based on metallocene type complexes, and their catalytic behaviors are surveyed. Advanced series of half-metallocene and non-Cp type catalyst systems are also summarized.

Yuushou Nakayama; Hajime Yasuda

2004-01-01

124

Theory of the Resistance of the Rare Earth Metals  

Microsoft Academic Search

The electrical resistance of the heavy rare earth metals shows strong anomalies at the temperatures where the magnetic order changes. These are most marked in measurements made along the hexagonal axis. A simple theory of the effect is given on the basis of two mechanisms. The spiral spin structures found in these materials cause an exchange field at the conduction

R. J. Elliott; F. A. Wedgwood

1963-01-01

125

Substrate Profile and Metal-ion Selectivity of Human Divalent Metal-ion Transporter-1*  

PubMed Central

Divalent metal-ion transporter-1 (DMT1) is a H+-coupled metal-ion transporter that plays essential roles in iron homeostasis. DMT1 exhibits reactivity (based on evoked currents) with a broad range of metal ions; however, direct measurement of transport is lacking for many of its potential substrates. We performed a comprehensive substrate-profile analysis for human DMT1 expressed in RNA-injected Xenopus oocytes by using radiotracer assays and the continuous measurement of transport by fluorescence with the metal-sensitive PhenGreen SK fluorophore. We provide validation for the use of PhenGreen SK fluorescence quenching as a reporter of cellular metal-ion uptake. We determined metal-ion selectivity under fixed conditions using the voltage clamp. Radiotracer and continuous measurement of transport by fluorescence assays revealed that DMT1 mediates the transport of several metal ions that were ranked in selectivity by using the ratio Imax/K0.5 (determined from evoked currents at ?70 mV): Cd2+ > Fe2+ > Co2+, Mn2+ ? Zn2+, Ni2+, VO2+. DMT1 expression did not stimulate the transport of Cr2+, Cr3+, Cu+, Cu2+, Fe3+, Ga3+, Hg2+, or VO+. 55Fe2+ transport was competitively inhibited by Co2+ and Mn2+. Zn2+ only weakly inhibited 55Fe2+ transport. Our data reveal that DMT1 selects Fe2+ over its other physiological substrates and provides a basis for predicting the contribution of DMT1 to intestinal, nasal, and pulmonary absorption of metal ions and their cellular uptake in other tissues. Whereas DMT1 is a likely route of entry for the toxic heavy metal cadmium, and may serve the metabolism of cobalt, manganese, and vanadium, we predict that DMT1 should contribute little if at all to the absorption or uptake of zinc. The conclusion in previous reports that copper is a substrate of DMT1 is not supported. PMID:22736759

Illing, Anthony C.; Shawki, Ali; Cunningham, Christopher L.; Mackenzie, Bryan

2012-01-01

126

Where metal ions bind in proteins.  

PubMed Central

The environments of metal ions (Li+, Na+, K+, Ag+, Cs+, Mg2+, Ca2+, Mn2+, Cu2+, Zn2+) in proteins and other metal-host molecules have been examined. Regardless of the metal and its precise pattern of ligation to the protein, there is a common qualitative feature to the binding site: the metal is ligated by a shell of hydrophilic atomic groups (containing oxygen, nitrogen, or sulfur atoms) and this hydrophilic shell is embedded within a larger shell of hydrophobic atomic groups (containing carbon atoms). That is, metals bind at centers of high hydrophobicity contrast. This qualitative observation can be described analytically by the hydrophobicity contrast function, C, evaluated from the structure. This function is large and positive for a sphere of hydrophilic atomic groups (characterized by atomic solvation parameters, delta sigma, having values less than 0) at the center of a larger sphere of hydrophobic atomic groups (characterized by delta sigma greater than 0). In the 23 metal-binding molecules we have examined, the maximum values of the contrast function lie near to observed metal binding sites. This suggests that the hydrophobicity contrast function may be useful for locating, characterizing, and designing metal binding sites in proteins. PMID:2377604

Yamashita, M M; Wesson, L; Eisenman, G; Eisenberg, D

1990-01-01

127

High-current pulsed ion source for metallic ions  

SciTech Connect

A new sputter-ion PIG source and magnet system, optimized for intermediate charge states, q/A of 0.02 to 0.03, is described. This source will be used with the new Wideroe-based injector for the SuperHILAC. Pulsed electrical currents of several emA of heavy metal ions have been produced in a normalized emittance area of .05..pi.. cm-mr. The source system is comprised of two electrically separate anode chambers, one in operation and one spare, which can be selected by remote control. The entire source head is small and quickly removable.

Gavin, B.; Abbott, S.; MacGill, R.; Sorensen, R.; Staples, J.; Thatcher, R.

1981-03-01

128

Fulvic acid: modifier of metal-ion chemistry  

Microsoft Academic Search

Fulvic acid, which is derived from the decay of plants and animals, is being studied for its role in the transport and toxicity of metal ions in soil and water. It is discussed in relation to the origin of humic substances and its interactions with metal ions. Techniques for investigating complexes of fulvic acid and metal ions are presented. They

Robert A. Saar; James H. Weber

1982-01-01

129

Detection of Heavy Metal Ions in Drinking Water Using a  

E-print Network

Detection of Heavy Metal Ions in Drinking Water Using a High-Resolution Differential Surface-resolution differential surface plasmon resonance (SPR) sensor for heavy metal ion detection. The sensor surface using this sensor. Introduction The detection and quantification of heavy metal ions are important

Chen, Wilfred

130

Mobility of Alkaline Earth Ions in Liquid Xenon  

NASA Astrophysics Data System (ADS)

Mobility studies of ions in super fluid helium have revealed snowball and bubble formations in the surrounding liquid. Unfortunately, experimental results and theoretical predictions are scarce for the structure and mobility of ions in the other noble gas liquids. The mobility of alkaline earth ions in liquid Xe has been measured for the first time in a temperature range from 163 to 182 K. The mobility of Ba+, 0.000141(30) cm2/Vs at 170 K, is much lower than that of O2-. This possibly indicates different structures for Ba+ and O2- in liquid Xe: snowball and bubble, respectively. The Ba+ mobility measurements are motivated by our development of a new method to search for the neutrino mass, which will use laser tagging of single 136Ba+ daughter ions of double beta decay in liquid 136Xe.

Taylor, Wade; Jeng, Shie-Chang; Hall, Kendy; Fairbank, J. R.; Miyajima, Mitsuhiro

2003-05-01

131

Interplay of metal ions and urease  

PubMed Central

Summary Urease, the first enzyme to be crystallized, contains a dinuclear nickel metallocenter that catalyzes the decomposition of urea to produce ammonia, a reaction of great agricultural and medical importance. Several mechanisms of urease catalysis have been proposed on the basis of enzyme crystal structures, model complexes, and computational efforts, but the precise steps in catalysis and the requirement of nickel versus other metals remain unclear. Purified bacterial urease is partially activated via incubation with carbon dioxide plus nickel ions; however, in vitro activation also has been achieved with manganese and cobalt. In vivo activation of most ureases requires accessory proteins that function as nickel metallochaperones and GTP-dependent molecular chaperones or play other roles in the maturation process. In addition, some microorganisms control their levels of urease by metal ion-dependent regulatory mechanisms. PMID:20046957

Carter, Eric L.; Flugga, Nicholas; Boer, Jodi L.; Mulrooney, Scott B.; Hausinger, Robert P.

2009-01-01

132

Rare earth-transition metal scrap treatment method  

DOEpatents

Rare earth-transition metal (e.g. iron) scrap (e.g. Nd-Fe-B scrap) is melted to reduce the levels of tramp oxygen and nitrogen impurities therein. The tramp impurities are reduced in the melt by virtue of the reaction of the tramp impurities and the rare earth to form dross on the melt. The purified melt is separated from the dross for reuse. The oxygen and nitrogen of the melt are reduced to levels acceptable for reuse of the treated alloy in the manufacture of end-use articles, such as permanent magnets.

Schmidt, Frederick A. (Ames, IA); Peterson, David T. (Ames, IA); Wheelock, John T. (Nevada, IA); Jones, Lawrence L. (Des Moines, IA); Lincoln, Lanny P. (Woodward, IA)

1992-02-11

133

Valence, coordination number, and PAV cells in metallic rare earth compounds F. L. Carter  

E-print Network

Valence, coordination number, and PAV cells in metallic rare earth compounds F. L. Carter Naval, generalized coordination numbers, and Pauling's metallic valences are given for 24 intermetallic rare earth self-consistently it was necessary to increase the rare earth metal (/-character and hence decrease

Paris-Sud XI, Université de

134

Effects of Metal Ion Adduction on the Gas-Phase Conformations of Protein Ions  

PubMed Central

Changes in protein ion conformation as a result of nonspecific adduction of metal ions to the protein during electrospray ionization (ESI) from aqueous solutions were investigated using traveling wave ion mobility spectrometry (TWIMS). For all proteins examined, protein cations (and in most cases anions) with nonspecific metal ion adducts are more compact than the fully protonated (or deprotonated) ions with the same charge state. Compaction of protein cations upon nonspecific metal ion binding is most significant for intermediate charge state ions, and there is a greater reduction in collisional cross section with increasing number of metal ion adducts and increasing ion valency, consistent with an electrostatic interaction between the ions and the protein. Protein cations with the greatest number of adducted metal ions are no more compact than the lowest protonated ions formed from aqueous solutions. These results show that smaller collisional cross sections for metal-attached protein ions are not a good indicator of a specific metal-protein interaction in solution, because nonspecific metal ion adduction also results in smaller gaseous protein cation cross sections. In contrast, the collisional cross section of ?-lactalbumin, which specifically binds one Ca2+, is larger for the holo-form compared to the apo-form, in agreement with solution-phase measurements. Because compaction of protein cations occurs when metal ion adduction is nonspecific, elongation of a protein cation may be a more reliable indicator that a specific metal ion-protein interaction occurs in solution. PMID:23733259

Flick, Tawnya G.; Merenbloom, Samuel I.; Williams, Evan R.

2013-01-01

135

On the Metal Ion Selectivity of Oxoacid Extractants  

SciTech Connect

Relationships between metal chelate stability, ligand basicity, and metal ion acidity are reviewed and the general applicability is illustrated by linear correlations between aqueous stability constants and ligand pKa values for 35 metals with 26 ligands. The results confirm that most individual ligands of this type exhibit a stability ordering that correlates with the Lewis acidity of the metal ion. It is concluded that the general metal ion selectivity exhibited by liquid-liquid oxoacid extractants such as carboxylic acids, -diketones, and alkylphosphoric acids reflects the intrinsic affinity of the metal ion for the negative oxygen donor ligand.

Hay, Benjamin [ORNL; Chagnes, Alexandre [Chimie ParisTech; Cote, Gerard [Chimie ParisTech

2013-01-01

136

High-voltage contactless conductivity detection of metal ions in capillary electrophoresis.  

PubMed

The detection of alkali, alkaline earth and heavy metal ions with a high-voltage capacitively coupled contactless conductivity detector (HV-C(4)D) was investigated. Eight alkali, alkaline earth metal ions and ammonium could be separated in less than 4 min with detection limits in the order of 5 x 10(-8) M. The heavy metals Mn2+, Pb2+, Cd2+ Fe2+, Zn2+, Co2+, Cu2+ and Ni2+ could also be successfully resolved with a 10 mM 2-(N-morpholino)ethanesulfonic acid/DL-histidine (MES/His)-buffer. Zn2+, Co2+, Cu2+ and Ni2+ showed an indirect response. The detection limits for the heavy metals were determined to range from about 1 to 5 microM. PMID:12432541

Tanyanyiwa, Jatisai; Hauser, Peter C

2002-11-01

137

Analysis of metallic pigments by ion microbeam  

NASA Astrophysics Data System (ADS)

Metallic paints consist of metallic flakes dispersed in a resinous binder, i.e. a light-element polymer matrix. The spatial distribution and orientation of metallic flakes inside the matrix determines the covering efficiency of the paint, glossiness, and its angular-dependent properties such as lightness flop or color flop (two-tone). Such coatings are extensively used for a functional (i.e. security) as well as decorative purpose. The ion microbeam analysis of two types of silver paint with imbedded metallic flakes has been performed to determine the spatial distribution of the aluminum flakes in paint layer. The average sizes of the aluminum flakes were 23 ?m (size distribution 10-37) and 49 ?m (size distribution 34-75), respectively. The proton beam with the size of 2×2 ?m 2 at Ljubljana ion microprobe has been used to scan the surface of the pigments. PIXE mapping of Al K? map shows lateral distribution of the aluminum flakes, whereas the RBS slicing method reveals tomograms of the flakes in uppermost 7 ?m of the pigment layer. The series of point analysis aligned over the single flake reveal the flake angle in respect to the polymer matrix surface. The angular sensitivity is well below 1 angular degree.

Pelicon, P.; Klanjšek-Gunde, M.; Kunaver, M.; Sim?i?, J.; Budnar, M.

2002-05-01

138

Incorporation of metal ions into polyimides  

NASA Technical Reports Server (NTRS)

The effects of the incorporation of metal ions into various polyimides on polyimide properties are investigated. Polyimide films derived from 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride (BDTA) 3,3'-diaminobenzophenone (m,m'-DABP), 4,4'-diaminobenzophenone (p,p'-DABP) or 4,4'-oxydianiline were prepared with the concurrent addition of approximately 20 metals in a variety of forms. In general, it is found that the films derived from BDTA + p,p'-DABP were brittle and of poor quality, with brittle films also produced in most of the BDTA + m, m'-DABP polyimides regardless of whether the added metal was hydrate or anhydrous. Thermomechanical analysis, torsional braid analysis, thermal gravimetric analysis, infrared spectral analysis and isothermal studies on many of the polyimide films produced indicate that the softening temperature is generally increased upon the addition of metal ions, at the expense of thermal stability, while no changes in chemical functionality are observed. The best system studied in regard to polymer property enhancement appears to be tri(acetylacetonato)aluminum(III) added to the m, m'-DABP polyamide, which has been found to exhibit four times the lap shear strength of the polyimide alone.

Taylor, L. T.; Carver, V. C.; Furtsch, T. A.; Saint Clair, A. K.

1980-01-01

139

Ionic Liquids as Extraction Media for Metal Ions  

NASA Astrophysics Data System (ADS)

In solvent extraction separation of metal ions, recently, many researchers have investigated possible use of hydrophobic ionic liquids as extraction media instead of organic solvents. Ionic liquids are salts of liquid state around room temperature and can act not only as solvents but also as ion-exchangers. Therefore, the extraction mechanism of metal ions into ionic liquids is complicated. This review presents current overview and perspective on evaluation of nature of hydrophobic ionic liquids as extraction media for metal ions.

Hirayama, Naoki

140

Homometallic rare-Earth metal phosphinidene clusters: synthesis and reactivity.  

PubMed

Two new trinuclear ?3 -bridged rare-earth metal phosphinidene complexes, [{L(Ln)(?-Me)}3 (?3 -Me)(?3 -PPh)] (L=[PhC(NC6 H4 iPr2 -2,6)2 ](-) , Ln=Y (2?a), Lu (2?b)), were synthesized through methane elimination of the corresponding carbene precursors with phenylphosphine. Heating a toluene solution of 2 at 120?°C leads to an unprecedented ortho?C?H bond activation of the PhP ligand to form the bridged phosphinidene/phenyl complexes. Reactions of 2 with ketones, thione, or isothiocyanate show clear phospha-Wittig chemistry, giving the corresponding organic phosphinidenation products and oxide (sulfide) complexes. Reaction of 2 with CS2 leads to the formation of novel trinuclear rare-earth metal thione dianion clusters, for which a possible pathway was determined by DFT calculation. PMID:24311456

Wang, Kai; Luo, Gen; Hong, Jianquan; Zhou, Xigeng; Weng, Linhong; Luo, Yi; Zhang, Lixin

2014-01-20

141

Metal Ion Levels in Maternal and Placental Blood After Metal-on-Metal Total Hip Arthroplasty.  

PubMed

There is concern regarding elevated metal ion levels in the blood during pregnancy and the potential fetal effects in women with metal-on-metal (MOM) implants. We obtained maternal and umbilical cord blood samples from 3 patients with a MOM hip arthroplasty and 7 control subjects without any metallic implants. Serum metal ion levels including chromium, cobalt, titanium, and nickel were tested using high-resolution sector-field inductively-coupled plasma-mass spectrometry. Mothers with MOM-bearing implants had significantly elevated levels of serum cobalt and chromium compared with control-group mothers, and umbilical cord blood from mothers with MOM implants also had significantly higher serum metal ion levels compared with control-group mothers. The results of this study show that circulating serum levels of metal ion degradation products from MOM bearings cross the placenta and expose the fetus to metal ions. However, the placenta exerts a modulatory effect on cord blood, resulting in decreased levels compared with maternal samples (approximately 15% of maternal chromium and 50% of maternal cobalt). Physicians and women of child-bearing age should be aware of this potential effect when considering the use of MOM-bearing implants. PMID:25490017

Novak, Clifford C; Hsu, Andrew R; Della Valle, Craig J; Skipor, Anastasia K; Campbell, Patricia; Amstutz, Harlan C; Jiranek, William A; Onyike, Aham; Pombar, Xavier F; Jacobs, Joshua J

2014-12-01

142

Pentadienyl chemistry of the heavy alkaline-earth metals revisited.  

PubMed

Open-metallocenes of the heavy alkaline-earth metals [(?(5)-Pdl')2M(thf)n] (M = Ca (1), Sr (2), n = 1; M = Ba (3), n = 2; Pdl' = 2,4-tBu2C5H5) are readily prepared by salt-metathesis between MI2 and KPdl' and characterized by NMR spectroscopy and X-ray diffraction studies. PMID:24652227

Reiners, Matthias; Fecker, Ann Christin; Freytag, Matthias; Jones, Peter G; Walter, Marc D

2014-05-14

143

Ion acoustic solitons in Earth's upward current region  

SciTech Connect

The formation and evolution of ion acoustic solitons in Earth's auroral upward current region are studied using one- and two-dimensional (2D) electrostatic particle-in-cell simulations. The one-dimensional simulations are confined to processes that occur in the auroral cavity and include four plasma populations: hot electrons, H{sup +} and O{sup +} anti-earthward ion beams, and a hot H{sup +} background population. Ion acoustic solitons are found to form for auroral-cavity ion beams consistent with acceleration through double-layer (DL) potentials measured by FAST. A simplified one-dimensional model simulation is then presented in order to isolate the mechanisms that lead to the formation of the ion acoustic soliton. Results of a two-dimensional simulation, which include both the ionosphere and the auroral cavity, separated by a low-altitude DL, are then presented in order to confirm that the soliton forms in a more realistic 2D geometry. The 2D simulation is initialized with a U-shaped potential structure that mimics the inferred shape of the low altitude transition region based on observations. In this simulation, a soliton localized perpendicular to the geomagnetic field is observed to form and reside next to the DL. Finally, the 2D simulation results are compared with FAST data and it is found that certain aspects of the data can be explained by assuming the presence of an ion acoustic soliton.

Main, D. S.; Scholz, C. [Department of Physics, John Brown University, Siloam Springs, Arkansas 72761 (United States); Newman, D. L. [Center for Integrated Plasma Studies, University of Colorado, Boulder, Colorado 80309 (United States); Ergun, R. E. [Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, Colorado 80303 (United States)

2012-07-15

144

Metal cation binding to gas-phase pentaalanine: divalent ions restructure the complex.  

PubMed

Ion-neutral complexes of pentaalalanine with several singly- and doubly charged metal ions are examined using conformation analysis by infrared multiple photon dissociation (IRMPD) spectroscopy and density functional theory (DFT) computations. The infrared spectroscopy in the 1500-1800 cm(-1) region is found to be conformationally informative; in particular, the frequency of the C?O stretching mode of the terminal carboxyl group is diagnostic for hydrogen bonding of the terminal hydroxyl. The doubly charged alkaline earth metal ions (Ca(2+) and Ba(2+)) enforce a highly structured chelation shell around the metal ion, with six strongly bound Lewis-basic chelation sites, and no hydroxyl hydrogen bonding. With the more weakly binding alkali metal ions (Na(+), K(+), and Cs(+)), structures with intramolecular hydrogen bonds are more favorable, leading to dominance of conformations with lower degrees of metal ion chelation. The favored coordination mode correlates with ionic charge and binding strength but is not related to the ionic radius of the metal ion. PMID:22928606

Dunbar, Robert C; Steill, Jeffrey D; Polfer, Nicolas C; Oomens, Jos

2013-02-14

145

Lightweight electroconductive solderless internal cell connector for alkaline or alkaline earth metal batteries  

SciTech Connect

This patent describes a combination with an alkaline metal or alkaline earth metal battery a lightweight solderless connector for internal battery electrical connection. It comprises a core of alkaline metal or alkaline earth metal, an outer electrically insulating covering on the core, the outer covering having an adhesive coating thereon in contact with the core.

Hope, H.F.; Hope, S.F.

1991-10-01

146

Observation of a rare earth ion-extractant complex arrested at the oil-water interface during solvent extraction.  

PubMed

Selective extraction of metal ions from a complex aqueous mixture into an organic phase is used to separate toxic or radioactive metals from polluted environments and nuclear waste, as well as to produce industrially relevant metals, such as rare earth ions. Selectivity arises from the choice of an extractant amphiphile, dissolved in the organic phase, which interacts preferentially with the target metal ion. The extractant-mediated process of ion transport from an aqueous to an organic phase takes place at the aqueous-organic interface; nevertheless, little is known about the molecular mechanism of this process despite its importance. Although state-of-the-art X-ray scattering is uniquely capable of probing molecular ordering at a liquid-liquid interface with subnanometer spatial resolution, utilizing this capability to investigate interfacial dynamical processes of short temporal duration remains a challenge. We show that a temperature-driven adsorption transition can be used to turn the extraction on and off by controlling adsorption and desorption of extractants at the oil-water interface. Lowering the temperature through this transition immobilizes a supramolecular ion-extractant complex at the interface during the extraction of rare earth erbium ions. Under the conditions of these experiments, the ion-extractant complexes condense into a two-dimensional inverted bilayer, which is characterized on the molecular scale with synchrotron X-ray reflectivity and fluorescence measurements. Raising the temperature above the transition leads to Er ion extraction as a result of desorption of ion-extractant complexes from the interface into the bulk organic phase. XAFS measurements of the ion-extractant complexes in the bulk organic phase demonstrate that they are similar to the interfacial complexes. PMID:25134605

Bu, Wei; Yu, Hao; Luo, Guangming; Bera, Mrinal K; Hou, Binyang; Schuman, Adam W; Lin, Binhua; Meron, Mati; Kuzmenko, Ivan; Antonio, Mark R; Soderholm, L; Schlossman, Mark L

2014-09-11

147

Accumulation of metal ions by pectinates  

NASA Astrophysics Data System (ADS)

The knowledge of the mechanisms which regulate the interactions of metal ions with partially methyl esterified linear polymers of ?-1,4 linked D-galacturonic acid units (pectinates), well represented in the root inner and outer apoplasm, is of great relevance to understand the processes which control their accumulation at the soil-root interface as well as their mobilization by plant metabolites. Accumulation of a metal by pectinates can be affected by the presence of other metals so that competition or distribution could be expected depending on the similar or different affinity of the metal ions towards the binding sites, mainly represented by the carboxylate groups. In order to better understand the mechanism of accumulation in the apoplasm of several metal ions, the sorption of Cd(II), Zn(II), Cu(II), Pb(II) and Cr(III) by a Ca-polygalacturonate gel, used as model of the soil-root interface, with a degree of esterification of 18% (PGAE1) and 65% (PGAE2) was studied at pH 3.0, 4.0, 5.0 and 6.0 in the presence of CaCl2 2.5 mM.. The results show that sorption increases with increasing both the initial metal concentration and pH. A similar sorption trend was evidenced for Cu(II) and Pb(II) and for Zn(II) and Cd(II), indicating that the mechanism of sorption for these two ionic couples is quite different. As an example, at pH 6.0 and an initial metal concentration equal to 2.0 mM, the amount of Cu(II) and Pb(II) sorbed was about 1.98 mg-1 of PGAE1 while that of Cd(II) and Zn(II) was about 1.2 mg-1. Cr(III) showed a rather different sorption trend and a much higher amount (2.8 mg-1of PGAE1 at pH 6.0) was recorded. The higher affinity of Cr(III) for the polysaccharidic matrix is attributable to the formation of Cr(III) polynuclear species in solution, as shown by the distribution diagrams obtained through the MEDUSA software. On the basis of these findings, the following affinity towards the PGAE1 can be assessed: Cr(III) > Cu(II) ? Pb(II) > Zn (II) ? Cd(II). Surprisingly, simultaneous sorption tests and SEM analyses indicate that a different mechanism regulates the sorption of Cu(II) and Pb(II) by PGAE1. In fact, the amount of Pb(II) sorbed (0.92 moles mg-1of PGAE1) by PGAE1 was nearly independent by the presence of Cu(II) ions, at least at the three different concentrations tested, that indicates a higher affinity of Pb(II). Such an aspect was further confirmed by exchange experiments. Samples of PGAE1 saturated with 1.96 moles mg-1of Cu(II) or 2.01 moles mg-1of Pb(II) were put in contact with 100 mL of solutions containing 97.3 moles of Pb(II) or 99.4 moles Cu(II), respectively. The exchange kinetics show that about 80% of Cu(II) was stochiometrically exchanged by Pb(II). In contrast, only about 10% of Pb(II) complexed by PGAE1 was exchanged by Cu(II). The kinetics of simultaneous sorption of all the metal ions tested indicate that Pb(II) is selectively sorbed by the PGAE1 gels. Cd(II) and Zn(II) show a similar affinity towards PGAE1. Thus, in the simultaneous presence of these ions, their selectivity towards this matrix follows the order: Pb > Cu > Cd ? Zn. Sorption of Cr(III) in the presence of the ions considered was not possible to carry out due to interference phenomena. The sorption of the same ions by 50 mg of PGAE2 evidences that the amount of Cu(II), Pb(II), and Cr(III) sorbed is markedly lower than that found for PGAE1. By considering that two carboxylic groups are involved in the complexation of a metal ion, the data show that such a stoichiometry is respected only for Pb(II). The amount of Cu(II) sorbed is about 50% lower than that of Pb(II) at all the pH values tested whereas those of Zn(II) and Cd(II) are negligible whereas that of Cr(III) is the highest. The different behaviour of Cu(II) compared to Pb(II) can be explained taking into account for both hydrophobic and steric effects of the methyl groups as well as to their different charge density. Thus, it can be concluded that the accumulation of metals at the soil-root interface strictly depends on the esterification degree of the root p

Deiana, S.; Deiana, L.; Palma, A.; Premoli, A.; Senette, C.

2009-04-01

148

'Pseudotumour' invading the proximal femur with normal metal ions following metal on metal hip resurfacing.  

PubMed

A 75-year-old woman who had undergone hybrid metal-on-metal hip resurfacing 8?years earlier underwent revision arthroplasty because of hip, groin and lateral thigh pain. The main differential was aseptic loosening; however, serum cobalt and chromium levels were normal. Multiple imaging modalities revealed a periprosthetic, cystic soft tissue mass adjacent to the proximal femur. A large 'pseudotumour' with proximal femoral invasion was found at revision arthroplasty. We report the first finding of a 'pseudotumour' invading the proximal femur with normal metal ions following metal on metal hip resurfacing. PMID:25670783

Krishnan, Harry; Sugand, Kapil; Ali, Ibrahim; Smith, Jay

2015-01-01

149

Metal-ion rescue revisited: Biochemical detection of site-bound metal ions important for RNA folding  

PubMed Central

Within the three-dimensional architectures of RNA molecules, divalent metal ions populate specific locations, shedding their water molecules to form chelates. These interactions help the RNA adopt and maintain specific conformations and frequently make essential contributions to function. Defining the locations of these site-bound metal ions remains challenging despite the growing database of RNA structures. Metal-ion rescue experiments have provided a powerful approach to identify and distinguish catalytic metal ions within RNA active sites, but the ability of such experiments to identify metal ions that contribute to tertiary structure acquisition and structural stability is less developed and has been challenged. Herein, we use the well-defined P4–P6 RNA domain of the Tetrahymena group I intron to reevaluate prior evidence against the discriminatory power of metal-ion rescue experiments and to advance thermodynamic descriptions necessary for interpreting these experiments. The approach successfully identifies ligands within the RNA that occupy the inner coordination sphere of divalent metal ions and distinguishes them from ligands that occupy the outer coordination sphere. Our results underscore the importance of obtaining complete folding isotherms and establishing and evaluating thermodynamic models in order to draw conclusions from metal-ion rescue experiments. These results establish metal-ion rescue as a rigorous tool for identifying and dissecting energetically important metal-ion interactions in RNAs that are noncatalytic but critical for RNA tertiary structure. PMID:22539523

Frederiksen, John K.; Li, Nan-Sheng; Das, Rhiju; Herschlag, Daniel; Piccirilli, Joseph A.

2012-01-01

150

Magnetism of the rare earth, 3d --Theoretical review Abstract. --Compounds of rare earth and transition metals exhibit unusual and quite different behaviour. In  

E-print Network

and secondly those determined mainly by rare earth metals. The first group are those rich in transition metal except TCo2, TNi5, T2Ni7, TNi3, TNi2. When the transition metal is magnetic, the coupling between rare-earth temperature are much smaller, and magnetic properties bear resemblances with rare earth metals. Thus we

Paris-Sud XI, Université de

151

Behavior of metal ions in bioelectrochemical systems: A review  

NASA Astrophysics Data System (ADS)

Bioelectrochemical systems (BESs) have been focused on by many researchers to treat wastewater and recover energy or valuable chemicals from wastes. In BESs, metal ions play an important role in the conductivity of solution, reactors' internal resistance, power generation, chemical production and activity of microorganisms. Additionally, the metal ions are also involved in anodic or cathodic reaction processes directly or indirectly in BESs. This paper reviews the behavior of metal ions in BESs, including (1) increase of the conductivity of electrolyte and decrease of internal resistance, (2) transfer for desalination, (3) enhancement or inhibition of the biocatalysis in anode, (4) improvement of cathodic performance by metal ions through electron acceptance or catalysis in cathodic process and (5) behavior of metal ions on membranes. Moreover, the perspectives of BESs removing heavy metal ions in wastewater or solid waste are discussed to realize recovery, reduction and detoxification simultaneously.

Lu, Zhihao; Chang, Dingming; Ma, Jingxing; Huang, Guangtuan; Cai, Lankun; Zhang, Lehua

2015-02-01

152

Separation of rare earths from transition metals by liquid-liquid extraction from a molten salt hydrate to an ionic liquid phase.  

PubMed

The solvent extraction of trivalent rare-earth ions and their separation from divalent transition metal ions using molten salt hydrates as the feed phase and an undiluted fluorine-free ionic liquid as the extracting phase were investigated in detail. The extractant was tricaprylmethylammonium nitrate, [A336][NO3], and the hydrated melt was calcium nitrate tetrahydrate, Ca(NO3)2·4H2O. The extraction behavior of rare-earth ions was studied for solutions of individual elements, as well as for mixtures of rare earths in the hydrated melt. The influence of different extraction parameters was investigated: the initial metal loading in the feed phase, percentage of water in the feed solution, equilibration time, and the type of hydrated melt. The extraction of rare earths from Ca(NO3)2·4H2O was compared with extraction from CaCl2·4H2O by [A336][Cl] (Aliquat 336). The nitrate system was found to be the better one. The extraction and separation of rare earths from the transition metals nickel, cobalt and zinc were also investigated. Remarkably high separation factors of rare-earth ions over transition metal ions were observed for extraction from Ca(NO3)2·4H2O by the [A336][NO3] extracting phase. Furthermore, rare-earth ions could be separated efficiently from transition metal ions, even in melts with very high concentrations of transition metal ions. Rare-earth oxides could be directly dissolved in the Ca(NO3)2·4H2O phase in the presence of small amounts of Al(NO3)3·9H2O or concentrated nitric acid. The efficiency of extraction after dissolving the rare-earth oxides in the hydrated nitrate melt was identical to extraction from solutions with rare-earth nitrates dissolved in the molten phase. The stripping of the rare-earth ions from the loaded ionic liquid phase and the reuse of the recycled ionic liquid were also investigated in detail. PMID:24352299

Rout, Alok; Binnemans, Koen

2014-02-28

153

Half-metallic to insulating behavior of rare-earth nitrides C. M. Aerts,1  

E-print Network

Half-metallic to insulating behavior of rare-earth nitrides C. M. Aerts,1 P. Strange,1 M. Horne,1 W in the literature that rare-earth nitrides may form half-metallic ferromagnets.6­8 This is sur- prising because 30 January 2004 The electronic structure of the rare-earth nitrides is studied systematically using

Svane, Axel Torstein

154

Separation of traces of metal ions from sodium matrices  

NASA Technical Reports Server (NTRS)

Method for isolating metal ion traces from sodium matrices consists of two extractions and an ion exchange step. Extraction is accomplished by using 2-thenoyltrifluoracetone and dithizone followed by cation exchange.

Korkisch, J.; Orlandini, K. A.

1969-01-01

155

Alkaline and alkaline earth metal phosphate halides and phosphors  

SciTech Connect

Compounds, phosphor materials and apparatus related to nacaphite family of materials are presented. Potassium and rubidium based nacaphite family compounds and phosphors designed by doping divalent rare earth elements in the sites of alkaline earth metals in the nacaphite material families are descried. An apparatus comprising the phosphors based on the nacaphite family materials are presented herein. The compounds presented is of formula A.sub.2B.sub.1-yR.sub.yPO.sub.4X where the elements A, B, R, X and suffix y are defined such that A is potassium, rubidium, or a combination of potassium and rubidium and B is calcium, strontium, barium, or a combination of any of calcium, strontium and barium. X is fluorine, chlorine, or a combination of fluorine and chlorine, R is europium, samarium, ytterbium, or a combination of any of europium, samarium, and ytterbium, and y ranges from 0 to about 0.1.

Lyons, Robert Joseph; Setlur, Anant Achyut; Cleaver, Robert John

2012-11-13

156

METALLIC HYDRIDES. Magnetic properties of laves-phase rare earth hydrides  

E-print Network

METALLIC HYDRIDES. Magnetic properties of laves-phase rare earth hydrides J. J. Rhyne and G. E on the rare earth site. The rare earth spins disorder at a temperature lower than the bulk Tc in ErFe2 H3 5 per formula unit assuming complete occupation of 3 tetrahedral sites. The heavy rare earth (RFe2

Boyer, Edmond

157

Magnetism of perovskite cobaltites with Kramers rare-earth ions  

SciTech Connect

The band-gap insulators RECoO{sub 3} (RE?=?Nd{sup 3+}, Sm{sup 3+}, and Dy{sup 3+}) with Co{sup 3+} ions stabilized in the non-magnetic low-spin state have been investigated by specific heat measurements. The experiments evidence an antiferromagnetic ordering of the rare earths with Néel temperature of T{sub N}?=?1.25, 1.50, and 3.60?K for NdCoO{sub 3}, SmCoO{sub 3}, and DyCoO{sub 3}, respectively. With increasing external field, the lambda peak in specific heat, indicative of the transition, shifts to lower temperatures and vanishes for field of about 3?T. Starting from this point, a broader Schottky peak is formed, centered in 1?K range, and its position is moved to higher temperatures proportionally to applied field. The origin of the peak is in Zeeman splitting of the ground Kramers doublet, and the gradual shift with field defines effective g-factors for the rare-earth pseudospins in studied compounds. The results obtained are confronted with the calculations of crystal field splitting of the rare-earth multiplets.

Jirák, Z., E-mail: jirak@fzu.cz; Hejtmánek, J.; Knížek, K.; Novák, P.; Šantavá, E. [Institute of Physics ASCR, Cukrovarnická 10, 162 00 Prague 6 (Czech Republic); Fujishiro, H. [Faculty of Engineering, Iwate University, Morioka 020-8551 (Japan)

2014-05-07

158

Effect of rare earth metal oxide additions to tungsten electrodes  

Microsoft Academic Search

A comparative study has been made on the operating characteristics of gas-tungsten arc (GTA) welding for several types of\\u000a electrodes. The work was carried out with a pure tungsten electrode and tungsten electrodes activated with a small quantity\\u000a of the rare earth metal oxides, La2O3, Y2O3, CeO2, and with ZrO2, ThO2, and MgO. Their behaviors during arcing were analyzed and

Alber A. Sadek; Masao Ushio; Fukuhisa Matsuda

1990-01-01

159

Molten metal containment vessel with rare earth oxysulfide protective coating thereon and method of making same  

DOEpatents

An improved molten metal containment vessel is disclosed in which wetting of the vessel's inner wall surfaces by molten metal is inhibited by coating at least the inner surfaces of the containment vessel with one or more rare earth oxysulfide or rare earth sulfide compounds to inhibit wetting and or adherence by the molten metal to the surfaces of the containment vessel.

Krikorian, Oscar H. (Danville, CA); Curtis, Paul G. (Tracy, CA)

1992-01-01

160

A biosystem for removal of metal ions from water  

SciTech Connect

The presence of heavy metal ions in ground and surface waters constitutes a potential health risk and is an environmental concern. Moreover, processes for the recovery of valuable metal ions are of interest. Bioaccumulation or biosorption is not only a factor in assessing the environmental risk posed by metal ions; it can also be used as a means of decontamination. A biological system for the removal and recovery of metal ions from contaminated water is reported here. Exopolysaccharide-producing microorganisms, including a methanotrophic culture, are demonstrated to have superior metal binding ability, compared with other microbial cultures. This paper describes a biosorption process in which dried biomass obtained from exopolysaccharide-producing microorganisms is encapsulated in porous plastic beads and is used for metal ion binding and recovery. 22 refs., 13 figs.

Kilbane, J.J. II.

1990-01-01

161

The possible role of metal ions and clays in prebiotic chemistry  

NASA Technical Reports Server (NTRS)

Eight homoionic bentonites were prepared using alkali, alkaline earth, and transition metal ions as counterions. The interaction of the clays with 5'-AMP was studied and it was found that the alkali metal-substituted clays did not remove any nucleotide from dilute solution, and that zinc-bentonite adsorbed the most (98%). In addition, study of the interaction of seven other nucleotides with zinc-bentonite showed that the purine nucleotides were more strongly absorbed than the pyrimidine nucleotides. Langmuir isotherms were obtained for these systems and the adsorption data were explained by the adsorption coefficient and the accessibility of metal for binding.

Lawless, J. G.; Edelson, E. H.

1980-01-01

162

Plasma immersion ion implantation for reducing metal ion release  

SciTech Connect

Plasma immersion ion implantation of Nitrogen and Oxygen on CoCrMo alloys was carried out to improve the tribological and corrosion behaviors of these biomedical alloys. In order to optimize the implantation results we were carried experiments at different temperatures. Tribocorrosion tests in bovine serum were used to measure Co, Cr and Mo releasing by using Inductively Coupled Plasma Mass Spectrometry analysis after tests. Also, X-ray Diffraction analysis were employed in order to explain any obtained difference in wear rate and corrosion tests. Wear tests reveals important decreases in rate of more than one order of magnitude for the best treatment. Moreover decreases in metal release were found for all the implanted samples, preserving the same corrosion resistance of the unimplanted samples. Finally this paper gathers an analysis, in terms of implantation parameters and achieved properties for industrial implementation of these treatments.

Diaz, C.; Garcia, J. A.; Maendl, S.; Pereiro, R.; Fernandez, B.; Rodriguez, R. J. [Centro de Ingenieria Avanzada de Superficies AIN, 31191, Cordovilla-Pamplona (Spain); Leibniz-Institut fuer Oberflaechenmodifizierung, 04318 Leipzig (Germany); Universidad de Oviedo, Departamento Quimica Fisica y Analitica (Spain); Centro de Ingenieria Avanzada de Superficies AIN, 31191, Cordovilla-Pamplona (Spain)

2012-11-06

163

Reduction Chemistry of Rare-Earth Metal Complexes: Toward New Reactivity and Properties.  

E-print Network

??Rare-earths are a group of metals with fascinating physical properties and intriguing chemical reactivity. Organometallic rare-earth chemistry is of particular interest because of the increasing… (more)

Huang, Wenliang

2013-01-01

164

Bimetallic cleavage of aromatic C-h bonds by rare-Earth-metal complexes.  

PubMed

A new type of C-H bond activation mediated by rare-earth metals under reducing conditions is reported. The synergy between reductants and rare-earth-metal complexes allows the cleavage of unactivated aromatic C-H bonds. The reaction between rare-earth-metal iodides supported by a 1,1'-ferrocenediamide ligand and potassium graphite in benzene leads to the formation of a 1:1 metal molar ratio of the corresponding metal hydride and metal phenyl complex. A proposed mechanism involving an inverse sandwich arene bimetallic intermediate is supported by experimental and computational studies. PMID:25431837

Huang, Wenliang; Dulong, Florian; Khan, Saeed I; Cantat, Thibault; Diaconescu, Paula L

2014-12-17

165

Origins of energetic ions in the Earth's magnetosheath  

NASA Technical Reports Server (NTRS)

The analysis and interpretation of the combined scientific data from the Hot Plasma Composition Experiment (HPCE) and the Charge Energy Mass (CHEM) spectrometer on the Active Mesospheric Particle Tracer Experiment (AMPTE) Charge Composition Explorer (CCE) spacecraft are discussed. These combined data sets have and will be used to survey the energetic ion environment in the Earth's magnetosheath to determine the origins and relative strengths of the energetic ion populations found there. A computer code was developed to analyze and interpret the data sets. The focus of the first year was on the determination of the contribution of leaked magnetospheric protons to the total energetic proton population. Emphasis was placed on intervals when the AMPTE spacecraft was in the plasma depletion layer because it was argued that in this region, only the leaked population contributes to the energetic ion population. Manipulation of the CHEM data and comparison of the CHEM and HPCE data over their common energy range near the magnetopause also contributed directly to a second study of that region.

Fuselter, S. A.; Shelley, E. G.; Klumpar, D. M.

1992-01-01

166

Molecular Rare-Earth-Metal Hydrides in Non-Cyclopentadienyl Environments.  

PubMed

Molecular hydrides of the rare-earth metals play an important role as homogeneous catalysts and as counterparts of solid-state interstitial hydrides. Structurally well-characterized non-metallocene-type hydride complexes allow the study of elementary reactions that occur at rare-earth-metal centers and of catalytic reactions involving bonds between rare-earth metals and hydrides. In addition to neutral hydrides, cationic derivatives have now become available. PMID:25413985

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

2014-11-20

167

Improvements in estimated entropies and related thermodynamic data for aqueous metal ions.  

PubMed

New estimated standard entropies for some aqueous metal ions are obtained by taking account of magnetic and symmetry contributions. By combining them with an analysis of literature data, improved experimental and estimated values are derived for the standard enthalpies and Gibbs energies of formation of the aqueous ions of titanium, vanadium, chromium, manganese, cerium, and praseodymium. Separate entropy correlations are used for each primary coordination number, and the size dependence is represented by the reciprocal of the metal-oxygen distance in that coordination. The new scheme is consistent with recent work on the coordination of Hg(2+)(aq), Pb(2+)(aq), and tripositive rare earth ions. It differs from its predecessors in indicating a larger variation of the standard molar entropies of aqueous ions with coordination number. The value of S(?)(Be(2+), aq) is discussed in this context. PMID:22621251

Johnson, David A; Nelson, Peter G

2012-06-01

168

The Transport of Solar Ions Through the Earth's Magnetosphere  

NASA Technical Reports Server (NTRS)

This report covers the initial phase of an investigation that was originally selected by NASA Headquarters for funding by a grant but was later transferred to NASA GSFC for continued funding under a new and separate contract. The principal objective of the investigation, led by Dr. O.W. Lennartsson, is to extract information about the solar origin plasma in Earth's magnetosphere, specifically about the entry and transport of this plasma, using energetic (10 eV/e to 18 keV/e) ion composition data from the Lockheed Plasma Composition Experiment on the NASA/ESA International Sun-Earth Explorer One (ISEE 1) satellite. These data were acquired many years ago, from November 1977 through March of 1982, but, because of subsequent failures of similar experiments on several other spacecraft, they are still the only substantial ion composition data available from Earth's magnetotail, beyond 10 R(sub E), in the critically important sub-kev to keV energy range. All of the Lockheed data now exist in a compacted scientific format, suitable for large-scale statistical investigations, which has been archived both at Lockheed Martin in Palo Alto and at the National Space Science Data Center (NSSDC) in Greenbelt. The completion of the archiving, by processing the remaining half of the data, was made possible by separate funding through a temporary NASA program for data restoration and was given priority over the data analysis by a no-cost extension of the subject grant. By chance, the period of performance coincided with an international study of source and loss processes of magnetospheric plasma, sponsored by the International Space Science Institute (ISSI) in Bern, Switzerland, for which Dr. Lennartsson was invited to serve as one of 12 co-chairs. This study meshed well with the continued analysis of the NASA/Lockheed ISEE ion composition data and provided a natural forum for a broader discussion of the results from this unique experiment. What follows is arranged, for the most part, in the context of the ISSI project.

Lennartsson, O. W.

1999-01-01

169

Boon and Bane of Metal Ions in Medicine  

Microsoft Academic Search

In biological systems metal ions promote responses that range from deficiency to toxicity. Some, such as iron and zinc, have a known optimal intake range for normal, healthy individuals. Metal ions contained within well-designed molecules already constitute a great boon for the medicinal pharmacopoeia. However, whether essential or not, the threshold for toxicity can be very low. One of the

Katherine H. Thompson; Chris Orvig

2003-01-01

170

Metal Ions: Supporting Actors in the Playbook of Small Ribozymes  

E-print Network

of large ribonucleoprotein complexes, many ribozymes can support catalysis without protein cofactors [16 Metal Ions: Supporting Actors in the Playbook of Small Ribozymes Alexander E. Johnson-Buck, Sarah 1. INTRODUCTION 176 2. INTERACTIONS BETWEEN METAL IONS AND SMALL RIBOZYMES 178 2.1. Modes

Walter, Nils G.

171

Oxidative mechanisms in the toxicity of metal ions.  

PubMed

The role of reactive oxygen species, with the subsequent oxidative deterioration of biological macromolecules in the toxicities associated with transition metal ions, is reviewed. Recent studies have shown that metals, including iron, copper, chromium, and vanadium undergo redox cycling, while cadmium, mercury, and nickel, as well as lead, deplete glutathione and protein-bound sulfhydryl groups, resulting in the production of reactive oxygen species as superoxide ion, hydrogen peroxide, and hydroxyl radical. As a consequence, enhanced lipid peroxidation. DNA damage, and altered calcium and sulfhydryl homeostasis occur. Fenton-like reactions may be commonly associated with most membranous fractions including mitochondria, microsomes, and peroxisomes. Phagocytic cells may be another important source of reactive oxygen species in response to metal ions. Furthermore, various studies have suggested that the ability to generate reactive oxygen species by redox cycling quinones and related compounds may require metal ions. Recent studies have suggested that metal ions may enhance the production of tumor necrosis factor alpha (TNF alpha) and activate protein kinase C, as well as induce the production of stress proteins. Thus, some mechanisms associated with the toxicities of metal ions are very similar to the effects produced by many organic xenobiotics. Specific differences in the toxicities of metal ions may be related to differences in solubilities, absorbability, transport, chemical reactivity, and the complexes that are formed within the body. This review summarizes current studies that have been conducted with transition metal ions as well as lead, regarding the production of reactive oxygen species and oxidative tissue damage. PMID:7744317

Stohs, S J; Bagchi, D

1995-02-01

172

Electron Capture Dissociation of Trivalent Metal Ion-Peptide Complexes  

PubMed Central

With electrospray ionization from aqueous solutions, trivalent metal ions readily adduct to small peptides resulting in formation of predominantly (peptide + MT – H)2+, where MT = La, Tm, Lu, Sm, Ho, Yb, Pm, Tb, or Eu, for peptides with molecular weights below ~1000 Da, and predominantly (peptide + MT)3+ for larger peptides. ECD of (peptide + MT – H)2+ results in extensive fragmentation from which nearly complete sequence information can be obtained, even for peptides for which only singly protonated ions are formed in the absence of the metal ions. ECD of these doubly charged complexes containing MT results in significantly higher electron capture efficiency and sequence coverage than peptide-divalent metal ion complexes that have the same net charge. Formation of salt-bridge structures in which the metal ion coordinates to a carboxylate group are favored even for (peptide + MT)3+. ECD of these latter complexes for large peptides results in electron capture by the protonation site located remotely from the metal ion and predominantly c/z fragments for all metals, except Eu3+, which undergoes a one electron reduction and only loss of small neutral molecules and b/y fragments are formed. These results indicate that solvation of the metal ion in these complexes is extensive, resulting in similar electrochemical properties of these metal ions both in the peptide environment and in water. PMID:23283726

Flick, Tawnya G.; Donald, William A.; Williams, Evan R.

2013-01-01

173

Distributions of rare earths and heavy metals in field-grown maize after application of rare earth-containing fertilizer  

Microsoft Academic Search

Rare earths are widely applied in Chinese agriculture to improve crop nutrition through the use of fertilizers, yet little is known of their accumulation in field-grown crops. We have studied the distribution of 16 rare earths (Sc, Y and 14 lanthanide elements) in field-grown maize and the concentration of heavy metals in the grains after application of rare earth-containing fertilizer.

Xingkai Xu; Wangzhao Zhu; Zijian Wang; Geert-Jan Witkamp

2002-01-01

174

Distributions of rare earths and heavy metals in field-grown maize after application of rare earth-containing fertilizer.  

PubMed

Rare earths are widely applied in Chinese agriculture to improve crop nutrition through the use of fertilizers, yet little is known of their accumulation in field-grown crops. We have studied the distribution of 16 rare earths (Sc, Y and 14 lanthanide elements) in field-grown maize and the concentration of heavy metals in the grains after application of rare earth-containing fertilizer. When maize entered the vigorous vegetation growth stage (e.g. early stem-elongation stage), rare earth-containing fertilizer was applied to the soil with irrigation water. At 10 days after application of the rare earths, significantly dose-dependent accumulative effects of individual rare earth concentrations in the roots and the plant tops of maize were observed, with the exception of Sc and Lu. At the level of 2 kg rare earths ha(-1), accumulative concentrations of most light rare earths (e.g. La, Ce, Pr and Nd) and Gd in the plant tops were much larger than those in the control. Concentrations of individual rare earths in a field-grown maize after application of rare earths decreased in the order of root>leaf>stem>grain. During the maize growth period, selective accumulation of individual rare earths (e.g. La, Ce) in the roots seemed to be in dynamic equilibrium, and the distribution of these elements in the plant tops was variable. At a dosage of less than 10 kg rare earths ha(-1), no apparent accumulative concentrations of individual rare earths appeared in the maize grains. Under the experimental conditions, application of rare earth-containing fertilizer did not induce an increase in the concentrations of heavy metals in the grains. We conclude that the present dosage of rare earths (<0.23 kg ha(-1) year(-1)) currently applied in China can hardly affect the safety of maize grains in arable soil, even over a long period. PMID:12109484

Xu, Xingkai; Zhu, Wangzhao; Wang, Zijian; Witkamp, Geert-Jan

2002-07-01

175

Saturation magnetic moments, magnetic hyperfine fields and electric field gradients at nuclei in the heavy rare earth metals  

Microsoft Academic Search

The contributions of 4f, 5d and 6s electrons to the saturation magnetic moments and magnetic hyperfine fields in the heavy rare earth metals are calculated using the model described in the previous paper. It is found that 4f shell moments are reduced from their free ion values by amounts varying from 0.05µB in Gd to several tenths of a Bohr

D. M. Eagles

1975-01-01

176

Existence of efficient divalent metal ion-catalyzed and inefficient divalent metal ion-independent channels in reactions catalyzed by a hammerhead ribozyme  

Microsoft Academic Search

The hammerhead ribozyme is generally accepted as a well characterized metalloenzyme. However, the precise nature of the interactions of the RNA with metal ions remains to be fully defined. Examination of metal ion-catalyzed hammerhead reactions at limited concentrations of metal ions is useful for evaluation of the role of metal ions, as demonstrated in this study. At concentrations of Mn2+

Jing-Min Zhou; De-Min Zhou; Yasuomi Takagi; Yasuhiro Kasai; Atsushi Inoue; Tadashi Baba; Kazunari Taira

2002-01-01

177

Metal Ion Sensors Based on DNAzymes and Related DNA Molecules  

PubMed Central

Metal ion sensors are an important yet challenging field in analytical chemistry. Despite much effort, only a limited number of metal ion sensors are available for practical use because sensor design is often a trial-and-error-dependent process. DNAzyme-based sensors, in contrast, can be developed through a systematic selection that is generalizable for a wide range of metal ions. Here, we summarize recent progress in the design of DNAzyme-based fluorescent, colorimetric, and electrochemical sensors for metal ions, such as Pb2+, Cu2+, Hg2+, and UO22+ In addition, we also describe metal ion sensors based on related DNA molecules, including T-T or C-C mismatches and G-quadruplexes. PMID:21370984

Kong, Rong-Mei

2011-01-01

178

Fulvic acid: modifier of metal-ion chemistry  

SciTech Connect

Fulvic acid, which is derived from the decay of plants and animals, is being studied for its role in the transport and toxicity of metal ions in soil and water. It is discussed in relation to the origin of humic substances and its interactions with metal ions. Techniques for investigating complexes of fulvic acid and metal ions are presented. They are separation and nonseparation analyses which are applied to speciation problems. The applicability, advantages, and disadvantages of both methods are presented. Separation of free and complexed metal ions can be done by chromatography, or with membranes that exclude the metal-ion complexes. Chromatographic techniques include liquid chromatography by size exclusion. Nonseparation techniques include voltametry and potentiometry, as well as fluorescence. A comparison of methods for calculation of the conditional stability constant K for complexes containing fulvic acid and copper (II) or cadmium (II) is presented.

Saar, R.A.; Weber, J.H.

1982-01-01

179

DNA as Sensors and Imaging Agents for Metal Ions  

PubMed Central

Increasing interests in detecting metal ions in many chemical and biomedical fields have created demands for developing sensors and imaging agents for metal ions with high sensitivity and selectivity. This review covers recent progress in DNA-based sensors and imaging agents for metal ions. Through both combinatorial selection and rational design, a number of metal ion-dependent DNAzymes and metal ion-binding DNA structures that can selectively recognize specific metal ions have been obtained. By attaching these DNA molecules with signal reporters such as fluorophores, chromophores, electrochemical tags, and Raman tags, a number of DNA-based sensors for both diamagnetic and paramagnetic metal ions have been developed for fluorescent, colorimetric, electrochemical, and surface Raman detections. These sensors are highly sensitive (with detection limit down to 11 ppt) and selective (with selectivity up to millions-fold) toward specific metal ions. In addition, through further development to simplify the operation, such as the use of “dipstick tests”, portable fluorometers, computer-readable discs, and widely available glucose meters, these sensors have been applied for on-site and real-time environmental monitoring and point-of-care medical diagnostics. The use of these sensors for in situ cellular imaging has also been reported. The generality of the combinatorial selection to obtain DNAzymes for almost any metal ion in any oxidation state, and the ease of modification of the DNA with different signal reporters make DNA an emerging and promising class of molecules for metal ion sensing and imaging in many fields of applications. PMID:24359450

Xiang, Yu

2014-01-01

180

Preparation and structure of carbonated calcium hydroxyapatite substituted with heavy rare earth ions  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer LnCaHap solid solution particles were prepared using five types of heavy rare earth ions by a precipitation method. Black-Right-Pointing-Pointer The length and the crystallinity of the LnCaHap particles first increased and then decreased with increasing Ln{sup 3+} contents. Black-Right-Pointing-Pointer A series of YCaHap solid solution particles formed with Y/(Y + Ca) = 0-0.10 were investigated using various methods in detail. -- Abstract: Calcium hydroxyapatite (CaHap) particles substituted five types of heavy rare earth ions (Ln: Y{sup 3+}, Gd{sup 3+}, Dy{sup 3+}, Er{sup 3+} and Yb{sup 3+}) were synthesized using a precipitation method and characterized using various means. These Ln ions strongly affected the crystal phases and the structures of the products. With increasing Ln/(Ln + Ca) in the starting solution ([X{sub Ln}]), the length and the crystallinity of the particles first increased and then decreased. The rare earth metal-calcium hydroxyapatite (LnCaHap) solid solution particles were obtained at [X{sub Y}] {<=} 0.10 for substituting Y system and at [X{sub Ln}] {<=} 0.01-0.03 for substituting the other Ln systems. LnPO{sub 4} was mixed with LnCaHap at higher [X{sub Ln}] for all Ln systems. A series of yttrium-calcium hydroxyapatite (YCaHap) solid solutions with [X{sub Y}] = 0-0.10 were investigated using XRD, TEM, ICP-AES, IR and TG-DTA in detail.

Yasukawa, Akemi, E-mail: yasukawa@cc.hirosaki-u.ac.jp [School of Home Economics, Faculty of Education, Hirosaki University, 1-bunkyo, Hirosaki, Aomori 036-8560 (Japan)] [School of Home Economics, Faculty of Education, Hirosaki University, 1-bunkyo, Hirosaki, Aomori 036-8560 (Japan); Kandori, Kazuhiko [School of Chemistry, Osaka University of Education, 4-698-1 Asahigaoka, Kashiwara, Osaka 582-8582 (Japan)] [School of Chemistry, Osaka University of Education, 4-698-1 Asahigaoka, Kashiwara, Osaka 582-8582 (Japan); Tanaka, Hidekazu [Department of Material Science, Faculty of Science and Engineering, Shimane University, 1060 Nishikawatsu, Matsue, Shimane 690-8504 (Japan)] [Department of Material Science, Faculty of Science and Engineering, Shimane University, 1060 Nishikawatsu, Matsue, Shimane 690-8504 (Japan); Gotoh, Keiko [Faculty of Human Life and Environment, Nara Women's University, Kita-uoya-nishi, Nara 630-8506 (Japan)] [Faculty of Human Life and Environment, Nara Women's University, Kita-uoya-nishi, Nara 630-8506 (Japan)

2012-05-15

181

The first external loop of the metal ion transporter DCT1 is involved in metal ion binding and specificity  

E-print Network

The first external loop of the metal ion transporter DCT1 is involved in metal ion binding mutant smf1 cannot grow on medium containing EGTA. Expression of Smf1p or the mammalian transporter DCT1 to analyze the properties of mutations in the predicted external loop I of DCT1. The sensitivity

Nelson, Nathan

182

Thermodynamics and pair structures of liquid alkali and alkaline-earth metals from the perturbative hypernetted-chain equation  

NASA Astrophysics Data System (ADS)

We have theoretically studied liquid alkali and alkaline-earth metals by combining the second-order pseudopotential (PP) theory of ion-electron interaction and a statistical mechanical method for calculating ionic thermal motion. The latter is done by utilizing the perturbative hypernetted-chain equation recently proposed by the author. The PP is modelled through an ab initio method presented by Shaw, i.e., through the use of the optimized nonlocal model potential (OMP). Calculations are carried out with two different methods for extracting parameters in the OMP. They are due to Animalu and Heine (AH), and Ballentine and Gupta (BG). Results show that both of thermodynamic properties and pair structures are in good agreements with experimental data for alkali metals with the AH set of parameters. For alkaline-earth metals other than Ba, calculations with the BG set give the radial distributions and structure factors in good agreement with experimental data.

Seok Kang, Hong

1999-09-01

183

Synthesis and catalytic activity of heterogeneous rare-earth metal catalysts coordinated with multitopic Schiff-base ligands.  

PubMed

Four multitopic Schiff-base ligand precursors were synthesized via condensation of 4,4'-diol-3,3'-diformyl-1,1'-diphenyl or 1,3,5-tris(4-hydroxy-5-formylphenyl)benzene with 2,6-diisopropylaniline or 2,6-dimethylaniline. Amine elimination reactions of Ln[N(SiMe(3))(2)](3) (Ln = La, Nd, Sm or Y) with these multitopic ligand precursors gave ten heterogeneous rare-earth metal catalysts. These heterogeneous rare-earth metal catalysts are active for intramolecular hydroalkoxylation of alkynols, and the catalytic activities are influenced by the ligand and metal ion. The recycling experiment on the most active heterogeneous catalyst showed the catalyst has a good reusability. PMID:22782285

Sun, Yilin; Wu, Guangming; Cen, Dinghai; Chen, Yaofeng; Wang, Limin

2012-08-28

184

Aspects on metal ion distribution models in pulp washing simulation  

Microsoft Academic Search

The closure of the liquid system in a pulp mill has increased the concentration of metal ions in the process as compared to traditional plants. These ions commonly referred to as non-process elements, NPE, enter the pulp mill with the wood chips, the water supply and the pulping chemicals. The presence of these ions may lead to various problems, e.g.

Karin Mattsson; Gunnar Eriksson; Urban Grén; Krister Ström

2007-01-01

185

Metal sulfide and rare-earth phosphate nanostructures and methods of making same  

DOEpatents

The present invention provides a method of producing a crystalline metal sulfide nanostructure. The metal is a transitional metal or a Group IV metal. In the method, a porous membrane is placed between a metal precursor solution and a sulfur precursor solution. The metal cations of the metal precursor solution and sulfur ions of the sulfur precursor solution react, thereby producing a crystalline metal sulfide nanostructure.

Wong, Stanislaus; Zhang, Fen

2014-05-13

186

Reusable chelating resins concentrate metal ions from highly dilute solutions  

NASA Technical Reports Server (NTRS)

Column chromatographic method uses new metal chelating resins for recovering heavy-metal ions from highly dilute solutions. The absorbed heavy-metal cations may be removed from the chelating resins by acid or base washes. The resins are reusable after the washes are completed.

Bauman, A. J.; Weetal, H. H.; Weliky, N.

1966-01-01

187

Detection of toxic metal ions with near-infrared compounds  

NASA Astrophysics Data System (ADS)

The determination of toxic metal ions in water using near-infrared compounds synthesized in our laboratories will be reported. Several near-infrared tetrasubstituted chloroaluminum 2,3-naphthalocyanine derivatives with spectral characteristics (absorbance and fluorescence) between 700 nm and 1000 nm have been used in these investigations. In the presence of metal ions the NIR dye's absorbance maximum undergoes a bathochromic shift of about 25 nm accompanied by changes in the fluorescence spectra along with molecular lifetime. The response of the NIR dye in the presence of several concentrations of toxic metal ions will be reported. The fluorescence intensity generated by the complex formed by the metal ion and the dye was monitored by (a) a modified commercially available spectrofluorometer and (b) an NIR instrument developed in our laboratories. The fluorescence intensity changes measured with the probe in the presence of metal ions can be used to construct a calibration curve for the monitoring of contaminants' metal ions in the environment. The effect of metal ions on the lifetime of the NIR dye as compared to the uncomplexed dye will be reported. The NIR instrument consists of a semiconductor laser diode, the NIR dye and a detector. The output wavelength of a 780 nm diode (used as the excitation source) matched the absorbance of these dyes and improved the detection limits of the analytes. Long term stability of the probe was investigated by a week-long period of observation. After one week the intensity varies by only 2%, suggesting suitably for long storage.

Casay, Guillermo A.; Czuppon, Tibor; Evans, Lawrence, III; Patonay, Gabor

1994-10-01

188

Correlation between volatility of rare-earth metals and encapsulation of their carbides in carbon nanocapsules  

Microsoft Academic Search

Encapsulation of metals in multilayered graphitic capsules has been studied for all the rare-earth elements (Sc, Y, and Ln = La, Ce, ..., Lu) excluding Pm by using electric arc discharge. Electron microscopy and X-ray diffraction of carbonaceous products revealed that most of rare-earth metals (Sc, Y, La, Ce, Pr, Nd, Gd, Tb, Dy, Ho, Er, and Lu) were encapsulated

Yahachi Saito; Mitsumasa Okuda; Tadanobu Yoshikawa; Atsuo Kasuya; Yuichiro Nishina

1994-01-01

189

ANALYSIS OF THE ELECTRON EXCITATION SPECTRA IN HEAVY RARE EARTH METALS, HYDRIDES AND OXIDES  

E-print Network

397 ANALYSIS OF THE ELECTRON EXCITATION SPECTRA IN HEAVY RARE EARTH METALS, HYDRIDES AND OXIDES C thin evaporated foils of heavy rare earths (Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) in three different chemical states (metal, hydride and oxide) exhibit two main peaks due to collective « plasmon » excitations

Boyer, Edmond

190

Tris(pyrazolyl)methanides of the Alkaline Earth Metals: Influence of the Substitution Pattern on Stability and Degradation.  

PubMed

Trispyrazolylmethanides commonly act as strong tridentate bases toward metal ions. This expected coordination behavior has been observed for tris(3,4,5-trimethylpyrazolyl)methane (1a), which yields the alkaline-earth-metal bis[tris(3,4,5-trimethylpyrazolyl)methanides] of magnesium (1b), calcium (1c), strontium (1d), and barium (1e) via deprotonation of 1a with dibutylmagnesium and [Ae{N(SiMe3)2}2] (Ae = Mg, Ca, Sr, and Ba, respectively). Barium complex 1e degrades during recrystallization that was attempted from aromatic hydrocarbons and ethers. In these scorpionate complexes, the metal ions are embedded in distorted octahedral coordination spheres. Contrarily, tris(3-thienylpyrazolyl)methane (2a) exhibits a strikingly different reactivity. Dibutylmagnesium is unable to deprotonate 2a, whereas [Ae{N(SiMe3)2}2] (Ae = Ca, Sr, and Ba) smoothly metalates 2a. However, the primary alkaline-earth-metal bis[tris(3-thienylpyrazolyl)methanides] of Ca (2c), Sr (2d), and Ba (2e) represent intermediates and degrade under the formation of the alkaline-earth-metal bis(3-thienylpyrazolates) of calcium (3c), strontium (3d), and barium (3e) and the elimination of tetrakis(3-thienylpyrazolyl)ethene (4). To isolate crystalline compounds, 3-thienylpyrazole has been metalated, and the corresponding derivatives [(HPz(Tp))4Mg(Pz(Tp))2] (3b), dinuclear [(tmeda)Ca(Pz(Tp))2]2 (3c), mononuclear [(pmdeta)Sr(Pz(Tp))2] (3d), and [(hmteta)Ba(Pz(Tp))2] (3e) have been structurally characterized. Regardless of the applied stoichiometry, magnesiation of thienylpyrazole 3a with dibutylmagnesium yields [(HPz(Tp))4Mg(Pz(Tp))2] (3b), which is stabilized in the solid state by intramolecular N-H···N···H-N hydrogen bridges. The degradation of [Ae{C(Pz(R))3}2] (R = Ph and Tp) has been studied by quantum chemical methods, the results of which propose an intermediate complex of the nature [{(Pz(R))2C}2Ca{Pz(R)}2]; thereafter, the singlet carbenes ([:C(Pz(R))2]) dimerize in the vicinity of the alkaline earth metal to tetrapyrazolylethene, which is liberated from the coordination sphere as a result of it being a very poor ligand for an s-block metal ion. PMID:25563345

Müller, Christoph; Koch, Alexander; Görls, Helmar; Krieck, Sven; Westerhausen, Matthias

2015-01-20

191

Fluorescent probes and bioimaging: alkali metals, alkaline earth metals and pH.  

PubMed

All living species and life forms have an absolute requirement for bio-functional metals and acid-base equilibrium chemistry owing to the critical roles they play in biological processes. Hence, a great need exists for efficient methods to detect and monitor biometals and acids. In the last few years, great attention has been paid to the development of organic molecule based fluorescent chemosensors. The availability of new synthetic fluorescent probes has made fluorescence microscopy an indispensable tool for tracing biologically important molecules and in the area of clinical diagnostics. This review highlights the recent advances that have been made in the design and bioimaging applications of fluorescent probes for alkali metals and alkaline earth metal cations, including lithium, sodium and potassium, magnesium and calcium, and for pH determination within biological systems. PMID:25317749

Yin, Jun; Hu, Ying; Yoon, Juyoung

2014-10-15

192

Silica-polyamine composite materials for heavy metal ion removal, recovery, and recycling. 2. Metal ion separations from mine wastewater and soft metal ion extraction efficiency  

SciTech Connect

Silica-polyamine composites have been synthesized which have metal ion capacities as high as 0.84 mmol/g for copper ions removed from aqueous solutions. In previous reports it has been demonstrated that these materials survive more than 3,000 cycles of metal ion extraction, elution, and regeneration with almost no loss of capacity (less than 10%). This paper describes two modified silica-polyamine composite materials and reveals the results of tests designed to determine the effectiveness of these materials for extracting and separating metal ions from actual mining wastewater samples. Using these materials, the concentration of copper, aluminum, and zinc in Berkeley Pit mine wastewater is reduced to below allowable discharge limits. The recovered copper and zinc solutions were greater than 90% pure, and metal ion concentration factors of over 20 for copper were realized. Further, the ability of one of these materials to decrease low levels of the soft metals cadmium, mercury, and lead from National Sanitation Foundation recommended challenge levels to below Environmental Protection Agency allowable limits is also reported.

Fischer, R.J.; Pang, D.; Beatty, S.T.; Rosenberg, E.

1999-12-01

193

Metal Ion Substrate Inhibition of Ferrochelatase*S?  

PubMed Central

Ferrochelatase catalyzes the insertion of ferrous iron into protoporphyrin IX to form heme. Robust kinetic analyses of the reaction mechanism are complicated by the instability of ferrous iron in aqueous solution, particularly at alkaline pH values. At pH 7.00 the half-life for spontaneous oxidation of ferrous ion is approximately 2 min in the absence of metal complexing additives, which is sufficient for direct comparisons of alternative metal ion substrates with iron. These analyses reveal that purified recombinant ferrochelatase from both murine and yeast sources inserts not only ferrous iron but also divalent cobalt, zinc, nickel, and copper into protoporphyrin IX to form the corresponding metalloporphyrins but with considerable mechanistic variability. Ferrous iron is the preferred metal ion substrate in terms of apparent kcat and is also the only metal ion substrate not subject to severe substrate inhibition. Substrate inhibition occurs in the order Cu2+ > Zn2+ > Co2+ > Ni2+ and can be alleviated by the addition of metal complexing agents such as ?-mercaptoethanol or imidazole to the reaction buffer. These data indicate the presence of two catalytically significant metal ion binding sites that may coordinately regulate a selective processivity for the various potential metal ion substrates. PMID:18593702

Hunter, Gregory A.; Sampson, Matthew P.; Ferreira, Gloria C.

2008-01-01

194

Metal ion removal from aqueous solution using physic seed hull.  

PubMed

The potential of physic seed hull (PSH), Jantropha curcas L. as an adsorbent for the removal of Cd(2+) and Zn(2+) metal ions from aqueous solution has been investigated. It has been found that the amount of adsorption for both Cd(2+) and Zn(2+) increased with the increase in initial metal ions concentration, contact time, temperature, adsorbent dosage and the solution pH (in acidic range), but decreased with the increase in the particle size of the adsorbent. The adsorption process for both metal ions on PSH consists of three stages-a rapid initial adsorption followed by a period of slower uptake of metal ions and virtually no uptake at the final stage. The kinetics of metal ions adsorption on PSH followed a pseudo-second-order model. The adsorption equilibrium data were fitted in the three adsorption isotherms-Freundlich, Langmuir and Dubinin-Radushkevich isotherms. The data best fit in the Langmuir isotherm indication monolayer chemisorption of the metal ions. The adsorption capacity of PSH for both Zn(2+) and Cd(2+) was found to be comparable with other available adsorbents. About 36-47% of the adsorbed metal could be leached out of the loaded PSH using 0.1M HCl as the eluting medium. PMID:20362390

Mohammad, Masita; Maitra, Saikat; Ahmad, Naveed; Bustam, Azmi; Sen, T K; Dutta, Binay K

2010-07-15

195

Catalytic metal ions and enzymatic processing of DNA and RNA.  

PubMed

Conspectus Two-metal-ion-dependent nucleases cleave the phosphodiester bonds of nucleic acids via the two-metal-ion (2M) mechanism. Several high-resolution X-ray structures portraying the two-metal-aided catalytic site, together with mutagenesis and kinetics studies, have demonstrated a functional role of the ions for catalysis in numerous metallonucleases. Overall, the experimental data confirm the general mechanistic hypothesis for 2M-aided phosphoryl transfer originally reported by Steitz and Steitz ( Proc. Natl. Acad. Sci. U.S.A. 1993 , 90 ( 14 ), 6498 - 6502 ). This seminal paper proposed that one metal ion favors the formation of the nucleophile, while the nearby second metal ion facilitates leaving group departure during RNA hydrolysis. Both metals were suggested to stabilize the enzymatic transition state. Nevertheless, static X-ray structures alone cannot exhaustively unravel how the two ions execute their functional role along the enzymatic reaction during processing of DNA or RNA strands when moving from reactants to products, passing through metastable intermediates and high-energy transition states. In this Account, we discuss the role of multiscale molecular simulations in further disclosing mechanistic insights of 2M-aided catalysis for two prototypical enzymatic targets for drug discovery, namely, ribonuclease H (RNase H) and type II topoisomerase (topoII). In both examples, first-principles molecular simulations, integrated with structural data, emphasize a cooperative motion of the bimetal motif during catalysis. The coordinated motion of both ions is crucial for maintaining a flexible metal-centered structural architecture exquisitely tailored to accommodate the DNA or RNA sugar-phosphate backbone during phosphodiester bond cleavage. Furthermore, our analysis of RNase H and the N-terminal domain (PAN) of influenza polymerase shows that classical molecular dynamics simulations coupled with enhanced sampling techniques have contributed to describe the modulatory effect of metal ion concentration and metal uptake on the 2M mechanism and efficiency. These aspects all point to the emerging and intriguing role of additional adjacent ions potentially involved in the modulation of phosphoryl transfer reactions and enzymatic turnover in 2M-catalysis, as recently observed experimentally in polymerase ? and homing endonuclease I-DmoI. These computational results, integrated with experimental findings, describe and reinforce the nascent concept of a functional and cooperative dynamics of the catalytic metal ions during the 2M-dependent enzymatic processing of DNA and RNA. Encouraged by the insights provided by computational approaches, we foresee further experiments that will feature the functional and joint dynamics of the catalytic metal ions for nucleic acid processing. This could impact the de novo design of artificial metallonucleases and the rational design of potent metal-chelating inhibitors of pharmaceutically relevant enzymes. PMID:25590654

Palermo, Giulia; Cavalli, Andrea; Klein, Michael L; Alfonso-Prieto, Mercedes; Dal Peraro, Matteo; De Vivo, Marco

2015-02-17

196

Release characteristics of alkali and alkaline earth metallic species during biomass pyrolysis and steam gasification process.  

PubMed

Investigating the release characteristics of alkali and alkaline earth metallic species (AAEMs) is of potential interest because of AAEM's possible useful service as catalysts in biomass thermal conversion. In this study, three kinds of typical Chinese biomass were selected to pyrolyse and their chars were subsequently steam gasified in a designed quartz fixed-bed reactor to investigate the release characteristics of alkali and alkaline earth metallic species (AAEMs). The results indicate that 53-76% of alkali metal and 27-40% of alkaline earth metal release in pyrolysis process, as well as 12-34% of alkali metal and 12-16% of alkaline earth metal evaporate in char gasification process, and temperature is not the only factor to impact AAEMs emission. The releasing characteristics of AAEMs during pyrolysis and char gasification process of three kinds of biomass were discussed in this paper. PMID:22525260

Long, Jiang; Song, Hu; Jun, Xiang; Sheng, Su; Lun-Shi, Sun; Kai, Xu; Yao, Yao

2012-07-01

197

Extracting metal ions with diphosphonic acid, or derivative thereof  

DOEpatents

Thermodynamically-unstable complexing agents which are diphosphonic acids and diphosphonic acid derivatives (or sulfur containing analogs), like carboxyhydroxymethanediphosphonic acid and vinylidene-1,1-diphosphonic acid, are capable of complexing with metal ions, and especially metal ions in the II, III, IV, V and VI oxidation states, to form stable, water-soluble metal ion complexes in moderately alkaline to highly-acidic media. However, the complexing agents can be decomposed, under mild conditions, into non-organic compounds which, for many purposes are environmentally-nondamaging compounds thereby degrading the complex and releasing the metal ion for disposal or recovery. Uses for such complexing agents as well as methods for their manufacture are also described. 1 fig.

Horwitz, E.P.; Gatrone, R.C.; Nash, K.L.

1994-07-26

198

Extracting metal ions with diphosphonic acid, or derivative thereof  

DOEpatents

Thermodynamically-unstable complexing agents which are diphosphonic acids and diphosphonic acid derivatives (or sulphur containing analogs), like carboxyhydroxymethanediphosphonic acid and vinylidene-1,1-diphosphonic acid, are capable of complexing with metal ions, and especially metal ions in the II, III, IV, V and VI oxidation states, to form stable, water-soluble metal ion complexes in moderately alkaline to highly-acidic media. However, the complexing agents can be decomposed, under mild conditions, into non-organic compounds which, for many purposes are environmentally-nondamaging compounds thereby degrading the complex and releasing the metal ion for disposal or recovery. Uses for such complexing agents as well as methods for their manufacture are also described.

Horwitz, Earl P. (Argonne, IL); Gatrone, Ralph C. (Argonne, IL); Nash, Kenneth L. (Argonne, IL)

1994-01-01

199

Ion plating seals microcracks or porous metal components  

NASA Technical Reports Server (NTRS)

Description of ion plating process is given. Advantage of this process is that any plating metal or alloy can be selected, whereas, for conventional welding, material selection is limited by compatability.

Spalvins, T.; Buckley, D. H.; Brainard, W. A.

1972-01-01

200

Extraction of rare earth metals by calix[4]arene solubilized in AOT reversed micellar solution  

Microsoft Academic Search

Extraction of rare earth metals (europium and yttrium) and their separation from zinc were investigated using a novel host compound, p-tert-octylcalix[4]arene carboxyl derivative as an extractant. Extraction behavior of the metals with a typical commercial extractant PC-88A or Versatic 10 was also examined. The cyclic ligand calixarene showed a high selectivity towards rare earth metals compared with PC-88A and Versatic

F Kubota; K Shinohara; K Shimojo; T Oshima; M Goto; S Furusaki; T Hano

2001-01-01

201

Metallic glass as a temperature sensor during ion plating  

NASA Technical Reports Server (NTRS)

The temperature of the interface and/or a superficial layer of a substrate during ion plating was investigated using a metallic glass of the composition Fe67Co18B14Si1 as the substrate and as the temperature sensor. Transmission electron microscopy and diffraction studies determined the microstructure of the ion-plated gold film and the substrate. Results indicate that crystallization occurs not only in the film, but also in the substrate. The grain size of crystals formed during ion plating was 6 to 60 nm in the gold film and 8 to 100 nm in the substrate at a depth of 10 to 15 micrometers from the ion-plated interface. The temperature rise of the substrate during ion plating was approximately 500 C. Discontinuous changes in metallurgical microstructure, and physical, chemical, and mechanical properties during the amorphous to crystalline transition in metallic glasses make metallic glasses extremely useful materials for temperature sensor applications in coating processes.

Miyoshi, K.; Spalvins, T.; Buckley, D. H.

1984-01-01

202

Metallic glass as a temperature sensor during ion plating  

NASA Technical Reports Server (NTRS)

The temperature of the interface and/or a superficial layer of a substrate during ion plating was investigated using a metallic glass of the composition Fe67Co18B14Si1 as the substrate and as the temperature sensor. Transmission electron microscopy and diffraction studies determined the microstructure of the ion-plated gold film and the substrate. Results indicate that crystallization occurs not only in the film, but also in the substrate. The grain size of crystals formed during ion plating was 6 to 60 nm in the gold film and 8 to 100 nm in the substrate at a depth of 10 to 15 micrometers from the ion-plated interface. The temperature rise of the substrate during ion plating was approximately 500 C. Discontinuous changes in metallurgical microstructure, and physical, chemical, and mechanical properties during the amorphous to crystalline transition in metallic glasses make metallic glasses extremely useful materials for temperature sensor applications in coating processes.

Miyoshi, K.; Spalvins, T.; Buckley, D. H.

1985-01-01

203

Smart textile device using ion polymer metal compound.  

PubMed

We have developed a smart textile device that detects angular displacement of attached surface using ion polymer metal compound. The device was composed of ion polymer metal compound (IPMC) which was fabricated from Nafion resin by heat-press and chemical gold plating. The generated voltage from IPMC was measured as a function of bending angle. Fabricated IPMC device was weaved into a cotton cloth and multidirectional movements were detected. PMID:24109750

Nakamura, Taro; Ihara, Tadashi

2013-01-01

204

Searching for new luminescent chemosensors for metal ions  

NASA Astrophysics Data System (ADS)

Aiming to develop new fluorescent chemosensors for biological and environmental applications, we have designed and synthesized new chemical species able to reversibly bind alkali, earth-alkali, and transition metal ions. For signaling the binding of the target analyte, we have inserted in the structure of the chemosensors different luminophores, such as dioxyxanthone derivatives, dansyl derivatives, ruthenium complexes, and hydroxyquinoline derivatives. In solution, the binding is always signaled by pronounced changes in the photophysical properties of the inserted luminophore such as emission wavelength and intensity, and excited state lifetime. The mechanism for the signal transduction strongly depends on the chosen receptor and luminophore moieties, and has been investigated in detail by means of steady state and time resolved spectroscopy. In all cases, the synthesized chemosensors have proved to be chemically and photochemically stable. Good selectivity and affinity has been obtained with different sensors for K+, Mg2+, Ba2+, Zn2+, Ni2+ and Cu2+, even in physiological pH conditions. Moreover the use of an array of these sensors in optodes could lead to the construction of the so called electronic tongues. All these features make these sensors promising candidates for analytical applications.

Prodi, Luca; Bolletta, Fabrizio; Montalti, Marco; Zaccheroni, Nelsi

1999-05-01

205

Oligomeric rare-earth metal cluster complexes with endohedral transition metal atoms  

NASA Astrophysics Data System (ADS)

Comproportionation reactions of rare-earth metal trihalides (RX3) with the respective rare-earth metals (R) and transition metals (T) led to the formation of 22 oligomeric R cluster halides encapsulating T, in 19 cases for the first time. The structures of these compounds were determined by single-crystal X-ray diffraction and are composed of trimers ({T3R11}X15-type, P63/m), tetramers ({T4R16}X28{R4} (P-43m), {T4R16}X20 (P42/nnm), {T4R16}X24(RX3)4 (I41/a) and {T4R16}X23 (C2/m) types of structure) and pentamers ({Ru5La14}2Br39, Cc) of {TRr}n (n=2-5) clusters. These oligomers are further enveloped by inner (Xi) as well as outer (Xa) halido ligands, which possess diverse functionalities and interconnect like oligomers through i-i, i-a and/or a-i bridges. The general features of the crystal structures for these new compounds are discussed and compared to literature entries as well as different structure types with oligomeric T centered R clusters. Dimers and tetramers originating from the aggregation of {TR6} octahedra via common edges are more frequent than trimers and pentamers, in which the {TRr} clusters share common faces.

Steinberg, Simon; Zimmermann, Sina; Brühmann, Matthias; Meyer, Eva; Rustige, Christian; Wolberg, Marike; Daub, Kathrin; Bell, Thomas; Meyer, Gerd

2014-11-01

206

Metal ion implantation for large scale surface modification  

SciTech Connect

Intense energetic beams of metal ions can be produced by using a metal vapor vacuum arc as the plasma discharge from which the ion beam is formed. We have developed a number of ion sources of this kind and have built a metal ion implantation facility which can produce repetitively pulsed ion beams with mean ion energy up to several hundred key, pulsed beam current of more than an ampere, and time averaged current of several tens of milliamperes delivered onto a downstream target. We've also done some preliminary work on scaling up this technology to very large size. For example, a 50-cm diameter (2000 cm[sup 2]) set of beam formation electrodes was used to produce a pulsed titanium beam with ion current over 7 amperes at a mean ion energy of 100 key. Separately, a dc embodiment has been used to produce a dc titanium ion beam with current over 600 mA, power supply limited in this work, and up to 6 amperes of dc plasma ion current was maintained for over an hour. In a related program we've developed a plasma immersion method for applying thin metallic and compound films in which the added species is atomically mixed to the substrate. By adding a gas flow to the process, well-bonded compound films can also be formed; metallic films and multilayers as well as oxides and nitrides with mixed transition zones some hundreds of angstroms thick have been synthesized. Here we outline these parallel metal-plasma-based research programs and describe the hardware that we've developed and some of the surface modification research that we've done with it.

Brown, I.G.

1992-10-01

207

Refinement of Cast Microstructure of Hypereutectic Al-Si Alloys Through the Addition of Rare Earth Metals  

Microsoft Academic Search

Microstructural observation and thermal analysis of Al-21 wt % Si alloys with different rare earth metals were performed to examine the effect of rare earth metal on the refinement of primary silicon phase. Simultaneous refinement of both primary and eutectic silicon morphology is achieved with the addition of rare earth and its effect increases with the amount of rare earth

Joonyeon Chang; Inge Moon; Chongsool Choi

1998-01-01

208

Detection of Metallic Compounds in Rocket Plumes Using Ion Probes  

NASA Technical Reports Server (NTRS)

This grant experimentally verified that ion probes can consistently detect metallic compounds in a hybrid rocket plume. Two electrostatic detection methods were tested. The first method used an unbiased ion probe. It responded to collisions or near collisions with charged particulates. The amplitude of the response to metallic ions always exceeded that of the combustion products. The second device was a cylindrical Gaussian surface that surrounded, but did not touch, the plume. A charge imbalance in the plume induced a current in cylinder that was detected by a sensitive amplifier. The probe was more sensitive to metallic compounds than the cylinder. However, the Gaussian cylinder demonstrated sufficient sensitivity to warrant serious future consideration. Since the cylinder is nonintrusive, it is particularly attractive. Apparently, ions formed during combustion transfer to the metallic impurities. The formation of these metallic ions slows the ion recombination rate and helps preserve charges in the plume. The electrostatic detectors, in turn, respond to the charges carried by the metallic impurities.

Dunn, Robert W.

1998-01-01

209

Structure of the Alkali-metal-atom-Strontium molecular ions: towards photoassociation and formation of cold molecular ions  

E-print Network

Structure of the Alkali-metal-atom-Strontium molecular ions: towards photoassociation and formation polarizability, of molecular ions composed of one alkali-metal atom and a Strontium ion are determined and a Strontium ion are discussed, as well as the formation of stable molecular ions. PACS numbers: 31.15.AR,31

210

Near equality of ion phase space densities at earth, Jupiter, and Saturn  

NASA Astrophysics Data System (ADS)

Energetic-ion phase-space density profiles are strikingly similar in the inner magnetospheres of earth, Jupiter, and Saturn for ions of first adiabatic invariant near 100 MeV/G and small mirror latitudes. Losses occur inside L approximately equal to 7 for Jupiter and Saturn and inside L approximately equal to 5 at earth. At these L values there exist steep plasma-density gradients at all three planets, associated with the Io plasma torus at Jupiter, the Rhea-Dione-Tethys torus at Saturn, and the plasmasphere at earth. Measurements of ion flux-tube contents at Jupiter and Saturn by the low-energy charged-particle experiment show that these are similar (for O ions at L = 5-9) to those at earth (for protons at L = 2-6). Furthermore, the thermal-ion flux-tube contents from Voyager plasma-science data at Jupiter and Saturn are also very nearly equal, and again similar to those at earth, differing by less than a factor of 3 at the respective L values. The near equality of energetic and thermal ion flux-tube contents at earth, Jupiter, and Saturn suggests the possibility of strong physical analogies in the interaction between plasma and energetic particles at the plasma tori/plasma sheets of Jupiter and Saturn and the plasmasphere of earth.

Cheng, A. F.; Krimigis, S. M.; Armstrong, T. P.

1985-01-01

211

MATERIALS WORLD January 201216 Dr Steve Barrett from the University of Liverpool, UK, has been studying rare earth metals for  

E-print Network

studying rare earth metals for 20 years. Here he explains how preparation of the surface layer is crucial to the functionality of these scarce elements. S tudies into the properties of rare earth metals have been active since of the geometric and electronic structure of single crystal rare earth metal surfaces were published. Studies

Barrett, Steve D.

212

Dynamic polarizabilities of rare-earth-metal atoms and dispersion coefficients for their interaction with helium atoms  

E-print Network

Dynamic polarizabilities of rare-earth-metal atoms and dispersion coefficients; published 29 March 2007 The dynamic scalar and tensor polarizabilities of the rare-earth-metal atoms coefficients for the interactions of the rare-earth-metal atoms with helium atoms. The static polarizabilities

Chu, Xi

213

Synergistic Catalysis of Dimetilan Hydrolysis by Metal Ions and  

E-print Network

Synergistic Catalysis of Dimetilan Hydrolysis by Metal Ions and Organic Ligands C H I N G - H U A H, The Johns Hopkins University, Baltimore, Maryland 21218 Hydrolysis of the insecticide dimetilan, which ion-organic ligandsynergisticeffectsonthedegradationofagrochemicals. Dimetilan hydrolysis is strongly

Huang, Ching-Hua

214

Oxidative mechanisms in the toxicity of metal ions  

Microsoft Academic Search

The role of reactive oxygen species, with the subsequent oxidative deterioration of biological macromolecules in the toxicities associated with transition metal ions, is reviewed. Recent studies have shown that metals, including iron, copper, chromium, and vanadium undergo redox cycling, while cadmium, mercury, and nickel, as well as lead, deplete glutathione and protein-bound sulfhydryl groups, resulting in the production of reactive

S. J. Stohs; D. Bagchi

1995-01-01

215

Current and prospective applications of metal ion–protein binding  

Microsoft Academic Search

Since immobilized metal ion affinity chromatography (IMAC) was first introduced, several variants of this method and many other metal affinity-based techniques have been devised. IMAC quickly established itself as a highly reliable purification procedure, showing rapid expansion in the number of preparative and analytical applications while not remaining confined to protein separation. It was soon applied to protein refolding (matrix-assisted

E. K. M Ueda; P. W Gout; L Morganti

2003-01-01

216

Metal ion deposition from ionized mangetron sputtering discharge  

Microsoft Academic Search

A technique has been developed for highly efficient postionization of sputtered metal atoms from a magnetron cathode. The process is based on conventional magnetron sputtering with the addition of a high density, inductively coupled rf (RFI) plasma in the region between the sputtering cathode and the sample. Metal atoms sputtered from the cathode due to inert gas ion bombardment transit

S. M. Rossnagel; J. Hopwood

1994-01-01

217

Surface Precipitation of Hydrolyzable Metal Ions on Oxide Surfaces  

E-print Network

Surface Precipitation of Hydrolyzable Metal Ions on Oxide Surfaces S. E. Fendorf Heavy metalO2 and TiO2 near and beyond monolayer coverage. Surface precipitation of Al(III) and La(III) was observed on MnO2, but was not apparent on TiO2 nor in bulk solution. Al(III) formed a surface precipitate

Sparks, Donald L.

218

Metal ion complexation by ionizable crown ethers. Final report, January 1, 1988--June 30, 1994  

SciTech Connect

During the report period a variety of new lipophilic ionizable crown ethers with pendent proton-ionizable groups has been synthesized. The ligands possess one or more ionizable group (carboxylic acid, phosphonic acid monoethyl ester, para-nitrophenol, phosphonic acid) attached to crown ether, monoazacrown ether or diazacrown ether frameworks. These novel chelating agents have either pendent or inward-facing proton-ionizable groups. Such lipophilic proton-ionizable crown ethers are designed for use in multiphase metal ion separations (solvent extraction, liquid membrane transport). In addition a series of proton-ionizable crown ethers without lipophilic groups was prepared to study how structural variations within the ligand influence metal ion complexation in homogeneous media as assessed by NMR spectroscopy or titration calorimetry. A third class of new metal ion-complexing agents is a series of lipophilic acyclic polyether dicarboxylic acids. Competitive solvent extractions of alkali metal and alkaline earth cations and of the mixed species have been conducted to reveal the influence of ring size, nature and attachment site of the lipophilic group, sidearm length, and proton-ionizable group identity and location upon the selectivity and efficiency of metal ion complexation. In addition to such studies of structural variation within the lipophilic proton-ionizable crown ether, the effect of changing the organic solvent and variation of the stripping conditions have been assessed. The influence of structural variations within lipophilic acyclic polyether dicarboxylic acids upon competitive solvent extraction of alkaline earth cations has been probed. Also a new chromogenic, di-ionizable crown ether with extremely high selectivity for Hg{sup 2+} has been discovered.

Bartsch, R.A.

1994-12-31

219

Electron-phonon coupling in the rare-earth metals  

NASA Astrophysics Data System (ADS)

We have estimated the strength of the mass enhancement of the conduction electrons due to electron-phonon interaction in the rare metals Sc, Y, and La-Lu. The underlying self-consistent energy bands were obtained by means of the scalar relativistic linear-muffin-tin-orbital method, and the electron-phonon parameters were calculated within the Gaspari-Gyorffy formulation. For the heavier rare earths Gd-Tm spin polarization was included both in the band-structure calculations and in the treatment of the electron-phonon coupling to take into account the spin splitting of the conduction electrons induced by the 4f states. The calculated electron-phonon mass enhancement ? exhibits a pronounced variation through the series with a maximum value of 1.07 in Pr and a minimum of 0.3 in Ho. We analyze the experimental data from specific heat and de Haas-van Alphen measurements in light of the calculated electron-phonon contribution to the mass enhancement. Finally, we present for the superconducting elements Sc, Y, La, and Lu a comparison with the empirical electron-phonon coupling constants derived from the transition temperatures.

Skriver, H. L.; Mertig, I.

1990-04-01

220

Quantum Computing Hardware based on Rare-Earth-Ion Doped Whispering-Gallery Mode Resonators.  

E-print Network

??Rare-earth-ion doped crystals are an interesting system for quantum computing investigations due to their long optical and hyperfine coherence times. In particular, the ground-state coherence… (more)

McAuslan, David Lee

2011-01-01

221

Near-Earth asteroids: Metals occurrence, extraction, and fabrication  

Microsoft Academic Search

Near-earth asteroids occur in three principle types of orbits: Amor, Apollo, and Aten. Amor asteroids make relatively close (within 0.3 AU) approaches to the earth's orbit, but do not actually overlap it. Apollo asteroids spend most of their time outside the earth's orbital path, but at some point of close approach to the sun, they cross the orbit of the

Richard Westfall

1991-01-01

222

When VSEPR Fails: Experimental and Theoretical Investigations of the Behavior of Alkaline-Earth-Metal Acetylides  

PubMed Central

The synthesis, structural, and spectral characterization as well as a theoretical study of a family of alkaline-earth-metal acetylides provides insights into synthetic access and the structural and bonding characteristics of this group of highly reactive compounds. Based on our earlier communication that reported unusual geometry for a family of triphenylsilyl-substituted alkaline-earth-metal acetylides, we herein present our studies on an expanded family of target derivatives, providing experimental and theoretical data to offer new insights into the intensively debated theme of structural chemistry in heavy alkaline-earth-metal chemistry. PMID:19844925

Guino-o, Marites A.; Alexander, Jacob S.; McKee, Michael L.; Hope, Håkon; Englich, Ulrich B.

2014-01-01

223

Ion source metal-arc fault current protection circuit  

SciTech Connect

Ion sources can be damaged by arcs between metallic components of the source if these arcs are permitted to last. The negative-biased low-work-function converter in a surface conversion negative ion source is especially susceptible to metal-arc breakdown damage. Here an electronic circuit for minimizing the damage caused by such an arc is described. The circuit uses a transistor switch and an inductor in series with the converter bias power supply to limit the damage during the metal-arc breakdown.

deVries, G.J.; Lietzke, A.F.; van Os, C.F.A.; Stearns, J.W. (Lawrence Berkeley Laboratory, University of California, Berkeley, California (USA))

1991-12-01

224

Synthesis and structural characterization of amido scorpionate rare earth metals complexes.  

PubMed

The reactivity of hybrid scorpionate/cyclopentadienyl ligands in the form of the protio derivatives as a mixture of two regioisomers, namely bpzcpH [1-{2,2-bis(3,5-dimethylpyrazol-1-yl)-1,1-diphenylethyl}-1,3-cyclopentadiene and 2-{2,2-bis(3,5-dimethylpyrazol-1-yl)-1,1-diphenylethyl}-1,3-cyclopentadiene] and bpztcpH [1-{2,2-bis(3,5-dimethylpyrazol-1-yl)-1-tert-butylethyl}-1,3-cyclopentadiene and 2-{2,2-bis(3,5-dimethylpyrazol-1-yl)-1-tert-butylethyl}-1,3-cyclopentadiene], with the tris(silylamide) precursors [M{N(SiHMe2)2}3(thf)x] of rare earth metals (including the group 3 metals scandium and yttrium) is related to the atomic radii of the metal centres. The reaction with the precursor containing the smallest ion, [Sc{N(SiHMe2)2}3(thf)], did not proceed even heating at reflux temperature in toluene. The reaction with the precursors that contain a medium-sized metal ion, i.e., [M{N(SiHMe2)2}3(thf)2] (M = Y, Lu), proceeded only at high temperature and gave good yields of the silylenediamide-containing derivatives [M{?(2)-NN-Me2Si(NSiHMe2)2}(bpzcp)] (M = Y , Lu ) and [M{?(2)-NN-Me2Si(NSiHMe2)2}(bpztcp)] (M = Y , Lu ) by an double activation of Si-H and Si-N bonds. However, the reaction with the precursors that contained the largest metal ions, i.e., [M{N(SiHMe2)2}3(thf)2] (M = Nd, Sm), proceeded rapidly at room temperature to afford the bis(silylamide) complexes [M{N(SiHMe2)2}2(bpzcp)] (M = Nd , Sm ) and [M{N(SiHMe2)2}2(bpztcp)] (M = Nd , Sm ). Additionally, the alkyl heteroscorpionate yttrium and lutetium complexes [M(CH2SiMe3)2(NNCp)] (M = Y, Lu) reacted with an excess of HN(SiHMe2)2 to give the mixed alkyl/amide derivatives [M{N(SiHMe2)2}(CH2SiMe3)(bpzcp)] (M = Y , Lu ) and [M{N(SiHMe2)2}(CH2SiMe3)(bpztcp)] (M = Y , Lu ). The structures of the complexes were determined by spectroscopic methods and the X-ray crystal structures of , and were also established. PMID:24829057

Márquez-Segovia, Isabel; Lara-Sánchez, Agustín; Otero, Antonio; Fernández-Baeza, Juan; Castro-Osma, José Antonio; Sánchez-Barba, Luis F; Rodríguez, Ana M

2014-07-01

225

Neutralization by Metal Ions of the Toxicity of Sodium Selenide  

PubMed Central

Inert metal-selenide colloids are found in animals. They are believed to afford cross-protection against the toxicities of both metals and selenocompounds. Here, the toxicities of metal salt and sodium selenide mixtures were systematically studied using the death rate of Saccharomyces cerevisiae cells as an indicator. In parallel, the abilities of these mixtures to produce colloids were assessed. Studied metal cations could be classified in three groups: (i) metal ions that protect cells against selenium toxicity and form insoluble colloids with selenide (Ag+, Cd2+, Cu2+, Hg2+, Pb2+ and Zn2+), (ii) metal ions which protect cells by producing insoluble metal-selenide complexes and by catalyzing hydrogen selenide oxidation in the presence of dioxygen (Co2+ and Ni2+) and, finally, (iii) metal ions which do not afford protection and do not interact (Ca2+, Mg2+, Mn2+) or weakly interact (Fe2+) with selenide under the assayed conditions. When occurring, the insoluble complexes formed from divalent metal ions and selenide contained equimolar amounts of metal and selenium atoms. With the monovalent silver ion, the complex contained two silver atoms per selenium atom. Next, because selenides are compounds prone to oxidation, the stabilities of the above colloids were evaluated under oxidizing conditions. 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB), the reduction of which can be optically followed, was used to promote selenide oxidation. Complexes with cadmium, copper, lead, mercury or silver resisted dissolution by DTNB treatment over several hours. With nickel and cobalt, partial oxidation by DTNB occurred. On the other hand, when starting from ZnSe or FeSe complexes, full decompositions were obtained within a few tens of minutes. The above properties possibly explain why ZnSe and FeSe nanoparticles were not detected in animals exposed to selenocompounds. PMID:23342137

Dauplais, Marc; Lazard, Myriam; Blanquet, Sylvain; Plateau, Pierre

2013-01-01

226

Experimental determination of the partitioning of gallium between solid iron metal and synthetic basaltic melt Electron and ion microprobe study  

NASA Technical Reports Server (NTRS)

The distribution of Ga between solid Fe metal and synthetic basaltic melt is investigated experimentally at temperatures of 1190 and 1330 C, and over a narrow range of oxygen fugacities. Metal-silicate reversal experiments were conducted, indicating a close approach to equilibrium. The analysis of the partitioned products was performed using electron and ion microprobes. At one bar total pressure, the solid metal/silicate melt partition coefficient D(Ga) is used to evaluate metal-silicate fractionation processes in the earth, moon, and Eucrite Parent Body (EPB). It is found that the depletion of Ga abundances in the EPB is due to the extraction of Ga into a metallic core. Likewise, the depletion of Ga in the lunar mantle is consistent with the extraction of Ga into a smaller lunar core if Ga was originally present in a subchondritic concentration. The relatively high Ga abundances in the earth's mantle are discussed, with reference to several theoretical models.

Drake, M. J.; Newsom, H. E.; Reed, S. J. B.; Enright, M. C.

1984-01-01

227

Metal ion implantation in inert polymers for strain gauge applications  

NASA Astrophysics Data System (ADS)

Metal ion implantation in inert polymers may produce ultra-thin conducting films below the polymer surface. These subsurface films are promising structures for strain gauge applications. To this purpose, polycarbonate substrates were irradiated at room temperature with low-energy metal ions (Cu + and Ni +) and with fluences in the range between 1 × 10 16 and 1 × 10 17 ions/cm 2, in order to promote the precipitation of dispersed metal nanoparticles or the formation of a continuous thin film. The nanoparticle morphology and the microstructural properties of polymer nanocomposites were investigated by glancing-incidence X-ray diffraction and transmission electron microscopy (TEM) measurements. At lower fluences (<5 × 10 16 ions/cm 2) a spontaneous precipitation of spherical-shaped metal nanoparticles occurred below the polymer top-surface (˜50 nm), whereas at higher fluences the aggregation of metal nanoparticles produced the formation of a continuous polycrystalline nanofilm. Furthermore, a characteristic surface plasmon resonance peak was observed for nanocomposites produced at lower ion fluences, due to the presence of Cu nanoparticles. A reduced electrical resistance of the near-surface metal-polymer nanocomposite was measured. The variation of electrical conductivity as a function of the applied surface load was measured: we found a linear relationship and a very small hysteresis.

Di Girolamo, Giovanni; Massaro, Marcello; Piscopiello, Emanuela; Tapfer, Leander

2010-10-01

228

Removal of metal ions from aqueous solution  

DOEpatents

A method of removing heavy metals from aqueous solution, a composition of matter used in effecting said removal, and apparatus used in effecting said removal. One or more of the polypeptides, poly (.gamma.-glutamylcysteinyl)glycines, is immobilized on an inert material in particulate form. Upon contact with an aqueous solution containing heavy metals, the polypeptides sequester the metals, removing them from the solution. There is selectivity of poly (.gamma.-glutamylcysteinyl)glycines having a particular number of monomer repeat unit for particular metals. The polypeptides are easily regenerated by contact with a small amount of an organic acid, so that they can be used again to remove heayv metals from solution. This also results in the removal of the metals from the column in a concentrated form.

Jackson, Paul J. (both Los Alamos, NM); Delhaize, Emmanuel (both Los Alamos, NM); Robinson, Nigel J. (Durham, GB2); Unkefer, Clifford J. (Los Alamos, NM); Furlong, Clement (Seattle, WA)

1990-11-13

229

Removal of metal ions from aqueous solution  

DOEpatents

A method of removing heavy metals from aqueous solution, a composition of matter used in effecting said removal, and apparatus used in effecting said removal. One or more of the polypeptides, poly (.gamma.-glutamylcysteinyl)glycines, is immobilized on an inert material in particulate form. Upon contact with an aqueous solution containing heavy metals, the polypeptides sequester the metals, removing them from the solution. There is selectivity of poly (.gamma.-glutamylcysteinyl)glycines having a particular number of monomer repeat units for particular metals. The polypeptides are easily regenerated by contact with a small amount of an organic acid, so that they can be used again to remove heavy metals from solution. This also results in the removal of the metals from the column in a concentrated form.

Jackson, Paul J. (Los Alamos, NM); Delhaize, Emmanuel (Los Alamos, NM); Robinson, Nigel J. (Durham, GB2); Unkefer, Clifford J. (Los Alamos, NM); Furlong, Clement (Seattle, WA)

1990-01-01

230

Effect of Metal Ions on Melanin – Local Anaesthetic Drug Complexes  

PubMed Central

The affinity of melanin biopolymers for metal ions, drugs and other organic compounds is an important factor in the etiology of toxic retinopathy, hiperpigmentation, otic lesions and irreversible extrapyramidal disorders. The aim of the presented work was to examine the interaction of local anaesthetic drugs used in ophthalmology with model DOPA-melanin in the presence of metal ions. It has been demonstrated that the analyzed drugs form complexes with melanin biopolymer. Based on the .values of association constants,, the following order of drugs affinity to melanin was found: tetracaine > procaine >> bupivacaine > lidocaine. It has also been shown that Cu2+ and Zn2+ ions administered to DOPA-melanin before complexing with drugs decrease the total amount of local anaesthetics bound to melanin. The blocking of some active centers in melanin molecules by metal ions, which potentially exist in living systems, may change the clinical therapeutic efficiency of the analyzed local anaesthetic drugs. PMID:18365047

Buszman, Ewa; Betlej, Bo?ena; Wrze?niok, Dorota; Radwa?ska-Wala, Bo?ena

2003-01-01

231

Analysis of metallic pigments by ion microbeam  

Microsoft Academic Search

Metallic paints consist of metallic flakes dispersed in a resinous binder, i.e. a light-element polymer matrix. The spatial distribution and orientation of metallic flakes inside the matrix determines the covering efficiency of the paint, glossiness, and its angular-dependent properties such as lightness flop or color flop (two-tone). Such coatings are extensively used for a functional (i.e. security) as well as

P. Pelicon; M. Klanjsek-Gunde; M. Kunaver; J. Simcic; M. Budnar

2002-01-01

232

Metal ion release after total hip replacement.  

PubMed

The concentration of cobalt (Co), chromium (Cr), molybdenum (Mo), nickel (Ni), iron (Fe) and zinc (Zn) was measured using neutron activation analysis in tissue taken from an 81 year old female at necropsy. The patient had bilateral cobalt chromium molybdenum (Co-Cr-Mo) total hip replacements: one, a metal-on-metal had been in place for 14 years, the other a metal-on-plastic for 5.5 years. Although the metal-on-metal side had become painful, the patient remained active until she died. The measurements indicated that the concentrations of Co and Cr in the lung, kidney, liver and spleen were up to fifty times "Standard Man" values. High values occurred also in the urine and in the hair. The tissue adjacent to the metal-on-metal joint was heavily laden with metal wear debris, whereas that adjacent to the metal-on-plastic joint was relatively uncontaminated. The concentration varied with distance from the implant. Co predominated in the urine, whereas Cr predominated near the implants. The existence of such high levels, especially in the organs, is a possible cause for concern. PMID:7470573

Dobbs, H S; Minski, M J

1980-10-01

233

Complexation-induced supramolecular assembly drives metal-ion extraction.  

PubMed

Combining experiment with theory reveals the role of self-assembly and complexation in metal-ion transfer through the water-oil interface. The coordinating metal salt Eu(NO3)3 was extracted from water into oil by a lipophilic neutral amphiphile. Molecular dynamics simulations were coupled to experimental spectroscopic and X-ray scattering techniques to investigate how local coordination interactions between the metal ion and ligands in the organic phase combine with long-range interactions to produce spontaneous changes in the solvent microstructure. Extraction of the Eu(3+)-3(NO3(-)) ion pairs involves incorporation of the "hard" metal complex into the core of "soft" aggregates. This seeds the formation of reverse micelles that draw the water and "free" amphiphile into nanoscale hydrophilic domains. The reverse micelles interact through attractive van der Waals interactions and coalesce into rod-shaped polynuclear Eu(III) -containing aggregates with metal centers bridged by nitrate. These preorganized hydrophilic domains, containing high densities of O-donor ligands and anions, provide improved Eu(III) solvation environments that help drive interfacial transfer, as is reflected by the increasing Eu(III) partitioning ratios (oil/aqueous) despite the organic phase approaching saturation. For the first time, this multiscale approach links metal-ion coordination with nanoscale structure to reveal the free-energy balance that drives the phase transfer of neutral metal salts. PMID:25169678

Ellis, Ross J; Meridiano, Yannick; Muller, Julie; Berthon, Laurence; Guilbaud, Philippe; Zorz, Nicole; Antonio, Mark R; Demars, Thomas; Zemb, Thomas

2014-09-26

234

Cellular responses to metal ions released from implants.  

PubMed

In the process of calcified tissue formation, cells secrete a protein-rich matrix into which they add a metal ion that nucleates in the presence of phosphorus to form an inorganic salt (usually calcium hydroxyapatite). Cellular and tissue responses to metal ions-released from implants, for example-can therefore be considered from the perspective of how cells handle calcium ions. A critical factor in determining cellular toxicity will be free ion concentrations and the competitive interactions that occur in a physicochemical manner. Three of the parameters used to assess the biocompatibility of implant materials are (1) the ability to influence mitotic activity, (2) intercellular adhesion, and (3) promotion of cell death. A spectrum of responses to free intracellular calcium ions can be identified, ranging from presence of the ion being essential for cell division through to an excess of the free ion that results in cell death (apoptosis). In between these extremes, cells may become postmitotic and express phenotypic variations as they adapt to their environment and establish equilibrium to maintain intracellular calcium homeostasis. The response of cells to implants can be linked to ions released and interactions between these and other ions and/or molecules present in the tissues, similar to the manner in which cells handle calcium ions. PMID:24914916

Kardos, Thomas B

2014-06-01

235

Means for obtaining a metal ion beam from a heavy-ion cyclotron source  

DOEpatents

A description is given of a modification to a cyclotron ion source used in producing a high intensity metal ion beam. A small amount of an inert support gas maintains the usual plasma arc, except that it is necessary for the support gas to have a heavy mass, e.g., xenon or krypton as opposed to neon. A plate, fabricated from the metal (or anything that can be sputtered) to be ionized, is mounted on the back wall of the ion source arc chamber and is bombarded by returning energetic low-charged gas ions that fail to cross the initial accelerating gap between the ion source and the accelerating electrode. Some of the atoms that are dislodged from the plate by the returning gas ions become ionized and are extracted as a useful beam of heavy ions. (auth)

Hudson, E.D.; Mallory, M.L.

1975-08-01

236

Does Ion Release Differ Between Hip Resurfacing and Metal-on-metal THA?  

PubMed Central

Modern metal-on-metal hip resurfacing was introduced as a bone-preserving method of joint reconstruction for young and active patients; however, the large diameter of the bearing surfaces is of concern for potential increased metal ion release. We hypothesized there were no differences in serum concentrations of chromium, cobalt, and molybdenum between patients who had metal-on-metal hip resurfacing (Group A; average head diameter, 48 mm; median followup, 24 months) and patients who had 28-mm metal-on-metal THA (Group B; median followup, 25 months). Serum concentrations also were compared with concentrations in healthy subjects. We identified no differences in ion levels between Groups A and B. A distinction was made according to gender. Women showed a higher chromium release in Group A whereas men had a higher cobalt release in Group B. Values obtained from Group A were higher than those of the control subjects. Our data suggest metal-on-metal bearings for THA should not be rejected because of concern regarding potential increased metal ion release; however, patients with elevated ion levels, even without loosening or toxicity, could be at higher risk and should be followed up periodically. Level of Evidence: Level III, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence. PMID:18196364

Moroni, Antonio; Cadossi, Matteo; Baldini, Nicola; Giannini, Sandro

2008-01-01

237

Effect of metal ions on the hydrolytic and transesterification activities of Candida rugosa lipase.  

PubMed

In order to study the effect of metal ions on lipase activity, hydrolytic and transesterification activities of Candida rugosa lipase were investigated in presence of alkali (Na? and K?), alkaline earth (Ca?² and Ba?²) and transition (Cr?³, Fe?³, Co?², Cu?² and Ni?²) metal ions. Maximum enhancement in hydrolytic activity of lipase was observed by Ca?², and in transesterification activity by Cr?³ and Co?². The kinetics of the lipase catalyzed transesterification (methanolysis and ethanolysis) reactions were also studied, and the activation energies of methanolysis and ethanolysis were reduced from 10.16 and 10.24 kcal mol?¹, respectively, to 5.41 and 7.55 kcal mol?¹, respectively, when reactions were performed in presence of Co?². Thus, in lipase catalyzed transesterification Cr?³ or Co?² could be added to the assay in order to produce the biodiesel in relatively shorter reaction duration. PMID:24200940

Katiyar, Madhu; Ali, Amjad

2013-01-01

238

Fluorescent carbon nanoparticles for the fluorescent detection of metal ions.  

PubMed

Fluorescent carbon nanoparticles (F-CNPs) as a new kind of fluorescent nanoparticles, have recently attracted considerable research interest in a wide range of applications due to their low-cost and good biocompatibility. The fluorescent detection of metal ions is one of the most important applications. In this review, we first present the general detection mechanism of F-CNPs for the fluorescent detection of metal ions, including fluorescence turn-off, fluorescence turn-on, fluorescence resonance energy transfer (FRET) and ratiometric response. We then focus on the recent advances of F-CNPs in the fluorescent detection of metal ions, including Hg(2+), Cu(2+), Fe(3+), and other metal ions. Further, we discuss the research trends and future prospects of F-CNPs. We envision that more novel F-CNPs-based nanosensors with more accuracy and robustness will be widely used to assay and remove various metal ions, and there will be more practical applications in coming years. PMID:25058940

Guo, Yongming; Zhang, Lianfeng; Zhang, Shushen; Yang, Yan; Chen, Xihan; Zhang, Mingchao

2015-01-15

239

Rapid in vitro screening of drug-metal ion interactions.  

PubMed

ABSTRACT The toxic side effects of synthetic drugs may, in part, be arising due to their interactions with essential metal ions, especially when the metal ions are administered along with the drug as mineral supplements. In this paper we report the feasibility of establishing such drug-metal ion interactions through in vitro spectrophotometric studies, which are rapid and can be used for routine screening prior to clinical studies. The interaction of the drugs levothyroxine and ranitidine with eight metal ions, copper(II), chromium(III), molybdenum(VI), magnesium(II), calcium(II), iron(II), manganese(II), and zinc(II), commonly used in mineral supplements, was verified through in vitro UV-visible spectrophotometric studies. The experiments were carried out at the physiological pH values 1.5, 7.4, and 8.0 and the concentrations of the drugs and mineral supplements used were comparable to those in their usual doses. These studies indicated interaction between ranitidine and calcium(II), magnesium(II), and iron(II) ions and between levothyroxine and copper(II) and iron(II) ions. A comparison of the results with those reported from clinical studies demonstrated the efficacy of this method. PMID:20020882

Sridevi, N; Yusuff, K K Mohammed

2007-01-01

240

Process for preparing higher oxides of the alkali and alkaline earth metals  

NASA Technical Reports Server (NTRS)

High purity inorganic higher oxides of the alkali and alkaline earth metals are prepared by subjecting the hydroxide of the alkali and alkaline earth metal to a radio frequency discharge sustained in oxygen. The process is particulary adaptable to the production of high purity potassium superoxide by subjecting potassium hydroxide to glow discharge sustained in oxygen under the pressure of about 0.75 to 1.00 torr.

Sadhukhan, P.; Bell, A. (inventors)

1978-01-01

241

Cationic rare earth metal alkyls as novel catalysts for olefin polymerization and copolymerization  

Microsoft Academic Search

Cationic rare earth metal alkyl species, generated by the treatment of mono(cyclopentadienyl) bis(alkyl) rare earth metal complexes with 1 equiv. of a borate compound such as [Ph3C][B(C6F5)4], act as an excellent catalyst for the polymerization and copolymerization of various olefins such as ethylene, 1-hexene, styrene, norbornene, dicyclopentadiene, and isoprene. These catalysts show unprecedented activity and regio- and stereo-selectivity and afford

Zhaomin Hou; Yunjie Luo; Xiaofang Li

2006-01-01

242

Non-metallocene rare earth metal catalysts for the diastereoselective and enantioselective hydroamination of aminoalkenes  

Microsoft Academic Search

In this short review we summarize our work on new cyclopentadienyl-free rare earth metal catalysts for the diastereoselective and enantioselective hydroamination of aminoalkenes. Non-metallocene rare earth metal catalysts based on diamidoamine, biphenolate and binaphtholate ligands are readily available through alkane and amine elimination procedures. Diamidoamine yttrium complexes are efficient catalysts for the highly diastereoselective cyclization of 1-methyl-pent-4-enylamine to yield trans-2,5-dimethyl-pyrroldine

Kai C. Hultzsch; Denis V. Gribkov; Frank Hampel

2005-01-01

243

Extraction and separation of rare earth metals using microcapsules containing bis(2-ethylhexyl)phosphinic acid  

Microsoft Academic Search

The separation of rare earth metals using microcapsules (MC) consisting styrene (St)–divinylbenzene (DVB) copolymer and containing bis(2-ethylhexyl)phosphinic acid (PIA-226) has been investigated. Microcapsules containing PIA-226 can be prepared by adding PIA-226 to the dispersed phase during the preparation process. The extraction of rare earth metals with the microcapsules progresses via the same scheme, as proposed in the conventional liquid–liquid extraction

Syouhei Nishihama; Nobuya Sakaguchi; Takayuki Hirai; Isao Komasawa

2002-01-01

244

Energization of solar wind ions by reflection from the earth's bow shock  

Microsoft Academic Search

The existence of ion beams with energies a few times the solar wind energy and streaming outward from the earth's bow shock has been known for some time. To explain the observed ion energies, a simple reflection model has been proposed in which the particles gain energy by displacement parallel to the interplanetary electric field. In this model the energy

G. Paschmann; N. Sckopke; J. R. Asbridge; S. J. Bame; J. T. Gosling

1980-01-01

245

Divalent cerium and praseodymium ions in crystals of alkaline-earth fluorides  

NASA Astrophysics Data System (ADS)

We have studied the absorption spectra of radiation-induced divalent cerium and praseodymium ions in crystals of alkaline-earth fluorides. Using ab initio quantum-mechanical methods, we have calculated absorption spectra of divalent praseodymium ions in CaF2 crystals for the first time. The theoretical spectrum agrees rather well with the experimentally registered spectra.

Shendrik, R. Yu.; Myasnikova, A. S.; Egranov, A. V.; Radzhabov, E. A.

2014-05-01

246

Catalytic asymmetric carbon-carbon bond-forming reaction utilizing rare earth metal complexes  

Microsoft Academic Search

Novel optically active rare earth complexes have made possible a catalytic asymmetric nitroaldol reaction for the first time. Structural elucidation reveals that the complexes consist of one rare earth metal, three lithium atoms, and three BINOL units. Applications of the catalytic asymmetric nitroaldol reaction to syntheses of several p-blockers and erythro-AYA have been also achieved. Although the lithium containing rare

Masakatsu Shibasaki; Hiroaki Sasai

1996-01-01

247

Membranes Remove Metal Ions Fron Industrial Liquids  

NASA Technical Reports Server (NTRS)

Use of membrane films affords convenient and economical alternative for removing and recovering metal cations present in low concentrations from large quantities of liquid solutions. Possible applications of membrane films include use in analytical chemistry for determination of small amounts of toxic metallic impurities in lakes, streams, and municipal effluents. Also suitable for use as absorber of certain pollutant gases and odors present in confined areas.

Hsu, W. P. L.; May, C.

1983-01-01

248

Determination of trace metallic impurities in high-purity quartz by ion chromatography.  

PubMed

A method has been developed for the determination of relevant trace impurities (alkali, alkaline and transition metals) in high purity quartz by ion-chromatography. In situ reagent (HF) purification and simultaneous sample dissolution was achieved in a multichannel vapour phase digestion assembly. Twenty-one samples can be digested at a time in this vapour phase system. Significant decrease in the process blank levels for all the analytes was observed. Drastic reduction (250 times) of NH4+ blank was achieved in the described vapour phase digestion, which enables the determination of trace concentration of sodium in high purity quartz. After volatilisation of the matrix and unreacted HF, the clear water leached solutions were injected into an ion-chromatograph equipped with conductivity detector for the determination of alkali and alkaline earth metals. In the case of transition metals, the trace residues were leached with 10 mM HCl and after separation on a mixed bed analytical column (IonPac CS5) were detected by spectrophotometry after post column derivatisation using 4-(2-pyridylazo)resorcinol (PAR). The accuracy of the result was checked by their comparison with those obtained by independent methods like inductively coupled plasma (ICP) MS and ICP atomic emission spectrometry. The achievable detection limits are between 0.4 ng/g (Li) and 22 ng/g (Mn). The application of the method to the determination of the above trace metals in two high-purity-grade quartz samples is demonstrated. PMID:14753768

Dash, K; Chandrasekaran, K; Thangavel, S; Dhaville, S M; Arunachalam, J

2004-01-01

249

Towards the ionic limit of two-dimensional materials: monolayer alkaline earth and transition metal halides.  

PubMed

We theoretically explored new two-dimensional materials near the ionic instability (three-dimensional structures are favored), with covalent bonded systems (graphene) sitting at the opposite end of the spectrum. Accordingly, monolayer alkaline earth and transition metal halides, many of their bulk forms being layered structures, were investigated by density functional calculations. We thus predicted a new class of two-dimensional materials by performing structure relaxation, cohesive/formation energy and full phonon dispersion calculations. These materials exhibit strong ionic bonding character, as revealed by significant charge transfers. The superior charge donating/accepting abilities and the large specific area make these new materials promising for adsorption and catalytic reactions. We demonstrated adsorption and diffusion of Li on these materials, which are relevant for Li ion battery electrodes and hydrogen storage. Also the new materials with varied charge donating abilities and their nanostructures can enhance and tune catalytic reactions, such as Ziegler-Natta catalysts. Moreover, they exhibit diverse electronic properties that can be of great application interest, ranging from insulators to metals, and even spin-polarized semiconductors. PMID:25163641

Lin, Shi-Hsin; Kuo, Jer-Lai

2014-10-14

250

High Pressure Phase Transformations in Heavy Rare Earth Metals and Connections to Actinide Crystal Structures  

SciTech Connect

High-pressure studies have been performed on heavy rare earth metals Terbium (Tb) to 155 GPa and Holmium (Ho) to 134 GPa in a diamond anvil cell at room temperature. The following crystal structure sequence was observed in both metals hcp {yields} Sm-type {yields} dhcp {yields} distorted fcc (hR-24) {yields} monoclinic (C2/m) with increasing pressure. The last transformation to a low symmetry monoclinic phase is accompanied by a volume collapse of 5 % for Tb at 51 GPa and a volume collapse of 3 % for Ho at 103 GPa. This volume collapse under high pressure is reminiscent of f-shell delocalization in light rare earth metal Cerium (Ce), Praseodymium (Pr), and heavy actinide metals Americium (Am) and Curium (Cm). The orthorhombic Pnma phase that has been reported in Am and Cm after f-shell delocalization is not observed in heavy rare earth metals under high pressures. (authors)

Vohra, Yogesh K.; Sangala, Bagvanth Reddy; Stemshorn, Andrew K. [Physics, University of Alabama at Birmingham (UAB), 310 Campbell Hall, 1300 University Boulevard, Birmingham, AL, 35294-1170 (United States); Hope, Kevin M. [Biology, Chemistry, and Mathematics, University of Montevallo, Harman Hall, Station 6480, Montevallo, AL, 35115 (United States)

2008-07-01

251

Multiple Metal Binding Domains Enhance the Zn(II) Selectivity of the Divalent Metal Ion Transporter AztA  

E-print Network

, Pb, Hg, and As, do not accumulate inside cells. The heavy metal ion-transporting CPxMultiple Metal Binding Domains Enhance the Zn(II) Selectivity of the Divalent Metal Ion Transporter 3, 2007; ReVised Manuscript ReceiVed July 17, 2007 ABSTRACT: Transition metal-transporting P1B

Scott, Robert A.

252

Biomimetic metal-sorbing vesicles for continuous extraction of heavy metal ions from dilute solution  

SciTech Connect

Biomimetic vesicle media which can selectivity extract and concentrate heavy metals (e.g., Pb{sup 2+}) from dilute solutions of 5 ppm and less have been prepared. At a concentration of only 1% 2/v, these non-covalently assembled, unilamellar, surfactant vesicles provide approximately 1,000m{sup 2} of exposed membrane surface area per liter of suspension which gives rise to very rapid rates of metal ion extraction. To facilitate the selective transport of heavy metal ions through the ion impermeable vesicle wall, the vesicles are doped with lipophilic ionophores, both natural and synthetic. In addition, the metal chelating agent, nitrolotriacetate, is encapsulated in the aqueous vesicle core to provide the driving force for metal ion uptake and concentration. Concentration factors in excess of 1000 fold have been observed. Metal-sorbing surfactant vesicles measuring approximately 100 nm in diameter are stable and have been tested in a bench-scale metal ion extraction process where the vesicles are recircled continuously through a hollow-fiber ultrafiltration cartridge.

Monbouquette, H.G.; Chang, D.; Walsh, A.J.; van Zanten, J.H. [Univ. of California, Los Angeles, CA (United States)

1993-12-31

253

Detection of Heavy Metal Ions in Water by High-Resolution Surface Plasmon Resonance  

E-print Network

Detection of Heavy Metal Ions in Water by High-Resolution Surface Plasmon Resonance Spectroscopy voltammetry (ASV) capability has been demonstrated for detecting heavy metal ions in water. Metal ions in water from part-per-million to sub-part-per-billion levels with good linearity. Heavy metal poisoning

Zhang, Yanchao

254

Diagnostics of hollow cathode discharge metal ion lasers  

NASA Astrophysics Data System (ADS)

Lasing properties of active media in sputtered hollow cathode discharge (HCD) He-Cu lasers operating on 780.8 nm transition have been investigated for several HC configurations. Direct measurements of small-signal gain and its spatial distribution have proved that a segmented hollow cathode discharge (SHCD) is the most efficient in achieving laser action on metal ions excited by thermal energy charge-transfer reaction. Results obtained for He-Cu lasers indicate that the observed linear dependency of gain on discharge current can be explained by limited flow of metal atoms into the region of laser generation and probably are valid for all kind of sputtered metal ion lasers oscillating on UV and IR transitions. The possibility of obtaining continuous or long-pulse laser operation in far UV range is also discussed. A new method of measuring diffusion coefficients of metal atoms in noble gases in sputtered HCD lasers is presented.

Adamowicz, Tadeusz M.

1997-08-01

255

What happens to serum metal ion levels after a metal-on-metal bearing is removed?  

PubMed

Serum cobalt (Co) and chromium (Cr) levels are commonly used to screen for excessive wear of metal-on-metal hip replacements. However, it is unknown how rapidly these should decline after revision. 25 patients with average Co and Cr ion levels of 56.3 ?g/L and 20.5 ?g/L were followed with serial ion level testing post-revision. Over the first 6 weeks post-revision, the rate of decline for Co and Cr was approximately 2% per day and this slowed to approximately 1% decline per day over the ensuing 6 weeks. This translated to a decline of approximately 80% from the starting value after 6 weeks and a decline of approximately 90% after 12 weeks post-revision. The rate of decline for both Co and Cr was significantly faster during the first 6 weeks (P<0.001). In patients with ultra-high Cr levels>20 ?g/L, the rate of Cr decline is less predictable and may be protracted leading to persistent elevation above 5 ?g/L for one year or more post-revision in some cases. PMID:23948123

Ball, Scott T; Severns, Dustyn; Linn, Michael; Meyer, R Scott; Swenson, F Craig

2013-09-01

256

Architectural design criteria for f-block metal ion sequestering agents. 1998 annual progress report  

SciTech Connect

'The objective of this project is to provide a means to optimize ligand architecture for f-block metal recognition. The authors strategy builds on an innovative and successful molecular modeling approach in developing polyether ligand design criteria for the alkali and alkaline earth cations. The hypothesis underlying this proposal is that differences in metal ion binding with multidentate ligands bearing the same number and type of donor groups are primarily attributable to intramolecular steric factors. They propose quantifying these steric factors through the application of molecular mechanics models. The research involves close integration of theoretical and experimental chemistry. The experimental work entails synthesizing novel ligands and experimentally determining structures and binding constants for metal ion complexation by series of ligands in which architecture is systematically varied. The theoretical work entails using electronic structure calculations to parameterize a molecular mechanics force field for a range of metal ions and ligand types. The resulting molecular mechanics force field will be used to predict low energy structures for unidentate, bidentate, and multidentate ligands and their metal complexes through conformational searches. Results will be analyzed to assess the relative importance of several steric factors including optimal M-L length, optimal geometry at the metal center, optimal geometry at the donor atoms (complementarity), and conformation prior to binding (preorganization). An accurate set of criteria for the design of ligand architecture will be obtained from these results. These criteria will enable researchers to target ligand structures for synthesis and thereby dramatically reduce the time and cost associated with metal-specific ligand development.'

Hay, B.P.; Dixon, D.A. [Pacific Northwest National Lab., Richland, WA (US); Roundhill, D.M. [Texas Tech Univ., Lubbock, TX (US); Rogers, R.D. [Univ. of Alabama, Tuscaloosa, AL (US); Paine, R.T. [Univ. of New Mexico, Albuquerque, NM (US); Raymond, K.N. [Univ. of California, Berkeley, CA (US)

1998-12-31

257

Determination of metal ions in biological purification of waste waters  

SciTech Connect

Chromium, nickel, copper, zinc, and manganese were determined in active sludge extracted for utilization from sewage purification works in biological purification of waste waters. The measurements were carried out by the atomic absorption method and with Merck colorimetric kits for rapid determination of metal ions. The results obtained by the rapid colorimetric method agree fairly well with those obtained by the atomic absorption method, which makes it possible to recommend rapid colorimetric methods for routine analysis of biological objects for the content of ions of heavy metals.

Tikhomirova, L.N.; Spiridonova, N.N.; Mandzhgaladze, I.D. [Moscow State Correspondence Inst. of the Food Industry, Moscow (Russian Federation)] [and others

1994-12-01

258

Adsorbent for metal ions and method of making and using  

DOEpatents

A method comprises the step of spray-drying a solution or slurry comprising (alkali metal or ammonium) (metal) hexacyanoferrate particles in a liquid, to provide monodisperse, substantially spherical particles in a yield of at least 70 percent of theoretical yield and having a particle size in the range of 1 to 500 micrometers, said particles being active towards Cs ions. The particles, which can be of a single salt or a combination of salts, can be used free flowing, in columns or beds, or entrapped in a nonwoven, fibrous web or matrix or a cast porous membrane, to selectively remove Cs ions from aqueous solutions.

White, Lloyd R. (Minneapolis, MN); Lundquist, Susan H. (White Bear Township, MN)

2000-01-01

259

Electronic energy-density effects in ion tracks of metals  

Microsoft Academic Search

High resolution Auger-electron spectroscopy has been applied to the interaction of swift heavy ions with atomically clean metallic solids. Spectra have been taken for fast projectile electrons and for charge-state equilibrated ions at normal incidence on microcrystalline beryllium samples, Al(100) single crystals and several metallic glasses (Al87La7Ni5Zr1, Ni78B14Si8, Co66Si16B12Fe4Mo2). From the energy shift and from the Auger-line width we have

F. Staufenbiel; G. Schiwietz; K. Czerski; M. Roth; P. L. Grande

2005-01-01

260

Adsorbent for metal ions and method of making and using  

DOEpatents

A method comprises the step of spray-drying a solution or slurry comprising (alkali metal or ammonium) (metal) hexacyanoferrate particles in a liquid, to provide monodisperse, substantially spherical particles in a yield of at least 70 percent of theoretical yield and having a particle size in the range of 1 to 500 micrometers, said particles being active towards Cs ions. The particles, which can be of a single salt or a combination of salts, can be used free flowing, in columns or beds, or entrapped in a nonwoven, fibrous web or matrix or a cast porous membrane, to selectively remove Cs ions from aqueous solutions.

White, Lloyd R. (Minneapolis, MN); Lundquist, Susan H. (White Bear Township, MN)

1999-01-01

261

Strong cation···? interactions promote the capture of metal ions within metal-seamed nanocapsule.  

PubMed

Thallium ions are transported to the interior of gallium-seamed pyrogallol[4]arene nanocapsules. In comparison to the capture of Cs ions, the extent of which depends on the type and position of the anion employed in the cesium salt, the enhanced strength of Tl···? vs Cs···? interactions facilitates permanent entrapment of Tl(+) ions on the capsule interior. "Stitching-up" the capsule seam with a tertiary metal (Zn, Rb, or K) affords new trimetallic nanocapsules in solid state. PMID:25405777

Kumari, Harshita; Jin, Ping; Teat, Simon J; Barnes, Charles L; Dalgarno, Scott J; Atwood, Jerry L

2014-12-10

262

Data mining of metal ion environments present in protein structures  

PubMed Central

Analysis of metal-protein interaction distances, coordination numbers, B-factors (displacement parameters), and occupancies of metal binding sites in protein structures determined by X-ray crystallography and deposited in the PDB shows many unusual values and unexpected correlations. By measuring the frequency of each amino acid in metal ion binding sites, the positive or negative preferences of each residue for each type of cation were identified. Our approach may be used for fast identification of metal-binding structural motifs that cannot be identified on the basis of sequence similarity alone. The analysis compares data derived separately from high and medium resolution structures from the PDB with those from very high resolution small-molecule structures in the Cambridge Structural Database (CSD). For high resolution protein structures, the distribution of metal-protein or metal-water interaction distances agrees quite well with data from CSD, but the distribution is unrealistically wide for medium (2.0 – 2.5 Å) resolution data. Our analysis of cation B-factors versus average B-factors of atoms in the cation environment reveals substantial numbers of structures contain either an incorrect metal ion assignment or an unusual coordination pattern. Correlation between data resolution and completeness of the metal coordination spheres is also found. PMID:18614239

Zheng, Heping; Chruszcz, Maksymilian; Lasota, Piotr; Lebioda, Lukasz; Minor, Wladek

2010-01-01

263

In vivo liberation of silver ions from metallic silver surfaces  

Microsoft Academic Search

In vivo liberation of electrically charged silver atoms\\/silver ions from metallic silver pellets, silver grids and silver\\u000a threads placed in the brain, skin and abdominal cavity was proved by way of the histochemical technique autometallography\\u000a (AMG). A bio-film or “dissolution membrane” inserted between the metallic surface and macrophages was recognized on the surface\\u000a of the implanted silver after a short

Gorm Danscher; Linda Jansons Locht

2010-01-01

264

Engineered allosteric ribozymes that respond to specific divalent metal ions  

Microsoft Academic Search

In vitro selection was used to isolate five classes of allosteric hammerhead ribozymes that are triggered by binding to certain divalent metal ion effectors. Each of these ribozyme classes are similarly activated by Mn21 ,F e21 ,C o21 ,N i21 ,Z n21 and Cd21, but their allo- steric binding sites reject other divalent metals such as Mg21 ,C a21 and

Maris Zivarts; Yong Liu; Ronald R. Breaker

2005-01-01

265

Smart responsive microcapsules capable of recognizing heavy metal ions.  

PubMed

Smart responsive microcapsules capable of recognizing heavy metal ions are successfully prepared with oil-in-water-in-oil double emulsions as templates for polymerization in this study. The microcapsules are featured with thin poly(N-isopropylacrylamide-co-benzo-18-crown-6-acrylamide) (P(NIPAM-co-BCAm)) membranes, and they can selectively recognize special heavy metal ions such as barium(II) or lead(II) ions very well due to the "host-guest" complexation between the BCAm receptors and barium(II) or lead(II) ions. The stable BCAm/Ba(2+) or BCAm/Pb(2+) complexes in the P(NIPAM-co-BCAm) membrane cause a positive shift of the volume phase transition temperature of the crosslinked P(NIPAM-co-BCAm) hydrogel to a higher temperature, and the repulsion among the charged BCAm/Ba(2+) or BCAm/Pb(2+) complexes and the osmotic pressure within the P(NIPAM-co-BCAm) membranes result in the swelling of microcapsules. Induced by recognizing barium(II) or lead(II) ions, the prepared microcapsules with P(NIPAM-co-BCAm) membranes exhibit isothermal and significant swelling not only in outer and inner diameters but also in the membrane thickness. The proposed microcapsules in this study are highly attractive for developing smart sensors and/or carriers for detection and/or elimination of heavy metal ions. PMID:20656104

Pi, Shuo-Wei; Ju, Xiao-Jie; Wu, Han-Guang; Xie, Rui; Chu, Liang-Yin

2010-09-15

266

Adsorption characteristics of metal ions on chitosan chemically modified by D-galactose  

SciTech Connect

The adsorption characteristics of metal ions on chitosan chemically modified by D-galactose were examined. The pH dependency on the distribution ratio was found to be affected by the valency of the metal ion, and the apparent adsorption equilibrium constants of the metal ions were determined. The order of adsorption of the metal ions is Ga > In > Nd > Eu for the trivalent metal ions and Cu > Ni > Co for the divalent metal ions. It is believed that amino and hydroxyl groups in the chitosan act as a chelating ligand.

Kondo, Kazuo; Sumi, Hisaharu; Matsumoto, Michiaki [Doshisha Univ., Tanabe, Kyoto (Japan)

1996-07-01

267

The chemistry of meteoric metals in the Earth's upper atmosphere  

Microsoft Academic Search

The presence of thin layers of free metal atoms at around 90 km in the upper atmosphere has been known for about fifty years. Layers of the alkali metals Na, K and Li, as well as Ca and Fe, have been observed. This discovery has posed two important questions. First, what is the source of the metals: interplanetary or terrestrial?

John M. C. Plane

1991-01-01

268

Heavy metal ions are potent inhibitors of protein folding  

SciTech Connect

Environmental and occupational exposure to heavy metals such as cadmium, mercury and lead results in severe health hazards including prenatal and developmental defects. The deleterious effects of heavy metal ions have hitherto been attributed to their interactions with specific, particularly susceptible native proteins. Here, we report an as yet undescribed mode of heavy metal toxicity. Cd{sup 2+}, Hg{sup 2+} and Pb{sup 2+} proved to inhibit very efficiently the spontaneous refolding of chemically denatured proteins by forming high-affinity multidentate complexes with thiol and other functional groups (IC{sub 50} in the nanomolar range). With similar efficacy, the heavy metal ions inhibited the chaperone-assisted refolding of chemically denatured and heat-denatured proteins. Thus, the toxic effects of heavy metal ions may result as well from their interaction with the more readily accessible functional groups of proteins in nascent and other non-native form. The toxic scope of heavy metals seems to be substantially larger than assumed so far.

Sharma, Sandeep K. [Biochemisches Institut, Universitaet Zuerich, CH-8057 Zuerich (Switzerland); Departement de Biologie Moleculaire Vegetale, Universite de Lausanne, CH-1015 Lausanne (Switzerland); Goloubinoff, Pierre [Departement de Biologie Moleculaire Vegetale, Universite de Lausanne, CH-1015 Lausanne (Switzerland); Christen, Philipp [Biochemisches Institut, Universitaet Zuerich, CH-8057 Zuerich (Switzerland)], E-mail: christen@bioc.uzh.ch

2008-07-25

269

Extraction of rare-earth metals by liquid surfactant membranes containing a novel cyclic carrier  

Microsoft Academic Search

Extraction behavior of three rare-earth metals (Ho, Er and Y), was systematically studied by liquid surfactant membranes (LSMs) containing a novel host compound, a calixarene carboxyl derivative, which is a cyclic compound connected to some phenol rings, as a mobile carrier in a stirred cell. Using the host compound, the extraction equilibrium of the metals in liquid-liquid extraction was also

Takahiko Kakoi; Takayuki Nishiyori; Tatsuya Oshima; Fukiko Kubota; Masahiro Goto; Seiji Shinkai; Fumiyuki Nakashio

1997-01-01

270

MAGNETIC ORDERING AND THE ELECTRONIC STRUCTURE OF RARE-EARTH METALS  

Microsoft Academic Search

The effects of magnetic ordering of the localized 4f electrons in rare ; earth metals on the structure of the Brillouin zones in these metals, and hence ; on the conduction-electron characteristics, are studied by means of a ; magneticsuperlattice model. The model takes into account the exchange ; interaction between the 4f and conduction electrons, and effects of spin-orbit

A. Mackintosh

1962-01-01

271

Minerals yearbook, 1988. Rare-earth minerals and metals  

SciTech Connect

Domestic production of rare-earth concentrates decreased in 1988. Foreign sources of processed rare earths obtained a slightly larger share of the U.S. market, while domestic exports saw a marked increase compared to 1987 levels. Rare earths were used in high-technology applications such as laser crystals, high-strength permanent magnets, optical fibers, magnetic resonance imaging (MRI) scanners, and high-temperature superconductors. Topics discussed in the report include domestic data coverage, legislation and government programs, environmental issues, domestic production, consumption and uses, stocks, prices, foreign trade, world capacity, world review--Australia, Brazil, Canada, China, Egypt, Greenland, Japan, Madagascar, Malaysia, Mozambique, Sri Lanka, Thailand--and technology.

Hedrick, J.B.; Templeton, D.A.

1988-01-01

272

Superconductivity in Metal-mixed Ion-Implanted Polymer Films  

E-print Network

Ion-implantation of normally insulating polymers offers an alternative to depositing conjugated organics onto plastic films to make electronic circuits. We used a 50 keV nitrogen ion beam to mix a thin 10 nm Sn/Sb alloy film into the sub-surface of polyetheretherketone (PEEK) and report the low temperature properties of this material. We observed metallic behavior, and the onset of superconductivity below 3 K. There are strong indications that the superconductivity does not result from a residual thin-film of alloy, but instead from a network of alloy grains coupled via a weakly conducting, ion-beam carbonized polymer matrix.

A. P. Micolich; E. Tavenner; B. J. Powell; A. R. Hamilton; M. T. Curry; R. E. Giedd; P. Meredith

2005-09-11

273

DUHOCAMIS: a dual hollow cathode ion source for metal ion beams.  

PubMed

In this paper we describe a novel ion source named DUHOCAMIS for multiply charged metal ion beams. This ion source is derived from the hot cathode Penning ion gauge ion source (JINR, Dubna, 1957). A notable characteristic is the modified Penning geometry in the form of a hollow sputter electrode, coaxially positioned in a compact bottle-magnetic field along the central magnetic line of force. The interaction of the discharge geometry with the inhomogeneous but symmetrical magnetic field enables this device to be operated as hollow cathode discharge and Penning discharge as well. The main features of the ion source are the very high metal ion efficiency (up to 25%), good operational reproducibility, flexible and efficient operations for low charged as well as highly charged ions, compact setup, and easy maintenance. For light ions, e.g., up to titanium, well-collimated beams in the range of several tens of milliamperes of pulsed ion current (1 ms, 10/s) have been reliably performed in long time runs. PMID:18315181

Zhao, W J; Müller, M W O; Janik, J; Liu, K X; Ren, X T

2008-02-01

274

Uptake of Metal Ions by Rhizopus arrhizus Biomass  

PubMed Central

Rhizopus arrhizus biomass was found to absorb a variety of different metal cations and anions but did not absorb alkali metal ions. The amount of uptake of the cations was directly related to ionic radii of La3+, Mn2+, Cu2+, Zn2+, Cd2+, Ba2+, Hg2+, Pb2+, UO22+, and Ag+. The uptake of all the cations is consistent with absorption of the metals by sites in the biomass containing phosphate, carboxylate, and other functional groups. The uptake of the molybdate and vanadate anions was strongly pH dependent, and it is proposed that the uptake mechanism involves electrostatic attraction to positively charged functional groups. PMID:16346521

Tobin, J. M.; Cooper, D. G.; Neufeld, R. J.

1984-01-01

275

Metallic ions in cometary comae and plasma tails  

NASA Astrophysics Data System (ADS)

A surprising result of the International Cometary Explorer (ICE) observations of the comet Giacobini-Zinner was the detection of ions of mass 23-24 AMU with a relatively high abundance. According to the experiments, these ions may be either Na(+) or C2(+), if not both. It is suggested here that the detected ions may indeed be in part Na(+) and/or Mg(+), and that these and other metallic ions, especially Si(+) and Fe(+), may be an important component of the cometary ionosphere and central plasma tail. The reasons are similar in principle to those which account for the prevalence of such ions in sporadic E layers in the terrestrial ionosphere, notably the comparatively short timescales for ionization of their neutral parent atoms and the large difference between the rates of dissociative and radiative recombination.

Ip, W.-H.; Axford, W. I.

1986-06-01

276

The metal vapor vacuum arc (MEVVA) high current ion source  

SciTech Connect

An ion source is described in which a metal vapor vacuum arc is used to create the plasma from which the ions are extracted. Beams of a variety of ions have been produced, ranging from lithium up to uranium. At an extraction voltage of 25 kV we've measured an ion beam current of over 1 Ampere, with over 550 ema of the beam in an emittance of 0.07..pi.. cm. mradians (normalized). The ion charge state distribution varies with cathode material and with arc power; for uranium a typical distribution is peaked at U/sup 5 +/, with up to 40% of the beam current in this charge state.

Brown, I.G.

1985-10-01

277

Metal vapor vacuum arc (MEVVA) high current ion source  

SciTech Connect

An ion source is described in which a metal vapor vacuum arc is used to create the plasma from which the ions are extracted. Beams of a variety of ions have been produced, ranging from lithium up to uranium. At an extraction voltage of 25 kV we've measured an ion beam current of over 1 Ampere, with over 550 ema of the beam in an emittance of 0.07..pi.. cm. mradians (normalized). The ion charge state distribution varies with cathode material and with arc power; for uranium a typical distribution is peaked at U/sup 5 +/, with up to 40% of the beam current in this charge state. 27 refs., 10 figs.

Brown, I.G.

1985-05-01

278

Metal ion bombardment of onion skin cell wall  

SciTech Connect

Ion bombardment of living cellular material is a novel subfield of ion beam surface modification that is receiving growing attention from the ion beam and biological communities. Although it has been demonstrated that the technique is sound, in that an adequate fraction of the living cells can survive both the vacuum environment and energetic ion bombardment, there remains much uncertainty about the process details. Here we report on our observations of onion skin cells that were subjected to ion implantation, and propose some possible physical models that tend to support the experimental results. The ion beams used were metallic (Mg, Ti, Fe, Ni, Cu), mean ion energy was typically 30keV, and the implantation fluence was in the range 1014 1016 ions/cm2. The cells were viewed using Atomic Force Microscopy, revealing the formation of microcrater-like structures due to ion bombardment. The implantation depth profile was measured with Rutherford backscattering spectrometry and compared to the results of the TRIM, T-DYN and PROFILE computer codes.

Sangyuenyongpipat, S.; Vilaithong, T.; Yu, L.D.; Verdaguer, A.; Ratera, I.; Ogletree, D.F.; Monteiro, O.R.; Brown, I.G.

2004-05-10

279

Ion beam sputter-deposited thin film coatings for protection of spacecraft polymers in low Earth orbit  

NASA Technical Reports Server (NTRS)

Ion beam sputter-deposited thin films of Al2O3, SiO2, and a codeposited mixture of predominantly SiO2 with small amounts of a fluoropolymer were evaluated both in laboratory plasma ashing tests and in space on board shuttle flight STS-8 for effectiveness in preventing oxidation of polyimide Kapton. Measurements of mass loss and optical performance of coated and uncoated polyimide samples exposed to the low Earth orbital environment are presented. Optical techniques were used to measure loss rates of protective films exposed to atomic oxygen. Results of the analysis of the space flight exposed samples indicate that thin film metal oxide coatings are very effective in protecting the polyimide. Metal oxide coatings with a small amount of fluoropolymer codeposited have the additional benefit of great flexibility.

Banks, B. A.; Mirtich, M. J.; Rutledge, S. K.; Swec, D. M.; Nahra, H. K.

1985-01-01

280

PARTITIONING-SEPARATION OF METAL IONS USING HETEROCYCLIC LIGANDS  

Microsoft Academic Search

Some guidelines are proposed for the effective design of heterocylic ligands for partitioning because there is no doubt that the correct design of a molecular extractant is required for the effective separation of metal ions such as actinides(III) from lanthanides(III). Heterocyclic ligands with aromatic ring systems have a rich chemistry, which is only now becoming sufficiently well understood in relation

Michael J. Hudson; Michael G. B. Drew; Peter B. Iveson; Charles Madic; Mark L. Russell

281

COAGULATION AND PRECIPITATION OF SELECTED METAL IONS FROM AQUEOUS SOLUTIONS  

EPA Science Inventory

The report gives results of laboratory jar tests to develop data on the removal from aqueous solution of 12 metal ions of environmental concern. The project, of very limited scope, provides initial screening data only: coagulants were evaluated at only two dose levels (1.1 and 1....

282

Accumulation of heavy-metal ions by Zoogloea ramigera  

Microsoft Academic Search

Biomass has been produced from glucose using the organism Zoogloea ramigera 115. This biomass has been used to remove copper, cadmium, and uranyl ions from water solutions. The metal uptake was studied with two different methods: either by spectrophotometric measurements on the solutions after flocculation or by potentiometric measurements with amalgam electrodes in order to follow the entire complex formation.

Anders B. Norberg; Hans Persson

1984-01-01

283

Laser-driven ion sources for metal ion implantation for the reduction of dry friction  

SciTech Connect

The anomalously high ion currents and very high ionization levels of laser-produced plasmas give laser-driven ion sources significant advantages over conventional ion sources. In particular, laser-driven ion sources should provide higher currents of metal ions at lower cost, for implantation into solids in order to improve their material properties such as friction. The energy and charge distributions for Pb and Sn ions produced by ablation of solid targets with {approx}25 J, {approx}300 ps iodine laser pulses, resulting in up to 48-times ionized MeV ions, as well as the optimization of focus position, are presented. Implantation of these ions into Ck-45 steel, without electrostatic acceleration, produced profiles with two regions. Almost all of the ions were implanted in a near surface region a few nm deep. However, a small but significant number of ions were implanted as deep as could be measured with Rutherford backscattering (RBS), here 150 nm for Sn and 250 nm for Pb. For the implanted ion densities and profiles achieved, no change in the coefficient of friction was measured for either ion.

Boody, F. P. [Fachhochschule Regensburg, Seybothstrasse 2, 93053 Regensburg (Germany); Juha, L. [Fachhochschule Regensburg, Seybothstrasse 2, 93053 Regensburg (Germany) and Institute of Physics, Academy Sciences of the Czech Republic, Na Slovance 2, 180 40 Prague 8 (Czech Republic); Kralikova, B.; Krasa, J.; Laska, L.; Masek, K.; Pfeifer, M.; Rohlena, K.; Skala, J.; Straka, P. [Institute of Physics, Academy Sciences of the Czech Republic, Na Slovance 2, 180 40 Prague 8 (Czech Republic); Perina, V. [Nuclear Physics Institute, Academy Sciences of the Czech Republic, 25068 Rez (Czech Republic); Woryna, E. [Institute of Plasma Physics and Laser Microfusion, 00908 Warsaw (Poland); Giersch, D. [BMW AG, 80788 Munich (Germany); Hoepfl, R. [Fachhochschule Deggendorf, Franz-Josef-Strauss-Str. 7, 94469 Deggendorf (Germany); Kelly, J. C.; Hora, H. [University of New South Wales, Sydney 2052 (Australia)

1997-04-15

284

Ion exchangers as adsorbents for removing metals from aquatic media.  

PubMed

A polyaniline-based composite cation-exchange material was synthesized by way of sol-gel method and studied to explore its analytical and environmental applications. It was characterized by using instrumental analyses [Fourier transform infrared (spectrometer), X-ray, thermogravimetric analysis/differential thermal analysis, standard electron microscopy, and transmission electron microscopy]. Physicochemical studies, such as ion-exchange capacity, pH titrations, and chemical stability, along with effect of eluent concentration and elution, were also performed to exploit the ion-exchange capabilities. pH titration studies showed that the material presents monofunctional strong cation-exchange behavior. This nanocomposite material is semicrystalline in nature and exhibits improved thermal and chemical stability. The partition coefficient studies of different metal ions in the material were performed in demineralised water and different surfactant media, and it was found to be selective for Pb(II) and Hg(II) ions. To exploit the usefulness of the material as an adsorbent, some important quantitative binary separations of metal ions were performed on polyaniline Zr(IV) molybdophosphate columns. This composite cation exchanger can be applied for the treatment of polluted water to remove heavy metals. PMID:24292693

Khan, Meraj A; Bushra, Rani; Ahmad, Anees; Nabi, Syed A; Khan, Dilwar A; Akhtar, Arshia

2014-02-01

285

Energetics and bonding in aluminosilicate rings with alkali metal and alkaline-earth metal charge-compensating cations.  

PubMed

The stabilizing effect of alkali and alkaline-earth metal ions on the oxygen donors of four- and six-membered faujausite-like rings has been calculated in terms of Kohn-Sham core-level (O1s) energy shifts with respect to these same complexes without cations. The results confirm and complement earlier investigations by Vayssilov and co-workers where Na(+) and K(+) were the only complexing cations. The oxygen donor centers in six-membered rings are stabilized by -3.6 ± 0.4, -3.9 ± 0.5, -7.3 ± 0.1, and -7.6 ± 0.2 eV by K(+), Na(+), Ca(2+), and Mg(2+) adions, respectively. The energy shifts are even greater for four-membered rings where the stabilization effects attain -3.7 ± 0.1, -4.1 ± 0.1, -8.1 ± 0.1, and -9.0 ± 0.1 eV, respectively. These effects are also observed on the low-lying ?-bonding and antibonding molecular orbitals (MOs) of the oxygen framework, but in a less systematic fashion. Clear relationships with the core-level shifts are found when the effects of alkali metal complexation are evaluated through electron localization/delocalization indices, which are defined in terms of the whole wave function and not just of the individual orbitals. Complexation with cations not only involves a small but significant electron sharing of the cation with the oxygen atoms in the ring but also enhances electron exchange among oxygen atoms while reducing that between the O atoms and the Si or Al atoms bonded to them. Such changes slightly increase from Na to K and from Mg to Ca, whereas they are significantly enhanced for alkaline-earth metals relative to alkali metals. With respect to Al-free complexes, Si/Al substitution and cation charge compensation generally enhance electron delocalization among the O atoms, except between those that are linked through an Al atom, and cause either an increased or a decreased Si-O ionicity (smaller/higher electron exchange) depending on the position of O in the chain relative to the Al atom(s). The generally increased electron delocalization among O atoms in the ring is induced by significant electron transfer from the adsorbed metal to the atoms in the ring. This same transfer establishes an electric field that leads to a noticeable change in the ring-atom core-level energies. The observed shifts are larger for the oxygen atoms because, being negatively charged, they are more easily polarizable than Al and Si. The enhanced electron delocalization among O atoms upon cation complexation is also manifest in Pauling's double-bond nature of the bent ?-bonding MO between nonadjacent oxygen centers in O-based ring structures. PMID:22809367

Gatti, Carlo; Ottonello, Giulio; Richet, Pascal

2012-08-23

286

The ligand-promoted mobilisation of metal ions from mineral surfaces  

NASA Astrophysics Data System (ADS)

Many metals such as Fe, Mo, Cu, Zn etc have been identified as essential micronutrients for plants and microorganisms. These metals have to be mobilised from mineral surfaces in contact with crustal fluids in order to be available to living cells. Many studies have shown the importance of chelation in the mobilisation of metal ions into these fluids. The ligand-promoted dissolution of minerals enables elements essential to life to be accessible. Organic acids with chelating properties are widely present on the surface of the earth (both anthropogenic and those produced naturally such as siderophores) and as well as releasing metal ions into solution for bioavailability, they control processes such as metal ion transport and adsorption and thereby are important in the understanding of toxicity and contamination. In this study we have compared mineral dissolution using a strong industrial chelator (DTPA -- diethylene triamine penta-acetic acid) and dissoluton using a synthetically produced naturally occurring siderophore, 2,3-dihydroxybenzoic acid produced by Azotobacter vinelandii. The dissolution kinetics of a number of minerals (barite, chalcopyrite, malachite) by DTPA solution has been studied as a function of DTPA concentration in the range 0.001--0.5 M. Batch experiments were carried out at pH 12 where the DTPA is effectively de-protonated and over a range of temperatures (22--90C^o) to investigate the factors controlling the dissolution rate.. Although the dissolution mechanism involves the chelation of one metal ion by each molecule of DTPA, the dissolution rate was found to be inversely related to the DTPA concentration in solution and not dependent on the initial grain size of the mineral. The high activation energy for the dissolution process suggests that the rate is controlled by a surface desorption process rather than diffusion in the solution. The inverse dependence on the DTPA concentration suggests steric hindrance associated with the metal-DTPA surface complex formation. Dissolution kinetics of the natural siderophore, known to be specfic to Fe chelation, was observed under similar conditions and comparisons made with the strong industrial chelator in an attempt to understand the dissolution process. The results have important applications to many aspects of mineral dissolution and therefore metal ion mobility as well as raising fundamental questions regarding the nature of the crystal-solution interface at an atomic level.

Putnis, C. V.

2003-04-01

287

Direct observation of rare-earth ions in ?-sialon:Ce phosphors.  

PubMed

Doping structures of Ce(3+) into the refractory ?-sialon crystal lattice have been examined via an atom-resolved Cs-corrected scanning transmission electron microscope. The location and coordination of the rare-earth ions are well-defined through direct observation in conjunction with structural modeling and image simulation. The stability and solubility of Ce(3+) ions could be remarkably enhanced via congregation into the planar defects formed by a 1/3 (210)-type lattice displacement along with an inversion operation. The formation of cylindrical chambers near the defects is believed to provide effective structural relaxation upon doping of large rare-earth ions into the interstices in their neighborhoods. The as-revealed structural information could be useful for understanding the luminescence properties of the promising rare-earth doped sialon materials. PMID:21370828

Xu, Fangfang; Sourty, Erwan; Shi, Wei; Mou, Xinliang; Zhang, Linlin

2011-04-01

288

The electromagnetic ion beam instability upstream of the earth's bow shock  

NASA Astrophysics Data System (ADS)

The linear theory of the electromagnetic ion beam instability for arbitrary angles of propagation has been studied. The parameters considered in the theory are typical of the solar wind upstream of the earth's bow shock when a 'reflected' proton beam is present. Maximum growth occurs for propagation parallel to the ambient magnetic field B, but this instability also displays significant growth at wave-vectors oblique to B. Oblique, unstable modes seem to be the likely source of the compressive magnetic fluctuations recently observed in conjunction with the 'diffuse' ion population. An energetic ion beam does not directly give rise to linear growth of either ion acoustic or whistler mode instabilities.

Gary, S. P.; Gosling, J. T.; Forslund, D. W.

1981-08-01

289

Magnetic exchange interaction between rare-earth and Mn ions in multiferroic hexagonal manganites  

SciTech Connect

The authors report a study of magnetic dynamics in multiferroic hexagonal manganite HoMnO{sub 3} by far-infrared spectroscopy. Low-temperature magnetic excitation spectrum of HoMnO{sub 3} consists of magnetic-dipole transitions of Ho ions within the crystal-field split J = 8 manifold and of the triangular antiferromagnetic resonance of Mn ions. They determine the effective spin Hamiltonian for the Ho ion ground state. The magnetic-field splitting of the Mn antiferromagnetic resonance allows us to measure the magnetic exchange coupling between the rare-earth and Mn ions.

Talbayev, Diyar [Los Alamos National Laboratory; Trugman, Stuart A [Los Alamos National Laboratory; Taylor, Antoinette J [Los Alamos National Laboratory; Averitt, Richard D [Los Alamos National Laboratory; Namjung, Hur [INHA UNIV; Andrew, Laforge D [UCSD; Dimitri, Basov N [UCSD

2008-01-01

290

A study of the structural properties of GaN implanted by various rare-earth ions  

NASA Astrophysics Data System (ADS)

GaN layers with <0 0 0 1> crystallographic orientation, grown by low-pressure metal-organic vapour-phase epitaxy (MOVPE) on c-plane sapphire substrates, were implanted with 200 and 400 keV Sm+, Tm+, Eu+, Tb+ and Ho+ ions at fluencies of 1 × 1015-1 × 1016 cm-2. The composition of the ion-implanted layers and concentration profiles of the implanted atoms were studied by Rutherford Back-Scattering spectrometry (RBS). The profiles were compared to SRIM 2008 simulations. The structural properties of the ion-implanted layers were characterised by RBS-channelling and Raman spectroscopy. Changes in the surface morphology caused by the ion implantation were examined by Atomic Force Microscopy (AFM). A structural analysis showed a high disorder of the atoms close to the amorphised structure at the surface layer above an implantation fluence of 5 × 1015 cm-2 while lower disorder density was observed in the bulk according to the projected range of 400 keV ions. The post-implantation annealing induced significant changes only in the Sm and Eu depth profiles; a diffusion of rare-earths implanted at a fluence of 5 × 1015 cm-2 to the surface was observed. The annealing caused the reconstruction of the surface layer accompanied by surface-roughness enhancement.

Mackova, A.; Malinský, P.; Sofer, Z.; Šimek, P.; Sedmidubský, D.; Mikulics, M.; Wilhelm, R. A.

2013-07-01

291

Electrospray Ionization Mass Spectrometry: From Cluster Ions to Toxic metal Ions in Biology  

SciTech Connect

This dissertation focused on using electrospray ionization mass spectrometry to study cluster ions and toxic metal ions in biology. In Chapter 2, it was shown that primary, secondary and quarternary amines exhibit different clustering characteristics under identical instrument conditions. Carbon chain length also played a role in cluster ion formation. In Chapters 3 and 4, the effects of solvent types/ratios and various instrumental parameters on cluster ion formation were examined. It was found that instrument interface design also plays a critical role in the cluster ion distribution seen in the mass spectrum. In Chapter 5, ESI-MS was used to investigate toxic metal binding to the [Gln{sup 11}]-amyloid {beta}-protein fragment (1-16). Pb and Cd bound stronger than Zn, even in the presence of excess Zn. Hg bound weaker than Zn. There are endless options for future work on cluster ions. Any molecule that is poorly ionized in positive ion mode can potentially show an increase in ionization efficiency if an appropriate anion is used to produce a net negative charge. It is possible that drug protein or drug/DNA complexes can also be stabilized by adding counter-ions. This would preserve the solution characteristics of the complex in the gas phase. Once in the gas phase, CID could determine the drug binding location on the biomolecule. There are many research projects regarding toxic metals in biology that have yet to be investigated or even discovered. This is an area of research with an almost endless future because of the changing dynamics of biological systems. What is deemed safe today may show toxic effects in the future. Evolutionary changes in protein structures may render them more susceptible to toxic metal binding. As the understanding of toxicity evolves, so does the demand for new toxic metal research. New instrumentation designs and software make it possible to perform research that could not be done in the past. What was undetectable yesterday will become routine tomorrow.

Nicholas B. Lentz

2007-12-01

292

Method for removing metal ions from solution with titanate sorbents  

DOEpatents

A method for removing metal ions from solution comprises the steps of providing titanate particles by spray-drying a solution or slurry comprising sorbent titanates having a particle size up to 20 micrometers, optionally in the presence of polymer free of cellulose functionality as binder, said sorbent being active towards heavy metals from Periodic Table (CAS version) Groups IA, IIA, IB, IIB, IIIB, and VIII, to provide monodisperse, substantially spherical particles in a yield of at least 70 percent of theoretical yield and having a particle size distribution in the range of 1 to 500 micrometers. The particles can be used free flowing in columns or beds, or entrapped in a nonwoven, fibrous web or matrix or a cast porous membrane, to selectively remove metal ions from aqueous or organic liquid.

Lundquist, Susan H. (White Bear Township, MN); White, Lloyd R. (Minneapolis, MN)

1999-01-01

293

Metal ion influence on eumelanin fluorescence and structure  

NASA Astrophysics Data System (ADS)

Melanin has long been thought to have an unworkably weak and complex fluorescence, but here we study its intrinsic fluorescence in order to demonstrate how metal ions can be used to control the rate of formation, constituents and structure of eumelanin formed from the well-known laboratory auto-oxidation of 3,4-dihydroxy-L-phenylalanine (L-DOPA). The effect on eumelanin absorption and fluorescence of a range of solvated metal ions is reported including Cu, Zn, Ni, Na and K. Monovalent cations and Zn have little effect, but the effect of transition metal cations can be considerable. For example, at pH 10, copper ions are shown to accelerate the onset of eumelanin formation, but not the rate of formation once it commences, and simplify the usual complex structure and intrinsic fluorescence of eumelanin in a way that is consistent with an increased abundance of 5,5-dihydroxyindole-2-carboxylic acid (DHICA). The presence of a dominant 6 ns fluorescence decay time at 480 nm, when excited at 450 nm describes a distinct photophysical species, which we tentatively assign to small oligomers. Copper is well-known to normally quench fluorescence, but increasing amounts of copper surprisingly leads to an increase in the fluorescence decay time of eumelanin, while reducing the fluorescence intensity, suggesting copper modification of the excited state. Such results have bearing on diverse areas. The most accepted morphology for melanin is that of a graphite-like sheet structure, and one which readily binds metal ions, an interaction that is thought to have an important, though as yet unclear bearing on several areas of medicine including neurology. There is also increasing interest in bio-mimicry by preparing and labelling sheet structures with metal ions for new electronic and photonic materials.

Sutter, Jens-Uwe; Birch, David J. S.

2014-06-01

294

Determination of uranium and rare-earth metals separation coefficients in LiCl KCl melt by electrochemical transient techniques  

NASA Astrophysics Data System (ADS)

The main step in the pyrometallurgical process of spent nuclear fuel recycling is a molten salt electrorefining. The knowledge of separation coefficients of actinides (U, Np, Pu and Am) and rare-earth metals (Y, La, Ce, Nd and Gd) is very important for this step. Usually the separation coefficients are evaluated from the formal standard potentials of metals in melts containing their own ions, values obtained by potentiometric method. Electrochemical experiments were carried out at 723-823 K in order to estimate separation coefficients in LiCl-KCl eutectic melt containing uranium and lanthanum trichlorides. It was shown that for the calculation of uranium and lanthanum separation coefficients it is necessary to determine the voltammetric peak potentials of U(III) and La(III), their concentration in the melt and the kinetic parameters relating to U(III) discharge such as transfer and diffusion coefficients, and standard rate constants of charge transfer.

Kuznetsov, S. A.; Hayashi, H.; Minato, K.; Gaune-Escard, M.

2005-09-01

295

Solution NMR Refinement of a Metal Ion Bound Protein Using Metal Ion Inclusive Restrained Molecular Dynamics Methods  

PubMed Central

Correctly calculating the structure of metal coordination sites in a protein during the process of nuclear magnetic resonance (NMR) structure determination and refinement continues to be a challenging task. In this study, we present an accurate and convenient means by which to include metal ions in the NMR structure determination process using molecular dynamics (MD) constrained by NMR-derived data to obtain a realistic and physically viable description of the metal binding site(s). This method provides the framework to accurately portray the metal ions and its binding residues in a pseudo-bond or dummy-cation like approach, and is validated by quantum mechanical/molecular mechanical (QM/MM) MD calculations constrained by NMR-derived data. To illustrate this approach, we refine the zinc coordination complex structure of the zinc sensing transcriptional repressor protein Staphylococcus aureus CzrA, generating over 130 ns of MD and QM/MM MD NMR-data compliant sampling. In addition to refining the first coordination shell structure of the Zn(II) ion, this protocol benefits from being performed in a periodically replicated solvation environment including long-range electrostatics. We determine that unrestrained (not based on NMR data) MD simulations correlated to the NMR data in a time-averaged ensemble. The accurate solution structure ensemble of the metal-bound protein accurately describes the role of conformational dynamics in allosteric regulation of DNA binding by zinc and serves to validate our previous unrestrained MD simulations of CzrA. This methodology has potentially broad applicability in the structure determination of metal ion bound proteins, protein folding and metal template protein-design studies. PMID:23609042

Chakravorty, Dhruva K.; Wang, Bing; Lee, Chul Won; Guerra, Alfredo J.; Giedroc, David P.; Merz, Kenneth M.

2013-01-01

296

Spectroscopic in situ examination of interactions of rare earth ions with humic substances.  

PubMed

This study utilized the methods of fluorescence quenching and differential absorbance to probe in situ the extent and the nature of the interactions between rare earth ions (REIs) and humic substances. Experiments were conducted with the standard Suwannee river humic acid (SRHA) in the presence of varying amount of lanthanum, europium and terbium. The data of differential absorbance showed that the mechanism of SRHA-metal complexation was largely the same for all the examined REIs. In all cases several discrete bands whose properties were discerned via numerical decomposition of the differential spectra absorbance were observed. Their nature was examined based on the comparison of the experimental data and those of NICA-Donnan modeling carried out for Eu(3+). The observed effects suggested that the changes of SRHA absorbance induced by REIs binding are likely to be caused by a bathochromic shift of the absorbance bands associated with such chromophores. The intensity of the Gaussian band with a maximum at 387 nm was observed to be proportional to the total concentration of SRHA-bound REIs. The data obtained in this study demonstrate the existence of complex yet quantifiable changes of the spectroscopic properties of humic species in the presence of REIs and their utility to quantify modes of interactions in such systems. PMID:25462735

Chen, Yao; Fabbricino, Massimiliano; Benedetti, Marc F; Korshin, Gregory V

2014-10-14

297

Polyols as scaffolds in the development of ion-selective polymer-supported reagents: the effect of auxiliary groups on the mechanism of metal ion complexation.  

PubMed

In developing ion-selective polymer-supported reagents, the inherent affinity of a given ligand for a targeted metal ion is found to be affected by auxiliary groups on a scaffold. A series of polyols (ethylene glycol, glycerol, tris(hydroxymethyl)ethane, pentaerythritol, and pentaerythritol triethoxylate) are immobilized onto cross-linked poly(vinylbenzyl chloride), then monophosphorylated. The pentaerythritol, glycerol, and pentaerythritol triethoxylate polymers have the highest affinities for both trivalent and divalent ions. The distribution coefficients of divalent ions (Pb(II), Cd(II), Cu(II), Ni(II), and Zn(II)) correlate with the Misono softness parameter, reflecting a single-site interaction between the metal ion and the phosphoryl oxygen. The distribution coefficients for trivalent ions are in the order Fe(III) < Al(III) < Y(III) less, approximately < La(III) approximately Eu(III) approximately Lu(III). For example, the phosphorylated pentaerythritol polymer has distribution coefficients (also reported as percent complexed) for Fe of 68.4 (75.3%); for Al of 182 (88.5%); and for the rare earth ions Y, Lu, Eu, and La of 374 (94.4%), 1390 (98.4%), 1690 (98.4%), and 708 (96.9%), respectively, from solutions at pH 2.0. The opposite trend (i.e., Fe(III) > Al(III) > (rare earths)) correlates with their hardness, acidity, electron affinity, electronegativity, and formation constants with soluble complexants, including tributyl phosphate. A binding mechanism is proposed wherein the polymer initially has the auxiliary -OH groups hydrogen-bonded to the phosphate ligand; then, binding to the polarizable phosphoryl oxygen with the divalent ions dominates, while the trivalent ions are drawn closer to the phosphoryl oxygen because of their greater charge and, once closer, bind in a multisite interaction with both the phosphate and -OH groups. PMID:18269222

Alexandratos, Spiro D; Zhu, Xiaoping

2008-04-01

298

Yttrium and rare earth stabilized fast reactor metal fuel  

DOEpatents

To increase the operating temperature of a reactor, the melting point and mechanical properties of the fuel must be increased. For an actinide-rich fuel, yttrium, lanthanum and/or rare earth elements can be added, as stabilizers, to uranium and plutonium and/or a mixture of other actinides to raise the melting point of the fuel and improve its mechanical properties. Since only about 1% of the actinide fuel may be yttrium, lanthanum, or a rare earth element, the neutron penalty is low, the reactor core size can be reduced, the fuel can be burned efficiently, reprocessing requirements are reduced, and the nuclear waste disposal volumes reduced. A further advantage occurs when yttrium, lanthanum, and/or other rare earth elements are exposed to radiation in a reactor, they produce only short half life radioisotopes, which reduce nuclear waste disposal problems through much shorter assured-isolation requirements.

Guon, Jerold (Woodland Hills, CA); Grantham, LeRoy F. (Calabasas, CA); Specht, Eugene R. (Simi Valley, CA)

1992-01-01

299

Surface Characterization of Alkali and Alkaline Earth Metals on Single Crystal Refractory Metals  

NASA Astrophysics Data System (ADS)

The experiments were conducted on the clean surfaces of W(110), Mo(110) and Nb(110) under ultrahigh vacuum conditions using techniques of line-of-sight thermal desorption mass spectrometry, Auger electron spectroscopy and retarding potential work function measurement. The clean work functions for W(110), Mo(110) and Nb(110) were found to be 5.38 eV, 5.08 eV and 4.62 eV, respectively. The behavior of the work function was characteristic of alkali and alkaline earth metal adsorption onto refractory metal surfaces with the minimum work function for the three surfaces of approximately 1.50 eV for cesium and 2.20 eV for barium. The results of the change in work function versus adsorption of cesium onto the bariated surfaces of W(110), Mo(110) and Nb(110) were similar. The energies of desorption for the different binding states were calculated for the various adsorbate-metal systems using first order desorption kinetics, that is, the adsorbates desorb at a rate linearly dependent on coverage. The desorption spectra for cesium from the various metal surfaces showed three distinct desorption sites, while barium had a more continuous decrease in activation energy of desorption up to a monolayer of coverage. The main difference between the desorption of the two adsorbates was the temperature of the terminal (lowest coverage) desorption energy site. The highest terminal desorption energy for cesium occurred on the W(110) surface at a temperature of 1200 K, while barium does not start to desorb from the W(110) surface until the temperature reaches approximately 1700 K. The temperature difference between the binding states of cesium and barium on all three of the substrates allowed for the adsorption and desorption of cesium without altering the barium adlayer. The desorption behavior of cesium from the various barium/substrate surfaces, like the work function change, was also very similar. As the coverage of pre -adsorbed barium increased, the activation energy of the cesium decreased.

Magera, Gerald Glenn

1995-11-01

300

Liquid metal ion source and alloy for ion emission of multiple ionic species  

DOEpatents

A liquid metal ion source and alloy for the simultaneous ion evaporation of arsenic and boron, arsenic and phosphorus, or arsenic, boron and phosphorus. The ionic species to be evaporated are contained in palladium-arsenic-boron and palladium-arsenic-boron-phosphorus alloys. The ion source, including an emitter means such as a needle emitter and a source means such as U-shaped heater element, is preferably constructed of rhenium and tungsten, both of which are readily fabricated. The ion sources emit continuous beams of ions having sufficiently high currents of the desired species to be useful in ion implantation of semiconductor wafers for preparing integrated circuit devices. The sources are stable in operation, experience little corrosion during operation, and have long operating lifetimes.

Clark, Jr., William M. (Thousand Oaks, CA); Utlaut, Mark W. (Saugus, CA); Wysocki, Joseph A. (Oxnard, CA); Storms, Edmund K. (Los Alamos, NM); Szklarz, Eugene G. (Los Alamos, NM); Behrens, Robert G. (Los Alamos, NM); Swanson, Lynwood W. (McMinnville, OR); Bell, Anthony E. (McMinnville, OR)

1987-06-02

301

Metal negative ion production by an RF sputter self-extraction ion source  

NASA Astrophysics Data System (ADS)

An 80 mm diameter 80 mm long RF sputter type self-extraction negative ion source equipped with a metal sputter target has been tested to investigate the performance of producing beams of negative aluminum (Al) ions. An RF power at 13.56 MHz is directly supplied to a 60 mm diameter target containing a cylindrical and ring permanent magnets to form planar magnetron magnetic field geometry. The target is self-biased to a DC potential at about -250 V with respect to the plasma, and negative ions produced at the surface are self-extracted from the target across the sheath to reach the ion beam extraction hole. Injection of cesium into the discharge enhanced the amount of Al- ions but it also enlarged the impurity ion beam current.

Yamada, N.; Kasuya, T.; Kenmotsu, T.; Vasquez, M. R., Jr.; Wada, M.

2013-02-01

302

Peptide immobilisation on porous silicon surface for metal ions detection  

NASA Astrophysics Data System (ADS)

In this work, a Glycyl-Histidyl-Glycyl-Histidine (GlyHisGlyHis) peptide is covalently anchored to the porous silicon PSi surface using a multi-step reaction scheme compatible with the mild conditions required for preserving the probe activity. In a first step, alkene precursors are grafted onto the hydrogenated PSi surface using the hydrosilylation route, allowing for the formation of a carboxyl-terminated monolayer which is activated by reaction with N-hydroxysuccinimide in the presence of a peptide-coupling carbodiimide N-ethyl- N'-(3-dimethylaminopropyl)-carbodiimide and subsequently reacted with the amino linker of the peptide to form a covalent amide bond. Infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy are used to investigate the different steps of functionalization. The property of peptides to form stable complexes with metal ions is exploited to achieve metal-ion recognition by the peptide-modified PSi-based biosensor. An electrochemical study of the GlyHisGlyHis-modified PSi electrode is achieved in the presence of copper ions. The recorded cyclic voltammograms show a quasi-irreversible process corresponding to the Cu(II)/Cu(I) couple. The kinetic factors (the heterogeneous rate constant and the transfer coefficient) and the stability constant of the complex formed on the porous silicon surface are determined. These results demonstrate the potential role of peptides grafted on porous silicon in developing strategies for simple and fast detection of metal ions in solution.

Sam, Sabrina S.; Chazalviel, Jean-Noël Jn; Gouget-Laemmel, Anne Chantal Ac; Ozanam, François F.; Etcheberry, Arnaud A.; Gabouze, Nour-Eddine N.

2011-06-01

303

Peptide immobilisation on porous silicon surface for metal ions detection  

PubMed Central

In this work, a Glycyl-Histidyl-Glycyl-Histidine (GlyHisGlyHis) peptide is covalently anchored to the porous silicon PSi surface using a multi-step reaction scheme compatible with the mild conditions required for preserving the probe activity. In a first step, alkene precursors are grafted onto the hydrogenated PSi surface using the hydrosilylation route, allowing for the formation of a carboxyl-terminated monolayer which is activated by reaction with N-hydroxysuccinimide in the presence of a peptide-coupling carbodiimide N-ethyl-N'-(3-dimethylaminopropyl)-carbodiimide and subsequently reacted with the amino linker of the peptide to form a covalent amide bond. Infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy are used to investigate the different steps of functionalization. The property of peptides to form stable complexes with metal ions is exploited to achieve metal-ion recognition by the peptide-modified PSi-based biosensor. An electrochemical study of the GlyHisGlyHis-modified PSi electrode is achieved in the presence of copper ions. The recorded cyclic voltammograms show a quasi-irreversible process corresponding to the Cu(II)/Cu(I) couple. The kinetic factors (the heterogeneous rate constant and the transfer coefficient) and the stability constant of the complex formed on the porous silicon surface are determined. These results demonstrate the potential role of peptides grafted on porous silicon in developing strategies for simple and fast detection of metal ions in solution. PMID:21711937

2011-01-01

304

Investigation of a tin liquid metal ion source  

NASA Astrophysics Data System (ADS)

In view of its importance in materials research, tin is a metal worth studying in a liquid metal ion source configuration, even if results complement or extend previous work. This is the more so if the new work corrects misconceptions of the past and adds to current thinking. We, therefore, prepared a Sn liquid metal ion source employing a Ni needle to anchor the liquid, cone-shaped, emitter. Source properties, such as the current-voltage curve, the mass spectra of the beam and the energy spread of the main ionic species, were studied in detail. The mass spectra show a considerable amount of Sn clusters, apart from the dominant species, Sn+ and Sn++. The source was stable down to 1-?A emission current, corresponding to an energy spread for the singly charged ions of 7 eV. Theoretical arguments, involving the peak energy deficit of the ion-energy distribution, strongly suggest that both Sn+ and Sn++ are emitted by direct field evaporation from the liquid surface. The same conclusion is reached from a careful examination of the beam mass spectra of the source.

Bischoff, L.; Akhmadaliev, C.; Mair, A. W. R.; Mair, G. L. R.; Ganetsos, T.; Aidinis, C. J.

305

New Catalytic DNA Biosensors for Radionuclides and Metal ion  

SciTech Connect

We aim to develop new DNA biosensors for simultaneous detection and quantification of bioavailable radionuclides, such as uranium, technetium, and plutonium, and metal contaminants, such as lead, chromium, and mercury. The sensors will be highly sensitive and selective. They will be applied to on-site, real-time assessment of concentration, speciation, and stability of the individual contaminants before and during bioremediation, and for long-term monitoring of DOE contaminated sites. To achieve this goal, we have employed a combinatorial method called “in vitro selection” to search from a large DNA library (~ 1015 different molecules) for catalytic DNA molecules that are highly specific for radionuclides or other metal ions through intricate 3-dimensional interactions as in metalloproteins. Comprehensive biochemical and biophysical studies have been performed on the selected DNA molecules. The findings from these studies have helped to elucidate fundamental principles for designing effective sensors for radionuclides and metal ions. Based on the study, the DNA have been converted to fluorescent or colorimetric sensors by attaching to it fluorescent donor/acceptor pairs or gold nanoparticles, with 11 part-per-trillion detection limit (for uranium) and over million fold selectivity (over other radionuclides and metal ions tested). Practical application of the biosensors for samples from the Environmental Remediation Sciences Program (ERSP) Field Research Center (FRC) at Oak Ridge has also been demonstrated.

Yi Lu

2008-03-01

306

Diastereoselective pinacol coupling of alkyl aryl ketones with rare earth metals in the presence of chlorosilanes  

Microsoft Academic Search

Rare earth metals (Ln) are found to act as useful reducing agents for the pinacol coupling reaction of alkyl aryl ketones in the presence of chlorosilanes. Although the hitherto known pinacol coupling reaction using rare earth reducing agents generally exhibits very low diastereoselectivities, the present pinacol coupling by use of a LnR3SiCl system usually indicates higher diastereoselectivities. In particular, a

Akiya Ogawa; Hiroki Takeuchi; Toshikazu Hirao

1999-01-01

307

Low Temperature Resistivity of Yttrium-Based Alloys Containing Small Amounts of Rare Earth Metals  

Microsoft Academic Search

The resistivity of the dilute alloys of rare earth metals with yttrium has been measured at low temperatures. The result is in qualitative agreement with the recent theories due to Kondo and others on the s--d or s--f scattering. The effective s--f exchange integrals for various rare-earth solutes have been derived from the analysis of the resistivity data and compared

Tadashi Sugawara

1965-01-01

308

Polymer filtration systems for dilute metal ion recovery  

SciTech Connect

Scientists at Los Alamos National Laboratory have developed a metal recovery system that meets the global treatment demands for all kinds of industrial and metal-processing streams. The Polymer Filtration (PF) System--a process that is easily operated and robust--offers metal-finishing businesses a convenient and inexpensive way to recover and recycle metal ions in-house, thus reducing materials costs, waste removal costs, and industrial liability. As a valuable economic and environmental asset, the PF System has been named a winner of a 1995 R and D 100 Award. These awards are presented annually by R and D Magazine to the one hundred most significant technical innovations of the year. The PF System is based on the use of water-soluble metal-binding polymers and on advanced ultrafiltration membranes. Customers for this technology will receive new soluble polymers, especially formulated for their waste stream, and the complete PF processing unit: a reaction reservoir, pumps, plumbing, controls, and the advanced ultrafiltration membranes, all in a skid mounted frame. Metal-bearing waste water is treated in the reaction reservoir, where the polymer binds with the metal ions under balanced acid/base conditions. The reservoir fluid is then pumped through the ultrafiltration system--a cartridge packed with ultrafiltration membranes shaped in hollow fibers. As the fluid travels inside the fiber, water and other small molecules--simple salts such as calcium and sodium, for example--pass through the porous membrane walls of the fibers and are discharged through the outlet as permeate. The polymer-bound metal, which is too large to pass through the pores, is both purified and concentrated inside the hollow fibers and is returned to the fluid reservoir for further waste water treatment.

Smith, B.F.; Robison, T.W.; Jarvinen, G.D.

1998-12-01

309

Monitoring of photoluminescence decay by alkali and alkaline earth metal cations using a photoluminescent bolaamphiphile self-assembly as an optical probe.  

PubMed

Photoluminescence (PL) decay induced by the displacement of an ionic fluorescence component, Tb(3+), with alkali and alkaline earth metal cations was investigated using photoluminescent spherical self-assemblies as optical probes. The photoluminescent spherical self-assembly was prepared by the self-organization of a tyrosine-containing bolaamphiphile molecule with a photosensitizer and Tb(3+) ion. The lanthanide ion, Tb(3+), electrically bound to the carboxyl group of the bolaamphiphile molecule, was displaced by alkali and alkaline earth metal cations that had stronger electrophilicity. The PL of the self-assembly decayed remarkably due to the substitution of lanthanide ions with alkali and alkaline earth metal cations. The PL decay showed a positive correlation with cation concentration and was sensitive to the cation valency. Generally, the PL decay was enhanced by the electrophilicity of the cations. However, Ca(2+) showed greater PL decay than Mg(2+) because Ca(2+) could create various complexes with the carboxyl groups of the bolaamphiphile molecule. Microscopic and spectroscopic investigations were conducted to study the photon energy transfer and displacement of Tb(3+) by the cation exchange. This study demonstrated that the PL decay by the displacement of the ionic fluorescent compound was applied to the detection of various cations in aqueous media and is applicable to the development of future optical sensors. PMID:24657611

Kim, Sunhyung; Kwak, Jinyoung; Lee, Sang-Yup

2014-05-01

310

Quantum CPF gates between rare earth ions through measurement  

Microsoft Academic Search

We propose a method to realize quantum controlled phase flip (CPF) through interaction between a single-photon pulse and two microsphere cavities with a single three-level ion respectively and final photonic measurement. Our CPF gates are scalable with extremely high fidelity and low error rate, and are more applicable based on current laboratory cavity-QED technology.

Yun-Feng Xiao; Zheng-Fu Han; Yong Yang; Guang-Can Guo

2004-01-01

311

Quantum CPF gates between rare earth ions through measurement  

NASA Astrophysics Data System (ADS)

We propose a method to realize quantum controlled phase flip (CPF) through interaction between a single-photon pulse and two microsphere cavities with a single three-level ion respectively and final photonic measurement. Our CPF gates are scalable with extremely high fidelity and low error rate, and are more applicable based on current laboratory cavity-QED technology.

Xiao, Yun-Feng; Han, Zheng-Fu; Yang, Yong; Guo, Guang-Can

2004-09-01

312

THE HEATS OF FUSION AND TRANSITION OF ALKALINE EARTH AND RARE EARTH METAL HALIDES  

Microsoft Academic Search

The heats of fusion of fifteen rare earth and alkaline earth halides ; were measured by means of a copper block drop calorimeter. The salts and their ; heats of fusion in kcal mole⁻¹ are LaClâ, 13.0; PrClâ, 12.1; ; NdClâ, 12.0; C eIâ, 12.4; PrIâ, 12.7; NdIâ, 9.7; CaCl\\/sub ; 2\\/, 6.78; CaBrâ, 6.95; C aIâ, 10.0; SrClâ, 3.88;

A. S. Dworkin; M. A. Bredig

1963-01-01

313

Ion beam mixing of metal/fluoropolymer interfaces  

SciTech Connect

Ion beam mixing of metals and polymers with very low dielectric constants such as Teflon can provide many applications in the area of electronic materials. This work is a study of the 'mixing' effect of 50 keV nitrogen implanted thin metal layers on Teflon PTFE (polytetrafluoroethylene) substrates. RBS analysis shows that the distribution of thin layers of copper and chromium (approximately 300-400 A thick) through the implant layer of the Teflon depends on the reactivity of the metal. As the implant fluence is increased, the distribution of metal atoms in the polymer matrix becomes concentrated over smaller ranges near the bottom of the implant layer. In situ RGA analysis during the implantation shows the liberation of an abundance of fluorine in many different forms. This is supported by results from a NRA experiment that shows the non-uniform concentration profile of fluorine throughout the implant layer. During the implantation process, the fluorine is released through the incident ion track leaving a carbon and metal rich region near the surface of the implant layer. The fluorine density increases with depth through the implant layer making a smooth transition to the undamaged bulk Teflon below. Low dielectric materials with highly conductive surfaces, such as this one, may provide an opportunity for a broad range of new microelectronic applications.

Dennis, D. L. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Giedd, R. E. [Southwest Missouri State University, Springfield, Missouri 65804 (United States); Wang, Y. Q. [Center for Interfacial Engineering, University of Minnesota, Minneapolis, Minnesota 55455 (United States); Glass, G. A. [Acadiana Research Laboratory, University of Southwestern Louisiana, Lafayette, Louisiana 70504 (United States)

1999-06-10

314

Ion beam mixing of metal/fluoropolymer interfaces  

SciTech Connect

Ion beam mixing of metals and polymers with very low dielectric constants such as Teflon can provide many applications in the area of electronic materials. This work is a study of the {open_quotes}mixing{close_quotes} effect of 50 keV nitrogen implanted thin metal layers on Teflon PTFE (polytetrafluoroethylene) substrates. RBS analysis shows that the distribution of thin layers of copper and chromium (approximately 300-400 {Angstrom} thick) through the implant layer of the Teflon depends on the reactivity of the metal. As the implant fluence is increased, the distribution of metal atoms in the polymer matrix becomes concentrated over smaller ranges near the bottom of the implant layer. {ital In situ} RGA analysis during the implantation shows the liberation of an abundance of fluorine in many different forms. This is supported by results from a NRA experiment that shows the non-uniform concentration profile of fluorine throughout the implant layer. During the implantation process, the fluorine is released through the incident ion track leaving a carbon and metal rich region near the surface of the implant layer. The fluorine density increases with depth through the implant layer making a smooth transition to the undamaged bulk Teflon below. Low dielectric materials with highly conductive surfaces, such as this one, may provide an opportunity for a broad range of new microelectronic applications. {copyright} {ital 1999 American Institute of Physics.}

Dennis, D.L. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Giedd, R.E. [Southwest Missouri State University, Springfield, Missouri 65804 (United States); Wang, Y.Q. [Center for Interfacial Engineering, University of Minnesota, Minneapolis, Minnesota 55455 (United States); Glass, G.A. [Acadiana Research Laboratory, University of Southwestern Louisiana, Lafayette, Louisiana 70504 (United States)

1999-06-01

315

Observations of nonadiabatic acceleration of ions in Earth's magnetotail  

NASA Technical Reports Server (NTRS)

We present observations of the three-dimensional velocity distributions of protons in the energy range 20 eV to 52 keV at locations within and near the current sheet of Earth's magnetotail at geocentric radial distances 35 to 87 R(sub E). These measurements were acquired on December 8, 1990, with a set of electrostatic analyzers on board the Galileo spacecraft during its approach to Earth in order to obtain one of its gravitational assists to Jupiter. It is found that the velocity distributions are inadequately described as quasi-Maxwellian distributions such as those found in the central plasma sheet at positions nearer to Earth. Instead the proton velocity distributions can be categorized into two major types. The first type is the 'lima bean' shaped distribution with high-speed bulk flows and high temperatures that are similar to those found nearer to Earth in the plasma sheet boundary layer. The second type consists of colder protons with considerably lesser bulk flow speeds. Examples of velocity distributions are given for the plasma mantle, a region near the magnetic neutral line, positions earthward and tailward of the neutral line, and the plasma sheet boundary layer. At positions near the neutral line, only complex velocity distributions consisting of the colder protons are found, whereas both of the above types of distributions are found in and near the current sheet at earthward and tailward locations. Bulk flows are directed generally earthward and tailward at positions earthward and tailward of the neutral line, respectively. Only the high-speed, hot distribution is present in the plasma sheet boundary layer. The observations are interpreted in terms of the nonadiabatic acceleration of protons that flow into the current sheet from the plasma mantle. For this interpretation the hot, 'lima bean' shaped distributions are associated with meandering, or Speiser, orbits in the current sheet. It is suggested that the colder, lower-speed proton velocity distributions are the result of fractional or few gyromotions before ejection out of the current sheet, but this speculation must be further investigated with appropriate kinetic simulation of trajectories.

Frank, L. A.; Paterson, W. R.; Kivelson, M. G.

1994-01-01

316

hammerhead ribozyme nor to these metal ions. Any RNA for which an assay is avail-  

E-print Network

hammerhead ribozyme nor to these metal ions. Any RNA for which an assay is avail- able to monitor metal exchange can, in principle, be used. Folded RNAs provide complex surfaces to which different metal unique metal ion sites on these complex folded RNA structures. REFERENCES AND NOTES

Tsien, Roger Y.

317

Novel synthetic phytochelatin-based capacitive biosensor for heavy metal ion detection  

E-print Network

Novel synthetic phytochelatin-based capacitive biosensor for heavy metal ion detection Ibolya on synthetic phytochelatins for sensitive detection of heavy metals is described. Synthetic phytochelatin (Glu: Biosensors; Heavy metals; Phytochelatins; Capacitance 1. Introduction Evolution of our society has lead

Chen, Wilfred

318

The Corrosion Protection of Metals by Ion Vapor Deposited Aluminum  

NASA Technical Reports Server (NTRS)

A study of the corrosion protection of substrate metals by ion vapor deposited aluminum (IVD Al) coats has been carried out. Corrosion protection by both anodized and unanodized IVD Al coats has been investigated. Base metals included in the study were 2219-T87 Al, 7075-T6 Al, Titanium-6 Al-4 Vanadium (Ti-6Al-4V), 4130 steel, D6AC steel, and 4340 steel. Results reveal that the anodized IVD Al coats provide excellent corrosion protection, but good protection is also achieved by IVD Al coats that have not been anodized.

Danford, M. D.

1993-01-01

319

Quantum computer hardware based on rare-earth-ion-doped inorganic crystals  

Microsoft Academic Search

We present a scheme for generating multiple, strongly interacting qubits in rare-earth-ion-doped inorganic crystals at cryogenic temperatures. Two ground state hyperfine levels, with hour long lifetimes and ms decoherence times are chosen as qubit states. Controlled logic between the qubits is accomplished using the change in permanent dipole moment induced by an optical transition between the ground and excited state

Nicklas Ohlsson; R Krishna Mohan; Stefan Kröll

2002-01-01

320

Controlled synthesis and alkaline earth ion binding of switchable formamidoxime-based crown ether analogs.  

PubMed

The partial positive charge of amide protons is used to promote macrocyclization and form crown-ether analogs. Their deprotonation generates very selective pH-switchable alkaline earth ion receptors only in the presence of an appropriate substrate. PMID:22751352

Yan, Yi; Zhao, Weiwen; Bhagavathy, Ganga Viswanathan; Faurie, Alexandre; Mosey, Nicholas J; Petitjean, Anne

2012-08-14

321

Performance and Comparison of Lithium-Ion Batteries Under Low-Earth-Orbit Mission Profiles  

NASA Technical Reports Server (NTRS)

The performance of two 28 V, 25 Ah lithium-ion batteries is being evaluated under low-Earth-orbit mission profiles for satellite and orbiter applications. The batteries are undergoing life testing and have achieved over 12,000 cycles to 40 percent depth-of-discharge.

Reid, Concha M.; Smart, Marshall C.; Bugga, Ratnakumar V.; Manzo, Michelle A.; Miller, Thomas B.; Gitzendanner, Rob

2007-01-01

322

Decay times of radiative and non-radiative transitions in rare-earth ions  

NASA Astrophysics Data System (ADS)

We present a theoretical method for evaluation of decay times of both radiative and non-radiative transitions in rare-earth ions in crystals and glasses. Relying on one experimentally known lifetime and known parameters of electrostatic and spin–orbit interaction, the fluorescence spectra can be modelled for various pumping wavelengths providing new insights into dynamical processes of fluorescence.

Kustov, E. F.; Loschenov, V. B.; Basieva, I. T.

2014-12-01

323

STRUCTURE OF PORPHYRIN TPPS4 AND ITS INTERACTION WITH METAL IONS AS ELUCIDATED BY 1H NMR AND UV-VISIBLE SPECTRA  

PubMed Central

Porphyrins are a group of tetrapyrrole pigments. Physical and chemical properties of porphyrins are often related to their compositions and structures. We conducted 1H solution NMR and UV-visible spectral analysis to characterize the structural feature of a water-soluble, synthetic porphyrin i.e. tetrakis (p-sulfonatophenyl) porphyrin, TPPS4, and its interaction with different metal ions in aqueous solutions. The results indicate that tetrapyrrole and tetraphenyl rings in TPPS4 molecule form a co-planar electron conjugation system; transition-metal ions show stronger binding capacity than alkali and alkali-earth metal ions; the relative stabilities of TPPS4-metal ion complexes can be well assessed by NMR and UV-visible spectral data. PMID:23564988

Song, Zhiyan; Adeyemo, Adegboye O.; Baker, Jannie; Traylor, Shakeya M.; Lightfoot, Marcia L.

2011-01-01

324

Interactions of metal ions with ? synuclein and amyloid ? peptides  

NASA Astrophysics Data System (ADS)

Amyloid ? (A?) and alfa synuclein (?S) share the ability to selectively bind copper ions (Cu(II) and Cu(I)). During the last decade large efforts have been directed to fully characterize Cu(II) binding domains in A? and ?S. On the other hand, the corresponding Cu(I) sites have been less considered. In this study we have analyzed Cu(I) interactions with peptides derived from A? and ?S, by means of CD and NMR spectroscopy. Beyond Cu(I), we have also used Ag(I) as a probe. By monitoring the metal induced effects on ?S and A? systems, the Cu(I)/Ag(I) binding domains have been identified. The corresponding protein structural rearrangements induced by the metal ions have been investigated as well. The Cu(I) coordination spheres are discussed with a particular emphasis to the role played by Met and His residues.

Valensin, Daniela; Kozlowski, Henryk; Tessari, Isabella; Dell'Acqua, Simone; Bubacco, Luigi; Casella, Luigi; Gaggelli, Elena; Valensin, Gianni

2014-10-01

325

Nanomagnetic chelators for removal of toxic metal ions  

NASA Astrophysics Data System (ADS)

Ethylenediamine trtraaceteic acid (EDTA) functionalized Fe3O4 nanomagnetic chelators (NMCs) were synthesized by co-precipitation method followed by in-situ grafting of EDTA. XRD and TEM analyses reveal the formation of highly crystalline single-phase Fe3O4 nanoparticles of size about 10 nm. Surface functionalization of Fe3O4 with EDTA was evident from FTIR spectroscopy, TGA analysis and zeta-potential measurement. These NMCs exhibit superparamagnetic behavior at room temperature with strong field dependent magnetic responsivity. It has been observed that NMCs have strong tendency for adsorption of various toxic metal ions (Ni2+, Cr3+, Cu2+, Cd2+, Co2+ and Pb2+) from waste-water. Furthermore, these magnetic chelators can be used as highly efficient separable and reusable material for removal of toxic metal ions.

Singh, Sarika; Barick, K. C.; Bahadur, D.

2013-02-01

326

How Cation-Pi Interactions Enhance and Structure the Binding of Metal Ions to Amino Acids and Peptides. Dialanine Probed by Irmpd Spectroscopy as a Prime Example  

NASA Astrophysics Data System (ADS)

Spectroscopic examination of metalated amino acids and model peptides in the infrared region gives incisive conformational information. The role of cation-pi interactions of the metal ions with aromatic amino acids in structuring the complexes and enforcing particular architectures is being clarified by such experiments using IRMPD action spectroscopy as the experimental probe. The presence of multiple aromatic groups as in dialanine gives particularly stringent conformational stabilization. Comparing spectroscopic peak shifts across a range of alkali and alkaline earth metal ions, ranging from lithium to cesium, and from calcium to barium, allows us to view the systematic relations between normal mode frequencies and ion/peptide interactions. The spectra of the ions were acquired by irradiating the cell of the Fourier-transform ion cyclotron resonance mass spectrometer with infrared light from the FELIX free electron laser at wavelengths in the approximate range 500 to 1900 cm-1.

Dunbar, Robert C.; Steill, Jeffrey; Oomens, Jos

2010-06-01

327

Note: An ion source for alkali metal implantation beneath graphene and hexagonal boron nitride monolayers on transition metals  

NASA Astrophysics Data System (ADS)

The construction of an alkali-metal ion source is presented. It allows the acceleration of rubidium ions to an energy that enables the penetration through monolayers of graphene and hexagonal boron nitride. Rb atoms are sublimated from an alkali-metal dispenser. The ionization is obtained by surface ionization and desorption from a hot high work function surface. The ion current is easily controlled by the temperature of ionizer. Scanning Tunneling Microscopy measurements confirm ion implantation.

de Lima, L. H.; Cun, H. Y.; Hemmi, A.; Kälin, T.; Greber, T.

2013-12-01

328

Note: An ion source for alkali metal implantation beneath graphene and hexagonal boron nitride monolayers on transition metals.  

PubMed

The construction of an alkali-metal ion source is presented. It allows the acceleration of rubidium ions to an energy that enables the penetration through monolayers of graphene and hexagonal boron nitride. Rb atoms are sublimated from an alkali-metal dispenser. The ionization is obtained by surface ionization and desorption from a hot high work function surface. The ion current is easily controlled by the temperature of ionizer. Scanning Tunneling Microscopy measurements confirm ion implantation. PMID:24387480

de Lima, L H; Cun, H Y; Hemmi, A; Kälin, T; Greber, T

2013-12-01

329

Equilibrium sorption isotherm for metal ions on tree fern  

Microsoft Academic Search

A new sorbent system for removing heavy metal ions, such as Zn(II), Cu(II) and Pb(II), from aqueous solutions has been investigated. This new sorbent is tree fern, an agriculture product. Variables of the system include solution temperature and sorbent particle size. The experimental results were fitted to the Langmuir, Freundlich and Redlich–Peterson isotherms to obtain the characteristic parameters of each

Y. S. Ho; C. T. Huang; H. W. Huang

2002-01-01

330

First-principles study of He point-defects in HCP rare-earth metals  

SciTech Connect

He defect properties in Sc, Y, Gd, Tb, Dy, Ho, Er and Lu were studied using first-principles calculations based on density functional theory. The results indicate that the formation energy of an interstitial He atom is smaller than that of a substitutional He atom in all hcp rare-earth metals considered. Furthermore, the tetrahedral interstitial position is more favorable than an octahedral position for He defects. The results are compared with those from bcc and fcc metals.

Li, Yang; Chen, Ru; Peng, SM; Long, XG; Wu, Z.; Gao, Fei; Zu, Xiaotao

2011-05-01

331

Membrane Interactions and Metal Ion Effects on Bilayer Permeation of the Lipophilic Ion Modulator DP-109  

E-print Network

describe the application of a colorimetric phospholipid/ polydiacetylene (PDA) biomimetic membrane assay a biphasic concentration-dependent interaction, with a break point around the critical micelle concentration). The molecule was designed to modify activities of metal ions such as copper, zinc, calcium, and iron in lipid

Jelinek, Raz

332

Selective extraction of metal ions with polymeric extractants by ion exchange/redox  

DOEpatents

The specification discloses a method for the extraction of metal ions having a reduction potential of above about +0.3 from an aqueous solution. The method includes contacting the aqueous solution with a polymeric extractant having primary phosphinic acid groups, secondary phosphine oxide groups, or both phosphinic acid and phosphine oxide groups.

Alexandratos, Spiro D. (Knoxville, TN)

1987-01-01

333

The free escape continuum of diffuse ions upstream of the Earth's quasi-parallel bow shock  

NASA Astrophysics Data System (ADS)

The Earth's bow shock is very efficient in accelerating ions out of the incident solar wind distribution to high energies (? 200 keV/e). Fluxes of energetic ions accelerated at the quasi-parallel bow shock, also known as diffuse ions, are best represented by exponential spectra in energy/charge, which require additional assumptions to be incorporated into these model spectra. One of these assumptions is a so-called "free escape boundary" along the interplanetary magnetic field into the upstream direction. Locations along the IBEX orbit are ideally suited for in situ measurements to investigate the existence of an upstream free escape boundary for bow shock accelerated ions. In this study we use 2 years of ion measurements from the background monitor on the IBEX spacecraft, supported by ACE solar wind observations. The IBEX Background Monitor is sensitive to protons > 14 keV, which includes the energy of the maximum flux for diffuse ions. With increasing distance from the bow shock along the interplanetary magnetic field, the count rates for diffuse ions stay constant for ions streaming away from the bow shock, while count rates for diffuse ions streaming toward the shock gradually decrease from a maximum value to ~1/e at distances of about 10 RE to 14 RE. These observations of a gradual decrease support the transition to a free escape continuum for ions of energy >14 keV at distances from 10 RE to 14 RE from the bow shock.

Trattner, K. J.; Allegrini, F.; Dayeh, M. A.; Funsten, H. O.; Fuselier, S. A.; Heirtzler, D.; Janzen, P.; Kucharek, H.; McComas, D. J.; Möbius, E.; Moore, T. E.; Petrinec, S. M.; Reisenfeld, D. B.; Schwadron, N. A.; Wurz, P.

2013-07-01

334

Superhydrogels of nanotubes capable of capturing heavy-metal ions.  

PubMed

Self-assembly regulated by hydrogen bonds was successfully achieved in the system of lithocholic acid (LCA) mixed with three organic amines, ethanolamine (EA), diethanolamine (DEA), and triethanolamine (TEA), in aqueous solutions. The mixtures of DEA/LCA exhibit supergelation capability and the hydrogels consist of plenty of network nanotubes with uniform diameters of about 60 nm determined by cryogenic TEM. Interestingly, the sample with the same concentration in a system of EA and LCA is a birefringent solution, in which spherical vesicles and can be transformed into nanotubes as the amount of LCA increases. The formation of hydrogels could be driven by the delicate balance of diverse noncovalent interactions, including electrostatic interactions, hydrophobic interactions, steric effects, van der Waals forces, and mainly hydrogen bonds. The mechanism of self-assembly from spherical bilayer vesicles into nanotubes was proposed. The dried hydrogels with nanotubes were explored to exhibit the excellent capability for capturing heavy-metal ions, for example, Cu(2+), Co(2+), Ni(2+), Pb(2+), and Hg(2+). The superhydrogels of nanotubes from the self-assembly of low-molecular-weight gelators mainly regulated by hydrogen bonds used for the removal of heavy-metal ions is simple, green, and high efficiency, and provide a strategic approach to removing heavy-metal ions from industrial sewage. PMID:24136830

Song, Shasha; Wang, Haiqiao; Song, Aixin; Hao, Jingcheng

2014-01-01

335

Acetabular bone density and metal ions after metal-on-metal versus metal-on-polyethylene total hip arthroplasty; short-term results.  

PubMed

Information on periprosthetic acetabular bone density is lacking for metal-on-metal total hip arthroplasties. These bearings use cobalt-chromium instead of titanium acetabular components, which could lead to stress shielding and hence periprosthetic bone loss. Cobalt and chromium ions have detrimental effects on bone. It is unknown whether serum metal ion levels affect bone density clinically. We compared cementless large femoral head (mean 48 mm) metal-on-metal total hip arthroplasties (M2a-Magnum, Biomet) to cementless 28 mm metal-on-polyethylene total hip arthroplasties (Mallory-Head, Biomet) in a randomised clinical trial. We evaluated periprosthetic acetabular bone density and serum metal ion levels at 1 year postoperatively. Acetabular bone density was analyzed with dual energy x-ray absorptiometry in four horizontal regions of interest in 70 patients. After one year, acetabular bone density decreased (-3.5% to -7.8%) in three of four regions of interest in metal-on-polyethylene patients, but was retained in metal-on-metal patients. Bone density preservation was most pronounced superior to the metal-on-metal cup (+1% versus -3.7%). Serum cobalt, chromium and titanium ion levels were not related to bone density, nor to acetabular inclination or femoral head size. Oxford and Harris hip scores were similar in both groups. Contrary to our hypothesis, acetabular bone density was retained with metal-on-metal total hip arthroplasty, compared to metal-on-polyethylene arthroplasty. Bone preservation was most pronounced in the area superior to the cup. This could be a benefit during future revision surgery. PMID:24186673

Zijlstra, Wierd P; van der Veen, Hugo C; van den Akker-Scheek, Inge; Zee, Mark J M; Bulstra, Sjoerd K; van Raay, Jos J A M

2014-01-01

336

Coupling of a locally implanted rare-earth ion ensemble to a superconducting micro-resonator  

NASA Astrophysics Data System (ADS)

We demonstrate the coupling of rare-earth ions locally implanted in a substrate (Gd3+ in Al2O3) to a superconducting NbN lumped-element micro-resonator. The hybrid device is fabricated by a controlled ion implantation of rare-earth ions in well-defined micron-sized areas, aligned to lithographically defined micro-resonators. The technique does not degrade the internal quality factor of the resonators which remain above 105. Using microwave absorption spectroscopy, we observe electron-spin resonances in good agreement with numerical modelling and extract corresponding coupling rates of the order of 1 MHz and spin linewidths of 50-65 MHz.

Wisby, I.; de Graaf, S. E.; Gwilliam, R.; Adamyan, A.; Kubatkin, S. E.; Meeson, P. J.; Tzalenchuk, A. Ya.; Lindström, T.

2014-09-01

337

In situ observations of suprathermal ion acceleration in the near-Earth jet braking region  

NASA Astrophysics Data System (ADS)

Plasma jet fronts and braking regions are sites of substantial particle acceleration in planetary magnetospheres and are considered to play a major role in other distant environments such as the solar corona and astrophysical jets. Jet fronts are the boundaries separating ambient from jetting plasma (e.g. due to reconnection) while jet braking regions is where jets are eventually stopped/diverted. A number of recent in situ observations in the Earth's magnetotail have allowed studying in detail electron acceleration mechanisms at jet fronts/braking region therein. Yet, observations of suprathermal ion acceleration are scarce. Here we show Cluster spacecraft observations of suprathermal ions up to ~ 1 MeV (about 10 times the thermal energy) in the near-Earth jet braking region. Observations indicate that ions are trapped between large-scale oppositely-directed jets and accelerated therein by strong electric fields.

Retinò, Alessandro; Khotyaintsev, Yuri; Vaivads, Andris; Le Contel, Olivier; Fu, Huishan; Zieger, Bertalan; Elena, Kronberg

2014-05-01

338

Ab initio calculations on the positive ions of the alkaline-earth oxides, fluorides, and hydroxides  

NASA Technical Reports Server (NTRS)

Theoretical dissociation energies are presented for the alkaline-earth fluoride, hydroxide, and oxide positive ions that are considered to be accurate to 0.1-0.2 eV. The r(e) for the positive ions are found to be consistently shorter than the corresponding neutrals by 0.07 + or -0.02 A. The bonding in the ground states is demonstrated to be of predominantly M + 2 X - character. The a 3 Pi and A 1 Pi are found to lie considerably above the X 1 Sigma + ground states of the alkaline-earth fluoride and hydroxide positive ions. The overall agreement of the theoretical ionization potentials with the available experimental appearance potentials is satisfactory; these values should represent the most accurate and consistent set available.

Partridge, H.; Langhoff, S. R.; Bauschlicher, C. W., Jr.

1986-01-01

339

Template-directed synthesis of oligoguanylic acids - Metal ion catalysis  

NASA Technical Reports Server (NTRS)

The effects of Zn(2+), Pb(2+) and other metal ions on the efficiency and stereo-selectivity of the template-directed oligomerization of guanosine 5'-phosphorimidazolide are investigated. Reactions were run in the presence of a polyC template in a 2,6-lutidine buffer, and products analyzed by high-performance liquid chromatography on an RPC-5 column. The presence of the Pb(2+) ion is found to lead to the formation of 2'-5' linked oligomers up to the 40-mer, while Zn(2+) favors the formation of predominantly 3'-5' linked oligomers up to the 35-mer. When amounts of uracil, cytidine or adenosine 5'-phosphorimidazole equal to those of the guanosine derivative are included in the reaction mixture, the incorrect base is incorporated into the oligomer about 10% of the time with a Pb(2+) catalyst, but less than 0.5% of the time with Zn(2+). The Sn(2+), Sb(3+) and Bi(3+) ions are also found to promote the formation of 2'-5' oligomers, although not as effectively as Pb(2+), while no metal ions other than Zn(2+) promote the formation of the 3'-5' oligomers. The results may be important for the understanding of the evolution of nucleic acid replication in the absence of enzymes.

Bridson, P. K.; Fakhrai, H.; Lohrmann, R.; Orgel, L. E.; Van Roode, M.

1981-01-01

340

Behaviour of zirconium, niobium, yttrium and the rare earth elements in the Thor Lake rare-metal  

E-print Network

Behaviour of zirconium, niobium, yttrium and the rare earth elements in the Thor Lake rare-metal © Emma Rebecca Sheard, 2010 #12;i ABSTRACT The Thor Lake rare-metal (Zr, Nb, Y, REE, Ta, Be, Ga) deposit and the heavy rare earth elements in the world. Much of the potentially economic mineralization was concentrated

341

An investigation into the mechanism of pseudospark producing metal ion beams  

NASA Astrophysics Data System (ADS)

A multiplate pseudospark chamber, whose electrodes were fabricated with different metal materials, was designed and tested as a metal ion source. The ion beam implantation combined with Rutherford backscattering (RBS) measurement was used to understand whether these ion beams come from the anode plasma or the cathode plasma. The RBS measurements have demonstrated the following results: (1) pseudospark produced metal ion beams mainly consist of ions from the cathode materials; (2) the ion beam current increases rapidly with the pseudospark discharge voltage first and then saturates; and (3) the energy of the extracted metal ions is much less than the voltage between the anode and the cathode, therefore the high discharge voltage does not correspond to the high ion energy. A possible mechanism of pseudospark producing metal ion beams is discussed.

Cai, C. G.; Zhao, W. J.; Yan, S.; Le, X. Y.; Han, B. X.; Xue, J. M.; Wang, Y. G.; Jiang, X. L.

2000-02-01

342

Density functional studies on Lewis acidity of alkaline earth metal exchanged faujasite zeolite  

Microsoft Academic Search

Lewis acidity of alkaline earth metal exchanged faujasite zeolite is investigated using density functional based reactivity descriptors with a 6T ring cluster which represents active site of the zeolite. We calculated global reactivity descriptors such as chemical hardness, chemical softness, electrophilicity index of the optimised cluster and local reactivity descriptors namely fukui function and relative electrophilicity of the exchanged cations

P. Mondal; K. K. Hazarika; A. Deka; R. C. Deka

2008-01-01

343

Shaping of diamond films by etching with molten rare-earth metals  

Microsoft Academic Search

A method is presented for shaping and thinning of CVD diamond films which does not involve high pressures of hydrogen atmospheres; it instead makes use of such molten rare-earth metals as Ce or La to etch away the surface of the diamond film. The process yields appreciable results over periods of a few hours, and may render diamond film applications

S. Jin; J. E. Graebner; M. McCormack; T. H. Tiefel; A. Katz; W. C. Dautremont-Smith

1993-01-01

344

Point-defect properties in HCP rare earth metals with analytic modified embedded atom potentials  

Microsoft Academic Search

The analytic embedded atom method (EAM) type many-body potentials of hcp rare earth metals (Dy, Er, Gd, Ho, Nd, Pr, and Tb) have been constructed. The hcp lattice is shown to be energetically most stable when compared with the fcc and bcc structure, and the hcp lattice with ideal c\\/a. The mechanical stability of the corresponding hcp lattice with respect

Wangyu Hu; Huiqiu Deng; Xiaojian Yuan; Masahiro Fukumoto

2003-01-01

345

Corrosion behavior of rare earth metal (REM) conversion coatings on aluminum alloy LY12  

Microsoft Academic Search

The processes of the double layer rare earth metal (REM) conversion coating on aluminum alloy LY12 (2024) were introduced. The results of polarization tests showed that the corrosion resistance of the double layer REM conversion coating was superior to that of chromate conversion coating. The corrosion behavior of REM conversion coatings on LY12 alloy was studied with optical microscopy and

Yu Xingwen; Cao Chunan; Yao Zhiming; Zhou Derui; Yin Zhongda

2000-01-01

346

Energy position of 4f levels in rare-earth metals  

Microsoft Academic Search

The energy position of the occupied and unoccupied 4f levels relative to the Fermi energy is studied for the rare-earth metals. This is done by treating the excited state as an impurity in an otherwise perfect crystal. This picture is first considered in the complete screening approximation. In this approximation thermochemical data can be used directly to give energy values

Börje Johansson

1979-01-01

347

SOME EFFECTS OF ANISOTROPY ON SPIRAL SPIN-CONFIGURATIONS WITH APPLICATION TO RARE-EARTH METALS  

Microsoft Academic Search

A theoretical study of effects of anisotropy on spiral spin-; configurations is presented, emphasizing the problem of the magnetic ordering in ; rare-earth metals. It is shown that the ferromagnetic spiral observed at low ; temperatures by Wilkinson, Koehler, Wollan, and Cable in erbium can be the ; classical ground state of a spin Hamiltonian containing exchange and anisotropy ;

T. Kaplan

1961-01-01

348

Rare earth metal oxides: formation, characterization and catalytic activity Thermoanalytical and applied pyrolysis review  

Microsoft Academic Search

This review provides a guide to the recent literature on the characterization of the decomposition routes of different precursors, especially carboxylates of rare earth metals (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y and Th), and the formation of the final oxide products. It also discusses the effects of 1.(1) the nature of

Gamal A. M. Hussein

1996-01-01

349

Study of double layer rare earth metal conversion coating on aluminum alloy LY12  

Microsoft Academic Search

The process of the double layer rare earth metal (REM) conversion coating on aluminum alloy LY12 (2024) was introduced in this paper. The corrosion resistance of REM conversion coating was examined by electrochemical impedance spectroscopy. The results showed that the coating increased the corrosion resistance (Rp) of the alloy surface, thus reducing the driving force of corrosion. The morphologies of

Yu Xingwen; Cao Chunan; Yao Zhiming; Zhou Derui; Yin Zhongda

2001-01-01

350

Shifted homologous relationships between the transplutonium and early rare-earth metals  

SciTech Connect

The physico-chemical properties of the late actinide metals americium through einsteinium are compared with their rare-earth counterparts. Localization of the 5f electrons beginning at americium signals the appearance of true rare-earth-like properties, but the homologous relationship is shifted to place americium below praseodymium, einsteinium then below europium. The comparison of crystal structure, phase transitions, vapor pressures and heats of vaporization reveals remarkable similarities, especially for Sm-Cf and Eu-Es, where the stability of the divalent metal becomes established and divalent chemistry then follows. There is of course a major perturbation at the half-filled shell at curium, and it may be argued that americium is the anomaly in the so-called second rare-earth series. However, the response of americium, berkelium and californium under pressure reveals the true perturbation to be a thermodynamic one, occurring at curium.

Ward, J.W.

1984-01-01

351

Rare earth metal oxazoline complexes in asymmetric catalysis.  

PubMed

Polydentate oxazolines have been employed as highly effective stereodirecting ligands for asymmetric catalysis with metals from across most of the periodic table. Despite their highly versatile coordination chemistry, the use of these ligands tends to be polarised towards late transition metals; their use with early transition metals and the f-elements is significantly less developed. This current article aims to review the coordination chemistry and catalytic applications of Group 3 and lanthanide complexes supported by ligands possessing oxazoline moieties. Oxazoline-containing ligands were first employed in molecular lanthanide catalysis as early as 1997, yet there is still a significant void in the chemical literature in this respect. The ligands generally employed include bis(oxazolinyl)methane ("BOX"), 2,6-bis(oxazolinyl)pyridine ("pybox"), 1,1,1-tris(oxazolinyl)ethane ("trisox"), and others. The complexes are employed in a wide-range of catalytic applications, especially in Lewis acid catalysis, but also in the stereospecific polymerisation of olefins. PMID:22982883

Ward, Benjamin D; Gade, Lutz H

2012-11-01

352

The free escape boundary of diffuse ions upstream of the Earth's quasi-parallel bow shock  

NASA Astrophysics Data System (ADS)

The Earth's bow shock is very efficient in accelerating ions out of the incident solar wind distribution to high energies (? 200 keV/e). Energetic ions accelerated at the quasi-parallel bow shock are also known as diffuse ions and are best represented by exponential spectra in energy/charge, which require additional assumptions to be incorporated into the models. One of these assumptions is a free escape boundary along the interplanetary magnetic field into the upstream direction. We use two years of data from the background monitor on the IBEX spacecraft to investigate the existence of an upstream free escape boundary for bow shock accelerated ions. The IBEX mission was launched into an 18000 km by 50 RE orbit with a 7.5 day period, which provides extended periods of time in the region upstream of the bow shock. The IBEX background monitor is sensitive to protons > 14 keV which includes the energy for the maximum flux for diffuse ions. With increasing distance from the bow shock along the interplanetary magnetic field, the background count rates from diffuse ions stays constant for ions streaming away from the bow shock while diffuse ion count rates streaming towards the shock decrease for distances > 10 - 15 RE. These observations appear to support the existence of a free escape boundary for ions > 14 keV at a distance of ~10 - 15 RE from the shock.

Trattner, K. J.; Allegrini, F.; Dayeh, M. A.; Funsten, H. O.; Fuselier, S. A.; Heirtzler, D.; Janzen, P.; Kucharek, H.; McComas, D. J.; Moebius, E.; Moore, T. E.; Petrinec, S. M.; Reisenfeld, D. B.; Schwadron, N. A.; Wurz, P.

2012-04-01

353

The free escape boundary of diffuse ions upstream of the Earth's quasi-parallel bow shock  

NASA Astrophysics Data System (ADS)

The Earth's bow shock is very efficient in accelerating ions out of the incident solar wind distribution to high energies (? 200 keV/e). Energetic ions accelerated at the quasi-parallel bow shock are also known as diffuse ions and are best represented by exponential spectra in energy/charge, which require additional assumptions to be incorporated into the models. One of these assumptions is a free escape boundary along the interplanetary magnetic field into the upstream direction. We use two years of data from the background monitor on the IBEX spacecraft, supported by ACE solar wind observations, to investigate the existence of an upstream free escape boundary for bow shock accelerated ions. The IBEX mission was launched into an 18000 km by 50 RE orbit with a 7.5 day period, which provides extended periods of time in the region upstream of the bow shock. The IBEX background monitor is sensitive to protons > 14 keV which includes the energy of the maximum flux for diffuse ions. With increasing distance from the bow shock along the interplanetary magnetic field, the background count rates from diffuse ions stay constant for ions streaming away from the bow shock while diffuse ion count rates streaming towards the shock decrease for distances > 10 - 15 RE. These observations appear to support the existence of a free escape boundary for ions > 14 keV at a distance of ~10 - 15 RE from the shock.

Trattner, K. J.; Allegrini, F.; Dayeh, M. A.; Funsten, H. O.; Fuselier, S. A.; Heirtzler, D.; Janzen, P. H.; Kucharek, H.; McComas, D. J.; Moebius, E.; Moore, T. E.; Petrinec, S. M.; Reisenfeld, D. B.; Schwadron, N. A.; Wurz, P.

2011-12-01

354

Radiation damage from single heavy ion impacts on metal surfaces  

SciTech Connect

The effects of single ion impacts on the surfaces of films of Au, Ag, In and Pb have been studied using in-situ transmission electron microscopy. On all of these materials, individual ion impacts produce surface craters, in some cases, with associated expelled material. The cratering efficiency scales with the density of the irradiated metal. For very thin Au foils ({approx} 20--50 nm), in some cases individual ions are seen to punch small holes completely through the foil. Continued irradiation results in a thickening of the foil. The process giving rise to crater and hole formation and other changes observed in the thin foils has been found to be due to pulsed localized flow--i.e. melting and flow due to the thermal spikes arising from individual ion impacts. Experiments carried out on thin films of silver sandwiched between SiO{sub 2} layers have indicated that pulsed localized flow also occurs in this system and contributes to the formation of Ag nanoclusters in SiO{sub 2}--a system of interest for its non-linear optical properties. Calculation indicates that, when ion-induced, collision cascades occur near surfaces (within {approx} 5 nm) with energy densities sufficient to cause melting, craters are formed. Crater formation occurs as a result of the explosive outflow of material from the hot molten core of the cascade. Processes occurring in the sandwiched layer are less well understood.

Donnelly, S.E. [Univ. of Salford, Manchester (United Kingdom); Birtcher, R.C. [Argonne National Lab., IL (United States). Materials Science Div.

1998-06-01

355

Influence of other rare earth ions on the optical refrigeration efficiency in Yb:YLF crystals.  

PubMed

We investigated the effect of rare earth impurities on the cooling efficiency of Yb³?:LiYF? (Yb:YLF). The refrigeration performance of two single crystals, doped with 5%-at. Yb and with identical history but with different amount of contaminations, have been compared by measuring the cooling efficiency curves. Spectroscopic and elemental analyses of the samples have been carried out to identify the contaminants, to quantify their concentrations and to understand their effect on the cooling efficiencies. A model of energy transfer processes between Yb and other rare earth ions is suggested, identifying Erbium and Holmium as elements that produce a detrimental effect on the cooling performance. PMID:25402099

Di Lieto, Alberto; Sottile, Alberto; Volpi, Azzurra; Zhang, Zhonghan; Seletskiy, Denis V; Tonelli, Mauro

2014-11-17

356

On the origin of the energetic ion events measured upstream of the Earth's bow shock by STEREO,  

E-print Network

On the origin of the energetic ion events measured upstream of the Earth's bow shock by STEREO of the solar cycle the energetic upstream ion events occurred mainly after a corotating interaction region to 30 RE). For this purpose, simultaneous measurements of energetic ions from STEREO A and STEREO B (far

Bergen, Universitetet i

357

Aluminum/alkaline earth metal composites and method for producing  

DOEpatents

A composite is provided having an electrically conducting Al matrix and elongated filaments comprising Ca and/or Sr and/or Ba disposed in the matrix and extending along a longitudinal axis of the composite. The filaments initially comprise Ca and/or Sr and/or Ba metal or allow and then may be reacted with the Al matrix to form a strengthening intermetallic compound comprising Al and Ca and/or Sr and/or Ba. The composite is useful as a long-distance, high voltage power transmission conductor.

Russell, Alan M; Anderson, Iver E; Kim, Hyong J; Freichs, Andrew E

2014-02-11

358

Features of the formation of magnetic moments of Tm3+ and Yb3+ rare-earth ions in LuB12 cage glass  

NASA Astrophysics Data System (ADS)

The features of the formation of the magnetic moments of Tm3+ and Yb3+ ions in a metallic matrix of LuB12 cage glass have been studied in measurements of the magnetization and specific heat in the temperature range of 1.9-300 K in magnetic fields up to 90 kOe. It has been shown that a paramagnetic response from the localized moments of isolated ions Tm3+ (7.6?B) and Yb3+ (4.5?B) is observed at temperatures of 150-300 K. A transition to the cage glass phase at low temperatures ( T ? T* ˜ 60 K) is accompanied by disordering in the system of rare-earth ions and by formation of many-body states near Tm3+ and Yb3+ ions. At low temperatures near T m in low magnetic fields, the appearance of an additional spin polarization, which is suppressed with an increase in the field, has been observed. The effective moments and g-factors of Tm and Yb obtained in high fields imply both the binding of a small fraction of magnetic ions to antiferromagnetic dimers and the ?6 ground state of the 2 F 7/2 multiplet of the ytterbium ion. A scenario alternative to the Kondo-type behavior has been proposed to explain the nature of many-body states and the appearance of the spin polarization in rare-earth dodecaborides.

Sluchanko, N. E.; Azarevich, A. N.; Anisimov, M. A.; Bogach, A. V.; Voronov, V. V.; Gavrilkin, S. Yu.; Glushkov, V. V.; Demishev, S. V.; Kuznetsov, A. V.; Mitsen, K. V.; Filippov, V. B.; Shitsevalova, N. Yu.; Gabani, S.; Flachbart, K.

2014-12-01

359

Ternary rare earth and actinoid transition metal carbides viewed as carbometalates  

NASA Astrophysics Data System (ADS)

Ternary carbides A xT yC z ( A=rare earth metals and actinoids; T=transition metals) with monoatomic species C 4- as structural entities are classified according to the criteria (i) metal to carbon ratio, (ii) coordination number of the transition metal by carbon atoms, and (iii) the dimensionality of the anionic network [ T yC z] n-. Two groups are clearly distinguishable, depending on the metal to carbon ratio. Those where this ratio is equal to or smaller than 2 may be viewed as carbometalates, thus extending the sequence of complex anions from fluoro-, oxo-, and nitridometalates to carbometalates. The second group, metal-rich carbides with metal to carbon ratios equal to or larger than 4 is better viewed as typical intermetallics ("interstitial carbides"). The chemical bonding properties have been investigated by analyzing the Crystal Orbital Hamilton Population (COHP). The chemical bonding situation with respect to individual T-C bonds is similar in both classes. The main difference is the larger number of metal-metal bonds in the crystal structures of the metal-rich carbides.

Dashjav, Enkhtsetseg; Kreiner, Guido; Schnelle, Walter; Wagner, Frank R.; Kniep, Rüdiger; Jeitschko, Wolfgang

2007-02-01

360

Aligned nanogold assisted one step sensing and removal of heavy metal ions.  

PubMed

We depict a novel strategy exploiting the chemistry of metal ion adsorption for detection and sequestration of toxic heavy metal from processed water using gold nanoparticles capped with 4-aminothiophenol. The interaction between 4-aminothiophenol capped gold nanoparticles and heavy metal ions was studied as a function of time and concentration using TEM, HRTEM, SEM, EDS, and I-V characterization. Experiments confirmed that pH is one of the crucial controlling parameters. Adsorption capacity was monitored using AAS, UV-vis spectroscopy and I-V measurement. In the absence of any alloy formation between Au and heavy metal ions, the desorption of the heavy metal ions from 4-aminothiophenol capped gold nanoparticles surface by pH modulation serves as a mean of collection of heavy metal ions. Experiments revealed that the concentration of heavy metal ions in processed water after adsorption is below the maximum permissible limit set by the WHO. PMID:21851947

Chauhan, Neha; Gupta, Shweta; Singh, Nahar; Singh, Sukhvir; Islam, Saikh S; Sood, Kedar N; Pasricha, Renu

2011-11-01

361

Earth  

NASA Technical Reports Server (NTRS)

The following aspects of the planet Earth are discussed: plate tectonics, the interior of the planet, the formation of the Earth, and the evolution of the atmosphere and hydrosphere. The Earth's crust, mantle, and core are examined along with the bulk composition of the planet.

Carr, M. H.

1984-01-01

362

Hydrolysis of Naptalam and Structurally Related Amides: Inhibition by Dissolved Metal Ions and Metal (Hydr)Oxide Surfaces  

E-print Network

Hydrolysis of Naptalam and Structurally Related Amides: Inhibition by Dissolved Metal Ions hydrolysis between pH 3.6 and pH 6.5. Metal ion-naptalam complex formation is important since additionOOH inhibit naptalam hydrolysis to a lesser degree; inhibition is proportional to the extent of naptalam

Huang, Ching-Hua

363

Rare earth zirconium oxide buffer layers on metal substrates  

DOEpatents

A laminate article comprises a substrate and a biaxially textured (RE.sub.x A.sub.(1-x)).sub.2 O.sub.2-(x/2) buffer layer over the substrate, wherein 0metal-organic decomposition. The laminate article can include a layer of YBCO over the (RE.sub.x A.sub.(1-x)).sub.2 O.sub.2-(x/2) buffer layer. A layer of CeO.sub.2 between the YBCO layer and the (RE.sub.x A.sub.(1-x)).sub.2 O.sub.2-(x/2) buffer layer can also be include. Further included can be a layer of YSZ between the CeO.sub.2 layer and the (RE.sub.x A.sub.(1-x)).sub.2 O.sub.2-(x/2) buffer layer. The substrate can be a biaxially textured metal, such as nickel. A method of forming the laminate article is also disclosed.

Williams, Robert K. (Knoxville, TN); Paranthaman, Mariappan (Knoxville, TN); Chirayil, Thomas G. (Knoxville, TN); Lee, Dominic F. (Knoxville, TN); Goyal, Amit (Knoxville, TN); Feenstra, Roeland (Knoxville, TN)

2001-01-01

364

Altering the Divalent Metal Ion Preference of RNase E.  

PubMed

RNase E is a major intracellular endoribonuclease in many bacteria and participates in most aspects of RNA processing and degradation. RNase E requires a divalent metal ion for its activity. We show that only Mg(2+) and Mn(2+) will support significant rates of activity in vitro against natural RNAs, with Mn(2+) being preferred. Both Mg(2+) and Mn(2+) also support cleavage of an oligonucleotide substrate with similar kinetic parameters for both ions. Salts of Ni(2+) and Zn(2+) permitted low levels of activity, while Ca(2+), Co(3+), Cu(2+), and Fe(2+) did not. A mutation to one of the residues known to chelate Mg(2+), D346C, led to almost complete loss of activity dependent on Mg(2+); however, the activity of the mutant enzyme was fully restored by the presence of Mn(2+) with kinetic parameters fully equivalent to those of wild-type enzyme. A similar mutation to the other chelating residue, D303C, resulted in nearly full loss of activity regardless of metal ion. The properties of RNase E D346C enabled a test of the ionic requirements of RNase E in vivo. Plasmid shuffling experiments showed that both rneD303C (i.e., the rne gene encoding a D-to-C change at position 303) and rneD346C were inviable whether or not the selection medium was supplied with MnSO4, implying that RNase E relies on Mg(2+) exclusively in vivo. PMID:25404697

Thompson, Katharine J; Zong, Jeff; Mackie, George A

2015-02-01

365

New Catalytic DNA Biosensors for Radionuclides and Metal ions  

SciTech Connect

The goals of the project are to develop new catalytic DNA biosensors for simultaneous detection and quantification of bioavailable radionuclides and metal ions, and apply the sensors for on-site, real-time assessment of concentration, speciation and stability of the individual contaminants during and after bioremediation. A negative selection strategy was tested and validated. In vitro selection was shown to yield highly active and specific transition metal ion-dependent catalytic DNA/RNA. A fluorescence resonance energy transfer (FRET) study of in vitro selected DNA demonstrated that the trifluorophore labeled system is a simple and powerful tool in studying complex biomolecules structure and dynamics, and is capable of revealing new sophisticated structural changes. New fluorophore/quenchers in a single fluorosensor yielded improved signal to noise ratio in detection, identification and quantification of metal contaminants. Catalytic DNA fluorescent and colorimetric sensors were shown useful in sensing lead in lake water and in leaded paint. Project results were described in two papers and two patents, and won an international prize.

Lu, Yi

2003-06-01

366

New Catalytic DNA Biosensors for Radionuclides and Metal ions  

SciTech Connect

The goals of the project are to develop new catalytic DNA biosensors for simultaneous detection and quantification of bioavailable radionuclides and metal ions, and apply the sensors for on-site, real-time assessment of concentration, speciation and stability of the individual contaminants during and after bioremediation. A negative selection strategy was tested and validated. In vitro selection was shown to yield highly active and specific transition metal ion-dependent catalytic DNA/RNA. A fluorescence resonance energy transfer (FRET) study of in vitro selected DNA demonstrated that the trifluorophore labeled system is a simple and powerful tool in studying complex biomolecules structure and dynamics, and is capable of revealing new sophisticated structural changes. New fluorophore/quenchers in a single fluorosensor yielded improved signal to noise ratio in detection, identification and quantification of metal contaminants. Catalytic DNA fluorescent and colorimetric sensors were shown useful in sensing lead in lake water and in leaded paint. Project results were described in two papers and two patents, and won an international prize.

Lu, Yi

2002-06-01

367

ION IMPLANTATION AND HYPERFINE INTERACTIONS IN METALS Institut de Physique Nuclaire, BP 1, 91406 Orsay, France  

E-print Network

575 ION IMPLANTATION AND HYPERFINE INTERACTIONS IN METALS H. BERNAS Institut de Physique Nucléaire is given, with a view to presenting their applications in ion-implantation studies of metals. Some typical in hyperfine interaction studies after ion-implantation. REVUE DE PHYSIQUE APPLIQU�E TOME 9, MAI 1974, PAGE

Boyer, Edmond

368

Estimation of Heavy Ion Densities From Linearly Polarized EMIC Waves At Earth  

SciTech Connect

Linearly polarized EMIC waves are expected to concentrate at the location where their wave frequency satisfies the ion-ion hybrid (IIH) resonance condition as the result of a mode conversion process. In this letter, we evaluate absorption coefficients at the IIH resonance in the Earth geosynchronous orbit for variable concentrations of helium and azimuthal and field-aligned wave numbers in dipole magnetic field. Although wave absorption occurs for a wide range of heavy ion concentration, it only occurs for a limited range of azimuthal and field-aligned wave numbers such that the IIH resonance frequency is close to, but not exactly the same as the crossover frequency. Our results suggest that, at L = 6.6, linearly polarized EMIC waves can be generated via mode conversion from the compressional waves near the crossover frequency. Consequently, the heavy ion concentration ratio can be estimated from observations of externally generated EMIC waves that have polarization.

Kim, Eun-Hwa; Johnson, Jay R.; Lee, Dong-Hun

2014-02-24

369

Orbital and spin contributions to magnetic hyperfine fields of tri-positive rare earth ions  

NASA Astrophysics Data System (ADS)

An alternative approach in the estimation of the magnetic field generated by atomic current densities is presented and applied to both the orbital and spin magnetic hyperfine fields of tri-positive rare earth ions. The application of the formulae offered is tested on the free ions Dy3+, Er3+ and Yb3+ in their ground states. The estimated magnetic hyperfine fields are in full agreement with those found in the literature. Our calculated magnetic hyperfine fields produced in the ground states of Er3+ ion in Er2Ge2O7 and Yb3+ ion in YbNi5 are also in good agreement with experimental and estimated data found in the literature.

Ayuel, K.; de Châtel, P. F.; El Hag, A.

2015-01-01

370

The kinetics of sorption of divalent metal ions onto sphagnum moss peat  

Microsoft Academic Search

A pseudo-second order rate equation describing the kinetics of sorption of divalent metal ions onto sphagnum moss peat at different initial metal ion concentrations and peat doses has been developed. The kinetics of sorption were followed based on the amounts of metal sorbed at various time intervals. Results show that sorption (chemical bonding) might be rate-limiting in the sorption of

Y. S. Ho; G. McKay

2000-01-01

371

High pressure phase transitions in the rare earth metal erbium to 151 GPa.  

PubMed

High pressure x-ray diffraction studies have been performed on the heavy rare earth metal erbium (Er) in a diamond anvil cell at room temperature to a pressure of 151 GPa and Er has been compressed to 40% of its initial volume. The rare earth crystal structure sequence hcp ? Sm type ? dhcp ? distorted fcc (hcp: hexagonal close packed; fcc: face centered cubic; dhcp: double hcp) is observed in Er below 58 GPa. We have carried out Rietveld refinement of crystal structures in the pressure range between 58 GPa and 151 GPa. We have examined various crystal structures that have been proposed for the distorted fcc (dfcc) phase and the post-dfcc phase in rare earth metals. We find that the hexagonal hR 24 structure is the best fit between 58 and 118 GPa. Above 118 GPa, a structural transformation from hR 24 phase to a monoclinic C 2/m phase is observed with a volume change of - 1.9%. We have also established a clear trend for the pressure at which a post-dfcc phase is formed in rare earth metals and show that there is a monotonic increase in this pressure with the filling of 4f shell. PMID:21753243

Samudrala, Gopi K; Thomas, Sarah A; Montgomery, Jeffrey M; Vohra, Yogesh K

2011-08-10

372

Removal and recovery of metal ions from process and waste streams using polymer filtration  

SciTech Connect

Polymer Filtration (PF) is an innovative, selective metal removal technology. Chelating, water-soluble polymers are used to selectively bind the desired metal ions and ultrafiltration is used to concentrate the polymer-metal complex producing a permeate with low levels of the targeted metal ion. When applied to the treatment of industrial metal-bearing aqueous process streams, the permeate water can often be reused within the process and the metal ions reclaimed. This technology is applicable to many types of industrial aqueous streams with widely varying chemistries. Application of PF to aqueous streams from nuclear materials processing and electroplating operations will be described.

Jarvinen, G.D.; Smith, B.F.; Robison, T.W.; Kraus, K.M.; Thompson, J.A.

1999-06-13

373

Measurements of the mobility of alkaline earth ions in liquid xenon  

NASA Astrophysics Data System (ADS)

The mobility of alkaline earth ions, Mg+, Ca+, Sr+ and Ba+, in liquid xenon is measured for the first time. The mobility of Tl+ is also determined for comparison with a measurement by other researchers. The Atkins cluster model for positive ions in non-polar liquids, based on the electrostriction effect, gives general agreement with the magnitude of the mobility values. This is some evidence that the positive ions form a snowball rather than a bubble structure in liquid xenon. However, the temperature dependence of the mobility does not match well with the Atkins theory, so there are still open theoretical questions on the nature of the environment of alkaline earth ions in liquid xenon. The lower mobility of Mg+ and Ba+ may be explained by a better size match to interstitial and substitutional sites, respectively, in solid Xe. These measurements are motivated by the development of a new technique to search for neutrino masses through 0??? decay of 136Xe. A key component of one version of the proposed experiment is tagging of 136Ba+ daughter ions in liquid 136Xe by laser-induced fluorescence.

Jeng, S.-C.; Fairbank, W. M., Jr.; Miyajima, M.

2009-02-01

374

Isotope fractionation in surface ionization ion source of alkaline-earth iodides  

SciTech Connect

The relationship between the isotope fractionation of alkaline-earth elements in the surface ionization ion source and the evaporation filament current, i.e., filament temperature, was studied. It was confirmed that the isotope fractionation depends on the evaporation filament temperature; the isotope fractionation in the case of higher temperature of filament becomes larger. The ionization and evaporation process in the surface ionization ion source was discussed, and it was concluded that the isotope fractionation is suppressed by setting at the lower temperature of evaporation filament because the dissociations are inhibited on the evaporation filament.

Suzuki, T.; Kanzaki, C.; Nomura, M.; Fujii, Y. [Research Laboratory for Nuclear Reactors, Tokyo Institute of Technology, O-okayama, Meguro-ku, Tokyo 152-8550 (Japan)

2012-02-15

375

Relationship between XMCD and molecular field in rare-earth (R) transition-metal (T) intermetallic compounds  

NASA Astrophysics Data System (ADS)

This work reports an x-ray magnetic circular dichroism (XMCD) study performed at the rare-earth L2,3 edges in several rare-earth transition-metal RT2 compounds (T = Fe, Co and Al). The transition metal contributes to the XMCD of the rare earth recorded at the L2 edge while no influence is detected at the L3 edge. This contribution shows the same spectral shape for both light and heavy rare earths and its amplitude reflects the sign and the magnitude of the magnetic moment of the transition metal. The results here presented point out that this contribution is associated with the molecular field due to the transition metal acting at the rare-earth sites.

Chaboy, J.; Laguna-Marco, M. A.; Piquer, C.; Maruyama, H.; Kawamura, N.

2007-10-01

376

Sensitive metal ions (II) determination with resonance Raman method  

NASA Astrophysics Data System (ADS)

In this paper, a new proposal for the quantitative evaluation of divalent metal ions (M2+) is developed by the use of the competitive resonance Raman (RR)-based method. Upon excitation with light of the appropriate wavelength (532 nm), a strong electric field is generated that couples with the resonance of the complex (zincon-M2+), increasing the character signals of these complexes, resulting in sensitive detection. Herein, the RR probe, zincon-M2+ complex that the RR intensity gets lower with the decreasing of the M2+ concentration, which leads to the transformation of the Raman information. As a result, by using the proposed RR-based method, we could find the liner calibration curves of Cu2+ and Ni2+, which show the potential in quantitative evaluation of an unknown sample. In addition, the abundant fingerprint information shows that RR leads to the successful analysis of a blended solution, which contains two ions: Cu2+ and Ni2+.

Yu, Zhi; Bracero, Lucas A.; Chen, Lei; Song, Wei; Wang, Xu; Zhao, Bing

2013-03-01

377

Printed disposable colorimetric array for metal ion discrimination.  

PubMed

One of the main limiting factors in optical sensing arrays is the reproducibility in the preparation, typically by spin coating and drop casting techniques, which produce membranes that are not fully homogeneous. In this paper, we increase the discriminatory power of colorimetric arrays by increasing the reproducibility in the preparation by inkjet printing and measuring the color from the image of the array acquired by a digital camera, using the H coordinate of the HSV color space as the analytical parameter, which produces robust and precise measurements. A disposable 31 mm × 19 mm nylon membrane with 35 sensing areas with 7 commercial chromogenic reagents makes it possible to identify 13 metal ions and to determine mixtures with up to 5 ions using a two-stage neural network approach with higher accuracy than with previous approaches. PMID:25088790

Ariza-Avidad, M; Salinas-Castillo, A; Cuéllar, M P; Agudo-Acemel, M; Pegalajar, M C; Capitán-Vallvey, L F

2014-09-01

378

JOURNAL DE PHYSIQUE Colloque C5, suppliment au no 5, Tome 40, Mai 1979,page C5-46 High-temperature Hall effect in rare earth metals  

E-print Network

-temperature Hall effect in rare earth metals M. V. Vedernikov, V. G. Dvunitkin and N. I. Moreva A. F. Ioffe. Abstract. - Up to date the Hall effect in rare earth metals (REM) was studied rather extensively below at http://dx.doi.org/10.1051/jphyscol:1979518 #12;HIGH-TEMPERATURE HALL EFFECT IN RARE EARTH METALS C5

Paris-Sud XI, Université de

379

Interaction of calcium with the human divalent metal-ion transporter-1  

SciTech Connect

Iron deficiency is the most prevalent micronutrient deficiency worldwide. Whereas dietary calcium is known to reduce the bioavailability of iron, the molecular basis of this interaction is not understood. We tested the hypothesis that divalent metal-ion transporter-1 (DMT1)-the principal or only mechanism by which nonheme iron is taken up at the intestinal brush border-is shared also by calcium. We expressed human DMT1 in RNA-injected Xenopus oocytes and examined its activity using radiotracer assays and the voltage clamp. DMT1 did not mediate {sup 45}Ca{sup 2+} uptake. Instead, we found that Ca{sup 2+} blocked the Fe{sup 2+}-evoked currents and inhibited {sup 55}Fe{sup 2+} uptake in a noncompetitive manner (K{sub i} {approx} 20 mM). The mechanism of inhibition was independent of voltage and did not involve intracellular Ca{sup 2+} signaling. The alkaline-earth metal ions Ba{sup 2+}, Sr{sup 2+}, and Mg{sup 2+} also inhibited DMT1-mediated iron-transport activity. We conclude that Ca{sup 2+} is a low-affinity noncompetitive inhibitor-but not a transported substrate-of DMT1, explaining in part the effect of high dietary calcium on iron bioavailability.

Shawki, Ali [Department of Molecular and Cellular Physiology, University of Cincinnati College of Medicine, P.O. Box 670576, Cincinnati, OH 45267-0576 (United States)] [Department of Molecular and Cellular Physiology, University of Cincinnati College of Medicine, P.O. Box 670576, Cincinnati, OH 45267-0576 (United States); Mackenzie, Bryan, E-mail: bryan.mackenzie@uc.edu [Department of Molecular and Cellular Physiology, University of Cincinnati College of Medicine, P.O. Box 670576, Cincinnati, OH 45267-0576 (United States)] [Department of Molecular and Cellular Physiology, University of Cincinnati College of Medicine, P.O. Box 670576, Cincinnati, OH 45267-0576 (United States)

2010-03-12

380

A THEORETICAL INVESTIGATION OF SOME MAGNETIC AND SPECTROSCOPIC PROPERTIES OF RARE-EARTH IONS  

Microsoft Academic Search

Investigations of some magnetic and spectroscopic properties of rare-; earths ions based on approximate HartreeFock calculations are reported. A set of ; convertional, nonrelativistic Hartree-Fock wave functions were obtained for Ce\\/; sup 3+\\/, Pr\\/sup 3+\\/, Nd\\/sup 3+\\/, Sm\\/sup 8+\\/, Eu\\/sup 2+\\/, Gd\\/sup 3+\\/, Dy\\/sup 3+\\/, ; Er\\/sup 3+\\/, and Yb\\/sup 3+\\/. After these calculations for Ce\\/sup 3+\\/ were carried ;

A. J. Freeman; R. E. Watson

1962-01-01

381

Nonradiative relaxation of rare-earth ions in YPO 4 crystal  

Microsoft Academic Search

The energy gap dependence of nonradiative relaxation rate is constructed for the YPO4 crystal based on the measurement of fluorescence decay time of rare-earth ions. Parameters A and ? in the expression of WNR=Ae???E (energy gap law) are found to be A=4.5×108s-1 and ?=1.45×10-3cm. Violet fluorescence from Nd3+:YPO4 crystal are also studied experimentally, and the corresponding radiative decay rates are

Hairong Zheng; Richard S. Meltzer

2007-01-01

382

New statistics on the solar wind control of Earth's ion outflow  

Microsoft Academic Search

Earth's high-latitude outflow of H+ and O+ ions has been examined with the TIMAS instrument on the Polar satellite in the 15-eV to 33-keV energy range over a nearly three-year period. This outflow is compared with solar wind plasma and magnetic field (IMF) data from the WIND spacecraft, the latter having been time shifted to the subsolar magnetopause and averaged

O. W. Lennartsson; H. L. Collin; W. K. Peterson

2004-01-01

383

Electrolyte materials containing highly dissociated metal ion salts  

DOEpatents

The present invention relates to metal ion salts which can be used in electrolytes for producing electrochemical devices, including both primary and secondary batteries, photoelectrochemical cells and electrochromic displays. The salts have a low energy of dissociation and may be dissolved in a suitable polymer to produce a polymer solid electrolyte or in a polar aprotic liquid solvent to produce a liquid electrolyte. The anion of the salts may be covalently attached to polymer backbones to produce polymer solid electrolytes with exclusive cation conductivity.

Lee, Hung-Sui (East Setauket, NY); Geng, Lin (Coram, NY); Skotheim, Terje A. (Shoreham, NY)

1996-07-23

384

Electrolyte materials containing highly dissociated metal ion salts  

DOEpatents

The present invention relates to metal ion salts which can be used in electrolytes for producing electrochemical devices, including both primary and secondary batteries, photoelectrochemical cells and electrochromic displays. The salts have a low energy of dissociation and may be dissolved in a suitable polymer to produce a polymer solid electrolyte or in a polar aprotic liquid solvent to produce a liquid electrolyte. The anion of the salts may be covalently attached to polymer backbones to produce polymer solid electrolytes with exclusive cation conductivity. 2 figs.

Lee, H.S.; Geng, L.; Skotheim, T.A.

1996-07-23

385

Laser polarization and phase control of up-conversion fluorescence in rare-earth ions.  

PubMed

We theoretically and experimentally demonstrate the up-conversion fluorescence control via resonance-mediated two-photon absorption in rare-earth ions by varying both the laser polarization and phase. We show that both the laser polarization and phase can control the up-conversion fluorescence, and the up-conversion fluorescence intensity is decreased when the laser polarization changes from linear through elliptical to circular. We also show that the laser polarization will affect the control efficiency of the up-conversion fluorescence by varying the laser phase, and the circular polarization will reduce the control efficiency. Furthermore, we suggest that the control efficiency by varying the laser polarization and the effect of the laser polarization on the control efficiency by varying the laser phase can be artificially manipulated by controlling the laser spectral bandwidth. This optical control method opens a new opportunity to control the up-conversion fluorescence of rare-earth ions, which may have significant impact on the related applications of rare-earth ions. PMID:25465401

Yao, Yunhua; Zhang, Shian; Zhang, Hui; Ding, Jingxin; Jia, Tianqing; Qiu, Jianrong; Sun, Zhenrong

2014-01-01

386

Systematic study of metal ion sorption on selected geologic media. Annual report, October 1978December 1979  

Microsoft Academic Search

This report summarizes results of the past fifteen months of research in the programs Selection of Multiple Tracers for Enhanced Oil Recovery Systems and that portion of Ion Exchange Characteristics of Enhanced Oil Recovery Systems concerned with alkaline earth ion-alkali ion equilibria on clay minerals. Because of funding reductions, we have suspended further activity in these areas except for a

R. E. Meyer; F. W. Burtch

1980-01-01

387

Rare-earth orbital contribution to the Fe K-edge x-ray magnetic circular dichroism in rare-earth transition-metal intermetallic compounds  

NASA Astrophysics Data System (ADS)

We present a systematic x-ray magnetic circular dichroism (XMCD) study performed at the Fe K-edge of the RFe11Ti intermetallic materials (R, rare earth). We have investigated the contribution of the rare-earth sublattice to the dichroism of the transition metal. The existence of a magnetic contribution of the rare earth has been identified and isolated from the whole spectrum. This contribution is found to be related to the rare-earth moment even when one is looking at the Fe K-edge absorption. The contribution of the rare earths to the total XMCD signal has been extracted for both pure and hydride derivatives, showing the decrease of the rare-earth magnetic moment upon hydrogen absorption.

Chaboy, J.; Laguna-Marco, M. A.; Sánchez, M. C.; Maruyama, H.; Kawamura, N.; Suzuki, M.

2004-04-01

388

The binding of cupric ions to bovine pancreatic ribonuclease studied with diligand metal-ion buffers  

PubMed Central

A procedure has been developed for the use of metal-ion buffers that depends on the formation of 2:1 complexes between suitable chelators and metal ions. ?-Alanine has been used as the chelator for Cu2+ ions in a study of Cu2+ binding by bovine pancreatic ribonuclease by the equilibrium-dialysis technique at pH7·0, 6·1 and 5·2. The results indicated the presence of two avid binding sites, the more avid group being implicated in the inhibition of enzyme activity by Cu2+ ions. The binding constants of the more avid site were 2·97×107, 7·97×105 and 1·25×104 at pH7·0, 6·1 and 5·2 respectively, and the binding constants of the less avid site were 5·27×106 and 1·71×105 at pH7·0 and 6·1 respectively. The data show that the Cu2+ is chelated to the protein through at least two ligand groups on the ribonuclease molecule. PMID:6070125

Saundry, R. H.; Stein, W. D.

1967-01-01

389

Alkaline earth metal salts of 1-naphthoic acid.  

PubMed

The structures of the Mg, Ca, Sr and Ba salts of 1-naphthoic acid are examined and compared with analogous structures of salts of benzoate derivatives. It is shown that catena-poly[[[diaquabis(1-naphthoato-?O)magnesium(II)]-?-aqua] dihydrate], {[Mg(C(11)H(7)O(2))(2)(H(2)O)(3)]·2H(2)O}(n), exists as a one-dimensional coordination polymer that propagates only through Mg-OH(2)-Mg interactions along the crystallographic b direction. In contrast with related benzoate salts, the naphthalene systems are large enough to prevent inorganic chain-to-chain interactions, and thus species with inorganic channels rather than layers are formed. The Ca, Sr and Ba salts all have metal centres that lie on a twofold axis (Z' = 1/2) and all have the common name catena-poly[[diaquametal(II)]-bis(?-1-naphthoato)-?(3)O,O':O;?(3)O:O,O'], [M(C(11)H(7)O(2))(2)(H(2)O)(2)](n), where M = Ca, Sr or Ba. The Ca and Sr salts are essentially isostructural, and all three species form one-dimensional coordination polymers through a carboxylate group that forms three M-O bonds. The polymeric chains propagate via c-glide planes and through MOMO four-membered rings. Again, inorganic channel structures are formed rather than layered structures, and the three structures are similar to those found for Ca and Sr salicylates and other substituted benzoates. PMID:22850845

Arlin, Jean-Baptiste; Kennedy, Alan R

2012-08-01

390

Selective exchange of divalent transition metal ions in cryptomelane-type manganic acid with tunnel structure  

SciTech Connect

The ion-exchange selectivity of divalent transition metal ions on cryptomelane-type manganic acid (CMA) with tunnel structure has been studied using the distribution coefficients ([ital K][sub [ital d

Tsuji, M. (Department of Chemistry, Faculty of Science, Tokyo Institute of Technology, 2-12-1, O-okayama, Meguro-ku, Tokyo 152 (Japan)); Komarneni, S. (Materials Research Laboratory and Department of Agronomy, The Pennsylvania State University, University Park, Pennsylvania 16802-4801 (United States))

1993-03-01

391

Dissecting the Metal Selectivity of MerR Monovalent Metal Ion Sensors in Salmonella  

PubMed Central

Two homologous transcription factors, CueR and GolS, that belong to the MerR metalloregulatory family are responsible for Salmonella Cu and Au sensing and resistance, respectively. They share similarities not only in their sequences, but also in their target transcription binding sites. While CueR responds similarly to Au, Ag, or Cu to induce the expression of its target genes, GolS shows higher activation by Au than by Ag or Cu. We showed that the ability of GolS to distinguish Au from Cu resides in the metal-binding loop motif. Here, we identify the amino acids within the motif that determine in vivo metal selectivity. We show that residues at positions 113 and 118 within the metal-binding loop are the main contributors to metal selectivity. The presence of a Pro residue at position 113 favors the detection of Cu, while the presence of Pro at position 118 disfavors it. Our results highlight the molecular bases that allow these regulators to coordinate the correct metal ion directing the response to a particular metal injury. PMID:23645605

Ibáñez, María M.; Cerminati, Sebastián; Checa, Susana K.

2013-01-01

392

Polymer hybrid thin films based on rare earth ion-functionalized MOF: photoluminescence tuning and sensing as a thermometer.  

PubMed

A series of photofunctional polymer hybrid thin films based on rare earth ion functionalized metal organic frameworks (MOFs, 1 for zinc complexes bio-MOF-1 (Zn8(ad)4(BPDC)6O·2Me2NH2) and 2 for rare earth complexes RE(BPDC)(Ad) (BPDC = biphenyl-4,4'-dicarboxylic acid, Ad = adenine) have been prepared via polymerization reaction of ethyl methacrylate (EMA) and 4-vinylpyridine (VPD). The as-obtained hybrid films were characterized by X-ray diffraction, FT-IR, and SEM, especially for the luminescence performance and sensing ability. These hybrid polymer thin films are dense and transparent and display multi-colors, including blue, red and blue-green. Among them, Y0.9Tb0.0999Eu0.0001-2 fabricated hybrid thin film displays a white light output. More significantly and interestingly, the Tb0.999Eu0.001-2 fabricated hybrid thin film can be used as luminescent ratiometric thermometer based on the energy transfer from Tb(3+) to Eu(3+), whose color will change from blue-green to pink from 100 K to 320 K. PMID:25485621

Shen, Xiang; Yan, Bing

2014-12-23

393

Amorphous Metallic Glass as New High Power and Energy Density Anodes For Lithium Ion Rechargeable Batteries  

E-print Network

We have investigated the use of aluminum based amorphous metallic glass as the anode in lithium ion rechargeable batteries. Amorphous metallic glasses have no long-range ordered microstructure; the atoms are less closely ...

Meng, Shirley Y.

394

Bulk and surface electronic structure of actinide, rare earth, and transition metal elements and compounds  

SciTech Connect

This is the final report for a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). This project sought to study of unusual magnetic and structural properties of rare earth, actinide, and transition metals through high-precision electronic structure calculations. Magnetic moment anisotropies in bulk and surface systems were studied, with emphasis on novel surfaces with unusual magnetic properties with possible applicability in magnetic recording. The structural stability, bonding properties, and elastic response of the actinides, as well as transition and rare earth elements and compounds, were also studied. The project sought to understand the unusual crystallographic and cohesive properties of the actinides and the importance of correlation to structural stability and the nature of the delocalization transition in these elements. Theoretical photoemission spectra, including surface effects, were calculated for rare earths and actinides.

Wills, J.W.; Eriksson, O.

1996-07-01

395

Electrospray droplet exposure to organic vapors: metal ion removal from proteins and protein complexes.  

PubMed

The exposure of aqueous nanoelectrospray droplets to various organic vapors can dramatically reduce sodium adduction on protein ions in positive ion mass spectra. Volatile alcohols, such as methanol, ethanol, and isopropanol lead to a significant reduction in sodium ion adduction but are not as effective as acetonitrile, acetone, and ethyl acetate. Organic vapor exposure in the negative ion mode, on the other hand, has essentially no effect on alkali ion adduction. Evidence is presented to suggest that the mechanism by which organic vapor exposure reduces alkali ion adduction in the positive mode involves the depletion of alkali metal ions via ion evaporation of metal ions solvated with organic molecules. The early generation of metal/organic cluster ions during the droplet desolvation process results in fewer metal ions available to condense on the protein ions formed via the charged residue mechanism. These effects are demonstrated with holomyoglobin ions to illustrate that the metal ion reduction takes place without detectable protein denaturation, which might be revealed by heme loss or an increase in charge state distribution. No evidence is observed for denaturation with exposure to any of the organic vapors evaluated in this work. PMID:25517019

DeMuth, J Corinne; McLuckey, Scott A

2015-01-20

396

Chemical and thermal stability of isotypic metal-organic frameworks: effect of metal ions.  

PubMed

Chemical and thermal stabilities of isotypic metal-organic frameworks (MOFs) like Al-BDC (Al-benzenedicarboxylate called MIL-53-Al), Cr-BDC (MIL-53-Cr) and V-BDC (MIL-47-V), after purification to remove uncoordinated organic linkers, have been compared to understand the effect of the central metal ions on the stabilities of the porous MOF-type materials. Chemical stability to acids, bases, and water decreases in the order of Cr-BDC>Al-BDC>V-BDC, suggesting stability increases with increasing inertness of the central metal ions. However, thermal stability decreases in the order of Al-BDC>Cr-BDC> V-BDC, and this tendency may be explained by the strength of the metal-oxygen bond in common oxides like Al(2)O(3), Cr(2)O(3), and V(2)O(5). In order to evaluate precisely the stability of a MOF, it is necessary to remove uncoordinated organic linkers that are located in the pores of the MOF, because a filled MOF may be more stable than the same MOF after purification. PMID:21547968

Kang, In Joong; Khan, Nazmul Abedin; Haque, Enamul; Jhung, Sung Hwa

2011-05-27

397

Heavy metals and rare earth elements in phosphate fertilizer components using instrumental neutron activation analysis.  

PubMed

The technique of instrumental neutron activation analysis was applied as a sensitive nondestructive analytical tool for the determination of heavy metals and rare earth elements in phosphate fertilizer ingredients. The contents of heavy metals Fe, Zn, Co, Cr and Sc as well as rare earth elements La, Ce, Hf, Eu, Yb and Sm were determined in four samples representing the phosphate fertilizer components (e.g. rock phosphate, limestone and sulfur). These samples were collected from the Abu-Zabal phosphate factory in El-Qalubia governarate, Egypt. The aim of this study was to determine the elemental pattern in phosphate ingredients as well as in the produced phosphate fertilizer. Fair agreement was found between the results obtained for the standard reference material Soil-7 and the certified values reported by the International Atomic Energy Agency. The results for the input raw materials (rock phosphate, limestone and sulfur) and the output product as final fertilizer are presented and discussed. PMID:11545513

Abdel-Haleem, A S; Sroor, A; El-Bahi, S M; Zohny, E

2001-10-01

398

Lattice vibrations and electronic transitions in the rare-earth metals: yttrium, gadolinium and lutetium.  

PubMed

Lattice vibrations in high-pressure phases of Y, Gd and Lu were studied by Raman spectroscopy. The observed phonon frequencies decrease towards the transitions to the dhcp and fcc phases. There is evidence that the entire structural sequence [Formula: see text] under pressure for the individual regular rare-earth metals and along the lanthanide series at ambient pressure involve softening of certain acoustic and optical phonon modes and of the elastic shear modulus C(44). Comparison is made to transitions between close-packed lattices in other metals, and possible correlations to s-d electron transfer are discussed. PMID:21690667

Olijnyk, Helmut

2005-01-12

399

Solvent extraction of rare-earth metals with bis(2-ethylhexyl)phosphinic acid  

Microsoft Academic Search

The extraction behavior of tervalent rare-earth metals (Ln) using a heptane solution containing bis(2-ethylhexyl)phosphinic\\u000a acid (PIA-8, HR) from 0.1?mol\\/dm3 sodium perchlorate media was studied. The pH0.5 values and separation factors obtained were compared among the metals. The stoichiometry of the extracted species and the\\u000a extraction constants for the present aqueous\\/heptane system were determined by slope analysis. It is demonstrated that

Yukio Nagaosa; Yao Binghua

1997-01-01

400

Mapping metal ions at the catalytic centres of two intron-encoded endonucleases  

Microsoft Academic Search

Divalent metal ions play a crucial role in forming the catalytic centres of DNA endonucleases. Substitution of Mg2+ ions by Fe2+ ions in two archaeal intron-encoded homing endonucleases, I-DmoI and I-PorI, yielded functional enzymes and enabled the generation of reactive hydroxyl radicals within the metal ion binding sites. Specific hydroxyl radical-induced cleavage was observed within, and immediately after, two conserved

Jens Lykke-Andersen; Roger A. Garrett; Jørgen Kjems

1997-01-01

401

Metal ion sorption by untreated and chemically treated biomass  

SciTech Connect

The metal-binding ability of biosorbents is well known; however, in comparison with commercial ion-exchange resins the capacity of biosorbents is low. The purpose of this research was to examine chemically modified biosorbents and biosorbents prepared from microorganisms isolated from extreme environments to determine if significant improvements in metal-binding capacity or biosorbents with unique capabilities could be produced. Chemical treatments examined included acid, alkali, carbon disulfide, phosphorus oxychloride, anhydrous formamide, sodium thiosulfate, sodium chloroacetic acid, and phenylsulfonate. Biosorbents were prepared from microorganisms isolated from pristine and acid mine drainage impacted sites and included heterotrophs, methanotrophs, algae, and sulfate reducers. Chemical modification with carbon disulfide, phosphorous oxychloride, and sodium thiosulfate yielded biosorbents with such as much as 74%, 133%, and 155% improvements, respectively, in metal-binding capacity, but the performance of these chemically modified biosorbents deteriorated upon repeated use. A culture isolated from an acid mine drainage impacted site, IGTM17, exhibits about 3-fold higher metal-binding capacity in comparison with other biosorbents examined in this study. IGTM17 also exhibits superior metal-binding ability at decreased pH or in the presence of interfering common cations in comparison with other biosorbents or some commercially available cation exchange resins. Some biosorbents, such as IGTM5, can bind anions. To our knowledge this is the first demonstration of the ability of biosorbents to bind anions. Moreover, preliminary data indicate that the chemical modification of biosorbents may be capable of imparting the ability to selectively bind certain anions. Further research is needed to optimize conditions for the chemical modification and stabilization of biosorbents.

Kilbane, J.J.; Xie, J.

1992-12-31

402

Optical and Electrical Properties of Rare Earth and Transition Metal Oxide Thin Films and Crystals  

Microsoft Academic Search

Optical and electrical properties of rare earth and transition metal oxide thin films and crystals have been studied in this work. We report the first explanation of the novel switching mechanism in two terminal devices based on the layered material rm V_2O_5cdot 1.6H_2O. The switching is shown to be associated with the existence of a current-induced channel between the contacts.

Ji-Guang Zhang

1990-01-01

403

Properties of the triplet metastable states of the alkaline-earth-metal atoms  

SciTech Connect

The static and dynamic properties of the alkaline-earth-metal atoms in their metastable state are computed in a configuration interaction approach with a semiempirical model potential for the core. Among the properties determined are the scalar and tensor polarizabilities, the quadrupole moment, some of the oscillator strengths, and the dispersion coefficients of the van der Waals interaction. A simple method for including the effect of the core on the dispersion parameters is described.

Mitroy, J.; Bromley, M.W.J. [Faculty of TIE, Charles Darwin University, Darwin NT 0909 (Australia)

2004-11-01

404

Formation and properties of new heavy rare-earth-based bulk metallic glasses  

Microsoft Academic Search

A series of new families of heavy rare-earth (RE) based bulk metallic glasses (BMGs) with excellent glass-forming ability and high thermal stability have been obtained by a copper mold casting method. Compared with the light RE-based BMGs, the heavy RE-based BMGs have much higher glass transition and crystallization temperatures and higher elastic moduli. It is found that the thermal stability

S. Li; X. K. Xi; Y. X. Wei; Q. Luo; Y. T. Wang; M. B. Tang; B. Zhang; Z. F. Zhao; R. J. Wang; M. X. Pan; D. Q. Zhao; W. H. Wang

2005-01-01

405

Heavy metals and rare earth elements (REEs) in soil from the Nam Co Basin, Tibetan Plateau  

Microsoft Academic Search

Twenty-eight soil samples collected from the Nam Co Basin, Tibetan Plateau, have been analyzed for heavy metals (Cd, Cr, Ni,\\u000a Cu, Zn, Pb and Mn), arsenic (As) and rare earth elements (REEs). In addition, for establishing the basic physio-chemical characteristics\\u000a of the soil, pH, total organic concentration, electrical conductivity, and effective cation exchange capacity were measured.\\u000a The results indicate that

Chaoliu Li; Shichang Kang; Xiaoping Wang; F. Ajmone-Marsan; Qianggong Zhang

2008-01-01

406

Revised model for 5 d electrons in the heavy rare earth metals  

Microsoft Academic Search

A revised version of a recently published model for 5d electrons in the ferromagnetic state of the heavy rare earth metals is described. The model involves the broadening of local 5d states into overlapping bands with individual widthsW. In the new approach it is assumed that the local 5d wave functions lie at some point between those for atomic 4fn

D. M. Eagles

1975-01-01

407

Corrosion Inhibition Mechanism of Rare Earth Metal on LC4 Al Alloy with Split Cell Technique  

Microsoft Academic Search

A new method of studying the corrosion inhibition mechanism of rare earth metal(REM) on LC4 Al alloy with the spilt cell technique was studied. The principle and experimental method of the spilt cell technique were analyzed. By measuring the change of net-electric current between the two electrodes caused by the change of the amount of oxygen in the solution and

Baoshan Gu; Jianhua Liu

2006-01-01

408

Extraction of Rare Earth Metals Using Liquid Surfactant Membranes Prepared by a Synthesized Surfactant  

Microsoft Academic Search

Three surfactants, l-glutamic acid dioleyl ester ribitol (nonionic, 2C18? GE), l-glutamic acid dioleyl ester quaternary ammonium chloride (cationic, 2C18? GEC2QA), and dioleyl dimethyl quaternary ammonium chloride (cationic, 2C18? QA) were synthesized for potential use in liquid membrane operations. These surfactants have strongly hydrophobic, twin oleyl chains as the hydrophobic moiety. Using the synthesized surfactants, extraction of rare earth metals was

Kazuya Uezu; Masahiro Goto; Shinji Irie; Kiyoshi Ikemizu; Fumiyuki Nakashio

1995-01-01

409

Probing the Kondo lattice model with alkaline-earth-metal atoms  

SciTech Connect

We study transport properties of alkaline-earth-metal atoms governed by the Kondo lattice Hamiltonian plus a harmonic confining potential, and suggest simple dynamical probes of several different regimes of the phase diagram that can be implemented with current experimental techniques. In particular, we show how Kondo physics at strong coupling, at low density, and in the heavy fermion phase is manifest in the dipole oscillations of the conduction band upon displacement of the trap center.

Foss-Feig, Michael [Department of Physics, University of Colorado, Boulder, Colorado 80309 (United States); JILA, Boulder, Colorado 80309 (United States); Hermele, Michael [Department of Physics, University of Colorado, Boulder, Colorado 80309 (United States); Rey, Ana Maria [Department of Physics, University of Colorado, Boulder, Colorado 80309 (United States); JILA, Boulder, Colorado 80309 (United States); NIST, Boulder, Colorado 80309 (United States)

2010-05-15

410

Structure of the alkali-metal-atom + strontium molecular ions: Towards photoassociation and formation of cold molecular ions  

SciTech Connect

The potential energy curves, permanent and transition dipole moments, and the static dipolar polarizability, of molecular ions composed of one alkali-metal atom and a strontium ion are determined with a quantum chemistry approach. The molecular ions are treated as effective two-electron systems and are treated using effective core potentials including core polarization, large gaussian basis sets, and full configuration interaction. In the perspective of upcoming experiments aiming at merging cold atom and cold ion traps, possible paths for radiative charge exchange, photoassociation of a cold lithium or rubidium atom and a strontium ion are discussed, as well as the formation of stable molecular ions.

Aymar, M.; Dulieu, O. [Laboratoire Aime Cotton, CNRS, UPR3321, Ba circumflex t. 505, Univ Paris-Sud, 91405 Orsay Cedex (France); Guerout, R. [Laboratoire Kastler-Brossel, CNRS, ENS, Univ Pierre et Marie Curie case 74, Campus Jussieu, F-75252 Paris Cedex 05 (France)

2011-08-14

411

Structure of the Alkali-metal-atom-Strontium molecular ions: towards photoassociation and formation of cold molecular ions  

E-print Network

The potential energy curves, permanent and transition dipole moments, and the static dipolar polarizability, of molecular ions composed of one alkali-metal atom and a Strontium ion are determined with a quantum chemistry approach. The molecular ions are treated as effective two-electron systems and are treated using effective core potentials including core polarization, large gaussian basis sets, and full configuration interaction. In the perspective of upcoming experiments aiming at merging cold atom and cold ion traps, possible paths for radiative charge exchange, photoassociation of a cold Lithium or Rubidium atom and a Strontium ion are discussed, as well as the formation of stable molecular ions.

Aymar, Mireille; Dulieu, Olivier

2011-01-01

412

Structure of the Alkali-metal-atom-Strontium molecular ions: towards photoassociation and formation of cold molecular ions  

E-print Network

The potential energy curves, permanent and transition dipole moments, and the static dipolar polarizability, of molecular ions composed of one alkali-metal atom and a Strontium ion are determined with a quantum chemistry approach. The molecular ions are treated as effective two-electron systems and are treated using effective core potentials including core polarization, large gaussian basis sets, and full configuration interaction. In the perspective of upcoming experiments aiming at merging cold atom and cold ion traps, possible paths for radiative charge exchange, photoassociation of a cold Lithium or Rubidium atom and a Strontium ion are discussed, as well as the formation of stable molecular ions.

Mireille Aymar; Romain Guérout; Olivier Dulieu

2011-02-24

413

Ion conics and counterstreaming electrons generated by lower hybrid waves in the earth's magnetosphere  

NASA Technical Reports Server (NTRS)

The exotic phenomenon of energetic ion-conic and counterstreaming electron formation by lower hybrid waves along discrete auroral field lines in the earth magnetosphere is considered. Mean-particle calculations, plasma simulations, and analytical treatments of the acceleration processes are described. It is shown that, in the primary auroral electron-beam region, lower hybrid waves could be an efficient mechanism for the transverse heating of H (+) and O(+) ions of ionospheric origin, as well as for the field-aligned heating of the ambient electrons leading to coincident counterstreaming electron distributions. For O(+) ions to be energized by such a wave-particle interaction process, however, some sort of preheating mechanism is required.

Chang, Tom; Crew, Geoffrey B.; Retterrer, John M.; Jasperse, John R.

1989-01-01

414

Ground-state properties of rare-earth metals: an evaluation of density-functional theory.  

PubMed

The rare-earth metals have important technological applications due to their magnetic properties, but are scarce and expensive. Development of high-performance magnetic materials with less rare-earth content is desired, but theoretical modeling is hampered by complexities of the rare earths electronic structure. The existence of correlated (atomic-like) 4f electrons in the vicinity of the valence band makes any first-principles theory challenging. Here, we apply and evaluate the efficacy of density-functional theory for the series of lanthanides (rare earths), investigating the influence of the electron exchange and correlation functional, spin-orbit interaction, and orbital polarization. As a reference, the results are compared with those of the so-called 'standard model' of the lanthanides in which electrons are constrained to occupy 4f core states with no hybridization with the valence electrons. Some comparisons are also made with models designed for strong electron correlations. Our results suggest that spin-orbit coupling and orbital polarization are important, particularly for the magnitude of the magnetic moments, and that calculated equilibrium volumes, bulk moduli, and magnetic moments show correct trends overall. However, the precision of the calculated properties is not at the level of that found for simpler metals in the Periodic Table of Elements, and the electronic structures do not accurately reproduce x-ray photoemission spectra. PMID:25237839

Söderlind, Per; Turchi, P E A; Landa, A; Lordi, V

2014-10-15

415

Prostate cancer outcome and tissue levels of metal ions  

USGS Publications Warehouse

BACKGROUND There are several studies examining prostate cancer and exposure to cadmium, iron, selenium, and zinc. Less data are available on the possible influence of these metal ions on prostate cancer outcome. This study measured levels of these ions in prostatectomy samples in order to examine possible associations between metal concentrations and disease outcome. METHODS We obtained formalin fixed paraffin embedded tissue blocks of prostatectomy samples of 40 patients with PSA recurrence, matched 1:1 (for year of surgery, race, age, Gleason grading, and pathology TNM classification) with tissue blocks from 40 patients without recurrence (n = 80). Case-control pairs were compared for the levels of metals in areas adjacent to tumors. Inductively coupled plasma-mass spectrometry (ICP-MS) was used for quantification of Cd, Fe, Zn, and Se. RESULTS Patients with biochemical (PSA) recurrence of disease had 12% lower median iron (95 ??g/g vs. 111 ??g/g; P = 0.04) and 21% lower zinc (279 ??g/g vs. 346 ??g/g; P = 0.04) concentrations in the normal-appearing tissue immediately adjacent to cancer areas. Differences in cadmium (0.489 ??g/g vs. 0.439 ??g/g; 4% higher) and selenium (1.68 ??g/g vs. 1.58 ??g/g; 5% higher) levels were not statistically significant in recurrence cases, when compared to non-recurrences (P = 0.40 and 0.21, respectively). CONCLUSIONS There is an association between low zinc and low iron prostate tissue levels and biochemical recurrence in prostate cancer. Whether these novel findings are a cause or effect of more aggressive tumors, or whether low zinc and iron prostatic levels raise implications for therapy, remains to be investigated. Copyright ?? 2011 Wiley-Liss, Inc.

Sarafanov, A.G.; Todorov, T.I.; Centeno, J.A.; MacIas, V.; Gao, W.; Liang, W.-M.; Beam, C.; Gray, Michael A.; Kajdacsy-Balla, A.

2011-01-01

416

Nanoparticles reduce nickel allergy by capturing metal ions  

NASA Astrophysics Data System (ADS)

Approximately 10% of the population in the USA suffer from nickel allergy, and many are unable to wear jewellery or handle coins and other objects that contain nickel. Many agents have been developed to reduce the penetration of nickel through skin, but few formulations are safe and effective. Here, we show that applying a thin layer of glycerine emollient containing nanoparticles of either calcium carbonate or calcium phosphate on an isolated piece of pig skin (in vitro) and on the skin of mice (in vivo) prevents the penetration of nickel ions into the skin. The nanoparticles capture nickel ions by cation exchange, and remain on the surface of the skin, allowing them to be removed by simple washing with water. Approximately 11-fold fewer nanoparticles by mass are required to achieve the same efficacy as the chelating agent ethylenediamine tetraacetic acid. Using nanoparticles with diameters smaller than 500 nm in topical creams may be an effective way to limit the exposure to metal ions that can cause skin irritation.

Vemula, Praveen Kumar; Anderson, R. Rox; Karp, Jeffrey M.

2011-05-01

417

Hydrated alkali metal ions: spectroscopic evidence for clathrates.  

PubMed

The origin of enhanced abundances for some hydrated alkali metal ions, M(+)(H2O)n, where M = Cs, Rb, K, Na, and Li with between 17 and 21 water molecules attached was investigated with infrared photodissociation (IRPD) spectroscopy and by blackbody infrared radiative dissociation (BIRD) at 133 K. The abundances of clusters of Cs(+), Rb(+), and K(+) with 18 and 20 water molecules are anomalously high compared to the corresponding clusters of Na(+), and Li(+) with 20 water molecules has only a slightly enhanced abundance. BIRD results indicate that the anomalous abundance at n = 20 for the larger ions is due to the high stability of this cluster, and the significant instability of the next largest cluster, consistent with a stable core structure with 20 water molecules. IRPD spectra in the free-OH region (?3600-3800 cm(-1)) for Cs(+), Rb(+), and K(+) with 18 and 20 water molecules indicates that water molecules with a free-OH stretch accept two hydrogen bonds and donate one hydrogen bond (acceptor-acceptor-donor water) to other water molecules. No acceptor-donor (AD) bands are observed, consistent with clathrate structures for these ions. In contrast, the AD band is significant for Na(+), indicating that these clusters adopt different structures. Results for Li(+) indicate a contribution from clathrate structures at n = 20, but not at other cluster sizes. This analysis is supported by the relative intensities of bands in the hydrogen-bonding region for n = 20. PMID:23808387

Cooper, Richard J; Chang, Terrence M; Williams, Evan R

2013-08-01

418

Most spin-1/2 transition-metal ions do have single ion anisotropy.  

PubMed

The cause for the preferred spin orientation in magnetic systems containing spin-1/2 transition-metal ions was explored by studying the origin of the easy-plane anisotropy of the spin-1/2 Cu(2+) ions in CuCl2·2H2O, LiCuVO4, CuCl2, and CuBr2 on the basis of density functional theory and magnetic dipole-dipole energy calculations as well as a perturbation theory treatment of the spin-orbit coupling. We find that the spin orientation observed for these spin-1/2 ions is not caused by their anisotropic spin exchange interactions, nor by their magnetic dipole-dipole interactions, but by the spin-orbit coupling associated with their crystal-field split d-states. Our study also predicts in-plane anisotropy for the Cu(2+) ions of Bi2CuO4 and Li2CuO2. The results of our investigations dispel the mistaken belief that magnetic systems with spin-1/2 ions have no magnetic anisotropy induced by spin-orbit coupling. PMID:25273418

Liu, Jia; Koo, Hyun-Joo; Xiang, Hongjun; Kremer, Reinhard K; Whangbo, Myung-Hwan

2014-09-28

419

Most spin-1/2 transition-metal ions do have single ion anisotropy  

NASA Astrophysics Data System (ADS)

The cause for the preferred spin orientation in magnetic systems containing spin-1/2 transition-metal ions was explored by studying the origin of the easy-plane anisotropy of the spin-1/2 Cu2+ ions in CuCl2.2H2O, LiCuVO4, CuCl2, and CuBr2 on the basis of density functional theory and magnetic dipole-dipole energy calculations as well as a perturbation theory treatment of the spin-orbit coupling. We find that the spin orientation observed for these spin-1/2 ions is not caused by their anisotropic spin exchange interactions, nor by their magnetic dipole-dipole interactions, but by the spin-orbit coupling associated with their crystal-field split d-states. Our study also predicts in-plane anisotropy for the Cu2+ ions of Bi2CuO4 and Li2CuO2. The results of our investigations dispel the mistaken belief that magnetic systems with spin-1/2 ions have no magnetic anisotropy induced by spin-orbit coupling.

Liu, Jia; Koo, Hyun-Joo; Xiang, Hongjun; Kremer, Reinhard K.; Whangbo, Myung-Hwan

2014-09-01

420

Solid Phase Luminescence of Several Rare Earth Ions on Ion-Exchange Films  

NASA Technical Reports Server (NTRS)

The development and characterization of a novel ion-exchange film for solid-phase fluorometry and phosphorimetry is reported. This new cation-exchange material is suitable for spectroscopic applications in the ultraviolet and visible regions. It is advantageous because it, as a single entity, is easily recovered from solution and mounted in the spectrofluorometers. After preconcentration on the film, the luminescence intensity of lanthanide ions is several orders of magnitude greater than that of the corresponding solution, depending on the volume of solution and the amount of film. This procedure allows emission spectral measurements and determination of lanthanide ions at solution concentrations of < 5 (micro)g/L. The film may be stored for subsequent reuse or as a permanent record of the analysis. The major drawback to the use of the film is slow uptake of analyte due to diffusion limitations.

Tanner, Stephen P.; Street, Kenneth W., Jr.

1999-01-01

421

Peroxide Stress Elicits Adaptive Changes in Bacterial Metal Ion Homeostasis  

PubMed Central

Abstract Exposure to hydrogen peroxide (H2O2) and other reactive oxygen species is a universal feature of life in an aerobic environment. Bacteria express enzymes to detoxify H2O2 and to repair the resulting damage, and their synthesis is typically regulated by redox-sensing transcription factors. The best characterized bacterial peroxide-sensors are Escherichia coli OxyR and Bacillus subtilis PerR. Analysis of their regulons has revealed that, in addition to inducible detoxification enzymes, adaptation to H2O2 is mediated by modifications of metal ion homeostasis. Analogous adaptations appear to be present in other bacteria as here reviewed for Deinococcus radiodurans, Neisseria gonorrhoeae, Streptococcus pyogenes, and Bradyrhizobium japonicum. As a general theme, peroxide stress elicits changes in cytosolic metal distribution with the net effect of reducing the damage caused by reactive ferrous iron. Iron levels are reduced by repression of uptake, sequestration in storage proteins, and incorporation into metalloenzymes. In addition, peroxide-inducible transporters elevate cytosolic levels of Mn(II) and/or Zn(II) that can displace ferrous iron from sensitive targets. Although bacteria differ significantly in the detailed mechanisms employed to modulate cytosolic metal levels, a high Mn:Fe ratio has emerged as one key correlate of reactive oxygen species resistance. Antioxid. Redox Signal. 15, 175–189. PMID:20977351

Faulkner, Melinda J.

2011-01-01

422

Metal cation/anion adsorption on calcium carbonate: Implications to metal ion concentrations in groundwater  

SciTech Connect

This chapter evaluates the sorption behavior of metallic ions on specimen calcite as a basis for determining the importance of calcite relative to other subsurface sorbents, such as layer silicates and oxides, in controlling metal ion concentration in calcareous groundwaters. A review of the literature shows the sorption of both metallic cations and anions on calcite over ranges in pH and CO{sub 2} partial pressure to be consistent with a surface-exchange process where cations exchange with surface Ca and anions exchange with surface CO{sub 3}. A general surface-exchange model was developed to account for the effects of Ca and CO{sub 3} concentrations, pH, and calcite surface area on cation and anion sorption onto calcite. The model was applied to recently developed experimental sorption data of Zn and SeO{sub 3} on specimen calcite in equilibrium CaCO{sub 3}(aq) suspensions. The surface-exchange model was able to describe the effects of pH on both cation and anion sorption, and provided good predictions of the effects of variable CO{sub 2}(g) pressure on Zn sorption and of PO{sub 4} on SeO{sub 3} sorption. The surface-exchange model, combined with sorption constants for other phases, was used to calculate Cd sorption to a hypothetical aquifer material containing a mixture of sorbents. The sorbent concentrations were fixed to those expected in groundwater zones. The multi-sorbent calculation documented the importance of calcite as a sorbent for metallic ions in groundwater.93 refs., 18 figs., 5 tabs.

Zachara, J.M.; Cowan, C.E.; Resch, C.T.

1990-05-01

423

Metal Ions, Not Metal-Catalyzed Oxidative Stress, Cause Clay Leachate Antibacterial Activity  

PubMed Central

Aqueous leachates prepared from natural antibacterial clays, arbitrarily designated CB-L, release metal ions into suspension, have a low pH (3.4–5), generate reactive oxygen species (ROS) and H2O2, and have a high oxidation-reduction potential. To isolate the role of pH in the antibacterial activity of CB clay mixtures, we exposed three different strains of Escherichia coli O157:H7 to 10% clay suspensions. The clay suspension completely killed acid-sensitive and acid-tolerant E. coli O157:H7 strains, whereas incubation in a low-pH buffer resulted in a minimal decrease in viability, demonstrating that low pH alone does not mediate antibacterial activity. The prevailing hypothesis is that metal ions participate in redox cycling and produce ROS, leading to oxidative damage to macromolecules and resulting in cellular death. However, E. coli cells showed no increase in DNA or protein oxidative lesions and a slight increase in lipid peroxidation following exposure to the antibacterial leachate. Further, supplementation with numerous ROS scavengers eliminated lipid peroxidation, but did not rescue the cells from CB-L-mediated killing. In contrast, supplementing CB-L with EDTA, a broad-spectrum metal chelator, reduced killing. Finally, CB-L was equally lethal to cells in an anoxic environment as compared to the aerobic environment. Thus, ROS were not required for lethal activity and did not contribute to toxicity of CB-L. We conclude that clay-mediated killing was not due to oxidative damage, but rather, was due to toxicity associated directly with released metal ions. PMID:25502790

Otto, Caitlin C.; Koehl, Jennifer L.; Solanky, Dipesh; Haydel, Shelley E.

2014-01-01

424

Transition metal ions at the crossroads of mucosal immunity and microbial pathogenesis  

PubMed Central

Transition metal ions are essential micronutrients for all living organisms. In mammals, these ions are often protein-bound and sequestered within cells, limiting their availability to microbes. Moreover, in response to infection, mammalian hosts further reduce the availability of metal nutrients by activating epithelial cells and recruiting neutrophils, both of which release metal-binding proteins with antimicrobial function. Microorganisms, in turn, have evolved sophisticated systems to overcome these limitations and acquire the metal ions essential for their growth. Here we review some of the mechanisms employed by the host and by pathogenic microorganisms to compete for transition metal ions, with a discussion of how evading “nutritional immunity” benefits pathogens. Furthermore, we provide new insights on the mechanisms of host-microbe competition for metal ions in the mucosa, particularly in the inflamed gut. PMID:24478990

Diaz-Ochoa, Vladimir E.; Jellbauer, Stefan; Klaus, Suzi; Raffatellu, Manuela

2013-01-01

425

Transition metal ions at the crossroads of mucosal immunity and microbial pathogenesis.  

PubMed

Transition metal ions are essential micronutrients for all living organisms. In mammals, these ions are often protein-bound and sequestered within cells, limiting their availability to microbes. Moreover, in response to infection, mammalian hosts further reduce the availability of metal nutrients by activating epithelial cells and recruiting neutrophils, both of which release metal-binding proteins with antimicrobial function. Microorganisms, in turn, have evolved sophisticated systems to overcome these limitations and acquire the metal ions essential for their growth. Here we review some of the mechanisms employed by the host and by pathogenic microorganisms to compete for transition metal ions, with a discussion of how evading "nutritional immunity" benefits pathogens. Furthermore, we provide new insights on the mechanisms of host-microbe competition for metal ions in the mucosa, particularly in the inflamed gut. PMID:24478990

Diaz-Ochoa, Vladimir E; Jellbauer, Stefan; Klaus, Suzi; Raffatellu, Manuela

2014-01-01

426

The Effect of Alkaline Earth Metal on the Cesium Loading of Ionsiv(R) IE910 and IE911  

Microsoft Academic Search

This study investigated the effect of variances in alkaline earth metal concentrations on cesium loading of IONSIV(R) IE-911. The study focused on Savannah River Site (SRS) ''average'' solution with varying amounts of calcium, barium and magnesium.

Fondeur

2001-01-01

427

The Effect of Alkaline Earth Metal on the Cesium Loading of Ionsiv(R) IE-910 and IE-911  

SciTech Connect

This study investigated the effect of variances in alkaline earth metal concentrations on cesium loading of IONSIV(R) IE-911. The study focused on Savannah River Site (SRS) ''average'' solution with varying amounts of calcium, barium and magnesium.

Fondeur, F.F.

2001-01-16

428

Calcium substitution in rare-earth metal germanides with the hexagonal Mn5Si3 structure type. structural characterization of the extended series RE5-xCaxGe3 (RE=Rare-earth metal)  

NASA Astrophysics Data System (ADS)

Reported are the synthesis and the structural characterization of an extended family of rare-earth metal-germanides with a general formula RE5-xCaxGe3 (RE=Y, Ce-Nd, Sm, Gd-Tm and Lu; x<2). All twelve phases are isotypic, crystallizing with the Mn5Si3 structure type (Pearson index hP16, hexagonal space group P63/mcm); they are the Ca-substituted variants of the corresponding RE5Ge3 binaries. Across the series, despite some small variations in the Ca-uptake, the unit cell volumes decrease monotonically, following the lanthanide contraction. Temperature dependent DC magnetization measurements reveal paramagnetic behavior in the high temperature range, and the obtained effective moments are consistent with free-ion RE3+ ground state, as expected from prior studies of the binary RE5Ge3 phases. The onset of magnetic ordering is observed in the low temperature range, and complex magnetic interactions (ferromagnetic/ferrimagnetic) can be inferred, different from the binary phases RE5Ge3, which are known as antiferromagnetic. In order to understand the role of Ca in the bonding, the electronic structures of the La5Ge3 and the hypothetical compounds La2Ca3Ge3 and La3Ca2Ge3 with ordered metal atoms are compared and discussed.

Suen, Nian-Tzu; Broda, Matthew; Bobev, Svilen

2014-09-01

429

MeRNA: a Database of Metal Ion Binding Sites in RNAStructures  

SciTech Connect

Metal ions are essential for the folding of RNA into stable tertiary structures and for the catalytic activity of some RNA enzymes. To aid in the study of the roles of metal ions in RNA structural biology, we have created MeRNA (Metals in RNA), a comprehensive compilation of all metal binding sites identified in RNA three-dimensional structures available from the Protein Data Bank (PDB) and Nucleic Acid Database (NDB). Currently, our database contains information relating to binding of 9764 metal ions corresponding to 23 distinct elements; in 256 RNA structures. The metal ion locations were confirmed and ligands characterized using original literature references. MeRNA includes eight manually identified metal-ion binding motifs, which are described in the literature. MeRNA is searchable by PDB identifier, metal ion, method of structure determination, resolution and R-values for X-ray structure, and distance from metal to any RNA atom or to water. New structures with their respective binding motifs will be added to the database as they become available. The MeRNA database will further our understanding of the roles of metal ions in RNA folding and catalysis and have applications in structural and functional analysis, RNA design and engineering.

Stefan, Liliana R.; Zhang, Rui; Levitan, Aaron G.; Hendrix, DonnaF.; Brenner, Steven E.; Holbrook, Stephen R.

2005-10-05

430

MeRNA: a database of metal ion binding sites in RNA structures  

PubMed Central

Metal ions are essential for the folding of RNA into stable tertiary structures and for the catalytic activity of some RNA enzymes. To aid in the study of the roles of metal ions in RNA structural biology, we have created MeRNA (Metals in RNA), a comprehensive compilation of all metal binding sites identified in RNA 3D structures available from the PDB and Nucleic Acid Database. Currently, our database contains information relating to binding of 9764 metal ions corresponding to 23 distinct elements, in 256 RNA structures. The metal ion locations were confirmed and ligands characterized using original literature references. MeRNA includes eight manually identified metal-ion binding motifs, which are described in the literature. MeRNA is searchable by PDB identifier, metal ion, method of structure determination, resolution and R-values for X-ray structure and distance from metal to any RNA atom or to water. New structures with their respective binding motifs will be added to the database as they become available. The MeRNA database will further our understanding of the roles of metal ions in RNA folding and catalysis and have applications in structural and functional analysis, RNA design and engineering. The MeRNA database is accessible at . PMID:16381830

Stefan, Liliana R.; Zhang, Rui; Levitan, Aaron G.; Hendrix, Donna K.; Brenner, Steven E.; Holbrook, Stephen R.

2006-01-01

431

Tidal decomposition of zonal neutral and ion flows in the earth's upper equatorial thermosphere  

NASA Technical Reports Server (NTRS)

Evidence is presented for strong coupling between the diurnal components of zonal neutral winds and ion drifts, suggesting that the relative importance of the E- and F-region dynamos be reevaluated. Measurements of zonal neutral winds in the equatorial region of the earth's thermosphere at an average altitude of about 350 km show that the nighttime zonal winds are very similar to the zonal ion-drifts. That similarity is examined, comparing the corresponding tidal components of the 24 hr variations of these two parameters. The amplitude spectrum of the neutral winds exhibits primary and secondary maxima at the diurnal and ter-diurnal frequencies respectively, while the ion-drift spectrum shows only the diurnal maximum. It is found that the simularity between neutral winds and ion-drifts is strongest in the diurnal mode where the phases differ by less than one half hour, the amplitude of the ion-drift being between 70 percent and 80 percent that of the neutral wind, suggesting a first-order relation between the two quantities. The largest difference is found in the steady component representing superrotation; under similar conditions of solar activity, the ions superrotate with a velocity of about 30 m/s and the neutrals with 10 m/s. For the ions, the steady component, the phase of the semi-diurnal component and the amplitude of the ter-diurnal component appear to be sensitive to solar activity and are responsible for the observed solar cycle variations in the times of eastward-to-westward reversals between 0400 and 0700 LT. The ion-drift diurnal amplitude and phase are relatively insensitive to changes in solar activity.

Herrero, F. A.; Mayr, H. G.

1986-01-01

432

Non-Ohmic Properties of ZnO-Rare Earth Metal Oxide-Co3O4 Ceramics  

Microsoft Academic Search

Zinc oxide ceramics containing rare earth metal oxide and cobalt oxide which exhibit non-ohmic current-voltage characteristics were studied. The nonlinearity was similar to that of the zinc oxide varistor containing Bi2O3 and other additives. According to microstructural observations, the intergranular layer of the ceramics was found to be a rare earth metal oxide compound without Zn and Co atoms, and

Kazuo Mukae; Kouichi Tsuda; Ikuo Nagasawa

1977-01-01

433

Solid-Liquid and Solid-Solid Transformations in the Rare-Earth Metals at High Pressures  

Microsoft Academic Search

The fusion behavior and solid-solid transformations in the rare-earth metals have been investigated at pressures in the range 6-65 kbar. The phase diagrams are presented for La, Pr, Nd, Sm, Gd, and Tb. The initial melting slopes of Dy to Lu have been obtained. Since most of the rare-earth (R.E.) metals melt from a bcc structure, they offer a series

A. Jayaraman

1965-01-01

434

Dispersion coefficients for H and He interactions with alkali-metal and alkaline-earth-metal atoms  

SciTech Connect

The van der Waals coefficients C{sub 6}, C{sub 8}, and C{sub 10} for H and He interactions with the alkali-metal (Li, Na, K, and Rb) and alkaline-earth-metal (Be, Mg, Ca, and Sr) atoms are determined from oscillator strength sum rules. The oscillator strengths were computed using a combination of ab initio and semiempirical methods. The dispersion parameters generally agree with close to exact variational calculations for Li-H and Li-He at the 0.1% level of accuracy. For larger systems, there is agreement with relativistic many-body perturbation theory estimates of C{sub 6} at the 1% level. These validations for selected systems attest to the reliability of the present dispersion parameters. About half the present parameters lie within the recommended bounds of the Standard and Certain compilation [J. Chem. Phys. 83, 3002 (1985)].

Mitroy, J.; Bromley, M.W.J. [Faculty of TIE, Charles Darwin University, Darwin NT 0909 (Australia)

2003-12-01

435

Comparing ceramic-metal to metal-metal total hip replacements--a simulator study of metal wear and ion release in 32- and 38-mm bearings.  

PubMed

Our 32 and 38 mm alumina ceramic-on-metal (COM) bearings were run in a hip simulator study for comparison with 32 mm metal-on-metal (MOM) controls. The 32 mm MOM bearings demonstrated an overall wear rate of 1.58 mm(3)/million cycles (Mc) that was comparable to previous simulator studies. The peak run-in MOM wear-rates (10, 15.7 mm(3)/Mc) were higher than in previous simulator studies. There was a noticeable graying in color of serum lubricants with MOM wear rates of 2-3 mm(3)/Mc and with wear rates of 10-15 mm(3)/Mc the serum became much darker. The COM lubricants darkened during two "break-away" wear events with wear-rates 5.8-6.7 mm(3)/Mc. The 32 and 38 mm COM bearings demonstrated overall wear-rates of 0.38 and 0.29 mm(3)/Mc, approximately four-fold reduced compared to MOM controls. The COM wear-rates were also much higher than in the one previous COM study. There may be methodological reasons that could explain this discrepancy. Our ion concentrations assessed from serum lubricants had Cobalt (Co) 68% and Chromium (Cr) 32% for average ratio of metal ion composition (i.e. averaging Co/Cr ratios: 2.26) in the parent alloy. Comparing Co ion concentrations during run-in, the COM bearings represented a 35-fold reduction compared to MOM. At 3.0 Mc, the COM represented a 33-fold reduction compared to MOM. Overall, our simulator study confirmed previously published advantages of low wear and reduced metal ions with the ceramic-metal coupling compared to standard metal-metal bearings. PMID:19598291

Ishida, Tsunehito; Clarke, Ian C; Donaldson, Thomas K; Shirasu, Hideo; Shishido, Takaaki; Yamamoto, Kengo

2009-11-01

436

GYROSURFING ACCELERATION OF IONS IN FRONT OF EARTH's QUASI-PARALLEL BOW SHOCK  

SciTech Connect

It is well known that shocks in space plasmas can accelerate particles to high energies. However, many details of the shock acceleration mechanism are still unknown. A critical element of shock acceleration is the injection problem; i.e., the presence of the so called seed particle population that is needed for the acceleration to work efficiently. In our case study, we present for the first time observational evidence of gyroresonant surfing acceleration in front of Earth's quasi-parallel bow shock resulting in the appearance of the long-suspected seed particle population. For our analysis, we use simultaneous multi-spacecraft measurements provided by the Cluster spacecraft ion (CIS), magnetic (FGM), and electric field and wave instrument (EFW) during a time period of large inter-spacecraft separation distance. The spacecraft were moving toward the bow shock and were situated in the foreshock region. The results show that the gyroresonance surfing acceleration takes place as a consequence of interaction between circularly polarized monochromatic (or quasi-monochromatic) transversal electromagnetic plasma waves and short large amplitude magnetic structures (SLAMSs). The magnetic mirror force of the SLAMS provides the resonant conditions for the ions trapped by the waves and results in the acceleration of ions. Since wave packets with circular polarization and different kinds of magnetic structures are very commonly observed in front of Earth's quasi-parallel bow shock, the gyroresonant surfing acceleration proves to be an important particle injection mechanism. We also show that seed ions are accelerated directly from the solar wind ion population.

Kis, Arpad; Lemperger, Istvan; Wesztergom, Viktor [Research Centre for Astronomy and Earth Sciences, Geodetic and Geophysical Institute, Sopron (Hungary); Agapitov, Oleksiy; Krasnoselskikh, Vladimir [LPC2E/CNRS, F-45071 Orleans (France); Khotyaintsev, Yuri V. [Swedish Institute of Space Physics, SE- 751 21 Uppsala (Sweden); Dandouras, Iannis, E-mail: akis@ggki.hu, E-mail: Kis.Arpad@csfk.mta.hu [CESR, F-31028 Toulouse (France)

2013-07-01

437

Gyrosurfing Acceleration of Ions in Front of Earth's Quasi-parallel Bow Shock  

NASA Astrophysics Data System (ADS)

It is well known that shocks in space plasmas can accelerate particles to high energies. However, many details of the shock acceleration mechanism are still unknown. A critical element of shock acceleration is the injection problem; i.e., the presence of the so called seed particle population that is needed for the acceleration to work efficiently. In our case study, we present for the first time observational evidence of gyroresonant surfing acceleration in front of Earth's quasi-parallel bow shock resulting in the appearance of the long-suspected seed particle population. For our analysis, we use simultaneous multi-spacecraft measurements provided by the Cluster spacecraft ion (CIS), magnetic (FGM), and electric field and wave instrument (EFW) during a time period of large inter-spacecraft separation distance. The spacecraft were moving toward the bow shock and were situated in the foreshock region. The results show that the gyroresonance surfing acceleration takes place as a consequence of interaction between circularly polarized monochromatic (or quasi-monochromatic) transversal electromagnetic plasma waves and short large amplitude magnetic structures (SLAMSs). The magnetic mirror force of the SLAMS provides the resonant conditions for the ions trapped by the waves and results in the acceleration of ions. Since wave packets with circular polarization and different kinds of magnetic structures are very commonly observed in front of Earth's quasi-parallel bow shock, the gyroresonant surfing acceleration proves to be an important particle injection mechanism. We also show that seed ions are accelerated directly from the solar wind ion population.

Kis, Arpad; Agapitov, Oleksiy; Krasnoselskikh, Vladimir; Khotyaintsev, Yuri V.; Dandouras, Iannis; Lemperger, Istvan; Wesztergom, Viktor

2013-07-01

438

Alkali and alkaline-earth metal amidoboranes: structure, crystal chemistry, and hydrogen storage properties.  

PubMed

Alkali- and alkaline-earth metal amidoboranes are a new class of compounds with rarely observed [NH2BH3](-) units. LiNH2BH3 and solvent-containing Ca(NH2BH3)2 x THF have been recently reported to significantly improve the dehydrogenation properties of ammonia borane. Therefore, metal amidoboranes, with accelerated desorption kinetics and suppressed toxic borazine, are of great interest for their potential applications for hydrogen storage. In this work, we successfully determined the structures of LiNH2BH3 and Ca(NH2BH3)2 using a combined X-ray diffraction and first-principles molecular dynamics simulated annealing method. Through detailed structural analysis and first-principles electronic structure calculations the improved dehydrogenation properties are attributed to the different bonding nature and reactivity of the metal amidoboranes compared to NH3BH3. PMID:18847204

Wu, Hui; Zhou, Wei; Yildirim, Taner

2008-11-01

439

Earth  

NSDL National Science Digital Library

With three levels to choose from on each page - beginner, intermediate or advanced - this site provides information on our plant Earth. There is a section about water on earth and its many different varities, like freshwater, groundwater, and frozen water. There is information about the chemical make-up of water and many images showing the different water anvironments. There is a section about life in water, such as animals, plants, and plankton.

2008-10-03

440

Lithium-Ion Batteries Being Evaluated for Low-Earth-Orbit Applications  

NASA Technical Reports Server (NTRS)

The performance characteristics and long-term cycle life of aerospace lithium-ion (Li-ion) batteries in low-Earth-orbit applications are being investigated. A statistically designed test using Li-ion cells from various manufacturers began in September 2004 to study the effects of temperature, end-of-charge voltage, and depth-of-discharge operating conditions on the cycle life and performance of these cells. Performance degradation with cycling is being evaluated, and performance characteristics and failure modes are being modeled statistically. As technology improvements are incorporated into aerospace Li-ion cells, these new designs can be added to the test to evaluate the effect of the design changes on performance and life. Cells from Lithion and Saft have achieved over 2000 cycles under 10 different test condition combinations and are being evaluated. Cells from Mine Safety Appliances (MSA) and modules made up of commercial-off-the-shelf 18650 Li-ion cells connected in series/parallel combinations are scheduled to be added in the summer of 2005. The test conditions include temperatures of 10, 20, and 30 C, end-of-charge voltages of 3.85, 3.95, and 4.05 V, and depth-of-discharges from 20 to 40 percent. The low-Earth-orbit regime consists of a 55 min charge, at a constant-current rate that is 110 percent of the current required to fully recharge the cells in 55 min until the charge voltage limit is reached, and then at a constant voltage for the remaining charge time. Cells are discharged for 35 min at the current required for their particular depth-of-discharge condition. Cells are being evaluated in four-cell series strings with charge voltage limits being applied to individual cells by the use of charge-control units designed and produced at the NASA Glenn Research Center. These charge-control units clamp the individual cell voltages as each cell reaches its end-of-charge voltage limit, and they bypass the excess current from that cell, while allowing the full current flow to the remaining cells in the pack. The goal of this evaluation is to identify conditions and cell designs for Li-ion technology that can achieve more than 30,000 low-Earth-orbit cycles. Testing is being performed at the Naval Surface Warfare Center, Crane Division, in Crane, Indiana.

McKissock, Barbara I.

2005-01-01

441

Grid-controlled metal ion sources for heavy ion fusion accelerators  

NASA Astrophysics Data System (ADS)

A variety of metal ions can be generated using vacuum arcs, but due to the nature of these arcs, the flux generated fluctuates in time. We have successfully employed electrostatically biased grids to control the plasma and to provide a well-behaved, space charge limited ion source. The grid prevents the plasma from entering the extraction gap before the main voltage pulse is applied. The extracte ion is space charge limited, resulting in a constant output current even though the ion flux from the vacuum arc source varies considerably. There are several advantages over conventional sources. For instance, thermionic sources are faced with heating problems for large area configurations, while gas-injection sources cause prefill problems because they take too long to reach equilibrium. We have performed extraction experiments with aluminum and indium arc sources. We have extracted 300 mA of pure Al+ at 30 kV for 10 ?s. The normalized beam emittance has been measured to be 3×10-7 ?-m-rad.

Len, L. K.; Humphries, S.; Burkhart, C.

1986-01-01

442

Alkali or alkaline earth metal promoted catalyst and a process for methanol synthesis using alkali or alkaline earth metals as promoters  

DOEpatents

The present invention relates to a novel route for the synthesis of methanol, and more specifically to the production of methanol by contacting synthesis gas under relatively mild conditions in a slurry phase with a heterogeneous catalyst comprising reduced copper chromite impregnated with an alkali or alkaline earth metal. There is thus no need to add a separate alkali or alkaline earth compound. The present invention allows the synthesis of methanol to occur in the temperature range of approximately 100--160 C and the pressure range of 40--65 atm. The process produces methanol with up to 90% syngas conversion per pass and up to 95% methanol selectivity. The only major by-product is a small amount of easily separated methyl formate. Very small amounts of water, carbon dioxide and dimethyl ether are also produced. The present catalyst combination also is capable of tolerating fluctuations in the H[sub 2]/CO ratio without major deleterious effect on the reaction rate. Furthermore, carbon dioxide and water are also tolerated without substantial catalyst deactivation.

Tierney, J.W.; Wender, I.; Palekar, V.M.

1995-01-31

443

Alkali or alkaline earth metal promoted catalyst and a process for methanol synthesis using alkali or alkaline earth metals as promoters  

DOEpatents

The present invention relates to a novel route for the synthesis of methanol, and more specifically to the production of methanol by contacting synthesis gas under relatively mild conditions in a slurry phase with a heterogeneous catalyst comprising reduced copper chromite impregnated with an alkali or alkaline earth metal. There is thus no need to add a separate alkali or alkaline earth compound. The present invention allows the synthesis of methanol to occur in the temperature range of approximately 100.degree.-160.degree. C. and the pressure range of 40-65 atm. The process produces methanol with up to 90% syngas conversion per pass and up to 95% methanol selectivity. The only major by-product is a small amount of easily separated methyl formate. Very small amounts of water, carbon dioxide and dimethyl ether are also produced. The present catalyst combination also is capable of tolerating fluctuations in the H.sub.2 /CO ratio without major deleterious effect on the reaction rate. Furthermore, carbon dioxide and water are also tolerated without substantial catalyst deactivation.

Tierney, John W. (Pittsburgh, PA); Wender, Irving (Pittsburgh, PA); Palekar, Vishwesh M. (Pittsburgh, PA)

1995-01-01

444

High current liquid metal ion source using porous tungsten multiemitters.  

PubMed

We recently developed an indium Liquid-Metal-Ion-Source that can emit currents from sub-?A up to several mA. It is based on a porous tungsten crown structure with 28 individual emitters, which is manufactured using Micro-Powder Injection Molding (?PIM) and electrochemical etching. The emitter combines the advantages of internal capillary feeding with excellent emission properties due to micron-size tips. Significant progress was made on the homogeneity of the emission over its current-voltage characteristic as well as on investigating its long-term stability. This LMIS seems very suitable for space propulsion as well as for micro/nano manufacturing applications with greatly increased milling/drilling speeds. This paper summarizes the latest developments on our porous multiemitters with respect to manufacturing, emission properties and long-term testing. PMID:21111260

Tajmar, M; Vasiljevich, I; Grienauer, W

2010-12-01

445

Highly charged Ar{sup q+} ions interacting with metals  

SciTech Connect

Using computer simulation, alternative methods of the interaction of highly charged ions Ar{sup q+} with metals (Au, Ag) are used and verified in the present work. Based on the classical over-barrier model, we discussed the promotion loss and peeling off processes. The simulated total potential electron yields agree well with the experiment data in incident energy ranging from 100 eV to 5 keV and all charge states of Ar{sup q+}. Based on the TRIM code, we obtain the side-feeding rate as well as the motion and charge transfer of HCI below the surface. Some results, including the array of KL{sup x} x-ray satellite lines, the respective contribution of autoionization, and side-feeding to inner shells, and the filling rates and lifetime of inner shells for Ar agree well with experiment or theory.

Wang Jijin; Zhang Jian; Gu Jiangang; Luo Xianwen; Hu Bitao [School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000 (China)

2009-12-15

446

Highly Emissive Transition Metal Ion Doped Semiconducting Nanocrystals  

SciTech Connect

Doped semiconductor nanocrystals (d-dots), specifically ones not containing heavy metal ions, have the potential to become a class of mainstream emissive materials. Mn- and Cu-doped ZnSe or ZnS d-dots can cover an emission window similar to that of the current workhorse of intrinsic quantum dot (q-dots) emitters, CdSe nanocrystals. We synthesized high quality stable Cu doped ZnSe in nonpolar as well as polar solvent. The emission intensity of these doped nanocrystals is found stable for months under UV irradiation, after different multifunctional ligand which is important for any biological detection. We have also synthesized the stable Mn doped ZnS in nonpolar solvent more than 50% QY.. The doped nanocrystals are characterized by TEM, XRD, EPR and ICP analysis.

Jana, Santanu; Srivastava, Bhupendra B.; Pradhan, Narayan [Department of Materials Science, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032 (India); Sarma, D. D. [Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore (India)

2011-07-15

447

Specific chemical interactions between metal ions and biological solids exemplified by sludge particulates.  

PubMed

The adsorption of metals onto biological surfaces was studied exemplified by municipal sludge particulates of the primary, the secondary, and the tertiary sludge types from four regional wastewater treatment plants. Major factors affecting the extent of metal adsorption including pH, DOM, total biomass, and total metal loading were studied. The acidity-basicity characteristics of the DOM, the metal ions (Lewis acids), and the surface of the sludge particulates make pH the most important parameter in metal adsorption. Change in pH can modify the speciation of the metal ions, the DOM, and the surface acidity of the sludge particulates and subsequently determines the degree of metal distribution between the aqueous phase and the sludge solids. Information on the acidity-basicity characteristics of the DOM and the sludge particulates are used to calculate the stability constant of metal ion-sludge complexes. PMID:24495800

Huang, C P; Wang, Jianmin

2014-05-01

448

Removal of Toxic\\/Heavy Metal Ions Using Ion-Imprinted Aminofunctionalized Silica Gel  

Microsoft Academic Search

The investigation reports the preparation and evaluation of Cr(III) and Fe(III)-imprinted amino-functionalized silica gel adsorbents (APTS-Cr(III)-Si and APTS-Fe(III)-Si) for selective solid-phase extraction of Cr(III) and Fe(III), respectively, from aqueous solutions. The adsorbent materials were prepared by a surface imprinting technique using 3-aminopropyltrimethoxysilane as the surface modifying ligand. The effects of solution pH, sorption time, temperature, and initial metal ion concentration

R. K. Dey; Usha Jha; Tanushree Patnaik; A. C. Singh; Varun K. Singh

2009-01-01

449

Engineering metal ion coordination to regulate amyloid fibril assembly and toxicity  

E-print Network

Engineering metal ion coordination to regulate amyloid fibril assembly and toxicity Jijun Dong, Athens, GA 30602; and §Departments of Pharmacology and Neurology, Emory University School of Medicine13 and H14 impl