Kinetics of tetravalent plutonium oxidation by cerium (4)

Energy Technology Data Exchange (ETDEWEB)

Nikitina, G P; Shumakov, V G; Egorova, V P

1975-01-01

Stoichiometry and kinetics of the Pu(4) + Ce(4) reaction is studied by spectrophotometric method at 5-30 deg C in nitric acid solutions (..mu..=(HNO/sub 3/)+(NaNO/sub 3/) = 1.0 - 5.7; (Ce(4)) = 5.10/sup -5/ - 1.2.10/sup -3/ g-ion/1, (Pu(4)) =1.10/sup -5/ - 8.5.10/sup -4/ g-ion/1. Oxidation of one Pu(4) ion to a hexavalent state requires two Ce(4) ions. The plutonium oxidation is not complicated by by-processes. Reverse Ce(3) + PuO/sub 2//sup +/ reaction does not contribute essentially to the process at (Ce(3)) 2.6.10/sup -2/ g-ion/1. The reaction rate obeys the kinetic equation - d(Pu(4))/dt = ksub(eff)(Pu(4))(Ce(4))/a sub(+-HNO/sub 3/). The thermodynamical activation parameters are found for solutions at the varied nitric acid concentrations:..delta..Gsup(not equal) = 17.0+-0.2 and ..delta..Hsup(not equal) = 21.8+-2 kcal/mole(..mu..=1.0); ..delta..Gsup(not equal) = 19.1+-0.1 and ..delta..Hsup(not equal) = 23.1+-1 kcal/mole(..mu..=4.9). The reaction mechanism is discussed in terms of the theory of absolute reaction rates and the model of long-range charge transfer.

Energy level schemes of f{sup N} electronic configurations for the di-, tri-, and tetravalent lanthanides and actinides in a free state

Energy Technology Data Exchange (ETDEWEB)

Ma, C.-G. [College of Sciences, Chongqing University of Posts and Telecommunications, Chongqing 400065 (China); Brik, M.G., E-mail: mikhail.brik@ut.ee [College of Sciences, Chongqing University of Posts and Telecommunications, Chongqing 400065 (China); Institute of Physics, University of Tartu, Ravila 14C, Tartu 50411 (Estonia); Institute of Physics, Jan Dlugosz University, Armii Krajowej 13/15, PL-42200 Czestochowa (Poland); Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw (Poland); Liu, D.-X.; Feng, B.; Tian, Ya [College of Sciences, Chongqing University of Posts and Telecommunications, Chongqing 400065 (China); Suchocki, A. [Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw (Poland)

2016-02-15

The energy level diagrams are theoretically constructed for the di-, tri-, tetravalent lanthanide and actinide ions, using the Hartree–Fock calculated parameters of the Coulomb and spin–orbit interactions within f{sup N} (N=1…13) electron configurations. These diagrams are analogous to Dieke's diagram, which was obtained experimentally. They can be used for an analysis of the optical spectra of all considered groups of ions in various environments. Systematic variation of some prominent energy levels (especially those ones with a potential for emission transitions) along the isoelectronic 4f/5f ions is considered. - Highlights: • Energy level schemes for di-, tri, tetravalent lanthanides/actinides are calculated. • Systematic variation of the characteristic energy levels across the series is considered. • Potentially interesting emission transitions are identified.

Ag29(BDT)12(TPP)4: A Tetravalent Nanocluster

KAUST Repository

AbdulHalim, Lina G.

2015-06-24

The bottom-up assembly of nanoparticles into diverse ordered solids is a challenge because it requires nanoparticles, which are often quasi-spherical, to have interaction anisotropy akin to atoms and molecules. Typically, anisotropy has been introduced by changing the shape of the inorganic nanoparticle core. Here, we present the design, self-assembly, optical properties and total structural determination of Ag29(BDT)12(TPP)4, an atomically precise tetravalent nanocluster (NC) (BDT: 1,3-benzenedithiols; TPP: triphenylphosphine). It features four unique tetrahedrally symmetrical binding surface sites facilitated by the supramolecular assembly of 12 BDT—wide footprint bidentate thiols—in the ligand shell. When each of these sites was selectively functionalized by a single phosphine ligand, particle stability, synthetic yield and the propensity to self-assemble into macroscopic crystals increased. The solid crystallized NCs have a substantially narrowed optical bandgap compared to that of the solution state, suggesting strong inter-particle electronic coupling occurs in the solid state.

Ag29(BDT)12(TPP)4: A Tetravalent Nanocluster

KAUST Repository

AbdulHalim, Lina G.; Bootharaju, Megalamane Siddaramappa; Tang, Qing; Del Gobbo, Silvano; AbdulHalim, Rasha; Eddaoudi, Mohamed; Jiang, De-en; Bakr, Osman

2015-01-01

The bottom-up assembly of nanoparticles into diverse ordered solids is a challenge because it requires nanoparticles, which are often quasi-spherical, to have interaction anisotropy akin to atoms and molecules. Typically, anisotropy has been introduced by changing the shape of the inorganic nanoparticle core. Here, we present the design, self-assembly, optical properties and total structural determination of Ag29(BDT)12(TPP)4, an atomically precise tetravalent nanocluster (NC) (BDT: 1,3-benzenedithiols; TPP: triphenylphosphine). It features four unique tetrahedrally symmetrical binding surface sites facilitated by the supramolecular assembly of 12 BDT—wide footprint bidentate thiols—in the ligand shell. When each of these sites was selectively functionalized by a single phosphine ligand, particle stability, synthetic yield and the propensity to self-assemble into macroscopic crystals increased. The solid crystallized NCs have a substantially narrowed optical bandgap compared to that of the solution state, suggesting strong inter-particle electronic coupling occurs in the solid state.

Development of a Novel Tetravalent Synthetic Peptide That Binds to Phosphatidic Acid.

Directory of Open Access Journals (Sweden)

Rina Ogawa

Full Text Available We employed a multivalent peptide-library screening technique to identify a peptide motif that binds to phosphatidic acid (PA, but not to other phospholipids such as phosphatidylcholine (PC, phosphatidylethanolamine (PE, and phosphatidylserine (PS. A tetravalent peptide with the sequence motif of MARWHRHHH, designated as PAB-TP (phosphatidic acid-binding tetravalent peptide, was shown to bind as low as 1 mol% of PA in the bilayer membrane composed of PC and cholesterol. Kinetic analysis of the interaction between PAB-TP and the membranes containing 10 mol% of PA showed that PAB-TP associated with PA with a low dissociation constant of KD = 38 ± 5 nM. Coexistence of cholesterol or PE with PA in the membrane enhanced the PAB-TP binding to PA by increasing the ionization of the phosphomonoester head group as well as by changing the microenvironment of PA molecules in the membrane. Amino acid replacement analysis demonstrated that the tryptophan residue at position 4 of PAB-TP was involved in the interaction with PA. Furthermore, a series of amino acid substitutions at positions 5 to 9 of PAB-TP revealed the involvement of consecutive histidine and arginine residues in recognition of the phosphomonoester head group of PA. Our results demonstrate that the recognition of PA by PAB-TP is achieved by a combination of hydrophobic, electrostatic and hydrogen-bond interactions, and that the tetravalent structure of PAB-TP contributes to the high affinity binding to PA in the membrane. The novel PA-binding tetravalent peptide PAB-TP will provide insight into the molecular mechanism underlying the recognition of PA by PA-binding proteins that are involved in various cellular events.

Hydrolysis constants of tetravalent neptunium by using solvent extraction method

International Nuclear Information System (INIS)

Fujiwara, K.; Kohara, Y.

2008-01-01

The hydrolysis constants of tetravalent neptunium (Np(IV)) were determined by solvent extraction method using thenoyltrifluoroacetone(TTA). In order to avoid colloid formation, a stock solution of carrier-free 239 Np(V) was from 243 Am milked. The valence of Np in the solution was then reduced to Np(IV) by using zinc amalgam. The hydrolysis constants (β m ) of the reactions, Np 4+ + mOH - = Np(OH) m (4-m)+ was evaluated by using distribution ratios at ionic strengths (I) = 0.1, 0.5 and 1.0. All experiments were performed in oxygen-free 0.5% H 2 -N 2 atmosphere (below 1.0 ppm of O 2 ) in a glove-box at room temperature (23 ± 2 C) to avoid oxidation of Np(IV). The β m values were extrapolated to the standard state (I = 0) by using the specific ion interaction theory (SIT), and the formation constants at I = 0 were determined to be log β 1 = 13.91 ± 0.23, log β 2 = 27.13 ± 0.15, log β 3 = 37.70 ± 0.30 and log β 4 = 46.16 ± 0.30. The ion interaction coefficients were also evaluated to be ε(NpOH 3+ , ClO 4 - ) = 0.49 ± 0.15, ε(Np(OH) 2 2+ , ClO 4 - ) = 0.35 ± 0.11, and ε(Np(OH) 3 + , ClO 4 - ) = 0.29 ± 0.15. (orig.)

Effect of thermal treatment conditions on properties of vanadium molybdenum oxide catalyst in acrolein oxidation reaction to acrylic acid

International Nuclear Information System (INIS)

Gorshkova, T.P.; Tarasova, D.V.; Olen'kova, I.P.; Andrushkevich, T.V.; Nikoro, T.A.

1984-01-01

The effect of thermal treatment conditions (temperature and gas medium) on properties of vanadium molybdenum oxide catalyst in acrolein oxidation reaction to acrylic acid is investigated. It is shown that active and selective catalysts are formed in the course of thermal decomposition of the drying product of ammonium metavanadate and paramolybdate under the conditions ensuring the vanadium ion reduction up to tetravalent state with conservation of molybdenum oxidation degree equal to 6. It is possible to realize it either by treatment of the catalyst calcinated in the air flow at 300 deg by the reaction mixture at the activation stage or by gas-reducer flow treatment at 280 deg. Thermal treatment in the reducing medium of the oxidized catalyst does not lead to complete regeneration of its properties

Dynamic profiles of neutralizing antibody responses elicited in rhesus monkeys immunized with a combined tetravalent DTaP-Sabin IPV candidate vaccine.

Science.gov (United States)

Sun, Mingbo; Ma, Yan; Xu, Yinhua; Yang, Huijuan; Shi, Li; Che, Yanchun; Liao, Guoyang; Jiang, Shude; Zhang, Shumin; Li, Qihan

2014-02-19

The World Health Organization has recommended that a Sabin inactivated polio vaccine (IPV) should gradually and synchronously replace oral polio vaccines for routine immunizations because its benefits in eliminating vaccine-associated paralytic poliomyelitis have been reported in different phases of clinical trials. It is also considered important to explore new tetravalent diphtheria, tetanus, and acellular pertussis-Sabin IPV (DTaP-sIPV) candidate vaccines for possible use in developing countries. In this study, the immunogenicity of a combined tetravalent DTaP-sIPV candidate vaccine was investigated in primates by evaluating the neutralizing antibody responses it induced. The dynamic profiles of the antibody responses to each of the separate antigenic components and serotypes of Sabin IPV were determined and their corresponding geometric mean titers were similar to those generated by the tetravalent diphtheria, tetanus, and acellular pertussis-conventional IPV (DTaP-cIPV), the tetravalent diphtheria, tetanus, and acellular pertussis (DTaP), and Sabin IPV vaccines in the control groups. This implies that protective immunogenic effects are conferred by this combined tetravalent formulation. Copyright © 2013 Elsevier Ltd. All rights reserved.

Hydrolysis constants of tetravalent neptunium by using solvent extraction method

Energy Technology Data Exchange (ETDEWEB)

Fujiwara, K. [Japan Atomic Energy Agency (JAEA), Naka-gun, Ibaraki-ken (Japan); Kohara, Y. [Inspection and Development Co., Naka-gun, Ibaraki-ken (Japan)

2008-07-01

The hydrolysis constants of tetravalent neptunium (Np(IV)) were determined by solvent extraction method using thenoyltrifluoroacetone(TTA). In order to avoid colloid formation, a stock solution of carrier-free {sup 239}Np(V) was from {sup 243}Am milked. The valence of Np in the solution was then reduced to Np(IV) by using zinc amalgam. The hydrolysis constants ({beta}{sub m}) of the reactions, Np{sup 4+} + mOH{sup -} = Np(OH){sub m}{sup (4-m)+} was evaluated by using distribution ratios at ionic strengths (I) = 0.1, 0.5 and 1.0. All experiments were performed in oxygen-free 0.5% H{sub 2}-N{sub 2} atmosphere (below 1.0 ppm of O{sub 2}) in a glove-box at room temperature (23 {+-} 2 C) to avoid oxidation of Np(IV). The {beta}{sub m} values were extrapolated to the standard state (I = 0) by using the specific ion interaction theory (SIT), and the formation constants at I = 0 were determined to be log {beta}{sub 1} = 13.91 {+-} 0.23, log {beta}{sub 2} = 27.13 {+-} 0.15, log {beta}{sub 3} = 37.70 {+-} 0.30 and log {beta}{sub 4} = 46.16 {+-} 0.30. The ion interaction coefficients were also evaluated to be {epsilon}(NpOH{sup 3+}, ClO{sub 4}{sup -}) = 0.49 {+-} 0.15, {epsilon}(Np(OH){sub 2}{sup 2+}, ClO{sub 4}{sup -}) = 0.35 {+-} 0.11, and {epsilon}(Np(OH){sub 3}{sup +}, ClO{sub 4}{sup -}) = 0.29 {+-} 0.15. (orig.)

Single crystal structures and theoretical calculations of uranium endohedral metallofullerenes (U@C2n , 2n = 74, 82) show cage isomer dependent oxidation states for U.

Science.gov (United States)

Cai, Wenting; Morales-Martínez, Roser; Zhang, Xingxing; Najera, Daniel; Romero, Elkin L; Metta-Magaña, Alejandro; Rodríguez-Fortea, Antonio; Fortier, Skye; Chen, Ning; Poblet, Josep M; Echegoyen, Luis

2017-08-01

Charge transfer is a general phenomenon observed for all endohedral mono-metallofullerenes. Since the detection of the first endohedral metallofullerene (EMF), La@C 82 , in 1991, it has always been observed that the oxidation state of a given encapsulated metal is always the same, regardless of the cage size. No crystallographic data exist for any early actinide endohedrals and little is known about the oxidation states for the few compounds that have been reported. Here we report the X-ray structures of three uranium metallofullerenes, U@ D 3h -C 74 , U@ C 2 (5)-C 82 and U@ C 2v (9)-C 82 , and provide theoretical evidence for cage isomer dependent charge transfer states for U. Results from DFT calculations show that U@ D 3h -C 74 and U@ C 2 (5)-C 82 have tetravalent electronic configurations corresponding to U 4+ @ D 3h -C 74 4- and U 4+ @ C 2 (5)-C 82 4- . Surprisingly, the isomeric U@ C 2v (9)-C 82 has a trivalent electronic configuration corresponding to U 3+ @ C 2v (9)-C 82 3- . These are the first X-ray crystallographic structures of uranium EMFs and this is first observation of metal oxidation state dependence on carbon cage isomerism for mono-EMFs.

Study of the chemical behaviour of technetium during irradiated fuels reprocessing

International Nuclear Information System (INIS)

Zelverte, A.

1988-04-01

This paper deals with the preparation of the lower oxidation states +III +IV and +V of technetium in nitric acid and its behaviour during the reprocessing of nuclear fuels (PUREX process). The first part of this work is a bibliographical study of this element in solution without any strong ligand. By chemical and electrochemical technics, pentavalent, tetravalent and trivalent technetium species, were prepared in nitric acid. The following chemical reactions are studied: - trivalent and tetravalent technetium oxidation by nitrate ion. - hydrazine and tetravalent uranium oxidation catalysed by technetium: in those reactions, we point out unequivocally the prominent part of trivalent and tetravalent technetium, - technetium behaviour towards hydroxylamine. Technetium should not cause any disturbance in the steps where hydroxylamine is employed to destroy nitrous acid and hydrazine replacement by hydroxylamine in uranium-plutonium partition could contribute to a best reprocessing of nuclear fuels [fr

Solid-state syntheses and single-crystal characterizations of three tetravalent thorium and uranium silicates

International Nuclear Information System (INIS)

Jin, Geng Bang; Soderholm, L.

2015-01-01

Colorless crystals of ThSiO 4 (huttonite) (1) and (Ca 0.5 Na 0.5 ) 2 NaThSi 8 O 20 (2) have been synthesized by the solid-state reactions of ThO 2 , CaSiO 3 , and Na 2 WO 4 at 1073 K. Green crystals of (Ca 0.5 Na 0.5 ) 2 NaUSi 8 O 20 (3) have been synthesized by the solid-state reactions of UO 2 , CaSiO 3 , and Na 2 WO 4 at 1003 K. All three compounds have been characterized by single-crystal X-ray diffraction. Compound 1 adopts a monazite-type three-dimensional condensed structure, which is built from edge- and corner-shared ThO 9 polyhedra and SiO 4 tetrahedra. Compounds 2 and 3 are isostructural and they crystallize in a steacyite-type structure. The structure consists of discrete pseudocubic [Si 8 O 20 ] 8− polyanions, which are connected by An 4+ cations into a three-dimensional framework. Each An atom coordinates to eight monodentate [Si 8 O 20 ] 8− moieties in a square antiprismatic geometry. Na + and Ca 2+ ions reside in the void within the framework. Raman spectra of 1, 2, and 3 were collected on single crystal samples. 1 displays more complex vibrational bands than thorite. Raman spectra of 2 and 3 are analogous with most of vibrational bands located at almost the same regions. - Graphical abstract: A Raman spectrum and crystal structures of (Ca 0.5 Na 0.5 ) 2 NaAnSi 8 O 20 (An=Th, U), which contain pseudocubic [Si 8 O 20 ] 8− polyanions and eight-coordinate An 4+ cations. - Highlights: • Single crystal growth of three tetravalent actinide silicates from melts. • Single-crystal structures and Raman spectra of (Ca 0.5 Na 0.5 ) 2 NaAnSi 8 O 20 (An=Th, U). • First report of Raman spectrum of huttonite on single crystal samples

Study of interaction of uranium, plutonium and rare earth fluorides with some metal oxides in fluoric salt melts

International Nuclear Information System (INIS)

Gorbunov, V.F.; Novoselov, G.P.; Ulanov, S.A.

1976-01-01

Interaction of plutonium, uranium, and rare-earth elements (REE) fluorides with aluminium and calcium oxides in melts of eutectic mixture LiF-NaF has been studied at 800 deg C by X-ray diffraction method. It has been shown that tetravalent uranium and plutonium are coprecipitated by oxides as a solid solution UO 2 -PuO 2 . Trivalent plutonium in fluorides melts in not precipitated in the presence of tetravalent uranium which can be used for their separation. REE are precipitated from a salt melt by calcium oxide and are not precipitated by aluminium oxide. Thus, aluminium oxide in a selective precipitator for uranium and plutonium in presence of REE. Addition of aluminium fluoride retains trivalent plutonium and REE in a salt melt in presence of Ca and Al oxides. The mechanism of interacting plutonium and REE trifluorides with metal oxides in fluoride melts has been considered

The unusual stability of homoleptic di- and tetravalent chromium alkyls

NARCIS (Netherlands)

Schulzke, C.; Enright, D.; Sugiyama, H.; LeBlanc, G.; Gambarotta, S.; Yap, G.P.A.; Thompson, L.K.; Wilson, D.R.; Duchateau, R.

2002-01-01

Reaction of CrCl3(THF)3 with 3 equiv of R-M [R = Me3CCH2 (a), Me3SiCH2 (b)] afforded either the previously reported tetravalent homoleptic R4Cr (1a, b) [M = MgCl] or the unprecedented divalent and tetranuclear homoleptic [R2Cr]4 (2b) [M = Li]. Both types of compounds display a remarkable chemical

Oxidation method of trivalent plutonium to tetravalent plutonium

International Nuclear Information System (INIS)

Ozawa, Masaki; Washitani, Tadahiro; Kawada, Tomio; Hayashi, Shotaro.

1993-01-01

The present invention concerns a Pu reoxidation step and a Pu condensation step in a purex process for recovering U and Pu in spent nuclear fuels. A nitric acid solution incorporating Pu 3+ , hydroxyl amine nitrate and hydrazine is oxidized under electrolysis. Pu 3+ is substantially completely oxidized into Pu 4+ . At the same time, also hydroxyl nitrate amine and hydrazine are substantially completely decomposed into nitrogen gas and hydrogen gas finally. Although hydroxyl nitrate amine which is a reducing agent is extremely electrochemically stable in a nitric acid solution if Pu 3+ is not present, it can be decomposed efficiently by electrolysis if Pu 3+ is present, since the latter acts as a catalyst in an electrode reaction system. (T.M.)

75 FR 6211 - Prospective Grant of Exclusive License: Purified Inactivated Dengue Tetravalent Vaccine...

Science.gov (United States)

2010-02-08

... Exclusive License: Purified Inactivated Dengue Tetravalent Vaccine Containing a Common 30 Nucleotide Deletion in the 3'-UTR of Dengue Types 1,2,3, and 4 AGENCY: National Institutes of Health, Public Health...., ``Development of Mutations Useful for Attenuating Dengue Viruses and Chimeric Dengue Viruses''-- European Patent...

Reduction of Tetravalent Plutonium in the Presence of Acetohydroxamic Acid

Energy Technology Data Exchange (ETDEWEB)

Tkac, Peter [Radiation Center, Oregon State University, Corvallis, OR (United States); Precek, Martin [Department of Chemistry, Oregon State University, Corvallis, OR (United States); Paulenova, Alena [Department of Nuclear Engineering and Radiation Health Physics, Oregon State University, Corvallis, OR (United States)

2009-06-15

in this work confirms that the reaction mechanism responsible for the decomposition of Pu-mono-aceto-hydroxamate species and reduction of Pu(IV) is more complex, and cannot be described by a simple reaction order mechanism. In the beginning, the tetravalent plutonium is stabilized against reduction to trivalent by the formation of a chelate complex with AHA. After some reaction period, Pu(III) can be re-oxidized back to Pu(IV). (authors)

In silico prediction of monovalent and chimeric tetravalent vaccines for prevention and treatment of dengue fever.

Science.gov (United States)

Vijayakumar, Subramaniyan; Ramesh, Venkatachalam; Prabhu, Srinivasan; Manogar, Palani

2017-11-01

Reverse vaccinology method was used to predict the monovalent peptide vaccine candidate to produce antibodies for therapeutic purpose and to predict tetravalent vaccine candidate to act as a common vaccine to cover all the fever dengue virus serotypes. Envelope (E)-proteins of DENV-1-4 serotypes were used for vaccine prediction using NCBI, Uniprot/Swissprot, Swiss-prot viewer, VaxiJen V2.0, TMHMM, BCPREDS, Propred-1, Propred and MHC Pred,. E-proteins of DENV-1-4 serotypes were identified as antigen from which T cell epitopes, through B cell epitopes, were predicted to act as peptide vaccine candidates. Each selected T cell epitope of E-protein was confirmed to act as vaccine and to induce complementary antibody against particular serotype of dengue virus. Chimeric tetravalent vaccine was formed by the conjugation of four vaccines, each from four dengue serotypes to act as a common vaccine candidate for all the four dengue serotypes. It can be justifiably concluded that the monovalent 9-mer T cell epitope for each DENV serotypes can be used to produce specific antibody agaomst dengue virus and a chimeric common tetravalent vaccine candidate to yield a comparative vaccine to cover any of the four dengue virus serotype. This vaccine is expected to act as highly immunogenic against preventing dengue fever.

An X-ray absorption near-edge structure (XANES) study of the Sn L_3 edge in zirconium alloy oxide films formed during autoclave corrosion

International Nuclear Information System (INIS)

Hulme, Helen; Baxter, Felicity; Babu, R. Prasath; Denecke, Melissa A.; Gass, Mhairi; Steuwer, Axel; Norén, Katarina; Carlson, Stefan; Preuss, Michael

2016-01-01

Highlights: • Characterisation of tin speciation in zirconium alloy metal and oxide films using Sn L_3-XANES. • Chemical environment of tin in Zircaloy-4 and ZIRLO™ oxide films shown to be similar. • Tin in the oxide films is present in both the di- and tetravalent states and oxidises progressively with oxide-layer growth. - Abstract: Application of Sn L_3-XANES to study the oxidation state of alloying additions of tin (1–1.2 wt%) in <2 μm oxide layers formed on nuclear grade zirconium alloy has been demonstrated. Data obtained for metallic and corroded ZIRLO™ (1 wt% Sn) and Zircaloy-4 (1.2 wt% Sn) indicate tin has a similar chemical speciation in both metal alloys but this differs in the oxidised surface layers. By recording XANES at various incident angles to vary the photon penetration depth and amount of the oxide layer probed in the measurement, the authors found evidence that the oxidation of tin progresses with increasing oxide thickness.

Polymerization of a divalent/tetravalent metal-storing atom-mimicking dendrimer

OpenAIRE

Albrecht, Ken; Hirabayashi, Yuki; Otake, Masaya; Mendori, Shin; Tobari, Yuta; Azuma, Yasuo; Majima, Yutaka; Yamamoto, Kimihisa

2016-01-01

The phenylazomethine dendrimer (DPA) has a layer-by-layer electron density gradient that is an analog of the Bohr atom (atom mimicry). In combination with electron pair mimicry, the polymerization of this atom-mimicking dendrimer was achieved. The valency of the mimicked atom was controlled by changing the chemical structure of the dendrimer. By mimicking a divalent atom, a one-dimensional (1D) polymer was obtained, and by using a planar tetravalent atom mimic, a 2D polymer was obtained. Thes...

Spinel-structured surface layers for facile Li ion transport and improved chemical stability of lithium manganese oxide spinel

Energy Technology Data Exchange (ETDEWEB)

Lee, Hae Ri [Center for Energy Convergence Research, Korea Institute of Science Technology, Hwarang-ro 14-gil 5, Seongbuk-gu, Seoul 136-791 (Korea, Republic of); Department of Chemical and Biological Engineering, Korea University, 145, Anam-ro, Seongbuk-gu, Seoul 136-701 (Korea, Republic of); Seo, Hyo Ree; Lee, Boeun; Cho, Byung Won [Center for Energy Convergence Research, Korea Institute of Science Technology, Hwarang-ro 14-gil 5, Seongbuk-gu, Seoul 136-791 (Korea, Republic of); Lee, Kwan-Young [Department of Chemical and Biological Engineering, Korea University, 145, Anam-ro, Seongbuk-gu, Seoul 136-701 (Korea, Republic of); Oh, Si Hyoung, E-mail: sho74@kist.re.kr [Center for Energy Convergence Research, Korea Institute of Science Technology, Hwarang-ro 14-gil 5, Seongbuk-gu, Seoul 136-791 (Korea, Republic of)

2017-01-15

Graphical abstract: Strategically-designed spinel-structured nano-scale surface layer, LiM{sub x}Mn{sup IV}{sub 1−x}O{sub 4}, featuring a high Li{sup +} ion conductivity and a good chemical stability was applied on Al-doped LiMn{sub 2}O{sub 4} spinel for the drastic improvement of the electrochemical performance at the elevated temperature as a promising cathode material for lithium rechargeable batteries. - Highlights: • Spinel-structured surface layer with a high Li-ion conductivity and a good chemical stability was prepared. • Simple wet process was developed to apply nano-scale surface layer on aluminum doped lithium manganese oxide spinel. • The properties of nano-scale surface layer were characterized by analytical tools including GITT, HR-TEM and XAS. • Materials with surface coating layer exhibit an excellent electrochemical performance at the elevated temperature. - Abstract: Li-ion conducting spinel-structured oxide layer with a manganese oxidation state close to being tetravalent was prepared on aluminum-doped lithium manganese oxide spinel for improving the electrochemical performances at the elevated temperatures. This nanoscale surface layer provides a good ionic conduction path for lithium ion transport to the core and also serves as an excellent chemical barrier for protecting the high-capacity core material from manganese dissolution into the electrolyte. In this work, a simple wet process was employed to prepare thin LiAlMnO{sub 4} and LiMg{sub 0.5}Mn{sub 1.5}O{sub 4} layers on the surface of LiAl{sub 0.1}Mn{sub 1.9}O{sub 4}. X-ray absorption studies revealed an oxidation state close to tetravalent manganese on the surface layer of coated materials. Materials with these surface coating layers exhibited excellent capacity retentions superior to the bare material, without undermining the lithium ion transport characteristics and the high rate performances.

Adjustment of valence state of Pu and Np in nitric solution containing N,N-dimethylhydroxylamine and monomethylhydrazine by electrolysis

Energy Technology Data Exchange (ETDEWEB)

Zhang, H.; Ye, G.A.; Cong, H.F. [China Institute of Atomic Energy, Beijing (China)] [and others

2012-07-01

A study of the electrochemical behaviors of N,N-dimethylhydroxylamine (DMHAN) and monomethyl hydrazine (MMH) in nitric acid solution on Pt electrodes were carried out by cyclic voltammetry (CV) and linear sweep voltammetry (LSV) methods. The diffusion coefficients of DMHAN and MMH were obtained by CV. The values are found to be 0.53 x 10{sup -6}6 cm{sup 2}/s D{sub (DMHAN)} and 0.88 x 10{sup -5} cm{sup 2}/s D{sub (MMH)}. The equilibrium potentials (+0.47 V vs. SCE for DMHAN and +0.31 V vs. SCE for MMH) were also measured using Tafel curves. Various valence states of Pu and Np in HNO{sub 3} solution containing DMHAN and MMH in the electrolytic process were investigated by an electrolytic cell using a platinum as the anode and a titanium plate as the cathode. In this procedure, MMH was first electro-oxidized on the Pt anode and Np(V) was reduced to Np(IV) on the Ti cathode. After MMH was entirely consumed, the accumulation of HNO{sub 2} (due to the electrochemical reduction of nitric acid on the Ti cathode) caused a significantly fast catalytic reaction of DMHAN with HNO{sub 3} to form HNO{sub 2}. HNO{sub 2} can oxidize Pu(III) to Pu(IV) quickly. As a result, both oxidation states of Pu and Np were found to be tetravalent in the post-electrolysis solution. A convenient method to keep the post-electrolysis solution at 70 C was used to adjust the oxidation state of Np in it's pentavalent state while retaining the tetravalent state of Pu. This study developed an electrolytic process for the preparation of 2AF feed (the feed of Pu purification cycle) in APOR (Advanced Purex Process Based on Organic Reductants) process by electrochemically oxidizing Pu(III) and selectively adjusting the valence state of neptunium to either Np(IV) or Np(V). (orig.)

Synthetic Smectite Colloids: Characterization of Nanoparticles after Co-Precipitation in the Presence of Lanthanides and Tetravalent Elements (Zr, Th

Directory of Open Access Journals (Sweden)

Muriel Bouby

2015-09-01

Full Text Available The magnesian smectite hectorite is a corrosion product frequently detected in nuclear waste glass alteration experiments. The structural incorporation of a single trivalent lanthanide was previously demonstrated. Hectorite was presently synthesized, for the first time, in the presence of several lanthanides (La, Eu, Yb following a multi-step synthesis protocol. The smallest-sized particles (nanoparticles, NPs were isolated by centrifugation and analyzed by asymmetrical flow field-flow fractionation (AsFlFFF coupled to ICP-MS, in order to obtain information on the elemental composition and distribution as a function of the size. Nanoparticles can be separated from the bulk smectite phase. The particles are able to accommodate even the larger-sized lanthanides such as La, however, with lower efficiency. We, therefore, assume that the incorporation proceeds by substitution for octahedral Mg accompanied by a concomitant lattice strain that increases with the size of the lanthanides. The presence of a mixture does not seem to affect the incorporation extent of any specific element. Furthermore, syntheses were performed where in addition the tetravalent zirconium or thorium elements were admixed, as this oxidation state may prevail for many actinide ions in a nuclear waste repository. The results show that they can be incorporated as well.

Surface Characterization and Electrochemical Oxidation of Metal Doped Uranium Dioxide

Energy Technology Data Exchange (ETDEWEB)

Lee, Jeongmook; Kim, Jandee; Youn, Young-Sang; Kim, Jong-Goo; Ha, Yeong-Keong; Kim, Jong-Yun [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2016-10-15

Trivalent element in UO{sub 2} matrix makes the oxygen vacancy from loss of oxygen for charge compensation. Tetravalent element alters lattice parameter of UO{sub 2} due to diameter difference between the tetravalent element and replaced U. These structural changes have significant effect on not only relevant fuel performance but also the kinetics of fuel oxidation. Park and Olander explained the stabilization of Ln (III)-doped UO{sub 2} against oxidation based on oxygen potential calculations. In this work, we have been investigated the effect of Gd{sup 3+} and Th{sup 4+} doping on the UO{sub 2} structure with Raman spectroscopy and X-ray diffraction to characterize the surface structure of nuclear fuel material. For Gd doped UO{sub 2}, its electrochemical oxidation behaviors are also investigated. The Gd and Th doped uranium dioxide solid solution pellets with various doping level were investigated by XRD, Raman spectroscopy, SEM, electrochemical experiments to investigate surface structure and electro chemical oxidation behaviors. The lattice parameter evaluated from XRD spectra indicated the formation of solid solutions. Raman spectra showed the existence of the oxygen vacancy. SEM images showed the grain structure on the surface of Gd doped uranium dioxide depending on doping level and oxygen-to-metal ratio.

Berkelium (4) and cerium (4) extraction with tertiary amines

International Nuclear Information System (INIS)

Milyukova, M.S.; Malikov, D.A.; Myasoedov, B.V.

1978-01-01

Oxidation of indicator quantities of berkelium and cerium by a mixture of silver nitrate and ammonium persulfate in the solutions of nitric and sulfuric acid has been examined. The stability of the elements in a tetravalent state and their extraction by the solutions of ternary amines have been investigated. It has been established that berkelium and cerium oxidation under these conditions occurs under the effect of ions of divalent silver which is formed owing to oxidation of monovalent silver by peroxide sulfate ions. The following supposition has been put forward: a difference in the behaviour of tetravalent berkelium and cerium during their extraction by ternary amines is explained by their different stability in this state, but not by the formation of complex compounds with nitrate ions

Coordination polymers: trapping of radionuclides and chemistry of tetravalent actinides (Th, U) carboxylates

International Nuclear Information System (INIS)

Falaise, Clement

2014-01-01

The use of nuclear energy obviously raises the question of the presence of radionuclides in the environment. Currently, their mitigation is a major issue associated with nuclear chemistry. This thesis focuses on both the trapping of radionuclides by porous solids called Metal-Organic Frameworks (MOF) and the crystal chemistry of the carboxylate of tetravalent actinides (AnIV). The academic knowledge of the reactivity of carboxylate of AnIV could help the understanding of actinides speciation in environment. We focused on the sequestration of iodine by aluminum based MOF. The functionalization (electron-donor group) of the MOF drastically enhances the iodine capture capacity. The removal of light actinides (Th and U) from aqueous solution was also investigated as well as the stability of (Al)-MOF under γ radiation. More than twenty coordination polymers based on tetravalent actinides have been synthesized and characterized by single crystal X-ray diffraction. The use of controlled hydrolysis promotes the formation of coordination polymers exhibiting polynuclear cluster ([U 4 ], [Th 6 ], [U 6 ] and [U 38 ]). In order to understand the formation of the largest cluster, the ex-situ study of the solvo-thermal synthesis of compound {U 38 } has also been investigated. (author)

Imidazolium ionic liquids as solvents for cerium(IV)-mediated oxidation reactions

OpenAIRE

Mehdi, Hasan; Bodor, Andrea; Lantos, Diana; Horváth, István T; De Vos, Dirk; Binnemans, Koen

2007-01-01

Use of imidazolium ionic liquids as solvents for organic transformations with tetravalent cerium salts as oxidizing agents was evaluated. Good solubility was found for ammonium hexanitratocerate(IV) (ceric ammonium nitrate, CAN) and cerium(IV) triflate in 1-alkyl-3-methylimidazolium triflate ionic liquids. Oxidation of benzyl alcohol to benzaldehyde in 1-ethyl-3-methylimidazolium triflate was studied by in-situ FTIR spectroscopy and 13C NMR spectroscopy on carbon-13-labeled benzyl alcohol. Ca...

Charge-transfer spectra of tetravalent lanthanide ions in oxides

NARCIS (Netherlands)

Hoefdraad, H.E.

The charge-transfer spectra of Ce4+, Pr4+ and Tb4+ in a number of oxides are reported. It is noted that the position of the first charge-transfer band is fixed for the metal ion in an oxygen coordination of VI, but varies in VIII coordination as a function of the host lattice. It is argued that this

Geochemical modelling of the sorption of tetravalent radioelements

International Nuclear Information System (INIS)

Bond, K.A.; Tweed, C.J.

1991-05-01

The results of an experimental study of the sorption of a range of tetravalent radioelements, plutonium (IV), tin (IV), thorium(IV) and uranium(IV), onto clay at pH8 and pH11 have been successfully simulated using a triple layer sorption model. The model has been incorporated into HARPHRQ, a geochemical program based on PHREEQE. The model has been parameterised using data for sorption onto ferric oxyhydroxide and goethite. The effects of hydroxycarboxylic acids on the sorption process have also been investigated experimentally. It was generally observed that in the presence of 2x10 -3 M gluconate, sorption was reduced by up two orders of magnitude. The model has satisfactorily simulated these lower sorptivities, through assuming competing sorption and complexation reactions. This work, therefore, further confirms the need to take account of such organic materials in safety assessment modelling. (author)

Oxidation state of uranium in metamict and annealed zircon: near-infrared spectroscopic quantitative analysis

CERN Document Server

Zhang Ming; Ewing, R C

2003-01-01

Radiation and thermally induced changes in the oxidation state of uranium in metamict zircon have been systematically analysed, for the first time, using polarized near-infrared spectroscopy. The results showed that in damaged zircon U ions in crystalline domains exhibited relatively sharp, anisotropic signals from tetravalent and pentavalent U ions in crystalline domains (U sub c sub r sub y sub s sub t sub a sub l sup 4 sup + and U sub c sub r sub y sub s sub t sub a sub l sup 5 sup +). The linewidths and peak positions of the 4834 cm sup - sup 1 band (U sub c sub r sub y sub s sub t sub a sub l sup 4 sup + , E || c) and the 6668 cm sup - sup 1 band (U sub c sub r sub y sub s sub t sub a sub l sup 5 sup + , E perp. c) are a non-linear function of the self-radiation dose. They reach nearly constant values at doses greater than approx 3.5 x 10 sup 1 sup 8 alpha-events g sup - sup 1. Quantitative analysis of U sub c sub r sub y sub s sub t sub a sub l sup 4 sup + and U sub c sub r sub y sub s sub t sub a sub l...

Kinetics of uranium (4) oxidation with nitrous acid in the presence of oxalate-ions in nitric and perchloric acid solutions

International Nuclear Information System (INIS)

Nikitenko, S.I.; Astafurova, L.N.

1991-01-01

Kinetics of uranium (4) oxidation with nitrous acid in the presence of oxalate-ions are studied spectrometrically. It is shown that even at small oxalate concentrations a notable effect of tetravalent uranium stabilization is observed relatively to the oxidation with nitrous acid. In case of a significant excess of oxalate-ions the oxidation rate will be considerably slower as a result of the formation of U(4) bisoxalate complex

Binuclear trivalent and tetravalent uranium halides and cyanides supported by cyclooctatetraene ligands

International Nuclear Information System (INIS)

Wang, Cong-Zhi; Wu, Qun-Yan; Lan, Jian-Hui; Shi, Wei-Qun; Gibson, John K.

2017-01-01

Although the first organoactinide chloride Cp_3UCl (Cp = η"5-C_5H_5) was synthesized more than 50 years ago, binuclear uranium halides remain very rare in organoactinide chemistry. Herein, a series of binuclear trivalent and tetravalent uranium halides and cyanides with cyclooctatetraene ligands, (COT)_2U_2X_n (COT = η"8-C_8H_8; X=F, Cl, CN; n=2, 4), have been systematically studied using scalar-relativistic density functional theory (DFT). The structures with bridging halide or cyanide ligands were predicted to be the most stable complexes of (COT)_2U_2X_n, and all the complexes show weak antiferromagnetic interactions between the uranium centers. However, for each species, there is no significant uranium-uranium bonding interaction. The bonding between the metal and the ligands shows some degree of covalent character, especially between the metal and terminal halide or cyanide ligands. The U-5f and 6d orbitals are predominantly involved in the metal-ligand bonding. All the (COT)_2U_2X_n species were predicted to be more stable compared to the mononuclear half-sandwich complexes at room temperature in the gas phase such that (COT)_2U_2X_4 might be accessible through the known (COT)_2U complex. The tetravalent derivatives (COT)_2U_2X_4 are more energetically favorable than the trivalent (COT)_2U_2X_2 analogs, which may be attributed to the greater number of strong metal-ligand bonds in the former complexes.

Preparation and use of crystalline bis-monoorganic phosphonate and phosphate salts of tetravalent metals

Science.gov (United States)

Maya, L.

1980-06-26

A method of preparing and using the crystalline organic derivatives of the tetravalent metal phosphates and phosphonates provides for the contacting of an aqueous solution of a metal nitrate, with a solution of an organophosphorus acid for a period of time at room temperature that is sufficient for the formation of a metal phosphate product, and thereafter recovering said product. According to the invention, the product of the disclosed process is used in effecting analytical separations, such as ion exchange and chromatography.

Binuclear trivalent and tetravalent uranium halides and cyanides supported by cyclooctatetraene ligands

Energy Technology Data Exchange (ETDEWEB)

Wang, Cong-Zhi; Wu, Qun-Yan; Lan, Jian-Hui; Shi, Wei-Qun [Chinese Academy of Sciences, Beijing (China). Laboratory of Nuclear Energy Chemistry and Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety; Chai, Zhi-Fang [Chinese Academy of Sciences, Beijing (China). Laboratory of Nuclear Energy Chemistry and Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety; Soochow Univ., Suzhou (China). School of Radiological and Interdisciplinary Sciences (RAD-X); Gibson, John K. [Lawrence Berkeley National Laboratory, CA (United States). Chemical Sciences Division

2017-03-01

Although the first organoactinide chloride Cp{sub 3}UCl (Cp = η{sup 5}-C{sub 5}H{sub 5}) was synthesized more than 50 years ago, binuclear uranium halides remain very rare in organoactinide chemistry. Herein, a series of binuclear trivalent and tetravalent uranium halides and cyanides with cyclooctatetraene ligands, (COT){sub 2}U{sub 2}X{sub n} (COT = η{sup 8}-C{sub 8}H{sub 8}; X=F, Cl, CN; n=2, 4), have been systematically studied using scalar-relativistic density functional theory (DFT). The structures with bridging halide or cyanide ligands were predicted to be the most stable complexes of (COT){sub 2}U{sub 2}X{sub n}, and all the complexes show weak antiferromagnetic interactions between the uranium centers. However, for each species, there is no significant uranium-uranium bonding interaction. The bonding between the metal and the ligands shows some degree of covalent character, especially between the metal and terminal halide or cyanide ligands. The U-5f and 6d orbitals are predominantly involved in the metal-ligand bonding. All the (COT){sub 2}U{sub 2}X{sub n} species were predicted to be more stable compared to the mononuclear half-sandwich complexes at room temperature in the gas phase such that (COT){sub 2}U{sub 2}X{sub 4} might be accessible through the known (COT){sub 2}U complex. The tetravalent derivatives (COT){sub 2}U{sub 2}X{sub 4} are more energetically favorable than the trivalent (COT){sub 2}U{sub 2}X{sub 2} analogs, which may be attributed to the greater number of strong metal-ligand bonds in the former complexes.

Relationships among oxidation-reduction and acid-base properties of the actinides in high oxidation states

International Nuclear Information System (INIS)

Morss, L.R.

1992-01-01

The first chemical identification of plutonium, its subsequent isolation on the macroscopic scale, and more recent chemical separation schemes were achieved by taking advantage of the differences among the oxidation states of uranium, neptunium, and plutonium. Many acid-base properties modify the relative stabilities of oxidation states of the actinides. In the solid state, strongly basic compounds such as Cs 2 O yield complex oxides with oxidation states of Np(VII), Pu(VI), and Am(VI) whereas more acidic compounds such as CsF yield complex fluorides with lower oxidation states. In aqueous solution, high basicity and strongly covalent complexes favor high oxidation states. In nonaqueous solvent systems, high acidity generally favors low oxidation states. This paper elucidates and attempts to interpret the effects of these acid-base properties in a systematic fashion

Plutonium-uranium mixed oxide characterization by coupling micro-X-ray diffraction and absorption investigations

Science.gov (United States)

Degueldre, C.; Martin, M.; Kuri, G.; Grolimund, D.; Borca, C.

2011-09-01

Plutonium-uranium mixed oxide (MOX) fuels are currently used in nuclear reactors. The potential differences of metal redox state and microstructural developments of the matrix before and after irradiation are commonly analysed by electron probe microanalysis. In this work the structure and next-neighbor atomic environments of Pu and U oxide features within unirradiated homogeneous MOX and irradiated (60 MW d kg -1) MOX samples was analysed by micro-X-ray fluorescence (μ-XRF), micro-X-ray diffraction (μ-XRD) and micro-X-ray absorption fine structure (μ-XAFS) spectroscopy. The grain properties, chemical bonding, valences and stoichiometry of Pu and U are determined from the experimental data gained for the unirradiated as well as for irradiated fuel material examined in the center of the fuel as well as in its peripheral zone (rim). The formation of sub-grains is observed as well as their development from the center to the rim (polygonization). In the irradiated sample Pu remains tetravalent (>95%) and no (oxidation in the rim zone. Any slight potential plutonium oxidation is buffered by the uranium dioxide matrix while locally fuel cladding interaction could also affect the redox of the fuel.

Plutonium disproportionation. Hydrolysis and local oxidation-state maxima

International Nuclear Information System (INIS)

Silver, G.L.

2014-01-01

Local maxima in the fractions of the trivalent and hexavalent oxidation states are inherent in the algebra of Pu disproportionation reactions. A new method predicts the pH and the oxidation-state fractions at maximum. Tabulated results illustrate the effects of the Pu oxidation number and Pu(IV) hydrolysis on the maxima. This method suggests a new laboratory approach for discovering Pu oxidation-state maxima. (author)

Magnetic properties of rare earth oxides with perovskite structure

International Nuclear Information System (INIS)

Hinatsu, Yukio

2008-01-01

A perovskite composite oxide is represented by the general formula of ABO 3 . Cations at the B site characterize magnetic properties of the oxide. Many studies have been accumulated for transition metal elements at the B sites. In this report the studies of rare earth elements at the B sites are reviewed. In rare elements, tetravalent ions such as Ce 4+ , Pr 4+ and Tb 4+ can occupy the B sites with Ba and Sr ions at the A sites. Both the SrTbO 3 and BaTbO 3 have an orthorhombic structure and show the antiferromagnetic transition at about 33 K, which is originated from terbium ions coupled antiferromagnetically with the six neighboring terbium ions. A tetravalent praseodymium perovskite SrPrO 3 shows no existence of the magnetic ordering down to 2.0 K. This is in contrast to the result of isomorphous BaPrO 3 , which shows an antiferromagnetic transition at 11.5 K. A double perovskite structure is represented by the formula A 2 LnMO 6 (A=Ba, Sr, Ca; M=Ru, Ir). In a double perovskite compound Ba 2 PrRuO 6 , the Pr 3+ and Ru 5+ ions are arranged with regularity over the six-coordinate B sites. This compound transforms to an antiferromagnetic state below 117 K. Antiferromagnetic transition temperatures T N for isomorphous Sr and Ca show a clear tendency, T N (A=Ba)>T N (Sr)>T N (Ca), in the compounds with the same rare earth elements (Ln). The 6H-perovskite structure Ba 3 LnRu 2 O 9 consists of linkages between LnO 6 octahedra and Ru 2 O 9 dimers made from face-shared RuO 6 octahedra. The 6H-perovskite structure Ba 3 MRu 2 O 9 (M=Sc, Y, La, Nd-Gd, Dy-Lu) have the valence state of Ba 3 M 3+ Ru 2 4.5+ O 9 . The magnetic susceptibilities show a broad maximum at 135-370 K. This magnetic behavior is ascribed to the antiferromagnetic coupling between two Ru ions in a Ru 2 O 9 dimer and to the magnetic interaction between the Ru 2 O 9 dimers. (author)

Contribution to the physicochemical investigation of monovalent thallium and tetravalent uranium fluorides

International Nuclear Information System (INIS)

Hsini, M.S.

1983-07-01

Ionic transport properties are studied in monovalent elements and tetravalent uranium fluorides and oxyfluorides. Crystal structure of the oxyfluoride: TlUsub(2.75)OF 10 was determined by X-ray diffraction on a monocrystal. The particular role played by oxygen is evidenced in the stabilization of the crystal structure based on an original arrangement of Archimedes antiprisms: UOF 7 corresponding to a long distance order oxygen-fluorine in the anionic network. Electric conductivity measurements in AC by the complex impedance method or in DC by the Van der Pauw method allowed performance estimation of these materials which are solid electrolytes. Correlations between electrical properties and structure give information in basic diffusion mechanism in these materials [fr

Crystalline insoluble acid salts of tetravalent metals

International Nuclear Information System (INIS)

Alberti, G.; Bernasconi, M.G.; Casciola, M.; Costantino, U.

1980-01-01

Several titration curves of crystalline acid salts of tetravalent metals show an evident decrease in the pH of the supernatant solution with an increasing addition of metal hydroxide. This phenomenon, very unusual for common organic ion-exchangers, seems to be quite general for inorganic ion-exchangers with layered structure of α-type. In order to throw light on this phenomenon, a detailed investigation was carried out on the titration curves of α-Zr(HPO 4 ) 2 .H 2 O with various metal hydroxides, particularly KOH. To obtain the presence of a distinct minimum in the titration curve, three conditions seem to be necessary: (1) high activation energy for H + /Msup(Z+) exchange (which, in turn, depends on the relative size of Msup(Z+) and size of the windows connecting the cavities), (2) formation of solid solution having high M-content and (3) formation of a phase, with a large inter-layer distance, in the external parts of the crystals. This last point is particularly important since the enlargement of the external part of the crystals lowers the activation energy for the exchange of large cations. Thus, once started, the exchange can take place at lower pH' values. (author)

Non-equilibrium oxidation states of zirconium during early stages of metal oxidation

International Nuclear Information System (INIS)

Ma, Wen; Yildiz, Bilge; Herbert, F. William; Senanayake, Sanjaya D.

2015-01-01

The chemical state of Zr during the initial, self-limiting stage of oxidation on single crystal zirconium (0001), with oxide thickness on the order of 1 nm, was probed by synchrotron x-ray photoelectron spectroscopy. Quantitative analysis of the Zr 3d spectrum by the spectrum reconstruction method demonstrated the formation of Zr 1+ , Zr 2+ , and Zr 3+ as non-equilibrium oxidation states, in addition to Zr 4+ in the stoichiometric ZrO 2 . This finding resolves the long-debated question of whether it is possible to form any valence states between Zr 0 and Zr 4+ at the metal-oxide interface. The presence of local strong electric fields and the minimization of interfacial energy are assessed and demonstrated as mechanisms that can drive the formation of these non-equilibrium valence states of Zr

Dengue envelope-based 'four-in-one' virus-like particles produced using Pichia pastoris induce enhancement-lacking, domain III-directed tetravalent neutralising antibodies in mice.

Science.gov (United States)

Rajpoot, Ravi Kant; Shukla, Rahul; Arora, Upasana; Swaminathan, Sathyamangalam; Khanna, Navin

2018-06-05

Dengue is a significant public health problem worldwide, caused by four antigenically distinct mosquito-borne dengue virus (DENV) serotypes. Antibodies to any given DENV serotype which can afford protection against that serotype tend to enhance infection by other DENV serotypes, by a phenomenon termed antibody-dependent enhancement (ADE). Antibodies to the viral pre-membrane (prM) protein have been implicated in ADE. We show that co-expression of the envelope protein of all four DENV serotypes, in the yeast Pichia pastoris, leads to their co-assembly, in the absence of prM, into tetravalent mosaic VLPs (T-mVLPs), which retain the serotype-specific antigenic integrity and immunogenicity of all four types of their monomeric precursors. Following a three-dose immunisation schedule, the T-mVLPs elicited EDIII-directed antibodies in mice which could neutralise all four DENV serotypes. Importantly, anti-T-mVLP antibodies did not augment sub-lethal DENV-2 infection of dengue-sensitive AG129 mice, based on multiple parameters. The 'four-in-one' tetravalent T-mVLPs possess multiple desirable features which may potentially contribute to safety (non-viral, prM-lacking and ADE potential-lacking), immunogenicity (induction of virus-neutralising antibodies), and low cost (single tetravalent immunogen produced using P. pastoris, an expression system known for its high productivity using simple inexpensive media). These results strongly warrant further exploration of this vaccine candidate.

Retention of redox sensitive waste elements in compacted bentonite

International Nuclear Information System (INIS)

Torstenfelt, B.; Allard, B.

1984-01-01

The diffusion of technetium, iodine, uranium and neptunium in compacted bentonite has been studied. The possible reduction of the transport rate of these elements (i.e. redoxsensitive elements) by mixing the clay with metallic iron (for technetium, uranium and neptunium) or by adding a chemisorbent (for iodine) to the clay is reported. Technetium has an apparent diffusivity about 5 times higher in the heptavalent state (TcO 4 - ) than in the tetravalent state (TcO(OH) 2 or TcO 2 ), uranium and neptunium in their higher oxidation state (VI and V) have apparent diffusivities about 6 and 50 times higher, respectively, than in the tetravalent state. Iodine, as I - (or IO 3 - ), has a transport rate more than one order of magnitude lower than TcO 4 - . 10 references, 5 figures, 3 tables

Characteristics of MOX dissolution with silver mediated electrolytic oxidation method

Energy Technology Data Exchange (ETDEWEB)

Umeda, Miki; Nakazaki, Masato; Kida, Takashi; Sato, Kenji; Kato, Tadahito; Kihara, Takehiro; Sugikawa, Susumu [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

2003-03-01

MOX dissolution with silver mediated electrolytic oxidation method is to be applied to the preparation of plutonium nitrate solution to be used for criticality safety experiments at Nuclear Fuel Cycle Safety Engineering Research Facility (NUCEF). Silver mediated electrolytic oxidation method uses the strong oxidisation ability of Ag(II) ion. This method is though to be effective for the dissolution of MOX, which is difficult to be dissolved with nitric acid. In this paper, the results of experiments on dissolution with 100 g of MOX are described. It was confirmed from the results that the MOX powder to be used at NUCEF was completely dissolved by silver mediated electrolytic oxidation method and that Pu(VI) ion in the obtained solution was reduced to tetravalent by means of NO{sub 2} purging. (author)

Symmetry transition via tetravalent impurity and investigations on magnetic properties of Li0.5Fe2.5O4

Science.gov (United States)

Kounsalye, Jitendra S.; Kharat, Prashant B.; Chavan, Apparao R.; Humbe, Ashok V.; Borade, R. M.; Jadhav, K. M.

2018-04-01

The present study, deals with the phase symmetry transformation of lithium ferrite after introducing tetravalent (Ti4+) impurity. The sol-gel auto combustion technique was adopted for the synthesis of nanoparticle samples with generic chemical formula Li0.5Fe2.5O4 and Li0.55Ti0.10Fe2.35O4. The synthesized nanoparticles were characterized by X-ray diffraction (XRD) technique for structural analysis. The XRD patterns show the single phase cubic structure without any impurity phase but the P4332 to Fd-3m transformation was observed after introducing Ti4+ impurity. The Nano size of the synthesized particles was confirmed by crystallite size ( 20nm) calculated using Debye-Scherrer's formula. The Fourier transform infrared spectroscopy (FTIR) studies shows shifting of band frequencies which reflect the structural changes after tetravalent substitutional impurities. The magnetic properties were studied through pulse field hysteresis loop (M-H loop) technique at room temperature, the M-H loops showdecrease in magnetic properties afternonmagnetic Ti4+ ion substitution. This is attributed to transition of inverse spinel structure of lithium ferrite to random spinel structure.

Chemistry of tetravalent plutonium and zirconium. Hydrolysis, solubility, colloid formation and redox reactions

International Nuclear Information System (INIS)

Cho, Hye-Ryun

2006-01-01

in acidic condition, the concentration of each oxidation state of Pu must be determined prior to each experiment. The solubility data are determined directly after preparation and then the redox reactions between four different plutonium oxidation states are observed at different pH and Pu concentrations as a function of time. The results indicate that the redox behavior of Pu cannot be described by disproportionation of Pu alone. Under the experimental conditions, the redox reactions of Pu seem to be divided into two groups, Pu(IV) aq <-> Pu(III) aq and Pu(IV) coll <-> Pu(V) aq <-> Pu(VI) aq . In the Pu solution containing initially only Pu(IV), the reduction of Pu(IV) to Pu(III) aq dominates rather than the oxidation to Pu(V) aq and Pu(VI) aq . The observed two groups of reactions show the dependency of pH due to the related hydrolysis and colloid formation of Pu(IV). With increasing pH, the [Pu 4+ ] decreases either through its hydrolysis and colloid formation (increase of Pu(IV) coll ) or through its reduction (increase of Pu(III) aq ). The polymer species or colloids may dissolve to Pu(V)aq through the second reaction group (increase Pu(V) aq + Pu(VI) aq ). Consequently, it is observed that with increase of pH, [Pu(IV) aq ] decreases, [Pu(III) aq ] increases, and [Pu(IV) coll ]+[Pu(V) aq ]+[Pu(VI) aq ] increases. This study is also performed under inert gas conditions in order to investigate the influence of dissolved oxygen on the oxidation of Pu(IV) (Pu(IV) coll <-> Pu(V) aq ). From the relative abundance of the Pu oxidation states, namely the couples PuO 2 2+ /PuO 2 + and PuO 2 + /Pu(IV) coll , the redox potential Eh(V) can be obtained. The respective values agree well with the measured Eh values. In order to use the redox couple Pu 4+ /Pu 3+ , one has to take into account the strong hydrolysis of Pu(IV) which sets in below pH 1. When the abundance of Pu 4+ is calculated from the amount of [Pu(IV) aq. ]=[Pu 4+ ]+ sum y=1 4 [Pu(OH) y 4-y ] by use of hydrolysis

Process for recovering uranium using an alkyl pyrophosphoric acid and alkaline stripping solution

International Nuclear Information System (INIS)

Worthington, R.E.; Magdics, A.

1987-01-01

A process is described for stripping uranium for a pregnant organic extractant comprising an alkyl pyrophosphoric acid dissolved in a substantially water-immiscible organic diluent. The organic extractant contains tetravalent uranium and an alcohol or phenol modifier in a quantity sufficient to retain substantially all the unhydrolyzed alkyl pyrophosphoric acid in solution in the diluent during stripping. The process comprises adding an oxidizing agent to the organic extractant and thereby oxidizing the tetravalent uranium to the +6 state in the organic extractant, and contacting the organic extractant containing the uranium in the +6 state with a stripping solution comprising an aqueous solution of an alkali metal or ammonium carbonate or hydroxide thereby stripping uranium from the organic extractant into the stripping solution. The resulting barren organic extractant containing substantially all of the unhydrolyzed alkyl pyrophosphoric acid dissolved in the diluent is separated from the stripping solution containing the stripped uranium, the barren extractant being suitable for recycle

Carbon monoxide oxidation over three different states of copper: Development of a model metal oxide catalyst

Energy Technology Data Exchange (ETDEWEB)

Jernigan, Glenn Geoffrey [California Univ., Berkeley, CA (United States). Dept. of Chemistry

1994-10-01

Carbon monoxide oxidation was performed over the three different oxidation states of copper -- metallic (Cu), copper (I) oxide (Cu₂O), and copper (II) oxide (CuO) as a test case for developing a model metal oxide catalyst amenable to study by the methods of modern surface science and catalysis. Copper was deposited and oxidized on oxidized supports of aluminum, silicon, molybdenum, tantalum, stainless steel, and iron as well as on graphite. The catalytic activity was found to decrease with increasing oxidation state (Cu > Cu₂O > CuO) and the activation energy increased with increasing oxidation state (Cu, 9 kcal/mol < Cu₂O, 14 kcal/mol < CuO, 17 kcal/mol). Reaction mechanisms were determined for the different oxidation states. Lastly, NO reduction by CO was studied. A Cu and CuO catalyst were exposed to an equal mixture of CO and NO at 300--350 C to observe the production of N₂ and CO₂. At the end of each reaction, the catalyst was found to be Cu₂O. There is a need to study the kinetics of this reaction over the different oxidation states of copper.

Efficacy of a tetravalent dengue vaccine in children in Latin America.

Science.gov (United States)

Villar, Luis; Dayan, Gustavo Horacio; Arredondo-García, José Luis; Rivera, Doris Maribel; Cunha, Rivaldo; Deseda, Carmen; Reynales, Humberto; Costa, Maria Selma; Morales-Ramírez, Javier Osvaldo; Carrasquilla, Gabriel; Rey, Luis Carlos; Dietze, Reynaldo; Luz, Kleber; Rivas, Enrique; Miranda Montoya, Maria Consuelo; Cortés Supelano, Margarita; Zambrano, Betzana; Langevin, Edith; Boaz, Mark; Tornieporth, Nadia; Saville, Melanie; Noriega, Fernando

2015-01-08

In light of the increasing rate of dengue infections throughout the world despite vector-control measures, several dengue vaccine candidates are in development. In a phase 3 efficacy trial of a tetravalent dengue vaccine in five Latin American countries where dengue is endemic, we randomly assigned healthy children between the ages of 9 and 16 years in a 2:1 ratio to receive three injections of recombinant, live, attenuated, tetravalent dengue vaccine (CYD-TDV) or placebo at months 0, 6, and 12 under blinded conditions. The children were then followed for 25 months. The primary outcome was vaccine efficacy against symptomatic, virologically confirmed dengue (VCD), regardless of disease severity or serotype, occurring more than 28 days after the third injection. A total of 20,869 healthy children received either vaccine or placebo. At baseline, 79.4% of an immunogenicity subgroup of 1944 children had seropositive status for one or more dengue serotypes. In the per-protocol population, there were 176 VCD cases (with 11,793 person-years at risk) in the vaccine group and 221 VCD cases (with 5809 person-years at risk) in the control group, for a vaccine efficacy of 60.8% (95% confidence interval [CI], 52.0 to 68.0). In the intention-to-treat population (those who received at least one injection), vaccine efficacy was 64.7% (95% CI, 58.7 to 69.8). Serotype-specific vaccine efficacy was 50.3% for serotype 1, 42.3% for serotype 2, 74.0% for serotype 3, and 77.7% for serotype 4. Among the severe VCD cases, 1 of 12 was in the vaccine group, for an intention-to-treat vaccine efficacy of 95.5%. Vaccine efficacy against hospitalization for dengue was 80.3%. The safety profile for the CYD-TDV vaccine was similar to that for placebo, with no marked difference in rates of adverse events. The CYD-TDV dengue vaccine was efficacious against VCD and severe VCD and led to fewer hospitalizations for VCD in five Latin American countries where dengue is endemic. (Funded by Sanofi Pasteur

Stripping of Uranium (IV) from D2EHPA + TBP system with ammonium oxalate and its recovery as uranium peroxide

International Nuclear Information System (INIS)

Singh, D.K.; Singh, H.

2014-01-01

Uranium is an important fissile material for the generation of electricity by nuclear reactors. To obtain uranium as a final product meeting the stringent nuclear specifications, many process steps are involved starting from ore processing to the precipitation of yellow cake. Solvent extraction is one of the process industrially adopted worldwide to achieve such purity of uranium from leach liquor and usually uses amine or organophosphorus types of extractant depending upon the composition of feed material. In solvent extraction technique, stripping is a prominent hydrometallurgical operation which brings the metal values of interest in aqueous solution for further treatment. In the case of uranium, stripping is dependent on its oxidation state. For hexavalent state generally carbonate solutions are used, where as in the case of tetravalent form salt solution such as ammonium oxalate is effective. Use of ammonium oxalate as stripping agent for tetravalent uranium from pyrophosphoric acid has been reported in patent however the details are not disclosed. In the present investigation an effort has been made to investigate the stripping behaviour of uranium from a synthetically loaded synergistic solvent mixture of uranium in tetravalent state

Determination of the oxidation states of metals and metalloids: An analytical review

Science.gov (United States)

Vodyanitskii, Yu. N.

2013-12-01

The hazard of many heavy metals/metalloids in the soil depends on their oxidation state. The problem of determining the oxidation state has been solved due to the use of synchrotron radiation methods with the analysis of the X-ray absorption near-edge structure (XANES). The determination of the oxidation state is of special importance for some hazardous heavy elements (arsenic, antimony, selenium, chromium, uranium, and vanadium). The mobility and hazard of each of these elements depend on its oxidation state. The mobilities are higher at lower oxidation states of As, Cr, V, and Se and at higher oxidation states of Sb and U. The determination of the oxidation state of arsenic has allowed revealing its fixation features in the rhizosphere of hydrophytes. The known oxidation states of chromium and uranium are used for the retention of these elements on geochemical barriers. Different oxidation states have been established for vanadium displacing iron in goethite. The determination of the oxidation state of manganese in the rhizosphere and the photosynthetic apparatus of plants is of special importance for agricultural chemists.

Tetravalent anti-CD20/CD3 bispecific antibody for the treatment of B cell lymphoma

Energy Technology Data Exchange (ETDEWEB)

Lu, Chia-Yen; Chen, Gregory J.; Tai, Pei-Han; Yang, Yu-Chen [Institute of Biologics, Development Center for Biotechnology, New Taipei City, Taiwan (China); Hsu, Yu-Shen, E-mail: yshsu@advagene.com.tw [Laboratory of Biopharmaceutical Research, Advagene Biopharma, Taipei, Taiwan (China); Chang, Mingi, E-mail: mingi.chang@advagene.com.tw [Laboratory of Biopharmaceutical Research, Advagene Biopharma, Taipei, Taiwan (China); Hsu, Chuan-Lung, E-mail: fabio@dcb.org.tw [Institute of Biologics, Development Center for Biotechnology, New Taipei City, Taiwan (China)

2016-05-13

Bispecific antibodies (bsAbs) are second generation antibodies for therapeutic application in immunotherapy. One of the major strategies of the bsAb platform is the recruitment of immune effector T cells by incorporating an anti-CD3 domain. A bispecific T-cell engager (BiTE), with one end having an affinity for CD3 and the other end with affinity for CD19, has been approved in the US and Europe for the treatment of acute lymphoblastic leukemia. However, due to their small size and lack of Fc region, these single-chain variable fragment (scFv) bsAbs have short half-lives in vivo. Additionally, poor solubility, structural instability, and low production yields have also become major challenges in the bulk production process. To overcome these challenges, we have engineered a tetravalent bsAb with bivalent binding specificity for the CD20 and CD3 antigen in an immunoglobulin G (IgG) format. The fusion of the anti-CD3 scFvs to the CD20 antibody via a linker-hinge domain (LHD) results in improved antibody stabilization and properties. Here we demonstrate this antibody's highly efficient cancer cell elimination in a dose-dependent manner in a CD20-expressing B lymphoblastoid cell line in vitro. Our data suggest the potential clinical application of this bsAb for the treatment of CD20-expressing B cell malignancies. - Highlights: • A bispecific antibody (bsAb) can increase immunotherapeutic efficacy. • A tetravalent bsAb with binding specificity for the CD20 and CD3 antigens is proposed. • A linker-hinge domain (LHD) within the bsAb results in improved antibody properties.

Study of lifetimes of fluorescence levels of tetravalent uranium in the incommensurate phase of thorium tetrabromide and tetrachloride

International Nuclear Information System (INIS)

Milicic, A.

1989-01-01

The lifetimes of radiative levels of tetravalent uranium in the incommensurate phase of thorium tetrahalides have been measured as a function of different parameters: site symmetry, temperature and concentration. The incommensurate phase of thorium tetrabromide and tetrachloride is characterized by a continuous distribution of site symmetries induced by a continuous and weak displacement of the halides around the thorium (uranium) ions. At low temperature, 4.2 K, the lifetime variation as a function of excited classes of symmetry is governed by the radiative process probability as well as the energy transfer between uranium ions in different sites. At higher temperature, a model based on a Boltzmann equilibrium between closed energy levels is able to reproduce the experimental lifetime variation as a function of the temperature, for a given class of symmetry. For the variation of lifetime as a function of uranium ion concentrations, at high dilution and in the case of U 4+ : ThBr 4 , there is a competition between the energy transfer and thermal population of excited states [fr

Chemical interaction of tetravalent actinides simulators and the engineering barrier

International Nuclear Information System (INIS)

Chain, Pablo; Alba, Maria D.; Castro, Miguel A.; Pavon, Esperanza; Mar Orta, M.

2010-01-01

simulator with the engineering barrier at conditions close to those of the repository. The methodology used consists in the hydrothermal treatment of different natural bentonites, including FEBEX and MX-80 bentonites, with aqueous solutions of the mentioned tetravalent lanthanide elements at subcritical conditions. The reaction products have been analysed with the help of X-ray diffraction, MAS-NMR spectroscopy and scanning electron microscopy. The results show that after the hydrothermal reaction two new phases containing zirconium have been formed, ZrSiO 4 and ZrO 2 , and their ratio depend on the nature of the bentonite. It demonstrates that the already explored chemical interaction between trivalent radionuclides and bentonite barrier is also possible with the tetravalent radionuclides. (authors)

Genetic and phenotypic characterization of manufacturing seeds for a tetravalent dengue vaccine (DENVax.

Directory of Open Access Journals (Sweden)

Claire Y-H Huang

Full Text Available We have developed a manufacturing strategy that can improve the safety and genetic stability of recombinant live-attenuated chimeric dengue vaccine (DENVax viruses. These viruses, containing the pre-membrane (prM and envelope (E genes of dengue serotypes 1-4 in the replicative background of the attenuated dengue-2 PDK-53 vaccine virus candidate, were manufactured under cGMP.After deriving vaccine viruses from RNA-transfected Vero cells, six plaque-purified viruses for each serotype were produced. The plaque-purified strains were then analyzed to select one stock for generation of the master seed. Full genetic and phenotypic characterizations of the master virus seeds were conducted to ensure these viruses retained the previously identified attenuating determinants and phenotypes of the vaccine viruses. We also assessed vector competence of the vaccine viruses in sympatric (Thai Aedes aegypti mosquito vectors.All four serotypes of master vaccine seeds retained the previously defined safety features, including all three major genetic loci of attenuation, small plaques, temperature sensitivity in mammalian cells, reduced replication in mosquito cell cultures, and reduced neurovirulence in new-born mice. In addition, the candidate vaccine viruses demonstrated greatly reduced infection and dissemination in Aedes aegypti mosquitoes, and are not likely to be transmissible by these mosquitoes. This manufacturing strategy has successfully been used to produce the candidate tetravalent vaccine, which is currently being tested in human clinical trials in the United States, Central and South America, and Asia.

In a randomized trial, the live attenuated tetravalent dengue vaccine TV003 is well-tolerated and highly immunogenic in subjects with flavivirus exposure prior to vaccination.

Directory of Open Access Journals (Sweden)

Stephen S Whitehead

2017-05-01

Full Text Available Infection caused by the four serotypes of dengue virus (DENV-1-4 is a leading cause of mosquito-borne disease. Clinically-severe dengue disease is more common when secondary dengue infection occurs following prior infection with a heterologous dengue serotype. Other flaviviruses such as yellow fever virus, Japanese encephalitis virus, and Zika virus, can also elicit antibodies which are cross-reactive to DENV. As candidate dengue vaccines become available in endemic settings and for individuals who have received other flavivirus vaccines, it is important to examine vaccine safety and immunogenicity in these flavivirus-experienced populations. We performed a randomized, controlled trial of the National Institutes of Health live attenuated tetravalent dengue vaccine candidate (TV003 in fifty-eight individuals with prior exposure to flavivirus infection or vaccine. As in prior studies of this vaccine in flavivirus-naive volunteers, flavivirus-experienced subjects received two doses of vaccine six months apart and were followed closely for clinical events, laboratory changes, viremia, and neutralizing antibody titers. TV003 was well tolerated with few adverse events other than rash, which was predominately mild. Following one dose, 87% of vaccinees had an antibody response to all four serotypes (tetravalent response, suggesting a robust immune response. In addition, 76% of vaccinees were viremic; mean peak titers ranged from 0.68–1.1 log10 PFU/mL and did not differ by serotype. The second dose of TV003 was not associated with viremia, rash, or a sustained boost in antibody titers indicating that a single dose of the vaccine is likely sufficient to prevent viral replication and thus protect against disease. In comparison to the viremia and neutralizing antibody response elicited by TV003 in flavivirus-naïve subjects from prior studies, we found that subjects who were flavivirus-exposed prior to vaccination exhibited slightly higher DENV-3 viremia

Influence of vanadium oxidation states on the performance of V-Mg-Al mixed-oxide catalysts for the oxidative dehydrogenation of propane

International Nuclear Information System (INIS)

Schacht, L.; Navarrete, J.; Schacht, P.; Ramirez, M. A.

2010-01-01

V-Mg-Al mixed-oxide catalysts for oxidative dehydrogenation of propane were prepared by thermal decomposition of Mg-Al-layered double hydroxides with vanadium interlayer doping. The obtained catalysts were tested for the oxidative dehydrogenation of propane, obtaining good results in catalytic activity (conversion 16.55 % and selectivity 99.97 %) Results indicated that catalytic performance of these materials depends on how vanadium is integrated in the layered structure, which is determined by the Mg/Al ratio. Vanadium interlayer doping modifies the oxidation state of vanadium and consequently catalytic properties. Surface properties were studied by X-ray photoelectron spectroscopic and diffuse reflectance, UV-visible spectroscopy, and temperature programmed reduction. The analyses provided information about the oxidation state, before and after the reaction. From these results, it is suggested that selectivity to propylene and catalytic activity depend mainly of vanadium oxidation state. (Author)

Influence of vanadium oxidation states on the performance of V-Mg-Al mixed-oxide catalysts for the oxidative dehydrogenation of propane

Energy Technology Data Exchange (ETDEWEB)

Schacht, L. [IPN, Escuela Superior de Fisica y Matematicas, Departamento de Ciencia de Materiales, Av. IPN s/n, Edificio 9, Col. Lindavista, 07738 Mexico D. F. (Mexico); Navarrete, J.; Schacht, P.; Ramirez, M. A., E-mail: pschacha@imp.m [Instituto Mexicano del Petroleo, Programa de Ingenieria Molecular, Eje Central Lazaro Cardenas No. 152, 07730 Mexico D. F. (Mexico)

2010-07-01

V-Mg-Al mixed-oxide catalysts for oxidative dehydrogenation of propane were prepared by thermal decomposition of Mg-Al-layered double hydroxides with vanadium interlayer doping. The obtained catalysts were tested for the oxidative dehydrogenation of propane, obtaining good results in catalytic activity (conversion 16.55 % and selectivity 99.97 %) Results indicated that catalytic performance of these materials depends on how vanadium is integrated in the layered structure, which is determined by the Mg/Al ratio. Vanadium interlayer doping modifies the oxidation state of vanadium and consequently catalytic properties. Surface properties were studied by X-ray photoelectron spectroscopic and diffuse reflectance, UV-visible spectroscopy, and temperature programmed reduction. The analyses provided information about the oxidation state, before and after the reaction. From these results, it is suggested that selectivity to propylene and catalytic activity depend mainly of vanadium oxidation state. (Author)

Higher Americium Oxidation State Research Roadmap

Energy Technology Data Exchange (ETDEWEB)

Mincher, Bruce J. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Law, Jack D. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Goff, George S. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Moyer, Bruce A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Burns, Jon D. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Lumetta, Gregg J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Sinkov, Sergey I. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Shehee, Thomas C. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Hobbs, David T. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

2015-12-18

The partitioning of hexavalent Am from dissolved nuclear fuel requires the ability to efficiently oxidize Am(III) to Am(VI) and to maintain that oxidation state for a length of time sufficient to perform the separation. Several oxidants have been, or are being developed. Chemical oxidants include Ag-catalyzed ozone, Ag-catalyzed peroxydisulfate, Cu(III) periodate, and sodium bismuthate. Hexavalent americium has also now successfully been prepared by electrolysis, using functionalized electrodes. So-called auto-reduction rates of Am(VI) are sufficiently slow to allow for separations. However, for separations based on solvent extraction or ion exchange using organic resins, the high valence state must be maintained under the reducing conditions of the organic phase contact, and a holding oxidant is probably necessary. Until now, only Cu(III) periodate and sodium bismuthate oxidation have been successfully combined with solvent extraction separations. Bismuthate oxidation provided the higher DAm, since it acts as its own holding oxidant, and a successful hot test using centrifugal contactors was performed. For the other oxidants, Ag-catalyzed peroxydisulfate will not oxidize americium in nitric acid concentrations above 0.3 M, and it is not being further investigated. Peroxydisulfate in the absence of Ag catalysis is being used to prepare Am(V) in ion exchange work, discussed below. Preliminary work with Ag-catalyzed ozone has been unsuccessful for extractions of Am(VI) from 6.5 M HNO3, and only one attempt at extraction, also from 6.5 M HNO3, using the electrolytic oxidation has been attempted. However, this high acid concentration was based on the highest Am extraction efficiency using the bismuthate oxidant; which is only sparingly soluble, and thus the oxidation yield is based on bismuthate solubility. Lower acid concentrations may be sufficient with alternative oxidants and work with Ag-ozone, Cu(III) and electrolysis is on-going. Two non

The Immunodominance Change and Protection of CD4+ T-Cell Responses Elicited by an Envelope Protein Domain III-Based Tetravalent Dengue Vaccine in Mice.

Directory of Open Access Journals (Sweden)

Hsin-Wei Chen

Full Text Available Dengue is the leading cause of mosquito-borne viral infections and no vaccine is available now. Envelope protein domain III (ED3 is the major target for the binding of dengue virus neutralizing antibodies; however, the ED3-specifc T-cell response is less well understood. To investigate the T-cell responses to four serotypes of dengue virus (DENV-1 to 4, we immunized mice using either a tetravalent ED3-based DNA or protein vaccine, or combined both as a DNA prime-protein boost strategy (prime-boost. A significant serotype-dependent IFN-γ or IL-4 response was observed in mice immunized with either the DNA or protein vaccine. The IFN-γ response was dominant to DENV-1 to 3, whereas the IL-4 response was dominant to DENV-4. Although the similar IgG titers for the four serotypes were observed in mice immunized with the tetravalent vaccines, the neutralizing antibody titers varied and followed the order of 2 = 3>1>4. Interestingly, the lower IFN-γ response to DENV-4 is attributable to the immunodominance change between two CD4+ T-cell epitopes; one T-cell epitope located at E349-363 of DENV-1 to 3 was more immunogenic than the DENV-4 epitope E313-327. Despite DENV-4 specific IFN-γ responses were suppressed by immunodominance change, either DENV-4-specific IFN-γ or neutralizing antibody responses were still recalled after DENV-4 challenge and contributed to virus clearance. Immunization with the prime-boost elicited both IFN-γ and neutralizing antibody responses and provided better protection than either DNA or protein immunization. Our findings shed light on how ED3-based tetravalent dengue vaccines sharpen host CD4 T-cell responses and contribute to protection against dengue virus.

New Data on Joint Extraction of Nitric Acid, Uranium(VI) and Tetravalent Elements by Diluted TBP and New Approach to Modeling of their Distribution

International Nuclear Information System (INIS)

Zilberman, B.Ya.; Fedorov, Yu.S.; Puzikov, E.A.; Blazheva, I.V.

2008-01-01

HNO 3 and U(IV) extraction by diluted TBP (tributyl phosphate) appeared significantly higher than believed earlier, requiring correction of mathematical model for extraction of all the species. The proposed model of HNO 3 extraction includes its dissolving in the extracted water, as well as its abduction to UO 2 (NO 3 ) 2 (TBP) 2 . Extraction of U(VI) and tetravalent elements is considered as reaction of their hydrated or partially hydrolyzed forms, the latter could be extracted themselves or as neutral forms with water liberation. The equation of element chemical reaction for modeling is determined by the slope of the linear part of the S-shaped curve representing D/S 2 function as a plot of HNO 3 concentration, where D is a distribution coefficient of the micro-component and S is a TBP concentration free of HNO 3 . The description of tetravalent element extraction in U(VI) presence needs the assumption of cation-cation interaction of element hydrolyzed forms with U(VI) in aqueous phase. Zr distribution is affected by micellar effects. (authors)

The in vivo characteristics of genetically engineered divalent and tetravalent single-chain antibody constructs

International Nuclear Information System (INIS)

Wittel, Uwe A.; Jain, Maneesh; Goel, Apollina; Chauhan, Subhash C.; Colcher, David; Batra, Surinder K.

2005-01-01

Engineered multivalent single-chain Fv (scFv) constructs have been demonstrated to exhibit rapid blood clearance and better tumor penetration. To understand the short plasma half-life of multivalent single-chain antibody fragments, the pharmacokinetic properties of covalent dimeric scFv [sc(Fv) 2 ], noncovalent tetrameric scFv {[sc(Fv) 2 ] 2 } and IgG of MAb CC49 were examined. The scFvs displayed an ability to form higher molecular aggregates in vivo. A specific proteolytic cleavage of the linker sequence of the covalent dimeric or a deterioration of the noncovalent association of the dimeric scFv into tetravalent scFv constructs was not observed. In conclusion, sc(Fv) 2 and [sc(Fv) 2 ] 2 are stable in vivo and have significant potential for diagnostic and therapeutic applications

Phase I Randomized Study of a Tetravalent Dengue Purified Inactivated Vaccine in Healthy Adults from Puerto Rico.

Science.gov (United States)

Diaz, Clemente; Lin, Leyi; Martinez, Luis J; Eckels, Kenneth H; Campos, Maribel; Jarman, Richard G; De La Barrera, Rafael; Lepine, Edith; Toussaint, Jean-François; Febo, Irma; Innis, Bruce L; Thomas, Stephen J; Schmidt, Alexander C

2018-05-01

The safety and immunogenicity of four adjuvanted formulations of an investigational tetravalent dengue purified inactivated vaccine (DPIV) were evaluated in a predominantly dengue-primed population in Puerto Rico. In this placebo-controlled, randomized, observer-blind, phase I trial, 100 healthy adults were randomized 1:1:1:1:1 to receive DPIV at Day (D)0 and D28 (1 μg per dengue virus [DENV] type 1-4 adjuvanted with either alum, AS01 E or AS03 B , or 4 μg per DENV type adjuvanted with alum) or saline placebo. Functional antibody responses were assessed using a microneutralization assay at D56, Month (M)7, and M13. All DPIV formulations were well tolerated and no safety signals were identified through M13. The M13 according-to-protocol (ATP) immunogenicity cohort included 83 participants. The ATP analysis of immunogenicity was performed only on the 78 subjects seropositive for ≥ 1 DENV type at baseline: 69 tetravalent, three trivalent, two bivalent, and four monovalent. In all DPIV groups, geometric mean antibody titers (GMTs) increased from D0 to D56 and waned modestly through M13, while remaining well above prevaccination levels. The 4 μg + alum and the AS01 E - and AS03 B -adjuvanted formulations were highly immunogenic, with M13-neutralizing antibody GMTs against all four DENV types above 1,000. M13/D0 GMT ratios were highest in the 1 μg + AS03 B group (ranging 3.2-3.7 depending on the DENV type). These results encourage continued clinical development of DPIV (ClinicalTrials.gov: NCT01702857).

Charge state of oxide layer of SIMOX-structures

CERN Document Server

Askinazi, A Y; Dmitriev, V A; Miloglyadova, L V

2001-01-01

The charge state of the oxide layer of the SIMOX-structures, obtained in the course of forming the oxide layers, bricked up in the silicon volume, through the oxygen ions implantation into the Si, is studied. The charge state of the given structures is studied through the method of the layer-by-layer profiling, which makes it possible to obtain the dependence of the plane zones potential on the oxide layer thickness. It is established, that during the process of the SIMOX-structures formation in the oxide layer near the boundary with the Si there appear defects, responsible for the charge. The radiation from the near-the-ultraviolet (NUV) area without the applied electric field neutralizes the given charge. The simultaneous impact of the NUV-radiation and electric field leads to the formation of significantly positive charge

Tuning Reactivity and Electronic Properties through Ligand Reorganization within a Cerium Heterobimetallic Framework

Energy Technology Data Exchange (ETDEWEB)

Robinson, Jerome R.; Gordon, Zachary; Booth, Corwin H.; Carroll, Patrick J.; Walsh, Patrick J.; Schelter, Eric J.

2014-06-24

Cerium compounds have played vital roles in organic, inorganic, and materials chemistry due to their reversible redox chemistry between trivalent and tetravalent oxidation states. However, attempts to rationally access molecular cerium complexes in both oxidation states have been frustrated by unpredictable reactivity in cerium(III) oxidation chemistry. Such oxidation reactions are limited by steric saturation at the metal ion, which can result in high energy activation barriers for electron transfer. An alternative approach has been realized using a rare earth/alkali metal/1,1'-BINOLate (REMB) heterobimetallic framework, which uses redox-inactive metals within the secondary coordination sphere to control ligand reorganization. The rational syntheses of functionalized cerium(IV) products and a mechanistic examination of the role of ligand reorganization in cerium(III) oxidation are presented.

Effect of microorganisms on the plutonium oxidation states

International Nuclear Information System (INIS)

Lukšienė, Benedikta; Druteikienė, Rūta; Pečiulytė, Dalia; Baltrūnas, Dalis; Remeikis, Vidmantas; Paškevičius, Algimantas

2012-01-01

Particular microbes from substrates at the low-level radioactive waste repository in the Ignalina NPP territory were exposed to 239 Pu (IV) at low pH under aerobic conditions. Pu(III) and Pu(IV) were separated and quantitatively evaluated using the modified anion exchange method and alpha spectrometry. Tested bacteria Bacillus mycoides and Serratia marcescens were more effective in Pu reduction than Rhodococcus fascians. Fungi Paecillomyces lilacinus and Absidia spinosa var. spinosa as well as bacterium Rhodococcus fascians did not alter the plutonium oxidation state. - Highlights: ► Particular microbes from low-level radioactive waste repository were exposed to Pu (IV). ► Some tested bacteria induced slight Pu (IV) reduction at low pH under aerobic conditions. ► Tested fungi did not show peculiarities to alter Pu oxidation state. ► The modified radiochemical method was applied to differentiate Pu oxidation states.

Partial equilibrium in induced redox reactions of plutonium

Energy Technology Data Exchange (ETDEWEB)

Nikol' skii, B P; Posvol' skii, M V; Krylov, L I; Morozova, Z P

1975-01-01

A study was made of oxidation-reduction reactions of Pu in buffer solutions containing bichromate and a reducing agent which reacted with hexavalent chromium at pH=3.5. In most cases sodium nitrite was used. A rather slow reduction of Pu (6) with NaNO/sub 2/ in the course of which tetravalent plutonium was formed via disproportionation reaction of plutonium (5), became very rapid upon the addition of bichromate to the solution. The yield of tetravalent plutonium increased with an increase in the concentration of NaNO/sub 2/ and the bichromate but never reached 100%. This was due to a simultaneous occurrenc of the induced oxidation reaction of Pu(4), leading to a partial equilibrium between the valence forms of plutonium in the nitrite-bichromate system which on the whole was in a nonequilibrium state. It was shown that in the series of reactions leading to the reduction of plutonium the presence of bivalent chromium was a necessary link.

Chemistry of tetravalent actinides phosphates. The thorium phosphate-diphosphate as immobilisation matrix of actinides

International Nuclear Information System (INIS)

Dacheux, N.

2002-01-01

The author presents in this document its scientific works from 1992 to 2001, in order to obtain the enabling to manage scientific and chemical researches at the university Paris Sud Orsay. The first part gives an abstract of the thesis on the characterizations, lixiviation and synthesis of uranium and thorium based phosphate matrix in the framework of the search for a ceramic material usable in the radioactive waste storage. The second part presents briefly the researches realized at the CEA, devoted to a reliable, independent and accurate measure of some isotopes activity. The last part presents the abstracts of researches activities from 1996 to 2001 on the tetravalent actinides phosphates chemistry, the sintering of PDT and solid solutions of PDTU and the kinetic and thermodynamical studies of the PDT dissolution. Many references and some publication in full text are provided. (A.L.B.)

Effect of microorganisms on the plutonium oxidation states

Energy Technology Data Exchange (ETDEWEB)

Luksiene, Benedikta, E-mail: bena@ar.fi.lt [Center for Physical Sciences and Technology, Savanoriu ave 231, LT-02300 Vilnius (Lithuania); Druteikiene, Ruta [Center for Physical Sciences and Technology, Savanoriu ave 231, LT-02300 Vilnius (Lithuania); Peciulyte, Dalia [Nature Research Centre, Akademijos street 2, LT-08412 Vilnius (Lithuania); Baltrunas, Dalis; Remeikis, Vidmantas [Center for Physical Sciences and Technology, Savanoriu ave 231, LT-02300 Vilnius (Lithuania); Paskevicius, Algimantas [Nature Research Centre, Akademijos street 2, LT-08412 Vilnius (Lithuania)

2012-03-15

Particular microbes from substrates at the low-level radioactive waste repository in the Ignalina NPP territory were exposed to {sup 239}Pu (IV) at low pH under aerobic conditions. Pu(III) and Pu(IV) were separated and quantitatively evaluated using the modified anion exchange method and alpha spectrometry. Tested bacteria Bacillus mycoides and Serratia marcescens were more effective in Pu reduction than Rhodococcus fascians. Fungi Paecillomyces lilacinus and Absidia spinosa var. spinosa as well as bacterium Rhodococcus fascians did not alter the plutonium oxidation state. - Highlights: Black-Right-Pointing-Pointer Particular microbes from low-level radioactive waste repository were exposed to Pu (IV). Black-Right-Pointing-Pointer Some tested bacteria induced slight Pu (IV) reduction at low pH under aerobic conditions. Black-Right-Pointing-Pointer Tested fungi did not show peculiarities to alter Pu oxidation state. Black-Right-Pointing-Pointer The modified radiochemical method was applied to differentiate Pu oxidation states.

Oxidation-state maxima in plutonium chemistry

International Nuclear Information System (INIS)

Silver, G.L.

2013-01-01

Maxima in the fractions of the trivalent and hexavalent oxidation states of plutonium are inherent in the algebra of its disproportionation reactions. The maxima do not support overall disproportionation equations as satisfactory representations of aqueous plutonium. (author)

Safety of Combination of a Tetravalent Meningococcal Conjugate Vaccine Against Serogroups A, C, Y, W-135 With Other Vaccine Preparations: a Prospective Study of a Series of Cases Among Healthy Children and Children With Various Health Abnormalities

Directory of Open Access Journals (Sweden)

Leyla S. Namazova-Baranova

2017-01-01

Full Text Available Meningococcal infection is an acute disease caused by Neisseria meningitidis, which proceeds with a diverse clinical aspect from nasopharyngitis to meningococcal meningitis and meningococcemia. Since 2014, a tetravalent meningococcal conjugate vaccine has been registered in Russia. This vaccine creates protection against serogroups A, C, W-135, Y and can be used from the age of nine months to 55 years. The actual issue is a vaccine tolerability, including when combined with other vaccine preparations.Objective: Our aim was to evaluate the safety of a tetravalent meningococcal conjugate vaccine against serogroups A, C, Y and W-135 when it is combined with other vaccine preparations.Methods. A prospective full-design study assessed the tolerability of immunization with a meningococcal conjugate vaccine, both in case of monovaccination and in combination with a pneumococcal 13-valent conjugate vaccine, measles-mumps-rubella, viral hepatitis A, influenza, and chicken pox vaccines.Results. 97 children aged from 9 months to 18 years were vaccinated, 20 of them were healthy and 77 had medical issues (with allergic pathology, ENT diseases, cardiovascular and nervous system diseases, lung diseases as well as orphan diseases. Among vaccinated children, general reactions were observed in 3/97 (3.1% children, local reactions — in 5 (5.2%. The post-vaccination period passed asymptomatically and uneventfully in the prevailing majority of children vaccinated with a tetravalent meningococcal conjugate vaccine (in 91, 93.8%.Conclusion. The immunization with a tetravalent meningococcal conjugate vaccine against serogroups A, C, Y, W-135 is well tolerated, both in case of monovaccination and in combination with other vaccine preparations, in healthy children of different age groups and in patients with different health status.

Shifts in oxidation states of cerium oxide nanoparticles detected inside intact hydrated cells and organelles

Energy Technology Data Exchange (ETDEWEB)

Szymanski, Craig J.; Munusamy, Prabhakaran; Mihai, Cosmin; Xie, Yumei; Hu, Dehong; Gilles, Marry K.; Tyliszczak, T.; Thevuthasan, Suntharampillai; Baer, Donald R.; Orr, Galya

2015-09-01

Cerium oxide nanoparticles (CNPs) have been shown to induce diverse biological effects, ranging from toxic to beneficial. The beneficial effects have been attributed to the potential antioxidant activity of CNPs via certain redox reactions, depending on their oxidation state or Ce3+/Ce4+ ratio. However, this ratio is strongly dependent on the environment and age of the nanoparticles and it is unclear whether and how the complex intracellular environment impacts this ratio and the possible redox reactions of CNPs. To identify any changes in the oxidation state of CNPs in the intracellular environment and better understand their intracellular reactions, we directly quantified the oxidation states of CNPs outside and inside intact hydrated cells and organelles using correlated scanning transmission x-ray and super resolution fluorescence microscopies. By analyzing hundreds of small CNP aggregates, we detected a shift to a higher Ce3+/Ce4+ ratio in CNPs inside versus outside the cells, indicating a net reduction of CNPs in the intracellular environment. We further found a similar ratio in the cytoplasm and in the lysosomes, indicating that the net reduction occurs earlier in the internalization pathway. Together with oxidative stress and toxicity measurements, our observations identify a net reduction of CNPs in the intracellular environment, which is consistent with their involvement in potentially beneficial oxidation reactions, but also point to interactions that can negatively impact the health of cells.

Separation method for uranium, plutonium, and neptunium with each other from spent nuclear fuel

International Nuclear Information System (INIS)

Uchiyama, Gunzo; Hotoku, Shinobu; Fujine, Sachio; Maeda, Mitsuru.

1994-01-01

In a nuclear fuel reprocessing step of the present invention, an Np oxidation step is provided on a high level side of a co-contamination step, and an Np separation step and a U/Pu recovering step provided preceding to a U/Pu distribution step. Np oxidation step uses an oxidizer which is not extracted by an organic solvent such as ammonium vanadate for oxidizing Np from pentavalence to hexavalence. The Np separation step uses n-butylaldehyde for selectively reducing only hexavalent Np into pentavalent Np in a system in which hexavalent Np and tetravalent Pu are present together. In the U/Pu recovering step, pentavalent U and tetravalent Pu which shift by so much as distribution equilibrium are extracted together with pentavalent Np by using an organic solvent. The U/Pu distribution step uses iso-butylaldehyde as a reagent for selectively reducing only tetravalent Pu present together with hexavalent U into trivalent. With such procedures, U, Pu and Np can be separated with each other by more simplified fuel processing process. (T.M.)

Incorporation of tetravalent actinides in three phosphated matrices: britholite, monazite/brabandite and thorium phosphate diphosphate (β-TPD)

International Nuclear Information System (INIS)

Terra, O.

2005-03-01

Three phosphate based ceramics were studied for the immobilization of tri- and tetravalent actinides: britholite Ca 9 Nd 1-x An x IV (PO 4 ) 5-x (SiO 4 ) 1+x F 2 , monazite/brabantite solid solutions Ln 1-2x III Ca x An x IP O 4 and Thorium Phosphate Diphosphate (β-TPD) Th 4- xAn x IV (PO 4 ) 4 P 2 O 7 . For each material, the incorporation of thorium and uranium (IV) was studied as a surrogate of plutonium. This work was the early beginning of the incorporation of 239 Pu and/or 238 Pu in order to evaluate the effects of α-decay on the three crystallographic structures. The incorporation of tetravalent cations was carried out by dry chemistry methods, using mechanical grinding to improve the reactivity of the initial mixture then the homogeneity of final solid prepared after calcination at high temperature (1200-1400 deg C). For britholites, the thorium incorporation was complete for weight loading up to 20 wt.%, leading to the preparation of homogeneous and single phase solid solutions when using the coupled substitution (Nd 3+ , PO 4 3- ) ↔ (Th 4+ , SiO 4 4- ). Due to redox problems, the incorporation of uranium was limited to 5 to 8 wt.% and always led to a two-phase mixture of U-britholite and CaU 2 O 5+y . The preparation of homogeneous solid solutions of β-TUPD and of brabantites containing thorium and uranium samples was successfully obtained using three steps of mechanical grinding/calcination. For each matrix, dense pellets were prepared prior to the study of their chemical behaviour during leaching tests. The chemical durability of brabantites and β-TUPD were found to be close to that reported in literature. The formation of neo-formed phases was also evidenced onto the surface of Th-britholite samples. (author)

Incorporation of tetravalent actinides in three phosphated matrices: britholite, monazite/brabandite and thorium phosphate diphosphate ({beta}-TPD); Incorporation d'actinides tetravalents dans trois matrices phosphatees: britholite, monazite/brabantite et phosphate - diphosphate de thorium ({beta}-PDT)

Energy Technology Data Exchange (ETDEWEB)

Terra, O

2005-03-01

Three phosphate based ceramics were studied for the immobilization of tri- and tetravalent actinides: britholite Ca{sub 9}Nd{sub 1-x}An{sub x}{sup IV}(PO{sub 4}){sub 5-x}(SiO{sub 4}){sub 1+x}F{sub 2}, monazite/brabantite solid solutions Ln{sub 1-2x}{sup III} Ca{sub x}An{sub x}{sup IP}O{sub 4} and Thorium Phosphate Diphosphate ({beta}-TPD) Th{sub 4-}xAn{sub x}{sup IV}(PO{sub 4}){sub 4}P{sub 2}O{sub 7}. For each material, the incorporation of thorium and uranium (IV) was studied as a surrogate of plutonium. This work was the early beginning of the incorporation of {sup 239}Pu and/or {sup 238}Pu in order to evaluate the effects of {alpha}-decay on the three crystallographic structures. The incorporation of tetravalent cations was carried out by dry chemistry methods, using mechanical grinding to improve the reactivity of the initial mixture then the homogeneity of final solid prepared after calcination at high temperature (1200-1400 deg C). For britholites, the thorium incorporation was complete for weight loading up to 20 wt.%, leading to the preparation of homogeneous and single phase solid solutions when using the coupled substitution (Nd{sup 3+}, PO{sub 4}{sup 3-}) {r_reversible} (Th{sup 4+}, SiO{sub 4}{sup 4-}). Due to redox problems, the incorporation of uranium was limited to 5 to 8 wt.% and always led to a two-phase mixture of U-britholite and CaU{sub 2}O{sub 5+y}. The preparation of homogeneous solid solutions of {beta}-TUPD and of brabantites containing thorium and uranium samples was successfully obtained using three steps of mechanical grinding/calcination. For each matrix, dense pellets were prepared prior to the study of their chemical behaviour during leaching tests. The chemical durability of brabantites and {beta}-TUPD were found to be close to that reported in literature. The formation of neo-formed phases was also evidenced onto the surface of Th-britholite samples. (author)

Influence of oxidation state on the pH dependence of hydrous iridium oxide films

International Nuclear Information System (INIS)

Steegstra, Patrick; Ahlberg, Elisabet

2012-01-01

Many electrochemical reactions taking place in aqueous solution consume or produce protons. The pH in the diffusion layer can therefore be significantly altered during the reaction and there is a need for in situ pH measurements tracing this near surface pH. In the present paper the rotating ring disc technique was used to measure near surface pH changes during oxygen reduction, utilising hydrous iridium oxide as the pH sensing probe. Before such experiments a good understanding of the pH sensing properties of these films is required and the impact of the oxidation state of the film on the pH sensing properties was investigated as well as the influence of solution redox species. The pH sensitivity (depicted by dE/dpH) was found to depend on the average oxidation state of the film in a manner resembling the cyclic voltammetry response. In all cases the pH response is “supernernstian” with more than one proton per electron. The origin of this behaviour is discussed in the context of acid-base properties of the film and the existence of both hydrous and anhydrous oxide phases. The pH response depends also on the redox properties of the solution but can be optimised for various purposes by conditioning the film at different potentials. This was clearly illustrated by adding hydrogen peroxide, an intermediate in the oxygen reduction reaction, to the solution. It was shown that hydrous iridium oxide can be used as a reliable in situ pH sensor provided that care is taken to optimise the oxidation state of the film.

Possible stabilization of the tetravalent oxidation state of berkelium and californium in acetonitrile with triphenylarsine oxide

International Nuclear Information System (INIS)

Payne, G.F.; Peterson, J.R.

1987-01-01

It appears that we may have prepared Bk(IV) nitrate.nTPAs0 and Bk(IV) perchlorate.nTPAs0 complexes which formed the corresponding Cf(IV) complexes through the beta decay of Bk-249. Definitive proof should come from similar experiments with quantities of Bk-249 large enough to allow spectrophotometric detection of the characteristic f→f transitions in these berkelium and californium species. It is clear, however, that TPAs0 and acetonitrile can play a pivotal role in the stabilization of lanact(IV) species

Chemistry of tetravalent actinides phosphates. The thorium phosphate-diphosphate as immobilisation matrix of actinides; Chimie des phosphates d'actinides tetravalents. Le phosphate-diphosphate de thorium en tant que matrice d'imobilisation des actinides

Energy Technology Data Exchange (ETDEWEB)

Dacheux, N

2002-07-01

The author presents in this document its scientific works from 1992 to 2001, in order to obtain the enabling to manage scientific and chemical researches at the university Paris Sud Orsay. The first part gives an abstract of the thesis on the characterizations, lixiviation and synthesis of uranium and thorium based phosphate matrix in the framework of the search for a ceramic material usable in the radioactive waste storage. The second part presents briefly the researches realized at the CEA, devoted to a reliable, independent and accurate measure of some isotopes activity. The last part presents the abstracts of researches activities from 1996 to 2001 on the tetravalent actinides phosphates chemistry, the sintering of PDT and solid solutions of PDTU and the kinetic and thermodynamical studies of the PDT dissolution. Many references and some publication in full text are provided. (A.L.B.)

Analytical determination of plutonium in the presence of complexing agents

International Nuclear Information System (INIS)

Nebel', D.

1975-01-01

The complexing of Pu(4) and Pu(6) with citrate and lactate were studied to establish possibilities which are provided by the complexing for analytical determination of plutonium in a solution. Plutonium in the sample analyzed is preliminarily reduced up to trivalent state. Then trivalent plutonium is oxidized up to tetravalent on the platinum electrode at +1.05 V. To avoid further oxidation complexing agents are added. The value of pH=2-4 is maintained to stabilize the oxidation degree. If hexavalent plutonium should be obtained, the oxidation is performed at the voltage of +1.5 V in the absence of complexing agents. Based on a detailed study of absorption spectra of plutonium complexes of various oxidation degrees it is stated that the most suitable for analytical purposes is the oxidation degree of Pu=4

Sorption behaviour of well-defined oxidation states

International Nuclear Information System (INIS)

Allard, B.; Olofsson, U.; Torstenfelt, B.; Kipatsi, H.

1983-05-01

The sorption of the actinides Am(III), Th(IV), Np(V), Pa(V), U(VI) and Pu has been studied as a function of pH (2-12) for two nuclide concentrations (10 -7 -10 -9 M) (only one for Pa and U) in the systems Al 2 0 3 - 0.01 M NaCl0 4 and Si0 2 - 0.01 M NaCl0 4 . Distribution coefficients have been determined by a batch technique after various contact times (6h - 6w) at constant temperature (25degreeC) in systems equilibrated with air. The observed sorption behaviour indicates a predominantly physical adsorption mechanism, where pH of the aqueous phase is the principal chemical parameter of influence. The sorption is highly related to the degree of hydrolysis, with a maximum in the pH-region where neutral species dominate and with a reduction of the sorption under conditions when anionic species (hydroxides or carbonates) would exist in solution. This is particularly the case for U(VI) at pH above 7-8 when anionic carbonate complexes would be formed. Plutonium is predominantly tetravalent under the present conditions, as indicated by the sorption behaviour. (authors)

Electrochemical investigation of tetravalent uranium β-diketones for active materials of all-uranium redox flow battery

International Nuclear Information System (INIS)

Yamamura, Tomoo; Shiokawa, Yoshinobu; Ikeda, Yasuhisa

2002-01-01

For active materials of the all-uranium redox flow battery for the power storage, tetravalent uranium β-diketones were investigated. The electrode reactions of U(ba) 4 and U(btfa) 4 were examined in comparison with that of U(acac) 4 , where ba denotes benzoylacetone, btfa benzoyltrifluoroacetone and acac acetylacetone. The cyclic voltammograms of U(ba) 4 and U(btfa) 4 solutions indicate that there are two series of redox reactions corresponding to the complexes with different coordination numbers of four and three. The electrode kinetics of the U(IV)/U(III) redox reactions for btfa complexes is examined. The obtained result supports that the uranium β-diketone complexes examined in the present study will serve as excellent active materials for negative electrolyte in the redox flow battery. (author)

Chemical ordering in substituted fluorite oxides: a computational investigation of Ho2Zr2O7 and RE2Th2O7 (RE=Ho, Y, Gd, Nd, La)

Science.gov (United States)

Solomon, Jonathan M.; Shamblin, Jacob; Lang, Maik; Navrotsky, Alexandra; Asta, Mark

2016-12-01

Fluorite-structured oxides find widespread use for applications spanning nuclear energy and waste containment, energy conversion, and sensing. In such applications the host tetravalent cation is often partially substituted by trivalent cations, with an associated formation of charge-compensating oxygen vacancies. The stability and properties of such materials are known to be influenced strongly by chemical ordering of the cations and vacancies, and the nature of such ordering and associated energetics are thus of considerable interest. Here we employ density-functional theory (DFT) calculations to study the structure and energetics of cation and oxygen-vacancy ordering in Ho2Zr2O7. In a recent neutron total scattering study, solid solutions in this system were reported to feature local chemical ordering based on the fluorite-derivative weberite structure. The calculations show a preferred chemical ordering qualitatively consistent with these findings, and yield values for the ordering energy of 9.5 kJ/mol-cation. Similar DFT calculations are applied to additional RE2Th2O7 fluorite compounds, spanning a range of values for the ratio of the tetravalent and trivalent (RE) cation radii. The results demonstrate that weberite-type order becomes destabilized with increasing values of this size ratio, consistent with an increasing energetic preference for the tetravalent cations to have higher oxygen coordination.

Chemical ordering in substituted fluorite oxides: a computational investigation of Ho2Zr2O7 and RE2Th2O7 (RE=Ho, Y, Gd, Nd, La)

OpenAIRE

Jonathan M. Solomon; Jacob Shamblin; Maik Lang; Alexandra Navrotsky; Mark Asta

2016-01-01

Fluorite-structured oxides find widespread use for applications spanning nuclear energy and waste containment, energy conversion, and sensing. In such applications the host tetravalent cation is often partially substituted by trivalent cations, with an associated formation of charge-compensating oxygen vacancies. The stability and properties of such materials are known to be influenced strongly by chemical ordering of the cations and vacancies, and the nature of such ordering and associated e...

Study of uranium oxidation states in geological material.

Science.gov (United States)

Pidchenko, I; Salminen-Paatero, S; Rothe, J; Suksi, J

2013-10-01

A wet chemical method to determine uranium (U) oxidation states in geological material has been developed and tested. The problem faced in oxidation state determinations with wet chemical methods is that U redox state may change when extracted from the sample material, thereby leading to erroneous results. In order to quantify and monitor U redox behavior during the acidic extraction in the procedure, an analysis of added isotopic redox tracers, (236)U(VI) and (232)U(IV), and of variations in natural uranium isotope ratio ((234)U/(238)U) of indigenous U(IV) and U(VI) fractions was performed. Two sample materials with varying redox activity, U bearing rock and U-rich clayey lignite sediment, were used for the tests. The Fe(II)/Fe(III) redox-pair of the mineral phases was postulated as a potentially disturbing redox agent. The impact of Fe(III) on U was studied by reducing Fe(III) with ascorbic acid, which was added to the extraction solution. We observed that ascorbic acid protected most of the U from oxidation. The measured (234)U/(238)U ratio in U(IV) and U(VI) fractions in the sediment samples provided a unique tool to quantify U oxidation caused by Fe(III). Annealing (sample heating) to temperatures above 500 °C was supposed to heal ionizing radiation induced defects in the material that can disturb U redox state during extraction. Good agreement between two independent methods was obtained for DL-1a material: an average 38% of U(IV) determined by redox tracer corrected wet chemistry and 45% for XANES. Copyright © 2013 Elsevier Ltd. All rights reserved.

A magnetic route to measure the average oxidation state of mixed-valent manganese in manganese oxide octahedral molecular sieves (OMS).

Science.gov (United States)

Shen, Xiong-Fei; Ding, Yun-Shuang; Liu, Jia; Han, Zhao-Hui; Budnick, Joseph I; Hines, William A; Suib, Steven L

2005-05-04

A magnetic route has been applied for measurement of the average oxidation state (AOS) of mixed-valent manganese in manganese oxide octahedral molecular sieves (OMS). The method gives AOS measurement results in good agreement with titration methods. A maximum analysis deviation error of +/-7% is obtained from 10 sample measurements. The magnetic method is able to (1) confirm the presence of mixed-valent manganese and (2) evaluate AOS and the spin states of d electrons of both single oxidation state and mixed-valent state Mn in manganese oxides. In addition, the magnetic method may be extended to (1) determine AOS of Mn in manganese oxide OMS with dopant "diamagnetic" ions, such as reducible V5+ (3d0) ions, which is inappropriate for the titration method due to interference of redox reactions between these dopant ions and titration reagents, such as KMnO4, (2) evaluate the dopant "paramagnetic" ions that are present as clusters or in the OMS framework, and (3) determine AOS of other mixed-valent/single oxidation state ion systems, such as Mo3+(3d3)-Mo4+(3d2) systems and Fe3+ in FeCl3.

Origin of interface states and oxide charges generated by ionizing radiation

International Nuclear Information System (INIS)

Sah, C.T.

1976-01-01

The randomly located trivalent silicon atoms are shown to account for the thermally generated interface states at the SiO 2 -Si interface. The interface state density is greatly reduced in water containing ambients at low temperatures (450 0 C) by forming trivalent silicon hydroxide bonds. Interface states are regenerated when the /triple bond/Si-OH bonds are broken by ionizing radiation and the OH ions are drifted away. In the bulk of the oxide film, the trivalent silicon and the interstitial oxygen donor centers are shown to be responsible for the heat and radiation generated positive space charge build-up (oxide charge) in thermally grown silicon oxide

Oxidative Stress and Heart Failure in Altered Thyroid States

Directory of Open Access Journals (Sweden)

Pallavi Mishra

2012-01-01

Full Text Available Increased or reduced action of thyroid hormone on certain molecular pathways in the heart and vasculature causes relevant cardiovascular derangements. It is well established that hyperthyroidism induces a hyperdynamic cardiovascular state, which is associated with a faster heart rate, enhanced left ventricular systolic and diastolic function whereas hypothyroidism is characterized by the opposite changes. Hyperthyroidism and hypothyroidism represent opposite clinical conditions, albeit not mirror images. Recent experimental and clinical studies have suggested the involvement of ROS tissue damage under altered thyroid status. Altered-thyroid state-linked changes in heart modify their susceptibility to oxidants and the extent of the oxidative damage they suffer following oxidative challenge. Chronic increase in the cellular levels of ROS can lead to a catastrophic cycle of DNA damage, mitochondrial dysfunction, further ROS generation and cellular injury. Thus, these cellular events might play an important role in the development and progression of myocardial remodeling and heart failure in altered thyroid states (hypo- and hyper-thyroidism. The present review aims at elucidating the various signaling pathways mediated via ROS and their modulation under altered thyroid state and the possibility of antioxidant therapy.

Adsorption properties versus oxidation states of rutile TiO2(110)

DEFF Research Database (Denmark)

Martinez, Umberto; Hammer, Bjørk

2011-01-01

Using density functional theory we have studied the adsorption properties of different atoms and molecules deposited on a stoichiometric, reduced, and oxidized rutile TiO2(110) surface. Depending on the oxidation state of the surface, electrons can flow from or to the substrate and, therefore...... of the charge flow depends on the oxidation state of the rutile surface and on the adsorption site. Generally, the charging effect leads to more stable complexes. However, the increase in the binding energy of the adsorbates is highly dependent on the electronic states of the surface prior to the adsorption...... event. In this work we have analyzed in details these mechanisms and we have also established a direct correlation between the enhanced binding energy of the adsorbates and the induced gap states...

Photochemical oxidants: state of the science.

Science.gov (United States)

Kley, D; Kleinmann, M; Sanderman, H; Krupa, S

1999-01-01

Atmospheric photochemical processes resulting in the production of tropospheric ozone (O(3)) and other oxidants are described. The spatial and temporal variabilities in the occurrence of surface level oxidants and their relationships to air pollution meteorology are discussed. Models of photooxidant formation are reviewed in the context of control strategies and comparisons are provided of the air concentrations of O(3) at select geographic locations around the world. This overall oxidant (O(3)) climatology is coupled to human health and ecological effects. The discussion of the effects includes both acute and chronic responses, mechanisms of action, human epidemiological and plant population studies and briefly, efforts to establish cause-effect relationships through numerical modeling. A short synopsis is provided of the interactive effects of O(3) with other abiotic and biotic factors. The overall emphasis of the paper is on identifying the current uncertainties and gaps in our understanding of the state of the science and some suggestions as to how they may be addressed.

Thermodynamic Ground States of Complex Oxide Heterointerfaces

DEFF Research Database (Denmark)

Gunkel, F.; Hoffmann-Eifert, S.; Heinen, R. A.

2017-01-01

The formation mechanism of 2-dimensional electron gases (2DEGs) at heterointerfaces between nominally insulating oxides is addressed with a thermodynamical approach. We provide a comprehensive analysis of the thermodynamic ground states of various 2DEG systems directly probed in high temperature...

Assessing Covalency in Cerium and Uranium Hexachlorides: A Correlated Wavefunction and Density Functional Theory Study

Directory of Open Access Journals (Sweden)

Reece Beekmeyer

2015-11-01

Full Text Available The electronic structure of a series of uranium and cerium hexachlorides in a variety of oxidation states was evaluated at both the correlated wavefunction and density functional (DFT levels of theory. Following recent experimental observations of covalency in tetravalent cerium hexachlorides, bonding character was studied using topological and integrated analysis based on the quantum theory of atoms in molecules (QTAIM. This analysis revealed that M–Cl covalency was strongly dependent on oxidation state, with greater covalency found in higher oxidation state complexes. Comparison of M–Cl delocalisation indices revealed a discrepancy between correlated wavefunction and DFT-derived values. Decomposition of these delocalisation indices demonstrated that the origin of this discrepancy lay in ungerade contributions associated with the f-manifold which we suggest is due to self-interaction error inherent to DFT-based methods. By all measures used in this study, extremely similar levels of covalency between complexes of U and Ce in the same oxidation state was found.

Oxidative Uranium Release from Anoxic Sediments under Diffusion-Limited Conditions.

Science.gov (United States)

Bone, Sharon E; Cahill, Melanie R; Jones, Morris E; Fendorf, Scott; Davis, James; Williams, Kenneth H; Bargar, John R

2017-10-03

Uranium (U) contamination occurs as a result of mining and ore processing; often in alluvial aquifers that contain organic-rich, reduced sediments that accumulate tetravalent U, U(IV). Uranium(IV) is sparingly soluble, but may be mobilized upon exposure to nitrate (NO 3 - ) and oxygen (O 2 ), which become elevated in groundwater due to seasonal fluctuations in the water table. The extent to which oxidative U mobilization can occur depends upon the transport properties of the sediments, the rate of U(IV) oxidation, and the availability of inorganic reductants and organic electron donors that consume oxidants. We investigated the processes governing U release upon exposure of reduced sediments to artificial groundwater containing O 2 or NO 3 - under diffusion-limited conditions. Little U was mobilized during the 85-day reaction, despite rapid diffusion of groundwater within the sediments and the presence of nonuraninite U(IV) species. The production of ferrous iron and sulfide in conjunction with rapid oxidant consumption suggested that the sediments harbored large concentrations of bioavailable organic carbon that fueled anaerobic microbial respiration and stabilized U(IV). Our results suggest that seasonal influxes of O 2 and NO 3 - may cause only localized mobilization of U without leading to export of U from the reducing sediments when ample organic carbon is present.

Use of Tetravalent Galabiose for Inhibition of Streptococcus Suis Serotype 2 Infection in a Mouse Model

Directory of Open Access Journals (Sweden)

Karen A. Krogfelt

2013-04-01

Full Text Available Streptococcus suis is an important swine pathogen associated with a variety of infections such as meningitis, arthritis and septicemia. The bacterium is zoonotic and has been found to cause meningitis especially in humans occupationally exposed to infected pigs. Since adhesion is a prerequisite for colonization and subsequent infection, anti-adhesion treatment seems a natural alternative to traditional treatment with antibiotics. In order to optimize the inhibitory potency a multivalency approach was taken in the inhibitor design. A synthetic tetravalent galabiose compound was chosen which had previously shown promising anti-adhesion effects with S. suis in vitro. The aim of this study was to evaluate the in vivo effects of the compound using an infection peritonitis mouse model. As such S. suis serotype 2 infection and treatment were tested in vivo and the effects were compared to the effect of treatment with penicillin.

Investigation of the growth defects in strontium titanate single crystals

Energy Technology Data Exchange (ETDEWEB)

Kulagin, N A; Landar, S V; Podus, L P [Khar' kovskij Gosudarstvennyj Univ. (Ukrainian SSR)

1981-02-01

Investigation results of characteristics and reasons for formation of macroscopic growth defects in SrTiO/sub 3/ monocrystals grown up by Wernail method are presented. It is shown that blue colour occurring in the specimen volume is caused by shortage of oxygen during growing which results in transition of some ions from tetravalent to trivalent state. The defect of another type is characterized by increased content of Fe and Ni oxides.

Oxidatively generated DNA/RNA damage in psychological stress states

DEFF Research Database (Denmark)

Jørgensen, Anders

2013-01-01

age-related somatic disorders. The overall aim of the PhD project was to investigate the relation between psychopathology, psychological stress, stress hormone secretion and oxidatively generated DNA and RNA damage, as measured by the urinary excretion of markers of whole-body DNA/RNA oxidation (8...... between the 24 h urinary cortisol excretion and the excretion of 8-oxodG/8-oxoGuo, determined in the same samples. Collectively, the studies could not confirm an association between psychological stress and oxidative stress on nucleic acids. Systemic oxidatively generated DNA/RNA damage was increased......Both non-pathological psychological stress states and mental disorders are associated with molecular, cellular and epidemiological signs of accelerated aging. Oxidative stress on nucleic acids is a critical component of cellular and organismal aging, and a suggested pathogenic mechanism in several...

The problem of oxidation state stabilisation and some regularities of a Periodic system of the elements

International Nuclear Information System (INIS)

Kiselev, Yurii M; Tretyakov, Yuri D

1999-01-01

The general principles of the concept of oxidation state stabilisation are formulated. Problems associated with the preparation and provision of the highest valent forms of transition elements are considered. The empirical data concerning the synthesis of new compounds of rare-earth elements and d elements in unusually high oxidation states are analysed. The possibility of occurrence of the oxidation states + 9 and + 10 for some elements (for example, for iridium and platinum in tetraoxo ions) are discussed. Approaches to the realisation of these states are outlined and it is demonstrated that solid phases or matrices containing alkali metal cations are the most promising systems for the stabilisation of these high oxidation states. Selected thermodynamic features typical of metal halides and oxides and the regularities of the changes in the extreme oxidation states of d elements are considered. The bibliography includes 266 references.

Heterogeneous Oxidation of Atmospheric Organic Aerosol: Kinetics of Changes to the Amount and Oxidation State of Particle-Phase Organic Carbon.

Science.gov (United States)

Kroll, Jesse H; Lim, Christopher Y; Kessler, Sean H; Wilson, Kevin R

2015-11-05

Atmospheric oxidation reactions are known to affect the chemical composition of organic aerosol (OA) particles over timescales of several days, but the details of such oxidative aging reactions are poorly understood. In this study we examine the rates and products of a key class of aging reaction, the heterogeneous oxidation of particle-phase organic species by the gas-phase hydroxyl radical (OH). We compile and reanalyze a number of previous studies from our laboratories involving the oxidation of single-component organic particles. All kinetic and product data are described on a common basis, enabling a straightforward comparison among different chemical systems and experimental conditions. Oxidation chemistry is described in terms of changes to key ensemble properties of the OA, rather than to its detailed molecular composition, focusing on two quantities in particular, the amount and the oxidation state of the particle-phase carbon. Heterogeneous oxidation increases the oxidation state of particulate carbon, with the rate of increase determined by the detailed chemical mechanism. At the same time, the amount of particle-phase carbon decreases with oxidation, due to fragmentation (C-C scission) reactions that form small, volatile products that escape to the gas phase. In contrast to the oxidation state increase, the rate of carbon loss is nearly uniform among most systems studied. Extrapolation of these results to atmospheric conditions indicates that heterogeneous oxidation can have a substantial effect on the amount and composition of atmospheric OA over timescales of several days, a prediction that is broadly in line with available measurements of OA evolution over such long timescales. In particular, 3-13% of particle-phase carbon is lost to the gas phase after one week of heterogeneous oxidation. Our results indicate that oxidative aging represents an important sink for particulate organic carbon, and more generally that fragmentation reactions play a major

Synergistic extraction of tetravalent actinides by mixtures of a β-diketone and a neutral donor : a review [Paper No. : IIIA-2

International Nuclear Information System (INIS)

Patil, S.K.; Ramakrishna, V.V.

1979-01-01

Synergistic extraction of metal ions by mixtures of a β-diketone and a neutral donor has been studied extensively. Due to large synergistic enhancement of extraction both the formulas of the extractable species and the adduct formation constants with various neutral donors have been ascertained. Relatively few such studies have been devoted to the extraction of tetravalent actinides and these are reviewed critically in the present paper. In addition the work on synergistic extraction of tetravelent actinides by HTTA in admixture with several neutral donors carried out at Radiochemistry Division, BARC, is included. Attempts are made to explain the observed trends in the adduct formation constants. (author)

Characterization of Interface State in Silicon Carbide Metal Oxide Semiconductor Capacitors

Science.gov (United States)

Kao, Wei-Chieh

Silicon carbide (SiC) has always been considered as an excellent material for high temperature and high power devices. Since SiC is the only compound semiconductor whose native oxide is silicon dioxide (SiO2), it puts SiC in a unique position. Although SiC metal oxide semiconductor (MOS) technology has made significant progress in recent years, there are still a number of issues to be overcome before more commercial SiC devices can enter the market. The prevailing issues surrounding SiC MOSFET devices are the low channel mobility, the low quality of the oxide layer and the high interface state density at the SiC/SiO2 interface. Consequently, there is a need for research to be performed in order to have a better understanding of the factors causing the poor SiC/SiO2 interface properties. In this work, we investigated the generation lifetime in SiC materials by using the pulsed metal oxide semiconductor (MOS) capacitor method and measured the interface state density distribution at the SiC/SiO2 interface by using the conductance measurement and the high-low frequency capacitance technique. These measurement techniques have been performed on n-type and p-type SiC MOS capacitors. In the course of our investigation, we observed fast interface states at semiconductor-dielectric interfaces in SiC MOS capacitors that underwent three different interface passivation processes, such states were detected in the nitrided samples but not observed in PSG-passivated samples. This result indicate that the lack of fast states at PSG-passivated interface is one of the main reasons for higher channel mobility in PSG MOSFETs. In addition, the effect of mobile ions in the oxide on the response time of interface states has been investigated. In the last chapter we propose additional methods of investigation that can help elucidate the origin of the particular interface states, enabling a more complete understanding of the SiC/SiO2 material system.

Investigation into formation of nanoparticles of tetravalent neptunium in slightly alkaline aqueous solution

International Nuclear Information System (INIS)

Husar, Richard

2015-01-01

H range from pH 3 to pH 10 with ζ = (-) 5 to (-) 30 mV. The zeta potentials of all particle systems containing silica are significantly shifted to more negative values below pH 7 where the isoelectrical point shifts from pH = 8.0 to 2.6 effecting negative charge under ambient conditions which supports electrostatic stabilization of Np(IV) particles. Particle surface charge at the slipping plane, particle size and shape necessarily depend on the initial magnitude of Si content in solution during particle formation. Particular changes of the morphology and internal structure of different Np(IV) silica colloids by aging are indicated by TEM and XPS. The composition and the crystallinity state of the initially formed amorphous phases partially changed into well-ordered nanocrystalline units characterized with fcc structure. The presence of silicate under conditions expected in a nuclear waste repository significantly influences the solubility of Np(IV) and provoke the stabilization of waterborne Np(IV) up to concentrations of 10 -3 M, exceeding Np's solubility limit by a factor of up 10.000. Neptunium and silicate significantly interact with each other, and thereby changing their individual hydrolysis and polymerization behavior. Silicate prevents the intrinsic formation of NpO 2 NCs in fcc-structure, and at the same time, Np(IV) prevents the polymerization of silicate. Both processes result in the formation of Np(IV) silica colloids which possibly influence the migration behavior and fate of Np in the waste repositories and surrounding environments. For tetravalent actinides in general, the most significant transport in the environment would occur by colloidal particles. Therefore, Np(IV) silica colloids could have a significant implication in the migration of Np, the important minor actinide in the waste repositories, via colloidal transport.

Photochemical reduction of uranyl nitrate

Energy Technology Data Exchange (ETDEWEB)

Duerksen, W.K.

1993-10-20

The photochemical reduction of uranyl nitrate solutions to tetravalent uranium was investigated as a means of producing uranium dioxide feed for the saltless direct oxide reduction (SDOR) process. At high uranium concentrations, reoxidation of U{sup +4} occurs rapidly. The kinetics of the nitric oxidation of tetravalent uranium depend on the concentrations of hydrogen ion, nitrate ion, nitrous acid, and tetravalent uranium in the same manner as was reported elsewhere for the nitrate oxidation of PU{sup +3}. Reaction rate data were successfully correlated with a mechanism in which nitrogen dioxide is the reactive intermediate. Addition of a nitrous acid scavenger suppresses the reoxidation reaction. An immersion reactor employing a mercury vapor lamp gave reduction times fast enough for routine production usage. Precipitation techniques for conversion of aqueous U(NO{sub 3}){sub 4} to hydrous UO{sub 2} were evaluated. Prolonged dewatering times tended to make the process time consuming. Use of 3- to 4-M aqueous NaOH gave the best dewatering times observed. Reoxidation of the UO{sub 2} by water of hydration was encountered, which required the drying process to be carried out under a reducing atmosphere.

Investigation of plutonium-239 conditioning in monazite and brabantite matrices: Synthesis and characterization

International Nuclear Information System (INIS)

Glorieux, B.; Jorion, F.; Montel, J.M.; Matecki, M.; Deschanels, X.; Coutures, JP.

2004-01-01

In response to the 1991 French radioactive waste management act, a research program was set up between the CNRS, the CEA and French universities to propose effective minor actinide disposal matrices capable of loading 10 wt% of actinide oxides and ensuring a hundred-fold better leaching performance than 'R7T7' glass. The lanthanide ortho-phosphates LaPO 4 could constitute an excellent matrix for this purpose. In this type of structure, the (PO 4 ) 3- negative entity is compensated by trivalent cations such as La, Ce, Gd, Pu, Am (monazite) or equal fractions of divalent and tetravalent cations such as Ca 2+ Th 4+ , Ca 2+ U 4+ , Ca 2+ Np 4+ (brabantite). Previous leach tests and geological discoveries have shown that these materials are highly resistant to leaching and conserve their crystalline state even in aqueous media. These points led us to investigate the incorporation of 10 wt% PuO 2 in monazite and brabantite materials and to study the effects of self-irradiation on their structural states. Prior to plutonium conditioning tests, experiments were performed in the laboratory using cerium and thorium oxides according to the following reactions: (1-3x)LaPO 4 + 2xCe 4+ O 2 + xLa(PO 3 ) 3 → La 1-2x Ce 2x 3+ PO 4 + x/2O 2 ; (1-3x)LaPO 4 + xTh 4+ O 2 + xCaO + xLa(PO 3 ) 3 → La 1-2x Ca x Th x 4+ PO 4 . Cerium oxide was used to study the reduction of a tetravalent cation to a trivalent state in a phosphate structure and to prepare for Pu 3+ conditioning. Thorium was used to study the conditioning of tetravalent cations such as Pu 4+ . The parameters and sintering reaction of the final product were optimized. In a radioactive laboratory, PuO 2 was then substituted for CeO 2 and ThO 2 in the first and second reactions mentioned above, respectively. The synthesis and sintering procedures were unchanged. X-ray diffraction analysis of the powder before and after sintering showed promising results that are discussed. (authors)

Extracellular redox state: refining the definition of oxidative stress in aging.

Science.gov (United States)

Jones, Dean P

2006-01-01

Oxidative stress in aging can result from an imbalance of prooxidants and antioxidants with excessive, destructive free radical chemistry. Thiol systems are important in the control of these processes, both by protecting against damage and serving in redox signaling mechanisms to sense danger and repair the damage. Studies by a number of research groups in collaboration with the Emory Clinical Biomarkers Laboratory show that the redox state of the central tissue antioxidant, glutathione (GSH), can be measured in human plasma and provides a quantitative systemic indicator of oxidative stress. Plasma GSH/GSSG redox in humans becomes oxidized with age, in response to chemotherapy, as a consequence of cigarette smoking, and in association with common age-related diseases (e.g., type 2 diabetes, cardiovascular disease). However, the GSH/GSSG redox is not equilibrated with the larger plasma cysteine/cystine (Cys/CySS) pool, and the Cys/CySS redox varies with age in a pattern that is distinct from that of GSH/GSSG redox. Furthermore, in vitro studies show that variation in Cys/CySS redox over the range found in vivo affects signaling pathways, which control cell proliferation and oxidant-induced apoptosis. The results point to the conclusion that free radical scavenging antioxidants are of increased importance when thiol/disulfide redox states are oxidized. Because thiol/disulfide redox states, per se, function in redox signaling and control as well as antioxidant protection, GSH/GSSG and Cys/CySS redox states may provide central parameters to link environmental influences and progression of changes associated with aging.

How different oxidation states of crystalline myoglobin are influenced by X-rays.

Science.gov (United States)

Hersleth, Hans-Petter; Andersson, K Kristoffer

2011-06-01

X-ray induced radiation damage of protein crystals is well known to occur even at cryogenic temperatures. Redox active sites like metal sites seem especially vulnerable for these radiation-induced reductions. It is essential to know correctly the oxidation state of metal sites in protein crystal structures to be able to interpret the structure-function relation. Through previous structural studies, we have tried to characterise and understand the reactions between myoglobin and peroxides. These reaction intermediates are relevant because myoglobin is proposed to take part as scavenger of reactive oxygen species during oxidative stress, and because these intermediates are similar among the haem peroxidases and oxygenases. We have in our previous studies shown that these different myoglobin states are influenced by the X-rays used. In this study, we have in detail investigated the impact that X-rays have on these different oxidation states of myoglobin. An underlying goal has been to find a way to be able to determine mostly unreduced states. We have by using single-crystal light absorption spectroscopy found that the different oxidation states of myoglobin are to a different extent influenced by the X-rays (e.g. ferric Fe(III) myoglobin is faster reduced than ferryl Fe(IV)═O myoglobin). We observe that the higher oxidation states are not reduced to normal ferrous Fe(II) or ferric Fe(III) states, but end up in some intermediate and possibly artificial states. For ferric myoglobin, it seems that annealing of the radiation-induced/reduced state can reversibly more or less give the starting point (ferric myoglobin). Both scavengers and different dose-rates might influence to which extent the different states are affected by the X-rays. Our study shows that it is essential to do a time/dose monitoring of the influence X-rays have on each specific redox-state with spectroscopic techniques like single-crystal light absorption spectroscopy. This will determine to which

Optoelectronic properties of valence-state-controlled amorphous niobium oxide

Science.gov (United States)

Onozato, Takaki; Katase, Takayoshi; Yamamoto, Akira; Katayama, Shota; Matsushima, Koichi; Itagaki, Naho; Yoshida, Hisao; Ohta, Hiromichi

2016-06-01

In order to understand the optoelectronic properties of amorphous niobium oxide (a-NbO x ), we have investigated the valence states, local structures, electrical resistivity, and optical absorption of a-NbO x thin films with various oxygen contents. It was found that the valence states of Nb ion in a-NbO x films can be controlled from 5+  to 4+  by reducing oxygen pressure during film deposition at room temperature, together with changing the oxide-ion arrangement around Nb ion from Nb2O5-like to NbO2-like local structure. As a result, a four orders of magnitude reduction in the electrical resistivity of a-NbO x films was observed with decreasing oxygen content, due to the carrier generation caused by the appearance and increase of an oxygen-vacancy-related subgap state working as an electron donor. The tunable optoelectronic properties of a-NbO x films by valence-state-control with oxygen-vacancy formation will be useful for potential flexible optoelectronic device applications.

Oxidation of extracellular cysteine/cystine redox state in bleomycin-induced lung fibrosis.

Science.gov (United States)

Iyer, Smita S; Ramirez, Allan M; Ritzenthaler, Jeffrey D; Torres-Gonzalez, Edilson; Roser-Page, Susanne; Mora, Ana L; Brigham, Kenneth L; Jones, Dean P; Roman, Jesse; Rojas, Mauricio

2009-01-01

Several lines of evidence indicate that depletion of glutathione (GSH), a critical thiol antioxidant, is associated with the pathogenesis of idiopathic pulmonary fibrosis (IPF). However, GSH synthesis depends on the amino acid cysteine (Cys), and relatively little is known about the regulation of Cys in fibrosis. Cys and its disulfide, cystine (CySS), constitute the most abundant low-molecular weight thiol/disulfide redox couple in the plasma, and the Cys/CySS redox state (E(h) Cys/CySS) is oxidized in association with age and smoking, known risk factors for IPF. Furthermore, oxidized E(h) Cys/CySS in the culture media of lung fibroblasts stimulates proliferation and expression of transitional matrix components. The present study was undertaken to determine whether bleomycin-induced lung fibrosis is associated with a decrease in Cys and/or an oxidation of the Cys/CySS redox state and to determine whether these changes were associated with changes in E(h) GSH/glutathione disulfide (GSSG). We observed distinct effects on plasma GSH and Cys redox systems during the progression of bleomycin-induced lung injury. Plasma E(h) GSH/GSSG was selectively oxidized during the proinflammatory phase, whereas oxidation of E(h) Cys/CySS occurred at the fibrotic phase. In the epithelial lining fluid, oxidation of E(h) Cys/CySS was due to decreased food intake. Thus the data show that decreased precursor availability and enhanced oxidation of Cys each contribute to the oxidation of extracellular Cys/CySS redox state in bleomycin-induced lung fibrosis.

Plant-expressed Fc-fusion protein tetravalent dengue vaccine with inherent adjuvant properties.

Science.gov (United States)

Kim, Mi Young; Copland, Alastair; Nayak, Kaustuv; Chandele, Anmol; Ahmed, Muhammad S; Zhang, Qibo; Diogo, Gil R; Paul, Matthew J; Hofmann, Sven; Yang, Moon-Sik; Jang, Yong-Suk; Ma, Julian K-C; Reljic, Rajko

2017-12-09

Dengue is a major global disease requiring improved treatment and prevention strategies. The recently licensed Sanofi Pasteur Dengvaxia vaccine does not protect children under the age of nine, and additional vaccine strategies are thus needed to halt this expanding global epidemic. Here, we employed a molecular engineering approach and plant expression to produce a humanized and highly immunogenic poly-immunoglobulin G scaffold (PIGS) fused to the consensus dengue envelope protein III domain (cEDIII). The immunogenicity of this IgG Fc receptor-targeted vaccine candidate was demonstrated in transgenic mice expressing human FcγRI/CD64, by induction of neutralizing antibodies and evidence of cell-mediated immunity. Furthermore, these molecules were able to prime immune cells from human adenoid/tonsillar tissue ex vivo as evidenced by antigen-specific CD4 + and CD8 + T-cell proliferation, IFN-γ and antibody production. The purified polymeric fraction of dengue PIGS (D-PIGS) induced stronger immune activation than the monomeric form, suggesting a more efficient interaction with the low-affinity Fcγ receptors on antigen-presenting cells. These results show that the plant-expressed D-PIGS have the potential for translation towards a safe and easily scalable single antigen-based tetravalent dengue vaccine. © 2017 The Authors. Plant Biotechnology Journal published by Society for Experimental Biology and The Association of Applied Biologists and John Wiley & Sons Ltd.

Oxidation state analyses of uranium with emphasis on chemical speciation in geological media

International Nuclear Information System (INIS)

Ervanne, H.

2004-01-01

This thesis focuses on chemical methods suitable for the determination of uranium redox species in geological materials. Nd-coprecipitation method was studied for the determination of uranium oxidation states in ground waters. This method is ideally suited for the separation of uranium oxidation states in the field, which means that problems associated with the instability of U(IV) during transport are avoided. An alternative method, such as ion exchange, is recommended for the analysis of high saline and calcium- and iron-rich ground waters. U(IV)/Utot was 2.8-7.2% in ground waters in oxidizing conditions and 60-93% in anoxic conditions. From thermodynamic model calculations applied to results from anoxic ground waters it was concluded that uranium can act as redox buffer in granitic ground waters. An ion exchange method was developed for the analysis of uranium oxidation states in different solid materials of geological origin. These included uranium minerals, uraniumbearing minerals, fracture coatings and bulk rock. U(IV)/Utot was 50-70% in uraninites, 5.8-8.7% in secondary uranium minerals, 15-49% in different fracture coatings and 64- 77% in samples from deep bedrock. In the uranium-bearing minerals, U(IV)/Utot was 33-43% (allanites), 5.9% (fergusonite) and 93% (monazite). Although the ion exchange method gave reliable results, there is a risk for the conversion of uranium oxidation states during analysis of heterogeneous samples due to the redox reactions that take place in the presence of some iron compounds. This risk was investigated in a study of several common iron-bearing minerals. The risk for conversion of uranium oxidation states can be screened by sample selection and minimized with use of a redox buffer compound such as polyacrylic acid (PAA). In studies of several carboxylic acids, PAA was found to be the most suitable for extending the application of the method. The stability of uranium oxidation states during analysis and the selectivity

Corrosion-product transport, oxidation state and remedial measures

International Nuclear Information System (INIS)

Sawicki, J.A.; Brett, M.E.; Tapping, R.L.

1998-10-01

The issues associated with monitoring and controlling corrosion-product transport (CPT) in the balance-of-plant (BOP) and steam generators (SG) of CANDU stations are briefly reviewed. Efforts are focused on minimizing corrosion of carbon steel, which is used extensively in the CANDU primary and secondary systems. Emphasis is placed on the corrosion-product oxidation state as a monitor of water chemistry effectiveness and as a monitor of system corrosion effects. The discussion is based mostly on the results of observations from Ontario Hydro plants, and their comparisons with pressurized-water reactors. The effects of low oxygen and elevated hydrazine chemistry are reviewed, as well as the effects of layup and various startup conditions. Progress in monitoring electrochemical potential (ECP) at Ontario Hydro plants and its relationship to the oxidation state of corrosion products is reviewed. Observations on CPT on the primary side of SGs are also discussed. (author)

Solvothermal synthesis of tetravalent uranium with isophthalate or pyromellitate ligands

Energy Technology Data Exchange (ETDEWEB)

Falaise, Clement; Delille, Jason; Volkringer, Christophe; Loiseau, Thierry [Contribution from Unite de Catalyse et Chimie du Solide (UCCS) - UMR CNRS 8181, Universite de Lille, USTL-ENSCL, Villeneuve d' Ascq (France)

2015-06-15

Three new coordination polymers bearing tetravalent uranium have been isolated with the O-donor ligands such as isophthalate (1,3-bdc) or pyromellitate (btec). The compounds 1 and 3 have been solvothermally synthesized in N,N-dimethylformamide (DMF). The crystal structure of U(1,3-bdc){sub 2}(DMF) (1) is built up from discrete tricapped trigonal-primastic UO{sub 9} units, for which one carbonyl oxygen atom from DMF is bound to uranium. The connection of the UO{sub 9} units with the isophthalate linkers occurs in a chelating and bidentate fashion and gives rise to the formation of a 3D framework, delimiting narrow channels running along the [101] direction. Upon heating, the DMF molecules are removed, generating the second phase U(1,3-bdc){sub 2} (2) compound, closely related to 1. Indeed, the coordination environment of uranium is reduced to eight with a distorted square-antiprismatic geometry. This transition induces the relative shrinkage of the network (ΔV = 23 %). The structure of the compound U(btec)(DMF){sub 2} (3) also exhibits a 3D framework composed of an isolated bicapped square-antiprismatic UO{sub 10} unit, for which two carbonyl oxygen atoms from DMF are bonded to uranium. Pyromellitate ensures the connection of the UO{sub 10} units through the carboxylate arms in a chelating mode. This results in the formation of a network with diamond-shaped channels, developed along the c axis and encapsulating the DMF molecules. In contrast to 1, no stable phase is observed upon removing the DMF species by heating. (Copyright copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Generalized molybdenum oxide surface chemical state XPS determination via informed amorphous sample model

Energy Technology Data Exchange (ETDEWEB)

Baltrusaitis, Jonas, E-mail: job314@lehigh.edu [Department of Chemical Engineering, Lehigh University, B336 Iacocca Hall, 111 Research Drive, Bethlehem, PA 18015 (United States); PhotoCatalytic Synthesis group, MESA+ Institute for Nanotechnology, Faculty of Science and Technology, University of Twente, Meander 229, P.O. Box 217, 7500 AE Enschede (Netherlands); Mendoza-Sanchez, Beatriz [CRANN, Chemistry School, Trinity College Dublin, Dublin (Ireland); Fernandez, Vincent [Institut des Matériaux Jean Rouxel, 2 rue de la Houssinière, BP 32229, F-44322 Nantes Cedex 3 (France); Veenstra, Rick [PhotoCatalytic Synthesis group, MESA+ Institute for Nanotechnology, Faculty of Science and Technology, University of Twente, Meander 229, P.O. Box 217, 7500 AE Enschede (Netherlands); Dukstiene, Nijole [Department of Physical and Inorganic Chemistry, Kaunas University of Technology, Radvilenu pl. 19, LT-50254 Kaunas (Lithuania); Roberts, Adam [Kratos Analytical Ltd, Trafford Wharf Road, Wharfside, Manchester, M17 1GP (United Kingdom); Fairley, Neal [Casa Software Ltd, Bay House, 5 Grosvenor Terrace, Teignmouth, Devon TQ14 8NE (United Kingdom)

2015-01-30

Highlights: • We analyzed and modeled spectral envelopes of complex molybdenum oxides. • Molybdenum oxide films of varying valence and crystallinity were synthesized. • MoO{sub 3} and MoO{sub 2} line shapes from experimental data were created. • Informed amorphous sample model (IASM) developed. • Amorphous molybdenum oxide XPS envelopes were interpreted. - Abstract: Accurate elemental oxidation state determination for the outer surface of a complex material is of crucial importance in many science and engineering disciplines, including chemistry, fundamental and applied surface science, catalysis, semiconductors and many others. X-ray photoelectron spectroscopy (XPS) is the primary tool used for this purpose. The spectral data obtained, however, is often very complex and can be subject to incorrect interpretation. Unlike traditional XPS spectra fitting procedures using purely synthetic spectral components, here we develop and present an XPS data processing method based on vector analysis that allows creating XPS spectral components by incorporating key information, obtained experimentally. XPS spectral data, obtained from series of molybdenum oxide samples with varying oxidation states and degree of crystallinity, were processed using this method and the corresponding oxidation states present, as well as their relative distribution was elucidated. It was shown that monitoring the evolution of the chemistry and crystal structure of a molybdenum oxide sample due to an invasive X-ray probe could be used to infer solutions to complex spectral envelopes.

Controlling Hexavalent Americium – A Centerpiece to a Compact Nuclear Fuel Cycle

Energy Technology Data Exchange (ETDEWEB)

Shafer/Braley, Jenifer; Nash, Kenneth L; Lumetta, Gregg; McCann, Kevin; Sinkov, Sergey I

2014-10-01

Closing the nuclear fuel cycle could be simplified by recovering the actinides U through Am as a group. This could be achieved by converting U, Np, Pu and Am to the hexavalent state. Uranium, Np and Pu are readily oxidized to the hexavalent state. Generation of hexavalent Am in acidic solutions is more difficult, as the standard reduction potential of the Am(VI) /Am(III) couple (+1.68 V in 1 M HClO4) is well outside of the electrochemical stability window of water. While the oxidation and separation of Am has been demonstrated under laboratory conditions, several issues could plague scale up and implementation of this separation with used fuel. Two primary concerns are considered. The first issue concerns the stability of the oxidized Am. The second involves the undesirable co-extraction of tetravalent f-elements with the hexavalent actinides. To address the first concern regarding Am redox instability, Am reduction will be monitored under a variety of different conditions to establish the means of improving the stability of Am(VI) in the organic phase. Identifying the components contributing most significantly to its reduction will allow thoughtful modification of the process. To address the second concern, we propose to apply branched chain extractants to separate hexavalent actinides from tetravalent f-elements. Both branched monoamide and organophosphorus extractants have demonstrated significant selectivity for UO22+ versus Th4+, with separation factors generally on the order of 100. The efforts of this two-pronged research program should represent a significant step forward in the development of aqueous separations approaches designed to recover the U-Am actinides based on the availability of the hexavalent oxidation state. For the purposes of this proposal, separations based on this approach will be called SAn(VI) separations, indicating the Separation of An(VI).

The oxidation states of elements in pure and Ca-doped BiCuSeO thermoelectric oxides

International Nuclear Information System (INIS)

Hsiao, Chun-Lung; Qi, Xiaoding

2016-01-01

Bi 1−x Ca x CuSeO (x = 0–0.3) was synthesized at 650 °C in an air-tight system flowing with pure argon. The Ca doping resulted in an increase in the thermoelectric figure of merit (ZT) as the consequence of increased carrier concentration. X-ray photoelectron spectroscopy (XPS) was carried out to check the oxidation states in Bi 1−x Ca x CuSeO. The results indicated that in addition to the expected Bi 3+ and Cu 1+ , there existed Bi 2+ and Cu 2+ in the undoped BiCuSeO, whereas in the Ca-doped BiCuSeO, Bi 4+ , Cu 3+ and Cu 2+ were observed. The Ca dopant was confirmed to be in the 2+ oxidation state. Two broad peaks centered at 54.22 and 58.59 eV were recorded in the vicinity around the binding energy of Se 3d. The former is often observed in the Se-containing intermetallics while the latter is often found in the Se-containing oxides, indicating that along with the expected Se–Cu bonding, a bonding between Se and O may also exist. Based on the XPS results, the charge compensation mechanisms were proposed for Bi 1−x Ca x CuSeO, which may shed some light on the origins of charge carriers. BiCuSeO based oxides have recently be discovered to have a large ZT comparable to the best alloys currently in use, because of the large Seebeck coefficient and small thermal conductivity. However, their electrical conductivity is lower compared to the best thermoelectrics. This work may provide some hints for the further improvement of ZT in BiCuSeO based oxides. - Graphical abstract: The oxidation states, charge compensation mechanisms, and origins of charge carriers in Bi 1−x Ca x CuSeO thermoelectrics. Display Omitted

Corrosion-product transport, oxidation state and remedial measures

International Nuclear Information System (INIS)

Sawicki, J.A.; Brett, M.E.; Tapping, R.L.

1998-01-01

The issues associated with monitoring and controlling corrosion-product transport (CPT) in the balance-of-plant (BOP) and steam generators (SG) of CANDU stations are briefly reviewed. The efforts are focused on minimizing corrosion of carbon steel, which is used extensively in the CANDU primary and secondary systems. Emphasis is placed on the corrosion-product oxidation state as a monitor of water chemistry effectiveness, and as a monitor of system corrosion effects. The discussion is based mostly on the results and observations from Ontario Hydro plants, and their comparisons with PWRs. The effects of low oxygen and elevated hydrazine chemistry are reviewed, as well as the effects of lay-up and various start-up conditions. Progress in monitoring electrochemical potential (ECP) at Ontario Hydro plants and its relationship to the oxidation state of corrosion products is reviewed. Observations on corrosion-product transport on the primary side of steam generators are also discussed. (author)

Chemical ordering in substituted fluorite oxides: A computational investigation of Ho2 Zr2 O7 and RE2 Th2 O7 (RE=Ho, Y, Gd, Nd, La)

OpenAIRE

Solomon, JM; Shamblin, J; Lang, M; Navrotsky, A; Asta, M

2016-01-01

© 2016 The Author(s). Fluorite-structured oxides find widespread use for applications spanning nuclear energy and waste containment, energy conversion, and sensing. In such applications the host tetravalent cation is often partially substituted by trivalent cations, with an associated formation of charge-compensating oxygen vacancies. The stability and properties of such materials are known to be influenced strongly by chemical ordering of the cations and vacancies, and the nature of such ord...

99Tc and Re incorporated into metal oxide polyoxometalates: oxidation state stability elucidated by electrochemistry and theory.

Science.gov (United States)

McGregor, Donna; Burton-Pye, Benjamin P; Mbomekalle, Israel M; Aparicio, Pablo A; Romo, Susanna; López, Xavier; Poblet, Josep M; Francesconi, Lynn C

2012-08-20

The radioactive element technetium-99 ((99)Tc, half-life = 2.1 × 10(5) years, β(-) of 253 keV), is a major byproduct of (235)U fission in the nuclear fuel cycle. (99)Tc is also found in radioactive waste tanks and in the environment at National Lab sites and fuel reprocessing centers. Separation and storage of the long-lived (99)Tc in an appropriate and stable waste-form is an important issue that needs to be addressed. Considering metal oxide solid-state materials as potential storage matrixes for Tc, we are examining the redox speciation of Tc on the molecular level using polyoxometalates (POMs) as models. In this study we investigate the electrochemistry of Tc complexes of the monovacant Wells-Dawson isomers, α(1)-P(2)W(17)O(61)(10-) (α1) and α(2)-P(2)W(17)O(61)(10-) (α2) to identify features of metal oxide materials that can stabilize the immobile Tc(IV) oxidation state accessed from the synthesized Tc(V)O species and to interrogate other possible oxidation states available to Tc within these materials. The experimental results are consistent with density functional theory (DFT) calculations. Electrochemistry of K(7-n)H(n)[Tc(V)O(α(1)-P(2)W(17)O(61))] (Tc(V)O-α1), K(7-n)H(n)[Tc(V)O(α(2)-P(2)W(17)O(61))] (Tc(V)O-α2) and their rhenium analogues as a function of pH show that the Tc-containing derivatives are always more readily reduced than their Re analogues. Both Tc and Re are reduced more readily in the lacunary α1 site as compared to the α2 site. The DFT calculations elucidate that the highest oxidation state attainable for Re is VII while, under the same electrochemistry conditions, the highest oxidation state for Tc is VI. The M(V)→ M(IV) reduction processes for Tc(V)O-α1 are not pH dependent or only slightly pH dependent suggesting that protonation does not accompany reduction of this species unlike the M(V)O-α2 (M = (99)Tc, Re) and Re(V)O-α1 where M(V/IV) reduction process must occur hand in hand with protonation of the terminal M═O to

Potentiometric determination of uranium with cobalt (3) acetate as oxidimetric titrant

International Nuclear Information System (INIS)

Muhammad, H.; Ishrat, P.; Zyka, J.

1972-01-01

A potentiometric method for the determination of uranium through the reduction of hexavalent to tetravalent state and its potentiometric oxidation in 8 N sulphuric acid with standard cobalt (3)-acetate has been worked out. The method is quite accurate with the error not exceeding 1% for mg amounts. Moreover an apparatus for preservation of reduced solution of uranium and its delivery for titrations has been designed. The same apparatus can be used for reducing and preserving solutions of strong reducing titrants. (author)

Method of stripping plutonium from tributyl phosphate solution which contains dibutyl phosphate-plutonium stable complexes

International Nuclear Information System (INIS)

Ochsenfeld, W.; Schmieder, H.

1976-01-01

Fast breeder fuel elements which have been highly burnt-up are reprocessed by extracting uranium and plutonium into an organic solution containing tributyl phosphate. The tributyl phosphate degenerates at least partially into dibutyl phosphate and monobutyl phosphate, which form stable complexes with tetravalent plutonium in the organic solution. This tetravalent plutonium is released from its complexed state and stripped into aqueous phase by contacting the organic solution with an aqueous phase containing tetravalent uranium. 6 claims, 1 drawing figure

Predicting spent fuel oxidation states in a tuff repository

International Nuclear Information System (INIS)

Einziger, R.E.; Woodley, R.E.

1987-01-01

Nevada Nuclear Waste Storage Investigations Project (NNWSI) is studying the suitability of the tuffaceous rocks at Yucca Mountain as a waste repository for spent fuel disposal. The oxidation state of the LWR spent fuel in the moist air environment of a tuff repository could be a significant factor in determining its leaching and dissolution characteristics. Predictions as to which oxidation states would be present are important in analyzing such a repository and thus the present study was undertaken. A set of TGA (thermogravimetric analysis) tests were conducted on well-controlled samples of irradiated PWR fuel with time and temperature as the only variables. The tests were conducted between 140 and 225 0 C for a duration up to 2200 hours. The weight gain curves were analyzed in terms of diffusion through a layer of U 3 O 7 , diffusion into the grains to form a solid solution, a simplified empirical representation of a combination of grain boundary diffusion and bulk grain oxidation. Reaction rate constants were determined in each case, but analysis of these data could not establish a definitive mechanism. 21 refs., 10 figs., 3 tabs

Speciation of 239U and 239Np by high performance liquid chromatography

International Nuclear Information System (INIS)

Almahamid, Ilham

1990-01-01

The objective of this research thesis is to contribute to a better knowledge of chemical effects associated with nuclear transformations of 238 U(n, γ) 239 U(β) and 239 Np in different uranium salts in solid state or aqueous solutions. A method of separation of tetravalent and hexavalent uranium and of tetravalent and pentavalent neptunium has been developed. The best separations have been obtained by using an equimolar aqueous solution of nitric acid and oxalic acid with elution durations between 2 and 9 minutes. Several uranyl and uranium compounds have been irradiated and the distribution of 239 U and 239 Np depending on the oxidation level has been measured with respect to the nature of the irradiated compound, to the irradiation duration, and to the composition of the dissolution medium. The stabilisation of 239 U and 239 Np is discussed in terms of chemical forces, mechanical recoil, and localised radiolysis due to Auger electrons [fr

A tetravalent vaccine comprising hexon-chimeric adenoviruses elicits balanced protective immunity against human adenovirus types 3, 7, 14 and 55.

Science.gov (United States)

Tian, Xingui; Jiang, Zaixue; Fan, Ye; Qiu, Shuyan; Zhang, Ling; Li, Xiao; Zhou, Zhichao; Liu, Tiantian; Ma, Qiang; Lu, Xiaomei; Zhong, Baimao; Zhou, Rong

2018-04-04

Human adenovirus (Ad) species B contains several of the most important types associated with acute respiratory diseases, Ad3, -7, -14 and -55, which often lead to severe lower respiratory tract diseases and epidemic outbreaks. However, there is currently no Ad vaccine approved for general use. The major capsid protein, hexon, is the primary determinant recognized by neutralizing antibodies (NAbs). In this study, four recombinant Ads that have the same genome sequence as Ad3 with the exception of the hexon genes, rAd3EGFP, rAd3H7, rAd3H14 and rAd3H55, were combined as a tetravalent Ad candidate vaccine against Ad3, -7, -14 and -55. The replication efficiencies of chimeric rAd3H14, rAd3H7 and rAd3H55 were similar to that of rAd3EGFP. Recombinant rAd3EGFP, rAd3H7, rAd3H14 and rAd3H55 induced high titers of NAbs against Ad3, -7, -14 and -55, respectively, which were comparable to those induced by wild-type Ads. The mixture of the four recombinant Ads in equal proportions, rAdMix, or rAdMix inactivated by β-propiolactone, induced balanced NAb responses against Ad3, -7, -14 and -55 in mice without reciprocal immunological interference. In co-culture the four recombinant Ads replicated with a similar efficiency without reciprocal inhibition, and the progeny virions may be chimeric. Purified co-culture, rAdMix-C, also elicited balanced immune responses, suggesting a simple method for multivalent vaccine production. These results indicate the possible advantage of the four Ads as a live combined vaccine. Importantly, pre-immunization with rAdMix conferred protection against Ad3, -7, -14 or -55 challenge in mice in vivo. Thus, this research provides a novel tetravalent Ad vaccine candidate against Ad3, -7, -14 and -55. Copyright © 2018 Elsevier B.V. All rights reserved.

Investigation of the oxidation states of Pu isotopes in a hydrochloric acid solution

Energy Technology Data Exchange (ETDEWEB)

Lee, M.H. [Nuclear Chemistry Research Division, Korea Atomic Energy Research Institute, P. O. Box 105, Yuseong, Daejeon 305-353 (Korea, Republic of)], E-mail: mhlee@kaeri.re.kr; Kim, J.Y.; Kim, W.H.; Jung, E.C.; Jee, K.Y. [Nuclear Chemistry Research Division, Korea Atomic Energy Research Institute, P. O. Box 105, Yuseong, Daejeon 305-353 (Korea, Republic of)

2008-12-15

The characteristics of the oxidation states of Pu in a hydrochloric acid solution were investigated and the results were applied to a separating of Pu isotopes from IAEA reference soils. The oxidation states of Pu(III) and Pu(IV) were prepared by adding hydroxylamine hydrochloride and sodium nitrite to a Pu stock solution, respectively. Also, the oxidation state of Pu(VI) was adjusted with concentrated HNO{sub 3} and HClO{sub 4}. The stability of the various oxidation states of plutonium in a HCl solution with elapsed time after preparation were found to be in the following order: Pu(III){approx}Pu(VI)>Pu(IV)>Pu(V). The chemical recoveries of Pu(IV) in a 9 M HCl solution with an anion exchange resin were similar to those of Pu(VI). This method for the determination of Pu isotopes with an anion exchange resin in a 9 M HCl medium was applied to IAEA reference soils where the activity concentrations of {sup 239,240}Pu and {sup 238}Pu in IAEA-375 and IAEA-326 were consistent with the reference values reported by the IAEA.

Selective hydrodeoxygenation of cyclic vicinal diols to cyclic alcohols over tungsten oxide-palladium catalysts.

Science.gov (United States)

Amada, Yasushi; Ota, Nobuhiko; Tamura, Masazumi; Nakagawa, Yoshinao; Tomishige, Keiichi

2014-08-01

Hydrodeoxygenation of cyclic vicinal diols such as 1,4-anhydroerythritol was conducted over catalysts containing both a noble metal and a group 5-7 transition-metal oxide. The combination of Pd and WOx allowed the removal of one of the two OH groups selectively. 3-Hydroxytetrahydrofuran was obtained from 1,4-anhydroerythritol in 72 and 74% yield over WOx -Pd/C and WOx -Pd/ZrO2 , respectively. The WOx -Pd/ZrO2 catalyst was reusable without significant loss of activity if the catalyst was calcined as a method of regeneration. Characterization of WOx -Pd/C with temperature-programmed reduction, X-ray diffraction, and transmission electron microscopy/energy-dispersive X-ray spectroscopy suggested that Pd metal particles approximately 9 nm in size were formed on amorphous tungsten oxide particles. A reaction mechanism was proposed on the basis of kinetics, reaction results with tungsten oxides under an atmosphere of Ar, and density functional theory calculations. A tetravalent tungsten center (W(IV) ) was formed by reduction of WO3 with the Pd catalyst and H2 , and this center served as the reductant for partial hydrodeoxygenation. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

In situ oxidation state profiling of nickel hexacyanoferrate derivatized electrodes using line-imaging Raman spectroscopy and multivariate calibration

International Nuclear Information System (INIS)

Haight, S.M.; Schwartz, D.T.

1999-01-01

Metal hexacyanoferrate compounds show promise as electrochemically switchable ion exchange materials for use in the cleanup of radioactive wastes such as those found in storage basins and underground tanks at the Department of Energy's Hanford Nuclear Reservation. Reported is the use of line-imaging Raman spectroscopy for the in situ determination of oxidation state profiles in nickel hexacyanoferrate derivatized electrodes under potential control in an electrochemical cell. Line-imaging Raman spectroscopy is used to collect 256 contiguous Raman spectra every ∼5 microm from thin films (ca. 80 nm) formed by electrochemical derivatization of nickel electrodes. The cyanide stretching region of the Raman spectrum of the film is shown to be sensitive to iron oxidation state and is modeled by both univariate and multivariate correlations. Although both correlations fit the calibration set well, the multivariate (principle component regression or PCR) model's predictions of oxidation state are less sensitive to noise in the spectrum, yielding a much smoother oxidation state profile than the univariate model. Oxidation state profiles with spatial resolution of approximately 5 microm are shown for a nickel hexacyanoferrate derivatized electrode in reduced, intermediate, and oxidized states. In situ oxidation state profiles indicate that the 647.1 nm laser illumination photo-oxidizes the derivatized electrodes. This observation is confirmed using photoelectrochemical methods

Superconducting state parameters of monovalent and polyvalent amorphous

Energy Technology Data Exchange (ETDEWEB)

Sonvane, Y. A., E-mail: yas@ashd.svnit.ac.in [Department of Applied Physics, S. V. National Institute of Technology, Surat 395 007, Gujarat (India); Patel, H. P., E-mail: patel.harshal2@gmail.com; Thakor, P. B., E-mail: pbthakor@rediffmail.com [Department of Physics, Veer Narmad South Gujarat University, Surat 395 007, Gujarat (India)

2015-08-28

In the present study deals, we have calculated superconducting state parameter (SSP) like electron-phonon coupling strength λ, coulomb pseudo potential, μ*, transition temperature Tc, isotope effect exponent α and effective interaction strength N{sub 0}V of monovalent (Li), divalent (Zn), trivalent (In) and tetravalent (Pb) amorphous. To carry out this work we have used our newly constructed model pseudo potential to describe electron ion interaction along with three different local field correction functions like Hartree, Taylor and Sarkar et al. The present results are found in good agreement with other available theoretical as well as experimental data.

Solid oxide fuel cells fueled with reducible oxides

Science.gov (United States)

Chuang, Steven S.; Fan, Liang Shih

2018-01-09

A direct-electrochemical-oxidation fuel cell for generating electrical energy includes a cathode provided with an electrochemical-reduction catalyst that promotes formation of oxygen ions from an oxygen-containing source at the cathode, a solid-state reduced metal, a solid-state anode provided with an electrochemical-oxidation catalyst that promotes direct electrochemical oxidation of the solid-state reduced metal in the presence of the oxygen ions to produce electrical energy, and an electrolyte disposed to transmit the oxygen ions from the cathode to the solid-state anode. A method of operating a solid oxide fuel cell includes providing a direct-electrochemical-oxidation fuel cell comprising a solid-state reduced metal, oxidizing the solid-state reduced metal in the presence of oxygen ions through direct-electrochemical-oxidation to obtain a solid-state reducible metal oxide, and reducing the solid-state reducible metal oxide to obtain the solid-state reduced metal.

Biodistribution and safety of a live attenuated tetravalent dengue vaccine in the cynomolgus monkey.

Science.gov (United States)

Ravel, Guillaume; Mantel, Nathalie; Silvano, Jeremy; Rogue, Alexandra; Guy, Bruno; Jackson, Nicholas; Burdin, Nicolas

2017-10-13

The first licensed dengue vaccine is a recombinant, live, attenuated, tetravalent dengue virus vaccine (CYD-TDV; Sanofi Pasteur). This study assessed the biodistribution, shedding, and toxicity of CYD-TDV in a non-human primate model as part of the nonclinical safety assessment program for the vaccine. Cynomolgus monkeys were given one subcutaneous injection of either one human dose (5log 10 CCID 50 /serotype) of CYD-TDV or saline control. Study endpoints included clinical observations, body temperature, body weight, food consumption, clinical pathology, immunogenicity, and post-mortem examinations including histopathology. Viral load, distribution, persistence, and shedding in tissues and body fluids were evaluated by quantitative reverse transcriptase polymerase chain reaction. The subcutaneous administration of CYD-TDV was well tolerated. There were no toxicological findings other than expected minor local reactions at the injection site. A transient low level of CYD-TDV viral RNA was detected in blood and the viral genome was identified primarily at the injection site and in the draining lymph nodes following immunization. These results, together with other data from repeat-dose toxicity and neurovirulence studies, confirm the absence of toxicological concern with CYD-TDV and corroborate clinical study observations. Copyright © 2017 Elsevier Ltd. All rights reserved.

Multifunctional organophosphorus extractants: a status report on development and applications

International Nuclear Information System (INIS)

Schulz, W.W.; Horwitz, E.P.

1988-01-01

Up-to-date state of the development of science and technology of multifunctional organophosphorus extractants is considered. The detailed classification of these extractants is presented. They attracted pasticular interest because of affinity of some bifunctional phosphonates, phosphine oxides, carbamoylalkylphosphonates to trivalent Am, tetravalent and hexavalent actinides, trivalent lanthanides in strong mineral acids, and because of ability of some alkylpyrophosphoric acids to extract effectively U(4) from concentrated solutions of phosphoric acid. Application of these extractants for analytic purposes and in the field of nuclear technology is considered

Clinical, serological and echocardiographic examination of healthy field dogs before and after vaccination with a commercial tetravalent leptospirosis vaccine.

Science.gov (United States)

Spiri, Andrea M; Rodriguez-Campos, Sabrina; Matos, José M; Glaus, Tony M; Riond, Barbara; Reusch, Claudia E; Hofmann-Lehmann, Regina; Willi, Barbara

2017-05-25

Leptospirosis is a re-emerging bacterial zoonosis caused by spirochetes of the genus Leptospira. Severe disease has been reported in dogs in Europe despite vaccination with bivalent Leptospira vaccines. Recently, a tetravalent canine Leptospira vaccine (Nobivac® L4) was licenced in Europe. The goal of this study was to investigate clinical signs, microscopic agglutination test (MAT) titres, haematology, blood biochemistry, cardiac (c) Troponin I levels and echocardiography before and after vaccination with this tetravalent vaccine. Forty-eight healthy dogs were prospectively enrolled and vaccinated twice, 3-4 weeks apart (T0 and T1). Before vaccination (T0) and 16-31 days after the second vaccination (T2), MAT (n = 48), haematology (n = 48), blood biochemistry (n = 36) and cTroponin I measurements (n = 29) were performed, and MAT was repeated 347-413 days after the second vaccination (T3, n = 44). Echocardiography was performed before the first and second vaccination (T0 and T1, n = 24). Mild and transient clinical signs within 5 days following the first and second vaccination occurred in 23% and 10% of the dogs, respectively. Before the first vaccination (T0), all dogs showed negative MAT titres for the tested serovars except for Canicola (50% with titres 100-400). At T2, positive MAT titres to the serovars Canicola (100%), Australis (89%), Grippotyphosa (86%), Bratislava (60%), Autumnalis (58%), Copenhageni (42%), Pomona (12%), Pyrogenes (8%) and Icterohaemorrhagiae (2%) were found. Median to high titres (≥ 400) were most common to the serovar Canicola (92%) and less common to the serovars Australis (41%), Grippotyphosa (21%), Bratislava (12%), Autumnalis (4%), Pyrogenes (4%) and Pomona (2%). At T3, positive MAT titres (titre range: 100-400) were found in 2-18% of the dogs to serovars of the vaccine serogroups and in 2-18% of the dogs to the non-vaccine serovars Pomona, Autumnalis, Pyrogenes and Ballum. Haematology, blood biochemistry, c

Acid Dissolution of Depleted Uranium from Catalyst using Microwave

Energy Technology Data Exchange (ETDEWEB)

Sung, Jin Hyun; Jeong, Seong Gi; Park, Kwang Heon [Kyunghee University, Yongin (Korea, Republic of)

2011-05-15

The separation process of uranium is one of the most important fields in nuclear industry because uranium is used primary in nuclear power plants. Uranium ores are treated by either acid or alkaline reagents. Uranium can be dissolved by acid or alkaline solutions. There are two oxidation states in which the hexavalent form, the oxide of which is UO{sub 3}, and the tetravalent form, the oxide of which is UO{sub 2}. However, depleted uranium(DU) has also been used as a catalyst in specialized chemical reaction such as ammoxidation. The preferred catalyst for propylene oxidation with ammonia was a uranium oxide-antimony oxide composition. The active phase of catalyst was known as USbO{sub 5} and USb{sub 3}O{sub 10}. There is pentavalent form. Waste catalyst containing DU was generated and stored in chemical industry. In this work, we removed DU from catalyst by acid dissolution

Plutonium uptake by Scenedesmus obliquus as a function of isotope and oxidation state

International Nuclear Information System (INIS)

Tkacik, M.F.; Giesy, J.P.; Wilhite, E.L.; Corey, J.C.

1979-01-01

Uptake of 238 Pu 4+ , 238 Pu 6+ , 239 Pu 4+ and 239 Pu 6+ by the green alga Scenedesmus obliquus (Turp) Kutz was studied to determine whether isotope or oxidation state differences affect Pu uptake from aqueous medium by algal cells. At equivalent 238 Pu and 239 PU concentrations, even when initial oxidation states differed, accumulations of these isotopes by S.obliquus were not significantly (p>0.05) different. Plutonium accumulation by S.obliquus was log-linear. (author)

Investigation of plutonium-239 conditioning in monazite and brabantite matrices: Synthesis and characterization

Energy Technology Data Exchange (ETDEWEB)

Glorieux, B.; Jorion, F.; Montel, J.M.; Matecki, M.; Deschanels, X.; Coutures, JP

2004-07-01

In response to the 1991 French radioactive waste management act, a research program was set up between the CNRS, the CEA and French universities to propose effective minor actinide disposal matrices capable of loading 10 wt% of actinide oxides and ensuring a hundred-fold better leaching performance than 'R7T7' glass. The lanthanide ortho-phosphates LaPO{sub 4} could constitute an excellent matrix for this purpose. In this type of structure, the (PO{sub 4}){sup 3-} negative entity is compensated by trivalent cations such as La, Ce, Gd, Pu, Am (monazite) or equal fractions of divalent and tetravalent cations such as Ca{sup 2+}Th{sup 4+}, Ca{sup 2+}U{sup 4+}, Ca{sup 2+}Np{sup 4+} (brabantite). Previous leach tests and geological discoveries have shown that these materials are highly resistant to leaching and conserve their crystalline state even in aqueous media. These points led us to investigate the incorporation of 10 wt% PuO{sub 2} in monazite and brabantite materials and to study the effects of self-irradiation on their structural states. Prior to plutonium conditioning tests, experiments were performed in the laboratory using cerium and thorium oxides according to the following reactions: (1-3x)LaPO{sub 4} + 2xCe{sup 4+}O{sub 2} + xLa(PO{sub 3}){sub 3} {yields} La{sub 1-2x}Ce{sub 2x}{sup 3+}PO{sub 4} + x/2O{sub 2}; (1-3x)LaPO{sub 4} + xTh{sup 4+}O{sub 2} + xCaO + xLa(PO{sub 3}){sub 3} {yields} La{sub 1-2x}Ca{sub x}Th{sub x}{sup 4+}PO{sub 4}. Cerium oxide was used to study the reduction of a tetravalent cation to a trivalent state in a phosphate structure and to prepare for Pu{sup 3+} conditioning. Thorium was used to study the conditioning of tetravalent cations such as Pu{sup 4+}. The parameters and sintering reaction of the final product were optimized. In a radioactive laboratory, PuO{sub 2} was then substituted for CeO{sub 2} and ThO{sub 2} in the first and second reactions mentioned above, respectively. The synthesis and sintering procedures were

Oxidation states of Fe in LaNi1-xFexO3

International Nuclear Information System (INIS)

Goeta, A.E.; Falcon, H.; Carbonio, R.

1994-01-01

The distribution of oxidation states in perovskites of the type LaA 1-x B x O 3 (A and B transition metal ions) can be ''tailored'' by x variation. In particular, in LaNiO 3 it has been shown that Fe substitution for Ni foces some Ni 3+ into Ni 2+ , while some Fe 3+ changes into the unusual Fe 4+ state. In addition, the existence of mixed oxidation states of Fe and/or Ni in LaNi 1-x Fe x O 3 has been related to its catalytic activity in hydrogen peroxide decomposition. The Fe 4+ population, obtained using Moessbauer spectroscopy, was found to be constant for all the analyzed annealing temperatures for x = 0.25 concentration, where the isomer shift difference for both states is the highest and the catalytic activity is maximum. (orig.)

The oxidation state of sulfur in apatite: A new oxybarometer?

Science.gov (United States)

Fiege, A.; Konecke, B.; Kim, Y.; Simon, A. C.; Becker, U.; Parat, F.

2016-12-01

Oxygen fugacity (fO2) of magmatic and hydrothermal systems influences, for instance, crystallization and degassing processes as well as metal solubilities in melts and fluids. Apatite is a ubiquitous mineral in magmatic and hydrothermal environments that can record and preserve volatile zonation. It can contain several thousand μg/g of the redox sensitive element sulfur (S), making S-in-apatite a potential fO2 sensor. Despite the polyvalent properties of S (e.g., S2-, S4+, S6+), the oxidation state and incorporation mechanisms of S in the apatite structure are poorly understood. In this study, the oxidation state of S-in-apatite as a function of fO2 is investigated using X-ray absorption near-edge structures (XANES) spectroscopy at the S K-edge. Apatites crystallized from lamproitic melts at 1000°C, 300 MPa and over a broad range of fO2 and sulfur fugacities (fS2) were measured. Peaks corresponding to S6+ ( 2482 eV), S4+ ( 2478 eV) and S2- ( 2470 eV) were identified in apatite. The integrated S6+/STotal (STotal = S6+ + S4+ + S2-) peak area ratios show a distinct positive correlation with fO2, increasing from 0.17 at FMQ+0 to 0.96 at FMQ+3. Ab-initio calculations were performed to further understand the energetics and geometry of incorporation of S6+, S4+ and S2- into the apatite (F-, Cl-, OH-) end-members. The results confirm that apatite can contain three different oxidations states of S (S6+, S4+, S2-) as a function of fO2. This makes apatite probably the first geologically relevant mineral to incorporate reduced (S2-), intermediate (S4+), and oxidized (S6+) S in variable proportions. We emphasize that the strong dependence of the S oxidation state in apatite as a function of fO2 is also coupled with changing S content of apatite and co-existing melt (i.e., with changing fS2), resulting in a complex correlation between [1] apatite-melt (or fluid) partitioning, [2] redox conditions and [3] the melt and/or fluid composition, making the application of previously

X-ray absorption spectroscopic study of trivalent and tetravalent actinides in solution at varying pH values

Energy Technology Data Exchange (ETDEWEB)

Brendebach, B.; Banik, N.L.; Marquardt, C.M.; Rothe, J.; Denecke, M.A.; Geckeis, H. [Forschungszentrum Karlsruhe (Germany). Inst. fuer Nukleare Entsorgung

2009-07-01

We perform X-ray absorption spectroscopy (XAS) investigations to monitor the stabilization of redox sensitive trivalent and tetravalent actinide ions in solution at acidic conditions in a pH range from 0 to 3 after treatment with holding reductants, hydroxylamine hydrochloride (NH{sub 2}OHHCl) and Rongalite (sodium hydroxymethanesulfinate, CH{sub 3}NaO{sub 3}S). X-ray absorption near edge structure (XANES) measurements clearly demonstrate the stability of the actinide species for several hours under the given experimental conditions. Hence, structural parameters can be accurately derived by extended X-ray absorption fine structure (EXAFS) investigations. The coordination structure of oxygen atoms belonging to water ligands surrounding the actinide ions does not change with increasing pH value (approximately 11 O atoms at 2.42 A in the case of U(IV) at pH 1, 9 0 atoms at 2.52 A for Np(III) at pH 1.5, and 10 O atoms at 2.49 A for Pu(III) up to pH 3), indicating that hydrolysis reactions are suppressed under the given chemical conditions. (orig.)

Safety and Immunogenicity of a Tetravalent Dengue Vaccine Candidate in Healthy Children and Adults in Dengue-Endemic Regions: A Randomized, Placebo-Controlled Phase 2 Study.

Science.gov (United States)

Sirivichayakul, Chukiat; Barranco-Santana, Elizabeth A; Esquilin-Rivera, Inés; Oh, Helen M L; Raanan, Marsha; Sariol, Carlos A; Shek, Lynette P; Simasathien, Sriluck; Smith, Mary Kathryn; Velez, Ivan Dario; Wallace, Derek; Gordon, Gilad S; Stinchcomb, Dan T

2016-05-15

A safe, effective tetravalent dengue vaccine is a global health priority. The safety and immunogenicity of a live attenuated, recombinant tetravalent dengue vaccine candidate (TDV) were evaluated in healthy volunteers from dengue-endemic countries. This multicenter, double-blind, phase 2 study was conducted in Puerto Rico, Colombia, Singapore, and Thailand. During stage I, 148 volunteers aged 1.5-45 years were sequentially enrolled into 4 age-descending groups and randomized at a ratio of 2:1 to receive TDV or placebo. In stage II (group 5), 212 children aged 1.5-11 years were randomized at a ratio of 3:1 to receive TDV or placebo. Participants received a subcutaneous injection of TDV or placebo on days 0 and 90 and were followed for analysis of safety, seropositivity, and neutralizing antibodies to DENV-1-4. Injection site pain, itching, and erythema (mostly mild) were the only solicited adverse events more frequently reported with TDV than with placebo in all age groups. After 2 TDV doses, seropositivity was >95% in all 5 groups for DENV-1-3 and 72.7%-100% for DENV-4; geometric mean titers ranged from 582 to 1187 for DENV-1, from 582 to 1187 for DENV-2, from 196 to 630 for DENV-3, and from 41 to 210 for DENV-4 among the 5 groups. TDV was well tolerated and immunogenic in volunteers aged 1.5-45 years, irrespective of prevaccination dengue exposure. © The Author 2015. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mailjournals.permissions@oup.com.

Influence of microorganisms on the oxidation state distribution of multivalent actinides under anoxic conditions

International Nuclear Information System (INIS)

Reed, Donald Timothy; Borkowski, Marian; Lucchini, Jean-Francois; Ams, David; Richmann, M.K.; Khaing, H.; Swanson, J.S.

2010-01-01

The fate and potential mobility of multivalent actinides in the subsurface is receiving increased attention as the DOE looks to cleanup the many legacy nuclear waste sites and associated subsurface contamination. Plutonium, uranium and neptunium are the near-surface multivalent contaminants of concern and are also key contaminants for the deep geologic disposal of nuclear waste. Their mobility is highly dependent on their redox distribution at their contamination source as well as along their potential migration pathways. This redox distribution is often controlled, especially in the near-surface where organic/inorganic contaminants often coexist, by the direct and indirect effects of microbial activity. Under anoxic conditions, indirect and direct bioreduction mechanisms exist that promote the prevalence of lower-valent species for multivalent actinides. Oxidation-state-specific biosorption is also an important consideration for long-term migration and can influence oxidation state distribution. Results of ongoing studies to explore and establish the oxidation-state specific interactions of soil bacteria (metal reducers and sulfate reducers) as well as halo-tolerant bacteria and Archaea for uranium, neptunium and plutonium will be presented. Enzymatic reduction is a key process in the bioreduction of plutonium and uranium, but co-enzymatic processes predominate in neptunium systems. Strong sorptive interactions can occur for most actinide oxidation states but are likely a factor in the stabilization of lower-valent species when more than one oxidation state can persist under anaerobic microbiologically-active conditions. These results for microbiologically active systems are interpreted in the context of their overall importance in defining the potential migration of multivalent actinides in the subsurface.

Initial oxidation of TiFe1−xMnx (x = 0–0.3) by low dose exposures to H2O and O2

International Nuclear Information System (INIS)

Shwartz, A.; Shamir, N.; Froumin, N.; Zalkind, S.; Edry, I.; Haim, A.; Mintz, M.H.

2014-01-01

Highlights: • Thermodynamics of adsorption and initial oxidation of TiFe 1−x Mn x by H 2 O versus O 2 . • Explanation of different oxide formations. • Explanation of the role of the different constituents of the alloys in the processes. - Abstract: The very initial room-temperature oxidation processes of the ternary pseudo-binary TiFe 1−x Mn x (x = 0–0.3) intermetallics by trace amounts of H 2 O vapor and O 2 were studied utilizing XPS and AES techniques. Different reactivities of the two gases were obtained, with a lower oxidation ability of H 2 O, relative to O 2 , as anticipated from thermodynamic considerations. The exposure to O 2 results in a two stage oxidation of the Ti ingredient, which first converts into a divalent TiO (up to exposures of about 2 L), then proceeds into a tetravalent TiO 2 form. Unlike oxygen, water exposure produces only the divalent oxide through the whole exposure range studied (11 L). The Mn component in these compounds is oxidized only by O 2 and not by H 2 O. The Fe ingredient is not oxidized at all and remains in its metallic form up to exposures of 30 L

Evaluation of several novel diamide based ligands for selective extraction of tetravalent plutonium

Energy Technology Data Exchange (ETDEWEB)

Sivaramakrishna, Mallampalli; Nayak, Shashikant K. [Heavy Water Board, V.S. Bhavan, Mumbai (India); Raut, Dhaval R.; Mohapatra, Prasanta K. [Bhabha Atomic Research Center, Mumbai (India). Radiochemistry Division; Nayak, Sandip K. [Bhabha Atomic Research Center, Mumbai (India). Bioorganic Division

2017-06-01

The present paper describes the selective extraction of tetravalent plutonium employing several diamide ligands containing aromatic spacer groups. The ligands containing two amide functional groups attached to a 2,4,6-tri-phenyl pyridine moiety with different substituents viz.; L{sub I} (iso-butyl), L{sub II}(n-butyl), L{sub III}(n-octyl), L{sub IV} (2-ethylhexyl) at the amidic nitrogen atom were evaluated for the extraction of Pu(IV) using their nitrobenzene solutions. The distribution ratio values of Pu(IV) with the diamide ligands followed the order: L{sub II}>L{sub I}>L{sub III}>L{sub IV} and were significantly higher than those of metal ions such as Cs(I), Sr(II), Am(III) and Eu(III). The distribution ratio values of U(VI) were about 2-3 orders magnitude lower than those of Pu(IV). The extraction and stripping kinetics were found to be moderately fast and it took less than 30 min (less than 5 min for L{sub I} and L{sub IV}) to obtain equilibrium D values. The extraction was found to be increasing with the aqueous phase nitric acid concentration conforming to a solvation mechanism of extraction. The extracted species contained two ligand molecules for L{sub I} and L{sub II} while monosolvates were observed for the other two extractants. The ligands showed good radiation stability up to an absorbed dose of 630 kGy.

Tetravalent Dengue Vaccine: A Review in the Prevention of Dengue Disease.

Science.gov (United States)

Scott, Lesley J

2016-09-01

Tetravalent, live-attenuated, dengue vaccine (Dengvaxia(®); CYD-TDV) is the first vaccine approved for the prevention of dengue disease caused by dengue virus (DENV) serotypes 1-4 in individuals aged 9-45 or 9-60 years living in high dengue endemic areas. This narrative review discusses the immunogenicity, protective efficacy, reactogenicity and safety of CYD-TDV in the prevention of dengue disease. In Latin American and Asian phase 3 trials in children and adolescents (n > 30,000), the recommended three-dose CYD-TDV regimen was efficacious in preventing virologically-confirmed dengue (VCD) during the period from 28 days after the last dose (month 13) to month 25, meeting the primary endpoint criteria. Protective efficacy against VCD in the respective individual trials was 60.8 and 56.5 % (primary analysis). During the 25-month active surveillance phase, CYD-TDV also provided protective efficacy against VCD, severe dengue, any grade of dengue haemorrhagic fever and VCD-related hospitalization in children aged 9 years and older. CYD-TDV was generally well tolerated, with no safety concerns identified after up to 4 years' follow-up (i.e. from post dose 1) in ongoing long-term studies. Based on evidence from the dengue clinical trial program, the WHO SAGE recommended that countries with high dengue endemicity consider introducing CYD-TDV as part of an integrated disease prevention strategy to lower disease burden. Pharmacoeconomic considerations will be pivotal to implementing dengue vaccination prevention strategies in these countries. The availability of a dengue vaccine is considered essential if the 2012 WHO global strategy targets for reducing the burden of dengue disease by 2020 are to be attained. Hence, CYD-TDV represents a major advance for the prevention of dengue disease in high dengue endemic regions.

Conformational Toggling of Yeast Iso-1-Cytochrome c in the Oxidized and Reduced States

Science.gov (United States)

Yang, Zhongzheng; Zhu, Jing; Ying, Tianlei; Jiang, Xianwang; Zhang, Xu; Wu, Houming; Liu, Maili; Tan, Xiangshi; Cao, Chunyang; Huang, Zhong-Xian

2011-01-01

To convert cyt c into a peroxidase-like metalloenzyme, the P71H mutant was designed to introduce a distal histidine. Unexpectedly, its peroxidase activity was found even lower than that of the native, and that the axial ligation of heme iron was changed to His71/His18 in the oxidized state, while to Met80/His18 in the reduced state, characterized by UV-visible, circular dichroism, and resonance Raman spectroscopy. To further probe the functional importance of Pro71 in oxidation state dependent conformational changes occurred in cyt c, the solution structures of P71H mutant in both oxidation states were determined. The structures indicate that the half molecule of cyt c (aa 50–102) presents a kind of “zigzag riveting ruler” structure, residues at certain positions of this region such as Pro71, Lys73 can move a big distance by altering the tertiary structure while maintaining the secondary structures. This finding provides a molecular insight into conformational toggling in different oxidation states of cyt c that is principle significance to its biological functions in electron transfer and apoptosis. Structural analysis also reveals that Pro71 functions as a key hydrophobic patch in the folding of the polypeptide of the region (aa 50–102), to prevent heme pocket from the solvent. PMID:22087268

Synthesis and characterization of ruthenium fluorides and oxide fluorides with high oxidation states

International Nuclear Information System (INIS)

Meublat, L.

1989-10-01

The synthesis of ruthenium fluorides and oxide fluorides with high oxidation states was attempted from dioxide RuO 2 and tetroxide RuO 4 . Three fluorinating agents were used: fluorine, chlorine trifluoride and krypton difluoride. The reactions were achieved in anhydrous hydrogen fluoride at room temperature. Thus, the reaction of RuO 4 with CIF 3 enabled us to prepare chloryl hexafluororuthenate (V), CIO 2 + RuF 6 - , a new compound well identified by vibrational spectroscopy (infra-red and Raman), the structure of which was determined. The reaction of KrF 2 with RuO 4 gave the oxide tetrafluoride RuOF 4 , the previously published syntheses and properties of which were not in agreement with each other. This compound was definitely characterized here by chemical analysis, infra-red spectroscopy and X-ray powder diffraction. The product of thermal decomposition (70 0 C) of RuOF 4 is presumably RuF 4 since only oxygen is liberated during this decomposition. At last, the reaction of KrF 2 with RuO 2 probably leads to the formation of the new oxide fluoride RuO 2 F 4 . Indeed, no oxygen is given off during this reaction, the chemical analysis of the red-orange coloured solid residue is almost in agreement with the one proposed and its infra-red absorption spectrum indicates the presence of ruthenium-oxygen and ruthenium-terminal and bridging fluorine bonds [fr

Synthesis and characterization of ruthenium fluorides and oxide fluorides with high oxidation states

International Nuclear Information System (INIS)

Meublat, L.

1989-01-01

The synthesis of ruthenium fluorides and oxide fluorides with high oxidation states was attempted from dioxide RuO 2 and tetroxide RuO 4 . Three fluorinating agents were used: fluorine, chlorine trifluoride and krypton difluoride. The reactions were achieved in anhydrous hydrogen fluoride at room temperature. Thus, the reaction of RuO 4 with CIF 3 enabled us to prepare chloryl hexafluororuthenate (V), ClO 2 + RuF 6 - , a new compound well idendified by vibrational spectroscopy (infra-red and Raman), the structure of which was determined. The reaction of KrF 2 with RuO 4 gave the oxide tetrafluoride RuOF 4 , the previously published syntheses and properties of which were not in agreement with each other. This compound was definitely characterized here by chemical analysis, infra-red spectroscopy and X-ray powder diffraction. The product of thermal decomposition (70 0 C) of RuOF 4 is presumably RuF 4 since only oxygen is liberated during this decomposition. At last, the reaction of KrF 2 with RuO 2 probably leads to the formation of the new oxide fluoride RuO 2 F 4 . Indeed, no oxygen is given off during this reaction, the chemical analysis of the red-orange coloured solid residue is almost in agreement with the one proposed and its infra-red absorption spectrum indicates the presence of ruthenium-oxygen and ruthenium-terminal and bridging fluorine bonds [fr

Development of a model for the anodic behavior of T60 titanium in chlorinated and oxygenated aqueous media. Application to the specific conditions of hydrothermal oxidation (1 MPa

International Nuclear Information System (INIS)

Frayret, C.; Jaszay, Th.; Lestienne, B.; Delville, M.H.

2003-01-01

This work evaluates the anodic electrochemical behavior of titanium metal in hydrothermal oxidation conditions (up to 400 deg. C and 28 MPa) in chlorinated media in order to estimate the supercritical water oxidation reactors reliability for the treatment of less than 10% organic-waste waters. The titanium room temperature dissolution mechanism in chlorinated acidic medium (pH 2 oxide formation with a very limited tetravalent dissolution). In hydrothermal oxidation (pH>1), only the second branch is effective. The titanium protection is directly related to the oxide stability in high pH systems. The mechanism model is expressed in terms of 'current-potential' laws, which provide kinetic parameters using optimization calculations. The different elementary steps reaction rates were estimated as well as the evolution of the reaction intermediates coverage ratios with the potential. The quantification of each elementary step was performed to understand and/or orient the materials behavior according to different factors (pH, chloride ions contents, potentials...)

Evolution of the Oxidation State of the Earth's Mantle

Science.gov (United States)

Danielson, L. R.; Righter, K.; Keller, L.; Christoffersen, E.; Rahman, Z.

2015-01-01

The oxidation state of the Earth's mantle during formation remains an unresolved question, whether it was constant throughout planetary accretion, transitioned from reduced to oxidized, or from oxidized to reduced. We investigate the stability of Fe3(+) at depth, in order to constrain processes (water, late accretion, dissociation of FeO) which may reduce or oxidize the Earth's mantle. In our previous experiments on shergottite compositions, variable fO2, T, and P less than 4 GPa, Fe3(+)/sigma Fe decreased slightly with increasing P, similar to terrestrial basalt. For oxidizing experiments less than 7GPa, Fe3(+)/sigma Fe decreased as well, but it's unclear from previous modelling whether the deeper mantle could retain significant Fe3(+). Our current experiments expand our pressure range deeper into the Earth's mantle and focus on compositions and conditions relevant to the early Earth. Preliminary multi-anvil experiments with Knippa basalt as the starting composition were conducted at 5-7 GPa and 1800 C, using a molybdenum capsule to set the fO2 near IW, by buffering with Mo-MoO3. TEM and EELS analyses revealed the run products quenched to polycrystalline phases, with the major phase pyroxene containing approximately equal to Fe3(+)/2(+). Experiments are underway to produce glassy samples that can be measured by EELS and XANES, and are conducted at higher pressures.

Selective extraction of actinides from high level liquid wastes. Study of the possibilities offered by the Redox properties of actinides

International Nuclear Information System (INIS)

Adnet, J.M.

1991-07-01

Partitioning of high level liquid wastes coming from nuclear fuel reprocessing by the PUREX process, consists in the elimination of minor actinides (Np, Am, and traces of Pu and U). Among the possible processes, the selective extraction of actinides with oxidation states higher than three is studied. First part of this work deals with a preliminary step; the elimination of the ruthenium from fission products solutions using the electrovolatilization of the RuO4 compound. The second part of this work concerns the complexation and oxidation reactions of the elements U, Np, Pu and Am in presence of a compound belonging to the insaturated polyanions family: the potassium phosphotungstate. For actinide ions with oxidation state (IV) complexed with phosphotungstate anion the extraction mechanism by dioctylamine was studied and the use of a chromatographic extraction technic permitted successful separations between tetravalents actinides and trivalents actinides. Finally, in accordance with the obtained results, the basis of a separation scheme for the management of fission products solutions is proposed

Arsenic (+3 oxidation state) methyltransferase and the inorganic arsenic methylation phenotype

International Nuclear Information System (INIS)

Li Jiaxin; Waters, Stephen B.; Drobna, Zuzana; Devesa, Vicenta; Styblo, Miroslav; Thomas, David J.

2005-01-01

Inorganic arsenic is enzymatically methylated; hence, its ingestion results in exposure to the parent compound and various methylated arsenicals. Both experimental and epidemiological evidences suggest that some of the adverse health effects associated with chronic exposure to inorganic arsenic may be mediated by these methylated metabolites. If i As methylation is an activation process, then the phenotype for inorganic arsenic methylation may determine risk associated with exposure to this metalloid. We examined inorganic arsenic methylation phenotypes and arsenic (+3 oxidation state) methyltransferase genotypes in four species: three that methylate inorganic arsenic (human (Homo sapiens), rat (Rattus norwegicus), and mouse (Mus musculus)) and one that does not methylate inorganic arsenic (chimpanzee, Pan troglodytes). The predicted protein products from arsenic (+3 oxidation state) methyltransferase are similar in size for rat (369 amino acid residues), mouse (376 residues), and human (375 residues). By comparison, a 275-nucleotide deletion beginning at nucleotide 612 in the chimpanzee gene sequence causes a frameshift that leads to a nonsense mutation for a premature stop codon after amino acid 205. The null phenotype for inorganic arsenic methylation in the chimpanzee is likely due to the deletion in the gene for arsenic (+3 oxidation state) methyltransferase that yields an inactive truncated protein. This lineage-specific loss of function caused by the deletion event must have occurred in the Pan lineage after Homo-Pan divergence about 5 million years ago

Approaches to Determining the Oxidation State of Nitrogen and Carbon Atoms in Organic Compounds for High School Students

Science.gov (United States)

Jurowski, Kamil; Krzeczkowska, Malgorzata Krystyna; Jurowska, Anna

2015-01-01

The concept of oxidation state (or oxidation number) and related issues have always been difficult for students. In addition, there are misunderstandings and obscurities, which can cause improper balancing of the chemical equations (mostly in organic reactions). In particular, these problems are related to determination of the oxidation state of…

On matrix stabilisation of d- and f-transition metal ions in unstable oxidation states

Energy Technology Data Exchange (ETDEWEB)

Kiselev, Yurii M [Department of Chemistry, M.V. Lomonosov Moscow State University, Moscow (Russian Federation)

2009-01-31

The state-of-the-art in matrix stabilisation of d- and f-transition metal ions in unstable oxidation states is analysed. Main aspects of this problem concerning the genealogy of appropriate matrix systems are classified. Relevant examples are given and the data that contradict the scheme proposed are discussed. The thermodynamics of the matrix stabilisation effect is considered using the concept of isomorphic miscibility. The influence of defects and non-equilibrium on the matrix stabilisation effect is discussed. The problem of identification of the oxidation states in matrix systems is examined and various types of matrix systems are considered.

On matrix stabilisation of d- and f-transition metal ions in unstable oxidation states

International Nuclear Information System (INIS)

Kiselev, Yurii M

2009-01-01

The state-of-the-art in matrix stabilisation of d- and f-transition metal ions in unstable oxidation states is analysed. Main aspects of this problem concerning the genealogy of appropriate matrix systems are classified. Relevant examples are given and the data that contradict the scheme proposed are discussed. The thermodynamics of the matrix stabilisation effect is considered using the concept of isomorphic miscibility. The influence of defects and non-equilibrium on the matrix stabilisation effect is discussed. The problem of identification of the oxidation states in matrix systems is examined and various types of matrix systems are considered.

Facile solid-state synthesis of oxidation-resistant metal nanoparticles at ambient conditions

Science.gov (United States)

Lee, Kyu Hyung; Jung, Hyuk Joon; Lee, Ju Hee; Kim, Kyungtae; Lee, Byeongno; Nam, Dohyun; Kim, Chung Man; Jung, Myung-Hwa; Hur, Nam Hwi

2018-05-01

A simple and scalable method for the synthesis of metal nanoparticles in the solid-state was developed, which can produce nanoparticles in the absence of solvents. Nanoparticles of coinage metals were synthesized by grinding solid hydrazine and the metal precursors in their acetates and oxides at 25 °C. The silver and gold acetates converted completely within 6 min into Ag and Au nanoparticles, respectively, while complete conversion of the copper acetate to the Cu sub-micrometer particles took about 2 h. Metal oxide precursors were also converted into metal nanoparticles by grinding alone. The resulting particles exhibit distinctive crystalline lattice fringes, indicating the formation of highly crystalline phases. The Cu sub-micrometer particles are better resistant to oxidation and exhibit higher conductivity compared to conventional Cu nanoparticles. This solid-state method was also applied for the synthesis of platinum group metals and intermetallic Cu3Au, which can be further extended to synthesize other metal nanoparticles.

Influence of processing conditions on the glass-crystal transition into borosilicate glasses

Energy Technology Data Exchange (ETDEWEB)

Deschanels, X.; Cachia, J.N.; Lopez, C.; Peuget, S. [CEA Marcoule, BP 17171, 30207 Bagnols sur Ceze (France)

2008-07-01

The precipitation of a crystalline phase in glass is observed when one element exceeds its loading limit (i.e.: solubility limit). In this work we have studied the solubility of different actinides and surrogates (lanthanides and hafnium) in borosilicate glass used for the immobilization of the high-level nuclear waste (HLW glasses). The results obtained show an increase of the solubility limits of these elements with the processing temperature and the redox potential of the melt. The elements at the oxidation state (III) exhibit a higher solubility than the element at oxidation state (IV). In this framework, cerium is an interesting element because its oxidation state tunes from (IV) to (III) as a function of the processing conditions. It is shown that the solubility of cerium can be multiplied by a factor of 20 at 1100 C. degrees. In order to have a better understanding of the mechanisms that underline the evolution of the solubility, XAFS and NMR investigation has been undertaken. Trivalent elements present the characteristics of network-modified cations while tetravalent elements look like network-former cations.

Arsenic K-edge X-ray absorption near-edge spectroscopy to determine oxidation states of arsenic of a coastal aquifer–aquitard system

International Nuclear Information System (INIS)

Wang, Ya; Jiao, Jiu Jimmy; Zhu, Sanyuan; Li, Yiliang

2013-01-01

Determination of oxidation states of solid-phase arsenic in bulk sediments is a valuable step in the evaluation of its bioavailability and environmental fate in deposits, but is difficult when the sediments have low arsenic contents and heterogeneous distribution of arsenic species. As K-edge X-ray absorption near-edge spectroscopy (XANES) was used to determine quantitatively the oxidation states of arsenic in sediments collected from different depths of boreholes in the Pearl River Delta, China, where the highest aquatic arsenic concentration is 161.4 μg/L, but the highest solid arsenic content only 39.6 mg/kg. The results demonstrated that XANES is efficient in determining arsenic oxidation states of the sediments with low arsenic contents and multiple arsenic species. The study on the high-resolution vertical variations of arsenic oxidation states also indicated that these states are influenced strongly by groundwater activities. With the help of geochemical data, solid arsenic speciation, toxicity and availability were further discussed. -- Highlights: •XANES is efficient in determining arsenic oxidation states of the bulk sediments. •Distribution of arsenic oxidation states is consistent with geochemical conditions. •Arsenic oxidation states are influenced strongly by groundwater activities. -- As K-edge X-ray absorption near-edge spectroscopy is efficient in determining arsenic oxidation states of the bulk sediments with low arsenic contents and heterogeneous distribution of arsenic species

DetOx: a program for determining anomalous scattering factors of mixed-oxidation-state species.

Science.gov (United States)

Sutton, Karim J; Barnett, Sarah A; Christensen, Kirsten E; Nowell, Harriott; Thompson, Amber L; Allan, David R; Cooper, Richard I

2013-01-01

Overlapping absorption edges will occur when an element is present in multiple oxidation states within a material. DetOx is a program for partitioning overlapping X-ray absorption spectra into contributions from individual atomic species and computing the dependence of the anomalous scattering factors on X-ray energy. It is demonstrated how these results can be used in combination with X-ray diffraction data to determine the oxidation state of ions at specific sites in a mixed-valance material, GaCl(2).

Uranium extraction history using pressure leaching

International Nuclear Information System (INIS)

Fraser, K.S.; Thomas, K.G.

2010-01-01

Over the past 60 years of uranium process development only a few commercial uranium plants have adopted a pressure leaching process in their flowsheet. The selection of acid versus alkaline pressure leaching is related to the uranium and gangue mineralogy. Tetravalent (U"+"4) uranium has to be oxidized to hexavalent (U"+"6) uranium to be soluble. Refractory tetravalent uranium requires higher temperature and pressure, as practised in pressure leaching, for conversation to soluble hexavalent uranium. This paper chronicles the history of these uranium pressure leaching facilities over the past 60 years, with specific details of each design and operation. (author)

Carbon oxidation state as a metric for describing the chemistry of atmospheric organic aerosol

Energy Technology Data Exchange (ETDEWEB)

Massachusetts Institute of Technology; Kroll, Jesse H.; Donahue, Neil M.; Jimenez, Jose L.; Kessler, Sean H.; Canagaratna, Manjula R.; Wilson, Kevin R.; Altieri, Katye E.; Mazzoleni, Lynn R.; Wozniak, Andrew S.; Bluhm, Hendrik; Mysak, Erin R.; Smith, Jared D.; Kolb, Charles E.; Worsnop, Douglas R.

2010-11-05

A detailed understanding of the sources, transformations, and fates of organic species in the environment is crucial because of the central roles that organics play in human health, biogeochemical cycles, and Earth's climate. However, such an understanding is hindered by the immense chemical complexity of environmental mixtures of organics; for example, atmospheric organic aerosol consists of at least thousands of individual compounds, all of which likely evolve chemically over their atmospheric lifetimes. Here we demonstrate the utility of describing organic aerosol (and other complex organic mixtures) in terms of average carbon oxidation state (OSC), a quantity that always increases with oxidation, and is readily measured using state-of-the-art analytical techniques. Field and laboratory measurements of OSC , using several such techniques, constrain the chemical properties of the organics and demonstrate that the formation and evolution of organic aerosol involves simultaneous changes to both carbon oxidation state and carbon number (nC).

Microbially catalyzed nitrate-dependent metal/radionuclide oxidation in shallow subsurface sediments

Science.gov (United States)

Weber, K.; Healy, O.; Spanbauer, T. L.; Snow, D. D.

2011-12-01

Anaerobic, microbially catalyzed nitrate-dependent metal/radionuclide oxidation has been demonstrated in a variety of sediments, soils, and groundwater. To date, studies evaluating U bio-oxidation and mobilization have primarily focused on anthropogenically U contaminated sites. In the Platte River Basin U originating from weathering of uranium-rich igneous rocks in the Rocky Mountains was deposited in shallow alluvial sediments as insoluble reduced uranium minerals. These reduced U minerals are subject to reoxidation by available oxidants, such nitrate, in situ. Soluble uranium (U) from natural sources is a recognized contaminant in public water supplies throughout the state of Nebraska and Colorado. Here we evaluate the potential of anaerobic, nitrate-dependent microbially catalyzed metal/radionuclide oxidation in subsurface sediments near Alda, NE. Subsurface sediments and groundwater (20-64ft.) were collected from a shallow aquifer containing nitrate (from fertilizer) and natural iron and uranium. The reduction potential revealed a reduced environment and was confirmed by the presence of Fe(II) and U(IV) in sediments. Although sediments were reduced, nitrate persisted in the groundwater. Nitrate concentrations decreased, 38 mg/L to 30 mg/L, with increasing concentrations of Fe(II) and U(IV). Dissolved U, primarily as U(VI), increased with depth, 30.3 μg/L to 302 μg/L. Analysis of sequentially extracted U(VI) and U(IV) revealed that virtually all U in sediments existed as U(IV). The presence of U(IV) is consistent with reduced Fe (Fe(II)) and low reduction potential. The increase in aqueous U concentrations with depth suggests active U cycling may occur at this site. Tetravalent U (U(IV)) phases are stable in reduced environments, however the input of an oxidant such as oxygen or nitrate into these systems would result in oxidation. Thus co-occurrence of nitrate suggests that nitrate could be used by bacteria as a U(IV) oxidant. Most probable number

Regulation of Ca2+ release from mitochondria by the oxidation-reduction state of pyridine nucleotides

Science.gov (United States)

Lehninger, Albert L.; Vercesi, Anibal; Bababunmi, Enitan A.

1978-01-01

Mitochondria from normal rat liver and heart, and also Ehrlich tumor cells, respiring on succinate as energy source in the presence of rotenone (to prevent net electron flow to oxygen from the endogenous pyridine nucleotides), rapidly take up Ca2+ and retain it so long as the pyridine nucleotides are kept in the reduced state. When acetoacetate is added to bring the pyridine nucleotides into a more oxidized state, Ca2+ is released to the medium. A subsequent addition of a reductant of the pyridine nucleotides such as β-hydroxybutyrate, glutamate, or isocitrate causes reuptake of the released Ca2+. Successive cycles of Ca2+ release and uptake can be induced by shifting the redox state of the pyridine nucleotides to more oxidized and more reduced states, respectively. Similar observations were made when succinate oxidation was replaced as energy source by ascorbate oxidation or by the hydrolysis of ATP. These and other observations form the basis of a hypothesis for feedback regulation of Ca2+-dependent substrate- or energy-mobilizing enzymatic reactions by the uptake or release of mitochondrial Ca2+, mediated by the cytosolic phosphate potential and the ATP-dependent reduction of mitochondrial pyridine nucleotides by reversal of electron transport. Images PMID:25436

Ground-state structures of Hafnium clusters

Energy Technology Data Exchange (ETDEWEB)

Ng, Wei Chun; Yoon, Tiem Leong [School of Physics, Universiti Sains Malaysia, 11800 USM, Penang (Malaysia); Lim, Thong Leng [Faculty of Engineering and Technoloty, Multimedia University, Melaca Campus, 75450 Melaka (Malaysia)

2015-04-24

Hafnium (Hf) is a very large tetra-valence d-block element which is able to form relatively long covalent bond. Researchers are interested to search for substitution to silicon in the semi-conductor industry. We attempt to obtain the ground-state structures of small Hf clusters at both empirical and density-functional theory (DFT) levels. For calculations at the empirical level, charge-optimized many-body functional potential (COMB) is used. The lowest-energy structures are obtained via a novel global-minimum search algorithm known as parallel tempering Monte-Carlo Basin-Hopping and Genetic Algorithm (PTMBHGA). The virtue of using COMB potential for Hf cluster calculation lies in the fact that by including the charge optimization at the valence shells, we can encourage the formation of proper bond hybridization, and thus getting the correct bond order. The obtained structures are further optimized using DFT to ensure a close proximity to the ground-state.

Study on the solid state chemistry of ternary uranium oxides

International Nuclear Information System (INIS)

Yamashita, Toshiyuki

1988-03-01

With the increase of burnup of uranium oxide fuels, various kinds of fission products are formed, and the oxygen atoms combined with the consumed heavy atoms are freed. The solid state chemical and/or thermodynamic properties of these elements at high temperatures are complex, and have not been well clarified. In the present report, an approach was taken that the chemical interactions between UO 2 and these fission products can be regarded as causing overlapped effects of composing ternary uranium oxides, and formation reactions and phase behavior were studied for several ternary uranium oxides with typical fission product elements such as alkaline earth metals and rare earth elements. Precise determination methods for the composition of ternary uranium oxides were developed. The estimated accuracies for x and y values in M y U 1-y O 2+x were ± 0.006 and ± 0.004, respectively. The thermodynamic properties and the lattice parameters of the phases in the Ca-U-O and Pr-U-O systems were discussed in relation to the composition determined by the methods. Crystal structure analyses of cadmium monouranates were made with X-ray diffraction method. (author) 197 refs

Oxygen perovskites with tetravalent neodymium

Energy Technology Data Exchange (ETDEWEB)

Brauer, G; Kristen, H [Freiburg Univ. (Germany, F.R.)

1979-09-01

Neodymium could be stabilized by incorporating it in host-lattices with the perovskite structure. BaCeO/sub 3/, BaPrO/sub 3/, BaThO/sub 3/, and BaZrO/sub 3/ have been used for host-lattices. The samples were prepared by heating the corresponding oxides on air and at 1250-1400 /sup 0/C. X-ray diffraction and chemical analysis showed that Nd(IV) has been stabilized in different rates by these four host-lattices. BaCeO/sub 3/ is able to incorporate Nd(IV) up to 30%. BaPrO/sub 3/ up to 18%, BaThO/sub 3/ up to 17% and BaZrO/sub 3/ up to 4%.

Influence of attrition scrubbing, ultrasonic treatment, and oxidant additions on uranium removal from contaminated soils

International Nuclear Information System (INIS)

Timpson, M.E.; Elless, M.P.; Francis, C.W.

1994-01-01

As part of the Uranium in Soils Integrated Demonstration Project being conducted by the US Department of Energy, bench-scale investigations of selective leaching of uranium from soils at the Fernald Environmental Management Project site in Ohio were conducted at Oak Ridge National Laboratory. Two soils (storage pad soil and incinerator soil), representing the major contaminant sources at the site, were extracted using carbonate- and citric acid-based lixiviants. Physical and chemical processes were used in combination with the two extractants to increase the rate of uranium release from these soils. Attrition scrubbing and ultrasonic dispersion were the two physical processes utilized. Potassium permanganate was used as an oxidizing agent to transform tetravalent uranium to the hexavalent state. Hexavalent uranium is easily complexed in solution by the carbonate radical. Attrition scrubbing increased the rate of uranium release from both soils when compared with rotary shaking. At equivalent extraction times and solids loadings, however, attrition scrubbing proved effective only on the incinerator soil. Ultrasonic treatments on the incinerator soil removed 71% of the uranium contamination in a single extraction. Multiple extractions of the same sample removed up to 90% of the uranium. Additions of potassium permanganate to the carbonate extractant resulted in significant changes in the extractability of uranium from the incinerator soil but had no effect on the storage pad soil

Treatment of phosphorus-uraniferous solution

International Nuclear Information System (INIS)

Araujo Figueiredo, C. de.

1984-01-01

A solvent extraction process for the recovery of uranium from Itataia wet process phosphoric acid was studied. The proposed process consists of two extraction cycles. Uranium, reduced to its tetravalent state, is extracted in the first cycle using octylpyrosphoric acid (OPPA) in a kerosene type diluent. Stripping is accomplished with concentrated raffinate phosphoric acid and an oxidizing agent, in order to convert U (IV) to its hexavalent state. The strip solution from the first cycle is processed in the second cycle with the synergistic combination of di-( 2- ethylhexyl) phosphoric acid and tri-n-octylphosphine oxide (D2EHPA-TOPO). The extract is scrubbed and uranium is stripped with ammonium carbonate solution and recovered as a commercial concentrate. The results obtained from batch tests were used to set up a bench scale array of mixer settlers so as to demonstrate the process. (Author) [pt

Uranium extraction from phosphoric acid

International Nuclear Information System (INIS)

Araujo Figueiredo, C. de

1984-01-01

The recovery of uranium from phosphoric liquor by two extraction process is studied. First, uranium is reduced to tetravalent condition and is extracted by dioctypyrophosphoric acid. The re-extraction is made by concentrated phosphoric acid with an oxidizing agent. The re-extract is submitted to the second process and uranium is extracted by di-ethylhexilphosphoric acid and trioctylphosphine oxide. (M.A.C.) [pt

The Immunogenicity and Safety of CYD-Tetravalent Dengue Vaccine (CYD-TDV) in Children and Adolescents: A Systematic Review.

Science.gov (United States)

Agarwal, Raksheeth; Wahid, Mardiastuti H; Yausep, Oliver E; Angel, Sharon H; Lokeswara, Angga W

2017-01-01

to assess the immunogenicity and safety of CYD-tetravalent dengue vaccine (CYD-TDV) in children. comprehensive literature searches were conducted on various databases. Randomized-controlled trials on children with CYD-TDV as intervention were selected based on inclusion and exclusion criteria. Data extracted from selected trials included safety of vaccine and immunogenicity in terms of Geometric Mean Titres (GMT) of antibodies.   six clinical trials were selected based on preset criteria. GMT values were obtained using 50% Plaque Reduction Neutralization Test (PRNT) and safety was semi-quantitatively assessed based on adverse effects. Additional data processing was done to obtain a better understanding on the trends among the studies. The results showed that the groups vaccinated with CYD-TDV showed higher immunogenicity against dengue virus antigens than the control groups. Safety results were satisfactory in all trials, and most severe side effects were unrelated to the vaccine. CYD-TDV is both effective and safe for patients in endemic regions. This gives promise for further development and large-scale research on this vaccine to assess its efficacy in decreasing dengue prevalence, and its pervasive implementation in endemic countries, such as Indonesia.

Short review of high-pressure crystal growth and magnetic and electrical properties of solid-state osmium oxides

Energy Technology Data Exchange (ETDEWEB)

Yamaura, Kazunari, E-mail: YAMAURA.Kazunari@nims.go.jp [Superconducting Properties Unit, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Graduate School of Chemical Sciences and Engineering, Hokkaido University, North 10 West 8, Kita-ku, Sapporo, Hokkaido 060-0810 (Japan)

2016-04-15

High-pressure crystal growth and synthesis of selected solid-state osmium oxides, many of which are perovskite-related types, are briefly reviewed, and their magnetic and electrical properties are introduced. Crystals of the osmium oxides, including NaOsO{sub 3}, LiOsO{sub 3}, and Na{sub 2}OsO{sub 4}, were successfully grown under high-pressure and high-temperature conditions at 6 GPa in the presence of an appropriate amount of flux in a belt-type apparatus. The unexpected discovery of a magnetic metal–insulator transition in NaOsO{sub 3}, a ferroelectric-like transition in LiOsO{sub 3}, and high-temperature ferrimagnetism driven by a local structural distortion in Ca{sub 2}FeOsO{sub 6} may represent unique features of the osmium oxides. The high-pressure and high-temperature synthesis and crystal growth has played a central role in the development of solid-state osmium oxides and the elucidation of their magnetic and electronic properties toward possible use in multifunctional devices. - Graphical Abstract: Flux-grown crystals of NaOsO{sub 3} under high-pressure and high-temperature conditions in a belt-type apparatus. The crystal shows a magnetically driven metal–insulator transition at a temperature of 410 K. - Highlights: • Short review of high-pressure crystal growth of solid-state osmium oxides. • Wide variety of magnetic properties of solid-state osmium oxides. • Perovskite and related dense structures stabilized at 3–17 GPa.

Microbial utilization of low molecular weight organic substrates in soil depends on their carbon oxidation state

Science.gov (United States)

Gunina, Anna; Smith, Andrew; Jones, Davey; Kuzyakov, Yakov

2017-04-01

Removal of low molecular weight organic substances (LMWOS), originating from plants and microorganisms, from soil solution is regulated by microbial uptake. In addition to the concentration of LMWOS in soil solution, the chemical properties of each substance (e.g. C oxidation state, number of C atoms, number of -COOH groups) can affect their uptake and subsequent partitioning of C within the soil microbial community. The aim of this study was to trace the initial fate of three dominant classes of LMWOS in soil (sugars, carboxylic and amino acids), including their removal from solution and utilization by microorganisms, and to reveal the effect of substance chemical properties on these processes. Soil solution, spiked at natural abundance levels with 14C-labelled glucose, fructose, malate, succinate, formate, alanine or glycine, was added to the soil and 14C was traced in the dissolved organic carbon (DOC), CO2, cytosol and soil organic carbon (SOC) over 24 hours. The half-life time of all LMWOS in the DOC (T1 /2-solution) varied between 0.6-5.0 min showing extremely fast initial uptake of LMWOS. The T1 /2-solution of substances was dependent on C oxidation state, indicating that less oxidized organic substances (with C oxidation state "0") were retained longer in soil solution than oxidized substances. The LMWOS-C T1 /2-fast, characterizing the half-life time of 14C in the fast mineralization pool, ranged between 30 and 80 min, with the T1 /2-fast of carboxylic acids (malic acid) being the fastest and the T1 /2-fast of amino acids (glycine) being the slowest. An absence of correlation between T1 /2-fast and either C oxidation state, number of C atoms, or number of -COOH groups suggests that intercellular metabolic pathways are more important for LMWOS transformation in soil than their basic chemical properties. The CO2 release during LMWOS mineralization accounted for 20-90% of 14C applied. Mineralization of LMWOS was the least for sugars and the greatest for

Influence of steam generator surface state on corrosion and oxide formation

International Nuclear Information System (INIS)

Mazenc, Arnaud; Leclercq, Stephanie; Seyeux, Antoine; Galtayries, Anouk; Marcus, Philippe

2012-09-01

The corrosion and release of nickel-based alloy Steam Generator tubes are partly due to their surface state. Among the most important parameters influencing the corrosion, the effect of grain size and the effect of grain crystallographic orientation have been chosen to be studied. The aim of this study is to determine how these parameters have an impact on the corrosion of Steam Generator tubes. Thermal treatments (700 deg. C and 1050 deg. C) have been performed on several samples in Alloy 690 to obtain homogeneous grain sizes, varying from 25 μm to 110 μm. Two samples have been oxidised for four days in a recirculating autoclave, reproducing primary conditions. The changes of oxide composition and thickness were examined by ToF-SIMS on samples exposed to primary water conditions. The intensity profiles versus thicknesses of characteristic oxide anions, such as CrO - , NiO - or FeO - enable us to evaluate the effect of grain size and crystallographic orientation on the formation of an enriched inner chromium layer. As regards to the grain size, there was no effect on the growth, but smaller grains led to a chromium-rich oxide layer. The effect of crystallographic orientation was observed on the oxidation kinetics and the composition of oxide scales. (authors)

Adsorption of CO, CO2, H2, and H2O on titania surfaces with different oxidation states

International Nuclear Information System (INIS)

Raupp, G.B.; Dumesic, J.A.

1985-01-01

The adsorptive properties of titania surfaces with different oxidation states were proved by temperature-programmed desorption (TPD) of CO, H 2 , CO 2 , and H 2 O. Auger electron spectroscopy and X-ray photoelectron spectroscopy revealed that vacuum annealing an oxidized titanium foil at temperatures from 300 to 800 K was an effective means of systematically varying the average surface oxidation state from Ti 4+ to Ti 2+ . Carbon monoxide weakly adsorbed (desorption energy of 44-49 kJ x mol -1 ) in a carbonyl fashion on coordinatively unsaturated cation sites. Titania surfaces were inert with respect to H 2 adsorption and dissociation. Carbon dioxide adsorbed in a linear molecular fashion. Water adsorbed both molecularly and dissociatively. Results are discussed in terms of the role of titania oxidation state in CO hydrogenation over titania-supported metal catalysts. 74 references, 7 figures

Chelation and stabilization of berkelium in oxidation state +IV

Science.gov (United States)

Deblonde, Gauthier J.-P.; Sturzbecher-Hoehne, Manuel; Rupert, Peter B.; An, Dahlia D.; Illy, Marie-Claire; Ralston, Corie Y.; Brabec, Jiri; de Jong, Wibe A.; Strong, Roland K.; Abergel, Rebecca J.

2017-09-01

Berkelium (Bk) has been predicted to be the only transplutonium element able to exhibit both +III and +IV oxidation states in solution, but evidence of a stable oxidized Bk chelate has so far remained elusive. Here we describe the stabilization of the heaviest 4+ ion of the periodic table, under mild aqueous conditions, using a siderophore derivative. The resulting Bk(IV) complex exhibits luminescence via sensitization through an intramolecular antenna effect. This neutral Bk(IV) coordination compound is not sequestered by the protein siderocalin—a mammalian metal transporter—in contrast to the negatively charged species obtained with neighbouring trivalent actinides americium, curium and californium (Cf). The corresponding Cf(III)-ligand-protein ternary adduct was characterized by X-ray diffraction analysis. Combined with theoretical predictions, these data add significant insight to the field of transplutonium chemistry, and may lead to innovative Bk separation and purification processes.

Composition and oxidation state of sulfur in atmospheric particulate matter

Directory of Open Access Journals (Sweden)

A. F. Longo

2016-10-01

Full Text Available The chemical and physical speciation of atmospheric sulfur was investigated in ambient aerosol samples using a combination of sulfur near-edge x-ray fluorescence spectroscopy (S-NEXFS and X-ray fluorescence (XRF microscopy. These techniques were used to determine the composition and oxidation state of sulfur in common primary emission sources and ambient particulate matter collected from the greater Atlanta area. Ambient particulate matter samples contained two oxidation states: S0 and S+VI. Ninety-five percent of the individual aerosol particles (> 1 µm analyzed contain S0. Linear combination fitting revealed that S+VI in ambient aerosol was dominated by ammonium sulfate as well as metal sulfates. The finding of metal sulfates provides further evidence for acidic reactions that solubilize metals, such as iron, during atmospheric transport. Emission sources, including biomass burning, coal fly ash, gasoline, diesel, volcanic ash, and aerosolized Atlanta soil, and the commercially available bacterium Bacillus subtilis, contained only S+VI. A commercially available Azotobacter vinelandii sample contained approximately equal proportions of S0 and S+VI. S0 in individual aerosol particles most likely originates from primary emission sources, such as aerosolized bacteria or incomplete combustion.

Oxidized Nitrogen Balance over 15 Months at Rural and Urban New York State Locations

Science.gov (United States)

Schwab, J. J.; Ninneman, M.; Marto, J.; Edgerton, E. S.; Blanchard, C. L.; Shaw, S. L.

2017-12-01

Continuous measurements of oxidized nitrogen species (NO, NO2, and HNO3), families of species (NOy, alkyl nitrates [or ANs], and peroxyacetyl nitrates [or PANs]), and particle nitrate (pNO3) were carried out for a fifteen-month period from August 2016 through October 2017 at two locations in New York State. The two sites were a rural research station at Pinnacle State Park in Addison, NY and an urban research station at Queens College in New York City. Four different chemiluminescence analyzers with various converters and denuders were employed to make these measurements. Instrumentation used for the study will be described, as well as some of the challenges created by combining data from these independent analyzers to address the oxidized nitrogen budget at the two sites. The Pinnacle State Park site often experiences quite clean air with low ppb levels of total NOy and a greater fraction of oxidized nitrogen products (NOz species). This contrasts with the urban Queens College location, which experiences stronger NOx sources. Seasonal differences in the NOx/NOy and NOz/NOy ratios, and the makeup of the NOz species, are also significant and will be explored in the presentation.

Quantitative chemical state XPS analysis of first row transition metals, oxides and hydroxides

International Nuclear Information System (INIS)

Biesinger, M C; Payne, B P; McIntryre, N S; Hart, B R; Lau, L Wm; Grosvenor, A P; Smart, R StC

2008-01-01

Practical quantitative chemical state X-ray photoelectron spectroscopy (XPS) analysis of first row transition metals, oxides and hydroxides is challenging due to the complexity of their M 2p spectra. Complex multiplet splitting, shake-up and plasmon loss structure can play a role in the interpretation of the chemical states present. This paper will show practical curve fitting procedures for the quantitative measurement of different chemical states for metal oxides and hydroxides from a survey of transition metals. It will also discuss some of the limitations and pitfalls present as well as give practical examples of their successful use. These curve-fitting procedures are based on 1) standard spectra from quality reference samples, 2) a survey of appropriate literature databases and/or a compilation of literature references, 3) fitting of multiplet split spectra based on spectra of numerous reference materials and theoretical modelling, 4) spectral subtractions routines, again using reference spectra, and 5) specific literature references where fitting procedures are available

Quantitative chemical state XPS analysis of first row transition metals, oxides and hydroxides

Energy Technology Data Exchange (ETDEWEB)

Biesinger, M C; Payne, B P; McIntryre, N S [Department of Chemistry, University of Western Ontario, London, Ontario, N6A 5B7 (Canada); Hart, B R; Lau, L Wm [Surface Science Western, Room G1, Western Science Centre, University of Western Ontario, London, Ontario, N6A 5B7 (Canada); Grosvenor, A P [Department of Chemistry, Gunning/Lemieux Chemistry Centre, University of Alberta, Edmonton, Alberta, T6G 2G2 (Canada); Smart, R StC [ACeSSS, Applied Centre for Structural and Synchrotron Studies, University of South Australia, Mawson Lakes, SA 5095 (Australia)], E-mail: biesingr@uwo.ca

2008-03-15

Practical quantitative chemical state X-ray photoelectron spectroscopy (XPS) analysis of first row transition metals, oxides and hydroxides is challenging due to the complexity of their M 2p spectra. Complex multiplet splitting, shake-up and plasmon loss structure can play a role in the interpretation of the chemical states present. This paper will show practical curve fitting procedures for the quantitative measurement of different chemical states for metal oxides and hydroxides from a survey of transition metals. It will also discuss some of the limitations and pitfalls present as well as give practical examples of their successful use. These curve-fitting procedures are based on 1) standard spectra from quality reference samples, 2) a survey of appropriate literature databases and/or a compilation of literature references, 3) fitting of multiplet split spectra based on spectra of numerous reference materials and theoretical modelling, 4) spectral subtractions routines, again using reference spectra, and 5) specific literature references where fitting procedures are available.

Initial oxidation of TiFe{sub 1−x}Mn{sub x} (x = 0–0.3) by low dose exposures to H{sub 2}O and O{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Shwartz, A. [Ben-Gurion University of the Negev, P.O. Box 653, Beer-Sheva 84105 (Israel); Shamir, N., E-mail: noah.shamir@gmail.com [Nuclear research Center – Negev, P.O. Box 9001, Beer-Sheva 84190 (Israel); Froumin, N. [Ben-Gurion University of the Negev, P.O. Box 653, Beer-Sheva 84105 (Israel); Zalkind, S.; Edry, I.; Haim, A. [Nuclear research Center – Negev, P.O. Box 9001, Beer-Sheva 84190 (Israel); Mintz, M.H. [Ben-Gurion University of the Negev, P.O. Box 653, Beer-Sheva 84105 (Israel); Nuclear research Center – Negev, P.O. Box 9001, Beer-Sheva 84190 (Israel)

2014-10-15

Highlights: • Thermodynamics of adsorption and initial oxidation of TiFe{sub 1−x}Mn{sub x} by H{sub 2}O versus O{sub 2}. • Explanation of different oxide formations. • Explanation of the role of the different constituents of the alloys in the processes. - Abstract: The very initial room-temperature oxidation processes of the ternary pseudo-binary TiFe{sub 1−x}Mn{sub x} (x = 0–0.3) intermetallics by trace amounts of H{sub 2}O vapor and O{sub 2} were studied utilizing XPS and AES techniques. Different reactivities of the two gases were obtained, with a lower oxidation ability of H{sub 2}O, relative to O{sub 2}, as anticipated from thermodynamic considerations. The exposure to O{sub 2} results in a two stage oxidation of the Ti ingredient, which first converts into a divalent TiO (up to exposures of about 2 L), then proceeds into a tetravalent TiO{sub 2} form. Unlike oxygen, water exposure produces only the divalent oxide through the whole exposure range studied (11 L). The Mn component in these compounds is oxidized only by O{sub 2} and not by H{sub 2}O. The Fe ingredient is not oxidized at all and remains in its metallic form up to exposures of 30 L.

Towards the improvement of the oxidation resistance of Nb-silicides in situ composites: A solid state diffusion approach

International Nuclear Information System (INIS)

Mathieu, S.; Knittel, S.; François, M.; Portebois, L.; Mathieu, S.; Vilasi, M.

2014-01-01

Highlights: •Local equilibrium is attained during oxidation at phase boundaries (steady state conditions). •A solid state diffusion model explains the oxidation mechanism of Nb-silicides composites. •The Nb ss fraction is not the only parameters governing the oxidation rate of Nb-silicides. •Aluminium increases the thermodynamic activity of Si in the Nb-silicides composites. •The results indicate the need to develop a Nb–Ti–Hf–Al–Cr–Si thermodynamic database. -- Abstract: The present study focuses on the oxidation mechanism of Nb-silicide composites and on the effect of the composition on the oxidation rate at 1100 °C. A theoretical approach is proposed based on experimental results and used to optimise the oxidation resistance. The growth model based on multiphase diffusion was experimentally tested and confirmed by manufacturing seven composites with different compositions. It was also found that the effect of the composition has to be evaluated at 1100 °C within a short time duration (50 h), where the oxide scale and the internal oxidation zone both grow according to parabolic kinetics

Effect of surface state on the oxidation behavior of welded 308L in simulated nominal primary water of PWR

Science.gov (United States)

Ming, Hongliang; Zhang, Zhiming; Wang, Jiazhen; Zhu, Ruolin; Ding, Jie; Wang, Jianqiu; Han, En-Hou; Ke, Wei

2015-05-01

The oxidation behavior of 308L weld metal (WM) with different surface state in the simulated nominal primary water of pressurized water reactor (PWR) was studied by scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) analyzer and X-ray photoelectron spectroscopy (XPS). After 480 h immersion, a duplex oxide film composed of a Fe-rich outer layer (Fe3O4, Fe2O3 and a small amount of NiFe2O4, Ni(OH)2, Cr(OH)3 and (Ni, Fe)Cr2O4) and a Cr-rich inner layer (FeCr2O4 and NiCr2O4) can be formed on the 308L WM samples with different surface state. The surface state has no influence on the phase composition of the oxide films but obviously affects the thickness of the oxide films and the morphology of the oxides (number & size). With increasing the density of dislocations and subgrain boundaries in the cold-worked superficial layer, the thickness of the oxide film, the number and size of the oxides decrease.

Pentavalent Uranium Chemistry - Synthetic Pursuit Of A Rare Oxidation State

Energy Technology Data Exchange (ETDEWEB)

Graves, Christopher R [Los Alamos National Laboratory; Kiplinger, Jaqueline L [Los Alamos National Laboratory

2009-01-01

This feature article presents a comprehensive overview of pentavalent uranium systems in non-aqueous solution with a focus on the various synthetic avenues employed to access this unusual and very important oxidation state. Selected characterization data and theoretical aspects are also included. The purpose is to provide a perspective on this rapidly evolving field and identify new possibilities for future developments in pentavalent uranium chemistry.

The influence of iridium chemical oxidation state on the performance and durability of oxygen evolution catalysts in PEM electrolysis

Science.gov (United States)

Siracusano, S.; Baglio, V.; Grigoriev, S. A.; Merlo, L.; Fateev, V. N.; Aricò, A. S.

2017-10-01

Nanosized Ir-black (3 nm) and Ir-oxide (5 nm) oxygen evolution electrocatalysts showing high performance in polymer electrolyte membrane (PEM) water electrolysis based on Aquivion® short-side chain ionomer membrane are investigated to understand the role of the Ir oxidation state on the electrocatalytic activity and stability. Despite the smaller mean crystallite size, the Ir-black electrocatalyst shows significantly lower initial performance than the Ir-oxide. During operation at high current density, the Ir-black shows a decrease of cell potential with time whereas the Ir-oxide catalyst shows increasing cell potential resulting in a degradation rate of about 10 μV/h, approaching 1000 h. The unusual behaviour of the Ir-black results from the oxidation of metallic Ir to IrOx. The Ir-oxide catalyst shows instead a hydrated structure on the surface and a negative shift of about 0.5 eV for the Ir 4f binding energy after 1000 h electrolysis operation. This corresponds to the formation of a sub-stoichiometric Ir-oxide on the surface. These results indicate that a hydrated IrO2 with high oxidation state on the surface is favourable in decreasing the oxygen evolution overpotential. Modifications of the Ir chemical oxidation state during operation can affect significantly the catalytic activity and durability of the electrolysis system.

Measurement of soil carbon oxidation state and oxidative ratio by 13C nuclear magnetic resonance

Science.gov (United States)

Hockaday, W.C.; Masiello, C.A.; Randerson, J.T.; Smernik, R.J.; Baldock, J.A.; Chadwick, O.A.; Harden, J.W.

2009-01-01

The oxidative ratio (OR) of the net ecosystem carbon balance is the ratio of net O2 and CO2 fluxes resulting from photosynthesis, respiration, decomposition, and other lateral and vertical carbon flows. The OR of the terrestrial biosphere must be well characterized to accurately estimate the terrestrial CO2 sink using atmospheric measurements of changing O2 and CO2 levels. To estimate the OR of the terrestrial biosphere, measurements are needed of changes in the OR of aboveground and belowground carbon pools associated with decadal timescale disturbances (e.g., land use change and fire). The OR of aboveground pools can be measured using conventional approaches including elemental analysis. However, measuring the OR of soil carbon pools is technically challenging, and few soil OR data are available. In this paper we test three solid-state nuclear magnetic resonance (NMR) techniques for measuring soil OR, all based on measurements of the closely related parameter, organic carbon oxidation state (Cox). Two of the three techniques make use of a molecular mixing model which converts NMR spectra into concentrations of a standard suite of biological molecules of known C ox. The third technique assigns Cox values to each peak in the NMR spectrum. We assess error associated with each technique using pure chemical compounds and plant biomass standards whose Cox and OR values can be directly measured by elemental analyses. The most accurate technique, direct polarization solid-state 13C NMR with the molecular mixing model, agrees with elemental analyses to ??0.036 Cox units (??0.009 OR units). Using this technique, we show a large natural variability in soil Cox and OR values. Soil Cox values have a mean of -0.26 and a range from -0.45 to 0.30, corresponding to OR values of 1.08 ?? 0.06 and a range from 0.96 to 1.22. We also estimate the OR of the carbon flux from a boreal forest fire. Analysis of soils from nearby intact soil profiles imply that soil carbon losses associated

The Impact of Environmental Factors in Influencing Epigenetics Related to Oxidative States in the Cardiovascular System

Directory of Open Access Journals (Sweden)

Francesco Angelini

2017-01-01

Full Text Available Oxidative states exert a significant influence on a wide range of biological and molecular processes and functions. When their balance is shifted towards enhanced amounts of free radicals, pathological phenomena can occur, as the generation of reactive oxygen species (ROS in tissue microenvironment or in the systemic circulation can be detrimental. Epidemic chronic diseases of western societies, such as cardiovascular disease, obesity, and diabetes correlate with the imbalance of redox homeostasis. Current advances in our understanding of epigenetics have revealed a parallel scenario showing the influence of oxidative stress as a major regulator of epigenetic gene regulation via modification of DNA methylation, histones, and microRNAs. This has provided both the biological link and a potential molecular explanation between oxidative stress and cardiovascular/metabolic phenomena. Accordingly, in this review, we will provide current insights on the physiological and pathological impact of changes in oxidative states on cardiovascular disorders, by specifically focusing on the influence of epigenetic regulation. A special emphasis will highlight the effect on epigenetic regulation of human’s current life habits, external and environmental factors, including food intake, tobacco, air pollution, and antioxidant-based approaches. Additionally, the strategy to quantify oxidative states in humans in order to determine which biological marker could best match a subject’s profile will be discussed.

Mechanisms of metasomatism in the calcite-pitchblende system: 2. Replacement of pitchblende by calcite

International Nuclear Information System (INIS)

Dymkov, Yu.M.

1996-01-01

The principal mechanisms of the nasturan replacement by calcite -intrametasomatism, frontal metasomatism, dispersive metasomatism, and transformative metasomatism - are discussed in terms of G.L. Pospelov's (1973) concept. The main chemical condition required by the process is an oxidized environment, in which the tetravalent uranium of pitchblende or transitional reduced phases (coffinite) oxidizes to yield readily soluble uranyl compounds. The latter are replaced by calcite

Homoleptic Ce(III) and Ce(IV) Nitroxide Complexes: Significant Stabilization of the 4+ Oxidation State

Energy Technology Data Exchange (ETDEWEB)

Bogart, Justin A.; Lewis, Andrew J.; Medling, Scott A.; Piro, Nicholas A.; Carroll, Patrick J.; Booth, Corwin H.; Schelter, Eric J.

2014-06-25

Electrochemical experiments performed on the complex Ce-IV[2-((BuNO)-Bu-t)py](4), where [2-((BuNO)-Bu-t)py](-) = N-tert-butyl-N-2-pyridylnitroxide, indicate a 2.51 V stabilization of the 4+ oxidation state of Ce compared to [(Bu4N)-Bu-n](2)[Ce(NO3)(6)] in acetonitrile and a 2.95 V stabilization compared to the standard potential for the ion under aqueous conditions. Density functional theory calculations suggest that this preference for the higher oxidation state is a result of the tetrakis(nitroxide) ligand framework at the Ce cation, which allows for effective electron donation into, and partial covalent overlap with, vacant 4f orbitals with delta symmetry. The results speak to the behavior of CeO2 and related solid solutions in oxygen uptake and transport applications, in particular an inherent local character of bonding that stabilizes the 4+ oxidation state. The results indicate a cerium(IV) complex that has been stabilized to an unprecedented degree through tuning of its ligand-field environment.

The effect of interfaces on solid-state reactions between oxides

International Nuclear Information System (INIS)

Johnson, M.T.; Carter, C.B.

1998-01-01

A thin-film geometry has been used to study fundamental solid-state reaction processes occurring at interfaces in two spinel-forming oxide systems. In the first system, NiO/Al 2 O 3 , epitactic NiO films were deposited on various orientations of single-crystal α-Al 2 O 3 . In this case, the reaction kinetics were studied and correlated with the interfacial structure (or substrate orientation). In the second, In 2 O 3 /MgO, solid-state reactions were studied under the influence of an electric field. The electric field provides a driving force for mass transport that affects both the reaction process and the morphological stability of an interface

Oxidation of an aluminium-magnesium alloy in liquid state. Methodology of determination of mechanisms from not necessarily repeatable experiments

International Nuclear Information System (INIS)

Surla, Karine

1998-01-01

This research thesis reports the study of the oxidation of an aluminium-5 pc magnesium alloy in its liquid state in an oxygen environment, using thermogravimetric analysis and that of magnesium in its solid state. In a first part, the author reports a thermodynamic and bibliographical study on magnesium transformation in its solid state (Mg/O 2 and Mg/H 2 O systems, transformation with dry and humid synthetic air, oxidation inhibitors) and on Al-Mg alloy transformation in presence of oxygen (thermodynamic properties of aluminium-rich Al-Mg alloys, Al-Mg/O 2 /N 2 and Al-Mg/O 2 /N 2 /H 2 O systems). The next parts address the selection of reaction systems for the different cases (oxidation of solid magnesium in oxygen, oxidation of the Al-Mg alloy in oxygen), the modelling of the formation of magnesia from solid magnesium and from the Al-Mg alloy, and the modelling of the liquid Al-Mg A5182 alloy oxidation in oxygen [fr

Coupled interactions between volatile activity and Fe oxidation state during arc crustal processes

Science.gov (United States)

Humphreys, Madeleine C.S.; Brooker, R; Fraser, D.C.; Burgisser, A; Mangan, Margaret T.; McCammon, C

2015-01-01

Arc magmas erupted at the Earth’s surface are commonly more oxidized than those produced at mid-ocean ridges. Possible explanations for this high oxidation state are that the transfer of fluids during the subduction process results in direct oxidation of the sub-arc mantle wedge, or that oxidation is caused by the effect of later crustal processes, including protracted fractionation and degassing of volatile-rich magmas. This study sets out to investigate the effect of disequilibrium crustal processes that may involve coupled changes in H2O content and Fe oxidation state, by examining the degassing and hydration of sulphur-free rhyolites. We show that experimentally hydrated melts record strong increases in Fe3+/∑Fe with increasing H2O concentration as a result of changes in water activity. This is relevant for the passage of H2O-undersaturated melts from the deep crust towards shallow crustal storage regions, and raises the possibility that vertical variations in fO2 might develop within arc crust. Conversely, degassing experiments produce an increase in Fe3+/∑Fe with decreasing H2O concentration. In this case the oxidation is explained by loss of H2 as well as H2O into bubbles during decompression, consistent with thermodynamic modelling, and is relevant for magmas undergoing shallow degassing en route to the surface. We discuss these results in the context of the possible controls on fO2 during the generation, storage and ascent of magmas in arc settings, in particular considering the timescales of equilibration relative to observation as this affects the quality of the petrological record of magmatic fO2.

Actinide science. Fundamental and environmental aspects

International Nuclear Information System (INIS)

Choppin, Gregory R.

2005-01-01

Nuclear test explosions and reactor wastes have deposited an estimated 16x10 15 Bq of plutonium into the world's aquatic systems. However, plutonium concentration in open ocean waters is orders of magnitude less, indicating that most of the plutonium is quite insolvable in marine waters and has been incorporated into sediments. Actinide ions in waters often are not in a state of thermodynamic equilibrium and their solubility and migration behavior is related to the form in which the nuclides were introduced into the aquatic system. Actinide solubility depends on such factors as pH(hydrolysis), E H (oxidation state), reaction with complexants (e.g. carbonate, phosphate, humic acid, etc.) sorption to surfaces of minerals and/or colloids, etc., in the water. The most significant of these variables is the oxidation sate of the metal ion. The simultaneous presence of more than one oxidation state for some actinides (e.g. plutonium) in a solution complicates actinide environmental behavior. Both Np(V)O 2 + and Pu(V)O 2 + , the most significant soluble states in natural oxic waters are relatively noncomplexing and resistant to hydrolysis and subsequent precipitation but can undergo reduction to the Pu(IV) oxidation state with its different elemental behavior. The solubility of NpO 2 + can be as high as 10 -4 M while that of PuO 2 + is more limited by reduction to the insoluble tetravalent species, Pu(OH) 4 , (pK SP - 56). The net solubility of hexavalent UO 2 2+ in sea water is also limited by hydrolysis; however, it has a relatively high concentration due to formation of carbonate complexes. The insoluble trivalent americium hydroxocarbonate, Am(CO) 3 (OH), is the limiting species for the solubility of Am(III) in sea water. Thorium is found exclusively as the tetravalent species and its solubility is limited by the formation of quite insoluble Th(OH) 4 . The chemistry of actinide ions in the environment is reviewed to show the spectrum of reactions that can occur in

Ion bombardment effects on surface states in selected oxide systems: rutile and alkaline earth titanates

International Nuclear Information System (INIS)

Gruen, D.M.

1978-01-01

In this paper, the nature of the surface states of n-type TiO 2 and SrTiO 3 is discussed and the role of ion bombardment in modifying the properties of these states is elucidated. Insofar as possible, the interrelationships between oxide nonstoichiometry, surface states, ion bombardment effects and photoelectrolysis are explored

On the valence state of Yb and Ce in transition metal intermetallic compounds

International Nuclear Information System (INIS)

Boer, F.R. de; Dijkman, W.H.; Mattens, W.C.M.

1979-01-01

In the pure state Yb is a divalent metal, similar to Ca; in alloys it can become trivalent like the majority of the rare earth metals. Using a value of 38 kJ (mol Yb) -1 for the energy difference between divalent and trivalent Yb metal and using model calculations for the heat of formation of intermetallic compounds, the authors are able to account for the existing information on the valence state of Yb in transition metal compounds. A similar analysis of compounds of Ce with transition metals shows that a model in which the 4f electron is treated as a core electron, i.e. being absent in the tetravalent modification of Ce and present as a fully localized electron in trivalent Ce, does not apply. (Auth.)

Optically induced bistable states in metal/tunnel-oxide/semiconductor /MTOS/ junctions

Science.gov (United States)

Lai, S. K.; Dressendorfer, P. V.; Ma, T. P.; Barker, R. C.

1981-01-01

A new switching phenomenon in metal-oxide semiconductor tunnel junction has been discovered. With a sufficiently large negative bias applied to the electrode, incident visible light of intensity greater than about 1 microW/sq cm causes the reverse-biased junction to switch from a low-current to a high-current state. It is believed that hot-electron-induced impact ionization provides the positive feedback necessary for switching, and causes the junction to remain in its high-current state after the optical excitation is removed. The junction may be switched back to the low-current state electrically. The basic junction characteristics have been measured, and a simple model for the switching phenomenon has been developed.

Actinide metals

Energy Technology Data Exchange (ETDEWEB)

Brown, Paul L. [Geochem Australia, Kiama, NSW (Australia); Ekberg, Christian [Chalmers Univ. of Technology, Goeteborg (Sweden). Nuclear Chemistry/Industrial Materials Recycling

2016-07-01

All isotopes of actinium are radioactive and exist in aqueous solution only in the trivalent state. There have been very few studies on the hydrolytic reactions of actinium(III). The hydrolysis reactions for uranium would only be important in alkaline pH conditions. Thermodynamic parameters for the hydrolysis species of uranium(VI) and its oxide and hydroxide phases can be determined from the stability and solubility constants. The hydrolytic behaviour of neptunium(VI) is quite similar to that of uranium(VI). The solubility constant of NpO{sub 2}OH(am) has been reported a number of times for both zero ionic strength and in fixed ionic strength media. Americium can form four oxidation states in aqueous solution, namely trivalent, tetravalent, pentavalent and hexavalent. Desire, Hussonnois and Guillaumont determined stability constants for the species AmOH{sup 2+} for the actinides, plutonium(III), americium(III), curium(III), berkelium(III) and californium(III) using a solvent extraction technique.

Actinide metals

International Nuclear Information System (INIS)

Brown, Paul L.; Ekberg, Christian

2016-01-01

All isotopes of actinium are radioactive and exist in aqueous solution only in the trivalent state. There have been very few studies on the hydrolytic reactions of actinium(III). The hydrolysis reactions for uranium would only be important in alkaline pH conditions. Thermodynamic parameters for the hydrolysis species of uranium(VI) and its oxide and hydroxide phases can be determined from the stability and solubility constants. The hydrolytic behaviour of neptunium(VI) is quite similar to that of uranium(VI). The solubility constant of NpO 2 OH(am) has been reported a number of times for both zero ionic strength and in fixed ionic strength media. Americium can form four oxidation states in aqueous solution, namely trivalent, tetravalent, pentavalent and hexavalent. Desire, Hussonnois and Guillaumont determined stability constants for the species AmOH 2+ for the actinides, plutonium(III), americium(III), curium(III), berkelium(III) and californium(III) using a solvent extraction technique.

Effect of high doses of L-ascorbic acid on the antioxidative/oxidative state in the rats

DEFF Research Database (Denmark)

Niemiec, T.; Sawosz, E.; Chwalibog, André

2005-01-01

The objective of this study was to determine the effects of mega-doses of vitamin C (0.3, 0.6 and 0.9% of diet) as a dietary supplement for rats on selected indices of the antioxidative/oxidative state in 40 growing Wistar rats (4x10). It was found that L-ascorbic acid and Total Antioxidative State...... (TAS) in plasma did not increase with increasing vitamin C supply. The results indicate that high doses of L-ascorbic acid (0.3 and 0.9 but not 0.6%) increased the concentration of this antioxidant in plasma. Supplementation of vitamin C above 0.3% to the diets had pro-oxidative effects on lipid...... structures, while application of 0.9% promoted oxidative degradation of rat livers....

Visualizing chemical states and defects induced magnetism of graphene oxide by spatially-resolved-X-ray microscopy and spectroscopy.

Science.gov (United States)

Wang, Y F; Singh, Shashi B; Limaye, Mukta V; Shao, Y C; Hsieh, S H; Chen, L Y; Hsueh, H C; Wang, H T; Chiou, J W; Yeh, Y C; Chen, C W; Chen, C H; Ray, Sekhar C; Wang, J; Pong, W F; Takagi, Y; Ohigashi, T; Yokoyama, T; Kosugi, N

2015-10-20

This investigation studies the various magnetic behaviors of graphene oxide (GO) and reduced graphene oxides (rGOs) and elucidates the relationship between the chemical states that involve defects therein and their magnetic behaviors in GO sheets. Magnetic hysteresis loop reveals that the GO is ferromagnetic whereas photo-thermal moderately reduced graphene oxide (M-rGO) and heavily reduced graphene oxide (H-rGO) gradually become paramagnetic behavior at room temperature. Scanning transmission X-ray microscopy and corresponding X-ray absorption near-edge structure spectroscopy were utilized to investigate thoroughly the variation of the C 2p(π*) states that are bound with oxygen-containing and hydroxyl groups, as well as the C 2p(σ*)-derived states in flat and wrinkle regions to clarify the relationship between the spatially-resolved chemical states and the magnetism of GO, M-rGO and H-rGO. The results of X-ray magnetic circular dichroism further support the finding that C 2p(σ*)-derived states are the main origin of the magnetism of GO. Based on experimental results and first-principles calculations, the variation in magnetic behavior from GO to M-rGO and to H-rGO is interpreted, and the origin of ferromagnetism is identified as the C 2p(σ*)-derived states that involve defects/vacancies rather than the C 2p(π*) states that are bound with oxygen-containing and hydroxyl groups on GO sheets.

Oxidative stress markers in hypertensive states of pregnancy: preterm and term disease.

Directory of Open Access Journals (Sweden)

Lesia Olha Kurlak

2014-08-01

Full Text Available Discussion continues as to whether de novo hypertension in pregnancy with significant proteinuria (pre-eclampsia; PE and non-proteinuric new hypertension (gestational hypertension; GH are parts of the same disease spectrum or represent different conditions. Non-pregnant hypertension, pregnancy and PE are all associated with oxidative stress. We have established a 6 weeks post-partum clinic for women who experienced a hypertensive pregnancy. We hypothesized that PE and GH could be distinguished by markers of oxidative stress; thiobarbituric acid reactive substances (TBARS and antioxidants (ferric ion reducing ability of plasma; FRAP. Since the severity of PE and GH is greater pre-term, we also compared pre-term and term disease. Fifty-eight women had term PE, 23 pre-term PE, 60 had term GH and 6 pre-term GH, 11 pre-existing (essential hypertension (EH without PE. Limited data were available from normotensive pregnancies (n=7 and non-pregnant controls (n=14. There were no differences in postpartum TBARS or FRAP between hypertensive states; TBARS (P=0.001 and FRAP (P=0.009 were lower in plasma of non-pregnant controls compared to recently-pregnant women. Interestingly FRAP was higher in preterm than term GH (P=0.013. In PE and GH, TBARS correlated with low density lipoprotein (LDL-cholesterol (P=0.036; this association strengthened with inclusion of EH ((P=0.011. The 10 year Framingham index for cardiovascular risk was positively associated with TBARS (P=0.003.Oxidative stress profiles do not differ between hypertensive states but appear to distinguish between recently-pregnant and non-pregnant states. This suggests that pregnancy may alter vascular integrity with changes remaining 6 weeks postpartum. LDL-cholesterol is a known determinant of oxidative stress in cardiovascular disease and we have shown this association to be present in hypertensive pregnancy further emphasizing that such a pregnancy may be revealing a pre-existing cardiovascular

Ultrathin reduced graphene oxide films as transparent top-contacts for light switchable solid-state molecular junctions

DEFF Research Database (Denmark)

Li, Tao; Jevric, Martyn; Hauptmann, Jonas Rahlf

2013-01-01

A new type of solid-state molecular junction is introduced, which employs reduced graphene oxide as a transparent top contact that permits a self-assembled molecular monolayer to be photoswitched in situ, while simultaneously enabling charge-transport measurements across the molecules. The electr......A new type of solid-state molecular junction is introduced, which employs reduced graphene oxide as a transparent top contact that permits a self-assembled molecular monolayer to be photoswitched in situ, while simultaneously enabling charge-transport measurements across the molecules...

Determination of Pu Oxidation states in the HCl Media Using with UV-Visible Absorption Spectroscopic Techniques

International Nuclear Information System (INIS)

Lee, Myung Ho; Suh, Mu Yeol; Park, Kyoung Kyun; Park, Yeong Jae; Kim, Won Ho

2006-01-01

The spectroscopic characteristics of Pu (III, IV, V, VI) in the HCl media were investigated by measuring Pu oxidation states using a UV-Vis-NIR spectrophotometer (400-1200 nm) after adjusting Pu oxidation states with oxidation/reduction reagents. Pu in stock solution was reduced to Pu(III) with NH 2 OH · HCl, and oxidized to Pu(IV) and Pu(VI) with NaNO 2 and HCIO 4 , respectively. Also, Pu(V) was adjusted in the Pu(VI) solution with NH 2 OH · HCl. The major absorption peaks of Pu (IV) and Pu(III) were measured in the 470 nm and 600 nm, respectively. The major absorption peaks of Pu (VI) and Pu(V) were measured in the 830 nm and 1135 nm, respectively. There was not found to be significant changes of UV-V is absorption spectra for Pu(III), Pu(IV) and Pu(VI) with aging time, except that an unstable Pu(V) immediately reduced to Pu(III).

Investigation on neptunium behavior in electrolytic partitioning process of uranium and plutonium

International Nuclear Information System (INIS)

Zhang Qingxuan; Zhang Jiajun; Tian Baosheng; Jiang Dongliang; Li Zhaoyi; He Jianyu

1988-01-01

The electrolytic oxidation-raduction of Np(V, VI) in HNO 3 solution was studied. Experimental results showed that the electrode process of Np(V)-Np(VI) couple is reversible, and the half reaction time of the process mentioned above is about 1.5 minutes under given conditions. The overpotential of reduction of Np(V) is high, which makes it difficult to reduce Np(V) into Np(IV) directly at cathode. Owing to a large quantity of U(IV) produced through electrolysis, it is presaged that neptunium will be mainly in tetravalent state in the electrolytic M-S battery. A new type of electrolytic M-S battery was developed, in which anodes were installed in each settling chamber without any specific anode chamber in the battery. Owing to using of the mechanical stirrer driven by a wheel gear, stage efficiency is high. Demonstration campaign was carried out. It follows from the results that the yield of Pu is 99.90 ∼ 99.99%. Separation factor of U from Pu is 3900 ∼ 33000. Material balance of U and Pu is satisfactory. Heavy accumulation of Np in the battery was observed. Np in the battery is mainly in the tetravalent state. It is believed that it is difficult to recover Np quantitatively from single fluent (e.g. 1BP or 1BU) under normal conditions of partitioning step of the PUREX process

The effect on phase separation of the oxidation state of molybdenum in a Na2O-B2O3-SiO2 glass

International Nuclear Information System (INIS)

Kawamoto, Y.; Clemens, K.; Tomozawa, M.; Warden, J.T.

1981-01-01

The effect of oxidation state on phase separation was studied for 13Na 2 O, 49B 2 O 3 , 38SiO 2 (mol%) glasses containing 1 mol% Mo oxide. The glasses were melted under various conditions to vary the oxidation states of Mo ions. The oxidation states of Mo ions were determined by chemical analysis and ESR. The crystallisation tendency, the immiscibility temperature, and the phase separation morphology of the glasses were examined by DTA, x-ray diffraction, opalescence method, and replica electron microscopy. Glasses containing Mo 4+ ions have a great tendency to precipitate MoO 2 crystals. The immiscibility temperature of glass goes through a minimum when the oxidation states of Mo ions are changed. It was suggested that there is an optimum oxidation state to prevent crystallisation and to suppress the phase separation tendency of this system. (author)

Obesity-Associated Oxidative Stress: Strategies Finalized to Improve Redox State

Directory of Open Access Journals (Sweden)

Valeria Gasperi

2013-05-01

Full Text Available Obesity represents a major risk factor for a plethora of severe diseases, including diabetes, cardiovascular disease, non-alcoholic fatty liver disease, and cancer. It is often accompanied by an increased risk of mortality and, in the case of non-fatal health problems, the quality of life is impaired because of associated conditions, including sleep apnea, respiratory problems, osteoarthritis, and infertility. Recent evidence suggests that oxidative stress may be the mechanistic link between obesity and related complications. In obese patients, antioxidant defenses are lower than normal weight counterparts and their levels inversely correlate with central adiposity; obesity is also characterized by enhanced levels of reactive oxygen or nitrogen species. Inadequacy of antioxidant defenses probably relies on different factors: obese individuals may have a lower intake of antioxidant- and phytochemical-rich foods, such as fruits, vegetables, and legumes; otherwise, consumption of antioxidant nutrients is normal, but obese individuals may have an increased utilization of these molecules, likewise to that reported in diabetic patients and smokers. Also inadequate physical activity may account for a decreased antioxidant state. In this review, we describe current concepts in the meaning of obesity as a state of chronic oxidative stress and the potential interventions to improve redox balance.

Obesity-Associated Oxidative Stress: Strategies Finalized to Improve Redox State

Science.gov (United States)

Savini, Isabella; Catani, Maria Valeria; Evangelista, Daniela; Gasperi, Valeria; Avigliano, Luciana

2013-01-01

Obesity represents a major risk factor for a plethora of severe diseases, including diabetes, cardiovascular disease, non-alcoholic fatty liver disease, and cancer. It is often accompanied by an increased risk of mortality and, in the case of non-fatal health problems, the quality of life is impaired because of associated conditions, including sleep apnea, respiratory problems, osteoarthritis, and infertility. Recent evidence suggests that oxidative stress may be the mechanistic link between obesity and related complications. In obese patients, antioxidant defenses are lower than normal weight counterparts and their levels inversely correlate with central adiposity; obesity is also characterized by enhanced levels of reactive oxygen or nitrogen species. Inadequacy of antioxidant defenses probably relies on different factors: obese individuals may have a lower intake of antioxidant- and phytochemical-rich foods, such as fruits, vegetables, and legumes; otherwise, consumption of antioxidant nutrients is normal, but obese individuals may have an increased utilization of these molecules, likewise to that reported in diabetic patients and smokers. Also inadequate physical activity may account for a decreased antioxidant state. In this review, we describe current concepts in the meaning of obesity as a state of chronic oxidative stress and the potential interventions to improve redox balance. PMID:23698776

Oxidation states of Fe and Ti in blue sapphire

International Nuclear Information System (INIS)

Wongrawang, P; Wongkokua, W; Monarumit, N; Thammajak, N; Wathanakul, P

2016-01-01

X-ray absorption near-edge spectroscopy (XANES) can be used to study the oxidation state of a dilute system such as transition metal defects in solid-state samples. In blue sapphire, Fe and Ti are defects that cause the blue color. Inter-valence charge transfer (IVCT) between Fe 2+ and Ti 4+ has been proposed to describe the optical color’s origin. However, the existence of divalent iron cations has not been thoroughly investigated. Fluorescent XANES is therefore employed to study K-edge absorptions of Fe and Ti cations in various blue sapphire samples including natural, synthetic, diffused and heat-treated sapphires. All the samples showed an Fe absorption edge at 7124 eV, corresponding to the Fe 3+ state; and Ti at 4984 eV, corresponding to Ti 4+ . From these results, we propose Fe 3+ -Ti 4+ mixed acceptor states located at 1.75 eV and 2.14 eV above the valence band of corundum, that correspond to 710 nm and 580 nm bands of UV–vis absorption spectra, to describe the cause of the color of blue sapphire. (paper)

Determination of cerium

International Nuclear Information System (INIS)

Stepin, V.V.; Kurbatova, V.I.; Fedorova, N.D.

1980-01-01

Techniques of cerium determination in steels and alloys are developed. Amperometric method of determination which is based on Ce(4) titration by a solution of double salt of sulfuric Fe(2) and ammonium when cerium amount exceeds 0.01% is suggested. Cerium is oxidated to tetravalent state by KMnO 4 . The elements interfering with the determination (Cr, Ni etc.) are separated by means of deposition. When cerium content exceeds 0.005% in steels and alloys the determination is carried out using photometric method with arsenazo 3 in hydrochloric medium (pH 1.8-2.3). Optimum concentration is 5-50 μg [ru

Graphite furnace atomic absorption spectrometric determination of vanadium after cloud point extraction in the presence of graphene oxide

Science.gov (United States)

López-García, Ignacio; Marín-Hernández, Juan José; Hernández-Córdoba, Manuel

2018-05-01

Vanadium (V) and vanadium (IV) in the presence of a small concentration of graphene oxide (0.05 mg mL-1) are quantitatively transferred to the coacervate obtained with Triton X-114 in a cloud point microextraction process. The surfactant-rich phase is directly injected into the graphite atomizer of an atomic absorption spectrometer. Using a 10-mL aliquot sample and 150 μL of a 15% Triton X-114 solution, the enrichment factor for the analyte is 103, which results in a detection limit of 0.02 μg L-1 vanadium. The separation of V(V) and V(IV) using an ion-exchanger allows speciation of the element at low concentrations. Data for seven reference water samples with certified vanadium contents confirm the reliability of the procedure. Several beer samples are also analyzed, those supplied as canned drinks showing low levels of tetravalent vanadium.

Solid-state electrochromic cell with anodic iridium oxide film electrodes

International Nuclear Information System (INIS)

Dautremont-Smith, W.C.; Beni, G.; Schiavone, L.M.; Shay, J.L.

1979-01-01

A new solid-state electrochromic cell has been fabricated using an anodic iridium oxide film (AIROF) display electrode. The cell has the symmetric sandwich structure AIROFvertical-barNafionvertical-barAIROF, with the Nafion solid electrolyte opacified by an in situ precipitation technique. A symmetric square-wave voltage of 1.5 V amplitude produces clearly perceivable color changes from pale to dark blue-gray in approx. =1 sec when viewed in diffuse reflection. Good open-circuit optical memory is exhibited:

Clinical Study of New Tetravalent (Type A, B, E, and F) Botulinum Toxoid Vaccine Derived from M Toxin in Japan.

Science.gov (United States)

Torii, Yasushi; Sugimoto, Nakaba; Kohda, Tomoko; Kozaki, Shunji; Morokuma, Kazunori; Horikawa, Yoshikane; Ginnaga, Akihiro; Yamamoto, Akihiko; Takahashi, Motohide

2017-07-24

Botulinum toxin is the most poisonous substance known, and is believed to be a highly lethal as a biological weapon; researchers of the toxin are exposed to this hazard. Botulinum toxoid vaccines have been produced and used in Japan. However, since clinical studies involving these vaccines were conducted before establishment of the Ethical Guidelines for Clinical Research in Japan, their immunogenicity and safety were not systematically assessed. In this study, we produced a new tetravalent (type A, B, E, and F) botulinum toxoid vaccine, the first ever to be derived from M toxin, and conducted quality control tests with reference to the Minimum Requirements in Japan for adsorbed tetanus toxoid vaccine. Subsequently, a clinical study using the new vaccine in 48 healthy adult volunteers was conducted according to the guidelines in Japan. No clinically serious adverse event was noted. Neutralizing antibody titers for each type of toxin in the participants' sera, 1 month after the 4th injection were more than 0.25 IU/mL, indicating sufficient protection. This study demonstrated that the vaccine has marked immunogenicity and is safe for use in humans.

Intestinal Oxidative State Can Alter Nutrient and Drug Bioavailability

Directory of Open Access Journals (Sweden)

Faria Ana

2009-01-01

Full Text Available Organic cations (OCs are substances of endogenous (e.g., dopamine, choline or exogenous (e.g., drugs like cimetidine origin that are positively charged at physiological ph. since many of these compounds can not pass the cell membrane freely, their transport in or out of cells must be mediated by specific transport systems. Transport by organic cation transporters (OCTs can be regulated rapidly by altering their trafficking and/or affinities in response to stimuli. However, for example, a specific disease could lead to modifications in the expression of OCTs. Chronic exposure to oxidative stress has been suggested to alter regulation and functional activity of proteins through several pathways. According to results from a previous work, oxidation-reduction pathways were thought to be involved in intestinal organic cation uptake modulation. The present work was performed in order to evaluate the influence of oxidative stressors, especially glutathione, on the intestinal organic cation absorption. For this purpose, the effect of compounds with different redox potential (glutathione, an endogenous antioxidant, and procyanidins, diet antioxidants was assessed on MPP+ (1-methyl-4-phenylpyridinium iodide uptake in an enterocyte cell line (Caco-2. Caco-2 cells were subcultured with two different media conditions (physiological: 5 mM glucose, referred as control cells; and high-glucose: 25 mM glucose, referred as HG cells. In HG cells, the uptake was significantly lower than in control cells. Redox changing interventions affected Mpp+ uptake, both in control and in high-glucose Caco-2 cells. Cellular glutathione levels could have an important impact on membrane transporter activity. The results indicate that modifications in the cellular oxidative state modulate MPP+ uptake by Caco-2 cells. Such modifications may reflect in changes of nutrient and drug bioavailability.

Teaching the Properties of Chromium's Oxidation States with a Case Study Method

Science.gov (United States)

Ozdilek, Zehra

2015-01-01

The purpose of this study was to investigate how a mixed-method case study affects pre-service science teachers' awareness of hexavalent chromium pollution and content knowledge about the properties of chromium's different oxidation states. The study was conducted in Turkey with 55 sophomores during the fall semester of 2013-2014. The students…

Immobilization of tetravalent actinides in three phosphate based ceramics: britholites, TPD and monazites/brabantites

International Nuclear Information System (INIS)

Terra, O.; Audubert, F.; Dacheux, N.; Guy, C.; Podor, R.

2004-01-01

Three phosphate based ceramics were studied for the immobilization of tri- and tetravalent actinides: britholites Ca 9 Nd 1-x An x IV (PO 4 ) 5-x (SiO 4 ) 1+x F 2 , monazites/brabantites Ln 1-2x III Ca x An x IV PO 4 and Thorium Phosphate Diphosphate (TPD) Th 4-x An x IV (PO 4 ) 4 P 2 O 7 . For each material, the incorporation of Th, U(IV), or Ce(IV) in the structure was examined. This work was the early beginning of the incorporation of 239 Pu and/or 238 Pu in order to evaluate the effects of α -decay on these three crystallographic structures. The syntheses were carried out using dry chemistry methods, involving mechanical grinding then heating treatment (1100 deg C ≤ θ ≤ 1400 deg C). For britholites, we showed that the incorporation of thorium was complete for weight loading lower than 20 wt.% through the (Nd 3+ , PO 4 3- ) ↔ (Th 4+ , SiO 4 4- ) coupled substitution, leading to the preparation of solid solutions. Due to redox problems, the incorporation of uranium was limited to 5 to 8 wt.% and always led to a two-phase mixture of U-britholite and CaU 2 O 5+y . For solid solutions based on TPD and for brabantites, the syntheses dealing with the incorporation of Th and/or U(IV) were improved by dry chemistry method using three mechanical grinding-calcination cycles. For both solids, homogeneous and single phase samples of the corresponding solid solutions were obtained. Finally, dense pellets of britholites, monazites/brabantites and TAn IV PD solid solutions were prepared in order to study their chemical durability during leaching tests. (authors)

Molecular beam epitaxy growth of niobium oxides by solid/liquid state oxygen source and lithium assisted metal-halide chemistry

Science.gov (United States)

Tellekamp, M. Brooks; Greenlee, Jordan D.; Shank, Joshua C.; Doolittle, W. Alan

2015-09-01

In order to consistently grow high quality niobium oxides and lithium niobium oxides, a novel solid/liquid state oxygen source, LiClO4, has been implemented in a molecular beam epitaxy (MBE) system. LiClO4 is shown to decompose into both molecular and atomic oxygen upon heating. This allows oxidation rates similar to that of molecular oxygen but at a reduced overall beam flux, quantified by in situ Auger analysis. LiClO4 operation is decomposition limited to less than 400 °C, and other material limitations are identified. The design of a custom near-ambient NbCl5 effusion cell is presented, which improves both short and long term stability. Films of Nb oxidation state +2, +3, and +5 are grown using these new tools, including the multi-functional sub-oxide LiNbO2.

Speciation of the oxidation states of plutonium in aqueous solutions by UV/Vis spectroscopy, CE-ICP-MS and CE-RIMS

International Nuclear Information System (INIS)

Buerger, S.; Banik, N.L.; Buda, R.A.; Kratz, J.V.; Kuczewski, B.; Trautmann, N.

2007-01-01

For the speciation of the plutonium oxidation states in aqueous solutions, the online coupling of capillary electrophoresis (CE) with inductively coupled plasma mass spectrometry (ICP-MS) has been developed. Depending on the radius/electrical charge ratio, the oxidation states III, IV, V, and VI of plutonium are separated by CE, based on the different migration times through the capillary and are detected by ICP-MS. The detection limit is 20 ppb, i.e. 10 9 -10 10 atoms (10 -12 -10 -13 g) for one oxidation state with an uncertainty of the reproducibility of the migration times of ≤ 1% and ≤ 5% for the peak area. The redox kinetics of the different plutonium oxidation states in the presence of humic substances (humic and fulvic acid) have been studied. A relatively rapid reduction of Pu(VI) (10 to 1000 h) in contact with Gorleben fulvic or Aldrich humic acid could be observed, depending on the pH of the solution. Furthermore, at pH=1, a reduction to Pu(III) and Pu(IV) in a mixture of all four oxidation states in contact with Gorleben fulvic acid after one month has been observed. In order to improve the sensitivity of the CE method, the offline coupling of CE to resonance ionization mass spectrometry (RIMS) has been explored. First applications of this new speciation method are presented. (orig.)

Raman spectroscopic study of the oxidation state of Eu in molten LiCl-KCl

Energy Technology Data Exchange (ETDEWEB)

Park, Seung; Yun, Jong-Il [KAIST, Daejeon(Korea, Republic of)

2016-10-15

Spectroscopy can provide high reliability for the quantitative analysis of such system. The molar absorptivity of Eu(II) at 325 nm is reported as about 1645 M{sup -1}cm{sup -1}, which is too high to apply to higher concentration. A high-temperature Raman spectroscopy has been set and employed for analyzing the molecular structure and coordination complex and investigating the oxidation state of europium in molten LiCl-KCl. Europium can be present in divalent state while many other lanthanides exist in trivalent state. The thermodynamic properties of europium ions have been studied using electrochemical methods, spectroscopic methods, and EPR technique. Although there has been discrepancy of the reduced amount of europium in previous works, the majority of Eu(III) is thought to be reduced to Eu(II) in molten LiCl-KCl spontaneously at relatively low concentration (< 7.5 × 10{sup -4} M). Raman spectroscopy was employed to investigate the oxidation state of EuClx in LiCl-KCl at 500 .deg. C. The Raman scattering results suggest the majority of trivalent europium is reduced to divalent state with the composition change by vaporization. The Raman bands show highly asymmetric structure, quite different from regular octahedral structure.

Chemical state analysis of oxidation products on steel surface by conversion electron Moessbauer spectrometry

International Nuclear Information System (INIS)

Ujihira, Yusuke; Nomura, Kiyoshi

1978-01-01

The polished NT-70H steel (Fe: 95.97%, C: 0.56%, diameter: 5 cm, thickness: 0.5 cm) was immersed in deionized water or in solutions containing (0.25 -- 0.5) M of chloride, sulfate and nitrate ions. The chemical states of oxidation products of iron on the surface were identified through the analysis of conversion electron Moessbauer spectra (CEMS). CEMS of the steel surface, which had been dipped in deionized water, revealed that γ-FeOOH was formed on the surface. The thickness of γ-FeOOH layer increased with the increase of the duration of dipping. Dissolved oxygen in the solution played an essential role in the oxidation of iron to γ-FeOOH. Oxidation product of iron dipped in the 0.5 M sodium chloride solution was identified as γ-FeOOH. Amorphous paramagnetic iron (III) compound tended to form in the presence of hydrogen peroxide or ammonium ions in the solutions. The increase of alkalinity of the solution up to pH 12 suppressed the oxidation rate and assisted the formation of green rust, which was confirmed by the appearance of the quadrupole splitting peaks of the green rust. In the 0.25 M sodium sulfate solution, oxidation of the steel surface proceeded slowly and the quadrupole splitting peaks of Fe(OH) 2 were seen in the CEMS. The peak intensity of Fe(OH) 2 gradually decreased and that of γ-FeOOH increased by the extension of immersion of steel in the solution. Magnetite (Fe 3 O 4 ) layer was developed beneath the γ-FeOOH layer, when steel was dipped in 0.5 M sodium nitrate solution. However, the peaks of Fe 3 O 4 were not seen on CEMS of steel surface immersed in 0.5 M ammonium nitrate solution. Thus, applying the feasibility of CEMS for the characterization of oxidated compounds of iron on the steel surface formed by the immersion in solutions, the oxidation mechanism of the steel surface was discussed based upon the results of chemical state analyses. (author)

Solid state chemistry of rare earth oxides. Final report, September 1, 1950--July 31, 1977

International Nuclear Information System (INIS)

Eyring, L.

1977-07-01

Work under Contract E(11-1)-1109 and its antecedents has been primarily for the purpose of obtaining detailed thermodynamic, kinetic and structural information on the complex rare earth oxides of praseodymium and terbium. These systems exhibit homologous series of ordered phases, order-disorder transformations, wide-range nonstoichiometric phases, chemical hysteresis in two-phase regions and many other solid state reaction phenomena. Fluorite-related materials of importance to ERDA occur as nuclear fuels, radiation power sources, insulators and solid electrolytes. The rare earth oxides serve directly as model systems for such similar materials and, in a more general sense, they serve as models of solids in general since they exhibit nearly the full range of solid state properties

Assigning Oxidation States to Organic Compounds via Predictions from X-Ray Photoelectron Spectroscopy: A Discussion of Approaches and Recommended Improvements

Science.gov (United States)

Gupta, Vipul; Ganegoda, Hasitha; Engelhard, Mark H.; Terry, Jeff; Linford, Matthew R.

2014-01-01

The traditional assignment of oxidation states to organic molecules is problematic. Accordingly, in 1999, Calzaferri proposed a simple and elegant solution that is based on the similar electronegativities of carbon and hydrogen: hydrogen would be assigned an oxidation state of zero when bonded to carbon. Here, we show that X-ray photoelectron…

SOLID STATE ENERGY CONVERSION ALLIANCE (SECA) SOLID OXIDE FUEL CELL PROGRAM

Energy Technology Data Exchange (ETDEWEB)

Unknown

2003-06-01

This report summarizes the progress made during the September 2001-March 2002 reporting period under Cooperative Agreement DE-FC26-01NT41245 for the U. S. Department of Energy, National Energy Technology Laboratory (DOE/NETL) entitled ''Solid State Energy Conversion Alliance (SECA) Solid Oxide Fuel Cell Program''. The program focuses on the development of a low-cost, high-performance 3-to-10-kW solid oxide fuel cell (SOFC) system suitable for a broad spectrum of power-generation applications. The overall objective of the program is to demonstrate a modular SOFC system that can be configured to create highly efficient, cost-competitive, and environmentally benign power plants tailored to specific markets. When fully developed, the system will meet the efficiency, performance, life, and cost goals for future commercial power plants.

What a difference a 5f element makes: trivalent and tetravalent uranium halide complexes supported by one and two bis[2-(diisopropylphosphino)-4-methylphenyl]amido (PNP) ligands.

Science.gov (United States)

Cantat, Thibault; Scott, Brian L; Morris, David E; Kiplinger, Jaqueline L

2009-03-02

The coordination behavior of the bis[2-(diisopropylphosphino)-4-methylphenyl]amido ligand (PNP) toward UI3(THF)4 and UCl4 has been investigated to access new uranium(III) and uranium(IV) halide complexes supported by one and two PNP ligands. The reaction between (PNP)K (6) and 1 equiv of UI3(THF)4 afforded the trivalent halide complex (PNP)UI2(4-tBu-pyridine)2 (7) in the presence of 4-tert-butylpyridine. The same reaction carried out with UCl4 and no donor ligand gave [(PNP)UCl3]2 (8), in which the uranium coordination sphere in the (PNP)UCl3 unit is completed by a bridging chloride ligand. When UCl4 is reacted with 1 equiv (PNP)K (6) in the presence of THF, trimethylphosphine oxide (TMPO), or triphenylphosphineoxide (TPPO), the tetravalent halide complexes (PNP)UCl3(THF) (9), (PNP)UCl3(TMPO)2 (10), and (PNP)UCl3(TPPO) (11), respectively, are formed in excellent yields. The bis(PNP) complexes of uranium(III), (PNP)2UI (12), and uranium(IV), (PNP)2UCl2 (13), were easily isolated from the analogous reactions between 2 equiv of 6 and UI3(THF)4 or UCl4, respectively. Complexes 12 and 13 represent the first examples of complexes featuring two PNP ligands coordinated to a single metal center. Complexes 7-13 have been characterized by single-crystal X-ray diffraction and 1H and 31P NMR spectroscopy. The X-ray structures demonstrate the ability of the PNP ligand to adopt new coordination modes upon coordination to uranium. The PNP ligand can adopt both pseudo-meridional and pseudo-facial geometries when it is kappa3-(P,N,P) coordinated, depending on the steric demand at the uranium metal center. Additionally, its hemilabile character was demonstrated with an unusual kappa2-(P,N) coordination mode that is maintained in both the solid-state and in solution. Comparison of the structures of the mono(PNP) and bis(PNP) complexes 7, 9, 11-13 with their respective C5Me5 analogues 1-4 undoubtedly show that a more sterically congested environment is provided by the PNP ligand. The

Solid-phase extraction of plutonium in various oxidation states from simulated groundwater using N-benzoylphenylhydroxylamine

International Nuclear Information System (INIS)

Perevalov, S.A.; Malofeeva, G.I.; Kuzovkina, E.V.; Spivakov, B.Ya.

2013-01-01

Solid-phase extraction of plutonium in different individual and mixed oxidation states from simulated groundwater (pH 8.5) was studied. The extraction of plutonium species was carried out in a dynamic mode using DIAPAK C16 cartridges modified by N-benzoylphenylhydroxylamine (BPHA). It was shown that the extent of recovery depends on the oxidation state of plutonium. The extraction of Pu(IV) was at the level of 98-99% regardless of the volume and flow-rate of the sample solution. Pu(V) was extracted by 90-95% and 75-80% from 10- and 100-mL aliquots of the samples, respectively, whereas the extraction of Pu(VI) did not exceed 45-50%. An equimolar mixture of Pu(IV), Pu(V), and Pu(VI) was extracted by 74%. The distribution coefficients (K d ) and kinetic exchange capacities (S) of plutonium in various oxidation states were measured. It was found that during the sorption process, Pu(V) was reduced to Pu(IV) by 80-90% after an hour-long contact with the solid phase. Pu(VI) is reduced to Pu(V) by 34% and to Pu(IV) by 55%. In the case of mixed-valent solution of plutonium, only Pu(V) and Pu(IV) were found in the effluents. (author)

Frustration under pressure: Exotic magnetism in new pyrochlore oxides

Directory of Open Access Journals (Sweden)

C. R. Wiebe

2015-04-01

Full Text Available Pyrochlore structures, of chemical formula A2B2O7 (A and B are typically trivalent and tetravalent ions, respectively, have been the focus of much activity in the condensed matter community due to the ease of substitution of rare earth and transition metal ions upon the two interpenetrating corner-shared tetrahedral lattices. Over the last few decades, superconductivity, spin liquid states, spin ice states, glassy states in the absence of chemical disorder, and metal-insulator transitions have all been discovered in these materials. Geometric frustration plays a role in the relevant physics of all of these phenomena. In the search for new pyrochlore materials, it is the RA/RB cation radius ratio which determines the stability of the lattice over the defect fluorite structure in the lower limit. Under ambient pressure, the pyrochlores are stable for 1.36 ≤ RA/RB ≤ 1.71. However, using high pressure synthesis techniques (1-10 GPa of pressure, metastable pyrochlores exist up to RA/RB = 2.30. Many of these compounds are stable on a timescale of years after synthesis, and provide a means to greatly enhance exchange, and thus test theories of quantum magnetism and search for new phenomena. Within this article, we review new pyrochlore compounds synthesized via high pressure techniques and show how the ground states are extremely sensitive to chemical pressure.

Exploratory Characterization of Phenolic Compounds with Demonstrated Anti-Diabetic Activity in Guava Leaves at Different Oxidation States

Science.gov (United States)

Díaz-de-Cerio, Elixabet; Verardo, Vito; Gómez-Caravaca, Ana María; Fernández-Gutiérrez, Alberto; Segura-Carretero, Antonio

2016-01-01

Psidium guajava L. is widely used like food and in folk medicine all around the world. Many studies have demonstrated that guava leaves have anti-hyperglycemic and anti-hyperlipidemic activities, among others, and that these activities belong mainly to phenolic compounds, although it is known that phenolic composition in guava tree varies throughout seasonal changes. Andalusia is one of the regions in Europe where guava is grown, thus, the aim of this work was to study the phenolic compounds present in Andalusian guava leaves at different oxidation states (low, medium, and high). The phenolic compounds in guava leaves were determined by HPLC-DAD-ESI-QTOF-MS. The results obtained by chromatographic analysis reported that guava leaves with low degree of oxidation had a higher content of flavonols, gallic, and ellagic derivatives compared to the other two guava leaf samples. Contrary, high oxidation state guava leaves reported the highest content of cyanidin-glucoside that was 2.6 and 15 times higher than guava leaves with medium and low oxidation state, respectively. The QTOF platform permitted the determination of several phenolic compounds with anti-diabetic properties and provided new information about guava leaf phenolic composition that could be useful for nutraceutical production. PMID:27187352

Exploratory Characterization of Phenolic Compounds with Demonstrated Anti-Diabetic Activity in Guava Leaves at Different Oxidation States

Directory of Open Access Journals (Sweden)

Elixabet Díaz-de-Cerio

2016-05-01

Full Text Available Psidium guajava L. is widely used like food and in folk medicine all around the world. Many studies have demonstrated that guava leaves have anti-hyperglycemic and anti-hyperlipidemic activities, among others, and that these activities belong mainly to phenolic compounds, although it is known that phenolic composition in guava tree varies throughout seasonal changes. Andalusia is one of the regions in Europe where guava is grown, thus, the aim of this work was to study the phenolic compounds present in Andalusian guava leaves at different oxidation states (low, medium, and high. The phenolic compounds in guava leaves were determined by HPLC-DAD-ESI-QTOF-MS. The results obtained by chromatographic analysis reported that guava leaves with low degree of oxidation had a higher content of flavonols, gallic, and ellagic derivatives compared to the other two guava leaf samples. Contrary, high oxidation state guava leaves reported the highest content of cyanidin-glucoside that was 2.6 and 15 times higher than guava leaves with medium and low oxidation state, respectively. The QTOF platform permitted the determination of several phenolic compounds with anti-diabetic properties and provided new information about guava leaf phenolic composition that could be useful for nutraceutical production.

Exploratory Characterization of Phenolic Compounds with Demonstrated Anti-Diabetic Activity in Guava Leaves at Different Oxidation States.

Science.gov (United States)

Díaz-de-Cerio, Elixabet; Verardo, Vito; Gómez-Caravaca, Ana María; Fernández-Gutiérrez, Alberto; Segura-Carretero, Antonio

2016-05-11

Psidium guajava L. is widely used like food and in folk medicine all around the world. Many studies have demonstrated that guava leaves have anti-hyperglycemic and anti-hyperlipidemic activities, among others, and that these activities belong mainly to phenolic compounds, although it is known that phenolic composition in guava tree varies throughout seasonal changes. Andalusia is one of the regions in Europe where guava is grown, thus, the aim of this work was to study the phenolic compounds present in Andalusian guava leaves at different oxidation states (low, medium, and high). The phenolic compounds in guava leaves were determined by HPLC-DAD-ESI-QTOF-MS. The results obtained by chromatographic analysis reported that guava leaves with low degree of oxidation had a higher content of flavonols, gallic, and ellagic derivatives compared to the other two guava leaf samples. Contrary, high oxidation state guava leaves reported the highest content of cyanidin-glucoside that was 2.6 and 15 times higher than guava leaves with medium and low oxidation state, respectively. The QTOF platform permitted the determination of several phenolic compounds with anti-diabetic properties and provided new information about guava leaf phenolic composition that could be useful for nutraceutical production.

Elevated oxidative stress monitored via the albumin-thiol redox state is correlated with matrix metalloproteinase-3 elevation in patients with rheumatoid arthritis.

Science.gov (United States)

Kizaki, Kazuha; Yoshizumi, Yusuke; Takahashi, Teppei; Era, Seiichi

2015-01-01

In rheumatoid arthritis (RA), matrix metalloproteinase-3 (MMP-3) and oxidative stress contribute to joint destruction. However, little is known about the relationship between MMP-3 and oxidative stress in RA. We measured the albumin-thiol redox state as a marker of oxidative stress, MMP-3, and the DAS-28 score calculated using CRP values among forty-seven patients (9 males and 38 females) with RA. According to the serum MMP-3 levels, they were divided into two groups (group A: within normal ranges of 36.9-121.0 ng/mL for men and 17.3-59.7 ng/mL for women; group B: above normal ranges). The albumin-thiol redox state in group B was significantly oxidized compared with that in group A (p < 0.01). The percentage of oxidized albumin-thiol showed a positive correlation with serum MMP-3 (r = 0.52). DAS-28 and CRP were also correlated with the percentage of oxidized albumin-thiol (r = 0.46, r = 0.44). The albumin-thiol redox state was significantly oxidized in correlation with serum MMP-3 elevation in RA.

Electrochemical determination of the oxidation potentials and the thermodynamic stability of the valence states of the transuranium elements in aqueous alkaline media

International Nuclear Information System (INIS)

Peretrukhin, V.F.; Spitsyn, V.I.

1982-01-01

The oxidation potentials of neptunium, plutonium, and americium in the valance states from (III) to (VII) have been determined experimentally in 0.1-15 M NaOH. Heptavalent plutonium and americium are thermodynamically able to oxidize water with the evolution of oxygen in 0.1-15 M NaOH, neptunium(VII) in 0.1-7 M NaOH. All valance states of plutonium resist disproportionation in alkaline solutions; in the case of neptunium and americium only one disproportionation reaction is possible; of the hexavalent state in to penta- and heptavalent states. The degree of completion of the reaction can be calculated accurately from the oxidation potentials determined

The Behavior of the Ru-bda Water Oxidation Catalysts at Low Oxidation States.

Science.gov (United States)

Matheu, Roc; Ghaderian, Abolfazl; Francas, Laia; Chernev, Petko; Ertem, Mehmed; Benet-Buchholz, Jordi; Batista, Victor; Haumann, Michael; Gimbert-Suriñach, Carolina; Sala, Xavier; Llobet, Antoni

2018-06-13

The Ru complex [RuII(bda-κ-N2O2)(N-NH2)2], 1, (bda2- = (2,2'-bipyridine)-6,6'-dicarboxylate; N-NH2 = 4-(pyridin-4-yl)aniline) is used as a synthetic intermediate to prepare Ru-bda complexes that contain the NO+, acetonitrile (MeCN) or H2O ligands at oxidation states II and III. Complex 1 reacts with excess NO+ to form a Ru complex where the aryl amine ligands N-NH2 in 1 are transformed into diazonium salts (N-N2+ = 4-(pyridin-4-yl)benzenediazonium)) together with the formation of a new Ru-NO group at the equatorial zone, to generate [RuII(bda-κ-N2O)(NO)(N-N2)2]3+, 23+. Similarly, complex 1 can also react with a coordinating solvent, such as MeCN, at room temperature leading to complex [RuII(bda-κ-N2O)(MeCN)(N-NH2)2], 3. Finally in acidic aqueous solutions solvent water coordinates the Ru center forming {[RuII(bda-κ-(NO)3)(H2O)(N-NH3)2](H2O)n}2+, 42+, that is strongly hydrogen bonded with additional water molecules at the second coordination sphere. We have additionally characterized the one electron oxidized complex {[RuIII(bda-κ-(NO)3.5)(H2O)(N-NH3)2](H2O)n}3+, 53+. The coordination mode of the complexes has been studied both in the solid state and in solution through single-crystal XRD, X-ray absorption spectroscopy, variable-temperature NMR and DFT calculations. While the κ-N2O is the main coordination mode for 23+ and 3, an equilibrium that involves isomers with κ-N2O and κ-NO2 coordination modes and neighboring hydrogen bonded water molecules is observed for 42+ and 53+. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Interface Controlled Oxidation States in Layered Cobalt Oxide Nanoislands on Gold

DEFF Research Database (Denmark)

Walton, Alexander; Fester, Jakob; Bajdich, Michal

2015-01-01

Layered cobalt oxides have been shown to be highly active catalysts for the oxygen evolution reaction (OER; half of the catalytic “water splitting” reaction), particularly when promoted with gold. However, the surface chemistry of cobalt oxides and in particular the nature of the synergistic effect...

Triplet-State Dissolved Organic Matter Quantum Yields and Lifetimes from Direct Observation of Aromatic Amine Oxidation.

Science.gov (United States)

Schmitt, Markus; Erickson, Paul R; McNeill, Kristopher

2017-11-21

Excited triplet state chromophoric dissolved organic matter ( 3 CDOM*) is a short-lived mixture of excited-state species that plays important roles in aquatic photochemical processes. Unlike the study of the triplet states of well-defined molecules, which are amenable to transient absorbance spectroscopy, the study of 3 CDOM* is hampered by it being a complex mixture and its low average intersystem crossing quantum yield (Φ ISC ). This study is an alternative approach to investigating 3 CDOM* using transient absorption laser spectroscopy. The radical cation of N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD), formed through oxidation by 3 CDOM*, was directly observable by transient absorption spectroscopy and was used to probe basic photophysical properties of 3 CDOM*. Quenching and control experiments verified that TMPD •+ was formed from 3 CDOM* under anoxic conditions. Model triplet sensitizers with a wide range of excited triplet state reduction potentials and CDOM oxidized TMPD at near diffusion-controlled rates. This gives support to the idea that a large cross-section of 3 CDOM* moieties are able to oxidize TMPD and that the complex mixture of 3 CDOM* can be simplified to a single signal. Using the TMPD •+ transient, the natural triplet lifetime and Φ ISC for different DOM isolates and natural waters were quantified; values ranged from 12 to 26 μs and 4.1-7.8%, respectively.

Evidences for the Formation of Chromium in the Unusual Oxidation State Cr(IV). I. Chemical Reactivity, Microhomogeneity, and Crystal Structures of the Nonstoichiometric Channel Compounds Tl xCr 5Se 8(0 ≤ x≤ 1)

Science.gov (United States)

Bensch, W.; Helmer, O.; Näther, C.

1996-11-01

are only slightly affected. These results suggest an oxidation of the formally trivalent Cr to the unusual tetravalent state Cr(IV), rather than the formation of valence band holes.

Effect of particle size on iron nanoparticle oxidation state

International Nuclear Information System (INIS)

Lombardo, Jeffrey J.; Lysaght, Andrew C.; Goberman, Daniel G.; Chiu, Wilson K.S.

2012-01-01

Selecting catalyst particles is a very important part of carbon nanotube growth, although the properties of these nanoscale particles are unclear. In this article iron nanoparticles are analyzed through the use of atomic force microscopy and x-ray photoelectron spectroscopy in order to understand how the size affects the chemical composition of nanoparticles and thus their physical structure. Initially, atomic force microscopy was used to confirm the presence of iron particles, and to determine the average size of the particles. Next an analytical model was developed to estimate particle size as a function of deposition time using inputs from atomic force microscopy measurement. X-ray photoelectron spectroscopy analysis was then performed with a focus on the spectra relating to the 2p Fe electrons to study the chemical state of the particles as a function of time. It was shown that as the size of nanoparticles decreased, the oxidation state of the particles changed due to a high proportion of atoms on the surface.

High-Pressure Reactivity of Kr and F2—Stabilization of Krypton in the +4 Oxidation State

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Dominik Kurzydłowski

2017-10-01

Full Text Available Since the synthesis of the first krypton compound, several other Kr-bearing connections have been obtained. However, in all of them krypton adopts the +2 oxidation state, in contrast to xenon which forms numerous compounds with an oxidation state as high as +8. Motivated by the possibility of thermodynamic stabilization of exotic compounds with the use of high pressure (exceeding 1 GPa = 10 kbar, we present here theoretical investigations into the chemistry of krypton and fluorine at such large compression. In particular we focus on krypton tetrafluoride, KrF4, a molecular crystal in which krypton forms short covalent bonds with neighboring fluorine atoms thus adopting the +4 oxidation state. We find that this hitherto unknown compound can be stabilized at pressures below 50 GPa. Our results indicate also that, at larger compressions, a multitude of other KrmFn fluorides should be stable, among them KrF which exhibits covalent Kr–Kr bonds. Our results set the stage for future high-pressure synthesis of novel krypton compounds.

Operando XAS Study of the Surface Oxidation State on a Monolayer IrO_x on RuO_x and Ru Oxide Based Nanoparticles for Oxygen Evolution in Acidic Media

DEFF Research Database (Denmark)

Pedersen, Anders Filsøe; Escribano, Maria Escudero; Sebok, Bela

2018-01-01

that the average Ir oxidation state change is strongly affected by the coverage of atomic O. The observed shifts in oxidation state suggest that the surface has a high coverage of O at potentials just below the potential where oxygen evolution is exergonic in free energy. This observation is consistent...

Determination of Model Kinetics for Forced Unsteady State Operation of Catalytic CH4 Oxidation

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Effendy Mohammad

2016-01-01

Full Text Available The catalytic oxidation of methane for abating the emission vented from coal mine or natural gas transportation has been known as most reliable method. A reverse flow reactor operation has been widely used to oxidize this methane emission due to its capability for autothermal operation and heat production. The design of the reverse flow reactor requires a proper kinetic rate expression, which should be developed based on the operating condition. The kinetic rate obtained in the steady state condition cannot be applied for designing the reactor operated under unsteady state condition. Therefore, new approach to develop the dynamic kinetic rate expression becomes indispensable, particularly for periodic operation such as reverse flow reactor. This paper presents a novel method to develop the kinetic rate expression applied for unsteady state operation. The model reaction of the catalytic methane oxidation over Pt/-Al2O3 catalyst was used with kinetic parameter determined from laboratory experiments. The reactor used was a fixed bed, once-through operation, with a composition modulation in the feed gas. The switching time was set at 3 min by varying the feed concentration, feed flow rate, and reaction temperature. The concentrations of methane in the feed and product were measured and analysed using gas chromatography. The steady state condition for obtaining the kinetic rate expression was taken as a base case and as a way to judge its appropriateness to be applied for dynamic system. A Langmuir-Hinshelwood reaction rate model was developed. The time period during one cycle was divided into some segments, depending on the ratio of CH4/O2. The experimental result shows that there were kinetic regimes occur during one cycle: kinetic regime controlled by intrinsic surface reaction and kinetic regime controlled by external diffusion. The kinetic rate obtained in the steady state operation was not appropriate when applied for unsteady state operation

Manganese oxidation state mediates toxicity in PC12 cells

International Nuclear Information System (INIS)

Reaney, S.H.; Smith, D.R.

2005-01-01

The role of the manganese (Mn) oxidation state on cellular Mn uptake and toxicity is not well understood. Therefore, undifferentiated PC12 cells were exposed to 0-200 μM Mn(II)-chloride or Mn(III)-pyrophosphate for 24 h, after which cellular manganese levels were measured along with measures of cell viability, function, and cytotoxicity (trypan blue exclusion, medium lactate dehydrogenase (LDH), 8-isoprostanes, cellular ATP, dopamine, serotonin, H-ferritin, transferrin receptor (TfR), Mn-superoxide dismutase (MnSOD), and copper-zinc superoxide dismutase (CuZnSOD) protein levels). Exposures to Mn(III) >10 μM produced 2- to 5-fold higher cellular manganese levels than equimolar exposures to Mn(II). Cell viability and ATP levels both decreased at the highest Mn(II) and Mn(III) exposures (150-200 μM), while Mn(III) exposures produced increases in LDH activity at lower exposures (≥50 μM) than did Mn(II) (200 μM only). Mn(II) reduced cellular dopamine levels more than Mn(III), especially at the highest exposures (50% reduced at 200 μM Mn(II)). In contrast, Mn(III) produced a >70% reduction in cellular serotonin at all exposures compared to Mn(II). Different cellular responses to Mn(II) exposures compared to Mn(III) were also observed for H-ferritin, TfR, and MnSOD protein levels. Notably, these differential effects of Mn(II) versus Mn(III) exposures on cellular toxicity could not simply be accounted for by the different cellular levels of manganese. These results suggest that the oxidation state of manganese exposures plays an important role in mediating manganese cytotoxicity

Proteomic indicators of oxidation and hydration state in colorectal cancer

Directory of Open Access Journals (Sweden)

Jeffrey M. Dick

2016-07-01

Full Text Available New integrative approaches are needed to harness the potential of rapidly growing datasets of protein expression and microbial community composition in colorectal cancer. Chemical and thermodynamic models offer theoretical tools to describe populations of biomacromolecules and their relative potential for formation in different microenvironmental conditions. The average oxidation state of carbon (ZC can be calculated as an elemental ratio from the chemical formulas of proteins, and water demand per residue ( ${\\overline{n}}_{{\\mathrm{H}}_{2}\\mathrm{O}}$ n ¯ H 2 O is computed by writing the overall formation reactions of proteins from basis species. Using results reported in proteomic studies of clinical samples, many datasets exhibit higher mean ZC or ${\\overline{n}}_{{\\mathrm{H}}_{2}\\mathrm{O}}$ n ¯ H 2 O of proteins in carcinoma or adenoma compared to normal tissue. In contrast, average protein compositions in bacterial genomes often have lower ZC for bacteria enriched in fecal samples from cancer patients compared to healthy donors. In thermodynamic calculations, the potential for formation of the cancer-related proteins is energetically favored by changes in the chemical activity of H2O and fugacity of O2 that reflect the compositional differences. The compositional analysis suggests that a systematic change in chemical composition is an essential feature of cancer proteomes, and the thermodynamic descriptions show that the observed proteomic transformations in host tissue could be promoted by relatively high microenvironmental oxidation and hydration states.

EXAFS analysis of the L3 edge of Ce in CeO2: effects of multielectron excitations and final-state mixed valence

International Nuclear Information System (INIS)

Fonda, E.; Andreatta, D.; Colavita, P.E.; Vlaic, G.

1999-01-01

Cerium oxide (IV) (CeO 2 ) is extensively employed in heterogeneous catalysis, particularly as a promoter of noble metal action in three-way catalysts. For this reason there is a great scientific and economical interest in the development of any possible chemical or structural analysis technique that could provide information on these systems. EXAFS spectroscopy has revealed itself as a powerful technique for structural characterization of such catalysts. Unfortunately, good quality K-edge spectra of cerium are not yet easily obtainable because of the high photon energy required (>40 keV). On the other hand, at lower energies it is easy to collect very good spectra of the L 3 edge (5.5 keV), but L 3 -edge spectra of cerium (IV) are characterized by the presence of two undesired additional phenomena that interfere with EXAFS analysis: final-state mixed-valence behaviour and intense multi-electron excitations. Here, a comparative analysis of the K, L 3 , L 2 and L 1 edges of Ce in CeO 2 has been made and a procedure for obtaining structural parameters from L 3 -edge EXAFS, even in the presence of these features, has been developed. This procedure could allow further studies of catalytic compounds containing tetravalent cerium surrounded by oxygen ligands. (au)

Surface State Capture Cross-Section at the Interface between Silicon and Hafnium Oxide

Directory of Open Access Journals (Sweden)

Fu-Chien Chiu

2013-01-01

Full Text Available The interfacial properties between silicon and hafnium oxide (HfO2 are explored by the gated-diode method and the subthreshold measurement. The density of interface-trapped charges, the current induced by surface defect centers, the surface recombination velocity, and the surface state capture cross-section are obtained in this work. Among the interfacial properties, the surface state capture cross-section is approximately constant even if the postdeposition annealing condition is changed. This effective capture cross-section of surface states is about 2.4 × 10−15 cm2, which may be an inherent nature in the HfO2/Si interface.

NeptuniumV Retention by Siderite under Anoxic Conditions: Precipitation of NpO2-Like Nanoparticles and of NpIV Pentacarbonate.

Science.gov (United States)

Scheinost, Andreas C; Steudtner, Robin; Hübner, René; Weiss, Stephan; Bok, Frank

2016-10-04

The Np V retention by siderite, an Fe II carbonate mineral with relevance for the near-field of high-level radioactive waste repositories, was investigated under anoxic conditions. Batch sorption experiments show that siderite has a high affinity for aqueous Np V O 2 + across pH 7 to 13 as expressed by solid-water distribution coefficients, log R d, > 5, similar to the log R d determined for the (solely) tetravalent actinide Th on calcite, suggesting reduction of Np V to Np IV by siderite. Np L 3 -edge X-ray absorption near edge (XANES) spectroscopy conducted in a pH range typical for siderite-containing host rocks (7-8), confirmed the tetravalent Np oxidation state. Extended X-ray absorption fine-structure (EXAFS) spectroscopy revealed a local structure in line with NpO 2 -like nanoparticles with diameter nanoparticles (∼10 -9 M), along with their negligible surface charge at neutral pH conditions which favors particle aggregation, suggest an efficient retention of Np in the near-field of radioactive waste repositories. When Np V was added to ferrous carbonate solution, the subsequent precipitation of siderite did not lead to a structural incorporation of Np IV by siderite, but caused precipitation of a Np IV pentacarbonate phase.

Stabilization of Plutonium in Subsurface Environments via Microbial Reduction and Biofilm Formation

International Nuclear Information System (INIS)

Hakim Boukhalfa; Gary A. Icopini; Sean D. Reilly; Mary P. Neu

2007-01-01

Plutonium has a long half-life (2.4 x 10 4 years) and is of concern because of its chemical and radiological toxicity, high-energy alpha radioactive decay. A full understanding of its speciation and interactions with environmental processes is required in order to predict, contain, or remediate contaminated sites. Under aerobic conditions Pu is sparingly soluble, existing primarily in its tetravalent oxidation state. To the extent that pentavalent and hexavalent complexes and small colloidal species form they will increase the solubility and resultant mobility from contamination sources. There is evidence that in both marine environments and brines substantial fractions of the plutonium in solution is present as hexavalent plutonyl, PuO 2 2+

Origin of major donor states in In–Ga–Zn oxide

Energy Technology Data Exchange (ETDEWEB)

Nakashima, Motoki; Oota, Masashi; Ishihara, Noritaka; Nonaka, Yusuke; Hirohashi, Takuya; Takahashi, Masahiro; Yamazaki, Shunpei [Semiconductor Energy Laboratory Co., Ltd., 398 Hase, Atsugi, Kanagawa 243-0036 (Japan); Obonai, Toshimitsu; Hosaka, Yasuharu; Koezuka, Junichi [Advanced Film Device Inc., 161-2 Masuzuka, Tsuga-machi, Tochigi, Tochigi 328-0114 (Japan)

2014-12-07

To clarify the origin of the major donor states in indium gallium zinc oxide (IGZO), we report measurement results and an analysis of several physical properties of IGZO thin films. Specifically, the concentration of H atoms and O vacancies (V{sub O}), carrier concentration, and conductivity are investigated by hard X-ray photoelectron spectroscopy, secondary ion mass spectroscopy, thermal desorption spectroscopy, and Hall effect measurements. The results of these experiments suggest that the origin of major donor states is H occupancy of V{sub O} sites. Furthermore, we use first-principles calculations to investigate the influence of the coexistence of V{sub O} and H in crystalline InGaO{sub 3}(ZnO){sub m} (m = 1). The results indicate that when H is trapped in V{sub O}, a stable complex is created that serves as a shallow-level donor.

Persistence of oxidation state III of gold in thione coordination

Science.gov (United States)

Jääskeläinen, Sirpa; Koskinen, Laura; Kultamaa, Matti; Haukka, Matti; Hirva, Pipsa

2017-05-01

Ligands N,N'-tetramethylthiourea and 2-mercapto-1-methyl-imidazole form stable Au(III) complexes [AuCl3(N,N'-tetramethylthiourea)] (1) and [AuCl3(2-mercapto-1-methyl-imidazole)] (2) instead of reducing the Au(III) metal center into Au(I), which would be typical for the attachment of sulfur donors. Compounds 1 and 2 were characterized by spectroscopic methods and by X-ray crystallography. The spectroscopic details were explained by simulation of the UV-Vis spectra via the TD-DFT method. Additionally, computational DFT studies were performed in order to find the reason for the unusual oxidation state in the crystalline materials. The preference for Au(III) can be explained via various weak intra- and intermolecular interactions present in the solid state structures. The nature of the interactions was further investigated by topological charge density analysis via the QTAIM method.

SOLID STATE ENERGY CONVERSION ALLIANCE (SECA) SOLID OXIDE FUEL CELL PROGRAM

Energy Technology Data Exchange (ETDEWEB)

Nguyen Minh; Jim Powers

2003-10-01

This report summarizes the work performed for April 2003--September 2003 reporting period under Cooperative Agreement DE-FC26-01NT41245 for the U.S. Department of Energy, National Energy Technology Laboratory (DOE/NETL) entitled ''Solid State Energy Conversion Alliance (SECA) Solid oxide Fuel Cell Program''. During this reporting period, the conceptual system design activity was completed. The system design, including strategies for startup, normal operation and shutdown, was defined. Sealant and stack materials for the solid oxide fuel cell (SOFC) stack were identified which are capable of meeting the thermal cycling and degradation requirements. A cell module was tested which achieved a stable performance of 0.238 W/cm{sup 2} at 95% fuel utilization. The external fuel processor design was completed and fabrication begun. Several other advances were made on various aspects of the SOFC system, which are detailed in this report.

Integrated immunogenicity analysis of a tetravalent dengue vaccine up to 4 y after vaccination.

Science.gov (United States)

Vigne, Claire; Dupuy, Martin; Richetin, Aline; Guy, Bruno; Jackson, Nicholas; Bonaparte, Matthew; Hu, Branda; Saville, Melanie; Chansinghakul, Danaya; Noriega, Fernando; Plennevaux, Eric

2017-09-02

Two large pivotal phase III studies demonstrated the efficacy of the tetravalent dengue vaccine (CYD-TDV; Dengvaxia®, Sanofi Pasteur) against all dengue serotypes. Here we present an unprecedented integrated summary of the immunogenicity of CYD-TDV to identify the parameters driving the neutralizing humoral immune response and evolution over time. We summarized the immunogenicity profiles of a 3-dose schedule of CYD-TDV administered 6 months apart across 10 phase II and 6 phase III trials undertaken in dengue endemic and non-endemic countries. Dengue neutralizing antibody titers in sera were determined at centralized laboratories using the 50% plaque reduction neutralization test (PRNT 50 ) at baseline, 28 d after the third dose, and annually thereafter for up to 4 y after the third dose in some studies. CYD-TDV elicits neutralizing antibody responses against all 4 dengue serotypes; geometric mean titers (GMTs) increased from baseline to post-dose 3. GMTs were influenced by several parameters including age, baseline dengue seropositivity and region. In the 2 pivotal studies, GMTs decreased initially during the first 2 y post-dose 3 but appear to stabilize or slightly increase again in the third year. GMTs persisted 1.2-3.2-fold higher than baseline levels for up to 4 y post-dose 3 in other studies undertaken in dengue endemic countries. Our integrated analysis captures the fullness of the CYD-TDV immunogenicity profile across studies, age groups and regions; by presenting the available data in this way general trends and substantial outliers within each grouping can be easily identified. CYD-TDV elicits neutralizing antibody responses against all dengue serotypes, with differences by age and endemicity, which persist above baseline levels in endemic countries.

Air oxidation of Zr65Cu17.5Ni10Al7.5 in its amorphous and supercooled liquid states, studied by thermogravimetric analysis

International Nuclear Information System (INIS)

Dhawan, A.; Sharma, S.K.; Raetzke, K.; Faupel, F.

2003-01-01

The oxidation behaviour of the bulk amorphous alloy Zr 65 Cu 17.5 Ni 10 Al 7.5 was studied in air at various temperatures in the temperature range 591-732 K using a thermogravimetric analyser (TGA). The oxidation kinetics of the alloy obeys the parabolic rate law showing two different linear regions (in the plots of mass gain versus square root of oxidation time) which are attributed to the amorphous and the supercooled liquid states of the alloy. The value of the activation energy Q for the amorphous state as calculated from the temperature dependence of the rate constants is found to be 1.80±0.1 eV and the corresponding value obtained for the supercooled liquid state is 1.20±0.1 eV. It is suggested that the rate controlling process during oxidation of the amorphous state is the back-diffusion of Ni, and possibly Cu also, while the oxidation in the supercooled liquid state is dominated by the inward diffusion of oxygen. (copyright 2003 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Origin of deep subgap states in amorphous indium gallium zinc oxide: Chemically disordered coordination of oxygen

International Nuclear Information System (INIS)

Sallis, S.; Williams, D. S.; Butler, K. T.; Walsh, A.; Quackenbush, N. F.; Junda, M.; Podraza, N. J.; Fischer, D. A.; Woicik, J. C.; White, B. E.; Piper, L. F. J.

2014-01-01

The origin of the deep subgap states in amorphous indium gallium zinc oxide (a-IGZO), whether intrinsic to the amorphous structure or not, has serious implications for the development of p-type transparent amorphous oxide semiconductors. We report that the deep subgap feature in a-IGZO originates from local variations in the oxygen coordination and not from oxygen vacancies. This is shown by the positive correlation between oxygen composition and subgap intensity as observed with X-ray photoelectron spectroscopy. We also demonstrate that the subgap feature is not intrinsic to the amorphous phase because the deep subgap feature can be removed by low-temperature annealing in a reducing environment. Atomistic calculations of a-IGZO reveal that the subgap state originates from certain oxygen environments associated with the disorder. Specifically, the subgap states originate from oxygen environments with a lower coordination number and/or a larger metal-oxygen separation.

Origin of deep subgap states in amorphous indium gallium zinc oxide: Chemically disordered coordination of oxygen

Energy Technology Data Exchange (ETDEWEB)

Sallis, S.; Williams, D. S. [Materials Science and Engineering, Binghamton University, Binghamton, New York 13902 (United States); Butler, K. T.; Walsh, A. [Center for Sustainable Technologies and Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY (United Kingdom); Quackenbush, N. F. [Department of Physics, Applied Physics, and Astronomy, Binghamton University, Binghamton, New York 13902 (United States); Junda, M.; Podraza, N. J. [Department of Physics and Astronomy, University of Toledo, Toledo, Ohio 43606 (United States); Fischer, D. A.; Woicik, J. C. [Materials Science and Engineering Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); White, B. E.; Piper, L. F. J., E-mail: lpiper@binghamton.edu [Department of Physics, Applied Physics, and Astronomy, Binghamton University, Binghamton, New York 13902 (United States); Materials Science and Engineering, Binghamton University, Binghamton, New York 13902 (United States)

2014-06-09

The origin of the deep subgap states in amorphous indium gallium zinc oxide (a-IGZO), whether intrinsic to the amorphous structure or not, has serious implications for the development of p-type transparent amorphous oxide semiconductors. We report that the deep subgap feature in a-IGZO originates from local variations in the oxygen coordination and not from oxygen vacancies. This is shown by the positive correlation between oxygen composition and subgap intensity as observed with X-ray photoelectron spectroscopy. We also demonstrate that the subgap feature is not intrinsic to the amorphous phase because the deep subgap feature can be removed by low-temperature annealing in a reducing environment. Atomistic calculations of a-IGZO reveal that the subgap state originates from certain oxygen environments associated with the disorder. Specifically, the subgap states originate from oxygen environments with a lower coordination number and/or a larger metal-oxygen separation.

Electrode-Impregnable and Cross-Linkable Poly(ethylene oxide)-Poly(propylene oxide)-Poly(ethylene oxide) Triblock Polymer Electrolytes with High Ionic Conductivity and a Large Voltage Window for Flexible Solid-State Supercapacitors.

Science.gov (United States)

Han, Jae Hee; Lee, Jang Yong; Suh, Dong Hack; Hong, Young Taik; Kim, Tae-Ho

2017-10-04

We present cross-linkable precursor-type gel polymer electrolytes (GPEs) that have large ionic liquid uptake capability, can easily penetrate electrodes, have high ion conductivity, and are mechanically strong as high-performance, flexible all-solid-state supercapacitors (SC). Our polymer precursors feature a hydrophilic-hydrophobic poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) triblock main-chain structure and trifunctional silane end groups that can be multi-cross-linked with each other through a sol-gel process. The cross-linked solid-state electrolyte film with moderate IL content (200 wt %) shows a well-balanced combination of excellent ionic conductivity (5.0 × 10 -3 S cm -1 ) and good mechanical stability (maximum strain = 194%). Moreover, our polymer electrolytes have various advantages including high thermal stability (decomposition temperature > 330 °C) and the capability to impregnate electrodes to form an excellent electrode-electrolyte interface due to the very low viscosity of the precursors. By assembling our GPE-impregnated electrodes and solid-state GPE film, we demonstrate an all-solid-state SC that can operate at 3 V and provides an improved specific capacitance (112.3 F g -1 at 0.1 A g -1 ), better rate capability (64% capacity retention until 20 A g -1 ), and excellent cycle stability (95% capacitance decay over 10 000 charge/discharge cycles) compared with those of a reference SC using a conventional PEO electrolyte. Finally, flexible SCs with a high energy density (22.6 W h kg -1 at 1 A g -1 ) and an excellent flexibility (>93% capacitance retention after 5000 bending cycles) can successfully be obtained.

Effect of charge state and stoichiometry on the structure and reactivity of nickel oxide clusters with CO

Science.gov (United States)

Johnson, Grant E.; Reilly, Nelly M.; Castleman, A. W., Jr.

2009-02-01

The collision induced fragmentation and reactivity of cationic and anionic nickel oxide clusters with carbon monoxide were studied experimentally using guided-ion-beam mass spectrometry. Anionic clusters with a stoichiometry containing one more oxygen atom than nickel atom (NiO2-, Ni2O3-, Ni3O4- and Ni4O5-) were found to exhibit dominant products resulting from the transfer of a single oxygen atom to CO, suggesting the formation of CO2. Of these four species, Ni2O3- and Ni4O5- were observed to be the most reactive having oxygen transfer products accounting for approximately 5% and 10% of the total ion intensity at a maximum pressure of 15 mTorr of CO. Our findings, therefore, indicate that anionic nickel oxide clusters containing an even number of nickel atoms and an odd number of oxygen atoms are more reactive than those with an odd number of nickel atoms and an even number of oxygen atoms. The majority of cationic nickel oxides, in contrast to anionic species, reacted preferentially through the adsorption of CO onto the cluster accompanied by the loss of either molecular O2 or nickel oxide units. The adsorption of CO onto positively charged nickel oxides, therefore, is exothermic enough to break apart the gas-phase clusters. Collision induced dissociation experiments, employing inert xenon gas, were also conducted to gain insight into the structural properties of nickel oxide clusters. The fragmentation products were found to vary considerably with size and stoichiometry as well as ionic charge state. In general, cationic clusters favored the collisional loss of molecular O2 while anionic clusters fragmented through the loss of both atomic oxygen and nickel oxide units. Our results provide insight into the effect of ionic charge state on the structure of nickel oxide clusters. Furthermore, we establish how the size and stoichiometry of nickel oxide clusters influences their ability to oxidize CO, an important reaction for environmental pollution abatement.

Molecular water oxidation mechanisms followed by transition metals: state of the art.

Science.gov (United States)

Sala, Xavier; Maji, Somnath; Bofill, Roger; García-Antón, Jordi; Escriche, Lluís; Llobet, Antoni

2014-02-18

One clean alternative to fossil fuels would be to split water using sunlight. However, to achieve this goal, researchers still need to fully understand and control several key chemical reactions. One of them is the catalytic oxidation of water to molecular oxygen, which also occurs at the oxygen evolving center of photosystem II in green plants and algae. Despite its importance for biology and renewable energy, the mechanism of this reaction is not fully understood. Transition metal water oxidation catalysts in homogeneous media offer a superb platform for researchers to investigate and extract the crucial information to describe the different steps involved in this complex reaction accurately. The mechanistic information extracted at a molecular level allows researchers to understand both the factors that govern this reaction and the ones that derail the system to cause decomposition. As a result, rugged and efficient water oxidation catalysts with potential technological applications can be developed. In this Account, we discuss the current mechanistic understanding of the water oxidation reaction catalyzed by transition metals in the homogeneous phase, based on work developed in our laboratories and complemented by research from other groups. Rather than reviewing all of the catalysts described to date, we focus systematically on the several key elements and their rationale from molecules studied in homogeneous media. We organize these catalysts based on how the crucial oxygen-oxygen bond step takes place, whether via a water nucleophilic attack or via the interaction of two M-O units, rather than based on the nuclearity of the water oxidation catalysts. Furthermore we have used DFT methodology to characterize key intermediates and transition states. The combination of both theory and experiments has allowed us to get a complete view of the water oxidation cycle for the different catalysts studied. Finally, we also describe the various deactivation pathways for

Method of isolation of traces of americium by using the +6 oxidation state properties

International Nuclear Information System (INIS)

Kwinta, Jean; Michel, Jean-Jacques

1969-05-01

The authors present a method to separate traces of americium from a solution containing fission products and actinides. This method comprises the following steps: firstly, the oxidation of americium at the +6 state by ammonium persulfate and carrying over of actinides and III and IV lanthanides by lanthanum fluoride; secondly, the reduction by hydrazine of the oxidized americium and carrying over of the reduced americium by lutetium fluoride; and thirdly, the americium-lutetium separation by selective extractions either with di 2 ethyl hexyl phosphoric acid, or by fractionated elution on an anionic resin column by a mixture of nitric acid and methanol [fr

The extraction neptunium by trilaurylamine

International Nuclear Information System (INIS)

Champion, J.; Chesne, A.

1964-01-01

The extraction by trilaurylamine of neptunium (IV) from nitric acid and sulfuric acid-nitric acid media has been studied with the aim of developing a purification process for this element. Relative to the plutonium-neptunium separation, conditions are given for the oxidation of neptunium (IV) in sulfuric acid-nitric acid medium and data are presented on the stabilisation of the + 4 oxidation state by the organic solvent. Two procedures have been developed for the simultaneous purification of the two actinides. Both are based on the trilaurylamine extraction of the tetravalent nitrate species. The first utilises a constant redox potential fixed by Fe +++ /Fe ++ couple, while in the second, valencies are determined by successive addition of nitrite and ferrous ions. Gram quantities of neptunium 237 has been recovered from plutonium process solution. Alternate procedures are suggested for the chemical processing of irradiated Np 237 . (authors) [fr

Spectroscopic and redox properties of curium and californium ions in concentrated aqueous carbonate-bicarbonate media

International Nuclear Information System (INIS)

Hobart, D.E.; Varlashkin, P.G.; Samhoun, K.; Haire, R.G.; Peterson, J.R.

1983-01-01

Multimilligram quantities of trivalent curium-248 and californium-249 were investigated by absorption spectroscopy, cyclic voltammetry, and bulk solution electrolysis in concentrated aqueous carbonate-bicarbonate solution. Actinide concentrations between 10 -4 and 10 -2 M were studied in 2 M sodium carbonate and 5.5 M potassium carbonate solutions at pH values from 8 to 14. The solution absorption spectra of Cm(III) and Cf(III) in carbonate media are presented for the first time and compared to literature spectra of these species in noncomplexing aqueous solution. It was anticipated that carbonate complexation of the actinide ions could provide a sufficient negative shift in the formal potentials of the M(IV)/M(III) couples of Cm and Cf to permit the generation and stabilization of their tetravalent states in aqueous carbonate-bicarbonate medium. No conclusive evidence was found in the present work to indicate the existence of any higher oxidation states of curium or californium in carbonate solution. Some possible reasons for our inability to generate and detect oxidized species of curium and californium in this medium are discussed

Diversity of Chemical Bonding and Oxidation States in MS4 Molecules of Group 8 Elements.

Science.gov (United States)

Huang, Wei; Jiang, Ning; Schwarz, W H Eugen; Yang, Ping; Li, Jun

2017-08-04

The geometric and electronic ground-state structures of 30 isomers of six MS 4 molecules (M=Group 8 metals Fe, Ru, Os, Hs, Sm, and Pu) have been studied by using quantum-chemical density functional theory and correlated wavefunction approaches. The MS 4 species were compared to analogous MO 4 species recently investigated (W. Huang, W.-H. Xu, W. H. E. Schwarz, J. Li, Inorg. Chem. 2016, 55, 4616). A metal oxidation state (MOS) with a high value of eight appeared in the low-spin singlet T d geometric species (Os,Hs)S 4 and (Ru,Os,Hs)O 4 , whereas a low MOS of two appeared in the high-spin septet D 2d species Fe(S 2 ) 2 and (slightly excited) metastable Fe(O 2 ) 2 . The ground states of all other molecules had intermediate MOS values, with S 2- , S 2 2- , S 2 1- (and O 2- , O 1- , O 2 2- , O 2 1- ) ligands bonded by ionic, covalent, and correlative contributions. The known tendencies toward lower MOS on going from oxides to sulfides, from Hs to Os to Ru, and from Pu to Sm, and the specific behavior of Fe, were found to arise from the different atomic orbital energies and radii of the (n-1)p core and (n-1)d and (n-2)f valence shells of the metal atoms in row n of the periodic table. The comparative results of the electronic and geometric structures of the MO 4 and MS 4 species provides insight into the periodicity of oxidation states and bonding. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Safety issues from a Phase 3 clinical trial of a live-attenuated chimeric yellow fever tetravalent dengue vaccine.

Science.gov (United States)

Halstead, Scott B

2018-02-26

A tetravalent live-attenuated 3-dose vaccine composed of chimeras of yellow fever 17D and the four dengue viruses (CYD, also called Dengvaxia) completed phase 3 clinical testing in over 35,000 children leading to a recommendation that vaccine be administered to >/ = 9 year-olds residing in highly dengue- endemic countries. When clinical trial results were assessed 2 years after the first dose, vaccine efficacy among seropositives was high, but among seronegatives efficacy was marginal. Breakthrough dengue hospitalizations of vaccinated children occurred continuously over a period of 4-5 years post 3rd dose in an age distribution suggesting these children had been vaccinated when seronegative. This surmise was validated recently when the manufacturer reported that dengue NS1 IgG antibodies were absent in sera from hospitalized vaccinated children, an observation consistent with their having received Dengvaxia when seronegative. Based upon published efficacy data and in compliance with initial published recommendations by the manufacturer and WHO the Philippine government undertook to vaccinate 800,000-plus 9 year-olds starting in April 2016. Eighteen months later, dengue hospitalizations and a deaths were reported among vaccinated children. The benefits of administering Dengvaxia predicted by the manufacturer, WHO and others derive from scoring dengue hospitalizations of vaccinated children as vaccine failures rather than as vaccine enhanced dengue disease. Recommended regimens for administration of Dengvaxia should have been structured to warn of and avoid serious adverse events.

Electrocatalytic oxidation of methanol by the [Ru3O(OAc6(py2(CH3OH]3+cluster: improving the metal-ligand electron transfer by accessing the higher oxidation states of a multicentered system

Directory of Open Access Journals (Sweden)

Henrique E. Toma

2010-01-01

Full Text Available The [Ru3O(Ac6(py2(CH3OH]+ cluster provides an effective electrocatalytic species for the oxidation of methanol under mild conditions. This complex exhibits characteristic electrochemical waves at -1.02, 0.15 and 1.18 V, associated with the Ru3III,II,II/Ru3III,III,II/Ru 3III,III,III /Ru3IV,III,III successive redox couples, respectively. Above 1.7 V, formation of two RuIV centers enhances the 2-electron oxidation of the methanol ligand yielding formaldehyde, in agreement with the theoretical evolution of the HOMO levels as a function of the oxidation states. This work illustrates an important strategy to improve the efficiency of the oxidation catalysis, by using a multicentered redox catalyst and accessing its multiple higher oxidation states.

Peptides for Specific Intracellular Delivery and Targeting of Nanoparticles: Implications for Developing Nanoparticle-Mediated Drug Delivery

Science.gov (United States)

2010-01-01

less in size and span an array of compositions including met- als, semiconductor quantum dots (QDs), oxides, polymers , vesicles (e.g., micelles...93,98] Polymers Poly(lactic-co-glycolic acid), poly(amido amine) and dendrimers Biocompatibility, biodegradability and controlled release High drug...Secondary interactions Covalent atachment to surface ligand Thiolated peptide Biotinylated peptide Aminated peptide Sulfo-NHS Tetravalent streptavidin

Introducing a Simple Equation to Express Oxidation States as an Alternative to Using Rules Associated with Words Alone

Science.gov (United States)

Minkiewicz, Piotr; Darewicz, Malgorzata; Iwaniak, Anna

2018-01-01

A simple equation to calculate the oxidation states (oxidation numbers) of individual atoms in molecules and ions may be introduced instead of rules associated with words alone. The equation includes two of three categories of bonds, classified as proposed by Goodstein: number of bonds with more electronegative atoms and number of bonds with less…

Uranium extraction in phosphoric acid

International Nuclear Information System (INIS)

Araujo Figueiredo, C. de

1984-01-01

Uranium is recovered from the phosphoric liquor produced from the concentrate obtained from phosphorus-uraniferous mineral from Itataia mines (CE, Brazil). The proposed process consists of two extraction cycles. In the first one, uranium is reduced to its tetravalent state and then extracted by dioctylpyrophosphoric acid, diluted in Kerosene. Re-extraction is carried out with concentrated phosphoric acid containing an oxidising agent to convert uranium to its hexavalent state. This extract (from the first cycle) is submitted to the second cycle where uranium is extracted with DEPA-TOPO (di-2-hexylphosphoric acid/tri-n-octyl phosphine oxide) in Kerosene. The extract is then washed and uranium is backextracted and precipitated as commercial concentrate. The organic phase is recovered. Results from discontinuous tests were satisfactory, enabling to establish operational conditions for the performance of a continuous test in a micro-pilot plant. (Author) [pt

The Effect of Precursor Ligands and Oxidation State in the Synthesis of Bimetallic Nano-Alloys

KAUST Repository

LaGrow, Alec P.; Knudsen, Kristian; AlYami, Noktan; Anjum, Dalaver H.; Bakr, Osman

2015-01-01

of variables on the characteristics of bimetallic nanomaterials are not completely understood. In this study, we used a continuous-flow synthetic strategy to explore the effects of the ligands and the oxidation state of a metal precursor in a shape

Probing the transition state region in catalytic CO oxidation on Ru

Energy Technology Data Exchange (ETDEWEB)

Ostrom, H. [Stockholm Univ. (Sweden); Oberg, H. [Stockholm Univ. (Sweden); Xin, H. [SLAC National Accelerator Lab., Menlo Park, CA (United States); LaRue, J. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Stanford Univ., Stanford, CA (United States); Beye, M. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Helmholtz Zentrum Berlin fur Materialien und Energie GmbH, Berlin (Germany); Dell' Angela, M. [Univ. of Hamburg and Center for Free Electron Laser Science, Hamburg (Germany); Gladh, J. [Stockholm Univ. (Sweden); Ng, M. L. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Sellberg, J. A. [Stockholm Univ. (Sweden); SLAC National Accelerator Lab., Menlo Park, CA (United States); Kaya, S. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Mercurio, G. [Univ. of Hamburg and Center for Free Electron Laser Science, Hamburg (Germany); Nordlund, D. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Hantschmann, M. [Helmholtz Zentrum Berlin fur Materialien und Energie GmbH, Berlin (Germany); Hieke, F. [Univ. of Hamburg and Center for Free Electron Laser Science, Hamburg (Germany); Kuhn, D. [Helmholtz Zentrum Berlin fur Materialien und Energie GmbH, Berlin (Germany); Schlotter, W. F. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Dakovski, G. L. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Turner, J. J. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Minitti, M. P. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Mitra, A. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Moeller, S. P. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Fohlisch, A. [Helmholtz Zentrum Berlin fur Materialien und Energie GmbH, Berlin (Germany); Univ. Potsdam, Potsdam (Germany); Wolf, M. [Fritz-Haber Institute of the Max-Planck-Society, Berlin (Germany); Wurth, W. [Univ. of Hamburg and Center for Free Electron Laser Science, Hamburg (Germany); DESY Photon Science, Hamburg (Germany); Persson, M. [The Univ. of Liverpool, Liverpool (United Kingdom); Norskov, J. K. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Stanford Univ., Stanford, CA (United States); Abild-Pedersen, F. [Stanford Univ., Stanford, CA (United States); Ogasawara, H. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Pettersson, L. G. M. [Stockholm Univ. (Sweden); Nilsson, A. [Stockholm Univ. (Sweden); SLAC National Accelerator Lab., Menlo Park, CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States)

2015-02-12

Femtosecond x-ray laser pulses are used to probe the CO oxidation reaction on ruthenium (Ru) initiated by an optical laser pulse. On a time scale of a few hundred femtoseconds, the optical laser pulse excites motions of CO and O on the surface, allowing the reactants to collide, and, with a transient close to a picosecond (ps), new electronic states appear in the O K-edge x-ray absorption spectrum. Density functional theory calculations indicate that these result from changes in the adsorption site and bond formation between CO and O with a distribution of OC–O bond lengths close to the transition state (TS). After 1 ps, 10% of the CO populate the TS region, which is consistent with predictions based on a quantum oscillator model.

A Semi-Analytical Extraction Method for Interface and Bulk Density of States in Metal Oxide Thin-Film Transistors.

Science.gov (United States)

Chen, Weifeng; Wu, Weijing; Zhou, Lei; Xu, Miao; Wang, Lei; Ning, Honglong; Peng, Junbiao

2018-03-11

A semi-analytical extraction method of interface and bulk density of states (DOS) is proposed by using the low-frequency capacitance-voltage characteristics and current-voltage characteristics of indium zinc oxide thin-film transistors (IZO TFTs). In this work, an exponential potential distribution along the depth direction of the active layer is assumed and confirmed by numerical solution of Poisson's equation followed by device simulation. The interface DOS is obtained as a superposition of constant deep states and exponential tail states. Moreover, it is shown that the bulk DOS may be represented by the superposition of exponential deep states and exponential tail states. The extracted values of bulk DOS and interface DOS are further verified by comparing the measured transfer and output characteristics of IZO TFTs with the simulation results by a 2D device simulator ATLAS (Silvaco). As a result, the proposed extraction method may be useful for diagnosing and characterising metal oxide TFTs since it is fast to extract interface and bulk density of states (DOS) simultaneously.

A Semi-Analytical Extraction Method for Interface and Bulk Density of States in Metal Oxide Thin-Film Transistors

Directory of Open Access Journals (Sweden)

Weifeng Chen

2018-03-01

Full Text Available A semi-analytical extraction method of interface and bulk density of states (DOS is proposed by using the low-frequency capacitance–voltage characteristics and current–voltage characteristics of indium zinc oxide thin-film transistors (IZO TFTs. In this work, an exponential potential distribution along the depth direction of the active layer is assumed and confirmed by numerical solution of Poisson’s equation followed by device simulation. The interface DOS is obtained as a superposition of constant deep states and exponential tail states. Moreover, it is shown that the bulk DOS may be represented by the superposition of exponential deep states and exponential tail states. The extracted values of bulk DOS and interface DOS are further verified by comparing the measured transfer and output characteristics of IZO TFTs with the simulation results by a 2D device simulator ATLAS (Silvaco. As a result, the proposed extraction method may be useful for diagnosing and characterising metal oxide TFTs since it is fast to extract interface and bulk density of states (DOS simultaneously.

Cellulose nanofibril/reduced graphene oxide/carbon nanotube hybrid aerogels for highly flexible and all-solid-state supercapacitors

Science.gov (United States)

Qifeng Zheng; Zhiyong Cai; Zhenqiang Ma; Shaoqin Gong

2015-01-01

A novel type of highly flexible and all-solid-state supercapacitor that uses cellulose nanofibril (CNF)/reduced graphene oxide (RGO)/carbon nanotube (CNT) hybrid aerogels as electrodes and H2SO4 poly (vinyl alcohol) PVA gel as the electrolyte was developed and is reported here. These flexible solid-state supercapacitors...

Synchrotron Micro-XANES Measurements of Vanadium Oxidation State in Glasses as a Function of Oxygen Fugacity: Experimental Calibration of Data Relevant to Partition Coefficient Determination

Science.gov (United States)

Delaney, J. S.; Sutton, S. R.; Newville, M.; Jones, J. H.; Hanson, B.; Dyar, M. D.; Schreiber, H.

2000-01-01

Oxidation state microanalyses for V in glass have been made by calibrating XANES spectral features with optical spectroscopic measurements. The oxidation state change with fugacity of O2 will strongly influence partitioning results.

Oxidation under electron bombardment. A tool for studying the initial states of silicon oxidation

Energy Technology Data Exchange (ETDEWEB)

Carriere, B.; Deville, J.P.; El Maachi, A.

1987-06-01

The exciting beam of an Auger electron spectrometer has been used to monitor the oxidation of silicon single crystals at room temperature and very low pressures of oxygen (approx. 10/sup -7/ Torr). This process allows us to build ultra-thin layers of silica on silicon (down to 30 A) but it is mostly used to investigate the mechanisms of the initial stages of oxidation. Auger spectra recorded continuously during the oxidation process provide information on (1) the nature of the silicon-oxygen chemical bonds which are interpreted through fine structure in the Auger peak, and (2) the kinetics of oxide formation which are deduced from curves of Auger signal versus time. An account is given of the contribution of these Auger studies to the description of the intermediate oxide layer during the reaction between silicon and oxygen and the influence of surface structural disorder, induced mainly by argon-ion bombardment, is discussed in terms of reactivity and oxide coverage.

Reduction of uranyl carbonate and hydroxyl complexes and neptunyl carbonate complexes studied with chemical-electrochemical methods and rixs spectroscopy

International Nuclear Information System (INIS)

Butorin, Sergei; Nordgren, Joseph; Ollila, Kaija; Albinsson, Yngve; Werme, Lars

2003-10-01

Sweden and Finland plan to dispose of spent fuel from commercial nuclear power plants in deep underground repositories sited in granitic rocks. The fuel assemblies will be placed in canisters consisting of an outer corrosion-resistant copper shell with an inner cast iron insert that gives mechanical strength and reduces void space in the canister. The canister will be placed in a disposal borehole lined with compacted bentonite blocks. After sealing of the borehole, groundwater seepage will saturate the bentonite. The water flow path and transport mechanism between the host rock and the canister will be via diffusion through the swollen bentonite. Any oxygen trapped in the repository will be consumed by reaction with the host rock, pyrite in the bentonite and through microbial activity, giving long-term conditions with low redox potentials. Under these conditions, uranium dioxide - the matrix of unirradiated fuel - is a stable phase. This reducing near-field environment can upset by radiolysis of water caused by the radioactivity of the fuel, which after a few hundred years will be primarily alpha activity. Radiolysis of water produces equal amounts of oxidising and reducing species, but the reducing species produced by alpha radiolysis is molecular hydrogen, which is expected to be far less reactive than the produced oxidising species, H 2 O 2 . Alpha radiolysis could create locally oxidising conditions close to the fuel surface and oxidise the U(IV) in the uranium dioxide fuel to the more soluble U(VI) oxidation state. Furthermore, the solubility of U(VI) is enhanced in the presence of bicarbonate/carbonate by the formation of strong anionic uranyl carbonate complexes. This increase in solubility can amount to 4 to 5 orders of magnitude depending on the composition of the groundwater in contact with the fuel. The other tetravalent actinides in the fuel, Np and Pu, also have higher solubilities when oxidised beyond 4 + to neptunyl and plutonyl species. Once these

Quantum confinement-induced tunable exciton states in graphene oxide.

Science.gov (United States)

Lee, Dongwook; Seo, Jiwon; Zhu, Xi; Lee, Jiyoul; Shin, Hyeon-Jin; Cole, Jacqueline M; Shin, Taeho; Lee, Jaichan; Lee, Hangil; Su, Haibin

2013-01-01

Graphene oxide has recently been considered to be a potential replacement for cadmium-based quantum dots due to its expected high fluorescence. Although previously reported, the origin of the luminescence in graphene oxide is still controversial. Here, we report the presence of core/valence excitons in graphene-based materials, a basic ingredient for optical devices, induced by quantum confinement. Electron confinement in the unreacted graphitic regions of graphene oxide was probed by high resolution X-ray absorption near edge structure spectroscopy and first-principles calculations. Using experiments and simulations, we were able to tune the core/valence exciton energy by manipulating the size of graphitic regions through the degree of oxidation. The binding energy of an exciton in highly oxidized graphene oxide is similar to that in organic electroluminescent materials. These results open the possibility of graphene oxide-based optoelectronic device technology.

Nature of the magnetic ground state in the mixed valence compound CeRuSn: a single-crystal study

International Nuclear Information System (INIS)

Fikáček, J; Prokleška, J; Prchal, J; Custers, J; Sechovský, V

2013-01-01

We report on detailed low-temperature measurements of the magnetization, the specific heat and the electrical resistivity on high-quality CeRuSn single crystals. The compound orders antiferromagnetically at T N = 2.8 K with the Ce 3+ ions locked within the a–c plane of the monoclinic structure. Magnetization shows that below T N CeRuSn undergoes a metamagnetic transition when applying a magnetic field of 1.5 and 0.8 T along the a- and c-axis, respectively. This transition manifests in a tremendous negative jump of ∼25% in the magnetoresistance. The value of the saturated magnetization along the easy magnetization direction (c-axis) and the magnetic entropy above T N derived from specific heat data correspond to the scenario of only one third of the Ce ions in the compound being trivalent and carrying a stable Ce 3+ magnetic moment, whereas the other two thirds of the Ce ions are in a nonmagnetic tetravalent and/or mixed valence state. This is consistent with the low-temperature CeRuSn crystal structure i.e., a superstructure consisting of three unit cells of the CeCoAl type piled up along the c-axis, and in which the Ce 3+ ions are characterized by large distances from the Ru ligands while the Ce–Ru distances of the other Ce ions are much shorter causing a strong 4f-ligand hybridization and hence leading to tetravalent and/or mixed valence Ce ions. (paper)

Actinide Oxidation State and O/M Ratio in Hypostoichiometric Uranium-Plutonium-Americium U0.750Pu0.246Am0.004O2-x Mixed Oxides.

Science.gov (United States)

Vauchy, Romain; Belin, Renaud C; Robisson, Anne-Charlotte; Lebreton, Florent; Aufore, Laurence; Scheinost, Andreas C; Martin, Philippe M

2016-03-07

Innovative americium-bearing uranium-plutonium mixed oxides U1-yPuyO2-x are envisioned as nuclear fuel for sodium-cooled fast neutron reactors (SFRs). The oxygen-to-metal (O/M) ratio, directly related to the oxidation state of cations, affects many of the fuel properties. Thus, a thorough knowledge of its variation with the sintering conditions is essential. The aim of this work is to follow the oxidation state of uranium, plutonium, and americium, and so the O/M ratio, in U0.750Pu0.246Am0.004O2-x samples sintered for 4 h at 2023 K in various Ar + 5% H2 + z vpm H2O (z = ∼ 15, ∼ 90, and ∼ 200) gas mixtures. The O/M ratios were determined by gravimetry, XAS, and XRD and evidenced a partial oxidation of the samples at room temperature. Finally, by comparing XANES and EXAFS results to that of a previous study, we demonstrate that the presence of uranium does not influence the interactions between americium and plutonium and that the differences in the O/M ratio between the investigated conditions is controlled by the reduction of plutonium. We also discuss the role of the homogeneity of cation distribution, as determined by EPMA, on the mechanisms involved in the reduction process.

General regularity of the oxidation potential variations and high oxidation states in the second half of the actinide series

International Nuclear Information System (INIS)

Spitsyn, V.I.; Vokhmin, V.G.; Ionova, G.V.; Pershina, V.G.

1984-01-01

Oxidation potentials (OP) PHI(4/3), PHI(5/3), PHI(6/3), PHI(5/4) and PHI(6/5) are calculated for the members of the actinide series. A semiemperic relation combining OP with explicit terms for ground level energies of actinide ions in Russell-Saunders approximation as well as known values of formal OP relative to the normal hydrogen electrode potential are used as an extrapolation function. It is shown that an increase of PHI(4/3) OP which occurs after Bsub(k) explains a low stability of the oxidation state 4 in solutions for actinides of the second half of the series. PHI(5/3) and PHI(5/4) OP in the section starting with Cm have the minimum at Cf. PHI(6/3) OP for Cm, Bk, Cf and Es are practically the same but for Cm, Bk and Es they are smaller than PHI(5/3) OP. A principle possibility of Bk(6), Cf(6) and Es(6) preparation is shown

Quantitative evaluation of the effect of H2O degassing on the oxidation state of magmas

Science.gov (United States)

Lange, R. A.; Waters, L.

2014-12-01

The extent to which degassing of the H2O component affects the oxidation state of hydrous magmas is widely debated. Several researchers have examined how degassing of mixed H-C-O-S-Cl fluids may change the Fe3+/FeT ratio of various magmas, whereas our focus is on the H2O component. There are two ways that degassing of H2O by itself may cause oxidation: (1) the reaction: H2O (melt) + 2FeO (melt) = H2 (fluid) + Fe2O3 (melt), and/or (2) if dissolved water preferentially enhances the activity of ferrous vs. ferric iron in magmatic liquids. In this study, a comparison is made between the pre-eruptive oxidation states of 14 crystal-poor, jet-black obsidian samples (obtained from two Fe-Ti oxides) and their post-eruptive values (analyzed with the Wilson 1960 titration method tested against USGS standards). The obsidians are from Medicine Lake (CA), Long Valley (CA), and the western Mexican arc; all have low FeOT (1.1-2.1 wt%), rendering their Fe2+/Fe3+ ratios highly sensitive to the possible effects of substantial H2O degassing. The Fe-Ti oxide thermometer/oxybarometer of Ghiorso and Evans, (2008) gave temperatures for the 14 samples that range for 720 to 940°C and ΔNNO values of -0.9 to +1.4. With temperature known, the plagioclase-liquid hygrometer was applied and show that ≤ 6.5 wt% H2O was dissolved in the melts prior to eruption. In addition, pre-eruptive Cl and S concentrations were constrained on the basis of apatite analyses (Webster et al., 2009) and sulfur concentrations needed for saturation with pyrrhotite (Clemente et al., 2004), respectively. Maximum pre-eruptive chlorine and sulfur contents are 6000 and 200 ppm, respectively. After eruption, the rhyolites lost nearly all of their volatiles. Our results indicate no detectable change between pre- and post-eruptive Fe2+ concentrations, with an average deviation of ± 0.1 wt % FeO. Although degassing of large concentrations of S and/or Cl may affect the oxidation state of magmas, at the pre-eruptive levels

Oxidative Stress State Is Associated with Left Ventricular Mechanics Changes, Measured by Speckle Tracking in Essential Hypertensive Patients

Directory of Open Access Journals (Sweden)

Luis Antonio Moreno-Ruíz

2015-01-01

Full Text Available The oxidative stress state is characterized by an increase in oxygen reactive species that overwhelms the antioxidant defense; we do not know if these pathological changes are correlated with alterations in left ventricular mechanics. The aim was correlating the oxidative stress state with the left ventricular global longitudinal strain (GLS and the left ventricular end diastolic pressure (LVEDP. Twenty-five patients with essential hypertension and 25 controls paired by age and gender were studied. All of the participants were subjected to echocardiography and biochemical determination of oxidative stress markers. The hypertensive patients, compared with control subjects, had significantly (p<0.05 higher levels of oxidized proteins (5.03±1.05 versus 4.06±0.63 nmol/mg, lower levels of extracellular superoxide dismutase (EC-SOD activity (0.045±0.02 versus 0.082±0.02 U/mg, higher LVEDP (16.2±4.5 versus 11.3±1.6 mm Hg, and lower GLS (−12% versus −16%. Both groups had preserved ejection fraction and the results showed a positive correlation of oxidized proteins with GLS (r=0.386, p=0.006 and LVEDP (r=0.389, p=0.005; we also found a negative correlation of EC-SOD activity with GLS (r=-0.404, p=0.004 and LVEDP (r=-0.347, p=0.014.

Chemical states of fission products in irradiated uranium-plutonium mixed oxide fuel

International Nuclear Information System (INIS)

Kurosaki, Ken; Uno, Masayoshi; Yamanaka, Shinsuke

1999-01-01

The chemical states of fission products (FPs) in irradiated uranium-plutonium mixed oxide (MOX) fuel for the light water reactor (LWR) were estimated by thermodynamic equilibrium calculations on system of fuel and FPs by using ChemSage program. A stoichiometric MOX containing 6.1 wt. percent PuO 2 was taken as a loading fuel. The variation of chemical states of FPs was calculated as a function of oxygen potential. Some pieces of information obtained by the calculation were compared with the results of the post-irradiation examination (PIE) of UO 2 fuel. It was confirmed that the multicomponent and multiphase thermodynamic equilibrium calculation between fuel and FPs system was an effective tool for understanding the behavior of FPs in fuel. (author)

Origin of stabilization and destabilization in solid-state redox reaction of oxide ions for lithium-ion batteries.

Science.gov (United States)

Yabuuchi, Naoaki; Nakayama, Masanobu; Takeuchi, Mitsue; Komaba, Shinichi; Hashimoto, Yu; Mukai, Takahiro; Shiiba, Hiromasa; Sato, Kei; Kobayashi, Yuki; Nakao, Aiko; Yonemura, Masao; Yamanaka, Keisuke; Mitsuhara, Kei; Ohta, Toshiaki

2016-12-23

Further increase in energy density of lithium batteries is needed for zero emission vehicles. However, energy density is restricted by unavoidable theoretical limits for positive electrodes used in commercial applications. One possibility towards energy densities exceeding these limits is to utilize anion (oxide ion) redox, instead of classical transition metal redox. Nevertheless, origin of activation of the oxide ion and its stabilization mechanism are not fully understood. Here we demonstrate that the suppression of formation of superoxide-like species on lithium extraction results in reversible redox for oxide ions, which is stabilized by the presence of relatively less covalent character of Mn 4+ with oxide ions without the sacrifice of electronic conductivity. On the basis of these findings, we report an electrode material, whose metallic constituents consist only of 3d transition metal elements. The material delivers a reversible capacity of 300 mAh g -1 based on solid-state redox reaction of oxide ions.

Origin of stabilization and destabilization in solid-state redox reaction of oxide ions for lithium-ion batteries

Science.gov (United States)

Yabuuchi, Naoaki; Nakayama, Masanobu; Takeuchi, Mitsue; Komaba, Shinichi; Hashimoto, Yu; Mukai, Takahiro; Shiiba, Hiromasa; Sato, Kei; Kobayashi, Yuki; Nakao, Aiko; Yonemura, Masao; Yamanaka, Keisuke; Mitsuhara, Kei; Ohta, Toshiaki

2016-01-01

Further increase in energy density of lithium batteries is needed for zero emission vehicles. However, energy density is restricted by unavoidable theoretical limits for positive electrodes used in commercial applications. One possibility towards energy densities exceeding these limits is to utilize anion (oxide ion) redox, instead of classical transition metal redox. Nevertheless, origin of activation of the oxide ion and its stabilization mechanism are not fully understood. Here we demonstrate that the suppression of formation of superoxide-like species on lithium extraction results in reversible redox for oxide ions, which is stabilized by the presence of relatively less covalent character of Mn4+ with oxide ions without the sacrifice of electronic conductivity. On the basis of these findings, we report an electrode material, whose metallic constituents consist only of 3d transition metal elements. The material delivers a reversible capacity of 300 mAh g−1 based on solid-state redox reaction of oxide ions. PMID:28008955

Separation and preconcentration of actinides from acidic media by extraction chromatography

International Nuclear Information System (INIS)

Horwitz, E. Philip; Chiarizia, Renato; Dietz, Mark L.; Diamond, Herbert; Nelson, Donald M.

1993-01-01

A systematic examination of the effect of nitric and hydrochloric acid concentrations and of macro levels of selected elements on the sorption of actinide ions by a novel extraction chromatographic resin comprised of a solution of octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide in tri-n-butyl phosphate supported on an inert polymeric substrate is described. Actinide sorption is demonstrated to be most efficient at high (>1 M) nitric acid concentrations, although tetra- and hexavalent actinides are strongly retained even from dilute (e.g., 0.05 M) nitric acid solutions. Macro concentrations of several common anions (e.g., PO 4 3- and SO 4 2- ) or complexing agents (e.g., oxalic acid) are shown not to adversely affect the sorption of trivalent actinides, while reducing the sorption of tetravalents. Such effects, together with oxidation state adjustments, are shown to provide a basis for the sequential elution of individual actinides and for actinide isolation from environmental and biological matrices

Radiation-chemical behaviour of neptunium ions in nitric acid solutions in the presence of curium-244

International Nuclear Information System (INIS)

Frolova, L.M.; Frolov, A.A.; Vasil'ev, V.Ya.

1984-01-01

Radiation-chemical behaviour of neptunium ions in nitric acid solutions is studied under the action of intensive internal alpha-irradiation conditioned by curium nuclides. In 0.3-1.1 mol/l solutions of nitric acid radiation-chemical oxidation of neptunium (4) and reduction of neptunium (6) is obeyed to the first order law of reaction rate in respect to neptunium concentration. Effective constants of neptunium (4) oxidation rates and neptuniumi(6) reduction rates are not dependent on neptunium ion in1tial concentration and increase with a growth of a dose rate of alpha-irradiation of solution. In equilibrium only neptunium (5) and neptunium (6) are present in solutions with HNO 3 concentration less than 1 mol/l. In more concentrated solutions equilibrium between sexa-, penta- and tetravalent neptunium forms is established. Equilibrium concentrations of neptunium valent forms are not dependent on neptunium initial oxidation state under the same initial conditions (dose rate, neptunium concentration and acidity. It is shown form experimental data that under the action of alpha-irradiation neptunium (5) both is oxidated to neptunium (6) and is reduced to neptunium (4)

Continuous precipitation process of plutonium salts

International Nuclear Information System (INIS)

Richard, P.

1967-03-01

This work concerns the continuous precipitation process of plutonium oxalate. Investigations about the solubility of different valence states in nitric-oxalic and in nitric-sulfuric-oxalic medium lead to select the precipitation process of tetravalent plutonium oxalate. Settling velocity and granulometry of tetravalent oxalate plutonium have been studied with variation of several precipitation parameters such as: temperature, acidity, excess of oxalic acid and aging time. Then are given test results of some laboratory continuous apparatus. Conditions of operation with adopted tubular apparatus are defined in conclusion. A flow-sheet is given for a process at industrial scale. (author) [fr

Single Crystal Growth of Pure Co3+ Oxidation State Material LaSrCoO4

Directory of Open Access Journals (Sweden)

Hanjie Guo

2016-08-01

Full Text Available We report on the single crystal growth of the single-layer perovskite cobaltate LaSrCoO4 that was grown by the optical floating zone method using high oxygen pressures. Phase purity and single crystallinity were confirmed by X-ray diffraction techniques. The pure Co3+ oxidation state was confirmed by X-ray absorbtion spectroscopy measurements. A transition to a spin glass state is observed at ∼7 K in magnetic susceptibility and specific heat measurements.

Rapid Synthesis of Lead Oxide Nanorods by One-step Solid-state Chemical Reaction at Room Temperature

Institute of Scientific and Technical Information of China (English)

CAO, Ya-Li(曹亚丽); JIA, Dian-Zeng(贾殿赠); LIU, Lang(刘浪); LUO, Jian-Min(骆建敏)

2004-01-01

A simple and facile method was reported to synthesize lead oxide nanorods. Nanorods of lead oxide were obtained directly from grinding solid metal salt and sodium hydroxide in agate mortar with the assistance of a suitable nonionic surfactant in only one step, which is different from the result of hydroxide in solution. The product has been characterized by XRD, TEM and SEM. The formation mechanism of rod-like morphology is discussed and the surfactant plays an important soft-template role in modifying the interface of solid-state reaction and according process of rod-formation.

Low oxidation state aluminum-containing cluster anions: Cp{sup ∗}Al{sub n}H{sup −}, n = 1–3

Energy Technology Data Exchange (ETDEWEB)

Zhang, Xinxing; Ganteför, Gerd; Bowen, Kit, E-mail: AKandalam@wcupa.edu, E-mail: kbowen@jhu.edu [Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218 (United States); Eichhorn, Bryan [Department of Chemistry, University of Maryland, College Park, Maryland 20742 (United States); Mayo, Dennis [EOD Technology Division, Naval Surface Warfare Center, Indian Head, Maryland 20640 (United States); Sawyer, William H.; Gill, Ann F.; Kandalam, Anil K., E-mail: AKandalam@wcupa.edu, E-mail: kbowen@jhu.edu [Department of Physics, West Chester University of PA, West Chester, Pennsylvania 19383 (United States); Schnöckel, Hansgeorg [Institute of Inorganic Chemistry, Karlsruhe Institute of Technology, D-76131 Karlsruhe (Germany)

2016-08-21

Three new, low oxidation state, aluminum-containing cluster anions, Cp*Al{sub n}H{sup −}, n = 1–3, were prepared via reactions between aluminum hydride cluster anions, Al{sub n}H{sub m}{sup −}, and Cp*H ligands. These were characterized by mass spectrometry, anion photoelectron spectroscopy, and density functional theory based calculations. Agreement between the experimentally and theoretically determined vertical detachment energies and adiabatic detachment energies validated the computed geometrical structures. Reactions between aluminum hydride cluster anions and ligands provide a new avenue for discovering low oxidation state, ligated aluminum clusters.

Long-living positron and positronium states in zeolites and microcrystalline oxides

International Nuclear Information System (INIS)

Kajcsos, Zs.; Liszkay, L.; Varga, L.; Lohonyai, L.; Lazar, K.

1995-01-01

Positron annihilation (PA) investigation were performed on zeolites (X, Y and ZSM-5) and on microcrystalline MgO, Al 2 O 3 and SiO 2 , providing long lifetime components attributed to o-Ps atoms. In addition to the positron lifetime (LT) measurements, the energy distribution (ED) of the annihilation gamma radiation spectrum was recorded in the 30 keV - 1.5 MeV range for different samples and was compared to reference distributions for Si and GaAs samples, where no long-living Ps states are formed. Apart from the strong correlation with the water content in the samples, the positron data collected testify much more pronounced positronium hosting features for powders of the mentioned oxides than for zeolites. Positron LT spectroscopy combined with recording of the ED of the annihilation radiation provides reliable information on the forming of long living 3γ states. (author) 15 refs.; 4 figs

Structural oxidation state studies of the manganese cluster in the oxygen evolving complex of photosystem II

Energy Technology Data Exchange (ETDEWEB)

Liang, Wenchuan [Univ. of California, Berkeley, CA (United States)

1994-11-01

X-ray absorption spectroscopy (XAS) was performed on Photosystem II (PSII)-enriched membranes prepared from spinach to explore: (1) the correlation between structure and magnetic spin state of the Mn cluster in the oxygen evolving complex (OEC) in the S₂ state; and (2) the oxidation state changes of the Mn cluster in the flash-induced S-states. The structure of the Mn cluster in the S₂ state with the g~4 electron paramagnetic resonance (EPR) signal (S₂-g4 state) was compared with that in the S₂ state with multiline signal (S₂-MLS state) and the S₁ state. The S₂-g4 state has a higher XAS inflection point energy than that of the S₁ state, indicating the oxidation of Mn in the advance from the S₁ to the S₂-g4 state. Differences in the edge shape and in the extended X-ray absorption fine structure (EXAFS) show that the structure of the Mn cluster in the S₂-g4 state is different from that in the S₂-MLS or the S₁ state. In the S₂-g4 state, the second shell of backscatterers from the Mn absorber contains two Mn-Mn distances of 2.73 Å and 2.85 Å. Very little distance disorder exists in the second shell of the S₁ or S₂-MLS states. The third shell of the S₂-g4 state at about 3.3 Å also contains increased heterogeneity relative to that of the S₂-MLS or the S₁ state. Various S-states were prepared at room-temperature by saturating, single-turnover flashes. The flash-dependent oscillation in the amplitude of the MLS was used to characterize the S-state composition and to construct "pure" S-state Mn K-edge spectra. The edge position shifts to higher energy by 1.8 eV upon the S₁ → S₂ transition.

Oxidation state of sulfur, iron and tin at the surface of float glasses

International Nuclear Information System (INIS)

Lagarde, P; Flank, A-M; Jupille, J; Montigaud, H

2009-01-01

Sulfur is an important element of glasses, not because of its amount, always very low (less than 0.4 % in weight of SO 3 ), but because of its role since it actively participates to the refinement process and, combined to other elements, it can be responsible for the coloration of the glass. Iron is also of a major importance in most of the glasses. In the case of the float glass, the two faces, because of the fabrication process, are different in terms of composition (presence of Sn for one face) and also in terms of oxidation state of these minority elements (Fe, Sn, S). There should be a subtle interplay between the concentrations and the oxidation states of these different minority elements, and anyway these variations occur over a thickness of the order of few micrometers below the surface. Using the high intensity and the focusing properties (3 x 3 μm 2 ) of the x-ray beam from the Lucia beamline, we have therefore studied the speciation of iron and sulfur near the face of a float glass in relation with the behavior of tin. This has been obtained by combining elemental x-ray fluorescence cartography and x-ray micro-absorption at the different K-edges.

Oxidation state of sulfur, iron and tin at the surface of float glasses

Energy Technology Data Exchange (ETDEWEB)

Lagarde, P; Flank, A-M [Synchrotron SOLEIL, l' Orme des Merisiers, BP 48 91192 Gif/Yvette cedex (France); Jupille, J [IMPMC, Universite P. and M. Curie, Campus de Boucicaut, 140 rue de Lourmel 75015 Paris (France); Montigaud, H [Saint-Gobain Recherche 39, quai Lucien Lefranc, BP 135 93303 Aubervilliers Cedex (France)

2009-11-15

Sulfur is an important element of glasses, not because of its amount, always very low (less than 0.4 % in weight of SO{sub 3}), but because of its role since it actively participates to the refinement process and, combined to other elements, it can be responsible for the coloration of the glass. Iron is also of a major importance in most of the glasses. In the case of the float glass, the two faces, because of the fabrication process, are different in terms of composition (presence of Sn for one face) and also in terms of oxidation state of these minority elements (Fe, Sn, S). There should be a subtle interplay between the concentrations and the oxidation states of these different minority elements, and anyway these variations occur over a thickness of the order of few micrometers below the surface. Using the high intensity and the focusing properties (3 x 3 {mu}m{sup 2}) of the x-ray beam from the Lucia beamline, we have therefore studied the speciation of iron and sulfur near the face of a float glass in relation with the behavior of tin. This has been obtained by combining elemental x-ray fluorescence cartography and x-ray micro-absorption at the different K-edges.

Control of lipid oxidation during exercise: role of energy state and mitochondrial factors

DEFF Research Database (Denmark)

Sahlin, K; Harris, R C

2008-01-01

Despite considerable progress during recent years our understanding of how lipid oxidation (LOx) is controlled during exercise remains incomplete. This review focuses on the role of mitochondria and energy state in the control of LOx. LOx increases in parallel with increased energy demand up...... to an exercise intensity of about 50-60% of VO(2max) after which the contribution of lipid decreases. The switch from lipid to carbohydrate (CHO) is of energetic advantage due to the increased ATP/O(2) yield. In the low-intensity domain (energy state will stimulate both LOx...... during high-intensity exercise. Another potential mechanism, suggested in this review, is that Acyl-CoA synthetase (ACS), an initial step in LCFA catabolism, functions as a regulator of LOx. ACS activity is suggested to be under control of CoASH and energy state. Furthermore, evidence exists...

Dissolving method for nuclear fuel oxide

International Nuclear Information System (INIS)

Tomiyasu, Hiroshi; Kataoka, Makoto; Asano, Yuichiro; Hasegawa, Shin-ichi; Takashima, Yoichi; Ikeda, Yasuhisa.

1996-01-01

In a method of dissolving oxides of nuclear fuels in an aqueous acid solution, the oxides of the nuclear fuels are dissolved in a state where an oxidizing agent other than the acid is present together in the aqueous acid solution. If chlorate ions (ClO 3 - ) are present together in the aqueous acid solution, the chlorate ions act as a strong oxidizing agent and dissolve nuclear fuels such as UO 2 by oxidation. In addition, a Ce compound which generates Ce(IV) by oxidation is added to the aqueous acid solution, and an ozone (O 3 ) gas is blown thereto to dissolve the oxides of nuclear fuels. Further, the oxides of nuclear fuels are oxidized in a state where ClO 2 is present together in the aqueous acid solution to dissolve the oxides of nuclear fuels. Since oxides of the nuclear fuels are dissolved in a state where the oxidizing agent is present together as described above, the oxides of nuclear fuels can be dissolved even at a room temperature, thereby enabling to use a material such as polytetrafluoroethylene and to dissolve the oxides of nuclear fuels at a reduced cost for dissolution. (T.M.)

Solid State Electrochemical Sensors for Nitrogen Oxide (NOx) Detection in Lean Exhaust Gases

OpenAIRE

Rheaume, Jonathan Michael

2010-01-01

Solid state electrochemical sensors that measure nitrogen oxides (NOx) in lean exhaust have been investigated in order to help meet future on-board diagnostic (OBD) regulations for diesel vehicles. This impedancemetric detection technology consists of a planar, single cell sensor design with various sensing electrode materials and yttria-stabilized zirconia (YSZ) as the electrolyte. No reference to ambient air is required. An impedance analysis method yields a signal that is proportional to t...

Pu-Th separation studies employing di(2-ethylhexyl)isobutyramide (D2EHIBA) as extractant from nitric acid medium

International Nuclear Information System (INIS)

Pathak, P.N.; Prabhu, D.R.; Rizvi, G.H.; Ruikar, P.B.; Kumbhare, L.B.; Mohapatra, P.K.; Manchanda, V.K.

2003-01-01

An attempt has been made to explore the use of di(2-ethylhexyl)isobutyramide (D2EHIBA) as an extractant for the recovery of Pu from the (proposed) AHWR fuel fabrication scrap solution. The extraction of Pu in the hexavalent state has been found to be distinctly more efficient than that in the tetravalent state. Distribution studies have been carried out by maintaining Pu as Pu(VI) employing AgO as the oxidant. Scrubbing at 5 M HNO 3 has been proposed to reduce the interference due to the co-extracted Th(IV). Quantitative stripping of the extracted Pu was achieved using hydroxyl ammonium-nitrate (HAN) as reductant. Ion exchange studies have been carried out for the final purification of Pu. It is proposed to employ the cation exchanger, Biorad AG 50X8 for the final purification of Pu from the stripped solution, keeping Pu as Pu(III). (orig.)

Enhanced catalytic hydrogenation activity of Ni/reduced graphene oxide nanocomposite prepared by a solid-state method

Science.gov (United States)

Li, Yizhao; Cao, Yali; Jia, Dianzeng

2018-01-01

A simple solid-state method has been applied to synthesize Ni/reduced graphene oxide (Ni/rGO) nanocomposite under ambient condition. Ni nanoparticles with size of 10-30 nm supported on reduced graphene oxide (rGO) nanosheets are obtained through one-pot solid-state co-reduction among nickel chloride, graphene oxide, and sodium borohydride. The Ni/rGO nanohybrid shows enhanced catalytic activity toward the reduction of p-nitrophenol (PNP) into p-aminophenol compared with Ni nanoparticles. The results of kinetic research display that the pseudo-first-order rate constant for hydrogenation reaction of PNP with Ni/rGO nanocomposite is 7.66 × 10-3 s-1, which is higher than that of Ni nanoparticles (4.48 × 10-3 s-1). It also presents superior turnover frequency (TOF, 5.36 h-1) and lower activation energy ( E a, 29.65 kJ mol-1) in the hydrogenation of PNP with Ni/rGO nanocomposite. Furthermore, composite catalyst can be magnetically separated and reused for five cycles. The large surface area and high electron transfer property of rGO support are beneficial for good catalytic performance of Ni/rGO nanocomposite. Our study demonstrates a simple approach to fabricate metal-rGO heterogeneous nanostructures with advanced functions.

Templated electrodeposition of Ag7NO11 nanowires with very high oxidation states of silver

NARCIS (Netherlands)

Rodijk, E.J.B.; Maijenburg, A.W.; Maas, M.G.; Blank, David H.A.; ten Elshof, Johan E.

2011-01-01

The templated electrodeposition of 200 nm diameter nanowires of the argentic oxynitrate Ag(Ag3O4)2NO3 phase is reported. Their high surface-to-volume ratio and the high average oxidation state of Ag make these wires promising candidates for nanoscale redox processes in which both a high volumetric

Non steady-state model for dry oxidation of nuclear wastes metallic containers in long term interim storage conditions

International Nuclear Information System (INIS)

Bertrand, Nathalie; Desgranges, Clara; Poquillon, Dominique; Monceau, Daniel

2006-01-01

oxidation tests. In a second step, in order to increase the reliability of the long term extrapolations from basic models, a non-steady state numerical model able to take into account several elementary steps is built. The aim is to get a more reliable tool to describe mechanisms that control oxide scale growth in this specific low temperature range. The paper has the following contains: Experimental results; Growth kinetics; Scale morphology; A basic model for kinetics of oxidation; Conclusion of the experimental study; EKINOX: Estimation KINetics OXidation: an advanced model; General description; Equations in the model; Results; Future developments; Conclusion. To summarize, the basic model consists in some extrapolations of available experimental data in the temperature range of interest following simple analytical laws deduced from classical oxidation theories. This leads to a very small oxide scale and thus to the loss of very small amounts of metal even for extrapolations to over 100 years. However, the reliability of this kind of basic models is very poor since it is based on the assumption that a single elementary process controls the oxidation rate. Indeed in the temperature range concerned by long term interim deposit of waste containers, several mechanisms can control the oxidation rate. A numerical model able to take in consideration several growth mechanisms is now in progress. At this stage of development, the originality of the proposed advanced model consists in explicitly calculating the vacancy profiles and treating these as non-conservative species. It is based on an original numerical treatment to correctly and easily describe elimination of vacancies at the metal/oxide interface and thus relative motion between the substrate lattice and the oxide one, even for non-stationary states. It can treat Wagner's model but without the quasi-steady state 'hypothesis or also take into account a partial control of the oxidation process by interfacial reaction. In

Magnetic susceptibility as a direct measure of oxidation state in LiFePO4 batteries and cyclic water gas shift reactors.

Science.gov (United States)

Kadyk, Thomas; Eikerling, Michael

2015-08-14

The possibility of correlating the magnetic susceptibility to the oxidation state of the porous active mass in a chemical or electrochemical reactor was analyzed. The magnetic permeability was calculated using a hierarchical model of the reactor. This model was applied to two practical examples: LiFePO4 batteries, in which the oxidation state corresponds with the state-of-charge, and cyclic water gas shift reactors, in which the oxidation state corresponds to the depletion of the catalyst. In LiFePO4 batteries phase separation of the lithiated and delithiated phases in the LiFePO4 particles in the positive electrode gives rise to a hysteresis effect, i.e. the magnetic permeability depends on the history of the electrode. During fast charge or discharge, non-uniform lithium distributionin the electrode decreases the hysteresis effect. However, the overall sensitivity of the magnetic response to the state-of-charge lies in the range of 0.03%, which makes practical measurement challenging. In cyclic water gas shift reactors, the sensitivity is 4 orders of magnitude higher and without phase separation, no hysteresis occurs. This shows that the method is suitable for such reactors, in which large changes of the magnetic permeability of the active material occurs.

The state-of-the-art and prospects of the oxidation titration method for the determination of uranium in geological samples

International Nuclear Information System (INIS)

Sun Jiayan

1986-01-01

The state-of-the-art of the oxidation titration method for the determination of uranium in geological samples is reviewed in some respects such as the prereduction of U(VI), oxidation of U(IV) and the detection of the end-point. Comments are also made on the prospects of further improvements of this method

Radiation oxidation of polypropylene: A solid-state 13C NMR study using selective isotopic labeling

International Nuclear Information System (INIS)

Mowery, Daniel M.; Assink, Roger A.; Derzon, Dora K.; Klamo, Sara B.; Bernstein, Robert; Clough, Roger L.

2007-01-01

Polypropylene samples, in which the three different carbon atoms along the chain were selectively labeled with carbon-13, were subjected to radiation under inert and air atmospheres, and to post-irradiation exposure in air at various temperatures. By using solid-state 13 C NMR measurements at room temperature, we have been able to identify and quantify the oxidation products. The isotopic labeling provides insight into chemical reaction mechanisms, since oxidation products can be traced back to their positions of origin on the macromolecule. The major products include peroxides and alcohols, both formed at tertiary carbon sites along the chain. Other products include methyl ketones, acids, esters, peresters, and hemiketals formed from reaction at the tertiary carbon, together with in-chain ketones and esters from reaction at the secondary chain carbon. No evidence is found of products arising from reactions at the methyl side chain. Significant temperature-dependent differences are apparent; for example much higher yields of chain-end methyl ketones, which are the indicator product of chain scission, are generated for both elevated temperature irradiation and for post-irradiation treatment at elevated temperatures. Time-dependent plots of yields of the various oxidation products have been obtained under a wide range of conditions, including the post-irradiation oxidation of a sample at room temperature in air that has been monitored for 2 years. Radiation-oxidation products of polypropylene are contrasted to products measured for 13 C-labeled polyethylene in an earlier investigation: the peroxides formed in irradiated polypropylene are remarkably longer lived, the non-peroxidic products are significantly different, and the overall ratios of oxidation products in polypropylene change relatively little as a function of the extent of oxidation

Studies on O/M ratio determination in uranium oxide, plutonium oxide and uranium-plutonium mixed oxide

International Nuclear Information System (INIS)

Sampath, S.; Chawla, K.L.

1975-01-01

Thermogravimetric studies were carried out in unsintered and sintered samples of uranium oxide, plutonium oxide and uranium-plutonium mixed oxide under different atmospheric conditions (air, argon and moist argon/hydrogen). Moisture loss was found to occur below 200 0 C for uranium dioxide samples, upto 700 0 C for sintered plutonium dioxide and negligible for sintered samples. The O/M ratios for non-stoichiometric uranium dioxide (sintered and unsintered), plutonium dioxide and mixed uranium and plutonium oxides (sintered) could be obtained with a precision of +- 0.002. Two reference states UOsub(2.000) and UOsub(2.656) were obtained for uranium dioxide and the reference state MOsub(2.000) was used for other cases. For unsintered plutonium dioxide samples, accurate O/M ratios could not be obtained of overlap of moisture loss with oxygen loss/gain. (author)

Determination of formal potential of Amsup((4))/Amsup((3)) pair in phosphoric-acid solutions

International Nuclear Information System (INIS)

Mikhajlov, V.M.; Myasoedov, B.F.

1977-01-01

Values of formal potentials of the system Amsup((4))/Amsup((3)) in 12 and 15 M phosphoric acid at 20+-2 deg C are determined by potentiometric method. The effect is studied of metallic platinum on the process of self-reduction of tetravalent americium, and the optimum conditions are found for potentiostatic oxidation of Amsup((3)) to Amsup((4)) in 12 M phosphoric acid

Solid State Energy Conversion Alliance (SECA) Solid Oxide Fuel Cell Program

Energy Technology Data Exchange (ETDEWEB)

Nguyen Minh

2006-07-31

This report summarizes the work performed for Phase I (October 2001 - August 2006) under Cooperative Agreement DE-FC26-01NT41245 for the U. S. Department of Energy, National Energy Technology Laboratory (DOE/NETL) entitled 'Solid State Energy Conversion Alliance (SECA) Solid Oxide Fuel Cell Program'. The program focuses on the development of a low-cost, high-performance 3-to-10-kW solid oxide fuel cell (SOFC) system suitable for a broad spectrum of power-generation applications. During Phase I of the program significant progress has been made in the area of SOFC technology. A high-efficiency low-cost system was designed and supporting technology developed such as fuel processing, controls, thermal management, and power electronics. Phase I culminated in the successful demonstration of a prototype system that achieved a peak efficiency of 41%, a high-volume cost of $724/kW, a peak power of 5.4 kW, and a degradation rate of 1.8% per 500 hours. . An improved prototype system was designed, assembled, and delivered to DOE/NETL at the end of the program. This prototype achieved an extraordinary peak efficiency of 49.6%.

Role of the oxidation state of cerium on the ceria surfaces for silicate adsorption

Energy Technology Data Exchange (ETDEWEB)

Seo, Jihoon [WCD Department of Energy Engineering, Hanyang University, Seoul (Korea, Republic of); Moon, Jinok [WCD Department of Energy Engineering, Hanyang University, Seoul (Korea, Republic of); Clean/CMP Technology Team, Memory, Samsung Electronics, Hwaseong (Korea, Republic of); Kim, Joo Hyun; Lee, Kangchun [WCD Department of Energy Engineering, Hanyang University, Seoul (Korea, Republic of); Hwang, Junha [WCD Department of Energy Engineering, Hanyang University, Seoul (Korea, Republic of); Materials R& D Center, K.C.Tech, Anseong (Korea, Republic of); Yoon, Heesung [WCD Department of Energy Engineering, Hanyang University, Seoul (Korea, Republic of); Yi, Dong Kee, E-mail: vitalis@mju.ac.kr [Department of Chemistry, Myongji University, Yongin (Korea, Republic of); Paik, Ungyu, E-mail: upaik@hanyang.ac.kr [WCD Department of Energy Engineering, Hanyang University, Seoul (Korea, Republic of)

2016-12-15

Highlights: • We investigated the role of Ce oxidation state (Ce{sup 3+}/Ce{sup 4+}) on the CeO{sub 2} surfaces for the silicate adsorption. • As the Ce{sup 3+} concentration increased from 19.3 to 27.6%, the surface density of −OH group increased from 0.34 to 0.72 OH/nm{sup 2}. • The Freundlich constant for the relative adsorption capacity (K{sub F}) and adsorption intensity (1/n) indicated that CeO{sub 2} NPs with high Ce{sup 3+} concentration show higher adsorption affinity with silicate ions. - Abstract: In this study, we have investigated the role of the Ce oxidation state (Ce{sup 3+}/Ce{sup 4+}) on the CeO{sub 2} surfaces for silicate adsorption. In aqueous medium, the Ce{sup 3+} sites lead to the formation of −OH groups at the CeO{sub 2} surface through H{sub 2}O dissociation. Silicate ions can adsorb onto the CeO{sub 2} surface through interaction with the −OH groups (−Ce−OH− + −Si−O{sup −} ↔ −Ce−O−Si− + OH{sup −}). As the Ce{sup 3+} concentration increased from 19.3 to 27.6%, the surface density of −OH group increased from 0.34 to 0.72 OH/nm{sup 2}. To evaluate the adsorption behaviors of silicate ions onto CeO{sub 2} NPs, we carried out an adsorption isothermal analysis, and the adsorption isotherm data followed the Freundlich model. The Freundlich constant for the relative adsorption capacity (K{sub F}) and adsorption intensity (1/n) indicated that CeO{sub 2} NPs with high Ce{sup 3+} concentration show higher adsorption affinity with silicate ions. As a result, we have demonstrated that the Ce oxidation state (Ce{sup 3+}/Ce{sup 4+}) on the CeO{sub 2} surface can have a significant influence on the silicate adsorption.

V6O13 films by control of the oxidation state from aqueous precursor to crystalline phase.

Science.gov (United States)

Peys, Nick; Ling, Yun; Dewulf, Daan; Gielis, Sven; De Dobbelaere, Christopher; Cuypers, Daniel; Adriaensens, Peter; Van Doorslaer, Sabine; De Gendt, Stefan; Hardy, An; Van Bael, Marlies K

2013-01-28

An aqueous deposition process for V(6)O(13) films is developed whereby the vanadium oxidation state is continuously controlled throughout the entire process. In the precursor stage, a controlled wet chemical reduction of the vanadium(V) source with oxalic acid is achieved and monitored by (51)Vanadium Nuclear Magnetic Resonance ((51)V-NMR) and Ultraviolet-Visible (UV-Vis) spectroscopy. The resulting vanadium(IV) species in the aqueous solution are identified as mononuclear citrato-oxovanadate(IV) complexes by Electron Paramagnetic Resonance (EPR) and Fourier Transform Infra-Red (FTIR) spectroscopy. This precursor is successfully employed for the deposition of uniform, thin films. The optimal deposition and annealing conditions for the formation of crystalline V(6)O(13), including the control of the vanadium oxidation state, are determined through an elaborate study of processing temperature and O(2) partial pressure. To ensure a sub 100 nm adjustable film thickness, a non-oxidative intermediate thermal treatment is carried out at the end of each deposition cycle, allowing maximal precursor decomposition while still avoiding V(IV) oxidation. The resulting surface hydrophilicity, indispensable for the homogeneous deposition of the next layer, is explained by an increased surface roughness and the increased availability of surface vanadyl groups. Crystalline V(6)O(13) with a preferential (002) orientation is obtained after a post deposition annealing in a 0.1% O(2) ambient for thin films with a thickness of 20 nm.

Solid-State Electrochromic Device Consisting of Amorphous WO3 and Various Thin Oxide Layers

Science.gov (United States)

Shizukuishi, Makoto; Shimizu, Isamu; Inoue, Eiichi

1980-11-01

A mixed oxide containing Cr2O3 was introduced into an amorphous WO3 solid-state electrochromic device (ECD) in order to improve its colour memory effect. The electrochromic characteristics were greatly affected by the chemical constituents of a dielectric layer on the a-WO3 layer. Particularly, long memory effect and low power dissipation were attained in a solid-state ECD consisting of a-WO3 and Cr2O3\\cdotV2O5(50 wt.%). Some electrochromic characteristics of the a-WO3/Cr2O3\\cdotV2O5 ECD and the role of V2O5 were investigated.

Theoretical studies of positron states and annihilation characteristics at the oxidized Cu(100) surface

Energy Technology Data Exchange (ETDEWEB)

Fazleev, N. G. [Department of Physics, Box 19059, University of Texas at Arlington, Arlington Texas 76019 (United States) and Institute of Physics, Kazan Federal University, Kremlevskaya18, Kazan 420008 (Russian Federation); Weiss, A. H. [Department of Physics, Box 19059, University of Texas at Arlington, Arlington Texas 76019 (United States)

2013-04-19

In this work we present the results of theoretical studies of positron surface and bulk states and annihilation probabilities of surface-trapped positrons with relevant core electrons at the oxidized Cu(100) surface under conditions of high oxygen coverage. An ab-initio study of the electronic properties of the Cu(100) missing row reconstructed surface at various on surface and sub-surface oxygen coverages has been performed on the basis of the density functional theory (DFT) using the Dmol3 code and the generalized gradient approximation (GGA). Surface structures in calculations have been constructed by adding oxygen atoms to various surface hollow and sub-surface octahedral sites of the 0.5 monolayer (ML) missing row reconstructed phase of the Cu(100) surface with oxygen coverages ranging from 0.5 to 1.5 ML. The charge redistribution at the surface and variations in atomic structure and chemical composition of the topmost layers associated with oxidation and surface reconstruction have been found to affect the spatial extent and localization of the positron surface state wave function and annihilation probabilities of surface trapped positrons with relevant core electrons. Theoretical results are compared with experimental data obtained from studies of oxidation of the Cu(100) surface using positron annihilation induced Auger electron spectroscopy (PAES). It has been shown that positron annihilation probabilities with Cu 3s and 3p core electrons decrease when total (on-surface and sub-surface) oxygen coverage of the Cu(100) surface increases up to 1 ML. The calculations show that for high oxygen coverage when total oxygen coverage is 1. 5 ML the positron is not bound to the surface.

Practice of the counter-current trickle leaching of uranium ore by refreshed liquor of bacterial oxidation

International Nuclear Information System (INIS)

Chen Shian; Huang Xiangfu; Fan Baotuan

1995-01-01

The uranium ore of the Mine No. 753 is a high-silicate type primary one, in which the tetravalent uranium accounts for 85%, and the uranium grade is in the range of 0.36% to 0.442%. To reduce the engineering investment and the operating cost a four-stage counter-current trickle leaching pilot-plant test was carried out with the leaching time 50 days and acid consumption 38 kg per ton of ore, and the recovery of more than 95% was obtained. Using the counter-current trickle leaching mode and controlling the limit concentration of the harmful matters in the bacterial leaching liquor, the latter can be effectively oxidized by the synchronical regeneration. A trickle leaching comparative test of 25 ton ore single heap also gave a good result of more than 95% in extraction rate, and 30% acid consumption was saved and the 2.0% pyrolusite (containing MnO 2 40%) was eliminated. This process is feasible in technology and worth-while in economy for treating the uranium ore of Mine No. 753, and provides a new method of uranium ore trickle leaching

X-ray Absorption Study of Graphene Oxide and Transition Metal Oxide Nanocomposites.

Science.gov (United States)

Gandhiraman, Ram P; Nordlund, Dennis; Javier, Cristina; Koehne, Jessica E; Chen, Bin; Meyyappan, M

2014-08-14

The surface properties of the electrode materials play a crucial role in determining the performance and efficiency of energy storage devices. Graphene oxide and nanostructures of 3d transition metal oxides were synthesized for construction of electrodes in supercapacitors, and the electronic structure and oxidation states were probed using near-edge X-ray absorption fine structure. Understanding the chemistry of graphene oxide would provide valuable insight into its reactivity and properties as the graphene oxide transformation to reduced-graphene oxide is a key step in the synthesis of the electrode materials. Polarized behavior of the synchrotron X-rays and the angular dependency of the near-edge X-ray absorption fine structures (NEXAFS) have been utilized to study the orientation of the σ and π bonds of the graphene oxide and graphene oxide-metal oxide nanocomposites. The core-level transitions of individual metal oxides and that of the graphene oxide nanocomposite showed that the interaction of graphene oxide with the metal oxide nanostructures has not altered the electronic structure of either of them. As the restoration of the π network is important for good electrical conductivity, the C K edge NEXAFS spectra of reduced graphene oxide nanocomposites confirms the same through increased intensity of the sp 2 -derived unoccupied states π* band. A pronounced angular dependency of the reduced sample and the formation of excitonic peaks confirmed the formation of extended conjugated network.

Research in actinide chemistry

International Nuclear Information System (INIS)

Choppin, G.R.

1993-01-01

This research studies the behavior of the actinide elements in aqueous solution. The high radioactivity of the transuranium actinides limits the concentrations which can be studied and, consequently, limits the experimental techniques. However, oxidation state analogs (trivalent lanthanides, tetravalent thorium, and hexavalent uranium) do not suffer from these limitations. Behavior of actinides in the environment are a major USDOE concern, whether in connection with long-term releases from a repository, releases from stored defense wastes or accidental releases in reprocessing, etc. Principal goal of our research was expand the thermodynamic data base on complexation of actinides by natural ligands (e.g., OH - , CO 3 2- , PO 4 3- , humates). The research undertakes fundamental studies of actinide complexes which can increase understanding of the environmental behavior of these elements

Comparison of the oxidation state of Fe in comet 81P/Wild 2 and chondritic-porous interplanetary dust particles

Energy Technology Data Exchange (ETDEWEB)

Ogliore, Ryan C.; Butterworth, Anna L.; Fakra, Sirine C.; Gainsforth, Zack; Marcus, Matthew A.; Westphal, Andrew J.

2010-07-16

The fragile structure of chondritic-porous interplanetary dust particles (CP-IDPs) and their minimal parent-body alteration have led researchers to believe these particles originate in comets rather than asteroids where aqueous and thermal alterations have occurred. The solar elemental abundances and atmospheric entry speed of CP-IDPs also suggest a cometary origin. With the return of the Stardust samples from Jupiter-family comet 81P/Wild 2, this hypothesis can be tested. We have measured the Fe oxidation state of 15 CP-IDPs and 194 Stardust fragments using a synchrotron-based x-ray microprobe. We analyzed {approx}300 ng of Wild 2 material - three orders of magnitude more material than other analyses comparing Wild 2 and CP-IDPs. The Fe oxidation state of these two samples of material are > 2{sigma} different: the CP-IDPs are more oxidized than the Wild 2 grains. We conclude that comet Wild 2 contains material that formed at a lower oxygen fugacity than the parent-body, or parent bodies, of CP-IDPs. If all Jupiter-family comets are similar, they do not appear to be consistent with the origin of CP-IDPs. However, comets that formed from a different mix of nebular material and are more oxidized than Wild 2 could be the source of CP-IDPs.

State-of-the-art technologies of gallium oxide power devices

Science.gov (United States)

Higashiwaki, Masataka; Kuramata, Akito; Murakami, Hisashi; Kumagai, Yoshinao

2017-08-01

Gallium oxide (Ga2 O3 ) has gained increased attention for power devices due to its superior material properties and the availability of economical device-quality native substrates. This review illustrates recent advances in Ga2 O3 device technologies, beginning with an overview of the social circumstances that motivate the development of new-generation switching devices. Following an introduction to the material properties of Ga2 O3 from the viewpoint of power electronics, growth technologies of Ga2 O3 bulk single crystals and epitaxial thin films are discussed. The fabrication and performance of state-of-the-art Ga2 O3 transistors and diodes are then described. We conclude by identifying the directions and challenges of Ga2 O3 power device development in the near future.

Dual passivation of intrinsic defects at the compound semiconductor/oxide interface using an oxidant and a reductant.

Science.gov (United States)

Kent, Tyler; Chagarov, Evgeniy; Edmonds, Mary; Droopad, Ravi; Kummel, Andrew C

2015-05-26

Studies have shown that metal oxide semiconductor field-effect transistors fabricated utilizing compound semiconductors as the channel are limited in their electrical performance. This is attributed to imperfections at the semiconductor/oxide interface which cause electronic trap states, resulting in inefficient modulation of the Fermi level. The physical origin of these states is still debated mainly because of the difficulty in assigning a particular electronic state to a specific physical defect. To gain insight into the exact source of the electronic trap states, density functional theory was employed to model the intrinsic physical defects on the InGaAs (2 × 4) surface and to model the effective passivation of these defects by utilizing both an oxidant and a reductant to eliminate metallic bonds and dangling-bond-induced strain at the interface. Scanning tunneling microscopy and spectroscopy were employed to experimentally determine the physical and electronic defects and to verify the effectiveness of dual passivation with an oxidant and a reductant. While subsurface chemisorption of oxidants on compound semiconductor substrates can be detrimental, it has been shown theoretically and experimentally that oxidants are critical to removing metallic defects at oxide/compound semiconductor interfaces present in nanoscale channels, oxides, and other nanostructures.

Coordination and Oxidation States of Iron Incorporated in Mesoporous MCM41

International Nuclear Information System (INIS)

Lazar, K.; Pal-Borbely, G.; Szegedi, A.; Beyer, H. K.

2002-01-01

Mesoporous Fe-MCM41 samples (Si/Fe=25) were synthesized and characterized under evacuation and reducing/oxidizing treatments by in situ FTIR and Moessbauer spectroscopies. Both Fe(II) and Fe(III) located in low coordination states in top layers of pore walls exhibit Lewis acidity and may participate in Fe(III) ↔ Fe(II) processes at low temperatures (570 K). Furthermore, Fe(III) ↔ Fe(II) cycles can be achieved and repeated with participation of the full amount of iron at higher temperatures (670 K). The accompanying formation of oxygen vacancies and restoration of the structure in the reverse process does not result in extended damages; the MCM41 structure retains its stability under the conditions applied.

Oxidation state inherited from the magma source and implications for mineralization: Late Jurassic to Early Cretaceous granitoids, Central Lhasa subterrane, Tibet

Science.gov (United States)

Cao, MingJian; Qin, KeZhang; Li, GuangMing; Evans, Noreen J.; McInnes, Brent I. A.; Li, JinXiang; Zhao, JunXing

2018-03-01

Arc magmas are more oxidized than mid-ocean ridge basalts; however, there is continuing debate as to whether this higher oxidation state is inherited from the source magma or developed during late-stage magmatic differentiation processes. Well-constrained Late Jurassic to Early Cretaceous arc-related intermediate to felsic rocks derived from distinct magma sources provide us with a good opportunity to resolve this enigma. A series of granitoids from the western Central Lhasa subterrane were analyzed for whole-rock magnetic susceptibility, Fe2O3/FeO ratios, and trace elements in zircon. Compared to Late Jurassic samples (1.8 ± 2.0 × 10-4 emu g-1 oe-1, Fe3+/Fetotal = 0.32 ± 0.07, zircon Ce4+/Ce3+* = 15.0 ± 13.4), Early Cretaceous rocks show higher whole-rock magnetic susceptibility (5.8 ± 2.5 × 10-4 emu g-1 oe-1), Fe3+/Fetotal ratios (0.43 ± 0.04), and zircon Ce4+/Ce3+* values (23.9 ± 22.3). In addition, positive correlations among whole-rock magnetic susceptibility, Fe3+/Fetotal ratios, and zircon Ce4+/Ce3+* reveal a slight increase in oxidation state from fO2 = QFM to NNO in the Late Jurassic to fO2 = ˜NNO in the Early Cretaceous. Obvious linear correlation between oxidation indices (whole-rock magnetic susceptibility, zircon Ce4+/Ce3+*) and source signatures (zircon ɛHf(t), TDM C ages) indicates that the oxidation state was predominantly inherited from the source with only a minor contribution from magmatic differentiation. Thus, the sources for both the Late Jurassic and Early Cretaceous rocks were probably influenced by mantle wedge-derived magma, contributing to the increased fO2. Compared to ore-forming rocks at giant porphyry Cu deposits, the relatively low oxidation state (QFM to NNO) and negative ɛHf(t) (-16 to 0) of the studied granitoids implies relative infertility. However, this study demonstrates two potential fast and effective indices ( fO2 and ɛHf(t)) to evaluate the fertility of granitoids for porphyry-style mineralization. In an

Neutralizing Antibody Response and Efficacy of Novel Recombinant Tetravalent Dengue DNA Vaccine Comprising Envelope Domain III in Mice

Directory of Open Access Journals (Sweden)

Ajit Kulkarni

2017-03-01

Full Text Available Background: Dengue is a global arboviral threat to humans; causing 390 million infections per year. The availability of safe and effective tetravalent dengue vaccine is a global requirement to prevent epidemics, morbidity, and mortality associated with it. Methods: Five experimental groups (6 mice per group each of 5-week-old BALB/c mice were immunized with vaccine and placebo (empty plasmid (100 µg, i.m. on days 0, 14 and 28. Among these, four groups (one group per serotype of each were subsequently challenged 3 weeks after the last boost with dengue virus (DENV serotypes 1-4 (100 LD50, 20 µl intracerebrally to determine vaccine efficacy. The fifth group of each was used as a control. The PBS immunized group was used as mock control. Serum samples were collected before and after subsequent immunizations. EDIII fusion protein expression was determined by Western blot. Total protein concentration was measured by Bradford assay. Neutralizing antibodies were assessed by TCID50-CPE inhibition assay. Statistical analysis was performed using Stata/IC 10.1 software for Windows. One-way repeated measures ANOVA and Mann-Whitney test were used for neutralizing antibody analysis and vaccine efficacy, respectively. Results: The recombinant EDIII fusion protein was expressed adequately in transfected 293T cells. Total protein concentration was almost 3 times more than the control. Vaccine candidate induced neutralizing antibodies against all four DENV serotypes with a notable increase after subsequent boosters. Vaccine efficacy was 83.3% (DENV-1, -3, -4 and 50% (DENV-2. Conclusion: Our results suggest that vaccine is immunogenic and protective; however, further studies are required to improve the immunogenicity particularly against DENV-2.

Room air versus carbon dioxide pneumoperitoneum: effects on oxidative state, apoptosis and histology of splanchnic organs.

Science.gov (United States)

Ypsilantis, Petros; Lambropoulou, Maria; Tentes, Ioannis; Chryssidou, Maria; Georgantas, Themistoklis; Simopoulos, Constantinos

2016-04-01

Although CO2 is the insufflation gas of choice in laparoscopic procedures, room air is usually used in natural orifice transluminal endoscopic surgery. The aim of the present study was to compare the safety of room air versus CO2 pneumoperitoneum in terms of their effect on the oxidative state, apoptosis and tissue injury of splanchnic organs. Eighteen Wistar rats were assigned to three groups (n = 6 per group) and were subjected to 8 mm Hg room air (group Pne-Air) or CO2 pneumoperitoneum (group Pne-CO2) or sham operation for 60 min. Forty-five minutes postdeflation, tissue samples were excised from the liver, stomach, ileum and kidneys for reduced glutathione-to-glutathione disulfide (GSH/GSSG) ratio, caspase-8 and caspase-3 and hypoxia-inducible factor-1α (HIF-1α) immunohistochemical assessment and histopathologic examination. GSH/GSSG ratio substantially declined in both pneumoperitoneum groups. No change was noted in HIF-1α expression. Mild upregulation of caspase-8 and caspase-3 was noted in both pneumoperitoneum groups being less pronounced in group Pne-Air. Histopathologic score was increased in all organs studied, but the stomach, in both pneumoperitoneum groups. Pneumoperitoneum established by either room air or CO2 induced substantial oxidative stress, mild apoptosis and mild tissue injury in splanchnic organs. While air pneumoperitoneum conferred a less pronounced apoptotic effect, the oxidative state and histopathologic profile of splanchnic organs did not differ between insufflation gases.

Monitoring the role of Mn and Fe in the As-removal efficiency of tetravalent manganese feroxyhyte nanoparticles from drinking water: An X-ray absorption spectroscopy study.

Science.gov (United States)

Pinakidou, F; Katsikini, M; Paloura, E C; Simeonidis, K; Mitraka, E; Mitrakas, M

2016-09-01

The implementation of amorphous tetravalent manganese feroxyhyte (TMFx) nanoparticles, prepared via co-precipitation synthesis, as an efficient As(V)-removal material is investigated using X-ray absorption fine structure (XAFS) spectroscopy at the Fe-, Mn- and As-K-edges. The optimum synthesis conditions and chemical composition of the TMFx adsorbent were determined by the degree of polymerization in the adsorbents' microstructure. Under synthesis into mildly acidic conditions, the change in the polymerization of the metal-oxyhydroxyl chains (metal=Fe, Mn) provides more adsorption sites at edges and corner sites in the bonding environment of Fe and Mn, respectively, thereby enhancing As uptake. After exposure to As-polluted water, similar microstructural changes related to As-bidentate and monodentate geometries are generated: As(V) preferentially occupies the high energy adsorption sites ((2)C complexes) available in the Mn-oxyhydroxyl groups and the low energy edge sites offered by Fe ((2)E complexes). It is revealed that optimum arsenic-removal by TMFx occurs into mildly acidic synthesis pH and for iron to manganese molar ratio equal to 3. Copyright © 2016 Elsevier Inc. All rights reserved.

X-ray Absorption Study of Graphene Oxide and Transition Metal Oxide Nanocomposites

OpenAIRE

Gandhiraman, Ram P.; Nordlund, Dennis; Javier, Cristina; Koehne, Jessica E.; Chen, Bin; Meyyappan, M.

2014-01-01

The surface properties of the electrode materials play a crucial role in determining the performance and efficiency of energy storage devices. Graphene oxide and nanostructures of 3d transition metal oxides were synthesized for construction of electrodes in supercapacitors, and the electronic structure and oxidation states were probed using near-edge X-ray absorption fine structure. Understanding the chemistry of graphene oxide would provide valuable insight into its reactivity and properties...

Oxidation mechanisms occurring in wines

OpenAIRE

Oliveira, Carla Maria; Ferreira, António César Silva; Freitas, Victor De; Silva, Artur M. S.

2011-01-01

The present review aims to show the state of the art on the oxidation mechanisms occurring in wines, as well as the methods to monitor, classify and diagnose wine oxidation. Wine oxidation can be divided in enzymatic oxidation and non-enzymatic oxidation. Enzymatic oxidation almost entirely occurs in grape must and is largely correlated with the content of hydroxycinnamates, such as caffeoyltartaric acid and paracoumaroyltartaric acid, and flavan-3-ols. Non-enzymatic oxidation, al...

Layered zeolite materials and methods related thereto

Science.gov (United States)

Tsapatsis, Michael; Maheshwari, Sudeep; Bates, Frank S; Koros, William J

2013-08-06

A novel oxide material (MIN-I) comprising YO.sub.2; and X.sub.2O.sub.3, wherein Y is a tetravalent element and X is a trivalent element, wherein X/Y=O or Y/X=30 to 100 is provided. Surprisingly, MIN-I can be reversibly deswollen. MIN-I can further be combined with a polymer to produce a nanocomposite, depolymerized to produce predominantly fully exfoliated layers (MIN-2), and pillared to produce a pillared oxide material (MIN-3), analogous to MCM-36. The materials are useful in a wide range of applications, such as catalysts, thin films, membranes, and coatings.

Comprehensive mechanism and structure-sensitivity of ethanol oxidation on platinum: new transition-state searching method for resolving the complex reaction network.

Science.gov (United States)

Wang, Hui-Fang; Liu, Zhi-Pan

2008-08-20

Ethanol oxidation on Pt is a typical multistep and multiselectivity heterogeneous catalytic process. A comprehensive understanding of this fundamental reaction would greatly benefit design of catalysts for use in direct ethanol fuel cells and the degradation of biomass-derived oxygenates. In this work, the reaction network of ethanol oxidation on different Pt surfaces, including close-packed Pt{111}, stepped Pt{211}, and open Pt{100}, is explored thoroughly with an efficient reaction path searching method, which integrates our new transition-state searching technique with periodic density functional theory calculations. Our new technique enables the location of the transition state and saddle points for most surface reactions simply and efficiently by optimization of local minima. We show that the selectivity of ethanol oxidation on Pt depends markedly on the surface structure, which can be attributed to the structure-sensitivity of two key reaction steps: (i) the initial dehydrogenation of ethanol and (ii) the oxidation of acetyl (CH3CO). On open surface sites, ethanol prefers C-C bond cleavage via strongly adsorbed intermediates (CH2CO or CHCO), which leads to complete oxidation to CO2. However, only partial oxidizations to CH3CHO and CH3COOH occur on Pt{111}. Our mechanism points out that the open surface Pt{100} is the best facet to fully oxidize ethanol at low coverages, which sheds light on the origin of the remarkable catalytic performance of Pt tetrahexahedra nanocrystals found recently. The physical origin of the structure-selectivity is rationalized in terms of both thermodynamics and kinetics. Two fundamental quantities that dictate the selectivity of ethanol oxidation are identified: (i) the ability of surface metal atoms to bond with unsaturated C-containing fragments and (ii) the relative stability of hydroxyl at surface atop sites with respect to other sites.

Poly[(ethylene oxide)-co-(methylene ethylene oxide)]: A hydrolytically-degradable poly(ethylene oxide) platform.

Science.gov (United States)

Lundberg, Pontus; Lee, Bongjae F; van den Berg, Sebastiaan A; Pressly, Eric D; Lee, Annabelle; Hawker, Craig J; Lynd, Nathaniel A

2012-11-20

A facile method for imparting hydrolytic degradability to poly(ethylene oxide) (PEO), compatible with current PEGylation strategies, is presented. By incorporating methylene ethylene oxide (MEO) units into the parent PEO backbone, complete degradation was defined by the molar incorporation of MEO, and the structure of the degradation byproducts was consistent with an acid-catalyzed vinyl-ether hydrolysis mechanism. The hydrolytic degradation of poly[(ethylene oxide)-co-(methylene ethylene oxide)] was pH-sensitive, with degradation at pH 5 being significantly faster than at pH 7.4 at 37 °C in PBS buffer while long-term stability could be obtained in either the solid-state or at pH 7.4 at 6 °C.

Electrochemically active nanocomposites of Li4Ti5O12 2D nanosheets and SnO2 0D nanocrystals with improved electrode performance

International Nuclear Information System (INIS)

Han, Song Yi; Kim, In Young; Lee, Sang-Hyup; Hwang, Seong-Ju

2012-01-01

Electrochemically active nanocomposites consisting of Li 4 Ti 5 O 12 2D nanosheets and SnO 2 0D nanocrystals are synthesized by the crystal growth of tin dioxide on the surface of 2D nanostructured lithium titanate. According to powder X-ray diffraction and electron microscopic analyses, the rutile-structured SnO 2 nanocrystals are stabilized on the surface of spinel-structured Li 4 Ti 5 O 12 2D nanosheets. The homogeneous hybridization of tin dioxide with lithium titanate is confirmed by elemental mapping analysis. Ti K-edge X-ray absorption near-edge structure and Sn 3d X-ray photoelectron spectroscopy indicate the stabilization of tetravalent titanium ions in the spinel lattice of Li 4 Ti 5 O 12 and the formation of SnO 2 phase with tetravalent Sn oxidation state. The electrochemical measurements clearly demonstrate the promising functionality of the present nanocomposites as anode for lithium secondary batteries. The Li 4 Ti 5 O 12 –SnO 2 nanocomposites show larger discharge capacity and better cyclability than do the uncomposited Li 4 Ti 5 O 12 and SnO 2 phases, indicating the synergistic effect of nanocomposite formation on the electrode performance of Li 4 Ti 5 O 12 and SnO 2 . The present experimental findings underscore the validity of 2D nanostructured lithium titanate as a useful platform for the stabilization of nanocrystalline electrode materials and also for the improvement of their functionality.

Study of transition metal oxides by photoelectron spectroscopy

International Nuclear Information System (INIS)

Rao, C.N.R.; Sarma, D.D.; Vasudevan, S.; Hegde, M.S.

1979-01-01

Systematics in the X-ray photoelectron spectra (X.p.e.s.) of Ti, V, Cr, Mn and Nb oxides with the metal ion in different oxidation states as well as of related series of mono-, sesqui- and di-oxides of the first row of transition metals have been investigated in detail. Core level binding energies, spin-orbit splittings and exchange splittings are found to exhibit interesting variations with the oxidation state of the metal or the nuclear charge. The 3d binding energies of the monoxides show a proportionality to Goodenough's (R - RC). Other aspects of interest in the study are the satellite structure and final state effects in the X.p.e.s. of the oxides, and identification of different valence states in oxides of the general formulae Mn02n-1 and M304. The nature of changes in the 3d bands of oxides undergoing metal-insulator transitions is also indicated. (author)

Long-Term Safety and Immunogenicity of a Tetravalent Live-Attenuated Dengue Vaccine and Evaluation of a Booster Dose Administered to Healthy Thai Children.

Science.gov (United States)

Watanaveeradej, Veerachai; Simasathien, Sriluck; Mammen, Mammen P; Nisalak, Ananda; Tournay, Elodie; Kerdpanich, Phirangkul; Samakoses, Rudiwilai; Putnak, Robert J; Gibbons, Robert V; Yoon, In-Kyu; Jarman, Richard G; De La Barrera, Rafael; Moris, Philippe; Eckels, Kenneth H; Thomas, Stephen J; Innis, Bruce L

2016-06-01

We evaluated the safety and immunogenicity of two doses of a live-attenuated, tetravalent dengue virus vaccine (F17/Pre formulation) and a booster dose in a dengue endemic setting in two studies. Seven children (7- to 8-year-olds) were followed for 1 year after dose 2 and then given a booster dose (F17/Pre formulation), and followed for four more years (Child study). In the Infant study, 49 2-year-olds, vaccinated as infants, were followed for approximately 3.5 years after dose 2 and then given a booster dose (F17) and followed for one additional year. Two clinically notable events were observed, both in dengue vaccine recipients in the Infant study: 1 case of dengue approximately 2.7 years after dose 2 and 1 case of suspected dengue after booster vaccinations. The booster vaccinations had a favorable safety profile in terms of reactogenicity and adverse events reported during the 1-month follow-up periods. No vaccine-related serious adverse events were reported during the studies. Neutralizing antibodies against dengue viruses 1-4 waned during the 1-3 years before boosting, which elicited a short-lived booster response but did not provide a long-lived, multivalent antibody response in most subjects. Overall, this candidate vaccine did not elicit a durable humoral immune response. © The American Society of Tropical Medicine and Hygiene.

All-solid-state flexible microsupercapacitors based on reduced graphene oxide/multi-walled carbon nanotube composite electrodes

Science.gov (United States)

Mao, Xiling; Xu, Jianhua; He, Xin; Yang, Wenyao; Yang, Yajie; Xu, Lu; Zhao, Yuetao; Zhou, Yujiu

2018-03-01

All-solid-state flexible microsupercapacitors have been intensely investigated in order to meet the rapidly growing demands for portable microelectronic devices. Herein, we demonstrate a facile, readily scalable and cost-effective laser induction process for preparing reduced graphene oxide/multi-walled carbon nanotube composite, which can be used as the interdigital electrodes in microsupercapacitors. The obtained composite exhibits high volumetric capacitance about 49.35 F cm-3, which is nearly 5 times higher than that of the pristine reduced graphene oxide film in aqueous 1.0 M H2SO4 solution (measured at a current density of 5 A cm-3 in a three-electrode testing). Additionally, an all-solid-state flexible microsupercapacitor employing these composite electrodes with PVA/H3PO4 gel electrolyte delivers high volumetric energy density of 6.47 mWh cm-3 at 10 mW cm-3 under the current density of 20 mA cm-3 as well as achieve excellent cycling stability retaining 88.6% of its initial value and outstanding coulombic efficiency after 10,000 cycles. Furthermore, the microsupercapacitors array connected in series/parallel can be easily adjusted to achieve the demands in practical applications. Therefore, this work brings a promising new candidate of prepare technologies for all-solid-state flexible microsupercapacitors as miniaturized power sources used in the portable and wearable electronics.

Effect of 50 and 80 MeV phosphorous ions on the contribution of interface and oxide state density in n-channel MOSFETs

Energy Technology Data Exchange (ETDEWEB)

Shinde, N.S.; Dhole, S.D.; Kanjilal, D.; Bhoraskar, V.N. E-mail: vnb@physics.unipune.ernet.in

1999-07-02

n-channel depletion MOS devices were irradiated with 50 and 80 MeV phosphorous ions, with different fluences varying in the range from 10{sup 11} to 10{sup 13} ions/cm{sup 2}. The pre and post irradiation I-V characteristics were measured and the corresponding threshold shift {delta}V{sub TH} was estimated. In both the cases, the drain current I{sub D} and the threshold voltage V{sub TH} were found to decrease with the ion fluence. The increase in the threshold voltage shift {delta}V{sub TH} with the ion fluence, was greater for the devices irradiated with 80 MeV ions than those irradiated with 50 MeV ions. The interface and oxide state densities were determined through the subthreshold voltage measurements. To separate the contributions of oxide and interface states towards the threshold voltage shift, the ion irradiated MOS devices were annealed at 150 deg. C. The threshold shift during annealing initially decreased and later increased with increasing annealing period. The rate of change of the interface states during annealing was higher than that of the oxide states. It was also found that depletion mode (normally ON) MOSFETs switched operation to enhancement mode (normally OFF)

Application of powerful oxidizers in the synthesis of new high-oxidation state actinide and related species

International Nuclear Information System (INIS)

Yeh, S.M.

1984-11-01

The fluorinating and oxide scavenging ability of XeF 6 have been studied by bringing XeF 6 into interaction with oxide-fluoride compounds of the third-transition-series elements (W, Re and Os) and uranium, in their highest oxidation states. A + MOF 5 - and A + M 2 O 2 F 9 - (A = K or Cs, M = W or U) were converted to A + MF 7 - by XeF 6 , but the rhenium and osmium compounds, K + ReO 2 F 4 - and XeF 5 + OsO 3 F 3 - , resisted interaction with XeF 6 . Strong interactions between XeF 2 or KrF 2 and the solvent have been observed for their solutions in anhydrous HF. Both XeF 2 and KrF 2 are seen to be effective in breaking up the polymeric (HF)/sub n/ chains. Only weak interactions occur between cations and anions of KrF + AuF 6 - and Kr 2 F 3 + AuF 6 - in HF. The AuF 6 - anions are slightly distorted from O/sub h/ symmetry. Kr 2 F 3 + cations in HF have the same dissymmetric V-shape which occurs in crystalline salts. A low-temperature orthorhombic form, β-ReF 6 + SbF 6 - , a high-temperature rhombohedral form, α-ReF 6 + SbF 6 - , and a ReF 6 + AuF 6 - have been prepared. These compounds possess only kinetic stability at ambient temperature and at approx. 20 0 C are best represented as ReF 6 + ReF 7 MF 6 - MF 5 . Thermochemical energy evaluations indicate that the ionization potential of ReF 6 is 261 kcal mole -1 and that the fluoride-ion affinity of ReF 6 + is -214 kcal mole -1 . This is more exothermal than the corresponding process for IF 6 + (-208 kcal mole -1 ). In contrast, ReOF 5 is shown to be a better fluoro-base than IOF 5 and also is a better base than ReF 7 . ReOF 4 + MF 6 - (M = Sb, Au and As) salts are of higher thermal stability than their ReF 6 + MF 6 - analogues

Anodic oxidation

CERN Document Server

Ross, Sidney D; Rudd, Eric J; Blomquist, Alfred T; Wasserman, Harry H

2013-01-01

Anodic Oxidation covers the application of the concept, principles, and methods of electrochemistry to organic reactions. This book is composed of two parts encompassing 12 chapters that consider the mechanism of anodic oxidation. Part I surveys the theory and methods of electrochemistry as applied to organic reactions. These parts also present the mathematical equations to describe the kinetics of electrode reactions using both polarographic and steady-state conditions. Part II examines the anodic oxidation of organic substrates by the functional group initially attacked. This part particular

Assigning Oxidation States to Organic Compounds via Predictions from X-ray Photoelectron Spectroscopy: A Discussion of Approaches and Recommended Improvements

Energy Technology Data Exchange (ETDEWEB)

Gupta, Vipul; Ganegoda, Hasitha; Engelhard, Mark H.; Terry, Jeff H.; Linford, Matthew R.

2014-02-11

The traditional assignment of oxidation numbers to organic molecules is problematic. Accordingly, in 1999, Calzaferri proposed a simple and elegant solution that is based on the similar electronegativities of carbon and hydrogen: hydrogen would be assigned an oxidation number of zero when bonded to carbon. Here we show that X-ray photoelectron spectroscopy (XPS), a core electron spectroscopy that is sensitive to oxidation states of elements, confirms his suggestion. In particular, in this work we: (i) list the typical rules for assigning oxidation numbers, (ii) discuss the traditional assignment of oxidation numbers to organic molecules, (iii) review Calzaferri’s solution, (iv) introduce X-ray photoelectron spectroscopy (XPS), (v) show the consistency of Calzaferri’s suggestion with XPS results, (vi) provide supporting examples from the literature, (vii) provide examples from our own research, and (viii) further confirm the Calzaferri suggestion/photoelectron spectroscopy results by discussing two organic well-known reactions. We end by reechoing Calzaferri’s suggestion that the traditional rules for assigning oxidation numbers to organic molecules be modified.

pH-sensor properties of electrochemically grown iridium oxide

NARCIS (Netherlands)

Olthuis, Wouter; Robben, M.A.M.; Bergveld, Piet; Bos, M.; van der Linden, W.E.

1990-01-01

The open-circuit potential of an electrochemically grown iridium oxide film is measured and shows a pH sensitivity between −60 and −80 mV/pH. This sensitivity is found to depend on the state of oxidation of the iridium oxide film; for a higher state of oxidation (or more of the oxide in the high

Homogeneity of Continuum Model of an Unsteady State Fixed Bed Reactor for Lean CH4 Oxidation

Directory of Open Access Journals (Sweden)

Subagjo

2014-07-01

Full Text Available In this study, the homogeneity of the continuum model of a fixed bed reactor operated in steady state and unsteady state systems for lean CH4 oxidation is investigated. The steady-state fixed bed reactor system was operated under once-through direction, while the unsteady-state fixed bed reactor system was operated under flow reversal. The governing equations consisting of mass and energy balances were solved using the FlexPDE software package, version 6. The model selection is indispensable for an effective calculation since the simulation of a reverse flow reactor is time-consuming. The homogeneous and heterogeneous models for steady state operation gave similar conversions and temperature profiles, with a deviation of 0.12 to 0.14%. For reverse flow operation, the deviations of the continuum models of thepseudo-homogeneous and heterogeneous models were in the range of 25-65%. It is suggested that pseudo-homogeneous models can be applied to steady state systems, whereas heterogeneous models have to be applied to unsteady state systems.

Study of oxidation states of the transition metals in a series of Prussian blue analogs using x-ray absorption near edge structure (XANES) spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Adak, S. [Department of Physics, New Mexico State University, Las Cruces, NM, 88003 (United States); Hartl, M., E-mail: monika.hartl@esss.se [European Spallation Source ESS AB, 22100, Lund (Sweden); Manuel Lujan Jr. Neutron Scattering Center (LANSCE-LC), Los Alamos National Laboratory, Los Alamos, NM, 87545 (United States); Daemen, L. [Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, TN, 37830 (United States); Manuel Lujan Jr. Neutron Scattering Center (LANSCE-LC), Los Alamos National Laboratory, Los Alamos, NM, 87545 (United States); Fohtung, E.; Nakotte, H. [Department of Physics, New Mexico State University, Las Cruces, NM, 88003 (United States)

2017-01-15

Highlights: • Systematic XANES measurements on Prussian blue analogs shows oxidation state of transition metals. • Cobal-iron bimetallic hexacyanometallates show unexpected oxidation states. • Iron(II) ions in hexacyanometallates(III) show varying spin state depending on their bond to the “N” end or “C” end of the cyanide ligand. • Thermal expansion coefficients have been linked to the XANES results. - Abstract: There have been renewed interests in metal-organic framework classes of materials such as Prussian blue analogues (PBAs) due to their potential usage in energy storage applications. In particular, due to their high surface areas, controllable structures and excellent electrochemical properties, PBAs such as hexacyanometalates M{sup II}{sub 3}[A{sup III}(CN){sub 6}]{sub 2*}nH{sub 2}O (M = Mn, Fe, Co, Ni, Cu, Zn; A = Co, Fe, Cr; n = no. of water molecules present), M{sup II}{sub 2}[Fe{sup II}(CN){sub 6}]{sub 2*}nH{sub 2}O (M = Mn, Co, Ni, Cu, Zn) and mixed hexacyanometalates(III) (Fe{sub 1-x}Co{sub x}){sub 3}[B{sup III}(CN){sub 6}]{sub 2}·nH{sub 2}O (x = 0.25, 0.5, 0.75; B = Co, Fe) could have possible usage as a new class of cathode and even anode materials for rechargeable batteries. Detailed knowledge of the oxidation states of the transition metals in PBAs is required to improve efficiency and durability of such devices. Furthermore, a link between the thermal expansion observed in these materials and the oxidation state of the transition metal is of interest to synthesize materials with a desired thermal expansion behavior, Here we demonstrate the use of Synchrotron based X-ray absorption near-edge structure (XANES) spectra to identify transition metal oxidation states. Our analysis reveals the presence of divalent, trivalent and/or mixed valence transition metals in the materials as well as high-spin and low-spin complexes.

Magnetic susceptibilities of Ca/sub y/U/sub 1-y/O/sub 2+x/ solid solutions

International Nuclear Information System (INIS)

Hinatsu, Y.; Fujino, T.

1988-01-01

Magnetic susceptibilities of Ca/sub y/U/sub 1-y/O/sub 2+x/ solid solutions with fluorite structure were measured from 4.2 K to room temperature. An antiferromagnetic transition was observed for all the solid solutions examined in this study (y ≤ 0.33). The Neel temperature of the oxygen-hypostoichiometric solid solutions (x 2 solid solutions, but different from that of (U,Th)O 2 solid solutions. The effective magnetic moment decreased with increasing calcium concentration, which indicates the oxidation of uranium in the solid solutions. From the analysis of the magnetic susceptibility data, it was found that the oxidation state of uranium was either tetravalent or pentavalent. The Neel temperature of the hyperstoichiometric solid solutions (x > 0) did not change appreciably with calcium concentrations. From the comparison of the magnetic susceptibility data of the hypostoichiometric solid solutions with those of the hyperstoichiometric solid solutions, the effect of oxygen vacancies is more significant than that of interstitial oxygens on the decrease of magnetic interactions between uranium ions

Molybdenum Oxides - From Fundamentals to Functionality.

Science.gov (United States)

de Castro, Isabela Alves; Datta, Robi Shankar; Ou, Jian Zhen; Castellanos-Gomez, Andres; Sriram, Sharath; Daeneke, Torben; Kalantar-Zadeh, Kourosh

2017-10-01

The properties and applications of molybdenum oxides are reviewed in depth. Molybdenum is found in various oxide stoichiometries, which have been employed for different high-value research and commercial applications. The great chemical and physical characteristics of molybdenum oxides make them versatile and highly tunable for incorporation in optical, electronic, catalytic, bio, and energy systems. Variations in the oxidation states allow manipulation of the crystal structure, morphology, oxygen vacancies, and dopants, to control and engineer electronic states. Despite this overwhelming functionality and potential, a definitive resource on molybdenum oxide is still unavailable. The aim here is to provide such a resource, while presenting an insightful outlook into future prospective applications for molybdenum oxides. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Efficacy, immunogenicity, and safety of two doses of a tetravalent rotavirus vaccine RRV-TV in Ghana with the first dose administered during the neonatal period.

Science.gov (United States)

Armah, George E; Kapikian, Albert Z; Vesikari, Timo; Cunliffe, Nigel; Jacobson, Robert M; Burlington, D Bruce; Ruiz, Leonard P

2013-08-01

Oral rhesus/rhesus-human reassortant rotavirus tetravalent vaccine (RRV-TV) was licensed in 1998 but withdrawn in 1999 due to a rare association with intussusception, which occurred disproportionately in infants receiving their first dose at ≥90 days of age. This study examined RRV-TV for the prevention of rotavirus gastroenteritis (RV-GE) in Ghana, West Africa, with infants receiving the first dose during the neonatal period and the second before 60 days of age. In a double-blinded, randomized, placebo-controlled trial in Navrongo, Ghana, we recruited neonates to receive 2 doses of RRV-TV or placebo and followed them to age 12 months. In the intention-to-treat population of 998 infants, we measured a vaccine efficacy of 63.1% against RV-GE of any severity associated with any of the 4 serotypes represented in the vaccine and 60.7% against RV-GE associated with any rotavirus serotype. RRV-TV in a 2-dose schedule with the first dose during the neonatal period is efficacious in preventing RV-GE in rural Ghana. Neonatal dosing results in early protection and may be the optimum schedule to avoid or significantly reduce intussusception, now reported to be associated in international settings with the 2 most widely marketed, licensed, live virus, oral rotavirus vaccines.

An unusual high-spin ground state of Co3+ in octahedral coordination in brownmillerite-type cobalt oxide.

Science.gov (United States)

Istomin, S Ya; Tyablikov, O A; Kazakov, S M; Antipov, E V; Kurbakov, A I; Tsirlin, A A; Hollmann, N; Chin, Y Y; Lin, H-J; Chen, C T; Tanaka, A; Tjeng, L H; Hu, Z

2015-06-21

The crystal and magnetic structures of brownmillerite-like Sr(2)Co(1.2)Ga(0.8)O(5) with a stable Co(3+) oxidation state at both octahedral and tetrahedral sites are refined using neutron powder diffraction data collected at 2 K (S.G. Icmm, a = 5.6148(6) Å, b = 15.702(2) Å, c = 5.4543(6) Å; R(wp) = 0.0339, R(p) = 0.0443, χ(2) = 0.775). The very large tetragonal distortion of CoO(6) octahedra (1.9591(4) Å for Co-O(eq) and 2.257(6) Å for Co-O(ax)) could be beneficial for the stabilization of the long-sought intermediate-spin state of Co(3+) in perovskite-type oxides. However, the large magnetic moment of octahedral Co(3+) (3.82(7)μ(B)) indicates the conventional high-spin state of Co(3+) ions, which is further supported by the results of a combined theoretical and experimental soft X-ray absorption spectroscopy study at the Co-L(2,3) edges on Sr(2)Co(1.2)Ga(0.8)O(5). A high-spin ground state of Co(3+) in Sr(2)Co(1.2)Ga(0.8)O(5) resulted in much lower in comparison with a LaCoO(3) linear thermal expansion coefficient of 13.1 ppm K(-1) (298-1073 K) determined from high-temperature X-ray powder diffraction data collected in air.

Influence of iron doping on tetravalent nickel content in catalytic oxygen evolving films

Energy Technology Data Exchange (ETDEWEB)

Li, Nancy; Bediako, D. Kwabena; Hadt, Ryan G.; Hayes, Dugan; Kempa, Thomas J.; von Cube, Felix; Bell, David C.; Chen, Lin X.; Nocera, Daniel G.

2017-01-30

Iron doping of nickel oxide films results in enhanced activity for promoting the oxygen evolution reaction (OER). Whereas this enhanced activity has been ascribed to a unique iron site within the nickel oxide matrix, we show here that Fe doping influences the Ni valency. The percent of Fe3+ doping promotes the formation of formal Ni4+, which in turn directly correlates with an enhanced activity of the catalyst in promoting OER. The role of Fe3+ is consistent with its behavior as a superior Lewis acid.

METAL OXIDE NANOPARTICLES

Energy Technology Data Exchange (ETDEWEB)

FERNANDEZ-GARCIA,M.; RODGRIGUEZ, J.A.

2007-10-01

This chapter covers the fundamental science, synthesis, characterization, physicochemical properties and applications of oxide nanomaterials. Explains fundamental aspects that determine the growth and behavior of these systems, briefly examines synthetic procedures using bottom-up and top-down fabrication technologies, discusses the sophisticated experimental techniques and state of the art theory results used to characterize the physico-chemical properties of oxide solids and describe the current knowledge concerning key oxide materials with important technological applications.

The Oxidation State of Fe in Glasses from the Galapagos Archipelago: Variable Oxygen Fugacity as a Function of Mantle Source

Science.gov (United States)

Peterson, M. E.; Kelley, K. A.; Cottrell, E.; Saal, A. E.; Kurz, M. D.

2015-12-01

The oxidation state of the mantle plays an intrinsic role in the magmatic evolution of the Earth. Here we present new μ-XANES measurements of Fe3+/ΣFe ratios (a proxy for ƒO2) in a suite of submarine glasses from the Galapagos Archipelago. Using previously presented major, trace, and volatile elements and isotopic data for 4 groups of glass that come from distinct mantle sources (depleted upper mantle, 2 recycled, and a primitive mantle source) we show that Fe3+/ΣFe ratios vary both with the influence of shallow level processes and with variations in mantle source. Fe3+/ΣFe ratios increase with differentiation (i.e. decreasing MgO), but show a large variation at a given MgO. Progressive degassing of sulfur accompanies decreasing Fe3+/ΣFe ratios, while assimilation of hydrothermally altered crust (as indicated by increasing Sr/Sr*) is shown to increase Fe3+/ΣFe ratios. After taking these processes into account, there is still variability in the Fe3+/ΣFe ratios of the isotopically distinct sample suites studied, yielding a magmatic ƒO2 that ranges from ΔQFM = +0.16 to +0.74 (error ITE = enriched Sr and Pb isotopes) shows evidence of mixing between oxidized and reduced sources (ITE oxidized end-member = 0.177). This suggests that mantle sources in the Galapagos that are thought to contain recycled components (i.e., WD and ITE groups) have distinct oxidation states. The high 3He/4He Fernandina samples (HHe group) are shown to be the most oxidized (ave. 0.175 ± 0.006). With C/3He ratios an order of magnitude greater than MORB this suggests that the primitive mantle is a more carbonated and oxidized source than the depleted upper mantle.

Resource Use and Costs of Dengue: Analysis of Data from Phase III Efficacy Studies of a Tetravalent Dengue Vaccine.

Science.gov (United States)

El Fezzazi, Hanna; Branchu, Marie; Carrasquilla, Gabriel; Pitisuttithum, Punnee; Perroud, Ana Paula; Frago, Carina; Coudeville, Laurent

2017-12-01

A tetravalent dengue vaccine (CYD-TDV) has recently been approved in 12 countries in southeast Asia and Latin America for individuals aged 9-45 years or 9-60 years (age indication approvals vary by country) living in endemic areas. Data on utilization of medical and nonmedical resources as well as time lost from school and work were collected during the active phase of two phase III efficacy studies performed in 10 countries in the Asia-Pacific region and Latin America (NCT01373281; NCT01374516). We compared dengue-related resource utilization and costs among vaccinated and nonvaccinated participants. Country-specific unit costs were derived from available literature. There were 901 virologically confirmed dengue episodes among participants aged ≥ 9 years ( N = 25,826): corresponding to 373 episodes in the CYD-TDV group ( N = 17,230) and 528 episodes in the control group ( N = 8,596). Fewer episodes in the CYD-TDV group resulted in hospitalization than in the control group (7.0% versus 13.3%; P = 0.002), but both had a similar average length of stay of 4 days. Overall, a two-thirds reduction in resource consumption and missed school/work days was observed in the CYD-TDV group relative to the control group. The estimated direct and indirect cost (2014 I$) associated with dengue episodes per participant in the CYD-TDV group was 73% lower than in the control group (I$6.72 versus I$25.08); representing a saving of I$I8.36 (95% confidence interval [CI]:17.05-19.78) per participant with vaccination. This is the first study providing information on dengue costs among vaccinated individuals and direct confirmation that vaccination has the potential to reduce dengue illness costs.

Measurements of the oxidation state and concentration of plutonium in interstitial waters of the Irish Sea

International Nuclear Information System (INIS)

Nelson, D.M.; Lovett, M.B.

1980-01-01

The question of plutonium movement in interstitial waters resulting from diffusion along concentration gradients or from advective flow is addressed. The results of measurements of both the concentration and the oxidation state of plutonium in interstitial water collected from sediments near the Windscale discharge, in the solid phases of these sediments and in seawater and suspended solids collected at the coring locations are discussed

Siderophore-mediated oxidation of Ce and fractionation of HREE by Mn (hydr)oxide-coprecipitation and sorption on MnO2: Experimental evidence for negative Ce-anomalies in abiogenic manganese precipitates

Science.gov (United States)

Krämer, Dennis; Tepe, Nathalie; Bau, Michael

2014-05-01

We conducted experiments with Rare Earths and Yttrium (REY), where the REY were sorbed on synthetic manganese dioxide as well as on coprecipitating manganese (hydr)oxide in the presence and absence of the siderophore desferrioxamine-B (DFOB). Siderophores are a group of globally abundant biogenic complexing agents which are excreted by plants and bacteria to enhance the bioavailability of Fe in oxic environments. The model siderophore used in this study, DFOB, is a hydroxamate siderophore occurring in almost all environmental settings with concentrations in the nanomolar to millimolar range and is one of the most thoroughly studied siderophores. In the absence of siderophores and other organic ligands, trivalent Ce is usually surface-oxidized to tetravalent Ce during sorption onto manganese (hydr)oxides. Such Mn precipitates, therefore, often show positive Ce anomalies, whereas the ambient solutions exhibit negative Ce anomalies (Ohta and Kawabe, 2001). In marked contrast, however, REY sorption in the presence of DFOB produces negative Ce anomalies in the Mn precipitates and a distinct and characteristic positive Ce anomaly in the residual siderophore-bearing solution. Furthermore, the heavy REY with ionic radii larger than the radius of Sm are also almost completely prevented from sorption onto the Mn solid phases. Sorption of REY onto Mn (hydr)oxides in the presence of DFOB creates a distinct and pronounced fractionation of Ce and the heavy REY from the light and middle REY. Apart from Ce, which is oxidized in solution by the siderophore, the distribution of the other REY mimics the stability constants for multi-dentate complexes of REY with DFOB, as determined by Christenson & Schijf (2011). Heavier REY are forming stronger complexes (and are hence better "protected" from sorption) than light REY, excluding Ce. Preferential partitioning of Ce into the liquid phase during the precipitation of Mn (hydr)oxides has only rarely been described for natural Mn (hydr)oxides

N-Oxide-N-oxide interactions and Cl...Cl halogen bonds in pentachloropyridine N-oxide: the many-body approach to interactions in the crystal state.

Science.gov (United States)

Wzgarda-Raj, Kinga; Rybarczyk-Pirek, Agnieszka J; Wojtulewski, Sławomir; Palusiak, Marcin

2018-02-01

Pentachloropyridine N-oxide, C 5 Cl 5 NO, crystallizes in the monoclinic space group P2 1 /c. In the crystal structure, molecules are linked by C-Cl...Cl halogen bonds into infinite ribbons extending along the crystallographic [100] direction. These molecular aggregates are further stabilized by very short intermolecular N-oxide-N-oxide interactions into herringbone motifs. Computations based on quantum chemistry methods allowed for a more detailed description of the N-oxide-N-oxide interactions and Cl...Cl halogen bonds. For this purpose, Hirshfeld surface analysis and the many-body approach to interaction energy were applied.

High modulus invert analog glass compositions containing beryllia

Science.gov (United States)

Bacon, J. F. (Inventor)

1974-01-01

Glass compositions having a Young's modulus of at least 15 million psi and a specific modulus of at least 110 million inches consisting essentially of, in mols, 10-45% SiO2, 2-15% Li2O, 3-34% BeO, 12-36% of at least one bivalent oxide selected from the group consisting of CaO, ZnO, MgO and CuO, 10-39% of at least one trivalent oxide selected from the group consisting of Al2O3, B2O3, La2O3, Y2O3 and the mixed rare earth oxides, the total number of said bivalent and trivalent oxides being at least three, and up to 10% of a tetravalent oxide selected from the group consisting of ZrO2, TiO2 and CeO2.

Ni–Ta–O mixed oxide catalysts for the low temperature oxidative dehydrogenation of ethane to ethylene

KAUST Repository

Zhu, Haibo; Rosenfeld, Devon C.; Anjum, Dalaver H.; Sangaru, Shiv; Saih, Youssef; Ould-Chikh, Samy; Basset, Jean-Marie

2015-01-01

The "wet" sol-gel and "dry" solid-state methods were used to prepare Ni-Ta-O mixed oxide catalysts. The resulting Ni-Ta oxides exhibit high activity and selectivity for the low temperature oxidative dehydrogenation of ethane to ethylene. The Ta

Serum oxidative-anti-oxidative stress balance is dysregulated in patients with hepatitis C virus-related hepatocellular carcinoma.

Science.gov (United States)

Nishimura, Mamoru; Takaki, Akinobu; Tamaki, Naofumi; Maruyama, Takayuki; Onishi, Hideki; Kobayashi, Sayo; Nouso, Kazuhiro; Yasunaka, Tetsuya; Koike, Kazuko; Hagihara, Hiroaki; Kuwaki, Kenji; Nakamura, Shinichiro; Ikeda, Fusao; Iwasaki, Yoshiaki; Tomofuji, Takaaki; Morita, Manabu; Yamamoto, Kazuhide

2013-10-01

Oxidative stress is associated with progression of chronic liver disease (CLD). This association is best established in chronic hepatitis C. However, the anti-oxidative state is not well characterized. The objective of the present study was to investigate the balance of oxidative and anti-oxidative stress in CLD patients. We recruited a study population of 208 patients, including healthy volunteers (HV; n = 15), patients with hepatitis B virus (HBV)-related CLD without or with hepatocellular carcinoma (HBV-non-HCC, n = 25, and HBV-HCC, n = 50, respectively), and patients with hepatitis C virus (HCV)-related CLD without or with HCC (HCV-non-HCC, n = 49, and HCV-HCC, n = 69, respectively). Serum levels of reactive oxygen metabolites (ROM) and anti-oxidative markers (OXY-adsorbent test; OXY) were determined, and the balance of these values was used as the oxidative index. Correlations among ROM, OXY, oxidative index and clinical characteristics were investigated. Patients with CLD exhibited elevated ROM and oxidative index compared to HV. Among patients with CLD, HCV positive status correlated with increased ROM. In CLD, HCV-HCC patients exhibited the highest ROM levels. Among HCV-related CLD patients, lower OXY correlated with HCC positive status, but was recovered by eradication of HCC. In HCV-HCC, lower OXY correlated with high PT-INR. HCV positive CLD patients displayed higher oxidative stress and HCV-HCC patients displayed lower anti-oxidative state. Anti-oxidative state depression was associated with liver reservoir-related data in HCV-HCC and could be reversed with HCC eradication. © 2012 The Japan Society of Hepatology.

Evolution of the Oxidation State of the Earth's Mantle: Challenges of High Pressure Quenching

Science.gov (United States)

Danielson, L. R.; Righter, K.; Keller, L.; Christoffersen, R.; Rahman, Z.

2015-01-01

The oxidation state of the Earth's mantle during formation remains an unresolved question, whether it was constant throughout planetary accretion, transitioned from reduced to oxidized, or from oxidized to reduced. We investigate the stability of Fe3+ at depth, in order to constrain processes (water, late accretion, dissociation of FeO) which may reduce or oxidize the Earth's mantle. Experiments of more mafic compositions and at higher pressures commonly form a polyphase quench intergrowth composed primarily of pyroxenes, with interstitial glass which hosts nearly all of the more volatile minor elements. In our previous experiments on shergottite compositions, variable fO2, T, and P is less than 4 GPa, Fe3+/TotFe decreased slightly with increasing P, similar to terrestrial basalt. For oxidizing experiments less than 7GPa, Fe3+/TotFe decreased as well, but it's unclear from previous modelling whether the deeper mantle could retain significant Fe3+. Our current experiments expand our pressure range deeper into the Earth's mantle and focus on compositions and conditions relevant to the early Earth. Experiments with Knippa basalt as the starting composition were conducted at 1-8 GPa and 1800 C, using a molybdenum capsule to set the fO2 near IW, by buffering with Mo-MoO3. TEM and EELS analyses revealed the run products from 7-8 GPa quenched to polycrystalline phases, with the major phase pyroxene containing approximately equal Fe3+/2+. A number of different approaches have been employed to produce glassy samples that can be measured by EELS and XANES. A more intermediate andesite was used in one experiment, and decompression during quenching was attempted after, but both resulted in a finer grained polyphase texture. Experiments are currently underway to test different capsule materials may affect quench texture. A preliminary experiment using liquid nitrogen to greatly enhance the rate of cooling of the assembly has also been attempted and this technique will be

Hydrophobic matrix-free graphene-oxide composites with isotropic and nematic states

Science.gov (United States)

Wåhlander, Martin; Nilsson, Fritjof; Carlmark, Anna; Gedde, Ulf W.; Edmondson, Steve; Malmström, Eva

2016-08-01

We demonstrate a novel route to synthesise hydrophobic matrix-free composites of polymer-grafted graphene oxide (GO) showing isotropic or nematic alignment and shape-memory effects. For the first time, a cationic macroinitiator (MI) has been immobilised on anionic GO and subsequently grafted with hydrophobic polymer grafts. Dense grafts of PBA, PBMA and PMMA with a wide range of average graft lengths (MW: 1-440 kDa) were polymerised by surface-initiated controlled radical precipitation polymerisation from the statistical MI. The surface modification is designed similarly to bimodal graft systems, where the cationic MI generates nanoparticle repulsion, similar to dense short grafts, while the long grafts offer miscibility in non-polar environments and cohesion. The state-of-the-art dispersions of grafted GO were in the isotropic state. Transparent and translucent matrix-free GO-composites could be melt-processed directly using only grafted GO. After processing, birefringence due to nematic alignment of grafted GO was observed as a single giant Maltese cross, 3.4 cm across. Permeability models for composites containing aligned 2D-fillers were developed, which were compared with the experimental oxygen permeability data and found to be consistent with isotropic or nematic states. The storage modulus of the matrix-free GO-composites increased with GO content (50% increase at 0.67 wt%), while the significant increases in the thermal stability (up to 130 °C) and the glass transition temperature (up to 17 °C) were dependent on graft length. The tuneable matrix-free GO-composites with rapid thermo-responsive shape-memory effects are promising candidates for a vast range of applications, especially selective membranes and sensors.We demonstrate a novel route to synthesise hydrophobic matrix-free composites of polymer-grafted graphene oxide (GO) showing isotropic or nematic alignment and shape-memory effects. For the first time, a cationic macroinitiator (MI) has been

Nanoscale probing of bandgap states on oxide particles using electron energy-loss spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Liu, Qianlang [School for the Engineering of Matter, Transport and Energy, Arizona State University, 85287 AZ (United States); March, Katia [Laboratoire de Physique des Solides, Bâtiment 510, Université Paris-Sud, 91405 Orsay Cedex (France); Crozier, Peter A., E-mail: CROZIER@asu.edu [School for the Engineering of Matter, Transport and Energy, Arizona State University, 85287 AZ (United States)

2017-07-15

Surface and near-surface electronic states were probed with nanometer spatial resolution in MgO and TiO{sub 2} anatase nanoparticles using ultra-high energy resolution electron energy-loss spectroscopy (EELS) coupled to a scanning transmission electron microscope (STEM). This combination allows the surface electronic structure determined with spectroscopy to be correlated with nanoparticle size, morphology, facet etc. By acquiring the spectra in aloof beam mode, radiation damage to the surface can be significantly reduced while maintaining the nanometer spatial resolution. MgO and TiO{sub 2} showed very different bandgap features associated with the surface/sub-surface layer of the nanoparticles. Spectral simulations based on dielectric theory and density of states models showed that a plateau feature found in the pre-bandgap region in the spectra from (100) surfaces of 60 nm MgO nanocubes is consistent with a thin hydroxide surface layer. The spectroscopy shows that this hydroxide species gives rise to a broad filled surface state at 1.1 eV above the MgO valence band. At the surfaces of TiO{sub 2} nanoparticles, pronounced peaks were observed in the bandgap region, which could not be well fitted to defect states. In this case, the high refractive index and large particle size may make Cherenkov or guided light modes the likely causes of the peaks. - Highlights: • Bandgap states detected with aloof beam monochromated EELS on oxide nanoparticle surfaces. • Dielectric theory applied to simulate the spectra and interpret surface structure. • Density of states models also be employed to understand the surface electronic structure. • In MgO, one states associate with water species was found close to the valence band edge. • In anatase, two mid-gap states associated with point defects were found.

The state of itinerant charge carriers and thermoelectric effects in correlated oxide metals

International Nuclear Information System (INIS)

Kuzemsky, A.L.; Abdus Salam International Centre for Theoretical Physics, Trieste

2000-10-01

We analyzed the physics of transport processes and, in particular, the thermoelectric power in the mercurocuprates and other cuprates to get a better insight into the state of the carriers in these compounds. The actual problems related to the complicated mechanisms of carriers scattering above Tc are discussed. The experimental studies of thermoelectric power showed that the state of carriers in cuprates can be influenced by many complicated scattering processes, however the underlying mechanism for the linear decreasing of the TEP with increasing the temperature for most hole-doped HTSC cuprates is still not yet known. The actual problems related to the complicated mechanisms of carriers scattering above Tc are discussed for a few models of charge transport. A comparison between the analytical and experimental results is also made. It is concluded that the crucial factor for the understanding of the transport properties of correlated oxide metals is the nature of itinerant charge carriers, i.e. renormalized quasiparticles. (author)

Moessbauer effect study of oxidation and coordination states of iron in some sodium borate glasse:;

International Nuclear Information System (INIS)

Eissa, N.A.; Sanad, A.M.; Youssef, S.M.; El-Henawii, S.A.; Gomaa, S.Sh.; Mostafa, A.G.

1980-01-01

A structural study of some sodium borate glasses containing iron was carried out applying ME spectroscopy. Both oxidation and coordination states of iron were investigated under the effect of gradual replacing of sodium carbonate by sodium nitrate in the glass batches. The glasses were melted in porcelain crucibles using an electrically heated furnace at 1000+-10 deg C, then were quenched on a steel plate at room temperature (R.T.). The ME source was 20 mCi radioactive Co-57 in chromium. The obtained ME spectra indicated that at lower sodium nitrate content both Fe 2+ and Fe 3+ are present in these glasses. At moderate concentrations some Fe 3+ ions were separated in a crystalline phase and the rest of the iron ions appeared as ferric ions in glassy state. At high sodium nitrate content only Fe 3+ ions in glassy state were detected. The values of the ME parameters for all iron ions indicated that all of them are in the octahedral coordination state. The density measurements confirm the separation of a crystalline phase at moderate sodium nitrate content. (author)

Study of the oxidation state of arsenic and uranium in individual particles from uranium mine tailings, Hungary

International Nuclear Information System (INIS)

Alsecz, A.; Osan, J.; Palfalvi, J.; Torok, Sz.; Sajo, I.; Mathe, Z.; Simon, R.; Falkenberg, G.

2007-01-01

Uranium ore mining and milling have been terminated in the Mecsek Mountains (southwest Hungary) in 1997. Mine tailings ponds are located between two important water bases, which are resources of the drinking water of the city of Pecs and the neighbouring villages. The average U concentration of the tailings material is 71.73 μg/g, but it is inhomogeneous. Some microscopic particles contain orders of magnitude more U than the rest of the tailings material. Other potentially toxic elements are As and Pb of which chemical state is important to estimate mobility, because in mobile form they can risk the water basis and the public health. Individual U-rich particles were selected with solid state nuclear track detector (SSNTD) and after localisation the particles were investigated by synchrotron radiation based microanalytical techniques. The distribution of elements over the particles was studied by micro beam X-ray fluorescence (μ-XRF) and the oxidation state of uranium and arsenic was determined by micro X-ray absorption near edge structure (μ-XANES) spectroscopy. Some of the measured U-rich particles were chosen for studying the heterogeneity with μ-XRF tomography. Arsenic was present mainly in As(V) and uranium in U(VI) form in the original uranium ore particles, but in the mine tailings samples uranium was present mainly in the less mobile U(IV) form. Correlation was found between the oxidation state of As and U in the same analyzed particles. These results suggest that dissolution of uranium is not expected in short term period. (authors)

Investigation of electrochemical behaviour and structure of oxide films on Ni60Nb40 alloy in amorphous and crystalline states

International Nuclear Information System (INIS)

Tomashov, N.D.; Skvortsova, I.B.; Gorodetskij, A.E.; Bogomolov, D.B.

1987-01-01

Electrochemical properties of Ni 60 Nb 40 alloy in amorphous and crystalline states as well as structure of oxide films forming during anode polarization in electrolytes on the surface of this alloy in both its states are investigated. It is stated that increased passive ability of Ni 60 Nb 40 alloys in amorphous state and high efficiency of chlorine evolution (2 n NaCl+HCl up to pH=0) anode process in comparison with crystalline state are defined by increased homogeneity and uniformity of passive films forming on amorphous alloy and their increased electron conductivity, that is in direct dependence on different structure of passive films forming on alloys in amorphous and crystalline states

OXIDATION OF TRANSURANIC ELEMENTS

Science.gov (United States)

Moore, R.L.

1959-02-17

A method is reported for oxidizing neptunium or plutonium in the presence of cerous values without also oxidizing the cerous values. The method consists in treating an aqueous 1N nitric acid solution, containing such cerous values together with the trivalent transuranic elements, with a quantity of hydrogen peroxide stoichiometrically sufficient to oxidize the transuranic values to the hexavalent state, and digesting the solution at room temperature.

Ni–Ta–O mixed oxide catalysts for the low temperature oxidative dehydrogenation of ethane to ethylene

KAUST Repository

Zhu, Haibo

2015-09-01

The "wet" sol-gel and "dry" solid-state methods were used to prepare Ni-Ta-O mixed oxide catalysts. The resulting Ni-Ta oxides exhibit high activity and selectivity for the low temperature oxidative dehydrogenation of ethane to ethylene. The Ta/(Ni + Ta) atomic ratios (varying from 0 to 0.11 in "wet" sol-gel method, and from 0 to 0.20 in "dry" solid-state method) as well as the preparation methods used in the synthesis, play important roles in controlling catalyst structure, activity, selectivity and stability in the oxidative dehydrogenation of ethane. Electron microscopy characterizations (TEM, EELS mapping, and HAADF-STEM) clearly demonstrate that the Ta atoms are inserted into NiO crystal lattice, resulting in the formation of a new Ni-Ta oxide solid solution. More Ta atoms are found to be located at the lattice sites of crystal surface in sol-gel catalyst. While, a small amount of thin layer of Ta2O5 clusters are detected in solid-state catalyst. Further characterization by XRD, N2 adsorption, SEM, H2-TPR, XPS, and Raman techniques reveal different properties of these two Ni-Ta oxides. Due to the different properties of the Ni-Ta oxide catalysts prepared by two distinct approaches, they exhibit different catalytic behaviors in the ethane oxidative dehydrogenation reaction at low temperature. Thus, the catalytic performance of Ni-Ta-O mixed oxide catalysts can be systematically modified and tuned by selecting a suitable synthesis method, and then varying the Ta content. ©2015 Elsevier Inc. All rights reserved.

Signatures of Quantized Energy States in Solution-Processed Ultrathin Layers of Metal-Oxide Semiconductors and Their Devices

KAUST Repository

Labram, John G.

2015-02-13

Physical phenomena such as energy quantization have to-date been overlooked in solution-processed inorganic semiconducting layers, owing to heterogeneity in layer thickness uniformity unlike some of their vacuum-deposited counterparts. Recent reports of the growth of uniform, ultrathin (<5 nm) metal-oxide semiconductors from solution, however, have potentially opened the door to such phenomena manifesting themselves. Here, a theoretical framework is developed for energy quantization in inorganic semiconductor layers with appreciable surface roughness, as compared to the mean layer thickness, and present experimental evidence of the existence of quantized energy states in spin-cast layers of zinc oxide (ZnO). As-grown ZnO layers are found to be remarkably continuous and uniform with controllable thicknesses in the range 2-24 nm and exhibit a characteristic widening of the energy bandgap with reducing thickness in agreement with theoretical predictions. Using sequentially spin-cast layers of ZnO as the bulk semiconductor and quantum well materials, and gallium oxide or organic self-assembled monolayers as the barrier materials, two terminal electronic devices are demonstrated, the current-voltage characteristics of which resemble closely those of double-barrier resonant-tunneling diodes. As-fabricated all-oxide/hybrid devices exhibit a characteristic negative-differential conductance region with peak-to-valley ratios in the range 2-7.

The protonation state around TyrD/TyrD• in photosystem II is reflected in its biphasic oxidation kinetics.

Science.gov (United States)

Sjöholm, Johannes; Ho, Felix; Ahmadova, Nigar; Brinkert, Katharina; Hammarström, Leif; Mamedov, Fikret; Styring, Stenbjörn

2017-02-01

The tyrosine residue D2-Tyr160 (Tyr D ) in photosystem II (PSII) can be oxidized through charge equilibrium with the oxygen evolving complex in PSII. The kinetics of the electron transfer from Tyr D has been followed using time-resolved EPR spectroscopy after triggering the oxidation of pre-reduced Tyr D by a short laser flash. After its oxidation Tyr D is observed as a neutral radical (Tyr D • ) indicating that the oxidation is coupled to a deprotonation event. The redox state of Tyr D was reported to be determined by the two water positions identified in the crystal structure of PSII [Saito et al. (2013) Proc. Natl. Acad. Sci. USA 110, 7690]. To assess the mechanism of the proton coupled electron transfer of Tyr D the oxidation kinetics has been followed in the presence of deuterated buffers, thereby resolving the kinetic isotope effect (KIE) of Tyr D oxidation at different H/D concentrations. Two kinetic phases of Tyr D oxidation - the fast phase (msec-sec time range) and the slow phase (tens of seconds time range) were resolved as was previously reported [Vass and Styring (1991) Biochemistry 30, 830]. In the presence of deuterated buffers the kinetics was significantly slower compared to normal buffers. Furthermore, although the kinetics were faster at both high pH and pD values the observed KIE was found to be similar (~2.4) over the whole pL range investigated. We assign the fast and slow oxidation phases to two populations of PSII centers with different water positions, proximal and distal respectively, and discuss possible deprotonation events in the vicinity of Tyr D . Copyright © 2016 Elsevier B.V. All rights reserved.

Pu oxidation state distributions in suspensions of the Mont Terri Opalinus Clay isolate Sporomusa sp. MT-2.99

Energy Technology Data Exchange (ETDEWEB)

Moll, Henry [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Biogeochemistry; Cherkouk, Andrea [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). HZDR Young Investigator Group; Bok, Frank [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Surface Processes

2017-06-01

The time-dependent {sup 242}Pu oxidation state distribution in the presence of Sporomusa sp. cells as a function of pH with or without Na-pyruvate was analyzed. In all cases, the presence of bacterial cells enhanced removal of Pu from solution and accelerated Pu interaction reactions, e.g. biosorption and bioreduction.

A detailed study on the transition from the blocked to the superparamagnetic state of reduction-precipitated iron oxide nanoparticles

International Nuclear Information System (INIS)

Witte, K.; Bodnar, W.; Mix, T.; Schell, N.; Fulda, G.; Woodcock, T.G.; Burkel, E.

2016-01-01

Magnetic iron oxide nanoparticles were prepared by salt-assisted solid-state chemical precipitation method with alternating fractions of the ferric iron content. The physical properties of the precipitated nanoparticles mainly consisting of magnetite were investigated by means of transmission electron microscopy, high energy X-ray diffraction, vibrating sample magnetometry and Mössbauer spectroscopy. With particle sizes ranging from 16.3 nm to 2.1 nm, a gradual transition from the blocked state to the superparamagnetic state was observed. The transition was described as a dependence of the ferric iron content used during the precipitation. Composition, mean particle size, coercivity, saturation polarisation, as well as hyperfine interaction parameters and their evolution were studied systematically over the whole series of iron oxide nanoparticles. - Highlights: • Study of superparamagnetic transition of magnetite varying ferric iron content. • Coercivity is mainly influenced by the particle size. • Saturation polarisation influenced by the goethite content and the particle size. • Number of vacancies tend to increase with increasing ferric iron content. • Fe 3 O 4 B-sites are stronger effected by the reduction of particle size than A-sites.

Reduction of Tc(VII) and Np(V) in solution by ferrous iron. A laboratory study of homogeneous and heterogeneous redox processes

International Nuclear Information System (INIS)

Cui, D.; Eriksen, T.E.

1996-03-01

The redox chemistry of Technetium and Neptunium in deep groundwater systems has been studied under well controlled conditions in laboratory experiments. The measured redox potentials in anoxic deep groundwater systems are consistent with redox reactions between Fe(II) in solution and hydrous Fe(III)-oxide phases. The fracture filling material and groundwater in transmissive fractures in bedrock constitute two different compartments in the groundwater system and experiments were therefore carried out in homogeneous Fe(II) containing solutions and in heterogeneous mixtures of solution with Fe(II) containing solid mineral phases. Reduction of the strongly sorbing neptunyl cation (NpO 2 + ) and the slightly sorbing pertechnetate anion (TcO 4 - ) by Fe(II) in solution was found to proceed very slowly, if at all, in reaction vessels with hydrophobic inner surfaces. However, in the heterogeneous systems we observed surface mediated reduction to the slightly soluble ( -8 mol*dm -3 ) tetravalent (hydr)oxides TcO 2 *nH 2 O (=Tc(OH) 4 ) and NpO 2 *nH 2 O (=Np(OH) 4 ) by Fe(II) sorbed on quartz,precipitated Fe(OH) 2 (s), Fe(II)CO 3 (s) and Fe(II) bearing minerals such as magnetite, hornblende and Fe(II)-chlorite. It is concluded that surface mediated redox-reactions will be the most effective pathway for the reduction of Tc(VII) and Np(V) in deep groundwater systems. On exposure of the surface-precipitated tetravalent (hydr)oxides to air saturated groundwater solutions the oxidative dissolution was found to be a very slow process and high concentration of hydrogen peroxide was required for oxidative dissolution. The slow rate of oxidative dissolution is most probably due to kinetic suppression of the reactions between dissolved oxygen and the precipitated (hydr)oxides. The kinetic suppression is caused by competing redox reactions at the surface of the Fe(II)-bearing minerals which consumes the dissolved oxygen. 30 refs, 22 figs

Reduction of Tc(VII) and Np(V) in solution by ferrous iron. A laboratory study of homogeneous and heterogeneous redox processes

Energy Technology Data Exchange (ETDEWEB)

Cui, D.; Eriksen, T.E. [Royal Inst. of Tech., Stockholm (Sweden). Dept. of Chemistry

1996-03-01

The redox chemistry of Technetium and Neptunium in deep groundwater systems has been studied under well controlled conditions in laboratory experiments. The measured redox potentials in anoxic deep groundwater systems are consistent with redox reactions between Fe(II) in solution and hydrous Fe(III)-oxide phases. The fracture filling material and groundwater in transmissive fractures in bedrock constitute two different compartments in the groundwater system and experiments were therefore carried out in homogeneous Fe(II) containing solutions and in heterogeneous mixtures of solution with Fe(II) containing solid mineral phases. Reduction of the strongly sorbing neptunyl cation (NpO{sub 2}{sup +}) and the slightly sorbing pertechnetate anion (TcO{sub 4}{sup -}) by Fe(II) in solution was found to proceed very slowly, if at all, in reaction vessels with hydrophobic inner surfaces. However, in the heterogeneous systems we observed surface mediated reduction to the slightly soluble (<10{sub -8} mol*dm{sup -3}) tetravalent (hydr)oxides TcO{sub 2}*nH{sub 2}O (=Tc(OH){sub 4}) and NpO{sub 2}*nH{sub 2}O (=Np(OH){sub 4}) by Fe(II) sorbed on quartz,precipitated Fe(OH){sub 2}(s), Fe(II)CO{sub 3}(s) and Fe(II) bearing minerals such as magnetite, hornblende and Fe(II)-chlorite. It is concluded that surface mediated redox-reactions will be the most effective pathway for the reduction of Tc(VII) and Np(V) in deep groundwater systems. On exposure of the surface-precipitated tetravalent (hydr)oxides to air saturated groundwater solutions the oxidative dissolution was found to be a very slow process and high concentration of hydrogen peroxide was required for oxidative dissolution. The slow rate of oxidative dissolution is most probably due to kinetic suppression of the reactions between dissolved oxygen and the precipitated (hydr)oxides. The kinetic suppression is caused by competing redox reactions at the surface of the Fe(II)-bearing minerals which consumes the dissolved oxygen.

Force-dominated non-equilibrium oxidation kinetics of tantalum

International Nuclear Information System (INIS)

Kar, Prasenjit; Wang, Ke; Liang, Hong

2008-01-01

Using a combined electrochemical and mechanical manipulation technique, we compared the equilibrium and non-equilibrium oxidation processes and states of tantalum. Experimentally, a setup was developed with an electrochemical system attached to a sliding mechanical configuration capable of friction force measurement. The surface chemistry of a sliding surface, i.e., tantalum, was modified through the electrolyte. The mechanically applied force was fixed and the dynamics of the surface was monitored in situ through a force sensor. The formation of non-equilibrium oxidation states of tantalum was found in oxidation limiting environment of acetic acid. An oxidative environment of deionized water saturated with KCl was used as comparison. We proposed a modified Arrhenius-Eyring equation in which the mechanical factor was considered. We found that the mechanical energy induced the non-stable-state reactions leading to metastable oxidation states of tantalum. This equation can be used to predict mechanochemical reactions that are important in many industrial applications

Pu oxidation state distributions in suspensions of the Mont Terri Opalinus Clay isolate Sporomusa sp. MT-2.99

International Nuclear Information System (INIS)

Moll, Henry; Cherkouk, Andrea; Bok, Frank

2017-01-01

The time-dependent "2"4"2Pu oxidation state distribution in the presence of Sporomusa sp. cells as a function of pH with or without Na-pyruvate was analyzed. In all cases, the presence of bacterial cells enhanced removal of Pu from solution and accelerated Pu interaction reactions, e.g. biosorption and bioreduction.

Plutonium uptake by the green alga Scenedesmus obliquus (Turp) Kutz, as a function of isotope and oxidation state

Energy Technology Data Exchange (ETDEWEB)

Tkacik, M.F.

1977-01-01

This study was designed to determine the effect of plutonium chemical valence state on the availability of small concentrations of /sup 238/Pu and /sup 239/Pu to algae. The uptake experiments involved the green alga Scenedesmus obliquus, grown in batch cultures. Plutonium concentrations accumulated by this alga were linearly related to plutonium concentrations. There was no significant difference (rho = 0.05) in algal plutonium accumulations, on a mass basis, of either /sup 238/Pu or /sup 239/Pu in either Pu/sup +4/ or Pu/sup +6/ oxidation state at the concentrations studied.

Plutonium uptake by the green alga Scenedesmus obliquus (Turp) Kutz, as a function of isotope and oxidation state

International Nuclear Information System (INIS)

Tkacik, M.F.

1977-01-01

This study was designed to determine the effect of plutonium chemical valence state on the availability of small concentrations of 238 Pu and 239 Pu to algae. The uptake experiments involved the green alga Scenedesmus obliquus, grown in batch cultures. Plutonium concentrations accumulated by this alga were linearly related to plutonium concentrations. There was no significant difference (rho = 0.05) in algal plutonium accumulations, on a mass basis, of either 238 Pu or 239 Pu in either Pu +4 or Pu +6 oxidation state at the concentrations studied

Solid-state voltammetry-based electrochemical immunosensor for Escherichia coli using graphene oxide-Ag nanoparticle composites as labels.

Science.gov (United States)

Jiang, Xiaochun; Chen, Kun; Wang, Jing; Shao, Kang; Fu, Tao; Shao, Feng; Lu, Donglian; Liang, Jiangong; Foda, M Frahat; Han, Heyou

2013-06-21

A new electrochemical immunosensor based on solid-state voltammetry was fabricated for the detection of Escherichia coli (E. coli) by using graphene oxide-Ag nanoparticle composites (P-GO-Ag) as labels. To construct the platform, Au nanoparticles (AuNPs) were first self-assembled on an Au electrode surface through cysteamine and served as an effective matrix for antibody (Ab) attachment. Under a sandwich-type immunoassay format, the analyte and the probe (P-GO-Ag-Ab) were successively captured onto the immunosensor. Finally, the bonded AgNPs were detected through a solid-state redox process in 0.2 M of KCl solution. Combining the advantages of the high-loading capability of graphene oxide with promoted electron-transfer rate of AuNPs, this immunosensor produced a 26.92-fold signal enhancement compared with the unamplified protocol. Under the optimal conditions, the immunosensor exhibited a wide linear dependence on the logarithm of the concentration of E. coli ranging from 50 to 1.0 × 10(6) cfu mL(-1) with a detection limit of 10 cfu mL(-1). Moreover, as a practical application, the proposed immunosensor was used to monitor E. coli in lake water with satisfactory results.

Green synthesis of Ni-Nb oxide catalysts for low-temperature oxidative dehydrogenation of ethane

KAUST Repository

Zhu, Haibo; Rosenfeld, Devon C.; Anjum, Dalaver H.; Caps, Valerie; Basset, Jean-Marie

2015-01-01

The straightforward solid-state grinding of a mixture of Ni nitrate and Nb oxalate crystals led to, after mild calcination (T<400°C), nanostructured Ni-Nb oxide composites. These new materials efficiently catalyzed the oxidative dehydrogenation (ODH

Solid state solubility of copper oxides in hydroxyapatite

Science.gov (United States)

Zykin, Mikhail A.; Vasiliev, Alexander V.; Trusov, Lev A.; Dinnebier, Robert E.; Jansen, Martin; Kazin, Pavel E.

2018-06-01

Samples containing copper oxide doped hydroxyapatite with the composition Ca10(PO4)6(CuxOH1-x-δ)2, x = 0.054 - 0.582, in the mixture with CuO/Cu2O were prepared by a solid-state high-temperature treatment at varying annealing temperatures and at different partial water vapor and oxygen pressures. The crystal structures of the apatite compounds were refined using powder X-ray diffraction patterns and the content of copper ions x in the apatite was determined. Copper ions enter exclusively into the apatite trigonal channels formally substituting protons of OH-groups and the hexagonal cell parameters grow approximately linearly with x, the channel volume mostly expanding while the remaining volume of the crystal lattice changing only slightly. The equilibrium copper content in the apatite increases drastically, by almost a factor of 10 with the annealing temperature rising from 800° to 1200°C. The reduction of the water partial pressure leads to a further increase of x, while the dependence of x on the oxygen partial pressure exhibits a maximum. The observed relations are consistent with the proposed chemical reactions implying the copper introduction is followed by the release of a considerable quantity of gaseous products - water and oxygen. The analysis of interatomic distances suggests that the maximum content of copper ions in the channel cannot exceed 2/3.

Molecular water oxidation catalysis

CERN Document Server

Llobet, Antoni

2014-01-01

Photocatalytic water splitting is a promising strategy for capturing energy from the sun by coupling light harvesting and the oxidation of water, in order to create clean hydrogen fuel. Thus a deep knowledge of the water oxidation catalysis field is essential to be able to come up with useful energy conversion devices based on sunlight and water splitting. Molecular Water Oxidation Catalysis: A Key Topic for New Sustainable Energy Conversion Schemes presents a comprehensive and state-of-the-art overview of water oxidation catalysis in homogeneous phase, describing in detail the most importan

Current emission trends for nitrogen oxides, sulfur dioxide, and volatile organic compounds by month and state: Methodology and results

International Nuclear Information System (INIS)

Kohout, E.J.; Miller, D.J.; Nieves, L.A.; Rothman, D.S.; Saricks, C.L.; Stodolsky, F.; Hanson, D.A.

1990-08-01

This report presents estimates of monthly sulfur dioxide (SO 2 ), nitrogen oxides (NO x ), and nonmethane voltatile organic compound (VOC) emissions by sector, region, and state in the contiguous United States for the years 1975 through 1988. This work has been funded as part of the National Acid Precipitation Assessment Program's Emissions and Controls Task Group by the US Department of Energy (DOE) Office of Fossil Energy (FE). The DOE project officer is Edward C. Trexler, DOE/FE Office of Planning and Environment

Remote mixed oxide fabrication facility development. Volume 2. State-of-the-art review of remote maintenance system technology

International Nuclear Information System (INIS)

Horgos, R.M.; Masch, M.L.

1979-06-01

This report provides a state-of-the-art review of remote systems technology, which includes manipulators, process connectors, vision systems and specialized process systems. A proposed mixed oxide fuel fabrication facility was reviewed and evaluated for identification of major remote maintenance and repair tasks. The technological areas were evaluated on the basis of their suitability or applicability for remote maintenance and repair of a proposed fully remote operating mixed oxide fuel fabrication facility. A technological base exists from which the design criteria for a reliable, remote operating facility can be established. Commercially available systems and components, along with those remote technologies now in development, will require modifications to adapt them to specific plant designs and requirements

Determination of plutonium and neptunium in various materials by coulometric titration with amperometric indicating

International Nuclear Information System (INIS)

Moiseev, I.V.; Kuperman, A.Ya.; Borodina, N.N.; Galkina, V.N.; Nikitskaya, V.N.

1976-01-01

Coulometric methods of determining Pu and Np in the products of complex composition containing, in addition to Pu and Np, Cr and Nn have been developed. The methods are based on titration of Pusup((6)) and Npsup((6)) to tetravalent state in H 2 SO 4 -H 3 PO 4 with iron (2) ions generated continuously. A new variant of amperometric method has been proposed for determining end-point of titration. The methods of preparing Pusup((6)) and Npsup((6)) solutions have been developed. It has been shown that, upon dissolution of PuO 2 and NpO 2 by boiling with a mixture of nitric and perchloric acids Pusup((4)) and Npsup((4)) are oxidized quantitatively to Pusup((6)) and Npsup((6)) while Cl 2 , Crsup((6)) and Mnsup((7,4,3)) in the solution obtained are selectively reduced by CHOOH and CH 2 (COOH) 2 . In 6-8 M in terms of H 2 SO 4 solution, ammonium bichromate oxidizes Npsup((4)) to Npsup((6)), Pusup((3)) to Pusup((4)), and Mnsup((2)) to Mnsup((3)). Oxidized Mn and excess of Crsup((6)) are selectively reduced by CHOOH and H 2 C 2 O 4 in 4M in terms of H 2 SO 4 solution

Control of anode supported SOFCs (solid oxide fuel cells): Part I. mathematical modeling and state estimation within one cell

International Nuclear Information System (INIS)

Amedi, Hamid Reza; Bazooyar, Bahamin; Pishvaie, Mahmoud Reza

2015-01-01

In this paper, a 3-dimensional mathematical model for one cell of an anode-supported SOFC (solid oxide fuel cells) is presented. The model is derived from the partial differential equations representing the conservation laws of ionic and electronic charges, mass, energy, and momentum. The model is implemented to fully characterize the steady state operation of the cell with countercurrent flow pattern of fuel and air. The model is also used for the comparison of countercurrent with concurrent flow patterns in terms of thermal stress (temperature distribution) and quality of operation (current density). Results reveal that the steady-state cell performance curve and output of simulations qualitatively match experimental data of the literature. Results also demonstrate that countercurrent flow pattern leads to an even distribution of temperature, more uniform current density along the cell and thus is more enduring and superior to the concurrent flow pattern. Afterward, the thorough 3-dimensional model is used for state estimation instead of a real cell. To estimate states, the model is simplified and changed to a 1-dimensional model along flow streams. This simplified model includes uncertainty (because of simplifying assumptions of the model), noise, and disturbance (because of measurements). The behaviors of extended and ensemble Kalman filter as an observer are evaluated in terms of estimating the states and filtering the noises. Results demonstrate that, like extended Kalman filter, ensemble Kalman filter properly estimates the states with 20 sets. - Highlights: • A 3-dimensional model for one cell of SOFC (solid oxide fuel cells) is presented. • Higher voltages and thermal stress in countercurrent than concurrent flow pattern. • State estimation of the cell is examined by ensemble and extended Kalman filters. • Ensemble with 20 sets is as good as extended Kalman filter.

Evaluating chemical extraction techniques for the determination of uranium oxidation state in reduced aquifer sediments

Science.gov (United States)

Stoliker, Deborah L.; Campbell, Kate M.; Fox, Patricia M.; Singer, David M.; Kaviani, Nazila; Carey, Minna; Peck, Nicole E.; Barger, John R.; Kent, Douglas B.; Davis, James A.

2013-01-01

Extraction techniques utilizing high pH and (bi)carbonate concentrations were evaluated for their efficacy in determining the oxidation state of uranium (U) in reduced sediments collected from Rifle, CO. Differences in dissolved concentrations between oxic and anoxic extractions have been proposed as a means to quantify the U(VI) and U(IV) content of sediments. An additional step was added to anoxic extractions using a strong anion exchange resin to separate dissolved U(IV) and U(VI). X-ray spectroscopy showed that U(IV) in the sediments was present as polymerized precipitates similar to uraninite and/or less ordered U(IV), referred to as non-uraninite U(IV) species associated with biomass (NUSAB). Extractions of sediment containing both uraninite and NUSAB displayed higher dissolved uranium concentrations under oxic than anoxic conditions while extractions of sediment dominated by NUSAB resulted in identical dissolved U concentrations. Dissolved U(IV) was rapidly oxidized under anoxic conditions in all experiments. Uraninite reacted minimally under anoxic conditions but thermodynamic calculations show that its propensity to oxidize is sensitive to solution chemistry and sediment mineralogy. A universal method for quantification of U(IV) and U(VI) in sediments has not yet been developed but the chemical extractions, when combined with solid-phase characterization, have a narrow range of applicability for sediments without U(VI).

Dense high temperature ceramic oxide superconductors

Science.gov (United States)

Landingham, Richard L.

1993-01-01

Dense superconducting ceramic oxide articles of manufacture and methods for producing these articles are described. Generally these articles are produced by first processing these superconducting oxides by ceramic processing techniques to optimize materials properties, followed by reestablishing the superconducting state in a desired portion of the ceramic oxide composite.

Multiscale structural characterizations of mixed U(iv)-An(iii) oxalates (An(iii) = Pu or Am) combining XAS and XRD measurements.

Science.gov (United States)

Arab-Chapelet, B; Martin, P M; Costenoble, S; Delahaye, T; Scheinost, A C; Grandjean, S; Abraham, F

2016-04-28

Mixed actinide(III,IV) oxalates of the general formula M2.2UAn(C2O4)5·nH2O (An = Pu or Am and M = H3O(+) and N2H5(+)) have been quantitatively precipitated by oxalic precipitation in nitric acid medium (yield >99%). Thorough multiscale structural characterization using XRD and XAS measurements confirmed the existence of mixed actinide oxalate solid solutions. The XANES analysis confirmed that the oxidation states of the metallic cations, tetravalent for uranium and trivalent for plutonium and americium, are maintained during the precipitation step. EXAFS measurements show that the local environments around U(+IV), Pu(+III) and Am(+III) are comparable, and the actinides are surrounded by ten oxygen atoms from five bidentate oxalate anions. The mean metal-oxygen distances obtained by XAS measurements are in agreement with those calculated from XRD lattice parameters.

The electronic structure of the lanthanides and actinides, a comparison

International Nuclear Information System (INIS)

Edelstein, N.M.

1998-01-01

Full text: Optical spectra of the two f-element series (the lanthanides and actinides) are comparable in many respects. For the trivalent ions isolated in single crystals, both series exhibit rich, narrow line spectra. These data can be analysed in terms of a parametric model based on a free-ion Hamiltonian plus the addition of a crystal field Hamiltonian. For most systems the agreement between the calculated and experimental energy levels is quite good. In the actinide series there appears to be a correlation between the magnitude of the crystal field and the inadequacy of the fits. The early actinides exhibit multiple oxidation states for which there is no precedent in the lanthanide series. The parametric model mentioned earlier has been utilized for some tetravalent actinide systems with reasonably good results. A selective survey of results describing the similarities and differences of various lanthanide and actinide systems will be given

Synthesis and characterization of charge-substituted garnets YCaLnGa5O12 (Ln = Ce,Pr,Tb)

International Nuclear Information System (INIS)

Gramsch, S.A.

1993-01-01

A low temperature method is described for the preparation of the new garnet compounds YCaLnGa 5 O l2 (Ln=Ce, Pr, Th). In this set of compounds (Ca 2+ + Ln 4+ ) replaces 2 Y 3+ in the parent gallium based garnet Y 3 Ga 5 O l2 in order to stabilize as effectively as possible the Ln 4+ species in the eight-coordinate ''A'' site of the garnet structure. Characterization of the oxides by x-ray powder diffraction and thermogravimetric analysis is discussed with regard to the structural relationship of the substituted compound to the parent material. The tetravalent ions Pr 4+ and Tb 4+ exhibit increased thermal stability in reducing conditions as compared to the Ln 4+ states in the fluorite (LnO 2 ) and perovskite (BaLnO 3 ) type structures. This result is discussed with reference to the complex crystal chemistry of these systems

Radiolytic synthesis of carbon-supported PtRu nanoparticles using high-energy electron beam: effect of pH control on the PtRu mixing state and the methanol oxidation activity

International Nuclear Information System (INIS)

Ohkubo, Yuji; Kageyama, Satoru; Seino, Satoshi; Nakagawa, Takashi; Kugai, Junichiro; Nitani, Hiroaki; Ueno, Koji; Yamamoto, Takao A.

2013-01-01

Electrode catalysts composed of carbon-supported PtRu nanoparticles (PtRu/C) for use as a direct methanol fuel cell anode were synthesized by the reduction of precursor ions in an aqueous solution via irradiation with a high-energy electron beam. The effect of pH control in the precursor solution on the PtRu mixing state and the methanol oxidation activity was studied in order to enhance the catalytic activity for methanol oxidation. The PtRu/C structures were characterized by transmission electron microscopy, inductively coupled plasma atomic emission spectrometry, X-ray fluorescence spectrometry, and X-ray diffraction and X-ray absorption fine structure techniques. The methanol oxidation activity was evaluated by linear sweep voltammetry. The initial pH of the precursor solution has little influence on the average grain size for the metal particles (approximately 3.5 nm) on the carbon particle supports, but the dispersibility of the metal particles, PtRu mixing state, and methanol oxidation activity differed. The maintenance of a low pH in the precursor solution gave the best dispersibility of the PtRu nanoparticles supported on the surface of the carbon particles, whereas, a high pH gave the best PtRu mixing state and the highest oxidation current although a low dispersibility of the PtRu nanoparticles supported on the surface of the carbon particles was obtained. The PtRu mixing state strongly correlated with the methanol oxidation current. In addition, a high pH was more effective for PtRu mixing when using an electron beam irradiation reduction method, because the complexation reaction of the chelating agents was improved, which resulted in an enhancement of the catalytic activity for methanol oxidation.

Radiolytic synthesis of carbon-supported PtRu nanoparticles using high-energy electron beam: effect of pH control on the PtRu mixing state and the methanol oxidation activity

Energy Technology Data Exchange (ETDEWEB)

Ohkubo, Yuji, E-mail: okubo@mit.eng.osaka-u.ac.jp; Kageyama, Satoru; Seino, Satoshi; Nakagawa, Takashi; Kugai, Junichiro [Osaka University, Graduate School of Engineering (Japan); Nitani, Hiroaki [High Energy Accelerator Research Organization (KEK), Institute of Materials Structure Science (Japan); Ueno, Koji [Japan Electron Beam Irradiation Service Ltd (Japan); Yamamoto, Takao A. [Osaka University, Graduate School of Engineering (Japan)

2013-05-15

Electrode catalysts composed of carbon-supported PtRu nanoparticles (PtRu/C) for use as a direct methanol fuel cell anode were synthesized by the reduction of precursor ions in an aqueous solution via irradiation with a high-energy electron beam. The effect of pH control in the precursor solution on the PtRu mixing state and the methanol oxidation activity was studied in order to enhance the catalytic activity for methanol oxidation. The PtRu/C structures were characterized by transmission electron microscopy, inductively coupled plasma atomic emission spectrometry, X-ray fluorescence spectrometry, and X-ray diffraction and X-ray absorption fine structure techniques. The methanol oxidation activity was evaluated by linear sweep voltammetry. The initial pH of the precursor solution has little influence on the average grain size for the metal particles (approximately 3.5 nm) on the carbon particle supports, but the dispersibility of the metal particles, PtRu mixing state, and methanol oxidation activity differed. The maintenance of a low pH in the precursor solution gave the best dispersibility of the PtRu nanoparticles supported on the surface of the carbon particles, whereas, a high pH gave the best PtRu mixing state and the highest oxidation current although a low dispersibility of the PtRu nanoparticles supported on the surface of the carbon particles was obtained. The PtRu mixing state strongly correlated with the methanol oxidation current. In addition, a high pH was more effective for PtRu mixing when using an electron beam irradiation reduction method, because the complexation reaction of the chelating agents was improved, which resulted in an enhancement of the catalytic activity for methanol oxidation.

Sputtered tin oxide and titanium oxide thin films as alternative transparent conductive oxides

Energy Technology Data Exchange (ETDEWEB)

Boltz, Janika

2011-12-12

Alternative transparent conductive oxides to tin doped indium oxide have been investigated. In this work, antimony doped tin oxide and niobium doped titanium oxide have been studied with the aim to prepare transparent and conductive films. Antimony doped tin oxide and niobium doped titanium oxide belong to different groups of oxides; tin oxide is a soft oxide, while titanium oxide is a hard oxide. Both oxides are isolating materials, in case the stoichiometry is SnO{sub 2} and TiO{sub 2}. In order to achieve transparent and conductive films free carriers have to be generated by oxygen vacancies, by metal ions at interstitial positions in the crystal lattice or by cation doping with Sb or Nb, respectively. Antimony doped tin oxide and niobium doped titanium oxide films have been prepared by reactive direct current magnetron sputtering (dc MS) from metallic targets. The process parameters and the doping concentration in the films have been varied. The films have been electrically, optically and structurally analysed in order to analyse the influence of the process parameters and the doping concentration on the film properties. Post-deposition treatments of the films have been performed in order to improve the film properties. For the deposition of transparent and conductive tin oxide, the dominant parameter during the deposition is the oxygen content in the sputtering gas. The Sb incorporation as doping atoms has a minor influence on the electrical, optical and structural properties. Within a narrow oxygen content in the sputtering gas highly transparent and conductive tin oxide films have been prepared. In this study, the lowest resistivity in the as deposited state is 2.9 m{omega} cm for undoped tin oxide without any postdeposition treatment. The minimum resistivity is related to a transition to crystalline films with the stoichiometry of SnO{sub 2}. At higher oxygen content the films turn out to have a higher resistivity due to an oxygen excess. After post

Chromium Oxidation State in Planetary Basalts: Oxygen Fugacity Indicator and Critical Variable for Cr-Spinel Stability

Science.gov (United States)

Bell, A. S.; Burger, P. V.; Le, Loan; Papike, J. J.; Jone, J.; Shearer, C. K.

2014-01-01

Cr is a ubiquitous and relatively abundant minor element in basaltic, planetary magmas. At the reduced oxidation states (oxidation state of Cr in in silicate melts. Here we present a series of 1-bar gas mixing experiments performed with a Fe-rich basaltic melt in which have determined the Cr redox ratio of the melt at over a range of fO2 values by measuring this quantity in olivine with X-ray Absorption Near Edge Spectroscopy (XANES). The measured Cr redox ratio of the olivine phenocrysts can be readily converted to the ratio present in the conjugate melt via the ratio of crystal-liquid partition coefficients for Cr3+ and Cr2+. We have applied these results to modeling Cr spinel stability and Cr redox ratios in a primitive, iron-rich martian basalt.

Tetravalent thulium

Energy Technology Data Exchange (ETDEWEB)

Kiselev, Yu.M.; Goryachenkov, S.A.; Martynenko, L.I.; Spitsyn, V.I. (Moskovskij Gosudarstvennyj Univ. (USSR))

It is shown by the DTA method that the CsTmCl/sub 6/ and Cs/sub 3/TmF/sub 6/ interaction with XeF/sub 2/ reagents ratio (1:6) proceeds exothermally respectively below 100 deg C and at 380 deg C. The results of IR-spectroscopic investigation and magnetic moment measurement have shown that in the first case in fluorination products there are about 50% of Tm(4) in the TmF/sub 7//sup 3 -/ form, in the second 20-30%. Lesser percent of Tm(4) in Tm(3) fluorocomplex fluorination products as compared with the Tm(3) chlorocomplex fluorination products is caused by kinetic reasons. Radiographically the Cs/sub 3/TmF/sub 6/ and Cs/sub 3/TmF/sub 7/ cubic structures similarity is shown which can be a reason of additional stabilization of the system containing Tm(4) for account of formation of solid solutions.

Oxidation-extraction of uranium from wet-process phosphoric acid

International Nuclear Information System (INIS)

Lawes, B.C.

1985-01-01

The invention involves an improvement to the reductive stripping process for recovering uranium values from wet-process phosphoric acid solution, where uranium in the solution is oxidized to uranium (VI) oxidation state and then extracted from the solution by contact with a water immiscible organic solvent, by adding sufficient oxidant, hydrogen peroxide, to obtain greater than 90 percent conversion of the uranium to the uranium (VI) oxidation state to the phosphoric acid solution and simultaneously extracting the uranium (VI)

Coherent diffractive imaging of solid state reactions in zinc oxide crystals

Science.gov (United States)

Leake, Steven J.; Harder, Ross; Robinson, Ian K.

2011-11-01

We investigated the doping of zinc oxide (ZnO) microcrystals with iron and nickel via in situ coherent x-ray diffractive imaging (CXDI) in vacuum. Evaporated thin metal films were deposited onto the ZnO microcrystals. A single crystal was selected and tracked through annealing cycles. A solid state reaction was observed in both iron and nickel experiments using CXDI. A combination of the shrink wrap and guided hybrid-input-output phasing methods were applied to retrieve the electron density. The resolution was 33 nm (half order) determined via the phase retrieval transfer function. The resulting images are nevertheless sensitive to sub-angstrom displacements. The exterior of the microcrystal was found to degrade dramatically. The annealing of ZnO microcrystals coated with metal thin films proved an unsuitable doping method. In addition the observed defect structure of one crystal was attributed to the presence of an array of defects and was found to change upon annealing.

The role of oxidation states in F A1 Tl n+ (n = 1, 3) lasers and CO interactions at the (1 0 0) surface of NaCl: An ab initio study

International Nuclear Information System (INIS)

Shalabi, A.S.; Abdel Aal, S.; Kamel, M.A.; Taha, H.O.; Ammar, H.Y.; Abdel Halim, W.S.

2006-01-01

The oxidation states of Thallium in F A1 Tl +n (n = 1, 3) color centers at the (1 0 0) surface of NaCl play important role in laser light generation and adsorbate-substrate interactions. Double-well potentials at these surfaces are investigated by using quantum mechanical ab initio methods. Quantum clusters of variable sizes were embedded in the simulated Coulomb fields that closely approximate the Madelung fields of the host surfaces, and ions that were the nearest neighbors to the F A1 Tl +n (n 1, 3) defect site were allowed to relax to equilibrium.The calculated Stokes shifts suggest that laser light generation is sensitive to the oxidation states of Thallium. The relaxed excited states of the defect-containing surface were deep below the lower edge of the conduction bands of the ground state defect-free surface, suggesting that the F A1 Tl +n (n = 1, 3) centers are suitable laser defects. The dependence of the orientational destruction and recording sensitivity on the oxidation state of Thallium is clarified. The Glasner-Tompkins empirical rule is generalized to include the oxidation state of the impurity cation. The adsorption energies of CO and OC over NaCl(1 0 0) was found to be sensitive to the oxidation state of the impurity cation. F A1 Tl +n (n = 1, 3) centers changed the physical adsorption of CO to chemical adsorption. While the artificial flow of charge was significant in the case of Tl +1 impurity, it was negligible in the case of Tl +3 impurity, and the results were explained in terms of the electrostatic potential curves

Condensation mechanisms of tetravalent technetium in chloride media

International Nuclear Information System (INIS)

Poineau, F.

2004-10-01

In deep storage technetium can exist in degree IV or III. Recent studies on Tc(IV) have shown that Tc n O y (4n-2y)+ , Tc IV (μ-O) 2 Tc IV structure, is a precursor for precipitation of TcO 2 . Few data are available on Tc n O y (4n-2y)+ Subject of this thesis is the mechanism of condensation of Tc(IV) leading to this form. Kinetic studies have shown that the condensation of Tc IV Cl 5 (H 2 O) - in chloride media leads to a dimer. XAS studies resulted in a linear structure Tc IV -O-Tc IV . This compound, formulated as Tc 2 OCl 10 4- , is stable at pH = 0.3, it undergoes cyclization to Tc n O y (4n-2y)+ at pH =1.5 and is oxidized to TcO 4 - under α radiation. In 3 M chloride media, TcO 2 lead to formation Tc 2 OCl 10 4- at pH = 0.3 and to Tc n O y (4n-2y)+ at pH = 1.5. An electrochemical cell permitting 'in situ' XAS measurement was developed. XANES studies have shown that the reduction of Tc(VII) lead to a Tc(IV)/Tc(III) mixture. (author)

Oxidation of tertiary amines by cytochrome p450-kinetic isotope effect as a spin-state reactivity probe.

Science.gov (United States)

Li, Chunsen; Wu, Wei; Cho, Kyung-Bin; Shaik, Sason

2009-08-24

Two types of tertiary amine oxidation processes, namely, N-dealkylation and N-oxygenation, by compound I (Cpd I) of cytochrome P450 are studied theoretically using hybrid DFT calculations. All the calculations show that both N-dealkylation and N-oxygenation of trimethylamine (TMA) proceed preferentially from the low-spin (LS) state of Cpd I. Indeed, the computed kinetic isotope effects (KIEs) for the rate-controlling hydrogen abstraction step of dealkylation show that only the KIE(LS) fits the experimental datum, whereas the corresponding value for the high-spin (HS) process is much higher. These results second those published before for N,N-dimethylaniline (DMA), and as such, they further confirm the conclusion drawn then that KIEs can be a sensitive probe of spin state reactivity. The ferric-carbinolamine of TMA decomposes most likely in a non-enzymatic reaction since the Fe-O bond dissociation energy (BDE) is negative. The computational results reveal that in the reverse reaction of N-oxygenation, the N-oxide of aromatic amine can serve as a better oxygen donor than that of aliphatic amine to generate Cpd I. This capability of the N-oxo derivatives of aromatic amines to transfer oxygen to the heme, and thereby generate Cpd I, is in good accord with experimental data previously reported.

Energetics and Defect Interactions of Complex Oxides for Energy Applications

Science.gov (United States)

Solomon, Jonathan Michael

investigated based on the present results and previous computational and experimental thermochemical studies of rare earth substituted fluorite oxides. A consistent trend towards increased energetic stability with larger size mismatch between the smaller host tetravalent cation and the larger rare earth trivalent cation is found for both actinide and non-actinide fluorite oxide systems where aliovalent substitution of M cations is compensated by oxygen vacancies. However, the large exothermic oxidation enthalpy in the UO2 based systems favors compositions with higher oxygen-to-metal ratios where charge compensation occurs through the formation of uranium cations with higher oxidation states.

Some processes affecting the mobility of thorium in natural ground waters

International Nuclear Information System (INIS)

Oesthols, E.

1994-04-01

Thorium is a useful model element for tetravalent actinides such as U(IV), Pu(IV) and Np(IV) which are important constituents of spent nuclear fuel. Thorium is also an important tracer element for particle pathways in natural environments. In order to correctly model the transport of Th in the environment, it is important to have quantitative models for processes that effect its mobility. Some of these processes have been experimentally investigated in laboratory studies, and interpreted with quantitative models where possible. The carbonate complexation in aqueous solution of Th has been investigated through solubility studies of ThO 2 in carbonate media. It is shown, that thorium carbonate complexes are likely to be predominant in many natural waters. They also increase solubility of the oxide significantly, and hence the mobility of Th. Carbonate also increases the dissolution rate of thorium oxide. This effect will only be important in environments with a pH and total carbonate alkalinity higher than those of most natural aquatic environments. Solubility studies of thorium oxide in phosphate media show that phosphate does not significantly increase the mobility of Th in aqueous media. The presence of phosphate may cause the precipitation of sparingly soluble thorium phosphates which will decrease the mobility of Th. The pentahydroxo complex for Th is shown to be significant up to pH 13. Potentiometric studies of Th sorption on amorphous colloidal silica indicate, that pure aluminosilicates will probably not be efficient scavengers of tetravalent actinides above pH values of approximately 6. In neutral to alkaline solutions, iron (hydr)oxides are likely to be the predominant sorbents. Th binds to the silica surface through corner-sharing bonds, where Th and Si share one, but not more oxygen atoms. 72 refs

Structure and electrical conduction of the system La sub(1-x)Ca sub(x)FeO sub(3-. cap alpha. )

Energy Technology Data Exchange (ETDEWEB)

Hombo, Jukichi; Urabe, Noriake [Kumamoto Univ. (Japan). Faculty of Engineering; Hiroshige, Gota; Hamada, Kotaro

1982-08-01

Perovskite phases in the system, La sub(1-x)Ca sub(x)FeO sub(3-..cap alpha..) were prepared with La/sub 2/O/sub 3/, CaCO/sub 3/, and Fe/sub 2/O/sub 3/ by firing in air and in vacuo. The compositions of samples fired in vacuo and in air are represented as La sub(1-x)Ca sub(x)FeO sub(3-x 2) and La sub(1-x)Ca sub(x)Fe sub(1-y)sup(3+)Fe sub(y)sup(4+)O sub(3-x/2+y/2), respectively. That is, samples fired in vacuo contain some oxygen vacancies and no tetravalent iron; in contrast, samples fired in air contain both oxygen vacancies and tetravalent iron in the structures. The electrical conductivities of these synthesized oxides depended extensively upon the content of tetravalent iron. For instance, the conductivity of the sample x = 0.6 fired in air was larger by 10/sup 6/ than that of the sample fired in vacuo. In this system, except for the two terminal compositions of x = 0 and x = 1.0, the values of activation energy for conduction are considerably small, and from the results of thermo-electromotive force measurement, the charge carrier was positive. Furthermore, the conductivity increased somewhat with time during the conductivity measurement by the direct-current method. These facts suggest that the electric conduction would not be ionic but electronic. The electrical conduction would then be carried out by the so-called hopping mechanism by which the positive charge is transferred.

Structure and electrical conduction of the system La sub(1-x)Ca sub(x)FeO sub(3-α)

International Nuclear Information System (INIS)

Hombo, Jukichi; Urabe, Noriake; Hiroshige, Gota; Hamada, Kotaro.

1982-01-01

Perovskite phases in the system, La sub(1-x)Ca sub(x)FeO sub(3-α) were prepared with La 2 O 3 , CaCO 3 , and Fe 2 O 3 by firing in air and in vacuo. The compositions of samples fired in vacuo and in air are represented as La sub(1-x)Ca sub(x)FeO sub(3-x 2) and La sub(1-x)Ca sub(x)Fe sub(1-y)sup(3+)Fe sub(y)sup(4+)O sub(3-x/2+y/2), respectively. That is, samples fired in vacuo contain some oxygen vacancies and no tetravalent iron; in contrast, samples fired in air contain both oxygen vacancies and tetravalent iron in the structures. The electrical conductivities of these synthesized oxides depended extensively upon the content of tetravalent iron. For instance, the conductivity of the sample x = 0.6 fired in air was larger by 10 6 than that of the sample fired in vacuo. In this system, except for the two terminal compositions of x = 0 and x = 1.0, the values of activation energy for conduction are considerably small, and from the results of thermo-electromotive force measurement, the charge carrier was positive. Furthermore, the conductivity increased somewhat with time during the conductivity measurement by the direct-current method. These facts suggest that the electrical conducted would not be ionic but electronic. The electrical conduction would then be carried out by the so-called hopping mechanism by which the positive charge is transferred. (author)

Analyzer for measurement of nitrogen oxide concentration by ozone content reduction in gas using solid state chemiluminescent sensor

Science.gov (United States)

Chelibanov, V. P.; Ishanin, G. G.; Isaev, L. N.

2014-05-01

Role of nitrogen oxide in ambient air is described and analyzed. New method of nitrogen oxide concentration measurement in gas phase is suggested based on ozone concentration measurement with titration by nitrogen oxide. Research of chemiluminescent sensor composition is carried out on experimental stand. The sensor produced on the base of solid state non-activated chemiluminescent composition is applied as ozone sensor. Composition is put on the surface of polymer matrix with developed surface. Sensor compositions includes gallic acid with addition of rodamine-6G. Model of interaction process between sensor composition and ozone has been developed, main products appeared during reaction are identified. The product determining the speed of luminescense appearance is found. This product belongs to quinone class. Then new structure of chemiluminescent composition was suggested, with absence of activation period and with high stability of operation. Experimental model of gas analyzer was constructed and operation algorithm was developed. It was demonstrated that developed NO measuring instrument would be applied for monitoring purposes of ambient air. This work was partially financially supported by Government of Russian Federation, Grant 074-U01

Final Report for research grant "Development of Methods for High Specific Activity Labeling of Biomolecules Using Astatine-211 in Different Oxidation States"

Energy Technology Data Exchange (ETDEWEB)

Wilbur, D. Scott [Univ. of Washington, Seattle, WA (United States)

2011-12-14

The overall objective of this research effort was to develop methods for labeling biomolecules with higher oxidation state species of At-211. This was to be done in an effort to develop reagents that had higher in vivo stability than the present carbon-bonded At-211-labeled compounds. We were unsuccessful in that effort, as none of the approaches studied provided reagents that were stable to in vivo deastatination. However, we gained a lot of information about At-211 in higher oxidation states. The studies proved to be very difficult as small changes in pH and other conditions appeared to change the nature of the species that obtained (by HPLC retention time analyses), with many of the species being unidentifiable. The fact that there are no stable isotopes of astatine, and the chemistry of the nearest halogen iodine is quite different, made it very difficult to interpret results of some experiments. With that said, we believe that a lot of valuable information was obtained from the studies. The research effort evaluated: (1) methods for chemical oxidation of At-211, (2) approaches to chelation of oxidized At-211, and (3) approaches to oxidation of astatophenyl compounds. A major hurdle that had to be surmounted to conduct the research was the development of HPLC conditions to separate and identify the various oxidized species formed. Attempts to develop conditions for separation of iodine and astatine species by normal and reversed-phase TLC and ITLC were not successful. However, we were successful in developing conditions (from a large number of attempts) to separate oxidized forms of iodine ([I-125]iodide, [I-125]iodate and [I-125]periodate) and astatine ([At-211]astatide, [At-211]astatate, [At-211]perastatate, and several unidentified At-211 species). Information on the basic oxidation and characterization of At-211 species is provided under Objective 1. Conditions were developed to obtain new At-211 labeling method where At-211 is chelated with the DOTA and

Tantalum high-temperature oxidation kinetics

International Nuclear Information System (INIS)

Grigor'ev, Yu.M.; Sarkisyan, A.A.; Merzhanov, A.G.

1981-01-01

Kinetics of heat release and scale growth during tantalum oxidation within 650-1300 deg C temperature range in oxygen-containing media is investigated. Kinetic equations and temperature and pressure dependences of constants are ound Applicability of the kinetic Lorie mechanism for the description of the tantalum oxidation kinetics applicably to rapid-passing processes is shown. It is stated that the process rate (reaction ability) is determined by adsorption desorption factors on the external surface of the ''protective'' oxide for the ''linear'' oxidation stage [ru

Characterization of copper oxides, iron oxides, and zinc copper ferrite desulfurization sorbents by X-ray photoelectron spectroscopy and scanning electron microscopy

Science.gov (United States)

Siriwardane, Ranjani V.; Poston, James A.

1993-05-01

Characterization of copper oxides, iron oxides, and zinc copper ferrite desulfurization sorbents was performed by X-ray photoelectron spectroscopy and scanning electron microscopy/energy-dispersive spectroscopy at temperatures of 298 to 823 K. Analysis of copper oxides indicated that the satellite structure of the Cu22p region was absent in the Cu(I) state but was present in the Cu(II) state. Reduction of CuO at room temperature was observed when the ion gauge was placed close to the sample. The satellite structure was absent in all the copper oxides at 823 K in vacuum. Differentiation of the oxidation state of copper utilizing both Cu(L 3M 4,5M 4,5) X-ray-induced Auger lines and Cu2p satellite structure, indicated that the copper in zinc copper ferrite was in the + 1 oxidation state at 823 K. This + 1 state of copper was not significantly changed after exposure to H 2, CO, and H 2O. There was an increase in Cu/Zn ratio and a decrease in Fe/Zn ratio on the surface of zinc copper ferrite at 823 K compared to that at room temperature. These conditions of copper offered the best sulfidation equilibrium for the zinc copper ferrite desulfurization sorbent. Analysis of iron oxides indicated that there was some reduction of both Fe 2O 3 and FeO at 823K. The iron in zinc copper ferrite was similar to that of Fe 2O 3 at room temperature but there was some reduction of this Fe(III) state to Fe(II) at 823 K. This reduction was more enhanced in the presence of H 2 and CO. Reduction to Fe(II) may not be desirable for the lifetime of the sorbent.

The Oxides of Nitrogen in Air Pollution.

Science.gov (United States)

California State Air Resources Board, Sacramento.

Research on the health effects of oxides of nitrogen and on the role of oxides of nitrogen in producing photochemical smog effects is presented in this report. Prepared by the California State Department of Public Health at the request of the State Legislature, it gives a comprehensive review of available information, as well as the need for air…

Oxidation and detoxification of trivalent arsenic species

International Nuclear Information System (INIS)

Aposhian, H. Vasken; Zakharyan, Robert A.; Avram, Mihaela D.; Kopplin, Michael J.; Wollenberg, Michael L.

2003-01-01

Arsenic compounds with a +3 oxidation state are more toxic than analogous compounds with a +5 oxidation state, for example, arsenite versus arsenate, monomethylarsonous acid (MMA III ) versus monomethylarsonic acid (MMA V ), and dimethylarsinous acid (DMA III ) versus dimethylarsinic acid (DMA V ). It is no longer believed that the methylation of arsenite is the beginning of a methylation-mediated detoxication pathway. The oxidation of these +3 compounds to their less toxic +5 analogs by hydrogen peroxide needs investigation and consideration as a potential mechanism for detoxification. Xanthine oxidase uses oxygen to oxidize hypoxanthine to xanthine to uric acid. Hydrogen peroxide and reactive oxygen are also products. The oxidation of +3 arsenicals by the hydrogen peroxide produced in the xanthine oxidase reaction was blocked by catalase or allopurinol but not by scavengers of the hydroxy radical, e.g., mannitol or potassium iodide. Melatonin, the singlet oxygen radical scavenger, did not inhibit the oxidation. The production of H 2 O 2 by xanthine oxidase may be an important route for decreasing the toxicity of trivalent arsenic species by oxidizing them to their less toxic pentavalent analogs. In addition, there are many other reactions that produce hydrogen peroxide in the cell. Although chemists have used hydrogen peroxide for the oxidation of arsenite to arsenate to purify water, we are not aware of any published account of its potential importance in the detoxification of trivalent arsenicals in biological systems. At present, this oxidation of the +3 oxidation state arsenicals is based on evidence from in vitro experiments. In vivo experiments are needed to substantiate the role and importance of H 2 O 2 in arsenic detoxication in mammals

The extraction neptunium by trilaurylamine; L'extraction du neptunium par le trilaurylamine

Energy Technology Data Exchange (ETDEWEB)

Champion, J.; Chesne, A. [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

1964-07-01

The extraction by trilaurylamine of neptunium (IV) from nitric acid and sulfuric acid-nitric acid media has been studied with the aim of developing a purification process for this element. Relative to the plutonium-neptunium separation, conditions are given for the oxidation of neptunium (IV) in sulfuric acid-nitric acid medium and data are presented on the stabilisation of the + 4 oxidation state by the organic solvent. Two procedures have been developed for the simultaneous purification of the two actinides. Both are based on the trilaurylamine extraction of the tetravalent nitrate species. The first utilises a constant redox potential fixed by Fe{sup +++} /Fe{sup ++} couple, while in the second, valencies are determined by successive addition of nitrite and ferrous ions. Gram quantities of neptunium 237 has been recovered from plutonium process solution. Alternate procedures are suggested for the chemical processing of irradiated Np{sup 237}. (authors) [French] L'extraction du neptunium par le trilaurylamine en milieu nitrique et sulfonitrique a ete etudiee dans le cadre de la recherche des procedes de purification de cet element. En vue d'effectuer la separation neptunium-plutonium on a precise d'une part les conditions d'oxydation du Np{sup 4+} en milieu sulfonitrique, d'autre part l'influence du solvant sur la stabilite des valences de ces deux elements. Deux procedes de purification simultanee des deux actinides ont ete developpes. Ils sont bases sur l'extraction du nitrate des elements tetravalents dans la trilaury lamine. Dans l'un, la solution a extraire a un potentiel redox fixe par un systeme auxiliaire (Fe{sup +++}/Fe{sup ++}), dans l'autre elle subit dans le meme extracteur des additions successives de nitrite et de fer ferreux. On decrit un essai semi-industriel de recuperation de neptunium 237 a partir de solution provenant de l'usine de production de plutonium de Marcoule. Differents schemas

The extraction neptunium by trilaurylamine; L'extraction du neptunium par le trilaurylamine

Energy Technology Data Exchange (ETDEWEB)

Champion, J; Chesne, A [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

1964-07-01

The extraction by trilaurylamine of neptunium (IV) from nitric acid and sulfuric acid-nitric acid media has been studied with the aim of developing a purification process for this element. Relative to the plutonium-neptunium separation, conditions are given for the oxidation of neptunium (IV) in sulfuric acid-nitric acid medium and data are presented on the stabilisation of the + 4 oxidation state by the organic solvent. Two procedures have been developed for the simultaneous purification of the two actinides. Both are based on the trilaurylamine extraction of the tetravalent nitrate species. The first utilises a constant redox potential fixed by Fe{sup +++} /Fe{sup ++} couple, while in the second, valencies are determined by successive addition of nitrite and ferrous ions. Gram quantities of neptunium 237 has been recovered from plutonium process solution. Alternate procedures are suggested for the chemical processing of irradiated Np{sup 237}. (authors) [French] L'extraction du neptunium par le trilaurylamine en milieu nitrique et sulfonitrique a ete etudiee dans le cadre de la recherche des procedes de purification de cet element. En vue d'effectuer la separation neptunium-plutonium on a precise d'une part les conditions d'oxydation du Np{sup 4+} en milieu sulfonitrique, d'autre part l'influence du solvant sur la stabilite des valences de ces deux elements. Deux procedes de purification simultanee des deux actinides ont ete developpes. Ils sont bases sur l'extraction du nitrate des elements tetravalents dans la trilaury lamine. Dans l'un, la solution a extraire a un potentiel redox fixe par un systeme auxiliaire (Fe{sup +++}/Fe{sup ++}), dans l'autre elle subit dans le meme extracteur des additions successives de nitrite et de fer ferreux. On decrit un essai semi-industriel de recuperation de neptunium 237 a partir de solution provenant de l'usine de production de plutonium de Marcoule. Differents schemas utilisables lors du traitement chimique des cibles de

Synthesis, characterization and structural refinement of polycrystalline uranium substituted zirconolite

International Nuclear Information System (INIS)

Shrivastava, O.P.; Narendra Kumar; Sharma, I.B.

2005-01-01

Ceramic precursors of Zirconolite (CaZrTi 2 O 7 ) family have a remarkable property of substitution Zr 4+ cationic sites. This makes them potential material for nuclear waste management in 'synroc' technology. In order to simulate the mechanism of partial substitution of zirconium by tetravalent actinides, a solid phase of composition CaZr 0.95 U 0.5 Ti 2 O 7 has been synthesized through ceramic route by taking calculated quantities of oxides of Ca, Ti and nitrates of uranium and zirconium respectively. Solid state synthesis has been carried out by repeated pelletizing and sintering the finely powdered oxide mixture in a muffle furnace at 1050 degC. The polycrystalline solid phase has been characterized by its typical powder diffraction pattern. Step analysis data has been used for ab initio calculation of structural parameters. The uranium substituted zirconolite crystallizes in monoclinic symmetry with space group C2/c (15). The following unit cell parameters have been calculated: a =12.4883(15), b =7.2448(5), c 11.3973(10) and β = 100.615(9)0. The structure was refined to satisfactory completion. The Rp and Rwp are found to be 7.48% and 9.74% respectively. (author)

Immunogenicity and safety of tetravalent dengue vaccine in 2-11 year-olds previously vaccinated against yellow fever: randomized, controlled, phase II study in Piura, Peru.

Science.gov (United States)

Lanata, Claudio F; Andrade, Teresa; Gil, Ana I; Terrones, Cynthia; Valladolid, Omar; Zambrano, Betzana; Saville, Melanie; Crevat, Denis

2012-09-07

In a randomized, placebo-controlled, monocenter, observer blinded study conducted in an area where dengue is endemic, we assessed the safety and immunogenicity of a recombinant, live, attenuated, tetravalent dengue vaccine candidate (CYD-TDV) in 2-11 year-olds with varying levels of pre-existing yellow-fever immunity due to vaccination 1-7 years previously. 199 children received 3 injections of CYD-TDV (months 0, 6 and 12) and 99 received placebo (months 0 and 6) or pneumococcal polysaccharide vaccine (month 12). One month after the third dengue vaccination, serotype specific neutralizing antibody GMTs were in the range of 178-190 (1/dil) (versus 16.7-38.1 in the control group), a 10-20 fold-increase from baseline, and 94% of vaccines were seropositive to all four serotypes (versus 39% in the control group). There were no vaccine-related SAEs. The observed reactogenicity profile was consistent with phase I studies, with severity grade 1-2 injection site pain, headache, malaise and fever most frequently reported and no increase after subsequent vaccinations. Virologically confirmed dengue cases were seen after completion of the 3 doses: 1 in the CYD-TDV group (N=199), and 3 in the control group (N=99). A 3-dose regimen of CYD-TDV had a good safety profile in 2-11 year olds with a history of YF vaccination and elicited robust antibody responses that were balanced against the four serotypes. Copyright © 2012 Elsevier Ltd. All rights reserved.

Solid-state ionics: Studies of lithium-conducting sulfide glasses and a superconducting oxide compound

International Nuclear Information System (INIS)

Ahn, Byung Tae.

1989-01-01

The first part of this work studies lithium-conducting sulfide glasses for battery applications, while the second part studies the thermodynamic properties of a superconducting oxide compound by using an oxide electrolyte. Lithium conducting glasses based on the SiS 2 -Li 2 S system are possible solid electrolytes for high-energy-density lithium batteries. The foremost requirement for solid electrolytes is that they should have high ionic conductivities. Unfortunately, most crystalline lithium conductors have low ionic conductivities at room temperature. However, glass ionic conductors show higher ionic conductivities than do crystalline forms of the same material. In addition to higher ionic conductivities, glasses appear to have several advantages over crystalline materials. These advantages include isotropic conductivity, absence of grain boundary effects, ease of glass forming, and the potential for a wide range of stability to oxidizing and reducing conditions. Using pyrolitic graphite-coated quartz ampoules, new ternary compounds and glasses in the SiS 2 -Li 2 S system were prepared. Several techniques were used to characterize the materials: powder x-ray diffraction, differential thermal analysis, differential scanning calorimetry, and AC impedance spectroscopy. The measured lithium conductivity of the sulfide glasses was one of the highest among the known solid lithium conductors. Measuring the equilibrium open circuit voltages assisted in determining the electrochemical stabilities of the ternary compounds and glasses with respect to pure Li. A solid-state ionic technique called oxygen coulometric titration was used to measure the thermodynamic stability, the oxygen stoichiometry, and the effects of the oxygen stoichiometry, and the effects of the oxygen stoichiometry and the cooling rate on superconductivity of the YBa 2 Cu 3 O 7-x compound were investigated

Stabilization of actinides and lanthanides in unusually high oxidation states

International Nuclear Information System (INIS)

Eller, P.G.; Penneman, R.A.

1986-01-01

Chemical environments can be chosen which stabilize actinides and lanthanides in unusually high or low oxidation states and in unusual coordination. In many cases, one can rationalize the observed species as resulting from strong charge/size influences provided by specific sites in host lattices (e.g., Tb(IV) in BaTbO 3 or Am(IV) in polytungstate anions). In other cases, the unusual species can be considered from an acid-base viewpoint (e.g., U(III) in AsF 5 /HF solution or Pu(VII) in Li 5 PuO 6 ). In still other cases, an interplay of steric and redox effects can lead to interesting comparisons (e.g., instability of double fluoride salts of Pu(V) and Pu(VI) relative to U, Np, and Am analogues). Generalized ways to rationalize compounds containing actinides and lanthanides in unusual valences (particularly high valences), including the above and numerous other examples, will form the focus of this paper. Recently developed methods for synthesizing high valent f-element fluorides using superoxidizers and superacids at low temperatures will also be described. 65 refs., 8 figs., 9 tabs

Rare Earth Oxide Thin Films

CERN Document Server

Fanciulli, Marco

2007-01-01

Thin rare earth (RE) oxide films are emerging materials for microelectronic, nanoelectronic, and spintronic applications. The state-of-the-art of thin film deposition techniques as well as the structural, physical, chemical, and electrical properties of thin RE oxide films and of their interface with semiconducting substrates are discussed. The aim is to identify proper methodologies for the development of RE oxides thin films and to evaluate their effectiveness as innovative materials in different applications.

Application of high-pressure techniques: stabilization and oxidation-state control of novel superconductive and related multi-layered copper oxides

International Nuclear Information System (INIS)

Yamauchi, H.; Karppinen, M.

2000-01-01

Copper oxide superconductors possess multi-layered structures with a layer sequence of -CuO 2 -(Q-CuO 2 ) n-1 -AO-(MO 1±δ ) m -AO- or -CuO 2 -B-(O 2 -B) s-1 -CuO 2 -AO-(MO 1±δ ) m -AO- along the elongated c axis. Based on this layer sequence, the known copper oxide structures are categorized as members of the homologous series, M m A r Q n-1 Cu n O m+r+2 +n ±δ (M-mr(n-1)n ; category A) or M m A 2k B s Cu 1+k O m +4k +2s±δ (M-m(2k)s (1+k ); category B). Stabilization of such structures especially in the case of high values of the n /s parameter, i.e. the higher members of the homologous series, has been demonstrated to be apparently promoted under high pressures and/or strongly oxidizing conditions. Consequently, techniques for applying both high oxygen gas pressures (10-2000 atm) and ultra-high solid-medium pressures (2-8 GPa) have been advantageously utilized in synthesizing various superconductive copper oxide phases. Especially the ultra-high solid-medium pressure synthesis carried out in the so-called cubic-anvil/belt-type apparatus has proven to be extremely successful in synthesizing novel superconductive phases. In order to achieve high partial pressures of oxygen in the solid-medium environment, 'external' oxygen-generating oxides such as KClO 4 , KClO 3 and Ag 2 O 2 are commonly added to the precursor mixtures. It is emphasized that in some cases it is possible to utilize 'internal' oxidizing agents alone, i.e. highly oxidized precursors such as BaCuO 2+δ and Ba 2 Cu 3 O 5+δ containing metal constituents common with the desired copper oxide phase only. In the present paper, the potential and applications of high-pressure techniques in synthesizing multi-layered copper oxides and related structures are reviewed and discussed with emphasis on the important 'historical' discoveries of novel phases and the present status of controlled production of high-quality samples of such phases. (author)

Safety Overview of a Recombinant Live-Attenuated Tetravalent Dengue Vaccine: Pooled Analysis of Data from 18 Clinical Trials.

Directory of Open Access Journals (Sweden)

Sophia Gailhardou

2016-07-01

Full Text Available A recombinant live attenuated tetravalent dengue vaccine (CYD-TDV has been shown to be efficacious in preventing virologically-confirmed dengue disease, severe dengue disease and dengue hospitalization in children aged 2-16 years in Asia and Latin America. We analyzed pooled safety data from 18 phase I, II and III clinical trials in which the dengue vaccine was administered to participants aged 2-60 years, including long-term safety follow-up in three efficacy trials. The participants were analyzed according to their age at enrollment. The percentage of participants aged 2-60 years reporting ≥1 solicited injection-site or systemic reactions was slightly higher in the CYD-TDV group than in the placebo group. The most common solicited injection-site reactions were pain. Headache and malaise were the most common solicited systemic reactions. In both groups 0.3% of participants discontinued for safety reasons. The most common unsolicited adverse events were injection-site reactions, gastrointestinal disorders, and infections. Reactogenicity did not increase with successive doses of CYD-TDV. The frequency and nature of SAEs occurring within 28 days of any dose were similar in the CYD-TDV and placebo groups and were common medical conditions that could be expected as a function of age. Baseline dengue virus serostatus did not appear to influence the safety profile. No vaccine-related anaphylactic reactions, neurotropic events or viscerotropic events were reported. In year 3 after dose 1, an imbalance for dengue hospitalization, including for severe dengue, observed in participants aged <9 years in the CYD-TDV group compared with the placebo group was not observed for participants aged ≥9 years. In Year 4, this imbalance in participants aged <9 years was less marked, giving an overall lower risk of dengue hospitalization or severe dengue from dose 1 to Year 4 in the CYD-TDV group. These results have contributed to the definition of the target

A study of relaxation mechanisms in the A{sup 2}{Sigma}{sup +} state of nitric oxide by time resolved double resonant polarization spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Stampanoni-Panariello, A; Bombach, R; Hemmerling, B; Hubschmid, W [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

1997-06-01

Double resonant polarization labeling spectroscopy is applied to detect nitric oxide in flames and to characterize rotational energy transfer and orientation changing collisions in its first excited electronic state. (author) 4 figs., 3 refs.

Energetic basis of catalytic activity of layered nanophase calcium manganese oxides for water oxidation.

Science.gov (United States)

Birkner, Nancy; Nayeri, Sara; Pashaei, Babak; Najafpour, Mohammad Mahdi; Casey, William H; Navrotsky, Alexandra

2013-05-28

Previous measurements show that calcium manganese oxide nanoparticles are better water oxidation catalysts than binary manganese oxides (Mn3O4, Mn2O3, and MnO2). The probable reasons for such enhancement involve a combination of factors: The calcium manganese oxide materials have a layered structure with considerable thermodynamic stability and a high surface area, their low surface energy suggests relatively loose binding of H2O on the internal and external surfaces, and they possess mixed-valent manganese with internal oxidation enthalpy independent of the Mn(3+)/Mn(4+) ratio and much smaller in magnitude than the Mn2O3-MnO2 couple. These factors enhance catalytic ability by providing easy access for solutes and water to active sites and facile electron transfer between manganese in different oxidation states.

Riboflavin photosensitized oxidation of myoglobin.

Science.gov (United States)

Grippa, Juliana M; de Zawadzki, Andressa; Grossi, Alberto B; Skibsted, Leif H; Cardoso, Daniel R

2014-02-05

The reaction of the fresh meat pigment oxymyoglobin, MbFe(II)O₂, and its oxidized form metmyoglobin, MbFe(III), with triplet-state riboflavin involves the pigment protein, which is oxidatively cleaved or dimerized as shown by SDS-PAGE and Western blotting. The overall rate constant for oxidation of MbFe(II)O₂ by ³Rib is (3.0 ± 0.5) × 10⁹ L·mol⁻¹·s⁻¹ and (3.1 ± 0.4) × 10⁹ L·mol⁻¹·s⁻¹ for MbFe(III) in phosphate buffer of pH 7.4 at 25 °C as determined by laser flash photolysis. The high rates are rationalized by ground state hydrophobic interactions as detected as static quenching of fluorescence from singlet-excited state riboflavin by myoglobins using time-resolved fluorescence spectroscopy and a Stern-Volmer approach. Binding of riboflavin to MbFe(III) has K(a) = (1.2 ± 0.2) × 10⁴ mol·L⁻¹ with ΔH° = -112 ± 22 kJ·mol⁻¹ and ΔS° = -296 ± 75 J·mol⁻¹·K⁻¹. For meat, riboflavin is concluded to be a photosensitizer for protein oxidation but not for discoloration.

Correlations between the electrochemical behaviour and surface film composition of TZM alloy exposed to divertor water coolant environments

International Nuclear Information System (INIS)

Maday, M.-F.; Giorgi, R.; Dikonimos-Makris, T.

1997-01-01

X-ray photoelectron spectroscopy (XPS) has been carried out on TZM alloy surfaces after short and long immersion tests in high temperature (250 C) aqueous environments simulating possible fusion reactor coolant conditions during operation. Phase identification by XPS was used in connection with the open circuit potential trends to suggest plausible hypotheses about TZM corrosion behaviour in the various chemical environments considered in this study. It was proposed that exposure of TZM to oxidizing water conditions produced poorly protective layers, which consist essentially of low (IV) and intermediate (V) valency Mo oxides/hydroxides. Conversely the results obtained in deaerated and reducing water conditions suggested that barrier films could develop in these environments: the phases exhibit a bilayered structure and consisted of an inner tetravalent Mo oxide/hydroxide and an outer hexavalent Mo oxide. The protective properties of such layers were attributed to the hexavalent Mo species. (orig.)

Micro-XANES measurements on experimental spinels and the oxidation state of vanadium in coexisting spinel and silicate melt

International Nuclear Information System (INIS)

Righter, K.; Sutton, S.R.; Newville, M.; Le, L.; Schwandt, C.S.

2006-01-01

We show that experimental spinels coexisting with silicate melt always have lower valence vanadium, and that spinels typically have 3+, whereas the coexisting melt has 4+ or 5+. Implications of these results for planetary basalts will be discussed. Spinel can be a significant host phase for V which has multiple oxidation states V 2+ , V 3+ , V 4+ or V 5+ at oxygen fugacities relevant to natural systems. The magnitude of D(V) spinel/melt is known to be a function of composition, temperature and fO 2 , but the uncertainty of the oxidation state under the range of natural conditions has made elusive a thorough understanding of D(V) spinel/melt. For example, V 3+ is likely to be stable in spinels, based on exchange with Al in experiments in the CaO-MgO-Al 2 O 3 -SiO 2 system. On the other hand, it has been argued that V 4+ will be stable across the range of natural oxygen fugacities in nature. In order to build on our previous work in more oxidized systems, we have carried out experiments at relatively reducing conditions from the FMQ buffer to 2 log fO 2 units below the IW buffer. These spinel-melt pairs, where V is present in the spinel at natural levels (∼300 ppm V), were analyzed using an electron microprobe at NASA-JSC and mi-cro-XANES at the Advanced Photon Source at Argonne National Laboratory. The new results will be used together with previous results to understand the valence of V in spinel-melt systems across 12 orders of magnitude of oxygen fugacity, and with application to natural systems.

New Technique for Speciation of Uranium in Sediments Following Acetate-Stimulated Bioremediation

Energy Technology Data Exchange (ETDEWEB)

2011-06-22

Acetate-stimulated bioremediation is a promising new technique for sequestering toxic uranium contamination from groundwater. The speciation of uranium in sediments after such bioremediation attempts remains unknown as a result of low uranium concentration, and is important to analyzing the stability of sequestered uranium. A new technique was developed for investigating the oxidation state and local molecular structure of uranium from field site sediments using X-Ray Absorption Spectroscopy (XAS), and was implemented at the site of a former uranium mill in Rifle, CO. Glass columns filled with bioactive Rifle sediments were deployed in wells in the contaminated Rifle aquifer and amended with a hexavalent uranium (U(VI)) stock solution to increase uranium concentration while maintaining field conditions. This sediment was harvested and XAS was utilized to analyze the oxidation state and local molecular structure of the uranium in sediment samples. Extended X-Ray Absorption Fine Structure (EXAFS) data was collected and compared to known uranium spectra to determine the local molecular structure of the uranium in the sediment. Fitting was used to determine that the field site sediments did not contain uraninite (UO{sub 2}), indicating that models based on bioreduction using pure bacterial cultures are not accurate for bioremediation in the field. Stability tests on the monomeric tetravalent uranium (U(IV)) produced by bioremediation are needed in order to assess the efficacy of acetate-stimulation bioremediation.

Oxidation State of Iron in the Izu-Bonin Arc Initial Magma and Its Influence Factors

Science.gov (United States)

Li, H.; Arculus, R. J.; Brandl, P. A.; Hamada, M.; Savov, I. P.; Zhu, S.; Hickey-Vargas, R.; Tepley, F. J., III; Meffre, S.; Yogodzinski, G. M.; McCarthy, A.; Barth, A. P.; Kanayama, K.; Kusano, Y.; Sun, W.

2014-12-01

The redox state of mantle-derived magmas is a controversial issue, especially whether island arc basalts are more oxidized than those from mid-ocean ridges. Usually, arc magmas have higher Fe3+/Fe2+ and calculated oxygen fugacity (fO2) than mid-ocean ridge basalts (MORB). It is the high fO2 of arc magma that apparently delays onset of sulfide fractionation and sequestration of precious/base metals thereby facilitating the formation of many giant gold-copper deposits typically associated with subduction zones. But due to a paucity of Fe3+/Fe2+ data for primary mantle-derived arc magmas, the cause for high fO2 of these magma types is still controversial; causes may include inter alia subduction-released oxidized material addition to the mantle wedge source of arc magma, partial melting of subducted slab, and redox changes occurring during ascent of the magma. Fortunately, IODP expedition 351 drilling at IODP Site U1438 in the Amami-Sankaku Basin of the northwestern Philipine Sea, adjacent to the proto-Izu-Bonin Arc at the Kyushu-Palau Ridge (KPR), recovered not only volcaniclastics derived from the inception of Izu-Bonin Mariana (IBM) arc in the Eocene, but also similar materials for the Arc's subsequent evolution through to the Late Oligocene and abandonment of the KPR as a remnant arc. Samples of the pre-Arc oceanic crustal basement were also recovered enabling us to determine the fO2of the mantle preceding arc inception. As the oxidation state of iron in basaltic glass directly relates to the fO2 , the Fe3+/∑Fe ratio [Fe3+/(Fe3++ Fe2+)] of basaltic glass are quantified by synchrotron-facilitated micro X-ray Absorption Near Edge Structure (XANES) spectroscopy to reflect its fO2. Fe K-edge µ-XANES spectra were recorded in fluorescence mode at Beamline 15U1, Shanghai Synchrotron Radiation Facility (SSRF). Synthetic silicate glass with known Fe3+/∑Fe ratio was used in data handling. The experimental results as well as preliminary data from IODP Expedition 351

Correlation of Mn charge state with the electrical resistivity of Mn doped indium tin oxide thin films

KAUST Repository

Kumar, S. R. Sarath

2010-09-15

Correlation of charge state of Mn with the increase in resistivity with Mn concentration is demonstrated in Mn-doped indium tin oxide films. Bonding analysis shows that Mn 2p3/2 core level can be deconvoluted into three components corresponding to Mn2+ and Mn4+ with binding energies 640.8 eV and 642.7 eV, respectively, and a Mn2+ satellite at ∼5.4 eV away from the Mn2+ peak. The presence of the satellite peak unambiguously proves that Mn exists in the +2 charge state. The ratio of concentration of Mn2+ to Mn4+ of ∼4:1 suggests that charge compensation occurs in the n-type films causing the resistivity increase.

Correlation of Mn charge state with the electrical resistivity of Mn doped indium tin oxide thin films

KAUST Repository

Kumar, S. R. Sarath; Hedhili, Mohamed N.; Alshareef, Husam N.; Kasiviswanathan, S.

2010-01-01

Correlation of charge state of Mn with the increase in resistivity with Mn concentration is demonstrated in Mn-doped indium tin oxide films. Bonding analysis shows that Mn 2p3/2 core level can be deconvoluted into three components corresponding to Mn2+ and Mn4+ with binding energies 640.8 eV and 642.7 eV, respectively, and a Mn2+ satellite at ∼5.4 eV away from the Mn2+ peak. The presence of the satellite peak unambiguously proves that Mn exists in the +2 charge state. The ratio of concentration of Mn2+ to Mn4+ of ∼4:1 suggests that charge compensation occurs in the n-type films causing the resistivity increase.

Effects of oxide traps, interface traps, and ''border traps'' on metal-oxide-semiconductor devices

International Nuclear Information System (INIS)

Fleetwood, D.M.; Winokur, P.S.; Reber, R.A. Jr.; Meisenheimer, T.L.; Schwank, J.R.; Shaneyfelt, M.R.; Riewe, L.C.

1993-01-01

We have identified several features of the 1/f noise and radiation response of metal-oxide-semiconductor (MOS) devices that are difficult to explain with standard defect models. To address this issue, and in response to ambiguities in the literature, we have developed a revised nomenclature for defects in MOS devices that clearly distinguishes the language used to describe the physical location of defects from that used to describe their electrical response. In this nomenclature, ''oxide traps'' are simply defects in the SiO 2 layer of the MOS structure, and ''interface traps'' are defects at the Si/SiO 2 interface. Nothing is presumed about how either type of defect communicates with the underlying Si. Electrically, ''fixed states'' are defined as trap levels that do not communicate with the Si on the time scale of the measurements, but ''switching states'' can exchange charge with the Si. Fixed states presumably are oxide traps in most types of measurements, but switching states can either be interface traps or near-interfacial oxide traps that can communicate with the Si, i.e., ''border traps'' [D. M. Fleetwood, IEEE Trans. Nucl. Sci. NS-39, 269 (1992)]. The effective density of border traps depends on the time scale and bias conditions of the measurements. We show the revised nomenclature can provide focus to discussions of the buildup and annealing of radiation-induced charge in non-radiation-hardened MOS transistors, and to changes in the 1/f noise of MOS devices through irradiation and elevated-temperature annealing

The electroreduction of pentavalent protactinium; Reduction electrolytique du protactinium pentavalent

Energy Technology Data Exchange (ETDEWEB)

Musikas, C [Commissariat a l' Energie Atomique, Centre d' Etudes Nucleaires de Fontenay-aux-Roses, 92 (France)

1966-05-01

The reduction of pentavalent protactinium to tetravalent protactinium, in sulfuric and hydrochloric media, on a milligram scale was demonstrated by electrolysis in a separate-compartment cell. There was no indication that protactinium may exist at the trivalent state in these solutions. Polarograms in fluoride solutions showed only one reduction wave. The principle of a volumetric method for the titration of protactinium is given. (author) [French] La reduction du protactinium pentavalent en protactinium tetravalent, dans des solutions sulfuriques et chlorhydriques a ete realisee a l'echelle du milligramme, par electrolyse, dans une cellule a compartiments separes. Aucun indice ne permet de penser que le protactinium puisse exister dans ces solutions a l'etat trivalent. De plus les polarogrammes traces en milieu fluorhydrique ne font apparaitre qu'une seule vague de reduction. Le principe d'une methode volumetrique de dosage du protactinium est donne. (auteur)

Heterogeneous Partial (ammOxidation and Oxidative Dehydrogenation Catalysis on Mixed Metal Oxides

Directory of Open Access Journals (Sweden)

Jacques C. Védrine

2016-01-01

reaching steady state, which makes characterisation of active and selective surface sites quite difficult. The use of oxidants other than O2, such as H2O2, N2O or CO2, is also briefly discussed. Based on such analysis and recent discoveries and process developments, our perspective is given.

Control of Surface and Edge Oxidation on Phosphorene.

Science.gov (United States)

Kuntz, Kaci L; Wells, Rebekah A; Hu, Jun; Yang, Teng; Dong, Baojuan; Guo, Huaihong; Woomer, Adam H; Druffel, Daniel L; Alabanza, Anginelle; Tománek, David; Warren, Scott C

2017-03-15

Phosphorene is emerging as an important two-dimensional semiconductor, but controlling the surface chemistry of phosphorene remains a significant challenge. Here, we show that controlled oxidation of phosphorene determines the composition and spatial distribution of the resulting oxide. We used X-ray photoemission spectroscopy to measure the binding energy shifts that accompany oxidation. We interpreted these spectra by calculating the binding energy shift for 24 likely bonding configurations, including phosphorus oxides and hydroxides located on the basal surface or edges of flakes. After brief exposure to high-purity oxygen or high-purity water vapor at room temperature, we observed phosphorus in the +1 and +2 oxidation states; longer exposures led to a large population of phosphorus in the +3 oxidation state. To provide insight into the spatial distribution of the oxide, transmission electron microscopy was performed at several stages during the oxidation. We found crucial differences between oxygen and water oxidants: while pure oxygen produced an oxide layer on the van der Waals surface, water oxidized the material at pre-existing defects such as edges or steps. We propose a mechanism based on the thermodynamics of electron transfer to interpret these observations. This work opens a route to functionalize the basal surface or edges of two-dimensional (2D) black phosphorus through site-selective chemical reactions and presents the opportunity to explore the synthesis of 2D phosphorene oxide by oxidation.

Solid-state Water-mediated Transport Reduction of Nanostructured Iron Oxides

International Nuclear Information System (INIS)

Smirnov, Vladimir M.; Povarov, Vladimir G.; Voronkov, Gennadii P.; Semenov, Valentin G.; Murin, Igor' V.; Gittsovich, Viktor N.; Sinel'nikov, Boris M.

2001-01-01

The Fe 2+ /Fe 3+ ratio in two-dimensional iron oxide nanosructures (nanolayers with a thickness of 0.3-1.5 nm on silica surface) may be precisely controlled using the transport reduction (TR) technique. The species ≡-O-Fe(OH) 2 and (≡Si-O-) 2 -FeOH forming the surface monolayer are not reduced at 400-600 deg. C because of their covalent bonding to the silica surface, as demonstrated by Moessbauer spectroscopy. Iron oxide microparticles (microstructures) obtained by the impregnation technique, being chemically unbound to silica, are subjected to reduction at T ≥ 500 deg. C with formation of metallic iron in the form of α-Fe. Transport reduction of supported nanostructures (consisting of 1 or 4 monolayers) at T ≥ 600 deg. C produces bulk iron(II) silicate and metallic iron phases. The structural-chemical transformations occurring in transport reduction of supported iron oxide nanolayers are proved to be governed by specific phase processes in the nanostructures themselves

Electronic state of ruthenium deposited onto oxide supports: An XPS study taking into account the final state effects

International Nuclear Information System (INIS)

Larichev, Yurii V.; Moroz, Boris L.; Bukhtiyarov, Valerii I.

2011-01-01

The electronic state of ruthenium in the supported Ru/EO x (EO x = MgO, Al 2 O 3 or SiO 2 ) catalysts prepared by with the use of Ru(OH)Cl 3 or Ru(acac) 3 (acac = acetylacetonate) and reduced with H 2 at 723 K is characterized by X-ray photoelectron spectroscopy (XPS) in the Ru 3d, Cl 2p and O 1s regions. The influence of the final state effects (the differential charging and variation of the relaxation energy) on the binding energy (BE) of Ru 3d 5/2 core level measured for supported Ru nanoparticles is estimated by comparison of the Fermi levels and the modified Auger parameters determined for the Ru/EO x samples with the corresponding characteristics of the bulk Ru metal. It is found that the negative shift of the Ru 3d 5/2 peak which is observed in the spectrum of ruthenium deposited onto MgO (BE = 279.5-279.7 eV) with respect to that of Ru black (BE = 280.2 eV) or ruthenium supported on γ-Al 2 O 3 and SiO 2 (BE = 280.4 eV) is caused not by the transfer of electron density from basic sites of MgO, as considered earlier, but by the differential charging of the supported Ru particles compared with the support surface. Correction for the differential charging value reveals that the initial state energies of ruthenium in the Ru/EO x systems are almost identical (BE = 280.5 ± 0.1 eV) irrespectively of acid-base properties of the support, the mean size of supported Ru crystallites (within the range of 2-10 nm) and the surface Cl content. The results obtained suggest that the difference in ammonia synthesis activity between the Ru catalysts supported on MgO and on the acidic supports is accounted for by not different electronic state of ruthenium on the surface of these oxides but by some other reasons.

Viscous properties of aluminum oxide nanotubes and aluminium oxide nanoparticles - silicone oil suspensions

Science.gov (United States)

Thapa, Ram; French, Steven; Delgado, Adrian; Ramos, Carlos; Gutierrez, Jose; Chipara, Mircea; Lozano, Karen

2010-03-01

Electrorheological (ER) fluids consisting of γ-aluminum oxide nanotubes and γ-aluminum oxide nanoparticles dispersed within silicone oil were prepared. The relationship between shear stress and shear rate was measured and theoretically simulated by using an extended Bingham model for both the rheological and electrorheological features of these systems. Shear stress and viscosity showed a sharp increase for the aluminum oxide nanotubes suspensions subjected to applied electric fields whereas aluminum oxide nanoparticles suspensions showed a moderate change. It was found that the transition from liquid to solid state (mediated by the applied electric field) can be described by a power law and that for low applied voltages the relationship is almost linear.

A first principles investigation of the electronic structure of actinide oxides

DEFF Research Database (Denmark)

Petit, Leon; Svane, Axel; Szotek, Zdzislawa

2010-01-01

The ground state electronic structures of the actinide oxides AO, A2O3 and AO2 (A=U, Np, Pu, Am, Cm, Bk, Cf) are determined from first-principles calculations using the selfinteraction corrected local spin-density approximation. Our study reveals a strong link between preferred oxidation number...... and degree of localization. The ionic nature of the actinide oxides emerges from the fact that those oxides where the ground state is calculated to be metallic do not exist in nature, as the corresponding delocalized f-states favour the accommodation of additional O atoms into the crystal lattice....

High pressure Moessbauer spectroscopy of perovskite iron oxide

International Nuclear Information System (INIS)

Nasu, Saburo; Suenaga, Tomoya; Morimoto, Shotaro; Kawakami, Takateru; Kuzushita, Kaori; Takano, Mikio

2003-01-01

High-pressure 57 Fe Moessbauer spectroscopy using a diamond anvil cell has been performed for perovskite iron oxides SrFeO 3 , CaFeO 3 and La 1/3 Sr 2/3 O 3 . The charge states and the magnetic dependency to pressure were determined. Pressure magnetic phase diagrams of these perovskite iron oxides are determined up to about 70 GPa. To be clear the magnetic ordered state, they are measured up to 7.8 T external magnetic fields at 4.5K. The phase transition of these perovskite oxides to ferromagnetisms with high magnetic ordered temperature is observed. In higher pressure, high spin-low spin transition of oxides besides CaFeO 3 is generated. The feature of Moessbauer spectroscopy, perovskite iron oxide and Moessbauer spectroscopy under high pressure are explained. (S.Y.)

Position Assignment and Oxidation State Recognition of Fe and Co Centers in Heterometallic Mixed-Valent Molecular Precursors for the Low-Temperature Preparation of Target Spinel Oxide Materials

Energy Technology Data Exchange (ETDEWEB)

Lieberman, Craig M. [Department of Chemistry, University at Albany, Albany, New York 12222, United States; Barry, Matthew C. [Department of Chemistry, University at Albany, Albany, New York 12222, United States; Wei, Zheng [Department of Chemistry, University at Albany, Albany, New York 12222, United States; Rogachev, Andrey Yu. [Department; Wang, Xiaoping [Chemical and Engineering Materials Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States; Liu, Jun-Liang [CNRS, CRPP, UPR 8641, F-33600 Pessac, France; Univ. Bordeaux, UPR 8641, F-33600 Pessac, France; MOE Key Lab of Bioinorganic and Synthetic Chemistry,; Clérac, Rodolphe [CNRS, CRPP, UPR 8641, F-33600 Pessac, France; Univ. Bordeaux, UPR 8641, F-33600 Pessac, France; Chen, Yu-Sheng [ChemMatCARS, Center for Advanced Radiation; Filatov, Alexander S. [Department; Dikarev, Evgeny V. [Department of Chemistry, University at Albany, Albany, New York 12222, United States

2017-07-31

A series of mixed-valent, heterometallic (mixed-transition metal) diketonates that can be utilized as prospective volatile single-source precursors for the low-temperature preparation of M_xM'_3–xO₄ spinel oxide materials is reported. Three iron–cobalt complexes with Fe/Co ratios of 1:1, 1:2, and 2:1 were synthesized by several methods using both solid-state and solution reactions. On the basis of nearly quantitative reaction yields, elemental analyses, and comparison of metal–oxygen bonds with those in homometallic analogues, heterometallic compounds were formulated as [Fe^III(acac)₃][Co^II(hfac)₂] (1), [Co^II(hfac)₂][Fe^III(acac)₃][Co^II(hfac)₂] (2), and [Fe^II(hfac)₂][Fe^III(acac)₃][Co^II(hfac)₂] (3). In the above heteroleptic complexes, the Lewis acidic, coordinatively unsaturated CoII/FeII centers chelated by two hexafluoroacetylacetonate (hfac) ligands maintain bridging interactions with oxygen atoms of acetylacetonate (acac) groups that chelate the neighboring Fe^III metal ion. Preliminary assignment of Fe and Co positions/oxidation states in 1–3 drawn from X-ray structural investigation was corroborated by a number of complementary techniques. Single-crystal resonant synchrotron diffraction and neutron diffraction experiments unambiguously confirmed the location of Fe and Co sites in the molecules of dinuclear (1) and trinuclear (2) complexes, respectively. Direct analysis in real time mass spectrometry revealed the presence of Fe^III- and Co^II-based fragments in the gas phase upon evaporation of precursors 1 and 2 as well as of Fe^III, Fe^II, and Co^II species for complex 3. Theoretical investigation of two possible “valent isomers”, [Fe^III(acac)₃

Study of crystalline morphology and phase structure in poly(styrene-b-ethylene oxide-b-styrene) triblock copolymers bu solid state RMN spin diffusion