Sample records for quartz manganese oxide

  1. 40 CFR 721.10011 - Barium calcium manganese strontium oxide.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...2014-07-01 2014-07-01 false Barium calcium manganese strontium oxide. 721.10011...Chemical Substances § 721.10011 Barium calcium manganese strontium oxide. (a...chemical substance identified as barium calcium manganese strontium oxide (PMN...

  2. 40 CFR 721.10011 - Barium calcium manganese strontium oxide.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...2013-07-01 2013-07-01 false Barium calcium manganese strontium oxide. 721.10011...Chemical Substances § 721.10011 Barium calcium manganese strontium oxide. (a...chemical substance identified as barium calcium manganese strontium oxide (PMN...

  3. 40 CFR 721.10011 - Barium calcium manganese strontium oxide.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...2011-07-01 2011-07-01 false Barium calcium manganese strontium oxide. 721.10011...Chemical Substances § 721.10011 Barium calcium manganese strontium oxide. (a...chemical substance identified as barium calcium manganese strontium oxide (PMN...

  4. 40 CFR 721.10011 - Barium calcium manganese strontium oxide.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...2012-07-01 2012-07-01 false Barium calcium manganese strontium oxide. 721.10011...Chemical Substances § 721.10011 Barium calcium manganese strontium oxide. (a...chemical substance identified as barium calcium manganese strontium oxide (PMN...

  5. Synthesis, characterization, optical and sensing property of manganese oxide nanoparticles

    SciTech Connect

    Manigandan, R.; Suresh, R.; Giribabu, K.; Narayanan, V., E-mail: vnnara@yahoo.co.in [Department of Inorganic Chemistry, University of Madras, Guindy Campus, Chennai 600 025 (India); Vijayalakshmi, L. [Annai Veilankanni's College for Women (Arts and Science), Saidapet, Chennai 600015 (India); Stephen, A. [Department of Nuclear Physics, University of Madras, Guindy Campus, Chennai 600 025 (India)

    2014-01-28

    Manganese oxide nanoparticles were prepared by thermal decomposition of manganese oxalate. Manganese oxalate was synthesized by reacting 1:1 mole ratio of manganese acetate and ammonium oxalate along with sodium dodecyl sulfate (SDS). The structural characterization of manganese oxalate and manganese oxide nanoparticles was analyzed by XRD. The XRD spectrum confirms the crystal structure of the manganese oxide and manganese oxalate. In addition, the average grain size, lattice parameter values were also calculated using XRD spectrum. Moreover, the diffraction peaks were broadened due to the smaller size of the particle. The band gap of manganese oxide was calculated from optical absorption, which was carried out by DRS UV-Visible spectroscopy. The morphology of manganese oxide nanoparticles was analyzed by SEM images. The FT-IR analysis confirms the formation of the manganese oxide from manganese oxalate nanoparticles. The electrochemical sensing behavior of manganese oxide nanoparticles were investigated using hydrogen peroxide by cyclic voltammetry.

  6. Manganese.

    PubMed

    Barceloux, D G

    1999-01-01

    Manganese is a very hard, brittle metal, which is used to increase the strength of steel alloys. Absorption from the gastrointestinal tract occurs in the divalent and tetravalent forms. Permanganates, which are strong oxidizing agents, have a +7 valence. The principal organomanganese compound is the anti-knock additive, methylcyclopentadienyl manganese tricarbonyl. Manganese is a ubiquitous constituent of the environment comprising about 0.1% of the earth's crust. For the general population, food is the most important source of manganese with daily intake ranging from 2-9 mg Mn. Combustion of gasoline containing methylcyclopentadienyl manganese tricarbonyl releases submicron particles of Mn3O4 that are potentially respirable. Biomagnification of manganese in the food chain probably does not occur. The lungs and gastrointestinal tract absorb some manganese, but the relative amounts absorbed from each site are not known. Homeostatic mechanisms limit the absorption of manganese from the gastrointestinal tract. Elimination of manganese occurs primarily by excretion into the bile. Animal studies indicate that manganese is an essential co-factor for enzymes, such as hexokinase, superoxide dismutase, and xanthine oxidase. However, no case of manganese deficiency in humans has been identified. Manganism is a central nervous system disease first described in the 1800s following exposure to high concentrations of manganese oxides. Manganese madness was the term used to describe the initial psychiatric syndrome (compulsive behavior, emotional lability, hallucinations). More commonly, these workers developed a Parkinson's-like syndrome. Currently, the risks of exposure to low concentrations of manganese in the industrial and in the environmental settings (e.g., methylcyclopentadienyl manganese tricarbonyl in gasoline) are being evaluated with regards to the development of subclinical neuropsychological changes. The American Conference of Governmental and Industrial Hygienists recently lowered the TLV-TWA for manganese compounds and inorganic manganese compounds to 0.2 mg Mn/m3. PMID:10382563

  7. 40 CFR 721.10201 - Cobalt lithium manganese nickel oxide.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...2013-07-01 false Cobalt lithium manganese nickel oxide. 721.10201 Section 721...721.10201 Cobalt lithium manganese nickel oxide. (a) Chemical substance and...identified as cobalt lithium manganese nickel oxide (PMN P-04-269; CAS...

  8. 40 CFR 721.10201 - Cobalt lithium manganese nickel oxide.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...2014-07-01 false Cobalt lithium manganese nickel oxide. 721.10201 Section 721...721.10201 Cobalt lithium manganese nickel oxide. (a) Chemical substance and...identified as cobalt lithium manganese nickel oxide (PMN P-04-269; CAS...

  9. 40 CFR 721.10201 - Cobalt lithium manganese nickel oxide.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...2012-07-01 false Cobalt lithium manganese nickel oxide. 721.10201 Section 721...721.10201 Cobalt lithium manganese nickel oxide. (a) Chemical substance and...identified as cobalt lithium manganese nickel oxide (PMN P-04-269; CAS...

  10. Magnetic and orbital excitations in manganese oxides

    Microsoft Academic Search

    W. Koshibae; S. Ishihara; Y. Kawamura; S. Okamoto; J. Inoue; S. Maekawa

    1997-01-01

    The magnetic and orbital structures in manganese oxides with perovskite structure are examined by using the exact diagonalization method on finite-size clusters. The orbital degeneracy in the eg states is taken into account based on the effective Hamiltonian derived in the insulating state with strong Coulomb interaction. It is shown that A-, C- and G-type antiferromagnetic ordering occur as a

  11. OXIDATION AND SORPTION KINETICS OF ARSENIC ON A POORLY CRYSTALLINE MANGANESE OXIDE

    E-print Network

    Sparks, Donald L.

    OXIDATION AND SORPTION KINETICS OF ARSENIC ON A POORLY CRYSTALLINE MANGANESE OXIDE by Brandon J. Lafferty All Rights Reserved #12;OXIDATION AND SORPTION KINETICS OF ARSENIC ON A POORLY CRYSTALLINE MANGANESE OXIDE by Brandon J. Lafferty Approved

  12. Manganese oxide reduction as a form of anaerobic respiration

    Microsoft Academic Search

    Henry L. Ehrlich

    1987-01-01

    Some instances of bacterial manganese oxide reduction observed in nature and under laboratory conditions are a form of respiration. Anaerobiosis is not a necessary condition for its occurrence, although anaerobic reduction of manganese oxide which is inhibited by air has been reported. It is the kind of manganese reducing microorganism involved which determines whether anaerobic conditions are required. In at

  13. Manganese Based Oxidative Technologies For Water/Wastewater Treatment

    E-print Network

    Desai, Ishan

    2013-08-27

    by facilitating redox reactions. The reactivity of manganese oxides with some emerging contaminants like 4-tert octylphenol (OP) in aqueous systems is yet to be explored. Additionally, manganese's use within treatment systems designed to remove trace organics...

  14. Microbial formation of manganese oxides. [Chlamydomonas sp

    SciTech Connect

    Greene, A.C.; Madgwick, J.C. (Univ. of New South Wales, Kensington (Australia))

    1991-04-01

    Microbial manganese oxidation was demonstrated at high Mn{sup 2+} concentrations (5 g/liter) in bacterial cultures in the presence of a microalga. The structure of the oxide produced varied depending on the bacterial strain and mode of culture. A nonaxenic, acid-tolerant microalga, a Chlamydomonas sp., was found to mediate formation of manganite ({gamma}-MnOOH). Bacteria isolated from associations with crude cultures of this alga grown in aerated bioreactors formed disordered {gamma}-MnO{sub 2} from Mn{sup 2+} at concentrations of 5 g/liter over 1 month, yielding 3.3 of a semipure oxide per liter. All algal-bacterial cultures removed Mn{sup 2+} from solution, but only those with the highest removal rates formed an insoluble oxide. While the alga was an essential component of the reaction, a Pseudomonas sp. was found to be primarily responsible for the formation of a manganese precipitate. Medium components - algal biomass and urea - showed optima at 5.7 and 10 g/liters, respectively. The scaled-up culture (50 times) gave a yield of 22.3 g (53 mg/liter/day from a 15-liter culture) of semipure disordered {gamma}MnO{sub 2}, identified by X-ray diffraction and Fourier transform infrared (FTIR) spectroscopy, and had a manganese oxide O/Mn ratio of 1.92. The Mn(IV) content in the oxide was low (30.5%) compared with that of mined or chemically formed {gamma}MnO{sub 2} (ca. 50%). The shortfall in the bacterial oxide manganese content was due to biological and inorganic contaminants.

  15. Sol-gel synthesis of manganese oxides

    NASA Astrophysics Data System (ADS)

    Bach, S.; Henry, M.; Baffier, N.; Livage, J.

    1990-10-01

    Transparent and stable manganese dioxide gels are obtained upon reduction of permanganate aqueous solutions AMnO 4 [ A = Li, Na, K, NH 4, N(CH 3) 4] by fumaric acid. All xerogels are amorphous when dried at room temperature. Their thermal behavior however depends on the nature of the counter cation A+. Ammonium permanganates lead to the formation of ?- or ?-Mn 2O 3 while AMnO 2 mixed oxides are obtained at high temperature when A = Li, Na, K. Other crystalline phases such as LiMn 2O 4 or Na 0.7MnO 2 are also formed at lower temperature around 500°C. Oxidation of these mixed oxides into sulfuric acid lead to the formation of ?- or ?-MnO 2 while A+ and Mn 2+ ions are released into the solution. Such manganese dioxides could be good candidates for making reversible cathodes in nonaqueous lithium batteries.

  16. Colossal magnetoresistance in manganese oxide perovskites

    Microsoft Academic Search

    M. R. Ibarra; J. M. De Teresa

    1998-01-01

    The large magnetoresistance observed in the manganese-oxide-based perovskites is explained on the basis of a strong electron-phonon and ferromagnetic interactions which provide the mechanism for the existence of dynamic electronic phase segregation in the form of magnetic polarons. These entities are responsible for the magnetic and lattice effects observed in these compounds. In this experimental work we give evidence of

  17. Sol-gel synthesis of manganese oxides

    SciTech Connect

    Bach, S.; Henry, M.; Baffier, N.; Livage, J. (Ecole Nationale Superieure de Chimie de Paris (France))

    1990-10-01

    Transparent and stable manganese dioxide gels are obtained upon reduction of permanganate aqueous solutions AMnO{sub 4} (A = Li, Na, K, NH{sub 4}, N(CH{sub 3}){sub 4}) by fumaric acid. All xerogels are amorphous when dried at room temperature. Their thermal behavior however depends on the nature of the counter cation A{sup +}. Ammonium permanganates lead to the formation of {alpha}- or {gamma}-Mn{sub 2}O{sub 3} while AMnO{sub 2} mixed oxides are obtained at high temperature when A = Li, Na, K. Other crystalline phases such as LiMn{sub 2}O{sub 4} or Na{sub 0.7}MnO{sub 2} are also formed at lower temperature around 500{degree}C. Oxidation of these mixed oxides into sulfuric acid lead to the formation of {lambda}- or {delta}-MnO{sub 2} while A{sup +} and Mn{sup 2+} ions are released into the solution. Such manganese dioxides could be good candidates for making reversible cathodes in nonaqueous lithium batteries.

  18. Pwave Pairing and Colossal Magnetoresistance in Manganese Oxides

    E-print Network

    ­ferromagnetic transition and metal­insulator transition simultaneously. These phenomena were explained by the doubleP­wave Pairing and Colossal Magnetoresistance in Manganese Oxides Yong­Jihn Kim y Department paid to the manganese oxides since the observa­ tion of colossal magnetoresistance (CMR). 1\\Gamma4

  19. Manganese binding and oxidation by spores of a marine bacillus.

    PubMed Central

    Rosson, R A; Nealson, K H

    1982-01-01

    Mature, dormant spores of a marine bacillus, SG-1, bound and oxidized (precipitated) manganese on their surfaces. The binding and oxidation occurred under dormant conditions, with mature spores suspended in natural seawater. These heat-stable spores were formed in the absence of added manganese in the growth medium. The rate and amount of manganese bound by SG-1 spores was a function of spore concentration. Temperatures greater than 45 degrees C, pH values below 6.5, or the addition of EDTA or the metabolic inhibitors sodium azide, potassium cyanide, and mercuric chloride inhibited manganese binding and oxidation. However, SG-1 spores bound and oxidized manganese after treatment with glutaraldehyde, formaldehyde, ethylene oxide gas, or UV light, all of which killed the spores. Manganese oxidation never occurred in the absence of manganese binding to spores. The data suggest that Mn2+ was complexed by a spore component, perhaps an exosporium or a spore coat protein: once bound, the manganese was rapidly oxidized. Images PMID:6212577

  20. Electrochromic reactions in manganese oxides I. Raman analysis

    SciTech Connect

    Bernard, M.C.; Hugot-Le Goff, A.; Thi, B.V. (Univ. Pierre et Marie Curie, Paris (France). UPR 15 du CNRS Physique des Liquides et Electrochimie); Cordoba de Torresi, S. (Univ. Estadual de Campinas (Brazil). Dept. de Fisica Aplicada)

    1993-11-01

    Like nickel oxide, manganese oxide is a widely studied material in the primary batteries field. The reactions taking place during voltametric cycling of manganese oxides can be determined using in situ Raman spectroscopy. The main difficulty for the oxide identification is to obtain relevant Raman reference spectra because of the many possible compounds and, for some of these compounds, of their instability in the laser beam. As a consequence, several modifications of different tetra-, tri- and divalent manganese oxides and oxyhydroxides were carefully studied. The electrochromic behavior of three types of manganese oxides, two prepared by thermal oxidations and the other by electrochemical deposition, were then compared. The presence of nonstoichiometry in the pristine material was necessary to obtain a reversible electrochromic effect. The reaction during electrochromic cycling is more complicated than a simple passage from MnO[sub 2] to MnOOH.

  1. [Ferrous-manganese oxidizing bacteria from the nature water].

    PubMed

    Qin, Song-yan; Ma, Fang; Huang, Peng

    2008-06-01

    Glass slides were hanged into a canal to acquire the ferrous-manganese oxidizing bacteria settled bio-film. Two isolated methods for ferrous-manganese oxidizing bacteria with special iron-manganese oxidizing matrix from the bio-film were tested. Element component of bacteria product and sheath structure of bacteria were analyzed. With two methods, plate cultivation and the novel semi-solid in situ cultivation method, strains belong to Family Leptothrix were isolated. XRF showed that the amorphous iron and manganese were two major metal elements of the precipitation formed by one strain of Leptothrix spp.. Through the microscope observation, one strain of Family Leptothrix was determined to form branch-like structured sheath, while another strain formed spider web-like structured sheath. Those isolated bacteria provide model strains for future testing of FISH probe and PCR primer of ferrous-manganese oxidizing bacteria. PMID:18763517

  2. Arsenic mobilization in the critical zone: Oxidation by hydrous manganese oxide Jason S. Fischel, fischjs06@juniata.edu1

    E-print Network

    Sparks, Donald L.

    Arsenic mobilization in the critical zone: Oxidation by hydrous manganese oxide GEOC 112 Jason S manganese (Mn) oxides, even in low concentrations, to oxidize trace metals such as arsenic from arsenite [As

  3. Effect of the temperature of calcination on the catalytic performance of manganese- and samarium-manganese-based oxides in the complete oxidation of acetone

    Microsoft Academic Search

    A. Gil; L. M. Gandía; S. A. Korili

    2004-01-01

    The effect of the calcination temperature on manganese-based catalysts used in the complete oxidation of acetone has been studied. The catalysts, containing manganese and samarium and being in bulk oxide form, were prepared in the laboratory and calcined at 673, 823, 1073 and 1273K. The calcination temperature controls and modifies the type of single manganese oxide present, the development of

  4. Biogenic manganese oxides: Properties and mechanisms of formation

    Microsoft Academic Search

    Bradley M. Tebo; Bradley M; Brian G. Clement; Gregory J. Dick; Karen J. Murray; Dorothy Parker; Rebecca Verity; Samuel M. Webb

    2004-01-01

    ? Abstract Manganese(IV) oxides produced through microbial activity, i.e., bio- genic Mn oxides or Mn biooxides, are believed to be the most abundant and highly reactive Mn oxide phases in the environment. They mediate,redox reactions with or- ganic and inorganic compounds,and sequester a variety of metals. The major pathway for bacterial Mn(II) oxidation is enzymatic, and although bacteria that oxidize

  5. The Molecular Geomicrobiology of Bacterial Manganese(II) Oxidation

    Microsoft Academic Search

    Bradley M. Tebo; Kati Geszvain; Sung-Woo Lee

    \\u000a Manganese is the second most abundant transition metal found in the Earth’s crust. It has a significant biological role as\\u000a it is a cofactor of enzymes such as superoxide dismutase and is the key metal in the reaction center of photosystem II. In\\u000a the environment, manganese is mostly found in three different oxidation states: II, III, and IV. Mn(II), primarily

  6. Lithium Isotope Selectivity of Sorbents Prepared from Lithium Manganese Oxides

    Microsoft Academic Search

    HIROTSUGU TAKEUCHI; TAKAO OI; MORIKAZU HOSOE

    1999-01-01

    Sorbents are prepared by extracting lithium ions from lithium manganese oxides with the lithium\\/manganese mole ratio (Li\\/Mn ratio) varying between 0.42 and 0.84, and their lithium isotope selectivities are investigated. All the sorbents are Li-specific and the values of the Li-to-Li isotopic separation factor (S) are between 1.0040 and 1.0092 at 25°C. The S value is slightly dependent on the

  7. Electrochemical supercapacitor material based on manganese oxide: preparation and characterization

    Microsoft Academic Search

    Junhua Jiang; Anthony Kucernak

    2002-01-01

    A novel class of electrochemical supercapacitor electrode material has been electrochemically synthesized from a manganese halide complex in water-containing acetonitrile electrolyte at room temperature. This material has been physically and chemically characterized by scanning electron microscopy, X-ray photoelectron microscopy (XPS), FT-Raman microscopy and cyclic voltammetry. XPS and FT-Raman characterization suggest that this material is composed of manganese oxide with a

  8. Giant negative magnetoresistance in Manganese-substituted Zinc Oxide

    PubMed Central

    Wang, X. L.; Shao, Q.; Zhuravlyova, A.; He, M.; Yi, Y.; Lortz, R.; Wang, J. N.; Ruotolo, A.

    2015-01-01

    We report a large negative magnetoresistance in Manganese-substituted Zinc Oxide thin films. This anomalous effect was found to appear in oxygen-deficient films and to increase with the concentration of Manganese. By combining magnetoresistive measurements with magneto-photoluminescence, we demonstrate that the effect can be explained as the result of a magnetically induced transition from hopping to band conduction where the activation energy is caused by the sp-d exchange interaction. PMID:25783664

  9. Energetic basis of catalytic activity of layered nanophase calcium manganese oxides for water oxidation

    PubMed Central

    Birkner, Nancy; Nayeri, Sara; Pashaei, Babak; Najafpour, Mohammad Mahdi; Casey, William H.; Navrotsky, Alexandra

    2013-01-01

    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 Mn3+/Mn4+ 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. PMID:23667149

  10. A manganese oxidation model for rivers

    SciTech Connect

    Hess, G.W. (Geological Survey, Doraville, GA (United States)); Kim, Byung R. (General Motors Research Lab., Warren, MI (United States)); Roberts, P.J.W. (Georgia Inst. of Tech, Atlanta (United States))

    1989-04-01

    The presence of manganese in natural waters (>0.05 mg/L) degrades water-supply quality. A model was devised to predict the variation of manganese concentrations in river water released from an impoundment with the distance downstream. The model is one-dimensional and was calibrated using dissolved oxygen, biochemical oxygen demand, pH, manganese, and hydraulic data collected in the Duck River, Tennessee. The results indicated that the model can predict manganese levels under various conditions. The model was then applied to the Chattahoochee River, Georgia. Discrepancies between observed and predicted may be due to inadequate pH data, precipitation of sediment particles, unsteady flow conditions in the Chattahoochee River, inaccurate rate expressions for the los pH conditions, or their combinations.

  11. Manganese cluster in photosynthesis: Where plants oxidize water to dioxygen

    Microsoft Academic Search

    Vittal K. Yachandra; M. P. Klein; K. Sauer

    1996-01-01

    The essential involvement of manganese in photosynthetic water oxidation was implicit in the observation by Pirson in 1937 that plants and algae deprived of Mn in their growth medium lost the ability to evolve Oâ. Addition of this essential element to the growth medium resulted in the restoration of water oxidation within 30 min. There is increased interest in the

  12. Interaction between graphene oxide nanoparticles and quartz sand

    NASA Astrophysics Data System (ADS)

    Sotirelis, Nikolaos P.; Chrysikopoulos, Constantinos V.

    2015-04-01

    In this study, the influence of pH, ionic strength (IS), and temperature on graphene oxide (GO) nanoparticles adsorption onto quartz sand were investigated. Batch experiments were conducted at three controlled temperatures (4, 12, and 25 °C) in solutions with different pH values (pH=4, 7, and 10), and ionic strengths (IS=1.4, 6.4, and 21.4 mM), under static and dynamic conditions. The surface properties of GO nanoparticles and quartz sand were evaluated by electrophoretic mobility measurements. Derjaguin-Landau-Verwey-Overbeek (DLVO), and extended-DLVO (XDLVO) potential energy profiles were constructed for the experimental conditions, using measured zeta potentials. The experimental results shown that GO nanoparticles were very stable under the experimental conditions. Both temperature and pH did not play a significant role in the adsorption of GO nanoparticles onto quartz sand. In contrast, IS was shown to influence adsorption. Increasing the IS, dramatically increased. The adsorption of GO particles onto quartz sand increased dramatically with increasing IS, mainly due to secondary-minimum deposition, as indicated by the XDLVO interaction energy profiles. Furthermore, the experimental data were fitted nicely with a Langmuir type sorption isotherm, and the adsorption kinetics were satisfactorily described with a pseudo-second-order model.

  13. 75 FR 70583 - Cobalt Lithium Manganese Nickel Oxide; Withdrawal of Significant New Use Rule

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-18

    ...RIN 2070-AB27 Cobalt Lithium Manganese Nickel Oxide; Withdrawal of Significant New...identified as cobalt lithium manganese nickel oxide (CAS No. 182442-95-1), which...rule issued for cobalt lithium manganese nickel oxide (PMN P-04-269; CAS No....

  14. 40 CFR 721.10008 - Manganese strontium oxide (MnSrO3).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 2014-07-01 false Manganese strontium oxide (MnSrO3). 721.10008 Section...Substances § 721.10008 Manganese strontium oxide (MnSrO3 ). (a) Chemical...chemical substance identified as manganese strontium oxide (MnSrO3 ) (PMN...

  15. 40 CFR 721.10008 - Manganese strontium oxide (MnSrO3).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 2013-07-01 false Manganese strontium oxide (MnSrO3). 721.10008 Section...Substances § 721.10008 Manganese strontium oxide (MnSrO3 ). (a) Chemical...chemical substance identified as manganese strontium oxide (MnSrO3 ) (PMN...

  16. 40 CFR 721.10008 - Manganese strontium oxide (MnSrO3).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 2010-07-01 false Manganese strontium oxide (MnSrO3). 721.10008 Section...Substances § 721.10008 Manganese strontium oxide (MnSrO3). (a) Chemical...chemical substance identified as manganese strontium oxide (MnSrO3 ) (PMN...

  17. 40 CFR 721.10008 - Manganese strontium oxide (MnSrO3).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 2012-07-01 false Manganese strontium oxide (MnSrO3). 721.10008 Section...Substances § 721.10008 Manganese strontium oxide (MnSrO3 ). (a) Chemical...chemical substance identified as manganese strontium oxide (MnSrO3 ) (PMN...

  18. Biochemical changes in pulmonary cells following manganese oxide inhalation

    SciTech Connect

    Adkins, B. Jr. (Northrop Services, Inc., Research Triangle Park, NC); Luginbuhl, G.H.; Gardner, D.E.

    1980-03-01

    Inhalation of manganese oxide (Mn dose, 879.0 ..mu..g/m/sup 3/) for 2 h reduced the total number of alveolar macrophages obtained by endotracheal lavage in pulmonary cell populations, slightly reduced cellular viability, and reduced both phagocytic capability and total protein in sonicated pulmonary cells. Increases in intracellular adenosine triphosphate and acid phosphatase specific activity were also exhibited by the pulmonary cells, but sonicated cells obtained from the exposed mice showed no change in lactic acid dehydrogenase specific activity. A slight increase in extracellular protein in the fluid phase of the lavage suspension was observed after manganese oxide exposure.

  19. Thermal and magnetic properties of manganese oxides

    NASA Astrophysics Data System (ADS)

    Smolyaninova, Vera Nikolaevna

    This thesis reports a study of the thermal, magnetic and transport properties of perovskite manganese oxides A1-xBxMnO3 (A = La, Nd, and Pr; B = Ca, Ba, and Sr). The ferromagnetic (FM) metallic (low x) and the charge-ordered (CO) (high x) doping regimes were studied in order to better understand the complex behavior of these materials. In the metallic doping range the low temperature magnetization was found to be in agreement with the Bloch law for ferromagnetic spin waves, and the spin-wave stiffness was determined. Important parameters such as the Debye temperature and the effective mass of the charge carriers were determined from low temperature specific heat experiments. The effective mass of the charge carriers was found to be 2--4 times heavier than the mass obtained from band structure calculations suggesting an important role of electron-phonon interactions in these materials. In order to better understand the nature of the metal-insulator transition at the ferromagnetic TC the resistivity and magnetization of epitaxial thin films of La0.67Ca 0.33MnO3 and Nd0.7Sr0.3MnO3 were studied. It was found that the behavior of the resistivity and magnetization near TC is inconsistent with Anderson localization as proposed by several theories. Various compositions of charge-ordered La1-xCaxMnO3 and Pr1-xCa1-xMnO 3 were studied to better understand the CO transition and its ground state. From powder neutron diffraction measurements we found that the CO antiferromagnetic (AFM) and ferromagnetic metallic phases coexist at low temperatures. Charge ordered Pr1-xCaxMnO3 and La1-xCax MnO3 (x ? 0.5) were found to have an anomalous excess specific heat ( C') at low temperatures (T < 20 K). This C' contribution has a temperature dependence consistent with non-magnetic excitations with a dispersion relation e = Delta' + Bq2. Surprisingly, it was found that a magnetic field sufficient to induce the transition from the insulating CO (and AFM) state to the metallic FM state is not sufficient to eliminate the C' contribution to the specific heat. The possible origin of these excitations and their relation to the CO ground state is discussed.

  20. Nano-sized manganese oxides as biomimetic catalysts for water oxidation in artificial photosynthesis: a review

    PubMed Central

    Najafpour, Mohammad Mahdi; Rahimi, Fahimeh; Aro, Eva-Mari; Lee, Choon-Hwan; Allakhverdiev, Suleyman I.

    2012-01-01

    There has been a tremendous surge in research on the synthesis of various metal compounds aimed at simulating the water-oxidizing complex (WOC) of photosystem II (PSII). This is crucial because the water oxidation half reaction is overwhelmingly rate-limiting and needs high over-voltage (approx. 1 V), which results in low conversion efficiencies when working at current densities required for hydrogen production via water splitting. Particular attention has been given to the manganese compounds not only because manganese has been used by nature to oxidize water but also because manganese is cheap and environmentally friendly. The manganese–calcium cluster in PSII has a dimension of about approximately 0.5 nm. Thus, nano-sized manganese compounds might be good structural and functional models for the cluster. As in the nanometre-size of the synthetic models, most of the active sites are at the surface, these compounds could be more efficient catalysts than micrometre (or bigger) particles. In this paper, we focus on nano-sized manganese oxides as functional and structural models of the WOC of PSII for hydrogen production via water splitting and review nano-sized manganese oxides used in water oxidation by some research groups. PMID:22809849

  1. Nanoscale manganese oxide within Faujasite zeolite as an efficient and biomimetic water oxidizing catalyst.

    PubMed

    Najafpour, Mohammad Mahdi; Pashaei, Babak

    2012-09-14

    Nanoscale manganese oxides within Faujasite zeolite have been synthesized with a simple method and characterized by scanning electron microscopy, X-ray diffraction spectrometry, N(2) adsorption-desorption isotherms, transmission electron microscopy, and atomic absorption spectroscopy. These oxides showed efficient water oxidizing activity in the presence of cerium(IV) ammonium nitrate as a non-oxo transfer oxidant. PMID:22833185

  2. Distributions of Manganese, Iron, and Manganese-Oxidizing Bacteria In Lake Superior Sediments of Different Organic Carbon Content

    NASA Technical Reports Server (NTRS)

    Richardson, Laurie L.; Nealson, Kenneth H.

    1989-01-01

    Profiles of oxygen, soluble and particulate manganese and iron, organic carbon and nitrogen were examined in Lake Superior sediment cores, along with the distribution and abundance of heterotrophic and manganese oxidizing bacteria. Analyses were performed using cores collected with the submersible Johnson Sea Link II. Three cores, exhibiting a range of organic carbon content, were collected from the deepest basin in Lake Superior and the north and south ends of the Caribou trough, and brought to the surface for immediate analysis. Minielectrode profiles of oxygen concentration of the three cores were carried out using a commercially available minielectrode apparatus. Oxygen depletion to less than 1% occurred within 4 cm of the surface for two of the cores, but not until approximately 15 cm for the core from the south basin of the Caribou trough. The three cores exhibited very different profiles of soluble, as well as leachable, manganese and iron, suggesting different degrees of remobilization of these metals in the sediments. Vertical profiles of viable bacteria and Mn oxidizing bacteria, determined by plating and counting, showed that aerobic (and facultatively aerobic) heterotrophic bacteria were present at the highest concentrations near the surface and decreased steadily with depth, while Mn oxidizing bacteria were concentrations primarily at and above the oxic/anoxic interface. Soluble manganese in the pore waters, along with abundant organic carbon, appeared to enhance the presence of manganese oxidizing bacteria, even below the oxic/anoxic interface. Profiles of solid-phase leachable manganese suggested a microbial role in manganese reprecipitation in these sediments.

  3. Manganese oxide nanowires, films, and membranes and methods of making

    DOEpatents

    Suib, Steven Lawrence (Storrs, CT); Yuan, Jikang (Storrs, CT)

    2008-10-21

    Nanowires, films, and membranes comprising ordered porous manganese oxide-based octahedral molecular sieves, and methods of making, are disclosed. A single crystal ultra-long nanowire includes an ordered porous manganese oxide-based octahedral molecular sieve, and has an average length greater than about 10 micrometers and an average diameter of about 5 nanometers to about 100 nanometers. A film comprises a microporous network comprising a plurality of single crystal nanowires in the form of a layer, wherein a plurality of layers is stacked on a surface of a substrate, wherein the nanowires of each layer are substantially axially aligned. A free standing membrane comprises a microporous network comprising a plurality of single crystal nanowires in the form of a layer, wherein a plurality of layers is aggregately stacked, and wherein the nanowires of each layer are substantially axially aligned.

  4. Preliminary LIBS analysis of Yucca Mountain manganese oxide minerals

    SciTech Connect

    Blacic, J.; Pettit, D.; Cremers, D.

    1996-01-01

    The licensing and performance of a potential repository at Yucca Mountain will require the characterization of radionuclide sorptive capacity of the host rock, which in turn calls for hundreds of analyses based on extensive sampling or in situ measurements. A rapid method specifically for characterizing the manganese oxide minerals occurring heterogeneously throughout the Yucca Mountain block as fracture surface coatings is needed. Our unique solution is a laser-induced breakdown spectroscopy (LIBS) surface-analysis technique that is usable in the field to produce high-resolution atomic emission spectra. In tests with manganese oxide minerals and fracture surface coatings from a few Yucca Mountain core samples, we used four spectral bands to show that qualitative measurement of all constituent elements except K and Na (in the presence of Mn) is possible with LIBS. Detailed calibration of final hardware will make the system quantitative.

  5. A redox-assisted supramolecular assembly of manganese oxide nanotube

    SciTech Connect

    Tao Li [College of Chemistry and Chemical Engineering, Hunan University, Key Laboratory of Chemometrics and Chemical Biological Sensing Technologies, Ministry of Education, Changsha 410082 (China); Sun Chenggao [College of Chemistry and Chemical Engineering, Hunan University and Key Laboratory of Chemometrics and Chemical Biological Sensing Technologies, Ministry of Education, Changsha 410082 (China); Fan Meilian [College of Chemistry and Chemical Engineering, Hunan University, Key Laboratory of Chemometrics and Chemical Biological Sensing Technologies, Ministry of Education, Changsha 410082 (China); Huang Caijuan [College of Chemistry and Chemical Engineering, Hunan University, Key Laboratory of Chemometrics and Chemical Biological Sensing Technologies, Ministry of Education, Changsha 410082 (China); Wu Hailong [College of Chemistry and Chemical Engineering, Hunan University, Key Laboratory of Chemometrics and Chemical Biological Sensing Technologies, Ministry of Education, Changsha 410082 (China); Chao Zisheng [College of Chemistry and Chemical Engineering, Hunan University, Key Laboratory of Chemometrics and Chemical Biological Sensing Technologies, Ministry of Education, Changsha 410082 (China)]. E-mail: zschao@yahoo.com; Zhai Hesheng [College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005 (China)]. E-mail: hszhai@xmu.edu.cn

    2006-11-09

    In this paper, we report the hydrothermal synthesis of manganese oxide nanotube from an aqueous medium of pH 7, using KMnO{sub 4} and MnCl{sub 2} as inorganic precursors, polyoxyethylene (10) nonyl phenyl ether (TX-10) a surfactant and acetaldehyde an additive. The characterization of X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and N{sub 2} adsorption at 77 K (BET) reveals that the synthesized manganese oxide nanotube has a mesopore size of ca. 3.65 nm and a wall thickness of ca. 12 nm, with the wall being composed of microporous crystals of monoclinic manganite. The X-ray photoelectron spectroscopy (XPS) result demonstrates a decrease of the binding energy of the Mn{sup 3+} in the manganese oxide nanotube, which may be related to both the nanotubular morphology and the crystalline pore wall. A mechanism of a redox-assisted supramolecular assembly, regulated by acetaldehyde, is postulated.

  6. Stabilization of cubic zirconia with manganese oxide

    SciTech Connect

    Dravid, V.P.; Ravikumar, V. (Northwestern Univ., Evanston, IL (United States). Dept. of Materials Science and Engineering); Notis, M.R.; Lyman, C.E. (Lehigh Univ., Bethlehem, PA (United States). Dept. of Materials Science and Engineering); Dhalenne, G.; Revcolevschi, A. (Univ. de Paris-Sud, Orsay (France). Lab. de Chimie des Solides)

    1994-10-01

    A directionally solidified eutectic (DSE) of MnO-ZrO[sub 2] has been investigated using a variety of electron optical techniques. It is found that considerable MnO goes into ZrO[sub 2] to form a substitutional solid solution. About 14 wt% of MnO is soluble in ZrO[sub 2] close to the eutectic temperature. The solubility of ZrO[sub 2] in MnO, however, is quite low, less than 0.50 wt%. Electron diffraction experiments indicate that ZrO[sub 2] (MnO) has the cubic fluorite structure. Diffuse scattering, similar to other cubic zirconias (e.g., CaO, MgO stabilized zirconia), is also observed in manganese-stabilized zirconia. Diffuse scattering indicates the presence of oxygen vacancies and thus confirms the defect nature of the fluorite structure. Electron energy loss spectrometry (EELS) fine structure analysis of the Mn L[sub 23] edge provided clear evidence that Mn is present as Mn[sup 2+] in Mn-stabilized cubic ZrO[sub 2].

  7. Manganese ion-assisted assembly of superparamagnetic graphene oxide microbowls

    SciTech Connect

    Tian, Zhengshan [State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing 210096 (China); School of Chemistry and Chemical Engineering, Pingdingshan University, Pingdingshan 467000 (China); Xu, Chunxiang, E-mail: xcxseu@seu.edu.cn; Li, Jitao; Zhu, Gangyi; Xu, Xiaoyong; Dai, Jun; Shi, Zengliang; Lin, Yi [State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing 210096 (China)

    2014-03-24

    A facile manganese ion Mn(II)-assisted assembly has been designed to fabricate microbowls by using graphene oxide nanosheets as basic building blocks, which were exfoliated ultrasonically from the oxidized soot powders in deionized water. From the morphology evolution observations of transmission electron microscope and scanning electron microscope, a coordinating-tiling-collapsing manner is proposed to interpret the assembly mechanism based on attractive Van der Waals forces, ?-? stacking, and capillary action. It is interesting to note that the as-prepared microbowls present a room temperature superparamagnetic behavior.

  8. Constraints on superoxide mediated formation of manganese oxides

    PubMed Central

    Learman, Deric R.; Voelker, Bettina M.; Madden, Andrew S.; Hansel, Colleen M.

    2013-01-01

    Manganese (Mn) oxides are among the most reactive sorbents and oxidants within the environment, where they play a central role in the cycling of nutrients, metals, and carbon. Recent discoveries have identified superoxide (O2?) both of biogenic and abiogenic origin as an effective oxidant of Mn(II) leading to the formation of Mn oxides. Here we examined the conditions under which abiotically produced superoxide led to oxidative precipitation of Mn and the solid-phases produced. Oxidized Mn, as both aqueous Mn(III) and Mn(III/IV) oxides, was only observed in the presence of active catalase, indicating that hydrogen peroxide (H2O2), a product of the reaction of O2? with Mn(II), inhibits the oxidation process presumably through the reduction of Mn(III). Citrate and pyrophosphate increased the yield of oxidized Mn but decreased the amount of Mn oxide produced via formation of Mn(III)-ligand complexes. While complexing ligands played a role in stabilizing Mn(III), they did not eliminate the inhibition of net Mn(III) formation by H2O2. The Mn oxides precipitated were highly disordered colloidal hexagonal birnessite, similar to those produced by biotically generated superoxide. Yet, in contrast to the large particulate Mn oxides formed by biogenic superoxide, abiotic Mn oxides did not ripen to larger, more crystalline phases. This suggests that the deposition of crystalline Mn oxides within the environment requires a biological, or at least organic, influence. This work provides the first direct evidence that, under conditions relevant to natural waters, oxidation of Mn(II) by superoxide can occur and lead to formation of Mn oxides. For organisms that oxidize Mn(II) by producing superoxide, these findings may also point to other microbially mediated processes, in particular enzymatic hydrogen peroxide degradation and/or production of organic ligand metabolites, that allow for Mn oxide formation. PMID:24027565

  9. Manganese oxide nanosheets and a 2D hybrid of graphene–manganese oxide nanosheets synthesized by liquid-phase exfoliation

    NASA Astrophysics Data System (ADS)

    Coelho, João; Mendoza-Sánchez, Beatriz; Pettersson, Henrik; Pokle, Anuj; McGuire, Eva K.; Long, Edmund; McKeon, Lorcan; Bell, Alan P.; Nicolosi, Valeria

    2015-06-01

    Manganese oxide nanosheets were synthesized using liquid-phase exfoliation that achieved suspensions in isopropanol (IPA) with concentrations of up to 0.45 mg ml?1. A study of solubility parameters showed that the exfoliation was optimum in N,N-dimethylformamide followed by IPA and diethylene glycol. IPA was the solvent of choice due to its environmentally friendly nature and ease of use for further processing. For the first time, a hybrid of graphene and manganese oxide nanosheets was synthesized using a single-step co-exfoliation process. The two-dimensional (2D) hybrid was synthesized in IPA suspensions with concentrations of up to 0.5 mg ml?1 and demonstrated stability against re-aggregation for up to six months. The co-exfoliation was found to be a energetically favorable process in which both solutes, graphene and manganese oxide nanosheets, exfoliate with an improved yield as compared to the single-solute exfoliation procedure. This work demonstrates the remarkable versatility of liquid-phase exfoliation with respect to the synthesis of hybrids with tailored properties, and it provides proof-of-concept ground work for further future investigation and exploitation of hybrids made of two or more 2D nanomaterials that have key complementary properties for various technological applications.

  10. Migration of Mn cations in delithiated lithium manganese oxides.

    PubMed

    Kan, Yongchun; Hu, Yuan; Lin, Chi-Kai; Ren, Yang; Sun, Yang-Kook; Amine, Khalil; Chen, Zonghai

    2014-10-14

    Li2MnO3 is an integrated component in lithium-manganese-rich nickel manganese cobalt oxides, and the conversion of Li2MnO3 to a spinel-like structure after electrochemical activation has been associated with the continuous potential decay of the material. Delithiated Li2MnO3 and delithiated LiMn2O4 were used as model materials to investigate the mechanism of forming the spinel-like structure. An in situ high-energy X-ray diffraction technique was used to trace the structural change of materials at elevated temperatures, a procedure to mimic the structural transformation during the normal cycling of batteries. It was also found that the migration of Mn atoms from the octahedral sites to tetrahedral sites is the key step for phase transformation from a monoclinic structure to a spinel structure. PMID:25162360

  11. Development of laminated nickel\\/manganese oxide and nickel\\/niobium oxide electrochromic devices

    Microsoft Academic Search

    Yan-Ping Ma; Phillip C. Yu; Carl M. Lampert

    1991-01-01

    This paper reports on the preparation, electrical, and optical analysis of electrodes and prototype electrochromic devices using a solid polymer ion conductor. For these devices electrodes were developed consisting of cobalt-doped nickel oxide, manganese-nickel oxide, and niobium oxide. Optical and voltammetric data was obtained for each electrode. Solid polymer electrolytes were synthesized from modified amorphous poly(ethylene oxide) [a-PEO] complexed with

  12. Support Information for Kinetic Modeling of Oxidation of Antibacterial Agents by Manganese Oxides

    E-print Network

    Huang, Ching-Hua

    Support Information for Kinetic Modeling of Oxidation of Antibacterial Agents by Manganese Oxides of antibacterials and structurally related compounds examined in this study. TABLE S2. Kinetic fitting conditions: [MnO2]0 = 0.1 mM, [TTC]0 = 20 M, and pH = 5. FIGURE S3. Effect of antibacterial loading on Srxn

  13. Development of laminated nickel/manganese oxide and nickel/niobium oxide electrochromic devices

    NASA Astrophysics Data System (ADS)

    Ma, Yan-Ping; Yu, Phillip C.; Lampert, Carl M.

    1991-12-01

    This paper reports on the preparation, electrical, and optical analysis of electrodes and prototype electrochromic devices using a solid polymer ion conductor. For these devices electrodes were developed consisting of cobalt-doped nickel oxide, manganese-nickel oxide, and niobium oxide. Optical and voltammetric data was obtained for each electrode. Solid polymer electrolytes were synthesized from modified amorphous poly(ethylene oxide) [a-PEO] complexed with a metal silicate. Electrochromic devices were made using cobalt-doped nickel oxide/niobium oxide, and cobalt-doped nickel oxide/manganese-nickel electrode laminations. Optical spectra as a function of voltage was obtained for each device. The best cobalt-doped nickel oxide/a-PEO/manganese-nickel oxide device showed photopic transmittance to be Tp(bleached) equals 0.76 and Tp(colored) equals 0.44. The corresponding integrated solar transmittance was Ts(bleached) equals 0.64, Ts(colored) equals 0.46. The best cobalt- doped nickel oxide/a-PEO/niobium oxide device had photopic transmittance of Tp(bleached) equals 0.65 and Tp(colored) equals 0.16. The corresponding integrated solar transmittance was Ts(bleached) equals 0.45 and Ts(colored) equals 0.15. Of the two devices, the nickel/niobium oxide device had the best combination of electrical and optical properties. Better device properties are expected with improvements in the solid polymer electrolyte and lamination process.

  14. Manganese chlorins immobilized on silica as oxidation reaction catalysts.

    PubMed

    Castro, Kelly A D F; Pires, Sónia M G; Ribeiro, Marcos A; Simões, Mário M Q; Neves, M Graça P M S; Schreiner, Wido H; Wypych, Fernando; Cavaleiro, José A S; Nakagaki, Shirley

    2015-07-15

    Synthetic strategies that comply with the principles of green chemistry represent a challenge: they will enable chemists to conduct reactions that maximize the yield of products with commercial interest while minimizing by-products formation. The search for catalysts that promote the selective oxidation of organic compounds under mild and environmentally friendly conditions constitutes one of the most important quests of organic chemistry. In this context, metalloporphyrins and analogues are excellent catalysts for oxidative transformations under mild conditions. In fact, their reduced derivatives chlorins are also able to catalyze organic compounds oxidation effectively, although they have been still little explored. In this study, we synthesized two chlorins through porphyrin cycloaddition reactions with 1.3-dipoles and prepared the corresponding manganese chlorins (MnCHL) using adequate manganese(II) salts. These MnCHL were posteriorly immobilized on silica by following the sol-gel process and the resulting solids were characterized by powder X-ray diffraction (PXRD), UVVIS spectroscopy, FTIR, XPS, and EDS. The catalytic activity of the immobilized MnCHL was investigated in the oxidation of cyclooctene, cyclohexene and cyclohexane and the results were compared with the ones obtained under homogeneous conditions. PMID:25841060

  15. Calcium manganese(IV) oxides: biomimetic and efficient catalysts for water oxidation.

    PubMed

    Najafpour, Mohammad Mahdi; Pashaei, Babak; Nayeri, Sara

    2012-04-28

    CaMnO(3) and Ca(2)Mn(3)O(8) were synthesized and characterized by SEM, XRD, FTIR and BET. Both oxides showed oxygen evolution activity in the presence of oxone, cerium(IV) ammonium nitrate and H(2)O(2). Oxygen evolution from water during irradiation with visible light (? > 400 nm) was also observed upon adding these manganese oxides to an aqueous solution containing tris(2,2'-bipyridyl) ruthenium(II), as photosensitizer, and chloro pentaammine cobalt(III) chloride, as electron acceptor, in an acetate buffer. The amounts of dissolved manganese and calcium from CaMnO(3) and Ca(2)Mn(3)O(8) in the oxygen evolving reactions were reported and compared with other (calcium) manganese oxides. Proposed mechanisms of oxygen evolution and proposed roles for the calcium ions are also considered. PMID:22382465

  16. Sol-gel route to the tunneled manganese oxide cryptomelane

    SciTech Connect

    Ching, S.; Roark, J.L. [Connecticut College, New London, CT (United States)] [Connecticut College, New London, CT (United States); Duan, N.; Suib, S.L. [Univ. of Connecticut, Storr, CT (United States)] [Univ. of Connecticut, Storr, CT (United States)

    1997-03-01

    The sol-gel reaction between KMnO{sub 4} and fumaric acid in a 3:1 mole ratio generates a flocculant gel that serves as a precursor to the tunneled manganese oxide, cryptomelane. The elemental composition of sol-gel cryptomelane has been determined to be K{sub 0.12}MnO{sub 2.0-} (H{sub 2}O){sub 0.09}. Further characterization has been performed using powder X-ray diffraction, scanning electron microscopy, and Auger electron spectroscopy. The sol-gel process is heavily dependent on reactant concentration. Solutions that are too concentrated produce the layered manganese oxide birnessite, whereas overly dilute reactions yield mixtures of cryptomelane and Mn{sub 2}O{sub 3}. The preference for cryptomelane over birnessite correlates with low potassium content in the gel. The sol-gel procedure for synthesizing cryptomelane is not easily transferred to the preparation of analogous manganese oxides with different tunnel cations. Reactions that employ permanganates other than KMnO{sub 4} generally yield Mn{sub 2}O{sub 3}, with cryptomelane being a minor product at best. Thermal analyses of cryptomelane gels indicate that calcination proceeds through a series of stages that involve loss of water, loss of residual organics, conversion to cryptomelane, and finally degradation to Mn{sub 3}O{sub 4}. The extraction of potassium ions from sol-gel cryptomelane by various foreign cations is minimal, with the loss of K{sup +} being on the order of 10%. 49 refs., 7 figs., 3 tabs.

  17. Manganese oxide composite electrodes for lithium batteries

    DOEpatents

    Thackeray, Michael M. (Naperville, IL); Johnson, Christopher S. (Naperville, IL); Li, Naichao (Croton on Hudson, NY)

    2007-12-04

    An activated electrode for a non-aqueous electrochemical cell is disclosed with a precursor of a lithium metal oxide with the formula xLi.sub.2MnO.sub.3.(1-x)LiMn.sub.2-yM.sub.yO.sub.4 for 0

  18. Manganese oxide composite electrodes for lithium batteries

    DOEpatents

    Johnson, Christopher S. (Naperville, IL); Kang, Sun-Ho (Naperville, IL); Thackeray, Michael M. (Naperville, IL)

    2009-12-22

    An activated electrode for a non-aqueous electrochemical cell is disclosed with a precursor thereof a lithium metal oxide with the formula xLi.sub.2MnO.sub.3.(1-x)LiMn.sub.2-yM.sub.yO.sub.4 for 0.5

  19. Solution synthesis and characterization of lithium manganese oxide cathode materials

    SciTech Connect

    Voigt, J.A.; Boyle, T.J.; Doughty, D.H. [and others

    1995-07-01

    A nonaqueous coprecipitation process has been developed to prepare controlled stoichiometry lithium manganese oxalate precipitates. The process involved mixing a methanolic Li-Mn nitrate solution with a methanolic solution containing tetramethylammonium oxalate as the precipitating agent. The resulting oxalates were readily converted to a variety of phase pure lithium manganese oxides at moderate temperatures ({le}600{degrees}C), where the phase formed was determined by the initial Li/Mn ratio in the starting solution. Metal cation dopants have been incorporated into the oxalate precipitate by dissolving the appropriate metal nitrate in the Li-Mn precursor solution The various starting solutions, oxalate precipitates, and calcined oxides have been extensively characterized using a variety of techniques, including {sup 7}Li NMR, TGA/DTA, SEM, and XRD. Results indicate that a strong interaction occurs between Li and Mn in the nitrate solution which carries over into the oxalate phase during precipitation. The morphology and the crystallite size of the oxide powders were shown to be controlled by the morphology of the oxalate precursor and the oxalate calcination temperature, respectively. The results of initial cathode performance tests with respect to dopant type (Al, Ni, Co) and concentration for LiMn{sub 2}O{sub 4} are also reported.

  20. Nanostructured lithium nickel manganese oxides for lithium-ion batteries

    Microsoft Academic Search

    Haixia Deng; Ilias Belharouak; Russel E. Cook; Huiming Wu; Yang-Kook Sun; Khalil Amine

    2010-01-01

    Nanostructured lithium nickel manganese oxides were investigated as advanced positive electrode materials for lithium-ion batteries designated to power plug-in hybrid electric vehicles and all-electric vehicles. The investigation included material characterization and electrochemical testing. In cell tests, the Li{sub 1.375}Ni{sub 0.25}Mn{sub 0.75}O{sub 2.4375} composition achieved high capacity (210 mAh g¹) at an elevated rate (230 mA g¹), which makes this material

  1. Comparison of manganese oxide nanoparticles and manganese sulfate with regard to oxidative stress, uptake and apoptosis in alveolar epithelial cells.

    PubMed

    Frick, Ramon; Müller-Edenborn, Björn; Schlicker, Andreas; Rothen-Rutishauser, Barbara; Raemy, David O; Günther, Detlef; Hattendorf, Bodo; Stark, Wendelin; Beck-Schimmer, Beatrice

    2011-08-28

    Due to their physicochemical characteristics, metal oxide nanoparticles (NPs) interact differently with cells compared to larger particles or soluble metals. Oxidative stress and cellular metal uptake were quantified in rat type II alveolar epithelial cells in culture exposed to three different NPs: manganese(II,III) oxide nanoparticles (Mn(3)O(4)-NPs), the soluble manganese sulfate (Mn-salt) at corresponding equivalent doses, titanium dioxide (TiO(2)-NPs) and cerium dioxide nanoparticles (CeO(2)-NPs). In the presence of reactive oxygen species an increased apoptosis rate was hypothesized. Oxidative stress was assessed by detection of fluorescently labeled reactive oxygen species and by measuring intracellular oxidized glutathione. Catalytic activity was determined by measuring catalyst-dependent oxidation of thiols (DTT-assay) in a cell free environment. Inductively coupled plasma mass spectrometry was used to quantify cellular metal uptake. Apoptosis rate was determined assessing the activity of caspase-3 and by fluorescence microscopic quantification of apoptotic nuclei. Reactive oxygen species were mainly generated in cells treated with Mn(3)O(4)-NPs. Only Mn(3)O(4)-NPs oxidized intracellular glutathione. Catalytic activity could be exclusively shown for Mn(3)O(4)-NPs. Cellular metal uptake was similar for all particles, whereas Mn-salt could hardly be detected within the cell. Apoptosis was induced by both, Mn(3)O(4)-NPs and Mn-salt. The combination of catalytic activity and capability of passing the cell membrane contributes to the toxicity of Mn(3)O(4)-NPs. Apoptosis of samples treated with Mn-salt is triggered by different, potentially extracellular mechanisms. PMID:21669262

  2. Composites of manganese oxide with carbon materials as catalysts for the ozonation of oxalic acid.

    PubMed

    Orge, C A; Órfão, J J M; Pereira, M F R

    2012-04-30

    Manganese oxide and manganese oxide-carbon composites were prepared and tested as catalysts for the removal of oxalic acid by ozonation. Their performances were compared with the parent carbon material (activated carbon or carbon xerogel) used to prepare the composites. Oxalic acid degradation by carbon materials is slower than that attained with manganese oxide or manganese oxide-carbon composites. A complete degradation after 90 and 45 min of reaction was obtained for carbon materials and for the catalysts containing manganese, respectively. The ozonation in the presence of the prepared composites are supposed to occur mainly by surface reactions, following a direct oxidation mechanism by molecular ozone and/or surface oxygenated radicals. PMID:22341747

  3. Population Structure of Manganese-Oxidizing Bacteria in Stratified Soils and Properties of Manganese Oxide Aggregates under Manganese–Complex Medium Enrichment

    PubMed Central

    Zhang, Zhongming; Chen, Hong; Liu, Jin; Ali, Muhammad; Liu, Fan; Li, Lin

    2013-01-01

    Manganese-oxidizing bacteria in the aquatic environment have been comprehensively investigated. However, little information is available about the distribution and biogeochemical significance of these bacteria in terrestrial soil environments. In this study, stratified soils were initially examined to investigate the community structure and diversity of manganese-oxidizing bacteria. Total 344 culturable bacterial isolates from all substrata exhibited Mn(II)-oxidizing activities at the range of 1 µM to 240 µM of the equivalent MnO2. The high Mn(II)-oxidizing isolates (>50 mM MnO2) were identified as the species of phyla Actinobacteria, Firmicutes and Proteobacteria. Seven novel Mn(II)-oxidizing bacterial genera (species), namely, Escherichia, Agromyces, Cellulomonas, Cupriavidus, Microbacterium, Ralstonia, and Variovorax, were revealed via comparative phylogenetic analysis. Moreover, an increase in the diversity of soil bacterial community was observed after the combined enrichment of Mn(II) and carbon-rich complex. The phylogenetic classification of the enriched bacteria represented by predominant denaturing gradient gel electrophoresis bands, was apparently similar to culturable Mn(II)-oxidizing bacteria. The experiments were further undertaken to investigate the properties of the Mn oxide aggregates formed by the bacterial isolates with high Mn(II)-oxidizing activity. Results showed that these bacteria were closely encrusted with their Mn oxides and formed regular microspherical aggregates under prolonged Mn(II) and carbon-rich medium enrichment for three weeks. The biotic oxidation of Mn(II) to Mn(III/IV) by these isolates was confirmed by kinetic examinations. X-ray diffraction assays showed the characteristic peaks of several Mn oxides and rhodochrosite from these aggregates. Leucoberbelin blue tests also verified the Mn(II)-oxidizing activity of these aggregates. These results demonstrated that Mn oxides were formed at certain amounts under the enrichment conditions, along with the formation of rhodochrosite in such aggregates. Therefore, this study provides insights into the structure and diversity of soil-borne bacterial communities in Mn(II)-oxidizing habitats and supports the contribution of soil-borne Mn(II)-oxidizing bacteria to Mn oxide mineralization in soils. PMID:24069232

  4. Oxidation kinetics of manganese (II) in seawater at nanomolar concentrations

    NASA Astrophysics Data System (ADS)

    von Langen, Peter J.; Johnson, Kenneth S.; Coale, Kenneth H.; Elrod, Virginia A.

    1997-12-01

    Manganese oxidation rates were determined at low (˜ 20 nM) concentrations in seawater by measuring dissolved manganese (Mn(II)) using flow injection analysis with chemiluminescence detection. Mn(II) was measured in samples that had been filtered (0.2 ?m) and kept in the dark under controlled temperature and pH conditions for time periods up to 6 months. Eight 9 L carboys with mean pH values ranging from 8 to 8.7 were held at 25°C, another carboy (pH = 9.32) was kept at 5°C. Oxidation followed the Morgan (1967) homogeneous rate equation ( d[Mn(II)]/ dt = k1 [O 2][OH -] 2[Mn(II)]). The mean rate constant k1 = 1.7 ± 0.7 × 10 12 M -3 d -1 (95% CI), determined using hydroxide ion activities determined with pH measurements on the NBS scale, was in agreement with work by Morgan (1967; k1 = 4 × 10 12 M -3 d -1) and Davies and Morgan (1989; k1 = 1.1 × 10 12 M -3 d -1) in dilute solutions. The rate constant at 5°C was 1.3 ± 0.3 × 10 12 M -3 d -1. If free hydroxide concentrations (based on the free proton pH scale) are used, then the rate constant at 25°C was k 1? = 0.34 ± 0.14 × 10 12 M -3d -1. Autocatalytic increases in Mn(II) oxidation rates, as predicted by a heterogeneous reaction mechanism (Morgan, 1967) ( d[Mn(II)]/ dt= k2'[Mn(II)][MnO 2]) were not observed, indicating that the homogeneous reaction dominates Mn(II) oxidation at low nM concentrations in seawater. Bacteria were enumerated by 4',6-diamidino-2-phenylindole (DAPI) staining during the experiments. No significant correlation between bacterial concentrations and Mn(II) oxidation rates was found.

  5. Electrochemical properties of iodine-containing lithium manganese oxide spinel

    NASA Astrophysics Data System (ADS)

    Han, Chi-Hwan; Hong, Young-Sik; Hong, Hyun-Sil; Kim, Keon

    Iodine-containing, cation-deficient, lithium manganese oxides (ICCD-LMO) are prepared by reaction of MnO 2 with LiI. The MnO 2 is completely transformed into spinel-structured compounds with a nominal composition of Li 1- ?Mn 2-2 ?O 4I x. A sample prepared at 800 °C, viz. Li 0.99Mn 1.98O 4I 0.02, exhibits an initial discharge capacity of 113 mA h g -1 with good cycleability and rate capability in the 4-V region. Iodine-containing, lithium-rich lithium manganese oxides (ICLR-LMO) are also prepared by reaction of LiMn 2O 4 with LiI, which results in a nominal composition of Li 1+ xMn 2- xO 4I x. Li 1.01Mn 1.99O 4I 0.02 shows a discharge capacity of 124 mA h g -1 on the first cycle and 119 mA h g -1 a on the 20th cycle. Both results indicate that a small amount of iodine species helps to maintain cycle performance.

  6. Sol-gel synthesis and adsorption properties of mesoporous manganese oxide

    NASA Astrophysics Data System (ADS)

    Ivanets, A. I.; Kuznetsova, T. F.; Prozorovich, V. G.

    2015-03-01

    Sol-gel synthesis of mesoporous xerogels of manganese oxide with different phase compositions has been performed. The manganese oxide sols were obtained by redox reactions of potassium permanganate with hydrogen peroxide or manganese(II) chloride in aqueous solutions. The isotherms of the low-temperature adsorption-desorption of nitrogen with manganese oxide xerogels treated at 80, 200, 400, and 600°C were measured. The samples were studied by electron microscopy and thermal and XRD analysis. The phase transformation and the changes in the adsorption and capillary-condensation properties of manganese oxide were shown to depend on the sol synthesis conditions and the temperature of the thermal treatment of the gel. The X-ray amorphous samples heated at 80°C were shown to have low values of the specific surface; at higher temperatures, the xerogel crystallized into mixed phases with various compositions and its surface area increased at 200-400°C and decreased at 600°C.

  7. Oxidative decolorization of direct light red F3B dye at natural manganese mineral surface

    Microsoft Academic Search

    Ruixia Liu; Hongxiao Tang

    2000-01-01

    In this paper, the characteristics of natural manganese mineral collected from Guangxi Province, China, including crystalline properties, elemental composition, organic substrates content (0.17%) and BET surface area (29.8 m2\\/g), were determined. By X-ray powder diffraction and fluorescence spectrograph analysis, it is shown that manganese oxide in the natural mineral exists in the crystal structure of ?-Mn2O3 and the contents of manganese

  8. Oxidation of chalcopyrite in the presence of manganese dioxide in hydrochloric acid medium

    Microsoft Academic Search

    N. B Devi; M Madhuchhanda; K. Srinivasa Rao; P. C Rath; R. K Paramguru

    2000-01-01

    Dissolution of chalcopyrite in hydrochloric acid medium in the presence of manganese dioxide (manganese ore containing pyrolusite) was studied at different temperatures, acid concentrations and mineral proportions. Chalcopyrite did not dissolve independently, but underwent oxidative dissolution in the presence of manganese dioxide, via (i) galvanic interaction, (ii) cyclic action of Fe3+\\/Fe2+ redox couple and (iii) chlorine gas generated by MnO2

  9. Biomineral nanostructures of manganese oxides in oceanic ferromanganese nodules

    NASA Astrophysics Data System (ADS)

    Lysyuk, G. N.

    2008-12-01

    Manganese oxides, which are widespread and of great practical importance, are formed and transformed by the active role of microorganisms. Manganese aggregates occur as both crystallized varieties and disordered fine-grained phases with significant ore grade and up to 50-60 vol % of X-ray amorphous components. X-ray amorphous nanosized Mn oxides in Fe-Mn nodules from the Pacific Ocean floor were examined from the standpoint of their biogenic origin. SEM examination showed abundant mineralized biofilms on the studied samples. The chemical composition of bacterial mass is as follows (wt %): 28.34 MnO, 17.14 Fe2O3, 7.11 SiO2, 2.41 CaO, 17.90 TiO2, 1.74 Na2O, 1.73 Al2O3, 1.30 MgO, 1.25 P2O5, 1.25 SO3, 0.68 CoO, 0.54 CuO, 0.53 NiO, and 0.50 K2O. The chemical composition of fossilized cyanobacterial mats within the interlayer space of nodulesis as follows (wt %): 48.35 MnO, 6.23 Fe2O3, 8.76 MgO, 5.05 Al2O3, 4.45 SiO2, 3.63 NiO, 2.30 Na2O, 2.19 CuO, 1.31 CaO, and 0.68 K2O is direct evidence for participation of bacteria in Mn oxide formation. This phase consists of mineralized glycocalix consisting of nanosized flakes of todorokite. Native metals (Cu, Fe, and Zn) as inclusions 10-20 ?m in size were identified in ferromanganese nodules as well. The formation of nativemetals can be explained by their crystallization at highly reducing conditions maintained by organic matter.

  10. Manganese

    MedlinePLUS

    ... no RDAs for a nutrient, the Adequate Intake (AI) is used as a guide. The AI is the estimated amount of the nutrient that ... assumed to be adequate. The daily Adequate Intake (AI) levels for manganese are: infants birth to 6 ...

  11. Characterization of manganese oxide precipitates from Appalachian coal mine drainage treatment systems

    Microsoft Academic Search

    Hui Tan; Gengxin Zhang; Peter J. Heaney; Samuel M. Webb; William D. Burgos

    2010-01-01

    The removal of Mn(II) from coal mine drainage (CMD) by chemical addition\\/active treatment can significantly increase treatment costs. Passive treatment for Mn removal involves promotion of biological oxidative precipitation of manganese oxides (MnOx). Manganese(II) removal was studied in three passive treatment systems in western Pennsylvania that differed based on their influent Mn(II) concentrations (20–150mg\\/L), system construction (±inoculation with patented Mn(II)-oxidizing

  12. Vanadia supported on nickel manganese oxide nanocatalysts for the catalytic oxidation of aromatic alcohols

    NASA Astrophysics Data System (ADS)

    Adil, Syed F.; Alabbad, Saad; Kuniyil, Mufsir; Khan, Mujeeb; Alwarthan, Abdulrahman; Mohri, Nils; Tremel, Wolfgang; Tahir, Muhammad Nawaz; Siddiqui, Mohammed Rafiq Hussain

    2015-02-01

    Vanadia nanoparticles supported on nickel manganese mixed oxides were synthesized by co-precipitation method. The catalytic properties of these materials were investigated for the oxidation of benzyl alcohol using molecular oxygen as oxidant. It was observed that the calcination temperature and the size of particles play an important role in the catalytic process. The catalyst was evaluated for its oxidation property against aliphatic and aromatic alcohols, which was found to display selectivity towards aromatic alcohols. The samples were characterized by employing scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Brunauer-Emmett-Teller analysis, thermogravimetric analysis, and X-ray photoelectron spectroscopy.

  13. Vanadia supported on nickel manganese oxide nanocatalysts for the catalytic oxidation of aromatic alcohols.

    PubMed

    Adil, Syed F; Alabbad, Saad; Kuniyil, Mufsir; Khan, Mujeeb; Alwarthan, Abdulrahman; Mohri, Nils; Tremel, Wolfgang; Tahir, Muhammad Nawaz; Siddiqui, Mohammed Rafiq Hussain

    2015-01-01

    Vanadia nanoparticles supported on nickel manganese mixed oxides were synthesized by co-precipitation method. The catalytic properties of these materials were investigated for the oxidation of benzyl alcohol using molecular oxygen as oxidant. It was observed that the calcination temperature and the size of particles play an important role in the catalytic process. The catalyst was evaluated for its oxidation property against aliphatic and aromatic alcohols, which was found to display selectivity towards aromatic alcohols. The samples were characterized by employing scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Brunauer-Emmett-Teller analysis, thermogravimetric analysis, and X-ray photoelectron spectroscopy. PMID:25852349

  14. New nanocrystalline manganese oxides as cathode materials for lithium batteries : electron microscopy, electrochemical and X-ray absorption studies

    E-print Network

    Paris-Sud XI, Université de

    1 New nanocrystalline manganese oxides as cathode materials for lithium batteries : electron.F. Abstract New nanostructured manganese oxi-iodides were prepared by redox reaction of sodium permanganate: manganese oxide, lithium batteries, nanomaterials Corresponding author: Pierre Strobel, tel. 33 476 887 940

  15. Sol-gel synthesis and characterization of mesoporous manganese oxide

    SciTech Connect

    Hong Xinlin; Zhang Gaoyong; Zhu Yinyan; Yang Hengquan

    2003-10-30

    Mesoporous manganese oxide (MPMO) from reduction of KMnO{sub 4} with maleic acid, was obtained and characterized in detail. The characterization of the material was confirmed by high-resolution transmission electron microscopy (HRTEM), X-ray powder diffractometry (XRD) and N{sub 2} sorptometry. The results showed that MPMO is a pseudo-crystalline material with complex network pore structure, of which BET specific surface area is 297 m{sup 2}/g and pore size distribution is approximately in the range of 0.7-6.0 nm. The MPMO material turns to cryptomelane when the calcinating temperature rises to 400 deg. C. The optimum sol-gel reaction conditions are KMnO{sub 4}/C{sub 4}H{sub 4}O{sub 4} molar ratio=3, pH=7 and gelation time>6 h.

  16. Manganese(III) binding to a pyoverdine siderophore produced by a manganese(II)-oxidizing bacterium

    NASA Astrophysics Data System (ADS)

    Parker, Dorothy L.; Sposito, Garrison; Tebo, Bradley M.

    2004-12-01

    The possible roles of siderophores (high affinity chelators of iron(III)) in the biogeochemistry of manganese remain unknown. Here we investigate the interaction of Mn(III) with a pyoverdine-type siderophore (PVD MnB1) produced by the model Mn(II)-oxidizing bacterium Pseudomonas putida strain MnB1. PVD MnB1 confirmed typical pyoverdine behavior with respect to: (a) its absorption spectrum at 350-600 nm, both in the absence and presence of Fe(III), (b) the quenching of its fluorescence by Fe(III), (c) the formation of a 1:1 complex with Fe(III), and (d) the thermodynamic stability constant of its Fe(III) complex. The Mn(III) complex of PVD MnB1 had a 1:1 Mn:pvd molar ratio, showed fluorescence quenching, and exhibited a light absorption spectrum (A max = 408-410 nm) different from that of either PVD MnB1-Fe(III) or uncomplexed PVD MnB1. Mn(III) competed strongly with Fe(III) for binding by PVD MnB1 in culture filtrates (pH 8, 4°C). Equilibration with citrate, a metal-binding ligand, did not detectably release Mn from its PVD MnB1 complex at a citrate/PVD MnB1 molar ratio of 830 (pH 8, 4°C), whereas pyrophosphate under the same conditions removed 55% of the Mn from its PVD MnB1 complex. Most of the PVD MnB1-complexed Mn was released by reaction with ascorbate, a reducing agent, or with EDTA, a ligand that is also oxidized by Mn(III). Data on the competition for binding to PVD MnB1 by Fe(III) vs. Mn(III) were used to determine a thermodynamic stability constant (nominally at 4°C) for the neutral species MnHPVD MnB1 (log K = 47.5 ± 0.5, infinite dilution reference state). This value was larger than that determined for FeHPVD MnB1 (log K = 44.6 ± 0.5). This result has important implications for the metabolism, solubility, speciation, and redox cycling of manganese, as well as for the biologic uptake of iron.

  17. Commercialization of cryptomelane-type manganese oxide (OMS-2) nanowire paper oil sorbent

    E-print Network

    Soo, Haw Yun

    2007-01-01

    Cryptomelane-type Manganese oxide (OMS-2, a group of Octahedral Molecular Sieves) nanowire paper exhibits interesting properties: reversible wettability, oleophilic while being hydrophobic, and high thermal stability. These ...

  18. Rapidly reversible redox transformation in nanophase manganese oxides at room temperature triggered by changes in hydration

    PubMed Central

    Birkner, Nancy; Navrotsky, Alexandra

    2014-01-01

    Chemisorption of water onto anhydrous nanophase manganese oxide surfaces promotes rapidly reversible redox phase changes as confirmed by calorimetry, X-ray diffraction, and titration for manganese average oxidation state. Surface reduction of bixbyite (Mn2O3) to hausmannite (Mn3O4) occurs in nanoparticles under conditions where no such reactions are seen or expected on grounds of bulk thermodynamics in coarse-grained materials. Additionally, transformation does not occur on nanosurfaces passivated by at least 2% coverage of what is likely an amorphous manganese oxide layer. The transformation is due to thermodynamic control arising from differences in surface energies of the two phases (Mn2O3 and Mn3O4) under wet and dry conditions. Such reversible and rapid transformation near room temperature may affect the behavior of manganese oxides in technological applications and in geologic and environmental settings. PMID:24733903

  19. Water-oxidation catalysis by manganese in a geochemical-like cycle

    Microsoft Academic Search

    Rosalie K. Hocking; Robin Brimblecombe; Lan-Yun Chang; Archana Singh; Mun Hon Cheah; Chris Glover; William H. Casey; Leone Spiccia

    2011-01-01

    Water oxidation in all oxygenic photosynthetic organisms is catalysed by the Mn4CaO4 cluster of Photosystem II. This cluster has inspired the development of synthetic manganese catalysts for solar energy production. A photoelectrochemical device, made by impregnating a synthetic tetranuclear-manganese cluster into a Nafion matrix, has been shown to achieve efficient water oxidation catalysis. We report here in situ X-ray absorption

  20. Manganese Superoxide Dismutase Protects nNOS Neurons from NMDA and Nitric Oxide-Mediated Neurotoxicity

    E-print Network

    Engelhardt, John F.

    Manganese Superoxide Dismutase Protects nNOS Neurons from NMDA and Nitric Oxide, Department of Radiology, University of Iowa College of Medicine, Iowa City, Iowa 52242 Neuronal nitric oxide to NMDA mediated neurotoxicity. Key words: nitric oxide; nNOS neuron; MnSOD; NMDA tox- icity; resistance

  1. Effects of FeS on Chromium Oxidation Mediated by Manganese Oxidizers

    SciTech Connect

    Wu, Youxian; Deng, Baolin

    2004-03-31

    Reductive immobilization of Cr(VI) has been widely explored as a cost-effective approach for Cr-contaminated site remediation. The long-term stability of the immobilized Cr(III), however, is a concern. Cr(III) is known to be oxidized by Mn oxides chemically and Mn-oxides could be produced through microbially mediated Mn(II) oxidation. This study examined the effect of FeS on Cr(III) oxidation mediated by Pseudomonas putida. The results showed that commercial granular FeS did not affect Cr(III) oxidation in the culture of P. putida with Mn(II), but freshly precipitated FeS slurry inhibited Cr(III) oxidation. A 10 mg/l of FeS did not inhibit the microbial growth, but delayed the production of Mn oxides, thus postponing potential Cr(III) oxidation. In the presence of excessive FeS slurry, both Cr(VI) and Mn oxides were reduced rapidly. The reduced Cr(III) could not be re-oxidized as long as freshly formed FeS was present, even in the presence of the manganese oxidizers.

  2. Oxidative damage and neurodegeneration in manganese-induced neurotoxicity

    PubMed Central

    Milatovic, Dejan; Zaja-Milatovic, Snjezana; Gupta, Ramesh C.; Yu, Yingchun; Aschner, Michael

    2009-01-01

    Exposure to excessive manganese (Mn) levels results in neurotoxicity to the extrapyramidal system and the development of Parkinson’s disease (PD)-like movement disorder, referred to as manganism. Although the mechanisms by which Mn induces neuronal damage are not well defined, its neurotoxicity appears to be regulated by a number of factors, including oxidative injury, mitochondrial dysfunction and neuroinflammation. To investigate the mechanisms underlying Mn neurotoxicity, we studied the effects of Mn on reactive oxygen species (ROS) formation, changes in high-energy phosphates (HEP), neuroinflammation mediators and associated neuronal dysfunctions both in vitro and in vivo. Primary cortical neuronal cultures showed concentration-dependent alterations in biomarkers of oxidative damage, F2-isoprostanes (F2-IsoPs) and mitochondrial dysfunction (ATP), as early as 2 hours following Mn exposure. Treatment of neurons with 500 µM Mn also resulted in time-dependent increases in the levels of the inflammatory biomarker, prostaglandin E2 (PGE2). In vivo analyses corroborated these findings, establishing that either a single or three (100 mg/kg, s.c.) Mn injections (days 1, 4 and 7) induced significant increases in F2-IsoPs and PGE2 in adult mouse brain 24 hours following the last injection. Quantitative morphometric analyses of Golgi-impregnated striatal sections from mice exposed to single or three Mn injections revealed progressive spine degeneration and dendritic damage of medium spiny neurons (MSNs). These findings suggest that oxidative stress, mitochondrial dysfunction and neuroinflammation are underlying mechanisms in Mn-induced neurodegeneration. PMID:19607852

  3. Visible and near-infrared spectra of manganese oxides: Detecting high manganese phases in Curiosity Mastcam multispectral images

    NASA Astrophysics Data System (ADS)

    Hardgrove, C. J.; Lanza, N.; Bell, J. F., III; Wiens, R. C.; Johnson, J. R.; Morris, R. V.

    2014-12-01

    The Mars Science Laboratory Curiosity rover's Chemcam instrument has identified manganese in relatively high abundance on several rock surfaces. The manganese abundances are several orders of magnitude greater than has been previously identified on Mars, indicating the presence of a manganese-rich phase. Although the specific phase has yet to be identified, these results suggest that the martian surface may have been much more highly oxidizing than has previously been recognized. The presence of a manganese-rich phase could provide an additional indicator of habitable aqueous environments. Given the importance of manganese for understanding past habitability, and the high abundances identified with Chemcam, we investigate the utility of using Mastcam multispectral imaging surveys to identify areas for subsequent detailed analysis with Chemcam. Vempati et al. showed that Mn3+ affect the reflectance spectra of Mn-bearing minerals. Specifically, relatively weak features due to electronic transitions and crystal field effects are observed in Mn-enriched hematites and geothites at 454, 554, 596 and 700 nm. The Mastcam-34 medium angle camera has filter band-passes at 550, 675 and 750nm, and we will explore the utility of using these bands (or combinations thereof) to determine if there is a contribution of Mn-bearing phases on spectra, specifically those that have been identified as having elevated Mn with Chemcam. The most common Mn-bearing mineral phase in terrestrial varnishes, Birnessite, has charge-transfer features that are similar to Fe-oxides but are centered at slightly longer wavelength band positions. Longer wavelength features are also common for other Mn-oxides, and this could be used to distinguish these phases from other Fe-oxide components. In this study we will present visible to near-infrared (0.4 - 3 µm) reflectance spectra on a suite of Mn-oxide laboratory standards. The set of standards includes Mn-oxide abundances that vary from less than 1 up to ~75 wt.%. Spectra will be downsampled to Mastcam bandpasses to determine if the effects of Mn-bearing phases could be identified from Mastcam multispectral observations in Gale Crater.

  4. Water-oxidation catalysis by synthetic manganese oxides--systematic variations of the calcium birnessite theme.

    PubMed

    Frey, Carolin E; Wiechen, Mathias; Kurz, Philipp

    2014-03-21

    Layered manganese oxides from the birnessite mineral family have been identified as promising heterogeneous compounds for water-oxidation catalysis (WOC), a key reaction for the conversion of renewable energy into storable fuels. High catalytic rates were especially observed for birnessites which contain calcium as part of their structures. With the aim to systematically improve the catalytic performance of such oxide materials, we used a flexible synthetic route to prepare three series of calcium birnessites, where we varied the calcium concentrations, the ripening times of the original precipitates and the temperature of the heat treatment following the initial synthetic steps (tempering) during the preparation process. The products were carefully analysed by a number of analytical techniques and then probed for WOC activity using the Ce(4+)-system. We find that our set of twenty closely related manganese oxides shows large, but somewhat systematic alterations in catalytic rates, indicating the importance of synthesis parameters for maximum catalytic performance. The catalyst of the series for which the highest water-oxidation rate was found is a birnessite of medium calcium content (Ca?:?Mn ratio 0.2?:?1) that had been subjected to a tempering temperature of 400 °C. On the basis of the detailed analysis of the results, a WOC reaction scheme for birnessites is proposed to explain the observed trends in reactivity. PMID:24225769

  5. Bismuth oxide coated amorphous manganese dioxide for electrochemical capacitors

    NASA Astrophysics Data System (ADS)

    Li, Xiaofeng; Zhang, Linsen; Dong, Huichao; Xia, Tongchi; Huang, Zhigang

    2015-05-01

    With MnSO4, NaOH and K2S2O8 as the raw materials, the amorphous and ?-type manganese dioxide (MnO2) is separately prepared by using different chemical precipitation-oxidation methods. The results of charge-discharge and electrochemical impedance spectroscopy (EIS) tests show that (i) the specific capacitance of the amorphous MnO2 reaches to 301.2 F g-1 at a current density of 200 mA g-1 and its capacitance retention rate after 2000 cycles is 97%, which is obviously higher than 250.8 F g-1 and 71% of the ?-type one, respectively; (ii) good electrochemical capacitance properties of the amorphous MnO2 should be contributed to easy insertion/extraction of ions within the material; (iii) when 5 wt% Bi2O3 is coated on the amorphous MnO2, its specific capacitance increases to 352.8 F g-1 and the capacitance retention rate is 90% after 2000 cycles.

  6. Role of manganese in protection against oxidative stress under iron starvation in cyanobacterium Anabaena 7120.

    PubMed

    Kaushik, Manish Singh; Srivastava, Meenakshi; Verma, Ekta; Mishra, Arun Kumar

    2015-06-01

    The cyanobacterium Anabaena sp. PCC 7120 was grown in presence and absence of iron to decipher the role of manganese in protection against the oxidative stress under iron starvation and growth, manganese uptake kinetics, antioxidative enzymes, lipid peroxidation, electrolyte leakage, thiol content, total peroxide, proline and NADH content was investigated. Manganese supported the growth of cyanobacterium Anabaena 7120 under iron deprived conditions where maximum uptake rate of manganese was observed with lower Km and higher Vmax values. Antioxidative enzymes were also found to be elevated in iron-starved conditions. Estimation of lipid peroxidation and electrolyte leakage depicted the role of manganese in stabilizing the integrity of the membrane which was considered as the prime target of oxygen free radicals in oxidative stress. The levels of total peroxide, thiol, proline and NADH content, which are the representative of oxidative stress response in Anabaena 7120, were also showed increasing trends in iron starvation. Hence, the results discerned, clearly suggested the role of manganese in protection against the oxidative stress in cyanobacterium Anabaena 7120 under iron starvation either due to its antioxidative properties or involvement as cofactor in a number of antioxidative enzymes. PMID:25572501

  7. Reactivity and transformation of antibacterial N-oxides in the presence of manganese oxide.

    PubMed

    Zhang, Huichun; Huang, Ching-Hua

    2005-01-15

    Organic N-oxides are an important structural class in many pharmaceutical and industrial chemicals. Little is known aboutthe potential transformation of organic N-oxides at the sediment-water interface. Veterinary antibacterial agents carbadox and olaquindox are examples of commonly used heterocyclic N-oxides. Investigation with various N-oxides including carbadox, olaquindox, quinoline N-oxide, and quindoxin revealed surprisingly high reactivity toward MnO2 for all of the compounds except olaquindox. Desoxycarbadox and quinoxaline, two structurally related compounds that lack an N-oxide functional group, showed much lower or no reactivity toward MnO2. Comparisons among the previous compounds indicate that N-oxide moiety is the primary reactive site to MnO2, and substitution at the alpha-C adjacent to the N-oxide group is critical in determining the overall reactivity. Reactions of N-oxides with MnO2 appeared to be oxidation, with generation of Mn2+ parallel to degradation of the parent organics. Product characterization confirmed that quinoline N-oxide and quindoxin transformed into 2-hydroxyquinoline and quinoxaline 2,3-diol, respectively, in reactions with MnO2. The transformation involves separate steps of N-oxide moiety deoxygenation and neighboring alpha-C hydroxylation as elucidated by 18O isotope experiments. All of the experimental results pointed to a mechanism that involves an N-oxide radical intermediate. This is the first study to report such transformation reactivity of organic N-oxides toward manganese oxide, offering a new degradation pathway that could be important for the fate of this group of compounds in the aquatic environment. PMID:15707060

  8. Abiotic sulfide oxidation via manganese reduction fuels the deep biosphere

    NASA Astrophysics Data System (ADS)

    Bottrell, S.; Böttcher, M. E.; Schippers, A.; Parkes, R.; Raiswell, R.

    2009-12-01

    The deep biosphere in marine sediments consists of large populations of metabolically active Bacteria and Archaea [1, 2]. Buried organic carbon is the main energy source for the deep biosphere and is anaerobically oxidized via nitrate-, Mn(IV)-, Fe(III)-, sulfate or carbonate-reduction. Sulfate reduction has been identified as the most important of these processes [3, 4] yet sulfate is typically quantitatively removed from pore waters in the upper few meters of marine sediments. A key question remains: “How is continued metabolic activity maintained in the deep biosphere?”. Buried organic carbon remains as an electron donor but the source of electron acceptors is less clear. Stable isotope compositions of sulfur and oxygen in sulfate are particularly useful in the study of biogeochemical processes and sediment-pore fluid interactions e.g. [5, 6]. Here we use stable sulfur and oxygen isotope compositions to show that the oxidant sulfate is generated by anoxic sulfide oxidation in deeply buried sediments of the Cascadia margin and Blake Ridge and controlled anoxic experiments to constrain the mechanisms involved on this reaction. Pore fluid sulfate in deep Cascadia margin and Blake Ridge sediments contained sulfur with similar isotopic composition to diagenetic sulfide in the sediment and oxygen that was depleted in 18O (in some cases depleted in 18O relative to pore water). Experiments with Mn(IV)-containing oxides confirmed that these can abiotically oxidize iron sulfides and also produce sulfate depleted in 18O relative to water. In another set of anoxic experiments, pyrite was mixed with different Fe(III) minerals. Crucially, experiments with synthesized pure Fe(III) minerals produced no sulfate but identical experiments with natural Fe(III) minerals containing trace Mn did. Sulfate concentrations in solution were stoichiometrically balanced by Mn concentrations, showing trace Mn(IV) in the natural minerals to be the oxidizing agent generating sulfate. Sulfate formed was again depleted in 18O relative to water. Experiments with 18O-labelled water show that all oxygen atoms in the sulfate formed are derived from water molecules, thus the sulfate oxygen isotopic composition represents a true fractionation from water. The depletion of 18O in sulfate relative to water thus acts as a fingerprint for sulfate produced by Mn (IV) reduction. Oxidized manganese stored within the mineral fraction of marine sediments can thus drive abiotic anaerobic sulfide oxidation which, together with microbial sulfate reduction, forms a closed sulfur cycle feeding the deep biosphere in marine sediments. [1] Parkes et al. (2005) Nature 436, 390. [2] Schippers et al. (2005) Nature 433, 861. [3] D’Hondt et al. (2002) Science 295, 2067. [4] D’Hondt et al. (2004) Science 306, 2216. Bottrell et al. (2000) J. Geol. Soc. Lond. 157, 711. [6] Böttcher et al. (2006) Proc. ODP Sci. Res. 201-109, 1.

  9. Early diagenetic quartz formation at a deep iron oxidation front in the Eastern Equatorial Pacific

    NASA Astrophysics Data System (ADS)

    Meister, Patrick; Chapligin, Bernhard; Picard, Aude; Meyer, Hanno; Fischer, Cornelius; Rettenwander, Daniel; Amthauer, Georg; Vogt, Christoph; Aiello, Ivano

    2015-04-01

    The mechanisms of early diagenetic quartz formation under low-temperature conditions are still poorly understood. We studied lithified cherts consisting of microcrystalline quartz recovered from ODP Site 1226 in the Eastern Equatorial Pacific. The cherts occur near the base of a 420-m-thick Miocene-Holocene sequence within unlithified nannofossil and diatom ooze. Palaeo-temperatures reconstructed from ?18O values in the cherts are near to present porewater temperatures and a sharp depletion in dissolved silica occurs around 385 mbsf indicating that silica precipitation is still ongoing. Also a deep iron oxidation front occurs at the same depth, which is caused by upward diffusing nitrate from an oxic seawater aquifer in the underlying basaltic crust. Sequential iron extraction and analysis of the X-ray absorption near-edge structure (XANES) revealed that iron in the cherts predominantly occurs as illite and amorphous iron oxide, whereas iron in the nannofossil and diatom ooze occurs mainly as smectites. Mössbauer spectroscopy confirmed that the illite iron in the cherts is largely oxidized. A possible mechanisms that may be operative is quartz precipitation initiated by adsorption of silica to freshly precipitated iron oxides. The decrease in porewater silica concentration below opal-A and opal-CT saturation then allows for the precipitation of the thermodynamically more stable phase: quartz. We suggest that the formation of early-diagenetic chert at iron oxidation fronts is an important process in suboxic zones of silica-rich sediments. The largest iron oxidation front ever occurred during the great oxidation event ca. 2.5 Ga ago, when large amounts of iron and chert beds were deposited.

  10. Cerium(IV)-driven water oxidation catalyzed by a manganese(V)-nitrido complex.

    PubMed

    Ma, Li; Wang, Qian; Man, Wai-Lun; Kwong, Hoi-Ki; Ko, Chi-Chiu; Lau, Tai-Chu

    2015-04-20

    The study of manganese complexes as water-oxidation catalysts (WOCs) is of great interest because they can serve as models for the oxygen-evolving complex of photosystem?II. In most of the reported Mn-based WOCs, manganese exists in the oxidation states III or IV, and the catalysts generally give low turnovers, especially with one-electron oxidants such as Ce(IV) . Now, a different class of Mn-based catalysts, namely manganese(V)-nitrido complexes, were explored. The complex [Mn(V) (N)(CN)4 ](2-) turned out to be an active homogeneous WOC using (NH4 )2 [Ce(NO3 )6 ] as the terminal oxidant, with a turnover number of higher than 180 and a maximum turnover frequency of 6?min(-1) . The study suggests that active WOCs may be constructed based on the Mn(V) (N) platform. PMID:25727326

  11. Catalytic role of Manganese oxides in prebiotic Nucleobases synthesis from Formamide

    NASA Astrophysics Data System (ADS)

    Bhushan, Brij

    2012-07-01

    The evolution of living cell from chemicals is more complicated reaction which could be studied in multistep. A study of prebiotic synthesis of naturally occurring purine and pyrimidine derivatives from formamide under catalytic condition with different oxides of manganese reveals a significant role. Manganese oxides are highly efficient in the conversion of formamide into different nucleobases. Neat formamide is converted to the purine, 9-(hydroxyacetyl) purine, cytosine, 4(3H)-pyrimidinone, thymine and adenine in good yield. Metal oxides have provided their surfaces and catalyzed the reactions from simple molecules to more complex bio-organic molecules. Our results show that probably prebiotic reactions might have occured on the sea floor where the existence of manganese oxide is second to iron transition metal minerals.

  12. Manganese Based Oxidative Technologies For Water/Wastewater Treatment 

    E-print Network

    Desai, Ishan

    2013-08-27

    and structural properties of ferrites. These laboratory prepared catalysts were thoroughly characterized using XRD, SEM, TEM, HR-TEM, and BET. Their magnetic properties have also been studied. These manganese ferrites offer the potential to enhance hydroxyl...

  13. EFFECTS OF SOLAR RADIATION ON MANGANESE OXIDE REACTIONS WITH SELECTED ORGANIC COMPOUNDS

    EPA Science Inventory

    The effects of sunlight on aqueous redox reactions between manganese oxides (MnOx) and selected organic substances are reported. o sunlight-induced rate enhancement was observed for the MnOx oxidation of substituted phenols, anisole, o-dichlorobenzene, or p-chloroaniline. n the o...

  14. Nanostructured lithium nickel manganese oxides for lithium-ion batteries.

    SciTech Connect

    Deng, H.; Belharouak, I.; Cook, R. E.; Wu, H.; Sun, Y.-K.; Amine, K.; Hanyang Univ.

    2010-02-25

    Nanostructured lithium nickel manganese oxides were investigated as advanced positive electrode materials for lithium-ion batteries designated to power plug-in hybrid electric vehicles and all-electric vehicles. The investigation included material characterization and electrochemical testing. In cell tests, the Li{sub 1.375}Ni{sub 0.25}Mn{sub 0.75}O{sub 2.4375} composition achieved high capacity (210 mAh g{sup -1}) at an elevated rate (230 mA g{sup -1}), which makes this material a promising candidate for high energy density Li-ion batteries, as does its being cobalt-free and uncoated. The material has spherical morphology with nanoprimary particles embedded in micrometer-sized secondary particles, possesses a multiphase character (spinel and layered), and exhibits a high packing density (over 2 g cm{sup -3}) that is essential for the design of high energy density positive electrodes. When combined with the Li{sub 4}Ti{sub 5}O{sub 12} stable anode, the cell showed a capacity of 225 mAh g{sup -1} at the C/3 rate (73 mA g{sup -1}) with no capacity fading for 200 cycles. Other chemical compositions, Li{sub (1+x)}Ni{sub 0.25}Mn{sub 0.75}O{sub (2.25+x/2)} (0.32 {le} x {le} 0.65), were also studied, and the relationships among their structural, morphological, and electrochemical properties are reported.

  15. Part I. Manganese oxide containing layered double hydroxides materials: Synthesis and characterization. Part II. Manganese oxide octahedral molecular sieves (OMS-2): Synthesis, particle size control, characterization, and catalytic applications

    Microsoft Academic Search

    Josanlet C. Villegas

    2006-01-01

    The work presented here comprises the development of new routes for the preparation of manganese oxide-based materials with controlled properties. The first part of the research consists of the preparation of a new series of layered double hydroxide (LDH) materials containing intercalated manganese oxide species. Characterization of the resulting materials will be sub-divided in two major parts: (1) Composition, structural,

  16. A very simple method to synthesize nano-sized manganese oxide: an efficient catalyst for water oxidation and epoxidation of olefins.

    PubMed

    Najafpour, Mohammad Mahdi; Rahimi, Fahimeh; Amini, Mojtaba; Nayeri, Sara; Bagherzadeh, Mojtaba

    2012-08-28

    Nano-sized particles of manganese oxides have been prepared by a very simple and cheap process using a decomposing aqueous solution of manganese nitrate at 100 °C. Scanning electron microscopy, transmission electron microscopy and X-ray diffraction spectrometry have been used to characterize the phase and the morphology of the manganese oxide. The nano-sized manganese oxide shows efficient catalytic activity toward water oxidation and the epoxidation of olefins in the presence of cerium(IV) ammonium nitrate and hydrogen peroxide, respectively. PMID:22858683

  17. THE EFFECTS OF IRON(II) ON ARSENIC(III) OXIDATION AND ARSENIC SORPTION/DESORPTION ON MANGANESE OXIDES

    E-print Network

    Sparks, Donald L.

    THE EFFECTS OF IRON(II) ON ARSENIC(III) OXIDATION AND ARSENIC SORPTION/DESORPTION ON MANGANESE © 2014 Yun Wu All Rights Reserved #12;THE EFFECTS OF IRON(II) ON ARSENIC(III) OXIDATION AND ARSENIC, Caroline Golt on arsenic speciation and UD Soil Test Lab. I thank all current and previous members

  18. What Are the Oxidation States of Manganese Required To Catalyze Photosynthetic Water Oxidation?

    PubMed Central

    Kolling, Derrick R.J.; Cox, Nicholas; Ananyev, Gennady M.; Pace, Ron J.; Dismukes, G. Charles

    2012-01-01

    Photosynthetic O2 production from water is catalyzed by a cluster of four manganese ions and a tyrosine residue that comprise the redox-active components of the water-oxidizing complex (WOC) of photosystem II (PSII) in all known oxygenic phototrophs. Knowledge of the oxidation states is indispensable for understanding the fundamental principles of catalysis by PSII and the catalytic mechanism of the WOC. Previous spectroscopic studies and redox titrations predicted the net oxidation state of the S0 state to be (MnIII)3MnIV. We have refined a previously developed photoassembly procedure that directly determines the number of oxidizing equivalents needed to assemble the Mn4Ca core of WOC during photoassembly, starting from free MnII and the Mn-depleted apo-WOC complex. This experiment entails counting the number of light flashes required to produce the first O2 molecules during photoassembly. Unlike spectroscopic methods, this process does not require reference to synthetic model complexes. We find the number of photoassembly intermediates required to reach the lowest oxidation state of the WOC, S0, to be three, indicating a net oxidation state three equivalents above four MnII, formally (MnIII)3MnII, whereas the O2 releasing state, S4, corresponds formally to (MnIV)3MnIII. The results from this study have major implications for proposed mechanisms of photosynthetic water oxidation. PMID:22853909

  19. Synthesis of nanostructured manganese oxides from a dipolar binary liquid (water\\/benzene) system and hydrogen storage ability research

    Microsoft Academic Search

    Hai Men; Peng Gao; Yuzeng Sun; Yujin Chen; Xiaona Wang; Longqiang Wang

    2010-01-01

    A new dipolar binary liquid strategy has been developed to manganese oxide nanostructure’s synthesis, in which different manganese oxide nanostructures have been easily obtained without using any templates or catalysts. It has been found that the reaction temperatures, alkali precipitators’ concentrations and Mn2+ concentrations play a significant role in our dipolar binary liquid technique. This novel approach can be potentially

  20. Processes of nickel and cobalt uptake by a manganese oxide forming sediment in Pinal Creek, Globe mining district, Arizona

    USGS Publications Warehouse

    Kay, J.T.; Conklin, M.H.; Fuller, C.C.; O'Day, P. A.

    2001-01-01

    A series of column experiments was conducted using manganese oxide coated sediments collected from the hyporheic zone in Pinal Creek (AZ), a metal-contaminated stream, to study the uptake and retention of Mn, Ni, and Co. Experimental variables included the absence (abiotic) and presence (biotic) of active Mn-oxidizing bacteria, the absence and presence of dissolved Mn, and sediment manganese oxide content. Uptake of Mn under biotic conditions was between 8 and 39% higher than under abiotic conditions. Continuous uptake of Mn due to biotic oxidation was evident from extraction of column sediments. Manganese uptake is hypothesized to initially occur as adsorption, which led to subsequent surface and/or microbial oxidation. Complete breakthrough of Ni within 100 pore volumes indicated no process of continuous uptake and was modeled as an equilibrium adsorption process. Nickel uptake in the presence of dissolved Mn was 67-100% reversible. Sediment extractions suggest that Ni uptake occurred through weak and strong adsorption. Continuous uptake of cobalt increased with sediment manganese oxide content, and Co uptake was up to 75% greater under biotic than abiotic conditions. Cobalt uptake was controlled by both existing and newly formed manganese oxides. Only a small amount of Co uptake was reversible (10-25%). XANES spectral analysis indicated that most Co(II) was oxidized to Co(III) and probably incorporated structurally into manganese oxides. Although manganese oxides were the primary phase controlling uptake and retention of Mn, Ni, and Co, the mechanisms varied among the metals.

  1. Oxidation and dechlorination of chlorophenols in dilute aqueous suspensions of manganese oxides: Reaction products

    SciTech Connect

    Ukrainczyk, L.; McBride, M.B. (Cornell Univ., Ithaca, NY (United States). Dept.of Soil, Crop, and Atmospheric Sciences)

    1993-11-01

    Some monomeric and dimeric oxidation products of para- and/or ortho-chlorinated phenols in dilute (1 mmol/L phenol), acidified, aqueous suspensions of manganese oxide (Na-buserite) were identified by MS, Fourier-transform IR spectroscopy and UV/visible spectroscopy. The para-chlorinated phenols (4-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol, 4-chloro-2-methylphenol) gave corresponding p-benzoquionones (benzoquinone, 2-chlorobenzoquinone, 2,6-dichlorobenzoquinone, 2-methylbenzoquinone) as the detectable water-soluble oxidation products. Dimeric products were present in the extracts obtained by washing the oxide with methylene chloride. Michael addition of phenolate to quinone seems to be the predominant mode of coupling. Chlorinated phenols without chlorine in the para-position (2-chlorophenol, 2,6-dichlorophenol) were more difficult to oxidize and afforded diphenoquinones as the only detectable water-soluble products. For all studied phenols, with the exception of 2,4,6-trichlorophenol, the amount of water-soluble products accounts only for a small fraction of oxidized phenol. The quinone and diphenoquinone products readily couple with phenols into humus like materials.

  2. Adsorption and desorption properties of arsenate onto nano-sized iron-oxide-coated quartz.

    PubMed

    Mostafa, M G; Chen, Yen-Hua; Jean, Jiin-Shuh; Liu, Chia-Chuan; Teng, Hsisheng

    2010-01-01

    This study was conducted to investigate the adsorption and desorption properties of arsenate [As(V)] on nano-sized iron-oxide-coated quartz (IOCQ) through batch experiments. The coating of nano-sized iron oxide on the quartz surface was performed using the heat treatment process which aimed to utilize the adsorption properties of the nano-sized iron oxide and the filtration properties of the quartz. Environmental SEM-EDAX and BET techniques were used to analyze the surface morphology, elemental composition, surface area and the porosity of the adsorbent. SEM-EDAX analyses confirmed that arsenate was adsorbed on the IOCQ surface. BET results showed that the IOCQ adsorbent had higher pore volumes and high specific surface areas compared with the pure quartz. The study revealed that the adsorption rate of As(V) ion was very rapid and reached the equilibrium within 5 min. This study also revealed that almost 100% of As(V) removal was achieved within 5 minutes of adsorption reaction from the initial solution containing 1,000 microg-As(V)/L. The Langmuir adsorption isotherm model suitably explained the sorption characteristics of As(V) onto IOCQ. This desorption study showed that the adsorbent could be reused after reacting with mild HCl solution but the concentration of acid eluant or pH has a great impact on the coated adsorbent surface. The results indicate that the nano-sized iron oxide-coated adsorbent is potentially suitable for removal of arsenate from drinking water. PMID:20651443

  3. Determination of methylcyclopentadienyl-manganese tricarbonyl by solid phase microextraction-direct thermal desorption-quartz furnace atomic absorption spectrometry

    Microsoft Academic Search

    Mar??a Sandra Fragueiro; Fausto Alava-Moreno; Isela Lavilla; Carlos Bendicho

    2001-01-01

    A new procedure that uses a pre-concentration system based on solid phase microextraction (SPME) and detection by quartz furnace-atomic absorption spectrometry after thermal desorption from the microextraction fiber has been proposed for the determination of methylcyclopentadienylmanganese tricarbonyl (MMT) in gasoline and water. Working MMT solutions were prepared in 40 ml amber vials, and sampling was performed by exposing the SPME

  4. Synthesis Of Different Phases Of Nano Manganese Oxides And Their Dielectric Behaviour In Chitosan Composites

    NASA Astrophysics Data System (ADS)

    Harshita, B. A.; Bhat, D. Krishna; Bhatt, Aarti S.

    2011-10-01

    Nanoscale oxides of transition metals, particularly manganese, are desirable for many applications in designing electric, magnetic and heterogeneous catalytic materials. Manganese oxides exist in different phases, viz. MnO, MnO2, Mn2O3, Mn2O7 and Mn3O4. Using different synthetic routes it is possible to synthesize different phases of manganese oxides. Moreover, composites of these oxides with polymer have the potential to address the needs of emerging dielectric technologies. In the present work, using manganese chloride and hydrazine hydrate, Mn3O4 and Mn2O3 nanoparticles were successfully synthesized by conventional and hydrothermal method respectively. The variation in the formation of the different phases has been discussed. The nanoparticles were well characterized by X-ray Diffraction and using the Debye Scherrer formula, the average size of Mn3O4 and Mn2O3 nanoparticles were calculated to be 35 nm and 25 nm respectively. Using solution casting method, nanocomposites of chitosan/Mn3O4 were prepared and their electrochemical properties were studied using electrochemical impedance spectroscopy. It was observed that with increase in the content of nano oxides, the conductivity of the films increased. Also, the variation in the permittivity of these samples with respect to frequency was studied. The results suggest that the composites have a fair chance to be used in energy storage devices.

  5. Influence of synthesis conditions on the electrochemical properties of nanostructured amorphous manganese oxide cryogels

    NASA Astrophysics Data System (ADS)

    Yang, Jingsi; Xu, Jun John

    Amorphous manganese oxides have received increasing attention in recent years as intercalation cathodes for rechargeable lithium batteries. The sol-gel method is a versatile method for achieving nanostructured amorphous oxides. In this paper, two different sol-gel routes are investigated, where nanostructured amorphous manganese oxide cryogels are obtained via freeze drying Mn(IV) oxide hydrogels formed in situ. In one route the hydrogels are formed by reaction between a solution of sodium permanganate and a solution of disodium fumarate, and in the other route by reaction between a solution of sodium permanganate and solid fumaric acid. Highly homogeneous monolithic manganese oxide hydrogels are obtained from both synthesis routes with precursor concentrations between 0.1 and 0.2 M. The freeze drying method proves to be an efficient method for obtaining nanostructured amorphous manganese oxide cryogels out of the hydrogels. Depending on the synthesis conditions of the hydrogels, the resultant cryogels can yield very high specific capacities for lithium intercalation and excellent rate performance. The cryogel with the best performance exhibits 289 mAh/g at a C/100 rate and 174 mAh/g at a 2 C rate. Strong dependence of electrochemical properties of the cryogels on the synthesis conditions of the parent hydrogels has been observed. The different electrochemical properties are believed to be due to different surface areas and local structures of the cryogels derived from hydrogels synthesized under different conditions. This strong dependence gives rise to the possibility of achieving promising intercalation materials through tailoring the surface area and the local structure of amorphous manganese oxides by adjusting sol-gel synthesis conditions.

  6. High-performance hybrid oxide catalyst of manganese and cobalt for low-pressure methanol synthesis

    NASA Astrophysics Data System (ADS)

    Li, Cheng-Shiuan; Melaet, Gérôme; Ralston, Walter T.; An, Kwangjin; Brooks, Christopher; Ye, Yifan; Liu, Yi-Sheng; Zhu, Junfa; Guo, Jinghua; Alayoglu, Selim; Somorjai, Gabor A.

    2015-03-01

    Carbon dioxide capture and use as a carbon feedstock presents both environmental and industrial benefits. Here we report the discovery of a hybrid oxide catalyst comprising manganese oxide nanoparticles supported on mesoporous spinel cobalt oxide, which catalyses the conversion of carbon dioxide to methanol at high yields. In addition, carbon–carbon bond formation is observed through the production of ethylene. We document the existence of an active interface between cobalt oxide surface layers and manganese oxide nanoparticles by using X-ray absorption spectroscopy and electron energy-loss spectroscopy in the scanning transmission electron microscopy mode. Through control experiments, we find that the catalyst’s chemical nature and architecture are the key factors in enabling the enhanced methanol synthesis and ethylene production. To demonstrate the industrial applicability, the catalyst is also run under high conversion regimes, showing its potential as a substitute for current methanol synthesis technologies.

  7. Size and morphology controlled lithium manganese oxide on silica sphere with core-shell structure.

    PubMed

    Ryu, Seong-Hyeon; Ju, Jeong-Hun; Cho, Sung-Woo; Ryu, Kwang-Sun

    2012-02-01

    Core-shell structures were prepared from synthesized SiO2-LiMn2O4 with manganese oxide as shell on the silica core by a precipitation method, which allowed control of core structure in terms of thickness and particle size. X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), field emission-transmission electron microscopy (FE-TEM), and energy dispersive spectroscopy (EDS) were used to characterize the SiO2-LiMn2O4. According to FE-SEM images, particle growth was controlled by controlling the amount of manganese precursor and the temperature. The synthesized core-shell structure was composed of silica, lithium silicate, Mn2O3, and the spinel phase of lithium manganese oxide. Electrochemical measurements show that the synthesized core-shell structure has poorer electrochemical performance than that of LiMn2O4. PMID:22629996

  8. Using nitrogen isotope fractionation to assess the oxidation of substituted anilines by manganese oxide.

    PubMed

    Skarpeli-Liati, Marita; Jiskra, Martin; Turgeon, Aurora; Garr, Ashley N; Arnold, William A; Cramer, Christopher J; Schwarzenbach, René P; Hofstetter, Thomas B

    2011-07-01

    We explored the N isotope fractionation associated with the oxidation of substituted primary aromatic amines, which are often the position of initial attack in transformation processes of environmental contaminants. Apparent (15)N-kinetic isotope effects, AKIE(N), were determined for the oxidation of various substituted anilines in suspensions of manganese oxide (MnO(2)) and compared to reference experiments in homogeneous solutions and at electrode surfaces, as well as to density functional theory calculations of intrinsic KIE(N)for electron and hydrogen atom transfer reactions. Owing to the partial aromatic imine formation after one-electron oxidation and corresponding increase in C-N bond strength, AKIE(N)-values were inverse, substituent-dependent, and confined to the range between 0.992 and 0.999 in agreement with theory. However, AKIE(N)-values became normal once the fraction of cationic species prevailed owing to (15)N-equilibrium isotope effects, EIE(N), of 1.02 associated with N atom deprotonation. The observable AKIE(N)-values are substantially modulated by the acid/base pre-equilibria of the substituted anilines and isotope fractionation may even vanish under conditions where normal EIE(N) and inverse AKIE(N) cancel each other out. The pH-dependent trends of the AKIE(N)-values provide a new line of evidence for the identification of contaminant degradation processes via oxidation of primary aromatic amino groups. PMID:21627095

  9. Direct measurements of small 14C samples after oxidation in quartz tubes

    NASA Astrophysics Data System (ADS)

    Fahrni, S. M.; Gäggeler, H. W.; Hajdas, I.; Ruff, M.; Szidat, S.; Wacker, L.

    2010-04-01

    Small 14C samples gain importance in environmental research and for dating purposes. However, throughput of such samples is limited by the preparation of graphite targets for accelerator mass spectrometry (AMS) measurements. In our approach, oxidation of samples with copper oxide in quartz tubes was applied to form CO 2 which was measured directly with the gas ion source of the small AMS facility MICADAS. The presented method was designed to meet the requirements for fast and easy handling of small samples (<100 ?g carbon). As combustion byproducts are likely to interfere with ionisation processes in the gas ion source, we additionally investigated the effects of several gases on C - currents.

  10. Growth and Dissolution of Iron and Manganese Oxide Films

    SciTech Connect

    Scot T. Martin

    2008-12-22

    Growth and dissolution of Fe and Mn oxide films are key regulators of the fate and transport of heavy metals in the environment, especially during changing seasonal conditions of pH and dissolved oxygen. The Fe and Mn are present at much higher concentrations than the heavy metals, and, when Fe and Mn precipitate as oxide films, heavy metals surface adsorb or co-precipitate and are thus essentially immobilized. Conversely, when the Fe and Mn oxide films dissolve, the heavy metals are released to aqueous solution and are thus mobilized for transport. Therefore, understanding the dynamics and properties of Fe and Mn oxide films and thus on the uptake and release of heavy metals is critically important to any attempt to develop mechanistic, quantitative models of the fate, transport, and bioavailablity of heavy metals. A primary capability developed in our earlier work was the ability to grow manganese oxide (MnO{sub x}) films on rhodochrosite (MnCO{sub 3}) substrate in presence of dissolved oxygen under mild alkaline conditions. The morphology of the films was characterized using contact-mode atomic force microscopy. The initial growth began by heteroepitaxial nucleation. The resulting films had maximum heights of 1.5 to 2 nm as a result of thermodynamic constraints. Over the three past years, we have investigated the effects of MnO{sub x} growth on the interactions of MnCO{sub 3} with charged ions and microorganisms, as regulated by the surface electrical properties of the mineral. In 2006, we demonstrated that MnO{sub x} growth could induce interfacial repulsion and surface adhesion on the otherwise neutral MnCO{sub 3} substrate under environmental conditions. Using force-volume microscopy (FVM), we measured the interfacial and adhesive forces on a MnO{sub x}/MnCO{sub 3} surface with a negatively charged silicon nitride tip in a 10-mM NaNO3 solution at pH 7.4. The interfacial force and surface adhesion of MnOx were approximately 40 pN and 600 pN, respectively, whereas those of MnCO{sub 3} were essentially zero. The force differences between MnO{sub x} and MnCO{sub 3} suggest that oxide film growth can focus adsorbates to certain parts of the surface and thereby templating a heterogeneous layout of them. We suspected that the force differences were in part due to the differences in surface electrical properties. In 2007, we investigated two important electrical properties of MnO{sub x} and MnCO{sub 3} surfaces, namely surface potential and ion mobility. Surface potential is a composite quantity that can be linked to the local lattice structure of the reconstructed surface and the adsorption of water layers. The mobile surface ions formed by dissolution can also contribute to surface potential. Using Kelvin probe force microscopy (KPFM) and scanning polarization force microscopy (SPFM), we found that MnOx possessed excess surface potentials of over +200 mV in humid nitrogen and the excess surface potential decreased with increasing relative humidity (i.e., increasing adsorbed water layers on the mineral surface). The dependence of the excess surface potential was attributed to the change of the contributions from mobile ions. These results supported our earlier hypothesis that MnO{sub x} and MnCO{sub 3} had different surface electrical properties. In the third year, we systematically characterized that the change of the electrical double layer (EDL) structure of MnCO{sub 3} surface due to MnO{sub x} growth in aqueous solution and its dependence on pH. The structure of the electrical double layer determines the electrostatic interactions between the mineral surface and charged adsorbates. As described by the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, the electrostatic force, together with van der Waals interaction, regulates surface adsorption and bacterial attachment. Once adsorbates establish contact with the surface, they must resist hydraulic shear forces through surface adhesion. The adhesion of mineral surfaces is also affected by their electrostatic interactions with adsorbates. To probe the EDL structure, we ap

  11. Manganese Homeostasis in Group A Streptococcus Is Critical for Resistance to Oxidative Stress and Virulence

    PubMed Central

    Turner, Andrew G.; Ong, Cheryl-lynn Y.; Gillen, Christine M.; Davies, Mark R.; West, Nicholas P.; McEwan, Alastair G.

    2015-01-01

    ABSTRACT Streptococcus pyogenes (group A Streptococcus [GAS]) is an obligate human pathogen responsible for a spectrum of human disease states. Metallobiology of human pathogens is revealing the fundamental role of metals in both nutritional immunity leading to pathogen starvation and metal poisoning of pathogens by innate immune cells. Spy0980 (MntE) is a paralog of the GAS zinc efflux pump CzcD. Through use of an isogenic mntE deletion mutant in the GAS serotype M1T1 strain 5448, we have elucidated that MntE is a manganese-specific efflux pump required for GAS virulence. The 5448?mntE mutant had significantly lower survival following infection of human neutrophils than did the 5448 wild type and the complemented mutant (5448?mntE::mntE). Manganese homeostasis may provide protection against oxidative stress, explaining the observed ex vivo reduction in virulence. In the presence of manganese and hydrogen peroxide, 5448?mntE mutant exhibits significantly lower survival than wild-type 5448 and the complemented mutant. We hypothesize that MntE, by maintaining homeostatic control of cytoplasmic manganese, ensures that the peroxide response repressor PerR is optimally poised to respond to hydrogen peroxide stress. Creation of a 5448?mntE-?perR double mutant rescued the oxidative stress resistance of the double mutant to wild-type levels in the presence of manganese and hydrogen peroxide. This work elucidates the mechanism for manganese toxicity within GAS and the crucial role of manganese homeostasis in maintaining GAS virulence. PMID:25805729

  12. Organ weight changes in mice after long-term inhalation exposure to manganese oxides nanoparticles

    NASA Astrophysics Data System (ADS)

    Zeman, T.; Buchtová, M.; Do?ekal, B.; Míšek, I.; Navrátil, J.; Mikuška, P.; Šerý, O.; Ve?e?a, Z.

    2015-05-01

    Recently, it has been proven that manganese from inhaled particles of manganese compounds can accumulate in the internal organs of laboratory animals. Nevertheless, there were only a few researches dealing with changes in body morphology induced by inhalation of these particles, even though results of some studies indicate existence of such changes. The aim of our research was to assess the effect of inhaled manganese oxides nanoparticles on weight of internal organs. For this purpose a long-term inhalation experiment on laboratory mice was performed, during which the mice were exposed to MnO.Mn2O3 nanoparticles in concentration 2 × 106 particles/cm3 for 17 weeks, 24 hours a day, 7 days a week. Manganese oxides nanoparticles were synthesized continuously via aerosol route in a hot wall tube flow reactor using thermal decomposition of metal organic precursor manganese(II)acetylacetonate in the flow tube reactor at temperature 750 °C in the presence of 30 vol% of oxygen. It was proven that inhaled nanoparticles can influence the weight of internal organs of mice. Moreover, it was discovered that the resulting change in weight of selected organs is disproportional. The mice from the experimental group had statistically significantly lighter kidneys, liver and spleen and heavier pancreas compared to the mice from the control group.

  13. Joining of highly aluminum-doped lanthanum strontium manganese oxide with tetragonal zirconia by plastic deformation

    E-print Network

    Dutta, Prabir K.

    , Argonne, IL 60439, United States c The Center for Industrial Sensors and Measurement, 177 Watts Hall, 2041; LSAM; LSM; Ceramic conductor; Fuel cell; Sensor; Raman microscopy 1. Introduction Yttria sensors that exploit its high ionic conductivity [1]. Lanthanum stron- tium manganese oxide, LaxSr1 - x

  14. PHYSICAL REVIEW B 89, 064415 (2014) Intrinsic insulating ferromagnetism in manganese oxide thin films

    E-print Network

    Gong, Xingao

    2014-01-01

    PHYSICAL REVIEW B 89, 064415 (2014) Intrinsic insulating ferromagnetism in manganese oxide thin films Y. S. Hou, H. J. Xiang,* and X. G. Gong Key Laboratory of Computational Physical Sciences studies, we have revealed that the exotic insulating ferromagnetism in LaMnO3 thin film originates from

  15. Tunable bandgap of a single layer graphene doped by the manganese oxide using the electrochemical doping

    NASA Astrophysics Data System (ADS)

    Soo Park, Chang; Zhao, Yu; Lee, Jae-Hyun; Whang, Dongmok; Shon, Yoon; Song, Yoon-Ho; Jin Lee, Cheol

    2013-01-01

    We studied the control of the bandgap energy of graphene by doping manganese oxide nanoparticles using an electrochemical method. The manganese oxide doping into the graphene was a main role for the bandgap opening and the defect generation was an effective method to increase the density of Mn doping on the graphene. The measured bandgap increased and finally saturated at 0.256 eV as the concentration of manganese oxide nanoparticles increased. The bandgap energies were 0.22, 0.244, 0.250, and 0.256 eV at the applied voltage of 0.5, 1.0, 1.5, and 2.0 V, respectively. In addition, the defect generation by the plasma treatment resulted in improved formations of the bandgap energy up to 0.4 eV. The combination of the manganese oxide doping and the defect generation can enhance the bandgap energy effectively in the graphene. It is considered that the electrochemical doping technique is an effective way to control the bandgap energy of graphene.

  16. Diclofenac and 2?anilinophenylacetate degradation by combined activity of biogenic manganese oxides and silver

    PubMed Central

    Meerburg, Francis; Hennebel, Tom; Vanhaecke, Lynn; Verstraete, Willy; Boon, Nico

    2012-01-01

    Summary The occurrence of a range of recalcitrant organic micropollutants in our aquatic environment has led to the development of various tertiary wastewater treatment methods. In this study, biogenic manganese oxides (Bio?MnOx), biogenic silver nanoparticles (Bio?Ag0) and ionic silver were used for the oxidative removal of the frequently encountered drug diclofenac and its dechlorinated form, 2?anilinophenylacetate (APA). Diclofenac was rapidly degraded during ongoing manganese oxidation by Pseudomonas putida MnB6. Furthermore, whereas preoxidized Bio?MnOx, Bio?Ag0 and Ag+ separately did not show any removal capacity for diclofenac, an enhanced removal occurred when Bio?MnOx and silver species were combined. Similar results were obtained for APA. Finally, a slow removal of diclofenac but more rapid APA degradation was observed when silver was added to manganese?free P.?putida biomass. Combining these results, three mechanisms of diclofenac and APA removal could be distinguished: (i) a co?metabolic removal during active Mn2+ oxidation by P.?putida; (ii) a synergistic interaction between preoxidized Bio?MnOx and silver species; and (iii) a (bio)chemical process by biomass enriched with silver catalysts. This paper demonstrates the use of P.?putida for water treatment purposes and is the first report of the application of silver combined with biogenic manganese for the removal of organic water contaminants. PMID:22221449

  17. Effect of copper doping on the crystal structure and morphology of 1D nanostructured manganese oxides.

    PubMed

    Lee, Sun Hee; Park, Dae Hoon; Hwang, Seong-Ju; Choy, Jin-Ho

    2007-11-01

    We have tried to control the aspect ratio and physicochemical properties of 1D nanostructured manganese oxides through copper doping. Copper-doped manganese oxide nanostructures have been synthesized by one-pot hydrothermal treatment for the mixed solution of permanganate anions and copper cations. According to powder X-ray diffraction and electron microscopic analyses, all the present materials commonly crystallize with alpha-MnO2-type structure but their aspect ratio decreases significantly with increasing the content of copper. Such a variation of crystallite dimension is attributable to the limitation of crystal growth by the incorporation of copper ions. X-ray absorption spectroscopic studies at Mn K- and Cu K-edges clearly demonstrate that the average oxidation state of manganese ions is increased by the substitution of divalent copper ions. Electrochemical measurements reveal the improvement of the electrode performance of nanostructured manganate upon copper doping, which can be interpreted as a result of the decrease of aspect ratio and the increase of Mn valence state. From the present experimental findings, it becomes certain that the present Cu doping method can provide an effective way of controlling the crystal dimension and electrochemical property of 1D nanostructured manganese oxide. PMID:18047111

  18. Highly efficient oxidation of alcohols catalyzed by a porphyrin-inspired manganese complex.

    PubMed

    Dai, Wen; Lv, Ying; Wang, Lianyue; Shang, Sensen; Chen, Bo; Li, Guosong; Gao, Shuang

    2015-06-30

    A novel strategy for catalytic oxidation of a variety of benzylic, allylic, propargylic, and aliphatic alcohols to the corresponding aldehydes or ketones by an in situ formed porphyrin-inspired manganese complex in excellent yields (up to 99%) has been successfully developed. PMID:26081898

  19. Chemical synthesis of oriented ferromagnetic LaSr-2 × 4 manganese oxide molecular sieve nanowires.

    PubMed

    Carretero-Genevrier, Adrián; Gazquez, Jaume; Magén, César; Varela, María; Ferain, Etienne; Puig, Teresa; Mestres, Narcís; Obradors, Xavier

    2012-06-25

    We report a chemical solution based method using nanoporous track-etched polymer templates for producing long and oriented LaSr-2 × 4 manganese oxide molecular sieve nanowires. Scanning transmission electron microscopy and electron energy loss spectroscopy analyses show that the nanowires are ferromagnetic at room temperature, single crystalline, epitaxially grown and self-aligned. PMID:22576968

  20. Determining the Oxidation States of Manganese in NT2 Cells and Cultured Astrocytes

    SciTech Connect

    Gunter,K.; Aschner, M.; Miller, L.; Eliseev, R.; Salter, J.; Andersen, K.; Gunter, T.

    2006-01-01

    Excessive brain manganese (Mn) can produce a syndrome called 'manganism', which correlates with loss of striatal dopamine and cell death in the striatum and globus pallidus. The prevalent hypothesis for the cause of this syndrome has been oxidation of cell components by the strong oxidizing agent, Mn{sup 3+}, either formed by oxidation of intracellular Mn{sup 2+} or transported into the cell as Mn{sup 3+}. We have recently used X-ray absorption near edge structure spectroscopy (XANES) to determine the oxidation states of manganese complexes in brain and liver mitochondria and in nerve growth factor (NGF)-induced and non-induced PC12 cells. No evidence was found for stabilization or accumulation of Mn{sup 3+} complexes because of oxidation of Mn{sup 2+} by reactive oxygen species in these tissues. Here we extend these studies of manganese oxidation state to cells of brain origin, human neuroteratocarcinoma (NT2) cells and primary cultures of rat astrocytes. Again we find no evidence for stabilization or accumulation of any Mn{sup 3+} complex derived from oxidation of Mn{sup 2+} under a range of conditions.

  1. Manganese deposits on Mars suggest a highly oxidized past

    NASA Astrophysics Data System (ADS)

    Rosen, Julia

    2014-11-01

    As the Curiosity rover picks its way across the Martian surface, sampling rocks and snapping photos, it searches for signs that the dusty craters and ridges under its treads may once have supported life or, at least, that they might have been habitable. Now, using measurements of manganese abundances in Martian rocks, Lanza et al. provide new evidence that Mars may have hosted liquid water and a more strongly oxygenated atmosphere at some point in its past.

  2. Environmental Factors Affecting Oxidation of Manganese in Pinal Creek, Arizona

    Microsoft Academic Search

    Justin C. Marble; Timothy L. Corley; Martha H. Conklin; Christopher C. Fuller

    The objectives of the laboratory work reported here were to quantify the net rates of removal of manganese (Mn(II)) by streambed sediments collected from a metals contaminated, perennial stream system (Pinal Creek near Globe AZ) and to determine the key variable(s) responsible for the limited removal of Mn(II) observed at this field site. Pinal Creek is characterized by significant spatial

  3. Manganese oxide/graphene aerogel composites as an outstanding supercapacitor electrode material.

    PubMed

    Wang, Chun-Chieh; Chen, Hsuan-Ching; Lu, Shih-Yuan

    2014-01-01

    Graphene aerogels (GA), prepared with an organic sol-gel process, possessing a high specific surface area of 793?m(2) ?g(-1) , a high pore volume of 3?cm(3) ?g(-1) , and a large average pore size of 17?nm, were applied as a support for manganese oxide for supercapacitor applications. The manganese oxide was electrochemically deposited into the highly porous GA to form MnO2 /GA composites. The composites, at a high manganese oxide loading of 61?wt.?%, exhibited a high specific capacitance of 410?F?g(-1) at 2?mV?s(-1) . More importantly, the high rate specific capacitances measured at 1000?mV?s(-1) for these composites were two-fold higher than those obtained with samples prepared in the absence of the GA support. The specific capacitance retention ratio, based on the specific capacitance obtained at 25?mV?s(-1) , was maintained high, at 85?%, even at the high scan rate of 1000?mV?s(-1) , in contrast with the significantly lower value of 67?% for the plain manganese oxide sample. For the cycling stability, the specific capacitance of the composite electrode decayed by only 5?% after 50,000 cycles at 1000?mV?s(-1) . The success of this MnO2 /GA composite may be attributed to the structural advantages of high specific surface areas, high pore volumes, large pore sizes, and three-dimensionally well-connected network of the GA support. These structural advantages made possible the high mass loading of the active material, manganese oxide, large amounts of electroactive surfaces for the superficial redox events, fast mass-transfer within the porous structure, and well-connected conductive paths for the involved charge transport. PMID:24327570

  4. Ozone decomposition and benzene oxidation catalysts based on iron and manganese oxides as industrial wastes from water decontamination by ozone treatment

    Microsoft Academic Search

    L. A. Zaloznaya; S. N. Tkachenko; G. V. Egorova; I. S. Tkachenko; A. V. Sobolev; E. Z. Golosman; V. A. Troshina; V. V. Lunin

    2009-01-01

    Effective ozone decomposition catalysts were created on the basis of iron oxides as side products from natural water treated\\u000a with ozone at water treatment plants. Iron oxide catalysts doped with manganese oxide are by 40% more active in benzene oxidation.\\u000a These iron-manganese catalysts can be recommended for industrial manufacture by the designed technologies and application\\u000a in ozone decomposition and benzene

  5. Phase relations in the MgO-La 2 O 3 -manganese oxides system

    Microsoft Academic Search

    L. L. Surat; B. V. Slobodin; E. V. Vladimirova

    2000-01-01

    In this paper we report a study of the composition and phase relations in the MgO-La203-manganese oxides system, which continues the investigations of oxide systems in which perovskite-like manganites Lal _~VI~MnO3 (M is a bivalent metal) with giant magnetic resistance (GMR) are formed [1-4]. The unusual electrophysical properties of magnesium-containing manganites generate a need for comprehensive investigations into the chemistry

  6. Thermally stable multicomponent manganese catalyst for the deep oxidation of methane to CO 2

    Microsoft Academic Search

    N. M. Popova; K. D. Dosumov; Z. T. Zheksenbaeva; L. V. Komashko; V. P. Grigor’eva; A. S. Sass; R. Kh. Salakhova

    2006-01-01

    A thermally stable manganese oxide catalyst for the deep oxidation of lean CH4 mixtures with air to CO2 was developed and characterized. To prepare this catalyst, new approaches to the synthesis of polyoxide catalysts based on\\u000a Mn modified with La, Ce, Ba, and Sr by supporting them from nitrate solutions onto alumina granules stabilized with 2% Ce\\u000a were used. The

  7. Preparation and characterization of polyaniline\\/manganese dioxide composites via oxidative polymerization: Effect of acids

    Microsoft Academic Search

    Ali H. Gemeay; Ikhlas A. Mansour; Rehab G. El-Sharkawy; Ahmed B. Zaki

    2005-01-01

    Polyaniline\\/manganese dioxide (PANI\\/MnO2) composites have been chemically prepared by oxidative polymerization of aniline in acidic medium containing MnO2 as an oxidant. The acids used were; H2SO4, HNO3, HCl, and H3PO4 The prepared composites were characterized by SEM, elemental analysis, FT-IR, XRD, TGA, and magnetic susceptibility. XRD measurements of the composites revealed that the crystal structure of incorporated MnO2 undergone a

  8. The Association of Cobalt with Iron and Manganese (Oxyhydr)oxides in Marine Sediment

    Microsoft Academic Search

    Anthony Stockdale; William Davison; Hao Zhang; John Hamilton-Taylor

    2010-01-01

    Formation and dissolution of authigenic Fe and Mn (oxyhydr)oxides influence cycling of trace metals in oxic\\/suboxic surface\\u000a sediments. We used the diffusive gradients in thin films technique (DGT) to estimate the association of cobalt with iron and\\u000a manganese oxides. We compared Co, Fe and Mn maxima measured by DGT in the pore waters of fresh and aged marine sediment cores

  9. Facile oxidative decarboxylation of 3,4-dihydroxyphenylacetic acid catalyzed by copper and manganese ions

    Microsoft Academic Search

    Ivan N. Mefford; Laurel Kincl; Kevin H. Dykstra; John T. Simpson; Sanford P. Markey; Susanne Dietz; R. Mark Wightman

    1996-01-01

    Under physiological conditions, we observed the rapid, pH- and temperature-dependent, oxidative decarboxylation and hydration of 3,4-dihydroxyphenylacetic acid (DOPAC) to form 3,4-dihydroxyphenyl alcohol (DBAlc). This product was oxidized and underwent tautomerization to form 3,4-dihydroxybenzaldehyde (DBAld). This reaction did not occur in the presence of EDTA, was catalyzed by copper (CuI, CuII) and manganese (MnII) and was oxygen dependent. A variety of

  10. Endowing manganese oxide with fast adsorption ability through controlling the manganese carbonate precursor assembled in ionic liquid.

    PubMed

    Ge, X; Gu, C D; Wang, X L; Tu, J P

    2015-01-15

    Manganese oxides with desired structure are controllably obtained through annealing MnCO3 precursors with required structures. The structures of MnCO3 precursors are determined by a "mesocrystal formation" process in an ionic liquid system of a choline chloride/urea (CU) mixture. Without addition of surfactants, only CU solvent and manganese chloride are needed in the reaction system, in which the CU acts as reaction medium as well as control agent for particle growth. A shape transformation of MnCO3 particles from well-defined rhombohedral mesocrystals to ellipsoidal polycrystal ensembles, and to nanoparticulate aggregates is observed when heating the reaction system for 4 h at 120, 150, and 180 °C, respectively. With a longer aging time at 120 °C, etching and disassembly of MnCO3 mesocrystals happened. The correlation between the microstructure and the underlying formation mechanism is highlighted. Porous and nanowire-like MnO(x) nanostructures are obtained through a facile thermal conversion process from the diverse MnCO3 precursors, which are demonstrated as effective and efficient adsorbents to remove organic waste (e.g. Congo red) from water. Significantly, the nanowire-like MnO(x) nanostructures obtained by annealing the MnCO3 mesocrystals at 300 °C for 4 h can remove about 95% Congo red in waste water at room temperature in only one minute, which is superior to the reported hierarchical hollow nanostructured MnO2. PMID:25454437

  11. Oxidation of volatile organic compounds on SBA-15 mesoporous molecular sieves modified with manganese.

    PubMed

    Orlov, Alexander; Klinowski, Jacek

    2009-01-01

    Catalytic combustion of volatile organic compounds, such as propene, has been studied on manganese modified mesoporous molecular sieves. Powder X-ray diffraction, (29)Si nuclear magnetic resonance, nitrogen sorption and transmission electron microscopy show that the SBA-15 mesoporous silica molecular sieve can be modified with manganese using Mn(2)(CO)(10) or Mn(O(2)CMe)(2) without significant distortion of the host structure. The two products were catalytically active in propene oxidation, with SBA-15 modified with Mn(2)(CO)(10) showing significantly higher activity, possibly due to higher Mn content, than SBA-15 modified with Mn(O(2)CMe)(2). PMID:18977012

  12. The oxidative dechlorination reaction of 2,4,6-trichlorophenol in dilute aqueous suspensions of manganese oxides

    SciTech Connect

    Ukrainczyk, L.; McBride, M.B. (Cornell Univ., Ithaca, NY (United States). Dept. of Soil, Crop and Atmospheric Sciences)

    1993-11-01

    Oxidation of 2,4,6-trichlorophenol (TCP) by layered manganese oxides (Na and Co-buserite) in dilute acidified aqueous suspension gives 2,6-dichloro-p-benzoquinone as a major product. This compound is likely to further polymerize and become incorporated into humus like materials. The oxidation rate was higher at lower pH and higher on Na-buserite compared to Co-buserite. TCP reacted at a faster rate than unsubstituted phenol at pH3 and 5.5, which is explained by (a) the lower half-wave potential of TCP compared to phenol; (b) a stronger bond dipole associated with the electronegative halogen, favoring an addition step in nucleophilic substitution; and (c) easier depronation of TCP at the manganese oxide-water interface due to its lower pK[sub a]. IR spectroscopy shows that TCP adsorbs in deprotonated form on the surface of manganese oxide, and it cannot be washed from the surface by water. Nucleophilic attack by addition-elimination is suggested as a mechanism of TCP dechlorination and oxidation.

  13. An Electrochemical Sensor Based on Nanostructured Hollandite-type Manganese Oxide for Detection of Potassium Ions

    PubMed Central

    Lima, Alex S.; Bocchi, Nerilso; Gomes, Homero M.; Teixeira, Marcos F. S.

    2009-01-01

    The participation of cations in redox reactions of manganese oxides provides an opportunity for development of chemical sensors for non-electroactive ions. A sensor based on a nanostructured hollandite-type manganese oxide was investigated for voltammetric detection of potassium ions. The detection is based on the measurement of anodic current generated by oxidation of Mn(III) to Mn(IV) at the surface of the electrode and the subsequent extraction of the potassium ions into the hollandite structure. In this work, an amperometric procedure at an operating potential of 0.80 V (versus SCE) is exploited for amperometric monitoring. The current signals are linearly proportional to potassium ion concentration in the range 4.97 × 10?5 to 9.05 × 10?4 mol L?1, with a correlation coefficient of 0.9997. PMID:22399969

  14. Manganese neurotoxicity.

    PubMed

    Dobson, Allison W; Erikson, Keith M; Aschner, Michael

    2004-03-01

    Manganese is an essential trace element and it is required for many ubiquitous enzymatic reactions. While manganese deficiency rarely occurs in humans, manganese toxicity is known to occur in certain occupational settings through inhalation of manganese-containing dust. The brain is particularly susceptible to this excess manganese, and accumulation there can cause a neurodegenerative disorder known as manganism. Characteristics of this disease are described as Parkinson-like symptoms. The similarities between the two disorders can be partially explained by the fact that the basal ganglia accumulate most of the excess manganese compared with other brain regions in manganism, and dysfunction in the basal ganglia is also the etiology of Parkinson's disease. It has been proposed that populations already at heightened risk for neurodegeneration may also be more susceptible to manganese neurotoxicity, which highlights the importance of investigating the human health effects of using the controversial compound, methylcyclopentadienyl manganese tricarbonyl (MMT), in gasoline to increase octane. The mechanisms by which increased manganese levels can cause neuronal dysfunction and death are yet to be elucidated. However, oxidative stress generated through mitochondrial perturbation may be a key event in the demise of the affected central nervous system cells. Our studies with primary astrocyte cultures have revealed that they are a critical component in the battery of defenses against manganese-induced neurotoxicity. Additionally, evidence for the role of oxidative stress in the progression of manganism is reviewed here. PMID:15105259

  15. The effect of zirconium oxide and quartz pigments on the heat and corrosion resistance properties of the silicone based coatings

    Microsoft Academic Search

    L. Mathivanan; A. K. Arof

    2000-01-01

    Silicone resin based protective coatings are generally used for high temperature applications. In this work, anti-corrosive and heat resistant properties of titanium dioxide, mica, zirconium oxide and quartz combination pigments with silicone resin as carrier vehicle in primer and top coat for mild steel surface have been evaluated. Promising results were obtained, showing that the ceramic pigments (zirconium oxide and

  16. Electroless preparation and ASAXS microstructural analysis of pseudocapacitive carbon manganese oxide supercapacitor electrodes.

    PubMed

    Weber, Christian; Reichenauer, Gudrun; Pflaum, Jens

    2015-01-20

    Anomalous small angle X-ray scattering (ASAXS) has been utilized as a noninvasive, integral tool to access the structural properties of carbon xerogel-manganese oxide electrodes with nanometer resolution. As these electrodes constitute the elementary functional units in supercapacitors and as their microstructure governs the macroscopic electrical performance, it is essential to gain a detailed morphological understanding of the underlying carbon particle scaffold coated with manganese oxide. We demonstrate that, in this regard, ASAXS provides a powerful technique and in combination with a theoretical core-shell model enables a quantitative estimation of the relevant structural parameters. As a result, we determined the thicknesses of the solution deposited MnO2 shells to range between 3 and 26 nm depending on the carbon particle size and thus on their effective surface area. By our core-shell modeling we conclude the revealed manganese oxide coatings on the carbon support to be rather thick, but nevertheless to show a high uniformity in thickness. At 1.8 ± 0.2 to 2.2 ± 0.1 g/cm(3) the related effective MnO2 densities of the shells are about 30% lower than the corresponding bulk density of 3.0 g/cm(3). This mainly originates from a substructure within the shell, whose growth is controlled by a pronounced reduction of the manganese precursor during layer formation. Finally, the presented ASAXS data are complemented by SEM and N2 sorption measurements, proving not only qualitatively the proposed flake-like MnO2 surface morphology but also confirming quantitatively the manganese shell thickness, complementary, on a local scale. PMID:25453192

  17. Redox-responsive degradable honeycomb manganese oxide nanostructures as effective nanocarriers for intracellular glutathione-triggered drug release.

    PubMed

    He, Dinggeng; He, Xiaoxiao; Wang, Kemin; Yang, Xue; Yang, Xiaoxiao; Zou, Zhen; Li, Xuecai

    2015-01-14

    Redox-responsive degradable honeycomb manganese oxide (hMnO2) nanostructures consisting of some lamellar MnO2 platelets were established as a new class of drug carriers for intracellular glutathione-triggered drug release. PMID:25421350

  18. Searching for biosignatures using electron paramagnetic resonance (EPR) analysis of manganese oxides.

    PubMed

    Kim, Soon Sam; Bargar, John R; Nealson, Kenneth H; Flood, Beverly E; Kirschvink, Joseph L; Raub, Timothy D; Tebo, Bradley M; Villalobos, Mario

    2011-10-01

    Manganese oxide (Mn oxide) minerals from bacterial sources produce electron paramagnetic resonance (EPR) spectral signatures that are mostly distinct from those of synthetic simulants and abiogenic mineral Mn oxides. Biogenic Mn oxides exhibit only narrow EPR spectral linewidths (?500 G), whereas abiogenic Mn oxides produce spectral linewidths that are 2-6 times broader and range from 1200 to 3000 G. This distinction is consistent with X-ray structural observations that biogenic Mn oxides have abundant layer site vacancies and edge terminations and are mostly of single ionic species [i.e., Mn(IV)], all of which favor narrow EPR linewidths. In contrast, abiogenic Mn oxides have fewer lattice vacancies, larger particle sizes, and mixed ionic species [Mn(III) and Mn(IV)], which lead to the broader linewidths. These properties could be utilized in the search for extraterrestrial physicochemical biosignatures, for example, on Mars missions that include a miniature version of an EPR spectrometer. PMID:21970705

  19. Calorimetric study on NH 3 insertion reaction into microporous manganese oxides with (2×2) tunnel and (2×?) layered structures

    Microsoft Academic Search

    Z.-M. Wang; H. Kanoh

    2001-01-01

    NH3 insertion mechanism into the (2×2) tunnel structure of a hollandite-type manganese oxide (H-Hol) and the (2×?) layered structure of a birnessite-type manganese oxide (H-Bir) were studied by direct adsorption calorimetry. It was found that H-Bir has a smaller NH3 adsorption enthalpy (??Hd,NH3) compared to H-Hol because of the structural flexibility of its MnO sheets. NH3 insertion into the tunnel

  20. Manganese oxide/carbon yolk-shell nanorod anodes for high capacity lithium batteries.

    PubMed

    Cai, Zhengyang; Xu, Lin; Yan, Mengyu; Han, Chunhua; He, Liang; Hercule, Kalele Mulonda; Niu, Chaojiang; Yuan, Zefan; Xu, Wangwang; Qu, Longbing; Zhao, Kangning; Mai, Liqiang

    2015-01-14

    Transition metal oxides have attracted much interest for their high energy density in lithium batteries. However, the fast capacity fading and the low power density still limit their practical implementation. In order to overcome these challenges, one-dimensional yolk-shell nanorods have been successfully constructed using manganese oxide as an example through a facile two-step sol-gel coating method. Dopamine and tetraethoxysilane are used as precursors to obtain uniform polymer coating and silica layer followed by converting into carbon shell and hollow space, respectively. As anode material for lithium batteries, the manganese oxide/carbon yolk-shell nanorod electrode has a reversible capacity of 660 mAh/g for initial cycle at 100 mA/g and exhibits excellent cyclability with a capacity of 634 mAh/g after 900 cycles at a current density of 500 mA/g. An enhanced capacity is observed during the long-term cycling process, which may be attributed to the structural integrity, the stability of solid electrolyte interphase layer, and the electrochemical actuation of the yolk-shell nanorod structure. The results demonstrate that the manganese oxide is well utilized with the one-dimensional yolk-shell structure, which represents an efficient way to realize excellent performance for practical applications. PMID:25490409

  1. Protective role of silymarin against manganese-induced nephrotoxicity and oxidative stress in rat.

    PubMed

    Chtourou, Yassine; Garoui, El mouldi; Boudawara, Tahia; Zeghal, Najiba

    2014-10-01

    Metal toxicity may occur after exposure from many sources. Oxidative stress is thought to be involved in manganese-induced toxicity and leads to various health disorders. Silymarin (SIL), a natural flavonoid, has been reported to have many benefits and medicinal properties. The aim of this study was to assess the toxicity of manganese (Mn) on oxidative stress and DNA damage in the kidney of rats and its alleviation by SIL. Manganese was given orally in drinking water (20 mg MnCl2 /mL) with or without SIL administration (100 mg /kg intraperitoneally) for 30 days. Our data showed that SIL significantly prevented Mn induced nephrotoxicity, indicated by both diagnostic indicators of kidney injury like plasma urea, uric acid and creatinine and urinary electrolyte levels and by histopathological analysis. Moreover, Mn-induced profound elevation of the production of reactive oxygen species (ROS) and altered the levels of oxidative stress related biomarkers in kidney tissue. This is evidenced by the increase of lipid peroxidation, protein carbonylation, DNA fragmentation and urinary hydrogen peroxide, while, the activities of enzymatic antioxidant and glutathione level were decreased. Treatment with SIL reduced the alterations in the renal and urine markers, decreasing lipid peroxidation markers, increasing the antioxidant cascade and decreasing the Mn-induced damage. All these changes were supported by histopathological observations. These findings suggested that the inhibition of Mn-induced damage by SIL was due at least in part to its antioxidant activity and its capacity to modulate the oxidative damage. PMID:23339144

  2. Iron-manganese binary oxide coated functionalized multiwalled carbon nanotubes for arsenic removal

    NASA Astrophysics Data System (ADS)

    Tamilarasan, P.; Ramaprabhu, S.

    2012-06-01

    In the present study, we report, iron-manganese based amorphous binary oxide coated functionalized multiwalled carbon nanotubes (f-MWNTs) as an efficient adsorbent for arsenic removal. The Fe-Mn binary oxide/f-MWNTs (FeMn/f-MWNT) has been synthesized by co-precipitation of both oxides in the presence of f-MWNTs and characterized. The arsenic (both arsenate and arsenite) adsorption capacity of the nanocomposite has been studied by batch adsorption method at pH around 7. Langmuir and Elovich equations were used to extract the isotherm and kinetic constants, respectively. This nanocomposite shows fast adsorption kinetics and high adsorption capacity.

  3. Regulating proton-coupled electron transfer for efficient water splitting by manganese oxides at neutral pH

    PubMed Central

    Yamaguchi, Akira; Inuzuka, Riko; Takashima, Toshihiro; Hayashi, Toru; Hashimoto, Kazuhito; Nakamura, Ryuhei

    2014-01-01

    Manganese oxides have been extensively investigated as model systems for the oxygen-evolving complex of photosystem II. However, most bioinspired catalysts are inefficient at neutral pH and functional similarity to the oxygen-evolving complex has been rarely achieved with manganese. Here we report the regulation of proton-coupled electron transfer involved in water oxidation by manganese oxides. Pyridine and its derivatives, which have pKa values intermediate to the water ligand bound to manganese(II) and manganese(III), are used as proton-coupled electron transfer induction reagents. The induction of concerted proton-coupled electron transfer is demonstrated by the detection of deuterium kinetic isotope effects and compliance of the reactions with the libido rule. Although proton-coupled electron transfer regulation is essential for the facial redox change of manganese in photosystem II, most manganese oxides impair these regulatory mechanisms. Thus, the present findings may provide a new design rationale for functional analogues of the oxygen-evolving complex for efficient water splitting at neutral pH. PMID:24977746

  4. Regulating proton-coupled electron transfer for efficient water splitting by manganese oxides at neutral pH

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Akira; Inuzuka, Riko; Takashima, Toshihiro; Hayashi, Toru; Hashimoto, Kazuhito; Nakamura, Ryuhei

    2014-06-01

    Manganese oxides have been extensively investigated as model systems for the oxygen-evolving complex of photosystem II. However, most bioinspired catalysts are inefficient at neutral pH and functional similarity to the oxygen-evolving complex has been rarely achieved with manganese. Here we report the regulation of proton-coupled electron transfer involved in water oxidation by manganese oxides. Pyridine and its derivatives, which have pKa values intermediate to the water ligand bound to manganese(II) and manganese(III), are used as proton-coupled electron transfer induction reagents. The induction of concerted proton-coupled electron transfer is demonstrated by the detection of deuterium kinetic isotope effects and compliance of the reactions with the libido rule. Although proton-coupled electron transfer regulation is essential for the facial redox change of manganese in photosystem II, most manganese oxides impair these regulatory mechanisms. Thus, the present findings may provide a new design rationale for functional analogues of the oxygen-evolving complex for efficient water splitting at neutral pH.

  5. Low-temperature, manganese oxide-based, thermochemical water splitting cycle

    PubMed Central

    Xu, Bingjun; Bhawe, Yashodhan; Davis, Mark E.

    2012-01-01

    Thermochemical cycles that split water into stoichiometric amounts of hydrogen and oxygen below 1,000?°C, and do not involve toxic or corrosive intermediates, are highly desirable because they can convert heat into chemical energy in the form of hydrogen. We report a manganese-based thermochemical cycle with a highest operating temperature of 850?°C that is completely recyclable and does not involve toxic or corrosive components. The thermochemical cycle utilizes redox reactions of Mn(II)/Mn(III) oxides. The shuttling of Na+ into and out of the manganese oxides in the hydrogen and oxygen evolution steps, respectively, provides the key thermodynamic driving forces and allows for the cycle to be closed at temperatures below 1,000?°C. The production of hydrogen and oxygen is fully reproducible for at least five cycles. PMID:22647608

  6. Three oxidation states and atomic-scale p–n junctions in manganese perovskite oxide from hydrothermal systems

    Microsoft Academic Search

    Shouhua Feng; Hongming Yuan; Zhan Shi; Yan Chen; Yongwei Wang; Keke Huang; Changmin Hou; Jixue Li; Guangsheng Pang; Ying Hou

    2008-01-01

    Perovskite oxides have provided magical structural models for superconducting and colossal magnetoresistance, and the search\\u000a for nano-scale and\\/or atomic-scale devices with particular property by specific preparations in the same systems has been\\u000a extensively conducted. We present here the three oxidation states of manganese (Mn3+, Mn4+, Mn5+) in the perovskite oxide, La0.66Ca0.29K0.05MnO3, which most interestingly shows the rectifying effect as atomic-scale

  7. Determination of methylcyclopentadienyl-manganese tricarbonyl by solid phase microextraction-direct thermal desorption-quartz furnace atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Fragueiro, María. Sandra; Alava-Moreno, Fausto; Lavilla, Isela; Bendicho, Carlos

    2001-02-01

    A new procedure that uses a pre-concentration system based on solid phase microextraction (SPME) and detection by quartz furnace-atomic absorption spectrometry after thermal desorption from the microextraction fiber has been proposed for the determination of methylcyclopentadienylmanganese tricarbonyl (MMT) in gasoline and water. Working MMT solutions were prepared in 40 ml amber vials, and sampling was performed by exposing the SPME fiber to the headspace over vigorously stirred samples for 15 min. The analytical performance characteristics of the proposed procedure were as follows: the detection limit for MMT was 0.71 ng ml -1 (as Mn), with a relative standard deviation of 4% for MMT determination of 25 ng ml -1 (as Mn, n=6) while the calibration curve was linear up to 100 ng ml -1 range. The proposed procedure was finally applied to the determination of MMT in gasoline and water samples and non significant differences (Student's t-test) were found between obtained values (using direct calibration and standard additions) and those expected values.

  8. Sorption of lead ions on diatomite and manganese oxides modified diatomite

    Microsoft Academic Search

    Y Al-Degs; M. A. M Khraisheh; M. F Tutunji

    2001-01-01

    Naturally occurring diatomaceous earth (diatomite) has been tested as a potential sorbent for Pb(II) ions. The intrinsic exchange properties were further improved by modification with manganese oxides. Modified adsorbent (referred to as Mn-diatomite) showed a higher tendency for adsorbing lead ions from solution at pH 4. The high performance exhibited by Mn-diatomite was attributed to increased surface area and higher

  9. Catalytic ozonation of fenofibric acid over alumina-supported manganese oxide

    Microsoft Academic Search

    Roberto Rosal; María S. Gonzalo; Antonio Rodríguez; Eloy García-Calvo

    2010-01-01

    The catalytic ozonation of fenofibric acid was studied using activated alumina and alumina-supported manganese oxide in a semicontinuous reactor. The rate constants at 20°C for the non-catalytic reaction of fenofibric acid with ozone and hydroxyl radicals were 3.43±0.20M?1s?1 and (6.55±0.33)×109M?1s?1, respectively. The kinetic constant for the catalytic reaction between fenofibric acid and hydroxyl radicals did not differ significantly from that

  10. Improved lithium manganese oxide spinel\\/graphite Li-ion cells for high-power applications

    Microsoft Academic Search

    K Amine; J Liu; S Kang; I Belharouak; Y Hyung; D Vissers; G Henriksen

    2004-01-01

    The degradation mechanism of lithium manganese oxide spinel\\/graphite Li-ion cells using LiPF6-based electrolyte was investigated by a Mn-dissolution approach during high-temperature storage, and by ac impedance measurement using a reference electrode-equipped cell. Through these studies, we confirmed that Mn ions were dissolved from the spinel cathode in the electrolyte and were subsequently reduced on the lithiated graphite electrode surface, due

  11. Controlled synthesis and characterization of layered manganese oxide nanostructures with different morphologies

    Microsoft Academic Search

    Naicai Xu; Zong-Huai Liu; Xiangrong Ma; Shanfeng Qiao; Jiaqi Yuan

    2009-01-01

    Layered manganese oxide nanostructures with different morphologies, such as nanowire bundles, cotton agglomerates, and platelikes\\u000a were successfully fabricated by a simple and template-free hydrothermal method based on a reaction of KMnO4 and KOH solutions with different concentrations. The obtained nanowire bundles were assembled by nanowires with diameters\\u000a of 10 to 200 nm and lengths up to 5–10 ?m. The cotton agglomerates were

  12. Effects of thickness and electrolytes on the capacitive characteristics of anodically deposited hydrous manganese oxide coatings

    Microsoft Academic Search

    Mengqiang Wu; Liping Zhang; Jiahui Gao; Chao Xiao; Dongmei Wang; Ai Chen; Shuren Zhang

    2008-01-01

    An amorphous nanostructured hydrous manganese oxide (MnO2·nH2O) coating was anodically deposited onto a graphite substrate from an aqueous MnSO4 solution. Various deposition charges were employed to achieve different coating thickness. The capacitive characteristics of the as-grown MnO2 coatings were evaluated in various neutral alkali metal chloride solutions by cyclic voltammetry and chronopotentiometry. The as-grown MnO2 coatings exhibited a capacitance of

  13. Overexpression of Manganese Superoxide Dismutase Protects Lung Epithelial Cells against Oxidant Injury

    Microsoft Academic Search

    Anatoliy M. Ilizarov; Hshi-Chi Koo; Jeffrey A. Kazzaz; Lin L. Mantell; Yuchi Li; Ritu Bhapat; Simcha Pollack; Stuart Horowitz; Jonathan M. Davis

    To determine whether overexpression of antioxidant enzymes in lung epithelial cells prevents damage from oxidant injury, stable cell lines were generated with complementary DNAs en- coding manganese superoxide dismutase (MnSOD) and\\/or catalase (CAT). Cell lines overexpressing MnSOD, CAT, or Mn- SOD 1 CAT were assessed for tolerance to hyperoxia or para- quat. After exposure to 95% O 2 for 10

  14. Bioaccumulation of Manganese and Its Toxicity in Feral Pigeons ( Columba livia) Exposed to Manganese Oxide Dust (Mn 3O 4)

    Microsoft Academic Search

    P. Sierra; S. Chakrabarti; R. Tounkara; S. Loranger; G. Kennedy; J. Zayed

    1998-01-01

    Manganese tetroxide (Mn3O4) is a product from the combustion of methylcyclopentadienyl manganese tricarbonyl. Exposure to high levels of manganese can lead to serious health effects especially to the central nervous and respiratory systems. Very few studies on the effects of long-term low level exposure to Mn3O4have been reported. The present study was therefore conducted to examine the bioaccumulation and toxicity

  15. Effect of enhanced manganese oxidation in the hyporheic zone on basin-scale geochemical mass balance

    USGS Publications Warehouse

    Harvey, J.W.; Fuller, C.C.

    1998-01-01

    We determined the role of the hyporheic zone (the subsurface zone where stream water and shallow groundwater mix) in enhancing microbially mediated oxidation of dissolved manganese (to form manganese precipitates) in a drainage basin contaminated by copper mining. The fate of manganese is of overall importance to water quality in Pinal Creek Basin, Arizona, because manganese reactions affect the transport of trace metals. The basin-scale role of the hyporheic zone is difficult to quantify because stream-tracer studies do not always reliably characterize the cumulative effects of the hyporheic zone. This study determined cumulative effects of hyporheic reactions in Pinal Creek basin by characterizing manganese uptake at several spatial scales (stream-reach scale, hyporheicflow-path scale, and sediment-grain scale). At the stream-reach scale a one-dimensional stream-transport model (including storage zones to represent hyporheic flow paths) was used to determine a reach-averaged time constant for manganese uptake in hyporheic zones, 1/??(s), of 1.3 hours, which was somewhat faster but still similar to manganese uptake time constants that were measured directly in centimeter-scale hyporheic flow paths (1/??(h) = 2.6 hours), and in laboratory batch experiments using streambed sediment (1/?? = 2.7 hours). The modeled depths of subsurface storage zones (d(s) = 4-17 cm) and modeled residence times of water in storage zones (t(s) = 3-12 min) were both consistent with direct measurements in hyporheic flow paths (d(h) = 0-15 cm, and t(h) = 1-25 min). There was also good agreement between reach-scale modeling and direct measurements of the percentage removal of dissolved manganese in hyporheic flow paths (f(s) = 8.9%, and f(h) = 9.3%). Manganese uptake experiments in the laboratory using sediment from Pinal Creek demonstrated (through comparison of poisoned and unpoisoned treatments) that the manganese removal process was enhanced by microbially mediated oxidation. The cumulative effect of hyporheic exchange in Pinal Creek basin was to remove approximately 20% of the dissolved manganese flowing out of the drainage basin. Our results illustrate that the cumulative significance of reactive uptake in the hyporheic zone depends on the balance between chemical reaction rates, hyporheic porewater residence time, and turnover of streamflow through hyporheic flow paths. The similarity between the hyporheic reaction timescale (1??(s) ??? 1.3 hours), and the hyporheic porewater residence timescale (t(s) ??? 8 min) ensured that there was adequate time for the reaction to progress. Furthermore, it was the similarity between the turnover length for stream water flow through hyporheic flow paths (L(s) = stream velocity/storage-zone exchange coefficient ??? 1.3 km) and the length of Pinal Creek (L ??? 7 km), which ensured that all stream water passed through hyporheic flow paths several times. As a means to generalize our findings to other sites where similar types of hydrologic and chemical information are available, we suggest a cumulative significance index for hyporheic reactions, R(s) = ??(s)t(s)L/L(s) (dimensionless); higher values indicate a greater potential for hyporheic reactions to influence geochemical mass balance. Our experience in Pinal Creek basin suggests that values of R(s) > 0.2 characterize systems where hyporheic reactions are likely to influence geochemical mass balance at the drainage-basin scale.

  16. Manganese (Mn) Oxidation Increases Intracellular Mn in Pseudomonas putida GB-1

    PubMed Central

    Banh, Andy; Chavez, Valarie; Doi, Julia; Nguyen, Allison; Hernandez, Sophia; Ha, Vu; Jimenez, Peter; Espinoza, Fernanda; Johnson, Hope A.

    2013-01-01

    Bacterial manganese (Mn) oxidation plays an important role in the global biogeochemical cycling of Mn and other compounds, and the diversity and prevalence of Mn oxidizers have been well established. Despite many hypotheses of why these bacteria may oxidize Mn, the physiological reasons remain elusive. Intracellular Mn levels were determined for Pseudomonas putida GB-1 grown in the presence or absence of Mn by inductively coupled plasma mass spectrometry (ICP-MS). Mn oxidizing wild type P. putida GB-1 had higher intracellular Mn than non Mn oxidizing mutants grown under the same conditions. P. putida GB-1 had a 5 fold increase in intracellular Mn compared to the non Mn oxidizing mutant P. putida GB-1-007 and a 59 fold increase in intracellular Mn compared to P. putida GB-1 ?2665 ?2447. The intracellular Mn is primarily associated with the less than 3 kDa fraction, suggesting it is not bound to protein. Protein oxidation levels in Mn oxidizing and non oxidizing cultures were relatively similar, yet Mn oxidation did increase survival of P. putida GB-1 when oxidatively stressed. This study is the first to link Mn oxidation to Mn homeostasis and oxidative stress protection. PMID:24147089

  17. Oxidative Transformation of Controlled Substances by Manganese Dioxide

    PubMed Central

    Lai, Webber Wei-Po; Lin, Angela Yu-Chen; Yang, Sheng-Yao; Huang, Ching-Hua

    2015-01-01

    This study investigated the oxidative transformation of four controlled substances (ketamine, methamphetamine, morphine, and codeine) by synthesized MnO2 (?-MnO2) in aqueous environments. The results indicated that ketamine and methamphetamine were negligibly oxidized by MnO2 and, thus, may be persistent in the aqueous environment. However, morphine and codeine were able to be oxidized by MnO2, which indicated that they are likely naturally attenuated in aqueous environments. Overall, lower solution pH values, lower initial compound concentrations, and higher MnO2 loading resulted in a faster reaction rate. The oxidation of morphine was inhibited in the presence of metal ions (Mn2+, Fe3+, Ca2+, and Mg2+) and fulvic acid. However, the addition of Fe3+ and fulvic acid enhanced codeine oxidation. A second-order kinetics model described the oxidation of morphine and codeine by MnO2; it suggested that the formation of a surface precursor complex between the target compound and the MnO2 surface was the rate-limiting step. Although the target compounds were degraded, the slow TOC removal indicated that several byproducts were formed and persist against further MnO2 oxidation.

  18. Enzymatic Manganese(II) Oxidation by a Marine ?-Proteobacterium

    PubMed Central

    Francis, Chris A.; Co, Edgie-Mark; Tebo, Bradley M.

    2001-01-01

    A yellow-pigmented marine bacterium, designated strain SD-21, was isolated from surface sediments of San Diego Bay, San Diego, Calif., based on its ability to oxidize soluble Mn(II) to insoluble Mn(III, IV) oxides. 16S rRNA analysis revealed that this organism was most closely related to members of the genus Erythrobacter, aerobic anoxygenic phototrophic bacteria within the ?-4 subgroup of the Proteobacteria (?-4 Proteobacteria). SD-21, however, has a number of distinguishing phenotypic features relative to Erythrobacter species, including the ability to oxidize Mn(II). During the logarithmic phase of growth, this organism produces Mn(II)-oxidizing factors of ?250 and 150 kDa that are heat labile and inhibited by both azide and o-phenanthroline, suggesting the involvement of a metalloenzyme. Although the expression of the Mn(II) oxidase was not dependent on the presence of Mn(II), higher overall growth yields were reached in cultures incubated with Mn(II) in the culture medium. In addition, the rate of Mn(II) oxidation appeared to be slower in cultures grown in the light. This is the first report of Mn(II) oxidation within the ?-4 Proteobacteria as well as the first Mn(II)-oxidizing proteins identified in a marine gram-negative bacterium. PMID:11526000

  19. Manganese oxide phases and morphologies: A study on calcination temperature and atmospheric dependence

    PubMed Central

    Fenske, Daniela; Bardenhagen, Ingo; Westphal, Anne; Knipper, Martin; Plaggenborg, Thorsten; Kolny-Olesiak, Joanna; Parisi, Jürgen

    2015-01-01

    Summary Manganese oxides are one of the most important groups of materials in energy storage science. In order to fully leverage their application potential, precise control of their properties such as particle size, surface area and Mnx + oxidation state is required. Here, Mn3O4 and Mn5O8 nanoparticles as well as mesoporous ?-Mn2O3 particles were synthesized by calcination of Mn(II) glycolate nanoparticles obtained through an economical route based on a polyol synthesis. The preparation of the different manganese oxides via one route facilitates assigning actual structure–property relationships. The oxidation process related to the different MnOx species was observed by in situ X-ray diffraction (XRD) measurements showing time- and temperature-dependent phase transformations occurring during oxidation of the Mn(II) glycolate precursor to ?-Mn2O3 via Mn3O4 and Mn5O8 in O2 atmosphere. Detailed structural and morphological investigations using transmission electron microscopy (TEM) and powder XRD revealed the dependence of the lattice constants and particle sizes of the MnOx species on the calcination temperature and the presence of an oxidizing or neutral atmosphere. Furthermore, to demonstrate the application potential of the synthesized MnOx species, we studied their catalytic activity for the oxygen reduction reaction in aprotic media. Linear sweep voltammetry revealed the best performance for the mesoporous ?-Mn2O3 species. PMID:25671151

  20. c-Type cytochromes and manganese oxidation in Pseudomonas putida MnB1

    SciTech Connect

    Caspi, R.; Tebo, B.M.; Haygood, M.G. [Univ. of California, San Diego, La Jolla, CA (United States). Scripps Institution of Oceanography

    1998-10-01

    Pseudomonas putida MnB1 is an isolate from an Mn oxide-encrusted pipeline that can oxidize Mn(II) to Mn oxides. The authors used transposon mutagenesis to construct mutants of strain MnB1 that are unable to oxidize manganese, and they characterized some of these mutants. The mutants were divided into three groups: mutants defective in the biogenesis of c-type cytochromes, mutants defective in genes that encode key enzymes of the tricarboxylic acid cycle, and mutants defective in the biosynthesis of tryptophan. The mutants in the first two groups were cytochrome c oxidase negative and did not contain c-type cytochromes. Mn(II) oxidation capability could be recovered in a c-type cytochrome biogenesis-defective mutant by complementation of the mutation.

  1. Manganese-oxidizing photosynthesis before the rise of cyanobacteria.

    PubMed

    Johnson, Jena E; Webb, Samuel M; Thomas, Katherine; Ono, Shuhei; Kirschvink, Joseph L; Fischer, Woodward W

    2013-07-01

    The emergence of oxygen-producing (oxygenic) photosynthesis fundamentally transformed our planet; however, the processes that led to the evolution of biological water splitting have remained largely unknown. To illuminate this history, we examined the behavior of the ancient Mn cycle using newly obtained scientific drill cores through an early Paleoproterozoic succession (2.415 Ga) preserved in South Africa. These strata contain substantial Mn enrichments (up to ?17 wt %) well before those associated with the rise of oxygen such as the ?2.2 Ga Kalahari Mn deposit. Using microscale X-ray spectroscopic techniques coupled to optical and electron microscopy and carbon isotope ratios, we demonstrate that the Mn is hosted exclusively in carbonate mineral phases derived from reduction of Mn oxides during diagenesis of primary sediments. Additional observations of independent proxies for O2--multiple S isotopes (measured by isotope-ratio mass spectrometry and secondary ion mass spectrometry) and redox-sensitive detrital grains--reveal that the original Mn-oxide phases were not produced by reactions with O2, which points to a different high-potential oxidant. These results show that the oxidative branch of the Mn cycle predates the rise of oxygen, and provide strong support for the hypothesis that the water-oxidizing complex of photosystem II evolved from a former transitional photosystem capable of single-electron oxidation reactions of Mn. PMID:23798417

  2. Weathering of the Rio Blanco quartz diorite, Luquillo Mountains, Puerto Rico: Coupling oxidation, dissolution, and fracturing

    USGS Publications Warehouse

    Buss, H.L.; Sak, P.B.; Webb, S.M.; Brantley, S.L.

    2008-01-01

    In the mountainous Rio Icacos watershed in northeastern Puerto Rico, quartz diorite bedrock weathers spheroidally, producing a 0.2-2 m thick zone of partially weathered rock layers (???2.5 cm thickness each) called rindlets, which form concentric layers around corestones. Spheroidal fracturing has been modeled to occur when a weathering reaction with a positive ??V of reaction builds up elastic strain energy. The rates of spheroidal fracturing and saprolite formation are therefore controlled by the rate of the weathering reaction. Chemical, petrographic, and spectroscopic evidence demonstrates that biotite oxidation is the most likely fracture-inducing reaction. This reaction occurs with an expansion in d (0 0 1) from 10.0 to 10.5 A??, forming 'altered biotite'. Progressive biotite oxidation across the rindlet zone was inferred from thin sections and gradients in K and Fe(II). Using the gradient in Fe(II) and constraints based on cosmogenic age dates, we calculated a biotite oxidation reaction rate of 8.2 ?? 10-14 mol biotite m-2 s-1. Biotite oxidation was documented within the bedrock corestone by synchrotron X-ray microprobe fluorescence imaging and XANES. X-ray microprobe images of Fe(II) and Fe(III) at 2 ??m resolution revealed that oxidized zones within individual biotite crystals are the first evidence of alteration of the otherwise unaltered corestone. Fluids entering along fractures lead to the dissolution of plagioclase within the rindlet zone. Within 7 cm surrounding the rindlet-saprolite interface, hornblende dissolves to completion at a rate of 6.3 ?? 10-13 mol hornblende m-2 s-1: the fastest reported rate of hornblende weathering in the field. This rate is consistent with laboratory-derived hornblende dissolution rates. By revealing the coupling of these mineral weathering reactions to fracturing and porosity formation we are able to describe the process by which the quartz diorite bedrock disaggregates and forms saprolite. In the corestone, biotite oxidation induces spheroidal fracturing, facilitating the influx of fluids that react with other minerals, dissolving plagioclase and chlorite, creating additional porosity, and eventually dissolving hornblende and precipitating secondary minerals. The thickness of the resultant saprolite is maintained at steady state by a positive feedback between the denudation rate and the weathering advance rate driven by the concentration of pore water O2 at the bedrock-saprolite interface. ?? 2008 Elsevier Ltd. All rights reserved.

  3. Oxidative degradation of non-phenolic lignin during lipid peroxidation by fungal manganese peroxidase.

    PubMed

    Bao, W; Fukushima, Y; Jensen, K A; Moen, M A; Hammel, K E

    1994-11-14

    A non-phenolic lignin model dimer, 1-(4-ethoxy-3-methoxyphenyl)-2-phenoxypropane-1,3-diol, was oxidized by a lipid peroxidation system that consisted of a fungal manganese peroxidase, Mn(II), and unsaturated fatty acid esters. The reaction products included 1-(4-ethoxy-3-methoxyphenyl)-1-oxo-2-phenoxy-3-hydroxypropane and 1-(4-ethoxy-3-methoxyphenyl)-1-oxo-3-hydroxypropane, indicating that substrate oxidation occurred via benzylic hydrogen abstraction. The peroxidation system depolymerized both exhaustively methylated (non-phenolic) and unmethylated (phenolic) synthetic lignins efficiently. It may therefore enable white-rot fungi to accomplish the initial delignification of wood. PMID:7957943

  4. Experimental Determination of Isotopic Fractionation of Chromium(III) During Oxidation by Manganese Oxides

    NASA Astrophysics Data System (ADS)

    Bain, D. J.; Bullen, T. D.

    2004-12-01

    In environmental conditions, chromium (Cr) exists in either the immobile, micronutrient trivalent form (Cr(III)) or the mobile, toxic hexavalent (Cr(VI)) form. Cr(VI) quickly reduces upon encountering Fe(II) or soil organic material (SOM). Therefore, it is often assumed that human Cr additions to terrestrial systems will impact localized areas and natural sources pose minimal threat to human or ecosystem health. However, oxidation and mobilization of Cr(III) by common manganese (Mn) oxides is less understood, especially in field settings. Moreover, Cr(VI)'s anionic form should enhance mobility through Fe- and SOM-poor soil and saprolite matrices. The variety of redox environments along a flowpath makes Cr source identification difficult with only concentration and speciation data. However, Cr has four stable isotopes (50, 52, 53, and 54), and characteristic fractionations during redox transformations might allow clarification of sources and flowpaths. For example, Cr(VI) reduction by a variety of reductants discriminates against heavy Cr, resulting in an increasingly heavy Cr(VI) fraction as reduction proceeds (? Cr(III)-Cr(VI) ˜ 0.996). Measurement of isotopic fractionation in other environmental Cr transformations, including oxidation, is necessary to understand Cr fate and transport. Recent estimates of isotopic fractionation between Cr aqueous species based on theoretical considerations indicate that at equilibrium ? Cr(III)-Cr(VI) ˜ 0.994. To test this theoretical prediction, we are assessing the isotopic variability of aqueous Cr during oxidation of Cr(III) on MnO2 materials such as birnessite in laboratory experiments. Initial results indicate that the isotopic composition of the product Cr(VI) ranges from -2.50 to +0.71 ‰ ? 53Cr, suggesting an important role for kinetic isotope effects during the initial oxidation process. Large fluctuations in isotopic composition continue after dissolved Cr(VI) and Cr(III) ratios stabilize and net Cr(VI) production rates are very slow. Moreover, the Cr(VI) isotopic composition fluctuates between heavy and light compositions several times over the course of reaction. Overall, however, the long term trend appears to be toward the equilibrium fractionation predicted by theory. This adds further credence to hypothesized multiple oxidation pathways existing in the system and suggests that multiple processes with off-setting fractionations are driving the system. If these results are representative of natural systems, environmental Cr samples that have been oxidized or been oxidized/reduced multiple times along a flowpath, will have isotopic compositions that vary widely, depending predominantly on sample collection time. In turn, this suggests that Cr isotopic compositions alone will not clarify Cr fate and transport, especially at larger scales (e.g., catchments), and other geochemical and hydrologic constraints will be required.

  5. Secondary cell with orthorhombic alkali metal/manganese oxide phase active cathode material

    DOEpatents

    Doeff, Marca M. (Hayward, CA); Peng, Marcus Y. (Cupertino, CA); Ma, Yanping (Albany, CA); Visco, Steven J. (Berkeley, CA); DeJonghe, Lutgard C. (Lafayette, CA)

    1996-01-01

    An alkali metal manganese oxide secondary cell is disclosed which can provide a high rate of discharge, good cycling capabilities, good stability of the cathode material, high specific energy (energy per unit of weight) and high energy density (energy per unit volume). The active material in the anode is an alkali metal and the active material in the cathode comprises an orthorhombic alkali metal manganese oxide which undergoes intercalation and deintercalation without a change in phase, resulting in a substantially linear change in voltage with change in the state of charge of the cell. The active material in the cathode is an orthorhombic structure having the formula M.sub.x Z.sub.y Mn.sub.(1-y) O.sub.2, where M is an alkali metal; Z is a metal capable of substituting for manganese in the orthorhombic structure such as iron, cobalt or titanium; x ranges from about 0.2 in the fully charged state to about 0.75 in the fully discharged state, and y ranges from 0 to 60 atomic %. Preferably, the cell is constructed with a solid electrolyte, but a liquid or gelatinous electrolyte may also be used in the cell.

  6. Transmission electron microscopy and electron energy-loss spectroscopy analysis of manganese oxide nanowires

    NASA Astrophysics Data System (ADS)

    Du, G. H.; Yuan, Z. Y.; Van Tendeloo, G.

    2005-02-01

    Single-crystalline MnOOH and Mn3O4 nanowires have been prepared by hydrothermal treatment of commercial bulky manganese oxide particles. ?-MnO2 and ?-Mn2O3 nanowires were prepared by calcination of MnOOH nanowires. Transmission electron microscopy analysis demonstrates that MnOOH nanowires grow directly from MnO2 raw particles. The diameter of the nanowires is 20-70 nm, while the length can reach several micrometers. MnOOH nanowires grow preferentially along the [010] direction and Mn3O4 nanowires prefer to grow along the [001] direction; the long dimension of both ?-MnO2 and ?-Mn2O3 nanowires is along [001]. Electron energy-loss spectroscopy analysis shows that the position of the prepeak of the oxygen K edge shifts to higher energy and the energy separation between the two main peaks of the oxygen K edge decreases with decreasing manganese oxidation state. The manganese-white-line ratios (L3/L2) were calculated.

  7. Resistive switching characteristics of manganese oxide nanoparticle assembly with crossbar arrays.

    PubMed

    Hu, Quanli; Shim, Jae Hyuk; Abbas, Yawar; Song, Woojin; Yoon, Tae-Sik; Choi, Young Jin; Kang, Chi Jung

    2014-11-01

    The fabrication of 3 x 3 crossbar arrays measuring 20 ?m in width was demonstrated. The bipolar resistive switching characteristics in manganese oxide nanoparticles were investigated in the crossbar structure of top electrode (Au)/nanoparticle assembly/bottom electrode (Ti) on SiO2/Si substrate. The monodisperse manganese oxide nanoparticles measuring 13 nm in diameter were chemically synthesized by thermal decomposition of manganese acetate in the presence of oleic acid at high temperature. The nanoparticles were assembled as a layer measuring 30 nm thick by repeated dip-coating and annealing steps. The Au/nanoparticle assembly/Ti devices performed the bipolar behavior associated with the formation and sequential rupture of multiple conducting filaments in applying bias on Au electrode. When the voltage was swept from to +5 V to the Au top electrode, the reset voltage was observed at - 4.4 V. As the applied voltage swept from 0 to -5 V, the set voltage occurred at (-) -1.8 V. PMID:25958496

  8. Electrochromic performance, wettability and optical study of copper manganese oxide thin films: Effect of annealing temperature

    NASA Astrophysics Data System (ADS)

    Falahatgar, S. S.; Ghodsi, F. E.; Tepehan, F. Z.; Tepehan, G. G.; Turhan, ?.

    2014-01-01

    In the present work, the nanostructured copper manganese oxide (CMO) thin films were prepared from acetate based sol-gel precursors and deposited on glass and indium tin oxide (ITO) substrates by dip-coating technique. The films were annealed at 300, 400 and 500 °C in ambient atmosphere. The effects of annealing temperature on structural, morphological, wettability, electrochromic and optical properties of CMO thin films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDX), water contact angle measurement (WCA), cyclic voltammetry (CV) measurements and ultraviolet-visible (UV-vis) spectrophotometery. The presence of mixed oxide phases comprising of copper manganese oxide (CuMn2O4) and manganese oxide at different annealing temperature was confirmed by XRD patterns. The results showed that the Mn3O4 phase has been changed to Mn2O3 when the annealing temperature is increased from 300 to 500 °C. The FESEM images indicated that the granular surface morphology was sensitive to annealing temperature. EDX studies indicated that the thin films contained O, Mn and Cu species. Wettability studies showed that the water contact angle of the nanostructured CMO thin films coated on glass substrates was influenced by the variation of annealing temperature and the surface nature of thin films was changed from hydrophilic to hydrophobic. The results of CVs measurement indicated that the anodic and cathodic charge density and capacitance of all CMO samples decreased with increasing scan rate in potential range of -1-1 eV. Also, the annealed CMO thin film at 500 °C showed better electrochromic performance with respect to other samples at lower scan rate. The thickness, refractive index, extinction coefficient and optical band gap of thin films coated on glass substrates were calculated from reflectance and transmittance spectra using an iterative numerical method. The optical band gap of nanostructured CMO thin films increased with increasing annealing temperature.

  9. Transformation from layered to tunnel structures: Synthesis, characterization, and applications of manganese oxide octahedral molecular sieves

    NASA Astrophysics Data System (ADS)

    Xia, Guan-Guang

    Manganese oxide based octahedral molecular sieves (OMS) have been found to have a wide variety of applications as catalysts, absorbents, and battery materials due to their unique structures and physical and chemical properties. OMS materials are made up of manganese oxide octahedral building blocks sharing comers and edges to form tunnel structures. Manganese species in the framework of OMS materials are mixed valent with various ion-exchangeable cations residing in the tunnels playing important roles in charge balancing and special chemical activities. With different synthetic parameters such as the template used, temperature, pressure, and the pH of the synthetic media, layered birnessite materials were hydrothermally transformed into distinct tunnel structures with different tunnel sizes, including Mg-3x3 (OMS-1), NH4-2x2 (NH4-OMS-2), Na-2x4 (OMS-5), and other manganese oxides. Characterization of the OMS materials with a wide variety of instruments has revealed that most of them are nano-fibrous hollow crystals ith large surface areas, high ion-exchange capabilities, and relatively high thermal stabilities. The Na-2x4 tunnel structure sodium MnOx has been synthesized for the first time and studied in detail, including synthetic strategies, structural analyses, and other physical and chemical property analyses. As catalysts, the synthetic OMS materials show high catalytic activities and shape-selective properties. For example, the results of the competitive oxidation of cycloalkanes with tertiary butyl hydrogen peroxide (TBHP) over different tunnel sized ONIS materials have proven that the OMS materials with larger tunnels are more favorable for the oxidation of the biggest molecule, cyclooctane, than the smallest one, cyclohexane. Besides the tunnel size effects, tunnel cations in the OMS materials also have influences on their catalytic activities. The study of carbon monoxide cleanup for fuel cell applications demonstrates that Ag-OMS-2 (a hollandite structured OMS catalyst with Ag cations residing in the tunnels) is the best oxidative catalyst among many other catalysts. The amount of Ag loading and the average oxidation state of Mn in a Ag-OMS-2 catalyst are the major influences on their catalytic performance. A suitable working temperature range for complete removal of CO from hydrogen-rich reformates using a Ag-OMS-2 catalyst may be adjusted by changing the Ag loading.

  10. Manganese sulfide formation via concomitant microbial manganese oxide and thiosulfate reduction.

    SciTech Connect

    Lee, Ji-Hoon; Kennedy, David W.; Dohnalkova, Alice; Moore, Dean A.; Nachimuthu, Ponnusamy; Reed, Samantha B.; Fredrickson, Jim K.

    2011-12-27

    The dissimilatory metal-reducing bacterium, Shewanella oneidensis MR-1 produced ?-MnS (rambergite) nanoparticles under the concurrent reduction of synthetic MnO2 and thiosulfate coupled to H2 oxidation. Using two MR-1 mutants defective in outer membrane c-type cytochromes (?mtrC/?omcA and ?mtrC/?omcA/?mtrF) to eliminate the direct reduction pathway for solid electron acceptors, it was determined that respiratory reduction of MnO2 was dominant relative to chemical reduction by biogenic sulfide generated from bacterial thiosulfate reduction. Although bicarbonate was excluded from the medium, incubations of MR-1 using lactate as the sole electron donor produced MnCO3 (rhodochrosite) as well as MnS in nearly equivalent amounts as estimated by micro X-ray diffraction (micro-XRD) analysis. It was concluded that carbonate released from lactate metabolism promoted MnCO3 formation and that Mn(II) mineralogy was strongly affected by carbonate ions even in the presence of abundant sulfide and weakly alkaline conditions that favor the precipitation of MnS. Formation of the biogenic MnS, as determined by a combination of micro-XRD, transmission electron microscopy, energy dispersive X-ray spectroscopy, and selected area electron diffraction analyses was consistent with equilibrium speciation modeling predictions. Although biogenic MnS likely only forms and is stable over a relatively narrow range of conditions, it may be a significant sink for Mn in anoxic marine basins and terrestrial subsurface sediments where Mn and sulfur compounds are undergoing concurrent reduction.

  11. Spinel lithium manganese oxide nanoparticles: unique molten salt synthesis strategy and excellent electrochemical performances.

    PubMed

    Wang, Xiong; Zhu, Juanjuan; Liu, Yingjie

    2009-11-01

    As a promising candidate cathode material, spinel lithium manganese oxide nanoparticles were successfully synthesized through a novel molten salt synthesis route at relatively low temperature, using manganese dioxide nanowires as precursor. A variety of techniques were applied to characterize the spinel nanomaterial, including X-ray diffraction, transmission electron microscopy, field-emission scanning electron microscopy, and X-ray photoelectron spectroscopy. The average particle size of the resulting spinel nanoparticles was about 80 nm with narrow distribution. As cathode material for rechargeable lithium ion battery, the electrochemical properties were investigated. All the results show that the electrochemical performances of the homogeneous spinel nanoparticles were improved, which might be ascribed to large specific surface area, fairly narrow size distribution, and the unique synthesis strategy. PMID:19908558

  12. Chemical etching of manganese oxides for electrocatalytic oxygen reduction reaction.

    PubMed

    Lei, Kaixiang; Han, Xiaopeng; Hu, Yuxiang; Liu, Xue; Cong, Liang; Cheng, Fangyi; Chen, Jun

    2015-07-25

    Mixed-valent MnOx (1 < x < 2) was selectively synthesized by chemically etching MnO and Mn2O3 with ceric ammonium nitrate. The obtained MnOx exhibited greatly enhanced electrocatalytic activity toward the oxygen reduction reaction (ORR) as compared to the corresponding pristine oxides. PMID:26097914

  13. Lewis-acid-promoted stoichiometric and catalytic oxidations by manganese complexes having cross-bridged cyclam ligand: a comprehensive study.

    PubMed

    Dong, Lei; Wang, Yujuan; Lv, Yanzong; Chen, Zhuqi; Mei, Fuming; Xiong, Hui; Yin, Guochuan

    2013-05-01

    Redox-inactive metal ions have been recognized to be able to participate in redox metal-ion-mediated biological and chemical oxidative events; however, their roles are still elusive. This work presents how the redox-inactive metal ions affect the oxidative reactivity of a well-investigated manganese(II) with its corresponding manganese(IV) complexes having cross-bridged cyclam ligand. In dry acetone, the presence of these metal ions can greatly accelerate stoichiometric oxidations of triphenylphosphine and sulfides by the manganese(IV) complexes through electron transfer or catalytic sulfoxidations by the corresponding manganese(II) complexes with PhIO. Significantly, the rate enhancements are highly Lewis-acid strength dependent on added metal ions. These metal ions like Al(3+) can also promote the thermodynamic driving force of the Mn(IV)-OH moiety to facilitate its hydrogen abstraction from ethylbenzene having a BDE(CH) value of 85 kcal/mol, while it is experimentally limited to 80 kcal/mol for Mn(IV)-OH alone. Adding Al(3+) may also improve the manganese(II)-catalyzed olefin epoxidation with PhIO. However, compared with those in electron transfer, improvements in hydrogen abstraction and electron transfer are minor. The existence of the interaction between Lewis acid and the manganese(IV) species was evidenced by the blue shift of the characteristic absorbance of the manganese(IV) species from 554 to 537 nm and by converting its EPR signal at g = 2.01 into a hyperfine 6-line signal upon adding Al(3+) (I = 5/2). Cyclic voltammograms of the manganese(IV) complexes reveal that adding Lewis acid would substantially shift its potential to the positive direction, thus enhancing its oxidizing capability. PMID:23600453

  14. Manganese-containing VOC oxidation catalysts prepared in molten salts

    Microsoft Academic Search

    Monica Raciulete; Pavel Afanasiev

    2009-01-01

    Mn-Zr and Mn-Ti supported oxide catalysts have been prepared by means of reactions in molten Na(K)NO3 fluxes at 500°C. The solids were characterized using X ray diffraction, textural measurements, optical spectroscopy and transmission electron microscopy. Highly dispersed ZrO2 and TiO2 covered with Mn(III, IV) species were obtained from the reaction in the melt. Due to the stabilizing effect of Mn,

  15. Manganese(II)-Oxidizing Bacillus Spores in Guaymas Basin Hydrothermal Sediments and Plumes

    PubMed Central

    Dick, Gregory J.; Lee, Yifan E.; Tebo, Bradley M.

    2006-01-01

    Microbial oxidation and precipitation of manganese at deep-sea hydrothermal vents are important oceanic biogeochemical processes, yet nothing is known about the types of microorganisms or mechanisms involved. Here we report isolation of a number of diverse spore-forming Mn(II)-oxidizing Bacillus species from Guaymas Basin, a deep-sea hydrothermal vent environment in the Gulf of California, where rapid microbially mediated Mn(II) oxidation was previously observed. mnxG multicopper oxidase genes involved in Mn(II) oxidation were amplified from all Mn(II)-oxidizing Bacillus spores isolated, suggesting that a copper-mediated mechanism of Mn(II) oxidation could be important at deep-sea hydrothermal vents. Phylogenetic analysis of 16S rRNA and mnxG genes revealed that while many of the deep-sea Mn(II)-oxidizing Bacillus species are very closely related to previously recognized isolates from coastal sediments, other organisms represent novel strains and clusters. The growth and Mn(II) oxidation properties of these Bacillus species suggest that in hydrothermal sediments they are likely present as spores that are active in oxidizing Mn(II) as it emerges from the seafloor. PMID:16672456

  16. Bioaccumulation of manganese and its toxicity in feral pigeons (Columba livia) exposed to manganese oxide dust (Mn3O4).

    PubMed

    Sierra, P; Chakrabarti, S; Tounkara, R; Loranger, S; Kennedy, G; Zayed, J

    1998-11-01

    Manganese tetroxide (Mn3O4) is a product from the combustion of methylcyclopentadienyl manganese tricarbonyl. Exposure to high levels of manganese can lead to serious health effects especially to the central nervous and respiratory systems. Very few studies on the effects of long-term low level exposure to Mn3O4 have been reported. The present study was therefore conducted to examine the bioaccumulation and toxicity of manganese in various organs of feral pigeons (Columba livia) when exposed to low levels of Mn3O4 via inhalation and hence to find any possible relationship between these two parameters. A total of 22 pigeons was exposed to 239 micrograms/m3 of manganese for 7 h/day, 5 days/week for 5, 9, and 13 consecutive weeks. Manganese concentrations in various tissues, e.g., brain (mesencephalon), lung, liver, intestine, pancreas, kidney, muscle, bone, and whole blood, were measured by neutron activation analysis. Various biochemical parameters in blood, e.g., hematocrit, total proteins, glucose, uric acid, alanine aminotransferase, total iron, blood urea nitrogen and triglycerides, were also measured. Manganese concentrations in brain, lung, and bone were significantly higher in Mn3O4-exposed pigeons (0.59, 0.58, and 3.02 micrograms wet tissue, respectively) than in the control group (0.46, 0.19, 1.74 micrograms/g wet tissue, respectively). However, except for total proteins such exposure did not produce any changes in various biochemical parameters which were within the normal values. Thus these results have shown that, despite significant bioaccumulation of manganese in some tissues, no significant toxic effects could be seen. PMID:9841807

  17. Coprecipitation and redox reactions of manganese oxides with copper and nickel

    USGS Publications Warehouse

    Hem, J.D.; Lind, Carol J.; Roberson, C.E.

    1989-01-01

    Open-system, continuous-titration experiments have been done in which a slow flux of ???0.02 molar solution of Mn2+ chloride, nitrate, or perchlorate with Cu2+ or Ni2+ in lesser concentrations was introduced into an aerated reactor solution held at constant temperature and at constant pH by a pH-stat titrator that added dilute NaOH. The resulting mixtures of metal oxyhydroxides and their native solutions were aged for periods as long as 2 1/2 years. Fresh and aged precipitates were characterized by chemical analysis, oxidation state determinations, X-ray and electron diffraction, and electron microscopy. The precipitates can be described as mixtures of oxide and oxyhydroxide species, using concepts of equilibrium and nonequilibrium chemical thermodynamics. The metal-ion content of the aged precipitates in systems that contained copper is distributed among three principal components. One of these is a mixed oxide Cu2Mn3O8 in which all Mn is in the 4+ oxidation state. A major component in all precipitates is feitknechtite, ??MnOOH. These forms are supplemented by CuO or by birnessite or ramsdellite forms of MnO2 where stoichiometry and thermodynamic calculations predict them. In systems that contained nickel and manganese, identifiable components included ??MnOOH, Ni(OH)2, and the same two forms of MnO2. The oxidation number of the precipitated manganese increased during aging, and the pH of the supernatant solution decreased. The maximum Mn oxidation number observed was 3.55 in an Mn + Cu precipitate aged for 18 months. Concentrations of Cu2+ and Ni2+ generally decreased to values substantially below those predicted by oxide or hydroxide equilibrium. Scavenging effects of this type are common in natural aqueous systems. ?? 1989.

  18. Illumina sequencing of fungi associated with manganese oxide deposits in cave systems

    NASA Astrophysics Data System (ADS)

    Zorn, B. T.; Santelli, C. M.; Carmichael, S. K.; Pepe-Ranney, C. P.; Roble, L.; Carmichael, M.; Bräuer, S.

    2013-12-01

    The environmental cycling of manganese (Mn) remains relatively poorly characterized when compared with other metals such as iron. However, fungi have been observed to produce Mn(III/IV) oxides resembling buserite, birnessite, and todorokite on the periphery of vegetative hyphae, hyphal branching points and at the base of fruiting bodies. Recent studies indicate that some of these oxides may be generated by a two-stage reaction with soluble Mn(II) and biogenic reactive oxygen species for some groups of fungi, in particular the Ascomycota. These oxides can provide a versatile protective barrier or aid in the capture of trace metals in the environment, although the exact evolutionary function and trigger is unclear. In this study, two caves in the southern Appalachians, a pristine cave and an anthropogenically impacted cave, were compared by analyzing fungal community assemblages in manganese oxide rich deposits. Quantitative PCR data indicated that fungi are present in a low abundance (<1%) in all locations sampled within the caves. Among amplified DNA sequences retrieved in an 18S rDNA clone library, over 88% were representative of the phylum Basidiomycota (predominantly Agaricomycetes), 2.74% of Ascomycota, 2.28% of Blastocladiomycota and Chytridiomycota, 0.46% of Zygomycota, and 3.65% of Eukarya or Fungi incertae sedis. Using Illumina's MiSeq to sequence amplicons of the fungal ITS1 gene has yielded roughly 100,000-200,000 paired-end reads per sample. These data are currently being analyzed to compare fungal communities before and after induced Mn oxidation in the field. In addition, sites within the pristine cave are being compared with analogous sites in the impacted cave. Culturing efforts have thus far yielded Mn oxide producing members of the orders Glomerales and Pleosporales as well as two Genus incertae sedis (Fungal sp. YECT1, and Fungal sp. YECT3, growing on discarded electrical tape) that do not appear to be closely related to any other known Mn oxidizing fungi.

  19. The Transparent Conductive Properties of Manganese-Doped Zinc Oxide Films Deposited by Chemical Bath Deposition

    NASA Astrophysics Data System (ADS)

    Fang, J. S.; Luo, W. H.; Hsu, C. H.; Yang, J. C.; Tsai, T. K.

    2012-01-01

    Manganese-doped zinc oxide (Mn-doped ZnO) thin films were prepared using chemical bath deposition (CBD), and the impacts of the manganese dopant concentration on the structure, electrical resistivity, optical transmission, and magnetic properties were investigated using x-ray diffractometry, Hall-effect measurements, ultraviolet-visible-near-infrared (UV-Vis-IR) spectrophotometry, and vibrating sample magnetometry (VSM), respectively. The concentration of the manganese dopant in the ZnO thin film critically impacted the resulting properties, and the 4.0 at.% Mn-doped ZnO film had a resistivity of 5.8 × 10-2 ?cm, transmittance of 75.6% in the visible light range, and bandgap of 3.30 eV when the film was annealed at 600°C in an Ar + H2 atmosphere. Annealing the film could enhance its magnetic properties such that the film had a saturation magnetization of 21.0 emu/cm3 and a coercivity of 45.7 Oe after annealing at 600°C. Because of these electrical, optical, and magnetic properties, Mn-doped thin films are promising for use in spintronic devices.

  20. Role of Reactive Intermediates in Manganese Oxide Formation By Filamentous Ascomycete Fungi

    NASA Astrophysics Data System (ADS)

    Zeiner, C. A.; Anderton, C.; Wu, S.; Purvine, S.; Zink, E.; Paša-Toli?, L.; Santelli, C. M.; Hansel, C. M.

    2014-12-01

    Biogenic manganese (Mn) oxide minerals are ubiquitous in the environment, and their high reactivity can profoundly impact the fate of contaminants and cycling of carbon and nutrients. In contrast to bacteria, the pathways utilized by fungi to oxidize Mn(II) to Mn(III,IV) oxides remain largely unknown. Here, we explore the mechanisms of Mn(II) oxidation by a phylogenetically diverse group of filamentous Ascomycete fungi using a combination of chemical assays and bulk and spatially-resolved mass spectrometry. We show that the mechanisms of Mn(II) oxidation vary with fungal species, over time during secretome compositional changes, and in the presence of other fungi. Specifically, our work implicates a dynamic transition in Mn(II) oxidation pathways that varies between species. In particular, while reactive oxygen species (ROS) produced via transmembrane NADPH oxidases are involved in initial oxidation, over time, secreted enzymes become important Mn(II) oxidation mediators for some species. In addition, the overall secretome oxidation capacity varies with time and fungal species. Secretome analysis reveals a surprising absence of enzymes currently considered to be Mn(II)-oxidizing enzymes in these organisms, and instead highlights a wide variety of redox-active enzymes. Furthermore, we implicate fungal cell defense mechanisms in the formation of distinct Mn oxide patterns when fungi are grown in head-to-head competition. The identification and regulation of these secreted enzymes are under current investigation within the bulk secretome and within the interaction zone of structured fungal communities. Overall, our findings illustrate that Ascomycete Mn(II) oxidation mechanisms are highly variable and are dictated by complex environmental and ecological interactions. Future work will explore the connection between Ascomycete Mn(II) oxidation and the ability to degrade cellulose, a key carbon reservoir for biofuel production.

  1. Electron beam deposition of amorphous manganese oxide thin film electrodes and their predominant electrochemical properties

    NASA Astrophysics Data System (ADS)

    Sarkar, Abhimanyu; Satpati, Ashis Kumar; Rao, Pritty; Kumar, Sanjiv

    2015-06-01

    Electron beam evaporated manganese oxide films display excellent electrochemical properties on post deposition oxidative annealing in air. The films annealed below 573 K are amorphous, exhibit minor deficiency in oxygen and are characterized by a specific discharge capacitance of 398 F g-1 at a discharge current of 1.1 A g-1 and 236 F g-1 at a discharge current of 5.5 A g-1. In terms of stability, these films retain 99.6% of their specific capacitance even after 400 cycles. The electrochemical properties of these films are explained in terms of their structure and composition which have been measured by X-ray diffraction and proton elastic backscattering spectrometry. In addition, the electrochemical properties are influenced by their morphology; the oxidatively annealed films contain nanometric, spherical and elongated grains which acquire extensive networking during electrochemical measurements.

  2. Pathogenic prion protein is degraded by a manganese oxide mineral found in soils

    USGS Publications Warehouse

    Russo, F.; Johnson, C.J.; McKenzie, D.; Aiken, Judd M.; Pedersen, J.A.

    2009-01-01

    Prions, the aetiological agents of transmissible spongiform encephalopathies, exhibit extreme resistance to degradation. Soil can retain prion infectivity in the environment for years. Reactive soil components may, however, contribute to the inactivation of prions in soil. Members of the birnessite family of manganese oxides (MnO2) rank among the strongest natural oxidants in soils. Here, we report the abiotic degradation of pathogenic prion protein (PrPTSE) by a synthetic analogue of naturally occurring birnessite minerals. Aqueous MnO2 suspensions degraded the PrPTSE as evidenced by decreased immunoreactivity and diminished ability to seed protein misfolding cyclic amplification reactions. Birnessite-mediated PrPTSE degradation increased as a solution's pH decreased, consistent with the pH-dependence of the redox potential of MnO2. Exposure to 5.6 mg MnO2 ml-1 (PrPTSE:MnO2=1 : 110) decreased PrPTSE levels by ???4 orders of magnitude. Manganese oxides may contribute to prion degradation in soil environments rich in these minerals. ?? 2009 SGM.

  3. Heterogeneous catalytic ozonation of ciprofloxacin in water with carbon nanotube supported manganese oxides as catalyst.

    PubMed

    Sui, Minghao; Xing, Sichu; Sheng, Li; Huang, Shuhang; Guo, Hongguang

    2012-08-15

    Carbon nanotube-supported manganese oxides (MnOx/MWCNT) were used as catalysts to assist ozone in degrading ciprofloxacin in water. Manganese oxides were successfully loaded on multi-walled carbon nanotube surfaces by simply impregnating the carbon nanotube with permanganate solution. The catalytic activities of MnOx/MWCNT in ciprofloxacin ozonation, including degradation, mineralization effectiveness, and antibacterial activity change, were investigated. The presence of MnOx/MWCNT significantly elevated the degradation and mineralization efficiency of ozone on ciprofloxacin. The microbiological assay with a reference Escherichia coli strain indicated that ozonation with MnOx/MWCNT results in more effective antibacterial activity inhibition of ciprofloxacin than that in ozonation alone. The effects of catalyst dose, initial ciprofloxacin concentration, and initial pH conditions on ciprofloxacin ozonation with MnOx/MWCNT were surveyed. Electron spin resonance trapping was applied to assess the role of MnOx/MWCNT in generating hydroxyl radicals (HO) during ozonation. Stronger 5,5-dimethyl-1-pyrroline-N-oxide-OH signals were observed in the ozonation with MnOx/MWCNT compared with those in ozonation alone, indicating that MnOx/MWCNT promoted the generation of hydroxyl radicals. The degradation of ciprofloxacin was studied in drinking water and wastewater process samples to gauge the potential effects of water background matrix on MnOx/MWCNT catalytic ozonation. PMID:22658829

  4. Application of Quantum Monte Carlo Methods to Describe the Properties of Manganese Oxide Polymorphs

    NASA Astrophysics Data System (ADS)

    Schiller, Joshua; Ertekin, Elif

    2015-03-01

    First-principles descriptions of the properties of correlated materials such as transition metal oxides has been a long-standing challenge. Manganese oxide is one such example: according to both conventional and hybrid functional density functional theory, the zinc blende polymorph is predicted to be lower in energy than the rock salt polymorph that occurs in nature. While the correct energy ordering can be obtained in density functional approaches by careful selection of modeling parameters, we present here an alternative approach based on quantum Monte Carlo methods, which are a suite of stochastic tools for solution of the many-body Schrodinger equation. Due to its direct treatment of electron correlation, the QMC method offers the possibility of parameter-free, high-accuracy, systematically improvable analysis. In manganese oxide, we find that the QMC methodology is able to accurately reproduce relative phase energies, lattice constants, and band gaps without the use of adjustable parameters. Additionally, statistical analysis of the many-body wave functions from QMC provides some diagnostic assessments to reveal the physics that may be missing from other modeling approaches.

  5. A sodium layered manganese oxides as 3 V cathode materials for secondary lithium batteries

    Microsoft Academic Search

    S. Bach; J. P. Pereira-Ramos; P. Willmann

    2006-01-01

    The synthesis of a new anhydrous sodium manganese oxide ?-Na0.66MnO2.13 obtained via a sol–gel process in organic medium is reported. The partial and limited removal of sodium ions from the layered host lattice (hexagonal symmetry; a=2.84Å, c=11.09Å) allows to get a high and stable specific capacity of 180mAhg?1 at C\\/20 in the cycling limits 4.3\\/2V with a mean working voltage

  6. Nanostructured and layered lithium manganese oxide and method of manufacturing the same

    NASA Technical Reports Server (NTRS)

    Singhal, Amit (Inventor); Skandan, Ganesh (Inventor)

    2005-01-01

    Nanostructured and layered lithium manganese oxide powders and methods of producing same. The powders are represented by the chemical formula, LixMn1-yMyO2, where 0.5

  7. Interaction of manganese(IV) oxide with aqueous solutions of citric and sulfuric acids

    NASA Astrophysics Data System (ADS)

    Godunov, E. B.; Artamonova, I. V.; Gorichev, I. G.; Lainer, Yu. A.

    2012-01-01

    The kinetic laws of the dissolution of manganese(IV) oxide using citric acid are studied as functions of the temperature and pH of a solution and the concentration of citric acid. The following kinetic parameters of the dissolution are calculated: the reaction rate, the reaction order with respect to citrate ions ( n = 0.6), and the activation energy ( E a = 47.4 kJ/mol). The optimum conditions favoring an increase in the leaching intensity and economical consumption of the reactants are experimentally determined.

  8. Electronic and magnetic structure of LaSr-2×4 manganese oxide molecular sieve nanowires.

    PubMed

    Gazquez, Jaume; Carretero-Genevrier, Adrián; Gich, Martí; Mestres, Narcís; Varela, María

    2014-06-01

    In this study we combine scanning transmission electron microscopy, electron energy loss spectroscopy and electron magnetic circular dichroism to get new insights into the electronic and magnetic structure of LaSr-2×4 manganese oxide molecular sieve nanowires integrated on a silicon substrate. These nanowires exhibit ferromagnetism with strongly enhanced Curie temperature (T c >500 K), and we show that the new crystallographic structure of these LaSr-2×4 nanowires involves spin orbital coupling and a mixed-valence Mn3+/Mn4+, which is a must for ferromagnetic ordering to appear, in line with the standard double exchange explanation. PMID:24735528

  9. Manganese-doped indium oxide and its application in organic light-emitting diodes

    SciTech Connect

    Liao Yaqin [Key Laboratory of Excited State Processes, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China); Graduate School of Chinese Academy of Sciences, Beijing 100080 (China); Lu Qipeng; Fan Yi; Liu Xingyuan [Key Laboratory of Excited State Processes, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China)

    2011-07-11

    Thin films of manganese-doped indium oxide (IMO) deposited by electron beam evaporation have been investigated as anodes in organic light-emitting diodes (OLEDs). The IMO films have a high work function of 5.35 eV, a desirable surface morphology with an average roughness of 1.1 nm, a high average optical transmittance of 87.2% in the visible region, and a maximum optical transmittance of 92% at 460 nm. It is demonstrated that an IMO anode can effectively improve hole injection at the anode/organic interface, resulting in OLEDs with an increased electroluminescent efficiency.

  10. Phase composition of ceramics in systems with oxides of rare-earth elements, manganese, and titanium

    Microsoft Academic Search

    S. V. Stefanovskii; S. V. Yudintsev; B. S. Nikonov; O. I. Stefanovskaya

    2007-01-01

    Ceramics based on systems with oxides of rare-earth elements (REE: Y2O3, Sm2O3, Gd2O3), manganese, and titanium, considered as hosts for immobilization of REE- and actinide-containing radioactive wastes (RAW),\\u000a were prepared by cold pressing and sintering at 1300–1400?C, and also by plasma treatment. Phases of the pyrochlore-murataite\\u000a series are prevalent in the ceramics, and perovskite-pyrophanite-type phases are impurity phases, as well

  11. Electrochemical Sensor Based on Carbon Paste Electrode Modified with Nanostructured Crypotomelane-Type Manganese Oxides for Detection of Heavy Metals

    SciTech Connect

    Cui, Xiaoli; Liu, Guodong; Li, Liyu; Yantasee, Wassana; Lin, Yuehe

    2005-02-03

    A carbon paste electrode modified with nanostructured crypotomelane type manganese oxides was evaluated as new electrochemical sensor for the detection of heavy metal ions in aqueous media. The crypotomelane type manganese oxides are nanofibrous crystals with sub-nanometer tunnels which provide excellent sites for ion-exchanges. The adsorptive stripping voltammetry (ASV) technique involves preconcentration of the metal ions into nanostructured crypotomelane type manganese oxides under an open circuit, then electrolysis of the preconcentrated species, followed by a square-wave potential sweep towards positive values. Factors affecting the preconcentration process were investigated using lead ion as the model analyte. The voltammetric responses increased with the preconcentration time from 2 to 30 min, and also linearly with lead ion concentrations ranging from 50 to 1200 ppb. The detection limits of target metal ion were 10 ppb after 4 min preconcentration and improved to 1 ppb after 20 min preconcentration. The potential for simultaneous detection of copper, silver and lead is also discussed.

  12. Manganese-oxide-coated redox bars as an indicator of reducing conditions in soils.

    PubMed

    Dorau, Kristof; Mansfeldt, Tim

    2015-03-01

    Identification of reducing conditions in soils is of concern not only for pedogenesis but also for nutrient and pollutant dynamics. We manufactured manganese (Mn)-oxide-coated polyvinyl chloride bars and proved their suitability for the identification of reducing soil conditions. Birnessite was synthesized and coated onto white polyvinyl chloride bars. The dark brown coatings were homogenous and durable. As revealed by microcosm devices with adjusted redox potentials (E), under oxidizing conditions (E ?450 mV at pH 7) there was no Mn-oxide removal. Reductive dissolution of Mn-oxides, which is expressed by the removal of the coatings, started under weakly reducing conditions (E ?175 mV) and was more intensive under moderately reducing conditions (?80 mV). According to thermodynamics, the removal of Mn-oxide coatings (225 mm d) exceeded the removal of iron (Fe)-oxide coatings (118 mm d) in soil column experiments. This was confirmed in a soil with a shallow and strongly fluctuating water table where both types of redox bars were inserted. Consequently, it was possible to identify reducing conditions in soils using Mn-oxide-coated bars. We recommend this methodology for short-term monitoring because tri- and tetravalent Mn is the preferred electron acceptor compared with trivalent Fe, and this additionally offers the possibility of distinguishing between weakly and moderately reducing conditions. If dissolved Fe is abundant in soils, the possibility of nonenzymatic reduction of Mn has to be taken into account. PMID:26023987

  13. Geology, alteration, age, and origin of iron oxide-apatite deposits in Upper Eocene quartz monzonite, Zanjan district, NW Iran

    NASA Astrophysics Data System (ADS)

    Nabatian, Ghasem; Ghaderi, Majid; Corfu, Fernando; Neubauer, Franz; Bernroider, Manfred; Prokofiev, Vsevolod; Honarmand, Maryam

    2014-02-01

    Iron oxide-apatite deposits are present in Upper Eocene pyroxene-quartz monzonitic rocks of the Zanjan district, northwestern Iran. Mineralization occurred in five stages: (1) deposition of disseminated magnetite and apatite in the host rock; (2) mineralization of massive and banded magnetite ores in veins and stockwork associated with minor brecciation and calcic alteration of host rocks; (3) deposition of sulfide ores together with potassic alteration; (4) formation of quartz and carbonate veins and sericite, chlorite, epidote, silica, carbonate, and tourmaline alteration; and (5) supergene alteration and weathering. U-Pb dating of monazite inclusions in the apatite indicates an age of 39.99 ± 0.24 Ma, which is nearly coeval with the time of emplacement of the host quartz monzonite, supporting the genetic connection. Fluid inclusions in the apatite have homogenization temperatures of about 300 °C and oxygen isotopic compositions of the magnetite support precipitation from magmatic fluids. Late-stage quartz resulted from the introduction of a cooler, less saline, and isotopically depleted fluid. The iron oxide-apatite deposits in the Tarom area of the Zanjan district are typical of a magmatic-hydrothermal origin and are similar to the Kiruna-type deposits with respect to mineral assemblages, fabric and structure of the iron ores, occurrence of the ore bodies, and wall rock alteration.

  14. Decoration of the layered manganese oxide birnessite with Mn(ii/iii) gives a new water oxidation catalyst with fifty-fold turnover number enhancement.

    PubMed

    McKendry, Ian G; Kondaveeti, Sandeep K; Shumlas, Samantha L; Strongin, Daniel R; Zdilla, Michael J

    2015-07-14

    The role of the manganese average oxidation state (AOS) in water oxidation catalysis by birnessite was investigated. Low AOS samples were most active, generating O2 immediately. Samples with a relatively high AOS showed an initial induction period and decreased turnover. Mn(ii- and iii)-enriched samples gave a 10-50 fold enhancement in turnover number. PMID:26134982

  15. Manganese oxide nanowires wrapped with nitrogen doped carbon layers for high performance supercapacitors.

    PubMed

    Li, Ying; Mei, Yuan; Zhang, Lin-Qun; Wang, Jian-Hai; Liu, An-Ran; Zhang, Yuan-Jian; Liu, Song-Qin

    2015-10-01

    In this study, manganese oxide nanowires wrapped by nitrogen-doped carbon layers (MnOx@NCs) were prepared by carbonization of poly(o-phenylenediamine) layer coated onto MnO2 nanowires for high performance supercapacitors. The component and structure of the MnOx@NCs were controlled through carbonization procedure under different temperatures. Results demonstrated that this composite combined the high conductivity and high specific surface area of nitrogen-doped carbon layers with the high pseudo-capacitance of manganese oxide nanowires. The as-prepared MnOx@NCs exhibited superior capacitive properties in 1M Na2SO4 aqueous solution, such as high conductivity (4.167×10(-3)Scm(-1)), high specific capacitance (269Fg(-1) at 10mVs(-1)) and long cycle life (134Fg(-1) after 1200 cycles at a scan rate of 50mVs(-1)). It is reckoned that the present novel hybrid nanowires can serve as a promising electrode material for supercapacitors and other electrochemical devices. PMID:26070189

  16. Growth of nano-needles of manganese(IV) oxide by atomic layer deposition.

    PubMed

    Nilsen, Ola; Foss, Steinar; Kjekshus, Arne; Fjellvåg, Helmer

    2008-02-01

    Needles of manganese (IV) oxide in the nanometer range have been synthesised using the atomic layer deposition technique. Traditionally the atomic layer deposition technique is used for the fabrication of thin films, however, we find that needles of beta-MnO2 are formed when manganese (IV) oxide is deposited as relatively thick (ca. 800 nm) thin films on substrates of alpha-Al2O3 [(001) and (012) oriented]. There is no formation of needles when the film is deposited on substrates such as Si(100) or soda lime glass. The film is formed using Mn(thd)3 (Hthd = 2,2,6,6-tetramethylheptane-3,5-dione) and ozone as precursors. While thin films (ca. 100 nm) consist of epsilon'-MnO2, the same process applied to thicker films results in the formation of nano-needles of beta-MnO2. These needles of beta-MnO2 have dimensions ranging from approximately 1.5 microm at the base down to very sharp tips. The nano-needles and the bulk of the films have been analysed by atomic force microscopy, scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. PMID:18464441

  17. Decolorization of methylene blue in layered manganese oxide suspension with H2O2.

    PubMed

    Zhang, Lili; Nie, Yulun; Hu, Chun; Hu, Xuexiang

    2011-06-15

    Layered birnessite-type manganese oxides (Na-OL-1) were prepared via a redox reaction involving MnO(4)(-) and Mn(2+) under markedly alkaline conditions. According to the XRD analysis, the resulting material exhibited a well-crystallized octahedral layer (OL) structure with several different phases, including ?-MnOOH, ?-MnOOH and ?-Mn(3)O(4). The catalyst was highly effective for the decolorization and degradation of methylene blue (MB) in the presence of H(2)O(2) at neutral pH. The tested MB was completely decolorized in Na-OL-1 suspension by the fraction dosing of H(2)O(2) (556.5mM at the beginning and then 183.8mM at 40 min). Based on the studies of electron spin resonance and the effect of radical scavengers, the (1)O(2) and O(2)(-) were the main reactive oxygen species (ROS) in the reaction. It was found that both oxygen and ROS were generated from the decomposition of H(2)O(2) in Na-OL-1 suspension, wherein the decomposition pathways were proposed. The generation of H(2)O(2) in Na-OL-1 suspension at air atmosphere indicated that the existence of multivalent manganese oxides greatly enhanced the interfacial electron transfer, leading to the high activity of Na-OL-1. PMID:21524842

  18. Adsorption of copper, cadmium, lead and zinc onto a synthetic manganese oxide.

    PubMed

    Della Puppa, Loïc; Komárek, Michael; Bordas, François; Bollinger, Jean-Claude; Joussein, Emmanuel

    2013-06-01

    Due to its simple and inexpensive synthesis, a new amorphous hydrous manganese oxide (AMO) has been studied as a possible chemical stabilizing agent for soils contaminated with metals. Preliminary experiments evaluating the stability of AMO in pure water have reported only minor dissolution (5.70% and 0.24% depending on the w/v ratio). Sorption kinetics have shown fast metal adsorption, especially for Pb. The sorption capacities of AMO for Cu, Cd, Pb, and Zn have been described and compared with synthetic birnessite for pH 4 and 5.5. Both oxides show similar sorption capacities at pH 4 despite the fact that birnessite characteristics (pH of zero point charge, specific surface area and cation exchange capacity) are more favorable for metal sorption. Moreover, the pH adsorption-edges show that the AMO is more pH-dependent than birnessite. PMID:23566588

  19. Electrochemical impedance spectroscopy studies of lithium diffusion in doped manganese oxide

    SciTech Connect

    Johnson, B.J.; Doughty, D.H.; Voigt, J.A.; Boyle, T.J.

    1996-06-01

    Cathode performance is critical to lithium ion rechargeable battery performance; effects of doping lithium manganese oxide cathode materials on cathode performance are being investigated. In this paper, Li diffusion in Al-doped LiMn{sub 2}O{sub 4} was studied and found to be controlled by the quantity of Al dopant. Electrochemical cycling was conducted at 0.5mA/cm{sub 2}; electrochemical impedance spectra were taken at open circuit potential, with impedance being measured at 65 kHz-0.01 Hz. As the Al dopant level was increased, the Li diffusion rate decreased; this was attributed to the decreased lattice parameter of the doped oxide.

  20. Nano-sized Lithium Manganese Oxide Dispersed on Carbon Nanotubes for Energy Storage Applications

    SciTech Connect

    Bak, S.B.

    2009-08-01

    Nano-sized lithium manganese oxide (LMO) dispersed on carbon nanotubes (CNT) has been synthesized successfully via a microwave-assisted hydrothermal reaction at 200 C for 30 min using MnO{sub 2}-coated CNT and an aqueous LiOH solution. The initial specific capacity is 99.4 mAh/g at a 1.6 C-rate, and is maintained at 99.1 mAh/g even at a 16 C-rate. The initial specific capacity is also maintained up to the 50th cycle to give 97% capacity retention. The LMO/CNT nanocomposite shows excellent power performance and good structural reversibility as an electrode material in energy storage systems, such as lithium-ion batteries and electrochemical capacitors. This synthetic strategy opens a new avenue for the effective and facile synthesis of lithium transition metal oxide/CNT nanocomposite.

  1. Manganese-oxide minerals in fractures of the Crater Flat Tuff in drill core USW G-4, Yucca Mountain, Nevada

    SciTech Connect

    Carlos, B.A.; Bish, D.L.; Chipera, S.J.

    1990-07-01

    The Crater Flat Tuff is almost entirely below the water table in drill hole USW G-4 at Yucca Mountain, Nevada. Manganese-oxide minerals from the Crater Flat Tuff in USW G-4 were studied using optical, scanning electron microscopic, electron microprobe, and x-ray powder diffraction methods to determine their distribution, mineralogy, and chemistry. Manganese-oxide minerals coat fractures in all three members of the Crater Flat Tuff (Prow Pass, Bullfrog, and Tram), but they are most abundant in fractures in the densely welded devitrified intervals of these members. The coatings are mostly of the cryptomelane/hollandite mineral group, but the chemistry of these coatings varies considerably. Some of the chemical variations, particularly the presence of calcium, sodium, and strontium, can be explained by admixture with todorokite, seen in some x-ray powder diffraction patterns. Other chemical variations, particularly between Ba and Pb, demonstrate that considerable substitution of Pb for Ba occurs in hollandite. Manganese-oxide coatings are common in the 10-m interval that produced 75% of the water pumped from USW G-4 in a flow survey in 1983. Their presence in water-producing zones suggests that manganese oxides may exert a significant chemical effect on groundwater beneath Yucca Mountain. In particular, the ability of the manganese oxides found at Yucca Mountain to be easily reduced suggests that they may affect the redox conditions of the groundwater and may oxidize dissolved or suspended species. Although the Mn oxides at Yucca Mountain have low exchange capacities, these minerals may retard the migration of some radionuclides, particularly the actinides, through scavenging and coprecipitation. 23 refs., 21 figs., 2 tabs.

  2. Applications of manganese oxides based catalyst for the destruction of VOCs

    SciTech Connect

    Singh, N.; Pisarczyk, K.S.; Sigmund, J.J. [Carus Chemical Co., LaSalle, IL (United States)

    1997-12-31

    Catalytic oxidation, as a proven control technology, has demonstrated a high level of efficiency in reducing Volatile Organic Compound (VOC`s) at competitive, and in many cases, lower cost than the other thermal incineration methods. Catalytic oxidation is the preferred technology for the destruction of VOC`s in a variety of industries; such as, flexographic printing, metal can coating, contract sterilization and bakeries. A key component of these catalytic systems is the catalyst itself, and transition metal oxide catalysts have demonstrated their advantage and overall superior applicability in numerous installations. The higher VOC destruction efficiencies of these catalysts, particularly for oxygenated VOC`s, allows for a lower temperature of operation making these catalysts an economically attractive alternative based upon the energy savings when compared to noble metal catalysts. Manganese based oxide catalysts are available in either homogenous extruded form or in monolith form, depending upon their application. The performance characteristics - measured as VOC destruction efficiencies - of these catalysts are dependent upon the operating conditions of the catalytic reactor. Reactor configuration and operating conditions; such as, catalyst operating temperature, gas phase linear velocity, contact time of the gas stream with the catalyst, and finally the characteristics of the hydrocarbon, all influence the efficiency of these catalytic systems. Models relating the hydrocarbon destruction efficiencies of these catalysts, as it is affected by these parameters, will be presented. These parametric models allow for comparison of various alternative catalyst strategies to be applied to a VOC destruction situation in the design phase. Data will be presented on a transition metal extruded catalyst, an extended temperature range manganese based catalyst, as well as a monolithic form of the transition metal catalyst.

  3. Electron Energy-Loss Safe-Dose Limits for Manganese Valence Measurements in Environmentally Relevant Manganese Oxides

    E-print Network

    Sparks, Donald L.

    Electron Energy-Loss Safe-Dose Limits for Manganese Valence Measurements in Environmentally-Claire Gaillot, and Donald L. Sparks The High-Resolution Analytical Electron Microbeam Facility+). In this study, the effects of beam damage during electron energy-loss spectroscopy (EELS) in the transmission

  4. Thiol-mediated oxidation of nonphenolic lignin model compounds by manganese peroxidase of Phanerochaete chrysosporium.

    PubMed

    Wariishi, H; Valli, K; Renganathan, V; Gold, M H

    1989-08-25

    In the presence of MnII, H2O2, and glutathione (GSH), manganese peroxidase oxidized veratryl alcohol (I) to veratraldehyde (IV). Anisyl alcohol (II) and benzyl alcohol (III) were also oxidized by this system to their corresponding aldehydes (V and VI). In the presence of GSH, chemically prepared MnIII or gamma-irradiation also catalyzed the oxidation of I, II, and III to IV, V, and VI, respectively. GSH and dithiothreitol rapidly reduced MnIII to MnII in the absence of aromatic substrates and the dithiothreitol was oxidized to its disulfide (4,5-dihydroxyl-1,2-dithiane). These results indicate that the thiol is oxidized by enzyme-generated MnIII to a thiyl radical. The latter abstracts a hydrogen from the substrate, forming a benzylic radical which reacts with another thiyl radical to yield an intermediate which decomposes to the benzaldehyde product. In the presence of MnII, GSH, and H2O2, manganese peroxidase also oxidized 1-(4-ethoxy-3-methoxy-phenyl)-2-(4'-hydroxymethyl-2'-methoxyphenoxy)- 1,3-dihydroxypropane (XII) to yield vanillyl alcohol (VII), vanillin (VIII), 1-(4-ethoxy-3-methoxyphenyl)-1,3-dihydroxypropane (XVI), 1-(4-ethoxy-3-methoxyphenyl)-1-oxo-3-hydroxypropane (XIX), and several C alpha oxidized dimeric products. Abstraction of the C alpha (A ring) hydrogen of the dimer (XII) yields a benzylic radical, leading to C beta oxygen ether cleavage. The resultant intermediates yield the ketone (XIX) and vanillyl alcohol (VII) or vanillin (VIII). Alternatively, benzylic radical formation at the C' alpha position (B ring) leads to radical cleavage, yielding a quinone methide and a C beta radical, which yield vanillin and the 1,3-diol (XVI), respectively. In these reactions, MnIII oxidizes a thiol to a thiyl radical which subsequently abstracts a hydrogen from the substrate to form a benzylic radical. The latter undergoes nonenzymatic reactions to yield the final products. PMID:2760063

  5. Stability of manganese-oxide-modified lanthanum strontium cobaltite in the presence of chromia

    NASA Astrophysics Data System (ADS)

    Ou, Ding Rong; Cheng, Mojie

    2014-12-01

    In order to restrain the decomposition and conductivity degradation of perovskite-type conductive material in the presence of chromia, manganese oxide modification of lanthanum strontium cobaltite has been studied. La0.7Sr0.3CoO3-? (LSC) and MnO2-modified LSC coatings are applied onto Ni-Cr alloy and exposed to long-term oxidation text to examine their chemical stability. In a LSC coating, chromium species migrating from the Ni-Cr alloy could induce the decomposition of LSC and produce SrCrO4 and Co-Cr spinel oxides. In contrast, in the MnO2-modified LSC, Sr is stable and the low-conductivity phase SrCrO4 phase is rarely seen even the coated alloy has gone through 1000 h of oxidation tests at 800 °C. It highlights that MnO2 modification could greatly improve the stability of LSC under Cr-rich conditions. The study of solid state reactions reveals that the influence of MnO2 is mainly due to the reaction between MnO2 and LSC, instead of the direct reaction between MnO2 and chromium oxides.

  6. Molecular-Level Processes Governing the Interaction of Contaminants with Iron and Manganese Oxides - Final Report

    SciTech Connect

    Brown Jr., G. E.; Chambers, S. A.

    1999-10-31

    Many of the inorganic and organic contaminants present in sediments at DOE sites can be altered or destroyed by reduction and oxidation (redox) reactions occurring at mineral surfaces. A fundamental understanding of such redox processes provided by molecular-level studies on structurally and compositionally well-defined mineral surfaces will lead to: (i) improved models of contaminant fate and transport in geochemical systems, and (ii) optimized manipulation of these processes for remediation purposes. To contribute to this understanding, we will study, both experimentally and theoretically, redox processes involving three important contaminants - chromate ion, carbon tetrachloride, and trichloroethene TCE, on the following iron and manganese oxides - hematite, magnetite, maghemite, and pyrolusite. These oxides and their hydroxylated analogs commonly occur as coatings on minerals or as interfaces in the subsurface environment. Single-crystal surfaces of these oxides will be synthesized in carefully controlled fashion by molecular beam epitaxy. These surfaces, as well as high surface are powdered samples of these oxides, will be used in spectroscopic and kinetic experiments in both aqueous and gas phases. Our goal is to identify products and to determine the kinetics and mechanisms of surface-catalyzed redox reaction of Cr(VI) and CR(III), and the reductive dechlorination of carbon tetrachloride and TCE. The combination of theory and experiment will provide the base information needed to scale from the molecular level to the microscopic grain level minerals.

  7. Electronic transport in Lithium Nickel Manganese Oxide, a high-voltage cathode material for Lithium-Ion batteries

    E-print Network

    Ransil, Alan Patrick Adams

    2013-01-01

    Potential routes by which the energy densities of lithium-ion batteries may be improved abound. However, the introduction of Lithium Nickel Manganese Oxide (LixNi1i/2Mn3/2O4, or LNMO) as a positive electrode material appears ...

  8. ADSORPTION OF LEAD FROM A CONTAMINATED SOIL TREATED WITH PHOSPHORUS AND MANGANESE OXIDES BY APRAGUE-DAWLEY RATS

    EPA Science Inventory

    In addition to the formation of insoluble lead (Pb) compounds as a mean of reducing Pb bioavalability, adsorption is another potentially important process controlling the bioavailability of Pb in soils. Less attention has been given to manganese (Mn) oxides, even though they are ...

  9. Purification and Characterization of the Manganese(II) Oxidizing Protein from Erythrobacter sp. SD-21

    NASA Astrophysics Data System (ADS)

    Nakama, K. R.; Lien, A.; Johnson, H. A.

    2013-12-01

    The manganese(II) oxidizing protein (Mop) found in the alpha-proteobacterium Erythrobacter sp. SD-21 catalyzes the formation of insoluble Mn(III/IV) oxides from soluble Mn(II). These Mn(III/IV) oxides formed are one of the strongest naturally occurring oxides, next to oxygen, and can be used to adsorb and oxidize toxic chemicals from the surrounding environment. Because of the beneficial use in the treatment of contaminated sources, the mechanism and biochemical properties of this novel enzyme are being studied. Due to low expression levels in the native host strain, purification of Mop has been problematic. To overcome this problem the gene encoding Mop, mopA, was cloned from the native host into a C-terminal histidine tag vector and expressed in Escherichia coli cells. Affinity chromatography under denaturing conditions have been applied in attempts to purify an active Mop. Western blots have confirmed that the protein is being expressed and is at the expected size of 250 kDa. Preliminary characterization on crude extract containing Mop has shown a Km and vmax value of 2453 uM and 0.025 uM min-1, respectively. Heme and pyrroloquinoline quinone can stimulate Mn(II) oxidizing activity, but hydrogen peroxide does not affect activity, despite the sequence similarity to animal heme peroxidase proteins. Research has been shown that calcium is essential for Mop activity. Purifying an active Mn(II) oxidizing protein will allow for a better understanding behind the enigmatic process of Mn(II) oxidation.

  10. Coprecipitation mechanisms and products in manganese oxidation in the presence of cadmium

    USGS Publications Warehouse

    Hem, J.D.; Lind, Carol J.

    1991-01-01

    Manganese oxidation products were precipitated in an aerated open-aqueous system where a continuous influx of mixed Mn2+ and Cd2+ solution was supplied and pH was maintained with an automated pH-stat adding dilute NaOH. X-ray diffraction and electron diffraction identified the solids produced as mixtures of Cd2Mn34+O8, Mn2+2Mn4+3O8, MnO2 (ramsdellite), and CdCO3. Mean oxidation numbers of the total precipitated Mn as great as 3.6 were reached during titrations. During subsequent aging in solution, oxidation numbers between 3.8 and 3.9 were reached in some precipitates in less than 40 days. Conditional oxidation rate constants calculated from a crystal-growth equation applied to titration data showed the overall precipitation rate, without considering manganese oxidation state in the precipitate, was increased by a factor of ~4 to ~7 when the mole ratio (Cd/Mn + Cd) of cadmium in the feed solution was 0.40 compared with rate constants for hausmannite (Mn2+Mn23+O4 precipitation under similar conditions but without accessory metals. Kinetic experiments were made to test effects of various Cd/Mn + Cd mole ratios and rates of addition of the feed solution, different temperatures from 5.0 to 35??C, and pH from 8.0 to 9.0. Oxidation rates were slower when the Cd mole ratio was less than 0.40. The rate increased by a factor of ~10 when pH was raised one-half unit. The effect of temperature on the rate constants was also substantial, but the meaning of this is uncertain because the rate of formation of Mn4+ oxide in the absence of Cd or other accessory metals was too slow to be measurable in titration experiments. The increased rate of Mn4+ oxide formation in the presence of Cd2+ can be ascribed to the formation of a labile adsorbed intermediate, CdMn2O4 Int, an analog of hausmannite, formed on precipitate surfaces at the beginning of the oxidation process. The increased lability of this structure, resulting from coordination-chemical behavior of Cd2+ during the titration, causes a rapid second-stage rearrangement and facilitates disproportionation of the Mn3+ ions. The Mn2+ ions thus released provide a positive feedback mechanism that couples the two steps of the conversion of Mn2+ to Mn4+ more closely than is possible when other metal ions besides manganese are not present. During aging of precipitates in contact with solutions, proportions of Cd2Mn3O8 and MnO2 increased at the expense of other precipitate components. ?? 1991.

  11. Preparation of poly(aniline-co-o-anisidine)-intercalated mesostructured manganese oxide composites by exchange reaction

    SciTech Connect

    Wang Gengchao [Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China)], E-mail: gengchaow@ecust.edu.cn; Yang Zhenyu; Li Xingwei; Li Chunzhong [Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China); Yuan Weikang [UNILAB, State Key Laboratory of Chemical Reaction Engineering, East China University of Science and Technology, Shanghai 200237 (China)

    2008-08-04

    Layered mesostructured manganese oxide (mesostructured MnO{sub 2}) was synthesized using manganese chloride and lithium hydroxide as the raw materials and cetyltrimethylammonium bromide (CTAB) as the structure-directing agent. Poly(aniline-co-o-anisidine)-intercalated mesostructured MnO{sub 2} composites (P(An-co-oAs)/MnO{sub 2}) were synthesized in an organic solvent through the exchange reaction between the CTAB in MnO{sub 2} gallery and the P(An-co-oAs). The interlayer spacing (I{sub c} values) of mesostructured MnO{sub 2} enlarged from 2.52 to 4.41 nm as the added amount of P(An-co-oAs) increased from 0 to 0.5 g per 0.5 g of mesostructured MnO{sub 2}. The regularity of the layered structure of the composites was firstly decreased due to intercalation of low amounts of P(An-co-oAs). However, with increasing the intercalated amount of P(An-co-oAs) the layered structure of the composites becomes more regular. The electrical conductivity of the composites is 10{sup 2} to 10{sup 3} times higher than that of the mesostructured MnO{sub 2}.

  12. Bio-templated synthesis of lithium manganese oxide microtubes and their application in Li+ recovery.

    PubMed

    Yu, Qianqian; Sasaki, Keiko; Hirajima, Tsuyoshi

    2013-11-15

    Microbial transformations, a primary pathway for the Mn oxides formation in nature, provide potential for material-oriented researchers to fabricate new materials. Using Mn oxidizing fungus Paraconiothyrium sp. WL-2 as a bio-oxidizer as well as a bio-template, a special lithium ion sieve with microtube morphology was prepared through a solid-state transformation. Varying the calcination temperature from 300 to 700 °C was found to influence sample properties and consequently, the adsorption of Li(+). Lithium manganese oxide microtube (LMO-MTs) calcined at different temperatures as well as their delithiated products (HMO-MTs) were characterized by X-ray diffraction (XRD), X-ray absorption fine structure (XAFS) spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Calcination temperatures affect not only the content but also the crystal structure of LMO spinel, which is important in Li(+) adsorption. The optimized sample was obtained after calcination at 500 °C for 4h, which shows higher Li(+) adsorption capacity than particulate materials. PMID:24007997

  13. Mesoporous iron–manganese oxides for sulphur mustard and soman degradation

    SciTech Connect

    Štengl, Václav, E-mail: stengl@iic.cas.cz [Department of Solid State Chemistry, Institute of Inorganic Chemistry AS CR, v.v.i., 250 68 ?ež (Czech Republic) [Department of Solid State Chemistry, Institute of Inorganic Chemistry AS CR, v.v.i., 250 68 ?ež (Czech Republic); J.E. Purkyn? University in Ústí nad Labem, Faculty of Environment, 400 96 Ústí nad Labem (Czech Republic); Grygar, TomᚠMatys [Department of Solid State Chemistry, Institute of Inorganic Chemistry AS CR, v.v.i., 250 68 ?ež (Czech Republic) [Department of Solid State Chemistry, Institute of Inorganic Chemistry AS CR, v.v.i., 250 68 ?ež (Czech Republic); J.E. Purkyn? University in Ústí nad Labem, Faculty of Environment, 400 96 Ústí nad Labem (Czech Republic); Bludská, Jana [Department of Solid State Chemistry, Institute of Inorganic Chemistry AS CR, v.v.i., 250 68 ?ež (Czech Republic)] [Department of Solid State Chemistry, Institute of Inorganic Chemistry AS CR, v.v.i., 250 68 ?ež (Czech Republic); Opluštil, František; N?mec, Tomᚠ[Military Technical Institute of Protection Brno, Vesla?ská 230, 628 00 Brno (Czech Republic)] [Military Technical Institute of Protection Brno, Vesla?ská 230, 628 00 Brno (Czech Republic)

    2012-12-15

    Graphical abstract: Display Omitted Highlights: ? New nanodispersive materials based on Fe and Mn oxides for degradations of warfare agents. ? The best activities for the degradation of sulphur mustard (97.9% in 64 min) and soman (97.9% in 64 min). ? One pot synthesis with friendly transformed to industrial conditions. -- Abstract: Substituted iron(III)–manganese(III, IV) oxides, ammonio-jarosite and birnessite, were prepared by a homogeneous hydrolysis of potassium permanganate and iron(III) sulphate with 2-chloroacetamide and urea, respectively. Synthesised oxides were characterised using Brunauer–Emmett–Teller (BET) surface area and Barrett–Joiner–Halenda porosity (BJH), X-ray diffraction (XRD), infrared spectroscopy (IR), Raman spectroscopy and scanning electron microscopy (SEM). The oxides were taken for an experimental evaluation of their reactivity against sulphur mustard (HD) and soman (GD). When ammonio-jarosite formation is suppressed by adding urea to the reaction mixture, the reaction products are mixtures of goethite, schwertmannite and ferrihydrite, and their degradation activity against soman considerably increases. The best activities for the degradation of sulphur mustard (97.9% in 64 min) and soman (97.9% in 64 min) were observed for FeMn{sub 7}5 with 32.6 wt.% Fe (36.8 wt.% Mn) and FeMn{sub 3}7U with 60.8 wt.% Fe (10.1 wt.% Mn) samples, respectively.

  14. Tremendous effect of the morphology of birnessite-type manganese oxide nanostructures on catalytic activity.

    PubMed

    Hou, Jingtao; Li, Yuanzhi; Mao, Mingyang; Ren, Lu; Zhao, Xiujian

    2014-09-10

    The octahedral layered birnessite-type manganese oxide (OL-1) with the morphologies of nanoflowers, nanowires, and nanosheets were prepared and characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric/differential scanning calorimetry (TG/DSC), Brunnauer-Emmett-Teller (BET), inductively coupled plasma (ICP), and X-ray photoelectron spectroscopy (XPS). The OL-1 nanoflowers possess the highest concentration of oxygen vacancies or Mn(3+), followed by the OL-1 nanowires and nanosheets. The result of catalytic tests shows that the OL-1 nanoflowers exhibit a tremendous enhancement in the catalytic activity for benzene oxidation as compared to the OL-1 nanowires and nanosheets. Compared to the OL-1 nanosheets, the OL-1 nanoflowers demonstrate an enormous decrease (?T(50) = 274 °C; ?T(90) > 248 °C) in reaction temperatures T50 and T90 (corresponding to 50 and 90% benzene conversion, respectively) for benzene oxidation. The origin of the tremendous effect of morphology on the catalytic activity for the nanostructured OL-1 catalysts is experimentally and theoretically studied via CO temperature-programmed reduction (CO-TPR) and density functional theory (DFT) calculation. The tremendous catalytic enhancement of the OL-1 nanoflowers compared to the OL-1 nanowires and nanosheets is attributed to their highest surface area as well as their highest lattice oxygen reactivity due to their higher concentration of oxygen vacancies or Mn(3+), thus tremendously improving the catalytic activity for the benzene oxidation. PMID:25140618

  15. Heterologous Expression and Characterization of the Manganese-Oxidizing Protein from Erythrobacter sp. Strain SD21

    PubMed Central

    Nakama, Katherine; Medina, Michael; Lien, Ahn; Ruggieri, Jordan; Collins, Krystle

    2014-01-01

    The manganese (Mn)-oxidizing protein (MopA) from Erythrobacter sp. strain SD21 is part of a unique enzymatic family that is capable of oxidizing soluble Mn(II). This enzyme contains two domains, an animal heme peroxidase domain, which contains the catalytic site, followed by a C-terminal calcium binding domain. Different from the bacterial Mn-oxidizing multicopper oxidase enzymes, little is known about MopA. To gain a better understanding of MopA and its role in Mn(II) oxidation, the 238-kDa full-length protein and a 105-kDa truncated protein containing only the animal heme peroxidase domain were cloned and heterologously expressed in Escherichia coli. Despite having sequence similarity to a peroxidase, hydrogen peroxide did not stimulate activity, nor was activity significantly decreased in the presence of catalase. Both pyrroloquinoline quinone (PQQ) and hemin increased Mn-oxidizing activity, and calcium was required. The Km for Mn(II) of the full-length protein in cell extract was similar to that of the natively expressed protein, but the Km value for the truncated protein in cell extract was approximately 6-fold higher than that of the full-length protein, suggesting that the calcium binding domain may aid in binding Mn(II). Characterization of the heterologously expressed MopA has provided additional insight into the mechanism of bacterial Mn(II) oxidation, which will aid in understanding the role of MopA and Mn oxidation in bioremediation and biogeochemical cycling. PMID:25172859

  16. Recovery of manganese oxides from spent alkaline and zinc-carbon batteries. An application as catalysts for VOCs elimination.

    PubMed

    Gallegos, María V; Falco, Lorena R; Peluso, Miguel A; Sambeth, Jorge E; Thomas, Horacio J

    2013-06-01

    Manganese, in the form of oxide, was recovered from spent alkaline and zinc-carbon batteries employing a biohydrometallurgy process, using a pilot plant consisting in: an air-lift bioreactor (containing an acid-reducing medium produced by an Acidithiobacillus thiooxidans bacteria immobilized on elemental sulfur); a leaching reactor (were battery powder is mixed with the acid-reducing medium) and a recovery reactor. Two different manganese oxides were recovered from the leachate liquor: one of them by electrolysis (EMO) and the other by a chemical precipitation with KMnO4 solution (CMO). The non-leached solid residue was also studied (RMO). The solids were compared with a MnOx synthesized in our laboratory. The characterization by XRD, FTIR and XPS reveal the presence of Mn2O3 in the EMO and the CMO samples, together with some Mn(4+) cations. In the solid not extracted by acidic leaching (RMO) the main phase detected was Mn3O4. The catalytic performance of the oxides was studied in the complete oxidation of ethanol and heptane. Complete conversion of ethanol occurs at 200°C, while heptane requires more than 400°C. The CMO has the highest oxide selectivity to CO2. The results show that manganese oxides obtained using spent alkaline and zinc-carbon batteries as raw materials, have an interesting performance as catalysts for elimination of VOCs. PMID:23562448

  17. Doubling the capacity of lithium manganese oxide spinel by a flexible skinny graphitic layer.

    PubMed

    Noh, Hyun Kuk; Park, Han-Saem; Jeong, Hu Young; Lee, Sang Uck; Song, Hyun-Kon

    2014-05-12

    By coating nanoparticular lithium manganese oxide (LMO) spinel with a few layers of graphitic basal planes, the capacity of the material reached up to 220?mA?h?g(-1) at a cutoff voltage of 2.5?V. The graphitic layers 1)?provided a facile electron-transfer highway without hindering ion access and, more interestingly, 2)?stabilized the structural distortion at the 3?V region reaction. The gain was won by a simple method in which microsized LMO was ball-milled in the presence of graphite with high energy. Vibratory ball milling pulverized the LMO into the nanoscale, exfoliated graphite of less than 10?layers and combined them together with an extremely intimate contact. Ab?initio calculations show that the intrinsically very low electrical conductivity of the tetragonal phase of the LMO is responsible for the poor electrochemical performance in the 3?V region and could be overcome by the graphitic skin strategy proposed. PMID:24706561

  18. Manganese oxide nanoparticle-assisted laser desorption/ionization mass spectrometry for medical applications

    NASA Astrophysics Data System (ADS)

    Taira, Shu; Kitajima, Kenji; Katayanagi, Hikaru; Ichiishi, Eiichiro; Ichiyanagi, Yuko

    2009-06-01

    We prepared and characterized manganese oxide magnetic nanoparticles (d =5.6 nm) and developed nanoparticle-assited laser desorption/ionization (nano-PALDI) mass spectrometry. The nanoparticles had MnO2 and Mn2O3 cores conjugated with hydroxyl and amino groups, and showed paramagnetism at room temperature. The nanoparticles worked as an ionization assisting reagent in mass spectroscopy. The mass spectra showed no background in the low m/z. The nanoparticles could ionize samples of peptide, drug and proteins (approx. 5000 Da) without using matrix, i.e., 2,5-dihydroxybenzoic acid (DHB), 4-hydroxy-?-cinnamic acid (CHCA) and liquid matrix, as conventional ionization assisting reagents. Post source decay spectra by nano-PALDI mass spectrometry will yield information of the chemical structure of analytes.

  19. Electrochemical Li insertion in lamellar (birnessite) and tunnel manganese oxides (todorokite)

    SciTech Connect

    Duncan, M.J.; Leroux, F.; Nazar, L.F.

    1998-07-01

    A comparison of Li insertion in manganese oxide phases with a tunnel (todorokite) framework, its two-dimensional layered precursor (birnessite/buserite), and Li-exchanged materials are presented. The results outline the effect of the MnO{sub 6} octahedral arrangement and framework composition on the electrochemical response. The interlayer cations in the lamellar materials are exchangeable for Li, giving rise to a lithiated birnessite that displays a sustainable capacity of 125 mAh/g. For todorokite, molten salt exchange using LiNO{sub 3} results in displacement of water from the tunnels, and incorporation of additional Li into the structure. Some of this Li is extractable during charge, resulting in a reversible capacity of 172 mAh/g in the voltage window 4.2--2.0V.

  20. Improved lithium manganese oxide spinel/graphite Li-ion cells for high-power applications

    NASA Astrophysics Data System (ADS)

    Amine, K.; Liu, J.; Kang, S.; Belharouak, I.; Hyung, Y.; Vissers, D.; Henriksen, G.

    The degradation mechanism of lithium manganese oxide spinel/graphite Li-ion cells using LiPF 6-based electrolyte was investigated by a Mn-dissolution approach during high-temperature storage, and by ac impedance measurement using a reference electrode-equipped cell. Through these studies, we confirmed that Mn ions were dissolved from the spinel cathode in the electrolyte and were subsequently reduced on the lithiated graphite electrode surface, due to the chemical activity of the lithiated graphite, and caused a huge increase in the charge-transfer impedance at the graphite/electrolyte interface, which consequently deteriorated cell performance. To overcome the significant degradation of the spinel/graphite Li-ion cells, we investigated a new electrolyte system using lithium bisoxalatoborate (LiBoB, LiB(C 2O 4) 2) salt not having fluorine species in its chemical structure. Superior cycling performance at elevated temperature was observed with the spinel/graphite cells using LiBoB-based electrolyte, which is attributed to the inert chemical structure of LiBoB that does not generate HF. Mn-ion leaching experiments showed that almost no Mn ions were dissolved from the spinel powder after 55 °C storage for 4 weeks. Through optimization of organic solvents for the LiBoB salt, we developed an advanced Li-ion cell chemistry that used lithium manganese oxide spinel, 0.7 M LiBoB/EC:PC:DMC (1:1:3), and graphite as the cathode, electrolyte, and anode, respectively. This cell provides excellent power characteristics, good calendar life, and improved thermal safety for hybrid electric vehicle applications.

  1. Dyes wastewater treatment by reduction-oxidation process in an electrochemical reactor packed with natural manganese mineral.

    PubMed

    Wang, Ai-Min; Qu, Jiu-Hui; Liu, Hui-Juan; Lei, Peng-Ju

    2006-01-01

    A novel technology which combined electrochemical process catalyzed by manganese mineral with electro-assisted coagulation process was proposed in this study. The mineralization of organic pollutant from simulated dye wastewater containing an azo dye Acid Red B (ARB) was experimentally investigated using this method. It was found that the manganese mineral could catalyze the electrochemical process dramatically. The TOC removal percentage of electrochemical treatment catalyzed by manganese mineral was 43.6% while the TOC removal percentage of the process using the manganese mineral alone and using the electrolysis alone were 9.3% and 20.8%, respectively. Moreover, it was found that combined electroxidation with electro-assisted coagulation process could more effectively eliminate ARB. After a period of 180 min electrooxidation and 300 min electroreduction, almost 66.9% of TOC was removed, and the dissolved Mn2+ could be effectivly removed. The effects of the order of oxidation and reduction, the proper ratio electrooxidation/reduction time, and current density on the removal efficiency were investigated in detail. In addition, a proposed mechanism of manganese-mineral-catalyzed electrooxidation-reduction process was discussed in this paper. PMID:20050542

  2. Manganese-induced effects on cerebral trace element and nitric oxide of Hyline cocks.

    PubMed

    Liu, Xiaofei; Zuo, Nan; Guan, Huanan; Han, Chunran; Xu, Shi Wen

    2013-08-01

    Exposure to Manganese (Mn) is a common phenomenon due to its environmental pervasiveness. To investigate the Mn-induced toxicity on cerebral trace element levels and crucial nitric oxide parameters on brain of birds, 50-day-old male Hyline cocks were fed either a commercial diet or a Mn-supplemented diet containing 600, 900, 1,800 mg kg(-1). After being treated with Mn for 30, 60, and 90 days, the following were determined: the changes in contents of copper (Cu), iron (Fe), zinc (Zn), calcium (Ca), selenium (Se) in brain; inducible nitric oxide synthase-nitric oxide (iNOS-NO) system activity in brain; and histopathology and ultrastructure changes of cerebral cortex. The results showed that Mn was accumulated in brain and the content of Cu and Fe increased. However, the levels of Zn and Se decreased and the Ca content presented no obvious regularity. Exposure to Mn significantly elevated the content of NO and the expression of iNOS mRNA. Activity of total NO synthase (T NOS) and iNOS appeared with an increased tendency. These findings suggested that Mn exposure resulted in the imbalance of cerebral trace elements and influenced iNOS in the molecular level, which are possible underlying nervous system injury mechanisms induced by Mn exposure. PMID:23813426

  3. Effects of oxidative stress on apoptosis in manganese-induced testicular toxicity in cocks.

    PubMed

    Liu, Xiao-fei; Zhang, Li-ming; Guan, Hua-nan; Zhang, Zi-wei; Xu, Shi-wen

    2013-10-01

    Manganese (Mn) is a trace element known to be essential for maintaining the proper function and regulation of many biochemical and cellular reactions. However, little is known about the reproductive toxicity of Mn in birds. To investigate the toxicity of Mn on male reproduction in birds, 50-day-old cocks were fed either a commercial diet or a Mn-supplemented diet containing 600, 900, and 1800 mg/kg MnCl?. After being treated with Mn for 30, 60, and 90 d, the following were determined: Mn content; histological and ultrastructural changes in the testes, apoptosis; the malondialdehyde (MDA) level; the activities of superoxide dismutase (SOD); the inhibition ability of hydroxyl radicals (OH); the levels of nitric oxide (NO), nitric oxide synthase (NOS), and protein carbonyl in the testes; the DNA-protein crosslinks (DPC); and the activity of the ATP enzyme. Exposure to Mn significantly lowered the activity of SOD and glutathione peroxidase (GPx) and the inhibition ability of OH. Mn exposure also increased the levels of MDA, NO, NOS, DPC, and protein carbonyl; the number of apoptotic cells; and the Mn content and caused obvious histopathological changes in the testes. These findings suggested that Mn exposure resulted in the oxidative damage of cock testicular tissue by altering radical formation, ATP enzyme systems, apoptosis, and DNA damage, which are possible underlying reproductive toxicity mechanisms induced by Mn exposure. PMID:23907021

  4. In depth analysis of apoptosis induced by silica coated manganese oxide nanoparticles in vitro.

    PubMed

    Yu, Chao; Zhou, Zhiguo; Wang, Jun; Sun, Jin; Liu, Wei; Sun, Yanan; Kong, Bin; Yang, Hong; Yang, Shiping

    2015-02-11

    Manganese oxide nanoparticles (MnO NPs) have been regarded as a new class of T1-positive contrast agents. The cytotoxicity of silica coated MnO NPs (MnO@SiO2 NPs) was investigated in human cervical carcinoma cells (HeLa) and mouse fibroblast cells (L929). The changes of cell viability, cell morphology, cellular oxidative stress, mitochondrial membrane potential and cell cycle induced by MnO@SiO2 NPs were evaluated. Compared to HeLa cells, L929 cells showed lower cell viability, more strongly response to oxidative stress and higher percentage in the G2/M phase of cell cycle. The appearance of sub-G1 peak, double staining with Annexin V-FITC/PI and the increase of Caspase-3 activity further confirmed apoptosis should be the major form of cell death. Moreover, the apoptotic pathway was clarified as follows. Firstly, reactive oxygen species (ROS) is generated induced by MnO@SiO2 NPs, then p53 is activated followed by an increase in the bax and a decrease in the bcl-2, ultimately leading to G2/M phase arrest, increasing the activity of caspase-3 and inducing apoptosis. PMID:25464291

  5. Early diagenetic processes generate iron and manganese oxide layers in the sediments of Lake Baikal, Siberia.

    PubMed

    Torres, Natascha T; Och, Lawrence M; Hauser, Peter C; Furrer, Gerhard; Brandl, Helmut; Vologina, Elena; Sturm, Michael; Bürgmann, Helmut; Müller, Beat

    2014-04-01

    Distinct layers of iron(III) and manganese(IV) (Fe/Mn) oxides are found buried within the reducing part of the sediments in Lake Baikal and cause considerable complexity and steep vertical gradients with respect to the redox sequence. For the on-site investigation of the responsible biogeochemical processes, we applied filter tube samplers for the extraction of sediment porewater combined with a portable capillary electrophoresis instrument for the analyses of inorganic cations and anions. On the basis of the new results, the sequence of diagenetic processes leading to the formation, transformation, and dissolution of the Fe/Mn layers was investigated. With two exemplary cores we demonstrate that the dissolution of particulate Fe and Mn is coupled to the anaerobic oxidation of CH? (AOM) either via the reduction of sulphate (SO?(2-)) and the subsequent generation of Fe(II) by S(-II) oxidation, or directly coupled to Fe reduction. Dissolved Fe(II) diffuses upwards to reduce particulate Mn(IV) thus forming a sharp mineral boundary. An alternative dissolution pathway is indicated by the occurrence of anaerobic nitrification of NH?(+) observed at locations with Mn(IV). Furthermore, the reasons and consequences of the non-steady-state sediment pattern and the resulting redox discontinuities are discussed and a suggestion for the burial of active Fe/Mn layers is presented. PMID:24619231

  6. Manganese Doping of Magnetic Iron Oxide Nanoparticles: Tailoring Surface Reactivity for a Regenerable Heavy Metal Sorbent

    SciTech Connect

    Warner, Cynthia L.; Chouyyok, Wilaiwan; Mackie, Katherine E.; Neiner, Doinita; Saraf, Laxmikant; Droubay, Timothy C.; Warner, Marvin G.; Addleman, Raymond S.

    2012-02-28

    A method for tuning the analyte affinity of magnetic, inorganic nanostructured sorbents for heavy metal contaminants is described. The manganese-doped iron oxide nanoparticle sorbents have a remarkably high affinity compared to the precursor material. Sorbent affinity can be tuned toward an analyte of interest simply by adjustment of the dopant quantity. The results show that following the Mn doping process there is a large increase in affinity and capacity for heavy metals (i.e., Co, Ni, Zn, As, Ag, Cd, Hg, and Tl). Capacity measurements were carried out for the removal of cadmium from river water and showed significantly higher loading than the relevant commercial sorbents tested for comparison. The reduction in Cd concentration from 100 ppb spiked river water to 1 ppb (less than the EPA drinking water limit of 5 ppb for Cd) was achieved following treatment with the Mn-doped iron oxide nanoparticles. The Mn-doped iron oxide nanoparticles were able to load 1 ppm of Cd followed by complete stripping and recovery of the Cd with a mild acid wash. The Cd loading and stripping is shown to be consistent through multiple cycles with no loss of sorbent performance.

  7. The effect of different metal ions between nanolayers of manganese oxide on water oxidation.

    PubMed

    Najafpour, Mohammad Mahdi; Isaloo, Mohsen Abbasi; Ghobadi, Mohadeseh Zarei; Amini, Emad; Haghighi, Behzad

    2014-12-01

    Here, we used a strategy to answer to the question that whether Ca(II) ion is specific for water oxidation or not? In the procedure, first we synthesized layered Mn oxides with K(I) between layers and then replaced K(I) by Ca(II), K(I), Mg(II), La(III) or Ni(II). We proposed that Ca(II), K(I), Mg(II), La(III) and Ni(II), between layers are important to form efficient water-oxidizing catalyst, but not specific in water oxidation. However, Cu(II) ions decrease water-oxidizing activity of layered Mn oxides. The result is important to find critical factors in water oxidation by low-cost and environmentally friendly nanolayered Mn oxides. PMID:25463674

  8. Chemical syntheses of manganese and tantalum oxide octahedral molecular sieves and their structural characterization by powder x-ray diffraction

    NASA Astrophysics Data System (ADS)

    Duan, Niangao

    This research consists of soft chemical synthesis and structural investigations of manganese and tantalum oxide octahedral molecular sieves. These include the use of sol-gel, hydrothermal and reflux methods for syntheses and the employment of various techniques for characterization, especially the Rietveld analysis of powder X-ray diffraction data for structural refinements. The manganese oxide cryptomelane (K-OMS-2) with a tunnel structure and birnessite layered materials (OL-1) were prepared by the sol gel method. The synthesis consists of reacting MnO4- solutions with fumaric acid or glucose to form a gel, and heating the xerogels at a temperature effective to produce the final manganese oxide materials. These sol-gel methods give many advantages, such as high thermal stabilities of products, over other preparation routes. The synthetic parameters have been optimized to prepare pure K-OMS-2 and OL-1. The crystal structure of K-OMS-2 has been refined by the Rietveld method from in-house powder X-ray diffraction data. The potassium tantalate defect pyrochlores were prepared by hydrothermal methods at a temperature of 200°C. The materials were crystallized from tantalum pentoxide in a potassium hydroxide solution, with a uniform crystal size of about 1 mum. They were ion-exchanged with H+ at low temperatures in a nitric acid solution. A BET surface area of 15 m 2/g was obtained. The structure of this defect pyrochlore and its acid exchanged form were determined by Rietveld refinement from powder X-ray diffraction data. The reflux method was also employed to search for new manganese oxide microporous materials. A ramsdellite material with a 1 x 2 tunnel structure and high surface area of 70 m2/g was prepared. Catalytic oxidations of hexane and cyclohexane with tert-butyl hydroperoxide have shown good activities with this catalyst. This investigation suggests that shape selectivity plays a role in the high catalytic activities of the oxidations of these saturated hydrocarbons.

  9. Photochemical oxidation of a manganese(III) complex with oxygen and toluene derivatives to form a manganese(V)-oxo complex.

    PubMed

    Jung, Jieun; Ohkubo, Kei; Prokop-Prigge, Katharine A; Neu, Heather M; Goldberg, David P; Fukuzumi, Shunichi

    2013-12-01

    Visible light photoirradiation of an oxygen-saturated benzonitrile solution of a manganese(III) corrolazine complex [(TBP8Cz)Mn(III)] (1): [TBP8Cz = octakis(p-tert-butylphenyl)corrolazinato(3-)] in the presence of toluene derivatives resulted in formation of the manganese(V)-oxo complex [(TBP8Cz)Mn(V)(O)]. The photochemical oxidation of (TBP8Cz)Mn(III) with O2 and hexamethylbenzene (HMB) led to the isosbestic conversion of 1 to (TBP8Cz)Mn(V)(O), accompanied by the selective oxidation of HMB to pentamethylbenzyl alcohol (87%). The formation rate of (TBP8Cz)Mn(V)(O) increased with methyl group substitution, from toluene, p-xylene, mesitylene, durene, pentamethylbenzene, up to hexamethylbenzene. Deuterium kinetic isotope effects (KIEs) were observed for toluene (KIE = 5.4) and mesitylene (KIE = 5.3). Femtosecond laser flash photolysis of (TBP8Cz)Mn(III) revealed the formation of a tripquintet excited state, which was rapidly converted to a tripseptet excited state. The tripseptet excited state was shown to be the key, activated state that reacts with O2 via a diffusion-limited rate constant. The data allow for a mechanism to be proposed in which the tripseptet excited state reacts with O2 to give the putative (TBP8Cz)Mn(IV)(O2(•-)), which then abstracts a hydrogen atom from the toluene derivatives in the rate-determining step. The mechanism of hydrogen abstraction is discussed by comparison of the reactivity with the hydrogen abstraction from the same toluene derivatives by cumylperoxyl radical. Taken together, the data suggest a new catalytic method is accessible for the selective oxidation of C-H bonds with O2 and light, and the first evidence for catalytic oxidation of C-H bonds was obtained with 10-methyl-9,10-dihydroacridine as a substrate. PMID:24219426

  10. Deposition and release of graphene oxide nanomaterials using a quartz crystal microbalance.

    PubMed

    Chowdhury, Indranil; Duch, Matthew C; Mansukhani, Nikhita D; Hersam, Mark C; Bouchard, Dermont

    2014-01-21

    Interactions of graphene oxide (GO) with silica surfaces were investigated using a quartz crystal microbalance with dissipation monitoring (QCM-D). Both GO deposition and release were monitored on silica- and poly-l-lysine (PLL) coated surfaces as a function of GO concentration and in NaCl, CaCl2, and MgCl2 as a function of ionic strength (IS). Under favorable conditions (PLL-coated positive surface), GO deposition rates increased with GO concentration, as expected from colloidal theory. Increased NaCl concentration resulted in a greater deposition attachment efficiency of GO on the silica surface, indicating that deposition of GO follows Derjaguin-Landau-Verwey-Overbeek (DLVO) theory; GO deposition rates decreased at high IS, however, due to large aggregate formation. GO critical deposition concentration (CDC) on the silica surface is determined to be 40 mM NaCl which is higher than the reported CDC values of fullerenes and lower than carbon nanotubes. A similar trend is observed for MgCl2 which has a CDC value of 1.2 mM MgCl2. Only a minimal amount of GO (frequency shift <2 Hz) was deposited on the silica surface in CaCl2 due to the bridging ability of Ca(2+) ions with GO functional groups. Significant GO release from silica surface was observed after adding deionized water, indicating that GO deposition is reversible. The release rates of GO were at least 10-fold higher than the deposition rates under similar conditions indicating potential high release and mobility of GO in the environment. Under favorable conditions, a significant amount of GO was released which indicates potential multilayer GO deposition. However, a negligible amount of deposited GO was released in CaCl2 under favorable conditions due to the binding of GO layers with Ca(2+) ions. Release of GO was significantly dependent on salt type with an overall trend of NaCl > MgCl2 > CaCl2. PMID:24345218

  11. Manganese scavenging and oxidation at hydrothermal vents and in vent plumes

    NASA Astrophysics Data System (ADS)

    Mandernack, Kevin W.; Tebo, Bradley M.

    1993-08-01

    Hydrothermal vents provide a major source of dissolved Mn(II) to the oceans, where concentrations range from 5 mM within the 350°C hot smokers to just above ambient seawater concentration in far field vent plumes. The Mn(II)-rich environments within warm vents and vent plumes provide a suitable habitat for Mn(II) oxidizing bacteria. In order to compare rates of scavenging and oxidation of Mn(II) proximally within vent fields (<30 m from venting water and temperatures <16°C) and distally within vent plumes, and to determine the relative contribution of microbes, incubation experiments using 54Mn as a radiotracer were conducted in situ and on collected water samples from three hydrothermal vent locations: the Guaymas basin (GB), the Galapagos spreading center (GA), and the Endeavor Ridge of the Juan de Fuca spreading center (JDF). Both the adsorbed and oxidized fractions of the total 54Mn scavenged were determined and found to often be significant (as high as 65 and 74%, respectively). Manganese scavenging rates were generally higher in in situ incubations than in incubations conducted on board ship. Inhibition of 54Mn scavenging by sodium azide provided evidence for microbially mediated Mn(II) uptake and oxidation in waters both proximal (GA and GB) and distal to the vents (GA and JDF), even at distances as great as 17 km from the ridge axis at JDF. The highest manganese scavenging rates were observed within the vent fields (up to 2.5 nM/day). The residence times of dissolved Mn(II) were shorter in the GB and GA vent fields (26 and 28 days) than in the JDF vent field (1.4 years). This difference may be due to different mechanisms of Mn(II) precipitation in operation. At the GA vent field Mn(II) precipitation was often strongly inhibited by sodium azide and therefore apparently due to microbial activity. In contrast, Mn(II) scavenging within the JDF vent field was not significantly affected by sodium azide. Because 54Mn scavenging in the JDF vent field was dependent on the presence of oxygen and a much larger fraction of the total 54Mn scavenged was adsorbed than oxidized, manganese scavenging appears to occur primarily by an abiological mechanism, perhaps coprecipitation with iron oxyhydroxides. In comparison to the vent fields, Mn(II) scavenging rates were lower within the vent plumes (<0.6 nM/ day for GA and <0.2 nM/day for JDF), whereas residence times were not significantly different (as low as 34 days for GA and 1.0 years for JDF). The short residence times (90 and 118 days) and high microbial activity measured in bottom waters beneath the vent plumes at GA and JDF probably resulted from enhanced scavenging by manganate-coated bacteria that settled out from the vent plume and accumulated near the bottom. Therefore, bacteria not only enhance the scavenging of Mn within vent waters, but also facilitate Mn deposition to the sediments.

  12. Understanding the role of gold nanoparticles in enhancing the catalytic activity of manganese oxides in water oxidation reactions.

    PubMed

    Kuo, Chung-Hao; Li, Weikun; Pahalagedara, Lakshitha; El-Sawy, Abdelhamid M; Kriz, David; Genz, Nina; Guild, Curtis; Ressler, Thorsten; Suib, Steven L; He, Jie

    2015-02-16

    The Earth-abundant and inexpensive manganese oxides (MnOx) have emerged as an intriguing type of catalysts for the water oxidation reaction. However, the overall turnover frequencies of MnOx catalysts are still much lower than that of nanostructured IrO2 and RuO2 catalysts. Herein, we demonstrate that doping MnOx polymorphs with gold nanoparticles (AuNPs) can result in a strong enhancement of catalytic activity for the water oxidation reaction. It is observed that, for the first time, the catalytic activity of MnOx/AuNPs catalysts correlates strongly with the initial valence of the Mn centers. By promoting the formation of Mn(3+) species, a small amount of AuNPs (<5%) in ?-MnO2/AuNP catalysts significantly improved the catalytic activity up to 8.2 times in the photochemical and 6 times in the electrochemical system, compared with the activity of pure ?-MnO2. PMID:25284796

  13. Transparent conductive tungsten-doped tin oxide thin films synthesized by sol–gel technique on quartz glass substrates

    Microsoft Academic Search

    Yanwei Huang; Dezeng Li; Jiahan Feng; Guifeng Li; Qun Zhang

    2010-01-01

    Transparent conductive tungsten-doped tin oxide (SnO2:W) thin films were synthesized on quartz glass substrates by sol–gel dip-coating method. It was found that the films were\\u000a highly transparent and the average optical transmission was about 90% in the visible and near infrared region from 400 to\\u000a 2,500 nm. The optical band gap is about 4.1 eV. The lowest resistivity of 5.8 × 10?3 ohm cm was obtained,

  14. Polyvinylpyrrolidone/reduced graphene oxide nanocomposites thin films coated on quartz crystal microbalance for NO2 detection at room temperature

    NASA Astrophysics Data System (ADS)

    Huang, Junlong; Xie, Guangzhong; Zhou, Yong; Xie, Tao; Tai, HuiLing; Yang, Guangjin

    2014-08-01

    Polyvinylpyrrolidone (PVP)/reduced graphene oxide (RGO) nanocomposites are sprayed on quartz crystal microbalance (QCM) for NO2 sensing. The thin films are characterized by Fourier transform infrared spectroscopy (FTIR) and ultraviolet-visible spectroscopy (UV-VIS). The experimental results reveal that PVP/RGO sensor exhibits higher sensitivity and shorter recovery time than those of PVP. Besides, the response to 20 ppm NO2 is higher than other gases such as CO, CO2 and NH3 even at 100ppm. When the PVP/RGO sensor is exposed to these gases, the good selectivity to NO2 makes the sensor ideal for NO2 detection.

  15. Computer Aided Factorial Analysis of the Adsorption of Calcium ion (Ca 2+ ) on Manganese (IV) oxide used in Leclanche dry cell

    Microsoft Academic Search

    Duncan Folorunsho Aloko; Kamoru Adio Salam; Emmanuel Okali Oklobia

    The adsorption of calcium ions on manganese (IV) oxide was investigated by pH measurement in potentiometric titration of 1M, 0.1M, 0.01M, and 0.001M solutions of the ions without and with 2g of manganese (IV) oxide at temperatures of 28 o C and 30 o C; using 0.1M trioxonitrate (V) acid solution as titrant. The factorial method of design; using Minitab®

  16. Effects of synthetic parameters on structure and electrochemical performance of spinel lithium manganese oxide by citric acid-assisted sol–gel method

    Microsoft Academic Search

    Tingfeng Yi; Changsong Dai; Kun Gao; Xinguo Hu

    2006-01-01

    The spinel lithium manganese oxide cathode materials were prepared by citric acid-assisted sol–gel method at 623–1073K in air. The effects of pH value, raw material, synthesis temperature and time on structure and electrochemical performance of spinel lithium manganese oxide are investigated by X-ray diffraction (XRD), scanning electronic microscope (SEM) and cyclic voltammetry (CV). XRD data results strongly suggest that the

  17. Manganese Oxidation State as a Cause of Irritant Patch Test Reactions

    PubMed Central

    Shallcross, Laurie; Ritchie, Simon; Harberts, Erin; Tammaro, Antonella; Gaitens, Joanna; Gaspari, Anthony A.

    2015-01-01

    Background Manganese chloride (MnCl2) 2.5% is included in the extended metals patch test series to evaluate patients for contact hypersensitivity to this metal salt. Objectives The objective of this study was to prospectively determine the rate of allergic and irritant patch test reactions to MnCl2 (Mn(II)), Mn2O3 (Mn(III)), and KMnO4 (Mn(VII)) in a cohort of patients undergoing patch testing. Methods Fifty-eight patients were patch tested with MnCl2, Mn2O3, and KMnO4, each at 2.5% in petrolatum. Patch readings were taken at 48, and 72 or 96 hours, and scored using standard methods. Cultured monolayers of keratinocytes (KCs) were exposed to MnCl2, Mn2O3, and KMnO4 in aqueous culture medium, and cell survival and cytokine release were studied. Conclusions MnCl2 caused irritant patch test reactions in 41% of the cohort, whereas Mn2O3 and KMnO4 caused a significantly lower rate of irritant reactions (both 3%). No allergic morphologies were observed. Similarly, in cultured KC monolayers, only MnCl2 was cytotoxic to KC and induced tumor necrosis factor ? release. The oxidation state of manganese used for patch testing affects the irritancy of this metal salt, as Mn(II) caused an unacceptably high rate of irritant reactions in a cohort of patients. In vitro studies confirmed these clinical data, as only Mn(II) was cytotoxic to cultured monolayers of KC. PMID:24603521

  18. Oxidative stress and mitochondrial-mediated apoptosis in dopaminergic cells exposed to methylcyclopentadienyl manganese tricarbonyl.

    PubMed

    Kitazawa, Masashi; Wagner, Jarrad R; Kirby, Michael L; Anantharam, Vellareddy; Kanthasamy, Anumantha G

    2002-07-01

    Methylcyclopentadienyl manganese tricarbonyl (MMT), an organic manganese-containing gasoline additive, was investigated to determine whether MMT potentially causes dopaminergic neurotoxic effects. MMT is acutely cytotoxic and dopamine-producing cells (PC-12) seemed to be more susceptible to cytotoxic effects than nondopaminergic cells (striatal gamma-aminobutyric acidergic and cerebellar granule cells). MMT also potently depleted dopamine apparently by cytoplasmic vesicular release to the cytosol, a neurochemical change resembling other dopaminergic neurotoxicants. Generation of reactive oxygen species (ROS), an early effect in toxicant-induced apoptosis, occurred within 15 min of MMT exposure. MMT caused a loss of mitochondrial transmembrane potential (DeltaPsim), a likely source of ROS generation. The ROS signal further activated caspase-3, an important effector caspase, which could be inhibited by antioxidants (Trolox or N-acetyl cysteine). Predepletion of dopamine by using alpha-methyl-p-tyrosine (tyrosine hydroxylase inhibitor) treatment partially prevented caspase-3 activation, denoting a significant dopamine and/or dopamine by-product contribution to initiation of apoptosis. Genomic DNA fragmentation, a terminal hallmark of apoptosis, was induced concentration dependently by MMT but completely prevented by pretreatment with Trolox, deprenyl (monoamine oxidase-B inhibitor), and alpha-methyl-p-tyrosine. A final set of critical experiments was performed to verify the pharmacological studies using a stable Bcl-2-overexpressing PC-12 cell line. Bcl-2-overexpressing cells were significantly refractory to MMT-induced ROS generation, caspase-3 activation, and loss of DeltaPsim and were completely resistant to MMT-induced DNA fragmentation. Taken together, the results presented herein demonstrate that oxidative stress plays an important role in mitochondrial-mediated apoptotic cell death in cultured dopamine-producing cells after exposure to MMT. PMID:12065696

  19. Nutrient input influences fungal community composition and size and can stimulate manganese (II) oxidation in caves.

    PubMed

    Carmichael, Sarah K; Zorn, Bryan T; Santelli, Cara M; Roble, Leigh A; Carmichael, Mary J; Bräuer, Suzanna L

    2015-08-01

    Little is known about the fungal role in biogeochemical cycling in oligotrophic ecosystems. This study compared fungal communities and assessed the role of exogenous carbon on microbial community structure and function in two southern Appalachian caves: an anthropogenically impacted cave and a near-pristine cave. Due to carbon input from shallow soils, the anthropogenically impacted cave had an order of magnitude greater fungal and bacterial quantitative-polymerase chain reaction (qPCR) gene copy numbers, had significantly greater community diversity, and was dominated by ascomycotal phylotypes common in early phase, labile organic matter decomposition. Fungal assemblages in the near-pristine cave samples were dominated by Basidiomycota typically found in deeper soils (and/or in late phase, recalcitrant organic matter decomposition), suggesting more oligotrophic conditions. In situ carbon and manganese (II) [Mn(II)] addition over 10 weeks resulted in growth of fungal mycelia followed by increased Mn(II) oxidation. A before/after comparison of the fungal communities indicated that this enrichment increased the quantity of fungal and bacterial cells, yet decreased overall fungal diversity. Anthropogenic carbon sources can therefore dramatically influence the diversity and quantity of fungi, impact microbial community function, and stimulate Mn(II) oxidation, resulting in a cascade of changes that can strongly influence nutrient and trace element biogeochemical cycles in karst aquifers. PMID:25865809

  20. Growth of different phases of yttrium manganese oxide thin films by pulsed laser deposition

    SciTech Connect

    Kumar, Manish; Choudhary, R. J.; Phase, D. M. [UGC-DAE Consortium for Scientific Research, Khandwa Road, Indore, 452001 (India)

    2012-06-05

    Various phases of yttrium manganese oxide (YMO) thin films have been synthesized on different substrates from a single target of h-YMnO{sub 3}. It is observed that the phase stability and crystallinity of YMO thin films depend on the substrate used and oxygen partial pressure (OPP). (110) oriented and polycrystalline growth of h-YMnO{sub 3} are observed on the Al{sub 2}O{sub 3} (0001) and NGO (110) substrates respectively, when grown in OPP {approx_equal} 10{sup -6} Torr. While for similar OPP value, growth of mixed phases (h-YMnO{sub 3} and o-YMn{sub 2}O{sub 5}) is observed on Si (001) substrate. Oriented growth of O-YMn{sub 2}O{sub 5} phase film on Si (001) substrate is observed first time, when deposited at OPP value of 225 and 350 mTorr. +3 and mixed oxidation states (+3 and +4) of Mn were confirmed by x-ray photoelectron spectroscopy in pure YMnO{sub 3} phase and YMn{sub 2}O{sub 5} phase respectively.

  1. Manganese oxide/titania materials for removal of NOx and elemental mercury from flue gas

    SciTech Connect

    Lei Ji; Pavani M. Sreekanth; Panagiotis G. Smirniotis; Stephen W. Thiel; Neville G. Pinto [University of Cincinnati, Cincinnati, OH (United States). Department of Chemical & Materials Engineering

    2008-07-15

    A novel catalyst for low temperature selective catalytic reduction (SCR) using CO as reductant, MnOx supported on titania, has been shown to be effective for both elemental mercury capture and low temperature SCR. In low temperature (200{sup o}C) SCR trials using an industrially relevant space velocity (50 000 h{sup -1}) and oxygen concentration (2 vol %), nearly quantitative reduction of NOx was obtained using CO as the reductant. Fresh catalyst used as an adsorbent for elemental mercury from an inert atmosphere showed remarkable mercury capture capacity, as high as 17.4 mg/g at 200{sup o}C. The catalyst effectively captured elemental mercury after use in NOx reduction. Mercury capture efficiency was not affected by the presence of water vapor. Mercury capacity was reduced in the presence of SO{sub 2}. Manganese loading and bed temperature, which influence surface oxide composition, were found to be important factors for mercury capture. X-ray photoelectron spectroscopy (XPS) results reveal that the mercury is present in its oxidized form (HgO) in spent catalyst, indicating the participation of lattice oxygen of the catalyst in the reaction. These results suggest that a single-step process integrating low temperature SCR and mercury capture from flue gas might be feasible. 42 refs., 10 figs., 2 tabs.

  2. Catalytic oxidation of ammonia over the SiO{sub 2}-pillared oxycompounds containing titanium and manganese with layered structure

    SciTech Connect

    Yahiro, Hidenori; Nakai, Toshihiro; Shiotani, Masaru; Yamanaka, Shoji

    1999-10-01

    A SiO{sub 2}-pillared manganese titanate (SiO{sub 2}-MTO) with layered structure, which has a surface area as large as more than 700 m{sup 2}/g, effectively catalyzed the NH{sup 3} oxidation with high selectivity to N{sub 2}. The H{sub 2} temperature-programmed reduction results suggested that the manganese ions in SiO{sub 2}-MTO were in an oxidation state of +3 even in the absence of either Rb{sup +} or C{sub 10}H{sub 21}NH{sub 3}{sup +} ions as a charge-balancing cation. The observed high selectivity to N{sub 2} is attributable to oxygen vacancies associated with Mn{sup 3+} ions in the layer.

  3. Energetics of the manganese oxide cluster cations MnNO+ (N=2-5): Role of oxygen in the binding of manganese atoms

    NASA Astrophysics Data System (ADS)

    Tono, Kensuke; Terasaki, Akira; Ohta, Toshiaki; Kondow, Tamotsu

    2006-05-01

    The photodissociation of manganese oxide cluster cations MnNO+ (N=2-5), into MnN -1O+ (one-atom loss) and MnN -2O+ (two-atom), was investigated in the photon-energy range of 1.08-2.76eV. The bond-dissociation energies D0(MnN -1O+⋯Mn) for N =3, 4, and 5 were determined to be 1.84±0.03, 0.99±0.05, and 1.25±0.14eV, respectively, from the threshold energies for the one- and two-atom losses. As Mn2O+ did not dissociate even at the highest photon energy used, the bond dissociation energy of Mn2O+, D0(Mn+⋯MnO), was obtained from a density-functional-theory calculation to be 3.04eV. The present findings imply that the core ion Mn2O+ is bound weakly with the rest of the manganese atoms in MnNO+.

  4. Protective effects of manganese(II) chloride on hyaluronan degradation by oxidative system ascorbate plus cupric chloride

    PubMed Central

    Valachová, Katarína; Kogan, Grigorij; Gemeiner, Peter; Šoltés, Ladislav

    2010-01-01

    The degradation of several high-molar-mass hyaluronan samples was investigated in the presence of ascorbic acid itself and further by an oxidative system composed of ascorbic acid plus transition metal ions, i.e. Fe(II) or Cu(II) ions. The latter oxidative system imitates conditions in a joint synovial fluid during early phase of acute joint inflammation and can be used as a model for monitoring oxidative degradation of hyaluronan under pathophysiological conditions. The system Cu(II) plus ascorbate (the Weissberger oxidative system) resulted in a more significant decrease of hyaluronan molar mass compared to the oxidative system Fe(II) plus ascorbate. Addition of manganese(II) chloride was found to decrease the rate of the oxidative damage of hyaluronan initiated by ascorbate itself and by the Weissberger system. PMID:21217868

  5. Protective effects of manganese(II) chloride on hyaluronan degradation by oxidative system ascorbate plus cupric chloride.

    PubMed

    Valachová, Katarína; Kogan, Grigorij; Gemeiner, Peter; Soltés, Ladislav

    2010-03-01

    The degradation of several high-molar-mass hyaluronan samples was investigated in the presence of ascorbic acid itself and further by an oxidative system composed of ascorbic acid plus transition metal ions, i.e. Fe(II) or Cu(II) ions. The latter oxidative system imitates conditions in a joint synovial fluid during early phase of acute joint inflammation and can be used as a model for monitoring oxidative degradation of hyaluronan under pathophysiological conditions. The system Cu(II) plus ascorbate (the Weissberger oxidative system) resulted in a more significant decrease of hyaluronan molar mass compared to the oxidative system Fe(II) plus ascorbate. Addition of manganese(II) chloride was found to decrease the rate of the oxidative damage of hyaluronan initiated by ascorbate itself and by the Weissberger system. PMID:21217868

  6. Isolation and characterization of a unicellular manganese-oxidizing bacterium from a freshwater lake in northwestern Russia

    Microsoft Academic Search

    A. A. Falamin; A. V. Pinevich

    2006-01-01

    A unicellular manganese-oxidizing bacterium (strain L7), isolated from Lake Ladoga, is identified as “Siderocapsa” sp. according to its morphology. However, this bacterium belongs to the phylogenetic cluster of Pseudomonas putida. The physiological characteristics (utilization of sugars, polyols, organic acids, and phenolic substrates as carbon and\\u000a energy sources) also indicate the similarity of strain L7 to representatives of the genus Pseudomonas.

  7. Low Temperature Synthesis of Nano-Sized Lithium Manganese Oxide Powder by the Sol-Gel Process Using PVA

    Microsoft Academic Search

    Chung-Hsin Lu; Susanta Kumar Saha

    2001-01-01

    Lithium manganese oxide (LiMn2O4) powder with spinel structure has been synthesized by a sol-gel method using an aqueous solution of metal nitrates containing polyvinyl alcohol (PVA). The role of PVA and the calcination conditions for the formation of LiMn2O4 have been studied. Homogeneity and reactivity of the precursor powder are enhanced with an increase in the amount of PVA in

  8. Bacterial removal in flow-through columns packed with iron-manganese bimetallic oxide-coated sand

    Microsoft Academic Search

    Seong-Jik Park; Chang-Gu Lee; Song-Bae Kim; Yoon-Young Chang; Jae-Kyu Yang

    2012-01-01

    The objective of this study was to investigate the performance of iron-manganese bimetallic oxide-coated sand (IMCS) in the removal of bacteria (Escherichia coli ATCC 11105) using small-scale (length = 20 cm, inner diameter = 2.5 cm) and 30-day long-term (length = 50 cm, inner diameter = 2.5 cm) column experiments. Results indicated that the bacterial removal capacity of IMCS (qeq =

  9. Curcumin protects against cytotoxic and inflammatory effects of quartz particles but causes oxidative DNA damage in a rat lung epithelial cell line

    SciTech Connect

    Li Hui; Berlo, Damien van; Shi Tingming [Institut fuer umweltmedizinische Forschung (IUF) at the Heinrich-Heine-University Duesseldorf gGmbH, Auf'm Hennekamp 50, 40225 Duesseldorf (Germany); Speit, Guenter [Institute of Human Genetics, University of Ulm (Germany); Knaapen, Ad M. [Department of Health Risk Analysis and Toxicology, Nutrition and Toxicology Research Institute Maastricht (NUTRIM), University of Maastricht (Netherlands); Borm, Paul J.A. [Institut fuer umweltmedizinische Forschung (IUF) at the Heinrich-Heine-University Duesseldorf gGmbH, Auf'm Hennekamp 50, 40225 Duesseldorf (Germany); Centre for Expertise in Life Sciences, Zuyd University, Heerlen (Netherlands); Albrecht, Catrin [Institut fuer umweltmedizinische Forschung (IUF) at the Heinrich-Heine-University Duesseldorf gGmbH, Auf'm Hennekamp 50, 40225 Duesseldorf (Germany); Schins, Roel P.F. [Institut fuer umweltmedizinische Forschung (IUF) at the Heinrich-Heine-University Duesseldorf gGmbH, Auf'm Hennekamp 50, 40225 Duesseldorf (Germany)], E-mail: roel.schins@uni-duesseldorf.de

    2008-02-15

    Chronic inhalation of high concentrations of respirable quartz particles has been implicated in various lung diseases including lung fibrosis and cancer. Generation of reactive oxygen species (ROS) and oxidative stress is considered a major mechanism of quartz toxicity. Curcumin, a yellow pigment from Curcuma longa, has been considered as nutraceutical because of its strong anti-inflammatory, antitumour and antioxidant properties. The aim of our present study was to investigate whether curcumin can protect lung epithelial cells from the cytotoxic, genotoxic and inflammatory effects associated with quartz (DQ12) exposure. Electron paramagnetic resonance (EPR) measurements using the spin-trap DMPO demonstrated that curcumin reduces hydrogen peroxide-dependent hydroxyl-radical formation by quartz. Curcumin was also found to reduce quartz-induced cytotoxicity and cyclooxygenase 2 (COX-2) mRNA expression in RLE-6TN rat lung epithelial cells (RLE). Curcumin also inhibited the release of macrophage inflammatory protein-2 (MIP-2) from RLE cells as observed upon treatment with interleukin-1 beta (IL-1{beta}) and tumour necrosis factor-alpha (TNF{alpha}). However, curcumin failed to protect the RLE cells from oxidative DNA damage induced by quartz, as shown by formamidopyrimidine glycosylase (FPG)-modified comet assay and by immunocytochemistry for 8-hydroxydeoxyguanosine. In contrast, curcumin was found to be a strong inducer of oxidative DNA damage itself at non-cytotoxic and anti-inflammatory concentrations. In line with this, curcumin also enhanced the mRNA expression of the oxidative stress response gene heme oxygenase-1 (ho-1). Curcumin also caused oxidative DNA damage in NR8383 rat alveolar macrophages and A549 human lung epithelial cells. Taken together, these observations indicate that one should be cautious in considering the potential use of curcumin in the prevention or treatment of lung diseases associated with quartz exposure.

  10. Removal and recovery of toxic silver ion using deep-sea bacterial generated biogenic manganese oxides.

    PubMed

    Pei, Yuanjun; Chen, Xiao; Xiong, Dandan; Liao, Shuijiao; Wang, Gejiao

    2013-01-01

    Products containing silver ion (Ag(+)) are widely used, leading to a large amount of Ag(+)-containing waste. The deep-sea manganese-oxidizing bacterium Marinobacter sp. MnI7-9 efficiently oxidizes Mn(2+) to generate biogenic Mn oxide (BMO). The potential of BMO for recovering metal ions by adsorption has been investigated for some ions but not for Ag(+). The main aim of this study was to develop effective methods for adsorbing and recovering Ag using BMO produced by Marinobacter sp. MnI7-9. In addition, the adsorption mechanism was determined using X-ray photoelectron spectroscopy analysis, specific surface area analysis, adsorption kinetics and thermodynamics. The results showed that BMO had a higher adsorption capacity for Ag(+) compared to the chemical synthesized MnO2 (CMO). The isothermal absorption curves of BMO and CMO both fit the Langmuir model well and the maximum adsorption capacities at 28°C were 8.097 mmol/g and 0.787 mmol/g, for BMO and CMO, respectively. The change in enthalpy (?H(?)) for BMO was 59.69 kJ/mol indicating that it acts primarily by chemical adsorption. The change in free energy (?G(?)) for BMO was negative, which suggests that the adsorption occurs spontaneously. Ag(+) adsorption by BMO was driven by entropy based on the positive ?S(?) values. The Ag(+) adsorption kinetics by BMO fit the pseudo-second order model and the apparent activation energy of Ea is 21.72 kJ/mol. X-ray photoelectron spectroscopy analysis showed that 15.29% Ag(+) adsorbed by BMO was transferred to Ag(0) and meant that redox reaction had happened during the adsorption. Desorption using nitric acid and Na2S completely recovered the Ag. The results show that BMO produced by strain MnI7-9 has potential for bioremediation and reutilization of Ag(+)-containing waste. PMID:24312566

  11. Translocation of Inhaled Ultrafine Manganese Oxide Particles to the Central Nervous System

    PubMed Central

    Elder, Alison; Gelein, Robert; Silva, Vanessa; Feikert, Tessa; Opanashuk, Lisa; Carter, Janet; Potter, Russell; Maynard, Andrew; Ito, Yasuo; Finkelstein, Jacob; Oberdörster, Günter

    2006-01-01

    Background Studies in monkeys with intranasally instilled gold ultrafine particles (UFPs; < 100 nm) and in rats with inhaled carbon UFPs suggested that solid UFPs deposited in the nose travel along the olfactory nerve to the olfactory bulb. Methods To determine if olfactory translocation occurs for other solid metal UFPs and assess potential health effects, we exposed groups of rats to manganese (Mn) oxide UFPs (30 nm; ~ 500 ?g/m3) with either both nostrils patent or the right nostril occluded. We analyzed Mn in lung, liver, olfactory bulb, and other brain regions, and we performed gene and protein analyses. Results After 12 days of exposure with both nostrils patent, Mn concentrations in the olfactory bulb increased 3.5-fold, whereas lung Mn concentrations doubled; there were also increases in striatum, frontal cortex, and cerebellum. Lung lavage analysis showed no indications of lung inflammation, whereas increases in olfactory bulb tumor necrosis factor-? mRNA (~ 8-fold) and protein (~ 30-fold) were found after 11 days of exposure and, to a lesser degree, in other brain regions with increased Mn levels. Macrophage inflammatory protein-2, glial fibrillary acidic protein, and neuronal cell adhesion molecule mRNA were also increased in olfactory bulb. With the right nostril occluded for a 2-day exposure, Mn accumulated only in the left olfactory bulb. Solubilization of the Mn oxide UFPs was < 1.5% per day. Conclusions We conclude that the olfactory neuronal pathway is efficient for translocating inhaled Mn oxide as solid UFPs to the central nervous system and that this can result in inflammatory changes. We suggest that despite differences between human and rodent olfactory systems, this pathway is relevant in humans. PMID:16882521

  12. Oxidation of arsenate(III) with manganese oxides in water treatment

    Microsoft Academic Search

    Wolfgang Driehaus; Reiner Seith; Martin Jekel

    1995-01-01

    Arsenate(III) is the more toxic form of inorganic arsenic and its removal from drinking water is less effective as compared to arsenate(V). Arsenate(III) persists in aerated water, even at high pH, but is easily oxidized by managanese dioxides. The oxidation of As(III) follows a second order rate law with respect to As(III). The reaction rate is effected by the initial

  13. A Quartz tuning fork-based humidity sensor using Nanocrystalline Zinc oxide thin film coatings

    Microsoft Academic Search

    Xiaofeng Zhou; Tao Jiang; Jian Zhang; Jianzhong Zhu; Xiaohua Wang; Ziqiang Zhu

    2006-01-01

    This paper describes an application of quartz tuning forks (QTF) coated with nanocrystalline ZnO films used as relative humidity sensors. The nanocrystalline ZnO thin films were deposited on the QTF by sol-gel method. The film was characterized by X-Ray Diffraction (XRD) and Atomic Force Microscope (AFM) to obtain the information on the structural and morphological properties. And the humidity sensitivity

  14. Weathering of the Rio Blanco quartz diorite, Luquillo Mountains, Puerto Rico: Coupling oxidation, dissolution, and fracturing

    Microsoft Academic Search

    Heather L. Buss; Peter B. Sak; Samuel M. Webb; Susan L. Brantley

    2008-01-01

    In the mountainous Rio Icacos watershed in northeastern Puerto Rico, quartz diorite bedrock weathers spheroidally, producing a 0.2–2m thick zone of partially weathered rock layers (?2.5cm thickness each) called rindlets, which form concentric layers around corestones. Spheroidal fracturing has been modeled to occur when a weathering reaction with a positive ?V of reaction builds up elastic strain energy. The rates

  15. Heavy metals and manganese oxides in the genesee watershed, New York state: effects of geology and land use

    USGS Publications Warehouse

    Whitney, P.R.

    1981-01-01

    Manganese oxide coatings on gravels from 255 sites on tributary streams in the Genesee River Watershed were analyzed for Mn, Fe, Zn, Cd, Co, Ni, Pb, and Cu. The results were compared with data on bedrock geology, surficial geology and land use, using factor analysis and stepwise multiple regression. All metals except Pb show strong positive correlation with Mn. This association results from the well-known tendency of Mn oxide precipitates to adsorb and incorporate dissolved trace metals. Pb may be present in a separate phase on the gravel surfaces; alternatively Pb abundance may be so strongly influenced by environmental factors that the effect of varying abundance of the carrier phase becomes relatively unimportant. When the effects of varying Mn abundance are allowed for, Pb and to a lesser extent Zn and Cu abundances are seen to be related to commercial, industrial and residential land use. In addition to this pollution effect, all the trace metals, Cd and Ni most strongly, tend to be more abundant in oxide coatings from streams in the forested uplands in the southern part of the area. This probably reflects increased geochemical mobility of the metals in the more acid soils and groundwater of the southern region. A strong Zn anomaly is present in streams draining areas underlain by the Lockport Formation. Oxide coatings in these streams contain up to 5% Zn, originating from disseminated sphalerite in the Lockport and secondary Zn concentrations in the overlying muck soils. The same group of metals, plus calcium and loss on ignition, were determined in the silt and clay (minus 230 mesh) fraction of stream sediments from 129 of the same sites, using a hot nitric acid leach. The amounts of manganese in the sediments are low (average 1020 ppm) and manganese oxides are, at most, of relatively minor significance in the trace-metal geochemistry of these sediments. The bulk of the trace metals in sediment appears to be associated with iron oxides, clays and organic matter. ?? 1981.

  16. Prevention against Oxidation of Mn Evaporant during Reactive Evaporation Process

    Microsoft Academic Search

    Masaaki Isai; Hiroshi Fujiyasu

    2001-01-01

    Manganese oxide films for lithium secondary batteries were prepared using a reactive evaporation method. The Mn metal in the crucible suffers severe oxidation during the reactive evaporation process, during which its deposition rate deteriorates with increasing deposition run. So it is difficult to maintain the stoichiometry of films from run to run. To prevent deteriorations, a quartz ampoule has been

  17. Modeling sorption of divalent metal cations on hydrous manganese oxide using the diffuse double layer model

    USGS Publications Warehouse

    Tonkin, J.W.; Balistrieri, L.S.; Murray, J.W.

    2004-01-01

    Manganese oxides are important scavengers of trace metals and other contaminants in the environment. The inclusion of Mn oxides in predictive models, however, has been difficult due to the lack of a comprehensive set of sorption reactions consistent with a given surface complexation model (SCM), and the discrepancies between published sorption data and predictions using the available models. The authors have compiled a set of surface complexation reactions for synthetic hydrous Mn oxide (HMO) using a two surface site model and the diffuse double layer SCM which complements databases developed for hydrous Fe (III) oxide, goethite and crystalline Al oxide. This compilation encompasses a range of data observed in the literature for the complex HMO surface and provides an error envelope for predictions not well defined by fitting parameters for single or limited data sets. Data describing surface characteristics and cation sorption were compiled from the literature for the synthetic HMO phases birnessite, vernadite and ??-MnO2. A specific surface area of 746 m2g-1 and a surface site density of 2.1 mmol g-1 were determined from crystallographic data and considered fixed parameters in the model. Potentiometric titration data sets were adjusted to a pH1EP value of 2.2. Two site types (???XOH and ???YOH) were used. The fraction of total sites attributed to ???XOH (??) and pKa2 were optimized for each of 7 published potentiometric titration data sets using the computer program FITEQL3.2. pKa2 values of 2.35??0.077 (???XOH) and 6.06??0.040 (???YOH) were determined at the 95% confidence level. The calculated average ?? value was 0.64, with high and low values ranging from 1.0 to 0.24, respectively. pKa2 and ?? values and published cation sorption data were used subsequently to determine equilibrium surface complexation constants for Ba2+, Ca2+, Cd 2+, Co2+, Cu2+, Mg2+, Mn 2+, Ni2+, Pb2+, Sr2+ and Zn 2+. In addition, average model parameters were used to predict additional sorption data for which complementary titration data were not available. The two-site model accounts for variability in the titration data and most metal sorption data are fit well using the pKa2 and ?? values reported above. A linear free energy relationship (LFER) appears to exist for some of the metals; however, redox and cation exchange reactions may limit the prediction of surface complexation constants for additional metals using the LFER. ?? 2003 Elsevier Ltd. All rights reserved.

  18. Catalytic oxidation of manganese(II) by multicopper oxidase CueO and characterization of the biogenic Mn oxide.

    PubMed

    Su, Jianmei; Deng, Lin; Huang, Liangbo; Guo, Shujin; Liu, Fan; He, Jin

    2014-06-01

    Manganese(II) contamination is naturally occurring in many groundwater and surface water sources. Moreover, industrial wastewater is also responsible for much of the Mn(II) contamination. Nowadays, Mn(II) contamination has become a serious environmental problem in some regions of the world. To explore a biological approach for removing excessive amounts of aqueous Mn(II) from water, we found a new biocatalyst multicopper oxidase CueO, which was firstly proved to catalyze the oxidation of Mn(II) both in vitro and in vivo. Subsequently, we established a CueO-mediated catalysis system to prepare biogenic Mn oxide (BioMnOx), which was confirmed to be ?-Mn3O4 by X-ray diffraction. This newly prepared BioMnOx consisted of 53.6% Mn(II), 18.4% Mn(III) and 28.0% Mn(IV) characterized by X-ray photoelectron spectroscopy. It exhibited distinct polyhedral structure with nanoparticles of 150-350 nm diameters observed by transmission electron microscopy. Importantly, CueO could remove 35.7% of Mn(II) after a seven-day reaction, and on the other hand, the cueO-overexpressing Escherichia coli strain (ECueO) could also oxidize 58.1% dissolved Mn(II), and simultaneously remove 97.7% Mn(II). Based on these results, we suggest that ECueO strain and CueO enzyme have potential applications on Mn(II) decontamination in water treatment. PMID:24699422

  19. Complexation and redox interactions between aqueous plutonium and manganese oxide interfaces

    SciTech Connect

    Shaughnessy, Dawn A.; Nitsche, Heino; Booth, Corwin H.; Shuh, David K.; Waychunas, Glenn A.; Wilson, Richard E.; Cantrell, Kirk J.; Serne, R. Jeffrey

    2001-11-01

    The sorption of Pu(VI) and Pu(V) onto manganite (MnOOH) and Hausmannite (Mn3O4) was studied at pH 5. Manganite sorbed 21-24% from a 1x10-4 M plutonium solution and the hausmannite removed between 43-66% of the plutonium. The increased sorption by hausmannite results from its larger surface area (about twice that of manganite) plus a larger number of active surface sites. X-ray absorption near-edge structure (XANES) spectra taken at the Pu LIII edge were compared to standard spectra of plutonium in single oxidation states. Based on these spectra, it appears that both manganite and hausmannite reduce the higher valent plutonium species to Pu(IV). Between 53-59% of the plutonium was present as Pu(IV) in the manganite samples while 55-61% of the plutonium complexed to the hausmannite had also been reduced to Pu(IV). The exact mechanism behind this redox interaction between the plutonium and the manganese needs to be identified.

  20. Relationship of crystal structure to interionic interactions in the lithium-manganese spinel oxides

    PubMed

    Piszora; Catlow; Woodley; Wolska

    2000-07-01

    Lithium manganese oxides in the form of cubic spinel phases (space group Fd3m) are formed in a LixMn3-xO4 system for rather limited values of x. Structural investigations by X-ray powder diffraction, applied to the Li-Mn-O compounds, indicate the formation of a second crystalline phase, Li2MnO3 (space group C2/m), with the increasing lithium content. Total Li+ content per unit cell and the cation distribution over a spinel lattice in LixMn3-xO4 have been studied by measurements of integrated intensities of X-ray reflections, and by structure refinement using Rietveld profile analysis. In an attempt to understand the factors affecting cation distribution in the spinel lattice, we applied the computer modelling techniques and investigated the Li+, Mn3+ and Mn4+ ion distribution by calculating the lattice energy, combined with energy minimisation procedures, using the General Utility Lattice Program (GULP), a program designed for simulation of ionic and semi-ionic solids, based on interatomic potential models. PMID:10890371

  1. The Influence of Manganese Oxide on the Sintering Behavior of Yttria Tetragonal Zirconia

    SciTech Connect

    Meenaloshini, S.; Amiriyan, M.; Sankar, U.; Tolouei, R.; Ramesh, S. [Ceramics Technology Laboratory, University Tenaga Nasional, 43009 Kajang Selangor (Malaysia)

    2011-01-17

    The sintering behavior of yttria-stabilized zirconia, with the influence of small additions of MnO{sub 2}(up to 1 wt %) sintered over the temperature range from 1250 deg. C to 1500 deg. C was investigated. It was found that the mechanical properties of Y-TZP were dependent on the dopant amount and sintering temperature. The results revealed that relative densities above 97.5% of theoretical (i.e. >5.95 Mgm{sup -3}) could be obtained in Y-TZPs sintered at low temperatures, 1250 deg. C and 1300 deg. C, with the additions of {<=}0.3 wt% MnO{sub 2}. In comparison to the undoped samples, the additions of up to 1 wt%MnO{sub 2} and for sintering up to 1350 deg. C was found to be beneficial in enhancing the Vickers hardness of the ceramic. The fracture toughness of Y-TZP however, was found to increase only in the 1 wt% MnO{sub 2}-doped samples when sintered above 1400 deg. C. The relation between the measured mechanical properties is discussed with the emphasis on the role of the manganese oxide.

  2. Quantum Femtosecond Magnetism: Phase Transition in Step with Light in a Strongly Correlated Manganese Oxide

    NASA Astrophysics Data System (ADS)

    Wang, Jigang

    2014-03-01

    Research of non-equilibrium phase transitions of strongly correlated electrons is built around addressing an outstanding challenge: how to achieve ultrafast manipulation of competing magnetic/electronic phases and reveal thermodynamically hidden orders at highly non-thermal, femtosecond timescales? Recently we reveal a new paradigm called quantum femtosecond magnetism-photoinduced femtosecond magnetic phase transitions driven by quantum spin flip fluctuations correlated with laser-excited inter-atomic coherent bonding. We demonstrate an antiferromagnetic (AFM) to ferromagnetic (FM) switching during about 100 fs laser pulses in a colossal magneto-resistive manganese oxide. Our results show a huge photoinduced femtosecond spin generation, measured by magnetic circular dichroism, with photo-excitation threshold behavior absent in the picosecond dynamics. This reveals an initial quantum coherent regime of magnetism, while the optical polarization/coherence still interacts with the spins to initiate local FM correlations that compete with the surrounding AFM matrix. Our results thus provide a framework that explores quantum non-equilibrium kinetics to drive phase transitions between exotic ground states in strongly correlated elecrons, and raise fundamental questions regarding some accepted rules, such as free energy and adiabatic potential surface. This work is in collaboration with Tianqi Li, Aaron Patz, Leonidas Mouchliadis, Jiaqiang Yan, Thomas A. Lograsso, Ilias E. Perakis. This work was supported by the National Science Foundation (contract no. DMR-1055352). Material synthesis at the Ames Laboratory was supported by the US Department of Energy-Basic Energy Sciences (contract no. DE-AC02-7CH11358).

  3. Solar-thermal Water Splitting Using the Sodium Manganese Oxide Process & Preliminary H2A Analysis

    SciTech Connect

    Todd M. Francis, Paul R. Lichty, Christopher Perkins, Melinda Tucker, Peter B. Kreider, Hans H. Funke, Allan Lewandowski, and Alan W. Weimer

    2012-10-24

    There are three primary reactions in the sodium manganese oxide high temperature water splitting cycle. In the first reaction, Mn2O3 is decomposed to MnO at 1,500°C and 50 psig. This reaction occurs in a high temperature solar reactor and has a heat of reaction of 173,212 J/mol. Hydrogen is produced in the next step of this cycle. This step occurs at 700°C and 1 atm in the presence of sodium hydroxide. Finally, water is added in the hydrolysis step, which removes NaOH and regenerates the original reactant, Mn2O3. The high temperature solar�driven step for decomposing Mn2O3 to MnO can be carried out to high conversion without major complication in an inert environment. The second step to produce H2 in the presence of sodium hydroxide is also straightforward and can be completed. The third step, the low temperature step to recover the sodium hydroxide is the most difficult. The amount of energy required to essentially distill water to recover sodium hydroxide is prohibitive and too costly. Methods must be found for lower cost recovery. This report provides information on the use of ZnO as an additive to improve the recovery of sodium hydroxide.

  4. Arsenic desorption from ferric and manganese binary oxide by competitive anions: significance of pH.

    PubMed

    Xu, Wei; Wang, Hongjie; Wu, Kun; Liu, Ruiping; Gong, Wenxin; Qu, Jiuhui

    2012-06-01

    Ferric and manganese binary oxide (FMBO) has been used to remediate an arsenic (As)-polluted river in China, but insufficient data was available to (1) evaluate its effects on the environment and (2) propose a feasible strategy of addressing the arsenic-bearing FMBO. The desorption behavior of arsenic in the presence of four competitive anions (i.e., phosphate, silicate, sulfate, and bicarbonate) at different concentrations was investigated with pH ranging from 3 to 11. The presence of these anions promoted the desorption of arsenic from arsenic-bearing FMBO and followed the sequence of phosphate > silicate > sulfate approximately equal to bicarbonate across a wide pH range. Desorption of arsenate (As[V]) was more significant than that of arsenite (As[III]). Sequence dissolution of arsenic-bearing FMBO particles by NH4-oxalate/oxalic acid and hydrochloric acid were performed. The laboratory results indicated that As(III) was primarily occluded in the crystalline parts of the FMBO. The desorption behavior of arsenic could be described by kinetic models using the Elovich and power function equations under different pH conditions and was related to the adsorption of phosphate and silicate. pH played an important role in the desorption of arsenic, because of its effects on the species distribution of anions, surface charge of the arsenic-bearing FMBO, and subsequent electrostatic forces between anions and FMBO. PMID:22866393

  5. Efficient activation of peroxymonosulfate by manganese oxide for the degradation of azo dye at ambient condition.

    PubMed

    Tang, Dandan; Zhang, Gaoke; Guo, Sheng

    2015-09-15

    This study determines the potential of manganese oxide (MnOx) nanoparticles for the activation of peroxymonosulfate (PMS). The MnOx nanoparticles were prepared by a facile co-precipitation method and the degradation rates of acid red G (ARG) by the as-prepared catalysts in the presence of PMS were measured. The results showed that the Mn3O4 nanoparticles with tetragonal structure exhibited high catalytic activity for the degradation of ARG by activating PMS to generate radicals. The effects of the operational parameters on the catalytic property of the obtained nanosized Mn3O4 catalyst were investigated in detail. The catalyst exhibits excellent catalytic activity in a wide range of pH from 2 to 12. Moreover, it still maintained high catalytic activity even after five reaction cycles, indicating the good stability of the catalyst. In addition, radical quenching studies were carried out to ascertain the dominating radical species and a proper mechanism was also proposed. PMID:26002338

  6. Revisiting the coordination chemistry for preparing manganese oxide nanocrystals in the presence of oleylamine and oleic acid

    NASA Astrophysics Data System (ADS)

    Zhang, Hongwei; Jing, Lihong; Zeng, Jianfeng; Hou, Yi; Li, Zhen; Gao, Mingyuan

    2014-05-01

    By pyrolyzing manganese(ii) acetate in 1-octadecene in the presence of oleylamine and oleic acid, manganese oxide nanocrystals were prepared. It was observed that both MnO and Mn3O4 nanocrystals were simultaneously formed by quickly heating the reaction mixture up to 250 °C, while a preheating procedure carried out at 100 °C led to uniform MnO nanocubes that developed into eight-arm MnO nanocrystals upon prolonged reaction. To understand the mechanisms for forming these two different kinds of manganese oxide nanocrystals, i.e., Mn3O4 and MnO, the coordination between oleic acid/oleylamine and Mn2+ was investigated. The detailed investigations suggest that Mn2+-oleylamine coordination is kinetically driven and favorable for the formation of Mn3O4 nanocrystals due to the relatively low electronegativity of N from oleylamine, while Mn2+-oleate coordination is thermodynamically driven and can prevent the central metal ion (Mn2+) from being oxidized owing to the relatively high electronegativity of O from the oleate ligand. Following these new insights, by properly balancing the coordination of oleic acid and oleylamine to Mn2+, the selective synthesis of MnO and Mn3O4 nanocrystals with uniform shapes was successfully achieved.By pyrolyzing manganese(ii) acetate in 1-octadecene in the presence of oleylamine and oleic acid, manganese oxide nanocrystals were prepared. It was observed that both MnO and Mn3O4 nanocrystals were simultaneously formed by quickly heating the reaction mixture up to 250 °C, while a preheating procedure carried out at 100 °C led to uniform MnO nanocubes that developed into eight-arm MnO nanocrystals upon prolonged reaction. To understand the mechanisms for forming these two different kinds of manganese oxide nanocrystals, i.e., Mn3O4 and MnO, the coordination between oleic acid/oleylamine and Mn2+ was investigated. The detailed investigations suggest that Mn2+-oleylamine coordination is kinetically driven and favorable for the formation of Mn3O4 nanocrystals due to the relatively low electronegativity of N from oleylamine, while Mn2+-oleate coordination is thermodynamically driven and can prevent the central metal ion (Mn2+) from being oxidized owing to the relatively high electronegativity of O from the oleate ligand. Following these new insights, by properly balancing the coordination of oleic acid and oleylamine to Mn2+, the selective synthesis of MnO and Mn3O4 nanocrystals with uniform shapes was successfully achieved. Electronic supplementary information (ESI) available: (1) TEM image and corresponding SAED pattern of the tiny particles shown in Fig. 1b; (2) TEM images of the branched nanoparticles (Fig. 1e) showing a self-organized superstructure; (3) TEM image and the electron diffraction pattern of the particles obtained by heating the Mn(Ac)2 in oleylamine at 100 °C for 540 min; (4) TEM image and the electron diffraction pattern of the particles obtained from the second reference experiment; (5) Temporal evolution of size and size distribution of manganese oxide nanocrystals shown in Fig. 5 and Fig. 6. See DOI: 10.1039/c4nr00761a

  7. Structural and magnetic properties of the iron substituted lithium manganese spinel oxides

    NASA Astrophysics Data System (ADS)

    Wolska, Emilia; Tovar, Michael; Andrzejewski, Bartlomiej; Nowicki, Waldemar; Darul, Jolanta; Piszora, Pawel; Knapp, Michael

    2006-01-01

    Most studies on the lithium-manganese oxide as a cathode material have concentrated on the stabilization of the cubic spinel structure, mainly by doping other transition metal ions into LiMn 2O 4 lattice. Partial substitution of Fe 3+ ions for Mn 3+ restrains the Jahn-Teller effect, owing to the reduction of Mn 3+/Mn 4+ ratio. In LiFe 0.1Mn 1.9O 4 spinel oxide the phase transitions from cubic to orthorhombic and/or tetragonal structure, appearing for LiMn 2O 4 below the room temperature, may be totally suppressed. The changes in stoichiometry of LiFe xMn 2- xO 4 system, modify the sequence of phase transitions and lower the transition temperature. A superexchange magnetic interaction between the Mn ions via oxygen atoms alters, with the Fe 3+-content in Li xMn 3- xO 4 increasing from x=0.0-0.1, showing the antiferromagnetic ordering at very low temperature. The Néel point increases from 7 to 27 K. Effect of Fe 3+ ions substitution in the LiFe xMn 2- xO 4 system on its low-temperature structural phase transitions, have been investigated using high-resolution synchrotron X-ray powder diffraction, neutron powder diffraction and the magnetic susceptibility measurements. Divergences appear in the interpretation of magnetic structure on the basis of experimental results, acquired from neutron diffraction data, and obtained from the direct current susceptibility measurements.

  8. Well-ordered organic-inorganic hybrid layered manganese oxide nanocomposites with excellent decolorization performance

    SciTech Connect

    Zhou, Junli, E-mail: Zhoujunli19851111@163.com [Faculty of Chemical Engineering and Light Industry, Guangdong University of Technology, Guangzhou 510006, Guangdong (China)] [Faculty of Chemical Engineering and Light Industry, Guangdong University of Technology, Guangzhou 510006, Guangdong (China); Yu, Lin, E-mail: gych@gdut.edu.cn [Faculty of Chemical Engineering and Light Industry, Guangdong University of Technology, Guangzhou 510006, Guangdong (China)] [Faculty of Chemical Engineering and Light Industry, Guangdong University of Technology, Guangzhou 510006, Guangdong (China); Sun, Ming; Ye, Fei; Lan, Bang; Diao, Guiqiang; He, Jun [Faculty of Chemical Engineering and Light Industry, Guangdong University of Technology, Guangzhou 510006, Guangdong (China)] [Faculty of Chemical Engineering and Light Industry, Guangdong University of Technology, Guangzhou 510006, Guangdong (China)

    2013-02-15

    Well-ordered organic-inorganic hybrid layered manganese oxide nanocomposites (CTAB-Al-MO) with excellent decolorization performance were prepared through a two-step process. Specifically, the MnO{sub 2} nanosheets were self-assembled in the presence of CTAB, and subsequently pillared with Keggin ions. The obtained CTAB-Al-MO with the basal spacing of 1.59 nm could be stable at 300 Degree-Sign C for 2 h and also possesses high total pore volumes (0.41 cm Superscript-Three g{sup -1}) and high specific BET surface area (161 m{sup 2} g{sup -1}), which is nine times larger than that of the pristine (19 m{sup 2} g{sup -1}). Possible formation process for the highly thermal stable CTAB-Al-MO is proposed here. The decolorization experiments of methyl orange showed that the obtained CTAB-Al-MO exhibit excellent performance in wastewater treatment and the decolorization rate could reach 95% within 5 min. - Graphical Abstract: Well-ordered organic-inorganic hybrid LMO nanocomposites (CTAB-Al-MO) with excellent decolorization performance were prepared through a two-step process. Specifically, the MnO{sub 2} nanosheets were self-assembled by CTAB, and subsequently pillared with Keggin ions. Highlights: Black-Right-Pointing-Pointer A two-step synthesis method was used to prepare the CTAB-Al-MO. Black-Right-Pointing-Pointer The CTAB-Al-MO has the large basal spacing and high specific BET surface area. Black-Right-Pointing-Pointer The thermal stability of the well-ordered CTAB-Al-MO could obviously improve. Black-Right-Pointing-Pointer The CTAB-Al-MO exhibits excellent oxidation and absorption ability to remove organic pollutants.

  9. Disruption of sitA Compromises Sinorhizobium meliloti for Manganese Uptake Required for Protection against Oxidative Stress?

    PubMed Central

    Davies, Bryan W.; Walker, Graham C.

    2007-01-01

    During the initial stages of symbiosis with the host plant Medicago sativa, Sinorhizobium meliloti must overcome an oxidative burst produced by the plant in order for proper symbiotic development to continue. While identifying mutants defective in symbiosis and oxidative stress defense, we isolated a mutant with a transposon insertion mutation of sitA, which encodes the periplasmic binding protein of the putative iron/manganese ABC transporter SitABCD. Disruption of sitA causes elevated sensitivity to the reactive oxygen species hydrogen peroxide and superoxide. Disruption of sitA leads to elevated catalase activity and a severe decrease in superoxide dismutase B (SodB) activity and protein level. The decrease in SodB level strongly correlates with the superoxide sensitivity of the sitA mutant. We demonstrate that all free-living phenotypes of the sitA mutant can be rescued by the addition of exogenous manganese but not iron, a result that strongly implies that SitABCD plays an important role in manganese uptake in S. meliloti. PMID:17172335

  10. The oxidative properties of a manganese(IV) hydroperoxide moiety and its relationships with the corresponding manganese(IV) oxo and hydroxo moieties.

    PubMed

    Wang, Yujuan; Shi, Song; Zhu, Dajian; Yin, Guochuan

    2012-03-01

    Clear elucidation of the oxidative relationships of the active metal hydroperoxide moiety with its corresponding metal oxo and hydroxo intermediates would help the understanding of the different roles they may play in redox metalloenzymes and oxidation chemistry. Using an Mn(Me(2)EBC)Cl(2) complex, it was found that, in t-butanol-water (4 : 1) with excess H(2)O(2) at pH 1.5, the Mn(IV)-OOH moiety may exist in the catalytic solution with a mass signal of m/z = 358.1, which provides a particular chance to investigate its oxidative properties. In catalytic oxidations, the Mn(IV)-OOH moiety demonstrates a relatively poor activity in hydrogen abstraction from diphenyl methane and ethylbenzene with TOF of only 1.2 h(-1) and 1.1 h(-1) at 50 °C, whereas it can efficiently oxygenate diphenyl sulfide, methyl phenyl sulfide and benzyl phenyl sulfide with TOF of 13.8 h(-1), 15.4 h(-1) and 17.8 h(-1), respectively. In mechanistic studies using H(2)(18)O and H(2)(18)O(2), it was found that, in the Mn(IV)-OOH moiety mediated hydrogen abstraction and sulfide oxygenations, the reaction proceeds by two parallel pathways: one by direct oxygen insertion/transfer, and the other by plausible electron transfer. Together with a good understanding of the corresponding manganese(IV) oxo and hydroxo intermediates, this work provides the first chance to compare the reactivity differences and similarities of the active metal oxo, hydroxo and hydroperoxide intermediates. The available evidence reveals that the Mn(IV)-OOH moiety has a much more powerful oxidizing capability than the corresponding Mn(IV)=O and Mn(IV)-OH functional groups in both hydrogen abstraction and oxygenation. PMID:22223076

  11. New divalent manganese complex with pyridine carboxylate N-oxide ligand: Synthesis, structure and magnetic properties

    SciTech Connect

    Liu Fuchen, E-mail: fuchenliutj@yahoo.co [School of Chemistry and Chemical Engineering, Tianjin University of Technology, Tianjin 300384 (China); Xue Min; Wang Haichao [School of Chemistry and Chemical Engineering, Tianjin University of Technology, Tianjin 300384 (China); Ouyang Jie, E-mail: ouyang@tjut.edu.c [School of Chemistry and Chemical Engineering, Tianjin University of Technology, Tianjin 300384 (China)

    2010-09-15

    Two new manganese complexes, [Mn{sub 3}(L{sup 1}){sub 4}(NO{sub 3}){sub 2}]{sub n} (1, HL{sup 1}=nicotinate N-oxide acid) and [MnL{sup 2}Cl]{sub n} (2, HL{sup 2}=isonicotinate N-oxide acid)], have been hydrothermally synthesized and characterized by elemental analysis, IR and single-crystal X-ray diffraction. In 1, the L{sup 1} ligands take two different coordinated modes bridging four and three Mn{sup II} ions. The nitrate anions take chelating coordination modes, leading one type of the Mn{sup II} ions as a 4-connected node. The whole net can be viewed as a 3, 4, 6-connected 4-nodal net with Schlaefli notation {l_brace}4{sup 3{r_brace}}2{l_brace}4{sup 4}; 6{sup 2{r_brace}}4{l_brace}4{sup 6}; 6{sup 6}; 8{sup 3{r_brace}}. Complex 2 has a honeycomb layer mixed bridged by chlorine, N-oxide and carboxylate. The adjacent layers are linked by the phenyl ring of L{sup 2} ligand, giving a 3D framework with a {l_brace}3{sup 4}; 5{sup 4{r_brace}} {l_brace}3{sup 2};4;5{sup 6};6{sup 6{r_brace}} 4, 6-connect net. Magnetic studies indicate that 1 is an antiferromagnet with low-dimensional characteristic, in which a -J{sub 1}J{sub 1}J{sub 2}- coupled alternating chain is predigested. Fitting the data of 1 gives the best parameters J{sub 1}=-2.77, J{sub 2}=-0.67 cm{sup -1}. The magnetic properties of complex 2 represent the character of the 2D honeycomb layer with the J{sub 1}=-2.05 and J{sub 2}=0.55 cm{sup -1}, which results in a whole antiferromagnetic state. - Graphical abstract: The synthesis, crystal structure and magnetic properties of two new MnII complexes with pyridyl-carboxylate N-oxide ligands are reported.

  12. Early diagenetic quartz formation at a deep iron oxidation front in the Eastern Equatorial Pacific - A modern analogue for banded iron/chert formations?

    NASA Astrophysics Data System (ADS)

    Meister, Patrick; Chapligin, Bernhard; Picard, Aude; Meyer, Hanno; Fischer, Cornelius; Rettenwander, Daniel; Amthauer, Georg; Vogt, Christoph; Aiello, Ivano W.

    2014-07-01

    The mechanisms of early diagenetic quartz formation under low-temperature conditions are still poorly understood. In this study we investigated lithified cherts consisting of microcrystalline quartz recovered near the base of a 420 m thick Miocene-Holocene sequence of nannofossil and diatom ooze at a drill site in the Eastern Equatorial Pacific (Ocean Drilling Program Site 1226). Precipitation seems still ongoing based on a sharp depletion in dissolved silica at the depth of the cherts. Also, palaeo-temperatures reconstructed from ?18O values in the cherts are in the range of adjacent porewater temperatures. Opal-A dissolution appears to control silica concentration throughout the sequence, while the solution remains oversaturated with respect to quartz. However, at the depth of the sharp depletion in dissolved silica, quartz is still saturated while the more soluble silica phases are strongly undersaturated. Hence, precipitation of quartz was initiated by an auxiliary process. A process, previously observed to assist in the nucleation of quartz is the adsorption of silica on freshly precipitated iron oxides. Indeed, a deep iron oxidation front is present at 400 m below seafloor, which is caused by upward diffusing nitrate from an oxic seawater aquifer in the underlying oceanic crust. Sequential iron extraction showed a higher content of the adsorbed iron hydroxide fraction in the chert than in the adjacent nannofossil and diatom ooze. X-ray absorption near-edge structure (XANES) spectroscopy revealed that iron in the cherts predominantly occurs in illite and amorphous iron oxide, whereas iron in the nannofossil and diatom ooze occurs mainly in smectite. Mössbauer spectroscopy also indicated the presence of illite that is to 97% oxidized. Two possible mechanisms may be operative during early diagenetic chert formation at iron oxidation fronts: (1) silica precipitation is catalysed by adsorption to freshly precipitated iron oxide surfaces, and (2) porewater silica concentration is locally decreased below opal-A and opal-CT saturation allowing for precipitation of the thermodynamically more stable phase: quartz. This mechanism of chert formation at the iron oxidation front in suboxic zones may explain why early-diagenetic microcrystalline chert only occurs sporadically in modern marine sediments. It may also serve as a modern analogue for the deposition of much more abundant banded iron/chert formations at the time of the great oxidation event around 2.4 Ga BP, which was probably the largest iron oxidation front in Earth's history.

  13. Electrodeposited Manganese Oxides on Three-Dimensional Carbon Nanotube Substrate: Supercapacitive Behaviour in Aqueous and Organic Electrolytes

    SciTech Connect

    Nam,K.W.; Yang,X.

    2009-03-01

    Thin amorphous manganese oxide layers with a thickness of 3-5nm are electrodeposited on a carbon nanotube (CNT) film substrate that has a three-dimensional nanoporous structure (denoted asMnO2/CNT electrode). For the purpose of comparison, manganese oxide films are also electrodeposited on a flat Pt-coated Si wafer substrate (denoted as MnO2 film electrode). The pseudocapacitive properties of the MnO2 film and MnO2/CNT electrodes are examined in both aqueous electrolyte (1.0M KCl) and nonaqueousorganic electrolyte (1.0M LiClO4 in propylene carbonate). While both types of electrode showpseudocapacitive behaviour in the aqueous electrolyte, only the MnO2/CNT electrode does so in the organic electrolyte, due to its high oxide/electrolyte interfacial area and improved electron conduction through the CNT substrate. Compared with the MnO2 film electrode, the MnO2/CNT electrode shows a much higher specific capacitance and better high-rate capability, regardless of the electrolyte used.Use of the organic electrolyte results in a ?6 times higher specific energy compared with that obtained with the aqueous electrolyte, while maintaining a similar specific power. The construction of a threedimensional nanoporous network structure consisting of a thin oxide layer on a CNT film substrate at the nm scale and the use of an organic electrolyte are promising approaches to improving the specific energyof supercapacitors.

  14. Ab initio molecular dynamics study of manganese porphine hydration and interaction with nitric oxide

    E-print Network

    Kevin Leung; Craig J. Medforth

    2007-01-23

    The authors use ab initio molecular dynamics and the density functional theory+U (DFT+U) method to compute the hydration environment of the manganese ion in manganese (II) and manganese (III) porphines (MnP) dispersed in liquid water. These are intended as simple models for more complex water soluble porphyrins, which have important physiological and electrochemical applications. The manganese ion in Mn(II)P exhibits significant out-of-porphine plane displacement and binds strongly to a single H2O molecule in liquid water. The Mn in Mn(III)P is on average coplanar with the porphine plane and forms a stable complex with two H2O molecules. The residence times of these water molecules exceed 15 ps. The DFT+U method correctly predicts that water displaces NO from Mn(III)P-NO, but yields an ambiguous spin state for the MnP(II)-NO complex.

  15. Template-free low temperature hydrothermal synthesis and characterization of rod-shaped manganese oxyhydroxides and manganese oxides

    NASA Astrophysics Data System (ADS)

    Sampanthar, Jeyagowry T.; Dou, Jian; Geok Joo, Gan; Widjaja, Effendi; Eunice, Low Qui Hui

    2007-01-01

    Single-crystalline MnOOH (?-MnOOH) and MnO2 nanorods (?-MnO2 and ?-MnO2) were synthesized by redox reaction of a mixture of KMnO4 and Mn(CH3COO)2 at various pH levels at a temperature range of 120-180 °C. The products were characterized by powder x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), Raman and infra-red spectroscopy, field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). It is interesting to find that the prepared MnOOH and MnO2 all have one-dimensional nanostructures. The catalytic activity of MnO2 nanorods was studied for selective catalytic sulfur oxidation of model diesel containing 4,6-dimethyl dibenzothiophene in the presence of air as oxidant.

  16. Long-term exposure to "low levels" of manganese oxides and neurofunctional changes in ferroalloy workers.

    PubMed

    Lucchini, R; Apostoli, P; Perrone, C; Placidi, D; Albini, E; Migliorati, P; Mergler, D; Sassine, M P; Palmi, S; Alessio, L

    1999-01-01

    Occupational exposure to manganese can cause early neurobehavioral effects in low- or a-symptomatic workers. A battery of neuropsychological tests was administered to a group of 61 ferroalloy male workers and 87 controls. The average (geometric mean) manganese concentrations in total dust at the plant have changed from 1981 to 1997 respectively from 1597.03 micrograms/m3 to 239 micrograms/m3 at the furnace area; from 151.53 to 255.76 micrograms/m3 at the casting area; from 167 to 54.7 micrograms/m3 at the maintenance (welding operations), yielding a current overall value of 54.25 micrograms/m3. A cumulative exposure index was calculated for each alloy worker and the average value (geometric mean) resulted to be 1204.87 micrograms/m3 x years, which divided by the average length of exposure (15.17 years), showed the concentration of 70.83 micrograms/m3 of manganese in total dust. Blood and urinary manganese geometric means resulted significantly higher in the exposed workers (9.18 micrograms/l and 1.53 micrograms/g creatinine, respectively) than in controls (5.74 micrograms/l and 0.40 microgram/g creatinine, respectively). A positive correlation was observed between the airborne manganese concentrations in total dust and blood manganese (n = 55; R = 0.36; R2 = 0.13; p = 0.0068), whereas no association resulted between cumulative exposure index and both blood manganese and urinary manganese. Higher prevalence of symptoms reporting was observed in the alloy workers concerning irritability, loss of equilibrium and rigidity. Tremor parameters including the central frequency and its dispersion, resulted to be statistically different in the exposed workers compared to the controls. Motor functions exploring the coordination of rapid and alternating movements and memory functions resulted to be impaired in the manganese workers. Dose-effect relationships were observed between the cumulative exposure index and some of the test results, whereas no relationship was found with the airborne manganese concentrations and the biological indicators of exposure. These findings are consistent with the existing knowledge of a cumulative mechanism of action of manganese, which must be carefully considered when setting safe exposure levels. In order to be protective for the entire working life, the average annual exposure level should be lower than 100 micrograms/m3. PMID:10385891

  17. Characterization of the Fe-Doped Mixed-Valent Tunnel Structure 2 Manganese Oxide KOMS-2

    SciTech Connect

    Hanson J. C.; Shen X.; Morey A.M.; Liu J.; Ding Y.; Cai J.; Durand J.; Wang Q.; Wen W.; Hines W.A.; Bai J.; Frenkel A.I.; Reiff W.; Aindow M.; Suib S.L.

    2011-11-10

    A sol-gel-assisted combustion method was used to prepare Fe-doped manganese oxide octahedral molecular sieve (Fe-KOMS-2) materials with the cryptomelane structure. Characterization of the nanopowder samples over a wide range of Fe-doping levels (0 {le} Fe/Mn {le} 1/2) was carried out using a variety of experimental techniques. For each sample, Cu K{alpha} XRD and ICP-AES were used to index the cryptomelane structure and determine the elemental composition, respectively. A combination of SEM and TEM images revealed that the morphology changes from nanoneedle to nanorod after Fe doping. Furthermore, TGA scans indicated that the thermal stability is also enhanced with the doping. Anomalous XRD demonstrated that the Fe ions replace the Mn ions in the cryptomelane structure, particularly in the (211) planes, and results in a lattice expansion along the c axis, parallel to the tunnels. Reasonable fits to EXAFS data were obtained using a model based on the cryptomelane structure. Moessbauer spectra for selected Fe-KOMS-2 samples indicated that the Fe is present as Fe{sup 3+} in an octahedral environment similar to Mn in the MnO{sub 6} building blocks of KOMS-2. Magnetization measurements detected a small amount of {gamma}-Fe{sub 2}O{sub 3} second phase (e.g., 0.6 wt % for the Fe/Mn = 1/10 sample), the vast majority of the Fe being in the structure as Fe{sup 3+} in the high-spin state.

  18. Microarray genomic profile of mitochondrial and oxidant response in Manganese Chloride treated PC12 cells

    PubMed Central

    Taka, Equar; Mazzio, Elizabeth; Soliman, Karam FA; Reams, R. Renee

    2012-01-01

    Environmental or occupational exposure to high levels of manganese (Mn) can lead to manganism, a symptomatic neuro-degenerative disorder similar to idiopathic Parkinson’s disease. The underlying mechanism of Mn neurotoxicity remains unclear. In this study, we evaluate the primary toxicological events associated with MnCl2 toxicity in rat PC12 cells using whole genome cDNA microarray, RT-PCR, western blot and functional studies. The results show that a sub-lethal dose range (38–300 µM MnCl2) initiated slight metabolic stress evidenced by heightened glycolytic rate and induction of enolase / aldolase - gene expression. The largest shift observed in the transcriptome was MnCl2 induction of heme-oxygenase 1 (HO-1) [7.7 fold, p <0.001], which was further corroborated by RT-PCR and western blot studies. Concentrations in excess of 300 µM corresponded to dose dependent loss of cell viability which was associated with enhanced production of H2O2 concomitant to elevation of of gene expression for diverse antioxidant enzymes; biliverdin reductase, arsenite inducible RNA associated protein, dithiolethione-inducible gene-1 (DIG-1) and .thioredoxin reductase 1. Moreover, Mn initiated significant reduction of gene expression of mitochondrial glutaryl-coenzyme A dehydrogenase (GCDH) -, an enzyme involved with glutaric acidemia, oxidative stress, lipid peroxidation and striatal degeneration observed in association with severe dystonic dyskinetic movement disorder. Future research will be required to elucidate a defined role for HO-1 and GCDH in Mn toxicity. PMID:22281203

  19. Microbially-mediated thiocyanate oxidation and manganese cycling control arsenic mobility in groundwater at an Australian gold mine

    NASA Astrophysics Data System (ADS)

    Horvath, A. S.; Baldisimo, J. G.; Moreau, J. W.

    2010-12-01

    Arsenic contamination of groundwater poses a serious environmental and human health problem in many regions around the world. Historical groundwater chemistry data for a Western-Central Victorian gold mine (Australia) revealed a strong inverse correlation between dissolved thiocyanate and iron(II), supporting the interpretation that oxidation of thiocyanate, a major groundwater contaminant by-product of cyanide-based gold leaching, was coupled to reductive dissolution of iron ox(yhydrox)ides in tailings dam sediments. Microbial growth was observed in this study in a selective medium using SCN- as the sole carbon and nitrogen source. The potential for use of SCN- as a tracer of mining contamination in groundwater was evaluated in the context of biological SCN- oxidation potential in the aquifer. Geochemical data also revealed a high positive correlation between dissolved arsenic and manganese, indicating that sorption on manganese-oxides most likely controls arsenic mobility at this site. Samples of groundwater and sediments along a roughly straight SW-NE traverse away from a large mine tailings storage facility, and parallel to the major groundwater flow direction, were analysed for major ions and trace metals. Groundwater from wells approaching the tailings along this traverse showed a nearly five-fold increase (roughly 25-125 ppb) in dissolved arsenic concentrations relative to aqueous Mn(II) concentrations. Thus, equivalent amounts of dissolved manganese released a five-fold difference in the amount of adsorbed arsenic. The interpretation that reductive dissolution of As-bearing MnO2 at the mine site has been mediated by groundwater (or aquifer) microorganisms is consistent with our recovery of synthetic birnessite-reducing enrichment cultures that were inoculated with As-contaminated groundwaters.

  20. Nitrogen-Enriched Porous Carbon Coating for Manganese Oxide Nanostructures toward High-Performance Lithium-Ion Batteries.

    PubMed

    Wang, Jiangan; Zhang, Cunbao; Kang, Feiyu

    2015-05-01

    Manganese oxides are promising high-capacity anode materials for lithium-ion batteries (LIBs) yet suffer from short cycle life and poor rate capability. Herein, we demonstrate a facile in situ interfacial synthesis of core-shell heterostructures comprising nitrogen-enriched porous carbon (pN-C) nanocoating and manganese oxide (MnOx) nanotubes. When MnOx/pN-C serves as an anode material for LIBs, the pN-C coating plays multiple roles in substantially improving the lithium storage performance. In combination with the nanosized structure and nanotubular architecture, the MnOx/pN-C nanocomposites exhibit an impressive reversible capacity of 1068 mAh g(-1) at 100 mA g(-1), a high-rate delivery of 361 mAh g(-1) at 8 A g(-1), and a stable cycling retention up to 300 cycles. The surface pN-C coating strategy can be extended to design and fabricate various metal oxide nanostructures for high-performance LIBs. PMID:25871883

  1. Influence of synthesis temperature on the crystal structure and electrode property of sulfur-doped manganese oxide nanowires.

    PubMed

    Park, Dae Hoon; Kim, Tae Woo; Oh, Eun-Jin; Hwang, Seong-Ju

    2008-10-01

    Sulfur-doped manganese oxide 1D nanostructures with controllable crystal structures and crystallite dimensions have been synthesized via one-pot non-hydrothermal solution route. Powder X-ray diffraction analysis clearly demonstrated that the crystal structures of the sulfur-doped manganates can be tailored by the change of reaction temperature; layered delta-MnO2-structured material was obtained at 60 degrees C while the reaction at 90 degrees C produced tunnel alpha-MnO2 structured material. According to field emission-scanning electron microscopy, both sulfur-doped manganates possess 1D nanostructure-type morphology with the diameter of approximately 20 nm and the length of approximately 1 microm for delta-MnO2-type material, and the diameter of approximately 100 nm and the length of approximately 800 nm for alpha-MnO2-type material, respectively. From X-ray photoelectron and X-ray absorption spectroscopic analyses, sulfur ions exist as highly oxidized sulfate cluster on surface or grain boundary of the manganate crystallite whereas manganese ions are stabilized in octahedral geometry with the mixed oxidation state of Mn+3/Mn+4. Of special importance is that both sulfur-doped manganate nanowires show promising electrode performances for lithium secondary batteries. PMID:19198483

  2. Search for new manganese-cobalt oxides as positive electrode materials for lithium batteries P. Strobel, J. Tillier, A. Diaz, A. Ibarra-Palos, F. Thiry and J.B. Soupart *

    E-print Network

    Boyer, Edmond

    Search for new manganese-cobalt oxides as positive electrode materials for lithium batteries P new mixed manganese-cobalt oxides for lithium battery positive electrode materials were obtained using material for rechargeable lithium batteries so far. Many efforts are underway to replace part or all cobalt

  3. Biological and Chemical Interactions with U(VI) During Anaerobic Enrichment in the Presence of Iron Oxide Coated Quartz

    SciTech Connect

    Brady D. Lee; Michelle R. Walton; Jodette L. Megio

    2005-11-01

    Microcosm experiments were performed to understand chemical and biological interactions with hexavalent uranium (U(VI)) in the presence of iron oxide bearing minerals and trichloroethylene (TCE) as a co-contaminant. Interactions of U(VI) and hydrous iron oxide moieties on the mineral oxide surfaces were studied during enrichments for dissimilatory iron reducing (DIRB) and sulfate reducing bacteria (SRB). Microbes enriched from groundwater taken from the Test Area North (TAN) site at the Idaho National Engineering and Environmental Laboratory (INEEL) were able to reduce the U(VI) in the adsorption medium as well as the iron on quartz surfaces. Early in the experiment disappearance of U(VI) from solution was a function of chemical interactions since no microbial activity was evident. Abiotic removal of U(VI) was enhanced in the presence of carbonate. As the experiment proceeded, further removal of U(VI) from solution was associated with the fermentation of lactate to propionate and acetate. During later phases of the experiment when lactate was depleted from the growth medium in the microcosm containing the DIRB enrichments, U(VI) concentrations in the solution phase increased until additional lactate was added. When lactate fermentation proceeded, U(VI) concentrations in the liquid phase again returned to near zero. Similar results were shown for the SRB enrichment but less uranium was released back into solution, while in the enrichment with carbonate uranium was not released back into solution. Chemical and biological interactions appear to be important on the mobilization/immobilization of U(VI) in an iron oxide system when TCE is present as a co-contaminant. Interestingly, TCE present in the microcosm experiments was not dechlorinated which was probably an effect of redox conditions that were unsuitable for reductive dechlorination by the microbial culture tested.

  4. Synthesis of Waste Cooking Oil Based Biodiesel via Ferric-Manganese Promoted Molybdenum Oxide / Zirconia Nanoparticle Solid acid Catalyst: Influence of Ferric and Manganese Dopants.

    PubMed

    Alhassan, Fatah H; Rashid, Umer; Taufiq-Yap, Yun Hin

    2015-05-01

    The utilization of ferric-manganese promoted molybdenum oxide/zirconia (Fe-Mn- MoO3/ZrO2) (FMMZ) solid acid catalyst for production of biodiesel was demonstrated. FMMZ is produced through impregnation reaction followed by calcination at 600°C for 3 h. The characterization of FMMZ had been done using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermal gravimetric analysis (TGA), temperature programmed desorption of NH3 (TPD-NH3), transmission electron microscopy(TEM) and Brunner-Emmett-Teller (BET) surface area measurement. The effect of waste cooking oil methyl esters (WCOME's) yield on the reactions variables such as reaction temperature, catalyst loading, molar ratio of methanol/oil and reusability were also assessed. The catalyst was used to convert the waste cooking oil into corresponding methyl esters (95.6%±0.15) within 5 h at 200? reaction temperature, 600 rpm stirring speed, 1:25 molar ratio of oil to alcohol and 4% w/w catalyst loading. The reported catalyst was successfully recycled in six connective experiments without loss in activity. Moreover, the fuel properties of WCOME's were also reported using ASTM D 6751 methods. PMID:25843280

  5. Structural study of biotic and abiotic poorly-crystalline manganese oxides using atomic pair distribution function analysis

    NASA Astrophysics Data System (ADS)

    Zhu, Mengqiang; Farrow, Christopher L.; Post, Jeffrey E.; Livi, Kenneth J. T.; Billinge, Simon J. L.; Ginder-Vogel, Matthew; Sparks, Donald L.

    2012-03-01

    Manganese (Mn) oxides are among the most reactive natural minerals and play an important role in elemental cycling in oceanic and terrestrial environments. A large portion of naturally-occurring Mn oxides tend to be poorly-crystalline and/or nanocrystalline, with not fully resolved crystal structures. In this study, the crystal structures of their synthetic analogs including acid birnessite (AcidBir), ?-MnO2, polymeric MnO2 (PolyMnO2) and a bacteriogenic Mn oxide (BioMnOx), have been revealed using atomic pair distribution function (PDF) analysis. Results unambiguously verify that these Mn oxides are layered materials. The best models that accurately allow simulation of pair distribution functions (PDFs) belong to the monoclinic C12/m1 space group with a disk-like shape. The single MnO6 layers in the average structures deviate significantly from hexagonal symmetry, in contrast to the results of previous studies based on X-ray diffraction analysis in reciprocal space. Manganese occupancies in MnO6 layers are estimated to be 0.936, 0.847, 0.930 and 0.935, for AcidBir, BioMnOx, ?-MnO2 and PolyMnO2, respectively; however, occupancies of interlayer cations and water molecules cannot be accurately determined using the models in this study. The coherent scattering domains (CSDs) of PolyMnO2, ?-MnO2 and BioMnOx are at the nanometer scale, comprising one to three MnO6 layers stacked with a high disorder in the crystallographic c-axis direction. Overall, the results of this study advance our understanding of the mineralogy of Mn oxide minerals in the environment.

  6. Quartz-Indium Tin Oxide-Magnesium Flouride Sandwich in a Low Density Plasma

    Microsoft Academic Search

    B. Vayner; D. Ferguson; J. Galofaro

    2006-01-01

    Indium tin oxide (ITO) coatings of solar cell coverglasses have been used for a long time to prevent electrostatic discharges on the array surface of a spacecraft in geosynchronous orbit. An antireflection layer of magnesium fluoride is also a common feature of solar cell design that allows increasing array efficiency by a few percent. Currently, some spacecraft in geosynchronous orbit

  7. Electrical transport properties of manganese containing pyrochlore type semiconducting oxides using impedance analyses

    SciTech Connect

    Sumi, S. [Materials and Minerals Division, National Institute for Interdisciplinary Science and Technology (NIIST), Trivandrum 695 019 (India)] [Materials and Minerals Division, National Institute for Interdisciplinary Science and Technology (NIIST), Trivandrum 695 019 (India); Prabhakar Rao, P., E-mail: padala_rao@yahoo.com [Materials and Minerals Division, National Institute for Interdisciplinary Science and Technology (NIIST), Trivandrum 695 019 (India); Mahesh, S.K. [Materials and Minerals Division, National Institute for Interdisciplinary Science and Technology (NIIST), Trivandrum 695 019 (India)] [Materials and Minerals Division, National Institute for Interdisciplinary Science and Technology (NIIST), Trivandrum 695 019 (India); Koshy, Peter [Mount Zion College of Engineering for Women, Chengannur 689 521 (India)] [Mount Zion College of Engineering for Women, Chengannur 689 521 (India)

    2012-12-15

    Graphical abstract: DC conductivity variation of CaCe{sub 1?x}Mn{sub x}SnNbO{sub 7??} (x = 0, 0.2, 0.4 and 0.6) with inverse of temperature. Variation of conductivity with Mn concentration at 600 °C is shown in the inset. Display Omitted Highlights: ? We have observed that the structural ordering as well as grain size increase with Mn substitution. ? Impedance analysis proved that a correlated barrier hopping type conduction mechanism is involved in the materials. ? Activation energy as well as electrical conductivity increases with increase in Mn substitution. ? Localization of electrons associated with Mn{sup 2+} and structural ordering are the key factors for the increased activation energy with Mn substitution. ? All the materials showed good NTC thermistor properties. -- Abstract: A new series of manganese containing pyrochlore type semiconducting oxides CaCe{sub 1?x}Mn{sub x}SnNbO{sub 7??} (x = 0, 0.2, 0.4 and 0.6) have been synthesized to study the effect of Mn substitution on the structure, microstructure and electrical properties of these samples. X-ray diffraction and scanning electron microscopy studies revealed an increase of structural ordering and grain size respectively with increase of Mn substitution. Rietveld analysis and Raman spectroscopy were also employed to corroborate the XRD results. The bulk resistance measurements with temperature exhibit negative temperature coefficient behavior. The impedance analysis of the samples revealed a non-Debye type relaxation existed in the materials. The ac conductivity variation with temperature and frequency indicates a correlated barrier hopping type conduction mechanism in these materials. The barrier height and the intersite separation for hopping influence the electrical conductivity of these samples and are found to be a function of localization of electrons associated with the Mn{sup 2+} ions and the unit cell volume respectively. The Mn substitution increases both electrical conductivity and activation energy contrastingly. This unusual behavior has been explained by correlating the structure, microstructure, defect states, electron localization and intersite separation with the conductivity data of the samples.

  8. Dissociation of manganese(III) oxide as part of a thermochemical water splitting cycle

    NASA Astrophysics Data System (ADS)

    Francis, Todd Michael

    A three-step thermochemical cycle to produce renewable hydrogen was proposed, which utilizes manganese(III) oxide and thermal energy to produce hydrogen. Most work on the cycle has focused on the hydrogen generating and product recovery steps with little work on the dissociation. It is essential to understand the dissociation because the feasibility of the cycle is based on this reaction having a high conversion. Because of the importance of the reduction step, this reaction has been selected as the topic of this dissertation. Additionally, because the dispersion of Mn2O3 particles into an Aerosol Flow Reactor (AFR) is important, feeding concepts were developed as well. Two powder feeding systems were developed: a Spinning Wheel Feeder (SWF) and a Fluidized Bed Feeder (FBF). Results of statistical particle size distribution studies indicated that the FBF was the better choice to disperse Mn2O3 powder. Additionally, results in an AFR demonstrated that the FBF was able to produce higher dissociation conversions. A study in a Thermogravimetric Analyzer (TGA) indicated multiple mechanisms were controlling Mn2O3 dissociation. The first half reaction of the dissociation was calculated to be controlled by an Avrami-Erofeev mechanism and had an activation energy of 106.4+/-1.9 kJ/mol. The second half reaction had a duel mechanism utilizing an Avrami-Erofeev and Order of Reaction (OOR) mechanism. The mechanisms had activation energies of 251.2+/-6.5 and 110.7+/-24.6 kJ/mol respectively. Mn2O3 dissociation investigations were done in an AFR. They revealed oxygen is a significant factor and to effectively control the dissociation with temperature and gas flow rate, the oxygen concentration must be below 0.25%. Experimental runs that had oxygen concentrations less than 0.25% were used to calculate reaction rate constants. The Avrami-Erofeev mechanisms were combined into a single mechanism. Rate constants for the Avrami-Erofeev and OOR mechanisms were 1.8E7+/-1.3E7 and 5.6E3+/-4.1E3 s -1 respectively. The results of a CFD model compared favorably with what was observed experimentally. A heavy feed concentration case predicted this as well. When the gas flow rate was higher the r-velocity was concluded to transport the more reacted powder near the wall to the center of the reactor, leading to higher conversions for the high gas flow rate.

  9. Chemical approach to a new crystal structure: phase control of manganese oxide on a carbon sphere template.

    PubMed

    Nam, Ki Min; Park, Joon T

    2014-12-01

    The stabilization and growth of a non-native structure, hexagonal wurtzite MnO (h-MnO), is explored via kinetic control of manganese precursor on a carbon sphere template. MnO is most stable in the cubic rock-salt structure (c-MnO), and a number of studies have focused on the synthesis and properties of this rock-salt phase. However, h-MnO has not been fully characterized before our work. Prolonged heating at a relatively low temperature yields c-MnO, whereas rapid heating of the reaction mixture at reflux produces h-MnO in the presence of carbon spheres. The effect of benzyl amine concentration on the formation of two different oxidation states (c-MnO and t-Mn3O4) was examined as well. Moreover, the structural stability of the manganese oxides and phase transition of MnO in terms of the wurtzite to rock-salt structural transformation have been investigated. PMID:25303773

  10. Rare earth element sorption onto hydrous manganese oxide A modeling study

    E-print Network

    Paris-Sud XI, Université de

    37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 1 Rare earth, Université Rennes 1, CNRS, 35042 Rennes cedex, France Keywords: rare earth element, manganese oxyhydroxides modeling, PHREEQC, PhreePlot 1. Introduction The distributions of rare earth elements (REE) in natural

  11. Oxidant Selection for the Treatment of Manganese (II), Iron (II), and Arsenic (III) in Groundwaters

    EPA Science Inventory

    In order to comply with the United States Environmental Protection Agency?s (U.S. EPA?s) arsenic standard and the manganese and iron secondary maximum contaminant levels (MCLs) in water (10µg/L, 50µg/L, and 300µg/L, respectively), many Midwestern water utilities must add a strong...

  12. Microbial Manganese Oxidation in the Lower Mississippi River: Methods and Evidence

    Microsoft Academic Search

    Alan M. Shiller; Tracey H. Stephens

    2005-01-01

    Recent work has led to the suggestion that biologically-mediated redox processes might be important in the regulation of dissolved trace element concentrations in rivers, especially with regard to manganese. Here, we focus on the removal of dissolved Mn from lower Mississippi River water. Experiments indicate that dissolved Mn can be rapidly removed from lower Mississippi River water on a timescale

  13. Catalytic oxidation of NO with O2 over FeMnOx/TiO2: Effect of iron and manganese oxides loading sequences and the catalytic mechanism study

    NASA Astrophysics Data System (ADS)

    Zhang, Mengying; Li, Caiting; Qu, Long; Fu, Mengfan; Zeng, Guangming; Fan, Chunzhen; Ma, Jinfeng; Zhan, Fuman

    2014-05-01

    FeMnOx/TiO2 with different iron and manganese oxides adding orders were prepared through isovolumetric impregnation and tested for catalytic oxidation of NO with O2. It was found that the sample obtained from one-step impregnation method had better catalytic activity. The excellent activity was attributed to higher surface area, lower crystalline of manganese oxides, abundant Mn3+, Fe3+ and chemisorbed oxygen species on the surface. Furthermore, effects of loading sequences on FeMnOx/TiO2 catalysts were investigated. The study showed that Fe and Mn would affect each other and change the surface physicochemical properties of FeMnOx/TiO2 when they were loaded step-by-step. In addition, the inhibiting effect of H2O on catalytic activity was reversible while the conversion of NO recovered to 40% when SO2 was cut off. XPS analysis between used and fresh catalysts revealed the electron transfer between Fen+ and Mnn+ ions in FeMnOx/TiO2. Possible reaction mechanism was put forward by comprehensive analysis of XPS and FT-IR results.

  14. Manganese metallurgy review. Part II: Manganese separation and recovery from solution

    Microsoft Academic Search

    Wensheng Zhang; Chu Yong Cheng

    2007-01-01

    Various methods for manganese separation and recovery from solution are reviewed, which are potentially applicable to leach solutions of secondary manganese sources, particularly nickel laterite waste effluents. The main methods include solvent extraction, sulfide precipitation, ion exchange, hydroxide precipitation and oxidative precipitation. These methods are briefly compared and assessed for both purification of manganese solutions and recovery of manganese from

  15. The Influence of the Local Lattice Distortion and Magnetic Ordering in Manganese Oxides on the Mn and O K-XANES

    SciTech Connect

    Krayzman, Victor; Maznichenko, Igor; Novakovich, Alexander; Vedrinskii, Rostislav [Rostov State University, 5 Zorge Str. Rostov-on-Don, 344090 (Russian Federation)

    2007-02-02

    Calculations of Mn and O K-XANES in perovskite-like structure manganese oxides performed by the full multiple scattering method within the spin-dependent exchange potential model enable to determine local lattice distortions and demonstrate the effect of the crystal magnetic order on the near-edge structure.

  16. Theoretical analysis of the spin effect on the electronic and magnetic properties of the calcium manganese oxide CaMnO 3: GGA+U calculation

    Microsoft Academic Search

    N. Hamdad; B. Bouhafs

    2010-01-01

    An electron is a magnetic solid that can perturb local moment via exchange interactions between spin and those of the ions. In our paper, we explore the fundamental physics behind the scarcity of ferromagnetic coexistence on the calcium manganese perovskite oxide CaMnO3, and examine the structural, electronic and magnetic properties of some known magnetically ordered systems. Various magnetic structures are

  17. High resolution electron energy loss spectroscopy of manganese oxides: Application to Mn{sub 3}O{sub 4} nanoparticles

    SciTech Connect

    Laffont, L., E-mail: Lydia.laffont@ensiacet.fr [Institut Carnot, Laboratoire CIRIMAT (equipe MEMO), CNRS UMR 5085, ENSIACET, 4 allee Emile Monso, BP 74233, 31432 Toulouse cedex 4 (France); Gibot, P. [Laboratoire de Reactivite et Chimie des Solides CNRS UMR 6007, Universite de Picardie Jules Verne, 33 rue Saint Leu, 80039 Amiens cedex 9 (France)

    2010-11-15

    Manganese oxides particularly Mn{sub 3}O{sub 4} Hausmannite are currently used in many industrial applications such as catalysis, magnetism, electrochemistry or air contamination. The downsizing of the particle size of such material permits an improvement of its intrinsic properties and a consequent increase in its performances compared to a classical micron-sized material. Here, we report a novel synthesis of hydrophilic nano-sized Mn{sub 3}O{sub 4}, a bivalent oxide, for which a precise characterization is necessary and for which the determination of the valency proves to be essential. X-ray diffraction (XRD), Transmission Electron Microscopy (TEM) and particularly High Resolution Electron Energy Loss Spectroscopy (HREELS) allow us to perform these measurements on the nanometer scale. Well crystallized 10-20 nm sized Mn{sub 3}O{sub 4} particles with sphere-shaped morphology were thus successfully synthesized. Meticulous EELS investigations allowed the determination of a Mn{sup 3+}/Mn{sup 2+} ratio of 1.5, i.e. slightly lower than the theoretical value of 2 for the bulk Hausmannite manganese oxide. This result emphasizes the presence of vacancies on the tetrahedral sites in the structure of the as-synthesized nanomaterial. - Research Highlights: {yields}Mn{sub 3}O{sub 4} bulk and nano were studied by XRD, TEM and EELS. {yields}XRD and TEM determine the degree of crystallinity and the narrow grain size. {yields}HREELS gave access to the Mn{sup 3+}/Mn{sup 2+} ratio. {yields}Mn{sub 3}O{sub 4} nano have vacancies on the tetrahedral sites.

  18. Investigation of the effect of a protective layer on parameters of quartz low-pressure gas-discharge lamps with oxide electrodes

    Microsoft Academic Search

    A. I. Vasil’ev; L. M. Vasilyak; S. V. Kostyuchenko; N. N. Kudryavtsev; M. E. Kuzmenko; V. Ya. Pecherkin

    2007-01-01

    Low pressure amalgam lamps are widely used for disinfection of air and water surfaces. The application of amalgam instead\\u000a of pure mercury makes it possible to design a high-efficiency powerful ultraviolet lamp and to improve the ecological impact\\u000a of disinfection equipment. This paper describes the effect of oxide electrodes and a quartz inner surface on the lifetime\\u000a of a lamp

  19. The development of manganese oxide coated ceramic membranes for combined catalytic ozonation and ultrafiltration of drinking water

    NASA Astrophysics Data System (ADS)

    Corneal, Lindsay Marie

    A novel method for the preparation of hydrated MnO2 by the ozonation of MnCl2 in water is described. The hydrated MnO 2 was used to coat titania water filtration membranes using a layer-by-layer technique. The coated membranes were then sintered in air at 500°C for 45 minutes. Upon sintering, the MnO2 is converted to alpha-Mn 2O3 (as characterized by x-ray and electron diffraction). Atomic force microscopy (AFM) imaging showed no significant change in the roughness or height of the surface features of coated membranes, while scanning electron microscopy (SEM) imaging showed an increase in grain size with increasing number of coating layers. Energy dispersive x-ray spectroscopy (EDS) mapping and line scans revealed manganese present throughout the membrane, indicating that manganese dispersed into the porous membrane during the coating process and diffused into the titania grains during sintering. Selected area diffraction (SAD) of the coated and sintered membrane was used to index the surface layer as alpha-Mn2O3. The surface layer was uneven, although there was a trend of increasing thickness with increasing coating layers. The coating acts as a catalyst for the oxidation of organic matter when coated membranes are used in a hybrid ozonation-membrane filtration system. A trend of decreasing total organic carbon (TOC) in the permeate water was observed with increasing number of coating layers. The catalytic activity also manifests itself as improved recovery of the water flux due to oxidation of foulants on the membrane surface. Ceramic nanoparticle coatings on ceramic water filtration membranes must undergo high temperature sintering. However, this means that the underlying membrane, which has been engineered for a given molecular weight cut-off (MWCO), also undergoes a high temperature heat treatment that serves to increase pore size that have resulted in increases in permeability of titania membranes. Coating the titania membrane with manganese oxide followed by sintering in air at 500°C maintains the MWCO of the membranes, with high DI water permeability, which may be favorable in terms of membrane use. SEM micrographs of titania membrane samples sintered between 500°C to 900°C were analyzed to identify a statistically significant increase in grain size with increasing sintering temperature. The grains however, generally retain a uniform shape until the 900°C sintering temperature, where large, irregularly shaped grains were observed. AFM analysis showed a corresponding increase in the surface roughness of the membrane for the sample sintered at 900°C.

  20. Electrochemical properties of spinel-type manganese oxide/porous carbon nanocomposite powders in 1 M KOH aqueous solution

    NASA Astrophysics Data System (ADS)

    Tsumura, Tomoki; Tsumori, Koichiro; Shimizu, Goichi; Toyoda, Masahiro

    2012-02-01

    Spinel-type manganese oxide/porous carbon (Mn3O4/C) nanocomposite powders have been simply prepared by a thermal decomposition of manganese gluconate dihydrate under an Ar gas flow at above 600 °C. The structure and texture of the Mn3O4/C nanocomposite powders are investigated by X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS) equipped scanning transmission electron microscopy (STEM), transmission electron microscopy (TEM), selected area-electron diffraction (SA-ED), thermogravimetric and differential thermal analysis (TG-DTA) and adsorption/desorption of N2 gas at -196 °C. The electrochemical properties of the nanocomposite powders in 1 M KOH aqueous solution are studied, focusing on the relationship between their structures and electrochemical capacitance.In the nanocomposite powders, Mn3O4 nano particles approximately 5 nm in size are dispersed in a porous carbon matrix. The nanocomposite powders prepared at 800 °C exhibit a high specific capacitance calculated from cyclic voltammogram of 350 and 600 F g-1 at a sweep rate of 1 and 0.1 mV s-1, respectively. The influence of the heating temperature on the structure and the electrochemical properties of nanocomposite powders is also discussed.

  1. Electronic Structure Measurements of Colossal Magnetoresistive Manganese-Oxides: Polaronic Effects on the Band Structure

    Microsoft Academic Search

    D. S. Dessau; T. Saitoh; C.-H. Park; Z.-X. Shen; P. Villella; N. Hamada; Y. Moritomo; Y. Tokura

    1999-01-01

    We have used high energy-resolution angle-resolved photoemission spectroscopy(ARPES) to map the k-dependent electronic structure of single-crystallinesamples of the manganese-based perovskites as a function of doping level, temperature,and layer number. The measured near-Fermi energy states display E vs. kand symmetry relationships which agree relatively well with the LSDA band theoryprediction through much of the Brillouin zone, and the locus of lowest

  2. Multivariate data analysis approach to understand magnetic properties of perovskite manganese oxides

    Microsoft Academic Search

    N. Imamura; T. Mizoguchi; H. Yamauchi; M. Karppinen

    2008-01-01

    Here we apply statistical multivariate data analysis techniques to obtain some insights into the complex structure-property relations in antiferromagnetic (AFM) and ferromagnetic (FM) manganese perovskite systems, AMnO3. The 131 samples included in the present analyses are described by 21 crystal-structure or crystal-chemical (CS\\/CC) parameters. Principal component analysis (PCA), carried out separately for the AFM and FM compounds, is used to

  3. Kinetics of Chromium(III) Oxidation by Manganese(IV) Oxides Using Quick Scanning X-ray Absorption Fine Structure Spectroscopy (Q-XAFS)

    SciTech Connect

    Landrot, G.; Ginder-Vogel, M; Sparks, D

    2010-01-01

    The initial kinetics of Cr(III) oxidation on mineral surfaces is poorly understood, yet a significant portion of the oxidation process occurs during the first seconds of reaction. In this study, the initial rates of Cr(III) oxidation on hydrous manganese oxide (HMO) were measured at three different pH values (pH 2.5, 3, and 3.5), using a quick X-ray absorption fine structure spectroscopy (Q-XAFS) batch method. The calculated rate constants were 0.201, 0.242, and 0.322 s{sup -1} at pH 2.5, 3, and 3.5, respectively. These values were independent of both [Cr(III)] and [Mn(II)] and mixing speed, suggesting that the reaction was 'chemically' controlled and not dependent upon diffusion at the time period the rate parameters were measured. A second-order overall rate was found at three pH values. This represents the first study to determine the chemical kinetics of Cr(III) oxidation on Mn-oxides. The results have important implications for the determination of rapid, environmentally important reactions that cannot be measured with traditional batch and flow techniques. An understanding of these reactions is critical to predicting the fate of contaminants in aquatic and terrestrial environments.

  4. Immobilization of manganese peroxidase from Lentinula edodes on alkylaminated emphaze TM AB 1 polymer for generation of Mn 3+ as an oxidizing agent

    Microsoft Academic Search

    Anthony C. Grabski; Jerald K. Rasmussen; Patrick L. Coleman; Richard R. Burgess

    1996-01-01

    Manganese peroxidase (MnP) is secreted by white-rot fungi and participates in the degradation of lignin by these organisms.\\u000a MnP uses H2O2 as an oxidant to oxidize MnII to MnIII as the manganic ion Mn3+. The Mn3+ stabilized by chelation, is a highly reactive nonspecific oxidant capable of oxidizing a variety of toxic organic compounds.\\u000a Previous attempts at immobilization of MnP,

  5. Graphite coated with manganese oxide/multiwall carbon nanotubes composites as anodes in marine benthic microbial fuel cells

    NASA Astrophysics Data System (ADS)

    Fu, Yubin; Yu, Jian; Zhang, Yelong; Meng, Yao

    2014-10-01

    Improving anode performance is of great significance to scale up benthic microbial fuel cells (BMFCs) for its marine application to drive oceanography instruments. In this study, manganese oxide (MnO2)/multiwall carbon nanotubes (MWCNTs) composites are prepared to be as novel anodes in the BMFCs via a direct redox reaction between permanganate ions (MnO4-) and MWCNTs. The results indicate that the MnO2/MWCNTs anode has a better wettability, greater kinetic activity and higher power density than that of the plain graphite (PG) anode. It is noted that the MnO2 (50% weight percent)/MWCNTs anode shows the highest electrochemical performance among them and will be a promising material for improving bioelectricity production of the BMFCs. Finally, a synergistic mechanism of electron transfer shuttle of Mn ions and their redox reactions in the interface between modified anode and bacteria biofilm are proposed to explain its excellent electrochemical performance.

  6. Lithium ion phase-transfer reaction at the interface between the lithium manganese oxide electrode and the nonaqueous electrolyte.

    PubMed

    Kobayashi, Shota; Uchimoto, Yoshiharu

    2005-07-14

    The lithium ion phase-transfer reaction between the spinel lithium manganese oxide electrode and a nonaqueous electrolyte was investigated by the ac impedance spectroscopic method. The dependence of the impedance spectra on the electrochemical potential of the lithium ion in the electrode, the lithium salt concentration in the electrolyte, the kind of solvent, and the measured temperature were examined. Nyquist plots, obtained from the impedance measurements, consist of two semicircles for high and medium frequency and warburg impedance for low frequency, indicating that the reaction process of two main steps for high and medium frequency obey the Butler-Volmer type equation and could be related to the charge-transfer reaction process accompanied with lithium ion phase-transfer at the interface. The dependency on the solvent suggests that both steps in the lithium ion phase-transfer at the electrode/electrolyte interface include the desolvation process and have high activation barriers. PMID:16852662

  7. Manganese-enhanced biotransformation of atrazine by the white rot fungus Pleurotus pulmonarius and its correlation with oxidation activity.

    PubMed Central

    Masaphy, S; Henis, Y; Levanon, D

    1996-01-01

    Manganese enhanced atrazine transformation by the fungus Pleurotus pulmonarius when added to a liquid culture medium at concentrations of up to 300 microM. Both N-dealkylated and propylhydroxylated metabolites accumulated in the culture medium, with the former accumulating to a greater extent than did the latter. Lipid peroxidation, oxygenase and peroxidase activities, and the cytochrome P-450 concentration increased. In addition, an increase in the spectral interactions between atrazine and components in the cell extract was observed. Antioxidants, mainly nordihydroguaiaretic acid, which inhibits lipoxygenase, peroxidase, and P-450 activities, and piperonyl butoxide, which inhibits P-450 activity, inhibited atrazine transformation by the mycelium. It is suggested that the stimulation of oxidative activity by Mn might be responsible for increasing the biotransformation of atrazine and for nonspecific transformations of other xenobiotic compounds. PMID:8967773

  8. Hybrid nickel manganese oxide nanosheet-3D metallic dendrite percolation network electrodes for high-rate electrochemical energy storage.

    PubMed

    Nguyen, Tuyen; Eugénio, Sónia; Boudard, Michel; Rapenne, Laetitia; Carmezim, M João; Silva, Teresa M; Montemor, M Fátima

    2015-08-01

    This work reports the fabrication, by electrodeposition and post-thermal annealing, of hybrid electrodes for high rate electrochemical energy storage composed of nickel manganese oxide (Ni0.86Mn0.14O) nanosheets over 3D open porous dendritic NiCu foams. The hybrid electrodes are made of two different percolation networks of nanosheets and dendrites, and exhibit a specific capacitance value of 848 F g(-1) at 1 A g(-1). The electrochemical tests revealed that the electrodes display an excellent rate capability, characterized by capacitance retention of approximately 83% when the applied current density increases from 1 A g(-1) to 20 A g(-1). The electrodes also evidenced high charge-discharge cycling stability, which attained 103% after 1000 cycles. PMID:26135715

  9. Manganese, the stress reliever.

    PubMed

    Latour, J-M

    2015-01-01

    Convergent evidence has emerged over the past decade to highlight the role of manganese as a key player in the defenses that many organisms are building to fight oxidative stress. For redox processes replacing iron by manganese requires adaptation at different levels. The aim of this perspective is to summarize recent important observations and to analyze the implications of the present knowledge for resolving future issues. PMID:25434324

  10. Design, synthesis, and characterization of materials for controlled line deposition, environmental remediation, and doping of porous manganese oxide material

    NASA Astrophysics Data System (ADS)

    Calvert, Craig A.

    This thesis covers three topics: (1) coatings formed from sol-gel phases, (2) environmental remediation, and (3) doping of a porous manganese oxide. Synthesis, characterization, and application were investigated for each topic. Line-formations were formed spontaneously by self-assembly from vanadium sol-gels and other metal containing solutions on glass substrates. The solutions were prepared by the dissolution of metal oxide or salt in water. A more straightforward method is proposed than used in previous work. Analyses using optical microscopy, atomic force microscopy, scanning electron microscopy, energy-dispersive X-ray analysis, and infrared spectroscopy showed discreet lines whose deposition could be controlled by varying the concentration. A mechanism was developed from the observed results. Microwave heating, the addition of graphite rods, and oxidants, can enhance HCB remediation from soil. To achieve remediation, a TeflonRTM vessel open to the atmosphere along with an oxidant, potassium persulfate (PerS) or potassium hydroxide, along with uncoated or aluminum oxide coated, graphite rods were heated in a research grade microwave oven. Microwave heating was used to decrease the heating time, and graphite rods were used to increase the absorption of the microwave energy by providing thermal centers. The results showed that the percent HCB removed was increased by adding graphite rods and oxidants. Tungsten, silver, and sulfur were investigated as doping agents for K--OMS-2. The synthesis of these materials was carried out with a reflux method. The doping of K--OMS-2 led to changes in the properties of a tungsten doped K--OMS-2 had an increased resistivity, the silver doped material showed improved epoxidation of trans-stilbene, and the addition of sulfur produced a paper-like material. Rietveld refinement of the tungsten doped K--OMS-2 showed that the tungsten was doped into the framework.

  11. One-step through-mask electrodeposition of a porous structure composed of manganese oxide nanosheets with electrocatalytic activity for oxygen reduction

    SciTech Connect

    Fukuda, Masaki; Iida, Chihiro [Department of Applied Chemistry, Yamaguchi University, 2-16-1 Tokiwadai, Ube 755-8611 (Japan); Nakayama, Masaharu, E-mail: nkymm@yamaguchi-u.ac.jp [Department of Applied Chemistry, Yamaguchi University, 2-16-1 Tokiwadai, Ube 755-8611 (Japan)

    2009-06-03

    Potentiostatic electrolysis of a mixed aqueous solution of Bu{sub 4}NBr and MnSO{sub 4} at +1.0 V (vs. Ag/AgCl) on Pt electrode led to the oxidation of Br{sup -} and Mn{sup 2+} ions. X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and X-ray diffraction (XRD) revealed that this anodic process was followed by the deposition of insulating crystals of bromide salt of Bu{sub 4}N{sup +} and the subsequent formation of layered manganese oxide in the interstitial spaces of the bromide grains already grown. Dissolution of the bromide crystals in water left a well-dispersed porous texture composed of manganese oxide nanosheets. The resulting MnO{sub x}-modified electrode exhibited a larger catalytic current for the reduction of oxygen in alkaline solution, compared to the bare Pt electrode.

  12. Effective microbes for simultaneous bio-oxidation of ammonia and manganese in biological aerated filter system.

    PubMed

    Abu Hasan, Hassimi; Abdullah, Siti Rozaimah Sheikh; Kofli, Noorhisham Tan; Kamarudin, Siti Kartom

    2012-11-01

    This study determined the most effective microbes acting as ammonia-oxidising (AOB) and manganese-oxidising bacteria (MnOB) for the simultaneous removal of ammonia (NH(4)(+)-N) and manganese (Mn(2+)) from water. Two conditions of mixed culture of bacteria: an acclimatised mixed culture (mixed culture: MC) in a 5-L bioreactor and biofilm attached on a plastic medium (stages of mixed culture: SMC) in a biological aerated filter were isolated and identified using Biolog MicroSystem and 16S rRNA sequencing. A screening test for determining the most effective microbe in the removal of NH(4)(+)-N and Mn(2+) was initially performed using SMC and MC, respectively, and found that Bacillus cereus was the most effective microbe for the removal of NH(4)(+)-N and Mn(2+). Moreover, the simultaneous NH(4)(+)-N and Mn(2+) removal (above 95% removal for both NH(4)(+)-N and Mn(2+)) was achieved using a biological aerated filter under various operating conditions. Thus, the strain could act as an effective microbe of AOB and a MnOB for the simultaneous removal of NH(4)(+)-N and Mn(2+). PMID:22995166

  13. Degradation of aqueous and soil-sorbed estradiol using a new class of stabilized manganese oxide nanoparticles.

    PubMed

    Han, Bing; Zhang, Man; Zhao, Dongye; Feng, Yucheng

    2015-03-01

    Manganese oxide (MnO?) was reported to be effective for degrading aqueous pharmaceutical chemicals. However, little is known about its potential use for degrading soil-sorbed contaminants. To bridge this knowledge gap, we synthesized, for the first time, a class of stabilized MnO? nanoparticles using carboxymethyl celluloses (CMC) as a stabilizer, and tested their effectiveness for degrading aqueous and soil-sorbed estradiol. The most desired particles (highest reactivity and soil deliverability) were obtained at a CMC/MnO? molar ratio of 1.39 × 10(-3), which yielded a mean hydrodynamic size of 39.5 nm and a narrow size distribution (SD = 0.8 nm). While non-stabilized MnO? particles rapidly aggregated and were not transportable through a soil column, CMC-stabilized nanoparticles remained fully dispersed in water and were soil deliverable. At typical aquatic pH (6-7), CMC-stabilized MnO? exhibited faster degradation kinetics for oxidation of 17?-estradiol than non-stabilized MnO?. The reactivity advantage becomes more evident when used for treating soil-sorbed estradiol owing to the ability of CMC to complex with metal ions and prevent the reactive sites from binding with inhibitive soil components. A retarded first-order rate model was able to interpret the oxidation kinetics for CMC-stabilized MnO?. When used for degrading soil-sorbed estradiol, several factors may inhibit the oxidation effectiveness, including desorption rate, soil-MnO? interactions, and soil-released metals and reductants. CMC-stabilized MnO? nanoparticles hold the potential for facilitating in situ oxidative degradation of various emerging contaminants in soil and groundwater. PMID:25543239

  14. Daily Manganese Intake Status and Its Relationship with Oxidative Stress Biomarkers under Different Body Mass Index Categories in Korean Adults

    PubMed Central

    Bu, So-Young

    2012-01-01

    Manganese (Mn) is an essential micronutrient for human and plays an important role as a cofactor for several enzymes involving fatty acid synthesis, hepatic gluconeogenesis, and oxidative stresses. Also, Mn intake status has been reported to have beneficial effects in reversing metabolic dysfunction including obesity and nonalcoholic steatosis which is linked to mitochondrial dysfunction and oxidative stresses, however, information on dietary Mn intake in Koreans are limited. Hence we investigated the relationship between dietary Mn intake and antioxidant defense factors in healthy and obese subjects. Total of 333 healthy subjects were recruited in the study and were assigned to one of three study groups: a normal group (18.5-22.9), a overweight group (23-24.9), and a obesity group (>25) according to their body mass index (BMI). We assessed Mn intakes (24-hr recall method) and several indicators for antioxidative defenses such as glutathione (GSH), glutathione peroxidase (GPx) and urinary malonaldehyde (MDA). Results showed that body weight and blood pressure of study subjects were increased in dependent of their BMI (p < 0.01). However dietary Mn intakes and oxidative stress biomarkers (GSH, GPx, and MDA) were not significantly different by groups defined by BMI. In correlation analysis adjusting for age, sex and energy intake, dietary Mn intake of the subjects in different BMI categories were not significantly correlated with GSH, GPx, MDA and showed a weak or no association with these oxidative stress markers. In conclusion dietary Mn intake at least in this study has a little or no influence on markers of oxidative status in both healthy and obese subjects. PMID:23431039

  15. Degradation of lithium ion batteries employing graphite negatives and nickel-cobalt-manganese oxide + spinel manganese oxide positives: Part 1, aging mechanisms and life estimation

    NASA Astrophysics Data System (ADS)

    Wang, John; Purewal, Justin; Liu, Ping; Hicks-Garner, Jocelyn; Soukazian, Souren; Sherman, Elena; Sorenson, Adam; Vu, Luan; Tataria, Harshad; Verbrugge, Mark W.

    2014-12-01

    We examine the aging and degradation of graphite/composite metal oxide cells. Non-destructive electrochemical methods were used to monitor the capacity loss, voltage drop, resistance increase, lithium loss, and active material loss during the life testing. The cycle life results indicated that the capacity loss was strongly impacted by the rate, temperature, and depth of discharge (DOD). Lithium loss and active electrode material loss were studied by the differential voltage method; we find that lithium loss outpaces active material loss. A semi-empirical life model was established to account for both calendar-life loss and cycle-life loss. For the calendar-life equation, we adopt a square root of time relation to account for the diffusion limited capacity loss, and an Arrhenius correlation is used to capture the influence of temperature. For the cycle life, the dependence on rate is exponential while that for time (or charge throughput) is linear.

  16. Water oxidation by manganese oxides, a new step towards a complete picture: simplicity is the ultimate sophistication.

    PubMed

    Najafpour, Mohammad Mahdi; Sedigh, Davood Jafarian

    2013-09-14

    We, for the first time, report that many Mn oxides (Mn3O4, ?-Mn2O3, ?-MnO2, CaMnO3, Ca2Mn3O8, CaMn3O6 and CaMn4O8) in the presence of cerium(IV) ammonium nitrate, in the water oxidation, convert to layered Mn oxide. This layered Mn oxide is an efficient water oxidizing catalyst. PMID:23838901

  17. Iron, copper, and manganese complexes with in vitro superoxide dismutase and/or catalase activities that keep Saccharomyces cerevisiae cells alive under severe oxidative stress.

    PubMed

    Ribeiro, Thales P; Fernandes, Christiane; Melo, Karen V; Ferreira, Sarah S; Lessa, Josane A; Franco, Roberto W A; Schenk, Gerhard; Pereira, Marcos D; Horn, Adolfo

    2015-03-01

    Due to their aerobic lifestyle, eukaryotic organisms have evolved different strategies to overcome oxidative stress. The recruitment of some specific metalloenzymes such as superoxide dismutases (SODs) and catalases (CATs) is of great importance for eliminating harmful reactive oxygen species (hydrogen peroxide and superoxide anion). Using the ligand HPClNOL {1-[bis(pyridin-2-ylmethyl)amino]-3-chloropropan-2-ol}, we have synthesized three coordination compounds containing iron(III), copper(II), and manganese(II) ions, which are also present in the active site of the above-noted metalloenzymes. These compounds were evaluated as SOD and CAT mimetics. The manganese and iron compounds showed both SOD and CAT activities, while copper showed only SOD activity. The copper and manganese in vitro SOD activities are very similar (IC50~0.4 ?mol dm(-3)) and about 70-fold higher than those of iron. The manganese compound showed CAT activity higher than that of the iron species. Analyzing their capacity to protect Saccharomyces cerevisiae cells against oxidative stress (H2O2 and the O2(•-) radical), we observed that all compounds act as antioxidants, increasing the resistance of yeast cells mainly due to a reduction of lipid oxidation. Especially for the iron compound, the data indicate complete protection when wild-type cells were exposed to H2O2 or O2(•-) species. Interestingly, these compounds also compensate for both superoxide dismutase and catalase deficiencies; their antioxidant activity is metal ion dependent, in the order iron(III)>copper(II)>manganese(II). The protection mechanism employed by the complexes proved to be independent of the activation of transcription factors (such as Yap1, Hsf1, Msn2/Msn4) and protein synthesis. There is no direct relation between the in vitro and the in vivo antioxidant activities. PMID:25511255

  18. One-step sonochemical synthesis of a graphene oxide-manganese oxide nanocomposite for catalytic glycolysis of poly(ethylene terephthalate)

    NASA Astrophysics Data System (ADS)

    Park, Gle; Bartolome, Leian; Lee, Kyoung G.; Lee, Seok Jae; Kim, Do Hyun; Park, Tae Jung

    2012-06-01

    Ultrasound-assisted synthesis of a graphene oxide (GO)-manganese oxide nanocomposite (GO-Mn3O4) was conducted without further modification of GO or employing secondary materials. With the GO nanoplate as a support, potassium permanganate oxidizes the carbon atoms in the GO support and gets reduced to Mn3O4. An intensive ultrasound method could reduce the number of reaction steps and temperature, enhance the reaction rate and furthermore achieve a Mn3O4 phase. The composite was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The coverage and crystallinity of Mn3O4 were controlled by changing the ratio of permanganate to GO dispersion. The synthesized nanocomposite was used as a catalyst for poly(ethylene terephthalate) (PET) depolymerization into its monomer, bis(2-hydroxylethyl) terephthalate (BHET). The highest monomer yield of 96.4% was obtained with the nanocomposite containing the lowest amount of Mn3O4, while PET glycolysis with the Mn3O4 without GO yielded 82.7% BHET.Ultrasound-assisted synthesis of a graphene oxide (GO)-manganese oxide nanocomposite (GO-Mn3O4) was conducted without further modification of GO or employing secondary materials. With the GO nanoplate as a support, potassium permanganate oxidizes the carbon atoms in the GO support and gets reduced to Mn3O4. An intensive ultrasound method could reduce the number of reaction steps and temperature, enhance the reaction rate and furthermore achieve a Mn3O4 phase. The composite was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The coverage and crystallinity of Mn3O4 were controlled by changing the ratio of permanganate to GO dispersion. The synthesized nanocomposite was used as a catalyst for poly(ethylene terephthalate) (PET) depolymerization into its monomer, bis(2-hydroxylethyl) terephthalate (BHET). The highest monomer yield of 96.4% was obtained with the nanocomposite containing the lowest amount of Mn3O4, while PET glycolysis with the Mn3O4 without GO yielded 82.7% BHET. Electronic supplementary information (ESI) available: XPS spectra of GO-Mn3O4 A and B, EDS mapping images of GO-Mn3O4 C, AFM analysis and TEM image of Mn3O4. See DOI: 10.1039/c2nr30168g

  19. In-situ X-Ray Absorption Spectroscopy (XAS) Investigation of a Bifunctional Manganese Oxide Catalyst with High Activity for Electrochemical Water Oxidation and Oxygen Reduction

    PubMed Central

    Benck, Jesse D.; Gul, Sheraz; Webb, Samuel M.; Yachandra, Vittal K.; Yano, Junko; Jaramillo, Thomas F.

    2013-01-01

    In-situ x-ray absorption spectroscopy (XAS) is a powerful technique that can be applied to electrochemical systems, with the ability to elucidate the chemical nature of electrocatalysts under reaction conditions. In this study, we perform in-situ XAS measurements on a bifunctional manganese oxide (MnOx) catalyst with high electrochemical activity for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). Using x-ray absorption near edge structure (XANES) and extended x-ray absorption fine structure (EXAFS), we find that exposure to an ORR-relevant potential of 0.7 V vs. RHE produces a disordered Mn3II,III,IIIO4 phase with negligible contributions from other phases. After the potential is increased to a highly anodic value of 1.8 V vs. RHE, relevant to the OER, we observe an oxidation of approximately 80% of the catalytic thin film to form a mixed MnIII,IV oxide, while the remaining 20% of the film consists of a less oxidized phase, likely corresponding to unchanged Mn3II,III,IIIO4. XAS and electrochemical characterization of two thin film catalysts with different MnOx thicknesses reveals no significant influence of thickness on the measured oxidation states, at either ORR or OER potentials, but demonstrates that the OER activity scales with film thickness. This result suggests that the films have porous structure, which does not restrict electrocatalysis to the top geometric layer of the film. As the portion of the catalyst film that is most likely to be oxidized at the high potentials necessary for the OER is that which is closest to the electrolyte interface, we hypothesize that the MnIII,IV oxide, rather than Mn3II,III,IIIO4, is the phase pertinent to the observed OER activity. PMID:23758050

  20. Low power loss and field-insensitive permeability of Fe-6.5%Si powder cores with manganese oxide-coated particles

    NASA Astrophysics Data System (ADS)

    Li, Junnan; Wang, Xian; Xu, Xiaojun; Gong, Rongzhou; Feng, Zekun; Chen, Yajie; Harris, V. G.

    2015-05-01

    Fe-6.5%Si alloy powders coated with manganese oxides using an innovative in situ process were investigated. The in-situ coating of the insulating oxides was realized with a KMnO4 solution by a chemical process. The insulating manganese oxides with mixed valance state were verified by X-ray photoelectron spectroscopy analysis. The thickness of the insulating layer on alloy particles was determined to be in a range of 20-210 nm, depending upon the KMnO4 concentration. The powder core loss and the change in permeability under a DC-bias field were measured at frequencies ranging from 50 to 100 kHz. The experiments indicated that the Fe-6.5%Si powder cores with a 210 nm-thick manganese oxide layer not only showed a low core loss of 459 mW/cm3 at 100 kHz but also showed a small reduction in permeability (?(H)/?(0) = 85% for ? = 42) at a DC-bias field of 80 Oe. This work has defined a novel pathway to realizing low core loss and field-insensitive permeability for Fe-Si powder cores.

  1. Transformation of triclosan to 2,8-dichlorodibenzo-p-dioxin by iron and manganese oxides under near dry conditions.

    PubMed

    Ding, Jiafeng; Su, Mian; Wu, Cuiwei; Lin, Kunde

    2015-08-01

    Triclosan (TCS) is a broad-spectrum antibacterial agent widely used in household and personal care products and is frequently detected in the environment. Previous studies have shown that TCS could be converted to the more toxic compound 2,8-dichlorodibenzo-p-dioxins (2,8-DCDD) in photochemical reactions and incineration processes. In this study, we demonstrated the formation of 2,8-DCDD from the oxidation of TCS by ?-FeOOH and a natural manganese oxides (MnOx) sand. Experiments at room temperature and under near dry conditions showed that Fe and Mn oxides readily catalyzed the conversion of TCS to 2,8-DCDD and other products. Approximately 5.5% of TCS was transformed to 2,8-DCDD by ?-FeOOH in 45d and a higher conversion percentage (6.7%) was observed for MnOx sand in 16d. However, the presence of water in the samples significantly inhibited the formation of 2,8-DCDD. Besides 2,8-DCDD, 2,4-dichlorphenol (2,4-DCP), 4-chlorobenzene-1,2-diol, 2-chloro-5-(2,4-dichlorophenoxy)benzene-1,4-diol, and 2-chloro-5-(2,4-dichlorophenoxy)-1,4-benzoquinone were identified in the reactions. The possible pathways for the formation of reaction products were proposed. This study suggests that Fe and Mn oxides-mediated transformation of TCS under near dry conditions might be another potential pathway for the formation of 2,8-DCDD in the natural environment. PMID:25880455

  2. The influence of manganese-cobalt oxide/graphene on reducing fire hazards of poly(butylene terephthalate).

    PubMed

    Wang, Dong; Zhang, Qiangjun; Zhou, Keqing; Yang, Wei; Hu, Yuan; Gong, Xinglong

    2014-08-15

    By means of direct nucleation and growth on the surface of graphene and element doping of cobalt oxide (Co3O4) nano-particles, manganese-cobalt oxide/graphene hybrids (MnCo2O4-GNS) were synthesized to reduce fire hazards of poly(butylene terephthalate) (PBT). The structure, elemental composition and morphology of the obtained hybrids were surveyed by X-ray diffraction, X-ray photoelectron spectrometer and transmission electron microscopy, respectively. Thermogravimetric analysis was applied to simulate and study the influence of MnCo2O4-GNS hybrids on thermal degradation of PBT during combustion. The fire hazards of PBT and its composites were assessed by the cone calorimeter. The cone test results had showed that peak HRR and SPR values of MnCo2O4-GNS/PBT composites were lower than that of pure PBT and Co3O4-GNS/PBT composites. Furthermore, the incorporation of MnCo2O4-GNS hybrids gave rise to apparent decrease of pyrolysis products containing aromatic compounds, carbonyl compounds, carbon monoxide and carbon dioxide, attributed to combined impact of physical barrier for graphene and cat O4 for organic volatiles and carbon monoxide. PMID:24997255

  3. Characterization of a mitochondrial manganese superoxide dismutase gene from Apis cerana cerana and its role in oxidative stress.

    PubMed

    Jia, Haihong; Sun, Rujiang; Shi, Weina; Yan, Yan; Li, Han; Guo, Xingqi; Xu, Baohua

    2014-01-01

    Mitochondrial manganese superoxide dismutase (mMnSOD) plays a vital role in the defense against reactive oxygen species (ROS) in eukaryotic mitochondria. In this study, we isolated and identified a mMnSOD gene from Apis cerana cerana, which we named AccSOD2. Several putative transcription factor-binding sites were identified within the 5'-flanking region of AccSOD2, which suggests that AccSOD2 may be involved in organismal development and/or environmental stress responses. Quantitative real-time PCR analysis showed that AccSOD2 is highly expressed in larva and pupae during different developmental stages. In addition, the expression of AccSOD2 could be induced by cold (4 °C), heat (42 °C), H2O2, ultraviolet light (UV), HgCl2, and pesticide treatment. Using a disc diffusion assay, we provide evidence that recombinant AccSOD2 protein can play a functional role in protecting cells from oxidative stress. Finally, the in vivo activities of AccSOD2 were measured under a variety of stressful conditions. Taken together, our results indicate that AccSOD2 plays an important role in cellular stress responses and anti-oxidative processes and that it may be of critical importance to honeybee survival. PMID:24269344

  4. Effects of Cobalt on Manganese Oxidation by Pseudomonas putida MnB1

    NASA Astrophysics Data System (ADS)

    Pena, J.; Bargar, J.; Sposito, G.

    2005-12-01

    The oxidation of Mn(II) in the environment is thought to occur predominantly through biologically mediated pathways. During the stationary phase of growth, the well-characterized freshwater and soil bacterium Pseudomonas putida MnB1 oxidizes soluble Mn(II) to a poorly crystalline layer type Mn(IV) oxide. These Mn oxide particles (2 - 5 nm thickness) are deposited in a matrix of extracellular polymeric substances (EPS) surrounding the cell, creating a multi-component system distinct from commonly studied synthetic Mn oxides. Accurate characterization of the reactivity of these biomineral assemblages is essential to understanding trace metal biogeochemistry in natural waters and sediments. Moreover, these biogenic oxides may potentially be used for the remediation of surface and ground waters impacted by mining, industrial pollution, and other anthropogenic activities. In this study, we consider the interactions between Co, P. putida MnB1, and its biogenic Mn oxide. Cobalt is a redox-active transition metal which exists in the environment as Co(II) and Co(III). While Co is not generally found in the environment at toxic concentrations, it may be released as a byproduct of mining activities (e.g. levels of up to 20 ?M are found in Pinal Creek, AZ, a stream affected by copper mining). In addition, the radionuclide 60Co, formed by neutron activation in nuclear reactors, is of concern at Department of Energy sites, such as that at Hanford, and has several industrial applications, including radiotherapy. We address the following questions: Do high levels of Co inhibit enzymatic processes such as Mn(II) oxidation? Can the multicopper oxidase enzyme involved in Mn(II) oxidation facilitate Co(II) oxidation? Lastly, does the organic matter surrounding the oxides affect Co or Mn oxide reactivity? These issues were approached via wet chemical analysis, synchrotron radiation X-ray diffraction (SR-XRD), and extended X-ray absorption fine structure (EXAFS) spectroscopy. In the presence of both Mn (1 mM) and Co (10-40 ?M), Mn oxidation proceeded as it does in the absence of Co; SR-XRD data did not indicate the formation of a separate Co oxide phase, and EXAFS data showed that Co is incorporated into the biooxide structure as Co(III). In the absence of Mn, Co oxide formation was not observed; EXAFS data showed that Co remains as Co(II) and is complexed to cells or EPS. While it cannot be ascertained that Co(II) oxidation and incorporation into the bioxides is completely abiotic, Co(II) is not oxidized by P. putida MnB1 in the absence of Mn.

  5. Complete oxidation of solid phase sulfides by manganese and bacteria in anoxic marine sediments

    Microsoft Academic Search

    R. C. Aller; P. D. Rude

    1988-01-01

    During the physical or biological reworking of surficial marine sediments, metal oxides are often brought into contact with both solid and dissolved sulfides. Experiments simulating these mixing processes demonstrate that in natural sediments Mn-oxides can completely oxidize solid phase sulfides to SO{sup =}â under anoxic conditions. The major source of sulfur is probably acid volatile sulfide. Minerals containing Mn{sup +4}

  6. Spatially Resolved Characterization of Biogenic Manganese Oxide Production within a Bacterial Biofilm

    Microsoft Academic Search

    Brandy Toner; Sirine Fakra; Mario Villalobos; Tony Warwick; Garrison Sposito

    2005-01-01

    Pseudomonas putida strain MnB1, a biofilm-forming bacterial culture, was used as a model for the study of bacterial Mn oxidation in freshwater and soil environments. The oxidation of aqueous Mn2 (Mn2(aq) )b y P. putida was characterized by spatially and temporally resolving the oxidation state of Mn in the presence of a bacterial biofilm, using scanning transmission X-ray microscopy (STXM)

  7. A self-seeded, surfactant-directed hydrothermal growth of single crystalline lithium manganese oxide nanobelts from the commercial bulky particles.

    PubMed

    Zhang, Lizhi; Yu, Jimmy C; Xu, An-Wu; Li, Quan; Kwong, Kwan Wai; Wu, Ling

    2003-12-01

    Single crystalline lithium manganese oxide nanobelts were obtained through a self-seeded, surfactant-directed growth process from the commercial bulky particles under hydrothermal treatment. A possible mechanism was proposed to explain the growth of the nanobelts. This new process could be extended to prepare other one-dimensional nanomaterials such as Se nanorods, Te nanotubes, and MnO2 nanowires. PMID:14680236

  8. Electrochemical catalysis of styrene epoxidation with films of manganese dioxide nanoparticles, and, Synthesis of mixed metal oxides using ultrasonic nozzle spray and microwaves

    Microsoft Academic Search

    Laura Espinal

    2005-01-01

    Films of polyions and octahedral layered manganese oxide (OL-1) nanoparticles on carbon electrodes made by layer-by-layer alternate electrostatic adsorption were active for electrochemical catalysis of styrene epoxidation in solution in the presence of hydrogen peroxide and oxygen. The highest catalytic turnover was obtained by using applied voltage -0.6 V vs. SCE, O2, and 100 mM H2O2. 18O isotope labeling experiments

  9. Oxidation of pyrite and iron sulfide by manganese dioxide in marine sediments

    NASA Astrophysics Data System (ADS)

    Schippers, A.; Jørgensen, B. B.

    2001-03-01

    Oxidation of pyrite (FeS 2) under anaerobic conditions in marine sediments is experimentally shown for the first time. In slurry experiments with 55FeS 2 and a MnO 2 rich marine sediment an oxidation of 55FeS 2 was detected which decreased with depth and decreasing concentration of MnO 2 in the sediment. FeS 2 and iron sulfide (FeS) were oxidized chemically at pH 8 by MnO 2 but not by nitrate or amorphic Fe(III) oxide. Elemental sulfur and sulfate were the only products of FeS oxidation, whereas FeS 2 was oxidized to a variety of sulfur compounds, mainly sulfate plus intermediates such as thiosulfate, trithionate, tetrathionate, and pentathionate. Thiosulfate was oxidized by MnO 2 to tetrathionate while other intermediates were oxidized to sulfate. The reaction products indicate that FeS 2 was oxidized via the "Thiosulfate-mechanism" and FeS via the "Polysulfide-mechanism" (Schippers and Sand, 1999). The processes are summarized by the overall equations: (1) FeS 2+7.5 MnO 2+11 H +?Fe(OH) 3+2 SO 42-+7.5 Mn 2++4 H 2O (2) FeS+1.5 MnO 2+3 H +?Fe(OH) 3+S O+1.5 Mn 2+ For FeS 2 oxidation the reaction rates related to the mineral surface area were 1.02 and 1.12 nmol m -2 s -1 for total dissolved S and total dissolved Fe, respectively. Since these values are in the same range as previously published rates for the oxidation of FeS 2 by Fe(III), and since Fe(III) is a well-known oxidant for FeS 2 even at circumneutral pH, Fe(III) is assumed also to be the oxidant for FeS and FeS 2 in the presence of MnO 2. At the iron sulfide surface, Fe(III) is reduced to Fe(II) which is reoxidized to Fe(III) by MnO 2. Thus, an Fe(II)/Fe(III) shuttle should transport electrons between the surfaces of the two solid compounds.

  10. Effects of NOM on oxidative reactivity of manganese dioxide in binary oxide mixtures with goethite or hematite.

    PubMed

    Zhang, Huichun; Taujale, Saru; Huang, Jianzhi; Lee, Gang-Juan

    2015-03-10

    MnO2 typically coexists with iron oxides as either discrete particles or coatings in soils and sediments. This work examines the effect of Aldrich humic acid (AHA), alginate, and pyromellitic acid (PA) as representative natural organic matter (NOM) analogues on the oxidative reactivity of MnO2, as quantified by pseudo-first-order rate constants of triclosan oxidation, in mixtures with goethite or hematite. Adsorption studies showed that there was low adsorption of the NOMs by MnO2, but high (AHA and alginate) to low (PA) adsorption by the iron oxides. Based on the ATR-FTIR spectra obtained for the adsorbed PA on goethite or goethite + MnO2, the adsorption of PA occurred mainly through formation of outer-sphere complexes. The Fe oxides by themselves inhibited MnO2 reactivity through intensive heteroaggregation between the positively charged Fe oxides and the negatively charged MnO2; the low solubility of the iron oxides limited surface complexation of soluble Fe(3+) with MnO2. In ternary mixtures of MnO2, Fe oxides, and NOM analogues, the reactivity of MnO2 varied from inhibited to promoted as compared with that in the respective MnO2 + NOM binary mixtures. The dominant interaction mechanisms include an enhanced extent of homoaggregation within the Fe oxides due to formation of oppositely charged patches within the Fe oxides but an inhibited extent of heteroaggregation between the Fe oxide and MnO2 at [AHA] < 2-4 mg-C/L or [alginate/PA] < 5-10 mg/L, and an inhibited extent of heteroaggregation due to the largely negatively charged surfaces for all oxides at [AHA] > 4 mg-C/L or [alginate/PA] > 10 mg/L. PMID:25652230

  11. The cytochrome c maturation operon is involved in manganese oxidation in Pseudomonas putida GB-1

    SciTech Connect

    Vrind, J.P.M. de; Brouwers, G.J.; Corstijens, P.L.A.M.; Dulk, J. den; Vrind-de Jong, E.W. de [Leiden Univ. (Netherlands)

    1998-10-01

    A Pseudomonas putida strain, strain GB-1, oxidizes Mn{sup 2+} to Mn oxide in the early stationary growth phase. It also secretes a siderophore (identified as pyoverdine) when it is subjected to iron limitation. After transposon (Tn5) mutagenesis several classes of mutants with differences in Mn{sup 2+} oxidation and/or secretion of the Mn{sup 2+}-oxidizing activity were identified. Preliminary analysis of the Tn5 insertion site in one of the nonoxidizing mutants suggested that a multicopper oxidase-related enzyme is involved in Mn{sup 2+} oxidation. The insertion site in another mutant was preliminarily identified as a gene involved in the general protein secretion pathway. Two mutants defective in Mn{sup 2+}-oxidizing activity also secreted porphyrins into the medium and appeared to be derepressed for pyoverdine production. These strains were chosen for detailed analysis. Both mutants were shown to contain Tn5 insertions in the ccmF gene, which is part of the cytochrome c maturation operon. They were cytochrome oxidase negative and did not contain c-type cytochromes. Complementation with part of the ccm operon isolated from the wild type restored the phenotype of the parent strain. These results indicate that a functional ccm operon is required for Mn{sup 2+} oxidation in P. putida GB-1. A possible relationship between porphyrin secretion resulting from the ccm mutation and stimulation of pyoverdine production is discussed.

  12. Enzymatic Manganese(II) Oxidation by Metabolically Dormant Spores of Diverse Bacillus Species

    PubMed Central

    Francis, Chris A.; Tebo, Bradley M.

    2002-01-01

    Bacterial spores are renowned for their longevity, ubiquity, and resistance to environmental insults, but virtually nothing is known regarding whether these metabolically dormant structures impact their surrounding chemical environments. In the present study, a number of spore-forming bacteria that produce dormant spores which enzymatically oxidize soluble Mn(II) to insoluble Mn(IV) oxides were isolated from coastal marine sediments. The highly charged and reactive surfaces of biogenic metal oxides dramatically influence the oxidation and sorption of both trace metals and organics in the environment. Prior to this study, the only known Mn(II)-oxidizing sporeformer was the marine Bacillus sp. strain SG-1, an extensively studied bacterium in which Mn(II) oxidation is believed to be catalyzed by a multicopper oxidase, MnxG. Phylogenetic analysis based on 16S rRNA and mnxG sequences obtained from 15 different Mn(II)-oxidizing sporeformers (including SG-1) revealed extensive diversity within the genus Bacillus, with organisms falling into several distinct clusters and lineages. In addition, active Mn(II)-oxidizing proteins of various sizes, as observed in sodium dodecyl sulfate-polyacrylamide electrophoresis gels, were recovered from the outer layers of purified dormant spores of the isolates. These are the first active Mn(II)-oxidizing enzymes identified in spores or gram-positive bacteria. Although extremely resistant to denaturation, the activities of these enzymes were inhibited by azide and o-phenanthroline, consistent with the involvement of multicopper oxidases. Overall, these studies suggest that the commonly held view that bacterial spores are merely inactive structures in the environment should be revised. PMID:11823231

  13. Manganese oxidation in pH and O2 microenvironments produced by phytoplankton

    NASA Technical Reports Server (NTRS)

    Richardson, Laurie L.; Aguilar, Carmen; Nealson, Kenneth H.

    1988-01-01

    This paper reports on the oxidation of Mn(II) by pure cultures of Chlorella. It is shown that these cultures establish strong microgradients of pH and O2 concentration due to their photosynthetic activity, and it is demonstrated that Mn oxidation in the pelagic zone of Oneida Lake, New York, is limited to a microzone of high pH and O2 associated with the near-surface aggregates of phytoplankton cells. The data suggest that visible light is important in catalyzing Mn oxidation by driving the photosynthetic removal of CO2 with concomitant increases in pH.

  14. Biodiesel synthesis catalyzed by transition metal oxides: ferric-manganese doped tungstated/molybdena nanoparticle catalyst.

    PubMed

    Alhassan, Fatah Hamid; Rashid, Umer; Taufiq-Yap, Yun Hin

    2015-01-01

    The solid acid Ferric-manganese doped tungstated/molybdena nananoparticle catalyst was prepared via impregnation reaction followed by calcination at 600°C for 3 h. The characterization was done using X-ray diffraction (XRD), Raman spectroscopy, thermal gravimetric analysis (TGA), temperature programmed desorption of NH3 (TPD-NH3), X-ray fluorescence (XRF), Transmission electron microscope (TEM) and Brunner-Emmett-Teller surface area measurement (BET). Moreover, dependence of biodiesel yield on the reaction variables such as the reaction temperature, catalyst loading, as well as molar ratio of methanol/oil and reusability were also appraised. The catalyst was reused six times without any loss in activity with maximum yield of 92.3% ±1.12 achieved in the optimized conditions of reaction temperature of 200°C; stirring speed of 600 rpm, 1:25 molar ratio of oil to alcohol, 6 % w/w catalyst loading as well as 8 h as time of the reaction. The fuel properties of WCOME's were evaluated, including the density, kinematic viscosity, pour point, cloud point and flash point whereas all properties were compared with the limits in the ASTM D6751 standard. PMID:25492234

  15. Redox processes at surfaces of manganese oxide and their effects on aqueous metal ions

    USGS Publications Warehouse

    Hem, J.D.

    1978-01-01

    Mn oxides precipitated from aerated solutions of Mn2+ by raising the pH are reported in various publications to have the approximate composition Mn3O4 or MnOOH. These oxyhydroxides in turn can disproportionate to Mn2+ and MnO2 resulting in a substantial decrease in equilibrium Mn solubility. The disproportionation can catalyze the oxidation of Mn2+ and other metals by facilitating electron-transfer processes. Diversion of some electron transfers from Mn species to other metal ions can greatly decrease the equilibrium solubility of Co, Pb, Ni and some other elements in the presence of mixed-valence Mn oxides. Some scavenging and coprecipitation effects involving Mn oxides may be attributable to redox processes. Equilibrium solubilities for Mn, Co and Pb are summarized in four graphs. ?? 1978.

  16. Models for the photosynthetic water oxidizing enzyme. 1. A binuclear manganese(III)-. beta. -cyclodextrin complex

    SciTech Connect

    Nair, B.U.; Dismukes, G.C.

    1983-01-12

    A binuclear Mn(III) model compound was synthesized by using ..beta..-cyclodextrin as a ligand. Reaction of the compound with various oxidizing agents has been investigated. The compound in 80:20 DMF-H/sub 2/O was not oxidized by excess potassium ferricyanide. On treatment with two equivalents of Ce(IV), the 482-nm band was bleached. One equivalent produced only partial bleaching, with no evidence again for the intervalence transition for a Mn(III)-Mn(IV) oxidation state. Evidently a two-electron oxidation to the (IV,IV) state is preferred, with eventual decomposition of ligand or water over hours, at least in aqueous DMF and DMSO.

  17. Pseudocapacitive mechanism of manganese oxide in 1-ethyl-3-methylimidazolium thiocyanate ionic liquid electrolyte studied using X-ray photoelectron spectroscopy.

    PubMed

    Chang, Jeng-Kuei; Lee, Ming-Tsung; Tsai, Wen-Ta; Deng, Ming-Jay; Cheng, Hui-Fang; Sun, I-Wen

    2009-10-01

    The electrochemical behavior of anodically deposited manganese oxide was studied in pyrrolidinium formate (P-HCOO), 1-butyl-3-methylimidazolium hexafluorophosphate (BMI-PF6), and 1-ethyl-3-methylimidazolium thiocyanate (EMI-SCN) ionic liquids (ILs). The experimental data indicate that the Mn oxide electrode showed ideal pseudocapacitive performance in aprotic EMI-SCN IL. In a potential window of approximately 1.5 V, the oxide specific capacitance, evaluated using cyclic voltammetry and chronopotentiometry, was about 55 F/g. The electrochemical energy storage reaction was examined using X-ray photoelectron spectroscopy (XPS). It was confirmed that the SCN- anions, instead of the EMI+ cations, were the primary working species that can become incorporated into the oxide and thus compensate the Mn3+/Mn4+ valent state variation upon the charge-discharge process. According to the analytical results, a pseudocapacitive mechanism of Mn oxide in the SCN- based aprotic IL was proposed. PMID:19621902

  18. Enzymatic Manganese(II) Oxidation by Metabolically Dormant Spores of Diverse Bacillus Species

    Microsoft Academic Search

    Chris A. Francis; Bradley M. Tebo

    2002-01-01

    Bacterial spores are renowned for their longevity, ubiquity, and resistance to environmental insults, but virtually nothing is known regarding whether these metabolically dormant structures impact their surrounding chemical environments. In the present study, a number of spore-forming bacteria that produce dormant spores which enzymatically oxidize soluble Mn(II) to insoluble Mn(IV) oxides were isolated from coastal marine sediments. The highly charged

  19. Reductive Dissolution of Biogenic Manganese Oxides in the Presence of a Hydrated Biofilm

    Microsoft Academic Search

    Brandy Toner; Garrison Sposito

    2005-01-01

    The chemical reactivity of the biogenic Mn oxide produced by Pseudomonas putida strain MnB1 was assessed in the presence of bacterial cells and biofilm through reductive dissolution experiments at pH 4.4, 5.2, and 6.0. The reactivity of the biogenic Mn oxide was compared to that of a synthetic (chemically produced) birnessite at pH 6.0. In addition, the effect of bacterial

  20. Protective effects of antioxidants and anti-inflammatory agents against manganese-induced oxidative damage and neuronal injury

    SciTech Connect

    Milatovic, Dejan, E-mail: dejan.milatovic@vanderbilt.edu [Vanderbilt University School of Medicine, Department of Pediatrics, Nashville, TN (United States)] [Vanderbilt University School of Medicine, Department of Pediatrics, Nashville, TN (United States); Gupta, Ramesh C. [Murray State University, Breathitt Veterinary Center, Hopkinsville, KY (United States)] [Murray State University, Breathitt Veterinary Center, Hopkinsville, KY (United States); Yu, Yingchun; Zaja-Milatovic, Snjezana [Vanderbilt University School of Medicine, Department of Pediatrics, Nashville, TN (United States)] [Vanderbilt University School of Medicine, Department of Pediatrics, Nashville, TN (United States); Aschner, Michael [Vanderbilt University School of Medicine, Department of Pediatrics, Nashville, TN (United States) [Vanderbilt University School of Medicine, Department of Pediatrics, Nashville, TN (United States); Pharmacology and the Kennedy Center for Research on Human Development, Nashville, TN (United States)

    2011-11-15

    Exposure to excessive manganese (Mn) levels leads to neurotoxicity, referred to as manganism, which resembles Parkinson's disease (PD). Manganism is caused by neuronal injury in both cortical and subcortical regions, particularly in the basal ganglia. The basis for the selective neurotoxicity of Mn is not yet fully understood. However, several studies suggest that oxidative damage and inflammatory processes play prominent roles in the degeneration of dopamine-containing neurons. In the present study, we assessed the effects of Mn on reactive oxygen species (ROS) formation, changes in high-energy phosphates and associated neuronal dysfunctions both in vitro and in vivo. Results from our in vitro study showed a significant (p < 0.01) increase in biomarkers of oxidative damage, F{sub 2}-isoprostanes (F{sub 2}-IsoPs), as well as the depletion of ATP in primary rat cortical neurons following exposure to Mn (500 {mu}M) for 2 h. These effects were protected when neurons were pretreated for 30 min with 100 of an antioxidant, the hydrophilic vitamin E analog, trolox (6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid), or an anti-inflammatory agent, indomethacin. Results from our in vivo study confirmed a significant increase in F{sub 2}-IsoPs levels in conjunction with the progressive spine degeneration and dendritic damage of the striatal medium spiny neurons (MSNs) of mice exposed to Mn (100 mg/kg, s.c.) 24 h. Additionally, pretreatment with vitamin E (100 mg/kg, i.p.) or ibuprofen (140 {mu}g/ml in the drinking water for two weeks) attenuated the Mn-induced increase in cerebral F{sub 2}-IsoPs? and protected the MSNs from dendritic atrophy and dendritic spine loss. Our findings suggest that the mediation of oxidative stress/mitochondrial dysfunction and the control of alterations in biomarkers of oxidative injury, neuroinflammation and synaptodendritic degeneration may provide an effective, multi-pronged therapeutic strategy for protecting dysfunctional dopaminergic transmission and slowing of the progression of Mn-induced neurodegenerative processes. -- Research highlights: Black-Right-Pointing-Pointer Mn exposure leads to neurotoxicity in vitro and in vivo. Black-Right-Pointing-Pointer Antioxidants and anti-inflammatory agents attenuate Mn-induced oxidative injury. Black-Right-Pointing-Pointer These agents also protect the striatal neurons from dendritic atrophy and spine loss. Black-Right-Pointing-Pointer These prophylactic strategies may be effective against Mn neurotoxicity.

  1. Electrochemical and structural characterization of titanium-substituted manganese oxides based on Na0.44MnO2

    SciTech Connect

    Doeff, Marca M.; Richardson, Thomas J.; Hwang, Kwang-Taek

    2004-03-01

    A series of titanium-substituted manganese oxides, Li{sub x}Ti{sub y}Mn{sub 1-y}O{sub 2} (y = 0.11, 0.22, 0.33, 0.44, and 0.55) with the Na{sub 0.44}MnO{sub 2} structure were prepared from Na{sub x}Ti{sub y}Mn{sub 1-y}O{sub 2} (x {approx} 0.44) precursors. The electrochemical characteristics of these compounds, which retain the unique double-tunnel structure during ion exchange, were examined in lithium/polymer electrolyte cells operating at 85 C. All of the substituted cathode materials intercalated lithium reversibly, with Li{sub x}Ti{sub 0.22}Mn{sub 0.78}O{sub 2} exhibiting the highest capacity in polymer cells, about 10-20% greater than that of unsubstituted Li{sub x}MnO{sub 2} made from Na{sub 0.44}MnO{sub 2}. In common with Li{sub x}MnO{sub 2}, the Ti-substituted materials exhibited good capacity retention over one hundred or more cycles, with some compositions exhibiting a fade rate of less than 0.03% per cycle.

  2. Trivalent manganese as an environmentally friendly oxidizing reagent for microwave- and ultrasound-assisted chemical oxygen demand determination.

    PubMed

    Domini, Claudia E; Vidal, Lorena; Canals, Antonio

    2009-06-01

    In the present work manganese(III) has been used as oxidant and microwave radiation and ultrasound energy have been assessed to speed up and to improve the efficiency of digestion step for the determination of chemical oxygen demand (COD). Microwave (MW) and ultrasound-assisted COD determination methods have been optimized by means of experimental design and the optimum conditions are: 40psi pressure, 855W power and 1min irradiation time; and 90% of maximum nominal power (180W), 0.9s (s(-1)) cycles and 1min irradiation time for microwaves and ultrasound, respectively. Chloride ion interference is removed as hydrochloric acid gas from acidified sample solutions at 150 degrees C in a closed reaction tube and captured by bismuth-based adsorbent suspended above the heated solution. Under optimum conditions, the evaluated assisted digestion methods have been successfully applied, with the exception of pyridine, to several pure organic compounds and two reference materials. COD recoveries obtained with MW and ultrasound-assisted digestion for five real wastewater samples were ranged between 86-97% and 68-91%, respectively, of the values obtained with the classical method (open reflux) used as reference, with relative standard deviation lower than 4% in most cases. Thus, the Mn(III) microwave-assisted digestion method seems to be an interesting and promising alternative to conventional COD digestion methods since it is faster and more environmentally friendly than the ones used for the same purpose. PMID:19250852

  3. Epitaxial growth of manganese oxide films on MgAl2O4 (001) substrates and the possible mechanism

    NASA Astrophysics Data System (ADS)

    Ren, Lizhu; Wu, Shuxiang; Zhou, Wenqi; Li, Shuwei

    2014-03-01

    Three types of manganese oxide films were grown on MgAl2O4 (001) substrates by plasma-assisted molecular beam epitaxy (PA-MBE) under different growth rates and substrate temperatures. The structural characteristics and chemical compositions of the films were investigated by using in-situ reflection high-energy electron diffraction (RHEED), ex-situ X-ray diffraction, Raman, and X-ray photoelectron spectra (XPS). At a lower substrate temperature (730 K), the epitaxial film tends to form mixed phases with a coexistence of Mn3O4 and Mn5O8 in order to relieve the mismatch-strain. However, at a higher substrate temperature (750 K), all of the films crystallize into Mn3O4; the critical thickness of the film grown under a lower growth rate (7 Å/min) is much larger than that under a high growth rate (10 Å/min). When the film reaches a certain critical thickness, the surface will become fairly rough, and another oriented phase Mn3O4 would crystallize on such a surface.

  4. In Situ XAS and XRD Studies of Substituted Spinel Lithium Manganese Oxides in the 4-5 V Region

    SciTech Connect

    McBreen, J.; Mukerjee, S.; Yang, X. Q.; Sun, X.; Ein-Eli, Y.

    1998-11-01

    Partial substitution of Mn in lithium manganese oxide spinel materials by Cu and Ni greatly affects the electrochemistry and the phase behavior of the cathode. Substitution with either metal or with a combination of both shortens the 4.2 V plateau and results in higher voltage plateaus. In situ x-ray absorption (XAS) studies indicate that the higher voltage plateaus are related to redox processes on the substituents. In situ x-ray diffraction (XRD) on LiCu{sub 0.5}Mn{sub 1.5}O{sub 4} shows single phase behavior during the charge and discharge process. Three phases are observed for LiNi{sub 0.5}Mn{sub 1.5}O{sub 4} and two phases are observed in the case of LiNi{sub 0.25}Cu{sub 0.25}Mn{sub 1.5}O{sub 4}. The electrolyte stability is dependent on both the operating voltage and the cathode composition. Even though Ni substituted materials have lower voltages, the electrolyte is more stable in cells with the Cu substituted materials.

  5. Silica-F127 nanohybrid-encapsulated manganese oxide nanoparticles for optimized T1 magnetic resonance relaxivity.

    PubMed

    Wei Hsu, Benedict You; Wang, Miao; Zhang, Yu; Vijayaragavan, Vimalan; Wong, Siew Yee; Yuang-Chi Chang, Alex; Bhakoo, Kishore Kumar; Li, Xu; Wang, John

    2014-01-01

    To properly engineer MnO nanoparticles (MONPs) of high r1 relaxivity, a nanohybrid coating consisting of silica and F127 (PEO106PPO70PEO106) is designed to encapsulate MONPs. Achieved by an interfacial templating scheme, the nanohybrid encapsulating layer is highly permeable and hydrophilic to allow for an optimal access of water molecules to the encapsulated manganese oxide core. Hence, the efficacy of MONPs as MRI contrast agents is significantly improved, as demonstrated by an enhancement of the MR signal measured with a pre-clinical 7.0 T MRI scanner. The nanohybrid encapsulation strategy also confers high colloidal stability to the hydrophobic MONPs by the surface decoration of PEO chains and a small overall diameter (<100 nm) of the PEO-SiO2 nanohybrid-encapsulated MONPs (PEOMSNs). The PEOMSNs are not susceptible to Mn-ion leaching, and their biocompatibility is affirmed by a low toxicity profile. Moreover, these hybrid nanocapsules exhibit a nano-rattle structure, which would favor the facile loading of various therapeutic reagents for theranostic applications. PMID:24193096

  6. One-pot synthesis of manganese oxide-carbon composite microspheres with three dimensional channels for Li-ion batteries.

    PubMed

    Ko, You Na; Park, Seung Bin; Choi, Seung Ho; Kang, Yun Chan

    2014-01-01

    The fabrication of manganese oxide-carbon composite microspheres with open nanochannels and their electrochemical performance as anode materials for lithium ion batteries are investigated. Amorphous-like Mn3O4 nanoparticles embedded in a carbon matrix with three-dimensional channels are fabricated by one-pot spray pyrolysis. The electrochemical properties of the Mn3O4 nanopowders are also compared with those of the Mn3O4-C composite microspheres possessing macropores resembling ant-cave networks. The discharge capacity of the Mn3O4-C composite microspheres at a current density of 500 mA g(-1) is 622 mA h g(-1) after 700 cycles. However, the discharge capacity of the Mn3O4 nanopowders is as low as 219 mA h g(-1) after 100 cycles. The Mn3O4-C composite microspheres with structural advantages and high electrical conductivity have higher initial discharge and charge capacities and better cycling and rate performances compared to those of the Mn3O4 nanopowders. PMID:25168839

  7. Rapid removal and separation of iron(II) and manganese(II) from micropolluted water using magnetic graphene oxide.

    PubMed

    Yan, Han; Li, Haijiang; Tao, Xue; Li, Kun; Yang, Hu; Li, Aimin; Xiao, Shoujun; Cheng, Rongshi

    2014-06-25

    A novel two-dimensional carbon-based magnetic nanomaterial, magnetic graphene oxide (MGO), was prepared and then used as an efficient adsorbent. MGO showed rapid and complete removal of iron(II) (Fe) and manganese(II) (Mn) from micropolluted water bodies over a wide pH range. After saturated adsorption, MGO could be rapidly separated from water under an external magnetic field. Results of the adsorption equilibrium study indicated that the adsorption of Fe and Mn by MGO took place via monolayer heterogeneous and spontaneous processes resulting from the heterogeneity of the MGO surface as well as from the electrostatic interactions between surface acidic groups of MGO and metal ions. In addition, both the Fe and Mn uptake of MGO was very slightly affected by NaCl, although it decreased with increased humic acid in solutions. In an Fe/Mn binary aqueous system, both metal ions can be efficiently removed at low concentrations, but MGO showed preferential adsorption of Fe in a concentrated aqueous mixture. The adsorption behavior in the binary system was due to different affinities of surface oxygen-containing functional groups on MGO to Fe and Mn. Finally, unlike traditional approaches in recycling and reusing an adsorbent, the Fe- and Mn-loaded MGO can be directly applied as a new adsorbent to achieve the efficient removal of fluoride from aqueous solutions. PMID:24787443

  8. Hydrogen and formate oxidation coupled to dissimilatory reduction of iron or manganese by Alteromonas putrefaciens

    USGS Publications Warehouse

    Lovley, D.R.; Phillips, E.J.P.; Lonergan, D.J.

    1989-01-01

    The ability of Alteromonas putrefaciens to obtain energy for growth by coupling the oxidation of various electron donors to dissimilatory Fe(III) or Mn(IV) reduction was investigated. A. putrefaciens grew with hydrogen, formate, lactate, or pyruvate as the sole electron donor and Fe(III) as the sole electron acceptor. Lactate and pyruvate were oxidized to acetate, which was not metabolized further. With Fe(III) as the electron acceptor, A. putrefaciens had a high affinity for hydrogen and formate and metabolized hydrogen at partial pressures that were 25-fold lower than those of hydrogen that can be metabolized by pure cultures of sulfate reducers or methanogens. The electron donors for Fe(III) reduction also supported Mn(IV) reduction. The electron donors for Fe(III) and Mn(IV) reduction and the inability of A. putrefaciens to completely oxidize multicarbon substrates to carbon dioxide distinguish A. putrefaciens from GS-15, the only other organism that is known to obtain energy for growth by coupling the oxidation of organic compounds to the reduction of Fe(III) or Mn(IV). The ability of A. putrefaciens to reduce large quantities of Fe(III) and to grow in a defined medium distinguishes it from a Pseudomonas sp., which is the only other known hydrogen-oxidizing, Fe(III)-reducing microorganism. Furthermore, A. putrefaciens is the first organism that is known to grow with hydrogen as the electron donor and Mn(IV) as the electron acceptor and is the first organism that is known to couple the oxidation of formate to the reduction of Fe(III) or Mn(IV). Thus, A. putrefaciens provides a much needed microbial model for key reactions in the oxidation of sediment organic matter coupled to Fe(III) and Mn(IV) reduction.

  9. Understanding the capacity fade mechanisms of spinel manganese oxide cathodes and improving their performance in lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Choi, Won Chang

    Lithium ion batteries have been successful in portable electronics market due to their high energy density, adopting the layered LiCoO2 as the cathode material in commercial lithium ion cells. However, increasing interest in lithium ion batteries for electric vehicle and hybrid electric vehicle applications requires alternative cathode materials due to the high cost, toxicity, and limited power capability of the layered LiCoO2 cathode. In this regard, spinel LiMn2O4 has become appealing as manganese is inexpensive and environmentally benign, but LiMn2O 4 is plagued by severe capacity fade at elevated temperatures. This dissertation explores the factors that control and limit the electrochemical performance of spinel LiMn2O4 cathodes and focuses on improving the performance parameters such as the capacity, cyclability, and rate capability of various spinel cathodes derived from LiMn2O 4. From a systematic investigation of a number of cationic and anionic (fluorine) substituted spinel oxide compositions, the improvements in electrochemical properties and performances are found to be due to the reduced manganese dissolution and suppressed lattice parameter difference between the two cubic phases formed during the charge-discharge process. Investigations focused on fluorine substitution reveal that spinel LiMn 2-y-zLiyZnzO4-etaFeta oxyfluoride cathodes synthesized by solid-state reactions at 800°C employing ZnF2 as a raw material and spinel LiMn2-y-zLiy NizO4-etaFeta oxyfluoride cathodes synthesized by firing the cation-substituted LiMn2-y-zLiy NizO4 oxides with NH4HF2 at a moderate temperature of 450°C show superior cyclability, increased capacity, reduced Mn dissolution, and excellent storage performance compared to the corresponding oxide analogs and the conventional LiMn2O 4. Spinel-layered composite cathodes are found to exhibit better electrochemical performance with graphite anode when charged to 4.7 V in the first cycle followed by cycling at 4.3--3.5 V compared to the normal cycling at 4.3--3.5 V. The improved performance is explained to be due to the trapping of trace amounts of protons that may be present in the electrolyte within the layered oxide lattice during the first charge to 4.7 V and the consequent reduction in Mn dissolution. Electrochemical performances of 3 V spinel Li4Mn5O 12 cathodes are also improved by fluorine substitution due to the suppression of the disproportionation of Li4Mn5O12 during synthesis and the formation of the Li2MnO3 phase.

  10. Surface complexation modeling of Co(II) adsorption on mixtures of hydrous ferric oxide, quartz and kaolinite

    Microsoft Academic Search

    Christopher J. Landry; Carla M. Koretsky; Tracy J. Lund; Melinda Schaller; Soumya Das

    2009-01-01

    Co sorption was measured as a function of pH, ionic strength (0.001–0.1M NaNO3) and sorbate\\/sorbent ratio on pure quartz, HFO and kaolinite and on binary and ternary mixtures of the three solids. Sorption data measured for the pure solids were used to derive internally-consistent diffuse layer surface complexation model (DLM) stability constants for Co sorption. Co sorption on HFO could

  11. Humidity sensor based on quartz tuning fork coated with sol–gel-derived nanocrystalline zinc oxide thin film

    Microsoft Academic Search

    Xiaofeng Zhou; Tao Jiang; Jian Zhang; Xiaohua Wang; Ziqiang Zhu

    2007-01-01

    This paper describes an application of quartz tuning forks (QTFs) coated with nanocrystalline ZnO films used as relative humidity sensors. The nanocrystalline ZnO thin films were deposited on the QTFs by a sol–gel method. The film was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) to obtain the information on the structural and morphological properties. And the humidity

  12. Mobilization of manganese by basalt associated Mn(II)-oxidizing bacteria from the Indian Ridge System.

    PubMed

    Sujith, P P; Mourya, B S; Krishnamurthi, S; Meena, R M; Loka Bharathi, P A

    2014-01-01

    The Indian Ridge System basalt bearing Mn-oxide coatings had todorokite as the major and birnesite as the minor mineral. We posit that microorganisms associated with these basalts participate in the oxidation of Mn and contribute to mineral deposition. We also hypothesized that, the Mn-oxidizing microbes may respond reversibly to pulses of fresh organic carbon introduced into the water column by mobilizing the Mn in Mn-oxides. To test these two hypotheses, we enumerated the number of Mn-oxidizers and -reducers and carried out studies on the mobilization of Mn by microbial communities associated with basalt. In medium containing 100 ?M Mn(2+), 10(3) colony forming units (CFU) were recovered with undetectable number of reducers on Mn-oxide amended medium, suggesting that the community was more oxidative. Experiments were then conducted with basalt fragments at 4±2 °C in the presence 'G(+)' and absence 'G(-)' of glucose (0.1%). Controls included set-ups, some of which were poisoned with 15 mM azide and the others of which were heat-killed. The mobilization of Mn in the presence of glucose was 1.76 ?g g(-1) d(-1) and in the absence, it was 0.17 ?g g(-1) d(-1) after 150 d. Mn mobilization with and without added glucose was 13 and 4 times greater than the corresponding azide treated controls. However, rates in 'G(+)' were 16 times and 'G(-)' 24 times more than the respective heat killed controls. The corresponding total counts in the presence of added glucose increased from 1.63×10(6) to 6.71×10(7) cells g(-1) and from 1.41×10(7) to 3.52×10(7) cells g(-1) in its absence. Thus, the addition of glucose as a proxy for organic carbon changed the community's response from Mn(II)-oxidizing to Mn(IV)-reducing activity. The results confirm the participation of Mn oxidizing bacteria in the mobilization of Mn. Identification of culturable bacteria by 16S rRNA gene analysis showed taxonomic affiliations to Bacillus, Exiguobacterium, Staphylococcus, Brevibacterium and Alcanivorax sp. PMID:24183631

  13. Relationship of manganese-iron oxides and associated heavy metals to grain size in stream sediments

    USGS Publications Warehouse

    Whitney, P.R.

    1975-01-01

    The distribution of ammonium citrate-leachable lead, zinc and cadmium among size fractions in stream sediments is strongly influenced by the presence of hydrous Mn-Fe oxides in the form of coatings on sediment grains. Distribution curves showing leachable metals as a function of particle size are given for eight samples from streams in New York State. These show certain features in common; in particular two concentrations of metals, one in the finest fractions, and a second peak in the coarse sand and gravel fraction. The latter can be explained as a result of the increasing prevalence and thickness of oxide coatings with increasing particle size, with the oxides serving as collectors for the heavy metals. The distribution of Zn and Cd in most of the samples closely parallels that of Mn; the distribution of Pb is less regular and appears to be related to Fe in some samples and Mn in others. The concentration of metals in the coarse fractions due to oxide coatings, combined with the common occurrence of oxide deposition in streams of glaciated regions, raises the possibility of using coarse materials for geochemical surveys and environmental heavy-metal studies. ?? 1975.

  14. The inhibitory effect of manganese on acetylcholinesterase activity enhances oxidative stress and neuroinflammation in the rat brain

    PubMed Central

    Santos, Dinamene; Milatovic, Dejan; Andrade, Vanda; Camila, Batoreu M.; Aschner, Michael; Marreilha dos Santos, A.P.

    2011-01-01

    Background Manganese (Mn) is a naturally occurring element and an essential nutrient for humans and animals. However, exposure to high levels of Mn may cause neurotoxic effects. The pathological mechanisms associated with Mn neurotoxicity are poorly understood, but several reports have established it is mediated, at least in part, by oxidative stress. Objectives The present study was undertaken to test the hypothesis that a decrease in acetylcholinesterase (AChE) activity mediates Mn-induced neurotoxicity. Methods Groups of 6 rats received 4 or 8 intraperitoneal (i.p.) injections of 25 mg MnCl2/kg/day, every 48 hours. Twenty-four hours after the last injection, brain AChE activity and the levels of F2-isoprostanes (F2-IsoPs) and F4-neuroprostanes (F4-NPs) (biomarkers of oxidative stress), as well as prostaglandin E2 (PGE2) (biomarker of neuroinflammation) were analyzed. Results The results showed that after either 4 or 8 Mn doses, brain AChE activity was significantly decreased (p<0.05), to 60 ± 16 % and 55 ± 13 % of control levels, respectively. Both treated groups exhibited clear signs of neurobehavioral toxicity, characterized by a significant (p<0.001) decrease in ambulation and rearings in open-field. Furthermore, Mn treatment caused a significant increase (p<0.05) in brain F2-IsoPs and PGE2 levels, but only after 8 doses. In rats treated with 4 Mn doses, a significant increase (p<0.05) in brain F4-NPs levels was found. To evaluate cellular responses to oxidative stress, we assessed brain nuclear factor-erythroid 2 p45-related factor 2 (Nrf2) and Mn-superoxide dismutase (Mn-SOD, SOD2) protein expression levels. A significant increase in Mn-SOD protein expression (p<0.05) and a trend towards increased Nrf2 protein expression was noted in rat brains after 4 Mn doses vs. the control group, but the expression of these proteins was decreased after 8 Mn doses. Taken together, these results suggest that the inhibitory effect of Mn on AChE activity promotes increased neuronal oxidative stress and neuroinflammatory biomarkers. PMID:22154916

  15. Protective effects of antioxidants and anti-inflammatory agents against manganese-induced oxidative damage and neuronal injury

    PubMed Central

    Milatovic, Dejan; Gupta, Ramesh C.; Yu, Yingchun; Zaja-Milatovic, Snjezana; Aschner, Michael

    2011-01-01

    Exposure to excessive manganese (Mn) levels leads to neurotoxicity, referred to as manganism, which resembles Parkinson’s disease (PD). Manganism is caused by neuronal injury in both cortical and subcortical regions, particularly in the basal ganglia. The basis for the selective neurotoxicity of Mn is not yet fully understood. However, several studies suggest that oxidative damage and inflammatory processes play prominent roles in the degeneration of dopamine-containing neurons. In the present study, we assessed the effects of Mn on reactive oxygen species (ROS) formation, changes in high-energy phosphates and associated neuronal dysfunctions both in vitro and in vivo. Results from our in vitro study showed a significant (P<0.01) increase in biomarkers of oxidative damage, F2-isoprostanes (F2-IsoPs), as well as the depletion of ATP in primary rat cortical neurons following exposure to Mn (500 µM) for 2 hours. These effects were protected when neurons were pretreated for 30 min with 100 µM of an antioxidant, the hydrophilic vitamin E analog, trolox (6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid), or an anti-inflammatory agent, indomethacin. Results from our in vivo study confirmed a significant increase in F2-IsoPs levels in conjunction with the progressive spine degeneration and dendritic damage of the striatal medium spiny neurons (MSNs) of mice exposed to Mn (100 mg/kg, s.c.) 24 hours. Additionally, pretreatment with vitamin E (100 mg/kg, i.p.) or ibuprofen (140 µg/ml in the drinking water for two weeks) attenuated the Mn-induced increase in cerebral F2-IsoPs and protected the MSNs from dendritic atrophy and dendritic spine loss. Our findings suggest that the mediation of oxidative stress/mitochondrial dysfunction and the control of alterations in biomarkers of oxidative injury, neuroinflammation and synaptodendritic degeneration may provide an effective, multi-pronged therapeutic strategy for protecting dysfunctional dopaminergic transmission and slowing of the progression of Mn-induced neurodegenerative processes. PMID:21684300

  16. MANGANESE TOURMALINES

    Microsoft Academic Search

    M. N. Slivko

    1961-01-01

    The role of manganese in the chemical composition and coloring of tourmaline is discussed. It is shown that manganese tourmaline-tsilaisite is similar to tourmaline-elbaite in composition and condition formation. The miscibility in the sherlite-elbaite-tsilaisite system is complete, but in the sherlite-dravite-tsilaisite system there is a gap between the dravite and tsilaisite, similar to the relationship between dravite and elbaite.Manganese may

  17. ROLE OF IRON AND MANGANESE OXIDES IN BIOSOLIDS AND BIOSOLIDS-AMENDED SOILS ON METAL BINDING

    EPA Science Inventory

    Biosolids contain high levels of Fe, Mn, and Al. Surfaces of freshly precipitated metal oxides, especially Fe and Mn, are known to be highly active sites for most dissolved metal ion species. We nw have metal sorption/desorption data that illustrate the importance of Fe and Mn fr...

  18. MOLECULAR-LEVEL PROCESS GOVERNING THE INTERACTION OF CONTAMINANTS WITH IRON AND MANGANESE OXIDES

    EPA Science Inventory

    Many of the inorganic and organic contaminants present in sediments at DOE sites can be altered or destroyed by reduction and oxidation (redox) reactions occurring at mineral surfaces. A fundamental understanding of such redox processes provided by molecular-level studies on stru...

  19. Scanning tunneling spectroscopy study of charge ordering, stripes and phase separation in manganese perovskite oxides

    Microsoft Academic Search

    Christoph Renner

    2007-01-01

    Colossal magnetoresistance (CMR) in perovskite-based transition metal oxides keeps challenging our understanding. Constant progress in scanning tunneling microscopy investigations is enabling increasingly detailed experimental insight into the different electronic and structural phases nucleating in these complex materials. I shall review the latest findings emerging from experiments on perovskite- and bilayer-manganites [1], which in particular, reveal the importance of lattice degrees

  20. Oxidation and adsorption of Co(II)EDTA 2- complexes in subsurface materials with iron and manganese oxide grain coatings

    NASA Astrophysics Data System (ADS)

    Zachara, J. M.; Gassman, P. L.; Smith, S. C.; Taylor, D.

    1995-11-01

    Batch interaction experiments were performed under aerobic conditions to characterize the adsorption behavior and valence speciation of CoEDTA complexes (equimolar at 10 -5 mol/L) in a series of Pliocene subsurface sediments containing various amounts of Fe and Mn oxides. The experiments were performed in 0.003 mol/L Ca(ClO 4) 2 with a solids concentration of 500 g/L at variable pH (4-9) and at the natural pH of the sediments (pH = 8.3). Three of these subaerial sediments (Ringold 1, 2, 3) contained significant quantities of extractable Fe and Mn, while the fourth (Ringold 4) was virtually devoid of sesquioxide precipitates. Microscopic and mineralogic analyses of the most heavily encrusted material (Ringold 2) showed that the oxides existed as intergrain cements and contained crystalline goethite and rancieite/todorokite. Adsorption on a synthetic analog sorbent (0.6 mass % ferrihydrite-coated sand) over a range in pH showed that, while both Co(II)EDTA 2- and Co(III)EDTA - sorb as anions, the divalent Co complex forms stronger surface complexes with FeOH sites. In the subsurface sediments containing both Fe and Mn oxides, however, the sorption of Co(II)EDTA 2- and Co(III)EDTA - was low and equivalent, suggesting transformation to a common valence form. Ion chromatography documented that Co(III)EDTA - was the equilibrium species and that the oxidation of Co(II)EDTA 2- was rapid. Sorption of Co(II)EDTA 2- in the Ringold 4 sediment was different: no oxidation was seen and Al (aq)3+ promoted dissociation of the complex. Sorption experiments with Co(III)EDTA - and Ni(II)EDTA 2- on Ringold 2 sediment demonstrated that the natural Fe oxide fraction was a poor anion sorbent, in contrast to ferrihydrite coated sand. Experimental evidence suggests Co(II)EDTA 2- remains intact during oxidation and that dissolved Si, and Si coreacted with the Fe oxides, influence McEDTA sorption. It is concluded that Mn oxides could greatly accelerate the potential migration of CoEDTA complexes in subsurface systems.

  1. High-temperature ferromagnetism in manganese-doped indium-tin oxide films

    Microsoft Academic Search

    John Philip; Nikoleta Theodoropoulou; Geetha Berera; Jagadeesh S. Moodera; Biswarup Satpati

    2004-01-01

    High-temperature ferromagnetism is demonstrated in Mn-doped indium-tin oxide (ITO) films deposited using reactive thermal evaporation. These films were grown on sapphire (0001), Si\\/SiO2 as well as Si (100) substrates with the highest magnetic moment observed around 0.8 muB\\/Mn in 5% Mn-doped ITO films. The electrical conduction is n type and the carrier concentration is ~2.5×1019 cm-3 for 5% Mn doping.

  2. A nano-sized manganese oxide in a protein matrix as a natural water-oxidizing site.

    PubMed

    Najafpour, Mohammad Mahdi; Ghobadi, Mohadeseh Zarei; Haghighi, Behzad; Tomo, Tatsuya; Carpentier, Robert; Shen, Jian-Ren; Allakhverdiev, Suleyman I

    2014-08-01

    The purpose of this review is to present recent advances in the structural and functional studies of water-oxidizing center of Photosystem II and its surrounding protein matrix in order to synthesize artificial catalysts for production of clean and efficient hydrogen fuel. PMID:24560883

  3. Removal of Mn(II) ions from aqueous neutral media by manganese-oxidizing fungus in the presence of carbon fiber.

    PubMed

    Sasaki, Keiko; Konno, Hidetaka; Endo, Mai; Takano, Keishi

    2004-03-01

    A manganese-oxidizing fungus was isolated from a hot spring in Japan. The fungus was increasingly effective at oxidizing Mn(II) ions as the concentration of organic carbon sources in the growth medium was decreased. The fungus oxidized 50 ppm of Mn(II) ions within 160 h in a pH 7.3 medium at 25 degrees C. The presence of carbon fiber shortened the time to 80 h, and promoted steady oxidation. The oxidation products were identified by XPS and XRD to be poorly crystallized and amorphous MnO(2), both with and without the fiber. These results suggest that the fiber participates in kinetically limited oxidation. The fungus was entangled with and clung to the fibers, and the oxidized Mn species accumulated on the fungus. Similarly shaped polyethylene telephthalate fiber did not enhance the oxidation, nor was adhesion of the fungus observed. Although the mechanism is still unknown, the present work shows that removal of Mn from solution through the precipitation and accumulation of Mn-oxides on the fungus in the presence of carbon fiber is a promising improvement for water treatment. PMID:14760689

  4. Biological manganese removal from potable water using trickling filters

    Microsoft Academic Search

    A. G. Tekerlekopoulou; I. A. Vasiliadou; D. V. Vayenas

    2008-01-01

    Two pilot-scale trickling filters were constructed and tested for manganese removal from potable water, using different fractions of silicic gravel as support media (mono- and multilayer filter). Manganese oxidation in drinking water was found to be cause by both biological oxidation and heterogeneous catalytic paths. Mixed culture populations were used to inoculate the trickling filters and the feed manganese concentrations

  5. Shewanella-mediated biosynthesis of manganese oxide micro-/nanocubes as efficient electrocatalysts for the oxygen reduction reaction.

    PubMed

    Jiang, Congcong; Guo, Zhaoyan; Zhu, Ying; Liu, Huan; Wan, Meixiang; Jiang, Lei

    2015-01-01

    Developing efficient electrocatalysts for the oxygen reduction reaction (ORR) is critical for promoting the widespread application of fuel cells and metal-air batteries. Here, we develop a biological low-cost, ecofriendly method for the synthesis of Mn2 O3 micro-/nanocubes by calcination of MnCO3 precursors in an oxygen atmosphere. Microcubic MnCO3 precursors with an edge length of 2.5??m were fabricated by dissimilatory metal-reducing Shewanella loihica PV-4 in the presence of MnO4 (-) as the sole electron acceptor under anaerobic conditions. After calcining the MnCO3 precursors at 500 and 700?°C, porous Mn2 O3 -500 and Mn2 O3 -700 also showed microcubic morphology, while their edge lengths decreased to 1.8??m due to thermal decomposition. Moreover, the surfaces of the Mn2 O3 microcubes were covered by granular nanoparticles with average diameters in the range of 18-202?nm, depending on the calcination temperatures. Electrochemical measurements demonstrated that the porous Mn2 O3 -500 micro-/nanocubes exhibit promising catalytic activity towards the ORR in an alkaline medium, which should be due to a synergistic effect of the overlapping molecular orbitals of oxygen/manganese and the hierarchically porous structures that are favorable for oxygen absorption. Moreover, these Mn2 O3 micro-/nanocubes possess better stability than commercial Pt/C catalysts and methanol-tolerance property in alkaline solution. Thus the Shewanella-mediated biosynthesis method we provided here might be a new strategy for the preparation of various transition metal oxides as high-performance ORR electrocatalysts at low cost. PMID:25425435

  6. Biodistribution and acute toxicity of a nanofluid containing manganese iron oxide nanoparticles produced by a mechanochemical process

    PubMed Central

    Bellusci, Mariangela; La Barbera, Aurelio; Padella, Franco; Mancuso, Mariateresa; Pasquo, Alessandra; Grollino, Maria Giuseppa; Leter, Giorgio; Nardi, Elisa; Cremisini, Carlo; Giardullo, Paola; Pacchierotti, Francesca

    2014-01-01

    Superparamagnetic iron oxide nanoparticles are candidate contrast agents for magnetic resonance imaging and targeted drug delivery. Biodistribution and toxicity assessment are critical for the development of nanoparticle-based drugs, because of nanoparticle-enhanced biological reactivity. Here, we investigated the uptake, in vivo biodistribution, and in vitro and in vivo potential toxicity of manganese ferrite (MnFe2O4) nanoparticles, synthesized by an original high-yield, low-cost mechanochemical process. Cultures of murine Balb/3T3 fibroblasts were exposed for 24, 48, or 72 hours to increasing ferrofluid concentrations. Nanoparticle cellular uptake was assessed by flow-cytometry scatter-light measurements and microscopy imaging after Prussian blue staining; cytotoxicity was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and colony-forming assays. After a single intravenous injection, in vivo nanoparticle biodistribution and clearance were evaluated in mice by Mn spectrophotometric determination and Prussian blue staining in the liver, kidneys, spleen, and brain at different posttreatment times up to 21 days. The same organs were analyzed for any possible histopathological change. The in vitro study demonstrated dose-dependent nanoparticle uptake and statistically significant cytotoxic effects from a concentration of 50 ?g/mL for the MTT assay and 20 ?g/mL for the colony-forming assay. Significant increases in Mn concentrations were detected in all analyzed organs, peaking at 6 hours after injection and then gradually declining. Clearance appeared complete at 7 days in the kidneys, spleen, and brain, whereas in the liver Mn levels remained statistically higher than in vehicle-treated mice up to 3 weeks postinjection. No evidence of irreversible histopathological damage to any of the tested organs was observed. A comparison of the lowest in vitro toxic concentration with the intravenously injected dose and the administered dose of other ferrofluid drugs currently in clinical practice suggests that there might be sufficient safety margins for further development of our formulation. PMID:24790434

  7. Manganese oxide and docetaxel co-loaded fluorescent polymer nanoparticles for dual modal imaging and chemotherapy of breast cancer.

    PubMed

    Abbasi, Azhar Z; Prasad, Preethy; Cai, Ping; He, Chunsheng; Foltz, Warren D; Amini, Mohammad Ali; Gordijo, Claudia R; Rauth, Andrew M; Wu, Xiao Yu

    2015-07-10

    Multifunctional nanoparticles (NPs) have found important applications in diagnosis, chemotherapy, and image-guided surgery of tumors. In this work, we have developed polymeric theranostic NPs (PTNPs) containing the anticancer drug docetaxel (DTX), a fluorescent dye, and magnetic manganese oxide (MnO) NPs for dual modal imaging and chemotherapy. PTNPs ~150nm in diameter were synthesized by co-loading hydrophobic DTX and MnO NPs ~5nm in diameter, into the matrix of a fluorescent dye-labeled amphiphilic polymer. The PTNPs enabled high loading efficiency and sustained in vitro release of DTX. Energy-dependent cellular uptake and extended cytoplasmic retention of the PTNPs in MDA-MB-231 human breast cancer cells were observed by fluorescence microscopy examination. DTX-loaded PTNPs exhibited higher cytotoxicity than free DTX with a 3 to 4.4-fold decrease in drug dose required for 50% cell growth inhibition. The hydrophilic backbone of the amphiphilic polymer improved the fluidity of PTNPs which enhanced the longitudinal relaxivity (r1) of loaded MnO NPs by 2.7-fold with r1=2.4mM(-1)s(-1). Whole body fluorescence imaging (FI) and magnetic resonance imaging (MRI) showed significant accumulation and prolonged retention of PTNPs in orthotopic MDA-MB-231 breast tumors. These results suggest that the new amphiphilic polymer-based PTNP system, able to simultaneously deliver a poorly soluble anticancer drug, enhance MRI contrast, and stain tumor tissue by fluorescence, is a good candidate for cancer theranostic applications. PMID:25908171

  8. Biodistribution and acute toxicity of a nanofluid containing manganese iron oxide nanoparticles produced by a mechanochemical process.

    PubMed

    Bellusci, Mariangela; La Barbera, Aurelio; Padella, Franco; Mancuso, Mariateresa; Pasquo, Alessandra; Grollino, Maria Giuseppa; Leter, Giorgio; Nardi, Elisa; Cremisini, Carlo; Giardullo, Paola; Pacchierotti, Francesca

    2014-01-01

    Superparamagnetic iron oxide nanoparticles are candidate contrast agents for magnetic resonance imaging and targeted drug delivery. Biodistribution and toxicity assessment are critical for the development of nanoparticle-based drugs, because of nanoparticle-enhanced biological reactivity. Here, we investigated the uptake, in vivo biodistribution, and in vitro and in vivo potential toxicity of manganese ferrite (MnFe2O4) nanoparticles, synthesized by an original high-yield, low-cost mechanochemical process. Cultures of murine Balb/3T3 fibroblasts were exposed for 24, 48, or 72 hours to increasing ferrofluid concentrations. Nanoparticle cellular uptake was assessed by flow-cytometry scatter-light measurements and microscopy imaging after Prussian blue staining; cytotoxicity was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and colony-forming assays. After a single intravenous injection, in vivo nanoparticle biodistribution and clearance were evaluated in mice by Mn spectrophotometric determination and Prussian blue staining in the liver, kidneys, spleen, and brain at different posttreatment times up to 21 days. The same organs were analyzed for any possible histopathological change. The in vitro study demonstrated dose-dependent nanoparticle uptake and statistically significant cytotoxic effects from a concentration of 50 ?g/mL for the MTT assay and 20 ?g/mL for the colony-forming assay. Significant increases in Mn concentrations were detected in all analyzed organs, peaking at 6 hours after injection and then gradually declining. Clearance appeared complete at 7 days in the kidneys, spleen, and brain, whereas in the liver Mn levels remained statistically higher than in vehicle-treated mice up to 3 weeks postinjection. No evidence of irreversible histopathological damage to any of the tested organs was observed. A comparison of the lowest in vitro toxic concentration with the intravenously injected dose and the administered dose of other ferrofluid drugs currently in clinical practice suggests that there might be sufficient safety margins for further development of our formulation. PMID:24790434

  9. Synthesis and Electrochemical Properties of Nano Fiber Hollandite-Type Manganese Oxides Using a Hydrothermal Method

    NASA Astrophysics Data System (ADS)

    Kadoma, Yoshihiro; Akahira, Tatsuya; Fukuda, Tsubasa; Ui, Koichi; Kumagai, Naoaki

    2012-03-01

    Hollandite-type MnO2 and its Co-substituted samples have been synthesized by hydrothermal method from MnSO4, CoSO4 and K2S2O8 solutions. The hydrothermal products from MnSO4 and K2S2O8 solutions consisted of the hollandite-type [2 × 2] tunnel structure at 100°C-150°C for 12 h, which was transformed to pyrolusite-type [1 × 1] tunnel structure by hydrothermal treatment at 150°C for longer times of 24-48 h or at a higher temperature of 180°C. On the other hand, the hydrothermal products from MnSO4, CoSO4 and K2S2O8 solutions at 150°C-180°C for 12-48 h consisted of the hollandite-type MnO2 phase. The Co-substituted samples showed higher initial discharge capacity (180-200 mAh (g-oxide)-1) than that of non-substituted hollandite-type MnO2 (130-160 mAh (g-oxide)-1) at 50 mA g-1.

  10. The destruction of dichloroethane over a gamma-alumina supported manganese oxide catalyst.

    PubMed

    Tseng, Ting Ke; Wang, Ling; Ho, Chiun Teh; Chu, Hsin

    2010-06-15

    Halogenated VOCs emissions are associated to a wide range of industrial processes; for instance, dichloroethane (DCEA) is mainly used in metal degreasing processes and known to be hazardous to the environment and public health. The effects of operating parameters on the catalytic incineration of DCEA over the Mn(2)O(3)/gamma-Al(2)O(3) catalyst were performed in this study. The results show that conversion of DCEA increases as inlet temperature and oxygen concentration increase, and decreases with the increases of DCEA concentration and space velocity. The effects of O(2) and DCEA content in carrier gas on the catalytic reaction rate are also observed. Experimental results indicate that the oxidation kinetic behavior of DCEA with the catalyst can be expressed by using the rate expression of the power rate law. The experimental results are compared with those predicted from the kinetic model. The products and reactants distributions from the oxidation of DCEA over Mn(2)O(3)/gamma-Al(2)O(3) were observed. The results show that the DCEA conversion starts from 15% at 450K and rises to 100% in the 700-800K ranges and the CO(2) yield is complete (100%) in the same temperature ranges. HCl and Cl(2) are the other main products with little halogenated VOC intermediates. PMID:20227177

  11. High Valent Manganese and Cobalt Complexes of Oxidatively Robust Nitrogen and Oxygen Donor Ligands.

    NASA Astrophysics Data System (ADS)

    Gordon-Wylie, Scott Wallace

    1995-01-01

    The focus of this thesis is to extend the range of ligands that satisfy the Collins criteria through a program of organic synthesis, and to apply the resulting high valent metal ligand complexes to the solution of current problems in structural inorganic chemistry, solid state chemistry (with a particular emphasis on magnetic interactions in solids) and to homogeneous and heterogeneous catalysis. Notable achievements along these directions to date are: (i) A streamlined synthesis of diamide dialkoxide and diamide diphenoxide acyclic ligands which allows for a wide range of both electron withdrawing and electron donating substituents to be incorporated into the ligand framework. (ii) The first example of a LMn(V)O species stable enough to be crystallographically characterized was obtained, utilizing the acyclic ligands of (i). (iii) Catalytic O-atom transfer oxidations utilizing acyclic ligands from (i) have been performed. Planar Co(III) complexes of these ligands can catalyze O-atom transfers, ^1 with 30-50 turnovers, including enantioselective ones,^2 implicating that the ligands remain at least partially intact during the catalytic process. (iv) Unusual magnetic ordering has been observed in an infinite linear chain of S = 2 LMn(III) centers, in collaboration with Edmund P. Day. (v) Ferromagnetic exchange has been obtained in a ((LCo(III)) _3Co(II)) ^{-} complex^4 Magnetic model building in collaboration with Gordon Yee and Emile Bominaar has led to an understanding of the magnetic data suitable for publication.^5 (vi) Adaptation of a range of electronic substituents (see (i)) into a macrocyclic framework^7 allows for the preparation of hydrolytically and oxidatively stable high valent metal complexes. The presence of a range of electronic substituents further allows redox potentials for a single (LM) ^{rm n+}/(LM) ^{(rm n+1)+ } oxidation process to be tuned over a range that spans ca. 1 V. (vii) Initial linear syntheses for these macrocycles involved the use of organic azide intermediates. (viii) A new macrocyclic switching ligand has been synthesized utilizing (vii), that allows H^{+} or other lewis acids to act at the secondary site as electron withdrawing groups from the metal. In the structurally characterized switching (Co(III)( kappa^4-L)) ^{ -} complex, there is a bidentate switching site consisting of a pyridine-N and an adjacent amide-O donor. It has been found that the cobalt(II) derivative (CO(II)(kappa^4-L)) ^{-} readily reduces O _2 by an outer sphere (presumably by 1 e ^{-}) process. (ix) Robust homogeneous metalloredox-active oxidants are an important strategic goal for primary pollution prevention, or what is often called "green chemistry". Use of (vii) provides access to quantities of a macrocyclic ligand, that is derivatized in such a way that it can be attached to a solid polymer support. (x) C-H bond activation has been observed in iron systems^{15} in collaboration with Mike Bartos (the principal investigator) where use of (vii) has allowed quantities of ligand to be synthesized and burned in reaction chemistry with nitriles and oxidants. (xi) Macrocyclic ligands with organic solubilizing groups have been prepared utilizing (vii) and metal complexes with substantial alkane solubility result. (Abstract shortened by UMI.).

  12. Development and application of 16S rRNA-targeted probes for detection of iron- and manganese-oxidizing sheathed bacteria in environmental samples.

    PubMed Central

    Siering, P L; Ghiorse, W C

    1997-01-01

    Comparative sequence analysis of the 16S rRNA genes from several Leptothrix and Sphaerotilus strains led to the design of an oligonucleotide probe (PS-1) based on a sequence within the hypervariable region 1 specific for four Leptothrix strains and for one of the four Sphaerotilus natans strains examined. Another probe (PSP-6) was based on a sequence within the hypervariable region 2. PSP-6 was specific for one of the two evolutionary lineages previously described for Leptothrix spp. (P. L. Siering and W. C. Ghiorse, Int. J. Syst. Bacteriol. 46:173-182, 1996). Fluorescein-labeled oligonucleotide probes were synthesized, and their specificity for fluorescence in situ hybridization identification was confirmed by a laser scanning microscopy technique (W. C. Ghiorse, D. N. Miller, R. L. Sandoli, and P. L. Siering, Microsc. Res. Tech. 33:73-86, 1996) to compare whole-cell hybridizations of closely related bacteria. Probe specificity was also tested in dot blot against total RNA isolated from four Leptothrix strains, four Sphaerotilus strains, and 15 other members of the class Proteobacteria. When the probes were tested on samples from the Sapsucker Woods wetland habitat where Leptothrix spp. are thought to play a role in manganese and iron oxidation, positive signals were obtained from several sheathed filamentous bacteria including some that were morphologically similar to previously isolated strains of "Leptothrix discophora." Other unknown filamentous sheathed bacteria also gave strong positive signals. This work provides a foundation for future studies correlating the presence of members of the Leptothrix-Sphaerotilus group of sheathed bacteria with manganese and iron oxidation activity in habitats where biological iron and manganese oxidation are important environmental processes. PMID:9023942

  13. High-temperature ferromagnetism in manganese-doped indium-tin oxide films

    NASA Astrophysics Data System (ADS)

    Philip, John; Theodoropoulou, Nikoleta; Berera, Geetha; Moodera, Jagadeesh S.; Satpati, Biswarup

    2004-08-01

    High-temperature ferromagnetism is demonstrated in Mn-doped indium-tin oxide (ITO) films deposited using reactive thermal evaporation. These films were grown on sapphire (0001), Si /SiO2 as well as Si (100) substrates with the highest magnetic moment observed around 0.8?B/Mn in 5% Mn-doped ITO films. The electrical conduction is n type and the carrier concentration is ˜2.5×1019cm-3 for 5% Mn doping. An anomalous Hall effect is observed in magnetotransport measurements, showing that the charge carriers are spin polarized, revealing the magnetic interaction between itinerant electrons and localized Mn spins. The carrier concentration can be varied independent of the Mn concentration in this transparent ferromagnetic semiconductor for its easy integration into magneto-optoelectronic devices.

  14. Spinel manganese-nickel-cobalt ternary oxide nanowire array for high-performance electrochemical capacitor applications.

    PubMed

    Li, Lu; Zhang, Yongqi; Shi, Fan; Zhang, Yijun; Zhang, Jiaheng; Gu, Changdong; Wang, Xiuli; Tu, Jiangping

    2014-10-22

    Aligned spinel Mn-Ni-Co ternary oxide (MNCO) nanowires are synthesized by a facile hydrothermal method. As an electrode of supercapacitors, the MNCO nanowire array on nickel foam shows an outstanding specific capacitance of 638 F g(-1) at 1 A g(-1) and excellent cycling stability. This exceptional performance benefits from its nanowire architecture, which can provide large reaction surface area, fast ion and electron transfer, and good structural stability. Furthermore, an asymmetric supercapacitor (ASC) with high energy density is assembled successfully by employing the MNCO nanowire array as positive electrode and carbon black as negative electrode. The excellent electrochemical performances indicate the promising potential application of the ASC device in the energy storage field. PMID:25247606

  15. Manganese Superoxide Dismutase Protects Mouse Cortical Neurons From Chronic Intermittent Hypoxia-Mediated Oxidative Damage

    PubMed Central

    Shan, Xiaoyang; Chi, Liying; Ke, Yan; Luo, Chun; Qian, Steven; Gozal, David; Liu, Rugao

    2007-01-01

    Obstructive Sleep Apnea (OSA) syndrome has been recognized as a highly prevalent public health problem and is associated with major neurobehavioral morbidity. Chronic intermittent hypoxia (CIH), a major pathological component of OSA, increases oxidative damage to the brain cortex and decreases neurocognitive function in rodent models resembling human OSA. We employed in vitro and in vivo approaches to identify the specific phases and subcellular compartments in which enhanced reactive oxygen species (ROS) are generated during CIH. In addition, we utilized the cell culture and animal models to analyze the consequences of enhanced production of ROS on cortical neuronal cell damage and neurocognitive dysfunction. In a primary cortical neuron culture system, we demonstrated that the transition phase from hypoxia to normoxia (NOX) during CIH generates more ROS than the transition phase from NOX to hypoxia or hypoxia alone, all of which generate more ROS than NOX. Using selective inhibitors of the major pathways underlying ROS generation in the cell membrane, cytosol, and mitochondria, we showed that the mitochondria are the predominant source of enhanced ROS generation during CIH in mouse cortical neuronal cells. Furthermore, in both cell culture and transgenic mice, we demonstrated that overexpression of MnSOD decreased CIH-mediated cortical neuronal apoptosis, and reduced spatial learning deficits measured with the Morris water maze assay. Together, the data from the in vitro and in vivo experiments indicate that CIH-mediated mitochondrial oxidative stress may play a major role in the neuronal cell loss and neurocognitive dysfunction in OSA. Thus, therapeutic strategies aiming at reducing ROS generation from mitochondria may improve the neurobehavioral morbidity in OSA. PMID:17719231

  16. Removing selected steroid hormones, biocides and pharmaceuticals from water by means of biogenic manganese oxide nanoparticles in situ at ppb levels.

    PubMed

    Furgal, Karolina M; Meyer, Rikke L; Bester, Kai

    2015-10-01

    The oxidation of organic micro-pollutants by biogenic manganese oxide nanoparticles (BioMnOx) has been studied with respect to possible implementation of BioMnOx in wastewater treatment. For this it would be prerequisite that microbial Mn(2+) oxidation and BioMnOx-driven pollutant removal can occur in situ, i.e. in the same reactor as the removal. Here we present the in situ reactivity of BioMnOx produced by Pseudomonas putida towards a range of micro-pollutants at environmentally relevant concentrations (10?gL(-1)). We found that in situ formed BioMnOx completely removed the steroid hormones estrone and 17-? ethinylestradiol, while only 26% removal of diclofenac was achieved. Ibuprofen, tebuconazole, carbamazepine, carbendazim, and terbutryn were not removed under in situ conditions. PMID:25532770

  17. Crystalline mesoporous K(2-x)Mn?O?? and ?-MnO? by mild transformations of amorphous mesoporous manganese oxides and their enhanced redox properties.

    PubMed

    Poyraz, Altug S; Song, Wenqiao; Kriz, David; Kuo, Chung-Hao; Seraji, Mohammad S; Suib, Steven L

    2014-07-23

    Synthesis of crystalline mesoporous K(2-x)Mn8O16 (Meso-OMS-2), and ?-MnO2 (Meso-?-MnO2) is reported. The synthesis is based on the transformation of amorphous mesoporous manganese oxide (Meso-Mn-A) under mild conditions: aqueous acidic solutions (0.5 M H(+) and 0.5 M K(+)), at low temperatures (70 °C), and short times (2 h). Meso-OMS-2 and Meso-?-MnO2 maintain regular mesoporosity (4.8-5.6 nm) and high surface areas (as high as 277 m(2)/g). The synthesized mesoporous manganese oxides demonstrated enhanced redox (H2-TPR) and catalytic performances (CO oxidation) compared to nonporous analogues. The order of reducibility and enhanced catalytic performance of the samples is Commercial-Mn2O3 < nonporous-OMS-2 < Meso-Mn2O3 < Meso-OMS-2 < Meso-?-MnO2 < Meso-Mn-A. PMID:24971574

  18. High-performance binder-free supercapacitor electrode by direct growth of cobalt-manganese composite oxide nansostructures on nickel foam

    NASA Astrophysics Data System (ADS)

    Jiang, Shulan; Shi, Tielin; Long, Hu; Sun, Yongming; Zhou, Wei; Tang, Zirong

    2014-09-01

    A facile approach composed of hydrothermal process and annealing treatment is proposed to directly grow cobalt-manganese composite oxide ((Co,Mn)3O4) nanostructures on three-dimensional (3D) conductive nickel (Ni) foam for a supercapacitor electrode. The as-fabricated porous electrode exhibits excellent rate capability and high specific capacitance of 840.2 F g-1 at the current density of 10 A g-1, and the electrode also shows excellent cycling performance, which retains 102% of its initial discharge capacitance after 7,000 cycles. The fabricated binder-free hierarchical composite electrode with superior electrochemical performance is a promising candidate for high-performance supercapacitors.

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

    SciTech Connect

    Liang, W.

    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 S{sub 2} 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 S{sub 2} state with the g{approx}4 electron paramagnetic resonance (EPR) signal (S{sub 2}-g4 state) was compared with that in the S{sub 2} state with multiline signal (S{sub 2}-MLS state) and the S{sub 1} state. The S{sub 2}-g4 state has a higher XAS inflection point energy than that of the S{sub 1} state, indicating the oxidation of Mn in the advance from the S{sub 1} to the S{sub 2}-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 S{sub 2}-g4 state is different from that in the S{sub 2}-MLS or the S{sub 1} state. In the S{sub 2}-g4 state, the second shell of backscatterers from the Mn absorber contains two Mn-Mn distances of 2.73 {angstrom} and 2.85 {angstrom}. Very little distance disorder exists in the second shell of the S{sub 1} or S{sub 2}-MLS states. The third shell of the S{sub 2}-g4 state at about 3.3 {angstrom} also contains increased heterogeneity relative to that of the S{sub 2}-MLS or the S{sub 1} 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 {open_quotes}pure{close_quotes} S-state Mn K-edge spectra. The edge position shifts to higher energy by 1.8 eV upon the S{sub 1} {yields} S{sub 2} transition.

  20. Ground-state properties of multivalent manganese oxides: Density functional and hybrid density functional calculations

    NASA Astrophysics Data System (ADS)

    Franchini, C.; Podloucky, R.; Paier, J.; Marsman, M.; Kresse, G.

    2007-05-01

    We present density functional theory (DFT) calculations for MnO, Mn3O4 , ?-Mn2O3 , and ?-MnO2 , using different gradient corrected functionals, such as Perdew-Burke-Ernzerhof (PBE), PBE+U , and the two hybrid density functional Hartree-Fock methods PBE0 and Heyd-Scuseria-Ernzerhof (HSE). We investigate the structural, electronic, magnetic, and thermodynamical properties of the mentioned compounds. Despite the lack of sufficient experimental information allowing for a comprehensive comparison of our results, we find overall that hybrid functionals provide a more consistent picture than standard PBE. Although PBE+U is limited due to the uncertainty of choosing the parameter U, it nevertheless provides satisfactory results in terms of magnetic properties and energies of formation. This is in line with results of PBE0 and HSE calculations, but the PBE+U approach tends to overestimate the equilibrium volumes, and also it favors a half-metallic state for the more reduced oxides Mn3O4 , ?-Mn2O3 , and ?-MnO2 , rather than an insulating character as derived from the hybrid functional approaches. The comparison of measured valence-band spectra with the HSE density of states offers a further assessment of the capability of hybrid approaches in overcoming the deficiencies of DFT in treating these kinds of materials.

  1. Reflections on Small Molecule Manganese Models that Seek to Mimic Photosynthetic Water Oxidation Chemistry

    PubMed Central

    Mullins, Christopher S.

    2008-01-01

    Recent advances in the study of the Oxygen Evolving Complex (OEC) of Photosystem II (PSII) include structural information attained from several X-ray crystallographic (XRD) and spectroscopic (XANES and EXAFS) investigations. The possible structural features gleaned from these studies have enabled synthetic chemists to design more accurate model complexes, which in turn, offer better insight into the possible pathways used by PSII to drive photosynthetic water oxidation catalysis. Mononuclear model compounds have been used to advance the knowledge base regarding the physical properties and reactivity of high-valent (MnIV or MnV) complexes. Such investigations have been especially important in regard to the manganyl (MnIV=O or MnV?O) species, as there are no reports, to date, of any structural characterized multinuclear model compounds that incorporate such a functionality. Dinuclear and trinuclear model compounds have also been thoroughly studied in attempts to draw further comparison to the physical properties observed in the natural system and to design systems of catalytic relevance. As the reactive center of the OEC has been shown to contain an oxo-Mn4Ca cluster, exact structural models necessitate a tetranuclear Mn core. The number of models that make use of Mn4 clusters has risen substantially in recent years, and these models have provided evidence to support and refute certain mechanistic proposals. Further work is needed to adequately address the rationale for Ca (and Cl) in the OEC and to determine the sequence of events that lead to O2 evolution. PMID:19081816

  2. Ferroelectric field effect studies of the colossal magnetoresistive oxide lanthanum(1-x) strontium(x) manganese oxide

    NASA Astrophysics Data System (ADS)

    Hong, Xia

    In this work, an electrostatic field effect approach is presented to modulate magnetism and metallicity of the colossal magnetoresistive oxide La1-xSrxMnO 3 (LSMO), using the polarization field of a ferroelectric oxide, Pb(Zr,Ti)O 3 (PZT). In its ferromagnetic metallic phase, LSMO possesses nearly metallic carrier densities, with corresponding electronic screening lengths of ˜1 nm. The field effect happens exclusively at the interface of PZT and LSMO, which requires ultrathin films with high structural and surface quality to observe a substantial modulation. Using off axis radio frequency magnetron sputtering, we have fabricated epitaxial single crystal LSMO thin films, PZT thin films, and PZT/LSMO heterostructures on 001 SrTiO3 substrates using off axis radio frequency magnetron sputtering, with excellent crystallinity and surface properties having been achieved. Using the polarization field of PZT, we have reversibly modulated the magnetic Curie temperature and magnetoresistance of the system. The electrostatic modulation of TC is also observed in Hall effect measurements. Within the temperature range between the Curie temperatures of the two states, one can turn on and off the magnetic ordering. In a heterostructure where the active layer is one atomic layer (˜2 A) thinner, insulating behavior has been observed over the entire temperature range by depleting the carriers, showing that we are working within the screening length of the system. This study also has implications for nanoscale devices, such as nonvolatile magnetic memories and Mott metal-insulator transition field effect transistors, providing a route to transcend the size scaling limits of mainstream semiconductor devices. Along this line, we have investigated some of the practical aspects of these devices, such as the on/off ratio, switching behavior, and stability. We have also studied the anistropic magnetoresistance (AMR), planar Hall effect, and giant planar Hall effect in LSMO. We have modulated the AMR in ultrathin manganite films using the field effect approach, where we have observed a striking difference between electric field doping and chemical doping results, deconvolving for the first time the effects of charge and chemical distortion/disorder on the fundamental properties, such as the magnetic anisotropy and spin-orbit coupling, in these materials.

  3. The synthesis, characterization of oxidized multi-walled carbon nanotubes, and application to surface acoustic wave quartz crystal gas sensor

    Microsoft Academic Search

    Hao-Lin Hsu; Jih-Mirn Jehng; Yuh Sung; Li-Chun Wang; Sang-Ren Yang

    2008-01-01

    Intermetallic alloy catalysts had been prepared by the polyol method, and used for the growth of the individual- or bundle-shaped multi-walled carbon nanotubes (MWCNTs) by thermal chemical vapor deposition method. The purified MWCNTs catalyzed by Mg28-Ni68-Mo4 alloy catalyst were oxidized with the nitric acid\\/hydrogen peroxide solution (volume ratio=2\\/1) to generate carboxylic acid groups. The oxidized MWCNTs (MWCNT-COOH) were further modified

  4. Oxidative induction of pro-inflammatory cytokine formation by human monocyte-derived macrophages following exposure to manganese in vitro.

    PubMed

    Mokgobu, Matlou I; Cholo, Moloko C; Anderson, Ronald; Steel, Helen C; Motheo, Maraki P; Hlatshwayo, Thembani N; Tintinger, Gregory R; Theron, Annette J

    2015-01-01

    Manganese (as Mn(2+)), a superoxide dismutase mimetic, catalyzes the formation of the relatively stable membrane-permeable reactive oxygen species (ROS) hydrogen peroxide (H2O2), a mediator of intracellular redox signaling in immune and inflammatory cells. The goal of this study was to investigate the potential for Mn(2+), via its pro-oxidative properties, to activate production of pro-inflammatory cytokines/chemokines IL-1?, IL-6, IL-8, IFN?, TNF?, and G-CSF by human monocyte-derived macrophages in vitro. For these studies, the cells were isolated from peripheral blood mononuclear leukocytes and matured to generate a population of large CD14/CD16 co-expressing cells. The monocyte-derived macrophages were then exposed to bacterial lipopolysaccharide (LPS, 1 ?g/ml) or MnCl2 (25-100 ?M)-alone or in combination-for 24 h at 37?°C, after which cell-free supernatants were analyzed using a multiplex cytokine assay procedure. Exposure of the cells to LPS caused modest statistically insignificant increases in cytokine production; MnCl2 caused dose-related increases in production of all six cytokines (achieving statistical significance of p < 0.0171-?< 0.0005 for IL-1?, IL-6, IL-8, IFN?, and TNF?). In the case of LPS and MnCl2 combinations, the observed increases in production of IL-1?, IL-6, IL-8, IFN?, and G-CSF were greater than those seen with cells exposed to the individual agents. The Mn(2+)-mediated induction of cytokine production was associated with increased production of H2O2 and completely attenuated by inclusion of the H2O2-scavenger dithiothreitol, and partially by inhibitors of NF-?B and p38MAP kinase. The findings from the studies here help to further characterize the pro-inflammatory mechanisms that may underpin clinical disorders associated with excess exposure to Mn(2+), particularly those disorders seen in the central nervous and respiratory systems. PMID:24806275

  5. Composition Optimization of Al-DOPING Lithium Manganese Oxide from Al2O3-Li2CO3-MnO2 Ternary System

    NASA Astrophysics Data System (ADS)

    He, Gang; Sun, Xinyan; Hong, Jianhe; He, Mingzhong

    2013-07-01

    In order to synthesize eutectic compound of Al doping lithium manganese oxide which can be used as cathode material in lithium battery, using ?-Al2O3, Li2CO3 and MnO2 as starting raw materials, the composition optimization research work has been done by the solid state synthesis method. A limited composition range was found in Al2O3-Li2CO3-MnO2 ternary system, in which the synthesized Al doping lithium manganese oxides have single spinel structure and good electrochemical performance. The results showed that the LiAl0.04Mn1.96O4 material presented better charge-discharge cycling behavior than pure LiMn2O4, and showed the best electrochemistry property among the compounds in the Al2O3-Li2O-Mn2O3 ternary system. LiAl0.04Mn1.96O4 still kept perfect cubic structure, but LiMn2O4 kept the coexistence of the cubic and tetragonal phases after 50 charge-discharge cycles.

  6. Valine-alanine manganese superoxide dismutase polymorphism is not associated with alcohol-induced oxidative stress or liver fibrosis

    Microsoft Academic Search

    Stephen F. Stewart; Julian B. Leathart; Yuanneng Chen; Ann K. Daly; Roberta Rolla; Daria Vay; Elisa Mottaran; Matteo Vidali; Emanuele Albano; Chris P. Day

    2002-01-01

    The role of genetic factors in the pathogenesis of alcohol-induced liver disease (ALD) is receiving increasing attention. Recently, it has been reported that homozygosity for a valine to alanine substitution in the mitochondrial targeting sequence of manganese superoxide dismutase (Mn-SOD) represents a risk factor for severe ALD. Because this mutation is postulated to modify enzyme transport into mitochondria, we have

  7. Elimination of Manganese(II,III) Oxidation in Pseudomonas putida GB-1 by a Double Knockout of Two Putative Multicopper Oxidase Genes

    PubMed Central

    McCarthy, James K.; Tebo, Bradley M.

    2013-01-01

    Bacterial manganese(II) oxidation impacts the redox cycling of Mn, other elements, and compounds in the environment; therefore, it is important to understand the mechanisms of and enzymes responsible for Mn(II) oxidation. In several Mn(II)-oxidizing organisms, the identified Mn(II) oxidase belongs to either the multicopper oxidase (MCO) or the heme peroxidase family of proteins. However, the identity of the oxidase in Pseudomonas putida GB-1 has long remained unknown. To identify the P. putida GB-1 oxidase, we searched its genome and found several homologues of known or suspected Mn(II) oxidase-encoding genes (mnxG, mofA, moxA, and mopA). To narrow this list, we assumed that the Mn(II) oxidase gene would be conserved among Mn(II)-oxidizing pseudomonads but not in nonoxidizers and performed a genome comparison to 11 Pseudomonas species. We further assumed that the oxidase gene would be regulated by MnxR, a transcription factor required for Mn(II) oxidation. Two loci met all these criteria: PputGB1_2447, which encodes an MCO homologous to MnxG, and PputGB1_2665, which encodes an MCO with very low homology to MofA. In-frame deletions of each locus resulted in strains that retained some ability to oxidize Mn(II) or Mn(III); loss of oxidation was attained only upon deletion of both genes. These results suggest that PputGB1_2447 and PputGB1_2665 encode two MCOs that are independently capable of oxidizing both Mn(II) and Mn(III). The purpose of this redundancy is unclear; however, differences in oxidation phenotype for the single mutants suggest specialization in function for the two enzymes. PMID:23124227

  8. Oxides of copper, ceria promoted copper, manganese and copper manganese on Al 2O 3 for the combustion of CO, ethyl acetate and ethanol

    Microsoft Academic Search

    Per-Olof Larsson; Arne Andersson

    2000-01-01

    Combustion of CO, ethyl acetate and ethanol was studied over CuOx\\/Al2O3, CuOx–CeO2\\/Al2O3, CuMn2O4\\/Al2O3 and Mn2O3\\/Al2O3 catalysts. It was found that modification of the alumina with ceria before subsequent copper oxide deposition increases the activity for combustion of CO substantially, but the effect of ceria was small on the combustion of ethyl acetate and ethanol. The activity increases with the CuOx

  9. Chemical effects on UV irradiation absorption of fouled quartz sleeves in ultraviolet disinfection

    Microsoft Academic Search

    Beibei Zhu Sun; Ernest Blatchley; Mike Oliver; Cheng Zheng; Kristofer Jennings

    2008-01-01

    The effects of foulant chemical composition on ultraviolet (UV) absorbance of fouled quartz sleeves in UV disinfection systems were studied. Statistical analysis was conducted to examine the effects of nine fouling chemicals on the UV transmittance changes of fouled quartz lamp sleeves. The results demonstrated that the main effects were attributable to surface concentrations of iron and manganese. The surface

  10. Immobilization of manganese peroxidase from Lentinula edodes on alkylaminated Emphaze{trademark} AB 1 polymer for generation of Mn{sup 3+} as an oxidizing agent

    SciTech Connect

    Grabski, A.C.; Burgess, R.R. [Univ. of Wisconsin Biotechnology Center, Madison, WI (United States); Rasmussen, J.K.; Coleman, P.L. [Corp. Research Technology Development Lab., St. Paul, MN (United States)

    1996-07-01

    Manganese peroxidase (MnP) is secreted by white-rot fungi and participates in the degradation of lignin by these organisms. MnP uses H{sub 2}O{sub 2} as an oxidant to oxidize Mn{sup II} to Mn{sup III} as the manganic ion Mn{sup 3+}. The Mn{sup 3+} stabilized by chelation, is a highly reactive nonspecific oxidant capable of oxidizing a variety of toxic organic compounds. Previous attempts at immobilization of MnP, purified from Lentinula edodes through reactive amino groups, have been hindered by the protein`s low lysine content of only 1% and its instability above pH 6.0. As an alternative to amine coupling, the enzyme has now been covalently immobilized through its carboxyl groups, using an azlactone-functional copolymer derivatized with ethylenediamine and 2-ethoxy-1-ethoxycarbonyl-1,2-dihydroquinoline (EEDQ) as a coupling reagent. The immobilization reaction was performed under acidic (pH 5.25) conditions, and 90% coupling efficiency was achieved within 2 h. Net immobilization efficiencies, expressed as the product of protein coupling efficiency and enzyme activity, have been measured at > 95% within 4 h. The MnP-NH-polymer and the free soluble protein were characterized and compared for their pH, temperature, and storage stabilities, as well as their H{sub 2}O{sub 2} dependence and kinetics. 61 refs., 8 figs.

  11. Correlating cation ordering and voltage fade in a lithium-manganese-rich lithium-ion battery cathode oxide: a joint magnetic susceptibility and TEM study.

    PubMed

    Mohanty, Debasish; Sefat, Athena S; Li, Jianlin; Meisner, Roberta A; Rondinone, Adam J; Payzant, E Andrew; Abraham, Daniel P; Wood, David L; Daniel, Claus

    2013-11-28

    Structure-electrochemical property correlation is presented for lithium-manganese-rich layered-layered nickel manganese cobalt oxide (LMR-NMC) having composition Li1.2Co0.1Mn0.55Ni0.15O2 (TODA HE5050) in order to examine the possible reasons for voltage fade during short-to-mid-term electrochemical cycling. The Li1.2Co0.1Mn0.55Ni0.15O2 based cathodes were cycled at two different upper cutoff voltages (UCV), 4.2 V and 4.8 V, for 1, 10, and 125 cycles; voltage fade was observed after 10 and 125 cycles only when the UCV was 4.8 V. Magnetic susceptibility and selected-area electron diffraction data showed the presence of cation ordering in the pristine material, which remained after 125 cycles when the UCV was 4.2 V. When cycled at 4.8 V, the magnetic susceptibility results showed the suppression of cation ordering after one cycle; the cation ordering diminished upon further cycling and was not observed after 125 cycles. Selected-area electron diffraction data from oxides oriented towards the [0001] zone axis revealed a decrease in the intensity of cation-ordering reflections after one cycle and an introduction of spinel-type reflections after 10 cycles at 4.8 V; after 125 cycles, only the spinel-type reflections and the fundamental O3 layered oxide reflections were observed. A significant decrease in the effective magnetic moment of the compound after one cycle at 4.8 V indicated the presence of lithium and/or oxygen vacancies; analysis showed a reduction of Mn(4+) (high spin/low spin) in the pristine oxide to Mn(3+) (low spin) after one cycle. The effective magnetic moment was higher after 10 and 125 cycles at 4.8 V, suggesting the presence of Mn(3+) in a high spin state, which is believed to originate from distorted spinel (Li2Mn2O4) and/or spinel (LiMn2O4) compounds. The increase in effective magnetic moments was not observed when the oxide was cycled at 4.2 V, indicating the stability of the structure under these conditions. This study shows that structural rearrangements in the LMR-NMC oxide happen only at higher potentials (4.8 V, for example) and provides evidence of a direct correlation between cation ordering and voltage fade. PMID:24129599

  12. Effects of properties of manganese oxide-impregnated catalysts and flue gas condition on multipollutant control of Hg0 and NO.

    PubMed

    Chiu, Chun-Hsiang; Hsi, Hsing-Cheng; Lin, Hong-Ping; Chang, Tien-Chin

    2015-06-30

    This research investigated the effects of manganese oxide (MnOx) impregnation on the physical/chemical properties and multi pollutant control effectiveness of Hg(0) and NO using a V2O5-WO3/TiO2-SiO2 selective catalytic reduction (SCR) catalyst. Raw and MnOx-treated SCR samples were bean-shaped nanoparticles with sizes within 10-30 nm. Impregnating MnOx of ? 5 wt% caused limited changes in physical properties of the catalyst. The decrease in surface area when the impregnated MnOx amount was 10 wt% may stem from the pore blockage and particle growth or aggregation of the catalyst. Mn(4+) was the main valence state of impregnated MnOx. Apparent crystallinity of MnOx was not observed based on X-ray diffraction. MnOx impregnation enhanced the Hg(0) oxidation and NO/SO2 removal of SCR catalyst. The 5 and 10% MnOx-impregnated samples had the greatest multi pollutant control potentials for Hg(0) oxidation and NO removal; however, the increasing SO2 removal that may be mainly due to SO2-SO3 conversion should be cautioned. HCl and O2 greatly promoted Hg(0) oxidation. SO2 enhanced Hg(0) oxidation at ? 200 ppm while NO and NH3 consistently inhibited Hg(0) oxidation. Elevating flue gas temperature enhanced Hg(0) oxidation. Overall, MnOx-impregnated catalysts show stable and consistent multi pollutant removal effectiveness under the test conditions. PMID:25748996

  13. Novel synthesis of manganese and vanadium mixed oxide (V{sub 2}O{sub 5}/OMS-2) as an efficient and selective catalyst for the oxidation of alcohols in liquid phase

    SciTech Connect

    Mahdavi, Vahid, E-mail: v-mahdavi@araku.ac.ir; Soleimani, Shima

    2014-03-01

    Graphical abstract: Oxidation of various alcohols is studied in the liquid phase over new composite mixed oxide (V{sub 2}O{sub 5}/OMS-2) catalyst using tert-butyl hydroperoxide (TBHP). The activity of V{sub 2}O{sub 5}/OMS-2 samples was considerably increased with respect to OMS-2 catalyst and these samples are found to be suitable for the selective oxidation of alcohols. - Highlights: • V{sub 2}O{sub 5}/K-OMS-2 with different V/Mn molar ratios prepared by the impregnation method. • Oxidation of alcohols was studied in the liquid phase over V{sub 2}O{sub 5}/K-OMS-2 catalyst. • V{sub 2}O{sub 5}/K-OMS-2 catalyst had excellent activity for alcohol oxidation. • Benzyl alcohol oxidation using excess TBHP followed a pseudo-first order kinetic. • The selected catalyst was reused without significant loss of activity. - Abstract: This work reports the synthesis and characterization of mixed oxide vanadium–manganese V{sub 2}O{sub 5}/K-OMS-2 at various V/Mn molar ratios and prepared by the impregnation method. Characterization of these new composite materials was made by elemental analysis, BET, XRD, FT-IR, SEM and TEM techniques. Results of these analyses showed that vanadium impregnated samples contained mixed phases of cryptomelane and crystalline V{sub 2}O{sub 5} species. Oxidation of various alcohols was studied in the liquid phase over the V{sub 2}O{sub 5}/K-OMS-2 catalyst using tert-butyl hydroperoxide (TBHP) and H{sub 2}O{sub 2} as the oxidant. Activity of the V{sub 2}O{sub 5}/K-OMS-2 samples was increased considerably with respect to K-OMS-2 catalyst due to the interaction of manganese oxide and V{sub 2}O{sub 5}. The kinetic of benzyl alcohol oxidation using excess TBHP over V{sub 2}O{sub 5}/K-OMS-2 catalyst was investigated at different temperatures and a pseudo-first order reaction was determined with respect to benzyl alcohol. The effects of reaction time, oxidant/alcohol molar ratio, reaction temperature, solvents, catalyst recycling potential and leaching were investigated.

  14. Iron and manganese removal by using manganese ore constructed wetlands in the reclamation of steel wastewater.

    PubMed

    Xu, Jing-Cheng; Chen, Gu; Huang, Xiang-Feng; Li, Guang-Ming; Liu, Jia; Yang, Na; Gao, Sai-Nan

    2009-09-30

    To reclaim treated steel wastewater as cooling water, manganese ore constructed wetland was proposed in this study for the removal of iron and manganese. In lab-scale wetlands, the performance of manganese ore wetland was found to be more stable and excellent than that of conventional gravel constructed wetland. The iron and manganese concentration in the former was below 0.05 mg/L at hydraulic retention time of 2-5 days when their influent concentrations were in the range of 0.16-2.24 mg/L and 0.11-2.23 mg/L, respectively. Moreover, its removals for COD, turbidity, ammonia nitrogen and total phosphorus were 55%, 90%, 67% and 93%, respectively, superior to the corresponding removals in the gravel wetland (31%, 86%, 58% and 78%, respectively). The good performance of manganese ore was ascribed to the enhanced biological manganese removal with the aid of manganese oxide surface and the smaller size of the medium. The presence of biological manganese oxidation was proven by the facts of good manganese removal in wetlands at chemical unfavorable conditions (such as ORP and pH) and the isolation of manganese oxidizing strains from the wetlands. Similar iron and manganese removal was later observed in a pilot-scale gravel-manganese-ore constructed wetland, even though the manganese ore portion in total volume was reduced from 100% (in the lab-scale) to only 4% (in the pilot-scale) for the sake of cost-saving. The quality of the polished wastewater not only satisfied the requirement for cooling water but also suitable as make-up water for other purposes. PMID:19443107

  15. Electrochemical quartz crystal microbalance, voltammetry, spectroelectrochemical, and microscopic studies of adsorption behavior for (7E,7â²Z)-diphenyl-7,7â²-diapocarotene electrochemical oxidation product

    Microsoft Academic Search

    Guoqiang Gao; David B. Wurm; Yeon-Taik Kim; Lowell D. Kispert

    1997-01-01

    Polymeric products, which are formed by reaction of the dications of (7E,7â²Z)-diphenyl-7,7â²-diapocarotene (I) generated by electrochemical oxidation in dichloromethane with the neutral carotenoid, are adsorbed on various electrode surfaces. An apparent average molar mass of 5400 g\\/(mol electrons) was calculated from simultaneous electrochemical quartz crystal microbalance (EQCM) measurements, and the green, fiber-like structure observed by optical microscopy confirms the formation

  16. Evaluation of the low temperature performance of lithium manganese oxide/lithium titanate lithium-ion batteries for start/stop applications

    NASA Astrophysics Data System (ADS)

    Chen, Kebin; Yu, Zhiqiang; Deng, Shawn; Wu, Qiang; Zou, Jianxin; Zeng, Xiaoqin

    2015-03-01

    The start/stop technology requires the battery to provide high cold cranking power at low temperatures. In this report, the low temperature performance of LMO/LTO (lithium manganese oxide/lithium titanate) lithium ion batteries with three different electrolytes were studied on pouch cells incorporated with the reference electrode (RE). Electrochemical impedance spectroscopy (EIS) analysis in conjunction with the reference electrode was applied to unravel the influence of electrolyte and individual electrodes on the battery's low temperature performance. Results demonstrate that it is the LMO electrode that limits the cell discharge performance at -30 °C and an electrolyte with a considerable amount of ester as co-solvent delivers the best low temperature performance. The LMO/LTO battery with the optimal electrolyte passes the U.S. Advanced Battery Consortium (USABC) cold cranking test at -30 °C using an assumed 40 Ah battery pack.

  17. Development of Surface Complexation Models of Cr(VI) Adsorption on Soils, Sediments and Model Mixtures of Kaolinite, Montmorillonite, ?-Alumina, Hydrous Manganese and Ferric Oxides and Goethite

    SciTech Connect

    Koretsky, Carla [Western Michigan University] [Western Michigan University

    2013-11-29

    Hexavalent chromium is a highly toxic contaminant that has been introduced into aquifers and shallow sediments and soils via many anthropogenic activities. Hexavalent chromium contamination is a problem or potential problem in the shallow subsurface at several DOE sites, including Hanford, Idaho National Laboratory, Los Alamos National Laboratory and the Oak Ridge Reservation (DOE, 2008). To accurately quantify the fate and transport of hexavalent chromium at DOE and other contaminated sites, robust geochemical models, capable of correctly predicting changes in chromium chemical form resulting from chemical reactions occurring in subsurface environments are needed. One important chemical reaction that may greatly impact the bioavailability and mobility of hexavalent chromium in the subsurface is chemical binding to the surfaces of particulates, termed adsorption or surface complexation. Quantitative thermodynamic surface complexation models have been derived that can correctly calculate hexavalent chromium adsorption on well-characterized materials over ranges in subsurface conditions, such pH and salinity. However, models have not yet been developed for hexavalent chromium adsorption on many important constituents of natural soils and sediments, such as clay minerals. Furthermore, most of the existing thermodynamic models have been developed for relatively simple, single solid systems and have rarely been tested for the complex mixtures of solids present in real sediments and soils. In this study, the adsorption of hexavalent chromium was measured as a function of pH (3-10), salinity (0.001 to 0.1 M NaNO3), and partial pressure of carbon dioxide(0-5%) on a suite of naturally-occurring solids including goethite (FeOOH), hydrous manganese oxide (MnOOH), hydrous ferric oxide (Fe(OH)3), ?-alumina (Al2O3), kaolinite (Al2Si2O5(OH)4), and montmorillonite (Na3(Al, Mg)2Si4O10(OH)2?nH2O). The results show that all of these materials can bind substantial quantities of hexavalent chromium, especially at low pH. Unexpectedly, experiments with the clay minerals kaolinite and montmorillonite suggest that hexavalent chromium may interact with these solids over much longer periods of time than expected. Furthermore, hexavalent chromium may irreversibly bind to these solids, perhaps because of oxidation-reduction reactions occurring on the surfaces of the clay minerals. More work should be done to investigate and quantify these chemical reactions. Experiments conducted with mixtures of goethite, hydrous manganese oxide, hydrous ferric oxide, ?-alumina, montmorillonite and kaolinite demonstrate that it is possible to correctly predict hexavalent chromium binding in the presence of multiple minerals using thermodynamic models derived for the simpler systems. Further, these models suggest that of the six solid considered in this study, goethite is typically the solid to which most of the hexavalent chromium will bind. Experiments completed with organic-rich and organic-poor natural sediments demonstrate that in organic-rich substrates, organic matter is likely to control uptake of the hexavalent chromium. The models derived and tested in this study for hexavalent chromium binding to ?-alumina, hydrous manganese oxide, goethite, hydrous ferric oxide and clay minerals can be used to better predict changes in hexavalent chromium bioavailability and mobility in contaminated sediments and soils.

  18. Caspase-3-dependent proteolytic cleavage of protein kinase Cdelta is essential for oxidative stress-mediated dopaminergic cell death after exposure to methylcyclopentadienyl manganese tricarbonyl.

    PubMed

    Anantharam, Vellareddy; Kitazawa, Masashi; Wagner, Jarrad; Kaul, Siddharth; Kanthasamy, Anumantha G

    2002-03-01

    In the present study, we characterized oxidative stress-dependent cellular events in dopaminergic cells after exposure to an organic form of manganese compound, methylcyclopentadienyl manganese tricarbonyl (MMT). In pheochromocytoma cells, MMT exposure resulted in rapid increase in generation of reactive oxygen species (ROS) within 5--15 min, followed by release of mitochondrial cytochrome C into cytoplasm and subsequent activation of cysteine proteases, caspase-9 (twofold to threefold) and caspase-3 (15- to 25-fold), but not caspase-8, in a time- and dose-dependent manner. Interestingly, we also found that MMT exposure induces a time- and dose-dependent proteolytic cleavage of native protein kinase Cdelta (PKCdelta, 72-74 kDa) to yield 41 kDa catalytically active and 38 kDa regulatory fragments. Pretreatment with caspase inhibitors (Z-DEVD-FMK or Z-VAD-FMK) blocked MMT-induced proteolytic cleavage of PKCdelta, indicating that cleavage is mediated by caspase-3. Furthermore, inhibition of PKCdelta activity with a specific inhibitor, rottlerin, significantly inhibited caspase-3 activation in a dose-dependent manner along with a reduction in PKCdelta cleavage products, indicating a possible positive feedback activation of caspase-3 activity by PKCdelta. The presence of such a positive feedback loop was also confirmed by delivering the catalytically active PKCdelta fragment. Attenuation of ROS generation, caspase-3 activation, and PKCdelta activity before MMT treatment almost completely suppressed DNA fragmentation. Additionally, overexpression of catalytically inactive PKCdelta(K376R) (dominant-negative mutant) prevented MMT-induced apoptosis in immortalized mesencephalic dopaminergic cells. For the first time, these data demonstrate that caspase-3-dependent proteolytic activation of PKCdelta plays a key role in oxidative stress-mediated apoptosis in dopaminergic cells after exposure to an environmental neurotoxic agent. PMID:11880503

  19. Using amorphous manganese oxide for remediation of smelter-polluted soils: a pH-dependent long-term stability study

    NASA Astrophysics Data System (ADS)

    Ettler, Vojtech; Tomasova, Zdenka; Komarek, Michael; Mihaljevic, Martin; Sebek, Ondrej

    2015-04-01

    In soil systems, manganese (Mn) oxides are commonly found to be powerful sorbents of metals and metalloids and are thus potentially useful in soil remediation. A novel amorphous manganese oxide (AMO) and a Pb smelter-polluted agricultural soil amended with the AMO and incubated for 2 and 6 months were subjected to a pH-static leaching procedure (pH = 3 - 8) to verify the chemical stabilization effect on metals and metalloids. The AMO stability in pure water was pH-dependent with the highest Mn release at pH 3 (47% dissolved) and the lowest at pH 8 (0.14% dissolved). Secondary rhodochrosite (MnCO3) was formed at the AMO surfaces at pH > 5. The AMO dissolved significantly less after 6 months of incubation. Sequential extraction analysis indicated that "labile" fraction of As, Pb and Sb in soil significantly decreased after AMO amendment. The pH-static experiments indicated that no effect on leaching was observed for Cd and Zn after AMO treatments, whereas the leaching of As, Cu, Pb and Sb decreased down to 20%, 35%, 7% and 11% of the control, respectively. The remediation efficiency was more pronounced under acidic conditions and the time of incubation generally led to increased retention of the targeted contaminants. The AMO was found to be a promising agent for the chemical stabilization of polluted soils and other in situ applications need to be evaluated. This study was supported by the Czech Science Foundation (GA?R 15-07117S).

  20. Determination of chemical oxygen demand values by a photocatalytic oxidation method using nano-TiO2 film on quartz.

    PubMed

    Li, Jiaqing; Li, Luoping; Zheng, Lei; Xian, Yuezhong; Jin, Litong

    2006-01-15

    A COD measurement by a photocatalytic oxidation method using nano-TiO(2) film was investigated. K(2)Cr(2)O(7) was added into the solution to enhance the efficiency of photocatalytic degradation, and simultaneously K(2)Cr(2)O(7) was reduced to Cr(III) by photogenerated electrons, which were adsorbed on the surface of TiO(2). The measuring principle was based on direct determination of Cr(III) concentration which was proportional to the COD value. Under the optimized experiment condition, the application range was 20-500 mgl(-1), and the detection limit was 20 mgl(-1). The immobilization of photocatalyst on the supports could not only solve the problem of low recovery of the catalyst and hard separation from the solution, but also overcome its shortcoming of poor stability. Applied this method to the determination of real samples, it was found to be rapid and environmentally friendly. Additionally, the method proposed above for determination of COD was in excellent correspondence with values obtained by using the conventional method. PMID:18970388

  1. A photo-oxidation procedure using UV radiation/H 2O 2 for decomposition of wine samples — Determination of iron and manganese content by flame atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    dos Santos, Walter N. L.; Brandão, Geovani C.; Portugal, Lindomar A.; David, Jorge M.; Ferreira, Sérgio L. C.

    2009-06-01

    This paper proposes the use of photo-oxidation with UV radiation/H 2O 2 as sample pretreatment for the determination of iron and manganese in wines by flame atomic absorption spectrometry (FAAS). The optimization involved the study of the following variables: pH and concentration of buffer solution, concentrated hydrogen peroxide volume and irradiation time. The evaluation of sample degradation was monitored by measuring the absorbance at the maximum wavelength of red wine (530 nm). Using the experimental conditions established during the optimization (irradiation time of 30 min, oxidant volume of 2.5 mL, pH 10, and a buffer concentration of 0.15 mol L - 1 ), this procedure allows the determination of iron and manganese with limits of detection of 30 and 22 ?g L - 1 , respectively, for a 5 mL volume of digested sample. The precision levels, expressed as relative standard deviation (RSD), were 2.8% and 0.65% for iron and 2.7% and 0.54% for manganese for concentrations of 0.5 and 2.0 mg L - 1 , respectively. Addition/recovery tests for evaluation of the accuracy were in the ranges of 90%-111% and 95%-107% for iron and manganese, respectively. This digestion procedure has been applied for the determination of iron and manganese in six wine samples. The concentrations varied from 1.58 to 2.77 mg L - 1 for iron and from 1.30 to 1.91 mg L - 1 for manganese. The results were compared with those obtained by an acid digestion procedure and determination of the elements by FAAS. There was no significant difference between the results obtained by the two methods based on a paired t-test (at 95% confidence level).

  2. Carbon deposition from a ?-irradiated CO 2/CO/CH 4/C 2H 6 gas mixture on the manganese oxides MnO, Mn 3O 4 and Mn 2O 3

    NASA Astrophysics Data System (ADS)

    Allen, G. C.; Hallam, K. R.

    1997-12-01

    The composition of oxides formed on steel surfaces within power reactors may influence heat transfer efficiency. Previous studies have indicated that carbon is deposited on spinal-type oxides containing manganese, iron, cobalt, nickel and chromium. In this investigation, characterised manganese oxides have been subjected to ?-irradiation under conditions similar to those experienced in reactors in an effort to understand the catalytic processes involved in deposit initiation and growth. Mn 3O 4 and Mn 2O 3, under the conditions present in the ?-cell, were reduced to MnO during the time of exposure. Relative carbon deposition rates were observed to follow the trend MnO>Mn 3O 4?Mn 2O 3.

  3. Synthesis and determination of manganese carbonate and manganese-54 carbonate

    SciTech Connect

    King, B.D.; Lassiter, J.W.; Neathery, M.W.; Miller, W.J.

    1980-04-01

    A method was developed by which radioactive manganese, manganese-54 carbonate could be produced. This was accomplished by reacting manganese-54 chloride, manganese chloride tetrahydrate, and sodium bicarbonate. This reaction produced manganese-54 carbonate mixed with stable manganese. The purity of the manganese carbonate (manganese-54 carbonate) was determined by the use of x-ray diffraction methods. All material was the carbonate form of manganese (manganese-54 carbonate).

  4. 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

    NASA Astrophysics Data System (ADS)

    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 (e.g., Tanaka et al., 2010, Loges et al., 2012). Our experimental results demonstrate that biogenic organic ligands such as hydroxamate siderophores, may produce solutions with positive Ce anomaly (Bau et al., 2013) and may even counteract the surface oxidation of Ce on Mn (hydr)oxides. References Bau, M., Tepe, N., Mohwinkel, D., 2013. Siderophore-promoted transfer of rare earth elements and iron from volcanic ash into glacial meltwater, river and ocean water. Earth Planet. Sci. Lett. 364, 30-36. Christenson E. A. and Schijf J. (2011) Stability of YREE complexes with the trihydroxamate siderophore desferrioxamine B at seawater ionic strength. Geochim. Cosmochim. Acta 75, 7047-7062. Loges, A., Wagner, T., Barth, M., Bau, M., Göb, S., and Markl, G. 2012. Negative Ce anomalies in Mn oxides: The role of Ce4+ mobility during water-mineral interaction. Geochimica and Cosmochimica Acta 86, 296-317 Ohta A. and Kawabe I. (2001) REE (III) adsorption onto Mn dioxide (delta-MnO2) and Fe oxyhydroxide: Ce(III) oxidation by delta-MnO2. Geochim. Cosmochim. Acta 65, 695-703. Tanaka K., Tani Y., Takahashi Y., Tanimizu M., Suzuki Y., Kozai N. and Ohnuki T. (2010) A specific Ce oxidation process during sorption of rare earth elements on biogenic Mn oxide produced by Acremonium sp. strain KR21-2. Geochim. Cosmochim. Acta 74, 5463-5477.

  5. Bacteriology of Manganese Nodules

    PubMed Central

    Ehrlich, H. L.

    1968-01-01

    A cell-free extract from Arthrobacter 37, isolated from a manganese nodule from the Atlantic Ocean, exhibited enzymatic activity which accelerated manganese accretion to synthetic Mn-Fe oxide as well as to crushed manganese nodule. The reaction required oxygen and was inhibited by HgCl2 and p-chloromercuribenzoate but not by Atebrine dihydrochloride. The rate of enzymatic action depended on the concentration of cell-free extract used. The enzymatic activity had a temperature optimum around 17.5 C and was destroyed by heating at 100 C. The amount of heat required for inactivation depended on the amount of nucleic acid in the preparation. In the cell-free extract, unlike the whole-cell preparation, peptone could not substitute for NaHCO3 in the reaction mixture. An enzyme-containing protein fraction and a nucleic acid fraction could be separated from cell extract by gel filtration, when prepared in 3% NaCl but not in seawater. The nucleic acid fraction was not required for enzymatic activity. PMID:5645405

  6. Concretionary manganese-iron oxides in streams and their usefulness as a sample medium for geochemical prospecting

    USGS Publications Warehouse

    Nowlan, G.A.

    1976-01-01

    Correlation studies of 400 samples of sieved stream sediments and 325 samples of fluvial, concretionary Mn-Fe oxides from Maine resulted in the separation of elements into the following categories: (1) elements not scavenged by Mn-Fe oxides - B, Cr, K, Mg, Rb, Sc, Ti, V, and Zr; (2) elements probably not scavenged by Mn-Fe oxides - Ag, Be, Ca, Ga, La, Sb, and Y; (3) elements scavenged weakly by Mn-Fe oxides - Cu, Mo, Pb, and Sr; (4) elements scavenged strongly by Mn oxides - Ba, Cd, Co, Ni, Tl, and Zn; and (5) elements scavenged strongly by Fe oxides - As and In. Studies of the scavenged elements showed that the deviation from the mean is characteristically greater in oxide samples as compared to sieved sediments from the same locality. However, a significant increase in contrast between anomalous and background localities, when oxides are the sample medium, more than offsets the disadvantage of data scatter. The use of oxides as a sampling medium clearly and significantly accentuates anomalous localities. In general, non-ratioed data on oxides give very nearly the same results as data consisting of scavenged elements ratioed to Mn and Fe. However, ratioed data expand the geographic area of specific anomalies. Cd and Zn consistently show strong correlations with concretionary Mn-Fe oxides, but their concentrations in the oxides do not generally show as much contrast between anomalous and background localities as do Cu, Mo, and Pb. These latter elements are strongly scavenged where rocks are mineralized. ?? 1976.

  7. Pulmonary inflammation in rats after intratracheal instillation of quartz, amorphous SiO2, carbon black, and coal dust and the influence of poly-2-vinylpyridine-N-oxide (PVNO).

    PubMed

    Ernst, Heinrich; Rittinghausen, Susanne; Bartsch, Wilfried; Creutzenberg, Otto; Dasenbrock, Clemens; Görlitz, Bernd-Detlef; Hecht, Matthias; Kairies, Ulf; Muhle, Hartwig; Müller, Meike; Heinrich, Uwe; Pott, Friedrich

    2002-08-01

    Effects of poly-2-vinylpyridine-N-oxide (PVNO) were investigated in numerous in vivo and in vitro studies published in the nineteen sixties and seventies. These studies showed that PVNO inhibited development of fibrosis from quartz dust and improved lung clearance of quartz after inhalation exposure. Ameliorating effects of PVNO were observed also for pulmonary damage from colloidal SiO2 and organic substances, and the fibrogenic inflammation caused by carrageenan. Although it is not proven that silicosis is a precondition for quartz-induced lung tumours, we investigated the hypothesis that PVNO could reduce the lung tumour risk from quartz in rats. A carcinogenicity study was therefore started in rats with the main focus on the quantitative relationships among pulmonary inflammation, fibrosis and neoplasia caused by intratracheal instillation of 3 mg quartz DQ 12 with or without additional subcutaneous PVNO treatment. Other study groups were treated with multiple dust instillations, i.e. 30 instillations of 0.5 mg amorphous SiO2 at intervals of 2 weeks, 10 instillations of 0.5 mg of ultrafine carbon black or 1 mg coal at weekly intervals. The analyses of the bronchoalveolar lavage fluid (BALF) 9 months after start of the life-time study showed that the aim of producing similar levels of increased enzyme concentrations in the four groups treated with quartz/PVNO, amorphous SiO2, carbon black and coal was achieved. A 2.5- to 7.7-fold increase for lactate dehydrogenase (LDH), total protein, alkaline phosphatase and gamma-glutamyl transferase (gamma-GT) was found in these groups as compared to the control. In contrast, quartz treatment without PVNO increased the LDH level up to 24-fold and of total protein to 13-fold. However, the cell counts in the BALF were not so much different in all five groups, i.e. quartz without PVNO (leukocytes: 480.000, PMN: 190.000), quartz with PVNO (leukocytes: 300.000, PMN: 100.000), amorphous SiO2 (leukocytes: 570.000, PMN: 315.000), carbon black (leukocytes: 390.000, PMN: 150.000) and coal (leukocytes: 200.000, PMN: 65.000). Histopathological investigations after four weeks and three months revealed that the used PVNO sample was active in the quartz and amorphous SiO2 groups and markedly reduced the incidences or severity of several pulmonary changes such as macrophage accumulation, inflammatory cell infiltration, interstitial fibrosis, bronchiolo-alveolar hyperplasia, alveolar lipoproteinosis and amorphous SiO2 -induced granulomatous alveolitis/interstitial fibrotic granulomas. Also in the lung-associated lymph nodes (LALN), PVNO treatment significantly reduced the incidence and severity of inflammation in both quartz and amorphous SiO2 groups as evidenced by the presence of well-circumscribed aggregates of intact particle-laden macrophages without signs of degeneration and accompanying granulocytic infiltration and fibrosis. Immunological investigations at the 9 months timepoint on the in vitro production of reactive nitrogen (RNI) or oxygen (ROI) intermediates and tumour necrosis factor (TNF-alpha) from BALF-derived cells indicated a diminished responsiveness to LPS in all particle treatment groups. A diminished production of ROI was also found in the quartz, carbon black, and coal dust groups, respectively, as compared to the values seen in the quartz/PVNO- and amorphous SiO2 treated groups. Treatment with quartz plus PVNO restored the capability of the cells to respond to LPS as compared to the treatment with quartz alone. TNF-alpha production was diminished in the groups treated with quartz, carbon black, and coal dust alone whereas in the quartz/PVNO- and amorphous SiO2-treated groups an elevated TNF-alpha production was seen. These results led to the conclusion that only amorphous SiO2 did not affect the "normal" ability of the cells to respond to LPS and that PVNO protected the cells from a toxic effect of the quartz particles. PMID:12211632

  8. The impact of partial manganese superoxide dismutase (SOD2)-deficiency on mitochondrial oxidant stress, DNA fragmentation and liver injury during acetaminophen hepatotoxicity

    SciTech Connect

    Ramachandran, Anup; Lebofsky, Margitta [Department of Pharmacology, Toxicology and Therapeutics, University of Kansas Medical Center, 3901 Rainbow Blvd, MS 1018, Kansas City, KS 66160 (United States); Weinman, Steven A. [Department of Medicine and Microbiology and Immunology, University of Kansas Medical Center, Kansas City, KS 66160 (United States); Jaeschke, Hartmut, E-mail: hjaeschke@kumc.edu [Department of Pharmacology, Toxicology and Therapeutics, University of Kansas Medical Center, 3901 Rainbow Blvd, MS 1018, Kansas City, KS 66160 (United States)

    2011-03-15

    Acetaminophen (APAP) hepatotoxicity is the most frequent cause of acute liver failure in many countries. The mechanism of cell death is initiated by formation of a reactive metabolite that binds to mitochondrial proteins and promotes mitochondrial dysfunction and oxidant stress. Manganese superoxide dismutase (SOD2) is a critical defense enzyme located in the mitochondrial matrix. The objective of this investigation was to evaluate the functional consequences of partial SOD2-deficiency (SOD2+/-) on intracellular signaling mechanisms of necrotic cell death after APAP overdose. Treatment of C57Bl/6J wild type animals with 200 mg/kg APAP resulted in liver injury as indicated by elevated plasma alanine aminotransferase activities (2870 {+-} 180 U/L) and centrilobular necrosis at 6 h. In addition, increased tissue glutathione disulfide (GSSG) levels and GSSG-to-GSH ratios, delayed mitochondrial GSH recovery, and increased mitochondrial protein carbonyls and nitrotyrosine protein adducts indicated mitochondrial oxidant stress. In addition, nuclear DNA fragmentation (TUNEL assay) correlated with translocation of Bax to the mitochondria and release of apoptosis-inducing factor (AIF). Furthermore, activation of c-jun-N-terminal kinase (JNK) was documented by the mitochondrial translocation of phospho-JNK. SOD2+/- mice showed 4-fold higher ALT activities and necrosis, an enhancement of all parameters of the mitochondrial oxidant stress, more AIF release and more extensive DNA fragmentation and more prolonged JNK activation. Conclusions: the impaired defense against mitochondrial superoxide formation in SOD2+/- mice prolongs JNK activation after APAP overdose and consequently further enhances the mitochondrial oxidant stress leading to exaggerated mitochondrial dysfunction, release of intermembrane proteins with nuclear DNA fragmentation and more necrosis.

  9. Stability and Rate Capability of Al Substituted Lithium-Rich High-Manganese Content Oxide Materials for Li-Ion Batteries

    SciTech Connect

    Li, Zheng; Chernova, Natasha A.; Feng, Jijun; Upreti, Shailesh; Omenya, Fredrick; Whittingham, M. Stanley (SUNY-Binghamton)

    2012-03-15

    The structures, electrochemical properties and thermal stability of Al-substituted lithium-excess oxides, Li{sub 1.2}Ni{sub 0.16} Mn{sub 0.56}Co{sub 0.08-y}Al{sub y}O{sub 2} (y = 0, 0.024, 0.048, 0.08), are reported, and compared to the stoichiometric compounds, LiNi{sub z}Mn{sub z}Co{sub 1-2z}O{sub 2}. A solid solution was found up to at least y = 0.06. Aluminum substitution improves the poor thermal stability while preserving the high energy density of lithium-excess oxides. However, these high manganese compositions are inferior to the lithium stoichiometric materials, LiNi{sub z}Mn{sub z}Co{sub 1-2z}O{sub 2} (z = 0.333, 0.4), in terms of both power and thermal stability.

  10. Effect of Thermal Annealing on the Structural and Optical Properties Nanostructured Cobalt-Manganese and Cobalt-Nickel Oxides Prepared by Co-Precipitation

    NASA Astrophysics Data System (ADS)

    Indulal, C. R.; Kumar, G. Sajeev; Vaidyan, A. V.; Raveendran, R.

    2011-10-01

    Cobalt-Manganese and Cobalt-Nickel oxide (CoMnO and CoNiO) nanoparticles were synthesized via chemical co-precipitation method by decomposition of their respective metal sulfides and sodium carbonate using ethylene diamene tetra acetic acid as the capping agent. The samples were heated at 400, 600 and 800 °C. The average particle sizes were determined from the X-ray line broadening. The diffractogram were compared with JCPDS data to identify the crystallographic phase and cubic structure of the particles. The samples were characterized by XRD, FTIR and UV analyses. The internal elastic micro strains were calculated and it was seen that as the particle size increases strain decreases. The FTIR studies have been used to confirm the metal oxide formation. The chemical compositions of the samples were verified using EDX spectra. The surface morphologies of the samples were studied from the SEM images. The absorption spectra of the materials in the UV-Vis-NIR range were recorded. From the analysis of the absorption spectra, the direct band gaps of the materials were calculated.

  11. Synthesis and determination of manganese carbonate and manganese-54 carbonate

    Microsoft Academic Search

    B. D. King; J. W. Lassiter; M. W. Neathery; W. J. Miller

    1980-01-01

    A method was developed by which radioactive manganese, manganese-54 carbonate could be produced. This was accomplished by reacting manganese-54 chloride, manganese chloride tetrahydrate, and sodium bicarbonate. This reaction produced manganese-54 carbonate mixed with stable manganese. The purity of the manganese carbonate (manganese-54 carbonate) was determined by the use of x-ray diffraction methods. All material was the carbonate form of manganese

  12. The reduction and oxidation of cationic carbonyl complexes of manganese with phosphoniodithioformate: X-ray crystal structure of [Mn(CO) 4(S 2CPCy 3)]ClO 4

    Microsoft Academic Search

    Gabino A. Carriedo; Julio A. Pérez-Martínez; Daniel Miguel; Víctor Riera; Santiago García-Granda; Enrique Pérez-Carreño

    1996-01-01

    Manganese carbonyl complexes of the types behaviour have been studied by cyclic voltammetry and controlled potential electrolysis, showing that they undergo one-electron reduction and one-electron oxidation at potentials that depend mainly on the number of carbonyls. The results have been explained on the basis on an MO study at an EH level carried out on the model complexes [Mn(CO)4(S2CPH3)]+ (1b),

  13. Microwave-assisted synthesis of La 1? x B x MnO 3.15 (B = Sr, Ag; x = 0 or 0.2) via manganese oxides susceptors and their activity in methane combustion

    Microsoft Academic Search

    A. Kaddouri; S. Ifrah

    2006-01-01

    La1?xBxMnO3.15 perovskites (B=Sr, Ag; x=0 or 0.2) were synthesised from metal nitrates in a short time (ca. 15min) using microwave irradiation. The manganese oxides formed, after metal nitrates decomposition, are efficient microwave receptors and absorb energy strongly at 2450MHz (microwave frequency). This absorption increased the microwave power loss in the material and led to local heating which provided the necessary

  14. Geodynamic and climate controls in the formation of Mio-Pliocene world-class oxidized cobalt and manganese ores in the Katanga province, DR Congo

    NASA Astrophysics Data System (ADS)

    Decrée, Sophie; Deloule, Étienne; Ruffet, Gilles; Dewaele, Stijn; Mees, Florias; Marignac, Christian; Yans, Johan; de Putter, Thierry

    2010-10-01

    The Katanga province, Democratic Republic of Congo, hosts world-class cobalt deposits accounting for ~50% of the world reserves. They originated from sediment-hosted stratiform copper and cobalt sulfide deposits within Neoproterozoic metasedimentary rocks. Heterogenite, the main oxidized cobalt mineral, is concentrated as “cobalt caps” along the top of silicified dolomite inselbergs. The supergene cobalt enrichment process is part of a regional process of residual ore formation that also forms world-class “manganese cap” deposits in western Katanga, i.e., the “black earths” that are exploited by both industrial and artisanal mining. Here, we provide constraints on the genesis and the timing of these deposits. Ar-Ar analyses of oxidized Mn ore and in situ U-Pb SIMS measurements of heterogenite yield Mio-Pliocene ages. The Ar-Ar ages suggest a multi-phase process, starting in the Late Miocene (10-5 Ma), when the metal-rich substratum was exposed to the action of meteoric fluids, due to major regional uplift. Further oxidation took place in the Pliocene (3.7-2.3 Ma) and formed most of the observed deposits under humid conditions: Co- and Mn-caps on metal-rich substrata, and coeval Fe laterites on barren areas. These deposits formed prior to the regional shift toward more arid conditions in Central Africa. Arid conditions still prevailed during the Quaternary and resulted in erosion and valley incision, which dismantled the metal-bearing caps and led to ore accumulation in valleys and along foot slopes.

  15. Induced oxidative stress and activated expression of manganese superoxide dismutase during hepatitis C virus replication: role of JNK, p38 MAPK and AP-1.

    PubMed Central

    Qadri, Ishtiaq; Iwahashi, Mieko; Capasso, Juan M; Hopken, Matthew W; Flores, Sonia; Schaack, Jerome; Simon, Francis R

    2004-01-01

    Activation of cellular kinases and transcription factors mediates the early phase of the cellular response to chemically or biologically induced stress. In the present study we investigated the oxidant/antioxidant balance in Huh-7 cells expressing the HCV (hepatitis C virus) subgenomic replicon, and observed a 5-fold increase in oxidative stress during HCV replication. We used MnSOD (manganese-superoxide dismutase) as an indicator of the cellular antioxidant response, and found that its activity, protein levels and promoter activity were significantly increased, whereas Cu/ZnSOD was not affected. The oxidative stress-induced protein kinases p38 MAPK (mitogen-activated protein kinase) and JNK (c-Jun N-terminal kinase) were activated in the HCV repliconcontaining cells and in Huh-7 cells transduced with Ad-NS5A [a recombinant adenovirus encoding NS5A (non-structural protein 5A)], coupled with a 4-5-fold increase in AP-1 (activator protein-1) DNA binding. Ava.1 cells, which encode a replication-defective HCV replicon, showed no significant changes in MnSOD, p38 MAPK or JNK activity. The AP-1 inhibitors dithiothreitol and N -acetylcysteine, as well as a dominant negative AP-1 mutant, significantly reduced AP-1 activation, demonstrating that this activation is oxidative stress-related. Exogenous NS5A had no effect on AP-1 activation in vitro, suggesting that NS5A acts at the upstream targets of AP-1 involving p38 MAPK and JNK signalling cascades. AP-1-dependent gene expression was increased in HCV subgenomic replicon-expressing Huh-7 cells. MnSOD activation was blocked by inhibitors of JNK (JNKI1) and p38 MAPK (SB203580), but not by an ERK (extracellular-signal-regulated kinase) inhibitor (U0126), in HCV-replicating and Ad-NS5A-transduced cells. Our results demonstrate that cellular responses to oxidative stress in HCV subgenomic replicon-expressing and Ad-NS5A-transduced cells are regulated by two distinct signalling pathways involving p38 MAPK and JNK via AP-1 that is linked to increased oxidative stress and therefore to an increased antioxidant MnSOD response. PMID:14670077

  16. Characteristics of manganese-coated sand using SEM and EDAX analysis

    Microsoft Academic Search

    Po-Yu Hu; Yung-Hsu Hsieh; Jen-Ching Chen; Chen-Yu Chang

    2004-01-01

    “Manganese-coated sand” is a type of silica medium coated with manganese oxides, formed from the sorption of manganese oxides during long-term filtration via the process of rapid sand filtration, followed by aeration in a water treatment plant. Locally available manganese-coated sand, both for packing and as a byproduct of filtration processes for water treatment plants in Taiwan, was found to

  17. Abstract Dormant spores of the marine Bacillus sp. strain SG-1 catalyze the oxidation of manganese(II),

    E-print Network

    Tebo, Brad

    transformation and transposon mutagenesis were developed in SG-1 (van Waasbergen et al. 1993). By generating transposon mutants which pro- duced spores incapable of oxidizing Mn(II), a cluster of seven genes involved

  18. 3- and 4-Pyridinecarboxylic acid N -oxide complexes with manganese(II), cobalt(II) and nickel(II) chlorides

    Microsoft Academic Search

    Larry S. Gelfand; Louis L. Pytlewski; Chester M. Mikulski; Anthony N. Speca; Nicholas M. Karayannis

    1979-01-01

    During interaction of ethanol-triethyl orthoformate solutions of nicotinic or isonicotinic acidN-oxides (LH and L'H, respectively) with MCl2 (M = Mn, Co, Ni), only one true adduct, of the Ni(LH)3Cl2 · 2 H2O type was obtained. In all other cases, partial substitution of Cl- ions with the corresponding pyridinecarboxylateN-oxide anionic ligands (L or L') occurred. As a result, mixed ligands (LH-L

  19. UNIVERSITY OF CALIFORNIA, SAN DIEGO Microbial Manganese(II) Oxidation: Biogeochemistry of a Deep-Sea Hydrothermal

    E-print Network

    Dick, Christopher

    .2. Control dMn removal experiments 64 Table 3.3. Effects of copper additions on dMn Removal 65 Table 4;vii List of Tables Table 2.1. Mn(II)-oxidizing Bacillus strains used in this study 32 Table 2.2. Plate counts of Mn(II)-oxidizing bacteria 33 Table 3.1. Summary of dMn removal rate measurements 63 Table 3

  20. Characterization of carbon paste electrodes modified with manganese based perovskites-type oxides from the amperometric determination of hydrogen peroxide

    Microsoft Academic Search

    Guillermina L. Luque; Nancy F. Ferreyra; A. Gabriela Leyva; Gustavo A. Rivas

    2009-01-01

    This work proposes the amperometric determination of hydrogen peroxide reduction and oxidation as a tool for the characterization of La1?xAxMnO3 perovskites dispersed in a graphite composite electrode (carbon paste electrode, CPE). The catalytic activity of perovskites towards the oxidation and reduction of hydrogen peroxide is highly dependent on the nature of the A cation and on the temperature and time

  1. Low activity of manganese superoxide dismutase (MnSOD) in blood of lung cancer patients with smoking history: relationship to oxidative stress.

    PubMed

    Margaret, Ay Ly; Syahruddin, Elisna; Wanandi, Septelia Inawati

    2011-01-01

    Lung cancer is the primary cause of cancer death in the world. Although it is well established that tobacco smoke causes lung cancer, not all smokers develop lung cancer. Manganese superoxide dismutase (MnSOD), a major determinant of antioxidants in matrix mitochondria, plays a pivotal role in eliminating anion superoxide free radical generated from the tobacco smoke. The aim of this study was to analyze the enzyme activity of MnSOD in blood of lung cancer patients with a smoking history in relationship to oxidative stress. Samples were taken from leukocyte cells of 20 lung cancer patients in Persahabatan Hospital Jakarta. Control groups included 50 healthy smokers and 50 non smokers, all aged over 40 years. The MnSOD activity determined biochemically based on the inhibition of xanthin oxidase, of lung cancer patients was lower than the control group's (p<0.001). Plasma MDA levels, determined by reaction with thiobarbituric acid (TBA), were not significantly different (p=0.479), whereas plasma carbonyl levels were elevated (p=0.003). Free radical production in lung cancer patients thus appeared high. Smoker controls also tended to exhibit lower MnSOD and higher carbonyl radicals than their non-smoking counterparts. Continue cigarette smoke exposure may increase production of ROS and bring about a reduction of MnSOD, which could play a role in lung cancer development. PMID:22393988

  2. AFM Nanolithography of Lanthanum Barium Manganese Oxide (LaBaMnO3)Thin Films: The Effect of Oxygen Pressure Variations During Film Growth

    NASA Astrophysics Data System (ADS)

    Stumpf, Christoper; Schaefer, David; Kolagani, Rajeswari; Yong, Grace; Warecki, Zoey

    2014-03-01

    In AFM nanolithography, a bias voltage applied between the tip of an atomic force microscope (AFM) and a sample is used to produce nanoscale modifications of material surfaces. AFM nanolithography has been studied extensively on a variety of materials, but limited studies have been performed on perovskite manganites such as Lanthanum Barium Manganese Oxide (LBMO). Studying such materials is important because of their potential applications for room-temperature nanoscale spintronic devices. Previous research on LBMO by our group has focused on how parameters such as applied tip voltage, temperature, and humidity affect the creation of nanopatterns. This paper reports on the influence of growth pressure of the LBMO films grown by pulsed laser deposition. Films grown on (100) SrTiO3 were studied for growth pressures ranging between 100 mTorr to 400 mTorr. Our studies indicate that the type of nanopatterns induced by AFM and the relaxation dynamics of these patterns are sensitive to the film growth pressure. The growth pressure is mainly known to affect the oxygen concentration and the surface roughness, but possible variations in cationic stoichiometry could also contribute to these results. RK and GY acknowledge support from the National Science Foundation Grant ECCS 1128586.

  3. The Manganese Site of the Photosynthetic Water-Splitting Enzyme

    NASA Astrophysics Data System (ADS)

    George, Graham N.; Prince, Roger C.; Cramer, Stephen P.

    1989-02-01

    As the originator of the oxygen in our atmosphere, the photosynthetic water-splitting enzyme of chloroplasts is vital for aerobic life on the earth. It has a manganese cluster at its active site, but it is poorly understood at the molecular level. Polarized synchrotron radiation was used to examine the x-ray absorption of manganese in oriented chloroplasts. The manganese site, in the ``resting'' (S1) state, is an asymmetric cluster, which probably contains four manganese atoms, with interatomic separations of 2.7 and 3.3 angstroms; the vector formed by the 3.3-angstrom manganese pair is oriented perpendicular to the membrane plane. Comparisons with model compounds suggest that the cluster contains bridging oxide or hydroxide ligands connecting the manganese atoms, perhaps with carboxylate bridges connecting the 3.3-angstrom manganese pair.

  4. Surface Mn(II) oxidation actuated by a multicopper oxidase in a soil bacterium leads to the formation of manganese oxide minerals.

    PubMed

    Zhang, Zhen; Zhang, Zhongming; Chen, Hong; Liu, Jin; Liu, Chang; Ni, Hong; Zhao, Changsong; Ali, Muhammad; Liu, Fan; Li, Lin

    2015-01-01

    In this manuscript, we report that a bacterial multicopper oxidase (MCO266) catalyzes Mn(II) oxidation on the cell surface, resulting in the surface deposition of Mn(III) and Mn(IV) oxides and the gradual formation of bulky oxide aggregates. These aggregates serve as nucleation centers for the formation of Mn oxide micronodules and Mn-rich sediments. A soil-borne Escherichia coli with high Mn(II)-oxidizing activity formed Mn(III)/Mn(IV) oxide deposit layers and aggregates under laboratory culture conditions. We engineered MCO266 onto the cell surfaces of both an activity-negative recipient and wild-type strains. The results confirmed that MCO266 governs Mn(II) oxidation and initiates the formation of deposits and aggregates. By contrast, a cell-free substrate, heat-killed strains, and intracellularly expressed or purified MCO266 failed to catalyze Mn(II) oxidation. However, purified MCO266 exhibited Mn(II)-oxidizing activity when combined with cell outer membrane component (COMC) fractions in vitro. We demonstrated that Mn(II) oxidation and aggregate formation occurred through an oxygen-dependent biotic transformation process that requires a certain minimum Mn(II) concentration. We propose an approximate electron transfer pathway in which MCO266 transfers only one electron to convert Mn(II) to Mn(III) and then cooperates with other COMC electron transporters to transfer the other electron required to oxidize Mn(III) to Mn(IV). PMID:26039669

  5. Surface Mn(II) oxidation actuated by a multicopper oxidase in a soil bacterium leads to the formation of manganese oxide minerals

    PubMed Central

    Zhang, Zhen; Zhang, Zhongming; Chen, Hong; Liu, Jin; Liu, Chang; Ni, Hong; Zhao, Changsong; Ali, Muhammad; Liu, Fan; Li, Lin

    2015-01-01

    In this manuscript, we report that a bacterial multicopper oxidase (MCO266) catalyzes Mn(II) oxidation on the cell surface, resulting in the surface deposition of Mn(III) and Mn(IV) oxides and the gradual formation of bulky oxide aggregates. These aggregates serve as nucleation centers for the formation of Mn oxide micronodules and Mn-rich sediments. A soil-borne Escherichia coli with high Mn(II)-oxidizing activity formed Mn(III)/Mn(IV) oxide deposit layers and aggregates under laboratory culture conditions. We engineered MCO266 onto the cell surfaces of both an activity-negative recipient and wild-type strains. The results confirmed that MCO266 governs Mn(II) oxidation and initiates the formation of deposits and aggregates. By contrast, a cell-free substrate, heat-killed strains, and intracellularly expressed or purified MCO266 failed to catalyze Mn(II) oxidation. However, purified MCO266 exhibited Mn(II)-oxidizing activity when combined with cell outer membrane component (COMC) fractions in vitro. We demonstrated that Mn(II) oxidation and aggregate formation occurred through an oxygen-dependent biotic transformation process that requires a certain minimum Mn(II) concentration. We propose an approximate electron transfer pathway in which MCO266 transfers only one electron to convert Mn(II) to Mn(III) and then cooperates with other COMC electron transporters to transfer the other electron required to oxidize Mn(III) to Mn(IV). PMID:26039669

  6. Artificial Neural Network Modelling of Photodegradation in Suspension of Manganese Doped Zinc Oxide Nanoparticles under Visible-Light Irradiation

    PubMed Central

    Abdollahi, Yadollah; Sairi, Nor Asrina; Amin Matori, Khamirul; Fard Masoumi, Hamid Reza

    2014-01-01

    The artificial neural network (ANN) modeling of m-cresol photodegradation was carried out for determination of the optimum and importance values of the effective variables to achieve the maximum efficiency. The photodegradation was carried out in the suspension of synthesized manganese doped ZnO nanoparticles under visible-light irradiation. The input considered effective variables of the photodegradation were irradiation time, pH, photocatalyst amount, and concentration of m-cresol while the efficiency was the only response as output. The performed experiments were designed into three data sets such as training, testing, and validation that were randomly splitted by the software's option. To obtain the optimum topologies, ANN was trained by quick propagation (QP), Incremental Back Propagation (IBP), Batch Back Propagation (BBP), and Levenberg-Marquardt (LM) algorithms for testing data set. The topologies were determined by the indicator of minimized root mean squared error (RMSE) for each algorithm. According to the indicator, the QP-4-8-1, IBP-4-15-1, BBP-4-6-1, and LM-4-10-1 were selected as the optimized topologies. Among the topologies, QP-4-8-1 has presented the minimum RMSE and absolute average deviation as well as maximum R-squared. Therefore, QP-4-8-1 was selected as final model for validation test and navigation of the process. The model was used for determination of the optimum values of the effective variables by a few three-dimensional plots. The optimum points of the variables were confirmed by further validated experiments. Moreover, the model predicted the relative importance of the variables which showed none of them was neglectable in this work. PMID:25538962

  7. Semi-empirical study of ortho-cresol photo degradation in manganese-doped zinc oxide nanoparticles suspensions

    PubMed Central

    2012-01-01

    The optimization processes of photo degradation are complicated and expensive when it is performed with traditional methods such as one variable at a time. In this research, the condition of ortho-cresol (o-cresol) photo degradation was optimized by using a semi empirical method. First of all, the experiments were designed with four effective factors including irradiation time, pH, photo catalyst’s amount, o-cresol concentration and photo degradation % as response by response surface methodology (RSM). The RSM used central composite design (CCD) method consists of 30 runs to obtain the actual responses. The actual responses were fitted with the second order algebraic polynomial equation to select a model (suggested model). The suggested model was validated by a few numbers of excellent statistical evidences in analysis of variance (ANOVA). The used evidences include high F-value (143.12), very low P-value (<0.0001), non-significant lack of fit, the determination coefficient (R2?=?0.99) and the adequate precision (47.067). To visualize the optimum, the validated model simulated the condition of variables and response (photo degradation %) be using a few number of three dimensional plots (3D). To confirm the model, the optimums were performed in laboratory. The results of performed experiments were quite close to the predicted values. In conclusion, the study indicated that the model is successful to simulate the optimum condition of o-cresol photo degradation under visible-light irradiation by manganese doped ZnO nanoparticles. PMID:22909072

  8. Processes of zinc attenuation by biogenic manganese oxides forming in the hyporheic zone of Pinal Creek, Arizona

    PubMed Central

    Fuller, Christopher C.; Bargar, John R.

    2014-01-01

    The distribution and speciation of Zn sorbed to biogenic Mn oxides forming in the hyporheic zone of Pinal Creek, AZ, was investigated using micro-focused Extended X-ray Absorption Fine Structure (EXAFS) and X-ray fluorescence (?SXRF) mapping , bulk EXAFS, and chemical extraction. ?SXRF and chemical extractions show that contaminant Zn co-varied with Mn in streambed sediment grain coatings. Bulk and micro-focused EXAFS spectra of Zn in the biogenic Mn oxides coating are indicative of Zn forming triple corner sharing inner-sphere complexes over octahedral vacancies in the Mn oxide sheet structure. Zn desorbed in response to decreasing in pH in batch experiments and resulted in near-equal dissolved Zn at each pH over a 10-fold range in solid to solution ratio. The geometry of sorbed Zn was unchanged after 50% desorption at pH 5, indicating desorption is not controlled by dissolution of secondary Zn phases. In sum, these findings support the idea that Zn attenuation in Pinal Creek is largely controlled by sorption to microbial Mn oxides forming in the streambed during hyporheic exchange. Sorption to biogenic Mn oxides is likely an important process in Zn attenuation in circum-neutral pH reaches of many acid-mine drainage contaminated streams when dissolved Mn is present. PMID:24460038

  9. Processes of zinc attenuation by biogenic manganese oxides forming in the hyporheic zone of Pinal Creek, Arizona

    USGS Publications Warehouse

    Fuller, Christopher C.; Bargar, John R.

    2014-01-01

    The distribution and speciation of Zn sorbed to biogenic Mn oxides forming in the hyporheic zone of Pinal Creek, AZ, was investigated using extended X-ray absorption fine structure (EXAFS) and microfocused synchrotron X-ray fluorescence (?SXRF) mapping, and chemical extraction. ?SXRF and chemical extractions show that contaminant Zn co-varied with Mn in streambed sediment grain coatings. Bulk and microfocused EXAFS spectra of Zn in the biogenic Mn oxide coating are indicative of Zn forming triple-corner-sharing inner-sphere complexes over octahedral vacancies in the Mn oxide sheet structure. Zn desorbed in response to the decrease in pH in batch experiments and resulted in near-equal dissolved Zn at each pH over a 10-fold range in the solid/solution ratio. The geometry of sorbed Zn was unchanged after 50% desorption at pH 5, indicating that desorption is not controlled by dissolution of secondary Zn phases. In summary, these findings support the idea that Zn attenuation in Pinal Creek is largely controlled by sorption to microbial Mn oxides forming in the streambed during hyporheic exchange. Sorption to biogenic Mn oxides is likely an important process of Zn attenuation in circum-neutral pH reaches of many acid-mine drainage contaminated streams when dissolved Mn is present.

  10. The Combined Role Of Manganese Oxides And Microbes In The yAbiotic Uptake Of Amino Acid Nitrogen Into Litter And Soil Organic yMatter

    NASA Astrophysics Data System (ADS)

    Filley, T. R.; Dria, K.

    2004-12-01

    Soil organic matter (SOM) is the largest terrestrial C and N store. Microbial yand abiotic processes that control the transformation of protein nitrogen in litter and ysoils into macromolecular humic materials play an important role in organic matter ystorage and soil productivity. There are major gaps, however, in our understanding of ythese processes and behaviors. Abiotic reactions of amines, phenols and sugars derived yfrom forest leachates or present in detrital and litter organic matter are known to be ykey processes in the formation of complex organic nitrogen. We present here the yresults from a study designed to investigate how the inherent chemistry of lignin, leaf ylitter, and progressively advanced brown-rot wood decay impact the chemical reaction yof amino acids with this organic matter. Additionally, experiments in the presence of ybirnessite (MnO2) were also conducted to investigate the role of mineral induced phenol yoxidation on specific amino acid chemical humifcation processes. Solid and liquid state yNMR, 13C-labelled tetramethyl ammonium hydroxide thermochemolysis and stable ycarbon and nitrogen isotope ratio mass spectrometry were used to track the alteration yof litter material and document uptake of 13C and 15N labeled amino acids. yPreliminary results from birnessite-containing experiments suggest that the metal-ypromoted oxidation of the lignin, leaf litter, and, in particular, demethylated brown rot ywood residues, is necessary to convert the phenols to quinones of some type permitting yamine addition. This relationship is particularly true for the production of soluble yfractions after two and six weeks of reaction in the presence of the manganese oxides. yAdditionally, the production of leachable organic matter with incorporated N was ypromoted in the soluble fractions. Ongoing NMR studies will elucidate the nature of ythe chemical binding in these experiments. y

  11. Manganese-induced oxidative DNA damage in neuronal SH-SY5Y cells: attenuation of thymine base lesions by glutathione and N-acetylcysteine.

    PubMed

    Stephenson, Adrienne P; Schneider, Jeffrey A; Nelson, Bryant C; Atha, Donald H; Jain, Ashok; Soliman, Karam F A; Aschner, Michael; Mazzio, Elizabeth; Renee Reams, R

    2013-04-26

    Manganese (Mn) is an essential trace element required for normal function and development. However, exposure to this metal at elevated levels may cause manganism, a progressive neurodegenerative disorder with neurological symptoms similar to idiopathic Parkinson's disease (IPD). Elevated body burdens of Mn from exposure to parental nutrition, vapors in mines and smelters and welding fumes have been associated with neurological health concerns. The underlying mechanism of Mn neurotoxicity remains unclear. Accordingly, the present study was designed to investigate the toxic effects of Mn(2+) in human neuroblastoma SH-SY5Y cells. Mn(2+) caused a concentration dependent decrease in SH-SY5Y cellular viability compared to controls. The LD50 value was 12.98 ?M Mn(2+) (p<0.001 for control vs. 24h Mn treatment). Both TUNEL and annexin V/propidium iodide (PI) apoptosis assays confirmed the induction of apoptosis in the cells following exposure to Mn(2+) (2 ?M, 62 ?M or 125 ?M). In addition, Mn(2+) induced both the formation and accumulation of DNA single strand breaks (via alkaline comet assay analysis) and oxidatively modified thymine bases (via gas chromatography/mass spectrometry analysis). Pre-incubation of the cells with characteristic antioxidants, either 1mM N-acetylcysteine (NAC) or 1mM glutathione (GSH) reduced the level of DNA strand breaks and the formation of thymine base lesions, suggesting protection against oxidative cellular damage. Our findings indicate that (1) exposure of SH-SY5Y cells to Mn promotes both the formation and accumulation of oxidative DNA damage, (2) SH-SY5Y cells with accumulated DNA damage are more likely to die via an apoptotic pathway and (3) the accumulated levels of DNA damage can be abrogated by the addition of exogenous chemical antioxidants. This is the first known report of Mn(2+)-induction and antioxidant protection of thymine lesions in this SH-SY5Y cell line and contributes new information to the potential use of antioxidants as a therapeutic strategy for protection against Mn(2+)-induced oxidative DNA damage. PMID:23296100

  12. Oxidative neuropathology and putative chemical entities for alzheimer’s disease: Neuroprotective effects of salen-manganese catalytic anti-oxidants

    Microsoft Academic Search

    H. Thomas R. Rupniak; Ken A. Joy; Charlotte Atkin; Gill Brown; Julie C. Barnes; Susan R. Doctrow; Bernard Malfroy; Tony Wong; Ian K. Anderson; Chris R. Molloy; Gary I. Mills; Peter Soden

    2000-01-01

    Considerable evidence exists that the brains of individuals with Alzheimer’s disease are subject to elevated levels of oxidative\\u000a stress, particularly in regions exhibiting pathological damage. A major contributor to this oxidative stress appears to be\\u000a the inflammatory process. Activation of rodent microglial cells by LPS or ?-amyloid peptide results in a marked up-regulation\\u000a of inducible nitric oxide synthase (iNOS) and

  13. Glutamate\\/Aspartate Transporter (GLAST), Taurine Transporter and Metallothionein mRNA Levels are Differentially Altered in Astrocytes Exposed to Manganese Chloride, Manganese Phosphate or Manganese Sulfate

    Microsoft Academic Search

    Keith M. Erikson; Robert L. Suber; Michael Aschner

    2002-01-01

    Manganese (Mn)-induced neurotoxicity can occur due to environmental exposure (air pollution, soil, water) and\\/or metabolic aberrations (decreased biliary excretion). High brain manganese levels lead to oxidative stress, as well as alterations in neurotransmitter metabolism with concurrent neurobehavioral deficits. Based on the few existing studies that have examined brain regional Mn concentration, it is likely that in pathological conditions, Mn concentration

  14. Chemical and catalytic activation of methane by metal oxide surfaces. Annual report, September 1989August 1990. [Iron and manganese perovskites

    Microsoft Academic Search

    J. G. McCarty; E. D. Wachsman

    1992-01-01

    The objectives of the research are to investigate the nature of surface oxygen centers capable of selective conversion of methane into hydrocarbon fuels through catalytic selective oxidation and to determine the role of homogeneous reactions in the catalytic coupling process. Major accomplishments of the current work include the development of stable redox coupling catalysts and the identification of impurity metals

  15. Effects of undoped and manganese-doped zinc oxide nanoparticles on the colour fading of dyed polyester fabrics

    Microsoft Academic Search

    Lu Sun; John A. Rippon; Peter G. Cookson; Olga Koulaeva; Xungai Wang

    2009-01-01

    This paper describes the effects of applying coatings of an acrylic polymer containing nanoparticles of zinc oxide (ZnO) on the fading rate in artificial sunlight of polyester fabrics dyed with disperse dyes containing anthraquinone and benzopyran chromophores. Factors affecting the transparency and UV absorbance of the coatings are discussed. Removing the UV component of sunlight with ZnO nanoparticles markedly decreased

  16. Field effect and magnetically induced capacitive tuning in hole doped lanthanum(1-x) strontium(x) manganese oxide

    NASA Astrophysics Data System (ADS)

    Marton, Zsolt

    Electrostatic modulation of interface conduction between semiconductors and insulating oxides is the foundation of semiconductor technology. This field effect concept can be applied on complex oxides, such as high temperature superconductors and colossal magnetoresistive manganites, in order to create new electronic and magnetic phases. Competition and coexistence of multiple nanoscale phases make them exciting to study around phase transitions. This study on hole doped La1-xSrxMnO3 systems has a two-fold purpose. One is the demonstration of the field effect on La1-xSr xMnO3 (x = 0.125, 0.2, 0.3, 0.5) thin films. It is an important step towards electrostatic control of material properties, however, a challenging task because of their charge carrier densities of 0.01-1 hole/unit cell, a few orders of magnitude larger than in doped semiconductors. Control by linear dielectrics needs huge, constantly applied bias. Energy efficient tuning with low voltages requires highly polar ferroelectric. Pb(Zr0.2Ti 0.8)O3 was chosen, whose remanence provides 0.5 charge carrier/unit cell on the manganite/ferroelectric interface. La1-xSrxMnO 3/Pb(Zr0.2Ti0.8)O3 heterostructures were synthesized by pulsed laser epitaxy and remarkable conduction modifications were observed in the La1-xSrxMnO3. This can be a strong foundation of a new tool to research electronic oxides. The second purpose of this work is to utilize the phase separation in manganites. There has been extensive research on multiferroic materials, in which dielectric and magnetic responses are controlled by magnetic and electric field, respectively. In order to demonstrate magnetically tuned capacitance, insulating La7/8Sr1/8MnO3 was studied. Drastic capacitance change in magnetic field was shown through a phase transitions and explained in the framework of electronic phase separation. It makes this material eligible for high frequency magnetoelectric applications. Modulating charge carriers, mobility and magnetism in magnetic oxides, superconductors and superlattices has a great impact on the emerging field of oxide electronics. These compounds overcome the scaling limitations of conventional semiconductors; using low operation voltage oxide ferroelectrics lowers energy consumption. This thesis shows that changing fundamental physical properties of complex oxides on the atomic scale is possible by ferroelectric field effect. This technique is proposed as a tool to study thin films, artificially stacked structures and to induce and optimize novel phases and phenomena.

  17. YREE sorption on hydrous manganese oxide (MnOx) in 0.5 M NaCl

    Microsoft Academic Search

    K. S. Marshall; J. Schijf

    2010-01-01

    Cerium is the only member of the yttrium and rare earth element (YREE) series that can be oxidized in natural waters from Ce(III) to less soluble Ce(IV), causing anomalous sorption behavior with respect to its strictly trivalent YREE neighbors. Sedimentary Ce anomaly records have been interpreted in terms of episodic shifts in the bottom water oxygenation of the paleo-ocean. However,

  18. Layer by Layer Ex-Situ Deposited Cobalt-Manganese Oxide as Composite Electrode Material for Electrochemical Capacitor

    PubMed Central

    Rusi; Chan, P. Y.; Majid, S. R.

    2015-01-01

    The composite metal oxide electrode films were fabricated using ex situ electrodeposition method with further heating treatment at 300°C. The obtained composite metal oxide film had a spherical structure with mass loading from 0.13 to 0.21 mg cm-2. The structure and elements of the composite was investigated using X-ray diffraction (XRD) and energy dispersive X-ray (EDX). The electrochemical performance of different composite metal oxides was studied by cyclic voltammetry (CV) and galvanostatic charge-discharge (CD). As an active electrode material for a supercapacitor, the Co-Mn composite electrode exhibits a specific capacitance of 285 Fg-1 at current density of 1.85 Ag-1 in 0.5M Na2SO4 electrolyte. The best composite electrode, Co-Mn electrode was then further studied in various electrolytes (i.e., 0.5M KOH and 0.5M KOH/0.04M K3Fe(CN) 6 electrolytes). The pseudocapacitive nature of the material of Co-Mn lead to a high specific capacitance of 2.2 x 103 Fg-1 and an energy density of 309 Whkg-1 in a 0.5MKOH/0.04MK3Fe(CN) 6 electrolyte at a current density of 10 Ag-1. The specific capacitance retention obtained 67% of its initial value after 750 cycles. The results indicate that the ex situ deposited composite metal oxide nanoparticles have promising potential in future practical applications. PMID:26158447

  19. Role of local and electronic structural changes with partially anion substitution lithium manganese spinel oxides on their electrochemical properties: X-ray absorption spectroscopy study.

    PubMed

    Okumura, Toyoki; Fukutsuka, Tomokazu; Matsumoto, Keisuke; Orikasa, Yuki; Arai, Hajime; Ogumi, Zempachi; Uchimoto, Yoshiharu

    2011-10-14

    The electronic and local structures of partially anion-substituted lithium manganese spinel oxides as positive electrodes for lithium-ion batteries were investigated using X-ray absorption spectroscopy (XAS). LiMn(1.8)Li(0.1)Ni(0.1)O(4-?)F(?) (? = 0, 0.018, 0.036, 0.055, 0.073, 0.110, 0.180) were synthesized by the reaction between LiMn(1.8)Li(0.1)Ni(0.1)O(4) and NH(4)HF(2). The shift of the absorption edge energy in the XANES spectra represented the valence change of Mn ion with the substitution of the low valent cation as Li(+), Ni(2+), or F(-) anion. The local structural change at each compound with the amount of a Jahn-Teller Mn(3+) ion could be observed by EXAFS spectra. The discharge capacity of the tested electrode was in the order of LiMn(2)O(4) > LiMn(1.8)Li(0.1)Ni(0.1)O(4-?)F(?) (? = 0.036) > LiMn(1.8)Li(0.1)Ni(0.1)O(4) while the cycleability was in the order of LiMn(1.8)Li(0.1)Ni(0.1)O(4-?)F(?) (? = 0.036) ? LiMn(1.8)Li(0.1)Ni(0.1)O(4) > LiMn(2)O(4). It was clarified that LiMn(1.8)Li(0.1)Ni(0.1)O(4-?)F(?) has a good cycleability because of the anion doping effect and simultaneously shows acceptable rechargeable capacity because of the large amount of the Jahn-Teller Mn(3+) ions in the pristine material. PMID:21869978

  20. Integrin-mediated osteoblastic adhesion on a porous manganese-incorporated TiO2 coating prepared by plasma electrolytic oxidation

    PubMed Central

    ZHANG, ZHENXIANG; GU, BEIBEI; ZHU, WEI; ZHU, LIXIAN

    2013-01-01

    This study was conducted to evaluate the bioactivity of manganese-incorporated TiO2 (Mn-TiO2) coating prepared on titanium (Ti) plate by plasma electrolytic oxidation (PEO) technique in Ca-, P- and Mn-containing electrolytes. The surface topography, phase and element compositions of the coatings were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectrometry (EDS), respectively. The adhesion of osteoblast-like MG63 cells onto Ti, TiO2 and Mn-TiO2 surfaces was evaluated, and the signal transduction pathway involved was confirmed by the sequential expression of the genes for integrins ?1, ?3, ?1 and ?3, focal adhesion kinase (FAK), and the extracellular regulated kinases (ERKs), including ERK1 and ERK2. The results obtained indicated that Mn was successfully incorporated into the porous nanostructured TiO2 coating, and did not alter the surface topography or the phase composition of the coating. The adhesion of the MG63 cells onto the Mn-incorporated TiO2 coating was significantly enhanced compared with that on the Mn-free TiO2 coating and the pure Ti plates. In addition, the enhanced cell adhesion on the Mn-TiO2 coatings may have been mediated by the binding of the integrin subunits, ?1 and ?1, and the subsequent signal transduction pathway, involving FAK and ERK2. The study indicated that the novel Mn-TiO2 coating has potential for orthopedic implant applications, and that further investigations are required. PMID:24137252

  1. Chronic manganese intoxication

    SciTech Connect

    Huang, C.C.; Chu, N.S.; Lu, C.S.; Wang, J.D.; Tsai, J.L.; Tzeng, J.L.; Wolters, E.C.; Calne, D.B. (Chang Gung Medical College Hospital, Taipei, Taiwan (China))

    1989-10-01

    We report six cases of chronic manganese intoxication in workers at a ferromanganese factory in Taiwan. Diagnosis was confirmed by assessing increased manganese concentrations in the blood, scalp, and pubic hair. In addition, increased manganese levels in the environmental air were established. The patients showed a bradykinetic-rigid syndrome indistinguishable from Parkinson's disease that responded to treatment with levodopa.

  2. Manganese in Narragansett Bay

    Microsoft Academic Search

    WILLIAM F. GRAHAM; MICHAEL L. BENDER; GARY P. KLINKHAMMER

    1976-01-01

    Concentrations of dissolved manganese and particulate mangancsc and aluminum were determined in samples from Narragansett Bay, Rhode Island, and its surrounding rivers. Total manganese is approximately conservative, but dissolved and particulate manganese are not. Desorption may occur in the tidal rivers at low salinities. Most riverine manga- nest is dissolved but mangancsc in the bay is predominantly particulate, probably due

  3. Boosting Properties of 3D Binder-Free Manganese Oxide Anodes by Preformation of a Solid Electrolyte Interphase.

    PubMed

    Zhou, Haitao; Wang, Xuehang; Sheridan, Edel; Chen, De

    2015-04-24

    Huge irreversible capacity loss prevents the successful use of metal oxide anodes in Li-ion full cells. Here, we focus on the critical prelithiation step and demonstrate the challenge of electrolyte decomposition on a pristine anode in a full cell. Both an electrochemical activation process (54?h) with Li metal and a new electrolytic process (75?min) without Li metal were used to preform complete solid electrolyte interphase (SEI) layers on 3?D binder-free MnOy -based anodes. The preformed SEI layers mitigated the electrolyte decomposition effectively and widened the working voltage for the MnOy /LiMn2 O4 full cell, which resulted in a big boost of the specific energy to 300 and 200?W?h?kgcathode (-1) , largely improved cycling stability, and much higher specific power (4200?W?h?kgtotal (-1) ) compared to conventional Li-ion batteries. Detailed characterization, such as cyclic voltammetry, scanning transmission electron microscopy, and FTIR spectroscopy, gives mechanistic insight into SEI preformation. This work provides guidance for the design of anode SEI layers and enables the application of oxides for Li-ion battery full cells. PMID:25760685

  4. Preparation of manganese(II), chromium(III) and ferric(III) oxides nanoparticles in situ metal citraconate complexes frameworks.

    PubMed

    Refat, Moamen S

    2014-12-10

    The new reactions of some divalent and trivalent transition metal ions (Mn(II), Cr(III), and Fe(III)) with citraconic acid has been studied. The obtained results indicate the formation of citraconic acid compounds with molar ratio of metal to citraconic acid of 2:2 or 2:3 with general formulas Mn2(C5H4O4)2 or M2(C5H4O4)3?nH2O where n=6 for Cr, and Fe(III). The thermal decomposition of the crystalline solid complexes was investigated. The IR spectra of citraconate suggested that the carboxylic groups are bidentatically bridging and chelating. In the course of decomposition the complexes are dehydrated and then decompose either directly to oxides in only one step or with intermediate formation of oxocarbonates. This proposal dealing the preparation of MnO2, Fe2O3 and Cr2O3 nanoparticles. The crystalline structure of oxide products were checked by X-ray powder diffraction (XRD), and the morphology of particles by scanning electron microscopy (SEM). PMID:24952090

  5. Sorption of trivalent cerium by a mixture of microbial cells and manganese oxides: Effect of microbial cells on the oxidation of trivalent cerium

    NASA Astrophysics Data System (ADS)

    Ohnuki, Toshihiko; Jiang, Mingyu; Sakamoto, Fuminori; Kozai, Naofumi; Yamasaki, Shinya; Yu, Qianqian; Tanaka, Kazuya; Utsunomiya, Satoshi; Xia, Xiaobin; Yang, Ke; He, Jianhua

    2015-08-01

    Sorption of Ce by mixtures of synthetic Mn oxides and microbial cells of Pseudomonas fluorescens was investigated to elucidate the role of microorganisms on Ce(III) oxidative migration in the environment. The mixtures, upon which Ce was sorbed following exposure to solutions containing 1.0 × 10-4 or 1.0 × 10-5 mol L-1 Ce(III), were analyzed by scanning electron microscopy energy dispersive X-ray spectroscopy (SEM-EDS) and micro-X-ray fluorescence (micro-XRF) at synchrotron facilities. A Ce LIII-edge micro XANES spectra analysis was also performed to determine the oxidation states of Ce adsorbed to the Mn oxides and microbial cells in the mixtures. The distribution ratios (Kd) of Ce between the individual solids and solution increased with increasing pH of the solution, and was nearly the same in mixtures containing varying amounts of microbial cells. SEM-EDS and micro-XRF analyses showed that Ce was sorbed by both MnO2 and microbial cells (1.7 × 10-1 or 3.3 × 10-1 g L-1). In addition, nano-particles containing Ce and P developed on the surface of the microbial cells. XANES analysis showed that lower fractions of Ce(III) were oxidized to Ce(IV) in the mixtures containing greater amounts of microbial cells. Micro-XANES analysis revealed that Ce was present as Ce(III) on the microbial cells and as Ce(IV) on Mn oxides. These results strongly suggest that the association of Ce(III) with the microbial cell surface and the formation of Ce phosphate nano-particles are responsible for suppressing the oxidation of Ce(III) to Ce(IV) in the mixtures.

  6. Respective role of Fe and Mn oxide contents for arsenic sorption in iron and manganese binary oxide: an X-ray absorption spectroscopy investigation.

    PubMed

    Zhang, Gaosheng; Liu, Fudong; Liu, Huijuan; Qu, Jiuhui; Liu, Ruiping

    2014-09-01

    In our previous studies, a synthesized Fe-Mn binary oxide was found to be very effective for both As(V) and As(III) removal in aqueous phase, because As(III) could be easily oxidized to As(V). As(III) oxidation and As(V) sorption by the Fe-Mn binary oxide may also play an important role in the natural cycling of As, because of its common occurrence in the environment. In the present study, the respective role of Fe and Mn contents present in the Fe-Mn binary oxide on As(III) removal was investigated via a direct in situ determination of arsenic speciation using X-ray absorption spectroscopy. X-ray absorption near edge structure results indicate that Mn atoms exist in a mixed valence state of +3 and +4 and further confirm that MnOx (1.5 < x < 2) content is mainly responsible for oxidizing As(III) to As(V) through a two-step pathway [reduction of Mn(IV) to Mn(III) and subsequent Mn(III) to Mn(II)] and FeOOH content is dominant for adsorbing the formed As(V). No significant As(III) oxidation by pure FeOOH had been observed during its sorption, when the system was exposed to air. The extended X-ray absorption fine structure results reveal that the As surface complex on both the As(V)- and As(III)-treated sample surfaces is an inner-sphere bidentate binuclear corner-sharing complex with an As-M (M = Fe or Mn) interatomic distance of 3.22-3.24 Å. In addition, the MnOx and FeOOH contents exist only as a mixture, and no solid solution is formed. Because of its high effectiveness, low cost, and environmental friendliness, the Fe-Mn binary oxide would play a beneficial role as both an efficient oxidant of As(III) and a sorbent for As(V) in drinking water treatment and environmental remediation. PMID:25093452

  7. THE STATE OF MANGANESE IN THE PHOTOSYNTHETIC APPARATUS. II. X-RAY ABSORPTION EDGE STUDIES ON MANGANESE IN PHOTOSYNTHETIC MEMBRANES

    SciTech Connect

    Kirby, J.A.; Goodin, D.B.; Wydrzynski, T.; Robertson, A.S.; Klein, M.P.

    1980-11-01

    X-ray absorption spectra at the Manganese K-edge are presented for spinach chloroplasts, and chloroplasts which have been Tris-treated and hence unable to evolve oxygen. A significant change in the electronic environment of manganese is observed and is attributed to the release of manganese from the thylakoid membranes with a concomitant change in oxidation state. A correlation of the K-edge energy, defined as the energy at the first inflection point, with coordination charge has been established for a number of manganese compounds of known structure and oxidation state. Comparison of the manganese K-edge energies of the chloroplast samples with the reference compounds places the average oxidation state of the chloroplasts between +2 and +3. Using the edge spectra for Tris-treated membranes which were osmotically shocked to remove the released manganese, difference edge spectra were synthesized to approximate the active pool of manganese. Coordination charge predictions for this fraction are consistent with an average resting oxidation state higher than +2. The shape at the edge is also indicative of heterogeneity of the manganese site, of low symmetry, or both.

  8. Synthesis and determination of manganese carbonate and manganese-54 carbonate.

    PubMed

    King, B D; Lassiter, J W; Neathery, M W; Miller, W J

    1980-04-01

    A method was developed by which radioactive manganese, manganese-54 carbonate (with a high specific activity), could be produced. This was accomplished by reacting manganese-54 chloride, manganese chloride tetrahydrate, and sodium bicarbonate. This reaction produced manganese-54 carbonate (specific activity .35 mCi/mg manganese mixed with stable manganese. The purity of the manganese carbonate (manganese-54 carbonate) was determined by the use of x-ray diffraction methods. One method compared "d" spacings (distance in angstroms between lattice planes of a crystal) with standard and index values for pure manganese carbonate. Another method compared x-ray diffractograms of the synthesized product with standard manganese carbonate. By both methods all material was the carbonate form of manganese (manganese-54 carbonate). PMID:7381087

  9. ROLE OF MANGANESE REDUCTION/OXIDATION (REDOX) ON FOAMING AND MELT RATE IN HIGH LEVEL WASTE (HLW) MELTERS (U)

    SciTech Connect

    Jantzen, C; Michael Stone, M

    2007-03-30

    High-level nuclear waste is being immobilized at the Savannah River Site (SRS) by vitrification into borosilicate glass at the Defense Waste Processing Facility (DWPF). Control of the Reduction/Oxidation (REDOX) equilibrium in the DWPF melter is critical for processing high level liquid wastes. Foaming, cold cap roll-overs, and off-gas surges all have an impact on pouring and melt rate during processing of high-level waste (HLW) glass. All of these phenomena can impact waste throughput and attainment in Joule heated melters such as the DWPF. These phenomena are caused by gas-glass disequilibrium when components in the melter feeds convert to glass and liberate gases such as H{sub 2}O vapor (steam), CO{sub 2}, O{sub 2}, H{sub 2}, NO{sub x}, and/or N{sub 2}. During the feed-to-glass conversion in the DWPF melter, multiple types of reactions occur in the cold cap and in the melt pool that release gaseous products. The various gaseous products can cause foaming at the melt pool surface. Foaming should be avoided as much as possible because an insulative layer of foam on the melt surface retards heat transfer to the cold cap and results in low melt rates. Uncontrolled foaming can also result in a blockage of critical melter or melter off-gas components. Foaming can also increase the potential for melter pressure surges, which would then make it difficult to maintain a constant pressure differential between the DWPF melter and the pour spout. Pressure surges can cause erratic pour streams and possible pluggage of the bellows as well. For these reasons, the DWPF uses a REDOX strategy and controls the melt REDOX between 0.09 {le} Fe{sup 2+}/{summation}Fe {le} 0.33. Controlling the DWPF melter at an equilibrium of Fe{sup +2}/{summation}Fe {le} 0.33 prevents metallic and sulfide rich species from forming nodules that can accumulate on the floor of the melter. Control of foaming, due to deoxygenation of manganic species, is achieved by converting oxidized MnO{sub 2} or Mn{sub 2}O{sub 3} species to MnO during melter preprocessing. At the lower redox limit of Fe{sup +2}/{summation}Fe {approx} 0.09 about 99% of the Mn{sup +4}/Mn{sup +3} is converted to Mn{sup +2}. Therefore, the lower REDOX limits eliminates melter foaming from deoxygenation.

  10. Factors Affecting the Enhancement of Oxidative Stress Tolerance in Transgenic Tobacco Overexpressing Manganese Superoxide Dismutase in the Chloroplasts.

    PubMed Central

    Slooten, L.; Capiau, K.; Van Camp, W.; Van Montagu, M.; Sybesma, C.; Inze, D.

    1995-01-01

    Two varieties of tobacco (Nicotiana tabacum var PBD6 and var SR1) were used to generate transgenic lines overexpressing Mn-superoxide dismutase (MnSOD) in the chloroplasts. The overexpressed MnSOD suppresses the activity of those SODs (endogenous MnSOD and chloroplastic and cytosolic Cu/ZnSOD) that are prominent in young leaves but disappear largely or completely during aging of the leaves. The transgenic and control plants were grown at different light intensities and were then assayed for oxygen radical stress tolerance in leaf disc assays and for abundance of antioxidant enzymes and substrates in leaves. Transgenic plants had an enhanced resistance to methylviologen (MV), compared with control plants, only after growth at high light intensities. In both varieties the activities of FeSOD, ascorbate peroxidase, dehydroascorbate reductase, and monodehydroascorbate reductase and the concentrations of glutathione and ascorbate (all expressed on a chlorophyll basis) increased with increasing light intensity during growth. Most of these components were correlated with MV tolerance. It is argued that SOD overexpression leads to enhancement of the tolerance to MV-dependent oxidative stress only if one or more of these components is also present at high levels. Furthermore, the results suggest that in var SR1 the overexpressed MnSOD enhances primarily the stromal antioxidant system. PMID:12228398

  11. Effects of chronic exposure to lead, cadmium, and manganese mixtures on oxidative stress in rat liver and heart.

    PubMed

    Markiewicz-Górka, Iwona; Januszewska, Lidia; Michalak, Aleksandra; Prokopowicz, Adam; Januszewska, Ewa; Pawlas, Natalia; Pawlas, Krystyna

    2015-03-01

    The aim of this study was to assess the effects of chronic combined exposure to low, environmental doses of Cd, Pb, and Mn on oxidative stress in the liver and heart of rats and on their liver function parameters. Male Wistar rats were divided randomly into eight groups. For nine months controls were receiving drinking water alone, whereas the exposed groups were receiving drinking water with Pb (0.2 mg L(-1)), Cd (1 mg L(-1)), and Mn (2 mg L(-1)) alone or in combinations. Malondialdehyde (MDA) significantly increased in both heart and liver of the animals after combined exposure to metals. Heart MDA correlated with blood Cd, Pb, and Mn and liver MDA with blood Cd. Aspartate aminotransferase (AST) activity and bilirubin concentration also increased significantly in the animal group exposed to all three metals and correlated positively with blood Cd, Pb, and Mn. Our study has confirmed the synergistic effect of the Cd, Mn, and Pb combination on the increase in heart MDA. A similar synergy was observed for Pb+Mn in the increase of serum alanine aminotransferase (ALT) activity as an indicator of liver function. PMID:25781514

  12. Fabrication of graphene sheets intercalated with manganese oxide/carbon nanofibers: toward high-capacity energy storage.

    PubMed

    Kwon, Oh Seok; Kim, Taejoon; Lee, Jun Seop; Park, Seon Joo; Park, Hyun-Woo; Kang, Minjeong; Lee, Ji Eun; Jang, Jyongsik; Yoon, Hyeonseok

    2013-01-28

    Herein, 3D nanohybrid architectures consisting of MnO(x) nanocrystals, carbon nanofibers (CNFs), and graphene sheets are fabricated. MnO(x) -decorated CNFs (MCNFs) with diameters of about 50 nm are readily obtained via single-nozzle co-electrospinning, followed by heat treatment. The MCNFs are then intercalated between graphene sheets, yielding the ternary nanohybrid MCNF/reduced graphene oxide (RGO). This straightforward synthesis process readily affords product on a scale of tens of grams. The ultrathin CNFs, which might be a promising alternative to carbon nanotubes (CNTs), overcome the low electrical conductivity of the excellent pseudocapacitive component, MnO(x) . Furthermore, the graphene sheets separated by the MCNFs boost the electrochemical performance of the nanohybrid electrodes. These nanohybrid electrodes exhibit enhanced specific capacitances compared with a sheet electrode fabricated of MCNF-only or RGO-only. Evidently, the RGO sheet acts as a conductive channel inside the nanohybrid, while the intercalated MCNFs increase the efficiency of the ion and charge transfer in the nanohybrid. The proposed nanohybrid architectures are expected to lay the foundation for the design and fabrication of high-performance electrodes. PMID:23034820

  13. Synthesis of poly(methacrylic acid)-manganese oxide dihydroxide/silica core-shell and the corresponding hollow microspheres.

    PubMed

    Sun, Shuxuan; Liu, Bin; Fu, Xiaomeng; Zhou, Meijun; Liu, Wei; Bian, Guomin; Qi, Yonglin; Yang, Xinlin

    2015-01-15

    Poly(methacrylic acid)-MnO(OH)2/SiO2 core-shell microspheres were prepared by sol-gel hydrolysis of tetraethylorthosilicate (TEOS) in the presence of poly(methacrylic acid)-Mn(II) (PMAA-Mn(2+)) as template with ammonium hydroxide anion as catalyst and n-octadecyltrimethoxysilane (C18TMS) as pore-directing reagent. The PMAA-Mn(2+) core was prepared by incubation of Mn(2+) cations with PMAA microspheres via the coordination between carboxylate anion group on PMAA microsphere and Mn(2+) cations. During this process, the Mn(II) species were formed as white Mn(OH)2 precipitates at first, which were subsequently oxidized into brown MnO(OH)2 in air. The Mn2O3/mesoporous silica (Mn2O3/m-SiO2) double-shelled hollow microspheres (DSHMs) were prepared through calcination of the PMAA-MnO(OH)2/SiO2 core-shell microspheres at 600 °C for the selective removal of PMAA template and pore-directing organic component from C18TMS, during which the crystalline structure of DSHM was developed into Braunite-1Q via the reaction between Mn2O3 inner-shell and silica outer-shell by annealing the DSHMs under higher temperatures of 800 and 900 °C. The Mn2O3 hollow microspheres (HMs) were prepared through the selective removal of the silica layer from the DSHMs by sodium hydroxide aqueous solution, which exhibited structure integrity and good ethanol dispersity due to the presence of mesoporous structure. PMID:25454451

  14. Formation of Color Centers in Sodium Silicate and Quartz Glasses Under the Action of Gamma Radiation

    Microsoft Academic Search

    G. V. Byurganovskaya; N. F. Orlov

    1962-01-01

    The dependence of the intensity of the induced absorption bands in fused ; quartz and sodium silicate glasses on the gamma dose is studied, as well as the ; influence of cerium, anti mony, arsenic, manganese, iron, and lead additives on ; the properties of the absorption bands of sodium silicate glasses. The ; uniformity of the color centers produced

  15. Environmental effects and exposures to manganese from use of methylcyclopentadienyl manganese tricarbonyl (MMT) in gasoline.

    PubMed

    Lynam, D R; Roos, J W; Pfeifer, G D; Fort, B F; Pullin, T G

    1999-01-01

    Methylcyclopentadienyl Manganese Tricarbonyl (MMT) has been used since the 1970s in the U.S. as a gasoline octane enhancer Extensive testing of the effects of MMT on regulated gaseous emissions carried out on a wide variety of automobiles showed that use of MMT resulted in significantly lower NOx emissions Tests showed that less than 15% of the manganese from MMT combustion was emitted from the tailpipe, mostly in the PM2.5 fraction as manganese phosphate, with some manganese sulfate and a very small amount of manganese oxide. MMT has been used in Canada in virtually all unleaded gasoline for about 20 years. A probability-based study involving over 900 personal exposure samples in Toronto confirmed exposures to airborne PM2.5 Mn in the general population are quite low (.008 microgram/m3-median). Ambient levels of airborne manganese in Toronto are about the same as those in areas where MMT is not used. Exposures to manganese among the general population in Toronto are well within safe limits determined by the U.S. EPA and other standard setting bodies around the world. PMID:10385878

  16. Manganese 2 -Complexes as Auxiliaries

    E-print Network

    Lepore, Salvatore D.

    reaction with methylcyclopentadienyl manganese tricarbonyl. This complex readily underwent aldol reactions by Franck-Neumann demonstrating that alkynyl esters 2 -complexed to methylcyclopentadienyl manganeseManganese 2 -Complexes as Auxiliaries for Stereoselective Aldol Synthesis of Allenyl Carbinols

  17. Deposition of manganese in a drinking water distribution system.

    PubMed Central

    Sly, L I; Hodgkinson, M C; Arunpairojana, V

    1990-01-01

    The deposition of manganese in a water distribution system with manganese-related "dirty water" problems was studied over a 1-year period. Four monitoring laboratories with Robbins biofilm sampling devices fitted to the water mains were used to correlate the relationship among manganese deposition, the level of manganese in the water, and the chlorination conditions. Manganese deposition occurred by both chemical and microbial processes. Chemical deposition occurred when Mn(II) not removed during water treatment penetrated the filters and entered the distribution system, where it was oxidized by chlorine and chlorine dioxide used for disinfection. Microbial deposition occurred in areas with insufficient chlorination to control the growth of manganese-depositing biofilm. At 0.05 mg of Mn(II) per liter, the chemical deposition rate was much greater than microbial deposition. Significant deposition occurred at 0.03 mg of manganese per liter, and dirty water complaints were not eliminated until manganese levels were continuously less than 0.02 mg/liter and chlorination levels were greater than 0.2 mg/liter. A guideline level of 0.01 mg of manganese per liter is recommended. Images PMID:2317040

  18. In-situ oxidation measurements of copper using the quartz crystal microbalance coupled with resistance measurements using an atmospheric corrosion monitor

    SciTech Connect

    Jaeger, P.F. [Cortec Corp., St. Paul, MN (United States); Smyrl, W.H. [Univ. of Minnesota, Minneapolis, MN (United States)

    1996-08-01

    A method for the detection of in situ corrosion monitoring due to atmospheric gases has been incorporated to measure not only the amount of corrosion on a copper surface but also the rate of corrosion and a study on the bonding of the adsorbent at the gas solid interface. The Quartz Crystal Microbalance (QCM) has recently been used for this corrosion monitoring. Results indicate a difference in the rate at which the adsorbent reacts with the solid in different atmospheric conditions versus the rate of corrosion as measured when there is no inhibitor present. Tests also indicate an asymptotic threshold may exist in the adsorption process which is reached after (x) amount of time. The adsorption measured was in dry nitrogen with a minimal to negligible effect from the influence of oxygen. This adsorption pretreatment of the surface in a dry inert atmosphere containing an inhibitor has shown to provide the copper surface with protection from atmospheric gases on what looks to be a very impressive time scale. Furthermore, the frequency change due to the chemical adsorption of the inhibitor is suspected to be identified and indicates excellent protection of the copper surface after the inhibitor has been taken away which may support the Bond-Order-Conservation (BOC) theory. The atmospheric corrosion sensor was used to monitor the in situ resistance measurements due to the formation of corrosion.

  19. Study of a QCM Dimethyl Methylphosphonate Sensor Based on a ZnO-Modified Nanowire-Structured Manganese Dioxide Film

    PubMed Central

    Pei, Zhifu; Ma, Xingfa; Ding, Pengfei; Zhang, Wuming; Luo, Zhiyuan; Li, Guang

    2010-01-01

    Sensitive, selective and fast detection of chemical warfare agents is necessary for anti-terrorism purposes. In our search for functional materials sensitive to dimethyl methylphosphonate (DMMP), a simulant of sarin and other toxic organophosphorus compounds, we found that zinc oxide (ZnO) modification potentially enhances the absorption of DMMP on a manganese dioxide (MnO2) surface. The adsorption behavior of DMMP was evaluated through the detection of tiny organophosphonate compounds with quartz crystal microbalance (QCM) sensors coated with ZnO-modified MnO2 nanofibers and pure MnO2 nanofibers. Experimental results indicated that the QCM sensor coated with ZnO-modified nanostructured MnO2 film exhibited much higher sensitivity and better selectivity in comparison with the one coated with pure MnO2 nanofiber film. Therefore, the DMMP sensor developed with this composite nanostructured material should possess excellent selectivity and reasonable sensitivity towards the tiny gaseous DMMP species. PMID:22163653

  20. Iron-manganese nanowires for magnetoresistance

    NASA Astrophysics Data System (ADS)

    Brown, Joshua M.; Wilson, Chester

    2010-04-01

    The research presented in this abstract pertains to nanowire-structured magnetic sensors fabricated by pulsed, template electrodeposition relying on giant magnetoresistance (GMR). System fabrication involves electrodepositing metals with a DC-biased square wave from a solution of iron-manganese solution into the porous aluminum oxide surface of an aluminum sheet. The chemical make-up of the resulting 20nm diameter, 500nm length nanowires was 6 at% manganese and 45 at% iron, which is desirable because the ferromagnetic layers (Fe) should be large in comparison with the nonmagnetic layers (Mn). The resulting nanowires exhibited a 73% drop in resistance when exposed to an external magnetic field.

  1. Quartz crystal growth

    DOEpatents

    Baughman, Richard J. (Albuquerque, NM)

    1992-01-01

    A process for growing single crystals from an amorphous substance that can undergo phase transformation to the crystalline state in an appropriate solvent. The process is carried out in an autoclave having a lower dissolution zone and an upper crystallization zone between which a temperature differential (.DELTA.T) is maintained at all times. The apparatus loaded with the substance, solvent, and seed crystals is heated slowly maintaining a very low .DELTA.T between the warmer lower zone and cooler upper zone until the amorphous substance is transformed to the crystalline state in the lower zone. The heating rate is then increased to maintain a large .DELTA.T sufficient to increase material transport between the zones and rapid crystallization. .alpha.-Quartz single crystal can thus be made from fused quartz in caustic solvent by heating to 350.degree. C. stepwise with a .DELTA.T of 0.25.degree.-3.degree. C., increasing the .DELTA.T to about 50.degree. C. after the fused quartz has crystallized, and maintaining these conditions until crystal growth in the upper zone is completed.

  2. Critical Aspects of Alloying of Sintered Steels with Manganese

    NASA Astrophysics Data System (ADS)

    Hryha, Eduard; Dudrova, Eva; Nyborg, Lars

    2010-11-01

    This study examines the sintering behavior and properties of Fe-0.8Mn-0.5C manganese powder metallurgy steels. The study focuses on the influence of mode of alloying—admixing using either high-purity electrolytic manganese or medium carbon ferromanganese as well as the fully prealloying of water-atomized powder. Three main aspects were studied during the whole sintering process—microstructure development, interparticle necks evolution, and changes in the behavior of manganese carrier particles during both heating and sintering stages. The prealloyed powder shows considerable improvement in carbon homogenization and interparticle neck development in comparison with admixed materials. The first indication of pearlite for the fully prealloyed material was registered at ~1013 K (740 °C) in comparison with ~1098 K (825 °C) in the case of the admixed systems. The negative effect of the oxidized residuals of manganese carrier particles and high microstructure inhomogeneity, which is a characteristic feature of admixed systems, is reflected in the lower values of the mechanical properties. The worst results in this respect were obtained for the system admixed with electrolytic manganese because of more intensive manganese sublimation and resulting oxidation at lower temperatures. According to the results of X-ray photoelectron spectroscopy and high-resolution scanning electron microscopy and energy dispersive X-ray analyses, the observed high brittleness of admixed materials is connected with intergranular decohesion failure associated with manganese oxide formation on the grain boundaries.

  3. Ferromagnetism in Manganese Compounds

    Microsoft Academic Search

    R. O. Zaitsev

    1998-01-01

    The ferromagnetic instability in a system of manganese cations and oxygen, nitrogen and phosphorus anions on the basis of the strong electron-electron interaction is studied. The phase diagram for the existence of ferromagnetic ordering depending on the filling p6-shells of anions and dl0-shells of manganese is constructed.

  4. BIOLOGICAL EFFECTS OF MANGANESE

    EPA Science Inventory

    The biological effects of manganese were studied in a town on the coast of Dalmatia in which a ferromanganese plant has been operating since before World War II. The study focused on the question of whether the exposure to manganese can cause a higher incidence of respiratory dis...

  5. Manganese porphyrin multilayer films assembled on ITO electrodes via zirconium phosphonate chemistry: chemical and electrochemical

    E-print Network

    Manganese porphyrin multilayer films assembled on ITO electrodes via zirconium phosphonate University, 2145 Sheridan Road, Evanston, IL 60208-3113 A supported manganese porphyrin-based oxidation oxidation of the film-based catalyst at pH 11 generated MnV (O)(porphyrin)(H2O) intermediate at a potential

  6. Mitochondrial Susceptibility to Oxidative Stress Exacerbates Cerebral Infarction That Follows Permanent Focal Cerebral Ischemia in Mutant Mice with Manganese Superoxide Dismutase Deficiency

    Microsoft Academic Search

    Kensuke Murakami; Takeo Kondo; Makoto Kawase; Yibing Li; Shuzo Sato; Sylvia F. Chen; Pak H. Chan

    superoxide anion (O2 2 ) production and the target of free radical attacks. We evaluated these mechanisms in an in vivo cerebral ischemia model, using mutant mice with a heterozygous knock- out gene (Sod2 2\\/1) encoding mitochondrial manganese su- peroxide dismutase (Mn-SOD). Sod2 2\\/1 mice demonstrated a prominent increase in O2 2 production under normal physio- logical conditions and in

  7. Health and environmental testing of manganese exhaust products from use of methylcyclopentadienyl manganese tricarbonyl in gasoline.

    PubMed

    Pfeifer, G D; Roper, J M; Dorman, D; Lynam, D R

    2004-12-01

    This paper reviews recent research on the environmental effects of methylcyclopentadienyl manganese tricarbonyl (MMT), personal exposures to airborne Mn as a result of MMT use, chemical characterization of the manganese particulates emitted from the tailpipe and progress in developing a (PBPK) model for manganese in rodents. Recent studies show that manganese is emitted as a mixture of compounds with an average valence of about 2.2. The major products are sulfate, phosphate, and smaller amounts of oxides. Because only small amounts of Mn are used in gasoline (<18 mg Mn/gal) and less than 15% of the combusted Mn is emitted, soil along busy roads is not elevated in Mn, even after long-term use of MMT. A very large population-based study of manganese exposures in the general population in Toronto, where MMT has been used continuously for over 20 years, showed that manganese exposures were quite low, the median annual exposure was 0.008 microg Mn/m(3). A great amount of toxicological research on Mn has been carried out during the past few years that provides data for use in developing a PBPK model in rodents. These data add greatly to the existing body of knowledge regarding the relationship between Mn exposure and tissue disposition. When complete, the PBPK model will contribute to our better understanding of the essential neurotoxic dynamics of Mn. PMID:15504525

  8. Electrochemical quartz crystal microbalance, voltammetry, spectroelectrochemical, and microscopic studies of adsorption behavior for (7E,7{prime}Z)-diphenyl-7,7{prime}-diapocarotene electrochemical oxidation product

    SciTech Connect

    Gao, G.; Wurm, D.B.; Kim, Y.T.; Kispert, L.D. [Univ. of Alabama, Tuscaloosa, AL (United States)] [Univ. of Alabama, Tuscaloosa, AL (United States)

    1997-03-13

    Polymeric products, which are formed by reaction of the dications of (7E,7{prime}Z)-diphenyl-7,7{prime}-diapocarotene (I) generated by electrochemical oxidation in dichloromethane with the neutral carotenoid, are adsorbed on various electrode surfaces. An apparent average molar mass of 5400 g/(mol electrons) was calculated from simultaneous electrochemical quartz crystal microbalance (EQCM) measurements, and the green, fiber-like structure observed by optical microscopy confirms the formation of polymers. X-ray microanalysis of the surface composed of an uneven, layered structure indicates that electrolyte counter anions PF{sub 6}{sup -} are associated with the deposited material. Cathodic stripping voltammetry indicates that the film thickness ranges from 0.16 to 0.84 {mu}m as the charge increases from 10.0 to 51.1 {mu}C. Cation radicals of I show no adsorption behavior nor do the dications of carotenoids terminally substituted with one cyclohexene ring (V) or containing a triple bond at C15 (IV). Apparently a diphenyl-substituted carotenoid containing only double bonds in the backbone is required to observe this unusual behavior. 57 refs., 12 figs., 1 tab.

  9. Manganese-rich red tourmaline from the Fowler talc belt, New York.

    USGS Publications Warehouse

    Ayuso, R.A.; Brown, C.E.

    1984-01-01

    Red uvite containing up to 4.34 wt.% MnO is found in the Arnold talc mine near Fowler, New York, USA. Microprobe analyses give a composition of 51% uvite in the uvite-dravite series. Associated minerals in this manganiferous metamorphic assemblage (possibly an evaporite) are manganese-rich tremolite (hexagonite) braunite and quartz.-R.A.G.

  10. Neutron activation analysis of fluid inclusions for copper, manganese, and zinc

    USGS Publications Warehouse

    Czamanske, G.K.; Roedder, E.; Burns, F.C.

    1963-01-01

    Microgram quantities of copper, manganese, and zinc, corresponding to concentrations greater than 100 parts per million, were found in milligram quantities of primary inclusion fluid extracted from samples of quartz and fluorite from two types of ore deposits. The results indicate that neutron activation is a useful analytical method for studying the content of heavy metal in fluid inclusions.

  11. Comparative pneumotoxicity of cyclopentadienyl manganese tricarbonyl and methylcyclopentadienyl manganese tricarbonyl.

    PubMed

    Clay, R J; Morris, J B

    1989-05-01

    The acute pneumotoxic effects of cyclopentadienyl manganese tricarbonyl (CMT) and methylcyclopentadienyl manganese tricarbonyl (MMT) were compared to delineate the role of the methyl side chain in the toxicity of these organomanganese compounds and to further our understanding of the mechanisms by which these compounds act. Specifically, lung manganese (Mn) burdens and the pneumotoxic response, as measured by bronchoalveolar lavage parameters, were determined in male Sprague-Dawley rats 24 hr after sc administration of 0.5, 1.0, or 2.5 mg Mn/kg as CMT or MMT. The pneumotoxic response to either compound was characterized by large increases in lavage albumin and protein content with smaller increases in lactate dehydrogenase levels. CMT was approximately twice as potent as MMT. This difference in potency may be due to methyl side chain oxidation, a metabolic detoxification pathway unavailable to CMT. Lung Mn content was significantly elevated after treatment with either CMT or MMT. Heptane extraction studies revealed that Mn was accumulated in a nonlipid soluble form, suggesting the accumulation of metabolites rather than heptane soluble parent MMT or CMT. A strong correlation between pulmonary Mn content and toxicity was observed, suggesting a causal relationship between the accumulation of CMT or MMT metabolites and toxicity. Piperonyl butoxide diminished both the pneumotoxicity and Mn accumulation resulting from CMT or MMT, suggesting both phenomena are due to monooxygenase metabolites. Pulmonary nonprotein sulfhydryl (NPSH) levels were increased twofold 24 hr after administration of either CMT or MMT. Depletion of NPSH was not observed 1.5 or 6 hr after administration. The mechanisms of this response are unclear but may be due to the metabolism of CMT or MMT to unstable compounds which release inorganic Mn within pulmonary cells. PMID:2718172

  12. Manganese-Zinc-Ferrites with Improved Magnetic and Mechanical Properties

    Microsoft Academic Search

    H. Baumgartner; J. Dreikorn; R. Dreyer; L. Michalowsky; E. Pippel; J. Woltersdorf

    1997-01-01

    The 3-component system of manganese-zinc-ferrites is being thoroughly investigated as regards its intrinsic properties. The macroscopic properties of these spinel are variable within broad limits over the process of microstructure formation. Oxides of the 3d and 4d elements are frequently used as additives to determine the temperature dependence of the initial permeability and the electrical conductivity of manganese-zinc-ferrites. Additives for

  13. Manganese (III) meso-tetrakis N-ethylpyridinium-2-yl porphyrin acts as a pro-oxidant to inhibit electron transport chain proteins, modulate bioenergetics, and enhance the response to chemotherapy in lymphoma cells.

    PubMed

    Jaramillo, Melba C; Briehl, Margaret M; Batinic-Haberle, Ines; Tome, Margaret E

    2015-06-01

    The manganese porphyrin, manganese (III) meso-tetrakis N-ethylpyridinium-2-yl porphyrin (MnTE-2-PyP(5+)), acts as a pro-oxidant in the presence of intracellular H2O2. Mitochondria are the most prominent source of intracellular ROS and important regulators of the intrinsic apoptotic pathway. Due to the increased oxidants near and within the mitochondria, we hypothesized that the mitochondria are a target of the pro-oxidative activity of MnTE-2-PyP(5+) and that we could exploit this effect to enhance the chemotherapeutic response in lymphoma. In this study, we demonstrate that MnTE-2-PyP(5+) modulates the mitochondrial redox environment and sensitizes lymphoma cells to antilymphoma chemotherapeutics. MnTE-2-PyP(5+) increased dexamethasone-induced mitochondrial ROS and oxidation of the mitochondrial glutathione pool in lymphoma cells. The combination treatment induced glutathionylation of Complexes I, III, and IV in the electron transport chain, and decreased the activity of Complexes I and III, but not the activity of Complex IV. Treatment with the porphyrin and dexamethasone also decreased cellular ATP levels. Rho(0) malignant T-cells with impaired mitochondrial electron transport chain function were less sensitive to the combination treatment than wild-type cells. These findings suggest that mitochondria are important for the porphyrin's ability to enhance cell death. MnTE-2-PyP(5+) also augmented the effects of 2-deoxy-D-glucose (2DG), an antiglycolytic agent. In combination with 2DG, MnTE-2-PyP(5+) increased protein glutathionylation, decreased ATP levels more than 2DG treatment alone, and enhanced 2DG-induced cell death in primary B-ALL cells. MnTE-2-PyP(5+) did not enhance dexamethasone- or 2DG-induced cell death in normal cells. Our findings suggest that MnTE-2-PyP(5+) has potential as an adjuvant for the treatment of hematologic malignancies. PMID:25725417

  14. Lack of p53 Decreases Basal Oxidative Stress Levels in the Brain Through Upregulation of Thioredoxin-1, Biliverdin Reductase-A, Manganese Superoxide Dismutase, and Nuclear Factor Kappa-B

    PubMed Central

    Barone, Eugenio; Cenini, Giovanna; Sultana, Rukhsana; Di Domenico, Fabio; Fiorini, Ada; Perluigi, Marzia; Noel, Teresa; Wang, Chi; Mancuso, Cesare; St. Clair, Daret K.

    2012-01-01

    Abstract Aims: The basal oxidative and nitrosative stress levels measured in cytosol, mitochondria, and nuclei as well as in the whole homogenate obtained from the brain of wild type (wt) and p53 knockout [p53(?/?)] mice were evaluated. We hypothesized that the loss of p53 could trigger the activation of several protective mechanisms such as those involving thioredoxin-1 (Thio-1), the heme-oxygenase-1/biliverdin reductase-A (HO-1/BVR-A) system, manganese superoxide dismutase (MnSOD), the IkB kinase type ? (IKK?)/nuclear factor kappa-B (NF-kB), and the nuclear factor-erythroid 2 (NF-E2) related factor 2 (Nrf-2). Results: A decrease of protein carbonyls, protein-bound 4-hydroxy-2-nonenal (HNE), and 3-nitrotyrosine (3-NT) was observed in the brain from p53(?/?) mice compared with wt. Furthermore, we observed a significant increase of the expression levels of Thio-1, BVR-A, MnSOD, IKK?, and NF-kB. Conversely a significant decrease of Nrf-2 protein levels was observed in the nuclear fraction isolated from p53(?/?) mice. No changes were found for HO-1. Innovation: This is the first study of basal oxidative/nitrosative stress in in vivo conditions of brain obtained from p53(?/?) mice. New insights into the role of p53 in oxidative stress have been gained. Conclusion: We demonstrated, for the first time, that the lack of p53 reduces basal oxidative stress levels in mice brain. Due to the pivotal role that p53 plays during cellular stress response our results provide new insights into novel therapeutic strategies to modulate protein oxidation and lipid peroxidation having p53 as a target. The implications of this work are profound, particularly for neurodegenerative disorders. Antioxid. Redox Signal. 16, 1407–1420. PMID:22229939

  15. Quartz resonator processing system

    DOEpatents

    Peters, Roswell D. M. (Rustburg, VA)

    1983-01-01

    Disclosed is a single chamber ultra-high vacuum processing system for the oduction of hermetically sealed quartz resonators wherein electrode metallization and sealing are carried out along with cleaning and bake-out without any air exposure between the processing steps. The system includes a common vacuum chamber in which is located a rotatable wheel-like member which is adapted to move a plurality of individual component sets of a flat pack resonator unit past discretely located processing stations in said chamber whereupon electrode deposition takes place followed by the placement of ceramic covers over a frame containing a resonator element and then to a sealing stage where a pair of hydraulic rams including heating elements effect a metallized bonding of the covers to the frame.

  16. Dual quartz crystal microbalance

    SciTech Connect

    Dunham, G.C.; Benson, N.H.; Petelenz, D.; Janata, J. (Pacific Northwest Lab., Richland, WA (United States))

    1995-01-15

    Construction and performance of a dual quartz crystal microbalance is described. The final probe has a dipstick configuration that is particularly suitable for sensing and monitoring applications in viscous and/or conducting liquids. The differential (heterodyned) frequency measurement substantially eliminates the deleterious effects of viscosity, temperature, and conductivity. The corresponding performance coefficients are temperature df/dT = 1.5 Hz/[degree]C, viscosity df/d[eta][sub L] = 103 Hz/cP, and conductivity df/dM = 108 Hz/M, where conductivity is expressed in terms of molarity of sodium chloride. As an example, the etching of a 2000-A-thick layer of aluminum has been monitored as a function of time. 13 refs., 8 figs., 1 tab.

  17. Spuriousless single wavelength quartz resonators

    Microsoft Academic Search

    Y. Nagaura; K. Nagaura; Z. Nagaura

    2004-01-01

    The primary research objective is to manufacture quartz resonators that can oscillate elastic waves with a single wavelength and a precise directional performance. This objective has been the dream of many researchers since the discovery of the piezoelectric effect of quartz in 1880 by the brothers Pierre and Jacques Curie who brought into being the development of the ultrasonic and

  18. Hydrothermal Synthesis of Quartz Nanocrystals

    E-print Network

    conditions where bulk quartz is known to precipitate from aqueous solutions saturated with silica mechanisms responsible for solid-state amorphization and the R- transition, and their solution phase applications motivated us to develop a solution-phase route to form nanoquartz. Quartz possesses features

  19. Astrocyte-derived nitric oxide in manganese neurotoxicity: from cellular and molecular mechanisms underlying selective neuronal vulnerability in the basal ganglia to potential therapeutic modalities

    E-print Network

    Liu, Xuhong

    2007-04-25

    oxide synthase (iNOS/NOS2) and production of nitric oxide (NO)/peroxynitrite (ONOO-). Activated astrocytes were detected primarily near the microvasculature in both the striatum and globus pallidus (GP). It is suggested that Mn exposure may damage...

  20. REGIOSELECTIVE OXIDATIONS OF EQUILENIN DERIVATIVES CATALYZED BY A RHODIUM (III) PORPHYRIN COMPLEX-CONTRAST WITH THE MANGANESE (III) PORPHYRIN. (R826653)

    EPA Science Inventory

    Abstract Equilenin acetate and dihydroequilenin acetate were oxidized with iodosobenzene and a rhodium(III) porphyrin catalyst. The selectivity of the reactions differs from that with the corresponding Mn(III) catalyst, or from that of free radical chain oxidation....

  1. Arsenic removal by manganese greensand filters

    SciTech Connect

    Phommavong, T. [Saskatchewan Environment, Regina (Canada); Viraraghavan, T. [Univ. of Regina, Saskatchewan (Canada). Faculty of Engineering

    1994-12-31

    Some of the small communities in Saskatchewan are expected to have difficulty complying with the new maximum acceptable concentration (MAC) of 25 {micro}g/L for arsenic. A test column was set up in the laboratory to study the removal of arsenic from the potable water using oxidation with KMnO{sub 4}, followed by manganese greensand filtration. Tests were run using water from the tap having a background arsenic concentration of <0.5 {micro}g/L and iron concentration in the range of 0.02 to 0.77 mg/L. The test water was spiked with arsenic and iron. Results showed that 61 % to 98% of arsenic can be removed from the potable water by oxidation with KMnO{sub 4} followed by manganese greensand filtration.

  2. Augmentation of pulmonary reactions to quartz inhalation by trace amounts of iron-containing particles.

    PubMed Central

    Castranova, V; Vallyathan, V; Ramsey, D M; McLaurin, J L; Pack, D; Leonard, S; Barger, M W; Ma, J Y; Dalal, N S; Teass, A

    1997-01-01

    Fracturing quartz produces silica-based radicals on the fracture planes and generates hydroxyl radicals (.OH) in aqueous media. .OH production has been shown to be directly associated with quartz-induced cell damage and phagocyte activation in vitro. This .OH production in vitro is inhibited by desferrioxamine mesylate, an Fe chelator, indicating involvement of a Fenton-like reaction. Our objective was to determine if Fe contamination increased the ability of inhaled quartz to cause inflammation and lung injury. Male Fischer 344 rats were exposed 5 hr/day for 10 days to filtered air, 20 mg/m3 freshly milled quartz (57 ppm Fe), or 20 mg/m3 freshly milled quartz contaminated with Fe (430 ppm Fe). High Fe contamination of quartz produced approximately 57% more reactive species in water than quartz with low Fe contamination. Compared to inhalation of quartz with low Fe contamination, high Fe contamination of quartz resulted in increases in the following responses: leukocyte recruitment (537%), lavageable red blood cells (157%), macrophage production of oxygen radicals measured by electron spin resonance or chemiluminescence (32 or 90%, respectively), nitric oxide production by macrophages (71%), and lipid peroxidation of lung tissue (38%). These results suggest that inhalation of freshly fractured quartz contaminated with trace levels of Fe may be more pathogenic than inhalation of quartz alone. PMID:9400745

  3. Application of pharmacokinetic data to the risk assessment of inhaled manganese.

    PubMed

    Dorman, David C; Struve, Melanie F; Clewell, Harvey J; Andersen, Melvin E

    2006-09-01

    There is increased interest within the scientific community concerning the neurotoxicity of manganese owing in part to the use of methylcyclopentadienyl manganese tricarbonyl (MMT) as a gasoline fuel additive and an enhanced awareness that this essential metal may play a role in hepatic encephalopathy and other neurologic diseases. Neurotoxicity generally arises over a prolonged period of time and results when manganese intake exceeds its elimination leading to increases in brain manganese concentration. Neurotoxicity can occur following high dose oral, inhalation, or parenteral exposure or when hepatobiliary clearance of this metal is impaired. Studies completed during the past several years have substantially improved our understanding of the health risks posed by inhaled manganese by determining exposure conditions that lead to increased concentrations of manganese within the central nervous system and other target organs. Many of these studies focused on phosphates, sulfates, and oxides of manganese since these are formed and emitted following MMT combustion by an automobile. These studies have evaluated the role of direct nose-to-brain transport of inhaled manganese and have examined differences in manganese toxicokinetics in potentially sensitive subpopulations (e.g., fetuses, neonates, individuals with compromised hepatic function or sub-optimal manganese intake, and the aged). This manuscript reviews the U.S. Environmental Protection Agency's current risk assessment for inhaled manganese, summarizes these contemporary pharmacokinetic studies, and considers how these data could inform future risk assessments of this metal following inhalation. PMID:16644014

  4. A2MnU3O11 (A = K, Rb) and Li3.2Mn1.8U6O22: Three New Alkali-Metal Manganese Uranium(VI) Oxides Related to Natrotantite.

    PubMed

    Read, Cory Michael; Morrison, Gregory; Yeon, Jeongho; Smith, Mark D; Zur Loye, Hans-Conrad

    2015-07-20

    Single crystals of three new alkali-metal manganese uranium oxides, K2MnU3O11, Rb2MnU3O11, and Li3.2Mn1.8U6O22, have been grown from molten chloride fluxes and structurally characterized by single-crystal X-ray diffraction. The first two compounds crystallize in the trigonal space group, R3?c, in the three-dimensional (3D), natrotantite structure composed of ?-U3O8-topological layers connected via MnO6 octahedra. The Li-containing compound crystallizes in the monoclinic space group, Cc, with a related 3D structure, composed of ?-U3O8-topological sheets connected via irregular MnO7 polyhedra. All three compounds exhibit typical uranyl, UO2(2+), coordination environments consisting of either UO7 pentagonal bipyramids or UO6 flattened octahedra. The lattice parameters of the new oxides are K2MnU3O11, a = 6.8280(2) Å, c = 36.8354(17) Å; Rb2MnU3O11, a = 6.8407(2) Å, c = 37.5520(17) Å; and Li3.2Mn1.8U6O22, a = 11.8958(8) Å, b = 10.9639(7) Å, c = 13.3269(8) Å, and ? = 91.442(4)°. The magnetic susceptibilities of the K and Rb phases are discussed. PMID:26158295

  5. Movement of dislocations in quartz

    NASA Astrophysics Data System (ADS)

    Murray, R. A.

    1992-04-01

    Dislocations in quartz crystals have been known to cause problems in the fabrication of resonators by the formation of etch channels. The etch channels are known to weaken the physical strength of quartz blanks and to reduce the yield in photolithographic production processes. While it is possible to reduce the etch channel density in quartz by post growth electro-diffusion, this does not reduce the dislocation density. It is suspected that dislocations contribute to acceleration sensitivity, thermal hysteresis, and possibly aging. The behavior of dislocations in quartz is also of interest to the fields of geophysics, seismology, and plate tectonics because it affects the underground movement of rock. Specifically, the movement of dislocations in quartz is the mechanism through which quartz can be plastically deformed. A large body of literature on the movement of dislocations in natural and cultured quartz has been published in various geophysical journals over the past thirty years. This paper is a review of this literature and its possible implications for frequency control.

  6. Fe-oxide grain coatings support bacterial Fe-reducing metabolisms in 1.7-2.0 km-deep subsurface quartz arenite sandstone reservoirs of the Illinois Basin (USA).

    PubMed

    Dong, Yiran; Sanford, Robert A; Locke, Randall A; Cann, Isaac K; Mackie, Roderick I; Fouke, Bruce W

    2014-01-01

    The Cambrian-age Mt. Simon Sandstone, deeply buried within the Illinois Basin of the midcontinent of North America, contains quartz sand grains ubiquitously encrusted with iron-oxide cements and dissolved ferrous iron in pore-water. Although microbial iron reduction has previously been documented in the deep terrestrial subsurface, the potential for diagenetic mineral cementation to drive microbial activity has not been well studied. In this study, two subsurface formation water samples were collected at 1.72 and 2.02 km, respectively, from the Mt. Simon Sandstone in Decatur, Illinois. Low-diversity microbial communities were detected from both horizons and were dominated by Halanaerobiales of Phylum Firmicutes. Iron-reducing enrichment cultures fed with ferric citrate were successfully established using the formation water. Phylogenetic classification identified the enriched species to be related to Vulcanibacillus from the 1.72 km depth sample, while Orenia dominated the communities at 2.02 km of burial depth. Species-specific quantitative analyses of the enriched organisms in the microbial communities suggest that they are indigenous to the Mt. Simon Sandstone. Optimal iron reduction by the 1.72 km enrichment culture occurred at a temperature of 40°C (range 20-60°C) and a salinity of 25 parts per thousand (range 25-75 ppt). This culture also mediated fermentation and nitrate reduction. In contrast, the 2.02 km enrichment culture exclusively utilized hydrogen and pyruvate as the electron donors for iron reduction, tolerated a wider range of salinities (25-200 ppt), and exhibited only minimal nitrate- and sulfate-reduction. In addition, the 2.02 km depth community actively reduces the more crystalline ferric iron minerals goethite and hematite. The results suggest evolutionary adaptation of the autochthonous microbial communities to the Mt. Simon Sandstone and carries potentially important implications for future utilization of this reservoir for CO2 injection. PMID:25324834

  7. Chemically activated manganese dioxide for dry batteries

    NASA Astrophysics Data System (ADS)

    Askar, M.; Abbas, H.

    1994-10-01

    The present investigation has enabled us to convert inactive beta-manganese dioxide to high electrochemically active types by chemical processes. Natural and chemically prepared beta-manganese dioxides were roasted at 1050 C to form Mn3O4. This compound was subjected to activation treatment using hydrochloric and sulfuric acid under various reaction conditions. The manganese dioxide so obtained was examined by x-ray diffraction, thermogravimetric, differential thermal, and chemical analyses. The structure of the dioxide obtained was found to be greatly dependent on the origin of MnO2 and type of acid used. Treatment with hydrochloric acid yielded the so-called gamma-variety while sulfuric acid tended to produce gamma- or alpha-MnO2. In addition, waste manganese sulfate obtained as by-product from sulfuric acid digestion treatment was recycled and electrolytically oxidized to gamma-MnO2. The discharge performance of the above-mentioned MnO2 samples as battery cathodic active material was evaluated and compared with the ordinary battery grade.

  8. Biological manganese removal from acid mine drainage in constructed wetlands and prototype bioreactors

    Microsoft Academic Search

    Kevin B. Hallberg; D. Barrie Johnson

    2005-01-01

    Mine drainage waters vary considerably in the range and concentration of heavy metals they contain. Besides iron, manganese is frequently present at elevated concentrations in waters draining both coal and metal mines. Passive treatment systems (aerobic wetlands and compost bioreactors) are designed to remove iron by biologically induced oxidation\\/precipitation. Manganese, however, is problematic as it does not readily form sulfidic

  9. Thermoelectrically-cooled quartz microbalance

    NASA Technical Reports Server (NTRS)

    Mckeown, D.

    1975-01-01

    Temperature of microbalance can be maintained at ambient temperature or held at some other desired temperature. Microbalance has tow-stage thermoelectric device that controls temperature of quartz crystal. Heat can be pumped to or from balance by Peltier effect.

  10. Preparation and characterization of lithium manganese oxide cubic spinel Li 1.03Mn 1.97O 4 doped with Mg and Fe

    NASA Astrophysics Data System (ADS)

    Singh, Priti; Sil, Anjan; Nath, Mala; Ray, Subrata

    2010-01-01

    Spinel powders of Li 1.03Mn 1.97O 4, Li 1.03[Mg xMn 1.97-x]O 4, Li 1.03[Fe yMn 1.97-y]O 4 and Li 1.03[Mg xFe yMn 1.97-x-y]O 4 systems were synthesized by sol-gel technique using lithium acetate, manganese acetate, magnesium acetate, iron nitrate and citric acid as the starting materials. The effect of Mg and Fe substitutions on the structure and surface morphology of spinel Li 1.03Mn 1.97O 4 has been examined by X-ray diffraction (XRD), Field emission scanning electron microscopy (FE-SEM) and Infrared spectroscopy (IR). Electrochemical characteristics such as the cyclic performance was also investigated. The materials for all the compositions exhibit a phase pure cubic spinel structure as evident from the XRD analyses. The crystallinity and average particle size of the material increases by doping with Fe and Mg. The particles of doped samples have truncated octahedral shape. The discharge capacity of Li 1.03Mn 1.97O 4 is 126 mAh/g. The doping increases cyclability; however, the discharge capacity reduces.

  11. Astrocyte-derived nitric oxide in manganese neurotoxicity: from cellular and molecular mechanisms underlying selective neuronal vulnerability in the basal ganglia to potential therapeutic modalities 

    E-print Network

    Liu, Xuhong

    2007-04-25

    enkephalin (ENK)-positive projection neurons, interneurons expressing neuronal nitric oxide synthetase (nNOS/NOS1), and choline acetyltransferase (ChAT)-expressing interneurons. Activation of surrounding astrocytes occurred with expression of inducible nitric...

  12. Synthesis, characterization and application of a nano-manganese-catalyst as an efficient solid catalyst for solvent free selective oxidation of ethylbenzene, cyclohexene, and benzylalcohol

    NASA Astrophysics Data System (ADS)

    Habibi, Davood; Faraji, Ali Reza

    2013-07-01

    The object of this study is to synthesize the heterogeneous Mn-nano-catalyst (MNC) which has been covalently anchored on a modified nanoscaleSiO2/Al2O3, and characterized by FT-IR, UV-Vis, CHN elemental analysis, EDS, TEM, and EDX. The method is efficient for the highly selective oxidation of ethylbenzene, cyclohexene, and benzylalcohol without the need to any solvents, using tert-butyl hydroperoxide (TBHP) as an oxidant. Oxidation of ethylbenzene, cyclohexene, and benzylalcohol gave acetophenone, 2-cyclohexene-1-one and benzaldehyde, respectively, as major products. Reaction conditions have been optimized by considering the effect of various factors such as reaction time, amounts of substrates and oxidant, Mn-nano-catalyst and application of various solvents.

  13. Thermodynamic analysis of manganese

    Microsoft Academic Search

    A. Fernández Guillermet; W. Huang

    1990-01-01

    A description of the Gibbs energy of the various solid modifications of manganese at 101325 Pa has been obtained for the whole temperature range from 298 K to the melting point. The present analysis accounts for the effect of a magnetic transition in a-, ?-, and d-Mn, which is treated using the Inden-Hillert-Jarl phenomenological model for the magnetic Gibbs energy.

  14. A practical innovative method for highly selective oxidation of alcohols in neat water using water-insoluble iron and manganese porphyrins as reusable heterogeneous catalysts

    Microsoft Academic Search

    Abdolreza Rezaeifard; Maasoumeh Jafarpour; Atena Naeimi

    2011-01-01

    A novel heterogeneous method for clean and selective oxidation of alcohols to the aldehydes and ketones using tetrabutylammonium peroxomonosulfate (n-Bu4NHSO5) in neat water catalyzed by simple Fe (III) and Mn (III) meso-tetraphenylporphyrin as a water-insoluble catalyst has been developed. The oxidation system proceeds well in the absence of organic co-solvents and surfactants. The presence of an electron-donating group on the

  15. Chemical and structural investigation of the role of both Mn and Mn oxide in the formation of manganese silicate barrier layers on SiO2

    NASA Astrophysics Data System (ADS)

    Casey, P.; Bogan, J.; Lozano, J. G.; Nellist, P. D.; Hughes, G.

    2011-09-01

    In this study, Mn silicate (MnSiO3) barrier layers were formed on thermally grown SiO2 using both metallic Mn and oxidized Mn films, in order to investigate the role of oxygen in determining the extent of the interaction between the deposited Mn and the SiO2 substrate. Using x-ray photoelectron spectroscopy, it has been shown that a metallic Mn film with an approximate thickness of 1 nm cannot be fully converted to Mn silicate following vacuum annealing to 500 °C. Transmission electron microscopy (TEM) analysis suggests the maximum MnSiO3 layer thickness obtainable using metallic Mn is ˜1.7 nm. In contrast, a ˜1 nm partially oxidized Mn film can be fully converted to Mn silicate following thermal annealing to 400 °C, forming a MnSiO3 layer with a measured thickness of 2.6 nm. TEM analysis also clearly shows that MnSiO3 growth results in a corresponding reduction in the SiO2 layer thickness. It has also been shown that a fully oxidized Mn oxide thin film can be converted to Mn silicate, in the absence of metallic Mn. Based on these results it is suggested that the presence of Mn oxide species at the Mn/SiO2 interface facilitates the conversion of SiO2 to MnSiO3, in agreement with previously published studies.

  16. Manganese micro-nodules on ancient brick walls.

    PubMed

    López-Arce, P; García-Guinea, J; Fierro, J L G

    2003-01-20

    Romans, Jews, Arabs and Christians built the ancient city of Toledo (Spain) with bricks as the main construction material. Manganese micro-nodules (circa 2 microm in diameter) have grown under the external bio-film surface of the bricks. Recent anthropogenic activities such as industrial emissions, foundries, or traffic and housing pollution have further altered these old bricks. The energy-dispersive X-ray microanalyses (XPS) of micro-nodules show Al, Si, Ca, K, Fe and Mn, with some carbon species. Manganese atoms are present only as Mn(4+) and iron as Fe(3+) (FeOOH-Fe(2)O(3) mixtures). The large concentration of alga biomass of the River Tagus and the Torcón and Guajaraz reservoirs suggest manganese micro-nodules are formed either from water solutions rich in anthropogenic MnO(4)K in a reduction environment (from Mn(7+) to Mn(4+)) or by oxidation mechanisms from dissolved Mn(2+) (from Mn(2+) to Mn(4+)) linked to algae biofilm onto the ancient brick surfaces. Ancient wall surfaces were also studied by scanning electron microscopy (SEM-EDS) and X-ray diffraction (XRD). Chemical and biological analyses of the waters around Toledo are also analysed for possible sources of manganese. Manganese micro-nodules on ancient brick walls are good indicators of manganese pollution. PMID:12526915

  17. THE STATE OF MANGANESE IN THE PHOTOSYNTHETIC APPARATUS: FIRST VIEW OF THE MANGANESE SITES BY X-RAY ABSORPTION SPECTROSCOPY

    SciTech Connect

    Kirby, Jon A.; Goodin, D.B.; Robertson, A.S.; Smith, J.P.; Thompson, A.C.; Klein, M.P.

    1980-11-01

    Manganese atoms have long been implicated as essential ingredients in photosynthetic oxygen evolution. Heretofore they have eluded direct observation. We report the first direct observation, by X-ray Absorption Spectroscopy, of the Mn sites in chloroplasts isolated from Spinacia oleracea. The manganese in chlorplasts is commonly thought to exist in two pools. The major pool, corresponding to two-thirds of the manganese, can be reversibly released with concomitant loss of oxygen evolving capacity, and has thus come to be assigned as the active pool. The role of the remanant one-third, or tightly bound pool is moot. Our analysis of the Extended X-ray Absorption Fine Structure of the active pool is consistent with a bridged dimeric structure involving two manganese atoms separated by about 2.7 {Angstroms}. The distance between manganese and bridging ligands is about 1.8 {Angstrom}. Analysis of the edge region suggests that the manganese in the active pool exists in oxidation states somewhat higher than Mn(II).

  18. Manganese-Cycling Microbial Communities Inside Deep-Sea Manganese Nodules.

    PubMed

    Blöthe, Marco; Wegorzewski, Anna; Müller, Cornelia; Simon, Frank; Kuhn, Thomas; Schippers, Axel

    2015-07-01

    Polymetallic nodules (manganese nodules) have been formed on deep sea sediments over millions of years and are currently explored for their economic potential, particularly for cobalt, nickel, copper, and manganese. Here we explored microbial communities inside nodules from the northeastern equatorial Pacific. The nodules have a large connected pore space with a huge inner surface of 120 m(2)/g as analyzed by computer tomography and BET measurements. X-ray photoelectron spectroscopy (XPS) and electron microprobe analysis revealed a complex chemical fine structure. This consisted of layers with highly variable Mn/Fe ratios (<1 to >500) and mainly of turbostratic phyllomanganates such as 7 and 10 Å vernadites alternating with layers of Fe-bearing vernadite (?-MnO2) epitaxially intergrown with amorphous feroxyhyte (?-FeOOH). Using molecular 16S rRNA gene techniques (clone libraries, pyrosequencing, and real-time PCR), we show that polymetallic nodules provide a suitable habitat for prokaryotes with an abundant and diverse prokaryotic community dominated by nodule-specific Mn(IV)-reducing and Mn(II)-oxidizing bacteria. These bacteria were not detected in the nodule-surrounding sediment. The high abundance and dominance of Mn-cycling bacteria in the manganese nodules argue for a biologically driven closed manganese cycle inside the nodules relevant for their formation and potential degradation. PMID:26020127

  19. Phylogenetic Relationships and Functional Genes: Distribution of a Gene (mnxG) Encoding a Putative Manganese-Oxidizing Enzyme in Bacillus Species?

    PubMed Central

    Mayhew, Lisa E.; Swanner, Elizabeth D.; Martin, Andy P.; Templeton, Alexis S.

    2008-01-01

    Several Bacillus and Paenibacillus species were isolated from Fe and Mn oxide minerals precipitating at a deep subsurface oxic-anoxic interface at Henderson Molybdenum Mine, Empire, CO. The isolates were investigated for their Mn(II)-oxidizing potential and interrogated for possession of the mnxG gene, a gene that codes for a putative Mn(II)-oxidizing enzyme in Bacillus species. Seven of eight Bacillus species were capable of Mn(II) oxidation; however, the mnxG gene was detected in only one isolate. Using sequences of known Bacillus species both with and without amplifiable mnxG genes and Henderson Mine isolates, the 16S rRNA and mnxG gene phylogenies were compared to determine if 16S rRNA sequences could be used to predict the presence or absence of an amplifiable mnxG gene within the genomes of the isolates. We discovered a strong correspondence between 16S rRNA sequence similarity and the presence/absence of an amplifiable mnxG gene in the isolates. The data revealed a complex phylogenetic distribution of the mnxG gene in which vertical inheritance and gene loss influence the distribution of the gene among the Bacillus species included in this study. Comparisons of 16S rRNA and functional gene phylogenies can be used as a tool to aid in unraveling the history and dispersal of the mnxG gene within the Bacillus clade. PMID:18849460

  20. 21 CFR 73.2775 - Manganese violet.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...Identity. The color additive manganese violet is a violet pigment obtained by reacting phosphoric acid, ammonium dihydrogen...and manganese dioxide at temperatures above 450 °F. The pigment is a manganese ammonium pyrophosphate complex having the...