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1

Oxidation-Reduction Potential in Sea Water  

Microsoft Academic Search

In bacteriological studies much attention is now given to oxidation-reduction potentials. The systems studied have usually potentials at least 0'4 V. below that of the reversible oxygen electrode, are reasonably well poised and obey laws thermodynamically deduced. Owing to the irreversibility of the oxygen electrode and to difficulties of measurement no such attention has been given to oxidation-reduction potentials in

L. H. N. Cooper

1937-01-01

2

Oxidation Reduction Potential network sensor based on Kalman filtering  

Microsoft Academic Search

This paper introduced an oxidation reduction potential network sensor based on Kalman filtering, which based on embedded system. This sensor uses depolarization measure to dispose platinum electrode and Ag-AgCl electrode, and it can detect oxidation reduction potential (ORP) fast and exactly. Also, this senor uses wireless mesh network to realize flexible network measure. So it can arbitrary add and delete

Gao Meijuan; Zhang Fan; Tian Jingwen

2008-01-01

3

The effect of shock on blood oxidation-reduction potential  

Microsoft Academic Search

Oxidation-reduction (redox) potential measurements were made in the blood of rabbits subjected to hemorrhagic shock followed by treatment with a mild oxidizing agent (albumin). Control redox potential reading corrected for pH was ?8.8±1.3 millivolts (mV) in arterial blood (A) and ?18.0±2.0 mV in venous blood (V). This A-V difference indicated that hydrogen equivalents coming from muscle and other tissues were

M. Jellinek; B. Chandel; R. Abdulla; M. J. Shapiro; A. E. Baue

1992-01-01

4

Oxidation-reduction potentials of different chlorophylls in methanol  

Microsoft Academic Search

It was found that the reversible decolorisation of some chlorophylls upon the subsequent addition of ferric and ferrous salts, as originally measured by Rabinowtich and Weiss for chlorophyll a, proceeded at a reproducible oxidation-reduction potential.\\u000a\\u000aA marked difference was found to occur between the redox potentials of the bacterial pigments and those of the green plant pigments.\\u000a\\u000aApart from these

J. C. Goedheer; G. H. Horreus de Haas; P. Schuller

1958-01-01

5

RELATIONSHIPS BETWEEN OXIDATION-REDUCTION POTENTIAL, OXIDANT, AND PH IN DRINKING WATER  

EPA Science Inventory

Oxidation and reduction (redox) reactions are very important in drinking water. Oxidation-reduction potential (ORP) measurements reflect the redox state of water. Redox measurements are not widely made by drinking water utilities in part because they are not well understood. The ...

6

The Oxidation-Reduction Potential in Lignifying Cells  

Microsoft Academic Search

DURING the lignification process of the cell walls the carbon content increases considerably. A strong reduction must take place in the living cells which begin to lignify. We have tried to determine the reduction potential of the tissues by means of the colorimetric method applied thus far only to isolated cells (unicellular organisms, and in yeast- and bacteria-suspensions). The results

K. Griffioen

1938-01-01

7

The generation and inactivation mechanism of oxidation–reduction potential of electrolyzed oxidizing water  

Microsoft Academic Search

The Nernst equations between the oxidation–reduction potential (ORP), the concentration of hypochlorous acid and chlorine and the value of pH in electrolyzed oxidizing water (EOW) were developed in three parts, which were in agreement in the measured values. The role of ORP in EOW for killing Escherichia coli O157:H7 was studied. The inactivation effect of EOW on E. coli O157:H7

Long B. Liao; Wei M. Chen; Xian M. Xiao

2007-01-01

8

Apparatus for controlling the Oxidation-reduction Potential of Waterlogged Soils  

Microsoft Academic Search

OXIDATION-REDUCTION or redox potential measurements have been widely used in the study of chemical and biological reactions in waterlogged soils. The oxidation-reduction potential is used to characterize aeration in waterlogged soils because the more commonly used measurements of oxygen concentration and oxygen diffusion rate are of little value. Dissolved oxygen is usually completely absent or present in very low concentration

William H. Patrick

1966-01-01

9

Development of Linear Irreversible Thermodynamic Model for Oxidation Reduction Potential in Environmental Microbial System  

Microsoft Academic Search

Nernst equation has been directly used to formulate the oxidation reduction potential (ORP) of reversible thermodynamic conditions but applied to irreversible conditions after several assumptions and\\/or modifications. However, the assumptions are sometimes inappropriate in the quantification of ORP in nonequilibrium system. We propose a linear nonequilibrium thermodynamic model, called microbial related reduction and oxidation reaction (MIRROR Model No. 1) for

Hong-Bang Cheng; Mathava Kumar; Jih-Gaw Lin

2007-01-01

10

Effect of estuarine sediment pH and oxidation-reduction potential on microbial hydrocarbon degradation  

Microsoft Academic Search

Microbial mineralization ratas of two petroleum hydrocarbons, as affected by pH and oxidation-reduction potential, were determined in a Barateria Bay, Louisiana, sediment using ¹⁴C-labeled hydrocarbons. Hydrocarbon mineralization rates were inferred from the activity of respired ¹⁴COâ. Sediment pH and oxidation-reduction potential were important factors in governing the population of hydrocarbon-degrading microorganisms in the sediment and subsequent mineralization rates. Highest mineralization

G. A. Hambrick; R. D. DeLaune; W. H. Jr. Patrick

1980-01-01

11

THE OXIDATION-REDUCT ION POTENTIAL OF RUMEN CONTENTS ~'2  

Microsoft Academic Search

SUMMARY The relationship between the Eh and ptI of rumen fluid was found to be represented by the equation Eh =Eo- 0.06 pit. Investigation of the reductive capacity of rumen fluid removed from cows on various rations indicated : 1. A very small proportion of the reduced substances found in rumen fluid is as- sociated with the bacterial cells. 2.

R. L. BALDWIN AXD; S. EMERY

12

Effect of estuarine sediment pH and oxidation-reduction potential on microbial hydrocarbon degradation  

SciTech Connect

Microbial mineralization ratas of two petroleum hydrocarbons, as affected by pH and oxidation-reduction potential, were determined in a Barateria Bay, Louisiana, sediment using /sup 14/C-labeled hydrocarbons. Hydrocarbon mineralization rates were inferred from the activity of respired /sup 14/CO/sub 2/. Sediment pH and oxidation-reduction potential were important factors in governing the population of hydrocarbon-degrading microorganisms in the sediment and subsequent mineralization rates. Highest mineralization rates occurred at pH 8.0, and the lowest occurred at pH 5.0. At all pH levels mineralization decreased with decreasing oxidation-reduction potential (i.e., increasing sediment anaerobiosis). Generally, mineralization rates for octadecane were greater than those for naphthalene. Aerobic microorganisms in the oxidized sediment were more capable of degrading hydrocarbons than anaerobic microorganisms in reduced sediment of the same pH.

Hambrick, G.A. III; DeLaune, R.D.; Patrick, W.H. Jr.

1980-08-01

13

Effect of Estuarine Sediment pH and Oxidation-Reduction Potential on Microbial Hydrocarbon Degradation  

PubMed Central

Microbial mineralization rates of two petroleum hydrocarbons, as affected by pH and oxidation-reduction potential, were determined in a Barataria Bay, Louisiana, sediment using 14C-labeled hydrocarbons. Hydrocarbon mineralization rates were inferred from the activity of respired 14CO2. Sediment pH and oxidation-reduction potential were important factors in governing the population of hydrocarbon-degrading microorganisms in the sediment and subsequent mineralization rates. Highest mineralization rates occurred at pH 8.0, and the lowest occurred at pH 5.0. At all pH levels mineralization decreased with decreasing oxidation-reduction potential (i.e., increasing sediment anaerobiosis). Generally, mineralization rates for octadecane were greater than those for naphthalene. Aerobic microorganisms in the oxidized sediment were more capable of degrading hydrocarbons than anaerobic microorganisms in reduced sediment of the same pH.

Hambrick, Gordon A.; DeLaune, Ronald D.; Patrick, W. H.

1980-01-01

14

INTRACELLULAR OXIDATION-REDUCTION STUDIES II. REDUCTION POTENTIALS OF MARINE OVA AS SHOWN BY INDICATORS1  

Microsoft Academic Search

A NEW approach to the problems of cellular metabolism was opened by J. and D. Needham(8) who used the micro-injection of reversible indicators to determine the oxidation-reduction intensity of living protoplasm. Prerequisites for this work were the elaboration of a series, as yet incomplete, of such indicators, and the electrometric standardisation of the position of each dye on the scale

ROBERT CHAMBERS; HERBERT POLLACK

15

Oxidation–reduction potential and paraoxonase–arylesterase activity in trauma patients  

Microsoft Academic Search

The amount of oxidative stress in severely traumatized patients is usually based on various individual parameters such as total antioxidants and lipid peroxidation. Serial measurements of plasma oxidation–reduction potential (ORP) in severely traumatized patients as a simple mean of assessing overall oxidative stress is described. Serial whole blood samples were obtained from multi-trauma patients (N=39) and healthy individuals (N=10). Plasma

Leonard T. Rael; Raphael Bar-Or; Rachel M. Aumann; Denetta S. Slone; Charles W. Mains; David Bar-Or

2007-01-01

16

Negative oxidation reduction potential as the limiting factor for exogastrulation in sea urchins  

Microsoft Academic Search

Summary The underlying factor in all these experiments is the matter of energy levels as indicated by oxidation-reduction potentials, and the importance of a correct potential in controlling the activation of the enzyme systems upon which growth and development of living cells depends.

Matilda Moldenhauer Brooks

1959-01-01

17

Relationship between release of nitric oxide and CO 2 and their dependence on oxidation reduction potential in wastewater treatment  

Microsoft Academic Search

Nitric oxide (NO) is an intermediate of denitrification process and can be produced by denitrifiers, nitrifiers and other bacteria. In our experiments we measured the dynamic flow of NO depending on oxidation reduction potential (ORP). Different ORP-ranges were related to various carbon loading stages in the wastewater treatment pilot plant. Nitrification and denitrification were achieved by a sequence of aeration

M. Fuerhacker; H. Bauer; R. Ellinger; U. Sree; H. Schmid; F. Zibuschka; H. Puxbaum

2001-01-01

18

The reduction potential of nitric oxide (NO) and its importance to NO biochemistry  

Microsoft Academic Search

A potential of about -0.8 (±0.2) V (at 1 M versus normal hydrogen electrode) for the reduction of nitric oxide (NO) to its one-electron reduced species, nitroxyl anion (3NO-) has been determined by a combination of quantum mechanical calculations, cyclic voltammetry measurements, and chemical reduction experiments. This value is in accord with some, but not the most commonly accepted, previous

Michael D. Bartberger; Wei Liu; Eleonora Ford; Katrina M. Miranda; Christopher Switzer; Jon M. Fukuto; Patrick J. Farmer; David A. Wink; Kendall N. Houk

2002-01-01

19

Characteristics of Volatile Fatty Acid and Oxidation Reduction Potential for Treating Municipal Wastewater in Modified EGSB  

Microsoft Academic Search

The traditional Expanded Granular Sludge Bed (EGSB) reactor was modified to treating municipal wastewater. The characteristics of Oxidation Reduction Potential (ORP) and Volatile Fatty Acid (VFA) concentration of effluent was studied to judge to the operation condition of anaerobic degradation process. The characteristics of ORP and VFA for treating municipal wastewater was studied in modified Expanded Granular Sludge Bed (EGSB).

Ma Limin; Sun Xiaojing; Ma Xiujuan

2009-01-01

20

The Measurement of Oxidation-Reduction Potentials, pH, and Oxygen Tension in Tumours  

Microsoft Academic Search

By use of the apparatus and techniques described in the previous paper (Cater, Phillips & Silver 1957a) the oxidation-reduction potentials in Walker carcinoma and Jensen rat sarcoma have been investigated, and compared with those of rat muscle, lactating mammary gland, liver, testis and brain. The changes which occur during the treatment of mammary carcinoma in man and the dog are

D. B. Cater; A. F. Phillips; I. A. Silver

1957-01-01

21

Monitoring Mortality of Pythium Zoospores in Chlorinated Water Using Oxidation Reduction Potential  

Microsoft Academic Search

Pythium species are frequently recovered from recycled irrigation water in greenhouse production systems and may cause damping off and root rot if the water is not disinfested properly. Chlorination is often employed as a disinfesting agent, but can be difficult to monitor accurately because its activity is pH- dependent. Oxidation reduction potential (ORP) is a reliable, real-time measurement of the

Jillian M. Lang; Brittany Rebits; Steven E. Newman; Ned Tisserat

22

The reduction potential of nitric oxide (NO) and its importance to NO biochemistry.  

PubMed

A potential of about -0.8 (+/-0.2) V (at 1 M versus normal hydrogen electrode) for the reduction of nitric oxide (NO) to its one-electron reduced species, nitroxyl anion (3NO-) has been determined by a combination of quantum mechanical calculations, cyclic voltammetry measurements, and chemical reduction experiments. This value is in accord with some, but not the most commonly accepted, previous electrochemical measurements involving NO. Reduction of NO to 1NO- is highly unfavorable, with a predicted reduction potential of about -1.7 (+/-0.2) V at 1 M versus normal hydrogen electrode. These results represent a substantial revision of the derived and widely cited values of +0.39 V and -0.35 V for the NO/3NO- and NO/1NO- couples, respectively, and provide support for previous measurements obtained by electrochemical and photoelectrochemical means. With such highly negative reduction potentials, NO is inert to reduction compared with physiological events that reduce molecular oxygen to superoxide. From these reduction potentials, the pKa of 3NO- has been reevaluated as 11.6 (+/-3.4). Thus, nitroxyl exists almost exclusively in its protonated form, HNO, under physiological conditions. The singlet state of nitroxyl anion, 1NO-, is physiologically inaccessible. The significance of these potentials to physiological and pathophysiological processes involving NO and O2 under reductive conditions is discussed. PMID:12177417

Bartberger, Michael D; Liu, Wei; Ford, Eleonora; Miranda, Katrina M; Switzer, Christopher; Fukuto, Jon M; Farmer, Patrick J; Wink, David A; Houk, Kendall N

2002-08-12

23

The reduction potential of nitric oxide (NO) and its importance to NO biochemistry  

PubMed Central

A potential of about ?0.8 (±0.2) V (at 1 M versus normal hydrogen electrode) for the reduction of nitric oxide (NO) to its one-electron reduced species, nitroxyl anion (3NO?) has been determined by a combination of quantum mechanical calculations, cyclic voltammetry measurements, and chemical reduction experiments. This value is in accord with some, but not the most commonly accepted, previous electrochemical measurements involving NO. Reduction of NO to 1NO? is highly unfavorable, with a predicted reduction potential of about ?1.7 (±0.2) V at 1 M versus normal hydrogen electrode. These results represent a substantial revision of the derived and widely cited values of +0.39 V and ?0.35 V for the NO/3NO? and NO/1NO? couples, respectively, and provide support for previous measurements obtained by electrochemical and photoelectrochemical means. With such highly negative reduction potentials, NO is inert to reduction compared with physiological events that reduce molecular oxygen to superoxide. From these reduction potentials, the pKa of 3NO? has been reevaluated as 11.6 (±3.4). Thus, nitroxyl exists almost exclusively in its protonated form, HNO, under physiological conditions. The singlet state of nitroxyl anion, 1NO?, is physiologically inaccessible. The significance of these potentials to physiological and pathophysiological processes involving NO and O2 under reductive conditions is discussed.

Bartberger, Michael D.; Liu, Wei; Ford, Eleonora; Miranda, Katrina M.; Switzer, Christopher; Fukuto, Jon M.; Farmer, Patrick J.; Wink, David A.; Houk, Kendall N.

2002-01-01

24

The oxidation-reduction potential and absorption spectra in the ultraviolet and visible regions of some homoannular disubstituted ferrocenes  

Microsoft Academic Search

1.We have measured the oxidation-reduction potentials and ultraviolet spectra of a series of isomeric disubstituted ferrocenes.2.In the case of amides of substituted ferrocene carboxylic acids, we found actual differences of the 1,2-isomers from the others,both in the ultraviolet spectra and the values of the oxidation-reduction potentials.

A. N. Nesmeyanov; É. G. Perevalova; L. N. Yur'eva; S. P. Gubin

1965-01-01

25

Fabrication of microelectrode arrays for in situ sensing of oxidation reduction potentials  

Microsoft Academic Search

There is a clear need for in situ monitoring of oxidation–reduction potential (ORP) in many environmental applications, particularly those involving water quality monitoring and wastewater treatment. This paper describes fabrication of microelectrode sensor arrays for measurements of ORP in situ in the environment, such as at Superfund sites. The four-probe microelectrode arrays were fabricated from glass using a two-step, HF-based

Jin-Hwan Lee; Am Jang; Prashant R. Bhadri; Rhonda R. Myers; William Timmons; Fred R. Beyette Jr.; Paul L. Bishop; Ian Papautsky

2006-01-01

26

The oxidation-reduction potential of aqueous soil solutions at the Mars Phoenix landing site  

Microsoft Academic Search

Results from the Mars Phoenix mission Wet Chemistry Laboratory (WCL) are used to determine the oxidation-reduction potential (Eh) of the Phoenix WCL Rosy Red sample soil solution. The measured Eh of the Rosy Red sample in the WCL aqueous test solution was 253 ± 6 mV at a pH of 7.7 ± 0.1. Measured solution Eh changes correspond to changes

Richard C. Quinn; Julie D. Chittenden; Samuel P. Kounaves; Michael H. Hecht

2011-01-01

27

Anaerobic DDT biotransformation: Enhancement by application of surfactants and low oxidation reduction potential  

Microsoft Academic Search

Enhancement of anaerobic DDT (1,1,1-trichloro-2,2-bis(p-chlorophenyl) ethane) biotransformation by mixed cultures was studied with application of surfactants and oxidation reduction potential reducing agents. Without amendments, DDT transformation resulted mainly in the production of DDD (1,1-dichloro-2,2-bis(p-chlorophenyl) ethane) upon removal of one aliphatic chlorine. The DDT transformation rate increased with the addition of the nonionic surfactants Triton X-114 or Brij 35. The addition

Guanrong You; Gregory D. Sayles; Margaret J. Kupferle; In S. Kim; Paul L. Bishop

1996-01-01

28

Effect of the oxidation – reduction potential on the proneness of glass to form bubbles  

Microsoft Academic Search

The fining of glass is closely related with the oxidation-reduction potential of the glass, which is determined by means of\\u000a an indication index—the fraction of bivalent iron, which is proportional to the absorption of the glass in the range 900 –\\u000a 1100 nm. The appearance of seeds in optical glasses is explained by elevated solubility of nitrogen in the molten

A. B. Atkarskaya

2010-01-01

29

The effect of various levels of nitrogen, potassium and phosphorus on oxidation reduction potentials in barley  

Microsoft Academic Search

The effect of nutrient solutions with certain essential elements lacking, on oxidation reduction potential (RP) of the first leaf was examined in two cultivars of barley seedlings NO3\\u000a ? and K+ decreasedRP considerably, PO\\u000a 4\\u000a 3?\\u000a did not. The effect of NO3\\u000a ? and K+ was dependent. on the illuminance. Under glasshouse conditions, the increased level of NO3\\u000a ? and

J. Benada; Marie Vá?ová

1972-01-01

30

Grey relational analysis on the relation between marine environmental factors and oxidation-reduction potential  

Microsoft Academic Search

The effects of marine environmental factors-temperature (T), dissolved oxygen (DO), salinity (S) and pH-on the oxidation-reduction\\u000a potential (ORP) of natural seawater were studied in laboratory. The results show an indistinct relationship between these\\u000a four factors and the ORP, but they did impact the ORP. Common mathematical methods were not applicable for describing the\\u000a relationship. Therefore, a grey relational analysis (GRA)

Xueqing Liu; Jia Wang; Dun Zhang; Yantao Li

2009-01-01

31

Improvement of nitrogen-removal efficiency using immobilized microorganisms with oxidation–reduction potential monitoring  

Microsoft Academic Search

  The use of an immobilized-cell reactor for simultaneous carbon–nitrogen removal in wastewater with the monitoring of oxidation–reduction\\u000a potential (ORP) in an intermittent aeration (IA) process was investigated. Under alternating aerated and nonaerated conditions,\\u000a the ORP-time profile showed distinctive turning points that directly correlated with changes in the system chemistry and biological\\u000a activity. The aeration ratio, defined as aeration time\\/cycle time,

K-C Chen; J-J Chen; J-Y Houng

2000-01-01

32

Control of a swine manure treatment process using a specific feature of oxidation reduction potential  

Microsoft Academic Search

A real-time control strategy for waste treatment, using a specific feature of oxidation–reduction potential (ORP) feature, was developed; the usefulness of this technology was evaluated through two separate operations. A newly designed, two-stage, bench-scale wastewater treatment process for swine wastewater was successfully operated with this real-time control technology. The nitrogen break point (NBP) on the ORP-time profile was designated as

C. s. Ra; K. v. Lo; D. s. Mavinic

1999-01-01

33

Haem exposure as the determinate of oxidation-reduction potential of haem proteins  

Microsoft Academic Search

KASSNER1 has proposed that the apolarity of the haem environment primarily determines the oxidation-reduction potential, E'0pH 7.0, of a haem protein. Since high resolution crystallographic models are now available for six haem proteins with E'0 values of between 20 and 320 mV, I have tested the Kassner proposal by comparing the kinds of atoms contacting the haem in each of

Earle Stellwagen

1978-01-01

34

Effects of Oxidation Reduction Potential and Organic Compounds on Anammox Reaction in Batch Cultures  

Microsoft Academic Search

The present study investigates the effect of oxidation-reduction potential (ORP) and organic compounds on specific anaerobic ammonium oxida- tion activity (SAA) using batch experiments. The batch tests were based on the measurement of nitrogen gas production. The relationship between ORP and dissolved oxygen (DO) concentration was found to be ORP (mV) = 160.38 + 68 log (O2), where (O2) is

Truong Nguyen Viet; Shishir Kumar Behera; Ji Won Kim; Hung-Suck Park

35

Variation in Arsenic Concentration Relative to Ammonium Nitrogen and Oxidation Reduction Potential in Surface and Groundwater  

Microsoft Academic Search

Arsenic (As), ammonium?nitrogen (N), nitrate?N concentrations, and oxidation–reduction potential (ORP) in the water samples from the river, pond, dug well, and shallow and deep tube wells (TW) were investigated in a farming village of southwestern Bangladesh. Concentrations of As and ammonium?N were the highest, whereas ORP was the lowest in the shallow TW water among the water sources. The ammonium?N

Kiyoshi Kurosawa; Kazuhiko Egashira; Masakazu Tani; M. Jahiruddin; Abu Zofar M. Moslehuddin; M. Zulfikar Rahman

2008-01-01

36

Relationship between tyrosinase inhibitory action and oxidation-reduction potential of cosmetic whitening ingredients and phenol derivatives  

Microsoft Academic Search

The oxidation-reduction potentials of cosmetic raw materials, showing tyrosinase inhibitory action, and phenolic compounds\\u000a structurally similar to L-tyrosine were determined by cyclic voltammetry. The voltammograms obtained could be classified into\\u000a 4 patterns (patterns 1–4). Pattern 1, characterized by oxidation and reduction peaks as a pair, was observed with catechol,\\u000a hydroquinone or phenol, and pattern 2 exhibiting another oxidation peak in

Katsuya Sakuma; Masayuki Ogawa; Kenji Sugibayashi; Koh-ichi Yamada; Katsumi Yamamoto

1999-01-01

37

Induced Changes in Oxidation-Reduction Potentials, pH, and Oxygen Tension in the Intact Lactating Mammary Gland  

Microsoft Academic Search

This work was undertaken to find if a study of oxidation-reduction potentials, pH and oxygen tension would yield information concerning physiological changes induced in lactating mammary glands of rats and rabbits by hormones and other substances. Breathing oxygen at atmospheric pressure caused a rapid rise in oxygen tension in lactating mammary gland, and a small, slower rise of oxidation-reduction potential.

D. B. Cater; A. F. Phillips; I. A. Silver

1957-01-01

38

Reduction of Iron Oxide Fines to Wustite with CO/CO2 Gas of Low Reducing Potential  

NASA Astrophysics Data System (ADS)

The reduction of iron oxide fines to wustite between 590 °C and 1000 °C with a CO-CO2 gas mixture of low reducing potential was studied. The reduction kinetics and the dominating reaction mechanism varied with the temperature, extent of reduction, and type of iron oxide. Reduction from hematite to wustite proceeded in two consecutive reaction steps with magnetite as an intermediate oxide. The first reduction step (hematite to magnetite) was fast and controlled by external gas mass transfer independently of the oxide type and the temperature employed. The second reduction step (magnetite to wustite) was the overall reaction-controlling step, and the reduction mechanism varied with the temperature and the oxide type. Moderately porous oxide fines followed the uniform internal reaction for the temperature range studied. For highly porous oxides, the second reduction step was controlled by external gas mass transfer above 700 °C. Below that temperature, a mixed regime that involves external gas mass transfer and limited mixed control, which comprises pore diffusion and chemical reaction, takes place. The rate equations for this mixed control reaction mechanism were developed, and the limited mixed control rate constant (klm) was computed. For denser oxides under uniform internal reaction, the product of the rate constant and pore surface area (k· S) was calculated.

Corbari, R.; Fruehan, R. J.

2010-04-01

39

Fenton oxidation process control using oxidation-reduction potential measurement for pigment wastewater treatment  

Microsoft Academic Search

The Fenton oxidation process was applied as a pretreatment process to degrade non-biodegradable organic matters in pigment\\u000a wastewater. It was necessary to continuously measure the fluctuating concentration of organics in the pigment wastewater and\\u000a to determine the amount of Fenton’s reagent required to oxidize the organics. Batch and continuous flow tests were used to\\u000a evaluate the relationship between the concentration

Young-O Kim; Hai-Uk Nam; Yu-Ri Park; Jong-Hyun Lee; Tae-Joo Park; Tae-Ho Lee

2004-01-01

40

Grey relational analysis on the relation between marine environmental factors and oxidation-reduction potential  

NASA Astrophysics Data System (ADS)

The effects of marine environmental factors-temperature (T), dissolved oxygen (DO), salinity (S) and pH-on the oxidation-reduction potential (ORP) of natural seawater were studied in laboratory. The results show an indistinct relationship between these four factors and the ORP, but they did impact the ORP. Common mathematical methods were not applicable for describing the relationship. Therefore, a grey relational analysis (GRA) method was developed. The degrees of correlation were calculated according to GRA and the values of T, pH, DO and S were 0.744, 0.710, 0.692 and 0.690, respectively. From these values, the relations of these factors to the ORP could be described and evaluated, and those of T and pH were relatively major. In general, ORP is influenced by the synergic effect of T, DO, pH and S, with no single factor having an outstanding role.

Liu, Xueqing; Wang, Jia; Zhang, Dun; Li, Yantao

2009-09-01

41

Effects of nano zero-valent iron on oxidation-reduction potential.  

PubMed

Oxidation-reduction potential (ORP) measurements have been widely used to assess the results of injection of nano zerovalent iron (nZVI) for groundwater remediation, but the significance of these measurements has never been established. Using rotating disk electrodes (RDE) in suspensions of nZVI, we found the electrode response to be highly complex but also a very sensitive probe for a range of fundamentally significant processes. The time dependence of the electrode response reflects both a primary effect (attachment of nZVI onto the electrode surface) and several secondary effects (esp., oxidation of iron and variations in dissolved H2 concentration). At nZVI concentrations above ?200 mg/L, attachment of nZVI to the electrode is sufficient to give it the electrochemical characteristics of an Fe(0) electrode, making the electrode relatively insensitive to changes in solution chemistry. Lower nZVI concentrations give a proportional response in ORP, but much of this effect is mediated by the secondary effects noted above. Coating the nZVI with natural organic matter (NOM), or the organic polymers used to make stabile suspensions of nZVI, moderates its effect on ORP measurments. Our results provide the basis for interpretating ORP measurements used to characterize the results of injecting nZVI into groundwater. PMID:21204580

Shi, Zhenqing; Nurmi, James T; Tratnyek, Paul G

2011-01-04

42

Mineral species as functions of p H and oxidation-reduction potentials, with special reference to the zone of oxidation and secondary enrichment of sulphide ore deposits  

Microsoft Academic Search

A series of diagrams has been prepared showing some stability and solubility relations among lead, zinc, and copper minerals found in the zones of oxidation and secondary enrichment of sulphide ore deposits. The stability and solubility relations are expressed as functions of p H and oxidation-reduction potential. These diagrams show theoretical equilibrium relations, and are sufficiently similar to relations found

Robert M. Garrels

1954-01-01

43

NO x monitoring of a simultaneous nitrifying–denitrifying (SND) activated sludge plant at different oxidation reduction potentials  

Microsoft Academic Search

Simultaneous nitrification–denitrification (SND) allows biological nitrogen removal in a single reactor without separation of the two processes in time or space but requires adapted control strategies (anoxic\\/aerobic conditions). In this study, the formation of gaseous nitric oxide (NOG) and nitrogen dioxide (NO2G) was monitored for SND in relation to the oxidation-reduction potential (ORP) and nitrogen removal in a lab batch

Norbert Weissenbacher; Christian Loderer; Katharina Lenz; Susanne N. Mahnik; Bernhard Wett; Maria Fuerhacker

2007-01-01

44

Computational prediction of one-electron reduction potentials and Acid dissociation constants for Guanine oxidation intermediates and products.  

PubMed

Reduction potentials and pKa values were calculated for intermediates and products along three major pathways for guanine oxidation using the B3LYP and CBS-QB3 levels of theory with the SMD implicit solvation model. N-methylated nucleobases were used as models for nucleoside species. Ensemble averaged reduction potentials at pH 7 (E7) were obtained by combining calculated standard reduction potentials with calculated pKa values in addition to accounting for tautomerization energies. Calculated pKa values are reasonable based on experimental estimates and chemical intuition. Pathway A leads to guanidinohydantoin (Gh) and spiroiminodihydantoin (Sp). The first step is the oxidation of 8-oxoguanine which proceeds by the loss of an electron followed by the loss of two protons and loss of another electron, yielding 8-oxopurine. The calculated E7 values for the remaining intermediates and products are at least 0.3 V higher than that of guanine, indicating that further oxidation of these species is unlikely. Pathway B leads to two formamidopyrimidine isomers (FAPyG and 2,5FAPyG). Species along this pathway have calculated reduction potentials that are much lower than the oxidation potential for guanine and would likely be very short-lived in an oxidatively stressed environment. Pathway C leads to reduced spiroiminodihydantoin and 5-carboxamido-5-formamido-2-iminohydantoin (2Ih). Similar to pathway A, the calculated reduction potentials for species along this pathway are at least 0.4 V higher than that of guanine. PMID:23875631

Psciuk, Brian T; Schlegel, H Bernhard

2013-08-07

45

Apparatus and Techniques for the Measurement of Oxidation-Reduction Potentials, pH and Oxygen Tension in vivo  

Microsoft Academic Search

In order to follow the changes which occur in tumours during treatment with radiation, and the effects of radiosensitizing or radioprotecting drugs, apparatus and techniques have been developed to record automatically changes of oxidation-reduction potential on eight different electrodes. Simultaneous records of pH and oxygen tension changes were used as controls in some experiments. The changes of oxygen tension were

D. B. Cater; A. F. Phillips; I. A. Silver

1957-01-01

46

Wireless network measurement instrument of oxidation reduction potential based on multi-sensor data fusion of kalman filtering  

Microsoft Academic Search

Oxidation-reduction potential (ORP) is one of the important parameters which directly bears on the quality and efficiency of the sewage treatment process. A kind of ORP wireless network measurement instrument based on Kalman filtering multi-sensor data fusion technology is presented in this paper and the embedded systems is used as control unit of instrument. The instrument uses the depolarization method

Meijuan Gao; Fan Zhang; Jingwen Tian

2008-01-01

47

Negative oxidation-reduction potentials resulting from the use of auxin in plants and tobacco smoke on animal cells  

Microsoft Academic Search

Conclusion The action of auxin when used on plant growth is explained. Auxin becomes activated and has its maximum activity in the negative region of the oxidation reduction scale, with an approximate redox potential in the vicinity of — .1737 to — .198 volts at pH 7.O.

Matilda Moldenhauer Brooks

1959-01-01

48

Rumen microbial volatile fatty acids in relation to oxidation reduction potential and electricity generation from straw in microbial fuel cells  

Microsoft Academic Search

This study determined volatile fatty acids (VFA) from ruminal microbial fermentation in relation to oxidation reduction potential (ORP) and electricity generation from straw in microbial fuel cells. The effect of substrate straw to grain ratio on gas production, VFA, pH, and ORP during rumen microbial incubation with or without the presence of protozoa was evaluated. Increasing straw relative to grain

Chin Tsan Wang; Che Ming J. Yang; Zih Sheng Chen

49

Determination of chemical oxygen demand (COD) using ultrasound digestion and oxidation-reduction potential-based titration  

Microsoft Academic Search

A new method for determining wastewater chemical oxygen demand (COD) using ultrasonic digestion and titration based on oxidation reduction potential (ORP) was developed. COD values of potassium hydrogen phthalate solution obtained by ultrasonic digestion were well matched with those obtained using Standard Methods. When applied to determine COD of real wastewater collected from a local treatment plant, results from the

Hyunook Kim; Honglae Lim; Mark F. Colosimo

2007-01-01

50

Relation between reactivity and electrochemical oxidation reduction potentials of organomercury compounds. I. Symmetrization of substituted ethyl. cap alpha. -bromomercuriophenylacetates  

Microsoft Academic Search

An approximate correlation equation relating the logarithms of the reaction rate constants for the symmetrization of para-substituted ethyl ..cap alpha..-bromomercuriophenylacetates simultaneously with the electrochemical reduction and oxidation potentials of these compounds was obtained on the basis of molecular orbital perturbation theory and was confirmed by experimental data. This equation makes it possible to assess the degree of concertedness of the

K. P. Butin; R. D. Rakhimov; O. A. Reutov

1987-01-01

51

Requirement of low oxidation-reduction potential for photosynthesis in a blue-green alga ( Phormidium sp.)  

Microsoft Academic Search

Photosynthesis in a Phormidium species which forms dense conical-shaped structures in thermal springs is strongly inhibited by aeration but is stimulated by sulfide and other agents (cysteine, thioglycolate, sulfite) which lower the oxidation-reduction potential. The compact structures which this alga forms in nature may restrict oxygen penetration from the environment so that the anaerobic or microaerophilic conditions necessary for photosynthesis

Donald Weller; William Doemel; Thomas D. Brock

1975-01-01

52

Correlations between reduction–oxidation potential profiles and growth patterns of Saccharomyces cerevisiae during very-high-gravity fermentation  

Microsoft Academic Search

When Saccharomyces cerevisiae was grown under three glucose concentrations (ca. 200, 250, and 300g\\/l), controlled at three reduction–oxidation (redox) potentials (no control, ?150 and ?100mV) by manipulating two aerations (0.82 and 1.3vvm), we observed that the recorded redox potential profiles resembled bathtub curves, and the profiles correlated well to the growth patterns measured under the same conditions. According to the

Yen-Han Lin; Wan-Shan Chien; Kow-Jen Duan

2010-01-01

53

pH and oxidation-reduction potential change of environment during growth of lactic acid bacteria: Effects of oxidizers and reducers  

Microsoft Academic Search

Decrease of pH and dropping of oxidation-reduction potential have been observed during growing Lactobacillus salivarius 1588 and 3823, Lactobacillus acidophilus 101E, and Lactococcus lactis 3690 in anaerobic conditions in medium with glucose fermentation. These parameters and membrane proton permeability of bacteria\\u000a ($$\\u000aC_m^{H^ + } \\u000a$$) changed in the mediums with different pH. Oxidizer ferrycianide and reducer DL-dithiothreitol affected the

D. Soghomonyan; K. Akopyan; A. Trchounian

2011-01-01

54

Use of ORP (oxidation-reduction potential) to control oxygen dosing for online sulfide oxidation in anaerobic treatment of high sulfate wastewater  

Microsoft Academic Search

In this study, oxidation-reduction potential (ORP) was used as a controlling parameter to regulate oxygen dosing to the recycled biogas for online sulfide oxidation in an upflow anaerobic filter (UAF) system. The UAF was operated with a constant influent COD of 18,000 mg\\/L, but with different influent sulfates of 1000, 3000 and 6000 mg\\/L. The reactor was initially operated under

S. K. Khanal; C. Shang; J.-C. Huang

2003-01-01

55

Production of xylitol from Candida tropicalis by using an oxidation-reduction potential-stat controlled fermentation  

Microsoft Academic Search

An on-line device, ORP (oxidation-reduction potential)-stat, was used to control glucose-feeding for enhancing xylitol conversion from d-xylose during an oxygen-limited fermentation by Candida tropicalis. The fermentation was carried out in a 5 l jar fermenter. After glucose in the medium was depleted, a switching to a limited aeration and feeding glucose controlled by ORP-stat was performed. The maximum xylitol yield was obtained

Dey-Chyi Sheu; Kow-Jen Duan; Shiuan-Ru Jou; Ying-Chou Chen; C. Will Chen

2003-01-01

56

Real-time treatment of dairy manure: Implications of oxidation reduction potential regimes to nutrient management strategies  

Microsoft Academic Search

A pilot-scale sequencing batch reactor (SBR) was operated at a dairy farm to test real-time based control in winter operation conditions. A combination of high loading and low oxidation reduction potential (ORP) conditions in the aerobic stage of SBR treatment (an end value of ?50 to ?150mV) inhibited nitrification while maintaining carbon removal. After a period of over-aeration over several

Asif Qureshi; K. Victor Lo; Ping H. Liao; Donald S. Mavinic

2008-01-01

57

Optimum concentration of dissolved oxygen for the survival of virulent Treponema pallidum under conditions of low oxidation-reduction potential  

Microsoft Academic Search

A maintenance medium with a low oxidation-reduction (redox) potential, when gently bubbled with 5% oxygen in nitrogen or with air for various periods of time, gave a range of dissolved oxygen concentrations between 1.6 and 5.8 micrograms\\/l. Virulent Treponema pallidum (Nichols strain) inoculated into these media were assayed 24 and 48 hours later for motility and virulence and were compared

S Graves; T Billington

1979-01-01

58

GAMMA RADIATION INTERACTS WITH MELANIN TO ALTER ITS OXIDATION-REDUCTION POTENTIAL AND RESULTS IN ELECTRIC CURRENT PRODUCTION  

SciTech Connect

The presence of melanin pigments in organisms is implicated in radioprotection and in some cases, enhanced growth in the presence of high levels of ionizing radiation. An understanding of this phenomenon will be useful in the design of radioprotective materials. However, the protective mechanism of microbial melanin in ionizing radiation fields has not yet been elucidated. Here we demonstrate through the electrochemical techniques of chronoamperometry, chronopotentiometry and cyclic voltammetry that microbial melanin is continuously oxidized in the presence of gamma radiation. Our findings establish that ionizing radiation interacts with melanin to alter its oxidation-reduction potential. Sustained oxidation resulted in electric current production and was most pronounced in the presence of a reductant, which extended the redox cycling capacity of melanin. This work is the first to establish that gamma radiation alters the oxidation-reduction behavior of melanin, resulting in electric current production. The significance of the work is that it provides the first step in understanding the initial interactions between melanin and ionizing radiation taking place and offers some insight for production of biomimetic radioprotective materials.

Turick, C.; Ekechukwu, A.; Milliken, C.

2011-05-17

59

Injury severity and serum amyloid A correlate with plasma oxidation-reduction potential in multi-trauma patients: a retrospective analysis  

Microsoft Academic Search

BACKGROUND: In critical injury, the occurrence of increased oxidative stress or a reduced antioxidant status has been observed. The purpose of this study was to correlate the degree of oxidative stress, by measuring the oxidation-reduction potential (ORP) of plasma in the critically injured, with injury severity and serum amyloid A (SAA) levels. METHODS: A total of 140 subjects were included

Leonard T Rael; Raphael Bar-Or; Kristin Salottolo; Charles W Mains; Denetta S Slone; Patrick J Offner; David Bar-Or

2009-01-01

60

Relation between the reactivity and electrochemical oxidation-reduction potentials of organomercury compounds. II. Bromodemercuration and iododemercuration of organomercury bromides  

SciTech Connect

The bromodemercuration rates of substituted ethyl ..cap alpha..-bromomercuriophenylacetates, phenylmercuric bromides, various alkylmercuric bromides, and p-methoxybenzyl-mercuric bromides in aqueous acetonitrile were measured by means of a rotating disc electrode with ring. In the series of mercurated phenylacetic esters the reaction is accelerated with the introduction of electron-withdrawing substituents (Alk < H < Hlg < NO/sub 2/) at the para position, while in the series of phenylmercuric bromides, on the other hand, it is accelerated with the introduction of electron-donating substitutents (NMe/sub 2/ < OMe < Alk < H < Hlg). The results are interpreted in terms of a concerted five-center six-electron reaction; it is suggested that the bromodemercurating agent in the Br/sub 3//sup -/ anion. The bromodemercuration rates are compared with the electrochemical oxidation and reduction potentials of the respective organomercury compounds and with the oxidation and reduction potentials of the tribromide ion on the assumption that these potentials reflect the relative levels of the HOMO and LUMO of the interacting reagents.

Butin, K.P.; Rakhimov, R.D.; Reutov, O.A.

1988-01-10

61

Relation between reactivity and electrochemical oxidation reduction potentials of organomercury compounds. I. Symmetrization of substituted ethyl. cap alpha. -bromomercuriophenylacetates  

SciTech Connect

An approximate correlation equation relating the logarithms of the reaction rate constants for the symmetrization of para-substituted ethyl ..cap alpha..-bromomercuriophenylacetates simultaneously with the electrochemical reduction and oxidation potentials of these compounds was obtained on the basis of molecular orbital perturbation theory and was confirmed by experimental data. This equation makes it possible to assess the degree of concertedness of the four-center reaction with respect to the terminal atoms of the reacting fragments of molecules and the role of nucleophilic assistance in the reaction. It is concluded that the organomercury compounds, which are oxidized relatively easily and are at the same time reduced relatively easily, must be readily symmetrized.

Butin, K.P.; Rakhimov, R.D.; Reutov, O.A.

1987-10-10

62

Oxidation-reduction potentials in a salt marsh: Spatial patterns and interactions with primary production  

Microsoft Academic Search

Spurtina alterniflora oxidizes the sediments in which it grows through both passive oxygen release and active metabolic processes. Eh is higher in the root zone of this grass than in the sediment below the root zone or in unvegetated sediments. Sediments underlying the tall form of S. aZterniJorcl are more oxidized than those under the short form, and sediment redox

BRIAN L. HOWES; ROBERT W. HOWARTH; JOHN M. TEAL; IVAN VALIELA

1981-01-01

63

Effect of reducing agents on oxidation-reduction potential and the outgrowth of Clostridium botulinum type E spores.  

PubMed Central

Oxidation-reduction potential (Eh) levels were measured and standardized to pH (Eh7) for Trypticase soy broth containing various concentrations of reducing agents. Prereduced Trypticase soy broth with no added reducing agents exhibited a potential of -141 mV. Ascorbic acid at 0.2 to 0.005% and sodium thioglycolate at concentrations below 0.05% produced an Eh7 higher than the prereduced Trypticase soy broth containing no added reducing agents. The addition of cysteine hydrochloride,2-mercaptoethanol, and sodium formaldehyde sulfoxylate to prereduced Trypticase soy broth resulted in a reduction of Eh7 compared to the system without added reducing agents. The order of relative reducing intensity (from highest to lowest) for the reducing agents when comparing molar concentration was: sodium formaldehyde sulfoxylate,2-mercaptoethanol, cysteine hydrochloride, sodium thioglycolate, and ascorbic acid. Optimal growth of the test organism occurred at low Eh7 and low concentration of the reducing agents. A direct correlation existed between growth of the test organism and -Eh7 x -log concentration of the reducing agent.

Smith, M V; Pierson, M D

1979-01-01

64

Oxidation-Reduction Potentials of Bound Iron-Sulfur Proteins of Photosystem I  

Microsoft Academic Search

Digitonin - fractionated photosystem - I subchloroplasts were titrated potentiometrically between -450 and -610 mV at pH 10. Examination of the titrated subchloroplasts by low-temperature (13 degrees K) electron paramagnetic resonance spectroscopy revealed resonances centered at values of 2.05, 1.94, 1.92, 1.89, and 1.86 on the g-factor scale. The peak heights depended on the potentials at which the chloroplasts were

Bacon Ke; Raymond E. Hansen; Helmut Beinert

1973-01-01

65

[Interaction of membrane proton conductivity, membrane and oxidation-reduction potential in Escherichia coli].  

PubMed

It was shown that the proton conductivity of Escherichia coli membranes depends on pH and other conditions of bacterial growth. It is considerably lower in cells fermenting glucose and accomplishing the nitrate-nitrite respiration compared with cells accomplishing the oxygen respiration. Proton conductivity increases substantially with decreasing pH of medium. It was found that proton conductivity is related to the redox and membrane potentials of cells. The energy-dependent flux of protons from cells and the ATPase activity of membrane vesicles considerably vary depending on whether bacteria are grown under aerobic or anaerobic conditions. The H+ flux from cells fermenting glucose (pH 7.5) was 1.7 times greater than the H+ flux from cells that accomplish the nitrate-nitrite and oxygen respiration. The N,N'-dicyclohexylcarbodiimide (DCCD)-sensitive ATPase activity increased 2.5 times as K+ concentration increased to 100 mM (including residual K+ in potassium-free medium). The DCCD-sensitive ATPase activity considerably decreased with decreasing pH of medium, whereas the ATPase activity that was not suppressed by DCCD was stimulated. These results can be used for establishing the relationship between membrane proton conductivity and the energy-dependent H+ flux and ATPase activity. PMID:12500569

Akopian, K; Zakharian, E; Kirakosian, G; Mnatsakanian, N; Bagramian, K; Trchunian, A

66

Roles of oxidation-reduction potential in electrolyzed oxidizing and chemically modified water for the inactivation of food-related pathogens.  

PubMed

This study investigates the properties of electrolyzed oxidizing (EO) water for the inactivation of pathogen and to evaluate the chemically modified solutions possessing properties similar to EO water in killing Escherichia coli O157:H7. A five-strain cocktail (10(10) CFU/ml) of E. coli O157:H7 was subjected to deionized water (control), EO water with 10 mg/liter residual chlorine (J.A.W-EO water), EO water with 56 mg/liter residual chlorine (ROX-EO water), and chemically modified solutions. Inactivation (8.88 log10 CFU/ml reduction) of E. coli O157:H7 occurred within 30 s after application of EO water and chemically modified solutions containing chlorine and 1% bromine. Iron was added to EO or chemically modified solutions to reduce oxidation-reduction potential (ORP) readings and neutralizing buffer was added to neutralize chlorine. J.A.W-EO water with 100 mg/liter iron, acetic acid solution, and chemically modified solutions containing neutralizing buffer or 100 mg/liter iron were ineffective in reducing the bacteria population. ROX-EO water with 100 mg/liter iron was the only solution still effective in inactivation of E. coli O157:H7 and having high ORP readings regardless of residual chlorine. These results suggest that it is possible to simulate EO water by chemically modifying deionized water and ORP of the solution may be the primary factor affecting microbial inactivation. PMID:10643764

Kim, C; Hung, Y C; Brackett, R E

2000-01-01

67

Electronic state of heme in cytochrome oxidase. II. Oxidation-reduction potential interactions and heme iron spin state behavior observed in reductive titrations  

Microsoft Academic Search

Magnetic circular dichroism (MCD), electron paramagnetic resonance (EPR), and optical absorption spectroscopies have been used to monitor the concentrations of oxidized and reduced heme and copper during stoichiometric reductive titrations of purified beef heart cytochrome oxidase. The MCD data are deconvoluted to obtain the concentrations of reduced cytochromes a and aâ during the titrations; analysis of the EPR spectra provides

G. T. Babcock; L. E. Vickery; G. Palmer

1978-01-01

68

Influence of soil oxidation-reduction potential and salinity on nutrition, N-15 uptake, and growth of Spartina patens  

Microsoft Academic Search

Nutrition, photosynthesis, and growth responses ofSpartina patens to various intensities of sediment reduction (redox potentials, Eh) ranging between — 115 mV to +475 mV and\\/or salinity of\\u000a < 1 and 6 ppt were evaluated under controiled environmental conditions. Reduction in soil Eh to — 115 mV seemed to have little\\u000a effect on net photosynthesis, but 6 ppt salinity combined with

B. K. Bandyopadhyay; S. R. Pezeshki; R. D. DeLaune; C. W. Lindau

1993-01-01

69

Evaluation of the hydrogen bonding interactions and their effects on the oxidation-reduction potentials for the riboflavin complex of the Desulfovibrio vulgaris flavodoxin  

Microsoft Academic Search

The oxidation-reduction potentials for the riboflavin complex of the Desulfovibrio vulgaris flavodoxin are substantially different from those of the flavin mononucleotide (FMN) containing native protein, with the midpoint potential for the semiquinone-hydroquinone couple for the riboflavin complex being 180 mV less negative. This increase has been attributed to the absence in the riboflavin complex of unfavorable electrostatic effects of the

Fu-Chung Chang; Luke H Bradley; Richard P Swenson

2001-01-01

70

Catalytic reduction of nitrogen oxides  

Microsoft Academic Search

This patent describes a method for catalytically reducing one or more nitrogen oxides from a gaseous stream containing one or more nitrogen oxides and optionally one or more sulfur oxides. It comprises contacting the gases stream and ammonia with a microporous molecular sieve composition deleted from a zeolitic or silica molecular sieve or mixtures thereof at effective reduction conditions in

M. T. Staniulis; A. P. Risch; J. G. Vassilakill; D. F. Best

1989-01-01

71

Continuous operation of commercial-scale plasma–chemical aftertreatment system of smoke tube boiler emission with oxidation reduction potential and pH control  

Microsoft Academic Search

NOx removal from an actual boiler flue gas is investigated using an indirect plasma and chemical hybrid system comprising a commercial ozonizer and an Na2SO3 chemical scrubber. A high NOx removal efficiency in the continuous operation of a commercial-scale apparatus is achieved by controlling pH and oxidation reduction potential (ORP) and injecting additional Na2SO3 and NaOH aqueous solutions into the

Tomoyuki Kuroki; Hidekatsu Fujishima; Keiichi Otsuka; Tomohiro Ito; Masaaki Okubo; Toshiaki Yamamoto; Keiichiro Yoshida

2008-01-01

72

Synthesis of polyhydroxyalkanoate (PHA) from excess activated sludge under various oxidation-reduction potentials (ORP) by using acetate and propionate as carbon sources  

Microsoft Academic Search

Accumulation of poly hydroxyalkanoate (PHA) from excess activated sludge (EAS) was monitored and controlled via the oxidation-reduction\\u000a potential (ORP) adjusting process. The ORP was adjusted and controlled by only regulating the gas-flow rate pumped into the\\u000a cultural broth in which sodium acetate (C2) and propionate (C3) were used as carbon sources. Productivity of PHA and the PHA\\u000a compositions at various

W. F. Hu; S. N. Sin; H. Chua; P. H. F. Yu

2005-01-01

73

Synthesis of Polyhydroxyalkanoate (PHA) from Excess Activated Sludge Under Various Oxidation-Reduction Potentials (ORP) by Using Acetate and Propionate as Carbon Sources  

Microsoft Academic Search

Accumulation of poly hydroxyalkanoate (PHA) from excess activated sludge (EAS) was monitored and controlled via the oxidation-reduction\\u000a potential (ORP) adjusting process. The ORP was adjusted and controlled by only regulating the gas-flow rate pumped into the\\u000a cultural broth in which sodium acetate (C2) and propionate (C3) were used as carbon sources. Productivity of PHA and the PHA\\u000a compositions at various

W. F. Hu; S. N. Sin; H. Chua; P. H. F. Yu

74

Assessing high resolution oxidation-reduction potential and soluble reactive phosphorus variation across vertical sediments and water layers in Xinghu Lake: A novel laboratory approach  

Microsoft Academic Search

To understand the transfer process of soluble reactive phosphorus (SRP) on the lake sediment-water interface in a mesotrophic shallow lake in South China, the SRP concentrations and the oxidation-reduction potential (ORP) across the sediment-water interfaces were continually monitored. Sediment samples were collected from Xinghu Lake in Guangdong Province. The ORP dynamics at different layers of overlying water was similar for

Yingzhi Li; Beicheng Xia; Jiaying Zhang; Chuanhong Li; Wenzhuan Zhu

2010-01-01

75

Effectiveness of oxidation-reduction potential and pH as monitoring and control parameters for nitrogen removal in swine wastewater treatment by sequencing batch reactors  

Microsoft Academic Search

Two bench-scale sequencing batch reactors (SBRs) were operated in a fixed hydraulic retention time study to investigate the effectiveness of oxidation-reduction potential (ORP), pH and dissolved oxygen as parameters for indicating denitrification followed by nitrification in SBRs for swine wastewater treatment. The ORP and pH profiles were monitored and evaluated under different denitrification and nitrification conditions with and without a

Naohiro Kishida; Ju-Hyun Kim; Meixue Chen; Hiroshi Sasaki; Ryuichi Sudo

2003-01-01

76

Catalytic reduction of nitrogen oxides  

Microsoft Academic Search

This patent describes a method for catalytically reducing one or more nitrogen oxides from a gaseous stream containing one or more nitrogen oxides and one or more sulfur oxides. It comprises contacting the gaseous stream and ammonia with a microporous non-zeolitic molecular sieve composition at effective reduction conditions, wherein the microporous non-zeolitic molecular sieve composition is hydrogen-forming cation exchanged prior

M. T. Staniulis; A. P. Risch

1989-01-01

77

Laboratory-Scale Study of Electrolytic Reduction of Uranium Oxides.  

National Technical Information Service (NTIS)

An exploratory study was undertaken to investigate potential improvements in the electrolytic reduction of uranium oxide to the metal. Potential advantages of the electrolytic procedure over existing chemical reduction processes are (1) lower operating te...

D. S. Poa L. Burris R. K. Steunenberg Z. Tomczuk

1988-01-01

78

Energetics of beta-oxidation. Reduction potentials of general fatty acyl-CoA dehydrogenase, electron transfer flavoprotein, and fatty acyl-CoA substrates.  

PubMed

We have determined reduction potentials for porcine mitochondrial general fatty acyl-CoA dehydrogenase (GAD) and electron transfer flavoprotein (ETF) using an anaerobic spectroelectrochemical titration method. Computer simulation techniques were used to analyze the absorbance data. Nernst plots of the simulated data gave E'0, 7.1, quinone/semiquinone = -0.014 V and E'0, 7.1, semiquinone/hydroquinone = -0.036 V for ETF and E'0, 7.1, quinone/semiquinone = -0.155 V and E'0, 7.1, semiquinone/hydroquinone = -0.122 V for GAD. Using these techniques we have also determined a conditional reduction potential of -0.156 V for the chromophore producing fatty acyl-CoA substrate beta-2-furylpropionyl-CoA. From this value and our previous determination of the equilibrium constant for the transhydrogenation reaction between beta-2-furylpropionyl-CoA and the oxidized substrate crotonyl-CoA (Keq = 10.4), we have determined a reduction potential of -0.126 V for the butyryl-CoA/crotonyl-CoA couple. In light of the structural similarity between butyryl-CoA and octanoyl-CoA, the optimal substrate for GAD, the reduction potential for octanoyl-CoA should be similar to that for butyryl-CoA; i.e. fatty acyl-CoA substrates and GAD are essentially isopotential. The ability of octanoyl-CoA to reduce GAD quantitatively (Keq = 9.0) poses a dilemma in light of the nearly equal reduction potentials. We postulate that the stable charge-transfer complex formed between enzyme and optimal product is significantly lower in energy than enzyme and product and thus is responsible for pulling the reaction toward completion. PMID:3711105

Gustafson, W G; Feinberg, B A; McFarland, J T

1986-06-15

79

Electro-catalytic reduction of nitrogen oxides  

SciTech Connect

Nitrogen oxides have been linked to a broad range of air pollution problems including acid rain and the atmospheric production of photochemical ozone. Over twenty million tons of nitrogen oxides are emitted into the atmosphere each year as a result of the high temperature combustion of fossil fuels. Efforts to control nitrogen oxides emissions have lagged because of the generally low discharge concentrations of nitrogen oxides in combustion exhaust and because nitrogen oxides are more difficult to remove due to their lower reactivity. No catalyst has yet been found that will achieve significant reduction of nitrogen oxides in an oxidizing environment. Oxygen in the exhaust stream competes with nitrogen oxides for the active catalyst sites. Also, the dissociated oxygen atoms produced by decomposition of nitrogen oxides deactivate the surface of the catalyst. Externally applied electric fields have been used to control oxygen adsorption on metal and semi-conductor surfaces. In this investigation, a stream containing nitric oxide has been subjected to intense electric fields in the presence of catalyst materials including steel, stainless steel, and gold plated stainless steel wools and glass wool. The electric fields have been generated using DC, AC and rectified AC potentials in the range of 0--20 KV. The effect of parameters such as inlet nitric oxide concentration, oxygen and water content, gas residence time and temperature have also been studied.

McLarnon, C.R.

1989-12-01

80

Oxidation-reduction reactions of metal ions.  

PubMed Central

Several metal or metalloid ions exist in multiple oxidation states and can undergo electron transfer reactions that are important in biological and environmental systems. There are endogenous metal ions such as iron, copper, and cobalt that participate in oxidation-reduction reactions with species of oxygen like molecular dioxygen, superoxide, and hydrogen peroxide. These reactions may be modulated by endogenous reducing agents such as glutathione, ascorbate, and tocopherol. The reactions can be described in terms of thermodynamics through the use of standard electrode potentials. A favorable reaction will depend on the concentrations of the reactants and may depend on the pH and/or on the presence of organic ligands that form complexes with the metal or metalloid. Arsenate (As(V)) can react with glutathione in buffered aqueous solutions to produce arsenite (As(III)) and oxidized glutathione. This reaction may be important in the methylation reactions of arsenic. Arsenic species can decrease the red blood cell levels of reduced glutathione, but the products of oxidation and the mechanism of oxidation are more complex than those found in water alone. Chromium (VI) is thought to interact with DNA after first reacting with a reducing agent such as glutathione to form lower oxidation states of chromium. These examples illustrate the importance of oxidation-reduction reactions for toxic metals and metalloids.

Carter, D E

1995-01-01

81

Injury severity and serum amyloid A correlate with plasma oxidation-reduction potential in multi-trauma patients: a retrospective analysis  

PubMed Central

Background In critical injury, the occurrence of increased oxidative stress or a reduced antioxidant status has been observed. The purpose of this study was to correlate the degree of oxidative stress, by measuring the oxidation-reduction potential (ORP) of plasma in the critically injured, with injury severity and serum amyloid A (SAA) levels. Methods A total of 140 subjects were included in this retrospective study comprising 3 groups: healthy volunteers (N = 21), mild to moderate trauma (ISS < 16, N = 41), and severe trauma (ISS ? 16, N = 78). For the trauma groups, plasma was collected on an almost daily basis during the course of hospitalization. ORP analysis was performed using a microelectrode, and ORP maxima were recorded for the trauma groups. SAA, a sensitive marker of inflammation in critical injury, was measured by liquid chromatography/mass spectrometry. Results ORP maxima were reached on day 3 (± 0.4 SEM) and day 5 (± 0.5 SEM) for the ISS < 16 and ISS ? 16 groups, respectively. ORP maxima were significantly higher in the ISS < 16 (-14.5 mV ± 2.5 SEM) and ISS ? 16 groups (-1.1 mV ± 2.3 SEM) compared to controls (-34.2 mV ± 2.6 SEM). Also, ORP maxima were significantly different between the trauma groups. SAA was significantly elevated in the ISS ? 16 group on the ORP maxima day compared to controls and the ISS < 16 group. Conclusion The results suggest the presence of an oxidative environment in the plasma of the critically injured as measured by ORP. More importantly, ORP can differentiate the degree of oxidative stress based on the severity of the trauma and degree of inflammation.

2009-01-01

82

Thermodynamic constraints on microbial iron oxide reduction  

NASA Astrophysics Data System (ADS)

Iron oxides are ubiquitous reactive constituents of soils, sediments and aquifers. They exhibit large surface areas which bind trace metals, nutrients and organic molecules. Under suboxic conditions, iron oxides can reductively dissolve via several abiotic and microbial pathways. In particular, they serve as terminal electron acceptors for the oxidation of organic matter by iron reducing bacteria. The aim of our study was to determine the thermodynamic energy yields of dissimilatory iron reduction for different Fe(III) substrates. We used the facultative anaerobic gram-positive bacterium Shewanella putrefaciens as model iron reducing bacterium, with ferrihydrite, hematite, goethite or Fe(III)-salicylate as electron acceptor, and lactate as electron donor. Experiments were conducted in an anaerobic pH-stat batch reactor, equipped with a polarographic electrode to monitor in situ the dissolved ferrous iron activity. The stoichiometry of total Fe(II) production and acid consumption during the experiments indicated that lactate was oxidized to acetate. From the Fe(II) activity and redox potential measurements, free energy yields were calculated for Fe(III) reduction coupled to lactate oxidation. The results showed that the redox potential of the overall reaction was poised by equilibrium between the Fe(III)-substrate and aqueous Fe(II). Hence, the energy yields decreased in the order ferrihydrite > Fe(III)-salicylate > hematite > goethite. Accumulation of Fe(II) in solution only caused small decreases in the energy yields over the course of the experiments. Cessation of iron reduction, which was observed in all experiments, was therefore not due to thermodynamic limitation, but more likely reflected the decline in cell level of activity.

Bonneville, S.; Behrends, T.; Haese, R.; van Cappellen, P.

2003-04-01

83

Evaluating operation strategies and process stability of a single stage nitritation-anammox SBR by use of the oxidation-reduction potential (ORP).  

PubMed

A single stage nitritation-anammox SBR was operated for 300 days to investigate the impact of cycle operation strategies on process performance and the oxidation-reduction potential (ORP) as process monitoring parameter. Different combinations of feeding (interval, continuous, one-time) and aeration (interval, continuous) strategies were tested revealing that interval feeding and interval aeration was the most suitable case in terms of process performance (ammonium removal, nitrate production and pH stability) and use of the ORP value as indicator parameter. Further investigations into the use of the ORP value showed clear correlations of the ORP slope with the air flow rate and the maximum ORP peak with the ammonium loading under varying operation conditions. Depletion of the main substrates (ammonium and oxygen) was also detectable fastest following the ORP value proofing its worth for process control. PMID:22209133

Lackner, Susanne; Horn, Harald

2011-12-14

84

The influence of oxidation reduction potential and water treatment processes on quartz lamp sleeve fouling in ultraviolet disinfection reactors  

Microsoft Academic Search

Ultraviolet (UV) disinfection systems are incorporated into drinking water production facilities because of their broad-spectrum antimicrobial capabilities, and the minimal disinfection by-product formation that generally accompanies their use. Selection of an optimal location for a UV system within a drinking water treatment facility depends on many factors; a potentially important consideration is the effect of system location on operation and

Isaac W. Wait; Cliff T. Johnston; Ernest R. Blatchley

2007-01-01

85

Molecular Modeling of Environmentally Important Processes: Reduction Potentials  

ERIC Educational Resources Information Center

|The increasing use of computational quantum chemistry in the modeling of environmentally important processes is described. The employment of computational quantum mechanics for the prediction of oxidation-reduction potential for solutes in an aqueous medium is discussed.|

Lewis, Anne; Bumpus, John A.; Truhlar, Donald G.; Cramer, Christopher J.

2004-01-01

86

Influence of pH and oxidation-reduction potential (Eh) on the dissolution of mercury-containing mine wastes from the Sulfur Bank Mercury mine  

Microsoft Academic Search

ABSTRACT This study was undertaken as a part of developin g treatment alternatives for waste materials, primari ly waste rock and roaster tailings, from sites contaminated with mercury (Hg) mining wastes. Leaching profiles of waste rock over a range of different pH and oxidation -reduction (Eh) conditions were performed. Since iron (Fe) is present in large quantities in mining wastes,

Paul Randall

87

INFLUENCE OF PH AND OXIDATION-REDUCTION POTENTIAL (EH) ON THE DISSOLUTION OF MERCURY-CONTAINING MINE WASTES FROM THE SULFUR BANK MERCURY MINE  

EPA Science Inventory

This study was undertaken as a part of developing treatment alternatives for waste materials, primarily waste rock and roaster tailings, from sites contaminated with mercury (Hg) mining wastes. Leaching profiles of waste rock over a range of different pH and oxidation-reduction (...

88

Catalytic reduction of nitrogen oxides by ammonia  

Microsoft Academic Search

Of all the methods for treating gases to remove nitrogen oxides, the most widely used are methods based on catalytic reduction. The capital expense required for such methods is relatively small, and the equipment can be simpler and at the same time quite efficient. Among these methods, the most promising is the catalytic reduction of nitrogen oxides by ammonia, forming

A. F. Lunin; Yu. A. Adzhiev; R. I. Fedorova

1994-01-01

89

Thermodynamic constraints on microbial iron oxide reduction  

Microsoft Academic Search

Iron oxides are ubiquitous reactive constituents of soils, sediments and aquifers. They exhibit large surface areas which bind trace metals, nutrients and organic molecules. Under suboxic conditions, iron oxides can reductively dissolve via several abiotic and microbial pathways. In particular, they serve as terminal electron acceptors for the oxidation of organic matter by iron reducing bacteria. The aim of our

S. Bonneville; T. Behrends; R. Haese; P. van Cappellen

2003-01-01

90

Oxidation and Reduction Reactions in Organic Chemistry  

ERIC Educational Resources Information Center

|A variety of approaches to the concept of oxidation and reduction appear in organic textbooks. The method proposed here is different than most published approaches. The oxidation state is calculated by totaling the number of heterogeneous atoms, [pi]-bonds, and rings. A comparison of the oxidation states of reactant and product determine what…

Shibley, Ivan A., Jr.; Amaral, Katie E.; Aurentz, David J.; McCaully, Ronald J.

2010-01-01

91

RELATIONSHIPS BETWEEN OXIDATION-REDUCTION, OXIDANT, AND PH IN DRINKING WATER  

EPA Science Inventory

Oxidation and reduction (redox) reactions are very important in drinking water. Oxidation-reduction potential (ORP) measurements reflect the redox state of water. Redox measurements are not widely made by drinking water utilities in part because they are not well understood. The ...

92

The reduction and oxidation behaviour of manganese oxides  

Microsoft Academic Search

The reduction of manganese oxides with methane was studied to investigate the suitability of manganese as an oxygen storage compound. Manganese oxides are reduced by CH4 to a lower-valent manganese oxide, producing CO2 and water. Once the manganese oxide is reduced, it can be regenerated, i.e. reoxidised. By integrating this exothermic oxidation cycle with endothermic methane reforming, a new setup

E. R. Stobbe; B. A. de Boer; J. W. Geus

1999-01-01

93

Dechlorination by combined electrochemical reduction and oxidation.  

PubMed

Chlorophenols are typical priority pollutants listed by USEPA (U.S. Environmental Protection Agency). The removal of chlorophenol could be carried out by a combination of electrochemical reduction and oxidation method. Results showed that it was feasible to degrade contaminants containing chlorine atoms by electrochemical reduction to form phenol, which was further degraded on the anode by electrochemical oxidation. Chlorophenol removal rate was more than 90% by the combined electrochemical reduction and oxidation at current of 6 mA and pH 6. The hydrogen atom is a powerful reducing agent that reductively dechlorinates chlorophenols. The instantaneous current efficiency was calculated and the results indicated that cathodic reduction was the main contributor to the degradation of chlorophenol. PMID:15909345

Cong, Yan-qing; Wu, Zu-cheng; Tan, Tian-en

2005-06-01

94

THE EFFECT OF $gamma$IRRADIATION ON THE MICROORGANISMS IN JAPANESE FOODS AND ITS APPLICATION TO STERILIZATION. VI. THE CHANGE IN THE OXIDATION-REDUCTION POTENTIALS OF SAKE AND ARTIFICIAL SAKEBY $gamma$IRRADIATION  

Microsoft Academic Search

The samples were irradiated by a 1400-c Co⁶° gamma -ray source at ; the rate of 2.5 x 10⁴ r\\/hr up to 2 x 10⁵to 3 x 10⁶r. The ; oxidation-reduction potentials of sake and the artificial sake were increased by ; gamma irradiation. However, the rH value of the irradiated sake was lower than ; the irradiated artificial sake

K. Yoshikawa; H. Taguchi

1960-01-01

95

Size dependent reduction-oxidation-reduction behaviour of cobalt oxide nanocrystals.  

PubMed

Morphologically similar cobalt oxide nanoparticles (Co3O4) of four different sizes (3 nm, 6 nm, 11 nm and 29 nm) with narrow size distribution were prepared by subtle variation of synthesis conditions. These nanoparticles were used as model materials to understand the structural and morphological changes that occur to cobalt oxide during sequential reduction, oxidation and further re-reduction process as a function of the initial size of cobalt oxide. On reduction, spherical cobalt nanoparticles were obtained independent of the original size of cobalt oxide. In contrast, subsequent oxidation of the metal particles led to solid spheres, hollow spheres or core-shell structures depending on the size of the initial metal particle. Further re-reduction of the oxidized structures was also observed to be size dependent. The hollow oxide shells formed by the large particles (29 nm) fragmented into smaller particles on reduction, while the hollow shells of the medium sized particles (11 nm) did not re-disperse on further reduction. Similarly, no re-dispersion was observed in the case of the small particles (6 nm). This model study provides useful insights into the size dependent behavior of metal/metal oxide particles during oxidation/reduction. This has important implications in petrochemical industry where cobalt is used as a catalyst in the Fischer-Tropsch process. PMID:24065040

Sadasivan, Sajanikumari; Bellabarba, Ronan M; Tooze, Robert P

2013-09-25

96

Suspension Hydrogen Reduction of Iron Oxide Concentrates  

SciTech Connect

The objective of the project is to develop a new ironmaking technology based on hydrogen and fine iron oxide concentrates in a suspension reduction process. The ultimate objective of the new technology is to replace the blast furnace and to drastically reduce CO2 emissions in the steel industry. The goals of this phase of development are; the performance of detailed material and energy balances, thermochemical and equilibrium calculations for sulfur and phosphorus impurities, the determination of the complete kinetics of hydrogen reduction and bench-scale testing of the suspension reduction process using a large laboratory flash reactor.

H.Y. Sohn

2008-03-31

97

Ethylene oxide potential toxicity.  

PubMed

The future of ethylene oxide (EO) sterilization has been questioned, owing to its associated toxicity. EO has been around for more than 60 years, mainly due to its recognized characteristics of reliability and effectiveness, coupled with the process flexibility, as well as its compatibility with most mechanical devices. Despite the well-known EO toxicity, the undesirable effects of medical devices' EO residues on the patient's health have not yet been well established. There are limitations related to the current risk-assessment studies. To overcome these drawbacks, demands on greater safety are increasing, which lead to improvements in sterilizers and aeration equipment, as well as the design of the processes. The paper under evaluation highlights risks related to EO sterilization of materials used during processing of stem cells for transplantation, but is an example of a study where the dose of the residues in the devices is not considered. PMID:18452382

da Cunha Mendes, Gisela Cristina; da Silva Brandão, Teresa Ribeiro; Miranda Silva, Cristina Luisa

2008-05-01

98

OXIDATION-REDUCTION CAPACITIES OF AQUIFER SOLIDS  

EPA Science Inventory

Measurements of the oxidation (i.e., of aqueous Cr2+) and reduction (i.e., of aqueous Cr2O72- and H202) capacities of aquifer solids and groundwater have been made on samples from a sand-and-gravel aquifer. The gro...

99

Electrochemical Study on the Reduction Mechanism of Uranium Oxide in a LiCl-Li2O Molten Salt  

Microsoft Academic Search

By means of a linear sweep voltammetry, a cyclic voltammetry and a chronopotentiometry, the electrolytic reduction of uranium oxide has been studied to establish the reduction mechanisms, which are based on a simultaneous uranium oxide reduction and a Li2O electrowinning, and the formation and electrolysis of lithium uranate. From the voltammograms, the reduction potentials of the uranium oxide and Li2O

Chung Seok SEO; Sung Bin PARK; Byung Heung PARK; Ki Jung JUNG; Seong Won PARK; Sung Hyun KIM

2006-01-01

100

Investigation of iron oxide reduction by TEM  

Microsoft Academic Search

An “environmental cell” located in a high voltage transmission electron microscope has been used to study the reduction of\\u000a single crystal iron oxides by hydrogen and hydrogen-argon mixtures. The cell enables a direct observation of the solid during\\u000a reaction, thus permitting the nucleation and growth of solid reaction products to be observed. Hematite was reduced at temperatures\\u000a in the range

Mann-Fu Rau; David Rieck; James W. Evans

1987-01-01

101

Coordinated reduction of genes of oxidative metabolism in humans with insulin resistance and diabetes: Potential role of PGC1 and NRF1.  

PubMed

Type 2 diabetes mellitus (DM) is characterized by insulin resistance and pancreatic beta cell dysfunction. In high-risk subjects, the earliest detectable abnormality is insulin resistance in skeletal muscle. Impaired insulin-mediated signaling, gene expression, glycogen synthesis, and accumulation of intramyocellular triglycerides have all been linked with insulin resistance, but no specific defect responsible for insulin resistance and DM has been identified in humans. To identify genes potentially important in the pathogenesis of DM, we analyzed gene expression in skeletal muscle from healthy metabolically characterized nondiabetic (family history negative and positive for DM) and diabetic Mexican-American subjects. We demonstrate that insulin resistance and DM associate with reduced expression of multiple nuclear respiratory factor-1 (NRF-1)-dependent genes encoding key enzymes in oxidative metabolism and mitochondrial function. Although NRF-1 expression is decreased only in diabetic subjects, expression of both PPAR gamma coactivator 1-alpha and-beta (PGC1-alpha/PPARGC1 and PGC1-beta/PERC), coactivators of NRF-1 and PPAR gamma-dependent transcription, is decreased in both diabetic subjects and family history-positive nondiabetic subjects. Decreased PGC1 expression may be responsible for decreased expression of NRF-dependent genes, leading to the metabolic disturbances characteristic of insulin resistance and DM. PMID:12832613

Patti, Mary Elizabeth; Butte, Atul J; Crunkhorn, Sarah; Cusi, Kenneth; Berria, Rachele; Kashyap, Sangeeta; Miyazaki, Yoshinori; Kohane, Isaac; Costello, Maura; Saccone, Robert; Landaker, Edwin J; Goldfine, Allison B; Mun, Edward; DeFronzo, Ralph; Finlayson, Jean; Kahn, C Ronald; Mandarino, Lawrence J

2003-06-27

102

Hydrogen reduction of oxidized nickel concentrates  

NASA Astrophysics Data System (ADS)

Thermal gravimetric analysis was used to investigate the weight change of Ni/Cu/Co calcines upon heating in an inert as well as hydrogen atmosphere. The two calcines investigated contained approximately 50 wt pct combined of hematite and magnetite in addition to sulfides of Ni, Cu, Co, and Fe. Mass spectrometry was used to analyze the gas species evolved during heating and reduction. The calcine samples are 100 pct less than 100 µm with hematite/magnetite rims around a central sulfide core. When heating the calcines at 10 °C/min in hydrogen, reduction starts at around 400 °C and is nearly complete at about 700 °C with all the reducible oxygen removed. Isothermal reduction tests show that at temperatures from 650 °C to 800 °C, half the oxygen is removed in less than 4 min. The TGA results combined with microscopic analysis show that the reduction followed a uniform internal reduction model. The reduced calcines will quickly get re-oxidized if they are allowed to contact air while they remain hot.

Crowe, C. J. B.; Utigard, T. A.

2003-12-01

103

Processing of effluent salt from the direct oxide reduction process.  

National Technical Information Service (NTIS)

The production of reactive metals by Direct Oxide Reduction (DOR) process using calcium in a molten calcium salt system generates significant amount of contaminated waste as calcium oxide saturated calcium chloride salt mix with calcium oxide content of u...

B. Mishra D. L. Olson W. A. Averill

1992-01-01

104

Methionine oxidation and reduction in proteins.  

PubMed

BACKGROUND: Cysteine and methionine are the two sulfur containing amino acids in proteins. While the roles of protein-bound cysteinyl residues as endogenous antioxidants are well appreciated, those of methionine remain largely unexplored. SCOPE: We summarize the key roles of methionine residues in proteins. MAJOR CONCLUSION: Recent studies establish that cysteine and methionine have remarkably similar functions. GENERAL SIGNIFICANCE: Both cysteine and methionine serve as important cellular antioxidants, stabilize the structure of proteins, and can act as regulatory switches through reversible oxidation and reduction. This article is part of a Special Issue entitled Current methods to study reactive oxygen species - pros and cons. PMID:23648414

Kim, Geumsoo; Weiss, Stephen J; Levine, Rodney L

2013-05-01

105

CHARACTERIZATION OF OXIDATION REDUCTION PROCESSES IN CONSTRUCTED WETLANDS FOR SWINE WASTEWATER TREATMENT  

Microsoft Academic Search

Constructed wetlands designed and properly operated for treatment of swine wastewater may enhance oxidation -reduction processes and nutrient treatment performance. The objective of this investigation was to characterize soil wetland processes related to nitrogen (N) treatment (nitrification-denitrification) and phosphorus (P) removal using soil oxidation -reduction potential (ORP) data. We evaluated three surface-flow wetland systems constructed for treatment of swine wastewater

A. A. Szögi; P. G. Hunt; E. J. Sadler; D. E. Evans

106

Impacts of operating parameters on oxidation-reduction potential and pretreatment efficacy in the pretreatment of printing and dyeing wastewater by Fenton process.  

PubMed

An experiment was conducted in a batch reactor for a real printing and dyeing wastewater pretreatment using Fenton process in this study. The results showed that original pH, hydrogen peroxide concentration and ferrous sulfate concentration affected ORP value and pretreatment efficacy greatly. Under experimental conditions, the optimal original pH was 6.61, and the optimal hydrogen peroxide and ferrous sulfate concentrations were 1.50 and 0.75 gL(-1), respectively. The relationship among ORP, original pH, hydrogen peroxide concentration, ferrous sulfate concentration, and color (COD or BOD(5)/COD) was established, which would be instructive in on-line monitoring and control of Fenton process using ORP. In addition, the effects of wastewater temperature and oxidation time on pretreatment efficacy were also investigated. With an increase of temperature, color and COD removal efficiencies and BOD(5)/COD ratio increased, and they were in proportion to the exponent of temperature reciprocal. Similarly, color and COD removal efficiencies increased with increasing oxidation time, and both color and COD removal obeyed the first-order kinetics. The BOD(5)/COD ratio could be expressed by a second-degree polynomial with respect to oxidation time, and the best biodegradability of wastewater was present at the oxidation time of 6.10h. PMID:23141379

Wu, Huifang; Wang, Shihe

2012-10-22

107

Gaseous reduction of iron oxides: Part III. Reduction-oxidation of porous and dense iron oxides and iron  

Microsoft Academic Search

The internal reduction of high-grade granular hematite ore in hydrogen and carbon monoxide, and also the internal oxidation\\u000a of porous iron granules in CO2-CO mixtures have been investigated. To assist the interpretation of the rate data for porous iron and iron oxides, rate measurements\\u000a have been made also with dense wustite, previously grown on iron by oxidation. The iron formed

E. T. Turkdogan; J. V. Vinters

1972-01-01

108

Glutathione-dependent reductive stress triggers mitochondrial oxidation and cytotoxicity  

PubMed Central

To investigate the effects of the predominant nonprotein thiol, glutathione (GSH), on redox homeostasis, we employed complementary pharmacological and genetic strategies to determine the consequences of both loss- and gain-of-function GSH content in vitro. We monitored the redox events in the cytosol and mitochondria using reduction-oxidation sensitive green fluorescent protein (roGFP) probes and the level of reduced/oxidized thioredoxins (Trxs). Either H2O2 or the Trx reductase inhibitor 1-chloro-2,4-dinitrobenzene (DNCB), in embryonic rat heart (H9c2) cells, evoked 8 or 50 mV more oxidizing glutathione redox potential, Ehc (GSSG/2GSH), respectively. In contrast, N-acetyl-l-cysteine (NAC) treatment in H9c2 cells, or overexpression of either the glutamate cysteine ligase (GCL) catalytic subunit (GCLC) or GCL modifier subunit (GCLM) in human embryonic kidney 293 T (HEK293T) cells, led to 3- to 4-fold increase of GSH and caused 7 or 12 mV more reducing Ehc, respectively. This condition paradoxically increased the level of mitochondrial oxidation, as demonstrated by redox shifts in mitochondrial roGFP and Trx2. Lastly, either NAC treatment (EC50 4 mM) or either GCLC or GCLM overexpression exhibited increased cytotoxicity and the susceptibility to the more reducing milieu was achieved at decreased levels of ROS. Taken together, our findings reveal a novel mechanism by which GSH-dependent reductive stress triggers mitochondrial oxidation and cytotoxicity.—Zhang, H., Limphong, P., Pieper, J., Liu, Q., Rodesch, C. K., Christians, E., Benjamin, I. J. Glutathione-dependent reductive stress triggers mitochondrial oxidation and cytotoxicity.

Zhang, Huali; Limphong, Pattraranee; Pieper, Joel; Liu, Qiang; Rodesch, Christopher K.; Christians, Elisabeth; Benjamin, Ivor J.

2012-01-01

109

Reduction Potentials of One-Electron Couples Involving Free Radicals in Aqueous Solution  

Microsoft Academic Search

Reduction of an electron acceptor (oxidant), A, or oxidation of an electron donor (reductant), A2?, is often achieved stepwise via one-electron processes involving the couples A\\/A?? or A??\\/A2? (or corresponding prototropic conjugates such as A\\/AH? or AH?\\/AH2). The intermediate A??(AH?) is a free radical. The reduction potentials of such one-electron couples are of value in predicting the direction or feasibility,

Peter Wardman

1989-01-01

110

Accurate topographic reduction of potential field data  

NASA Astrophysics Data System (ADS)

Topographic reduction of potential fields (gravity and magnetics) is an important processing step for geophysical applications. The topographic signal can obscure subsurface anomalies, so measurements have to be corrected for its influence. Several algorithms are available for topographic reduction. These are based on cylindrical ring compartments, rectangular prisms, mass lines or mass points. Earth curvature is often taken into account using various different approaches. Calculations are done in the space or frequency (FFT) domain. In general, the mass correction of gravity data is done to a radius of about 167 km around an observation point. Although mass correction is a crucial processing step, these standards are often used without modification. However, the choice of limiting radius is questionable and the approximation error can be higher than the accuracy of the measurements. In particular, planar corrections are erroneous for surveys covering large areas. In our study, we analyzed the influence of distant topography (>167 km) and approximations on gravity data. We developed two algorithms for this purpose. The first calculates the topographic effect with an exact surface integral of a polyhedron on a sphere. The other calculates the topographic effect with an exact calculation of spherically-shaped prisms using numerical integration. Furthermore, we use an adaptive approach to change the resolution of topographic data depending on its influence on the station. We also used elevation from a digital terrain model (DTM) and the elevations of ground stations are included in the approach to avoid systematic errors. Data from high mountains (the Andes and the Himalaya) were examined to test the new methods. Finally, we identify a) the influence of distant topography on the measured gravity, b) the effect of different topography resolutions and c) the differences to other approaches. All approaches differ in speed and accuracy. Our results show that some algorithms have large errors due to approximations. Depending on the investigation area and the objective of the survey, it is advisable to put more effort into obtaining an accurate, exact and reliable method for the reduction of topographic effects.

Köther, N. K.; Szwillus, W. S.; Goetze, H. G.; Schmidt, S. S.

2012-04-01

111

Manganese oxide reduction as a form of anaerobic respiration  

Microsoft Academic Search

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

Henry L. Ehrlich

1987-01-01

112

Simultaneous iridium catalysed oxidation and enzymatic reduction employing orthogonal reagents.  

PubMed

An iridium catalysed oxidation was coupled concurrently to an asymmetric biocatalytic reduction in one-pot; thus it was shown for the first time that iridium- and alcohol dehydrogenase-catalysed redox reactions are compatible. As a model system racemic chlorohydrins were transformed to enantioenriched chlorohydrins via an oxidation-asymmetric reduction sequence. PMID:20871888

Mutti, Francesco G; Orthaber, Andreas; Schrittwieser, Joerg H; de Vries, Johannes G; Pietschnig, Rudolf; Kroutil, Wolfgang

2010-09-27

113

Reduction of amine N-oxides by diboron reagents.  

PubMed

Facile reduction of alkylamino-, anilino-, and pyridyl-N-oxides can be achieved via the use of diboron reagents, predominantly bis(pinacolato)- and in some cases bis(catecholato)diboron [(pinB)(2) and (catB)(2), respectively]. Reductions occur upon simply mixing the amine N-oxide and the diboron reagent in a suitable solvent, at a suitable temperature. Extremely fast reductions of alkylamino- and anilino-N-oxides occur, whereas pyridyl-N-oxides undergo slower reduction. The reaction is tolerant of a variety of functionalities such as hydroxyl, thiol, and cyano groups, as well as halogens. Notably, a sensitive nucleoside N-oxide has also been reduced efficiently. The different rates with which alkylamino- and pyridyl-N-oxides are reduced has been used to perform stepwise reduction of the N,N'-dioxide of (S)-(-)-nicotine. Because it was observed that (pinB)(2) was unaffected by the water of hydration in amine oxides, the feasibility of using water as solvent was evaluated. These reactions also proceeded exceptionally well, giving high product yields. In constrast to the reactions with (pinB)(2), triethylborane reduced alkylamino-N-oxides, but pyridine N-oxide did not undergo efficient reduction even at elevated temperature. Finally, the mechanism of the reductive process by (pinB)(2) has been probed by (1)H and (11)B NMR. PMID:21812467

Kokatla, Hari Prasad; Thomson, Paul F; Bae, Suyeal; Doddi, Venkata Ramana; Lakshman, Mahesh K

2011-08-31

114

Reduction of Amine N-Oxides by Diboron Reagents  

PubMed Central

Facile reduction of alkylamino-, anilino-, and pyridyl-N-oxides can be achieved via the use of diboron reagents, predominantly bis(pinacolato)- and in some cases bis(catecholato)diboron [(pinB)2 and (catB)2, respectively]. Reductions occur upon simply mixing the amine N-oxide and the diboron reagent in a suitable solvent, at a suitable temperature. Extremely fast reductions of alkylamino- and anilino-N-oxides occur, whereas pyridyl-N-oxides undergo slower reduction. The reaction is tolerant of a variety of functionalities such as hydroxyl, thiol, and cyano groups, as well as halogens. Notably, a sensitive nucleoside N-oxide has also been reduced efficiently. The different rates with which alkylamino- and pyridyl-N-oxides are reduced has been used to perform stepwise reduction of the N,N’-dioxide of (S)-(–)-nicotine. Because it was observed that (pinB)2 was unaffected by the water of hydration in amine oxides, the feasibility of using water as solvent was evaluated. These reactions also proceeded exceptionally well, giving high product yields. In constrast to the reactions with (pinB)2, triethylborane reduced alkylamino-N-oxides, but pyridine N-oxide did not undergo efficient reduction even at elevated temperature. Finally, the mechanism of the reductive process by (pinB)2 has been probed by 1H and 11B NMR.

Kokatla, Hari Prasad; Thomson, Paul F.; Bae, Suyeal; Doddi, Venkata Ramana; Lakshman, Mahesh K.

2011-01-01

115

Treatment of oxide spent fuel using the lithium reduction process  

SciTech Connect

The wide variety in the composition of DOE spent nuclear fuel complicates its long-term disposition because of the potential requirement to individually qualify each type of fuel for repository disposal. Argonne National Laboratory (ANL) has developed the electrometallurgical treatment technique to convert all of these spent fuel types into a single set of disposal forms, simplifying the qualification process. While metallic fuels can be directly processed using the electrometallurgical treatment technique, oxide fuels must first be reduced to the metallic form. The lithium reduction process accomplishes this pretreatment. In the lithium process the oxide components of the fuel are reduced using lithium at 650 C in the presence of molten LiCl, yielding the corresponding metals and Li{sub 2}O. The reduced metal components are then separated from the LiCl salt phase and become the feed material for electrometallurgical treatment. A demonstration test of the lithium reduction process was successfully conducted using a 10-kg batch of simulated oxide spent fuel and engineering-scale equipment specifically constructed for that purpose. This paper describes the lithium process, the equipment used in the demonstration test, and the results of the demonstration test.

Karell, E.J.; Pierce, R.D.; Mulcahey, T.P. [Argonne National lab., IL (United States). Chemical Technology Div.

1996-05-01

116

Hexavalent chromium reduction, uptake and oxidative biomarkers in Halimione portulacoides.  

PubMed

The in situ reduction of Cr (VI) to its less toxic form Cr (III) may be a useful detoxification mechanism for phytoremediation. Using a hydroponics mesocosmos approach, we evaluated the ability of Halimione portulacoides to reduce and uptake Cr (VI) and its anti-oxidative feedback and biomarkers. It was found that this specie can, not only reduce large amounts of Cr (VI) in the external medium, but also withdrawn and accumulate this element in its roots and aboveground organs. Both these mechanisms were found to be dose dependent. Jointly with this phytoremediative potential the oxidative feedback was also assessed. Chromium uptake had its major implications on the chlorophyll content and flavonoid content, with potential consequences in the photosynthetic and photo-protective mechanisms. Although the high Cr root accumulation in H. portulacoides, there were no inactivation of the enzymatic defenses, allowing a continuous defense against reactive oxygen species. In fact, GPX and specially SOD revealed to be an excellent dose-related biomarker of Cr induced stress. All these aspects make this specie suitable for Cr (VI) phytoremediation processes, either by phytoextraction or by reduction of Cr (VI) to Cr (III) and also for monitoring programs using SOD and GPX as biomarkers of Cr environmental contamination. PMID:22784818

Duarte, B; Silva, V; Caçador, I

2012-07-09

117

Lithium metal reduction of plutonium oxide to produce plutonium metal  

SciTech Connect

This patent describes a method for production of plutonium metal from plutonium oxide by metallic lithium reduction, with regeneration of lithium reactant. It comprises: reacting the plutonium oxide with metallic lithium; oxides and unreacted lithium; subliming the product lithium oxide and unreacted lithium from unreacted plutonium oxide with high heat and low pressure; recapturing the product lithium oxides; reacting the recaptured product lithium oxides with anhydrous hydrochloric acid to produce lithium chloride salt; and decomposing product lithium chloride salt by electrolysis to regenerate lithium metal.

Coops, M.S.

1992-06-02

118

Reduction Kinetics of Graphene Oxide Determined by Temperature Programmed Desorption  

Microsoft Academic Search

Graphene oxide, which is an electrical insulator, shows promise for use in several technological applications such as dielectric layers in nanoscale electronic devices or as the active region of chemical sensors. In principle, graphene oxide films could also be used as a precursor for the formation of large-scale graphene films by either thermal or chemical reduction of the graphene oxide.

Carl Ventrice; Nicholas Clark; Daniel Field; Heike Geisler; Inhwa Jung; Dongxing Yang; Richard Piner; Rodney Ruoff

2009-01-01

119

Outer cell surface components essential for Fe(III) oxide reduction by Geobacter metallireducens.  

PubMed

Geobacter species are important Fe(III) reducers in a diversity of soils and sediments. Mechanisms for Fe(III) oxide reduction have been studied in detail in Geobacter sulfurreducens, but a number of the most thoroughly studied outer surface components of G. sulfurreducens, particularly c-type cytochromes, are not well conserved among Geobacter species. In order to identify cellular components potentially important for Fe(III) oxide reduction in Geobacter metallireducens, gene transcript abundance was compared in cells grown on Fe(III) oxide or soluble Fe(III) citrate with whole-genome microarrays. Outer-surface cytochromes were also identified. Deletion of genes for c-type cytochromes that had higher transcript abundance during growth on Fe(III) oxides and/or were detected in the outer-surface protein fraction identified six c-type cytochrome genes, that when deleted removed the capacity for Fe(III) oxide reduction. Several of the c-type cytochromes which were essential for Fe(III) oxide reduction in G. metallireducens have homologs in G. sulfurreducens that are not important for Fe(III) oxide reduction. Other genes essential for Fe(III) oxide reduction included a gene predicted to encode an NHL (Ncl-1-HT2A-Lin-41) repeat-containing protein and a gene potentially involved in pili glycosylation. Genes associated with flagellum-based motility, chemotaxis, and pili had higher transcript abundance during growth on Fe(III) oxide, consistent with the previously proposed importance of these components in Fe(III) oxide reduction. These results demonstrate that there are similarities in extracellular electron transfer between G. metallireducens and G. sulfurreducens but the outer-surface c-type cytochromes involved in Fe(III) oxide reduction are different. PMID:23183974

Smith, Jessica A; Lovley, Derek R; Tremblay, Pier-Luc

2012-11-26

120

Highly active oxide photocathode for photoelectrochemical water reduction  

NASA Astrophysics Data System (ADS)

A clean and efficient way to overcome the limited supply of fossil fuels and the greenhouse effect is the production of hydrogen fuel from sunlight and water through the semiconductor/water junction of a photoelectrochemical cell, where energy collection and water electrolysis are combined into a single semiconductor electrode. We present a highly active photocathode for solar H2 production, consisting of electrodeposited cuprous oxide, which was protected against photocathodic decomposition in water by nanolayers of Al-doped zinc oxide and titanium oxide and activated for hydrogen evolution with electrodeposited Pt nanoparticles. The roles of the different surface protection components were investigated, and in the best case electrodes showed photocurrents of up to -7.6?mA?cm-2 at a potential of 0?V versus the reversible hydrogen electrode at mild pH. The electrodes remained active after 1?h of testing, cuprous oxide was found to be stable during the water reduction reaction and the Faradaic efficiency was estimated to be close to 100%.

Paracchino, Adriana; Laporte, Vincent; Sivula, Kevin; Grätzel, Michael; Thimsen, Elijah

2011-06-01

121

THE SELECTIVE CATALYTIC REDUCTION OF NITRIC OXIDE WITH METHANE OVER NONZEOLITIC CATALYSTS  

Microsoft Academic Search

This article deals with recent progress in the development of nonzeolitic catalysts for the selective catalytic reduction (SCR) of nitrogen oxides (NOx) with methane. Although metal-exchanged zeolitic catalysts exhibit high activities for this reaction, most of these metastable structures suffer from deactivation problems when exposed to wet exhaust streams at elevated temperatures. Nonzeolitic oxide catalysts have the potential for improved

Mark D. Fokema; Jackie Y. Ying

2001-01-01

122

One-step reduction of graphene oxide with l-glutathione  

Microsoft Academic Search

The preparation of graphene nanosheets from graphene oxide by chemical reduction is one of the important topics in areas of nanotechnology because graphene-based nanomaterials have potential applications. Herein, we developed a green and facile approach to produce graphene by using an environmentally friendly reagent, namely, l-glutathione as a reducing agent. Graphene was prepared via one-step reduction from graphene oxide under

Tuan Anh Pham; Jeong Sik Kim; Jeong Su Kim; Yeon Tae Jeong

2011-01-01

123

Oxidation and Reduction: Too Many Definitions?  

ERIC Educational Resources Information Center

|IUPAC gives several different definitions of oxidation: loss of electrons, increase in oxidation state, loss of hydrogen, or gain of oxygen. Most introductory or general chemistry textbooks use all of these definitions at one time or another, which can lead to some confusion in the minds of first-year chemistry students. Some paradoxical…

Silverstein, Todd P.

2011-01-01

124

Three-Electrode Metal Oxide Reduction Cell  

DOEpatents

A method of electrochemically reducing a metal oxide to the metal in an electrochemical cell is disclosed along with the cell. Each of the anode and cathode operate at their respective maximum reaction rates. An electrolyte and an anode at which oxygen can be evolved, and a cathode including a metal oxide to be reduced are included as is a third electrode with independent power supplies connecting the anode and the third electrode and the cathode and the third electrode.

Dees, Dennis W. (Downers Grove, IL); Ackerman, John P. (Downers Grove, IL)

2005-06-28

125

Three-electrode metal oxide reduction cell  

DOEpatents

A method of electrochemically reducing a metal oxide to the metal in an electrochemical cell is disclosed along with the cell. Each of the anode and cathode operate at their respective maximum reaction rates. An electrolyte and an anode at which oxygen can be evolved, and a cathode including a metal oxide to be reduced are included as is a third electrode with independent power supplies connecting the anode and the third electrode and the cathode and the third electrode.

Dees, Dennis W. (Downers Groves, IL); Ackerman, John P. (Downers Grove, IL)

2008-08-12

126

Oxidation-Reduction Behavior of Platinum-Rhodium Alloys,  

National Technical Information Service (NTIS)

The reduction behavior of platinum-rhodium gauze catalysts used in ammonia oxidation have been investigated by XPS. The results are compared to corresponding measurements for vapor deposited films of platinum and platinum-rhodium. Low exposure (< 10 to th...

A. Holmen E. Bergene J. K. Grepstad

1987-01-01

127

DEVELOPMENT OF ELECTROCHEMICAL REDUCTION TECHNOLOGY FOR SPENT OXIDE FUELS  

SciTech Connect

The Advanced Spent Fuel Conditioning Process (ACP) has been under development at Korea Atomic Energy Research Institute (KAERI) since 1997. The concept is to convert spent oxide fuel into metallic form and to remove high heat-load fission products such as Cs and Sr from the spent fuel. The heat power, volume, and radioactivity of spent fuel can decrease by a factor of a quarter via this process. For the realization of ACP, a concept of electrochemical reduction of spent oxide fuel in Li2O-LiCl molten salt was proposed and several cold tests using fresh uranium oxides have been carried out. In this new electrochemical reduction process, electrolysis of Li2O and reduction of uranium oxide are taking place simultaneously at the cathode part of electrolysis cell. The conversion of uranium oxide to uranium metal can reach more than 99% ensuring the feasibility of this process.

Hur, Jin-Mok; Seo, Chung-Seok; Kim, Ik-Soo; Hong, Sun-Seok; Kang, Dae-Seung; Park, Seong-Won

2003-02-27

128

STUDIES ON THE OXIDATION AND REDUCTION OF IMMUNOLOGICAL SUBSTANCES  

PubMed Central

The "spontaneous deterioration" of streptolysin has been studied by the methods already used in investigations of the oxidation-reduction of blood pigments and of the lysins of other bacteria. From the results of this study, it may be concluded that the commonly observed "spontaneous deterioration" of streptolysin consists in the conversion of the originally active lysin to a hemolytically inactive oxidation product. This process is a reversible one, and the activity of the lysin is restored by reduction.

Neill, James M.; Mallory, Tracy B.

1926-01-01

129

Oxidative reduction of glove box wipers with a downdraft thermal oxidation system  

SciTech Connect

Wipers (rags) used for decontamination and glove box cleanup in the Plutonium Finishing Plant often become soaked with acid and plutonium-rich solutions. After use, these wipers are rinsed in a dilute NaOH solution and dried, but the formation of unstable nitrates and the hydrogen gas caused by hydrolysis are concerns that still must be addressed. This report gives the results of testing with a small downdraft thermal oxidation system that was constructed by Pacific Northwest National Laboratory to stabilize glove wiper waste, reduce the waste volume, and reclaim plutonium. Proof-of-principle testing was conducted with eight runs using various combinations of rag moisture and chemical pretreatment. All runs went to planned completion. Results of these tests indicate that the thermal oxidation system has the potential for providing significant reductions in waste volume. Weight reductions of 150:1 were easily obtainable during this project. Modifications could result in weight reductions of over 200:1, with possible volume reductions of 500:1.

Phelps, M.R.; Wilcox, W.A.

1996-04-01

130

[Fundamental studies in oxidation reduction in relation to water photolysis  

SciTech Connect

Objectives were to understand 3 elementary processes central to developing membrane-based integrated chemical systems for water photolysis: role of interfaces in charge separation/recombination reactions, pathways for transmembrane charge separation, and mechanisms of water oxidation catalyzed by transition metal coordination complexes. Research during this period is arranged under the headings transmembrane oxidation-reduction mechanisms, optically gated transmembrane redox, and mechanisms of water oxidation catalysis. Viologens are involved.

Hurst, J.K.

1992-01-01

131

Facile synthesis of graphene nanosheets via Fe reduction of exfoliated graphite oxide.  

PubMed

The synthesis of graphene nanosheets from graphite oxide typically involves harmful chemical reductants that are undesirable for most practical applications of graphene. Here, we demonstrate a green and facile approach to the synthesis of graphene nanosheets based on Fe reduction of exfoliated graphite oxide, resulting in a substantial removal of oxygen functionalities of the graphite oxide. More interestingly, the resulting graphene nanosheets with residual Fe show a high adsorption capacity of 111.62 mg/g for methylene blue at room temperature, as well as easy magnetic separation from the solution. This approach offers a potential for cost-effective, environmentally friendly, and large-scale production of graphene nanosheets. PMID:21230006

Fan, Zhuang-Jun; Kai, Wang; Yan, Jun; Wei, Tong; Zhi, Lin-Jie; Feng, Jing; Ren, Yue-Ming; Song, Li-Ping; Wei, Fei

2010-12-07

132

Titanium(III) Citrate as a Nontoxic Oxidation-Reduction Buffering System for the Culture of Obligate Anaerobes  

Microsoft Academic Search

An oxidation-reduction buffering system based on titanium(III) citrate eliminates any traces of oxygen in a culture medium, serves as an indicator for low oxidation-reduction potentials, and prevents the growth of facultative anaerobes, which frequently contaminate anaerobic cultures.

Alexander J. B. Zehnder; Karl Wuhrmann

1976-01-01

133

A microbial fuel cell using manganese oxide oxygen reduction catalysts  

Microsoft Academic Search

Microbial fuel cells (MFCs) are a potential method for enhanced water and waste treatment, which offer the additional benefit\\u000a of energy generation. Manganese oxide was prepared by a simple chemical oxidation using potassium permanganate. Carbon-supported\\u000a manganese oxide nanoparticles were successfully characterised as cathode materials for MFCs. The manganese oxide particles\\u000a when used in a two-chamber MFC, using inoculum from an

I. Roche; K. Katuri; K. Scott

2010-01-01

134

ASSESSMENT OF HOUSEHOLD CARBON FOOTPRINT REDUCTION POTENTIALS  

SciTech Connect

The term ?household carbon footprint? refers to the total annual carbon emissions associated with household consumption of energy, goods, and services. In this project, Lawrence Berkeley National Laboratory developed a carbon footprint modeling framework that characterizes the key underlying technologies and processes that contribute to household carbon footprints in California and the United States. The approach breaks down the carbon footprint by 35 different household fuel end uses and 32 different supply chain fuel end uses. This level of end use detail allows energy and policy analysts to better understand the underlying technologies and processes contributing to the carbon footprint of California households. The modeling framework was applied to estimate the annual home energy and supply chain carbon footprints of a prototypical California household. A preliminary assessment of parameter uncertainty associated with key model input data was also conducted. To illustrate the policy-relevance of this modeling framework, a case study was conducted that analyzed the achievable carbon footprint reductions associated with the adoption of energy efficient household and supply chain technologies.

Kramer, Klaas Jan; Homan, Greg; Brown, Rich; Worrell, Ernst; Masanet, Eric

2009-04-15

135

Oxide reduction during triggered-lightning fulgurite formation  

NASA Astrophysics Data System (ADS)

In this study triggered-lightning induced fulgurites were formed in 99.9% pure binary oxides of manganese (MnO) and nickel (NiO) in order to study oxide reduction mechanisms. The fulgurite formation process involved packing the oxide in PVC holders and using the standard rocket-and-wire technique to trigger a lightning strike through the oxide at the International Center for Lightning Research and Testing in Camp Blanding, Florida. These two oxides were chosen from the thermodynamic extrapolation of the oxide stability using the Ellingham Diagram. This diagram indicates that NiO is significantly less stable than MnO. Fulgurites from the pure oxides were analyzed in a scanning electron microscope (SEM); secondary electron images, backscattered images and energy dispersive spectroscopy (EDS) were used to determine the microstructure and composition of the fulgurites. SEM/EDS analysis of the NiO and MnO prior to fulgurite formation confirmed they were pure binary oxides with no metallic contamination. After fulgurite formation, it was found that the nickel oxide fulgurite contained metallic nickel particles; the manganese oxide fulgurite showed no metallic phase formation. Transmission electron microscopy (TEM) examination confirmed that the MnO was a pure oxide with no sign of metallic phase formation. However, TEM results of the NiO showed that approximately 50% of the NiO was reduced to metallic face-centered cubic Ni. The Ni and NiO were observed to be coherent with the [1 0 0]Ni//[1 0 0]NiO and [1 1 0]Ni//[1 1 0]NiO. These results are consistent with the aforementioned thermodynamic stability calculations and show that the presence of carbonaceous material or mixtures of oxides is not necessary for oxide reduction during fulgurite formation. These studies do not rule out the possibility that electrolysis plays a role in oxide reduction. However, these fulgurites were made simultaneously during the same lightning strike and therefore were subjected to the same electrical current, and thus it is proposed the thermodynamic stability of the oxide must play a role in oxide reduction.

Jones, B. E.; Jones, K. S.; Rambo, K. J.; Rakov, V. A.; Jerald, J.; Uman, M. A.

2005-03-01

136

Reductive mobilization of oxide-bound metals  

SciTech Connect

This project is concerned with the mobilization of MnO{sub 2}- and FeOOH-bound toxic metals in subsurface environments arising from an influx of natural organic matter or organic-containing wastes. Our work to date emphasizes the importance of characterizing the reductant, complexant, and adsorptive characteristics of constituent organic chemicals. Organic chemicals may interact with pollutant metals directly, or may bring about changes in speciation and solubility indirectly by acting upon MnO{sub 2} and FeOOH host phases. The primary application of this work is the understanding of metal sorption and release processes within subsurface environments undergoing changes in redox status.

Stone, A.T.

1992-01-01

137

Reduction Kinetics of Graphene Oxide Determined by Temperature Programmed Desorption  

NASA Astrophysics Data System (ADS)

Graphene oxide, which is an electrical insulator, shows promise for use in several technological applications such as dielectric layers in nanoscale electronic devices or as the active region of chemical sensors. In principle, graphene oxide films could also be used as a precursor for the formation of large-scale graphene films by either thermal or chemical reduction of the graphene oxide. In order to determine the thermal stability and reduction kinetics of graphene oxide, temperature program desorption (TPD) measurements have been performed on multilayer films of graphene oxide deposited on SiO2/Si(100) substrates. The graphene oxide was exfoliated from the graphite oxide source material by slow-stirring in aqueous solution, which produces single-layer platelets with an average lateral size of ˜10 ?m. From the TPD measurements, it was determined that the decomposition process begins at ˜80 ^oC. The primary desorption products of the graphene oxide films for temperatures up to 300 ^oC are H2O, CO2, and CO, with only trace amounts of O2 being detected. An activation energy of 1.4 eV/molecule was determined by assuming an Arrhenius dependence for the decomposition process.

Ventrice, Carl; Clark, Nicholas; Field, Daniel; Geisler, Heike; Jung, Inhwa; Yang, Dongxing; Piner, Richard; Ruoff, Rodney

2009-10-01

138

In-situ IR studies of graphene oxide reduction  

Microsoft Academic Search

Thermal reduction of graphene oxide (GO) synthesized by Hummer's method is studied by in-situ infrared absorption spectroscopy in a vacuum reactor. Initially, water and hydroxyl groups are removed (100^oC), with release of CO2. Upon reduction of epoxides and carbonyl groups, the appearance of sp2-bonded carbon (C=C bonds) is evident with detection of in-plane and out of plane vibrations. However, oxygen

Muge Acik; Laurence Goux; Yves Chabal

2009-01-01

139

Electrochemical investigation of polyhalide ion oxidation–reduction on carbon nanotube electrodes for redox flow batteries  

Microsoft Academic Search

Polyhalide ions, Br?\\/BrCl2-(ClBr2-), are an important redox couple for redox flow batteries. The oxidation–reduction behavior of polyhalide ions on carbon nanotube (CNT) electrodes has been investigated with cyclic voltammetry and electrochemical impedance spectroscopy. The onset oxidation potential of Br?\\/BrCl2-(ClBr2-) is negatively shifted by>100mV, and the redox current peaks are greatly enhanced on the CNT electrode compared with that on the

Yuyan Shao; Mark H. Engelhard; Yuehe Lin

2009-01-01

140

Electrolytic reduction of spent oxide fuel -- bench-scale test preparations.  

SciTech Connect

Preparations are underway to demonstrate the electrolytic reduction of spent oxide nuclear fuel in the Hot Fuel Examination Facility (HFEF) and Argonne National Laboratory--West (ANL-W). The electrolytic reduction process, developed by the Laboratory's Chemical Technology Division, operates in an electrochemical cell that uses a molten solution of lithium chloride and dissolved lithium oxide as the electrolyte. The spent oxide fuel is loaded into a permeable steel basket as the cathode in the electrochemical cell and a platinum electrode functions as the anode. When an electrical potential is applied, the uranium oxide and other metal oxides are reduced to metal and remain in the cathode basket. Oxygen gas is formed at the platinum anode and dissipates into the system's argon atmosphere. Once reduced to metal, the spent fuel is capable of further electrometallurgical treatment in an electrorefiner to recover uranium and to ultimately effect the disposition of fission products into ceramic and metal waste forms. Thus, the electrolytic reduction process expands the electrometallurgical treatment capability to include spent oxide fuel. This report describes the bench-scale test preparations that are underway to demonstrate the electrolytic reduction of spent oxide fuel.

Herrmann, S. D.; Li, S. X.; Simpson, M. F.; Wahlquist, D. R.

2002-08-12

141

Deep reduction behavior of iron oxide and its effect on direct CO oxidation  

NASA Astrophysics Data System (ADS)

Reduction of metal oxide oxygen carrier has been attractive for direct CO oxidation and CO2 separation. To investigate the reduction behaviors of iron oxide prepared by supporting Fe2O3 on ?-Al2O3 and its effect on CO oxidation, fluidized-bed combustion experiments, thermogravimetric analyzer (TGA) experiments, and density functional theory (DFT) calculations were carried out. Gas yield (?) increases significantly with the increase of temperature from 693 K to 1203 K, while carbon deposition decreases with the increase of temperature from 743 K to 1203 K, where temperature is a very important factor for CO oxidation by iron oxide. Further, it were quantitatively detected that the interaction between CO and Fe2O3, breakage of O-Fe bonds and formation of new C-O bonds, and effect of reduction degree were quantitatively detected. Based on adsorptions under different temperatures and reducing processes from Fe3+ into Fe2+, Fe+ and then into Fe, it was found that Fe2+ ? Fe+ was the reaction-controlling step and the high oxidation state of iron is active for CO oxidation, where efficient partial reduction of Fe2O3 into FeO rather than complete reduction into iron may be more energy-saving for CO oxidation.

Dong, Changqing; Liu, Xinglei; Qin, Wu; Lu, Qiang; Wang, Xiaoqiang; Shi, Simo; Yang, Yongping

2012-01-01

142

Direct Observation of Iron Oxide Reduction Using High Voltage Microscopy.  

National Technical Information Service (NTIS)

The microstructure of reaction products resulting from gaseous reduction of iron oxide has been examined in situ and ex situ by high voltage electron microscopy (HVEM). In order to perform in situ experiments it was necessary to construct a special enviro...

N. J. Tighe P. R. Swann

1972-01-01

143

No sub x control for high nitric oxide concentration flows through combustion-driven reduction  

Microsoft Academic Search

This patent describes an improved method for removing nitrogen oxides from concentrated waste gas streams, in which nitrogen oxides are ignited with a carbonaceous material in the presence of substoichiometric quantities of a primary oxidant, such as air. Additionally, reductants may be ignited along with the nitrogen oxides, carbonaceous material and primary oxidant to achieve greater reduction of nitrogen oxides.

J. T. Yeh; J. M. Ekmann; H. W. Pennline; C. J. Drummond

1989-01-01

144

Nox control for high nitric oxide concentration flows through combustion-driven reduction  

Microsoft Academic Search

An improved method for removing nitrogen oxides from concentrated waste gas streams, in which nitrogen oxides are ignited with a carbonaceous material in the presence of substoichiometric quantities of a primary oxidant, such as air. Additionally, reductants may be ignited along with the nitrogen oxides, carbonaceous material and primary oxidant to achieve greater reduction of nitrogen oxides. A scrubber and

James T. Yeh; James M. Ekmann; Henry W. Pennline; Charles J. Drummond

1989-01-01

145

Reflectance and structure changes of iridium oxide films by reduction  

SciTech Connect

The reflectance and structure changes of iridium oxide films by reduction were investigated in an attempt to apply the films to optical data storage media. The films were prepared by the thermal oxidation of iridium-carbon composite films. The films were easily reduced by heating them in 5% H/sub 2/ in Ar at temperatures in the range 100/sup 0/-300/sup 0/C. When the films were reduced, the particles size of Ir metal and the reflectance of the films increased with an increase in the reducing temperature. The reduced films were stable against oxidation at temperatures of 250/sup 0/C or higher. Optical writing on the films was carried out with an argon laser at 0.84W power. The writing mechanism was based on changes in the film's optical properties caused by laser-induced reduction.

Sato, Y.; Yanagida, M.; Yamanaka, H.; Tanigawa, H.

1989-03-01

146

Nox control for high nitric oxide concentration flows through combustion-driven reduction  

DOEpatents

An improved method for removing nitrogen oxides from concentrated waste gas streams, in which nitrogen oxides are ignited with a carbonaceous material in the presence of substoichiometric quantities of a primary oxidant, such as air. Additionally, reductants may be ignited along with the nitrogen oxides, carbonaceous material and primary oxidant to achieve greater reduction of nitrogen oxides. A scrubber and regeneration system may also be included to generate a concentrated stream of nitrogen oxides from flue gases for reduction using this method.

Yeh, James T. (Bethel Park, PA); Ekmann, James M. (Bethel Park, PA); Pennline, Henry W. (Bethel Park, PA); Drummond, Charles J. (Churchill, PA)

1989-01-01

147

Does acetogenesis really require especially low reduction potential?  

PubMed

Acetogenesis is one of the oldest metabolic processes on Earth, and still has a major global significance. In this process, acetate is produced via the reduction and condensation of two carbon dioxide molecules. It has long been assumed that acetogenesis requires ferredoxin with an exceptionally low reduction potential of ?-500mV in order to drive CO(2) reduction to CO and the reductive carboxylation of acetyl-CoA to pyruvate. However, no other metabolic pathway requires electron donors with such low reduction potential. Is acetogenesis a special case, necessitating unique cellular conditions? In this paper, I suggest that it is not. Rather, by keeping CO as a bound metabolite, the CO-dehydrogenase-acetyl-CoA-synthase complex can couple the unfavorable CO(2) reduction to CO with the favorable acetyl-CoA synthesis, thus enabling the former process to proceed using ferredoxin of moderate reduction potential of -400mV. I further show that pyruvate synthesis can also take place using the same ferredoxins. In fact, the synthesis of pyruvate from CO(2), methylated-protein-carrier and -400mV ferredoxins is an energy-neutral process. These findings suggest that acetogenesis can take place at normal cellular redox state. Mechanistic coupling of reactions as suggested here can flatten energetic landscapes and diminish thermodynamic barriers and can be another role for enzymatic complexes common in nature and a useful tool for metabolic engineering. PMID:23103387

Bar-Even, Arren

2012-10-24

148

Blockage by acetylene of nitrous oxide reduction in Pseudomonas perfectomarinus.  

PubMed Central

Suspensions of denitrifying cells of Pseudomonas perfectomarinus reduced nitrate and nitrate as expected to dinitrogen; but, in the presence of acetylene, nitrous oxide accumulated when nitrate or nitrate was reduced. When supplied at the outset in place of nitrate and nitrate, nitrous oxide was rapidly reduced to dinitrogen by cells incubated in anaerobic vessels in the absence of acetylene. In the presence of 0.01 atmospheres of acetylene, however, nitrous oxide was not reduced. Ethylene was not produced, nor did it influence the rate of nitrous oxide reduction when provided instead of acetylene. Cells exposed to 0.01 atmospheres of acetylene for as long as 400 min were able to reduce nitrous oxide after removal of acetylene at a rate comparable to that of cells not exposed to acetylene. Acetylene did not affect the production or functioning of assimilatory nitrate or nitrite reductase in axenic cultures of Enterobacter aerogenes or Trichoderma uride. While exposed to acetylene, bacteria in marine sediment slurries produced measurable quantities of nitrous oxide from glucose- or acetate-dependent reduction of added nitrate. Possible use of acetylene blockage for measurement of denitrification in unamended marine sediments is discussed.

Balderston, W L; Sherr, B; Payne, W J

1976-01-01

149

Reduction of aqueous transition metal species on the surfaces of Fe(II)-containing oxides  

USGS Publications Warehouse

Experimental studies demonstrate that structural Fe(II) in magnetite and ilmenite heterogeneously reduce aqueous ferric, cupric, vanadate, and chromate ions at the oxide surfaces over a pH range of 1-7 at 25??C. For an aqueous transition metal m, such reactions are 3[Fe2+Fe3+2]O4(magnetite) + 2/nmz ??? 4[Fe3+2]O3(maghemite) + Fe2+ + 2/nmz-n and 3[Fe2+Ti]O3(ilmenite) + 2/nmz ??? Fe3+2Ti3O9(pseudorutile) + Fe2+ + 2/nmz-n, where z is the valance state and n is the charge transfer number. The half cell potential range for solid state oxidation [Fe(II)] ??? [Fe(III)] is -0.34 to -0.65 V, making structural Fe(II) a stronger reducing agent than aqueous Fe2+ (-0.77 V). Reduction rates for aqueous metal species are linear with time (up to 36 h), decrease with pH, and have rate constants between 0.1 and 3.3 ?? 10-10 mol m-2 s-1. Iron is released to solution both from the above reactions and from dissolution of the oxide surface. In the presence of chromate, Fe2+ is oxidized homogeneously in solution to Fe3+. X-ray photoelectron spectroscopy (XPS) denotes a Fe(III) oxide surface containing reduced Cr(III) and V(IV) species. Magnetite and ilmenite electrode potentials are insensitive to increases in divalent transition metals including Zn(II), Co(II), Mn(II), and Ni(II) and reduced V(IV) and Cr(III) but exhibit a log-linear concentration-potential response to Fe(III) and Cu(II). Complex positive electrode responses occur with increasing Cr(VI) and V(V) concentrations. Potential dynamic scans indicate that the high oxidation potential of dichromate is capable of suppressing the cathodic reductive dissolution of magnetite. Oxide electrode potentials are determined by the Fe(II)/Fe(III) composition of the oxide surface and respond to aqueous ion potentials which accelerate this oxidation process. Natural magnetite sands weathered under anoxic conditions are electrochemically reactive as demonstrated by rapid chromate reduction and the release of aqueous Fe(III) to experimental solution. In contrast, magnetite weathered under oxidizing vadose conditions show minimum reactivity toward chromate ions. The ability of Fe(II) oxides to reduce transition metals in soils and groundwaters will be strongly dependent on the redox environment.

White, A. F.; Peterson, M. L.

1996-01-01

150

Patients’ perceptions of the potential complications of bilateral reduction mammaplasty  

Microsoft Academic Search

Reduction mammaplasty aims to reduce breast mass whilst improving aesthetic appearance. Post-operative complications may include\\u000a scar and nipple-related problems, haematoma, infection and glandular necrosis. In our unit, patients undergoing surgical procedures\\u000a are counselled by a nurse practitioner in addition to initial specialist consultation to establish patients’ understanding\\u000a of the potential complications and risks of bilateral reduction mammaplasty. Fifty patients completed

D. C. G. Sainsbury; M. S. U. Hassan; P. Rorison; M. W. H. Erdmann

2007-01-01

151

Reduction of tertiary phosphine oxides with DIBAL-H.  

PubMed

The reduction of tertiary phosphine oxides (TPOs) and sulfides with diisobutylaluminum hydride (DIBAL-H) has been studied in detail. An extensive solvent screen has revealed that hindered aliphatic ethers, such as MTBE, are optimum for this reaction at ambient temperature. Many TPOs undergo considerable reduction at ambient temperature and then stall due to inhibition. 31P and 13C NMR studies using isotopically labeled substrates as well as competition studies have revealed that the source of this inhibition is tetraisobutyldialuminoxane (TIBAO), which builds up as the reaction proceeds. TIBAO selectively coordinates the TPO starting material, preventing further reduction. Several strategies have been found to circumvent this inhibition and obtain full conversion with this extremely inexpensive reducing agent for the first time. Practical reduction protocols for these critical targets have been developed. PMID:18197688

Busacca, Carl A; Raju, Ravinder; Grinberg, Nelu; Haddad, Nizar; James-Jones, Paul; Lee, Heewon; Lorenz, Jon C; Saha, Anjan; Senanayake, Chris H

2008-01-16

152

Nanosized Iron Oxide Colloids Strongly Enhance Microbial Iron Reduction? †  

PubMed Central

Microbial iron reduction is considered to be a significant subsurface process. The rate-limiting bioavailability of the insoluble iron oxyhydroxides, however, is a topic for debate. Surface area and mineral structure are recognized as crucial parameters for microbial reduction rates of bulk, macroaggregate iron minerals. However, a significant fraction of iron oxide minerals in the subsurface is supposed to be present as nanosized colloids. We therefore studied the role of colloidal iron oxides in microbial iron reduction. In batch growth experiments with Geobacter sulfurreducens, colloids of ferrihydrite (hydrodynamic diameter, 336 nm), hematite (123 nm), goethite (157 nm), and akaganeite (64 nm) were added as electron acceptors. The colloidal iron oxides were reduced up to 2 orders of magnitude more rapidly (up to 1,255 pmol h?1 cell?1) than bulk macroaggregates of the same iron phases (6 to 70 pmol h?1 cell?1). The increased reactivity was not only due to the large surface areas of the colloidal aggregates but also was due to a higher reactivity per unit surface. We hypothesize that this can be attributed to the high bioavailability of the nanosized aggregates and their colloidal suspension. Furthermore, a strong enhancement of reduction rates of bulk ferrihydrite was observed when nanosized ferrihydrite aggregates were added.

Bosch, Julian; Heister, Katja; Hofmann, Thilo; Meckenstock, Rainer U.

2010-01-01

153

The reduction of iron oxides by volatiles in a rotary hearth furnace process: Part II. The reduction of iron oxide\\/carbon composites  

Microsoft Academic Search

The reduction of iron oxide\\/carbon composite pellets with hydrogen at 900 ?C to 1000 ?C was studied. Compared to hydrogen,\\u000a the reduction by carbon was negligible at 900 ?C and below. However, significant carbon oxidation of the iron oxide\\/graphite\\u000a pellets by H2O generated from the reduction of Fe2O3 by H2 was observed. At higher temperatures, reduction by carbon complicates the

I. Sohn; R. J. Fruehan

2006-01-01

154

Reduction in oxidatively generated DNA damage following smoking cessation  

Microsoft Academic Search

Background  Cigarette smoking is a known cause of cancer, and cancer may be in part due to effects of oxidative stress. However, whether\\u000a smoking cessation reverses oxidatively induced DNA damage unclear. The current study sought to examine the extent to which\\u000a three DNA lesions showed significant reductions after participants quit smoking.\\u000a \\u000a \\u000a \\u000a \\u000a Methods  Participants (n = 19) in this study were recruited from

Harold C Box; Richard J O’Connor; Helen B Patrzyc; Herbert Iijima; Jean B Dawidzik; Harold G Freund; Edwin E Budzinski; K Michael Cummings; Martin C Mahoney

2011-01-01

155

Direct oxide reduction demonstration, small-scale studies  

SciTech Connect

This project was initiated to provide process design information to the Plutonium Recovery Project (PRP). Although direct oxide reduction (DOR) has been operated in a production mode both at the Rocky Flats Plant (now operated by EG G, Inc.) and Los Alamos National Laboratory, many aspects of the process are ill-defined. Because the PRP plans include significant DOR capability, a well-defined process should minimize capital cost and maximize productivity. Reduced radiation exposure may also be realized. A detailed, statistically valid investigation of the direct oxide reduction process was carried out utilizing 100 grams or less of plutonium dioxide per experiment. Conditions were established for obtaining 95% + yields. Conclusions drawn from the results of the experimental work were utilized to make recommendations for future large-scale investigative and confirmative work as well large-scale production demonstration work. 4 refs., 5 figs., 14 tabs.

Long, J.L.; Santi, D.J.; Fisher, D.C.; Humiston, T.J.

1991-12-09

156

A Spectrofluorometer for Recording of Intracellular Oxidation-Reduction States  

Microsoft Academic Search

A simple and versatile microspectrofluorometer is described together with suitable electronic circuits for single-differential-or double-aperture operation. The apparatus is suitable for measuring oxidation-reduction states of mitochondrial and cytoplasmic pyridine nucleotide in various organs with apertures ranging from 15 microns up to a few millimeters. Suitable optical and electronic components are briefly described together with some of their limitations. The application

B. Chance; V. Legallais

1963-01-01

157

Direct reduction processes for titanium oxide in molten salt  

Microsoft Academic Search

Molten salt electrolysis using CaCl2 is employed to produce pure titanium and its alloys directly from TiO2 and a mixture of elemental oxides, respectively, as an alternate to the Kroll process. This is because CaO, which is a reduction by-product, is highly soluble in CaCl2. Good-quality titanium containing only a small amount of residual oxygen has been successfully produced and

Ryosuke O. Suzuki

2007-01-01

158

Direct reduction processes for titanium oxide in molten salt  

Microsoft Academic Search

Molten salt electrolysis using CaCl2 is employed to produce pure titanium and its alloys directly from TiO2 and a mixture of elemental oxides, respectively, as an alternate to the Kroll process. This is because CaO, which is a reduction\\u000a by-product, is highly soluble in CaCl2. Good-quality titanium containing only a small amount of residual oxygen has been successfully produced and

Ryosuke O. Suzuki

2007-01-01

159

Reduction of Iron-Oxide-Carbon Composites: Part III. Shrinkage of Composite Pellets during Reduction  

NASA Astrophysics Data System (ADS)

This article involves the evaluation of the volume change of iron-oxide-carbon composite pellets and its implications on reduction kinetics under conditions prevalent in a rotary hearth furnace (RHF) that were simulated in the laboratory. The pellets, in general, were found to shrink considerably during the reduction due to the loss of carbon and oxygen from the system, sintering of the iron-oxide, and formation of a molten slag phase at localized regions inside the pellets due to the presence of binder and coal/wood-charcoal ash at the reduction temperatures. One of the shortcomings of the RHF ironmaking process has been the inability to use multiple layers of composite pellets because of the impediment in heat transport to the lower layers of a multilayer bed. However, pellet shrinkage was found to have a strong effect on the reduction kinetics by virtue of enhancing the external heat transport to the lower layers. The volume change of the different kinds of composite pellets was studied as a function of reduction temperature and time. The estimation of the change in the amount of external heat transport with varying pellet sizes for a particular layer of a multilayer bed was obtained by conducting heat-transfer tests using inert low-carbon steel spheres. It was found that if the pellets of the top layer of the bed shrink by 30 pct, the external heat transfer to the second layer increases by nearly 6 times.

Halder, S.; Fruehan, R. J.

2008-12-01

160

Dissimilatory selenate reduction potentials in a diversity of sediment types  

SciTech Connect

We measured potential rates of bacterial dissimilatory reduction of {sup 75}SeO{sub 4}{sup 2{minus}} to {sup 75}Se{sup 0} in a diversity of sediment types, with salinities ranging from freshwater (salinity = 1 g/liter) to hypersaline salinity = 320 g/liter and with pH values ranging from 7.1 to 9.8. Results indicate that a capacity for microbial selenate reduction is a common feature of a diversity of surficial sediment types in nature. Potential DSeR did not correlate with a variety of chemical factors (salinity, pH, or organic carbon) but was related to bacterial activity expressed as potential denitrification. Furthermore, the expression of potential selenate reduction activity in sediments appears to be limited by the concentration of selenate in a manner that displays Michaelis-Menten kinetics. The extent to which the presence of other group VI oxyanions or nitrate may inhibit selenate reduction appears to vary in different milieus.

Steinberg, N.A.; Oremland, R.S. (Geological Survey, Menlo Park, CA (USA))

1990-11-01

161

Energetic and Methane Emission Reduction Potentials from an Unsanitary Landfill  

Microsoft Academic Search

Al Akeeder is the largest landfill site in northern Jordan. The site operation started in 1981 by open dumping and combusting then converted to unsanitary landfilling (without biogas and leachate management). The objective of this article is to estimate the energy and methane emission reduction potentials of the landfill. The amount and composition of the landfill gas were estimated by

H. A. Abu Qdais; A. M. Maqableh; L. M. Al Nawayseh; N. M. Al Jamal

2011-01-01

162

In-situ IR studies of graphene oxide reduction.  

NASA Astrophysics Data System (ADS)

Thermal reduction of graphene oxide (GO) synthesized by Hummer's method is studied by in-situ infrared absorption spectroscopy in a vacuum reactor. Initially, water and hydroxyl groups are removed (100^oC), with release of CO2. Upon reduction of epoxides and carbonyl groups, the appearance of sp2-bonded carbon (C=C bonds) is evident with detection of in-plane and out of plane vibrations. However, oxygen remains in the structure in the form of COC bonds even after 700^oC anneal. Around 290^oC, a strong increase of the absorbance associated with structure changes of GO is observed. The increase of the refractive index is attributed to an increase of electrical conductivity after reduction of GO.

Acik, Muge; Goux, Laurence; Chabal, Yves

2009-03-01

163

Mechanistic study of the selective catalytic reduction of nitric oxide with methane over yttrium oxide  

SciTech Connect

The catalytic activity of nanocrystalline Group IIIB metal oxides for the reduction of nitric oxide with methane was shown to be comparable to that of Co-ZSM-5. The mechanism of selective catalytic reduction of nitric oxide with methane in excess oxygen was examined over nanocrystalline yttrium oxide. A series of heterogeneous and homogeneous reaction steps was proposed to account for the observed trends in catalytic properties. Methyl radicals generated at the catalyst surface desorb into the gas phase, where they react with nitric oxide to form nitrosomethane. Nitrosomethane then decomposes in a series of homogeneous and heterogeneous reactions to produce nitrogen and nitrous oxide. Evidence for gas-phase reaction of methyl radicals with nitric oxide was found in the adsorption studies of nitric oxide on yttrium oxide, the presence of ethane and ethene in the reactor effluent, catalytic studies involving nitrosomethane and nitromethane, as well as the successful prediction of methane selectivities based on a homogeneous reaction mechanism for methyl radical consumption. The proposed pathway for nitrogen production was supported by the observation of hydrogen cyanide under certain operating conditions, as well as adsorbed NCO species detected by infrared spectroscopy.

Fokema, M.D.; Ying, J.Y.

2000-05-15

164

Oxidation-Reduction Calculations in the Biochemistry Course  

ERIC Educational Resources Information Center

|Redox calculations have the potential to reinforce important concepts in bioenergetics. The intermediacy of the NAD[superscript +]/NADH couple in the oxidation of food by oxygen, for example, can be brought out by such calculations. In practice, students have great difficulty and, even when adept at the calculations, frequently do not understand…

Feinman, Richard D.

2004-01-01

165

Oxidation Potentials in Iron and Steel Making  

NASA Astrophysics Data System (ADS)

The state of oxidation of a pyrometallurgical process given by the partial pressure of oxygen and the temperature (the oxidation potential) is one of the important properties monitored and controlled in the smelting and refining of iron and the nonferrous metals. Solid electrolyte sensors based on ZrO2 and a reference electrode such as Cr/Cr2O3 to measure the oxygen pressure found early application in the steel industry, followed soon after in copper, nickel, lead, and zinc smelting. Similar devices are installed in automobile postcombustion/exhaust trains as part of emission control systems. The current discussion reviews this technology as applied in the primary steps of iron and steel making and refining.

Matousek, J. W.

2013-08-01

166

Multiple reaction fronts in the oxidation-reduction of iron-rich uranium ores  

SciTech Connect

When a container of radioactive waste is buried underground, it eventually corrodes, and leakage of radioactive material to the surrounding rock occurs. Depending on the chemistry of the rock, many different reactions may occur. A particular case concerns the oxidation and reduction of uranium ores by infiltrating groundwater, since UO[sub 3] is relatively soluble (and hence potentially transportable to the water supply), whereas UO[sub 2] is essentially insoluble. It is therefore of concern to those involved with radioactive waste disposal to understand the mechanics of uranium transport through reduction and oxidation reactions. This paper describes the oxidation of iron-rich uranium-bearing rocks by infiltration of groundwater. A reaction-diffusion model is set up to describe the sequence of reactions involving iron oxidation, uranium oxidation and reduction, sulfuric acid production, and dissolution of the host rock that occur. On a geological timescale of millions of years, the reactions occur very fast in very thin reaction fronts. It is shown that the redox front that separates oxidized (orange) rock from reduced (black) rock must actually consist of two separate fronts that move together, at which the two separate processes of uranium oxidation and iron reduction occur, respectively. Between these fronts, a high concentration of uranium is predicted. The mechanics of this process are not specific to uranium-mediated redox reactions, but apply generally and may be used to explain the formation of concentrated ore deposits in extended veins. On the long timescales of relevance, a quasi-static response results, and the problem can be solved explicitly in one dimension. This provides a framework for studying more realistic two-dimensional problems in fissured rocks and also for the future study of uraninite nodule formation.

Dewynne, J.N. (Univ. of Southampton (United Kingdom). Faculty of Mathematical Studies); Fowler, A.C. (Oxford Univ. (United Kingdom). Mathematical Inst.); Hagan, P.S. (Los Alamos National Lab., NM (United States))

1993-08-01

167

Pre-converted nitric oxide gas in catalytic reduction system  

DOEpatents

A two-stage catalyst comprises an oxidative first stage and a reductive second stage. The first stage is intended to convert NO to NO{sub 2} in the presence of O{sub 2}. The second stage serves to convert NO{sub 2} to environmentally benign gases that include N{sub 2}, CO{sub 2}, and H{sub 2}O. By preconverting NO to NO{sub 2} in the first stage, the efficiency of the second stage for NO{sub x} reduction is enhanced. For example, an internal combustion engine exhaust is connected by a pipe to a first chamber. An oxidizing first catalyst converts NO to NO{sub 2} in the presence of O{sub 2} and includes platinum/alumina, e.g., Pt/Al{sub 2}O{sub 3} catalyst. A flow of hydrocarbons (C{sub x}H{sub y}) is input from a pipe into a second chamber. For example, propene can be used as a source of hydrocarbons. The NO{sub 2} from the first catalyst mixes with the hydrocarbons in the second chamber. The mixture proceeds to a second reduction catalyst that converts NO{sub 2} to N{sub 2}, CO{sub 2}, and H{sub 2}O, and includes a {gamma}-Al{sub 2}O{sub 3}. The hydrocarbons and NO{sub x} are simultaneously reduced while passing through the second catalyst. 9 figs.

Hsiao, M.C.; Merritt, B.T.; Penetrante, B.M.; Vogtlin, G.E.

1999-04-06

168

Potential role of bicarbonate during pyrite oxidation  

SciTech Connect

The need to prevent the development of acid mine drainage (AMD) by oxidation of pyrite has triggered numerous investigations into the mechanisms of its oxidation. According to Frontier molecular orbital (FMO) theory, the surface-exposed sulfur atom of pyrite possesses an unshared electron pair which produces a slightly negatively charged pyrite surface that can attract cations such as Fe{sup 2+}. Because of surface electroneutrality and pH considerations, however, the pyrite surface Fe{sup 2+} coordinates OH. The authors proposed that this surface Fe{sup 2+} OH when in the presence of CO{sub 2} is converted to {minus}FeCO{sub 3} or {minus}FeHCO{sub 3}, depending on pH. In this study, using Fourier transform infrared spectroscopy (FT-IR) they demonstrated that such complexes form on the surface of pyrite and continue to persist even after a significant fraction of the surface Fe{sup 2+} was oxidized to Fe{sup 3+}. FT-IR spectra also showed the presence of two carbonyl absorption bands (1,682 and 1,653 cm{sup {minus}1}) on the surface of pyrite upon exposure to CO{sub 2} which suggested that pyrite surface carbon complexes existed in two different surface chemical environments, pointing out two potential mechanisms of pyrite surface-CO{sub 2} interactions. One potential mechanism involved formation of a pyrite surface-Fe(II)HCO{sub 3} complex, whereas a second potential mechanism involved formation of a pyrite surface-carboxylic acid group complex [{minus}Fe(II)SSCOOFe-(II)].

Evangelou, V.P.; Holt, A. [Univ. of Kentucky, Lexington, KY (United States). Dept. of Agronomy; Seta, A.K. [Univ. Bengkulu (Indonesia). Fakultas Pertanian

1998-07-15

169

Aggregate-scale heterogeneity in iron (hydr)oxide reductive transformations  

Microsoft Academic Search

There is growing awareness of the complexity of potential reaction pathways and the associated solid-phase transformations during the reduction of Fe (hydr)oxides, especially ferrihydrite. An important observation in static and advective-dominated systems is that microbially produced Fe(II) accelerates Ostwald ripening of ferrihydrite, thus promoting the formation of thermodynamically more stable ferric phases (lepidocrocite and goethite) and, at higher Fe(II) surface

Katharine J. Tufano; Shawn G. Benner; Klaus U. Mayer; Matthew A. Marcus; Peter S. Nico; Scott Fendorf

2009-01-01

170

Mercury oxidation over a vanadia-based selective catalytic reduction catalyst  

Microsoft Academic Search

The process of the reaction among elemental mercury (Hg°) and reactive flue gas components across the selective catalytic reduction (SCR) catalyst was studied in a laboratory-scale reactor. Prepared vanadia-based SCR catalysts were characterized and analyzed to understand the potential reaction pathways. Mercury oxidation was observed when pro-exposure of the SCR catalyst to HCl, followed by passing through Hg°\\/N in the

Sheng He; Jinsong Zhou; Yanqun Zhu; Zhongyang Luo; Mingjiang Ni; Kefa Cen

2009-01-01

171

Electrochemical oxidation by square-wave potential pulses in the imitation of phenacetin to acetaminophen biotransformation.  

PubMed

Electrochemistry in combination with mass spectrometry is emerging as a versatile analytical technique in the imitation of oxidative drug metabolism during the early stages of drug discovery and development. Here, we present electrochemical O-dealkylation of phenacetin to acetaminophen by square-wave potential pulses consisting of consecutive sub-second oxidation and reduction steps. This O-dealkylation could not be achieved by oxidation at constant potential or longer potential pulses because of the fast hydrolysis of the reactive intermediates. Electrochemical conversion by square-wave potential pulses can thus widen the scope of electrochemical synthesis of metabolites and imitation of in vivo drug metabolism. PMID:21984979

Nouri-Nigjeh, Eslam; Bischoff, Rainer; Bruins, Andries P; Permentier, Hjalmar P

2011-10-07

172

Reversible biological Birch reduction at an extremely low redox potential.  

PubMed

The Birch reduction of aromatic rings to cyclohexadiene compounds is widely used in chemical synthesis and requires solvated electrons, the most potent reductants known in organic chemistry. Benzoyl-coenzyme A (CoA) reductases (BCR) are key enzymes in the anaerobic bacterial degradation of aromatic compounds and catalyze an analogous reaction under physiological conditions. Class I BCRs are FeS enzymes and couple the reductive dearomatization of benzoyl-CoA to cyclohexa-1,5-diene-1-carboxyl-CoA (dienoyl-CoA) to a stoichiometric ATP hydrolysis. Here, we report on a tungsten-containing class II BCR from Geobacter metallireducens that catalyzed the fully reversible, ATP-independent dearomatization of benzoyl-CoA to dienoyl-CoA. BCR additionally catalyzed the disproportionation of dienoyl-CoA to benzoyl-CoA/monoenoyl-CoA and the four- and six-electron reduction of benzoyl-CoA in the presence of a reduced low-potential bridged 2,2'-bipyridyl redox dye. Reversible redox titration experiments in the presence of this redox dye revealed a midpoint potential of E(0)' = -622 mV for the benzoyl-CoA/dienoyl-CoA couple, which is far below the values of other known reversible substrate/product redox couples in enzymology. This work demonstrates the efficiency of reversible metalloenzyme catalysis, which in chemical synthesis can only be achieved under essentially irreversible conditions. PMID:20578740

Kung, Johannes W; Baumann, Sven; von Bergen, Martin; Müller, Michael; Hagedoorn, Peter-Leon; Hagen, Wilfred R; Boll, Matthias

2010-07-21

173

Solid oxide membrane process for the direct reduction of magnesium from magnesium oxide  

Microsoft Academic Search

The Solid Oxide Membrane (SOM) process is an emerging generic technology for the environmentally friendly extraction of high-energy-content metals directly from their oxides. This process has the potential to offer a viable, cost effective and cleaner alternative to existing state of the art primary magnesium extraction processes. The SOM process in principle uses a tubular yttria stabilized-zirconia-based solid oxide fuel

Ajay Krishnan

2006-01-01

174

The Role of Methionine Oxidation/Reduction in the Regulation of Immune Response.  

PubMed

Methionine oxidation by reactive oxygen species and reduction mediated by the methionine sulfoxide reductase (Msr) system may attenuate protein function in signal transduction pathways. This review will focus on two potential protein targets for methionine oxidation involved in signal transduction of the immune response: Ca(2+)/calmodulin-regulated phosphatase calcineurin (Cn) and inhibitor of kappa B-alpha (IkB?). The major known function of Cn is to regulate nuclear localization of the nuclear factor of activated T cells (NFAT), a family of transcription factors during immune stimulus. Like wise, I?B? inhibits the activity of nuclear factor kappa B (NFkB), which is known to regulate the transcription of various genes participating in immunological and oxidative stress response. Modification of Met (45) in I?B? enhances its resistance to protein-degredation; thereby, preventing NFkB from activating transcription in cells of the immune system. Similarly, the human Cn molecule contains several methionine residues that are either located next to a cysteine residue or a methionine residue. Accordingly, it is suggested that oxidation of a specific Cn-methionine may interfere with the proper NFAT nuclear-localization and transcriptional activation in T-cell. Thus, the roles of oxidized-methionine residues and their reduction, by the Msr system, are discussed as potential regulators of cellular immune response. PMID:19823697

Agbas, Abdulbaki; Moskovitz, Jackob

2009-01-01

175

Quantifying the potential for dose reduction with visual grading regression.  

PubMed

Objectives To propose a method to study the effect of exposure settings on image quality and to estimate the potential for dose reduction when introducing dose-reducing measures. Methods Using the framework of visual grading regression (VGR), a log(mAs) term is included in the ordinal logistic regression equation, so that the effect of reducing the dose can be quantitatively related to the effect of adding post-processing. In the ordinal logistic regression, patient and observer identity are treated as random effects using generalised linear latent and mixed models. The potential dose reduction is then estimated from the regression coefficients. The method was applied in a single-image study of coronary CT angiography (CTA) to evaluate two-dimensional (2D) adaptive filters, and in an image-pair study of abdominal CT to evaluate 2D and three-dimensional (3D) adaptive filters. Results For five image quality criteria in coronary CTA, dose reductions of 16-26% were predicted when adding 2D filtering. Using five image quality criteria for abdominal CT, it was estimated that 2D filtering permits doses were reduced by 32-41%, and 3D filtering by 42-51%. Conclusions VGR including a log(mAs) term can be used for predictions of potential dose reduction that may be useful for guiding researchers in designing subsequent studies evaluating diagnostic value. With appropriate statistical analysis, it is possible to obtain direct numerical estimates of the dose-reducing potential of novel acquisition, reconstruction or post-processing techniques. PMID:23239690

Smedby, O; Fredrikson, M; De Geer, J; Borgen, L; Sandborg, M

2013-01-01

176

Oxidation-reduction induced roughening of platinum (111) surface  

SciTech Connect

Platinum (111) single crystal surface was roughened by repeated cycles of oxidation and reduction to study dynamic evolution of surface roughening. The interface roughens progressively upon repeated cycles. The measured width of the interface was fit to an assumed pow law, W {approximately}t{sup {beta}}, with {beta} = 0.38(1). The results are compared with a simulation based on a random growth model. The fraction of the singly stepped surface apparently saturates to 0. 25 monolayer, which explains the apparent saturation to a steady roughness observed in previous studies.

You, H.; Nagy, Z.

1993-06-01

177

Nitrogen loss from soil through anaerobic ammonium oxidation coupled to iron reduction  

NASA Astrophysics Data System (ADS)

The oxidation of ammonium is a key step in the nitrogen cycle, regulating the production of nitrate, nitrous oxide and dinitrogen. In marine and freshwater ecosystems, anaerobic ammonium oxidation coupled to nitrite reduction, termed anammox, accounts for up to 67% of dinitrogen production. Dinitrogen production through anaerobic ammonium oxidation has not been observed in terrestrial ecosystems, but the anaerobic oxidation of ammonium to nitrite has been observed in wetland soils under iron-reducing conditions. Here, we incubate tropical upland soil slurries with isotopically labelled ammonium and iron(III) to assess the potential for anaerobic ammonium oxidation coupled to iron(III) reduction, otherwise known as Feammox, in these soils. We show that Feammox can produce dinitrogen, nitrite or nitrate in tropical upland soils. Direct dinitrogen production was the dominant Feammox pathway, short-circuiting the nitrogen cycle and resulting in ecosystem nitrogen losses. Rates were comparable to aerobic nitrification and to denitrification, the latter being the only other process known to produce dinitrogen in terrestrial ecosystems. We suggest that Feammox could fuel nitrogen losses in ecosystems rich in poorly crystalline iron minerals, with low or fluctuating redox conditions.

Yang, Wendy H.; Weber, Karrie A.; Silver, Whendee L.

2012-08-01

178

Removal of oxides from alkali metal melts by reductive titration to electrical resistance-change end points  

DOEpatents

Alkali metal oxides dissolved in alkali metal melts are reduced with soluble metals which are converted to insoluble oxides. The end points of the reduction is detected as an increase in electrical resistance across an alkali metal ion-conductive membrane interposed between the oxide-containing melt and a material capable of accepting the alkali metal ions from the membrane when a difference in electrical potential, of the appropriate polarity, is established across it. The resistance increase results from blocking of the membrane face by ions of the excess reductant metal, to which the membrane is essentially non-conductive.

Tsang, Floris Y. (Walnut Creek, CA)

1980-01-01

179

Reduction and oxidation of oxide ion conductors with conductive atomic force microscopy  

NASA Astrophysics Data System (ADS)

Local accumulation and dissipation of charges on the surface of oxide ion conductors resulting from electric potentials were observed with conductive atomic force microscopy (AFM). After a negative bias was applied at the tip, a sequence of surface potential maps appeared compatible with electron injection onto the electrolyte surface. Applying a positive bias, in contrast, generated a positive surface charge adjacent to the tip contact area. This observation is consistent with the formation of oxide ion vacancies on the oxide surface. In addition, oxide ion conductivity at a low temperature range (100-200 °C) was obtained, and the activation energy for diffusion in gadolinia-doped ceria (GDC) was calculated as ~0.56 eV, implying that the majority of oxide ion vacancies diffuse on the surface rather than inside the bulk of the electrolyte.

Lee, Wonyoung; Lee, Minhwan; Kim, Young-Beom; Prinz, Fritz B.

2009-11-01

180

Redox-inactive metals modulate the reduction potential in heterometallic manganese-oxido clusters  

NASA Astrophysics Data System (ADS)

Redox-inactive metals are found in biological and heterogeneous water oxidation catalysts, but, at present, their roles in catalysis are not well understood. Here, we report a series of high-oxidation-state tetranuclear-dioxido clusters comprising three manganese centres and a redox-inactive metal (M). Crystallographic studies show an unprecedented Mn3M(µ4-O)(µ2-O) core that remains intact on changing M or the manganese oxidation state. Electrochemical studies reveal that the reduction potentials span a window of 700 mV and are dependent on the Lewis acidity of the second metal. With the pKa of the redox-inactive metal-aqua complex as a measure of Lewis acidity, these compounds demonstrate a linear dependence between reduction potential and acidity with a slope of ˜100 mV per pKa unit. The Sr2+ and Ca2+ compounds show similar potentials, an observation that correlates with the behaviour of the oxygen-evolving complex of photosystem II, which is active only if one of these two metals is present.

Tsui, Emily Y.; Tran, Rosalie; Yano, Junko; Agapie, Theodor

2013-04-01

181

Redox-Inactive Metals Modulate the Reduction Potential in Heterometallic Manganese-Oxido Clusters  

PubMed Central

Redox-inactive metals are found in biological and heterogeneous water oxidation catalysts, but their roles in catalysis are currently not well understood. A series of high oxidation state tetranuclear-dioxido clusters comprised of three manganese centers and a redox-inactive metal (M) of various charge is reported. Crystallographic studies show an unprecedented Mn3M(?4-O)(?2-O) core that remains intact upon changing M or the manganese oxidation state. Electrochemical studies reveal that the reduction potentials span a window of 700 mV, dependent upon the Lewis acidity of the second metal. With the pKa of the redox-inactive metal-aqua complex as a measure of Lewis acidity, these compounds display a linear dependence between reduction potential and acidity with a slope of ca. 100 mV per pKa unit. The Sr2+ and Ca2+ compounds show similar potentials, an observation that correlates with the behavior of the OEC, which is active only in the presence of one of these two metals.

Tsui, Emily Y.; Tran, Rosalie; Yano, Junko; Agapie, Theodor

2013-01-01

182

Transparent Conducting Oxides as Potential Thermoelectrics  

NASA Astrophysics Data System (ADS)

Transparent conducting oxides (TCOs) in their less-doped semiconducting states have potential as thermoelectric oxides or TEOs. They are attractive as TEOs owing to: 1) their good thermochemical stability, 2) their n-type character (to complement existing p-type TEOs), and 3) their high electronic mobilities. The numerator of the TE figure of merit (Z), also known as the ``power factor'' (PF), is the product of the electronic conductivity and the square of the Seebeck coefficient. An experimental procedure named after its developer, ``Jonker'' analysis plots Seebeck coefficient vs. the natural logarithm of the electronic conductivity. Data for bulk ceramic specimens just prior to the onset of degeneracy tend to fall on a line of slope, k/e (k=Boltzmann constant, e=charge of the electron). From this line, the doping composition corresponding to the highest power factor can be determined and the PF optimized, based upon data from a few carefully chosen compositions. Subsequently, following a procedure originally derived by Ioffe, the zero-thermopower intercept of these Jonker lines can be directly related to the maximum achievable power factor for a given TEO. So-called ``Ioffe'' plots allow for meaningful comparisons between candidate TEO materials, and also indicate the minimum thermal conductivity required to achieve a target ZT value at the temperature of measurement. Results for TCO-based TEOs will be discussed for both simple and compound (including layered) materials.

Mason, Thomas

2013-03-01

183

Facile and controllable electrochemical reduction of graphene oxide and its applications  

SciTech Connect

Graphene oxide is electrochemically reduced which is called electrochemically reduced graphene oxide (ER-G). ER-G is characterized with scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. The oxygen content is significantly decreased and the sp 2 carbon is restored after electrochemical reduction. ER-G exhibits much higher electrochemical capacitance and cycling durability than carbon nanotubes (CNTs) and chemically reduced graphene; the specific capacitance measured with cyclic voltammetry (20 mV/s) is ~165 F/g, ~86 F/g, and ~100 F/g for ER-G, CNTs, and chemically reduced graphene,1 respectively. The electrochemical reduction of oxygen and hydrogen peroxide was greatly enhanced on ER-G electrodes as compared with CNTs. ER-G has shown a good potential for applications in energy storage, biosensors, and electrocatalysis.

Shao, Yuyan; Wang, Jun; Engelhard, Mark H.; Wang, Chong M.; Lin, Yuehe

2010-01-01

184

Drag reduction in turbulent pipe flow by applied electric potentials  

NASA Astrophysics Data System (ADS)

A novel approach to drag reduction is presented on the basis of applied positive electric potentials to a pipe. This has been studied by measuring the pressure drop over a 13.1 m epoxy-coated pipe made of carbon steel, through which water was flowing under conditions of constant flow rate. Potentials were applied between the pipe and the counter electrode located at the pipe inlet. The results show a decrease in the pressure drop (up to 2%) when positive electric DC-potentials in the range 0.6 -- 1.6V were applied to the pipe. However, no significant changes was obtained for applied potentials in the ranges of 0 to 0.6 V, 1.6 to 2.0 V or 0 to -2.0 V. Waterflow through an epoxy coated turbine pipe (length 1562 m, diameter 1 m, total fall 380 m) in a hydroelectric power plant has also been studied. A 1.1 V potential was applied between the pipe and the manlock (made of stainless steel and electrically insulated from the pipe). Results show that the head loss decreased from 45.9 m to 39.8 m at maximum flow rate, which corresponds to a 1.8% increase in the electricity production. Although small, the effect represents the possibility of significant cost savings. The mechanism by which the drag is reduced is not currently understood.

Waskaas, Magne; Daujotis, Vytautas; Wolden, Kjell; Raudonis, Rimantas; Plausinaitis, Deivis

2006-11-01

185

Reduction of Oxidative Melt Loss of Aluminum and Its Alloys  

SciTech Connect

This project led to an improved understanding of the mechanisms of dross formation. The microstructural evolution in industrial dross samples was determined. Results suggested that dross that forms in layers with structure and composition determined by the local magnesium concentration alone. This finding is supported by fundamental studies of molten metal surfaces. X-ray photoelectron spectroscopy data revealed that only magnesium segregates to the molten aluminum alloy surface and reacts to form a growing oxide layer. X-ray diffraction techniques that were using to investigate an oxidizing molten aluminum alloy surface confirmed for the first time that magnesium oxide is the initial crystalline phase that forms during metal oxidation. The analytical techniques developed in this project are now available to investigate other molten metal surfaces. Based on the improved understanding of dross initiation, formation and growth, technology was developed to minimize melt loss. The concept is based on covering the molten metal surface with a reusable physical barrier. Tests in a laboratory-scale reverberatory furnace confirmed the results of bench-scale tests. The main highlights of the work done include: A clear understanding of the kinetics of dross formation and the effect of different alloying elements on dross formation was obtained. It was determined that the dross evolves in similar ways regardless of the aluminum alloy being melted and the results showed that amorphous aluminum nitride forms first, followed by amorphous magnesium oxide and crystalline magnesium oxide in all alloys that contain magnesium. Evaluation of the molten aluminum alloy surface during melting and holding indicated that magnesium oxide is the first crystalline phase to form during oxidation of a clean aluminum alloy surface. Based on dross evaluation and melt tests it became clear that the major contributing factor to aluminum alloy dross was in the alloys with Mg content. Mg was identified as the primary factor that accelerates dross formation specifically in the transition from two phases to three phase growth. Limiting magnesium oxidation on the surface of molten aluminum therefore becomes the key to minimizing melt loss, and technology was developed to prevent magnesium oxidation on the aluminum surface. This resulted in a lot of the work being focused on the control of Mg oxidation. Two potential molten metal covering agents that could inhibit dross formation during melting and holding consisting of boric acid and boron nitride were identified. The latter was discounted by industry as it resulted in Boron pick up by the melt beyond that allowed by specifications during plant trials. The understanding of the kinetics of dross formation by the industry partners helped them understand how temperature, alloy chemistry and furnace atmosphere (burner controls--e.g. excess air) effected dross formation. This enables them to introduce in their plant process changes that reduced unnecessary holding at high temperatures, control burner configurations, reduce door openings to avoid ingress of air and optimize charge mixes to ensure rapid melting and avoid excess oxidation.

Dr. Subodh K. Das; Shridas Ningileri

2006-03-17

186

Facile Synthesis of Graphene Nanosheets via Fe Reduction of Exfoliated Graphite Oxide  

Microsoft Academic Search

The synthesis of graphene nanosheets from graphite oxide typically involves harmful chemical reductants that are undesirable for most practical applications of graphene. Here, we demonstrate a green and facile approach to the synthesis of graphene nanosheets based on Fe reduction of exfoliated graphite oxide, resulting in a substantial removal of oxygen functionalities of the graphite oxide. More interestingly, the resulting

Zhuang-Jun Fan; Wang Kai; Jun Yan; Tong Wei; Lin-Jie Zhi; Jing Feng; Yue-ming Ren; Li-Ping Song; Fei Wei

2011-01-01

187

Inhibition of bacterially promoted uranium reduction: Ferric (hydr)oxides as competitive electron acceptors  

Microsoft Academic Search

Reduction of hexavalent to tetravalent uranium results in a marked decrease in the mobility of this hazardous element. Microbial reduction is the most kinetic viable mechanism for such a reaction. Unfortunately, alternate terminal electron acceptors may thus compete with uranyl. We examine the role of common iron oxides on uranyl reduction. Only poorly ordered iron oxides altered the degree and

Bruce Wielinga; Benjamin Bostick; R. F. Rosenzweig; S. Fendorf

2000-01-01

188

Reduction characteristics of copper oxide in cerium and zirconium oxide systems  

Microsoft Academic Search

The reduction of CuO dispersed on fluorite-type oxide catalysts, namely La-doped CeO2 and Y-doped ZrO2 was studied in this work. On both supports distinct copper species were identified as a function of copper content by temperature-programmed reduction (TPR) by H2 and CH4, X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD) and scanning transmission electron microscopy\\/energy dispersive X-ray (STEM\\/EDX) analyses. At

Lj. Kundakovic; M. Flytzani-Stephanopoulos

1998-01-01

189

Geochemical control of microbial Fe(III) reduction potential in wetlands: comparison of the rhizosphere to non-rhizosphere soil  

Microsoft Academic Search

We compared the reactivity and microbial reduction potential of Fe(III) minerals in the rhizosphere and non-rhizosphere soil to test the hypothesis that rapid Fe(III) reduction rates in wetland soils are explained by rhizosphere processes. The rhizosphere was defined as the area immediately adjacent to a root encrusted with Fe(III)-oxides or Fe plaque, and non-rhizosphere soil was >0.5 cm from the

Johanna V. Weiss; David Emerson; J. Patrick Megonigal

2004-01-01

190

Photocatalytic reduction of benzonitrile to benzylamine in aqueous suspensions of palladium-loaded titanium(iv) oxide.  

PubMed

Benzonitrile (PhCN) was successfully reduced to benzyl amine in acidic aqueous suspensions of a palladium (Pd)-loaded titanium(iv) oxide (TiO2) photocatalyst in the presence of oxalic acid as a hole scavenger, although the reduction potential of PhCN is believed to be much higher than the potential of the conduction band (CB) of TiO2, indicating that a Pd co-catalyst strongly contributes to PhCN reduction and that the applicability of photocatalytic reduction is not limited by the CB position of semiconductor photocatalysts. PMID:24129580

Imamura, Kazuya; Yoshikawa, Takayuki; Nakanishi, Kousuke; Hashimoto, Keiji; Kominami, Hiroshi

2013-10-29

191

Effect of oxidation-reduction condition on wettability alteration  

SciTech Connect

This paper presents results of a laboratory study exploring the effect of the oxidation-reduction (redox) condition on crude-oil adsorption on rock mineral surfaces and consequent wettability alteration. Experiments were performed by aging Berea outcrop and Loudon reservoir sandstones with crude oil under various redox conditions and water saturations. Wettability alterations after aging were evaluated by the US Bureau of Mines (USBM) method and by waterflood tests. The natural, oxidized Brea cores changed from strongly water-wet to mixed-wet conditions when aged at irreducible water saturation. Wettability alteration was greatly reduced when aging experiments were conducted under reduced conditions. The degree of wettability alteration depended on availability and redox state of iron on the mineral surfaces and also on aging time. The authors suggest two possible mechanisms to explain the role of iron in the wettability-alternation process. Wettability alteration in the water-wet Berea cores was insignificant when the cores were aged at residual oil saturation (ROS). Wettability alteration was also significant in the mixed-wettability Loudon reservoir cores, regardless of the water saturation or redox condition used in the aging experiments. The authors present the implications of these finding on core-handling procedures for wettability preservation.

Wang, F.H.L.; Guidry, L.J. (Exxon Production Research Co., Houston, TX (United States))

1994-06-01

192

The effects of freeze–thaw and sonication on mitochondrial oxygen consumption, electron transport chain-linked metmyoglobin reduction, lipid oxidation, and oxymyoglobin oxidation  

Microsoft Academic Search

Mitochondria potentially influence Mb redox stability in meat by (1) decreasing partial oxygen pressure via oxygen consumption, (2) mitochondrial electron transport chain (ETC)-linked reduction of MetMb, and\\/or (3) oxidation of mitochondrial membrane lipid. The objective of this study was to investigate the effect of freeze–thaw and sonication treatments on mitochondrial oxygen consumption, ETC-dependent MetMb reducing activity, lipid oxidation, and Mb

Jiali Tang; Cameron Faustman; Richard A. Mancini; Mark Seyfert; Melvin C. Hunt

2006-01-01

193

Chemical and thermal reduction of thin films of copper (II) oxide and copper (I) oxide  

NASA Astrophysics Data System (ADS)

Chemical and thermal reduction of copper oxide thin films (~20 Å) has been studied with x-ray photoelectron spectroscopy (XPS) and temperature programmed desorption (TPD) for application in microelectronic device interconnects. XPS showed that copper (I) oxide (Cu2O) and copper (II) oxide (CuO) were reduced to copper metal at 400 K within a 30 min exposure to deuterium atoms (D*) and molecules at 1×10-4 Torr. Similarly, XPS showed that Cu2O was reduced to copper metal at 400 K within a 30 min exposure to methyl radicals (CH3*) and acetone molecules at 1×10-4 Torr. After D* exposure, TPD showed O leaves the Cu2O surface as D2O from 400 K to 700 K with a peak desorption temperature of 510 K. After CH3* exposure, TPD showed O leaves the Cu2O surface as CO2 over a range from 400 to 700 K with a peak temperature at 590 K. With carbon impurity below the XPS detection limit, thermal reduction of CuO to Cu2O was verified by XPS near 890 K. TPD experiments showed that O leaves the CuO surface as O2 at 890 K. Without surface C, thermal reduction of Cu2O was not observed up to 1073 K. Reduction of Cu2O without reactive radical species (D* or CH3*) was negligible. These results suggest that thin films of copper oxide can be reduced at 400 K with D* and CH3*.

Kirsch, P. D.; Ekerdt, J. G.

2001-10-01

194

Novel graphite salts of high oxidizing potential  

SciTech Connect

The intercalation of graphite by the third-transition-series metal hexafluorides has yielded the graphite salts, C/sub 8//sup +/OsF/sub 6//sup -/, C/sub 8//sup +/IrF/sub 6//sup -/ and C/sub 12//sup 2 +/PtF/sub 6//sup 2 -/. The fluoroplatinate salt represents the highest electron withdrawal from the graphite network yet achieved. Analogues to the Os and Ir salts have been obtained both by fluorination of Group V pentaflouride intercalates, C/sub 8/MF/sub 5/ (M = As, Sb), and by the interaction of the dioxygenyl salts with graphite (8C + O/sub 2/MF/sub 6/ ..-->.. C/sub 8/MF/sub 6/ + O/sub 2/+). Non-intercalating binary fluorides have been observed to intercalate in the presence of a fluorine-rich environment (e.g., 8C + PF/sub 5/ + 1/2 F/sub 2/ ..-->.. C/sub 8/PF/sub 6/). GeF/sub 4/, which also does not spontaneously intercalate graphite, has been observed to interact with graphite in the presence of 2 atmospheres of fluorine overpressure to give the fluoroplatinate salt analogue, C/sub 12//sup 2 +/GeF/sub 6//sup 2 -/. This material is in equilibrium with the pentafluorogermanate at ordinary pressures and temperatures. C/sub 12//sup 2 +/GeF/sub 6//sup 2 -/ ..-->.. C/sub 12//sup +/GeF/sub 5//sup -/ + 1/2 F/sub 2/. C/sub 12/GeF/sub 6/ must have an oxidizing potential close to that of fluorine itself. The graphite fluorometallate salts are both electronic and ionic (F/sup -/) conductors. For the C/sub 8//sup +/MF/sub 6//sup -/ salts, a maximum electronic conductivity an order of magnitude greater than the parent graphite has been observed for stage two. The high oxidizing potential, coupled with the fluoride ion transport capability of the graphite salts, has been exploited in the construction of solid-state galvanic cells. These cells use the graphite fluorometallate salts as electrode materials in combination with a superionic fluoride-ion-conducting solid electrolyte.

McCarron, E.M. III

1980-08-01

195

Electrochemistry at Very High Potentials: Oxidation of the Rare Gases and other Gases in Non-Aqueous Solvents at Ultramicroelectrodes.  

National Technical Information Service (NTIS)

The accessible potential region in a conventional electrochemical experiment is limited by the oxidation or reduction of the solvent or supporting electrolyte. It is impossible to study the redox reactions of species with very low electron affinities or h...

S. Pons T. Dibble S. Bandyopadhyay J. Ghoroghchian J. J. Smith

1986-01-01

196

Reduction potentials of heterometallic manganese-oxido cubane complexes modulated by redox-inactive metals.  

PubMed

Understanding the effect of redox-inactive metals on the properties of biological and heterogeneous water oxidation catalysts is important both fundamentally and for improvement of future catalyst designs. In this work, heterometallic manganese-oxido cubane clusters [MMn3O4] (M = Sr(2+), Zn(2+), Sc(3+), Y(3+)) structurally relevant to the oxygen-evolving complex (OEC) of photosystem II were prepared and characterized. The reduction potentials of these clusters and other related mixed metal manganese-tetraoxido complexes are correlated with the Lewis acidity of the apical redox-inactive metal in a manner similar to a related series of heterometallic manganese-dioxido clusters. The redox potentials of the [SrMn3O4] and [CaMn3O4] clusters are close, which is consistent with the observation that the OEC is functional only with one of these two metals. Considering our previous studies of [MMn3O2] moieties, the present results with more structurally accurate models of the OEC ([MMn3O4]) suggest a general relationship between the reduction potentials of heterometallic oxido clusters and the Lewis acidities of incorporated cations that applies to diverse structural motifs. These findings support proposals that one function of calcium in the OEC is to modulate the reduction potential of the cluster to allow electron transfer. PMID:23744039

Tsui, Emily Y; Agapie, Theodor

2013-06-06

197

ELECTROCHEMICAL REDUCTION OF URANIUM OXIDES IN Li2O-LiCl MOLTEN-SALT  

Microsoft Academic Search

A concept of electrochemical reduction of spent oxide fuel in Li2O-LiCl molten-salt was proposed and several cold tests using fresh uranium oxides have been carried out at KAERI. In this new electrochemical reduction process, electrolysis of Li2O and reduction of uranium oxide are taking place simultaneously at the cathode part of electrolysis cell. Li produced via Li2O electrolysis reacts with

Jin-Mok Hur; Chung-Seok Seo; Sun-Seok Hong; Dae-Seung Kang; Seong-Won Park

198

Oxidation and reduction in irradiated binary crystals of resorcinol and progesterone  

SciTech Connect

The binary single crystals of resorcinol and progesterone were x-irradiated at 4.2 K. The semiquinone of resorcinol was generated by radiation induced oxidation. The oxidation and reduction products were identified from ESR and ENDOR measurements. (AIP)

Box, H.C.; Budzinski, E.E.

1985-12-01

199

Reduction of aromatic nitrocompounds with hydrazine hydrate in the presence of an iron oxide hydroxide catalyst  

Microsoft Academic Search

The catalytic activities of several iron oxides and oxide hydroxides have been tested in the reduction of substituted nitroarenes using hydrazine hydrate as reducing agent. An iron oxide catalyst, prepared by rapid precipitation of iron hydroxides from solutions of iron(III)chloride, showed the highest activity mainly due to its large BET surface area compared to other iron oxides. Mössbauer spectroscopy and

M Benz; A. M van der Kraan; R Prins

1998-01-01

200

Oxygen reduction by lithium on model carbon and oxidized carbon structures  

SciTech Connect

Li-air batteries have attracted substantial interest for their high theoretical specific energies, but the oxygen reduction reaction by Li (Li-ORR) that occurs at the carbon cathode remains poorly understood. Periodic density functional theory calculations have been performed to examine the Li-ORR on several model carbon structures, including the graphite(0001) basal plane, the (8,0) single-wall nanotube, the armchair-type edge, and a di-vacancy in the basal plane. The inertness of the basal plane limits the reversible potential of O{sub 2} reduction to 1.1 V, and slightly higher to 1.2 V on the curved nanotube. The armchair edge and di-vacancy are highly reactive and significantly oxidized at ambient conditions to various CO{sub x} groups, which are reduced by Li via redox mechanisms at 1.2-1.4 V. These CO{sub x} groups can also catalyze O{sub 2} reduction at up to 2.3 V (an overpotential of 0.4 V vs. the calculated equilibrium potential for bulk Li{sub 2}O{sub 2} formation) by chelating and stabilizing the LiO{sub 2} intermediate. The Li-ORR on graphitic carbon, if via concerted Li{sup +}/e{sup -} transfer and involving carbon, lithium, and oxygen only, is therefore expected to initiate with the smallest overpotential at under-coordinated carbon centers that are oxidized at ambient conditions.

Xu, Ye [ORNL; Shelton Jr, William Allison [ORNL

2011-01-01

201

Peroxynitrite: a potential initiator of lipid oxidation in food  

Microsoft Academic Search

Peroxynitrite is formed from the nearly diffusion limited reaction between nitric oxide and superoxide. This reactive nitrogen species has received intense interest in the biomedical field as an initiator of potentially harmful oxidation reactions. Peroxynitrite can also be viewed as an important pro-oxidant that affects food quality. Since most biological tissues used for foods contain systems that produce both nitric

Robert G. Brannan; Brian J. Connolly; Eric A. Decker

2001-01-01

202

Electrodeposition and electrochemical reduction of epitaxial metal oxide thin films and superlattices  

NASA Astrophysics Data System (ADS)

The focus of this dissertation is the electrodeposition and electrochemical reduction of epitaxial metal oxide thin films and superlattices. The electrochemical reduction of metal oxides to metals has been studied for decades as an alternative to pyrometallurgical processes for the metallurgy industry. However, the previous work was conducted on bulk polycrystalline metal oxides. Paper I in this dissertation shows that epitaxial face-centered cubic magnetite (Fe3O4 ) thin films can be electrochemically reduced to epitaxial body-centered cubic iron (Fe) thin films in aqueous solution on single-crystalline Au substrates at room temperature. This technique opens new possibilities to produce special epitaxial metal/metal oxide heterojunctions and a wide range of epitaxial metallic alloy films from the corresponding mixed metal oxides. Electrodeposition, like biomineralization, is a soft solution processing method which can produce functional materials with special properties onto conducting or semiconducting solid surfaces. Paper II in this dissertation presents the electrodeposition of cobalt-substituted magnetite (CoxFe3-xO4, 0 of cobalt-substituted magnetite (CoxFe3-xO4, 0potentially used in spintronics and memory devices. Paper III in this dissertation reports the electrodeposition of crystalline cobalt oxide (Co3O4) thin films on stainless steel and Au single-crystalline substrates. The crystalline Co3O4 thin films exhibit high catalytic activity towards the oxygen evolution reaction in an alkaline solution. A possible application of the electrodeposited Co 3O4 is the fabrication of highly active and low-cost photoanodes for photoelectrochemical water-splitting cells.

He, Zhen

203

On the reduction potentials of Fe and Cu-Zn containing superoxide dismutases.  

PubMed

The reduction potentials of bovine erythrocyte copper-zinc superoxide dismutase and Escherichia coli iron superoxide dismutase were determined in EPR-monitored redox titrations in homogeneous solution. The copper-zinc enzyme is reduced and reoxidized with a midpoint potential of +120 mV versus standard hydrogen electrode (SHE) at pH 7.5. The iron enzyme can be reduced with an apparent midpoint potential of -67 mV versus SHE at pH 7.5. However, reaction with ferricyanide affords only slow, partial re-oxidation. Cyclic voltammetry of the copper-zinc enzyme in the presence of 50 mM Sc3+ at pH 4.0 using a glassy carbon electrode results in asymmetric voltammograms. The midpoint potential of the enzyme at this pH value, calculated as the average of the anodic and cathodic peak potentials, is +400 mV versus SHE. The physiological relevance of this value is limited, since EPR experiments indicated that reduction of the copper-zinc enzyme at pH 4.0 is not reversible. Consequences of the irreversible behavior of the two dismutases for the previously reported studies on their redox properties are discussed. PMID:7766675

Verhagen, M F; Meussen, E T; Hagen, W R

1995-05-11

204

Geochemical control of microbial Fe(III) reduction potential in wetlands: comparison of the rhizosphere to non-rhizosphere soil.  

PubMed

We compared the reactivity and microbial reduction potential of Fe(III) minerals in the rhizosphere and non-rhizosphere soil to test the hypothesis that rapid Fe(III) reduction rates in wetland soils are explained by rhizosphere processes. The rhizosphere was defined as the area immediately adjacent to a root encrusted with Fe(III)-oxides or Fe plaque, and non-rhizosphere soil was >0.5 cm from the root surface. The rhizosphere had a significantly higher percentage of poorly crystalline Fe (66+/-7%) than non-rhizosphere soil (23+/-7%); conversely, non-rhizosphere soil had a significantly higher proportion of crystalline Fe (50+/-7%) than the rhizosphere (18+/-7%, P<0.05 in all cases). The percentage of poorly crystalline Fe(III) was significantly correlated with the percentage of FeRB (r=0.76), reflecting the fact that poorly crystalline Fe(III) minerals are labile with respect to microbial reduction. Abiotic reductive dissolution consumed about 75% of the rhizosphere Fe(III)-oxide pool in 4 h compared to 23% of the soil Fe(III)-oxide pool. Similarly, microbial reduction consumed 75-80% of the rhizosphere pool in 10 days compared to 30-40% of the non-rhizosphere soil pool. Differences between the two pools persisted when samples were amended with an electron-shuttling compound (AQDS), an Fe(III)-reducing bacterium (Geobacter metallireducens), and organic carbon. Thus, Fe(III)-oxide mineralogy contributed strongly to differences in the Fe(III) reduction potential of the two pools. Higher amounts of poorly crystalline Fe(III) and possibly humic substances, and a higher Fe(III) reduction potential in the rhizosphere compared to the non-rhizosphere soil, suggested the rhizosphere is a site of unusually active microbial Fe cycling. The results were consistent with previous speculation that rapid Fe cycling in wetlands is due to the activity of wetland plant roots. PMID:19712434

Weiss, Johanna V; Emerson, David; Megonigal, J Patrick

2004-04-01

205

Anomalous oxidation reactions at noble metal surfaces at low potentials: With particular reference to palladium  

SciTech Connect

Multilayer palladium hydrous oxide films, produced by potential cycling, were more stable in acid solution at 0 C (as compared with room temperature). The electrochemical responses for the reduction of such films were more consistent at the lower temperature and were remarkably similar to those of platinum under similar conditions. Both metals yield a hydrous oxide containing two components, HO1 and HO2. The cyclic voltammogram for the bare metal (Pd or Pt) in acid contains an unusual feature at low potentials in the absorbed hydrogen region. This feature, a low level reversible transition at ca. 0.24 V(RHE) for palladium, was reported in earlier independent work. It is attributed here to a premonolayer oxidation effect, i.e., an active metal atom/incipient hydrous oxide transition. The peak maximum potential (E{sub p}) for HO2 reduction in multilayer Pd hydrous oxide reduction experiments, on extrapolation to either very low sweep rates or low film thicknesses, gave a similar potential value. The relevance of this result to noble metal electrocatalysis is outlined. Electrocatalysis is a topic of major interest at the present time, especially in connection with fuel cell development.

Burke, L.D.; Buckley, D.T. [University College Cork (Ireland). Dept. of Chemistry

1996-03-01

206

Electronic structure of the reduced blue copper active site. Contributions to reduction potentials and geometry  

SciTech Connect

A detailed electronic structure description of the reduced blue copper active site has now been developed. Photoelectron spectroscopy (PES) of imidazole, dimethyl sulfide, and methanethiolate bound to Cu(I) sites at single crystal surfaces has been used to define normal Cu(I) bonding to ligands relevant to the blue copper site. Variable photon energy PES has been used to assign valence band spectra, assess metal-ligand covalency, and probe specific orbital contributions to Cu(I) bonding. Self Consistent Field-X{alpha}-Scattered Wave (SCF-X{alpha}-SW) molecular orbital calculations calibrated to the photoelectron spectra have been performed to quantitatively complement the experimental bonding descriptions. These calculations have been extended to the reduced blue copper active site in plastocyanin, the prototypical blue copper protein, to detail the electronic structure changes that occur relative to normal Cu(I) bonding and upon oxidation. Ionization energies have been used to estimate the electronic structure contributions to the reduction potential. The long Cu-thioether axial bond present at the active site destabilizes the oxidized state and is therefore a key determining factor in the high reduction potentials generally observed for blue copper proteins. Linear coupling terms have been evaluated for the distortions of a blue copper site unconstrained by the protein backbone. 99 refs., 22 figs., 12 tabs.

Guckert, J.A.; Lowery, M.D.; Solomon, E.I. [Stanford Univ., CA (United States)

1995-03-15

207

Linking methane oxidation with perchlorate reduction: a microbial base for possible Martian life  

NASA Astrophysics Data System (ADS)

Recent observations of methane (CH4) and perchlorate (ClO4-) within the atmosphere and surface of Mars, respectively, provide impetus for establishing a metabolic linkage between these compounds whereby CH4 acts as an electron donor and perchlorate acts as an electron acceptor. Direct linkage through anaerobic oxidation of methane (AOM) has not been observed. However, indirect syntrophic oxygenase-dependent oxidation of CH4 with an aerobic methane oxidizer is feasible. The pathway for anaerobic dissimilatory perchlorate reduction includes 3 steps. The first 2 are sequential reductions of (1) perchlorate to chlorate and (2) chlorate to chlorite, mediated by perchlorate reductase. The third step is disproportionation of chlorite to chloride and molecular oxygen, mediated by chlorite dismutase. Utilization of thusly derived oxygen by hydrocarbon-degrading organisms in anoxic environments was first demonstrated by Coates et. al. (1998)1, however the link to aerobic methane oxidation was not examined at that time. Here, we systematically explore the potential for several species of aerobic methanotrophs to couple with chlorite during dissimilatory perchlorate reduction. In one experiment, 0.5 kPa CH4 was completely removed in one day from the headspace of combined cell suspensions of Dechloromonas agitata strain CKB and Methylococcus capsulatus in the presence of 5 mM chlorite. Oxidation of labeled 14CH4 to 14CO2 under similar conditions was later confirmed. Another experiment demonstrated complete removal of 0.2 kPa CH4 over several days by Methylobacter albus strain BG8 with strain CKB in the presence of 5 mM chlorite. Finally, we observed complete removal of 0.2 kPa CH4 in bottles containing natural soil (enriched in methanotrophs by CH4 additions over several weeks) and strain CKB and in the presence of 10 mM chlorite. This soil, collected from a pristine lake shoreline, demonstrated endogenous methane, perchlorate, chlorate and chlorite uptake. Other soil and sediment environments are being tested for methane oxidation linked either directly or indirectly with perchlorate reduction. 1 Coates, JD, Bruce, Haddock, JD, (1998) Anoxic bioremediation of hydrocarbons. Nature, 396, 730.

Miller, L. G.; Carlstrom, C.; Baesman, S. M.; Coates, J. D.; Oremland, R. S.

2011-12-01

208

Influence of Mn oxides on the reduction of U(VI) by the metal-reducing bacterium Shewanella putrefaciens  

SciTech Connect

Dissimilatory metal-reducing bacteria (DMRB) enzymatically reduce Fe(III), Mn(III/IV), U(VI), and other polyvalent metals during anaerobic respiration. Previous investigations of the bacterial reduction of U(VI) in the presence of goethite (a-FeOOH) found that, in spite of potential competition as an electron acceptor, goethite had little impact on the bacterial reduction of U(VI) to insoluble U(IV). Mn(III/IV) oxides are also electron acceptors for DMRB but are stronger oxidants than Fe(III) oxides. Differences in the solubility of oxidized Mn and U challenges predictions of their biogeochemical behavior during redox cycling. The potential for Mn oxides to modify the biogeochemical behavior of U during reduction by a subsurface bacterium Shewanella putrefaciens CN32 was investigated using synthetic Mn(III/IV) oxides [pyrolusite ({beta}-MnO{sub 2}), bixbyite (Mn{sub 2}O{sub 3}) and K{sup +}-birnessite (K{sub 4}Mn{sub 14}O{sub 27} {center_dot} 8H{sub 2}O)]. In the absence of bacteria, pyrolusite and bixbyite oxidized biogenic uraninite (UO{sub 2}(s)) to soluble U(VI) species, with bixbyite being the most rapid oxidant. The Mn(III/IV) oxides lowered the bioreduction rate of U(VI) relative to rates in their absence, or in the presence of gibbsite [Al(OH){sub 3}] added as a non-redox reactive surface. Evolved Mn(II) increased with increasing initial U(VI) concentration in the biotic experiments, indicating that valence cycling of U facilitated the reduction of Mn(III/IV). Despite an excess of the Mn oxide, 43-100% of the initial U was bioreduced after extended incubation. Analysis of thin sections of bacterial-Mn oxide suspensions revealed that the reduced U resided in the periplasmic space of the bacterial cells. In the absence of Mn(III/IV) oxides, UO{sub 2}(s) accumulated as copius fine-grained particles external to the cell. These results indicate that the presence of Mn(III/IV) oxides may impede the biological reduction of U(VI) in subsoils and sediments?.

Fredrickson, Jim K.; Zachara, John M.; Kennedy, David W.; Liu, Chongxuan; Duff, Martine C.; Hunter, David; Dohnalkova, Alice

2002-09-16

209

The Role of Reactive Transport Modeling in Understanding Biogeochemical Processes Associated With Iron Oxide Reduction  

Microsoft Academic Search

In a series of column and batch experiments, we are investigating mineral phase transformations during microbially mediated reduction of the iron oxide ferrihydrite. Quantification of the solid phase over time, using XAS and HRTEM, indicates that the primary sinks during iron oxide reduction, for both Fe (II) and Fe (III), are the secondary iron phases goethite and magnetite. While goethite

S. G. Benner; C. M. Hansel; S. Fendorf; K. U. Mayer

2002-01-01

210

Renal and systemic nitric oxide synthesis in rats with renal mass reduction  

Microsoft Academic Search

Renal and systemic nitric oxide synthesis in rats with renal mass reduction. In rats undergoing renal mass reduction (RMR) oral supplementation with the nitric oxide (NO) precursor L-arginine increases glomerular filtration rate and ameliorates signs of glomerular injury, suggesting that chronic renal failure in the rats is a condition of low NO formation in the kidney. On the contrary, data

Sistiana Aiello; Marina Noris; Marta Todeschini; Sergio Zappella; Chiara Foglieni; Ariela Benigni; Daniela Corna; Carla Zoja; Daniela Cavallotti; Giuseppe Remuzzi

1997-01-01

211

Direct electron transfer from pseudoazurin to nitrous oxide reductase in catalytic N2O reduction.  

PubMed

Pseudoazurin (PAz), a well-characterized blue copper electron-transfer protein, is shown herein to be capable of mediating electron transfer to the nitrous oxide reductase (N(2)OR) from Achromobacter cycloclastes (Ac). Spectroscopic measurements demonstrate that reduced PAz is efficiently re-oxidized by a catalytic amount of N(2)OR in the presence of N(2)O. Fits of the kinetics resulted in K(M) (N(2)O) and k(cat) values of 19.1±3.8 ?M and 89.3±4.2s(-1) respectively. The K(M) (PAz) was 28.8±6.6 ?M. The electrochemistry of Ac pseudoazurin (AcPAz) in the presence of Ac nitrous oxide reductase (AcN(2)OR) and N(2)O displayed an enhanced cathodic sigmoidal current-potential curve, in excellent agreement with the re-oxidation of reduced AcPAz during the catalytic reduction of N(2)O by AcN(2)OR. Modeling the structure of the AcPAz-AcN(2)OR electron transfer complex indicates that AcPAz binds near Cu(A) in AcN(2)OR, with parameters consistent with the formation of a transient, weakly-bound complex. Multiple, potentially efficient electron-transfer pathways between the blue-copper center in AcPAz and Cu(A) were also identified. Collectively, the data establish that PAz is capable of donating electrons to N(2)OR in N(2)O reduction and is a strong candidate for the physiological electron donor to N(2)OR in Ac. PMID:22910335

Fujita, Koyu; Hirasawa-Fujita, Mika; Brown, Doreen E; Obara, Yuji; Ijima, Fumihiro; Kohzuma, Takamitsu; Dooley, David M

2012-07-26

212

Early stages of reduction of nickel oxide single crystals: An investigation by transmission electron microscope  

NASA Astrophysics Data System (ADS)

Because of the practical importance of the reaction, a great deal of work has been done on the reduction of metallic oxides to metals. In this laboratory all stages of the reduction of nickel oxide to nickel are being studied using a transmission electron microscope. Small, pre-thinned single crystals of nickel oxide have been reduced outside the microscope in a hydrogen atmosphere and the reduction temperatures and times were varied. The resulting foils were then examined in a Phillips 301 100 kV electron microscope and the relationships between the nickel metal particles and the nickel oxide single crystal matrix were established. During the early stages of the reduction both epitaxial and non-epitaxial nuclei were observed, the latter becoming predominant as reduction time progressed. The nuclei were frequently separated from the nickel oxide matrix by a fissure and as they impinged and coalesced, a large scale structure resulted with internal porosity as often seen by optical microscopy.

Little, J. A.; Evans, J. W.; Westmacott, K. H.

1980-09-01

213

Biological oxidation of Fe(II) in reduced nontronite coupled with nitrate reduction by Pseudogulbenkiania sp. Strain 2002  

NASA Astrophysics Data System (ADS)

The importance of microbial nitrate-dependent Fe(II) oxidation to iron biogeochemistry is well recognized. Past research has focused on oxidation of aqueous Fe2+ and structural Fe(II) in oxides, carbonates, and phosphate, but the importance of structural Fe(II) in phyllosilicates in this reaction is only recently studied. However, the effect of clay mineralogy on the rate and the mechanism of the reaction, and subsequent mineralogical end products are still poorly known. The objective of this research was to study the coupled process of microbial oxidation of Fe(II) in clay mineral nontronite (NAu-2), and nitrate reduction by Pseudogulbenkiania species strain 2002, and to determine mineralogical changes associated with this process. Bio-oxidation experiments were conducted using Fe(II) in microbially reduced nontronite as electron donor and nitrate as electron acceptor in bicarbonate-buffered medium under both growth and nongrowth conditions to investigate cell growth on this process. The extents of Fe(II) oxidation and nitrate reduction were measured by wet chemical methods. X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM), and 57Fe-Mössbauer spectroscopy were used to observe mineralogical changes associated with Fe(III) reduction and Fe(II) oxidation in NAu-2. The bio-oxidation extent under growth and nongrowth conditions reached 67% and 57%, respectively. Over the same time period, nitrate was completely reduced under both conditions to nitrogen gas (N2), via an intermediate product nitrite. Abiotic oxidation by nitrite partly accelerated Fe(II) oxidation rate under the growth condition. The oxidized Fe(III) largely remained in the nontronite structure, but secondary minerals such as vivianite, ferrihydrite, and magnetite formed depending on specific experimental conditions. The results of this study highlight the importance of iron-bearing clay minerals in the global nitrogen cycle with potential applications in nitrate removal in natural environments.

Zhao, Linduo; Dong, Hailiang; Kukkadapu, Ravi; Agrawal, Abinash; Liu, Deng; Zhang, Jing; Edelmann, Richard E.

2013-10-01

214

Kinetics of microbial Fe(III) oxide reduction in freshwater wetland sediments  

Microsoft Academic Search

The kinetics of microbial amorphous Fe(III) oxide reduction was investigated in sediments from a freshwater wetland in north central Alabama, USA. Fe(III) oxide concentrations decreased exponentially with time during anaerobic incubation of sediment slurries and homogenized surface sediments. Rates of organic carbon minerali- zation (SCO2 1 CH4 accumulation) did not change markedly during the course of Fe(III) oxide reduction, which

Eric E. Roden; Robert G. Wetzel

2002-01-01

215

Dissimilatory nitrate reduction to nitrate, nitrous oxide, and ammonium by Pseudomonas putrefaciens.  

PubMed Central

The influence of redox potential on dissimilatory nitrate reduction to ammonium was investigated on a marine bacterium, Pseudomonas putrefaciens. Nitrate was consumed (3.1 mmol liter-1), and ammonium was produced in cultures with glucose and without sodium thioglycolate. When sodium thioglycolate was added, nitrate was consumed at a lower rate (1.1 mmol liter-1), and no significant amounts of nitrite or ammonium were produced. No growth was detected in glucose media either with or without sodium thioglycolate. When grown on tryptic soy broth, the production of nitrous oxide paralleled growth. In the same medium, but with sodium thioglycolate, nitrous oxide was first produced during growth and then consumed. Acetylene caused the nitrous oxide to accumulate. These results and the mass balance calculations for different nitrogen components indicate that P. putrefaciens has the capacity to dissimilate nitrate to ammonium as well as to dinitrogen gas and nitrous oxide (denitrification). The dissimilatory pathway to ammonium dominates except when sodium thioglycolate is added to the medium.

Samuelsson, M O

1985-01-01

216

Manganese potentiates nitric oxide production by microglia.  

PubMed

Manganese toxicity has been associated with clinical symptoms of neurotoxicity which are similar to the symptoms observed in Parkinson's disease. Earlier reports indicated that reactive microglia was present in the substantia nigra of patients with Parkinson's disease. Using N9 microglial cells, the current study was designed to determine whether high levels of manganese were associated with microglial activation. Results indicated that manganese significantly increased the bacterial lipopolysaccharide-induced nitric oxide production. This potent activity of manganese was not shared by other transition metals tested, including iron, cobalt, nickel, copper and zinc. Immunohistochemical staining and Western blot analysis indicated that manganese increased the cellular production of inducible nitric oxide synthase. Northern blot analysis indicated that manganese likely increased iNOS gene transcription since this agent increased the mRNA level of the inducible nitric oxide synthase. In contrast to other transition metals tested, manganese did not appear to be cytotoxic to microglial cells. These results suggested that manganese could induce sustained production of neurotoxic nitric oxide by activated microglial cells, which might cause detrimental consequences to surrounding neurons. PMID:10320780

Chang, J Y; Liu, L Z

1999-05-01

217

Oxidative Stress in Cardiovascular Disease: Potential Biomarkers and Their Measurements  

Microsoft Academic Search

\\u000a The oxygen atmosphere surrounding us produces continuous oxidative stress because of the incomplete reduction of the O2 molecule. Oxidative stress mainly occurs in any system when the generation of reactive oxygen species (ROS) exceeds the system’s\\u000a ability to neutralize and eliminate them. This imbalance of ROS can result from various pathways. Overproduction of ROS and\\u000a their limited removal can result

Subhendu Mukherjee; Dipak K. Das

218

Mercury oxidation over a vanadia-based selective catalytic reduction catalyst  

SciTech Connect

The process of the reaction among elemental mercury (Hg{sup 0}) and reactive flue gas components across the selective catalytic reduction (SCR) catalyst was studied in a laboratory-scale reactor. Prepared vanadia-based SCR catalysts were characterized and analyzed to understand the potential reaction pathways. Mercury oxidation was observed when pro-exposure of the SCR catalyst to HCl, followed by passing through Hg{sup 0}/N{sub 2} in the absence of gas-phase HCl. At testing conditions, Hg{sup 0} was found to desorb from the catalyst surface by adding HCl to the gas stream, which implies that HCl adsorption onto the SCR catalyst is strong relative to the mercury. Surface analysis verified the absorption of HCl onto the SCR catalysts, and the potential reaction pathways were proposed. Indeed, the monomeric vanadyl sites on the catalyst surface were found to be responsible for the adsorption of both Hg{sup 0} and HCl, which means they are active for mercury oxidation. Furthermore, the detailed Langmuir-Hinshelwood mechanism was proposed to explain the mercury oxidation on the SCR catalyst, where reactive Cl generated from adsorbed HCl reacts with adjacent Hg{sup 0}. 44 refs., 10 figs.

Sheng He; Jinsong Zhou; Yanqun Zhu; Zhongyang Luo; Mingjiang Ni; Kefa Cen [Zhejiang University, Hangzhou (China). State Key Laboratory of Clean Energy Utilization

2009-01-15

219

Role of ammonia oxidation in selective catalytic reduction of nitric oxide over vanadia catalysts  

SciTech Connect

The role of direct oxidation of ammonia in SCR reactions and the catalytic anisotropy of V[sub 2]O[sub 5] catalysts in this reaction network were investigated. The catalysts were characterized using BET surface area measurement, X-ray diffraction, laser Raman spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and 3-D imaging. Temperature-programmed reduction experiments using ammonia and hydrogen as reducing agents and temperature-programmed desorption studies were also performed. A steady-state fixed-bed reactor system was used for activity and selectivity measurements. The product analysis was carried out by a combination of techniques including chemiluminescence NO[sub x] analysis, on-line gas chromatography and on-line mass spectrometry, and chemical titration methods. The results obtained in this study, when combined with our previous studies in SCR reactions, indicate that over vanadium pentoxide catalysts, ammonia oxidation and NO reduction reactions are closely coupled. The results suggest that ammonia adsorption takes place on at least two types of sites located on the (010) and (100) planes of V[sub 2]O[sub 5]. The sites that selectively reduce NO to N[sub 2] are the V-O-V sites located on the side planes, whereas V[double bond]O sites promote direct oxidation of ammonia to NO and the formation of N[sub 2]O from NO and NH[sub 3] interaction more readily. It is found that the V[double bond]O sites are more easily reduced with both hydrogen and ammonia. 35 refs., 13 figs., 2 tabs.

Ozkan, U.S.; Cai, Y.; Kumthekar, M.W.; Zhang, L. (Ohio State Univ., Columbus (United States))

1993-07-01

220

Microorganisms pumping iron: anaerobic microbial iron oxidation and reduction.  

PubMed

Iron (Fe) has long been a recognized physiological requirement for life, yet for many microorganisms that persist in water, soils and sediments, its role extends well beyond that of a nutritional necessity. Fe(II) can function as an electron source for iron-oxidizing microorganisms under both oxic and anoxic conditions and Fe(III) can function as a terminal electron acceptor under anoxic conditions for iron-reducing microorganisms. Given that iron is the fourth most abundant element in the Earth's crust, iron redox reactions have the potential to support substantial microbial populations in soil and sedimentary environments. As such, biological iron apportionment has been described as one of the most ancient forms of microbial metabolism on Earth, and as a conceivable extraterrestrial metabolism on other iron-mineral-rich planets such as Mars. Furthermore, the metabolic versatility of the microorganisms involved in these reactions has resulted in the development of biotechnological applications to remediate contaminated environments and harvest energy. PMID:16980937

Weber, Karrie A; Achenbach, Laurie A; Coates, John D

2006-10-01

221

Reduction of Nitrogen Oxide Emissions for lean Burn Engine Technology  

SciTech Connect

Lean-burn engines offer the potential for significant fuel economy improvements in cars and trucks, perhaps the next great breakthrough in automotive technology that will enable greater savings in imported petroleum. The development of lean-burn engines, however, has been an elusive goal among automakers because of the emissions challenges associated with lead-burn engine technology. Presently, cars operate with sophisticated emissions control systems that require the engine's air-fuel ratio to be carefully controlled around the stoichiometric point (chemically correct mixture). Catalysts in these systems are called "three-way" catalysts because they can reduce hydrocarbon, carbon monoxide, and nitrogen oxide emissions simultaneously, but only because of the tight control of the air-fuel ratio. The purpose of this cooperative effort is to develop advanced catalyst systems, materials, and necessary engine control algorithms for reducing NOX emissions in oxygen-rich automotive exhaust (as with lean-burn engine technology) to meet current and near-future mandated Clean Air Act standards. These developments will represent a breakthrough in both emission control technology and automobile efficiency. The total project is a joint effort among five national laboratories, together with US CAR. The role of Lockheed-Martin Energy Systems in the total project is two fold: characterization of catalyst performance through laboratory evaluations from bench-scale flow reactor tests to engine laboratory tests of full-scale prototype catalysts, and microstructural characterization of catalyst material before and after test stand and/or engine testing.

McGill, R.N.

1998-08-04

222

Decoupled anaerobic oxidation of methane and sulfate reduction within the methanogenic zone of Arctic sediments (Beaufort Sea, Alaska)?  

NASA Astrophysics Data System (ADS)

Piston cores taken at two stations along a depth transect on the continental margin of the Beaufort Sea (Alaska) revealed an at first sight "classical" sulfate-methane transition zone (SMTZ) with organoclastic sulfate reduction on top, followed by an intermediate zone of anaerobic methane consumption, and a methanogenic zone at the bottom. Surprisingly, however, sulfate did not completely disappear within the methanogenic zone but concentrations remained at levels around 300-500 µM. Further investigations revealed that sulfate reduction and anaerobic oxidation of methane (AOM) activity was still detectable and deeply distributed within the methanogenic zone, and that the two processes were probably not coupled. This poster will discuss (1) potential mineralogical sources of sulfur that could support sulfate reduction in the methanogenic zone, (2) potential electron acceptors of AOM, and (3) thermodynamic considerations about the unusual co-presence of sulfate reduction, AOM, and methanogenesis in the very same sediment zone.

Treude, T.; Krause, S.; Hamdan, L.; Schweers, J.; Coffin, R.

2012-04-01

223

Reversible half-wave potentials of reduction processes on nitroxide radicals  

Microsoft Academic Search

The reversible half-wave potential (E12rev) of the reduction process was determined for six nitroxide radicals by cyclic voltammetry as the midpoint potential between reduction and reoxidation peaks. The variations of E12rev with pH were interpreted as the protonation induced by the one-electron reduction of nitroxide radicals.

Yoshikiyo Kato; Yoshiyuki Shimizu; Lin Yijing; Kei Unoura; Hideo Utsumi; Tateaki Ogata

1995-01-01

224

Method for selective catalytic reduction of nitrogen oxides  

DOEpatents

A method for catalytically reducing nitrogen oxide compounds (NO.sub.x, defined as nitric oxide, NO, +nitrogen dioxide, NO.sub.2) in a gas by a material comprising a base metal consisting essentially of CuO and Mn, and oxides of Mn, on an activated metal hydrous metal oxide support, such as HMO:Si. A promoter, such as tungsten oxide or molybdenum oxide, can be added and has been shown to increase conversion efficiency. This method provides good conversion of NO.sub.x to N.sub.2, good selectivity, good durability, resistance to SO.sub.2 aging and low toxicity compared with methods utilizing vanadia-based catalysts.

Mowery-Evans, Deborah L. (Broomfield, CO); Gardner, Timothy J. (Albuquerque, NM); McLaughlin, Linda I. (Albuquerque, NM)

2005-02-15

225

Method For Selective Catalytic Reduction Of Nitrogen Oxides  

DOEpatents

A method for catalytically reducing nitrogen oxide compounds (NO.sub.x, defined as nitric oxide, NO, +nitrogen dioxide, NO.sub.2) in a gas by a material comprising a base metal consisting essentially of CuO and Mn, and oxides of Mn, on an activated metal hydrous metal oxide support, such as HMO:Si. A promoter, such as tungsten oxide or molybdenum oxide, can be added and has been shown to increase conversion efficiency. This method provides good conversion of NO.sub.x to N.sub.2, good selectivity, good durability, resistance to SO.sub.2 aging and low toxicity compared with methods utilizing vanadia-based catalysts.

Mowery-Evans, Deborah L. (Broomfield, CO); Gardner, Timothy J. (Albuquerque, NM); McLaughlin, Linda I. (Albuquerque, NM)

2005-02-15

226

Comparative studies on single-layer reduced graphene oxide films obtained by electrochemical reduction and hydrazine vapor reduction  

PubMed Central

The comparison between two kinds of single-layer reduced graphene oxide (rGO) sheets, obtained by reduction of graphene oxide (GO) with the electrochemical method and hydrazine vapor reduction, referred to as E-rGO and C-rGO, respectively, is systematically studied. Although there is no morphology difference between the E-rGO and C-rGO films adsorbed on solid substrates observed by AFM, the reduction process to obtain the E-rGO and C-rGO films is quite different. In the hydrazine vapor reduction, the nitrogen element is incorporated into the obtained C-rGO film, while no additional element is introduced to the E-rGO film during the electrochemical reduction. Moreover, Raman spectra show that the electrochemical method is more effective than the hydrazine vapor reduction method to reduce the GO films. In addition, E-rGO shows better electrocatalysis towards dopamine than does C-rGO. This study is helpful for researchers to understand these two different reduction methods and choose a suitable one to reduce GO based on their experimental requirements.

2012-01-01

227

Potential of gold nanoparticles for oxidation in fine chemical synthesis.  

PubMed

In recent years supported gold nanoparticles have emerged as efficient catalysts with considerable synthetic potential for liquid-phase oxidation reactions based on molecular oxygen as oxidant. Here we critically review the most attractive applications related to the selective oxidation of functional groups containing O, N, or Si heteroatoms. The reactions include the oxidation of alcohols, aldehydes, and organosilanes; the diverse transformations of amines; benzylic oxidations; and some one-pot multistep reactions starting with alcohol or amine oxidation. In complex liquid-phase transformations relying on bifunctional catalysis, appropriate choice of the support is frequently more important than the size of the gold particles. In some oxidation reactions gold nanoparticles outperform the traditional platinum-group metal catalysts, but the latest results indicate the superiority of bimetallic particles containing gold and platinum, palladium, or rhodium. The environmentally benign nature of the transformations is discussed. PMID:22691089

Mallat, Tamas; Baiker, Alfons

2012-01-01

228

Mercury mobilization by chemical and microbial iron oxide reduction in soils of French Guyana  

Microsoft Academic Search

Iron oxy(hydr)oxides (oxides) are important mercury sinks in tropical oxisols and the geochemistry of these two elements are\\u000a thus closely entwined. We hypothesized that bacterial Fe-oxide reduction in anoxic conditions could be a significant mechanism\\u000a for mobilizing associated Hg. Iron oxide and mercury solubilisation in presence of two chemical reducers (ascorbate and dithionite,\\u000a dissolving amorphous and amorphous plus well crystallized

Jennifer Harris-Hellal; Michel Grimaldi; Evelyne Garnier-Zarli; Noureddine Bousserrhine

2011-01-01

229

The kinetics of formation of h2o and co2 during iron oxide reduction  

Microsoft Academic Search

The kinetics of the chemical reaction-controlled reduction of iron oxides by H2\\/H2O and CO\\/CO2 gas mixtures are discussed. From an analysis of the systems it is concluded that the decomposition of the oxides takes place by the two dimensional nucleation and lateral growth of oxygen vacancy clusters at the gas\\/oxide interface. The rates of decomposition of the oxides under conditions

P. C. Hayes

1979-01-01

230

The kinetics of formation of h 2 o and co 2 during iron oxide reduction  

Microsoft Academic Search

The kinetics of the chemical reaction-controlled reduction of iron oxides by H2\\/H2O and CO\\/CO2 gas mixtures are discussed. From an analysis of the systems it is concluded that the decomposition of the oxides takes place\\u000a by the two dimensional nucleation and lateral growth of oxygen vacancy clusters at the gas\\/oxide interface. The rates of decomposition\\u000a of the oxides under conditions

P. C. Hayes

1979-01-01

231

Effects of Eh (Oxidation Potential) on Borosilicate Waste Glass Durability.  

National Technical Information Service (NTIS)

Solid state materials can be used to control the oxidation potential (Eh) of waste glass leachants. These materials are chosen based on known Eh-pH relations for redox species in the presence of dissolved silica. Experiments under oxidized conditions have...

C. M. Jantzen

1984-01-01

232

Reduction of Titanium Oxide in Molten Salt Medium  

Microsoft Academic Search

Production of titanium powder directly from titanium dioxide (TiO2) through an electronically mediated reaction (EMR) using calcium as a reductant was investigated. Feed material (TiO2 powder or preform) and reductant (Ca-Ni alloy) were charged in electronically isolated locations in a molten calcium chloride (CaCl2) salt at 1173 K. The current flow through an external circuit between the feed and reductant

T. Abiko; T. H. Okabe

233

Aggregate-scale heterogeneity in iron (hydr)oxide reductive transformations  

SciTech Connect

There is growing awareness of the complexity of potential reaction pathways and the associated solid-phase transformations during the reduction of Fe (hydr)oxides, especially ferrihydrite. An important observation in static and advective-dominated systems is that microbially produced Fe(II) accelerates Ostwald ripening of ferrihydrite, thus promoting the formation of thermodynamically more stable ferric phases (lepidocrocite and goethite) and, at higher Fe(II) surface loadings, the precipitation of magnetite; high Fe(II) levels can also lead to green rust formation, and with high carbonate levels siderite may also be formed. This study expands this emerging conceptual model to a diffusion-dominated system that mimics an idealized micropore of a ferrihydrite-coated soil aggregate undergoing reduction. Using a novel diffusion cell, coupled with micro-x-ray fluorescence and absorption spectroscopies, we determined that diffusion-controlled gradients in Fe{sup 2+}{sub (aq)} result in a complex array of spatially distributed secondary mineral phases. At the diffusive pore entrance, where Fe{sup 2+} concentrations are highest, green rust and magnetite are the dominant secondary Fe (hydr)oxides (30 mol% Fe each). At intermediate distances from the inlet, green rust is not observed and the proportion of magnetite decreases from approximately 30 to <10%. Across this same transect, the proportion of goethite increases from undetectable up to >50%. At greater distances from the advective-diffusive boundary, goethite is the dominant phase, comprising between 40 and 95% of the Fe. In the presence of magnetite, lepidocrocite forms as a transient-intermediate phase during ferrihydrite-to-goethite conversion; in the absence of magnetite, conversion to goethite is more limited. These experimental observations, coupled with results of reactive transport modeling, confirm the conceptual model and illustrate the potential importance of diffusion-generated concentration gradients in dissolved Fe{sup 2+} on the fate of ferrihydrite during reduction in structured soils.

Tufano, K.J.; Benner, S.G.; Mayer, K.U.; Marcus, M.A.; Nico, P.S.; Fendorf, S.

2009-06-15

234

Effect of preadsorbed sulfur on the electrochemical reduction of nitric oxide  

SciTech Connect

The effect of adsorbed sulfur on platinum black/Teflon gas diffusion electrodes has been studied. The controlled deposition and characterization of intermediate coverages of sulfur (fractional sulfur coverages, {Theta}, between 0 and 1.0, based on the total number of Pt surface sites) was first studied, followed by an investigation of the effects of this preadsorbed sulfur on the electrogenerative (i.e. galvanic) reduction of pure and dilute (3%) NO feeds. These effects are discussed in terms of possible applications for electrogenerative NO reduction, especially hydroxylamine production and flue gas scrubbing applications. Sulfur was deposited through electrochemical reduction of sulfur dioxide which had bene previously adsorbed from SO{sub 2}-containing aqueous sulfuric acid solutions. The sulfur layers deposited in this manner were electrochemically characterized using linear sweep and cyclic voltammetry. Sulfur/hydrogen coadsorption coverage plots constructed from coulometric measurements were studied and yielded evidence that a sulfur bilayer is formed on the electrode. In the presence of adsorbed sulfur (0.2 < {Theta} < 1.0) the current generated by the nitric oxide-hydrogen electrogenerative cell was diminished. This effect was more pronounced with pure NO feeds. The decreased cell current involved not only diminished NO conversion, but also a change in product distribution brought about by adsorbed sulfur. At low sulfur coverages and low cell potentials ammonia is the predominant product, but at higher sulfur coverages selectivity shifts to favor hydroxylamine production. Nitrous oxide is formed only at high cell potentials at all sulfur coverages, and nitrogen formation is allowed at lower sulfur coverages but inhibited at higher coverages.

Foral, M.J.

1988-01-01

235

Reduction of Soluble Iron and Reductive Dissolution of Ferric Iron-Containing Minerals by Moderately Thermophilic Iron-Oxidizing Bacteria  

Microsoft Academic Search

Five moderately thermophilic iron-oxidizing bacteria, including representative strains of the three classified species (Sulfobacillus thermosulfidooxidans, Sulfobacillus acidophilus, and Acidimicrobium ferrooxidans), were shown to be capable of reducing ferric iron to ferrous iron when they were grown under oxygen limitation conditions. Iron reduction was most readily observed when the isolates were grown as mixotrophs or hetero- trophs with glycerol as an

TONI A. M. BRIDGE; D. BARRIE JOHNSON

1998-01-01

236

Unified interatomic potential and energy barrier distributions for amorphous oxides  

NASA Astrophysics Data System (ADS)

Amorphous tantala, titania, and hafnia are important oxides for biomedical implants, optics, and gate insulators. Understanding the effects of oxide doping is crucial to optimize performance in these applications. However, no molecular dynamics potentials have been created to date that combine these and other oxides that would allow computational analyses of doping-dependent structural and mechanical properties. We report a novel set of computationally efficient, two-body potentials modeling van der Waals and covalent interactions that reproduce the structural and elastic properties of both pure and doped amorphous oxides. In addition, we demonstrate that the potential accurately produces energy barrier distributions for pure and doped samples. The distributions can be directly compared to experiment and used to calculate physical quantities such as internal friction to understand how doping affects material properties. Future analyses using these potentials will be of great value to determine optimal doping concentrations and material combinations for myriad material science applications.

Trinastic, J. P.; Hamdan, R.; Wu, Y.; Zhang, L.; Cheng, Hai-Ping

2013-10-01

237

Computational studies of polysiloxanes : oxidation potentials and decomposition reactions.  

SciTech Connect

Silicon-containing solvents have tremendous potential for application as electrolytes for electrical energy storage devices such as lithium-ion (air) batteries and supercapacitors. Quantum chemical methods were employed to investigate trends in oxidation potentials and decomposition reactions of a series of polysiloxanes. Various electron-donating and -withdrawing substituents can be used to tune the oxidation potential in shorter chain siloxanes but not in longer ones. Decomposition reactions of siloxanes in their oxidized states were investigated and compared against their carbon analogues. These studies suggest that the Si-O group provides added stability for siloxanes over their carbon analogues. Computational studies have also been performed for various disiloxanes and siloxanes with spacer groups to understand their thermochemical stability and oxidation potentials.

Assary, R. S.; Curtiss, L. A.; Redfern, P. C.; Zhang, Z.; Amine, K. (Center for Nanoscale Materials); ( CSE); ( MSD); (Northwestern Univ.)

2011-06-23

238

Unified interatomic potential and energy barrier distributions for amorphous oxides.  

PubMed

Amorphous tantala, titania, and hafnia are important oxides for biomedical implants, optics, and gate insulators. Understanding the effects of oxide doping is crucial to optimize performance in these applications. However, no molecular dynamics potentials have been created to date that combine these and other oxides that would allow computational analyses of doping-dependent structural and mechanical properties. We report a novel set of computationally efficient, two-body potentials modeling van der Waals and covalent interactions that reproduce the structural and elastic properties of both pure and doped amorphous oxides. In addition, we demonstrate that the potential accurately produces energy barrier distributions for pure and doped samples. The distributions can be directly compared to experiment and used to calculate physical quantities such as internal friction to understand how doping affects material properties. Future analyses using these potentials will be of great value to determine optimal doping concentrations and material combinations for myriad material science applications. PMID:24160526

Trinastic, J P; Hamdan, R; Wu, Y; Zhang, L; Cheng, Hai-Ping

2013-10-21

239

DISSOLVED OXYGEN AND OXIDATION-REDUCTION POTENTIALS IN GROUND WATER  

EPA Science Inventory

Water samples were collected from various depths in a pristine sand and gravel water table aquifer at monthly intervals over a period of one year. Dissolved oxygen concentrations were near saturation 9 feet below the water table and decreased to nearly zero at 78 feet below the w...

240

Oxidation-reduction Potentials and Capillary Activities of Humic Acids  

Microsoft Academic Search

APART from the effects which humic acids have on the physical properties of the soil, such as its structure, permeability and water retention, and through which they influence the growth of plants, it has been shown that humic acids also have a directly stimulating effect on plant growth1-3. In an attempt to trace the cause of this stimulation, Flaig and

S. A. Visser

1964-01-01

241

Studies on the oxidation-reduction potential of protozoan cultures  

Microsoft Academic Search

Summary  \\u000a \\u000a \\u000a \\u000a 1. \\u000a \\u000a Positive evidence is offered of an acceleration of cell division by-SH in bacteria-free cultures ofChilomonas paramecium.\\u000a \\u000a \\u000a \\u000a \\u000a 2. \\u000a \\u000a When hydrogen peroxide is added to standard culture medium no growth is obtained, but relatively rapid growth occurs if both\\u000a peroxide and a high concentration of-SH are added.\\u000a \\u000a \\u000a \\u000a \\u000a 3. \\u000a \\u000a This antagonistic action of-SH and peroxide is explained on the basis of

Theo L. Jahn

1933-01-01

242

A NEW SOURCE REDUCTION PROJECT: THE POTENTIAL FOR SAFE SUBSTITUTES  

EPA Science Inventory

One of the clean product research projects being funded by the EPA's Pollution Prevention Research Branch in Cincinnati, Ohio, involves evaluating the possibility of dramatic reductions in hazardous waste and toxic chemical exposure associated with commercial products. y identify...

243

Lightning-induced reduction of phosphorus oxidation state  

Microsoft Academic Search

Phosphorus is frequently the limiting nutrient in marine and terrestrial ecosystems, largely owing to its poor solubility and slow movement through the rock cycle. Phosphorus is viewed to exist in geological systems almost exclusively in its fully oxidized state as orthophosphate. However, many microorganisms use the partially oxidized forms-phosphite and hypophosphite-as alternative phosphorus sources, and genomic evidence suggests that this

Matthew Pasek; Kristin Block

2009-01-01

244

Method for direct reduction of iron oxide utilizing induction heating  

Microsoft Academic Search

A method of reducing iron oxide by induction heating. The method involves the following steps: charging iron oxide and a carbonaceous material into the inlet end of a plurality of compartments whose walls comprise a material which is adaptable to being heated by induction wherein the plurality of compartments commonly share an induction coil means which surrounds the plurality of

Calderon

1985-01-01

245

REDUCTION OF OXIDATIVE DNA DAMAGE WITH N-ACETYLCYSTEINE  

Microsoft Academic Search

Cancer is thought to be the result of accumu- lated mutations in the DNA. A major contrib- utor to these mutations is the damage due to oxidative stress caused by free radicals. Strat- egies that reduce oxidative stress on cells should result in less damage to DNA, less mutations, and thus less cancer. Prevention of cancer could include the consumption

Coralis Rodriguez; Thomas Armstrong; Eugenio Munoz; Wilfredo Hernandez

246

High-Quality Reduced Graphene Oxide by a Dual-Function Chemical Reduction and Healing Process  

NASA Astrophysics Data System (ADS)

A new chemical dual-functional reducing agent, thiophene, was used to produce high-quality reduced graphene oxide (rGO) as a result of a chemical reduction of graphene oxide (GO) and the healing of rGO. Thiophene reduced GO by donation of electrons with acceptance of oxygen while it was converted into an intermediate oxidised polymerised thiophene that was eventually transformed into polyhydrocarbon by loss of sulphur atoms. Surprisingly, the polyhydrocarbon template helped to produce good-quality rGOC (chemically reduced) and high-quality rGOCT after thermal treatment. The resulting rGOCT nanosheets did not contain any nitrogen or sulphur impurities, were highly deoxygenated and showed a healing effect. Thus the electrical properties of the as-prepared rGOCT were superior to those of conventional hydrazine-produced rGO that require harsh reaction conditions. Our novel dual reduction and healing method with thiophene could potentially save energy and facilitate the commercial mass production of high-quality graphene.

Some, Surajit; Kim, Youngmin; Yoon, Yeoheung; Yoo, Heejoun; Lee, Saemi; Park, Younghun; Lee, Hyoyoung

2013-05-01

247

Raney-platinum film electrodes for potentially implantable glucose fuel cells. Part 2: Glucose-tolerant oxygen reduction cathodes  

Microsoft Academic Search

We report the fabrication and characterization of glucose-tolerant Raney-platinum cathodes for oxygen reduction in potentially implantable glucose fuel. Fabricated by extraction of aluminum from 1?m thin platinum–aluminum bi-layers annealed at 300°C, the novel cathodes show excellent resistance against hydrolytic and oxidative attack. This renders them superior over previous cathodes fabricated from hydrogel-bound catalyst particles. Annealing times of 60, 120, and

S. Kerzenmacher; U. Kräling; M. Schroeder; R. Brämer; R. Zengerle; F. von Stetten

2010-01-01

248

Applications and potential toxicity of magnetic iron oxide nanoparticles.  

PubMed

Owing to their unique physical and chemical properties, magnetic iron oxide nanoparticles have become a powerful platform in many diverse aspects of biomedicine, including magnetic resonance imaging, drug and gene delivery, biological sensing, and hyperthermia. However, the biomedical applications of magnetic iron oxide nanoparticles arouse serious concerns about their pharmacokinetics, metabolism, and toxicity. In this review, the updated research on the biomedical applications and potential toxicity of magnetic iron oxide nanoparticles is summarized. Much more effort is required to develop magnetic iron oxide nanoparticles with improved biocompatible surface engineering to achieve minimal toxicity, for various applications in biomedicine. PMID:23019129

Liu, Gang; Gao, Jinhao; Ai, Hua; Chen, Xiaoyuan

2012-09-28

249

Oxygen Reduction Kinetics Enhancement on a 2 Heterostructured Oxide Surface for Solid Oxide Fuel Cells  

SciTech Connect

Heterostructured interfaces of oxides, which can exhibit transport and reactivity characteristics remarkably different from those of bulk oxides, are interesting systems to explore in search of highly active cathodes for the oxygen reduction reaction (ORR). Here, we show that the ORR of {approx}85 nm thick La{sub 0.8}Sr{sub 0.2}CoO{sub 3-{delta}} (LSC{sub 113}) films prepared by pulsed laser deposition on (001)-oriented yttria-stabilized zirconia (YSZ) substrates is dramatically enhanced ({approx} 3-4 orders of magnitude above bulk LSC{sub 113}) by surface decorations of (La{sub 0.5}Sr{sub 0.5}){sub 2}CoO{sub 4{+-}{delta}} (LSC{sub 214}) with coverage in the range from {approx}0.1 to {approx}15 nm. Their surface and atomic structures were characterized by atomic force, scanning electron, and scanning transmission electron microscopy, and the ORR kinetics were determined by electrochemical impedance spectroscopy. Although the mechanism for ORR enhancement is not yet fully understood, our results to date show that the observed ORR enhancement can be attributed to highly active interfacial LSC{sub 113}/LSC{sub 214} regions, which were shown to be atomically sharp.

Crumlin, Ethan [Massachusetts Institute of Technology (MIT); Mutoro, Eva [ORNL; Ahn, Sung Jin [Massachusetts Institute of Technology (MIT); Jose la O', Gerardo [Massachusetts Institute of Technology (MIT); Leonard, Donovan N [ORNL; Borisevich, Albina Y [ORNL; Biegalski, Michael D [ORNL; Christen, Hans M [ORNL; Shao-Horn, Yang [Massachusetts Institute of Technology (MIT)

2010-01-01

250

Cathodic Reduction of Cuprous Oxide in Vinyl Antifouling Paints.  

National Technical Information Service (NTIS)

On the cathodically protected bottoms of Canadian naval ships, when coated with a vinyl system including a cuprous oxide pigmented antifouling paint, black patches are frequently observed. It has been shown that these patches are electrically conductive a...

W. A. Anderton

1969-01-01

251

SPATIAL AND TEMPORAL GRADIENTS IN AQUIFER OXIDATION-REDUCTION CONDITIONS  

EPA Science Inventory

The study was undertaken to identify principal oxidizing and reducing chemical species in groundwater with the goal of determining the utility of platinum electrode (Eh) measurements to characterize subsurface redox conditions. erial measurements of Eh and groundwater analyses we...

252

SPATIAL AND TEMPORAL GRADIENTS IN AQUIFER OXIDATION- REDUCTION CONDITIONS  

EPA Science Inventory

The study was undertaken to identify principal oxidizing and reducing chemical species in groundwater with the goal of determining the utility of platinum electrode (Eh) measurements to characterize subsurface redox conditions. Serial measurements of Eh and groundwater analyses w...

253

Oxidative stress in pregnant women and birth weight reduction  

Microsoft Academic Search

The purpose of this study is to evaluate the role of maternal oxidative stress in lowering neonatal birth weight. Women (N=261) with singleton pregnancy were analyzed for biomarker levels of oxidative stress after recruitment at the time of hospitalization for delivery in Korea between 2000 and 2001. Among the neonates, 247 births were full-term infants and 14 births were pre-term

Young-Ju Kim; Yun-Chul Hong; Kwan-Hee Lee; Heon Joo Park; Eun Ae Park; Hye-Sung Moon; Eun-Hee Ha

2005-01-01

254

Oxidation-reduction reagents for a wet desulfurization process and a process for preparing same  

SciTech Connect

An oxidation-reduction reagent is described for a wet desulfurization process, which comprises (A) one or more compounds selected from the group consisting of salts of substituted anthraquinonesulfonic acids.

Higuchi, C.; Kato, T.; Mita, R.; Murakami, H.; Sakai, K.

1981-06-30

255

Sequential Oxidative and Reductive Bleaching in a Multicomponent Single Liquor System.  

National Technical Information Service (NTIS)

The present invention relates to processes for oxidative (using hydrogen peroxide) and reductive bleaching of fibers, and fibers bleached by the aforementioned processes. Both of the bleaching processes of the present invention may be utilized to great ad...

W. N. Marmer

1989-01-01

256

Characterization Study of Polycrystalline Tin Oxide Surfaces Before and after Reduction in CO.  

National Technical Information Service (NTIS)

Polycrystalline tin oxide surfaces have been examined before and after reduction in 40 Torr of CO at 100 and 175 C using Auger electron spectroscopy (AES), electron spectroscopy for chemical analysis (ESCA), ion scattering spectroscopy (ISS) and electron ...

J. E. Drawdy G. B. Hoflund M. R. Davidson D. R. Schryer

1990-01-01

257

WORKSHOP ON MONITORING OXIDATION-REDUCTION PROCESSES FOR GROUND-WATER RESTORATION  

EPA Science Inventory

Redox conditions are among the most important parameters for controlling contaminant transport and fate in ground-water systems. Oxidation-reduction (redox) reactions mediate the chemical behavior of both inorganic and organic chemical constituents by affecting solubility, rea...

258

CHARACTERIZATION OF OXIDATION-REDUCTION PROCESSES IN CONSTRUCTED WETLANDS FOR SWINE WASTEWATER TREATMENT  

Technology Transfer Automated Retrieval System (TEKTRAN)

Constructed wetlands designed and properly operated for treatment of swine wastewater treatment may enhance oxidation-reduction processes and nutrient treatment performance. The objective of this investigation was to characterize soil wetland processes related to nitrogen (N) treatment (nitrificatio...

259

Hydrogen production using solid oxide membrane electrolyzer with solid carbon reductant in liquid metal anode  

SciTech Connect

A laboratory-scale solid oxide membrane (SOM) steam electrolyzer that can potentially utilize the energy value of coal or any hydrocarbon reductant to produce high purity hydrogen has been fabricated and evaluated. The SOM electrolyzer consists of an oxygen-ion-conducting yttria-stabilized zirconia (YSZ) electrolyte with a Ni-YSZ cermet cathode coated on one side and liquid tin anode on the other side. Hydrogen production using the SOM electrolyzer was successfully demonstrated between 900 and 1000{sup o}C by feeding a steam-rich gas to the Ni-YSZ cermet cathode and solid carbon reductant into the liquid tin anode. It was confirmed that the energy required for hydrogen production can be effectively lowered by feeding a solid carbon reductant in the liquid tin anode. A polarization model for the SOM electrolyzer was developed. The experimental data obtained under different operating conditions were curve fitted into the model to identify the various polarization losses. Based on the results of this study, work needed toward increasing the electrochemical performance of the SOM electrolyzer is discussed.

Pati, S.; Yoon, K.J.; Gopalan, S.; Pal, U.B. [Boston University, Boston, MA (United States). Dept. of Mechanical Engineering

2009-07-01

260

Cerebroprotective potential of resveratrol through anti-oxidant and anti-inflammatory mechanisms in rats.  

PubMed

Oxidative stress and inflammation are two important pathological mechanisms involved in cerebral ischemia and reperfusion injury. In pathological conditions such as cerebral infarction, the free radical production is greater than that of elimination by endogenous anti-oxidant system, by this undesirable effect brain is highly injured. Resveratrol is reported to have anti-oxidant and anti-inflammatory, athero-protective activities. Therefore, the aim of the present study is to evaluate the therapeutic potential of resveratrol against cerebral infarction induced by ischemia and reperfusion injury in Wistar rats. Bi-common carotid occlusion followed by 4 h reperfusion model was used to induce cerebral infarction. Percent infarction, oxidative stress markers (malondialdehyde, catalase, superoxide dismutase) and inflammatory markers (myeloperoxidase, TNF-?, IL-6, ICAM-1 and IL-10) were measured. TNF-?, IL-6, IL-10, and intracellular adhesive molecule-I (ICAM-1) levels were quantified by enzyme-linked immunosorbent assay (ELISA). Resveratrol produced significant dose-dependent reduction in percent cerebral infarct volume. At resveratrol 20 mg/kg dose, there was a significant reduction in oxidative stress and inflammatory markers like malondialdehyde, TNF-?, IL-6, myeloperoxidase and ICAM-I and in contrast there was a significant increase in anti-oxidants and anti-inflammatory markers like superoxide dismutase, catalase and IL-10 levels. Resveratrol showed significant cerebroprotective action mediated by anti-oxidant and anti-inflammatory mechanisms. PMID:23371441

Orsu, Prabhakar; Murthy, B V S N; Akula, Annapurna

2013-01-31

261

Oxidation-reduction treatment of rhodium supported on nonporous silica spheres  

Microsoft Academic Search

The structure of Rh crystallites subjected to oxidation-reduction treatment has been investigated by high-resolution transmission electron microscopy. The Rh was supported on 130-nm nonporous silica spheres so that the three-dimensional structure of the metal crystallites could be readily observed. After oxidation at 823 K and subsequent reduction at 473 K, the particles show images characterized by a lower contrast at

S. Chakraborti; A. K. Datye; N. J. Long

1987-01-01

262

Cyclic oxidation and reduction of protein methionine residues is an important antioxidant mechanism  

Microsoft Academic Search

Almost all forms of reactive oxygen species (ROS) oxidize methionine residues of proteins to a mixture of the R- and S-isomers of methionine sulfoxide. Because organisms contain methionine sulfoxide reductases (Msr's) that can catalyze the thioredoxin-dependent reduction of the sulfoxides back to methionine, it was proposed that the cyclic oxidation\\/reduction of methionine residues might serve as antioxidants to scavenge ROS,

Earl R. Stadtman; Jackob Moskovitz; Barbara S. Berlett; Rodney L. Levine

2002-01-01

263

EQCM study on the oxidation\\/reduction of bismuth sulfide thin films  

Microsoft Academic Search

The oxidation\\/reduction of bismuth sulfide thin films deposited on an Au electrode using the successive ionic layer adsorption and reaction method has been investigated by electrochemical quartz crystal microbalance combined with cyclic voltammetry and X-ray photoelectron spectroscopy. It has been shown that the oxidation\\/reduction of bismuth sulfide film depends on the nature of anion. In the acetate solution the bismuth

L. Tamašauskait?-Tamaši?nait?; G. Valiulien?; A. Žielien?; B. Šimk?nait?-Stanynien?; L. Naruškevi?ius; A. Sudavi?ius

2010-01-01

264

Advanced experimental analysis of controls on microbial Fe(III) oxide reduction. 1998 annual progress report  

SciTech Connect

'Understanding factors which control the long-term survival and activity of Fe(III)-reducing bacteria (FeRB) in subsurface sedimentary environments is important for predicting their ability to serve as agents for bioremediation of organic and inorganic contaminants. This project seeks to refine the authors quantitative understanding of microbiological and geochemical controls on bacterial Fe(III) oxide reduction and growth of FeRB, using laboratory reactor systems which mimic to varying degrees the physical and chemical conditions of subsurface sedimentary environments. Methods for studying microbial Fe(III) oxide reduction and FeRB growth in experimental systems which incorporate advective aqueous phase flux are being developed for this purpose. These methodologies, together with an accumulating database on the kinetics of Fe(III) reduction and bacterial growth with various synthetic and natural Fe(III) oxide minerals, will be applicable to experimental and modeling studies of subsurface contaminant transformations directly coupled to or influenced by bacterial Fe(III) oxide reduction and FeRB activity. This report summarizes research accomplished after approximately 1.5 yr of a 3-yr project. A central hypothesis of the research is that advective elimination of the primary end-product of Fe(III) oxide reduction, Fe(II), will enhance the rate and extent of microbial Fe(III) oxide reduction in open experimental systems. This hypothesis is based on previous studies in the laboratory which demonstrated that association of evolved Fe(II) with oxide and FeRB cell surfaces (via adsorption or surface precipitation) is a primary cause for cessation of Fe(III) oxide reduction activity in batch culture experiments. Semicontinuous culturing was adopted as a first approach to test this basic hypothesis. Synthetic goethite or natural Fe(III) oxide-rich subsoils were used as Fe(III) sources, with the Fe(III)-reducing bacterium Shewanella alga as the test organism.'

Roden, E.E.; Urrutia, M.M.

1998-06-01

265

Electrochemical oxidation by square-wave potential pulses in the imitation of oxidative drug metabolism.  

PubMed

Electrochemistry combined with mass spectrometry (EC-MS) is an emerging analytical technique in the imitation of oxidative drug metabolism at the early stages of new drug development. Here, we present the benefits of electrochemical oxidation by square-wave potential pulses for the oxidation of lidocaine, a test drug compound, on a platinum electrode. Lidocaine was oxidized at constant potential and by square-wave potential pulses with different cycle times, and the reaction products were analyzed by liquid chromatography-mass spectrometry [LC-MS(/MS)]. Application of constant potentials of up to +5.0 V resulted in relatively low yields of N-dealkylation and 4-hydroxylation products, while oxidation by square-wave potential pulses generated up to 50 times more of the 4-hydroxylation product at cycle times between 0.2 and 12 s (estimated yield of 10%). The highest yield of the N-dealkylation product was obtained at cycle times shorter than 0.2 s. Tuning of the cycle time is thus an important parameter to modulate the selectivity of electrochemical oxidation reactions. The N-oxidation product was only obtained by electrochemical oxidation under air atmosphere due to reaction with electrogenerated hydrogen peroxide. Square-wave potential pulses may also be applicable to modulate the selectivity of electrochemical reactions with other drug compounds in order to generate oxidation products with greater selectivity and higher yield based on the optimization of cycle times and potentials. This considerably widens the scope of direct electrochemistry-based oxidation reactions for the imitation of in vivo oxidative drug metabolism. PMID:21644593

Nouri-Nigjeh, Eslam; Permentier, Hjalmar P; Bischoff, Rainer; Bruins, Andries P

2011-06-27

266

Reversible phenol oxidation and reduction in the structurally well-defined 2-Mercaptophenol-??C protein.  

PubMed

2-Mercaptophenol-??C serves as a biomimetic model for enzymes that use tyrosine residues in redox catalysis and multistep electron transfer. This model protein was tailored for electrochemical studies of phenol oxidation and reduction with specific emphasis on the redox-driven protonic reactions occurring at the phenol oxygen. This protein contains a covalently modified 2-mercaptophenol-cysteine residue. The radical site and the phenol compound were specifically chosen to bury the phenol OH group inside the protein. A solution nuclear magnetic resonance structural analysis (i) demonstrates that the synthetic 2-mercaptophenol-??C model protein behaves structurally as a natural protein, (ii) confirms the design of the radical site, (iii) reveals that the ligated phenol forms an interhelical hydrogen bond to glutamate 13 (phenol oxygen-carboxyl oxygen distance of 3.2 ± 0.5 Å), and (iv) suggests a proton-transfer pathway from the buried phenol OH (average solvent accessible surface area of 3 ± 5%) via glutamate 13 (average solvent accessible surface area of the carboxyl oxygens of 37 ± 18%) to the bulk solvent. A square-wave voltammetry analysis of 2-mercaptophenol-??C further demonstrates that (v) the phenol oxidation-reduction cycle is reversible, (vi) formal phenol reduction potentials can be obtained, and (vii) the phenol-O(•) state is long-lived with an estimated lifetime of ?180 millisecond. These properties make 2-mercaptophenol-??C a unique system for characterizing phenol-based proton-coupled electron transfer in a low-dielectric and structured protein environment. PMID:23373469

Tommos, Cecilia; Valentine, Kathleen G; Martínez-Rivera, Melissa C; Liang, Li; Moorman, Veronica R

2013-02-14

267

Dipyridamole potentiates platelet inhibition by nitric oxide.  

PubMed

In a placebo-controlled double blind cross-over experiment the adenosine uptake inhibitor dipyridamole (400 mg/day) did not affect ex vivo platelet aggregation induced by collagen or adenosine-diphosphate (ADP) in an electronic whole blood aggregometer (WBA). Dipyridamole was also inactive in vitro, unless red blood cell injury was deliberately enhanced, thereby increasing the level of free adenine nucleotides. Since dipyridamole also inhibits cyclic guanosine monophosphate (GMP) phosphodiesterase (PDE), we used platelet rich plasma (PRP) to study its interaction with authentic and endothelium-derived nitric oxide (NO). The latter inhibits platelets by increasing cyclic GMP. Dipyridamole (1 to 30 microM), either alone or in combination with a subthreshold concentration of prostacyclin (PGI2), was inactive. However, when combined with a subthreshold concentration of NO, dipyridamole caused a concentration-dependent platelet suppression, which became more pronounced when PGI2 was present as well. It is concluded that dipyridamole could reduce the threshold for platelet suppression by NO through inhibition of cyclic GMP PDE. PMID:1746006

Bult, H; Fret, H R; Jordaens, F H; Herman, A G

1991-09-01

268

Interconnected Pt-Nanodendrite/DNA/Reduced-Graphene-Oxide Hybrid Showing Remarkable Oxygen Reduction Activity and Stability.  

PubMed

Controlling the morphology and size of platinum nanodendrites (PtDs) is a key factor in improving their catalytic activity and stability. Here, we report the synthesis of PtDs on genomic-double-stranded-DNA/reduced-graphene-oxide (gdsDNA/rGO) by the NaBH4 reduction of H2PtCl6 in the presence of plant gdsDNA. Compared to industrially adopted catalysts (i.e., state-of-the-art Pt/C catalyst, Pt/rGO, Pt3Co, etc.), the as-synthesized PtDs/gdsDNA/rGO hybrid displays very high oxygen reduction reaction (ORR) catalytic activities (much higher than the 2015 U.S. Department of Energy (DOE) target values), which are the rate-determining steps in electrochemical energy devices, in terms of onset-potential, half-wave potential, specific-activity, mass-activity, stability, and durability. Moreover, the hybrid exhibits a highly stable mass activity for the ORR over a wide pH range of 1-13. These exceptional properties would make the hybrid applicable in next-generation electrochemical energy devices. PMID:23991709

Tiwari, Jitendra N; Kemp, Kingsley Christian; Nath, Krishna; Tiwari, Rajanish N; Nam, Hong-Gil; Kim, Kwang S

2013-09-05

269

Synthesis of free standing conducting graphene paper by thermal reduction of graphene oxide paper  

NASA Astrophysics Data System (ADS)

Graphene is one atom thick two dimensional material with unusual mechanical, electrical, thermal and optical properties. Graphene, on larger scale is produced through reduction of graphene oxide which in turn is synthesized by chemical oxidation of graphite. Generally large area graphene oxide paper can be easily fabricated by solution filtration process, spin casting method and Langmuir-Blodgett assembly. In present study graphene oxide was synthesized by modified Hummers method. Free standing graphene oxide paper (GOP) was developed by simple drying of graphene oxide suspended in water followed by reduction by thermal treatment to synthesize free standing conducting graphene paper (Thermally Reduced Graphene Paper, TRGP). Thermal reduction was carried out for 30, 60, 90 and 120min and samples referred as TRGP_30, TRGP_60, TRGP_90 and TRGP_120 respectively. XRD results show decrease in inter layer spacing (d002) from 0.87 nm to ~0.35 nm after reduction of GO paper. This shows gradual removal of oxygen functionalities and adsorbed water during reduction. Meanwhile the size of sp2 domains of graphene also decrease as studied by Raman spectroscopy. SEM results also show change in morphology of thermally reduced graphene paper. The electrical conductivity of reduced graphene paper increases from 2.8 × 10-2 S/m for as such graphene oxide paper to 1.3 × 102 S/m for graphene paper.

Manocha, L. M.; Gajera, H. L.; Manocha, S.

2013-06-01

270

Potential of solar cooling systems for peak demand reduction  

SciTech Connect

We investigated the technical feasibility of solar cooling for peak demand reduction using a building energy simulation program (DOE2.1D). The system studied was an absorption cooling system with a thermal coefficient of performance of 0.8 driven by a solar collector system with an efficiency of 50% with no thermal storage. The analysis for three different climates showed that, on the day with peak cooling load, about 17% of the peak load could be met satisfactorily with the solar-assisted cooling system without any thermal storage. A performance availability analysis indicated that the solar cooling system should be designed for lower amounts of available solar resources that coincide with the hours during which peak demand reduction is required. The analysis indicated that in dry climates, direct-normal concentrating collectors work well for solar cooling; however, in humid climates, collectors that absorb diffuse radiation work better.

Pesaran, A.A. [National Renewable Energy Lab., Golden, CO (United States); Neymark, J. [Neymark (Joel), Golden, CO (United States)

1994-11-01

271

DEVELOPMENT AND EVALUATION OF A MATHEMATICAL MODEL FOR THE TRANSPORT AND OXIDATION-REDUCTION OF COEDTA  

EPA Science Inventory

Oxidation-reduction reactions, catalyzed by iron and manganese oxides, influence the subsurface mobility of a variety of toxic metals. In the work reported here, we develop a new model for the transport of the redox-sensitive CoEDTA complex, and we test the model against publishe...

272

Continuum mechanics simulations of NiO\\/Ni–YSZ composites during reduction and re-oxidation  

Microsoft Academic Search

Repeated reduction–oxidation (redox) cycles on Ni-based solid oxide fuel cells (SOFC) have been experimentally well investigated and are known to be detrimental to the thermomechanical stability of the composites, especially on anode supported structures. In the present work the mechanistic analysis of the internal factors leading to the dimensional changes and the thermomechanical instability have been addressed, to our knowledge

M. H. Pihlatie; H. L. Frandsen; A. Kaiser; M. Mogensen

2010-01-01

273

Calcium-centred phosphine oxide reactivity: P-C metathesis, reduction and P-P coupling.  

PubMed

Reactions of triphenylphosphine oxide and diphenylphosphine oxide with calcium alkyls and amides in the presence of PhSiH(3) occur to give P-C bond cleavage, P(V) to P(III) reduction and P-P coupling. PMID:20379562

Hill, Michael S; Mahon, Mary F; Robinson, Thomas P

2010-01-28

274

Oxidation of diesel-generated volatile organic compounds in the selective catalytic reduction process  

Microsoft Academic Search

The main part of the VOCs (volatile organic compounds) contained in diesel exhaust (â80%) is oxidized to CO and COâ over an SCR (selective catalytic reduction) catalyst. CO is the major product of this oxidation, representing about 50--70% of the formed products (CO + COâ). This preferential formation of CO leads to a pronounced increase of CO emissions when an

M. Koebel; M. Elsener

1998-01-01

275

Oxidation versus reductive detoxification of SO sub 2 by chloroplasts  

SciTech Connect

Intact chloroplasts isolated from spinach (Spinacia oleracea L. cv Yates) both oxidized and reduced added sulfite in the light. Oxidation was fast only when endogenous superoxide dismutase was inhibited by cyanide. It was largely suppressed by scavengers of oxygen radicals. After addition of O-acetylserine, chloroplasts reduced sulfite to cysteine and exhibited sulfite-dependent oxygen evolution. Cysteine synthesis from sulfite was faster than from sulfate. The results are discussed in relation to species-specific differences in the phytotoxicity of SO{sub 2}.

Ghisi, R.; Dittrich, A.P.M.; Heber, U. (Universitaet Wuerzburg (West Germany))

1990-03-01

276

Method for catalyzing oxidation/reduction reactions of simple molecules  

SciTech Connect

A method for oxidizing carbon monoxide to carbon dioxide is described comprising: (1) contacting, together, carbon monoxide, a nitrogen-containing chelating agent and water; wherein the chelating agent is at least one member selected from the group consisting of methmeoglobin bound to a support, ferric hemoglobin bound to a support, iron-containing porphyrins bound to a support, and sperm whale myoglobin bound to a support, wherein the support is glass, a natural fiber, a synthetic fiber, a gel, charcoal, carbon ceramic material, a metal oxide, a synthetic polymer, a zeolite, a silica compound of an alumina compound; and (2) obtaining carbon dioxide.

Bicker, D.; Bonaventura, J.

1988-06-14

277

Removing nitric oxide from flue gases by catalytic reduction  

SciTech Connect

A Ti-W-V catalyst has been proposed for removing NO by means of ammonia reduction from flue gases from power stations and boiler systems operating with natural gas; it contains 10% WO{sub 3} and 5% V{sub 2}O{sub 5} deposited on anatase. The optimum NH{sub 3}/NO ration is 0.8. oxygen at levels of 0.1-7.8 vol. % does not affect the reduction of the NO. Industrial tests in flue gas from a power station show that the reduction of the NO is 96% at 240-270{degrees}C. The basic technological parameters have been determined. 2 figs., 2 tabs.

Semenova, T.A.; Lileikina, T.N.; Mednikova, T.A. [State Research and Development Institute for the Nitrogen Industry and Organic Synthesis Products, Moscow (Russian Federation)

1992-03-01

278

A green approach for the reduction of graphene oxide by wild carrot root  

Microsoft Academic Search

A green approach for the reduction of graphene oxide (GO) using wild carrot root is reported in this work. It avoids the use of toxic and environmentally harmful reducing agents commonly used in the chemical reduction of GO to obtain graphene. The endophytic microorganisms present in the carrot root, reduces exfoliated GO to graphene at room temperature in an aqueous

Tapas Kuila; Saswata Bose; Partha Khanra; Ananta Kumar Mishra; Nam Hoon Kim; Joong Hee Lee

279

Defense Budget (1994): Potential Reductions, Rescissions, and Restrictions to Procurement Programs.  

National Technical Information Service (NTIS)

We examined the Department of Defense's fiscal year 1994 budget request and prior years' appropriations for selected procurement programs. Out objectives were to identify potential reductions to the fiscal year 1994 budget request and potential rescission...

1993-01-01

280

Solid oxide membrane process for the direct reduction of magnesium from magnesium oxide  

NASA Astrophysics Data System (ADS)

The Solid Oxide Membrane (SOM) process is an emerging generic technology for the environmentally friendly extraction of high-energy-content metals directly from their oxides. This process has the potential to offer a viable, cost effective and cleaner alternative to existing state of the art primary magnesium extraction processes. The SOM process in principle uses a tubular yttria stabilized-zirconia-based solid oxide fuel cell with liquid metal (copper or tin) as an anode in the temperature range of 1100--1300°C. Magnesium oxide is dissolved in a molten ionic flux and oxygen ions are pumped out of the flux through the zirconia membrane and are oxidized at, the liquid metal anode. Magnesium vapor evolves at the cathode and is condensed in a separate chamber (condenser). The proof of concept for the SOM process was initially demonstrated at 1300°C using a magnesium fluoride-based flux. Since the membrane is the most expensive part of the process, its long-term stability is critical to the scale up and eventual commercialization of the process. Temperature, flux chemistry and cell operating conditions have been identified as key process parameters for membrane stability. A new low temperature flux based on the eutectic: magnesium fluoride-calcium fluoride system, has been developed which has lowered the operating temperature of the SOM cell to 1150°C. Additionally, a minor addition of yttrium fluoride to the flux minimized yttria diffusion from the yttria-stabilized-zirconia membrane, thereby further enhancing membrane stability. Important thermo-physical properties of the selected flux compositions critical to the process such as viscosity, density, volatility, solubility and electrical conductivity have been measured. The SOM cell has been electrochemically characterized and concepts related to MgO dissociation voltage, observed leakage current and mass transfer in the SOM cell are explained. The viability of the SOM process has been demonstrated by the operation of a 100 g scale reactor. Preliminary cost estimates and design of a commercial reactor based on this investigation are also discussed.

Krishnan, Ajay

281

Sodium citrate: A universal reducing agent for reduction \\/ decoration of graphene oxide with au nanoparticles  

Microsoft Academic Search

A facile method is proposed for the synthesis of reduced graphene oxide nanosheets (RGONS) and Au nanoparticle-reduced graphene\\u000a oxide nanosheet (Au-RGONS) hybrid materials, using graphene oxide (GO) as precursor and sodium citrate as reductant and stabilizer.\\u000a The resulting RGONS and Au-RGONS hybrid materials were characterized by UV-vis spectroscopy, X-ray photoelectron spectroscopy,\\u000a Fourier transform infrared spectroscopy, Raman spectroscopy, atomic force microscopy,

Zhe Zhang; Huihui Chen; Chunyan Xing; Mingyi Guo; Fugang Xu; Xiaodan Wang; Hermann J. Gruber; Bailin Zhang; Jilin Tang

2011-01-01

282

Bacterial reduction of crystalline Fe{sup 3+} oxides in single phase suspensions and subsurface materials  

Microsoft Academic Search

Microbiologic reduction of synthetic and geologic Fe{sup 3+} oxides associated with four Pleistocene-age, Atlantic coastal plain sediments was investigated using a dissimilatory Fe reducing bacterium (Shewanella putrefaciens, strain CN32) in bicarbonate buffer. Experiments investigated whether phosphate and anthraquinone-2,6-disulfonate, (AQDS, a humic acid analogue) influenced the extent of crystalline Fe{sup 3+} oxide bioreduction and whether crystalline Fe{sup 3+} oxides in geologic

John M. Zachara; JAMES K. FREDRICKSON; Shu-Mei W. Li; David W. Kennedy; Steven C. Smith; Paul L. Gassman

1998-01-01

283

Perchlorate reduction by a novel chemolithoautotrophic, hydrogen-oxidizing bacterium  

Microsoft Academic Search

Summary Water treatment technologies are needed that can remove perchlorate from drinking water without introducing organic chemicals that stimulate bacterial growth in water distribution systems. Hydrogen is an ideal energy source for bacterial degradation of per- chlorate as it leaves no organic residue and is spar- ingly soluble. We describe here the isolation of a perchlorate-respiring, hydrogen-oxidizing bacterium ( Dechloromonas

Husen Zhang; Mary Ann Bruns; Bruce E. Logan

2002-01-01

284

DEVELOPMENT OF ELECTROCHEMICAL REDUCTION TECHNOLOGY FOR SPENT OXIDE FUELS  

Microsoft Academic Search

The Advanced Spent Fuel Conditioning Process (ACP) has been under development at Korea Atomic Energy Research Institute (KAERI) since 1997. The concept is to convert spent oxide fuel into metallic form and to remove high heat-load fission products such as Cs and Sr from the spent fuel. The heat power, volume, and radioactivity of spent fuel can decrease by a

Jin-Mok Hur; Chung-Seok Seo; Ik-Soo Kim; Sun-Seok Hong; Dae-Seung Kang; Seong-Won Park

2003-01-01

285

Sequential Oxidative and Reductive Bleaching of Pigmented and Unpigmented Fibers.  

National Technical Information Service (NTIS)

The occurrence of dark (i.e. pigmented and/or stained) fibers often gives rise to annoying and expensive problems for manufacturers at all stages of fiber processing. The present invention relates to processes for oxidative (using hydrogen peroxide) and r...

M. Arifoglu W. N. Marmer

1989-01-01

286

Galvanic interpretation of self-potential signals associated withmicrobial sulfate-reduction  

SciTech Connect

We have evaluated the usefulness of the self-potential (SP)geophysical method to track the onset and location of microbialsulfate-reduction in saturated sediments during organic carbon amendment.Following stimulation of sulfate-reducing bacteria (SRB) by addition oflactate, anomalous voltages exceeding 600 mV correlated in space and timewith the accumulation of dissolved sulfide. Abiotic experiments in whichthe sulfide concentration at the measurement electrode was systematicallyvaried showed a positive correlation between the magnitude of the SPanomaly and differences in the half-cell potential associated with themeasurement and reference electrodes. Thus, we infer that the SPanomaliesresulted from electrochemical differences that developedbetween sulfide-rich regions and areas having higher oxidation potential.In neither experiment did generation of an SP anomaly require thepresence of an in situ electronic conductor, as is required by othermodels. These findings emphasize the importance of incorporation ofelectrochemical effects at electrode surfaces in interpretation of SPdata from geophysical studies. We conclude that SP measurements provide aminimally invasive means for monitoring stimulated sulfate-reductionwithin saturated sediments.

Williams, Kenneth H.; Hubbard, Susan S.; Banfield, Jillian F.

2007-05-02

287

In vitro enzymatic reduction kinetics of mineral oxides by membrane fractions from Shewanella oneidensis MR1  

Microsoft Academic Search

This study documents the first example of in vitro solid-phase mineral oxide reduction by enzyme-containing membrane fractions. Previous in vitro studies have only reported the reduction of aqueous ions. Total membrane (TM) fractions from iron-grown cultures of Shewanella oneidensis MR-1 were isolated and shown to catalyze the reduction of goethite, hematite, birnessite, and ramsdellite\\/pyrolusite using formate. In contrast, nicotinamide adenine

Shane S. Ruebush; Gary A. Icopini; Susan L. Brantley; Ming Tien

2006-01-01

288

A model for the electrochemical reduction of metal oxides in molten salt electrolytes  

Microsoft Academic Search

The reduction of numerous metal oxides is being investigated by electro-deoxidation in molten salts due to the low-oxygen content advantage these processes offer. One of these processes is the Fray–Farthing–Chen (FFC) process that involves the direct reduction of titanium dioxide to titanium. A model for the multi-stage reduction of titanium dioxide to titanium is reported herein. The modeling approach adopted

Pritish Kar; James W. Evans

2008-01-01

289

Reduction–Oxidation Effects on Soil Potassium and Plant Uptake  

Microsoft Academic Search

Potassium ions (K) may become “fixed” between adjacent phyllosilicate layers under waterlogged conditions, rendering K less available to plant uptake. This phenomenon was investigated under greenhouse conditions to determine if K fixation due to biogeochemical reduction contributed to the K deficiency in corn (Zea mays L.) in the northern Great Plains (South Dakota). The objective of this study was to

Frank V. Schindler; Howard J. Woodard; James J. Doolittle

2003-01-01

290

Catalyst and method for reduction of nitrogen oxides  

Microsoft Academic Search

A Selective Catalytic Reduction (SCR) catalyst was prepared by slurry coating ZSM-5 zeolite onto a cordierite monolith, then subliming an iron salt onto the zeolite, calcining the monolith, and then dipping the monolith either into an aqueous solution of manganese nitrate and cerium nitrate and then calcining, or by similar treatment with separate solutions of manganese nitrate and cerium nitrate.

Ott; Kevin C

2008-01-01

291

Redox potential and equilibria in the reductive half-reaction of Vibrio harveyi NADPH-FMN oxidoreductase.  

PubMed

Vibrio harveyi NADPH:FMN oxidoreductase P (FRP(Vh)) is a homodimeric enzyme having a bound FMN per enzyme monomer. The bound FMN functions as a cofactor of FRP(Vh) in transferring reducing equivalents from NADPH to a flavin substrate in the absence of V. harveyi luciferase but as a substrate for FRP(Vh) in the luciferase-coupled bioluminescent reaction. As part of an integral plan to elucidate the regulation of functional coupling between FRP(Vh) and luciferase, this study was carried out to characterize the equilibrium bindings, reductive potential, and the reversibility of the reduction of the bound FMN in the reductive half-reaction of FRP(Vh). Results indicate that, in addition to NADPH binding, NADP(+) also bound to FRP(Vh) in either the oxidized (K(d) 180 microM) or reduced (K(d) 230 microM) form. By titrations with NADP(+) and NADPH and by an isotope exchange experiment, the reduction of the bound FMN by NADPH was found to be readily reversible (K(eq) = 0.8). Hence, the reduction of FRP(Vh)-bound FMN is not the committed step in coupling the NADPH oxidation to bioluminescence. To our knowledge, such an aspect of flavin reductase catalysis has only been clearly established for FRP(Vh). Although the reductive potentials and some other properties of a R203A variant of FRP(Vh) and an NADH/NADPH-utilizing flavin reductase from Vibrio fischeri are quite similar to that of the wild-type FRP(Vh), the reversal of the reduction of bound FMN was not detected for either of these two enzymes. PMID:15628867

Lei, Benfang; Wang, He; Yu, Yimin; Tu, Shiao-Chun

2005-01-11

292

Synthesis of transition-metal phosphides from oxidic precursors by reduction in hydrogen plasma  

NASA Astrophysics Data System (ADS)

A series of transition metal phosphides, including MoP, WP, CoP, Co2P, and Ni2P, were synthesized from their oxidic precursors by means of hydrogen plasma reduction under mild conditions. The effects of reduction conditions, such as metal to phosphorus molar ratio, power input, and reduction time, on the synthesis of metal phosphides were investigated. The products were identified by means of XRD characterization. It is indicated that metal phosphides were readily synthesized stoichiometrically from their oxides in hydrogen plasma under mild conditions.

Guan, Jie; Wang, Yao; Qin, Minglei; Yang, Ying; Li, Xiang; Wang, Anjie

2009-06-01

293

In vitro enzymatic reduction kinetics of mineral oxides by membrane fractions from Shewanella oneidensis MR-1  

NASA Astrophysics Data System (ADS)

This study documents the first example of in vitro solid-phase mineral oxide reduction by enzyme-containing membrane fractions. Previous in vitro studies have only reported the reduction of aqueous ions. Total membrane (TM) fractions from iron-grown cultures of Shewanella oneidensis MR-1 were isolated and shown to catalyze the reduction of goethite, hematite, birnessite, and ramsdellite/pyrolusite using formate. In contrast, nicotinamide adenine dinucleotide (NADH) and succinate cannot function as electron donors. The significant implications of observations related to this cell-free system are: (i) both iron and manganese mineral oxides are reduced by the TM fraction, but aqueous U(VI) is not; (ii) TM fractions from anaerobically grown, but not aerobically grown, cells can reduce the mineral oxides; (iii) electron shuttles and iron chelators are not needed for this in vitro reduction, documenting conclusively that reduction can occur by direct contact with the mineral oxide; (iv) electron shuttles and EDTA stimulate the in vitro Fe(III) reduction, documenting that exogenous molecules can enhance rates of enzymatic mineral reduction; and (v) multiple membrane components are involved in solid-phase oxide reduction. The membrane fractions, consisting of liposomes of cytoplasmic and outer membrane segments, contain at least 100 proteins including the enzyme that oxidizes formate, formate dehydrogenase. Mineral oxide reduction was inhibited by the addition of detergent Triton X-100, which solubilizes membranes and their associated proteins, consistent with the involvement of multiple electron carriers that are disrupted by detergent addition. In contrast, formate dehydrogenase activity was not inhibited by Triton X-100. The addition of anthraquinone-2,6-disulfonate (AQDS) and menaquinone-4 was unable to restore activity; however, menadione (MD) restored 33% of the activity. The addition of AQDS and MD to reactions without added detergent increased the rate of goethite reduction. The Michaelis Menten Km values of 71 ± 22 m2/L for hematite and 50 ± 16 m2/L for goethite were calculated as a function of surface area of the two insoluble minerals. Vmax was determined to be 123 ± 14 and 156 ± 13 nmol Fe(II)/min/mg of TM protein for hematite and goethite, respectively. These values are consistent with in vivo rates of reduction reported in the literature. These observations are consistent with our conclusion that the enzymatic reduction of mineral oxides is an effective probe that will allow elucidation of molecular chemistry of the membrane mineral interface where electron transfer occurs.

Ruebush, Shane S.; Icopini, Gary A.; Brantley, Susan L.; Tien, Ming

2006-01-01

294

Iron-mediated microbial oxidation and abiotic reduction of organic contaminants under anoxic conditions.  

PubMed

In anoxic environments, the oxidation of organic compounds, such as BTEX fuel components, by dissimilatory Fe(III) reduction can generate reactive mineral-bound Fe(II) species, which in turn are able to reduce other classes of organic and inorganic groundwater contaminants. In this study, we designed and evaluated an anaerobic batch reactor that mimicks iron-reducing conditions to investigate the factors that favor the coupling of microbial toluene oxidation and abiotic reduction of nitroaromatic contaminants. We investigated the influence of different Fe(III)-bearing minerals and combinations thereof on the coupling of these two processes. Results from laboratory model systems show that complete oxidation of toluene to CO2 by Geobacter metallireducens in the presence of Fe(III)-bearing minerals leads to the formation of mineral-bound Fe(II) species capable of the reduction of 4-nitroacetophenone. Whereas significant microbial toluene oxidation was only observed in the presence of amorphous Fe(III) phases, reduction of nitroaromatic compounds only proceeded with Fe(II) species bound to crystalline Fe(III) oxides. Our results suggest that in anoxic soils and sediments containing amorphous and crystalline iron phases simultaneously, coupling of microbial oxidation and abiotic reduction of organic compounds may allow for concurrent natural attenuation of different contaminant classes. PMID:18075086

Tobler, Nicole B; Hofstetter, Thomas B; Straub, Kristina L; Fontana, Daniela; Schwarzenbach, René P

2007-11-15

295

Process for making hydrogen. [reduction of zinc oxide; reaction of zinc and steam; recycling zinc oxide  

Microsoft Academic Search

A process for making hydrogen is described which comprises reducing zinc oxide to zinc metal, combining the metallic zinc with molten lead and spraying the mixture under pressure to an oxidizer where metallic zinc is reacted with steam to yield hydrogen and zinc oxide, separating the hydrogen product under pressure, separating the zinc oxide from the molten lead, recycling zinc

Seitzer

1975-01-01

296

Selective reduction of metals in the lattice of a complex oxide  

NASA Astrophysics Data System (ADS)

The results of our experiments on the carbon reduction of metals from iron-containing rich and lean monometallic ores and complex ores in which iron is present along with other metal oxides in a common crystal lattice are analyzed. It is concluded that reduction should be considered as an electrochemical process consisting in the supply of electrons to the cations to be reduced. The source of electrons in the experiments is a chemical reaction on the surface of interaction between a reducer and oxides. Electron transport deep into ore lumps is performed by anion vacancies. Vacancies draw cations with a high electron affinity and neutral atoms, which ensures selective metal reduction. A continuous metallic shell does not form on the surface of lean and complex ores, and oxide layers, along which vacancies move into an ore lump, are retained. As a result, the entire ore lump undergoes reduction. Therefore, lean and complex ores can easily be reduced as compared to rich ores.

Roshchin, V. E.; Roshchin, A. V.

2013-03-01

297

Prediction of reduction potentials from calculated electron affinities for metal-salen compounds  

PubMed Central

Summary The electron affinities (EAs) of a training set of 19 metal-salen compounds were calculated using density functional theory. Concurrently, the experimental reduction potentials for the training set were measured using cyclic voltammetry. The EAs and reduction potentials were found to be linearly correlated by metal. The reduction potentials of a test set of 14 different metal-salens were then measured and compared to the predicted reduction potentials based upon the training set correlation. The method was found to work well, with a mean unsigned error of 99 mV for the entire test set. This method could be used to predict the reduction potentials of a variety of metal-salen compounds, an important class of coordination compounds used in synthetic organic electrochemistry as electrocatalysts.

Bateni, Sarah B; England, Kellie R; Galatti, Anthony T; Kaur, Handeep; Mendiola, Victor A; Mitchell, Alexander R; Vu, Michael H; Gherman, Benjamin F

2009-01-01

298

Mechanisms for Accessing Insoluble Fe(III) Oxide during Dissimilatory Fe(III) Reduction by Geothrix fermentans  

Microsoft Academic Search

Mechanisms for Fe(III) oxide reduction were investigated in Geothrix fermentans, a dissimilatory Fe(III)- reducing microorganism found within the Fe(III) reduction zone of subsurface environments. Culture filtrates of G. fermentans stimulated the reduction of poorly crystalline Fe(III) oxide by washed cell suspensions, suggesting that G. fermentans released one or more extracellular compounds that promoted Fe(III) oxide reduction. In order to determine

Kelly P. Nevin; Derek R. Lovley

2002-01-01

299

Microorganisms pumping iron: anaerobic microbial iron oxidation and reduction  

Microsoft Academic Search

Iron (Fe) has long been a recognized physiological requirement for life, yet for many microorganisms that persist in water, soils and sediments, its role extends well beyond that of a nutritional necessity. Fe(II) can function as an electron source for iron-oxidizing microorganisms under both oxic and anoxic conditions and Fe(III) can function as a terminal electron acceptor under anoxic conditions

Karrie A. Weber; Laurie A. Achenbach; John D. Coates

2006-01-01

300

Reactor-permeator for reduction of tritium oxide on iron  

Microsoft Academic Search

Tritiated water (QâO) is produced during fusion fuel purification or air detritiation. Before recovering the tritium by isotope separation, the QâO needs to be reduced to form Qâ gas. The reduction of tritiated water on iron is an alternative to electrolysis and gas-shift reactors. It allows a simple, compact, configuration with low tritium inventory. The reactor design incorporates a palladium

G. Modica; R. A. H. Edwards

1995-01-01

301

Radiographic Evaluation of the Potential Lung Volume Reduction Surgery Candidate  

PubMed Central

Delineating the extent and distribution of emphysema is an essential component of the evaluation of candidates for lung volume reduction surgery (LVRS). Imaging also may identify contraindications to LVRS, including bronchiectasis and pleural scarring. The chest X-ray is of limited utility in LVRS evaluation. Chest computed tomography (CT) scanning is an essential component of the evaluation, demonstrating the presence of emphysema and its amount and distribution. Clinical experience has shown that a substantial minority of chest CT scans will also demonstrate pulmonary nodules, some of which represent lung cancers. Published series, including the National Emphysema Treatment Trial, consistently demonstrate that patients with upper lobe predominant or heterogeneous emphysema are most likely to benefit from LVRS. Heterogeneity and distribution can also be assessed by radionuclide ventilation perfusion scanning, but this modality adds little additional information to CT scanning.

Washko, George R.; Hoffman, Eric; Reilly, John J.

2008-01-01

302

Radiographic evaluation of the potential lung volume reduction surgery candidate.  

PubMed

Delineating the extent and distribution of emphysema is an essential component of the evaluation of candidates for lung volume reduction surgery (LVRS). Imaging also may identify contraindications to LVRS, including bronchiectasis and pleural scarring. The chest X-ray is of limited utility in LVRS evaluation. Chest computed tomography (CT) scanning is an essential component of the evaluation, demonstrating the presence of emphysema and its amount and distribution. Clinical experience has shown that a substantial minority of chest CT scans will also demonstrate pulmonary nodules, some of which represent lung cancers. Published series, including the National Emphysema Treatment Trial, consistently demonstrate that patients with upper lobe predominant or heterogeneous emphysema are most likely to benefit from LVRS. Heterogeneity and distribution can also be assessed by radionuclide ventilation perfusion scanning, but this modality adds little additional information to CT scanning. PMID:18453349

Washko, George R; Hoffman, Eric; Reilly, John J

2008-05-01

303

Molecular Underpinnings of Fe(III) Oxide Reduction by Shewanella oneidensis MR-1  

SciTech Connect

In the absence of O2 and other electron acceptors, the Gram-negative bacterium Shewanella oneidensis MR-1 can use ferric [Fe(III)] (oxy)(hydr)oxide minerals as the terminal electron acceptors for anaerobic respiration. At circumneutral pH and in the absence of strong complexing ligands, Fe(III) oxides are relatively insoluble and thus are external to the bacterial cells. S. oneidensis MR-1 and related strains of metal-reducing Shewanella have evolved the machinery (i.e., metal-reducing or Mtr pathway) for transferring electrons from the inner-membrane, through the periplasm and across the outer-membrane to the surface of extracellular Fe(III) oxides. The protein components identified to date for the Mtr pathway include CymA, MtrA, MtrB, MtrC and OmcA. CymA is an inner-membrane tetraheme c-type cytochrome (c-Cyt) that belongs to the NapC/NrfH family of quinol dehydrogenases. It is proposed that CymA oxidizes the quinol in the inner-membrane and transfers the released electrons to redox proteins in the periplasm. Although the periplasmic proteins receiving electrons from CymA during Fe(III) oxidation have not been identified, they are believed to relay the electrons in the periplasm to MtrA. A decaheme c-Cyt, MtrA is thought to be embedded in the trans outer-membrane and porin-like protein MtrB. Together, MtrAB deliver the electrons through the outer-membrane to the MtrC and OmcA on the outmost bacterial surface. MtrC and OmcA are the outer-membrane decaheme c-Cyts that are translocated across the outer-membrane by the bacterial type II secretion system. Functioning as terminal reductases, MtrC and OmcA can bind the surface of Fe(III) oxides and transfer electrons directly to these minerals via their solvent-exposed hemes. To increase their reaction rates, MtrC and OmcA can use the flavins secreted by S. oneidensis MR-1 cells as diffusible co-factors for reduction of Fe(III) oxides. Because of their extracellular location and broad redox potentials, MtrC and OmcA can also serve as the terminal reductases for soluble forms of Fe(III). Although our understanding of the Mtr pathway is still far from complete, it is the best characterized microbial pathway used for extracellular electron exchange. Characterizations of the Mtr pathway have made significant contributions to the molecular understanding of microbial reduction of Fe(III) oxides.

Shi, Liang; Rosso, Kevin M.; Clarke, Thomas A.; Richardson, David J.; Zachara, John M.; Fredrickson, Jim K.

2012-02-15

304

Influence of the oxidizing species on the reactivity of iron-based Bimetallic reductants.  

PubMed

Anticipating which pollutants are amenable to treatment by iron-based bimetallic reductants requires an understanding of the mechanism(s) driving pollutant reduction. Here, batch studies with six bimetals (Au/Fe, Co/Fe, Cu/Fe, Ni/ Fe, Pd/Fe, and Pt/Fe) and four oxidants (alkyl polyhalides, vinyl polyhalides, alkynes, and water) explored the influence of the electron acceptor on reductant reactivity. Bimetals exhibited disparate reactivity toward some oxidant classes. For example, Pt/Fe enhanced rates of cis-dichloroethylene reduction, but it inhibited the reduction of several alkyl polyhalides. Moreover, the rate increase for vinyl polyhalide reduction by Ni/Fe (approximately 100-fold) and Pd/Fe (approximately 1000-fold) was far greater than that measured for alkyl polyhalides (approximately 10-fold), and reactivity toward vinyl polyhalides exhibited a more pronounced dependence on Ni and Pd loadings than did reactivity toward alkyl polyhalides. These results suggest that the reactions of alkyl and vinyl polyhalides with iron-based bimetals involve different active reductants. Neither rates of alkyl nor vinyl polyhalide reduction correlated with rates of iron corrosion by water, contrary to expectations if galvanic corrosion was primarily responsible for organohalide reduction. Trends observed for the hydrogenation of 2-butyne did mirror the sequence we identified for 1,1,1-trichloroethane reduction, consistent with a role for atomic hydrogen as the principal electron donor in these two systems. PMID:17547205

Cwiertny, David M; Bransfield, Stephen J; Roberts, A Lynn

2007-05-15

305

Sulfonamide antibiotic reduction in aquatic environment by application of fenton oxidation process.  

PubMed

Presence of antibiotics in the environment may cause potential risk for aquatic environment and organisms. In this research, Fenton oxidation process was offered as an effective method for removal of antibiotic sulfamethoxazole from aqueous solutions. The experiments were performed on laboratory-scale study under complete mixing at 25±2°C. The effects of initial antibiotic concentration, molar ratio of H2O2/Fe+2, solution pH, concentration of H2O2, Fe+2 and reaction time was studied on the oxidation of sulfamethoxazole in three level. The results indicated that the optimal parameters for Fenton process were as follows: molar ratio of [H2O2]/[Fe+2] = 1.5, pH= 4.5, and contact time= 15 min. In this situation, the antibiotic removal and COD reduction were achieved 99.99% and 64.7-70.67%, respectively. Although, Fenton reaction could effectively degrade antibiotic sulfamethoxazole under optimum experimental conditions, however, the rate of mineralization was not completed. This process can be considered to eliminate other refractory antibiotics with similar structure or to increase their biodegradability. PMID:23570238

Dehghani, Somayyeh; Jonidi Jafari, Ahmad; Farzadkia, Mahdi; Gholami, Mitra

2013-04-09

306

Evaluation of tire-derived fuel for use in nitrogen oxide reduction by reburning.  

PubMed

Tire-derived fuel (TDF) was tested in a small-scale (44 kW or 150,000 Btu/hr) combustor to determine its feasibility as a fuel for use in reburning for control of nitrogen oxide (NO). TDF was gravity-fed into upward flowing combustion gases from a primary natural gas flame doped with ammonia to simulate a high NO combustion process. Emissions of NO, oxygen, carbon dioxide, carbon monoxide, and particulate matter were measured. The tests varied the nominal primary NO level from 600 to 1,200 ppm and the primary stoichiometry from 1.1 to 1.2, and used both natural gas and TDF as reburn fuels. The reburn injection rate was varied to achieve 8-20% of the total heat input from the reburn fuel. NO emissions reductions ranged between 20 and 63% when using TDF, depending upon the rate of TDF injection, primary NO, and primary stoichiometry. NO emission reductions when using natural gas as the reburn fuel were consistently higher than those when using TDF. While additional work remains to optimize the process and evaluate costs, TDF has been shown to have the potential to be a technically viable reburning fuel. PMID:9739625

Miller, C A; Lemieux, P M; Touati, A

1998-08-01

307

Electric-field control of magnetism by reversible surface reduction and oxidation reactions  

NASA Astrophysics Data System (ADS)

Electric control of magnetism is a vision which drives intense research on magnetic semiconductors and multiferroics. Recently, ultrathin metallic films were also reported to show magnetoelectric effects at room temperature. Here we demonstrate much stronger effects by exploiting reduction/oxidation reactions in a naturally grown oxide layer exchange coupled to an underlying ferromagnet. For the exemplarily studied FePt/iron oxide composite in an electrolyte, a large and reversible change of magnetization and anisotropy is obtained. The principle can be transferred to various metal/oxide combinations. It represents an approach towards multifunctionality.

Leistner, K.; Wunderwald, J.; Lange, N.; Oswald, S.; Richter, M.; Zhang, H.; Schultz, L.; Fähler, S.

2013-06-01

308

The high-temperature oxidation, reduction, and volatilization reactions of silicon and silicon carbide  

Microsoft Academic Search

A thermochemical analysis was made of the oxidation, reduction, and volatilization reactions which occur in the Si-O-C system. One characteristic feature is the high SiO(g) and SiO(g) + CO(g) pressures at the Si(s)-SiO2 and SiC(s)-SiO2(s) interfaces. Active oxidation with weight losses and passive oxidation with weight gains were found on oxidizing Si(s) and SiC(s) in low oxygen pressures above 1000°C.

Earl A. Gulbransen; Sven A. Jansson

1972-01-01

309

Identifying active surface phases for metal oxide electrocatalysts: a study of manganese oxide bi-functional catalysts for oxygen reduction and water oxidation catalysis.  

PubMed

Progress in the field of electrocatalysis is often hampered by the difficulty in identifying the active site on an electrode surface. Herein we combine theoretical analysis and electrochemical methods to identify the active surfaces in a manganese oxide bi-functional catalyst for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). First, we electrochemically characterize the nanostructured ?-Mn(2)O(3) and find that it undergoes oxidation in two potential regions: initially, between 0.5 V and 0.8 V, a potential region relevant to the ORR and, subsequently, between 0.8 V and 1.0 V, a potential region between the ORR and the OER relevant conditions. Next, we perform density function theory (DFT) calculations to understand the changes in the MnO(x) surface as a function of potential and to elucidate reaction mechanisms that lead to high activities observed in the experiments. Using DFT, we construct surface Pourbaix and free energy diagrams of three different MnO(x) surfaces and identify 1/2 ML HO* covered Mn(2)O(3) and O* covered MnO(2), as the active surfaces for the ORR and the OER, respectively. Additionally, we find that the ORR occurs through an associative mechanism and that its overpotential is highly dependent on the stabilization of intermediates through hydrogen bonds with water molecules. We also determine that OER occurs through direct recombination mechanism and that its major source of overpotential is the scaling relationship between HOO* and HO* surface intermediates. Using a previously developed Sabatier model we show that the theoretical predictions of catalytic activities match the experimentally determined onset potentials for the ORR and the OER, both qualitatively and quantitatively. Consequently, the combination of first-principles theoretical analysis and experimental methods offers an understanding of manganese oxide oxygen electrocatalysis at the atomic level, achieving fundamental insight that can potentially be used to design and develop improved electrocatalysts for the ORR and the OER and other important reactions of technological interest. PMID:22990481

Su, Hai-Yan; Gorlin, Yelena; Man, Isabela C; Calle-Vallejo, Federico; Nørskov, Jens K; Jaramillo, Thomas F; Rossmeisl, Jan

2012-09-18

310

Anaerobic methane oxidation in metalliferous hydrothermal sediments: influence on carbon flux and decoupling from sulfate reduction.  

PubMed

The anaerobic oxidation of methane (AOM) is a globally significant sink that regulates methane flux from sediments into the oceans and atmosphere. Here we examine mesophilic to thermophilic AOM in hydrothermal sediments recovered from the Middle Valley vent field, on the Juan de Fuca Ridge. Using continuous-flow sediment bioreactors and batch incubations, we characterized (i) the degree to which AOM contributes to net dissolved inorganic carbon flux, (ii) AOM and sulfate reduction (SR) rates as a function of temperature and (iii) the distribution and density of known anaerobic methanotrophs (ANMEs). In sediment bioreactors, inorganic carbon stable isotope mass balances results indicated that AOM accounted for between 16% and 86% of the inorganic carbon produced, underscoring the role of AOM in governing inorganic carbon flux from these sediments. At 90°C, AOM occurred in the absence of SR, demonstrating a striking decoupling of AOM from SR. An abundance of Fe(III)-bearing minerals resembling mixed valent Fe oxides, such as green rust, suggests the potential for a coupling of AOM to Fe(III) reduction in these metalliferous sediments. While SR bacteria were only observed in cooler temperature sediments, ANMEs allied to ANME-1 ribotypes, including a putative ANME-1c group, were found across all temperature regimes and represented a substantial proportion of the archaeal community. In concert, these results extend and reshape our understanding of the nature of high temperature methane biogeochemistry, providing insight into the physiology and ecology of thermophilic anaerobic methanotrophy and suggesting that AOM may play a central role in regulating biological dissolved inorganic carbon fluxes to the deep ocean from the organic-poor, metalliferous sediments of the global mid-ocean ridge hydrothermal vent system. PMID:22827909

Wankel, Scott D; Adams, Melissa M; Johnston, David T; Hansel, Colleen M; Joye, Samantha B; Girguis, Peter R

2012-07-25

311

Limitation of Acetylene Reduction (Nitrogen Fixation) by Photosynthesis in Soybean Having Low Water Potentials 1  

PubMed Central

The role of photosynthesis and transpiration in the desiccation-induced inhibition of acetylene reduction (nitrogen fixation) was investigated in soybean (Glycine max [L.] Merr. var. Beeson) using an apparatus that permitted simultaneous measurements of acetylene reduction, net photosynthesis, and transpiration. The inhibition of acetylene reduction caused by low water potentials and their aftereffects could be reproduced by depriving shoots of atmospheric CO2 even though the soil remained at water potentials that should have favored rapid acetylene reduction. The inhibition of acetylene reduction at low water potentials could be partially reversed by exposing the shoots to high CO2 concentrations. When transpiration was varied independently of photosynthesis and dark respiration in plants having high water potentials, no effects on acetylene reduction could be observed. There was no correlation between transpiration and acetylene reduction in the CO2 experiments. Therefore, the correlation that was observed between transpiration and acetylene reduction during desiccation was fortuitous. We conclude that the inhibition of shoot photosynthesis accounted for the inhibition of nodule acetylene reduction at low water potentials.

Huang, Chi-Ying; Boyer, John S.; Vanderhoef, Larry N.

1975-01-01

312

Consistency of Kaluza-Klein sphere reductions of symmetric potentials  

NASA Astrophysics Data System (ADS)

In a recent paper, the complete (nonlinear) Kaluza-Klein Ansatz for the consistent embedding of certain scalar plus gravity subsectors of gauged maximal supergravity in D=4, 5, and 7 was presented in terms of sphere reductions from D=11 or type-IIB supergravity. The scalar fields included in the truncations were the diagonal fields in the SL(N,R)/SO(N) scalar submanifolds of the full scalar sectors of the corresponding maximal supergravities, with N=8, 6, and 5. The embeddings were used for obtaining an interpretation of extremal D=4, 5, or 7 AdS domain walls in terms of distributed M-branes or D-branes in the higher dimensions. Although strong supporting evidence for the correctness of the embedding Ansätze was presented, a full proof of the consistency was not given. Here we complete the proof by showing explicitly that the full set of higher-dimensional equations of motion is satisfied if and only if the lower-dimensional fields satisfy the relevant scalar plus gravity equations.

Cveti?, M.; Lü, H.; Pope, C. N.; Sadrzadeh, A.

2000-08-01

313

Quantifying food losses and the potential for reduction in Switzerland.  

PubMed

A key element in making our food systems more efficient is the reduction of food losses across the entire food value chain. Nevertheless, food losses are often neglected. This paper quantifies food losses in Switzerland at the various stages of the food value chain (agricultural production, postharvest handling and trade, processing, food service industry, retail, and households), identifies hotspots and analyses the reasons for losses. Twenty-two food categories are modelled separately in a mass and energy flow analysis, based on data from 31 companies within the food value chain, and from public institutions, associations, and from the literature. The energy balance shows that 48% of the total calories produced (edible crop yields at harvest time and animal products, including slaughter waste) is lost across the whole food value chain. Half of these losses would be avoidable given appropriate mitigation measures. Most avoidable food losses occur at the household, processing, and agricultural production stage of the food value chain. Households are responsible for almost half of the total avoidable losses (in terms of calorific content). PMID:23270687

Beretta, Claudio; Stoessel, Franziska; Baier, Urs; Hellweg, Stefanie

2012-12-25

314

Reduction of Iron-Oxide-Carbon Composites: Part I. Estimation of the Rate Constants  

NASA Astrophysics Data System (ADS)

A new ironmaking concept using iron-oxide-carbon composite pellets has been proposed, which involves the combination of a rotary hearth furnace (RHF) and an iron bath smelter. This part of the research focuses on studying the two primary chemical kinetic steps. Efforts have been made to experimentally measure the kinetics of the carbon gasification by CO2 and wüstite reduction by CO by isolating them from the influence of heat- and mass-transport steps. A combined reaction model was used to interpret the experimental data and determine the rate constants. Results showed that the reduction is likely to be influenced by the chemical kinetics of both carbon oxidation and wüstite reduction at the temperatures of interest. Devolatilized wood-charcoal was observed to be a far more reactive form of carbon in comparison to coal-char. Sintering of the iron-oxide at the high temperatures of interest was found to exert a considerable influence on the reactivity of wüstite by virtue of altering the internal pore surface area available for the reaction. Sintering was found to be predominant for highly porous oxides and less of an influence on the denser ores. It was found using an indirect measurement technique that the rate constants for wüstite reduction were higher for the porous iron-oxide than dense hematite ore at higher temperatures (>1423 K). Such an indirect mode of measurement was used to minimize the influence of sintering of the porous oxide at these temperatures.

Halder, S.; Fruehan, R. J.

2008-12-01

315

Potential genotoxicity of chronically elevated nitric oxide: A review  

Microsoft Academic Search

Several human cancers are associated with chronic bacterial, viral and parasitic infections. Nitric oxide, which is a short-lived free radical produced by many types of cells for a number of important physiological functions, is elevated in these infections. Long-term exposure to elevated NO · cells could have potential genotoxic effects on hosts. There are at least three mechanisms by which

Rui Hai Liu; Joseph H. Hotchkiss

1995-01-01

316

CLINICAL RESEARCH • Potential oxidative stress in children with chronic constipation  

Microsoft Academic Search

AIM: To investigate the potential oxidative stress in children with chronic constipation and to explore its mechanisms. METHODS: Seventy children with chronic constipation and 70 age- and sex-matched healthy children were enrolled in a randomized controlled study. Plasma levels of vitamins C and E, activities of superoxide dismutase and catalase and lipoperoxide level in erythrocytes were determined by spectrophotometry. RESULTS:

Jun-Fu Zhou; Jian-Guo Lou; Sheng-Li Zhou; Ji-Yue Wang

317

Remote fabrication and irradiation test of recycled nuclear fuel prepared by the oxidation and reduction of spent oxide fuel  

NASA Astrophysics Data System (ADS)

A direct dry recycling process was developed in order to reuse spent pressurized light water reactor (LWR) nuclear fuel in CANDU reactors without the separation of sensitive nuclear materials such as plutonium. The benefits of the dry recycling process are the saving of uranium resources and the reduction of spent fuel accumulation as well as a higher proliferation resistance. In the process of direct dry recycling, fuel pellets separated from spent LWR fuel rods are oxidized from UO2 to U3O8 at 500 °C in an air atmosphere and reduced into UO2 at 700 °C in a hydrogen atmosphere, which is called OREOX (oxidation and reduction of oxide fuel). The pellets are pulverized during the oxidation and reduction processes due to the phase transformation between cubic UO2 and orthorhombic U3O8. Using the oxide powder prepared from the OREOX process, the compaction and sintering processes are performed in a remote manner in a shielded hot cell due to the high radioactivity of the spent fuel. Most of the fission gas and volatile fission products are removed during the OREOX and sintering processes. The mini-elements fabricated by the direct dry recycling process are irradiated in the HANARO research reactor for the performance evaluation of the recycled fuel pellets. Post-irradiation examination of the irradiated fuel showed that microstructural evolution and fission gas release behavior of the dry-recycled fuel were similar to high burnup UO2 fuel.

Jin Ryu, Ho; Chan Song, Kee; Il Park, Geun; Won Lee, Jung; Seung Yang, Myung

2005-02-01

318

Potential CO2 Emission Reduction by Development of Non-Grain-Based Bioethanol in China  

NASA Astrophysics Data System (ADS)

Assessment of the potential CO2 emission reduction by development of non-grain-based ethanol in China is valuable for both setting up countermeasures against climate change and formulating bioethanol policies. Based on the land occupation property, feedstock classification and selection are conducted, identifying sweet sorghum, cassava, and sweet potato as plantation feedstocks cultivated from low-quality arable marginal land resources and molasses and agricultural straws as nonplantation feedstocks derived from agricultural by-products. The feedstock utilization degree, CO2 reduction coefficient of bioethanol, and assessment model of CO2 emission reduction potential of bioethanol are proposed and established to assess the potential CO2 emission reduction by development of non-grain-based bioethanol. The results show that China can obtain emission reduction potentials of 10.947 and 49.027 Mt CO2 with non-grain-based bioethanol in 2015 and 2030, which are much higher than the present capacity, calculated as 1.95 Mt. It is found that nonplantation feedstock can produce more bioethanol so as to obtain a higher potential than plantation feedstock in both 2015 and 2030. Another finding is that developing non-grain-based bioethanol can make only a limited contribution to China’s greenhouse gas emission reduction. Moreover, this study reveals that the regions with low and very low potentials for emission reduction will dominate the spatial distribution in 2015, and regions with high and very high potentials will be the majority in 2030.

Li, Hongqiang; Wang, Limao; Shen, Lei

2010-10-01

319

DEVELOPMENT OF IMPROVED CATALYSTS FOR THE SELECTIVE CATALYTIC REDUCTION OF NITROGEN OXIDES WITH HYDROCARBONS  

SciTech Connect

Significant work has been done by the investigators on the cerium oxide-copper oxide based sorbent/catalysts for the combined removal of sulfur and nitrogen oxides from the flue gases of stationary sources. A relatively wide temperature window was established for the use of alumina-supported cerium oxide-copper oxide mixtures as regenerable sorbents for SO{sub 2} removal. Preliminary evaluation of these sorbents as catalysts for the selective reduction of NO{sub x} gave promising results with ammonia, but indicated low selectivity when methane was used as the reductant. Since the replacement of ammonia by another reductant is commercially very attractive, in this project, four research components will be undertaken. The investigation of the reaction mechanism, the first component, will help in the selection of promoters to improve the catalytic activity and selectivity of the sorbents in the SCR with methane. This will result in new catalyst formulations (second component). If this research is successful, the combined SO{sub 2}-NO{sub x} removal process based on alumina-supported copper oxide-ceria sorbent/catalysts will become very attractive for commercial applications. The objective of the third component of the project is to develop an alternative SCR process using another inexpensive fuel, residual fuel oil, instead of natural gas. This innovative proposal is based on very scant evidence concerning the good performance of coked catalysts in the selective reduction of NO and if proven to work the process will certainly be commercially viable. The fourth component of the project involves our industrial partner TDA Research, and the objective is to evaluate long-term stability and durability of the prepared sorbent/catalysts. In the first year of the project, the catalysts were investigated by the temperature-programmed reduction (TPR) technique. The results from TPR indicated that the interaction with support appears to promote reduction at lower temperatures. Copper oxide in excess of monolayer coverage reduces at temperatures close to the reduction temperature of the unsupported copper oxide. Increased dispersion increases the support effect. Low activity of ceria in NO reduction may be due to its resistance to reduction at low temperatures.

Dr. Ates Akyurtlu; Dr. Jale F. Akyurtlu

2001-05-31

320

Personal carbon trading: a potential "stealth intervention" for obesity reduction?  

PubMed

The obesity epidemic and global warming are linked through energy use. A personal carbon trading scheme aimed at reducing fossil fuel usage could act as a "stealth intervention" for reducing obesity by increasing personal energy use. Such a scheme would complement a corporate "cap and trade" system for carbon emissions, which should increase the relative price of processed, energy-dense foods. The scheme would work by reducing global carbon emissions to a sustainable level (contraction), while offering potential for trade of emission rights between frugal and profligate users of non-renewable energy (convergence). A key goal would be changed attitudes to conspicuous (and obesogenic) consumption. Adoption of the scheme would make healthy choices the easy choice. PMID:17680749

Egger, Garry

2007-08-01

321

Microsensor Measurements of Sulfate Reduction and Sulfide Oxidation in Compact Microbial Communities of Aerobic Biofilms  

PubMed Central

The microzonation of O2 respiration, H2S oxidation, and SO42- reduction in aerobic trickling-filter biofilms was studied by measuring concentration profiles at high spatial resolution (25 to 100 ?m) with microsensors for O2, S2-, and pH. Specific reaction rates were calculated from measured concentration profiles by using a simple one-dimensional diffusion reaction model. The importance of electron acceptor and electron donor availability for the microzonation of respiratory processes and their reaction rates was investigated. Oxygen respiration was found in the upper 0.2 to 0.4 mm of the biofilm, whereas sulfate reduction occurred in deeper, anoxic parts of the biofilm. Sulfate reduction accounted for up to 50% of the total mineralization of organic carbon in the biofilms. All H2S produced from sulfate reduction was reoxidized by O2 in a narrow reaction zone, and no H2S escaped to the overlying water. Turnover times of H2S and O2 in the reaction zone were only a few seconds owing to rapid bacterial H2S oxidation. Anaerobic H2S oxidation with NO3- could be induced by addition of nitrate to the medium. Total sulfate reduction rates increased when the availability of SO42- or organic substrate increased as a result of deepening of the sulfate reduction zone or an increase in the sulfate reduction intensity, respectively.

Kuhl, Michael; J?rgensen, Bo Barker

1992-01-01

322

Immobilization of strontium during iron biomineralization coupled to dissimilatory hydrous ferric oxide reduction  

SciTech Connect

Abstract: The potential for incorporation of strontium (Sr) into biogenic Fe(II)-bearing minerals formed during microbial reduction of synthetic hydrous ferric oxide (HFO) was investigated in circumneutral bicarbonate-buffered medium containing SrCl2 at concentrations of 10 muM, 100 muM, or 1.0 mM. CaCl2 (10 mM) was added to some experiments to simulate a Ca-rich groundwater. In Ca-free systems, 89 to 100% of total Sr was captured in solid-phase compounds formed during reduction of 30 to 40 mmol Fe(III) L-1 over a 1-month period. A smaller fraction of total Sr (25 to 34%) was incorporated into the solid phase in cultures amended with 10 mM CaCl2. X-ray diffraction identified siderite and ferroan ankerite as major end products of HFO reduction in Ca-free and Ca-amended cultures, respectively. Scanning electron microscopy-energy dispersive x-ray spectroscopy revealed the presence of Sr associated with carbonate phases. Selective extraction of HFO reduction end products indicated that 46 to 100% of the solid-phase Sr was associated with carbonates. The sequestration of Sr into carbonate phases in the Ca-free systems occurred systematically according to a heterogeneous (Doerner-Hoskins) partition coefficient (DD-H) of 1.81+/-0.15. This DD-H value was 2 to 10 times higher than values determined for incorporation of Sr (10 muM) into FeCO3(S) precipitated abiotically at rates comparable to or greater than rates observed during HFO reduction, and fivefold higher than theoretical partition coefficients for equilibrium Fe(Sr)CO3 solid solution formation. Surface complexation and entrapment of Sr by rapidly growing siderite crystals (and possibly other biogenic Fe(II) solids) provides an explanation for the intensive scavenging of Sr in the Ca-free systems. The results of abiotic siderite precipitation experiments in the presence and absence of excess Ca indicate that substitution of Ca for Sr at foreign element incorporation sites (mass action effect) on growing FeCO3(S) surfaces can account for the inhibition of Sr incorporation into the siderite component of ankerite formed in the Ca-amended HFO reduction experiments. Likewise, substitution of Fe(II) for Sr may explain the absence of major Sr partitioning into the calcite component of ankerite. The findings indicate that under appropriate conditions, sequestration of metals in siderite produced during bacterial Fe(III) oxide reduction may provide a mechanism for retarding the migration of Sr and other divalent metal contaminants in anaerobic, carbonate-rich sedimentary environments. Copyright (C) 2002 Elsevier Science Ltd.

Roden, Eric E.; Leonardo, Michael R.; Ferris, F. G.

2002-08-15

323

Visible light-mediated atom transfer radical addition via oxidative and reductive quenching of photocatalysts.  

PubMed

Herein, the development of visible light-mediated atom transfer radical addition (ATRA) of haloalkanes onto alkenes and alkynes using the reductive and oxidative quenching of [Ir{dF(CF(3))ppy}(2)(dtbbpy)]PF(6) and [Ru(bpy)(3)]Cl(2) is presented. Initial investigations indicated that the oxidative quenching of photocatalysts could effectively be utilized for ATRA, and since that report, the protocol has been expanded by broadening the scope of the reaction in terms of the photocatalysts, substrates, and solvents. In addition, further modifications of the reaction conditions allowed for the efficient ATRA of perfluoroalkyl iodides onto alkenes and alkynes utilizing the reductive quenching cycle of [Ru(bpy)(3)]Cl(2) with sodium ascorbate as the sacrificial electron donor. These results signify the complementary nature of the oxidative and reductive quenching pathways of photocatalysts and the ability to predictably direct reaction outcome through modification of the reaction conditions. PMID:22486313

Wallentin, Carl-Johan; Nguyen, John D; Finkbeiner, Peter; Stephenson, Corey R J

2012-05-16

324

Use of chiral liquid chromatography for the evaluation of stereospecificity in the carbonyl reduction of potential benzo[ c]fluorene antineoplastics benfluron and dimefluron in various species  

Microsoft Academic Search

Benfluron (B) [5-(2-dimethylaminoethoxy)-7H-benzo[c]fluorene-7-one hydrochloride] is a potential antineoplastic agent. In the organism, B undergoes a rapid phase I biotransformation through oxidative and reductive metabolic pathways. The carbonyl reduction of B leads to reduced benfluron, red-B, this is one of the principal pathways for the deactivation of this compound.The structure of B was modified to suppress its rapid deactivation via the

R. Ku?era; M. Nobilis; L. Skálová; B. Szotáková; P. Císa?; Th. Jira; J. Klimeš; V. Wsól

2005-01-01

325

Enhanced wastewater treatment efficiency through microbially catalyzed oxidation and reduction: synergistic effect of biocathode microenvironment.  

PubMed

Microbially catalyzed treatment of wastewater was evaluated in both the anode and cathode chambers in dual chambered microbial fuel cell (MFC) under varying biocathode microenvironment. MFC operation with aerobic biocathode showed significant increment in both TDS (cathode, 90.2±1%; anode, 39.7±0.5%) and substrate (cathode, 98.07±0.06%; anode, 96.2±0.3%) removal compared to anaerobic biocathode and abiotic cathode operations (COD, 80.25±0.3%; TDS, 30.5±1.2%). Microbially catalyzed reduction of protons and electrons at cathode will be higher during aerobic biocathode operation which leads to gradual substrate removal resulting in stable bio-potential for longer periods facilitating salts removal. Bio-electro catalytic behavior showed higher exchange current density during aerobic biocathode operation resulting in induced electrochemical oxidation which supports the enhanced treatment. Anaerobic biocathode operation depicted relatively less TDS removal (anode, 16.35%; cathode, 16.04%) in both the chambers in spite of good substrate degradation (anode, 84%; cathode, 87.39%). Both the chambers during anaerobic biocathode operation competed as electron donors resulting in negligible bio-potential development. PMID:21920735

Mohan, S Venkata; Srikanth, S

2011-08-16

326

Reduction of nitric oxide by hydroxylamine. 1. Kinetics and mechanism  

SciTech Connect

The reaction of nitric oxide with hydroxylamine conforms to the rate law -dP/sub NO//dt = k/sub 2/(NH/sub 2/O/sup -/)P/sub NO/ in the pH range 7.29-13.14, confirming the rate-determining abstraction of an N-bound H atom by NO. Measured kinetic quantities: k/sub 2/ = 6.68 x 10/sup -3/ M/sup -1/ s/sup -1/ at 25/sup 0/C; ..delta.. H double dagger = 29.6 kJ mol/sup -1/; ..delta.. S double dagger = -189 J K/sup -1/ mol/sup -1/. Thermodynamic values have been obtained for the pK/sub a/ of NH/sub 2/OH at several temperatures; ..delta.. H of dissociation = 55.29 kJ mol/sup -1/. The presence of trace amounts of O/sub 2/ in the NO-NH/sub 2/OH reaction system catalyzes the reaction and leads to a reduced molar product ratio n/sub N/sub 2/O/, effects that are ascribed at least in part to reactive N/sub 2/O/sub 3/. The difference in reactivity between the NO/sup -/ intermediate formed in this reaction and that produced in trioxodinitrate decomposition is discussed.

Bonner, F.T.; Wang, N.Y.

1986-05-21

327

Energy conservation via electron bifurcating ferredoxin reduction and proton/Na(+) translocating ferredoxin oxidation.  

PubMed

The review describes four flavin-containing cytoplasmatic multienzyme complexes from anaerobic bacteria and archaea that catalyze the reduction of the low potential ferredoxin by electron donors with higher potentials, such as NAD(P)H or H(2) at ? 100 kPa. These endergonic reactions are driven by concomitant oxidation of the same donor with higher potential acceptors such as crotonyl-CoA, NAD(+) or heterodisulfide (CoM-S-S-CoB). The process called flavin-based electron bifurcation (FBEB) can be regarded as a third mode of energy conservation in addition to substrate level phosphorylation (SLP) and electron transport phosphorylation (ETP). FBEB has been detected in the clostridial butyryl-CoA dehydrogenase/electron transferring flavoprotein complex (BcdA-EtfBC), the multisubunit [FeFe]hydrogenase from Thermotoga maritima (HydABC) and from acetogenic bacteria, the [NiFe]hydrogenase/heterodisulfide reductase (MvhADG-HdrABC) from methanogenic archaea, and the transhydrogenase (NfnAB) from many Gram positive and Gram negative bacteria and from anaerobic archaea. The Bcd/EtfBC complex that catalyzes electron bifurcation from NADH to the low potential ferredoxin and to the high potential crotonyl-CoA has already been studied in some detail. The bifurcating protein most likely is EtfBC, which in each subunit (??) contains one FAD. In analogy to the bifurcating complex III of the mitochondrial respiratory chain and with the help of the structure of the human ETF, we propose a conformational change by which ?-FADH(-) in EtfBC approaches ?-FAD to enable the bifurcating one-electron transfer. The ferredoxin reduced in one of the four electron bifurcating reactions can regenerate H(2) or NADPH, reduce CO(2) in acetogenic bacteria and methanogenic archaea, or is converted to ??H(+)/Na(+) by the membrane-associated enzyme complexes Rnf and Ech, whereby NADH and H(2) are recycled, respectively. The mainly bacterial Rnf complexes couple ferredoxin oxidation by NAD(+) with proton/sodium ion translocation and the more diverse energy converting [NiFe]hydrogenases (Ech) do the same, whereby NAD(+) is replaced by H(+). Many organisms also use Rnf and Ech in the reverse direction to reduce ferredoxin driven by ??H(+)/Na(+). Finally examples are shown, in which the four bifurcating multienzyme complexes alone or together with Rnf and Ech are integrated into energy metabolisms of nine anaerobes. This article is part of a Special Issue entitled: The evolutionary aspects of bioenergetic systems. PMID:22800682

Buckel, Wolfgang; Thauer, Rudolf K

2012-07-16

328

Sulfide Alleviation of the Acetylene Inhibition of Nitrous Oxide Reduction in Soil  

PubMed Central

The alleviation of the acetylene blockage of nitrous oxide reduction by sulfide was studied in anaerobically incubated Brookston soil to better characterize the process. Removal of nitrate-derived nitrous oxide from soil amended with acetylene and sulfide occurred earlier in the presence of glucose than it did in its absence. This was attributed to the influence of glucose on nitrous oxide production rather than reduction during the early stages of the soil incubation. Glucose was found to have no effect on reduction of injected nitrous oxide in the presence of acetylene- and sulfide-amended soil, whereas carbon dioxide significantly stimulated reduction. It is suggested that the microorganism(s) involved may use carbon dioxide as a cellular carbon source. The sulfide added to the soil probably did not act solely as an electron donor, as the number of electrons required to reduce the added nitrous oxide in our systems was greater than the amount supplied by the sulfide. The soil pH at which the alleviation occurred was 6.7 and was not affected by the sulfide treatment.

Evans, David G.; Beauchamp, Eric; Trevors, Jack T.

1985-01-01

329

In-situ Resistive Measurements of Graphite Oxide Reduction for Spin-Transport Based Devices  

Microsoft Academic Search

In this work, the thermal reduction to graphene of single and few-layer graphite oxide (GO) was characterized as a function of time using in-situ, four-point resistivity measurements. GO was produced chemically using a modified Hummer's method and then spray deposited onto an oxidized Si wafer. 100 nm Au with a 5 nm Cr adhesion layer was thermally evaporated onto the

Ira Jewell; Chien-Chih Huang; Sean Smith; Ashley Mason; Albrecht Jander; John Conley

2010-01-01

330

Reduction of nitrogen oxide blow-out on Kansko-Achinsk coal combustion  

Microsoft Academic Search

Measurements made of the Krasnoyarsk energy systems showed that nitrogen oxide concentration on combustion of Kansko-Achinsk basin coal in solid-bottom furnaces is slightly less than in boilers of the same capacity during combustion of Ekibastuz, Donbas, and Juznetsk coal. Special studies were conducted to clarify a possible reduction in nitrogen oxide blow-out. It is concluded that recirculation of 15% of

V. R. Kotler; S. I. Suchkov; S. V. Sryvkov; G. V. Lobov

1979-01-01

331

Oxygen reduction behavior of rutile-type iridium oxide in sulfuric acid solution  

Microsoft Academic Search

Two different forms of rutile-type iridium oxide catalysts were prepared: IrO2-coated titanium plate electrocatalysts prepared by a dip-coating method (IrO2\\/Ti) and iridium oxide nanoparticles (IrO2) prepared by a wet method, the Adams fusion method. The catalytic behavior of the oxygen reduction reaction (ORR) was evaluated by cyclic voltammetry in 0.5M H2SO4 at 60°C. Both catalysts were found to exhibit considerable

Norihiro Yoshinaga; Wataru Sugimoto; Yoshio Takasu

2008-01-01

332

Elimination or reduction of magnesium oxide as the engineered barrier at the waste isolation pilot plant  

NASA Astrophysics Data System (ADS)

The EPA certification requires the DOE to emplace MgO adjacent to each contact handled (CH) TRU waste container for a total of 85,600 tons of magnesium oxide. Shortly after certification and prior to receiving any waste, the DOE Carlsbad Area Office (DOE/CAO) expressed a desire to reduce or eliminate the use of magnesium oxide. Elimination or reduction in the amount of MgO reopens a litany of concerns raised during the certification process. .

Silva, Matthew K.

2000-07-01

333

Contribution of oxidative-reductive reactions to high-molecular-weight hyaluronan catabolism.  

PubMed

Since the content of hyaluronan (HA)-degrading enzymes in synovial fluid (SF), if any, is extremely low, the high rate of HA turnover in SF is to result from a cause different from enzymatic catabolism. An alternative and plausible mechanism is that of oxidative-reductive degradation of HA chains by a combined action of oxygen and transition metal cations maintained in a reduced oxidation state by ascorbate. PMID:17193206

Soltés, Ladislav; Stankovská, Monika; Kogan, Grigorij; Gemeiner, Peter; Stern, Robert

2005-09-01

334

Direct electrochemical reduction of solid uranium oxide in molten fluoride salts  

Microsoft Academic Search

The direct electrochemical reduction of UO2 solid pellets was carried out in LiF–CaF2 (+2mass.% Li2O) at 850°C. An inert gold anode was used instead of the usual reactive sacrificial carbon anode. In this case, oxidation of oxide ions present in the melt yields O2 gas evolution on the anode. Electrochemical characterisations of UO2 pellets were performed by linear sweep voltammetry

Mathieu Gibilaro; Laurent Cassayre; Olivier Lemoine; Laurent Massot; Olivier Dugne; Rikard Malmbeck; Pierre Chamelot

2011-01-01

335

Catalytic reduction of nitric oxide by methane over CaO catalyst  

Microsoft Academic Search

The selective catalytic reduction of nitric oxide by methane was studied over CaO catalyst in a bubbling fluidized bed in\\u000a the temperature range of 800–900 °C, in which NO cannot be reduced by CH4 without CaO catalyst. The nitric oxide conversion was found to depend on oxygen and CH4 feed concentration, and also on temperature. In addition, the presence of

Wei Xu; Huiling Tong; Changhe Chen; Xuchang Xu

2008-01-01

336

Contemporary Problems in the Selective Catalytic Reduction of Nitrogen Oxides (NO x )  

Microsoft Academic Search

The results from investigation of the processes involved in the catalytic reduction of nitrogen oxides are reviewed: 1) with carbon monoxide and other combustible gases (H2, CnHm) at a developed block honeycomb palladium-containing catalysts; 2) with ammonia (the SCR process) at vanadium-containing and complex oxide (Cu-Cr, Fe-Cr\\/?-Al2O3) catalysts; 3) with light C1-C4 hydrocarbons at cation-exchange zeolites (pentasils, natural and synthetic

S. N. Orlik

2001-01-01

337

Selective reduction of nitrogen oxides by C 3 -C 4 hydrocarbons on metal zeolite catalysts  

Microsoft Academic Search

A study was carried out on the activity of high silicon cation-exchanged zeolites containing Period IV metals (Fe, Cu, Zn, and Co) and lanthanides (La and Ce) in the reduction of nitrogen oxides by C3-C4 hydrocarbons in an oxidizing atmosphere and the kinetics of this process for the copper and cerium catalysts, which display the highest activity. The catalyst activity

S. N. Orlik; V. L. Struzhko; V. P. Stasevich; M. G. Martsenyuk-Kukharuk

1995-01-01

338

Reduction of nitrogen oxides with catalytic acid resistant aluminosilicate molecular sieves and ammonia  

Microsoft Academic Search

Noxious nitrogen oxides in a waste gas stream such as the stack gas from a fossil-fuel-fired power generation plant or other industrial plant off-gas stream is catalytically reduced to elemental nitrogen and\\/or innocuous nitrogen oxides employing ammonia as reductant in the presence of a zeolite catalyst in the hydrogen or sodium form having pore openings of about 3 to 10

D. T. Pence; T. R. Thomas

1980-01-01

339

Doping metal-organic frameworks for water oxidation, carbon dioxide reduction, and organic photocatalysis.  

PubMed

Catalytically competent Ir, Re, and Ru complexes H(2)L(1)-H(2)L(6) with dicarboxylic acid functionalities were incorporated into a highly stable and porous Zr(6)O(4)(OH)(4)(bpdc)(6) (UiO-67, bpdc = para-biphenyldicarboxylic acid) framework using a mix-and-match synthetic strategy. The matching ligand lengths between bpdc and L(1)-L(6) ligands allowed the construction of highly crystalline UiO-67 frameworks (metal-organic frameworks (MOFs) 1-6) that were doped with L(1)-L(6) ligands. MOFs 1-6 were isostructural to the parent UiO-67 framework as shown by powder X-ray diffraction (PXRD) and exhibited high surface areas ranging from 1092 to 1497 m(2)/g. MOFs 1-6 were stable in air up to 400 °C and active catalysts in a range of reactions that are relevant to solar energy utilization. MOFs 1-3 containing [Cp*Ir(III)(dcppy)Cl] (H(2)L(1)), [Cp*Ir(III)(dcbpy)Cl]Cl (H(2)L(2)), and [Ir(III)(dcppy)(2)(H(2)O)(2)]OTf (H(2)L(3)) (where Cp* is pentamethylcyclopentadienyl, dcppy is 2-phenylpyridine-5,4'-dicarboxylic acid, and dcbpy is 2,2'-bipyridine-5,5'-dicarboxylic acid) were effective water oxidation catalysts (WOCs), with turnover frequencies (TOFs) of up to 4.8 h(-1). The [Re(I)(CO)(3)(dcbpy)Cl] (H(2)L(4)) derivatized MOF 4 served as an active catalyst for photocatalytic CO(2) reduction with a total turnover number (TON) of 10.9, three times higher than that of the homogeneous complex H(2)L(4). MOFs 5 and 6 contained phosphorescent [Ir(III)(ppy)(2)(dcbpy)]Cl (H(2)L(5)) and [Ru(II)(bpy)(2)(dcbpy)]Cl(2) (H(2)L(6)) (where ppy is 2-phenylpyridine and bpy is 2,2'-bipyridine) and were used in three photocatalytic organic transformations (aza-Henry reaction, aerobic amine coupling, and aerobic oxidation of thioanisole) with very high activities. The inactivity of the parent UiO-67 framework and the reaction supernatants in catalytic water oxidation, CO(2) reduction, and organic transformations indicate both the molecular origin and heterogeneous nature of these catalytic processes. The stability of the doped UiO-67 catalysts under catalytic conditions was also demonstrated by comparing PXRD patterns before and after catalysis. This work illustrates the potential of combining molecular catalysts and MOF structures in developing highly active heterogeneous catalysts for solar energy utilization. PMID:21780787

Wang, Cheng; Xie, Zhigang; deKrafft, Kathryn E; Lin, Wenbin

2011-08-05

340

Oxide weathering and trace metal release by bacterial reduction in a New Caledonia Ferralsol  

Microsoft Academic Search

Bacterial reduction of Fe- and Mn-oxides was studied in a surfacehorizon of a New-Caledonian Ferralsol in batch experiments. Twotreatments were imposed containing different sources of organicmatter (soil organic matter with or without glucose addition) tolink organic matter biodegradation with reduction process. Theconcomitant solubilization of Ni and Co was also studied. Resultsshowed that anaerobic Fe- and Mn-reducing bacterial activity wasresponsible for

C. Quantin; T. Becquer; J. H. Rouiller; J. Berthelin

2001-01-01

341

Nitrate requirement for acetylene inhibition of nitrous oxide reduction in marine sediments  

Microsoft Academic Search

The inhibition of nitrous oxide (N2O) reduction by acetylene (C2H2) in saltmarsh sediment was temporary; we investigated this phenomenon and possible causes. The reduction of N2O in the presence of C2H2 was biological. N2O consumption in the presence of C2H2 began when nitrate concentration became very low. The time course of N2O consumption after periods of N2O accumulation was unaffected

Jennifer M. Slater; Douglas G. Capone

1989-01-01

342

Strontium desorption from bacteriogenic iron oxides (BIOS) subjected to microbial Fe(III) reduction  

Microsoft Academic Search

The effect of microbial reduction of bacteriogenic iron oxides (BIOS) on the release of sorbed Sr was examined using a naturally low-Sr BIOS (n-BIOS) collected from Chalk River, Canada, and a naturally high-Sr BIOS (Äspö-BIOS) collected from Äspö, Sweden. EXAFS analysis suggested that Sr was bound to the Äspö-BIOS as an outer-sphere complex of hydrated Sr2+. During reduction, Sr desorption

Sean Langley; Andrew G. Gault; Alex Ibrahim; Yoshio Takahashi; Rob Renaud; Danielle Fortin; Ian D. Clark; F. Grant Ferris

2009-01-01

343

Lithium assisted electrochemical reduction of uranium oxide in room temperature ionic liquid  

Microsoft Academic Search

Lithium assisted electrochemical reduction of U3O8 in the room temperature ionic liquid (RTIL), N-methyl-N-propylpiperidinium bis(trifluoromethylsulfonyl)imide (MPPiNTf2), was studied to explore the feasibility of using RTILs for direct electrochemical reduction of uranium oxide at near ambient\\u000a temperature. The electrochemical behavior of Li+ in MPPiNTf2 at stainless steel electrode was investigated by cyclic voltammetry and chronoamperometry. The cyclic voltammogram of LiNTf2 in

Biju Joseph; K. A. Venkatesan; K. Nagarajan; T. G. Srinivasan; P. R. Vasudeva Rao

2011-01-01

344

Contribution of Oxygen Reduction to Charge Injection on Platinum and Sputtered Iridium Oxide Neural Stimulation Electrodes  

Microsoft Academic Search

The extent to which oxygen reduction occurs on sputtered iridium oxide (SIROF) and platinum neural stimulation electrodes was quantified by cyclic voltammetry and voltage-transient measurements in oxygen-saturated physiological saline. Oxygen reduction was the dominant charge-admittance reaction on platinum electrodes during slow-sweep-rate cyclic voltammetry, contributing ~12 mC\\/cm2 (88% of total charge) to overall cathodal charge capacity. For a 300-nm-thick SIROF electrode,

Stuart F. Cogan; Julia Ehrlich; Timothy D. Plante; Marcus D. Gingerich; Douglas B. Shire

2010-01-01

345

Reductive Dissolution of Iron Oxides and Iron-Rich Clays Enhanced by Sulfate-Reducing Bacteria  

Microsoft Academic Search

Iron oxides and iron-rich clays are abundant in low-temperature sedimentary environments where sulfate-reducing bacteria are also present. This study summarizes our research on reductive dissolution of ferrihydrite, goethite, hematite, magnetite, and a nontronite clay by Desulfovibrio spp. strain G-20 and strain G-11. The goal was twofold: (1) to understand the enzymatic processes of iron reduction by sulfate-reducing bacteria (SRB) using

C. L. Zhang

2003-01-01

346

Selective Reduction of NO with CO Over Titania Supported Transition Metal Oxide Catalysts  

Microsoft Academic Search

A series of transition metal oxides promoted titania catalysts (MO\\u000a x\\u000a \\/TiO2; M = Cr, Mn, Fe, Ni, Cu) were prepared by wet impregnation method using dilute solutions of metal nitrate precursors. The\\u000a catalytic activity of these materials was evaluated for the selective catalytic reduction (SCR) of NO with CO as reductant\\u000a in the presence of excess oxygen (2 vol.%). Among various promoted

Pavani M. Sreekanth; Panagiotis G. Smirniotis

2008-01-01

347

Selection of oxygen reduction catalysts for rechargeable lithium–air batteries—Metal or oxide?  

Microsoft Academic Search

Carbon-supported Pd and PdO nanocatalysts were synthesised using either chemical reduction or thermal synthesis procedures and were used as model metal and oxide catalysts for oxygen reduction in rechargeable lithium–air batteries. The Pd metal catalyst showed excellent initial performance, e.g. a discharge capacity of 855mAh (gsolids)?1. However, the PdO catalyst displayed superior capacity retention to the Pd catalyst, producing a

H. Cheng; K. Scott

2011-01-01

348

H2S generation and Eh reduction in cysteine challenge testing as a means of determining the potential of test products and treatments for inhibiting oral malodor  

Microsoft Academic Search

Bacterial degradation of the sulfur-containing amino acid, cysteine, involves two biochemical processes that contribute significantly to oral malodor generation. The first is production of hydrogen sulfide, a major component and common indicator of oral malodor formation. The second is generation of the sulfhydryl anion, HS?, an anion that is central to the lowering of the oxidation–reduction potential (Eh). A reduced

I Kleinberg; D Codipilly

2008-01-01

349

Scenario analysis on CO 2 emissions reduction potential in China's electricity sector  

Microsoft Academic Search

With the approach of the year 2012, a new round of international negotiations has energized the entire climate change community. With this, analyses on sector-based emissions reduction and mitigation options will provide the necessary information to form the debate. In order to assess the CO2 emissions reduction potential of China's electricity sector, this research employs three scenarios based on the

Wenjia Cai; Can Wang; Ke Wang; Ying Zhang; Jining Chen

2007-01-01

350

Mercury reduction and oxidation by reduced natural organic matter in anoxic environments  

SciTech Connect

Natural organic matter (NOM)-mediated redox cycling of elemental mercury Hg(0) and mercuric Hg(II) is critically important in affecting inorganic mercury transformation and bioavailability. However, these processes are not well understood, particularly in anoxic water and sediments where NOM can be reduced and toxic methylmercury is formed. We show that under dark anoxic conditions reduced organic matter (NOMre) simultaneously reduces and oxidizes Hg via different reaction mechanisms. Reduction of Hg(II) is primarily caused by reduced quinones. However, Hg(0) oxidation is controlled by thiol functional groups via oxidative complexation, which is demonstrated by the oxidation of Hg(0) by low-molecular-weight thiol compounds, including glutathione and mercaptoacetic acid under reducing conditions. Depending on the NOM source, oxidation state, and NOM:Hg ratio, NOM reduces Hg(II) at initial rates ranging from 0.4 to 5.5 h-1, which are about 2 to 6 times higher than observed for photochemical reduction of Hg(II) in open surface waters. However, rapid reduction of Hg(II) by NOMre can be offset by oxidation of Hg(0) with an estimated initial rate as high as 5.4 h-1. This dual role of NOMre is expected to strongly influence the availability of reactive Hg and thus to have important implications for microbial uptake and methylation in anoxic environments.

Zheng, Wang [ORNL; Liang, Liyuan [ORNL; Gu, Baohua [ORNL

2012-01-01

351

Filtrates and Residues. Galvanic Cells and the Standard Reduction Potential Table.  

ERIC Educational Resources Information Center

Presented is an activity designed to introduce introductory chemistry students to the standard reduction potential table. Included are lists of equipment and reagents, procedures, sample worksheets, and teaching directions. (CW)

Tanis, David O.

1990-01-01

352

Near Term Weight Reduction Potential in a 1977 General Motors B Body Vehicle.  

National Technical Information Service (NTIS)

The report presents an analysis of the potential for weight reduction through lightweight material and component substitutions in a 1977 General Motors Corporation B body vehicle. The changes were limited to those that appeared producible in the 1980 to 1...

D. A. Hurter P. G. Gott J. Staley

1978-01-01

353

Study on the Reduction Behavior of Zirconia Supported Iron Oxide Catalysts by Temperature-Programmed Reduction Combined with in SituMössbauer Spectroscopy  

Microsoft Academic Search

The reduction properties of Fe2O3\\/ZrO2catalysts with various Fe2O3loading and the interactions between iron oxide and zirconia have been studied by using temperature-programmed reduction combined within situMössbauer spectroscopy. This is shown that the intermediates formed during reduction depend strongly not only on the reduction temperature but also on the iron loading. Several iron species such as bulk phase ?-Fe2O3, small ?-Fe2O3particles,

Kaidong Chen; Yining Fan; Zheng Hu; Qijie Yan

1996-01-01

354

Superior catalysts for selective catalytic reduction of nitric oxide. Quarterly technical progress report, January 1, 1995--March 31, 1995  

SciTech Connect

During this quarter, progress was made on the following tasks: TPD techniques were employed to study the reaction mechanism of the selective catalytic reduction of nitrogen oxide with ammonia over iron oxide pillared clay catalyst; and a sulfur dioxide resistant iron oxide/titanium oxide catalyst was developed.

Li, W.B.; Yang, R.T.

1995-12-01

355

Superior catalysts for selective catalytic reduction of nitric oxide. Quarterly technical progress report, April 1, 1995--June 30, 1995  

SciTech Connect

Efforts continued towards the synthesis of new pillared clay catalysts for the selective catalytic reduction of nitric oxide by ammonia. The possibility of utilizing hydrocarbons was also investigated.

Li, W.B.; Yang, R.T.

1995-12-01

356

Superior catalysts for selective catalytic reduction of nitric oxide. Quarterly technical progress report, April 1, 1995--June 30, 1995.  

National Technical Information Service (NTIS)

Efforts continued towards the synthesis of new pillared clay catalysts for the selective catalytic reduction of nitric oxide by ammonia. The possibility of utilizing hydrocarbons was also investigated.

W. B. Li R. T. Yang

1995-01-01

357

The low-temperature reduction of Pd-doped transition metal oxide surfaces with hydrogen  

Microsoft Academic Search

The reaction of hydrogen with a series of polyvalent metal oxides (Fe2O3, WO3, MoO3, V2O5, Sb2O3, PbO2, Cr2O3, NiO, CuO, Co3O4, MnO2, PdO, Ag2O) was investigated at low temperatures (77–320K) and pressures (0.001–0.7kPa). Pd-doped (0.1–0.5wt.%) transition metal oxides can be reduced by hydrogen at 77–320K whereas the onset of the reduction of the pure oxides occurs at temperatures higher than

V. M. Belousov; M. A. Vasylyev; L. V. Lyashenko; N. Yu. Vilkova; B. E. Nieuwenhuys

2003-01-01

358

Process for catalytic vapor phase reduction of nitrogen oxides and catalyst composition used therefor  

SciTech Connect

A catalyst composition is disclosed for the vapor phase reduction of nitrogen oxides with ammonia, which consists essentially of a non-noble transition metal compound supported on a shaped carrier comprising a titanium oxide and a clay mineral having an average particle size of 0.1 to 100 microns. The shaped carrier preferably contains an additional component which is an inorganic fibrous material, silica hydrogel, silica sol, or a mixture of at least two of these. An exhaust gas containing nitrogen oxides is treated, with a high percent no removal, by contacting it with the catalyst composition in the presence of ammonia gas at 200 to 600/sup 0/C.

Arima, Y.; Itaya, S.; Tanaka, H.; Yoshioka, T.

1980-02-12

359

Nanophase transition metal oxides show large thermodynamically driven shifts in oxidation-reduction equilibria.  

PubMed

Knowing the thermodynamic stability of transition metal oxide nanoparticles is important for understanding and controlling their role in a variety of industrial and environmental systems. Using calorimetric data on surface energies for cobalt, iron, manganese, and nickel oxide systems, we show that surface energy strongly influences their redox equilibria and phase stability. Spinels (M(3)O(4)) commonly have lower surface energies than metals (M), rocksalt oxides (MO), and trivalent oxides (M(2)O(3)) of the same metal; thus, the contraction of the stability field of the divalent oxide and expansion of the spinel field appear to be general phenomena. Using tabulated thermodynamic data for bulk phases to calculate redox phase equilibria at the nanoscale can lead to errors of several orders of magnitude in oxygen fugacity and of 100 to 200 kelvin in temperature. PMID:20929770

Navrotsky, Alexandra; Ma, Chengcheng; Lilova, Kristina; Birkner, Nancy

2010-10-01

360

Potential toxicity of superparamagnetic iron oxide nanoparticles (SPION)  

PubMed Central

Superparamagnetic iron oxide nanoparticles (SPION) are being widely used for various biomedical applications, for example, magnetic resonance imaging, targeted delivery of drugs or genes, and in hyperthermia. Although, the potential benefits of SPION are considerable, there is a distinct need to identify any potential cellular damage associated with these nanoparticles. Besides focussing on cytotoxicity, the most commonly used determinant of toxicity as a result of exposure to SPION, this review also mentions the importance of studying the subtle cellular alterations in the form of DNA damage and oxidative stress. We review current studies and discuss how SPION, with or without different surface coating, may cause cellular perturbations including modulation of actin cytoskeleton, alteration in gene expression profiles, disturbance in iron homeostasis and altered cellular responses such as activation of signalling pathways and impairment of cell cycle regulation. The importance of protein-SPION interaction and various safety considerations relating to SPION exposure are also addressed.

Singh, Neenu; Jenkins, Gareth J.S.; Asadi, Romisa; Doak, Shareen H.

2010-01-01

361

Investigation of Wüstite (FeO) dissolution: implications for reductive dissolution of ferric oxides.  

PubMed

The pH-dependent dissolution flux of FeO (wüstite, a ferrous oxide) was measured in this study; flux = k{H+}n (moV/m2/s), where k = 10(-4.95) and n = 0.64. This flux was consistent with theoretical predictions based on the rate of water exchange of hexaaquo Fe2+. Interestingly, when compared to published data, the pH-dependent dissolution flux of FeO defined an upper limit for the reductive dissolution fluxes of iron(III) (oxyhydr)oxides, including bacterial dissimilatory iron reduction (DIR). A wide range of dissolution fluxes across several orders of magnitude has been reported for iron(III) (oxyhydr)oxides in the literature and the fluxes were affected by various experimental variables, e.g., pH, ligands, chemical reductants, and bacteria. We concluded that (i) the reductive dissolution fluxes of iron(III) (oxyhydr)oxides, including bacterial DIR, are ultimately bracketed by the detachment rate of reduced Fe(II) from the surface and (ii) the maximum flux can be approached when the mole fraction of reduced Fe(II) at the surface is close to unity. PMID:19320162

Jang, Je-Hun; Brantley, Susan L

2009-02-15

362

Synthesis of carbon-encapsulated iron nanoparticles via solid state reduction of iron oxide nanoparticles  

SciTech Connect

The encapsulation of iron nanoparticles in protective carbon cages leads to unique hybrid core-shell nanomaterials. Recent literature reports suggest that such nanocomposites can be obtained in a relatively simple process involving the solid state carbothermal reduction of iron oxide nanoparticles. This approach is very attractive because it does not require advanced equipment and consumes less energy in comparison to widely used plasma methods. The presented more-in-depth study shows that the carbothermal approach is sensitive to temperature and the process yield strongly depends on the morphology and crystallinity of the carbon material used as a reductant. - Graphical abstract: Reduction of iron oxide nanoparticles by carbon black at 1200 deg. C yields well crystallized carbon-encapsulated iron nanoparticles. Highlights: > Carbon-encapsulated iron nanoparticles were synthesized by carbothermal reduction of iron oxide nanoparticles. > The process has the highest selectivity at 1200 C. > Lower temperatures result in iron oxide nanoparticles wrapped in carbon matrix. > The encapsulation rate of Fe at 1200 deg. C was found to be 15%.

Bystrzejewski, M., E-mail: mibys@chem.uw.edu.pl [Dept of Chemistry, Warsaw University, Pasteura 1, 02-093 Warsaw (Poland)

2011-06-15

363

Superior Fe-ZSM-5 catalyst for selective catalytic reduction of nitric oxide by ammonia  

Microsoft Academic Search

Nitrogen oxides in the exhaust gases from combustion of fossil fuels remain a major source for air pollution and acid rain. The current technology for reducing NOâ (NO + NOâ) emissions from power plants is selective catalytic reduction (SCR) with ammonia in the presence of oxygen. For the SCR reaction, VâOâ + WOâ (or MoOâ) supported on TiOâ are the

Richard Q. Long; Ralph T. Yang

1999-01-01

364

FINAL REPORT. ADVANCED EXPERIMENTAL ANALYSIS OF CONTROLS ON MICROBIAL FE(III) OXIDE REDUCTION  

EPA Science Inventory

The objectives of this research project were to refine existing models of microbiological and geochemical controls on Fe(III) oxide reduction, using laboratory reactor systems which mimic to varying degrees the physical and chemical conditions of the subsurface. Novel experimenta...

365

The Science and Magic of Chemistry. A Learning Cycle Laboratory on Oxidation-Reduction.  

ERIC Educational Resources Information Center

|Discusses the goals of learning cycle laboratories in helping students acquire knowledge about a specific topic and to do so moving in a non-threatening way from the concrete operational level to the formal operational level. Describes an experiment designed for such laboratories dealing with the topic of oxidation-reduction. (TW)|

Silberman, Robert G.; Zipp, Arden P.

1986-01-01

366

Mechanism of leakage current reduction of tantalum oxide capacitors by titanium doping  

Microsoft Academic Search

In this letter, the authors will point out that defect states related to oxygen vacancies in tantalum oxide capacitors can be suppressed by titanium doping, resulting in significant leakage current reduction. The theory is that titanium forms an acceptor which can move at high temperature and neutralize other donors. However, defect states which cannot be suppressed by titanium doping were

W. S. Lau; T. S. Tan; Premila Babu; Nathan P. Sandler

2007-01-01

367

Oxidation-Reduction Processes in Ground Water at Naval Weapons Industrial Reserve Plant, Dallas, Texas.  

National Technical Information Service (NTIS)

This report describes the oxidation-reduction (redox) processes in ground water at Naval Weapons Industrial Reserve (NWIRP) on the basis of data collected and analyzed by the U.S. Geological Survey (USGS) and private companies. The USGS collected ground-w...

S. A. Jones C. L. Braun R. W. Lee

2003-01-01

368

NITRIC OXIDE REDUCTION IN KILNS AND HEATERS BY FUEL/AIR STAGING  

EPA Science Inventory

The paper gives results of studies of the applicability and effectiveness of fuel/air staging (variously called In-furnace NOx Reduction, reburning, or biased firing) in controlling nitrogen oxide (NOx) emissions from refinery process heaters and cement kilns. The studies were co...

369

MODELED RESPONSE OF PHOTOCHEMICAL OXIDANTS TO SYSTEMATIC REDUCTIONS IN ANTHROPOGENIC VOC AND NOX EMISSIONS  

EPA Science Inventory

As an exercise in model sensitivity, the Environmental Protection Agency's Regional Oxidant Model (ROM) was run for several simulations to study the impact of across-the-board reductions in anthropogenic VOC and NOx emissions on the photochemical environment of the eastern United...

370

Materials compatibility testing for a pilot-scale oxide reduction system.  

National Technical Information Service (NTIS)

Materials compatibility tests were performed on five candidate steels for the pilot-scale oxide reduction system currently under development at Argonne National Laboratory-West. Three stainless steels (type 316L, 304, 347) and two alloy steels (2.25Cr-1Mo...

T. C. Totemeier S. D. Herrmann

2000-01-01

371

Production of N2 through Anaerobic Ammonium Oxidation Coupled to Nitrate Reduction in Marine Sediments  

Microsoft Academic Search

In the global nitrogen cycle, bacterial denitrification is recognized as the only quantitatively important process that converts fixed nitrogen to atmospheric nitrogen gas, N2, thereby influencing many aspects of ecosystem function and global biogeochemistry. However, we have found that a process novel to the marine nitrogen cycle, anaerobic oxidation of ammonium coupled to nitrate reduction, contributes substantially to N2 production

Bo Thamdrup; Tage Dalsgaard

2002-01-01

372

Electrolytic Reduction of Spent Oxide Fuel – Bench-Scale Test Results  

SciTech Connect

A series of tests were performed to demonstrate the electrolytic reduction of spent light water reactor fuel at bench-scale in a hot cell at the Idaho National Laboratory Materials and Fuels Complex (formerly Argonne National Laboratory - West). The process involves the conversion of oxide fuel to metal by electrolytic means, which would then enable subsequent separation and recovery of actinides via existing electrometallurgical technologies, i.e., electrorefining. Four electrolytic reduction runs were performed at bench scale using ~500 ml of molten LiCl -- 1 wt% Li2O electrolyte at 650 ºC. In each run, ~50 g of crushed spent oxide fuel was loaded into a permeable stainless steel basket and immersed into the electrolyte as the cathode. A spiral wound platinum wire was immersed into the electrolyte as the anode. When a controlled electric current was conducted through the anode and cathode, the oxide fuel was reduced to metal in the basket and oxygen gas was evolved at the anode. Salt samples were extracted before and after each electrolytic reduction run and analyzed for fuel and fission product constituents. The fuel baskets following each run were sectioned and sampled, revealing an extent of uranium oxide reduction in excess of 98%.

S. D. Herrmann; S. X. Li; M. F. Simpson

2005-10-01

373

The mechanism of the selective reduction of nitrogen oxides by hydrocarbons on zeolite catalysts  

Microsoft Academic Search

The mechanism of the selective catalytic reduction (SCR) of nitrogen oxides over 3d transition metal zeolites has been investigated in a variety of ways. The initial step is the abstraction of hydrogen from the hydrocarbon by adsorbed NO2 species which is rate determining with methane but not with isobutane. The subsequent path appears to involve nitroso and\\/or nitro compounds. Comparative

Noel W. Cant; Irene O. Y. Liu

2000-01-01

374

Correlation between surface area reduction and ultrasonic velocity in sintered zinc oxide powders  

Microsoft Academic Search

Specific surface area and longitudinal wave ultrasonic velocity were measured in zinc oxide (ZnO) powder compacts partially sintered to different pore fractions (P). A linear correlation was observed between the reduction in surface area and the increase in ultrasonic velocity at all P up to the onset of pore closure. During the initial stage of sintering, the ultrasonic velocity increased

L. P. Martin; M. Rosen

1997-01-01

375

Comparison of oxidation and reduction methods in the determination of forms of sulfur in coal  

Microsoft Academic Search

Results obtained by analyzing nine coals for various sulfur forms using a lithium aluminum hydride (LAH) reduction method and a standard oxidation method (American Society for Testing and Materials) were compared to evaluate the effectiveness of the two methods for quantitative removal and subsequent determination of pyrite. Total iron and total sulfur were determined by x-ray fluorescence analysis of the

J. K. Kuhn; L. B. Kohlenberger; N. F. Shimp

1973-01-01

376

Advanced experimental analysis of controls on microbial Fe(III) oxide reduction. First year progress report  

SciTech Connect

'The authors have made considerable progress toward a number of project objectives during the first several months of activity on the project. An exhaustive analysis was made of the growth rate and biomass yield (both derived from measurements of cell protein production) of two representative strains of Fe(III)-reducing bacteria (Shewanellaalga strain BrY and Geobactermetallireducens) growing with different forms of Fe(III) as an electron acceptor. These two fundamentally different types of Fe(III)-reducing bacteria (FeRB) showed comparable rates of Fe(III) reduction, cell growth, and biomass yield during reduction of soluble Fe(III)-citrate and solid-phase amorphous hydrous ferric oxide (HFO). Intrinsic growth rates of the two FeRB were strongly influenced by whether a soluble or a solid-phase source of Fe(III) was provided: growth rates on soluble Fe(III) were 10--20 times higher than those on solid-phase Fe(III) oxide. Intrinsic FeRB growth rates were comparable during reduction of HF0 and a synthetic crystalline Fe(III) oxide (goethite). A distinct lag phase for protein production was observed during the first several days of incubation in solid-phase Fe(III) oxide medium, even though Fe(III) reduction proceeded without any lag. No such lag between protein production and Fe(III) reduction was observed during growth with soluble Fe(III). This result suggested that protein synthesis coupled to solid-phase Fe(III) oxide reduction in batch culture requires an initial investment of energy (generated by Fe(III) reduction), which is probably needed for synthesis of materials (e.g. extracellular polysaccharides) required for attachment of the cells to oxide surfaces. This phenomenon may have important implications for modeling the growth of FeRB in subsurface sedimentary environments, where attachment and continued adhesion to solid-phase materials will be required for maintenance of Fe(III) reduction activity. Despite considerable differences in the rate and pattern of FeRB growth with different Fe(III) forms, a roughly consistent long-term biomass yield of 5 to 15 mg protein per mmol Fe(III) reduced was observed during growth on different forms of Fe(III). These results should prove useful for quantitative modeling of FeRB growth and metabolism in various types of experimental and in situ anaerobic sedimentary systems.'

Roden, E.E.; Urrutia, M.M.

1997-07-01

377

Control of combustion-generated nitrogen oxides by selective non-catalytic reduction.  

PubMed

Controlling nitrogen oxides (NO(x)) emissions is becoming a daunting technical challenge as increasingly strict emission limits are being imposed. The stringent regulations have prompted the innovation and characterization of NO(x) control technologies suitable for various applications. This paper presents a review on NO(x) removal techniques with particular reference to selective non-catalytic reduction (SNCR) technology. This includes initially how SNCR emerged as a technology along with a comparison with other relevant technologies. A review of various features related to selective non-catalytic gas phase injection of ammonia and ammonium salts (as reducing agent) is presented. The use of urea solution as a reducing agent and its performance in laboratory and pilot scale tests as well as large-scale applications is also discussed. Use of cyanuric acid as a potential reducing agent is also presented. The underlying reaction mechanisms have been reviewed for ammonia, urea and cyanuric acid for the explanation of various observations. Computational fluid dynamics (CFD) modeling as applied to SNCR is also presented. Subsequently the use of SNCR coupled with other in-combustion and post-combustion NO(x) control techniques is elaborated. Additionally, a two-stage NO(x) removal strategy to control un-reacted ammonia slip and to improve overall efficiency is discussed. At the end a summary is given which highlights various areas needing further research. PMID:16842901

Javed, M Tayyeb; Irfan, Naseem; Gibbs, B M

2006-07-13

378

Bacterial reduction of crystalline Fe{sup 3+} oxides in single phase suspensions and subsurface materials  

SciTech Connect

Microbiologic reduction of synthetic and geologic Fe{sup 3+} oxides associated with four Pleistocene-age, Atlantic coastal plain sediments was investigated using a dissimilatory Fe reducing bacterium (Shewanella putrefaciens, strain CN32) in bicarbonate buffer. Experiments investigated whether phosphate and anthraquinone-2,6-disulfonate, (AQDS, a humic acid analogue) influenced the extent of crystalline Fe{sup 3+} oxide bioreduction and whether crystalline Fe{sup 3+} oxides in geologic materials are more or less reducible than comparable synthetic phases. Anaerobic incubations (10{sup 8} organisms/mL) were performed both with and without PO{sub 4} and AQDS that functions as an electron repository and shuttle. The production of Fe{sup 2+} (solid and aqueous) was followed with time, as was mineralogy by X-ray diffraction. The synthetic oxides were reduced in a qualitative trend consistent with their surface area and free energy: hydrous ferric oxide (HFO) > goethite > hematite. Bacterial reduction of the crystalline oxides was incomplete in spite of excess electron donor. Biogenic formation of vivianite [Fe{sub 3}(PO{sub 4}){sub 2}{center_dot}8H{sub 2}O] and siderite (FeCO{sub 3}) was observed; the conditions of their formation was consistent with their solubility. The geologic Fe{sup 3+} oxides showed a large range in reducibility, approaching 100% in some materials. The natural oxides were equally or more reducible than their synthetic counterparts, in spite of association with non-reducible mineral phases (e.g., kaolinite). The reducibility of the synthetic and geologic oxides was weakly effected by PO{sub 4}, but was accelerated by AQDS. CN32 produced the hydroquinone form of AQDS (AHDS), that, in turn, had thermodynamic power to reduce the Fe{sup 3+} oxides. As a chemical reductant, it could reach physical regions of the oxide not accessible by the organism. Electron microscopy showed that crystallite size was not the primary factor that caused differences in reducibility between natural and synthetic crystalline Fe{sup 3+} oxide phases. Crystalline disorder and microheterogeneities may be more important.

Zachara, J.M.; Fredrickson, J.K.; Li, S.M.; Kennedy, D.W.; Smith, S.C.; Gassman, P.L. [Pacific Northwest National Lab., Richland, WA (United States)

1998-11-01

379

Oxidative Dissolution Potential of Biogenic and Abiogenic TcO2 in Subsurface Sediments  

SciTech Connect

Technetium-99 (Tc) is an important fission product contaminant associated with sites of nuclear fuels reprocessing and geologic nuclear waste disposal. Exhibiting an intermediate redox potential, Tc is highly mobile in its anionic, oxidized state [Tc(VII)O4-]; and less mobile as a poorly soluble oxyhydroxide precipitate [Tc(IV)O2•nH2O] in its reduced state. Here we investigate the potential for oxidation of Tc(IV) that was heterogeneously reduced by reaction with biogenic Fe(II) in two sediments differing in mineralogy and aggregation state (FRC, RG). Both sediments contained Fe(III) and Mn(III/IV) as redox active phases, but FRC also contained mass-dominant Fe-phyllosilicates of different types. Biogenic Tc(IV)O2•nH2O was oxidized in anoxic, but unreduced RG and FRC sediments through redox interaction with Mn(III/IV) oxides. Bioreduction by Shewanella putrefaciens CN32 dissolved Mn(III/IV) oxides and generated biogenic Fe(II) that was reactive with Tc(VII) in heat-killed, bioreduced sediment. Biogenic Fe(II) in the FRC exceeded that in RG by a factor of two. More rapid reduction rates were observed in the RG that had lower biogenic Fe(II), and less particle aggregation. EXAFS measurements indicated that the primary reduction product was a TcO2-like phase in both sediments. Redox product Tc(IV) oxidized rapidly and completely in RG when contacted with air. Oxidation, in contrast, was slow and incomplete in the FRC, in spite of similar molecular speciation to RG. X-ray microprobe, electron microprobe, x-ray absorption spectroscopy, and micro x-ray diffraction were applied to the whole sediment and isolated Tc-contained particles. These analyses revealed that non-oxidizable Tc(IV) in the FRC existed as complexes with octahedral Fe(III) within intra-grain domains of 50-100 µm-sized, Fe-containing micas presumptively identified as celadonite. The markedly slower oxidation rates in FRC as compared to RG were attributed to mass-transfer-limited migration of O2 into intra-aggregate and intraparticle domains where Tc(IV) existed; and the formation of unique, oxidation-resistant, intragrain Tc(IV)-Fe(III) molecular species.

Fredrickson, Jim K.; Zachara, John M.; Plymale, Andrew E.; Heald, Steve M.; McKinley, James P.; Kennedy, David W.; Liu, Chongxuan; Nachimuthu, Ponnusamy

2009-04-15

380

Iron Sulfide and Pyrite as Potential Electron Donors for Microbial Nitrate Reduction in Freshwater Wetlands  

Microsoft Academic Search

The potential of iron sulfide minerals to function as electron donors for microbial nitrate reduction has important consequences for freshwater wetland ecosystems. Nitrate influxes in iron sulfide-rich soils, could ultimately lead to adverse processes, such as internal eutrophication or metal toxicity. In the present study, the potential of two iron sulfide minerals (pyrite and iron sulfide) to function as electron

Suzanne C. M. Haaijer; Leon P. M. Lamers; Alfons J. P. Smolders; Mike S. M. Jetten

2007-01-01

381

The CO2 Reduction Potential of Combined Heat and Power in California's Commercial Buildings  

Microsoft Academic Search

The Ernest Orlando Lawrence Berkeley National Laboratory (LBNL) is working with the California Energy Commission (CEC) to determine the potential role of commercial sector distributed generation (DG) with combined heat and power (CHP) capability deployment in greenhouse gas emissions (GHG) reductions. CHP applications at large industrial sites are well known, and a large share of their potential has already been

Michael Stadler; Chris Marnay; Goncalo Cardoso; Tim Lipman; Olivier Megel; Srirupa Ganguly; Afzal Siddiqui; Judy Lai

2009-01-01

382

Scenario analysis on CO 2 emissions reduction potential in China's iron and steel industry  

Microsoft Academic Search

The international climate community has begun to assess a range of possible options for strengthening the international climate change effort after 2012. Analysis of the potential for sector-based emissions reduction and relevant mitigation options will provide the necessary background information for the debate. In order to assess the CO2 abatement potential of China's steel industry, a model was developed using

Ke Wang; Can Wang; Xuedu Lu; Jining Chen

2007-01-01

383

Topotactic oxidative and reductive control of the structures and properties of layered manganese oxychalcogenides.  

PubMed

Topotactic modification, by both oxidation and reduction, of the composition, structures, and magnetic properties of the layered oxychalcogenides Sr4Mn3O7.5Cu2Ch2 (Ch=S, Se) is described. These Mn3+ compounds are composed of alternating perovskite-type strontium manganese oxide slabs separated by anti-fluorite-type copper chalcogenide layers and are intrinsically oxide deficient in the central layer of the perovskite slabs. The systems are unusual examples of perovskite-related compounds that may topotactically be both oxidized by fluorination and reduced by deintercalation of oxygen from the oxide-deficient part of the structure. The compounds exhibit antiferromagnetic ordering of the manganese magnetic moments in the outer layers of the perovskite slabs, while the other moments, in the central layers, exhibit spin-glass-like behavior. Fluorination has the effect of increasing the antiferromagnetic ordering temperature and the size of the ordered moment, whereas reduction destroys magnetic long-range order by introducing chemical disorder which leads to both further disorder and frustration of the magnetic interactions in the manganese oxide slab. PMID:17705487

Hyett, Geoffrey; Barrier, Nicolas; Clarke, Simon J; Hadermann, Joke

2007-08-18

384

Effect of applied voltage, initial concentration and natural organic matter on sequential reduction/oxidation of nitrobenzene by graphite electrodes  

PubMed Central

Carbon electrodes are proposed in reactive sediment caps for in situ treatment of contaminants. The electrodes produce reducing conditions and H2 at the cathode and oxidizing conditions and O2 at the anode. Emplaced perpendicular to seepage flow, the electrodes provide the opportunity for sequential reduction and oxidation of contaminants. The objectives of this study are to demonstrate degradation of nitrobenzene (NB) as a probe compound for sequential electrochemical reduction and oxidation, and to determine the effect of applied voltage, initial concentration and natural organic matter on the degradation rate. In H-cell reactors with graphite electrodes and buffer solution, NB was reduced stoichiometrically to aniline (AN) at the cathode with nitrosobenzene (NSB) as the intermediate. AN was then removed at the anode, faster than the reduction step. No common AN oxidation intermediate was detected in the system. Both the first order reduction rate constants of NB (kNB) and NSB (kNSB) increased with applied voltage between 2V and 3.5 V (when the initial NB concentration was 100 µM, kNB=0.3 d?1 and kNSB=0.04 d?1at 2V; kNB=1.6 d?1 and kNSB=0.64 d?1at 3.5 V) but stopped increasing beyond the threshold of 3.5V. When initial NB concentration decreased from 100 to 5 µM, kNB and kNSB became 9 and 5 times faster, respectively, suggesting that competition for active sites on the electrode surface is an important factor in NB degradation. Presence of natural organic matter (in forms of either humic acid or Anacostia River sediment porewater) decreased kNB while slightly increased kNSB, but only to a limited extent (~factor of 3) for dissolved organic carbon content up to 100 mg/l. These findings suggest that electrode-based reactive sediment capping via sequential reduction/oxidation is a potentially robust and tunable technology for in situ contaminants degradation.

Sun, Mei; Reible, Danny D.; Lowry, Gregory V.; Gregory, Kelvin B.

2012-01-01

385

Microsensor measurements of sulfate reduction and sulfide oxidation in compact microbial communities of aerobic biofilms  

SciTech Connect

The microzonation of O{sub 2} respiration, H{sub 2}S oxidation, and SO{sub 4}{sup 2{minus}} reduction in aerobic trickling-filter biofilms was studied by measuring concentration profiles at high spatial resolution (25 to 100 {mu}m) with microsensors for O{sub 2}, S{sup 2{minus}}, and pH. Specific reaction rates were calculated from measured concentration profiles by using a simple one-dimensional diffusion reaction model. The importance of electron acceptor and electron donor availability for the microzonation of respiratory processes and their reaction rates was investigated. Oxygen respiration was found in the upper 0.2 to 0.4 mm of the biofilm, whereas sulfate reduction occurred in deeper, anoxic parts of the biofilm. Sulfate reduction accounted for up to 50% of the total mineralization of organic carbon in the biofilms. All H{sub 2}S produced from sulfate reduction was reoxidized by O{sub 2} in a narrow reaction zone, and no H{sub 2}S escaped to the overlying water. Turnover times of H{sub 2}S and O{sub 2} in the reaction zone were only a few seconds owing to rapid bacterial H{sub 2}S oxidation. Anaerobic H{sub 2}S oxidation with NO{sub 3}{sup {minus}} could be induced by addition of nitrate to the medium. Total sulfate reduction rates increased when the availability of SO{sub 4}{sup 2{minus}} or organic substrate increased as a result of deepening of the sulfate reduction zone or an increase in the sulfate reduction intensity, respectively.

Kuehl, M.; Joergensen, B.B. (Univ. of Aarhus (Denmark))

1992-04-01

386

Reduction and Oxidation of the Active Site Iron in Tyrosine Hydroxylase: Kinetics and Specificity†  

PubMed Central

Tyrosine hydroxylase (TyrH) is a pterin-dependent enzyme that catalyzes the hydroxylation of tyrosine to form dihydroxyphenylalanine. The oxidation state of the active site iron atom plays a central role in the regulation of the enzyme. The kinetics of reduction of ferric TyrH by several reductants were determined by anaerobic stopped-flow spectroscopy. Anaerobic rapid freeze–quench EPR confirmed that the change in the near-UV absorbance of TyrH upon adding reductant corresponded to iron reduction. Tetrahydrobiopterin reduces wild-type TyrH following a simple second-order mechanism with a rate constant of 2.8 ± 0.1 mM?1 s?1. 6-Methyltetrahydropterin reduces the ferric enzyme with a second-order rate constant of 6.1 ± 0.1 mM?1 s?1 and exhibits saturation kinetics. No EPR signal for a radical intermediate was detected. Ascorbate, glutathione, and 1,4-benzoquinone all reduce ferric TyrH, but much more slowly than tetrahydrobiopterin, suggesting that the pterin is a physiological reductant. E332A TyrH, which has an elevated Km for tetrahydropterin in the catalytic reaction, is reduced by tetrahydropterins with the same kinetic parameters as those of the wild-type enzyme, suggesting that BH4 does not bind in the catalytic conformation during the reduction. Oxidation of ferrous TyrH by molecular oxygen can be described as a single-step second-order reaction, with a rate constant of 210 mM?1 s?1. S40E TyrH, which mimics the phosphorylated state of the enzyme, has oxidation and reduction kinetics similar to those of the wild-type enzyme, suggesting that phosphorylation does not directly regulate the interconversion of the ferric and ferrous forms.

Frantom, Patrick A.; Seravalli, Javier; Ragsdale, Stephen W.; Fitzpatrick, Paul F.

2006-01-01

387

Potential-modulated reflectance study of the oxidation state of iridium in anodic iridium oxide films  

SciTech Connect

In an attempt to identify the changes of oxidation state involved in the electrochromic effect of anodic iridium oxide films (AIROF's) the authors obtained potential-modulated reflectance (PMR) spectra of AIROF's at three pH values: 0.9, 6.7, and 13.0, in the wavelength range 200-650 nm and at an angle of incidence of 45/sup 0/. Depending on pH, the voltammograms show up to four peaks (I-IV) in the anodic scan, the coloration-bleaching process corresponding to the main voltammetric peak II. The PMR spectra measured at a given voltammetric feature were nearly independent of pH, which shows that (i) the chemical composition of the AIROF is largely independent of the pH of the solution in which it was grown; (ii) the reflectance signal is originated by changes of the oxidation state of iridium in the AIROF. The PMR spectra were independent of the thickness of the AIROF, and therefore were not a trivial interference effect. The PMR maximum at 580-610 nm at voltammetric peak II has been tentatively assigned to an Ir(IV) oxide or oxyhydroxide, as have the PMR maximum at 330-360 nm at the minimum between voltammetric peaks II and III and the PMR maximum at 220-260 nm at potentials at or above voltammetric peak III. Apparently an Ir(IV) oxide or oxyhydroxide predominates in the potential range between voltammetric peaks II and IV, and different transitions become possible in this oxide at increasingly positive potentials.

Gutierrez, C.; Sanchez, M.; Pena, J.I.; Martinez, C.; Martinez, M.A.

1987-09-01

388

Nitric oxide and prostaglandins potentiate the liver regeneration cascade  

PubMed Central

The liver has the remarkable ability to regenerate following damage or surgical resection. Although this feature of the liver has been studied for over 100 years, the trigger of the liver regeneration cascade remains controversial. Recent experimental evidence supports the hypothesis that nitric oxide (NO) and prostaglandins (PGs), released secondary to an increase in the blood flow-to-liver mass ratio following two-thirds partial hepatectomy (PHx), work synergistically to trigger liver regeneration. To extend this research, the hypothesis that NO and PGs are potential therapeutic targets to potentiate the liver regeneration cascade is tested. The NO donor s-nitroso-n-acetylpenicillamine, the phosphodiesterase V antagonist zaprinast (ZAP) and PGI2 each potentiated c-fos messenger RNA expression, an index of initiation of the liver regeneration cascade, following PHx. Also, the triple combination of s-nitroso-n-acetylpenicillamine, ZAP and PGI2 potentiated c-fos messenger RNA expression. These results support the hypothesis that NO and PGs can potentiate initiation of the regeneration cascade. An additional index of liver weight restoration 48 h after PHx was also used to test the hypothesis, because this index encompasses the entire liver regeneration cascade. ZAP and 6-keto-PGF1?, a stable metabolite of PGI2, and the combination of ZAP and 6-keto-PGF1?, each potentiated liver weight restoration 48 h after PHx. These results also provide support for the hypothesis that NO and PGs are possible therapeutic targets to potentiate liver regeneration following surgical resection.

Smith, Jodi M Schoen; Lautt, W Wayne

2006-01-01

389

Hydrogen permeation rate reduction by post-oxidation of aluminide coatings on DIN 1.4914 martensitic steel (MANET)  

Microsoft Academic Search

In a previous work, it has been shown that lower aluminium content aluminide, having the same permeation rate reduction as the higher aluminium content, exhibited a lower hardness and greater ductility and therefore greater crack resistance than the higher aluminium content. In this work we combine this characteristic with a post-oxidation to obtain a further deuterium permeation reduction. The post-oxidation

A. Perujo; E. Serra; H. Kolbe; T. Sample

1996-01-01

390

Impurity evaluation of fused lithium chloride salt for a pilot-scale oxide reduction.  

SciTech Connect

The inorganic and physical chemistry of reactants (e.g., impurities) produced during the reduction of spent light water reactor fuel in a hot cell has been analyzed. Two source terms were identified that influence the composition and quantity of these impurities in the salt matrix. One source comes from the reduction process, which occurs between the fuel and the Li/LiCl salt matrix, and the other from chemical reactions that occur between the hot cell atmosphere and the salt matrix. The spent-fuel-oxide chemistry and energy of formation for the reactants were evaluated. Most of the rare-earth-oxide reactions were not thermodynamically feasible with molten lithium, except when nitrogen was present during the reduction process. A model of the reaction at a vapor-liquid interface was developed and applied to the pilot-scale oxide reduction device design. A predominance diagram for the Li-O-N reactions was constructed to determine the possible reactions during operation of the device, and from these results, the mass accumulation was determined from hot cell conditions.

Eberle, C. S.; Herrmann, S. D.; King, R. W.; Engineering Division

1999-12-01

391

Bacterial Reductive Dissolution of Crystalline Fe(III) Oxide in Continuous-Flow Column Reactors  

PubMed Central

Bacterial reductive dissolution of synthetic crystalline Fe(III) oxide-coated sand was studied in continuous-flow column reactors in comparison with parallel batch cultures. The cumulative amount of aqueous Fe(II) exported from the columns over a 6-month incubation period corresponded to (95.0 ± 3.7)% (n = 3) of their original Fe(III) content. Wet-chemical analysis revealed that only (6.5 ± 3.2)% of the initial Fe(III) content remained in the columns at the end of the experiment. The near-quantitative removal of Fe was visibly evidenced by extensive bleaching of color from the sand in the columns. In contrast to the column reactors, Fe(II) production quickly reached an asymptote in batch cultures, and only (13.0 ± 2.2)% (n = 3) of the Fe(III) oxide content was reduced. Sustained bacterial-cell growth occurred in the column reactors, leading to the production and export of a quantity of cells 100-fold greater than that added during inoculation. Indirect estimates of cell growth, based on the quantity of Fe(III) reduced, suggest that only an approximate doubling of initial cell abundance was likely to have occurred in the batch cultures. Our results indicate that removal of biogenic Fe(II) via aqueous-phase transport in the column reactors decreased the passivating influence of surface-bound Fe(II) on oxide reduction activity, thereby allowing a dramatic increase in the extent of Fe(III) oxide reduction and associated bacterial growth. These findings have important implications for understanding the fate of organic and inorganic contaminants whose geochemical behavior is linked to Fe(III) oxide reduction.

Roden, Eric E.; Urrutia, Matilde M.; Mann, Carroll J.

2000-01-01

392

Nitric Oxide is a Potential Diagnostic Marker for Hepatocellular Carcinoma  

PubMed Central

Hepatocellular carcinoma (HCC) is the fifth most common cancer in men and the seventh most common in women. This cancer varies widely in incidence throughout the world, with rising incidence in Egypt. HCC is considered the second most frequent cause of cancer incidence and mortality among men in Egypt. This study aimed to estimate the serum levels of nitric oxide (NO) and glutathione reductase in order to evaluate their role as oxidative status markers in HCC development and progression. For this purpose, serum levels of these parameters were assessed in 50 HCC patients, and 30 cirrhotic patients in addition to 15 healthy subjects as a control group. In the present study, glutathione reductase activity showed a significant increase in HCC as compared to the control group (P= 0.019). On the other hand, no significant difference was observed between the cirrhotic and HCC patients (P= 0.492). Serum NO was significantly higher in patients with HCC than in cirrhotic patients (P= 0.001) or the control group (P= 0.001), with a sensitivity of (74%) and specificity of (88.89%) at a cut-off level of 614.1 ?mol/l. While AFP, alpha-fetoprotein, at a cutoff level of 200 ng/ml had a sensitivity of (52%), the specificity was (100%). Indeed, nitric oxide was high in 62.5% of AFP-negative HCC patients. In conclusion, glutathione reductase has no role in HCC diagnosis. However, nitric oxide is a potential diagnostic marker for HCC. The simultaneous determination of serum nitric oxide and AFP gave significant improvement in the detection of HCC patients compared to that of AFP alone.

Eissa, Laila A.; Eisa, Nada H.; Ebrahim, Mohamed A.; Ragab, Maha; El-Gayar, Amal M.

2013-01-01

393

Nitric Oxide is a Potential Diagnostic Marker for Hepatocellular Carcinoma.  

PubMed

Hepatocellular carcinoma (HCC) is the fifth most common cancer in men and the seventh most common in women. This cancer varies widely in incidence throughout the world, with rising incidence in Egypt. HCC is considered the second most frequent cause of cancer incidence and mortality among men in Egypt. This study aimed to estimate the serum levels of nitric oxide (NO) and glutathione reductase in order to evaluate their role as oxidative status markers in HCC development and progression. For this purpose, serum levels of these parameters were assessed in 50 HCC patients, and 30 cirrhotic patients in addition to 15 healthy subjects as a control group. In the present study, glutathione reductase activity showed a significant increase in HCC as compared to the control group (P= 0.019). On the other hand, no significant difference was observed between the cirrhotic and HCC patients (P= 0.492). Serum NO was significantly higher in patients with HCC than in cirrhotic patients (P= 0.001) or the control group (P= 0.001), with a sensitivity of (74%) and specificity of (88.89%) at a cut-off level of 614.1 ?mol/l. While AFP, alpha-fetoprotein, at a cutoff level of 200 ng/ml had a sensitivity of (52%), the specificity was (100%). Indeed, nitric oxide was high in 62.5% of AFP-negative HCC patients. In conclusion, glutathione reductase has no role in HCC diagnosis. However, nitric oxide is a potential diagnostic marker for HCC. The simultaneous determination of serum nitric oxide and AFP gave significant improvement in the detection of HCC patients compared to that of AFP alone. PMID:24106672

Eissa, Laila A; Eisa, Nada H; Ebrahim, Mohamed A; Ragab, Maha; El-Gayar, Amal M

2013-08-08

394

Selective reduction of N-oxides to amines: application to drug metabolism.  

PubMed

Phase I oxidative metabolism of nitrogen-containing drug molecules to their corresponding N-oxides is a common occurrence. There are instances where liquid chromatography/tandem mass spectometry techniques are inadequate to distinguish this pathway from other oxidation processes, including C-hydroxylations and other heteroatom oxidations, such as sulfur to sulfoxide. Therefore, the purpose of the present study was to develop and optimize an efficient and practical chemical method to selectively convert N-oxides to their corresponding amines suitable for drug metabolism applications. Our results indicated that efficient conversion of N-oxides to amines could be achieved with TiCl(3) and poly(methylhydrosiloxane). Among them, we found TiCl(3) to be a facile and easy-to-use reagent, specifically applicable to drug metabolism. There are a few reports describing the use of TiCl(3) to reduce N-O bonds in drug metabolism studies, but this methodology has not been widely used. Our results indicated that TiCl(3) is nearly as efficient when the reductions were carried out in the presence of biological matrices, including plasma and urine. Finally, we have shown a number of examples where TiCl(3) can be successfully used to selectively reduce N-oxides in the presence of sulfoxides and other labile groups. PMID:15319338

Kulanthaivel, Palaniappan; Barbuch, Robert J; Davidson, Rita S; Yi, Ping; Rener, Gregory A; Mattiuz, Edward L; Hadden, Chad E; Goodwin, Lawrence A; Ehlhardt, William J

2004-09-01

395

IMPACTS OF ANTIFOAM ADDITIONS AND ARGON BUBBLING ON DEFENSE WASTE PROCESSING FACILITY REDUCTION/OXIDATION  

SciTech Connect

During melting of HLW glass, the REDOX of the melt pool cannot be measured. Therefore, the Fe{sup +2}/{Sigma}Fe ratio in the glass poured from the melter must be related to melter feed organic and oxidant concentrations to ensure production of a high quality glass without impacting production rate (e.g., foaming) or melter life (e.g., metal formation and accumulation). A production facility such as the Defense Waste Processing Facility (DWPF) cannot wait until the melt or waste glass has been made to assess its acceptability, since by then no further changes to the glass composition and acceptability are possible. therefore, the acceptability decision is made on the upstream process, rather than on the downstream melt or glass product. That is, it is based on 'feed foward' statistical process control (SPC) rather than statistical quality control (SQC). In SPC, the feed composition to the melter is controlled prior to vitrification. Use of the DWPF REDOX model has controlled the balanjce of feed reductants and oxidants in the Sludge Receipt and Adjustment Tank (SRAT). Once the alkali/alkaline earth salts (both reduced and oxidized) are formed during reflux in the SRAT, the REDOX can only change if (1) additional reductants or oxidants are added to the SRAT, the Slurry Mix Evaporator (SME), or the Melter Feed Tank (MFT) or (2) if the melt pool is bubble dwith an oxidizing gas or sparging gas that imposes a different REDOX target than the chemical balance set during reflux in the SRAT.

Jantzen, C.; Johnson, F.

2012-06-05

396

Restructuring Transition Metal Oxide Nanorods for 100% Selectivity in Reduction of Nitric Oxide with Carbon Monoxide.  

PubMed

Transition metal oxide is one of the main categories of heterogeneous catalysts. They exhibit multiple phases and oxidation states. Typically, they are prepared and/or synthesized in solution or by vapor deposition. Here we report that a controlled reaction, in a gaseous environment, after synthesis can restructure the as-synthesized, transition metal oxide, nanorods into a new catalytic phase. Co3O4 nanorods with a preferentially exposed (110) surface can be restructured into nonstoichiometric CoO1-x nanorods. Structure and surface chemistry during the process were tracked with ambient pressure X-ray photoelectron spectros-copy (AP-XPS) and environmental transition electron mi-croscopy (E-TEM). The restructured nanorods are highly active in reducing NO with CO, with 100% selectivity for the formation of N2 in temperatures of 250oC-520oC. AP-XPS and E-TEM studies revealed the nonstoichiometric CoO1-x nanorods with a rock-salt structure as the active phase re-sponsible for the 100% selectivity. This study suggests a route to generate new oxide catalysts. PMID:23731229

Zhang, Shiran; Shan, Jun-Jun; Zhu, Yuan; Nguyen, Luan; Huang, Weixin; Yoshida, Hideto; Takeda, Seiji; Tao, Franklin Feng

2013-06-01

397

Process for the catalytic reduction of nitrogen oxides in gaseous mixtures  

SciTech Connect

A process for the reductive removal of a nitrogen oxide from a gaseous stream, particularly a stream containing oxygen, water, sulfur dioxide, nitrogen oxide and nitrogen, by contacting the stream with ammonia in the presence of a mixture of two catalysts. The first catalyst comprises copper or a copper compound, preferably copper sulfate supported on a porous carrier material. The second catalyst is a combination of metals or compounds thereof, preferably sulfates of vanadium and iron or tungsten and iron, also dispersed on a porous carrier material.

Ginger, E.A.

1981-05-19

398

Mechanism of reduction of nitrogen oxides with propene in excess oxygen catalyzed by bifunctional catalysts  

Microsoft Academic Search

HC-SCR (selective reduction of nitrogen oxide by hydrocarbon) and our view on its reaction mechanism are briefly described,\\u000a and then our attempts in the last few years to design catalysts based on the concept of bifunctional catalysis for HC-SCR\\u000a are reviewed. The example chosen is the NO-C3H6-O2-H2O reaction catalyzed by mechanical mixtures of transition metal oxides (e.g., Mn2O3) and metal-loaded

Makoto Misono; Hideaki Niiro; Yoshifumi Hirao

1998-01-01

399

Kinetics of the reductive dissolution of lead(IV) oxide by iodide.  

PubMed

Lead(IV) oxide (PbO(2)) is a corrosion product found in lead service lines used to convey drinking water. The presence of reductants can accelerate PbO(2) dissolution and enhance lead release to drinking water. The dissolution rate rather than the equilibrium solubility of PbO(2) can control the dissolved lead concentrations in water distributed through pipes containing PbO(2). Iodide, a known reductant for PbO(2), was selected as a model reductant for investigating the kinetics and mechanisms of the reductive dissolution of PbO(2). The dissolution rate of plattnerite (?-PbO(2)) was determined as a function of pH, iodide concentration, and dissolved inorganic carbon (DIC) concentration using continuously stirred tank reactors. The dissolution rate of plattnerite increased with decreasing pH and increasing iodide concentrations. The presence of 10 mg C/L DIC accelerated plattnerite dissolution, but further increases in DIC concentration did not affect the dissolution rate. The reductive dissolution of PbO(2) can be interpreted as a coupled process involving chemical reduction of Pb(IV) to Pb(II) at the PbO(2) surface followed by detachment of Pb(II) to solution. The data suggest that chemical reduction is the rate-limiting step for PbO(2) dissolution in the presence of iodide. PMID:22540764

Wang, Yin; Wu, Jiewei; Giammar, Daniel E

2012-05-09

400

Effects of RE 2O 3 doping on the reduction behavior of molybdenum oxide and properties of molybdenum powder  

Microsoft Academic Search

The reduction of molybdenum oxide doped with rare earth oxides (RE2O3) and the properties of molybdenum powder with RE2O3 additions have been studied by TG-DTA, X-ray diffraction, temperature programmed reduction (TPR), and X-ray photoelectron spectrometry (XPS). The TPR results show that the reduction peak of doped MoO3 shifts to lower temperature as compared with that of pure MoO3. The interaction

Jinshu Wang; Zhiyuan Ren; Wei Liu; Fei Gao; Meiling Zhou

2009-01-01

401

Preparing hydrogenation catalysts via the simultaneous reduction of graphite oxide and platinum(IV)  

NASA Astrophysics Data System (ADS)

The simultaneous reduction of Pt(IV) and graphite oxide is performed for the preparation of hydrogenation catalysts. It is shown that of the four studied reducing agents (formate ion, ethylene glycol, sodium borohydride, and hydrazine), only NaBH4 and hydrazine can be used in the preparation of catalysts. It is assumed that Pt particles (?2 nm) are fixed to the defects, vacancies, and functional groups that are formed as a result of reduction. The prepared compositions catalyze the hydrogenation of decene-1 and nitrobenzene (45°C, 1 atm H2) with specific activities comparable to those in the literature.

Kushch, S. D.; Kuyunko, N. S.; Muradyan, V. E.; Tarasov, B. P.

2013-11-01

402

Nitrogen oxides reduction by carbonaceous materials and carbon dioxide separation using regenerative metal oxides from fossil fuel based flue gas  

NASA Astrophysics Data System (ADS)

The ever-growing energy demands due to rising global population and continuing lifestyle improvements has placed indispensable emphasis on fossil fuels. Combustion of fossil fuels leads to the emission of harmful gaseous pollutants such as oxides of sulfur (SOx) and nitrogen (NOx), carbon dioxide (CO2), mercury, particulate matter, etc. Documented evidence has proved that this air pollution leads to adverse environmental health. This dissertation focuses on the development of technologies for the control of NOx and CO2 emissions. The first part of the thesis (Chapters 2--6) deals with the development of carbon based post combustion NOx reduction technology called CARBONOX process. High temperature combustion oxidizes both atmospheric nitrogen and organic nitrogen in coal to nitric oxide (NO). The reaction rate between graphite and NO is slow and requires high temperature (>900°C). The presence of metallic species in coal char catalyzes the reaction. The reaction temperature is lowered in the presence of oxygen to about 600--850°C. Chemical impregnation, specifically sodium compounds, further lowers the reaction temperature to 350--600°C. Activated high sodium lignite char (HSLC) provided the best performance for NO reduction. The requirement of char for NOx reduction is about 8--12 g carbon/g NO reduced in the presence of 2% oxygen in the inlet gas. The second part of this dissertation (chapter 7--8) focuses on the development of a reaction-based process for the separation of CO2 from combustion flue gas. Certain metal oxides react with CO2 forming metal carbonates under flue gas conditions. They can be calcined separately to yield CO2. Calcium oxide (CaO) has been identified as a viable metal oxide for the carbonation-calcination reaction (CCR) scheme. CaO synthesized from naturally occurring precursors (limestone and dolomite) attained 45--55% of their stoichiometric conversion due to the susceptibility of their microporous structure. High surface area precipitated calcium carbonate (PCC) was synthesized that provided a mesoporous CaO structure upon calcination. This CaO structure attained more than 90% conversion towards the carbonation reaction at 650°C. The reactivity of the novel CaO structure was maintained close to 95% over two reaction-regeneration cycles at 700°C. Vacuum calcination proved beneficial in maintaining the structural integrity of the sorbent.

Gupta, Himanshu

403

Electrochemical oxidation and reduction of chemisorbed ligninsulfonic acid species and aromatic compounds simulating lignin  

SciTech Connect

The electrochemical oxidation and reduction of chemisorbed ligninsulfonic acid species and of aromatic compounds simulating lignin (4-hydroxy-3-methoxybenzylsulfonic acid, vanillic alcohol) were examined at the platinum electrode. It was shown that the slow step of the oxidation and reduction processes is the reaction of the chemisorbed organic species with H/sub ads/ and OH/sub ads/ species generated electrochemically from the solvent. The drop in steady-state coverage which is found to occur with all the materials studied at E/sub r/ < 0.2 V is due to hydrogenation of the chemisorbed species, but the drop which is found to occur at E/sub r/ > 0.2 v is not due to any electrooxidation process, since electrooxidation of the chemisorbed species only starts to occur with noticeable rates at E/sub r/ > 0.7 V.

Shchukin, I.V.; Vasil'ev, Yu.B.; Kazarinov, V.E.; Babkin, V.A.

1987-09-01

404

Reduction and functionalization of graphene oxide sheets using biomimetic dopamine derivatives in one step.  

PubMed

An easy and environmentally friendly chemical method for the simultaneous reduction and noncovalent functionalization of graphene oxide (GO) using dopamine derivatives is described. The reaction takes place at room temperature under ultrasonication of an aqueous suspension of GO and a dopamine derivative. X-ray photoelectron spectroscopy, FT-IR spectroscopy, and cyclic voltammetry characterizations revealed that the resulting material consists of graphene functionalized with the dopamine derivative. This one-step protocol is applied for simultaneous reduction and functionalization of graphene oxide with a dopamine derivative bearing an azide function. The chemical reactivity of the azide function was demonstrated by a postfunctionalization with ethynylferrocene using the Cu(I) catalyzed 1,3-dipolar cyloaddition. PMID:22214550

Kaminska, Izabela; Das, Manash R; Coffinier, Yannick; Niedziolka-Jonsson, Joanna; Sobczak, Jonusz; Woisel, Patrice; Lyskawa, Joel; Opallo, Marcin; Boukherroub, Rabah; Szunerits, Sabine

2012-02-02

405

Synthesis and characterization of Pt-Pd catalysts for methanol oxidation and oxygen reduction.  

PubMed

Pt-Pd nanoparticles supported on carbon black were prepared and characterized as electrocatalysts for methanol oxidation and oxygen reduction in an acidic solution. The Pt and Pd nanoparticles were impregnated spontaneously on the carbon black through a simple reducing process. X-ray diffraction, transmission electron microscopy, and electrochemical measurement were carried out to characterize the crystal structure, particle size, and catalytic activities of the Pt-Pd catalysts. The results showed that the Pt-Pd catalysts had higher catalytic activities for methanol oxidation reaction than pure Pt catalysts. The catalytic activity of the Pt-Pd catalysts for oxygen reduction reactions in the presence of methanol was higher than that of pure Pt and Pd. These results indicate that the Pt-Pd catalysts are suitable as electrocatalysts of both the anode and the cathode in direct methanol fuel cells. PMID:19198443

Kim, In-Tae; Lee, Hong-Ki; Shim, Joongpyo

2008-10-01

406

Hydrogen peroxide-induced reduction of delayed rectifier potassium current in hippocampal neurons involves oxidation of sulfhydryl groups.  

PubMed

This study examined the effect of H2O2 on the delayed rectifier potassium current (IKDR) in isolated hippocampal neurons. Whole-cell voltage-clamp experiments were performed on freshly dissociated hippocampal CA1 neurons of SD rats before and after treatment with H2O2. To reveal the mechanism behind H2O2-induced changes in IKDR, cells were treated with different oxidizing and reducing agents. External application of membrane permeable H2O2 reduced the amplitude and voltage-dependence of IKDR in a concentration dependent manner. Desferoxamine (DFO), an iron-chelator that prevents hydroxyl radical (OH) generation, prevented H2O2-induced reduction in IKDR. Application of the sulfhydryl-oxidizing agent 5,5 dithio-bis-nitrobenzoic acid (DTNB) mimicked the effect of H2O2. Sulfhydryl-reducing agents dithiothreitol (DTT) and glutathione (GSH) alone did not affect IKDR; however, DTT and GSH reversed and prevented the H2O2-induced inhibition of IKDR, respectively. Membrane impermeable agents GSH and DTNB showed effects only when added intracellularly identifying intracellular sulfhydryl groups as potential targets for hydroxyl-mediated oxidation. However, the inhibitory effects of DTNB and H2O2 at the positive test potentials were completely and partially abolished by DTT, respectively, suggesting an additional mechanism of action for H2O2, that is not shared by DTNB. In summary, this study provides evidence for the redox modulation of IKDR, identifies hydroxyl radical as an intermediate oxidant responsible for the H2O2-induced decrease in current amplitude and identifies intracellular sulfhydryl groups as an oxidative target. PMID:23688542

Hasan, Sonia M K; Redzic, Zoran B; Alshuaib, Waleed B

2013-05-18

407

Dye-sensitization-induced visible-light reduction of graphene oxide for the enhanced TiO2 photocatalytic performance.  

PubMed

The reduction of graphene oxide (GO) with a large-scale production has been demonstrated to be one of the key steps for the preparation of graphene-based composite materials with various potential applications. Therefore, it is highly required to develop a facile, green, and environmentally friendly route for the effective reduction of GO. In this study, a new and effective reduced method of GO nanosheets, based on the dye-sensitization-induced visible-light reduction mechanism, was developed to prepare reduced GO (rGO) and graphene-based TiO2 composite in the absence of any additional reducing agents. It was found that the dye-sensitization-induced reduction process of GO was accompanied with the formation of TiO2-rGO composite nanostructure. The photocatalytic experimental results indicated that the resultant TiO2-rGO nanocomposites exhibited significantly higher photocatalytic performance than pure TiO2 because of a rapid separation of photogenerated electrons and holes by the rGO cocatalyst. PMID:23534830

Wang, Ping; Wang, Jin; Ming, Tingsen; Wang, Xuefei; Yu, Huogen; Yu, Jiaguo; Wang, Yonggang; Lei, Ming

2013-04-03

408

The effect of oxidizing water on metallic restorations in the mouth: in vitro reduction behavior of oxidizing water.  

PubMed

Mouth-rinsing with oxydized water which contains electrolytically generated chlorine is known to hinder dental plaque formation and growth, but it also accelerates the deterioration of metallic restorations in the mouth. The present work consists of an in vitro study to elucidate the electrochemical reactions involved in the reduction of oxydized water on dental alloys through a systematic investigation of the potentiostatic polarization behavior of dental alloy electrodes. The five dental alloys selected for investigation were gold alloy, gold alloy containing platinum, silver-palladium-gold alloy, conventional amalgam and high copper amalgam. The corrosion potentials of all dental alloy electrodes were shown to be more noble in oxydized water than in 0.1N sodium chloride solution. The potential differences between the corrosion potentials were relatively small in the case of amalgam electrodes. The polarization curves for all of the dental alloy electrodes in oxydized water revealed reduction currents of chlorine, hypochlorous acid, dissolved oxygen and oxonium ion. The reduction of chlorine and hypochlorous acid started at a more noble potential than that of dissolved oxygen. The dental alloys studied, except the amalgams, did not dissolve excessively at the corrosion potentials in oxydized water. PMID:9198335

Nishida, T

1997-03-01

409

Global Change Simulations Affect Potential Methane Oxidation in Upland Soils  

NASA Astrophysics Data System (ADS)

Atmospheric concentrations of methane (CH4) are higher now than they have ever been during the past 420,000 years. However, concentrations have remained stable since 1999. Emissions associated with livestock husbandry are unlikely to have changed, so some combination of reduced production in wetlands, more efficient capture by landfills, or increased consumption by biological CH4 oxidation in upland soils may be responsible. Methane oxidizing bacteria are ubiquitous in upland soils and little is known about how these bacteria respond to anthropogenic global change, and how they will influence - or already are influencing - the radiative balance of the atmosphere. Might ongoing and future global changes increase biological CH4 oxidation? Soils were sampled from two field experiments to assess changes in rates of CH4 oxidation in response to global change simulations. Potential activities of CH4 oxidizing bacterial communities were measured through laboratory incubations under optimal temperature, soil moisture, and atmospheric CH4 concentrations (~18 ppm, or 10x ambient). The ongoing 6-year multifactorial Jasper Ridge Global Change Experiment (JRGCE) simulates warming, elevated precipitation, elevated atmospheric CO2, elevated atmospheric N deposition, and increased wildfire frequency in an annual grassland in a Mediterranean-type climate in central California. The ongoing 1-year multifactorial Merriam Climate Change Experiment (MCCE) simulates warming, elevated precipitation, and reduced precipitation in four different types of ecosystems along an elevational gradient in a semi-arid climate in northern Arizona. The high desert grassland, pinyon-juniper woodland, ponderosa pine forest, and mixed conifer forest ecosystems range in annual precipitation from 100 to 1000 mm yr-1, and from productivity being strongly water limited to strongly temperature limited. Among JRGCE soils, elevated atmospheric CO2 increased potential CH4 oxidation rates (p=0.052) and wildfire decreased rates (p=0.014). These responses may be explained by improved soil aggregate stability in the first case, and reduced aggregate stability in the latter case. No effects of warming, elevated precipitation, elevated N deposition, or multifactor interactions were found. Among MCCE soils, similarly, no effects of elevated or reduced precipitation were found. While warming did not affect low elevation ecosystems, it did significantly decrease rates in the highest elevation mixed conifer forest (p=0.004). This suggests a vulnerability of cold-adapted CH4 oxidizing bacteria to elevated temperature. However, bacterial communities in all sampled ecosystems appear to be resistant to drier conditions and unaffected by wetter conditions. If biological oxidation is responsible for the current stability in atmospheric CH4 concentrations, then the improved function of this global CH4 sink is likely driven by indirect plant effects under elevated atmospheric CO2. Improved function, however, may be absent or reversed in future ecosystems that experience increased wildfire frequency and in high altitude and latitude ecosystems that experience rapid warming.

Blankinship, J. C.; Hungate, B. A.

2004-12-01

410

Preparation of graphene by the rapid and mild thermal reduction of graphene oxide induced by microwaves  

Microsoft Academic Search

Rapid and mild thermal reduction of graphene oxide (GO) to graphene was achieved with the assistance of microwaves in a mixed solution of N,N-dimethylacetamide and water (DMAc\\/H2O). The mixed solution works as both a solvent for the produced graphene and a medium to control the temperature of the reactive system up to 165°C. Fourier transform infrared spectrometry, X-ray diffraction, atomic

Wufeng Chen; Lifeng Yan; Prakriti R. Bangal

2010-01-01

411

Bacterial reductive dissolution of crystalline Fe(III) oxide in continuous-flow column reactors  

Microsoft Academic Search

Bacterial reductive dissolution of synthetic crystalline Fe(III) oxide-coated sand was studied in continuous-flow column reactors in comparison with parallel batch cultures. The cumulative amount of aqueous Fe(II) exported from the columns over a 6-month incubation period corresponded to (95.0 {+-} 3.7)% (n = 3) of their original Fe(III) content. Wet-chemical analysis revealed that only (6.5 {+-} 3.2)% of the initial

ERIC E. RODEN; MATILDE M. URRUTIA; CARROLL J. MANN

2000-01-01

412

Carbothermic reduction of zinc sulfide in the presence of calcium oxide and lithium carbonate  

Microsoft Academic Search

The carbothermic reduction of zinc sulfide in the presence of calcium oxide and lithium carbonate was studied using a thermogravimetric\\u000a analysis system (TGA), an X-ray diffractometer (XRD), an atomic absorption spectrometer (AAS), a carbon and sulfur determinator\\u000a (CSD), an elemental analyzer (EA), a scanning electron microscope (SEM) and a surface area analyzer (SAA). Experimental results\\u000a revealed that the reaction rate

Y. C. Peng; C. I. Lin; H. K. Chen

2007-01-01

413

Biogenic gases and the oxidation and reduction of carbon in Amazon River and floodplain waters  

Microsoft Academic Search

Concentrations of COZ, 02, CH4, and N,O in the Amazon River system reflect an oxidation- reduction sequence in combination with physical mixing between the floodplain and the mainstem. Concentrations of CO, ranged from 150 PM in the Amazon mainstem to 200-300 PM in aerobic environments and up to 1,000 PM in oxygen-depleted environments of the floodplain. Apparent oxygen utilization (AOU)

JEFFREY E. RICHEY; ALLAN H. DEVOL; STEVEN C. WOFSY; REYNALDO VICTORIA; MARIA N. G. RIBERIO

1988-01-01

414

Graphene nanosheets by low-temperature thermal reduction of graphene oxide using RF-CVD  

Microsoft Academic Search

A novel technique for synthesis of thin-layered graphene sheets (GNS) were established by hydrogen-induced reduction of graphene oxide at low temperature of 200°C, using radio frequency chemical vapour deposition. The functional group and microstructures of the prepared GNS were characterised by various techniques such as Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, Raman spectroscopy and particle-size analyser. Further

P. Manivel; S. Ramakrishnan; Nikhil K. Kothurkar; N. Ponpandian; D. Mangalaraj; C. Viswanathan

2012-01-01

415

Vanadia-Titania Catalysts for Selective Catalytic Reduction of Nitric-Oxide by Ammonia  

Microsoft Academic Search

The reaction mechanism and catalytic cycle for the selective catalytic reduction of nitric oxide by ammonia over vanadia\\/titania catalysts has been elucidated by in situ on-line FTIR studies under steady-state conditions. Under all reaction conditions, a large concentration of ammonia is adsorbed on both Lewis and Brønsted acid sites, whereas no significant amounts of adsorbed NO are adsorbed. The catalytic

N.-Y. Topsoe; J. A. Dumesic; H. Topsoe

1995-01-01

416

Electrochemical reduction of niobium from oxide-fluoride melts upon electroslag melting  

Microsoft Academic Search

Some regularities of electrochemical reduction of niobium from oxide-fluoride melts upon electroslag melting (ESM) have been\\u000a established for various electrical regimes. It has been found that the use of an asymmetric electric current during ESM substantially\\u000a improves the technological parameters of the electrolysis process. Based on the experimental data obtained, a special program\\u000a has been developed for correcting the electrical

S. A. Istomin; E. A. Pastukhov; S. A. Krasikov; V. V. Ryabov

2007-01-01

417

NO\\/sub x\\/ control for high nitric oxide concentration flows through combustion-driven reduction  

Microsoft Academic Search

The method described herein provides a technique for removing nitrogen oxides from gas streams, discharged from the combustion of carbonaceous materials. Other objectives include: the removal of NO\\/sub x\\/ removal in which a reductant gas is used to further lower the concentration of NO\\/sub x\\/ in the effluent stream, and to provide a method wherein unconverted NO\\/sub x\\/ is removed

J. T. Yeh; J. M. Ekmann; H. W. Pennline; C. J. Drummond

1988-01-01

418

Application of electrolyzed oxidizing water on the reduction of bacterial contamination for seafood  

Microsoft Academic Search

For reducing bacterial contamination, electrolyzed oxidizing water (EO water) has been used to reduce microbial population on seafood and platform of fish retailer. The specimens of tilapia were inoculated with Escherichia coli and Vibrio parahaemolyticus, and then soaked into EO water for up to 10min. EO water achieved additional 0.7logCFU\\/cm2 reduction than tap water on E. coli after 1min treatment

Yu-Ru Huang; Hung-Sheng Hsieh; Shin-Yuan Lin; Shin-Jung Lin; Yen-Con Hung; Deng-Fwu Hwang

2006-01-01

419

Synthesis of graphene-based nanosheets via chemical reduction of exfoliated graphite oxide  

Microsoft Academic Search

Reduction of a colloidal suspension of exfoliated graphene oxide sheets in water with hydrazine hydrate results in their aggregation and subsequent formation of a high-surface-area carbon material which consists of thin graphene-based sheets. The reduced material was characterized by elemental analysis, thermo-gravimetric analysis, scanning electron microscopy, X-ray photoelectron spectroscopy, NMR spectroscopy, Raman spectroscopy, and by electrical conductivity measurements.

Sasha Stankovich; Dmitriy A. Dikin; Richard D. Piner; Kevin A. Kohlhaas; Alfred Kleinhammes; Yuanyuan Jia; Yue Wu; SonBinh T. Nguyen; Rodney S. Ruoff

2007-01-01

420

Mechanism of leakage current reduction of tantalum oxide capacitors by titanium doping  

NASA Astrophysics Data System (ADS)

In this letter, the authors will point out that defect states related to oxygen vacancies in tantalum oxide capacitors can be suppressed by titanium doping, resulting in significant leakage current reduction. The theory is that titanium forms an acceptor which can move at high temperature and neutralize other donors. However, defect states which cannot be suppressed by titanium doping were detected. These are explained by H2O-related contamination occurring at low temperature (<400 °C) during the cooling down period.

Lau, W. S.; Tan, T. S.; Babu, Premila; Sandler, Nathan P.

2007-03-01

421

High-quality single-layer graphene via reparative reduction of graphene oxide  

Microsoft Academic Search

Reduction of graphene oxide (GO) is a promising low-cost synthetic approach to bulk graphene, which offers an accessible route\\u000a to transparent conducting films and flexible electronics. Unfortunately, the release of oxygen-containing functional groups\\u000a inevitably leaves behind vacancies and topological defects on the reduced GO sheet, and its low electrical conductivity hinders\\u000a the development of practical applications. Here, we present a

Boya Dai; Lei Fu; Lei Liao; Nan Liu; Kai Yan; Yongsheng Chen; Zhongfan Liu

2011-01-01

422

The reactions of possible intermediates in the selective catalytic reduction of nitrogen oxides by hydrocarbons  

Microsoft Academic Search

The reactions of formamide and nitromethane, two possible intermediates in the selective catalytic reduction of nitrogen oxides by methane, have been studied over Co-ZSM5, H-ZSM5 and Cu-ZSM5. Formamide, a possible surrogate for nitrosomethane, reacts completely below 250°C over Co-ZSM5 with formation of NH3 and CO by one route and HCN and H2O by another. Inclusion of NO causes partial conversion

N. W. Cant; A. D. Cowan; I. O. Y. Liu; A. Satsuma

1999-01-01

423

DEVELOPMENT OF IMPROVED CATALYSTS FOR THE SELECTIVE CATALYTIC REDUCTION OF NITROGEN OXIDES WITH HYDROCARBONS  

SciTech Connect

Significant work has been done by the investigators on the cerium oxide-copper oxide based sorbent/catalysts for the combined removal of sulfur and nitrogen oxides from the flue gases of stationary sources. A relatively wide temperature window was established for the use of alumina-supported cerium oxide-copper oxide mixtures as regenerable sorbents for SO{sub 2} removal. Preliminary evaluation of these sorbents as catalysts for the selective reduction of NO{sub x} gave promising results with ammonia, but indicated low selectivity when methane was used as the reductant. Since the replacement of ammonia by another reductant is commercially very attractive, in this project, four research components will be undertaken. The investigation of the reaction mechanism, the first component, will help in the selection of promoters to improve the catalytic activity and selectivity of the sorbents in the SCR with methane. This will result in new catalyst formulations (second component). If this research is successful, the combined SO{sub 2}-NO{sub x} removal process based on alumina-supported copper oxide-ceria sorbent/catalysts will become very attractive for commercial applications. The objective of the third component of the project is to develop an alternative SCR process using another inexpensive fuel, residual fuel oil, instead of natural gas. This innovative proposal is based on very scant evidence concerning the good performance of coked catalysts in the selective reduction of NO and if proven to work the process will certainly be commercially viable. The fourth component of the project involves our industrial partner TDA Research, and the objective is to evaluate long- term stability and durability of the prepared sorbent/catalysts. In the second year of the project, the catalysts were investigated for their SCR activity with methane in a microreactor setup and also, by the temperature-programmed desorption (TPD) technique. The results from the SCR experiments indicated that manganese is a more effective promoter than rhodium on the supported copper oxide-ceria catalysts under study; the effectiveness of the promoter increases with the increase in Ce/Cu ratio. The TPD profiles of the unpromoted catalyst (Cu/Ce=3) is different than those promoted with 0.1% rhodium.

Ates Akyurtlu; Jale F. Akyurtlu

2001-09-01

424

Visible light Cr(VI) reduction and organic chemical oxidation by TiO2 photocatalysis.  

PubMed

Here we report the simultaneous Cr(VI) reduction and 4-chlorophenol (4-CP) oxidation in water under visible light (wavelength > 400 nm) using commercial Degussa P25 TiO2. This remarkable observation was attributed to a synergistic effect among TiO2, Cr(VI), and 4-CP. It is well known that TiO2 alone cannot remove either 4-CP or Cr(VI) efficiently under visible light. Moreover, the interaction between Cr(VI) and 4-CP is minimal if not negligible. However, we found that the combination of TiO2, Cr(VI), and 4-CP together can enable efficient Cr(VI) reduction and 4-CP oxidation under visible light. The specific roles of the three ingredients in the synergistic system were studied parametrically. It was found that optimal concentrations of Cr(VI) and TiO2 exist for the Cr(VI) reduction and 4-CP oxidation. Cr(VI) was compared experimentally with other metals such as Cu(ll), Fe(lll), Mn(IV), Ce(IV), and V(V). Among all these metal ions, only Cr(VI) promotes the photocatalytic oxidation of 4-CP. The amount of 4-CP removed was directly related to the initial concentration of Cr(VI). The system was also tested with four other chemicals (aniline, salicylic acid, formic acid, and diethyl phosphoramidate). We found that the same phenomenon occurred for organics containing acid and/or phenolic groups. Cr(VI) was reduced at the same time as the organic chemicals being oxidized during photoreaction under visible light. The synergistic effect was also found with pure anatase TiO2 and rutile TiO2. This study demonstrates a possible economical way for environmental cleanup under visible light. PMID:16173589

Sun, Bo; Reddy, Ettireddy P; Smirniotis, Panagiotis G

2005-08-15

425

Study on the oxidation and reduction of tungsten surface for sub-50 nm patterning process  

SciTech Connect

The oxidation characteristics of tungsten line pattern during the carbon-based mask-layer removal process using oxygen plasmas have been investigated for sub-50 nm patterning processes, in addition to the reduction characteristics of the WO{sub x} layer formed on the tungsten line surface using hydrogen plasmas. The surface oxidation of tungsten lines during the mask layer removal process could be minimized by using low-temperature (300 K) plasma processing for the removal of the carbon-based material. Using this technique, the thickness of WO{sub x} on the tungsten line could be decreased to 25% compared to results from high-temperature processing. The WO{sub x} layer could also be completely removed at a low temperature of 300 K using a hydrogen plasma by supplying bias power to the tungsten substrate to provide a activation energy for the reduction. When this oxidation and reduction technique was applied to actual 40-nm-CD device processing, the complete removal of WO{sub x} formed on the sidewall of tungsten line could be observed.

Kim, Jong Kyu; Nam, Seok Woo; Cho, Sung Il; Jhon, Myung S.; Min, Kyung Suk; Kim, Chan Kyu; Jung, Ho Bum; Yeom, Geun Young [Memory Division Semiconductor Business, Samsung Electronics, San No. 16 Banwol-Ri, Taean-Eup, Hwasung-City, Gyeonggi-Do 449-711, South Korea and Department of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, Gyeonggi-do 440-746 (Korea, Republic of); Memory Division Semiconductor Business, Samsung Electronics, San No. 16 Banwol-Ri, Taean-Eup, Hwasung-City, Gyeonggi-Do 449-711 (Korea, Republic of); Department of Chemical Engineering and Data Storage Systems Center, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213 (United States); Department of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, Gyeonggi-do 440-746 (Korea, Republic of)

2012-11-15

426

Topotactic reduction yielding black titanium oxide nanostructures as metallic electronic conductors.  

PubMed

Detailed analyses of reduced, single crystal, rutile-type TiO(2) via high-resolution transmission electron microscopy (TEM) are reported which reveal that the reduction proceeds topotactically via interstitial diffusion of Ti ions at low temperature, around 350 °C. This important finding encouraged the production of various nanostructured reduced titanium oxides from TiO(2) precursors with morphology retention, and in the process, the synthesis of black titanium oxide nanorods using TiO(2) nanorods was demonstrated. Interestingly, as opposed to the semiconductive behavior of Ti(2)O(3) synthesized at high temperature, topotactically synthesized Ti(2)O(3) exhibits metallic electrical resistance, and the value at room temperature is quite low (<6 ?? m, comparable to graphite). These unique properties are probably due to the lattice strains generally observed for topotactically synthesized Ti(2)O(3). This work shows that topotactically reduced titanium oxides can have fascinating properties as well as nanostructures. PMID:22671142

Tominaka, Satoshi

2012-06-06

427

Sulfide Oxidation Coupled to Arsenate Reduction by a Diverse Microbial Community in a Soda Lake†  

PubMed Central

We characterized the arsenate-reducing, sulfide-oxidizing population of Mono Lake, California, by analyzing the distribution and diversity of rrnA, cbbL, and dissimilatory arsenate reductase (arrA) genes in environmental DNA, arsenate-plus sulfide-amended lake water, mixed cultures, and isolates. The arsenate-reducing community was diverse. An organism represented by an rrnA sequence previously retrieved from Mono Lake and affiliated with the Desulfobulbaceae (Deltaproteobacteria) appears to be an important member of the arsenate-reducing, sulfide-oxidizing community. Sulfide oxidation coupled with arsenate reduction appears to proceed via a two-electron transfer, resulting in the production of arsenite and an intermediate S compound that is subsequently disproportionated. A realgar-like As/S mineral was formed in some experiments.

Hollibaugh, James T.; Budinoff, Charles; Hollibaugh, Ryan A.; Ransom, Briana; Bano, Nasreen

2006-01-01

428

One-pot green synthesis of silver/iron oxide composite nanoparticles for 4-nitrophenol reduction.  

PubMed

Silver/iron oxide composite nanoparticles have been synthesized successfully via a facile one-pot green route by the use of l-arginine, which created an aqueous solution of about pH 10 and acted as a reducing agent for the successive formation of iron oxide and Ag nanoparticles. The product was characterized to be silver-coated iron oxide and iron oxide hydroxide composite nanoparticles with a mean diameter of about 13.8 ± 3.0 nm and 8.53% of Ag in weight. It exhibited good catalytic activity for the reduction of 4-nitrophenol to 4-aminophenol with sodium borohydride. The reduction reaction followed the pseudo-first-order kinetics. The corresponding rate constants increased with the increases of temperature and catalyst amount but decreased with the increase of initial 4-NP concentration, revealing an activation energy of 28.2 kJ/mol and a diffusion controlled mechanism. In addition, this product had quite good stability. No significant activity loss was observed after reuse for 5 cycles. PMID:23416483

Chiou, Jau-Rung; Lai, Bo-Hung; Hsu, Kai-Chih; Chen, Dong-Hwang

2013-01-24

429

Quinone reduction by Rhodothermus marinus succinate:menaquinone oxidoreductase is not stimulated by the membrane potential  

Microsoft Academic Search

Succinate:quinone oxidoreductase (SQR), a di-haem enzyme purified from Rhodothermus marinus, reveals an HQNO-sensitive succinate:quinone oxidoreductase activity with several menaquinone analogues as electron acceptors that decreases with lowering the redox midpoint potential of the quinones. A turnover with the low-potential 2,3-dimethyl-1,4-naphthoquinone that is the closest analogue of menaquinone, although low, can be detected in liposome-reconstituted SQR. Reduction of the quinone is

Andreia S. Fernandes; Alexander A. Konstantinov; Miguel Teixeira; Manuela M.. Pereira

2005-01-01

430

Biogenic iron mineralization accompanying the dissimilatory reduction of hydrous ferric oxide by a groundwater bacterium  

NASA Astrophysics Data System (ADS)

Dissimilatory iron-reducing bacteria (DIRB) couple the oxidation of organic matter or H 2 to the reduction of iron oxides. The factors controlling the rate and extent of these reduction reactions and the resulting solid phases are complex and poorly understood. Batch experiments were conducted with amorphous hydrous ferric oxide (HFO) and the DIRB Shewanella putrefaciens , strain CN32, in well-defined aqueous solutions to investigate the reduction of HFO and formation of biogenic Fe(II) minerals. Lactate-HFO solutions buffered with either bicarbonate or 1,4-piperazinediethanesulfonic acid (PIPES) containing various combinations of phosphate and anthraquinone-2,6-disulfonate (AQDS), were inoculated with S. putrefaciens CN32. AQDS, a humic acid analog that can be reduced to dihydroanthraquinone by CN32, was included because of its ability to function as an electron shuttle during microbial iron reduction and as an indicator of pe. Iron reduction was measured with time, and the resulting solids were analyzed by X-ray diffraction, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) with energy-dispersive X-ray spectroscopy (EDS) and selected area electron diffraction (SAED). In HCO 3 - buffered medium with AQDS, HFO was rapidly and extensively reduced, and the resulting solids were dominated by ferrous carbonate (siderite). Ferrous phosphate (vivianite) was also present in HCO 3 - medium containing P, and fine-grained magnetite was present as a minor phase in HCO 3 - medium with or without P. In the PIPES-buffered medium, the rate and extent of reduction was strongly influenced by AQDS and P. With AQDS, HFO was rapidly converted to highly crystalline magnetite whereas in its absence, magnetite mineralization was slower and the final material less crystalline. In PIPES with both P and AQDS, a green rust type compound [Fe (6-x) II Fe x III (OH) 12 ] x+ [(A 2- ) x/2 · yH 2 O] x- was the dominant solid phase formed; in the absence of AQDS a poorly crystalline product was observed. The measured pe and nature of the solids identified were consistent with thermodynamic considerations. The composition of aqueous media in which microbial iron reduction occurred strongly impacted the rate and extent of iron reduction and the nature of the reduced solids. This, in turn, can provide a feedback control mechanism on microbial metabolism. Hence, in sediments where geochemical conditions promote magnetite formation, two-thirds of the Fe(III) will be sequestered in a form that may not be available for anaerobic bacterial respiration.

Fredrickson, James K.; Zachara, John M.; Kennedy, David W.; Dong, Hailang; Onstott, Tullis C.; Hinman, Nancy W.; Li, Shu-Mei

1998-10-01

431

Oxidation of fugitive methane in ground water linked to bacterial sulfate reduction.  

PubMed

When fugitive methane migrates upward along boreholes of oil and gas wells, it may migrate into shallow ground water or pass through overlying soil to the atmosphere. Prior to this study, there was little information on the fate of fugitive methane that migrates into ground water. In a field study near Lloydminster, Alberta, Canada, we found hydrogeochemical evidence that fugitive methane from an oil well migrated into a shallow aquifer but has been attenuated by dissimilatory bacterial sulfate reduction at low temperature ( approximately 5 degrees C) under anaerobic conditions. Evidence includes spatial and temporal trends in concentrations of methane and sulfate in ground water and associated trends in concentrations of bicarbonate and sulfide. Within 10 m of the oil well, sulfate concentrations were low, and sulfate was enriched in both 34S and 18O. Sulfate concentrations had a strong positive correlation with delta13C values of bicarbonate, and sulfide was depleted in 34S compared to sulfate. These data indicate that bacterial sulfate reduction occurred near the production well. Near the oil well, elevated concentrations of bicarbonate were observed, and the bicarbonate was depleted in 13C. Modeling indicates that the main source of this excess 13C-depleted bicarbonate is oxidized methane. In concert with the sulfate concentration and isotope data, these results support an interpretation that in situ bacterial oxidation of methane has occurred, linked to bacterial sulfate reduction. Bacterial sulfate reduction may play a major role in bioattenuation of fugitive natural gas in ground water in western Canada. PMID:15819940

Van Stempvoort, Dale; Maathuis, Harm; Jaworski, Ed; Mayer, Bernhard; Rich, Kathleen

432

Scalable solid-template reduction for designed reduced graphene oxide architectures.  

PubMed

Herein, we report a solid-state reduction process (in contrast to solution-based approach) by using an environmentally friendly reductant, such as vitamin C (denoted VC), to be directly employed to solid-state graphene oxide (GO) templates to give the highly active rGO architecture with a sheet resistance of as low as 10 ? sq(-1). In addition, predesigned rGO patterns/tracks with tunable resistivity can be directly "written" on a preprepared solid GO film via the inkjet-printing technique using VC/H2O as the printing-ink. This advanced reduction process allows foreign active materials to be preincorporated into the GO matrix to form quality active composite architectures. PMID:23790146

Chen, Jun; Shepherd, Roderick L; Razal, Joselito M; Huang, Xiao; Zhang, Weimin; Zhao, Jie; Harris, Andrew T; Wang, Shu; Minett, Andrew I; Zhang, Hua

2013-07-01

433

Reduction of Mn-oxides by ferrous iron in a flow system: column experiment and reactive transport modeling  

Microsoft Academic Search

The reduction of Mn-oxide by Fe2+ was studied in column experiments, using a column filled with natural Mn-oxide coated sand. Analysis of the Mn-oxide indicated the presence of both Mn(III) and Mn(IV) in the Mn-oxide. The initial exchange capacity of the column was determined by displacement of adsorbed Ca2+ with Mg2+. Subsequently a FeCl2 solution was injected into the column

D. Postma; C. A. J. Appelo

2000-01-01

434

Potential fire behavior in pine flatwood forests following three different fuel reduction techniques  

Microsoft Academic Search

A computer modeling study to determine the potential fire behavior in pine flatwood forests following three fuel hazard reduction treatments: herbicide, prescribed fire and thinning was conducted in Florida following the 1998 wildfire season. Prescribed fire provided immediate protection but this protection quickly disappeared as the rough recovered. Thinning had a similar effect on fireline intensity. Herbicides produced a dramatic

Patrick Brose; Dale Wade

2002-01-01

435

Potential for reduction in utility fuel oil consumption using natural gas  

Microsoft Academic Search

An examination of over 200 electric utility plants that consume residual fuel oil, indicates that in the short term any reduction in electric utility residual fuel oil consumption would be confined to dual-fuel plants and that these plants have the potential to reduce their resid consumption approximately 45 MB\\/D, or about 7% of total electric utility resid consumption in 1989.

S. Thumb; N. Pozar

1991-01-01

436

THEORETICAL INVESTIGATION INTO THE POTENTIAL OF HALOGENATED METHANES TO UNDERGO REDUCTIVE METABOLISM  

EPA Science Inventory

The density-functional theory (DFT) based computational chemistry software package DMol was used to provide insight into the reductive potentials of a series of halomethanes. t is known that certain members of this series are readily reduced in vivo via catalysis by cytochrome P4...

437

The Potential for Automobile Weight Reduction Outlook as of 1975-1976.  

National Technical Information Service (NTIS)

A study has been carried out to evaluate the potential for weight reduction of automobiles. It is concluded that automobiles of lighter weight than those current (1976 models) in the domestic market may be built in each of three size classes, 4, 5, and 6 ...

F. J. Hooven F. E. Kennedy

1978-01-01

438

DEVELOPMENT OF IMPROVED CATALYSTS FOR THE SELECTIVE CATALYTIC REDUCTION OF NITROGEN OXIDES WITH HYDROCARBONS  

SciTech Connect

Significant work has been done by the investigators on the cerium oxide-copper oxide based sorbent/catalysts for the combined removal of sulfur and nitrogen oxides from the flue gases of stationary sources. A relatively wide temperature window was established for the use of alumina-supported cerium oxide-copper oxide mixtures as regenerable sorbents for SO{sub 2} removal. Evaluation of these sorbents as catalysts for the selective reduction of NO{sub x} gave promising results with methane. Since the replacement of ammonia by methane is commercially very attractive, in this project, it was planned to investigate the effect of promoters on the activity and selectivity of copper oxide/cerium oxide-based catalysts and to obtain data on the reaction mechanism for the SCR with methane. The investigation of the reaction mechanism will help in the selection of promoters to improve the catalytic activity and selectivity of the sorbents in the SCR with methane. This will result in new catalyst formulations. The last component of the project involves our industrial partner TDA Research, and the objective is to evaluate long- term stability and durability of the prepared sorbent/catalysts. In the second year of the project, the catalysts were investigated for their SCR activity with methane in a microreactor setup and also, by the temperature-programmed desorption (TPD) technique. The results from the SCR experiments indicated that manganese is a more effective promoter than rhodium on the supported copper oxide-ceria catalysts under study; the effectiveness of the promoter increases with the increase in Ce/Cu ratio. The TPD profiles of the unpromoted catalyst (Cu/Ce=3) is different than those promoted with 0.1% rhodium. In the current reporting period, the screening of the promoted catalysts were completed, sufficient amount of the selected catalysts were prepared and delivered to TDA for long term deactivation testing.

Dr. Ates Akyurlu; Dr. Jale F. Akyurtlu

2003-01-28

439

DNA damaging potential of zinc oxide nanoparticles in human epidermal cells.  

PubMed

At present, more than 20 countries worldwide are manufacturing and marketing different varieties of nanotech-based consumer products of which cosmetics form the largest category. Due to the extremely small size of the nanoparticles (NPs) being used, there is a concern that they may interact directly with macromolecules such as DNA. The present study was aimed to assess the genotoxicity of zinc oxide (ZnO) NPs, one of the widely used ingredients of cosmetics, and other dermatological preparations in human epidermal cell line (A431). A reduction in cell viability as a function of both NP concentration as well as exposure time was observed. ZnO NPs demonstrated a DNA damaging potential as evident from an increased Olive tail moment (OTM) of 2.13 +/- 0.12 (0.8 g/ml) compared to control 1.37 +/- 0.12 in the Comet assay after an exposure of 6 h. ZnO NPs were also found to induce oxidative stress in cells indicated by depletion of glutathione (59% and 51%); catalase (64% and 55%) and superoxide dismutase (72% and 75%) at 0.8 and 0.08 g/ml respectively. Our data demonstrates that ZnO NPs even at low concentrations possess a genotoxic potential in human epidermal cells which may be mediated through lipid peroxidation and oxidative stress. Hence, caution should be taken in their use in dermatological preparations as well as while handling. PMID:19382294

Sharma, Vyom; Shukla, Ritesh K; Saxena, Neha; Parmar, Devendra; Das, Mukul; Dhawan, Alok

2009-03-28

440

Observations of Oxygen Ion Behavior in the Lithium-Based Electrolytic Reduction of Uranium Oxide  

SciTech Connect

Parametric studies were performed on a lithium-based electrolytic reduction process at bench-scale to investigate the behavior of oxygen ions in the reduction of uranium oxide for various electrochemical cell configurations. Specifically, a series of eight electrolytic reduction runs was performed in a common salt bath of LiCl – 1 wt% Li2O. The variable parameters included fuel basket containment material (i.e., stainless steel wire mesh and sintered stainless steel) and applied electrical charge (i.e., 75 – 150% of the theoretical charge for complete reduction of uranium oxide in a basket to uranium metal). Samples of the molten salt electrolyte were taken at regular intervals throughout each run and analyzed to produce a time plot of Li2O concentrations in the bulk salt over the course of the runs. Following each run, the fuel basket was sectioned and the fuel was removed. Samples of the fuel were analyzed for the extent of uranium oxide reduction to metal and for the concentration of salt constituents, i.e., LiCl and Li2O. Extents of uranium oxide reduction ranged from 43 – 70% in stainless steel wire mesh baskets and 8 – 33 % in sintered stainless steel baskets. The concentrations of Li2O in the salt phase of the fuel product from the stainless steel wire mesh baskets ranged from 6.2 – 9.2 wt%, while those for the sintered stainless steel baskets ranged from 26 – 46 wt%. Another series of tests was performed to investigate the dissolution of Li2O in LiCl at 650 °C across various cathode containment materials (i.e., stainless steel wire mesh, sintered stainless steel and porous magnesia) and configurations (i.e., stationary and rotating cylindrical baskets). Dissolution of identical loadings of Li2O particulate reached equilibrium within one hour for stationary stainless steel wire mesh baskets, while the same took several hours for sintered stainless steel and porous magnesia baskets. Rotation of an annular cylindrical basket of stainless steel wire mesh accelerated the Li2O dissolution rate by more than a factor of six.

Steven D. Herrmann; Shelly X. Li; Brenda E. Serrano-Rodriguez

2009-09-01

441

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

PubMed

The dissimilatory metal-reducing bacterium, Shewanella oneidensis MR-1 produced ?-MnS (rambergite) nanoparticles during the concurrent reduction of MnO? and thiosulfate coupled to H? oxidation. To investigate effect of direct microbial reduction of MnO? on MnS formation, two MR-1 mutants defective in outer membrane c-type cytochromes (?mtrC/?omcA and ?mtrC/?omcA/?mtrF) were also used and it was determined that direct reduction of MnO? was dominant relative to chemical reduction by biogenic sulfide generated from thiosulfate reduction. Although bicarbonate was excluded from the medium, incubations of strain MR-1 with lactate as the electron donor produced MnCO? (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 MnCO? formation and that Mn(II) mineralogy was strongly affected by carbonate ions even in the presence of abundant sulfide and weakly alkaline conditions expected to favour the precipitation of MnS. Formation of 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 modelling predictions. Biogenic manganese sulfide may be a manganese sink in the Mn biogeochemical cycle in select environments such as deep anoxic marine basins within the Baltic Sea. PMID:21951417

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

2011-09-27

442

Oxidative Stress and Redox Modulation Potential in Type 1 Diabetes  

PubMed Central

Redox reactions are imperative to preserving cellular metabolism yet must be strictly regulated. Imbalances between reactive oxygen species (ROS) and antioxidants can initiate oxidative stress, which without proper resolve, can manifest into disease. In type 1 diabetes (T1D), T-cell-mediated autoimmune destruction of pancreatic ?-cells is secondary to the primary invasion of macrophages and dendritic cells (DCs) into the islets. Macrophages/DCs, however, are activated by intercellular ROS from resident pancreatic phagocytes and intracellular ROS formed after receptor-ligand interactions via redox-dependent transcription factors such as NF-?B. Activated macrophages/DCs ferry ?-cell antigens specifically to pancreatic lymph nodes, where they trigger reactive T cells through synapse formation and secretion of proinflammatory cytokines and more ROS. ROS generation, therefore, is pivotal in formulating both innate and adaptive immune responses accountable for islet cell autoimmunity. The importance of ROS/oxidative stress as well as potential for redox modulation in the context of T1D will be discussed.

Delmastro, Meghan M.; Piganelli, Jon D.

2011-01-01

443

Radiolytic reductions and oxidations in dimethyl sulfoxide solutions. Solvent effects on reactivity of halogen atom complexes  

SciTech Connect

Radiolysis of dimethyl sulfoxide (DMSO) solutions containing various additives was used to achieve clean one-electron reduction or oxidation of solutes. Pulse radiolysis of benzoquinone in DMSO solutions containing acetone and triethylamine permitted conversion of all primary radicals into reducing species. The total yield of reduction in the {gamma}-radiolysis of methyl viologen solutions was found to be 0.37 {mu}mol/J. In the pulse radiolysis of TMPD and triphenylamine in aerated DMSO containing LiCl and/or CCl{sub 4}, all the primary radicals were converted into oxidizing species and gave a maximum yield of 0.39 {mu}mol/J. In the latter systems, oxidation, was partly by halogen atom complexes. The reactivity of complexes of DMSO (DMSO-Cl DMSO-Br) and of halide ions (Br{sub 2}{sup {sm_bullet}{minus}}, I{sub 2}{sup {sm_bullet}{minus}}) was examined for several organic compounds. DMSO-Cl oxidizes chlorpromazine triphenylamine, and zinc porphyrin with rate constants of the order of 10{sup 7}-10{sup 8} M{sup {minus}1}s{sup {minus}1}, and the rates increase upon addition of CH{sub 2}Cl{sub 2} as well as upon addition of water and formamide. DMSO-Cl also reacts with olefins by addition of Cl to the double bond; the rate constants increase upon increasing the electron-donating properties of the substituents on the double bond. The rate constants for oxidation of chlorpromazine by Br{sub 2}{sup {sm_bullet}{minus}} and I{sub 2}{sup {sm_bullet}{minus}} increase by more than 2 orders of magnitude upon changing the solvent from DMSO gradually to water. The change was less with acetonitrile/water mixtures, and the difference is probably due to differences in ion solvation. 28 refs., 3 figs., 4 tabs.

Kumar, M.; Neta, P. [National Institute of Standards and Technology, Gaithersburg, MD (United States)

1992-04-16

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