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Sample records for oxidation reduction potentials

  1. OXIDATION-REDUCTION POTENTIAL MEASUREMENTS OF IMPORTANT OXIDANTS IN DRINKING WATER

    EPA Science Inventory

    Oxidation-reduction (redox) reactions are important in drinking water treatment and distribution. Oxidation-reduction potential (ORP) measurements of water reflect the tendency of major constituents in the water to accept or lose electrons. Although ORP measurements are valuable...

  2. 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 ...

  3. Iron oxide reduction in deep Baltic Sea sediments: the potential role of anaerobic oxidation of methane

    NASA Astrophysics Data System (ADS)

    Egger, Matthias; Slomp, Caroline P.; Dijkstra, Nikki; Sapart, Célia J.; Risgaard-Petersen, Nils; Kasten, Sabine; Riedinger, Natascha; Barker Jørgensen, Bo

    2015-04-01

    Methane is a powerful greenhouse gas and its emission from marine sediments to the atmosphere is largely controlled by anaerobic oxidation of methane (AOM). Traditionally, sulfate is considered to be the most important electron acceptor for AOM in marine sediments. However, recent studies have shown that AOM may also be coupled to the reduction of iron (Fe) oxides (Beal et al., 2009; Riedinger et al., 2014; Egger et al., 2014). In the Baltic Sea, the transition from the Ancylus freshwater phase to the Littorina brackish/marine phase (A/L-transition) ca. 9-7 ka ago (Zillén et al., 2008) resulted in the accumulation of methanogenic brackish/marine sediments overlying Fe-oxide rich lacustrine deposits. The downward diffusion of methane from the brackish/marine sediments into the lake sediments leads to an ideal diagenetic system to study a potential coupling between Fe oxide reduction and methane oxidation. Here, we use porewater and sediment geochemical data obtained at sites M0063 and M0065 during the IODP Baltic Sea Paleoenvironment Expedition 347 in 2013 to identify the potential mechanisms responsible for the apparent Fe oxide reduction in the non-sulfidic limnic sediments below the A/L transition. In this presentation, we will review the various explanations for the elevated ferrous Fe in the porewater in the lake sediments and we will specifically address the potential role of the reaction of methane with Fe-oxides. References: Beal E. J., House C. H. and Orphan V. J. (2009) Manganese- and iron-dependent marine methane oxidation. Science 325, 184-187. Egger M., Rasigraf O., Sapart C. J., Jilbert T., Jetten M. S. M., Röckmann T., van der Veen C., Banda N., Kartal B., Ettwig K. F. and Slomp C. P. (2014) Iron-mediated anaerobic oxidation of methane in brackish coastal sediments. Environ. Sci. Technol. 49, 277-283. Riedinger N., Formolo M. J., Lyons T. W., Henkel S., Beck A. and Kasten S. (2014) An inorganic geochemical argument for coupled anaerobic oxidation of

  4. ANAEROBIC DDT BIOTRANSFORMATION: ENHANCEMENT BY APPLICATION OF SURFACTANTS AND LOW OXIDATION REDUCTION POTENTIAL

    EPA Science Inventory

    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 pr...

  5. Oxidation-reduction potential of semen: what is its role in the treatment of male infertility?

    PubMed Central

    Agarwal, Ashok; Roychoudhury, Shubhadeep; Bjugstad, Kimberly B.; Cho, Chak-Lam

    2016-01-01

    The diagnosis of male infertility relies largely on conventional semen analysis, and its interpretation has a profound influence on subsequent management of patients. Despite poor correlation between conventional semen parameters and male fertility potential, inclusion of advanced semen quality tests to routine male infertility workup algorithms has not been widely accepted. Oxidative stress is one of the major mediators in various etiologies of male infertility; it has deleterious effects on spermatozoa, including DNA damage. Alleviation of oxidative stress constitutes a potential treatment strategy for male infertility. Measurement of seminal oxidative stress is of crucial role in the identification and monitoring of patients who may benefit from treatments. Various tests including reactive oxygen species (ROS) assay, total antioxidant capacity (TAC) assay or malondialdehyde (MDA) assay used by different laboratories have their own drawbacks. Oxidation-reduction potential (ORP) is a measure of overall balance between oxidants and antioxidants, providing a comprehensive measure of oxidative stress. The MiOXSYS™ System is a novel technology based on a galvanostatic measure of electrons; it presents static ORP (sORP) measures with static referring to the passive or current state of activity between oxidants and antioxidants. Preliminary studies have correlated sORP to poor semen qualities. It is potentially useful in prognostication of assisted reproductive techniques outcomes, screening of antioxidants either in vivo or during IVF cycles, identification of infertile men who may benefit from treatment of oxidative stress, and monitoring of treatment success. The simplified laboratory test requiring a small amount of semen would facilitate clinical application and research in the field. In this paper, we discuss the measurement of ORP by the MiOXSYS System as a real-time assessment of seminal oxidative stress, and argue that it is a potential valuable clinical test

  6. Oxidation-reduction potential of semen: what is its role in the treatment of male infertility?

    PubMed Central

    Agarwal, Ashok; Roychoudhury, Shubhadeep; Bjugstad, Kimberly B.; Cho, Chak-Lam

    2016-01-01

    The diagnosis of male infertility relies largely on conventional semen analysis, and its interpretation has a profound influence on subsequent management of patients. Despite poor correlation between conventional semen parameters and male fertility potential, inclusion of advanced semen quality tests to routine male infertility workup algorithms has not been widely accepted. Oxidative stress is one of the major mediators in various etiologies of male infertility; it has deleterious effects on spermatozoa, including DNA damage. Alleviation of oxidative stress constitutes a potential treatment strategy for male infertility. Measurement of seminal oxidative stress is of crucial role in the identification and monitoring of patients who may benefit from treatments. Various tests including reactive oxygen species (ROS) assay, total antioxidant capacity (TAC) assay or malondialdehyde (MDA) assay used by different laboratories have their own drawbacks. Oxidation-reduction potential (ORP) is a measure of overall balance between oxidants and antioxidants, providing a comprehensive measure of oxidative stress. The MiOXSYS™ System is a novel technology based on a galvanostatic measure of electrons; it presents static ORP (sORP) measures with static referring to the passive or current state of activity between oxidants and antioxidants. Preliminary studies have correlated sORP to poor semen qualities. It is potentially useful in prognostication of assisted reproductive techniques outcomes, screening of antioxidants either in vivo or during IVF cycles, identification of infertile men who may benefit from treatment of oxidative stress, and monitoring of treatment success. The simplified laboratory test requiring a small amount of semen would facilitate clinical application and research in the field. In this paper, we discuss the measurement of ORP by the MiOXSYS System as a real-time assessment of seminal oxidative stress, and argue that it is a potential valuable clinical test

  7. The azo dye Disperse Red 13 and its oxidation and reduction products showed mutagenic potential.

    PubMed

    Chequer, Farah Maria Drumond; Lizier, Thiago Mescoloto; de Felício, Rafael; Zanoni, Maria Valnice Boldrin; Debonsi, Hosana Maria; Lopes, Norberto Peporine; de Oliveira, Danielle Palma

    2015-10-01

    Common water pollutants, azo dyes and their degradation products have frequently shown toxicity, including carcinogenic and mutagenic effects, and can induce serious damage in aquatic organisms and humans. In the present study, the mutagenic potential of the azo dye Disperse Red 13 (DR13) was first evaluated using the Micronucleus Assay in human lymphocytes. Subsequently, in order to mimic hepatic biotransformation, controlled potential electrolysis was carried out with a DR13 solution using a Potentiostat/Galvanostat. In addition, a DR13 solution was oxidized using S9 (homogenate of rat liver cells). DR13 oxidation and the reduction products were identified using HPLC-DAD and GC/MS, and their mutagenic potential investigated by way of a Salmonella/microsome assay using TA98 and YG1041 strains, with no S9. The original azo dye DR13 induced chromosomal damage in human lymphocytes, and the respective oxidation and reduction products also showed mutagenic activity, as detected by the Salmonella/microsome assay. Furthermore sulfate 2-[(4-aminophenyl)ethylamino]-ethanol monohydrate, 2-chloro-4-nitro-benzamine, 4-nitro-benzamine and 2-(ethylphenylamine)-ethanol were identified as products of the DR13 reduction/oxidation reactions. Thus it was concluded that the contamination of water effluents with DR13 is a health risk not only due to the dye itself, but also due to the possibility of drinking contaminated water, considering the harmful compounds that can be produced after hepatic biotransformation. PMID:26247324

  8. The azo dye Disperse Red 13 and its oxidation and reduction products showed mutagenic potential.

    PubMed

    Chequer, Farah Maria Drumond; Lizier, Thiago Mescoloto; de Felício, Rafael; Zanoni, Maria Valnice Boldrin; Debonsi, Hosana Maria; Lopes, Norberto Peporine; de Oliveira, Danielle Palma

    2015-10-01

    Common water pollutants, azo dyes and their degradation products have frequently shown toxicity, including carcinogenic and mutagenic effects, and can induce serious damage in aquatic organisms and humans. In the present study, the mutagenic potential of the azo dye Disperse Red 13 (DR13) was first evaluated using the Micronucleus Assay in human lymphocytes. Subsequently, in order to mimic hepatic biotransformation, controlled potential electrolysis was carried out with a DR13 solution using a Potentiostat/Galvanostat. In addition, a DR13 solution was oxidized using S9 (homogenate of rat liver cells). DR13 oxidation and the reduction products were identified using HPLC-DAD and GC/MS, and their mutagenic potential investigated by way of a Salmonella/microsome assay using TA98 and YG1041 strains, with no S9. The original azo dye DR13 induced chromosomal damage in human lymphocytes, and the respective oxidation and reduction products also showed mutagenic activity, as detected by the Salmonella/microsome assay. Furthermore sulfate 2-[(4-aminophenyl)ethylamino]-ethanol monohydrate, 2-chloro-4-nitro-benzamine, 4-nitro-benzamine and 2-(ethylphenylamine)-ethanol were identified as products of the DR13 reduction/oxidation reactions. Thus it was concluded that the contamination of water effluents with DR13 is a health risk not only due to the dye itself, but also due to the possibility of drinking contaminated water, considering the harmful compounds that can be produced after hepatic biotransformation.

  9. Microbial Fe(III) oxide reduction potential in Chocolate Pots hot spring, Yellowstone National Park.

    PubMed

    Fortney, N W; He, S; Converse, B J; Beard, B L; Johnson, C M; Boyd, E S; Roden, E E

    2016-05-01

    Chocolate Pots hot springs (CP) is a unique, circumneutral pH, iron-rich, geothermal feature in Yellowstone National Park. Prior research at CP has focused on photosynthetically driven Fe(II) oxidation as a model for mineralization of microbial mats and deposition of Archean banded iron formations. However, geochemical and stable Fe isotopic data have suggested that dissimilatory microbial iron reduction (DIR) may be active within CP deposits. In this study, the potential for microbial reduction of native CP Fe(III) oxides was investigated, using a combination of cultivation dependent and independent approaches, to assess the potential involvement of DIR in Fe redox cycling and associated stable Fe isotope fractionation in the CP hot springs. Endogenous microbial communities were able to reduce native CP Fe(III) oxides, as documented by most probable number enumerations and enrichment culture studies. Enrichment cultures demonstrated sustained DIR driven by oxidation of acetate, lactate, and H2 . Inhibitor studies and molecular analyses indicate that sulfate reduction did not contribute to observed rates of DIR in the enrichment cultures through abiotic reaction pathways. Enrichment cultures produced isotopically light Fe(II) during DIR relative to the bulk solid-phase Fe(III) oxides. Pyrosequencing of 16S rRNA genes from enrichment cultures showed dominant sequences closely affiliated with Geobacter metallireducens, a mesophilic Fe(III) oxide reducer. Shotgun metagenomic analysis of enrichment cultures confirmed the presence of a dominant G. metallireducens-like population and other less dominant populations from the phylum Ignavibacteriae, which appear to be capable of DIR. Gene (protein) searches revealed the presence of heat-shock proteins that may be involved in increased thermotolerance in the organisms present in the enrichments as well as porin-cytochrome complexes previously shown to be involved in extracellular electron transport. This analysis offers

  10. Development of polymer lab-on-a-chip (LOC) for oxidation-reduction potential (ORP) measurement.

    PubMed

    Jang, A; Lee, K K; Bishop, P L; Kim, I S; Ahn, C H

    2011-01-01

    Reverse osmosis (RO) desalination has been recognized as a promising method to solve the water shortage problem. Nevertheless, since it is energy intensive and has many problems associated with biofouling/fouling of RO membranes in RO plants, its commercial acceptance is still slow. Especially, as high levels of oxidizing agents negatively affect RO membrane efficiency and life span. So, there is a need to develop sensitive, selective, portable and rapid methods to determine oxidation-reduction potential (ORP) in feed solution. For developing a polymer ORP lab-on-a-chip (LOC), a microchannel patterned on a polymer substrate was successfully filled with 800 nm diameter silica beads using self-assembly bead packing technology. The measured ORPs using the three kinds of redox potential solutions were typically slightly lower than those of the nominal redox potential. But, all of the measurements should be deemed acceptable. The ORP LOC has also a much shorter response time than the conventional potentiometric sensor.

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

    PubMed Central

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

    2007-01-01

    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 the interpretation of ORP in biological process. The ORP was related to the affinities of catabolism and anabolism. The energy expenditure of catabolism and anabolism was directly proportional to overpotential (η), straight coefficient of electrode (LEE), and degree of coupling between catabolism and ORP electrode, respectively. Finally, the limitations of MIRROR Model No. 1 were discussed for expanding the applicability of the model. PMID:17496027

  12. Biological versus mineralogical chromium reduction: potential for reoxidation by manganese oxide.

    PubMed

    Butler, Elizabeth C; Chen, Lixia; Hansel, Colleen M; Krumholz, Lee R; Elwood Madden, Andrew S; Lan, Ying

    2015-11-01

    Hexavalent chromium (Cr(vi), present predominantly as CrO4(2-) in water at neutral pH) is a common ground water pollutant, and reductive immobilization is a frequent remediation alternative. The Cr(iii) that forms upon microbial or abiotic reduction often co-precipitates with naturally present or added iron (Fe), and the stability of the resulting Fe-Cr precipitate is a function of its mineral properties. In this study, Fe-Cr solids were formed by microbial Cr(vi) reduction using Desulfovibrio vulgaris strain RCH1 in the presence of the Fe-bearing minerals hematite, aluminum substituted goethite (Al-goethite), and nontronite (NAu-2, Clay Minerals Society), or by abiotic Cr(vi) reduction by dithionite reduced NAu-2 or iron sulfide (FeS). The properties of the resulting Fe-Cr solids and their behavior upon exposure to the oxidant manganese (Mn) oxide (birnessite) differed significantly. In microcosms containing strain RCH1 and hematite or Al-goethite, there was significant initial loss of Cr(vi) in a pattern consistent with adsorption, and significant Cr(vi) was found in the resulting solids. The solid formed when Cr(vi) was reduced by FeS contained a high proportion of Cr(iii) and was poorly crystalline. In microcosms with strain RCH1 and hematite, Cr precipitates appeared to be concentrated in organic biofilms. Reaction between birnessite and the abiotically formed Cr(iii) solids led to production of significant dissolved Cr(vi) compared to the no-birnessite controls. This pattern was not observed in the solids generated by microbial Cr(vi) reduction, possibly due to re-reduction of any Cr(vi) generated upon oxidation by birnessite by active bacteria or microbial enzymes. The results of this study suggest that Fe-Cr precipitates formed in groundwater remediation may remain stable only in the presence of active anaerobic microbial reduction. If exposed to environmentally common Mn oxides such as birnessite in the absence of microbial activity, there is the potential

  13. Biological versus mineralogical chromium reduction: potential for reoxidation by manganese oxide.

    PubMed

    Butler, Elizabeth C; Chen, Lixia; Hansel, Colleen M; Krumholz, Lee R; Elwood Madden, Andrew S; Lan, Ying

    2015-11-01

    Hexavalent chromium (Cr(vi), present predominantly as CrO4(2-) in water at neutral pH) is a common ground water pollutant, and reductive immobilization is a frequent remediation alternative. The Cr(iii) that forms upon microbial or abiotic reduction often co-precipitates with naturally present or added iron (Fe), and the stability of the resulting Fe-Cr precipitate is a function of its mineral properties. In this study, Fe-Cr solids were formed by microbial Cr(vi) reduction using Desulfovibrio vulgaris strain RCH1 in the presence of the Fe-bearing minerals hematite, aluminum substituted goethite (Al-goethite), and nontronite (NAu-2, Clay Minerals Society), or by abiotic Cr(vi) reduction by dithionite reduced NAu-2 or iron sulfide (FeS). The properties of the resulting Fe-Cr solids and their behavior upon exposure to the oxidant manganese (Mn) oxide (birnessite) differed significantly. In microcosms containing strain RCH1 and hematite or Al-goethite, there was significant initial loss of Cr(vi) in a pattern consistent with adsorption, and significant Cr(vi) was found in the resulting solids. The solid formed when Cr(vi) was reduced by FeS contained a high proportion of Cr(iii) and was poorly crystalline. In microcosms with strain RCH1 and hematite, Cr precipitates appeared to be concentrated in organic biofilms. Reaction between birnessite and the abiotically formed Cr(iii) solids led to production of significant dissolved Cr(vi) compared to the no-birnessite controls. This pattern was not observed in the solids generated by microbial Cr(vi) reduction, possibly due to re-reduction of any Cr(vi) generated upon oxidation by birnessite by active bacteria or microbial enzymes. The results of this study suggest that Fe-Cr precipitates formed in groundwater remediation may remain stable only in the presence of active anaerobic microbial reduction. If exposed to environmentally common Mn oxides such as birnessite in the absence of microbial activity, there is the potential

  14. Microbial Fe(III) oxide reduction potential in Chocolate Pots hot spring, Yellowstone National Park.

    PubMed

    Fortney, N W; He, S; Converse, B J; Beard, B L; Johnson, C M; Boyd, E S; Roden, E E

    2016-05-01

    Chocolate Pots hot springs (CP) is a unique, circumneutral pH, iron-rich, geothermal feature in Yellowstone National Park. Prior research at CP has focused on photosynthetically driven Fe(II) oxidation as a model for mineralization of microbial mats and deposition of Archean banded iron formations. However, geochemical and stable Fe isotopic data have suggested that dissimilatory microbial iron reduction (DIR) may be active within CP deposits. In this study, the potential for microbial reduction of native CP Fe(III) oxides was investigated, using a combination of cultivation dependent and independent approaches, to assess the potential involvement of DIR in Fe redox cycling and associated stable Fe isotope fractionation in the CP hot springs. Endogenous microbial communities were able to reduce native CP Fe(III) oxides, as documented by most probable number enumerations and enrichment culture studies. Enrichment cultures demonstrated sustained DIR driven by oxidation of acetate, lactate, and H2 . Inhibitor studies and molecular analyses indicate that sulfate reduction did not contribute to observed rates of DIR in the enrichment cultures through abiotic reaction pathways. Enrichment cultures produced isotopically light Fe(II) during DIR relative to the bulk solid-phase Fe(III) oxides. Pyrosequencing of 16S rRNA genes from enrichment cultures showed dominant sequences closely affiliated with Geobacter metallireducens, a mesophilic Fe(III) oxide reducer. Shotgun metagenomic analysis of enrichment cultures confirmed the presence of a dominant G. metallireducens-like population and other less dominant populations from the phylum Ignavibacteriae, which appear to be capable of DIR. Gene (protein) searches revealed the presence of heat-shock proteins that may be involved in increased thermotolerance in the organisms present in the enrichments as well as porin-cytochrome complexes previously shown to be involved in extracellular electron transport. This analysis offers

  15. Changes in oxidation-reduction potential during milk fermentation by wild lactic acid bacteria.

    PubMed

    Morandi, Stefano; Silvetti, Tiziana; Tamburini, Alberto; Brasca, Milena

    2016-08-01

    Oxidation-reduction potential (E h) is a fundamental physicochemical property of lactic acid bacteria that determines the microenvironment during the cheese manufacture and ripening. For this reason the E h is of growing interest in dairy research and the dairy industry. The objective of the study was to perform a comprehensive study on the reduction activity of wild lactic acid bacteria strains collected in different periods (from 1960 to 2012) from Italian dairy products. A total of 709 strains belonging to Lactococcus lactis, Enterococcus durans, E. faecium, E. faecalis and Streptococcus thermophilus species were studied for their reduction activity in milk. Kinetics of milk reduction were characterised by the minimum redox potential (E h7) and time of reaching E h7 (t min), the maximum difference between two measures (Δmax) and the time at which these maximum differences occurred (t*). Broad diversity in kinetic parameters was observed at both species and strain levels. E. faecalis and L. lactis resulted to be the most reducing species, while S. thermophilus was characterised by the lowest reducing power while the greatest heterogeneity was pointed out among E. durans and E. faecium strains. Considering the period of collection (1960-2012) we observed that the more recently isolated strains generally showed less reducing activity. This trend was particularly evident for the species E. durans, E. faecium and L. lactis while an opposite trend was observed in E. faecalis species. Data reported in this research provide new information for a deeper understanding of redox potential changes during milk fermentation due to bacterial growth. Gain knowledge of the redox potential of the LAB cultures could allow a better control and standardisation of cheesemaking process. PMID:27600976

  16. Oxidation-Reduction Potential as a Biomarker for Severity and Acute Outcome in Traumatic Brain Injury

    PubMed Central

    Levy, Stewart; Carrick, Matthew; Mains, Charles W.; Slone, Denetta S.

    2016-01-01

    There are few reliable markers for assessing traumatic brain injury (TBI). Elevated levels of oxidative stress have been observed in TBI patients. We hypothesized that oxidation-reduction potential (ORP) could be a potent biomarker in TBI. Two types of ORP were measured in patient plasma samples: the static state of oxidative stress (sORP) and capacity for induced oxidative stress (icORP). Differences in ORP values as a function of time after injury, severity, and hospital discharge were compared using ANOVAs with significance at p ≤ 0.05. Logit regression analyses were used to predict acute outcome comparing ORP, Injury Severity Score (ISS), Abbreviated Injury Scale (AIS), and Glasgow Coma Scale (GCS). Antioxidant capacity (icORP) on day 4 was prognostic for acute outcomes (p < 0.05). An odds ratio of 4.08 was associated with poor acute outcome when icORP > 7.25 μC. IcORP was a better predictor than ISS, AIS, or GCS scores. sORP increased in those with the highest ISS values (p < 0.05). Based on these findings ORP is useful biomarker for severity and acute outcome in TBI patients. Changes in ORP values on day 4 after injury were the most prognostic, suggesting that patients' response to brain injury over time is a factor that determines outcome.

  17. Oxidation-Reduction Potential as a Biomarker for Severity and Acute Outcome in Traumatic Brain Injury.

    PubMed

    Bjugstad, Kimberly B; Rael, Leonard T; Levy, Stewart; Carrick, Matthew; Mains, Charles W; Slone, Denetta S; Bar-Or, David

    2016-01-01

    There are few reliable markers for assessing traumatic brain injury (TBI). Elevated levels of oxidative stress have been observed in TBI patients. We hypothesized that oxidation-reduction potential (ORP) could be a potent biomarker in TBI. Two types of ORP were measured in patient plasma samples: the static state of oxidative stress (sORP) and capacity for induced oxidative stress (icORP). Differences in ORP values as a function of time after injury, severity, and hospital discharge were compared using ANOVAs with significance at p ≤ 0.05. Logit regression analyses were used to predict acute outcome comparing ORP, Injury Severity Score (ISS), Abbreviated Injury Scale (AIS), and Glasgow Coma Scale (GCS). Antioxidant capacity (icORP) on day 4 was prognostic for acute outcomes (p < 0.05). An odds ratio of 4.08 was associated with poor acute outcome when icORP > 7.25 μC. IcORP was a better predictor than ISS, AIS, or GCS scores. sORP increased in those with the highest ISS values (p < 0.05). Based on these findings ORP is useful biomarker for severity and acute outcome in TBI patients. Changes in ORP values on day 4 after injury were the most prognostic, suggesting that patients' response to brain injury over time is a factor that determines outcome. PMID:27642494

  18. Oxidation-Reduction Potential as a Biomarker for Severity and Acute Outcome in Traumatic Brain Injury

    PubMed Central

    Levy, Stewart; Carrick, Matthew; Mains, Charles W.; Slone, Denetta S.

    2016-01-01

    There are few reliable markers for assessing traumatic brain injury (TBI). Elevated levels of oxidative stress have been observed in TBI patients. We hypothesized that oxidation-reduction potential (ORP) could be a potent biomarker in TBI. Two types of ORP were measured in patient plasma samples: the static state of oxidative stress (sORP) and capacity for induced oxidative stress (icORP). Differences in ORP values as a function of time after injury, severity, and hospital discharge were compared using ANOVAs with significance at p ≤ 0.05. Logit regression analyses were used to predict acute outcome comparing ORP, Injury Severity Score (ISS), Abbreviated Injury Scale (AIS), and Glasgow Coma Scale (GCS). Antioxidant capacity (icORP) on day 4 was prognostic for acute outcomes (p < 0.05). An odds ratio of 4.08 was associated with poor acute outcome when icORP > 7.25 μC. IcORP was a better predictor than ISS, AIS, or GCS scores. sORP increased in those with the highest ISS values (p < 0.05). Based on these findings ORP is useful biomarker for severity and acute outcome in TBI patients. Changes in ORP values on day 4 after injury were the most prognostic, suggesting that patients' response to brain injury over time is a factor that determines outcome. PMID:27642494

  19. Oxidation-Reduction Potential as a Biomarker for Severity and Acute Outcome in Traumatic Brain Injury.

    PubMed

    Bjugstad, Kimberly B; Rael, Leonard T; Levy, Stewart; Carrick, Matthew; Mains, Charles W; Slone, Denetta S; Bar-Or, David

    2016-01-01

    There are few reliable markers for assessing traumatic brain injury (TBI). Elevated levels of oxidative stress have been observed in TBI patients. We hypothesized that oxidation-reduction potential (ORP) could be a potent biomarker in TBI. Two types of ORP were measured in patient plasma samples: the static state of oxidative stress (sORP) and capacity for induced oxidative stress (icORP). Differences in ORP values as a function of time after injury, severity, and hospital discharge were compared using ANOVAs with significance at p ≤ 0.05. Logit regression analyses were used to predict acute outcome comparing ORP, Injury Severity Score (ISS), Abbreviated Injury Scale (AIS), and Glasgow Coma Scale (GCS). Antioxidant capacity (icORP) on day 4 was prognostic for acute outcomes (p < 0.05). An odds ratio of 4.08 was associated with poor acute outcome when icORP > 7.25 μC. IcORP was a better predictor than ISS, AIS, or GCS scores. sORP increased in those with the highest ISS values (p < 0.05). Based on these findings ORP is useful biomarker for severity and acute outcome in TBI patients. Changes in ORP values on day 4 after injury were the most prognostic, suggesting that patients' response to brain injury over time is a factor that determines outcome.

  20. Improved myocardial preservation by control of the oxidation-reduction potential.

    PubMed

    Miller, L W; Jellinek, M; Codd, J E; Kolata, R J

    1985-05-01

    Simple cold storage remains the current method of preservation of human heart allografts between removal and transplantation, but this technique is not adequate for prolonged periods of preservation. An alternative to cold storage is machine perfusion of the isolated organ. Although this technique has yielded promising results in kidney preservation, there is limited experience with the heart. One factor limiting the effectiveness of perfusion preservation is the toxicity of oxygen free radicals generated during the perfusion. The generation and reduction of these radicals results in an electron transfer, producing an electrochemical potential known as the redox potential. This study examines the role of machine perfusion in heart preservation with and without the use of a new electrochemical cell that is able to control the redox potential during the perfusion. Hearts were preserved for twenty-four hours by either simple cold storage (Group I), or by machine perfusion with redox monitoring (Group II), or redox control (Group III). Control of the oxidation-reduction potential of the perfusate during machine perfusion of isolated hearts resulted in significantly improved systolic and diastolic function after perfusion compared to hearts that underwent machine perfusion without redox control or simple cold storage.

  1. Chapter A6. Section 6.5. Reduction-Oxidation Potential (Electrode Method)

    USGS Publications Warehouse

    Nordstrom, Darrell Kirk; Wilde, Franceska D.

    2005-01-01

    Reduction-oxidation (redox) potential--also referred to as Eh--is a measure of the equilibrium potential, relative to the standard hydrogen electrode, developed at the interface between a noble metal electrode and an aqueous solution containing electroactive chemical species. Measurements of Eh are used to evaluate geochemical speciation models, and Eh data can provide insights on the evolution and status of water chemistry in an aqueous system. Nevertheless, the measurement is fraught with inherent interferences and limitations that must be understood and considered to determine applicability to the aqueous system being studied. For this reason, Eh determination is not one of the field parameters routinely measured by the U.S. Geological Survey (USGS). This section of the National Field Manual (NFM) describes the equipment and procedures needed to measure Eh in water using a platinum electrode. Guidance as to the limitations and interpretation of Eh measurement also is included.

  2. Development of polymer lab-on-a-chip (LOC) for oxidation-reduction potential (ORP) measurement.

    PubMed

    Jang, A; Lee, K K; Bishop, P L; Kim, I S; Ahn, C H

    2011-01-01

    Reverse osmosis (RO) desalination has been recognized as a promising method to solve the water shortage problem. Nevertheless, since it is energy intensive and has many problems associated with biofouling/fouling of RO membranes in RO plants, its commercial acceptance is still slow. Especially, as high levels of oxidizing agents negatively affect RO membrane efficiency and life span. So, there is a need to develop sensitive, selective, portable and rapid methods to determine oxidation-reduction potential (ORP) in feed solution. For developing a polymer ORP lab-on-a-chip (LOC), a microchannel patterned on a polymer substrate was successfully filled with 800 nm diameter silica beads using self-assembly bead packing technology. The measured ORPs using the three kinds of redox potential solutions were typically slightly lower than those of the nominal redox potential. But, all of the measurements should be deemed acceptable. The ORP LOC has also a much shorter response time than the conventional potentiometric sensor. PMID:21977654

  3. High-Potential Electrocatalytic O2 Reduction with Nitroxyl / NOx Mediators: Implications for Fuel Cells and Aerobic Oxidation Catalysis

    SciTech Connect

    Gerken, James B.; Stahl, Shannon S.

    2015-07-15

    Efficient reduction of O2 to water is a central challenge in energy conversion and aerobic oxidation catalysis. In the present study, we investigate the electrochemical reduction of O2 with soluble organic nitroxyl and nitrogen oxide (NOx) mediators. When used alone, neither organic nitroxyls, such as TEMPO (2,2,6,6-tetramethyl-1-piperidinyl-N-oxyl), nor NOx species, such as sodium nitrite, are effective mediators of electrochemical O2 reduction. The combination of nitroxyl/NOx species, however, mediates sustained O2 reduction at electrochemical potentials of 0.19–0.33 V (vs. Fc/Fc+) in acetonitrile containing trifluoroacetic acid. Mechanistic analysis of the coupled redox reactions supports a process in which the nitrogen oxide catalyst drives aerobic oxidation of a nitroxyl mediator to an oxoammonium species, which then is reduced back to the nitroxyl at the cathode. The electrolysis potential is dictated by the oxoammonium/nitroxyl reduction potential. The high potentials observed with this ORR system benefit from the mechanism-based specificity for four-electron reduction of oxygen to water mediated by NOx species, together with kinetically efficient reduction of oxidized NOx species by TEMPO and other organic nitroxyls. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center, funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences.

  4. Influence of protein interactions on oxidation/reduction midpoint potentials of cofactors in natural and de novo metalloproteins.

    PubMed

    Olson, T L; Williams, J C; Allen, J P

    2013-01-01

    As discussed throughout this special issue, oxidation and reduction reactions play critical roles in the function of many organisms. In photosynthetic organisms, the conversion of light energy drives oxidation and reduction reactions through the transfer of electrons and protons in order to create energy-rich compounds. These reactions occur in proteins such as cytochrome c, a heme-containing water-soluble protein, the bacteriochlorophyll-containing reaction center, and photosystem II where water is oxidized at the manganese cluster. A critical measure describing the ability of cofactors in proteins to participate in such reactions is the oxidation/reduction midpoint potential. In this review, the basic concepts of oxidation/reduction reactions are reviewed with a summary of the experimental approaches used to measure the midpoint potential of metal cofactors. For cofactors in proteins, the midpoint potential not only depends upon the specific chemical characteristics of cofactors but also upon interactions with the surrounding protein, such as the nature of the coordinating ligands and protein environment. These interactions can be tailored to optimize an oxidation/reduction reaction carried out by the protein. As examples, the midpoint potentials of hemes in cytochromes, bacteriochlorophylls in reaction centers, and the manganese cluster of photosystem II are discussed with an emphasis on the influence that protein interactions have on these potentials. This article is part of a Special Issue entitled: Metals in Bioenergetics and Biomimetics Systems.

  5. Analysis of flow decay potential on Galileo. [oxidizer flow rate reduction by iron nitrate precipitates

    NASA Technical Reports Server (NTRS)

    Cole, T. W.; Frisbee, R. H.; Yavrouian, A. H.

    1987-01-01

    The risks posed to the NASA's Galileo spacecraft by the oxidizer flow decay during its extended mission to Jupiter is discussed. The Galileo spacecraft will use nitrogen tetroxide (NTO)/monomethyl hydrazine bipropellant system with one large engine thrust-rated at a nominal 400 N, and 12 smaller engines each thrust-rated at a nominal 10 N. These smaller thrusters, because of their small valve inlet filters and small injector ports, are especially vulnerable to clogging by iron nitrate precipitates formed by NTO-wetted stainless steel components. To quantify the corrosion rates and solubility levels which will be seen during the Galileo mission, corrosion and solubility testing experiments were performed with simulated Galileo materials, propellants, and environments. The results show the potential benefits of propellant sieving in terms of iron and water impurity reduction.

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

    NASA Astrophysics Data System (ADS)

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

    2009-09-01

    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.

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

    PubMed

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

    2011-02-15

    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.

  8. High-Potential Electrocatalytic O2 Reduction with Nitroxyl/NOx Mediators: Implications for Fuel Cells and Aerobic Oxidation Catalysis

    PubMed Central

    2015-01-01

    Efficient reduction of O2 to water is a central challenge in energy conversion and many aerobic oxidation reactions. Here, we show that the electrochemical oxygen reduction reaction (ORR) can be achieved at high potentials by using soluble organic nitroxyl and nitrogen oxide (NOx) mediators. When used alone, neither organic nitroxyls, such as 2,2,6,6-tetramethyl-1-piperidinyl-N-oxyl (TEMPO), nor NOx species, such as sodium nitrite, are effective ORR mediators. The combination of nitroxyl/NOx species, however, mediates sustained O2 reduction with overpotentials as low as 300 mV in acetonitrile containing trifluoroacetic acid. Mechanistic analysis of the coupled redox reactions supports a process in which the nitrogen oxide catalyst drives aerobic oxidation of a nitroxyl mediator to an oxoammonium species, which then is reduced back to the nitroxyl at the cathode. The electrolysis potential is dictated by the oxoammonium/nitroxyl reduction potential. The overpotentials accessible with this ORR system are significantly lower than widely studied molecular metal-macrocycle ORR catalysts and benefit from the mechanism-based specificity for four-electron reduction of oxygen to water mediated by NOx species, together with kinetically efficient reduction of oxidized NOx species by TEMPO and other organic nitroxyls. PMID:27162977

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

    PubMed

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

    1978-04-10

    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 a3 during the titrations; analysis of the EPR spectra provides complementary data on the concentrations of the EPR-detectable species. For the native enzyme in the absence of exogenous ligands, cytochromes a and a3 are reduced to approximately the same extent at all points in the titration. The reduction of the EPR-detectable copper, on the other hand, initially lags the reduction of the two cytochromes but in the final stages of the titration is completely reduced prior to either cytochrome a or a3. These non-Nernstian titration results are interpreted to indicate that the primary mode of heme-heme interaction in cytochrome oxidase involves shifts in oxidation-reduction potential for each of the two cytochromes such that a change in oxidation state for one of the hemes lowers the oxidation-reduction potential of the second heme by approximately 135 mV. In these titrations high spin species are detected which account for 0.25 spin/oxidase maximally. Evidence is presented to indicate that at least some of these signals can be attributed to cytochrome a3+ which has undergone a low-spin to high-spin state transition in the course of the titration. In the presence of carbon monoxide the oxidation-reduction properties of cytochromes a and a3 are markedly altered. The a32+. CO complex is fully formed prior to reduction of either cytochrome a3+ or the EPR-detectable copper. The g = 3 EPR signal attributed to cytochrome a3+ decreases as the MCD intensity of cytochrome a2+ increases; no significant high-spin intensity is observed at any intermediate stage of reduction. We interpret these Nernstian titration

  10. Effect of voltage polarity on oxidation-reduction potential by plasma in water

    NASA Astrophysics Data System (ADS)

    Miyahara, Takashi; Oizumi, Masanobu; Nakatani, Tatsuyuki; Sato, Takehiko

    2014-04-01

    Use of plasma in water for water treatment and medical treatment is growing and raises expectations of finding advanced functions such as an increase of biological compatibility. In the present study with a focus on the variation of oxidation-reduction potential (ORP), relationships between the electrode polarities of plasma in water and the change of water quality such as conductivity, H2O2 concentration, dissolved hydrogen concentration, pH and ORP were revealed. Similar line spectra of radiation at the electrode tip were observed for each case of positive and negative electrode polarity. The emission intensities of OH (309 nm), Hα (656 nm), and OI (777 nm) for the positive discharge were significantly higher than those for the negative one, though the energy consumption during the discharge period of both cases was nearly the same. Positive electrode polarity was found to be more suitable than negative electrode polarity for increasing dissolved hydrogen gas and hydrogen peroxide. The ORP for the positive polarity decreased from 460 to 45 mV and that for the negative polarity decreased from 460 to 183 mV, although the pH and conductivity were not significantly changed.

  11. Effect of voltage polarity on oxidation-reduction potential by plasma in water

    SciTech Connect

    Miyahara, Takashi; Oizumi, Masanobu; Nakatani, Tatsuyuki; Sato, Takehiko

    2014-04-15

    Use of plasma in water for water treatment and medical treatment is growing and raises expectations of finding advanced functions such as an increase of biological compatibility. In the present study with a focus on the variation of oxidation-reduction potential (ORP), relationships between the electrode polarities of plasma in water and the change of water quality such as conductivity, H{sub 2}O{sub 2} concentration, dissolved hydrogen concentration, pH and ORP were revealed. Similar line spectra of radiation at the electrode tip were observed for each case of positive and negative electrode polarity. The emission intensities of OH (309 nm), Hα (656 nm), and OI (777 nm) for the positive discharge were significantly higher than those for the negative one, though the energy consumption during the discharge period of both cases was nearly the same. Positive electrode polarity was found to be more suitable than negative electrode polarity for increasing dissolved hydrogen gas and hydrogen peroxide. The ORP for the positive polarity decreased from 460 to 45 mV and that for the negative polarity decreased from 460 to 183 mV, although the pH and conductivity were not significantly changed.

  12. The structure-function relationship and reduction potentials of high oxidation states of myoglobin and peroxidase.

    PubMed

    He, B; Sinclair, R; Copeland, B R; Makino, R; Powers, L S; Yamazaki, I

    1996-02-20

    In these studies, we substitute electron-withdrawing (diacetyl) or -donating (diethyl) groups at the 2- and 4-positions of the heme in sperm whale Mb and HRP, and examine the structural and biochemical consequences. X-ray absorption spectroscopy shows that increased electron density at the heme results in an increased iron-pyrrole nitrogen average distance in both HRP and Mb, while decreased electron density results in shorter average distances. In HRP, the proximal ligand is constrained by a H-bonding network, and axial effects are manifested entirely at the distal site. Conversely, in Mb, where the proximal ligand is less constrained, axial effects are seen at the proximal side. In HRP, electron density at the heme iron depends linearly on pK3, a measure of the basicity of the porphyrin pyrrole nitrogens [Yamada, H., Makino, R., & Yamazaki, I. (1975) Arch. Biochem. Biophys. 169, 344-353]. Using diethyl substitution (pK3 = 5.8) and diacetyl substitution (pK3 = 3.3) in HRP and Mb, we measured the one-electron reduction potentials (E(O)') of HRP compounds I and II and ferryl Mb. Compound I showed a decreased E(O)' with increasing electron density at the heme (pK3), similar to E(O)' of ferric HRP. E(O)' of HRP compound II and ferryl Mb showed an opposite dependence. This behavior of E(O)', while initially surprising, can be explained by the apparent net positive charge on the iron porphyrin in each oxidation state of the hemoproteins.

  13. Sulfide oxidation and nitrate reduction for potential mitigation of H2S in landfills.

    PubMed

    Fang, Yuan; Du, Yao; Feng, Huan; Hu, Li-Fang; Shen, Dong-Sheng; Long, Yu-Yang

    2015-04-01

    Because H2S emitted by landfill sites has seriously endangered human health, its removal is urgent. H2S removal by use of an autotrophic denitrification landfill biocover has been reported. In this process, nitrate-reducing and sulfide-oxidizing bacteria use a reduced sulfur source as electron donor when reducing nitrate to nitrogen gas and oxidizing sulfur compounds to sulfate. The research presented here was performed to investigate the possibility of endogenous mitigation of H2S by autotrophic denitrification of landfill waste. The sulfide oxidation bioprocess accompanied by nitrate reduction was observed in batch tests inoculated with mineralized refuse from a landfill site. Repeated supply of nitrate resulted in rapid oxidation of the sulfide, indicating that, to a substantial extent, the bioprocess may be driven by functional microbes. This bioprocess can be realized under conditions suitable for the autotrophic metabolic process, because the process occurred without addition of acetate. H2S emissions from landfill sites would be substantially reduced if this bioprocess was introduced.

  14. Anaerobic methane oxidation coupled to nitrite reduction can be a potential methane sink in coastal environments.

    PubMed

    Shen, Li-Dong; Hu, Bao-Lan; Liu, Shuai; Chai, Xiao-Ping; He, Zhan-Fei; Ren, Hong-Xing; Liu, Yan; Geng, Sha; Wang, Wei; Tang, Jing-Liang; Wang, Yi-Ming; Lou, Li-Ping; Xu, Xiang-Yang; Zheng, Ping

    2016-08-01

    In the current study, we investigated nitrite-dependent anaerobic methane oxidation (N-DAMO) as a potential methane sink in the Hangzhou Bay and the adjacent Zhoushan sea area. The potential activity of the N-DAMO process was primarily observed in Hangzhou Bay by means of (13)C-labeling experiments, whereas very low or no potential N-DAMO activity could be detected in the Zhoushan sea area. The measured potential N-DAMO rates ranged from 0.2 to 1.3 nmol (13)CO2 g(-1) (dry sediment) day(-1), and the N-DAMO potentially contributed 2.0-9.4 % to the total microbial methane oxidation in the examined sediments. This indicated that the N-DAMO process may be an alternative pathway in the coastal methane cycle. Phylogenetic analyses confirmed the presence of Candidatus Methylomirabilis oxyfera-like bacteria in all the examined sediments, while the group A members (the dominant bacteria responsible for N-DAMO) were found mainly in Hangzhou Bay. Quantitative PCR showed that the 16S rRNA gene abundance of Candidatus M. oxyfera-like bacteria varied from 5.4 × 10(6) to 5.0 × 10(7) copies g(-1) (dry sediment), with a higher abundance observed in Hangzhou Bay. In addition, the overlying water NO3 (-) concentration and salinity were identified as the most important factors influencing the abundance and potential activity of Candidatus M. oxyfera-like bacteria in the examined sediments. This study showed the evidence of N-DAMO in coastal environments and indicated the importance of N-DAMO as a potential methane sink in coastal environments.

  15. Anaerobic methane oxidation coupled to nitrite reduction can be a potential methane sink in coastal environments.

    PubMed

    Shen, Li-Dong; Hu, Bao-Lan; Liu, Shuai; Chai, Xiao-Ping; He, Zhan-Fei; Ren, Hong-Xing; Liu, Yan; Geng, Sha; Wang, Wei; Tang, Jing-Liang; Wang, Yi-Ming; Lou, Li-Ping; Xu, Xiang-Yang; Zheng, Ping

    2016-08-01

    In the current study, we investigated nitrite-dependent anaerobic methane oxidation (N-DAMO) as a potential methane sink in the Hangzhou Bay and the adjacent Zhoushan sea area. The potential activity of the N-DAMO process was primarily observed in Hangzhou Bay by means of (13)C-labeling experiments, whereas very low or no potential N-DAMO activity could be detected in the Zhoushan sea area. The measured potential N-DAMO rates ranged from 0.2 to 1.3 nmol (13)CO2 g(-1) (dry sediment) day(-1), and the N-DAMO potentially contributed 2.0-9.4 % to the total microbial methane oxidation in the examined sediments. This indicated that the N-DAMO process may be an alternative pathway in the coastal methane cycle. Phylogenetic analyses confirmed the presence of Candidatus Methylomirabilis oxyfera-like bacteria in all the examined sediments, while the group A members (the dominant bacteria responsible for N-DAMO) were found mainly in Hangzhou Bay. Quantitative PCR showed that the 16S rRNA gene abundance of Candidatus M. oxyfera-like bacteria varied from 5.4 × 10(6) to 5.0 × 10(7) copies g(-1) (dry sediment), with a higher abundance observed in Hangzhou Bay. In addition, the overlying water NO3 (-) concentration and salinity were identified as the most important factors influencing the abundance and potential activity of Candidatus M. oxyfera-like bacteria in the examined sediments. This study showed the evidence of N-DAMO in coastal environments and indicated the importance of N-DAMO as a potential methane sink in coastal environments. PMID:27225473

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

    SciTech Connect

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

    2011-05-17

    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.

  17. Gamma radiation interacts with melanin to alter its oxidation-reduction potential and results in electric current production.

    PubMed

    Turick, Charles E; Ekechukwu, Amy A; Milliken, Charles E; Casadevall, Arturo; Dadachova, Ekaterina

    2011-08-01

    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.

  18. [PH and oxidation-reduction potential change of environment during a growth of lactic acid bacteria: effects of oxidizers and reducers].

    PubMed

    Sogomonian, D; Akopian, K; Trchunian, A

    2011-01-01

    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 acidification. These parameters and membrane proton permeability of bacteria (C(M)(H+)) changed in the mediums with different pH. Oxidizer ferrycianide and reducer DL-dithiothreitol affected the bacterial growth and their changed H+ extrusion from the cells and K+ uptake by the cells in experiment conditions. Application of oxidizers and reducers are suggested for regulation of growth related with H+ ion transport in lactic acid bacteria.

  19. Oxidation-reduction potential (ORP) regulation of nutrient removal in activated sludge wastewater treatment plants.

    PubMed

    Li, B; Bishop, P

    2002-01-01

    Redox potential (ORP) regulation of nutrient removal in aeration tanks was tested for one year in three activated sludge wastewater treatment plants in Cincinnati, OH. The experiment results show a good relationship between ORP values and nutrient removal. Macro-biodegradation and sorption of substrate by activated sludge can significantly increase wastewater ORP, indicating the improvement of redox status of the bulk liquor. DO higher than 1.0 mg/L is necessary for good biodegradation and the improvement of liquid redox status. ORP values at higher temperatures (Twater = 20-26 degrees C) were lower than ORP values at lower temperatures (Twater = 14-19 degrees C), caused by the lower oxygen saturation capacity in wastewater and the more rapid oxygen consumption by microorganism under warmer conditions. Nitrification occurred at higher ORP values (380 mV) than did organic substrate oxidation (250 mV). This verifies that different metabolic processes dominate in different ORP ranges. The pilot-scale experiment results demonstrate that the wastewater ORP values continued to increase throughout the whole 6-hour cycle when the influent COD was higher than 1,000 mg/L. For influent with low COD (40-120 mg/L), the wastewater ORP values did not increase in the second 3 hours of the cycle, during which time the microbial-biodegradation within the activated sludge floc dominated. High DO concentrations (6-8 mg/L) did not help improve the redox status. In fully-aerated wastewater, oxygen deeply penetrated into the activated sludge flocs, and microorganisms biodegraded the substrates within the flocs. Endogenous metabolism predominated.

  20. Oxidation, Reduction, and Deoxygenation

    NASA Astrophysics Data System (ADS)

    Madsen, Robert

    In this chapter, methods for oxidation, reduction, and deoxygenation of carbohydrates are presented. In most cases, the reactions have been used on aldoses and their derivatives including glycosides, uronic acids, glycals, and other unsaturated monosaccharides. A number of reactions have also been applied to aldonolactones. The methods include both chemical and enzymatic procedures and some of these can be applied for regioselective transformation of unprotected or partially protected carbohydrates.

  1. Effects of oxidation reduction potential in the bypass micro-aerobic sludge zone on sludge reduction for a modified oxic-settling-anaerobic process.

    PubMed

    Li, Kexun; Wang, Yi; Zhang, Zhongpin; Liu, Dongfang

    2014-01-01

    Batch experiments were conducted to determine the effect of oxidation reduction potential (ORP) on sludge reduction in a bypass micro-aerobic sludge reduction system. The system was composed of a modified oxic-settling-anaerobic process with a sludge holding tank in the sludge recycle loop. The ORPs in the micro-aerobic tanks were set at approximately +350, -90, -150, -200 and -250 mV, by varying the length of aeration time for the tanks. The results show that lower ORP result in greater sludge volume reduction, and the sludge production was reduced by 60% at the lowest ORP. In addition, low ORP caused extracellular polymer substances dissociation and slightly reduced sludge activity. Comparing the sludge backflow characteristics of the micro-aerobic tank's ORP controlled at -250 mV with that of +350 mV, the average soluble chemical oxygen (SCOD), TN and TP increased by 7, 0.4 and 2 times, median particle diameter decreased by 8.5 μm and the specific oxygen uptake rate (SOUR) decreased by 0.0043 milligram O2 per gram suspended solids per minute. For the effluent, SCOD and TN and TP fluctuated around 30, 8.7 and 0.66 mg/L, respectively. Therefore, the effective assignment of ORP in the micro-aerobic tank can remarkably reduce sludge volume and does not affect final effluent quality.

  2. Electrolytic oxide reduction system

    DOEpatents

    Wiedmeyer, Stanley G; Barnes, Laurel A; Williamson, Mark A; Willit, James L; Berger, John F

    2015-04-28

    An electrolytic oxide reduction system according to a non-limiting embodiment of the present invention may include a plurality of anode assemblies, a plurality of cathode assemblies, and a lift system configured to engage the anode and cathode assemblies. The cathode assemblies may be alternately arranged with the anode assemblies such that each cathode assembly is flanked by two anode assemblies. The lift system may be configured to selectively engage the anode and cathode assemblies so as to allow the simultaneous lifting of any combination of the anode and cathode assemblies (whether adjacent or non-adjacent).

  3. Influence of the sewage sludge stabilization process on the value of its oxidation-reduction potential.

    PubMed

    Bartkowska, Izabela

    2014-01-01

    The paper presents the study of a sewage sludge subjected to the process of the autothermal thermophilic stabilization (autothermal thermophilic aerobic digestion (ATAD)), which occurs in a two-stage installation. This study was conducted at the municipal wastewater treatment installation in 2010 and 2011. A thickened sludge was examined in an intermediate tank from which it was next being transferred to successive ATAD installation reactors. The content of the dry mass and organic substances was checked in a raw sludge after the first installation stage and after the ATAD process. Also, the levels of the chemical oxygen demand, the pH and the temperature were measured. During the process, the redox potential was measured. Collected results were subjected to statistical analysis. Our main attention was focused on measurements of the redox potential and further the usefulness of this measurement for the evaluation of the process was considered. The way its values were changing was determined. In the thickened sludge prior to the ATAD process, the value of the redox potential oscillated from 329.90 mV to -108.50 mV. In the first-stage reactor, this value dropped significantly and held within a range between -509.80 mV and -214.60 mV. In the second installation stage, this value ranged between -561.60 mV and -306.40 mV. During the study, fully sanitized and stabilized sludge was obtained. The paper presents the evaluation of the conducted research and conclusions ensuing from it. PMID:25145168

  4. Changes in oxidation reduction potentials and volatile fatty acid production by rumen bacteria when methane synthesis is inhibited.

    PubMed

    Sauer, F D; Teather, R M

    1987-09-01

    Rumen inoculum was cultured in specially designed fermenters that allowed simultaneous measurement of pH, oxidation-reduction potentials, and gas production. The cultures were maintained at pH 6.8 by addition of 1 M NaHCO3 and continuous infusion of artificial saliva. Gas flow was maintained at 20.0 ml/min with a stream of O2-free N2. Monensin at 7.0 micrograms/ml inhibited CH4 production 49% below control concentrations. The sodium salt of 2-bromoethanesulfonic acid added at an initial concentration of 5 x 10(-5) M inhibited CH4 production by 86% and increased H2 production from less than .5 mumol/min in the control to 24.5 mumol/min in the inhibited fermenter. The redox potentials in the control fermenter remained above -.20 V and did not change with the addition of monensin. Bromoethanesulfonic acid rapidly decreased the redox potential in the fermenter to -.33 V. Volatile fatty acid production was not significantly altered by the addition of 2-bromoethanesulfonic acid. The addition of monensin gave the expected decrease in acetate:propionate ratios, decreased acetate and butyrate production, and increased valerate (but not propionate) production.

  5. Impact of oxidation and reduction on the leaching potential of trace metals from spent oil shale. [Reducing and oxidizing environment

    SciTech Connect

    Sullivan, P.J.; Carroll, R.B.

    1985-12-01

    The long-term quality of water produced at spent oil shale disposal facilities is a critical concern. Understanding the release and mobility of trace elements as natural weathering of the disposal pile occurs is particularly important. Because spent oil shale leachates are highly alkaline, weathering reactions that increase leachate acidity, thus trace element release and mobility, must be characterized. In order to simulate weathering environments that would occur in a waste disposal pile (i.e., saturated and unsaturated groundwater environments), spent oil shale has been leached under saturated and unsaturated conditions. Unsaturated conditions (an oxidizing environment) allow the oxidation of iron sulfides and adsorption of carbon dioxide. Saturated leaching conditions (a reducing environment) should not allow the acid generation by oxidation or carbon dioxide adsorption. Both of these conditions generate hydrogen ions and should reduce pH in spent oil shale leachate. Spent oil shale was leached for six weeks and the leachate analyzed for pH, sulfates, arsenic, boron, cadimum, calcium, copper, lithium, magnesium, manganese, sodium, strontium, and zinc. The leaching studies indicate that the oxidizing simulation did not significantly decrease the leachate pH, and under reducing conditions the greatest concentration of trace elements were leached from the shale. The trace elements extracted from the spent oil shale in the greatest concentrations are all soluble in high pH solutions. These results indicate that spent oil shale disposal piles in arid to semiarid environments may maintain an alkaline pH because of an extremely high alkaline buffering capacity. These data also indicate that research on carbon dioxide absorption is needed to assess the long-term contribution of acidity to modify solution pH and trace element mobility. 15 refs., 2 tabs.

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

    PubMed

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

    2007-06-01

    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 maintenance issues, including the potential for fouling of quartz surfaces. To examine the effect of system location on fouling, experiments were conducted at a groundwater treatment facility, wherein aeration, chlorination, and sand filtration were applied sequentially for treatment. In this facility, access to the water stream was available prior to and following each of the treatment steps. Therefore, it was possible to examine the effects of each of these unit operations on fouling dynamics within a UV system. Results indicated zero-order formation kinetics for the fouling reactions at all locations. Increases in oxidation reduction potential, caused by water treatment steps such as aeration and chlorination, increased the rate of sleeve fouling and the rate of irradiance loss within the reactor. Analysis of metals in the sleeve foulant showed that calcium and iron predominate, and relative comparisons of foulant composition to water chemistry highlighted a high affinity for incorporation into the foulant matrix for both iron and manganese, particularly after oxidizing treatment steps. Fouling behavior was observed to be in qualitative agreement with representations of the degree of saturation, relative to the metal:ligand combinations that are believed to comprise a large fraction of the foulants that accumulate on the surfaces of quartz jackets in UV systems used to treat water.

  7. High-Potential Electrocatalytic O2 Reduction with Nitroxyl/NO x Mediators: Implications for Fuel Cells and Aerobic Oxidation Catalysis.

    PubMed

    Gerken, James B; Stahl, Shannon S

    2015-08-26

    Efficient reduction of O2 to water is a central challenge in energy conversion and many aerobic oxidation reactions. Here, we show that the electrochemical oxygen reduction reaction (ORR) can be achieved at high potentials by using soluble organic nitroxyl and nitrogen oxide (NO x ) mediators. When used alone, neither organic nitroxyls, such as 2,2,6,6-tetramethyl-1-piperidinyl-N-oxyl (TEMPO), nor NO x species, such as sodium nitrite, are effective ORR mediators. The combination of nitroxyl/NO x species, however, mediates sustained O2 reduction with overpotentials as low as 300 mV in acetonitrile containing trifluoroacetic acid. Mechanistic analysis of the coupled redox reactions supports a process in which the nitrogen oxide catalyst drives aerobic oxidation of a nitroxyl mediator to an oxoammonium species, which then is reduced back to the nitroxyl at the cathode. The electrolysis potential is dictated by the oxoammonium/nitroxyl reduction potential. The overpotentials accessible with this ORR system are significantly lower than widely studied molecular metal-macrocycle ORR catalysts and benefit from the mechanism-based specificity for four-electron reduction of oxygen to water mediated by NO x species, together with kinetically efficient reduction of oxidized NO x species by TEMPO and other organic nitroxyls.

  8. Chemical and biological reduction of Mn (III)-pyrophosphate complexes: Potential importance of dissolved Mn (III) as an environmental oxidant

    NASA Astrophysics Data System (ADS)

    Kostka, Joel E.; Luther, George W., III; Nealson, Kenneth H.

    1995-03-01

    Dissolved Mn (III) is a strong oxidant which could play an important role in the biogeochemistry of aquatic environments, but little is known about this form of Mn. Mn(III) was shown to form a stable complex with pyrophosphate which is easily measured by uv-vis spectrophotometry. The Mn(III)-pyrophosphate complex was produced at concentrations of 5 μM to 10 mM Mn at neutral pH. Inorganic electron donors, Fe(II) and sulfide, abiotically reduced Mn(III)-pyrophosphate in seconds with a stoichiometry of 1:1 and near 1:2 reductant:Mn (III), respectively. Shewanella putrefaciens strain MR-1 catalyzed the reduction of Mn(III)-pyrophosphate with formate or lactate as electron donors. Reduction of Mn(III) catalyzed by MR-1 was inhibited under aerobic conditions but only slightly under anaerobic conditions upon addition of the alternate electron acceptor, nitrate. MR-1 catalyzed reduction was also inhibited by metabolic inhibitors including formaldehyde, tetrachlorosalicylanilide (TCS), carbonyl cyanide m-chlorophenylhydrazone (CCCP), 2- n-heptyl-4-hydroxyquinoline N-oxide (HQNO), but not antimycin A. When formate or lactate served as electron donor for Mn(III) reduction, carbon oxidation to CO 2 was coupled to the respiration of Mn (III). Using the incorporation of 3H-leucine into the TCA-insoluble fraction of culture extracts, it was shown that Mn (III) reduction was coupled to protein synthesis in MR-1. These data indicate that Mn (III) complexes may be produced under conditions found in aquatic environments and that the reduction of Mn(III) can be coupled to the cycling of Fe, S, and C.

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

    PubMed

    Khanal, S K; Shang, C; Huang, J C

    2003-01-01

    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 a natural ORP of -290 mV (without oxygen injection), and was then followed by oxygenation to raise its ORP by 25 mV above the natural level for each influent sulfate condition. At 6,000 mg/L sulfate without oxygen injection, the dissolved sulfide reached 733.8 mg S/L with a corresponding free sulfide of 250.3 mg S/L, thus showing a considerable inhibition to methanogens. Upon oxygenation to raise its ORP to -265 mV (i.e., a 25 mV increase), the dissolved sulfide was reduced by more than 98.5% with a concomitant 45.9% increase of the methane yield. Under lower influent sulfate levels of 1,000 and 3,000 mg/L, the levels of sulfides produced, even under the natural ORP, did not impose any noticeable toxicity to methanogens. Upon oxygenation to raise the ORP by +25 mV, the corresponding methane yields were actually reduced by 15.5% and 6.2%, respectively. However, such reductions were not due to the adverse impact of the elevated ORP; instead, they were due to a diversion of some organic carbon to support the facultative activities inside the reactor as a result of excessive oxygenation. In other words, to achieve satisfactory sulfide oxidation for the lower influent sulfate conditions, it was not necessary to raise the ORP by as much as +25 mV. The ORP increase actually needed depended on both the influent sulfate and also actual wastewater characteristics. This study had proved that the ORP controlled oxygenation was reliable for achieving consistent online sulfide control.

  10. [Effects of the thiol reagent dithiothreitol on the oxidation-reduction potential and the growth of Escherichia coli in anaerobic conditions at different pH].

    PubMed

    Kirakosian, G; Bagramian, K; Trchunian, A

    2005-01-01

    Changes in the oxidation-reduction potential of medium during the growth of Escherichia coli bacteria under anaerobic conditions in the pH range 5.5-7.5 were studied. It was shown that dithiothreitol, a reducer of thiol groups, at a concentration of 3 mM decreased the initial value of oxidation-reduction potential to negative values of -60 to -220 mV, increased the duration of the lag growth phase, decreased the growth rate, and lowered the acidification of the medium and accumulation of potassium ions independently of pH. The value of the potential in the presence of 3 mM dithiothreitol decreased by 15-20 mV both at alkaline and acidic pH. Dithiothreitol at a concentration of 10 mM stopped molecular hydrogen production at pH 5.5 only. The effects of dithiothreitol on the oxidation-reduction potential and bacterial growth were probably associated with changes in the state of thiol groups in membrane proteins, which affects the generation of membrane potential, proton secretion from cells, K+ accumulation in bacteria, and the activity of membrane-associated enzymes.

  11. Direct electrochemical reduction of metal-oxides

    DOEpatents

    Redey, Laszlo I.; Gourishankar, Karthick

    2003-01-01

    A method of controlling the direct electrolytic reduction of a metal oxide or mixtures of metal oxides to the corresponding metal or metals. A non-consumable anode and a cathode and a salt electrolyte with a first reference electrode near the non-consumable anode and a second reference electrode near the cathode are used. Oxygen gas is produced and removed from the cell. The anode potential is compared to the first reference electrode to prevent anode dissolution and gas evolution other than oxygen, and the cathode potential is compared to the second reference electrode to prevent production of reductant metal from ions in the electrolyte.

  12. [Growth and proton-potassium exchange in Enterococcus hirae: protonophore effect and the role of oxidation-reduction potential].

    PubMed

    Poladian, A; Kirakosian, G; Trchunian, A

    2006-01-01

    Enterococcus hirae ATCC 9790 are able to grow under anaerobic conditions during the fermentation of sugars (pH 8.0) in the presence of the protonophore carbonylcyanide-m-chlorophenylhydrazone at a lesser specific growth rate. As bacteria grow, the acidification of the external medium and a drop in the redox potential from positive to negative (up to -220 mV) values occur. The reducer dithiothreitol, which maintains the negative values of the redox potential, increases the growth rate and acidification of the medium, recovering thereby the effect of the protonophore (without interacting with it). Conversely, the impermeable oxidizer ferricyanide, while maintaining positive values of the redox potential, inhibits the bacterial growth. These results indicate the role of the proton-motive force and importance of reducing processes in bacterial growth. The proton-potassium exchange is inhibited by carbonylcyanide-m-chlorophenylhydazone but is restored with dithiothreitol. Dithiothreiol is able to substitute the proton-motive force; however, ferricyanide and dithiothreitol may also directly affect the bacterial membrane.

  13. Influence on the oxidative potential of a heavy-duty engine particle emission due to selective catalytic reduction system and biodiesel blend.

    PubMed

    Godoi, Ricardo H M; Polezer, Gabriela; Borillo, Guilherme C; Brown, Andrew; Valebona, Fabio B; Silva, Thiago O B; Ingberman, Aline B G; Nalin, Marcelo; Yamamoto, Carlos I; Potgieter-Vermaak, Sanja; Penteado Neto, Renato A; de Marchi, Mary Rosa R; Saldiva, Paulo H N; Pauliquevis, Theotonio; Godoi, Ana Flavia L

    2016-08-01

    Although the particulate matter (PM) emissions from biodiesel fuelled engines are acknowledged to be lower than those of fossil diesel, there is a concern on the impact of PM produced by biodiesel to human health. As the oxidative potential of PM has been suggested as trigger for adverse health effects, it was measured using the Electron Spin Resonance (OP(ESR)) technique. Additionally, Energy Dispersive X-ray Fluorescence Spectroscopy (EDXRF) was employed to determine elemental concentration, and Raman Spectroscopy was used to describe the amorphous carbon character of the soot collected on exhaust PM from biodiesel blends fuelled test-bed engine, with and without Selective Catalytic Reduction (SCR). OP(ESR) results showed higher oxidative potential per kWh of PM produced from a blend of 20% soybean biodiesel and 80% ULSD (B20) engine compared with a blend of 5% soybean biodiesel and 95% ULSD (B5), whereas the SCR was able to reduce oxidative potential for each fuel. EDXRF data indicates a correlation of 0.99 between concentration of copper and oxidative potential. Raman Spectroscopy centered on the expected carbon peaks between 1100cm(-1) and 1600cm(-1) indicate lower molecular disorder for the B20 particulate matter, an indicative of a more graphitic carbon structure. The analytical techniques used in this study highlight the link between biodiesel engine exhaust and increased oxidative potential relative to biodiesel addition on fossil diesel combustion. The EDXRF analysis confirmed the prominent role of metals on free radical production. As a whole, these results suggest that 20% of biodiesel blends run without SCR may pose an increased health risk due to an increase in OH radical generation. PMID:27101453

  14. Influence on the oxidative potential of a heavy-duty engine particle emission due to selective catalytic reduction system and biodiesel blend.

    PubMed

    Godoi, Ricardo H M; Polezer, Gabriela; Borillo, Guilherme C; Brown, Andrew; Valebona, Fabio B; Silva, Thiago O B; Ingberman, Aline B G; Nalin, Marcelo; Yamamoto, Carlos I; Potgieter-Vermaak, Sanja; Penteado Neto, Renato A; de Marchi, Mary Rosa R; Saldiva, Paulo H N; Pauliquevis, Theotonio; Godoi, Ana Flavia L

    2016-08-01

    Although the particulate matter (PM) emissions from biodiesel fuelled engines are acknowledged to be lower than those of fossil diesel, there is a concern on the impact of PM produced by biodiesel to human health. As the oxidative potential of PM has been suggested as trigger for adverse health effects, it was measured using the Electron Spin Resonance (OP(ESR)) technique. Additionally, Energy Dispersive X-ray Fluorescence Spectroscopy (EDXRF) was employed to determine elemental concentration, and Raman Spectroscopy was used to describe the amorphous carbon character of the soot collected on exhaust PM from biodiesel blends fuelled test-bed engine, with and without Selective Catalytic Reduction (SCR). OP(ESR) results showed higher oxidative potential per kWh of PM produced from a blend of 20% soybean biodiesel and 80% ULSD (B20) engine compared with a blend of 5% soybean biodiesel and 95% ULSD (B5), whereas the SCR was able to reduce oxidative potential for each fuel. EDXRF data indicates a correlation of 0.99 between concentration of copper and oxidative potential. Raman Spectroscopy centered on the expected carbon peaks between 1100cm(-1) and 1600cm(-1) indicate lower molecular disorder for the B20 particulate matter, an indicative of a more graphitic carbon structure. The analytical techniques used in this study highlight the link between biodiesel engine exhaust and increased oxidative potential relative to biodiesel addition on fossil diesel combustion. The EDXRF analysis confirmed the prominent role of metals on free radical production. As a whole, these results suggest that 20% of biodiesel blends run without SCR may pose an increased health risk due to an increase in OH radical generation.

  15. Large Scale Reduction of Graphite Oxide Project

    NASA Technical Reports Server (NTRS)

    Calle, Carlos; Mackey, Paul; Falker, John; Zeitlin, Nancy

    2015-01-01

    This project seeks to develop an optical method to reduce graphite oxide into graphene efficiently and in larger formats than currently available. Current reduction methods are expensive, time-consuming or restricted to small, limited formats. Graphene has potential uses in ultracapacitors, energy storage, solar cells, flexible and light-weight circuits, touch screens, and chemical sensors. In addition, graphite oxide is a sustainable material that can be produced from any form of carbon, making this method environmentally friendly and adaptable for in-situ reduction.

  16. Potential Role of Nitrite for Abiotic Fe(II) Oxidation and Cell Encrustation during Nitrate Reduction by Denitrifying Bacteria

    PubMed Central

    Klueglein, Nicole; Zeitvogel, Fabian; Stierhof, York-Dieter; Floetenmeyer, Matthias; Konhauser, Kurt O.; Obst, Martin

    2014-01-01

    Microorganisms have been observed to oxidize Fe(II) at neutral pH under anoxic and microoxic conditions. While most of the mixotrophic nitrate-reducing Fe(II)-oxidizing bacteria become encrusted with Fe(III)-rich minerals, photoautotrophic and microaerophilic Fe(II) oxidizers avoid cell encrustation. The Fe(II) oxidation mechanisms and the reasons for encrustation remain largely unresolved. Here we used cultivation-based methods and electron microscopy to compare two previously described nitrate-reducing Fe(II) oxidizers ( Acidovorax sp. strain BoFeN1 and Pseudogulbenkiania sp. strain 2002) and two heterotrophic nitrate reducers (Paracoccus denitrificans ATCC 19367 and P. denitrificans Pd 1222). All four strains oxidized ∼8 mM Fe(II) within 5 days in the presence of 5 mM acetate and accumulated nitrite (maximum concentrations of 0.8 to 1.0 mM) in the culture media. Iron(III) minerals, mainly goethite, formed and precipitated extracellularly in close proximity to the cell surface. Interestingly, mineral formation was also observed within the periplasm and cytoplasm; intracellular mineralization is expected to be physiologically disadvantageous, yet acetate consumption continued to be observed even at an advanced stage of Fe(II) oxidation. Extracellular polymeric substances (EPS) were detected by lectin staining with fluorescence microscopy, particularly in the presence of Fe(II), suggesting that EPS production is a response to Fe(II) toxicity or a strategy to decrease encrustation. Based on the data presented here, we propose a nitrite-driven, indirect mechanism of cell encrustation whereby nitrite forms during heterotrophic denitrification and abiotically oxidizes Fe(II). This work adds to the known assemblage of Fe(II)-oxidizing bacteria in nature and complicates our ability to delineate microbial Fe(II) oxidation in ancient microbes preserved as fossils in the geological record. PMID:24271182

  17. Destruction of TCE Using Oxidative and Reductive Pathways as Potential In-Situ Treatments for the Contaminated Paducah Groundwater

    SciTech Connect

    Lewis, S; Li, Y; Xu, J; Tee, Y; Lynch, Andrew

    2007-05-01

    When considering reductive technologies for ground water remediation, it is important to understand the underlying principles that govern kinetics of zero-valent metal dechlorination. Studies involving the use of nanoscale metals (characteristic length <100nm) for chloro-organic degradation have increased reaction rates by 1-2 orders of magnitude with minimal intermediate formation. Typically, these metals are synthesized using modifications of the aqueous phase reduction of metal ions using sodium borohydride presented by Glavee and coworkers. The use of a bimetallic system increases the reactivity of the particle surface by incorporating a second metal that can typically act as a hydrogenation promotor.

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

    PubMed Central

    2009-01-01

    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. PMID:19925664

  19. Potential benefits of physical activity during pregnancy for the reduction of gestational diabetes prevalence and oxidative stress.

    PubMed

    Cid, Marcela; González, Marcelo

    2016-03-01

    Changes in quality of nutrition, habits, and physical activity in modern societies increase susceptibility to obesity, which can deleteriously affect pregnancy outcome. In particular, a sedentary lifestyle causes dysfunction in blood flow, which impacts the cardiovascular function of pregnant women. The main molecular mechanism responsible for this effect is the synthesis and bioavailability of nitric oxide, a phenomenon regulated by the antioxidant capacity of endothelial cells. These alterations affect the vascular health of the mother and vascular performance of the placenta, the key organ responsible for the healthy development of the fetus. In addition to the increases in systemic vascular resistance in the mother, placental oxidative stress also affects the feto-placental blood flow. These changes can be integrated into the proteomics and metabolomics of newborns.

  20. Benzene oxidation coupled to sulfate reduction

    USGS Publications Warehouse

    Lovley, D.R.; Coates, J.D.; Woodward, J.C.; Phillips, E.J.P.

    1995-01-01

    Highly reduced sediments from San Diego Bay, Calif., that were incubated under strictly anaerobic conditions metabolized benzene within 55 days when they were exposed initially to I ??M benzene. The rate of benzene metabolism increased as benzene was added back to the benzene-adapted sediments. When a [14C]benzene tracer was included with the benzene added to benzene-adapted sediments, 92% of the added radioactivity was recovered as 14CO2. Molybdate, an inhibitor of sulfate reduction, inhibited benzene uptake and production of 14CO2 from [14C]benzene. Benzene metabolism stopped when the sediments became sulfate depleted, and benzene uptake resumed when sulfate was added again. The stoichiometry of benzene uptake and sulfate reduction was consistent with the hypothesis that sulfate was the principal electron acceptor for benzene oxidation. Isotope trapping experiments performed with [14C]benzene revealed that there was no production of such potential extracellular intermediates of benzene oxidation as phenol, benzoate, p-hydroxybenzoate, cyclohexane, catechol, and acetate. The results demonstrate that benzene can be oxidized in the absence of O2, with sulfate serving as the electron acceptor, and suggest that some sulfate reducers are capable of completely oxidizing benzene to carbon dioxide without the production of extracellular intermediates. Although anaerobic benzene oxidation coupled to chelated Fe(III) has been documented previously, the study reported here provides the first example of a natural sediment compound that can serve as an electron acceptor for anaerobic benzene oxidation.

  1. Thermodynamic constraints on microbial iron oxide reduction

    NASA Astrophysics Data System (ADS)

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

    2003-04-01

    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.

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

    PubMed

    Lackner, Susanne; Horn, Harald

    2012-03-01

    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.

  3. Oxidation-reduction potential changes in aeration tanks and microprofiles of activated sludge floc in medium- and low-strength wastewaters.

    PubMed

    Li, Baikun; Bishop, Paul L

    2004-01-01

    Real-time control of aeration tank operation is key to high-efficiency pollutant removal and energy savings. One of the aims of this study was to examine the potential for using redox potential (oxidation-reduction potential [ORP]) to indicate wastewater quality online in aeration tanks treating medium (chemical oxygen demand [COD] of 70 to 150 mg/L) and low (COD of 15 to 30 mg/L) pollutant-concentration wastewaters. The field-scale data provide a good relationship between ORP values and nutrient removal along the length of the aeration tanks. The ORP values increased dramatically as organic matter was removed along the aeration tanks, indicating the improvement of the bulk liquor redox status. Dissolved oxygen higher than 1.0 mg/L was necessary for good biodegradation and improvement of the liquid redox status. Nitrification occurred at higher ORP values (380 to 420 mV) than was the case for organic substrate oxidation (250 to 300 mV). The microprofiles obtained from microelectrode measurements substantiate the heterogeneity of the microbial processes inside activated sludge flocs. Because of microbial oxygen utilization, the aerobic region in the activated sludge floc was limited to the top layer (0.1 to 0.2 mm) of the activated sludge aggregate present in medium-strength wastewater, with an anoxic zone dominating inside the flocs. When dissolved oxygen in the bulk water was higher than 4.0 mg/L, the anoxic zone inside the floc disappeared. At low wastewater pollutant concentrations, the ORP and dissolved oxygen inside the activated sludge aggregates were higher than those from medium-strength wastewater. The prospect of using ORP as an online control approach for aeration tank operation and the potential reasons for activated sludge floc size varying with pollutant strengths are also discussed.

  4. Intrinsic anion oxidation potentials.

    PubMed

    Johansson, Patrik

    2006-11-01

    Anions of lithium battery salts have been investigated by electronic structure calculations with the objective to find a computational measure to correlate with the observed (in)stability of nonaqueous lithium battery electrolytes vs oxidation often encountered in practice. Accurate prediction of intrinsic anion oxidation potentials is here made possible by computing the vertical free energy difference between anion and neutral radical (Delta Gv) and further strengthened by an empirical correction using only the anion volume as a parameter. The 6-311+G(2df,p) basis set, the VSXC functional, and the C-PCM SCRF algorithm were used. The Delta Gv calculations can be performed using any standard computational chemistry software. PMID:17078600

  5. Molecular Modeling of Environmentally Important Processes: Reduction Potentials

    ERIC Educational Resources Information Center

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

    2004-01-01

    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.

  6. 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 (...

  7. Oxidation reduction potential as a parameter to regulate micro-oxygen injection into anaerobic digester for reducing hydrogen sulphide concentration in biogas.

    PubMed

    Nghiem, Long D; Manassa, Patrick; Dawson, Marcia; Fitzgerald, Shona K

    2014-12-01

    This study aims to evaluate the use of oxidation reduction potential (ORP) to regulate the injection of a small amount of oxygen into an anaerobic digester for reducing H2S concentration in biogas. The results confirm that micro-oxygen injection can be effective for controlling H2S formation during anaerobic digestion without disturbing the performance of the digester. Biogas production, composition, and the removal of volatile solids (VS) and chemical oxygen demand (COD) were monitored to assessment the digester's performance. Six days after the start of the micro-oxygen injection, the ORP values increased to between -320 and -270 mV, from the natural baseline value of -485 mV. Over the same period the H2S concentration in the biogas decreased from over 6000 ppm to just 30 ppm. No discernible changes in the VS and COD removal rates, pH and alkalinity of the digestate or in the biogas production or composition were observed.

  8. Relationship of arsenic concentration with ammonium-nitrogen concentration, oxidation reduction potential and pH of groundwater in arsenic-contaminated areas in Asia

    NASA Astrophysics Data System (ADS)

    Kurosawa, Kiyoshi; Egashira, Kazuhiko; Tani, Masakazu

    This study examines how arsenic (As) concentration is related to ammonium-nitrogen (NH4-N) concentration, oxidation reduction potential (ORP) and pH in groundwater to determine if they have common characteristics in groundwater with high As concentrations in the As-contaminated areas of Bangladesh, Nepal, Cambodia and Vietnam. For the groundwater samples having the three highest As concentrations (top three groundwaters) selected as representatives at each location, As and NH4-N concentrations varied, but ORP and pH did not vary by locations. The ORP value of 30-110 mV, indicating the reducing condition, and the neutral to slightly alkaline pH (pH 7.0-7.6) were presumed to be the key conditions for high As concentrations in groundwater of the study areas. According to the ORP (Eh)-pH diagram, the dominant As species in the top three groundwaters from each location was hydrogen arsenate (HAsO42-). Out of the correlations between the four elements for the top three groundwaters in the areas, only the correlation between As and NH4-N concentrations was positive and significant. Thus, it was identified that NH4-N had an effect on increasing As concentration in groundwater.

  9. Oxidation and Reduction Reactions in Organic Chemistry

    ERIC Educational Resources Information Center

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

    2010-01-01

    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 type…

  10. 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 ...

  11. The variations of Oxidation-Reduction Potential in paddy soil and effects on the methane emission from a periodically irrigated paddy field.

    NASA Astrophysics Data System (ADS)

    Yagi, K.; Iwata, T.; Wakikuromaru, N.

    2014-12-01

    Paddy fields are one of the most important eco-system in monsoon Asia and one of the largest source of CH4 emission. CH4 has significant contribution to the global warming next to CO2 and its greenhouse effect is about 21 times as large as same amount of CO2. CH4 is generated by decomposition of organic matter in soil under anaerobic condition. Oxidation-Reduction Potential (ORP) is the most suitable index representing soil aerobic condition. Or, CH4 is more generated under lower ORP conditions. In this study, ORP in paddy soil was measured during rice cultivated season at a periodically irrigated paddy field, and some effects on the methane flux from the paddy soil was investigated. 3-days flood and 4-days drained condition were regularly repeated at the site from late-June to early October. ORP under flooded condition was measured during irrigated term in 2013 at two mode; regular interval measurement every 2 weeks and intensive measurements during two flooded periods. Methane flux was also measured by the aerodynamic gradient technique. ORP showed rapid decrease when irrigation water was introduced in the paddy field, and lower ORP was shown under the longer flooded condition. From the seasonal-term point of view, lower ORP was shown in later rice season. ORP was suitably modeled as a function of irrigation time. During an irrigation period for four days, higher methane emissions were shown under lower OPR conditions as shown in Fig.1. From the seasonal-term point of view, however, no significant relationship between ORP and methane fluxes. Rapid rise of CH4 flux in early August and gradual decrease between late August and September were shown. It is suggested that seasonal change of methane flux is affected by seasonal changes of soil temperature or the growth level of rice plants.

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

    PubMed

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

    2005-01-01

    Accumulation of poly hydroxyalkanoate (PHA) from excess activated sludge (EAS) was monitored and controlled via the oxidation-reduction potential (ORP) adjusting process. The ORP was adjusted and controlled by only regulating the gas-flow rate pumped into the cultural broth in which sodium acetate (C2) and propionate (C3) were used as carbon sources. Productivity of PHA and the PHA compositions at various C2 to C3 ratios were also investigated. When ORP was maintained at +30 mV, 35% (w/w) of PHA of cell dry weight obtained when C2 was used as sole carbon source. The PHA copolymer, poly-(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), accumulated by EAS with different 3-hydroxyvalarate (3HV) molar fractions ranged from 8% to 78.0% when C2 and C3 was used as sole carbon source, By using ORP to monitor and control the fermentation process instead DO meter, the ORP system provided more precise control to the PHA accumulation process from EAS under low dissolved oxygen (DO) concentrations. Adjusting the C2 to C3 ratios in the media could control the composition such as the 3HV/3HB ratios of the PHBV. Furthermore, it might be an effective way to adjust the 3HV molar fractions in PHBV by controlling the DO concentration via the ORP monitoring system. The 3HV molar fractions in the PHBV declined with increasing ORP from -30 mV to +100 mV by adjusting the gas-flow rate (i.e. the DO concentration). It is concluded that the DO plays a very important role in the synthesis of 3HV subunits in PHBV co-polymer from the EAS. Therefore, a hypothetic metabolic model for PHA synthesis from EAS was proposed to try to explain the results in this study.

  13. Solvothermal reduction of graphene oxide in dimethylformamide

    NASA Astrophysics Data System (ADS)

    Kim, Sujin; Choi, Kwangrok; Park, Sungjin

    2016-11-01

    The reduction of graphene oxide (G-O) is one of the most promising methods for the large scale production of graphene-based materials. In this paper, we report a simple and non-toxic method to produce reduced graphene oxide (rG-O) by refluxing G-O in N, N-dimethylformamide without the aid of a reducing agent. The rG-O materials with high degrees of reduction are prepared and the levels of reduction are controlled using reflux time. Successful reduction is confirmed by combustion-based elemental analysis and X-ray photoelectron and Fourier transform infrared spectroscopy.

  14. Reduction of oxidative stress by bioaugmented strain Pseudomonas sp. HF-1 and selection of potential biomarkers in sequencing batch reactor treating tobacco wastewater.

    PubMed

    Shao, Tiejuan; Yang, Guiqin; Wang, Meizhen; Lu, Zhenmei; Min, Hang; Zhao, Long

    2010-08-01

    Oxidative stress induced by toxic pollutants is generally responsible for the poor performance of many sequencing batch reactors (SBRs) treating organic wastewater. In this study, the oxidative stress in two SBR systems that dealt with tobacco wastewater was monitored by measuring four popular biomarkers (superoxide dismutase, SOD; catalase, CAT; glutathione, GSH; and malondialdehyde, MDA). In the non-BA (non-bio-augmented) system, more intense oxidative stress was induced by a higher concentration of nicotine in tobacco wastewater, and excessive oxidative stress was induced by 250 mg/l of nicotine at the final stage. However, when a nicotine-degrading bacterial strain Pseudomonas sp. HF-1 was added to the BA (bio-augmented) system, the oxidative stress was significantly reduced compared to the non-BA system (p < 0.01).These results suggested that the oxidative stress was mainly induced by nicotine in the SBR treatment of tobacco wastewater, and that bioaugmentation with strain HF-1 would be a potential strategy to reduce the oxidative stress and thereby improve the performance in SBRs. Additionally, the positive correlation between the nicotine content and CAT, GSH and MDA activity in both systems implied that these parameters can be used as biomarkers for reflecting the performance of SBR treatment of tobacco wastewater, and in monitoring nicotine environmental pollution. PMID:20396945

  15. Reduction of metal oxides through mechanochemical processing

    DOEpatents

    Froes, Francis H.; Eranezhuth, Baburaj G.; Senkov, Oleg N.

    2000-01-01

    The low temperature reduction of a metal oxide using mechanochemical processing techniques. The reduction reactions are induced mechanically by milling the reactants. In one embodiment of the invention, titanium oxide TiO.sub.2 is milled with CaH.sub.2 to produce TiH.sub.2. Low temperature heat treating, in the range of 400.degree. C. to 700.degree. C., can be used to remove the hydrogen in the titanium hydride.

  16. Production-scale Direct Oxide Reduction demonstration

    SciTech Connect

    Humiston, T.J.; Santi, D.J.; Long, J.L.; Thomas, R.L.; Delaney, I.C.

    1989-01-23

    A detailed, statistically valid, examination of the direct oxide reduction parameters affecting process yield and purity was planned and executed. Guidelines for attaining yields approaching 100% are presented. Feed oxide, percent excess calcium, and stirrer design affected yield and product purity. Experiments were performed in production-scale equipment utilizing 800 grams of plutonium dioxide per charge. 1 ref., 9 figs., 3 tabs.

  17. Stabilized tin-oxide-based oxidation/reduction catalysts

    NASA Technical Reports Server (NTRS)

    Jordan, Jeffrey D. (Inventor); Schryer, David R. (Inventor); Davis, Patricia P. (Inventor); Leighty, Bradley D. (Inventor); Watkins, Anthony Neal (Inventor); Schryer, Jacqueline L. (Inventor); Oglesby, Donald M. (Inventor); Gulati, Suresh T. (Inventor); Summers, Jerry C. (Inventor)

    2008-01-01

    The invention described herein involves a novel approach to the production of oxidation/reduction catalytic systems. The present invention serves to stabilize the tin oxide reducible metal-oxide coating by co-incorporating at least another metal-oxide species, such as zirconium. In one embodiment, a third metal-oxide species is incorporated, selected from the group consisting of cerium, lanthanum, hafnium, and ruthenium. The incorporation of the additional metal oxide components serves to stabilize the active tin-oxide layer in the catalytic process during high-temperature operation in a reducing environment (e.g., automobile exhaust). Moreover, the additional metal oxides are active components due to their oxygen-retention capabilities. Together, these features provide a mechanism to extend the range of operation of the tin-oxide-based catalyst system for automotive applications, while maintaining the existing advantages.

  18. High-Resolution Distribution of Temperature, Particle and Oxidation/Reduction Potential Anomalies From a Submarine Hydrothermal System: Brothers Volcano, Kermadec Arc

    NASA Astrophysics Data System (ADS)

    Walker, S. L.; Baker, E. T.; de Ronde, C. E.; Yoerger, D.; Embley, R. W.; Davy, B.; Merle, S. G.; Resing, J. A.; Nakamura, K.

    2008-12-01

    The complex relationships between geological setting and hydrothermal venting have, to date, largely been explored with ship-based surveys that effectively examine regional relationships, or with remotely operated vehicles (ROV) and manned submersibles which allow close examination of individual vent fields. Higher- resolution surveys than are possible with ship-based techniques and broader surveys than are practical with ROVs and manned submersibles are necessary for more thoroughly understanding hydrothermal systems and their impact on ocean ecosystems. Autonomous vehicles (AUVs), such as the WHOI Autonomous Benthic Explorer (ABE) can be programmed to conduct high-resolution surveys that systematically cover a broad area of seafloor. Brothers volcano, a hydrothermally active submarine caldera volcano located on the Kermadec arc northwest of New Zealand, was surveyed in July-August 2007 using ABE. Brothers caldera is ~3 km in diameter with a floor depth of 1850 m and walls that rise 290-530 m above the caldera floor. A dacite cone with a summit depth of ~1200 m sits within the caldera, partially merging with the southern caldera wall. Prior to the survey, active hydrothermal vents were known to be perched along the NW caldera wall and located at three sites on the cone. The enclosed caldera, presence of known vent fields with differing geochemical characteristics, and existence of at least one currently inactive site made Brothers volcano an ideal site for a high-resolution survey to explore in greater detail the mass, thermal and geochemical exchanges of hydrothermal systems. During our expedition, the caldera walls and dacite cone (~7 km2) were completely surveyed by ABE with 50-60 m trackline spacing at an altitude of 50 m above the seafloor. Hydrothermal plumes were mapped with ABE's integrated CTD (conductivity- temperature-depth) and sensors measuring optical backscatter (particle concentrations) and oxidation- reduction potential (ORP; indicating the

  19. Graphene oxide reduction by microwave heating

    NASA Astrophysics Data System (ADS)

    Longo, Angela; Carotenuto, Gianfranco

    2016-05-01

    The possibility to prepare thermal reduced graphene oxide (Tr-GO) colloidal suspensions by microwave heating of graphene oxide (GO) suspensions in N-methyl-2-pyrrolidone (NMP) has been investigated. According to transmission electron microscopy (TEM) and absorption and emission spectroscopy characterization, such a type of thermal reduction does not lead to graphene quantum dots formation because only mono-functional oxygen-containing groups are removed.

  20. Oxidation-reduction capacities of aquifer solids

    SciTech Connect

    Barcelona, M.J.; Holm, T.R.

    1991-01-01

    Oxidation-reduction processes play a major role in the mobility, transport, and fate of inorganic and organic chemical constituents in natural waters. Therefore, the manipulation of redox conditions in natural and treated water systems is assumed to be a common option for the control of contaminant concentrations. Measurements of the oxidation (i.e., of aqueous Cr(2+)) and reduction (i.e., of aqueous Cr2O7(2-) and H2O2) capacities of aquifer solids and groundwater have been made on samples from a sand-and-gravel aquifer. The groundwater contributed less than 1% of the system oxidation or reduction poising capacity. Reduction capacities averaged 0.095, 0.111, and 0.136 mequiv/g of dry solids for oxic, transitional, and reducing Eh conditions, respectively. Measured oxidation capacities averaged 0.4 mequiv/g of dry solids over the range of redox intensity conditions. These capacities represent considerable resistance to the adjustment of redox conditions even at uncontaminated sites. Hydrogen peroxide reduction by aquifer solid samples proceeds rapidly relative to microbially mediated decomposition. The study indicates the need for closer scrutiny of the predictability and cost effectiveness of attempts to manipulate redox conditions in poorly poised aquifer systems.

  1. Reduction of Metal Oxide to Metal using Ionic Liquids

    SciTech Connect

    Dr. Ramana Reddy

    2012-04-12

    A novel pathway for the high efficiency production of metal from metal oxide means of electrolysis in ionic liquids at low temperature was investigated. The main emphasis was to eliminate the use of carbon and high temperature application in the reduction of metal oxides to metals. The emphasis of this research was to produce metals such as Zn, and Pb that are normally produced by the application of very high temperatures. The reduction of zinc oxide to zinc and lead oxide to lead were investigated. This study involved three steps in accomplishing the final goal of reduction of metal oxide to metal using ionic liquids: 1) Dissolution of metal oxide in an ionic liquid, 2) Determination of reduction potential using cyclic voltammetry (CV) and 3) Reduction of the dissolved metal oxide. Ionic liquids provide additional advantage by offering a wide potential range for the deposition. In each and every step of the process, more than one process variable has been examined. Experimental results for electrochemical extraction of Zn from ZnO and Pb from PbO using eutectic mixtures of Urea ((NH2)2CO) and Choline chloride (HOC2H4N(CH3)3+Cl-) or (ChCl) in a molar ratio 2:1, varying voltage and temperatures were carried out. Fourier Transform Infra-Red (FTIR) spectroscopy studies of ionic liquids with and without metal oxide additions were conducted. FTIR and induction coupled plasma spectroscopy (ICPS) was used in the characterization of the metal oxide dissolved ionic liquid. Electrochemical experiments were conducted using EG&G potentiostat/galvanostat with three electrode cell systems. Cyclic voltammetry was used in the determination of reduction potentials for the deposition of metals. Chronoamperometric experiments were carried out in the potential range of -0.6V to -1.9V for lead and -1.4V to -1.9V for zinc. The deposits were characterized using XRD and SEM-EDS for phase, morphological and elemental analysis. The results showed that pure metal was deposited on the cathode

  2. Suspension Hydrogen Reduction of Iron Oxide Concentrates

    SciTech Connect

    H.Y. Sohn

    2008-03-31

    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.

  3. Cleanup of plutonium oxide reduction black salts

    SciTech Connect

    Giebel, R.E.; Wing, R.O.

    1986-12-17

    This work describes pyrochemical processes employed to convert direc oxide reduction (DOR) black salts into discardable white salt and plutonium metal. The DOR process utilizes calcium metal as the reductant in a molten calcium chloride solvent salt to convert plutonium oxide to plutonium metal. An insoluble plutonium-rich dispersion called black salt sometimes forms between the metal phase and the salt phase. Black salts accumulated for processing were treated by one of two methods. One method utilized a scrub alloy of 70 wt % magnesium/30 wt % zinc. The other method utilized a pool of plutonium metal to agglomerate the metal phase. The two processes were similar in that calcium metal reductant and calcium chloride solvent salt were used in both cases. Four runs were performed by each method, and each method produced greater than 93% conversion of the black salt.

  4. Electrostatic effects of surface acidic amino acid residues on the oxidation-reduction potentials of the flavodoxin from Desulfovibrio vulgaris (Hildenborough).

    PubMed

    Zhou, Z; Swenson, R P

    1995-03-14

    The flavodoxin from Desulfovibrio vulgaris (Hildenborough) is a member of a family of small, acidic proteins that contain a single noncovalently bound flavin mononucleotide (FMN) cofactor. These proteins function as low-potential one-electron transferases in bacteria. A distinguishing feature of these flavoproteins is the dramatic decrease in the midpoint potential of the semiquinone/hydroquinone couple of the FMN upon binding to the apoprotein (-172 mV for FMN free in solution versus -443 mV when bound), a perturbation thought to be essential for physiological function. The structural basis of this phenomenon is not yet thoroughly understood. In this study, the contribution of six acidic residues (Asp62, Asp63, Glu66, Asp95, Glu99, and Asp106) to the perturbation of the redox properties of the cofactor has been investigated. These residues are clustered about the FMN binding site within 13 A of the N(1) atom of the cofactor. Using oligonucleotide-directed mutagenesis, these residues were neutralized in various combinations through the substitution of asparagine for aspartate and glutamine for glutamate. Seventeen mutant flavodoxins were generated in which one to all six acidic residues were systematically neutralized, often in various spatial configurations. There was no obvious correlation between the midpoint potentials for the oxidized/semiquinone couple and general electrostatic environment, although some differences were noted. However, the midpoint potential for the semiquinone/hydroquinone couple for each of the mutants was less negative than that of the wild type. These increases are strongly correlated with the number of acid to amide substitutions, with an average contribution of about 15 mV per substitution. Collectively, the unfavorable electrostatic environment provided by these acidic residues accounts for approximately one-third of the large midpoint potential shift for the semiquinone/hydroquinone couple that typifies the flavodoxin family

  5. Preliminary reduction of oxidized nickel ores

    NASA Astrophysics Data System (ADS)

    Pakhomov, R. A.; Starykh, R. V.

    2014-11-01

    The laws of gas reduction of oxidized nickel ores (ONOs) are studied. The theoretical prerequisites of the selective reduction of ONO nickel, which are based on the difference between the oxygen partial pressures over the NiO-Ni and FeO-Fe systems, are discussed. The effect of the oxygen partial pressure during reducing roasting of ONOs of ferruginous and magnesia types on the reduction parameters and the quality of the ferronickel formed upon subsequent melting of cinders is experimentally investigated. The optimum conditions of preliminary gas reduction of ONOs are determined. Melting of the cinder of reducing roasting leads to the formation of nickel-rich ferronickel (20-50 wt % Ni for various types of ores) upon the extraction of nickel into ferronickel of >95%, which substantially exceeds the parameters of the existing commercial processes.

  6. Sequential electrolytic oxidation and reduction of aqueous phase energetic compounds.

    PubMed

    Gilbert, David M; Sale, Tom C

    2005-12-01

    Contamination of soils and groundwater with energetic compounds has been documented at many former ammunition manufacturing plants and ranges. Recent research at Colorado State University (CSU) has demonstrated the potential utility of electrolytic degradation of organic compounds using an electrolytic permeable reactive barrier (e-barrier). In principle, an electrolytic approach to degrade aqueous energetic compounds such as hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) or 2,4,6-trinitrotoluene (TNT) can overcome limitations of management strategies that involve solely oxidation or reduction, through sequential oxidation-reduction or reduction-oxidation. The objective of this proof-of-concept research was to evaluate transformation of aqueous phase RDX and TNT in flow-through electrolytic reactors. Laboratory experiments were conducted using six identical column reactors containing porous media and expanded titanium-mixed-metal-oxide electrodes. Three columns tested TNT transformation and three tested RDXtransformation. Electrode sequence was varied between columns and one column for each contaminant acted as a no-voltage control. Over 97% of TNT and 93% of RDX was transformed in the reactors under sequential oxidation-reduction. Significant accumulation of known degradation intermediates was not observed under sequential oxidation-reduction. Removal of approximately 90% of TNT and 40% of RDX was observed under sequential reduction-oxidation. Power requirements on the order of 3 W/m2 were measured during the experiment. This suggests that an in-situ electrolytic approach may be cost-practical for managing groundwater contaminated with explosive compounds.

  7. 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...

  8. Reduction Rates for Higher Americium Oxidation States in Nitric Acid

    SciTech Connect

    Grimes, Travis Shane; Mincher, Bruce Jay; Schmitt, Nicholas C

    2015-09-30

    The stability of hexavalent americium was measured using multiple americium concentrations and nitric acid concentrations after contact with the strong oxidant sodium bismuthate. Contrary to our hypotheses Am(VI) was not reduced faster at higher americium concentrations, and the reduction was only zero-order at short time scales. Attempts to model the reduction kinetics using zero order kinetic models showed Am(VI) reduction in nitric acid is more complex than the autoreduction processes reported by others in perchloric acid. The classical zero-order reduction of Am(VI) was found here only for short times on the order of a few hours. We did show that the rate of Am(V) production was less than the rate of Am(VI) reduction, indicating that some Am(VI) undergoes two electron-reduction to Am(IV). We also monitored the Am(VI) reduction in contact with the organic diluent dodecane. A direct comparison of these results with those in the absence of the organic diluent showed the reduction rates for Am(VI) were not statistically different for both systems. Additional americium oxidations conducted in the presence of Ce(IV)/Ce(III) ions showed that Am(VI) is reduced without the typical growth of Am(V) observed in the systems sans Ce ion. This was an interesting result which suggests a potential new reduction/oxidation pathway for Am in the presence of Ce; however, these results were very preliminary, and will require additional experiments to understand the mechanism by which this occurs. Overall, these studies have shown that hexavalent americium is fundamentally stable enough in nitric acid to run a separations process. However, the complicated nature of the reduction pathways based on the system components is far from being rigorously understood.

  9. Some Tungsten Oxidation-Reduction Chemistry: A Paint Pot Titration.

    ERIC Educational Resources Information Center

    Pickering, Miles; Monts, David L.

    1982-01-01

    Reports an oxidation-reduction experiment using tungsten, somewhat analogous to the classical student experiment involving oxidation-reduction of vanadium. Includes experimental procedures, results, and toxicity/cost of tungsten compounds. (Author/JN)

  10. Oxidation-reduction catalyst and its process of use

    NASA Technical Reports Server (NTRS)

    Jordan, Jeffrey D. (Inventor); Watkins, Anthony Neal (Inventor); Schryer, Jacqueline L. (Inventor); Oglesby, Donald M. (Inventor)

    2008-01-01

    This invention relates generally to a ruthenium stabilized oxidation-reduction catalyst useful for oxidizing carbon monoxide, and volatile organic compounds, and reducing nitrogen oxide species in oxidizing environments, substantially without the formation of toxic and volatile ruthenium oxide species upon said oxidizing environment being at high temperatures.

  11. Lithium metal reduction of plutonium oxide to produce plutonium metal

    DOEpatents

    Coops, Melvin S.

    1992-01-01

    A method is described for the chemical reduction of plutonium oxides to plutonium metal by the use of pure lithium metal. Lithium metal is used to reduce plutonium oxide to alpha plutonium metal (alpha-Pu). The lithium oxide by-product is reclaimed by sublimation and converted to the chloride salt, and after electrolysis, is removed as lithium metal. Zinc may be used as a solvent metal to improve thermodynamics of the reduction reaction at lower temperatures. Lithium metal reduction enables plutonium oxide reduction without the production of huge quantities of CaO--CaCl.sub.2 residues normally produced in conventional direct oxide reduction processes.

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

    PubMed

    Wu, Huifang; Wang, Shihe

    2012-12-01

    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

  13. Analysis of potential helicopter vibration reduction concepts

    NASA Technical Reports Server (NTRS)

    Landgrebe, A. J.; Davis, M. W.

    1985-01-01

    Results of analytical investigations to develop, understand, and evaluate potential helicopter vibration reduction concepts are presented in the following areas: identification of the fundamental sources of vibratory loads, blade design for low vibration, application of design optimization techniques, active higher harmonic control, blade appended aeromechanical devices, and the prediction of vibratory airloads. Primary sources of vibration are identified for a selected four-bladed articulated rotor operating in high speed level flight. The application of analytical design procedures and optimization techniques are shown to have the potential for establishing reduced vibration blade designs through variations in blade mass and stiffness distributions, and chordwise center-of-gravity location.

  14. Copper N-Heterocyclic Carbene: A Catalyst for Aerobic Oxidation or Reduction Reactions.

    PubMed

    Zhan, Le-Wu; Han, Lei; Xing, Ping; Jiang, Biao

    2015-12-18

    Copper N-heterocyclic carbene complexes can be readily used as catalysts for both aerobic oxidation of alcohols to aldehydes and reduction of imines to amines. Our methodology is universal for aromatic substrates and shows versatile tolerance to potential cascade reactions. A one-pot tandem synthetic strategy could afford useful imines and secondary amines via an oxidation-reduction strategy.

  15. Copper N-Heterocyclic Carbene: A Catalyst for Aerobic Oxidation or Reduction Reactions.

    PubMed

    Zhan, Le-Wu; Han, Lei; Xing, Ping; Jiang, Biao

    2015-12-18

    Copper N-heterocyclic carbene complexes can be readily used as catalysts for both aerobic oxidation of alcohols to aldehydes and reduction of imines to amines. Our methodology is universal for aromatic substrates and shows versatile tolerance to potential cascade reactions. A one-pot tandem synthetic strategy could afford useful imines and secondary amines via an oxidation-reduction strategy. PMID:26633757

  16. Catalyst for reduction of nitrogen oxides

    DOEpatents

    Ott, Kevin C.

    2010-04-06

    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. The supported catalyst containing iron, manganese, and cerium showed 80 percent conversion at 113 degrees Celsius of a feed gas containing nitrogen oxides having 4 parts NO to one part NO.sub.2, about one equivalent ammonia, and excess oxygen; conversion improved to 94 percent at 147 degrees Celsius. N.sub.2O was not detected (detection limit: 0.6 percent N.sub.2O).

  17. Graphite Oxide: Structure, Reduction and Applications

    NASA Astrophysics Data System (ADS)

    Gao, Wei

    This thesis proposes a modified structure model for graphite oxide (GO), an important precursor in graphene chemistry, develops a new strategy to convert GO back to graphene-like structure, and demonstrates its possible applications in both water purification and supercapacitor technologies. GO, a nontraditional compound first obtained from graphite oxidation over 150 years ago, is now becoming an important player in the production of graphene-based materials, which has high technological relevance. GO structure and reduction have been vigorously investigated, but its precise chemical structure still remains obscure, and the complete restoration of the sp2 carbon lattice has not yet been achieved. In our work, solid state 13C NMR (MAS) analysis offered a piece of evidence for five or six-membered ring lactol structure existing in GO that had never been assigned before, leading to a modified Lerf-Klinowski model for GO. A three-step reduction strategy, involving sodium borohydride (NaBH4), sulfuric acid, and high temperature thermal annealing, described in the thesis, successfully reduced GO back to chemically converted graphene (CCG) with the lowest heteroatom abundance among all those previously reported. In addition to the chemical significance of graphene/CCG production, GO and its derivatives were used as novel adsorbents in water purification. GO-coated sand showed higher retention than ordinary sand for both Rhodamine B and mercuric ion (Hg2+) contaminants in water. Further functionalization of GO with thiophenol resulted in better adsorption capacity toward Hg2+ than that of activated carbon. In addition, free-standing films of GO were treated and reduced with a CO 2 laser beam into different conductive reduced GO (RGO) patterns, and directly used as supercapacitor devices which showed good cyclic stability and energy storage capacities comparable to that of existing thin film ultracapacitors. GO turned out to be a solid electrolyte with anisotropic proton

  18. Potential reduction of DSN uplink energy cost

    NASA Technical Reports Server (NTRS)

    Dolinsky, S.; Degroot, N. F.

    1982-01-01

    DSN Earth stations typically transmit more power than that required to meet minimum specifications for uplink performance. Energy and cost savings that could result from matching the uplink power to the amount required for specified performance are studied. The Galileo mission was selected as a case study. Although substantial reduction in transmitted energy is possible, potential savings in source energy (oil or electricity) savings are much less. This is because of the rising inefficiency in power conversion and radio frequency power generation that accompanies reduced power output.

  19. REPEATED REDUCTIVE AND OXIDATIVE TREATMENTS ON GRANULAR ACTIVATED CARBON

    EPA Science Inventory

    Fenton oxidation and Fenton oxidation preceded by reduction solutions were applied to granular activated carbon (GAC) to chemically regenerate the adsorbent. No adsorbate was present on the GAC so physicochemical effects from chemically aggressive regeneration of the carbon coul...

  20. Reduction of Amine N-Oxides by Diboron Reagents

    PubMed Central

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

    2011-01-01

    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. PMID:21812467

  1. Treatment of oxide spent fuel using the lithium reduction process

    SciTech Connect

    Karell, E.J.; Pierce, R.D.; Mulcahey, T.P.

    1996-05-01

    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.

  2. Oxidation-Reduction Resistance of Advanced Copper Alloys

    NASA Technical Reports Server (NTRS)

    Greenbauer-Seng, L. (Technical Monitor); Thomas-Ogbuji, L.; Humphrey, D. L.; Setlock, J. A.

    2003-01-01

    Resistance to oxidation and blanching is a key issue for advanced copper alloys under development for NASA's next generation of reusable launch vehicles. Candidate alloys, including dispersion-strengthened Cu-Cr-Nb, solution-strengthened Cu-Ag-Zr, and ODS Cu-Al2O3, are being evaluated for oxidation resistance by static TGA exposures in low-p(O2) and cyclic oxidation in air, and by cyclic oxidation-reduction exposures (using air for oxidation and CO/CO2 or H2/Ar for reduction) to simulate expected service environments. The test protocol and results are presented.

  3. SERS speciation of the electrochemical oxidation-reduction of riboflavin.

    PubMed

    Bailey, Matthew R; Schultz, Zachary D

    2016-08-15

    The reduction and oxidation of the flavin system is an important electron transfer reaction in biological systems. Several reaction pathways exist to connect oxidized to fully reduced riboflavin, each with unique intermediates including a semi-quinone radical. By performing surface-enhanced Raman scattering (SERS) with simultaneous electrochemical detection of riboflavin at different pH values, we are able to correlate reversible changes in spectral features to the current changes observed in the cyclic voltammetry. Multivariate curve resolution analysis of the SERS spectra indicates that three distinct components were present at the SERS electrode at each pH during the potential sweep. To verify and better understand the variations in Raman bands across the voltammogram, density functional theory (DFT) calculations were performed to model the effect of pH and oxidation state on the riboflavin Raman spectrum. The calculated spectra show qualitative agreement with the species identified in the chemometric analysis. This combination of results indicates the presence of the oxidized, semi-quinone, and reduced forms of riboflavin and provides insight into the mechanism of the flavin redox system. PMID:27297697

  4. High potential for iron reduction in upland soils.

    PubMed

    Yang, Wendy H; Liptzin, Daniel

    2015-07-01

    Changes in the redox state of iron (Fe) can be coupled to the biogeochemical cycling of carbon (C), nitrogen, and phosphorus, and thus regulate soil C, ecosystem nutrient availability, and greenhouse gas production. However, its importance broadly in non-flooded upland terrestrial ecosystems is unknown. We measured Fe reduction in soil samples from an annual grassland, a drained peatland, and a humid tropical forest We incubated soil slurries in an anoxic glovebox for 5.5 days and added sodium acetate daily at rates up to 0.4 mg C x (g soil)(-1) x d(-1). Soil moisture, poorly crystalline Fe oxide concentrations, and Fe(II) concentrations differed among study sites in the following order: annual grassland < drained peatland < tropical forest (P < 0.001 for all characteristics). All of the soil samples demonstrated high Fe reduction potential with maximum rates over the course of the incubation averaging 1706 ± 66, 2016 ± 12, and 2973 ± 115 μg Fe x (g soil)(-1) x d(-1) (mean ± SE) for the tropical forest, annual grassland, and drained peatland, respectively. Our results suggest that upland soils from diverse ecosystems have the potential to exhibit high short-term rates of Fe reduction that may play an important role in driving soil biogeochemical processes during periods of anaerobiosis. PMID:26378323

  5. Oxidation and Reduction: Too Many Definitions?

    ERIC Educational Resources Information Center

    Silverstein, Todd P.

    2011-01-01

    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…

  6. Three-Electrode Metal Oxide Reduction Cell

    DOEpatents

    Dees, Dennis W.; Ackerman, John P.

    2005-06-28

    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.

  7. Three-electrode metal oxide reduction cell

    DOEpatents

    Dees, Dennis W.; Ackerman, John P.

    2008-08-12

    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.

  8. STUDIES ON OXIDATION AND REDUCTION BY PNEUMOCOCCUS

    PubMed Central

    Neill, James M.; Avery, Oswald T.

    1924-01-01

    1. Certain enzymes of Pneumococcus are destroyed by oxidizing agents formed when sterile extracts of the cellular substances are exposed to air. The carbohydrate-hydrolyzing enzymes (sucrase, raffinase, inulase, and amylase) are the most easily inactivated under these conditions, although the bacteriolytic enzyme is also reduced in activity. Similar treatment is without effect upon the active concentration of pneumococcus lipase and peptonase. 2. The enzymes which are destroyed during the oxidation of unwashed cell extracts are themselves non-reactive with molecular oxygen. The reactions by which they are destroyed seem to represent oxidations of a type similar to those proposed in previous papers for the oxidation of hemotoxin and of hemoglobin. 3. A study has been made of the relative resistance of different pneumococcus enzymes to heat and to the action of hydrogen peroxide. 4. The various enzymes may be arranged in the same order of relative resistance whether the rating be made from the standpoint of resistance to heat or of resistance to oxidation. Nevertheless, it appears that by a proper regulation of conditions of oxidation, certain labile constituents of a mixture of cellular enzymes may be inactivated with less effect upon the activity of other constituents of the mixture than when inactivation is brought about by heat. PMID:19868928

  9. DEVELOPMENT OF ELECTROCHEMICAL REDUCTION TECHNOLOGY FOR SPENT OXIDE FUELS

    SciTech Connect

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

    2003-02-27

    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.

  10. [Competitive Microbial Oxidation and Reduction of Arsenic].

    PubMed

    Yang, Ting-ting; Bai, Yao-hui; Liang, Jin-song; Huo, Yang; Wang, Ming-xing; Yuan, Lin-ijang

    2016-02-15

    Filters are widely applied in drinking water treatment plants. Our previous study, which explored the asenic redox in a filter of drinking water plant treating underground water, found that As3+ could be oxidized to As5+ by biogenic manganese oxides, while As5+ could be reduced to As3+ by some microbial arsenic reductases in the biofilter system. This microbial competition could influence the system stability and treatment efficiency. To explore its mechanism, this study selected a manganese-oxidizing bacterial strain (Pseudomonas sp. QJX-1) and a arsenic-reducing strain (Brevibacterium sp. LSJ-9) to investigate their competitive relationship in nutrient acquisition and arsenic redox in the presence of Mn2+, As3+ or As5+ The results revealed that the concentration and valence of Mn and As varied with different reaction time; biological manganese oxides dominated the arsenic redox by rapidly oxidizing the As3+ in the existing system and the As3+ generated by arsenic reductase into As. PCR and RT-PCR results indicated that the arsenic reductase (arsC) was inhibited by the manganese oxidase (cumA). The expression of 16S rRNA in QJX-1 was two orders of magnitude higher than that in LSJ-9, which implied QJX-1 was dominant in the bacterial growth. Our data revealed that hydraulic retention time was critical to the valence of arsenic in the effluent of filter in drinking water treatment plant.

  11. [Competitive Microbial Oxidation and Reduction of Arsenic].

    PubMed

    Yang, Ting-ting; Bai, Yao-hui; Liang, Jin-song; Huo, Yang; Wang, Ming-xing; Yuan, Lin-ijang

    2016-02-15

    Filters are widely applied in drinking water treatment plants. Our previous study, which explored the asenic redox in a filter of drinking water plant treating underground water, found that As3+ could be oxidized to As5+ by biogenic manganese oxides, while As5+ could be reduced to As3+ by some microbial arsenic reductases in the biofilter system. This microbial competition could influence the system stability and treatment efficiency. To explore its mechanism, this study selected a manganese-oxidizing bacterial strain (Pseudomonas sp. QJX-1) and a arsenic-reducing strain (Brevibacterium sp. LSJ-9) to investigate their competitive relationship in nutrient acquisition and arsenic redox in the presence of Mn2+, As3+ or As5+ The results revealed that the concentration and valence of Mn and As varied with different reaction time; biological manganese oxides dominated the arsenic redox by rapidly oxidizing the As3+ in the existing system and the As3+ generated by arsenic reductase into As. PCR and RT-PCR results indicated that the arsenic reductase (arsC) was inhibited by the manganese oxidase (cumA). The expression of 16S rRNA in QJX-1 was two orders of magnitude higher than that in LSJ-9, which implied QJX-1 was dominant in the bacterial growth. Our data revealed that hydraulic retention time was critical to the valence of arsenic in the effluent of filter in drinking water treatment plant. PMID:27363151

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

    SciTech Connect

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

    1996-04-01

    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.

  13. Wilder Bancroft's Study of Oxidant-Reductant Cells

    NASA Astrophysics Data System (ADS)

    Stock, John T.

    1998-07-01

    Wilder Dwight Bancroft (1867 -1953), a Harvard graduate, entered Ostwald's Leipzig laboratory in 1890. Bancroft made a systematic study of potentiometric cells in which one half contained an oxidant solution, the other half a reductant solution. He stressed the importance of the equilibration of the platinum electrodes, examined the effects of acidity and of concentration on the emf of a cell, and demonstrated that this emf was the algebraic sum of the potentials of the half-cells. After receipt of his Ph.D. in 1892, Bancroft continued his potentiometric studies in Amsterdam. Following a brief return to Harvard, Bancroft moved to Cornell, and remained there until his retirement in 1937. He founded and edited the Journal of Physical Chemistry, and was President of the American Chemical Society in 1910. He was also twice President of the Electrochemical Society.

  14. Harm reduction agencies as a potential site for buprenorphine treatment

    PubMed Central

    Fox, Aaron D.; Chamberlain, Adam; Frost, Taeko; Cunningham, Chinazo O.

    2015-01-01

    Introduction Harm reduction agencies complement addiction treatment by providing diverse services that improve the health of people who use drugs. Buprenorphine maintenance treatment (BMT) is an effective opioid addiction treatment that may be provided from flexible settings, potentially including harm reduction agencies. This study investigated attitudes toward different potential sites for BMT (harm reduction agencies, general medical clinics, and drug treatment programs) among harm reduction clients. Methods Using computer-based interviews, participants indicated preferred potential site for BMT (harm reduction agency, drug treatment program, or general medical clinic), interest in BMT by potential site, motivation for treatment, and barriers to BMT. We used multivariable logistic regression to determine factors associated with harm reduction agency preference. Results Of 102 opioid users, the most preferred potential site for BMT was a harm reduction agency (51%), while fewer preferred general medical clinics (13%), drug treatment programs (12%) or were not interested in BMT (25%). In multivariable analysis, experiencing ≥ 1 barrier to BMT was strongly associated with preferring harm reduction agencies (aOR = 3.39, 95% CI: 1.00 – 11.43). Conclusion The potential to initiate BMT at harm reduction agencies is highly favorable among harm reduction clients, especially among those experiencing barriers to BMT. Offering BMT at harm reduction agencies could improve access to treatment, but studies are needed to determine safety and efficacy of this approach. PMID:25837290

  15. Reductive mobilization of oxide-bound metals

    SciTech Connect

    Stone, A.T.

    1991-01-01

    We have completed a large number of experiments which examine the release of MnO{sub 2}-bound Co, Ni, and Cu. Our work has focused upon the following areas: (1) competitive adsorption among the three toxic metals and Mn(II); (2) toxic metal release upon addition of low MW organic reductants and complexants; and (3) toxic metal release upon addition of natural organic matter-rich surface waters and IHSS organic matter reference material.

  16. ASSESSMENT OF HOUSEHOLD CARBON FOOTPRINT REDUCTION POTENTIALS

    SciTech Connect

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

    2009-04-15

    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.

  17. Monothiolation and Reduction of Graphene Oxide via One-Pot Synthesis: Hybrid Catalyst for Oxygen Reduction.

    PubMed

    Chua, Chun Kiang; Pumera, Martin

    2015-04-28

    The functionalization of graphene provides diverse possibilities to improve the handling of graphene and enable further chemical transformation on graphene. Graphene functionalized with mainly heteroatom-based functional groups to enhance its chemical and physical properties is intensively pursued but often resulted in grafting of the heteroatoms as various functional groups. Here, we show that graphene oxide can be functionalized with predominantly a single type of sulfur moiety and reduced simultaneously to form monothiol-functionalized graphene. The thiol-functionalized graphene shows a high electrical conductivity and heterogeneous electron transfer rate. Graphene is also embedded with a trace amount of manganese impurities originating from a prior graphite oxidation process, which facilitates the thiol-functionalized graphene to function as a hybrid electrocatalyst for oxygen reduction reactions in alkaline medium with an onset potential lower than for Pt/C. Further characterizations of the graphene are performed with X-ray photoelectron spectroscopy, scanning electron microscopy with energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, Raman spectroscopy, and electrochemical impedance spectroscopy. This material contributes to the class of hybrids that are highly active electrocatalysts. PMID:25816194

  18. A superior method for the reduction of secondary phosphine oxides.

    PubMed

    Busacca, Carl A; Lorenz, Jon C; Grinberg, Nelu; Haddad, Nizar; Hrapchak, Matt; Latli, Bachir; Lee, Heewon; Sabila, Paul; Saha, Anjan; Sarvestani, Max; Shen, Sherry; Varsolona, Richard; Wei, Xudong; Senanayake, Chris H

    2005-09-15

    [reaction: see text] Diisobutylaluminum hydride (DIBAL-H) and triisobutylaluminum have been found to be outstanding reductants for secondary phosphine oxides (SPOs). All classes of SPOs can be readily reduced, including diaryl, arylalkyl, and dialkyl members. Many SPOs can now be reduced at cryogenic temperatures, and conditions for preservation of reducible functional groups have been found. Even the most electron-rich and sterically hindered phosphine oxides can be reduced in a few hours at 50-70 degrees C. This new reduction has distinct advantages over existing technologies. PMID:16146406

  19. Oxidation of aromatic contaminants coupled to microbial iron reduction

    USGS Publications Warehouse

    Lovley, D.R.; Baedecker, M.J.; Lonergan, D.J.; Cozzarelli, I.M.; Phillips, E.J.P.; Siegel, D.I.

    1989-01-01

    THE contamination of sub-surface water supplies with aromatic compounds is a significant environmental concern1,2. As these contaminated sub-surface environments are generally anaerobic, the microbial oxidation of aromatic compounds coupled to nitrate reduction, sulphate reduction and methane production has been studied intensively1-7. In addition, geochemical evidence suggests that Fe(III) can be an important electron acceptor for the oxidation of aromatic compounds in anaerobic groundwater. Until now, only abiological mechanisms for the oxidation of aromatic compounds with Fe(III) have been reported8-12. Here we show that in aquatic sediments, microbial activity is necessary for the oxidation of model aromatic compounds coupled to Fe(III) reduction. Furthermore, a pure culture of the Fe(III)-reducing bacterium GS-15 can obtain energy for growth by oxidizing benzoate, toluene, phenol or p-cresol with Fe(III) as the sole electron acceptor. These results extend the known physiological capabilities of Fe(III)-reducing organisms and provide the first example of an organism of any type which can oxidize an aromatic hydrocarbon anaerobically. ?? 1989 Nature Publishing Group.

  20. Potential role of punicalagin against oxidative stress induced testicular damage

    PubMed Central

    Rao, Faiza; Tian, Hui; Li, Wenqing; Hung, Helong; Sun, Fei

    2016-01-01

    Punicalagin is isolated from pomegranate and widely used for the treatment of different diseases in Chinese traditional medicine. This study aimed to evaluate the effect of Punicalagin (purity ≥98%) on oxidative stress induced testicular damage and its effect on fertility. We detected the antioxidant potential of punicalagin in lipopolysaccharide (LPS) induced oxidative stress damage in testes, also tried to uncover the boosting fertility effect of Punicalagin (PU) against oxidative stress-induced infertility. Results demonstrated that 9 mg kg−1 for 7 days treatment significantly decreases LPS induced oxidative damage in testes and nitric oxide production. The administration of oxidative stress resulted in a significant reduction in testes antioxidants GSH, T-SOD, and CAT raised LPO, but treatment with punicalagin for 7 days increased antioxidant defense GSH, T-SOD, and CAT by the end of the experiment and reduced LPO level as well. PU also significantly activates Nrf2, which is involved in regulation of antioxidant defense systems. Hence, the present research categorically elucidates the protective effect of punicalagin against LPS induced oxidative stress induced perturbation in the process of spermatogenesis and significantly increased sperm health and number. Moreover, fertility success significantly decreased in LPS-injected mice compared to controls. Mice injected with LPS had fertility indices of 12.5%, while others treated with a combination of PU + LPS exhibited 75% indices. By promoting fertility and eliminating oxidative stress and inflammation, PU may be a useful nutrient for the treatment of infertility. PMID:26763544

  1. Chemical labeling of carbohydrates by oxidation and sodium borohydride reduction.

    PubMed

    Fukuda, M

    2001-05-01

    This unit describes a collection of methods for chemical labeling of carbohydrates (free oligosaccharides or oligosaccharides conjugated to proteins, peptides, or lipids) by oxidation followed by reduction or by direct reduction. Oligosaccharides can be labeled with either radioisotopes or nonradioactive fluorescent molecules. These labelings allow one to follow the oligosaccharides during chromatography and in cells if labeled by fluorescent molecules. Selective oxidation with mild periodate followed by reduction with tritiated sodium borohydride results in selective radiolabeling of sialic acid residues on oligosaccharides or glycoproteins. Alternatively, treatment of samples with galactose oxidase results in oxidation of galactose or N-acetylgalactosamine residues at nonreducing termini, rendering these residues susceptible to labeling with NaB[3H]4. Oxidized glycoconjugates can also be labeled using the fluorescent probe lucifer yellow CH. Free oligosaccharides can be labeled by reduction with NaB[3H]4. An additional protocol describes the release and simultaneous labeling of O-glycan oligosaccharides by alkaline beta-elimination in the presence of NaB[3H]4.

  2. Methodology for the effective stabilization of tin-oxide-based oxidation/reduction catalysts

    NASA Technical Reports Server (NTRS)

    Jordan, Jeffrey D. (Inventor); Schryer, David R. (Inventor); Davis, Patricia P. (Inventor); Leighty, Bradley D. (Inventor); Watkins, Anthony N. (Inventor); Schryer, Jacqueline L. (Inventor); Oglesby, Donald M. (Inventor); Gulati, Suresh T. (Inventor); Summers, Jerry C. (Inventor)

    2011-01-01

    The invention described herein involves a novel approach to the production of oxidation/reduction catalytic systems. The present invention serves to stabilize the tin oxide reducible metal-oxide coating by co-incorporating at least another metal-oxide species, such as zirconium. In one embodiment, a third metal-oxide species is incorporated, selected from the group consisting of cerium, lanthanum, hafnium, and ruthenium. The incorporation of the additional metal oxide components serves to stabilize the active tin-oxide layer in the catalytic process during high-temperature operation in a reducing environment (e.g., automobile exhaust). Moreover, the additional metal oxides are active components due to their oxygen-retention capabilities. Together, these features provide a mechanism to extend the range of operation of the tin-oxide-based catalyst system for automotive applications, while maintaining the existing advantages.

  3. [Characteristics of sulfate reduction-ammonia oxidation reaction].

    PubMed

    Yuan, Yi; Huang, Yong; Li, Xiang; Zhang, Chun-Lei; Zhang, Li; Pan, Yang; Liu, Fu-Xin

    2013-11-01

    The sulfate reduction-ammonia oxidation reaction with ANAMMOX sludge at autotrophic condition was implemented. It was found that the pH level decreased during the reaction. Elemental sulfur and nitrogen gas were the final products, while NO3(-) -N was the intermediate product during the sulfate reduction-ammonia oxidation reaction. The conversion ratio of NH4(+) -N/SO4(2-) -S decreased with the decrease in n(N)/n(S) (molar ratio) of raw water. n(N)/n(S) of raw water had little effect on the ammonia conversion ratio. Lower n(N)/n(S) could improve the SO4(2-)-S conversion ratio, but with more NH4(+) -N oxidized into NO3(-) -N, resulting in decreased n(TN)/n(TS) removal ratio. This indicates that the sulfate reduction-ammonia oxidation reaction is not an elementary reaction. Ammonia can be oxidized into NO2(-) -N or NO3(-) -N by sulfate. Shortening the reaction time would be conducive to nitrogen losses, because the reaction of NO3(-) -N production is the rate-limiting step.

  4. Unification of catalytic water oxidation and oxygen reduction reactions: amorphous beat crystalline cobalt iron oxides.

    PubMed

    Indra, Arindam; Menezes, Prashanth W; Sahraie, Nastaran Ranjbar; Bergmann, Arno; Das, Chittaranjan; Tallarida, Massimo; Schmeißer, Dieter; Strasser, Peter; Driess, Matthias

    2014-12-17

    Catalytic water splitting to hydrogen and oxygen is considered as one of the convenient routes for the sustainable energy conversion. Bifunctional catalysts for the electrocatalytic oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) are pivotal for the energy conversion and storage, and alternatively, the photochemical water oxidation in biomimetic fashion is also considered as the most useful way to convert solar energy into chemical energy. Here we present a facile solvothermal route to control the synthesis of amorphous and crystalline cobalt iron oxides by controlling the crystallinity of the materials with changing solvent and reaction time and further utilize these materials as multifunctional catalysts for the unification of photochemical and electrochemical water oxidation as well as for the oxygen reduction reaction. Notably, the amorphous cobalt iron oxide produces superior catalytic activity over the crystalline one under photochemical and electrochemical water oxidation and oxygen reduction conditions.

  5. Ion Association, Solubilities, and Reduction Potentials in Aqueous Solution.

    ERIC Educational Resources Information Center

    Russo, Steven O.; Hanania, George I. H.

    1989-01-01

    Incorporates the combined effects of ionic strength and ion association to show how calculations involving ionic equilibria are carried out. Examines the variability of reduction potential data for two aqueous redox systems. Provides several examples. (MVL)

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

    DOEpatents

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

    1989-01-01

    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.

  7. Tyrosine can protect against oxidative stress through ferryl hemoglobin reduction.

    PubMed

    Lu, Naihao; He, Yingjie; Chen, Chao; Tian, Rong; Xiao, Qiang; Peng, Yi-Yuan

    2014-08-01

    The toxic mechanism of hemoglobin (Hb) under oxidative stress is linked to the formations of highly cytotoxic ferryl species and subsequently heme-to-protein cross-linked derivative of Hb (Hb-X). In this study, we have examined the effects of free tyrosine and its analogues (3-chlorotyrosine, phenylalanine) on the stability of ferryl hemoglobin and the formation of Hb-X. The results showed that free tyrosine (not phenylalanine, 10-500 μM) was an efficient reducing agent of ferryl species and also effective at preventing the formation of cytotoxic Hb-X. Meanwhile, the dimeric tyrosine was formed as the oxidation product of tyrosine during Hb redox reaction. Compared with free tyrosine, 3-chlorotyrosine, an oxidation product of tyrosine and a proposed biomarker for hypochlorous acid (HOCl) in vivo, exhibited stronger antioxidant properties in Hb-induced oxidative stress, which was consistent with its more efficient ability in the reduction of ferryl species. These results showed that the presence of tyrosine and its derivative in vivo and vitro could ameliorate oxidative damage through ferryl heme reduction. The antioxidant ability, therefore, may provide new insights into the nutritional and physiological significance of free tyrosine with redox active heme proteins-related oxidative stress.

  8. Stereoselective S-oxidation and reduction of flosequinan in rat.

    PubMed

    Kashiyama, E; Yokoi, T; Odomi, M; Kamataki, T

    1999-08-01

    1. The stereoselective S-oxidation and reduction pathways of flosequinan [(+/-)-7-fluoro-1-methyl-3-methylsulphinyl-4-quinolone] in rat were investigated in vitro. 2. Cytosol from both the liver and kidney catalysed the reduction of R(+)-flosequinan (R-FSO) and S(-)-flosequinan (S-FSO) to flosequinan sulphide (FS, 7-fluoro-1-methyl-3-methylthio-4-quinolone). Flosequinan sulphone (FSO2, 7-fluoro-1-methyl-3-methylsulphonyl-4-quinolone) was not reduced to R-FSO or S-FSO. 3. Liver microsomes catalysed four different S-oxidation pathways in the presence of NADPH, namely oxidation of FS to R-FSO and S-FSO and from R-FSO and S-FSO to FSO2. The formation of R-FSO and S-FSO from FS each exhibited a biphasic kinetic pattern, indicating that at least two distinct enzymes were involved. The pathway from FS to R-FSO appeared mainly catalysed by flavin-containing monooxygenases (FMO). 4. S-oxidation of FS to R-FSO was more rapid than that of FS to S-FSO. S-oxidation of FS to either R-FSO or S-FSO in liver microsomes was more rapid than that of either R-FSO or S-FSO to FSO2. 5. Microsomes from both the kidney and lung catalysed the stereoselective S-oxidation of FS to R-FSO, and FMO was likely to have participated in these reactions.

  9. Electrochemical reduction of nitroaromatic compounds by single sheet iron oxide coated electrodes.

    PubMed

    Huang, Li-Zhi; Hansen, Hans Christian B; Bjerrum, Morten Jannik

    2016-04-01

    Nitroaromatic compounds are substantial hazard to the environment and to the supply of clean drinking water. We report here the successful reduction of nitroaromatic compounds by use of iron oxide coated electrodes, and demonstrate that single sheet iron oxides formed from layered iron(II)-iron(III) hydroxides have unusual electrocatalytic reactivity. Electrodes were produced by coating of single sheet iron oxides on indium tin oxide electrodes. A reduction current density of 10 to 30μAcm(-2) was observed in stirred aqueous solution at pH 7 with concentrations of 25 to 400μM of the nitroaromatic compound at a potential of -0.7V vs. SHE. Fast mass transfer favors the initial reduction of the nitroaromatic compound which is well explained by a diffusion layer model. Reduction was found to comprise two consecutive reactions: a fast four-electron first-order reduction of the nitro-group to the hydroxylamine-intermediate (rate constant=0.28h(-1)) followed by a slower two-electron zero-order reduction resulting in the final amino product (rate constant=6.9μM h(-1)). The zero-order of the latter reduction was attributed to saturation of the electrode surface with hydroxylamine-intermediates which have a more negative half-wave potential than the parent compound. For reduction of nitroaromatic compounds, the SSI electrode is found superior to metal electrodes due to low cost and high stability, and superior to carbon-based electrodes in terms of high coulombic efficiency and low over potential.

  10. Electrochemical reduction of nitroaromatic compounds by single sheet iron oxide coated electrodes.

    PubMed

    Huang, Li-Zhi; Hansen, Hans Christian B; Bjerrum, Morten Jannik

    2016-04-01

    Nitroaromatic compounds are substantial hazard to the environment and to the supply of clean drinking water. We report here the successful reduction of nitroaromatic compounds by use of iron oxide coated electrodes, and demonstrate that single sheet iron oxides formed from layered iron(II)-iron(III) hydroxides have unusual electrocatalytic reactivity. Electrodes were produced by coating of single sheet iron oxides on indium tin oxide electrodes. A reduction current density of 10 to 30μAcm(-2) was observed in stirred aqueous solution at pH 7 with concentrations of 25 to 400μM of the nitroaromatic compound at a potential of -0.7V vs. SHE. Fast mass transfer favors the initial reduction of the nitroaromatic compound which is well explained by a diffusion layer model. Reduction was found to comprise two consecutive reactions: a fast four-electron first-order reduction of the nitro-group to the hydroxylamine-intermediate (rate constant=0.28h(-1)) followed by a slower two-electron zero-order reduction resulting in the final amino product (rate constant=6.9μM h(-1)). The zero-order of the latter reduction was attributed to saturation of the electrode surface with hydroxylamine-intermediates which have a more negative half-wave potential than the parent compound. For reduction of nitroaromatic compounds, the SSI electrode is found superior to metal electrodes due to low cost and high stability, and superior to carbon-based electrodes in terms of high coulombic efficiency and low over potential. PMID:26716570

  11. Real-Time Manganese Phase Dynamics during Biological and Abiotic Manganese Oxide Reduction.

    PubMed

    Johnson, Jena E; Savalia, Pratixa; Davis, Ryan; Kocar, Benjamin D; Webb, Samuel M; Nealson, Kenneth H; Fischer, Woodward W

    2016-04-19

    Manganese oxides are often highly reactive and easily reduced, both abiotically, by a variety of inorganic chemical species, and biologically during anaerobic respiration by microbes. To evaluate the reaction mechanisms of these different reduction routes and their potential lasting products, we measured the sequence progression of microbial manganese(IV) oxide reduction mediated by chemical species (sulfide and ferrous iron) and the common metal-reducing microbe Shewanella oneidensis MR-1 under several endmember conditions, using synchrotron X-ray spectroscopic measurements complemented by X-ray diffraction and Raman spectroscopy on precipitates collected throughout the reaction. Crystalline or potentially long-lived phases produced in these experiments included manganese(II)-phosphate, manganese(II)-carbonate, and manganese(III)-oxyhydroxides. Major controls on the formation of these discrete phases were alkalinity production and solution conditions such as inorganic carbon and phosphate availability. The formation of a long-lived Mn(III) oxide appears to depend on aqueous Mn(2+) production and the relative proportion of electron donors and electron acceptors in the system. These real-time measurements identify mineralogical products during Mn(IV) oxide reduction, contribute to understanding the mechanism of various Mn(IV) oxide reduction pathways, and assist in interpreting the processes occurring actively in manganese-rich environments and recorded in the geologic record of manganese-rich strata. PMID:27018915

  12. Direct electrochemical reduction of solid uranium oxide in molten fluoride salts

    NASA Astrophysics Data System (ADS)

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

    2011-07-01

    The direct electrochemical reduction of UO 2 solid pellets was carried out in LiF-CaF 2 (+2 mass.% Li 2O) 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 O 2 gas evolution on the anode. Electrochemical characterisations of UO 2 pellets were performed by linear sweep voltammetry at 10 mV/s and reduction waves associated to oxide direct reduction were observed at a potential 150 mV more positive in comparison to the solvent reduction. Subsequent, galvanostatic electrolyses runs were carried out and products were characterised by SEM-EDX, EPMA/WDS, XRD and microhardness measurements. In one of the runs, uranium oxide was partially reduced and three phases were observed: nonreduced UO 2 in the centre, pure metallic uranium on the external layer and an intermediate phase representing the initial stage of reduction taking place at the grain boundaries. In another run, the UO 2 sample was fully reduced. Due to oxygen removal, the U matrix had a typical coral-like structure which is characteristic of the pattern observed after the electroreduction of solid oxides.

  13. Biological reduction of graphene oxide using plant leaf extracts.

    PubMed

    Lee, Geummi; Kim, Beom Soo

    2014-01-01

    Two-dimensional graphene has attracted significant attention due to its unique mechanical, electrical, thermal, and optical properties. Most commonly employed methods to chemically reduce graphene oxide to graphene use hydrazine or its derivatives as the reducing agent. However, they are highly hazardous and explosive. Various phytochemicals obtained from different natural sources such as leaves and peels of a plant are used as reducing agents in the preparation of different gold, silver, copper, and platinum nanoparticles. In this study, seven plant leaf extracts (Cherry, Magnolia, Platanus, Persimmon, Pine, Maple, and Ginkgo) were compared for their abilities to reduce graphene oxide. The optimized reaction conditions for the reduction of graphene oxide were determined as follows. Type of plant: Cherry (Prunus serrulata), reaction time: 12 h, composition of the reaction mixture: 16.7% v/v of plant leaf extract in total suspension, and temperature: 95°C. The degree of reduction caused by Cherry leaf extract was analyzed by elemental analysis and X-ray photoelectron spectroscopy. The reduction of graphene oxide was also confirmed by ultraviolet-visible spectroscopy, Fourier transform-infrared spectroscopy, Raman spectroscopy, X-ray diffraction, transmission electron microscopy, and thermogravimetric analysis. PMID:24375994

  14. Effects of Manganese Oxide on Arsenic Reduction and Leaching from Contaminated Floodplain Soil.

    PubMed

    Ehlert, Katrin; Mikutta, Christian; Kretzschmar, Ruben

    2016-09-01

    Reductive release of the potentially toxic metalloid As from Fe(III) (oxyhydr)oxides has been identified as an important process leading to elevated As porewater concentrations in soils and sediments. Despite the ubiquitous presence of Mn oxides in soils and their oxidizing power toward As(III), their impact on interrelated As, Fe, and Mn speciation under microbially reducing conditions remains largely unknown. For this reason, we employed a column setup and X-ray absorption spectroscopy to investigate the influence of increasing birnessite concentrations (molar soil Fe-to-Mn ratios: 4.8, 10.2, and 24.7) on As speciation and release from an As-contaminated floodplain soil (214 mg As/kg) under anoxic conditions. Our results show that birnessite additions significantly decreased As leaching. The reduction of both As and Fe was delayed, and As(III) accumulated in birnessite-rich column parts, indicating the passivation of birnessite and its transformation products toward As(III) oxidation and the precipitation of Fe(III)(oxyhydr)oxides. Microbial Mn reduction resulted in elevated soil pH values, which in turn lowered the microbial activity in the birnessite-enriched soil. We conclude that in Mn-oxide-rich soil environments undergoing redox fluctuations, the enhanced As adsorption to newly formed Fe(III) (oxyhydr)oxides under reducing conditions leads to a transient stabilization of As. PMID:27508335

  15. Oxidative shift in tissue redox potential increases beat-to-beat variability of action potential duration.

    PubMed

    Kistamás, Kornél; Hegyi, Bence; Váczi, Krisztina; Horváth, Balázs; Bányász, Tamás; Magyar, János; Szentandrássy, Norbert; Nánási, Péter P

    2015-07-01

    Profound changes in tissue redox potential occur in the heart under conditions of oxidative stress frequently associated with cardiac arrhythmias. Since beat-to-beat variability (short term variability, SV) of action potential duration (APD) is a good indicator of arrhythmia incidence, the aim of this work was to study the influence of redox changes on SV in isolated canine ventricular cardiomyocytes using a conventional microelectrode technique. The redox potential was shifted toward a reduced state using a reductive cocktail (containing dithiothreitol, glutathione, and ascorbic acid) while oxidative changes were initiated by superfusion with H2O2. Redox effects were evaluated as changes in "relative SV" determined by comparing SV changes with the concomitant APD changes. Exposure of myocytes to the reductive cocktail decreased SV significantly without any detectable effect on APD. Application of H2O2 increased both SV and APD, but the enhancement of SV was the greater, so relative SV increased. Longer exposure to H2O2 resulted in the development of early afterdepolarizations accompanied by tremendously increased SV. Pretreatment with the reductive cocktail prevented both elevation in relative SV and the development of afterdepolarizations. The results suggest that the increased beat-to-beat variability during an oxidative stress contributes to the generation of cardiac arrhythmias.

  16. Methods of Nitrogen Oxide Reduction in Pellet Boilers

    NASA Astrophysics Data System (ADS)

    Zandeckis, Aivars; Blumberga, Dagnija; Rochas, Claudio; Veidenbergs, Ivars; Silins, Kaspars

    2010-01-01

    The main goal of this research was to create and test technical solutions that reduce nitrogen oxide emissions in low-capacity pellet boiler. During the research, wood pellets were incinerated in a pellet boiler produced in Latvia with a rated capacity of 15 kW. During the research two NOx emission reduction methods were tested: secondary air supply in the chamber and recirculation of flue gases. Results indicated a drop of NOx concentration only for flue gas recirculation methods. Maximum reduction of 21% was achieved.

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

    USGS Publications Warehouse

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

    1996-01-01

    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

  18. Predictive tests to evaluate oxidative potential of engineered nanomaterials

    NASA Astrophysics Data System (ADS)

    Ghiazza, Mara; Carella, Emanuele; Oliaro-Bosso, Simonetta; Corazzari, Ingrid; Viola, Franca; Fenoglio, Ivana

    2013-04-01

    Oxidative stress constitutes one of the principal injury mechanisms through which particulate toxicants (asbestos, crystalline silica, hard metals) and engineered nanomaterials can induce adverse health effects. ROS may be generated indirectly by activated cells and/or directly at the surface of the material. The occurrence of these processes depends upon the type of material. Many authors have recently demonstrated that metal oxides and carbon-based nanoparticles may influence (increasing or decreasing) the generation of oxygen radicals in a cell environment. Metal oxide, such as iron oxides, crystalline silica, and titanium dioxide are able to generate free radicals via different mechanisms causing an imbalance within oxidant species. The increase of ROS species may lead to inflammatory responses and in some cases to the development of cancer. On the other hand carbon-based nanomaterials, such as fullerene, carbon nanotubes, carbon black as well as cerium dioxide are able to scavenge the free radicals generated acting as antioxidant. The high numbers of new-engineered nanomaterials, which are introduced in the market, are exponentially increasing. Therefore the definition of toxicological strategies is urgently needed. The development of acellular screening tests will make possible the reduction of the number of in vitro and in vivo tests to be performed. An integrated protocol that may be used to predict the oxidant/antioxidant potential of engineered nanoparticles will be here presented.

  19. Dissimilatory Selenate Reduction Potentials in a Diversity of Sediment Types

    PubMed Central

    Steinberg, Nisan A.; Oremland, Ronald S.

    1990-01-01

    We measured potential rates of bacterial dissimilatory reduction of 75SeO42− to 75Se0 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. Significant biological selenate reduction occurred in all samples with salinities from 1 to 250 g/liter but not in samples with a salinity of 320 g/liter. Potential selenate reduction rates (25 nmol of SeO42− per ml of sediment added with isotope) ranged from 0.07 to 22 μmol of SeO42− reduced liter−1 h−1. Activity followed Michaelis-Menten kinetics in relation to SeO42− concentration (Km of selenate = 7.9 to 720 μM). There was no linear correlation between potential rates of SeO42− reduction and salinity, pH, concentrations of total Se, porosity, or organic carbon in the sediments. However, potential selenate reduction was correlated with apparent Km for selenate and with potential rates of denitrification (r = 0.92 and 0.81, respectively). NO3−, NO2−, MoO42−, and WO42− inhibited selenate reduction activity to different extents in sediments from both Hunter Drain and Massie Slough, Nev. Sulfate partially inhibited activity in sediment from freshwater (salinity = 1 g/liter) Massie Slough samples but not from the saline (salinity = 60 g/liter) Hunter Drain samples. We conclude that dissimilatory selenate reduction in sediments is widespread in nature. In addition, in situ selenate reduction is a first-order reaction, because the ambient concentrations of selenium oxyanions in the sediments were orders of magnitude less than their Kms. PMID:16348359

  20. Dissimilatory selenate reduction potentials in a diversity of sediment types

    USGS Publications Warehouse

    Steinberg, N.A.; Oremland, R.S.

    1990-01-01

    We measured potential rates of bacterial dissimilatory reduction of 75SeO42- to 75Se0 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. Significant biological selenate reduction occurred in all samples with salinities from 1 to 250 g/liter but not in samples with a salinity of 320 g/liter. Potential selenate reduction rates (25 nmol of SeO42- per ml of sediment added with isotope) ranged from 0.07 to 22 ??mol of SeO42- reduced liter-1 h-1. Activity followed Michaelis-Menten kinetics in relation to SeO42- concentration (K(m) of selenate = 7.9 to 720 ??M). There was no linear correlation between potential rates of SeO42- reduction and salinity, pH, concentrations of total Se, porosity, or organic carbon in the sediments. However, potential selenate reduction was correlated with apparent K(m) for selenate and with potential rates of denitrification (r = 0.92 and 0.81, respectively). NO3-, NO2-, MoO42-, and WO42- inhibited selenate reduction activity to different extents in sediments from both Hunter Drain and Massie Slough, Nev. Sulfate partially inhibited activity in sediment from freshwater (salinity = 1 g/liter) Massie Slough samples but not from the saline (salinity = 60 g/liter) Hunter Drain samples. We conclude that dissimilatory selenate reduction in sediments is widespread in nature. In addition, in situ selenate reduction is a first-order reaction, because the ambient concentrations of selenium oxyanions in the sediments were orders of magnitude less than their K(m)s.

  1. Potential Toxic Effects of Nano-Oxides

    NASA Astrophysics Data System (ADS)

    Xu, Mingsheng; Chen, Hongzheng; Shi, Minmin; Wu, Gang; Fujita, Daisuke; Hanagata, Nobutaka

    2013-09-01

    The increasing use of nanomaterials in industrial and consumer products has aroused global concern regarding their potential impact on environment and human health. A number of studies on the effects of nanomaterials in in vitro and in vivo systems have been shown that some nanomaterials are potentially toxic. We address the understanding of the link of physicochemical characteristics of some nano-oxides including SiO2, TiO2, and ZnO to the observed toxic effects. Understanding the contribution of physicochemical characteristics of nanomaterials to toxic effects would allow safety to be built into the design of nanomaterials and their applications, to allow their safe integration into products.

  2. Direct oxide reduction demonstration, small-scale studies

    SciTech Connect

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

    1991-12-09

    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.

  3. Direct oxide reduction demonstration, small-scale studies

    SciTech Connect

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

    1991-12-09

    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.

  4. Use of ion conductors in the pyrochemical reduction of oxides

    DOEpatents

    Miller, W.E.; Tomczuk, Z.

    1994-02-01

    An electrochemical process and electrochemical cell for reducing a metal oxide are provided. First the oxide is separated as oxygen gas using, for example, a ZrO[sub 2] oxygen ion conductor anode and the metal ions from the reduction salt are reduced and deposited on an ion conductor cathode, for example, sodium ion reduced on a [beta]-alumina sodium ion conductor cathode. The generation of and separation of oxygen gas avoids the problem with chemical back reaction of oxygen with active metals in the cell. The method also is characterized by a sequence of two steps where an inert cathode electrode is inserted into the electrochemical cell in the second step and the metallic component in the ion conductor is then used as the anode to cause electrochemical reduction of the metal ions formed in the first step from the metal oxide where oxygen gas formed at the anode. The use of ion conductors serves to isolate the active components from chemically reacting with certain chemicals in the cell. While applicable to a variety of metal oxides, the invention has special importance for reducing CaO to Ca[sup o] used for reducing UO[sub 2] and PuO[sub 2] to U and Pu. 2 figures.

  5. Use of ion conductors in the pyrochemical reduction of oxides

    DOEpatents

    Miller, William E.; Tomczuk, Zygmunt

    1994-01-01

    An electrochemical process and electrochemical cell for reducing a metal oxide are provided. First the oxide is separated as oxygen gas using, for example, a ZrO.sub.2 oxygen ion conductor anode and the metal ions from the reduction salt are reduced and deposited on an ion conductor cathode, for example, sodium ion reduced on a .beta.-alumina sodium ion conductor cathode. The generation of and separation of oxygen gas avoids the problem with chemical back reaction of oxygen with active metals in the cell. The method also is characterized by a sequence of two steps where an inert cathode electrode is inserted into the electrochemical cell in the second step and the metallic component in the ion conductor is then used as the anode to cause electrochemical reduction of the metal ions formed in the first step from the metal oxide where oxygen gas formed at the anode. The use of ion conductors serves to isolate the active components from chemically reacting with certain chemicals in the cell. While applicable to a variety of metal oxides, the invention has special importance for reducing CaO to Ca.degree. used for reducing UO.sub.2 and PuO.sub.2 to U and Pu.

  6. Selective catalytic reduction of nitric oxide with ammonia over silica-supported vanadium oxide catalyst

    SciTech Connect

    Qajar, J.; Mowla, D.

    2009-07-01

    The selective catalytic reduction (SCR) of nitric oxide with excess ammonia in the presence of oxygen on silica-supported vanadium oxide catalyst was studied in a packed-bed reactor, and a mathematical model was proposed for the processes occurring in the reactor. Experimental data were presented for evaluation of the accuracy of the proposed model. Good agreement was observed between the measured and calculated values of the conversion in the outlet of the reactor. Once the validity of the proposed model was verified, it was used to examine the effects of different parameters such as feed temperature, inlet feed composition, and gas hourly space velocity (GHSV) on the conversion of NO over V{sub 2}O{sub 5}/SiO{sub 2} catalyst for practical application. The results for the employed catalyst showed that high NO conversion occurred at temperatures of 280-300C, GHSV less than 2000h{sup -1} (STP), and O{sub 2} concentration greater than 10% v/v. These results clearly demonstrate the high potential for this catalyst to be applied commercially for the control of NOx emissions from flue gases of different sources.

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

    NASA Astrophysics Data System (ADS)

    Halder, S.; Fruehan, R. J.

    2008-12-01

    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.

  8. Reduction of iron-oxide-carbon composites: part III. Shrinkage of composite pellets during reduction

    SciTech Connect

    Halder, S.; Fruehan, R.J.

    2008-12-15

    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.

  9. Removal of the X-ray contrast media diatrizoate by electrochemical reduction and oxidation.

    PubMed

    Radjenovic, Jelena; Flexer, Victoria; Donose, Bogdan C; Sedlak, David L; Keller, Jurg

    2013-01-01

    Due to their resistance to biological wastewater treatment, iodinated X-ray contrast media (ICM) have been detected in municipal wastewater effluents at relatively high concentrations (i.e., up to 100 μg L(-1)), with hospitals serving as their main source. To provide a new approach for reducing the concentrations of ICMs in wastewater, electrochemical reduction at three-dimensional graphite felt and graphite felt doped with palladium nanoparticles was examined as a means for deiodination of the common ICM diatrizoate. The presence of palladium nanoparticles significantly enhanced the removal of diatrizoate and enabled its complete deiodination to 3,5-diacetamidobenzoic acid. When the system was employed in the treatment of hospital wastewater, diatrizoate was reduced, but the extent of electrochemical reduction decreased as a result of competing reactions with solutes in the matrix. Following electrochemical reduction of diatrizoate to 3,5-diacetamidobenzoic acid, electrochemical oxidation with boron-doped diamond (BDD) anodes was employed. 3,5-Diacetamidobenzoic acid disappeared from solution at a rate that was similar to that of diatrizoate, but it was more readily mineralized than the parent compound. When electrochemical reduction and oxidation were coupled in a three-compartment reactor operated in a continuous mode, complete deiodination of diatrizoate was achieved at an applied cathode potential of -1.7 V vs SHE, with the released iodide ions electrodialyzed in a central compartment with 80% efficiency. The resulting BDD anode potential (i.e., +3.4-3.5 V vs SHE) enabled efficient oxidation of the products of the reductive step. The presence of other anions (e.g., chloride) was likely responsible for a decrease in I(-) separation efficiency when hospital wastewater was treated. Reductive deiodination combined with oxidative degradation provides benefits over oxidative treatment methods because it does not produce stable iodinated intermediates. Nevertheless

  10. Direct printing and reduction of graphite oxide for flexible supercapacitors

    SciTech Connect

    Jung, Hanyung; Ve Cheah, Chang; Jeong, Namjo; Lee, Junghoon

    2014-08-04

    We report direct printing and photo-thermal reduction of graphite oxide (GO) to obtain a highly porous pattern of interdigitated electrodes, leading to a supercapacitor on a flexible substrate. Key parameters optimized include the amount of GO delivered, the suitable photo-thermal energy level for effective flash reduction, and the substrate properties for appropriate adhesion after reduction. Tests with supercapacitors based on the printed-reduced GO showed performance comparable with commercial supercapacitors: the energy densities were 1.06 and 0.87 mWh/cm{sup 3} in ionic and organic electrolytes, respectively. The versatility in the architecture and choice of substrate makes this material promising for smart power applications.

  11. Atropa belladonna hairy roots: orchestration of concurrent oxidation and reduction reactions for biotransformation of carbonyl compounds.

    PubMed

    Srivastava, Vikas; Negi, Arvind Singh; Ajayakumar, P V; Khan, Shamshad A; Banerjee, Suchitra

    2012-03-01

    The biotransformation potential of a selected Atropa belladonna hairy root clone (AB-09) had been evaluated with regard to three different aromatic carbonyl compounds, i.e., 3,4,5-trimethoxybenzaldehyde (1), 3,4,5-trimethoxyacetophenone (2), and 3,4,5-trimethoxy benzoic acid (3). The results demonstrated for the first time the untapped potentials of the selected hairy root clone to perform simultaneous oxidation (34.49%) and reduction (32.68%) of 3,4,5-trimethoxy benzaldehyde (1) into 3,4,5-trimethoxy benzoic acid (3), and 3,4,5-trimethoxy benzyl alcohol (4), respectively, without any intermediate separation or addition of reagents. The same hairy root clone also demonstrated reduction (<5%) of a 3,4,5-trimethoxyacetophenone (2) into a secondary alcohol, i.e., 1-(3,4,5-trimethoxyphenyl) ethanol (5), while in the case of aromatic carboxylic acid substrate (3), no biotransformation could be obtained under the similar conditions. The current observations revealed oxidation and reduction of the formyl group of the aromatic ring, and only reduction of the carbonyl group of acetophenone through the specific hairy root clone. The concurrent oxidation and reduction reactions by the selected hairy root clone highlight the importance of this study, which, as per our observations, is the first of its kind relating the hairy root culture of A. belladonna.

  12. Oxidation Potentials in Iron and Steel Making

    NASA Astrophysics Data System (ADS)

    Matousek, J. W.

    2013-11-01

    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.

  13. Heterogeneous oxidation of SO2 by O3-aged black carbon and its dithiothreitol oxidative potential.

    PubMed

    Xu, Weiwei; Li, Qian; Shang, Jing; Liu, Jia; Feng, Xiang; Zhu, Tong

    2015-10-01

    Ozone (O3) is an important atmospheric oxidant. Black carbon (BC) particles released into the atmosphere undergo an aging process via O3 oxidation. O3-aged BC particles may change their uptake ability toward trace reducing gases such as SO2 in the atmosphere, leading to different environmental and health effects. In this paper, the heterogeneous reaction process between O3-aged BC and SO2 was explored via in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Combined with ion chromatography (IC), DRIFTS was used to qualitatively and quantitatively analyze the sulfate product. The results showed that O3-aged BC had stronger SO2 oxidation ability than fresh BC, and the reactive species/sites generated on the surface had an important role in the oxidation of SO2. Relative humidity or 254nm UV (ultraviolet) light illumination enhanced the oxidation uptake of SO2 on O3-aged BC. The oxidation potentials of the BC particles were detected via dithiothreitol (DTT) assay. The DTT activity over BC was decreased in the process of SO2 reduction, with the consumption of oxidative active sites.

  14. Heterogeneous oxidation of SO2 by O3-aged black carbon and its dithiothreitol oxidative potential.

    PubMed

    Xu, Weiwei; Li, Qian; Shang, Jing; Liu, Jia; Feng, Xiang; Zhu, Tong

    2015-10-01

    Ozone (O3) is an important atmospheric oxidant. Black carbon (BC) particles released into the atmosphere undergo an aging process via O3 oxidation. O3-aged BC particles may change their uptake ability toward trace reducing gases such as SO2 in the atmosphere, leading to different environmental and health effects. In this paper, the heterogeneous reaction process between O3-aged BC and SO2 was explored via in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Combined with ion chromatography (IC), DRIFTS was used to qualitatively and quantitatively analyze the sulfate product. The results showed that O3-aged BC had stronger SO2 oxidation ability than fresh BC, and the reactive species/sites generated on the surface had an important role in the oxidation of SO2. Relative humidity or 254nm UV (ultraviolet) light illumination enhanced the oxidation uptake of SO2 on O3-aged BC. The oxidation potentials of the BC particles were detected via dithiothreitol (DTT) assay. The DTT activity over BC was decreased in the process of SO2 reduction, with the consumption of oxidative active sites. PMID:26456606

  15. High Potential for Iron Reduction in Upland Soils from Diverse Terrestrial Ecosystems

    NASA Astrophysics Data System (ADS)

    Yang, W. H.; Liptzin, D.

    2014-12-01

    Changes in the redox state of iron (Fe) can be coupled to the biogeochemical cycling of carbon (C), nitrogen, and phosphorus. The importance of Fe in catalyzing redox-driven biogeochemical cycling has been underappreciated in terrestrial ecosystems because they are not typically thought of as anaerobic environments. However, upland soils can experience anaerobic conditions following rainfall events or in microsites of high biological oxygen consumption. Measurements of Fe reduction rates in soils are difficult to compare among studies from different ecosystems, so we used the same assay to quantify potential Fe reduction in soils from upland environments (annual grassland, drained peatland pasture, and a rainforest) that varied in poorly crystalline Fe and total C. We slurried the soils and incubated them in a glovebox with a dinitrogen headspace. To evaluate the role of C availability in potential Fe reduction, we added sodium acetate daily at rates up to 0.6 mg C/g soil/d. We measured methane (CH4) production, acid- extractable Fe(II), citrate-ascorbate extractable Fe oxides, and pH over 5 days to determine the timing and magnitude of Fe reduction. In relatively dry soils (< 20 % gravimetric soil moisture), Fe reduction began after one day of anaerobic incubation as slurries, but all of the soils demonstrated high Fe reduction potential. On day 3, Fe reduction rates for the 0.05 mg C/g soil/d treatment were 1535 ± 51 μg Fe(III) g-1 d-1 in the annual grassland soil, 1205 ± 42 μg Fe(III) g-1 d-1 in the drained peatland soil, and 826 ± 54 μg Fe(III) g-1 d-1 in the rainforest soil. This contrasts with the trend in poorly crystalline Fe oxide pools across the sites: 3.87 ± 0.06 μg Fe(III) g-1 in the annual grassland, 7.49 μg Fe(III) g-1 in the drained peatland, and 20.84 ± 0.19 μg Fe(III) g-1 in the rainforest soil. Across all sites, small C additions (< 0.05 mg C/g soil/day) increased Fe reduction rates while larger C additions decreased Fe reduction. Iron

  16. 1. West facade of Plutonium Concentration Facility (Building 233S), ReductionOxidation ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    1. West facade of Plutonium Concentration Facility (Building 233-S), Reduction-Oxidation Building (REDOX-202-S) to the right. Looking east. - Reduction-Oxidation Complex, Plutonium Concentration Facility, 200 West Area, Richland, Benton County, WA

  17. Processing of effluent salt from the direct oxide reduction process

    SciTech Connect

    Mishra, B.; Olson, D.L. . Kroll Inst. for Extractive Metallurgy); Averill, W.A. )

    1992-01-01

    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 up to 15 wt. pct. Fused salt electrolysis of a simulated salt mix has been carried out to electrowin calcium, which can be recycled to the DOR reactor along with the calcium chloride salt or may be used in-situ in a combined DOR and electrowinning process. Many reactive metal oxides could thus be reduced in a one-step process without generating a significant amount of waste. The process has been optimized in terms of the calcium solubility, cell temperature, current density and the cell design to maximize the current efficiency. Based on the information available regarding the solubility of calcium in calcium chloride salt in the presence of calcium oxide, and the back reactions occurring in-situ between the electrowon calcium and other components present in the cell, e.g. carbon, oxygen, carbon dioxide and calcium oxide, it is difficult to recover elemental calcium within the system. However, a liquid cathode or a rising cathode has been used in the past to recover calcium. The solubility has also been found to depend on the use of graphite as the anode material as evidenced by the presence of calcium carbonate in the final salt. The rate of recovery for metallic calcium has to be enhanced to levels that overcome the back reactions in a system where quick removal of anodic gases is achieved. Calcium has been detected by the hydrogen evolution technique and the amount of calcia has been determined by titration. A porous ceramic sheath has been used in the cell to prevent the chemical reaction of electrowon calcium to produce oxide or carbonate and to prevent the contamination of salt by the anodic carbon.

  18. Processing of effluent salt from the direct oxide reduction process

    SciTech Connect

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

    1992-05-01

    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 up to 15 wt. pct. Fused salt electrolysis of a simulated salt mix has been carried out to electrowin calcium, which can be recycled to the DOR reactor along with the calcium chloride salt or may be used in-situ in a combined DOR and electrowinning process. Many reactive metal oxides could thus be reduced in a one-step process without generating a significant amount of waste. The process has been optimized in terms of the calcium solubility, cell temperature, current density and the cell design to maximize the current efficiency. Based on the information available regarding the solubility of calcium in calcium chloride salt in the presence of calcium oxide, and the back reactions occurring in-situ between the electrowon calcium and other components present in the cell, e.g. carbon, oxygen, carbon dioxide and calcium oxide, it is difficult to recover elemental calcium within the system. However, a liquid cathode or a rising cathode has been used in the past to recover calcium. The solubility has also been found to depend on the use of graphite as the anode material as evidenced by the presence of calcium carbonate in the final salt. The rate of recovery for metallic calcium has to be enhanced to levels that overcome the back reactions in a system where quick removal of anodic gases is achieved. Calcium has been detected by the hydrogen evolution technique and the amount of calcia has been determined by titration. A porous ceramic sheath has been used in the cell to prevent the chemical reaction of electrowon calcium to produce oxide or carbonate and to prevent the contamination of salt by the anodic carbon.

  19. Fe(III) oxides accelerate microbial nitrate reduction and electricity generation by Klebsiella pneumoniae L17.

    PubMed

    Liu, Tongxu; Li, Xiaomin; Zhang, Wei; Hu, Min; Li, Fangbai

    2014-06-01

    Klebsiella pneumoniae L17 is a fermentative bacterium that can reduce iron oxide and generate electricity under anoxic conditions, as previously reported. This study reveals that K. pneumoniae L17 is also capable of dissimilatory nitrate reduction, producing NO2(-), NH4(+), NO and N2O under anoxic conditions. The presence of Fe(III) oxides (i.e., α-FeOOH, γ-FeOOH, α-Fe2O3 and γ-Fe2O3) significantly accelerates the reduction of nitrate and generation of electricity by K. pneumoniae L17, which is similar to a previous report regarding another fermentative bacterium, Bacillus. No significant nitrate reduction was observed upon treatment with Fe(2+) or α-FeOOH+Fe(2+), but a slight facilitation of nitrate reduction and electricity generation was observed upon treatment with L17+Fe(2+). This result suggests that aqueous Fe(II) or mineral-adsorbed Fe(II) cannot reduce nitrate abiotically but that L17 can catalyze the reduction of nitrate and generation of electricity in the presence of Fe(II) (which might exist as cell surface-bound Fe(II)). To rule out the potential effect of Fe(II) produced by L17 during microbial iron reduction, treatments with the addition of TiO2 or Al2O3 instead of Fe(III) oxides also exhibited accelerated microbial nitrate reduction and electricity generation, indicating that cell-mineral sorption did account for the acceleration effect. However, the acceleration caused by Fe(III) oxides is only partially attributed to the cell surface-bound Fe(II) and cell-mineral sorption but may be driven by the iron oxide conduction band-mediated electron transfer from L17 to nitrate or an electrode, as proposed previously. The current study extends the diversity of bacteria of which nitrate reduction and electricity generation can be facilitated by the presence of iron oxides and confirms the positive role of Fe(III) oxides on microbial nitrate reduction and electricity generation by particular fermentative bacteria in anoxic environments.

  20. Oxidation-Reduction Calculations in the Biochemistry Course

    ERIC Educational Resources Information Center

    Feinman, Richard D.

    2004-01-01

    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…

  1. Cell oxidation-reduction imbalance after modulated radiofrequency radiation.

    PubMed

    Marjanovic, Ana Marija; Pavicic, Ivan; Trosic, Ivancica

    2015-01-01

    Aim of this study was to evaluate an influence of modulated radiofrequency field (RF) of 1800 MHz, strength of 30 V/m on oxidation-reduction processes within the cell. The assigned RF field was generated within Gigahertz Transversal Electromagnetic Mode cell equipped by signal generator, modulator, and amplifier. Cell line V79, was irradiated for 10, 30, and 60 min, specific absorption rate was calculated to be 1.6 W/kg. Cell metabolic activity and viability was determined by MTT assay. In order to define total protein content, colorimetric method was used. Concentration of oxidised proteins was evaluated by enzyme-linked immunosorbent assay. Reactive oxygen species (ROS) marked with fluorescent probe 2',7'-dichlorofluorescin diacetate were measured by means of plate reader device. In comparison with control cell samples, metabolic activity and total protein content in exposed cells did not differ significantly. Concentrations of carbonyl derivates, a product of protein oxidation, insignificantly but continuously increase with duration of exposure. In exposed samples, ROS level significantly (p < 0.05) increased after 10 min of exposure. Decrease in ROS level was observed after 30-min treatment indicating antioxidant defence mechanism activation. In conclusion, under the given laboratory conditions, modulated RF radiation might cause impairment in cell oxidation-reduction equilibrium within the growing cells. PMID:25119294

  2. Cell oxidation-reduction imbalance after modulated radiofrequency radiation.

    PubMed

    Marjanovic, Ana Marija; Pavicic, Ivan; Trosic, Ivancica

    2015-01-01

    Aim of this study was to evaluate an influence of modulated radiofrequency field (RF) of 1800 MHz, strength of 30 V/m on oxidation-reduction processes within the cell. The assigned RF field was generated within Gigahertz Transversal Electromagnetic Mode cell equipped by signal generator, modulator, and amplifier. Cell line V79, was irradiated for 10, 30, and 60 min, specific absorption rate was calculated to be 1.6 W/kg. Cell metabolic activity and viability was determined by MTT assay. In order to define total protein content, colorimetric method was used. Concentration of oxidised proteins was evaluated by enzyme-linked immunosorbent assay. Reactive oxygen species (ROS) marked with fluorescent probe 2',7'-dichlorofluorescin diacetate were measured by means of plate reader device. In comparison with control cell samples, metabolic activity and total protein content in exposed cells did not differ significantly. Concentrations of carbonyl derivates, a product of protein oxidation, insignificantly but continuously increase with duration of exposure. In exposed samples, ROS level significantly (p < 0.05) increased after 10 min of exposure. Decrease in ROS level was observed after 30-min treatment indicating antioxidant defence mechanism activation. In conclusion, under the given laboratory conditions, modulated RF radiation might cause impairment in cell oxidation-reduction equilibrium within the growing cells.

  3. Pre-converted nitric oxide gas in catalytic reduction system

    DOEpatents

    Hsiao, Mark C.; Merritt, Bernard T.; Penetrante, Bernardino M.; Vogtlin, George E.

    1999-01-01

    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 N2, CO2, 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 N2, CO2, and H.sub.2 O, and includes a gamma-alumina .gamma.-Al.sub.2 O.sub.3. The hydrocarbons and NO.sub.x are simultaneously reduced while passing through the second catalyst.

  4. Pre-converted nitric oxide gas in catalytic reduction system

    DOEpatents

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

    1999-04-06

    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.

  5. Landscape planning for agricultural nonpoint source pollution reduction III: Assessing phosphorus and sediment reduction potential

    USGS Publications Warehouse

    Diebel, M.W.; Maxted, J.T.; Robertson, D.M.; Han, S.; Vander Zanden, M. J.

    2009-01-01

    Riparian buffers have the potential to improve stream water quality in agricultural landscapes. This potential may vary in response to landscape characteristics such as soils, topography, land use, and human activities, including legacies of historical land management. We built a predictive model to estimate the sediment and phosphorus load reduction that should be achievable following the implementation of riparian buffers; then we estimated load reduction potential for a set of 1598 watersheds (average 54 km2) in Wisconsin. Our results indicate that land cover is generally the most important driver of constituent loads in Wisconsin streams, but its influence varies among pollutants and according to the scale at which it is measured. Physiographic (drainage density) variation also influenced sediment and phosphorus loads. The effect of historical land use on present-day channel erosion and variation in soil texture are the most important sources of phosphorus and sediment that riparian buffers cannot attenuate. However, in most watersheds, a large proportion (approximately 70%) of these pollutants can be eliminated from streams with buffers. Cumulative frequency distributions of load reduction potential indicate that targeting pollution reduction in the highest 10% of Wisconsin watersheds would reduce total phosphorus and sediment loads in the entire state by approximately 20%. These results support our approach of geographically targeting nonpoint source pollution reduction at multiple scales, including the watershed scale. ?? 2008 Springer Science+Business Media, LLC.

  6. Landscape planning for agricultural nonpoint source pollution reduction III: assessing phosphorus and sediment reduction potential.

    PubMed

    Diebel, Matthew W; Maxted, Jeffrey T; Robertson, Dale M; Han, Seungbong; Vander Zanden, M Jake

    2009-01-01

    Riparian buffers have the potential to improve stream water quality in agricultural landscapes. This potential may vary in response to landscape characteristics such as soils, topography, land use, and human activities, including legacies of historical land management. We built a predictive model to estimate the sediment and phosphorus load reduction that should be achievable following the implementation of riparian buffers; then we estimated load reduction potential for a set of 1598 watersheds (average 54 km(2)) in Wisconsin. Our results indicate that land cover is generally the most important driver of constituent loads in Wisconsin streams, but its influence varies among pollutants and according to the scale at which it is measured. Physiographic (drainage density) variation also influenced sediment and phosphorus loads. The effect of historical land use on present-day channel erosion and variation in soil texture are the most important sources of phosphorus and sediment that riparian buffers cannot attenuate. However, in most watersheds, a large proportion (approximately 70%) of these pollutants can be eliminated from streams with buffers. Cumulative frequency distributions of load reduction potential indicate that targeting pollution reduction in the highest 10% of Wisconsin watersheds would reduce total phosphorus and sediment loads in the entire state by approximately 20%. These results support our approach of geographically targeting nonpoint source pollution reduction at multiple scales, including the watershed scale.

  7. Highly controllable and green reduction of graphene oxide to flexible graphene film with high strength

    SciTech Connect

    Wan, Wubo; Zhao, Zongbin; Hu, Han; Gogotsi, Yury; Qiu, Jieshan

    2013-11-15

    Graphical abstract: Highly controllable and green reduction of GO to chemical converted graphene (CCG) was achieved with sodium citrate as a facile reductant. Self-assembly of the as-made CCG sheets results in a flexible CCG film, of which the tensile strength strongly depends on the deoxygenation degree of graphene sheets. - Highlights: • Graphene was synthesized by an effective and environmentally friendly approach. • We introduced a facile X-ray diffraction analysis method to investigate the reduction process from graphene oxide to graphene. • Flexible graphene films were prepared by self-assembly of the graphene sheets. • The strength of the graphene films depends on the reduction degree of graphene. - Abstract: Graphene film with high strength was fabricated by the assembly of graphene sheets derived from graphene oxide (GO) in an effective and environmentally friendly approach. Highly controllable reduction of GO to chemical converted graphene (CCG) was achieved with sodium citrate as a facile reductant, in which the reduction process was monitored by XRD analysis and UV–vis absorption spectra. Self-assembly of the as-made CCG sheets results in a flexible CCG film. This method may open an avenue to the easy and scalable preparation of graphene film with high strength which has promising potentials in many fields where strong, flexible and electrically conductive films are highly demanded.

  8. Oxidation-reduction induced roughening of platinum (111) surface

    SciTech Connect

    You, H.; Nagy, Z.

    1993-06-01

    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.

  9. Calculating Standard Reduction Potentials of [4Fe–4S] Proteins

    SciTech Connect

    Perrin, Bradley S.; Niu, Shuqiang; Ichiye, Toshiko

    2013-03-15

    The oxidation–reduction potentials of electron transfer proteins determine the driving forces for their electron transfer reactions. Although the type of redox site determines the intrinsic energy required to add or remove an electron, the electrostatic interaction energy between the redox site and its surrounding environment can greatly shift the redox potentials. Here, a method for calculating the reduction potential versus the standard hydrogen electrode, E°, of a metalloprotein using a combinatio of density functional theory and continuum electrostatics is presented. This work focuses on the methodology for the continuum electrostatics calculations, including various factors that may affect the accuracy. The calculations are demonstrated using crystal structures of six homologous HiPIPs, which give E° that are in excellent agreement with experimental results.

  10. Nanomaterial resistant microorganism mediated reduction of graphene oxide.

    PubMed

    Chouhan, Raghuraj S; Pandey, Ashish; Qureshi, Anjum; Ozguz, Volkan; Niazi, Javed H

    2016-10-01

    In this study, soil bacteria were isolated from nanomaterials (NMs) contaminated pond soil and enriched in the presence of graphene oxide (GO) in mineral medium to obtain NMs resistant bacteria. The isolated resistant bacteria were biochemically and genetically identified as Fontibacillus aquaticus. The resistant bacteria were allowed to interact with engineered GO in order to study the biotransformation in GO structure. Raman spectra of GO extracted from culture medium revealed decreased intensity ratio of ID/IG with subsequent reduction of CO which was consistent with Fourier transform infrared (FTIR) results. The structural changes and exfoliatied GO nanosheets were also evident from transmission electron microscopy (TEM) images. Ultraviolet-visible spectroscopy, high resolution X-ray diffraction (XRD) and current-voltage measurements confirmed the reduction of GO after the interaction with resistant bacteria. X-ray photoelectron spectroscopy (XPS) analysis of biotransformed GO revealed reduction of oxygen-containing species on the surface of nanosheets. Our results demonstrated that the presented method is an environment friendly, cost effective, simple and based on green approaches for the reduction of GO using NMs resistant bacteria.

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

    NASA Astrophysics Data System (ADS)

    Sohn, I.; Fruehan, R. J.

    2006-04-01

    The reduction of iron oxide/carbon composite pellets with hydrogen at 900 °C to 1000 °C was studied. Compared to hydrogen, the reduction by carbon was negligible at 900 °C and below. However, significant carbon oxidation of the iron oxide/graphite pellets by H2O generated from the reduction of Fe2O3 by H2 was observed. At higher temperatures, reduction by carbon complicates the overall reduction mechanism, with the iron oxide/graphite composite pellet found to be more reactive than the iron oxide/char composite pellet. From the scanning electron micrographs, partially reduced composite pellets showed a typical topochemical interface with an intermediate region between an oxygen-rich unreacted core and an iron-rich outer shell. To determine the possibility of reduction by volatiles, a layer of iron oxide powders was spread on top of a high volatile containing bituminous coal and heated inside a reactor using infra-red radiation. By separating the individual reactions involved for an iron oxide/coal mixture where a complex set of reactions occur simultaneously, it was possible to determine the sole effect of volatile reduction. It was found that the light reducing gases evolve initially and react with the iron oxide, with complex hydrocarbons evolving at the later stages. The volatiles caused about 20 to 50 pct reduction of the iron oxide.

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

    SciTech Connect

    Sohn, I.; Fruehan, R.J.

    2006-04-15

    The reduction of iron oxide/carbon composite pellets with hydrogen at 900{sup o}C to 1000{sup o}C was studied. Compared to hydrogen, the reduction by carbon was negligible at 900 degrees C and below. However, significant carbon oxidation of the iron oxide/graphite pellets by H{sub 2O generated from the reduction of Fe{sub 2}O{sub 3} by H-2 was observed. At higher temperatures, reduction by carbon complicates the overall reduction mechanism, with the iron oxide/graphite composite pellet found to be more reactive than the iron oxide/char composite pellet. From the scanning electron micrographs, partially reduced composite pellets showed a typical topochemical interface with an intermediate region between an oxygen-rich unreacted core and an iron-rich outer shell. To determine the possibility of reduction by volatiles, a layer of iron oxide powders was spread on top of a high volatile containing bituminous coal and heated inside a reactor using infra-red radiation. By separating the individual reactions involved for an iron oxide/coal mixture where a complex set of reactions occur simultaneously, it was possible to determine the sole effect of volatile reduction. It was found that the light reducing gases evolve initially and react with the iron oxide, with complex hydrocarbons evolving at the later stages. The volatiles caused about 20 to 50% reduction of the iron oxide.

  13. Simultaneous reductive dissolution of iron oxide and oxidation of iodide in ice.

    NASA Astrophysics Data System (ADS)

    Kim, Kitae; Choi, Wonyong

    2015-04-01

    Iron is an important trace element controlling the metabolism and growth of all kinds of living species. Especially, the bio-availability of iron has been regarded as the limiting factor for primary productivity in HNLC (High Nutrients Low Chlorophyll) regions including Southern ocean. The dissolution of iron oxide provides enhanced the bio-availability of iron for phytoplankton growth. The halogen chemistry in polar regions is related to various important environmental processes such as Antarctic Ozone Depletion Event(ODE), mercury depletion, oxidative processes in atmosphere, and the formation of CCN (Cloud Condensation Nuclei). In this study, we investigated the reductive dissolution of iron oxide particles to produce Fe(II)aq and simultaneous oxidation of I- (iodide) to I3- (tri-iodide) in ice phase under UV irradiation or dark condition. The reductive generation of Fe(II)aq from iron oxides and oxidation of iodide to I3- were negligible in water but significantly accelerated in frozen solution both in the presence and absence of light. The enhanced reductive generation of Fe(II)aq and oxidative formation of I3- in ice were observed regardless of the various types of iron oxides [hematite (α-Fe2O3) maghemite (γ- Fe2O3), goethite (α-FeOOH), lepidocrocite (γ-FeOOH) and, magnetite (Fe3O4)]. We explained that the enhanced redox production of Fe(II)aq and I3- in ice is contributed to the freeze concentration of iodides, protons, and dissolved oxygen in the unfrozen solution. When the concentration of both iodides and protons were raised by 10-fold each, the formation of Fe(II)aq in water under UV irradiation was approached to those in ice. The outdoor experiments were carried out under ambient solar radiation in winter season of mid-latitude (Pohang, Korea: 36°N latitude) and also confirmed that the production of Fe(II)aq via reductive dissolution of iron oxide and I3- generation via I- oxidation were enhanced in frozen solution. These results suggest that iron

  14. Redox Sensitivities of Global Cellular Cysteine Residues under Reductive and Oxidative Stress.

    PubMed

    Araki, Kazutaka; Kusano, Hidewo; Sasaki, Naoyuki; Tanaka, Riko; Hatta, Tomohisa; Fukui, Kazuhiko; Natsume, Tohru

    2016-08-01

    The protein cysteine residue is one of the amino acids most susceptible to oxidative modifications, frequently caused by oxidative stress. Several applications have enabled cysteine-targeted proteomics analysis with simultaneous detection and quantitation. In this study, we employed a quantitative approach using a set of iodoacetyl-based cysteine reactive isobaric tags (iodoTMT) and evaluated the transient cellular oxidation ratio of free and reversibly modified cysteine thiols under DTT and hydrogen peroxide (H2O2) treatments. DTT treatment (1 mM for 5 min) reduced most cysteine thiols, irrespective of their cellular localizations. It also caused some unique oxidative shifts, including for peroxiredoxin 2 (PRDX2), uroporphyrinogen decarboxylase (UROD), and thioredoxin (TXN), proteins reportedly affected by cellular reactive oxygen species production. Modest H2O2 treatment (50 μM for 5 min) did not cause global oxidations but instead had apparently reductive effects. Moreover, with H2O2, significant oxidative shifts were observed only in redox active proteins, like PRDX2, peroxiredoxin 1 (PRDX1), TXN, and glyceraldehyde 3-phosphate dehydrogenase (GAPDH). Overall, our quantitative data illustrated both H2O2- and reduction-mediated cellular responses, whereby while redox homeostasis is maintained, highly reactive thiols can potentiate the specific, rapid cellular signaling to counteract acute redox stress.

  15. Design Principles for Oxygen Reduction and Evolution on Oxide Catalysts

    NASA Astrophysics Data System (ADS)

    Shao-Horn, Yang

    2012-02-01

    Driven by growing concerns about global warming and the depletion of petroleum resources, developing renewable energy production and storage technologies represent one of the major scientific challenges of the 21^st century. A critical element in pursuit of this quest is the discovery of efficient and cost-effective catalysts used in solar fuel production via electrochemical energy conversion processes such as oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), both of which are central to the efficiencies of direct-solar and electrolytic water-splitting devices, fuel cells, and metal-air batteries. Although the Sabatier's principle provides a qualitative argument in tuning catalytic activity by varying the bond strength between catalyst surface and reactant/product (neither too strong nor too weak leading to the maximum activity at moderate bond strength), it has no predictive power to find catalysts with enhanced activity. Identifying a ``design principle'' that links catalyst properties to the catalytic activity is critical to accelerate the search for highly active catalysts based on abundant elements, and minimize the use of precious metals. Here we establish a molecular principle that governs the activities of oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) for oxide catalysts, where the activities primarily correlate to the σ* orbital (``eg'') occupation of surface transition-metal cations established by systematic examination of more than ten to fifteen transition-metal oxides. The intrinsic ORR and OER activities exhibit a volcano-shaped dependence on the eg occupancy and the activities peak at an eg occupancy close to unity. Our findings reflect the critical influence of the σ* orbital on the energetics of surface reaction intermediates on surface transition metal ions such as the O2^2-/OH^- displacement and the OH^- regeneration, and thus highlight the importance of surface oxide electronic structure in controlling

  16. Oxidative and reductive metabolism of lipid-peroxidation derived carbonyls

    PubMed Central

    Singh, Mahavir; Kapoor, Aniruddh; Bhatnagar, Aruni

    2015-01-01

    Extensive research has shown that increased production of reactive oxygen species (ROS) results in tissue injury under a variety of pathological conditions and chronic degenerative diseases. While ROS are highly reactive and can incite significant injury, polyunsaturated lipids in membranes and lipoproteins are their main targets. ROS-triggered lipid peroxidation reactions generate a range of reactive carbonyl species (RCS), and these RCS spread and amplify ROS-related injury. Several RCS generated in oxidizing lipids, such as 4-hydroxy trans-2-nonenal (HNE), 4-oxo-2-(E)-nonenal (ONE), acrolein, malondialdehyde (MDA) and phospholipid aldehydes have been shown to be produced under conditions of oxidative stress and contribute to tissue injury and dysfunction by depleting glutathione and other reductants leading to the modification of proteins, lipids, and DNA. To prevent tissue injury, these RCS are metabolized by several oxidoreductases, including members of the aldo-keto reductase (AKR) superfamily, aldehyde dehydrogenases (ALDHs), and alcohol dehydrogenases (ADHs). Metabolism via these enzymes results in RCS inactivation and detoxification, although under some conditions, it can also lead to the generation of signaling molecules that trigger adaptive responses. Metabolic transformation and detoxification of RCS by oxidoreductases prevent indiscriminate ROS toxicity, while at the same time, preserving ROS signaling. A better understanding of RCS metabolism by oxidoreductases could lead to the development of novel therapeutic interventions to decrease oxidative injury in several disease states and to enhance resistance to ROS-induced toxicity. PMID:25559856

  17. Direct growth of flower-like manganese oxide on reduced graphene oxide towards efficient oxygen reduction reaction.

    PubMed

    Zhang, Jintao; Guo, Chunxian; Zhang, Lianying; Li, Chang Ming

    2013-07-18

    Three-dimensional manganese oxide is directly grown on reduced graphene oxide (RGO) sheets, exhibiting comparable catalytic activity, higher selectivity and better stability towards oxygen reduction reaction than those of the commercial Pt/XC-72 catalyst. PMID:23745182

  18. Floating Potential Probe Langmuir Probe Data Reduction Results

    NASA Technical Reports Server (NTRS)

    Morton, Thomas L.; Minow, Joseph I.

    2002-01-01

    During its first five months of operations, the Langmuir Probe on the Floating Potential Probe (FPP) obtained data on ionospheric electron densities and temperatures in the ISS orbit. In this paper, the algorithms for data reduction are presented, and comparisons are made of FPP data with ground-based ionosonde and Incoherent Scattering Radar (ISR) results. Implications for ISS operations are detailed, and the need for a permanent FPP on ISS is examined.

  19. Interfacial Reduction-Oxidation Mechanisms Governing Fate and Transport of Contaminants in the Vadose Zone

    SciTech Connect

    Deng, Baolin; Thornton, Edward C.; Cantrell, Kirk J.; Olsen, Khris B.; Amonette, James E.

    2003-06-01

    Immobilization of toxic and radioactive metals (e.g., Cr, Tc, and U) in the vadose zone by the In Situ Gaseous Reduction (ISGR) using hydrogen sulfide (H2S) is a promising technology for soil remediation. Earlier laboratory studies have shown that Cr(VI) in soil samples can be effectively immobilized by treatment with dilute gaseous H2S. A field test completed in 1999 at White Sand Missile Range, New Mexico, has shown a 70% immobilization of Cr(VI). The objective of this EMSP project is to characterize the interactions among H2S, the metal contaminants, and soil components. Understanding these interactions is needed to optimize the remediation system and to assess the long-term effectiveness of the technology. Proposed research tasks included: (A) Evaluation of the potential catalytic effect of mineral surfaces on the rate of Cr(VI) reduction by H2S and the rate of H2S oxidation by air; (B) Identification of the reactions of soil minerals with H2S and determination of associated reaction rates; (C) Evaluation of the role of soil water chemistry on the reduction of Cr(VI) by H2S; (D) Assessment of the reductive buffering capacity of H2S-reduced soil and the potential for emplacement of long-term vadose zone reactive barriers; and (E) Evaluation of the potential for immobilization of Tc and U in the vadose zone by reduction and an assessment of the potential for remobilization by subsequent reoxidation.

  20. Efficient Direct Reduction of Graphene Oxide by Silicon Substrate

    PubMed Central

    Chan Lee, Su; Some, Surajit; Wook Kim, Sung; Jun Kim, Sun; Seo, Jungmok; Lee, Jooho; Lee, Taeyoon; Ahn, Jong-Hyun; Choi, Heon-Jin; Chan Jun, Seong

    2015-01-01

    Graphene has been studied for various applications due to its excellent properties. Graphene film fabrication from solutions of graphene oxide (GO) have attracted considerable attention because these procedures are suitable for mass production. GO, however, is an insulator, and therefore a reduction process is required to make the GO film conductive. These reduction procedures require chemical reducing agents or high temperature annealing. Herein, we report a novel direct and simple reduction procedure of GO by silicon, which is the most widely used material in the electronics industry. In this study, we also used silicon nanosheets (SiNSs) as reducing agents for GO. The reducing effect of silicon was confirmed by various characterization methods. Furthermore, the silicon wafer was also used as a reducing template to create a reduced GO (rGO) film on a silicon substrate. By this process, a pure rGO film can be formed without the impurities that normally come from chemical reducing agents. This is an easy and environmentally friendly method to prepare large scale graphene films on Si substrates. PMID:26194107

  1. Hydrogen Reduction of Zinc and Iron Oxides Containing Mixtures

    NASA Astrophysics Data System (ADS)

    de Siqueira, Rogério Navarro C.; de Albuquerque Brocchi, Eduardo; de Oliveira, Pamela Fernandes; Motta, Marcelo Senna

    2013-10-01

    Zinc is a metal of significant technological importance and its production from secondary sources has motivated the development of alternative processes, such as the chemical treatment of electrical arc furnace (EAF) dust. Currently, the extraction of zinc from the mentioned residue using a carbon-containing reducing agent is in the process of being established commercially and technically. In the current study, the possibility of reducing zinc from an EAF dust sample through a H2 constant flux in a horizontal oven is studied. The reduction of a synthetic oxide mixture of analogous composition is also investigated. The results indicated that the reduction process is thermodynamically viable for temperatures higher than 1123 K (850 °C), and all zinc metal produced is transferred to the gas stream, enabling its complete separation from iron. The same reaction in the presence of zinc crystals was considered for synthesizing FeZn alloys. However, for the experimental conditions employed, although ZnO reduction was indeed thermodynamically hindered because of the presence of zinc crystals (the metal's partial pressure was enhanced), the zinc metal's escape within the gaseous phase could not be effectively avoided.

  2. Microtrench/oxide island reduction with electron beam irradiation in high aspect ratio oxide etching

    NASA Astrophysics Data System (ADS)

    Watanabe, M.; Shaw, D. M.; Collins, G. J.

    2001-10-01

    During high aspect ratio oxide etching, the feature surface charges up and deflects the subsequent ion trajectories to the sidewalls due to local electric field, which results in microtrenching at the feature edges. At the etch end point, the microtrench reaches the conducting underlayer, which does not accumulate charge, and an oxide island remains at the center if no overetching is used. An electron beam source [1] is developed to neutralize the positive charge buildup at the feature bottom during etching. SEM images of the etch profiles show that the microtrench/oxide island formation is reduced with the electron beam irradiation. The electric field and ion trajectories within an etch feature are calculated, indicating that the reduction of the microtrench/oxide island formation is achieved by electron beam charge neutralization te at the feature bottom. [1] D. M. Shaw, M. Watanabe, G. J. Collins, and H. Sugai, Jpn. J. Appl. Phys. 38, 87 (1999).

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

    DOEpatents

    Tsang, Floris Y.

    1980-01-01

    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.

  4. Reduction in oxidatively generated DNA damage following smoking cessation

    PubMed Central

    2011-01-01

    Background Cigarette smoking is a known cause of cancer, and cancer may be in part due to effects of oxidative stress. However, whether smoking cessation reverses oxidatively induced DNA damage unclear. The current study sought to examine the extent to which three DNA lesions showed significant reductions after participants quit smoking. Methods Participants (n = 19) in this study were recruited from an ongoing 16-week smoking cessation clinical trial and provided blood samples from which leukocyte DNA was extracted and assessed for 3 DNA lesions (thymine glycol modification [d(TgpA)]; formamide breakdown of pyrimidine bases [d(TgpA)]; 8-oxo-7,8-dihydroguanine [d(Gh)]) via liquid chromatography tandem mass spectrometry (LC-MS/MS). Change in lesions over time was assessed using generalized estimating equations, controlling for gender, age, and treatment condition. Results Overall time effects for the d(TgpA) (χ2(3) = 8.068, p < 0.045), d(PfpA) (χ2(3) = 8.477, p < 0.037), and d(Gh) (χ2(3) = 37.599, p < 0.001) lesions were seen, indicating levels of each decreased significantly after CO-confirmed smoking cessation. The d(TgpA) and d(PfpA) lesions show relatively greater rebound at Week 16 compared to the d(Gh) lesion (88% of baseline for d(TgpA), 64% of baseline for d(PfpA), vs 46% of baseline for d(Gh)). Conclusions Overall, results from this analysis suggest that cigarette smoking contributes to oxidatively induced DNA damage, and that smoking cessation appears to reduce levels of specific damage markers between 30-50 percent in the short term. Future research may shed light on the broader array of oxidative damage influenced by smoking and over longer durations of abstinence, to provide further insights into mechanisms underlying carcinogenesis. PMID:21569419

  5. The reduction of nitrous oxide to dinitrogen by Escherichia coli.

    PubMed

    Kaldorf, M; Linne von Berg, K H; Meier, U; Servos, U; Bothe, H

    1993-01-01

    Escherichia coli K12 reduces nitrous oxide stoichiometrically to molecular nitrogen with rates of 1.9 mumol/h x mg protein. The activity is induced by anaerobiosis and nitrate. N2-formation from N2O is inhibited by C2H2 (Ki approximately 0.03 mM in the medium) and nitrite (Ki = 0.3 mM) but not by azide. A mutant defective in FNR synthesis is unable to reduce N2O to N2. The reaction in the wild type could routinely be followed by gas chromatography and alternatively by mass spectrometry measuring the formation of 15N2 from 15N2O. The enzyme catalyzing N2O-reduction in E. coli could not be identified; it is probably neither nitrate reductase nor nitrogenase. E. coli does not grow with N2O as sole respiratory electron acceptor. N2O-reduction might not have a physiological role in E. coli, and the enzyme involved might catalyze something else in nature, as it has a low affinity for the substrate N2O (apparent Km approximately 3.0 mM). The capability for N2O-reduction to N2 is not restricted to E. coli but is also demonstrable in Yersinia kristensenii and Buttiauxella agrestis of the Enterobacteriaceae. E. coli is able to produce NO and N2O from nitrite by nitrate reductase, depending on the assay conditions. In such experiments NO2- is not reduced to N2 because of the high demand for N2O of N2O-reduction and the inhibitory effect of NO2- on this reaction.

  6. Facile and controllable electrochemical reduction of graphene oxide and its applications

    SciTech Connect

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

    2010-01-01

    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.

  7. Reduction of Oxidative Melt Loss of Aluminum and Its Alloys

    SciTech Connect

    Dr. Subodh K. Das; Shridas Ningileri

    2006-03-17

    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.

  8. Thermogravimetric study of reduction of oxides present in oxidized nickel-base alloy powders

    NASA Technical Reports Server (NTRS)

    Herbell, T. P.

    1976-01-01

    Carbon, hydrogen, and hydrogen plus carbon reduction of three oxidized nickel-base alloy powders (a solid solution strengthened alloy both with and without the gamma prime formers aluminum and titanium and the solid solution strengthened alloy NiCrAlY) were evaluated by thermogravimetry. Hydrogen and hydrogen plus carbon were completely effective in reducing an alloy containing chromium, columbium, tantalum, molybdenum, and tungsten. However, with aluminum and titanium present the reduction was limited to a weight loss of about 81 percent. Carbon alone was not effective in reducing any of the alloys, and none of the reducing conditions were effective for use with NiCrAlY.

  9. Potential for Landing Gear Noise Reduction on Advanced Aircraft Configurations

    NASA Technical Reports Server (NTRS)

    Thomas, Russell H.; Nickol, Craig L.; Burley, Casey L.; Guo, Yueping

    2016-01-01

    The potential of significantly reducing aircraft landing gear noise is explored for aircraft configurations with engines installed above the wings or the fuselage. An innovative concept is studied that does not alter the main gear assembly itself but does shorten the main strut and integrates the gear in pods whose interior surfaces are treated with acoustic liner. The concept is meant to achieve maximum noise reduction so that main landing gears can be eliminated as a major source of airframe noise. By applying this concept to an aircraft configuration with 2025 entry-into-service technology levels, it is shown that compared to noise levels of current technology, the main gear noise can be reduced by 10 EPNL dB, bringing the main gear noise close to a floor established by other components such as the nose gear. The assessment of the noise reduction potential accounts for design features for the advanced aircraft configuration and includes the effects of local flow velocity in and around the pods, gear noise reflection from the airframe, and reflection and attenuation from acoustic liner treatment on pod surfaces and doors. A technical roadmap for maturing this concept is discussed, and the possible drag increase at cruise due to the addition of the pods is identified as a challenge, which needs to be quantified and minimized possibly with the combination of detailed design and application of drag reduction technologies.

  10. Catalyst and method for reduction of nitrogen oxides

    DOEpatents

    Ott, Kevin C.

    2008-05-27

    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. The supported catalyst containing iron, manganese, and cerium showed 80 percent conversion at 113 degrees Celsius of a feed gas containing nitrogen oxides having 4 parts NO to one part NO.sub.2, about one equivalent ammonia, and excess oxygen; conversion improved to 94 percent at 147 degrees Celsius. N.sub.2O was not detected (detection limit: 0.6 percent N.sub.2O).

  11. Catalyst and method for reduction of nitrogen oxides

    DOEpatents

    Ott, Kevin C.

    2008-08-19

    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. The supported catalyst containing iron, manganese, and cerium showed 80 percent conversion at 113 degrees Celsius of a feed gas containing nitrogen oxides having 4 parts NO to one part NO.sub.2, about one equivalent ammonia, and excess oxygen; conversion improved to 94 percent at 147 degrees Celsius. N.sub.2O was not detected (detection limit: 0.6 percent N.sub.2O).

  12. Chemical reduction of individual graphene oxide sheets as revealed by electrostatic force microscopy.

    PubMed

    Kulkarni, Dhaval D; Kim, Songkil; Chyasnavichyus, Marius; Hu, Kesong; Fedorov, Andrei G; Tsukruk, Vladimir V

    2014-05-01

    We report continuous monitoring of heterogeneously distributed oxygenated functionalities on the entire surface of the individual graphene oxide flake during the chemical reduction process. The charge densities over the surface with mixed oxidized and graphitic domains were observed for the same flake after a step-by-step chemical reduction process using electrostatic force microscopy. Quantitative analysis revealed heavily oxidized nanoscale domains (50-100 nm across) on the graphene oxide surface and a complex reduction mechanism involving leaching of sharp oxidized asperities from the surface followed by gradual thinning and formation of uniformly mixed oxidized and graphitic domains across the entire flake.

  13. Direct chemical reduction of neptunium oxide to neptunium metal using calcium and calcium chloride

    NASA Astrophysics Data System (ADS)

    Squires, Leah N.; Lessing, Paul

    2016-04-01

    A process of direct reduction of neptunium oxide to neptunium metal using calcium metal as the reducing agent is discussed. After reduction of the oxide to metal, the metal is separated by density from the other components of the reaction mixture and can be easily removed upon cooling. The direct reduction technique consistently produces high purity (98%-99% pure) neptunium metal.

  14. Rheostat Re-Wired: Alternative Hypotheses for the Control of Thioredoxin Reduction Potentials

    PubMed Central

    Bewley, Kathryn D.; Dey, Mishtu; Bjork, Rebekah E.; Mitra, Sangha; Chobot, Sarah E.; Drennan, Catherine L.; Elliott, Sean J.

    2015-01-01

    Thioredoxins are small soluble proteins that contain a redox-active disulfide (CXXC). These disulfides are tuned to oxidizing or reducing potentials depending on the function of the thioredoxin within the cell. The mechanism by which the potential is tuned has been controversial, with two main hypotheses: first, that redox potential (Em) is specifically governed by a molecular ‘rheostat’—the XX amino acids, which influence the Cys pKa values, and thereby, Em; and second, the overall thermodynamics of protein folding stability regulates the potential. Here, we use protein film voltammetry (PFV) to measure the pH dependence of the redox potentials of a series of wild-type and mutant archaeal Trxs, PFV and glutathionine-equilibrium to corroborate the measured potentials, the fluorescence probe BADAN to measure pKa values, guanidinium-based denaturation to measure protein unfolding, and X-ray crystallography to provide a structural basis for our functional analyses. We find that when these archaeal thioredoxins are probed directly using PFV, both the high and low potential thioredoxins display consistent 2H+:2e- coupling over a physiological pH range, in conflict with the conventional ‘rheostat’ model. Instead, folding measurements reveals an excellent correlation to reduction potentials, supporting the second hypothesis and revealing the molecular mechanism of reduction potential control in the ubiquitous Trx family. PMID:25874934

  15. Nitrate Reduction Functional Genes and Nitrate Reduction Potentials Persist in Deeper Estuarine Sediments. Why?

    PubMed Central

    Papaspyrou, Sokratis; Smith, Cindy J.; Dong, Liang F.; Whitby, Corinne; Dumbrell, Alex J.; Nedwell, David B.

    2014-01-01

    Denitrification and dissimilatory nitrate reduction to ammonium (DNRA) are processes occurring simultaneously under oxygen-limited or anaerobic conditions, where both compete for nitrate and organic carbon. Despite their ecological importance, there has been little investigation of how denitrification and DNRA potentials and related functional genes vary vertically with sediment depth. Nitrate reduction potentials measured in sediment depth profiles along the Colne estuary were in the upper range of nitrate reduction rates reported from other sediments and showed the existence of strong decreasing trends both with increasing depth and along the estuary. Denitrification potential decreased along the estuary, decreasing more rapidly with depth towards the estuary mouth. In contrast, DNRA potential increased along the estuary. Significant decreases in copy numbers of 16S rRNA and nitrate reducing genes were observed along the estuary and from surface to deeper sediments. Both metabolic potentials and functional genes persisted at sediment depths where porewater nitrate was absent. Transport of nitrate by bioturbation, based on macrofauna distributions, could only account for the upper 10 cm depth of sediment. A several fold higher combined freeze-lysable KCl-extractable nitrate pool compared to porewater nitrate was detected. We hypothesised that his could be attributed to intracellular nitrate pools from nitrate accumulating microorganisms like Thioploca or Beggiatoa. However, pyrosequencing analysis did not detect any such organisms, leaving other bacteria, microbenthic algae, or foraminiferans which have also been shown to accumulate nitrate, as possible candidates. The importance and bioavailability of a KCl-extractable nitrate sediment pool remains to be tested. The significant variation in the vertical pattern and abundance of the various nitrate reducing genes phylotypes reasonably suggests differences in their activity throughout the sediment column. This

  16. Removal of the X-ray contrast media diatrizoate by electrochemical reduction and oxidation.

    PubMed

    Radjenovic, Jelena; Flexer, Victoria; Donose, Bogdan C; Sedlak, David L; Keller, Jurg

    2013-01-01

    Due to their resistance to biological wastewater treatment, iodinated X-ray contrast media (ICM) have been detected in municipal wastewater effluents at relatively high concentrations (i.e., up to 100 μg L(-1)), with hospitals serving as their main source. To provide a new approach for reducing the concentrations of ICMs in wastewater, electrochemical reduction at three-dimensional graphite felt and graphite felt doped with palladium nanoparticles was examined as a means for deiodination of the common ICM diatrizoate. The presence of palladium nanoparticles significantly enhanced the removal of diatrizoate and enabled its complete deiodination to 3,5-diacetamidobenzoic acid. When the system was employed in the treatment of hospital wastewater, diatrizoate was reduced, but the extent of electrochemical reduction decreased as a result of competing reactions with solutes in the matrix. Following electrochemical reduction of diatrizoate to 3,5-diacetamidobenzoic acid, electrochemical oxidation with boron-doped diamond (BDD) anodes was employed. 3,5-Diacetamidobenzoic acid disappeared from solution at a rate that was similar to that of diatrizoate, but it was more readily mineralized than the parent compound. When electrochemical reduction and oxidation were coupled in a three-compartment reactor operated in a continuous mode, complete deiodination of diatrizoate was achieved at an applied cathode potential of -1.7 V vs SHE, with the released iodide ions electrodialyzed in a central compartment with 80% efficiency. The resulting BDD anode potential (i.e., +3.4-3.5 V vs SHE) enabled efficient oxidation of the products of the reductive step. The presence of other anions (e.g., chloride) was likely responsible for a decrease in I(-) separation efficiency when hospital wastewater was treated. Reductive deiodination combined with oxidative degradation provides benefits over oxidative treatment methods because it does not produce stable iodinated intermediates. Nevertheless

  17. Predicting Reduction Rates of Energetic Nitroaromatic Compounds Using Calculated One-Electron Reduction Potentials

    SciTech Connect

    Salter-Blanc, Alexandra; Bylaska, Eric J.; Johnston, Hayley; Tratnyek, Paul G.

    2015-02-11

    The evaluation of new energetic nitroaromatic compounds (NACs) for use in green munitions formulations requires models that can predict their environmental fate. The susceptibility of energetic NACs to nitro reduction might be predicted from correlations between rate constants (k) for this reaction and one-electron reduction potentials (E1NAC) / 0.059 V, but the mechanistic implications of such correlations are inconsistent with evidence from other methods. To address this inconsistency, we have reevaluated existing kinetic data using a (non-linear) free-energy relationship (FER) based on the Marcus theory of outer-sphere electron transfer. For most reductants, the results are inconsistent with rate limitation by an initial, outer-sphere electron transfer, suggesting that the strong correlation between k and E1NAC is justified only as an empirical model. This empirical correlation was used to calibrate a new quantitative structure-activity relationship (QSAR) using previously reported values of k for non-energetic NAC reduction by Fe(II) porphyrin and newly reported values of E1NAC determined using density functional theory at the B3LYP/6-311++G(2d,2p) level with the COSMO solvation model. The QSAR was then validated for energetic NACs using newly measured kinetic data for 2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (2,4-DNT), and 2,4-dinitroanisole (DNAN). The data show close agreement with the QSAR, supporting its applicability to energetic NACs.

  18. Predicting Reduction Rates of Energetic Nitroaromatic Compounds Using Calculated One-Electron Reduction Potentials

    DOE PAGESBeta

    Salter-Blanc, Alexandra; Bylaska, Eric J.; Johnston, Hayley; Tratnyek, Paul G.

    2015-02-11

    The evaluation of new energetic nitroaromatic compounds (NACs) for use in green munitions formulations requires models that can predict their environmental fate. The susceptibility of energetic NACs to nitro reduction might be predicted from correlations between rate constants (k) for this reaction and one-electron reduction potentials (E1NAC) / 0.059 V, but the mechanistic implications of such correlations are inconsistent with evidence from other methods. To address this inconsistency, we have reevaluated existing kinetic data using a (non-linear) free-energy relationship (FER) based on the Marcus theory of outer-sphere electron transfer. For most reductants, the results are inconsistent with rate limitation bymore » an initial, outer-sphere electron transfer, suggesting that the strong correlation between k and E1NAC is justified only as an empirical model. This empirical correlation was used to calibrate a new quantitative structure-activity relationship (QSAR) using previously reported values of k for non-energetic NAC reduction by Fe(II) porphyrin and newly reported values of E1NAC determined using density functional theory at the B3LYP/6-311++G(2d,2p) level with the COSMO solvation model. The QSAR was then validated for energetic NACs using newly measured kinetic data for 2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (2,4-DNT), and 2,4-dinitroanisole (DNAN). The data show close agreement with the QSAR, supporting its applicability to energetic NACs.« less

  19. A micro-nano porous oxide hybrid for efficient oxygen reduction in reduced-temperature solid oxide fuel cells.

    PubMed

    Da Han; Liu, Xuejiao; Zeng, Fanrong; Qian, Jiqin; Wu, Tianzhi; Zhan, Zhongliang

    2012-01-01

    Tremendous efforts to develop high-efficiency reduced-temperature (≤ 600°C) solid oxide fuel cells are motivated by their potentials for reduced materials cost, less engineering challenge, and better performance durability. A key obstacle to such fuel cells arises from sluggish oxygen reduction reaction kinetics on the cathodes. Here we reported that an oxide hybrid, featuring a nanoporous Sm(0.5)Sr(0.5)CoO(3-δ) (SSC) catalyst coating bonded onto the internal surface of a high-porosity La(0.9)Sr(0.1)Ga(0.8)Mg(0.2)O(3-δ) (LSGM) backbone, exhibited superior catalytic activity for oxygen reduction reactions and thereby yielded low interfacial resistances in air, e.g., 0.021 Ω cm(2) at 650°C and 0.043 Ω cm(2) at 600°C. We further demonstrated that such a micro-nano porous hybrid, adopted as the cathode in a thin LSGM electrolyte fuel cell, produced impressive power densities of 2.02 W cm(-2) at 650°C and 1.46 W cm(-2) at 600°C when operated on humidified hydrogen fuel and air oxidant.

  20. A micro-nano porous oxide hybrid for efficient oxygen reduction in reduced-temperature solid oxide fuel cells

    PubMed Central

    Da Han; Liu, Xuejiao; Zeng, Fanrong; Qian, Jiqin; Wu, Tianzhi; Zhan, Zhongliang

    2012-01-01

    Tremendous efforts to develop high-efficiency reduced-temperature (≤ 600°C) solid oxide fuel cells are motivated by their potentials for reduced materials cost, less engineering challenge, and better performance durability. A key obstacle to such fuel cells arises from sluggish oxygen reduction reaction kinetics on the cathodes. Here we reported that an oxide hybrid, featuring a nanoporous Sm0.5Sr0.5CoO3−δ (SSC) catalyst coating bonded onto the internal surface of a high-porosity La0.9Sr0.1Ga0.8Mg0.2O3−δ (LSGM) backbone, exhibited superior catalytic activity for oxygen reduction reactions and thereby yielded low interfacial resistances in air, e.g., 0.021 Ω cm2 at 650°C and 0.043 Ω cm2 at 600°C. We further demonstrated that such a micro-nano porous hybrid, adopted as the cathode in a thin LSGM electrolyte fuel cell, produced impressive power densities of 2.02 W cm−2 at 650°C and 1.46 W cm−2 at 600°C when operated on humidified hydrogen fuel and air oxidant. PMID:22708057

  1. Niobium oxide-supported platinum ultra-low amount electrocatalysts for oxygen reduction.

    PubMed

    Sasaki, K; Zhang, L; Adzic, R R

    2008-01-01

    We demonstrate a new approach to synthesizing high-activity electrocatalysts for the O(2) reduction reaction with ultra low Pt content. The synthesis involves placing a small amount of Pt, the equivalent of a monolayer, on carbon-supported niobium oxide nanoparticles (NbO(2) or Nb(2)O(5)). Rotating disk electrode measurements show that the Pt/NbO(2)/C electrocatalyst has three times higher Pt mass activity for the O(2) reduction reaction than a commercial Pt/C electrocatalyst. The observed high activity of the Pt deposit is attributed to the reduced OH adsorption caused by lateral repulsion between PtOH and oxide surface species. The new electrocatalyst also exhibits improved stability against Pt dissolution under a potential cycling regime (30,000 cycles from 0.6 V to 1.1 V). These findings demonstrate that niobium-oxide (NbO(2)) nanoparticles can be adequate supports for Pt and facilitate further reducing the noble metal content in electrocatalysts for the oxygen reduction reaction.

  2. Nanorecycling: Monolithic Integration of Copper and Copper Oxide Nanowire Network Electrode through Selective Reversible Photothermochemical Reduction.

    PubMed

    Han, Seungyong; Hong, Sukjoon; Yeo, Junyeob; Kim, Dongkwan; Kang, Bongchul; Yang, Min-Yang; Ko, Seung Hwan

    2015-11-01

    Laser induced selective photothermochemical reduction is demonstrated to locally and reversibly control the oxidation state of Cu and Cu oxide nanowires in ambient conditions without any inert gas environment. This new concept of "nanorecycling" can monolithically integrate Cu and Cu oxide nanowires by restoring oxidized Cu, considered unusable for the electrode, back to a metallic state for repetitive reuse.

  3. Potential for mercury reduction by microbes in the high arctic.

    PubMed

    Poulain, Alexandre J; Ní Chadhain, Sinéad M; Ariya, Parisa A; Amyot, Marc; Garcia, Edenise; Campbell, Peter G C; Zylstra, Gerben J; Barkay, Tamar

    2007-04-01

    The contamination of polar regions due to the global distribution of anthropogenic pollutants is of great concern because it leads to the bioaccumulation of toxic substances, methylmercury among them, in Arctic food chains. Here we present the first evidence that microbes in the high Arctic possess and express diverse merA genes, which specify the reduction of ionic mercury [Hg(II)] to the volatile elemental form [Hg(0)]. The sampled microbial biomass, collected from microbial mats in a coastal lagoon and from the surface of marine macroalgae, was comprised of bacteria that were most closely related to psychrophiles that had previously been described in polar environments. We used a kinetic redox model, taking into consideration photoredox reactions as well as mer-mediated reduction, to assess if the potential for Hg(II) reduction by Arctic microbes can affect the toxicity and environmental mobility of mercury in the high Arctic. Results suggested that mer-mediated Hg(II) reduction could account for most of the Hg(0) that is produced in high Arctic waters. At the surface, with only 5% metabolically active cells, up to 68% of the mercury pool was resolved by the model as biogenic Hg(0). At a greater depth, because of incident light attenuation, the significance of photoredox transformations declined and merA-mediated activity could account for up to 90% of Hg(0) production. These findings highlight the importance of microbial redox transformations in the biogeochemical cycling, and thus the toxicity and mobility, of mercury in polar regions.

  4. Oxidation of alpha-ketoglutarate is required for reductive carboxylation in cancer cells with mitochondrial defects

    PubMed Central

    Mullen, Andrew R.; Hu, Zeping; Shi, Xiaolei; Jiang, Lei; Boroughs, Lindsey K.; Kovacs, Zoltan; Boriack, Richard; Rakheja, Dinesh; Sullivan, Lucas B.; Linehan, W. Marston; Chandel, Navdeep S.; DeBerardinis, Ralph J.

    2014-01-01

    Summary Mammalian cells generate citrate by decarboxylating pyruvate in the mitochondria to supply the tricarboxylic acid (TCA) cycle. In contrast, hypoxia and other impairments of mitochondrial function induce an alternative pathway that produces citrate by reductively carboxylating α-ketoglutarate (AKG) via NADPH-dependent isocitrate dehydrogenase (IDH). It is unknown how cells generate reducing equivalents necessary to supply reductive carboxylation in the setting of mitochondrial impairment. Here we identified shared metabolic features in cells using reductive carboxylation. Paradoxically, reductive carboxylation was accompanied by concomitant AKG oxidation in the TCA cycle. Inhibiting AKG oxidation decreased reducing equivalent availability and suppressed reductive carboxylation. Interrupting transfer of reducing equivalents from NADH to NADPH by nicotinamide nucleotide transhydrogenase increased NADH abundance and decreased NADPH abundance while suppressing reductive carboxylation. The data demonstrate that reductive carboxylation requires bidirectional AKG metabolism along oxidative and reductive pathways, with the oxidative pathway producing reducing equivalents used to operate IDH in reverse. PMID:24857658

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

    PubMed

    Lehninger, A L; Vercesi, A; Bababunmi, E A

    1978-04-01

    Mitochondria from normal rat liver and heart, and also Ehrlich tumor cells, respiring on succinate as energy source in the presence of rotenone (to prevent net electron flow to oxygen from the endogenous pyridine nucleotides), rapidly take up Ca(2+) and retain it so long as the pyridine nucleotides are kept in the reduced state. When acetoacetate is added to bring the pyridine nucleotides into a more oxidized state, Ca(2+) is released to the medium. A subsequent addition of a reductant of the pyridine nucleotides such as beta-hydroxybutyrate, glutamate, or isocitrate causes reuptake of the released Ca(2+). Successive cycles of Ca(2+) release and uptake can be induced by shifting the redox state of the pyridine nucleotides to more oxidized and more reduced states, respectively. Similar observations were made when succinate oxidation was replaced as energy source by ascorbate oxidation or by the hydrolysis of ATP. These and other observations form the basis of a hypothesis for feedback regulation of Ca(2+)-dependent substrate- or energy-mobilizing enzymatic reactions by the uptake or release of mitochondrial Ca(2+), mediated by the cytosolic phosphate potential and the ATP-dependent reduction of mitochondrial pyridine nucleotides by reversal of electron transport.

  6. Simultaneous arsenite oxidation and nitrate reduction at the electrodes of bioelectrochemical systems.

    PubMed

    Nguyen, Van Khanh; Park, Younghyun; Yu, Jaecheul; Lee, Taeho

    2016-10-01

    Arsenic and nitrate contaminations in the soil and groundwater have urged the scientific community to explore suitable technologies for treatment of both contaminants. This study reports, for the first time, a novel application of bioelectrochemical systems for coupling As detoxification at the anode and denitrification at the cathode. A similar As(III) oxidation efficiency was achieved when anode potential was controlled by a potentiostat or a direct current (DC) power supply. However, a slightly lower nitrate reduction rate was obtained in reactors using DC power supply during simultaneous operation of nitrate reduction and As(III) oxidation. Microbial community analysis by denaturing gradient gel electrophoresis indicated the presence of some autotrophic As(III)-oxidizing bacteria, including Achromobacter spp., Ensifer spp., and Sinorhizobium spp., that can flexibly switch their original metabolism of using oxygen as sole electron acceptor to a new metabolism mode of using solid-state anode as sole electron acceptor driving for As(III) oxidation under anaerobic conditions. Although further research is required for validating their applicability, bioelectrochemical systems represent a brilliant technology for remediation of groundwater contaminated with nitrate and/or arsenite. PMID:27438874

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

    PubMed Central

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

    1978-01-01

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

  8. Simultaneous arsenite oxidation and nitrate reduction at the electrodes of bioelectrochemical systems.

    PubMed

    Nguyen, Van Khanh; Park, Younghyun; Yu, Jaecheul; Lee, Taeho

    2016-10-01

    Arsenic and nitrate contaminations in the soil and groundwater have urged the scientific community to explore suitable technologies for treatment of both contaminants. This study reports, for the first time, a novel application of bioelectrochemical systems for coupling As detoxification at the anode and denitrification at the cathode. A similar As(III) oxidation efficiency was achieved when anode potential was controlled by a potentiostat or a direct current (DC) power supply. However, a slightly lower nitrate reduction rate was obtained in reactors using DC power supply during simultaneous operation of nitrate reduction and As(III) oxidation. Microbial community analysis by denaturing gradient gel electrophoresis indicated the presence of some autotrophic As(III)-oxidizing bacteria, including Achromobacter spp., Ensifer spp., and Sinorhizobium spp., that can flexibly switch their original metabolism of using oxygen as sole electron acceptor to a new metabolism mode of using solid-state anode as sole electron acceptor driving for As(III) oxidation under anaerobic conditions. Although further research is required for validating their applicability, bioelectrochemical systems represent a brilliant technology for remediation of groundwater contaminated with nitrate and/or arsenite.

  9. Molecular Underpinnings of Fe(III) Oxide Reduction by Shewanella Oneidensis MR-1

    PubMed Central

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

    2012-01-01

    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 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 MtrA either directly or indirectly through other periplasmic proteins. 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). In addition to Fe(III) oxides, Mtr pathway is also involved in reduction of

  10. Catalytic Reduction of a Tetrahydrobiopterin Radical within Nitric-oxide Synthase*

    PubMed Central

    Wei, Chin-Chuan; Wang, Zhi-Qiang; Tejero, Jesús; Yang, Ya-Ping; Hemann, Craig; Hille, Russ; Stuehr, Dennis J.

    2008-01-01

    Nitric-oxide synthases (NOS) are catalytically self-sufficient flavo-heme enzymes that generate NO from arginine (Arg) and display a novel utilization of their tetrahydrobiopterin (H4B) cofactor. During Arg hydroxylation, H4B acts as a one-electron donor and is then presumed to redox cycle (i.e. be reduced back to H4B) within NOS before further catalysis can proceed. Whereas H4B radical formation is well characterized, the subsequent presumed radical reduction has not been demonstrated, and its potential mechanisms are unknown. We investigated radical reduction during a single turnover Arg hydroxylation reaction catalyzed by neuronal NOS to document the process, determine its kinetics, and test for involvement of the NOS flavoprotein domain. We utilized a freeze-quench instrument, the biopterin analog 5-methyl-H4B, and a method that could separately quantify the flavin and pterin radicals that formed in NOS during the reaction. Our results establish that the NOS flavoprotein domain catalyzes reduction of the biopterin radical following Arg hydroxylation. The reduction is calmodulin-dependent and occurs at a rate that is similar to heme reduction and fast enough to explain H4B redox cycling in NOS. These results, in light of existing NOS crystal structures, suggest a “through-heme” mechanism may operate for H4B radical reduction in NOS. PMID:18283102

  11. Effects of oxidants and reductants on the efficiency of excitation transfer in green photosynthetic bacteria.

    PubMed

    Wang, J; Brune, D C; Blankenship, R E

    1990-02-22

    The efficiency of energy transfer in chlorosome antennas in the green sulfur bacteria Chlorobium vibrioforme and Chlorobium limicola was found to be highly sensitive to the redox potential of the suspension. Energy transfer efficiencies were measured by comparing the absorption spectrum of the bacteriochlorophyll c or d pigments in the chlorosome to the excitation spectrum for fluorescence arising from the chlorosome baseplate and membrane-bound antenna complexes. The efficiency of energy transfer approaches 100% at low redox potentials induced by addition of sodium dithionite or other strong reductants, and is lowered to 10-20% under aerobic conditions or after addition of a variety of membrane-permeable oxidizing agents. The redox effect on energy transfer is observed in whole cells, isolated membranes and purified chlorosomes, indicating that the modulation of energy transfer efficiency arises within the antenna complexes and is not directly mediated by the redox state of the reaction center. It is proposed that chlorosomes contain a component that acts as a highly quenching center in its oxidized state, but is an inefficient quencher when reduced by endogenous or exogenous reductants. This effect may be a control mechanism that prevents cellular damage resulting from reaction of oxygen with reduced low-potential electron acceptors found in the green sulfur bacteria. The redox modulation effect is not observed in the green gliding bacterium Chloroflexus aurantiacus, which contains chlorosomes but does not contain low-potential electron acceptors.

  12. Effects of oxidants and reductants on the efficiency of excitation transfer in green photosynthetic bacteria

    NASA Technical Reports Server (NTRS)

    Wang, J.; Brune, D. C.; Blankenship, R. E.

    1990-01-01

    The efficiency of energy transfer in chlorosome antennas in the green sulfur bacteria Chlorobium vibrioforme and Chlorobium limicola was found to be highly sensitive to the redox potential of the suspension. Energy transfer efficiencies were measured by comparing the absorption spectrum of the bacteriochlorophyll c or d pigments in the chlorosome to the excitation spectrum for fluorescence arising from the chlorosome baseplate and membrane-bound antenna complexes. The efficiency of energy transfer approaches 100% at low redox potentials induced by addition of sodium dithionite or other strong reductants, and is lowered to 10-20% under aerobic conditions or after addition of a variety of membrane-permeable oxidizing agents. The redox effect on energy transfer is observed in whole cells, isolated membranes and purified chlorosomes, indicating that the modulation of energy transfer efficiency arises within the antenna complexes and is not directly mediated by the redox state of the reaction center. It is proposed that chlorosomes contain a component that acts as a highly quenching center in its oxidized state, but is an inefficient quencher when reduced by endogenous or exogenous reductants. This effect may be a control mechanism that prevents cellular damage resulting from reaction of oxygen with reduced low-potential electron acceptors found in the green sulfur bacteria. The redox modulation effect is not observed in the green gliding bacterium Chloroflexus aurantiacus, which contains chlorosomes but does not contain low-potential electron acceptors.

  13. Depletion of reduction potential and key energy generation metabolic enzymes underlies tellurite toxicity in Deinococcus radiodurans.

    PubMed

    Anaganti, Narasimha; Basu, Bhakti; Gupta, Alka; Joseph, Daisy; Apte, Shree Kumar

    2015-01-01

    Oxidative stress resistant Deinococcus radiodurans surprisingly exhibited moderate sensitivity to tellurite induced oxidative stress (LD50 = 40 μM tellurite, 40 min exposure). The organism reduced 70% of 40 μM potassium tellurite within 5 h. Tellurite exposure significantly modulated cellular redox status. The level of ROS and protein carbonyl contents increased while the cellular reduction potential substantially decreased following tellurite exposure. Cellular thiols levels initially increased (within 30 min) of tellurite exposure but decreased at later time points. At proteome level, tellurite resistance proteins (TerB and TerD), tellurite reducing enzymes (pyruvate dehydrogense subunits E1 and E3), ROS detoxification enzymes (superoxide dismutase and thioredoxin reductase), and protein folding chaperones (DnaK, EF-Ts, and PPIase) displayed increased abundance in tellurite-stressed cells. However, remarkably decreased levels of key metabolic enzymes (aconitase, transketolase, 3-hydroxy acyl-CoA dehydrogenase, acyl-CoA dehydrogenase, electron transfer flavoprotein alpha, and beta) involved in carbon and energy metabolism were observed upon tellurite stress. The results demonstrate that depletion of reduction potential in intensive tellurite reduction with impaired energy metabolism lead to tellurite toxicity in D. radiodurans.

  14. Depletion of reduction potential and key energy generation metabolic enzymes underlies tellurite toxicity in Deinococcus radiodurans.

    PubMed

    Anaganti, Narasimha; Basu, Bhakti; Gupta, Alka; Joseph, Daisy; Apte, Shree Kumar

    2015-01-01

    Oxidative stress resistant Deinococcus radiodurans surprisingly exhibited moderate sensitivity to tellurite induced oxidative stress (LD50 = 40 μM tellurite, 40 min exposure). The organism reduced 70% of 40 μM potassium tellurite within 5 h. Tellurite exposure significantly modulated cellular redox status. The level of ROS and protein carbonyl contents increased while the cellular reduction potential substantially decreased following tellurite exposure. Cellular thiols levels initially increased (within 30 min) of tellurite exposure but decreased at later time points. At proteome level, tellurite resistance proteins (TerB and TerD), tellurite reducing enzymes (pyruvate dehydrogense subunits E1 and E3), ROS detoxification enzymes (superoxide dismutase and thioredoxin reductase), and protein folding chaperones (DnaK, EF-Ts, and PPIase) displayed increased abundance in tellurite-stressed cells. However, remarkably decreased levels of key metabolic enzymes (aconitase, transketolase, 3-hydroxy acyl-CoA dehydrogenase, acyl-CoA dehydrogenase, electron transfer flavoprotein alpha, and beta) involved in carbon and energy metabolism were observed upon tellurite stress. The results demonstrate that depletion of reduction potential in intensive tellurite reduction with impaired energy metabolism lead to tellurite toxicity in D. radiodurans. PMID:25331933

  15. Potential Modulation of Sirtuins by Oxidative Stress.

    PubMed

    Santos, Leonardo; Escande, Carlos; Denicola, Ana

    2016-01-01

    Sirtuins are a conserved family of NAD-dependent protein deacylases. Initially proposed as histone deacetylases, it is now known that they act on a variety of proteins including transcription factors and metabolic enzymes, having a key role in the regulation of cellular homeostasis. Seven isoforms are identified in mammals (SIRT1-7), all of them sharing a conserved catalytic core and showing differential subcellular localization and activities. Oxidative stress can affect the activity of sirtuins at different levels: expression, posttranslational modifications, protein-protein interactions, and NAD levels. Mild oxidative stress induces the expression of sirtuins as a compensatory mechanism, while harsh or prolonged oxidant conditions result in dysfunctional modified sirtuins more prone to degradation by the proteasome. Oxidative posttranslational modifications have been identified in vitro and in vivo, in particular cysteine oxidation and tyrosine nitration. In addition, oxidative stress can alter the interaction with other proteins, like SIRT1 with its protein inhibitor DBC1 resulting in a net increase of deacetylase activity. In the same way, manipulation of cellular NAD levels by pharmacological inhibition of other NAD-consuming enzymes results in activation of SIRT1 and protection against obesity-related pathologies. Nevertheless, further research is needed to establish the molecular mechanisms of redox regulation of sirtuins to further design adequate pharmacological interventions. PMID:26788256

  16. Potential Modulation of Sirtuins by Oxidative Stress

    PubMed Central

    Santos, Leonardo; Escande, Carlos; Denicola, Ana

    2016-01-01

    Sirtuins are a conserved family of NAD-dependent protein deacylases. Initially proposed as histone deacetylases, it is now known that they act on a variety of proteins including transcription factors and metabolic enzymes, having a key role in the regulation of cellular homeostasis. Seven isoforms are identified in mammals (SIRT1–7), all of them sharing a conserved catalytic core and showing differential subcellular localization and activities. Oxidative stress can affect the activity of sirtuins at different levels: expression, posttranslational modifications, protein-protein interactions, and NAD levels. Mild oxidative stress induces the expression of sirtuins as a compensatory mechanism, while harsh or prolonged oxidant conditions result in dysfunctional modified sirtuins more prone to degradation by the proteasome. Oxidative posttranslational modifications have been identified in vitro and in vivo, in particular cysteine oxidation and tyrosine nitration. In addition, oxidative stress can alter the interaction with other proteins, like SIRT1 with its protein inhibitor DBC1 resulting in a net increase of deacetylase activity. In the same way, manipulation of cellular NAD levels by pharmacological inhibition of other NAD-consuming enzymes results in activation of SIRT1 and protection against obesity-related pathologies. Nevertheless, further research is needed to establish the molecular mechanisms of redox regulation of sirtuins to further design adequate pharmacological interventions. PMID:26788256

  17. Microbially Induced Reductive Dissolution of Trace Element-Rich Lacustrine Iron-Oxides

    NASA Astrophysics Data System (ADS)

    Crowe, S. A.; Kulczykci, E.; O'Neill, A. H.; Roberts, J. A.; Fowle, D. A.

    2004-12-01

    nutrient bearing phases were dissolved. It was found that during DIR many trace elements (e.g. Ni, Mn, Co, Cr, P, and Si) were redistributed between the aqueous and solid phases. However trace element release was not congruent with Fe-oxide dissolution and the maximum aqueous concentrations of Mn, and Co were observed after less than three days of incubation. The rapid release of metals, particularly Co, Mn and Ni, suggest that these elements may be present in discrete phases more readily reduced than the bulk iron (oxy)hydroxides (e.g. MnO2). Cr is initially solubilized but is subsequently removed with progressive Fe reduction. This is consistent with the reduction of aqueous Cr (VI) to Cr (III) by Fe2+. Thus, in natural Fe-oxides there is potential for significant Fe2+ re-oxidation following the release of solid phase oxidants. In summary, our experiments suggest that in lacustrine environments Fe-oxides may be reductively dissolved at higher rates than predicted from laboratory experiments using single-phase pure iron (oxy)hydroxides. The release of the macronutrient phosphorus during DIR may enable sustained reduction in carbon rich anaerobic lake sediments. Furthermore, MnO2 may place a significant role in controlling trace element cycling even in very Fe-rich sediments.

  18. Perchlorate reduction by a novel chemolithoautotrophic, hydrogen-oxidizing bacterium.

    PubMed

    Zhang, Husen; Bruns, Mary Ann; Logan, Bruce E

    2002-10-01

    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 perchlorate as it leaves no organic residue and is sparingly soluble. We describe here the isolation of a perchlorate-respiring, hydrogen-oxidizing bacterium (Dechloromonas sp. strain HZ) that grows with carbon dioxide as sole carbon source. Strain HZ is a Gram-negative, rod-shaped facultative anaerobe that was isolated from a gas-phase anaerobic packed-bed biofilm reactor treating perchlorate-contaminated groundwater. The ability of strain HZ to grow autotrophically with carbon dioxide as the sole carbon source was confirmed by demonstrating that biomass carbon (100.9%) was derived from CO2. Chemolithotrophic growth with hydrogen was coupled with complete reduction of perchlorate (10 mM) to chloride with a maximum doubling time of 8.9 h. Strain HZ also grew using acetate as the electron donor and chlorate, nitrate, or oxygen (but not sulphate) as an electron acceptor. Phylogenetic analysis of the 16S rRNA sequence placed strain HZ in the genus Dechloromonas within the beta subgroup of the Proteobacteria. The study of this and other novel perchlorate-reducing bacteria may lead to new, safe technologies for removing perchlorate and other chemical pollutants from drinking water.

  19. Iron isotope fractionation during microbial dissimilatory iron oxide reduction in simulated Archaean seawater.

    PubMed

    Percak-Dennett, E M; Beard, B L; Xu, H; Konishi, H; Johnson, C M; Roden, E E

    2011-05-01

    The largest Fe isotope excursion yet measured in marine sedimentary rocks occurs in shales, carbonates, and banded iron formations of Neoarchaean and Paleoproterozoic age. The results of field and laboratory studies suggest a potential role for microbial dissimilatory iron reduction (DIR) in producing this excursion. However, most experimental studies of Fe isotope fractionation during DIR have been conducted in simple geochemical systems, using pure Fe(III) oxide substrates that are not direct analogues to phases likely to have been present in Precambrian marine environments. In this study, Fe isotope fractionation was investigated during microbial reduction of an amorphous Fe(III) oxide-silica coprecipitate in anoxic, high-silica, low-sulphate artificial Archaean seawater at 30 °C to determine if such conditions alter the extent of reduction or isotopic fractionations relative to those observed in simple systems. The Fe(III)-Si coprecipitate was highly reducible (c. 80% reduction) in the presence of excess acetate. The coprecipitate did not undergo phase conversion (e.g. to green rust, magnetite or siderite) during reduction. Iron isotope fractionations suggest that rapid and near-complete isotope exchange took place among all Fe(II) and Fe(III) components, in contrast to previous work on goethite and hematite, where exchange was limited to the outer few atom layers of the substrate. Large quantities of low-δ(56)Fe Fe(II) (aqueous and solid phase) were produced during reduction of the Fe(III)-Si coprecipitate. These findings shed new light on DIR as a mechanism for producing Fe isotope variations observed in Neoarchaean and Paleoproterozoic marine sedimentary rocks.

  20. Iron isotope fractionation during microbial dissimilatory iron oxide reduction in simulated Archaean seawater.

    PubMed

    Percak-Dennett, E M; Beard, B L; Xu, H; Konishi, H; Johnson, C M; Roden, E E

    2011-05-01

    The largest Fe isotope excursion yet measured in marine sedimentary rocks occurs in shales, carbonates, and banded iron formations of Neoarchaean and Paleoproterozoic age. The results of field and laboratory studies suggest a potential role for microbial dissimilatory iron reduction (DIR) in producing this excursion. However, most experimental studies of Fe isotope fractionation during DIR have been conducted in simple geochemical systems, using pure Fe(III) oxide substrates that are not direct analogues to phases likely to have been present in Precambrian marine environments. In this study, Fe isotope fractionation was investigated during microbial reduction of an amorphous Fe(III) oxide-silica coprecipitate in anoxic, high-silica, low-sulphate artificial Archaean seawater at 30 °C to determine if such conditions alter the extent of reduction or isotopic fractionations relative to those observed in simple systems. The Fe(III)-Si coprecipitate was highly reducible (c. 80% reduction) in the presence of excess acetate. The coprecipitate did not undergo phase conversion (e.g. to green rust, magnetite or siderite) during reduction. Iron isotope fractionations suggest that rapid and near-complete isotope exchange took place among all Fe(II) and Fe(III) components, in contrast to previous work on goethite and hematite, where exchange was limited to the outer few atom layers of the substrate. Large quantities of low-δ(56)Fe Fe(II) (aqueous and solid phase) were produced during reduction of the Fe(III)-Si coprecipitate. These findings shed new light on DIR as a mechanism for producing Fe isotope variations observed in Neoarchaean and Paleoproterozoic marine sedimentary rocks. PMID:21504536

  1. Microorganisms pumping iron: anaerobic microbial iron oxidation and reduction.

    PubMed

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

    2006-10-01

    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.

  2. Note: Rapid reduction of graphene oxide paper by glow discharge plasma

    SciTech Connect

    Bo, Zheng; Qian, Jiajing; Duan, Liangping; Qiu, Kunzan Yan, Jianhua; Cen, Kefa; Han, Zhao Jun; Ostrikov, Kostya

    2015-05-15

    This note reports on a novel method for the rapid reduction of graphene oxide (GO) paper using a glow discharge plasma reactor. Glow discharge is produced and sustained between two parallel-plate graphite electrodes at a pressure of 240 mTorr. By exposing GO paper at the junction of negative-glow and Faraday-dark area for 4 min, the oxygen-containing groups can be effectively removed (C/O ratio increases from 2.6 to 7.9), while the material integrality and flexibility are kept well. Electrochemical measurements demonstrate that the as-obtained reduced GO paper can be potentially used for supercapacitor application.

  3. Investigation on the Oxidation and Reduction of Titanium in Molten Salt with the Soluble TiC Anode

    NASA Astrophysics Data System (ADS)

    Wang, Shulan; Wan, Chaopin; Liu, Xuan; Li, Li

    2015-12-01

    To reveal the oxidation process of titanium from TiC anode and the reduction mechanism of titanium ions in molten NaCl-KCl, the polarization curve of TiC anode in molten NaCl-KCl and cyclic voltammograms of the molten salt after polarization were studied. Investigation on the polarization curve shows that titanium can be oxidized and dissociated from the TiC anode at very low potential. The cyclic voltammograms demonstrated that the reduction reaction of titanium ions in the molten salt is a one-step process. By potentiostatic electrolysis, dendritic titanium is obtained on the steel plate. The work promotes the understanding on the process of electrochemical oxidization/dissociation of titanium from TiC anode and the reduction mechanism of titanium ions in molten salt.

  4. Electrochemical investigation of polyhalide ion oxidation-reduction on carbon nanotube electrodes for redox flow batteries

    SciTech Connect

    Shao, Yuyan; Engelhard, Mark H.; Lin, Yuehe

    2009-10-01

    Polyhalide ions (Br-/BrCl2-) are an important redox couple for redox flow batteries. The oxidation-reduction behavior of polyhalide ions on a carbon nanotube (CNT) electrode has been investigated with cyclic voltammetry and electrochemical impedance spectroscopy. The onset oxidation potential of Br-/BrCl2- is negatively shifted by >100 mV, and the redox current peaks are greatly enhanced on a CNT electrode compared with that on the most widely-used graphite electrode. The reaction resistance of the redox couple (Br-/BrCl2-) is decreased on a CNT electrode. The redox reversibility is increased on a CNT electrode even though it still needs further improvement. CNT is a promising electrode material for redox flow batteries.

  5. Phosphonated nanocelluloses from sequential oxidative-reductive treatment-Physicochemical characteristics and thermal properties.

    PubMed

    Sirviö, Juho Antti; Hasa, Tapani; Ahola, Juha; Liimatainen, Henrikki; Niinimäki, Jouko; Hormi, Osmo

    2015-11-20

    Nanocellulosic materials with good thermal stability are highly desirable for applications, such as reinforcement and filler agents in composites. In the present work, phosphonated cellulose was utilized to obtain nanocelluloses with good thermal stability and potential intumescent properties. Phosphonated cellulose was synthetized from birch pulp via sequential periodate oxidation and reductive amination using a bisphosphonate group-containing amine, sodium alendronate, as a phosphonating reagent. After high-pressure homogenization, bisphosphonate cellulose nanofibres or nanocrystals were obtained, depending on the initial oxidation degree. Nanofibres had a typical diameter of 3.8nm and length of several micrometers, whereas nanocrystals exhibited a width of about 6nm and an average length of 103-129nm. All nanocelluloses exhibited cellulose I crystalline structures and high transparency in water solutions. Phosphonated nanocelluloses exhibited good thermal stability and a greater amount of residual char was formed at 700°C compared to birch pulp and mechanically produced, non-chemically modified NFC. PMID:26344310

  6. Biological Oxidation of Fe(II) in Reduced Nontronite Coupled with Nitrate Reduction by Pseudogulbenkiania sp. Strain 2002

    SciTech Connect

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

    2013-10-15

    Nitrate contamination in soils, sediments, and water bodies is a significant issue. Although much is known about nitrate degradation in these environments, especially via microbial pathways, a complete understanding of all degradation processes, especially in clay mineral-rich soils, is still lacking. The objective of this study was to study the potential of removing nitrate contaminant using structural Fe(II) in clay mineral nontronite. Specifically, the coupled processes of microbial oxidation of Fe(II) in microbially reduced nontronite (NAu-2) and nitrate reduction by Pseudogulbenkiania species strain 2002 was investigated. Bio-oxidation experiments were conducted in bicarbonate-buffered medium under both growth and nongrowth conditions. 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 nontronite. The bio-oxidation extent under growth and nongrowth conditions reached 93% and 57%, respectively. Over the same time period, nitrate was completely reduced under both conditions to nitrogen gas (N2), via an intermediate product nitrite. Magnetite was a mineral product of nitrate-dependent Fe(II) oxidation, as evidenced by XRD data and TEM diffraction patterns. 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 soils.

  7. The Electrochemical Reduction of Chromium Sesquioxide in Molten Calcium Chloride under Cathodic Potential Control

    NASA Astrophysics Data System (ADS)

    Schwandt, Carsten; Fray, Derek J.

    2007-11-01

    Electrochemical polarization and reduction experiments are reported which were performed with a three-terminal cell and a molten salt electrolyte consisting of calcium chloride with additions of calcium oxide. Employing a metal cathode, a graphite anode and a pseudo-reference electrode also made from graphite, polarization measurements were carried out with the aim to validate the performance of the pseudo-reference electrode and to assess the stability of the electrolyte. Using a chromium sesquioxide cathode in conjunction with a graphite anode and a graphite pseudo-reference electrode, electrochemical reduction experiments were conducted under potentiostatic control. The key results are: a graphite pseudo-reference electrode has been shown to be appropriate in the present type of molten salt electrochemical experiments that take place on a time scale of many hours; the conversion of chromium oxide into chromium metal has been accomplished under cathodic potential control and in the absence of calcium metal deposition; a significant amount of calcium oxide in the calcium chloride has been found necessary to preclude anodic chlorine formation throughout the entire experiment; a considerable overpotential has been identified at the anode.

  8. Extraction of copper from an oxidized (lateritic) ore using bacterially catalysed reductive dissolution.

    PubMed

    Nancucheo, Ivan; Grail, Barry M; Hilario, Felipe; du Plessis, Chris; Johnson, D Barrie

    2014-01-01

    An oxidized lateritic ore which contained 0.8 % (by weight) copper was bioleached in pH- and temperature-controlled stirred reactors under acidic reducing conditions using pure and mixed cultures of the acidophilic chemolithotrophic bacterium Acidithiobacillus ferrooxidans. Sulfur was provided as the electron donor for the bacteria, and ferric iron present in goethite (the major ferric iron mineral present in the ore) acted as electron acceptor. Significantly more copper was leached by bacterially catalysed reductive dissolution of the laterite than in aerobic cultures or in sterile anoxic reactors, with up to 78 % of the copper present in the ore being extracted. This included copper that was leached from acid-labile minerals (chiefly copper silicates) and that which was associated with ferric iron minerals in the lateritic ore. In the anaerobic bioreactors, soluble iron in the leach liquors was present as iron (II) and copper as copper (I), but both metals were rapidly oxidized (to iron (III) and copper (II)) when the reactors were aerated. The number of bacteria added to the reactors had a critical role in dictating the rate and yield of copper solubilised from the ore. This work has provided further evidence that reductive bioprocessing, a recently described approach for extracting base metals from oxidized deposits, has the potential to greatly extend the range of metal ores that can be biomined. PMID:24687752

  9. Extraction of copper from an oxidized (lateritic) ore using bacterially catalysed reductive dissolution.

    PubMed

    Nancucheo, Ivan; Grail, Barry M; Hilario, Felipe; du Plessis, Chris; Johnson, D Barrie

    2014-01-01

    An oxidized lateritic ore which contained 0.8 % (by weight) copper was bioleached in pH- and temperature-controlled stirred reactors under acidic reducing conditions using pure and mixed cultures of the acidophilic chemolithotrophic bacterium Acidithiobacillus ferrooxidans. Sulfur was provided as the electron donor for the bacteria, and ferric iron present in goethite (the major ferric iron mineral present in the ore) acted as electron acceptor. Significantly more copper was leached by bacterially catalysed reductive dissolution of the laterite than in aerobic cultures or in sterile anoxic reactors, with up to 78 % of the copper present in the ore being extracted. This included copper that was leached from acid-labile minerals (chiefly copper silicates) and that which was associated with ferric iron minerals in the lateritic ore. In the anaerobic bioreactors, soluble iron in the leach liquors was present as iron (II) and copper as copper (I), but both metals were rapidly oxidized (to iron (III) and copper (II)) when the reactors were aerated. The number of bacteria added to the reactors had a critical role in dictating the rate and yield of copper solubilised from the ore. This work has provided further evidence that reductive bioprocessing, a recently described approach for extracting base metals from oxidized deposits, has the potential to greatly extend the range of metal ores that can be biomined.

  10. Simulation of catalytic oxidation and selective catalytic NOx reduction in lean-exhaust hybrid vehicles

    SciTech Connect

    Gao, Zhiming; Daw, C Stuart; Chakravarthy, Veerathu K

    2012-01-01

    We utilize physically-based models for diesel exhaust catalytic oxidation and urea-based selective catalytic NOx reduction to study their impact on drive cycle performance of hypothetical light-duty diesel powered hybrid vehicles. The models have been implemented as highly flexible SIMULINK block modules that can be used to study multiple engine-aftertreatment system configurations. The parameters of the NOx reduction model have been adjusted to reflect the characteristics of Cu-zeolite catalysts, which are of widespread current interest. We demonstrate application of these models using the Powertrain System Analysis Toolkit (PSAT) software for vehicle simulations, along with a previously published methodology that accounts for emissions and temperature transients in the engine exhaust. Our results illustrate the potential impact of DOC and SCR interactions for lean hybrid electric and plug-in hybrid electric vehicles.

  11. Electron Shuttles Enhance Anaerobic Ammonium Oxidation Coupled to Iron(III) Reduction.

    PubMed

    Zhou, Guo-Wei; Yang, Xiao-Ru; Li, Hu; Marshall, Christopher W; Zheng, Bang-Xiao; Yan, Yu; Su, Jian-Qiang; Zhu, Yong-Guan

    2016-09-01

    Anaerobic ammonium oxidation coupled to iron(III) reduction, termed Feammox, is a newly discovered nitrogen cycling process. However, little is known about the roles of electron shuttles in the Feammox reactions. In this study, two forms of Fe(III) (oxyhydr)oxide ferrihydrite (ex situ ferrihydrite and in situ ferrihydrite) were used in dissimilatory Fe(III) reduction (DIR) enrichments from paddy soil. Evidence for Feammox in DIR enrichments was demonstrated using the (15)N-isotope tracing technique. The extent and rate of both the (30)N2-(29)N2 and Fe(II) formation were enhanced when amended with electron shuttles (either 9,10-anthraquinone-2,6-disulfonate (AQDS) or biochar) and further simulated when these two shuttling compounds were combined. Although the Feammox-associated Fe(III) reduction accounted for only a minor proportion of total Fe(II) formation compared to DIR, it was estimated that the potentially Feammox-mediated N loss (0.13-0.48 mg N L(-1) day(-1)) was increased by 17-340% in the enrichments by the addition of electron shuttles. The addition of electron shuttles led to an increase in the abundance of unclassified Pelobacteraceae, Desulfovibrio, and denitrifiers but a decrease in Geobacter. Overall, we demonstrated a stimulatory effect of electron shuttles on Feammox that led to higher N loss, suggesting that electron shuttles might play a crucial role in Feammox-mediated N loss from soils. PMID:27494694

  12. Microbial reduction of graphene oxide by Escherichia coli: a green chemistry approach.

    PubMed

    Gurunathan, Sangiliyandi; Han, Jae Woong; Eppakayala, Vasuki; Kim, Jin-Hoi

    2013-02-01

    Graphene and graphene related materials are an important area of research in recent years due to their unique properties. The extensive industrial application of graphene and related compounds has led researchers to devise novel and simple methods for the synthesis of high quality graphene. In this paper, we developed an environment friendly, cost effective, simple method and green approaches for the reduction of graphene oxide (GO) using Escherichia coli biomass. In biological method, we can avoid use of toxic and environmentally harmful reducing agents commonly used in the chemical reduction of GO to obtain graphene. The biomass of E. coli reduces exfoliated GO to graphene at 37°C in an aqueous medium. The E. coli reduced graphene oxide (ERGO) was characterized with UV-visible absorption spectroscopy, particle analyzer, high resolution X-ray diffractometer, scanning electron microscopy and Raman spectroscopy. Besides the reduction potential, the biomass could also play an important role as stabilizing agent, in which synthesized graphene exhibited good stability in water. This method can open up the new avenue for preparing graphene in cost effective and large scale production. Our findings suggest that GO can be reduced by simple eco-friendly method by using E. coli biomass to produce water dispersible graphene. PMID:23107955

  13. Sulfidation and reduction of zinc titanate and zinc oxide sorbents for injection in gasifier exit ducts

    SciTech Connect

    Ishikawa, K. |; Krueger, C.; Flytzani-Stephanopoulos, M.; Jl, W.; Higgins, R.J.; Bishop, B.A.; Goldsmith, R.L.

    1995-12-31

    The sulfidation reaction kinetics of fine particles of zinc titanate and zinc oxide with H{sub 2}S were studied in order to test the potential of the sorbent injection hot-gas desulfurization process. Fine sorbent particles with diameter between 0.3 and 60 {mu}m were sulfided with H{sub 2}S and/or reduced with H{sub 2} in a laminar flow reactor over the temperature range of 500-900{degrees}C. Sulfidation/reduction conversion was compared for different particle sizes and sorbents with various porosities and atomic ratios of Zn and Ti. In reduction of ZnO with H{sub 2} and without H{sub 2}S, significant amount of Zn was formed and vaporized, while the presence of H{sub 2}S suppressed elemental Zn formation. This suggests that H{sub 2}S may suppress the surface reduction of ZnO and/or gaseous Zn may react with H{sub 2}S homogeneously and form fine particles of ZnS. Formation and vaporization of elemental Zn from zinc titanate sorbents was slower than from zinc oxide with and without H{sub 2}S.

  14. Electron Shuttles Enhance Anaerobic Ammonium Oxidation Coupled to Iron(III) Reduction.

    PubMed

    Zhou, Guo-Wei; Yang, Xiao-Ru; Li, Hu; Marshall, Christopher W; Zheng, Bang-Xiao; Yan, Yu; Su, Jian-Qiang; Zhu, Yong-Guan

    2016-09-01

    Anaerobic ammonium oxidation coupled to iron(III) reduction, termed Feammox, is a newly discovered nitrogen cycling process. However, little is known about the roles of electron shuttles in the Feammox reactions. In this study, two forms of Fe(III) (oxyhydr)oxide ferrihydrite (ex situ ferrihydrite and in situ ferrihydrite) were used in dissimilatory Fe(III) reduction (DIR) enrichments from paddy soil. Evidence for Feammox in DIR enrichments was demonstrated using the (15)N-isotope tracing technique. The extent and rate of both the (30)N2-(29)N2 and Fe(II) formation were enhanced when amended with electron shuttles (either 9,10-anthraquinone-2,6-disulfonate (AQDS) or biochar) and further simulated when these two shuttling compounds were combined. Although the Feammox-associated Fe(III) reduction accounted for only a minor proportion of total Fe(II) formation compared to DIR, it was estimated that the potentially Feammox-mediated N loss (0.13-0.48 mg N L(-1) day(-1)) was increased by 17-340% in the enrichments by the addition of electron shuttles. The addition of electron shuttles led to an increase in the abundance of unclassified Pelobacteraceae, Desulfovibrio, and denitrifiers but a decrease in Geobacter. Overall, we demonstrated a stimulatory effect of electron shuttles on Feammox that led to higher N loss, suggesting that electron shuttles might play a crucial role in Feammox-mediated N loss from soils.

  15. Microbial reduction of graphene oxide by Escherichia coli: a green chemistry approach.

    PubMed

    Gurunathan, Sangiliyandi; Han, Jae Woong; Eppakayala, Vasuki; Kim, Jin-Hoi

    2013-02-01

    Graphene and graphene related materials are an important area of research in recent years due to their unique properties. The extensive industrial application of graphene and related compounds has led researchers to devise novel and simple methods for the synthesis of high quality graphene. In this paper, we developed an environment friendly, cost effective, simple method and green approaches for the reduction of graphene oxide (GO) using Escherichia coli biomass. In biological method, we can avoid use of toxic and environmentally harmful reducing agents commonly used in the chemical reduction of GO to obtain graphene. The biomass of E. coli reduces exfoliated GO to graphene at 37°C in an aqueous medium. The E. coli reduced graphene oxide (ERGO) was characterized with UV-visible absorption spectroscopy, particle analyzer, high resolution X-ray diffractometer, scanning electron microscopy and Raman spectroscopy. Besides the reduction potential, the biomass could also play an important role as stabilizing agent, in which synthesized graphene exhibited good stability in water. This method can open up the new avenue for preparing graphene in cost effective and large scale production. Our findings suggest that GO can be reduced by simple eco-friendly method by using E. coli biomass to produce water dispersible graphene.

  16. Treatment of halogenated phenolic compounds by sequential tri-metal reduction and laccase-catalytic oxidation.

    PubMed

    Dai, Yunrong; Song, Yonghui; Wang, Siyu; Yuan, Yu

    2015-03-15

    Halogenated phenolic compounds (HPCs) are exerting negative effects on human beings and ecological health. Zero-valence metal reduction can dehalogenate HPCs rapidly but cannot mineralize them. Enzymatic catalysis can oxidize phenolic compounds but fails to dehalogenate efficiently, and sometimes even produces more toxic products. In this study, [Fe|Ni|Cu] tri-metallic reduction (TMR) and laccase-catalytic oxidation (LCO) processes were combined to sequentially remove HPCs, including triclosan, tetrabromobisphenol A, and 2-bromo-4-fluorophenol in water. The kinetics, pH and temperature dependences of TMR and LCO were obtained. The detailed TMR, LCO, and TMR-LCO transformation pathways of three HPCs were well described based on the identification of intermediate products and frontier molecular orbitals (FMOs) theory. The results showed that the two-stage process worked synergically: TMR that reductively dehalogenated HPCs followed by LCO that completely removed dehalogenated products. TMR was proven to not only improve biodegradability of HPCs but also reduce the yield of potential carcinogenic by-products. Furthermore, a TMR-LCO flow reactor was assembled and launched for 256 h, during which >95% HPCs and >75% TOC were removed. Meanwhile, monitored by microorganism indicators, 83.2%-92.7% acute toxicity of HPCs was eliminated, and the genotoxicity, produced by LCO, was also avoided by using TMR as pretreatment process. PMID:25596562

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

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

    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

  18. Method For Selective Catalytic Reduction Of Nitrogen Oxides

    DOEpatents

    Mowery-Evans, Deborah L.; Gardner, Timothy J.; McLaughlin, Linda I.

    2005-02-15

    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.

  19. Method for selective catalytic reduction of nitrogen oxides

    DOEpatents

    Mowery-Evans, Deborah L.; Gardner, Timothy J.; McLaughlin, Linda I.

    2005-02-15

    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.

  20. Mercury oxidation over a vanadia-based selective catalytic reduction catalyst

    SciTech Connect

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

    2009-01-15

    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.

  1. Particulate Matter Oxidative Potential from Waste Transfer Station Activity

    PubMed Central

    Godri, Krystal J.; Duggan, Sean T.; Fuller, Gary W.; Baker, Tim; Green, David; Kelly, Frank J.; Mudway, Ian S.

    2010-01-01

    Background Adverse cardiorespiratory health is associated with exposure to ambient particulate matter (PM). The highest PM concentrations in London occur in proximity to waste transfer stations (WTS), sites that experience high numbers of dust-laden, heavy-duty diesel vehicles transporting industrial and household waste. Objective Our goal was to quantify the contribution of WTS emissions to ambient PM mass concentrations and oxidative potential. Methods PM with a diameter < 10 μm (PM10) samples were collected daily close to a WTS. PM10 mass concentrations measurements were source apportioned to estimate local versus background sources. PM oxidative potential was assessed using the extent of antioxidant depletion from a respiratory tract lining fluid model. Total trace metal and bioavailable iron concentrations were measured to determine their contribution to PM oxidative potential. Results Elevated diurnal PM10 mass concentrations were observed on all days with WTS activity (Monday–Saturday). Variable PM oxidative potential, bioavailable iron, and total metal concentrations were observed on these days. The contribution of WTS emissions to PM at the sampling site, as predicted by microscale wind direction measurements, was correlated with ascorbate (r = 0.80; p = 0.030) and glutathione depletion (r = 0.76; p = 0.046). Increased PM oxidative potential was associated with aluminum, lead, and iron content. Conclusions PM arising from WTS activity has elevated trace metal concentrations and, as a consequence, increased oxidative potential. PM released by WTS activity should be considered a potential health risk to the nearby residential community. PMID:20368130

  2. H{sub 2} from biosyngas via iron reduction and oxidation

    SciTech Connect

    Straus, J.; Terry, P.

    1995-09-01

    The production of hydrogen from the steam-oxidation of iron is a long-known phenomenon. The rise in interest in the production and storage of hydrogen justifies the examination of this process (and of the reverse process, the reduction of iron oxide) for commercial use. Under NREL subcontract ZAR-4-13294-02, a process simulation program was developed and used as a design tool to analyze various configurations of the iron-hydrogen purification/storage scheme. Specifically, analyses were performed to determine the effectiveness of this scheme in conjunction with biomass-derived gasified fuel streams (biosyngas). The results of the computer simulations led to a selection of a two-stage iron oxide reduction process incorporating interstage water and CO{sub 2} removal. Thermal analysis shows that the iron-hydrogen process would yield essentially the same quantity of clean hydrogen per unit of biomass as the conventional route. The iron-hydrogen process benefits from the excellent match potentially achievable between the otherwise-unusable energy fraction in the off-gas of the reduction reactor and the parasitic thermal, mechanical and electrical energy needs of some typical gasifier systems. The program simulations and economic analysis suggest that clean hydrogen from biomass feedstock could cost about 20% less via the iron-hydrogen method than by conventional methods of purification (using the same feedstock). Cost analyses show that lower capital costs would be incurred in generating clean hydrogen by utilizing this approach, especially in response to the fluctuating demand profile of a utility.

  3. Humin as an electron donor for enhancement of multiple microbial reduction reactions with different redox potentials in a consortium.

    PubMed

    Zhang, Dongdong; Zhang, Chunfang; Xiao, Zhixing; Suzuki, Daisuke; Katayama, Arata

    2015-02-01

    A solid-phase humin, acting as an electron donor, was able to enhance multiple reductive biotransformations, including dechlorination of pentachlorophenol (PCP), dissimilatory reduction of amorphous Fe (III) oxide (FeOOH), and reduction of nitrate, in a consortium. Humin that was chemically reduced by NaBH4 served as an electron donor for these microbial reducing reactions, with electron donating capacities of 0.013 mmol e(-)/g for PCP dechlorination, 0.15 mmol e(-)/g for iron reduction, and 0.30 mmol e(-)/g for nitrate reduction. Two pairs of oxidation and reduction peaks within the humin were detected by cyclic voltammetry analysis. 16S rRNA gene sequencing-based microbial community analysis of the consortium incubated with different terminal electron acceptors, suggested that Dehalobacter sp., Bacteroides sp., and Sulfurospirillum sp. were involved in the PCP dechlorination, dissimilatory iron reduction, and nitrate reduction, respectively. These findings suggested that humin functioned as a versatile redox mediator, donating electrons for multiple respiration reactions with different redox potentials.

  4. Computational studies of polysiloxanes : oxidation potentials and decomposition reactions.

    SciTech Connect

    Assary, R. S.; Curtiss, L. A.; Redfern, P. C.; Zhang, Z.; Amine, K.

    2011-06-23

    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.

  5. Improved free energy profile for reduction of NO in cytochrome c dependent nitric oxide reductase (cNOR).

    PubMed

    Blomberg, Margareta R A; Siegbahn, Per E M

    2016-07-15

    Quantum chemical calculations play an essential role in the elucidation of reaction mechanisms for redox-active metalloenzymes. For example, the cleavage and the formation of covalent bonds can usually not be described only on the basis of experimental information, but can be followed by the calculations. Conversely, there are properties, like reduction potentials, which cannot be accurately calculated. Therefore, computational and experimental data has to be carefully combined to obtain reliable descriptions of entire catalytic cycles involving electron and proton uptake from donors outside the enzyme. Such a procedure is illustrated here, for the reduction of nitric oxide (NO) to nitrous oxide and water in the membrane enzyme, cytochrome c dependent nitric oxide reductase (cNOR). A surprising experimental observation is that this reaction is nonelectrogenic, which means that no energy is conserved. On the basis of hybrid density functional calculations a free energy profile for the entire catalytic cycle is obtained, which agrees much better with experimental information on the active site reduction potentials than previous ones. Most importantly the energy profile shows that the reduction steps are endergonic and that the entire process is rate-limited by high proton uptake barriers during the reduction steps. This result implies that, if the reaction were electrogenic, it would become too slow when the gradient is present across the membrane. This explains why this enzyme does not conserve any of the free energy released. © 2016 Wiley Periodicals, Inc.

  6. DNAPL mass transfer and permeability reduction during in situ chemical oxidation with permanganate

    NASA Astrophysics Data System (ADS)

    Li, X. David; Schwartz, Franklin W.

    2004-03-01

    This study utilized a series of laboratory experiments to examine the DNAPL mass removal rate and permeability reduction during ISCO using permanganate (MnO4-). Results show that MnO4- oxidation is effective in removing residual DNAPL from a porous medium. The DNAPL mass removal rate correlated positively with both the hydraulic stress and the oxidant load. A power relationship model of DNAPL mass removal under ISCO was proposed. Results also show that oxidation by-products CO2(g) and Mn oxide can cause pore plugging and flow by-passing. The reduction in hydraulic conductivity due to the Mn oxide precipitates was quantified. Hydraulic conductivity reduction as high as 80% was observed for oxidizing a small quantity of TCE.

  7. Effect of hydrogen peroxide and camellia sinensis extract on reduction of oxygen level in graphene oxide

    NASA Astrophysics Data System (ADS)

    Celina Selvakumari, J.; Dhanalakshmi, J.; Pathinettam Padiyan, D.

    2016-10-01

    The intention of this work is to reduce the oxygen level in graphene oxide. The reduction process was initiated while preparing graphene oxide using modified Hummer’s method. In this new method, increase in hydrogen peroxide concentration during the preparation process results in the oxygen content reduction. Adding green tea (camellia sinensis) extract with increased hydrogen peroxide results in further reduction of oxygen content and changed the graphene oxide to reduced graphene oxide. The structural and optical properties of the new found reduced graphene oxide was analysed using XRD, FTIR, TEM, Raman and UV–vis spectra. The overall observation reflects that the sp3 carbon network of graphene oxide changed into sp2 carbon lattice of graphene which is very handful in supercapacitor and biosensor fields.

  8. IN-SITU CHEMICAL OXIDATION - DNAPL MASS REDUCTION TECHNOLOGY

    EPA Science Inventory

    In-situ chemical oxidation (ISCO) is a rapidly developing technology used at hazardous waste sites where oxidants and complimentary reagents are injected into the subsurface to transform organic contaminants into less toxic byproducts. This technology is being used at new sites ...

  9. Artificial electron acceptors decouple archaeal methane oxidation from sulfate reduction.

    PubMed

    Scheller, Silvan; Yu, Hang; Chadwick, Grayson L; McGlynn, Shawn E; Orphan, Victoria J

    2016-02-12

    The oxidation of methane with sulfate is an important microbial metabolism in the global carbon cycle. In marine methane seeps, this process is mediated by consortia of anaerobic methanotrophic archaea (ANME) that live in syntrophy with sulfate-reducing bacteria (SRB). The underlying interdependencies within this uncultured symbiotic partnership are poorly understood. We used a combination of rate measurements and single-cell stable isotope probing to demonstrate that ANME in deep-sea sediments can be catabolically and anabolically decoupled from their syntrophic SRB partners using soluble artificial oxidants. The ANME still sustain high rates of methane oxidation in the absence of sulfate as the terminal oxidant, lending support to the hypothesis that interspecies extracellular electron transfer is the syntrophic mechanism for the anaerobic oxidation of methane.

  10. Thermodynamics of Manganese Oxides at Bulk and Nanoscale: Phase Formation, Transformation, Oxidation-Reduction, and Hydration

    NASA Astrophysics Data System (ADS)

    Birkner, Nancy R.

    spinel Mn3O4) for smaller particle size and in the presence of surface hydration. Chemisorption of water onto anhydrous nanophase Mn2O 3 surfaces promotes rapidly reversible redox phase changes at room temperature as confirmed by calorimetry, X-ray diffraction, and titration for manganese average oxidation state. Water adsorption microcalorimetry (in situ) at room temperature measured the strongly exothermic integral enthalpy of water adsorption (-103.5 kJ/mol) and monitored the energetics of the redox phase transformation. Hydration-driven redox transformation of anhydrous nanophase Mn(III) 2O3, (high surface enthalpy of anhydrous surfaces 1.77 +/- 0.10 J/m2) to Mn(II,III)3O4 (lower surface enthalpy 0.96 +/- 0.08 J/m2) occurred during the first few doses of water vapor. Surface reduction of nanoparticle bixbyite (Mn 2O3) to hausmannite (Mn3O4) occurs under conditions where no such reactions are seen or expected on grounds of bulk thermodynamics in coarse-grained materials. Layered structure manganese oxides contain alkali or alkaline earth cations and water, are generally fine-grained, and have considerable thermodynamic stability. The surface enthalpies (SE) of layered and tunnel structure complex manganese oxides are significantly lower than those of the binary manganese oxide phases. The SE for hydrous surfaces and overall manganese average oxidation state (AOS) (value in parentheses) are: cryptomelane 0.77 +/- 0.10 J/m 2 (3.78), sodium birnessite 0.69 +/- 0.13 J/m2 (3.56), potassium birnessite 0.55 +/- 0.11 J/m2 (3.52), and calcium birnessite 0.41 +/- 0.11 J/m2 (3.50). Surface enthalpies of hydrous surfaces of the calcium manganese oxide nanosheets are: deltaCa 0.39MnO2.3nH2O 0.75 +/- 0.10 J/m2 (3.89) and deltaCa0.43MnO2.3nH2O 0.57 +/- 0.12 J/m2 (3.68). The surface enthalpy of the complex manganese oxides appears to decrease with decreasing manganese average oxidation state, that is, with greater mixed valence manganese (Mn 3+/4+). Low surface energy suggests loose

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

    SciTech Connect

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

    2009-06-15

    A series of transition metal phosphides, including MoP, WP, CoP, Co{sub 2}P, and Ni{sub 2}P, 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. - Graphical abstract: Metal phosphides were obtained stoichiometrically from their oxidic precursors by hydrogen plasma reaction under mild conditions.

  12. Exoelectrogens Leading to Precise Reduction of Graphene Oxide by Flexibly Switching Their Environment during Respiration.

    PubMed

    Bansal, Prerna; Doshi, Sejal; Panwar, Ajay S; Bahadur, Dhirendra

    2015-09-23

    Reduced graphene oxide (RGO) has been prepared by a simple, cost-effective, and green route. In this work, graphene oxide (GO) has been reduced using Gram-negative facultative anaerobe S. dysenteriae, having exogenic properties of electron transfer via electron shuttling. Apparently, different concentrations of GO were successfully reduced with almost complete mass recovery. An effective role of lipopolysaccharide has been observed while comparing RGO reduced by S. dysenteriae and S. aureus. It was observed that the absence of lipopolysaccharide in Gram-positive S. aureus leads to a disrupted cell wall and that S.aureus could not survive in the presence of GO, leading to poor and inefficient reduction of GO, as shown in our results. However, S. dysenteriae having an outer lipopolysaccharide layer on its cell membrane reduced GO efficiently and the reduction process was extracellular for it. RGO prepared in our work has been characterized by X-ray diffraction, ζ potential, X-ray photoelectron spectroscopy, and Raman spectroscopy techniques, and the results were found to be in good agreement with those of chemically reduced GO. As agglomeration of RGO is the major issue to overcome while chemically reducing GO, we observed that RGO prepared by a bacterial route in our work has ζ potential value of -26.62 mV, good enough to avoid restacking of RGO. The role of exoelectrogens in electron transfer in the extracellular space has been depicted. Toxin released extracellularly during the process paves the way for reduction of GO due to its affinity towards oxygen. PMID:26288348

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

    SciTech Connect

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

    2009-06-15

    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

  14. Oxidation Potentials in Matte Smelting of Copper and Nickel

    NASA Astrophysics Data System (ADS)

    Matousek, Jan W.

    2014-09-01

    The oxidation potential, given as the base-ten logarithm of the oxygen partial pressure in bars and the temperature [log pO2/ T, °C], defines the state of oxidation of pyrometallurgical extraction and refining processes. This property varies from copper making, [-6/1150]; to lead/zinc smelting, [-10/1200]; to iron smelting, [-13/1600]. The current article extends the analysis to the smelting of copper and nickel/copper sulfide concentrates to produce mattes of the type Cu(Ni)FeS(O) and iron silicate slags, FeOxSiO2—with oxidation potentials of [-7.5/1250].

  15. Dissimilatory perchlorate reduction linked to aerobic methane oxidation via chlorite dismutase

    NASA Astrophysics Data System (ADS)

    Oremland, R. S.; Baesman, S. M.; Miller, L. G.

    2013-12-01

    The presence of methane (CH4) in the atmosphere of Mars is controversial yet the evidence has aroused scientific interest, as CH4 could be a harbinger of extant or extinct microbial life. There are various oxidized compounds present on the surface of Mars that could serve as electron acceptors for the anaerobic oxidation of CH4, including perchlorate (ClO4-). We examined the role of perchlorate, chlorate (ClO3-) and chlorite (ClO2-) as oxidants linked to CH4 oxidation. Dissimilatory perchlorate reduction begins with reduction of ClO4- to ClO2- and ends with dismutation of chlorite to yield chloride (Cl-) and molecular oxygen (O2). We explored the potential for aerobic CH4 oxidizing bacteria to couple with oxygen derived from chlorite dismutation during dissimilatory perchlorate reduction. Methane (0.2 kPa) was completely removed within several days from the N2-flushed headspace above cell suspensions of methanotrophs (Methylobacter albus strain BG8) and perchlorate reducing bacteria (Dechloromonas agitata strain CKB) in the presence of 5 mM ClO2-. Similar rates of CH4 consumption were observed for these mixed cultures whether they were co-mingled or segregated under a common headspace, indicating that direct contact of cells was not required for methane consumption to occur. We also observed complete removal of 0.2 kPa CH4 in bottles containing dried soil (enriched in methanotrophs by CH4 additions over several weeks) and D. agitata CKB and in the presence of 10 mM ClO2-. This soil (seasonally exposed sediment) collected from the shoreline of a freshwater lake (Searsville Lake, CA) demonstrated endogenous CH4 uptake as well as perchlorate, chlorate and chlorite reduction/dismutation. However, these experiments required physical separation of soil from the aqueous bacterial culture to allow for the partitioning of O2 liberated from chlorite dismutation into the shared headspace. Although dissimilatory reduction of ClO4- and ClO3- could be inferred from the

  16. A bifunctional nonprecious metal catalyst for oxygen reduction and water oxidation.

    PubMed

    Gorlin, Yelena; Jaramillo, Thomas F

    2010-10-01

    There is a growing interest in oxygen electrochemistry as conversions between O(2) and H(2)O play an important role in a variety of renewable energy technologies. The goal of this work is to develop active bifunctional catalyst materials for water oxidation and oxygen reduction. Drawing inspiration from a cubane-like CaMn(4)O(x), the biological catalyst found in the oxygen evolving center (OEC) in photosystem II, nanostructured manganese oxide surfaces were investigated for these reactions. Thin films of nanostructured manganese oxide were found to be active for both oxygen reduction and water oxidation, with similar overall oxygen electrode activity to the best known precious metal nanoparticle catalysts: platinum, ruthenium, and iridium. Physical and chemical characterization of the nanostructured Mn oxide bifunctional catalyst reveals an oxidation state of Mn(III), akin to one of the most commonly observed Mn oxidation states found in the OEC. PMID:20839797

  17. Bacterial manganese reduction and growth with manganese oxide as the sole electron acceptor

    NASA Technical Reports Server (NTRS)

    Myers, Charles R.; Nealson, Kenneth H.

    1988-01-01

    Microbes that couple growth to the reduction of manganese could play an important role in the biogeochemistry of certain anaerobic environments. Such a bacterium, Alteromonas putrefaciens MR-1, couples its growth to the reduction of manganese oxides only under anaerobic conditions. The characteristics of this reduction are consistent with a biological, and not an indirect chemical, reduction of manganese, which suggest that this bacterium uses manganic oxide as a terminal electron acceptor. It can also utilize a large number of other compounds as terminal electron acceptors; this versatility could provide a distinct advantage in environments where electron-acceptor concentrations may vary.

  18. Gate oxide damage reduction using a protective dielectric layer

    NASA Astrophysics Data System (ADS)

    Gabriel, Calvin T.; Weling, Milind G.

    1994-08-01

    Gate oxide damage from charge entering through the top surface of the gate electrode during plasma ashing, ion implantation, and LDD spacer oxide etching was measured using antenna structures. Significant charge damage to the 9.0 nm-thick gate oxide was detected for each of these processes. The damage was reduced by using a protective dielectric layer, in this case a thermally deposited TEOS oxide, over the polycide gate electrode before gate definition. The dielectric appears to block charge penetration into the antenna. Damage can be reduced further by increasing the thickness of the dielectric layer; for a sufficiently thick layer (about 150 nm), charge entering through the top surface of the antenna was effectively eliminated.

  19. 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...

  20. Biomineralization associated with microbial reduction of Fe3+ and oxidation of Fe2+ in solid minerals

    USGS Publications Warehouse

    Zhang, G.; Dong, H.; Jiang, H.; Kukkadapu, R.K.; Kim, J.; Eberl, D.; Xu, Z.

    2009-01-01

    Iron-reducing and oxidizing microorganisms gain energy through reduction or oxidation of iron, and by doing so play an important role in the geochemical cycling of iron. This study was undertaken to investigate mineral transformations associated with microbial reduction of Fe3+ and oxidation of Fe2+ in solid minerals. A fluid sample from the 2450 m depth of the Chinese Continental Scientific Drilling project was collected, and Fe3+-reducing and Fe2+-oxidizing microorganisms were enriched. The enrichment cultures displayed reduction of Fe3+ in nontronite and ferric citrate, and oxidation of Fe2+ in vivianite, siderite, and monosulfide (FeS). Additional experiments verified that the iron reduction and oxidation was biological. Oxidation of FeS resulted in the formation of goethite, lepidocrocite, and ferrihydrite as products. Although our molecular microbiological analyses detected Thermoan-aerobacter ethanolicus as a predominant organism in the enrichment culture, Fe3+ reduction and Fe2+ oxidation may be accomplished by a consortia of organisms. Our results have important environmental and ecological implications for iron redox cycling in solid minerals in natural environments, where iron mineral transformations may be related to the mobility and solubility of inorganic and organic contaminants.

  1. Effect of magnetic field on reduction of nickel oxide

    NASA Technical Reports Server (NTRS)

    Rowe, M. W.; Fanick, R.; Jewett, J.; Rowe, J. D.

    1976-01-01

    Results of observations recorded during constant temperature reduction of NiO, a paramagnetic substance, to Ni, a ferromagnetic element, are presented. The application of a large magnetic field (4,200 oersted) does not result in an acceleration of the reduction rate. To explain earlier observations that 500- and 1,400-oersted magnetic fields increase the reduction rate of iron ore which contains hematite (Fe2O3), Peters (1973) had suggested that thermodynamics theory could predict the acceleration in reaction rate when product and reactant species differ widely in their magnetic properties.

  2. Electrochemical Potential Gradient as a Quantitative in Vitro Test Platform for Cellular Oxidative Stress

    PubMed Central

    Bryant, Carson; Atha, Donald; Reipa, Vytas

    2016-01-01

    Oxidative stress in a biological system is often defined as a redox imbalance within cells or groups of cells within an organism. Reductive-oxidative (redox) imbalances in cellular systems have been implicated in several diseases, such as cancer. To better understand the redox environment within cellular systems, it is important to be able to characterize the relationship between the intensity of the oxidative environment, characterized by redox potential, and the biomolecular consequences of oxidative damage. In this study, we show that an in situ electrochemical potential gradient can serve as a tool to simulate exogenous oxidative stress in surface-attached mammalian cells. A culture plate design, which permits direct imaging and analysis of the cell viability, following exposure to a range of solution redox potentials, was developed. The in vitro oxidative stress test vessel consists of a cell growth flask fitted with two platinum electrodes that support a direct current along the flask bottom. The applied potential span and gradient slope can be controlled by adjusting the constant current magnitude across the vessel with spatially localized media potentials measured with a sliding reference electrode. For example, the viability of Chinese Hamster Ovary cells under a gradient of redox potentials indicated that cell death was initiated at approximately 0.4 V vs. standard hydrogen electrode (SHE) media potential and this potential could be modified with antioxidants. This experimental platform may facilitate studies of oxidative stress characteristics on different types of cells by enabling imaging live cell cultures that have been exposed to a gradient of exogenous redox potentials. PMID:27409641

  3. Electrochemical Potential Gradient as a Quantitative in Vitro Test Platform for Cellular Oxidative Stress.

    PubMed

    Bryant, Carson; Atha, Donald; Reipa, Vytas

    2016-01-01

    Oxidative stress in a biological system is often defined as a redox imbalance within cells or groups of cells within an organism. Reductive-oxidative (redox) imbalances in cellular systems have been implicated in several diseases, such as cancer. To better understand the redox environment within cellular systems, it is important to be able to characterize the relationship between the intensity of the oxidative environment, characterized by redox potential, and the biomolecular consequences of oxidative damage. In this study, we show that an in situ electrochemical potential gradient can serve as a tool to simulate exogenous oxidative stress in surface-attached mammalian cells. A culture plate design, which permits direct imaging and analysis of the cell viability, following exposure to a range of solution redox potentials, was developed. The in vitro oxidative stress test vessel consists of a cell growth flask fitted with two platinum electrodes that support a direct current along the flask bottom. The applied potential span and gradient slope can be controlled by adjusting the constant current magnitude across the vessel with spatially localized media potentials measured with a sliding reference electrode. For example, the viability of Chinese Hamster Ovary cells under a gradient of redox potentials indicated that cell death was initiated at approximately 0.4 V vs. standard hydrogen electrode (SHE) media potential and this potential could be modified with antioxidants. This experimental platform may facilitate studies of oxidative stress characteristics on different types of cells by enabling imaging live cell cultures that have been exposed to a gradient of exogenous redox potentials. PMID:27409641

  4. Electrochemical Potential Gradient as a Quantitative in Vitro Test Platform for Cellular Oxidative Stress.

    PubMed

    Bryant, Carson; Atha, Donald; Reipa, Vytas

    2016-01-01

    Oxidative stress in a biological system is often defined as a redox imbalance within cells or groups of cells within an organism. Reductive-oxidative (redox) imbalances in cellular systems have been implicated in several diseases, such as cancer. To better understand the redox environment within cellular systems, it is important to be able to characterize the relationship between the intensity of the oxidative environment, characterized by redox potential, and the biomolecular consequences of oxidative damage. In this study, we show that an in situ electrochemical potential gradient can serve as a tool to simulate exogenous oxidative stress in surface-attached mammalian cells. A culture plate design, which permits direct imaging and analysis of the cell viability, following exposure to a range of solution redox potentials, was developed. The in vitro oxidative stress test vessel consists of a cell growth flask fitted with two platinum electrodes that support a direct current along the flask bottom. The applied potential span and gradient slope can be controlled by adjusting the constant current magnitude across the vessel with spatially localized media potentials measured with a sliding reference electrode. For example, the viability of Chinese Hamster Ovary cells under a gradient of redox potentials indicated that cell death was initiated at approximately 0.4 V vs. standard hydrogen electrode (SHE) media potential and this potential could be modified with antioxidants. This experimental platform may facilitate studies of oxidative stress characteristics on different types of cells by enabling imaging live cell cultures that have been exposed to a gradient of exogenous redox potentials.

  5. Fluidized reduction of oxides on fine metal powders without sintering

    NASA Technical Reports Server (NTRS)

    Hayashi, T.

    1985-01-01

    In the process of reducing extremely fine metal particles (av. particle size or = 1000 angstroms) covered with an oxide layer, the metal particles are fluidized by a gas flow contg. H, heated, and reduced. The method uniformly and easily reduces surface oxide layers of the extremely fine metal particles without causing sintering. The metal particles are useful for magnetic recording materials, conductive paste, powder metallurgy materials, chem. reagents, and catalysts.

  6. Controlling the Formation of Nanocavities in Kirkendall Nanoobjects through Sequential Thermal Ex Situ Oxidation and In Situ Reduction Reactions.

    PubMed

    Mel, Abdel-Aziz El; Tessier, Pierre-Yves; Buffiere, Marie; Gautron, Eric; Ding, JunJun; Du, Ke; Choi, Chang-Hwan; Konstantinidis, Stephanos; Snyders, Rony; Bittencourt, Carla; Molina-Luna, Leopoldo

    2016-06-01

    Controlling the porosity, the shape, and the morphology of Kirkendall hollow nanostructures is the key factor to tune the properties of these tailor-made nanomaterials which allow in turn broadening their applications. It is shown that by applying a continuous oxidation to copper nanowires following a temperature ramp protocol, one can synthesize cuprous oxide nanotubes containing periodic copper nanoparticles. A further oxidation of such nanoobjects allows obtaining cupric oxide nanotubes with a bamboo-like structure. On the other hand, by applying a sequential oxidation and reduction reactions to copper nanowires, one can synthesize hollow nanoobjects with complex shapes and morphologies that cannot be obtained using the Kirkendall effect alone, such as necklace-like cuprous oxide nanotubes, periodic solid copper nanoparticles or hollow cuprous oxide nanospheres interconnected with single crystal cuprous oxide nanorods, and aligned and periodic hollow nanospheres embedded in a cuprous oxide nanotube. The strategy demonstrated in this study opens new avenues for the engineering of hollow nanostructures with potential applications in gas sensing, catalysis, and energy storage.

  7. 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...

  8. Developing Investigation Skills in an Introductory Multistep Synthesis Using Fluorene Oxidation and Reduction

    ERIC Educational Resources Information Center

    Stocksdale, Mark G; Pointer, Roy D; Benson, Barret W.; Fletcher, Steven E. S.; Henry, Ian; Ogren, Paul J.; Berg, Michael A. G.

    2004-01-01

    A two-step oxidation-reduction sequence that incorporates several important aspects of synthesis into introductory organic chemistry laboratories is described. This experiment is an excellent vehicle for introducing elements of discovery and intermediate yield improvement strategies.

  9. H2O2 Detection at Carbon Nanotubes and Nitrogen-Doped Carbon Nanotubes: Oxidation, Reduction, or Disproportionation?

    PubMed

    Goran, Jacob M; Phan, Ethan N H; Favela, Carlos A; Stevenson, Keith J

    2015-06-16

    The electrochemical behavior of hydrogen peroxide (H2O2) at carbon nanotubes (CNTs) and nitrogen-doped carbon nanotubes (N-CNTs) was investigated over a wide potential window. At CNTs, H2O2 will be oxidized or reduced at large overpotentials, with a large potential region between these two processes where electrochemical activity is negligible. At N-CNTs, the overpotential for both H2O2 oxidation and reduction is significantly reduced; however, the reduction current from H2O2, especially at low overpotentials, is attributed to increased oxygen reduction rather than the direct reduction of H2O2, due to a fast chemical disproportionation of H2O2 at the N-CNT surface. Additionally, N-CNTs do not display separation between observable oxidation and reduction currents from H2O2. Overall, the analytical sensitivity of N-CNTs to H2O2, either by oxidation or reduction, is considerably higher than CNTs, and obtained at significantly lower overpotentials. N-CNTs display an anodic sensitivity and limit of detection of 830 mA M(-1) cm(-2) and 0.5 μM at 0.05 V, and a cathodic sensitivity and limit of detection of 270 mA M(-1) cm(-2) and 10 μM at -0.25 V (V vs Hg/Hg2SO4). N-CNTs are also a superior platform for the creation of bioelectrodes from the spontaneous adsorption of enzyme, compared to CNTs. Glucose oxidase (GOx) was allowed to adsorb onto N-CNTs, producing a bioelectrode with a sensitivity and limit of detection to glucose of 80 mA M(-1) cm(-2) and 7 μM after only 30 s of adsorption time from a 81.3 μM GOx solution.

  10. Size dependent microbial oxidation and reduction of magnetite nano- and micro-particles.

    PubMed

    Byrne, James M; van der Laan, Gerrit; Figueroa, Adriana I; Qafoku, Odeta; Wang, Chongmin; Pearce, Carolyn I; Jackson, Michael; Feinberg, Joshua; Rosso, Kevin M; Kappler, Andreas

    2016-01-01

    The ability for magnetite to act as a recyclable electron donor and acceptor for Fe-metabolizing bacteria has recently been shown. However, it remains poorly understood whether microbe-mineral interfacial electron transfer processes are limited by the redox capacity of the magnetite surface or that of whole particles. Here we examine this issue for the phototrophic Fe(II)-oxidizing bacteria Rhodopseudomonas palustris TIE-1 and the Fe(III)-reducing bacteria Geobacter sulfurreducens, comparing magnetite nanoparticles (d ≈ 12 nm) against microparticles (d ≈ 100-200 nm). By integrating surface-sensitive and bulk-sensitive measurement techniques we observed a particle surface that was enriched in Fe(II) with respect to a more oxidized core. This enables microbial Fe(II) oxidation to occur relatively easily at the surface of the mineral suggesting that the electron transfer is dependent upon particle size. However, microbial Fe(III) reduction proceeds via conduction of electrons into the particle interior, i.e. it can be considered as more of a bulk electron transfer process that is independent of particle size. The finding has potential implications on the ability of magnetite to be used for long range electron transport in soils and sediments. PMID:27492680

  11. Size dependent microbial oxidation and reduction of magnetite nano- and micro-particles

    PubMed Central

    Byrne, James M.; van der Laan, Gerrit; Figueroa, Adriana I.; Qafoku, Odeta; Wang, Chongmin; Pearce, Carolyn I.; Jackson, Michael; Feinberg, Joshua; Rosso, Kevin M.; Kappler, Andreas

    2016-01-01

    The ability for magnetite to act as a recyclable electron donor and acceptor for Fe-metabolizing bacteria has recently been shown. However, it remains poorly understood whether microbe-mineral interfacial electron transfer processes are limited by the redox capacity of the magnetite surface or that of whole particles. Here we examine this issue for the phototrophic Fe(II)-oxidizing bacteria Rhodopseudomonas palustris TIE-1 and the Fe(III)-reducing bacteria Geobacter sulfurreducens, comparing magnetite nanoparticles (d ≈ 12 nm) against microparticles (d ≈ 100–200 nm). By integrating surface-sensitive and bulk-sensitive measurement techniques we observed a particle surface that was enriched in Fe(II) with respect to a more oxidized core. This enables microbial Fe(II) oxidation to occur relatively easily at the surface of the mineral suggesting that the electron transfer is dependent upon particle size. However, microbial Fe(III) reduction proceeds via conduction of electrons into the particle interior, i.e. it can be considered as more of a bulk electron transfer process that is independent of particle size. The finding has potential implications on the ability of magnetite to be used for long range electron transport in soils and sediments. PMID:27492680

  12. Size dependent microbial oxidation and reduction of magnetite nano- and micro-particles

    NASA Astrophysics Data System (ADS)

    Byrne, James M.; van der Laan, Gerrit; Figueroa, Adriana I.; Qafoku, Odeta; Wang, Chongmin; Pearce, Carolyn I.; Jackson, Michael; Feinberg, Joshua; Rosso, Kevin M.; Kappler, Andreas

    2016-08-01

    The ability for magnetite to act as a recyclable electron donor and acceptor for Fe-metabolizing bacteria has recently been shown. However, it remains poorly understood whether microbe-mineral interfacial electron transfer processes are limited by the redox capacity of the magnetite surface or that of whole particles. Here we examine this issue for the phototrophic Fe(II)-oxidizing bacteria Rhodopseudomonas palustris TIE-1 and the Fe(III)-reducing bacteria Geobacter sulfurreducens, comparing magnetite nanoparticles (d ≈ 12 nm) against microparticles (d ≈ 100–200 nm). By integrating surface-sensitive and bulk-sensitive measurement techniques we observed a particle surface that was enriched in Fe(II) with respect to a more oxidized core. This enables microbial Fe(II) oxidation to occur relatively easily at the surface of the mineral suggesting that the electron transfer is dependent upon particle size. However, microbial Fe(III) reduction proceeds via conduction of electrons into the particle interior, i.e. it can be considered as more of a bulk electron transfer process that is independent of particle size. The finding has potential implications on the ability of magnetite to be used for long range electron transport in soils and sediments.

  13. The chemistry of O in reduction processes of the GaAs native oxides

    NASA Astrophysics Data System (ADS)

    Cuberes, M. T.; Sacedon, J. L.

    1992-05-01

    We present an X-ray photoelectron spectroscopy (XPS) study of the interfacial chemical reactions during the total reduction of a 5 Å thick GaAs native oxide layer accomplished in two separate stages. First, the As2O3 has been selectively reduced by annealing the oxidized surface at increasing temperatures. In the second stage, the reduction of the Ga oxides has been completed at room temperature by Si deposition. The total amount of O at the GaAs interface remains constant during both processes. During the As2O3 thermal reduction, the analysis of the Ga2p{3}/{2} and Ga LMM spectra shows that, depending on the annealing temperature, GaOx (x < {3}/{2}) or Ga2O3 growth occurs. The Si promoted of the Ga oxides results in the formation of Si oxides of different stoichiometry at the GaAs surface.

  14. A facile approach to prepare graphene via solvothermal reduction of graphite oxide

    SciTech Connect

    Yuan, Bihe; Bao, Chenlu; Qian, Xiaodong; Wen, Panyue; Xing, Weiyi; Song, Lei; Hu, Yuan

    2014-07-01

    Highlights: • Graphene was prepared via a novel and facile solvothermal reduction method for graphite oxide. • Most of the oxygen functional groups of graphite oxide were removed. • The reduced graphene oxide obtained was featured with bilayer nanosheets. - Abstract: In this work, a facile reduction strategy is reported for the fabrication of graphene. Graphite oxide (GO) is reduced via a novel solvothermal reaction in a mixed solution of acetone and sodium hypochlorite (NaClO). The structure, surface chemistry, morphology and thermal stability of the as-prepared reduced graphene oxide (RGO) are characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, transmission electron microscopy (TEM), atomic force microscopy (AFM), thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). The results indicate that most of the oxygenated groups in GO are effectively removed in this solvothermal reaction. The novel reduction method provides a simple, cost-effective and efficient strategy for the fabrication of graphene.

  15. Interfacial Reduction-Oxidation Mechanisms Governing Fate and Transport of Contaminants in the Vadose Zone

    SciTech Connect

    Principal Investigator: Baolin Deng, University of Missouri, Columbia, MO; Co-Principal Investigator: Silvia Sabine Jurisson, University of Missouri, Columbia, MO; Co-Principal Investigator: Edward C. Thornton, Pacific Northwest National Laboratory Richland, WA; Co-Principal Investigator: Jeff Terry, Illinois Institute of Technology, Chicago, IL

    2008-05-12

    objective of this project was to understand the complex interactions among the contaminants (i.e., Cr, Tc, and U), H{sub 2}S, and various soil constituents. The reaction with iron sulfide is also the focus of the research, which could be formed from iron oxide reduction by hydrogen sulfide. Factors controlling the reductive immobilization of these contaminants were identified and quantified. The results and fundamental knowledge obtained from this project shall help better evaluate the potential of in situ gaseous treatment to immobilize toxic and radioactive metals examined.

  16. The potential for metal release by reductive dissolution of weathered mine tailings

    NASA Astrophysics Data System (ADS)

    Ribeta, I.; Ptacek, C. J.; Blowes, D. W.; Jambor, J. L.

    1995-01-01

    Remediation programs proposed for decommissioned sulphide tailings may include the addition of a cover layer rich in organic-carbon material such as sewage sludge or composted municipal waste. These covers are designed to consume oxygen and prevent the oxidation of underlying sulphide minerals. The aerobic and anaerobic degradation of such organic-carbon-rich waste can release soluble organic compounds to infiltrating precipitation water. In laboratory experiments, and in natural settings, biotic and abiotic interactions between similar dissolved organic compounds and ferric-bearing secondary minerals have been observed to result in the reductive dissolution of ferric (oxy)hydroxides and the release of ferrous iron to pore waters. In weathered tailings, oxidation of sulphide minerals typically results in the formation of abundant ferric-bearing secondary precipitates near the tailings surface. These secondary precipitates may contain high concentrations of potentially toxic metals, either coprecipitated with or adsorbed onto ferric (oxy)hydroxides. Reductive dissolution reactions, resulting from the addition of the organic-carbon covers, may remobilize metals previously attenuated near the tailings surface. To assess the potential for metal release to tailings pore water by reductive dissolution reactions, a laboratory study was conducted on weathered tailings collected from the Nickel Rim mine tailings impoundment near Sudbury, Ontario, Canada. This site was selected for study because it is representative of many tailings sites. Mineralogical study indicates that sulphide minerals originally present in the vadose zone at the time of tailings deposition have been replaced by a series of secondary precipitates. The most abundant secondary minerals are goethite, gypsum and jarosite. Scanning electron microscopy, coupled with elemental analyses by X-ray energy dispersion analysis, and electron microprobe analysis indicate that trace metals including Ni, Cr and Cu are

  17. Conceptual difficulties experienced by senior high school students of electrochemistry: Electric circuits and oxidation-reduction equations

    NASA Astrophysics Data System (ADS)

    Garnett, Pamela J.; Treagust, David F.

    The purpose of this research was to investigate students' understanding of electrochemistry following a course of instruction. A list of conceptual and propositional knowledge statements was formulated to identify the knowledge base necessary for students to understand electric circuits and oxidation-reduction equations. The conceptual and propositional knowledge statements provided the framework for the development of a semistructured interview protocol which was administered to 32 students in their final year of high school chemistry. The interview questions about electric circuits revealed that several students in the sample were confused about the nature of electric current both in metallic conductors and in electrolytes. Students studying both physics and chemistry were more confused about current flow in metallic conductors than students who were only studying chemistry. In the section of the interview which focused on oxidation and reduction, many students experienced problems in identifying oxidation-reduction equations. Several misconceptions relating to the inappropriate use of definitions of oxidation and reduction were identified. The data illustrate how students attempted to make sense of the concepts of electrochemistry with the knowledge they had already developed or constructed. The implications of the research are that teachers, curriculum developers, and textbook writers, if they are to minimize potential misconceptions, need to be cognizant of the relationship between physics and chemistry teaching, of the need to test for erroneous preconceptions about current before teaching about electrochemical (galvanic) and electrolytic cells, and of the difficulties experienced by students when using more than one model to explain scientific phenomena.

  18. Reduction study of oxidized two-dimensional graphene-based materials by chemical and thermal reduction methods

    NASA Astrophysics Data System (ADS)

    Douglas, Amber M.

    Graphene is a two-dimensional (2D) sp2-hybridized carbon-based material possessing properties which include high electrical conductivity, ballistic thermal conductivity, tensile strength exceeding that of steel, high flexural strength, optical transparency, and the ability to adsorb and desorb atoms and molecules. Due to the characteristics of said material, graphene is a candidate for applications in integrated circuits, electrochromic devices, transparent conducting electrodes, desalination, solar cells, thermal management materials, polymer nanocomposites, and biosensors. Despite the above mentioned properties and possible applications, very few technologies have been commercialized utilizing graphene due to the high cost associated with the production of graphene. Therefore, a great deal of effort and research has been performed to produce a material that provides similar properties, reduced graphene oxide due (RGO) to the ease of commercial scaling of the production processes. This material is typically prepared through the oxidation of graphite in an aqueous media to graphene oxide (GO) followed by reduction to yield RGO. Although this material has been extensively studied, there is a lack of consistency in the scientific community regarding the analysis of the resulting RGO material. In this dissertation, a study of the reduction methods for GO and an alternate 2D carbon-based material, humic acid (HA), followed by analysis of the materials using Raman spectroscopy and Energy Dispersive X-ray Spectroscopy (EDS). Means of reduction will include chemical and thermal methods. Characterization of the material has been carried out on both before and after reduction.

  19. Ceruloplasmin copper induces oxidant damage by a redox process utilizing cell-derived superoxide as reductant

    NASA Technical Reports Server (NTRS)

    Mukhopadhyay, C. K.; Fox, P. L.

    1998-01-01

    Oxidative damage by transition metals bound to proteins may be an important pathogenic mechanism. Ceruloplasmin (Cp) is a Cu-containing plasma protein thought to be involved in oxidative modification of lipoproteins. We have previously shown that Cp increased cell-mediated low-density lipoprotein (LDL) oxidation by a process requiring cell-derived superoxide, but the underlying chemical mechanism(s) is (are) unknown. We now show that superoxide reduction of Cp Cu is a critical reaction in cellular LDL oxidation. By bathocuproine disulfonate (BCS) binding and by superoxide utilization, we showed that exogenous superoxide reduces a single Cp Cu atom, the same Cu required for LDL oxidation. The Cu atom remained bound to Cp during the redox cycle. Three avenues of evidence showed that vascular cells reduce Cp Cu by a superoxide-dependent process. The 2-fold higher rate of Cp Cu reduction by smooth muscle cells (SMC) compared to endothelial cells (EC) was consistent with their relative rates of superoxide release. Furthermore, Cp Cu reduction by cells was blocked by Cu,Zn superoxide dismutase (SOD1). Finally, the level of superoxide produced by EC and SMC was sufficient to cause the amount of Cu reduction observed. An important role of Cp Cu reduction in LDL oxidation was suggested by results showing that SOD1 inhibited Cp Cu reduction and LDL oxidation by SMC with equal potency, while tumor necrosis factor-alpha stimulated both processes. In summary, these results show that superoxide is a critical cellular reductant of divalent transition metals involved in oxidation, and that protein-bound Cu is a substrate for this reaction. The role of these mechanisms in oxidative processes in vivo has yet to be defined.

  20. Oxidative and reductive transformations of arsenic by photosynthetic microbial communities from hot springs on Pahoa Island, Mono Lake, California

    NASA Astrophysics Data System (ADS)

    Kulp, T. R.; Hoeft, S. E.; Miller, L. G.; Culbertson, C. W.; Baesman, S. M.; Oremland, R. S.

    2007-12-01

    The shoreline of Pahoa Island in hypersaline Mono Lake in California is characterized by numerous volcanogenic hot springs that display a wide range of temperatures between 30 and 85 degrees C. A variety of distinctive photosynthetic microbial mats are evident in these hot springs and their spatial distribution appears to be a function of water temperature. The suboxic hydrothermal waters of these seeps typically contain ~100 uM dissolved arsenic, which is rapidly oxidized from arsenite [As(III)] to arsenate [As(V)] as the springs flow over these microbial communities. We conducted experiments with anaerobic cultures of red or green photosynthetic bacteria from these hot springs, which we amended with radio-labeled 73As(III) or 73As(V) and incubated at 42 degrees C to measure arsenite oxidation and arsenate reduction activity. In order to assess the potential for As(III) to serve as an electron donor during anoxygenic photosynthesis, As(III) oxidation incubations were conducted under both light and dark conditions. Both light and dark incubations of these thermophiles rapidly oxidized amendments of 100 uM As(III) within 7 hours of incubation, however no significant difference was observed in the rate of As(III) oxidation for light compared to dark samples. Arsenate reduction was also observed in both light and dark anaerobic cultures after 48 hours incubation. In all cases, As oxidation or reduction activity was eliminated by autoclaving. These results suggest that biological As(III) oxidation by these bacteria is primarily a mechanism of detoxification or chemoautotrophy, however the potential significance of As(III) as a photosynthetic electron acceptor will be discussed.

  1. Simultaneous nitrate reduction and acetaminophen oxidation using the continuous-flow chemical-less VUV process as an integrated advanced oxidation and reduction process.

    PubMed

    Moussavi, Gholamreza; Shekoohiyan, Sakine

    2016-11-15

    This work was aimed at investigating the performance of the continuous-flow VUV photoreactor as a novel chemical-less advanced process for simultaneously oxidizing acetaminophen (ACT) as a model of pharmaceuticals and reducing nitrate in a single reactor. Solution pH was an important parameter affecting the performance of VUV; the highest ACT oxidation and nitrate reduction attained at solution pH between 6 and 8. The ACT was oxidized mainly by HO while the aqueous electrons were the main working agents in the reduction of nitrate. The performance of VUV photoreactor improved with the increase of hydraulic retention time (HRT); the complete degradation of ACT and ∼99% reduction of nitrate with 100% N2 selectivity achieved at HRT of 80min. The VUV effluent concentrations of nitrite and ammonium at HRT of 80min were below the drinking water standards. The real water sample contaminated with the ACT and nitrate was efficiently treated in the VUV photoreactor. Therefore, the VUV photoreactor is a chemical-less advanced process in which both advanced oxidation and advanced reduction reactions are accomplished. This unique feature possesses VUV photoreactor as a promising method of treating water contaminated with both pharmaceutical and nitrate. PMID:27434736

  2. Simultaneous nitrate reduction and acetaminophen oxidation using the continuous-flow chemical-less VUV process as an integrated advanced oxidation and reduction process.

    PubMed

    Moussavi, Gholamreza; Shekoohiyan, Sakine

    2016-11-15

    This work was aimed at investigating the performance of the continuous-flow VUV photoreactor as a novel chemical-less advanced process for simultaneously oxidizing acetaminophen (ACT) as a model of pharmaceuticals and reducing nitrate in a single reactor. Solution pH was an important parameter affecting the performance of VUV; the highest ACT oxidation and nitrate reduction attained at solution pH between 6 and 8. The ACT was oxidized mainly by HO while the aqueous electrons were the main working agents in the reduction of nitrate. The performance of VUV photoreactor improved with the increase of hydraulic retention time (HRT); the complete degradation of ACT and ∼99% reduction of nitrate with 100% N2 selectivity achieved at HRT of 80min. The VUV effluent concentrations of nitrite and ammonium at HRT of 80min were below the drinking water standards. The real water sample contaminated with the ACT and nitrate was efficiently treated in the VUV photoreactor. Therefore, the VUV photoreactor is a chemical-less advanced process in which both advanced oxidation and advanced reduction reactions are accomplished. This unique feature possesses VUV photoreactor as a promising method of treating water contaminated with both pharmaceutical and nitrate.

  3. Determination of carbon by the oxidation reduction reaction with chromium

    NASA Technical Reports Server (NTRS)

    Mashkovich, L.; Kuteynikov, A. F.

    1978-01-01

    Free carbon was determined in silicon and boron carbides in ash, oxides, and other materials by oxidation to carbon dioxide with a mixture of K2Cr2O7 + H2SO4. The determination was made from the amount of CR(6) consumed, by adding excess Mohr's salt and titrating with a standard solution of KMnO4. The amount of Cr(6) self reduced was determined in a blank test. Optimum oxidation and conditions were achieved when the volumes of 5% k2Cr2Oz and H2SO4 were equal. The mixture was boiled for 1-2 hours using a reflex condenser. The volume should not be reduced, in order to avoid an increase in the sulfuric acid concentration. The relative error was 4-7% for 0.005-0.04 g C and less than or equal to 3.5% for 0.1 g C.

  4. Coupled reductive and oxidative sulfur cycling in the phototrophic plate of a meromictic lake.

    PubMed

    Hamilton, T L; Bovee, R J; Thiel, V; Sattin, S R; Mohr, W; Schaperdoth, I; Vogl, K; Gilhooly, W P; Lyons, T W; Tomsho, L P; Schuster, S C; Overmann, J; Bryant, D A; Pearson, A; Macalady, J L

    2014-09-01

    Mahoney Lake represents an extreme meromictic model system and is a valuable site for examining the organisms and processes that sustain photic zone euxinia (PZE). A single population of purple sulfur bacteria (PSB) living in a dense phototrophic plate in the chemocline is responsible for most of the primary production in Mahoney Lake. Here, we present metagenomic data from this phototrophic plate--including the genome of the major PSB, as obtained from both a highly enriched culture and from the metagenomic data--as well as evidence for multiple other taxa that contribute to the oxidative sulfur cycle and to sulfate reduction. The planktonic PSB is a member of the Chromatiaceae, here renamed Thiohalocapsa sp. strain ML1. It produces the carotenoid okenone, yet its closest relatives are benthic PSB isolates, a finding that may complicate the use of okenone (okenane) as a biomarker for ancient PZE. Favorable thermodynamics for non-phototrophic sulfide oxidation and sulfate reduction reactions also occur in the plate, and a suite of organisms capable of oxidizing and reducing sulfur is apparent in the metagenome. Fluctuating supplies of both reduced carbon and reduced sulfur to the chemocline may partly account for the diversity of both autotrophic and heterotrophic species. Collectively, the data demonstrate the physiological potential for maintaining complex sulfur and carbon cycles in an anoxic water column, driven by the input of exogenous organic matter. This is consistent with suggestions that high levels of oxygenic primary production maintain episodes of PZE in Earth's history and that such communities should support a diversity of sulfur cycle reactions.

  5. Comparative survey of potential nitrate and sulfate reduction rates in aquatic sediments

    NASA Astrophysics Data System (ADS)

    Laverman, Anniet M.; Pallud, Céline; Abell, Jeffrey; Cappellen, Philippe Van

    2012-01-01

    Nitrate and sulfate are two major terminal electron acceptors of anaerobic respiration in nearshore sediments. Potential nitrate and sulfate reduction rates (NRR and SRR) were determined on surficial sediments sampled at 14 sites representing a wide range of shallow-water depositional environments. The rates were obtained by supplying undisturbed slices of sediments with nitrate, sulfate or both using a flow-through reactor technique. No external electron donor was added to the sediments. The results indicate that all studied sediments harbored viable and coexisting nitrate- and sulfate-reducing communities, which were able to instantaneously consume the electron acceptors supplied to the reactors. On average, NRR exceeded SRR by about one order of magnitude (309 ± 180 nmol NO3- cm-3 h-1versus 37 ± 29 nmol SO42- cm-3 h-1). The NRR:SRR molar ratio, however, varied significantly from site to site, with values ranging from 1.7 to 59. Nitrite production, indicative of incomplete nitrate reduction, was observed in all studied sediments and, on average, accounted for 45% of NRR (range 3-80%). Production of sulfate under nitrate-reducing conditions was observed in 10 out of 14 of the studied sediments, suggesting a common occurrence of sulfide oxidation coupled to nitrate reduction. Oxidation of sulfide accounted for 0 to 40% of NRR in the nitrate-only experiments. When both electron acceptors were supplied simultaneously, net sulfate consumption decreased on average by 45%. The effect of nitrate on SRR was highly variable, however, ranging from near complete inhibition to a 25% enhancement of SRR. Overall, the results of this study point to the need to critically reassess the model formulations used to represent anaerobic respiration processes and their interactions in early diagenetic models.

  6. Method for catalyzing oxidation/reduction reactions of simple molecules

    SciTech Connect

    Bicker, D.; Bonaventura, J.

    1988-06-14

    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.

  7. Oxidation versus reductive detoxification of SO sub 2 by chloroplasts

    SciTech Connect

    Ghisi, R.; Dittrich, A.P.M.; Heber, U. )

    1990-03-01

    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}.

  8. Nitrate reduction by denitrifying anaerobic methane oxidizing microorganisms can reach a practically useful rate.

    PubMed

    Cai, Chen; Hu, Shihu; Guo, Jianhua; Shi, Ying; Xie, Guo-Jun; Yuan, Zhiguo

    2015-12-15

    Methane in biogas has been proposed to be an electron donor to facilitate complete nitrogen removal using denitrifying anaerobic methane oxidizing (DAMO) microorganisms in an anaerobic ammonium oxidation (anammox) reactor, by reducing the nitrate produced. However, the slow growth and the low activity of DAMO microorganisms cast a serious doubt about the practical usefulness of such a process. In this study, a previously established lab-scale membrane biofilm reactor (MBfR), with biofilms consisting of a coculture of DAMO and anammox microorganisms, was operated to answer if the DAMO reactor can achieve a nitrate reduction rate that can potentially be applied for wastewater treatment. Through progressively increasing nitrate and ammonium loading rates to the reactor, a nitrate removal rate of 684 ± 10 mg-N L(-1) d(-1) was achieved after 453 days of operation. This rate is, to our knowledge, by far the highest reported for DAMO reactors, and far exceeds what is predicted to be required for nitrate removal in a sidestream (5.6-135 mg-N L(-1) d(-1)) or mainstream anammox reactor (3.2-124 mg-N L(-1) d(-1)). Mass balance analysis showed that the nitrite produced by nitrate reduction was jointly reduced by anammox bacteria at a rate of 354 ± 3 mg-N L(-1) d(-1), accompanied by an ammonium removal rate of 268 ± 2 mg-N L(-1) d(-1), and DAMO bacteria at a rate of 330 ± 9 mg-N L(-1) d(-1). This study shows that the nitrate reduction rate achieved by the DAMO process can be high enough for removing nitrate produced by anammox process, which would enable complete nitrogen removal from wastewater. PMID:26414889

  9. Variation of electronic transitions and reduction potentials of cerium(IV) complexes.

    PubMed

    Williams, Ursula J; Schneider, David; Dorfner, Walter L; Maichle-Mössmer, Cäcilia; Carroll, Patrick J; Anwander, Reiner; Schelter, Eric J

    2014-11-21

    The trivalent compound K[Ce[N(SiHMe2)2]4] was synthesized and oxidized, providing a convenient route to the reported cerium(IV) compound Ce[N(SiHMe2)2]4. Protonolysis reactions of Ce[N(SiHMe2)2]4 with tert-butanol, substituted benzyl alcohols, and 2,6-diphenylphenol yielded the neutral tetravalent compounds Ce(O(t)Bu)4(py)2, Ce2(OCH2C6R5)8(thf)2 (R = Me, F), and Ce(Odpp)4 (dpp = 2,6-(C6H5)2-C6H3). Spectroscopic and electrochemical characterization of the monometallic cerium(IV) silylamide, alkoxide, and aryloxide compounds revealed variable ligand-to-metal charge transfer transitions and metal-based reduction potentials. Computational bonding analyses were performed to complement the physical characterization of the complexes.

  10. Superior Catalytic Activity of Electrochemically Reduced Graphene Oxide Supported Iron Phthalocyanines toward Oxygen Reduction Reaction.

    PubMed

    Liu, Dong; Long, Yi-Tao

    2015-11-01

    Structure and surface properties of supporting materials are of great importance for the catalytic performance of the catalysts. Herein, we prepared the iron phthalocyanine (FePc) functionalized electrochemically reduced graphene oxide (ERGO) by the electrochemical reduction of FePc/GO. The resultant FePc/ERGO exhibits higher catalytic activity toward ORR than that of FePc/graphene. More importantly, the onset potential for ORR at FePc/ERGO positively shifts by 45 mV compared with commercial Pt/C in alkaline media. Besides, FePc/ERGO displays enhanced durability and selectivity toward ORR. The superior catalytic performance of FePc/ERGO for ORR are ascribed to the self-supported structure of ERGO, uniformly morphology and size of FePc nanoparticles.

  11. Thermodynamic Versus Surface Area Control of Microbial Fe(III) Oxide Reduction Kinetics

    NASA Astrophysics Data System (ADS)

    Roden, E. E.

    2003-12-01

    Recent experimental studies of synthetic and natural Fe(III) oxide reduction permit development of conceptual and quantitative models of enzymatic Fe(III) oxide reduction at circumneutral pH that can be compared to and contrasted with established models of abiotic mineral dissolution. The findings collectively support a model for controls on enzymatic reduction that differs fundamentally from those applied to abiotic reductive dissolution as a result of two basic phenomena: (1) the relatively minor influence of oxide mineralogical and thermodynamic properties on surface area-normalized rates of enzymatic reduction compared to abiotic reductive dissolution; and (2) the major limitation which sorption and/or surface precipitation of biogenic Fe(II) on residual oxide and Fe(III)-reducing bacterial cell surfaces poses to enzymatic electron transfer in the presence of excess electron donor. Parallel studies with two major Fe(III)-reducing bacteria genera (Shewanella and Geobacter) lead to common conclusions regarding the importance of these phenomena in regulating the rate and long-term extent of Fe(III) oxide reduction. Although the extent to which these phenomena can be traced to underlying kinetic vs. thermodynamic effects cannot be resolved with current information, models in which rates of enzymatic reduction are limited kinetically by the abundance of "available" oxide surface sites (as controlled by oxide surface area and the abundance of surface-bound Fe(II)) provide an adequate macroscopic description of controls on the initial rate and long-term extent of oxide reduction. In some instances, thermodynamic limitation posed by the accumulation of aqueous reaction end-products (i.e. Fe(II) and alkalinity) must also be invoked to explain observed long-term patterns of reduction. In addition, the abundance of Fe(III)-reducing microorganisms plays an important role in governing rates of reduction and needs to be considered in models of Fe(III) reduction in nonsteady

  12. Body temperature reduction of graphene oxide through chitosan functionalisation and its application in drug delivery.

    PubMed

    Justin, Richard; Chen, Biqiong

    2014-01-01

    The reduction of graphene oxide at body temperature by using a biopolymer, chitosan, was proven to be successful. This biocompatible reduction approach will provide a versatile platform for applying graphene in biomedical fields including tissue engineering and therapeutic delivery. The use of this approach for therapeutic delivery is demonstrated. PMID:24268232

  13. Selective reduction of nitric oxides with ammonia using a cellular block catalyst

    SciTech Connect

    M.V. D'yakov; A.I. Kozlov; E.S. Lukin

    2004-03-15

    An aluminum-vanadium cellular block catalyst for selective reduction of nitric oxides with ammonia has been developed. With an average degree of conversion of oxides over 90%, the efficiency of the proposed catalyst is significantly higher than that of industrial catalysts currently used. Such catalyst can be recommended for use in selective plants for purification of waste gases from nitric oxides, which makes it possible to significantly decrease the cost of making a catalyst block.

  14. Conclusion: Developing a Process to Deal with Potential Faculty Reduction.

    ERIC Educational Resources Information Center

    Rose, Homer C., Jr.; Hample, Stephen R.

    1981-01-01

    Lessons and strategies for the institutional researcher dealing with faculty reduction are reviewed: developing a database; defining circumstances necessary for retrenchment; developing policies regarding participation and program discontinuance; examining alternatives; reviewing role and mission statements, legal standards and procedures;…

  15. Effects of Adiponectin Including Reduction of Androstenedione Secretion and Ovarian Oxidative Stress Parameters In Vivo

    PubMed Central

    Comim, Fabio V.; Gutierrez, Karina; Bridi, Alessandra; Bochi, Guilherme; Chemeris, Raisa; Rigo, Melânia L.; Dau, Andressa Minussi P.; Cezar, Alfredo S.; Moresco, Rafael Noal; Gonçalves, Paulo Bayard Dias

    2016-01-01

    Adiponectin is the most abundantly produced human adipokine with anti-inflammatory, anti-oxidative, and insulin-sensitizing properties. Evidence from in vitro studies has indicated that adiponectin has a potential role in reproduction because it reduces the production of androstenedione in bovine theca cells in vitro. However, this effect on androgen production has not yet been observed in vivo. The current study evaluated the effect of adiponectin on androstenedione secretion and oxidative stress parameters in a rodent model. Seven-week-old female Balb/c mice (n = 33), previously treated with equine gonadotropin chorionic, were assigned to one of four different treatments: Group 1, control (phosphate-buffered saline); Group 2, adiponectin 0.1 μg/mL; Group 3, adiponectin 1.0 μg/mL; Group 4, adiponectin 5.0 μg/mL. After 24 h, all animals were euthanized and androstenedione levels were measured in the serum while oxidative stress markers were quantified in whole ovary tissue. Female mice treated with adiponectin exhibited a significant reduction (about 60%) in serum androstenedione levels in comparison to controls. Androstenedione levels decreased from 0.78 ± 0.4 ng/mL (mean ± SD) in controls to 0.28 ± 0.06 ng/mL after adiponectin (5 μg/mL) treatment (P = 0.01). This change in androgen secretion after 24 hours of treatment was associated with a significant reduction in the expression of CYP11A1 and STAR (but not CYP17A1). In addition, ovarian AOPP product levels, a direct product of protein oxidation, decreased significantly in adiponectin-treated mice (5 μg/mL); AOPP (mean ± SD) decreased to 4.3 ± 2.1 μmol/L in comparison with that of the controls (11.5 ± 1.7 μmol/L; P = 0.0003). Our results demonstrated for the first time that acute treatment with adiponectin reduced the levels of a direct oxidative stress marker in the ovary as well as decreased androstenedione serum levels in vivo after 24 h. PMID:27158926

  16. Thermodynamic Analysis and Reduction of Bismuth Oxide by Ethanol

    NASA Astrophysics Data System (ADS)

    Korkmaz, Fatih; Cetinkaya, Senol; Eroglu, Serafettin

    2016-08-01

    In this study, ethanol (C2H5OH) was used as an alternative reducing agent for Bi2O3 because ethanol is renewable, increasingly available, and low in toxicity. Thermodynamic analysis was performed to predict experimental conditions for Bi formation in the Bi2O3-C2H5OH-Ar system at Ar/C2H5OH molar ratio of 10.5. Ar was used as a carrier gas for ethanol. Bi2O3 reduction kinetics was investigated at 600 K to 800 K (327 °C to 527 °C) at Ar flow rate 85 sccm. Ar flow rate was also varied at 600 K and 800 K (327 °C and 527 °C) in order to clarify the mechanism controlling the process. Mass measurements and XRD analyses were carried out to determine the extent of reduction. Fractional conversion increased with time and temperature. Full reduction time decreased from ~180 minutes at 600 K (327 °C) to ~30 minutes at 700 K and 800 K (427 °C and 527 °C). The reduction process was external mass transfer limited ( Q a = 7.2 kJ/mole) above 700 K (427 °C). It was controlled by intrinsic chemical kinetics ( Q a = 54.7 kJ/mole) below 700 K (427 °C). In the mass-transport-controlled regime, the extent of reduction increased with flow rate as predicted by a mass-transport theory. Possible reaction pathways were discussed using the thermodynamic and experimental results.

  17. Solid Oxide Fuel Cell Cathodes. Unraveling the Relationship Between Structure, Surface Chemistry and Oxygen Reduction

    SciTech Connect

    Gopalan, Srikanth

    2013-03-31

    In this work we have considered oxygen reduction reaction on LSM and LSCF cathode materials. In particular we have used various spectroscopic techniques to explore the surface composition, transition metal oxidation state, and the bonding environment of oxygen to understand the changes that occur to the surface during the oxygen reduction process. In a parallel study we have employed patterned cathodes of both LSM and LSCF cathodes to extract transport and kinetic parameters associated with the oxygen reduction process.

  18. The effect of ammonia upon the electrocatalysis of hydrogen oxidation and oxygen reduction on polycrystalline platinum

    NASA Astrophysics Data System (ADS)

    Verdaguer-Casadevall, Arnau; Hernandez-Fernandez, Patricia; Stephens, Ifan E. L.; Chorkendorff, Ib; Dahl, Søren

    2012-12-01

    The influence of ammonium ions on the catalysis of hydrogen oxidation and oxygen reduction is studied by means of rotating ring-disk electrode experiments on polycrystalline platinum in perchloric acid. While ammonium does not affect the hydrogen oxidation reaction, the oxygen reduction reaction is severely poisoned. Poisoning at the cathode explains the majority of the losses observed in polymer electrolyte membrane fuel cells contaminated with ammonia. Voltammetry in deaerated solution suggest that the poisoning can be attributed to either ammonium oxidation or increased binding to OH species.

  19. Anaerobic oxidation of methane associated with sulfate reduction in a natural freshwater gas source

    PubMed Central

    Timmers, Peer HA; Suarez-Zuluaga, Diego A; van Rossem, Minke; Diender, Martijn; Stams, Alfons JM; Plugge, Caroline M

    2016-01-01

    The occurrence of anaerobic oxidation of methane (AOM) and trace methane oxidation (TMO) was investigated in a freshwater natural gas source. Sediment samples were taken and analyzed for potential electron acceptors coupled to AOM. Long-term incubations with 13C-labeled CH4 (13CH4) and different electron acceptors showed that both AOM and TMO occurred. In most conditions, 13C-labeled CO2 (13CO2) simultaneously increased with methane formation, which is typical for TMO. In the presence of nitrate, neither methane formation nor methane oxidation occurred. Net AOM was measured only with sulfate as electron acceptor. Here, sulfide production occurred simultaneously with 13CO2 production and no methanogenesis occurred, excluding TMO as a possible source for 13CO2 production from 13CH4. Archaeal 16S rRNA gene analysis showed the highest presence of ANME-2a/b (ANaerobic MEthane oxidizing archaea) and AAA (AOM Associated Archaea) sequences in the incubations with methane and sulfate as compared with only methane addition. Higher abundance of ANME-2a/b in incubations with methane and sulfate as compared with only sulfate addition was shown by qPCR analysis. Bacterial 16S rRNA gene analysis showed the presence of sulfate-reducing bacteria belonging to SEEP-SRB1. This is the first report that explicitly shows that AOM is associated with sulfate reduction in an enrichment culture of ANME-2a/b and AAA methanotrophs and SEEP-SRB1 sulfate reducers from a low-saline environment. PMID:26636551

  20. Anaerobic oxidation of methane associated with sulfate reduction in a natural freshwater gas source.

    PubMed

    Timmers, Peer Ha; Suarez-Zuluaga, Diego A; van Rossem, Minke; Diender, Martijn; Stams, Alfons Jm; Plugge, Caroline M

    2016-06-01

    The occurrence of anaerobic oxidation of methane (AOM) and trace methane oxidation (TMO) was investigated in a freshwater natural gas source. Sediment samples were taken and analyzed for potential electron acceptors coupled to AOM. Long-term incubations with (13)C-labeled CH4 ((13)CH4) and different electron acceptors showed that both AOM and TMO occurred. In most conditions, (13)C-labeled CO2 ((13)CO2) simultaneously increased with methane formation, which is typical for TMO. In the presence of nitrate, neither methane formation nor methane oxidation occurred. Net AOM was measured only with sulfate as electron acceptor. Here, sulfide production occurred simultaneously with (13)CO2 production and no methanogenesis occurred, excluding TMO as a possible source for (13)CO2 production from (13)CH4. Archaeal 16S rRNA gene analysis showed the highest presence of ANME-2a/b (ANaerobic MEthane oxidizing archaea) and AAA (AOM Associated Archaea) sequences in the incubations with methane and sulfate as compared with only methane addition. Higher abundance of ANME-2a/b in incubations with methane and sulfate as compared with only sulfate addition was shown by qPCR analysis. Bacterial 16S rRNA gene analysis showed the presence of sulfate-reducing bacteria belonging to SEEP-SRB1. This is the first report that explicitly shows that AOM is associated with sulfate reduction in an enrichment culture of ANME-2a/b and AAA methanotrophs and SEEP-SRB1 sulfate reducers from a low-saline environment. PMID:26636551

  1. In Vitro Enzymatic Reduction Kinetics of Mineral Oxides by Membrane Fractions from Shewanella oneidensis MR-1

    SciTech Connect

    Ruebush,S.; Icopini, G.; Brantley, S.; Tien, M.

    2006-01-01

    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

  2. Kinetics of reduction of iron oxides using microwaves as power source

    SciTech Connect

    Gomez, I.; Aguilar, J.; Gonzalez, M.; Morales, J.

    1996-12-31

    This work deals with kinetic description of carbothermic reduction of iron oxides using microwaves as power source. Previous researches show that it is possible to conduct this kind of process successfully, but real kinetic comparisons between conventional and microwaves procedure have been presented partially. The aim of this work is to describe reduction kinetics, taking into account how the iron oxide is reduced by microwaves compared with conventional energy supply. In this study the authors used iron ore in pellet shape and dust. They found that both, pellet and dust reduction stops when it reaches approximately 40%, even at whole power.

  3. Elevated acetate concentrations in the rhizosphere of Spartina alterniflora and potential influences on sulfate reduction

    NASA Technical Reports Server (NTRS)

    Hines, Mark E.; Tugel, Joyce B.; Giblin, A. E.; Banta, G. T.; Hobbie, J. E.

    1992-01-01

    Acetate is important in anaerobic metabolism of non-vegetated sediments but its role in salt marsh soils was not investigated thoroughly. Acetate concentrations, oxidation (C-14) and SO4(2-) reduction (S-35) were measured in S. alterniflora soils in NH and MA. Pore water from cores contained greater than 0.1 mM acetate and in some instances greater than 1.0 mM. Non-destructive samples contained less than 0.01 mM. Acetate was associated with roots and concentrations were highest during vegetative growth and varied with changes in plant physiology. Acetate turnover was very low whether whole core or slurry incubations were used. Radiotracers injected directly into soils yielded rates of SO4(2-) reduction and acetate oxidation not significantly different from core incubation techniques. Regardless of incubation method, acetate oxidation did not account for a significant percentage of SO4(2-) reduction. These results differ markedly from data for non-vegetated coastal sediments where acetate levels are low, oxidation rate constants are high and acetate oxidation rates greatly exceed rates of SO4(2-) reduction. The discrepancy between rates of acetate oxidation and SO4(2-) reduction in marsh soils may be due either to the utilization of substrates other than acetate by SO4(2-) reducers or artifacts associated with measurements of organic utilization by rhizosphere bacteria.

  4. Use of Carnosine for Oxidative Stress Reduction in Different Pathologies

    PubMed Central

    Prokopieva, V. D.; Yarygina, E. G.; Bokhan, N. A.; Ivanova, S. A.

    2016-01-01

    The main properties and biological effects of the antioxidant carnosine, the natural dipeptide β-alanyl-L-histidine, are considered. Data on the effective use of carnosine in different pathologies are presented. Special attention is paid to issues of use of carnosine in neurologic and mental diseases, in alcoholism as well as in physiological states accompanied by activation of free-radical processes and formation of oxidative stress. PMID:26904160

  5. Potential of solar cooling systems for peak demand reduction

    SciTech Connect

    Pesaran, A A; Neymark, J

    1994-11-01

    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.

  6. Electric coupling between distant nitrate reduction and sulfide oxidation in marine sediment.

    PubMed

    Marzocchi, Ugo; Trojan, Daniela; Larsen, Steffen; Meyer, Rikke Louise; Revsbech, Niels Peter; Schramm, Andreas; Nielsen, Lars Peter; Risgaard-Petersen, Nils

    2014-08-01

    Filamentous bacteria of the Desulfobulbaceae family can conduct electrons over centimeter-long distances thereby coupling oxygen reduction at the surface of marine sediment to sulfide oxidation in deeper anoxic layers. The ability of these cable bacteria to use alternative electron acceptors is currently unknown. Here we show that these organisms can use also nitrate or nitrite as an electron acceptor thereby coupling the reduction of nitrate to distant oxidation of sulfide. Sulfidic marine sediment was incubated with overlying nitrate-amended anoxic seawater. Within 2 months, electric coupling of spatially segregated nitrate reduction and sulfide oxidation was evident from: (1) the formation of a 4-6-mm-deep zone separating sulfide oxidation from the associated nitrate reduction, and (2) the presence of pH signatures consistent with proton consumption by cathodic nitrate reduction, and proton production by anodic sulfide oxidation. Filamentous Desulfobulbaceae with the longitudinal structures characteristic of cable bacteria were detected in anoxic, nitrate-amended incubations but not in anoxic, nitrate-free controls. Nitrate reduction by cable bacteria using long-distance electron transport to get privileged access to distant electron donors is a hitherto unknown mechanism in nitrogen and sulfur transformations, and the quantitative importance for elements cycling remains to be addressed.

  7. New potential of the reductive alkylation of amines

    NASA Astrophysics Data System (ADS)

    Gusak, K. N.; Ignatovich, Zh V.; Koroleva, E. V.

    2015-03-01

    Available data on the reductive alkylation of amines with carbonyl compounds — a key method for the preparation of secondary and tertiary amines — are described systematically. The review provides information on the relevant reducing agents and catalysts and on the use of chiral catalysts in stereo- and enantiocontrolled reactions of amine synthesis. The effect of the reactant and catalyst structures on the reaction rates and chemo- and stereo(enantio)selectivity is considered. The bibliography includes 156 references.

  8. Novel method of screening the oxidation and reduction abilities of photocatalytic materials.

    PubMed

    Katayama, K; Takeda, Y; Shimaoka, K; Yoshida, K; Shimizu, R; Ishiwata, T; Nakamura, A; Kuwahara, S; Mase, A; Sugita, T; Mori, M

    2014-04-21

    Two analytical methods for the evaluation of photocatalytic oxidation and reduction abilities were developed using a photocatalytic microreactor; one is product analysis and the other is reaction rate analysis. Two simple organic conversion reactions were selected for the oxidation and reduction. Since the reactions were one-to-one conversions from the reactant species to the product species, the product analysis was simply performed using gas chromatography, and the reactions were monitored in situ in the photocatalytic microreactor using the UV absorption spectra. The partial oxidation and reduction abilities for each functional group can be judged from the yield and selectivity, and the corresponding reaction rate, while the total oxidation ability can be judged from the conversion. We demonstrated the application of these methods for several kinds of visible light photocatalysts.

  9. Corannulene reduction. Spectroscopic detection of all anionic oxidation states

    SciTech Connect

    Baumgarten, M.; Gherghel, L.; Wagner, M.; Weitz, A.; Rabinovitz, M. |; Cheng, P.C.; Scott, L.T.

    1995-06-14

    The reduction of corannulene (1) has been followed by parallel detection of optical absorption, electron paramagnetic resonance (EPR), and nuclear magnetic resonance (NMR) spectroscopies. The major findings are the existence of a diamagnetic dianion that can be observed in NMR and negligible counterion influences in the mono- and dianion. The diamagnetic state of the dianion is also supported by vanishing EPR intensity and semiempirical calculations and exhibits one indistinguishable proton NMR resonance at -5.6 ppm for potassium and lithium as counterions, respectively. The NMR signal is strongly temperature dependent and can only be obtained at low temperature (T < 230 K) where the line width decreases with temperature. Further reduction to the trianion and tetraanion succeeds with Li as the reducing metal, but not with K even at ambient temperatures. The EPR spectra of the trianion show a pronounced temperature dependence with at least two Li cations being strongly coupled. 18 refs., 3 figs., 3 tabs.

  10. Nitrogen oxide reduction strategies for compression ignition engines

    NASA Astrophysics Data System (ADS)

    Chapman, Elana M.

    2008-05-01

    The scope of this investigation is to explore strategies to reduce NOx emissions from compression ignition engines. Two methods are presented in this collection of studies: (1) NOx reduction accomplished through a change in fuel formulation, specifically through a change in the saturated fuel carbon chains of biodiesel; and (2) NOx reduction accomplished through a mixed mode combustion process utilizing a fumigated fuel and a pilot injection of diesel fuel. In the first study, a light duty diesel engine was used to investigate the change in saturation of a biodiesel fuel and its impact on NOx emissions. Previous studies have shown that a reduction in the iodine value of a biodiesel fuel produces a reduction in NOx emissions. The iodine value of the fuel is reduced through the saturation of the C18 molecules via hydrogenation of biodiesel fuel. Experiments were performed at several speeds and loads without exhaust gas recirculation (EGR), and a NOx reduction with the hydrogenated diesel fuel was observed. For all the modes studied, the NOx emission was higher for the biodiesel and lower for the hydrogenated biodiesel in comparison to the ultra low sulfur diesel (ULSD) fuel. Results from the calculation of the adiabatic flame temperature shows that the results could be explained by the difference in adiabatic flame temperature of the fuel, thus influencing the prompt NOx contribution in addition to the thermal contribution. Since the adiabatic flame temperatures are similar for the hydrogenated biodiesel and the ULSD, yet the NOx reduction with the hydrogenated biodiesel is much lower than the ULSD levels, another explanation for the reduction is suggested: the additional prompt NOx contribution from the change in fuel chemistry. The second study investigated the NOx reductions which could be achieved with a mixed mode combustion process utilizing a fumigated fuel and a pilot injection of diesel fuel. In this research, the fumigated fuel was dimethyl ether (DME) and

  11. Anoxic nitrate reduction coupled with iron oxidation and attenuation of dissolved arsenic and phosphate in a sand and gravel aquifer

    USGS Publications Warehouse

    Smith, Richard L.; Kent, Douglas B.; Repert, Deborah A.; Bohlke, J.K.

    2017-01-01

    Nitrate has become an increasingly abundant potential electron acceptor for Fe(II) oxidation in groundwater, but this redox couple has not been well characterized within aquifer settings. To investigate this reaction and some of its implications for redox-sensitive groundwater contaminants, we conducted an in situ field study in a wastewater-contaminated aquifer on Cape Cod. Long-term (15 year) geochemical monitoring within the contaminant plume indicated interacting zones with variable nitrate-, Fe(II)-, phosphate-, As(V)-, and As(III)-containing groundwater. Nitrate and phosphate were derived predominantly from wastewater disposal, whereas Fe(II), As(III), and As(V) were mobilized from the aquifer sediments. Multiple natural gradient, anoxic tracer tests were conducted in which nitrate and bromide were injected into nitrate-free, Fe(II)-containing groundwater. Prior to injection, aqueous Fe(II) concentrations were approximately 175 μM, but sorbed Fe(II) accounted for greater than 90% of the total reactive Fe(II) in the aquifer. Nitrate reduction was stimulated within 1 m of transport for 100 μM and 1000 μM nitrate additions, initially producing stoichiometric quantities of nitrous oxide (>300 μM N). In subsequent injections at the same site, nitrate was reduced even more rapidly and produced less nitrous oxide, especially over longer transport distances. Fe(II) and nitrate concentrations decreased together and were accompanied by Fe(III) oxyhydroxide precipitation and decreases in dissolved phosphate, As(III), and As(V) concentrations. Nitrate N and O isotope fractionation effects during nitrate reduction were approximately equal (ε15N/ε18O = 1.11) and were similar to those reported for laboratory studies of biological nitrate reduction, including denitrification, but unlike some reported effects on nitrate by denitrification in aquifers. All constituents affected by the in situ tracer experiments returned to pre-injection levels after several

  12. Crystallographic studies of V44 mutants of Clostridium pasteurianum rubredoxin: Effects of side-chain size on reduction potential

    SciTech Connect

    Park, Il Yeong; Eidsness, Marly K.; Lin, I-Jin; Gebel, Erika B.; Youn, Buhyun; Harley, Jill L.; Machonkin, Timothy E.; Frederick, Ronnie O.; Markley, John L.; Smith, Eugene T.; Ichiye, Toshiko; Kang, ChulHee

    2010-11-16

    Understanding the structural origins of differences in reduction potentials is crucial to understanding how various electron transfer proteins modulate their reduction potentials and how they evolve for diverse functional roles. Here, the high-resolution structures of several Clostridium pasteurianum rubredoxin (Cp Rd) variants with changes in the vicinity of the redox site are reported in order to increase this understanding. Our crystal structures of [V44L] (at 1.8 {angstrom} resolution), [V44A] (1.6 {angstrom}), [V44G] (2.0 {angstrom}) and [V44A, G45P] (1.5 {angstrom}) Rd (all in their oxidized states) show that there is a gradual decrease in the distance between Fe and the amide nitrogen of residue 44 upon reduction in the size of the side chain of residue 44; the decrease occurs from leucine to valine, alanine or glycine and is accompanied by a gradual increase in their reduction potentials. Mutation of Cp Rd at position 44 also changes the hydrogen-bond distance between the amide nitrogen of residue 44 and the sulfur of cysteine 42 in a size-dependent manner. Our results suggest that residue 44 is an important determinant of Rd reduction potential in a manner dictated by side-chain size. Along with the electric dipole moment of the 43-44 peptide bond and the 44-42 NHS type hydrogen bond, a modulation mechanism for solvent accessibility through residue 41 might regulate the redox reaction of the Rds. Proteins 2004.

  13. Hydrogen and formate oxidation coupled to dissimilatory reduction of iron or manganese by Alteromonas putrefaciens

    USGS Publications Warehouse

    Lovley, D.R.; Phillips, E.J.P.; Lonergan, D.J.

    1989-01-01

    The ability of Alteromonas putrefaciens to obtain energy for growth by coupling the oxidation of various electron donors to dissimilatory Fe(III) or Mn(IV) reduction was investigated. A. putrefaciens grew with hydrogen, formate, lactate, or pyruvate as the sole electron donor and Fe(III) as the sole electron acceptor. Lactate and pyruvate were oxidized to acetate, which was not metabolized further. With Fe(III) as the electron acceptor, A. putrefaciens had a high affinity for hydrogen and formate and metabolized hydrogen at partial pressures that were 25-fold lower than those of hydrogen that can be metabolized by pure cultures of sulfate reducers or methanogens. The electron donors for Fe(III) reduction also supported Mn(IV) reduction. The electron donors for Fe(III) and Mn(IV) reduction and the inability of A. putrefaciens to completely oxidize multicarbon substrates to carbon dioxide distinguish A. putrefaciens from GS-15, the only other organism that is known to obtain energy for growth by coupling the oxidation of organic compounds to the reduction of Fe(III) or Mn(IV). The ability of A. putrefaciens to reduce large quantities of Fe(III) and to grow in a defined medium distinguishes it from a Pseudomonas sp., which is the only other known hydrogen-oxidizing, Fe(III)-reducing microorganism. Furthermore, A. putrefaciens is the first organism that is known to grow with hydrogen as the electron donor and Mn(IV) as the electron acceptor and is the first organism that is known to couple the oxidation of formate to the reduction of Fe(III) or Mn(IV). Thus, A. putrefaciens provides a much needed microbial model for key reactions in the oxidation of sediment organic matter coupled to Fe(III) and Mn(IV) reduction.

  14. The Fundamental Role of Nano-Scale Oxide Films in the Oxidation of Hydrogen and the Reduction of Oxygen on Noble Metal Electrocatalysts

    SciTech Connect

    Digby Macdonald

    2005-04-15

    The derivation of successful fuel cell technologies requires the development of more effective, cheaper, and poison-resistant electrocatalysts for both the anode (H{sub 2} oxidation in the presence of small amounts of CO from the reforming of carbonaceous fuels) and the cathode (reduction of oxygen in the presence of carried-over fuel). The proposed work is tightly focused on one specific aspect of electrocatalysis; the fundamental role(s) played by nanoscale (1-2 nm thick) oxide (''passive'') films that form on the electrocatalyst surfaces above substrate-dependent, critical potentials, on charge transfer reactions, particularly at elevated temperatures (25 C < T < 200 C). Once the role(s) of these films is (are) adequately understood, we will then use this information to specify, at the molecular level, optimal properties of the passive layer for the efficient electrocatalysis of the oxygen reduction reaction.

  15. Methylmercury oxidative degradation potentials in contaminated and pristine sediments of the Carson River, Nevada

    USGS Publications Warehouse

    Oremland, R.S.; Miller, L.G.; Dowdle, P.; Connell, T.; Barkay, T.

    1995-01-01

    Sediments from mercury-contaminated and uncontaminated reaches of the Carson River, Nevada, were assayed for sulfate reduction, methanogenesis, denitrification, and monomethylmercury (MeHg) degradation. Demethylation of [14C]MeHg was detected at all sites as indicated by the formation of 14CO2 and 14CH4. Oxidative demethylation was indicated by the formation of 14CO2 and was present at significant levels in all samples. Oxidized/reduced demethylation product ratios (i.e., 14CO2/14CH4 ratios) generally ranged from 4.0 in surface layers to as low as 0.5 at depth. Production of 14CO2 was most pronounced at sediment surfaces which were zones of active denitrification and sulfate reduction but was also significant within zones of methanogenesis. In a core taken from an uncontaminated site having a high proportion of oxidized, coarse-grain sediments, sulfate reduction and methanogenic activity levels were very low and 14CO2 accounted for 98% of the product formed from [14C]MeHg. There was no apparent relationship between the degree of mercury contamination of the sediments and the occurrence of oxidative demethylation. However, sediments from Fort Churchill, the most contaminated site, were most active in terms of demethylation potentials. Inhibition of sulfate reduction with molybdate resulted in significantly depressed oxidized/reduced demethylation product ratios, but overall demethylation rates of inhibited and uninhibited samples were comparable. Addition of sulfate to sediment slurries stimulated production of 14CO2 from [14C]MeHg, while 2-bromoethanesulfonic acid blocked production of 14CH4. These results reveal the importance of sulfate-reducing and methanogenic bacteria in oxidative demethylation of MeHg in anoxic environments.

  16. In-situ X-Ray Absorption Spectroscopy (XAS) Investigation of a Bifunctional Manganese Oxide Catalyst with High Activity for Electrochemical Water Oxidation and Oxygen Reduction

    PubMed Central

    Benck, Jesse D.; Gul, Sheraz; Webb, Samuel M.; Yachandra, Vittal K.; Yano, Junko; Jaramillo, Thomas F.

    2013-01-01

    In-situ x-ray absorption spectroscopy (XAS) is a powerful technique that can be applied to electrochemical systems, with the ability to elucidate the chemical nature of electrocatalysts under reaction conditions. In this study, we perform in-situ XAS measurements on a bifunctional manganese oxide (MnOx) catalyst with high electrochemical activity for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). Using x-ray absorption near edge structure (XANES) and extended x-ray absorption fine structure (EXAFS), we find that exposure to an ORR-relevant potential of 0.7 V vs. RHE produces a disordered Mn3II,III,IIIO4 phase with negligible contributions from other phases. After the potential is increased to a highly anodic value of 1.8 V vs. RHE, relevant to the OER, we observe an oxidation of approximately 80% of the catalytic thin film to form a mixed MnIII,IV oxide, while the remaining 20% of the film consists of a less oxidized phase, likely corresponding to unchanged Mn3II,III,IIIO4. XAS and electrochemical characterization of two thin film catalysts with different MnOx thicknesses reveals no significant influence of thickness on the measured oxidation states, at either ORR or OER potentials, but demonstrates that the OER activity scales with film thickness. This result suggests that the films have porous structure, which does not restrict electrocatalysis to the top geometric layer of the film. As the portion of the catalyst film that is most likely to be oxidized at the high potentials necessary for the OER is that which is closest to the electrolyte interface, we hypothesize that the MnIII,IV oxide, rather than Mn3II,III,IIIO4, is the phase pertinent to the observed OER activity. PMID:23758050

  17. Transition Metal Oxide Alloys as Potential Solar Energy Conversion Materials

    SciTech Connect

    Toroker, Maytal; Carter, Emily A.

    2013-02-21

    First-row transition metal oxides (TMOs) are inexpensive potentia alternative materials for solar energy conversion devices. However, some TMOs, such as manganese(II) oxide, have band gaps that are too large for efficiently absorbing solar energy. Other TMOs, such as iron(II) oxide, have conduction and valence band edges with the same orbital character that may lead to unfavorably high electron–hole recombination rates. Another limitation of iron(II) oxide is that the calculated valence band edge is not positioned well for oxidizing water. We predict that key properties, including band gaps, band edge positions, and possibly electron–hole recombination rates, may be improved by alloying TMOs that have different band alignments. A new metric, the band gap center offset, is introduced for simple screening of potential parent materials. The concept is illustrated by calculating the electronic structure of binary oxide alloys that contain manganese, nickel, iron, zinc, and/or magnesium, within density functional theory (DFT)+U and hybrid DFT theories. We conclude that alloys of iron(II) oxide are worth evaluating further as solar energy conversion materials.

  18. Evidence of Nitrogen Loss from Anaerobic Ammonium Oxidation Coupled with Ferric Iron Reduction in an Intertidal Wetland.

    PubMed

    Li, Xiaofei; Hou, Lijun; Liu, Min; Zheng, Yanling; Yin, Guoyu; Lin, Xianbiao; Cheng, Lv; Li, Ye; Hu, Xiaoting

    2015-10-01

    Anaerobic ammonium oxidation coupled with nitrite reduction is an important microbial pathway of nitrogen removal in intertidal wetlands. However, little is known about the role of anaerobic ammonium oxidation coupled with ferric iron reduction (termed Feammox) in intertidal nitrogen cycling. In this study, sediment slurry incubation experiments were combined with an isotope-tracing technique to examine the dynamics of Feammox and its association with tidal fluctuations in the intertidal wetland of the Yangtze Estuary. Feammox was detected in the intertidal wetland sediments, with potential rates of 0.24-0.36 mg N kg(-1) d(-1). The Feammox rates in the sediments were generally higher during spring tides than during neap tides. The tidal fluctuations affected the growth of iron-reducing bacteria and reduction of ferric iron, which mediated Feammox activity and the associated nitrogen loss from intertidal wetlands to the atmosphere. An estimated loss of 11.5-18 t N km(-2) year(-1) was linked to Feammox, accounting for approximately 3.1-4.9% of the total external inorganic nitrogen transported into the Yangtze Estuary wetland each year. Overall, the co-occurrence of ferric iron reduction and ammonium oxidation suggests that Feammox can act as an ammonium removal mechanism in intertidal wetlands.

  19. Evidence of Nitrogen Loss from Anaerobic Ammonium Oxidation Coupled with Ferric Iron Reduction in an Intertidal Wetland.

    PubMed

    Li, Xiaofei; Hou, Lijun; Liu, Min; Zheng, Yanling; Yin, Guoyu; Lin, Xianbiao; Cheng, Lv; Li, Ye; Hu, Xiaoting

    2015-10-01

    Anaerobic ammonium oxidation coupled with nitrite reduction is an important microbial pathway of nitrogen removal in intertidal wetlands. However, little is known about the role of anaerobic ammonium oxidation coupled with ferric iron reduction (termed Feammox) in intertidal nitrogen cycling. In this study, sediment slurry incubation experiments were combined with an isotope-tracing technique to examine the dynamics of Feammox and its association with tidal fluctuations in the intertidal wetland of the Yangtze Estuary. Feammox was detected in the intertidal wetland sediments, with potential rates of 0.24-0.36 mg N kg(-1) d(-1). The Feammox rates in the sediments were generally higher during spring tides than during neap tides. The tidal fluctuations affected the growth of iron-reducing bacteria and reduction of ferric iron, which mediated Feammox activity and the associated nitrogen loss from intertidal wetlands to the atmosphere. An estimated loss of 11.5-18 t N km(-2) year(-1) was linked to Feammox, accounting for approximately 3.1-4.9% of the total external inorganic nitrogen transported into the Yangtze Estuary wetland each year. Overall, the co-occurrence of ferric iron reduction and ammonium oxidation suggests that Feammox can act as an ammonium removal mechanism in intertidal wetlands. PMID:26360245

  20. Microbial Fe(III) Oxide Reduction in Chocolate Pots Hot Springs, Yellowstone National Park

    NASA Astrophysics Data System (ADS)

    Fortney, N. W.; Roden, E. E.; Boyd, E. S.; Converse, B. J.

    2014-12-01

    Previous work on dissimilatory iron reduction (DIR) in Yellowstone National Park (YNP) has focused on high temperature, low pH environments where soluble Fe(III) is utilized as an electron acceptor for respiration. Much less attention has been paid to DIR in lower temperature, circumneutral pH environments, where solid phase Fe(III) oxides are the dominant forms of Fe(III). This study explored the potential for DIR in the warm (ca. 40-50°C), circumneutral pH Chocolate Pots hot springs (CP) in YNP. Most probable number (MPN) enumerations and enrichment culture studies confirmed the presence of endogenous microbial communities that reduced native CP Fe(III) oxides. Enrichment cultures demonstrated sustained DIR coupled to acetate and lactate oxidation through repeated transfers over ca. 450 days. Pyrosequencing of 16S rRNA genes indicated that the dominant organisms in the enrichments were closely affiliated with the well known Fe(III) reducer Geobacter metallireducens. Additional taxa included relatives of sulfate reducing bacterial genera Desulfohalobium and Thermodesulfovibrio; however, amendment of enrichments with molybdate, an inhibitor of sulfate reduction, suggested that sulfate reduction was not a primary metabolic pathway involved in DIR in the cultures. A metagenomic analysis of enrichment cultures is underway in anticipation of identifying genes involved in DIR in the less well-characterized dominant organisms. Current studies are aimed at interrogating the in situ microbial community at CP. Core samples were collected along the flow path (Fig. 1) and subdivided into 1 cm depth intervals for geochemical and microbiological analysis. The presence of significant quantities of Fe(II) in the solids indicated that DIR is active in situ. A parallel study investigated in vitro microbial DIR in sediments collected from three of the coring sites. DNA was extracted from samples from both studies for 16S rRNA gene and metagenomic sequencing in order to obtain a

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

    SciTech Connect

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

    2012-02-15

    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

  2. Characterization of methionine oxidation and methionine sulfoxide reduction using methionine-rich cysteine-free proteins

    PubMed Central

    2012-01-01

    Background Methionine (Met) residues in proteins can be readily oxidized by reactive oxygen species to Met sulfoxide (MetO). MetO is a promising physiological marker of oxidative stress and its inefficient repair by MetO reductases (Msrs) has been linked to neurodegeneration and aging. Conventional methods of assaying MetO formation and reduction rely on chromatographic or mass spectrometry procedures, but the use of Met-rich proteins (MRPs) may offer a more streamlined alternative. Results We carried out a computational search of completely sequenced genomes for MRPs deficient in cysteine (Cys) residues and identified several proteins containing 20% or more Met residues. We used these MRPs to examine Met oxidation and MetO reduction by in-gel shift assays and immunoblot assays with antibodies generated against various oxidized MRPs. The oxidation of Cys-free MRPs by hydrogen peroxide could be conveniently monitored by SDS-PAGE and was specific for Met, as evidenced by quantitative reduction of these proteins with Msrs in DTT- and thioredoxin-dependent assays. We found that hypochlorite was especially efficient in oxidizing MRPs. Finally, we further developed a procedure wherein antibodies made against oxidized MRPs were isolated on affinity resins containing same or other oxidized or reduced MRPs. This procedure yielded reagents specific for MetO in these proteins, but proved to be ineffective in developing antibodies with broad MetO specificity. Conclusion Our data show that MRPs provide a convenient tool for characterization of Met oxidation, MetO reduction and Msr activities, and could be used for various aspects of redox biology involving reversible Met oxidation. PMID:23088625

  3. Regioselective electrochemical reduction of 2,4-dichlorobiphenyl - Distinct standard reduction potentials for carbon-chlorine bonds using convolution potential sweep voltammetry

    NASA Astrophysics Data System (ADS)

    Muthukrishnan, A.; Sangaranarayanan, M. V.; Boyarskiy, V. P.; Boyarskaya, I. A.

    2010-04-01

    The reductive cleavage of carbon-chlorine bonds in 2,4-dichlorobiphenyl (PCB-7) is investigated using the convolution potential sweep voltammetry and quantum chemical calculations. The potential dependence of the logarithmic rate constant is non-linear which indicates the validity of Marcus-Hush theory of quadratic activation-driving force relationship. The ortho-chlorine of the 2,4-dichlorobiphenyl gets reduced first as inferred from the quantum chemical calculations and bulk electrolysis. The standard reduction potentials pertaining to the ortho-chlorine of 2,4-dichlorobiphenyl and that corresponding to para chlorine of the 4-chlorobiphenyl have been estimated.

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

    SciTech Connect

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

    2007-05-02

    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.

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

    PubMed Central

    2013-01-01

    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

  6. Assessment of potential carbon dioxide reductions due to biomass-coal cofiring in the United States.

    PubMed

    Robinson, A L; Rhodes, J S; Keith, D W

    2003-11-15

    Cofiring biomass with coal in existing power plants offers a relatively inexpensive and efficient option for increasing near-term biomass energy utilization. Potential benefits include reduced emissions of carbon dioxide, sulfur, and nitrogen oxides and development of biomass energy markets. To understand the economics of this strategy, we develop a model to calculate electricity and pollutant mitigation costs with explicit characterization of uncertainty in fuel and technology costs and variability in fuel properties. The model is first used to evaluate the plant-level economics of cofiring as a function of biomass cost. It is then integrated with state-specific coal consumption and biomass supply estimates to develop national supply curves for cofire electricity and carbon mitigation. A delivered cost of biomass below 15 dollars per ton is required for cofire to be competitive with existing coal-based generation. Except at low biomass prices (less than 15 dollars per ton), cofiring is unlikely to be competitive for NOx or SOx control, but it can provide comparatively inexpensive control of CO2 emissions: we estimate that emissions reductions of 100 Mt-CO2/year (a 5% reduction in electric-sector emissions) can be achieved at 25 +/- 20 dollars/tC. The 2-3 year time horizon for deployment--compared with 10-20 years for other CO2 mitigation options--makes cofiring particularly attractive. PMID:14655692

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

    PubMed

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

    2012-10-28

    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 α-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

  8. Single-step treatment of 2,4-dinitrotoluene via zero-valent metal reduction and chemical oxidation.

    PubMed

    Thomas, J Mathew; Hernandez, Rafael; Kuo, Chiang-Hai

    2008-06-30

    Many nitroaromatic compounds (NACs) are considered toxic and potential carcinogens. The purpose of this study was to develop an integrated reductive/oxidative process for treating NACs contaminated waters. The process consists of the combination of zero-valent iron and an ozonation based treatment technique. Corrosion promoters are added to the contaminated water to minimize passivation of the metallic species. Water contaminated with 2,4-dinitrotoluene (DNT) was treated with the integrated process using a recirculated batch reactor. It was demonstrated that addition of corrosion promoters to the contaminated water enhances the reduction of 2,4-DNT with zero-valent iron. The addition of corrosion promoters resulted in 62% decrease in 2,4-DNT concentration to 2,4-diaminotoluene. The data shows that iron reduced the 2,4-DNT and ozone oxidized these products resulting in a 73% removal of TOC and a 96% decrease in 2,4-DNT concentration.

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

    NASA Astrophysics Data System (ADS)

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

    2005-02-01

    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.

  10. Breakdown into nanoscale of graphene oxide: Confined hot spot atomic reduction and fragmentation

    NASA Astrophysics Data System (ADS)

    Gonçalves, Gil; Vila, Mercedes; Bdikin, Igor; de Andrés, Alicia; Emami, Nazanin; Ferreira, Rute A. S.; Carlos, Luís D.; Grácio, José; Marques, Paula A. A. P.

    2014-10-01

    Nano-graphene oxide (nano-GO) is a new class of carbon based materials being proposed for biomedical applications due to its small size, intrinsic optical properties, large specific surface area, and easy to functionalize. To fully exploit nano-GO properties, a reproducible method for its production is of utmost importance. Herein we report, the study of the sequential fracture of GO sheets onto nano-GO with controllable lateral width, by a simple, and reproducible method based on a mechanism that we describe as a confined hot spot atomic fragmentation/reduction of GO promoted by ultrasonication. The chemical and structural changes on GO structure during the breakage were monitored by XPS, FTIR, Raman and HRTEM. We found that GO sheets starts breaking from the defects region and in a second phase through the disruption of carbon bonds while still maintaining crystalline carbon domains. The breaking of GO is accompanied by its own reduction, essentially by the elimination of carboxylic and carbonyl functional groups. Photoluminescence and photothermal studies using this nano-GO are also presented highlighting the potential of this nanomaterial as a unique imaging/therapy platform.

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

    PubMed

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

    1998-08-01

    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.

  12. Reduction of iron-oxide-carbon composites: part I. Estimation of the rate constants

    SciTech Connect

    Halder, S.; Fruehan, R.J.

    2008-12-15

    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 CO{sub 2} and wustite 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 wustite 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 wustite 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 wustite 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.

  13. Reduction of carbon monoxide emissions with regenerative thermal oxidizers

    SciTech Connect

    Firmin, S.M.; Lipke, S.; Baturay, A.

    1996-09-01

    Regenerative thermal oxidizers (RTOs) have been extensively used for the control of volatile organic compound (VOC) emissions from various sources. However, very little information is available on the ability of RTOs to control carbon monoxide (CO) emissions. This paper presents the results of extensive tests conducted on two RTOs to determine their VOC and CO control efficiencies. The inlet gas stream to the RTOs includes VOC and CO concentrations as high as 2,000 ppm and 3,600 ppm, respectfully. The testing demonstrated that both RTOs were capable of controlling greater than 98% of both inlet VOCs and CO. While the destruction efficiencies within the combustion chambers exceeded 99.9%, direct leakage past valves accounted for the lower control efficiencies. The tests indicated that the overall VOC and CO control efficiencies of the RTOs may be limited by valve leakage. The design and permitting of a RTO should include conservative control estimates which account for possible valve leakage.

  14. Reduction of oxide microtrenching by electron beam assisted etching

    NASA Astrophysics Data System (ADS)

    Watanabe, M.; Shaw, D. M.; Collins, G. J.

    2000-10-01

    High density plasma etching of submicron wide oxide trenches often results in non-ideal etched features. For example, microtrenching is the result of higher etch rate near the side wall as compared to the center of the trench. Herein, we apply a previously reported[1] high energy (100 - 900 eV) electron beam directed at the etching wafer surface to reduce microtrenching during the etching of 0.5 micron wide silicon dioxide (SiO2) trench patterns in an inductively coupled fluorocarbon plasma. The directed electron beam neutralizes the positive charge buildup at the bottom of the trench and reduces the microtrench formation. Scanning Electron Microscopy (SEM) images of features etched with and without the electron beam show that the electron beam is effective in reducing microtrenching. [1] D. M. Shaw, M. Watanabe, G. J. Collins, and H. Sugai, Jpn. J. Appl. Phys. 38, 87 (1999).

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

    USGS Publications Warehouse

    Weiss, J.V.; Emerson, D.; Megonigal, J.P.

    2004-01-01

    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. ?? 2004 Federation of European Microbiological Societies. Published by Elsevier B.V. All rights reserved.

  16. Potential for Sonic Boom Reduction of the Boeing HSCT

    NASA Technical Reports Server (NTRS)

    Haglund, George T.

    1999-01-01

    The HSR sonic boom technology program includes a goal of reducing the objectionable aspects of sonic boom. Earlier HSCT sonic boom studies considered achieving significant sonic boom reduction by the use of arrow-wing planforms and detailed shaping of the airplane to produce shaped waveforms (non N-waves) at the ground. While these design efforts were largely successful, the added risk and cost of the airplanes were judged to be unacceptable. The objective of the current work is to explore smaller configuration refinements that could lead to reduced sonic boom impact, within design and operational constraints. A somewhat modest target of 10% reduction in sonic boom maximum overpressure was selected to minimize the effect on the configuration performance. This work was a joint NASA/Industry effort, utilizing the respective strengths of team members at Boeing, NASA Langley, and NASA Ames. The approach used was to first explore a wide range of modifications and airplane characteristics for their effects on sonic boom and drag, using classical Modified Linear Theory (MLT) methods. CFD methods were then used to verify promising, modifications and to analyze modifications for which the MLT methods were not appropriate. The tea m produced a list of configuration changes with their effects on sonic boom and, in some cases, an estimate of the drag penalty. The most promising modifications were applied to produce a boom-softened derivative of the baseline Boeing High Speed Civil Transport (HSCT) configuration. This boom-softened configuration was analyzed in detail for the reduce sonic boom impact and also for the effect of the configuration modifications on drag, weight, and overall performance relative to the baseline.

  17. Capacity of reductants and chelators to prevent lipid oxidation catalyzed by fish hemoglobin.

    PubMed

    Maestre, Rodrigo; Pazos, Manuel; Iglesias, Jacobo; Medina, Isabel

    2009-10-14

    The efficiency of different reductants (reduced glutathione, ascorbic acid, and catalase) and metal chelators [ethylenediaminetetraacetic acid (EDTA), citric acid, sodium tripolyphosphate (STPP), and adenosine-5'-triphosphate (ATP)] to inhibit lipid oxidation promoted by fish hemoglobin was investigated. The inhibitory activity on hemoglobin-catalyzed lipid oxidation was also evaluated for grape oligomeric catechins (proanthocyanidins), which have both reducing and chelating properties. The antioxidant activity was studied in two different lipid oxidation models, liposomes and washed minced fish muscle. Grape proanthocyanidins were found to be significantly more effective than other reductants to prevent hemoglobin-mediated lipid oxidation in both liposomes and washed fish muscle. Reduced glutathione was also efficient to retard lipid oxidation at the same molarity in washed fish muscle, whereas catalase and ascorbic acid showed a lower antioxidant activity. Metal chelators were less active than reductants, and consequently, the former were necessarily evaluated at much higher concentration than grape proanthocyanidins and reducing compounds. STPP was found to be the iron chelator with the strongest efficiency to delay hemoglobin-mediated lipid oxidation followed by EDTA. Citric acid and ATP were ineffective in retarding lipid oxidation in both systems. Grape proanthocyanidins provided the most extensive protection to preserve hemoglobin at ferrous state in washed fish muscle. Our results draw attention to the greater capacity of reducing compounds to prevent fish hemoglobin-mediated lipid oxidation in comparison with iron chelators, suggesting that the free radical scavenging and/or reduction of ferrylHb species are crucial actions to avoid the pro-oxidant capacity of fish hemoglobin.

  18. Capacity of reductants and chelators to prevent lipid oxidation catalyzed by fish hemoglobin.

    PubMed

    Maestre, Rodrigo; Pazos, Manuel; Iglesias, Jacobo; Medina, Isabel

    2009-10-14

    The efficiency of different reductants (reduced glutathione, ascorbic acid, and catalase) and metal chelators [ethylenediaminetetraacetic acid (EDTA), citric acid, sodium tripolyphosphate (STPP), and adenosine-5'-triphosphate (ATP)] to inhibit lipid oxidation promoted by fish hemoglobin was investigated. The inhibitory activity on hemoglobin-catalyzed lipid oxidation was also evaluated for grape oligomeric catechins (proanthocyanidins), which have both reducing and chelating properties. The antioxidant activity was studied in two different lipid oxidation models, liposomes and washed minced fish muscle. Grape proanthocyanidins were found to be significantly more effective than other reductants to prevent hemoglobin-mediated lipid oxidation in both liposomes and washed fish muscle. Reduced glutathione was also efficient to retard lipid oxidation at the same molarity in washed fish muscle, whereas catalase and ascorbic acid showed a lower antioxidant activity. Metal chelators were less active than reductants, and consequently, the former were necessarily evaluated at much higher concentration than grape proanthocyanidins and reducing compounds. STPP was found to be the iron chelator with the strongest efficiency to delay hemoglobin-mediated lipid oxidation followed by EDTA. Citric acid and ATP were ineffective in retarding lipid oxidation in both systems. Grape proanthocyanidins provided the most extensive protection to preserve hemoglobin at ferrous state in washed fish muscle. Our results draw attention to the greater capacity of reducing compounds to prevent fish hemoglobin-mediated lipid oxidation in comparison with iron chelators, suggesting that the free radical scavenging and/or reduction of ferrylHb species are crucial actions to avoid the pro-oxidant capacity of fish hemoglobin. PMID:19736927

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

    SciTech Connect

    Dr. Ates Akyurtlu; Dr. Jale F. Akyurtlu

    2001-05-31

    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

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

    PubMed Central

    Kühl, Michael; Jørgensen, Bo Barker

    1992-01-01

    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 μm) 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. PMID:16348687

  1. Kinetically induced irreversibility in electro-oxidation and reduction of Pt surface.

    PubMed

    Jinnouchi, Ryosuke; Kodama, Kensaku; Suzuki, Takahisa; Morimoto, Yu

    2015-05-14

    A mean field kinetic model was developed for electrochemical oxidations and reductions of Pt(111) on the basis of density functional theory calculations, and the reaction mechanisms were analyzed. The model reasonably describes asymmetric shapes of cyclic voltammograms and small Tafel slopes of relevant redox reactions observed in experiments without assuming any unphysical forms of rate equations. Simulations using the model indicate that the oxidation of Pt(111) proceeds via an electrochemical oxidation from Pt to PtOH and a disproportionation reaction from PtOH to PtO and Pt, while its reduction proceeds via two electrochemical reductions from PtO to PtOH and from PtOH to Pt.

  2. Electron transfer of Pseudomonas aeruginosa CP1 in electrochemical reduction of nitric oxide.

    PubMed

    Zhou, Shaofeng; Huang, Shaobin; He, Jiaxin; Li, Han; Zhang, Yongqing

    2016-10-01

    This study reports catalytic electro-chemical reduction of nitric oxide (NO) enhanced by Pseudomonas aeruginosa strain CP1. The current generated in the presence of bacteria was 4.36times that in the absence of the bacteria. The strain was able to catalyze electro-chemical reduction of NO via indirect electron transfer with an electrode, revealed by a series of cyclic voltammetry experiments. Soluble electron shuttles secreted into solution by live bacteria were responsible for the catalytic effects. The enhancement of NO reduction was also confirmed by detection of nitrous oxide; the level of this intermediate was 46.4% higher in the presence of bacteria than in controls, illustrated that the electron transfer pathway did not directly reduce nitric oxide to N2. The findings of this study may offer a new model for bioelectrochemical research in the field of NO removal by biocatalysts. PMID:27426634

  3. Potential for microbial oxidation of ferrous iron in basaltic glass.

    PubMed

    Xiong, Mai Yia; Shelobolina, Evgenya S; Roden, Eric E

    2015-05-01

    Basaltic glass (BG) is an amorphous ferrous iron [Fe(II)]-containing material present in basaltic rocks, which are abundant on rocky planets such as Earth and Mars. Previous research has suggested that Fe(II) in BG can serve as an energy source for chemolithotrophic microbial metabolism, which has important ramifications for potential past and present microbial life on Mars. However, to date there has been no direct demonstration of microbially catalyzed oxidation of Fe(II) in BG. In this study, three different culture systems were used to investigate the potential for microbial oxidation of Fe(II) in BG, including (1) the chemolithoautotrophic Fe(II)-oxidizing, nitrate-reducing "Straub culture"; (2) the mixotrophic Fe(II)-oxidizing, nitrate-reducing organism Desulfitobacterium frappieri strain G2; and (3) indigenous microorganisms from a streambed Fe seep in Wisconsin. The BG employed consisted of clay and silt-sized particles of freshly quenched lava from the TEB flow in Kilauea, Hawaii. Soluble Fe(II) or chemically reduced NAu-2 smectite (RS) were employed as positive controls to verify Fe(II) oxidation activity in the culture systems. All three systems demonstrated oxidation of soluble Fe(II) and/or structural Fe(II) in RS, whereas no oxidation of Fe(II) in BG material was observed. The inability of the Straub culture to oxidize Fe(II) in BG was particularly surprising, as this culture can oxidize other insoluble Fe(II)-bearing minerals such as biotite, magnetite, and siderite. Although the reason for the resistance of the BG toward enzymatic oxidation remains unknown, it seems possible that the absence of distinct crystal faces or edge sites in the amorphous glass renders the material resistant to such attack. These findings have implications with regard to the idea that Fe(II)-Si-rich phases in basalt rocks could provide a basis for chemolithotrophic microbial life on Mars, specifically in neutral-pH environments where acid-promoted mineral dissolution and

  4. Potential for microbial oxidation of ferrous iron in basaltic glass.

    PubMed

    Xiong, Mai Yia; Shelobolina, Evgenya S; Roden, Eric E

    2015-05-01

    Basaltic glass (BG) is an amorphous ferrous iron [Fe(II)]-containing material present in basaltic rocks, which are abundant on rocky planets such as Earth and Mars. Previous research has suggested that Fe(II) in BG can serve as an energy source for chemolithotrophic microbial metabolism, which has important ramifications for potential past and present microbial life on Mars. However, to date there has been no direct demonstration of microbially catalyzed oxidation of Fe(II) in BG. In this study, three different culture systems were used to investigate the potential for microbial oxidation of Fe(II) in BG, including (1) the chemolithoautotrophic Fe(II)-oxidizing, nitrate-reducing "Straub culture"; (2) the mixotrophic Fe(II)-oxidizing, nitrate-reducing organism Desulfitobacterium frappieri strain G2; and (3) indigenous microorganisms from a streambed Fe seep in Wisconsin. The BG employed consisted of clay and silt-sized particles of freshly quenched lava from the TEB flow in Kilauea, Hawaii. Soluble Fe(II) or chemically reduced NAu-2 smectite (RS) were employed as positive controls to verify Fe(II) oxidation activity in the culture systems. All three systems demonstrated oxidation of soluble Fe(II) and/or structural Fe(II) in RS, whereas no oxidation of Fe(II) in BG material was observed. The inability of the Straub culture to oxidize Fe(II) in BG was particularly surprising, as this culture can oxidize other insoluble Fe(II)-bearing minerals such as biotite, magnetite, and siderite. Although the reason for the resistance of the BG toward enzymatic oxidation remains unknown, it seems possible that the absence of distinct crystal faces or edge sites in the amorphous glass renders the material resistant to such attack. These findings have implications with regard to the idea that Fe(II)-Si-rich phases in basalt rocks could provide a basis for chemolithotrophic microbial life on Mars, specifically in neutral-pH environments where acid-promoted mineral dissolution and

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

    NASA Astrophysics Data System (ADS)

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

    2002-09-01

    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 SrCl 2 at concentrations of 10 μM, 100 μM, or 1.0 mM. CaCl 2 (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 CaCl 2. 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 (D D-H) of 1.81 ± 0.15. This D D-H value was 2 to 10 times higher than values determined for incorporation of Sr (10 μM) into FeCO 3(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)CO 3 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 FeCO 3(s

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

    SciTech Connect

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

    2002-08-15

    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

  7. Effects of surface chemistry and microstructure of electrolyte on oxygen reduction kinetics of solid oxide fuel cells

    SciTech Connect

    Park, Joong Sun; An, Jihwan; Lee, Min Hwan; Prinz, Friedrich B.; Lee, Wonyoung

    2015-11-01

    In this study, we report systematic investigation of the surface properties of yttria-stabilized zirconia (YSZ) electrolytes with the control of the grain boundary (GB) density at the surface, and its effects on electrochemical activities. The GB density of thin surface layers deposited on single crystal YSZ substrates is controlled by changing the annealing temperature (750-1450 °C). Higher oxygen reduction reactions (ORR) kinetics is observed in samples annealed at lower temperatures. The higher ORR activity is ascribed to the higher GB density at the YSZ surface where 'mobile' oxide ion vacancies are more populated. Meanwhile, oxide ion vacancies concurrently created with yttrium segregation at the surface at the higher annealing temperature are considered inactive to oxygen incorporation reactions. Our results provide additional insight into the interplay between the surface chemistry, microstructures, and electrochemical activity. They potentially provide important guidelines for engineering the electrolyte electrode interfaces of solid oxide fuel cells for higher electrochemical performance.

  8. Quantifying food losses and the potential for reduction in Switzerland.

    PubMed

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

    2013-03-01

    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

  9. Jet Noise Reduction Potential From Emerging Variable Cycle Technologies

    NASA Technical Reports Server (NTRS)

    2012-01-01

    Acoustic and flow-field experiments were conducted on exhaust concepts for the next generation supersonic, commercial aircraft. The concepts were developed by Lockheed Martin (LM), Rolls-Royce Liberty Works (RRLW), and General Electric Global Research (GEGR) as part of an N+2 (next generation forward) aircraft system study initiated by the Supersonics Project in NASA s Fundamental Aeronautics Program. The experiments were conducted in the Aero-Acoustic Propulsion Laboratory at the NASA Glenn Research Center. The exhaust concepts utilized ejectors, inverted velocity profiles, and fluidic shields. One of the ejector concepts was found to produce stagnant flow within the ejector and the other ejector concept produced discrete-frequency tones that degraded the acoustic performance of the model. The concept incorporating an inverted velocity profile and fluid shield produced overall-sound-pressure-level reductions of 6 dB relative to a single stream nozzle at the peak jet noise angle for some nozzle pressure ratios. Flow separations in the nozzle degraded the acoustic performance of the inverted velocity profile model at low nozzle pressure ratios.

  10. Jet Noise Reduction Potential from Emerging Variable Cycle Technologies

    NASA Technical Reports Server (NTRS)

    Henderson, Brenda; Bridges, James; Wernet, Mark

    2012-01-01

    Acoustic and flow-field experiments were conducted on exhaust concepts for the next generation supersonic, commercial aircraft. The concepts were developed by Lockheed Martin (LM), Rolls-Royce Liberty Works (RRLW), and General Electric Global Research (GEGR) as part of an N+2 (next generation forward) aircraft system study initiated by the Supersonics Project in NASA s Fundamental Aeronautics Program. The experiments were conducted in the Aero-Acoustic Propulsion Laboratory at the NASA Glenn Research Center. The exhaust concepts utilized ejectors, inverted velocity profiles, and fluidic shields. One of the ejector concepts was found to produce stagnant flow within the ejector and the other ejector concept produced discrete-frequency tones that degraded the acoustic performance of the model. The concept incorporating an inverted velocity profile and fluid shield produced overall-sound-pressure-level reductions of 6 dB relative to a single stream nozzle at the peak jet noise angle for some nozzle pressure ratios. Flow separations in the nozzle degraded the acoustic performance of the inverted velocity profile model at low nozzle pressure ratios.

  11. Quantifying food losses and the potential for reduction in Switzerland.

    PubMed

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

    2013-03-01

    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).

  12. Localized conductive patterning via focused electron beam reduction of graphene oxide

    SciTech Connect

    Kim, Songkil; Henry, Mathias; Kulkarni, Dhaval D.; Zackowski, Paul; Jang, Seung Soon; Tsukruk, Vladimir V.; Fedorov, Andrei G.

    2015-03-30

    We report on a method for “direct-write” conductive patterning via reduction of graphene oxide (GO) sheets using focused electron beam induced deposition (FEBID) of carbon. FEBID treatment of the intrinsically dielectric graphene oxide between two metal terminals opens up the conduction channel, thus enabling a unique capability for nanoscale conductive domain patterning in GO. An increase in FEBID electron dose results in a significant increase of the domain electrical conductivity with improving linearity of drain-source current vs. voltage dependence, indicative of a change of graphene oxide electronic properties from insulating to semiconducting. Density functional theory calculations suggest a possible mechanism underlying this experimentally observed phenomenon, as localized reduction of graphene oxide layers via interactions with highly reactive intermediates of electron-beam-assisted dissociation of surface-adsorbed hydrocarbon molecules. These findings establish an unusual route for using FEBID as nanoscale lithography and patterning technique for engineering carbon-based nanomaterials and devices with locally tailored electronic properties.

  13. Localized conductive patterning via focused electron beam reduction of graphene oxide

    NASA Astrophysics Data System (ADS)

    Kim, Songkil; Kulkarni, Dhaval D.; Henry, Mathias; Zackowski, Paul; Jang, Seung Soon; Tsukruk, Vladimir V.; Fedorov, Andrei G.

    2015-03-01

    We report on a method for "direct-write" conductive patterning via reduction of graphene oxide (GO) sheets using focused electron beam induced deposition (FEBID) of carbon. FEBID treatment of the intrinsically dielectric graphene oxide between two metal terminals opens up the conduction channel, thus enabling a unique capability for nanoscale conductive domain patterning in GO. An increase in FEBID electron dose results in a significant increase of the domain electrical conductivity with improving linearity of drain-source current vs. voltage dependence, indicative of a change of graphene oxide electronic properties from insulating to semiconducting. Density functional theory calculations suggest a possible mechanism underlying this experimentally observed phenomenon, as localized reduction of graphene oxide layers via interactions with highly reactive intermediates of electron-beam-assisted dissociation of surface-adsorbed hydrocarbon molecules. These findings establish an unusual route for using FEBID as nanoscale lithography and patterning technique for engineering carbon-based nanomaterials and devices with locally tailored electronic properties.

  14. Direct Reduction of Ferrous Oxides to form an Iron-Rich Alternative Charge Material

    NASA Astrophysics Data System (ADS)

    Ünal, H. İbrahim; Turgut, Enes; Atapek, Ş. H.; Alkan, Attila

    2015-12-01

    In this study, production of sponge iron by direct reduction of oxides and the effect of reductant on metallization were investigated. In the first stage of the study, scale formed during hot rolling of slabs was reduced in a rotating furnace using solid and gas reductants. Coal was used as solid reductant and hydrogen released from the combustion reaction of LNG was used as the gas one. The sponge iron produced by direct reduction was melted and solidified. In the second stage, Hematite ore in the form of pellets was reduced using solid carbon in a furnace heated up to 1,100°C for 60 and 120 minutes. Reduction degree of process was evaluated as a function of time and the ratio of Cfix/Fetotal. In the third stage, final products were examined using scanning electron microscope and microanalysis was carried out by energy dispersive x-ray spectrometer attached to the electron microscope. It is concluded that (i) direct reduction using both solid and gas reductants caused higher metallization compared to using only solid reductant, (ii) as the reduction time and ratio of Cfix/Fetotal increased %-reduction of ore increased.

  15. Fabrication of palladium/graphene oxide composite by plasma reduction at room temperature.

    PubMed

    Yu, Yue; Li, Yingzhi; Pan, Yunxiang; Liu, Chang-Jun

    2012-01-01

    Pd nanoparticles were fabricated on graphene oxide (GO) using a deposition-precipitation method with a glow discharge plasma reduction at room temperature. Argon was employed as the plasma-generating gas. The novel plasma method selectively reduces the metal ions. The graphene oxide has no change with this plasma reduction according to the Fourier transform infrared analysis. The Pd nanoparticles on the GO were uniformly distributed with an average diameter of 1.6 nm. The functional groups on the GO not only prevent Pd nanoparticles from further aggregation but also provide a strong hydrophilic property to the Pd/GO composite, which can form stable colloidal dispersions in water. PMID:22533915

  16. Fabrication of palladium/graphene oxide composite by plasma reduction at room temperature

    NASA Astrophysics Data System (ADS)

    Yu, Yue; Li, Yingzhi; Pan, Yunxiang; Liu, Chang-jun

    2012-04-01

    Pd nanoparticles were fabricated on graphene oxide (GO) using a deposition-precipitation method with a glow discharge plasma reduction at room temperature. Argon was employed as the plasma-generating gas. The novel plasma method selectively reduces the metal ions. The graphene oxide has no change with this plasma reduction according to the Fourier transform infrared analysis. The Pd nanoparticles on the GO were uniformly distributed with an average diameter of 1.6 nm. The functional groups on the GO not only prevent Pd nanoparticles from further aggregation but also provide a strong hydrophilic property to the Pd/GO composite, which can form stable colloidal dispersions in water.

  17. Removal of PCBs in contaminated soils by means of chemical reduction and advanced oxidation processes.

    PubMed

    Rybnikova, V; Usman, M; Hanna, K

    2016-09-01

    Although the chemical reduction and advanced oxidation processes have been widely used individually, very few studies have assessed the combined reduction/oxidation approach for soil remediation. In the present study, experiments were performed in spiked sand and historically contaminated soil by using four synthetic nanoparticles (Fe(0), Fe/Ni, Fe3O4, Fe3 - x Ni x O4). These nanoparticles were tested firstly for reductive transformation of polychlorinated biphenyls (PCBs) and then employed as catalysts to promote chemical oxidation reactions (H2O2 or persulfate). Obtained results indicated that bimetallic nanoparticles Fe/Ni showed the highest efficiency in reduction of PCB28 and PCB118 in spiked sand (97 and 79 %, respectively), whereas magnetite (Fe3O4) exhibited a high catalytic stability during the combined reduction/oxidation approach. In chemical oxidation, persulfate showed higher PCB degradation extent than hydrogen peroxide. As expected, the degradation efficiency was found to be limited in historically contaminated soil, where only Fe(0) and Fe/Ni particles exhibited reductive capability towards PCBs (13 and 18 %). In oxidation step, the highest degradation extents were obtained in presence of Fe(0) and Fe/Ni (18-19 %). The increase in particle and oxidant doses improved the efficiency of treatment, but overall degradation extents did not exceed 30 %, suggesting that only a small part of PCBs in soil was available for reaction with catalyst and/or oxidant. The use of organic solvent or cyclodextrin to improve the PCB availability in soil did not enhance degradation efficiency, underscoring the strong impact of soil matrix. Moreover, a better PCB degradation was observed in sand spiked with extractable organic matter separated from contaminated soil. In contrast to fractions with higher particle size (250-500 and <500 μm), no PCB degradation was observed in the finest fraction (≤250 μm) having higher organic matter content. These findings

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

    DOEpatents

    Pence, Dallas T.; Thomas, Thomas R.

    1980-01-01

    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 A.

  19. Yttrium oxide/gadolinium oxide-modified platinum nanoparticles as cathodes for the oxygen reduction reaction.

    PubMed

    Luo, Yun; Habrioux, Aurélien; Calvillo, Laura; Granozzi, Gaetano; Alonso-Vante, Nicolas

    2014-07-21

    Rare-earth-element (Y, Gd) modified Pt nanoparticles (NPs) supported on a carbon substrate (Vulcan XC-72) are synthesized via a water-in-oil chemical route. In both cases, X-ray diffraction (XRD) measurements show the non-formation of an alloyed material. Photoemission spectroscopy (XPS) results reveal that Y and Gd are oxidized. Additionally, no evidence of an electronic modification of Pt can be brought to light. Transmission electron microscopy (TEM) studies indicate that Pt-Y(2)O(3) and Pt-Gd(2)O(3) particles are well dispersed on the substrate-and that their average particle sizes are smaller than the Pt-NP sizes. The catalytic activity of the Pt-Y(2)O(3)/C and Pt-Gd(2)O(3)/C catalysts towards the oxygen reduction reaction (ORR) is studied in a 0.5 M H(2)SO(4) electrolyte. The surface and mass specific activities of the Pt-Y(2)O(3)/C catalyst towards the ORR at 0.9 V (vs. the reversible hydrogen electrode, RHE) are (54.3±1.2) μA cm(-2)(Pt) and MA=(23.1±0.5) mA mg(-1)(Pt), respectively. These values are 1.3-, and 1.6-fold higher than the values obtained with a Pt/C catalyst. Although the as-prepared Pt-Gd(2)O(3)/C catalyst has a lower catalytic activity for the ORR compared to Pt/C, the heat-treated sample shows a surface specific activity of about (53.0±0.7) μA cm(-2) Pt , and a mass specific activity (MA) of about (18.2±0.5) mA mg(-1) Pt at 0.9 V (vs. RHE). The enhancement of the ORR kinetics on the Pt-Y(2)O(3)/C and heat-treated Pt-Gd(2)O(3)/C catalysts could be associated with the formation of platinum NPs presenting modified surface properties.

  20. Mechanism of sodium chloride in promoting reduction of high-magnesium low-nickel oxide ore.

    PubMed

    Zhou, Shiwei; Wei, Yonggang; Li, Bo; Wang, Hua; Ma, Baozhong; Wang, Chengyan

    2016-01-01

    Sodium chloride has been proved that it is an effective promoter for the reduction of high-magnesium, low-nickel oxide ore. The aim of current work is to clarify the promotion behavior of sodium chloride in the roasting reduction process. The influence of moisture on the reduction of ore in the presence of sodium chloride is studied to get clear comprehension of promotion process. In the presence of moisture, the HCl is produced by pyrohydrolysis of sodium chloride for chlorinating nickel and iron oxides, moreover, interactions between metallic oxides and sodium chloride are also a way for chlorination at high temperature (>802 °C); subsequently, the metal chloride would be reduced by reductant. In the absence of moisture, the magnetic separation results show that the recoveries of iron and nickel have a significant increase; moreover, olivine structure would be destroyed gradually with the increase of roasting temperature in the action of sodium chloride, and the sodium chloride existed in high-magnesium, low-nickel oxide ore could make the NiO isolate from NiO-bearing minerals. The NiO reacts with Fe2O3 at high temperature to form NiFe2O4, which is conductive to the formation of Ni-Fe alloy during the reduction process. PMID:27374991

  1. Mechanism of sodium chloride in promoting reduction of high-magnesium low-nickel oxide ore

    NASA Astrophysics Data System (ADS)

    Zhou, Shiwei; Wei, Yonggang; Li, Bo; Wang, Hua; Ma, Baozhong; Wang, Chengyan

    2016-07-01

    Sodium chloride has been proved that it is an effective promoter for the reduction of high-magnesium, low-nickel oxide ore. The aim of current work is to clarify the promotion behavior of sodium chloride in the roasting reduction process. The influence of moisture on the reduction of ore in the presence of sodium chloride is studied to get clear comprehension of promotion process. In the presence of moisture, the HCl is produced by pyrohydrolysis of sodium chloride for chlorinating nickel and iron oxides, moreover, interactions between metallic oxides and sodium chloride are also a way for chlorination at high temperature (>802 °C) subsequently, the metal chloride would be reduced by reductant. In the absence of moisture, the magnetic separation results show that the recoveries of iron and nickel have a significant increase; moreover, olivine structure would be destroyed gradually with the increase of roasting temperature in the action of sodium chloride, and the sodium chloride existed in high-magnesium, low-nickel oxide ore could make the NiO isolate from NiO-bearing minerals. The NiO reacts with Fe2O3 at high temperature to form NiFe2O4, which is conductive to the formation of Ni-Fe alloy during the reduction process.

  2. Mechanism of sodium chloride in promoting reduction of high-magnesium low-nickel oxide ore.

    PubMed

    Zhou, Shiwei; Wei, Yonggang; Li, Bo; Wang, Hua; Ma, Baozhong; Wang, Chengyan

    2016-07-04

    Sodium chloride has been proved that it is an effective promoter for the reduction of high-magnesium, low-nickel oxide ore. The aim of current work is to clarify the promotion behavior of sodium chloride in the roasting reduction process. The influence of moisture on the reduction of ore in the presence of sodium chloride is studied to get clear comprehension of promotion process. In the presence of moisture, the HCl is produced by pyrohydrolysis of sodium chloride for chlorinating nickel and iron oxides, moreover, interactions between metallic oxides and sodium chloride are also a way for chlorination at high temperature (>802 °C); subsequently, the metal chloride would be reduced by reductant. In the absence of moisture, the magnetic separation results show that the recoveries of iron and nickel have a significant increase; moreover, olivine structure would be destroyed gradually with the increase of roasting temperature in the action of sodium chloride, and the sodium chloride existed in high-magnesium, low-nickel oxide ore could make the NiO isolate from NiO-bearing minerals. The NiO reacts with Fe2O3 at high temperature to form NiFe2O4, which is conductive to the formation of Ni-Fe alloy during the reduction process.

  3. Mechanism of sodium chloride in promoting reduction of high-magnesium low-nickel oxide ore

    PubMed Central

    Zhou, Shiwei; Wei, Yonggang; Li, Bo; Wang, Hua; Ma, Baozhong; Wang, Chengyan

    2016-01-01

    Sodium chloride has been proved that it is an effective promoter for the reduction of high-magnesium, low-nickel oxide ore. The aim of current work is to clarify the promotion behavior of sodium chloride in the roasting reduction process. The influence of moisture on the reduction of ore in the presence of sodium chloride is studied to get clear comprehension of promotion process. In the presence of moisture, the HCl is produced by pyrohydrolysis of sodium chloride for chlorinating nickel and iron oxides, moreover, interactions between metallic oxides and sodium chloride are also a way for chlorination at high temperature (>802 °C); subsequently, the metal chloride would be reduced by reductant. In the absence of moisture, the magnetic separation results show that the recoveries of iron and nickel have a significant increase; moreover, olivine structure would be destroyed gradually with the increase of roasting temperature in the action of sodium chloride, and the sodium chloride existed in high-magnesium, low-nickel oxide ore could make the NiO isolate from NiO-bearing minerals. The NiO reacts with Fe2O3 at high temperature to form NiFe2O4, which is conductive to the formation of Ni-Fe alloy during the reduction process. PMID:27374991

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

    PubMed Central

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

    1975-01-01

    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. PMID:16659277

  5. Evidence of alloy formation during reduction of platinized tin oxide surfaces

    NASA Technical Reports Server (NTRS)

    Gardner, Steven D.; Hoflund, Gar B.; Davidson, Mark R.; Schryer, David R.

    1989-01-01

    Ion scattering spectroscopy, Auger electron spectroscopy, and electron spectroscopy for chemical analysis have been used to examine a platinized tin oxide catalyst surface before, during, and after reduction by annealing under vacuum at 250 to 450 C. These techniques were then used to examine the reduced surface after a room-temperature, low-pressure oxygen exposure. The spectral results and the behavior of the reduced surface toward oxygen exposure both indicate that a Pt/Sn alloy is produced during reduction.

  6. Reduction and structural evolution of graphene oxide sheets under hydrothermal treatment

    NASA Astrophysics Data System (ADS)

    Niu, Yongan; Fang, Qinghong; Zhang, Xin; Zhang, Panpan; Li, Yao

    2016-09-01

    This work carefully investigated the hydrothermal reduction of graphene oxide (GO) sheets. To evaluate the reduced extent, the as-prepared GO and RGO sheets in different conditions were measured by FT-IR, UV-Vis, Raman spectra and TEM morphologies. It revealed that the hydrothermal reduction of GO sheets was undergone four steps and the optimal condition was treated at 180 °C for 24 h. These RGO sheets exhibited the expectant morphologies and maintained the original sizes.

  7. Synthesis of highly active and dual-functional electrocatalysts for methanol oxidation and oxygen reduction reactions

    NASA Astrophysics Data System (ADS)

    Zhao, Qi; Zhang, Geng; Xu, Guangran; Li, Yingjun; Liu, Baocang; Gong, Xia; Zheng, Dafang; Zhang, Jun; Wang, Qin

    2016-12-01

    The promising Pt-based ternary catalyst is crucial for polymer electrolyte membrane fuel cells (PEMFCs) due to improving catalytic activity and durability for both methanol oxidation reaction and oxygen reduction reaction. In this work, a facile strategy is used for the synthesis ternary RuMPt (M = Fe, Co, Ni, and Cu) nanodendrities catalysts. The ternary RuMPt alloys exhibit enhanced specific and mass activity, positive half-wave potential, and long-term stability, compared with binary Pt-based alloy and the commercial Pt/C catalyst, which is attributed to the high electron density and upshifting of the d-band center for Pt atoms, and synergistic catalytic effects among Pt, M, and Ru atoms by introducing a transition metal. Impressively, the ternary RuCoPt catalyst exhibits superior mass activity (801.59 mA mg-1) and positive half-wave potential (0.857 V vs. RHE) towards MOR and ORR, respectively. Thus, the RuMPt nanocomposite is a very promising material to be used as dual electrocatalyst in the application of PEMFCs.

  8. Reduction of a thin chromium oxide film on Inconel surface upon treatment with hydrogen plasma

    NASA Astrophysics Data System (ADS)

    Vesel, Alenka; Mozetic, Miran; Balat-Pichelin, Marianne

    2016-11-01

    Inconel samples with a surface oxide film composed of solely chromium oxide with a thickness of approximately 700 nm were exposed to low-pressure hydrogen plasma at elevated temperatures to determine the suitable parameters for reduction of the oxide film. The hydrogen pressure during treatment was set to 60 Pa. Plasma was created by a surfaguide microwave discharge in a quartz glass tube to allow for a high dissociation fraction of hydrogen molecules. Auger electron depth profiling (AES) was used to determine the decay of the oxygen in the surface film and X-ray diffraction (XRD) to measure structural modifications. During hydrogen plasma treatment, the oxidized Inconel samples were heated to elevated temperatures. The reduction of the oxide film started at temperatures of approximately 1300 K (considering the emissivity of 0.85) and the oxide was reduced in about 10 s of treatment as revealed by AES. The XRD showed sharper substrate peaks after the reduction. Samples treated in hydrogen atmosphere under the same conditions have not been reduced up to approximately 1500 K indicating usefulness of plasma treatment.

  9. Doping Metal–Organic Frameworks for Water Oxidation, Carbon Dioxide Reduction, and Organic Photocatalysis

    SciTech Connect

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

    2011-07-22

    Catalytically competent Ir, Re, and Ru complexes H2L1–H2L6 with dicarboxylic acid functionalities were incorporated into a highly stable and porous Zr6O4(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 L1–L6 ligands allowed the construction of highly crystalline UiO-67 frameworks (metal–organic frameworks (MOFs) 1–6) that were doped with L1–L6 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 m2/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*IrIII(dcppy)Cl] (H2L1), [Cp*IrIII(dcbpy)Cl]Cl (H2L2), and [IrIII(dcppy)2(H2O)2]OTf (H2L3) (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 [ReI(CO)3(dcbpy)Cl] (H2L4) derivatized MOF 4 served as an active catalyst for photocatalytic CO2 reduction with a total turnover number (TON) of 10.9, three times higher than that of the homogeneous complex H2L4. MOFs 5 and 6 contained phosphorescent [IrIII(ppy)2(dcbpy)]Cl (H2L5) and [RuII(bpy)2(dcbpy)]Cl2 (H2L6) (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, CO2 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

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

    PubMed

    Egger, Garry

    2007-08-01

    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

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

    PubMed

    Egger, Garry

    2007-08-01

    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.

  12. LC-MS/MS Analysis and Comparison of Oxidative Damages on Peptides Induced by Pathogen Reduction Technologies for Platelets

    NASA Astrophysics Data System (ADS)

    Prudent, Michel; Sonego, Giona; Abonnenc, Mélanie; Tissot, Jean-Daniel; Lion, Niels

    2014-04-01

    Pathogen reduction technologies (PRT) are photochemical processes that use a combination of photosensitizers and UV-light to inactivate pathogens in platelet concentrates (PCs), a blood-derived product used to prevent hemorrhage. However, different studies have questioned the impact of PRT on platelet function and transfusion efficacy, and several proteomic analyses revealed possible oxidative damages to proteins. The present work focused on the oxidative damages produced by the two main PRT on peptides. Model peptides containing residues prone to oxidation (tyrosine, histidine, tryptophane, and cysteine) were irradiated with a combination of amotosalen/UVA (Intercept process) or riboflavin/UVB (Mirasol-like process). Modifications were identified and quantified by liquid chromatography coupled to tandem mass spectrometry. Cysteine-containing peptides formed disulfide bridges (R-SS-R, -2 Da; favored following amotosalen/UVA), sulfenic and sulfonic acids (R-SOH, +16 Da, R-SO3H, +48 Da, favored following riboflavin/UVB) upon treatment and the other amino acids exhibited different oxidations revealed by mass shifts from +4 to +34 Da involving different mechanisms; no photoadducts were detected. These amino acids were not equally affected by the PRT and the combination riboflavin/UVB generated more oxidation than amotosalen/UVA. This work identifies the different types and sites of peptide oxidations under the photochemical treatments and demonstrates that the two PRT may behave differently. The potential impact on proteins and platelet functions may thus be PRT-dependent.

  13. Fabrication and Characteristics of Reduced Graphene Oxide Produced with Different Green Reductants

    PubMed Central

    Ji, An; Shi, Lina; Zhou, Chen; Cui, Yunqi

    2015-01-01

    There has been an upsurge of green reductants for the preparation of graphene materials taking consideration of human health and the environment in recent years. In this paper, reduced graphene oxides (RGOs) were prepared by chemical reduction of graphene oxide (GO) with three green reductants, L-ascorbic acid (L-AA), D-glucose (D-GLC) and tea polyphenol (TP), and comparatively characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectra, Raman spectra and electrical conductivity analysis. Results showed that all these three reductants were effective to remove oxygen-containing functional groups in GO and restore the electrical conductivity of the obtained RGO. The RGO sample with L-ascorbic acid as a reductant and reduced with the existence of ammonia had the highest electrical conductivity (9.8 S·cm-1) among all the obtained RGO samples. The mechanisms regarding to the reduction of GO and the dispersion of RGO in water were also proposed. It is the good dispersibility of reduced graphene oxide in water that will facilitate its further use in composite materials and conductive ink. PMID:26658644

  14. Fabrication and Characteristics of Reduced Graphene Oxide Produced with Different Green Reductants.

    PubMed

    Xu, Changyan; Shi, Xiaomei; Ji, An; Shi, Lina; Zhou, Chen; Cui, Yunqi

    2015-01-01

    There has been an upsurge of green reductants for the preparation of graphene materials taking consideration of human health and the environment in recent years. In this paper, reduced graphene oxides (RGOs) were prepared by chemical reduction of graphene oxide (GO) with three green reductants, L-ascorbic acid (L-AA), D-glucose (D-GLC) and tea polyphenol (TP), and comparatively characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectra, Raman spectra and electrical conductivity analysis. Results showed that all these three reductants were effective to remove oxygen-containing functional groups in GO and restore the electrical conductivity of the obtained RGO. The RGO sample with L-ascorbic acid as a reductant and reduced with the existence of ammonia had the highest electrical conductivity (9.8 S·cm(-1)) among all the obtained RGO samples. The mechanisms regarding to the reduction of GO and the dispersion of RGO in water were also proposed. It is the good dispersibility of reduced graphene oxide in water that will facilitate its further use in composite materials and conductive ink. PMID:26658644

  15. Slide fastener reduction of graphene-oxide edges by calcium: insight from ab initio molecular dynamics.

    PubMed

    Xie, Sheng-Yi; Li, Xian-Bin; Tian, Wei Quan; Wang, Dan; Chen, Nian-Ke; Han, Dong; Sun, Hong-Bo

    2014-09-15

    The reduction of graphene oxide can be used as a simple way to produce graphene on a large scale. However, the numerous edges produced by the oxidation of graphite seriously degrade the quality of the graphene and its carrier transport property. In this work, the reduction of oxygen-passivated graphene edges and the subsequent linking of separated graphene sheets by calcium are investigated by using first-principles calculations. The calculations show that calcium can effectively remove the oxygen groups from two adjacent edges. The joining point of the edges serves as the starting point of the reduction and facilitates the reaction. Once the oxygen groups are removed, the crack is sutured. If the joining point is lacking, it becomes difficult to zip the separated fragments. A general electron-reduction model and a random atom-reduction model are suggested for these two situations. The present study sheds light on the reduction of graphene-oxide edges by using reactive metals to give large-sized graphene through a simple chemical reaction.

  16. Mechanisms for chelator stimulation of microbial Fe(III) -oxide reduction

    USGS Publications Warehouse

    Lovley, D.R.; Woodward, J.C.

    1996-01-01

    The mechanisms by which nitrilotriacetic acid (NTA) stimulated Fe(III) reduction in sediments from a petroleum-contaminated aquifer were investigated in order to gain insight into how added Fe(III) chelators stimulate the activity of hydrocarbon-degrading, Fe(III)-reducing microorganisms in these sediments, and how naturally occurring Fe(III) chelators might promote Fe(III) reduction in aquatic sediments. NTA solubilized Fe(III) from the aquifer sediments. NTA stimulation of microbial Fe(III) reduction did not appear to be the result of making calcium, magnesium, potassium, or trace metals more available to the microorganisms. Stimulation of Fe(III) reduction could not be attributed to NTA serving as a source of carbon or fixed nitrogen for Fe(III)-reducing bacteria as NTA was not degraded in the sediments. Studies with the Fe(III)-reducing microorganism, Geobacter metallireducens, and pure Fe(III)-oxide forms, demonstrated that NTA stimulated the reduction of a variety of Fe(III) forms, including highly crystalline Fe(III)-oxides such as goethite and hematite. The results suggest that NTA solubilization of insoluble Fe(III)-oxide is an important mechanism for the stimulation of Fe(III) reduction by NTA in aquifer sediments.

  17. Spinel-type lithium cobalt oxide as a bifunctional electrocatalyst for the oxygen evolution and oxygen reduction reactions.

    PubMed

    Maiyalagan, Thandavarayan; Jarvis, Karalee A; Therese, Soosairaj; Ferreira, Paulo J; Manthiram, Arumugam

    2014-05-27

    Development of efficient, affordable electrocatalysts for the oxygen evolution reaction and the oxygen reduction reaction is critical for rechargeable metal-air batteries. Here we present lithium cobalt oxide, synthesized at 400 °C (designated as LT-LiCoO2) that adopts a lithiated spinel structure, as an inexpensive, efficient electrocatalyst for the oxygen evolution reaction. The catalytic activity of LT-LiCoO2 is higher than that of both spinel cobalt oxide and layered lithium cobalt oxide synthesized at 800 °C (designated as HT-LiCoO2) for the oxygen evolution reaction. Although LT-LiCoO2 exhibits poor activity for the oxygen reduction reaction, the chemically delithiated LT-Li1-xCoO2 samples exhibit a combination of high oxygen reduction reaction and oxygen evolution reaction activities, making the spinel-type LT-Li0,5CoO2 a potential bifunctional electrocatalyst for rechargeable metal-air batteries. The high activities of these delithiated compositions are attributed to the Co4O4 cubane subunits and a pinning of the Co(3+/4+):3d energy with the top of the O(2-):2p band.

  18. Potential CO2 emission reduction by development of non-grain-based bioethanol in China.

    PubMed

    Li, Hongqiang; Wang, Limao; Shen, Lei

    2010-10-01

    Assessment of the potential CO(2) 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, CO(2) reduction coefficient of bioethanol, and assessment model of CO(2) emission reduction potential of bioethanol are proposed and established to assess the potential CO(2) 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 CO(2) 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.

  19. Investigation on Burden Particle Softening and Melting Process under High Reduction Potential Condition

    NASA Astrophysics Data System (ADS)

    Guo, Wentao; Xue, Qingguo; Liu, Yingli; She, Xuefeng; Wang, Jingsong

    2016-09-01

    The present study using a single-particle softening under a load equipment was designed to better understand the softening and melting process of pellet, sinter and a mixture of both under a high reduction potential condition. Additionally, the experiment was interrupted at different shrinkage stages, and the evolvement of particle structure was analyzed. The softening and melting behavior of ferrous burden in high reduction potential compared with the general conditions was ascertained. In comparison with the general case, the thickness of the iron shell and the fineness of the metallic iron phase increased in high reduction potential. In the general condition the melting process is impacted by the low melting point of the slag with wustite outflow from the metallic iron shell, while in high reduction potential, the higher melting point of the slag without wustite exuded from the metallic iron phase. Under high reduction potential, the liquid slag was distributed in the metallic iron phase, which hindered the interaction between pellet and sinter. Thus, the temperature of interaction in high reduction potential is obviously higher than that in the general condition. The thicker iron shell and the higher melting point of slag lead to the improvement of the softening behavior under high reduction potential.

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

    NASA Astrophysics Data System (ADS)

    Li, Hongqiang; Wang, Limao; Shen, Lei

    2010-10-01

    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.

  1. Determinants of the relative reduction potentials of type-1 copper sites in proteins.

    PubMed

    Li, Hui; Webb, Simon P; Ivanic, Joseph; Jensen, Jan H

    2004-06-30

    The relative Cu(2+)/Cu(+) reduction potentials of six type-1 copper sites (cucumber stellacyanin, P. aeruginosa azurin, poplar plastocyanin, C. cinereus laccase, T. ferrooxidans rusticyanin, and human ceruloplasmin), which lie in a reduction potential range from 260 mV to over 1000 mV, have been studied by quantum mechanical calculations. The range and relative orderings of the reduction potentials are reproduced very well compared to experimental values. The study suggests that the main structural determinants of the relative reduction potentials of the blue copper sites are located within 6 A of the Cu atoms. Further analysis suggests that the reduction potential differences of type-1 copper sites are caused by axial ligand interactions, hydrogen bonding to the S(Cys), and protein constraint on the inner sphere ligand orientations. The low reduction potential of cucumber stellacyanin is due mainly to a glutamine ligand at the axial position, rather than a methionine or a hydrophobic residue as in the other proteins. A stronger interaction with a backbone carbonyl group is a prime contributor to the lower reduction potential of P. aeruginosa azurin as compared to poplar plastocyanin, whereas the reverse is true for C. cinereus laccase and T. ferrooxidans rusticyanin. The lack of an axial methonine ligand also contributes significantly to the increased reduction potentials of C. cinereus laccase and human ceruloplasmin. However, in the case of C. cinereus laccase, this increase is attenuated by the presence of only one amide NH hydrogen bond to the S(Cys) rather than two in the other proteins. In human ceruloplasmin the reduction potential is further increased by the structural distortion of the equatorial ligand orientation. PMID:15212551

  2. Multifunctional Low-Pressure Turbine for Core Noise Reduction, Improved Efficiency, and Nitrogen Oxide (NOx) Reduction

    NASA Technical Reports Server (NTRS)

    Miller, Christopher J.; Shyam, Vikram; Rigby, David L.

    2013-01-01

    This work studied the feasibility of using Helmholtz resonator cavities embedded in low-pressure-turbine (LPT) airfoils to (1) reduce core noise by damping acoustic modes; (2) use the synthetic jets produced by the liner hole acoustic oscillations to improve engine efficiency by maintaining turbulent attached flow in the LPT at low-Reynolds-number cruise conditions; and (3) reduce engine nitrogen oxide emissions by lining the internal cavities with materials capable of catalytic conversion. Flat plates with embedded Helmholtz resonators, designed to resonate at either 3000 or at 400 Hz, were simulated using computational fluid dynamics. The simulations were conducted for two inlet Mach numbers, 0.25 and 0.5, corresponding to Reynolds numbers of 90 000 and 164 000 based on the effective chordwise distance to the resonator orifice. The results of this study are (1) the region of acoustic treatment may be large enough to have a benefit; (2) the jets may not possess sufficient strength to reduce flow separation (based on prior work by researchers in the flow control area); and (3) the additional catalytic surface area is not exposed to a high velocity, so it probably does not have any benefit.

  3. Characterization study of polycrystalline tin oxide surfaces before and after reduction in CO

    NASA Technical Reports Server (NTRS)

    Drawdy, Jean E.; Hoflund, Gar B.; Davidson, Mark R.; Schryer, David R.

    1990-01-01

    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 stimulated desorption (ESD). The changes in the surface composition and chemical states of the surface species generally are subtle for the reductive conditions used. However, significant changes do occur with regard to the amounts and the chemical forms of the hydrogen-containing species remaining after both the 100 and 175 C reductions.

  4. Relationship Between Iron Whisker Growth and Doping Amount of Oxide During Fe2O3 Reduction

    NASA Astrophysics Data System (ADS)

    Gong, Xuzhong; Zhao, Zhilong; Wang, Zhi; Zhang, Ben; Guo, Lei; Guo, Zhancheng

    2016-04-01

    Iron whisker growth during Fe2O3 doped with oxide reduced by CO was investigated by using in situ observation and scanning electron microscopy. The results indicated that the minimum doping amount (MDA) of various oxides, hindering the iron whisker growth, was different. The MDA of Al2O3, Li2O, Na2O, and K2O was 0.5, 0.4, 4, and 12 pct, respectively. From the reduction rate, it was found that Li2O, MgO, and Al2O3 had some suppressive effects on the Fe2O3 reduction process, thus, confining the growth of iron whisker. However, other oxides had some catalytic effects on the Fe2O3 reduction process (Fe2O3-Fe3O4-FeO-Fe), such as CaO, SrO, BaO, Na2O, and K2O. As long as their doping amount was enough, these oxides could inhibit the diffusion of the Fe atom. When the metal ionic radius in doped oxide was bigger than that of Fe3+, such as Ca2+, Sr2+, Ba2+, Na+, and K+, there were lots of spaces left in Fe2O3 doped with oxide after reduction, improving Fe atom diffusion. Consequently, their MDA was more than that of small radius to restrain the growth of iron whisker. Finally, the relationship between corresponding metal ionic radius, electron layer number, valence electron number, and MDA of oxide was expressed by using data fitting as follows: N_{{{{A}}y {{O}}x }} = 1.3 × 10^{ - 5} × {r_{{{{A}}^{x + } }}2 × √{n_{{{{A}}^{x + } }} } }/{f_{q }}

  5. Pyrite oxidation and reduction - Molecular orbital theory considerations. [for geochemical redox processes

    NASA Technical Reports Server (NTRS)

    Luther, George W., III

    1987-01-01

    In this paper, molecular orbital theory is used to explain a heterogeneous reaction mechanism for both pyrite oxidation and reduction. The mechanism demonstrates that the oxidation of FeS2 by Fe(3+) may occur as a result of three important criteria: (1) the presence of a suitable oxidant having a vacant orbital (in case of liquid phase) or site (solid phase) to bind to the FeS2 via sulfur; (2) the initial formation of a persulfido (disulfide) bridge between FeS2 and the oxidant, and (3) an electron transfer from a pi(asterisk) orbital in S2(2-) to a pi or pi(asterisk) orbital of the oxidant.

  6. Redox Potentials, Laccase Oxidation, and Antilarval Activities of Substituted Phenols

    PubMed Central

    Prasain, Keshar; Nguyen, Thi D. T.; Gorman, Maureen J.; Barrigan, Lydia M.; Peng, Zeyu; Kanost, Michael R.; Syed, Lateef U.; Li, Jun; Zhu, Kun Yan; Hua, Duy H.

    2012-01-01

    Laccases are copper-containing oxidases that are involved in sclerotization of the cuticle of mosquitoes and other insects. Oxidation of exogenous compounds by insect laccases may have the potential to produce reactive species toxic to insects. We investigated two classes of substituted phenolic compounds, halogenated di- and trihydroxybenzenes and substituted di-tert-butylphenols, on redox potential, oxidation by laccase and effects on mosquito larval growth. An inverse correlation between the oxidation potentials and laccase activity of halogenated hydroxybenzenes was found. Substituted di-tert-butylphenols however were found to impact mosquito larval growth and survival. In particular, 2,4-di-tert-butyl-6-(3-methyl-2-butenyl)phenol (15) caused greater than 98% mortality of Anopheles gambiae larvae in a concentration of 180 nM, whereas 2-(3,5-di-tert-butyl-4-hydroxyphenyl)-2-methylpropanal oxime (13) and 6,8-di-tert-butyl-2,2-dimethyl-3,4-dihydro-2H-chromene (33) caused 93% and 92% mortalities in concentrations of 3.4 and 3.7 μM, respectively. Larvae treated with di-tert-butylphenolic compounds died just before pupation. PMID:22300888

  7. High rates of anaerobic methane oxidation in freshwater wetlands reduce potential atmospheric methane emissions.

    PubMed

    Segarra, K E A; Schubotz, F; Samarkin, V; Yoshinaga, M Y; Hinrichs, K-U; Joye, S B

    2015-06-30

    The role of anaerobic oxidation of methane (AOM) in wetlands, the largest natural source of atmospheric methane, is poorly constrained. Here we report rates of microbially mediated AOM (average rate=20 nmol cm(-3) per day) in three freshwater wetlands that span multiple biogeographical provinces. The observed AOM rates rival those in marine environments. Most AOM activity may have been coupled to sulphate reduction, but other electron acceptors remain feasible. Lipid biomarkers typically associated with anaerobic methane-oxidizing archaea were more enriched in (13)C than those characteristic of marine systems, potentially due to distinct microbial metabolic pathways or dilution with heterotrophic isotope signals. On the basis of this extensive data set, AOM in freshwater wetlands may consume 200 Tg methane per year, reducing their potential methane emissions by over 50%. These findings challenge precepts surrounding wetland carbon cycling and demonstrate the environmental relevance of an anaerobic methane sink in ecosystems traditionally considered strong methane sources.

  8. Enhanced reduction of Fe(III) oxides and methyl orange by Klebsiella oxytoca in presence of anthraquinone-2-disulfonate.

    PubMed

    Yu, Lei; Wang, Shi; Tang, Qing-Wen; Cao, Ming-Yue; Li, Jia; Yuan, Kun; Wang, Ping; Li, Wen-Wei

    2016-05-01

    Klebsiella oxytoca GS-4-08 is capable of azo dye reduction, but its quinone respiration and Fe(III) reduction abilities have not been reported so far. In this study, the abilities of this strain were reported in detail for the first time. As the biotic reduction of Fe(III) plays an important role in the biogeochemical cycles, two amorphous Fe(III) oxides were tested as the sole electron acceptor during the anaerobic respiration of strain GS-4-08. For the reduction of goethite and hematite, the biogenic Fe(II) concentrations reached 0.06 and 0.15 mM, respectively. Humic acid analog anthraquinone-2-disulfonate (AQS) was found to serve as an electron shuttle to increase the reduction of both methyl orange (MO) and amorphous Fe(III) oxides, and improve the dye tolerance of the strain. However, the formation of Fe(II) was not accelerated by biologically reduced AQS (B-AH2QS) because of the high bioavailability of soluble Fe(III). For the K. oxytoca strain, high soluble Fe(III) concentrations (above 1 mM) limit its growth and decolorization ability, while lower soluble Fe(III) concentrations produce an electron competition with MO initially, and then stimulate the decolorization after the electron couples of Fe(III)/Fe(II) are formed. With the ability to respire both soluble Fe(III) and insoluble Fe(III) oxides, this formerly known azo-reducer may be used as a promising model organism for the study of the interaction of these potentially competing processes in contaminated environments. PMID:26762391

  9. Synthesis of reduced graphene oxide (rGO) via chemical reduction

    SciTech Connect

    Thakur, Alpana Rangra, V. S.; Kumar, Sunil

    2015-05-15

    Natural flake Graphite was used as the starting material for the graphene synthesis. In the first step flake graphite was treated with oxidizing agents under vigorous conditions to obtain graphite oxide. Layered graphite oxide decorated with oxygen has large inter-layer distance leading easy exfoliation into single sheets by ultrasonication giving graphene oxide. In the last step exfoliated graphene oxide sheets were reduced slowly with the help of reducing agent to obtain fine powder which is labeled as reduced graphene oxide (rGO). This rGO was further characterized by X-Ray Diffraction (XRD), Scanning Tunneling Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR), Raman Spectroscopy techniques. XRD pattern shows peaks corresponding to (002) graphitic lattice planes indicating the formation of network of sp{sup 2} like carbon structure. SEM images show the ultrathin, wrinkled, paper-like morphology of graphene sheets. IR study shows that the graphite has been oxidized to graphite oxide with the presence of various absorption bands confirming the presence of oxidizing groups. The FTIR spectrum of rGO shows no sharp peaks confirming the efficient reduction of rGO. The Raman spectrum shows disorder in the graphene sheets.

  10. Explosive thermal reduction of graphene oxide-based materials: mechanism and safety implications.

    PubMed

    Qiu, Yang; Guo, Fei; Hurt, Robert; Külaots, Indrek

    2014-06-01

    Thermal reduction of graphene oxide or graphite oxide (GO) is an important processing step in the fabrication of many graphene-based materials and devices. Here we show that some bulk solid GO samples can undergo explosive decomposition when small samples are heated slowly in inert gas environments, while others do not. These micro-explosions can occur for samples as small as few milligrams and are sufficiently energetic to cause laboratory equipment damage. Thermochemical analysis methods are used to understand the factors that lead to the explosive reduction mode. The studies show that the explosive mode of reduction is caused by the exothermicity of GO reduction coupled with a threshold sample mass/size that causes heat and mass transfer limitations leading to local temperature rise and a thermal runaway reaction. The explosive mode of reduction is not caused or promoted by interstitial water, and its onset temperature can be lowered by immersion in potassium hydroxide solution. By allowing early release of internal gas pressure, the explosive mode reduces the extent of surface area development in GO exfoliation from an optimum value of 1470 m(2)g(-1) obtained under non-explosive reduction conditions. Explosive reduction of bulk GO poses industrial safety hazards during large-scale storage, handling, and processing.

  11. Explosive thermal reduction of graphene oxide-based materials: mechanism and safety implications

    PubMed Central

    Qiu, Yang; Guo, Fei; Hurt, Robert; Külaots, Indrek

    2014-01-01

    Thermal reduction of graphene oxide or graphite oxide (GO) is an important processing step in the fabrication of many graphene-based materials and devices. Here we show that some bulk solid GO samples can undergo explosive decomposition when small samples are heated slowly in inert gas environments, while others do not. These micro-explosions can occur for samples as small as few milligrams and are sufficiently energetic to cause laboratory equipment damage. Thermochemical analysis methods are used to understand the factors that lead to the explosive reduction mode. The studies show that the explosive mode of reduction is caused by the exothermicity of GO reduction coupled with a threshold sample mass/size that causes heat and mass transfer limitations leading to local temperature rise and a thermal runaway reaction. The explosive mode of reduction is not caused or promoted by interstitial water, and its onset temperature can be lowered by immersion in potassium hydroxide solution. By allowing early release of internal gas pressure, the explosive mode reduces the extent of surface area development in GO exfoliation from an optimum value of 1470 m2g−1 obtained under non-explosive reduction conditions. Explosive reduction of bulk GO poses industrial safety hazards during large-scale storage, handling, and processing. PMID:25018560

  12. Reduction of coherence of the human brain electric potentials

    NASA Astrophysics Data System (ADS)

    Novik, Oleg; Smirnov, Fedor

    Plenty of technological processes are known to be damaged by magnetic storms. But technology is controlled by men and their functional systems may be damaged as well. We are going to consider the electro-neurophysiological aspect of the general problem: men surrounded by physical fields including ones of cosmic origination. Magnetic storms’ influence had been observed for a group of 13 students (practically healthy girls and boys from 18 to 23 years old, Moscow). To control the main functional systems of the examinees, their electroencephalograms (EEG) were being registered along with electrocardiograms, respiratory rhythms, arterial blood pressure and other characteristics during a year. All of these characteristics, save for the EEG, were within the normal range for all of the examinees during measurements. According to the EEG investigations by implementation of the computer proof-reading test in absence of magnetic storms, the values of the coherence function of time series of the theta-rhythm oscillations (f = 4 - 7.9 Hz, A = 20 μV) of electric potentials of the frontal-polar and occipital areas of the head belong to the interval [0.3, 0.8] for all of the students under investigation. (As the proof-reading test, it was necessary to choose given symbols from a random sequence of ones demonstrated at a monitor and to enter the number of the symbols discovered in a computer. Everyone was known that the time for determination of symbols is unlimited. On the other hand, nobody was known that the EEG and other registrations mentioned are connected with electromagnetic geophysical researches and geomagnetic storms). Let us formulate the main result: by implementation of the same test during a magnetic storm, 5 ≤ K ≤ 6, or no later then 24 hours after its beginning (different types of moderate magnetic storms occurred, the data of IZMIRAN were used), the values of the theta-rhythm frontal - occipital coherence function of all of the students of the group under

  13. In-Situ Chemical Reduction and Oxidation of VOCs in Groundwater: Groundwater Treatability Studies

    NASA Technical Reports Server (NTRS)

    Keith, Amy; Glasgow, Jason; McCaleh, Rececca C. (Technical Monitor)

    2001-01-01

    This paper presents NASA Marshall Space Flight Center's treatability studies for volatile organic compounds in groundwater. In-Situ groundwater treatment technologies include: 1) Chemical Reduction(Ferox); 2) Chemical Oxidation (Fenton Reagents, Permanganate, and Persulfate); and 3) Thermal (Dynamic Underground Stripping, Six-Phase Heating). This paper is presented in viewgraph form.

  14. Synthesis of carbon-encapsulated iron nanoparticles via solid state reduction of iron oxide nanoparticles

    SciTech Connect

    Bystrzejewski, M.

    2011-06-15

    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%.

  15. The Simulation of an Oxidation-Reduction Titration Curve with Computer Algebra

    ERIC Educational Resources Information Center

    Whiteley, Richard V., Jr.

    2015-01-01

    Although the simulation of an oxidation/reduction titration curve is an important exercise in an undergraduate course in quantitative analysis, that exercise is frequently simplified to accommodate computational limitations. With the use of readily available computer algebra systems, however, such curves for complicated systems can be generated…

  16. Some Aspects of Oxidation-Reduction Reactions under Carbon-Bearing Flux Welding

    NASA Astrophysics Data System (ADS)

    Kryukov, R. E.; Kozyrev, N. A.; Galevsky, G. V.; Bendre, Y. V.; Goryushkin, V. F.; Valuev, D. V.

    2015-09-01

    The authors have completed thermodynamic calculations of oxidation-reduction processes under submerged arc welding with application of carbon containing additive. The calculations have shown that carbon, due to its high reducing properties under T = 1950 - 2200 K, introduced into the system can significantly decrease the amount of non-metallic inclusions in the weld metal and so improve its mechanical properties.

  17. Theoretical simulation of the reduction of graphene oxide by lithium naphthalenide.

    PubMed

    Chen, Chu; Kong, Weixing; Duan, Haiming; Zhang, Jun

    2015-05-28

    Based on density functional theory, we investigated the mechanism of graphene oxide reduction by lithium naphthalenide (C10H8Li). C10H8(-) easily reacts with GO to form a neutral C10H8 and the negatively charged GO, which can attach to Li(+) ions to form lithium oxide on a graphene skeleton. The reduction mechanism is similar to the reduction of GO by metallic Li; the C10H8 is used to disperse Li in THF solution. Furthermore, the lithium oxide on GO can react with CO2 to form Li2CO3 and be further reduced by MeOH washing. In the negatively charged GO, the carboxyl at the edge of GO transfers an electron to GO and releases a CO2 molecule by overcoming a barrier of 0.19 eV. CO2 can also be adsorbed by lithium oxide to form Li2CO3 that is tightly attached on graphene skeleton. After GO is partially reduced, the adsorption of CO2 eliminates O in the form of Li2CO3 without any barrier. This mechanism can be helpful for further understanding the nature of GO reduction among various reducing agents and for exploring new and efficient GO reducing agents.

  18. The co-immobilization of P450-type nitric oxide reductase and glucose dehydrogenase for the continuous reduction of nitric oxide via cofactor recycling.

    PubMed

    Garny, Seike; Beeton-Kempen, Natasha; Gerber, Isak; Verschoor, Jan; Jordaan, Justin

    2016-04-01

    The co-immobilization of enzymes on target surfaces facilitates the development of self-contained, multi-enzyme biocatalytic platforms. This generally entails the co-immobilization of an enzyme with catalytic value in combination with another enzyme that performs a complementary function, such as the recycling of a critical cofactor. In this study, we co-immobilized two enzymes from different biological sources for the continuous reduction of nitric oxide, using epoxide- and carboxyl-functionalized hyper-porous microspheres. Successful co-immobilization of a fungal nitric oxide reductase (a member of the cytochrome P450 enzyme family) and a bacterial glucose dehydrogenase was obtained with the carboxyl-functionalized microspheres, with enzyme activity maintenance of 158% for nitric oxide reductase and 104% for glucose dehydrogenase. The optimal stoichiometric ratio of these two enzymes was subsequently determined to enable the two independent chemical reactions to be catalyzed concomitantly, allowing for near-synchronous cofactor conversion rates. This dual-enzyme system provides a novel research tool with potential for in vitro investigations of nitric oxide, and further demonstrates the successful immobilization of a P450 enzyme with potential application towards the immobilization of other cytochrome P450 enzymes.

  19. Maillard reaction, mitochondria and oxidative stress: potential role of antioxidants.

    PubMed

    Edeas, M; Attaf, D; Mailfert, A-S; Nasu, M; Joubet, R

    2010-06-01

    Glycation and oxidative stress are two important processes known to play a key role in complications of many disease processes. Oxidative stress, either via increasing reactive oxygen species (ROS), or by depleting the antioxidants may modulate the genesis of early glycated proteins in vivo. Maillard Reactions, occur in vivo as well as in vitro and are associated with the chronic complications of diabetes, aging and age-related diseases. Hyperglycaemia causes the autoxidation of glucose, glycation of proteins, and the activation of polyol metabolism. These changes facilitate the generation of reactive oxygen species and decrease the activity of antioxidant enzymes such as Cu,Zn-superoxide dismutase, resulting in a remarkable increase of oxidative stress. A large body of evidence indicates that mitochondria alteration is involved and plays a central role in various oxidative stress-related diseases. The damaged mitochondria produce more ROS (increase oxidative stress) and less ATP (cellular energy) than normal mitochondria. As they are damaged, they cannot burn or use glucose or lipid and cannot provide cell with ATP. Further, glucose, amino acids and lipid will not be correctly used and will accumulate outside the mitochondria; they will undergo more glycation (as observed in diabetes, obesity, HIV infection and lipodystrophia). The objective of this paper is to discuss how to stop the vicious circle established between oxidative stress, Maillard Reaction and mitochondria. The potential application of some antioxidants to reduce glycation phenomenon and to increase the antioxidant defence system by targeting mitochondria will be discussed. Food and pharmaceutical companies share the same challenge, they must act now, urgently and energetically. PMID:20031340

  20. Advanced experimental analysis of controls on microbial Fe(III) oxide reduction. First year progress report

    SciTech Connect

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

    1997-07-01

    '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

  1. Plasma in-liquid method for reduction of zinc oxide in zinc nanoparticle synthesis

    NASA Astrophysics Data System (ADS)

    Amaliyah, Novriany; Mukasa, Shinobu; Nomura, Shinfuku; Toyota, Hiromichi; Kitamae, Tomohide

    2015-02-01

    Metal air-batteries with high-energy density are expected to be increasingly applied in electric vehicles. This will require a method of recycling air batteries, and reduction of metal oxide by generating plasma in liquid has been proposed as a possible method. Microwave-induced plasma is generated in ethanol as a reducing agent in which zinc oxide is dispersed. Analysis by energy-dispersive x-ray spectrometry (EDS) and x-ray diffraction (XRD) reveals the reduction of zinc oxide. According to images by transmission electron microscopy (TEM), cubic and hexagonal metallic zinc particles are formed in sizes of 30 to 200 nm. Additionally, spherical fiber flocculates approximately 180 nm in diameter are present.

  2. Reduction Kinetics of Electric Arc Furnace Oxidizing Slag by Al-Fe Alloy

    NASA Astrophysics Data System (ADS)

    Lee, Jaehong; Oh, Joon Seok; Lee, Joonho

    2016-07-01

    Effects of temperature and slag basicity on the reduction rate of iron oxide in molten synthetic electric arc furnace oxidizing slag by Al-40 wt.%Fe alloy was investigated. An alloy sample was dropped into molten slag in an MgO crucible. When the initial slag temperature was 1723 K, there was no reduction. However, when the initial slag temperature was 1773 K and the slag basicity was 1.1, the reduction was initiated and the temperature of the slag rapidly increased. When the slag basicity was 1.1, increasing the initial slag temperature from 1773 K to 1823 K increases the reaction rate. As the slag basicity increased from 1.1 to 1.4 at 1773 K, the reaction rate increased. From SEM analysis, it was found that an Al2O3 or a spinel phase at the slag-metal interface inhibited the reaction at a lower temperature and a lower slag basicity.

  3. Reduction Kinetics of Electric Arc Furnace Oxidizing Slag by Al-Fe Alloy

    NASA Astrophysics Data System (ADS)

    Lee, Jaehong; Oh, Joon Seok; Lee, Joonho

    2016-09-01

    Effects of temperature and slag basicity on the reduction rate of iron oxide in molten synthetic electric arc furnace oxidizing slag by Al-40 wt.%Fe alloy was investigated. An alloy sample was dropped into molten slag in an MgO crucible. When the initial slag temperature was 1723 K, there was no reduction. However, when the initial slag temperature was 1773 K and the slag basicity was 1.1, the reduction was initiated and the temperature of the slag rapidly increased. When the slag basicity was 1.1, increasing the initial slag temperature from 1773 K to 1823 K increases the reaction rate. As the slag basicity increased from 1.1 to 1.4 at 1773 K, the reaction rate increased. From SEM analysis, it was found that an Al2O3 or a spinel phase at the slag-metal interface inhibited the reaction at a lower temperature and a lower slag basicity.

  4. A One-Step, Solvothermal Reduction Method for Producing Reduced Graphene Oxide Dispersions in Organic Solvents

    PubMed Central

    Dubin, Sergey; Gilje, Scott; Wang, Kan; Tung, Vincent C.; Cha, Kitty; Hall, Anthony S.; Farrar, Jabari; Varshneya, Rupal; Yang, Yang; Kaner, Richard B.

    2014-01-01

    Refluxing graphene oxide (GO) in N-methyl-2-pyrrolidinone (NMP) results in deoxygenation and reduction to yield a stable colloidal dispersion. The solvothermal reduction is accompanied by a color change from light brown to black. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) images of the product confirm the presence of single sheets of the solvothermally reduced graphene oxide (SRGO). X-ray photoelectron spectroscopy (XPS) of SRGO indicates a significant increase in intensity of the C=C bond character, while the oxygen content decreases markedly after the reduction is complete. X-ray diffraction analysis of SRGO shows a single broad peak at 26.24° 2θ (3.4 Å), confirming the presence of graphitic stacking of reduced sheets. SRGO sheets are redispersible in a variety of organic solvents, which may hold promise as an acceptor material for bulk heterojunction photovoltaic cells, or electromagnetic interference shielding applications. PMID:20586422

  5. Dominance of sulfur-fueled iron oxide reduction in low-sulfate freshwater sediments.

    PubMed

    Hansel, Colleen M; Lentini, Chris J; Tang, Yuanzhi; Johnston, David T; Wankel, Scott D; Jardine, Philip M

    2015-11-01

    A central tenant in microbial biogeochemistry is that microbial metabolisms follow a predictable sequence of terminal electron acceptors based on the energetic yield for the reaction. It is thereby oftentimes assumed that microbial respiration of ferric iron outcompetes sulfate in all but high-sulfate systems, and thus sulfide has little influence on freshwater or terrestrial iron cycling. Observations of sulfate reduction in low-sulfate environments have been attributed to the presumed presence of highly crystalline iron oxides allowing sulfate reduction to be more energetically favored. Here we identified the iron-reducing processes under low-sulfate conditions within columns containing freshwater sediments amended with structurally diverse iron oxides and fermentation products that fuel anaerobic respiration. We show that despite low sulfate concentrations and regardless of iron oxide substrate (ferrihydrite, Al-ferrihydrite, goethite, hematite), sulfidization was a dominant pathway in iron reduction. This process was mediated by (re)cycling of sulfur upon reaction of sulfide and iron oxides to support continued sulfur-based respiration--a cryptic sulfur cycle involving generation and consumption of sulfur intermediates. Although canonical iron respiration was not observed in the sediments amended with the more crystalline iron oxides, iron respiration did become dominant in the presence of ferrihydrite once sulfate was consumed. Thus, despite more favorable energetics, ferrihydrite reduction did not precede sulfate reduction and instead an inverse redox zonation was observed. These findings indicate that sulfur (re)cycling is a dominant force in iron cycling even in low-sulfate systems and in a manner difficult to predict using the classical thermodynamic ladder.

  6. Morphine as a Potential Oxidative Stress-Causing Agent

    PubMed Central

    Skrabalova, Jitka; Drastichova, Zdenka; Novotny, Jiri

    2013-01-01

    Morphine exhibits important pharmacological effects for which it has been used in medical practice for quite a long time. However, it has a high addictive potential and can be abused. Long-term use of this drug can be connected with some pathological consequences including neurotoxicity and neuronal dysfunction, hepatotoxicity, kidney dysfunction, oxidative stress and apoptosis. Therefore, most studies examining the impact of morphine have been aimed at determining the effects induced by chronic morphine exposure in the brain, liver, cardiovascular system and macrophages. It appears that different tissues may respond to morphine diversely and are distinctly susceptible to oxidative stress and subsequent oxidative damage of biomolecules. Importantly, production of reactive oxygen/nitrogen species induced by morphine, which have been observed under different experimental conditions, can contribute to some pathological processes, degenerative diseases and organ dysfunctions occurring in morphine abusers or morphine-treated patients. This review attempts to provide insights into the possible relationship between morphine actions and oxidative stress. PMID:24376392

  7. Oxidative Dissolution Potential of Biogenic and Abiogenic TcO2 in Subsurface Sediments

    SciTech Connect

    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

    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

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

    NASA Astrophysics Data System (ADS)

    Halder, S.; Fruehan, R. J.

    2008-12-01

    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.

  9. Reductions in Northeast Refining Activity: Potential Implications for Petroleum Product Markets

    EIA Publications

    2011-01-01

    This report is the Energy Information Administration's (EIA) initial effort to provide information and analysis on the potential impacts on petroleum product markets from reductions in Northeast petroleum refining activity.

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

    ERIC Educational Resources Information Center

    Tanis, David O.

    1990-01-01

    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)

  11. Biomineralization Associated with Microbial Reduction of Fe3+ and Oxidation of Fe2+ in Solid Minerals

    SciTech Connect

    Zhang, Gengxin; Dong, Hailiang; Jiang, Hongchen; Kukkadapu, Ravi K.; Kim, Jinwook; Eberl, Dennis D.; Xu, Zhiqin

    2009-07-01

    Iron- reducing and oxidizing microorganisms gain energy through reduction or oxidation of iron, and by doing so they play an important role in geochemical cycling of iron in a wide range of environments. This study was undertaken to investigate iron redox cycling in the deep subsurface by taking an advantage of the Chinese Continental Scientific Deep Drilling project. A fluid sample from 2450 m was collected and Fe(III)-reducing microorganisms were enriched using specific media (pH 6.2). Nontronite, an Fe(III)-rich clay mineral, was used in initial enrichments with lactate and acetate as electron donors under strictly anaerobic condition at the in-situ temperature of the fluid sample (65oC). Instead of a monotonic increase in Fe(II) concentration with time as would have been expected if Fe(III) bioreduction was the sole process, Fe(II) concentration initially increased, reached a peak, but then decreased to a minimum level. Continued incubation revealed an iron cycling with a cycling period of five to ten days. These initial results suggested that there might be Fe(III) reducers and Fe(II) oxidizers in the enrichment culture. Subsequently, multiple transfers were made with an attempt to isolate individual Fe(III) reducers and Fe(II) oxidizers. However, iron cycling persisted after multiple transfers. Additional experiments were conducted to ensure that iron reduction and oxidation was indeed biological. Biological Fe(II) oxidation was further confirmed in a series of roll tubes (with a pH gradient) where FeS and siderite were used as the sole electron donor. The oxidation of FeS occurred only at pH 10, and goethite, lepidocrocite, and ferrihydrite formed as oxidation products. Although molecular evidence (16S rRNA gene analysis) collectively suggested that only a single organism (a strain of Thermoanaerobacter ethanolicus) might be responsible for both Fe(III) reduction and Fe(II) oxidation, we could not rule out the possibility that Fe(III) reduction and Fe

  12. Reduction and persulfate oxidation of nitro explosives in contaminated soils using Fe-bearing materials.

    PubMed

    Oh, Seok-Young; Yoon, Hyun-Su; Jeong, Tae-Yong; Kim, Sang Don; Kim, Dong-Wook

    2016-07-13

    The oxidative and reductive transformation of nitro explosives in contaminated soils with Fe-bearing materials and persulfate (S2O8(2-)) was examined via batch experiments. Zero-valent cast iron [Fe(0)], steel dust from a steel manufacturing plant, and FeS rapidly reduced 2,4,6-trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in soil under anaerobic conditions as long as a sufficient amount of water was present. The Fe-bearing materials also effectively activated persulfate to enhance the oxidative transformation of TNT and RDX in soil-water systems. Kinetically, reductive and oxidative transformations removed more than 90% of the explosives from a soil-water system within 5 h under the given conditions. Pseudo-first-order rates in the range of 0.7-23.4 h(-1) were observed. By increasing the concentration of persulfate or Fe-bearing materials, the oxidative transformation could be promoted. Treated soils via redox reactions using the Fe-bearing materials did not show significant toxicity, except for the case of TNT-contaminated soils oxidized by FeS-assisted persulfate. Considering the kinetics of explosive degradation and the toxicity of treated wastewaters and soils, Fe(0) or steel dust-assisted persulfate oxidation may be a safe option as an ex situ remediation process for the treatment of explosive-contaminated soils.

  13. Reduction and persulfate oxidation of nitro explosives in contaminated soils using Fe-bearing materials.

    PubMed

    Oh, Seok-Young; Yoon, Hyun-Su; Jeong, Tae-Yong; Kim, Sang Don; Kim, Dong-Wook

    2016-07-13

    The oxidative and reductive transformation of nitro explosives in contaminated soils with Fe-bearing materials and persulfate (S2O8(2-)) was examined via batch experiments. Zero-valent cast iron [Fe(0)], steel dust from a steel manufacturing plant, and FeS rapidly reduced 2,4,6-trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in soil under anaerobic conditions as long as a sufficient amount of water was present. The Fe-bearing materials also effectively activated persulfate to enhance the oxidative transformation of TNT and RDX in soil-water systems. Kinetically, reductive and oxidative transformations removed more than 90% of the explosives from a soil-water system within 5 h under the given conditions. Pseudo-first-order rates in the range of 0.7-23.4 h(-1) were observed. By increasing the concentration of persulfate or Fe-bearing materials, the oxidative transformation could be promoted. Treated soils via redox reactions using the Fe-bearing materials did not show significant toxicity, except for the case of TNT-contaminated soils oxidized by FeS-assisted persulfate. Considering the kinetics of explosive degradation and the toxicity of treated wastewaters and soils, Fe(0) or steel dust-assisted persulfate oxidation may be a safe option as an ex situ remediation process for the treatment of explosive-contaminated soils. PMID:27327861

  14. Flat-Band Potentials of Molecularly Thin Metal Oxide Nanosheets.

    PubMed

    Xu, Pengtao; Milstein, Tyler J; Mallouk, Thomas E

    2016-05-11

    Exfoliated nanosheets derived from Dion-Jacobson phase layer perovskites (TBAxH1-xA2B3O10, A = Sr, Ca, B = Nb, Ta) were grown layer-by-layer on fluorine-doped tin oxide and gold electrode surfaces. Electrochemical impedance spectra (EIS) of the five-layer nanosheet films in contact with aqueous electrolyte solutions were analyzed by the Mott-Schottky method to obtain flat-band potentials (VFB) of the oxide semiconductors as a function of pH. Despite capacitive contributions from the electrode-solution interface, reliable values could be obtained from capacitance measurements over a limited potential range near VFB. The measured values of VFB shifted -59 mV/pH over the pH range of 4-8 and were in close agreement with the empirical correlation between conduction band-edge potentials and optical band gaps proposed by Matsumoto ( J. Solid State Chem. 1996, 126 (2), 227-234 ). Density functional theory calculations showed that A-site substitution influenced band energies by modulating the strength of A-O bonding, and that subsitution of Ta for Nb on B-sites resulted in a negative shift of the conduction band-edge potential. PMID:27102083

  15. Flat-Band Potentials of Molecularly Thin Metal Oxide Nanosheets.

    PubMed

    Xu, Pengtao; Milstein, Tyler J; Mallouk, Thomas E

    2016-05-11

    Exfoliated nanosheets derived from Dion-Jacobson phase layer perovskites (TBAxH1-xA2B3O10, A = Sr, Ca, B = Nb, Ta) were grown layer-by-layer on fluorine-doped tin oxide and gold electrode surfaces. Electrochemical impedance spectra (EIS) of the five-layer nanosheet films in contact with aqueous electrolyte solutions were analyzed by the Mott-Schottky method to obtain flat-band potentials (VFB) of the oxide semiconductors as a function of pH. Despite capacitive contributions from the electrode-solution interface, reliable values could be obtained from capacitance measurements over a limited potential range near VFB. The measured values of VFB shifted -59 mV/pH over the pH range of 4-8 and were in close agreement with the empirical correlation between conduction band-edge potentials and optical band gaps proposed by Matsumoto ( J. Solid State Chem. 1996, 126 (2), 227-234 ). Density functional theory calculations showed that A-site substitution influenced band energies by modulating the strength of A-O bonding, and that subsitution of Ta for Nb on B-sites resulted in a negative shift of the conduction band-edge potential.

  16. Intermolecular potential energy surface and thermophysical properties of ethylene oxide

    SciTech Connect

    Crusius, Johann-Philipp Hassel, Egon; Hellmann, Robert; Bich, Eckard

    2014-10-28

    A six-dimensional potential energy hypersurface (PES) for two interacting rigid ethylene oxide (C{sub 2}H{sub 4}O) molecules was determined from high-level quantum-chemical ab initio calculations. The counterpoise-corrected supermolecular approach at the MP2 and CCSD(T) levels of theory was utilized to determine interaction energies for 10178 configurations of two molecules. An analytical site-site potential function with 19 sites per ethylene oxide molecule was fitted to the interaction energies and fine tuned to agree with data for the second acoustic virial coefficient from accurate speed of sound measurements. The PES was validated by computing the second virial coefficient, shear viscosity, and thermal conductivity. The values of these properties are substantiated by the best experimental data as they tend to fall within the uncertainty intervals and also obey the experimental temperature functions, except for viscosity, where experimental data are insufficient. Due to the lack of reliable data, especially for the transport properties, our calculated values are currently the most accurate estimates for these properties of ethylene oxide.

  17. Control of combustion-generated nitrogen oxides by selective non-catalytic reduction.

    PubMed

    Javed, M Tayyeb; Irfan, Naseem; Gibbs, B M

    2007-05-01

    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.

  18. Palladium and gold nanotubes as oxygen reduction reaction and alcohol oxidation reaction catalysts in base.

    PubMed

    Alia, Shaun M; Duong, Kathlynne; Liu, Toby; Jensen, Kurt; Yan, Yushan

    2014-06-01

    Palladium (PdNTs) and gold nanotubes (AuNTs) were synthesized by the galvanic displacement of silver nanowires. PdNTs and AuNTs have wall thicknesses of 6 nm, outer diameters of 60 nm, and lengths of 5-10 and 5-20 μm, respectively. Rotating disk electrode experiments showed that the PdNTs and AuNTs have higher area normalized activities for the oxygen reduction reaction (ORR) than conventional nanoparticle catalysts. The PdNTs produced an ORR area activity that was 3.4, 2.2, and 3.7 times greater than that on carbon-supported palladium nanoparticles (Pd/C), bulk polycrystalline palladium, and carbon-supported platinum nanoparticles (Pt/C), respectively. The AuNTs produced an ORR area activity that was 2.3, 9.0, and 2.0 times greater than that on carbon-supported gold nanoparticles (Au/C), bulk polycrystalline gold, and Pt/C, respectively. The PdNTs also had lower onset potentials than Pd/C and Pt/C for the oxidation of methanol (0.236 V), ethanol (0.215 V), and ethylene glycol (0.251 V). In comparison to Pt/C, the PdNTs and AuNTs further demonstrated improved alcohol tolerance during the ORR.

  19. Amino-modified cellulose nanocrystals with adjustable hydrophobicity from combined regioselective oxidation and reductive amination.

    PubMed

    Sirviö, Juho Antti; Visanko, Miikka; Laitinen, Ossi; Ämmälä, Ari; Liimatainen, Henrikki

    2016-01-20

    The controlled revision of surface properties to alter the hydrophobic features of nanocellulose is a potential technique to obtain materials for many novel applications and to replace oil-based materials acting as amphiphilic polyelectrolytes, among others. In this study, linear amines with increasing chain length were used to adjust the hydrophobicity of amphiphilic cellulose nanocrystals (CNCs). Methyl-, ethyl-, n-propyl-, n-butyl-, n-pentylamine, and n-hexylamine were introduced into a cellulose backbone using combined periodate oxidation and reductive amination in an aqueous environment. A high-pressure homogenizer was used to liberate a highly transparent (over 85% at visible light range) nanocrystal dispersion containing CNCs with a length of 73-131 nm and a width of 5-6 nm. All of the CNCs had similar charge density but the hydrophobicity, indicated by the contact angle measurement from the films, increased gradually from 64° to 109° as a function of amine chain length. Thus, this study demonstrated the fabrication of uniform, amphiphilic nanosized polyelectrolytes with modifiable hydrophobicity. PMID:26572390

  20. Measurement of the Md3+/Md2+ reduction potential studied with flow electrolytic chromatography.

    PubMed

    Toyoshima, Atsushi; Li, Zijie; Asai, Masato; Sato, Nozomi; Sato, Tetsuya K; Kikuchi, Takahiro; Kaneya, Yusuke; Kitatsuji, Yoshihiro; Tsukada, Kazuaki; Nagame, Yuichiro; Schädel, Matthias; Ooe, Kazuhiro; Kasamatsu, Yoshitaka; Shinohara, Atsushi; Haba, Hiromitsu; Even, Julia

    2013-11-01

    The reduction behavior of mendelevium (Md) was studied using a flow electrolytic chromatography apparatus. By application of the appropriate potentials on the chromatography column, the more stable Md(3+) is reduced to Md(2+). The reduction potential of the Md(3+) + e(-) → Md(2+) couple was determined to be -0.16 ± 0.05 V versus a normal hydrogen electrode. PMID:24116851

  1. Potential Impacts of Reductions in Refinery Activity on Northeast Petroleum Product Markets

    EIA Publications

    2012-01-01

    Potential Impacts of Reductions in Refinery Activity on Northeast Petroleum Product Markets is an update to a previous Energy Information Administration (EIA) report, Reductions in Northeast Refining Activity: Potential Implications for Petroleum Product Markets, released in December 2011. This update analyzes possible market responses and impacts in the event Sunoco's Philadelphia refinery closes this summer, in addition to the recently idled refineries on the East Coast and in the U.S. Virgin Islands.

  2. Microsensor measurements of sulfate reduction and sulfide oxidation in compact microbial communities of aerobic biofilms

    SciTech Connect

    Kuehl, M.; Joergensen, B.B. )

    1992-04-01

    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.

  3. Protein-bound acrolein: Potential markers for oxidative stress

    PubMed Central

    Uchida, Koji; Kanematsu, Masamichi; Sakai, Kensuke; Matsuda, Tsukasa; Hattori, Nobutaka; Mizuno, Yoshikuni; Suzuki, Daisuke; Miyata, Toshio; Noguchi, Noriko; Niki, Etsuo; Osawa, Toshihiko

    1998-01-01

    Acrolein (CH2=CH—CHO) is known as a ubiquitous pollutant in the environment. Here we show that this notorious aldehyde is not just a pollutant, but also a lipid peroxidation product that could be ubiquitously generated in biological systems. Upon incubation with BSA, acrolein was rapidly incorporated into the protein and generated the protein-linked carbonyl derivative, a putative marker of oxidatively modified proteins under oxidative stress. To verify the presence of protein-bound acrolein in vivo, the mAb (mAb5F6) against the acrolein-modified keyhole limpet hemocyanin was raised. It was found that the acrolein-lysine adduct, Nɛ-(3-formyl-3,4-dehydropiperidino)lysine, constitutes an epitope of the antibody. Immunohistochemical analysis of atherosclerotic lesions from a human aorta demonstrated that antigenic materials recognized by mAb5F6 indeed constituted the lesions, in which intense positivity was associated primarily with macrophage-derived foam cells and the thickening neointima of arterial walls. The observations that (i) oxidative modification of low-density lipoprotein with Cu2+ generated the acrolein-low-density lipoprotein adducts and (ii) the iron-catalyzed oxidation of arachidonate in the presence of protein resulted in the formation of antigenic materials suggested that polyunsaturated fatty acids are sources of acrolein that cause the production of protein-bound acrolein. These data suggest that the protein-bound acrolein represents potential markers of oxidative stress and long-term damage to protein in aging, atherosclerosis, and diabetes. PMID:9560197

  4. Real-time monitoring of graphene oxide reduction in acrylic printable composite inks

    NASA Astrophysics Data System (ADS)

    Porro, S.; Giardi, R.; Chiolerio, A.

    2014-06-01

    This work reports the electrical characterization of a water-based graphene oxide/acrylic composite material, which was directly inkjet printed to fabricate dissipative patterns. The graphene oxide filler, which is strongly hydrophilic due to its heavily oxygenated surface and can be readily dispersed in water, was reduced by UV irradiation during photo-curing of the polymeric matrix. The concurrent polymerization of the acrylic matrix and reduction of graphene oxide filler was demonstrated by real-time resistance measurements during UV light irradiation. The presence of graphene filler allowed decreasing the resistance of the pure polymeric matrix by nearly five orders of magnitude. This was explained by the fact that clusters of reduced graphene oxide inside the polymer matrix act as preferential pathways for the mobility of charge carriers, thus leading to an overall decrease of the material's resistance.

  5. Effect of applied voltage, initial concentration and natural organic matter on sequential reduction/oxidation of nitrobenzene by graphite electrodes

    PubMed Central

    Sun, Mei; Reible, Danny D.; Lowry, Gregory V.; Gregory, Kelvin B.

    2012-01-01

    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. PMID:22571797

  6. Oxidation potential and state of some vanadium ores and the relation of woody material to their deposition

    USGS Publications Warehouse

    Pommer, Alfred Michael

    1956-01-01

    Oxidation potential studies with a multiple pH-potential recorder designed and constructed for this purpose demonstrated that some uranium-vanadium ores in the Colorado Plateau were in a reduced state when deposited. Any oxidation which took place occurred after deposition. Experimental and theoretical reducing studies on fresh wood, wood degraded by burial for 450 years, and lignite, indicate that such ores may have been deposited by reduction of oxidized vanadium solutions by woody material. A vanadium (III) mineral, V2O(OH)4, was prepared synthetically by reduction of a vanadium (V) solution with wood. This is the only reported synthesis of any reduced vanadium mineral by any method. It was shown that the origin of almost all vanadium deposits currently of commercial importance involves life processes and products.

  7. Reduction of bacteria on spinach, lettuce, and surfaces in food service areas using neutral electrolyzed oxidizing water.

    PubMed

    Guentzel, Jane L; Liang Lam, Kang; Callan, Michael A; Emmons, Stuart A; Dunham, Valgene L

    2008-02-01

    Food safety issues and increases in food borne illnesses have promulgated the development of new sanitation methods to eliminate pathogenic organisms on foods and surfaces in food service areas. Electrolyzed oxidizing water (EO water) shows promise as an environmentally friendly broad spectrum microbial decontamination agent. EO water is generated by the passage of a dilute salt solution ( approximately 1% NaCl) through an electrochemical cell. This electrolytic process converts chloride ions and water molecules into chlorine oxidants (Cl(2), HOCl/ClO(-)). At a near-neutral pH (pH 6.3-6.5), the predominant chemical species is the highly biocidal hypochlorous acid species (HOCl) with the oxidation reduction potential (ORP) of the solution ranging from 800 to 900mV. The biocidal activity of near-neutral EO water was evaluated at 25 degrees C using pure cultures of Escherichia coli, Salmonella typhimurium, Staphylococcus aureus, Listeria monocytogenes, and Enterococcus faecalis. Treatment of these organisms, in pure culture, with EO water at concentrations of 20, 50, 100, and 120ppm total residual chlorine (TRC) and 10min of contact time resulted in 100% inactivation of all five organisms (reduction of 6.1-6.7log(10)CFU/mL). Spray treatment of surfaces in food service areas with EO water containing 278-310ppm TRC (pH 6.38) resulted in a 79-100% reduction of microbial growth. Dip (10min) treatment of spinach at 100 and 120ppm TRC resulted in a 4.0-5.0log(10)CFU/mL reduction of bacterial counts for all organisms tested. Dipping (10min) of lettuce at 100 and 120ppm TRC reduced bacterial counts of E. coli by 0.24-0.25log(10)CFU/mL and reduced all other organisms by 2.43-3.81log(10)CFU/mL. PMID:17993375

  8. Coupling carbon dioxide reduction with water oxidation in nanoscale photocatalytic assemblies.

    PubMed

    Kim, Wooyul; McClure, Beth Anne; Edri, Eran; Frei, Heinz

    2016-06-01

    The reduction of carbon dioxide by water with sunlight in an artificial system offers an opportunity for utilizing non-arable land for generating renewable transportation fuels to replace fossil resources. Because of the very large scale required for the impact on fuel consumption, the scalability of artificial photosystems is of key importance. Closing the photosynthetic cycle of carbon dioxide reduction and water oxidation on the nanoscale addresses major barriers for scalability as well as high efficiency, such as resistance losses inherent to ion transport over macroscale distances, loss of charge and other efficiency degrading processes, or excessive need for the balance of system components, to mention a few. For the conversion of carbon dioxide to six-electron or even more highly reduced liquid fuel products, introduction of a proton conducting, gas impermeable separation membrane is critical. This article reviews recent progress in the development of light absorber-catalyst assemblies for the reduction and oxidation half reactions with focus on well defined polynuclear structures, and on novel approaches for optimizing electron transfer among the molecular or nanoparticulate components. Studies by time-resolved optical and infrared spectroscopy for the understanding of charge transfer processes between the chromophore and the catalyst, and of the mechanism of water oxidation at metal oxide nanocatalysts through direct observation of surface reaction intermediates are discussed. All-inorganic polynuclear units for reducing carbon dioxide by water at the nanoscale are introduced, and progress towards core-shell nanotube assemblies for completing the photosynthetic cycle under membrane separation is described.

  9. Modeling electron competition among nitrogen oxides reduction and N2O accumulation in denitrification.

    PubMed

    Pan, Yuting; Ni, Bing-Jie; Yuan, Zhiguo

    2013-10-01

    Competition for electrons among different steps of denitrification has previously been shown to occur, and to play an important role in the accumulation and emission of N2O in wastewater treatment. However, this electron competition is not recognized in the current denitrification models, limiting their ability to predict N2O accumulation during denitrification. In this work, a new denitrification model is developed for wastewater treatment processes. It describes electron competition among the four steps of denitrification, through modeling the carbon oxidation and nitrogen reduction processes separately, in contrast to the existing models that directly couple these two types of processes. Electron carriers are introduced to link carbon oxidation, which donates electrons to carriers, and nitrogen oxides reduction, which receives electrons from these carriers. The relative ability of each denitrification step to compete for electrons is modeled through the use of different affinity constants with reduced carriers. Model calibration and validation results demonstrate that the developed model is able to reasonably describe the nitrate, nitrite, and N2O reduction rates of a methanol-utilizing denitrifying culture under various carbon and nitrogen oxides supplying conditions. The model proposed, while subject to further validation, is expected to enhance our ability to predict N2O accumulation in denitrification.

  10. Potential disruption of protein-protein interactions by graphene oxide.

    PubMed

    Feng, Mei; Kang, Hongsuk; Yang, Zaixing; Luan, Binquan; Zhou, Ruhong

    2016-06-14

    Graphene oxide (GO) is a promising novel nanomaterial with a wide range of potential biomedical applications due to its many intriguing properties. However, very little research has been conducted to study its possible adverse effects on protein-protein interactions (and thus subsequent toxicity to human). Here, the potential cytotoxicity of GO is investigated at molecular level using large-scale, all-atom molecular dynamics simulations to explore the interaction mechanism between a protein dimer and a GO nanosheet oxidized at different levels. Our theoretical results reveal that GO nanosheet could intercalate between the two monomers of HIV-1 integrase dimer, disrupting the protein-protein interactions and eventually lead to dimer disassociation as graphene does [B. Luan et al., ACS Nano 9(1), 663 (2015)], albeit its insertion process is slower when compared with graphene due to the additional steric and attractive interactions. This study helps to better understand the toxicity of GO to cell functions which could shed light on how to improve its biocompatibility and biosafety for its wide potential biomedical applications.

  11. Potential disruption of protein-protein interactions by graphene oxide

    NASA Astrophysics Data System (ADS)

    Feng, Mei; Kang, Hongsuk; Yang, Zaixing; Luan, Binquan; Zhou, Ruhong

    2016-06-01

    Graphene oxide (GO) is a promising novel nanomaterial with a wide range of potential biomedical applications due to its many intriguing properties. However, very little research has been conducted to study its possible adverse effects on protein-protein interactions (and thus subsequent toxicity to human). Here, the potential cytotoxicity of GO is investigated at molecular level using large-scale, all-atom molecular dynamics simulations to explore the interaction mechanism between a protein dimer and a GO nanosheet oxidized at different levels. Our theoretical results reveal that GO nanosheet could intercalate between the two monomers of HIV-1 integrase dimer, disrupting the protein-protein interactions and eventually lead to dimer disassociation as graphene does [B. Luan et al., ACS Nano 9(1), 663 (2015)], albeit its insertion process is slower when compared with graphene due to the additional steric and attractive interactions. This study helps to better understand the toxicity of GO to cell functions which could shed light on how to improve its biocompatibility and biosafety for its wide potential biomedical applications.

  12. Sequential reductive and oxidative conditions used to biodegradation of organochlorine pesticides by native bacteria.

    NASA Astrophysics Data System (ADS)

    Kopytko, M.; Correa-Torres, S. N.; Plata, A.

    2016-07-01

    Despite restrictions and bans on the use of many organochlorine pesticides in the 1970s and 1980s, they continue to persist in the environment today. This is the case of Agustin Codazzi, Cesar where the organochlorine pesticides were buried without control in the soil in 1999, after being banned their use. Nowadays is necessary to find the best method, which allows remediation of this soils. Reductive dechlorination is the first and limiting step in the metabolism of many organochlorine pesticides by anaerobic bacteria. In this study the reductive conditions were enhanced by addition of biogas as an auxiliary electron donors.The soil sample was taken from the zone at Agustin Codazzi, Cesar, and their characteristics correspond to a loam soil with low nutrient and slight compaction. The experimental tests were performed by varying the exposure time of a reducer to oxidative environment. Reductive conditions were enhanced by methane from biogas and oxidative environment was generated by air blown to stimulate a metabolic process of the soil native bacteria. Removals between 70 and 78.9% of compounds such as 4,4'-DDT, 4, 4'-DDD, 4,4'-DDE, Endrin and Trans- Chlordane, detected by gas chromatography analysis, were achieved under reductive/oxidative conditions during 120 days. Furthermore, bacterial strains capable of degrading organochlorine pesticides were selected from the native bacteria, and identified by the purified and identified based on its morphological characteristics and 16S rDNA sequencing.

  13. The Reduction of Aqueous Metal Species on the Surfaces of Fe(II)-Containing Oxides: The Role of Surface Passivation

    USGS Publications Warehouse

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

    1998-01-01

    The reduction of aqueous transition metal species at the surfaces of Fe(II)- containing oxides has important ramifications in predicting the transport behavior in ground water aquifers. Experimental studies using mineral suspensions and electrodes demonstrate that structural Fe(II) heterogeneously reduces aqueous ferric, cupric, vanadate and chromate ions on magnetite and ilmenite surfaces. The rates of metal reduction on natural oxides is strongly dependent on the extent of surface passivation and redox conditions in the weathering environment. Synchrotron studies show that surface oxidation of Fe(II)-containing oxide minerals decreases their capacity for Cr(VI) reduction at hazardous waste disposal sites.

  14. Coupled mercury-cell sorption, reduction, and oxidation on methylmercury production by Geobacter sulfurreducens PCA.

    PubMed

    Lin, Hui; Morrell-Falvey, Jennifer L; Rao, Balaji; Liang, Liyuan; Gu, Baohua

    2014-10-21

    G. sulfurreducens PCA cells have been shown to reduce, sorb, and methylate Hg(II) species, but it is unclear whether this organism can oxidize and methylate dissolved elemental Hg(0) as shown for Desulfovibrio desulfuricans ND132. Using Hg(II) and Hg(0) separately as Hg sources in washed cell assays in phosphate buffered saline (pH 7.4), we report how cell-mediated Hg reduction and oxidation compete or synergize with sorption, thus affecting the production of toxic methylmercury by PCA cells. Methylation is found to be positively correlated to Hg sorption (r = 0.73) but negatively correlated to Hg reduction (r = -0.62). These reactions depend on the Hg and cell concentrations or the ratio of Hg to cellular thiols (-SH). Oxidation and methylation of Hg(0) are favored at relatively low Hg to cell-SH molar ratios (e.g., <1). Increasing Hg to cell ratios from 0.25 × 10(-19) to 25 × 10(-19) moles-Hg/cell (equivalent to Hg/cell-SH of 0.71 to 71) shifts the major reaction from oxidation to reduction. In the absence of five outer membrane c-type cytochromes, mutant ΔomcBESTZ also shows decreases in Hg reduction and increases in methylation. However, the presence of competing thiol-binding ions such as Zn(2+) leads to increased Hg reduction and decreased methylation. These results suggest that the coupled cell-Hg sorption and redox transformations are important in controlling the rates of Hg uptake and methylation by G. sulfurreducens PCA in anoxic environments.

  15. Coupled Mercury–Cell Sorption, Reduction, and Oxidation on Methylmercury Production by Geobacter sulfurreducens PCA

    DOE PAGESBeta

    Lin, Hui; Morrell-Falvey, Jennifer L.; Rao, Balaji; Liang, Liyuan; Gu, Baohua

    2014-09-30

    G. sulfurreducens PCA cells have been shown to reduce, sorb, and methylate Hg(II) species, but it is unclear whether this organism can oxidize and methylate dissolved elemental Hg(0) as shown for Desulfovibrio desulfuricans ND132. Using Hg(II) and Hg(0) separately as Hg sources in washed cell assays in phosphate buffered saline (pH 7.4), in this paper we report how cell-mediated Hg reduction and oxidation compete or synergize with sorption, thus affecting the production of toxic methylmercury by PCA cells. Methylation is found to be positively correlated to Hg sorption (r = 0.73) but negatively correlated to Hg reduction (r = -0.62).more » These reactions depend on the Hg and cell concentrations or the ratio of Hg to cellular thiols (-SH). Oxidation and methylation of Hg(0) are favored at relatively low Hg to cell–SH molar ratios (e.g., <1). Increasing Hg to cell ratios from 0.25 × 10–19 to 25 × 10–19 moles-Hg/cell (equivalent to Hg/cell–SH of 0.71 to 71) shifts the major reaction from oxidation to reduction. In the absence of five outer membrane c-type cytochromes, mutant ΔomcBESTZ also shows decreases in Hg reduction and increases in methylation. However, the presence of competing thiol-binding ions such as Zn2+ leads to increased Hg reduction and decreased methylation. Finally, these results suggest that the coupled cell-Hg sorption and redox transformations are important in controlling the rates of Hg uptake and methylation by G. sulfurreducens PCA in anoxic environments.« less

  16. Coupled Mercury–Cell Sorption, Reduction, and Oxidation on Methylmercury Production by Geobacter sulfurreducens PCA

    SciTech Connect

    Lin, Hui; Morrell-Falvey, Jennifer L.; Rao, Balaji; Liang, Liyuan; Gu, Baohua

    2014-09-30

    G. sulfurreducens PCA cells have been shown to reduce, sorb, and methylate Hg(II) species, but it is unclear whether this organism can oxidize and methylate dissolved elemental Hg(0) as shown for Desulfovibrio desulfuricans ND132. Using Hg(II) and Hg(0) separately as Hg sources in washed cell assays in phosphate buffered saline (pH 7.4), in this paper we report how cell-mediated Hg reduction and oxidation compete or synergize with sorption, thus affecting the production of toxic methylmercury by PCA cells. Methylation is found to be positively correlated to Hg sorption (r = 0.73) but negatively correlated to Hg reduction (r = -0.62). These reactions depend on the Hg and cell concentrations or the ratio of Hg to cellular thiols (-SH). Oxidation and methylation of Hg(0) are favored at relatively low Hg to cell–SH molar ratios (e.g., <1). Increasing Hg to cell ratios from 0.25 × 10–19 to 25 × 10–19 moles-Hg/cell (equivalent to Hg/cell–SH of 0.71 to 71) shifts the major reaction from oxidation to reduction. In the absence of five outer membrane c-type cytochromes, mutant ΔomcBESTZ also shows decreases in Hg reduction and increases in methylation. However, the presence of competing thiol-binding ions such as Zn2+ leads to increased Hg reduction and decreased methylation. Finally, these results suggest that the coupled cell-Hg sorption and redox transformations are important in controlling the rates of Hg uptake and methylation by G. sulfurreducens PCA in anoxic environments.

  17. Facilitated biological reduction of nitroaromatic compounds by reduced graphene oxide and the role of its surface characteristics

    PubMed Central

    Li, Lei; Liu, Qi; Wang, Yi-Xuan; Zhao, Han-Qing; He, Chuan-Shu; Yang, Hou-Yun; Gong, Li; Mu, Yang; Yu, Han-Qing

    2016-01-01

    How reduced graphene oxide (RGO) mediates the reductive transformation of nitroaromatic pollutants by mixed cultures and the role of its surface characteristics were evaluated in this study. Different electron donors were applied to investigate the interaction between RGO and anaerobic microbes. Moreover, the influence of the surface properties of RGO on biological nitroaromatic removal was further elucidated. The results show that RGO could achieve an approximate one-fold rate increase of nitrobenzene reduction by mixed culture with glucose as an electron donor. Selective elimination of oxygen moieties on the RGO surface, such as quinone groups, decreased the nitrobenzene transformation rate, whereas doping nitrogen into the RGO framework exhibited a positive effect. The study indicates that graphene-based carbon nanomaterials have the potential to accelerate the biological transformation of nitroaromatic compounds and that the functionalization of these carbon nanomaterials, especially through surface modification, would further enhance the conversion efficiency of contaminants. PMID:27439321

  18. IMPACTS OF ANTIFOAM ADDITIONS AND ARGON BUBBLING ON DEFENSE WASTE PROCESSING FACILITY REDUCTION/OXIDATION

    SciTech Connect

    Jantzen, C.; Johnson, F.

    2012-06-05

    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.

  19. 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)

    Gupta, Himanshu

    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

  20. Surface potential determination in metal-oxide-semiconductor capacitors

    NASA Astrophysics Data System (ADS)

    Moragues, J. M.; Ciantar, E.; Jerisian, R.; Sagnes, B.; Oualid, J.

    1994-11-01

    Different methods using the relationship between surface potential Psi(sub S) and gate bias V(sub G) in metal-oxide-semiconductor (MOS) capacitors have been compared. These methods can be applied even if the doping profile is very abrupt and the interface state density very high. The shifts of midgap, flatband, and threshold voltages, observed after Fowler-Nordheim electron injection, and deduced from the various Psi(sub S(V (sub G)) relationships obtained by these different methods, are in good agreement. These shifts give the number of effective oxide trapped charges (N(sub ox)) per unit area and acceptor-like and donor-like interface states (N(sub SS)A and N(sub SS)D) which are created during the electron injection. We reveal that the number of positive charges created in the gate oxide, unlike the number of generated interface states, strongly depends on the position of the post-metallization annealing step in the process. After relaxation of the stressed MOS capacitors, most of the generated positive charges can be attributed, in the MOS capacitors studied, to hydrogen-related species. It seems that the interface states are essentially created by the recombination of holes generated by electron impact.

  1. Rapid and scalable reduction of dense surface-supported metal-oxide catalyst with hydrazine vapor.

    PubMed

    Pint, Cary L; Kim, Seung Min; Stach, Eric A; Hauge, Robert H

    2009-07-28

    An efficient technique using hydrazine (N(2)H(4)) vapor as an agent for the rapid reduction of high-density layers of catalytic nanoparticles is demonstrated. With as little as 10 mTorr hydrazine bled into a thermal chemical vapor deposition (CVD) apparatus, efficient reduction of metal-oxide catalyst particles is achieved more rapidly than when using atomic hydrogen as the reducing agent. Postreduction catalyst imaging emphasizes the differences in nanoparticle formation under different reduction environments, with the most uniform and compact catalyst size distribution observed following hydrazine exposure. Low-temperature reduction studies suggest that as little as 15 s N(2)H(4) exposure at temperatures of 350 °C can yield a reduced catalyst layer preceding the synthesis of dense, aligned arrays of single-walled carbon nanotubes (SWNT) with uniform height. This work demonstrates a simple route toward scalable, vapor transport reduction of metal-oxide catalyst relevant to a number of catalytic applications, including the synthesis and selective synthesis of aligned SWNT arrays.

  2. Solid-phase electrochemical reduction of graphene oxide films in alkaline solution

    PubMed Central

    2013-01-01

    Graphene oxide (GO) film was evaporated onto graphite and used as an electrode to produce electrochemically reduced graphene oxide (ERGO) films by electrochemical reduction in 6 M KOH solution through voltammetric cycling. Fourier transformed infrared and Raman spectroscopy confirmed the presence of ERGO. Electrochemical impedance spectroscopy characterization of ERGO and GO films in ferrocyanide/ferricyanide redox couple with 0.1 M KCl supporting electrolyte gave results that are in accordance with previous reports. Based on the EIS results, ERGO shows higher capacitance and lower charge transfer resistance compared to GO. PMID:24059434

  3. Process for the catalytic reduction of nitrogen oxides in gaseous mixtures

    SciTech Connect

    Ginger, E.A.

    1981-05-19

    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.

  4. Potential benefits of solar reflective car shells: cooler cabins, fuel savings and emission reductions

    SciTech Connect

    Levinson, Ronnen; Pan, Heng; Ban-Weiss, George; Rosado, Pablo; Paolini, Riccardo; Akbari, Hashem

    2011-05-11

    Abstract: Vehicle thermal loads and air conditioning ancillary loads are strongly influenced by the absorption of solar energy. The adoption of solar reflective coatings for opaque surfaces of the vehicle shell can decrease the ?soak? temperature of the air in the cabin of a vehicle parked in the sun, potentially reducing the vehicle?s ancillary load and improving its fuel economy by permitting the use of a smaller air conditioner. An experimental comparison of otherwise identical black and silver compact sedans indicated that increasing the solar reflectance (?) of the car?s shell by about 0.5 lowered the soak temperature of breath-level air by about 5?6?C. Thermal analysis predicts that the air conditioning capacity required to cool the cabin air in the silver car to 25?C within 30min is 13percent less than that required in the black car. Assuming that potential reductions in AC capacity and engine ancillary load scale linearly with increase in shell solar reflectance, ADVISOR simulations of the SC03 driving cycle indicate that substituting a typical cool-colored shell (?=0.35) for a black shell (?=0.05) would reduce fuel consumption by 0.12L per 100km (1.1percent), increasing fuel economy by 0.10kmL?1 [0.24mpg] (1.1percent). It would also decrease carbon dioxide (CO2) emissions by 2.7gkm?1 (1.1percent), nitrogen oxide (NOx) emissions by 5.4mgkm?1 (0.44percent), carbon monoxide (CO) emissions by 17mgkm?1 (0.43percent), and hydrocarbon (HC) emissions by 4.1mgkm?1 (0.37percent). Selecting a typical white or silver shell (?=0.60) instead of a black shell would lower fuel consumption by 0.21L per 100km (1.9percent), raising fuel economy by 0.19kmL?1 [0.44mpg] (2.0percent). It would also decrease CO2 emissions by 4.9gkm?1 (1.9percent), NOx emissions by 9.9mgkm?1 (0.80percent), CO emissions by 31mgkm?1 (0.79percent), and HC emissions by 7.4mgkm?1 (0.67percent). Our simulations may underestimate emission reductions because emissions in standardized driving cycles are

  5. Potential of front-face fluorescence to monitor OM reduction in drinking water during potabilization process

    NASA Astrophysics Data System (ADS)

    Lacotte, Pierre

    2014-05-01

    Elimination of OM in drinking water represents a great challenge for municipalities and technical actors to ensure that it can be safely used for consumption purposes. Indeed, current indicators such as Total Organic Carbon (TOC), turbidity or UV-Absorbance at 254 nm (UVA254) enable only non-specific overview of the amount of organic residuals in water. Fluorescence EEMs are a potent tool for discrimination and deep analysis of OM detailed composition and behaviour. It has been shown that several forms of OM co-exist in raw water, and come from various origins (bacteria, humic compounds…). Potabilization operation is composed of different steps that aim at decreasing all forms of OM using chemical as well as physical methods (ozone oxidation, filtration on activated carbon or sand, flocculation etc.). Unfortunately, it has been observed that reduction of OM during this process was not identical for all the forms, and the process showed a particular lack of efficiency during raining periods. 130 samples of water at various stages of potabilization were analyzed using home-made compact fluorometer, an apparatus composed of UV excitation LEDs. Using chemometrical treatment of spectral data, we put into highlight 5 different forms of OM that were identified according to litterature data. We evidenced the critical steps of the purification on OM reduction, as well as the relative content of each form from raw to product water. In particular, we showed that two forms were less reduced than the other three, so that progressive enrichment of total OM in the former was observed throughout the process. Moreover, a study was carried out in order to establish calibration models over conventional analyses using the spectral information. Highly satisfying models were thus obtained over TOC, turbidity and UVA254, with average RMSEC values of 13%, 7% and 16% respectively. These results demonstrate the potential of the fluorescence analyzer to simultaneously predict three major

  6. Graphene transistors via in situ voltage-induced reduction of graphene-oxide under ambient conditions.

    PubMed

    Mativetsky, Jeffrey M; Liscio, Andrea; Treossi, Emanuele; Orgiu, Emanuele; Zanelli, Alberto; Samorì, Paolo; Palermo, Vincenzo

    2011-09-14

    Here, we describe a simple approach to fabricate graphene-based field-effect-transistors (FETs), starting from aqueous solutions of graphene-oxide (GO), processed entirely under ambient conditions. The process relies on the site-selective reduction of GO sheets deposited in between or on the surface of micro/nanoelectrodes. The same electrodes are first used for voltage-induced electrochemical GO reduction, and then as the source and drain contacts of FETs, allowing for the straightforward production and characterization of ambipolar graphene devices. With the use of nanoelectrodes, we could reduce different selected areas belonging to one single sheet as well.

  7. Self-Supplied Nano-Fusing and Transferring Metal Nanostructures via Surface Oxide Reduction.

    PubMed

    Ahn, Jaeho; Seo, Ji-Won; Kim, Jong Yun; Lee, Jaemin; Cho, Changsoon; Kang, Juhoon; Choi, Sung-Yool; Lee, Jung-Yong

    2016-01-20

    Here, we demonstrate that chemical reduction of oxide layers on metal nanostructures fuses junctions at nanoscale to improve the opto-electrical performance, and to ensure environmental stability of the interconnected nanonetwork. In addition, the reducing reaction lowers the adhesion force between metal nanostructures and substrates, facilitating the detachment of them from substrates. Detached metal nanonetworks can be easily floated on water and transferred onto various substrates including hydrophobic, floppy, and curved surfaces. Utilizing the detached metal nanostructures, semitransparent organic photovoltaics is fabricated, presenting the applicability of proposed reduction treatment in the device applications. PMID:26700597

  8. The reduction and distillation of isotopically enriched zinc oxides under high vacuum conditions

    NASA Astrophysics Data System (ADS)

    Marcus, C.; Zevenbergen, L. A.

    1999-12-01

    Historically, enriched zinc (Zn) metal was produced at the Oak Ridge National Laboratory's Isotope Enrichment Facility (IEF) by either electrodeposition, followed by melting to produce a metal ingot, or purified by hydrogen reduction and distillation at atmospheric pressure in a tube furnace as a prelude to electroplating. Electroplated material was generally poor in quality, and losses were high during subsequent melting. Adapting the distillation purifying technique as an ultimate means of recovery of Zn metal proved to be difficult and inefficient. To resolve these problems, the well-established vacuum reduction/distillation process was adapted for the conversion of Zn oxide to metal.

  9. Global Change Simulations Affect Potential Methane Oxidation in Upland Soils

    NASA Astrophysics Data System (ADS)

    Blankinship, J. C.; Hungate, B. A.

    2004-12-01

    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

  10. Oxidation-reduction processes in ground water at Naval Weapons Industrial Reserve Plant, Dallas, Texas

    USGS Publications Warehouse

    Jones, S.A.; Braun, Christopher L.; Lee, Roger W.

    2003-01-01

    Concentrations of trichloroethene in ground water at the Naval Weapons Industrial Reserve Plant in Dallas, Texas, indicate three source areas of chlorinated solvents?building 1, building 6, and an off-site source west of the facility. The presence of daughter products of reductive dechlorination of trichloroethene, which were not used at the facility, south and southwest of the source areas are evidence that reductive dechlorination is occurring. In places south of the source areas, dissolved oxygen concentrations indicated that reduction of oxygen could be the dominant process, particularly south of building 6; but elevated dissolved oxygen concentrations south of building 6 might be caused by a leaking water or sewer pipe. The nitrite data indicate that denitrification is occurring in places; however, dissolved hydrogen concentrations indicate that iron reduction is the dominant process south of building 6. The distributions of ferrous iron indicate that iron reduction is occurring in places south-southwest of buildings 6 and 1; dissolved hydrogen concentrations generally support the interpretation that iron reduction is the dominant process in those places. The generally low concentrations of sulfide indicate that sulfate reduction is not a key process in most sampled areas, an interpretation that is supported by dissolved hydrogen concentrations. Ferrous iron and dissolved hydrogen concentrations indicate that ferric iron reduction is the primary oxidation-reduction process. Application of mean first-order decay rates in iron-reducing conditions for trichloroethene, dichloroethene, and vinyl chloride yielded half-lives for those solvents of 231, 347, and 2.67 days, respectively. Decay rates, and thus half-lives, at the facility are expected to be similar to those computed. A weighted scoring method to indicate sites where reductive dechlorination might be likely to occur indicated strong evidence for anaerobic biodegradation of chlorinated solvents at six sites

  11. A potential biomarker for fatigue: Oxidative stress and anti-oxidative activity.

    PubMed

    Fukuda, Sanae; Nojima, Junzo; Motoki, Yukari; Yamaguti, Kouzi; Nakatomi, Yasuhito; Okawa, Naoko; Fujiwara, Kazumi; Watanabe, Yasuyoshi; Kuratsune, Hirohiko

    2016-07-01

    We sought to determine whether oxidative stress and anti-oxidative activity could act as biomarkers that discriminate patients with chronic fatigue syndrome (CFS) from healthy volunteers at acute and sub-acute fatigue and resting conditions. We calculated the oxidative stress index (OSI) from reactive oxygen metabolites-derived compounds (d-ROMs) and the biological antioxidant potential (BAP). We determined changes in d-ROMs, BAP, and OSI in acute and sub-acute fatigue in two healthy groups, and compared their values at rest between patients with CFS (diagnosed by Fukuda 1994 criteria) and another group of healthy controls. Following acute fatigue in healthy controls, d-ROMs and OSI increased, and BAP decreased. Although d-ROMs and OSI were significantly higher after sub-acute fatigue, BAP did not decrease. Resting condition yielded higher d-ROMs, higher OSI, and lower BAP in patients with CFS than in healthy volunteers, but lower d-ROMs and OSI when compared with sub-acute controls. BAP values did not significantly differ between patients with CFS and controls in the sub-acute condition. However, values were significantly higher than in the resting condition for controls. Thus, measured of oxidative stress (d-ROMS) and anti-oxidative activity (BAP) might be useful for discriminating acute, sub-acute, and resting fatigue in healthy people from patients with CFS, or for evaluating fatigue levels in healthy people.

  12. A potential biomarker for fatigue: Oxidative stress and anti-oxidative activity.

    PubMed

    Fukuda, Sanae; Nojima, Junzo; Motoki, Yukari; Yamaguti, Kouzi; Nakatomi, Yasuhito; Okawa, Naoko; Fujiwara, Kazumi; Watanabe, Yasuyoshi; Kuratsune, Hirohiko

    2016-07-01

    We sought to determine whether oxidative stress and anti-oxidative activity could act as biomarkers that discriminate patients with chronic fatigue syndrome (CFS) from healthy volunteers at acute and sub-acute fatigue and resting conditions. We calculated the oxidative stress index (OSI) from reactive oxygen metabolites-derived compounds (d-ROMs) and the biological antioxidant potential (BAP). We determined changes in d-ROMs, BAP, and OSI in acute and sub-acute fatigue in two healthy groups, and compared their values at rest between patients with CFS (diagnosed by Fukuda 1994 criteria) and another group of healthy controls. Following acute fatigue in healthy controls, d-ROMs and OSI increased, and BAP decreased. Although d-ROMs and OSI were significantly higher after sub-acute fatigue, BAP did not decrease. Resting condition yielded higher d-ROMs, higher OSI, and lower BAP in patients with CFS than in healthy volunteers, but lower d-ROMs and OSI when compared with sub-acute controls. BAP values did not significantly differ between patients with CFS and controls in the sub-acute condition. However, values were significantly higher than in the resting condition for controls. Thus, measured of oxidative stress (d-ROMS) and anti-oxidative activity (BAP) might be useful for discriminating acute, sub-acute, and resting fatigue in healthy people from patients with CFS, or for evaluating fatigue levels in healthy people. PMID:27224647

  13. Climate change reduces warming potential of nitrous oxide by an enhanced Brewer-Dobson circulation

    NASA Astrophysics Data System (ADS)

    Kracher, Daniela; Reick, Christian H.; Manzini, Elisa; Schultz, Martin G.; Stein, Olaf

    2016-06-01

    The Brewer-Dobson circulation (BDC), which is an important driver of the stratosphere-troposphere exchange, is expected to accelerate with climate change. One particular consequence of this acceleration is the enhanced transport of nitrous oxide (N2O) from its sources at the Earth's surface toward its main sink region in the stratosphere, thus inducing a reduction in its lifetime. N2O is a potent greenhouse gas and the most relevant currently emitted ozone-depleting substance. Here we examine the implications of a reduced N2O lifetime in the context of climate change. We find a decrease in its global warming potential (GWP) and, due to a decline in the atmospheric N2O burden, also a reduction in its total radiative forcing. From the idealized transient global warming simulation we can identify linear regressions for N2O sink, lifetime, and GWP with temperature rise. Our findings are thus not restricted to a particular scenario.

  14. Electrically rechargeable anionically active reduction-oxidation electrical storage-supply system

    SciTech Connect

    Remick, R.J.; Ang, P.G.P.

    1984-11-27

    An electrically rechargeable anionically active reduction-oxidation electric storage-supply system and process is disclosed using a sodium or potassium sulfidepolysulfide anolyte reaction and an iodide-polyiodide, chloride-chlorine or bromide-bromine species catholyte reaction. The catholyte and anolyte are separated by an ion selective membrane permeable to positive sodium and potassium ions and substantially impermeable to negative bromide, chloride, iodide, sulfide and polysulfide ions. A flowing electrolyte system is disclosed with external electrolyte storage vessels. The apparatus and process provide an electrically rechargeable anionically active reduction-oxidation system in which the electrolytes may be maintained at near neutral or slightly basic pH, with virtually no parasitic side reactions upon charging, such as hydrogen or oxygen evolution, and the disclosed storage and supply system provides higher energy densities than referenced prior art systems.

  15. Anion exchange membranes for electrochemical oxidation-reduction energy storage system

    NASA Technical Reports Server (NTRS)

    Odonnell, P. M.; Sheibley, D. W.; Gahn, R. F.

    1977-01-01

    Oxidation-reduction couples in concentrated solutions separated by appropriate ion selective membranes were considered as an attractive approach to bulk electrical energy storage. A key problem is the development of the membrane. Several promising types of anionic membranes are discussed which were developed and evaluated for redox energy storage systems. The copolymers of ethyleneglycoldimethacrylate with either 2-vinylpyridine or vinylbenzl chloride gave stable resistance values compared to the copolymer of vinylbenzlchloride and divinylbenzene which served as the baseline membrane. A polyvinylchloride film aminated with tetraethylenepentamine had a low resistance but a high ion transfer rate. A slurry coated vinylpyridine had the lowest ion transfer rate. All these membranes functioned well in laboratory cells at ambient temperatures with the acidic chloride oxidant/reductant system, Fe 3, Fe 2/Ti 3, Ti 4.

  16. Anode shroud for off-gas capture and removal from electrolytic oxide reduction system

    SciTech Connect

    Bailey, James L.; Barnes, Laurel A.; Wiedmeyer, Stanley G.; Williamson, Mark A.; Willit, James L.

    2014-07-08

    An electrolytic oxide reduction system according to a non-limiting embodiment of the present invention may include a plurality of anode assemblies and an anode shroud for each of the anode assemblies. The anode shroud may be used to dilute, cool, and/or remove off-gas from the electrolytic oxide reduction system. The anode shroud may include a body portion having a tapered upper section that includes an apex. The body portion may have an inner wall that defines an off-gas collection cavity. A chimney structure may extend from the apex of the upper section and be connected to the off-gas collection cavity of the body portion. The chimney structure may include an inner tube within an outer tube. Accordingly, a sweep gas/cooling gas may be supplied down the annular space between the inner and outer tubes, while the off-gas may be removed through an exit path defined by the inner tube.

  17. THE EFFECT OF NITRIC OXIDE ON SYNAPTIC VESICLE PROTON GRADIENT AND MITOCHONDRIAL POTENTIAL OF BRAIN NERVE TERMINALS.

    PubMed

    Tarasenko, A S

    2015-01-01

    The effect of nitric oxide on synaptic vesicle proton gradient and membrane potential of rat brain nerve terminals was studied. It has been shown that nitric oxide in the form of S-nitrosothiols at nanomolar concentrations had no effect on the studied parameters, but caused a rapid dissipation of synaptic vesicle proton gradient and depolarization of mitochondrial membrane in the presence of a SH-reducing compound such as dithiothreitol. Both processes were reversible and the rate of H(+)-gradient restoration depended on the redox potential of nerve terminals, namely the molar ratio of reductant/oxidant. This facts, as well as insensitivity of the studied processes to the inhibitor of NO-sensitive guanylate cyclase such as ODQ, allow suggesting that post-translational modification of thiol residues of the mitochondrial and synaptic vesicle proteins underlies the effect of nitric oxide on the key functional parameters ofpresynaptic nerve terminals. PMID:27025060

  18. Graphenothermal reduction synthesis of 'exfoliated graphene oxide/iron (II) oxide' composite for anode application in lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Petnikota, Shaikshavali; Marka, Sandeep Kumar; Banerjee, Arkaprabha; Reddy, M. V.; Srikanth, V. V. S. S.; Chowdari, B. V. R.

    2015-10-01

    Graphenothermal Reduction process is used to obtain exfoliated graphene oxide (EG)/iron (II) oxide (FeO) composite prepared at 650 °C for 5 h in argon. Structural and compositional analyses of the sample confirm the formation of EG/FeO composite. This composite shows a reversible capacity of 857 mAh g-1 at a current rate of 50 mA g-1 in the voltage range 0.005-3.0 V versus Li. An excellent capacity retention up to 60 cycles and high coulombic efficiency of 98% are also observed. Characteristic Fe2+/0 redox peaks observed in Cyclic Voltammetry measurement are explained in correlation with lithium storage mechanism. Thermal, electrical and impedance spectroscopy studies of EG/FeO composite are discussed in detail. Comparative electrochemical cycling studies of EG/FeO composite with Fe2O3 and Fe3O4 materials prepared under controlled conditions are also discussed.

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

    SciTech Connect

    Ates Akyurtlu; Jale F. Akyurtlu

    2001-09-01

    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

  20. Reduction in plasma potential by applying negative DC cathode bias in RF magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Isomura, Masao; Yamada, Toshinori; Osuga, Kosuke; Shindo, Haruo

    2016-11-01

    We applied a negative DC bias voltage to the cathode of an RF magnetron sputtering system and successfully reduced the plasma potential in both argon plasma and hydrogen-diluted argon plasma. The crystallinity of the deposited Ge films is improved by increasing the negative DC bias voltage. It is indicated that the reduction in plasma potential is effective for reducing the plasma damage on deposited materials, caused by the electric potential between the plasma and substrates. In addition, the deposition rate is increased by the increased electric potential between the plasma and the cathode owing to the negative DC bias voltage. The present method successfully gives us higher speed and lower damage sputtering deposition. The increased electric potential between the plasma and the cathode suppresses the evacuation of electrons from the plasma and also enhances the generation of secondary electrons on the cathode. These probably suppress the electron loss from the plasma and result in the reduction in plasma potential.

  1. Visible light Cr(VI) reduction and organic chemical oxidation by TiO2 photocatalysis.

    PubMed

    Sun, Bo; Reddy, Ettireddy P; Smirniotis, Panagiotis G

    2005-08-15

    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.

  2. Anaerobic Oxidation of Methane Coupled to Nitrite Reduction by Halophilic Marine NC10 Bacteria.

    PubMed

    He, Zhanfei; Geng, Sha; Cai, Chaoyang; Liu, Shuai; Liu, Yan; Pan, Yawei; Lou, Liping; Zheng, Ping; Xu, Xinhua; Hu, Baolan

    2015-08-15

    Anaerobic oxidation of methane (AOM) coupled to nitrite reduction is a novel AOM process that is mediated by denitrifying methanotrophs. To date, enrichments of these denitrifying methanotrophs have been confined to freshwater systems; however, the recent findings of 16S rRNA and pmoA gene sequences in marine sediments suggest a possible occurrence of AOM coupled to nitrite reduction in marine systems. In this research, a marine denitrifying methanotrophic culture was obtained after 20 months of enrichment. Activity testing and quantitative PCR (qPCR) analysis were then conducted and showed that the methane oxidation activity and the number of NC10 bacteria increased correlatively during the enrichment period. 16S rRNA gene sequencing indicated that only bacteria in group A of the NC10 phylum were enriched and responsible for the resulting methane oxidation activity, although a diverse community of NC10 bacteria was harbored in the inoculum. Fluorescence in situ hybridization showed that NC10 bacteria were dominant in the enrichment culture after 20 months. The effect of salinity on the marine denitrifying methanotrophic culture was investigated, and the apparent optimal salinity was 20.5‰, which suggested that halophilic bacterial AOM coupled to nitrite reduction was obtained. Moreover, the apparent substrate affinity coefficients of the halophilic denitrifying methanotrophs were determined to be 9.8 ± 2.2 μM for methane and 8.7 ± 1.5 μM for nitrite.

  3. Green Approach for the Effective Reduction of Graphene Oxide Using Salvadora persica L. Root (Miswak) Extract

    NASA Astrophysics Data System (ADS)

    Khan, Mujeeb; Al-Marri, Abdulhadi H.; Khan, Merajuddin; Shaik, Mohammed Rafi; Mohri, Nils; Adil, Syed Farooq; Kuniyil, Mufsir; Alkhathlan, Hamad Z.; Al-Warthan, Abdulrahman; Tremel, Wolfgang; Tahir, Muhammad Nawaz; Siddiqui, Mohammed Rafiq H.

    2015-07-01

    Recently, green reduction of graphene oxide (GRO) using various natural materials, including plant extracts, has drawn significant attention among the scientific community. These methods are sustainable, low cost, and are more environmentally friendly than other standard methods of reduction. Herein, we report a facile and eco-friendly method for the bioreduction of GRO using Salvadora persica L. ( S. persica L.) roots (miswak) extract as a bioreductant. The as-prepared highly reduced graphene oxide (SP-HRG) was characterized using powder X-ray diffraction (XRD), ultraviolet-visible (UV-vis) spectroscopy, Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, X-ray photoelectron (XPS) spectroscopy, and transmission electron microscopy (TEM). Various results have confirmed that the biomolecules present in the root extract of miswak not only act as a bioreductant but also functionalize the surface of SP-HRG by acting as a capping ligand to stabilize it in water and other solvents. The dispersion quality of SP-HRG in deionized water was investigated in detail by preparing different samples of SP-HRG with increasing concentration of root extract. Furthermore, the dispersibility of SP-HRG was also compared with chemically reduced graphene oxide (CRG). The developed eco-friendly method for the reduction of GRO could provide a better substitute for a large-scale production of dispersant-free graphene and graphene-based materials for various applications in both technological and biological fields such as electronics, nanomedicine, and bionic materials.

  4. Green Approach for the Effective Reduction of Graphene Oxide Using Salvadora persica L. Root (Miswak) Extract.

    PubMed

    Khan, Mujeeb; Al-Marri, Abdulhadi H; Khan, Merajuddin; Shaik, Mohammed Rafi; Mohri, Nils; Adil, Syed Farooq; Kuniyil, Mufsir; Alkhathlan, Hamad Z; Al-Warthan, Abdulrahman; Tremel, Wolfgang; Tahir, Muhammad Nawaz; Siddiqui, Mohammed Rafiq H

    2015-12-01

    Recently, green reduction of graphene oxide (GRO) using various natural materials, including plant extracts, has drawn significant attention among the scientific community. These methods are sustainable, low cost, and are more environmentally friendly than other standard methods of reduction. Herein, we report a facile and eco-friendly method for the bioreduction of GRO using Salvadora persica L. (S. persica L.) roots (miswak) extract as a bioreductant. The as-prepared highly reduced graphene oxide (SP-HRG) was characterized using powder X-ray diffraction (XRD), ultraviolet-visible (UV-vis) spectroscopy, Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, X-ray photoelectron (XPS) spectroscopy, and transmission electron microscopy (TEM). Various results have confirmed that the biomolecules present in the root extract of miswak not only act as a bioreductant but also functionalize the surface of SP-HRG by acting as a capping ligand to stabilize it in water and other solvents. The dispersion quality of SP-HRG in deionized water was investigated in detail by preparing different samples of SP-HRG with increasing concentration of root extract. Furthermore, the dispersibility of SP-HRG was also compared with chemically reduced graphene oxide (CRG). The developed eco-friendly method for the reduction of GRO could provide a better substitute for a large-scale production of dispersant-free graphene and graphene-based materials for various applications in both technological and biological fields such as electronics, nanomedicine, and bionic materials.

  5. Study on the oxidation and reduction of tungsten surface for sub-50 nm patterning process

    SciTech Connect

    Kim, Jong Kyu; Nam, Seok Woo; Cho, Sung Il; Jhon, Myung S.; Min, Kyung Suk; Kim, Chan Kyu; Jung, Ho Bum; Yeom, Geun Young

    2012-11-15

    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.

  6. Nitrous oxide reduction in nodules: denitrification or N/sub 2/ fixation

    SciTech Connect

    Coyne, M.S.; Focht, D.D.

    1987-05-01

    Detached cowpea nodules that contained a nitrous oxide reductase-positive (Nor/sup +/) rhizobium strain (8A55) and a nitrous oxide reductase-negative (Nor/sup -/) rhizobium strain (32H1) were incubated with 1% /sup 15/N/sub 2/O (95 atom% /sup 15/N) in the following three atmospheres: aerobic with C/sub 2/H/sub 2/ (10%), aerobic without C/sub 2/H/sub 2/, and anaerobic (argon atmosphere) without C/sub 2/H/sub 2/. The greatest production of /sup 15/N/sub 2/ occurred anaerobically with 8A55, yet very little was formed with 32H1. Although acetylene reduction activity was slightly higher with 32H1, about 10 times more /sup 15/N/sub 2/ was produced aerobically by 8A55 than by 32H1 in the absence of acetylene. The major reductive pathway of N/sub 2/O reduction by denitrifying rhizobium strain 8A55 is by nitrous oxide reductase rather than nitrogenase.

  7. Reduction of mixed Mn-Zr oxides: in situ XPS and XRD studies.

    PubMed

    Bulavchenko, O A; Vinokurov, Z S; Afonasenko, T N; Tsyrul'nikov, P G; Tsybulya, S V; Saraev, A A; Kaichev, V V

    2015-09-21

    A series of mixed Mn-Zr oxides with different molar ratios Mn/Zr (0.1-9) have been prepared by coprecipitation of manganese and zirconium nitrates and characterized by X-ray diffraction (XRD) and BET methods. It has been found that at concentrations of Mn below 30 at%, the samples are single-phase solid solutions (MnxZr1-xO2-δ) based on a ZrO2 structure. X-ray photoelectron spectroscopy (XPS) measurements showed that manganese in these solutions exists mainly in the Mn(4+) state on the surface. An increase in Mn content mostly leads to an increase in the number of Mn cations in the structure of solid solutions; however, a part of the manganese cations form Mn2O3 and Mn3O4 in the crystalline and amorphous states. The reduction of these oxides with hydrogen was studied by a temperature-programmed reduction technique, in situ XRD, and near ambient pressure XPS in the temperature range from 100 to 650 °C. It was shown that the reduction of the solid solutions MnxZr1-xO2-δ proceeds via two stages. During the first stage, at temperatures between 100 and 500 °C, the Mn cations incorporated into the solid solutions MnxZr1-xO2-δ undergo partial reduction. During the second stage, at temperatures between 500 and 700 °C, Mn cations segregate on the surface of the solid solution. In the samples with more than 30 at% Mn, the reduction of manganese oxides was observed: Mn2O3 → Mn3O4 → MnO.

  8. Nitrate Reduction to Nitrite, Nitric Oxide and Ammonia by Gut Bacteria under Physiological Conditions

    PubMed Central

    Tiso, Mauro; Schechter, Alan N.

    2015-01-01

    The biological nitrogen cycle involves step-wise reduction of nitrogen oxides to ammonium salts and oxidation of ammonia back to nitrites and nitrates by plants and bacteria. Neither process has been thought to have relevance to mammalian physiology; however in recent years the salivary bacterial reduction of nitrate to nitrite has been recognized as an important metabolic conversion in humans. Several enteric bacteria have also shown the ability of catalytic reduction of nitrate to ammonia via nitrite during dissimilatory respiration; however, the importance of this pathway in bacterial species colonizing the human intestine has been little studied. We measured nitrite, nitric oxide (NO) and ammonia formation in cultures of Escherichia coli, Lactobacillus and Bifidobacterium species grown at different sodium nitrate concentrations and oxygen levels. We found that the presence of 5 mM nitrate provided a growth benefit and induced both nitrite and ammonia generation in E.coli and L.plantarum bacteria grown at oxygen concentrations compatible with the content in the gastrointestinal tract. Nitrite and ammonia accumulated in the growth medium when at least 2.5 mM nitrate was present. Time-course curves suggest that nitrate is first converted to nitrite and subsequently to ammonia. Strains of L.rhamnosus, L.acidophilus and B.longum infantis grown with nitrate produced minor changes in nitrite or ammonia levels in the cultures. However, when supplied with exogenous nitrite, NO gas was readily produced independently of added nitrate. Bacterial production of lactic acid causes medium acidification that in turn generates NO by non-enzymatic nitrite reduction. In contrast, nitrite was converted to NO by E.coli cultures even at neutral pH. We suggest that the bacterial nitrate reduction to ammonia, as well as the related NO formation in the gut, could be an important aspect of the overall mammalian nitrate/nitrite/NO metabolism and is yet another way in which the microbiome

  9. The effect of oxidizing water on metallic restorations in the mouth: in vitro reduction behavior of oxidizing water.

    PubMed

    Nishida, T

    1997-03-01

    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.

  10. Pilot-scale equipment development for lithium-based reduction of spent oxide fuel.

    SciTech Connect

    Herrmann, S. D.

    1998-04-24

    An integral function of the electrometallurgical conditioning of DOE spent nuclear fuel is the standardization of waste forms. Argonne National Laboratory (ANL) has developed and is presently demonstrating the electrometallurgical conditioning of sodium-bonded metal fuel from Experimental Breeder Reactor II, resulting in uranium, ceramic waste, and metal waste forms. Engineering studies are underway at ANL in support of pilot-scale equipment development, which would precondition irradiated oxide fuel and likewise demonstrate the application of electrometallurgical conditioning to such non-metallic fuels. This paper highlights the integration of proposed spent oxide fuel conditioning with existing electrometallurgical processes. Additionally, technical bases for engineering activities to support a scale up of an oxide reduction process are described.

  11. Reduction of etched AlGaAs sidewall roughness by oxygen-enhanced wet thermal oxidation

    NASA Astrophysics Data System (ADS)

    Liang, D.; Hall, D. C.

    2007-08-01

    The authors demonstrate that the oxidation smoothing of sidewall roughness of dry-etched Al0.3Ga0.7As ridge structures is enabled through a modified wet thermal oxidation process which involves the addition of dilute amounts of O2 to the water vapor ambient. High magnification cross-section and top-view scanning electron microscope imagings both before and after oxide removal clearly show a substantial reduction of photolithography- and dry-etching-induced sidewall roughness (from σ ˜100nm down to σ ˜1-2nm), occurring only with the participation of added O2. The smoothing process provides means to realize high-index-contrast GaAs-based optical waveguides with both low bend and scattering losses.

  12. Consequence of one-electron oxidation and one-electron reduction for aniline.

    PubMed

    Raczyńska, Ewa D; Stępniewski, Tomasz M; Kolczyńska, Katarzyna

    2011-12-01

    Quantum-chemical calculations were performed for all possible isomers of neutral aniline and its redox forms, and intramolecular proton-transfer (prototropy) accompanied by π-electron delocalization was analyzed. One-electron oxidation (PhNH(2) - e → [PhNH(2)](+•)) has no important effect on tautomeric preferences. The enamine tautomer is preferred for oxidized aniline similarly as for the neutral molecule. Dramatical changes take place when proceeding from neutral to reduced aniline. One-electron reduction (PhNH(2) + e → [PhNH(2)](-•)) favors the imine tautomer. Independently on the state of oxidation, π- and n-electrons are more delocalized for the enamine than imine tautomers. The change of the tautomeric preferences for reduced aniline may partially explain the origin of the CH tautomers for reduced nucleobases (cytosine, adenine, and guanine).

  13. Biogenic iron mineralization accompanying the dissimilatory reduction of hydrous ferric oxide by a groundwater bacterium

    NASA Astrophysics Data System (ADS)

    Fredrickson, James K.; Zachara, John M.; Kennedy, David W.; Dong, Hailang; Onstott, Tullis C.; Hinman, Nancy W.; Li, Shu-mei

    1998-10-01

    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)IIFe xIII(OH) 12] x+[(A 2-) x/2 · yH 2O] x- was the dominant solid phase formed; in the absence of AQDS a poorly

  14. Oxidation of fugitive methane in ground water linked to bacterial sulfate reduction.

    PubMed

    Van Stempvoort, Dale; Maathuis, Harm; Jaworski, Ed; Mayer, Bernhard; Rich, Kathleen

    2005-01-01

    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

  15. Effects of microbial iron reduction and oxidation on the immobilization and mobilization of copper in synthesized Fe(III) minerals and Fe-rich soils.

    PubMed

    Hu, Chaohua; Zhang, Youchi; Zhang, Lei; Luo, Wensui

    2014-04-01

    The effects of microbial iron reduction and oxidation on the immobilization and mobilization of copper were investigated in a high concentration of sulfate with synthesized Fe(III) minerals and red earth soils rich in amorphous Fe (hydr)oxides. Batch microcosm experiments showed that red earth soil inoculated with subsurface sediments had a faster Fe(III) bioreduction rate than pure amorphous Fe(III) minerals and resulted in quicker immobilization of Cu in the aqueous fraction. Coinciding with the decrease of aqueous Cu, SO4(2-) in the inoculated red earth soil decreased acutely after incubation. The shift in the microbial community composite in the inoculated soil was analyzed through denaturing gradient gel electrophoresis. Results revealed the potential cooperative effect of microbial Fe(III) reduction and sulfate reduction on copper immobilization. After exposure to air for 144 h, more than 50% of the immobilized Cu was remobilized from the anaerobic matrices; aqueous sulfate increased significantly. Sequential extraction analysis demonstrated that the organic matter/sulfide-bound Cu increased by 52% after anaerobic incubation relative to the abiotic treatment but decreased by 32% after oxidation, indicating the generation and oxidation of Cu-sulfide coprecipitates in the inoculated red earth soil. These findings suggest that the immobilization of copper could be enhanced by mediating microbial Fe(III) reduction with sulfate reduction under anaerobic conditions. The findings have an important implication for bioremediation in Cucontaminated and Fe-rich soils, especially in acid-mine-drainage-affected sites.

  16. Reduction of antibiotic resistance genes in municipal wastewater effluent by advanced oxidation processes.

    PubMed

    Zhang, Yingying; Zhuang, Yao; Geng, Jinju; Ren, Hongqiang; Xu, Ke; Ding, Lili

    2016-04-15

    This study investigated the reduction of antibiotic resistance genes (ARGs), intI1 and 16S rRNA genes, by advanced oxidation processes (AOPs), namely Fenton oxidation (Fe(2+)/H2O2) and UV/H2O2 process. The ARGs include sul1, tetX, and tetG from municipal wastewater effluent. The results indicated that the Fenton oxidation and UV/H2O2 process could reduce selected ARGs effectively. Oxidation by the Fenton process was slightly better than that of the UV/H2O2 method. Particularly, for the Fenton oxidation, under the optimal condition wherein Fe(2+)/H2O2 had a molar ratio of 0.1 and a H2O2 concentration of 0.01molL(-1) with a pH of 3.0 and reaction time of 2h, 2.58-3.79 logs of target genes were removed. Under the initial effluent pH condition (pH=7.0), the removal was 2.26-3.35 logs. For the UV/H2O2 process, when the pH was 3.5 with a H2O2 concentration of 0.01molL(-1) accompanied by 30min of UV irradiation, all ARGs could achieve a reduction of 2.8-3.5 logs, and 1.55-2.32 logs at a pH of 7.0. The Fenton oxidation and UV/H2O2 process followed the first-order reaction kinetic model. The removal of target genes was affected by many parameters, including initial Fe(2+)/H2O2 molar ratios, H2O2 concentration, solution pH, and reaction time. Among these factors, reagent concentrations and pH values are the most important factors during AOPs.

  17. The use of coal in a solid phase reduction of iron oxide

    NASA Astrophysics Data System (ADS)

    Nokhrina, O. I.; Rozhihina, I. D.; Hodosov, I. E.

    2015-09-01

    The results of the research process of producing metalized products by solid-phase reduction of iron using solid carbonaceous reducing agents. Thermodynamic modeling was carried out on the model of the unit the Fe-C-O and system with iron ore and coal. As a result of modeling the thermodynamic boundary reducing, oxidizing, and transition areas and the value of the ratio of carbon and oxygen in the system. Simulation of real systems carried out with the gas phase obtained in the pyrolys of coal. The simulation results allow to determine the optimal cost of coal required for complete reduction of iron ore from a given composition. The kinetics of the processes of solid-phase reduction of iron using coal of various technological brands.

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

    SciTech Connect

    Dr. Ates Akyurlu; Dr. Jale F. Akyurtlu

    2003-01-28

    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.

  19. Isolation of microorganisms involved in reduction of crystalline iron(III) oxides in natural environments.

    PubMed

    Hori, Tomoyuki; Aoyagi, Tomo; Itoh, Hideomi; Narihiro, Takashi; Oikawa, Azusa; Suzuki, Kiyofumi; Ogata, Atsushi; Friedrich, Michael W; Conrad, Ralf; Kamagata, Yoichi

    2015-01-01

    Reduction of crystalline Fe(III) oxides is one of the most important electron sinks for organic compound oxidation in natural environments. Yet the limited number of isolates makes it difficult to understand the physiology and ecological impact of the microorganisms involved. Here, two-stage cultivation was implemented to selectively enrich and isolate crystalline iron(III) oxide reducing microorganisms in soils and sediments. Firstly, iron reducers were enriched and other untargeted eutrophs were depleted by 2-years successive culture on a crystalline ferric iron oxide (i.e., goethite, lepidocrocite, hematite, or magnetite) as electron acceptor. Fifty-eight out of 136 incubation conditions allowed the continued existence of microorganisms as confirmed by PCR amplification. High-throughput Illumina sequencing and clone library analysis based on 16S rRNA genes revealed that the enrichment cultures on each of the ferric iron oxides contained bacteria belonging to the Deltaproteobacteria (mainly Geobacteraceae), followed by Firmicutes and Chloroflexi, which also comprised most of the operational taxonomic units (OTUs) identified. Venn diagrams indicated that the core OTUs enriched with all of the iron oxides were dominant in the Geobacteraceae while each type of iron oxides supplemented selectively enriched specific OTUs in the other phylogenetic groups. Secondly, 38 enrichment cultures including novel microorganisms were transferred to soluble-iron(III) containing media in order to stimulate the proliferation of the enriched iron reducers. Through extinction dilution-culture and single colony isolation, six strains within the Deltaproteobacteria were finally obtained; five strains belonged to the genus Geobacter and one strain to Pelobacter. The 16S rRNA genes of these isolates were 94.8-98.1% identical in sequence to cultured relatives. All the isolates were able to grow on acetate and ferric iron but their physiological characteristics differed considerably in

  20. Isolation of microorganisms involved in reduction of crystalline iron(III) oxides in natural environments.

    PubMed

    Hori, Tomoyuki; Aoyagi, Tomo; Itoh, Hideomi; Narihiro, Takashi; Oikawa, Azusa; Suzuki, Kiyofumi; Ogata, Atsushi; Friedrich, Michael W; Conrad, Ralf; Kamagata, Yoichi

    2015-01-01

    Reduction of crystalline Fe(III) oxides is one of the most important electron sinks for organic compound oxidation in natural environments. Yet the limited number of isolates makes it difficult to understand the physiology and ecological impact of the microorganisms involved. Here, two-stage cultivation was implemented to selectively enrich and isolate crystalline iron(III) oxide reducing microorganisms in soils and sediments. Firstly, iron reducers were enriched and other untargeted eutrophs were depleted by 2-years successive culture on a crystalline ferric iron oxide (i.e., goethite, lepidocrocite, hematite, or magnetite) as electron acceptor. Fifty-eight out of 136 incubation conditions allowed the continued existence of microorganisms as confirmed by PCR amplification. High-throughput Illumina sequencing and clone library analysis based on 16S rRNA genes revealed that the enrichment cultures on each of the ferric iron oxides contained bacteria belonging to the Deltaproteobacteria (mainly Geobacteraceae), followed by Firmicutes and Chloroflexi, which also comprised most of the operational taxonomic units (OTUs) identified. Venn diagrams indicated that the core OTUs enriched with all of the iron oxides were dominant in the Geobacteraceae while each type of iron oxides supplemented selectively enriched specific OTUs in the other phylogenetic groups. Secondly, 38 enrichment cultures including novel microorganisms were transferred to soluble-iron(III) containing media in order to stimulate the proliferation of the enriched iron reducers. Through extinction dilution-culture and single colony isolation, six strains within the Deltaproteobacteria were finally obtained; five strains belonged to the genus Geobacter and one strain to Pelobacter. The 16S rRNA genes of these isolates were 94.8-98.1% identical in sequence to cultured relatives. All the isolates were able to grow on acetate and ferric iron but their physiological characteristics differed considerably in

  1. Oxidation-reduction reactions in Ehrlich cells treated with copper-neocuproine.

    PubMed

    Byrnes, R W; Antholine, W E; Petering, D H

    1992-11-01

    The interaction of 2,9-dimethyl-1,10-phenanthroline (neocuproine or NC) and its copper complex with Ehrlich ascites tumor cells was studied. NC is frequently used as a negative control in studies of in vitro DNA degradation by copper phenanthroline and has also found use as a potential inhibitor of damage from oxidative stress in biological systems. NC inhibited Ehrlich cell growth in monolayer culture over 48 h treatment by 50% at 0.05 nmol/10(5) cells. Addition of 5- to 100-fold ratios of CuCl2 to NC (at 0.035 nmol NC/10(5) cells) produced progressively more growth inhibition. Addition of 1:0.5 ratios of NC to CuCl2 over the range of NC concentrations 0.08-0.2 nmol/10(5) cells/mL resulted in DNA single-strand breakage during 1-h treatments as measured by DNA alkaline elution. Concomitant addition of catalase or dimethyl sulfoxide (DMSO) inhibited DNA strand scission, while superoxide dismutase enhanced breakage. Catalase and DMSO also inhibited induction of membrane permeability by the copper complex of NC. These cellular effects apparently result from the intracellular generation of hydroxyl radical from H2O2. NC facilitated the uptake of copper into cells, though it was initially bound as a copper-histidine-like complex. The internalized copper was reduced to Cu(I), bound mostly as (NC)2Cu(I). To explain the (NC)2Cu-dependent generation of hydroxyl radical, it is hypothesized that glutathione successfully competes for Cu(I), converting it to a redox-active form that can catalyze the reduction of molecular oxygen to .OH. Model studies support this view. Radical scavengers did not reverse growth inhibition produced by NC or NC + CuCl2.

  2. Probing the oxidation reduction properties of terrestrially and microbially derived dissolved organic matter

    NASA Astrophysics Data System (ADS)

    Fimmen, Ryan L.; Cory, Rose M.; Chin, Yu-Ping; Trouts, Tamara D.; McKnight, Diane M.

    2007-06-01

    Dissolved organic matter (DOM) has been shown to be an integral component in biogeochemical electron transfer reactions due to its demonstrated ability to facilitate redox reactions. While the role of DOM as a facilitator of electron transfer processes has been demonstrated, greater knowledge would lead to better understanding of the structural components responsible for redox behavior, such as quinones and nitrogen and sulfur (N/S) functional groups. This investigation uses direct scan voltammetry (DSV) coupled with fluorescence and NMR spectroscopy as well as thermochemolysis gas chromatography mass spectrometry (GC-MS) and X-ray photoelectron spectroscopy (XPS) to elucidate the organic moieties responsible for facilitating electron transfer reactions. We contrast electrochemical properties and structural details of three organic matter isolates from diverse sources; Great Dismal Swamp DOM (terrestrially derived, highly aromatic), Pony Lake DOM (microbially derived, highly aliphatic) and Toolik Lake (terrestrially derived, photochemically and microbially altered) with juglone (a redox-active model quinone). Aromatic and phenolic constituents were detected (by 13C NMR) and recovered (by thermochemolysis GC-MS) from all three fulvic acid samples, highlighting the ubiquity of these compounds and suggesting that the quinone-phenol redox couple is not limited to DOM derived from lignin precursors. The range of hydroxy-benzene and benzoic acid derivatives may explain the lack of a single pair of well-defined oxidation and reduction peaks in the DSV scans. The presence of a wide-range of hydroxylated benzoic acid isomers and other redox-active aromatic residues implies that native DOM possesses overlapping redox potentials analogous to their characteristic range of p Ka values.

  3. Direct Reduction of Graphene Oxide by Ni Foam as a High-Capacitance Supercapacitor Electrode.

    PubMed

    Yang, Jing; Zhang, Enwei; Li, Xiaofeng; Yu, Yunhua; Qu, Jin; Yu, Zhong-Zhen

    2016-01-27

    Three dimensional reduced graphene oxide (RGO)/Ni foam composites are prepared by a facile approach without using harmful reducing agents. Graphene oxide is reduced by Ni foam directly in its aqueous suspension at pH 2 at room temperature, and the resultant RGO sheets simultaneously assemble around the pillars of the Ni foam. The RGO/Ni foam composite is used as a binder-free supercapacitor electrode and exhibits high electrochemical properties. Its areal capacitance is easily tuned by varying the reduction time for different RGO loadings. When the reduction time increases from 3 to 15 days, the areal capacitance of the composite increases from 26.0 to 136.8 mF cm(-2) at 0.5 mA cm(-2). Temperature is proven to be a key factor in influencing the reduction efficiency. The composite prepared by 5 h reduction at 70 °C exhibits even better electrochemical properties than its counterpart prepared by 15 day reduction at ambient temperature. The 5 h RGO/Ni foam composite shows an areal capacitance of 206.7 mF cm(-2) at 0.5 mA cm(-2) and good rate performance and cycling stability with areal capacitance retention of 97.4% after 10000 cycles at 3 mA cm(-2). Further extending the reduction time to 9 h at 70 °C, the composite shows a high areal capacitance of 323 mF cm(-2) at 0.5 mA cm(-2). Moreover, the good rate performance and cycling stability are still maintained.

  4. Risk and potential risk reduction in diabetes type 2 patients in Germany.

    PubMed

    Häussler, Bertram; Berger, Ursula; Mast, Oliver; Thefeld, Wolfgang

    2005-06-01

    Avoiding serious complications such as stroke, myocardial infarction, and amputations in diabetes patients is the main interest of long-term treatment. Given the considerable prevalence of diabetes type 2 in industrialized countries this is a major public health concern as well as a burden to health care systems. The present study estimated the current risk of major complications occurring in the German diabetes type 2 population and explored the potential for further risk reduction. Risk reduction can be achieved when physiological and behavioral parameters (HbAlc, blood pressure, cholesterol level, body mass index, smoking) are set to target values recommended in guidelines. To estimate individual risk and potential risk reduction the multifactor disease model Mellibase was employed. Data were obtained from the German Health Survey of 1998, which includes a sample of 7,124 individuals representative of the German population. The survey shows a prevalence rate of 6.3% for diabetes type 2 in persons older than 35 years. The analyses reveal that the overall potential for risk reduction is moderate (e.g., the average reduction potential of the 10-year risk of stroke is 5.7%). A majority of parameter ranges found in the patient population are either already close to the recommended values (HbA1c), are not alarmingly higher than in the general population (blood pressure) or have little impact on risk reduction. In addition nonmodifiable risk factors such as duration of the illness and advanced age constrain possible improvements. However, there is a wide variation in the actual risk between individuals (e.g., the 10-year risk of stroke varies between 2.2% and 79.8%), and thus a wide variation in potential risk reduction (the risk reduction potential for stroke varies between 0% and 53.4%). Intensified treatment should therefore (a) focus on relevant subgroups of patients taking their risk reduction potential into account and (b) aim at improvement in the overall

  5. Transition Metal Oxides for the Oxygen Reduction Reaction: Influence of the Oxidation States of the Metal and its Position on the Periodic Table.

    PubMed

    Toh, Rou Jun; Sofer, Zdeněk; Pumera, Martin

    2015-11-16

    Electrocatalysts have been developed to meet the needs and requirements of renewable energy applications. Metal oxides have been well explored and are promising for this purpose, however, many reports focus on only one or a few metal oxides at once. Herein, thirty metal oxides, which were either commercially available or synthesized by a simple and scalable method, were screened for comparison with regards to their electrocatalytic activity towards the oxygen reduction reaction (ORR). We show that although manganese, iron, cobalt, and nickel oxides generally displayed the ability to enhance the kinetics of oxygen reduction under alkaline conditions compared with bare glassy carbon, there is no significant correlation between the position of a metal on the periodic table and the electrocatalytic performance of its respective metal oxides. Moreover, it was also observed that mixed valent (+2, +3) oxides performed the poorest, compared with their respective pure metal oxides. These findings may be of paramount importance in the field of renewable energy. PMID:26351175

  6. Transition Metal Oxides for the Oxygen Reduction Reaction: Influence of the Oxidation States of the Metal and its Position on the Periodic Table.

    PubMed

    Toh, Rou Jun; Sofer, Zdeněk; Pumera, Martin

    2015-11-16

    Electrocatalysts have been developed to meet the needs and requirements of renewable energy applications. Metal oxides have been well explored and are promising for this purpose, however, many reports focus on only one or a few metal oxides at once. Herein, thirty metal oxides, which were either commercially available or synthesized by a simple and scalable method, were screened for comparison with regards to their electrocatalytic activity towards the oxygen reduction reaction (ORR). We show that although manganese, iron, cobalt, and nickel oxides generally displayed the ability to enhance the kinetics of oxygen reduction under alkaline conditions compared with bare glassy carbon, there is no significant correlation between the position of a metal on the periodic table and the electrocatalytic performance of its respective metal oxides. Moreover, it was also observed that mixed valent (+2, +3) oxides performed the poorest, compared with their respective pure metal oxides. These findings may be of paramount importance in the field of renewable energy.

  7. Observations of Oxygen Ion Behavior in the Lithium-Based Electrolytic Reduction of Uranium Oxide

    SciTech Connect

    Steven D. Herrmann; Shelly X. Li; Brenda E. Serrano-Rodriguez

    2009-09-01

    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

  8. Noise and Fuel Burn Reduction Potential of an Innovative Subsonic Transport Configuration

    NASA Technical Reports Server (NTRS)

    Guo, Yueping; Nickol, Craig L.; Thomas, Russell H.

    2014-01-01

    A study is presented for the noise and fuel burn reduction potential of an innovative double deck concept aircraft with two three-shaft direct-drive turbofan engines. The engines are mounted from the fuselage so that the engine inlet is over the main wing. It is shown that such an aircraft can achieve a cumulative Effective Perceived Noise Level (EPNL) about 28 dB below the current aircraft noise regulations of Stage 4.