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Sample records for acetate oxidation coupled

  1. Reduction of bromate to bromide coupled to acetate oxidation by anaerobic mixed microbial cultures.

    PubMed

    van Ginkel, C G; van Haperen, A M; van der Togt, B

    2005-01-01

    Bromate, a weakly mutagenic oxidizing agent, exists in surface waters. The biodegradation of bromate was investigated by assessing the ability of mixed cultures of micro-organisms for utilization of bromate as electron acceptor and acetate as electron donor. Reduction of bromate was only observed at relatively low concentrations (<3.0 mM) in the absence of molecular oxygen. Under these conditions bromate was reduced stoichiometrically to bromide. Unadapted sludge from an activated sludge treatment plant and a digester reduced bromate without lag period at a constant rate. Using an enrichment culture adapted to bromate, it was demonstrated that bromate was a terminal electron acceptor for anaerobic growth. Approximately 50% of the acetate was utilized for growth with bromate by the enrichment culture. A doubling of 20 h was estimated from a logarithmic growth curve. Other electron acceptors, like perchlorate, chlorate and nitrate, were not reduced or at negligible rates by bromate-utilizing microorganisms. PMID:15607164

  2. Acetaldehyde partial oxidation on the Au(111) model catalyst surface: C-C bond activation and formation of methyl acetate as an oxidative coupling product

    NASA Astrophysics Data System (ADS)

    Karatok, Mustafa; Vovk, Evgeny I.; Shah, Asad A.; Turksoy, Abdurrahman; Ozensoy, Emrah

    2015-11-01

    Partial oxidation of acetaldehyde (CH3CHO) on the oxygen pre-covered Au(111) single crystal model catalyst was investigated via Temperature Programmed Desorption (TPD) and Temperature Programmed Reaction Spectroscopy (TPRS) techniques, where ozone (O3) was utilized as the oxygen delivery agent providing atomic oxygen to the reacting surface. We show that for low exposures of O3 and small surface oxygen coverages, two partial oxidation products namely, methyl acetate (CH3COOCH3) and acetic acid (CH3COOH) can be generated without the formation of significant quantities of carbon dioxide. The formation of methyl acetate as the oxidative coupling reaction product implies that oxygen pre-covered Au(111) single crystal model catalyst surface can activate C-C bonds. In addition to the generation of these products; indications of the polymerization of acetaldehyde on the gold surface were also observed as an additional reaction route competing with the partial and total oxidation pathways. The interplay between the partial oxidation, total oxidation and polymerization pathways reveals the complex catalytic chemistry associated with the interaction between the acetaldehyde and atomic oxygen on catalytic gold surfaces.

  3. Methane Production and Syntrophic Acetate Oxidation in the Florida Everglades

    NASA Astrophysics Data System (ADS)

    Holmes, M. E.; Chanton, J.; Bae, H.; Ogram, A.

    2012-12-01

    Methane production pathways in the Florida Everglades are influenced by factors such as nutrient levels, H2 concentrations, and temperature. Syntrophic acetate oxidizers can outcompete methanogens for acetate when conditions are right (high temperatures and low H2). During syntrophic acetate oxidation (SAO), which becomes more exergonic with increasing temperature, acetate is oxidized to carbon dioxide and H2, which can be utilized to produce methane via CO2 reduction. Everglades soil from along a nutrient gradient was incubated at 25°C and 45°C. The shift to the CO2 reduction pathway for methane formation that would be expected in high temperature incubations due to SAO should result in a decrease in δ13C-CH4 and increase in δ2H-CH4. Instead, we observed higher δ13C and lower δ2H in the methane produced in high temperature incubations. The higher than expected δ13C may be partly explained by lower kinetic isotope effects caused by temperature. Coupling between the syntrophic acetate oxidizers and the CO2 reducers, whereby isotopically light hydrogen from acetate is used in methane formation could lower δ2H-CH4. Separate experiments using 13C-labelled acetate revealed that potential SAO activity is low in soils collected from the Everglades.

  4. Non-redox metal ion promoted oxidative coupling of indoles with olefins by the palladium(ii) acetate catalyst through dioxygen activation: experimental results with DFT calculations.

    PubMed

    Zhang, Sicheng; Chen, Zhuqi; Qin, Shuhao; Lou, Chenlin; Senan, Ahmed M; Liao, Rong-Zhen; Yin, Guochuan

    2016-04-26

    Developing new catalytic technologies through C-H bond activation to synthesize versatile pharmaceuticals has attracted much attention in recent decades. This work introduces a new strategy in catalyst design for Pd(ii)-catalyzed C-H bond activation in which non-redox metal ions serving as Lewis acids play significant roles. In the oxidative coupling of indoles with olefins using dioxygen, it was found that Pd(OAc)2 alone as the catalyst is very sluggish at ambient temperature which provided a low yield of the olefination product, whereas adding non-redox metal ions to Pd(OAc)2 substantially improves its catalytic efficiency. In particular, it provided bis(indolyl)methane derivatives as the dominant product, a category of pharmacological molecules which could not be synthesized by Pd(ii)-catalyzed oxidative coupling previously. Detailed investigations revealed that the reaction proceeds by heterobimetallic Pd(ii)/Sc(iii)-catalyzed oxidative coupling of an indole with an olefin followed by Sc(iii)-catalyzed addition with a second indole molecule. DFT calculations disclosed that the formation of heterobimetallic Pd(ii)/Sc(iii) species substantially decreases the C-H bond activation energy barrier, and shifts the rate determining step from C-H bond activation of indole to the olefination step. This non-redox metal ion promoted Pd(ii)-catalyzed C-H bond activation may offer a new opportunity for catalyst design in organic synthesis, which has not been fully recognized yet. PMID:27075840

  5. Acetate concentrations and oxidation in salt marsh sediments

    NASA Technical Reports Server (NTRS)

    1992-01-01

    Acetate concentrations and rates of acetate oxidation and sulfate reduction were measured in S. alterniflora sediments in New Hampshire and Massachusetts. Pore water extracted from cores by squeezing or centrifugation contained in greater than 0.1 mM acetate and, in some instances, greater than 1.0 mM. Pore water sampled nondestructively contained much less acetate, often less than 0.01 mM. Acetate was associated with roots, and concentrations 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 sulfate reduction and acetate oxidation not significantly different from core incubation techniques. Regardless of incubation method, acetate oxidation did not account for a substantial percentage of sulfate reduction. These results differ markedly from data for unvegetated coastal sediments where acetate levels are low, oxidation rate constants are high, and acetate oxication rates greatly exceed rates of sulfate reduction. The discrepancy between rates of acetate oxidation and sulfate reduction in these marsh soils may be due either to the utilization of substrates other than acetate by sulfate reducers or artifacts associated with measurements of organic utilization by rhizosphere bacteria. Care must be taken when interpreting data from salt marsh sediments since the release of material from roots during coring may affect the concentrations of certain compounds as well as influencing results obtained when sediment incubations are employed.

  6. Homogeneous gold-catalyzed efficient oxidative dimerization of propargylic acetates.

    PubMed

    Cui, Li; Zhang, Guozhu; Zhang, Liming

    2009-07-15

    A highly efficient gold-catalyzed oxidative dimerization of propargylic acetates is developed. In this chemistry, Selectfluor oxidation of Au(I) to Au(III) is readily incorporated into Au-catalyzed tandem reactions of propargylic acetates, and transmetallation and reductive elimination on Au(III) intermediates are likely involved. PMID:19362834

  7. Acetic acid oxidation and hydrolysis in supercritical water

    SciTech Connect

    Meyer, J.C.; Marrone, P.A.; Tester, J.W.

    1995-09-01

    Acetic acid (CH{sub 3}COOH) hydrolysis and oxidation in supercritical water were examined from 425--600 C and 246 bar at reactor residence times of 4.4 to 9.8 s. Over the range of conditions studied, acetic acid oxidation was globally 0.72 {+-} 0.15 order in acetic acid and 0.27 {+-} 0.15 order in oxygen to a 95% confidence level, with an activation energy of 168 {+-} 21 kJ/mol, a preexponential factor of 10{sup 9.9{+-}1.7}, and an induction time of about 1.5 s at 525 C. Isothermal kinetic measurements at 550 C over the range 160 to 263 bar indicated that pressure or density did not affect the rate of acetic acid oxidation as much as was previously observed in the oxidation of hydrogen or carbon monoxide in supercritical water. Major products of acetic acid oxidation in supercritical water are carbon dioxide, carbon monoxide, methane, and hydrogen. Trace amounts of propenoic acid were occasionally detected. Hydrolysis or hydrothermolysis in the absence of oxygen resulted in approximately 35% conversion of acetic acid at 600 C, 246 bar, and 8-s reactor residence time. Regression of the limited hydrolysis runs assuming a reaction rate first-order in organic gave a global rate expression with a preexponential factor of 10{sup 4.4{+-}1.1} and an activation energy of 94 {+-} 17 kJ/mol.

  8. Catalytic oxidation of butyl acetate over silver-loaded zeolites.

    PubMed

    Wong, Cheng Teng; Abdullah, Ahmad Zuhairi; Bhatia, Subhash

    2008-09-15

    The performance of silver-loaded zeolite (HY and HZSM-5) catalysts in the oxidation of butyl acetate as a model volatile organic compound (VOC) was studied. The objective was to find a catalyst with superior activity, selectivity towards deep oxidation product and stability. The catalyst activity was measured under excess oxygen condition in a packed bed reactor operated at gas hourly space velocity (GHSV)=15,000-32,000 h(-1), reaction temperature between 150 and 500 degrees C and butyl acetate inlet concentration of 1000-4000 ppm. Both AgY and AgZSM-5 catalysts exhibited high activity in the oxidation of butyl acetate. Despite lower silver content, AgY showed better activity, attributed to better metal dispersion, surface characteristics and acidity, and its pore system. Total conversion of butyl acetate was achieved at above 400 degrees C. The oxidation of butyl acetate followed a simple power law model. The reaction orders, n and m were evaluated under differential mode by varying the VOC partial pressure between 0.004 and 0.018 atm and partial pressure of oxygen between 0.05 and 0.20 atm. The reaction rate was independent of oxygen concentration and single order with respect to VOC concentration. The activation energies were 19.78 kJ/mol for AgY and 32.26 kJ/mol for AgZSM-5, respectively. PMID:18294771

  9. Rhodium(III)-catalyzed C-C coupling of 7-azaindoles with vinyl acetates and allyl acetates.

    PubMed

    Li, Shuai-Shuai; Wang, Cheng-Qi; Lin, Hui; Zhang, Xiao-Mei; Dong, Lin

    2016-01-01

    The behaviour of electron-rich alkenes with 7-azaindoles in rhodium(III)-catalyzed C-H activation is investigated. Various substituted vinyl acetates and allyl acetates as coupling partners reacted smoothly providing a wide variety of 7-azaindole derivatives, and the selectivity of the coupling reaction is alkene-dependent. In addition, the approaches of rhodium(III)-catalyzed dehydrogenative Heck-type reaction (DHR) and carbonylation reaction were quite novel and simple. PMID:26553424

  10. Syntrophic acetate oxidation in industrial CSTR biogas digesters.

    PubMed

    Sun, Li; Müller, Bettina; Westerholm, Maria; Schnürer, Anna

    2014-02-10

    The extent of syntrophic acetate oxidation (SAO) and the levels of known SAO bacteria and acetate- and hydrogen-consuming methanogens were determined in sludge from 13 commercial biogas production plants. Results from these measurements were statistically related to the prevailing operating conditions, through partial least squares (PLS) analysis. This revealed that high abundance of microorganisms involved in SAO was positively correlated with relatively low abundance of aceticlastic methanogens and high concentrations of free ammonia (>160 mg/L) and volatile fatty acids (VFA). Temperature was identified as another influencing factor for the population structure of the syntrophic acetate oxidising bacteria (SAOB). Overall, there was a high abundance of SAOB in the different digesters despite differences in their operating parameters, indicating that SAOB are an enduring and important component of biogas-producing consortia. PMID:24333792

  11. Oxidation of indole-3-acetic acid to oxindole-3-acetic acid by an enzyme preparation from Zea mays

    NASA Technical Reports Server (NTRS)

    Reinecke, D. M.; Bandurski, R. S.

    1988-01-01

    Indole-3-acetic acid is oxidized to oxindole-3-acetic acid by Zea mays tissue extracts. Shoot, root, and endosperm tissues have enzyme activities of 1 to 10 picomoles per hour per milligram protein. The enzyme is heat labile, is soluble, and requires oxygen for activity. Cofactors of mixed function oxygenase, peroxidase, and intermolecular dioxygenase are not stimulatory to enzymic activity. A heat-stable, detergent-extractable component from corn enhances enzyme activity 6- to 10-fold. This is the first demonstration of the in vitro enzymic oxidation of indole-3-acetic acid to oxindole-3-acetic acid in higher plants.

  12. Growth of geobacter sulfurreducens with acetate in syntrophic cooperation with hydrogen-oxidizing anaerobic partners

    PubMed

    Cord-Ruwisch; Lovley; Schink

    1998-06-01

    Pure cultures of Geobacter sulfurreducens and other Fe(III)-reducing bacteria accumulated hydrogen to partial pressures of 5 to 70 Pa with acetate, butyrate, benzoate, ethanol, lactate, or glucose as the electron donor if electron release to an acceptor was limiting. G. sulfurreducens coupled acetate oxidation with electron transfer to an anaerobic partner bacterium in the absence of ferric iron or other electron acceptors. Cocultures of G. sulfurreducens and Wolinella succinogenes with nitrate as the electron acceptor degraded acetate efficiently and grew with doubling times of 6 to 8 h. The hydrogen partial pressures in these acetate-degrading cocultures were considerably lower, in the range of 0.02 to 0.04 Pa. From these values and the concentrations of the other reactants, it was calculated that in this cooperation the free energy change available to G. sulfurreducens should be about -53 kJ per mol of acetate oxidized, assuming complete conversion of acetate to CO2 and H2. However, growth yields (18.5 g of dry mass per mol of acetate for the coculture, about 14 g for G. sulfurreducens) indicated considerably higher energy gains. These yield data, measurement of hydrogen production rates, and calculation of the diffusive hydrogen flux indicated that electron transfer in these cocultures may not proceed exclusively via interspecies hydrogen transfer but may also proceed through an alternative carrier system with higher redox potential, e.g., a c-type cytochrome that was found to be excreted by G. sulfurreducens into the culture fluid. Syntrophic acetate degradation was also possible with G. sulfurreducens and Desulfovibrio desulfuricans CSN but only with nitrate as electron acceptor. These cultures produced cell yields of 4.5 g of dry mass per mol of acetate, to which both partners contributed at about equal rates. These results demonstrate that some Fe(III)-reducing bacteria can oxidize organic compounds under Fe(III) limitation with the production of hydrogen

  13. Measurement of the rates of oxindole-3-acetic acid turnover, and indole-3-acetic acid oxidation in Zea mays seedlings

    NASA Technical Reports Server (NTRS)

    Nonhebel, H. M.; Bandurski, R. S. (Principal Investigator)

    1986-01-01

    Oxindole-3-acetic acid is the principal catabolite of indole-3-acetic acid in Zea mays seedlings. In this paper measurements of the turnover of oxindole-3-acetic acid are presented and used to calculate the rate of indole-3-acetic acid oxidation. [3H]Oxindole-3-acetic acid was applied to the endosperm of Zea mays seedlings and allowed to equilibrate for 24 h before the start of the experiment. The subsequent decrease in its specific activity was used to calculate the turnover rate. The average half-life of oxindole-3-acetic acid in the shoots was found to be 30 h while that in the kernels had an average half-life of 35h. Using previously published values of the pool sizes of oxindole-3-acetic acid in shoots and kernels from seedlings of the same age and variety, and grown under the same conditions, the rate of indole-3-acetic acid oxidation was calculated to be 1.1 pmol plant-1 h-1 in the shoots and 7.1 pmol plant-1 h-1 in the kernels.

  14. Conductive iron oxides accelerate thermophilic methanogenesis from acetate and propionate.

    PubMed

    Yamada, Chihaya; Kato, Souichiro; Ueno, Yoshiyuki; Ishii, Masaharu; Igarashi, Yasuo

    2015-06-01

    Anaerobic digester is one of the attractive technologies for treatment of organic wastes and wastewater, while continuous development and improvements on their stable operation with efficient organic removal are required. Particles of conductive iron oxides (e.g., magnetite) are known to facilitate microbial interspecies electron transfer (termed as electric syntrophy). Electric syntrophy has been reported to enhance methanogenic degradation of organic acids by mesophilic communities in soil and anaerobic digester. Here we investigated the effects of supplementation of conductive iron oxides (magnetite) on thermophilic methanogenic microbial communities derived from a thermophilic anaerobic digester. Supplementation of magnetite accelerated methanogenesis from acetate and propionate under thermophilic conditions, while supplementation of ferrihydrite also accelerated methanogenesis from propionate. Microbial community analysis revealed that supplementation of magnetite drastically changed bacterial populations in the methanogenic acetate-degrading cultures, in which Tepidoanaerobacter sp. and Coprothermobacter sp. dominated. These results suggest that supplementation of magnetite induce electric syntrophy between organic acid-oxidizing bacteria and methanogenic archaea and accelerate methanogenesis even under thermophilic conditions. Findings from this study would provide a possibility for the achievement of stably operating thermophilic anaerobic digestion systems with high efficiency for removal of organics and generation of CH4. PMID:25488041

  15. 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.

  16. Stable carbon isotope discrimination in rice field soil during acetate turnover by syntrophic acetate oxidation or acetoclastic methanogenesis

    NASA Astrophysics Data System (ADS)

    Conrad, Ralf; Klose, Melanie

    2011-03-01

    Rice fields are an important source for the greenhouse gas methane. In Italian rice field soil CH 4 is produced either by hydrogenotrophic and acetoclastic methanogenesis, or by hydrogenotrophic methanogenesis and syntrophic acetate oxidation when temperatures are below and above about 40-45 °C, respectively. In order to see whether these acetate consumption pathways differently discriminate the stable carbon isotopes of acetate, we measured the δ 13C of total acetate and acetate-methyl as well as the δ 13C of CO 2 and CH 4 in rice field soil that had been pre-incubated at 45 °C and then shifted to different temperatures between 25 and 50 °C. Acetate transiently accumulated to about 6 mM, which is about one-third of the amount of CH 4 produced, irrespective of the incubation temperature and the CH 4 production pathway involved. However, the patterns of δ 13C of the CH 4 and CO 2 produced were different at low (25, 30, 35 °C) versus high (40, 45, 50 °C) temperatures. These patterns were consistent with CH 4 being exclusively formed by hydrogenotrophic methanogenesis at high temperatures, and by a combination of acetoclastic and hydrogenotrophic methanogenesis at low temperatures. The patterns of δ 13C of total acetate and acetate-methyl were also different at high versus low temperatures, indicating the involvement of different pathways of production and consumption of acetate at the two temperature regimes. Isotope fractionation during consumption of the methyl group of acetate was more pronounced at low ( α = 1.010-1.025) than at high ( α = 1.0-1.01) temperatures indicating that acetoclastic methanogenesis exhibits a stronger isotope effect than syntrophic acetate oxidation. Small amounts of propionate also transiently accumulated and were analyzed for δ 13C. The δ 13C values slightly increased (by about 10‰) during production and consumption of propionate, but were not affected by incubation temperature. Collectively, our results showed distinct

  17. Propionate stimulates pyruvate oxidation in the presence of acetate

    PubMed Central

    Purmal, Colin; Kucejova, Blanka; Sherry, A. Dean; Burgess, Shawn C.; Malloy, Craig. R.

    2014-01-01

    Flux through pyruvate dehydrogenase (PDH) in the heart may be reduced by various forms of injury to the myocardium, or by oxidation of alternative substrates in normal heart tissue. It is important to distinguish these two mechanisms because imaging of flux through PDH based on the appearance of hyperpolarized (HP) [13C]bicarbonate derived from HP [1-13C]pyruvate has been proposed as a method for identifying viable myocardium. The efficacy of propionate for increasing PDH flux in the setting of PDH inhibition by an alternative substrate was studied using isotopomer analysis paired with exams using HP [1-13C]pyruvate. Hearts from C57/bl6 mice were supplied with acetate (2 mM) and glucose (8.25 mM). 13C NMR spectra were acquired in a cryogenically cooled probe at 14.1 Tesla. After addition of hyperpolarized [1-13C]pyruvate, 13C NMR signals from lactate, alanine, malate, and aspartate were easily detected, in addition to small signals from bicarbonate and CO2. The addition of propionate (2 mM) increased appearance of HP [13C]bicarbonate >30-fold without change in O2 consumption. Isotopomer analysis of extracts from the freeze-clamped hearts indicated that acetate was the preferred substrate for energy production, glucose contribution to energy production was minimal, and anaplerosis was stimulated in the presence of propionate. Under conditions where production of acetyl-CoA is dominated by the availability of an alternative substrate, acetate, propionate markedly stimulated PDH flux as detected by the appearance of hyperpolarized [13C]bicarbonate from metabolism of hyperpolarized [1-13C]pyruvate. PMID:25320331

  18. Geobacter sulfurreducens sp. nov., a hydrogen- and acetate-oxidizing dissimilatory metal-reducing microorganism.

    PubMed Central

    Caccavo, F; Lonergan, D J; Lovley, D R; Davis, M; Stolz, J F; McInerney, M J

    1994-01-01

    A dissimilatory metal- and sulfur-reducing microorganism was isolated from surface sediments of a hydrocarbon-contaminated ditch in Norman, Okla. The isolate, which was designated strain PCA, was an obligately anaerobic, nonfermentative nonmotile, gram-negative rod. PCA grew in a defined medium with acetate as an electron donor and ferric PPi, ferric oxyhydroxide, ferric citrate, elemental sulfur, Co(III)-EDTA, fumarate, or malate as the sole electron acceptor. PCA also coupled the oxidation of hydrogen to the reduction of Fe(III) but did not reduce Fe(III) with sulfur, glucose, lactate, fumarate, propionate, butyrate, isobutyrate, isovalerate, succinate, yeast extract, phenol, benzoate, ethanol, propanol, or butanol as an electron donor. PCA did not reduce oxygen, Mn(IV), U(VI), nitrate, sulfate, sulfite, or thiosulfate with acetate as the electron donor. Cell suspensions of PCA exhibited dithionite-reduced minus air-oxidized difference spectra which were characteristic of c-type cytochromes. Phylogenetic analysis of the 16S rRNA sequence placed PCA in the delta subgroup of the proteobacteria. Its closest known relative is Geobacter metallireducens. The ability to utilize either hydrogen or acetate as the sole electron donor for Fe(III) reduction makes strain PCA a unique addition to the relatively small group of respiratory metal-reducing microorganisms available in pure culture. A new species name, Geobacter sulfurreducens, is proposed. Images PMID:7527204

  19. Perovskite catalysts for oxidative coupling

    DOEpatents

    Campbell, Kenneth D.

    1991-01-01

    Perovskites of the structure A.sub.2 B.sub.2 C.sub.3 O.sub.10 are useful as catalysts for the oxidative coupling of lower alkane to heavier hydrocarbons. A is alkali metal; B is lanthanide or lanthanum, cerium, neodymium, samarium, praseodymium, gadolinium or dysprosium; and C is titanium.

  20. Perovskite catalysts for oxidative coupling

    DOEpatents

    Campbell, K.D.

    1991-06-25

    Perovskites of the structure A[sub 2]B[sub 2]C[sub 3]O[sub 10] are useful as catalysts for the oxidative coupling of lower alkane to heavier hydrocarbons. A is alkali metal; B is lanthanide or lanthanum, cerium, neodymium, samarium, praseodymium, gadolinium or dysprosium; and C is titanium.

  1. Heterogeneous Reactions of Acetic Acid with Oxide Surfaces: Effects of Mineralogy and Relative Humidity.

    PubMed

    Tang, Mingjin; Larish, Whitney A; Fang, Yuan; Gankanda, Aruni; Grassian, Vicki H

    2016-07-21

    We have investigated the heterogeneous uptake of gaseous acetic acid on different oxides including γ-Al2O3, SiO2, and CaO under a range of relative humidity conditions. Under dry conditions, the uptake of acetic acid leads to the formation of both acetate and molecularly adsorbed acetic acid on γ-Al2O3 and CaO and only molecularly adsorbed acetic acid on SiO2. More importantly, under the conditions of this study, dimers are the major form for molecularly adsorbed acetic acid on all three particle surfaces investigated, even at low acetic acid pressures under which monomers are the dominant species in the gas phase. We have also determined saturation surface coverages for acetic acid adsorption on these three oxides under dry conditions as well as Langmuir adsorption constants in some cases. Kinetic analysis shows that the reaction rate of acetic acid increases by a factor of 3-5 for γ-Al2O3 when relative humidity increases from 0% to 15%, whereas for SiO2 particles, acetic acid and water are found to compete for surface adsorption sites. PMID:27322707

  2. Oxidation of indole-3-acetic acid to oxindole-3-acetic acid by etiolated and green corn tissues

    SciTech Connect

    Reinecke, D. )

    1989-04-01

    Etiolated corn tissues oxidase indole-3-acetic acid (IAA) to oxindole-3-acetic acid (OxIAA). This oxidation results in loss of auxin activity and may plant a role in regulating IAA-stimulated growth. The enzyme has been partially purified and characterized and shown to require O{sub 2}, and a heat-stable lipid-soluble corn factor which can be replaced by linolenic or linoleic acids in the oxidation of IAA. Corn oil was tested as a cofactor in the IAA oxidation reaction. Corn oil stimulated enzyme activity by 30% while trilinolein was inactive. The capacity of green tissue to oxidize IAA was examined by incubating leaf sections from 2 week old light-grown corn seedlings with {sup 14}C-IAA. OxIAA and IAA were separated from other IAA metabolites on a 3 ml anion exchange column. Of the IAA taken up by the sections, 13% was oxidized to OxIAA. This is the first evidence that green tissue of corn may also regulate IAA levels by oxidizing IAA to OxIAA.

  3. Effects of trimetazidine in ethanol- and acetic acid-induced colitis: oxidant/anti-oxidant status.

    PubMed

    Girgin; Karaoglu; Tüzün; Erkus; Ozütemiz; Dinçer; Batur; Tanyalçin

    1999-11-01

    There is overwhelming evidence in favour of a significant role of reactive oxygen metabolites (ROM) in the pathophysiology of inflammatory bowel disease (IBD) in man and in experimental animal models. This study was undertaken to investigate the possible protective effects of pretreatment with trimetazidine (TMZ) on the oxidant-anti-oxidant balance in ethanol- and acetic acid-induced colonic damage in rats. TMZ was chosen because of its various cytoprotective features (preserving cellular ATP levels, limiting intracellular acidosis and limiting inorganic phosphate, Na(+) and Ca(2+) accumulation) and anti-oxy characteristics which were previously reported. A total of 80 rats were randomized into eight major groups each consisting of 10 animals. Animals in groups 1, 2 and 3 served as models of ethanol-induced colitis (0.25 ml of 30% (v/v) ethanol), while group 4 served as their control. Animals in groups 5, 6 and 7 served as models of acetic acid-induced colitis (1 ml of 4% (v/v) acetic acid), while group 8 served as their control. TMZ was administered 5 mg/kg by intrarectal (i.r.) and intraperitoneal (i.p.) routes to groups 1, 2, 5 and 6. Intraperitoneal administration of TMZ was used in order to evaluate its systemic effect while i.r. administration was used to determine its local effect. After decapitation, colon mucosa samples were obtained and evaluated macroscopically and microscopically. Myeloperoxidase (MPO) activities as markers for inflammation, malondialdehyde (MDA) levels as markers for oxidant stress and reduced glutathione (GSH) and oxidized glutathione (GSSG) levels as markers for anti-oxidant status were determined. Acute colitis was observed in macroscopic and microscopic evaluation in ethanol- and acetic acid-administered groups compared with controls (P = 0.000). The macroscopic and microscopic scores in colitis groups were correlated with MPO activities (r = 0.5365, P = 0.000 and r = 0.5499, P = 0.000, respectively). MDA

  4. A Phase Transfer Catalyzed Permanganate Oxidation: Preparation of Vanillin from Isoeugenol Acetate.

    ERIC Educational Resources Information Center

    Lampman, Gary M.; Sharpe, Steven D.

    1983-01-01

    Background information, laboratory procedures, and results are provided for the preparation of vanillin from isoeugenol acetate. Reaction scheme used to prepare the vanillin and a table indicating the different oxidation experiments carried out on isoeugenol or isoeugenol acetate are also provided. (JN)

  5. Coupling Reaction of Enol Derivatives with Silyl Ketene Acetals Catalyzed by Gallium Trihalides.

    PubMed

    Nishimoto, Yoshihiro; Kita, Yuji; Ueda, Hiroki; Imaoka, Hiroto; Chiba, Kouji; Yasuda, Makoto; Baba, Akio

    2016-08-01

    A cross-coupling reaction between enol derivatives and silyl ketene acetals catalyzed by GaBr3 took place to give the corresponding α-alkenyl esters. GaBr3 showed the most effective catalytic ability, whereas other metal salts such as BF3 ⋅OEt2 , AlCl3 , PdCl2 , and lanthanide triflates were not effective. Various types of enol ethers and vinyl carboxylates as enol derivatives are amenable to this coupling. The scope of the reaction with silyl ketene acetals was also broad. We successfully observed an alkylgallium intermediate by using NMR spectroscopy, suggesting a mechanism involving anti-carbogallation among GaBr3 , an enol derivative, and a silyl ketene acetal, followed by syn-β-alkoxy elimination from the alkylgallium. Based on kinetic studies, the turnover-limiting step of the reaction using a vinyl ether and a vinyl carboxylate involved syn-β-alkoxy elimination and anti-carbogallation, respectively. Therefore, the leaving group had a significant effect on the progress of the reaction. Theoretical calculations analysis suggest that the moderate Lewis acidity of gallium would contribute to a flexible conformational change of the alkylgallium intermediate and to the cleavage of the carbon-oxygen bond in the β-alkoxy elimination process, which is the turnover-limiting step in the reaction between a vinyl ether and a silyl ketene acetal. PMID:27400389

  6. Microbial community dynamics and stability during an ammonia-induced shift to syntrophic acetate oxidation.

    PubMed

    Werner, Jeffrey J; Garcia, Marcelo L; Perkins, Sarah D; Yarasheski, Kevin E; Smith, Samuel R; Muegge, Brian D; Stadermann, Frank J; DeRito, Christopher M; Floss, Christine; Madsen, Eugene L; Gordon, Jeffrey I; Angenent, Largus T

    2014-06-01

    Anaerobic digesters rely on the diversity and distribution of parallel metabolic pathways mediated by complex syntrophic microbial communities to maintain robust and optimal performance. Using mesophilic swine waste digesters, we experimented with increased ammonia loading to induce a shift from aceticlastic methanogenesis to an alternative acetate-consuming pathway of syntrophic acetate oxidation. In comparison with control digesters, we observed shifts in bacterial 16S rRNA gene content and in functional gene repertoires over the course of the digesters' 3-year operating period. During the first year, under identical startup conditions, all bioreactors mirrored each other closely in terms of bacterial phylotype content, phylogenetic structure, and evenness. When we perturbed the digesters by increasing the ammonia concentration or temperature, the distribution of bacterial phylotypes became more uneven, followed by a return to more even communities once syntrophic acetate oxidation had allowed the experimental bioreactors to regain stable operation. The emergence of syntrophic acetate oxidation coincided with a partial shift from aceticlastic to hydrogenotrophic methanogens. Our 16S rRNA gene analysis also revealed that acetate-fed enrichment experiments resulted in communities that did not represent the bioreactor community. Analysis of shotgun sequencing of community DNA suggests that syntrophic acetate oxidation was carried out by a heterogeneous community rather than by a specific keystone population with representatives of enriched cultures with this metabolic capacity. PMID:24657858

  7. Quantification of syntrophic acetate-oxidizing microbial communities in biogas processes.

    PubMed

    Westerholm, Maria; Dolfing, Jan; Sherry, Angela; Gray, Neil D; Head, Ian M; Schnürer, Anna

    2011-08-01

    Changes in communities of syntrophic acetate-oxidizing bacteria (SAOB) and methanogens caused by elevated ammonia levels were quantified in laboratory-scale methanogenic biogas reactors operating at moderate temperature (37°C) using quantitative polymerase chain reaction (qPCR). The experimental reactor was subjected to gradually increasing ammonia levels (0.8-6.9 g NH4 (+) -N l(-1) ), whereas the level of ammonia in the control reactor was kept low (0.65-0.90 g NH4 (+) -N l(-1) ) during the entire period of operation (660 days). Acetate oxidation in the experimental reactor, indicated by increased production of (14) CO2 from acetate labelled in the methyl carbon, occurred when ammonia levels reached 5.5 and 6.9 g NH4 (+) -N l(-1) . Syntrophic acetate oxidizers targeted by newly designed qPCR primers were Thermacetogenium phaeum, Clostridium ultunense, Syntrophaceticus schinkii and Tepidanaerobacter acetatoxydans. The results showed a significant increase in abundance of all these bacteria except T. phaeum in the ammonia-stressed reactor, coincident with the shift to syntrophic acetate oxidation. As the abundance of the bacteria increased, a simultaneous decrease was observed in the abundance of aceticlastic methanogens from the families Methanosaetaceae and Methanosarcinaceae. qPCR analyses of sludge from two additional high ammonia processes, in which methane production from acetate proceeded through syntrophic acetate oxidation (reactor SB) or through aceticlastic degradation (reactor DVX), demonstrated that SAOB were significantly more abundant in the SB reactor than in the DVX reactor. PMID:23761313

  8. Quantification of syntrophic acetate-oxidizing microbial communities in biogas processes

    PubMed Central

    Westerholm, Maria; Dolfing, Jan; Sherry, Angela; Gray, Neil D; Head, Ian M; Schnürer, Anna

    2011-01-01

    Changes in communities of syntrophic acetate-oxidizing bacteria (SAOB) and methanogens caused by elevated ammonia levels were quantified in laboratory-scale methanogenic biogas reactors operating at moderate temperature (37°C) using quantitative polymerase chain reaction (qPCR). The experimental reactor was subjected to gradually increasing ammonia levels (0.8–6.9 g NH4+-N l−1), whereas the level of ammonia in the control reactor was kept low (0.65–0.90 g NH4+-N l−1) during the entire period of operation (660 days). Acetate oxidation in the experimental reactor, indicated by increased production of 14CO2 from acetate labelled in the methyl carbon, occurred when ammonia levels reached 5.5 and 6.9 g NH4+-N l−1. Syntrophic acetate oxidizers targeted by newly designed qPCR primers were Thermacetogenium phaeum, Clostridium ultunense, Syntrophaceticus schinkii and Tepidanaerobacter acetatoxydans. The results showed a significant increase in abundance of all these bacteria except T. phaeum in the ammonia-stressed reactor, coincident with the shift to syntrophic acetate oxidation. As the abundance of the bacteria increased, a simultaneous decrease was observed in the abundance of aceticlastic methanogens from the families Methanosaetaceae and Methanosarcinaceae. qPCR analyses of sludge from two additional high ammonia processes, in which methane production from acetate proceeded through syntrophic acetate oxidation (reactor SB) or through aceticlastic degradation (reactor DVX), demonstrated that SAOB were significantly more abundant in the SB reactor than in the DVX reactor. PMID:23761313

  9. Indigofera oblongifolia Prevents Lead Acetate-Induced Hepatotoxicity, Oxidative Stress, Fibrosis and Apoptosis in Rats

    PubMed Central

    Abdel Moneim, Ahmed E.

    2016-01-01

    The current study was aimed to evaluate the preventive effects of Indigofera oblongifolia leaf extract (IOLE) on lead acetate (PbAc)-induced hepatotoxicity in adult male Wistar rats. PbAc was intraperitoneally injected at a dose of 20 mg/kg body weight for 5 days alone or in combination with the IOLE (100 mg/kg). Liver lead concentration and oxidative stress markers such as lipid peroxidation, hydrogen peroxide, nitric oxide, and glutathione content were investigated in addition to the enzymatic antioxidant activities. PbAc injection caused a significant elevation in the liver function parameters, lead level, lipid peroxidation, hydrogen peroxide, and nitric oxide, with a concomitant decline in the glutathione content compared with the control, accompanied by a significant inhibition of antioxidant enzyme activities. The induction of oxidative stress, lead accumulation, and histological alterations in the liver were successfully minimized by pre-administration of IOLE. In addition, the PbAc group showed increase in the levels of Bax, caspase-3, and matrix metalloproteinase-9 proteins, while the expression of Bcl-2 protein was decreased. Prior administration of IOLE significantly mitigated apoptosis and fibrosis in the liver. Finally, the major components in I. oblongifolia extract were identified as polyphenols, flavonoids, and organic acids using liquid chromatography coupled mass spectroscopy. Thus, the findings of the current study revealed that I. oblongifolia had protective, anti-fibrotic, antioxidant, and anti-apoptotic activities on PbAc-induced hepatotoxicity. The beneficial effects of I. oblongifolia were in part mediated by Nrf2/HO-1 pathway. PMID:27391413

  10. Quantifying contribution of synthrophic acetate oxidation to methane production in thermophilic anaerobic reactors by membrane inlet mass spectrometry.

    PubMed

    Mulat, Daniel Girma; Ward, Alastair James; Adamsen, Anders Peter S; Voigt, Niels Vinther; Nielsen, Jeppe Lund; Feilberg, Anders

    2014-02-18

    A unique method was developed and applied for monitoring methanogenesis pathways based on isotope labeled substrates combined with online membrane inlet quadrupole mass spectrometry (MIMS). In our study, a fermentation sample from a full-scale biogas plant fed with pig and cattle manure, maize silage, and deep litter was incubated with 100 mM of [2-(13)C] sodium acetate under thermophilic anaerobic conditions. MIMS was used to measure the isotopic distribution of dissolved CO2 and CH4 during the degradation of acetate, while excluding interference from water by applying a cold trap. After 6 days of incubation, the proportion of methane derived from reduction of CO2 had increased significantly and reached up to 87% of total methane, suggesting that synthrophic acetate oxidation coupled to hydrogenotrophic methanogenesis (SAO-HM) played an important role in the degradation of acetate. This study provided a new approach for online quantification of the relative contribution of methanogenesis pathways to methane production with a time resolution shorter than one minute. The observed contribution of SAO-HM to methane production under the tested conditions challenges the current widely accepted anaerobic digestion model (ADM1), which strongly emphasizes the importance of the acetoclastic methanogenesis. PMID:24437339

  11. A Multistep Synthesis of 4-Nitro-1-ethynylbenzene Involving Palladium Catalysis, Conformational Analysis, Acetal Hydrolysis, and Oxidative Decarbonylation

    NASA Astrophysics Data System (ADS)

    Goodwin, Thomas E.; Hurst, Eva M.; Ross, Ashley S.

    1999-01-01

    Palladium-catalyzed reactions, particularly carbon-carbon bond formations, are rapidly becoming a mainstay of organic synthesis in industrial and academic laboratories. Although these important procedures are covered in advanced organic chemistry texts, they have rarely permeated into introductory organic texts or laboratory manuals. One of the more useful processes involves the coupling of a terminal alkyne to an aromatic bromide or iodide. We describe a convenient coupling procedure for the preparation of the tetrahydropyranyl ether of a propargyl alcohol derivative. This product can be easily hydrolyzed to the propargyl alcohol, then oxidatively decarbonylated to produce 4-nitro-1-ethynylbenzene. Several important topics may be illustrated and discussed in conjunction with the multistep microscale reaction series which has been developed. These include the following: palladium-catalyzed carbon-carbon bond formation, conformational analysis by NMR spectroscopy and molecular modeling, hydrolysis of an acetal, and oxidative decarbonylation via nucleophilic acyl substitution.

  12. Genome-guided analysis of physiological and morphological traits of the fermentative acetate oxidizer Thermacetogenium phaeum

    PubMed Central

    2012-01-01

    Background Thermacetogenium phaeum is a thermophilic strictly anaerobic bacterium oxidizing acetate to CO2 in syntrophic association with a methanogenic partner. It can also grow in pure culture, e.g., by fermentation of methanol to acetate. The key enzymes of homoacetate fermentation (Wood-Ljungdahl pathway) are used both in acetate oxidation and acetate formation. The obvious reversibility of this pathway in this organism is of specific interest since syntrophic acetate oxidation operates close to the energetic limitations of microbial life. Results The genome of Th. phaeum is organized on a single circular chromosome and has a total size of 2,939,057 bp. It comprises 3.215 open reading frames of which 75% could be assigned to a gene function. The G+C content is 53.88 mol%. Many CRISPR sequences were found, indicating heavy phage attack in the past. A complete gene set for a phage was found in the genome, and indications of phage action could also be observed in culture. The genome contained all genes required for CO2 reduction through the Wood-Ljungdahl pathway, including two formyl tetrahydrofolate ligases, three carbon monoxide dehydrogenases, one formate hydrogenlyase complex, three further formate dehydrogenases, and three further hydrogenases. The bacterium contains a menaquinone MQ-7. No indications of cytochromes or Rnf complexes could be found in the genome. Conclusions The information obtained from the genome sequence indicates that Th. phaeum differs basically from the three homoacetogenic bacteria sequenced so far, i.e., the sodium ion-dependent Acetobacterium woodii, the ethanol-producing Clostridium ljungdahlii, and the cytochrome-containing Moorella thermoacetica. The specific enzyme outfit of Th. phaeum obviously allows ATP formation both in acetate formation and acetate oxidation. PMID:23259483

  13. Oxidized cellulose esters: I. Preparation and characterization of oxidized cellulose acetates--a new class of biodegradable polymers.

    PubMed

    Kumar, V; Yang, D

    2002-01-01

    Oxidized cellulose acetates (OCA), with a degree of substitution (DS) value ranging between 1.1 and 2.3 and a free carboxylic acid group content of 20% (w/w), have been prepared by reacting oxidized cellulose (OC, COOH content 20% w/w) with a mixture of acetic acid and acetic anhydride in the presence of sulfuric acid as a catalyst. The DS of OCA, in general, increased with increasing reaction temperature, reaction time, and concentration of acetic anhydride in the reaction mixture. The yield of OCA, in contrast, increased with increasing concentration of acetic anhydride and decreased with increasing reaction time and temperature. The intrinsic viscosity of OCA varied between 0.100 and 0.275, depending on the reaction conditions used during its preparation. In general, an increase in reaction temperature and the use of a prolonged reaction time decreased the intrinsic viscosity of OCA. No correlation was found between DS and intrinsic viscosity of OCA. The apparent pKa of OCA is 3.7-3.9. The new OCA polymers are practically insoluble in water and slowly dissolve in pH 7.4 phosphate buffer solution. They are, however, soluble in a range of organic solvents (e.g. ethyl acetate, acetone, acetone/water, chloroform/methylene chloride, dimethylsulfoxide, dimethylformamide, and/or chloroform/methanol). PMID:12102594

  14. Draft Genome Sequence of Clostridium ultunense Strain Esp, a Syntrophic Acetate-Oxidizing Bacterium.

    PubMed

    Manzoor, Shahid; Müller, Bettina; Niazi, Adnan; Bongcam-Rudloff, Erik; Schnürer, Anna

    2013-01-01

    Clostridium ultunense strain Esp belongs to the functional group of syntrophic acetate-oxidizing bacteria (SAOB), which have been identified as key organisms for efficient biogas production from protein-rich materials. Genome analysis and comparative genomics might aid us to define physiological features that are essential for maintaining this particular syntrophic lifestyle. PMID:23538905

  15. Draft Genome Sequence of Clostridium ultunense Strain Esp, a Syntrophic Acetate-Oxidizing Bacterium

    PubMed Central

    Manzoor, Shahid; Niazi, Adnan; Bongcam-Rudloff, Erik; Schnürer, Anna

    2013-01-01

    Clostridium ultunense strain Esp belongs to the functional group of syntrophic acetate-oxidizing bacteria (SAOB), which have been identified as key organisms for efficient biogas production from protein-rich materials. Genome analysis and comparative genomics might aid us to define physiological features that are essential for maintaining this particular syntrophic lifestyle. PMID:23538905

  16. First Genome Sequence of a Syntrophic Acetate-Oxidizing Bacterium, Tepidanaerobacter acetatoxydans Strain Re1.

    PubMed

    Manzoor, Shahid; Bongcam-Rudloff, Erik; Schnürer, Anna; Müller, Bettina

    2013-01-01

    Syntrophic acetate-oxidizing bacteria (SAOB) have been identified as key organisms for efficient biogas production from protein-rich materials. Tepidanaerobacter acetatoxydans is the first reported SAOB for which the genome has been sequenced. Genome analysis will aid us in understanding the mechanisms regulating syntrophy, particularly energy-conserving and electron transfer mechanisms. PMID:23469343

  17. First Genome Sequence of a Syntrophic Acetate-Oxidizing Bacterium, Tepidanaerobacter acetatoxydans Strain Re1

    PubMed Central

    Manzoor, Shahid; Bongcam-Rudloff, Erik; Schnürer, Anna

    2013-01-01

    Syntrophic acetate-oxidizing bacteria (SAOB) have been identified as key organisms for efficient biogas production from protein-rich materials. Tepidanaerobacter acetatoxydans is the first reported SAOB for which the genome has been sequenced. Genome analysis will aid us in understanding the mechanisms regulating syntrophy, particularly energy-conserving and electron transfer mechanisms. PMID:23469343

  18. Sphere of influence of indole acetic acid and nitric oxide in bacteria.

    PubMed

    Koul, Vatsala; Adholeya, Alok; Kochar, Mandira

    2015-05-01

    Bacterial biosynthesis of the phytohormone, indole-3-acetic acid (IAA) is well established and along with the diffusible gaseous molecule, nitric oxide (NO) is known to positively regulate the developmental processes of plant roots. IAA and NO act as signaling molecules in plant-microbe interactions as they modulate the gene expression in both, plants and microorganisms. Although IAA and NO may not be required for essential bacterial physiological processes, numerous studies point towards a crosstalk between IAA and NO in the rhizosphere. In this review, we describe various IAA and NO-responsive or sensing genes/proteins/regulators. There is also growing evidence for the interaction of IAA and NO with other plant growth regulators and the involvement of NO with the quorum sensing system in biofilm formation and virulence. This interactive network can greatly impact the host plant-microbe interactions in the soil. Coupled with this, the specialized σ(54) -dependent transcription observed in some of the IAA and NO-influenced genes can confer inducibility to these traits in bacteria and may allow the expression of IAA and NO-influenced microbial genes in nutrient limiting or changing environmental conditions for the benefit of plants. PMID:24913042

  19. Three manganese oxide-rich marine sediments harbor similar communities of acetate-oxidizing manganese-reducing bacteria.

    PubMed

    Vandieken, Verona; Pester, Michael; Finke, Niko; Hyun, Jung-Ho; Friedrich, Michael W; Loy, Alexander; Thamdrup, Bo

    2012-11-01

    Dissimilatory manganese reduction dominates anaerobic carbon oxidation in marine sediments with high manganese oxide concentrations, but the microorganisms responsible for this process are largely unknown. In this study, the acetate-utilizing manganese-reducing microbiota in geographically well-separated, manganese oxide-rich sediments from Gullmar Fjord (Sweden), Skagerrak (Norway) and Ulleung Basin (Korea) were analyzed by 16S rRNA-stable isotope probing (SIP). Manganese reduction was the prevailing terminal electron-accepting process in anoxic incubations of surface sediments, and even the addition of acetate stimulated neither iron nor sulfate reduction. The three geographically distinct sediments harbored surprisingly similar communities of acetate-utilizing manganese-reducing bacteria: 16S rRNA of members of the genera Colwellia and Arcobacter and of novel genera within the Oceanospirillaceae and Alteromonadales were detected in heavy RNA-SIP fractions from these three sediments. Most probable number (MPN) analysis yielded up to 10(6) acetate-utilizing manganese-reducing cells cm(-3) in Gullmar Fjord sediment. A 16S rRNA gene clone library that was established from the highest MPN dilutions was dominated by sequences of Colwellia and Arcobacter species and members of the Oceanospirillaceae, supporting the obtained RNA-SIP results. In conclusion, these findings strongly suggest that (i) acetate-dependent manganese reduction in manganese oxide-rich sediments is catalyzed by members of taxa (Arcobacter, Colwellia and Oceanospirillaceae) previously not known to possess this physiological function, (ii) similar acetate-utilizing manganese reducers thrive in geographically distinct regions and (iii) the identified manganese reducers differ greatly from the extensively explored iron reducers in marine sediments. PMID:22572639

  20. Studies of LDL oxidation following alpha-, gamma-, or delta-tocotrienyl acetate supplementation of hypercholesterolemic humans.

    PubMed

    O'Byrne, D; Grundy, S; Packer, L; Devaraj, S; Baldenius, K; Hoppe, P P; Kraemer, K; Jialal, I; Traber, M G

    2000-11-01

    In vitro tocotrienols (T3s) have potent vitamin E antioxidant activity, but unlike tocopherols can inhibit cholesterol synthesis by suppressing 3-hydroxy-3-methyl-glutarylCoA (HMG-CoA) reductase. Because hypercholesterolemia is a major risk factor for coronary artery disease and oxidative modification of low-density lipoprotein (LDL) may be involved in atherogenesis, we investigated whether daily supplements of placebo, or alpha-, gamma-, or delta- (alpha-, gamma-, or delta-) tocotrienyl acetates would alter serum cholesterol or LDL oxidative resistance in hypercholesterolemics in a double-blind placebo controlled study. Subjects were randomly assigned to receive placebo (n = 13), alpha- (n = 13), gamma- (n = 12), or delta- (n = 13) tocotrienyl acetate supplements (250 mg/d). All subjects followed a low-fat diet for 4 weeks, then took supplements with dinner for the following 8 weeks while still continuing diet restrictions. Plasma alpha- and gamma-tocopherols were unchanged by supplementation. Plasma T3s were undetectable initially and always in the placebo group. Following supplementation in the respective groups plasma concentrations were: alpha-T3 0.98 +/- 0.80 micromol/l, gamma-T3 0.54 +/- 0.45 micromol/l, and delta-T3 0.09 +/- 0.07 micromol/l. Alpha-T3 increased in vitro LDL oxidative resistance (+22%, p <.001) and decreased its rate of oxidation (p <. 01). Neither serum or LDL cholesterol nor apolipoprotein B were significantly decreased by tocotrienyl acetate supplements. This study demonstrates that: (i) tocotrienyl acetate supplements are hydrolyzed, absorbed, and detectable in human plasma; (ii) tocotrienyl acetate supplements do not lower cholesterol in hypercholesterolemic subjects on low-fat diets; and (iii) alpha-T3 may be potent in decreasing LDL oxidizability. PMID:11063909

  1. Multifunctional Pd/Ni-Co catalyst for hydrogen production by chemical looping coupled with steam reforming of acetic acid.

    PubMed

    Fermoso, Javier; Gil, María V; Rubiera, Fernando; Chen, De

    2014-11-01

    High yield of high-purity H2 from acetic acid, a model compound of bio-oil obtained from the fast pyrolysis of biomass, was produced by sorption-enhanced steam reforming (SESR). An oxygen carrier was introduced into a chemical loop (CL) coupled to the cyclical SESR process to supply heat in situ for the endothermic sorbent regeneration to increase the energy efficiency of the process. A new multifunctional 1 %Pd/20 %Ni-20 %Co catalyst was developed for use both as oxygen carrier in the CL and as reforming catalyst in the SESR whereas a CaO-based material was used as CO2 sorbent. In the sorbent-air regeneration step, the Ni-Co atoms in the catalyst undergo strong exothermic oxidation reactions that provide heat for the CaO decarbonation. The addition of Pd to the Ni-Co catalyst makes the catalyst active throughout the whole SESR-CL cycle. Pd significantly promotes the reduction of Ni-Co oxides to metallic Ni-Co during the reforming stage, which avoids the need for a reduction step after regeneration. H2 yield above 90 % and H2 purity above 99.2 vol % were obtained. PMID:25209388

  2. Covalent modification of graphite oxide with acetic anhydride to enhance dispersibility in organic solvents

    NASA Astrophysics Data System (ADS)

    Li, Jingjing; Yang, Anwei; Zhang, Chen; Zhang, Lei; Sun, Feifei; Ma, Ning

    2016-05-01

    Graphite oxide (GO) was modified by acetic anhydride via a catalyzed ring-opening reaction of the attached epoxy groups at very mild condition. The dispersion of the modified GO is thus largely imporved in many organic solvents and the highest GO concentration reaches 2.0mg/mL in alkyl(aryl) chlorides, ethers, alcohols and cyclohexane, which is amongst the highest value for GO in organics.

  3. Magnetostructural coupling in spinel oxides

    NASA Astrophysics Data System (ADS)

    Kemei, Moureen

    2015-03-01

    Spinels oxides are of great interest functionally as multiferroic, battery, and magnetic materials as well as fundamentally because they exhibit novel spin, structural, and orbital ground states. Competing interactions are at the heart of novel functional behavior in spinels. Here, we explore the intricate landscape of spin, lattice, and orbital interactions in magnetic spinels by employing variable-temperature high-resolution synchrotron x-ray powder diffraction, total neutron scattering, magnetic susceptibility, dielectric, and heat capacity measurements. We show that the onset of long-range magnetic interactions often gives rise to lattice distortions. Our work illustrates that the spinels NiCr2O4, CuCr2O4,andMn3O4, which are tetragonal at room temperature due to Jahn-Teller ordering, undergo further spin-driven structural distortions at the onset of long-range ferrimagnetic order. We have also studied the complete structural description of the ground states of several spinels including the geometrically frustrated spinels ZnCr2O4andMgCr2O4. The detailed spin-lattice studies of spinel oxides presented here illustrate the prevalence of structural phase coexistence when magnetostructural changes occur below 50 K. The new understanding of structural ground states in spinel oxides will guide the design of structure-property relationships in these materials. Broadly, this work highlights the importance of variable-temperature high-resolution synchrotron x-ray diffraction in understanding phase transitions in functional materials. Schlumberger Foundation Faculty for the Future fellowship, MRL Facilities funded by the NSF under Award No. DMR 1121053, and the Advanced Photon Source supported by the DOE, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.

  4. The Aerobic Oxidation of Bromide to Dibromine Catalyzed by Homogeneous Oxidation Catalysts and Initiated by Nitrate in Acetic Acid

    SciTech Connect

    Partenheimer, Walt; Fulton, John L.; Sorensen, Christina M.; Pham, Van Thai; Chen, Yongsheng

    2014-06-01

    A small amount of nitrate, ~0.002 molal, initiates the Co/Mn catalyzed aerobic oxidation of bromide compounds (HBr,NaBr,LiBr) to dibromine in acetic acid at room temperature. At temperatures 40oC or less , the reaction is autocatalytic. Co(II) and Mn(II) themselves and mixed with ionic bromide are known homogeneous oxidation catalysts. The reaction was discovered serendipitously when a Co/Br and Co/Mn/Br catalyst solution was prepared for the aerobic oxidation of methyaromatic compounds and the Co acetate contained a small amount of impurity i.e. nitrate. The reaction was characterized by IR, UV-VIS, MALDI and EXAFS spectroscopies and the coordination chemistry is described. The reaction is inhibited by water and its rate changed by pH. The change in these variables, as well as others, are identical to those observed during homogeneous, aerobic oxidation of akylaromatics. A mechanism is proposed. Accidental addition of a small amount of nitrate compound into a Co/Mn/Br/acetic acid mixture in a large, commercial feedtank is potentially dangerous.

  5. First insights into the syntrophic acetate-oxidizing bacteria – a genetic study

    PubMed Central

    Müller, Bettina; Sun, Li; Schnürer, Anna

    2013-01-01

    Syntrophic acetate-oxidizing bacteria have been identified as key organisms for efficient biogas production from protein-rich materials. They normally grow as lithotrophs or heterotrophs, producing acetate through the Wood–Ljungdahl pathway, but when growing in syntrophy with methanogens, they reportedly reverse this pathway and oxidize acetate to hydrogen and carbon dioxide. However, the biochemical and regulatory mechanisms behind the shift and the way in which the bacteria regain energy remain unknown. In a genome-walking approach, starting with degenerated primers, we identified those gene clusters in Syntrophaceticus schinkii, Clostridium ultunense, and Tepidanaerobacter acetatoxydans that comprise the formyltetrahydrofolate synthetase gene (fhs), encoding a key enzyme of the Wood–Ljungdahl pathway. We also discovered that the latter two harbor two fhs alleles. The fhs genes are phylogenetically separated and in the case of S. schinkii functionally linked to sulfate reducers. The T. acetatoxydans fhs1 cluster combines features of acetogens, sulfate reducers, and carbon monoxide oxidizers and is organized as a putative operon. The T. acetatoxydans fhs2 cluster encodes Wood–Ljungdahl pathway enzymes, which are also known to be involved in C1 carbon metabolism. Isolation of the enzymes illustrated that both formyltetrahydrofolate synthetases of T. acetatoxydans were functionally active. However, only fhs1 was expressed, confirming bidirectional usage of the pathway. PMID:23239474

  6. Differential responses of ammonia/ammonium-oxidizing microorganisms in mangrove sediment to amendment of acetate and leaf litter.

    PubMed

    Wang, Yong-Feng; Li, Xiao-Yan; Gu, Ji-Dong

    2014-04-01

    The effects of acetate and leaf litter powder on ammonia/ammonium-oxidizing microorganisms (AOMs) in mangrove sediment were investigated in a laboratory incubation study for a period of 60 days. The results showed that different AOMs responded differently to the addition of acetate and leaf litter. A higher diversity of anaerobic ammonium-oxidizing (anammox) bacteria was observed when acetate or leaf litter was added than the control. However, acetate and leaf litter generally inhibited the growth of anammox bacteria despite that leaf litter promoted their growth in the first 5 days. The inhibitory effects on anammox bacteria were more pronounced by acetate than by leaf litter. Neither acetate nor leaf litter affected ammonia-oxidizing archaea (AOA) community structures, but promoted their growth. For ammonia-oxidizing bacteria (AOB), the addition of acetate or leaf litter resulted in changes of community structures and promoted their growth in the early phase of the incubation. In addition, the promoting effects by leaf litter on AOB growth were more obvious than acetate. These results indicated that organic substances affect AOM community structures and abundances. The study suggests that leaf litter has an important influence on the community structures and abundances of AOMs in mangrove sediment and affects the nitrogen cycle in such ecosystem. PMID:24169949

  7. Controllable Tuning Plasmonic Coupling with Nanoscale Oxidation

    PubMed Central

    2015-01-01

    The nanoparticle on mirror (NPoM) construct is ideal for the strong coupling of localized plasmons because of its simple fabrication and the nanometer-scale gaps it offers. Both of these are much harder to control in nanoparticle dimers. Even so, realizing controllable gap sizes in a NPoM remains difficult and continuous tunability is limited. Here, we use reactive metals as the mirror so that the spacing layer of resulting metal oxide can be easily and controllably created with specific thicknesses resulting in continuous tuning of the plasmonic coupling. Using Al as a case study, we contrast different approaches for oxidation including electrochemical oxidation, thermal annealing, oxygen plasma treatments, and photo-oxidation by laser irradiation. The thickness of the oxidation layer is calibrated with depth-mode X-ray photoemission spectroscopy (XPS). These all consistently show that increasing the thickness of the oxidation layer blue-shifts the plasmonic resonance peak while the transverse mode remains constant, which is well matched by simulations. Our approach provides a facile and reproducible method for scalable, local and controllable fabrication of NPoMs with tailored plasmonic coupling, suited for many applications of sensing, photochemistry, photoemission, and photovoltaics. PMID:25978297

  8. Synthesis of 1,4‐Diketones from β‐Oxo Esters and Enol Acetates by ­Cerium‐Catalyzed Oxidative Umpo­lung Reaction†

    PubMed Central

    Geibel, Irina

    2016-01-01

    Abstract Cyclic β‐oxo esters are converted with enol acetates in a cerium‐catalyzed, oxidative Umpolung reaction to furnish 1,4‐diketones with up to 95 % yield. Atmospheric oxygen is the oxidant in this process, which can be regarded as ideal from economic and ecological points of view. Further advantages of this new C–C coupling reaction are its operational simplicity and the application of nontoxic and inexpensive CeCl3 ·7H2O as precatalyst.

  9. Convenient synthesis of allenylphosphoryl compounds via Cu-catalysed couplings of P(O)H compounds with propargyl acetates.

    PubMed

    Shen, Ruwei; Luo, Bing; Yang, Jianlin; Zhang, Lixiong; Han, Li-Biao

    2016-05-11

    A novel Cu-catalysed substitution reaction of propargyl acetates with P(O)H compounds is developed to afford allenylphosphoryl compounds via C-P bond coupling in high yields under mild conditions. A plausible mechanism involving the nucleophilic interception of the Cu-allenylidene intermediates is proposed. PMID:27097899

  10. Hydroxymethylation beyond Carbonylation: Enantioselective Iridium-Catalyzed Reductive Coupling of Formaldehyde with Allylic Acetates via Enantiotopic π-Facial Discrimination.

    PubMed

    Garza, Victoria J; Krische, Michael J

    2016-03-23

    Chiral iridium complexes modified by SEGPHOS catalyze the 2-propanol-mediated reductive coupling of branched allylic acetates 1a-1o with formaldehyde to form primary homoallylic alcohols 2a-2o with excellent control of regio- and enantioselectivity. These processes, which rely on enantiotopic π-facial discrimination of σ-allyliridium intermediates, represent the first examples of enantioselective formaldehyde C-C coupling beyond aldol addition. PMID:26958737

  11. ["Candidatus contubernalis alkalaceticum," an obligately syntrophic alkaliphilic bacterium capable of anaerobic acetate oxidation in a coculture with Desulfonatronum cooperativum].

    PubMed

    Zhilina, T N; Zavarzina, D G; Kolganova, T V; Turova, T P; Zavarzin, G A

    2005-01-01

    From the silty sediments of the Khadyn soda lake (Tuva), a binary sulfidogenic bacterial association capable of syntrophic acetate oxidation at pH 10.0 was isolated. An obligately syntrophic, gram-positive, spore-forming alkaliphilic rod-shaped bacterium performs acetate oxidation in a syntrophic association with a hydrogenotrophic, alkaliphilic sulfate-reducing bacterium; the latter organism was previously isolated and characterized as the new species Desulfonatronum cooperativum. Other sulfate-reducing bacteria of the genera Desulfonatronum and Desulfonatronovibrio can also act as the hydrogenotrophic partner. Apart from acetate, the syntrophic culture can oxidize ethanol, propanol, isopropanol, serine, fructose, and isobutyric acid. Selective amplification of 16S rRNA gene fragments of the acetate-utilizing syntrophic component of the binary culture was performed; it was found to cluster with clones of uncultured gram-positive bacteria within the family Syntrophomonadaceae. The acetate-oxidizing bacterium is thus the first representative of this cluster obtained in a laboratory culture. Based on its phylogenetic position, the new acetate-oxidizing syntrophic bacterium is proposed to be assigned, in a Candidate status, to a new genus and species: "Candidatus Contubernalis alkalaceticum." PMID:16400991

  12. Protective effects of Spirulina maxima on hyperlipidemia and oxidative-stress induced by lead acetate in the liver and kidney

    PubMed Central

    2010-01-01

    Background Oxidative damage has been proposed as a possible mechanism involved in lead toxicity, specially affecting the liver and kidney. Previous studies have shown the antioxidant effect of Spirulina maxima in several experimental models of oxidative stress. The current study was carried out to evaluate the antioxidant activity of Spirulina maxima against lead acetate-induced hyperlipidemia and oxidative damage in the liver and kidney of male rats. Control animals were fed on a standard diet and did not receive lead acetate (Control group). Experimental animals were fed on a standard laboratory diet with or without Spirulina maxima 5% in the standard laboratory diet and treated with three doses of lead acetate (25 mg each/weekly, intraperitoneal injection) (lead acetate with Spirulina, and lead acetate without Spirulina groups). Results The results showed that Spirulina maxima prevented the lead acetate-induced significant changes on plasma and liver lipid levels and on the antioxidant status of the liver and kidney. On the other hand, Spirulina maxima succeeded to improve the biochemical parameters of the liver and kidney towards the normal values of the Control group. Conclusions It was concluded that Spirulina maxima has protective effects on lead acetate-induced damage, and that the effects are associated with the antioxidant effect of Spirulina. PMID:20353607

  13. Bioaugmentation of Syntrophic Acetate-Oxidizing Culture in Biogas Reactors Exposed to Increasing Levels of Ammonia

    PubMed Central

    Westerholm, Maria; Levén, Lotta

    2012-01-01

    The importance of syntrophic acetate oxidation for process stability in methanogenic systems operating at high ammonia concentrations has previously been emphasized. In this study we investigated bioaugmentation of syntrophic acetate-oxidizing (SAO) cultures as a possible method for decreasing the adaptation period of biogas reactors operating at gradually increased ammonia concentrations (1.5 to 11 g NH4+-N/liter). Whole stillage and cattle manure were codigested semicontinuously for about 460 days in four mesophilic anaerobic laboratory-scale reactors, and a fixed volume of SAO culture was added daily to two of the reactors. Reactor performance was evaluated in terms of biogas productivity, methane content, pH, alkalinity, and volatile fatty acid (VFA) content. The decomposition pathway of acetate was analyzed by isotopic tracer experiments, and population dynamics were monitored by quantitative PCR analyses. A shift in dominance from aceticlastic methanogenesis to SAO occurred simultaneously in all reactors, indicating no influence by bioaugmentation on the prevailing pathway. Higher abundances of Clostridium ultunense and Tepidanaerobacter acetatoxydans were associated with bioaugmentation, but no influence on Syntrophaceticus schinkii or the methanogenic population was distinguished. Overloading or accumulation of VFA did not cause notable dynamic effects on the population. Instead, the ammonia concentration had a substantial impact on the abundance level of the microorganisms surveyed. The addition of SAO culture did not affect process performance or stability against ammonia inhibition, and all four reactors deteriorated at high ammonia concentrations. Consequently, these findings further demonstrate the strong influence of ammonia on the methane-producing consortia and on the representative methanization pathway in mesophilic biogas reactors. PMID:22923397

  14. Escherichia coli W shows fast, highly oxidative sucrose metabolism and low acetate formation.

    PubMed

    Arifin, Yalun; Archer, Colin; Lim, SooA; Quek, Lake-Ee; Sugiarto, Haryadi; Marcellin, Esteban; Vickers, Claudia E; Krömer, Jens O; Nielsen, Lars K

    2014-11-01

    Sugarcane is the most efficient large-scale crop capable of supplying sufficient carbon substrate, in the form of sucrose, needed during fermentative feedstock production. However, sucrose metabolism in Escherichia coli is not well understood because the two most common strains, E. coli K-12 and B, do not grow on sucrose. Here, using a sucrose utilizing strain, E. coli W, we undertake an in-depth comparison of sucrose and glucose metabolism including growth kinetics, metabolite profiling, microarray-based transcriptome analysis, labelling-based proteomic analysis and (13)C-fluxomics. While E. coli W grew comparably well on sucrose and glucose integration of the omics, datasets showed that during growth on each carbon source, metabolism was distinct. The metabolism was generally derepressed on sucrose, and significant flux rearrangements were observed in central carbon metabolism. These included a reduction in the flux of the oxidative pentose phosphate pathway branch, an increase in the tricarboxylic acid cycle flux and a reduction in the glyoxylate shunt flux due to the dephosphorylation of isocitrate dehydrogenase. But unlike growth on other sugars that induce cAMP-dependent Crp regulation, the phosphoenol-pyruvate-glyoxylate cycle was not active on sucrose. Lower acetate accumulation was also observed in sucrose compared to glucose cultures. This was linked to induction of the acetate catabolic genes actP and acs and independent of the glyoxylic shunt. Overall, the cells stayed highly oxidative. In summary, sucrose metabolism was fast, efficient and led to low acetate accumulation making it an ideal carbon source for industrial fermentation with E. coli W. PMID:25125039

  15. Vanadium-catalyzed regioselective oxidative coupling of 2-hydroxycarbazoles.

    PubMed

    Liu, Lei; Carroll, Patrick J; Kozlowski, Marisa C

    2015-02-01

    The first regioselective oxidative coupling of 2-hydroxycarbazoles is described. With a vanadium catalyst and oxygen as the terminal oxidant, dimers with an ortho-ortho' coupling pattern were obtained with high selectivity. Further oxidation led to ortho'-ortho' coupling to generate a tetramer, which provided insight that the atropisomerization barriers of the unsymmetrical biaryl bonds are much lower than expected. PMID:25590578

  16. Use of radiolabeled acetate to evaluate the rate of clearance of cerebral oxidative metabolites

    SciTech Connect

    Lear, J.L.; Kasliwal, R.; Duryea, R.A.

    1994-05-01

    Radiolabel derived from glucose (GLC) has been shown to have different cerebral retention kinetics than radiolabel derived from deoxyglucose (DG). In particular, activated structures with high metabolic rates have more rapid loss of GLC-derived radiolabel than DG-derived radiolabel. Because GLC-derived radiolabel can be lost from the brain glycolytically through lactate or oxidatively through CO{sub 2}, the cause of the difference between GLC and FDG is uncertain. We investigated the isolated oxidative pathway using radiolabeled acetate, which is only metabolized through the Krebs cycle. Male albino rats were anesthetized with halothane and femoral vein and artery catheters were placed. The rats were allowed to awaken for two hours prior to the studies. 100 uCi of {sup 14}C-acetate was administered as a 30 second IV infusion to each rat. Arterial samples were obtained at regular intervals. Groups of rats were killed at 5, 10, 15, 30, and 60 minutes. Brains were rapidly removed, sectioned, and used to produce autoradiograms. The extracted and retained radiolabel was calculated as the brain concentration at time of death divided by the integral of the arterial tracer concentration. No detectable loss of radiolabel was found over the initial 10 minutes. Thereafter the rate of loss gradually increased reaching a maximum of 1.2% per minute by 60 minutes. This corresponds to a k4 rate constant of 0.012 min{sup -1}. The rate of loss of oxidative metabolites from rat brain was found to be very slow. This probably results from exchange of radiolabel with amino acid pools as the tracer is metabolized through the Krebs cycle. Therefore in conditions were glycolysis is increased out of proportion to oxidation and cerebral lactate concentration rises, radiolabel loss through lactate efflux can be a substantial fraction of overall loss.

  17. Nitric oxide metabolism and indole acetic acid biosynthesis cross-talk in Azospirillum brasilense SM.

    PubMed

    Koul, Vatsala; Tripathi, Chandrakant; Adholeya, Alok; Kochar, Mandira

    2015-04-01

    Production of nitric oxide (NO) and the presence of NO metabolism genes, nitrous oxide reductase (nosZ), nitrous oxide reductase regulator (nosR) and nitric oxide reductase (norB) were identified in the plant-associated bacterium (PAB) Azospirillum brasilense SM. NO presence was confirmed in all overexpressing strains, while improvement in the plant growth response of these strains was mediated by increased NO and indole-3-acetic acid (IAA) levels in the strains. Electron microscopy showed random distribution to biofilm, with surface colonization of pleiomorphic Azospirilla. Quantitative IAA estimation highlighted a crucial role of nosR and norBC in regulating IAA biosynthesis. The NO quencher and donor reduced/blocked IAA biosynthesis by all strains, indicating their common regulatory role in IAA biosynthesis. Tryptophan (Trp) and l-Arginine (Arg) showed higher expression of NO genes tested, while in the case of ipdC, only Trp and IAA increased expression, while Arg had no significant effect. The highest nosR expression in SMnosR in the presence of IAA and Trp, along with its 2-fold IAA level, confirmed the relationship of nosR overexpression with Trp in increasing IAA. These results indicate a strong correlation between IAA and NO in A. brasilense SM and suggest the existence of cross-talk or shared signaling mechanisms in these two growth regulators. PMID:25700632

  18. Effects of surfactant mixtures, including Corexit 9527, on bacterial oxidation of acetate and alkanes in crude oil

    SciTech Connect

    Bruheim, P.; Bredholt, H.; Eimhjellen, K.

    1999-04-01

    Mixtures of nonionic and anionic surfactants, including Corexit 9527, were tested to determine their effects on bacterial oxidation of acetate and alkanes in crude oil by cells pregrown on these substrates. Corexit 9527 inhibited oxidation of the alkanes in crude oil by Acinetobacter calcoaceticus ATCC 31012, while Span 80, a Corexit 9527 constituent, markedly increased the oil oxidation rate. Another Corexit 9257 constituent, the negatively charged dioctyl sulfosuccinate (AOT), strongly reduced the oxidation rate. The combination of Span 80 and AOT increased the rate, but not as much as Span 80 alone increased it, which tentatively explained the negative effect of Corexit 9527. The results of acetate uptake and oxidation experiments indicated that the nonionic surfactants interacted with the acetate uptake system while the anionic surfactant interacted with the oxidation system of the bacteria. The overall effect of Corexit 9527 on alkane oxidation by A. calcoaceticus ATCC 31012 thus seems to be the sum of the independent effects of the individual surfactants in the surfactant mixture. When Rhodococcus sp. strain 094 was used, the alkane oxidation rate decreased to almost zero in the presence of a mixture of Tergitol 15-S-7 and AOT even though the Tergitol 15-S-7 surfactant increased the alkane oxidation rate and AOT did not affect it. This indicated that there was synergism between the two surfactants rather than an additive effect like that observed for A. calcoaceticus ATCC 31012.

  19. Bidirectional microbial electron transfer: Switching an acetate oxidizing biofilm to nitrate reducing conditions.

    PubMed

    Pous, Narcís; Carmona-Martínez, Alessandro A; Vilajeliu-Pons, Anna; Fiset, Erika; Bañeras, Lluis; Trably, Eric; Balaguer, M Dolors; Colprim, Jesús; Bernet, Nicolas; Puig, Sebastià

    2016-01-15

    Up to date a few electroactive bacteria embedded in biofilms are described to catalyze both anodic and cathodic reactions in bioelectrochemical systems (i.e. bidirectional electron transfer). How these bacteria transfer electrons to or from the electrode is still uncertain. In this study the extracellular electron transfer mechanism of bacteria within an electroactive biofilm was investigated by using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). First, a mature anodic electroactive biofilm was developed from an activated sludge sample (inoculum), acetate as electron donor and a poised electrode (+397mV vs. SHE). Later, this biofilm was "switched" to biocathodic conditions by feeding it with a medium containing nitrates and poising the electrode at -303mV vs. SHE. The electrochemical characterization indicated that both, acetate oxidation and nitrate reduction took place at a similar formal potential of -175±05 and -175±34mV vs. SHE, respectively. The biofilm was predominantly composed by Geobacter sp. at both experimental conditions. Taken together, the results indicated that both processes could be catalyzed by using the same electron conduit, and most likely by the same bacterial consortium. Hence, this study suggests that electroactive bacteria within biofilms could use the same electron transfer conduit for catalyzing anodic and cathodic reactions. PMID:26339932

  20. A nitrilo-tri-acetic-acid/acetic acid route for the deposition of epitaxial cerium oxide films as high temperature superconductor buffer layers

    SciTech Connect

    Thuy, T.T.; Lommens, P.; Narayanan, V.; Van de Velde, N.; De Buysser, K.; Herman, G.G.; Cloet, V.; Van Driessche, I.

    2010-09-15

    A water based cerium oxide precursor solution using nitrilo-tri-acetic-acid (NTA) and acetic acid as complexing agents is described in detail. This precursor solution is used for the deposition of epitaxial CeO{sub 2} layers on Ni-5at%W substrates by dip-coating. The influence of the complexation behavior on the formation of transparent, homogeneous solutions and gels has been studied. It is found that ethylenediamine plays an important role in the gelification. The growth conditions for cerium oxide films were Ar-5% gas processing atmosphere, a solution concentration level of 0.25 M, a dwell time of 60 min at 900 {sup o}C and 5-30 min at 1050 {sup o}C. X-ray diffraction (XRD), scanning electron microscope (SEM), atomic force microscopy (AFM), pole figures and spectroscopic ellipsometry were used to characterize the CeO{sub 2} films with different thicknesses. Attenuated total reflection-Fourier transform infrared (ATR-FTIR) was used to determine the carbon residue level in the surface of the cerium oxide film, which was found to be lower than 0.01%. Textured films with a thickness of 50 nm were obtained. - Graphical abstract: Study of the complexation and hydrolysis behavior of Ce{sup 4+} ions in the presence of nitrilo-tri-acetic acid and the subsequent development of an aqueous chemical solution deposition route suited for the processing of textured CeO{sub 2} buffer layers on Ni-W tapes.

  1. Protective effect of Aquilegia vulgaris (L.) against lead acetate-induced oxidative stress in rats.

    PubMed

    El-Nekeety, Aziza A; El-Kady, Ahmed A; Soliman, Mahmoud S; Hassan, Nabila S; Abdel-Wahhab, Mosaad A

    2009-09-01

    Oxidative stress has been proposed as a possible mechanism involved in lead toxicity. The current study was carried out to evaluate the antioxidant activity of the ethanol extract of Aquilegia vulgaris (L.) against lead acetate (LA)-induced oxidative stress in male rats. Tested animals were treated orally with A. vulgaris extract (100 ppm) in combination with, before, or after LA treatment (20 ppm). The results indicated that the extract alone did not induce any significant changes in body weight gain, food intake, serum biochemical chemistry or the histological picture of the liver and kidney. However, it increased significantly the level of Glutathione (GSH). On the other hand, LA decreased food intake, body weight gain and induced oxidative stress as indicated by the significant changes in serum biochemical parameters and histological picture of liver and kidney and increased lipid peroxide and reduces GSH levels in liver tissues. The extract succeeded to improve the histological pictures of liver and kidney and the biochemical parameters towards the normal values of the control. Moreover, this improvement was pronounced in the animals treated with the extract after LA intoxication. PMID:19531368

  2. Reduced toxicity of olive mill waste waters by oxidative coupling with biomimetic catalysis.

    PubMed

    Celano, Giuseppe; Smejkalová, Daniela; Spaccini, Riccardo; Piccolo, Alessandro

    2008-07-01

    Large quantities of environmentally toxic olive mill waste waters (OMWW) result from olive oil production worldwide. A synthetic water-soluble meso-tetra(2,6-dichloro-3-sulfonatophenyl)porphyrinate of iron(III) chloride (FePha) was used as biomimetic catalystto oxidatively couple toxic phenols in OMWW fractions obtained by micro-, ultra-, and nanofiltration, and reverse osmosis. The occurrence of oxidative coupling in different OMWW size-fractions was assessed by high performance size exclusion chromatography (HPSEC), before and after conformational disruption with acetic acid, and measurements of proton spin-lattice relaxation time in the rotating frame (T1(rho)H) through 13C-CPMAS-NMR spectroscopy. The concurrent reduction in toxicity of OMWW size-fractions brought about by the FePha treatment was monitored by an algal bioassay. HPSEC chromatograms of OMWW samples subjected to catalyzed coupling showed apparent weight-average molecular weight (Mwa) values varying from 18 to 185% larger than for control. Moreover, when such FePha-treated fractions were added to acetic acid prior to HPSEC, the Mwa values still ranged from 14 to 162% larger than for control fractions similarly treated with acetic acid. This evidence of polymerization among toxic phenols was confirmed by T1(rho)(H) values which were significantly enhanced by the FePha treatment, thereby indicating an increased conformational rigidity of OMWW materials. These molecular changes were reflected in a significantly reduced toxicity exerted on microalgae by the OMWW size-fractions subjected to catalyzed oxidative couplings. Our results suggest that OMWW can be effectively treated with a biomimetic catalyst to induce oxidative phenol polymerization and reduce their toxicity before amendments to soils or other disposal means. PMID:18678023

  3. Vanadium-Catalyzed Regioselective Oxidative Coupling of 2-Hydroxycarbazoles

    PubMed Central

    2016-01-01

    The first regioselective oxidative coupling of 2-hydroxycarbazoles is described. With a vanadium catalyst and oxygen as the terminal oxidant, dimers with an ortho–ortho′ coupling pattern were obtained with high selectivity. Further oxidation led to ortho′–ortho′ coupling to generate a tetramer, which provided insight that the atropisomerization barriers of the unsymmetrical biaryl bonds are much lower than expected. PMID:25590578

  4. Oxidative Dehydrogenative Couplings of Pyrazol-5-amines Selectively Forming Azopyrroles

    PubMed Central

    2015-01-01

    New oxidative dehydrogenative couplings of pyrazol-5-amines for the selective synthesis of azopyrrole derivatives have been described. The former reaction simultaneously installs C–I and N–N bonds through iodination and oxidation, whereas the latter involved a copper-catalyzed oxidative coupling process. The resulting iodo-substituted azopyrroles were employed by treatment with various terminal alkynes through Sonogashira cross-coupling leading to new azo compounds. PMID:24731223

  5. Gold-catalyzed homogeneous oxidative cross-coupling reactions.

    PubMed

    Zhang, Guozhu; Peng, Yu; Cui, Li; Zhang, Liming

    2009-01-01

    Oxidizing gold? A gold(I)/gold(III) catalytic cycle is essential for the first oxidative cross-coupling reaction in gold catalysis. By using Selectfluor for gold(I) oxidation, this chemistry reveals the synthetic potential of incorporating gold(I)/gold(III) catalytic cycles into contemporary gold chemistry and promises a new area of gold research by merging powerful gold catalysis and oxidative metal-catalyzed cross-coupling reactions. PMID:19322869

  6. Ethyl Acetate Abatement on Copper Catalysts Supported on Ceria Doped with Rare Earth Oxides.

    PubMed

    Carabineiro, Sónia Alexandra Correia; Konsolakis, Michalis; Marnellos, George Emmanouil-Nontas; Asad, Muhammad Faizan; Soares, Olívia Salomé Gonçalves Pinto; Tavares, Pedro Bandeira; Pereira, Manuel Fernando Ribeiro; Órfão, José Joaquim de Melo; Figueiredo, José Luís

    2016-01-01

    Different lanthanide (Ln)-doped cerium oxides (Ce0.5Ln0.5O1.75, where Ln: Gd, La, Pr, Nd, Sm) were loaded with Cu (20 wt. %) and used as catalysts for the oxidation of ethyl acetate (EtOAc), a common volatile organic compound (VOC). For comparison, both Cu-free (Ce-Ln) and supported Cu (Cu/Ce-Ln) samples were characterized by N₂ adsorption at -196 °C, scanning/transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy and temperature programmed reduction in H₂. The following activity sequence, in terms of EtOAc conversion, was found for bare supports: CeO₂ ≈ Ce0.5Pr0.5O1.75 > Ce0.5Sm0.5O1.75 > Ce0.5Gd0.5O1.75 > Ce0.5Nd0.5O1.75 > Ce0.5La0.5O1.75. Cu addition improved the catalytic performance, without affecting the activity order. The best catalytic performance was obtained for Cu/CeO₂ and Cu/Ce0.5Pr0.5O1.75 samples, both achieving complete EtOAc conversion below ca. 290 °C. A strong correlation was revealed between the catalytic performance and the redox properties of the samples, in terms of reducibility and lattice oxygen availability. Νo particular correlation between the VOC oxidation performance and textural characteristics was found. The obtained results can be explained in terms of a Mars-van Krevelen type redox mechanism involving the participation of weakly bound (easily reduced) lattice oxygen and its consequent replenishment by gas phase oxygen. PMID:27196886

  7. [Research progress in microbial methane oxidation coupled to denitrification].

    PubMed

    Zhu, Jing; Yuan, Meng-Dong; Liu, Jing-Jing; Huang, Xiao-Xiao; Wu, Wei-Xiang

    2013-12-01

    Methane oxidation coupled to denitrification is an essential bond to connect carbon- and nitrogen cycling. To deeply research this process will improve our understanding on the biochemical cycling of global carbon and nitrogen. As an exogenous gaseous carbon source of denitrification, methane can both regulate the balance of atmospheric methane to effectively mitigate the greenhouse effect caused by methane, and reduce the cost of exogenous carbon source input in traditional wastewater denitrification treatment process. As a result, great attention has being paid to the mechanical study of the process. This paper mainly discussed the two types of methane oxidation coupled to denitrification, i. e., aerobic methane oxidation coupled to denitrification (AME-D) and anaerobic methane oxidation coupled to denitrification (ANME-D), with the focus on the microbiological coupling mechanisms and related affecting factors. The existing problems in the engineering application of methane oxidation coupled to denitrification were pointed out, and the application prospects were approached. PMID:24697087

  8. Exciton-Plasmon Coupling Enhancement via Metal Oxidation.

    PubMed

    Todisco, Francesco; D'Agostino, Stefania; Esposito, Marco; Fernández-Domínguez, Antonio I; De Giorgi, Milena; Ballarini, Dario; Dominici, Lorenzo; Tarantini, Iolena; Cuscuná, Massimo; Della Sala, Fabio; Gigli, Giuseppe; Sanvitto, Daniele

    2015-10-27

    In this paper, we report on the effect of metal oxidation on strong coupling interactions between silver nanostructures and a J-aggregated cyanine dye. We show that metal oxidation can sensibly affect the plexcitonic system, inducing a change in the coupling strength. In particular, we demonstrate that the presence of oxide prevents the appearance of Rabi splitting in the extinction spectra for thick spacers. In contrast, below a threshold percentage, the oxide layer results in an higher coupling strength between the plasmon and the Frenkel exciton. Contrary to common belief, a thin oxide layer seems thus to act, under certain conditions, as a coupling mediator between an emitter and a localized surface plasmon excited in a metallic nanostructure. This suggests that metal oxidation can be exploited as a means to enhance light-matter interactions in strong coupling applications. PMID:26378956

  9. Constructing a polyfunctional zeolite-encaged metal catalyst for the multistage oxidation of ethanol into ethyl acetate

    SciTech Connect

    Shakhtakhtinskii, T.N.; Aliev, A.M.; Kuliev, A.R.

    1995-08-01

    To construct an efficient polyfunctional catalyst for the given multistage reaction, the authors previously studied the catalysts HNaY, clinosorb, H-clinoptilolite, and H-mordenite in the reaction of esterification of ethanol with acetic acid; CuH-clinoptilolite, Cu-clinosorb, CuH-mordenite, and CuHNaY in the reaction of oxidative dehydration of ethanol; PdH-clinoptilolite, Pd-clinosorb, PdH-mordenite, and PdHNaY in the oxidation of ethanol; and CuPdH-clinoptilolite in the oxidative transformation of ethanol into ethyl acetate. The catalytic activity of these zeolites and other Pd- and Cu-containing zeolite catalysts, which the authors synthesized by the ion-exchange technique, was studied in a flow-circulating set-up.

  10. Kinetics of cytochrome P450 2E1-catalyzed oxidation of ethanol to acetic acid via acetaldehyde.

    PubMed

    Bell-Parikh, L C; Guengerich, F P

    1999-08-20

    The P450 2E1-catalyzed oxidation of ethanol to acetaldehyde is characterized by a kinetic deuterium isotope effect that increases K(m) with no effect on k(cat), and rate-limiting product release has been proposed to account for the lack of an isotope effect on k(cat) (Bell, L. C., and Guengerich, F. P. (1997) J. Biol. Chem. 272, 29643-29651). Acetaldehyde is also a substrate for P450 2E1 oxidation to acetic acid, and k(cat)/K(m) for this reaction is at least 1 order of magnitude greater than that for ethanol oxidation to acetaldehyde. Acetic acid accounts for 90% of the products generated from ethanol in a 10-min reaction, and the contribution of this second oxidation has been overlooked in many previous studies. The noncompetitive intermolecular kinetic hydrogen isotope effects on acetaldehyde oxidation to acetic acid ((H)(k(cat)/K(m))/(D)(k(cat)/K(m)) = 4.5, and (D)k(cat) = 1.5) are comparable with the isotope effects typically observed for ethanol oxidation to acetaldehyde, and k(cat) is similar for both reactions, suggesting a possible common catalytic mechanism. Rapid quench kinetic experiments indicate that acetic acid is formed rapidly from added acetaldehyde (approximately 450 min(-1)) with burst kinetics. Pulse-chase experiments reveal that, at a subsaturating concentration of ethanol, approximately 90% of the acetaldehyde intermediate is directly converted to acetic acid without dissociation from the enzyme active site. Competition experiments suggest that P450 2E1 binds acetic acid and acetaldehyde with relatively high K(d) values, which preclude simple tight binding as an explanation for rate-limiting product release. The existence of a rate-determining step between product formation and release is postulated. Also proposed is a conformational change in P450 2E1 occurring during the course of oxidation and the discrimination of P450 2E1 between acetaldehyde and its hydrated form, the gem-diol. This multistep P450 reaction is characterized by kinetic

  11. Punicalagin Mollifies Lead Acetate-Induced Oxidative Imbalance in Male Reproductive System.

    PubMed

    Rao, Faiza; Zhai, Yiwen; Sun, Fei

    2016-01-01

    Punicalagin (PU) is a known antioxidant. The present study examined PU to protect against lead-induced oxidative stress (OS) testicular damage in mice. Significant increase in lipid peroxidation (LPO) after intraperitoneal injection of lead acetate (LA) indicated enormous generation of reactive oxygen species (ROS). Lead-induced OS has a direct effect on the differentiation of spermatogonial cells, showing a significant decline in sperm count. Supplementation of PU significantly changes values of LPO and glutathione (GSH) with a concomitant increase in sperm count, a marked decrease in the abnormal sperms, and a decline in the morphologically abnormal sperm population. Moreover, the histopathological evaluation of testes and epididymides showed severe changes in mice treated with LA. PU significantly induced nuclear factor erythroid-2 related factor 2-like 2 (Nrf2) expression and phase II enzymes, and data suggest that PU may inhibit OS through Nrf2 activation. The fertility test proved that PU might play an important role in male infertility treatment, especially in the type of infertility induced by OS. PMID:27529221

  12. Punicalagin Mollifies Lead Acetate-Induced Oxidative Imbalance in Male Reproductive System

    PubMed Central

    Rao, Faiza; Zhai, Yiwen; Sun, Fei

    2016-01-01

    Punicalagin (PU) is a known antioxidant. The present study examined PU to protect against lead-induced oxidative stress (OS) testicular damage in mice. Significant increase in lipid peroxidation (LPO) after intraperitoneal injection of lead acetate (LA) indicated enormous generation of reactive oxygen species (ROS). Lead-induced OS has a direct effect on the differentiation of spermatogonial cells, showing a significant decline in sperm count. Supplementation of PU significantly changes values of LPO and glutathione (GSH) with a concomitant increase in sperm count, a marked decrease in the abnormal sperms, and a decline in the morphologically abnormal sperm population. Moreover, the histopathological evaluation of testes and epididymides showed severe changes in mice treated with LA. PU significantly induced nuclear factor erythroid-2 related factor 2-like 2 (Nrf2) expression and phase II enzymes, and data suggest that PU may inhibit OS through Nrf2 activation. The fertility test proved that PU might play an important role in male infertility treatment, especially in the type of infertility induced by OS. PMID:27529221

  13. Ammonia effect on hydrogenotrophic methanogens and syntrophic acetate-oxidizing bacteria.

    PubMed

    Wang, Han; Fotidis, Ioannis A; Angelidaki, Irini

    2015-11-01

    Ammonia-rich substrates can cause inhibition on anaerobic digestion process. Syntrophic acetate-oxidizing bacteria (SAOB) and hydrogenotrophic methanogens are important for the ammonia inhibitory mechanism on anaerobic digestion. The roles and interactions of SAOB and hydrogenotrophic methanogens to ammonia inhibition effect are still unclear. The aim of the current study was to determine the ammonia toxicity levels of various pure strains of SAOB and hydrogenotrophic methanogens. Moreover, ammonia toxicity on the syntrophic-cultivated strains of SAOB and hydrogenotrophic methanogens was tested. Thus, four hydrogenotrophic methanogens (i.e. Methanoculleus bourgensis, Methanobacterium congolense, Methanoculleu thermophilus and Methanothermobacter thermautotrophicus), two SAOB (i.e. Tepidanaerobacter acetatoxydans and Thermacetogenium phaeum) and their syntrophic cultivation were assessed under 0.26, 3, 5 and 7 g NH4 (+)-N L(-1). The results showed that some hydrogenotrophic methanogens were equally, or in some cases, more tolerant to high ammonia levels compared to SAOB. Furthermore, a mesophilic hydrogenotrophic methanogen was more sensitive to ammonia toxicity compared to thermophilic methanogens tested in the study, which is contradicting to the general belief that thermophilic methanogens are more vulnerable to high ammonia loads compared to mesophilic. This unexpected finding underlines the fact that the complete knowledge of ammonia inhibition effect on hydrogenotrophic methanogens is still absent. PMID:26490748

  14. Myrrh attenuates oxidative and inflammatory processes in acetic acid-induced ulcerative colitis

    PubMed Central

    Fatani, Amal Jamil; Alrojayee, Fatima Salih; Parmar, Mihir Yogeshkumar; Abuohashish, Hatem Mustafa; Ahmed, Mohammed Mahboobuddin; Al-Rejaie, Salim Salih

    2016-01-01

    The pathogenesis of ulcerative colitis (UC) has been associated with a weakened antioxidant capacity and increased inflammatory processes. Myrrh is traditionally used for the treatment of inflammatory diseases due to its antioxidant and anti-inflammatory properties. The present study aimed to evaluate the effects of myrrh on an experimental rat model of UC. UC was induced in rats using acetic acid (AA) after pre-treatment with myrrh (125, 250 or 500 mg/kg/day) or mesalazine (MES; 300 mg/kg/day) for 7 days. The levels of various inflammatory cytokines, prostaglandin E2 (PGE2) and nitric oxide (NO) in the rat colon tissues were assessed. In addition, the colonic levels of thiobarbituric acid reactive substances (TBARS) and non-protein sulfhydryl groups (NP-SH), as well as the activities of superoxide dismutase (SOD) and catalase (CAT), were estimated. Furthermore, total protein (TP) contents and the levels of DNA and RNA were measured, and histopathological changes in colonic tissues were analyzed. The results indicated that the levels of pro-inflammatory cytokines, PGE2, NO and TBARS were markedly increased. By contrast, the levels of interleukin-10, NP-SH, TP and nucleic acids, and the enzymatic activities of SOD and CAT were significantly decreased in the AA model group. In addition, pretreatment with myrrh and MES was able to attenuate the impaired oxidative stress response and upregulation of inflammatory biomarkers. Furthermore, the enzymatic activities of SOD and CAT were near to normal in the myrrh and MES pretreated groups. The ability of myrrh to protect against UC was further confirmed by histopathological analysis, and the high dose of myrrh exerted an effect comparable to MES. In conclusion, the results of the present study suggested that myrrh has potent therapeutic value in the amelioration of experimental colitis in laboratory animals by downregulating the expression of proinflammatory mediators and improving endogenous antioxidative activities. PMID

  15. Titanium oxidation by rf inductively coupled plasma

    NASA Astrophysics Data System (ADS)

    Valencia-Alvarado, R.; de la Piedad-Beneitez, A.; López-Callejas, R.; Barocio, S. R.; Mercado-Cabrera, A.; Peña-Eguiluz, R.; Muñoz-Castro, A. E.; Rodríguez-Méndez, B. G.; de la Rosa-Vázquez, J. M.

    2014-05-01

    The development of titanium dioxide (TiO2) films in the rutile and anatase phases is reported. The films have been obtained from an implantation/diffusion and sputtering process of commercially pure titanium targets, carried out in up to 500 W plasmas. The experimental outcome is of particular interest, in the case of anatase, for atmospheric pollution degradation by photocatalysis and, as to the rutile phase, for the production of biomaterials required by prosthesis and implants. The reactor employed consists in a cylindrical pyrex-like glass vessel inductively coupled to a 13.56 MHz RF source. The process takes place at a 5×10-2 mbar pressure with the target samples being biased from 0 to -3000 V DC. The anatase phase films were obtained from sputtering the titanium targets over glass and silicon electrically floated substrates placed 2 cm away from the target. The rutile phase was obtained by implantation/diffusion on targets at about 700 °C. The plasma was developed from a 4:1 argon/oxygen mixture for ~5 hour processing periods. The target temperature was controlled by means of the bias voltage and the plasma source power. The obtained anatase phases did not require annealing after the plasma oxidation process. The characterization of the film samples was conducted by means of x-ray diffraction, scanning electron microscopy, x-ray photoelectron spectroscopy and Raman spectroscopy.

  16. Magnetostructural and magnetodielectric coupling in spinel oxides

    NASA Astrophysics Data System (ADS)

    Kemei, Moureen Chemurgor

    Spinels oxides are of great interest functionally as multiferroic, battery, and magnetic materials as well as fundamentally because they exhibit novel spin, structural, and orbital ground states. Competing interactions are at the heart of novel functional behavior in spinels. Here, we explore the intricate landscape of spin, lattice, and orbital interactions in magnetic spinels by employing variable-temperature high-resolution synchrotron x-ray powder diffraction, total neutron scattering, magnetic susceptibility, dielectric, and heat capacity measurements. We show that the onset of long-range magnetic interactions often gives rise to lattice distortions. We present the complete crystallographic descriptions of the ground state structures of several spinels, thereby paving the way for accurate modeling and design of structure-property relationships in these materials. We also report the emergence of magnetodielectric coupling in the magnetostructural phases of some of the studied spinels. We begin by examining spin-lattice coupling in the Jahn-Teller active systems NiCr2O4 and CuCr2O4. Orbital ordering yields a cubic to tetragonal lattice distortion in these materials above their magnetic ordering temperatures, however, we find that magnetic ordering also drives structural distortions in these spinels through exchange striction. We provide the first orthorhombic structural descriptions of NiCr 2O4 and CuCr2O4. Our observation of strong spin-lattice coupling in NiCr2O4 and CuCr 2O4 inspired the study of magnetodielectric coupling in these spinels. Magnetocapacitance measurements of NiCr2O4 reveal multiferroic behavior and new magnetostructural distortions below the Neel temperature. This observation illustrates the sensitivity of dielectric measurements to magnetostructural transitions in spinel materials. Finally, in the examination of NiCr2O4 we show that magnetodielectric coupling is well described by Ginzburg-Landau theory. In addition to exchange striction

  17. Solvent-Controlled, Tunable β-OAc and β-H Elimination in Rh(III)-Catalyzed Allyl Acetate and Aryl Amide Coupling via C-H Activation.

    PubMed

    Dai, Huimin; Yu, Chao; Wang, Zihao; Yan, Hong; Lu, Changsheng

    2016-07-15

    The Heck reaction between arenes and allyl acetate has led to cinnamyl derivatives and allyl products depending on the regioselectivity of β-elimination. The regioselectivity can be controlled by the solvent in the Rh(III)-catalyzed arene-allyl acetate coupling via C-H activation: (1) in THF, cinnamyl derivatives via β-H elimination were generated; (2) in MeOH, allyl products via β-OAc elimination were produced. Both routes have advantages such as excellent γ-selectivity toward allyl acetate, good to excellent yields, and broad substrate scope. PMID:27351917

  18. Role of nitric oxide in the convulsive seizures induced by fluoroquinolones coadministered with 4-biphenyl acetic acid.

    PubMed

    Kohno, K; Niwa, M; Nozaki, M; Uematsu, T; Fujimura, H

    1997-11-01

    1. Contribution of nitric oxide to the convulsive seizures induced by fluoroquinolones (FQs) coadministered with 4-biphenyl acetic acid (BPAA), the active metabolite of fenbufen, was assessed in mice. 2. Enoxacin + 4-biphenyl acetic acid caused clonic seizures in all treated mice, followed by tonic seizures and death. These events were associated with a significant increase in intracerebellar cyclic GMP. 3. Pretreatment with the nitric oxide synthase (NOS) inhibitor, NG-nitro-L-arginine methylester (L-NAME), but not with D-NAME, significantly reduced the incidence of convulsions and lethality, as well as the increase in cyclic GMP. 4. Pretreatment with N-methyl-D-aspartic acid (NMDA)-receptor antagonist, MK-801, inhibited only the transition of clonic seizure to tonic seizure without affecting the incidence of clonic seizure and lethality. 5. These findings suggest that FQs + BPAA exert convulsions by activating NOS partly through the mediation of the NMDA receptor in the brain cells. PMID:9347323

  19. Oxidation of indole-3-acetic acid and oxindole-3-acetic acid to 2,3-dihydro-7-hydroxy-2-oxo-1H indole-3-acetic acid-7'-O-beta-D-glucopyranoside in Zea mays seedlings

    NASA Technical Reports Server (NTRS)

    Nonhebel, H. M.; Bandurski, R. S.

    1984-01-01

    Radiolabeled oxindole-3-acetic acid was metabolized by roots, shoots, and caryopses of dark grown Zea mays seedlings to 2,3-dihydro-7-hydroxy-2-oxo-1H indole-3-acetic acid-7'-O-beta-D-glycopyranoside with the simpler name of 7-hydroxyoxindole-3-acetic acid-glucoside. This compound was also formed from labeled indole-3-acetic acid supplied to intact seedlings and root segments. The glucoside of 7-hydroxyoxindole-3-acetic acid was also isolated as an endogenous compound in the caryopses and shoots of 4-day-old seedlings. It accumulates to a level of 4.8 nanomoles per plant in the kernel, more than 10 times the amount of oxindole-3-acetic acid. In the shoot it is present at levels comparable to that of oxindole-3-acetic acid and indole-3-acetic acid (62 picomoles per shoot). We conclude that 7-hydroxyoxindole-3-acetic acid-glucoside is a natural metabolite of indole-3-acetic acid in Z. mays seedlings. From the data presented in this paper and in previous work, we propose the following route as the principal catabolic pathway for indole-3-acetic acid in Zea seedlings: Indole-3-acetic acid --> Oxindole-3-acetic acid --> 7-Hydroxyoxindole-3-acetic acid --> 7-Hydroxyoxindole-3-acetic acid-glucoside.

  20. Application of Anaerobic Digestion Model No. 1 to describe the syntrophic acetate oxidation of poultry litter in thermophilic anaerobic digestion.

    PubMed

    Rivera-Salvador, Víctor; López-Cruz, Irineo L; Espinosa-Solares, Teodoro; Aranda-Barradas, Juan S; Huber, David H; Sharma, Deepak; Toledo, J Ulises

    2014-09-01

    A molecular analysis found that poultry litter anaerobic digestion was dominated by hydrogenotrophic methanogens which suggests that bacterial acetate oxidation is the primary pathway in the thermophilic digestion of poultry litter. IWA Anaerobic Digestion Model No. 1 (ADM1) was modified to include the bacterial acetate oxidation process in the thermophilic anaerobic digestion (TAD). Two methods for ADM1 parameter estimation were applied: manual calibration with non-linear least squares (MC-NLLS) and an automatic calibration using differential evolution algorithms (DEA). In terms of kinetic parameters for acetate oxidizing bacteria, estimation by MC-NLLS and DEA were, respectively, km 1.12 and 3.25 ± 0.56 kg COD kg COD(-1)d(-1), KS 0.20 and 0.29 ± 0.018 kg COD m(-3) and Yac-st 0.14 and 0.10 ± 0.016 kg COD kg COD(-1). Experimental and predicted volatile fatty acids and biogas composition were in good agreement. Values of BIAS, MSE or INDEX demonstrate that both methods (MC-NLLS and DEA) increased ADM1 accuracy. PMID:25011081

  1. Hydrogen and Formate Oxidation Coupled to Dissimilatory Reduction of Iron or Manganese by Alteromonas putrefaciens

    PubMed Central

    Lovley, Derek R.; Phillips, Elizabeth J. P.; Lonergan, Debra 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. PMID:16347876

  2. 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.

  3. Genome-guided analysis of physiological capacities of Tepidanaerobacter acetatoxydans provides insights into environmental adaptations and syntrophic acetate oxidation.

    PubMed

    Müller, Bettina; Manzoor, Shahid; Niazi, Adnan; Bongcam-Rudloff, Erik; Schnürer, Anna

    2015-01-01

    This paper describes the genome-based analysis of Tepidanaerobacter acetatoxydans strain Re1, a syntrophic acetate-oxidising bacterium (SAOB). Principal issues such as environmental adaptations, metabolic capacities, and energy conserving systems have been investigated and the potential consequences for syntrophic acetate oxidation discussed. Briefly, in pure culture, T. acetatoxydans grows with different organic compounds and produces acetate as the main product. In a syntrophic consortium with a hydrogenotrophic methanogen, it can also reverse its metabolism and instead convert acetate to formate/H2 and CO2. It can only proceed if the product formed is continuously removed. This process generates a very small amount of energy that is scarcely enough for growth, which makes this particular syntrophy of special interest. As a crucial member of the biogas-producing community in ammonium-rich engineered AD processes, genomic features conferring ammonium resistance, bacterial defense, oxygen and temperature tolerance were found, as well as attributes related to biofilm formation and flocculation. It is likely that T. acetatoxydans can form an electrochemical gradient by putative electron-bifurcating Rnf complex and [Fe-Fe] hydrogenases, as observed in other acetogens. However, genomic deficiencies related to acetogenic metabolism and anaerobic respiration were discovered, such as the lack of formate dehydrogenase and F1F0 ATP synthase. This has potential consequences for the metabolic pathways used under SAO and non-SAO conditions. The two complete sets of bacteriophage genomes, which were found to be encoded in the genome, are also worthy of mention. PMID:25811859

  4. Genome-Guided Analysis of Physiological Capacities of Tepidanaerobacter acetatoxydans Provides Insights into Environmental Adaptations and Syntrophic Acetate Oxidation

    PubMed Central

    Niazi, Adnan; Bongcam-Rudloff, Erik; Schnürer, Anna

    2015-01-01

    This paper describes the genome-based analysis of Tepidanaerobacter acetatoxydans strain Re1, a syntrophic acetate-oxidising bacterium (SAOB). Principal issues such as environmental adaptations, metabolic capacities, and energy conserving systems have been investigated and the potential consequences for syntrophic acetate oxidation discussed. Briefly, in pure culture, T. acetatoxydans grows with different organic compounds and produces acetate as the main product. In a syntrophic consortium with a hydrogenotrophic methanogen, it can also reverse its metabolism and instead convert acetate to formate/H2 and CO2. It can only proceed if the product formed is continuously removed. This process generates a very small amount of energy that is scarcely enough for growth, which makes this particular syntrophy of special interest. As a crucial member of the biogas-producing community in ammonium-rich engineered AD processes, genomic features conferring ammonium resistance, bacterial defense, oxygen and temperature tolerance were found, as well as attributes related to biofilm formation and flocculation. It is likely that T. acetatoxydans can form an electrochemical gradient by putative electron-bifurcating Rnf complex and [Fe-Fe] hydrogenases, as observed in other acetogens. However, genomic deficiencies related to acetogenic metabolism and anaerobic respiration were discovered, such as the lack of formate dehydrogenase and F1F0 ATP synthase. This has potential consequences for the metabolic pathways used under SAO and non-SAO conditions. The two complete sets of bacteriophage genomes, which were found to be encoded in the genome, are also worthy of mention. PMID:25811859

  5. Methanosarcinaceae and Acetate-Oxidizing Pathways Dominate in High-Rate Thermophilic Anaerobic Digestion of Waste-Activated Sludge

    PubMed Central

    Ho, Dang P.; Jensen, Paul D.

    2013-01-01

    This study investigated the process of high-rate, high-temperature methanogenesis to enable very-high-volume loading during anaerobic digestion of waste-activated sludge. Reducing the hydraulic retention time (HRT) from 15 to 20 days in mesophilic digestion down to 3 days was achievable at a thermophilic temperature (55°C) with stable digester performance and methanogenic activity. A volatile solids (VS) destruction efficiency of 33 to 35% was achieved on waste-activated sludge, comparable to that obtained via mesophilic processes with low organic acid levels (<200 mg/liter chemical oxygen demand [COD]). Methane yield (VS basis) was 150 to 180 liters of CH4/kg of VSadded. According to 16S rRNA pyrotag sequencing and fluorescence in situ hybridization (FISH), the methanogenic community was dominated by members of the Methanosarcinaceae, which have a high level of metabolic capability, including acetoclastic and hydrogenotrophic methanogenesis. Loss of function at an HRT of 2 days was accompanied by a loss of the methanogens, according to pyrotag sequencing. The two acetate conversion pathways, namely, acetoclastic methanogenesis and syntrophic acetate oxidation, were quantified by stable carbon isotope ratio mass spectrometry. The results showed that the majority of methane was generated by nonacetoclastic pathways, both in the reactors and in off-line batch tests, confirming that syntrophic acetate oxidation is a key pathway at elevated temperatures. The proportion of methane due to acetate cleavage increased later in the batch, and it is likely that stable oxidation in the continuous reactor was maintained by application of the consistently low retention time. PMID:23956388

  6. Radical Monocationic Guanidino-Functionalized Aromatic Compounds (GFAs) as Bridging Ligands in Dinuclear Metal Acetate Complexes: Synthesis, Electronic Structure, and Magnetic Coupling.

    PubMed

    Eberle, Benjamin; Damjanović, Marko; Enders, Markus; Leingang, Simone; Pfisterer, Jessica; Krämer, Christoph; Hübner, Olaf; Kaifer, Elisabeth; Himmel, Hans-Jörg

    2016-02-15

    In this work, the oxidation of several new dinuclear metal (M) acetate complexes of the redox-active guanidino-functionalized aromatic compound (GFA) 1,2,4,5-tetrakis(tetramethylguanidino)benzene (1) was studied. The complexes [1{M(OAc)2}2] (M = Ni or Pd) were oxidized to the radical monocationic complexes [1{M(OAc)2}2](+ •). From CV (cyclic voltammetry) measurements, the Gibbs free enthalpy for disproportionation of [1{M(OAc)2}2](+ •) into [1{M(OAc)2}2] and [1{M(OAc)2}2](2+) could be estimated to be roughly +20 kJ mol(-1) in CH2Cl2 solution. A characteristic feature of the [1{M(OAc)2}2](+ •) complexes is the presence of intense metal-ligand charge-transfer bands in the electronic absorption spectra. The complex [1{Ni(OAc)2}2](+ •) combines three paramagnetic centers with four metal-centered unpaired electrons and a ligand centered π-radical and exhibits a sextet electronic ground state. Spin distribution of the Ni complexes was evaluated by paramagnetic (1)H and (13)C NMR and was correlated with calculations. The strong ferromagnetic metal-ligand magnetic coupling was studied in the solid state by magnetometric (SQUID) measurements and by quantum chemical (DFT) calculations. The temperature dependence of the paramagnetic NMR shift was used for the evaluation of the magnetic coupling between the Ni centers and the π-radical in solution. PMID:26814470

  7. IMPACT OF OXYGEN MEDIATED OXIDATIVE COUPLING ON ADSORPTION KINETICS

    EPA Science Inventory

    The presence of molecular oxygen in the test environment promotes oxidative coupling (polymer formation) of phenolic compounds on the surface of granular activated carbon (GAC). Both adsorption equilibria and adsorption kinetics are affected by these chemical reactions. Lack of...

  8. Synthesis of polymer electrolyte membranes from cellulose acetate/poly(ethylene oxide)/LiClO4 for lithium ion battery application

    NASA Astrophysics Data System (ADS)

    Nurhadini, Arcana, I. Made

    2015-09-01

    This study was conducted to determine the effect of cellulose acetate on poly(ethylene oxide)-LiClO4 membranes as the polymer electrolyte. Cellulose acetate is used as an additive to increase ionic conductivity and mechanical property of polymer electrolyte membranes. The increase the percentage of cellulose acetate in membranes do not directly effect on the ionic conductivity, and the highest ionic conductivity of membranes about 5,7 × 10-4 S/cm was observed in SA/PEO/LiClO4 membrane with cellulose ratio of 10-25% (w/w). Cellulose acetate in membranes increases mechanical strength of polymer electrolyte membranes. Based on TGA analysis, this polymer electrolyte thermally is stable until 270 °C. The polymer electrolyte membrane prepared by blending the cellulose acetate, poly(ethylene oxide), and lithium chlorate could be potentially used as a polymer electrolyte for lithium ion battery application.

  9. Synthesis of polymer electrolyte membranes from cellulose acetate/poly(ethylene oxide)/LiClO{sub 4} for lithium ion battery application

    SciTech Connect

    Nurhadini, Arcana, I Made

    2015-09-30

    This study was conducted to determine the effect of cellulose acetate on poly(ethylene oxide)-LiClO{sub 4} membranes as the polymer electrolyte. Cellulose acetate is used as an additive to increase ionic conductivity and mechanical property of polymer electrolyte membranes. The increase the percentage of cellulose acetate in membranes do not directly effect on the ionic conductivity, and the highest ionic conductivity of membranes about 5,7 × 10{sup −4} S/cm was observed in SA/PEO/LiClO{sub 4} membrane with cellulose ratio of 10-25% (w/w). Cellulose acetate in membranes increases mechanical strength of polymer electrolyte membranes. Based on TGA analysis, this polymer electrolyte thermally is stable until 270 °C. The polymer electrolyte membrane prepared by blending the cellulose acetate, poly(ethylene oxide), and lithium chlorate could be potentially used as a polymer electrolyte for lithium ion battery application.

  10. Oxidant-free dehydrogenative coupling reactions via hydrogen evolution.

    PubMed

    He, Ke-Han; Li, Yang

    2014-10-01

    Oxidant-free dehydrogenative coupling reactions: Recently, coupling reactions have followed a novel strategy for the construction of C==C, C==N, C==P, and S==S bonds by dehydrogenation without using any extra oxidant, via H2 evolution. These breakthroughs inspire a new direction in the construction of chemical bonds, towards more sustainable, highly atom-economical, and environmentally benign synthetic methods. PMID:25139249

  11. The effect of lead acetate on oxidative stress and antioxidant status in rat bronchoalveolar lavage fluid and lung tissue.

    PubMed

    Samarghandian, Saeed; Borji, Abasalt; Afshari, Reza; Delkhosh, Mohammad Bagher; gholami, Ali

    2013-07-01

    Despite the wide spread of lead environmental pollution, the effect of this heavy metal on respiratory disease was not shown yet. In respect to increased oxidative stress is an important mechanism in the pathogenesis of respiratory disease, the present study was designed to examine the association between lead toxicity and lung disease via measuring oxidative stress biomarkers in bronchoalveolar lavage fluid (BALF) and lung tissue of rat. For this aim, 32 rats were divided into the following groups of eight animals each: control, three lead tested (received lead acetate in the drinking water for a period of 14 d at concentrations of 250, 500 and 1000 ppm) groups. At the end of the 2 week period, malondialdehyde (MDA), nitric oxide (NO) and reduced glutathione (GSH) contents were measured to assess free radical activity in the BALF and lung tissue. Superoxide dismutase (SOD) was also determined. A significant dose-dependent increase in the BALF supernatant and lung homogenate levels of MDA and NO with decrease GSH level and SOD activity were observed in the lead-treated groups compared with the control group (p < 0.05). Thus, lead acetate may be contributed to respiratory disorders via increased oxidative stress. PMID:23419166

  12. High ethylene to ethane processes for oxidative coupling

    DOEpatents

    Chafin, Richard B.; Warren, Barbara K.

    1991-01-01

    Oxidative coupling of lower alkane to higher hydrocarbon is conducted using catalyst comprising barium and/or strontium component and a metal oxide combustion promoter in the presence of vapor phase halogen component. High ethylene to ethane mole ratios in the product can be obtained over extended operating periods.

  13. High ethylene to ethane processes for oxidative coupling

    DOEpatents

    Chafin, R.B.; Warren, B.K.

    1991-12-17

    Oxidative coupling of lower alkane to higher hydrocarbon is conducted using a catalyst comprising barium and/or strontium component and a metal oxide combustion promoter in the presence of vapor phase halogen component. High ethylene to ethane mole ratios in the product can be obtained over extended operating periods.

  14. Manganese(III) Acetate-Promoted Cross-Coupling Reaction of Benzothiazole/Thiazole Derivatives with Organophosphorus Compounds under Ball-Milling Conditions.

    PubMed

    Li, Liang; Wang, Jun-Jie; Wang, Guan-Wu

    2016-07-01

    The first solvent-free manganese(III) acetate-promoted reaction of benzothiazole/thiazole derivatives with organophosphorus compounds including phosphine oxides, phosphinate ester, and phosphonate diester has been efficiently developed under ball-milling conditions, providing a highly efficient and green protocol to structurally diverse C2-phosphonylated benzothiazole/thiazole derivatives with remarkable functional group tolerance and excellent yields. PMID:27248000

  15. Protective Effect of Vitamins C and E on Depot-Medroxyprogesterone Acetate-Induced Ovarian Oxidative Stress In Vivo

    PubMed Central

    Ismiyati, Atik; Wiyasa, I. Wayan Arsana; Hidayati, Dwi Yuni Nur

    2016-01-01

    A study was designed to investigate ameliorates effect of combined vitamins C and E able to against depot-medroxyprogesterone acetate- (DMPA-) induced ovarian oxidative stress in rat. Twenty-five female Wistar rats were divided into the following groups (n = 5 rats each): control (untreated) (C); depot-medroxyprogesterone acetate (DMPA); DMPA plus green vitamin C (at dose of 0.2 mg/gram; 0.4 mg/gram; 0.8 mg/gram) and vitamin E (0.04 IU/gram). The treatment with combined vitamins C and E was performed for four weeks. Analysis of malondialdehyde (MDA) level as a marker of oxidative stress was done colorimetrically. Analysis of SOD level was done by enzyme linked immunosorbent assay (ELISA) technically. This increase in ovarium MDA was significantly (P < 0.05) attenuated by medium dose treatments of combined vitamins C and E. DMPA insignificantly decreased SOD levels compared to the untreated group. This decrease in ovarian SOD level was significantly attenuated by all doses of the combined vitamins C and E. In conclusion, DMPA induces ovarian oxidative stress. Combined vitamins C and E prohibit the increase in ovarian lipid peroxidation, at least in part by modulating of superoxide dismutase. Therefore, this may provide an antioxidant therapy for attenuating the ovarian toxicity found in the DMPA therapy. PMID:26966434

  16. Acetate represents a major product of heptanoate and octanoate beta-oxidation in hepatocytes isolated from neonatal piglets.

    PubMed Central

    Lin, X; Adams, S H; Odle, J

    1996-01-01

    An experiment was conducted to explore the nature of the radiolabel distribution in acid-soluble products (ASPs) resulting from the oxidation of [1-14C]C7:0 or C8:0 by isolated piglet hepatocytes. The differences between odd and even chain-length and the impacts of valproate and malonate upon the rate of beta-oxidation and ASP characteristics were tested. A minor amount of fatty acid carboxyl carbon (< or = 10% of organic acids identified by radio-HPLC) accumulated in ketone bodies regardless of chain-length or inhibitor used. In all cases, acetate represented the major reservoir of carboxyl carbon, accounting for 60-70% of radiolabel in identified organic acids. Cells given [1-14C]C7:0 accumulated 85% more carboxyl carbon in Krebs cycle intermediates when compared with C8:0, while accumulation in acetate was unaffected. The results are consistent with the hypothesis that anaplerosis from odd-carbon fatty acids affects the oxidative fate of fatty acid carbon. The piglet appears unique in that non-ketogenic routes of fatty acid carbon flow (i.e. acetogenesis) predominate in the liver of this species. PMID:8761477

  17. Determination of the fractions of syntrophically oxidized acetate in a mesophilic methanogenic reactor through an (12)C and (13)C isotope-based kinetic model.

    PubMed

    Gehring, Tito; Niedermayr, Andrea; Berzio, Stephan; Immenhauser, Adrian; Wichern, Marc; Lübken, Manfred

    2016-10-01

    In order to accurately describe the carbon flow in anaerobic digestion processes, this work investigates the acetate degradation pathways through the use of stable carbon isotope analysis and a mathematical model. Batch assays using labeled (13)C acetate were employed to distinguish the acetate consumption through methanogenic Archaea and acetate-oxidizing Bacteria. Suspended and sessile biomass, with over 400 days of retention time, from a mesophilic (36.5 °C) upflow anaerobic filter was used as inocula in these assays. A three-process model for acetoclastic methanogenesis and syntrophic acetate oxidation (SAO) was developed to allow for a precise quantification of the SAO contribution. The model distinguishes carbon atoms in light and heavy isotopes, (12)C and (13)C, respectively, which permitted the simulation of the isotope ratios variation in addition to gas production, gas composition and acetate concentrations. The model indicated oxidized fractions of acetate between 7 and 18%. Due to the low free ammonia inhibition potential for the acetoclastic methanogens in these assays these findings point to the biomass retention times as a driven factor for the SAO pathway. The isotope-based kinetic model developed here also describes the δ(13)C variations in unlabeled assays accurately and has the potential to determine biological (13)C fractionation factors. PMID:27390036

  18. Coupling Oxidative Signals to Protein Phosphorylation via Methionine Oxidation in Arabidopsis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The mechanisms involved in sensing oxidative signaling molecules such as H2O2 in plant and animal cells are not completely understood. In the present study, we tested the postulate that oxidation of methionine (Met) to Met sulfoxide (MetSO) can couple oxidative signals to changes in protein phosphor...

  19. Transition-Metal-Free Cross-Coupling of Indium Organometallics with Chromene and Isochroman Acetals Mediated by BF3·OEt2.

    PubMed

    Gil-Negrete, José M; Pérez Sestelo, José; Sarandeses, Luis A

    2016-09-01

    A transition-metal-free coupling of triorganoindium reagents with benzopyranyl acetals mediated by a Lewis acid has been developed. The reaction of R3In with chromene and isochroman acetals in the presence of BF3·OEt2 afforded 2-substituted chromenes and 1-substituted isochromans, respectively, in good yields. The reactions proceed with a variety of triorganoindium reagents (aryl, heteroaryl, alkynyl, alkenyl, alkyl) using only 50 mol % of the organometallic, thus demonstrating the efficiency of these species. Preliminary mechanistic studies indicate the formation of an oxocarbenium ion intermediate in the presence of the Lewis acid. PMID:27530143

  20. Silver nanoparticles in combination with acetic acid and zinc oxide quantum dots for antibacterial activities improvement-A comparative study

    NASA Astrophysics Data System (ADS)

    Sedira, Sofiane; Ayachi, Ahmed Abdelhakim; Lakehal, Sihem; Fateh, Merouane; Achour, Slimane

    2014-08-01

    Due to their remarkable antibacterial/antivirus properties, silver nanoparticles (Ag NPs) and zinc oxide quantum dots (ZnO Qds) have been widely used in the antimicrobial field. The mechanism of action of Ag NPs on bacteria was recently studied and it has been proven that Ag NPs exerts their antibacterial activities mainly by the released Ag+. In this work, Ag NPs and ZnO Qds were synthesized using polyol and hydrothermal method, respectively. It was demonstrated that Ag NPs can be oxidized easily in aqueous solution and the addition of acetic acid can increase the Ag+ release which improves the antibacterial activity of Ag NPs. A comparative study between bactericidal effect of Ag NPs/acetic acid and Ag NPs/ZnO Qds on Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumonia and Staphylococcus aureus was undertaken using agar diffusion method. The obtained colloids were characterized using UV-vis spectroscopy, Raman spectrometry, X-ray diffraction (XRD), transmission electron microscopy (TEM) and atomic force microscopy (AFM).

  1. Effects of metal and acidic sites on the reaction by-products of butyl acetate oxidation over palladium-based catalysts.

    PubMed

    Yue, Lin; He, Chi; Hao, Zhengping; Wang, Shunbing; Wang, Hailin

    2014-03-01

    Catalytic oxidation is widely used in pollution control technology to remove volatile organic compounds. In this study, Pd/ZSM-5 catalysts with different Pd contents and acidic sites were prepared via the impregnation method. All the catalysts were characterized by means of N2 adsorption-desorption, X-ray fluorescence (XRF), H2 temperature programmed reduction (H2-TPR), and NH3 temperature programmed desorption (NH3-TPD). Their catalytic performance was investigated in the oxidation of butyl acetate experiments. The by-products of the reaction were collected in thermal desorption tubes and identified by gas chromatography/mass spectrometry. It was found that the increase of Pd content slightly changed the catalytic activity of butyl acetate oxidation according to the yield of CO2 achieved at 90%, but decreased the cracking by-products, whereas the enhancement of strong acidity over Pd-based catalysts enriched the by-product species. The butyl acetate oxidation process involves a series of reaction steps including protolysis, dehydrogenation, dehydration, cracking, and isomerization. Generally, butyl acetate was cracked to acetic acid and 2-methylpropene and the latter was an intermediate of the other by-products, and the oxidation routes of typical by-products were proposed. Trace amounts of 3-methylpentane, hexane, 2-methylpentane, pentane, and 2-methylbutane originated from isomerization and protolysis reactions. PMID:25079284

  2. Samarium electrodeposited acetate and oxide thin films on stainless steel substrate characterized by XPS

    DOE PAGESBeta

    Myhre, Kristian; Burns, Jonathan; Meyer, Harry; Sims, Nathan; Boll, Rose

    2016-06-01

    Characterization of a samarium thin film deposited on a stainless steel substrate using molecular electrodeposition was carried out using a Thermo Scientific K-Alpha X-ray photoelectron spectrometer. We studied two types of samarium electrodeposition samples, one as-deposited and one heated to 700 °C in an air flow. Survey scans include peaks coming from the stainless steel substrate, such as Fe and Cr. An X-ray photoelectron spectroscopy (XPS) survey spectrum, Sm 3d, C 1s, and O 1s narrow scans are shown. It was determined that the heating process decomposed the deposited Sm acetate to Sm2O3 using XPS.

  3. Imaging Tumor Perfusion and Oxidative Metabolism in Patients With Head-and-Neck Cancer Using 1- [{sup 11}C]-Acetate PET During Radiotherapy: Preliminary Results

    SciTech Connect

    Sun Aijun; Johansson, Silvia; Turesson, Ingela; Dasu, Alexandru; Soerensen, Jens

    2012-02-01

    Background: A growing body of in vitro evidence links alterations of the intermediary metabolism in cancer to treatment outcome. This study aimed to characterize tumor oxidative metabolism and perfusion in vivo using dynamic positron emission tomography (PET) with 1- [{sup 11}C]-acetate (ACE) during radiotherapy. Methods and Materials: Nine patients with head-and-neck cancer were studied. Oxidative metabolic rate (k{sub mono}) and perfusion (rF) of the primary tumors were assessed by dynamic ACE-PET at baseline and after 15, 30, and 55 Gy was delivered. Tumor glucose uptake (Tglu) was evaluated with [{sup 18}F]-fluorodeoxyglucose PET at baseline. Patients were grouped into complete (CR, n = 6) and partial responders (PR, n = 3) to radiotherapy. Results: The 3 PR patients died within a median follow-up period of 33 months. Baseline k{sub mono} was almost twice as high in CR as in PR (p = 0.02) and Tglu was lower in CR than in PR (p = 0.04). k{sub mono} increased during radiotherapy in PR (p = 0.004) but remained unchanged in CR. There were no differences in rF between CR and PR at any dosage. k{sub mono} and rF were coupled in CR (p = 0.001), but not in PR. Conclusions: This study shows that radiosensitive tumors might rely predominantly on oxidative metabolism for their bioenergetic needs. The impairment of oxidative metabolism in radioresistant tumors is potentially reversible, suggesting that therapies targeting the intermediary metabolism might improve treatment outcome.

  4. Analytical evaluation of nebulizers for the introduction of acetic acid extracts aiming at the determination of trace elements by inductively coupled plasma mass spectrometry

    NASA Astrophysics Data System (ADS)

    de Gois, Jefferson S.; Maranhão, Tatiane de A.; Oliveira, Fernando J. S.; Frescura, Vera L. A.; Curtius, Adilson J.; Borges, Daniel L. G.

    2012-11-01

    Most of the official procedures aiming at classification of solid waste toxicity take into account metal solubility and bioavailability by means of extraction experiments using acetic acid solutions. Hence, the aim of this work was to investigate and optimize conditions to suppress the effect of acetic acid on the determination of trace elements using inductively coupled plasma mass spectrometry. The performance of four nebulizers (cross-flow (CFN), ultrasonic (USN), Meinhard (MN) and MicroMist (MMN)) were compared as to their efficiency in minimizing spectral and non-spectral effects on the determination of Ag, As, Ba, Cd, Cr, Hg, Pb and Se, with the ultimate goal to analyze acetic acid extracts obtained from solid waste residues. Operating conditions (desolvation temperatures for USN, RF power and nebulizer gas flow rates) were optimized individually for each nebulizer and for all analytes maintained in 0.14 mol L- 1 HNO3 solutions and in solutions prepared with acetic acid and acetic acid + NaOH, adjusted to pH 2.88 and 4.93, respectively. Pronounced non-spectral interferences for 75As and 82Se were observed in the presence of acetic acid for CF and MN, although to a less extent also for MMN and USN. Signal increase for blank solutions measured at m/z 208 (208Pb) for CFN and MN, 107 (107Ag) for USN and MN coupled to a cyclonic chamber and, m/z 82 (82Se) for USN was observed, indicating an increased risk of spectral interference upon an increase in the concentration of acetic acid. Signal increase at specific m/z ratios, however, was not significant when the MMN was used, with the exception of m/z 52 (52Cr) in acetic acid solutions, arising from the formation of 40Ar12C+. This same effect was noticed for all nebulizers, although at noticeably different intensities. A signal stability study was performed, demonstrating that variations in the analytical signal were within a 20% range for all analytes, with the exception of Hg, after continuous aspiration for 70 min

  5. Oxidative coupling and the irreversible adsorption of phenol by graphite.

    PubMed

    de Oliveira Pimenta, Aluisio Cesar; Kilduff, James E

    2006-01-15

    Uptake of phenol by graphite, and regeneration by methanol extraction, was measured to evaluate irreversible adsorption of phenols to carbon surfaces. The emphasis of this work was to identify the role of oxidative coupling, which has been invoked to explain irreversible phenol sorption by activated carbons. Graphite was chosen as a model carbon surface to eliminate potentially confounding effects of microporosity present in other types of carbonaceous sorbents. The isotherm data were well described by the Langmuir-Freundlich isotherm from pH 3 to 9. At pH 12, measured uptakes were higher than expected based on model predictions, suggesting the occurrence of an adsorption mechanism besides physisorption. One oxidative coupling product, 2,2'-dihydroxybiphenyl, was obtained exclusively after adsorption at pH values above 7, and appeared both in aqueous solution and in the methanol regenerant solution. The fraction of total uptake that was not recoverable by methanol extraction decreased with increasing phenol concentration in solution, suggesting preferential sorption by high-energy sites. However, absolute irreversible adsorption increased with phenol concentration in solution. Both fractional irreversible adsorption and 2,2'-dihydroxybiphenyl oxidative coupling product recovery as a function of pH and contact time demonstrated that irreversible sorption of phenol by graphite could not be explained by an oxidative coupling mechanism alone. PMID:16054157

  6. Vapor phase ketonization of acetic acid on ceria based metal oxides

    SciTech Connect

    Liu, Changjun; Karim, Ayman M.; Lebarbier, Vanessa MC; Mei, Donghai; Wang, Yong

    2013-12-01

    The activities of CeO2, Mn2O3-CeO2 and ZrO2-CeO2 were measured for acetic acid ketonization under reaction conditions relevant to pyrolysis vapor upgrading. We show that the catalyst ranking changed depending on the reaction conditions. Mn2O3-CeO2 was the most active catalyst at 350 oC, while ZrO2 - CeO2 was the most active catalyst at 450 oC. Under high CO2 and steam concentration in the reactants, Mn2O3-CeO2 was the most active catalyst at 350 and 450 °C. The binding energies of steam and CO2 with the active phase were calculated to provide the insight into the tolerance of Mn2O3-CeO2 to steam and CO2.

  7. Electron microscopic investigation of the hydrogen-oxidizing acetate-forming anaerobic bacterium Acetobacterium woodii.

    PubMed

    Mayer, F; Lurz, R; Schoberth, S

    1977-11-18

    Acetobacterium woodii is a Gram-positive anaerobic nonsporeforming bacterium able to grow on H2 and CO2 as sole sources of energy. The product of fermentation is acetic acid. Fine structural analysis showed rod-shaped flagellated cells, and coccoid cells without flagella arranged predominantly in pairs and chains. The cell wall was found to be composed of three layers. The cell surface exhibited a periodic array of particles consisting of subunits. The cytoplasmic membrane showed particles either in random distribution or in a hexagonal pattern. Intracytoplasmic membranes were rarely observed, whereas inclusion bodies of varying shapes, predominantly in an uncommon disc-shape, could frequently be observed. Their content was dissolved in ultrathin sections indicating hydrophobic nature. PMID:596994

  8. 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.

  9. General approach on chemistry and stress coupling effects during oxidation

    NASA Astrophysics Data System (ADS)

    Suo, Yaohong; Shen, Shengping

    2013-10-01

    In this paper, the mechanism of growth strain is discussed based on the irreversible evolving equations by considering the coupling effects of stress and chemical reaction during isothermal oxidation, and a simple model relating the growth strain and the oxide thickness is developed. If the effect of the stress on the chemical reaction is not taken into account, the model reduces to the Clarke assumption. The expression of Dox is exhibited, and its value can be determined by experiments. The stress evolving equations are derived, where the viscoplastic strain of the oxide and metal and the growth strain of the oxide are considered. Numerical results are given and compared with results from experiments and the existing model. There is good agreement between the proposed model and the experimental data.

  10. The effect of lipopolysaccharide (LPS) and phorbol 12-myristate 13-acetate (PMA) on whole blood oxidative response as assessed by luminol-amplified chemiluminescence in dairy cows

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The differences between lipopolysaccharide (LPS) and phorbol 12-myristate 13-acetate (PMA) on whole blood oxidative response using luminol-amplified chemiluminescence (CL) are currently unknown in cattle. Luminol-dependent CL measures the amount of reactive oxygen species released from leukocytes a...

  11. Hydrogen sulfide oxidation is coupled to oxidative phosphorylation in mitochondria of Solemya reidi

    SciTech Connect

    Powell, M.A.; Somero, G.N.

    1986-08-01

    Solemya reidi, a gutless clam found in sulfide-rich habitats, contains within its gills bacterial symbionts thought to oxidize sulfur compounds and provide a reduced carbon food source to the clam. However, the initial step or steps in sulfide oxidation occur in the animal tissue, and mitochondria isolated from both gill and symbiont-free foot tissue of the clam coupled the oxidation of sulfide to oxidative phosphorylation (adenosine triphosphate (ATP) synthesis). The ability of Solemya reidi to exploit directly the energy in sulfide for ATP synthesis is unprecedented, and suggests that sulfide-habitat animals that lack bacterial symbionts may also use sulfide as an inorganic energy source.

  12. Copper/Manganese Cocatalyzed Oxidative Coupling of Vinylarenes with Ketones.

    PubMed

    Lan, Xing-Wang; Wang, Nai-Xing; Zhang, Wei; Wen, Jia-Long; Bai, Cui-Bing; Xing, Yalan; Li, Yi-He

    2015-09-18

    A novel copper/manganese cocatalyzed direct oxidative coupling of terminal vinylarenes with ketones via C(sp(3))-H bond functionalization following C-C bond formation has been developed using tert-butyl hydroperoxide as the radical initiator. Various ketones underwent a free-radical addition of terminal vinylarenes to give the corresponding 1,4-dicarbonyl products with excellent regioselectivity and efficiency through one step. A possible reaction mechanism has been proposed. PMID:26348870

  13. Magnetoelectric coupling effects in multiferroic complex oxide composite structures.

    PubMed

    Vaz, Carlos A F; Hoffman, Jason; Ahn, Charles H; Ramesh, Ramamoorthy

    2010-07-20

    The study of magnetoelectric materials has recently received renewed interest, in large part stimulated by breakthroughs in the controlled growth of complex materials and by the search for novel materials with functionalities suitable for next generation electronic devices. In this Progress Report, we present an overview of recent developments in the field, with emphasis on magnetoelectric coupling effects in complex oxide multiferroic composite materials. PMID:20414887

  14. Characterization of Two Tetrachloroethene-Reducing, Acetate-Oxidizing Anaerobic Bacteria and Their Description as Desulfuromonas michiganensis sp. nov.

    PubMed Central

    Sung, Youlboong; Ritalahti, Kirsti M.; Sanford, Robert A.; Urbance, John W.; Flynn, Shannon J.; Tiedje, James M.; Löffler, Frank E.

    2003-01-01

    Two tetrachlorethene (PCE)-dechlorinating populations, designated strains BB1 and BRS1, were isolated from pristine river sediment and chloroethene-contaminated aquifer material, respectively. PCE-to-cis-1,2-dichloroethene-dechlorinating activity could be transferred in defined basal salts medium with acetate as the electron donor and PCE as the electron acceptor. Taxonomic analysis based on 16S rRNA gene sequencing placed both isolates within the Desulfuromonas cluster in the δ subdivision of the Proteobacteria. PCE was dechlorinated at rates of at least 139 nmol min−1 mg of protein−1 at pH values between 7.0 and 7.5 and temperatures between 25 and 30°C. Dechlorination also occurred at 10°C. The electron donors that supported dechlorination included acetate, lactate, pyruvate, succinate, malate, and fumarate but not hydrogen, formate, ethanol, propionate, or sulfide. Growth occurred with malate or fumarate alone, whereas oxidation of the other electron donors depended strictly on the presence of fumarate, malate, ferric iron, sulfur, PCE, or TCE as an electron acceptor. Nitrate, sulfate, sulfite, thiosulfate, and other chlorinated compounds were not used as electron acceptors. Sulfite had a strong inhibitory effect on growth and dechlorination. Alternate electron acceptors (e.g., fumarate or ferric iron) did not inhibit PCE dechlorination and were consumed concomitantly. The putative fumarate, PCE, and ferric iron reductases were induced by their respective substrates and were not constitutively present. Sulfide was required for growth. Both strains tolerated high concentrations of PCE, and dechlorination occurred in the presence of free-phase PCE (dense non-aqueous-phase liquids). Repeated growth with acetate and fumarate as substrates yielded a BB1 variant that had lost the ability to dechlorinate PCE. Due to the 16S rRNA gene sequence differences with the closest relatives and the unique phenotypic characteristics, we propose that the new isolates are

  15. In-vivo Antioxidant Effects of Ethyl Acetate Fraction of Mentha spicata L. on 4-Nitroquinoline-1-Oxide Injected Mice

    PubMed Central

    Arumugam, Ponnan; Ramesh, Arabandi

    2011-01-01

    Antioxidant effects of ethyl acetate fraction of Mentha spicata (L.) were evaluated against 4-nitroquinoline-1-oxide injected mice. For this study, experiment setup consisted of 36 albino mice of either sex divided into 6 groups: Control (25% DMSO in water), ethyl acetate fraction (EAF) alone group (80, 160 mg/Kg body weight-bwt), 4-NQO (7.5 mg/Kg bwt-IP) alone and 4-NQO + EAF. EAF and vehicles were administered orally for five consecutive days. 4-NQO (7.5 mg/Kg bwt) was injected intraperitoneally on the 6th day. After 24 h, the animals were killed; liver sample was extracted and used for bio-assay. 4-NQO alone treated group decreased (27-60%) the antioxidant activities and promoted lipid peroxidation (LPO-60%) over their respective control values. Pretreatment with EAF, at the maximum dose (160 mg/Kg bwt) brought down the LPO up to 87% enhanced by 4-NQO. Among the enzymatic antioxidants, glutathione S-transferase (GST) was the most affected enzyme with 4-NQO and the least was catalase (CAT). Pretreatment with EAF (160 mg/Kg bwt), the restoration of antioxidants like glutathione peroxidase, superoxide dismutase, and CAT were found equal or less than 1.2 fold higher than that of the respective control values whereas, GST was observed to be the most restored antioxidant. Be reduced glutathione (GSH) and the least vitamin C over their control values. EAF restored the GSH and Vitamin E levels were found to be 1.2 fold higher than the respective control values. PMID:24250414

  16. In-vivo Antioxidant Effects of Ethyl Acetate Fraction of Mentha spicata L. on 4-Nitroquinoline-1-Oxide Injected Mice.

    PubMed

    Arumugam, Ponnan; Ramesh, Arabandi

    2011-01-01

    Antioxidant effects of ethyl acetate fraction of Mentha spicata (L.) were evaluated against 4-nitroquinoline-1-oxide injected mice. For this study, experiment setup consisted of 36 albino mice of either sex divided into 6 groups: Control (25% DMSO in water), ethyl acetate fraction (EAF) alone group (80, 160 mg/Kg body weight-bwt), 4-NQO (7.5 mg/Kg bwt-IP) alone and 4-NQO + EAF. EAF and vehicles were administered orally for five consecutive days. 4-NQO (7.5 mg/Kg bwt) was injected intraperitoneally on the 6(th) day. After 24 h, the animals were killed; liver sample was extracted and used for bio-assay. 4-NQO alone treated group decreased (27-60%) the antioxidant activities and promoted lipid peroxidation (LPO-60%) over their respective control values. Pretreatment with EAF, at the maximum dose (160 mg/Kg bwt) brought down the LPO up to 87% enhanced by 4-NQO. Among the enzymatic antioxidants, glutathione S-transferase (GST) was the most affected enzyme with 4-NQO and the least was catalase (CAT). Pretreatment with EAF (160 mg/Kg bwt), the restoration of antioxidants like glutathione peroxidase, superoxide dismutase, and CAT were found equal or less than 1.2 fold higher than that of the respective control values whereas, GST was observed to be the most restored antioxidant. Be reduced glutathione (GSH) and the least vitamin C over their control values. EAF restored the GSH and Vitamin E levels were found to be 1.2 fold higher than the respective control values. PMID:24250414

  17. Oxidative coupling of rhodium phenyl imido/amido complexes

    SciTech Connect

    Ge, Y.W.; Ye, Y.; Sharp, P.R.

    1994-09-07

    In previous work, we found that tautomeric mixtures of the late transition metal imido and amido complexes Rh{sub 2}({mu}-NPh)(CO){sub 2} ({mu}-dppm){sub 2} (1) and Rh{sub 2}({mu}-NHPh)(CO){sub 2}({mu}-dppm)({mu}-dppm-H){sup 2} (2) (hereafter designated as 1/2) undergo electrophilic ring addition reactions at the NPh group. A single electron transfer mechanism was considered. Such a mechanism would require oxidation of the imido/amido complex to a radical cation. To establish this possibility, we investigated the oxidation chemistry of this system. We found a rich chemistry consistent with formation and coupling of an amido radical cation. This chemistry, described here, is closely related to the well-studied oxidation chemistry of aniline and its derivatives. 16 refs.

  18. OXIDATIVE COUPLING OF METHANE USING INORGANIC MEMBRANE REACTORS

    SciTech Connect

    Dr. Y.H. Ma; Dr. W.R. Moser; Dr. A.G. Dixon; Dr. A.M. Ramachandra; Dr. Y. Lu; C. Binkerd

    1998-04-01

    The objective of this research is to study the oxidative coupling of methane in catalytic inorganic membrane reactors. A specific target is to achieve conversion of methane to C{sub 2} hydrocarbons at very high selectivity and higher yields than in conventional non-porous, co-feed, fixed bed reactors by controlling the oxygen supply through the membrane. A membrane reactor has the advantage of precisely controlling the rate of delivery of oxygen to the catalyst. This facility permits balancing the rate of oxidation and reduction of the catalyst. In addition, membrane reactors minimize the concentration of gas phase oxygen thus reducing non selective gas phase reactions, which are believed to be a main route for the formation of CO{sub x} products. Such gas phase reactions are a cause of decreased selectivity in the oxidative coupling of methane in conventional flow reactors. Membrane reactors could also produce higher product yields by providing better distribution of the reactant gases over the catalyst than the conventional plug flow reactors. Membrane reactor technology also offers the potential for modifying the membranes both to improve catalytic properties as well as to regulate the rate of the permeation/diffusion of reactants through the membrane to minimize by-product generation. Other benefits also exist with membrane reactors, such as the mitigation of thermal hot-spots for highly exothermic reactions such as the oxidative coupling of methane. The application of catalytically active inorganic membranes has potential for drastically increasing the yield of reactions which are currently limited by either thermodynamic equilibria, product inhibition, or kinetic selectivity.

  19. Occurrence of microbial acetate-oxidation in ~2 km-deep coal-bearing sediments off the Shimokita Peninsula, Japan (IODP Expedition 337)

    NASA Astrophysics Data System (ADS)

    Ijiri, A.; Inagaki, F.

    2015-12-01

    During the Integrated Ocean Drilling Program (IODP) Expedition 337 in 2012, the riser-drilling vessel Chikyu extended the previous world depth record of scientific ocean drilling and made one of the deepest scientific borehole down to 2466 m below the seafloor (mbsf) at Site C0020 Hole A off the Shimokita Peninsula, Japan. The sedimentary sequence consists of 17 lignite layers below 1.5 km bellow the seafloor. Microbiological and geochemical data consistently showed evidence for the existence of microbial communities associated with lignite coal beds in the coal-bearing sediments (Inagaki and Hinrichs et al., Science, 2015). Since lignite coals produce substantial dissolved organic compounds during the burial alternation process, volatile fatty acids may play important roles for microbial life and its activity in the deep sedimentary environment. To address this hypothesis, we measured methanogenic and acetate-oxidation activities by radiotracer incubation experiments using 14C-labelled substrate ([2-14C]-acetate) immediately after core recovery. Activity of aceticlastic methanogenesis was observed in the sediment above the coal-baring layers (>1990 mbsf), ranging from 0.2 to 1.2 pmol cm-3 d-1. The highest activity was observed in a coal-bed horizon at 1990 mbsf. However, aceticlastic methanogenesis was below the detection limit in sediment samples below the 2 km-coal layers. Activity of acetate oxidation to CO2 was measured by 14CO2 production rate from [2-14C]-acetate. Interestingly, the acetate-oxidation activity was observed in sediments above the coal beds, which values were generally higher than those of methanogenesis with the maximum value of 33 pmol cm-3 d-1 at 1800 mbsf. The rates gradually decreased with increasing depth from 1800 mbsf and reached below the detection limit (i.e., 0.05 pmol cm-3 d-1) in 2 km-deep coal-bed samples. The occurrence of relatively high acetate oxidation at ~1800 mbsf above the coal formation suggests that microbes respire

  20. Oxidative coupling of methane using inorganic membrane reactor

    SciTech Connect

    Ma, Y.H.; Moser, W.R.; Dixon, A.G.

    1995-12-31

    The goal of this research is to improve the oxidative coupling of methane in a catalytic inorganic membrane reactor. A specific target is to achieve conversion of methane to C{sub 2} hydrocarbons at very high selectivity and relatively higher yields than in fixed bed reactors by controlling the oxygen supply through the membrane. A membrane reactor has the advantage of precisely controlling the rate of delivery of oxygen to the catalyst. This facility permits balancing the rate of oxidation and reduction of the catalyst. In addition, membrane reactors minimize the concentration of gas phase oxygen thus reducing non selective gas phase reactions, which are believed to be a main route for formation of CO{sub x} products. Such gas phase reactions are a cause for decreased selectivity in oxidative coupling of methane in conventional flow reactors. Membrane reactors could also produce higher product yields by providing better distribution of the reactant gases over the catalyst than the conventional plug flow reactors. Modeling work which aimed at predicting the observed experimental trends in porous membrane reactors was also undertaken in this research program.

  1. Indole-3-acetic acid-induced oxidative burst and an increase in cytosolic calcium ion concentration in rice suspension culture.

    PubMed

    Nguyen, Hieu T H; Umemura, Kenji; Kawano, Tomonori

    2016-08-01

    Indole-3-acetic acid (IAA) is the major natural auxin involved in the regulation of a variety of growth and developmental processes such as division, elongation, and polarity determination in growing plant cells. It has been shown that dividing and/or elongating plant cells accompanies the generation of reactive oxygen species (ROS) and a number of reports have suggested that hormonal actions can be mediated by ROS through ROS-mediated opening of ion channels. Here, we surveyed the link between the action of IAA, oxidative burst, and calcium channel activation in a transgenic cells of rice expressing aequorin in the cytosol. Application of IAA to the cells induced a rapid and transient generation of superoxide which was followed by a transient increase in cytosolic Ca(2+) concentration ([Ca(2+)]c). The IAA-induced [Ca(2+)]c elevation was inhibited by Ca(2+) channel blockers and a Ca(2+) chelator. Furthermore, ROS scavengers effectively blocked the action of IAA on [Ca(2+)]c elevation. PMID:27149194

  2. Effects of an endogenous nitric oxide synthase inhibitor on phorbol myristate acetate-induced acute lung injury in rats.

    PubMed

    Lin, Hen I; Chu, Shi Jye; Wang, David; Chen, Hsing I; Hsu, Kang

    2003-01-01

    1. In the present study, we determined whether the endogenous nitric oxide (NO) synthase (NOS) inhibitor Nomega-nitro-l-arginine methyl ester (l-NAME) could ameliorate the acute lung injury (ALI) induced by phorbol myristate acetate (PMA) in rat isolated lung. 2. Typical ALI was induced successfully by PMA during 60 min of observation. At 2 micro g/kg, PMA elicited a significant increase in microvascular permeability (measured using the capillary filtration coefficient Kfc), lung weight gain, lung weight/bodyweight ratio, pulmonary arterial pressure (PAP) and protein concentration of bronchoalveolar lavage fluid. 3. Pretreatment with the NOS inhibitor l-NAME (5 mmol/L) significantly attenuated ALI. None of the parameters reflective of lung injury showed significant increase, except for PAP (P < 0.001). The addition of l-arginine (4 mmol/L) blocked the protective effective of l-NAME. Pretreatment with l-arginine exacerbated PMA-induced lung injury. 4. These data suggest that l-NAME significantly ameliorates ALI induced by PMA in rats, indicating that endogenous NO plays a key role in the development of lung oedema in PMA-induced lung injury. PMID:12859432

  3. Release of substituents from phenolic compounds during oxidative coupling reactions.

    PubMed

    Dec, Jerzy; Haider, Konrad; Bollag, Jean-Marc

    2003-07-01

    Phenolic compounds originating from plant residue decomposition or microbial metabolism form humic-like polymers during oxidative coupling reactions mediated by various phenoloxidases or metal oxides. Xenobiotic phenols participating in these reactions undergo either polymerization or binding to soil organic matter. Another effect of oxidative coupling is dehalogenation, decarboxylation or demethoxylation of the substrates. To investigate these phenomena, several naturally occurring and xenobiotic phenols were incubated with various phenoloxidases (peroxidase, laccase, tyrosinase) or with birnessite (delta-MnO(2)), and monitored for chloride release, CO(2) evolution, and methanol or methane production. The release of chloride ions during polymerization and binding ranged between 0.2% and 41.4%. Using the test compounds labeled with 14C in three different locations (carboxyl group, aromatic ring, or aliphatic chain), it was demonstrated that 14CO(2) evolution was mainly associated with the release of carboxyl groups (17.8-54.8% of the initial radioactivity). Little mineralization of 14C-labeled aromatic rings or aliphatic carbons occurred in catechol, ferulic or p-coumaric acids (0.1-0.7%). Demethoxylation ranged from 0.5% to 13.9% for 2,6-dimethoxyphenol and syringic acid, respectively. Methylphenols showed no demethylation. In conclusion, dehalogenation, decarboxylation and demethoxylation of phenolic substrates appear to be controlled by a common mechanism, in which various substituents are released if they are attached to carbon atoms involved in coupling. Electron-withdrawing substituents, such as -COOH and -Cl, are more susceptible to release than electron-donating ones, such as -OCH(3) and -CH(3). The release of organic substituents during polymerization and binding of phenols may add to CO(2) production in soil. PMID:12738292

  4. Assessment of the effects of dobutamine on myocardial blood flow and oxidative metabolism in normal human subjects using nitrogen-13 ammonia and carbon-11 acetate.

    PubMed

    Krivokapich, J; Huang, S C; Schelbert, H R

    1993-06-01

    The dual purposes of this study with positron emission tomography were to measure the effects of dobutamine on myocardial blood flow and oxidative metabolism, and to compare carbon-11 (C-11) acetate versus nitrogen-13 (N-13) ammonia in quantitating flow in normal subjects. Flow was quantitated with N-13 ammonia at rest and at peak dobutamine infusion (40 micrograms/kg/min) in 21 subjects. In 11 subjects, oxidative metabolism was also estimated at rest and peak dobutamine infusion using the clearance rate of C-11 acetate, k mono (min-1). A 2-compartment kinetic model was applied to the early phase of the C-11 acetate data to estimate flow. The rest and peak dobutamine rate-pressure products were 7,318 +/- 1,102 and 19,937 +/- 3,964 beats/min/mm Hg, respectively, and correlated well (r = 0.77) with rest and peak dobutamine flows of 0.77 +/- 0.14 and 2.25 ml/min/g determined using N-13 ammonia as a flow tracer. Rest and dobutamine flows estimated with C-11 acetate were highly correlated with those determined with N-13 ammonia (r = 0.92). k mono increased from 0.05 +/- 0.01 to 0.18 +/- 0.02 min-1, and correlated highly with the increase in flows (r = 0.91) and rate-pressure products (r = 0.94). Thus, the increase in cardiac demand associated with dobutamine is highly correlated with an increase in supply and oxidative metabolism. C-11 acetate is a unique tracer that can be used to image both flow and metabolism simultaneously. PMID:8498380

  5. Oxidative aromatic coupling of meso-arylamino-porphyrins.

    PubMed

    Nowak-Król, Agnieszka; Gryko, Daniel T

    2013-11-15

    Strategic placement of the bis-arylamino group at the meso-position of porphyrins allowed fusion of these two moieties via aromatic dehydrogenation. By placing two di(naphthalene-2-yl)amine or bis(3,5-dimethoxyphenyl)amine groups at positions 5 and 15 of the porphyrin, the oxidative aromatic coupling was directed toward closing one six-membered ring. The extension of the porphyrin chromophore leads to significant change in linear optical properties, such as a bathochromic shift of absorption and broadening of the Q-band. PMID:24168727

  6. Beating of Coupled Ultraviolet Light Modes in Zinc Oxide Nanoresonators

    NASA Astrophysics Data System (ADS)

    Schirra, M.; Feneberg, M.; Prinz, G. M.; Reiser, A.; Röder, T.; Thonke, K.; Sauer, R.

    2009-02-01

    Periodic spatial intensity modulations of near-band-gap luminescence light at 3.36 eV photon energy are reported in nanometer-sized resonators of single zinc oxide nanorods. These modulations are observed when the luminescence light, due to excitonic recombination, is excited by a focused low-energy electron beam scanned along the rods. The acceleration energy of only 2 keV allows for a spatial resolution of a few ten nanometers. Numerical calculations based on the theory of dielectric cylindrical waveguides are performed identifying the intensity modulations as beating patterns of coupled TE01 and TM01 modes in the nanoresonator.

  7. Methane oxidation coupled to oxygenic photosynthesis in anoxic waters

    PubMed Central

    Milucka, Jana; Kirf, Mathias; Lu, Lu; Krupke, Andreas; Lam, Phyllis; Littmann, Sten; Kuypers, Marcel MM; Schubert, Carsten J

    2015-01-01

    Freshwater lakes represent large methane sources that, in contrast to the Ocean, significantly contribute to non-anthropogenic methane emissions to the atmosphere. Particularly mixed lakes are major methane emitters, while permanently and seasonally stratified lakes with anoxic bottom waters are often characterized by strongly reduced methane emissions. The causes for this reduced methane flux from anoxic lake waters are not fully understood. Here we identified the microorganisms and processes responsible for the near complete consumption of methane in the anoxic waters of a permanently stratified lake, Lago di Cadagno. Interestingly, known anaerobic methanotrophs could not be detected in these waters. Instead, we found abundant gamma-proteobacterial aerobic methane-oxidizing bacteria active in the anoxic waters. In vitro incubations revealed that, among all the tested potential electron acceptors, only the addition of oxygen enhanced the rates of methane oxidation. An equally pronounced stimulation was also observed when the anoxic water samples were incubated in the light. Our combined results from molecular, biogeochemical and single-cell analyses indicate that methane removal at the anoxic chemocline of Lago di Cadagno is due to true aerobic oxidation of methane fuelled by in situ oxygen production by photosynthetic algae. A similar mechanism could be active in seasonally stratified lakes and marine basins such as the Black Sea, where light penetrates to the anoxic chemocline. Given the widespread occurrence of seasonally stratified anoxic lakes, aerobic methane oxidation coupled to oxygenic photosynthesis might have an important but so far neglected role in methane emissions from lakes. PMID:25679533

  8. Novel mode of microbial energy metabolism: organic carbon oxidation coupled to dissimilatory reduction of iron or manganese.

    PubMed

    Lovley, D R; Phillips, E J

    1988-06-01

    A dissimilatory Fe(III)- and Mn(IV)-reducing microorganism was isolated from freshwater sediments of the Potomac River, Maryland. The isolate, designated GS-15, grew in defined anaerobic medium with acetate as the sole electron donor and Fe(III), Mn(IV), or nitrate as the sole electron acceptor. GS-15 oxidized acetate to carbon dioxide with the concomitant reduction of amorphic Fe(III) oxide to magnetite (Fe(3)O(4)). When Fe(III) citrate replaced amorphic Fe(III) oxide as the electron acceptor, GS-15 grew faster and reduced all of the added Fe(III) to Fe(II). GS-15 reduced a natural amorphic Fe(III) oxide but did not significantly reduce highly crystalline Fe(III) forms. Fe(III) was reduced optimally at pH 6.7 to 7 and at 30 to 35 degrees C. Ethanol, butyrate, and propionate could also serve as electron donors for Fe(III) reduction. A variety of other organic compounds and hydrogen could not. MnO(2) was completely reduced to Mn(II), which precipitated as rhodochrosite (MnCO(3)). Nitrate was reduced to ammonia. Oxygen could not serve as an electron acceptor, and it inhibited growth with the other electron acceptors. This is the first demonstration that microorganisms can completely oxidize organic compounds with Fe(III) or Mn(IV) as the sole electron acceptor and that oxidation of organic matter coupled to dissimilatory Fe(III) or Mn(IV) reduction can yield energy for microbial growth. GS-15 provides a model for how enzymatically catalyzed reactions can be quantitatively significant mechanisms for the reduction of iron and manganese in anaerobic environments. PMID:16347658

  9. Bioactive peptide carnosin protects against lead acetate-induced hepatotoxicity by abrogation of oxidative stress in rats.

    PubMed

    Hasanein, Parisa; Kazemian-Mahtaj, Azam; Khodadadi, Iraj

    2016-08-01

    Context Oxidative stress is a common mechanism of liver injury. Carnosine is a dipeptide having strong antioxidant effects. Objectives We investigated the effects of carnosine on lead-induced hepatotoxicity and oxidative stress in rats. Materials and methods Animals received an aqueous solution of lead acetate (500 mg Pb/L in the drinking water) and/or daily oral gavage of carnosine (10 mg/kg) for 8 weeks. Rats were then weighed and used for the biochemical (commercial kits), molecular (standard chemical methods) and histological (microscopic) evaluations. Results Lead-induced oxidative stress in liver tissue was indicated by a significant increase in the level of malondialdehyde (MDA) (8.25 ± 0.15 nmol/mg) as well as decrease in the level of total antioxidant capacity (TAC) (1.72 ± 0.25 μmol/g) and total thiol (SH) groups) 1.9 ± 0.22 μmol/g). Carnosine treatment decreased MDA (4 ± 0.08 nmol/mg), whereas it increased the contents of total thiol (3.25 ± 0.04 μmol/g) and TAC (3.44 ± 0.32 μmol/g) in the lead group. Carnosine also prevented the decreased body weight (p < 0.001), albumin (p < 0.05) and total protein levels (p < 0.001) and increased liver weight (p < 0.05) and activates of hepatic enzymes (p's < 0.001) (alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase and lactate dehydrogenase) in the lead group. Furthermore, histopathological study showed that carnosine attenuates liver damage by decreasing necrosis and infiltration of inflammatory cells. Conclusion Carnosine prevented lead-induced hepatotoxicity, indicated by molecular, biochemical and histopathological analyses through inhibiting lipid peroxidation and enhancing antioxidant defence systems. Therefore, carnosine makes a good candidate to protect against the deleterious effect of chronic lead intoxication. PMID:26808926

  10. A Car-Parrinello and path integral molecular dynamics study of the intramolecular lithium bond in the lithium 2-pyridyl-N-oxide acetate

    NASA Astrophysics Data System (ADS)

    Durlak, Piotr; Latajka, Zdzisław; Berski, Sławomir

    2009-07-01

    Lithium bonding in lithium 2-pyridyl-N-oxide acetate has been investigated using classic Car-Parrinello molecular dynamics (CPMD) and the path integral approach [path integrals molecular dynamics (PIMD)]. The simulations have been performed in 300 K. Structures, energies, and lithium trajectories have been determined. The CPMD results show that the lithium atom is generally equidistant between heavy atoms in the (O⋯Li⋯O) bridge. Applying quantum effects through the PIMD leads to similar conclusion. The theoretical lithium 2-pyridyl-N-oxide acetate infrared spectrum has also been determined using the CPMD calculations. This shows very good agreement with available experimental results and reproduces well the broad low-frequency band observed experimentally. In order to gain deeper understanding of the nature of the lithium bonding topological analysis of the electron localization function has been applied.

  11. Coupled polaronic and ion transport in nanocrystalline metal oxide electrodes

    NASA Astrophysics Data System (ADS)

    Rosso, Kevin

    2012-02-01

    We report new computational methods and fundamental understanding in the dynamics of coupled charge and ion transport in nanoscale metal oxides. The methods attack the multi-scale problem of simulating the collective diffusivities of ions and charge compensating e-/h+ carriers in single crystal particles, across particle-particle grain boundaries, and through networks of grains for select systems. Methods include embedded quantum mechanical clusters at the DFT and MP2 levels of theory for atomic-scale polaronic and ion transport kinetics, classical DFT-based free energy calculations for grain-scale conductivity in the framework of the Poisson-Nernst-Planck formalism, and phase field simulation of charged particle diffusivity for conductivity at the grain network scale. This combination of approaches is one of a kind in terms of its multi-scale range, scaling, and computational efficiency. We are presently focused on coupled electron and Li+ ion transport in polymorphs of TiO2, and also in mixed valence spinel oxides, for electrode conductivity optimization and improving energy storage materials performance for Li+ batteries.

  12. Selective synthesis of substituted pyrrole-2-phosphine oxides and -phosphonates from 2H-azirines and enolates from acetyl acetates and malonates.

    PubMed

    Palacios, Francisco; Ochoa de Retana, Ana M; Vélez del Burgo, Ander

    2011-11-18

    A simple and efficient selective synthesis of 1H-pyrrole-2-phosphine oxides 3 and -phosphonates 7 by addition of enolates derived from acetyl acetates to 2H-azirinylphosphine oxide 1 and -phosphonate 6 is reported. Nucleophilic addition of enolates derived from diethyl malonate to 2H-azirines 1 and 6 led to the formation of functionalized 2-hydroxy-1H-pyrrole-5-phosphine oxide 9 and -phosphonate 10, while vinylogous α-aminoalkylphosphine oxides 14 and -phosphonate 15 may be obtained from azirines and the enolate derived from diethyl 2-phenylmalonate. Ring closure of vinylogous derivatives 14 and 15 in the presence of base led to the formation of 1,5-dihydro-3-pyrrolin-2-ones containing a phosphine oxide 17 or a phosphonate group 18. PMID:21999212

  13. UV-visible spectral identification of the solution-phase and solid-phase permanganate oxidation reactions of thymine acetic acid.

    PubMed

    Bui, Chinh T; Sam, Lien A; Cotton, Richard G H

    2004-03-01

    Solution-phase and solid-phase permanganate oxidation reactions of thymine acetic acid were investigated by spectroscopy. The spectral data showed the formation of a stable organomanganese intermediate, which was responsible for the rise in the absorbance at 420 nm. This result enables unambiguous interpretation of the absorbance change at 420 nm, as the intermediate permanganate ions could be isolated on the solid supports. PMID:14980689

  14. Discovering Green, Aqueous Suzuki Coupling Reactions: Synthesis of Ethyl (4-Phenylphenyl)Acetate, a Biaryl with Anti-Arthritic Potential

    ERIC Educational Resources Information Center

    Costa, Nancy E.; Pelotte, Andrea L.; Simard, Joseph M.; Syvinski, Christopher A.; Deveau, Amy M.

    2012-01-01

    Suzuki couplings are powerful chemical reactions commonly employed in academic and industrial research settings to generate functionalized biaryls. We have developed and implemented a discovery-based, microscale experiment for the undergraduate organic chemistry laboratory that explores green Suzuki coupling using water as the primary solvent.…

  15. Oxidative coupling of methane with ac and dc corona discharges

    SciTech Connect

    Liu, C.; Marafee, A.; Hill, B.; Xu, G.; Mallinson, R.; Lobban, L.

    1996-10-01

    The oxidative coupling of methane (OCM) is being actively studied for the production of higher hydrocarbons from natural gas. The present study concentrated on the oxidative conversion of methane in an atmospheric pressure, nonthermal plasma formed by ac or dc corona discharges. Methyl radicals are formed by reaction with negatively-charged oxygen species created in the corona discharge. The selectivity to products ethane and ethylene is affected by electrode polarity, frequency, and oxygen partial pressure in the feed. Higher C{sub 2} yields were obtained with the ac corona. All the ac corona discharges are initiated at room temperature (i.e., no oven or other heat source is used), and the temperature increases to 300--500 C due to the exothermic reactions and the discharge itself. The largest C{sub 2} yield is 21% with 43.3% methane conversion and 48.3% C{sub 2} selectivity at a flowrate of 100 cm{sup 3}/min when the ac corona is at 30 Hz, 5 kV (rms) input power was used. The methane conversion may be improved to more than 50% by increasing the residence time, but the C{sub 2} selectivity decreases. A reaction mechanism including the oxidative dehydrogenation (OXD) of ethane to ethylene is presented to explain the observed phenomena. The results suggest that ac and/or dc gas discharge techniques have significant promise for improving the economics of OCM processes.

  16. Coupling Oxygen Consumption with Hydrocarbon Oxidation in Bacterial Multicomponent Monooxygenases.

    PubMed

    Wang, Weixue; Liang, Alexandria D; Lippard, Stephen J

    2015-09-15

    A fundamental goal in catalysis is the coupling of multiple reactions to yield a desired product. Enzymes have evolved elegant approaches to address this grand challenge. A salient example is the biological conversion of methane to methanol catalyzed by soluble methane monooxygenase (sMMO), a member of the bacterial multicomponent monooxygenase (BMM) superfamily. sMMO is a dynamic protein complex of three components: a hydroxylase, a reductase, and a regulatory protein. The active site, a carboxylate-rich non-heme diiron center, is buried inside the 251 kDa hydroxylase component. The enzyme processes four substrates: O2, protons, electrons, and methane. To couple O2 activation to methane oxidation, timely control of substrate access to the active site is critical. Recent studies of sMMO, as well as its homologues in the BMM superfamily, have begun to unravel the mechanism. The emerging and unifying picture reveals that each substrate gains access to the active site along a specific pathway through the hydroxylase. Electrons and protons are delivered via a three-amino-acid pore located adjacent to the diiron center; O2 migrates via a series of hydrophobic cavities; and hydrocarbon substrates reach the active site through a channel or linked set of cavities. The gating of these pathways mediates entry of each substrate to the diiron active site in a timed sequence and is coordinated by dynamic interactions with the other component proteins. The result is coupling of dioxygen consumption with hydrocarbon oxidation, avoiding unproductive oxidation of the reductant rather than the desired hydrocarbon. To initiate catalysis, the reductase delivers two electrons to the diiron(III) center by binding over the pore of the hydroxylase. The regulatory component then displaces the reductase, docking onto the same surface of the hydroxylase. Formation of the hydroxylase-regulatory component complex (i) induces conformational changes of pore residues that may bring protons to the

  17. Pd-Catalyzed oxidative isomerization of propargylic acetates: highly efficient access to α-acetoxyenones via alkenyl Csp(2)-O bond-forming reductive elimination from Pd(IV).

    PubMed

    Li, Jun; Yang, Wenjie; Yan, Fachao; Liu, Qing; Wang, Ping; Li, Yueyun; Zhao, Yi; Dong, Yunhui; Liu, Hui

    2016-08-23

    A Pd(ii)/(iv)-catalyzed oxidative isomerization of propargylic acetates developed for the synthesis of polysubstituted alkenyl acetates is described. The reductive elimination of alkenyl Csp(2)-OAc bonds from Pd(IV) intermediates is achieved. Mechanistic studies indicate that the reaction mechanism consists of trans acetoxypalladation of a triple bond, isomerization, oxidative addition with PhI(OAc)2 and alkenyl C-OAc bond reductive elimination. PMID:27500292

  18. Oxidation of ethyl acetate by a high performance nanostructure (Ni, Mn)-Ag/ZSM-5 bimetallic catalysts and development of an artificial neural networks predictive modeling.

    PubMed

    Jodaei, Azadeh; Salari, Darush; Niaei, Ali; Khatamian, Masumeh; Hosseini, Seyed Ali

    2011-01-01

    The catalytic oxidation of ethyl acetate in low concentration was investigated over mono-metallic Ag/ZSM5 and bimetallic (Ni, Mn)-Ag/ZSM-5 catalysts. Catalytic studies were carried out in a catalytic fixed bed reactor under atmospheric pressure. The sequence of catalytic activity was as follows: Ni-Ag-ZSM-5 > Mn-Ag-ZSM-5 > Ag-ZSM-5 > H-ZSM-5. The catalysts were characterized by ICP-AES, X-ray diffraction (XRD), low temperature nitrogen adsorption, NH(3)-TPD, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and diffuse reflectance UV-vis spectra (UV-vis). An artificial neural networks (ANN) model was developed to predict the performance of catalytic oxidation process over bimetallic Ni-Ag/ZSM-5 catalyst based on experimental data. For this purpose the standard feed forward back propagation algorithm was employed to train the model by using laboratory experimental data. A good agreement was resulted between experimental results and those obtained by ANN. Following order for variables effects on conversion yield of ethyl acetate was predicted by ANN model: reaction temperature (32.99%) > Ag loading (27.38%) > initial ethyl acetate concentration (23.58%) > Ni loading (16.05%). PMID:21104495

  19. Ethyl 2-cyano-2-(2-nitrobenzenesulfonyloxyimino)acetate (o-NosylOXY): a recyclable coupling reagent for racemization-free synthesis of peptide, amide, hydroxamate, and ester.

    PubMed

    Dev, Dharm; Palakurthy, Nani Babu; Thalluri, Kishore; Chandra, Jyoti; Mandal, Bhubaneswar

    2014-06-20

    Ubiquitousness of amide and ester functionality makes coupling reactions extremely important. Although numerous coupling reagents are available, methods of preparation of the common and efficient reagents are cumbersome. Those reagents generate a substantial amount of chemical waste and lack recyclability. Ethyl 2-cyano-2-(2-nitrobenzenesulfonyloxyimino)acetate (o-NosylOXY), the first member of a new generation of coupling reagents, produces byproducts that can be easily recovered and reused for the synthesis of the same reagent, making the method more environmentally friendly and cost-effective. The synthesis of amides, hydroxamates, peptides, and esters using this reagent is described. The synthesis of the difficult sequences, for example, the islet amyloid polypeptide (22-27) fragment (with a C-terminal Gly, H-Asn-Phe-Gly-Ala-Ile-Leu-Gly-NH2) and acyl carrier protein (65-74) fragment (H-Val-Gln-Ala-Ala-Ile-Asp-Tyr-Ile-Asn-Gly-OH), following the solid-phase peptide synthesis (SPPS) protocol and Amyloid β (39-42) peptide (Boc-Val-Val-IIe-Ala-OMe), following solution-phase strategy is demonstrated. Remarkable improvement is noticed with respect to reaction time, yield, and retention of stereochemistry. A mechanistic investigation and recyclability are also described. PMID:24849944

  20. Protective effect of marine mangrove Rhizophora apiculata on acetic acid induced experimental colitis by regulating anti-oxidant enzymes, inflammatory mediators and nuclear factor-kappa B subunits.

    PubMed

    V, Vinod Prabhu; C, Guruvayoorappan

    2014-01-01

    Ulcerative colitis is a disease that causes inflammation and ulcer in the lining of the large intestine. In this study we investigate the effect of Rhizophora apiculata (R. apiculata) on acetic acid induced colitis in mouse model. Experimental animals were randomized into four groups: normal untreated, colitis control, R. apiculata treated group and sulfasalazine treated group. R. apiculata significantly (p<0.01) decreased macroscopic score and wet weight of damaged colon compared to colitis control. This effect was confirmed biochemically by significant (p<0.01) reduction of colitis associated increase in myeloperoxidase activity. R. apiculata significantly (p<0.05) increased anti-oxidant enzymes such as superoxide dismutase (SOD) and glutathione (GSH) levels compared to colitis control. R. apiculata significantly (p<0.01) reduced lipid peroxides (LPO), nitric oxide (NO) and inflammatory mediators such as myeloperoxidase (MPO), lactate dehydrogenase (LDH), inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2) and tumor necrosis factor-α (TNF-α) expressions compared to colitis control. R. apiculata treatment significantly (p<0.01) inhibits the translocation of NF-kB p65 and p50 subunits. Taken together these findings suggest that R. apiculata prevents acetic acid induced colitis in experimental mouse model and may serve as an excellent anti-oxidant and anti-inflammatory agent that could potentially be useful as a (natural) therapy for inflammatory bowel disease (IBD). PMID:24269623

  1. Rapid isolation of a facultative anaerobic electrochemically active bacterium capable of oxidizing acetate for electrogenesis and azo dyes reduction.

    PubMed

    Shen, Nan; Yuan, Shi-Jie; Wu, Chao; Cheng, Yuan-Yuan; Song, Xiang-Ning; Li, Wen-Wei; Tong, Zhong-Hua; Yu, Han-Qing

    2014-05-01

    In this study, 27 strains of electrochemically active bacteria (EAB) were rapidly isolated and their capabilities of extracellular electron transfer were identified using a photometric method based on WO3 nanoclusters. These strains caused color change of WO3 from white to blue in a 24-well agar plate within 40 h. Most of the isolated EAB strains belonged to the genera of Aeromonas and Shewanella. One isolate, Pantoea agglomerans S5-44, was identified as an EAB that can utilize acetate as the carbon source to produce electricity and reduce azo dyes under anaerobic conditions. The results confirmed the capability of P. agglomerans S5-44 for extracellular electron transfer. The isolation of this acetate-utilizing, facultative EBA reveals the metabolic diversity of environmental bacteria. Such strains have great potential for environmental applications, especially at interfaces of aerobic and anaerobic environments, where acetate is the main available carbon source. PMID:24648142

  2. Chemistry of α-pinene and naphthalene oxidation products generated in a Potential Aerosol Mass (PAM) chamber as measured by acetate chemical ionization mass spectrometry

    DOE PAGESBeta

    Chhabra, P. S.; Lambe, A. T.; Canagaratna, M. R.; Stark, H.; Jayne, J. T.; Onasch, T. B.; Davidovits, P.; Kimmel, J. R.; Worsnop, D. R.

    2014-07-01

    Recent developments in high resolution, time-of-flight chemical ionization mass spectrometry (HR-ToF-CIMS) have made possible the direct detection of atmospheric organic compounds in real-time with high sensitivity and with little or no fragmentation, including low volatility, highly oxygenated organic vapors that are precursors to secondary organic aerosol formation. Here, for the first time, we examine gas-phase O3 and OH oxidation products of α-pinene and naphthalene formed in the PAM flow reactor with an HR-ToF-CIMS using acetate reagent ion chemistry. Integrated OH exposures ranged from 1.2 × 1011 to 9.7 × 1011 molec cm−3 s, corresponding to approximately 1.0 to 7.5 daysmore » of equivalent atmospheric oxidation. Measured gas-phase organic acids are similar to those previously observed in environmental chamber studies. For both precursors, we find that acetate-CIMS spectra capture both functionalization (oxygen addition) and fragmentation (carbon loss) as a function of OH exposure. The level of fragmentation is observed to increase with increased oxidation. We present a method that estimates vapor pressures of organic molecules using the measured O/C ratio, H/C ratio, and carbon number for each compound detected by the CIMS. The predicted condensed-phase SOA average acid yields and O/C and H/C ratios agree within uncertainties with previous AMS measurements and ambient CIMS results. While acetate reagent ion chemistry is used to selectively measure organic acids, in principle this method can be applied to additional reagent ion chemistries depending on the application.« less

  3. Surface Proton Hopping and Coupling Pathway of Water Oxidation on Cobalt Oxide Catalyst

    NASA Astrophysics Data System (ADS)

    Pham, Hieu; Cheng, Mu-Jeng; Frei, Heinz; Wang, Lin-Wang

    We propose an oxidation pathway of water splitting on cobalt oxide surface with clear thermodynamic and kinetic details. The density-functional theory studies suggest that the coupled proton-electron transfer is not necessarily sequential and implicit in every elementary step of this mechanistic cycle. Instead, the initial O-O bond could be formed by the landing of water molecule on the surface oxos, which is then followed by the dispatch of protons through the hopping manner and subsequent release of di-oxygen. Our theoretical investigations of intermediates and transition states indicate that all chemical conversions in this pathway, including the proton transfers, are possible with low activation barriers, in addition to their favorable thermodynamics. Our hypothesis is supported by recent experimental observations of surface superoxide that is stabilized by hydrogen bonding to adjacent hydroxyl group, as an intermediate on fast-kinetics catalytic site.

  4. Effects of uncoated and citric acid coated cerium oxide nanoparticles, bulk cerium oxide, cerium acetate, and citric acid on tomato plants.

    PubMed

    Barrios, Ana Cecilia; Rico, Cyren M; Trujillo-Reyes, Jesica; Medina-Velo, Illya A; Peralta-Videa, Jose R; Gardea-Torresdey, Jorge L

    2016-09-01

    Little is known about the physiological and biochemical responses of plants exposed to surface modified nanomaterials. In this study, tomato (Solanum lycopersicum L.) plants were cultivated for 210days in potting soil amended with uncoated and citric acid coated cerium oxide nanoparticles (nCeO2, CA+nCeO2) bulk cerium oxide (bCeO2), and cerium acetate (CeAc). Millipore water (MPW), and citric acid (CA) were used as controls. Physiological and biochemical parameters were measured. At 500mg/kg, both the uncoated and CA+nCeO2 increased shoot length by ~9 and ~13%, respectively, while bCeO2 and CeAc decreased shoot length by ~48 and ~26%, respectively, compared with MPW (p≤0.05). Total chlorophyll, chlo-a, and chlo-b were significantly increased by CA+nCeO2 at 250mg/kg, but reduced by bCeO2 at 62.5mg/kg, compared with MPW. At 250 and 500mg/kg, nCeO2 increased Ce in roots by 10 and 7 times, compared to CA+nCeO2, but none of the treatments affected the Ce concentration in above ground tissues. Neither nCeO2 nor CA+nCeO2 affected the homeostasis of nutrient elements in roots, stems, and leaves or catalase and ascorbate peroxidase in leaves. CeAc at 62.5 and 125mg/kg increased B (81%) and Fe (174%) in roots, while at 250 and 500mg/kg, increased Ca in stems (84% and 86%, respectively). On the other hand, bCeO2 at 62.5 increased Zn (152%) but reduced P (80%) in stems. Only nCeO2 at 62.5mg/kg produced higher total number of tomatoes, compared with control and the rest of the treatments. The surface coating reduced Ce uptake by roots but did not affect its translocation to the aboveground organs. In addition, there was no clear effect of surface coating on fruit production. To our knowledge, this is the first study comparing the effects of coated and uncoated nCeO2 on tomato plants. PMID:26672385

  5. Long-term nitrogen fertilization of paddy soil shifts iron-reducing microbial community revealed by RNA-(13)C-acetate probing coupled with pyrosequencing.

    PubMed

    Ding, Long-Jun; Su, Jian-Qiang; Xu, Hui-Juan; Jia, Zhong-Jun; Zhu, Yong-Guan

    2015-03-01

    Iron reduction is an important biogeochemical process in paddy soils, yet little is known about the microbial coupling between nitrogen and iron reduction. Here, we investigated the shift of acetate-metabolizing iron-reducers under long-term nitrogen fertilization using (13)C-acetate-based ribosomal RNA (rRNA)-stable isotope probing (SIP) and pyrosequencing in an incubation experiment, and the shift of putative iron-reducers in original field samples were investigated by 16S rRNA gene-based pyrosequencing. During SIP incubations, in the presence of iron(III) oxyhydroxides, more iron(II) formation and less methane production were detected in nitrogen-fertilized (N) compared with non-fertilized (NF) soil. In (13)C-rRNA from microcosms amended with ferrihydrite (FER), Geobacter spp. were the important active iron-reducers in both soils, and labeled to a greater extent in N (31% of the bacterial classified sequences) than NF soils (11%). Pyrosequencing of the total 16S rRNA transcripts from microcosms at the whole community level further revealed hitherto unknown metabolisms of potential FER reduction by microorganisms including Pseudomonas and Solibacillus spp. in N soil, Dechloromonas, Clostridium, Bacillus and Solibacillus spp. in NF soil. Goethite (GOE) amendment stimulated Geobacter spp. to a lesser extent in both soils compared with FER treatment. Pseudomonas spp. in the N soil and Clostridium spp. in the NF soil may also be involved in GOE reduction. Pyrosequencing results from field samples showed that Geobacter spp. were the most abundant putative iron-reducers in both soils, and significantly stimulated by long-term nitrogen fertilization. Overall, for the first time, we demonstrate that long-term nitrogen fertilization promotes iron(III) reduction and modulates iron-reducing bacterial community in paddy soils. PMID:25171335

  6. Quantum chemical study of the catalytic oxidative coupling of methane

    SciTech Connect

    Onal, I.; Senkan, S.

    1997-10-01

    Oxidative coupling of methane reaction pathways on MgO and lithium-modified MgO were theoretically studied using the semiempirical MNDO-PM3 molecular orbital method. The surface of the MgO catalyst was modeled by a Mg{sub 9}O{sub 9} molecular cluster containing structural defects such as edges and corners. Lithium-promoted magnesia was simulated by isomorphic substitution of Mg{sup 2+} by Li{sup +}; the excess negative charge of the cluster was compensated by a proton connected to a neighboring O{sup 2{minus}} site. Heterolytic adsorption of methane was found to be directly related to the coordination number of both the lattice oxygen and the metal sites. Energetically the most favorable site pair was Mg{sub 3c}-O{sub 3c} with a neighboring Li{sub 4c} site present. Various sequential oxygen and methane adsorption pathways were explored resulting in CH{sub 3}OH formation with lower energy barriers for the Li-modified MgO cluster as compared to unmodified MgO.

  7. Photolytic degradation of chlorophenols from industrial wastewaters by organic oxidants peroxy acetic acid, para nitro benzoic acid and methyl ethyl ketone peroxide: identification of reaction products.

    PubMed

    Sharma, Swati; Mukhopadhyay, Mausumi; Murthy, Zagabathuni Venkata Panchakshari

    2014-01-01

    In this investigation, chlorophenol (CP) containing industrial wastewater was remediated by ultraviolet irradiation in conjunction with organic oxidants, peroxy acetic acid (PAA); para nitro benzoic acid (PNBA); and methyl ethyl ketone peroxide (MEKP). CP mineralization was studied with regard to chemical oxygen demand (COD) and chloride ion release under identical test conditions. COD depletion to the extent of 81% by PAA, 66% by PNBA, and 67% by MEKP was noted along with an upwardly mobile trend of chloride ion release upon irradiation of samples at 254 nm. A 90-99% decrease in CP concentration (as per high pressure liquid chromatography (HPLC) analysis) was achieved with an additional 15.0 ml of organic oxidant in all cases. Gas chromatography high resolution mass spectroscopy (GC-HRMS) results also indicated the formation of such reaction products as are free from chlorine substitutions. This treatment also leads to total decolorization of the collected samples. PMID:24647192

  8. Microbiology and potential applications of aerobic methane oxidation coupled to denitrification (AME-D) process: A review.

    PubMed

    Zhu, Jing; Wang, Qian; Yuan, Mengdong; Tan, Giin-Yu Amy; Sun, Faqian; Wang, Cheng; Wu, Weixiang; Lee, Po-Heng

    2016-03-01

    Aerobic methane oxidation coupled to denitrification (AME-D) is an important link between the global methane and nitrogen cycles. This mini-review updates discoveries regarding aerobic methanotrophs and denitrifiers, as a prelude to spotlight the microbial mechanism and the potential applications of AME-D. Until recently, AME-D was thought to be accomplished by a microbial consortium where denitrifying bacteria utilize carbon intermediates, which are excreted by aerobic methanotrophs, as energy and carbon sources. Potential carbon intermediates include methanol, citrate and acetate. This mini-review presents microbial thermodynamic estimations and postulates that methanol is the ideal electron donor for denitrification, and may serve as a trophic link between methanotrophic bacteria and denitrifiers. More excitingly, new discoveries have revealed that AME-D is not only confined to the conventional synergism between methanotrophic bacteria and denitrifiers. Specifically, an obligate aerobic methanotrophic bacterium, Methylomonas denitrificans FJG1, has been demonstrated to couple partial denitrification with methane oxidation, under hypoxia conditions, releasing nitrous oxide as a terminal product. This finding not only substantially advances the understanding of AME-D mechanism, but also implies an important but unknown role of aerobic methanotrophs in global climate change through their influence on both the methane and nitrogen cycles in ecosystems. Hence, further investigation on AME-D microbiology and mechanism is essential to better understand global climate issues and to develop niche biotechnological solutions. This mini-review also presents traditional microbial techniques, such as pure cultivation and stable isotope probing, and powerful microbial techniques, such as (meta-) genomics and (meta-) transcriptomics, for deciphering linked methane oxidation and denitrification. Although AME-D has immense potential for nitrogen removal from wastewater, drinking

  9. Comparison of various advanced oxidation processes and chemical treatment methods for COD and color removal from a polyester and acetate fiber dyeing effluent.

    PubMed

    Azbar, N; Yonar, T; Kestioglu, K

    2004-04-01

    In this paper, a comparison of various advanced oxidation processes (O3, O3/UV, H2O2/UV, O3/H2O2/UV, Fe2+/H2O2) and chemical treatment methods using Al2(SO4)3.18H2O, FeCl3 and FeSO4 for the chemical oxygen demand (COD) and color removal from a polyester and acetate fiber dyeing effluent is undertaken. Advanced oxidation processes (AOPs) showed a superior performance compared to conventional chemical treatment, which maximum achievable color and COD removal for the textile effluent used in this study was 50% and 60%, respectively. Although O3/H2O2/UV combination among other AOPs methods studied in this paper was found to give the best result (99% removal for COD and 96% removal for color), use of Fe2+/H2O2 seems to show a satisfactory COD and color removal performance and to be economically more viable choice for the acetate and polyester fiber dyeing effluent on the basis of 90% removal. PMID:14720544

  10. Ammonium acetate

    Integrated Risk Information System (IRIS)

    Ammonium acetate ; CASRN 631 - 61 - 8 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic

  11. Vinyl acetate

    Integrated Risk Information System (IRIS)

    Vinyl acetate ; CASRN 108 - 05 - 4 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic Eff

  12. Ethyl acetate

    Integrated Risk Information System (IRIS)

    Ethyl acetate ; CASRN 141 - 78 - 6 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic Eff

  13. Phenylmercuric acetate

    Integrated Risk Information System (IRIS)

    Phenylmercuric acetate ; CASRN 62 - 38 - 4 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinog

  14. Thallium acetate

    Integrated Risk Information System (IRIS)

    Jump to main content . Integrated Risk Information System Recent Additions | Contact Us Search : All EPA IRIS • You are here : EPA Home • Research • Environmental Assessment • IRIS • IRIS Summaries Redirect Page As of September 30 , 2009 , the assessment summary for Thallium acetate is included in t

  15. Lactate Oxidation Coupled to Iron or Electrode Reduction by Geobacter sulfurreducens PCA▿

    PubMed Central

    Call, Douglas F.; Logan, Bruce E.

    2011-01-01

    Geobacter sulfurreducens PCA completely oxidized lactate and reduced iron or an electrode, producing pyruvate and acetate intermediates. Compared to the current produced by Shewanella oneidensis MR-1, G. sulfurreducens PCA produced 10-times-higher current levels in lactate-fed microbial electrolysis cells. The kinetic and comparative analyses reported here suggest a prominent role of G. sulfurreducens strains in metal- and electrode-reducing communities supplied with lactate. PMID:22003020

  16. Selective deposition of dietary α-Lipoic acid in mitochondrial fraction and its synergistic effect with α-Tocoperhol acetate on broiler meat oxidative stability

    PubMed Central

    2013-01-01

    The use of bioactive antioxidants in feed of broiler to mitigate reactive oxygen species (ROS) in biological systems is one of promising nutritional strategies. The aim of present study was to alleviate ROS production in mitochondrial fraction (MF) of meat by supplemented dietary antioxidant in feed of broiler. For this purpose, mitochondria specific antioxidant: α-lipoic acid (25 mg, 75 mg and 150 mg) with or without combination of α-tocopherol acetate (200 mg) used in normal and palm olein oxidized oil (4%) supplemented feed. One hundred and eighty one day old broiler birds were randomly divided into six treatments and provided the mentioned feed from third week. Feed intake, feed conversion ratio (FCR) remained statistically same in all groups while body weight decreased in supplemented groups accordingly at the end of study. The broiler meat MF antioxidant potential was significantly improved by feeding supplemented feed estimated as 1,1-di phenyl-2-picrylhydrazyl (DPPH) free radical scavenging activity, 2,2-azinobis-(3- ethylbenzothiazoline-6-sulphonic acid) (ABTS+) and thiobarbituric acid reactive substances (TBARS). The maximum antioxidant activity was depicted in group fed on 150 mg/kg α-lipoic acid (ALA) and 200 mg/kg α-tocopherol acetate (ATA) (T4) in both breast and leg MF. Moreover, TBARS were higher in leg as compared to breast MF. Although, oxidized oil containing feed reduced the growth, lipid stability and antioxidant potential of MF whilst these traits were improved by receiving feed containing ALA and ATA. ALA and ATA showed higher deposition in T4 group while least in group received oxidized oil containing feed (T5). Positive correlation exists between DPPH free radical scavenging activity and the ABTS + reducing activity. In conclusion, ALA and ATA supplementation in feed had positive effect on antioxidant status of MF that consequently diminished the oxidative stress in polyunsaturated fatty acid enriched meat. PMID:23617815

  17. Selective deposition of dietary α-lipoic acid in mitochondrial fraction and its synergistic effect with α-tocoperhol acetate on broiler meat oxidative stability.

    PubMed

    Parveen, Rashida; Asghar, Ali; Anjum, Faqir M; Khan, Muhammad I; Arshad, Muhammad Sajid; Yasmeen, Ammara

    2013-01-01

    The use of bioactive antioxidants in feed of broiler to mitigate reactive oxygen species (ROS) in biological systems is one of promising nutritional strategies. The aim of present study was to alleviate ROS production in mitochondrial fraction (MF) of meat by supplemented dietary antioxidant in feed of broiler. For this purpose, mitochondria specific antioxidant: α-lipoic acid (25 mg, 75 mg and 150 mg) with or without combination of α-tocopherol acetate (200 mg) used in normal and palm olein oxidized oil (4%) supplemented feed. One hundred and eighty one day old broiler birds were randomly divided into six treatments and provided the mentioned feed from third week. Feed intake, feed conversion ratio (FCR) remained statistically same in all groups while body weight decreased in supplemented groups accordingly at the end of study. The broiler meat MF antioxidant potential was significantly improved by feeding supplemented feed estimated as 1,1-di phenyl-2-picrylhydrazyl (DPPH) free radical scavenging activity, 2,2-azinobis-(3- ethylbenzothiazoline-6-sulphonic acid) (ABTS+) and thiobarbituric acid reactive substances (TBARS). The maximum antioxidant activity was depicted in group fed on 150 mg/kg α-lipoic acid (ALA) and 200 mg/kg α-tocopherol acetate (ATA) (T4) in both breast and leg MF. Moreover, TBARS were higher in leg as compared to breast MF. Although, oxidized oil containing feed reduced the growth, lipid stability and antioxidant potential of MF whilst these traits were improved by receiving feed containing ALA and ATA. ALA and ATA showed higher deposition in T4 group while least in group received oxidized oil containing feed (T5). Positive correlation exists between DPPH free radical scavenging activity and the ABTS + reducing activity. In conclusion, ALA and ATA supplementation in feed had positive effect on antioxidant status of MF that consequently diminished the oxidative stress in polyunsaturated fatty acid enriched meat. PMID:23617815

  18. Indole-3-acetic acid biosensor based on G-rich DNA labeled AuNPs as chemiluminescence probe coupling the DNA signal amplification

    NASA Astrophysics Data System (ADS)

    Hun, Xu; Mei, Zhenghua; Wang, Zhouping; He, Yunhua

    2012-09-01

    A highly sensitive chemiluminescence (CL) method for detection of phytohormone indole-3-acetic acid (IAA) was developed by using G-rich DNA labeled gold nanoparticles (AuNPs) as CL probe coupling the DNA signal amplification technology. The IAA antibody was immobilized on carboxyl terminated magnetic beads (MBs). In the presence of IAA, antibody labeled AuNPs were captured by antibody functionalized MBs. The DNA on AuNPs is released by a ligand exchange process induced by the addition of DTT. The released DNA is then acted as the linker and hybridized with the capture DNA on MBs and probe DNA on AuNPs CL probe. The CL signal is obtained via the instantaneous derivatization reaction between a specific CL reagent, 3,4,5-trimethoxyl-phenylglyoxal (TMPG), and the G-rich DNA on AuNPs CL probe. IAA can be detected in the concentration range from 0.02 ng/mL to 30 ng/mL, and the limit of detection is 0.01 ng/mL.

  19. Dispersive solvent-free ultrasound-assisted ionic liquid dispersive liquid-liquid microextraction coupled with HPLC for determination of ulipristal acetate.

    PubMed

    Gong, Aiqin; Zhu, Xiashi

    2015-01-01

    In this paper, a simple and efficient ultrasound-assisted ionic liquid dispersive liquid-liquid microextraction (UA IL-DLLME) coupled with high-performance liquid chromatography for the analysis of ulipristal acetate (UPA) was developed. UPA could be easily migrated into 1-octyl-3-methylimidazolium hexafluorophosphate [C8mimPF6] IL phase without dispersive solvent. The research of extraction mechanism showed that hydrophobic interaction force played a key role in the IL-DLLME. Several important parameters affecting the extraction recovery were optimized. Under the optimized conditions, 25-fold enrichment factor was obtained and the limit of detection (LOD) was 6.8 ng mL(-1) (tablet) or 9.3 ng mL(-1) (serum) at a signal-to-noise ratio of 3. The calibration curve was linear over the range of 0.03-6.0 µg mL(-1). The proposed method was successfully applied to the UPA tablets and the real mice serum samples. PMID:25281147

  20. Diosmectite-zinc oxide composite improves intestinal barrier restoration and modulates TGF-β1, ERK1/2, and Akt in piglets after acetic acid challenge.

    PubMed

    Song, Z-H; Ke, Y-L; Xiao, K; Jiao, L-F; Hong, Q-H; Hu, C-H

    2015-04-01

    The present study evaluated the beneficial effect of diosmectite-zinc oxide composite (DS-ZnO) on improving intestinal barrier restoration in piglets after acetic acid challenge and explored the underlying mechanisms. Twenty-four 35-d-old piglets (Duroc × Landrace × Yorkshire), with an average weight of 8.1 kg, were allocated to 4 treatment groups. On d 1 of the trial, colitis was induced via intrarectal injection of acetic acid (10 mL of 10% acetic acid [ACA] solution for ACA, DS-ZnO, and mixture of diosmectite [DS] and ZnO [DS+ZnO] groups) and the control group was infused with saline. Twenty-four hours after challenged, piglets were fed with the following diets: 1) control group (basal diet), 2) ACA group (basal diet), 3) DS-ZnO group (basal diet supplemented with DS-ZnO), and 4) DS+ZnO group (mixture of 1.5 g diosmectite [DS]/kg and 500 mg Zn/kg from ZnO [equal amount of DS and ZnO in the DS-ZnO treatment group]). On d 8 of the trial, piglets were sacrificed. The results showed that DS-ZnO supplementation improved (P < 0.05) ADG, ADFI, and transepithelial electrical resistance and decreased (P < 0.05) fecal scores, crypt depth, and fluorescein isothiocyanate-dextran 4 kDa (FD4) influx as compared with ACA group. Moreover, DS-ZnO increased (P < 0.05) occludin, claudin-1, and zonula occluden-1 expressions; reduced (P < 0.05) caspase-9 and caspase-3 activity and Bax expression; and improved (P < 0.05) Bcl2, XIAP, and PCNA expression. Diosmectite-zinc oxide composite supplementation also increased (P < 0.05) TGF-β1 expression and ERK1/2 and Akt activation. These results suggest that DS-ZnO attenuates the acetic acid-induced colitis by improving mucosa barrier restoration, inhibiting apoptosis, and improving intestinal epithelial cells proliferation and modulation of TGF-β1 and ERK1/2 and Akt signaling pathway. PMID:26020182

  1. Electronic structure and magnetic coupling in copper oxide superconductors

    SciTech Connect

    Wang, Y.J. ); Newton, M.D. ); Davenport, J.W. )

    1992-11-01

    The electronic structure and magnetic coupling in La{sub 2}CuO{sub 4} and Nd{sub 2}CuO{sub 4} have been analyzed using the results of all-valence-electron calculations for (Cu{sub 2}O{sub 11}){sup 18{minus}}, (Cu{sub 4}O{sub 12}){sup 16{minus}}, and (Cu{sub 4}O{sub 20}){sup 32{minus}} clusters, and their {ital p}- and {ital n}-doped variants, embedded in a Madelung potential to represent the crystal environment. The calculations employ the semiempirical incomplete neglect of differential overlap (INDO) method, which is parametrized on the basis of atomic and molecular spectroscopic data, but which makes use of no data from copper oxide materials. The energies of the low-lying cluster spin states are fitted to a Heisenberg Hamiltonian and yield values of {ital J} (134 meV for La{sub 2}CuO{sub 4} and 117 meV for Nd{sub 2}CuO{sub 4}) in close agreement with experiment. The evaluation of {ital J} can be compactly represented in terms of the parameters ({ital t}, {ital U}, and {ital V}) of a one-band Hamiltonian that controls resonance among covalent and ionic valence-bond structures. The resonance mixing is achieved by configuration interaction (CI) among valence-band structures defined in terms of localized molecular orbitals (LMO's) obtained from self-consistent field (SCF) INDO calculations. {ital P} doping is found to involve strong hybridization of the 2{ital p}{sigma} orbitals of the in-plane oxygen ions and the 3{ital d}{sub {ital x}}{sup 2}{minus}{ital y}{sup 2} orbitals of the Cu ions, and the resulting holes are predominantly ({similar to}60%) located in the 2{ital p}{sigma} orbitals. The lowest-energy {ital n}-doped cluster states involve addition of electrons to the 4{ital s}/4{ital p} Cu atom manifolds. However, the separation of these states from low-spin (3{ital d}{sup 10}) alternatives is uncertain because of apparent sensitivity to the representation of the crystal potential, as found by Martin.

  2. Zinc Oxide Nanoparticles Supported Lipase Immobilization for Biotransformation in Organic Solvents: A Facile Synthesis of Geranyl Acetate, Effect of Operative Variables and Kinetic Study.

    PubMed

    Patel, Vrutika; Shah, Chandani; Deshpande, Milind; Madamwar, Datta

    2016-04-01

    The present study describes grafting of zinc oxide (ZnO) nanoparticles with polyethyleneimine (PEI) followed by modification with glutraldehyde used as the bridge for binding the enzyme to support. The prepared nanocomposites were then characterized using Fourier transform infrared spectroscopy, thermogravimetric analysis, and transmission electron microscopy, utilized for synthesis of geranyl acetate in n-hexane. Among all the three prepared nanocomposites (ZnO + PEI, ZnO + PEI + SAA, ZnO + PEI + GLU), Candida rugosa lipase immobilized on ZnO-PEI-GLU was found to be best for higher ester synthesis. The operating conditions that maximized geranyl acetate resulted in the highest yield of 94 % in 6 h, molar ratio of 0.1:0.4 M (geraniol/vinyl acetate) in the presence of n-hexane as reaction medium. Various kinetic parameters such as V max, K i(G), K m(G), and K m(VA) were determined using nonlinear regression analysis for order bi-bi mechanism. The kinetic study showed that reaction followed order bi-bi mechanism with inhibition by geraniol. Activation energy (E a ) was found to be lower for immobilized lipase (12.31 kJ mol(-1)) than crude lipase (19.04 kJ mol(-1)) indicating better catalytic efficiency of immobilized lipase. Immobilized biocatalyst demonstrated 2.23-fold increased catalytic activity than crude lipase and recycled 20 times. The studies revealed in this work showed a promising perspective of using low-cost nanobiocatalysts to overcome the well-known drawbacks of the chemical-catalyzed route. PMID:26749293

  3. Facile preparation of Pd nanoparticles supported on single-layer graphene oxide and application for the Suzuki-Miyaura cross-coupling reaction

    NASA Astrophysics Data System (ADS)

    Yamamoto, Shun-Ichi; Kinoshita, Hiroshi; Hashimoto, Hideki; Nishina, Yuta

    2014-05-01

    Pd nanoparticles supported on single layer graphene oxide (Pd-slGO) were prepared by gentle heating of palladium(ii) acetate (Pd(OAc)2) and GO in ethanol that served as a mild reductant of the Pd precursor. Pd-slGO showed a high catalytic performance (TON and TOF = 237 000) in the Suzuki-Miyaura cross-coupling reaction.Pd nanoparticles supported on single layer graphene oxide (Pd-slGO) were prepared by gentle heating of palladium(ii) acetate (Pd(OAc)2) and GO in ethanol that served as a mild reductant of the Pd precursor. Pd-slGO showed a high catalytic performance (TON and TOF = 237 000) in the Suzuki-Miyaura cross-coupling reaction. Electronic supplementary information (ESI) available: Synthesis details, peak separation of XPS spectra of GO and Pd-slGO composites, TEM and XPS analyses of the spent composite catalysts. See DOI: 10.1039/c4nr00715h

  4. Highly enantioselective oxidative couplings of 2-naphthols catalyzed by chiral bimetallic oxovanadium complexes with either oxygen or air as oxidant.

    PubMed

    Guo, Qi-Xiang; Wu, Zhi-Jun; Luo, Zhi-Bin; Liu, Quan-Zhong; Ye, Jian-Liang; Luo, Shi-Wei; Cun, Lin-Feng; Gong, Liu-Zhu

    2007-11-14

    The chiral bimetallic oxovanadium complexes have been designed for the enantioselective oxidative coupling of 2-naphthols bearing various substituents at C6 and/or C7. The chirality transferring from the amino acid to the axis of the biphenyl in oxovanadium complexes 2 was found to occur with the use of UV and CD spectra and DFT calculation. The homo-coupling reaction with oxygen as the oxidant was promoted by 5 mol % of an oxovanadium complex derived from L-isoleucine and achiral biphenol to afford binaphthols in nearly quantitative yields with high enantioselectivities of up to 98% ee. An oxovanadium complex derived from L-isoleucine and H8-binaphthol is highly efficient at catalyzing the air-oxidized coupling of 2-naphthols with excellent enantioselectivities of up to 97% ee. 51V NMR study shows that the oxovanadium complexes have two vanadium(V) species. Kinetic studies, the cross-coupling reaction, and HRMS spectral studies on the reaction have been carried out and illustrate that two vanadium(V) species are both involved in catalysis and that the coupling reaction undergoes a radical-radical mechanism in an intramolecular manner. Quantum mechanical calculations rationalize the importance of the cooperative effects of the axial chirality matching S-amino acids on the stereocontrol of the oxidative coupling reaction. The application of the transformation in the preparation of chiral ligands and conjugated polymers confirms the importance of the current process in organic synthesis. PMID:17956093

  5. Molecular characterization of a microbial consortium involved in methane oxidation coupled to denitrification under micro-aerobic conditions

    PubMed Central

    Liu, Jingjing; Sun, Faqian; Wang, Liang; Ju, Xi; Wu, Weixiang; Chen, Yingxu

    2014-01-01

    Methane can be used as an alternative carbon source in biological denitrification because it is nontoxic, widely available and relatively inexpensive. A microbial consortium involved in methane oxidation coupled to denitrification (MOD) was enriched with nitrite and nitrate as electron acceptors under micro-aerobic conditions. The 16S rRNA gene combined with pmoA phylogeny of methanotrophs and nirK phylogeny of denitrifiers were analysed to reveal the dominant microbial populations and functional microorganisms. Real-time quantitative polymerase chain reaction results showed high numbers of methanotrophs and denitrifiers in the enriched consortium. The 16S rRNA gene clone library revealed that Methylococcaceae and Methylophilaceae were the dominant populations in the MOD ecosystem. Phylogenetic analyses of pmoA gene clone libraries indicated that all methanotrophs belonged to Methylococcaceae, a type I methanotroph employing the ribulose monophosphate pathway for methane oxidation. Methylotrophic denitrifiers of the Methylophilaceae that can utilize organic intermediates (i.e. formaldehyde, citrate and acetate) released from the methanotrophs played a vital role in aerobic denitrification. This study is the first report to confirm micro-aerobic denitrification and to make phylogenetic and functional assignments for some members of the microbial assemblages involved in MOD. PMID:24245852

  6. Evidence of anoxic methane oxidation coupled to denitrification.

    PubMed

    Islas-Lima, S; Thalasso, F; Gómez-Hernandez, J

    2004-01-01

    Denitrification using methane as sole electron donor under anoxic condition was investigated. Sludge produced by a denitrifying reactor using acetate as electron donor was put in contact with methane at partial pressures from 1.8 to 35.7kPa. Nitrate depletion and gaseous nitrogen production were measured. The denitrification rate was independent of the methane partial pressure when superior or equal to 8.8kPa. The nitrate depletion was asymptotic. A denitrification rate of 0.25g NO(3)(-)-Ng(-1) VSSd(-1) was observed at the onset of culturing, followed by a slower and lineal denitrification rate of 4.9x10(-3)g NO(3)(-)-Ng(-1) VSSd(-1). Abiotic nitrate removal or the availability of another carbon source were discarded from control experiments made in the absence of methane or using sterilized inoculum. PMID:14630098

  7. Molecular imprinting method for fabricating novel glucose sensor: polyvinyl acetate electrode reinforced by MnO2/CuO loaded on graphene oxide nanoparticles.

    PubMed

    Farid, Mohammad Masoudi; Goudini, Leila; Piri, Farideh; Zamani, Abbasali; Saadati, Fariba

    2016-03-01

    An enzyme free glucose sensor was prepared by a molecular imprinting method (MIP). The procedure was developed by in situ preparation of a new polyvinyl acetate (PVA) electrode reinforced by MnO2/CuO loaded on graphene oxide (GO) nanoparticles (PVA/MnO2@GO/CuO). The nanocomposite was modified in the presence of glucose and then imprinted. A carbone paste method with voltammetry was used in the fabrication of the sensor from prepared MIP nanocomposite. PVA/MnO2@GO/CuO electrode was characterized by X-ray diffraction, FT-IR spectroscopy and scanning electron microscopy. Electrocatalytic activity of the electrode toward glucose oxidation was then investigated by cyclic voltammetry in alkaline medium. The results show that the response of PVA/MnO2@GO/CuO MIP is much higher than PVA/MnO2@GO/CuO non-imprinted electrode toward glucose oxidation. The detection limit was 53μM, and the sensor responses are linear for concentrations from 0.5 to 4.4mM. Relative standard deviations for intra- and inter-day determination were less than 6.0%. The relative recoveries for different samples were 96%. PMID:26471527

  8. Protection against oxidative damage in human erythrocytes and preliminary photosafety assessment of Punica granatum seed oil nanoemulsions entrapping polyphenol-rich ethyl acetate fraction.

    PubMed

    Baccarin, Thaisa; Mitjans, Montserrat; Lemos-Senna, Elenara; Vinardell, Maria Pilar

    2015-12-25

    The main purpose of the present study is to evaluate the ability of nanoemulsion entrapping pomegranate peel polyphenol-rich ethyl acetate fraction (EAF) prepared from pomegranate seed oil and medium chain triglyceride to protect human erythrocyte membrane from oxidative damage and to assess preliminary in vitro photosafety. In order to evaluate the phototoxic effect of nanoemulsions, human red blood cells (RBCs) are used as a biological model and the rate of haemolysis and photohaemolysis (5 J cm(-2) UVA) is assessed in vitro. The level of protection against oxidative damage caused by the peroxyl radical generator AAPH in human RBCs as well as its effects on bilayer membrane characteristics such as fluidity, protein profile and RBCs morphology are determined. EAF-loaded nanoemulsions do not promote haemolysis or photohaemolysis. Anisotropy measurements show that nanoemulsions significantly retrain the increase in membrane fluidity caused by AAPH. SDS-PAGE analysis reveals that AAPH induced degradation of membrane proteins, but that nanoemulsions reduce the extension of degradation. Scanning electron microscopy examinations corroborate the interaction between AAPH, nanoemulsions and the RBC membrane bilayer. Our work demonstrates that Punica granatum nanoemulsions are photosafe and protect RBCs against oxidative damage and possible disturbance of the lipid bilayer of biomembranes. Moreover it suggests that these nanoemulsions could be promising new topical products to reduce the effects of sunlight on skin. PMID:26407526

  9. Chemical and enzymatic oxidative coupling of 5-hydroxy-N,N-dimethyltryptamine with amines.

    PubMed

    Babin, F; Huynh-Dinh, T

    1987-07-01

    As part of a program aiming to obtain a covalent labeling of serotoninergic receptors we have studied the oxidative coupling of serotonin derivatives with amino compounds. The oxidation of bufotenine (2) by MnO2 and human ceruloplasmin followed by the Michael type addition with dansylcadaverine and dansyllysine gave a fluorescent adduct identified as fused oxazole structure 4. PMID:3599029

  10. Potential of casein as a nutrient intervention to alleviate lead (Pb) acetate-mediated oxidative stress and neurotoxicity: First evidence in Drosophila melanogaster.

    PubMed

    Venkareddy, Lalith Kumar; Muralidhara

    2015-05-01

    Understanding the interaction between dietary protein deficits and neurotoxicants such as lead (Pb) is critical since oxidative stress is a common denominator under such conditions. The Drosophila system is an extensively used model to investigate the interaction between nutrients and environmental toxicants. Accordingly, we have examined the hypothesis that casein (CSN) enrichment has the propensity to attenuate Pb-associated phenotype, oxidative stress and neurotoxicity in Drosophila melanogaster. Exposure of young (2-3 d) and adult flies (10-12 d old) to Pb acetate (0-20 mM, 7 d) in the medium resulted in a concentration dependent mortality and the survivors exhibited a hyperactive phenotype. While males showed higher susceptibility to Pb among both age groups, young flies were relatively more susceptible than adults. Pb exposure (5-10 mM, 5 d) among young flies caused robust oxidative stress as evidenced by markedly elevated levels of reactive oxygen species with concomitant perturbations in the activities of antioxidant enzymes (diminished SOD and elevated thioredoxin reductase) and altered redox state. Further, Pb caused significant elevation in the activity of acetylcholinesterase and dopamine levels. In a satellite study, we assessed the modulatory effect of CSN-enriched diet (1-2%) on Pb intoxication in terms of lethality, hyperactivity, oxidative stress and neurotoxicity. CSN markedly offset Pb-induced lethality and diminished the hyperactivity response. While CSN enrichment among Pb (5 mM) treated flies caused further elevation in ROS levels and thioredoxin reductase activity, the SOD levels were restored to normalcy. Further, CSN improved the activity levels of complex I-III and restored the dopamine levels. Our data suggest that Pb-induced toxicity in the Drosophila system may be predominantly mediated through oxidative stress mechanisms and the propensity of casein-enriched diet to abrogate such responses. Hence, we propose that enrichment of diet

  11. New bipyridyl/phenanthroline ruthenium(II) and ruthenium(III) complexes possessing acetate appended thioether. Evidence for oxidative linkage isomerization

    NASA Astrophysics Data System (ADS)

    Prasad, Rajendra; Kumar, Ajay; Kumar, Rajeev

    2006-03-01

    The acetate bearing dithioether, sodium di(2-carboxymethylsufanyl)maleonitrile, L 1 upon reaction with [Ru II(bpy) 2Cl 2]·2H 2O, [Ru II(phen) 2Cl 2]·2H 2O, [Ru III(bpy) 2Cl 2] + or [Ru III(phen) 2Cl 2] + in methanol formed complexes of the type [(bpy) 2Ru{S 2(CH 2COO) 2C 2(CN) 2}], ( 1), [(phen) 2Ru{S 2(CH 2COO) 2C 2(CN) 2}], ( 2), [(bpy) 2Ru{(OOCCH 2) 2S 2C 2(CN) 2}] +, ( 5) and [(phen) 2Ru{(OOCCH 2) 2S 2C 2(CN) 2}] +, ( 6) respectively. Four other Ru(III) complexes with di(benzylsulfanyl)maleonitrile, L 2, [(bpy) 2Ru{S 2(PhCH 2)C 2(CN) 2}] 3+, ( 7) and [(phen) 2Ru{S 2(PhCH 2) 2C 2(CN) 2}] 3+, ( 8), and with acetate, [(bpy) 2Ru(OOCCH 3) 2] +, ( 9) and [(phen) 2Ru(OOCCH 3) 2] +, ( 10) were also synthesized. In the cyclic voltammetry, complexes ( 1) and ( 2) exhibited quasireversible oxidation waves at 1.01 and 1.02 V vs. Ag/AgCl over GC electrode in DMF, while the corresponding Ru(III) L 1 complexes ( 5) and ( 6) exhibit reversible oxidation at E1/2 0.59 and 0.58 V, respectively, under identical conditions. This is unlike the voltammetric behavior of the Ru(II) and Ru(III) L 2 complexes, wherein the complex pairs ( 3), ( 7) and ( 4), ( 8) exhibited identical voltammograms with single reversible one electron waves at E1/2 0.98 and 0.92 V, respectively under identical conditions. The voltammograms of Ru(II)-L 2 complexes (3) and (4) also became irreversible in presence of nearly four molar equivalent of sodium acetate. Hence, the irreversible redox behavior of complexes (1) and (2) has been interpreted in terms of rapid linkage isomerization, i.e. shift in κ 2-S,S' to κ 2-O,O' coordination, following the Ru(II)/Ru(III) electrode process. The electronic spectra of Ru(III)-L 1 complexes ( 5) and ( 6) resemble closely with that of ( 9) and ( 10) instead of Ru(III)-L 2 complexes ( 7) and ( 8), further supports proposed linkage isomerization. The cationic complexes were obtained as [PF 6] - salts and all compounds were characterized using analytical and spectral (IR

  12. Carbon-isotopic analysis of dissolved acetate

    NASA Technical Reports Server (NTRS)

    Gelwicks, J. T.; Hayes, J. M.

    1990-01-01

    Heating of dried, acetate-containing solids together with oxalic acid dihydrate conveniently releases acetic acid for purification by gas chromatography. For determination of the carbon-isotopic composition of total acetate, the acetate-containing zone of the chromatographic effluent can be routed directly to a combustion furnace coupled to a vacuum system allowing recovery, purification, and packaging of CO2 for mass-spectrometric analysis. For analysis of methyl carbon, acetic acid can be cryogenically trapped from the chromatographic effluent, then transferred to a tube containing excess NaOH. The tube is evacuated, sealed, and heated to 500 degrees C to produce methane by pyrolysis of sodium acetate. Subsequent combustion of the methane allows determination of the 13C content at the methyl position in the parent acetate. With typical blanks, the standard deviation of single analyses is less than 0.4% for acetate samples larger than 5 micromoles. A full treatment of uncertainties is outlined.

  13. Copper-catalyzed aerobic oxidative coupling: From ketone and diamine to pyrazine

    PubMed Central

    Wu, Kun; Huang, Zhiliang; Qi, Xiaotian; Li, Yingzi; Zhang, Guanghui; Liu, Chao; Yi, Hong; Meng, Lingkui; Bunel, Emilio E.; Miller, Jeffrey T.; Pao, Chih-Wen; Lee, Jyh-Fu; Lan, Yu; Lei, Aiwen

    2015-01-01

    Copper-catalyzed aerobic oxidative C–H/N–H coupling between simple ketones and diamines was developed toward the synthesis of a variety of pyrazines. Various substituted ketones were compatible for this transformation. Preliminary mechanistic investigations indicated that radical species were involved. X-ray absorption fine structure experiments elucidated that the Cu(II) species 5 coordinated by two N atoms at a distance of 2.04 Å and two O atoms at a shorter distance of 1.98 Å was a reactive one for this aerobic oxidative coupling reaction. Density functional theory calculations suggested that the intramolecular coupling of cationic radicals was favorable in this transformation. PMID:26601302

  14. Plasma-Chemical Synthesis of Oxide Powders Using Transformer-Coupled Discharge

    NASA Astrophysics Data System (ADS)

    M. Ulanov, I.; V. Isupov, M.; Yu Litvinsev, A.; A. Mischenko, P.

    2013-04-01

    An experimental investigation of transformer-coupled discharge in an Ar-O2 mixture with the addition of SiCl4, TiCl4 and ZrCl4 has been carried out under the atmospheric pressure of plasma-forming gases. Discharge power and discharge heat losses have been determined, and the dispersion and phase composition of reaction products (oxide powders) has been analyzed with SEM and X-ray diffraction analysis. Investigations reveal the formation of ultrafine oxide powders in the case of vaporized chloride (SiCl4 and TiCl4) injecting into the transformer coupled discharge. In the case of fine powder (ZrCl4) injection, full oxidation was not observed and reaction products consisted of a mixture of ZrO2 and ZrOCl2. A conclusion has been made regarding the perspectives of using transformer-coupled discharge to produce ultrafine oxide powders.

  15. Catalytic liquid-phase oxidation of acetaldehyde to acetic acid over a Pt/CeO2-ZrO2-SnO2/γ-alumina catalyst.

    PubMed

    Choi, Pil-Gyu; Ohno, Takanobu; Masui, Toshiyuki; Imanaka, Nobuhito

    2015-10-01

    Pt/CeO2-ZrO2-SnO2/γ-Al2O3 catalysts were prepared by co-precipitation and wet impregnation methods for catalytic oxidation of acetaldehyde to acetic acid in water. In the present catalysts, Pt and CeO2-ZrO2-SnO2 were successfully dispersed on the γ-Al2O3 support. Dependences of platinum content and reaction time on the selective oxidation of acetaldehyde to acetic acid were investigated to optimize the reaction conditions for obtaining both high acetaldehyde conversion and highest selectivity to acetic acid. Among the catalysts, a Pt(6.4wt.%)/Ce0.68Zr0.17Sn0.15O2.0(16wt.%)/γ-Al2O3 catalyst showed the highest acetaldehyde oxidation activity. On this catalyst, acetaldehyde was completely oxidized after the reaction at 0°C for 8hr, and the selectivity to acetic acid reached to 95% and higher after the reaction for 4hr and longer. PMID:26456607

  16. Carbohydrate oxidation coupled to Fe(III) reduction, a novel form of anaerobic metabolism.

    PubMed

    Coates, J D; Councell, T; Ellis, D J; Lovley, D R

    1998-12-01

    An isolate, designated GC-29, that could incompletely oxidize glucose to acetate and carbon dioxide with Fe(III) serving as the electron acceptor was recovered from freshwater sediments of the Potomac River, Maryland. This metabolism yielded energy to support cell growth. Strain GC-29 is a facultatively anaerobic, gram-negative motile rod which, in addition to glucose, also used sucrose, lactate, pyruvate, yeast extract, casamino acids or H2 as alternative electron donors for Fe(III) reduction. Stain GC-29 could reduce NO3(-), Mn(IV), U(VI), fumarate, malate, S2O3(2-), and colloidal S0 as well as the humics analog, 2,6-anthraquinone disulfonate. Analysis of the almost complete 16S rRNA sequence indicated that strain GC-29 belongs in the Shewanella genus in the epsilon subdivision of the Proteobacteria. The name Shewanella saccharophilia is proposed. Shewanella saccharophilia differs from previously described fermentative microorganisms that metabolize glucose with the reduction of Fe(III) because it transfers significantly more electron equivalents to Fe(III); acetate and carbon dioxide are the only products of glucose metabolism; energy is conserved from Fe(III) reduction; and glucose is not metabolized in the absence of Fe(III). The metabolism of organisms like S. saccharophilia may account for the fact that glucose is metabolized primarily to acetate and carbon dioxide in a variety of sediments in which Fe(III) reduction is the terminal electron accepting process. PMID:16887653

  17. Carbohydrate oxidation coupled to Fe(III) reduction, a novel form of anaerobic metabolism

    USGS Publications Warehouse

    Coates, J.D.; Councell, T.; Ellis, D.J.; Lovley, D.R.

    1998-01-01

    An isolate, designated GC-29, that could incompletely oxidize glucose to acetate and carbon dioxide with Fe(III) serving as the electron acceptor was recovered from freshwater sediments of the Potomac River, Maryland. This metabolism yielded energy to support cell growth. Strain GC-29 is a facultatively anaerobic, Gram-negative motile rod which, in addition to glucose, also used sucrose, lactate, pyruvate, yeast extract, casamino acids or H2 as alternative electron donors for Fe(III) reduction. Stain GC-29 could reduce NO-3, Mn(IV), U(VI), fumarate, malate, S2O32-, and colloidal S0 as well as the humics analog, 2,6-anthraquinone disulfonate. Analysis of the almost complete 16S rRNA sequence indicated that strain GC-29 belongs in the Shewanella genus in the epsilon subdivision of the Proteobacteria. The name Shewanella saccharophilia is proposed. Shewanella saccharophilia differs from previously described fermentative microorganisms that metabolize glucose with the reduction of Fe(III) because it transfers significantly more electron equivalents to Fe(III); acetate and carbon dioxide are the only products of glucose metabolism; energy is conserved from Fe(III) reduction; and glucose is not metabolized in the absence of Fe(III). The metabolism of organisms like S. saccharophilia may account for the fact that glucose is metabolized primarily to acetate and carbon dioxide in a variety of sediments in which Fe(III) reduction is the terminal electron accepting process.

  18. Antioxidant phenolic profile from ethyl acetate fraction of Fructus Ligustri Lucidi with protection against hydrogen peroxide-induced oxidative damage in SH-SY5Y cells.

    PubMed

    Ju, Heng-Yin; Chen, Shiu Ching; Wu, Kuo-Jen; Kuo, Hui-Chun; Hseu, You-Cheng; Ching, Hui; Wu, Chi-Rei

    2012-03-01

    In this study, we demonstrated the antioxidant and protective properties of crude extract and fractions from Fructus Ligustri Lucidi (FLL) against hydrogen peroxide (H2O2)-induced oxidative damage in SH-SY5Y cells. The contents of their phytochemical profiles were determined by spectrophotometric methods and high performance liquid chromatography using a photodiode array detector. FLL crude extract possessed appreciable scavenging capacity against 1,1-diphenyl-2-picrylhydrazyl and H2O2. The ethyl acetate (EtOAc) fraction was the most active fraction in scavenging free radicals and H2O2. Following exposure of cells to H2O2, there was a marked decrease in cell survival and intracellular antioxidant enzymes, and then intracellular oxidative stress, the level of lipid peroxidation, and caspase-3 activity were increased. Simultaneous treatment with the EtOAc fraction blocked these H2O2-induced cellular events. Hydroxytyrosol and salidroside are major components of the EtOAc fraction. These results show that the phenolic-enriched EtOAc fraction of FLL contains tyrosol-related derivatives and exerts the protective effects against H2O2 toxicity via its free radical scavenging activity and ability to elevate the levels of antioxidant enzymes. PMID:22142696

  19. A fully coupled model for water-gas-heat reactive transport with methane oxidation in landfill covers.

    PubMed

    Ng, C W W; Feng, S; Liu, H W

    2015-03-01

    Methane oxidation in landfill covers is a complex process involving water, gas and heat transfer as well as microbial oxidation. The coupled phenomena of microbial oxidation, water, gas, and heat transfer are not fully understood. In this study, a new model is developed that incorporates water-gas-heat coupled reactive transport in unsaturated soil with methane oxidation. Effects of microbial oxidation-generated water and heat are included. The model is calibrated using published data from a laboratory soil column test. Moreover, a series of parametric studies are carried out to investigate the influence of microbial oxidation-generated water and heat, initial water content on methane oxidation efficiency. Computed and measured results of gas concentration and methane oxidation rate are consistent. It is found that the coupling effects between water-gas-heat transfer and methane oxidation are significant. Ignoring microbial oxidation-generated water and heat can result in a significant difference in methane oxidation efficiency by 100%. PMID:25489976

  20. Electrochemical production of hydrogen coupled with the oxidation of arsenite.

    PubMed

    Kim, Jungwon; Kwon, Daejung; Kim, Kitae; Hoffmann, Michael R

    2014-01-01

    The production of hydrogen accompanied by the simultaneous oxidation of arsenite (As(III)) was achieved using an electrochemical system that employed a BiOx-TiO2 semiconductor anode and a stainless steel (SS) cathode in the presence of sodium chloride (NaCl) electrolyte. The production of H2 was enhanced by the addition of As(III) during the course of water electrolysis. The synergistic effect of As(III) on H2 production can be explained in terms of (1) the scavenging of reactive chlorine species (RCS), which inhibit the production of H2 by competing with water molecules (or protons) for the electrons on the cathode, by As(III) and (2) the generation of protons, which are more favorably reduced on the cathode than water molecules, through the oxidation of As(III). The addition of 1.0 mM As(III) to the electrolyte at a constant cell voltage (E cell) of 3.0 V enhanced the production of H2 by 12% even though the cell current (I cell) was reduced by 5%. The net effect results in an increase in the energy efficiency (EE) for H2 production (ΔEE) by 17.5%. Furthermore, the value ΔEE, which depended on As(III) concentration, also depended on the applied E cell. For example, the ΔEE increased with increasing As(III) concentration in the micromolar range but decreased as a function of E cell. This is attributed to the fact that the reactions between RCS and As(III) are influenced by both RCS concentration depending on E cell and As(III) concentration in the solution. On the other hand, the ΔEE decreased with increasing As(III) concentration in the millimolar range due to the adsorption of As(V) generated from the oxidation of As(III) on the semiconductor anode. In comparison to the electrochemical oxidation of certain organic compounds (e.g., phenol, 4-chlorophenol, 2-chlorophenol, salicylic acid, catechol, maleic acid, oxalate, and urea), the ΔEE obtained during As(III) oxidation (17.5%) was higher than that observed during the oxidation of the above organic compounds

  1. Cr(III) Oxidation Coupled With Microbially-Mediated Mn(II) Oxidation

    SciTech Connect

    Youxian Wu; Baolin Deng

    2006-04-05

    Cr(VI) can be reduced to less toxic and mobile Cr(III) species through abiotic and biological processes. Reductive immobilization of Cr(VI) has been widely explored as a cost effective technology for site remediation; Mn oxides are regarded as primary oxidants for Cr(III) oxidation in the environment; and Generation of Mn oxides from Mn(II) in natural environments is believed to be biologically catalyzed.

  2. Oxidation and hydrolysis of acetic acid and methylene chloride in supercritical water as a means of remediation

    SciTech Connect

    Marrone, P.A.; Lachance, R.P.; DiNaro, J.L.

    1995-10-01

    Supercritical water oxidation (SCWO) is a promising technology proposed for the destruction of hazardous organic wastes. Unlike its well known behavior under ambient conditions, water above its critical point (374{degrees}C, 221 bar) has properties similar to that of a nonpolar solvent, primarily due to the effect of a decrease in hydrogen bonding and density that occurs near and above the critical point. The result is that nonpolar organics and oxygen exhibit complete solubility in supercritical water, while polar species such as inorganic salts are insoluble and precipitate out. In the single homogeneous phase formed, oxidation of organics with oxygen in supercritical water is rapid and complete to CO{sub 2} and H{sub 2}O. Organic heteroatoms such as halogens, sulfur, or phosphorus are converted to inorganic acids (HCl, H{sub 2}SO{sub 4}, H{sub 3}PO{sub 4}) which precipitate as salts when neutralized with added base, while nitrogen is converted to N{sub 2} and N{sub 2}O. No NO{sub x} compounds are formed due to the relatively low temperatures that exist in the SCWO process (400 - 650{degrees}C) relative to that of air incineration processes (typically 900 - 1300{degrees}C). Oxidation in supercritical water is thus an appealing means of destroying toxic organic compounds while simultaneously separating out undesired inorganics by precipitation. Applications to decontaminating soils and dilute aqueous wastes are of special interest. Earlier work has demonstrated high destruction efficiencies for various organics in SCWO.

  3. Pioneering Metal-Free Oxidative Coupling Strategy of Aromatic Compounds Using Hypervalent Iodine Reagents.

    PubMed

    Kita, Yasuyuki; Dohi, Toshifumi

    2015-10-01

    We started our hypervalent iodine research about 30 years ago in the mid-1980s. We soon successfully developed the single-electron-transfer oxidation ability of a hypervalent iodine reagent, specifically, phenyliodine(III) bis(trifluoroacetate) (PIFA), toward aromatic rings of phenyl ethers for forming aromatic cation radicals. This was one of the exciting and unexpected events in our research studies so far, and the discovery was reported in 1991. It also led to the next challenge, developing the metal-free oxidative couplings for C-H functionalizations and direct couplings between the C-H bonds of valuable aromatic compounds in organic synthesis. In order to realize the effective oxidative coupling, pioneering new aromatic ring activations was essential and several useful methodologies have been found for oxidizable arenes. The achievements regarding this objective obtained in our continuous research are herein summarized with classification of the aromatic ring activation strategies. PMID:26223195

  4. Powerful fluoroalkoxy molybdenum(V) reagent for selective oxidative arene coupling reaction.

    PubMed

    Schubert, Moritz; Leppin, Jana; Wehming, Kathrin; Schollmeyer, Dieter; Heinze, Katja; Waldvogel, Siegfried R

    2014-02-24

    We introduce the novel fluoroalkoxy molybdenum(V) reagent 1 which has superior reactivity and selectivity in comparison to MoCl5 or the MoCl5 /TiCl4 reagent mixture in the oxidative coupling reactions of aryls. Common side reactions, such as chlorination and/or oligomer formation, are drastically diminished creating a powerful and useful reagent for oxidative coupling. Theoretical treatment of the reagent interaction with 1,2-dimethoxybenzene-type substrates indicates an inner-sphere electron transfer followed by a radical cationic reaction pathway for the oxidative-coupling process. EPR spectroscopic and electrochemical studies, X-ray analyses, computational investigations, and the experimental scope provide a highly consistent picture. The substitution of chlorido ligands by hexafluoroisopropoxido moieties seems to boost both the reactivity and selectivity of the metal center which might be applied to other reagents as well. PMID:24478061

  5. Transcription-coupled homologous recombination after oxidative damage.

    PubMed

    Wei, Leizhen; Levine, Arthur Samuel; Lan, Li

    2016-08-01

    Oxidative DNA damage induces genomic instability and may lead to mutagenesis and carcinogenesis. As severe blockades to RNA polymerase II (RNA POLII) during transcription, oxidative DNA damage and the associated DNA strand breaks have a profoundly deleterious impact on cell survival. To protect the integrity of coding regions, high fidelity DNA repair at a transcriptionally active site in non-dividing somatic cells, (i.e., terminally differentiated and quiescent/G0 cells) is necessary to maintain the sequence integrity of transcribed regions. Recent studies indicate that an RNA-templated, transcription-associated recombination mechanism is important to protect coding regions from DNA damage-induced genomic instability. Here, we describe the discovery that G1/G0 cells exhibit Cockayne syndrome (CS) B (CSB)-dependent assembly of homologous recombination (HR) factors at double strand break (DSB) sites within actively transcribed regions. This discovery is a challenge to the current dogma that HR occurs only in S/G2 cells where undamaged sister chromatids are available as donor templates. PMID:27233112

  6. Sulfur oxidation to sulfate coupled with electron transfer to electrodes by Desulfuromonas strain TZ1

    SciTech Connect

    Zhang, T; Bain, TS; Barlett, MA; Dar, SA; Snoeyenbos-West, OL; Nevin, KP; Lovley, DR

    2014-01-02

    Microbial oxidation of elemental sulfur with an electrode serving as the electron acceptor is of interest because this may play an important role in the recovery of electrons from sulfidic wastes and for current production in marine benthic microbial fuel cells. Enrichments initiated with a marine sediment inoculum, with elemental sulfur as the electron donor and a positively poised (+300 mV versus Ag/AgCl) anode as the electron acceptor, yielded an anode biofilm with a diversity of micro-organisms, including Thiobacillus, Sulfurimonas, Pseudomonas, Clostridium and Desulfuromonas species. Further enrichment of the anode biofilm inoculum in medium with elemental sulfur as the electron donor and Fe(III) oxide as the electron acceptor, followed by isolation in solidified sulfur/Fe(III) medium yielded a strain of Desulfuromonas, designated strain TZ1. Strain TZ1 effectively oxidized elemental sulfur to sulfate with an anode serving as the sole electron acceptor, at rates faster than Desulfobulbus propionicus, the only other organism in pure culture previously shown to oxidize S with current production. The abundance of Desulfuromonas species enriched on the anodes of marine benthic fuel cells has previously been interpreted as acetate oxidation driving current production, but the results presented here suggest that sulfur-driven current production is a likely alternative.

  7. Enhanced c2 yields from methane oxidative coupling by means of a separative chemical reactor.

    PubMed

    Tonkovich, A L; Carr, R W; Aris, R

    1993-10-01

    Of the processes for converting natural gas into a more useful chemical feedstock, the oxidative coupling of methane to form ethane and ethylene (C(2)) has perhaps been the most intensively investigated in recent years, but it has proved extremely difficult to obtain C(2) yields in excess of 20 to 25%. Methane oxidative coupling was carried out in a separative chemical reactor that simulated a countercurrent chromatographic moving-bed. This reaction gives 65% methane conversion, 80% C(2) selectivity, and a C(2) yield slightly better than 50% with Sm(2)O(3) catalyst at approximately 1000 K. PMID:17841868

  8. Oxidative Coupling of Enolates, Enol Silanes and Enamines: Methods and Natural Product Synthesis

    PubMed Central

    Guo, Fenghai; Clift, Michael D.

    2013-01-01

    The oxidative coupling of enolates, enol silanes, and enamines provides a direct method for the construction of useful 1,4-dicarbonyl synthons. Despite being first reported in 1935, with subsequent important advances beginning in the 1970’s, the development of this powerful reaction into a reliable methodology was somewhat limited. In recent years, there have been a number of reports from several research groups demonstrating advances in several neglected areas of oxidative coupling. This microreview summarizes these new advances in methodology and provides an overview of recent natural product syntheses that showcase the power of these transformations. PMID:23471479

  9. Impact of orthogonal exchange coupling on magnetic anisotropy in antiferromagnetic oxides/ferromagnetic systems.

    PubMed

    Kuświk, Piotr; Gastelois, Pedro Lana; Głowiński, Hubert; Przybylski, Marek; Kirschner, Jürgen

    2016-10-26

    The influence of interface exchange coupling on magnetic anisotropy in the antiferromagnetic oxide/Ni system is investigated. We show how interfacial exchange coupling can be employed not only to pin the magnetization of the ferromagnetic layer but also to support magnetic anisotropy to orient the easy magnetization axis perpendicular to the film plane. The fact that this effect is only observed below the Néel temperature of all investigated antiferromagnetic oxides with significantly different magnetocrystalline anisotropies gives evidence that antiferromagnetic ordering is a source of the additional contribution to the perpendicular effective magnetic anisotropy. PMID:27589202

  10. Biomimetic Synthesis of Moschamine-Related Indole Alkaloids via Iron-Catalyzed Selectively Oxidative Radical Coupling.

    PubMed

    Liang, Kangjiang; Yang, Jing; Tong, Xiaogang; Shang, Wenbin; Pan, Zhiqiang; Xia, Chengfeng

    2016-03-18

    An iron-catalyzed oxidative radical coupling reaction was developed to selectively construct indolofuran or bisphenolic indole cores, which exist in two types of moschamine-related indole alkaloids. Both (+)-decursivine and 4,4″-bis(N-feruloyl)serotonin were biomimetically synthesized by using coupling reactions. The proposed reassignment of the structure of montamine as 4,4″-bis(N-feruloyl)serotonin was excluded. PMID:26949004

  11. Coupling characteristics of thin-film metal-oxide-metal diodes at 10.6 microns

    NASA Technical Reports Server (NTRS)

    Wang, S. Y.; Gustafson, T. K.; Izawa, T.

    1975-01-01

    Direct detection experiments have demonstrated the coherent coupling of 10.6 micrometer radiation into photolithographically fabricated metal-oxide-metal tunnel junctions. A CO2 laser beam mechanically chopped at 1 KHz was focused at a variable angle of incidence with a power density of about 10 W/sq cm at the diodes. Diodes in which the junction resistance was much greater than the lead resistance displayed angular characteristics dominated by coherent antenna coupling.

  12. Coupled Mn(II) Oxidation Pathways by a Planktonic Roseobacter-like Bacterium

    NASA Astrophysics Data System (ADS)

    Hansel, C. M.; Francis, C. A.

    2005-12-01

    Bacteria belonging to the Roseobacter clade of the alpha-Proteobacteria are numerically abundant in coastal waters, ecologically significant in the cycling of (in)organic sulfur, and occupy a wide range of environmental niches. Here we reveal that Roseobacter-like bacteria may play a previously unrecognized role in the oxidation and cycling of manganese (Mn) in coastal waters. A diverse array of Mn(II)-oxidizing Roseobacter-like species were isolated from Elkhorn Slough, a coastal estuary adjacent to Monterey Bay, California. One isolate (designated AzwK-3b), in particular, rapidly oxidizes Mn(II) to insoluble Mn(III, IV) oxides. Interestingly, AzwK-3b is 100% identical (at the 16S rRNA level) to a previously reported Pfiesteria-associated Roseobacter-like bacterium, which does not posses the ability to oxidize Mn(II). Manganese(II) oxidation rates by live cultures and cell-free filtrates are substantially higher when incubated in the presence of light. Rates of oxidation by washed cell extracts, however, are light independent, which are actually identical to rates by cell-free filtrates incubated in the dark. Thus, AwwK-3b induces two Mn(II) oxidation mechanisms when incubated in the presence of light as opposed to predominantly direct enzymatic oxidation in the dark. Within the light, production of photochemically-active metabolites is coupled with initial direct enzymatic Mn(II) oxidation, resulting in substantially accelerated Mn(II) oxidation rates. Thus, Roseobacter-like bacteria may not only greatly influence Mn(II) oxidation and cycling within coastal surface waters, but may also induce a novel photo-oxidation pathway providing an alternative means of Mn(II) oxidation within the photic zone.

  13. Preparation and characterization of magnetic allylamine modified graphene oxide-poly(vinyl acetate-co-divinylbenzene) nanocomposite for vortex assisted magnetic solid phase extraction of some metal ions.

    PubMed

    Khan, Mansoor; Yilmaz, Erkan; Sevinc, Basak; Sahmetlioglu, Ertugrul; Shah, Jasmin; Jan, Muhammad Rasul; Soylak, Mustafa

    2016-01-01

    Magnetic allylamine modified graphene oxide-poly(vinyl acetate-co-divinylbenzene) (MGO-DVB-VA) was synthesized and used for magnetic solid phase extraction of Pb(II), Cd(II), Cu(II), Ni(II) and Co(II) prior to their determination by flame atomic absorption spectroscopy. The adsorbent surface functional group was characterized by using FT-IR and Raman spectroscopy. XRD pattern was used to determine the layers of GO. Surface morphology and elemental composition of the adsorbent were evaluated by using SEM and EDX analysis. Various parameters, effecting adsorption efficiency like initial solution pH, adsorbent dose, type and volume of eluent, volume of sample and diverse ions effects were optimized. The preconcentration factor (PF) is 40 for all the metals and the limits of detection for Pb, Cd, Cu, Ni and Co are in the range of 0.37-2.39 µg L(-1) and relative standard deviation below 3.1%. The method was validated by using the method for certified reference materials (Tobacco Leaves (INCT-OBTL-5), Tomato Leaves (1573a), Certified Water (SPS-ww2) and Certified Water (TMDA 64-2)). The method was successfully applied for natural water and food samples. PMID:26695244

  14. Photoelectrochemistry of the thallic/thallous couple - The thallic ion catalyzed photo-oxidation of propylene

    NASA Astrophysics Data System (ADS)

    Switzer, J. A.; Moorehead, E. L.; Dalesandro, D. M.

    1982-10-01

    Liquid-junction photovoltaic and photoelectrosynthetic applications of the thallic/thallous couple have been investigated. In the liquid-junction photovoltaic mode the redox couple produces large photovoltages with several semiconductors (TiO2, MoS2, CdS, and GaAs), and does not absorb appreciable semiconductor ultra-bandgap light. The couple also shows photoelectrosynthetic utility, since the thallic ion is a selective two-electron oxidizing agent for a variety of organic substrates. Preliminary work on the photoassisted epoxidation of propylene at n-type semiconductor electrodes (TiO2) and powders (TiO2, WO3, and ZnO) is discussed.

  15. Oxidative coupling of alcohols on gold: insights from experiments and theory.

    PubMed

    Xu, Bingjun; Friend, Cynthia M

    2011-01-01

    Molecular level understanding of the mechanism of oxidative coupling of alcohols on metallic Au(111) activated by oxygen is achieved through a combination of experiments and theoretical calculations. The facility of the beta-H elimination of the alkoxys, which increases with the length of the alkyl chain, is identified to be critical in determining the product distributions. Dioxymethylene serves as a formaldehyde reservoir in the cross-coupling reaction between methanol and formaldehyde through its reversible formation and decomposition, contributing to the high selectivity for the coupling products. PMID:22455052

  16. Direct Synthesis of Polyaryls by Consecutive Oxidative Cross-Coupling of Phenols with Arenes.

    PubMed

    Dyadyuk, Alina; Sudheendran, Kavitha; Vainer, Yulia; Vershinin, Vlada; Shames, Alexander I; Pappo, Doron

    2016-09-01

    A bioinspired iron-catalyzed consecutive oxidative cross-coupling reaction between a single phenolic unit and nucleophilic arenes was developed. This sustainable transformation offers a selective synthetic strategy for the preparation of complex polyaryl compounds directly from readily available phenols. With the aid of electron paramagnetic resonance spectroscopy, it was demonstrated that the groups ortho to the phenolic functionality (whether hydrogen, methyl, or methoxy) direct the regioselectivity (ortho, para, or meta via dienone-phenol rearrangement) and chemoselectivity (C-C coupling or C-O coupling) in this multistep process. PMID:27529128

  17. Hydrogen measurement during steam oxidation using coupled thermogravimetric analysis and quadrupole mass spectrometry

    DOE PAGESBeta

    Parkison, Adam J.; Nelson, Andrew Thomas

    2016-01-11

    An analytical technique is presented with the goal of measuring reaction kinetics during steam oxidation reactions for three cases in which obtaining kinetics information often requires a prohibitive amount of time and cost. The technique presented relies on coupling thermogravimetric analysis (TGA) with a quantitative hydrogen measurement technique using quadrupole mass spectrometry (QMS). The first case considered is in differentiating between the kinetics of steam oxidation reactions and those for simultaneously reacting gaseous impurities such as nitrogen or oxygen. The second case allows one to independently measure the kinetics of oxide and hydride formation for systems in which both ofmore » these reactions are known to take place during steam oxidation. The third case deals with measuring the kinetics of formation for competing volatile and non-volatile oxides during certain steam oxidation reactions. In order to meet the requirements of the coupled technique, a methodology is presented which attempts to provide quantitative measurement of hydrogen generation using QMS in the presence of an interfering fragmentation species, namely water vapor. This is achieved such that all calibrations and corrections are performed during the TGA baseline and steam oxidation programs, making system operation virtually identical to standard TGA. Benchmarking results showed a relative error in hydrogen measurement of 5.7–8.4% following the application of a correction factor. Lastly, suggestions are made for possible improvements to the presented technique so that it may be better applied to the three cases presented.« less

  18. Photoinduced Cross-Linking of Dynamic Poly(disulfide) Films via Thiol Oxidative Coupling.

    PubMed

    Feillée, Noémi; Chemtob, Abraham; Ley, Christian; Croutxé-Barghorn, Céline; Allonas, Xavier; Ponche, Arnaud; Le Nouen, Didier; Majjad, Hicham; Jacomine, Léandro

    2016-01-01

    Initially developed as an elastomer with an excellent record of barrier and chemical resistance properties, poly(disulfide) has experienced a revival linked to the dynamic nature of the S-S covalent bond. A novel photobase-catalyzed oxidative polymerization of multifunctional thiols to poly(disulfide) network is reported. Based solely on air oxidation, the single-step process is triggered by the photodecarboxylation of a xanthone acetic acid liberating a strong bicyclic guanidine base. Starting with a 1 μm thick film based on trithiol poly(ethylene oxide) oligomer, the UV-mediated oxidation of thiols to disulfides occurs in a matter of minutes both selectively, i.e., without overoxidation, and quantitatively as assessed by a range of spectroscopic techniques. Thiolate formation and film thickness determine the reaction rates and yield. Spatial control of the photopolymerization serves to generate robust micropatterns, while the reductive cleavage of S-S bridges allows the recycling of 40% of the initial thiol groups. PMID:26502361

  19. Coupled Photochemical and Enzymatic Mn(II) Oxidation Pathways of a Planktonic Roseobacter-Like Bacterium

    PubMed Central

    Hansel, Colleen M.; Francis, Chris A.

    2006-01-01

    Bacteria belonging to the Roseobacter clade of the α-Proteobacteria occupy a wide range of environmental niches and are numerically abundant in coastal waters. Here we reveal that Roseobacter-like bacteria may play a previously unrecognized role in the oxidation and cycling of manganese (Mn) in coastal waters. A diverse array of Mn(II)-oxidizing Roseobacter-like species were isolated from Elkhorn Slough, a coastal estuary adjacent to Monterey Bay in California. One isolate (designated AzwK-3b), in particular, rapidly oxidizes Mn(II) to insoluble Mn(III, IV) oxides. Interestingly, AzwK-3b is 100% identical (at the 16S rRNA gene level) to a previously described Pfiesteria-associated Roseobacter-like bacterium, which is not able to oxidize Mn(II). The rates of manganese(II) oxidation by live cultures and cell-free filtrates are substantially higher when the preparations are incubated in the presence of light. The rates of oxidation by washed cell extracts, however, are light independent. Thus, AzwK-3b invokes two Mn(II) oxidation mechanisms when it is incubated in the presence of light, in contrast to the predominantly direct enzymatic oxidation in the dark. In the presence of light, production of photochemically active metabolites is coupled with initial direct enzymatic Mn(II) oxidation, resulting in higher Mn(II) oxidation rates. Thus, Roseobacter-like bacteria may not only play a previously unrecognized role in Mn(II) oxidation and cycling in coastal surface waters but also induce a novel photooxidation pathway that provides an alternative means of Mn(II) oxidation in the photic zone. PMID:16672501

  20. Substituent-enabled oxidative dehydrogenative cross-coupling of 1,4-naphthoquinones with alkenes.

    PubMed

    Zhang, Chi; Wang, Meining; Fan, Zhoulong; Sun, Li-Ping; Zhang, Ao

    2014-08-15

    A Rh-catalyzed oxidative dehydrogenative cross-coupling of 1,4-naphthquinones with alkenes was achieved by using a substituent-enabled C(sp(2))-H functionalization (SEF) strategy. The method shows high functional group tolerance, broad substrate scope, and great potential for further functional transformations. PMID:25075553

  1. Direct detection of nitrotyrosine-containing proteins using an aniline-based oxidative coupling strategy.

    PubMed

    Sangsuwan, Rapeepat; Obermeyer, Allie C; Tachachartvanich, Phum; Palaniappan, Krishnan K; Francis, Matthew B

    2016-08-21

    A convenient two-step method is described for the detection of nitrotyrosine-containing proteins. First, nitrotyrosines are reduced to aminophenols using sodium dithionite. Following this, an oxidative coupling reaction is used to attach anilines bearing fluorescence reporters or affinity probes. Features of this approach include fast reaction times, pmol-level sensitivity, and excellent chemoselectivity. PMID:27447346

  2. 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. PMID:24577351

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

    PubMed Central

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

    2014-01-01

    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. PMID:24577351

  4. Oxide Defect Engineering Enables to Couple Solar Energy into Oxygen Activation.

    PubMed

    Zhang, Ning; Li, Xiyu; Ye, Huacheng; Chen, Shuangming; Ju, Huanxin; Liu, Daobin; Lin, Yue; Ye, Wei; Wang, Chengming; Xu, Qian; Zhu, Junfa; Song, Li; Jiang, Jun; Xiong, Yujie

    2016-07-20

    Modern development of chemical manufacturing requires a substantial reduction in energy consumption and catalyst cost. Sunlight-driven chemical transformation by metal oxides holds great promise for this goal; however, it remains a grand challenge to efficiently couple solar energy into many catalytic reactions. Here we report that defect engineering on oxide catalyst can serve as a versatile approach to bridge light harvesting with surface reactions by ensuring species chemisorption. The chemisorption not only spatially enables the transfer of photoexcited electrons to reaction species, but also alters the form of active species to lower the photon energy requirement for reactions. In a proof of concept, oxygen molecules are activated into superoxide radicals on defect-rich tungsten oxide through visible-near-infrared illumination to trigger organic aerobic couplings of amines to corresponding imines. The excellent efficiency and durability for such a highly important process in chemical transformation can otherwise be virtually impossible to attain by counterpart materials. PMID:27351805

  5. Predicting gold-mediated catalytic oxidative-coupling reactions from single crystal studies.

    PubMed

    Xu, Bingjun; Madix, Robert J; Friend, Cynthia M

    2014-03-18

    Though metallic gold is chemically inert under ambient conditions, its surface is extremely reactive and selective for many key oxidative chemical transformations when activated by atomic oxygen. A molecular-level understanding of the mechanism of these processes could allow researchers to design "green" catalytic processes mediated by gold-based materials. This Account focuses on the mechanistic framework for oxidative-coupling reactions established by fundamental studies on oxygen-activated Au(111) and the application of these principles to steady-state catalytic conditions. We also discuss the importance of the paradigms discovered both for predicting new oxidative-coupling reactions and for understanding existing literature. The mechanistic framework for the oxidative coupling of alcohols on gold surfaces predicts that new oxidative-coupling reactions should occur between amines and aldehydes and amines and alcohols as well as through alcohol carbonylation. Adsorbed atomic oxygen on the gold surface facilitates the activation of the substrates, and nucleophilic attack and β-H elimination are the two fundamental reactions that propagate the versatile chemistry that ensues. In the self-coupling of primary alcohols, adsorbed atomic oxygen first activates the O-H bond in the hydroxyl group at ∼150 K, which forms the corresponding adsorbed alkoxy groups. The rate-limiting step of the self-coupling reaction is the β-H elimination reaction of alkoxy groups to form the corresponding aldehydes and occurs with an activation barrier of approximately 12 kcal/mol. The remaining alkoxy groups nucleophilically attack the electron-deficient aldehyde carbonyl carbon to yield the adsorbed "hemiacetal". This intermediate undergoes facile β-H elimination to produce the final coupling products, esters with twice the number of carbon atoms as the starting alcohols. This mechanistic insight suggests that cross-coupling occurs between alcohols and aldehydes, based on the logic

  6. Oxidative Cross-Coupling of Two Different Phenols: An Efficient Route to Unsymmetrical Biphenols.

    PubMed

    More, Nagnath Yadav; Jeganmohan, Masilamani

    2015-06-19

    An efficient synthesis of unsymmetrical biphenols via the oxidative cross-coupling of two different phenols in the presence of K2S2O8 and Bu4N(+)·HSO3(-) (10 mol %) in CF3COOH at ambient conditions is described. 1:1 Cross-coupling of substituted phenols with naphthols and 1:2 cross-coupling of naphthols with phenol are also disclosed. By using Bu4N(+)·HSO3(-), the homocoupling of phenols or naphthols was controlled. In these reactions, the ortho C-H bond of two different phenols and the ortho and para C-H bond of phenols were coupled together. PMID:26023816

  7. Ternary and coupled binary zinc tin oxide nanopowders: Synthesis, characterization, and potential application in photocatalytic processes

    SciTech Connect

    Ivetić, T.B.; Finčur, N.L.; Đačanin, Lj. R.; Abramović, B.F.; Lukić-Petrović, S.R.

    2015-02-15

    Highlights: • Mechanochemically synthesized nanocrystalline zinc tin oxide (ZTO) powders. • Photocatalytic degradation of alprazolam in the presence of ZTO water suspensions. • Coupled binary ZTO exhibits enhanced photocatalytic activity compared to ternary ZTO. - Abstract: In this paper, ternary and coupled binary zinc tin oxide nanocrystalline powders were prepared via simple solid-state mechanochemical method. X-ray diffraction, scanning electron microscopy, Raman and reflectance spectroscopy were used to study the structure and optical properties of the obtained powder samples. The thermal behavior of zinc tin oxide system was examined through simultaneous thermogravimetric-differential scanning calorimetric analysis. The efficiencies of ternary (Zn{sub 2}SnO{sub 4} and ZnSnO{sub 3}) and coupled binary (ZnO/SnO{sub 2}) zinc tin oxide water suspensions in the photocatalytic degradation of alprazolam, short-acting anxiolytic of the benzodiazepine class of psychoactive drugs, under UV irradiation were determined and compared with the efficiency of pure ZnO and SnO{sub 2}.

  8. Coupling Between and Among Ammonia Oxidizers and Nitrite Oxidizers in Grassland Mesocosms Submitted to Elevated CO2 and Nitrogen Supply.

    PubMed

    Simonin, Marie; Le Roux, Xavier; Poly, Franck; Lerondelle, Catherine; Hungate, Bruce A; Nunan, Naoise; Niboyet, Audrey

    2015-10-01

    Many studies have assessed the responses of soil microbial functional groups to increases in atmospheric CO2 or N deposition alone and more rarely in combination. However, the effects of elevated CO2 and N on the (de)coupling between different microbial functional groups (e.g., different groups of nitrifiers) have been barely studied, despite potential consequences for ecosystem functioning. Here, we investigated the short-term combined effects of elevated CO2 and N supply on the abundances of the four main microbial groups involved in soil nitrification: ammonia-oxidizing archaea (AOA), ammonia-oxidizing bacteria (AOB), and nitrite-oxidizing bacteria (belonging to the genera Nitrobacter and Nitrospira) in grassland mesocosms. AOB and AOA abundances responded differently to the treatments: N addition increased AOB abundance, but did not alter AOA abundance. Nitrobacter and Nitrospira abundances also showed contrasted responses to the treatments: N addition increased Nitrobacter abundance, but decreased Nitrospira abundance. Our results support the idea of a niche differentiation between AOB and AOA, and between Nitrobacter and Nitrospira. AOB and Nitrobacter were both promoted at high N and C conditions (and low soil water content for Nitrobacter), while AOA and Nitrospira were favored at low N and C conditions (and high soil water content for Nitrospira). In addition, Nitrobacter abundance was positively correlated to AOB abundance and Nitrospira abundance to AOA abundance. Our results suggest that the couplings between ammonia and nitrite oxidizers are influenced by soil N availability. Multiple environmental changes may thus elicit rapid and contrasted responses between and among the soil ammonia and nitrite oxidizers due to their different ecological requirements. PMID:25877793

  9. Organo-Iodine(III)-Catalyzed Oxidative Phenol-Arene and Phenol-Phenol Cross-Coupling Reaction.

    PubMed

    Morimoto, Koji; Sakamoto, Kazuma; Ohshika, Takao; Dohi, Toshifumi; Kita, Yasuyuki

    2016-03-01

    The direct oxidative coupling reaction has been an attractive tool for environmentally benign chemistry. Reported herein is that the hypervalent iodine catalyzed oxidative metal-free cross-coupling reaction of phenols can be achieved using Oxone as a terminal oxidant in 1,1,1,3,3,3-hexafluoropropan-2-ol (HFIP). This method features a high efficiency and regioselectivity, as well as functional-group tolerance under very mild reaction conditions without using metal catalysts. PMID:26879796

  10. Effects of exchange coupling between cap layer and oxide layer on the recording performance in perpendicular media

    NASA Astrophysics Data System (ADS)

    Zhang, Kezhao; Choe, Gunn; Duan, Shanlin

    2009-04-01

    To understand the effects of exchange coupling between the CoCr-alloy cap layer and the CoCrPt-oxide layer in perpendicular media, we measured switching dynamics and recording performances of a series of media with various exchange-coupling layer thicknesses on a high-precision spinstand. This study shows that the cap and the oxide layers have different switching dynamics and sufficiently strong exchange coupling is necessary for adequate thermal stability. Exchange coupling improves the signal-to-noise ratio (SNR) through improved writability and reduced noise from the cap. In the strong coupling region, overwrite and write widths can be varied without loss in SNR.

  11. Concurrent Formation of Carbon-Carbon Bonds and Functionalized Graphene by Oxidative Carbon-Hydrogen Coupling Reaction.

    PubMed

    Morioku, Kumika; Morimoto, Naoki; Takeuchi, Yasuo; Nishina, Yuta

    2016-01-01

    Oxidative C-H coupling reactions were conducted using graphene oxide (GO) as an oxidant. GO showed high selectivity compared with commonly used oxidants such as (diacetoxyiodo) benzene and 2,3-dichloro-5,6-dicyano-p-benzoquinone. A mechanistic study revealed that radical species contributed to the reaction. After the oxidative coupling reaction, GO was reduced to form a material that shows electron conductivity and high specific capacitance. Therefore, this system could concurrently achieve two important reactions: C-C bond formation via C-H transformation and production of functionalized graphene. PMID:27181191

  12. Concurrent Formation of Carbon–Carbon Bonds and Functionalized Graphene by Oxidative Carbon-Hydrogen Coupling Reaction

    NASA Astrophysics Data System (ADS)

    Morioku, Kumika; Morimoto, Naoki; Takeuchi, Yasuo; Nishina, Yuta

    2016-05-01

    Oxidative C–H coupling reactions were conducted using graphene oxide (GO) as an oxidant. GO showed high selectivity compared with commonly used oxidants such as (diacetoxyiodo) benzene and 2,3-dichloro-5,6-dicyano-p-benzoquinone. A mechanistic study revealed that radical species contributed to the reaction. After the oxidative coupling reaction, GO was reduced to form a material that shows electron conductivity and high specific capacitance. Therefore, this system could concurrently achieve two important reactions: C–C bond formation via C–H transformation and production of functionalized graphene.

  13. Concurrent Formation of Carbon–Carbon Bonds and Functionalized Graphene by Oxidative Carbon-Hydrogen Coupling Reaction

    PubMed Central

    Morioku, Kumika; Morimoto, Naoki; Takeuchi, Yasuo; Nishina, Yuta

    2016-01-01

    Oxidative C–H coupling reactions were conducted using graphene oxide (GO) as an oxidant. GO showed high selectivity compared with commonly used oxidants such as (diacetoxyiodo) benzene and 2,3-dichloro-5,6-dicyano-p-benzoquinone. A mechanistic study revealed that radical species contributed to the reaction. After the oxidative coupling reaction, GO was reduced to form a material that shows electron conductivity and high specific capacitance. Therefore, this system could concurrently achieve two important reactions: C–C bond formation via C–H transformation and production of functionalized graphene. PMID:27181191

  14. Simultaneous determination of sulfur mustard and related oxidation products by isotope-dilution LC-MS/MS method coupled with a chemical conversion.

    PubMed

    Qi, Meiling; Xu, Bin; Wu, Jianfeng; Zhang, Yajiao; Zong, Cheng; Chen, Jia; Guo, Lei; Xie, Jianwei

    2016-08-15

    Sulfur mustard (SM) is a highly reactive alkylating vesicant with high toxicity and complicated metabolism, the in vivo profile of its oxidation metabolism is not still fully known and urgently needs to be clarified well. In this work, an isotope-dilution high performance liquid chromatography-tandem mass spectrometric method coupled with chemical conversion was developed for the simultaneous quantification of SM and its oxidation products, i.e., mustard sulfoxide (SMO) and mustard sulfone (SMO2). The accurate measurement of SM and its oxidation products with high reaction activity was achived via the method of chemical conversion of 2-(3,5-bis(mercaptomethyl)phenoxy) acetic acid into stable derivative products. Method validation was performed in whole blood matrix, the linear range of the method was between 0.2 and 1000μg/L with correlation coefficients (r(2))>0.99, and the lower limits of quantification for SM, SMO and SMO2 were 1, 1, 0.2μg/L, respectively. The validated method was successfully applied to a toxicokinetics research of SM and its oxidation products after SM dermal exposed rats in a single dose. All three target analytes were found in whole blood samples from poisoned rats, and significant time-dependent responses were also observed. Among them, SMO2 with relatively high toxicity was identified and quantified in vivo for the first time, while SMO was the major product in whole blood and some of them continued to be oxidized to SMO2in vivo. These results give a direct experimental evidence to support that a large amount of SM is converted into the corresponding SMO and SMO2, and these oxidation products might cause potential combined toxic effects. PMID:27322628

  15. Bimolecular Coupling Reactions through Oxidatively Generated Aromatic Cations: Scope and Stereocontrol

    PubMed Central

    Cui, Yubo; Villafane, Louis A.; Clausen, Dane J.

    2013-01-01

    Chromenes, isochromenes, and benzoxathioles react with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone to form stable aromatic cations that react with a range of nucleophiles. These oxidative fragment coupling reactions provide rapid access to structurally diverse heterocycles. Conducting the reactions in the presence of a chiral Brønsted acid results in the formation of an asymmetric ion pair that can provide enantiomerically enriched products in a rare example of a stereoselective process resulting from the generation of a chiral electrophile through oxidative carbon–hydrogen bond cleavage. PMID:23913987

  16. Transient characteristics for proton gating in laterally coupled indium-zinc-oxide transistors.

    PubMed

    Liu, Ning; Zhu, Li Qiang; Xiao, Hui; Wan, Chang Jin; Liu, Yang Hui; Chao, Jin Yu

    2015-03-25

    The control and detection over processing, transport and delivery of chemical species is of great importance in sensors and biological systems. The transient characteristics of the migration of chemical species reflect the basic properties in the processings of chemical species. Here, we observed the field-configurable proton effects in a laterally coupled transistor gated by phosphorosilicate glass (PSG). The bias on the lateral gate would modulate the interplay between protons and electrons at the PSG/indium-zinc-oxide (IZO) channel interface. Due to the modulation of protons flux within the PSG films, the IZO channel current would be modified correspondingly. The characteristic time for the proton gating is estimated to be on the order of 20 ms. Such laterally coupled oxide based transistors with proton gating are promising for low-cost portable biosensors and neuromorphic system applications. PMID:25741771

  17. Spatially coupled catalytic ignition of CO oxidation on Pt: mesoscopic versus nano-scale

    PubMed Central

    Spiel, C.; Vogel, D.; Schlögl, R.; Rupprechter, G.; Suchorski, Y.

    2015-01-01

    Spatial coupling during catalytic ignition of CO oxidation on μm-sized Pt(hkl) domains of a polycrystalline Pt foil has been studied in situ by PEEM (photoemission electron microscopy) in the 10−5 mbar pressure range. The same reaction has been examined under similar conditions by FIM (field ion microscopy) on nm-sized Pt(hkl) facets of a Pt nanotip. Proper orthogonal decomposition (POD) of the digitized FIM images has been employed to analyze spatiotemporal dynamics of catalytic ignition. The results show the essential role of the sample size and of the morphology of the domain (facet) boundary in the spatial coupling in CO oxidation. PMID:26021411

  18. Nanocellulose coupled flexible polypyrrole@graphene oxide composite paper electrodes with high volumetric capacitance

    NASA Astrophysics Data System (ADS)

    Wang, Zhaohui; Tammela, Petter; Strømme, Maria; Nyholm, Leif

    2015-02-01

    A robust and compact freestanding conducting polymer-based electrode material based on nanocellulose coupled polypyrrole@graphene oxide paper is straightforwardly prepared via in situ polymerization for use in high-performance paper-based charge storage devices, exhibiting stable cycling over 16 000 cycles at 5 A g-1 as well as the largest specific volumetric capacitance (198 F cm-3) so far reported for flexible polymer-based electrodes.A robust and compact freestanding conducting polymer-based electrode material based on nanocellulose coupled polypyrrole@graphene oxide paper is straightforwardly prepared via in situ polymerization for use in high-performance paper-based charge storage devices, exhibiting stable cycling over 16 000 cycles at 5 A g-1 as well as the largest specific volumetric capacitance (198 F cm-3) so far reported for flexible polymer-based electrodes. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr07251k

  19. Heterogeneous Rhodium-Catalyzed Aerobic Oxidative Dehydrogenative Cross-Coupling: Nonsymmetrical Biaryl Amines.

    PubMed

    Matsumoto, Kenji; Yoshida, Masahiro; Shindo, Mitsuru

    2016-04-18

    The first heterogeneously catalyzed oxidative dehydrogenative cross-coupling of aryl amines is reported herein. 2-Naphthylamine analogues were reacted with various electron-rich arenes using a heterogeneous Rh/C catalyst under mild aerobic conditions, thus affording nonsymmetrical biaryl amines in excellent yields with high selectivities. This reaction provides a mild, operationally simple, and efficient approach for the synthesis of biaryls which are important to pharmaceutical and materials chemistry. PMID:26996772

  20. Practical Synthesis of Amides via Copper/ABNO-Catalyzed Aerobic Oxidative Coupling of Alcohols and Amines.

    PubMed

    Zultanski, Susan L; Zhao, Jingyi; Stahl, Shannon S

    2016-05-25

    A modular Cu/ABNO catalyst system has been identified that enables efficient aerobic oxidative coupling of alcohols and amines to amides. All four permutations of benzylic/aliphatic alcohols and primary/secondary amines are viable in this reaction, enabling broad access to secondary and tertiary amides. The reactions exhibit excellent functional group compatibility and are complete within 30 min-3 h at rt. All components of the catalyst system are commercially available. PMID:27171973

  1. Solvent-dependent oxidative coupling of 1-aryl-1,3-dicarbonyls and styrene.

    PubMed

    Casey, Brian M; Eakin, Cynthia A; Jiao, Jingliang; Sadasivam, Dhandapani V; Flowers, Robert A

    2009-12-26

    This report describes the scope and mechanism of the solvent-dependent, chemoselective oxidative coupling of 1-aryl-1,3-dicarbonyls with styrene using Ce(IV) reagents. Dihydrofuran derivatives are obtained when reactions are performed in methanol whereas alpha-tetralones can be selectively synthesized in acetonitrile and methylene chloride. Mechanistic studies are consistent with the rate of solvent-assisted deprotonation of a radical cation intermediate playing an integral role in the selective formation of products. PMID:20625455

  2. Corrigendum to Solvent-dependent oxidative coupling of 1-aryl-1,3-dicarbonyls and styrene.

    PubMed

    Casey, Brian M; Eakin, Cynthia A; Jiao, Jingliang; Sadasivam, Dhandapani V; Flowers, Robert A

    2010-07-24

    This report describes the scope and mechanism of the solvent-dependent, chemoselective oxidative coupling of 1-aryl-1,3-dicarbonyls with styrene using Ce(IV) reagents. Dihydrofuran derivatives are obtained when reactions are performed in methanol whereas nitrate esters can be selectively synthesized in acetonitrile and methylene chloride. Mechanistic studies are consistent with the rate of solvent-assisted deprotonation of a radical cation intermediate playing an integral role in the selective formation of products. PMID:20806051

  3. Oxidation of butane to butanol coupled to electrochemical redox reaction of NAD+/NADH.

    PubMed

    Kang, Hye Sun; Na, Byung Kwan; Park, Doo Hyun

    2007-08-01

    A crude cell extract from a butane-utilizing bacterium, Alcaligenes sp., catalyzed the oxidation of butane to butanol coupled to NADH. A graphite electrode modified with Neutral Red (NR-electrode) catalyzed the reduction of NAD(+) to NADH. About 4.9 mM butanol was produced from 50% n-butane/O(2) mixture through the combined reactions of the crude enzyme and the NR-electrode in 250 ml reactor for 3 h. PMID:17549436

  4. Visible-Light-Promoted Direct Amination of Phenols via Oxidative Cross-Dehydrogenative Coupling Reaction.

    PubMed

    Zhao, Yating; Huang, Binbin; Yang, Chao; Xia, Wujiong

    2016-07-15

    A transition-metal-free approach was disclosed for intermolecular aryl C-N bonds formation between phenols and cyclic anilines via cross-dehydrogenative coupling (CDC) amination that was mediated by visible light, wherein K2S2O8 served as an external oxidant. The salient features of this protocol include circumventing the requirement for prefunctionalized starting materials and achieving single regioselectivity of amination adducts at room temperature. PMID:27364730

  5. 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. PMID:26048927

  6. Anaerobic Oxidation of Methane Coupled to Nitrite Reduction by Halophilic Marine NC10 Bacteria

    PubMed Central

    He, Zhanfei; Geng, Sha; Cai, Chaoyang; Liu, Shuai; Liu, Yan; Pan, Yawei; Lou, Liping; Zheng, Ping; Xu, Xinhua

    2015-01-01

    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. PMID:26048927

  7. Determination of Oxidized Phosphatidylcholines by Hydrophilic Interaction Liquid Chromatography Coupled to Fourier Transform Mass Spectrometry

    PubMed Central

    Sala, Pia; Pötz, Sandra; Brunner, Martina; Trötzmüller, Martin; Fauland, Alexander; Triebl, Alexander; Hartler, Jürgen; Lankmayr, Ernst; Köfeler, Harald C.

    2015-01-01

    A novel liquid chromatography-mass spectrometry (LC-MS) approach for analysis of oxidized phosphatidylcholines by an Orbitrap Fourier Transform mass spectrometer in positive electrospray ionization (ESI) coupled to hydrophilic interaction liquid chromatography (HILIC) was developed. This method depends on three selectivity criteria for separation and identification: retention time, exact mass at a resolution of 100,000 and collision induced dissociation (CID) fragment spectra in a linear ion trap. The process of chromatography development showed the best separation properties with a silica-based Kinetex column. This type of chromatography was able to separate all major lipid classes expected in mammalian samples, yielding increased sensitivity of oxidized phosphatidylcholines over reversed phase chromatography. Identification of molecular species was achieved by exact mass on intact molecular ions and CID tandem mass spectra containing characteristic fragments. Due to a lack of commercially available standards, method development was performed with copper induced oxidation products of palmitoyl-arachidonoyl-phosphatidylcholine, which resulted in a plethora of lipid species oxidized at the arachidonoyl moiety. Validation of the method was done with copper oxidized human low-density lipoprotein (LDL) prepared by ultracentrifugation. In these LDL samples we could identify 46 oxidized molecular phosphatidylcholine species out of 99 possible candidates. PMID:25874761

  8. Proton Coupled Electron Transfer Reactions at the Surface of Metal Oxide Nanomaterials

    NASA Astrophysics Data System (ADS)

    Braten, Miles N.

    Nanostructured metal oxide materials are found in many products and processes in our society today, but they play a particularly important role in the conversion and storage of energy. The materials are used as catalysts and redox active supports in devices such as dye sensitized solar cells, solid oxide fuel cells, and flow batteries, where they transfer and store electrons and charge balancing cations. Oftentimes electron transfer is modulated by the cations and when the cation is a proton, these redox reactions are known as proton coupled electron transfer (PCET) reactions. The work described in this dissertation focuses on understanding the PCET reactivity of nanocrystalline metal oxide materials. Chapter 1 introduces the concept of PCET and provides background information on the zinc oxide (ZnO) nanocrystals (NCs) which the majority of the research is focused on. Chapter 2 examines the chemistry that occurs during the photoreduction of ZnO NCs. Chapter 3 describes experiments probing how ZnO NC capping ligand concentration and NC size modulate PCET reaction rates. Chapter 4 describes experiments that compare the PCET reactivity of ZnO NCs with different numbers of electrons and protons stored on them. Chapter 5 describes attempts to observe the electrochemical reduction of ZnO NCs attached to gold electrodes. Finally, Chapter 6 contains attempts to identify a nanostructured metal oxide alkane oxidation catalyst for use in fuel cell.

  9. [Degradation of oxytetracycline with ozonation in acetic acid solvent].

    PubMed

    Li, Shi-Yin; Li, Xiao-Rong; Zhu, Yi-Ping; Zhu, Jiang-Peng; Wang, Guo-Xiang

    2012-12-01

    Use acetic acid as the media of ozone degradation of oxytetracycline (OTC), and effects of the initial dosing ratio of ozone/OTC, ozone flow, free radical scavenger, metal ions on the removal rate of OTC were investigated respectively. The results showed that acetic acid had a high ozone stability and solubility. OTC had a high removal rate and degradation rate in acetic acid solution. With the increase of OTC dosage, the removal rate of OTC decreased in acetic acid. Removal rate of OTC was increased distinctly when ozone flow increased properly. It was also observed that free radical scavenger had a significantly negative effect on OTC ozonation degradation in acetic acid. Furthermore the main reactions of OTC ozone oxidation were direct oxidation and indirect oxidation in acetic acid. When Fe3+ and Co2+ were existent in acetic acid, the degradation of OTC was inhibited significantly. PMID:23379161

  10. Novel magnetic states in insulating d4 oxides with strong spin-orbit coupling

    NASA Astrophysics Data System (ADS)

    Svoboda, Christopher; Trivedi, Nandini

    2015-03-01

    The comparable energy scales in 4 d and 5 d transition metal oxides, arising from Coulomb correlations, spin-orbit coupling and bandwidth, can lead to new phases and phenomena. With this motivation we examine an ion with d4 electron configuration in the t2 g sector separated from the other states by crystal field splitting. Upon including spin-orbit coupling, the completely filled j = 3 / 2 manifold is nonmagnetic but with a nonzero magnetic susceptibility. Upon introducing hopping between two d4 atoms, we find novel entangled ferromagnetism generated by the superexchange interaction in a significant part of the phase diagram. We further present results for the temperature dependent susceptibility calculated using exact diagonalization to illustrate this novel magnetic behavior and the role Hund's coupling plays in producing these phases. We make predictions for resonant X-ray scattering and magnetic measurements in pyrochlore osmates. We acknowledge the support of the CEM, and NSF MRSEC, under Grant DMR-1420451.

  11. Nanoporous gold catalysts for selective gas-phase oxidative coupling of methanol at low temperature.

    PubMed

    Wittstock, A; Zielasek, V; Biener, J; Friend, C M; Bäumer, M

    2010-01-15

    Gold (Au) is an interesting catalytic material because of its ability to catalyze reactions, such as partial oxidations, with high selectivities at low temperatures; but limitations arise from the low O2 dissociation probability on Au. This problem can be overcome by using Au nanoparticles supported on suitable oxides which, however, are prone to sintering. Nanoporous Au, prepared by the dealloying of AuAg alloys, is a new catalyst with a stable structure that is active without any support. It catalyzes the selective oxidative coupling of methanol to methyl formate with selectivities above 97% and high turnover frequencies at temperatures below 80 degrees C. Because the overall catalytic characteristics of nanoporous Au are in agreement with studies on Au single crystals, we deduced that the selective surface chemistry of Au is unaltered but that O2 can be readily activated with this material. Residual silver is shown to regulate the availability of reactive oxygen. PMID:20075249

  12. Improved photoelectric conversion efficiency from titanium oxide-coupled tin oxide nanoparticles formed in flame

    NASA Astrophysics Data System (ADS)

    Gu, Feng; Huang, Wenjuan; Wang, Shufen; Cheng, Xing; Hu, Yanjie; Li, Chunzhong

    2014-12-01

    The charge losses as a result of recombination to redox electrolyte and dye cation make tin oxide (SnO2)-based dye-sensitized solar cells (DSSCs) particularly inferior when compared with its titanium oxide (TiO2) counterpart. In this article, TiO2 nanocrystal is sealed in SnO2 by a modified flame spray pyrolysis (FSP) approach and the recombination losses to dye cation of SnO2 photoanode are effectively suppressed due to the negatively shifted Fermi level with the formation of bandedge-engineered core/shell structure. The fabricated TiO2@SnO2 (TSN)-device shows an open circuit voltage of 0.59 V and an efficiency of 3.82%, significantly better than those of the TiO2-, and SnO2-DSSCs devices. After surface modification, the conversion efficiency could be further improved to 7.87% while the open circuit voltage reaches 0.70 V. The higher efficiency of the TSN-based device is attributed to the enhanced electron injection arising from decreased interfacial charge recombination losses and improved electron transport. This strategy renders a new concept for further improvement of photovoltaic performance by engineering the dynamics of electron transport and recombination in DSSCs.

  13. COUPLING

    DOEpatents

    Hawke, B.C.

    1963-02-26

    This patent relates to a releasable coupling connecting a control rod to a control rod drive. This remotely operable coupling mechanism can connect two elements which are laterally and angviarly misaligned, and provides a means for sensing the locked condition of the elements. The coupling utilizes a spherical bayonet joint which is locked against rotation by a ball detent lock. (AEC)

  14. Enhanced spin-phonon-electronic coupling in a 5d oxide.

    PubMed

    Calder, S; Lee, J H; Stone, M B; Lumsden, M D; Lang, J C; Feygenson, M; Zhao, Z; Yan, J-Q; Shi, Y G; Sun, Y S; Tsujimoto, Y; Yamaura, K; Christianson, A D

    2015-01-01

    Enhanced coupling of material properties offers new fundamental insights and routes to multifunctional devices. In this context 5d oxides provide new paradigms of cooperative interactions that drive novel emergent behaviour. This is exemplified in osmates that host metal-insulator transitions where magnetic order appears intimately entwined. Here we consider such a material, the 5d perovskite NaOsO3, and observe a coupling between spin and phonon manifested in a frequency shift of 40 cm(-1), the largest measured in any material. The anomalous modes are shown to involve solely Os-O interactions and magnetism is revealed as the driving microscopic mechanism for the phonon renormalization. The magnitude of the coupling in NaOsO3 is primarily due to a property common to all 5d materials: the large spatial extent of the ion. This allows magnetism to couple to phonons on an unprecedented scale and in general offers multiple new routes to enhanced coupled phenomena in 5d materials. PMID:26608626

  15. Enhanced spin-phonon-electronic coupling in a 5d oxide

    NASA Astrophysics Data System (ADS)

    Calder, S.; Lee, J. H.; Stone, M. B.; Lumsden, M. D.; Lang, J. C.; Feygenson, M.; Zhao, Z.; Yan, J.-Q.; Shi, Y. G.; Sun, Y. S.; Tsujimoto, Y.; Yamaura, K.; Christianson, A. D.

    2015-11-01

    Enhanced coupling of material properties offers new fundamental insights and routes to multifunctional devices. In this context 5d oxides provide new paradigms of cooperative interactions that drive novel emergent behaviour. This is exemplified in osmates that host metal-insulator transitions where magnetic order appears intimately entwined. Here we consider such a material, the 5d perovskite NaOsO3, and observe a coupling between spin and phonon manifested in a frequency shift of 40 cm-1, the largest measured in any material. The anomalous modes are shown to involve solely Os-O interactions and magnetism is revealed as the driving microscopic mechanism for the phonon renormalization. The magnitude of the coupling in NaOsO3 is primarily due to a property common to all 5d materials: the large spatial extent of the ion. This allows magnetism to couple to phonons on an unprecedented scale and in general offers multiple new routes to enhanced coupled phenomena in 5d materials.

  16. Enhanced spin-phonon-electronic coupling in a 5d oxide

    SciTech Connect

    Calder, Stuart A.; Yamaura, K.; Tsujimoto, Y.; Sun, Y. S.; Stone, Matthew B.; Shi, Y. G.; Lang, Jonathan; Christianson, Andrew D.; Lumsden, Mark D.; Lee, Jun Hee; Feygenson, Mikhail; Zhao, Zhiying; Yan, Jiaqiang

    2015-11-26

    Enhanced coupling of material properties offers new fundamental insights and routes to multifunctional devices. In this context 5d oxides provide new paradigms of cooperative interactions that drive novel emergent behaviour. This is exemplified in osmates that host metal insulator transitions where magnetic order appears intimately entwined. Here we consider such a material, the 5d perovskite NaOsO3, and observe a coupling between spin and phonon manifested in a frequency shift of 40 cm 1, the largest measured in any material. The anomalous modes are shown to involve solely Os O interactions and magnetism is revealed as the driving microscopic mechanism for the phonon renormalization. The magnitude of the coupling in NaOsO3 is primarily due to a property common to all 5d materials: the large spatial extent of the ion. This allows magnetism to couple to phonons on an unprecedented scale and in general offers multiple new routes to enhanced coupled phenomena in 5d materials.

  17. Enhanced spin-phonon-electronic coupling in a 5d oxide

    DOE PAGESBeta

    Calder, Stuart A.; Yamaura, K.; Tsujimoto, Y.; Sun, Y. S.; Stone, Matthew B.; Shi, Y. G.; Lang, Jonathan; Christianson, Andrew D.; Lumsden, Mark D.; Lee, Jun Hee; et al

    2015-11-26

    Enhanced coupling of material properties offers new fundamental insights and routes to multifunctional devices. In this context 5d oxides provide new paradigms of cooperative interactions that drive novel emergent behaviour. This is exemplified in osmates that host metal insulator transitions where magnetic order appears intimately entwined. Here we consider such a material, the 5d perovskite NaOsO3, and observe a coupling between spin and phonon manifested in a frequency shift of 40 cm 1, the largest measured in any material. The anomalous modes are shown to involve solely Os O interactions and magnetism is revealed as the driving microscopic mechanism formore » the phonon renormalization. The magnitude of the coupling in NaOsO3 is primarily due to a property common to all 5d materials: the large spatial extent of the ion. This allows magnetism to couple to phonons on an unprecedented scale and in general offers multiple new routes to enhanced coupled phenomena in 5d materials.« less

  18. Enhanced spin-phonon-electronic coupling in a 5d oxide

    PubMed Central

    Calder, S.; Lee, J. H.; Stone, M. B.; Lumsden, M. D.; Lang, J. C.; Feygenson, M.; Zhao, Z.; Yan, J.-Q.; Shi, Y. G.; Sun, Y. S.; Tsujimoto, Y.; Yamaura, K.; Christianson, A. D.

    2015-01-01

    Enhanced coupling of material properties offers new fundamental insights and routes to multifunctional devices. In this context 5d oxides provide new paradigms of cooperative interactions that drive novel emergent behaviour. This is exemplified in osmates that host metal–insulator transitions where magnetic order appears intimately entwined. Here we consider such a material, the 5d perovskite NaOsO3, and observe a coupling between spin and phonon manifested in a frequency shift of 40 cm−1, the largest measured in any material. The anomalous modes are shown to involve solely Os–O interactions and magnetism is revealed as the driving microscopic mechanism for the phonon renormalization. The magnitude of the coupling in NaOsO3 is primarily due to a property common to all 5d materials: the large spatial extent of the ion. This allows magnetism to couple to phonons on an unprecedented scale and in general offers multiple new routes to enhanced coupled phenomena in 5d materials. PMID:26608626

  19. In situ high temperature oxidation analysis of Zircaloy-4 using acoustic emission coupled with thermogravimetry

    NASA Astrophysics Data System (ADS)

    Omar, Al Haj; Véronique, Peres; Eric, Serris; François, Grosjean; Jean, Kittel; François, Ropital; Michel, Cournil

    2015-06-01

    Zircaloy-4 oxidation behavior at high temperature (900 °C), which can be reached in case of severe accidental situations in nuclear pressurised water reactor, was studied using acoustic emission analysis coupled with thermogravimetry. Two different atmospheres were used to study the oxidation of Zircaloy-4: (a) helium and pure oxygen, (b) helium and oxygen combined with slight addition of air. The experiments with 20% of oxygen confirm the dependence on oxygen anions diffusion in the oxide scale. Under a mixture of oxygen and air in helium, an acceleration of the corrosion was observed due to the detrimental effect of nitrogen. The kinetic rate increased significantly after a kinetic transition (breakaway). This acceleration was accompanied by an acoustic emission activity. Most of the acoustic emission bursts were recorded after the kinetic transition (post-transition) or during the cooling of the sample. The characteristic features of the acoustic emission signals appear to be correlated with the different populations of cracks and their occurrence in the ZrO2 layer or in the α-Zr(O) layer. Acoustic events were recorded during the isothermal dwell time at high temperature under air. They were associated with large cracks in the zirconia porous layer. Acoustic events were also recorded during cooling after oxidation tests both under air or oxygen. For the latter, cracks were observed in the oxygen enriched zirconium metal phase and not in the dense zirconia layer after 5 h of oxidation.

  20. Free-standing α-Co(OH)2/graphene oxide thin films fabricated through delamination and reassembling of acetate anions intercalated α-Co(OH)2 and graphene oxide in water.

    PubMed

    Ma, KeYuan; Zhao, WenJia; Cheng, J P; Liu, Fu; Zhang, XiaoBin

    2016-04-15

    A novel hydrothermal process is demonstrated to prepare acetate anions intercalated α-Co(OH)2 that can be delaminated in water without any additional anion exchange processes. Positively charged Co(OH)2 nanosheets with lateral size of hundreds of nanometers and thickness less than 2 nm can be obtained by dispersing the as-obtained α-Co(OH)2 into water followed by sonication. The exfoliated Co(OH)2 nanosheets can be restacked into its original structure with different interlayer d-spacings. A flexible free-standing film with stacking Co(OH)2 nanosheets and graphene oxide (GO) layers can be obtained through flocculation of the Co(OH)2 nanosheets with GO nanosheets suspensions followed by a vacuum filtration, but the content of Co(OH)2 has to be kept under a low value so as to obtain films with flexible nature. Electrochemical tests show that this kind of film is not suitable to be used as electrode material for supercapacitor and lithium ion battery, because the content of active material is not high and the compacted junction between opposite charged nanosheets will prevent the electrolyte from diffusing into the interlayer space. PMID:26852347

  1. Metabolic and mutagenicity studies on DDT and 15 derivatives. Detection of 1,1-bis(p-chlorophenyl)-2,2-dichloroethane and 1,1-bis(p-chlorophenyl)-2,2,2-trichloroethyl acetate (kelthane acetate) as mutagens in Salmonella typhimurium and of 1,1-bis(p-chlorophenyl) ethylene oxide, a likely metabolite, as an alkylating agent.

    PubMed

    Planche, G; Croisy, A; Malaveille, C; Tomatis, L; Bartsch, H

    1979-05-01

    Using a novel in vitro technique, whereby microsomal enzymes were embedded in an agar layer to prolong their viability, 1,1-bis(p-chlorophenyl) ethylene(DDNU), a mammalian metabolite of 1,1-bis(p-chlorophenyl)-2,2,2-trichloroethane (DDT), was converted by microsomal mono-oxygenases of mouse liver into 1,1-bis(p-chlorophenyl)-1,2-ethanediol (DDNU-diol). The putative epoxide intermediate, 1,1-bis(p-chlorophenyl)ethylene oxide (DDNU-oxide), a new compound, was synthesized; it showed weak alkylating activity with 4-(4-nitrobenzyl)pyridine but was not mutagenic in Salmonella typhimurium strains TA100 and TA98. DDT and 13 of its metabolites or putative synthetic derivatives, including 1,1-bis(p-chlorophenyl)-2,2-dichloroethylene (DDE), 1 1,1-bis(p-chlorophenyl)-2-chloroethylene (DDMU), 1,1-bis(p-chlorophenyl)-2-chloroethane (DDMS)-DDNU, 2,2-bis(p-chlorophenyl)ethanol (DDOH), bis(p-chlorophenyl)acetic acid (DDA) and 1,1-bis(p-chlorophenyl)-2,2,2-trichloroethanol (Kethane), caused no mutagenic effects in S. typhimurium strains TA100 or TA98, either in the presence or absence of a mouse-liver microsomal fraction. 1,1-Bis(p-chlorophenyl)-2,2,2-trichloroethyl acetate (Kelthane acetate) was a direct-acting mutagen in strain TA100, whereas 1,1-bis(p-chlorophenyl)-2,2-dichloroethane (DDD) was mutagenic in TA98, only in the presence of a mouse-liver microsomal system. The results are discussed in relation to possible pathways whereby DDT is activated to mutagenic and/or carcinogenic metabolites. PMID:380827

  2. Electric-induced oxide breakdown of a charge-coupled device under femtosecond laser irradiation.

    PubMed

    Gao, Liuzheng; Zhu, Zhiwu; Shao, Zhengzheng; Cheng, Xiang'ai; Chang, Shengli

    2013-11-01

    A femtosecond laser provides an ideal source to investigate the laser-induced damage of a charge-coupled device (CCD) owing to its thermal-free and localized damage properties. For conventional damage mechanisms in the nanosecond laser regime, a leakage current and degradation of a point spread function or modulation transfer function of the CCD are caused by the thermal damages to the oxide and adjacent electrodes. However, the damage mechanisms are quite different for a femtosecond laser. In this paper, an area CCD was subjected to Ti: sapphire laser irradiation at 800 nm by 100 fs single pulses. Electric-induced oxide breakdown is considered to be the primary mechanism to cause a leakage current, and the injured oxide is between the gate and source in the metal-oxide semiconductor field-effect transistor (MOSFET) structure for one CCD pixel. Optical microscopy and scanning electron microscopy are used to investigate the damaged areas and the results show that the electrodes and the oxide underneath are not directly affected by the femtosecond laser, which helps to get rid of the conventional damage mechanisms. For the primary damage mechanism, direct damage by hot carriers, anode hole injection, and an enlarged electric field in the insulating layer are three possible ways to cause oxide breakdown. The leakage current is proved by the decrease of the resistance of electrodes to the substrate. The output saturated images and the dynamics of an area CCD indicate that the leakage current is from an electrode to a light sensing area (or gate to source for a MOSFET), which proves the oxide breakdown mechanism. PMID:24216654

  3. Toluene derivatives as simple coupling precursors for cascade palladium-catalyzed oxidative C-H bond acylation of acetanilides.

    PubMed

    Wu, Yinuo; Choy, Pui Ying; Mao, Fei; Kwong, Fuk Yee

    2013-01-25

    A palladium-catalyzed cascade cross-coupling of acetanilide and toluene for the synthesis of ortho-acylacetanilide is described. Toluene derivatives can act as effective acyl precursors (upon sp(3)-C-H bond oxidation by a Pd/TBHP system) in the oxidative coupling between two C-H bonds. This dehydrogenative Pd-catalyzed ortho-acylation proceeds under mild reaction conditions. PMID:23230572

  4. Design and analysis of a coupled solid oxide fuel cell and metal hydride bed system

    NASA Astrophysics Data System (ADS)

    Song, Ke

    Solid oxide fuel cells have exhibited excellent performance at high temperature for a few years. However, the fuel supply and the practical fuel cell application need to be improved especially for transportation or stand-alone facility usage. Two modified hydrogen storage models (two vessel and three vessel hydrogen storage system) are presented in this study. The gravimetric density and volumetric density are calculated in order to meet the DOE requirements. Furthermore, the time dependence model of hydrogen releasing in metal hydride bed (MHB) is built up. And the simulations are carried on in isothermal and adiabatic conditions. The simulation results indicate: the isothermal model can provide sufficient hydrogen flow until the MHB is emptied; the adiabatic model can only last short period because of the fast temperature decreasing in MHB. The steady state and time dependence model of coupled solid oxide fuel cells (SOFC) and MHB system are also investigated. The steady state model focuses on the heat recycle process for coupled system. The calculation shows the heat generated in system can provide enough energy for inner recycle. On the other hand, the time de-pendence model mainly concerns the time delay in such a coupled system. The simu-lation shows the time delay mainly comes from hydrogen feed.

  5. Different Sources of Nitric Oxide Mediate Neurovascular Coupling in the Lateral Geniculate Nucleus of the Cat

    PubMed Central

    de Labra, Carmen; Rivadulla, Casto; Espinosa, Nelson; Dasilva, Miguel; Cao, Ricardo; Cudeiro, Javier

    2009-01-01

    Understanding the link between neuronal responses (NRs) and metabolic signals is fundamental to our knowledge of brain function and it is a milestone in our efforts to interpret data from modern non invasive optical techniques such as fMRI, which are based on the close coupling between metabolic demand of active neurons and local changes in blood flow. The challenge is to unravel the link. Here we show, using spectrophotometry to record oxyhaemoglobin and methemoglobin (surrogate markers of cerebral flow and nitric oxide levels respectively) together with extracellular neuronal recordings in vivo and applying a multiple polynomial regression model, that the markers are able to predict up about 80% of variability in NR. Furthermore, we show that the coupling between blood flow and neuronal activity is heavily influenced by nitric oxide (NO). While NRs show the typical saturating response, blood flow shows a linear behaviour during contrast-response curves, with nitric oxide from different sources acting differently for low and high intensity. PMID:19826613

  6. Cr(VI) reduction coupled with anaerobic oxidation of methane in a laboratory reactor.

    PubMed

    Lu, Yong-Ze; Fu, Liang; Ding, Jing; Ding, Zhao-Wei; Li, Na; Zeng, Raymond J

    2016-10-01

    The process of anaerobic oxidation of methane (AOM) is globally important because of its contribution to the carbon cycle in the environment. Besides, microorganisms play important roles in the environmental fate of chromium. However, there have been no studies to date on the interaction between methane and chromium in batch reactor systems. In this study, biological Cr(VI) reduction was investigated using methane as the sole electron donor. Isotopic (13)CH4 in the batch experiments and long-term performance in the reactor demonstrated that Cr(VI) reduction is coupled with methane oxidation. High-throughput sequencing of the 16S rRNA genes demonstrated that the microbial community had changed substantially after Cr(VI) reduction. The populations of ANME-2d archaea were enhanced, and they became the only predominant AOM-related microbe. Interestingly, other bacteria with significant increases in abundance were not reported as having the ability to reduce Cr(VI). According to these results, two mechanisms were proposed: 1) Cr(VI) is reduced by ANME-2d alone; 2) Cr(VI) is reduced by unknown Cr(VI)-reducing microbes coupled with ANME-2d. This study revealed the potential relationship between Cr(VI) reduction and CH4 oxidation, and extended our knowledge of the relationship between the AOM process and biogeochemical cycles. PMID:27395029

  7. Cobalt-Catalyzed Oxidative C-H/C-H Cross-Coupling between Two Heteroarenes.

    PubMed

    Tan, Guangying; He, Shuang; Huang, Xiaolei; Liao, Xingrong; Cheng, Yangyang; You, Jingsong

    2016-08-22

    The first example of cobalt-catalyzed oxidative C-H/C-H cross-coupling between two heteroarenes is reported, which exhibits a broad substrate scope and a high tolerance level for sensitive functional groups. When the amount of Co(OAc)2 ⋅4 H2 O is reduced from 6.0 to 0.5 mol %, an excellent yield is still obtained at an elevated temperature with a prolonged reaction time. The method can be extended to the reaction between an arene and a heteroarene. It is worth noting that the Ag2 CO3 oxidant is renewable. Preliminary mechanistic studies by radical trapping experiments, hydrogen/deuterium exchange experiments, kinetic isotope effect, electron paramagnetic resonance (EPR), and high resolution mass spectrometry (HRMS) suggest that a single electron transfer (SET) pathway is operative, which is distinctly different from the dual C-H bond activation pathway that the well-described oxidative C-H/C-H cross-coupling reactions between two heteroarenes typically undergo. PMID:27460406

  8. Coupled biotic-abiotic oxidation of organic matter by biogenic MnO_{2}

    NASA Astrophysics Data System (ADS)

    Gonzalez, Julia; Peña, Jasquelin

    2016-04-01

    Some reactive soil minerals are strongly implicated in stabilising organic matter. However, others can play an active role in the oxidation of organic molecules. In natural systems, layer-type manganese oxide minerals (MnO2) typically occur as biomineral assemblages consisting of mineral particles and microbial biomass. Both the mineral and biological fractions of the assemblage can be powerful oxidants of organic C. The biological compartment relies on a set of enzymes to drive oxidative transformations of reduced C-substrates, whereas MnO2 minerals are strong, less specific abiotic oxidants that are assumed to rely on interfacial interactions between C-substrates and the mineral surface. This project aims to understand the coupling between microbial C mineralization and abiotic C oxidation mediated by MnO2 in bacterial-MnO2 assemblages. Specifically, under conditions of high C turnover, microbial respiration can significantly alter local pH, dissolved oxygen and pool of available reductants, which may modify rates and mechanism of C oxidation by biotic and abiotic components. We first investigated changes in the solution chemistry of Pseudomonas putida suspensions exposed to varying concentrations of glucose, chosen to represent readily bioavailable substrates in soils. Glucose concentrations tested ranged between 0 and 5.5mM and changes in pH, dissolved oxygen and dissolved organic and inorganic carbon were tracked over 48h. We then combined literature review and wet-chemical experiments to compile the pH dependence of rates of organic substrate oxidation by MnO2, including glucose. Our results demonstrate a strong pH dependence for these abiotic reactions. In assemblages of P. putida - MnO2, kinetic limitations for abiotic C oxidation by MnO2 are overcome by changes in biogeochemical conditions that result from bacterial C metabolism. When extrapolated to a soil solution confronted to an input of fresh dissolved organic matter, bacterial C metabolism of the

  9. Ag/Au mixed sites promote oxidative coupling of methanol on the alloy surface.

    PubMed

    Xu, Bingjun; Siler, Cassandra G F; Madix, Robert J; Friend, Cynthia M

    2014-04-14

    Nanoporous gold, a dilute alloy of Ag in Au, activates molecular oxygen and promotes the oxygen-assisted catalytic coupling of methanol. Because this trace amount of Ag inherent to nanoporous gold has been proposed as the source of oxygen activation, a thin film Ag/Au alloy surface was studied as a model system for probing the origin of this reactivity. Thin alloy layers of Ag(x)Au(1-x), with 0.15≤x≤0.40, were examined for dioxygen activation and methanol self-coupling. These alloy surfaces recombine atomic oxygen at different temperatures depending on the alloy composition. Total conversion of methanol to selective oxidation products, that is, formaldehyde and methyl formate, was achieved at low initial oxygen coverage and at low temperature. Reaction channels for methyl formate formation occurred on both Au and Au/Ag mixed sites with a ratio, as was predicted from the local 2-dimensional composition. PMID:24633724

  10. Strongly coupled phase transition in ferroelectric/correlated electron oxide heterostructures

    NASA Astrophysics Data System (ADS)

    Jiang, Lu; Seok Choi, Woo; Jeen, Hyoungjeen; Egami, Takeshi; Nyung Lee, Ho

    2012-07-01

    We fabricated ultrathin ferroelectric/correlated electron oxide heterostructures composed of the ferroelectric Pb(Zr0.2Ti0.8)O3 and the correlated electron oxide (CEO) La0.8Sr0.2MnO3 on SrTiO3 substrates by pulsed laser epitaxy. The hole accumulation in the ultrathin CEO layer was substantially modified by heterostructuring with the ferroelectric layer, resulting in an insulator-metal transition. In particular, our thickness dependent study showed that drastic changes in transport and magnetic properties were strongly coupled to the modulation of charge carriers by ferroelectric field effect, which was confined to the vicinity of the interface. Thus, our results provide crucial evidence that strong ferroelectric field effect control can be achieved in ultrathin (10 nm) heterostructures, yielding at least a 100 000-fold change in resistivity.

  11. Mechanism of the cathodic process coupled to the oxidation of iron monosulfide by dissolved oxygen.

    PubMed

    Duinea, Mădălina I; Costas, Andreea; Baibarac, Mihaela; Chiriță, Paul

    2016-04-01

    This study investigated the mechanism of iron monosulfide (FeS) oxidation by dissolved oxygen (O2(aq)). Synthetic FeS was reacted with O2(aq) for 6days and at 25°C. We have characterized the initial and reacted FeS surface using Scanning Electron Microscopy coupled with Energy Dispersive X-ray (SEM/EDX) analysis, Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR). It was found that during the aqueous oxidation of FeS new solid phases (disulfide, polysulfide, elemental sulfur, ferric oxyhydroxides and Fe3O4) develop on the mineral surface. The results of potentiodynamic polarization experiments show that after 2days of FeS electrode immersion in oxygen bearing solution (OBS) at initial pH 5.1 and 25°C the modulus of cathodic Tafel slopes dramatically decreases, from 393mV/dec to 86mV/dec. This decrease is ascribed to the change of the mechanism of electron transfer from cathodic sites to O2 (mechanism of cathodic process). The oxidation current densities (jox) indicate that mineral oxidative dissolution is not inhibited by pH increase up to 6.7. Another conclusion, which emerges from the analysis of jox, is that the dissolved Fe(3+) does not intermediate the aqueous oxidation of FeS. The results of electrochemical impedance spectroscopy (EIS) show that after 2days of contact between electrode and OBS the properties of FeS/water interface change. From the analysis of the EIS, FTIR spectroscopy, Raman spectroscopy and SEM/EDX data we can conclude that the change of FeS/water interface properties accompanies the formation of new solid phases on the mineral surface. The new characteristics of the surface layer and FeS/water interface do not cause the inhibition of mineral oxidation. PMID:26773612

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

    USGS Publications Warehouse

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

    2015-01-01

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

  13. Directly-coupled dc-SQUID magnetometers made of Bi-Sr-Ca-Cu oxide films

    SciTech Connect

    Matsuda, M.; Murayama, Y.; Kiryu, S.; Kasai, N.; Kashiwaya, S.; Koyanagi, M.; Endo, T. ); Kuriki, S. . Research Inst. of Applied Electricity)

    1991-03-01

    This paper reports on all high-T{sub c} dc- SQUID magnetometers made of Bi-Sr-Ca-Cu oxide films that were designed and fabricated. A directly-coupled scheme where a SQUID loop and a pick-up loop are connected directly in parallel was chosen to avoid fabricating the multi-layered structure. The flux noise which was measured in FLL operation at 4.2K increased in a form of 1/f as the frequency decreased below 20Hz.

  14. Pinball liquid phase from Hund's coupling in frustrated transition-metal oxides

    NASA Astrophysics Data System (ADS)

    Ralko, Arnaud; Merino, Jaime; Fratini, Simone

    2015-04-01

    The interplay of nonlocal Coulomb repulsion and Hund's coupling in the d -orbital manifold in frustrated triangular lattices is analyzed by a multiband extended Hubbard model. We find a rich phase diagram with several competing phases, including a robust pinball liquid phase, which is an unconventional metal characterized by threefold charge order, bad metallic behavior, and the emergence of high-spin local moments. Our results naturally explain the anomalous charge-ordered metallic state observed in the triangular layered compound AgNiO2. The potential relevance to other triangular transition-metal oxides is discussed.

  15. Synthetic and Predictive Approach to Unsymmetrical Biphenols by Iron-Catalyzed Chelated Radical-Anion Oxidative Coupling.

    PubMed

    Libman, Anna; Shalit, Hadas; Vainer, Yulia; Narute, Sachin; Kozuch, Sebastian; Pappo, Doron

    2015-09-01

    An iron-catalyzed oxidative unsymmetrical biphenol coupling in 1,1,1,3,3,3-hexafluoropropan-2-ol that proceeds via a chelated radical-anion coupling mechanism was developed. Based on mechanistic studies, electrochemical methods, and density functional theory calculations, we suggest a general model that enables prediction of the feasibility of cross-coupling for a given pair of phenols. PMID:26287435

  16. Assessment of the stoichiometry and efficiency of CO2 fixation coupled to reduced sulfur oxidation

    PubMed Central

    Klatt, Judith M.; Polerecky, Lubos

    2015-01-01

    Chemolithoautotrophic sulfur oxidizing bacteria (SOB) couple the oxidation of reduced sulfur compounds to the production of biomass. Their role in the cycling of carbon, sulfur, oxygen, and nitrogen is, however, difficult to quantify due to the complexity of sulfur oxidation pathways. We describe a generic theoretical framework for linking the stoichiometry and energy conservation efficiency of autotrophic sulfur oxidation while accounting for the partitioning of the reduced sulfur pool between the energy generating and energy conserving steps as well as between the main possible products (sulfate vs. zero-valent sulfur). Using this framework, we show that the energy conservation efficiency varies widely among SOB with no apparent relationship to their phylogeny. Aerobic SOB equipped with reverse dissimilatory sulfite reductase tend to have higher efficiency than those relying on the complete Sox pathway, whereas for anaerobic SOB the presence of membrane-bound, as opposed to periplasmic, nitrate reductase systems appears to be linked to higher efficiency. We employ the framework to also show how limited rate measurements can be used to estimate the primary productivity of SOB without the knowledge of the sulfate-to-zero-valent-sulfur production ratio. Finally, we discuss how the framework can help researchers gain new insights into the activity of SOB and their niches. PMID:26052315

  17. Online Measurement of the Intramolecular Isotopic Composition of Acetate in Natural Porewater Samples

    NASA Astrophysics Data System (ADS)

    Thomas, R. B.; Arthur, M. A.; Freeman, K. H.

    2006-12-01

    other volatile acids and water on a polar column (Nukol, Supelco). Following the GC, the acetic acid is reacted with either a combustion furnace (for total acetate) or a pyrolysis furnace for the carboxyl carbon only. The pyrolysis furnace operates at 600°C with Pd wire catalyst and a continuous trickle of H2. The resulting CO2 is then analyzed by conventional IRMS. This GC-PY-IRMS technique is coupled to a GC-C-IRMS such that switching between oxidation and pyrolysis is accomplished by a simple switch followed by a short stabilization period. The above pyrolysis conditions result in a small but characterizable oxidation of methyl carbon to CO2. The cross-contamination of acetate methyl into the acetate carboxyl signal is estimated to be approximately 15 to 20% of the IRMS signal and an isotope dilution series is used to estimate and correct for this contamination. Since this technique is online and allows for the injection of water samples the need for sample extraction and separation are eliminated. This method also significantly improves detection limits over the Dias 2002 method by avoiding SPME injections which have unfavorable partition coefficients for aqueous solutions of acetate.

  18. Control of the neurovascular coupling by nitric oxide-dependent regulation of astrocytic Ca2+ signaling

    PubMed Central

    Muñoz, Manuel F.; Puebla, Mariela; Figueroa, Xavier F.

    2015-01-01

    Neuronal activity must be tightly coordinated with blood flow to keep proper brain function, which is achieved by a mechanism known as neurovascular coupling. Then, an increase in synaptic activity leads to a dilation of local parenchymal arterioles that matches the enhanced metabolic demand. Neurovascular coupling is orchestrated by astrocytes. These glial cells are located between neurons and the microvasculature, with the astrocytic endfeet ensheathing the vessels, which allows fine intercellular communication. The neurotransmitters released during neuronal activity reach astrocytic receptors and trigger a Ca2+ signaling that propagates to the endfeet, activating the release of vasoactive factors and arteriolar dilation. The astrocyte Ca2+ signaling is coordinated by gap junction channels and hemichannels formed by connexins (Cx43 and Cx30) and channels formed by pannexins (Panx-1). The neuronal activity-initiated Ca2+ waves are propagated among neighboring astrocytes directly via gap junctions or through ATP release via connexin hemichannels or pannexin channels. In addition, Ca2+ entry via connexin hemichannels or pannexin channels may participate in the regulation of the astrocyte signaling-mediated neurovascular coupling. Interestingly, nitric oxide (NO) can activate connexin hemichannel by S-nitrosylation and the Ca2+-dependent NO-synthesizing enzymes endothelial NO synthase (eNOS) and neuronal NOS (nNOS) are expressed in astrocytes. Therefore, the astrocytic Ca2+ signaling triggered in neurovascular coupling may activate NO production, which, in turn, may lead to Ca2+ influx through hemichannel activation. Furthermore, NO release from the hemichannels located at astrocytic endfeet may contribute to the vasodilation of parenchymal arterioles. In this review, we discuss the mechanisms involved in the regulation of the astrocytic Ca2+ signaling that mediates neurovascular coupling, with a special emphasis in the possible participation of NO in this process

  19. The role of Ile87 of CYP158A2 in oxidative coupling reaction

    SciTech Connect

    Zhao, Bin; Bellamine, Aouatef; Lei, Li; Waterman, Michael R.

    2012-05-15

    Both CYP158A1 and CYP158A2 are able to catalyze an oxidative C-C coupling reaction producing biflaviolin or triflaviolin in Streptomyces coelicolor A3(2). The substrate-bound crystal structures of CYP158A2 and CYP158A1 reveal that the side chain of Ile87 in CYP158A2 points to the active site contacting the distal flaviolin molecule, however, the bulkier side chain of Lys90 in CYP158A1 (corresponding to Ile87 in CYP158A2) is toward the distal surface of the protein. These results suggest that these residues could be important in determining product regiospecificity. In order to explore the role of the two residues in catalysis, the reciprocal mutants, Ile87Lys and Lys90Ile, of CYP158A2 and CYP158A1, respectively, were generated and characterized. The mutant Ile87Lys enzyme forms two isomers of biflaviolin instead of three isomers of biflaviolin in wild-type CYP158A2. CYP158A1 containing the substitution of lysine with isoleucine has the same catalytic activity compared with the wild-type CYP158A1. The crystal structure of Ile87Lys showed that the BC loop in the mutant is in a very different orientation compared with the BC loop in both CYP158A1/A2 structures. These results shed light on the mechanism of the oxidative coupling reaction catalyzed by cytochrome P450.

  20. Ubiquitous long-range antiferromagnetic coupling across the interface between superconducting and ferromagnetic oxides

    NASA Astrophysics Data System (ADS)

    de Luca, G. M.; Ghiringhelli, G.; Perroni, C. A.; Cataudella, V.; Chiarella, F.; Cantoni, C.; Lupini, A. R.; Brookes, N. B.; Huijben, M.; Koster, G.; Rijnders, G.; Salluzzo, M.

    2014-11-01

    The so-called proximity effect is the manifestation, across an interface, of the systematic competition between magnetic order and superconductivity. This phenomenon has been well documented and understood for conventional superconductors coupled with metallic ferromagnets; however it is still less known for oxide materials, where much higher critical temperatures are offered by copper oxide-based superconductors. Here we show that, even in the absence of direct Cu-O-Mn covalent bonding, the interfacial CuO2 planes of superconducting La1.85Sr0.15CuO4 thin films develop weak ferromagnetism associated to the charge transfer of spin-polarised electrons from the La0.66Sr0.33MnO3 ferromagnet. Theoretical modelling confirms that this effect is general to all cuprate/manganite heterostructures and the presence of direct bonding only affects the strength of the coupling. The Dzyaloshinskii-Moriya interaction, also at the origin of the weak ferromagnetism of bulk cuprates, propagates the magnetisation from the interface CuO2 planes into the superconductor, eventually depressing its critical temperature.

  1. Stoichiometry of Proton Translocation Coupled to Substrate Oxidation in Plant Mitochondria

    PubMed Central

    Moreau, François; de Virville, Jacques Davy

    1985-01-01

    The proton translocation coupled to the electron flux from succinate, exogenous NADH, and NAD+-linked substrates (malate and isocitrate) to cytochrome c and to oxygen was studied in purified potato (Solanum tuberosum) mitochondria using oxygen and ferricyanide pulse techniques. In the presence of valinomycin plus K+ (used as a charge compensating cation), optimum values of H+/2 e− were obtained when low amounts of electron acceptors (oxygen or ferricyanide) were added to the mitochondria (1-2 nanogram [2 e−] equivalents per milligram protein). The stoichiometry of proton translocation to electron flux was unaffected in the presence of N-ethylmaleimide, an inhibitor of the Pi/H+ symport. With succinate as substrate, H+/2 e− ratios were 4.0 ± 0.2 and 3.7 ± 0.3 with oxygen and ferricyanide as electron acceptors, respectively. With exogenous NADH, H+/2e− ratios were 4.1 ± 0.9 and 3.4 ± 0.2, respectively. The proton translocation coupled to the oxidation of NAD+-linked substrates (malate, isocitrate) was dependent upon the presence of adenylates (ADP, AMP, or ATP). For malate (+ glutamate) oxidation the observed H+/2 e− ratios were increased from 3.6 ± 2.2 to 6.5 ± 0.5 in the presence of 20 micromolar ADP. PMID:16663992

  2. Coupling membrane separation and photocatalytic oxidation processes for the degradation of pharmaceutical pollutants.

    PubMed

    Martínez, F; López-Muñoz, M J; Aguado, J; Melero, J A; Arsuaga, J; Sotto, A; Molina, R; Segura, Y; Pariente, M I; Revilla, A; Cerro, L; Carenas, G

    2013-10-01

    The coupling of membrane separation and photocatalytic oxidation has been studied for the removal of pharmaceutical pollutants. The retention properties of two different membranes (nanofiltration and reverse osmosis) were assessed. Comparable selectivity on the separation of pharmaceuticals were observed for both membranes, obtaining a permeate stream with concentrations of each pharmaceutical below 0.5 mg L(-)(1) and a rejected flux highly concentrated (in the range of 16-25 mg L(-)(1) and 18-32 mg L(-)(1) of each pharmaceutical for NF-90 and BW-30 membranes, respectively), when an initial stream of six pharmaceuticals was feeding to the membrane system (10 mg L(-)(1) of each pharmaceutical). The abatement of concentrated pharmaceuticals of the rejected stream was evaluated by means of heterogeneous photocatalytic oxidation using TiO2 and Fe2O3/SBA-15 in presence of hydrogen peroxide as photo-Fenton system. Both photocatalytic treatments showed remarkable removals of pharmaceutical compounds, achieving values between 80 and 100%. The nicotine was the most refractory pollutant of all the studied pharmaceuticals. Photo-Fenton treatment seems to be more effective than TiO2 photocatalysis, as high mineralization degree and increased nicotine removal were attested. This work can be considered an interesting approach of coupling membrane separation and heterogeneous photocatalytic technologies for the successful abatement of pharmaceutical compounds in effluents of wastewater treatment plants. PMID:23863375

  3. The Role of Ile87 of CYP158A2 in Oxidative Coupling Reaction

    PubMed Central

    Zhao, Bin; Bellamine, Aouatef; Lei, Li; Waterman, Michael R.

    2012-01-01

    Both CYP158A1 and CYP158A2 are able to catalyze an oxidative C-C coupling reaction producing biflaviolin or triflaviolin in Streptomyces coelicolor A3(2). The substrate-bound crystal structures of CYP158A2 and CYP158A1 reveal that the side chain of Ile87 in CYP158A2 points to the active site contacting the distal flaviolin molecule, however, the bulkier side chain of Lys90 in CYP158A1 (corresponding to Ile87 in CYP158A2) is toward the distal surface of the protein. These results suggest that these residues could be important in determining product regiospecificity. In order to explore the role of the two residues in catalysis, the reciprocal mutants, Ile87Lys and Lys90Ile, of CYP158A2 and CYP158A1, respectively, were generated and characterized. The mutant Ile87Lys enzyme forms two isomers of biflaviolin instead of three isomers of biflaviolin in wild-type CYP158A2. CYP158A1 containing the substitution of lysine with isoleucine has the same catalytic activity compared with the wild-type CYP158A1. The crystal structure of Ile87Lys showed that the BC loop in the mutant is in a very different orientation compared with the BC loop in both CYP158A1/A2 structures. These results shed light on the mechanism of the oxidative coupling reaction catalyzed by cytochrome P450. PMID:22203090

  4. Metal Azolate/Carboxylate Frameworks as Catalysts in Oxidative and C-C Coupling Reactions.

    PubMed

    Tăbăcaru, Aurel; Xhaferaj, Nertil; Martins, Luísa M D R S; Alegria, Elisabete C B A; Chay, Rogério S; Giacobbe, Carlotta; Domasevitch, Konstantin V; Pombeiro, Armando J L; Galli, Simona; Pettinari, Claudio

    2016-06-20

    The five metal azolate/carboxylate (MAC) compounds [Cd(dmpzc)(DMF)(H2O)] (Cd-dmpzc), [Pd(H2dmpzc)2Cl2] (Pd-dmpzc), [Cu(Hdmpzc)2] (Cu-dmpzc), [Zn4O(dmpzc)3]·Solv (Zn-dmpzc·S), and [Co4O(dmpzc)3]·Solv (Co-dmpzc·S) were isolated by coupling 3,5-dimethyl-1H-pyrazol-4-carboxylic acid (H2dmpzc) to cadmium(II), palladium(II), copper(II), zinc(II), and cobalt(II) salts. While Cd-dmpzc and Pd-dmpzc had never been prepared in the past, for Cu-dmpzc, Zn-dmpzc·S, and Co-dmpzc·S we optimized alternative synthetic paths that, in the case of the copper(II) and cobalt(II) derivatives, are faster and grant higher yields than the previously reported ones. The crystal structure details were determined ab initio (Cd-dmpzc and Pd-dmpzc) or refined (Cu-dmpzc, Zn-dmpzc·S, and Co-dmpzc·S) by means of powder X-ray diffraction (PXRD). While Cd-dmpzc is a nonporous 3D MAC framework, Pd-dmpzc shows a 3D hybrid coordination/hydrogen-bonded network, in which Pd(H2dmpzc)2Cl2 monomers are present. The thermal behavior of the five MAC compounds was investigated by coupling thermal analysis to variable-temperature PXRD. Their catalytic activity was assessed in oxidative and C-C coupling reactions, with the copper(II) and cadmium(II) derivatives being the first nonporous MAC frameworks to be tested as catalysts. Cu-dmpzc is the most active catalyst in the partial oxidation of cyclohexane by tert-butyl hydroperoxide in acetonitrile (yields up to 12% after 9 h) and is remarkably active in the solvent-free microwave-assisted oxidation of 1-phenylethanol to acetophenone (yields up to 99% at 120 °C in only 0.5 h). On the other hand, activated Zn-dmpzc·S (Zn-dmpzc) is the most active catalyst in the Henry C-C coupling reaction of aromatic aldehydes with nitroethane, showing appreciable diastereoselectivity toward the syn-nitroalkanol isomer (syn:anti selectivity up to 79:21). PMID:27266480

  5. Studies of Zinc Oxide Nanocrystals: Quantification of Capping Ligands and the Coupling of Protons and Electrons

    NASA Astrophysics Data System (ADS)

    Valdez, Carolyn N.

    The energetics of semiconductors are widely relevant to technologies ranging from chemical- and photo-catalysis to charge injection in photovoltaic materials. In these processes involving electron transfer, protons often play a critical but overlooked role in facilitating charge transfer. For example, the conduction band energies of most metal oxides in contact with an aqueous solution demonstrate a Nernstian pH dependence, an observation that cannot be explained by surface protonation models. Given that a Nernstian dependence is typically attributed to proton coupled electron transfer (PCET), we are interested in determining if the reduction of metal oxides can also be described by PCET. Zinc oxide (ZnO) nanocrystals (NCs) were chosen as a model system given the broad range of previous research on bulk and nanocrystalline forms of ZnO, the relative ease of synthesis and characterization, and their use in developing a fundamental understanding of interfacial electron transfer. We demonstrate that photochemically reduced NCs react with hydrogen-atom acceptors, indicating that both electrons and protons are transferred by the NCs. To isolate the influence of a proton coupled to the extra electron in the conduction band, the NCs have also been reduced chemically. Addition of an excess of the one-electron reductant CoCp*2 (Cp* = pentamethylcyclopentadienyl, -1.94 V vs. Fc/Fc+) gives NCs that contain extra electrons in the conduction band, without protons that arise from photoreduction. Protons can also be individually added stoichiometrically to the NCs by either a photoreduction/oxidation sequence or by addition of acid. Using these methods, we have shown that the presence of one extra proton drastically alters the redox potential of the NCs. With the addition of acid the NC orbitals are lowered, allowing the systematic variation of driving force for electron transfer from the reductant to the NCs. In the presence of excess reductant and acid, the number of electrons

  6. COUPLING

    DOEpatents

    Frisch, E.; Johnson, C.G.

    1962-05-15

    A detachable coupling arrangement is described which provides for varying the length of the handle of a tool used in relatively narrow channels. The arrangement consists of mating the key and keyhole formations in the cooperating handle sections. (AEC)

  7. Dynamic Jahn-Teller Coupling, Anharmonic Oxygen Vibrations and HIGH-Tc Superconductivity in Oxides

    NASA Astrophysics Data System (ADS)

    Johnson, K. H.; Clougherty, D. P.; McHenry, M. E.

    A universal dynamic Jahn-Teller (DJT) mechanism for superconductivity and its applications to CuO and BaBiO3 high-Tc oxides are reviewed. Dynamical interconversion between the shallow "double-well" potentials of degenerate delocalized oxygen-oxygen "pπ-bonds" at the Fermi energy (EF) induces anharmonic oxygen vibrations, lattice-electron coupling, and Cooper pairing. This mechanism yields high Tc's and small-to-vanishing isotope shifts for cuprates, where O(pπ)-O(pπ) bond overlap at EF is promoted by Cu(dπ*)-O(pπ) hybridization. It yields lower Tc's and larger isotope shifts for BaBiO3's, where O(pπ)-O(pπ) overlap is small. For vanishing bond overlap at EF, DJT coupling reduces to harmonic phonon coupling in BCS theory. Simple formulae for calculating Tc and isotope shifts for any superconductor from the "real-space" chemical bonding at EF are presented, yielding (Tc)max ≈ 230 K.

  8. Thickness dependence of exchange coupling in (111)-oriented perovskite oxide superlattices

    NASA Astrophysics Data System (ADS)

    Jia, Yue; Chopdekar, Rajesh V.; Arenholz, Elke; Liu, Zhiqi; Biegalski, Michael D.; Porter, Zachary D.; Mehta, Apurva; Takamura, Yayoi

    2016-03-01

    Epitaxial L a0.7S r0.3Mn O3(LSMO )/L a0.7S r0.3Fe O3 (LSFO) superlattices on (111)-oriented SrTi O3 substrates with sublayer thicknesses ranging from 3 to 60 unit cells (u.c.) were synthesized and characterized. Detailed analysis of their structural, electronic, and magnetic properties were performed to explore the effect of sublayer thickness on the magnetic structure and exchange coupling at (111)-oriented perovskite oxide interfaces. In the ultrathin limit (3-6 u.c.), we find that the antiferromagnetic (AF) properties of the LSFO sublayers are preserved with an out-of-plane canting of the AF spin axis, while the ferromagnetic (FM) properties of the LSMO sublayers are significantly depressed. For thicker LSFO layers (>9 u.c.), the out-of-plane canting of the AF spin axis is only present in superlattices with thick LSMO sublayers. As a result, exchange coupling in the form of spin-flop coupling exists only in superlattices which display both robust ferromagnetism and out-of-plane canting of the AF spin axis.

  9. The possible role of proton-coupled electron transfer (PCET) in water oxidation by photosystem II.

    PubMed

    Meyer, Thomas J; Huynh, My Hang V; Thorp, H Holden

    2007-01-01

    All higher life forms use oxygen and respiration as their primary energy source. The oxygen comes from water by solar-energy conversion in photosynthetic membranes. In green plants, light absorption in photosystem II (PSII) drives electron-transfer activation of the oxygen-evolving complex (OEC). The mechanism of water oxidation by the OEC has long been a subject of great interest to biologists and chemists. With the availability of new molecular-level protein structures from X-ray crystallography and EXAFS, as well as the accumulated results from numerous experiments and theoretical studies, it is possible to suggest how water may be oxidized at the OEC. An integrated sequence of light-driven reactions that exploit coupled electron-proton transfer (EPT) could be the key to water oxidation. When these reactions are combined with long-range proton transfer (by sequential local proton transfers), it may be possible to view the OEC as an intricate structure that is "wired for protons". PMID:17604381

  10. Coupled molybdenum carbide and reduced graphene oxide electrocatalysts for efficient hydrogen evolution.

    PubMed

    Li, Ji-Sen; Wang, Yu; Liu, Chun-Hui; Li, Shun-Li; Wang, Yu-Guang; Dong, Long-Zhang; Dai, Zhi-Hui; Li, Ya-Fei; Lan, Ya-Qian

    2016-01-01

    Electrochemical water splitting is one of the most economical and sustainable methods for large-scale hydrogen production. However, the development of low-cost and earth-abundant non-noble-metal catalysts for the hydrogen evolution reaction remains a challenge. Here we report a two-dimensional coupled hybrid of molybdenum carbide and reduced graphene oxide with a ternary polyoxometalate-polypyrrole/reduced graphene oxide nanocomposite as a precursor. The hybrid exhibits outstanding electrocatalytic activity for the hydrogen evolution reaction and excellent stability in acidic media, which is, to the best of our knowledge, the best among these reported non-noble-metal catalysts. Theoretical calculations on the basis of density functional theory reveal that the active sites for hydrogen evolution stem from the pyridinic nitrogens, as well as the carbon atoms, in the graphene. In a proof-of-concept trial, an electrocatalyst for hydrogen evolution is fabricated, which may open new avenues for the design of nanomaterials utilizing POMs/conducting polymer/reduced-graphene oxide nanocomposites. PMID:27032372

  11. Sulfur-Bridged Terthiophene Dimers: How Sulfur Oxidation State Controls Interchromophore Electronic Coupling.

    PubMed

    Cruz, Chad D; Christensen, Peter R; Chronister, Eric L; Casanova, David; Wolf, Michael O; Bardeen, Christopher J

    2015-10-01

    Symmetric dimers have the potential to optimize energy transfer and charge separation in optoelectronic devices. In this paper, a combination of optical spectroscopy (steady-state and time-resolved) and electronic structure theory is used to analyze the photophysics of sulfur-bridged terthiophene dimers. This class of dimers has the unique feature that the interchromophore (intradimer) electronic coupling can be modified by varying the oxidation state of the bridging sulfur from sulfide (S), to sulfoxide (SO), to sulfone (SO2). Photoexcitation leads to the formation of a delocalized charge resonance state (S1) that relaxes quickly (<10 ps) to a charge-transfer state (S1*). The amount of charge-transfer character in S1* can be enhanced by increasing the oxidation state of the bridging sulfur group as well as the solvent polarity. The S1* state has a decreased intersystem crossing rate when compared to monomeric terthiophene, leading to an enhanced photoluminescence quantum yield. Computational results indicate that electrostatic screening by the bridging sulfur electrons is the key parameter that controls the amount of charge-transfer character. Control of the sulfur bridge oxidation state provides the ability to tune interchromophore interactions in covalent assemblies without altering the molecular geometry or solvent polarity. This capability provides a new strategy for the design of functional supermolecules with applications in organic electronics. PMID:26331195

  12. Coupled molybdenum carbide and reduced graphene oxide electrocatalysts for efficient hydrogen evolution

    PubMed Central

    Li, Ji-Sen; Wang, Yu; Liu, Chun-Hui; Li, Shun-Li; Wang, Yu-Guang; Dong, Long-Zhang; Dai, Zhi-Hui; Li, Ya-Fei; Lan, Ya-Qian

    2016-01-01

    Electrochemical water splitting is one of the most economical and sustainable methods for large-scale hydrogen production. However, the development of low-cost and earth-abundant non-noble-metal catalysts for the hydrogen evolution reaction remains a challenge. Here we report a two-dimensional coupled hybrid of molybdenum carbide and reduced graphene oxide with a ternary polyoxometalate-polypyrrole/reduced graphene oxide nanocomposite as a precursor. The hybrid exhibits outstanding electrocatalytic activity for the hydrogen evolution reaction and excellent stability in acidic media, which is, to the best of our knowledge, the best among these reported non-noble-metal catalysts. Theoretical calculations on the basis of density functional theory reveal that the active sites for hydrogen evolution stem from the pyridinic nitrogens, as well as the carbon atoms, in the graphene. In a proof-of-concept trial, an electrocatalyst for hydrogen evolution is fabricated, which may open new avenues for the design of nanomaterials utilizing POMs/conducting polymer/reduced-graphene oxide nanocomposites. PMID:27032372

  13. Coupled molybdenum carbide and reduced graphene oxide electrocatalysts for efficient hydrogen evolution

    NASA Astrophysics Data System (ADS)

    Li, Ji-Sen; Wang, Yu; Liu, Chun-Hui; Li, Shun-Li; Wang, Yu-Guang; Dong, Long-Zhang; Dai, Zhi-Hui; Li, Ya-Fei; Lan, Ya-Qian

    2016-04-01

    Electrochemical water splitting is one of the most economical and sustainable methods for large-scale hydrogen production. However, the development of low-cost and earth-abundant non-noble-metal catalysts for the hydrogen evolution reaction remains a challenge. Here we report a two-dimensional coupled hybrid of molybdenum carbide and reduced graphene oxide with a ternary polyoxometalate-polypyrrole/reduced graphene oxide nanocomposite as a precursor. The hybrid exhibits outstanding electrocatalytic activity for the hydrogen evolution reaction and excellent stability in acidic media, which is, to the best of our knowledge, the best among these reported non-noble-metal catalysts. Theoretical calculations on the basis of density functional theory reveal that the active sites for hydrogen evolution stem from the pyridinic nitrogens, as well as the carbon atoms, in the graphene. In a proof-of-concept trial, an electrocatalyst for hydrogen evolution is fabricated, which may open new avenues for the design of nanomaterials utilizing POMs/conducting polymer/reduced-graphene oxide nanocomposites.

  14. Preparation of vinyl acetate

    DOEpatents

    Tustin, Gerald Charles; Zoeller, Joseph Robert; Depew, Leslie Sharon

    1998-01-01

    This invention pertains to the preparation of vinyl acetate by contacting a mixture of hydrogen and ketene with a heterogeneous catalyst containing a transition metal to produce acetaldehyde, which is then reacted with ketene in the presence of an acid catalyst to produce vinyl acetate.

  15. Preparation of vinyl acetate

    DOEpatents

    Tustin, G.C.; Zoeller, J.R.; Depew, L.S.

    1998-03-24

    This invention pertains to the preparation of vinyl acetate by contacting a mixture of hydrogen and ketene with a heterogeneous catalyst containing a transition metal to produce acetaldehyde, which is then reacted with ketene in the presence of an acid catalyst to produce vinyl acetate.

  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. 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

  18. Anaerobic methane oxidation coupled to denitrification is the dominant methane sink in a deep lake

    PubMed Central

    Deutzmann, Joerg S.; Stief, Peter; Brandes, Josephin; Schink, Bernhard

    2014-01-01

    Anaerobic methane oxidation coupled to denitrification, also known as “nitrate/nitrite-dependent anaerobic methane oxidation” (n-damo), was discovered in 2006. Since then, only a few studies have identified this process and the associated microorganisms in natural environments. In aquatic sediments, the close proximity of oxygen- and nitrate-consumption zones can mask n-damo as aerobic methane oxidation. We therefore investigated the vertical distribution and the abundance of denitrifying methanotrophs related to Candidatus Methylomirabilis oxyfera with cultivation-independent molecular techniques in the sediments of Lake Constance. Additionally, the vertical distribution of methane oxidation and nitrate consumption zones was inferred from high-resolution microsensor profiles in undisturbed sediment cores. M. oxyfera-like bacteria were virtually absent at shallow-water sites (littoral sediment) and were very abundant at deep-water sites (profundal sediment). In profundal sediment, the vertical distribution of M. oxyfera-like bacteria showed a distinct peak in anoxic layers that coincided with the zone of methane oxidation and nitrate consumption, a strong indication for n-damo carried out by M. oxyfera-like bacteria. Both potential n-damo rates calculated from cell densities (660–4,890 µmol CH4⋅m−2⋅d−1) and actual rates calculated from microsensor profiles (31–437 µmol CH4⋅m−2⋅d−1) were sufficiently high to prevent methane release from profundal sediment solely by this process. Additionally, when nitrate was added to sediment cores exposed to anoxic conditions, the n-damo zone reestablished well below the sediment surface, completely preventing methane release from the sediment. We conclude that the previously overlooked n-damo process can be the major methane sink in stable freshwater environments if nitrate is available in anoxic zones. PMID:25472842

  19. Complete genome sequence of 'Halanaeroarchaeum sulfurireducens' M27-SA2, a sulfur-reducing and acetate-oxidizing haloarchaeon from the deep-sea hypersaline anoxic lake Medee.

    PubMed

    Messina, Enzo; Sorokin, Dimitry Y; Kublanov, Ilya V; Toshchakov, Stepan; Lopatina, Anna; Arcadi, Erika; Smedile, Francesco; La Spada, Gina; La Cono, Violetta; Yakimov, Michail M

    2016-01-01

    Strain M27-SA2 was isolated from the deep-sea salt-saturated anoxic lake Medee, which represents one of the most hostile extreme environments on our planet. On the basis of physiological studies and phylogenetic positioning this extremely halophilic euryarchaeon belongs to a novel genus 'Halanaeroarchaeum' within the family Halobacteriaceae. All members of this genus cultivated so far are strict anaerobes using acetate as the sole carbon and energy source and elemental sulfur as electron acceptor. Here we report the complete genome sequence of the strain M27-SA2 which is composed of a 2,129,244-bp chromosome and a 124,256-bp plasmid. This is the second complete genome sequence within the genus Halanaeroarchaeum. We demonstrate that genome of 'Halanaeroarchaeum sulfurireducens' M27-SA2 harbors complete metabolic pathways for acetate and sulfur catabolism and for de novo biosynthesis of 19 amino acids. The genomic analysis also reveals that 'Halanaeroarchaeum sulfurireducens' M27-SA2 harbors two prophage loci and one CRISPR locus, highly similar to that of Kulunda Steppe (Altai, Russia) isolate 'H. sulfurireducens' HSR2(T). The discovery of sulfur-respiring acetate-utilizing haloarchaeon in deep-sea hypersaline anoxic lakes has certain significance for understanding the biogeochemical functioning of these harsh ecosystems, which are incompatible with life for common organisms. Moreover, isolations of Halanaeroarchaeum members from geographically distant salt-saturated sites of different origin suggest a high degree of evolutionary success in their adaptation to this type of extreme biotopes around the world. PMID:27182430

  20. Weathering of the Rio Blanco Quartz Diorite, Luquillo Mountains, Puerto Rico: Coupling Oxidation, Dissolution, And Fracturing

    SciTech Connect

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

    2009-05-12

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

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

    USGS Publications Warehouse

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

    2008-01-01

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

  2. Optimal control strategies for hydrogen production when coupling solid oxide electrolysers with intermittent renewable energies

    NASA Astrophysics Data System (ADS)

    Cai, Qiong; Adjiman, Claire S.; Brandon, Nigel P.

    2014-12-01

    The penetration of intermittent renewable energies requires the development of energy storage technologies. High temperature electrolysis using solid oxide electrolyser cells (SOECs) as a potential energy storage technology, provides the prospect of a cost-effective and energy efficient route to clean hydrogen production. The development of optimal control strategies when SOEC systems are coupled with intermittent renewable energies is discussed. Hydrogen production is examined in relation to energy consumption. Control strategies considered include maximizing hydrogen production, minimizing SOEC energy consumption and minimizing compressor energy consumption. Optimal control trajectories of the operating variables over a given period of time show feasible control for the chosen situations. Temperature control of the SOEC stack is ensured via constraints on the overall temperature difference across the cell and the local temperature gradient within the SOEC stack, to link materials properties with system performance; these constraints are successfully managed. The relative merits of the optimal control strategies are analyzed.

  3. Efficient oxidative coupling of 2,6-disubstituted phenol catalyzed by a dicopper(II) complex.

    PubMed

    Liao, Bei-Sih; Liu, Yi-Hung; Peng, Shei-Ming; Liu, Shiuh-Tzung

    2012-01-28

    Complexation of a rigid multi-pyridine ligand bis(2-pyridyl)-1,8-naphthyridine (bpnp) with [Cu(2)(TFA)(4)] (TFA = trifluoroacetate) resulted in the formation of a dinuclear copper(II) complex, namely [Cu(2)(bpnp)(μ-OH)(TFA)(3)] (1). This complex has been characterized by X-ray crystallographic, spectroscopic and elemental analyses. Complex 1 is an efficient catalyst for the oxidative coupling of various 2,6-disubstituted phenols with molecular oxygen. Yields and selectivity depend on the reaction conditions employed, the best results being obtained in isopropanol or dioxane at 90 °C with yields of >99%. Mechanistic pathway of the catalysis is discussed. PMID:22116574

  4. Infrared rectification in a nanoantenna-coupled metal-oxide-semiconductor tunnel diode.

    PubMed

    Davids, Paul S; Jarecki, Robert L; Starbuck, Andrew; Burckel, D Bruce; Kadlec, Emil A; Ribaudo, Troy; Shaner, Eric A; Peters, David W

    2015-12-01

    Direct rectification of electromagnetic radiation is a well-established method for wireless power conversion in the microwave region of the spectrum, for which conversion efficiencies in excess of 84% have been demonstrated. Scaling to the infrared or optical part of the spectrum requires ultrafast rectification that can only be obtained by direct tunnelling. Many research groups have looked to plasmonics to overcome antenna-scaling limits and to increase the confinement. Recently, surface plasmons on heavily doped Si surfaces were investigated as a way of extending surface-mode confinement to the thermal infrared region. Here we combine a nanostructured metallic surface with a heavily doped Si infrared-reflective ground plane designed to confine infrared radiation in an active electronic direct-conversion device. The interplay of strong infrared photon-phonon coupling and electromagnetic confinement in nanoscale devices is demonstrated to have a large impact on ultrafast electronic tunnelling in metal-oxide-semiconductor (MOS) structures. Infrared dispersion of SiO2 near a longitudinal optical (LO) phonon mode gives large transverse-field confinement in a nanometre-scale oxide-tunnel gap as the wavelength-dependent permittivity changes from 1 to 0, which leads to enhanced electromagnetic fields at material interfaces and a rectified displacement current that provides a direct conversion of infrared radiation into electric current. The spectral and electrical signatures of the nanoantenna-coupled tunnel diodes are examined under broadband blackbody and quantum-cascade laser (QCL) illumination. In the region near the LO phonon resonance, we obtained a measured photoresponsivity of 2.7 mA W(-1) cm(-2) at -0.1 V. PMID:26414194

  5. Infrared rectification in a nanoantenna-coupled metal-oxide-semiconductor tunnel diode

    NASA Astrophysics Data System (ADS)

    Davids, Paul S.; Jarecki, Robert L.; Starbuck, Andrew; Burckel, D. Bruce; Kadlec, Emil A.; Ribaudo, Troy; Shaner, Eric A.; Peters, David W.

    2015-12-01

    Direct rectification of electromagnetic radiation is a well-established method for wireless power conversion in the microwave region of the spectrum, for which conversion efficiencies in excess of 84% have been demonstrated. Scaling to the infrared or optical part of the spectrum requires ultrafast rectification that can only be obtained by direct tunnelling. Many research groups have looked to plasmonics to overcome antenna-scaling limits and to increase the confinement. Recently, surface plasmons on heavily doped Si surfaces were investigated as a way of extending surface-mode confinement to the thermal infrared region. Here we combine a nanostructured metallic surface with a heavily doped Si infrared-reflective ground plane designed to confine infrared radiation in an active electronic direct-conversion device. The interplay of strong infrared photon-phonon coupling and electromagnetic confinement in nanoscale devices is demonstrated to have a large impact on ultrafast electronic tunnelling in metal-oxide-semiconductor (MOS) structures. Infrared dispersion of SiO2 near a longitudinal optical (LO) phonon mode gives large transverse-field confinement in a nanometre-scale oxide-tunnel gap as the wavelength-dependent permittivity changes from 1 to 0, which leads to enhanced electromagnetic fields at material interfaces and a rectified displacement current that provides a direct conversion of infrared radiation into electric current. The spectral and electrical signatures of the nanoantenna-coupled tunnel diodes are examined under broadband blackbody and quantum-cascade laser (QCL) illumination. In the region near the LO phonon resonance, we obtained a measured photoresponsivity of 2.7 mA W-1 cm-2 at -0.1 V.

  6. Nitrate reduction coupled with pyrite oxidation in the surface sediments of a sulfide-rich ecosystem

    NASA Astrophysics Data System (ADS)

    Hayakawa, Atsushi; Hatakeyama, Mizuho; Asano, Ryoki; Ishikawa, Yuichi; Hidaka, Shin

    2013-06-01

    studies of denitrification have focused on organic carbon as an electron donor, but reduced sulfur can also support denitrification. Few studies have reported nitrate (NO3-) reduction coupled with pyrite oxidation and its stoichiometry in surface sediments, especially without experimental pyrite addition. In this study, we evaluated NO3- reduction coupled with sulfur oxidation by long-term incubation of surface sediments from a sulfide-rich ecosystem in Akita Prefecture, Japan. The surface sediments were sampled from a mud pool and a riverbed. Fresh sediments and water were incubated under anoxic conditions (and one oxic condition) at 20°C. NO3- addition increased the SO42- concentration and decreased the NO3- concentration. SO42- production (∆SO42-) was strongly and linearly correlated with NO3- consumption (∆NO3-) during the incubation period (R2 = 0.983, P < 0.01, and n = 8), and the slope of the regression (∆NO3-/∆SO42-) and the stoichiometry indicated sulfur-driven NO3- reduction by indigenous autotrophic denitrifying bacteria. Framboidal pyrite and marcasite (both FeS2) were present in the sediments and functioned as the electron donors for autotrophic denitrification. Both ∆NO3- and ∆SO42- were higher in the riverbed sediment than in the mud pool sediment, likely because of the higher amount of easily oxidizable S (pyrite) in the riverbed sediment. Consistently low ammonium (NH4+) concentrations indicated that NO3- reduction by dissimilatory NO3- reduction to NH4+ was small but could not be disregarded. Our results demonstrate that sulfide-rich ecosystems with easily oxidizable metal-bound sulfides such as FeS2 near the ground surface may act as denitrification hot spots.

  7. Reactor modeling of the oxidative coupling of methane in membranes reactors

    SciTech Connect

    Lu, Y.; Ramachandra, A.; Ma, Y.H.

    1994-12-31

    A reactor model has been developed to analyze the performance of membrane reactors for the high temperature oxidative coupling of methane and to compare their operation with fixed bed reactors. Three reactor configurations of the shell and tube type were this study: a conventional fixed bed reactor, a tubular porous membrane reactor, dense membrane reactor. For the membrane reactors, oxygen is fed on the shell side and methane into the tube side, and the catalyst is present only inside the tube. Both streams are diluted with helium and the feed ratio is maintained at a methane to oxygen ratio of 2:1 for all three configurations. The ratio of the volumetric flow rate of each reactant to the amount of catalyst is kept the same for the three configurations. Kinetic equations for the oxidative coupling of methane have been taken from the simplified mechanism on Li/MgO proposed by Tung and Lobban, where C{sub 2}H{sub 6}, CO{sub 2} and H{sub 2}O are the reaction products considered. The modeling study indicates an improved performance of the membrane reactors over the conventional packed bed reactor. For the porous membrane reactor, a 4 angstrom pore size membrane gives higher C{sub 2}H{sub 6} selectivities and C{sub 2}H{sub 6} yields than a 40 Angstrom pore size membrane. For the dense membrane reactor, a lower oxygen permeability gives higher C{sub 2}H{sub 6} yield. Of the three types of reactors, the dense membrane reactor offers the highest C{sub 2}H{sub 6} yields but a longer reactor length is needed because of the lower permeation rate of oxygen from the shell to the tube side, and hence the lower oxygen partial pressure and lower reaction rate on the tube side.

  8. Thiosulphate conversion in a methane and acetate fed membrane bioreactor.

    PubMed

    Suarez-Zuluaga, Diego A; Timmers, Peer H A; Plugge, Caroline M; Stams, Alfons J M; Buisman, Cees J N; Weijma, Jan

    2016-02-01

    The use of methane and acetate as electron donors for biological reduction of thiosulphate in a 5-L laboratory membrane bioreactor was studied and compared to disproportionation of thiosulphate as competing biological reaction. The reactor was operated for 454 days in semi-batch mode; 30 % of its liquid phase was removed and periodically replenished (days 77, 119, 166, 258, 312 and 385). Although the reactor was operated under conditions favourable to promote thiosulphate reduction coupled to methane oxidation, thiosulphate disproportionation was the dominant microbial process. Pyrosequencing analysis showed that the most abundant microorganisms in the bioreactor were phototrophic green sulphur bacteria (GSB) belonging to the family Chlorobiaceae and thiosulphate-disproportionating bacteria belonging to the genus Desulfocapsa. Even though the reactor system was surrounded with opaque plastic capable of filtering most of the light, the GSB used it to oxidize the hydrogen sulphide produced from thiosulphate disproportionation to elemental sulphur. Interrupting methane and acetate supply did not have any effect on the microbial processes taking place. The ultimate goal of our research was to develop a process that could be applied for thiosulphate and sulphate removal and biogenic sulphide formation for metal precipitation. Even though the system achieved in this study did not accomplish the targeted conversion using methane as electron donor, it does perform microbial conversions which allow to directly obtain elemental sulphur from thiosulphate. PMID:26423279

  9. Gold-catalyzed oxidative cross-coupling of terminal alkynes: selective synthesis of unsymmetrical 1,3-diynes.

    PubMed

    Peng, Haihui; Xi, Yumeng; Ronaghi, Nima; Dong, Boliang; Akhmedov, Novruz G; Shi, Xiaodong

    2014-09-24

    Gold-catalyzed oxidative cross-coupling of alkynes to unsymmetrical diynes has been achieved for the first time. A N,N-ligand (1,10-Phen) and PhI(OAc)2 were identified as crucial factors to promote this transformation, giving the desired cross-coupled conjugated diynes in excellent heteroselectivity (>10:1), in good to excellent yields, and with large substrate tolerability. PMID:25184690

  10. Copper-catalyzed domino synthesis of quinazolinones via Ullmann-type coupling and aerobic oxidative C-H amidation.

    PubMed

    Xu, Wei; Jin, Yibao; Liu, Hongxia; Jiang, Yuyang; Fu, Hua

    2011-03-18

    An efficient copper-catalyzed approach to quinazolinone derivatives has been developed, and the protocol uses cheap and readily available substituted 2-halobenzamides and (aryl)methanamines as the starting materials as well as economical and environmentally friendly air as the oxidant. This can be the first example of constructing N-heterocycles via sequential Ullmann-type coupling under air and aerobic oxidative C-H amidation. PMID:21344914

  11. Mechanistic study of silver-mediated furan formation by oxidative coupling.

    PubMed

    Daru, János; Benda, Zsuzsanna; Póti, Ádám; Novák, Zoltán; Stirling, András

    2014-11-17

    Density functional calculations and experiments have been carried out to unravel the mechanism of a silver-mediated furan formation by oxidative coupling. Various possible reaction paths were considered and the most favorable channel has been identified on the basis of the calculated solvent-corrected Gibbs free-energy profiles. The mechanism represented by this route consists of a radical and a subsequent ionic route. The silver cation has a double role in the mechanism: it is the oxidant in the radical steps and the catalyst for the ionic steps, which is in accordance with the experimental observations. The two most important aspects of the optimal route are the formation of a silver-acetylide, reacting subsequently with the enolate radical, and the aromatic furan-ring formation in a single step at the latter, ionic segment of the reaction path. Our findings could explain several experimental observations, including the "key-promoter role" of silver, the preference for ionic cyclization, and the reduced reactivity of internal acetylides. PMID:25284602

  12. 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

  13. Steady-state coupling of four membrane systems in mitochondrial oxidative phosphorylation.

    PubMed

    Hill, T L

    1979-05-01

    According to Alexandre, Reynafarje, and Lehninger, four different membrane systems are involved, with definite stoichiometry, in the mitochondrial synthesis of ATP by electron transport, via proton transport. We adopt this model and pursue some of its thermodynamic consequences. At steady state, each of the four systems must have the same flux J through the membrane and the overall thermodynamic force X for oxidative phosphorylation is the sum of the four separate forces. From these properties, using an empirical linear flux-force relation for each system, it is easy to obtain J as a function of X. In turn, X depends on the inside [NAD+]/[NADH] and the outside [ATP]/[ADP][Pi] quotients (and on the pH inside). Thus, J is related to these quotients. The relationship we derive is similar to that described by Erecińska and Wilson, as deduced from a quite different model of oxidative phosphorylation. Proton transport is involved explicitly in three of the four systems of the present model. However, because of the steady-state stoichiometric coupling of the four systems, proton transport does not appear in the overall reaction. On the other hand, Erecińska and Wilson use, in their model, a direct connection between electron transport and ATP synthesis. The present paper demonstrates that J can be related to the quotients mentioned above without this direct connection. PMID:287064

  14. Facet-Controlled CeO2 Nanocrystals for Oxidative Coupling of Methane.

    PubMed

    Sun, Yongnan; Shen, Yue; Song, Jianjun; Ba, Rongbin; Huang, Shuangshuang; Zhao, Yonghui; Zhang, Jun; Sun, Yuhan; Zhu, Yan

    2016-05-01

    Whether the catalysts of the high temperature reaction such methane oxidation coupling has a structure-sensitive catalytic behavior or not, it is discussed and confirmed the shape-specific impact on methane activity by designing the catalysts with different crystal facets exposed. CeO2 nanowires enclosed by {110} and {100} planes show the higher CH4 conversion and higher C2 hydrocarbons (C2H4 and C2H6) selectivity, compared with particle CeO2 rounded by {111} and {100} planes, suggesting that CeO2 (110) surface favors the activation of CH4. Encouraged by the result, to control facet-controlled synthesis of catalysts for tailoring the catalytic properties at high temperature, the CeO2 (110) surface is chosen as doped sites to form the doped catalyst such as Ca doped CeO2 nanowires for OCM reaction, enhancing C2 hydrocarbons selectivity dramatically and suppressing the deep oxidation product (CO and CO2) selectivity. PMID:27483809

  15. Tyrosine oxidation in heme oxygenase: examination of long-range proton-coupled electron transfer.

    PubMed

    Smirnov, Valeriy V; Roth, Justine P

    2014-10-01

    Heme oxygenase is responsible for the degradation of a histidine-ligated ferric protoporphyrin IX (Por) to biliverdin, CO, and the free ferrous ion. Described here are studies of tyrosyl radical formation reactions that occur after oxidizing Fe(III)(Por) to Fe(IV)=O(Por(·+)) in human heme oxygenase isoform-1 (hHO-1) and the structurally homologous protein from Corynebacterium diphtheriae (cdHO). Site-directed mutagenesis on hHO-1 probes the reduction of Fe(IV)=O(Por(·+)) by tyrosine residues within 11 Å of the prosthetic group. In hHO-1, Y58· is implicated as the most likely site of oxidation, based on the pH and pD dependent kinetics. The absence of solvent deuterium isotope effects in basic solutions of hHO-1 and cdHO contrasts with the behavior of these proteins in the acidic solution, suggesting that long-range proton-coupled electron transfer predominates over electron transfer. PMID:25023856

  16. Two pathways of carbon dioxide catalyzed oxidative coupling of phenol by peroxynitrite.

    PubMed

    Papina, Alina A; Koppenol, Willem H

    2006-03-01

    Carbon dioxide catalyzed oxidative coupling of phenol by peroxynitrite occurs by two pathways distinguished by the isomer ratio of 2,2'- to 4,4'-biphenols. As already established, at neutral pH and moderate phenol concentrations, both biphenols are formed in comparable yields by the coupling of two phenoxyl radicals. However, at high pH and phenol concentration, 2,2'-biphenol is the only identified coupled product, and its formation does not involve phenoxyl radicals. Instead, under these conditions, a previously unreported long-lived (t(1/2) approximately 10 s at pH 10 and 1 mM phenol) diamagnetic intermediate with an absorption maximum at 400 nm is observed. This intermediate is formed from phenolate concomitantly with the decay of peroxynitrite and disappears via reaction with phenol [k = (2.4 +/- 0.1) x 10 M(-)(1) s(-)(1) at pH 10.5] to form 2,2'-biphenol. We also find that para-benzoquinone, previously unreported, is formed in up to 5% yield relative to the initial peroxynitrite concentration. The appearance of an absorption band above 500 nm, which might be due to quinhydrone, indicates that hydroquinone is a likely para-benzoquinone precursor. The dependence of para-benzoquinone yields on pH and phenol concentration suggests that its formation is related to the nonradical pathway of 2,2'-biphenol formation. This novel nonradical pathway of 2,2'-biphenol formation might be relevant to the mechanisms of reaction of phenolic antioxidants with peroxynitrite. The existence of two distinct pathways of biphenol formation implies that, apart from a CO(3)(*)(-)/NO(2)(*) radical pair, another reactive intermediate is formed during the carbon dioxide catalyzed decay of peroxynitrite. PMID:16544942

  17. Solar water oxidation using nickel-borate coupled BiVO4 photoelectrodes.

    PubMed

    Choi, Sung Kyu; Choi, Wonyong; Park, Hyunwoong

    2013-05-01

    A naturally abundant nickel-borate (Ni-Bi) complex is demonstrated to successfully catalyze the photoelectrochemical (PEC) water oxidation of BiVO4 electrodes at 1.23 VRHE with nearly 100% faradaic efficiency for oxygen evolution. Ni-Bi is electrodeposited (ED) and photodeposited (PD) for varying times on BiVO4 electrodes in the 0.1 M borate electrolyte with 1 mM Ni(2+) at pH 9.2. Surprisingly, optimally deposited Ni-Bi films (ED-10 s and PD-30 min) display the same layer thickness of ca. 40 nm. Both Ni-Bi films enhance the photocurrent generation of BiVO4 at 1.23 VRHE by a factor of 3-4 under AM 1.5-light irradiation (100 mW cm(-2)) along with ca. 250% increase in the incident and absorbed photon-to-current efficiencies. Impedance analysis further reveals that the charge transfer resistance at BiVO4 is markedly decreased by Ni-Bi deposits. The primary role of Ni-Bi has been suggested to be a hole-conductor making photogenerated electrons more mobile and catalyzing a four-hole transfer to water through cyclic changes between the lower and higher Ni oxidation states. However, thick Ni-Bi films (>~40 nm) significantly reduce the PEC performance of BiVO4 due to the kinetic bottleneck and charge recombination. Under identical PEC conditions (0.1 M, pH 9.2), the borate electrolyte (good proton acceptor) is found to be better than nitrate (poor proton acceptor), indicative of a proton-coupled electron transfer pathway in PEC water oxidation. PMID:23529529

  18. Methane to acetic acid over Cu-exchanged zeolites: mechanistic insights from a site-specific carbonylation reaction.

    PubMed

    Narsimhan, Karthik; Michaelis, Vladimir K; Mathies, Guinevere; Gunther, William R; Griffin, Robert G; Román-Leshkov, Yuriy

    2015-02-11

    The selective low temperature oxidation of methane is an attractive yet challenging pathway to convert abundant natural gas into value added chemicals. Copper-exchanged ZSM-5 and mordenite (MOR) zeolites have received attention due to their ability to oxidize methane into methanol using molecular oxygen. In this work, the conversion of methane into acetic acid is demonstrated using Cu-MOR by coupling oxidation with carbonylation reactions. The carbonylation reaction, known to occur predominantly in the 8-membered ring (8MR) pockets of MOR, is used as a site-specific probe to gain insight into important mechanistic differences existing between Cu-MOR and Cu-ZSM-5 during methane oxidation. For the tandem reaction sequence, Cu-MOR generated drastically higher amounts of acetic acid when compared to Cu-ZSM-5 (22 vs 4 μmol/g). Preferential titration with sodium showed a direct correlation between the number of acid sites in the 8MR pockets in MOR and acetic acid yield, indicating that methoxy species present in the MOR side pockets undergo carbonylation. Coupled spectroscopic and reactivity measurements were used to identify the genesis of the oxidation sites and to validate the migration of methoxy species from the oxidation site to the carbonylation site. Our results indicate that the Cu(II)-O-Cu(II) sites previously associated with methane oxidation in both Cu-MOR and Cu-ZSM-5 are oxidation active but carbonylation inactive. In turn, combined UV-vis and EPR spectroscopic studies showed that a novel Cu(2+) site is formed at Cu/Al <0.2 in MOR. These sites oxidize methane and promote the migration of the product to a Brønsted acid site in the 8MR to undergo carbonylation. PMID:25562431

  19. Peroxidase-catalyzed oxidative coupling of phenols in the presence of geosorbents: rates of non-extractable product formation.

    PubMed

    Huang, Qingguo; Selig, Hildegarde; Weber, Walter J

    2002-02-15

    Oxidative coupling processes in subsurface systems comprise a form of natural contaminant attenuation in which hydroxylated aromatic compounds (HACs) are incorporated into soil/sediment organic matter matrices. Here we describe the oxidative coupling of phenol catalyzed by horseradish peroxidase (HRP) in systems containing two geosorbents having organic matter of different composition; specifically Chelsea soil, a near-surface geologically young soil having a predominantly humic-type soil/sediment organic matter (SOM) matrix, and Lachine shale, a diagenetically older natural material having a predominantly kerogen-type SOM matrix. It was found that each of these two different types of natural geosorbents increased the formation of non-extractable coupling products (NEPs) over that which occurred in solids-free systems. The extent of coupling was higher in the systems containing humic-type Chelsea SOM than in those containing kerogen-type Lachine SOM. It was observed that HRP inactivation by free radical attack was significantly reduced in the presence of each geosorbent. A rate model was developed to facilitate quantitative evaluation and mechanistic interpretation of such coupling processes. Experimental rate measurements revealed thatthe greater extent of reaction observed in the presence of Chelsea soil than in the presence of Lachine shale can be attributed to two factors: (i) more effective protection of HRP from inactivation by the Chelsea SOM and (ii) the greater reactivity of Chelsea SOM with respect to cross-coupling. Interrelationships among enzyme protection, cross-coupling reactivity, and SOM chemistry are discussed. PMID:11878372

  20. A Comparison of Natural (D-α-tocopherol) and Synthetic (DL-α-tocopherol Acetate) Vitamin E Supplementation on the Growth Performance, Meat Quality and Oxidative Status of Broilers

    PubMed Central

    Cheng, K.; Niu, Y.; Zheng, X. C.; Zhang, H.; Chen, Y. P.; Zhang, M.; Huang, X. X.; Zhang, L. L.; Zhou, Y. M.; Wang, T.

    2016-01-01

    The present study was conducted to compare the supplementation of natural (D-α-tocopherol) and synthetic (DL-α-tocopherol acetate) vitamin E on the growth performance, meat quality, muscular antioxidant capacity and genes expression related to oxidative status of broilers. A total of 144 1 day-old Arbor Acres broiler chicks were randomly allocated into 3 groups with 6 replicates of 8 birds each. Birds were given a basal diet (control group), and basal diet supplemented with either 20 IU D-α-tocopherol or DL-α-tocopherol acetate for 42 days, respectively. The results indicated that treatments did not alter growth performance of broilers (p>0.05). Compared with the control group, concentration of α-tocopherol in the breast muscle was increased by the supplementation of vitamin E (p<0.05). In the thigh, α-tocopherol content was also enhanced by vitamin E inclusion, and this effect was more pronounced in the natural vitamin E group (p<0.05). Vitamin E supplementation increased the redness of breast (p<0.05). In the contrast, the inclusion of synthetic vitamin E decreased lightness of thigh (p<0.05). Dietary vitamin E inclusion reduced drip loss at 24 h of thigh muscle (p<0.05), and this effect was maintained for drip loss at 48 h in the natural vitamin E group (p<0.05). Broilers given diet supplemented with vitamin E showed decreased malondialdehyde (MDA) content in the breast (p<0.05). Additionally, natural rather than synthetic vitamin E reduced MDA accumulation in the thigh (p<0.05). Neither natural nor synthetic vitamin E supplementation altered muscular mRNA abundance of genes related to oxidative stress (p>0.05). It was concluded that vitamin E supplementation, especially the natural vitamin E, can enhance the retention of muscular α-tocopherol, improve meat quality and muscular antioxidant capacity of broilers. PMID:26954216

  1. A Comparison of Natural (D-α-tocopherol) and Synthetic (DL-α-tocopherol Acetate) Vitamin E Supplementation on the Growth Performance, Meat Quality and Oxidative Status of Broilers.

    PubMed

    Cheng, K; Niu, Y; Zheng, X C; Zhang, H; Chen, Y P; Zhang, M; Huang, X X; Zhang, L L; Zhou, Y M; Wang, T

    2016-05-01

    The present study was conducted to compare the supplementation of natural (D-α-tocopherol) and synthetic (DL-α-tocopherol acetate) vitamin E on the growth performance, meat quality, muscular antioxidant capacity and genes expression related to oxidative status of broilers. A total of 144 1 day-old Arbor Acres broiler chicks were randomly allocated into 3 groups with 6 replicates of 8 birds each. Birds were given a basal diet (control group), and basal diet supplemented with either 20 IU D-α-tocopherol or DL-α-tocopherol acetate for 42 days, respectively. The results indicated that treatments did not alter growth performance of broilers (p>0.05). Compared with the control group, concentration of α-tocopherol in the breast muscle was increased by the supplementation of vitamin E (p<0.05). In the thigh, α-tocopherol content was also enhanced by vitamin E inclusion, and this effect was more pronounced in the natural vitamin E group (p<0.05). Vitamin E supplementation increased the redness of breast (p<0.05). In the contrast, the inclusion of synthetic vitamin E decreased lightness of thigh (p<0.05). Dietary vitamin E inclusion reduced drip loss at 24 h of thigh muscle (p<0.05), and this effect was maintained for drip loss at 48 h in the natural vitamin E group (p<0.05). Broilers given diet supplemented with vitamin E showed decreased malondialdehyde (MDA) content in the breast (p<0.05). Additionally, natural rather than synthetic vitamin E reduced MDA accumulation in the thigh (p<0.05). Neither natural nor synthetic vitamin E supplementation altered muscular mRNA abundance of genes related to oxidative stress (p>0.05). It was concluded that vitamin E supplementation, especially the natural vitamin E, can enhance the retention of muscular α-tocopherol, improve meat quality and muscular antioxidant capacity of broilers. PMID:26954216

  2. (14C)acetate assimilation by a type I obligate methylotroph, Methylococcus capsulatus.

    PubMed Central

    Patel, R N; Hoare, S L; Hoare, D S; Taylor, B F

    1977-01-01

    Methanol and formate oxidation supported the assimilation of [14C]acetate by cell suspensions of Methylococcus capsulatus; oxidation of other primary alcohols, except ethanol, did not. The extent of [1-14C]acetate assimilation supported by methanol oxidation was decreased in the presence of primary alcohols, except ethanol. Potassium cyanide (0.33 mM) completely inhibited the oxidation of formate and its stimulation of [1-14C]acetate assimilation. The amount of [1-14C]acetate assimilation supported by methanol oxidation was significantly inhibited by cyanide. PMID:412469

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

    PubMed Central

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

    2014-01-01

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

  4. Biological Function of Acetic Acid-Improvement in Obesity and Glucose Tolerance by Acetic Acid in Type 2 Diabetic Rats.

    PubMed

    Yamashita, Hiromi

    2016-07-29

    Fatty acids derived from adipose tissue are oxidized by β-oxidation to form ketone bodies as final products under the starving condition. Previously, we found that free acetic acid was formed concomitantly with the production of ketone bodies in isolated rat liver perfusion, and mitochondrial acetyl CoA hydrolase was appeared to be involved with the acetic acid production. It was revealed that acetic acid was formed as a final product of enhanced β-oxidation of fatty acids and utilized as a fuel in extrahepatic tissues under the starving condition. Under the fed condition, β-oxidation is suppressed and acetic acid production is decreased. When acetic acid was taken daily by obesity-linked type 2 diabetic Otsuka Long-Evans Tokushima Fatty (OLETF) rats under the fed condition, it protected OLETF rats against obesity. Furthermore, acetic acid contributed to protect from the accumulation of lipid in the liver as well as abdominal fat in OLETF rats. Transcripts of lipogenic genes in the liver were decreased, while transcripts of myoglobin and Glut4 genes in abdominal muscles were increased in the acetic acid-administered OLETF rats. It is indicated that exogenously administered acetic acid would have effects on lipid metabolism in both the liver and the skeletal muscles, and have function that works against obesity and obesity-linked type 2 diabetes. PMID:26176799

  5. A novel mechanism of bisphenol A removal during electro-enzymatic oxidative process: chain reactions from self-polymerization to cross-coupling oxidation.

    PubMed

    Li, Haitao; Zhao, He; Liu, Chenming; Li, Yuping; Cao, Hongbin; Zhang, Yi

    2013-08-01

    The catalyzed removal of bisphenol A (BPA) by a horseradish peroxidase (HRP) cathode in the presence of humic acid (HA) was investigated. At an optimal condition, the removal of BPA achieved 100% within 2min reaction. In the electro-enzymatic process, products were analyzed by high performance liquid chromatography with diode array detector (HPLC-DAD) and high performance size exclusion chromatography (HPSEC). HPLC-DAD results showed that BPA was oxidized into self-polymers and then self-polymers as important intermediate products decreased and disappeared. HPSEC results showed the order of molecular weight (MW): HA+BPA cross-coupling products>HA self-coupling products>initial HA. According to above results, a novel mechanism of BPA transformation in the presence of HA was proposed in electro-enzymatic process. In summary, under oxidation of in situ hydrogen peroxide on HRP electrode, the BPA first are polymerized into self-polymers, and then, the polymers may be incorporated into HA matrix and finally larger MW of BPAn-HA might be formed. The presence of HA can provide chain reactions from BPA self-polymerization to cross-coupling oxidation. Therefore, in the presence of HA, the electro-enzymatic oxidation is an effective way to improve BPA removal. PMID:23732003

  6. Electron/proton coupling in bacterial nitric oxide reductase during reduction of oxygen.

    PubMed

    Flock, Ulrika; Watmough, Nicholas J; Adelroth, Pia

    2005-08-01

    The respiratory nitric oxide reductase (NOR) from Paracoccus denitrificans catalyzes the two-electron reduction of NO to N(2)O (2NO + 2H(+) + 2e(-) --> N(2)O + H(2)O), which is an obligatory step in the sequential reduction of nitrate to dinitrogen known as denitrification. NOR has four redox-active cofactors, namely, two low-spin hemes c and b, one high-spin heme b(3), and a non-heme iron Fe(B), and belongs to same superfamily as the oxygen-reducing heme-copper oxidases. NOR can also use oxygen as an electron acceptor; this catalytic activity was investigated in this study. We show that the product in the steady-state reduction of oxygen is water. A single turnover of the fully reduced NOR with oxygen was initiated using the flow-flash technique, and the progress of the reaction monitored by time-resolved optical absorption spectroscopy. Two major phases with time constants of 40 micros and 25 ms (pH 7.5, 1 mM O(2)) were observed. The rate constant for the faster process was dependent on the O(2) concentration and is assigned to O(2) binding to heme b(3) at a bimolecular rate constant of 2 x 10(7) M(-)(1) s(-)(1). The second phase (tau = 25 ms) involves oxidation of the low-spin hemes b and c, and is coupled to the uptake of protons from the bulk solution. The rate constant for this phase shows a pH dependence consistent with rate limitation by proton transfer from an internal group with a pK(a) = 6.6. This group is presumably an amino acid residue that is crucial for proton transfer to the catalytic site also during NO reduction. PMID:16060680

  7. Insights into proton-coupled electron transfer mechanisms of electrocatalytic H2 oxidation and production

    PubMed Central

    Horvath, Samantha; Fernandez, Laura E.; Soudackov, Alexander V.; Hammes-Schiffer, Sharon

    2012-01-01

    The design of molecular electrocatalysts for H2 oxidation and production is important for the development of alternative renewable energy sources that are abundant, inexpensive, and environmentally benign. Recently, nickel-based molecular electrocatalysts with pendant amines that act as proton relays for the nickel center were shown to effectively catalyze H2 oxidation and production. We developed a quantum mechanical approach for studying proton-coupled electron transfer processes in these types of molecular electrocatalysts. This theoretical approach is applied to a nickel-based catalyst in which phosphorous atoms are directly bonded to the nickel center, and nitrogen atoms of the ligand rings act as proton relays. The catalytic step of interest involves electron transfer between the nickel complex and the electrode as well as intramolecular proton transfer between the nickel and nitrogen atoms. This process can occur sequentially, with either the electron or proton transferring first, or concertedly, with the electron and proton transferring simultaneously without a stable intermediate. The electrochemical rate constants are calculated as functions of overpotential for the concerted electron-proton transfer reaction and the two electron transfer reactions in the sequential mechanisms. Our calculations illustrate that the concerted electron-proton transfer standard rate constant will increase as the equilibrium distance between the nickel and nitrogen atoms decreases and as the pendant amines become more flexible to facilitate the contraction of this distance with a lower energy penalty. This approach identifies the favored mechanisms under various experimental conditions and provides insight into the impact of substituents on the nitrogen and phosphorous atoms. PMID:22529352

  8. NON-ENZYMATIC REDUCTION OF QUINONE METHIDES DURING OXIDATIVE COUPLING OF MONOLIGNOLS: IMPLICATIONS FOR THE ORIGIN OF BENZYL STRUCTURES IN LIGNINS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Lignin is believed to be synthesized by oxidative coupling of 4-hydroxyphenylpropanoids. In native lignin there are some types of reduced structures that cannot be explained by oxidative coupling. In the present work we showed via biomimetic model experiments that nicotinamide adenine dinucleotide (...

  9. Successive C-C Coupling of Dienes to Vicinally Dioxygenated Hydrocarbons: Ruthenium Catalyzed [4+2] Cycloaddition across the Diol, Hydroxycarbonyl or Dione Oxidation Levels

    PubMed Central

    Geary, Laina M.; Glasspoole, Ben W.; Kim, Mary M.; Krische, Michael J.

    2013-01-01

    The ruthenium(0) catalyst generated from Ru3(CO)12 and tricyclohexylphosphine or BIPHEP promotes successive C-C coupling of dienes to vicinally dioxygenated hydrocarbons across the diol, hydroxyketone and dione oxidation levels to form products of [4+2] cycloaddition. A mechanism involving diene-carbonyl oxidative coupling followed by intramolecular carbonyl addition from the resulting allylruthenium intermediate is postulated. PMID:23448269

  10. Diminution of Hepatic Response to 7, 12-dimethylbenz(α)anthracene by Ethyl Acetate Fraction of Acacia catechu Willd. through Modulation of Xenobiotic and Anti-Oxidative Enzymes in Rats

    PubMed Central

    Kumar, Rakesh; Kaur, Rajbir; Singh, Amrit Pal; Arora, Saroj

    2014-01-01

    Background Liver is the primary metabolizing site of body and is prone to damage by exogenous as well as endogenous intoxicants. Polycyclic aromatic hydrocarbons such as 7, 12- dimethylbenz(α)anthracene (DMBA) is an exogenous hepatotoxin, which is well known for modulating phase I, II and anti-oxidative enzymes of liver. Plants contain plethora of polyphenolic compounds which can reverse the damaging effect of various xenobiotics. The present study investigated protective role of the ethyl acetate fraction of Acacia catechu Willd. (EAF) against DMBA induced alteration in hepatic metabolizing and anti-oxidative enzymes in rats. Methodology and Principal Findings The rats were subjected to hepatic damage by treating with DMBA for 7 weeks on alternative days and treatment schedule was terminated at the end of 14 weeks. The rats were euthanized at the end of protocol and livers were homogenized. The liver homogenates were used to analyse phase I (NADPH-cytochrome P450 reducatse, NADH-cytochrome b5 reductase, cytochrome P420, cytochrome b5), phase II (glutathione-S-transferase, DT diaphorase and γ-Glutamyl transpeptidase) and antioxidative enzymes (catalase, superoxide dismutase, ascorbate peroxidase, glutathione reductase, guiacol peroxidase and lactate dehydrogenase). Furthermore, other oxidative stress parameters (thiobarbituric acid reactive substances, lipid hydroperoxides and conjugated dienes and reduced glutathione) and liver marker enzymes (serum glutamic oxaloacetic transaminase, serum glutamic pyruvic transaminase and alkaline phosphatase) were also studied. The DMBA induced significant changes in activity of hepatic enzymes that was reversed by treatment with three dose levels of EAF. Conclusion It is concluded that EAF affords hepato-protection against DMBA in rats through modulation of phase I, II and anti-oxidative enzymes. PMID:24587216

  11. Pristine graphdiyne-hybridized photocatalysts using graphene oxide as a dual-functional coupling reagent.

    PubMed

    Zhang, Xiao; Zhu, Mingshan; Chen, Penglei; Li, Yongjun; Liu, Huibiao; Li, Yuliang; Liu, Minghua

    2015-01-14

    Advanced functional hybrids based on carbon materials (CMs) represent one of the main achievements of scientific communities. To achieve the hybridization, pristine CMs have to be chemically modified, or surfactants, which are nonfunctional for the performances of the hybrids, have to be employed as a cross-linkage. The construction of pristine CM-based hybrids using dual-functional coupling reagents, which work not only as a glue for hybridization but also as a functional component for enhanced performance, is strongly desired. Here, we report that pristine graphdiyne (GD), a recently synthesized new carbon allotrope, can be facilely hybridized with Ag/AgBr using graphene oxide (GO) as a cross-linkage. We demonstrate that compared to Ag/AgBr, Ag/AgBr/GO, and Ag/AgBr/GD, our Ag/AgBr/GO/GD exhibits an enhanced photocatalytic performance toward the degradation of methyl orange (MO) pollutant under visible light irradiation. In our Ag/AgBr/GO/GD, GO serves not only as a glue for a successful hybridization, but also as a functional component for enhanced catalytic performance. Beyond GD, our work likely paves a new avenue for the fabrication of advanced functional hybrids based on pristine carbon allotropes, wherein desired functions or properties might be achieved by choosing desired CMs and desired hybridized components. PMID:25418916

  12. Stoichiometry of mitochondrial H+ translocation coupled to succinate oxidation at level flow.

    PubMed

    Costa, L E; Reynafarje, B; Lehninger, A L

    1984-04-25

    The mechanistic stoichiometry of vectorial H+ translocation coupled to succinate oxidation by rat liver mitochondria in the presence of a permeant cation has been determined under level flow conditions with a membraneless fast responding O2 electrode kinetically matched with a glass pH electrode. The reactions were initiated by rapid injection of O2 into the anaerobically preincubated test system under conditions in which interfering H+ backflow was minimized. The rates of O2 uptake and H+ ejection, obtained from computer-fitted regression lines, were monotonic and first order over 75% of the course of O2 consumption. Extrapolation of the observed rates to zero time, at which zero delta mu H+ and thus level flow prevails, yielded vectorial H+/O flow ratios above 7 and closely approaching 8. The mitochondria undergo no irreversible change and give identical H+/O ratios on repeated tests. In a further refinement, the lower and upper limits of the mechanistic H+/O ratio were determined to be 7.55 and 8.56, respectively, from plots of the rates of O2 uptake versus H+ ejection at increasing malonate and increasing valinomycin concentrations, respectively. It is therefore concluded that the mechanistic H+/O ratio for energy-conserving sites 2 + 3 is 8, in confirmation of earlier measurements. KCl concentration is critical for maximal observed H+/O ratios. Optimum conditions and possible errors in determination of mechanistic H+/O translocation ratios are discussed. PMID:6232269

  13. Soil remediation using a coupled process: soil washing with surfactant followed by photo-Fenton oxidation.

    PubMed

    Villa, Ricardo D; Trovó, Alam G; Nogueira, Raquel F Pupo

    2010-02-15

    In the present work the use of a coupled process, soil washing and photo-Fenton oxidation, was investigated for remediation of a soil contaminated with p,p'-DDT (DDT) and p,p'-DDE (DDE), and a soil artificially contaminated with diesel. In the soil washing experiments, Triton X-100 (TX-100) aqueous solutions were used at different concentrations to obtain wastewaters with different compositions. Removal efficiencies of 66% (DDT), 80% (DDE) and 100% (diesel) were achieved for three sequential washings using a TX-100 solution strength equivalent to 12 times the effective critical micelle concentration of the surfactant (12 CMC(eff)). The wastewater obtained was then treated using a solar photo-Fenton process. After 6h irradiation, 99, 95 and 100% degradation efficiencies were achieved for DDT, DDE and diesel, respectively. In all experiments, the concentration of dissolved organic carbon decreased by at least 95%, indicating that residual concentration of contaminants and/or TX-100 in the wastewater was very low. The co-extraction of metals was also evaluated. Among the metals analyzed (Pb, Cr, Ni, Cu, Cd, Mn and Co), only Cr and Mn were detected in the wastewater at concentrations above the maximum value permitted by current Brazilian legislation. The effective removal of contaminants from soil by the TX-100 washing process, together with the high degradation efficiency of the solar photo-Fenton process, suggests that this procedure could be a useful option for soil remediation. PMID:19853992

  14. Effect of oxidation on interlayer exchange coupling in Fe|MgO|Fe tunnel junctions

    NASA Astrophysics Data System (ADS)

    Yang, H.-X.; Chshiev, M.; Kalitsov, A.; Schuhl, A.; Butler, W. H.

    2010-03-01

    The interlayer exchange coupling (IEC) in MgO-based magnetic tunnel junctions (MTJ) is a subject of major interest for spintronics community [1,2]. Recent experiments demonstrated that oxydation conditions strongly affect the character of the IEC in Fe/MgO/Fe(001) MTJs [3]. In order to elucidate the effect of over- and under-oxidation on the nature of the IEC in Fe|MgO|Fe MTJs, we performed systematic studies of the influence of O impurities and vacancies on the IEC using ab-initio and tight-binding approaches. We found that the O vacancies cause strong AF IEC in agreement with previous studies [2-4]. Furthermore, an additional O atom at the Fe|MgO interface makes the IEC ferromagnetic in for 3ML and above MgO thicknesses in agreement with experiment [3]. We demonstrate also that the full structural relaxation of ideal Fe|MgO|Fe MTJs may lead to the antiferromagnetic IEC. Tight-binding calculations of the IEC in the framework of the Keldysh formalism were also performed. The results obtained support our first principles calculations. [1] J. Faure-Vincent et al, Phys. Rev. Lett. 89, 107206 (2002); [2] T. Katayama et al., Appl. Phys. Lett. 89, 112503 (2006); [3] Y.F. Chiang et al, Phys. Rev. B 79, 184410 (2009); [4] M.Y. Zhuravlev et al, Phys. Rev. Lett. 94, 026806 (2005).

  15. 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.

  16. Computer simulation of spatial coupling in chemical oscillations of CO oxidation on two Pd(110) single crystals

    NASA Astrophysics Data System (ADS)

    Park, I. J.; Woo, S. I.

    1993-09-01

    Gas-phase coupling between two Pd(110) single crystals in a UHV CO oxidation reaction in a continuous stirred tank reactor (CSTR) has been simulated by solving gas-phase mass balance equations with kinetic rate equations. This work was motivated by the experimental results which show that the frequency of partial pressure change in carbon monoxide is the same as the frequency of the work function change in the oscillation region and that the coupling between the two crystals occurred entirely via CO partial pressure. The computer simulation described here gives qualitative agreement with the experimental results. The change in the oscillatory region originating from the coupling of chemical oscillators which are slightly different to each other is successfully demonstrated by this model. The coupling of two oscillators having a simple periodic oscillation to produce mixed-mode oscillation was also successfully simulated.

  17. Stenoxybacter acetivorans gen. nov., sp. nov., an Acetate-Oxidizing Obligate Microaerophile among Diverse O2-Consuming Bacteria from Termite Guts▿

    PubMed Central

    Wertz, John T.; Breznak, John A.

    2007-01-01

    In termite hindguts, fermentative production of acetate—a major carbon and energy source for the insect—depends on efficient removal of inwardly diffusing oxygen by microbes residing on and near the hindgut wall. However, little is known about the identity of these organisms or about the substrate(s) used to support their respiratory activity. A cultivation-based approach was used to isolate O2-consuming organisms from hindguts of Reticulitermes flavipes. A consistently greater (albeit not statistically significant) number of colonies developed under hypoxia (2% [vol/vol] O2) than under air, and the increase coincided with the appearance of morphologically distinct colonies of a novel, rod-shaped, obligately microaerophilic β-proteobacterium that was <95% similar (based on the 16S rRNA gene sequence) to its closest known relative (Eikenella corrodens). Nearly identical organisms (and/or their 16S rRNA genes) were obtained from geographically separated and genetically distinct populations of Reticulitermes. PCR-based procedures implied that the novel isolates were autochthonous to the hindgut of R. flavipes and comprised ca. 2 to 7% of the hindgut prokaryote community. Representative strain TAM-DN1 utilized acetate and a limited range of other organic and amino acids as energy sources and possessed catalase and superoxide dismutase. On solid medium, the optimal O2 concentration for growth was about 2%, and no growth occurred with O2 concentrations above 4% or under anoxia. However, cells in liquid medium could grow with higher O2 concentrations (up to 16%), but only after proportionately extended lag phases. The genetic and physiological distinctiveness of TAM-DN1 and related strains supports their recognition as a new genus and species, for which the name Stenoxybacter acetivorans gen. nov., sp. nov. is proposed. PMID:17827334

  18. Rate enhancement of photocatalytic cyanide oxidation by the application of an anodic bias/coupled semiconductor configuration

    SciTech Connect

    Munroe, N.D.H.; Tilleux, R.

    1996-12-31

    In this study, photocatalytic cyanide degradation was investigated utilizing ultraviolet light (UV), an increase in titanium (IV) oxide (TiO{sub 2}) photocatalyst surface area, platinization of the photocatalyst, appropriate adjustment of pH, and the immobilization of TiO{sub 2}/ tin (IV) oxide (SnO{sub 2}) coupled semi-conductor film on an optically transparent electrode. The cyanide concentration was monitored using an ion selective electrode. The focus of this study was to explore the possibility of a viable process for the effective and complete photodegradation of cyanide ion. The long-term goal is the application of this process to industry. Cyanide detoxification has been successfully achieved in recent years. Research has shown that photocatalytic oxidation can completely degrade cyanide to nitrate via nitrite. However, the rate at which this oxidation occurs is not yet suitable for application in industry. Therefore, the need for an effective treatment is most urgent.

  19. Reaction progress kinetic analysis of a copper-catalyzed aerobic oxidative coupling reaction with N-phenyl tetrahydroisoquinoline.

    PubMed

    Scott, Martin; Sud, Abhishek; Boess, Esther; Klussmann, Martin

    2014-12-19

    The results from a kinetic investigation of a Cu-catalyzed oxidative coupling reaction between N-phenyl tetrahydroisoquinoline and a silyl enol ether using elemental oxygen as oxidant are presented. By using reaction progress kinetic analysis as an evaluation method for the obtained data, we discovered information regarding the reaction order of the substrates and catalysts. Based on this information and some additional experiments, a refined model for the initial oxidative activation of the amine substrate and the activation of the nucleophile by the catalyst was developed. The mechanistic information also helped to understand why silyl nucleophiles have previously failed in a related Cu-catalyzed reaction using tert-butyl hydroperoxide as oxidant and how to overcome this limitation. PMID:25203932

  20. Direct oxidative coupling of amidine hydrochlorides and methylarenes: TBHP-mediated synthesis of substituted 1,3,5-triazines under metal-free conditions.

    PubMed

    Guo, Wei

    2015-11-01

    Various 2,4,6-trisubstituted 1,3,5-triazines were smoothly formed via TBHP-mediated direct oxidative coupling of amidine and methylarenes. This tandem oxidation-imination-cyclization transformation exhibits a straightforward protocol to prepare 1,3,5-triazines from easily available starting materials and green oxidants under metal-free conditions. PMID:26411699

  1. Tuning the Reactivity of Radical through a Triplet Diradical Cu(II) Intermediate in Radical Oxidative Cross-Coupling

    PubMed Central

    Zhou, Liangliang; Yi, Hong; Zhu, Lei; Qi, Xiaotian; Jiang, Hanpeng; Liu, Chao; Feng, Yuqi; Lan, Yu; Lei, Aiwen

    2015-01-01

    Highly selective radical/radical cross-coupling is paid more attention in bond formations. However, due to their intrinsic active properties, radical species are apt to achieve homo-coupling instead of cross-coupling, which makes the selective cross-coupling as a great challenge and almost untouched. Herein a notable strategy to accomplish direct radical/radical oxidative cross-coupling has been demonstrated, that is metal tuning a transient radical to a persistent radical intermediate followed by coupling with another transient radical. Here, a transient nitrogen-centered radical is tuned to a persistent radical complex by copper catalyst, followed by coupling with a transient allylic carbon-centered radical. Firstly, nitrogen-centered radical generated from N-methoxybenzamide stabilized by copper catalyst was successfully observed by EPR. Then DFT calculations revealed that a triplet diradical Cu(II) complex formed from the chelation N-methoxybenzamide nitrogen-centered radical to Cu(II) is a persistent radical species. Moreover, conceivable nitrogen-centered radical Cu(II) complex was observed by high-resolution electrospray ionization mass spectrometry (ESI-MS). Ultimately, various allylic amides derivatives were obtained in good yields by adopting this strategy, which might inspire a novel and promising landscape in radical chemistry. PMID:26525888

  2. Tuning the Reactivity of Radical through a Triplet Diradical Cu(II) Intermediate in Radical Oxidative Cross-Coupling

    NASA Astrophysics Data System (ADS)

    Zhou, Liangliang; Yi, Hong; Zhu, Lei; Qi, Xiaotian; Jiang, Hanpeng; Liu, Chao; Feng, Yuqi; Lan, Yu; Lei, Aiwen

    2015-11-01

    Highly selective radical/radical cross-coupling is paid more attention in bond formations. However, due to their intrinsic active properties, radical species are apt to achieve homo-coupling instead of cross-coupling, which makes the selective cross-coupling as a great challenge and almost untouched. Herein a notable strategy to accomplish direct radical/radical oxidative cross-coupling has been demonstrated, that is metal tuning a transient radical to a persistent radical intermediate followed by coupling with another transient radical. Here, a transient nitrogen-centered radical is tuned to a persistent radical complex by copper catalyst, followed by coupling with a transient allylic carbon-centered radical. Firstly, nitrogen-centered radical generated from N-methoxybenzamide stabilized by copper catalyst was successfully observed by EPR. Then DFT calculations revealed that a triplet diradical Cu(II) complex formed from the chelation N-methoxybenzamide nitrogen-centered radical to Cu(II) is a persistent radical species. Moreover, conceivable nitrogen-centered radical Cu(II) complex was observed by high-resolution electrospray ionization mass spectrometry (ESI-MS). Ultimately, various allylic amides derivatives were obtained in good yields by adopting this strategy, which might inspire a novel and promising landscape in radical chemistry.

  3. Tuning the Reactivity of Radical through a Triplet Diradical Cu(II) Intermediate in Radical Oxidative Cross-Coupling.

    PubMed

    Zhou, Liangliang; Yi, Hong; Zhu, Lei; Qi, Xiaotian; Jiang, Hanpeng; Liu, Chao; Feng, Yuqi; Lan, Yu; Lei, Aiwen

    2015-01-01

    Highly selective radical/radical cross-coupling is paid more attention in bond formations. However, due to their intrinsic active properties, radical species are apt to achieve homo-coupling instead of cross-coupling, which makes the selective cross-coupling as a great challenge and almost untouched. Herein a notable strategy to accomplish direct radical/radical oxidative cross-coupling has been demonstrated, that is metal tuning a transient radical to a persistent radical intermediate followed by coupling with another transient radical. Here, a transient nitrogen-centered radical is tuned to a persistent radical complex by copper catalyst, followed by coupling with a transient allylic carbon-centered radical. Firstly, nitrogen-centered radical generated from N-methoxybenzamide stabilized by copper catalyst was successfully observed by EPR. Then DFT calculations revealed that a triplet diradical Cu(II) complex formed from the chelation N-methoxybenzamide nitrogen-centered radical to Cu(II) is a persistent radical species. Moreover, conceivable nitrogen-centered radical Cu(II) complex was observed by high-resolution electrospray ionization mass spectrometry (ESI-MS). Ultimately, various allylic amides derivatives were obtained in good yields by adopting this strategy, which might inspire a novel and promising landscape in radical chemistry. PMID:26525888

  4. Biological reduction of uranium coupled with oxidation of ammonium by Acidimicrobiaceae bacterium A6 under iron reducing conditions.

    PubMed

    Gilson, Emily R; Huang, Shan; Jaffé, Peter R

    2015-11-01

    This study investigated the possibility of links between the biological immobilization of uranium (U) and ammonium oxidation under iron (Fe) reducing conditions. The recently-identified Acidimicrobiaceae bacterium A6 (ATCC, PTA-122488) derives energy from ammonium oxidation coupled with Fe reduction. This bacterium has been found in various soil and wetland environments, including U-contaminated wetland sediments. Incubations of Acidimicrobiaceae bacteria A6 with nontronite, an Fe(III)-rich clay, and approximately 10 µM U indicate that these bacteria can use U(VI) in addition to Fe(III) as an electron acceptor in the presence of ammonium. Measurements of Fe(II) production and ammonium oxidation support this interpretation. Concentrations of approximately 100 µM U were found to entirely inhibit Acidimicrobiaceae bacteria A6 activity. These results suggest that natural sites of active ammonium oxidation under Fe reducing conditions by Acidimicrobiaceae bacteria A6 could be hotspots of U immobilization by bioreduction. This is the first report of biological U reduction that is not coupled to carbon oxidation. PMID:26525893

  5. Theoretical studies on CuCl-catalyzed C-H activation/C-O coupling reactions: oxidant and catalyst effects.

    PubMed

    Zhang, Lu-Lu; Li, Shi-Jun; Zhang, Lei; Fang, De-Cai

    2016-05-11

    Copper-complex catalyzed coupling reactions have been widely applied in the production of many important organic moieties from a synthetic perspective. In this work, a series of density functional theory (DFT) calculations, employing the B3LYP + IDSCRF/DZVP method, have been performed for a typical CuCl-catalyzed C-O cross-coupling reaction. The novel reaction mechanism was reported as four successive processes: oxidative radical generation (ORG) or oxidative addition (OA), hydrogen abstraction (HA), C-H activation/reductive elimination, and separation of product and recycling of catalyst (SP & RC). Our calculations provided a deep understanding on the dissimilar chemical activities associated with varying the oxidants used; detailed energy profile analyses suggested that the first oxidation process could proceed via either of the two competing channels (ORG and OA mechanisms) which is the basis to explain the different experimental yields. In addition, our molecular modelling gave theoretical evidence that Cu(ii) → Cu(i) reduction by solvent DMF (and a water molecule) might serve as a preliminary step to produce some more active Cu(i) species that could subsequently be oxidized into Cu(iii) favorably. In contrast, the Cu(ii) → Cu(iii) direct pathway was estimated to be prohibited from thermodynamics. All the calculation results in this work are parallel with the experimental observations. PMID:27088885

  6. Dehydrogenative Coupling Reactions with Oxidized Guanidino-Functionalized Aromatic Compounds: Novel Options for σ-Bond Activation.

    PubMed

    Wild, Ute; Federle, Stefanie; Wagner, Arne; Kaifer, Elisabeth; Himmel, Hans-Jörg

    2016-08-16

    We present a new option for metal-free σ-bond activation, making use of oxidized, guanidino-functionalized aromatic compounds (GFAs). We demonstrate this new option by the homocoupling reactions of thiols and phosphines. The kinetics and the reaction pathway were studied by a number of experiments (including heterocoupling of thiols and phosphines), supported by quantum-chemical computations. Reaction of the oxidized GFA with p-dihydrobenzoquinone to give p-benzoquinone shows that typical proton-coupled electron-transfer reactions are also possible. PMID:27430589

  7. Catalytic Chan–Lam coupling using a ‘tube-in-tube’ reactor to deliver molecular oxygen as an oxidant

    PubMed Central

    Mallia, Carl J; Burton, Paul M; Smith, Alexander M R; Walter, Gary C

    2016-01-01

    Summary A flow system to perform Chan–Lam coupling reactions of various amines and arylboronic acids has been realised employing molecular oxygen as an oxidant for the re-oxidation of the copper catalyst enabling a catalytic process. A tube-in-tube gas reactor has been used to simplify the delivery of the oxygen accelerating the optimisation phase and allowing easy access to elevated pressures. A small exemplification library of heteroaromatic products has been prepared and the process has been shown to be robust over extended reaction times. PMID:27559412

  8. Catalytic Chan-Lam coupling using a 'tube-in-tube' reactor to deliver molecular oxygen as an oxidant.

    PubMed

    Mallia, Carl J; Burton, Paul M; Smith, Alexander M R; Walter, Gary C; Baxendale, Ian R

    2016-01-01

    A flow system to perform Chan-Lam coupling reactions of various amines and arylboronic acids has been realised employing molecular oxygen as an oxidant for the re-oxidation of the copper catalyst enabling a catalytic process. A tube-in-tube gas reactor has been used to simplify the delivery of the oxygen accelerating the optimisation phase and allowing easy access to elevated pressures. A small exemplification library of heteroaromatic products has been prepared and the process has been shown to be robust over extended reaction times. PMID:27559412

  9. Copper catalyzed oxidative esterification of aldehydes with alkylbenzenes via cross dehydrogenative coupling.

    PubMed

    Rout, Saroj Kumar; Guin, Srimanta; Ghara, Krishna Kanta; Banerjee, Arghya; Patel, Bhisma K

    2012-08-01

    Copper(II) as the catalyst in a cross dehydrogenative coupling (CDC) reaction has been demonstrated for the synthesis of benzylic esters using aldehydes and alkylbenzenes as coupling partners. PMID:22817825

  10. Coupling between crystal structure and magnetism in transition-metal oxides

    NASA Astrophysics Data System (ADS)

    Barton, Phillip Thomas

    Transition-metal oxides exhibit a fascinating array of phenomena ranging from superconductivity to negative thermal expansion to catalysis. This dissertation focuses on magnetism, which is integral to engineering applications such as data storage, electric motors/generators, and transformers. The investigative approach follows structure-property relationships from materials science and draws on intuition from solid-state chemistry. The interplay between crystal structure and magnetic properties is studied experimentally in order to enhance the understanding of magnetostructural coupling mechanisms and provide insight into avenues for tuning behavior. A combination of diffraction and physical property measurements were used to study structural and magnetic phase transitions as a function of chemical composition, temperature, and magnetic field. The systems examined are of importance in Li-ion battery electrochemistry, condensed-matter physics, solid-state chemistry, and p-type transparent conducting oxides. The materials were prepared by solid-state reaction of powder reagents at high temperatures for periods lasting tens of hours. The first project discussed is of a solid solution between NiO, a correlated insulator, and LiNiO2, a layered battery cathode. Despite the deceptive structural and compositional simplicity of this system, a complete understanding of its complex magnetic properties has remained elusive. This study shows that nanoscale domains of chemical order form at intermediate compositions, creating interfaces between antiferromagnetism and ferrimagnetism that give rise to magnetic exchange bias. A simple model of the magnetism is presented along with a comprehensive phase diagram. The second set of investigations focus on the Ge-Co-O system where the spin-orbit coupling of Co(II) plays a significant role. GeCo2O 4 is reported to exhibit unusual magnetic behavior that arises from Ising spin in its spinel crystal structure. Studies by variable

  11. Iodine-Catalyzed Cross Dehydrogenative Coupling Reaction: A Regioselective Sulfenylation of Imidazoheterocycles Using Dimethyl Sulfoxide as an Oxidant.

    PubMed

    Siddaraju, Yogesh; Prabhu, Kandikere Ramaiah

    2016-09-01

    A regioselective formation of C-S bonds has been achieved using a cross dehydrogenative coupling (CDC) protocol using iodine as a catalyst and dimethyl sulfoxide as an oxidant under green chemistry conditions. This strategy employs the reaction of easily available heterocyclic thiols or thiones with imidazoheterocycles. This protocol provides an efficient, mild, and inexpensive method for sulfenylation of imidazoheterocycles with a diverse range of heterocyclic thiols and heterocyclic thiones. PMID:27490357

  12. Synthesis and Application of Chiral Spiro Cp Ligands in Rhodium-Catalyzed Asymmetric Oxidative Coupling of Biaryl Compounds with Alkenes.

    PubMed

    Zheng, Jun; Cui, Wen-Jun; Zheng, Chao; You, Shu-Li

    2016-04-27

    The vastly increasing application of chiral Cp ligands in asymmetric catalysis results in growing demand for novel chiral Cp ligands. Herein, we report a new class of chiral Cp ligands based on 1,1'-spirobiindane, a privileged scaffold for chiral ligands and catalysts. The corresponding Rh complexes are shown to be excellent catalysts in asymmetric oxidative coupling reactions, providing axially chiral biaryls in 19-97% yields with up to 98:2 er. PMID:27070297

  13. Self-assembly of a superparamagnetic raspberry-like silica/iron oxide nanocomposite using epoxy-amine coupling chemistry.

    PubMed

    Cano, Manuel; de la Cueva-Méndez, Guillermo

    2015-02-28

    The fabrication of colloidal nanocomposites would benefit from controlled hetero-assembly of ready-made particles through covalent bonding. Here we used epoxy-amine coupling chemistry to promote the self-assembly of superparamagnetic raspberry-like nanocomposites. This adaptable method induced the covalent attachment of iron oxide nanoparticles sparsely coated with amine groups onto epoxylated silica cores in the absence of other reactants. PMID:25635377

  14. Source of Selectivity in Oxidative Cross-Coupling of Aryls by Solvent Effect of 1,1,1,3,3,3-Hexafluoropropan-2-ol.

    PubMed

    Elsler, Bernd; Wiebe, Anton; Schollmeyer, Dieter; Dyballa, Katrin M; Franke, Robert; Waldvogel, Siegfried R

    2015-08-24

    Solvents such as 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) with a high capacity for donating hydrogen bonds generate solvates that enter into selective cross-coupling reactions of aryls upon oxidation. When electric current is employed for oxidation, reagent effects can be excluded and a decoupling of nucleophilicity from oxidation potential can be achieved. The addition of water or methanol to the electrolyte allows a shift of oxidation potentials in a specific range, creating suitable systems for selective anodic cross-coupling reactions. The shift in the redox potentials depends on the substitution pattern of the substrate employed. The concept has been expanded from arene-phenol to phenol-phenol as well as phenol-aniline cross-coupling. This driving force for selectivity in oxidative coupling might also explain previous findings using HFIP and hypervalent iodine reagents. PMID:26189655

  15. Platinum Metal-Free Catalysts for Selective Soft Oxidative Methane → Ethylene Coupling. Scope and Mechanistic Observations.

    PubMed

    Peter, Matthias; Marks, Tobin J

    2015-12-01

    Using abundant soft oxidants, a high methane-to-ethylene conversion might be achievable due to the low thermodynamic driving force for over-oxidation. Here we report on the oxidative coupling of methane by gaseous S2 (SOCM). The catalytic properties of Pd/Fe3O4 are compared with those of Fe3O4, and it is found that high ethylene selectivities can be achieved without noble metals; conversion and selectivity on Fe3O4 are stable for at least 48 h at SOCM conditions. SOCM data for 10 oxides are compared, and ethylene selectivities as high as 33% are found; the C2H4/C2H6 ratios of 9-12 observed at the highest S2 conversions are significantly higher than the C2H4/C2H6 ratios usually found in the CH4 coupling with O2. Complementary in-detail analytical studies show that, on Mg, Zr, Sm, W, and La catalysts, which strongly coke during the reaction, lower ethylene selectivities are observed than on Fe, Ti, and Cr catalysts, which only coke to a minor extent. Further catalyst-dependent changes during SOCM in surface area, surface composition, and partial conversion to oxysulfides and sulfides are discussed. Evidence concerning the reaction mechanism is obtained taking into account the selectivity for the different reaction products versus the contact time. CH4 coupling proceeds non-oxidatively with the evolution of H2 on some catalysts, and evidence is presented that C2H4 and C2H2 formation occur via C2H6 and C2H4 dehydrogenation, respectively. PMID:26551955

  16. Mechanism of protein oxidative damage that is coupled to long-range electron transfer to high-valent haems.

    PubMed

    Ma, Zhongxin; Williamson, Heather R; Davidson, Victor L

    2016-06-15

    In the absence of its substrate, the auto-reduction of the high-valent bis-Fe(IV) state of the dihaem enzyme MauG is coupled to oxidative damage of a methionine residue. Transient kinetic and solvent isotope effect studies reveal that this process occurs via two sequential long-range electron transfer (ET) reactions from methionine to the haems. The first ET is coupled to proton transfer (PT) to the haems from solvent via an ordered water network. The second ET is coupled to PT at the methionine site and occurs during the oxidation of the methionine to a sulfoxide. This process proceeds via Compound I- and Compound II-like haem intermediates. It is proposed that the methionine radical is stabilized by a two-centre three-electron (2c3e) bond. This provides insight into how oxidative damage to proteins may occur without direct contact with a reactive oxygen species, and how that damage can be propagated through the protein. PMID:27076451

  17. Controlled surface modification of Ti-40Nb implant alloy by electrochemically assisted inductively coupled RF plasma oxidation.

    PubMed

    Göttlicher, Markus; Rohnke, Marcus; Helth, Arne; Leichtweiß, Thomas; Gemming, Thomas; Gebert, Annett; Eckert, Jürgen; Janek, Jürgen

    2013-11-01

    Low temperature metal oxidation induced by plasma in the absence of liquid electrolytes can be useful for the surface preparation of orthopedic devices since residues from these may be harmful and need to be removed before implantation. In this study the oxidation of Ti-40Nb for biomedical application was achieved by employing an inductively coupled radio frequency oxygen plasma. The correlation between the growth mode of the surface oxide and the electric conductivity ratio of the plasma and the oxide phase were studied by varying the sample temperature, oxygen gas pressure and additional bias potential. The plasma treated samples were characterised by confocal laser microscopy, SEM, EBSD, XPS, TEM and ToF-SIMS. The surface energy was determined by contact angle measurements using the Owens-Wendt-Rabel-Kaelble method. Well adhering oxide layers consisting of TiO2 and Nb2O5 with thicknesses between 50 and 150 nm were obtained. Surface roughness values and microstructure indicate that the growth mode of the oxide can be well controlled by the sample temperature and oxygen gas pressure. At temperatures above 450°C a migration of Ti ions towards the surface controls the growth process. A bias potential higher than +50 V causes rough and defective surfaces with high surface energies. PMID:23891813

  18. 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.

  19. Comparative proteomic analysis of sulfur-oxidizing Acidithiobacillus ferrooxidans CCM 4253 cultures having lost the ability to couple anaerobic elemental sulfur oxidation with ferric iron reduction.

    PubMed

    Kucera, Jiri; Sedo, Ondrej; Potesil, David; Janiczek, Oldrich; Zdrahal, Zbynek; Mandl, Martin

    2016-09-01

    In extremely acidic environments, ferric iron can be a thermodynamically favorable electron acceptor during elemental sulfur oxidation by some Acidithiobacillus spp. under anoxic conditions. Quantitative 2D-PAGE proteomic analysis of a resting cell suspension of a sulfur-grown Acidithiobacillus ferrooxidans CCM 4253 subculture that had lost its iron-reducing activity revealed 147 protein spots that were downregulated relative to an iron-reducing resting cell suspension of the antecedent sulfur-oxidizing culture and 111 that were upregulated. Tandem mass spectrometric analysis of strongly downregulated spots identified several physiologically important proteins that apparently play roles in ferrous iron oxidation, including the outer membrane cytochrome Cyc2 and rusticyanin. Other strongly repressed proteins were associated with sulfur metabolism, including heterodisulfide reductase, thiosulfate:quinone oxidoreductase and sulfide:quinone reductase. Transcript-level analyses revealed additional downregulation of other respiratory genes. Components of the iron-oxidizing system thus apparently play central roles in anaerobic sulfur oxidation coupled with ferric iron reduction in the studied microbial strain. PMID:27394989

  20. Mitochondrial coupling and capacity of oxidative phosphorylation in skeletal muscle of Inuit and Caucasians in the arctic winter.

    PubMed

    Gnaiger, E; Boushel, R; Søndergaard, H; Munch-Andersen, T; Damsgaard, R; Hagen, C; Díez-Sánchez, C; Ara, I; Wright-Paradis, C; Schrauwen, P; Hesselink, M; Calbet, J A L; Christiansen, M; Helge, J W; Saltin, B

    2015-12-01

    During evolution, mitochondrial DNA haplogroups of arctic populations may have been selected for lower coupling of mitochondrial respiration to ATP production in favor of higher heat production. We show that mitochondrial coupling in skeletal muscle of traditional and westernized Inuit habituating northern Greenland is identical to Danes of western Europe haplogroups. Biochemical coupling efficiency was preserved across variations in diet, muscle fiber type, and uncoupling protein-3 content. Mitochondrial phenotype displayed plasticity in relation to lifestyle and environment. Untrained Inuit and Danes had identical capacities to oxidize fat substrate in arm muscle, which increased in Danes during the 42 days of acclimation to exercise, approaching the higher level of the Inuit hunters. A common pattern emerges of mitochondrial acclimatization and evolutionary adaptation in humans at high latitude and high altitude where economy of locomotion may be optimized by preservation of biochemical coupling efficiency at modest mitochondrial density, when submaximum performance is uncoupled from VO2max and maximum capacities of oxidative phosphorylation. PMID:26589126

  1. An Adenosine Triphosphate-Phosphate Exchange Catalyzed by a Soluble Enzyme Couple Inhibited by Uncouplers of Oxidative Phosphorylation

    PubMed Central

    Allison, William S.; Benitez, Lita V.

    1972-01-01

    The sulfenic acid form of glyceraldehyde-3-phosphate dehydrogenase (EC 1.2.1.12), which is an acyl phosphatase, will catalyze an acetyl phosphate-Pi exchange reaction. This exchange reaction is reversibly inhibited by the uncouplers of oxidative phosphorylation, 2,4-dinitrophenol, m-Cl carbonylcyanide-phenylhydrazone, pentachlorophenol, and 5-chloro-3-tert-butyl-2′-chloro-4′-nitrosalicylanalide, and is irreversibly inhibited by cyanide and dicumarol. An ATP-Pi exchange reaction similar to that catalyzed by mitochondria can be simulated by a system composed of oxidized glyceraldehyde-3-phosphate dehydrogenase, phosphoglycerate kinase (EC 2.7.1.28), 3-phosphoglycerate, ATP, 32Pi, and appropriate cofactors. The ATP-Pi exchange is inhibited by uncouplers of oxidative phosphorylation. Higher concentrations of uncouplers will also inhibit the ATPase reaction catalyzed by the coupled enzyme system. The exchange reactions catalyzed by the sulfenic acid form of glyceraldehyde-3-phosphate are consistent with a sulfenyl carboxylate intermediate. On the basis of these observations, a reaction scheme has been postulated for covalent coupling in oxidative phosphorylation that includes a sulfenyl carboxylate as a nonphosphorylated, high energy intermediate and an acyl phosphate as a phosphorylated, high energy intermediate. PMID:4507619

  2. Silylesterification of oxidized multi-wall carbon nanotubes by catalyzed dehydrogenative cross-coupling between carboxylic and hydrosilane functions

    NASA Astrophysics Data System (ADS)

    Seffer, J.-F.; Detriche, S.; Nagy, J. B.; Delhalle, J.; Mekhalif, Z.

    2014-06-01

    Surface modification of oxidized carbon nanotubes (O-CNTs) with silicon based anchoring groups (R-SiR3) is a relatively uncommon approach of the CNTs functionalization. Hydrosilane derivatives constitute an attractive subclass of compounds for silanization reactions on the CNTs surface. In this work, we report on the ZnCl2 catalytically controlled reaction (hydrosilane dehydrogenative cross-coupling, DHCC) of fluorinated hydrosilane probes with the carboxylic functions present on the surface of oxidized multi-wall carbon nanotubes. Carbon nanotubes functionalized with essentially alcohol groups are also used to compare the selectivity of zinc chloride toward carboxylic groups. To assess the efficiency of functionalization, X-ray Photoelectron Spectroscopy is used to determine the qualitative and quantitative composition of the different samples. Solubility tests on the oxidized and silanized MWNTs are also carried out in the framework of the Hansen Solubility Parameters (HSP) theory to apprehend at another scale the effect of DHCC.

  3. Acetate Dependence of Tumors

    PubMed Central

    Comerford, Sarah A.; Huang, Zhiguang; Du, Xinlin; Wang, Yun; Cai, Ling; Witkiewicz, Agnes; Walters, Holly; Tantawy, Mohammed N.; Fu, Allie; Manning, H. Charles; Horton, Jay D.; Hammer, Robert E.; McKnight, Steven L.; Tu, Benjamin P.

    2014-01-01

    SUMMARY Acetyl-CoA represents a central node of carbon metabolism that plays a key role in bioenergetics, cell proliferation and the regulation of gene expression. How highly glycolytic or hypoxic tumors are able to produce sufficient quantities of this metabolite to support cell growth and survival under nutrient-limiting conditions remains poorly understood. Here we show that the nucleocytosolic acetyl-CoA synthetase enzyme, ACSS2, supplies a key source of acetyl-CoA for tumors by capturing acetate as a carbon source. Despite exhibiting no gross deficits in growth or development, adult mice lacking ACSS2 exhibit a significant reduction in tumor burden in two different models of hepatocellular carcinoma. ACSS2 is expressed in a large proportion of human tumors and its activity is responsible for the majority of cellular acetate uptake into both lipids and histones. These observations may qualify ACSS2 as a targetable metabolic vulnerability of a wide spectrum of tumors. PMID:25525877

  4. Peroxidase-Catalyzed Oxidative Coupling of Phenols in the Presence of Geosorbents

    SciTech Connect

    Huang, Qingguo; Weber, Walter J., Jr.

    2003-03-26

    This study focuses on elucidation of the reaction behaviors of peroxidase-mediated phenol coupling in the presence of soil/sediment materials. Our goal is a mechanistic understanding of the influences of geosorbent materials on enzymatic coupling reactions in general and the development of methods for predicting such influences. Extensive experimental investigations of coupling reactions were performed under strategically selected conditions in systems containing model geosorbents having different properties and chemical characteristics. The geosorbents tested were found to influence peroxidase-mediated phenol coupling through one or both of two principal mechanisms; i.e., (1) mitigation of enzyme inactivation and/or (2) participation in cross-coupling reactions. Such influences were found to correlate with the chemical characteristics of the sorbent materials and to be simulated well by a modeling approach designed in this paper. The results of the study have important implications for potential engineering implementation and enhancement of enzymatic coupling reactions in soil/subsurface remediation practice.

  5. Visible-light induced oxidant-free oxidative cross-coupling for constructing allylic sulfones from olefins and sulfinic acids.

    PubMed

    Zhang, Guoting; Zhang, Lingling; Yi, Hong; Luo, Yi; Qi, Xiaotian; Tung, Chen-Ho; Wu, Li-Zhu; Lei, Aiwen

    2016-08-16

    An oxidant-free dehydrogenative sulfonylation of α-methyl-styrene derivatives was developed for the construction of allylic sulfones by using eosin Y as a photosensitizer in conjunction with a cobaloxime catalyst. The process features a low-cost metal catalyst and atom economy, which provides an appealing strategy for future synthetic chemistry. PMID:27481529

  6. Oxidative Cross-Coupling of sp(3)- and sp(2)-Hybridized C-H Bonds: Vanadium-Catalyzed Aminomethylation of Imidazo[1,2-a]pyridines.

    PubMed

    Kaswan, Pinku; Porter, Ashley; Pericherla, Kasiviswanadharaju; Simone, Marissa; Peters, Sean; Kumar, Anil; DeBoef, Brenton

    2015-11-01

    The vanadium-catalyzed oxidative coupling of substituted 2-arylimidiazo[1,2-a]pyridines to N-methylmorpholine oxide, which acts as both a coupling partner and an oxidant, has been achieved. This reaction was applied to various substituted imidiazo[1,2-a]pyridine and indole substrates, resulting in yields as high as 90%. Mechanistic investigations indicate that the reaction may proceed via a Mannich-type process. This work demonstrates how oxidative aminomethylation can be used as a useful method to introduce tertiary amines into heterocycles, thus providing an alternative method for conventional Mannich-type reactions. PMID:26479446

  7. Induction of Apoptosis in MCF-7 Cells via Oxidative Stress Generation, Mitochondria-Dependent and Caspase-Independent Pathway by Ethyl Acetate Extract of Dillenia suffruticosa and Its Chemical Profile.

    PubMed

    Tor, Yin Sim; Yazan, Latifah Saiful; Foo, Jhi Biau; Wibowo, Agustono; Ismail, Norsharina; Cheah, Yoke Kqueen; Abdullah, Rasedee; Ismail, Maznah; Ismail, Intan Safinar; Yeap, Swee Keong

    2015-01-01

    Dillenia suffruticosa, which is locally known as Simpoh air, has been traditionally used to treat cancerous growth. The ethyl acetate extract of D. suffruticosa (EADs) has been shown to induce apoptosis in MCF-7 breast cancer cells in our previous study. The present study aimed to elucidate the molecular mechanisms involved in EADs-induced apoptosis and to identify the major compounds in the extract. EADs was found to promote oxidative stress in MCF-7 cells that led to cell death because the pre-treatment with antioxidants α-tocopherol and ascorbic acid significantly reduced the cytotoxicity of the extract (P<0.05). DCFH-DA assay revealed that treatment with EADs attenuated the generation of intracellular ROS. Apoptosis induced by EADs was not inhibited by the use of caspase-inhibitor Z-VAD-FMK, suggesting that the cell death is caspase-independent. The use of JC-1 dye reflected that EADs caused disruption in the mitochondrial membrane potential. The related molecular pathways involved in EADs-induced apoptosis were determined by GeXP multiplex system and Western blot analysis. EADs is postulated to induce cell cycle arrest that is p53- and p21-dependent based on the upregulated expression of p53 and p21 (P<0.05). The expression of Bax was upregulated with downregulation of Bcl-2 following treatment with EADs. The elevated Bax/Bcl-2 ratio and the depolarization of mitochondrial membrane potential suggest that EADs-induced apoptosis is mitochondria-dependent. The expression of oxidative stress-related AKT, p-AKT, ERK, and p-ERK was downregulated with upregulation of JNK and p-JNK. The data indicate that induction of oxidative-stress related apoptosis by EADs was mediated by inhibition of AKT and ERK, and activation of JNK. The isolation of compounds in EADs was carried out using column chromatography and elucidated using the nuclear resonance magnetic analysis producing a total of six compounds including 3-epimaslinic acid, kaempferol, kaempferide, protocatechuic

  8. Induction of Apoptosis in MCF-7 Cells via Oxidative Stress Generation, Mitochondria-Dependent and Caspase-Independent Pathway by Ethyl Acetate Extract of Dillenia suffruticosa and Its Chemical Profile

    PubMed Central

    Tor, Yin Sim; Yazan, Latifah Saiful; Foo, Jhi Biau; Wibowo, Agustono; Ismail, Norsharina; Cheah, Yoke Kqueen; Abdullah, Rasedee; Ismail, Maznah; Ismail, Intan Safinar; Yeap, Swee Keong

    2015-01-01

    Dillenia suffruticosa, which is locally known as Simpoh air, has been traditionally used to treat cancerous growth. The ethyl acetate extract of D. suffruticosa (EADs) has been shown to induce apoptosis in MCF-7 breast cancer cells in our previous study. The present study aimed to elucidate the molecular mechanisms involved in EADs-induced apoptosis and to identify the major compounds in the extract. EADs was found to promote oxidative stress in MCF-7 cells that led to cell death because the pre-treatment with antioxidants α-tocopherol and ascorbic acid significantly reduced the cytotoxicity of the extract (P<0.05). DCFH-DA assay revealed that treatment with EADs attenuated the generation of intracellular ROS. Apoptosis induced by EADs was not inhibited by the use of caspase-inhibitor Z-VAD-FMK, suggesting that the cell death is caspase-independent. The use of JC-1 dye reflected that EADs caused disruption in the mitochondrial membrane potential. The related molecular pathways involved in EADs-induced apoptosis were determined by GeXP multiplex system and Western blot analysis. EADs is postulated to induce cell cycle arrest that is p53- and p21-dependent based on the upregulated expression of p53 and p21 (P<0.05). The expression of Bax was upregulated with downregulation of Bcl-2 following treatment with EADs. The elevated Bax/Bcl-2 ratio and the depolarization of mitochondrial membrane potential suggest that EADs-induced apoptosis is mitochondria-dependent. The expression of oxidative stress-related AKT, p-AKT, ERK, and p-ERK was downregulated with upregulation of JNK and p-JNK. The data indicate that induction of oxidative-stress related apoptosis by EADs was mediated by inhibition of AKT and ERK, and activation of JNK. The isolation of compounds in EADs was carried out using column chromatography and elucidated using the nuclear resonance magnetic analysis producing a total of six compounds including 3-epimaslinic acid, kaempferol, kaempferide, protocatechuic

  9. Solar-terrestrial coupling: Solar soft X-rays and thermospheric nitric oxide

    NASA Astrophysics Data System (ADS)

    Barth, Charles A.; Bailey, Scott M.; Solomon, Stanley C.

    Simultaneous measurements were made of the solar soft x-ray irradiances and the thermospheric nitric oxide density in the tropics from the Student Nitric Oxide Explorer (SNOE) satellite. The analysis of these observations for 44 days of low geomagnetic activity in the spring of 1998 show that there is a correlation between the solar soft x-ray irradiances and thermospheric nitric oxide densities in the tropics. Photochemical model calculations that used the measured solar soft x-ray irradiances as input parameters adequately reproduce the magnitude of the time-varying component of the thermospheric nitric oxide in the tropics. An additional amount of nitric oxide is present in the tropics that does not vary with the time period of the solar rotation. The conclusion of this analysis is that solar soft x-rays are the primary cause of the variation in the thermospheric nitric oxide densities in the tropics during times of low geomagnetic activity.

  10. Distant electric coupling between nitrate reduction and sulphide oxidation investigated by an improved nitrate microscale biosensor

    NASA Astrophysics Data System (ADS)

    Marzocchi, U.; Revsbech, N. P.; Nielsen, L. P.; Risgaard-Petersen, N.

    2012-04-01

    Bacteria are apparently able to transmit electrons to other bacteria (Summers et al. 2010) or to electrodes (Malvankar et al. 2011) by some kind of nanowires (Reguera et al. 2005, Gorbi et al. 2006). Lately it has been shown that such transfer may occur over distances of centimetres in sediments, thereby coupling sulphide oxidation in deeper layers with oxygen reduction near the surface (Nielsen 2011). The finding of these long-distance electrical connections originated from analysis of O2, H2S, and pH profiles measured with microsensors. Nitrate is thermodynamically almost as good an electron acceptor as O2, and we therefore set up an experiment to investigate whether long-distance electron transfer also happens with NO3-. Aquaria were filled with sulphidic marine sediment from Aarhus Bay that was previously used to show long-distance electron transfer to O2. The aquaria were equipped with a lid so that they could be completely filled without a gas phase. Anoxic seawater with 300 μM NO3- was supplied at a constant rate resulting in a steady state concentration in the aquatic phase of 250 μM NO3-. The reservoir with the nitrate-containing water was kept anoxic by bubbling it with a N2/CO2 mixture and was kept at an elevated temperature. The water was cooled on the way to the aquaria to keep the water in the aquaria undersaturated with gasses, so that bubble formation by denitrification in the sediment could be minimised. Profiles of NO3-, H2S, and pH were measured as a function of time (2 months) applying commercial sensors for H2S and pH and an improved microscale NO3- biosensor developed in our laboratory. The penetration of NO3- in the sediment was 4-5 mm after 2 months, whereas sulphide only could be detected below 8-9 mm depth. The electron acceptor and electron donor were thus separated by 4-5 mm, indicating long distance electron transfer. A pH maximum of about 8.6 pH units at the NO3- reduction zone similar to a pH maximum observed in the O2 reduction

  11. Microbial Reduction of Fe(III) in Acidic Sediments: Isolation of Acidiphilium cryptum JF-5 Capable of Coupling the Reduction of Fe(III) to the Oxidation of Glucose

    PubMed Central

    Küsel, Kirsten; Dorsch, Tanja; Acker, Georg; Stackebrandt, Erko

    1999-01-01

    To evaluate the microbial populations involved in the reduction of Fe(III) in an acidic, iron-rich sediment, the anaerobic flow of supplemental carbon and reductant was evaluated in sediment microcosms at the in situ temperature of 12°C. Supplemental glucose and cellobiose stimulated the formation of Fe(II); 42 and 21% of the reducing equivalents that were theoretically obtained from glucose and cellobiose, respectively, were recovered in Fe(II). Likewise, supplemental H2 was consumed by acidic sediments and yielded additional amounts of Fe(II) in a ratio of approximately 1:2. In contrast, supplemental lactate did not stimulate the formation of Fe(II). Supplemental acetate was not consumed and inhibited the formation of Fe(II). Most-probable-number estimates demonstrated that glucose-utilizing acidophilic Fe(III)-reducing bacteria approximated to 1% of the total direct counts of 4′,6-diamidino-2-phenylindole-stained bacteria. From the highest growth-positive dilution of the most-probable-number series at pH 2.3 supplemented with glucose, an isolate, JF-5, that could dissimilate Fe(III) was obtained. JF-5 was an acidophilic, gram-negative, facultative anaerobe that completely oxidized the following substrates via the dissimilation of Fe(III): glucose, fructose, xylose, ethanol, glycerol, malate, glutamate, fumarate, citrate, succinate, and H2. Growth and the reduction of Fe(III) did not occur in the presence of acetate. Cells of JF-5 grown under Fe(III)-reducing conditions formed blebs, i.e., protrusions that were still in contact with the cytoplasmic membrane. Analysis of the 16S rRNA gene sequence of JF-5 demonstrated that it was closely related to an Australian isolate of Acidiphilium cryptum (99.6% sequence similarity), an organism not previously shown to couple the complete oxidation of sugars to the reduction of Fe(III). These collective results indicate that the in situ reduction of Fe(III) in acidic sediments can be mediated by heterotrophic Acidiphilium

  12. Simultaneous removal and degradation characteristics of sulfonamide, tetracycline, and quinolone antibiotics by laccase-mediated oxidation coupled with soil adsorption.

    PubMed

    Ding, Huijun; Wu, Yixiao; Zou, Binchun; Lou, Qian; Zhang, Weihao; Zhong, Jiayou; Lu, Lei; Dai, Guofei

    2016-04-15

    The uses of laccase in the degradation and removal of antibiotics have recently been reported because of the high efficiency and environmental friendliness of laccase. However, these removal studies mostly refer to a limited number of antibiotics. In this study, soil adsorption was introduced into the laccase-oxidation system to assist the simultaneous removal of 14 kinds of sulfonamide, tetracycline, and quinolone antibiotics, which differed in structures and chemical properties. The complementary effects of laccase-mediated oxidation and soil adsorption enabled the simultaneous removal. Removal characteristics were determined by a comprehensive consideration of the separate optimum conditions for laccase oxidation and soil adsorption removal experiments. With concentrations of laccase, syringaldehyde (SA), and soil of 0.5mg/mL, 0.5mmol/L, and 50g/L, respectively, and at pH 6 and 25°C, the removal rates of each antibiotic exceeded 70% in 15min and were close to 100% in 180min. Sulfonamide antibiotics (SAs) were removed mainly by laccase oxidation and quinolone antibiotics (QUs) mainly by soil adsorption. Tetracycline antibiotics (TCs) were removed by both treatments in the coupled system, but laccase oxidation dominated. Electrostatic adsorption was speculated to be one of the adsorption mechanisms in soil adsorption with QUs and TCs. PMID:26826938

  13. Indium-zinc-oxide electric-double-layer thin-film transistors gated by silane coupling agents 3-triethoxysilylpropylamine-graphene oxide solid electrolyte

    NASA Astrophysics Data System (ADS)

    Guo, Liqiang; Huang, Yukai; Shi, Yangyang; Cheng, Guanggui; Ding, Jianning

    2015-07-01

    Silane coupling agents 3-triethoxysilylpropyla-mine-graphene oxide (KH550-GO) solid electrolyte are prepared by spin coating process. A high proton conductivity of ~1.2   ×   10-3 Scm-1 is obtained at room temperature. A strong electric-double-layer (EDL) effect is observed due to the accumulation of protons at KH550-GO/IZO interface. Indium-Zinc-Oxide thin film transistors gated by KH550-GO solid electrolyte are self-assembled on ITO glass substrates. Good electrical performances are obtained, such as a low subthreshold swing of ~140 mV/dec., a high current on/off ratio of ~2.9   ×   107 and a high field-effect mobility of ~13.2 cm2 V-1 S-1, respectively.

  14. Linalyl Acetate Is Metabolized by Pseudomonas incognita with the Acetoxy Group Intact

    PubMed Central

    Renganathan, V.; Madyastha, K. Madhava

    1983-01-01

    Metabolism of linalyl acetate by Pseudomonas incognita isolated by enrichment culture on the acyclic monoterpene alcohol linalool was studied. Biodegradation of linalyl acetate by this strain resulted in the formation of linalool, linalool-8-carboxylic acid, oleuropeic acid, and Δ5-4-acetoxy-4-methyl hexenoic acid. Cells adapted to linalyl acetate metabolized linalyl acetate-8-aldehyde to linalool-8-carboxylic acid, linalyl acetate-8-carboxylic acid, Δ5-4-acetoxy-4-methyl hexenoic acid, and geraniol-8-carboxylic acid. Resting cell suspensions previously grown with linalyl acetate oxidized linalyl acetate-8-aldehyde to linalyl acetate-8-carboxylic acid, Δ5-4-acetoxy-4-methyl hexenoic acid, and pyruvic acid. The crude cell-free extract (10,000 g of supernatant), obtained from the sonicate of linalyl acetate-grown cells, was shown to contain enzyme systems responsible for the formation of linalyl acetate-8-carboxylic acid and linalool-8-carboxylic acid from linalyl acetate. The same supernatant contained NAD-linked alcohol and aldehyde dehydrogenases involved in the formation of linalyl acetate-8-aldehyde and linalyl acetate-8-carboxylic acid, respectively. On the basis of various metabolites isolated from the culture medium, resting cell experiments, growth and manometric studies carried out with the isolated metabolites as well as related synthetic analogs, and the preliminary enzymatic studies performed with the cell-free extract, a probable pathway for the microbial degradation of linalyl acetate with the acetoxy group intact is suggested. PMID:16346182

  15. Coupling of Dimethylsulfide Oxidation to Biomass Production by a Marine Flavobacterium▿

    PubMed Central

    Green, David H.; Shenoy, Damodar M.; Hart, Mark C.; Hatton, Angela D.

    2011-01-01

    Dimethylsulfide (DMS) is an important climatically active gas. In the sea, DMS is produced primarily by microbial metabolism of the compatible solute dimethylsulfoniopropionate. Laboratory growth of Bacteroidetes with DMS resulted in its oxidation to dimethyl sulfoxide but only in the presence of glucose. We hypothesized that electrons liberated from sulfur oxidation were used to augment biomass production. PMID:21378049

  16. The Stabilized Cation Pool Method: Metal- and Oxidant-Free Benzylic C-H/Aromatic C-H Cross-Coupling.

    PubMed

    Hayashi, Ryutaro; Shimizu, Akihiro; Yoshida, Jun-Ichi

    2016-07-13

    Electrochemical oxidation of toluene derivatives in the presence of a sulfilimine gave benzylaminosulfonium ions as stabilized benzyl cation pools, which reacted with subsequently added aromatic nucleophiles to give the corresponding cross-coupling products. The transformation serves as a powerful metal- and chemical-oxidant-free method for benzylic C-H/aromatic C-H cross-coupling. The method has been successfully applied to synthesis of TP27, an inhibitor of PTPase. PMID:27341676

  17. Coupling Ferroelectricity with Spin-Valley Physics in Oxide-Based Heterostructures

    NASA Astrophysics Data System (ADS)

    Yamauchi, Kunihiko; Barone, Paolo; Shishidou, Tatsuya; Oguchi, Tamio; Picozzi, Silvia

    2015-07-01

    The coupling of spin and valley physics is nowadays regarded as a promising route toward next-generation spintronic and valleytronic devices. In the aim of engineering functional properties for valleytronic applications, we focus on the ferroelectric heterostructure BiAlO3/BiIrO3 , where the complex interplay among a trigonal crystal field, layer degrees of freedom, and spin-orbit coupling mediates a strong spin-valley coupling. Furthermore, we show that ferroelectricity provides a nonvolatile handle to manipulate and switch the emerging valley-contrasting spin polarization.

  18. Metal-Free Oxidation of Primary Amines to Nitriles through Coupled Catalytic Cycles.

    PubMed

    Lambert, Kyle M; Bobbitt, James M; Eldirany, Sherif A; Kissane, Liam E; Sheridan, Rose K; Stempel, Zachary D; Sternberg, Francis H; Bailey, William F

    2016-04-01

    Synergism among several intertwined catalytic cycles allows for selective, room temperature oxidation of primary amines to the corresponding nitriles in 85-98 % isolated yield. This metal-free, scalable, operationally simple method employs a catalytic quantity of 4-acetamido-TEMPO (ACT; TEMPO=2,2,6,6-tetramethylpiperidine N-oxide) radical and the inexpensive, environmentally benign triple salt oxone as the terminal oxidant under mild conditions. Simple filtration of the reaction mixture through silica gel affords pure nitrile products. PMID:26868873

  19. Photoelectrocatalytic/photoelectro-Fenton coupling system using a nanostructured photoanode for the oxidation of a textile dye: Kinetics study and oxidation pathway.

    PubMed

    Almeida, Lucio C; Silva, Bianca F; Zanoni, Maria V B

    2015-10-01

    In this study, a coupled photoelectrocatalytic/photoelectro-Fenton reactor was designed to enhance the degradation efficiency of organic pollutants and tested using the azo dye Orange G as a model compound. Pt-decorated TiO2 nanotubes were used as a photoanode with an air-diffusion polytetrafluoroethylene cathode for H2O2 generation. The sum of individual effects of coupling the photoelectrocatalytic and photoelectro-Fenton processes was evaluated as a function of the decolorization and mineralization of Orange G solutions. The dye solutions were only completely decolorized in more acidic conditions (pH 3.0). The mineralization of the Orange G solutions increased in the sequence photoelectrocatalyticcoupled photoelectrocatalytic/photoelectro-Fenton due to the gradual increase in the production of OH radicals. Total organic carbon reductions of 80% for photoelectrocatalysis, 87% for electro-Fenton and 97% for the coupled processes were obtained when using an applied electric charge per unit volume of electrolyzed solution of 200 mA h L(-1). The Orange G decays for all treatments followed pseudo-first-order kinetics, suggesting the attack of a constant concentration of OH radicals. Aromatics such as naphthalenic and benzenic compounds were formed as by-products and were identified using LC-MS/MS analysis. In addition, the generated aliphatic acids were identified using ion-exclusion high-performance liquid chromatography. The final by-products of oxalic and formic acid were identified as ultimate by-products and formed Fe(III) complexes that were rapidly mineralized to CO2 by UV-Vis irradiation. Then, according to the identified oxidation by-products, a plausible pathway was proposed for the degradation of Orange G dye by the coupled process. PMID:25935699

  20. Palladium(II) Catalyzed Cyclization-Carbonylation-Cyclization Coupling Reaction of (ortho-Alkynyl Phenyl) (Methoxymethyl) Sulfides Using Molecular Oxygen as the Terminal Oxidant.

    PubMed

    Shen, Rong; Kusakabe, Taichi; Yatsu, Tomofumi; Kanno, Yuichiro; Takahashi, Keisuke; Nemoto, Kiyomitsu; Kato, Keisuke

    2016-01-01

    An efficient Pd(II)/Pd⁰-p-benzoquinone/hydroquinone-CuCl₂/CuCl catalyst system was developed that uses environmentally friendly molecular oxygen as the terminal oxidant to catalyze the cyclization-carbonylation-cyclization coupling reaction (CCC-coupling reaction) of (o-alkynyl phenyl) (methoxymethyl) sulfides. PMID:27607997

  1. The Efficacy of Oxidative Coupling for Promoting In-Situ Immobilization of Hydroxylated Aromatics in Contaminated Soil and Sediments Systems - Final Report

    SciTech Connect

    Weber Jr., W. J.

    2000-10-01

    The study clearly shows that the structure and composition of the organic matter of soils and sediments are essential considerations for the selection of materials for engineered applications of oxidative coupling processes. A rate model was developed to facilitate quantitative evaluation and mechanistic interpretation of these fairly complex coupling processes.

  2. Carbon-coated magnetic palladium: applications in partial oxidation of alcohols and coupling reactions.

    EPA Science Inventory

    Magnetic carbon supported Pd catalyst has been synthesized via in situ generation of nanoferrites and incorporation of carbon from renewable cellulose via calcination; catalyst can be used for oxidation of alcohols, amination reaction and arylation of aryl halides (cross coupli...

  3. Solar-powered electrochemical oxidation of organic compounds coupled with the cathodic production of molecular hydrogen.

    PubMed

    Park, Hyunwoong; Vecitis, Chad D; Hoffmann, Michael R

    2008-08-21

    A Bi-doped TiO2 anode, which is prepared from a mixed metal oxide coating deposited on Ti metal, is shown to be efficient for conventional water splitting. In this hybrid photovoltaic-electrochemical system, a photovoltaic (PV) cell is used to convert solar light to electricity, which is then used to oxidize a series of phenolic compounds at the semiconductor anode to carbon dioxide with the simultaneous production of molecular hydrogen from water/proton reduction at the stainless steel cathode. Degradation of phenol in the presence of a background NaCl electrolyte produces chlorinated phenols as reaction intermediates, which are subsequently oxidized completely to carbon dioxide and low-molecular weight carboxylic acids. The anodic current efficiency for the complete oxidation of phenolic compounds ranges from 3% to 17%, while the cathodic current efficiency and the energy efficiency for hydrogen gas generation range from 68% to 95% and 30% to 70%, respectively. PMID:18656909

  4. Demonstrating Advanced Oxidation Coupled with Biodegradation for Removal of Carbamazepine (WERF Report INFR6SG09)

    EPA Science Inventory

    Carbamazepine is an anthropogenic pharmaceutical found in wastewater effluents that is quite resistant to removal by conventional wastewater treatment processes. Hydroxyl radical-based advanced oxidation processes can transform carbamazepine into degradation products but cannot m...

  5. Critical Role for Tetrahydrobiopterin Recycling by Dihydrofolate Reductase in Regulation of Endothelial Nitric-oxide Synthase Coupling

    PubMed Central

    Crabtree, Mark J.; Tatham, Amy L.; Hale, Ashley B.; Alp, Nicholas J.; Channon, Keith M.

    2009-01-01

    Tetrahyrobiopterin (BH4) is a required cofactor for the synthesis of nitric oxide by endothelial nitric-oxide synthase (eNOS), and BH4 bioavailability within the endothelium is a critical factor in regulating the balance between NO and superoxide production by eNOS (eNOS coupling). BH4 levels are determined by the activity of GTP cyclohydrolase I (GTPCH), the rate-limiting enzyme in de novo BH4 biosynthesis. However, BH4 levels may also be influenced by oxidation, forming 7,8-dihydrobiopterin (BH2), which promotes eNOS uncoupling. Conversely, dihydrofolate reductase (DHFR) can regenerate BH4 from BH2, but the functional importance of DHFR in maintaining eNOS coupling remains unclear. We investigated the role of DHFR in regulating BH4 versus BH2 levels in endothelial cells and in cell lines expressing eNOS combined with tet-regulated GTPCH expression in order to compare the effects of low or high levels of de novo BH4 biosynthesis. Pharmacological inhibition of DHFR activity by methotrexate or genetic knockdown of DHFR protein by RNA interference reduced intracellular BH4 and increased BH2 levels resulting in enzymatic uncoupling of eNOS, as indicated by increased eNOS-dependent superoxide but reduced NO production. In contrast to the decreased BH4:BH2 ratio induced by DHFR knockdown, GTPCH knockdown greatly reduced total biopterin levels but with no change in BH4:BH2 ratio. In cells expressing eNOS with low biopterin levels, DHFR inhibition or knockdown further diminished the BH4:BH2 ratio and exacerbated eNOS uncoupling. Taken together, these data reveal a key role for DHFR in eNOS coupling by maintaining the BH4:BH2 ratio, particularly in conditions of low total biopterin availability. PMID:19666465

  6. Salicylic acid degradation by advanced oxidation processes. Coupling of solar photoelectro-Fenton and solar heterogeneous photocatalysis.

    PubMed

    Garza-Campos, Benjamin; Brillas, Enric; Hernández-Ramírez, Aracely; El-Ghenymy, Abdellatif; Guzmán-Mar, Jorge Luis; Ruiz-Ruiz, Edgar J

    2016-12-01

    A 3.0 L solar flow plant with a Pt/air-diffusion (anode/cathode) cell, a solar photoreactor and a photocatalytic photoreactor filled with TiO2-coated glass spheres has been utilized to couple solar photoelectro-Fenton (SPEF) and solar heterogeneous photocatalysis (SPC) for treating a 165mgL(-1) salicylic acid solution of pH 3.0. Organics were destroyed by OH radicals formed on the TiO2 photocatalyst and at the Pt anode during water oxidation and in the bulk from Fenton's reaction between added Fe(2+) and cathodically generated H2O2, along with the photolytic action of sunlight. Poor salicylic acid removal and mineralization were attained using SPC, anodic oxidation with electrogenerated H2O2 (AO-H2O2) and coupled AO-H2O2-SPC. The electro-Fenton process accelerated the substrate decay, but with low mineralization by the formation of byproducts that are hardly destroyed by OH. The mineralization was strongly increased by SPEF due to the photolysis of products by sunlight, being enhanced by coupled SPEF-SPC due to the additional oxidation by OH at the TiO2 surface. The effect of current density on the performance of both processes was examined. The most potent SPEF-SPC process at 150mAcm(-2) yielded 87% mineralization and 13% current efficiency after consuming 6.0AhL(-1). Maleic, fumaric and oxalic acids detected as final carboxylic acids were completely removed by SPEF and SPEF-SPC. PMID:26947802

  7. Direct preparation of N-quaternized and N-oxidized polycyclic azines by palladium-catalyzed cross-coupling. An unequivocal isomer synthesis

    SciTech Connect

    Zoltewicz, J.A.; Cruskie, M.P. Jr.; Dill, C.D.

    1995-01-13

    The authors report several examples of unequivocal isomer preparations using palladium-catalyzed cross-coupling to yield N-oxides and N-quaternized polycyclic azines. This approach serves as a model for such syntheses where selective N-quaternization, N-oxidation, or other types of N-functionalization of several rings is now possible in a regioncontrolled manner.

  8. Rapid synthesis of an electron-deficient t-BuPHOX ligand: cross-coupling of aryl bromides with secondary phosphine oxides.

    PubMed

    McDougal, Nolan T; Streuff, Jan; Mukherjee, Herschel; Virgil, Scott C; Stoltz, Brian M

    2010-10-20

    Herein an efficient and direct copper-catalyzed coupling of oxazoline-containing aryl bromides with electron-deficient secondary phosphine oxides is reported. The resulting tertiary phosphine oxides can be reduced to prepare a range of PHOX ligands. The presented strategy is a useful alternative to known methods for constructing PHOX derivatives. PMID:21076623

  9. Proton-Conducting Graphene Oxide-Coupled Neuron Transistors for Brain-Inspired Cognitive Systems.

    PubMed

    Wan, Chang Jin; Zhu, Li Qiang; Liu, Yang Hui; Feng, Ping; Liu, Zhao Ping; Cao, Hai Liang; Xiao, Peng; Shi, Yi; Wan, Qing

    2016-05-01

    Proton-conducting graphene oxide electrolyte films with very high electric-double-layer capacitance are used as the gate dielectrics for oxide-based neuron transistor fabrication. Paired-pulse facilitation, dendritic integration, and orientation tuning are successfully emulated. Additionally, neuronal gain controls (arithmetic) are also experimentally demonstrated. The results provide a new-concept approach for building brain-inspired cognitive systems. PMID:26972820

  10. Weak coupling BCS-like superconductivity in the pnictide oxide Ba1-xNaxTi2Sb2O

    NASA Astrophysics Data System (ADS)

    Lorenz, B.; Gooch, M.; Doan, P.; Tang, Z.; Guloy, A. M.; Chu, C. W.

    2014-03-01

    We report the results of low-temperature heat capacity measurements of the pnictide oxide superconductor BaTi2Sb2O and the optimally Na-doped compound Na0.15Ba0.85Ti2Sb2O. Temperature- and field-dependent heat capacity data are well described by a single-gap BCS theory. The estimated values for the normal-state Sommerfeld constant, the heat capacity jump at Tc, and the electron-phonon coupling constant are in favor of a conventional weak coupling superconductivity, possibly mediated by electron-phonon interaction. The results are discussed with regard to and compared with recent first-principles calculations. Supported by the DOE, the AFOSR, the T.L.L. Temple Foundation, the J.J. and R. Moores Endowment, and the State of Texas through TCSUH.

  11. Three-dimensional fully-coupled electrical and thermal transport model of dynamic switching in oxide memristors

    SciTech Connect

    Gao, Xujiao; Mamaluy, Denis; Mickel, Patrick R.; Marinella, Matthew

    2015-09-08

    In this paper, we present a fully-coupled electrical and thermal transport model for oxide memristors that solves simultaneously the time-dependent continuity equations for all relevant carriers, together with the time-dependent heat equation including Joule heating sources. The model captures all the important processes that drive memristive switching and is applicable to simulate switching behavior in a wide range of oxide memristors. The model is applied to simulate the ON switching in a 3D filamentary TaOx memristor. Simulation results show that, for uniform vacancy density in the OFF state, vacancies fill in the conduction filament till saturation, and then fill out a gap formed in the Ta electrode during ON switching; furthermore, ON-switching time strongly depends on applied voltage and the ON-to-OFF current ratio is sensitive to the filament vacancy density in the OFF state.

  12. Three-dimensional fully-coupled electrical and thermal transport model of dynamic switching in oxide memristors

    DOE PAGESBeta

    Gao, Xujiao; Mamaluy, Denis; Mickel, Patrick R.; Marinella, Matthew

    2015-09-08

    In this paper, we present a fully-coupled electrical and thermal transport model for oxide memristors that solves simultaneously the time-dependent continuity equations for all relevant carriers, together with the time-dependent heat equation including Joule heating sources. The model captures all the important processes that drive memristive switching and is applicable to simulate switching behavior in a wide range of oxide memristors. The model is applied to simulate the ON switching in a 3D filamentary TaOx memristor. Simulation results show that, for uniform vacancy density in the OFF state, vacancies fill in the conduction filament till saturation, and then fill outmore » a gap formed in the Ta electrode during ON switching; furthermore, ON-switching time strongly depends on applied voltage and the ON-to-OFF current ratio is sensitive to the filament vacancy density in the OFF state.« less

  13. Hydrogen Evolution from Water Coupled with the Oxidation of As(III) in a Photocatalytic System.

    PubMed

    Zou, Jian-Ping; Wu, Dan-Dan; Bao, Shao-Kui; Luo, Jinming; Luo, Xu-Biao; Lei, Si-Liang; Liu, Hui-Long; Du, Hong-Mei; Luo, Sheng-Lian; Au, Chak-Tong; Suib, Steven L

    2015-12-30

    A series of heterostructured CdS/Sr2(Nb17/18Zn1/18)2O7-δ composites with excellent photocatalytic ability for simultaneous hydrogen evolution and As(III) oxidation under simulated sunlight were synthesized and characterized. Among them, 30% CdS/Sr2(Nb17/18Zn1/18)2O7-δ (30CSNZO) has the highest in activity, exhibiting a H2 production rate of 1669.1 μmol·h(-1)·g(-1) that is higher than that of many photocatalysts recently reported in the literature. At pH 9, As(III) is completely oxidized to As(V) over 30CSNZO in 30 min of irradiation of simulated sunlight. In the photocatalytic system, H2 production rate decreases with the increase of As(III) concentration, and the recycle experiments show that 30CSNZO exhibits excellent stability, durability, and recyclability for photocatalytic hydrogen evolution and As(III) oxidation. We propose a mechanism in which superoxide radical (·O2(-)) is the active species for As(III) oxidation and the oxidation of As(III) has an effect on hydrogen evolution. For the first time, it is demonstrated that simultaneous hydrogen evolution and arsenite oxidation is possible in a photocatalytic system. PMID:26650610

  14. Oxide Etch Behavior in an Inductively Coupled C4F8 Discharge Characterized by Diode Laser Spectroscopy.

    NASA Astrophysics Data System (ADS)

    Anderson, Harold; Barela, Marcus; Courtin, Geoff; Waters, Karla

    2001-10-01

    This study reports on oxide and photoresist etch characteristics in an inductively coupled GEC Reference Cell as a function of reactor source power, bias power and pressure using C4F8. Diode laser absorption spectroscopy (DLAS) has shown that C4F8 is largely dissociated to form C2F4, CF2 and CF in the discharge. Over an oxide surface, CF2 and CF are consumed in the oxide etch process, but only when the bias power is sufficient to keep the oxide surface clean through energetic ion bombardment. For C4F8, this transition occurs at 60 eV (75 W bias power) in the GEC Cell. At higher bias powers (125 W) where oxide etching is fast ( 600 nm/min.), CF2 appears to be the key radical for the etch process since 50 percent (2.7-3.0 mTorr in a 15 mTorr C4F8 discharge) is consumed. These values were obtained by comparing the CF2 concentrations over non-reactive wafer surfaces versus blanket oxide wafer surfaces undergoing etching. CF is shown to display a similar trend, but its concentration is an order of magnitude less than CF2, and consequently cannot account on a mass basis for the amount of reactants necessary to balance the amount of etch products. Over a PR surface, neither CF2 nor CF concentrations vary as a function of PR etch rate. Consequently, they do not appear to be involved in the PR etch mechanism. However, PR etching is also critically dependent on bias power. PR films etch presumably due to energetic ion bombardment that degrades the PR film, making it liable to attack by fluorine.

  15. Regiodivergent Cross-Dehydrogenative Coupling of Pyridines and Benzoxazoles: Discovery of Organic Halides as Regio-Switching Oxidants.

    PubMed

    Yamada, Shuya; Murakami, Kei; Itami, Kenichiro

    2016-05-20

    Cross-dehydrogenative coupling (CDC) of two unfunctionalized heteroarenes has been recognized as an ideal transformation to synthesize privileged heterobiaryl scaffolds. However, regioselective activation and transformation of a specific set of two heterocyclic C-H bonds among other bonds have been extremely challenging. Thus, discovering a new controlling element to achieve regio-controlled and regio-divergent heterocyclic CDCs is considered crucial. In this Letter, the unprecedented use of organic halides as an oxidant to achieve the CDC reaction of pyridines and benzoxazoles with palladium catalyst is described. Moreover, the regioselectivity of the pyridine functionalization site can be controlled by the choice of organic halides. PMID:27162109

  16. Mechanistic study of copper-catalyzed aerobic oxidative coupling of arylboronic esters and methanol: insights into an organometallic oxidase reaction.

    PubMed

    King, Amanda E; Brunold, Thomas C; Stahl, Shannon S

    2009-04-15

    Copper-catalyzed aerobic oxidative coupling of arylboronic acid derivatives and heteroatom nucleophiles is a highly useful method for the formation of aryl-heteroatom bonds. Mechanistic studies reveal that this reaction proceeds via an "oxidase"-style mechanism. Kinetic and spectroscopic studies establish that transmetalation of the aryl group from boron to Cu(II) is the turnover-limiting step and reoxidation of the reduced catalyst by O(2) is rapid. Further mechanistic analysis implicates the involvement of an aryl-copper(III) intermediate that undergoes facile C-O bond formation. PMID:19309072

  17. Methane oxidation coupled to nitrate reduction under hypoxia by the Gammaproteobacterium Methylomonas denitrificans, sp. nov. type strain FJG1.

    PubMed

    Kits, K Dimitri; Klotz, Martin G; Stein, Lisa Y

    2015-09-01

    Obligate methanotrophs belonging to the Phyla Proteobacteria and Verrucomicrobia require oxygen for respiration and methane oxidation; nevertheless, aerobic methanotrophs are abundant and active in low oxygen environments. While genomes of some aerobic methanotrophs encode putative nitrogen oxide reductases, it is not understood whether these metabolic modules are used for NOx detoxification, denitrification or other purposes. Here we demonstrate using microsensor measurements that a gammaproteobacterial methanotroph Methylomonas denitrificans sp. nov. strain FJG1(T) couples methane oxidation to nitrate reduction under oxygen limitation, releasing nitrous oxide as a terminal product. Illumina RNA-Seq data revealed differential expression of genes encoding a denitrification pathway previously unknown to methanotrophs as well as the pxmABC operon in M. denitrificans sp. nov. strain FJG1(T) in response to hypoxia. Physiological and transcriptome data indicate that genetic inventory encoding the denitrification pathway is upregulated only upon availability of nitrate under oxygen limitation. In addition, quantitation of ATP levels demonstrates that the denitrification pathway employs inventory such as nitrate reductase NarGH serving M. denitrificans sp. nov. strain FJG1(T) to conserve energy during oxygen limitation. This study unravelled an unexpected metabolic flexibility of aerobic methanotrophs, thereby assigning these bacteria a new role at the metabolic intersection of the carbon and nitrogen cycles. PMID:25580993

  18. Mechanistic studies on a Cu-catalyzed aerobic oxidative coupling reaction with N-phenyl tetrahydroisoquinoline: structure of intermediates and the role of methanol as a solvent.

    PubMed

    Boess, Esther; Sureshkumar, Devarajulu; Sud, Abhishek; Wirtz, Cornelia; Farès, Christophe; Klussmann, Martin

    2011-06-01

    The mechanism of an aerobic copper-catalyzed oxidative coupling reaction with N-phenyl tetrahydroisoquinoline was investigated. The oxidized species formed from the reaction of the amine with the copper catalyst were analyzed by NMR-spectroscopy. An iminium dichlorocuprate was found to be the reactive intermediate and could be structurally characterized by X-ray crystallography. The effect of methanol to effectively stabilize the iminium ion was investigated and shown to be beneficial in an oxidative allylation reaction. PMID:21561084

  19. Nitrogen isotope fractionation during archaeal ammonia oxidation: Coupled estimates from isotopic measurements of ammonium and nitrite

    NASA Astrophysics Data System (ADS)

    Mooshammer, Maria; Stieglmeier, Michaela; Bayer, Barbara; Jochum, Lara; Melcher, Michael; Wanek, Wolfgang

    2014-05-01

    Ammonia-oxidizing archaea (AOA) are ubiquitous in marine and terrestrial environments and knowledge about the nitrogen (N) isotope effect associated with their ammonia oxidation activity will allow a better understanding of natural abundance isotope ratios, and therefore N transformation processes, in the environment. Here we examine the kinetic isotope effect for ammonia oxidation in a pure soil AOA culture (Ca. Nitrososphaera viennensis) and a marine AOA enrichment culture. We estimated the isotope effect from both isotopic signatures of ammonium and nitrite over the course of ammonia oxidation. Estimates of the isotope effect based on the change in the isotopic signature of ammonium give valuable insight, because these estimates are not subject to the same concerns (e.g., accumulation of an intermediate) as estimates based on isotopic measurements of nitrite. Our results show that both the pure soil AOA culture and a marine AOA enrichment culture have similar but substantial isotope effect during ammonia consumption (31-34 per mill; based on ammonium) and nitrite production (43-45 per mill; based on nitrite). The 15N fractionation factors of both cultures tested fell in the upper range of the reported isotope effects for archaeal and bacterial ammonia oxidation (10-41 per mill) or were even higher than those. The isotope fractionation for nitrite production was significantly larger than for ammonium consumption, indicating that (1) some intermediate (e.g., hydroxylamine) of ammonia oxidation accumulates, allowing for a second 15N fractionation step to be expressed, (2) a fraction of ammonia oxidized is lost via gaseous N forms (e.g., NO or N2O), which is 15N-enriched or (3) a fraction of ammonium is assimilated into AOA biomass, biomass becoming 15N-enriched. The significance of these mechanisms will be explored in more detail for the soil AOA culture, based on isotope modeling and isotopic measurements of biomass and N2O.

  20. Facile hydrolysis and alcoholysis of palladium acetate.

    PubMed

    Bedford, Robin B; Bowen, John G; Davidson, Russell B; Haddow, Mairi F; Seymour-Julen, Annabelle E; Sparkes, Hazel A; Webster, Ruth L

    2015-05-26

    Palladium(II) acetate is readily converted into [Pd3 (μ(2) -OH)(OAc)5 ] (1) in the presence of water in a range of organic solvents and is also slowly converted in the solid state. Complex 1 can also be formed in nominally anhydrous solvents. Similarly, the analogous alkoxide complexes [Pd3 (μ(2) -OR)(OAc)5 ] (3) are easily formed in solutions of palladium(II) acetate containing a range of alcohols. An examination of a representative Wacker-type oxidation shows that the Pd-OH complex 1 and a related Pd-oxo complex 4 can be excluded as potential catalytic intermediates in the absence of exogenous water. PMID:25865439

  1. [Nomegestrol acetate: clinical pharmacology].

    PubMed

    Lello, S

    2009-10-01

    Progestogens are used in clinical practice in some conditions. Their effects depend on their chemical structure, pharmacokinetics, pharmacodynamics, with important differences among various progestogens. Generally, progestins are classified according to their parent molecule, of which often they keep some features. Derivatives of 19-nor-progesterone are characterized by high selectivity of action on progestin receptor. In particular, nomegestrol acetate (NomAc) shows an important progestational potency, neutral gluco-lipid profile, and antigonadotropic activity. It is used for treating menstrual cycle disorders and for hormone replacement therapy in menopause in association with an estrogen. In future, thanks to its antigonadotropic activity, NomAc will be used in estroprogestin combinations in fertile women, thus taking advantage of its tolerability profile and obtaining numerous non-contraceptive benefits as well. PMID:19749678

  2. Bioinspired syntheses of dimeric hydroxycinnamic acids (lignans) and hybrids, using phenol oxidative coupling as key reaction, and medicinal significance thereof.

    PubMed

    Magoulas, George E; Papaioannou, Dionissios

    2014-01-01

    Lignans are mainly dimers of 4-hydroxycinnamic acids (HCAs) and reduced analogs thereof which are produced in Nature through phenol oxidative coupling (POC) as the primary C-C or C-O bond-forming reaction under the action of the enzymes peroxidases and laccases. They present a large structural variety and particularly interesting biological activities, therefore, significant efforts has been devoted to the development of efficient methodologies for the synthesis of lignans isolated from natural sources, analogs and hybrids with other biologically interesting small molecules. We summarize in the present review those methods which mimic Nature for the assembly of the most common lignan skeleta by using either enzymes or one-electron inorganic oxidants to effect POC of HCAs and derivatives, such as esters and amides, or cross-POC of pairs of HCAs or HCAs with 4-hydrocycinnamyl alcohols. We, furthermore, provide outlines of mechanistic schemes accounting for the formation of the coupled products and, where applicable, indicate their potential application in medicine. PMID:25460307

  3. Reaction-based colorimetric signaling of Cu(2+) ions by oxidative coupling of phenols with 4-aminoantipyrine.

    PubMed

    Kim, Hong Yeong; Lee, Hyo Jin; Chang, Suk-Kyu

    2015-01-01

    A new Cu(2+)-selective chromogenic probe system based on the oxidative coupling of phenols with 4-aminoantipyrine was developed. Cu(2+) ions promoted facile coupling of phenols with 4-aminoantipyrine to yield quinoneimine dyes. Signaling with a number of phenols having no para-substituent, such as o-cresol and m-cresol, as well as p-chlorophenol having para substituent that could be expelled during the oxidation process was possible. The signaling of Cu(2+) ions was not interfered by the presence of representative metal ions except for Al(3+) ions. The possible interference from Al(3+) ions was successfully removed by using fluoride ions as a masking agent. The phenol-4-aminoantipyrine probe system showed chromogenic Cu(2+) signaling by prominent color change from colorless to pink with a detection limit of 8.5×10(-7) M. The signaling of Cu(2+) ions in practical samples using tap water and simulated semiconductor wastewater was also tested. PMID:25476354

  4. Overcoming Heterogeneity Effects Through Polymer-Enhanced Groundwater Remediation Techniques: Coupling Polymer Floods with Chemical Oxidants and Bio-agents

    NASA Astrophysics Data System (ADS)

    Smith, M. M.; Silva, J. A.; Munakata-Marr, J.; McCray, J. E.

    2008-12-01

    Even small heterogeneity contrasts in contaminated systems (resulting from differences in permeability or contaminant saturation) can affect the distribution of injected remediation agents by channeling fluids through high-permeability flowpaths, thus bypassing some regions and leaving contaminants uncontacted. The addition of a viscous polymer solution to the remediation agent may enhance agent delivery as a result of increased cross-flow (or "sweep efficiency") into different layers of the system, if the polymer solution remains stable in the presence of the remediation agent. Our research combines various non-toxic, food- grade polymer solutions with the remediation techniques of chemical oxidation and bio-remediation, to increase the effectiveness of treatment at sites contaminated with non-aqueous phase liquids (NAPLs). The coupling of polymer floods with oxidants may help to combat contaminant "rebound" sometimes associated with incomplete contaminant destruction in low-permeability zones. Initial compatibility testing has shown that certain robust polymer/oxidant mixtures possess stable viscosities and pose low additional oxidant demands over multi-day timescales. Transport of these solutions through natural porous media was studied in column experiments, and small two-dimensional experiments with heterogeneous layering were conducted to assess effectiveness of contaminant destruction. Limitations of these compatible polymer/oxidant combinations as well as possible experimental strategies to optimize delivery are also discussed. In addition, results of polymer/microbial screening tests reveal that polymer solutions do not inhibit the dechlorinating capabilities of a microbial consortium. Preliminary findings have also raised the possibility that certain polymers may successfully serve as electron donors in the subsurface. The implications of these results for either bioaugmentation or delivery of biostimulants are presented.

  5. Palladium-catalyzed dehydrogenation/oxidative cross-coupling sequence of β-heteroatom-substituted ketones.

    PubMed

    Moon, Youngtaek; Kwon, Daeil; Hong, Sungwoo

    2012-11-01

    Concise and selective: the title one-pot sequence allows formation of the enone functionality and subsequent cross-coupling. The process provides access to highly functionalized cyclic enolones and enaminones from readily accessible β-heteroatom-substituted cyclic ketones. PMID:23038616

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

    NASA Astrophysics Data System (ADS)

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

    2011-09-01

    Plutonium-uranium mixed oxide (MOX) fuels are currently used in nuclear reactors. The potential differences of metal redox state and microstructural developments of the matrix before and after irradiation are commonly analysed by electron probe microanalysis. In this work the structure and next-neighbor atomic environments of Pu and U oxide features within unirradiated homogeneous MOX and irradiated (60 MW d kg -1) MOX samples was analysed by micro-X-ray fluorescence (μ-XRF), micro-X-ray diffraction (μ-XRD) and micro-X-ray absorption fine structure (μ-XAFS) spectroscopy. The grain properties, chemical bonding, valences and stoichiometry of Pu and U are determined from the experimental data gained for the unirradiated as well as for irradiated fuel material examined in the center of the fuel as well as in its peripheral zone (rim). The formation of sub-grains is observed as well as their development from the center to the rim (polygonization). In the irradiated sample Pu remains tetravalent (>95%) and no (<5%) Pu(V) or Pu(VI) can be detected while the fuel could undergo slight oxidation in the rim zone. Any slight potential plutonium oxidation is buffered by the uranium dioxide matrix while locally fuel cladding interaction could also affect the redox of the fuel.

  7. Chiral Brønsted Acid Catalyzed Enantioselective Phosphonylation of Allylamine via Oxidative Dehydrogenation Coupling.

    PubMed

    Cheng, Ming-Xing; Ma, Ran-Song; Yang, Qiang; Yang, Shang-Dong

    2016-07-01

    A new strategy for the synthesis of chiral α-amino phosphonates by enantioselective C-H phosphonylation of allylamine with phosphite in the presence of a chiral Brønsted acid catalyst has been developed. This protocol successfully integrates direct C-H oxidation with asymmetric phosphonylation and exhibits high enantioselectivity. PMID:27331612

  8. Size determination and quantification of engineered cerium oxide nanoparticles by flow field-flow fractionation coupled to inductively coupled plasma mass spectrometry.

    PubMed

    Sánchez-García, L; Bolea, E; Laborda, F; Cubel, C; Ferrer, P; Gianolio, D; da Silva, I; Castillo, J R

    2016-03-18

    Facing the lack of studies on characterization and quantification of cerium oxide nanoparticles (CeO2 NPs), whose consumption and release is greatly increasing, this work proposes a method for their sizing and quantification by Flow Field-flow Fractionation (FFFF) coupled to Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). Two modalities of FFFF (Asymmetric Flow- and Hollow Fiber-Flow Field Flow Fractionation, AF4 and HF5, respectively) are compared, and their advantages and limitations discussed. Experimental conditions (carrier composition, pH, ionic strength, crossflow and carrier flow rates) are studied in detail in terms of NP separation, recovery, and repeatability. Size characterization of CeO2 NPs was addressed by different approaches. In the absence of feasible size standards of CeO2 NPs, suspensions of Ag, Au, and SiO2 NPs of known size were investigated. Ag and Au NPs failed to show a comparable behavior to that of the CeO2 NPs, whereas the use of SiO2 NPs provided size estimations in agreement to those predicted by the theory. The latter approach was thus used for characterizing the size of CeO2 NPs in a commercial suspension. Results were in adequate concordance with those achieved by transmission electron microscopy, X-ray diffraction and dynamic light scattering. The quantification of CeO2 NPs in the commercial suspension by AF4-ICP-MS required the use of a CeO2 NPs standards, since the use of ionic cerium resulted in low recoveries (99±9% vs. 73±7%, respectively). A limit of detection of 0.9μgL(-1) CeO2 corresponding to a number concentration of 1.8×1012L(-1) for NPs of 5nm was achieved for an injection volume of 100μL. PMID:26903472

  9. Surface coordination number and surface redox couples on catalyst oxides, a new approach of the interpretation of activity and selectivity III. Interpretation of chemical and catalytic oxidation reactions on some oxides

    NASA Astrophysics Data System (ADS)

    Arnaud, Y. P.

    The concepts of surface coordination number n, and of surface redox couples MO [ n] /MO ( n+1) presented previously, are exploited to explain experimental results. Two cases are considered: reactions of chemical gaseous species such as CO, CO 2, H 2, H 2O,N 2O, propene and methanol on the surface of the oxides NiO, TiO 2, and Cr 2O 3, in the absence of oxygen: activated catalytic reactions of oxygen on reductive species such as CO, H 2,C 2H 6, and CH 3OH. The knowledge of the potential of surface redox couples permits a rationalization of the study of these reactions. The efficiency of the two concepts is obvious in many cases. For example, the origin of an athermal oxidative process occurring for the oxidations of CO or H 2 on TiO 2 is easily understood, as well as those of the poisoning of the catalysts or of the inactivity of a surface saturated by oxygen. In addition, the study of chemical reactions on the oxides confirms and completes the theoretical approach used. Particularly, the existence of the surface states, which are postulated in the case of Cr 2O 3, is corroborated by experimental observations concerning the number of surface states and the value of the chemical potentials. Even though the theory is based upon thermodynamical and structural data, it also leads to a better understanding of kinetic features.

  10. Metallic nanoparticle shape and size effects on aluminum oxide-induced enhancement of exciton-plasmon coupling and quantum dot emission

    SciTech Connect

    Wing, Waylin J.; Sadeghi, Seyed M. Gutha, Rithvik R.; Campbell, Quinn; Mao, Chuanbin

    2015-09-28

    We investigate the shape and size effects of gold metallic nanoparticles on the enhancement of exciton-plasmon coupling and emission of semiconductor quantum dots induced via the simultaneous impact of metal-oxide and plasmonic effects. This enhancement occurs when metallic nanoparticle arrays are separated from the quantum dots by a layered thin film consisting of a high index dielectric material (silicon) and aluminum oxide. Our results show that adding the aluminum oxide layer can increase the degree of polarization of quantum dot emission induced by metallic nanorods by nearly two times, when these nanorods have large aspect ratios. We show when the aspect ratio of these nanorods is reduced to half, the aluminum oxide loses its impact, leading to no improvement in the degree of polarization. These results suggest that a silicon/aluminum oxide layer can significantly enhance exciton-plasmon coupling when quantum dots are in the vicinity of metallic nanoantennas with high aspect ratios.

  11. Metallic nanoparticle shape and size effects on aluminum oxide-induced enhancement of exciton-plasmon coupling and quantum dot emission

    NASA Astrophysics Data System (ADS)

    Wing, Waylin J.; Sadeghi, Seyed M.; Gutha, Rithvik R.; Campbell, Quinn; Mao, Chuanbin

    2015-09-01

    We investigate the shape and size effects of gold metallic nanoparticles on the enhancement of exciton-plasmon coupling and emission of semiconductor quantum dots induced via the simultaneous impact of metal-oxide and plasmonic effects. This enhancement occurs when metallic nanoparticle arrays are separated from the quantum dots by a layered thin film consisting of a high index dielectric material (silicon) and aluminum oxide. Our results show that adding the aluminum oxide layer can increase the degree of polarization of quantum dot emission induced by metallic nanorods by nearly two times, when these nanorods have large aspect ratios. We show when the aspect ratio of these nanorods is reduced to half, the aluminum oxide loses its impact, leading to no improvement in the degree of polarization. These results suggest that a silicon/aluminum oxide layer can significantly enhance exciton-plasmon coupling when quantum dots are in the vicinity of metallic nanoantennas with high aspect ratios.

  12. Lateral-coupling coplanar-gate oxide-based thin-film transistors on bare paper substrates

    NASA Astrophysics Data System (ADS)

    Wu, Guodong; Wan, Xiang; Yang, Yi; Jiang, Shuanghe

    2014-11-01

    For conventional thin-film transistors (TFTs), bottom-gate or top-gate configuration is always adopted because the channel current is generally controlled by vertical capacitive coupling. In this article, depending on huge lateral electric-double-layer (EDL) capacitor induced by spatial movement of protons in phosphosilicate glass (PSG) solid electrolyte dielectrics, coplanar-gate indium-zinc-oxide (IZO)-TFTs based on the lateral capacitive coupling were fabricated on bare paper substrates. The PSG solid electrolyte films here were used at the same time as gate dielectrics and smooth buffer layers. These TFTs showed a low-voltage operation of only 1 V with a large field-effect mobility of 13.4 cm2 V-1·s, a high current on/off ratio of 6  ×  106 and a small subthreshold swing of 75 mV/decade. Furthermore, with introducing another coplanar gate, AND logic operation was also demonstrated on the coplanar dual-gate TFTs. These simple lateral-coupling coplanar-gate IZO-TFTs on bare paper substrates are very promising for low-cost portable sensors and bio-electronics.

  13. Pd loaded amphiphilic COF as catalyst for multi-fold Heck reactions, C-C couplings and CO oxidation

    PubMed Central

    Mullangi, Dinesh; Nandi, Shyamapada; Shalini, Sorout; Sreedhala, Sheshadri; Vinod, Chathakudath P.; Vaidhyanathan, Ramanathan

    2015-01-01

    COFs represent a class of polymers with designable crystalline structures capable of interacting with active metal nanoparticles to form excellent heterogeneous catalysts. Many valuable ligands/monomers employed in making coordination/organic polymers are prepared via Heck and C-C couplings. Here, we report an amphiphilic triazine COF and the facile single-step loading of Pd0 nanoparticles into it. An 18–20% nano-Pd loading gives highly active composite working in open air at low concentrations (Conc. Pd(0) <0.05 mol%, average TON 1500) catalyzing simultaneous multiple site Heck couplings and C-C couplings using ‘non-boronic acid’ substrates, and exhibits good recyclability with no sign of catalyst leaching. As an oxidation catalyst, it shows 100% conversion of CO to CO2 at 150 °C with no loss of activity with time and between cycles. Both vapor sorptions and contact angle measurements confirm the amphiphilic character of the COF. DFT-TB studies showed the presence of Pd-triazine and Pd-Schiff bond interactions as being favorable. PMID:26057044

  14. Design of a visible light driven photo-electrochemical/electro-Fenton coupling oxidation system for wastewater treatment.

    PubMed

    Ding, Xing; Ai, Zhihui; Zhang, Lizhi

    2012-11-15

    In this study, we report on a photo-electrochemical/electro-Fenton oxidation (PEC/EF) system by coupling visible light driven photo-electrochemical oxidation (PEC) and electro-Fenton oxidation (EF) in an undivided cell. Bi2WO6 nanoplates deposited on FTO glass (Bi2WO6/FTO) and Fe@Fe2O3 core-shell nanowires supported on activated carbon fiber (Fe@Fe2O3/ACF) were used as the anode and the cathode in the PEC/EF system, respectively. This novel PEC/EF system showed much higher activity than the single PEC and EF systems on degradation of rhodamine B in aqueous solution at natural pH. Moreover, the degradation and the instantaneous current efficiencies of the PEC/EF system were increased by 154% and 26% in comparison with the sum of those of single PEC and EF systems, respectively. These significant enhancements could be attributed to the synergetic effect from better separation of photo-generated carriers in the photo-anode and the transfer of photo-electrons to the oxygen diffusion cathode to generate more electro-generated H2O2 and hydroxyl radicals on the Fenton cathode. The better separation of photo-generated carriers contribute more to the overall degradation enhancement than the photo-electrons generated H2O2 and the subsequent Fenton reaction on the cathode during the PEC/EF process. PMID:23017238

  15. 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. PMID:27121982

  16. Activated carbon electrodes: electrochemical oxidation coupled with desalination for wastewater treatment.

    PubMed

    Duan, Feng; Li, Yuping; Cao, Hongbin; Wang, Yi; Crittenden, John C; Zhang, Yi

    2015-04-01

    The wastewater usually contains low-concentration organic pollutants and some inorganic salts after biological treatment. In the present work, the possibility of simultaneous removal of them by combining electrochemical oxidation and electrosorption was investigated. Phenol and sodium chloride were chosen as representative of organic pollutants and inorganic salts and a pair of activated carbon plate electrodes were used as anode and cathode. Some important working conditions such as oxygen concentration, applied potential and temperature were evaluated to reach both efficient phenol removal and desalination. Under optimized 2.0 V of applied potential, 38°C of temperature, and 500 mL min(-1) of oxygen flow, over 90% of phenol, 60% of TOC and 20% of salinity were removed during 300 min of electrolysis time. Phenol was removed by both adsorption and electrochemical oxidation, which may proceed directly or indirectly by chlorine and hypochlorite oxidation. Chlorophenols were detected as degradation intermediates, but they were finally transformed to carboxylic acids. Desalination was possibly attributed to electrosorption of ions in the pores of activated carbon electrodes. The charging/regeneration cycling experiment showed good stability of the electrodes. This provides a new strategy for wastewater treatment and recycling. PMID:25585871

  17. Hepatic gluconeogenesis influences (13)C enrichment in lactate in human brain tumors during metabolism of [1,2-(13)C]acetate.

    PubMed

    Pichumani, Kumar; Mashimo, Tomoyuki; Vemireddy, Vamsidhara; Kovacs, Zoltan; Ratnakar, James; Mickey, Bruce; Malloy, Craig R; DeBerardinis, Ralph J; Bachoo, Robert M; Maher, Elizabeth A

    2016-07-01

    (13)C-enriched compounds are readily metabolized in human malignancies. Fragments of the tumor, acquired by biopsy or surgical resection, may be acid-extracted and (13)C NMR spectroscopy of metabolites such as glutamate, glutamine, 2-hydroxyglutarate, lactate and others provide a rich source of information about tumor metabolism in situ. Recently we observed (13)C-(13)C spin-spin coupling in (13)C NMR spectra of lactate in brain tumors removed from patients who were infused with [1,2-(13)C]acetate prior to the surgery. We found, in four patients, that infusion of (13)C-enriched acetate was associated with synthesis of (13)C-enriched glucose, detectable in plasma. (13)C labeled glucose derived from [1,2-(13)C]acetate metabolism in the liver and the brain pyruvate recycling in the tumor together lead to the production of the (13)C labeled lactate pool in the brain tumor. Their combined contribution to acetate metabolism in the brain tumors was less than 4.0%, significantly lower than the direct oxidation of acetate in the citric acid cycle in tumors. PMID:27020407

  18. An efficient proton-coupled electron-transfer process during oxidation of ferulic acid by horseradish peroxidase: coming full cycle.

    PubMed

    Derat, Etienne; Shaik, Sason

    2006-10-25

    Quantum mechanics/molecular mechanics calculations were utilized to study the process of oxidation of a native substrate (ferulic acid) by the active species of horseradish peroxidase (Dunford, H. B. Heme Peroxidases; Wiley-VCH: New York, 1999), Compound I and Compound II, and the manner by which the enzyme returns to its resting state. The results match experimental findings and reveal additional novel features. The calculations demonstrate that both oxidation processes are initiated by a proton-coupled electron-transfer (PCET) step, in which the active species of the enzyme participate only as electron-transfer partners, while the entire proton-transfer event is being relayed from the substrate to and from the His42 residue by a water molecule (W402). The reason for the observed (Henriksen, A; Smith, A. T.; Gajhede, M. J. Biol. Chem. 1999, 274, 35005-35011) similar reactivities of Compound I and Compound II toward ferulic acid is that the reactive isomer of Compound II is the, hitherto unobserved, Por(*)(+)Fe(III)OH isomer that resembles Compound I. The PCET mechanism reveals that His42 and W402 are crucial moieties and they determine the function of the HRP enzyme and account for its ability to perform substrate oxidation (Poulos, T. L. Peroxidases and Cytochrome P450. In The Porphyrin Handbook; Kadish, K. M., Smith, K. M., Guilard, R., Eds.; Academic Press: New York, 2000; Vol. 4, pp 189). In view of the results, the possibility of manipulating substrate oxidation by magnetic fields is an intriguing possibility. PMID:17044722

  19. Experimental study of the hydrothermal reactivity of organic acids and acid anions: II. Acetic acid, acetate, and valeric acid

    NASA Astrophysics Data System (ADS)

    McCollom, Thomas M.; Seewald, Jeffrey S.

    2003-10-01

    Organic acids and acid anions occur in substantial concentrations in many aqueous geologic fluids and are thought to take part in a variety of geochemical processes ranging from the transport of metals in ore-forming fluids to the formation of natural gas to serving as a metabolic energy source for microbes in subsurface habitats. The widespread occurrence of organic acids and their potential role in diverse geologic processes has led to numerous experimental studies of their thermal stability, yet there remain substantial gaps in our knowledge of the factors that control the rates and reaction pathways for the decomposition of these compounds under geologic conditions. In order to address some of these uncertainties, a series of laboratory experiments were conducted to examine the behavior of organic acids and acid anions under hydrothermal conditions in the presence of minerals. Reported here are results of experiments where aqueous solutions of acetic acid, sodium acetate, or valeric acid ( n-pentanoic acid) were heated at 325°C, 350 bars in the presence of the mineral assemblages hematite + magnetite + pyrite, pyrite + pyrrhotite + magnetite, and hematite + magnetite. The results indicate that aqueous acetic acid and acetate decompose by a combination of two reaction pathways: decarboxylation and oxidation. Both reactions are promoted by minerals, with hematite catalyzing the oxidation reaction while magnetite catalyzes decarboxylation. The oxidation reaction is much faster, so that oxidation dominates the decomposition of acetic acid and acetate when hematite is present. In contrast to previous reports that acetate decomposed more slowly than acetic acid, we found that acetate decomposed at slightly faster rates than the acid in the presence of minerals. Although longer-chain monocarboxylic acids are generally thought to decompose by decarboxylation, valeric acid appeared to decompose primarily by "deformylation" to 1-butene plus formic acid. Subsequent

  20. Production date determination of uranium-oxide materials by inductively coupled plasma mass spectrometry.

    PubMed

    Varga, Zsolt; Surányi, Gergely

    2007-09-01

    The paper describes analytical methods developed for the production date determination of uranium-based nuclear materials by the measurement of 230Th/234U isotope ratio. An improved sample preparation method for the destructive analysis involving extraction chromatographic separation with TEVA resin was applied prior to the measurement by isotope dilution inductively coupled plasma sector field mass spectrometry (ICP-SFMS). The results obtained were compared with the direct, quasi-non-destructive measurement using laser ablation ICP-SFMS technique for age determination. The advantages and limitations of both methods are discussed. PMID:17765059

  1. Nitrous Oxide as a Hydrogen Acceptor for the Dehydrogenative Coupling of Alcohols.

    PubMed

    Gianetti, Thomas L; Annen, Samuel P; Santiso-Quinones, Gustavo; Reiher, Markus; Driess, Matthias; Grützmacher, Hansjörg

    2016-01-26

    The oxidation of alcohols with N2O as the hydrogen acceptor was achieved with low catalyst loadings of a rhodium complex that features a cooperative bis(olefin)amido ligand under mild conditions. Two different methods enable the formation of either the corresponding carboxylic acid or the ester. N2 and water are the only by-products. Mechanistic studies supported by DFT calculations suggest that the oxygen atom of N2O is transferred to the metal center by insertion into the Rh-H bond of a rhodium amino hydride species, generating a rhodium hydroxy complex as a key intermediate. PMID:26693955

  2. Strong interlayer coupling mediated giant two-photon absorption in MoS e2 /graphene oxide heterostructure: Quenching of exciton bands

    NASA Astrophysics Data System (ADS)

    Sharma, Rituraj; Aneesh, J.; Yadav, Rajesh Kumar; Sanda, Suresh; Barik, A. R.; Mishra, Ashish Kumar; Maji, Tuhin Kumar; Karmakar, Debjani; Adarsh, K. V.

    2016-04-01

    A complex few-layer MoS e2 /graphene oxide (GO) heterostructure with strong interlayer coupling was prepared by a facile hydrothermal method. In this strongly coupled heterostructure, we demonstrate a giant enhancement of two-photon absorption that is in stark contrast to the reverse saturable absorption of a weakly coupled MoS e2 /GO heterostructure and saturable absorption of isolated MoS e2 . Spectroscopic evidence of our study indicates that the optical signatures of isolated MoS e2 and GO domains are significantly modified in the heterostructure, displaying a direct coupling of both domains. Furthermore, our first-principles calculations indicate that strong interlayer coupling between the layers dramatically suppresses the MoS e2 excitonic bands. We envision that our findings provide a powerful tool to explore different optical functionalities as a function of interlayer coupling, which may be essential for the development of device technologies.

  3. Phenol coupling initiated by one-electron oxidation of tyrosine units in peptides and histone.

    PubMed

    Prütz, W A; Butler, J; Land, E J

    1983-08-01

    Phenoxyl radicals generated pulse radiolytically by the reaction of N.3 with Gly-Tyr decay biomolecularly (2k = 4.7 X 10(8)M-1 s-1) with efficient formation of 2,2'-dimers, which enolize rapidly (k = 2.7 X 10(4) s-1) to produce the 2,2'-biphenolic product. The build-up of the characteristic 2,2'-biphenol fluorescence (400 nm) and absorption also indicated a delayed (k = 80 s-1) process, probably involving the phenoxyl <-> phenoxy-quinol equilibrium. About 60 per cent of the Gly-Tyr phenoxyls were found to dimerize to the 2,2'-biphenol, and a similarly efficient 2,2'-coupling seems to occur with other tyrosyls, such as Lys-Tyr-Lys and histone. gamma-Radiolysis was applied to estimate relative yields of formation of 2,2'-biphenols under various conditions. Dimerization is almost completely inhibited by cysteine or oxygen, consistent with phenoxyl 'repair' by cysteine or O-.2; disproportionation of O-.2 with SOD prevents repair. The phenol 2,2'-coupling is less efficient for .OH- and inefficient for e-aq-initiation. PMID:6603438

  4. Bioactive glass coupling with natural polyphenols: Surface modification, bioactivity and anti-oxidant ability

    NASA Astrophysics Data System (ADS)

    Cazzola, Martina; Corazzari, Ingrid; Prenesti, Enrico; Bertone, Elisa; Vernè, Enrica; Ferraris, Sara

    2016-03-01

    Polyphenols are actually achieving an increasing interest due to their potential health benefits, such as antioxidant, anticancer, antibacterial and bone stimulation abilities. However their poor bioavailability and stability hamper an effective clinical application as therapeutic principles. The opportunity to couple these biomolecules with synthetic biomaterials, in order to obtain local delivery at the site of interest, improve their bioavailability and stability and combine their properties with the ones of the substrate, is a challenging opportunity for the biomedical research. A silica based bioactive glass, CEL2, has been successfully coupled with gallic acid and natural polyphenols extracted from red grape skins and green tea leaves. The effectiveness of grafting has been verified by means of XPS analyses and the Folin&Ciocalteu tests. In vitro bioactivity has been investigated by soaking in simulated body fluid (SBF). Surface modification after functionalization and early stage reactivity in SBF have been studied by means of zeta potential electrokinetic measurements in KCl and SBF. Finally the antioxidant properties of bare and modified bioactive glasses has been investigated by means of the evaluation of free radical scavenging activity by Electron Paramagnetic Resonance (EPR)/spin trapping technique after UV photolysis of H2O2 highlighting scavenging activity of the bioactive glass.

  5. Methanogens couple anaerobic Fe(O) oxidation and CHCl{sub 3} reduction

    SciTech Connect

    Weathres, L.J.; Parkin, G.F.; Novak, P.J.; Alvarez, P.J.J.

    1995-12-01

    Recent studies have shown that chlorinated aliphatic hydrocarbons (CAHs) may be reduced by metallic iron. These studies have focused on abiotic processes, while limited attention has been given to combined microbial and abiotic dechlorination. Methanogenic bacteria can use metallic iron as an energy source, by coupling the anodic dissolution of iron with the consumption of water-derived hydrogen. Hence, under methanogenic conditions in the presence of zero-valent iron, two degradation mechanisms may be important Fe(O) may reduce CAHs abiotically, and Fe(O) may indirectly reduce CAHs via biodehalogenation. Our results using steel wool and methanogenic cell suspension indicate that methanogens coupled the biocorrosion of iron metal and biodehalogenation of CHCl{sub 3} via cometabolism, with water-derived hydrogen acting as energy source. This work demonstrates that, at least under specific conditions, biodehalogenation dominates abiotic mechanisms in aqueous systems containing zero-valent g iron. Further work is required to determine if these results are sustainable in flow-through environments.

  6. Application of FIGAERO (Filter Inlet for Gases and AEROsol) coupled to a high resolution time of flight chemical ionization mass spectrometer to field and chamber organic aerosol: Implications for carboxylic acid formation and gas-particle partitioning from monoterpene oxidation

    NASA Astrophysics Data System (ADS)

    Lopez-Hilfiker, F.; Mohr, C.; Ehn, M.; Rubach, F.; Mentel, T. F.; Kleist, E.; Wildt, J.; Thornton, J. A.

    2013-12-01

    We present measurements of a large suite of gas and particle phase carboxylic acid containing compounds made with a Filter Inlet for Gas and AEROsol (FIGAERO) coupled to a high resolution time of flight chemical ionization mass spectrometer (HR-ToF-CIMS) developed at the University of Washington. A prototype operated with acetate negative ion proton transfer chemistry was deployed on the Julich Plant Atmosphere Chamber to study a-pinene oxidation, and a modified version was deployed at the SMEAR II forest station in Hyytiälä, Finland and SOAS, in Brent Alabama. We focus here on results from JPAC and Hyytiälä, where we utilized the same ionization method most selective towards carboxylic acids. In all locations, 100's of organic acid compounds were observed in the gas and particles and many of the same composition acids detected in the gas-phase were detected in the particles upon temperature programmed thermal desorption. Particulate organics detected by FIGAERO are highly correlated with organic aerosol mass measured by an AMS, providing additional volatility and molecular level information about collected aerosol. The fraction of a given compound measured in the particle phase follows expected trends with elemental composition, but many compounds would not be well described by an absorptive partitioning model assuming unity activity coefficients. Moreover the detailed structure in the thermal desorption signals reveals a contribution from thermal decomposition of large molecular weight organics and or oligomers with implications for partitioning measurements and model validation

  7. An Alignment Medium for Measuring Residual Dipolar Couplings in Pure DMSO: Liquid Crystals from Graphene Oxide Grafted with Polymer Brushes.

    PubMed

    Zong, Wen; Li, Gao-Wei; Cao, Jiang-Ming; Lei, Xinxiang; Hu, Mao-Lin; Sun, Han; Griesinger, Christian; Tan, Ren Xiang

    2016-03-01

    Residual dipolar couplings (RDCs) have attracted attention in light of their great impact on the structural elucidation of organic molecules. However, the effectiveness of RDC measurements is limited by the shortage of alignment media compatible with widely used organic solvents, such as DMSO. Herein, we present the first liquid crystal (LC) based alignment medium that is compatible with pure DMSO, thus enabling RDC measurements of polar and intermediate polarity molecules. The liquid crystals were obtained by grafting polymer brushes onto graphene oxide (GO) using free radical polymerization. The resulting new medium offers several advantages, such as absence of background signals, narrow line shapes, and tunable alignment. Importantly, this medium is compatible with π-conjugated molecules. Moreover, sonication-induced fragmentation can reduce the size of GO sheets. The resulting anisotropic medium has moderate alignment strength, which is a prerequisite for an accurate RDC measurement. PMID:26890579

  8. Doped Mott Insulators in (111) Bilayers of Perovskite Transition-Metal Oxides with a Strong Spin-Orbit Coupling

    SciTech Connect

    Okamoto, Satoshi

    2013-01-01

    The electronic properties of Mott insulators realized in (111) bilayers of perovskite transition-metal oxides are studied. The low-energy effective Hamiltonians for such Mott insulators are derived in the presence of a strong spin-orbit coupling. These models are characterized by the antiferromagnetic Heisenberg interaction and the anisotropic interaction whose form depends on the $d$ orbital occupancy. From exact diagonalization analyses on finite clusters, the ground state phase diagrams are derived, including a Kitaev spin liquid phase in a narrow parameter regime for $t_{2g}$ systems. Slave-boson mean-field analyses indicate the possibility of novel superconducting states induced by carrier doping into the Mott-insulating parent systems, suggesting the present model systems as unique playgrounds for studying correlation-induced novel phenomena. Possible experimental realizations are also discussed.

  9. Thermo-economic modeling of an indirectly coupled solid oxide fuel cell/gas turbine hybrid power plant

    NASA Astrophysics Data System (ADS)

    Cheddie, Denver F.; Murray, Renique

    Power generation using gas turbine (GT) power plants operating on the Brayton cycle suffers from low efficiencies, resulting in poor fuel to power conversion. A solid oxide fuel cell (SOFC) is proposed for integration into a 10 MW gas turbine power plant, operating at 30% efficiency, in order to improve system efficiencies and economics. The SOFC system is indirectly coupled to the gas turbine power plant, paying careful attention to minimize the disruption to the GT operation. A thermo-economic model is developed for the hybrid power plant, and predicts an optimized power output of 20.6 MW at 49.9% efficiency. The model also predicts a break-even per-unit energy cost of USD 4.65 ¢ kWh -1 for the hybrid system based on futuristic mass generation SOFC costs. This shows that SOFCs may be indirectly integrated into existing GT power systems to improve their thermodynamic and economic performance.

  10. Surface modification of organic polymers with bioactive titanium oxide without the aid of a silane-coupling agent.

    PubMed

    Balas, F; Kokubo, T; Kawashita, M; Nakamura, T

    2007-06-01

    Polyethylene (PE), polyethylene terephthalate (PET), ethylene-vinyl alcohol copolymer (EVOH), and poly(epsilon-caprolactam) (Nylon 6) were successfully modified with a thin crystalline titanium oxide layer on their surfaces by a simple dipping into a titanium alkoxide solution and a subsequent soak in hot HCl solution, without the aid of a silane-coupling agent. The surface modified polymers formed a bone-like apatite layer in a simulated body fluid (SBF) within a period of 2 days. PE, PET, and Nylon 6 formed an apatite layer faster and had a higher adhesive strength to the apatite. Three-dimensional fabrics with open spaces in various sizes containing such surface modified polymer fibers are expected to be useful as bone substitutes, since they may be able to form apatite on their constituent fibers in the living body, and thus, integrate with living bone. PMID:17277978

  11. Inorganic proton conducting electrolyte coupled oxide-based dendritic transistors for synaptic electronics

    NASA Astrophysics Data System (ADS)

    Wan, Chang Jin; Zhu, Li Qiang; Zhou, Ju Mei; Shi, Yi; Wan, Qing

    2014-04-01

    Ionic/electronic hybrid devices with synaptic functions are considered to be the essential building blocks for neuromorphic systems and brain-inspired computing. Here, artificial synapses based on indium-zinc-oxide (IZO) transistors gated by nanogranular SiO2 proton-conducting electrolyte films are fabricated on glass substrates. Spike-timing dependent plasticity and paired-pulse facilitation are successfully mimicked in an individual bottom-gate transistor. Most importantly, dynamic logic and dendritic integration established by spatiotemporally correlated spikes are also mimicked in dendritic transistors with two in-plane gates as the presynaptic input terminals.Ionic/electronic hybrid devices with synaptic functions are considered to be the essential building blocks for neuromorphic systems and brain-inspired computing. Here, artificial synapses based on indium-zinc-oxide (IZO) transistors gated by nanogranular SiO2 proton-conducting electrolyte films are fabricated on glass substrates. Spike-timing dependent plasticity and paired-pulse facilitation are successfully mimicked in an individual bottom-gate transistor. Most importantly, dynamic logic and dendritic integration established by spatiotemporally correlated spikes are also mimicked in dendritic transistors with two in-plane gates as the presynaptic input terminals. Electronic supplementary information (ESI) available: The structures and transfer characteristics of the IZO junctionless transistor working in bottom-gate mode and in-plane gate mode. See DOI: 10.1039/c3nr05882d

  12. Sequential reductive and oxidative biodegradation of chloroethenes stimulated in a coupled bioelectro-process.

    PubMed

    Lohner, Svenja T; Becker, Dirk; Mangold, Klaus-Michael; Tiehm, Andreas

    2011-08-01

    This article for the first time demonstrates successful application of electrochemical processes to stimulate sequential reductive/oxidative microbial degradation of perchloroethene (PCE) in mineral medium and in contaminated groundwater. In a flow-through column system, hydrogen generation at the cathode supported reductive dechlorination of PCE to cis-dichloroethene (cDCE), vinyl chloride (VC), and ethene (ETH). Electrolytically generated oxygen at the anode allowed subsequent oxidative degradation of the lower chlorinated metabolites. Aerobic cometabolic degradation of cDCE proved to be the bottleneck for complete metabolite elimination. Total removal of chloroethenes was demonstrated for a PCE load of approximately 1.5 μmol/d. In mineral medium, long-term operation with stainless steel electrodes was demonstrated for more than 300 days. In contaminated groundwater, corrosion of the stainless steel anode occurred, whereas DSA (dimensionally stable anodes) proved to be stable. Precipitation of calcareous deposits was observed at the cathode, resulting in a higher voltage demand and reduced dechlorination activity. With DSA and groundwater from a contaminated site, complete degradation of chloroethenes in groundwater was obtained for two months thus demonstrating the feasibility of the sequential bioelectro-approach for field application. PMID:21678913

  13. Glutamate Utilization Couples Oxidative Stress Defense and the Tricarboxylic Acid Cycle in Francisella Phagosomal Escape

    PubMed Central

    Ramond, Elodie; Gesbert, Gael; Rigard, Mélanie; Dairou, Julien; Dupuis, Marion; Dubail, Iharilalao; Meibom, Karin; Henry, Thomas; Barel, Monique; Charbit, Alain

    2014-01-01

    Intracellular bacterial pathogens have developed a variety of strategies to avoid degradation by the host innate immune defense mechanisms triggered upon phagocytocis. Upon infection of mammalian host cells, the intracellular pathogen Francisella replicates exclusively in the cytosolic compartment. Hence, its ability to escape rapidly from the phagosomal compartment is critical for its pathogenicity. Here, we show for the first time that a glutamate transporter of Francisella (here designated GadC) is critical for oxidative stress defense in the phagosome, thus impairing intra-macrophage multiplication and virulence in the mouse model. The gadC mutant failed to efficiently neutralize the production of reactive oxygen species. Remarkably, virulence of the gadC mutant was partially restored in mice defective in NADPH oxidase activity. The data presented highlight links between glutamate uptake, oxidative stress defense, the tricarboxylic acid cycle and phagosomal escape. This is the first report establishing the role of an amino acid transporter in the early stage of the Francisella intracellular lifecycle. PMID:24453979

  14. Quantification of β-carotene, retinol, retinyl acetate and retinyl palmitate in enriched fruit juices using dispersive liquid-liquid microextraction coupled to liquid chromatography with fluorescence detection and atmospheric pressure chemical ionization-mass spectrometry.

    PubMed

    Viñas, Pilar; Bravo-Bravo, María; López-García, Ignacio; Hernández-Córdoba, Manuel

    2013-02-01

    A detailed optimization of dispersive liquid-liquid microextraction (DLLME) was carried out for developing liquid chromatographic (HPLC) techniques, using both fluorescence and atmospheric pressure chemical ionization mass spectrometric (APCI-MS) detection, for the simultaneous analysis of preforms of vitamin A: retinol (R), retinyl acetate (RA), retinyl palmitate (RP) and β-carotene (β-C). The HPLC analyses were carried out using a mobile phase composed of methanol and water, with gradient elution. The APCI-MS and fluorescence spectra permitted the correct identification of compounds in the analyzed samples. Parameters affecting DLLME were optimized using 2 mL of methanol (disperser solvent) containing 150 μL carbon tetrachloride (extraction solvent). The precision ranged from 6% to 8% (RSD) and the limits of detection were between 0.03 and 1.4 ng mL(-1), depending on the compound. The enrichment factor values were in the 21-44 range. Juice samples were analyzed without saponification and no matrix effect was found when using fluorescence detection, so calibration was possible with aqueous standards. However, a matrix effect appeared with APCI-MS, in which case it was necessary to apply matrix-matched calibration. There was great variability in the forms of vitamin A present in the juices, the most abundant ester being retinyl acetate (0.04 to 3.4 μg mL(-1)), followed by the amount of retinol (0.01 to 0.16 μg mL(-1)), while retinyl palmitate was not detected, except in the milk-containing juice, in which RP was the main form. The representative carotenoid β-carotene was present in the orange, peach, mango and multifruit juices in high amounts. The method was validated using two certified reference materials. PMID:23290361

  15. Coupling of Molecular Imprinted Polymer Nanoparticles by High Performance Liquid Chromatography as an Efficient Technique for Sensitive and Selective Trace Determination of 4-Chloro-2-Methylphenoxy Acetic Acid in Complex Matrices

    PubMed Central

    OMIDI, Fariborz; BEHBAHANI, Mohammad; SAMADI, Saadi; SEDIGHI, Alireza; SHAHTAHERI, Seyed Jamaleddin

    2014-01-01

    Abstract Background 4-chloro-2-methylphenoxy acetic acid (MCPA) is one of the most important pesticides which is extensively used to control weeds in arable farmland. Exposure to this compound occurs in general population and persons who occupationally handle it. The aim of this present work was the preparation of MCPA imprinting polymer and its application as a selective sample preparation technique for trace determination of MCPA in biological and environmental samples. Methods In this study, MCPA imprinting polymer was obtained by precipitation polymerization using methacrylic acid (the functional monomer), ethylene glycol dimethacrylate (the cross-linker), 2, 2’-azobisisobutyronitrile (the initiator) and MCPA (the template molecule) in acetonitrile solution. The MIP-NPs were characterized by thermogravimetric analysis and scanning electron microscopy. The optimization process was carried out applying batch method. After optimization of the parameters, affecting the adsorption and desorption of analyte, urine and different water samples were used to determine MCPA. Results Imprinted MCPA molecules were removed from the polymeric structure using acetic acid in methanol (20:80 v/v %) as the eluting solvent. Both sorption and desorption process occur within 10 min. The maximum sorbent capacity of the molecular imprinted polymer is 87.4 mg g-1. The relative standard deviation and limit of detection for water samples by introduced selective solid phase extraction were 4.8% and 0.9 μg L-1, and these data for urine samples were 4.5% and 1.60 μg L-1, respectively. Conclusion The developed method was successfully applied to determine MCPA in urine and different water samples. PMID:26060766

  16. 21 CFR 184.1185 - Calcium acetate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    .... No. 62-54-4), also known as acetate of lime or vinegar salts, is the calcium salt of acetic acid. It may be produced by the calcium hydroxide neutralization of acetic acid. (b) The ingredient meets...

  17. High-temperature catalytic oxidative conversion of propane to propylene and ethylene involving coupling of exothermic and endothermic reactions

    SciTech Connect

    Choudhary, V.R.; Rane, V.H.; Rajput, A.M.

    2000-04-01

    Coupling of the exothermic catalytic oxidative conversion and endothermic thermal cracking (noncatalytic) reactions of propane to propylene and ethylene over the SrO/La{sub 2}O{sub 3}/SA5205 catalyst in the presence of steam and limited oxygen was investigated at different process conditions (temperature, 700--850 C; C{sub 3}H{sub 8}/O{sub 2} ratio in feed, 2.0--8.0; H{sub 2}O/C{sub 3}H{sub 8} ratio, 0.5--2.5; space velocity, 2,000--15,000 cm{sup 3}/g h). In the presence of steam and limited O{sub 2}, the endothermic thermal cracking and exothermic oxidative conversion reactions occur simultaneously and there is no coke formation on the catalyst. Because of the direct coupling of exothermic and endothermic reactions, this process occurs in a most energy efficient and safe manner. The propane conversion, selectivity for propylene, and net heat of reaction ({Delta}H{sub r}) in the process are strongly influenced by the temperature and concentration of O{sub 2} relative to the propane in the feed. The C{sub 3}H{sub 6}/C{sub 2}H{sub 4} product ratio is also strongly influenced by the temperature, C{sub 3}H{sub 8}/O{sub 2} feed ratio, and space velocity. The net heat of reaction can be controlled by manipulating the reaction temperature and C{sub 3}H{sub 8}/O{sub 2} ratio in the feed; the process exothermicity is reduced drastically with increasing the temperature and/or C{sub 3}H{sub 8}/O{sub 2} feed ratio.

  18. Pulsed radio-frequency discharge inductively coupled plasma mass spectrometry for oxide analysis

    NASA Astrophysics Data System (ADS)

    Li, Weifeng; Yin, Zhibin; Hang, Wei; Li, Bin; Huang, Benli

    2016-08-01

    A direct solid sampling technique has been developed based on a pulsed radio-frequency discharge (RFD) in mixture of N2 and Ar environment at atmospheric pressure. With an averaged input power of 65 W, a crater with the diameter of 80 μm and depth of 50 μm can be formed on sample surface after discharge for 1 min, suggesting the feasibility of the pulsed RFD for sampling nonconductive solids. Combined with inductively coupled plasma mass spectrometry (ICPMS), this technique allows to measure elemental composition of solids directly with relative standard deviation (RSD) of ~ 20%. Capability of quantitative analysis was demonstrated by the use of soil standards and artificial standards. Good calibration linearity and limits of detection (LODs) in range of 10- 8-10- 9 g/g were achieved for most elements.

  19. 1D Coulomb drag between coupled nanowires formed at oxide interfaces

    NASA Astrophysics Data System (ADS)

    Tang, Yuhe; Tomczyk, Michelle; Huang, Mengchen; Lee, Hyungwoo; Eom, Chang-Beom; Irvin, Patrick; Levy, Jeremy

    ``Coulomb drag'' is a transport phenomenon where Coulomb interaction between two close but electrically isolated conductors induces voltage in one conductor when an electric current is injected in the other conductor. It is a powerful approach to probe electronic correlations. Here we examine 1D electronic correlations in a proximally coupled nanowire system where two parallel nanowires are created with conductive atomic force microscopy at the LaAlO3/SrTiO3 interface. Coulomb drag measurements are made by injecting current into one wire (drive wire) and measuring the induced voltage in the other wire (drag wire). This geometry offers experimental insights into the interplay of electron pairing and superconductivity in reduced dimensions. We gratefully acknowledge financial support from DOE DE-SC0014417 (JL).

  20. Catalytic Alkene Carboaminations Enabled by Oxidative Proton-Coupled Electron Transfer

    PubMed Central

    Choi, Gilbert J.; Knowles, Robert R.

    2015-01-01

    Here we describe a dual catalyst system comprised of an iridium photocatalyst and weak phosphate base that is capable of both selectively homolyzing the N–H bonds of N-arylamides (bond dissociation free energies ~ 100 kcal/mol) via concerted proton-coupled electron transfer (PCET) and mediating efficient carboamination reactions of the resulting amidyl radicals. This manner of PCET activation, which finds its basis in numerous biological redox processes, enables the formal homolysis of a stronger amide N–H bond in the presence of weaker allylic C–H bonds, a selectivity that is uncommon in conventional molecular H atom acceptors. Moreover, this transformation affords access to a broad range of structurally complex heterocycles from simple amide starting materials. The design, synthetic scope, and mechanistic evaluation of the PCET process are described. PMID:26166022

  1. Strongly coupled Pd nanotetrahedron/tungsten oxide nanosheet hybrids with enhanced catalytic activity and stability as oxygen reduction electrocatalysts.

    PubMed

    Lu, Yizhong; Jiang, Yuanyuan; Gao, Xiaohui; Wang, Xiaodan; Chen, Wei

    2014-08-20

    The design and synthesis of highly active oxygen reduction reaction (ORR) catalysts with strong durability at low cost is extremely desirable but still remains a significant challenge. Here we develop an efficient strategy that utilizes organopalladium(I) complexes containing palladium-palladium bonds as precursors for the synthesis of strongly coupled Pd tetrahedron-tungsten oxide nanosheet hybrids (Pd/W18O49) to improve the electrocatalytic activity and stability of Pd nanocrystals. The hybrid materials are synthesized by direct nucleation, growth, and anchoring of Pd tetrahedral nanocrystals on the in situ-synthesized W18O49 nanosheets. Compared to supportless Pd nanocrystals and W18O49, their hybrids exhibited not only surprisingly high activity but also superior stability to Pt for the ORR in alkaline solutions. X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, and electrochemical analyses indicated that the enhanced electrocatalytic activity and durability are associated with the increased number and improved catalytic activity of active sites, which is induced by the strong interaction between the Pd tetrahedrons and W18O49 nanosheet supports. The present study provides a novel strategy for synthesizing hybrid catalysts with strong chemical attachment and electrical coupling between nanocatalysts and supports. The strategy is expected to open up exciting opportunities for developing a novel class of metal-support hybrid nanoelectrocatalysts with improved ORR activity and durability for both fuel cells and metal-air batteries. PMID:25054583

  2. Electro-optic switching in iron oxide nanoparticle embedded paramagnetic chiral liquid crystal via magneto-electric coupling

    SciTech Connect

    Goel, Puja; Arora, Manju; Biradar, Ashok M.

    2014-03-28

    The variation in optical texture, electro-optic, and dielectric properties of iron oxide nanoparticles (NPs) embedded ferroelectric liquid crystal (FLC) with respect to change in temperature and electrical bias conditions are demonstrated in the current investigations. Improvement in spontaneous polarization and response time in nanocomposites has been attributed to magneto-electric (ME) coupling resulting from the strong interaction among the ferromagnetic nanoparticle's exchange field (due to unpaired e{sup −}) and the field of liquid crystal molecular director. Electron paramagnetic resonance spectrum of FLC material gives a broad resonance signal with superimposed components indicating the presence of a source of spin. This paramagnetic behavior of host FLC material had been a major factor in strengthening the guest host interaction by giving an additional possibility of (a) spin-spin interaction and (b) interactions between magnetic-dipole and electric-dipole moments (ME effects) in the composite materials. Furthermore, the phenomenon of dielectric and static memory effect in these composites are also observed which yet again confirms the coupling of magnetic NP's field with FLC's director orientation. We therefore believe that such advanced soft materials holding the optical and electrical properties of conventional LCs with the magnetic and electronic properties of ferromagnetic nanoparticles are going to play a key role in the development of futuristic multifunctional optical devices.

  3. Monomolecular layers and thin films of silane coupling agents by vapor-phase adsorption on oxidized aluminum

    SciTech Connect

    Kurth, D.G.; Bein, T.

    1992-08-06

    Thin films of tetraethoxysilane [TEOS], (3-bromopropyl)trimethoxysilane [BPS], trimethoxyvinylsilane [VS], and 3-(trimethoxysilyl) propyl methacrylate [TPM] on oxidized aluminum surfaces have been investigated by reflection-absorption FTIR spectroscopy, ellipsometry, contact angle, and quartz crystal microbalance (QCM) measurements. Gravimetric measurements with the QCM can reveal quantitative aspects of adsorption and film formation, even for films as thin as monolayers. Adsorption of these silane coupling agents from solution typically produces multilayer films. Vapor-phase adsorption of TEOS and TPM at room temperature results in monomolecular layers. The coupling agents VS and BPS require additional heating after the vapor-phase adsorption to initiate the hydrolysis and condensation reactions necessary for the surface attachment, which produces one to three layers. For vapor adsorbed films a packing density of 4-7 molecules/nm{sup 2} was found. The data strongly suggest that the organic moieties in several of these films have a preferential orientation on the surface; they can be viewed as two-dimensional, oligomeric siloxane networks with oriented organic chains. Subsequent heating of TPM films results in structural rearrangements; heating of TEOS results in complete condensation to SiO{sub 2} films. 43 refs., 6 figs., 4 tabs.

  4. Electro-optic switching in iron oxide nanoparticle embedded paramagnetic chiral liquid crystal via magneto-electric coupling

    NASA Astrophysics Data System (ADS)

    Goel, Puja; Arora, Manju; Biradar, Ashok M.

    2014-03-01

    The variation in optical texture, electro-optic, and dielectric properties of iron oxide nanoparticles (NPs) embedded ferroelectric liquid crystal (FLC) with respect to change in temperature and electrical bias conditions are demonstrated in the current investigations. Improvement in spontaneous polarization and response time in nanocomposites has been attributed to magneto-electric (ME) coupling resulting from the strong interaction among the ferromagnetic nanoparticle's exchange field (due to unpaired e-) and the field of liquid crystal molecular director. Electron paramagnetic resonance spectrum of FLC material gives a broad resonance signal with superimposed components indicating the presence of a source of spin. This paramagnetic behavior of host FLC material had been a major factor in strengthening the guest host interaction by giving an additional possibility of (a) spin-spin interaction and (b) interactions between magnetic-dipole and electric-dipole moments (ME effects) in the composite materials. Furthermore, the phenomenon of dielectric and static memory effect in these composites are also observed which yet again confirms the coupling of magnetic NP's field with FLC's director orientation. We therefore believe that such advanced soft materials holding the optical and electrical properties of conventional LCs with the magnetic and electronic properties of ferromagnetic nanoparticles are going to play a key role in the development of futuristic multifunctional optical devices.

  5. Proton conducting sodium alginate electrolyte laterally coupled low-voltage oxide-based transistors

    NASA Astrophysics Data System (ADS)

    Liu, Yang Hui; Qiang Zhu, Li; Shi, Yi; Wan, Qing

    2014-03-01

    Solution-processed sodium alginate electrolyte film shows a high proton conductivity of ˜5.5 × 10-3 S/cm and a high lateral electric-double-layer (EDL) capacitance of ˜2.0 μF/cm2 at room temperature with a relative humidity of 57%. Low-voltage in-plane-gate indium-zinc-oxide-based EDL transistors laterally gated by sodium alginate electrolytes are fabricated on glass substrates. The field-effect mobility, current ON/OFF ratio, and subthreshold swing of such EDL transistors are estimated to be 4.2 cm2 V-1 s-1, 2.8 × 106, and 130 mV/decade, respectively. At last, a low-voltage driven resistor-load inverter is also demonstrated. Such in-plane-gate EDL transistors have potential applications in portable electronics and low-cost biosensors.

  6. Low-temperature catalytic oxidative coupling of methane in an electric field over a Ce–W–O catalyst system

    PubMed Central

    Sugiura, Kei; Ogo, Shuhei; Iwasaki, Kousei; Yabe, Tomohiro; Sekine, Yasushi

    2016-01-01

    We examined oxidative coupling of methane (OCM) over various Ce–W–O catalysts at 423 K in an electric field. Ce2(WO4)3/CeO2 catalyst showed high OCM activity. In a periodic operation test over Ce2(WO4)3/CeO2 catalyst, C2 selectivity exceeded 60% during three redox cycles. However, Ce2(WO4)3/CeO2 catalyst without the electric field showed low activity, even at 1073 K: CH4 Conv., 6.0%; C2 Sel., 2.1%. A synergetic effect between the Ce2(WO4)3 structure and electric field created the reactive oxygen species for selective oxidation of methane. Results of XAFS, in-situ Raman and periodic operation tests demonstrated that OCM occurred as the lattice oxygen in Ce2(WO4)3 (short W–O bonds in distorted WO4 unit) was consumed. The consumed oxygen was reproduced by a redox mechanism in the electric field. PMID:27118726

  7. Effects of CO[sub 2] during oxidative coupling of methane over Li/MgO: Mechanisms and models

    SciTech Connect

    Al-Zahrani, S.; Qi Song; Lobban, L.L. . School of Chemical Engineering and Materials Science)

    1994-02-01

    The effects of CO[sub 2] partial pressure on oxidative methane coupling over a Li/MgO catalyst were studied under low conversion conditions in a flow reactor. Methane to oxygen ratios from 0.5 to 35 and temperatures from 973 to 1073 K were used in the experiments and modeling. Varying flow rates of CO[sub 2] were mixed with the methane and oxygen prior to the reaction. Results indicate that CO[sub 2] has a poisoning effect on both carbon oxides (CO and CO[sub 2]) and C[sub 2] hydrocarbon (C[sub 2]H[sub 4] and C[sub 2]H[sub 6]) formation rates, while selectivity to the C[sub 2] hydrocarbon was not significantly affected. The apparent activation energy increased with CO[sub 2] partial pressure in the feed. Results also indicate that a small amount of methane reacts with carbon dioxide to produce carbon monoxide. Empirical rate expressions and rate expressions rigorously derived from proposed mechanisms were obtained. The rate expressions agree well with the measured rates and also predict the observed trend in apparent activation energy.

  8. Low-temperature catalytic oxidative coupling of methane in an electric field over a Ce-W-O catalyst system.

    PubMed

    Sugiura, Kei; Ogo, Shuhei; Iwasaki, Kousei; Yabe, Tomohiro; Sekine, Yasushi

    2016-01-01

    We examined oxidative coupling of methane (OCM) over various Ce-W-O catalysts at 423 K in an electric field. Ce2(WO4)3/CeO2 catalyst showed high OCM activity. In a periodic operation test over Ce2(WO4)3/CeO2 catalyst, C2 selectivity exceeded 60% during three redox cycles. However, Ce2(WO4)3/CeO2 catalyst without the electric field showed low activity, even at 1073 K: CH4 Conv., 6.0%; C2 Sel., 2.1%. A synergetic effect between the Ce2(WO4)3 structure and electric field created the reactive oxygen species for selective oxidation of methane. Results of XAFS, in-situ Raman and periodic operation tests demonstrated that OCM occurred as the lattice oxygen in Ce2(WO4)3 (short W-O bonds in distorted WO4 unit) was consumed. The consumed oxygen was reproduced by a redox mechanism in the electric field. PMID:27118726

  9. Low-temperature catalytic oxidative coupling of methane in an electric field over a Ce–W–O catalyst system

    NASA Astrophysics Data System (ADS)

    Sugiura, Kei; Ogo, Shuhei; Iwasaki, Kousei; Yabe, Tomohiro; Sekine, Yasushi

    2016-04-01

    We examined oxidative coupling of methane (OCM) over various Ce–W–O catalysts at 423 K in an electric field. Ce2(WO4)3/CeO2 catalyst showed high OCM activity. In a periodic operation test over Ce2(WO4)3/CeO2 catalyst, C2 selectivity exceeded 60% during three redox cycles. However, Ce2(WO4)3/CeO2 catalyst without the electric field showed low activity, even at 1073 K: CH4 Conv., 6.0%; C2 Sel., 2.1%. A synergetic effect between the Ce2(WO4)3 structure and electric field created the reactive oxygen species for selective oxidation of methane. Results of XAFS, in-situ Raman and periodic operation tests demonstrated that OCM occurred as the lattice oxygen in Ce2(WO4)3 (short W–O bonds in distorted WO4 unit) was consumed. The consumed oxygen was reproduced by a redox mechanism in the electric field.

  10. Antioxidant inhibition of skin inflammation induced by reactive oxidants: evaluation of the redox couple dihydrolipoate/lipoate.

    PubMed

    Fuchs, J; Milbradt, R

    1994-01-01

    Reactive oxygen species play an important role in mediating skin inflammation, and antioxidants may provide protection. We investigated the anti-inflammatory activity of natural antioxidants, such as superoxide dismutase, catalase, trolox (a water-soluble tocopherol analog) and the redox couple dihydrolipoate/lipoate in skin. Furthermore we compared the anti-inflammatory potency of natural R and racemic dihydrolipoate, as well as R and S lipoate. Skin inflammation in hairless mice was induced by intradermal injection of the hydrogen peroxide producing enzyme glucose oxidase (GOD) or by topical application of the prooxidant drug anthralin. Intradermal injection of the antioxidants inhibited skin inflammation caused by GOD (catalase, dihydrolipoate) and anthralin (trolox, superoxide dismutase, dihydrolipoate). There was no statistically significant difference between the anti-inflammatory activity of the natural R and racemic dihydrolipoate. R or S lipoate did not inhibit skin inflammation when injected intradermally. In feeding experiments, however, R lipoate significantly inhibited GOD-mediated skin inflammation, while S lipoate was only marginally protective. We conclude that (1) several natural antioxidants such as catalase, superoxide dismutase and dihydrolipoate have anti-inflammatory properties in dermatitis induced by reactive oxidants, (2) lipoate (oxidized dihydrolipoate) has skin anti-inflammatory activity when administered orally and (3) naturally occurring R lipoate is a more potent anti-inflammatory agent than the non-physiological S lipoate. PMID:8054210

  11. 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

  12. Conformation analysis of d-glucaric acid in deuterium oxide by NMR based on its JHH and JCH coupling constants.

    PubMed

    Enomoto-Rogers, Yukiko; Masaki, Hisaharu; Ito, Tetsuya; Furihata, Kazuo; Iwata, Tadahisa

    2016-07-01

    d-Glucaric acid (GA) is an aldaric acid and consists of an asymmetric acyclic sugar backbone with a carboxyl group positioned at either end of its structure (i.e., the C1 and C6 positions). The purpose of this study was to conduct a conformation analysis of flexible GA as a solution in deuterium oxide by NMR spectroscopy, based on J-resolved conformation analysis using proton-proton ((3) JHH ) and proton-carbon ((2) JCH and (3) JCH ) coupling constants, as well as nuclear overhauser effect spectroscopy (NOESY). The (2) JCH and (3) JCH coupling constants were measured using the J-resolved heteronuclear multiple bond correlation (HMBC) NMR technique. NOESY correlation experiments indicated that H2 and H5 were in close proximity, despite the fact that these protons were separated by too large distance in the fully extended form of the chain structure to provide a NOESY correlation. The validities of the three possible conformers along the three different bonds (i.e., C2C3, C3C4, and C4C5) were evaluated sequentially based on the J-coupling values and the NOESY correlations. The results of these analyses suggested that there were three dominant conformers of GA, including conformer 1, which was H2H3:gauche, H3H4:anti, and H4H5:gauche; conformer 2, which was H2H3:gauche, H3H4:anti, and H4H5:anti; and conformer 3, which was H2H3:gauche, H3H4: gauche, and H4H5:anti. These results also suggested that all three of these conformers exist in equilibrium with each other. Lastly, the results of the current study suggested that the conformational structures of GA in solution were 'bent' rather than being fully extended. Copyright © 2016 John Wiley & Sons, Ltd. PMID:26749401

  13. Mechanism and modelling of aluminium nanoparticle oxidation coupled with crystallisation of amorphous Al2O3 shell

    NASA Astrophysics Data System (ADS)

    Kong, Chengdong; Yu, Dan; Li, Shuiqing; Yao, Qiang

    2016-03-01

    The oxidation of aluminium nanoparticles coupled with crystallisation of amorphous alumina shell is investigated through the thermogravimetric analyser and differential scanning calorimetry (TGA-DSC) and the transmission electron microscope (TEM). The thermogravimetric (TG) curves show stepwise shapes with temperature increase and could be divided into four stages. The reaction at the second stage is complex, including the simultaneous crystallisation of amorphous alumina (am-Al2O3) and Al oxidation. The crystallisation of am-Al2O3 promotes the reaction through generating fast diffusion channels, like micro-cracks and grain boundaries in the oxide shell to accelerate the ionic diffusion. An enhancement factor (freact), which follows a power-law formula with the crystallisation rate, is introduced to quantify the impact of crystallisation on reaction. With heating rate increase, the second stage of TG curves shifts to the high temperature regime and the total weight gain at the second stage decreases slowly. A crystallisation-reaction model is constructed to fit and predict the weight gain after derivation of diffusivities and crystallisation kinetics. Modelling indicates that with heating rate rise, the mass increment at the second stage of TG curves decreases owing to the reduced reaction time, although the reaction is accelerated. The shift of TG curve to higher temperature is due to the polymorphic phase transition. Actually the derived kinetics of the crystallisation of amorphous alumina indicates that the polymorphic phase transformation mechanism works mainly below the heating rate of 3 K s-1. At higher heating rate, the melting of Al takes place firstly and the crystallisation of am-Al2O3 follows to enhance the ionic diffusion. Therefore, when the heating rate is fast during ignition or combustion, the Al nanoparticles undergo both the melting of Al and the polymorphic phase transition of am-Al2O3 to accelerate the reaction.

  14. Bioinspired heme, heme/nonheme diiron, heme/copper, and inorganic NOx chemistry: *NO((g)) oxidation, peroxynitrite-metal chemistry, and *NO((g)) reductive coupling.

    PubMed

    Schopfer, Mark P; Wang, Jun; Karlin, Kenneth D

    2010-07-19

    The focus of this Forum Article highlights work from our own laboratories and those of others in the area of biochemical and biologically inspired inorganic chemistry dealing with nitric oxide [nitrogen monoxide, *NO((g))] and its biological roles and reactions. The latter focus is on (i) oxidation of *NO((g)) to nitrate by nitric oxide dioxygenases (NODs) and (ii) reductive coupling of two molecules of *NO((g)) to give N(2)O(g). In the former case, NODs are described, and the highlighting of possible peroxynitrite/heme intermediates and the consequences of this are given by a discussion of recent works with myoglobin and a synthetic heme model system for NOD action. Summaries of recent copper complex chemistries with *NO((g)) and O(2)(g), leading to peroxynitrite species, are given. The coverage of biological reductive coupling of *NO((g)) deals with bacterial nitric oxide reductases (NORs) with heme/nonheme diiron active sites and on heme/copper oxidases such as cytochrome c oxidase, which can mediate the same chemistry. Recently designed protein and synthetic model compounds (heme/nonheme/diiron or heme/copper) as functional mimics are discussed in some detail. We also highlight examples from the chemical literature, not necessarily involving biologically relevant metal ions, that describe the oxidation of *NO((g)) to nitrate (or nitrite) and possible peroxynitrite intermediates or reductive coupling of *NO((g)) to give nitrous oxide. PMID:20666386

  15. Antibiofilm Properties of Acetic Acid

    PubMed Central

    Bjarnsholt, Thomas; Alhede, Morten; Jensen, Peter Østrup; Nielsen, Anne K.; Johansen, Helle Krogh; Homøe, Preben; Høiby, Niels; Givskov, Michael; Kirketerp-Møller, Klaus

    2015-01-01

    Bacterial biofilms are known to be extremely tolerant toward antibiotics and other antimicrobial agents. These biofilms cause the persistence of chronic infections. Since antibiotics rarely resolve these infections, the only effective treatment of chronic infections is surgical removal of the infected implant, tissue, or organ and thereby the biofilm. Acetic acid is known for its antimicrobial effect on bacteria in general, but has never been thoroughly tested for its efficacy against bacterial biofilms. In this article, we describe complete eradication of both Gram-positive and Gram-negative biofilms using acetic acid both as a liquid and as a dry salt. In addition, we present our clinical experience of acetic acid treatment of chronic wounds. In conclusion, we here present the first comprehensive in vitro and in vivo testing of acetic acid against bacterial biofilms. PMID:26155378

  16. Isolation and Characterization of Microbes Mediating Thermodynamically Favorable Coupling of Anaerobic Oxidation of Methane and Metal Reduction

    NASA Astrophysics Data System (ADS)

    Glass, J. B.; Reed, B. C.; Sarode, N. D.; Kretz, C. B.; Bray, M. S.; DiChristina, T. J.; Stewart, F. J.; Fowle, D. A.; Crowe, S.

    2014-12-01

    Methane is the third most reduced environmentally relevant electron donor for microbial metabolisms after organic carbon and hydrogen. In anoxic ecosystems, the major sink for methane is anaerobic oxidation of methane (AOM) mediated by syntrophic microbial consortia that couple AOM to reduction of an oxidized electron acceptor to yield free energy. In marine sediments, AOM is generally coupled to reduction of sulfate despite an extremely small amount of free energy yield because sulfate is the most abundant electron acceptor in seawater. While AOM coupled to Fe(III) and Mn(IV) reduction (Fe- and Mn-AOM) is 10-30x more thermodynamically favorable than sulfate-AOM, and geochemical data suggests that it occurs in diverse environments, the microorganisms mediating Fe- and Mn-AOM remain unknown. Lake Matano, Indonesia is an ideal ecosystem to enrich for Fe- and Mn-AOM microbes because its anoxic ferruginous deep waters and sediments contain abundant Fe(III), Mn(IV) and methane, and extremely low sulfate and nitrate. Our research aims to isolate and characterize the microbes mediating Fe- and Mn-AOM from three layers of Lake Matano sediments through serial enrichment cultures in minimal media lacking nitrate and sulfate. 16S rRNA amplicon sequencing of sediment inoculum revealed the presence of the Fe(III)-reducing bacterium Geobacter (5-10% total microbial community in shallow sediment and 35-60% in deeper sediment) as well as 1-2% Euryarchaeota implicated in methane cycling, including ANME-1 and 2d and Methanosarcinales. After 90 days of primary enrichment, all three sediment layers showed high levels of Fe(III) reduction (60-90 μM Fe(II) d-1) in the presence of methane compared to no methane and heat-killed controls. Treatments with added Fe(III) as goethite contained higher abundances of Geobacter than the inoculum (60-80% in all layers), suggesting that Geobacter may be mediating Fe(III) reduction in these enrichments. Quantification of AOM rates is underway, and

  17. Acetate in recent anoxic sediments: Direct and indirect measurements of concentration and turnover rates

    NASA Astrophysics Data System (ADS)

    Shaw, David G.; McIntosh, Douglas J.

    1990-12-01

    While acetate is generally regarded as an important intermediate in the mineralization of organic matter in anoxic sediment systems, some quantitative studies in marine systems (including our own) have measured acetate oxidation rates in excess of sulphate reduction rates where sulphate is known to be the principal electron acceptor. We revisited Skan Bay, Alaska, where we had previously made such observations, for a reexamination of acetate turnover. Measurements of acetate concentrations, production rate, oxidation rate and sulphate reduction rate as well as bioenergetic considerations led to the conclusion that acetate oxidation rate in 15-18-cm deep sediment is 1·1-1·5 μM h -1. The possibility that previous measurements were high because of a non-citric-acid-cycle pathway of acetate oxidation (suggested by recent laboratory studies) was excluded. It appears that our previous turnover measurements were high mainly because of high acetate concentrations. Procedures used for the isolation of porewater for acetate determination may influence results to an extent not previously recognized.

  18. Long-range transfer of electron-phonon coupling in oxide superlattices.

    PubMed

    Driza, N; Blanco-Canosa, S; Bakr, M; Soltan, S; Khalid, M; Mustafa, L; Kawashima, K; Christiani, G; Habermeier, H-U; Khaliullin, G; Ulrich, C; Le Tacon, M; Keimer, B

    2012-08-01

    The electron-phonon interaction is of central importance for the electrical and thermal properties of solids, and its influence on superconductivity, colossal magnetoresistance and other many-body phenomena in correlated-electron materials is the subject of intense research at present. However, the non-local nature of the interactions between valence electrons and lattice ions, often compounded by a plethora of vibrational modes, presents formidable challenges for attempts to experimentally control and theoretically describe the physical properties of complex materials. Here we report a Raman scattering study of the lattice dynamics in superlattices of the high-temperature superconductor YBa(2)Cu(3)O(7) (YBCO) and the colossal-magnetoresistance compound La(2/3)Ca(1/3)MnO(3) that suggests a new approach to this problem. We find that a rotational mode of the MnO(6) octahedra in La(2/3)Ca(1/3)MnO(3) experiences pronounced superconductivity-induced line-shape anomalies, which scale linearly with the thickness of the YBCO layers over a remarkably long range of several tens of nanometres. The transfer of the electron-phonon coupling between superlattice layers can be understood as a consequence of long-range Coulomb forces in conjunction with an orbital reconstruction at the interface. The superlattice geometry thus provides new opportunities for controlled modification of the electron-phonon interaction in complex materials. PMID:22797829

  19. Proton conducting sodium alginate electrolyte laterally coupled low-voltage oxide-based transistors

    SciTech Connect

    Liu, Yang Hui; Wan, Qing; Qiang Zhu, Li; Shi, Yi

    2014-03-31

    Solution-processed sodium alginate electrolyte film shows a high proton conductivity of ∼5.5 × 10{sup −3} S/cm and a high lateral electric-double-layer (EDL) capacitance of ∼2.0 μF/cm{sup 2} at room temperature with a relative humidity of 57%. Low-voltage in-plane-gate indium-zinc-oxide-based EDL transistors laterally gated by sodium alginate electrolytes are fabricated on glass substrates. The field-effect mobility, current ON/OFF ratio, and subthreshold swing of such EDL transistors are estimated to be 4.2 cm{sup 2} V{sup −1} s{sup −1}, 2.8 × 10{sup 6}, and 130 mV/decade, respectively. At last, a low-voltage driven resistor-load inverter is also demonstrated. Such in-plane-gate EDL transistors have potential applications in portable electronics and low-cost biosensors.

  20. Using Coupled Mesoscale Experiments and Simulations to Investigate High Burn-Up Oxide Fuel Thermal Conductivity

    NASA Astrophysics Data System (ADS)

    Teague, Melissa C.; Fromm, Bradley S.; Tonks, Michael R.; Field, David P.

    2014-12-01

    Nuclear energy is a mature technology with a small carbon footprint. However, work is needed to make current reactor technology more accident tolerant and to allow reactor fuel to be burned in a reactor for longer periods of time. Optimizing the reactor fuel performance is essentially a materials science problem. The current understanding of fuel microstructure have been limited by the difficulty in studying the structure and chemistry of irradiated fuel samples at the mesoscale. Here, we take advantage of recent advances in experimental capabilities to characterize the microstructure in 3D of irradiated mixed oxide (MOX) fuel taken from two radial positions in the fuel pellet. We also reconstruct these microstructures using Idaho National Laboratory's MARMOT code and calculate the impact of microstructure heterogeneities on the effective thermal conductivity using mesoscale heat conduction simulations. The thermal conductivities of both samples are higher than the bulk MOX thermal conductivity because of the formation of metallic precipitates and because we do not currently consider phonon scattering due to defects smaller than the experimental resolution. We also used the results to investigate the accuracy of simple thermal conductivity approximations and equations to convert 2D thermal conductivities to 3D. It was found that these approximations struggle to predict the complex thermal transport interactions between metal precipitates and voids.

  1. Coupled molecular-dynamics and first-principle transport calculations of metal/oxide/metal heterostructures

    NASA Astrophysics Data System (ADS)

    Zapol, Peter; Karpeyev, Dmitry; Maheshwari, Ketan; Zhong, Xiaoliang; Narayanan, Badri; Sankaranarayanan, Subramanian; Wilde, Michael; Heinonen, Olle; Rungger, Ivan

    2015-03-01

    The electronic conduction in Hf-oxide heterostructures for use in, e.g., resistive switching devices, depends sensitively on local oxygen stoichiometry and interactions at interfaces with metal electrodes. In order to model the electronic structure of different disordered configurations near interfaces, we have combined molecular dynamics (MD) simulations with first-principle based non-equilibrium Green's functions (NEGF) methods, including self-interaction corrections. We have developed an approach to generating automated workflows that combine MD and NEGF computations over many parameter values using the Swift parallel scripting language. A sequence of software tools transforms the result of one calculation into the input of the next allowing for a high-throughput concurrent parameter sweep. MD simulations generate systems with quenched disorder, which are then directly fed to NEGF and on to postprocessing. Different computations can be run on different computer platforms matching the computational load to the hardware resources. We will demonstrate results for metal-HfO2-metal heterostructures obtained using this workflow. Argonne National Laboratory's work was supported under U.S. Department of Energy Contract DE-AC02-06CH11357.

  2. Spin structure in an interfacially-coupled epitaxial ferromagnetic oxide heterostructure

    NASA Astrophysics Data System (ADS)

    Ke, Xianglin

    2014-03-01

    We report the spin structure of an exchange-biased ferromagnetic oxide heterostructure, La0.67Sr0.33MnO3 / SrRuO3, through magnetization and polarized neutron reflectometry measurements. We reveal that the magnetization reversal process of the La0.67Sr0.33MnO3 biased layer critically depends on the frozen-in spin structure of the SrRuO3 biasing layer during the cooling process. Furthermore, we observe unexpected double-shifted hysteresis loops of the biased layer that originates from the formation of lateral 180° magnetic domains within the biasing layer, a new mechanism not found in conventional exchange-bias systems. The effects of the thus-formed spin structure on the magnetotransport properties will be presented as well. This work was done in collaboration with L. J. Belenky, V. Lauter, H. Ambaye, C. W. Bark, C. B. Eom, M. S. Rzchowski, J. Smith, and M. Zhu.

  3. Stimulation of Ca²+ signals in neurons by electrically coupled electrolyte-oxide-semiconductor capacitors.

    PubMed

    Giacomello, M; Girardi, S; Scorzeto, M; Peruffo, A; Maschietto, M; Cozzi, B; Vassanelli, S

    2011-05-15

    Electrolyte-oxide-semiconductor capacitors (EOSCs) are a class of microtransducers for extracellular electrical stimulation that have been successfully employed to activate voltage-dependent sodium channels at the neuronal soma to generate action potentials in vitro. In the present work, we report on their use to control Ca²+ signalling in cultured mammalian cells, including neurons. Evidence is provided that EOSC stimulation with voltage waveforms in the microsecond or nanosecond range activates two distinct Ca²+ pathways, either by triggering Ca²+ entry through the plasma membrane or its release from intracellular stores. Ca²+ signals were activated in non-neuronal and neuronal cell lines, CHO-K1 and SH-SY5Y. On this basis, stimulation was tailored to rat and bovine neurons to mimic physiological somatic Ca²+ transients evoked by glutamate. Being minimally invasive and easy to use, the new method represents a versatile complement to standard electrophysiology and imaging techniques for the investigation of Ca²+ signalling in dissociated primary neurons and cell lines. PMID:21345350

  4. Ruthenium-catalyzed oxidative coupling of 2-aryl-4-quinazolinones with olefins: synthesis of pyrrolo[2,1-b]quinazolin-9(1H)-one motifs.

    PubMed

    Zheng, Yong; Song, Wei-Bin; Zhang, Shu-Wei; Xuan, Li-Jiang

    2015-06-21

    A ruthenium-catalyzed oxidative coupling of 2-aryl-quinazolinones with olefins via C-H bond activation followed by an intramolecular aza-Michael reaction is described. This strategy allows the direct and efficient construction of pyrrolo[2,1-b]quinazolin-9(1H)-one scaffolds. PMID:25996242

  5. A versatile approach to flavones via a one-pot Pd(II)-catalyzed dehydrogenation/oxidative boron-Heck coupling sequence of chromanones.

    PubMed

    Lee, Jun; Yu, Jihyun; Son, Seung Hwan; Heo, Jinyuk; Kim, Taelim; An, Ji-Young; Inn, Kyung-Soo; Kim, Nam-Jung

    2016-01-14

    A variety of flavones were expediently synthesized from readily accessible chromanones via a one-pot sequence involving Pd(II)-catalyzed dehydrogenation and oxidative boron-Heck coupling with arylboronic acid pinacol esters. In particular, the use of arylboronic acid pinacol esters was found to significantly improve the yield of the reaction. PMID:26592753

  6. One-pot synthesis of amides by aerobic oxidative coupling of alcohols or aldehydes with amines using supported gold and base as catalysts.

    PubMed

    Kegnæs, Søren; Mielby, Jerrik; Mentzel, Uffe V; Jensen, Thomas; Fristrup, Peter; Riisager, Anders

    2012-02-28

    Synthesis of amides by aerobic oxidative coupling of alcohols or aldehydes with amines via intermediate formation of methyl esters is highly efficient and selective when using a catalytic system comprised of supported gold nanoparticles and added base in methanol. PMID:22274843

  7. Rhodium-catalyzed oxidative coupling of triarylmethanols with internal alkynes via successive C-H and C-C bond cleavages.

    PubMed

    Uto, Toshihiko; Shimizu, Masaki; Ueura, Kenji; Tsurugi, Hayato; Satoh, Tetsuya; Miura, Masahiro

    2008-01-01

    The rhodium-catalyzed oxidative coupling of triarylmethanols with internal alkynes effectively proceeds in a 1:2 manner via cleavage of C-H and C-C bonds to produce the corresponding naphthalene derivatives. Addition of tri- or tetraphenylcyclopentadiene as a ligand is crucial for the reaction to occur efficiently. PMID:18052297

  8. Organocatalyzed asymmetric oxidative coupling of α-Csp3-H of tertiary amines to α,β-unsaturated γ-butyrolactam: synthesis of MBH-type products.

    PubMed

    Ma, Yunxia; Zhang, Gen; Zhang, Jinlong; Yang, Dongxu; Wang, Rui

    2014-10-17

    A unique organocatalytic asymmetric oxidative cross-dehydrogenative coupling of a α-Csp(3)-H bond of tertiary amines with α,β-unsaturated γ-butyrolactams to generate Morita-Baylis-Hillman-type products has been realized for the first time. This method provides an efficient way to access a series of α-heterocyclic optically active tetrahydroisoquinoline scaffolds. PMID:25260156

  9. Electron-phonon coupling and structural phase transitions in early transition metal oxides and chalcogenides

    NASA Astrophysics Data System (ADS)

    Farley, Katie Elizabeth

    Pronounced nonlinear variation of electrical transport characteristics as a function of applied voltage, temperature, magnetic field, strain, or photo-excitation is usually underpinned by electronic instabilities that originate from the complex interplay of spin, orbital, and lattice degrees of freedom. This dissertation focuses on two canonical materials that show pronounced discontinuities in their temperature-dependent resistivity as a result of electron---phonon and electron---electron correlations: orthorhombic TaS3 and monoclinic VO2. Strong electron-phonon interactions in transition metal oxides and chalcogenides results in interesting structural and electronic phase transitions. The properties of the material can be changed drastically in response to external stimuli such as temperature, voltage, or light. Understanding the influence these interactions have on the electronic structure and ultimately transport characteristics is of utmost importance in order to take these materials from a fundamental aspect to prospective applications such as low-energy interconnects, steep-slope transistors, and synaptic neural networks. This dissertation describes synthetic routes to nanoscale TaS3 and VO2, develops mechanistic understanding of their electronic instabilities, and in the case of the latter system explores modulation of the electronic and structural phase transition via the incorporation of substitutional dopant atoms. We start in chapter 2 with a detailed study of the synthesis and electronic transport properties of TaS3, which undergoes a Peierls' distortion to form a charge density wave. Scaling this material down to the nanometer-sized regime allows for interrogation of single or discrete phase coherent domains. Using electrical transport and broad band noise measurements, the dynamics of pinning/depinning of the charge density wave is investigated. Chapter 3 provides a novel synthetic approach to produce high-edge-density MoS2 nanorods. MoS2 is a

  10. New Effective Material Couple--Oxide Ceramic and Carbon Nanotube-- Developed for Aerospace Microsystem and Micromachine Technologies

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa; VanderWal, Randall L.; Tomasek, Aaron J.; Sayir, Ali; Farmer, Serene C.

    2004-01-01

    The prime driving force for using microsystem and micromachine technologies in transport vehicles, such as spacecraft, aircraft, and automobiles, is to reduce the weight, power consumption, and volume of components and systems to lower costs and increase affordability and reliability. However, a number of specific issues need to be addressed with respect to using microsystems and micromachines in aerospace applications--such as the lack of understanding of material characteristics; methods for producing and testing the materials in small batches; the limited proven durability and lifetime of current microcomponents, packaging, and interconnections; a cultural change with respect to system designs; and the use of embedded software, which will require new product assurance guidelines. In regards to material characteristics, there are significant adhesion, friction, and wear issues in using microdevices. Because these issues are directly related to surface phenomena, they cannot be scaled down linearly and they become increasingly important as the devices become smaller. When microsystems have contacting surfaces in relative motion, the adhesion and friction affect performance, energy consumption, wear damage, maintenance, lifetime and catastrophic failure, and reliability. Ceramics, for the most part, do not have inherently good friction and wear properties. For example, coefficients of friction in excess of 0.7 have been reported for ceramics and ceramic composite materials. Under Alternate Fuels Foundation Technologies funding, two-phase oxide ceramics developed for superior high-temperature wear resistance in NASA's High Operating Temperature Propulsion Components (HOTPC) project and new two-layered carbon nanotube (CNT) coatings (CNT topcoat/iron bondcoat/quartz substrate) developed in NASA's Revolutionary Aeropropulsion Concepts (RAC) project have been chosen as a materials couple for aerospace applications, including micromachines, in the nanotechnology

  11. Over-Oxidation as the Key Step in the Mechanism of the MoCl5-Mediated Dehydrogenative Coupling of Arenes.

    PubMed

    Schubert, Moritz; Franzmann, Peter; Wünsche von Leupoldt, Anica; Koszinowski, Konrad; Heinze, Katja; Waldvogel, Siegfried R

    2016-01-18

    Molybdenum pentachloride is an unusually powerful reagent for the dehydrogenative coupling of arenes. Owing to the high reaction rate using MoCl5, several labile moieties are tolerated in this transformation. The mechanistic course of the reaction was controversially discussed although indications for a single electron transfer as the initial step were found recently. Herein, based on a combined study including synthetic investigations, electrochemical measurements, EPR spectroscopy, DFT calculations, and mass spectrometry, we deduct a highly consistent mechanistic scenario: MoCl5 acts as a one-electron oxidant in the absence of TiCl4 and as two-electron oxidant in the presence of TiCl4, but leads to an over-oxidized intermediate in both cases, which protects it from side reactions. In the course of aqueous work-up the reagent waste (Mo(III/IV) species) acts as reducing agent generating the desired organic C-C coupling product. PMID:26473303

  12. Novel method for controlled oxidation

    SciTech Connect

    Benjamin, B.M.; Raaen, V.F.

    1981-01-01

    The purpose of this paper is to describe a novel method for the oxidative degradation of coal or other organic material. The procedure is potentially useful for structure determination. As originally conceived, this method was intended for use with aqueous potassium permanganate as oxidant, but it is equally applicable with other oxidizing agents. Sodium hyprochlorite can be substituted for KMnO/sub 4/ except that controlling the pH and monitoring the end pilot become more difficult. Results with potassium permanganate only are described here but sodium hypochlorite was tried. An advantageous feature of the method is the simultaneous removal of soluble products from further contact with oxidizing agent as the oxidizing agent attacks the substrate. In principle, the experimental approach resembles that of column chromatography. Any oxidative degradation of a natural product for structure determination is of little use if carried out too far; for example, to the smallest, most oxidation-resistant materials such as carbon dioxide, acetic acid, and benzoic acid. Potassium permanganate oxidations of reactive species such as coal and kerogen are particularly difficult to control. Partially oxidized fragments which go into solution can be attacked more effectively than the solid starting phase, a situation which results in loss of structural information. Another difficulty is that phenolic materials can undergo coupling reactions thus generating larger molecules and giving misleading results due to a larger number of substituents. The procedure used is described.

  13. Developmental competence of bovine early embryos depends on the coupled response between oxidative and endoplasmic reticulum stress.

    PubMed

    Yoon, Seung-Bin; Choi, Seon-A; Sim, Bo-Woong; Kim, Ji-Su; Mun, Seong-Eun; Jeong, Pil-Soo; Yang, Hae-Jun; Lee, Youngjeon; Park, Young-Ho; Song, Bong-Seok; Kim, Young-Hyun; Jeong, Kang-Jin; Huh, Jae-Won; Lee, Sang-Rae; Kim, Sun-Uk; Chang, Kyu-Tae

    2014-05-01

    The stress produced by the coupling of reactive oxygen species (ROS) and endoplasmic reticulum (ER) has been explored extensively, but little is known regarding their roles in the early development of mammalian embryos. Here, we demonstrated that the early development of in vitro-produced (IVP) bovine embryos was governed by the cooperative action between ROS and ER stress. Compared with the tension produced by 5% O2, 20% O2 significantly decreased the blastocyst formation rate and cell survival, which was accompanied by increases in ROS and in levels of sXBP-1 transcript, which is an ER stress indicator. In addition, treatment with glutathione (GSH), a ROS scavenger, decreased ROS levels, which resulted in increased blastocyst formation and cell survival rates. Importantly, levels of sXBP-1 and ER stress-associated transcripts were reduced by GSH treatment in developing bovine embryos. Consistent with this observation, tauroursodeoxycholate (TUDCA), an ER stress inhibitor, improved blastocyst developmental rate, trophectoderm proportion, and cell survival. Moreover, ROS and sXBP-1 transcript levels were markedly decreased by supplementation with TUDCA, suggesting a possible mechanism governing the mutual regulation between ROS and ER stress. Interestingly, knockdown of XBP-1 transcripts resulted in both elevation of ROS and decrease of antioxidant transcripts, which ultimately reduced in vitro developmental competence of bovine embryos. Based on these results, in vitro developmental competence of IVP bovine embryos was highly dependent on the coupled response between oxidative and ER stresses. These results increase our understanding of the mechanism(s) governing early embryonic development and may improve strategies for the generation of IVP embryos with high developmental competence. PMID:24695629

  14. Sum-frequency generation of acetate adsorption on Au and Pt surfaces: Molecular structure effects

    NASA Astrophysics Data System (ADS)

    Braunschweig, Björn; Mukherjee, Prabuddha; Kutz, Robert B.; Wieckowski, Andrzej; Dlott, Dana D.

    2010-12-01

    The reversible adsorption of acetate on polycrystalline Au and Pt surfaces was investigated with broadband sum-frequency generation (SFG) and cyclic voltammetry. Specifically adsorbed acetate as well as coadsorbed sulfuric acid anions are observed for the first time with SFG and give rise to dramatically different SFG intensities on Au and Pt surfaces. While similar coverages of acetate adlayers on Au and Pt surfaces are well established by previous studies, an identification of the interfacial molecular structure has been elusive. However, we have applied the high sensitivity of SFG for interfacial polar ordering to identify different acetate structures at Au and Pt surfaces in contact with HClO4 and H2SO4 electrolytes. Acetate competes with the formation of surface oxides and shifts the oxidation threshold of both Au and Pt electrodes anodically. Effects of the supporting electrolyte on the formation of acetate adlayers are revealed by comparing SFG spectra in HClO4 and H2SO4 solutions: Sulfuric acid anions modify the potential-dependent acetate adsorption, compete with adsorbed acetate on Au and coadsorb with acetate on Pt surfaces.

  15. Metabolic Activity of Fatty Acid-Oxidizing Bacteria and the Contribution of Acetate, Propionate, Butyrate, and CO2 to Methanogenesis in Cattle Waste at 40 and 60°C

    PubMed Central

    Mackie, Roderick I.; Bryant, Marvin P.

    1981-01-01

    The quantitative contribution of fatty acids and CO2 to methanogenesis was studied by using stirred, 3-liter bench-top digestors fed on a semicontinuous basis with cattle waste. The fermentations were carried out at 40 and 60°C under identical loading conditions (6 g of volatile solids per liter of reactor volume per day, 10-day retention time). In the thermophilic digestor, acetate turnover increased from a prefeeding level of 16 μM/min to a peak (49 μM/min) 1 h after feeding and then gradually decreased. Acetate turnover in the mesophilic digestor increased from 15 to 40 μM/min. Propionate turnover ranged from 2 to 5.2 and 1.5 to 4.5 μM/min in the thermophilic and mesophilic digestors, respectively. Butyrate turnover (0.7 to 1.2 μM/min) was similar in both digestors. The proportion of CH4 produced via the methyl group of acetate varied with time after feeding and ranged from 72 to 75% in the mesophilic digestor and 75 to 86% in the thermophilic digestor. The contribution from CO2 reduction was 24 to 29% and 19 to 27%, respectively. Propionate and butyrate turnover accounted for 20% of the total CH4 produced. Acetate synthesis from CO2 was greatest shortly after feeding and was higher in the thermophilic digestor (0.5 to 2.4 μM/min) than the mesophilic digestor (0.3 to 0.5 μM/min). Counts of fatty acid-degrading bacteria were related to their turnover activity. PMID:16345789

  16. 21 CFR 184.1185 - Calcium acetate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Calcium acetate. 184.1185 Section 184.1185 Food and... Substances Affirmed as GRAS § 184.1185 Calcium acetate. (a) Calcium acetate (Ca (C2H3O2)2, CAS Reg. No. 62-54-4), also known as acetate of lime or vinegar salts, is the calcium salt of acetic acid. It may...

  17. Thermodynamic properties and ideal-gas enthalpies of formation for 2-aminoisobutyric acid (2-methylalanine), acetic acid, (Z)-5-ethylidene-2-norbornene, mesityl oxide (4-methyl-3-penten-2-one), 4-methylpent-1-ene, 2,2{prime}-bis(phenylthio)propane, and glycidyl phenyl ether (1,2-epoxy-3-phenoxypropane)

    SciTech Connect

    Steele, W.V.; Chirico, R.D.; Cowell, A.B.; Knipmeyer, S.E.; Nguyen, A.

    1997-11-01

    The results of a study aimed at improvement of group-contribution methodology for estimation of thermodynamic properties of organic substances are reported. Specific weaknesses where particular group-contribution terms were unknown, or estimated because of lack of experimental data, are addressed by experimental studies of enthalpies of combustion in the condensed phase, vapor-pressure measurements, and differential scanning calorimetric (DSC) heat-capacity measurements. Ideal-gas enthalpies of formation of acetic acid, (Z)-5-ethylidene-2-norbornene, mesityl oxide (4-methyl-3-penten-2-one), 4-methylpent-1-ene, glycidyl phenyl ether (1,2-epoxy-3-phenoxypropane), and 2,2{prime}-bis(phenylthio)propane are reported. An enthalpy of formation of 2-aminoisobutyric acid (2-methylalanine) in the crystalline phase was determined. Using a literature value for the enthalpy of sublimation of 2-aminoisobutyric acid, a value for the ideal-gas enthalpy of formation was derived. An enthalpy of fusion was determined for 2,2{prime}-bis(phenylthio)propane. Two-phase (solid + vapor) or (liquid + vapor) heat capacities were determined from 300 K to the critical region or earlier decomposition temperature for all the compounds except acetic acid. For mesityl oxide and 4-methylpent-1-ene, critical temperatures and critical densities were determined from the DSC results and corresponding critical pressures derived from the fitting procedures. Group-additivity parameters and ring strain energies useful in the application of group-contribution correlations were derived.

  18. Enhancement of aerosol responses to changes in emissions over East Asia by gas-oxidant-aerosol coupling and detailed aerosol processes

    NASA Astrophysics Data System (ADS)

    Matsui, H.; Koike, M.

    2016-06-01

    We quantify the responses of aerosols to changes in emissions (sulfur dioxide, black carbon (BC), primary organic aerosol, nitrogen oxides (NOx), and volatile organic compounds) over East Asia by using simulations including gas-oxidant-aerosol coupling, organic aerosol (OA) formation, and BC aging processes. The responses of aerosols to NOx emissions are complex and are dramatically changed by simulating gas-phase chemistry and aerosol processes online. Reduction of NOx emissions by 50% causes a 30-40% reduction of oxidant (hydroxyl radical and ozone) concentrations and slows the formation of sulfate and OA by 20-30%. Because the response of OA to changes in NOx emissions is sensitive to the treatment of emission and oxidation of semivolatile and intermediate volatility organic compounds, reduction of the uncertainty in these processes is necessary to evaluate gas-oxidant-aerosol coupling accurately. Our simulations also show that the sensitivity of aerosols to changes in emissions is enhanced by 50-100% when OA formation and BC aging processes are resolved in the model. Sensitivity simulations show that the increase of NOx emissions from 1850 to 2000 explains 70% (40%) of the enhancement of aerosol mass concentrations (direct radiative effects) over East Asia during that period through enhancement of oxidant concentrations and that this estimation is sensitive to the representation of OA formation and BC aging processes. Our results demonstrate the importance of simultaneous simulation of gas-oxidant-aerosol coupling and detailed aerosol processes. The impact of NOx emissions on aerosol formation will be a key to formulating effective emission reduction strategies such as BC mitigation and aerosol reduction policies in East Asia.

  19. Interplay between spin-orbit coupling and Hubbard interaction in SrIrO3 and related Pbnm perovskite oxides

    NASA Astrophysics Data System (ADS)

    Zeb, M. Ahsan; Kee, Hae-Young

    2012-08-01

    There has been a rapidly growing interest in the interplay between spin-orbit coupling (SOC) and the Hubbard interaction U in correlated materials. A current consensus is that the stronger the SOC, the smaller is the critical interaction Uc required for a spin-orbit Mott insulator, because the atomic SOC splits a band into different total angular momentum bands, narrowing the effective bandwidth. It was further claimed that at large enough SOC, the stronger the SOC, the weaker the Uc, because in general the effective SOC is enhanced with increasing electron-electron interaction strength. Contrary to this expectation, we find that, in orthorhombic perovskite oxides (Pbnm), the stronger the SOC, the bigger the Uc. This originates from a line of Dirac nodes in Jeff=1/2 bands near the Fermi level, inherited from a combination of the lattice structure and a large SOC. Due to this protected line of nodes, there are small hole and electron pockets in SrIrO3, and such a small density of states makes the Hubbard interaction less efficient in building a magnetic insulator. The full phase diagram in U vs SOC is obtained, where nonmagnetic semimetal, magnetic metal, and magnetic insulator are found. Magnetic ordering patterns beyond Uc are also presented. We further discuss implications of our finding in relation to other perovskites such as SrRhO3 and SrRuO3.

  20. Mild ring-opening coupling of liquid-phase cyclohexane to diesel components using sulfated metal oxides.

    PubMed

    Mao, Wei; Ma, Hongzhu; Wang, Bo

    2010-04-15

    We have investigated a mild simple synthesis method for ring-opening coupling of liquid-phase cyclohexane to diesel components using various sulfated metal oxides [SO(4)(2-)/Fe(2)O(3) (SF), SO(4)(2-)/TiO(2) (ST) and SO(4)(2-)/ZrO(2) (SZ)] under low temperature (333K) and atmospheric pressure. Neither solvent nor promoters are needed in the reaction system so as to be a clean approach. Operating under these reaction conditions, a maximum activity of 6% was obtained with SF as catalyst, and a significantly high selectivity of 74.5% for nicer diesel components (n-C(14)-C(18)) was obtained simultaneously. Whereas, ST and SZ displayed low activity for cyclohexane reaction. By utilization of the temperature-programmed desorption of ammonia (NH(3)-TPD) measurement and the N(2) adsorption method, the results suggested that a satisfied acid strength distribution and high density of acid sites appeared in SF catalyst in comparison with other catalysts, which may play an important role in the reaction. PMID:19962237

  1. Study on the O2 Plasma Treatment of Indium Tin Oxide for Organic Light Emitting Diodes Using Inductively Coupled Plasma

    NASA Astrophysics Data System (ADS)

    Jeong, Chang Hyun; Lee, June Hee; Lim, Jong Hyeuk; Lim, Jong Tae; Yeom, Geun Young

    2006-04-01

    In this study, the effect of O2 inductively coupled plasma (ICP) conditions for the indium tin oxide (ITO) surface treatment on the organic light emitting diode (OLED) device performances were investigated. By the O2 plasma treatment of ITO glass, better OLED device performances such as a lower turn-on voltage, a higher luminescence, and a higher power efficiency could be obtained and the use of lower oxygen pressure and higher ICP power improved the device properties further. DC-biasing of the ITO glass substrate degraded the device properties. The use of lower oxygen pressure and higher ICP power increased the densities of O2+ and O* in the plasma, and the plasma-treated ITO surface showed a lower carbon, a higher O/(Sn+In), and a higher Sn4+/In for the condition of lower oxygen pressure and higher ICP power. The improved OLED device properties with the ITO treated at the higher ICP power and the lower pressure appear to be from the increased hole injection to the OLED materials by decreasing the resistance of ITO and by increasing the work function of the ITO.

  2. Infinitely high selective inductively coupled plasma etching of an indium tin oxide binary mask structure for extreme ultraviolet lithography

    SciTech Connect

    Park, Y. R.; Ahn, J. H.; Kim, J. S.; Kwon, B. S.; Lee, N.-E.; Kang, H. Y.; Hwangbo, C. K.; Ahn, Jinho; Seo, Hwan Seok

    2010-07-15

    Currently, extreme ultraviolet lithography (EUVL) is being investigated for next generation lithography. Among the core EUVL technologies, mask fabrication is of considerable importance due to the use of new reflective optics with a completely different configuration than those of conventional photolithography. This study investigated the etching properties of indium tin oxide (ITO) binary mask materials for EUVL, such as ITO (absorber layer), Ru (capping/etch-stop layer), and a Mo-Si multilayer (reflective layer), by varying the Cl{sub 2}/Ar gas flow ratio, dc self-bias voltage (V{sub dc}), and etch time in inductively coupled plasmas. The ITO absorber layer needs to be etched with no loss in the Ru layer on the Mo-Si multilayer for fabrication of the EUVL ITO binary mask structure proposed here. The ITO layer could be etched with an infinitely high etch selectivity over the Ru etch-stop layer in Cl{sub 2}/Ar plasma even with a very high overetch time.

  3. Platinum(II)-mediated dehydrosulfurization and oxidative carbon-carbon coupling in the gas-phase decomposition of thioethers

    NASA Astrophysics Data System (ADS)

    Butschke, Burkhard; Schlangen, Maria; Schröder, Detlef; Schwarz, Helmut

    2009-06-01

    The ion/molecule reaction (IMR) of "roll-over" cyclometalated [Pt(bipy-H)]+ (1) (bipy = 2,2'-bipyridine) with dimethyl sulfide (2) leads to the loss of ethene in the main reaction channel (55%); this corresponds to a formal dehydrosulfurization accompanied by the dehydrogenative ("oxidative") C-C coupling of the two methyl groups in dimethyl sulfide to form ethene. In order to obtain deeper insight into this rare reaction, the IMRs of 1 with several symmetric, asymmetric as well as cyclic thioethers and some thiols are probed. Common to many substrates is the formal transfer of H2S from the organic sulfur compound to the [Pt(bipy-H)]+ core accompanied by the expulsion of one or more alkene units. In contrast to the behavior of [Pt(bipy-H)]+ (1), bare Pt+, diatomic PtH+, and also the complex [Pt(phpy-H)]+ (phpy = 2-phenyl pyridine) are not able to bring about dehydrosulfurization. It is accordingly suggested that the (bipy-H)-ligand does not only affect the electronic structure of the platinum(II) core but, moreover, plays an active role as an acceptor in the initial hydrogen transfer from the thioether ligand to the LPt+ core (L = heterocyclic ligand).

  4. The Conserved G-Protein Coupled Receptor FSHR-1 Regulates Protective Host Responses to Infection and Oxidative Stress.

    PubMed

    Miller, Elizabeth V; Grandi, Leah N; Giannini, Jennifer A; Robinson, Joseph D; Powell, Jennifer R

    2015-01-01

    The innate immune system's ability to sense an infection is critical so that it can rapidly respond if pathogenic microorganisms threaten the host, but otherwise maintain a quiescent baseline state to avoid causing damage to the host or to commensal microorganisms. One important mechanism for discriminating between pathogenic and non-pathogenic bacteria is the recognition of cellular damage caused by a pathogen during the course of infection. In Caenorhabditis elegans, the conserved G-protein coupled receptor FSHR-1 is an important constituent of the innate immune response. FSHR-1 activates the expression of antimicrobial infection response genes in infected worms and delays accumulation of the ingested pathogen Pseudomonas aeruginosa. FSHR-1 is central not only to the worm's survival of infection by multiple pathogens, but also to the worm's survival of xenobiotic cadmium and oxidative stresses. Infected worms produce reactive oxygen species to fight off the pathogens; FSHR-1 is required at the site of infection for the expression of detoxifying genes that protect the host from collateral damage caused by this defense response. Finally, the FSHR-1 pathway is important for the ability of worms to discriminate pathogenic from benign bacteria and subsequently initiate an aversive learning program that promotes selective pathogen avoidance. PMID:26360906

  5. Covalently coupled hybrid of graphitic carbon nitride with reduced graphene oxide as a superior performance lithium-ion battery anode

    NASA Astrophysics Data System (ADS)

    Fu, Yongsheng; Zhu, Junwu; Hu, Chong; Wu, Xiaodong; Wang, Xin

    2014-10-01

    An in situ chemical synthetic approach has been designed for the fabrication of a covalently coupled hybrid consisting of graphitic carbon nitride (g-C3N4) with reduced graphene oxide (rGO) with differing g-C3N4/rGO ratio. The epoxy groups of graphene oxide (GO) undergo a nucleophilic substitution reaction with dicyandiamide (C2H4N4) to form the C2H4N4-GO composite via a covalent C-N bond, and then both the in situ polymerization of C2H4N4 and the thermal reduction of GO can be achieved at higher temperatures, forming the covalently coupled g-C3N4-rGO. FT-IR, CP-MAS NMR and XPS analyses, clearly revealed a covalent interaction between the g-C3N4 and rGO sheets. The g-C3N4-rGO exhibits an unprecedented high, stable and reversible capacity of 1525 mA h g-1 at a current density of 100 mA g-1 after 50 cycles. Even at a large current density of 1000 mA g-1, a reversible capacity of 943 mA h g-1 can still be retained. The superior electrochemical performance of g-C3N4-rGO is attributed to the specific characteristics of the unique nanostructure of g-C3N4-rGO and the concerted effects of g-C3N4 and rGO, including covalent interactions between the two moieties, the good conductivity and high special surface area of the nanocomposite, as well as the template effect of the planar amino group of g-C3N4 for the dispersed decoration of Li+ ions.An in situ chemical synthetic approach has been designed for the fabrication of a covalently coupled hybrid consisting of graphitic carbon nitride (g-C3N4) with reduced graphene oxide (rGO) with differing g-C3N4/rGO ratio. The epoxy groups of graphene oxide (GO) undergo a nucleophilic substitution reaction with dicyandiamide (C2H4N4) to form the C2H4N4-GO composite via a covalent C-N bond, and then both the in situ polymerization of C2H4N4 and the thermal reduction of GO can be achieved at higher temperatures, forming the covalently coupled g-C3N4-rGO. FT-IR, CP-MAS NMR and XPS analyses, clearly revealed a covalent interaction between

  6. Etching characteristics and mechanism of indium tin oxide films in an inductively coupled HBr/Ar plasma

    SciTech Connect

    Kwon, Kwang-Ho; Efremov, Alexander; Ham, Yong-Hyun; Min, Nam Ki; Lee, Hyun Woo; Hong, Mun Pyo; Kim, Kwangsoo

    2010-01-15

    The investigations of etch characteristics and mechanisms for indium tin oxide (In{sub 2}O{sub 3}){sub 0.9}:(SnO{sub 2}){sub 0.1} (ITO) thin films using HBr/Ar inductively coupled plasma were carried out. The ITO etch rate was measured in the range of 0%-100% Ar in the HBr/Ar mixture at fixed gas pressure (6 mTorr), input power (700 W), and bias power (200 W). Plasma parameters and composition were examined with a combination of plasma diagnostics by double Langmuir probe and global (zero-dimensional) plasma model. It was found that the ITO etch rate follows the behavior of Br atom flux but contradicts with that for H atoms and positive ions. This suggests that the ITO etch process is not limited by the ion-surface interaction kinetics and appears in the reaction-rate-limited etch regime with the Br atoms as the main chemically active species.

  7. Modeling of the simulated countercurrent moving-bed chromatographic reactor used for the oxidative coupling of methane

    SciTech Connect

    Tonkovich, A.L.Y.; Carr, R.W.

    1994-09-01

    The oxidative coupling reaction of methane (OCM) is a potential industrial reaction for the efficient production of ethylene. Replacement of current technologies requires significant product yield improvements. An experimental novel reactor design, the modified simulated countercurrent moving-bed chromatographic reactor (SCMCR), has reported improved ethane and ethylene product yields over other reported values. An understanding of the reactor operation is aided by concurrent mathematical modeling. The model mimics the exact experimental reactor configuration. Four sections are used; each section contains a reaction column and two separation columns connected in series. The feed is switched from section to section at discrete intervals. Reaction occurs in the first column and is followed by product and reactant separation in the ensuing section columns. Langmuir adsorption isotherms are used. The model does not incorporate the realistic and complex kinetics rising, from the OCM, rather a simplified reaction term is used to qualitatively gain insight into the operation of the modified SCMCR. A unimolecular reaction network is used in the model. The rate constants are set to permit a small fractional conversion, 5% per pass, at the concentrations during the first cycle. Similarly to the experimental reactor, the model adds a make-up feed (defined as percentage of the original feed, where excess methane is fed during the first cycle of the experimental reactor) to augment lost reactants.

  8. Effects of steam and liquid water treatment on the oxidative coupling of methane over a Li/MgO catalyst

    SciTech Connect

    Al-Zahrani, S.M.S.; Lobban, L.L.

    1995-04-01

    The effects of adding H{sub 2}O to the gas feed on the oxidative coupling of methane over Li/MgO catalyst at different partial pressures of H{sub 2}O and temperatures and in the presence of cofed CO{sub 2} have been studied. Results indicated that H{sub 2}O enhanced the deactivation rate. The deactivation rate increased with increasing partial pressure of the steam in the feed as well as with increasing temperature. The deactivation rate is decreased by adding small amounts of CO{sub 2} to the reaction mixture. The effects of injecting different amounts of liquid water into the catalyst bed under different reaction conditions have also been investigated. Results showed that under the conditions of the experiments water significantly enhanced the activity of the catalyst. The methane conversion increased by 86%--124% while the C{sub 2} selectivity remained relatively unchanged. The liquid water treatment significantly increased the product C{sub 2}H{sub 4}: C{sub 2}H{sub 6} ratio. The catalyst lithium content decreased and the BET surface area increased due to the water treatment. Some of the lithium lost from the catalyst was deposited on the walls of the reactor; however, this lithium was not responsible for the enhanced activity.

  9. Insulin acutely improves mitochondrial function of rat and human skeletal muscle by increasing coupling efficiency of oxidative phosphorylation.

    PubMed

    Nisr, Raid B; Affourtit, Charles

    2014-02-01

    Insulin is essential for the regulation of fuel metabolism and triggers the uptake of glucose by skeletal muscle. The imported glucose is either stored or broken down, as insulin stimulates glycogenesis and ATP synthesis. The mechanism by which ATP production is increased is incompletely understood at present and, generally, relatively little functional information is available on the effect of insulin on mitochondrial function. In this paper we have exploited extracellular flux technology to investigate insulin effects on the bioenergetics of rat (L6) and human skeletal muscle myoblasts and myotubes. We demonstrate that a 20-min insulin exposure significantly increases (i) the cell respiratory control ratio, (ii) the coupling efficiency of oxidative phosphorylation, and (iii) the glucose sensitivity of anaerobic glycolysis. The improvement of mitochondrial function is explained by an insulin-induced immediate decrease of mitochondrial proton leak. Palmitate exposure annuls the beneficial mitochondrial effects of insulin. Our data improve the mechanistic understanding of insulin-stimulated ATP synthesis, and reveal a hitherto undisclosed insulin sensitivity of cellular bioenergetics that suggests a novel way of detecting insulin responsiveness of cells. PMID:24212054

  10. The Conserved G-Protein Coupled Receptor FSHR-1 Regulates Protective Host Responses to Infection and Oxidative Stress

    PubMed Central

    Giannini, Jennifer A.; Robinson, Joseph D.; Powell, Jennifer R.

    2015-01-01

    The innate immune system’s ability to sense an infection is critical so that it can rapidly respond if pathogenic microorganisms threaten the host, but otherwise maintain a quiescent baseline state to avoid causing damage to the host or to commensal microorganisms. One important mechanism for discriminating between pathogenic and non-pathogenic bacteria is the recognition of cellular damage caused by a pathogen during the course of infection. In Caenorhabditis elegans, the conserved G-protein coupled receptor FSHR-1 is an important constituent of the innate immune response. FSHR-1 activates the expression of antimicrobial infection response genes in infected worms and delays accumulation of the ingested pathogen Pseudomonas aeruginosa. FSHR-1 is central not only to the worm’s survival of infection by multiple pathogens, but also to the worm’s survival of xenobiotic cadmium and oxidative stresses. Infected worms produce reactive oxygen species to fight off the pathogens; FSHR-1 is required at the site of infection for the expression of detoxifying genes that protect the host from collateral damage caused by this defense response. Finally, the FSHR-1 pathway is important for the ability of worms to discriminate pathogenic from benign bacteria and subsequently initiate an aversive learning program that promotes selective pathogen avoidance. PMID:26360906

  11. A novel use of oxidative coupling reactions for determination of some statins (cholesterol-lowering drugs) in pharmaceutical formulations

    NASA Astrophysics Data System (ADS)

    Ashour, Safwan; Bahbouh, Mahmoud; Khateeb, Mouhammed

    2011-03-01

    New, accurate and reliable spectrophotometric methods for the assay of three statin drugs, atorvastatin calcium (AVS), fluvastatin sodium (FVS) and pravastatin sodium (PVS) in pure form and pharmaceutical formulations have been described. All methods involve the oxidative coupling reaction of AVS, FVS and PVS with 3-methyl-2-benzothiazolinone hydrazone hydrochloride monohydrate (MBTH) in the presence of Ce(IV) in an acidic medium to form colored products with λmax at 566, 615 and 664 nm, respectively. Beer's law was obeyed in the ranges of 2.0-20.0, 4.9-35.4 and 7.0-30.0 μg mL -1 for AVS-MBTH, FVS-MBTH and PVS-MBTH, respectively. Molar absorptivities for the above three methods were found to be 3.24 × 10 4, 1.05 × 10 4 and 0.68 × 10 4 L mol -1 cm -1, respectively. Statistical treatment of the experimental results indicates that the methods are precise and accurate. The proposed methods have been applied to the determination of the components in commercial forms with no interference from the excipients. A comparative study between the suggested procedures and the official methods for these compounds in the commercial forms showed no significant difference between the two methods.

  12. Geobacter metallireducens gen. nov. sp. nov., a microorganism capable of coupling the complete oxidation of organic compounds to the reduction of iron and other metals

    USGS Publications Warehouse

    Lovley, D.R.; Giovannoni, S.J.; White, D.C.; Champine, J.E.; Phillips, E.J.P.; Gorby, Y.A.; Goodwin, S.

    1993-01-01

    The gram-negative metal-reducing microorganism, previously known as strain GS-15, was further characterized. This strict anaerobe oxidizes several short-chain fatty acids, alcohols, and monoaromatic compounds with Fe(III) as the sole electron acceptor. Furthermore, acetate is also oxidized with the reduction of Mn(IV), U(VI), and nitrate. In whole cell suspensions, the c-type cytochrome(s) of this organism was oxidized by physiological electron acceptors and also by gold, silver, mercury, and chromate. Menaquinone was recovered in concentrations comparable to those previously found in gram-negative sulfate reducers. Profiles of the phospholipid ester-linked fatty acids indicated that both the anaerobic desaturase and the branched pathways for fatty acid biosynthesis were operative. The organism contained three lipopolysaccharide hydroxy fatty acids which have not been previously reported in microorganisms, but have been observed in anaerobic freshwater sediments. The 16S rRNA sequence indicated that this organism belongs in the delta proteobacteria. Its closest known relative is Desulfuromonas acetoxidans. The name Geobacter metallireducens is proposed.

  13. 0.1 V 13 GHz Transformer-Based Quadrature Voltage-Controlled Oscillator with a Capacitor Coupling Technique in 90 nm Complementary Metal Oxide Semiconductor

    NASA Astrophysics Data System (ADS)

    Kamimura, Tatsuya; Lee, Sang-yeop; Tanoi, Satoru; Ito, Hiroyuki; Ishihara, Noboru; Masu, Kazuya

    2012-04-01

    A low power-supply voltage and high-frequency quadrature voltage-controlled oscillator (QVCO) using a combination of capacitor coupling and transformer feedback techniques is presented. The capacitor coupling technique can boost the transconductance of the LC-VCO core and coupling transconductance of QVCO at high frequency. Also, this technique can improve the quality factor of the QVCO at high frequency with low power-supply voltage, compared with the conventional QVCO. In addition, the capacitor coupling QVCO with transformer feedback can improve the quality factor of QVCO. Using this topology, the QVCO is able to operate at over 10 GHz with lower power-supply voltage. Implemented in the 90 nm complementary metal oxide semiconductor (CMOS) process, the proposed QVCO measures 1-MHz-offset phase noise of -94 dBc/Hz at 13 GHz while consuming 0.68 mW from a 0.1 V power-supply.

  14. Adiabatic calorimetry (RSST and VSP) tests with sodium acetate

    SciTech Connect

    Kirch, N.W.

    1993-09-01

    As requested in the subject reference, adiabatic calorimetry (RSST and VSP) tests have been performed with sodium acetate covering TOC concentrations from 3 to 7% with the following results: Exothermic activity noted around 200{degrees}C. Propagating reaction initiated at about 300{degrees}C. Required TOC concentration for propagation estimated at about 6 w% (dry mixture) or about 20 w% sodium acetate. Heat of reaction estimated to be 3.7 MJ per kg of sodium acetate (based on VSP test with 3 w% TOC and using a dry mixture specific heat of 1000 J kg{sup {minus}1} K{sup {minus}1}). Based upon the above results we estimate that a moisture content in excess of 14 w% would prevent a propagating reaction of a stoichiometric mixture of fuel and oxidizer ({approximately} 38 w% sodium acetate and {approximately}62 w% sodium nitrate). Assuming that the fuel can be treated as sodium acetate equivalent, and considering that the moisture content in the organic containing waste generally is believed to be in excess of 14 w%, it follows that the possibility of propagating reactions in the Hanford waste tanks can be ruled out.

  15. Desmopressin Acetate in Intracranial Haemorrhage

    PubMed Central

    Kapapa, Thomas; Röhrer, Stefan; Struve, Sabine; Petscher, Matthias; König, Ralph; Wirtz, Christian Rainer; Woischneck, Dieter

    2014-01-01

    Introduction. The secondary increase in the size of intracranial haematomas as a result of spontaneous haemorrhage or trauma is of particular relevance in the event of prior intake of platelet aggregation inhibitors. We describe the effect of desmopressin acetate as a means of temporarily stabilising the platelet function. Patients and Methods. The platelet function was analysed in 10 patients who had received single (N = 4) or multiple (N = 6) doses of acetylsalicylic acid and 3 patients (control group) who had not taken acetylsalicylic acid. All subjects had suffered intracranial haemorrhage. Analysis was performed before, half an hour and three hours after administration of desmopressin acetate. Statistical analysis was performed by applying a level of significance of P ≤ 0.05. Results. (1) Platelet function returned to normal 30 minutes after administration of desmopressin acetate. (2) The platelet function worsened again after three hours. (3) There were no complications related to electrolytes or fluid balance. Conclusion. Desmopressin acetate can stabilise the platelet function in neurosurgical patients who have received acetylsalicylic acid prior to surgery without causing transfusion-related side effects or a loss of time. The effect is, however, limited and influenced by the frequency of drug intake. Further controls are needed in neurosurgical patients. PMID:25610644

  16. Reduction of Matrix-Induced Oxide Interferences on Rare Earth Elements and Platinum Using a Desolvating Nebulizer System with Quadrupole Inductively Coupled Plasma Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Smith, F.

    2013-12-01

    This paper will examine the use of a specialized low-flow desolvating nebulizer system for reduction of oxide mass spectral interferences that can occur in quadrupole inductively coupled plasma mass spectrometry (Q-ICP-MS). This nebulizer system uses an inert low-flow nebulizer (100 microliters/min) coupled to an inert, heated membrane desolvator for efficient water vapor removal before sample aerosol injection to the Q-ICP-MS instrument. Water vapor from conventional nebulizer / spray chamber systems used with Q-ICP-MS can cause numerous mass spectral interferences. One general example is metal oxides formed from the combination of oxygen (from injected water) with sample matrix components. Two specific examples of metal oxide interferences will be investigated with and without membrane desolvation: Ba and Ce oxides on several low-mass rare earth elements (Sm, Eu, and Gd) and Hf oxides on platinum. Rare earth elements are critically important components of modern electronics (ex. magnets, lasers, cell phones, computers) and platinum is a widely used catalyst. Figures of merit for both a conventional nebulizer/spray chamber and the desolvating nebulizer systems will include operating conditions, interference intensities and reduction factors, background equivalent concentrations (BECs), and instrument detection limits (IDLs).

  17. Synthesis and regeneration of lead (IV) acetate

    SciTech Connect

    Boyle, T.J.; Al-Shareef, H.N.; Moore, G.J.

    1996-11-01

    Lead acetate [Pb(O{sub 2}CMe){sub 4}] was easily synthesized from a warm solution of Pb{sub 3}O{sub 4}, HO{sub 2}CMe and O(OCMe){sub 2} following literature preparations when the appropriate measures to minimize water contamination were followed. Furthermore, Pb(O{sub 2}CMe){sub 4} which has been decomposed (evidenced by the appearance of a purple color due to oxidation) can be regenerated using a similar preparatory route. Introduction of Pb(O{sub 2}CMe){sub 4} from the two routes outlined above into the IMO process for production of PZT thin films gave films with comparable ferroelectric properties to commercially available Pb(O{sub 2}CMe){sub 4} precursors. However, the freshly synthesized material yields PZT films with better properties compared to the recycled material.

  18. CuBr catalyzed aerobic oxidative coupling of 2-aminopyridines with cinnamaldehydes: direct access to 3-formyl-2-phenyl-imidazo[1,2-a]pyridines.

    PubMed

    Bharate, Jaideep B; Abbat, Sheenu; Bharatam, Prasad V; Vishwakarma, Ram A; Bharate, Sandip B

    2015-07-28

    Copper bromide catalyzed aerobic oxidative coupling of 2-aminopyridines with cinnamaldehydes directly led to the formation of 3-formyl-2-phenyl-imidazo[1,2-a]pyridines. The quantum chemical calculations were performed to trace the reaction mechanism and get insights into the possible reaction pathway. 2-Aminopyridines on coupling with cinnamaldehyde generate (E)-3-phenyl-3-(pyridin-2-ylamino)acrylaldehyde IV as a key intermediate, which undergoes C-N bond formation reaction to produce 3-formyl-2-phenyl-imidazo[1,2-a]pyridines. PMID:26103156

  19. Reductive opening of carbohydrate phenylsulfonylethylidene (PSE) acetals.

    PubMed

    Chéry, Florence; Cabianca, Elena; Tatibouët, Arnaud; De Lucchi, Ottorino; Lindhorst, Thisbe K; Rollin, Patrick

    2015-11-19

    The phenylsulfonylethylidene (PSE) acetal is a relatively new protecting group in carbohydrate chemistry. However, carbohydrate-derived phenylsulfonylethylidene (PSE) acetals show a different behavior in reductive desulfonylation than simple symmetrical acetals. Here we have investigated various SET-type reaction conditions in order to open PSE acetals regioselectively and to produce chiral ω-hydroxyethenyl ethers. Whereas sodium amalgam leads to a mixture of regioisomeric vinyl ethers besides the ethylidene acetal, samarium iodide is suited for regioselective ring opening. This is shown with seven different carbohydrate PSE acetals, both of the 1,3-dioxane and the 1,3-dioxolane type. PMID:26469209

  20. Acetate as a Metabolic and Epigenetic Modifier of Cancer Therapy.

    PubMed

    Jaworski, Diane M; Namboodiri, Aryan M A; Moffett, John R

    2016-03-01

    Metabolic networks are significantly altered in neoplastic cells. This altered metabolic program leads to increased glycolysis and lipogenesis and decreased dependence on oxidative phosphorylation and oxygen consumption. Despite their limited mitochondrial respiration, cancer cells, nonetheless, derive sufficient energy from alternative carbon sources and metabolic pathways to maintain cell proliferation. They do so, in part, by utilizing fatty acids, amino acids, ketone bodies, and acetate, in addition to glucose. The alternative pathways used in the metabolism of these carbon sources provide opportunities for therapeutic manipulation. Acetate, in particular, has garnered increased attention in the context of cancer as both an epigenetic regulator of posttranslational protein modification, and as a carbon source for cancer cell biomass accumulation. However, to date, the data have not provided a clear understanding of the precise roles that protein acetylation and acetate oxidation play in carcinogenesis, cancer progression or treatment. This review highlights some of the major issues, discrepancies, and opportunities associated with the manipulation of acetate metabolism and acetylation-based signaling in cancer development and treatment. PMID:26251955

  1. Thermodynamic analysis of acetic acid steam reforming for hydrogen production

    NASA Astrophysics Data System (ADS)

    Goicoechea, Saioa; Ehrich, Heike; Arias, Pedro L.; Kockmann, Norbert

    2015-04-01

    A thermodynamic analysis of hydrogen generation by acetic acid steam reforming has been carried out with respect to applications in solid oxide fuel cells. The effect of operating parameters on equilibrium composition has been examined focusing especially on hydrogen and carbon monoxide production, which are the fuels in this type of fuel cell. The temperature, steam to acetic acid ratio, and to a lesser extent pressure affect significantly the equilibrium product distribution due to their influence on steam reforming, thermal decomposition and water-gas shift reaction. The study shows that steam reforming of acetic acid with a steam to acetic acid ratio of 2 to 1 is thermodynamically feasible with hydrogen, carbon monoxide and water as the main products at the equilibrium at temperatures higher than 700 °C, and achieving CO/CO2 ratios higher than 1. Thus, it can be concluded that within the operation temperature range of solid oxide fuel cells - between 700 °C and 1000 °C - the production of a gas rich in hydrogen and carbon monoxide is promoted.

  2. Determination of rare earth impurities in high purity samarium oxide using inductively coupled plasma mass spectrometry after extraction chromatographic separation

    NASA Astrophysics Data System (ADS)

    Zhang, Xinquan; Liu, Jinglei; Yi, Yong; Liu, Yonglin; Li, Xiang; Su, Yaqin; Lin, Ping

    2007-01-01

    A method for the determination of trace of 14 rare earth elements (REEs) as impurities in high purity samarium oxide (Sm2O3) using inductively coupled plasma mass spectrometry (ICP-MS) was described. Analytes, such as La, Ce, Pr, Nd, Eu, Gd, Tb, Lu and Y were measured without Sm matrix separation because of no interference problems occurring that could affect the analysis of these elements. On the other hand, analytes, such as Dy, Ho, Er, Tm and Yb were carried out after Sm matrix being eliminated completely by means of 2-ethylhexyl hydrogen-ethylhexy phosphonate (EHEHP) extraction chromatographic separation. The inherent problem associated with matrix-induced suppression was effectively compensated with spiking In as internal standard element and the mass spectra isobaric interferences of atomic and molecular ions arose from Sm matrix had been overcome after the removal of Sm matrix. The limits of quantitations (LOQ) for 14 REEs impurities were from 0.01 to 0.07 [mu]g g-1 together with the recoveries of spiking sample of 14 REEs were found to be in the range of 85-110% and the proposed method precision was less than 5%. A synthetic standard Sm2O3 sample with well-known 14 REEs concentrations was prepared and analysed in order to prove the accuracy and precision of the proposed method together with another high purity Sm2O3 was also measured using ICP-MS. The methodology had been found to be suitable for the determination of trace of 14 REEs in 99.999-99.9999% high purity Sm2O3.

  3. Hemoglobin α / eNOS Coupling at Myoendothelial Junctions is Required for Nitric Oxide Scavenging During Vasoconstriction

    PubMed Central

    Straub, Adam C.; Butcher, Joshua T.; Billaud, Marie; Mutchler, Stephanie M.; Artamonov, Mykhaylo V.; Nguyen, Anh T.; Johnson, Tyler; Best, Angela K.; Miller, Megan P.; Palmer, Lisa A.; Columbus, Linda; Somlyo, Avril V.; Le, Thu H.; Isakson, Brant E.

    2014-01-01

    Objective Hb α and eNOS form a macromolecular complex at myoendothelial junctions; the functional role of this interaction remains undefined. To test if coupling of eNOS and Hb α regulates NO signaling, vascular reactivity and blood pressure using a mimetic peptide of Hb α to disrupt this interaction. Approach and Results In silico modeling of Hb α and eNOS identified a conserved sequence of interaction. By mutating portions of Hb α, we identified a specific sequence that binds eNOS. A mimetic peptide of the Hb α sequence (Hb α X) was generated to disrupt this complex. Utilizing in vitro binding assays with purified Hb α and eNOS and ex vivo proximity ligation assays on resistance arteries, we have demonstrated that Hb α X significantly decreased interaction between eNOS and Hb α. FITC-labeling of Hb α X revealed localization to holes in the internal elastic lamina (i.e., myoendothelial junctions). To test the functional effects of Hb α X, we measured cGMP and vascular reactivity. Our results reveal augmented cGMP production and altered vasoconstriction with Hb α X. To test the in vivo effects of these peptides on blood pressure, normotensive and hypertensive mice were injected with Hb α X which caused a significant decrease in blood pressure; injection of Hb α X into eNOS−/− mice had no effect. Conclusion These results identify a novel sequence on Hb α that is important for Hb α / eNOS complex formation and is critical for nitric oxide signaling at myoendothelial junctions. PMID:25278292

  4. Multimetallic catalysed radical oxidative C(sp(3))-H/C(sp)-H cross-coupling between unactivated alkanes and terminal alkynes.

    PubMed

    Tang, Shan; Wang, Pan; Li, Haoran; Lei, Aiwen

    2016-01-01

    Radical involved transformations are now considered as extremely important processes in modern organic synthetic chemistry. According to the demand by atom-economic and sustainable chemistry, direct C(sp(3))-H functionalization through radical oxidative coupling represents an appealing strategy for C-C bond formations. However, the selectivity control of reactive radical intermediates is still a great challenge in these transformations. Here we show a selective radical oxidative C(sp(3))-H/C(sp)-H cross-coupling of unactivated alkanes with terminal alkynes by using a combined Cu/Ni/Ag catalytic system. It provides a new way to access substituted alkynes from readily available materials. Preliminary mechanistic studies suggest that this reaction proceeds through a radical process and the C(sp(3))-H bond cleavage is the rate-limiting step. This study may have significant implications for controlling selective C-C bond formation of reactive radical intermediates by using multimetallic catalytic systems. PMID:27339161

  5. Verification of the Major Metabolic Oxidation Path for the Naphthoyl Group in Chemoattractant Receptor-Homologous Molecule Expressed on Th2 Cells (CRTh2) Antagonist 2-(2-(1-Naphthoyl)-8-fluoro-3,4-dihydro-1H-pyrido[4,3-b]indol-5(2H)-yl)acetic Acid (Setipiprant/ACT-129968).

    PubMed

    Risch, Philippe; Pfeifer, Thomas; Segrestaa, Jerome; Fretz, Heinz; Pothier, Julien

    2015-10-22

    Various racemic and enantioenriched (trans)-X,Y-dihydroxy-X,Y-dihydronaphthoyl analogues as well as X-hydroxy-naphthoyl analogues of CRTh2 antagonist 2-(2-(1-naphthoyl)-8-fluoro-3,4-dihydro-1H-pyrido[4,3-b]indol-5(2H)-yl)acetic acid (1, Setipiprant/ACT-129968) were synthesized in order to gain insight into regio- and enantioselectivity of the metabolic oxidation of 1 and to verify the structures of four metabolites that were proposed earlier in a clinical ADME study. Analytical data of the synthetic standards were compared with data from samples of biological origin. The two major metabolites M7 and M9 were unambiguously verified as 2-(2-((trans)-3,4-dihydroxy-3,4-dihydronaphthalene-1-carbonyl)- and 2-(2-((trans)-5,6-dihydroxy-5,6-dihydronaphthalene-1-carbonyl)-8-fluoro-3,4-dihydro-1H-pyrido[4,3-b]indol-5(2H)-yl)acetic acid, respectively, each composed of two enantiomers with 68% and 44% ee in favor of (+)-(3S,4S)-M7 and (+)-(5S,6S)-M9, respectively. Likewise, minor metabolites M3 and M13 were identified as 2-(8-fluoro-2-(5-hydroxy-1-naphthoyl)- and 2-(8-fluoro-2-(4-hydroxy-1-naphthoyl)-1,2,3,4-tetrahydro-5H-pyrido[4,3-b]indol-5-yl)acetic acid, respectively. PMID:26398218

  6. Scalable synthesis of oxazolones from propargylic alcohols through multistep palladium(II) catalysis: β-selective oxidative Heck coupling of cyclic sulfonyl enamides and aryl boroxines.

    PubMed

    Alamsetti, Santosh Kumar; Persson, Andreas K Å; Jiang, Tuo; Bäckvall, Jan-E

    2013-12-16

    A whale of a scale: The title oxidative Heck coupling proceeded with unusual β selectivity to generate a variety of branched substituted oxazolones (see scheme; Ts=p-toluenesulfonyl). The three-step synthesis from readily available starting materials with a simple palladium catalyst and inexpensive reagents could be carried out in a single reaction vessel or scaled up for the preparation of large amounts of these amino acid precursors. PMID:24174347

  7. Microbiosensor for the detection of acetate in electrode-respiring biofilms.

    PubMed

    Atci, Erhan; Babauta, Jerome T; Sultana, Sujala T; Beyenal, Haluk

    2016-07-15

    The goal of this work was to develop a microbiosensor to measure acetate concentration profiles inside biofilms in situ. The working principle of the microbiosensor was based on the correlation between the acetate concentration and the current generated during acetate oxidation by Geobacter sulfurreducens. The microbiosensor consisted of a 30-µm carbon microelectrode with an open tip as a working electrode, with G. sulfurreducens biofilm on the tip and a pseudo Ag/AgCl reference electrode, all enclosed in a glass outer case with a 30-µm tip diameter. The microbiosensor showed a linear response in the 0-1.6mM acetate concentration range with a 79±8µM limit of detection (S/N=2). We quantified the stirring effect and found it negligible. However, the interfering effect of alternative electron donors (lactate, formate, pyruvate, or hydrogen) was found to be significant. The usefulness of the acetate microbiosensor was demonstrated by measuring acetate concentration depth profiles within a G. sulfurreducens biofilm. The acetate concentration remained at bulk values throughout the biofilm when no current was passed, but it decreased from the bulk values to below the detection limit within 200µm when current was allowed to pass. The zero acetate concentration at the bottom of the biofilm showed that the biofilm was acetate-limited. PMID:27016913

  8. 21 CFR 522.533 - Deslorelin acetate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... Deslorelin acetate. (a) Specifications. Each implant contains 2.1 milligrams deslorelin acetate. (b) Sponsor.... One implant per mare. (ii) Indications for use. For inducing ovulation within 48 hours in...

  9. Ozone decomposition in aqueous acetate solutions

    SciTech Connect

    Sehested, K.; Holcman, J.; Bjergbakke, E.; Hart, E.J.

    1987-01-01

    The acetate radical ion reacts with ozone with a rate constant of k = (1.5 +/- 0.5) x 10Z dmT mol s . The products from this reaction are CO2, HCHO, and O2 . By subsequent reaction of the peroxy radical with ozone the acetate radical ion is regenerated through the OH radical. A chain decomposition of ozone takes place. It terminates when the acetate radical ion reacts with oxygen forming the unreactive peroxy acetate radical. The chain is rather short as oxygen is developed, as a result of the ozone consumption. The inhibiting effect of acetate on the ozone decay is rationalized by OH scavenging by acetate and successive reaction of the acetate radical ion with oxygen. Some products from the bimolecular disappearance of the peroxy acetate radicals, however, react further with ozone, reducing the effectiveness of the stabilization.

  10. Azo dye removal in a membrane-free up-flow biocatalyzed electrolysis reactor coupled with an aerobic bio-contact oxidation reactor.

    PubMed

    Cui, Dan; Guo, Yu-Qi; Cheng, Hao-Yi; Liang, Bin; Kong, Fan-Ying; Lee, Hyung-Sool; Wang, Ai-Jie

    2012-11-15

    Azo dyes that consist of a large quantity of dye wastewater are toxic and persistent to biodegradation, while they should be removed before being discharged to water body. In this study, Alizarin Yellow R (AYR) as a model azo dye was decolorized in a combined bio-system of membrane-free, continuous up-flow bio-catalyzed electrolysis reactor (UBER) and subsequent aerobic bio-contact oxidation reactor (ABOR). With the supply of external power source 0.5 V in the UBER, AYR decolorization efficiency increased up to 94.8±1.5%. Products formation efficiencies of p-phenylenediamine (PPD) and 5-aminosalicylic acid (5-ASA) were above 90% and 60%, respectively. Electron recovery efficiency based on AYR removal in cathode zone was nearly 100% at HRTs longer than 6 h. Relatively high concentration of AYR accumulated at higher AYR loading rates (>780 gm(-3) d(-1)) likely inhibited acetate oxidation of anode-respiring bacteria on the anode, which decreased current density in the UBER; optimal AYR loading rate for the UBER was 680 gm(-3) d(-1) (HRT 2.5 h). The subsequent ABOR further improved effluent quality. Overall the Chroma decreased from 320 times to 80 times in the combined bio-system to meet the textile wastewater discharge standard II in China. PMID:23009797

  11. A finite element analysis modeling tool for solid oxide fuel cell development: coupled electrochemistry, thermal and flow analysis in MARC ®

    NASA Astrophysics Data System (ADS)

    Khaleel, M. A.; Lin, Z.; Singh, P.; Surdoval, W.; Collin, D.

    A 3D simulation tool for modeling solid oxide fuel cells is described. The tool combines the versatility and efficiency of a commercial finite element analysis code, MARC ®, with an in-house developed robust and flexible electrochemical (EC) module. Based upon characteristic parameters obtained experimentally and assigned by the user, the EC module calculates the current density distribution, heat generation, and fuel and oxidant species concentration, taking the temperature profile provided by MARC ® and operating conditions such as the fuel and oxidant flow rate and the total stack output voltage or current as the input. MARC ® performs flow and thermal analyses based on the initial and boundary thermal and flow conditions and the heat generation calculated by the EC module. The main coupling between MARC ® and EC is for MARC ® to supply the temperature field to EC and for EC to give the heat generation profile to MARC ®. The loosely coupled, iterative scheme is advantageous in terms of memory requirement, numerical stability and computational efficiency. The coupling is iterated to self-consistency for a steady-state solution. Sample results for steady states as well as the startup process for stacks with different flow designs are presented to illustrate the modeling capability and numerical performance characteristic of the simulation tool.

  12. Recruitment of the adaptor protein Nck to PECAM-1 couples oxidative stress to canonical NF-κB signaling and inflammation.

    PubMed

    Chen, Jie; Leskov, Igor L; Yurdagul, Arif; Thiel, Bonnie; Kevil, Christopher G; Stokes, Karen Y; Orr, A Wayne

    2015-02-24

    Oxidative stress stimulates nuclear factor κB (NF-κB) activation and NF-κB-dependent proinflammatory gene expression in endothelial cells during several pathological conditions, including ischemia/reperfusion injury. We found that the Nck family of adaptor proteins linked tyrosine kinase signaling to oxidative stress-induced activation of NF-κB through the classic IκB kinase-dependent pathway. Depletion of Nck prevented oxidative stress induced by exogenous hydrogen peroxide or hypoxia/reoxygenation injury from activating NF-κB in endothelial cells, increasing the abundance of the proinflammatory molecules ICAM-1 (intracellular adhesion molecule-1) and VCAM-1 (vascular cell adhesion molecule-1) and recruiting leukocytes. Nck depletion also attenuated endothelial cell expression of genes encoding proinflammatory factors but not those encoding antioxidants. Nck promoted oxidative stress-induced activation of NF-κB by coupling the tyrosine phosphorylation of PECAM-1 (platelet endothelial cell adhesion molecule-1) to the activation of p21-activated kinase, which mediates oxidative stress-induced NF-κB signaling. Consistent with this mechanism, treatment of mice subjected to ischemia/reperfusion injury in the cremaster muscle with a Nck inhibitory peptide blocked leukocyte adhesion and emigration and the accompanying vascular leak. Together, these data identify Nck as an important mediator of oxidative stress-induced inflammation and a potential therapeutic target for ischemia/reperfusion injury. PMID:25714462

  13. Recruitment of the adaptor protein Nck to PECAM-1 couples oxidant stress to canonical NF-κB signaling and inflammation

    PubMed Central

    Chen, Jie; Leskov, Igor L.; Yurdagul, Arif; Thiel, Bonnie; Kevil, Christopher G.; Stokes, Karen Y.; Orr, A. Wayne

    2015-01-01

    Oxidant stress drives nuclear factor κB (NF-κB) activation and NF-κB-dependent proinflammatory gene expression in endothelial cells during several pathological conditions, including ischemia/reperfusion injury. We showed that the Nck family of adaptor proteins linked tyrosine kinase signaling to oxidant stress-induced activation of NF-κB through the classic IκB kinase (IKK)-dependent pathway. Depletion of Nck prevented oxidant stress induced by exogenous peroxide or hypoxia/reoxygenation injury from triggering the activation of NF-κB in endothelial cells, increases in the abundance of the pro-inflammatory molecules ICAM-1 (intracellular adhesion molecule 1) and VCAM-1 (vascular cell adhesion molecule 1), and leukocyte recruitment. Nck depletion also attenuated endothelial cell expression of genes encoding proinflammatory factors, but not those encoding antioxidants. We further showed that Nck promoted oxidant stress-induced activation of NF-κB by coupling the tyrosine phosphorylation of platelet-endothelial cell adhesion molecule-1 (PECAM-1) to the activation of p21 activated kinase, which mediates oxidant stress-induced NF-κB signaling. Consistent with this model, treatment of mice subjected to ischemia/reperfusion injury in the cremaster muscle with a Nck inhibitory peptide inhibited leukocyte adhesion and emigration and the accompanying vascular leak. Together, these data identify Nck as an important mediator of oxidant stress-induced inflammation and a potential therapeutic target for ischemia/reperfusion injury. PMID:25714462

  14. 21 CFR 184.1721 - Sodium acetate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Sodium acetate. 184.1721 Section 184.1721 Food and....1721 Sodium acetate. (a) Sodium acetate (C2H3O2Na, CAS Reg. No. 127-09-3 or C2H3O2Na·3H2O, CAS Reg. No. 6131-90-4) is the sodium salt of acetic acid and occurs naturally in plant and animal tissues....

  15. N-phosphorylated ketene S,N-acetals

    SciTech Connect

    Kozlov, V.A.; Dol'nikova, T.Yu.; Grapov, A.F.; Mel'nikov, N.N.

    1987-09-20

    The authors investigate the reactions of phosphorisocyanitidic and phosphorisocyanatidothioc esters with organic CH acids and determine that the products, depending on the substituent on the beta-carbon atom, are either ketene S,N-acetals or equilibrium mixtures of these and phosphorylated imino thioesters. IR spectra were determined in chloroform. H 1 and P 31 NMR spectra were determined in deuterated acetone. An analysis of the spectra, including the determination of spin-spin coupling constants, is conducted.

  16. Denitrification-coupled iron(ii) oxidation: a key process regulating the fate and transport of nitrate, phosphate, and arsenic in a wastewater-contaminated aquifer

    USGS Publications Warehouse

    Smith, Richard L.; Kent, Douglas B.; Repert, Deborah A.; Hart, C. P.

    2008-01-01

    Denitrification in the subsurface is often viewed as a heterotrophic process. However, some denitrifiers can also utilize inorganic electron donors. In particular, Fe(II), which is common in many aquifers, could be an important reductant for contaminant nitrate. Anoxic iron oxidation would have additional consequences, including decreased mobility for species like arsenic and phosphate, which bind strongly to hydrous Fe(III) oxide. A study was conducted in a wastewater contaminant plume on Cape Cod to assess the potential for denitrification- coupled Fe(II) oxidation. Previous changes in wastewater disposal upgradient of the study area had resulted in nitrate being transported into a portion of the anoxic zone of the plume and decreased concentrations of Fe(II), phosphate, and arsenic. A series of anoxic tracers (groundwater + nitrate + bromide) were injected into the unaffected, Fe(II)-containing zone under natural gradient conditions. Denitrification was stimulated within 1 m of transport (4 days) for both low and high (100 & 1000 μM) nitrate additions, initially producing stiochiometric quantities of nitrous oxide (>300 μM N) and trace amounts of nitrite. Subsequent injections at the same site reduced nitrate even more rapidly and produced less nitrous oxide, especially over longer transport distances. Fe(II) and nitrate concentrations decreased together and this was accompanied by an increase in colloidal Fe(III) and decreases in pH, total arsenic, and phosphate concentrations. All plume constituents returned to background levels several weeks after the tracer tests were completed. Groundwater microorganisms collected on filters during the tracer test rapidly and immediately reduced nitrite and oxidized Fe(II) in 3-hr laboratory incubations. Several pure cultures of Fe(II)-oxidizing denitrifying bacteria were isolated from core material and subsequently characterized. All of the isolates were mixotrophic, simultaneously oxidizing organic carbon and Fe

  17. Denitrification-Coupled Iron(II) Oxidation: A Key Process Regulating the Fate and Transport of Nitrate, Phosphate, and Arsenic in a Wastewater-Contaminated Aquifer

    NASA Astrophysics Data System (ADS)

    Smith, R. L.; Kent, D. B.; Repert, D. A.; Hart, C. P.

    2007-12-01

    Denitrification in the subsurface is often viewed as a heterotrophic process. However, some denitrifiers can also utilize inorganic electron donors. In particular, Fe(II), which is common in many aquifers, could be an important reductant for contaminant nitrate. Anoxic iron oxidation would have additional consequences, including decreased mobility for species like arsenic and phosphate, which bind strongly to hydrous Fe(III) oxide. A study was conducted in a wastewater contaminant plume on Cape Cod to assess the potential for denitrification- coupled Fe(II) oxidation. Previous changes in wastewater disposal upgradient of the study area had resulted in nitrate being transported into a portion of the anoxic zone of the plume and decreased concentrations of Fe(II), phosphate, and arsenic. A series of anoxic tracers (groundwater + nitrate + bromide) were injected into the unaffected, Fe(II)-containing zone under natural gradient conditions. Denitrification was stimulated within 1 m of transport (4 days) for both low and high (100 & 1000 μM) nitrate additions, initially producing stiochiometric quantities of nitrous oxide (>300 μM N) and trace amounts of nitrite. Subsequent injections at the same site reduced nitrate even more rapidly and produced less nitrous oxide, especially over longer transport distances. Fe(II) and nitrate concentrations decreased together and this was accompanied by an increase in colloidal Fe(III) and decreases in pH, total arsenic, and phosphate concentrations. All plume constituents returned to background levels several weeks after the tracer tests were completed. Groundwater microorganisms collected on filters during the tracer test rapidly and immediately reduced nitrite and oxidized Fe(II) in 3-hr laboratory incubations. Several pure cultures of Fe(II)-oxidizing denitrifying bacteria were isolated from core material and subsequently characterized. All of the isolates were mixotrophic, simultaneously oxidizing organic carbon and Fe

  18. The influence of starch oxidization and aluminate coupling agent on interfacial interaction, rheological behavior, mechanical and thermal properties of poly(propylene carbonate)/starch blends

    NASA Astrophysics Data System (ADS)

    Jiang, Guo; Zhang, Shui-Dong; Huang, Han-Xiong; The Key Laboratory of Polymer Processing Engineering of the Ministry of Education Team

    Poly(propylene carbonate) (PPC) is a kind of new biodegradable polymer that is synthesized by copolymerization of propylene oxide and carbon dioxide. In this work, PPC end-capped with maleic anhydride (PPCMA)/thermoplastic starch (TPS), PPCMA/thermoplastic oxidized starch (TPOS) and PPCMA/AL-TPOS (TPOS modified by aluminate coupling agent) blends were prepared by melt blending to improve its thermal and mechanical properties. FTIR results showed that there existed hydrogen-bonding interaction between PPCMA and starch. SEM observation revealed that the compatibility between PPCMA and TPOS was improved by the oxidation of starch. The enhanced interfacial interactions between PPCMA and TPOS led to a better performance of PPC blends such as storage modulus (G'), loss modulus (G''), complex viscosity (η*), tensile strength and thermal properties. Furthermore, the modification of TPOS by aluminate coupling agent (AL) facilitated the dispersion of oxidized starch in PPC matrix, and resulted in increasing the tensile strength and thermal stability. National Natural Science Foundation of China, National Science Fund of Guangdong Province.

  19. A highly active recyclable gold-graphene nanocomposite material for oxidative esterification and Suzuki cross-coupling reactions in green pathway.

    PubMed

    Mondal, Paramita; Salam, Noor; Mondal, Avijit; Ghosh, Kajari; Tuhina, K; Islam, Sk Manirul

    2015-12-01

    A graphene based composite with gold nanoparticles has been synthesized via a simple chemical route and the structure and compositions of nanocomposite has been characterized. The catalyst was found to be remarkably stable and active for the oxidative esterification of alcohols under present reaction conditions using molecular oxygen as green oxidant and Suzuki cross-coupling reactions between aryl halides and phenylboronic acids using environmentally friendly water as solvent. The versatility of both the protocols was demonstrated by taking a number of substrates. This protocol offers several advantages like high yields, clean reactions, recyclability of the catalyst, reaction in water and use of green oxidant. This study suggests graphene, as an economical substitute for carbon nanotubes, could act as a prominent support in heterogeneous catalysis. PMID:26275502

  20. Kinetics of the Methanogenic Fermentation of Acetate

    PubMed Central

    Fukuzaki, Satoshi; Nishio, Naomichi; Nagai, Shiro

    1990-01-01

    Inhibition of the fermentation of acetate to methane and carbon dioxide by acetate was analyzed with an acetate-acclimatized sludge and with Methanosarcina barkeri Fusaro under mesophilic conditions. A second-order substrate inhibition model, qch4 = qmS/[Ks + S + (S2/Ki)], where S was the concentration of undissociated acetic acid, not ionized acetic acid, could be applicable in both cases. The analysis resulted in substrate saturation constants, Ks, of 4.0 μM for the acclimatized sludge and 104 μM for M. barkeri. The threshold concentrations of undissociated acetic acid when no further acetate utilization was observed were 0.078 μM (pH 7.50) for the acclimatized sludge and 4.43 μM (pH 7.45) for M. barkeri. These kinetic results suggested that the concentration of undissociated acetic acid became a key factor governing the actual threshold acetate concentration for acetate utilization and that the acclimatized sludge in which Methanothrix spp. appeared dominant could utilize acetate better and survive at a lower concentration of undissociated acetic acid than could M. barkeri. Images PMID:16348323