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Sample records for acceptors including nitrate

  1. Enhanced natural attenuation of BTEX in the nitrate-reducing environment by different electron acceptors.

    PubMed

    Zhao, Yongsheng; Qu, Dan; Hou, Zhimin; Zhou, Rui

    2015-01-01

    Enhancing natural attenuation of benzene, toluene, ethylbenzene, and xylene (BTEX) in groundwater is a potential remediation technology. This study focused on selecting appropriate electron acceptors to promote BTEX degradation in a nitrate-reducing environment. Nitrate-reducing soil was obtained from simulated BTEX-contaminated column. Enhancing experiments were conducted in the microcosm with nitrate-reducing material and simulated BTEX-polluted groundwater to investigate the promoting feasibility of adding dissolved oxygen (DO), nitrate, chelated Fe(III), and sulphate as electron acceptors. The concentrations of BTEX, electron acceptors, and their reducing products were measured. The order of promoting BTEX degradation with four electron acceptors was nitrate>sulphate>chelated Fe(III)>DO, and the first-order decay coefficients were 0.0432, 0.0333, 0.0240, and 0.0155, respectively. Nitrate, sulphate, and chelated Fe(III) enhanced attenuation. Nitrate was the most effective electron acceptor under nitrate-reducing conditions. Selecting proper electron acceptor is significant in promoting BTEX degradation according to the biogeochemical characteristics of local underground environment.

  2. Effect of cathode electron acceptors on simultaneous anaerobic sulfide and nitrate removal in microbial fuel cell.

    PubMed

    Cai, Jing; Zheng, Ping; Mahmood, Qaisar

    2016-01-01

    The current investigation reports the effect of cathode electron acceptors on simultaneous sulfide and nitrate removal in two-chamber microbial fuel cells (MFCs). Potassium permanganate and potassium ferricyanide were common cathode electron acceptors and evaluated for substrate removal and electricity generation. The abiotic MFCs produced electricity through spontaneous electrochemical oxidation of sulfide. In comparison with abiotic MFC, the biotic MFC showed better ability for simultaneous nitrate and sulfide removal along with electricity generation. Keeping external resistance of 1,000 Ω, both MFCs showed good capacities for substrate removal where nitrogen and sulfate were the main end products. The steady voltage with potassium permanganate electrodes was nearly twice that of with potassium ferricyanide. Cyclic voltammetry curves confirmed that the potassium permanganate had higher catalytic activity than potassium ferricyanide. The potassium permanganate may be a suitable choice as cathode electron acceptor for enhanced electricity generation during simultaneous treatment of sulfide and nitrate in MFCs. PMID:26901739

  3. Molecular and biokinetic characterization of methylotrophic denitrification using nitrate and nitrite as terminal electron acceptors.

    PubMed

    Baytshtok, Vladimir; Kim, Sungpyo; Yu, Ran; Park, Hongkeun; Chandran, Kartik

    2008-01-01

    Although methanol is a widely employed carbon source for denitrification, relatively little is known on the abundance and diversity of methylotrophic bacteria in activated sludge. The primary aim of this study was to specifically identify bacteria that metabolized methanol in a sequencing batch denitrifying reactor (SBDR), using a novel technique, stable isotope probing (SIP) of 13C labeled DNA. A secondary aim was to quantitatively track dominant methylotrophic bacteria in the SBDR exposed to different terminal electron acceptors. SIP enabled 13C 16S rDNA clone libraries revealed that SBDR methylotrophic populations were related to Methyloversatilis spp. and Hyphomicrobium spp. Based on newly developed quantitative polymerase chain reaction (qPCR) assays, Hyphomicrobium spp. were more abundant than Methyloversatilis spp. throughout the period of SBDR operation. The relative population abundance was stable despite a shift in electron acceptor from nitrate to nitrite (keeping the same methanol dose). However, the shift to nitrite resulted in a significant decrease in denitrification biokinetics on both nitrate and nitrite. PMID:18701786

  4. Selection of denitrifying phosphorous accumulating organisms in IFAS systems: comparison of nitrite with nitrate as an electron acceptor.

    PubMed

    Jabari, Pouria; Munz, Giulio; Oleszkiewicz, Jan A

    2014-08-01

    Nitrite and nitrate were compared as electron acceptors to select for denitrifying phosphorous accumulating organisms (DPAO) in two integrated fixed film activated sludge (IFAS 1 and IFAS 2) systems operated as sequencing batch reactors. The bench-scale experiment lasted one year and synthetic wastewater was used as feed. During anoxic conditions 20mgNO3(-)-NL(-1) were dosed into IFAS-1 and 20mgNO2(-)-NL(-1) were dosed into IFAS-2. Long term phosphorous and ammonia removal via nitritation were achieved in both systems and both attached and suspended biomass contributed to phosphorous and ammonia removal. DPAO showed no specific adaptation to the electron acceptor as evidenced by short term switch of feeding with nitrate or nitrite. Anoxic phosphorus uptake rate was significantly higher with nitrite than with nitrate. Results showed that DPAO activity with nitrite could be integrated into attached and suspended biomass of IFAS systems in long term operation.

  5. Nitrate

    Integrated Risk Information System (IRIS)

    Nitrate ; CASRN 14797 - 55 - 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 Effects

  6. BIODEGRADATION OF MONOAROMATIC HYDROCARBONS BY AQUIFER MICROORGANISMS USING OXYGEN, NITRATE, OR NITROUS OXIDE AS THE TERMINAL ELECTRON ACCEPTOR

    EPA Science Inventory

    Microcosms were prepared from aquifer material, spiked with monoaromatic hydrocarbons, and amended with oxygen, nitrate, and nitrous oxide. Benzene and alkylbenzenes were degraded to concentrations below 5 µg/liter within 7 days under aerobic conditions, whereas only the alkylbe...

  7. Electron acceptor dependence of electron shuttle secretion and extracellular electron transfer by Shewanella oneidensis MR-1.

    PubMed

    Wu, Chao; Cheng, Yuan-Yuan; Li, Bing-Bing; Li, Wen-Wei; Li, Dao-Bo; Yu, Han-Qing

    2013-05-01

    Shewanella oneidensis MR-1 is an extensively studied dissimilatory metal-reducing bacterium with a great potential for bioremediation and electricity generation. It secretes flavins as electron shuttles which play an important role in extracellular electron transfer. However, the influence of various environmental factors on the secretion of flavins is largely unknown. Here, the effects of electron acceptors, including fumarate, ferrihydrite, Fe(III)-nitrilotriacetic acid (NTA), nitrate and trimethylamine oxide (TMAO), on the secretion of flavins were investigated. The level of riboflavin and riboflavin-5'-phosphate (FMN) secreted by S. oneidensis MR-1 varied considerably with different electron acceptors. While nitrate and ferrihydrite suppressed the secretion of flavins in relative to fumarate, Fe(III)-NTA and TMAO promoted such a secretion and greatly enhanced ferrihydrite reduction and electricity generation. This work clearly demonstrates that electron acceptors could considerably affect the secretion of flavins and consequent microbial EET. Such impacts of electron acceptors in the environment deserve more attention.

  8. Electron acceptor dependence of electron shuttle secretion and extracellular electron transfer by Shewanella oneidensis MR-1.

    PubMed

    Wu, Chao; Cheng, Yuan-Yuan; Li, Bing-Bing; Li, Wen-Wei; Li, Dao-Bo; Yu, Han-Qing

    2013-05-01

    Shewanella oneidensis MR-1 is an extensively studied dissimilatory metal-reducing bacterium with a great potential for bioremediation and electricity generation. It secretes flavins as electron shuttles which play an important role in extracellular electron transfer. However, the influence of various environmental factors on the secretion of flavins is largely unknown. Here, the effects of electron acceptors, including fumarate, ferrihydrite, Fe(III)-nitrilotriacetic acid (NTA), nitrate and trimethylamine oxide (TMAO), on the secretion of flavins were investigated. The level of riboflavin and riboflavin-5'-phosphate (FMN) secreted by S. oneidensis MR-1 varied considerably with different electron acceptors. While nitrate and ferrihydrite suppressed the secretion of flavins in relative to fumarate, Fe(III)-NTA and TMAO promoted such a secretion and greatly enhanced ferrihydrite reduction and electricity generation. This work clearly demonstrates that electron acceptors could considerably affect the secretion of flavins and consequent microbial EET. Such impacts of electron acceptors in the environment deserve more attention. PMID:23558182

  9. Alkalilimnicola ehrlichii sp. nov., a novel, arsenite-oxidizing haloalkaliphilic gammaproteobacterium capable of chemoautotrophic or heterotrophic growth with nitrate or oxygen as the electron acceptor

    USGS Publications Warehouse

    Hoeft, S.E.; Blum, J.S.; Stolz, J.F.; Tabita, F.R.; Witte, B.; King, G.M.; Santini, J.M.; Oremland, R.S.

    2007-01-01

    A facultative chemoautotrophic bacterium, strain MLHE-1T, was isolated from Mono Lake, an alkaline hypersaline soda lake in California, USA. Cells of strain MLHE-1T were Gram-negative, short motile rods that grew with inorganic electron donors (arsenite, hydrogen, sulfide or thiosulfate) coupled with the reduction of nitrate to nitrite. No aerobic growth was attained with arsenite or sulfide, but hydrogen sustained both aerobic and anaerobic growth. No growth occurred when nitrite or nitrous oxide was substituted for nitrate. Heterotrophic growth was observed under aerobic and anaerobic (nitrate) conditions. Cells of strain MLHE-1T could oxidize but not grow on CO, while CH4 neither supported growth nor was it oxidized. When grown chemoautotrophically, strain MLHE-1T assimilated inorganic carbon via the Calvin-Benson-Bassham reductive pentose phosphate pathway, with the activity of ribulose 1,5-bisphosphate carboxylase (RuBisCO) functioning optimally at 0.1 M NaCl and at pH 7.3. Strain MLHE-1T grew over broad ranges of pH (7.3-10.0; optimum, 9.3), salinity (115-190 g l-1; optimum 30 g l-1) and temperature (113-40 ??C; optimum, 30 ??C). Phylogenetic analysis of 16S rRNA gene sequences placed strain MLHE-1T in the class Gammaproteobacteria (family Ectothiorhodospiraceae) and most closely related to Alkalispirillum mobile (98.5%) and Alkalilimnicola halodurans (98.6%), although none of these three haloalkaliphilic micro-organisms were capable of photoautotrophic growth and only strain MLHE-1T was able to oxidize As(III). On the basis of physiological characteristics and DNA-DNA hybridization data, it is suggested that strain MLHE-1T represents a novel species within the genus Alkalilimnicola for which the name Alkalilimnicola ehrlichii is proposed. The type strain is MLHE-1T (=DSM 17681T =ATCC BAA-1101T). Aspects of the annotated full genome of Alkalilimnicola ehrlichii are discussed in the light of its physiology. ?? 2007 IUMS.

  10. Anaerobic electron acceptor chemotaxis in Shewanella putrefaciens

    NASA Technical Reports Server (NTRS)

    Nealson, K. H.; Moser, D. P.; Saffarini, D. A.

    1995-01-01

    Shewanella putrefaciens MR-1 can grow either aerobically or anaerobically at the expense of many different electron acceptors and is often found in abundance at redox interfaces in nature. Such redox interfaces are often characterized by very strong gradients of electron acceptors resulting from rapid microbial metabolism. The coincidence of S. putrefaciens abundance with environmental gradients prompted an examination of the ability of MR-1 to sense and respond to electron acceptor gradients in the laboratory. In these experiments, taxis to the majority of the electron acceptors that S. putrefaciens utilizes for anaerobic growth was seen. All anaerobic electron acceptor taxis was eliminated by the presence of oxygen, nitrate, nitrite, elemental sulfur, or dimethyl sulfoxide, even though taxis to the latter was very weak and nitrate and nitrite respiration was normal in the presence of dimethyl sulfoxide. Studies with respiratory mutants of MR-1 revealed that several electron acceptors that could not be used for anaerobic growth nevertheless elicited normal anaerobic taxis. Mutant M56, which was unable to respire nitrite, showed normal taxis to nitrite, as well as the inhibition of taxis to other electron acceptors by nitrite. These results indicate that electron acceptor taxis in S. putrefaciens does not conform to the paradigm established for Escherichia coli and several other bacteria. Carbon chemo-taxis was also unusual in this organism: of all carbon compounds tested, the only positive response observed was to formate under anaerobic conditions.

  11. Associative Memory Acceptors.

    ERIC Educational Resources Information Center

    Card, Roger

    The properties of an associative memory are examined in this paper from the viewpoint of automata theory. A device called an associative memory acceptor is studied under real-time operation. The family "L" of languages accepted by real-time associative memory acceptors is shown to properly contain the family of languages accepted by one-tape,…

  12. Microbial Uranium Immobilization Independent of Nitrate Reduction

    SciTech Connect

    Madden, Andrew; Smith, April; Balkwill, Dr. David; Fagan, Lisa Anne; Phelps, Tommy Joe

    2007-01-01

    At many uranium processing and handling facilities, including sites in the U.S. Department of Energy (DOE) complex, high levels of nitrate are present as co-contamination with uranium in groundwater. The daunting prospect of complete nitrate removal prior to the reduction of uranium provides a strong incentive to explore bioremediation strategies that allow for uranium bioreduction and stabilization in the presence of nitrate. Typical in-situ strategies involving the stimulation of metal-reducing bacteria are hindered by low pH environments at this study site and require that the persistent nitrate must first and continuously be removed or transformed prior to uranium being a preferred electron acceptor. This project investigates the possibility of stimulating nitrate-indifferent, pH-tolerant microorganisms to achieve bioreduction of U(VI) despite nitrate persistence. Successful enrichments from U-contaminated sediments demonstrated nearly complete reduction of uranium with very little loss of nitrate from pH 4.9-5.6 using methanol or glycerol as a carbon source. Higher pH enrichments also demonstrated similar U reduction capacity with 5-30% nitrate loss within one week. Bacterial 16S rRNA genes were amplified from uranium-reducing enrichments (pH 5.7-6.7) and sequenced. Phylogenetic analyses classified the clone sequences into four distinct clusters. Data from sequencing and T-RFLP profiles indicated that the majority of the microorganisms stimulated by these enrichment conditions consisted of low G+C Gram-positive bacteria most closely related to Clostridium and Clostridium-like organisms. This research demonstrates that the stimulation of a natural microbial community to immobilize U through bioreduction is possible without the removal of nitrate.

  13. Nitrate reduction in sulfate-reducing bacteria.

    PubMed

    Marietou, Angeliki

    2016-08-01

    Sulfate-reducing bacteria (SRBs) gain their energy by coupling the oxidation of organic substrate to the reduction of sulfate to sulfide. Several SRBs are able to use alternative terminal electron acceptors to sulfate such as nitrate. Nitrate-reducing SRBs have been isolated from a diverse range of environments. In order to be able to understand the significance of nitrate reduction in SRBs, we need to examine the ecology and physiology of the nitrate-reducing SRB isolates.

  14. Microbial uranium immobilization independent of nitrate reduction.

    PubMed

    Madden, Andrew S; Smith, April C; Balkwill, David L; Fagan, Lisa A; Phelps, Tommy J

    2007-09-01

    At many uranium processing and handling facilities, including sites in the US Department of Energy (DOE) complex, high levels of nitrate are present as co-contamination with uranium in groundwater. The daunting prospect of complete nitrate removal prior to the reduction of uranium provides a strong incentive to explore bioremediation strategies that allow for uranium bioreduction and stabilization in the presence of nitrate. Typical in situ strategies involving the stimulation of metal-reducing bacteria are hindered by low-pH environments and require that the persistent nitrate must first and continuously be removed or transformed prior to uranium being a preferred electron acceptor. This work investigated the possibility of stimulating nitrate-indifferent, pH-tolerant microorganisms to achieve bioreduction of U(VI) despite nitrate persistence. Enrichments from U-contaminated sediments demonstrated nearly complete reduction of uranium with very little loss of nitrate from pH 5.7-6.2 using methanol or glycerol as a carbon source. Bacterial 16S rRNA genes were amplified from uranium-reducing enrichments (pH 5.7-6.2) and sequenced. Phylogenetic analyses classified the clone sequences into four distinct clusters. Data from sequencing and terminal-restriction fragment length polymorphism (T-RFLP) profiles indicated that the majority of the microorganisms stimulated by these enrichment conditions consisted of low G+C Gram-positive bacteria most closely related to Clostridium and Clostridium-like organisms. This research demonstrates that the stimulation of a natural microbial community to immobilize U through bioreduction is possible without the removal of nitrate.

  15. Fate of microbial metabolites of hydrocarbons in a coastal plain aquifer: The role of electron acceptors

    USGS Publications Warehouse

    Cozzarelli, I.M.; Herman, J.S.; Baedecker, M. Jo

    1995-01-01

    A combined field and laboratory study was undertaken to understand the distribution and geochemical conditions that influence the prevalence of low molecular weight organic acids in groundwater of a shallow aquifer contaminated with gasoline. Aromatic hydrocarbons from gasoline were degraded by microbially mediated oxidation-reduction reactions, including reduction of nitrate, sulfate, and Fe(III). The biogeochemical reactions changed overtime in response to changes in the hydrogeochemical conditions in the aquifer. Aliphatic and aromatic organic acids were associated with hydrocarbon degradation in anoxic zones of the aquifer. Laboratory microcosms demonstrated that the biogeochemical fate of specific organic acids observed in groundwater varied with the structure of the acid and the availability of electron acceptors. Benzoic and phenylacetic acid were degraded by indigenous aquifer microorganisms when nitrate was supplied as an electron acceptor. Aromatic acids with two or more methyl substituants on the benzene ring persisted under nitrate-reducing conditions. Although iron reduction and sulfate reduction were important processes in situ and occurred in the microcosms, these reactions were not coupled to the biological oxidation of aromatic organic acids that were added to the microcosms as electron donors. ?? 1995 American Chemical Society.

  16. Oxygen as Acceptor.

    PubMed

    Borisov, Vitaliy B; Verkhovsky, Michael I

    2015-01-01

    Like most bacteria, Escherichia coli has a flexible and branched respiratory chain that enables the prokaryote to live under a variety of environmental conditions, from highly aerobic to completely anaerobic. In general, the bacterial respiratory chain is composed of dehydrogenases, a quinone pool, and reductases. Substrate-specific dehydrogenases transfer reducing equivalents from various donor substrates (NADH, succinate, glycerophosphate, formate, hydrogen, pyruvate, and lactate) to a quinone pool (menaquinone, ubiquinone, and dimethylmenoquinone). Then electrons from reduced quinones (quinols) are transferred by terminal reductases to different electron acceptors. Under aerobic growth conditions, the terminal electron acceptor is molecular oxygen. A transfer of electrons from quinol to O₂ is served by two major oxidoreductases (oxidases), cytochrome bo₃ encoded by cyoABCDE and cytochrome bd encoded by cydABX. Terminal oxidases of aerobic respiratory chains of bacteria, which use O₂ as the final electron acceptor, can oxidize one of two alternative electron donors, either cytochrome c or quinol. This review compares the effects of different inhibitors on the respiratory activities of cytochrome bo₃ and cytochrome bd in E. coli. It also presents a discussion on the genetics and the prosthetic groups of cytochrome bo₃ and cytochrome bd. The E. coli membrane contains three types of quinones that all have an octaprenyl side chain (C₄₀). It has been proposed that the bo₃ oxidase can have two ubiquinone-binding sites with different affinities. "WHAT'S NEW" IN THE REVISED ARTICLE: The revised article comprises additional information about subunit composition of cytochrome bd and its role in bacterial resistance to nitrosative and oxidative stresses. Also, we present the novel data on the electrogenic function of appBCX-encoded cytochrome bd-II, a second bd-type oxidase that had been thought not to contribute to generation of a proton motive force in E

  17. Oxygen as Acceptor.

    PubMed

    Borisov, Vitaliy B; Verkhovsky, Michael I

    2015-01-01

    Like most bacteria, Escherichia coli has a flexible and branched respiratory chain that enables the prokaryote to live under a variety of environmental conditions, from highly aerobic to completely anaerobic. In general, the bacterial respiratory chain is composed of dehydrogenases, a quinone pool, and reductases. Substrate-specific dehydrogenases transfer reducing equivalents from various donor substrates (NADH, succinate, glycerophosphate, formate, hydrogen, pyruvate, and lactate) to a quinone pool (menaquinone, ubiquinone, and dimethylmenoquinone). Then electrons from reduced quinones (quinols) are transferred by terminal reductases to different electron acceptors. Under aerobic growth conditions, the terminal electron acceptor is molecular oxygen. A transfer of electrons from quinol to O₂ is served by two major oxidoreductases (oxidases), cytochrome bo₃ encoded by cyoABCDE and cytochrome bd encoded by cydABX. Terminal oxidases of aerobic respiratory chains of bacteria, which use O₂ as the final electron acceptor, can oxidize one of two alternative electron donors, either cytochrome c or quinol. This review compares the effects of different inhibitors on the respiratory activities of cytochrome bo₃ and cytochrome bd in E. coli. It also presents a discussion on the genetics and the prosthetic groups of cytochrome bo₃ and cytochrome bd. The E. coli membrane contains three types of quinones that all have an octaprenyl side chain (C₄₀). It has been proposed that the bo₃ oxidase can have two ubiquinone-binding sites with different affinities. "WHAT'S NEW" IN THE REVISED ARTICLE: The revised article comprises additional information about subunit composition of cytochrome bd and its role in bacterial resistance to nitrosative and oxidative stresses. Also, we present the novel data on the electrogenic function of appBCX-encoded cytochrome bd-II, a second bd-type oxidase that had been thought not to contribute to generation of a proton motive force in E

  18. Physiological and electrochemical effects of different electron acceptors on bacterial anode respiration in bioelectrochemical systems.

    PubMed

    Yang, Yonggang; Xiang, Yinbo; Xia, Chunyu; Wu, Wei-Min; Sun, Guoping; Xu, Meiying

    2014-07-01

    To understand the interactions between bacterial electrode respiration and the other ambient bacterial electron acceptor reductions, alternative electron acceptors (nitrate, Fe2O3, fumarate, azo dye MB17) were added singly or multiply into Shewanella decolorationis microbial fuel cells (MFCs). All the added electron acceptors were reduced simultaneously with current generation. Adding nitrate or MB17 resulted in more rapid cell growth, higher flavin concentration and higher biofilm metabolic viability, but lower columbic efficiency (CE) and normalized energy recovery (NER) while the CE and NER were enhanced by Fe2O3 or fumarate. The added electron acceptors also significantly influenced the cyclic voltammetry profile of anode biofilm probably via altering the cytochrome c expression. The highest power density was observed in MFCs added with MB17 due to the electron shuttle role of the naphthols from MB17 reduction. The results provided important information for MFCs applied in practical environments where contains various electron acceptors.

  19. Modelling transport and degradation of de-icing chemicals in soil, assuming Monod kinetics with multiple electron-acceptors

    NASA Astrophysics Data System (ADS)

    Schotanus, D.; Meeussen, J. C. L.; van der Ploeg, M. J.; van der Zee, S. E. A. T. M.

    2012-04-01

    De-icing chemicals that contain propylene glycol are used at Oslo airport during winter time. A fraction of these chemicals is spilled on the runway and can be transported rapidly in the sandy soil in spring during snowmelt. Better insight into the chemical and physical processes that govern the fate of these chemicals in soil will help to estimate potential effects on the large unconfined aquifer in this area, and makes it possible to evaluate potential remedial actions. Micro-organisms in the soil can degrade propylene glycol, for which they need electron-acceptors. Under aerobic conditions, oxygen will be used as an electron-acceptor. From experiments, it is known that also anaerobic degradation occurs in this soil. During snowmelt, high infiltration rates can lead to locally saturated soil. In these parts, oxygen diffusion is limited and thus anaerobic conditions will occur. In these anaerobic regions, other electron-acceptors, such as manganese-oxides that are present in this soil, are used. However, frequent propylene glycol application may lead to a depletion of manganese-oxides and so to increased persistence and migration of propylene glycol in soil. To prevent this depletion and to enhance biodegradation, other electron-acceptors can be applied at the soil surface. Examples are the application of nitrate to the soil surface, and air injection. Model calculations could help to estimate required concentrations. The objectives of this study are 1) to create the reactive model, 2) to use this model to evaluate which parameters are determining leaching fluxes of propylene glycol from the soil, and 3) to evaluate the effectiveness of the different remediation strategies. Therefore, transient water flow, kinetic degradation, and redox chemistry were combined in one model. Degradation is modelled with Monod kinetics using multiple electron-acceptors. Oxygen diffusion in the gas phase, biomass growth, and oxidation and reduction of the important electron-acceptors

  20. Candidatus Accumulibacter phosphatis clades enriched under cyclic anaerobic and microaerobic conditions simultaneously use different electron acceptors.

    PubMed

    Camejo, Pamela Y; Owen, Brian R; Martirano, Joseph; Ma, Juan; Kapoor, Vikram; Santo Domingo, Jorge; McMahon, Katherine D; Noguera, Daniel R

    2016-10-01

    Lab- and pilot-scale simultaneous nitrification, denitrification and phosphorus removal-sequencing batch reactors were operated under cyclic anaerobic and micro-aerobic conditions. The use of oxygen, nitrite, and nitrate as electron acceptors by Candidatus Accumulibacter phosphatis during the micro-aerobic stage was investigated. A complete clade-level characterization of Accumulibacter in both reactors was performed using newly designed qPCR primers targeting the polyphosphate kinase gene (ppk1). In the lab-scale reactor, limited-oxygen conditions led to an alternated dominance of Clade IID and IC over the other clades. Results from batch tests when Clade IC was dominant (i.e., >92% of Accumulibacter) showed that this clade was capable of using oxygen, nitrite and nitrate as electron acceptors for P uptake. A more heterogeneous distribution of clades was found in the pilot-scale system (Clades IIA, IIB, IIC, IID, IA, and IC), and in this reactor, oxygen, nitrite and nitrate were also used as electron acceptors coupled to phosphorus uptake. However, nitrite was not an efficient electron acceptor in either reactor, and nitrate allowed only partial P removal. The results from the Clade IC dominated reactor indicated that either organisms in this clade can simultaneously use multiple electron acceptors under micro-aerobic conditions, or that the use of multiple electron acceptors by Clade IC is due to significant microdiversity within the Accumulibacter clades defined using the ppk1 gene. PMID:27340814

  1. Nitrate reduction

    DOEpatents

    Dziewinski, Jacek J.; Marczak, Stanislaw

    2000-01-01

    Nitrates are reduced to nitrogen gas by contacting the nitrates with a metal to reduce the nitrates to nitrites which are then contacted with an amide to produce nitrogen and carbon dioxide or acid anions which can be released to the atmosphere. Minor amounts of metal catalysts can be useful in the reduction of the nitrates to nitrites. Metal salts which are formed can be treated electrochemically to recover the metals.

  2. Gallium nitrate revisited.

    PubMed

    Chitambar, Christopher R

    2003-04-01

    Gallium nitrate, the nitrate salt of the "near-metal" element gallium, is highly effective in the treatment of cancer-related hypercalcemia. Unlike bisphosphonates, gallium nitrate is effective in both parathyroid hormone-related protein-mediated and non-parathyroid hormone-related protein-mediated hypercalcemia. Gallium nitrate's effects on bone are clearly different from those of bisphosphonates. Gallium nitrate enhances calcium and phosphate content of bone and has direct, noncytotoxic effects on osteoclasts at markedly lower doses than those used for the treatment of cancer-related hypercalcemia. The drug may have clinical application in a variety of disorders associated with accelerated bone loss, including multiple myeloma. Gallium nitrate was originally evaluated as an antitumor agent. Its antitumor activity occurs at somewhat higher doses than those used in the treatment of cancer-related hypercalcemia. Gallium nitrate has substantial single-agent activity in the treatment of advanced lymphoma, particularly diffuse large cell lymphoma, small lymphocytic lymphoma, and follicular lymphoma. Because of its profile, including a different mechanism of action and minimal myelosuppression, the drug merits further evaluation in the treatment of advanced lymphoma. Gallium nitrate also has activity in advanced bladder cancer and may be useful in patients with metastatic or unresectable disease failing first-line chemotherapy regimens. Gallium nitrate exhibits a range of dose-dependent pharmacologic actions that provide a basis for its therapeutic potential in a variety of diseases and warrants further investigational evaluation as an antiresorptive and antitumor agent. PMID:12776253

  3. Nitrate and periplasmic nitrate reductases

    PubMed Central

    Sparacino-Watkins, Courtney; Stolz, John F.; Basu, Partha

    2014-01-01

    The nitrate anion is a simple, abundant and relatively stable species, yet plays a significant role in global cycling of nitrogen, global climate change, and human health. Although it has been known for quite some time that nitrate is an important species environmentally, recent studies have identified potential medical applications. In this respect the nitrate anion remains an enigmatic species that promises to offer exciting science in years to come. Many bacteria readily reduce nitrate to nitrite via nitrate reductases. Classified into three distinct types – periplasmic nitrate reductase (Nap), respiratory nitrate reductase (Nar) and assimilatory nitrate reductase (Nas), they are defined by their cellular location, operon organization and active site structure. Of these, Nap proteins are the focus of this review. Despite similarities in the catalytic and spectroscopic properties Nap from different Proteobacteria are phylogenetically distinct. This review has two major sections: in the first section, nitrate in the nitrogen cycle and human health, taxonomy of nitrate reductases, assimilatory and dissimilatory nitrate reduction, cellular locations of nitrate reductases, structural and redox chemistry are discussed. The second section focuses on the features of periplasmic nitrate reductase where the catalytic subunit of the Nap and its kinetic properties, auxiliary Nap proteins, operon structure and phylogenetic relationships are discussed. PMID:24141308

  4. Nitrate Removal in Stream Riparian Zones: The Last Fifteen Years

    NASA Astrophysics Data System (ADS)

    Duval, T. P.

    2009-05-01

    Anthropogenic loadings of nitrate from agricultural fertilizer use and deforestation can result in levels deleterious to stream ecosystems and downstream receiving water bodies. Riparian zones represent perhaps our most effective management tool in mitigating these elevated stream nitrate levels. In many settings these interfaces between the terrestrial and the aquatic have been shown to efficiently remove elevated nitrate loadings through denitrification and/or plant uptake. However, it was realized early that some riparian zones are not effective nitrate removers, and the relative importance of plant uptake versus denitrification was unclear. The uncertainty that existed 15 years ago fueled a plethora of studies on nitrate removal in stream riparian zones. This talk will highlight the most important findings of this research over the last decade and a half. Notably, the detailed description of hydrological flowpaths into and through riparian zones to the downstream environment has gone a long way to explaining the ineffectiveness of some riparian zones. Furthermore, the use of 15-N isotope tracers and field and lab incubation studies have aided in quantifying the importance of the denitrification pathway of removal. Patterns of terminal electron donors and acceptors and the importance of the intersection of the nitrate-elevated water with a source of bioavailable organic carbon, including deeply buried carbon, were a series of key achievements. Somewhat surprisingly, it has been shown that hydrogeology/landscape setting has a greater control on nitrate removal that climate/geography, as indicated by studies in different hydrogeologic settings in southern Ontario and uniform settings across a climatic gradient in Europe. Finally, the integration and generalization of these findings to the watershed-regional scale has aided in the transfer of knowledge from the scientist to the manager.

  5. Elevated nitrate enriches microbial functional genes for potential bioremediation of complexly contaminated sediments

    PubMed Central

    Xu, Meiying; Zhang, Qin; Xia, Chunyu; Zhong, Yuming; Sun, Guoping; Guo, Jun; Yuan, Tong; Zhou, Jizhong; He, Zhili

    2014-01-01

    Nitrate is an important nutrient and electron acceptor for microorganisms, having a key role in nitrogen (N) cycling and electron transfer in anoxic sediments. High-nitrate inputs into sediments could have a significant effect on N cycling and its associated microbial processes. However, few studies have been focused on the effect of nitrate addition on the functional diversity, composition, structure and dynamics of sediment microbial communities in contaminated aquatic ecosystems with persistent organic pollutants (POPs). Here we analyzed sediment microbial communities from a field-scale in situ bioremediation site, a creek in Pearl River Delta containing a variety of contaminants including polybrominated diphenyl ethers (PBDEs) and polycyclic aromatic hydrocarbons (PAHs), before and after nitrate injection using a comprehensive functional gene array (GeoChip 4.0). Our results showed that the sediment microbial community functional composition and structure were markedly altered, and that functional genes involved in N-, carbon (C)-, sulfur (S)-and phosphorus (P)- cycling processes were highly enriched after nitrate injection, especially those microorganisms with diverse metabolic capabilities, leading to potential in situ bioremediation of the contaminated sediment, such as PBDE and PAH reduction/degradation. This study provides new insights into our understanding of sediment microbial community responses to nitrate addition, suggesting that indigenous microorganisms could be successfully stimulated for in situ bioremediation of POPs in contaminated sediments with nitrate addition. PMID:24671084

  6. 2012 ELECTRON DONOR-ACCEPTOR INTERACTIONS GORDON RESEARCH CONFERENCE, AUGUST 5-10, 2012

    SciTech Connect

    McCusker, James

    2012-08-10

    The upcoming incarnation of the Gordon Research Conference on Electron Donor Acceptor Interactions will feature sessions on classic topics including proton-coupled electron transfer, dye-sensitized solar cells, and biological electron transfer, as well as emerging areas such as quantum coherence effects in donor-acceptor interactions, spintronics, and the application of donor-acceptor interactions in chemical synthesis.

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

    PubMed

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

    2016-10-01

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

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

    PubMed

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

    2016-10-01

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

  9. Dynamics of iron-acceptor-pair formation in co-doped silicon

    SciTech Connect

    Bartel, T.; Gibaja, F.; Graf, O.; Gross, D.; Kaes, M.; Heuer, M.; Kirscht, F.; Möller, C.; Lauer, K.

    2013-11-11

    The pairing dynamics of interstitial iron and dopants in silicon co-doped with phosphorous and several acceptor types are presented. The classical picture of iron-acceptor pairing dynamics is expanded to include the thermalization of iron between different dopants. The thermalization is quantitatively described using Boltzmann statistics and different iron-acceptor binding energies. The proper understanding of the pairing dynamics of iron in co-doped silicon will provide additional information on the electronic properties of iron-acceptor pairs and may become an analytical method to quantify and differentiate acceptors in co-doped silicon.

  10. Acceptors in ZnO

    SciTech Connect

    Mccluskey, Matthew D.; Corolewski, Caleb; Lv, Jinpeng; Tarun, Marianne C.; Teklemichael, Samuel T.; Walter, Eric D.; Norton, M. G.; Harrison, Kale W.; Ha, Su Y.

    2015-03-21

    Zinc oxide (ZnO) has potential for a range of applications in the area of optoelectronics. The quest for p-type ZnO has focused much attention on acceptors. In this paper, Cu, N, and Li acceptor impurities are discussed. Experimental evidence shows that these point defects have acceptor levels 3.2, 1.5, and 0.8 eV above the valence-band maximum, respectively. The levels are deep because the ZnO valence band is quite low compared to conventional, non-oxide semiconductors. Using MoO2 contacts, the electrical resistivity of ZnO:Li was measured and showed behavior consistent with bulk hole conduction for temperatures above 400 K. A photoluminescence peak in ZnO nanocrystals has been attributed to an acceptor, which may involve a zinc vacancy. High field (W-band) electron paramagnetic resonance measurements on the nanocrystals revealed an axial center with g = 2.0033 and g = 2.0075, along with an isotropic center at g = 2.0053.

  11. Acceptors in ZnO

    SciTech Connect

    McCluskey, Matthew D. Corolewski, Caleb D.; Lv, Jinpeng; Tarun, Marianne C.; Teklemichael, Samuel T.; Walter, Eric D.; Norton, M. Grant; Harrison, Kale W.; Ha, Su

    2015-03-21

    Zinc oxide (ZnO) has potential for a range of applications in the area of optoelectronics. The quest for p-type ZnO has focused much attention on acceptors. In this paper, Cu, N, and Li acceptor impurities are discussed. Experimental evidence indicates these point defects have acceptor levels 3.2, 1.4, and 0.8 eV above the valence-band maximum, respectively. The levels are deep because the ZnO valence band is quite low compared to conventional, non-oxide semiconductors. Using MoO{sub 2} contacts, the electrical resistivity of ZnO:Li was measured and showed behavior consistent with bulk hole conduction for temperatures above 400 K. A photoluminescence peak in ZnO nanocrystals is attributed to an acceptor, which may involve a Zn vacancy. High field (W-band) electron paramagnetic resonance measurements on the nanocrystals revealed an axial center with g{sub ⊥} = 2.0015 and g{sub //} = 2.0056, along with an isotropic center at g = 2.0035.

  12. Modeling the Effect of External Carbon Source Addition under Different Electron Acceptor Conditions in Biological Nutrient Removal Activated Sludge Systems.

    PubMed

    Hu, Xiang; Wisniewski, Kamil; Czerwionka, Krzysztof; Zhou, Qi; Xie, Li; Makinia, Jacek

    2016-02-16

    The aim of this study was to expand the International Water Association Activated Sludge Model No. 2d (ASM2d) to predict the aerobic/anoxic behavior of polyphosphate accumulating organisms (PAOs) and "ordinary" heterotrophs in the presence of different external carbon sources and electron acceptors. The following new aspects were considered: (1) a new type of the readily biodegradable substrate, not available for the anaerobic activity of PAOs, (2) nitrite as an electron acceptor, and (3) acclimation of "ordinary" heterotrophs to the new external substrate via enzyme synthesis. The expanded model incorporated 30 new or modified process rate equations. The model was evaluated against data from several, especially designed laboratory experiments which focused on the combined effects of different types of external carbon sources (acetate, ethanol and fusel oil) and electron acceptors (dissolved oxygen, nitrate and nitrite) on the behavior of PAOs and "ordinary" heterotrophs. With the proposed expansions, it was possible to improve some deficiencies of the ASM2d in predicting the behavior of biological nutrient removal (BNR) systems with the addition of external carbon sources, including the effect of acclimation to the new carbon source. PMID:26783836

  13. Modeling the Effect of External Carbon Source Addition under Different Electron Acceptor Conditions in Biological Nutrient Removal Activated Sludge Systems.

    PubMed

    Hu, Xiang; Wisniewski, Kamil; Czerwionka, Krzysztof; Zhou, Qi; Xie, Li; Makinia, Jacek

    2016-02-16

    The aim of this study was to expand the International Water Association Activated Sludge Model No. 2d (ASM2d) to predict the aerobic/anoxic behavior of polyphosphate accumulating organisms (PAOs) and "ordinary" heterotrophs in the presence of different external carbon sources and electron acceptors. The following new aspects were considered: (1) a new type of the readily biodegradable substrate, not available for the anaerobic activity of PAOs, (2) nitrite as an electron acceptor, and (3) acclimation of "ordinary" heterotrophs to the new external substrate via enzyme synthesis. The expanded model incorporated 30 new or modified process rate equations. The model was evaluated against data from several, especially designed laboratory experiments which focused on the combined effects of different types of external carbon sources (acetate, ethanol and fusel oil) and electron acceptors (dissolved oxygen, nitrate and nitrite) on the behavior of PAOs and "ordinary" heterotrophs. With the proposed expansions, it was possible to improve some deficiencies of the ASM2d in predicting the behavior of biological nutrient removal (BNR) systems with the addition of external carbon sources, including the effect of acclimation to the new carbon source.

  14. Determination of intracellular nitrate.

    PubMed Central

    Romero, J M; Lara, C; Guerrero, M G

    1989-01-01

    A sensitive procedure has been developed for the determination of intracellular nitrate. The method includes: (i) preparation of cell lysates in 2 M-H3PO4 after separation of cells from the outer medium by rapid centrifugation through a layer of silicone oil, and (ii) subsequent nitrate analysis by ion-exchange h.p.l.c. with, as mobile phase, a solution containing 50 mM-H3PO4 and 2% (v/v) tetrahydrofuran, adjusted to pH 1.9 with NaOH. The determination of nitrate is subjected to interference by chloride and sulphate when present in the samples at high concentrations. Nitrite also interferes, but it is easily eliminated by treatment of the samples with sulphamic acid. The method has been successfully applied to the study of nitrate transport in the unicellular cyanobacterium Anacystis nidulans. PMID:2497740

  15. Enhanced biodegradation of cyclotetramethylenetetranitramine (HMX) under mixed electron-acceptor condition.

    PubMed

    Boopathy, R

    2001-02-01

    The biodegradation of cyclotetramethylenetetranitramine, commonly known as 'high melting explosive' (HMX), under various electron-acceptor conditions was investigated using enrichment cultures developed from the anaerobic digester sludge of Thibodaux sewage treatment plant. The results indicated that the HMX was biodegraded under sulfate reducing, nitrate reducing, fermenting, methanogenic, and mixed electron accepting conditions. However, the rates of degradation varied among the various conditions studied. The fastest removal of HMX (from 22 ppm on day 0 to < 0.05 ppm on day 11) was observed under mixed electron-acceptor conditions, followed in order by sulfate reducing, fermenting, methanogenic, and nitrate reducing conditions. Under aerobic conditions, HMX was not biodegraded, which indicated that HMX degradation takes place under anaerobic conditions via reduction. HMX was converted to methanol and chloroform under mixed electron-acceptor conditions. This study showed evidence for HMX degradation under anaerobic conditions in a mixed microbial population system similar to any contaminated field sites, where a heterogeneous population exists.

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

    USGS Publications Warehouse

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

    2017-01-01

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

  17. Alkyl Chlorides as Hydrogen Bond Acceptors

    SciTech Connect

    Nadas, Janos I; Vukovic, Sinisa; Hay, Benjamin

    2012-01-01

    To gain an understanding of the role of an alkyl chloride as a hydrogen bond acceptor, geometries and interaction energies were calculated at the MP2/aug-cc-pVDZ level of theory for complexes between ethyl chloride and representative hydrogen donor groups. The results establish that these donors, which include hydrogen cyanide, methanol, nitrobenzene, pyrrole, acetamide, and N-methylurea, form X-H {hor_ellipsis} Cl hydrogen bonds (X = C, N, O) of weak to moderate strength, with {Delta}E values ranging from -2.8 to -5.3 kcal/mol.

  18. Denitrification and patterns of electron donors and acceptors in 8 riparian zones with contrasting hydrogeology

    NASA Astrophysics Data System (ADS)

    Vidon, P.; Hill, A.

    2004-12-01

    A better understanding of nitrate removal mechanisms is important for managing the water quality function of stream riparian zones. We examined the linkages between hydrologic flow paths, patterns of electron donors and acceptors and the importance of denitrification as a nitrate removal mechanism in 8 riparian zones on glacial till and outwash landscapes in southern Ontario, Canada. Nitrate-N concentrations in shallow groundwater from adjacent cropland declined from levels that were often 10-30 mg L-1 near the field-riparian edge to <1 mg L-1 in the riparian zones throughout the year. Chloride data suggest that dilution cannot account for most of this nitrate decline. Despite contrasting hydrogeologic settings, these riparian zones displayed a well-organized pattern of electron donors and acceptors that resulted from the transport of oxic nitrate-rich groundwater to portions of the riparian zones where low DO concentrations and an increase in DOC concentrations were encountered. The natural abundances of d15N and in situ acetylene injection to piezometers indicate that denitrification is the primary mechanism of nitrate removal in all of the riparian zones. Our data indicate that effective nitrate removal by denitrification occurs in riparian zones with hydric soils as well as in non-hydric riparian zones and that a shallow water table is not always necessary for efficient nitrate removal by denitrification. The location of "hot spots" of denitrification within riparian areas can be explained by the influence of key landscape variables such as slope, sediment texture and depth of confining layers on hydrologic pathways that link supplies of electron donors and acceptors.

  19. Anaerobic methanotrophy in tidal wetland: Effects of electron acceptors

    NASA Astrophysics Data System (ADS)

    Lin, Li-Hung; Yu, Zih-Huei; Wang, Pei-Ling

    2016-04-01

    Wetlands have been considered to represent the largest natural source of methane emission, contributing substantially to intensify greenhouse effect. Despite in situ methanogenesis fueled by organic degradation, methanotrophy also plays a vital role in controlling the exact quantity of methane release across the air-sediment interface. As wetlands constantly experience various disturbances of anthropogenic activities, biological burrowing, tidal inundation, and plant development, rapid elemental turnover would enable various electron acceptors available for anaerobic methanotrophy. The effects of electron acceptors on stimulating anaerobic methanotrophy and the population compositions involved in carbon transformation in wetland sediments are poorly explored. In this study, sediments recovered from tidally influenced, mangrove covered wetland in northern Taiwan were incubated under the static conditions to investigate whether anaerobic methanotrophy could be stimulated by the presence of individual electron acceptors. Our results demonstrated that anaerobic methanotrophy was clearly stimulated in incubations amended with no electron acceptor, sulfate, or Fe-oxyhydroxide. No apparent methane consumption was observed in incubations with nitrate, citrate, fumarate or Mn-oxides. Anaerobic methanotrophy in incubations with no exogenous electron acceptor appears to proceed at the greatest rates, being sequentially followed by incubations with sulfate and Fe-oxyhydroxide. The presence of basal salt solution stimulated methane oxidation by a factor of 2 to 3. In addition to the direct impact of electron acceptor and basal salts, incubations with sediments retrieved from low tide period yielded a lower rate of methane oxidation than from high tide period. Overall, this study demonstrates that anaerobic methanotrophy in wetland sediments could proceed under various treatments of electron acceptors. Low sulfate content is not a critical factor in inhibiting methane

  20. Effect of nitrate on microbial perchlorate reduction

    NASA Astrophysics Data System (ADS)

    Sun, Y.; Coates, J. D.

    2007-12-01

    nitrate, transcripts of perchlorate reductase and chlorite dismutase were analyzed to determine possible transcriptional regulation from nitrate. During growth transition studies, increase in the level of transcripts necessary for nitrate reduction and perchlorate reduction was observed concomitantly with decrease in the concentration of nitrate and perchlorate respectively suggesting transcriptional regulation was involved in the preferential utilization of nitrate and that nitrate might be a transcriptional inhibitor of perchlorate reduction. Again, using non-growth washed cell suspensions of perchlorate grown D. aromatica, a decrease of transcript level of the perchlorate reductase but not the chlorite dismutase was observed after incubation with nitrate. In conclusion, from physiological and molecular evidence, nitrate negatively regulates transcription of perchlorate reductase thus inhibiting perchlorate reduction. This result is unexpected as it is in contrast to the accepted dogma that microorganisms regulate their metabolisms to utilize electron acceptors in a sequential manner based on thermodynamic optimization which would imply that perchlorate should be used preferentially to nitrate.

  1. Spectral, thermal and kinetic studies of charge-transfer complexes formed between the highly effective antibiotic drug metronidazole and two types of acceptors: σ- and π-acceptors

    NASA Astrophysics Data System (ADS)

    Refat, Moamen S.; Saad, Hosam A.; Adam, Abdel Majid A.

    2015-04-01

    Understanding the interaction between drugs and small inorganic or organic molecules is critical in being able to interpret the drug-receptor interactions and acting mechanism of these drugs. A combined solution and solid state study was performed to describe the complexation chemistry of drug metronidazole (MZ) which has a broad-spectrum antibacterial activity with two types of acceptors. The acceptors include, σ-acceptor (i.e., iodine) and π-acceptors (i.e., dichlorodicyanobenzoquinone (DDQ), chloranil (CHL) and picric acid (PA)). The molecular structure, spectroscopic characteristics, the binding modes as well as the thermal stability were deduced from IR, UV-vis, 1H NMR and thermal studies. The binding ratio of complexation (MZ: acceptor) was determined to be 1:2 for the iodine acceptor and 1:1 for the DDQ, CHL or PA acceptor, according to the CHN elemental analyses and spectrophotometric titrations. It has been found that the complexation with CHL and PA acceptors increases the values of enthalpy and entropy, while the complexation with DDQ and iodine acceptors decreases the values of these parameters compared with the free MZ donor.

  2. Importance of the Two Dissimilatory (Nar) Nitrate Reductases in the Growth and Nitrate Reduction of the Methylotrophic Marine Bacterium Methylophaga nitratireducenticrescens JAM1

    PubMed Central

    Mauffrey, Florian; Martineau, Christine; Villemur, Richard

    2015-01-01

    Methylophaga nitratireducenticrescens JAM1 is the only reported Methylophaga species capable of growing under anaerobic conditions with nitrate as electron acceptor. Its genome encodes a truncated denitrification pathway, which includes two nitrate reductases, Nar1 and Nar2; two nitric oxide reductases, Nor1 and Nor2; and one nitrous oxide reductase, Nos; but no nitrite reductase (NirK or NirS). The transcriptome of strain JAM1 cultivated with nitrate and methanol under anaerobic conditions showed the genes for these enzymes were all expressed. We investigated the importance of Nar1 and Nar2 by knocking out narG1, narG2 or both genes. Measurement of the specific growth rate and the specific nitrate reduction rate of the knockout mutants JAM1ΔnarG1 (Nar1) and JAM1ΔnarG2 (Nar2) clearly demonstrated that both Nar systems contributed to the growth of strain JAM1 under anaerobic conditions, but at different levels. The JAM1ΔnarG1 mutant exhibited an important decrease in the nitrate reduction rate that consequently impaired its growth under anaerobic conditions. In JAM1ΔnarG2, the mutation induced a 20-h lag period before nitrate reduction occurred at specific rate similar to that of strain JAM1. The disruption of narG1 did not affect the expression of narG2. However, the expression of the Nar1 system was highly downregulated in the presence of oxygen with the JAM1ΔnarG2 mutant. These results indicated that Nar1 is the major nitrate reductase in strain JAM1 but Nar2 appears to regulate the expression of Nar1. PMID:26733997

  3. Protective effect of salivary nitrate and microbial nitrate reductase activity against caries.

    PubMed

    Doel, J J; Hector, M P; Amirtham, C V; Al-Anzan, L A; Benjamin, N; Allaker, R P

    2004-10-01

    To test the hypothesis that a combination of high salivary nitrate and high nitrate-reducing capacity are protective against dental caries, 209 children attending the Dental Institute, Barts and The London NHS Trust were examined. Salivary nitrate and nitrite levels, counts of Streptococcus mutans and Lactobacillus spp., and caries experience were recorded. Compared with control subjects, a significant reduction in caries experience was found in patients with high salivary nitrate and high nitrate-reducing ability. Production of nitrite from salivary nitrate by commensal nitrate-reducing bacteria may limit the growth of cariogenic bacteria as a result of the production of antimicrobial oxides of nitrogen, including nitric oxide. PMID:15458501

  4. Comment on Egami's concept of the evolution of nitrate respiration

    NASA Technical Reports Server (NTRS)

    Rambler, M.; Margulis, L.

    1976-01-01

    Recent results suggest that the presence of common nitrogen salts (sodium nitrite and nitrate) in the irradiation medium can markedly protect filamentous blue-green algae from potentially lethal ultraviolet irradiation. The present results as well as general biological arguments of Egami support and extend Egami's original view that anaerobic respiratory pathways using nitrite and nitrate as terminal electron acceptors evolved prior to oxygen requiring aerobic respiratory pathways.

  5. The structure and bonding of iron-acceptor pairs in silicon

    SciTech Connect

    Zhao, S.; Assali, L.V.C.; Kimerling, L.C.

    1995-08-01

    The highly mobile interstitial iron and Group III impurities (B, Al, Ga, In) form iron-acceptor pairs in silicon. Based on the migration kinetics and taking host silicon as a dielectric medium, we have simulated the pairing process in a static silicon lattice. Different from the conventional point charge ionic model, our phenomenological calculations include (1) a correction that takes into account valence electron cloud polarization which adds a short range, attractive interaction in the iron-acceptor pair bonding; and (2) silicon lattice relaxation due to the atomic size difference which causes a local strain field. Our model explains qualitatively (1) trends among the iron-acceptor pairs revealing an increase of the electronic state hole emission energy with increasing principal quantum number of acceptor and decreasing pair separation distance; and (2) the stable and metastable sites and configurational symmetries of the iron-acceptor pairs. The iron-acceptor pairing and bonding mechanism is also discussed.

  6. Widespread occurrence of nitrate storage and denitrification among Foraminifera and Gromiida

    PubMed Central

    Piña-Ochoa, Elisa; Høgslund, Signe; Geslin, Emmanuelle; Cedhagen, Tomas; Revsbech, Niels Peter; Nielsen, Lars Peter; Schweizer, Magali; Jorissen, Frans; Rysgaard, Søren; Risgaard-Petersen, Nils

    2009-01-01

    Benthic foraminifers inhabit a wide range of aquatic environments including open marine, brackish, and freshwater environments. Here we show that several different and diverse foraminiferal groups (miliolids, rotaliids, textulariids) and Gromia, another taxon also belonging to Rhizaria, accumulate and respire nitrates through denitrification. The widespread occurrence among distantly related organisms suggests an ancient origin of the trait. The diverse metabolic capacity of these organisms, which enables them to respire with oxygen and nitrate and to sustain respiratory activity even when electron acceptors are absent from the environment, may be one of the reasons for their successful colonization of diverse marine sediment environments. The contribution of eukaryotes to the removal of fixed nitrogen by respiration may equal the importance of bacterial denitrification in ocean sediments. PMID:20080540

  7. Higher excited states of acceptors in cubic semiconductors

    NASA Astrophysics Data System (ADS)

    Said, M.; Kanehisa, M. A.; Balkanski, M.

    1986-02-01

    For the first time, higher excited states of shallow acceptors up to the 3s and 4s states are calculated based on the Balderschi and Lipari theory including the cubic correction. The eigenvalues and eigenvectors of the effective mass Hamiltonian for shallow acceptor states were obtained by the finite element method. The resultant sparse matrix is diagonalized by a newly developed Saad's method based on Arnoldi's algorithm. Comparison with experimental spectra on ZnTe:Li and ZnTe:P gives best valence band parameters for ZnTe; μ = 0.60 and δ = 0.12.

  8. Donor-acceptor chemistry in the main group.

    PubMed

    Rivard, Eric

    2014-06-21

    This Perspective article summarizes recent progress from our laboratory in the isolation of reactive main group species using a general donor-acceptor protocol. A highlight of this program is the use of carbon-based donors in combination with suitable Lewis acidic acceptors to yield stable complexes of parent Group 14 element hydrides (e.g. GeH2 and H2SiGeH2). It is anticipated that this strategy could be extended to include new synthetic targets from throughout the Periodic Table with possible applications in bottom-up materials synthesis and main group element catalysis envisioned. PMID:24788390

  9. Insights on alterations to the rumen ecosystem by nitrate and nitrocompounds

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Nitrate and certain short chain nitrocompounds are being investigated as dietary supplements to reduce economic and environmental costs associated with ruminal methane emissions. Thermodynamically, nitrate is a preferred electron acceptor in the rumen that consumes electrons at the expense of metha...

  10. Growth of strain SES-3 with arsenate and other diverse electron acceptors

    USGS Publications Warehouse

    Laverman, A.M.; Blum, J.S.; Schaefer, J.K.; Phillips, E.J.P.; Lovley, D.R.; Oremland, R.S.

    1995-01-01

    The selenate-respiring bacterial strain SES-3 was able to use a variety of inorganic electron acceptors to sustain growth. SES-3 grew with the reduction of arsenate to arsenite, Fe(III) to Fe(II), or thiosulfate to sulfide. It also grew in medium in which elemental sulfur, Mn(IV), nitrite, trimethylamine N-oxide, or fumarate was provided as an electron acceptor. Growth on oxygen was microaerophilic. There was no growth with arsenite or chromate. Washed suspensions of cells grown on selenate or nitrate had a constitutive ability to reduce arsenate but were unable to reduce arsenite. These results suggest that strain SES-3 may occupy a niche as an environmental opportunist by being able to take advantage of a diversity of electron acceptors.

  11. Phthalimides as exceptionally efficient single electron transfer acceptors in reductive coupling reactions promoted by samarium diiodide.

    PubMed

    Vacas, Tatiana; Alvarez, Eleuterio; Chiara, Jose Luis

    2007-12-20

    Experimental and theoretical evidence shows that phthalimides are highly efficient single electron transfer acceptors in reactions promoted by samarium diiodide, affording ketyl radical anion intermediates, which participate in high-yielding inter- and intramolecular reductive coupling processes with different radicophiles including imides, oxime ethers, nitrones, and Michael acceptors.

  12. Influence of alternative electron acceptors on the anaerobic biodegradability of chlorinated phenols and benzoic acids

    SciTech Connect

    Haeggblom, M.M.; Rivera, M.D.; Young, L.Y.

    1993-01-01

    Nitrate, sulfate, and carbonate were used as electron acceptors to examine the anaerobic biodegradability of chlorinated aromatic compounds in estuarine and freshwater sediments. The respective denitrifying, sulfidogenic, and methanogenic enrichment cultures were established on each of the monochlorinated phenol and monochlorinated benzoic acid isomers, using sediment from the upper (freshwater) and lower (estuarine) Hudson River and the East River (estuarine) as source materials. (Copyright (c) 1993 American Society for Microbiology.)

  13. The OpdQ porin of Pseudomonas aeruginosa is regulated by environmental signals associated with cystic fibrosis including nitrate-induced regulation involving the NarXL two-component system.

    PubMed

    Fowler, Randal C; Hanson, Nancy D

    2015-12-01

    Pseudomonas aeruginosa is a versatile opportunistic pathogen that causes chronic infections in immunocompromised hosts. Multiple porins modulate outer membrane permeability under various environmental conditions. The lung environment of cystic fibrosis (CF) patients is unique with changes occurring in nutrient availability, osmolarity, and oxygen content. Although P. aeruginosa gene expression is modified under these conditions, little is known about how they influence porin regulation. In this study, we evaluated the regulation of the outer membrane porin OpdQ, a member of the OprD family of porins, with regard to oxygen, nitrate, and/or NaCl levels. We demonstrated using promoter::fusion clones of P. aeruginosa PAO1 and clinical strains collected from CF patients that OpdQ was transcriptionally repressed under low oxygen but increased in the presence of nitrate. The nitrate-induced regulation of OpdQ was found to be dependent on the transcription factor NarL via the NarXL two-component system. In addition, NaCl-induced osmotic stress increased OpdQ production among most of the clinical strains evaluated. In conclusion, these data identify for the first time that specific environmental cues associated with the CF microenvironment influence porin regulation, and that the nitrate-induced regulation of OpdQ is associated with nitrate metabolism via the NarXL two-component system of P. aeruginosa.

  14. Conformation-selective coordination-driven self-assembly of a ditopic donor with Pd(II) acceptors.

    PubMed

    Howlader, Prodip; Mukherjee, Sandip; Saha, Rajat; Mukherjee, Partha Sarathi

    2015-12-21

    Coordination-driven self-assembly of 3-(5-(pyridin-3-yl)-1H-1,2,4-triazol-3-yl)pyridine (L) was investigated with 90°cis-blocked Pd(II) acceptors and tetratopic Pd(NO3)2. Although the ligand is capable of binding in several different conformations (acting as a ditopic donor through the pyridyl nitrogens), the experimental results (including X-ray structures) showed that it adopts a particular conformation when it binds with 90°cis-blocked Pd(II) acceptors (two available sites) to yield [2 + 2] self-assembled macrocycles. On the other hand, with Pd(NO3)2 (where four available sites are present) a different conformer of the same donor was selectively bound to form a molecular cubic cage. The experimental findings were corroborated well with the density functional theory (B3LYP) calculations. The tetratopic Pd(NO3)2 yielded a [6 + 12] self-assembled Pd6L12 molecular cube, which contains a potential void occupied by nitrate and perchlorate ions. Being a triazole based ligand, the free space inside the cage is enriched with several sp(2) hybridised nitrogen atoms with lone pairs of electrons to act as Lewis basic sites. Knoevenagel condensation reactions of several aromatic aldehydes with active methylene compounds were successfully performed in reasonably high yields in the presence of the cage. PMID:26544720

  15. Improvement of biological nitrogen removal with nitrate-dependent Fe(II) oxidation bacterium Aquabacterium parvum B6 in an up-flow bioreactor for wastewater treatment.

    PubMed

    Zhang, Xiaoxin; Li, Ang; Szewzyk, Ulrich; Ma, Fang

    2016-11-01

    Aquabacterium parvum strain B6 exhibited efficient nitrate-dependent Fe(II) oxidation ability using nitrate as an electron acceptor. A continuous up-flow bioreactor that included an aerobic and an anoxic section was constructed, and strain B6 was added to the bioreactor as inocula to explore the application of microbial nitrate-dependent Fe(II) oxidizing (NDFO) efficiency in wastewater treatment. The maximum NRE (anoxic section) and TNRE of 46.9% and 79.7%, respectively, could be obtained at a C/N ratio of 5.3:1 in the influent with HRT of 17. Meanwhile, the taxonomy composition of the reactor was assessed, as well. The NDFO metabolism of strain B6 could be expected because of its relatively dominant position in the anoxic section, whereas potential heterotrophic nitrification and aerobic denitrification developed into the prevailing status in the aerobic section after 50days of continuous operation. PMID:27544912

  16. Bright Solid-State Emission of Disilane-Bridged Donor-Acceptor-Donor and Acceptor-Donor-Acceptor Chromophores.

    PubMed

    Shimada, Masaki; Tsuchiya, Mizuho; Sakamoto, Ryota; Yamanoi, Yoshinori; Nishibori, Eiji; Sugimoto, Kunihisa; Nishihara, Hiroshi

    2016-02-24

    The development of disilane-bridged donor-acceptor-donor (D-Si-Si-A-Si-Si-D) and acceptor-donor-acceptor (A-Si-Si-D-Si-Si-A) compounds is described. Both types of compound showed strong emission (λem =ca. 500 and ca. 400 nm, respectively) in the solid state with high quantum yields (Φ: up to 0.85). Compound 4 exhibited aggregation-induced emission enhancement in solution. X-ray diffraction revealed that the crystal structures of 2, 4, and 12 had no intermolecular π-π interactions to suppress the nonradiative transition in the solid state.

  17. Nitrate transport and its regulation by O2 in Pseudomonas aeruginosa.

    PubMed

    Hernandez, D; Dias, F M; Rowe, J J

    1991-04-01

    Pseudomonas aeruginosa is an obligate respirer which can utilize nitrate as a terminal electron acceptor under anaerobic conditions (denitrification). Immediate, transient regulation of nitrate respiration is mediated by oxygen through the inhibition of nitrate uptake. In order to gain an understanding of the bioenergetics of nitrate transport and its regulation by oxygen, the effects of various metabolic inhibitors on the uptake process and on oxygen regulation were investigated. Nitrate uptake was stimulated by the protonophores carbonyl cyanide m-chlorophenylhydrazone and 2,4-dinitrophenol, indicating that nitrate uptake is not strictly energized by, but may be affected by the proton motive force. Oxygen regulation of nitrate uptake might in part be through redox-sensitive thiol groups since N-ethylmaleimide at high concentrations decreased the rate of nitrate transport. Cells grown with tungstate (deficient in nitrate reductase activity) and azide-treated cells transported nitrate at significantly lower rates than untreated cells, indicating that physiological rates of nitrate transport are dependent on nitrate reduction. Furthermore, tungstate grown cells transported nitrate only in the presence of nitrite, lending support to the nitrate/nitrite antiport model for transport. Oxygen regulation of nitrate transport was relieved (10% that of typical anaerobic rates) by the cytochrome oxygen reductase inhibitors carbon monoxide and cyanide. PMID:1910283

  18. Synthetic CO.sub.2 acceptor

    DOEpatents

    Lancet, Michael S.; Curran, George P.

    1981-08-18

    A synthetic CO.sub.2 acceptor consisting essentially of at least one compound selected from the group consisting of calcium oxide and calcium carbonate supported in a refractory carrier matrix, the carrier having the general formula Ca.sub.5 (SiO.sub.4).sub.2 CO.sub.3. A method for producing the synthetic CO.sub.2 acceptor is also disclosed.

  19. Nitrate ammonification in mangrove soils: a hidden source of nitrite?

    PubMed Central

    Balk, Melike; Laverman, Anniet M.; Keuskamp, Joost A.; Laanbroek, Hendrikus J.

    2015-01-01

    Nitrate reduction is considered to be a minor microbial pathway in the oxidation of mangrove-derived organic matter due to a limited supply of nitrate in mangrove soils. At a limited availability of this electron acceptor compared to the supply of degradable carbon, nitrate ammonification is thought to be the preferential pathway of nitrate reduction. Mangrove forest mutually differ in their productivity, which may lead to different available carbon to nitrate ratios in their soil. Hence, nitrate ammonification is expected to be of more importance in high- compared to low-productive forests. The hypothesis was tested in flow-through reactors that contain undisturbed mangrove soils from high-productive Avicennia germinans and Rhizophora mangle forests in Florida and low-productive Avicennia marina forests in Saudi Arabia. Nitrate was undetectable in the soils from both regions. It was assumed that a legacy of nitrate ammonification would be reflected by a higher ammonium production from these soils upon the addition of nitrate. Unexpectedly, the soils from the low-productive forests in Saudi Arabia produced considerably more ammonium than the soils from the high-productive forests in Florida. Hence, other environmental factors than productivity must govern the selection of nitrate ammonification or denitrification. A rather intriguing observation was the 1:1 production of nitrite and ammonium during the consumption of nitrate, more or less independent from sampling region, location, sampling depth, mangrove species and from the absence or presence of additional degradable carbon. This 1:1 ratio points to a coupled production of ammonium and nitrite by one group of nitrate-reducing microorganisms. Such a production of nitrite will be hidden by the presence of active nitrite-reducing microorganisms under the nitrate-limited conditions of most mangrove forest soils. PMID:25784903

  20. Nitrate ammonification in mangrove soils: a hidden source of nitrite?

    PubMed

    Balk, Melike; Laverman, Anniet M; Keuskamp, Joost A; Laanbroek, Hendrikus J

    2015-01-01

    Nitrate reduction is considered to be a minor microbial pathway in the oxidation of mangrove-derived organic matter due to a limited supply of nitrate in mangrove soils. At a limited availability of this electron acceptor compared to the supply of degradable carbon, nitrate ammonification is thought to be the preferential pathway of nitrate reduction. Mangrove forest mutually differ in their productivity, which may lead to different available carbon to nitrate ratios in their soil. Hence, nitrate ammonification is expected to be of more importance in high- compared to low-productive forests. The hypothesis was tested in flow-through reactors that contain undisturbed mangrove soils from high-productive Avicennia germinans and Rhizophora mangle forests in Florida and low-productive Avicennia marina forests in Saudi Arabia. Nitrate was undetectable in the soils from both regions. It was assumed that a legacy of nitrate ammonification would be reflected by a higher ammonium production from these soils upon the addition of nitrate. Unexpectedly, the soils from the low-productive forests in Saudi Arabia produced considerably more ammonium than the soils from the high-productive forests in Florida. Hence, other environmental factors than productivity must govern the selection of nitrate ammonification or denitrification. A rather intriguing observation was the 1:1 production of nitrite and ammonium during the consumption of nitrate, more or less independent from sampling region, location, sampling depth, mangrove species and from the absence or presence of additional degradable carbon. This 1:1 ratio points to a coupled production of ammonium and nitrite by one group of nitrate-reducing microorganisms. Such a production of nitrite will be hidden by the presence of active nitrite-reducing microorganisms under the nitrate-limited conditions of most mangrove forest soils.

  1. A Metagenomics-Based Metabolic Model of Nitrate-Dependent Anaerobic Oxidation of Methane by Methanoperedens-Like Archaea

    PubMed Central

    Arshad, Arslan; Speth, Daan R.; de Graaf, Rob M.; Op den Camp, Huub J. M.; Jetten, Mike S. M.; Welte, Cornelia U.

    2015-01-01

    Methane oxidation is an important process to mitigate the emission of the greenhouse gas methane and further exacerbating of climate forcing. Both aerobic and anaerobic microorganisms have been reported to catalyze methane oxidation with only a few possible electron acceptors. Recently, new microorganisms were identified that could couple the oxidation of methane to nitrate or nitrite reduction. Here we investigated such an enrichment culture at the (meta) genomic level to establish a metabolic model of nitrate-driven anaerobic oxidation of methane (nitrate-AOM). Nitrate-AOM is catalyzed by an archaeon closely related to (reverse) methanogens that belongs to the ANME-2d clade, tentatively named Methanoperedens nitroreducens. Methane may be activated by methyl-CoM reductase and subsequently undergo full oxidation to carbon dioxide via reverse methanogenesis. All enzymes of this pathway were present and expressed in the investigated culture. The genome of the archaeal enrichment culture encoded a variety of enzymes involved in an electron transport chain similar to those found in Methanosarcina species with additional features not previously found in methane-converting archaea. Nitrate reduction to nitrite seems to be located in the pseudoperiplasm and may be catalyzed by an unusual Nar-like protein complex. A small part of the resulting nitrite is reduced to ammonium which may be catalyzed by a Nrf-type nitrite reductase. One of the key questions is how electrons from cytoplasmically located reverse methanogenesis reach the nitrate reductase in the pseudoperiplasm. Electron transport in M. nitroreducens probably involves cofactor F420 in the cytoplasm, quinones in the cytoplasmic membrane and cytochrome c in the pseudoperiplasm. The membrane-bound electron transport chain includes F420H2 dehydrogenase and an unusual Rieske/cytochrome b complex. Based on genome and transcriptome studies a tentative model of how central energy metabolism of nitrate-AOM could work is

  2. A Metagenomics-Based Metabolic Model of Nitrate-Dependent Anaerobic Oxidation of Methane by Methanoperedens-Like Archaea.

    PubMed

    Arshad, Arslan; Speth, Daan R; de Graaf, Rob M; Op den Camp, Huub J M; Jetten, Mike S M; Welte, Cornelia U

    2015-01-01

    Methane oxidation is an important process to mitigate the emission of the greenhouse gas methane and further exacerbating of climate forcing. Both aerobic and anaerobic microorganisms have been reported to catalyze methane oxidation with only a few possible electron acceptors. Recently, new microorganisms were identified that could couple the oxidation of methane to nitrate or nitrite reduction. Here we investigated such an enrichment culture at the (meta) genomic level to establish a metabolic model of nitrate-driven anaerobic oxidation of methane (nitrate-AOM). Nitrate-AOM is catalyzed by an archaeon closely related to (reverse) methanogens that belongs to the ANME-2d clade, tentatively named Methanoperedens nitroreducens. Methane may be activated by methyl-CoM reductase and subsequently undergo full oxidation to carbon dioxide via reverse methanogenesis. All enzymes of this pathway were present and expressed in the investigated culture. The genome of the archaeal enrichment culture encoded a variety of enzymes involved in an electron transport chain similar to those found in Methanosarcina species with additional features not previously found in methane-converting archaea. Nitrate reduction to nitrite seems to be located in the pseudoperiplasm and may be catalyzed by an unusual Nar-like protein complex. A small part of the resulting nitrite is reduced to ammonium which may be catalyzed by a Nrf-type nitrite reductase. One of the key questions is how electrons from cytoplasmically located reverse methanogenesis reach the nitrate reductase in the pseudoperiplasm. Electron transport in M. nitroreducens probably involves cofactor F420 in the cytoplasm, quinones in the cytoplasmic membrane and cytochrome c in the pseudoperiplasm. The membrane-bound electron transport chain includes F420H2 dehydrogenase and an unusual Rieske/cytochrome b complex. Based on genome and transcriptome studies a tentative model of how central energy metabolism of nitrate-AOM could work is

  3. Multiple influences of nitrate on uranium solubility during bioremediation of uranium-contaminated subsurface sediments.

    PubMed

    Finneran, Kevin T; Housewright, Meghan E; Lovley, Derek R

    2002-09-01

    Microbiological reduction of soluble U(VI) to insoluble U(IV) has been proposed as a remediation strategy for uranium-contaminated groundwater. Nitrate is a common co-contaminant with uranium. Nitrate inhibited U(VI) reduction in acetate-amended aquifer sediments collected from a uranium-contaminated site in New Mexico. Once nitrate was depleted, both U(VI) and Fe(III) were reduced concurrently. When nitrate was added to sediments in which U(VI) had been reduced, U(VI) reappeared in solution. Parallel studies with the dissimilatory Fe(III)-, U(VI)- and nitrate-reducing microorganism, Geobacter metallireducens, demonstrated that nitrate inhibited reduction of Fe(III) and U(VI) in cell suspensions of cells that had been grown with nitrate as the electron acceptor, but not in Fe(III)-grown cells. Suspensions of nitrate-grown G. metallireducens oxidized Fe(II) and U(IV) with nitrate as the electron acceptor. U(IV) oxidation was accelerated when Fe(II) was also added, presumably due to the Fe(III) being formed abiotically oxidizing U(IV). These studies demonstrate that although the presence of nitrate is not likely to be an impediment to the bioremediation of uranium contamination with microbial U(VI) reduction, it is necessary to reduce nitrate before U(VI) can be reduced. These results also suggest that anaerobic oxidation of U(IV) to U(VI) with nitrate serving as the electron acceptor may provide a novel strategy for solubilizing and extracting microbial U(IV) precipitates from the subsurface.

  4. Analysis of Shewanella oneidensis Membrane Protein Expression in Response to Electron Acceptor Availability

    SciTech Connect

    Giometti, Carol S.; Khare, Tripti; Verberkmoes, Nathan; O'Loughlin, Ed; Lindberg, Carl; Thompson, Melissa; Hettich, Robert

    2006-04-05

    Shewanella oneidensis MR-1, a gram negative metal-reducing bacterium, can utilize a large number of electron acceptors. In the natural environment, S. oneidensis utilizes insoluble metal oxides as well as soluble terminal electron acceptors. The purpose of this ERSP project is to identify differentially expressed proteins associated with the membranes of S. oneidensis MR-1 cells grown with different electron acceptors, including insoluble metal oxides. We hypothesize that through the use of surface labeling, subcellular fractionation, and a combination of proteome analysis tools, proteins involved in the reduction of different terminal electron acceptors will be elucidated. We are comparing the protein profiles from cells grown with the soluble electron acceptors oxygen and fumarate and with those from cells grown with the insoluble iron oxides goethite, ferrihydrite and lepidocrocite. Comparison of the cell surface proteins isolated from cells grown with oxygen or anaerobically with fumarate revealed an increase in the abundance of over 25 proteins in anaerobic cells, including agglutination protein and flagellin proteins along with the several hypothetical proteins. In addition, the surface protein composition of cells grown with the insoluble iron oxides varies considerably from the protein composition observed with either soluble electron acceptor as well as between the different insoluble acceptors.

  5. Alkali metal nitrate purification

    DOEpatents

    Fiorucci, Louis C.; Morgan, Michael J.

    1986-02-04

    A process is disclosed for removing contaminants from impure alkali metal nitrates containing them. The process comprises heating the impure alkali metal nitrates in solution form or molten form at a temperature and for a time sufficient to effect precipitation of solid impurities and separating the solid impurities from the resulting purified alkali metal nitrates. The resulting purified alkali metal nitrates in solution form may be heated to evaporate water therefrom to produce purified molten alkali metal nitrates suitable for use as a heat transfer medium. If desired, the purified molten form may be granulated and cooled to form discrete solid particles of purified alkali metal nitrates.

  6. Oligosaccharide synthesis by dextransucrase: new unconventional acceptors.

    PubMed

    Demuth, Kristin; Jördening, Hans Joachim; Buchholz, Klaus

    2002-11-01

    The acceptor reactions of dextransucrase offer the potential for a targeted synthesis of a wide range of di-, tri- and higher oligosaccharides by the transfer of a glucosyl group from sucrose to the acceptor. We here report on results which show that the synthetic potential of this enzyme is not restricted to 'normal' saccharides. Additionally functionalized saccharides, such as alditols, aldosuloses, sugar acids, alkyl saccharides, and glycals, and rather unconventional saccharides, such as fructose dianhydride, may also act as acceptors. Some of these acceptors even turned out to be relatively efficient: alpha-D-glucopyranosyl-(1-->5)-D-arabinonic acid, alpha-D-glucopyranosyl-(1-->4)-D-glucitol, alpha-D-glucopyranosyl-(1-->6)-D-glucitol, alpha-D-glucopyranosyl-(1-->6)-D-mannitol, alpha-D-fructofuranosyl-beta-D-fructofuranosyl-(1,2':2,3')-dianhydride, 1,5-anhydro-2-deoxy-D-arabino-hex-1-enitol ('D-glucal'), and may therefore be of interest for future applications of the dextransucrase acceptor reaction.

  7. Photoconductivity in donor-acceptor heterojunction organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Renshaw, C. K.; Zimmerman, J. D.; Lassiter, B. E.; Forrest, S. R.

    2012-08-01

    Organic photovoltaics (OPVs) differ from ideal inorganic solar cells due to their pronounced voltage dependence under reverse bias. This feature is commonly modeled in an ad hoc fashion by including a parallel junction resistance (Rp) that bypasses the heterojunction energy barrier between donor and acceptor. The existence of a finite Rp has variously been attributed to rough interfaces, pinhole defects, or to the electric field dependence of the dissociation of polaron pairs that are bound at the heterojunction. Here we show that the voltage dependence of the photocurrent can also arise from photoconductivity resulting from exciton generation followed by dissociation into free polarons within the bulk of the donor and acceptor layers. The presence of photoconductivity of the active layers does not result in an increase in power conversion efficiency, and places a constraint on the maximum fill factor that can be achieved in an OPV cell.

  8. Mechanisms of electron acceptor utilization: Implications for simulating anaerobic biodegradation

    USGS Publications Warehouse

    Schreiber, M.E.; Carey, G.R.; Feinstein, D.T.; Bahr, J.M.

    2004-01-01

    Simulation of biodegradation reactions within a reactive transport framework requires information on mechanisms of terminal electron acceptor processes (TEAPs). In initial modeling efforts, TEAPs were approximated as occurring sequentially, with the highest energy-yielding electron acceptors (e.g. oxygen) consumed before those that yield less energy (e.g., sulfate). Within this framework in a steady state plume, sequential electron acceptor utilization would theoretically produce methane at an organic-rich source and Fe(II) further downgradient, resulting in a limited zone of Fe(II) and methane overlap. However, contaminant plumes often display much more extensive zones of overlapping Fe(II) and methane. The extensive overlap could be caused by several abiotic and biotic processes including vertical mixing of byproducts in long-screened monitoring wells, adsorption of Fe(II) onto aquifer solids, or microscale heterogeneity in Fe(III) concentrations. Alternatively, the overlap could be due to simultaneous utilization of terminal electron acceptors. Because biodegradation rates are controlled by TEAPs, evaluating the mechanisms of electron acceptor utilization is critical for improving prediction of contaminant mass losses due to biodegradation. Using BioRedox-MT3DMS, a three-dimensional, multi-species reactive transport code, we simulated the current configurations of a BTEX plume and TEAP zones at a petroleum- contaminated field site in Wisconsin. Simulation results suggest that BTEX mass loss due to biodegradation is greatest under oxygen-reducing conditions, with smaller but similar contributions to mass loss from biodegradation under Fe(III)-reducing, sulfate-reducing, and methanogenic conditions. Results of sensitivity calculations document that BTEX losses due to biodegradation are most sensitive to the age of the plume, while the shape of the BTEX plume is most sensitive to effective porosity and rate constants for biodegradation under Fe(III)-reducing and

  9. Donor-acceptor heteroleptic open sandwiches.

    PubMed

    Merino, Gabriel; Beltrán, Hiram I; Vela, Alberto

    2006-02-01

    A series of donor-acceptor heteroleptic open sandwiches with formula CpM-M'Pyl (M = B, Al, Ga; M' = Li, Na; Cp = cyclopentadienyl; Pyl = pentadienyl) has been designed in silico using density functional theory. The most stable complexes are those containing boron as a donor atom. A molecular orbital analysis shows that the s character of the lone pair located at the group 13 element is mainly responsible for the complex stabilization. It is also found that the surrounding medium has a similar effect on these sandwiches such as in the "classical" donor-acceptor complexes, showing a decrement in the group 13 element-alkaline metal bond lengths.

  10. [Effects of carbon sources, temperature and electron acceptors on biological phosphorus removal].

    PubMed

    Han, Yun; Xu, Song; Dong, Tao; Wang, Bin-Fan; Wang, Xian-Yao; Peng, Dang-Cong

    2015-02-01

    Effects of carbon sources, temperature and electron acceptors on phosphorus uptake and release were investigated in a pilot-scale oxidation ditch. Phosphorus uptake and release rates were measured with different carbon sources (domestic sewage, sodium acetate, glucose) at 25 degrees C. The results showed that the minimum phosphorus uptake and release rates of glucose were 5.12 mg x (g x h)(-1) and 6.43 mg x (g x h)(-1), respectively, and those of domestic sewage are similar to those of sodium acetate. Phosphorus uptake and release rates increased with the increase of temperature (12, 16, 20 and 25 degrees C) using sodium acetate as carbon sources. Anoxic phosphorus uptake rate decreased with added COD. Electron acceptors (oxygen, nitrate, nitrite) had significant effects on phosphorus uptake rate and their order was in accordance with oxygen > nitrate > nitrite. The mass ratio of anoxic P uptake and N consumption (P(uptake)/N (consumption)) of nitrate and nitrite were 0.96 and 0.65, respectively.

  11. [Effects of carbon sources, temperature and electron acceptors on biological phosphorus removal].

    PubMed

    Han, Yun; Xu, Song; Dong, Tao; Wang, Bin-Fan; Wang, Xian-Yao; Peng, Dang-Cong

    2015-02-01

    Effects of carbon sources, temperature and electron acceptors on phosphorus uptake and release were investigated in a pilot-scale oxidation ditch. Phosphorus uptake and release rates were measured with different carbon sources (domestic sewage, sodium acetate, glucose) at 25 degrees C. The results showed that the minimum phosphorus uptake and release rates of glucose were 5.12 mg x (g x h)(-1) and 6.43 mg x (g x h)(-1), respectively, and those of domestic sewage are similar to those of sodium acetate. Phosphorus uptake and release rates increased with the increase of temperature (12, 16, 20 and 25 degrees C) using sodium acetate as carbon sources. Anoxic phosphorus uptake rate decreased with added COD. Electron acceptors (oxygen, nitrate, nitrite) had significant effects on phosphorus uptake rate and their order was in accordance with oxygen > nitrate > nitrite. The mass ratio of anoxic P uptake and N consumption (P(uptake)/N (consumption)) of nitrate and nitrite were 0.96 and 0.65, respectively. PMID:26031087

  12. 21 CFR 181.33 - Sodium nitrate and potassium nitrate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Sodium nitrate and potassium nitrate. 181.33...-Sanctioned Food Ingredients § 181.33 Sodium nitrate and potassium nitrate. Sodium nitrate and potassium nitrate are subject to prior sanctions issued by the U.S. Department of Agriculture for use as sources...

  13. 21 CFR 181.33 - Sodium nitrate and potassium nitrate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Sodium nitrate and potassium nitrate. 181.33 Section 181.33 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES... nitrate and potassium nitrate. Sodium nitrate and potassium nitrate are subject to prior sanctions...

  14. 21 CFR 181.33 - Sodium nitrate and potassium nitrate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Sodium nitrate and potassium nitrate. 181.33...-Sanctioned Food Ingredients § 181.33 Sodium nitrate and potassium nitrate. Sodium nitrate and potassium nitrate are subject to prior sanctions issued by the U.S. Department of Agriculture for use as sources...

  15. 21 CFR 181.33 - Sodium nitrate and potassium nitrate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Sodium nitrate and potassium nitrate. 181.33...-Sanctioned Food Ingredients § 181.33 Sodium nitrate and potassium nitrate. Sodium nitrate and potassium nitrate are subject to prior sanctions issued by the U.S. Department of Agriculture for use as sources...

  16. Modeling the long-term fate of agricultural nitrate in groundwater in the San Joaquin Valley, California

    USGS Publications Warehouse

    Chapelle, Francis H.; Campbell, Bruce G.; Widdowson, Mark A.; Landon, Mathew K.

    2013-01-01

    Nitrate contamination of groundwater systems used for human water supplies is a major environmental problem in many parts of the world. Fertilizers containing a variety of reduced nitrogen compounds are commonly added to soils to increase agricultural yields. But the amount of nitrogen added during fertilization typically exceeds the amount of nitrogen taken up by crops. Oxidation of reduced nitrogen compounds present in residual fertilizers can produce substantial amounts of nitrate which can be transported to the underlying water table. Because nitrate concentrations exceeding 10 mg/L in drinking water can have a variety of deleterious effects for humans, agriculturally derived nitrate contamination of groundwater can be a serious public health issue. The Central Valley aquifer of California accounts for 13 percent of all the groundwater withdrawals in the United States. The Central Valley, which includes the San Joaquin Valley, is one of the most productive agricultural areas in the world and much of this groundwater is used for crop irrigation. However, rapid urbanization has led to increasing groundwater withdrawals for municipal public water supplies. That, in turn, has led to concern about how contaminants associated with agricultural practices will affect the chemical quality of groundwater in the San Joaquin Valley. Crop fertilization with various forms of nitrogen-containing compounds can greatly increase agricultural yields. However, leaching of nitrate from soils due to irrigation has led to substantial nitrate contamination of shallow groundwater. That shallow nitrate-contaminated groundwater has been moving deeper into the Central Valley aquifer since the 1960s. Denitrification can be an important process limiting the mobility of nitrate in groundwater systems. However, substantial denitrification requires adequate sources of electron donors in order to drive the process. In many cases, dissolved organic carbon (DOC) and particulate organic carbon

  17. Effects of acceptors on halogenated organic compound biotransformations in a biofilm column

    SciTech Connect

    Cobb, G.D.; Bouwer, E.J. )

    1991-06-01

    The transformability of trihalomethanes, carbon tetrachloride, 1,1,1-trichlorethane, 1,2-dibromomethane, tetrachlorethylene, dibromochloropropane, and chlorinated benzenes was evaluated by a biofilm utilizing a mixture of primary electron acceptors (oxygen, nitrate, and sulfate). These compounds at concentrations commonly found in groundwater were continuously administered for 4 years to a biofilm column reactor that resembled polluted groundwater environments. Acetate was the primary substrate to support microbial growth. Sequential biofilm zones or aerobic respiration, denitrification, and sulfate reduction developed within the column. Transformation of the halogenated aliphatic compounds coincided with the onset of sulfate in the column feed decreased the steady-state removals for several of the halogenated aliphatic compounds. These results suggest that sulfate was an important primary electron acceptor. Aerobic transformations of the chlorinated benzenes were incomplete due to the rapid depletion of oxygen and limited aerobic zone at the column inlet.

  18. Influence of alternative electron acceptors on the anaerobic biodegradability of chlorinated phenols and benzoic acids

    SciTech Connect

    Haeggblom, M.M.; Rivera, M.D.; Young, L.Y. )

    1993-04-01

    Methanogeneic conditions can promote the biodegradation of a number of halogenated aromatic compounds. This study, using sediments from freshwater and estuarine sites, is an evaluation of the anaerobic biodegradability of monochlorinated phenols and benzoic acids coupled to denitrification, sulfidogenesis, and methanogenesis. The results indicate that chlorinated phenols and benzoic acids are biodegradable under at least one set of anaerobic conditions. Metabolism depends both on the electron acceptor available and on the position of the chlorine substituent. Presence of alternative electron acceptors, nitrate, sulfate, and carbonate, can affect degradation rates and substrate specificities. Since contaminated sites usually have mixtures of wastes, bioremediation efforts may need to consider the activities of diverse anaerobic communities to carry out effective treatment of all components. 37 refs., 4 figs., 4 tabs.

  19. Influence of alternative electron acceptors on the anaerobic biodegradability of chlorinated phenols and benzoic acids

    SciTech Connect

    Haeggblom, M.M.; Rivera, M.D.; Young, L.Y.

    1993-01-01

    Nitrate, sulfate, and carbonate were used as electron acceptors to examine the anaerobic biodegradability of chlorinated aromatic compounds in estuarine and freshwater sediments. The respective denitrifying, sulfidogenic, and methanogenic enrichment cultures were established on each of the monochlorinated phenol and monochlorinated benzoic acid isomers, using sediment from the upper (freshwater) and lower (estuarine) Hudson River and the East River (estuarine) as source materials. Utilization of each chlorophenol and chlorobenzoate isomer was observed under at least one reducing condition; however, no single reducing condition permitted the metabolism of all six compounds tested. The anaerobic biodegradation of the chlorophenols and chlorobenzoates depended on the electron acceptor available and on the position of the chlorine substituent. In general, similar activities were observed under the different reducing conditions in both the freshwater and estuarine sediments.

  20. 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.

  1. Nitrate Enhanced Microbial Cr(VI) Reduction-Final Report

    SciTech Connect

    John F. Stolz

    2011-06-15

    A major challenge for the bioremediation of radionuclides (i.e., uranium, technetium) and metals (i.e., Cr(VI), Hg) is the co-occurrence of nitrate as it can inhibit metal transformation. Denitrification (nitrate reduction to dinitrogen gas) is considered the most important ecological process. For many metal and metalloid reducing bacteria, however, ammonia is the end product through respiratory nitrate reduction (RNRA). The focus of this work was to determine how RNRA impacts Cr(VI) transformation. The goal was to elucidate the specific mechanism(s) that limits Cr(VI) reduction in the presence of nitrate and to use this information to develop strategies that enhance Cr(VI) reduction (and thus detoxification). Our central hypothesis is that nitrate impacts the biotransformation of metals and metalloids in three ways 1) as a competitive alternative electron acceptor (inhibiting transformation), 2) as a co-metabolite (i.e., concomitant reduction, stimulating transformation), and 3) as an inducer of specific proteins and pathways involved in oxidation/reduction reactions (stimulating transformation). We have identified three model organisms, Geobacter metallireducens (mechanism 1), Sulfurospirillum barnesii, (mechasism 2), and Desulfovibrio desulfuricans (mechanisms 3). Our specific aims were to 1) investigate the role of Cr(VI) concentration on the kinetics of both growth and reduction of nitrate, nitrite, and Cr(VI) in these three organisms; 2) develop a profile of bacterial enzymes involved in nitrate transformation (e.g., oxidoreductases) using a proteomic approach; 3) investigate the function of periplasmic nitrite reductase (Nrf) as a chromate reductase; and 4) develop a strategy to maximize microbial chromium reduction in the presence of nitrate. We found that growth on nitrate by G. metallireducens was inhibited by Cr(VI). Over 240 proteins were identified by LC/MS-MS. Redox active proteins, outer membrane heavy metal efflux proteins, and chemotaxis sensory

  2. Electron Donor Acceptor Interactions. Final Progress Report

    SciTech Connect

    2002-08-16

    The Gordon Research Conference (GRC) on Electron Donor Acceptor Interactions was held at Salve Regina University, Newport, Rhode Island, 8/11-16/02. Emphasis was placed on current unpublished research and discussion of the future target areas in this field.

  3. Influence of different electron donors and acceptors on dehalorespiration of tetrachloroethene by Desulfitobacterium frappieri TCE1

    SciTech Connect

    Gerritse, J.; Drzyzga, O.; Kloetstra, G.; Keijmel, M.; Wiersum, L.P.; Hutson, R.; Collins, M.D.; Gottschal, J.C.

    1999-12-01

    Strain TCE1, a strictly anaerobic bacterium that can grow by reductive dechlorination of tetrachloroethene (PCE) and trichloroethane (TCE), was isolated by selective enrichment from a PCE-dechlorinating chemostat mixed culture. Strain TCE1 is a gram-positive, motile, curved rod-shaped organism that is 2 to 4 by 0.6 to 0.8 {micro}m and has approximately six lateral flagella. The pH and temperature optima for growth are 7.2 and 35 C, respectively. On the basis of a comparative 16S rRNA sequence analysis, this bacterium was identified as a new strain of Desulfitobacterium frappieri, because it exhibited 99.7% relatedness to the D. frappieri type strain, strain PCP-1. Growth with H{sub 2}, format, L-lactate, butyrate, crotonate, or ethanol as the electron donor depends on the availability of an external electron acceptor. Pyruvate and serine can also be used fermentatively. Electron donors (except format and H{sub 2}) are oxidized to acetate and CO{sub 2}. when L-lactate is the growth substrate, strain TCE1 can use the following electron acceptors: PCE and TCE (to produce cis-1,2-dichloroethene), sulfite and thiosulfate (to produce sulfide), nitrate (to produce nitrite), and fumarate (to produce succinate). Strain TCE1 is not able to reductively dechlorinate 3-chloro-4-hydroxyphenylacetate. The growth yields of the newly isolated bacterium when PCE is the electron acceptor are similar to those obtained for other dehalorespiring anaerobes (e.g., Desulfitobacterium sp. strain PCE1 and Desulfitobacterium hafniense) and the maximum specific reductive dechlorination rates are 4 to 16 times higher. Dechlorination of PCE and TCE is an inducible process. In PCE-limited chemostat cultures of strain TCE1, dechlorination is strongly inhibited by sulfite but not by other alternative electron acceptors, such as fumate or nitrate.

  4. Influence of Different Electron Donors and Acceptors on Dehalorespiration of Tetrachloroethene by Desulfitobacterium frappieri TCE1

    PubMed Central

    Gerritse, Jan; Drzyzga, Oliver; Kloetstra, Geert; Keijmel, Mischa; Wiersum, Luit P.; Hutson, Roger; Collins, Matthew D.; Gottschal, Jan C.

    1999-01-01

    Strain TCE1, a strictly anaerobic bacterium that can grow by reductive dechlorination of tetrachloroethene (PCE) and trichloroethene (TCE), was isolated by selective enrichment from a PCE-dechlorinating chemostat mixed culture. Strain TCE1 is a gram-positive, motile, curved rod-shaped organism that is 2 to 4 by 0.6 to 0.8 μm and has approximately six lateral flagella. The pH and temperature optima for growth are 7.2 and 35°C, respectively. On the basis of a comparative 16S rRNA sequence analysis, this bacterium was identified as a new strain of Desulfitobacterium frappieri, because it exhibited 99.7% relatedness to the D. frappieri type strain, strain PCP-1. Growth with H2, formate, l-lactate, butyrate, crotonate, or ethanol as the electron donor depends on the availability of an external electron acceptor. Pyruvate and serine can also be used fermentatively. Electron donors (except formate and H2) are oxidized to acetate and CO2. When l-lactate is the growth substrate, strain TCE1 can use the following electron acceptors: PCE and TCE (to produce cis-1,2-dichloroethene), sulfite and thiosulfate (to produce sulfide), nitrate (to produce nitrite), and fumarate (to produce succinate). Strain TCE1 is not able to reductively dechlorinate 3-chloro-4-hydroxyphenylacetate. The growth yields of the newly isolated bacterium when PCE is the electron acceptor are similar to those obtained for other dehalorespiring anaerobes (e.g., Desulfitobacterium sp. strain PCE1 and Desulfitobacterium hafniense) and the maximum specific reductive dechlorination rates are 4 to 16 times higher (up to 1.4 μmol of chloride released · min−1 · mg of protein−1). Dechlorination of PCE and TCE is an inducible process. In PCE-limited chemostat cultures of strain TCE1, dechlorination is strongly inhibited by sulfite but not by other alternative electron acceptors, such as fumarate or nitrate. PMID:10583967

  5. Dietary nitrate and cardiovascular health

    USGS Publications Warehouse

    Ahluwalia, A.; Gladwin, M.T.; Harman, Jane L.; Ward, M.H.; Nolan, Bernard T.

    2014-01-01

    The National Heart, Lung, and Blood Institute convened this workshop to discuss the results of recent research on the effects of inorganic nitrate and nitrite on the cardiovascular system, possible long term effects of these compounds in the diet and drinking water, and future research needs including population-wide effects examined through epidemiological studies.

  6. Shewanella oneidensis MR-1 mutants selected for their inability to produce soluble organic-Fe(III) complexes are unable to respire Fe(III) as anaerobic electron acceptor.

    PubMed

    Jones, Morris E; Fennessey, Christine M; DiChristina, Thomas J; Taillefert, Martial

    2010-04-01

    Recent voltammetric analyses indicate that Shewanella putrefaciens strain 200 produces soluble organic-Fe(III) complexes during anaerobic respiration of sparingly soluble Fe(III) oxides. Results of the present study expand the range of Shewanella species capable of producing soluble organic-Fe(III) complexes to include Shewanella oneidensis MR-1. Soluble organic-Fe(III) was produced by S. oneidensis cultures incubated anaerobically with Fe(III) oxides, or with Fe(III) oxides and the alternate electron acceptor fumarate, but not in the presence of O(2), nitrate or trimethylamine-N-oxide. Chemical mutagenesis procedures were combined with a novel MicroElectrode Screening Array (MESA) to identify four (designated Sol) mutants with impaired ability to produce soluble organic-Fe(III) during anaerobic respiration of Fe(III) oxides. Two of the Sol mutants were deficient in anaerobic growth on both soluble Fe(III)-citrate and Fe(III) oxide, yet retained the ability to grow on a suite of seven alternate electron acceptors. The rates of soluble organic-Fe(III) production were proportional to the rates of iron reduction by the S. oneidensis wild-type and Sol mutant strains, and all four Sol mutants retained wild-type siderophore production capability. Results of this study indicate that the production of soluble organic-Fe(III) may be an important intermediate step in the anaerobic respiration of both soluble and sparingly soluble forms of Fe(III) by S. oneidensis.

  7. Dietary nitrates, nitrites, and cardiovascular disease.

    PubMed

    Hord, Norman G

    2011-12-01

    Dietary nitrate (NO(3)), nitrite (NO(2)), and arginine can serve as sources for production of NO(x) (a diverse group of metabolites including nitric oxide, nitrosothiols, and nitroalkenes) via ultraviolet light exposure to skin, mammalian nitrate/nitrite reductases in tissues, and nitric oxide synthase enzymes, respectively. NO(x) are responsible for the hypotensive, antiplatelet, and cytoprotective effects of dietary nitrates and nitrites. Current regulatory limits on nitrate intakes, based on concerns regarding potential risk of carcinogenicity and methemoglobinemia, are exceeded by normal daily intakes of single foods, such as soya milk and spinach, as well as by some recommended dietary patterns such as the Dietary Approaches to Stop Hypertension diet. This review includes a call for regulatory bodies to consider all available data on the beneficial physiologic roles of nitrate and nitrite in order to derive rational bases for dietary recommendations.

  8. Microbiology to help solve our energy needs: methanogenesis from oil and the impact of nitrate on the oil-field sulfur cycle.

    PubMed

    Grigoryan, Alexander; Voordouw, Gerrit

    2008-03-01

    Our society depends greatly on fossil fuels, and the environmental consequences of this are well known and include significant increases of the CO(2) concentration in the earth's atmosphere. Although microbiology has traditionally played only a minor role in fossil-fuel extraction, two novel key discoveries indicate that this may change. First, the realization that oil components can be converted to methane and CO(2) by methanogenic consortia in the absence of electron acceptors (oxygen, nitrate, sulfate) explains how much of the world's oil has been biodegraded in situ. In addition to inorganic nutrients, only water is needed for these methanogenic conversions. Hence, continued methanogenic biodegradation may have shaped the heavy-oil reservoirs that are so prevalent today. The potential to exploit these reactions, for example, by in situ gasification, is currently being actively investigated. Second, injection of nitrate in oil and gas fields can lower sulfide concentrations. High sulfide concentrations, caused by the action of sulfate-reducing bacteria (SRB), are associated with increased risk of corrosion, reservoir plugging (through precipitated sulfides), and human safety. Nitrate injection into an oil field stimulates subsurface heterotrophic nitrate-reducing bacteria (hNRB) and nitrate-reducing, sulfide-oxidizing bacteria (NR-SOB). Nitrite, formed by these NRB by partial reduction of nitrate, is a strong and specific SRB inhibitor. Nitrate injection has, therefore, promise in positively controlling the oil-field sulfur cycle. There is now more interest in and potential to apply petroleum microbiology than there has been in the past, allowing microbiologists to contribute to a sustainable energy future. PMID:18378604

  9. Cylodextrin Polymer Nitrate

    NASA Technical Reports Server (NTRS)

    Kosowski, Bernard; Ruebner, Anja; Statton, Gary; Robitelle, Danielle; Meyers, Curtis

    2000-01-01

    The development of the use of cyclodextrin nitrates as possible components of insensitive, high-energy energetics is outlined over a time period of 12 years. Four different types of cyclodextrin polymers were synthesized, nitrated, and evaluated regarding their potential use for the military and aerospace community. The synthesis of these novel cyclodextrin polymers and different nitration techniques are shown and the potential of these new materials is discussed.

  10. 21 CFR 181.33 - Sodium nitrate and potassium nitrate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Sodium nitrate and potassium nitrate. 181.33...-Sanctioned Food Ingredients § 181.33 Sodium nitrate and potassium nitrate. Sodium nitrate and potassium... nitrite, with or without sodium or potassium nitrite, in the production of cured red meat products...

  11. Thermochemical nitrate destruction

    DOEpatents

    Cox, John L.; Hallen, Richard T.; Lilga, Michael A.

    1992-01-01

    A method is disclosed for denitrification of nitrates and nitrates present in aqueous waste streams. The method comprises the steps of (1) identifying the concentration nitrates and nitrites present in a waste stream, (2) causing formate to be present in the waste stream, (3) heating the mixture to a predetermined reaction temperature from about 200.degree. C. to about 600.degree. C., and (4) holding the mixture and accumulating products at heated and pressurized conditions for a residence time, thereby resulting in nitrogen and carbon dioxide gas, and hydroxides, and reducing the level of nitrates and nitrites to below drinking water standards.

  12. Nitrate removal from drinking water -- Review

    SciTech Connect

    Kapoor, A.; Viraraghavan, T.

    1997-04-01

    Nitrate concentrations in surface water and especially in ground water have increased in Canada, the US, Europe, and other areas of the world. This trend has raised concern because nitrates cause methemoglobiinemia in infants. Several treatment processes including ion exchange, biological denitrification, chemical denitrification, reverse osmosis, electrodialysis, and catalytic denitrification can remove nitrates from water with varying degrees of efficiency, cost, and ease of operation. Available technical data, experience, and economics indicate that ion exchange and biological denitrification are more acceptable for nitrate removal than reverse osmosis. Ion exchange is more viable for ground water while biological denitrification is the preferred alternative for surface water. This paper reviews the developments in the field of nitrate removal processes.

  13. Approximate prediction of melting point of nitramines, nitrate esters, nitrate salts and nitroaliphatics energetic compounds.

    PubMed

    Keshavarz, Mohammad Hossein

    2006-12-01

    A simple new procedure is introduced to predict melting point of selected class of energetic compounds containing nitramines, nitrate esters, nitrate salts and nitroaliphatics energetic compounds. The number of nitrogen and oxygen as well as the number of nitramine group and the contribution of some specific functional groups would be needed in the new method. Energetic compounds should contain at least one of the functional groups including N-NO(2), C-ONO(2) or nonaromatic C-NO(2). Calculated melting point for 33 nitramines, nitrate esters, nitrate salt and nitroaliphatics are compared with experimental data. Predicted melting points have average deviation of 5.4% for these energetic compounds.

  14. Cyanomethylbenzoic acid: an acceptor for donor-π-acceptor chromophores used in dye-sensitized solar cells.

    PubMed

    Xiang, Wanchun; Gupta, Akhil; Kashif, Muhammad Kalim; Duffy, Noel; Bilic, Ante; Evans, Richard A; Spiccia, Leone; Bach, Udo

    2013-02-01

    Sensing the sun: Incorporation of a cyanomethyl benzoic acid electron acceptor into donor-π-acceptor sensitizers for dye-sensitized-solar cell is shown to lead to devices with improved conversion efficiency when compared with more widely used cyanoacetic acid acceptor.

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

    NASA Astrophysics Data System (ADS)

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

    2012-01-01

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

  16. An investigation of acceptor-doped grain boundaries in ?

    NASA Astrophysics Data System (ADS)

    Ravikumar, V.; Rodrigues, R. P.; Dravid, V. P.

    1996-07-01

    Grain boundary (GB) doped 0022-3727/29/7/014/img2 exhibits interesting electroceramic phenomena including varistor and barrier layer capacitor behaviour. We present here our investigation of GB acceptor-doped 0022-3727/29/7/014/img2 using analytical electron microscopy including electron holography. Mn was diffused into sintered polycrystalline 0022-3727/29/7/014/img2 to attain GBs which are rich in Mn. The presence and spatial extent of Mn at the GBs were analysed using x-ray emission spectroscopy (XES) and parallel electron energy loss spectroscopy (PEELS). The valence state of Mn was determined using PEELS to be predominantly +2. Finally, transmission high-energy electron holography was utilized to directly image and quantify the electrostatic potential and associated space-charge across the GBs directly. The holography results reveal a negatively charged GB with positive space-charge, indicating that Mn with a valence of +2 resides as an acceptor dopant on the Ti site at the GB core. The barrier height and local charge density distribution, including the Debye length, of the double Schottky barrier at the GB are derived from these holography results. This investigation demonstrates the usefulness of electron holography as a bulk-sensitive technique to probe the statics and dynamics of electrostatic field distribution and electrical charge across interfaces in technologically useful materials, and the need to employ diverse analytical techniques for such an investigation.

  17. Electromigration of microbial electron acceptors and nutrients: (I) transport in synthetic media.

    PubMed

    Lohner, Svenja T; Katzoreck, Daniel; Tiehm, Andreas

    2008-07-01

    Microbiological cleanup is a widely used in situ remediation strategy for organic soil and groundwater contaminations. However, often the availability of electron acceptors and nutrients are limiting factors for microbial pollutant degradation in the field. Electromigration represents a new approach for the transport of microbiological agents in soil. In this study, the electrokinetic transport of the microbial electron acceptors nitrate and sulfate and of the nutrients ammonium and phosphate was compared. All experiments were performed under standardized conditions, i.e. with constant voltage in demineralized water and a model sandy soil. Average transport rates for nitrate, sulfate, poly-phosphate, and ammonium were 1.34 cm/h, 1.91 cm/h, 0.48 cm/h, and 0.40 cm/h, respectively, in single compound studies. Transport velocities were dependent on applied voltage gradient but not on the initial ion concentration. Additionally, electrokinetic transport was studied with ion mixtures. The ion distribution in the soil was significantly influenced by the pH profile and the associated voltage gradient.

  18. Binomial distribution-based quantitative measurement of multiple-acceptors fluorescence resonance energy transfer by partially photobleaching acceptor

    NASA Astrophysics Data System (ADS)

    Zhang, Lili; Yu, Huaina; Zhang, Jianwei; Chen, Tongsheng

    2014-06-01

    We report that binomial distribution depending on acceptor photobleaching degree can be used to characterize the proportions of various kinds of FRET (Fluorescence Resonance Energy Transfer) constructs resulted from partial acceptor photobleaching of multiple-acceptors FRET system. On this basis, we set up a rigorous quantitation theory for multiple-acceptors FRET construct named as Mb-PbFRET which is not affected by the imaging conditions and fluorophore properties. We experimentally validate Mb-PbFRET with FRET constructs consisted of one donor and two or three acceptors inside living cells on confocal and wide-field microscopes.

  19. Experimental investigation of donor-acceptor electron transfer and back transfer in solid solutions

    SciTech Connect

    Dorfman, R.C.; Lin, Y.; Fayer, M.D. )

    1989-08-24

    Electron transfer from an optically excited donor (rubrene) to randomly distributed acceptors (duroquinone) followed by electron back transfer in a rigid solution (sucrose octaacetate) has been studied experimentally. The forward electron-transfer process was observed by time-dependent fluorescence quenching measurements, while the electron back transfer from the radical anion to the radical cation was monitored by use of the picosecond transient grating technique. A statistical mechanics theory is used to describe the time-dependent dynamics of the system and to extract the forward- and back-transfer parameters from the data. The theory includes donor-acceptor and acceptor-acceptor excluded volume. It is found that the inclusion of excluded volume is necessary to obtain accurate transfer parameters. These parameters enable a detailed description of the electron transfer and recombination dynamics to be given. The agreement between theory and experiment is excellent. A variety of time-dependent properties of the system are calculated. These include the time-dependent ion populations and the probability that the ith acceptor is an ion as a function of time and distance. In addition, (R(t)) and ({tau}(t)), which are the average ion separation as a function of time and the average ion existence time as a function of ion separation, respectively, are calculated.

  20. Photodegradation of Paracetamol in Nitrate Solution

    SciTech Connect

    Meng Cui; Qu Ruijuan; Liang Jinyan; Yang Xi

    2010-11-24

    The photodegradation of paracetamol in nitrate solution under simulated solar irradiation has been investigated. The degradation rates were compared by varying environmental parameters including concentrations of nitrate ion, humic substance and pH values. The quantifications of paracetamol were conducted by HPLC method. The results demonstrate that the photodegradation of paracetamol followed first-order kinetics. The photoproducts and intermediates of paracetamol in the presence of nitrate ions were identified by extensive GC-MS method. The photodegradation pathways involving. OH radicals as reactive species were proposed.

  1. Anaerobic growth and potential for amino acid production by nitrate respiration in Corynebacterium glutamicum.

    PubMed

    Takeno, Seiki; Ohnishi, Junko; Komatsu, Tomoha; Masaki, Tatsuya; Sen, Kikuo; Ikeda, Masato

    2007-07-01

    Oxygen limitation is a crucial problem in amino acid fermentation by Corynebacterium glutamicum. Toward this subject, our study was initiated by analysis of the oxygen-requiring properties of C. glutamicum, generally regarded as a strict aerobe. This organism formed colonies on agar plates up to relatively low oxygen concentrations (0.5% O(2)), while no visible colonies were formed in the absence of O(2). However, in the presence of nitrate (NO3-), the organism exhibited limited growth anaerobically with production of nitrite (NO2-), indicating that C. glutamicum can use nitrate as a final electron acceptor. Assays of cell extracts from aerobic and hypoxic cultures yielded comparable nitrate reductase activities, irrespective of nitrate levels. Genome analysis revealed a narK2GHJI cluster potentially relevant to nitrate reductase and transport. Disruptions of narG and narJ abolished the nitrate-dependent anaerobic growth with the loss of nitrate reductase activity. Disruption of the putative nitrate/nitrite antiporter gene narK2 did not affect the enzyme activity but impaired the anaerobic growth. These indicate that this locus is responsible for nitrate respiration. Agar piece assays using L-lysine- and L-arginine-producing strains showed that production of both amino acids occurred anaerobically by nitrate respiration, indicating the potential of C. glutamicum for anaerobic amino acid production.

  2. Effect of Nitrate Injection on the Microbial Community in an Oil Field as Monitored by Reverse Sample Genome Probing

    PubMed Central

    Telang, A. J.; Ebert, S.; Foght, J. M.; Westlake, D.; Jenneman, G. E.; Gevertz, D.; Voordouw, G.

    1997-01-01

    The reverse sample genome probe (RSGP) method, developed for monitoring the microbial community in oil fields with a moderate subsurface temperature, has been improved by (i) isolation of a variety of heterotrophic bacteria and inclusion of their genomes on the oil field master filter and (ii) use of phosphorimaging technology for the rapid quantitation of hybridization signals. The new master filter contains the genomes of 30 sulfate-reducing, 1 sulfide-oxidizing, and 16 heterotrophic bacteria. Most have been identified by partial 16S rRNA sequencing. Use of improved RSGP in monitoring the effect of nitrate injection in an oil field indicated that the sulfide-oxidizing, nitrate-reducing isolate CVO (a Campylobacter sp.) becomes the dominant community component immediately after injection. No significant enhancement of other community members, including the sulfate-reducing bacteria, was observed. The elevated level of CVO decayed at most sampling sites within 30 days after nitrate injection was terminated. Chemical analyses indicated a corresponding decrease and subsequent increase in sulfide concentrations. Thus, transient injection of a higher potential electron acceptor into an anaerobic subsurface system can have desirable effects (i.e., reduction of sulfide levels) without a permanent adverse influence on the resident microbial community. PMID:16535595

  3. High performance ammonium nitrate propellant

    NASA Technical Reports Server (NTRS)

    Anderson, F. A. (Inventor)

    1979-01-01

    A high performance propellant having greatly reduced hydrogen chloride emission is presented. It is comprised of: (1) a minor amount of hydrocarbon binder (10-15%), (2) at least 85% solids including ammonium nitrate as the primary oxidizer (about 40% to 70%), (3) a significant amount (5-25%) powdered metal fuel, such as aluminum, (4) a small amount (5-25%) of ammonium perchlorate as a supplementary oxidizer, and (5) optionally a small amount (0-20%) of a nitramine.

  4. Genetic basis for nitrate resistance in Desulfovibrio strains

    PubMed Central

    Korte, Hannah L.; Fels, Samuel R.; Christensen, Geoff A.; Price, Morgan N.; Kuehl, Jennifer V.; Zane, Grant M.; Deutschbauer, Adam M.; Arkin, Adam P.; Wall, Judy D.

    2014-01-01

    Nitrate is an inhibitor of sulfate-reducing bacteria (SRB). In petroleum production sites, amendments of nitrate and nitrite are used to prevent SRB production of sulfide that causes souring of oil wells. A better understanding of nitrate stress responses in the model SRB, Desulfovibrio vulgaris Hildenborough and Desulfovibrio alaskensis G20, will strengthen predictions of environmental outcomes of nitrate application. Nitrate inhibition of SRB has historically been considered to result from the generation of small amounts of nitrite, to which SRB are quite sensitive. Here we explored the possibility that nitrate might inhibit SRB by a mechanism other than through nitrite inhibition. We found that nitrate-stressed D. vulgaris cultures grown in lactate-sulfate conditions eventually grew in the presence of high concentrations of nitrate, and their resistance continued through several subcultures. Nitrate consumption was not detected over the course of the experiment, suggesting adaptation to nitrate. With high-throughput genetic approaches employing TnLE-seq for D. vulgaris and a pooled mutant library of D. alaskensis, we determined the fitness of many transposon mutants of both organisms in nitrate stress conditions. We found that several mutants, including homologs present in both strains, had a greatly increased ability to grow in the presence of nitrate but not nitrite. The mutated genes conferring nitrate resistance included the gene encoding the putative Rex transcriptional regulator (DVU0916/Dde_2702), as well as a cluster of genes (DVU0251-DVU0245/Dde_0597-Dde_0605) that is poorly annotated. Follow-up studies with individual D. vulgaris transposon and deletion mutants confirmed high-throughput results. We conclude that, in D. vulgaris and D. alaskensis, nitrate resistance in wild-type cultures is likely conferred by spontaneous mutations. Furthermore, the mechanisms that confer nitrate resistance may be different from those that confer nitrite resistance

  5. Thermochemical nitrate destruction

    DOEpatents

    Cox, J.L.; Hallen, R.T.; Lilga, M.A.

    1992-06-02

    A method is disclosed for denitrification of nitrates and nitrites present in aqueous waste streams. The method comprises the steps of (1) identifying the concentration nitrates and nitrites present in a waste stream, (2) causing formate to be present in the waste stream, (3) heating the mixture to a predetermined reaction temperature from about 200 C to about 600 C, and (4) holding the mixture and accumulating products at heated and pressurized conditions for a residence time, thereby resulting in nitrogen and carbon dioxide gas, and hydroxides, and reducing the level of nitrates and nitrites to below drinking water standards.

  6. The environmental controls that govern the end product of bacterial nitrate respiration

    SciTech Connect

    Kraft, Beate; Tegetmeyer, Halina E.; Sharma, Ritin; Klotz, Martin G.; Ferdelman, Timothy G.; Hettich, Robert L.; Geelhoed, Jeanine S.; Strous, Marc

    2014-08-08

    In the biogeochemical nitrogen cycle, microbial respiration processes compete for nitrate as an electron acceptor. Denitrification converts nitrate into nitrogenous gas and thus removes fixed nitrogen from the biosphere, whereas ammonification converts nitrate into ammonium, which is directly reusable by primary producers. In this paper, we combined multiple parallel long-term incubations of marine microbial nitrate-respiring communities with isotope labeling and metagenomics to unravel how specific environmental conditions select for either process. Microbial generation time, supply of nitrite relative to nitrate, and the carbon/nitrogen ratio were identified as key environmental controls that determine whether nitrite will be reduced to nitrogenous gas or ammonium. Finally, our results define the microbial ecophysiology of a biogeochemical feedback loop that is key to global change, eutrophication, and wastewater treatment.

  7. The environmental controls that govern the end product of bacterial nitrate respiration

    DOE PAGES

    Kraft, Beate; Tegetmeyer, Halina E.; Sharma, Ritin; Klotz, Martin G.; Ferdelman, Timothy G.; Hettich, Robert L.; Geelhoed, Jeanine S.; Strous, Marc

    2014-08-08

    In the biogeochemical nitrogen cycle, microbial respiration processes compete for nitrate as an electron acceptor. Denitrification converts nitrate into nitrogenous gas and thus removes fixed nitrogen from the biosphere, whereas ammonification converts nitrate into ammonium, which is directly reusable by primary producers. In this paper, we combined multiple parallel long-term incubations of marine microbial nitrate-respiring communities with isotope labeling and metagenomics to unravel how specific environmental conditions select for either process. Microbial generation time, supply of nitrite relative to nitrate, and the carbon/nitrogen ratio were identified as key environmental controls that determine whether nitrite will be reduced to nitrogenous gasmore » or ammonium. Finally, our results define the microbial ecophysiology of a biogeochemical feedback loop that is key to global change, eutrophication, and wastewater treatment.« less

  8. Purification and properties of a dissimilatory nitrate reductase from Haloferax denitrificans

    NASA Technical Reports Server (NTRS)

    Hochstein, L. I.; Lang, F.

    1991-01-01

    A membrane-bound nitrate reductase (nitrite:(acceptor) oxidoreductase, EC 1.7.99.4) from the extremely halophilic bacterium Haloferax denitrificans was solubilized by incubating membranes in buffer lacking NaCl and purified by DEAE, hydroxylapatite, and Sepharose 6B gel filtration chromatography. The purified nitrate reductase reduced chlorate and was inhibited by azide and cyanide. Preincubating the enzyme with cyanide increased the extent of inhibition which in turn was intensified when dithionite was present. Although cyanide was a noncompetitive inhibitor with respect to nitrate, nitrate protected against inhibition. The enzyme, as isolated, was composed of two subunits (Mr 116,000 and 60,000) and behaved as a dimer during gel filtration (Mr 380,000). Unlike other halobacterial enzymes, this nitrate reductase was most active, as well as stable, in the absence of salt.

  9. Simultaneous reduction of nitrate and selenate by cell suspensions of selenium-respiring bacteria

    USGS Publications Warehouse

    Oremland, R.S.; Blum, J.S.; Bindi, A.B.; Dowdle, P.R.; Herbel, M.; Stolz, J.F.

    1999-01-01

    Washed-cell suspensions of Sulfurospirillum barnesii reduced selenate [Se(VI)] when cells were cultured with nitrate, thiosulfate, arsenate, or fumarate as the electron acceptor. When the concentration of the electron donor was limiting, Se(VI) reduction in whole cells was approximately fourfold greater in Se(VI)-grown cells than was observed in nitrate-grown cells; correspondingly, nitrate reduction was ~11-fold higher in nitrate-grown cells than in Se(VI)-grown cells. However, a simultaneous reduction of nitrate and Se(VI) was observed in both cases. At nonlimiting electron donor concentrations, nitrate- grown cells suspended with equimolar nitrate and selenate achieved a complete reductive removal of nitrogen and selenium oxyanions, with the bulk of nitrate reduction preceding that of selenate reduction. Chloramphenicol did not inhibit these reductions. The Se(VI)-respiring haloalkaliphile Bacillus arsenicoselenatis gave similar results, but its Se(VI) reductase was not constitutive in nitrate-grown cells. No reduction of Se(VI) was noted for Bacillus selenitireducens, which respires selenite. The results of kinetic experiments with cell membrane preparations of S. barnesii suggest the presence of constitutive selenate and nitrate reduction, as well as an inducible, high- affinity nitrate reductase in nitrate-grown cells which also has a low affinity for selenate. The simultaneous reduction of micromolar Se(VI) in the presence of millimolar nitrate indicates that these organisms may have a functional use in bioremediating nitrate-rich, seleniferous agricultural wastewaters. Results with 75Se-selenate tracer show that these organisms can lower ambient Se(VI) concentrations to levels in compliance with new regulations proposed for release of selenium oxyanions into the environment.

  10. The Periplasmic Nitrate Reductase Nap Is Required for Anaerobic Growth and Involved in Redox Control of Magnetite Biomineralization in Magnetospirillum gryphiswaldense

    PubMed Central

    Li, Yingjie; Katzmann, Emanuel; Borg, Sarah

    2012-01-01

    The magnetosomes of many magnetotactic bacteria consist of membrane-enveloped magnetite crystals, whose synthesis is favored by a low redox potential. However, the cellular redox processes governing the biomineralization of the mixed-valence iron oxide have remained unknown. Here, we show that in the alphaproteobacterium Magnetospirillum gryphiswaldense, magnetite biomineralization is linked to dissimilatory nitrate reduction. A complete denitrification pathway, including gene functions for nitrate (nap), nitrite (nir), nitric oxide (nor), and nitrous oxide reduction (nos), was identified. Transcriptional gusA fusions as reporters revealed that except for nap, the highest expression of the denitrification genes coincided with conditions permitting maximum magnetite synthesis. Whereas microaerobic denitrification overlapped with oxygen respiration, nitrate was the only electron acceptor supporting growth in the entire absence of oxygen, and only the deletion of nap genes, encoding a periplasmic nitrate reductase, and not deletion of nor or nos genes, abolished anaerobic growth and also delayed aerobic growth in both nitrate and ammonium media. While loss of nosZ or norCB had no or relatively weak effects on magnetosome synthesis, deletion of nap severely impaired magnetite biomineralization and resulted in fewer, smaller, and irregular crystals during denitrification and also microaerobic respiration, probably by disturbing the proper redox balance required for magnetite synthesis. In contrast to the case for the wild type, biomineralization in Δnap cells was independent of the oxidation state of carbon substrates. Altogether, our data demonstrate that in addition to its essential role in anaerobic respiration, the periplasmic nitrate reductase Nap has a further key function by participating in redox reactions required for magnetite biomineralization. PMID:22730130

  11. The periplasmic nitrate reductase nap is required for anaerobic growth and involved in redox control of magnetite biomineralization in Magnetospirillum gryphiswaldense.

    PubMed

    Li, Yingjie; Katzmann, Emanuel; Borg, Sarah; Schüler, Dirk

    2012-09-01

    The magnetosomes of many magnetotactic bacteria consist of membrane-enveloped magnetite crystals, whose synthesis is favored by a low redox potential. However, the cellular redox processes governing the biomineralization of the mixed-valence iron oxide have remained unknown. Here, we show that in the alphaproteobacterium Magnetospirillum gryphiswaldense, magnetite biomineralization is linked to dissimilatory nitrate reduction. A complete denitrification pathway, including gene functions for nitrate (nap), nitrite (nir), nitric oxide (nor), and nitrous oxide reduction (nos), was identified. Transcriptional gusA fusions as reporters revealed that except for nap, the highest expression of the denitrification genes coincided with conditions permitting maximum magnetite synthesis. Whereas microaerobic denitrification overlapped with oxygen respiration, nitrate was the only electron acceptor supporting growth in the entire absence of oxygen, and only the deletion of nap genes, encoding a periplasmic nitrate reductase, and not deletion of nor or nos genes, abolished anaerobic growth and also delayed aerobic growth in both nitrate and ammonium media. While loss of nosZ or norCB had no or relatively weak effects on magnetosome synthesis, deletion of nap severely impaired magnetite biomineralization and resulted in fewer, smaller, and irregular crystals during denitrification and also microaerobic respiration, probably by disturbing the proper redox balance required for magnetite synthesis. In contrast to the case for the wild type, biomineralization in Δnap cells was independent of the oxidation state of carbon substrates. Altogether, our data demonstrate that in addition to its essential role in anaerobic respiration, the periplasmic nitrate reductase Nap has a further key function by participating in redox reactions required for magnetite biomineralization.

  12. The reaction of choline dehydrogenase with some electron acceptors.

    PubMed Central

    Barrett, M C; Dawson, A P

    1975-01-01

    1. The choline dehydrogenase (EC 1.1.99.1) WAS SOLUBILIZED FROM ACETONE-DRIED POWDERS OF RAT LIVER MITOCHONDRIA BY TREATMENT WITH Naja naja venom. 2. The kinetics of the reaction of enzyme with phenazine methosulphate and ubiquinone-2 as electron acceptors were investigated. 3. With both electron acceptors the reaction mechanism appears to involve a free, modified-enzyme intermediate. 4. With some electron acceptors the maximum velocity of the reaction is independent of the nature of the acceptor. With phenazine methosulphate and ubiquinone-2 as acceptors the Km value for choline is also independent of the nature of the acceptor molecule. 5. The mechanism of the Triton X-100-solubilized enzyme is apparently the smae as that for the snake venom solubilized enzyme. PMID:1218095

  13. The reaction of choline dehydrogenase with some electron acceptors.

    PubMed

    Barrett, M C; Dawson, A P

    1975-12-01

    1. The choline dehydrogenase (EC 1.1.99.1) WAS SOLUBILIZED FROM ACETONE-DRIED POWDERS OF RAT LIVER MITOCHONDRIA BY TREATMENT WITH Naja naja venom. 2. The kinetics of the reaction of enzyme with phenazine methosulphate and ubiquinone-2 as electron acceptors were investigated. 3. With both electron acceptors the reaction mechanism appears to involve a free, modified-enzyme intermediate. 4. With some electron acceptors the maximum velocity of the reaction is independent of the nature of the acceptor. With phenazine methosulphate and ubiquinone-2 as acceptors the Km value for choline is also independent of the nature of the acceptor molecule. 5. The mechanism of the Triton X-100-solubilized enzyme is apparently the smae as that for the snake venom solubilized enzyme.

  14. Electronic structure of acceptor-donor complexes in silicon

    NASA Astrophysics Data System (ADS)

    Atoro, E.; Ohama, Y.; Hayafuji, Y.

    2003-10-01

    The electronic structure of trimer acceptor-donor complexes in silicon Si clusters is studied using the ab initio discrete variational-Xα molecular-orbital (MO) method. The trimer complexes In2D (D=phosphorus P, arsenic As, antimony Sb, or bismuth Bi) consist of two indium In acceptor elements and a centered donor element D from the group V elements. Calculations are performed under the assumption that the three atoms are arranged in the nearest neighbor substitutional trimer configuration. Results indicate that the trimer complexes act as shallower acceptors having smaller ionization activation energies than In acceptor. The potential of In2D as an acceptor in Si is then discussed and In2D is proposed as a promising acceptor for the formation of channels and source/drains in ultralarge scaled integration.

  15. Measurement and Chemistry of Atmospheric Organic Nitrates

    NASA Astrophysics Data System (ADS)

    Buhr, Martin Patrick

    1990-01-01

    Organic nitrates are important reservoir species for NO_{rm x} (NO + NO_2) in the atmosphere. Typically formed in and around urban areas, the organic nitrates sequester NO_{rm x} and allow it to be transported to rural and remote regions, wherein it may be released into the atmosphere and participate in catalytic cycles leading to the formation of ozone. The research described in this work focusses on two problems related to our understanding of the atmospheric chemistry of the organic nitrates, (1) measuring the organic nitrates contributions to total reactive nitrogen (NO_ {rm y}) in the atmosphere, and (2) determining the conditions under which the organic nitrates release NO_{rm x} into the atmosphere and thereby participate in ozone formation. The work performed included development of measurement methods for the organic nitrates, ambient measurements of several organic nitrates made under a variety of conditions, and data interpretation using a combination of bivariate and multivariate analysis. The instrument development that was performed centered around incorporation of capillary column technology in a gas chromatographic method. Use of a capillary column resulted in improved chromatographic resolution and instrument sensitivity. In addition to the work on the chromatographic separation of the organic nitrates, some work was done regarding the sensitivity of the electron capture detector (ECD) as a function of electrical mode of operation. Ambient measurements of several of the organic nitrates were made during three field experiments in conjunction with NOAA's Aeronomy laboratory, including PAN rm CH_3C(O)O_2NO_2), PPN rm (C_2H_5C(O)O_2NO _2), and the C_1-C _5 alkyl nitrates (RONO_2 ). The measurements were made in conjunction with a wide variety of other chemical and physical parameters. Data interpretation was performed using bivariate analysis in order to understand the diurnal variation of the concentrations of the organic nitrates and their

  16. Protein tyrosine nitration

    PubMed Central

    Chaki, Mounira; Leterrier, Marina; Barroso, Juan B

    2009-01-01

    Nitric oxide metabolism in plant cells has a relative short history. Nitration is a chemical process which consists of introducing a nitro group (-NO2) into a chemical compound. in biological systems, this process has been found in different molecules such as proteins, lipids and nucleic acids that can affect its function. This mini-review offers an overview of this process with special emphasis on protein tyrosine nitration in plants and its involvement in the process of nitrosative stress. PMID:19826215

  17. Charge and energy transfer in a bithiophene perylenediimide based donor-acceptor-donor system for use in organic photovoltaics.

    PubMed

    Wenzel, Jan; Dreuw, Andreas; Burghardt, Irene

    2013-07-28

    The elementary charge and excitation energy transfer steps in a novel symmetric donor-acceptor-donor triad first described in Roland et al. Phys. Chem. Chem. Phys., 2012, 14, 273, consisting of a central perylenediimide moiety as a potential electron acceptor and two identical electron rich bithiophene compounds, have been investigated using quantum chemical methodology. These elementary processes determine the applicability of such systems in photovoltaic devices. The molecular structure, excited states and the photo-physical properties are investigated using smaller model systems and including solvation effects. The donor and acceptor π-systems are separated by an ethyl bridge such that the molecular orbitals are either located on the donor or acceptor moiety making the identification of locally excited versus charge transfer states straightforward. Using excited state geometry optimizations, the mechanism of photo-initiated charge separation could be identified. Geometry relaxation in the excited donor state leads to a near-degeneracy with the locally excited acceptor state, entailing strong excitonic coupling and resonance energy transfer. This energy transfer process is driven by planarization and bond length alternation of the donor molecule. Geometry relaxation of the locally excited acceptor state in turn reveals a crossing with the energetically lowest charge transfer excited state. The energetic position of the latter depends in a sensitive fashion on the solvent. This provides an explanation of the sequential process observed in the experiment, favoring ultrafast (∼130 fs) formation of the excited acceptor state followed by slower (∼3 ps scale) formation of the charge separated state.

  18. Non-fullerene electron acceptors for use in organic solar cells.

    PubMed

    Nielsen, Christian B; Holliday, Sarah; Chen, Hung-Yang; Cryer, Samuel J; McCulloch, Iain

    2015-11-17

    a large intramolecular twist, which suppresses both nucleation and crystal growth. The generic design concept of rotationally symmetrical aromatic small molecules with extended π orbital delocalization, including polyaromatic hydrocarbons, phthalocyanines, etc., has also provided some excellent small molecule acceptors. In most cases, additional electron withdrawing functionality, such as imide or ester groups, can be incorporated to stabilize the LUMO and improve properties. New calamitic acceptors have been developed, where molecular orbital hybridization of electron rich and poor segments can be judiciously employed to precisely control energy levels. Conformation and intermolecular associations can be controlled by peripheral functionalization leading to optimization of crystallization length scales. In particular, the use of rhodanine end groups, coupled electronically through short bridged aromatic chains, has been a successful strategy, with promising device efficiencies attributed to high lying LUMO energy levels and subsequently large open circuit voltages. PMID:26505279

  19. Non-fullerene electron acceptors for use in organic solar cells.

    PubMed

    Nielsen, Christian B; Holliday, Sarah; Chen, Hung-Yang; Cryer, Samuel J; McCulloch, Iain

    2015-11-17

    a large intramolecular twist, which suppresses both nucleation and crystal growth. The generic design concept of rotationally symmetrical aromatic small molecules with extended π orbital delocalization, including polyaromatic hydrocarbons, phthalocyanines, etc., has also provided some excellent small molecule acceptors. In most cases, additional electron withdrawing functionality, such as imide or ester groups, can be incorporated to stabilize the LUMO and improve properties. New calamitic acceptors have been developed, where molecular orbital hybridization of electron rich and poor segments can be judiciously employed to precisely control energy levels. Conformation and intermolecular associations can be controlled by peripheral functionalization leading to optimization of crystallization length scales. In particular, the use of rhodanine end groups, coupled electronically through short bridged aromatic chains, has been a successful strategy, with promising device efficiencies attributed to high lying LUMO energy levels and subsequently large open circuit voltages.

  20. Non-Fullerene Electron Acceptors for Use in Organic Solar Cells

    PubMed Central

    2015-01-01

    , forming dimers with a large intramolecular twist, which suppresses both nucleation and crystal growth. The generic design concept of rotationally symmetrical aromatic small molecules with extended π orbital delocalization, including polyaromatic hydrocarbons, phthalocyanines, etc., has also provided some excellent small molecule acceptors. In most cases, additional electron withdrawing functionality, such as imide or ester groups, can be incorporated to stabilize the LUMO and improve properties. New calamitic acceptors have been developed, where molecular orbital hybridization of electron rich and poor segments can be judiciously employed to precisely control energy levels. Conformation and intermolecular associations can be controlled by peripheral functionalization leading to optimization of crystallization length scales. In particular, the use of rhodanine end groups, coupled electronically through short bridged aromatic chains, has been a successful strategy, with promising device efficiencies attributed to high lying LUMO energy levels and subsequently large open circuit voltages. PMID:26505279

  1. Insights on the design and electron-acceptor properties of conjugated organophosphorus materials.

    PubMed

    Baumgartner, Thomas

    2014-05-20

    The development of conjugated organic materials has become a rapidly evolving field of research, particularly with a view toward practical applications in so-called organic electronics that encompass a variety of device types, such as OLEDs, OPVs, and OFETs. Almost all of these devices minimally require the presence of electron-donor and -acceptor components that act as p- and n-type semiconductors, respectively. Research over the past two decades has shown that while there is an abundant resource of organic p-type materials, suitable n-type species are few and far between. To overcome this severe bottleneck for the further development of organic electronics, researchers have identified organo-main-group avenues as valuable alternatives toward organic electron-acceptor materials that may ultimately be used as n-type components in practical devices. One particular element of interest in this context is phosphorus, which at first glance may not necessarily suggest such properties. In this Account, I provide detailed insights on the origin of the electron-acceptor properties of organophosphorus-based conjugated materials and include an overview of important molecular species that have been developed by my group and others. To this end, I explain that the electron-acceptor properties of conjugated organophosphorus materials originate from an interaction known as negative hyperconjugation. While this particular interaction creates a simply inductively withdrawing phosphoryl substituent for π-conjugated scaffolds, incorporation of a phosphorus atom as an integral part of a cyclic substructure within a π-conjugated system provides a much more complex, versatile, and consequently highly valuable tool for the tuning of the electron-acceptor properties of the materials. Notably, the degree of negative hyperconjugation can effectively be tailored in various ways via simple substitution at the phosphorus center. This is now well established for phosphole-based molecular

  2. Insights on the design and electron-acceptor properties of conjugated organophosphorus materials.

    PubMed

    Baumgartner, Thomas

    2014-05-20

    The development of conjugated organic materials has become a rapidly evolving field of research, particularly with a view toward practical applications in so-called organic electronics that encompass a variety of device types, such as OLEDs, OPVs, and OFETs. Almost all of these devices minimally require the presence of electron-donor and -acceptor components that act as p- and n-type semiconductors, respectively. Research over the past two decades has shown that while there is an abundant resource of organic p-type materials, suitable n-type species are few and far between. To overcome this severe bottleneck for the further development of organic electronics, researchers have identified organo-main-group avenues as valuable alternatives toward organic electron-acceptor materials that may ultimately be used as n-type components in practical devices. One particular element of interest in this context is phosphorus, which at first glance may not necessarily suggest such properties. In this Account, I provide detailed insights on the origin of the electron-acceptor properties of organophosphorus-based conjugated materials and include an overview of important molecular species that have been developed by my group and others. To this end, I explain that the electron-acceptor properties of conjugated organophosphorus materials originate from an interaction known as negative hyperconjugation. While this particular interaction creates a simply inductively withdrawing phosphoryl substituent for π-conjugated scaffolds, incorporation of a phosphorus atom as an integral part of a cyclic substructure within a π-conjugated system provides a much more complex, versatile, and consequently highly valuable tool for the tuning of the electron-acceptor properties of the materials. Notably, the degree of negative hyperconjugation can effectively be tailored in various ways via simple substitution at the phosphorus center. This is now well established for phosphole-based molecular

  3. Thermochemical nitrate reduction

    SciTech Connect

    Cox, J.L.; Lilga, M.A.; Hallen, R.T.

    1992-09-01

    A series of preliminary experiments was conducted directed at thermochemically converting nitrate to nitrogen and water. Nitrates are a major constituent of the waste stored in the underground tanks on the Hanford Site, and the characteristics and effects of nitrate compounds on stabilization techniques must be considered before permanent disposal operations begin. For the thermochemical reduction experiments, six reducing agents (ammonia, formate, urea, glucose, methane, and hydrogen) were mixed separately with {approximately}3 wt% NO{sub 3}{sup {minus}} solutions in a buffered aqueous solution at high pH (13); ammonia and formate were also mixed at low pH (4). Reactions were conducted in an aqueous solution in a batch reactor at temperatures of 200{degrees}C to 350{degrees}C and pressures of 600 to 2800 psig. Both gas and liquid samples were analyzed. The specific components analyzed were nitrate, nitrite, nitrous oxide, nitrogen, and ammonia. Results of experimental runs showed the following order of nitrate reduction of the six reducing agents in basic solution: formate > glucose > urea > hydrogen > ammonia {approx} methane. Airnmonia was more effective under acidic conditions than basic conditions. Formate was also effective under acidic conditions. A more thorough, fundamental study appears warranted to provide additional data on the mechanism of nitrate reduction. Furthermore, an expanded data base and engineering feasibility study could be used to evaluate conversion conditions for promising reducing agents in more detail and identify new reducing agents with improved performance characteristics.

  4. New methods of nitrate removal from water.

    PubMed

    Shrimali, M; Singh, K P

    2001-01-01

    Nitrate contamination in groundwater resources originates mainly from the excessive use of fertilisers and uncontrolled land discharges of treated wastewater. This can cause potential health hazards to infants and pregnant women, thus limiting the direct use of the groundwater resources for the human consumption in several parts of the world, including India. The conventional processes used to eliminate nitrate from water are ion exchange, reverse osmosis and electro-dialysis. The utility of these processes has been limited due to their expensive operation and subsequent disposal problem of the generated nitrate waste brine. This paper presents a comprehensive account of the methods/techniques used for the removal of nitrate ion from water during the last 10 years with special reference to the biological denitrification and fate of the metals in decontamination processes.

  5. Quantum computing with acceptor spins in silicon.

    PubMed

    Salfi, Joe; Tong, Mengyang; Rogge, Sven; Culcer, Dimitrie

    2016-06-17

    The states of a boron acceptor near a Si/SiO2 interface, which bind two low-energy Kramers pairs, have exceptional properties for encoding quantum information and, with the aid of strain, both heavy hole and light hole-based spin qubits can be designed. Whereas a light-hole spin qubit was introduced recently (arXiv:1508.04259), here we present analytical and numerical results proving that a heavy-hole spin qubit can be reliably initialised, rotated and entangled by electrical means alone. This is due to strong Rashba-like spin-orbit interaction terms enabled by the interface inversion asymmetry. Single qubit rotations rely on electric-dipole spin resonance (EDSR), which is strongly enhanced by interface-induced spin-orbit terms. Entanglement can be accomplished by Coulomb exchange, coupling to a resonator, or spin-orbit induced dipole-dipole interactions. By analysing the qubit sensitivity to charge noise, we demonstrate that interface-induced spin-orbit terms are responsible for sweet spots in the dephasing time [Formula: see text] as a function of the top gate electric field, which are close to maxima in the EDSR strength, where the EDSR gate has high fidelity. We show that both qubits can be described using the same starting Hamiltonian, and by comparing their properties we show that the complex interplay of bulk and interface-induced spin-orbit terms allows a high degree of electrical control and makes acceptors potential candidates for scalable quantum computation in Si. PMID:27171901

  6. Quantum computing with acceptor spins in silicon.

    PubMed

    Salfi, Joe; Tong, Mengyang; Rogge, Sven; Culcer, Dimitrie

    2016-06-17

    The states of a boron acceptor near a Si/SiO2 interface, which bind two low-energy Kramers pairs, have exceptional properties for encoding quantum information and, with the aid of strain, both heavy hole and light hole-based spin qubits can be designed. Whereas a light-hole spin qubit was introduced recently (arXiv:1508.04259), here we present analytical and numerical results proving that a heavy-hole spin qubit can be reliably initialised, rotated and entangled by electrical means alone. This is due to strong Rashba-like spin-orbit interaction terms enabled by the interface inversion asymmetry. Single qubit rotations rely on electric-dipole spin resonance (EDSR), which is strongly enhanced by interface-induced spin-orbit terms. Entanglement can be accomplished by Coulomb exchange, coupling to a resonator, or spin-orbit induced dipole-dipole interactions. By analysing the qubit sensitivity to charge noise, we demonstrate that interface-induced spin-orbit terms are responsible for sweet spots in the dephasing time [Formula: see text] as a function of the top gate electric field, which are close to maxima in the EDSR strength, where the EDSR gate has high fidelity. We show that both qubits can be described using the same starting Hamiltonian, and by comparing their properties we show that the complex interplay of bulk and interface-induced spin-orbit terms allows a high degree of electrical control and makes acceptors potential candidates for scalable quantum computation in Si.

  7. Quantum computing with acceptor spins in silicon

    NASA Astrophysics Data System (ADS)

    Salfi, Joe; Tong, Mengyang; Rogge, Sven; Culcer, Dimitrie

    2016-06-01

    The states of a boron acceptor near a Si/SiO2 interface, which bind two low-energy Kramers pairs, have exceptional properties for encoding quantum information and, with the aid of strain, both heavy hole and light hole-based spin qubits can be designed. Whereas a light-hole spin qubit was introduced recently (arXiv:1508.04259), here we present analytical and numerical results proving that a heavy-hole spin qubit can be reliably initialised, rotated and entangled by electrical means alone. This is due to strong Rashba-like spin-orbit interaction terms enabled by the interface inversion asymmetry. Single qubit rotations rely on electric-dipole spin resonance (EDSR), which is strongly enhanced by interface-induced spin-orbit terms. Entanglement can be accomplished by Coulomb exchange, coupling to a resonator, or spin-orbit induced dipole-dipole interactions. By analysing the qubit sensitivity to charge noise, we demonstrate that interface-induced spin-orbit terms are responsible for sweet spots in the dephasing time {T}2* as a function of the top gate electric field, which are close to maxima in the EDSR strength, where the EDSR gate has high fidelity. We show that both qubits can be described using the same starting Hamiltonian, and by comparing their properties we show that the complex interplay of bulk and interface-induced spin-orbit terms allows a high degree of electrical control and makes acceptors potential candidates for scalable quantum computation in Si.

  8. Electrochemical cell having an alkali-metal-nitrate electrode

    DOEpatents

    Roche, M.F.; Preto, S.K.

    1982-06-04

    A power-producing secondary electrochemical cell includes a molten alkali metal as the negative-electrode material and a molten-nitrate salt as the positive-electrode material. The molten material in the respective electrodes are separated by a solid barrier of alkali-metal-ion conducting material. A typical cell includes active materials of molten sodium separated from molten sodium nitrate and other nitrates in mixture by a layer of sodium ..beta..'' alumina.

  9. Responses of Aromatic-Degrading Microbial Communities to Elevated Nitrate in Sediments.

    PubMed

    Xu, Meiying; He, Zhili; Zhang, Qin; Liu, Jin; Guo, Jun; Sun, Guoping; Zhou, Jizhong

    2015-10-20

    A high number of aromatic compounds that have been released into aquatic ecosystems have accumulated in sediment because of their low solubility and high hydrophobicity, causing significant hazards to the environment and human health. Since nitrate is an essential nitrogen component and a more thermodynamically favorable electron acceptor for anaerobic respiration, nitrate-based bioremediation has been applied to aromatic-contaminated sediments. However, few studies have focused on the response of aromatic-degrading microbial communities to nitrate addition in anaerobic sediments. Here we hypothesized that high nitrate inputs would stimulate aromatic-degrading microbial communities and their associated degrading processes, thus increasing the bioremediation efficiency in aromatic compound-contaminated sediments. We analyzed the changes of key aromatic-degrading genes in the sediment samples from a field-scale site for in situ bioremediation of an aromatic-contaminated creek in the Pearl River Delta before and after nitrate injection using a functional gene array. Our results showed that the genes involved in the degradation of several kinds of aromatic compounds were significantly enriched after nitrate injection, especially those encoding enzymes for central catabolic pathways of aromatic compound degradation, and most of the enriched genes were derived from nitrate-reducing microorganisms, possibly accelerating bioremediation of aromatic-contaminated sediments. The sediment nitrate concentration was found to be the predominant factor shaping the aromatic-degrading microbial communities. This study provides new insights into our understanding of the influences of nitrate addition on aromatic-degrading microbial communities in sediments. PMID:26390227

  10. Responses of Aromatic-Degrading Microbial Communities to Elevated Nitrate in Sediments.

    PubMed

    Xu, Meiying; He, Zhili; Zhang, Qin; Liu, Jin; Guo, Jun; Sun, Guoping; Zhou, Jizhong

    2015-10-20

    A high number of aromatic compounds that have been released into aquatic ecosystems have accumulated in sediment because of their low solubility and high hydrophobicity, causing significant hazards to the environment and human health. Since nitrate is an essential nitrogen component and a more thermodynamically favorable electron acceptor for anaerobic respiration, nitrate-based bioremediation has been applied to aromatic-contaminated sediments. However, few studies have focused on the response of aromatic-degrading microbial communities to nitrate addition in anaerobic sediments. Here we hypothesized that high nitrate inputs would stimulate aromatic-degrading microbial communities and their associated degrading processes, thus increasing the bioremediation efficiency in aromatic compound-contaminated sediments. We analyzed the changes of key aromatic-degrading genes in the sediment samples from a field-scale site for in situ bioremediation of an aromatic-contaminated creek in the Pearl River Delta before and after nitrate injection using a functional gene array. Our results showed that the genes involved in the degradation of several kinds of aromatic compounds were significantly enriched after nitrate injection, especially those encoding enzymes for central catabolic pathways of aromatic compound degradation, and most of the enriched genes were derived from nitrate-reducing microorganisms, possibly accelerating bioremediation of aromatic-contaminated sediments. The sediment nitrate concentration was found to be the predominant factor shaping the aromatic-degrading microbial communities. This study provides new insights into our understanding of the influences of nitrate addition on aromatic-degrading microbial communities in sediments.

  11. Competition between Methane and Alkylbenzenes for Electron Acceptors during Natural Attenuation of Crude Oil in the Subsurface

    NASA Astrophysics Data System (ADS)

    Bekins, B. A.; Amos, R. T.; Cozzarelli, I.; Voytek, M. A.

    2009-12-01

    At a crude-oil spill site near the town of Bemidji, MN, entrapped oil is present at residual saturations exceeding 10% in the vadose zone and floating at the water table at saturations of 30-60%. The degradable fraction of the light crude oil includes n-alkanes, aromatics, and alkyl-cyclohexanes. Together these compounds constitute a reduced carbon concentration at least 500 times greater than is present in the dissolved hydrocarbon groundwater plume comprised mainly of aromatics. Methanogenic degradation of the stationary oil body has been occurring for at least 20 years providing a continuous supply of methane emanating from the oil. Transport of methane away from the oil body occurs in both the vapor phase through the vadose zone and in the dissolved phase with the groundwater flow. Within the vadose zone the supply of oxygen and other electron acceptors from the surface is completely consumed by the process of methane oxidation in a zone 2-3 meters above the water table. In the groundwater, the 1 ppm contour of the methane plume extends beyond the 0.5 ppb contour for benzene, which is located at the aerobic/anaerobic boundary in the plume approximately 120 m downgradient of the oil body. Between 75 m and 120 m downgradient, methane concentrations decrease steadily from >0.6 mmol/L to <0.06 mmol/L, accompanied by increases in the δ13C-CH4 indicating that methane attenuation occurs through microbially-mediated oxidation. Anaerobic methane oxidation under iron-reducing conditions has recently been demonstrated by Beal et al. (Science, 325, 184, 2009) and is indicated at this site by several lines of evidence. In the methane oxidation zone, values of bioavailable Fe(III) extracted from the sediments averaged 8 mmol/kg (n=16), or >8 times the amount required to degrade 0.5 mmol methane, while all other electron acceptors together can account for complete oxidation of only 0.07 mmol (sulfate <0.06 mmol/L, dissolved oxygen <3 µmol/L, and nitrate <0.02 mmol

  12. Enhanced in situ bioremediation of BTEX-contaminated groundwater by combined injection of nitrate and sulfate.

    PubMed

    Cunningham, J A; Rahme, H; Hopkins, G D; Lebron, C; Reinhard, M

    2001-04-15

    Enhancement of in situ anaerobic biodegradation of BTEX compounds was demonstrated at a petroleum-contaminated aquifer in Seal Beach, CA. Specifically, combined injection of nitrate and sulfate into the contaminated aquifer was used to accelerate BTEX removal as compared to remediation by natural attenuation. An array of multi-level sampling wells was used to monitor the evolution of the in situ spatial distributions of the electron acceptors and the BTEX compounds. Nitrate was utilized preferentially over sulfate and was completely consumed within a horizontal distance of 4-6 m from the injection well; sulfate reduction occurred in the region outside the denitrifying zone. By combining injection of both nitrate and sulfate, the total electron acceptor capacity was enhanced without violating practical considerations that limit the amount of nitrate or sulfate that can be added individually. Degradation of total xylene appears linked to sulfate utilization, indicating another advantage of combined injection versus injection of nitrate alone. Benzene degradation also appears to have been stimulated by the nitrate and sulfate injection close to the injection well but only toward the end of the 15-month demonstration. The results are consistent with the hypothesis that benzene can be biodegraded anaerobically after other preferentially degraded hydrocarbons have been removed. PMID:11329718

  13. Enhanced in situ bioremediation of BTEX-contaminated groundwater by combined injection of nitrate and sulfate.

    PubMed

    Cunningham, J A; Rahme, H; Hopkins, G D; Lebron, C; Reinhard, M

    2001-04-15

    Enhancement of in situ anaerobic biodegradation of BTEX compounds was demonstrated at a petroleum-contaminated aquifer in Seal Beach, CA. Specifically, combined injection of nitrate and sulfate into the contaminated aquifer was used to accelerate BTEX removal as compared to remediation by natural attenuation. An array of multi-level sampling wells was used to monitor the evolution of the in situ spatial distributions of the electron acceptors and the BTEX compounds. Nitrate was utilized preferentially over sulfate and was completely consumed within a horizontal distance of 4-6 m from the injection well; sulfate reduction occurred in the region outside the denitrifying zone. By combining injection of both nitrate and sulfate, the total electron acceptor capacity was enhanced without violating practical considerations that limit the amount of nitrate or sulfate that can be added individually. Degradation of total xylene appears linked to sulfate utilization, indicating another advantage of combined injection versus injection of nitrate alone. Benzene degradation also appears to have been stimulated by the nitrate and sulfate injection close to the injection well but only toward the end of the 15-month demonstration. The results are consistent with the hypothesis that benzene can be biodegraded anaerobically after other preferentially degraded hydrocarbons have been removed.

  14. New acceptor-donor-acceptor (A-D-A) type copolymers for efficient organic photovoltaic devices

    NASA Astrophysics Data System (ADS)

    Ghomrasni, S.; Ayachi, S.; Alimi, K.

    2015-01-01

    Three new conjugated systems alternating acceptor-donor-acceptor (A-D-A) type copolymers have been investigated by means of Density Functional Theory (DFT) and Time-Dependent DFT (TD-DFT) at the 6-31g (d) level of theory. 4,4‧-Dimethoxy-chalcone, also called the 1,3-bis(4-methoxyphenyl)prop-2-en-1-one (BMP), has been used as a common acceptor moiety. It forced intra-molecular S⋯O interactions through alternating oligo-thiophene derivatives: 4-AlkylThiophenes (4-ATP), 4-AlkylBithiophenes (4-ABTP) and 4-Thienylene Vinylene (4-TEV) as donor moieties. The band gap, HOMO and LUMO electron distributions as well as optical properties were analyzed for each molecule. The fully optimized resulting copolymers showed low band gaps (2.2-2.8 eV) and deep HOMO energy levels ranging from -4.66 to -4.86 eV. A broad absorption [300-900 nm] covering the solar spectrum and absorption maxima ranges from 486 to 604 nm. In addition, organic photovoltaic cells (OPCs) based on alternating copolymers in bulk heterojunction (BHJ) composites with the 1-(3-methoxycarbonyl) propyl-1-phenyl-[6,6]-C61 (PCBM), as an acceptor, have been optimized. Thus, the band gap decreased to 1.62 eV, the power conversion efficiencies (PCEs) were about 3-5% and the open circuit voltage Voc of the resulting molecules decreased from 1.50 to 1.27 eV.

  15. Hybrid coconut seedlings, scholarships, and discount cards for family planning acceptors.

    PubMed

    Sumarsono

    1989-10-01

    Having learned from failed family planning (FP) incentive schemes in other countries, Indonesia implemented a reward system designed to popularize FP in the community. In order to overcome cultural opposition to FP, many countries in the 1970s opted to give incentives--money, materials, etc.--to new contraceptive acceptors and the FP workers who successfully recruited them. These countries, which oftentimes spent up to 1/4 of their program budget on incentives, saw rapid increases in the number of new acceptors. The results, however, only reflected a superficial acceptance of FP. When the incentives stopped, the number of acceptors dropped considerably. Recognizing this, the Indonesian government set out to increase FP acceptance by making the small family the norm in the community. And one of the approaches for doing so was a reward system. The goals of the reward program were: 1) to raise awareness of the recognition given to individuals or groups that have accepted FP; 2) to create pride among FP workers and new acceptors; and 3) to generate leadership in the community. Villages with high FP acceptance receive rewards such as deep-wells that provide clean water or income generating projects. Individuals also receive rewards that sometimes include hybrid coconut seedlings which, after 3 years, can yield up to 700 coconuts, which can provide a family with a significant supplemental income. The government also gives scholarships to children of FP acceptors. Also, the president of Indonesia publicly recognized family planning acceptors. In 1989, over 800,000 couples received awards for practicing contraception over the past 5-16 years. PMID:12315968

  16. Hybrid coconut seedlings, scholarships, and discount cards for family planning acceptors.

    PubMed

    Sumarsono

    1989-10-01

    Having learned from failed family planning (FP) incentive schemes in other countries, Indonesia implemented a reward system designed to popularize FP in the community. In order to overcome cultural opposition to FP, many countries in the 1970s opted to give incentives--money, materials, etc.--to new contraceptive acceptors and the FP workers who successfully recruited them. These countries, which oftentimes spent up to 1/4 of their program budget on incentives, saw rapid increases in the number of new acceptors. The results, however, only reflected a superficial acceptance of FP. When the incentives stopped, the number of acceptors dropped considerably. Recognizing this, the Indonesian government set out to increase FP acceptance by making the small family the norm in the community. And one of the approaches for doing so was a reward system. The goals of the reward program were: 1) to raise awareness of the recognition given to individuals or groups that have accepted FP; 2) to create pride among FP workers and new acceptors; and 3) to generate leadership in the community. Villages with high FP acceptance receive rewards such as deep-wells that provide clean water or income generating projects. Individuals also receive rewards that sometimes include hybrid coconut seedlings which, after 3 years, can yield up to 700 coconuts, which can provide a family with a significant supplemental income. The government also gives scholarships to children of FP acceptors. Also, the president of Indonesia publicly recognized family planning acceptors. In 1989, over 800,000 couples received awards for practicing contraception over the past 5-16 years.

  17. Aromatic donor-acceptor interactions in non-polar environments.

    PubMed

    Prentice, Giles M; Pascu, Sofia I; Filip, Sorin V; West, Kevin R; Pantoş, G Dan

    2015-05-14

    We have evaluated the strength of aromatic donor-acceptor interactions between dialkyl naphthalenediimide and dialkoxynaphthalene in non-polar environments. (1)H NMR, UV-vis spectroscopy and isothermal titration calorimetry were used to characterise this interaction. We concluded that the strength of donor-acceptor interactions in heptane is sufficient to drive supramolecular assemblies in this and other aliphatic solvents. PMID:25875729

  18. Effect of nitrate, acetate, and hydrogen on native perchlorate-reducing microbial communities and their activity in vadose soil.

    PubMed

    Nozawa-Inoue, Mamie; Jien, Mercy; Yang, Kun; Rolston, Dennis E; Hristova, Krassimira R; Scow, Kate M

    2011-05-01

    The effect of nitrate, acetate, and hydrogen on native perchlorate-reducing bacteria (PRB) was examined by conducting microcosm tests using vadose soil collected from a perchlorate-contaminated site. The rate of perchlorate reduction was enhanced by hydrogen amendment and inhibited by acetate amendment, compared with unamendment. Nitrate was reduced before perchlorate in all amendments. In hydrogen-amended and unamended soils, nitrate delayed perchlorate reduction, suggesting that the PRB preferentially use nitrate as an electron acceptor. In contrast, nitrate eliminated the inhibitory effect of acetate amendment on perchlorate reduction and increased the rate and the extent, possibly because the preceding nitrate reduction/denitrification decreased the acetate concentration that was inhibitory to the native PRB. In hydrogen-amended and unamended soils, perchlorate reductase gene (pcrA) copies, representing PRB densities, increased with either perchlorate or nitrate reduction, suggesting that either perchlorate or nitrate stimulates the growth of the PRB. In contrast, in acetate-amended soil pcrA increased only when perchlorate was depleted: a large portion of the PRB may have not utilized nitrate in this amendment. Nitrate addition did not alter the distribution of the dominant pcrA clones in hydrogen-amended soil, likely because of the functional redundancy of PRB as nitrate-reducers/denitrifiers, whereas acetate selected different pcrA clones from those with hydrogen amendment.

  19. Effect of nitrate, acetate and hydrogen on native perchlorate-reducing microbial communities and their activity in vadose soil

    PubMed Central

    Nozawa-Inoue, Mamie; Jien, Mercy; Yang, Kun; Rolston, Dennis E.; Hristova, Krassimira R.; Scow, Kate M.

    2011-01-01

    Effect of nitrate, acetate and hydrogen on native perchlorate-reducing bacteria (PRB) was examined by conducting microcosm tests using vadose soil collected from a perchlorate-contaminated site. The rate of perchlorate reduction was enhanced by hydrogen amendment and inhibited by acetate amendment, compared to unamendment. Nitrate was reduced before perchlorate in all amendments. In hydrogen-amended and unamended soils, nitrate delayed perchlorate reduction, suggesting the PRB preferentially use nitrate as an electron acceptor. In contrast, nitrate eliminated the inhibitory effect of acetate amendment on perchlorate reduction and increased the rate and the extent, possibly because the preceding nitrate reduction/denitrification decreased the acetate concentration which was inhibitory to the native PRB. In hydrogen-amended and unamended soils, perchlorate reductase gene (pcrA) copies, representing PRB densities, increased with either perchlorate or nitrate reduction, suggesting either perchlorate or nitrate stimulates growth of the PRB. In contrast, in acetate-amended soil pcrA increased only when perchlorate was depleted: a large portion of the PRB may have not utilized nitrate in this amendment. Nitrate addition did not alter the distribution of the dominant pcrA clones in hydrogen-amended soil, likely because of the functional redundancy of PRB as nitrate-reducers/denitrifiers, whereas acetate selected different pcrA clones from those with hydrogen amendment. PMID:21284679

  20. Evaluation of Nitrate Sources and Nitrate Management Strategies in California Suburban Growth Areas

    NASA Astrophysics Data System (ADS)

    Singleton, M. J.; Moran, J. E.; Esser, B. K.; Leif, R. N.; McNab, W. W.; Carle, S. F.; Moore, K. B.

    2005-12-01

    Population growth in California has pushed the boundaries of suburban communities into formerly agricultural areas. As a result there is considerable uncertainty as to whether nitrate contamination in groundwater wells results from current sources or is a legacy of agriculture. Fertilizer application for historical agriculture is frequently assumed to be a major source, but septic system leachate, other animal waste, and residential fertilizer application may also contribute. Potential remediation strategies may include improved fertilizer management and/or conversion from septic tanks to sewer systems, but the sources of nitrate and pathways to groundwater must first be identified in order to develop a plan of action. We combine the detection of trace organic compounds that are specific to domestic waste with isotopic compositions of nitrogen and oxygen in nitrate in order to determine nitrate sources. Under anaerobic conditions and in the presence of an electron donor such as organic carbon, microbially mediated denitrification may transform nitrate to harmless nitrogen gas, and fractionate the isotopologues of any residual nitrate. The occurrence of saturated zone denitrification is detected by measuring excess dissolved nitrogen gas with a field-portable membrane inlet mass spectrometer system. Groundwater age dating using the 3H/3He method provides a means of tracking the history of nitrate inputs to groundwater, including changes in nitrate flux after implementation of a remediation program. Groundwater that pre-dates agricultural or suburban activity is used to define natural background levels of nitrate. Study areas in California include Chico, Livermore, and Gilroy. This work was performed under the auspices of the U.S. Department of Energy by University of California, Lawrence Livermore National Laboratory under Contract W-7405-Eng-48.

  1. Acceptor impurity activation in III-nitride light emitting diodes

    SciTech Connect

    Römer, Friedhard Witzigmann, Bernd

    2015-01-12

    In this work, the role of the acceptor doping and the acceptor activation and its impact on the internal quantum efficiency (IQE) of a Gallium Nitride (GaN) based multi-quantum well light emitting diode is studied by microscopic simulation. Acceptor impurities in GaN are subject to a high activation energy which depends on the presence of proximate dopant atoms and the electric field. A combined model for the dopant ionization and activation barrier reduction has been developed and implemented in a semiconductor carrier transport simulator. By model calculations, we demonstrate the impact of the acceptor activation mechanisms on the decay of the IQE at high current densities, which is known as the efficiency droop. A major contributor to the droop is the electron leakage which is largely affected by the acceptor doping.

  2. Organic Nitrate Therapy, Nitrate Tolerance, and Nitrate-Induced Endothelial Dysfunction: Emphasis on Redox Biology and Oxidative Stress

    PubMed Central

    2015-01-01

    Abstract Organic nitrates, such as nitroglycerin (GTN), isosorbide-5-mononitrate and isosorbide dinitrate, and pentaerithrityl tetranitrate (PETN), when given acutely, have potent vasodilator effects improving symptoms in patients with acute and chronic congestive heart failure, stable coronary artery disease, acute coronary syndromes, or arterial hypertension. The mechanisms underlying vasodilation include the release of •NO or a related compound in response to intracellular bioactivation (for GTN, the mitochondrial aldehyde dehydrogenase [ALDH-2]) and activation of the enzyme, soluble guanylyl cyclase. Increasing cyclic guanosine-3′,-5′-monophosphate (cGMP) levels lead to an activation of the cGMP-dependent kinase I, thereby causing the relaxation of the vascular smooth muscle by decreasing intracellular calcium concentrations. The hemodynamic and anti-ischemic effects of organic nitrates are rapidly lost upon long-term (low-dose) administration due to the rapid development of tolerance and endothelial dysfunction, which is in most cases linked to increased intracellular oxidative stress. Enzymatic sources of reactive oxygen species under nitrate therapy include mitochondria, NADPH oxidases, and an uncoupled •NO synthase. Acute high-dose challenges with organic nitrates cause a similar loss of potency (tachyphylaxis), but with distinct pathomechanism. The differences among organic nitrates are highlighted regarding their potency to induce oxidative stress and subsequent tolerance and endothelial dysfunction. We also address pleiotropic effects of organic nitrates, for example, their capacity to stimulate antioxidant pathways like those demonstrated for PETN, all of which may prevent adverse effects in response to long-term therapy. Based on these considerations, we will discuss and present some preclinical data on how the nitrate of the future should be designed. Antioxid. Redox Signal. 23, 899–942. PMID:26261901

  3. Organic Nitrate Therapy, Nitrate Tolerance, and Nitrate-Induced Endothelial Dysfunction: Emphasis on Redox Biology and Oxidative Stress.

    PubMed

    Daiber, Andreas; Münzel, Thomas

    2015-10-10

    Organic nitrates, such as nitroglycerin (GTN), isosorbide-5-mononitrate and isosorbide dinitrate, and pentaerithrityl tetranitrate (PETN), when given acutely, have potent vasodilator effects improving symptoms in patients with acute and chronic congestive heart failure, stable coronary artery disease, acute coronary syndromes, or arterial hypertension. The mechanisms underlying vasodilation include the release of •NO or a related compound in response to intracellular bioactivation (for GTN, the mitochondrial aldehyde dehydrogenase [ALDH-2]) and activation of the enzyme, soluble guanylyl cyclase. Increasing cyclic guanosine-3',-5'-monophosphate (cGMP) levels lead to an activation of the cGMP-dependent kinase I, thereby causing the relaxation of the vascular smooth muscle by decreasing intracellular calcium concentrations. The hemodynamic and anti-ischemic effects of organic nitrates are rapidly lost upon long-term (low-dose) administration due to the rapid development of tolerance and endothelial dysfunction, which is in most cases linked to increased intracellular oxidative stress. Enzymatic sources of reactive oxygen species under nitrate therapy include mitochondria, NADPH oxidases, and an uncoupled •NO synthase. Acute high-dose challenges with organic nitrates cause a similar loss of potency (tachyphylaxis), but with distinct pathomechanism. The differences among organic nitrates are highlighted regarding their potency to induce oxidative stress and subsequent tolerance and endothelial dysfunction. We also address pleiotropic effects of organic nitrates, for example, their capacity to stimulate antioxidant pathways like those demonstrated for PETN, all of which may prevent adverse effects in response to long-term therapy. Based on these considerations, we will discuss and present some preclinical data on how the nitrate of the future should be designed.

  4. Transformation of Nitrate and Toluene in Groundwater by Sulfur Modified Iron(SMI-III)

    NASA Astrophysics Data System (ADS)

    Lee, W.; Park, S.; Lim, J.; Hong, U.; Kwon, S.; Kim, Y.

    2009-12-01

    In Korea, nitrate and benzene, toluene, ethylbenzene, and xylene isomers (BTEX) are frequently detected together as ground water contaminants. Therefore, a system simultaneously treating both nitrate (inorganic compound) and BTEX (organic compounds) is required to utilize groundwater as a water resource. In this study, we investigated the efficiency of Sulfur Modified Iron (SMI-III) in treating both nitrate and BTEX contaminated groundwater. Based on XRD (X-Ray Diffraction) analysis, the SMI-III is mainly composed of Fe3O4, S, and Fe. A series of column tests were conducted at three different empty bed contact times (EBCTs) for each compound. During the experiments, removal efficiency for both nitrate and toluene were linearly correlated with EBCT, suggesting that SMI-III have an ability to transform both nitrate and toluene. The concentration of SO42- and oxidation/reduction potential (ORP) were also measured. After exposed to nitrate contaminated groundwater, the composition of SMI-III was changed to Fe2O3, Fe3O4, Fe, and Fe0.95S1.05. The trends of effluent sulfate concentrations were inversely correlated with effluent nitrate concentrations, while the trends of ORP values, having the minimum values of -480 mV, were highly correlated with effluent nitrate concentrations. XRD analysis before and after exposed to nitrate contaminated groundwater, sulfate production, and nitrite detection as a reductive transformation by-product of nitrate suggest that nitrate is reductively transformed by SMI-III. Interestingly, in the toluene experiments, the trends of ORP values were inversely correlated with effluent toluene concentrations, suggesting that probably degrade through oxidation reaction. Consequently, nitrate and toluene probably degrade through reduction and oxidation reaction, respectively and SMI-III could serve as both electron donor and acceptor.

  5. Nitration of Hsp90 on Tyrosine 33 Regulates Mitochondrial Metabolism*

    PubMed Central

    Franco, Maria C.; Ricart, Karina C.; Gonzalez, Analía S.; Dennys, Cassandra N.; Nelson, Pascal A.; Janes, Michael S.; Mehl, Ryan A.; Landar, Aimee; Estévez, Alvaro G.

    2015-01-01

    Peroxynitrite production and tyrosine nitration are present in several pathological conditions, including neurodegeneration, stroke, aging, and cancer. Nitration of the pro-survival chaperone heat shock protein 90 (Hsp90) in position 33 and 56 induces motor neuron death through a toxic gain-of-function. Here we show that nitrated Hsp90 regulates mitochondrial metabolism independently of the induction of cell death. In PC12 cells, a small fraction of nitrated Hsp90 was located on the mitochondrial outer membrane and down-regulated mitochondrial membrane potential, oxygen consumption, and ATP production. Neither endogenous Hsp90 present in the homogenate nor unmodified and fully active recombinant Hsp90 was able to compete with the nitrated protein for the binding to mitochondria. Moreover, endogenous or recombinant Hsp90 did not prevent the decrease in mitochondrial activity but supported nitrated Hsp90 mitochondrial gain-of-function. Nitrotyrosine in position 33, but not in any of the other four tyrosine residues prone to nitration in Hsp90, was sufficient to down-regulate mitochondrial activity. Thus, in addition to induction of cell death, nitrated Hsp90 can also regulate mitochondrial metabolism, suggesting that depending on the cell type, distinct Hsp90 nitration states regulate different aspects of cellular metabolism. This regulation of mitochondrial homeostasis by nitrated Hsp90 could be of particular relevance in cancer cells. PMID:26085096

  6. Nitrate contamination in private wells in rural Alabama, United States.

    PubMed

    Liu, Aiguo; Ming, Jinghua; Ankumah, Ramble O

    2005-06-15

    Nitrate-N (NO(3)(-)-N) concentrations in random water samples from rural residential wells in Alabama, USA, were analyzed over an 8-year period from 1992 to 1999. Data collected included land use, well depth, septic tank use and distance from the well and also livestock and cropping activities around wells. Of 1021 available data sets, 36% of samples showed nitrate-N concentration of higher than 1.0 mg/l, indicating the possible influence of anthropogenic activities. About 1.7% of samples had a nitrate-N concentration of higher than 10 mg/l. Results indicate nitrate contamination in groundwater was relatively low and stable in Alabama. Logistic regression analysis indicated that well depth, pH, and cropping activity were factors of statistical significance in influencing nitrate-N concentration in these wells. Factors such as septic tank use and livestock activities did not show a close link to nitrate-N concentration in wells tested.

  7. Three holes bound to a double acceptor - Be(+) in germanium

    NASA Technical Reports Server (NTRS)

    Haller, E. E.; Mcmurray, R. E., Jr.; Falicov, L. M.; Haegel, N. M.; Hansen, W. L.

    1983-01-01

    A double acceptor binding three holes has been observed for the first time with photoconductive far-infrared spectroscopy in beryllium-doped germanium single crystals. This new center, Be(+), has a hole binding energy of about 5 meV and is only present when free holes are generated by ionization of either neutral shallow acceptors or neutral Be double acceptors. The Be(+) center thermally ionizes above 4 K. It disappears at a uniaxial stress higher than about a billion dyn/sq cm parallel to (111) as a result of the lifting of the valence-band degeneracy.

  8. Femtosecond transient grating studies of electron transfer in porphyrin and chlorophyll donor-acceptor molecules

    SciTech Connect

    Wiederrecht, G.P.; Svec, W.A.; Wasielewski, M.R.

    1994-04-01

    Transient grating studies of electron transfer in artificial photosynthetic systems are described. These systems include simple donor-acceptor molecules where the donor, a chlorophyll or porphyrin, is rigidly attached to an easily reduced species such as napthoquinone or benzoquinone. We have previously synthesized acceptor molecules which have well defined absorption bands upon reduction and are well removed from the excited and cationic states of porphyrins and chlorophylls. They also possess large molar extinction coefficients that dominate the spectra and have well defined polarization characteristics. These traits are ideal for polarization sensitive transient grating experiments which enable accurate determination of the angle of the transition dipole between the initial excitation and the acceptor probe, dynamic solvation effects on the charge separated species, and any time dependent rotation of the chromophores relative to each other. An example of the type of molecule utilized for these experiments is a free base porphyrin (HP) donor and a pyromellitic diimide (PI) acceptor directly bonded to the porphyrin ring.

  9. Nitrate isotope fractionations during biological nitrate reduction: Insights from first principles theoretical modeling

    NASA Astrophysics Data System (ADS)

    Guo, W.; Granger, J.; Sigman, D. M.

    2010-12-01

    :15ɛ ratios among different nitrate reductases suggests that the nitrate isotope fractionations by nitrate reductases are governed by the kinetics of the O-N bond cleavage, which incurs negligible differences from variations in surrounding moieties at the active sites. However, our model similarly predicts a 15ɛ of 36.6‰ and 18ɛ:15ɛ of 0.9 for the auxiliary Nap, although it exhibits a 15ɛ of ~15‰ and 18ɛ:15ɛ of ~0.6 in vivo [1]. This discrepancy is suspected to arise from slower binding and release of NO3- from Nap, which could be partially rate-determining in this enzymatic catalysis, or from the assumptions of our modeled enzyme structures. By extending our above models to include the multiply-substituted (clumped) isotopologues, we predict that isotope fractionations during biological nitrate reduction decrease the proportion of 15N-18O bonds in the residual nitrate relative to their expected equilibrium abundances (~0.02‰ decrease for every 1‰ kinetic enrichment in nitrate δ15N). Future quantification of 15N-18O clumped isotope anomalies in natural nitrate may provide additional constraints on the nitrogen cycle in the ocean. Reference: [1] Granger et al. (2010) GCA, 74: 1030-1040.

  10. Who is drinking nitrate in their well water?

    SciTech Connect

    Mitchell, T.J.; Harding, A.K.

    1996-10-01

    This study evaluated the health risks for a rural northeastern Oregon population which is exposed to high nitrate levels in well water. The study also identified possible sources of nitrate contamination, and investigated measures the resident had taken to reduce their nitrate exposure from well water. Three data sets were used in the study, including a telephone survey of the residents, existing information collected by the Oregon Department of Environmental Quality about well water nitrate concentrations, and demographic information from census records. Results revealed that 23% of the surveyed population was drinking well water that contained nitrate in excess of the 10 ppm nitrate-nitrogen maximum contaminant level adopted by the US Environmental Protection Agency for drinking water. Seventy-two percent of the households with nitrate levels exceeding the 10 ppm level did not use devices that effectively remove nitrates. The population included few women of childbearing age, and was generally older than other nearby urban or rural populations. Resident infants were not exposed to well water nitrate in excess of the 10 ppm level, and were therefore not at apparent risk for methemoglobinemia (blue-baby syndrome). Although the risk of infant methemoglobinemia was low in this area, it is recommended that alternative water sources be explored, and that follow-up monitoring be performed by state and/or local agencies.

  11. New enzyme belonging to the family of molybdenum-free nitrate reductases.

    PubMed Central

    Antipov, Alexey N; Sorokin, Dimitry Y; L'Vov, Nikolay P; Kuenen, J Gijs

    2003-01-01

    A novel molybdenum-free nitrate reductase was isolated from the obligate chemolithoautotrophic and facultative anaerobic, (halo)alkaliphilic sulphur-oxidizing bacterium Thioalkalivibrio nitratireducens strain ALEN 2. The enzyme was found to contain vanadium and haem c as cofactors. Its native molecular mass was determined as 195 kDa, and the enzyme consists of four identical subunits with apparent molecular masses of 57 kDa. Apart from nitrate, the enzyme can utilize nitrite, chlorate, bromate, selenate and sulphite as electron acceptors. Moreover, it also has a haloperoxidase activity. PMID:12238951

  12. Modeling the current and future role of particulate organic nitrates in the southeastern United States

    EPA Science Inventory

    Organic nitrates are an important aerosol constituent in locations where biogenic hydrocarbon emissions mix with anthropogenic NOx sources. While regional and global chemical transport models may include a representation of organic aerosol from monoterpene reactions with nitrate ...

  13. Nitrogen is a deep acceptor in ZnO

    DOE PAGES

    Tarun, M. C.; Iqbal, M. Zafar; McCluskey, M. D.

    2011-04-14

    Zinc oxide is a promising material for blue and UV solid-state lighting devices, among other applications. Nitrogen has been regarded as a potential p-type dopant for ZnO. However, recent calculations indicate that nitrogen is a deep acceptor. This paper presents experimental evidence that nitrogen is, in fact, a deep acceptor and therefore cannot produce p-type ZnO. A broad photoluminescence (PL) emission band near 1.7 eV, with an excitation onset of ~2.2 eV, was observed, in agreement with the deep-acceptor model of the nitrogen defect. Thus the deep-acceptor behavior can be explained by the low energy of the ZnO valence bandmore » relative to the vacuum level.« less

  14. Nitrogen is a deep acceptor in ZnO

    SciTech Connect

    Tarun, M. C.; Iqbal, M. Zafar; McCluskey, M. D.

    2011-04-14

    Zinc oxide is a promising material for blue and UV solid-state lighting devices, among other applications. Nitrogen has been regarded as a potential p-type dopant for ZnO. However, recent calculations indicate that nitrogen is a deep acceptor. This paper presents experimental evidence that nitrogen is, in fact, a deep acceptor and therefore cannot produce p-type ZnO. A broad photoluminescence (PL) emission band near 1.7 eV, with an excitation onset of ~2.2 eV, was observed, in agreement with the deep-acceptor model of the nitrogen defect. Thus the deep-acceptor behavior can be explained by the low energy of the ZnO valence band relative to the vacuum level.

  15. Electron Transfer Rate Maxima at Large Donor-Acceptor Distances.

    PubMed

    Kuss-Petermann, Martin; Wenger, Oliver S

    2016-02-01

    Because of their low mass, electrons can transfer rapidly over long (>15 Å) distances, but usually reaction rates decrease with increasing donor-acceptor distance. We report here on electron transfer rate maxima at donor-acceptor separations of 30.6 Å, observed for thermal electron transfer between an anthraquinone radical anion and a triarylamine radical cation in three homologous series of rigid-rod-like donor-photosensitizer-acceptor triads with p-xylene bridges. Our experimental observations can be explained by a weak distance dependence of electronic donor-acceptor coupling combined with a strong increase of the (outer-sphere) reorganization energy with increasing distance, as predicted by electron transfer theory more than 30 years ago. The observed effect has important consequences for light-to-chemical energy conversion. PMID:26800279

  16. NOx in the atmospheres of aquaplanets as electron acceptors for life

    NASA Astrophysics Data System (ADS)

    Wong, M. L.; Yung, Y. L.; Russell, M. J.

    2014-12-01

    A high potential electron acceptor is required to drive the highly endergonic reactions at the entry points to the autotrophic metabolic pathways that would lead to life on any wet rocky world. Nitrate and nitrite in the earliest oceans are the most attractive candidates (Ducluzeau et al., 2009, 2014). It has been estimated that, given a CO2 and N2 atmosphere, lightning (a proportion of it volcanic), meteorite impacts and volcanic gases would have produced enough NOx in a million years or so (>1018 g) to generate micromolar amounts of NO3- and NO2- in the ocean (Yung and McElroy, 1979; Kasting, 1990; Navarro-González et al., 1998; Martin et al., 2007). It is notable that lightning has been detected on Venus and Mars along with evidence of atmospheric NO. Because a figure 1018 g of nitrate/nitrite is controversial, we will present new calculations based on 10 atmospheres of CO2, two atmospheres of N2 and stepped concentrations of water vapor dependent on surface temperatures.

  17. Synthesis, Properties, and Design Principles of Donor-Acceptor Nanohoops.

    PubMed

    Darzi, Evan R; Hirst, Elizabeth S; Weber, Christopher D; Zakharov, Lev N; Lonergan, Mark C; Jasti, Ramesh

    2015-09-23

    We have synthesized a series of aza[8]cycloparaphenylenes containing one, two, and three nitrogens to probe the impact of nitrogen doping on optoelectronic properties and solid state packing. Alkylation of these azananohoops afforded the first donor-acceptor nanohoops where the phenylene backbone acts as the donor and the pyridinium units act as the acceptor. The impact on the optoelectronic properties was then studied experimentally and computationally to provide new insight into the effect of functionalization on nanohoops properties. PMID:27162989

  18. Synthesis, Properties, and Design Principles of Donor–Acceptor Nanohoops

    PubMed Central

    2015-01-01

    We have synthesized a series of aza[8]cycloparaphenylenes containing one, two, and three nitrogens to probe the impact of nitrogen doping on optoelectronic properties and solid state packing. Alkylation of these azananohoops afforded the first donor–acceptor nanohoops where the phenylene backbone acts as the donor and the pyridinium units act as the acceptor. The impact on the optoelectronic properties was then studied experimentally and computationally to provide new insight into the effect of functionalization on nanohoops properties. PMID:27162989

  19. Ion Pairing in Alkali Nitrate Electrolyte Solutions.

    PubMed

    Xie, Wen Jun; Zhang, Zhen; Gao, Yi Qin

    2016-03-10

    In this study, we investigate the thermodynamics of alkali nitrate salt solutions, especially the formation of contact ion pairs between alkali cation and nitrate anion. The ion-pairing propensity shows an order of LiNO3 < NaNO3 < KNO3. Such results explain the salt activity coefficients and suggest that the empirical "law of matching water affinity" is followed by these alkali nitrate salt solutions. The spatial patterns of contact ion pairs are different in the three salt solutions studied here: Li(+) forms the contact ion pair with only one oxygen of the nitrate while Na(+) and K(+) can also be shared by two oxygens of the nitrate. In reproducing the salt activity coefficient using Kirkwood-Buff theory, we find that it is essential to include electronic polarization for Li(+) which has a high charge density. The electronic continuum correction for nonpolarizable force field significantly improves the agreement between the calculated activity coefficients and their experimental values. This approach also improves the performance of the force field on salt solubility. From these two aspects, this study suggests that electronic continuum correction can be a promising approach to force-field development for ions with high charge densities. PMID:26901167

  20. Measurement of Isoprene Nitrates by GCMS

    NASA Astrophysics Data System (ADS)

    Mills, Graham; Hiatt-Gipson, Glyn; Bew, Sean; Reeves, Claire

    2016-04-01

    We have, for the first time, synthesised and identified the majority of the primary isoprene nitrates (INs), formed by reaction of isoprene with the hydroxyl radical (OH) and nitrate radical (NO3) as described in the Master Chemical Mechanism (MCM). An instrument based on gas chromatography/mass spectrometry (GCMS) and the associated calibration methods is described for the speciated measurements of individual isoprene nitrate isomers. Seven of the primary isoprene nitrates formed by reaction of the OH with isoprene in the MCM and three primary isoprene nitrates from the reaction of the NO3 and isoprene are identified, including six newly synthesised INs. Simple photochemistry bag experiments were performed to demonstrate the capability to measure speciated INs in complex mixtures. Interestingly, the results showed isomeric distributions of INs that were quite different to those predicted by model calculations in earlier studies. In addition, we observed INs that we would expect from NO3 addition to isoprene despite the bag experiments being carried out in daylight conditions when we would expect OH to be the only isoprene oxidant.

  1. Ion Pairing in Alkali Nitrate Electrolyte Solutions.

    PubMed

    Xie, Wen Jun; Zhang, Zhen; Gao, Yi Qin

    2016-03-10

    In this study, we investigate the thermodynamics of alkali nitrate salt solutions, especially the formation of contact ion pairs between alkali cation and nitrate anion. The ion-pairing propensity shows an order of LiNO3 < NaNO3 < KNO3. Such results explain the salt activity coefficients and suggest that the empirical "law of matching water affinity" is followed by these alkali nitrate salt solutions. The spatial patterns of contact ion pairs are different in the three salt solutions studied here: Li(+) forms the contact ion pair with only one oxygen of the nitrate while Na(+) and K(+) can also be shared by two oxygens of the nitrate. In reproducing the salt activity coefficient using Kirkwood-Buff theory, we find that it is essential to include electronic polarization for Li(+) which has a high charge density. The electronic continuum correction for nonpolarizable force field significantly improves the agreement between the calculated activity coefficients and their experimental values. This approach also improves the performance of the force field on salt solubility. From these two aspects, this study suggests that electronic continuum correction can be a promising approach to force-field development for ions with high charge densities.

  2. Purification of alkali metal nitrates

    DOEpatents

    Fiorucci, Louis C.; Gregory, Kevin M.

    1985-05-14

    A process is disclosed for removing heavy metal contaminants from impure alkali metal nitrates containing them. The process comprises mixing the impure nitrates with sufficient water to form a concentrated aqueous solution of the impure nitrates, adjusting the pH of the resulting solution to within the range of between about 2 and about 7, adding sufficient reducing agent to react with heavy metal contaminants within said solution, adjusting the pH of the solution containing reducing agent to effect precipitation of heavy metal impurities and separating the solid impurities from the resulting purified aqueous solution of alkali metal nitrates. The resulting purified solution of alkali metal nitrates may be heated to evaporate water therefrom to produce purified molten alkali metal nitrate suitable for use as a heat transfer medium. If desired, the purified molten form may be granulated and cooled to form discrete solid particles of alkali metal nitrates.

  3. Ammonium nitrate explosive systems

    DOEpatents

    Stinecipher, Mary M.; Coburn, Michael D.

    1981-01-01

    Novel explosives which comprise mixtures of ammonium nitrate and an ammonium salt of a nitroazole in desired ratios are disclosed. A preferred nitroazole is 3,5-dinitro-1,2,4-triazole. The explosive and physical properties of these explosives may readily be varied by the addition of other explosives and oxidizers. Certain of these mixtures have been found to act as ideal explosives.

  4. Photochemical Production of Alkyl Nitrates in the Tropical Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Dahl, E. E.; Yvon-Lewis, S. A.; Saltzman, E. S.

    2005-12-01

    Alkyl nitrates are important to the tropospheric NOx/ozone cycle because they represent a significant fraction of the reactive nitrogen (NOy). Previous work has shown that there is an oceanic source of alkyl nitrates. A photochemical mechanism for the formation of alkyl nitrates in seawater has been proposed. This mechanism involves the reaction of ROO and NO, where ROO is an alkyl peroxy radical. ROO and NO radicals in seawater are derived from the photolysis of DOM and nitrite, respectively. In this study, the photochemical production of low molecular weight alkyl nitrates (C1-C3) was observed in shipboard incubation experiments in the tropical Pacific during the PHASE 1 cruise. Seawater samples from several regions, including high and low-chlorophyll areas, were collected and incubated. Alkyl nitrate production rates as high as 2 nM/hour were observed. The production rate of alkyl nitrates was clearly dependent upon the initial concentration of nitrite, most likely as the source for NO radicals. While the magnitude of production varied between sample locations, the ratios of the production rates of the various alkyl nitrates remained relatively constant. The observed production ratios of methyl, ethyl, isopropyl, and n-propyl nitrate were 5.9:1.0:0.1:0.2. These ratios presumably reflect the speciation of peroxy radicals formed in seawater, and the yield of alkyl nitrates from the ROO+NO reaction. The observed production rate ratios are similar to the concentration ratios of alkyl nitrates observed in ambient seawater and the overlying atmosphere during the study. A comparison of the measured production rates and the observed concentrations, suggests that photochemically produced alkyl nitrates are a major source of atmospheric alkyl nitrates in the surface ocean and marine atmosphere.

  5. Hydrothermal oxidation of organic wastes using reclaimed ammonium nitrate

    SciTech Connect

    Proesmans, P.I.; Luan, L.; Buelow, S.J.

    1996-04-01

    Ammonium nitrate is being studied as an alternative for ammonium perchlorate as an oxidizing agent in Department of Defense 1.1 and 1.3 rocket propellants. Use of ammonium nitrate would eliminate the HCl produced by ammonium perchlorate upon thermal decomposition. To stabilize the ammonium nitrate, which suffers from phase instability, potassium dinitramide (KDN) is added. This increased use of ammonium nitrate will ultimately create a need for environmentally responsible processes to reuse ammonium nitrate extracted from demilitarized rocket motors. Ammonium Nitrate was investigated as an oxidizing agent for methanol, acetic acid and phenol. High removal of organic, ammonia and nitrate was achieved at stoichiometric concentrations. The oxidation of ammonia by nitrate was much faster than the oxidation of either methanol or acetic acid. Phenol, however, was in strong competition with ammonia for the oxidizer (nitrate). Nitrogen products included N{sub 2}, N{sub 2}O, NO{sub 2{sup {minus}}} as well as toxic NO and trace amounts of NO{sub 2}. Carbon products were CO{sub 2}, HCO{sub 3{sup {minus}}}, CO{sub 3}{sup 2{minus}}, and CO.

  6. Nitrate Storage and Dissimilatory Nitrate Reduction by Eukaryotic Microbes.

    PubMed

    Kamp, Anja; Høgslund, Signe; Risgaard-Petersen, Nils; Stief, Peter

    2015-01-01

    The microbial nitrogen cycle is one of the most complex and environmentally important element cycles on Earth and has long been thought to be mediated exclusively by prokaryotic microbes. Rather recently, it was discovered that certain eukaryotic microbes are able to store nitrate intracellularly and use it for dissimilatory nitrate reduction in the absence of oxygen. The paradigm shift that this entailed is ecologically significant because the eukaryotes in question comprise global players like diatoms, foraminifers, and fungi. This review article provides an unprecedented overview of nitrate storage and dissimilatory nitrate reduction by diverse marine eukaryotes placed into an eco-physiological context. The advantage of intracellular nitrate storage for anaerobic energy conservation in oxygen-depleted habitats is explained and the life style enabled by this metabolic trait is described. A first compilation of intracellular nitrate inventories in various marine sediments is presented, indicating that intracellular nitrate pools vastly exceed porewater nitrate pools. The relative contribution by foraminifers to total sedimentary denitrification is estimated for different marine settings, suggesting that eukaryotes may rival prokaryotes in terms of dissimilatory nitrate reduction. Finally, this review article sketches some evolutionary perspectives of eukaryotic nitrate metabolism and identifies open questions that need to be addressed in future investigations. PMID:26734001

  7. Nitrate Storage and Dissimilatory Nitrate Reduction by Eukaryotic Microbes.

    PubMed

    Kamp, Anja; Høgslund, Signe; Risgaard-Petersen, Nils; Stief, Peter

    2015-01-01

    The microbial nitrogen cycle is one of the most complex and environmentally important element cycles on Earth and has long been thought to be mediated exclusively by prokaryotic microbes. Rather recently, it was discovered that certain eukaryotic microbes are able to store nitrate intracellularly and use it for dissimilatory nitrate reduction in the absence of oxygen. The paradigm shift that this entailed is ecologically significant because the eukaryotes in question comprise global players like diatoms, foraminifers, and fungi. This review article provides an unprecedented overview of nitrate storage and dissimilatory nitrate reduction by diverse marine eukaryotes placed into an eco-physiological context. The advantage of intracellular nitrate storage for anaerobic energy conservation in oxygen-depleted habitats is explained and the life style enabled by this metabolic trait is described. A first compilation of intracellular nitrate inventories in various marine sediments is presented, indicating that intracellular nitrate pools vastly exceed porewater nitrate pools. The relative contribution by foraminifers to total sedimentary denitrification is estimated for different marine settings, suggesting that eukaryotes may rival prokaryotes in terms of dissimilatory nitrate reduction. Finally, this review article sketches some evolutionary perspectives of eukaryotic nitrate metabolism and identifies open questions that need to be addressed in future investigations.

  8. Nitrate Storage and Dissimilatory Nitrate Reduction by Eukaryotic Microbes

    PubMed Central

    Kamp, Anja; Høgslund, Signe; Risgaard-Petersen, Nils; Stief, Peter

    2015-01-01

    The microbial nitrogen cycle is one of the most complex and environmentally important element cycles on Earth and has long been thought to be mediated exclusively by prokaryotic microbes. Rather recently, it was discovered that certain eukaryotic microbes are able to store nitrate intracellularly and use it for dissimilatory nitrate reduction in the absence of oxygen. The paradigm shift that this entailed is ecologically significant because the eukaryotes in question comprise global players like diatoms, foraminifers, and fungi. This review article provides an unprecedented overview of nitrate storage and dissimilatory nitrate reduction by diverse marine eukaryotes placed into an eco-physiological context. The advantage of intracellular nitrate storage for anaerobic energy conservation in oxygen-depleted habitats is explained and the life style enabled by this metabolic trait is described. A first compilation of intracellular nitrate inventories in various marine sediments is presented, indicating that intracellular nitrate pools vastly exceed porewater nitrate pools. The relative contribution by foraminifers to total sedimentary denitrification is estimated for different marine settings, suggesting that eukaryotes may rival prokaryotes in terms of dissimilatory nitrate reduction. Finally, this review article sketches some evolutionary perspectives of eukaryotic nitrate metabolism and identifies open questions that need to be addressed in future investigations. PMID:26734001

  9. Assessing the Role of Sewers and Atmospheric Deposition as Nitrate Contamination Sources to Urban Surface Waters using Stable Nitrate Isotopes

    NASA Astrophysics Data System (ADS)

    Sikora, M. T.; Elliott, E. M.

    2009-12-01

    Excess nitrate (NO3-) contributes to the overall degraded quality of streams in many urban areas. These systems are often dominated by impervious surfaces and storm sewers that can route atmospherically deposited nitrogen, from both wet and dry deposition, to waterways. Moreover, in densely populated watersheds there is the potential for interaction between urban waterways and sewer systems. The affects of accumulated nitrate in riverine and estuary systems include low dissolved oxygen, loss of species diversity, increased mortality of aquatic species, and general eutrophication of the waterbody. However, the dynamics of nitrate pollution from each source and it’s affect on urban waterways is poorly constrained. The isotopes of nitrogen and oxygen in nitrate have been proven effective in helping to distinguish contamination sources to ground and surface waters. In order to improve our understanding of urban nitrate pollution sources and dynamics, we examined nitrate isotopes (δ15N and δ18O) in base- and stormflow samples collected over a two-year period from a restored urban stream in Pittsburgh, Pennsylvania (USA). Nine Mile Run drains a 1,600 hectare urban watershed characterized by 38% impervious surface cover. Prior work has documented high nitrate export from the watershed (~19 kg NO3- ha-1 yr-1). Potential nitrate sources to the watershed include observed sewer overflows draining directly to the stream, as well as atmospheric deposition (~23 kg NO3- ha-1 yr-1). In this and other urban systems with high percentages of impervious surfaces, there is likely minimal input from nitrate derived from soil or fertilizer. In this presentation, we examine spatial and temporal patterns in nitrate isotopic composition collected at five locations along Nine Mile Run characterized by both sanitary and combined-sewer cross-connections. Preliminary isotopic analysis of low-flow winter streamwater samples suggest nitrate export from Nine Mile Run is primarily influenced by

  10. Optimizing Sampling Strategies for Riverine Nitrate Using High-Frequency Data in Agricultural Watersheds.

    PubMed

    Reynolds, Kaycee N; Loecke, Terrance D; Burgin, Amy J; Davis, Caroline A; Riveros-Iregui, Diego; Thomas, Steven A; St Clair, Martin A; Ward, Adam S

    2016-06-21

    Understanding linked hydrologic and biogeochemical processes such as nitrate loading to agricultural streams requires that the sampling bias and precision of monitoring strategies be known. An existing spatially distributed, high-frequency nitrate monitoring network covering ∼40% of Iowa provided direct observations of in situ nitrate concentrations at a temporal resolution of 15 min. Systematic subsampling of nitrate records allowed for quantification of uncertainties (bias and precision) associated with estimates of various nitrate parameters, including: mean nitrate concentration, proportion of samples exceeding the nitrate drinking water standard (DWS), peak (>90th quantile) nitrate concentration, and nitrate flux. We subsampled continuous records for 47 site-year combinations mimicking common, but labor-intensive, water-sampling regimes (e.g., time-interval, stage-triggered, and dynamic-discharge storm sampling). Our results suggest that time-interval sampling most efficiently characterized all nitrate parameters, except at coarse frequencies for nitrate flux. Stage-triggered storm sampling most precisely captured nitrate flux when less than 0.19% of possible 15 min observations for a site-year were used. The time-interval strategy had the greatest return on sampling investment by most precisely and accurately quantifying nitrate parameters per sampling effort. These uncertainty estimates can aid in designing sampling strategies focused on nitrate monitoring in the tile-drained Midwest or similar agricultural regions.

  11. Characterization of the Reduction of Selenate and Tellurite by Nitrate Reductases

    PubMed Central

    Sabaty, Monique; Avazeri, Cécile; Pignol, David; Vermeglio, André

    2001-01-01

    Preliminary studies showed that the periplasmic nitrate reductase (Nap) of Rhodobacter sphaeroides and the membrane-bound nitrate reductases of Escherichia coli are able to reduce selenate and tellurite in vitro with benzyl viologen as an electron donor. In the present study, we found that this is a general feature of denitrifiers. Both the periplasmic and membrane-bound nitrate reductases of Ralstonia eutropha, Paracoccus denitrificans, and Paracoccus pantotrophus can utilize potassium selenate and potassium tellurite as electron acceptors. In order to characterize these reactions, the periplasmic nitrate reductase of R. sphaeroides f. sp. denitrificans IL106 was histidine tagged and purified. The Vmax and Km were determined for nitrate, tellurite, and selenate. For nitrate, values of 39 μmol · min−1 · mg−1 and 0.12 mM were obtained for Vmax and Km, respectively, whereas the Vmax values for tellurite and selenate were 40- and 140-fold lower, respectively. These low activities can explain the observation that depletion of the nitrate reductase in R. sphaeroides does not modify the MIC of tellurite for this organism. PMID:11679335

  12. The effects of organic nitrates on osteoporosis: a systematic review.

    PubMed

    Jamal, S A; Reid, L S; Hamilton, C J

    2013-03-01

    Current treatments for osteoporosis are limited by lack of effect on cortical bone, side effects, and, in some cases, cost. Organic nitrates, which act as nitric oxide donors, may be a potential alternative. This systematic review summarizes the clinical data that reports on the effects of organic nitrates and bone. Organic nitrates, which act as nitric oxide donors, are novel agents that have several advantages over the currently available treatments for osteoporosis. This systematic review summarizes the clinical data that reports on the effects of organic nitrates on bone. We searched Medline (1966 to November 2012), EMBASE (1980 to November 2012), and the Cochrane Central Register of Controlled Trials (Issue 11, 2012). Keywords included nitrates, osteoporosis, bone mineral density (BMD), and fractures. We identified 200 citations. Of these, a total of 29 were retrieved for more detailed evaluation and we excluded 19 manuscripts: 15 because they did not present original data and four because they did not provide data on the intervention or outcome of interest. As such, we included ten studies in literature review. Of these ten studies two were observational cohort studies reporting nitrate use was associated with increased BMD; two were case control studies reporting that use of nitrates were associated with lower risk of hip fracture; two were randomized controlled trials (RCT) comparing alendronate to organic nitrates for treatment of postmenopausal women and demonstrating that both agents increased lumbar spine BMD. The two largest RCT with the longest follow-up, both of which compared effects of organic nitrates to placebo on BMD in women without osteoporosis, reported conflicting results. Headaches were the most common adverse event among women taking nitrates. No studies have reported on fracture efficacy. Further research is needed before recommending organic nitrates for the treatment of postmenopausal osteoporosis.

  13. The Periplasmic Nitrate Reductase NapABC Supports Luminal Growth of Salmonella enterica Serovar Typhimurium during Colitis

    PubMed Central

    Lopez, Christopher A.; Rivera-Chávez, Fabian; Byndloss, Mariana X.

    2015-01-01

    The food-borne pathogen Salmonella enterica serovar Typhimurium benefits from acute inflammation in part by using host-derived nitrate to respire anaerobically and compete successfully with the commensal microbes during growth in the intestinal lumen. The S. Typhimurium genome contains three nitrate reductases, encoded by the narGHI, narZYV, and napABC genes. Work on homologous genes present in Escherichia coli suggests that nitrate reductase A, encoded by the narGHI genes, is the main enzyme promoting growth on nitrate as an electron acceptor in anaerobic environments. Using a mouse colitis model, we found, surprisingly, that S. Typhimurium strains with defects in either nitrate reductase A (narG mutant) or the regulator inducing its transcription in the presence of high concentrations of nitrate (narL mutant) exhibited growth comparable to that of wild-type S. Typhimurium. In contrast, a strain lacking a functional periplasmic nitrate reductase (napA mutant) exhibited a marked growth defect in the lumen of the colon. In E. coli, the napABC genes are transcribed maximally under anaerobic growth conditions in the presence of low nitrate concentrations. Inactivation of narP, encoding a response regulator that activates napABC transcription in response to low nitrate concentrations, significantly reduced the growth of S. Typhimurium in the gut lumen. Cecal nitrate measurements suggested that the murine cecum is a nitrate-limited environment. Collectively, our results suggest that S. Typhimurium uses the periplasmic nitrate reductase to support its growth on the low nitrate concentrations encountered in the gut, a strategy that may be shared with other enteric pathogens. PMID:26099579

  14. Analysis of nonlinear optical properties in donor–acceptor materials

    SciTech Connect

    Day, Paul N.; Pachter, Ruth; Nguyen, Kiet A.

    2014-05-14

    Time-dependent density functional theory has been used to calculate nonlinear optical (NLO) properties, including the first and second hyperpolarizabilities as well as the two-photon absorption cross-section, for the donor-acceptor molecules p-nitroaniline and dimethylamino nitrostilbene, and for respective materials attached to a gold dimer. The CAMB3LYP, B3LYP, PBE0, and PBE exchange-correlation functionals all had fair but variable performance when compared to higher-level theory and to experiment. The CAMB3LYP functional had the best performance on these compounds of the functionals tested. However, our comprehensive analysis has shown that quantitative prediction of hyperpolarizabilities is still a challenge, hampered by inadequate functionals, basis sets, and solvation models, requiring further experimental characterization. Attachment of the Au{sub 2}S group to molecules already known for their relatively large NLO properties was found to further enhance the response. While our calculations show a modest enhancement for the first hyperpolarizability, the enhancement of the second hyperpolarizability is predicted to be more than an order of magnitude.

  15. Nitrate postdeposition processes in Svalbard surface snow

    NASA Astrophysics Data System (ADS)

    Björkman, Mats P.; Vega, Carmen P.; Kühnel, Rafael; Spataro, Francesca; Ianniello, Antonietta; Esposito, Giulio; Kaiser, Jan; Marca, Alina; Hodson, Andy; Isaksson, Elisabeth; Roberts, Tjarda J.

    2014-11-01

    The snowpack acts as a sink for atmospheric reactive nitrogen, but several postdeposition pathways have been reported to alter the concentration and isotopic composition of snow nitrate with implications for atmospheric boundary layer chemistry, ice core records, and terrestrial ecology following snow melt. Careful daily sampling of surface snow during winter (11-15 February 2010) and springtime (9 April to 5 May 2010) near Ny-Ålesund, Svalbard reveals a complex pattern of processes within the snowpack. Dry deposition was found to dominate over postdeposition losses, with a net nitrate deposition rate of (0.6 ± 0.2) µmol m-2 d-1 to homogeneous surface snow. At Ny-Ålesund, such surface dry deposition can either solely result from long-range atmospheric transport of oxidized nitrogen or include the redeposition of photolytic/bacterial emission originating from deeper snow layers. Our data further confirm that polar basin air masses bring 15N-depleted nitrate to Svalbard, while high nitrate δ(18O) values only occur in connection with ozone-depleted air, and show that these signatures are reflected in the deposited nitrate. Such ozone-depleted air is attributed to active halogen chemistry in the air masses advected to the site. However, here the Ny-Ålesund surface snow was shown to have an active role in the halogen dynamics for this region, as indicated by declining bromide concentrations and increasing nitrate δ(18O), during high BrO (low-ozone) events. The data also indicate that the snowpack BrO-NOx cycling continued in postevent periods, when ambient ozone and BrO levels recovered.

  16. Glycine lithium nitrate crystals

    NASA Astrophysics Data System (ADS)

    González-Valenzuela, R.; Hernández-Paredes, J.; Medrano-Pesqueira, T.; Esparza-Ponce, H. E.; Jesús-Castillo, S.; Rodriguez-Mijangos, R.; Terpugov, V. S.; Alvarez-Ramos, M. E.; Duarte-Möller, A.

    Crystals of glycine lithium nitrate with non-linear optical properties have been grown in a solution by slow evaporation at room temperature. The crystal shows a good thermal stability from room temperature to 175 °C where the crystal begins to degrade. This property is desirable for future technological applications. Also, a good performance on the second harmonic generation was found, characterizing the emitted dominant wavelength by a customized indirect procedure using luminance and chromaticity measured data based on the CIE-1931 standard. Additionally, the 532 nm signal was detected by using a variant to the Kurtz and Perry method.

  17. Electron acceptor-dependent respiratory and physiological stratifications in biofilms.

    PubMed

    Yang, Yonggang; Xiang, Yinbo; Sun, Guoping; Wu, Wei-Min; Xu, Meiying

    2015-01-01

    Bacterial respiration is an essential driving force in biogeochemical cycling and bioremediation processes. Electron acceptors respired by bacteria often have solid and soluble forms that typically coexist in the environment. It is important to understand how sessile bacteria attached to solid electron acceptors respond to ambient soluble alternative electron acceptors. Microbial fuel cells (MFCs) provide a useful tool to investigate this interaction. In MFCs with Shewanella decolorationis, azo dye was used as an alternative electron acceptor in the anode chamber. Different respiration patterns were observed for biofilm and planktonic cells, with planktonic cells preferred to respire with azo dye while biofilm cells respired with both the anode and azo dye. The additional azo respiration dissipated the proton accumulation within the anode biofilm. There was a large redox potential gap between the biofilms and anode surface. Changing cathodic conditions caused immediate effects on the anode potential but not on the biofilm potential. Biofilm viability showed an inverse and respiration-dependent profile when respiring with only the anode or azo dye and was enhanced when respiring with both simultaneously. These results provide new insights into the bacterial respiration strategies in environments containing multiple electron acceptors and support an electron-hopping mechanism within Shewanella electrode-respiring biofilms.

  18. Peroxyacetyl nitrate and peroxypropionyl nitrate in Porto Alegre, Brazil

    NASA Astrophysics Data System (ADS)

    Grosjean, Eric; Grosjean, Daniel; Woodhouse, Luis F.; Yang, Yueh-Jiun

    For 41 days between 25 May 1996 and 27 March 1997, peroxyacetyl nitrate (PAN) and peroxypropionyl nitrate (PPN) have been measured by electron capture gas chromatography at Santa Rita near Porto Alegre, RS, Brazil, where light-duty vehicles used either ethanol or a gasoline-MTBE blend. Daily maximum concentrations ranged from 0.19 to 6.67 ppb for PAN and 0.06 to 0.72 ppb for PPN. Linear regression of maximum PPN vs. maximum PAN yielded a slope of 0.105±0.004 ( R2=0.974). Diurnal variations of ambient PAN often followed those of ozone with respect to time of day but not with respect to amplitude. This was reflected in the large relative standard deviations associated with the study-averaged PAN/ozone concentration ratio, 0.037±0.105 (ppb/ppb, n=789) and the maximum PAN/maximum ozone concentration ratio, 0.028±0.015 (ppb/ppb, range 0.005-0.078, n=41). On several days PAN accounted for large fractions of the total ambient NO x in the late morning and afternoon hours, e.g., PAN/NO x⩽0.58 and PAN/(NO x-NO) ⩽0.76 on 27 March 1997. The amount of PAN lost by thermal decomposition (TPAN) was comparable in magnitude to that present in ambient air. The ratios TPAN/(PAN+TPAN) were up to 0.53, 0.67 and 0.64 during the warm afternoons of 25, 26 and 27 March 1997, respectively. The highest calculated value of TPAN was 5.6 ppb on 27 March 1997. On that day the 24 h-averaged value of TPAN (1.01 ppb) was nearly the same as that of PAN (1.09 ppb). Using computer kinetic modeling (SAPRC 97 chemical mechanism) and sensitivity analysis of VOC incremental reactivity, we ranked VOC present in Porto Alegre ambient air for their importance as precursors to PAN and to PPN. Using as input data the averages of VOC concentrations measured in downtown Porto Alegre during the ca. 1 yr period March 1996-April 1997, we calculated that the most important precursors to PAN and PPN were the SAPRC 97 model species ARO2 (which includes the aromatics xylenes, trimethylbenzenes, ethyltoluenes, etc

  19. Phanta: A Non-Fluorescent Photochromic Acceptor for pcFRET

    PubMed Central

    Don Paul, Craig; Kiss, Csaba; Traore, Daouda A. K.; Gong, Lan; Wilce, Matthew C. J.; Devenish, Rodney J.; Bradbury, Andrew; Prescott, Mark

    2013-01-01

    We have developed an orange non-fluorescent photochromic protein (quantum yield, 0.003) we call Phanta that is useful as an acceptor in pcFRET applications. Phanta can be repeatedly inter-converted between the two absorbing states by alternate exposure to cyan and violet light. The absorption spectra of Phanta in one absorbing state shows excellent overlap with the emission spectra of a number of donor green fluorescent proteins including the commonly used EGFP. We show that the Phanta-EGFP FRET pair is suitable for monitoring the activation of caspase 3 in live cells using readily available instrumentation and a simple protocol that requires the acquisition of two donor emission images corresponding to Phanta in each of its photoswitched states. This the first report of a genetically encoded non-fluorescent acceptor for pcFRET. PMID:24098733

  20. Proteomic analysis of nitrate-dependent acetone degradation by Alicycliphilus denitrificans strain BC.

    PubMed

    Oosterkamp, Margreet J; Boeren, Sjef; Atashgahi, Siavash; Plugge, Caroline M; Schaap, Peter J; Stams, Alfons J M

    2015-06-01

    Alicycliphilus denitrificans strain BC grows anaerobically on acetone with nitrate as electron acceptor. Comparative proteomics of cultures of A. denitrificans strain BC grown on either acetone or acetate with nitrate was performed to study the enzymes involved in the acetone degradation pathway. In the proposed acetone degradation pathway, an acetone carboxylase converts acetone to acetoacetate, an AMP-dependent synthetase/ligase converts acetoacetate to acetoacetyl-CoA, and an acetyl-CoA acetyltransferase cleaves acetoacetyl-CoA to two acetyl-CoA. We also found a putative aldehyde dehydrogenase associated with acetone degradation. This enzyme functioned as a β-hydroxybutyrate dehydrogenase catalyzing the conversion of surplus acetoacetate to β-hydroxybutyrate that may be converted to the energy and carbon storage compound, poly-β-hydroxybutyrate. Accordingly, we confirmed the formation of poly-β-hydroxybutyrate in acetone-grown cells of strain BC. Our findings provide insight in nitrate-dependent acetone degradation that is activated by carboxylation of acetone. This will aid studies of similar pathways found in other microorganisms degrading acetone with nitrate or sulfate as electron acceptor.

  1. Denitrification in anoxic sediments supported by biological nitrate transport

    NASA Astrophysics Data System (ADS)

    Prokopenko, M. G.; Sigman, D. M.; Berelson, W. M.; Hammond, D. E.; Barnett, B.; Chong, L.; Townsend-Small, A.

    2011-11-01

    Biologically available nitrogen (fixed N) is removed from the oceans by metabolic conversion of inorganic N forms (nitrate and ammonium) to N 2 gas. Much of this removal occurs in marine sediments, where reaction rates are thought to be limited by diffusion. We measured the concentration and isotopic composition of major dissolved nitrogen species in anoxic sediments off the coast of California. At depths below the diffusive penetration of nitrate, we found evidence of a large nitrate pool transported into the sediments by motile microorganisms. A ˜20‰ enrichment in 15N and 18O of this biologically transported nitrate over bottom water values and elevated [N 2] and δ 15N-N 2 at depth indicate that this nitrate is consumed by enzymatic redox reactions with the production of N 2 as the end product. Elevated N 2O concentrations in pore waters below the nitrate diffusion depth confirm that these reactions include the denitrification pathway. A data-constrained model shows that at least 31% of the total N 2 production in anoxic sediments is linked to nitrate bio-transport. Under suboxic/anoxic regimes, this nitrate bio-transport augments diffusive transport, thus increasing benthic fixed nitrogen losses and the reducing burial efficiency of sedimentary organic matter.

  2. Regulation of Nitrate Assimilation and Nitrate Respiration in Aerobacter aerogenes

    PubMed Central

    Van 'T Riet, J.; Stouthamer, A. H.; Planta, R. J.

    1968-01-01

    The influence of growth conditions on assimilatory and respiratory nitrate reduction in Aerobacter aerogenes was studied. The level of nitrate reductase activity in cells, growing in minimal medium with nitrate as the sole nitrogen source, was much lower under aerobic than anaerobic conditions. Further, the enzyme of the aerobic cultures was very sensitive to sonic disintegration, as distinct from the enzyme of anaerobic cultures. When a culture of A. aerogenes was shifted from anaerobic growth in minimal medium with nitrate and NH4+ to aerobiosis in the same medium, but without NH4+, the production of nitrite stopped instantaneously and the total activity of nitrate reductase decreased sharply. Moreover, there was a lag in growth of about 3 hr after such a shift. After resumption of growth, the total enzymatic activity increased again slowly and simultaneously became gradually sensitive to sonic disintegration. These findings show that oxygen inactivates the anaerobic nitrate reductase and represses its further formation; only after a de novo synthesis of nitrate reductase with an assimilatory function will growth be resumed. The enzyme in aerobic cultures was not significantly inactivated by air, only by pure oxygen. The formation of the assimilatory enzyme complex was repressed, however, by NH4+, under both aerobic and anaerobic conditions. The results indicate that the formation of the assimilatory enzyme complex and that of the respiratory enzyme complex are regulated differently. We suggest that both complexes have a different composition, but that the nitrate reductase in both cases is the same protein. PMID:5726295

  3. Impacts of Nitrate and Nitrite on Physiology of Shewanella oneidensis

    PubMed Central

    Zhang, Haiyan; Fu, Huihui; Wang, Jixuan; Sun, Linlin; Jiang, Yaoming; Zhang, Lili; Gao, Haichun

    2013-01-01

    Shewanella oneidensis exhibits a remarkable versatility in anaerobic respiration, which largely relies on its diverse respiratory pathways. Some of these are expressed in response to the existence of their corresponding electron acceptors (EAs) under aerobic conditions. However, little is known about respiration and the impact of non-oxygen EAs on the physiology of the microorganism when oxygen is present. Here we undertook a study to elucidate the basis for nitrate and nitrite inhibition of growth under aerobic conditions. We discovered that nitrate in the form of NaNO3 exerts its inhibitory effects as a precursor to nitrite at low concentrations and as an osmotic-stress provider (Na+) at high concentrations. In contrast, nitrite is extremely toxic, with 25 mM abolishing growth completely. We subsequently found that oxygen represses utilization of all EAs but nitrate. To order to utilize EAs with less positive redox potential, such as nitrite and fumarate, S. oneidensis must enter the stationary phase, when oxygen respiration becomes unfavorable. In addition, we demonstrated that during aerobic respiration the cytochrome bd oxidase confers S. oneidensis resistance to nitrite, which likely functions via nitric oxide (NO). PMID:23626841

  4. Organic solar cells based on acceptor-functionalized diketopyrrolopyrrole derivatives

    NASA Astrophysics Data System (ADS)

    Ghosh, Sanjay S.; Serrano, Luis A.; Ebenhoch, Bernd; Rotello, Vincent M.; Cooke, Graeme; Samuel, Ifor D. W.

    2015-01-01

    The synthesis and characterization of three solution processable diketopyrrolopyrrole (DPP) derivatives featuring acceptor units attached to the core by alkyne linker units is reported. Cyclic voltammetry and density functional theory calculations indicate that the DPP derivatives possess similar HOMO and LUMO energies. Solar cells were fabricated by blending the synthesized DPP derivatives with [6,6]-phenyl-C71-butyrate methyl ester. The influence of donor:acceptor blend ratio, film thickness, annealing temperature, and annealing time on device performance was studied. Differences in device performance were related to atomic force microscopy measurements of the films. The highest power conversion efficiency of 1.76% was achieved for the DPP derivative functionalized with an aldehyde electron-withdrawing group with a 1∶0.7 donor:acceptor ratio when the active layer was annealed for 10 min at 110°C.

  5. Theory of Primary Photoexcitations in Donor-Acceptor Copolymers

    NASA Astrophysics Data System (ADS)

    Aryanpour, Karan; Dutta, Tirthankar; Huynh, Uyen N. V.; Vardeny, Zeev Valy; Mazumdar, Sumit

    2015-12-01

    We present a generic theory of primary photoexcitations in low band gap donor-acceptor conjugated copolymers. Because of the combined effects of strong electron correlations and broken symmetry, there is considerable mixing between a charge-transfer exciton and an energetically proximate triplet-triplet state with an overall spin singlet. The triplet-triplet state, optically forbidden in homopolymers, is allowed in donor-acceptor copolymers. For an intermediate difference in electron affinities of the donor and the acceptor, the triplet-triplet state can have a stronger oscillator strength than the charge-transfer exciton. We discuss the possibility of intramolecular singlet fission from the triplet-triplet state, and how such fission can be detected experimentally.

  6. In situ reductive dechlorination of chlorinated ethenes in high nitrate groundwater.

    PubMed

    Bennett, Peter; Gandhi, Deepa; Warner, Scott; Bussey, Julia

    2007-11-19

    In situ bioremediation using carbohydrate was evaluated as an in situ treatment alternative for trichloroethene (TCE) and cis-1,2-dichloroethene (cDCE) in groundwater containing high nitrate concentrations. Upon addition of carbohydrate to groundwater, sequential reduction of electron acceptors was observed, where nitrate was reduced early in the pilot test, followed by sulfate and TCE. Reduction of cDCE to vinyl chloride and ethene occurred in conjunction with increased iron and manganese, and increased methane concentrations, approximately 7 months into the evaluation period, following depletion of nitrate and sulfate. TCE, cDCE, and vinyl chloride concentrations decreased from approximately 500 to >10 microg/L within 21 months of operation.

  7. Host-derived nitrate boosts growth of E. coli in the inflamed gut.

    PubMed

    Winter, Sebastian E; Winter, Maria G; Xavier, Mariana N; Thiennimitr, Parameth; Poon, Victor; Keestra, A Marijke; Laughlin, Richard C; Gomez, Gabriel; Wu, Jing; Lawhon, Sara D; Popova, Ina E; Parikh, Sanjai J; Adams, L Garry; Tsolis, Renée M; Stewart, Valley J; Bäumler, Andreas J

    2013-02-01

    Changes in the microbial community structure are observed in individuals with intestinal inflammatory disorders. These changes are often characterized by a depletion of obligate anaerobic bacteria, whereas the relative abundance of facultative anaerobic Enterobacteriaceae increases. The mechanisms by which the host response shapes the microbial community structure, however, remain unknown. We show that nitrate generated as a by-product of the inflammatory response conferred a growth advantage to the commensal bacterium Escherichia coli in the large intestine of mice. Mice deficient in inducible nitric oxide synthase did not support the growth of E. coli by nitrate respiration, suggesting that the nitrate generated during inflammation was host-derived. Thus, the inflammatory host response selectively enhances the growth of commensal Enterobacteriaceae by generating electron acceptors for anaerobic respiration. PMID:23393266

  8. Host-derived nitrate boosts growth of E. coli in the inflamed gut

    PubMed Central

    Winter, Sebastian E.; Winter, Maria G.; Xavier, Mariana N.; Thiennimitr, Parameth; Poon, Victor; Keestra, A. Marijke; Laughlin, Richard C.; Gomez, Gabriel; Wu, Jing; Lawhon, Sara D.; Popova, Ina; Parikh, Sanjai J.; Adams, L. Garry; Tsolis, Renée M.; Stewart, Valley J.; Bäumler, Andreas J.

    2014-01-01

    Changes in the microbial community structure are observed in individuals with intestinal inflammatory disorders. These changes are often characterized by a depletion of obligate anaerobic bacteria, whereas the relative abundance of facultative anaerobic Enterobacteriaceae increases. The mechanisms by which the host response shapes the microbial community structure, however, remain unknown. We show that nitrate generated as a by-product of the inflammatory response conferred a growth advantage to the commensal bacterium Escherichia coli in the large intestine of mice. Mice deficient for inducible nitric oxide synthase (iNOS) did not support growth of E. coli by nitrate respiration, suggesting that nitrate generated during inflammation was host-derived. Thus the inflammatory host response selectively enhances growth of commensal Enterobacteriaceae by generating electron acceptors for anaerobic respiration. PMID:23393266

  9. Acceptors in bulk and nanoscale ZnO

    NASA Astrophysics Data System (ADS)

    McCluskey, M. D.

    2012-02-01

    Zinc oxide (ZnO) is a semiconductor that emits bright UV light, with little wasted heat. This intrinsic feature makes it a promising material for energy-efficient white lighting, nano-lasers, and other optical applications. For devices to be competitive, however, it is necessary to develop reliable p-type doping. Although substitutional nitrogen has been considered as a potential p-type dopant for ZnO, theoretical and experimental work indicates that nitrogen is a deep acceptor and will not lead to p-type conductivity. This talk will highlight recent experiments on ZnO:N at low temperatures. A red/near-IR photoluminescence (PL) band is correlated with the presence of deep nitrogen acceptors. PL excitation (PLE) measurements show an absorption threshold of 2.26 eV, in good agreement with theory. Magnetic resonance experiments provide further evidence for this assignment. The results of these studies seem to rule out group-V elements as shallow acceptors in ZnO, contradicting numerous reports in the literature. If these acceptors do not work as advertised, is there a viable alternative? Optical studies on ZnO nanocrystals show some intriguing leads. At liquid-helium temperatures, a series of sharp IR absorption peaks arise from an unknown acceptor impurity. The data are consistent with a hydrogenic acceptor 0.46 eV above the valence band edge. While this binding energy is still too deep for many practical applications, it represents a significant improvement over the ˜ 1.3 eV binding energy for nitrogen acceptors. Nanocrystals present another twist. Due to their high surface-to-volume ratio, surface states are especially important. Specifically, electron-hole recombination at the surface give rises to a red luminescence band. From our PL and IR experiments, we have developed a ``unified'' model that attempts to explain acceptor and surface states in ZnO nanocrystals. This model could provide a useful framework for designing future nanoscale ZnO devices.

  10. Microbial Diversity in Coastal Subsurface Sediments: a Cultivation Approach Using Various Electron Acceptors and Substrate Gradients

    PubMed Central

    Köpke, Beate; Wilms, Reinhard; Engelen, Bert; Cypionka, Heribert; Sass, Henrik

    2005-01-01

    Microbial communities in coastal subsurface sediments are scarcely investigated and have escaped attention so far. But since they are likely to play an important role in biogeochemical cycles, knowledge of their composition and ecological adaptations is important. Microbial communities in tidal sediments were investigated along the geochemical gradients from the surface down to a depth of 5.5 m. Most-probable-number (MPN) series were prepared with a variety of different carbon substrates, each at a low concentration, in combination with different electron acceptors such as iron and manganese oxides. These achieved remarkably high cultivation efficiencies (up to 23% of the total cell counts) along the upper 200 cm. In the deeper sediment layers, MPN counts dropped significantly. Parallel to the liquid enrichment cultures in the MPN series, gradient cultures with embedded sediment subcores were prepared as an additional enrichment approach. In total, 112 pure cultures were isolated; they could be grouped into 53 different operational taxonomic units (OTU). The isolates belonged to the Proteobacteria, “Bacteroidetes,” “Fusobacteria,” Actinobacteria, and “Firmicutes.” Each cultivation approach yielded a specific set of isolates that in general were restricted to this single isolation procedure. Analysis of the enrichment cultures by PCR and denaturing gradient gel electrophoresis revealed an even higher diversity in the primary enrichments that was only partially reflected by the culture collection. The majority of the isolates grew well under anoxic conditions, by fermentation, or by anaerobic respiration with nitrate, sulfate, ferrihydrite, or manganese oxides as electron acceptors. PMID:16332756

  11. Optical Spectroscopy of Acceptors in Semiconductors: I. Acceptor Complexes in Neutron Transmutation-Doped Silicon. I. Piezospectroscopy of Beryllium Double Acceptors in Germanium.

    NASA Astrophysics Data System (ADS)

    Labrec, Charles Raymond

    Substitutional group III impurities in group IV elemental semiconductors bind a hole from the valence band and are solid-state analogs of the hydrogen atom; likewise, group II impurities bind two holes and are analogs of the helium atom. In these materials, the electronic transitions from the acceptor s-like ground state to the p-like excited states are infrared active. A high-resolution Fourier transform spectrometer, and a liquid-helium cooled germanium bolometer and glass sample cryostat are ideally suited to study these effects. When silicon is exposed to neutron radiation, a fraction of the atoms are converted to phosphorus. After annealing, these impurity atoms occupy substitutional locations and are thus donors. When the initial crystal is p-type and the final phosphorus concentration is less than that of the acceptor, the sample is left p-type but highly compensated. This results in broadening of the transition lines. However, before complete annealing, it is discovered that a new, extremely shallow acceptor is formed, with an ionization energy of 28.24 meV, which is far shallower than any previously known. Neutral Be in Ge is known to be a double acceptor. Under uniaxial stress, the single hole (1s)^2 to (1s)(np) excitation spectrum shows splittings and polarization effects. These piezospectroscopic effects were observed for a compressive force vec F | (111) and vec F | (100). The phenomenological shear deformation potential constants have been deduced for the ground and excited states of the D transition.

  12. Some History of Nitrates

    NASA Astrophysics Data System (ADS)

    Barnum, Dennis W.

    2003-12-01

    The history of saltpeter is an interesting combination of chemistry, world trade, technology, politics, and warfare. Originally it was obtained from the dirt floors of stables, sheep pens, pigeon houses, caverns, and even peasants' cottages; any place manure and refuse accumulated in soil under dry conditions. When these sources became inadequate to meet demand it was manufactured on saltpeter plantations, located in dry climates, where piles of dirt, limestone, and manure were allowed to stand for three to five years while soil microbes oxidized the nitrogen to nitrate—an example of early bioengineering. Extensive deposits of sodium nitrate were mined in the Atacama Desert in northern Chile from 1830 until the mid 1920s when the mines were displaced by the Haber Ostwald process.

  13. [Effects of Nitrate and CH4 on Anaerobic Oxidation of BETX in Landfill Cover Soils].

    PubMed

    Liu, Rong; Long, Yan; Wang, Li-li; He, Ting; Ye, Jin-shao

    2015-05-01

    BETX is one of the important components of stink organic gases in landfills, which simultaneously release much of greenhouse CH4. The microorganisms in landfill cover soils are able to degrade CH4 and BETX. Therefore, improving the capacity of biological oxidation of microorganisms in landfill cover soils can effectively reduce and control pollution caused by landfill gases. Some electron acceptors can couple to anaerobic oxidation of methane and some organic pollutants, thus eliminating methane and organic substances. Based on the above theory, this research investigated the effect of nitrate (NO3-) and CH4 on anaerobic degradation of benzene series (toluene, xylene and isopropyl benzene) with coexistence of SO4(2-) in landfill cover soils through static incubation experiment. The results showed that BTEX inhibited the degradation of CH4 without adding nitrate, however, BTEX instead improved the removal of CH4 after nitrate addition. Although single addition of nitrate or CH4 could improve the removal of BTEX in landfill cover soils, adding both of them could improve the removal of BTEX better as the removal efficiencies for benzene, toluene and isopropyl benzene were respectively reached 65%, 88% and 82%, much higher than those of 53%, 76% and 31% when not adding nitrate and CH4. The process of anaerobic methane oxidation coupled to nitrate reduction was able to synchronously improve anaerobic oxidation of BETX.

  14. Biological Redox Cycling Of Iron In Nontronite And Its Potential Application In Nitrate Removal

    SciTech Connect

    Zhao, Linduo; Dong, Hailiang; Kukkadapu, Ravi K.; Zeng, Qiang; Edelmann, Richard E.; Pentrak, Martin; Agrawal, Abinash

    2015-05-05

    Redox cycling of structural Fe in phyllosilicates provides a potential method to remediate nitrate contamination in natural environment. Past research has only studied chemical redox cycles or a single biologically mediated redox cycle of Fe in phyllosilicates. The objective of this research was to study three microbially driven redox cycles of Fe in one phyllosilicate, nontronite (NAu-2). During the reduction phase structural Fe(III) in NAu-2 served as electron acceptor, lactate as electron donor, AQDS as electron shuttle, and dissimilatory Fe(III)-reducing bacteria Shewanella putrefaciens CN32 as mediator in bicarbonate-buffered and PIPES-buffered media. During the oxidation phase, biogenic Fe(II) served an electron donor, nitrate as electron acceptor, and nitrate-dependent Fe(II)-oxidizing bacteria Pseudogulbenkiania sp. strain 2002 as mediator in the same media. For all three cycles, structural Fe in NAu-2 was able to reversibly undergo 3 redox cycles without significant reductive or oxidative dissolution. X-ray diffraction and scanning and transmission electron microscopy revealed that NAu-2 was the dominant residual mineral throughout the 3 redox cycles with some dissolution textures but no significant secondary mineralization. Mössbauer spectroscopy revealed that Fe(II) in bio-reduced samples likely occurred in two distinct environments, at edges and the interior of the NAu-2 structure. Nitrate was completely reduced to nitrogen gas under both buffer conditions and this extent and rate did not change with Fe redox cycles. Mössbauer spectroscopy further revealed that nitrate reduction was coupled to predominant/preferred oxidation of edge Fe(II). These results suggest that structural Fe in phyllosilicates may represent a renewable source to continuously remove nitrate in natural environments.

  15. Nitrate reductase from Rhodopseudomonas sphaeroides.

    PubMed Central

    Kerber, N L; Cardenas, J

    1982-01-01

    The facultative phototroph Rhodopseudomonas sphaeroides DSM158 was incapable of either assimilating or dissimilating nitrate, although the organism could reduce it enzymatically to nitrite either anaerobically in the light or aerobically in the dark. Reduction of nitrate was mediated by a nitrate reductase bound to chromatophores that could be easily solubilized and functioned with chemically reduced viologens or photochemically reduced flavins as electron donors. The enzyme was solubilized, and some of its kinetic and molecular parameters were determined. It seemed to be nonadaptive, ammonia did not repress its synthesis, and its activity underwent a rapid decline when the cells entered the stationary growth phase. Studies with inhibitors and with metal antagonists indicated that molybdenum and possibly iron participate in the enzymatic reduction of nitrate. The conjectural significance of this nitrate reductase in phototrophic bacteria is discussed. PMID:6978883

  16. TREATMENT OF AMMONIUM NITRATE SOLUTIONS

    DOEpatents

    Boyer, T.W.; MacHutchin, J.G.; Yaffe, L.

    1958-06-10

    The treatment of waste solutions obtained in the processing of neutron- irradiated uranium containing fission products and ammonium nitrate is described. The object of this process is to provide a method whereby the ammonium nitrate is destroyed and removed from the solution so as to permit subsequent concentration of the solution.. In accordance with the process the residual nitrate solutions are treated with an excess of alkyl acid anhydride, such as acetic anhydride. Preferably, the residual nitrate solution is added to an excess of the acetic anhydride at such a rate that external heat is not required. The result of this operation is that the ammonium nitrate and acetic anhydride react to form N/sub 2/ O and acetic acid.

  17. Tetrathiafulvalene-based mixed-valence acceptor-donor-acceptor triads: a joint theoretical and experimental approach.

    PubMed

    Calbo, Joaquín; Aragó, Juan; Otón, Francisco; Lloveras, Vega; Mas-Torrent, Marta; Vidal-Gancedo, José; Veciana, Jaume; Rovira, Concepció; Ortí, Enrique

    2013-12-01

    This work presents a joint theoretical and experimental characterisation of the structural and electronic properties of two tetrathiafulvalene (TTF)-based acceptor-donor-acceptor triads (BQ-TTF-BQ and BTCNQ-TTF-BTCNQ; BQ is naphthoquinone and BTCNQ is benzotetracyano-p-quinodimethane) in their neutral and reduced states. The study is performed with the use of electrochemical, electron paramagnetic resonance (EPR), and UV/Vis/NIR spectroelectrochemical techniques guided by quantum-chemical calculations. Emphasis is placed on the mixed-valence properties of both triads in their radical anion states. The electrochemical and EPR results reveal that both BQ-TTF-BQ and BTCNQ-TTF-BTCNQ triads in their radical anion states behave as class-II mixed-valence compounds with significant electronic communication between the acceptor moieties. Density functional theory calculations (BLYP35/cc-pVTZ), taking into account the solvent effects, predict charge-localised species (BQ(.-)-TTF-BQ and BTCNQ(.-)-TTF-BTCNQ) as the most stable structures for the radical anion states of both triads. A stronger localisation is found both experimentally and theoretically for the BTCNQ-TTF-BTCNQ anion, in accordance with the more electron-withdrawing character of the BTCNQ acceptor. CASSCF/CASPT2 calculations suggest that the low-energy, broad absorption bands observed experimentally for the BQ-TTF-BQ and BTCNQ-TTF-BTCNQ radical anions are associated with the intervalence charge transfer (IV-CT) electronic transition and two nearby donor-to-acceptor CT excitations. The study highlights the molecular efficiency of the electron-donor TTF unit as a molecular wire connecting two acceptor redox centres.

  18. Amperometric nitrate biosensor based on Carbon nanotube/Polypyrrole/Nitrate reductase biofilm electrode.

    PubMed

    Can, Faruk; Korkut Ozoner, Seyda; Ergenekon, Pinar; Erhan, Elif

    2012-01-01

    This study describes the construction and characterization of an amperometric nitrate biosensor based on the Polypyrrole (PPy)/Carbon nanotubes (CNTs) film. Nitrate reductase (NR) was both entrapped into the growing PPy film and chemically immobilized via the carboxyl groups of CNTs to the CNT/PPy film electrode. The optimum amperometric response for nitrate was obtained in 0.1 M phosphate buffer solution (PBS), pH 7.5 including 0.1 M lithium chloride and 7 mM potassium ferricyanide with an applied potential of 0.13 V (vs. Ag/AgCl, 3 M NaCl). Sensitivity was found to be 300 nA/mM in a linear range of 0.44-1.45 mM with a regression coefficient of 0.97. The biosensor response showed a higher linear range in comparison to standard nitrate analysis methods which were tested in this study and NADH based nitrate biosensors. A minimum detectable concentration of 0.17 mM (S/N=3) with a relative standard deviation (RSD) of 5.4% (n=7) was obtained for the biosensor. Phenol and glucose inhibit the electrochemical reaction strictly at a concentration of 1 μg/L and 20 mg/L, respectively. The biosensor response retained 70% of its initial response over 10 day usage period when used everyday.

  19. C-H-Activated Direct Arylation of Strong Benzothiadiazole and Quinoxaline-Based Electron Acceptors.

    PubMed

    Zhang, Junxiang; Parker, Timothy C; Chen, Wayne; Williams, LaRita; Khrustalev, Victor N; Jucov, Evgheni V; Barlow, Stephen; Timofeeva, Tatiana V; Marder, Seth R

    2016-01-15

    Electron acceptors are important components of π-conjugated materials, but the strong electron-withdrawing properties of the required synthetic intermediates often make them poor substrates in synthetic schemes designed around conventional organometallic cross-coupling. Here, strong benzodiimine-based acceptors, including 5,6-difluoro[2,1,3]benzothiadiazole, 5,6-dicyano[2,1,3]benzothiadiazole, 5,6-dicyanobenzo[d][1,2,3]triazole, 6,7-dicyanoquinoxaline, and 6,7-dinitroquinoxaline, are shown to undergo facile palladium-catalyzed C-H direct arylation with a variety of bromoarenes in moderate to high yields. The electrochemical characteristics of di-2-thienyl derivatives synthesized using this methodology are compared and suggest that, in an electron-transfer sense, 5,6-dicyano[2,1,3]benzothiadiazole is a comparably strong acceptor to benzo[1,2-c:4,5-c']bis[1,2,5]thiadiazole. The synthetic results suggest that high electron-withdrawing ability, which has traditionally limited reaction yields and structural variety in organic electronic materials, may be advantageous when employing C-H activated direct arylation in certain circumstances.

  20. Polar lipid fatty acids, LPS-hydroxy fatty acids, and respiratory quinones of three Geobacter strains, and variation with electron acceptor

    SciTech Connect

    Hedrick, David B.; Peacock, Aaron; Lovley, Derek; Woodard, Trevor L.; Nevin, Kelly P.; Long, Philip E.; White, David C.

    2009-02-01

    The polar lipid fatty acids, lipopolysaccharide hydroxy-fatty acids, and respiratory quinones of Geobacter metallireducens str. GS-15, Geobacter sulfurreducens str. PCA, and Geobacter bemidjiensis str. Bem are reported. Also, the lipids of G. metallireducens were compared when grown with Fe3+ or nitrate as electron acceptors and G. sulfurreducens with Fe3+ or fumarate. In all experiments, the most abundant polar lipid fatty acids were 14:0, i15:0, 16:1*7c, 16:1*5c, and 16:0; lipopolysaccharide hydroxyfatty acids were dominated by 3oh16:0, 3oh14:0, 9oh16:0, and 10oh16:0; and menaquinone-8 was the most abundant respiratory quinone. Some variation in lipid proWles with strain were observed, but not with electron acceptor.

  1. Effects of mineral dust on global atmospheric nitrate concentrations

    NASA Astrophysics Data System (ADS)

    Karydis, V. A.; Tsimpidi, A. P.; Pozzer, A.; Astitha, M.; Lelieveld, J.

    2016-02-01

    This study assesses the chemical composition and global aerosol load of the major inorganic aerosol components, focusing on mineral dust and aerosol nitrate. The mineral dust aerosol components (i.e., Ca2+, Mg2+, K+, Na+) and their emissions are included in the ECHAM5/MESSy Atmospheric Chemistry model (EMAC). Gas/aerosol partitioning is simulated using the ISORROPIA-II thermodynamic equilibrium model that considers K+, Ca2+, Mg2+, NH4+, Na+, SO42-, NO3-, Cl-, and H2O aerosol components. Emissions of mineral dust are calculated online by taking into account the soil particle size distribution and chemical composition of different deserts worldwide. Presence of metallic ions can substantially affect the nitrate partitioning into the aerosol phase due to thermodynamic interactions. The model simulates highest fine aerosol nitrate concentration over urban and industrialized areas (1-3 µg m-3), while coarse aerosol nitrate is highest close to deserts (1-4 µg m-3). The influence of mineral dust on nitrate formation extends across southern Europe, western USA, and northeastern China. The tropospheric burden of aerosol nitrate increases by 44 % when considering interactions of nitrate with mineral dust. The calculated global average nitrate aerosol concentration near the surface increases by 36 %, while the coarse- and fine-mode concentrations of nitrate increase by 53 and 21 %, respectively. Other inorganic aerosol components are affected by reactive dust components as well (e.g., the tropospheric burden of chloride increases by 9 %, ammonium decreases by 41 %, and sulfate increases by 7 %). Sensitivity tests show that nitrate aerosol is most sensitive to the chemical composition of the emitted mineral dust, followed by the soil size distribution of dust particles, the magnitude of the mineral dust emissions, and the aerosol state assumption.

  2. Nitrate behavior in ground waters of the southeastern USA

    USGS Publications Warehouse

    Nolan, B.T.

    1999-01-01

    Principal components analysis (PCA) was performed with water-quality data from studies conducted during 1993 to 1995 to explore potential nitrate- attenuation processes in ground waters of the southeastern USA. Nitrate reduction is an important attenuation process in selected areas of the Southeast. A nitrate-reduction component explains 23% of the total variance in the data and indicates that nitrate and dissolved oxygen (DO) are inversely related to ammonium, iron, manganese, and dissolved organic carbon (DOC). Additional components extracted by PCA include calcite dissolution (18% of variance explained) and phosphate dissolution (9% of variance explained). Reducing conditions in ground waters of the region influence nitrate behavior through bacterially mediated reduction in the presence of organic matter, and by inhibition of nitrate formation in anoxic ground water beneath forested areas. Component scores are consistent with observed water- quality conditions in the region. For example, median nitrate concentration in ground-water samples from the Albemarle-Pamlico Drainage Basin (ALBE) Coastal Plain is <0.05 mg L-1, median DOC concentration is 4.2 mg L-1, and median DO concentration is 2.1 mg L-1, consistent with denitrification. Nitrate reduction does not occur uniformly throughout the Southeast. Median DO concentrations in ground-water samples from the Apalachicola- Chattahoochee-Flint River Basin (ACFB) are 6.2 to 7.1 mg L-1, and median nitrate concentrations are 0.61 to 2.2 mg L-1, inconsistent with denitrification. Similarly, median DO concentration in samples from the Georgia-Florida Coastal Plain (GAFL) is 6.0 mg L-1 and median nitrate concentration is 5.8 mg L-1.

  3. Nitrate behavior in ground water of the southeastern USA

    SciTech Connect

    Nolan, B.T.

    1999-10-01

    Principal components analysis (PCA) was performed with water-quality data from studies conducted during 1993 to 1995 to explore potential nitrate-attenuation processes in ground waters of the southeastern USA. Nitrate reduction is an important attenuation process in selected areas of the Southeast. A nitrate-reduction component explains 23% of the total variance in the data and indicates that nitrate and dissolved oxygen (DO) are inversely related to ammonium, iron, manganese, and dissolved organic carbon (DOC). Additional components extracted by PCA include calcite dissolution (18% of variance explained) and phosphate dissolution (9% of variance explained). Reducing conditions in ground waters of the region influence nitrate behavior through bacterially mediated reduction in the presence of organic matter, and by inhibition of nitrate formation in anoxic ground water beneath forested areas. Component scores are consistent with observed water-quality conditions in the region. For example, median nitrate concentration in ground-water samples from the Albemarle-Pamlico Drainage Basin (ALBE) Coastal Plain is {lt}0.05 mg L{sup {minus}1}, median DOC concentration is 4.2 mg L{sup {minus}1}, and median DO concentration is 2.1 mg L{sup {minus}1}, consistent with denitrification. Nitrate reduction does not occur uniformly throughout the Southeast. Median DO concentrations in ground-water samples from the Apalachicola-Chattahoochee-Flint River Basin (ACFB) are 6.2 to 7.1 mg L{sup {minus}1}, and median nitrate concentrations are 0.61 to 2.2 mg L{sup {minus}1}, inconsistent with denitrification. Similarly, median DO concentration in samples from the Georgia-Florida Coastal Plain (GAFL) is 6.0 mg L{sup {minus}1} and median nitrate concentration is 5.8 mg L{sup {minus}1}.

  4. Mortality of nitrate fertiliser workers.

    PubMed

    Al-Dabbagh, S; Forman, D; Bryson, D; Stratton, I; Doll, R

    1986-08-01

    An epidemiological cohort study was conducted to investigate the mortality patterns among a group of workers engaged in the production of nitrate based fertilisers. This study was designed to test the hypothesis that individuals exposed to high concentrations of nitrates might be at increased risk of developing cancers, particularly gastric cancer. A total of 1327 male workers who had been employed in the production of fertilisers between 1946 and 1981 and who had been occupationally exposed to nitrates for at least one year were followed up until 1 March 1981. In total, 304 deaths were observed in this group and these were compared with expected numbers calculated from mortality rates in the northern region of England, where the factory was located. Analysis was also carried out separately for a subgroup of the cohort who had been heavily exposed to nitrates--that is, working in an environment likely to contain more than 10 mg nitrate/m3 for a year or longer. In neither the entire cohort nor the subgroup was any significant excess observed for all causes of mortality or for mortality from any of five broad categories of cause or from four specific types of cancer. A small excess of lung cancer was noted more than 20 years after first exposure in men heavily exposed for more than 10 years. That men were exposed to high concentrations of nitrate was confirmed by comparing concentrations of nitrates in the saliva of a sample of currently employed men with control men, employed at the same factory but not in fertiliser production. The men exposed to nitrate had substantially raised concentrations of nitrate in their saliva compared with both controls within the industry and with men in the general population and resident nearby. The results of this study therefore weight against the idea that exposure to nitrates in the environment leads to the formation in vivo of material amounts of carcinogens. PMID:3015194

  5. Decarboxylative 1,4-Addition of α-Oxocarboxylic Acids with Michael Acceptors Enabled by Photoredox Catalysis.

    PubMed

    Wang, Guang-Zu; Shang, Rui; Cheng, Wan-Min; Fu, Yao

    2015-10-01

    Enabled by iridium photoredox catalysis, 2-oxo-2-(hetero)arylacetic acids were decarboxylatively added to various Michael acceptors including α,β-unsaturated ester, ketone, amide, aldehyde, nitrile, and sulfone at room temperature. The reaction presents a new type of acyl Michael addition using stable and easily accessible carboxylic acid to formally generate acyl anion through photoredox-catalyzed radical decarboxylation. PMID:26366608

  6. Three Redox States of a Diradical Acceptor-Donor-Acceptor Triad: Gating the Magnetic Coupling and the Electron Delocalization.

    PubMed

    Souto, Manuel; Lloveras, Vega; Vela, Sergi; Fumanal, Maria; Ratera, Imma; Veciana, Jaume

    2016-06-16

    The diradical acceptor-donor-acceptor triad 1(••), based on two polychlorotriphenylmethyl (PTM) radicals connected through a tetrathiafulvalene(TTF)-vinylene bridge, has been synthesized. The generation of the mixed-valence radical anion, 1(•-), and triradical cation species, 1(•••+), obtained upon electrochemical reduction and oxidation, respectively, was monitored by optical and ESR spectroscopy. Interestingly, the modification of electron delocalization and magnetic coupling was observed when the charged species were generated and the changes have been rationalized by theoretical calculations.

  7. Nitrate Transport System in Neurospora crassa

    PubMed Central

    Schloemer, Robert H.; Garrett, Reginald H.

    1974-01-01

    Nitrate uptake in Neurospora crassa has been investigated under various conditions of nitrogen nutrition by measuring the rate of disappearance of nitrate from the medium and by determining mycelial nitrate accumulation. The nitrate transport system is induced by either nitrate or nitrite, but is not present in mycelia grown on ammonia or Casamino Acids. The appearance of nitrate uptake activity is prevented by cycloheximide, puromycin, or 6-methyl purine. The induced nitrate transport system displays a Km for nitrate of 0.25 mM. Nitrate uptake is inhibited by metabolic poisons such as 2,4-dinitrophenol, cyanide, and antimycin A. Furthermore, mycelia can concentrate nitrate 50-fold. Ammonia and nitrite are non-competitive inhibitors with respect to nitrate, with Ki values of 0.13 and 0.17 mM, respectively. Ammonia does not repress the formation of the nitrate transport system. In contrast, the nitrate uptake system is repressed by Casamino Acids. All amino acids individually prevent nitrate accumulation, with the exception of methionine, glutamine, and alanine. The influence of nitrate reduction and the nitrate reductase protein on nitrate transport was investigated in wild-type Neurospora lacking a functional nitrate reductase and in nitrate non-utilizing mutants, nit-1, nit-2, and nit-3. These mycelia contain an inducible nitrate transport system which displays the same characteristics as those found in the wild-type mycelia having the functional nitrate reductase. These findings suggest that nitrate transport is not dependent upon nitrate reduction and that these two processes are separate events in the assimilation of nitrate. PMID:4274457

  8. Covalent non-fused tetrathiafulvalene-acceptor systems.

    PubMed

    Pop, Flavia; Avarvari, Narcis

    2016-06-28

    Covalent donor-acceptor (D-A) systems have significantly contributed to the development of many organic materials and to molecular electronics. Tetrathiafulvalene (TTF) represents one of the most widely studied donor precursors and has been incorporated into the structure of many D-A derivatives with the objective of obtaining redox control and modulation of the intramolecular charge transfer (ICT), in order to address switchable emissive systems and to take advantage of its propensity to form regular stacks in the solid state. In this review, we focus on the main families of non-fused TTF-acceptors, which are classified according to the nature of the acceptor: nitrogen-containing heterocycles, BODIPY, perylenes and electron poor unsaturated hydrocarbons, as well as radical acceptors. We describe herein the most representative members of each family with a brief mention of their synthesis and a special focus on their D-A characteristics. Special attention is given to ICT and its modulation, fluorescence quenching and switching, photoconductivity, bistability and spin distribution by discussing and comparing spectroscopic and electrochemical features, photophysical properties, solid-state properties and theoretical calculations. PMID:27193500

  9. Fine structure of the Mn acceptor in GaAs

    NASA Astrophysics Data System (ADS)

    Krainov, I. V.; Debus, J.; Averkiev, N. S.; Dimitriev, G. S.; Sapega, V. F.; Lähderanta, E.

    2016-06-01

    We reveal the electronic level structure of the Mn acceptor, which consists of a valence-band hole bound to an Mn2 + ion, in presence of applied uniaxial stress and an external magnetic field in bulk GaAs. Resonant spin-flip Raman scattering is used to measure the g factor of the AMn0 center in the ground and excited states with the total angular momenta F =1 and F =2 and characterize the optical selection rules of the spin-flip transitions between these Mn-acceptor states. We determine the random stress fields near the Mn acceptor, the constant of the antiferromagnetic exchange interaction between the valence-band holes and the electrons of the inner Mn2 + shell as well as the deformation potential for the exchange energy. The p -d exchange energy, in particular, decreases significantly with increasing compressive stress. By combining the experimental Raman study with the developed theoretical model on the scattering efficiency, in which also the random local and external uniaxial stresses and magnetic field are considered, the fine structure of the Mn acceptor is determined in full detail.

  10. Molten nitrate salt technology development status report

    SciTech Connect

    Carling, R.W.; Kramer, C.M.; Bradshaw, R.W.; Nissen, D.A.; Goods, S.H.; Mar, R.W.; Munford, J.W.; Karnowsky, M.M.; Biefeld, R.N.; Norem, N.J.

    1981-03-01

    Recognizing thermal energy storage as potentially critical to the successful commercialization of solar thermal power systems, the Department of Energy (DOE) has established a comprehensive and aggressive thermal energy storage technology development program. Of the fluids proposed for heat transfer and energy storage molten nitrate salts offer significant economic advantages. The nitrate salt of most interest is a binary mixture of NaNO/sub 3/ and KNO/sub 3/. Although nitrate/nitrite mixtures have been used for decades as heat transfer and heat treatment fluids the use has been at temperatures of about 450/sup 0/C and lower. In solar thermal power systems the salts will experience a temperature range of 350 to 600/sup 0/C. Because central receiver applications place more rigorous demands and higher temperatures on nitrate salts a comprehensive experimental program has been developed to examine what effects, if any, the new demands and temperatures have on the salts. The experiments include corrosion testing, environmental cracking of containment materials, and determinations of physical properties and decomposition mechanisms. This report details the work done at Sandia National Laboratories in each area listed. In addition, summaries of the experimental programs at Oak Ridge National Laboratory, the University of New York, EIC Laboratories, Inc., and the Norwegian Institute of Technology on molten nitrate salts are given. Also discussed is how the experimental programs will influence the near-term central receiver programs such as utility repowering/industrial retrofit and cogeneration. The report is designed to provide easy access to the latest information and data on molten NaNO/sub 3//KNO/sub 3/ for the designers and engineers of future central receiver projects.

  11. Development of imide- and imidazole-containing electron acceptors for use in donor-acceptor conjugated compounds and polymers

    NASA Astrophysics Data System (ADS)

    Li, Duo

    Conjugated organic compounds and polymers have attracted significant attention due to their potential application in electronic devices as semiconducting materials, such as organic solar cells (OSCs). In order to tune band gaps, donor-acceptor (D-A) structure is widely used, which has been proved to be one of the most effective strategies. This thesis consists of three parts: 1) design, syntheses and characterization of new weak acceptors based on imides and the systematic study of the structure-property relationship; (2) introduction of weak and strong acceptors in one polymer to achieve a broad coverage of light absorption and improve the power conversion efficiency (PCE); (3) modification of benzothiadiazole (BT) acceptor in order to increase the electron withdrawing ability. Imide-based electron acceptors, 4-(5-bromothiophen-2-y1)-2-(2-ethylhexyl)-9- phenyl- 1H-benzo[f]isoindole-1,3(2H)-dione (BIDO-1) and 4,9-bis(5-bromothiophen-2-yl)-2-(2-ethylhexyl)-benzo[f]isoindole-1,3-dione (BIDO-2), were designed and synthesized. In this design, naphthalene is selected as its main core to maintain a planar structure, and thienyl groups are able to facilitate the bromination reaction and lower the band gap. BIDO-1 and BIDO-2 were successfully coupled with different donors by both Suzuki cross-coupling and Stille cross-coupling reactions. Based on the energy levels and band gaps of the BIDO-containing compounds and polymers, BIDO-1 and BIDO-2 are proved to be weak electron acceptors. Pyromellitic diimide (PMDI) was also studied and found to be a stronger electron acceptor than BIDO . In order to obtain broad absorption coverage, both weak acceptor ( BIDO-2) and strong acceptor diketopyrrolopyrrole (DPP) were introduced in the same polymer. The resulting polymers show two absorption bands at 400 and 600 nm and two emission peaks at 500 and 680 nm. The band gaps of the polymers are around 1.6 eV, which is ideal for OSC application. The PCE of 1.17% was achieved. Finally

  12. Acceptor conductivity in bulk zinc oxide (0001) crystals

    NASA Astrophysics Data System (ADS)

    Adekore, Bababunmi Tolu

    ZnO is a promising wide bandgap semiconductor. Its renowned and prominent properties as its bandgap of 3.37eV at 4.2K; its very high excitonic binding energy, 60meV; its high melting temperature, 2248K constitute the basis for the recently renewed and sustained scientific interests in the material. In addition to the foregoing, the availability of bulk substrates of industrially relevant sizes provides important opportunities such as homoepitaxial deposition of the material which is a technological asset in the production of efficient optoelectronic and electronic devices. The nemesis of wide bandgap materials cannot be more exemplified than in ZnO. The notorious limitation of asymmetric doping and the haunting plague of electrically active point defects dim the bright future of the material. In this case, the search for reliable and consistent acceptor conductivity in bulk substrates has been hitherto, unsuccessful. In the dissertation that now follows, our efforts have been concerted in the search for a reliable acceptor. We have carefully investigated the science of point defects in the material, especially those responsible for the high donor conductivity. We also investigated and herein report variety of techniques of introducing acceptors into the material. We employ the most relevant and informative characterization techniques in verifying both the intended conductivity and the response of intrinsic crystals to variation in temperature and strain. And finally we explain deviations, where they exist, from ideal acceptor characteristics. Our work on reliable acceptor has been articulated in four papers. The first establishing capacitance based methods of monitoring electrically active donor defects. The second investigates the nature of anion acceptors on the oxygen sublattice. A study similar to the preceding study was conducted for cation acceptors on the zinc sublattice and reported in the third paper. Finally, an analysis of the response of the crystal to

  13. Fourier-transform photoluminescence spectroscopy of excitons bound to group-III acceptors in silicon: Uniaxial stress

    NASA Astrophysics Data System (ADS)

    Karasyuk, V. A.; Thewalt, M. L. W.; An, S.; Lightowlers, E. C.

    1997-12-01

    Photoluminescence of excitons bound to Al, Ga, In, and Tl acceptors in Si crystals subjected to <001>, <111>, or <110> uniaxial stress was studied at liquid-He temperatures with 0.0025-meV spectral resolution. The deformation-potential constants of the group-III acceptors in the ground state are (in eV) b=-1.01+/-0.02, d=-3.31+/-0.06 for Al, b=-1.03+/-0.02, d=-3.10+/-0.06 for Ga, b=-0.43+/-0.01, d=-2.41+/-0.05 for In, and b=-0.30+/-0.03, d=-1.95+/-0.2 for Tl. The shear deformation-potential constant for electrons in acceptor bound excitons Ξu=8.6 eV for all group-III acceptors within an experimental error of +/-0.15 eV for Al, Ga, and In, and +/-0.8 eV for Tl. The order of the valley-orbit states in Tl bound excitons is Γ1, Γ3, Γ5 with the Γ5 energy 1.21 meV above Γ1, and 0.10 meV above Γ3. All details of the spectra including positions, relative amplitudes, and polarizations of the components have been explained on the basis of a simple model of acceptor bound excitons with holes in the J=0 state taking into account the valley-orbit splitting and the spin-orbit coupling of the electron. Significant deviations from the theoretical predictions were observed only for very small strains producing acceptor splittings comparable with the intrinsic zero-stress splitting.

  14. Nitrate concentrations under irrigated agriculture

    USGS Publications Warehouse

    Zaporozec, A.

    1983-01-01

    In recent years, considerable interest has been expressed in the nitrate content of water supplies. The most notable toxic effect of nitrate is infant methemoglobinemia. The risk of this disease increases significantly at nitrate-nitrogen levels exceeding 10 mg/l. For this reason, this concentration has been established as a limit for drinking water in many countries. In natural waters, nitrate is a minor ionic constituent and seldom accounts for more than a few percent of the total anions. However, nitrate in a significant concentration may occur in the vicinity of some point sources such as septic tanks, manure pits, and waste-disposal sites. Non-point sources contributing to groundwater pollution are numerous and a majority of them are related to agricultural activities. The largest single anthropogenic input of nitrate into the groundwater is fertilizer. Even though it has not been proven that nitrogen fertilizers are responsible for much of nitrate pollution, they are generally recognized as the main threat to groundwater quality, especially when inefficiently applied to irrigated fields on sandy soils. The biggest challenge facing today's agriculture is to maintain the balance between the enhancement of crop productivity and the risk of groundwater pollution. ?? 1982 Springer-Verlag New York Inc.

  15. Observations of Fine and Coarse Particle Nitrate at Several Rural Locations in the United States

    SciTech Connect

    Lee, Taehyoung; Yu, Xiao-Ying; Ayres, Benjamin; Kreidenweis, Sonia M.; Malm, William C.; Collett, Jeffrey L.

    2008-04-01

    Nitrate comprises an important part of aerosol mass at many non-urban locations during some times of the year. Little is known, however, about the chemical form and size distribution of particulate nitrate in these environments. While submicron ammonium nitrate is often assumed to be the dominant species, this assumption is rarely tested. Properties of aerosol nitrate were characterized at several IMPROVE monitoring sites during a series of field studies. Study sites included Bondville, Illinois (February 2003), San Gorgonio Wilderness Area, California (April and July 2003), Grand Canyon National Park, Arizona (May 2003), Brigantine National Wildlife Refuge, New Jersey (November 2003), and Great Smoky Mountains National Park, Tennessee (July/August 2004). Nitrate was found predominantly in submicron ammonium nitrate particles during the Bondville and San Gorgonio (April) campaigns. Coarse mode nitrate particles, resulting from reactions of nitric acid or its precursors with sea salt or soil dust, were more important at Grand Canyon and Great Smoky Mountains. Both fine and coarse mode nitrate were important during the studies at Brigantine and San Gorgonio (July). These results, which complement earlier findings about the importance of coarse particle nitrate at Yosemite and Big Bend National Parks, suggest a need to more closely examine common assumptions regarding the importance of ammonium nitrate at non-urban sites, to include pathways for coarse mode nitrate formation in regional models, and to consider impacts of coarse particle nitrate on visibility. Because coarse particle nitrate modes often extend well below 2.5 µm aerodynamic diameter, measurements of PM2.5 nitrate in these environments should not automatically be assumed to contain only ammonium nitrate.

  16. Tolerance of developing salmonid eggs and fry to nitrate exposure

    USGS Publications Warehouse

    Kincheloe, John W.; Wedemeyer, Gary A.; Koch, David L.

    1979-01-01

    This paper reports on tests which show significant effects on early salmonid life stages of nitrates at levels commonly found in groundwaters in geographical areas that are influenced by fertilizer application. It has long been known, from fish cultural experience, that in certain site specific locations, chronic problems can be expected with salmonid egg development and early fry mortality. However, fingerlings which survive usually grow normally. A complete explanation is lacking although several environmental factors have been proposed to account for this phenomenon. One, which has so far received little attention, is that nitrate levels in the ground and surface waters of many areas have been increasing significantly over historical background levels. Ammonia, urea, and other potential sources of nitrate can enter natural waters from a variety of sources, such as domestic or industrial sewage, animal feedlots, or seepage and return flows from agricultural lands. The latter may be the largest contributor, since billions of tons of nitrate fertilizers are applied to agricultural crops on a worldwide basis each year. In addition, intensive forest management techniques include the aerial application of nitrate fertilizer to increase the yield of wood products, while range management practices call for use of nitrates to increase forage production. The nitrate that is not taken up by plants ultimately appears in ground or surface waters.

  17. Nitrite- and Nitrate-Dependent Methanotrophs - Environmental Detection and Relevance in Freshwater Ecosystems

    NASA Astrophysics Data System (ADS)

    Ettwig, K. F.

    2014-12-01

    Humans continue to have an enormous impact on global C and N cycles. While a clear stimulation of methane emissions through human activities is evident, the role of also increasingly released nitrogenous compounds as electron acceptors for microbial methane oxidation is not well constrained. We have developed diverse methods for environmental detection of nitrate(NO3-)- and - predominantly - nitrite(NO2-)-dependent methanotrophs, which have been applied to several freshwater environments. In contrast to most metabolically flexible heterotrophic denitrifiers, the microorganisms responsible for methane-dependent nitrate/nitrite reduction seem to be specialized to use methane only, grow slowly and employ pathways different from each other and from model organisms, which necessitate new approaches for the assessment of their environmental relevance. Nitrite-dependent methane oxidation is carried out by bacteria of the NC10 phylum, whereas nitrate-dependent methane oxidizers are close relatives of methanogenic archaea and sulfate-dependent anaerobic methanotrophs (ANME-2). Laboratory enrichment cultures of the nitrite-reducing methanotroph Methylomirabilis oxyfera (NC10 phylum) have formed the basis for its genetic and physiological characterization and the development of several independent methods for its sensitive detection. M. oxyfera differs from all known microorganisms by encoding an incomplete denitrification pathway, in which the last 2 steps, the reduction of NO via N2O to N2, apparently is replaced by the dismutation of NO to N2 and O2. The intracellularly produced O2 is used for methane oxidation via a methane monooxygenase, analogously to the phylogenetically unrelated proteobacterial methanotrophs. But unlike in proteobacteria, C is not assimilated from methane, but rather CO2, with important consequences for the interpretation of environmental isotope labelling studies. In addition, M. oxyfera is characterized by a distinct PLFA profile, including

  18. Effects of auxiliary carbon sources and electron acceptors on methanogenic degradation of chlorinated phenols

    SciTech Connect

    Haeggblom, M.M.; Rivera, M.D.; Young, L.Y. )

    1993-08-01

    The authors studied the degradation of chlorinated phenols under methanogenic conditions by establishing enrichment cultures on 4-chlorophenol and 2,4-dichlorophenol with or without a supplementary substrate. p-Cresol was chosen as a nonchlorinated aromatic compound structurally similar to the chlorophenols, and propionate was chosen as a readily utilizable carbon source. 2,4-Dichlorophenol was dechlorinated to 4-chlorophenol, which was degraded without further detection of metabolites. The rates of chlorophenols and supplementary substrates. The addition of p-cresol or propionate as an auxiliary carbon source enhanced the rate of 4-chlorophenol degradation. Methanogenic cultures capable of ortho dechlorination were repeatedly subcultured by dilution into fresh media and refeeding of 2,6-dichlorophenol and either p-cresol or propionate as auxiliary substrates. 2,6-Dichlorophenol was sequentially dechlorinated to 2-chlorophenol and phenol and ultimately mineralized to methane and carbon dioxide. Cultures adapted to 2,4- or 2,6-dichlorophenol also readily dechlorinated other dichlorophenols containing an ortho chlorine. The alternative electron acceptors nitrate, sulfite, and thiosulfate completely inhibited dechlorination of 2,6-dichlorophenol, whereas sulfate slowed the dechlorination rate.

  19. NOx in the Atmosphere of Early Earth as Electron Acceptors for Life

    NASA Astrophysics Data System (ADS)

    Wong, M. L.; Charnay, B.; Gao, P.; Yung, Y. L.; Russell, M. J.

    2015-12-01

    We quantify the amount of NOx produced in the Hadean atmosphere and available in the Hadean ocean for the emergence of life. Atmospherically generated nitrate (NO3-) and nitrite (NO2-) are the most attractive high-potential electron acceptors for driving the highly endergonic reactions at the entry points to autotrophic metabolic pathways at submarine alkaline hydrothermal vents (Ducluzeau, 2008; Russell, 2014). The Hadean atmosphere, dominated by CO2 and N2, will produce nitric oxide (NO) when shocked by lightning and impacts (Ducluzeau, 2008; Nna Mvondo, 2001). Photochemical reactions involving NO and H2O vapor will then produce acids such as HNO3 and HNO2 that rain into the ocean and dissociate into NO3- and NO2-. Previous work suggests that 1018 g of NOx can be produced in a million years or so, satisfying the need for micromolar concentrations of NO3- and NO2- in the ocean (Ducluzeau, 2008). But because this number is controversial, we present new calculations based on a novel combination of early-Earth GCM and photochemical modeling, calculating the sources and sinks for fixed nitrogen. Finally, it is notable that lightning has been detected on Venus and Mars along with evidence of atmospheric NO; in the distant past, could NOx have been created and available for the emergence of life on numerous wet, rocky worlds?

  20. Metal-catalyzed protein tyrosine nitration in biological systems.

    PubMed

    Campolo, Nicolás; Bartesaghi, Silvina; Radi, Rafael

    2014-11-01

    Protein tyrosine nitration is an oxidative postranslational modification that can affect protein structure and function. It is mediated in vivo by the production of nitric oxide-derived reactive nitrogen species (RNS), including peroxynitrite (ONOO(-)) and nitrogen dioxide ((•)NO₂). Redox-active transition metals such as iron (Fe), copper (Cu), and manganese (Mn) can actively participate in the processes of tyrosine nitration in biological systems, as they catalyze the production of both reactive oxygen species and RNS, enhance nitration yields and provide site-specificity to this process. Early after the discovery that protein tyrosine nitration can occur under biologically relevant conditions, it was shown that some low molecular weight transition-metal centers and metalloproteins could promote peroxynitrite-dependent nitration. Later studies showed that nitration could be achieved by peroxynitrite-independent routes as well, depending on the transition metal-catalyzed oxidation of nitrite (NO₂(-)) to (•)NO₂ in the presence of hydrogen peroxide. Processes like these can be achieved either by hemeperoxidase-dependent reactions or by ferrous and cuprous ions through Fenton-type chemistry. Besides the in vitro evidence, there are now several in vivo studies that support the close relationship between transition metal levels and protein tyrosine nitration. So, the contribution of transition metals to the levels of tyrosine nitrated proteins observed under basal conditions and, specially, in disease states related with high levels of these metal ions, seems to be quite clear. Altogether, current evidence unambiguously supports a central role of transition metals in determining the extent and selectivity of protein tyrosine nitration mediated both by peroxynitrite-dependent and independent mechanisms.

  1. Probability-based nitrate contamination map of groundwater in Kinmen.

    PubMed

    Liu, Chen-Wuing; Wang, Yeuh-Bin; Jang, Cheng-Shin

    2013-12-01

    Groundwater supplies over 50% of drinking water in Kinmen. Approximately 16.8% of groundwater samples in Kinmen exceed the drinking water quality standard (DWQS) of NO3 (-)-N (10 mg/L). The residents drinking high nitrate-polluted groundwater pose a potential risk to health. To formulate effective water quality management plan and assure a safe drinking water in Kinmen, the detailed spatial distribution of nitrate-N in groundwater is a prerequisite. The aim of this study is to develop an efficient scheme for evaluating spatial distribution of nitrate-N in residential well water using logistic regression (LR) model. A probability-based nitrate-N contamination map in Kinmen is constructed. The LR model predicted the binary occurrence probability of groundwater nitrate-N concentrations exceeding DWQS by simple measurement variables as independent variables, including sampling season, soil type, water table depth, pH, EC, DO, and Eh. The analyzed results reveal that three statistically significant explanatory variables, soil type, pH, and EC, are selected for the forward stepwise LR analysis. The total ratio of correct classification reaches 92.7%. The highest probability of nitrate-N contamination map presents in the central zone, indicating that groundwater in the central zone should not be used for drinking purposes. Furthermore, a handy EC-pH-probability curve of nitrate-N exceeding the threshold of DWQS was developed. This curve can be used for preliminary screening of nitrate-N contamination in Kinmen groundwater. This study recommended that the local agency should implement the best management practice strategies to control nonpoint nitrogen sources and carry out a systematic monitoring of groundwater quality in residential wells of the high nitrate-N contamination zones.

  2. Vasodilator Therapy: Nitrates and Nicorandil.

    PubMed

    Tarkin, Jason M; Kaski, Juan Carlos

    2016-08-01

    Nitrates have been used to treat symptoms of chronic stable angina for over 135 years. These drugs are known to activate nitric oxide (NO)-cyclic guanosine-3',-5'-monophasphate (cGMP) signaling pathways underlying vascular smooth muscle cell relaxation, albeit many questions relating to how nitrates work at the cellular level remain unanswered. Physiologically, the anti-angina effects of nitrates are mostly due to peripheral venous dilatation leading to reduction in preload and therefore left ventricular wall stress, and, to a lesser extent, epicardial coronary artery dilatation and lowering of systemic blood pressure. By counteracting ischemic mechanisms, short-acting nitrates offer rapid relief following an angina attack. Long-acting nitrates, used commonly for angina prophylaxis are recommended second-line, after beta-blockers and calcium channel antagonists. Nicorandil is a balanced vasodilator that acts as both NO donor and arterial K(+) ATP channel opener. Nicorandil might also exhibit cardioprotective properties via mitochondrial ischemic preconditioning. While nitrates and nicorandil are effective pharmacological agents for prevention of angina symptoms, when prescribing these drugs it is important to consider that unwanted and poorly tolerated hemodynamic side-effects such as headache and orthostatic hypotension can often occur owing to systemic vasodilatation. It is also necessary to ensure that a dosing regime is followed that avoids nitrate tolerance, which not only results in loss of drug efficacy, but might also cause endothelial dysfunction and increase long-term cardiovascular risk. Here we provide an update on the pharmacological management of chronic stable angina using nitrates and nicorandil.

  3. Controlled field study on the use of nitrate and oxygen for bioremediation of a gasoline source zone

    USGS Publications Warehouse

    Barbaro, J.R.; Barker, J.F.

    2000-01-01

    Controlled releases of unleaded gasoline were utilized to evaluate the biotransformation of the soluble aromatic hydrocarbons (benzene, toluene, ethylbenzene, xylene isomers, trimethylbenzene isomers, and naphthalene) within a source zone using nitrate and oxygen as electron acceptors. Experiments were conducted within two 2 m ?? 2 m ?? 3.5 m deep sheet-piling cells. In each treatment cell, a gasoline-contaminated zone was created below the water table. Groundwater amended with electron acceptors was then flushed continuously through the cells for 174 day. Electron-acceptor utilization and hydrocarbon-metabolite formation were noted in both cells, indicating that some microbial activity had been induced in response to flushing. Relative to the cell residence time, nitrate utilization was slow and aromatic-hydrocarbon mass losses in response to microaerophilic dissolved oxygen addition were not obvious under these in situ conditions. There was relatively little biotransformation of the aromatic hydrocarbons over the 2-m flow path monitored in this experiment. A large denitrifying population capable of aromatic hydrocarbon biotransformation failed to develop within the gasoline source zone over a 14-mo period of nitrate exposure.

  4. Food sources of nitrates and nitrites: the physiologic context for potential health benefits.

    PubMed

    Hord, Norman G; Tang, Yaoping; Bryan, Nathan S

    2009-07-01

    The presence of nitrates and nitrites in food is associated with an increased risk of gastrointestinal cancer and, in infants, methemoglobinemia. Despite the physiologic roles for nitrate and nitrite in vascular and immune function, consideration of food sources of nitrates and nitrites as healthful dietary components has received little attention. Approximately 80% of dietary nitrates are derived from vegetable consumption; sources of nitrites include vegetables, fruit, and processed meats. Nitrites are produced endogenously through the oxidation of nitric oxide and through a reduction of nitrate by commensal bacteria in the mouth and gastrointestinal tract. As such, the dietary provision of nitrates and nitrites from vegetables and fruit may contribute to the blood pressure-lowering effects of the Dietary Approaches to Stop Hypertension (DASH) diet. We quantified nitrate and nitrite concentrations by HPLC in a convenience sample of foods. Incorporating these values into 2 hypothetical dietary patterns that emphasize high-nitrate or low-nitrate vegetable and fruit choices based on the DASH diet, we found that nitrate concentrations in these 2 patterns vary from 174 to 1222 mg. The hypothetical high-nitrate DASH diet pattern exceeds the World Health Organization's Acceptable Daily Intake for nitrate by 550% for a 60-kg adult. These data call into question the rationale for recommendations to limit nitrate and nitrite consumption from plant foods; a comprehensive reevaluation of the health effects of food sources of nitrates and nitrites is appropriate. The strength of the evidence linking the consumption of nitrate- and nitrite-containing plant foods to beneficial health effects supports the consideration of these compounds as nutrients.

  5. Generality of Nitrate Removal in Streambed Sediment on the Southern Delmarva Peninsula

    NASA Astrophysics Data System (ADS)

    McFadden, G.; Flewelling, S. A.; Herman, J. S.; Mills, A. L.

    2013-12-01

    Nitrogen fertilizers have accumulated in the unconfined Columbia aquifer on the Eastern Shore of Virginia (ESVA) and increased nitrate concentrations, which could potentially affect water quality in down-gradient surface-water bodies. The streambeds and riparian zones of the small, low-gradient ESVA streams appear to be attenuating the nitrate load of discharging groundwater via denitrification, thereby reducing groundwater nitrate concentrations by an order of magnitude or more in some cases. We measured concentrations of nitrate, chloride, and dissolved oxygen in sediment pore water as well as vertical head gradients and hydraulic conductivity in the streambed of four streams on the ESVA (Coal Kiln, Machipongo, Phillips Creek, and Parker Creek). Unlike measurements made in some other streams on the ESVA, the data did not show a consistent decrease in nitrate concentrations as groundwater discharged upward through the streambed. For Coal Kiln, Machipongo, and Phillips Creek, dissolved oxygen concentrations were consistently low (generally <3 mg/L) throughout sediment pore water, down to at least 60 cm (maximum depth of measurements). In Parker Creek, dissolved oxygen concentrations were higher and there was a general proportionality between nitrate and oxygen concentrations, consistent with microbially mediated redox reactions gradually shifting the electron acceptor from oxygen to nitrate as pore-water moved upward through the sediments. Whereas previous measurements at another stream (Cobb Mill Creek) on the ESVA indicated that denitrification occurred primarily in the upper 30-60 cm of the streambed sediment, the data from Coal Kiln, Machipongo, and Phillips Creek suggest that denitrification may also be important elsewhere in the catchment, perhaps deeper in the sediment profile. In Parker Creek, the streambed appeared to be reducing nitrate concentrations as groundwater discharged to the stream, however, the magnitude of nitrate removal during vertical flow

  6. 21 CFR 172.170 - Sodium nitrate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Sodium nitrate. 172.170 Section 172.170 Food and... Preservatives § 172.170 Sodium nitrate. The food additive sodium nitrate may be safely used in or on specified... sablefish, smoked, cured salmon, and smoked, cured shad, so that the level of sodium nitrate does not...

  7. 21 CFR 172.170 - Sodium nitrate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Sodium nitrate. 172.170 Section 172.170 Food and... Preservatives § 172.170 Sodium nitrate. The food additive sodium nitrate may be safely used in or on specified... sablefish, smoked, cured salmon, and smoked, cured shad, so that the level of sodium nitrate does not...

  8. 21 CFR 172.170 - Sodium nitrate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Sodium nitrate. 172.170 Section 172.170 Food and... Preservatives § 172.170 Sodium nitrate. The food additive sodium nitrate may be safely used in or on specified... sablefish, smoked, cured salmon, and smoked, cured shad, so that the level of sodium nitrate does not...

  9. 21 CFR 172.170 - Sodium nitrate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Sodium nitrate. 172.170 Section 172.170 Food and... Preservatives § 172.170 Sodium nitrate. The food additive sodium nitrate may be safely used in or on specified... sablefish, smoked, cured salmon, and smoked, cured shad, so that the level of sodium nitrate does not...

  10. Ultrafast electron transfer in all-carbon-based SWCNT-C60 donor-acceptor nanoensembles connected by poly(phenylene-ethynylene) spacers.

    PubMed

    Barrejón, Myriam; Gobeze, Habtom B; Gómez-Escalonilla, María J; Fierro, José Luis G; Zhang, Minfang; Yudasaka, Masako; Iijima, Sumio; D'Souza, Francis; Langa, Fernando

    2016-08-21

    Building all-carbon based functional materials for light energy harvesting applications could be a solution to tackle and reduce environmental carbon output. However, development of such all-carbon based donor-acceptor hybrids and demonstration of photoinduced charge separation in such nanohybrids is a challenge since in these hybrids part of the carbon material should act as an electron donating or accepting photosensitizer while the second part should fulfil the role of an electron acceptor or donor. In the present work, we have successfully addressed this issue by synthesizing covalently linked all-carbon-based donor-acceptor nanoensembles using single-walled carbon nanotubes (SWCNTs) as the donor and C60 as the acceptor. The donor-acceptor entities in the nanoensembles were connected by phenylene-ethynylene spacer units to achieve better electronic communication and to vary the distance between the components. These novel SWCNT-C60 nanoensembles have been characterized by a number of techniques, including TGA, FT-IR, Raman, AFM, absorbance and electrochemical methods. The moderate number of fullerene addends present on the side-walls of the nanotubes largely preserved the electronic structure of the nanotubes. The thermodynamic feasibility of charge separation in these nanoensembles was established using spectral and electrochemical data. Finally, occurrence of ultrafast electron transfer from the excited nanotubes in these donor-acceptor nanohybrids has been established by femtosecond transient absorption studies, signifying their utility in building light energy harvesting devices.

  11. Ultrafast electron transfer in all-carbon-based SWCNT-C60 donor-acceptor nanoensembles connected by poly(phenylene-ethynylene) spacers.

    PubMed

    Barrejón, Myriam; Gobeze, Habtom B; Gómez-Escalonilla, María J; Fierro, José Luis G; Zhang, Minfang; Yudasaka, Masako; Iijima, Sumio; D'Souza, Francis; Langa, Fernando

    2016-08-21

    Building all-carbon based functional materials for light energy harvesting applications could be a solution to tackle and reduce environmental carbon output. However, development of such all-carbon based donor-acceptor hybrids and demonstration of photoinduced charge separation in such nanohybrids is a challenge since in these hybrids part of the carbon material should act as an electron donating or accepting photosensitizer while the second part should fulfil the role of an electron acceptor or donor. In the present work, we have successfully addressed this issue by synthesizing covalently linked all-carbon-based donor-acceptor nanoensembles using single-walled carbon nanotubes (SWCNTs) as the donor and C60 as the acceptor. The donor-acceptor entities in the nanoensembles were connected by phenylene-ethynylene spacer units to achieve better electronic communication and to vary the distance between the components. These novel SWCNT-C60 nanoensembles have been characterized by a number of techniques, including TGA, FT-IR, Raman, AFM, absorbance and electrochemical methods. The moderate number of fullerene addends present on the side-walls of the nanotubes largely preserved the electronic structure of the nanotubes. The thermodynamic feasibility of charge separation in these nanoensembles was established using spectral and electrochemical data. Finally, occurrence of ultrafast electron transfer from the excited nanotubes in these donor-acceptor nanohybrids has been established by femtosecond transient absorption studies, signifying their utility in building light energy harvesting devices. PMID:27305145

  12. Nitrate Utilization by the Diatom Skeletonema costatum

    PubMed Central

    Serra, Juan L.; Llama, Maria J.; Cadenas, Eduardo

    1978-01-01

    Nitrate utilization has been characterized in nitrogen-deficient cells of the marine diatom Skeletonema costatum. In order to separate nitrate uptake from nitrate reduction, nitrate reductase activity was suppressed with tungstate. Neither nitrite nor the presence of amino acids in the external medium or darkness affects nitrate uptake kinetics. Ammonium strongly inhibits carrier-mediated nitrate uptake, without affecting diffusion transfer. A model is proposed for the uptake and assimilation of nitrate in S. costatum and their regulation by ammonium ions. PMID:16660653

  13. Interface effects on acceptor qubits in silicon and germanium.

    PubMed

    Abadillo-Uriel, J C; Calderón, M J

    2016-01-15

    Dopant-based quantum computing implementations often require the dopants to be situated close to an interface to facilitate qubit manipulation with local gates. Interfaces not only modify the energies of the bound states but also affect their symmetry. Making use of the successful effective mass theory we study the energy spectra of acceptors in Si or Ge taking into account the quantum confinement, the dielectric mismatch and the central cell effects. The presence of an interface puts constraints to the allowed symmetries and leads to the splitting of the ground state in two Kramers doublets (Mol et al 2015 Appl. Phys. Lett. 106 203110). Inversion symmetry breaking also implies parity mixing which affects the allowed optical transitions. Consequences for acceptor qubits are discussed. PMID:26618443

  14. Electron Acceptors Induce Secretion of Enterotoxigenic Escherichia coli Heat-Labile Enterotoxin under Anaerobic Conditions through Promotion of GspD Assembly.

    PubMed

    Lu, Xi; Fu, Enqing; Xie, Yonghong; Jin, Faguang

    2016-10-01

    Heat-labile enterotoxin (LT), the major virulence factor of enterotoxigenic Escherichia coli (ETEC), can lead to severe diarrhea and promotes ETEC adherence to intestinal epithelial cells. Most previous in vitro studies focused on ETEC pathogenesis were conducted under aerobic conditions, which do not reflect the real situation of ETEC infection because the intestine is anoxic. In this study, the expression and secretion of LT under anaerobic or microaerobic conditions were determined; LT was not efficiently secreted into the supernatant under anaerobic or microaerobic conditions unless terminal electron acceptors (trimethylamine N-oxide dihydrate [TMAO] or nitrate) were available. Furthermore, we found that the restoration effects of TMAO and nitrate on LT secretion could be inhibited by amytal or ΔtorCAD and ΔnarG E. coli strains, indicating that LT secretion under anaerobic conditions was dependent on the integrity of the respiratory chain. At the same time, electron acceptors increase the ATP level of ETEC, but this increase was not the main reason for LT secretion. Subsequently, the relationship between the integrity of the respiratory chain and the function of the type II secretion system was determined. The GspD protein, the secretin of ETEC, was assembled under anaerobic conditions and was accompanied by LT secretion when TMAO or nitrate was added. Our data also demonstrated that TMAO and nitrate could not induce the GspD assembly and LT secretion in ΔtorCAD and ΔnarG strains, respectively. Moreover, GspD assembly under anaerobic conditions was assisted by the pilot protein YghG.

  15. Electron Acceptors Induce Secretion of Enterotoxigenic Escherichia coli Heat-Labile Enterotoxin under Anaerobic Conditions through Promotion of GspD Assembly.

    PubMed

    Lu, Xi; Fu, Enqing; Xie, Yonghong; Jin, Faguang

    2016-10-01

    Heat-labile enterotoxin (LT), the major virulence factor of enterotoxigenic Escherichia coli (ETEC), can lead to severe diarrhea and promotes ETEC adherence to intestinal epithelial cells. Most previous in vitro studies focused on ETEC pathogenesis were conducted under aerobic conditions, which do not reflect the real situation of ETEC infection because the intestine is anoxic. In this study, the expression and secretion of LT under anaerobic or microaerobic conditions were determined; LT was not efficiently secreted into the supernatant under anaerobic or microaerobic conditions unless terminal electron acceptors (trimethylamine N-oxide dihydrate [TMAO] or nitrate) were available. Furthermore, we found that the restoration effects of TMAO and nitrate on LT secretion could be inhibited by amytal or ΔtorCAD and ΔnarG E. coli strains, indicating that LT secretion under anaerobic conditions was dependent on the integrity of the respiratory chain. At the same time, electron acceptors increase the ATP level of ETEC, but this increase was not the main reason for LT secretion. Subsequently, the relationship between the integrity of the respiratory chain and the function of the type II secretion system was determined. The GspD protein, the secretin of ETEC, was assembled under anaerobic conditions and was accompanied by LT secretion when TMAO or nitrate was added. Our data also demonstrated that TMAO and nitrate could not induce the GspD assembly and LT secretion in ΔtorCAD and ΔnarG strains, respectively. Moreover, GspD assembly under anaerobic conditions was assisted by the pilot protein YghG. PMID:27430271

  16. Free Carrier Generation in Organic Photovoltaic Bulk Heterojunctions of Conjugated Polymers with Molecular Acceptors: Planar versus Spherical Acceptors

    SciTech Connect

    Nardes, Alexandre M.; Ferguson, Andrew J.; Wolfer, Pascal; Gui, Kurt; Burn, Paul L.; Meredith, Paul; Kopidakis, Nikos

    2014-03-05

    We present a comparative study of the photophysical performance of the prototypical fullerene derivative PC61BM with a planar small-molecule acceptor in an organic photovoltaic device. The small-molecule planar acceptor is 2-[{7-(9,9-di-n-propyl-9H-fluoren-2-yl)benzo[c][1,2,5]thiadiazol-4-yl}methylene]malononitrile, termed K12. We discuss photoinduced free charge-carrier generation and transport in blends of PC61BM or K12 with poly(3-n-hexylthiophene) (P3HT), surveying literature results for P3HT:PC61BM and presenting new results on P3HT:K12. For both systems we also review previous work on film structure and correlate the structural and photophysical results. In both cases, a disordered mixed phase is formed between P3HT and the acceptor, although the photophysical properties of this mixed phase differ markedly for PC61BM and K12. In the case of PC61BM the mixed phase acts as a free carrier generation region that can efficiently shuttle carriers to the pure polymer and fullerene domains. As a result, the vast majority of excitons quenched in P3HT:PC61BM blends yield free carriers detected by the contactless time-resolved microwave conductivity (TRMC) method. In contrast, approximately 85 % of the excitons quenched in P3HT:K12 do not result in free carriers over the nanosecond timescale of the TRMC experiment. We attribute this to poor electron-transport properties in the mixed P3HT:K12 phase. Here, we propose that the observed differences can be traced to the respective shapes of PC61BM and K12: the three-dimensional nature of the fullerene cage facilitates coupling between PC61BM molecules irrespective of their relative orientation, whereas for K12 strong electronic coupling is only expected for molecules oriented with their π systems parallel to each other. Comparison between the eutectic compositions of the P3HT:PC61BM and P3HT:K12 shows that the former contains enough fullerene to form a percolation pathway for electrons, whereas the latter contains a sub

  17. Free carrier generation in organic photovoltaic bulk heterojunctions of conjugated polymers with molecular acceptors: planar versus spherical acceptors.

    PubMed

    Nardes, Alexandre M; Ferguson, Andrew J; Wolfer, Pascal; Gui, Kurt; Burn, Paul L; Meredith, Paul; Kopidakis, Nikos

    2014-06-01

    A comparative study of the photophysical performance of the prototypical fullerene derivative PC61BM with a planar small-molecule acceptor in an organic photovoltaic device is presented. The small-molecule planar acceptor is 2-[{7-(9,9-di-n-propyl-9H-fluoren-2-yl)benzo[c][1,2,5]thiadiazol-4-yl}methylene]malononitrile, termed K12. We discuss photoinduced free charge-carrier generation and transport in blends of PC61BM or K12 with poly(3-n-hexylthiophene) (P3HT), surveying literature results for P3HT:PC61BM and presenting new results on P3HT:K12. For both systems we also review previous work on film structure and correlate the structural and photophysical results. In both cases, a disordered mixed phase is formed between P3HT and the acceptor, although the photophysical properties of this mixed phase differ markedly for PC61BM and K12. In the case of PC61BM the mixed phase acts as a free carrier generation region that can efficiently shuttle carriers to the pure polymer and fullerene domains. As a result, the vast majority of excitons quenched in P3HT:PC61BM blends yield free carriers detected by the contactless time-resolved microwave conductivity (TRMC) method. In contrast, approximately 85% of the excitons quenched in P3HT:K12 do not result in free carriers over the nanosecond timescale of the TRMC experiment. We attribute this to poor electron-transport properties in the mixed P3HT:K12 phase. We propose that the observed differences can be traced to the respective shapes of PC61BM and K12: the three-dimensional nature of the fullerene cage facilitates coupling between PC61BM molecules irrespective of their relative orientation, whereas for K12 strong electronic coupling is only expected for molecules oriented with their π systems parallel to each other. Comparison between the eutectic compositions of the P3HT:PC61BM and P3HT:K12 shows that the former contains enough fullerene to form a percolation pathway for electrons, whereas the latter contains a sub

  18. Free carrier generation in organic photovoltaic bulk heterojunctions of conjugated polymers with molecular acceptors: planar versus spherical acceptors.

    PubMed

    Nardes, Alexandre M; Ferguson, Andrew J; Wolfer, Pascal; Gui, Kurt; Burn, Paul L; Meredith, Paul; Kopidakis, Nikos

    2014-06-01

    A comparative study of the photophysical performance of the prototypical fullerene derivative PC61BM with a planar small-molecule acceptor in an organic photovoltaic device is presented. The small-molecule planar acceptor is 2-[{7-(9,9-di-n-propyl-9H-fluoren-2-yl)benzo[c][1,2,5]thiadiazol-4-yl}methylene]malononitrile, termed K12. We discuss photoinduced free charge-carrier generation and transport in blends of PC61BM or K12 with poly(3-n-hexylthiophene) (P3HT), surveying literature results for P3HT:PC61BM and presenting new results on P3HT:K12. For both systems we also review previous work on film structure and correlate the structural and photophysical results. In both cases, a disordered mixed phase is formed between P3HT and the acceptor, although the photophysical properties of this mixed phase differ markedly for PC61BM and K12. In the case of PC61BM the mixed phase acts as a free carrier generation region that can efficiently shuttle carriers to the pure polymer and fullerene domains. As a result, the vast majority of excitons quenched in P3HT:PC61BM blends yield free carriers detected by the contactless time-resolved microwave conductivity (TRMC) method. In contrast, approximately 85% of the excitons quenched in P3HT:K12 do not result in free carriers over the nanosecond timescale of the TRMC experiment. We attribute this to poor electron-transport properties in the mixed P3HT:K12 phase. We propose that the observed differences can be traced to the respective shapes of PC61BM and K12: the three-dimensional nature of the fullerene cage facilitates coupling between PC61BM molecules irrespective of their relative orientation, whereas for K12 strong electronic coupling is only expected for molecules oriented with their π systems parallel to each other. Comparison between the eutectic compositions of the P3HT:PC61BM and P3HT:K12 shows that the former contains enough fullerene to form a percolation pathway for electrons, whereas the latter contains a sub

  19. Quantum confined acceptors and donors in InSe nanosheets

    SciTech Connect

    Mudd, G. W.; Patanè, A. Makarovsky, O.; Eaves, L.; Kudrynskyi, Z. R.; Kovalyuk, Z. D.; Fay, M. W.; Zólyomi, V.; Falko, V.

    2014-12-01

    We report on the radiative recombination of photo-excited carriers bound at native donors and acceptors in exfoliated nanoflakes of nominally undoped rhombohedral γ-polytype InSe. The binding energies of these states are found to increase with the decrease in flake thickness, L. We model their dependence on L using a two-dimensional hydrogenic model for impurities and show that they are strongly sensitive to the position of the impurities within the nanolayer.

  20. Dietary nitrate and nitrite: Benefits, risks, and evolving perceptions.

    PubMed

    Bedale, Wendy; Sindelar, Jeffrey J; Milkowski, Andrew L

    2016-10-01

    Consumers have an illogical relationship with nitrite (and its precursor, nitrate) in food. Despite a long history of use, nitrite was nearly banned from use in foods in the 1970s due to health concerns related to the potential for carcinogenic nitrosamine formation. Changes in meat processing methods reduced those potential risks, and nitrite continued to be used in foods. Since then, two opposing movements continue to shape how consumers view dietary nitrate and nitrite. The discovery of the profound physiological importance of nitric oxide led to the realization that dietary nitrate contributes significantly to the nitrogen reservoir for nitric oxide formation. Numerous clinical studies have also demonstrated beneficial effects from dietary nitrate consumption, especially in vascular and metabolic health. However, the latest wave of consumer sentiment against food additives, the clean-label movement, has renewed consumer fear and avoidance of preservatives, including nitrite. Education is necessary but may not be sufficient to resolve this disconnect in consumer perception. PMID:26994928

  1. An extended Foerster-Dexter model for correlated donor-acceptor placement in solid state materials

    NASA Astrophysics Data System (ADS)

    Rotman, S. R.; Hartmann, F. X.

    1987-09-01

    The current theory of donor-acceptor interactions in solid-state materials is based on a random distribution of donors and acceptors through the crystal. In this paper, we present a model to calculate the observable transfer rates for the correlated positioning of donors and acceptors in laser materials. Chemical effects leading to such correlations are discussed.

  2. Donor acceptor electronic couplings in π-stacks: How many states must be accounted for?

    NASA Astrophysics Data System (ADS)

    Voityuk, Alexander A.

    2006-04-01

    Two-state model is commonly used to estimate the donor-acceptor electronic coupling Vda for electron transfer. However, in some important cases, e.g. for DNA π-stacks, this scheme fails to provide accurate values of Vda because of multistate effects. The Generalized Mulliken-Hush method enables a multistate treatment of Vda. In this Letter, we analyze the dependence of calculated electronic couplings on the number of the adiabatic states included in the model. We suggest a simple scheme to determine this number. The superexchange correction of the two-state approximation is shown to provide good estimates of the electronic coupling.

  3. Autotrophic, hydrogen-oxidizing, denitrifying bacteria in groundwater, potential agents for bioremediation of nitrate contamination

    USGS Publications Warehouse

    Smith, R.L.; Ceazan, M.L.; Brooks, M.H.

    1994-01-01

    Addition of hydrogen or formate significantly enhanced the rate of consumption of nitrate in slurried core samples obtained from an active zone of denitrification in a nitrate-contaminated sand and gravel aquifer (Cape Cod, Mass.). Hydrogen uptake by the core material was immediate and rapid, with an apparent K(m) of 0.45 to 0.60 ??M and a V(max) of 18.7 nmol cm-3 h-1 at 30??C. Nine strains of hydrogen-oxidizing denitrifying bacteria were subsequently isolated from the aquifer. Eight of the strains grew autotrophically on hydrogen with either oxygen or nitrate as the electron acceptor. One strain grew mixotrophically. All of the isolates were capable of heterotrophic growth, but none were similar to Paracoccus denitrificans, a well-characterized hydrogen-oxidizing denitrifier. The kinetics for hydrogen uptake during denitrification were determined for each isolate with substrate depletion progress curves; the K(m)s ranged from 0.30 to 3.32 ??M, with V(max)s of 1.85 to 13.29 fmol cell-1 h-1. Because these organisms appear to be common constituents of the in situ population of the aquifer, produce innocuous end products, and could be manipulated to sequentially consume oxygen and then nitrate when both were present, these results suggest that these organisms may have significant potential for in situ bioremediation of nitrate contamination in groundwater.

  4. Perchlorate and Nitrate Remediation Efficiency and Microbial Diversity in a Containerized Wetland Bioreactor

    SciTech Connect

    Jr., B D; Dibley, V; Pinkart, H; Legler, T

    2004-06-09

    We have developed a method to remove perchlorate (14 to 27 {micro}g/L) and nitrate (48 mg/L) from contaminated groundwater using a wetland bioreactor. The bioreactor has operated continuously in a remote field location for more than two years with a stable ecosystem of indigenous organisms. This study assesses the bioreactor for long-term perchlorate and nitrate remediation by evaluating influent and effluent groundwater for reduction-oxidation conditions and nitrate and perchlorate concentrations. Total community DNA was extracted and purified from 10-g sediment samples retrieved from vertical coring of the bioreactor during winter. Analysis by denaturing gradient gel electrophoresis of short, 16S rDNA, polymerase-chain-reaction products was used to identify dominant microorganisms. Bacteria genera identified were closely affiliated with bacteria widely distributed in soils, mud layers, and fresh water. Of the 17 dominant bands sequenced, most were gram negative and capable of aerobic or anaerobic respiration with nitrate as the terminal electron acceptor (Pseudomonas, Acinetobacter, Halomonas, and Nitrospira). Several identified genera (Rhizobium, Acinetobactor, and Xanthomonas) are capable of fixing atmospheric nitrogen into a combined form (ammonia) usable by host plants. Isolates were identified from the Proteobacteria class, known for the ability to reduce perchlorate. Initial bacterial assessments of sediments confirm the prevalence of facultative anaerobic bacteria capable of reducing perchlorate and nitrate in situ.

  5. Autotrophic, hydrogen-oxidizing, denitrifying bacteria in groundwater, potential agents for bioremediation of nitrate contamination.

    PubMed

    Smith, R L; Ceazan, M L; Brooks, M H

    1994-06-01

    Addition of hydrogen or formate significantly enhanced the rate of consumption of nitrate in slurried core samples obtained from an active zone of denitrification in a nitrate-contaminated sand and gravel aquifer (Cape Cod, Mass.). Hydrogen uptake by the core material was immediate and rapid, with an apparent K(m) of 0.45 to 0.60 muM and a V(max) of 18.7 nmol cm h at 30 degrees C. Nine strains of hydrogen-oxidizing denitrifying bacteria were subsequently isolated from the aquifer. Eight of the strains grew autotrophically on hydrogen with either oxygen or nitrate as the electron acceptor. One strain grew mixotrophically. All of the isolates were capable of heterotrophic growth, but none were similar to Paracoccus denitrificans, a well-characterized hydrogen-oxidizing denitrifier. The kinetics for hydrogen uptake during denitrification were determined for each isolate with substrate depletion progress curves; the K(m)s ranged from 0.30 to 3.32 muM, with V(max)s of 1.85 to 13.29 fmol cell h. Because these organisms appear to be common constituents of the in situ population of the aquifer, produce innocuous end products, and could be manipulated to sequentially consume oxygen and then nitrate when both were present, these results suggest that these organisms may have significant potential for in situ bioremediation of nitrate contamination in groundwater.

  6. Development of hydraulic properties and nitrate turnover processes in minerotrophic fen soil on differnet scales

    NASA Astrophysics Data System (ADS)

    Kleimeier, Christian; Lennartz, Bernd

    2014-05-01

    Generally, it is recommended to remove the uppermost highly degraded peat layer from fens prior to rewetting to eliminate a potential source of organic pollutants for downstream water bodies. We investigated this material as a potential medium for denitrifying filters to further use the organic material. We are aiming to remove nitrate from tile drainage runoff at the outlet drainage dominated catchments to fullfill the requirements of the European Water Framework Directive. In a lysimeter scale long term mesocosm experiments we were aiming to reveal the peats behavior after disturbing and rewetting under constant flow conditions. Tracer experiments revealed a restructuring of the peat ending up at 20/80 percentage of mobile immobile pore volume. Additionally we observed the nitrate turnover. The turnover rate was determined by the hydraulic load. Absolute turnover rates were equal at lower and higher concentrations as well as flow rates, whereas the turnover reached higher percentages at lower concentrations. To further reveal the nitrate turnover processes flow through rector experiments were conducted in an anaerobic environment. We found that strongly reducing conditions can be created in peat even at the presence of nitrate. Thus we can conclude that the minerotrophic peat with its high iron and sulfur concentrations also enables autotrophic denitrification oxidizing iron and sulfur. While the conditions are favorable to re-reduce iron and sulfur,thus an electron shuttling system developed transporting electrons from the organic material as initial e- donor to nitrate as terminal e- acceptor.

  7. Perchlorate and nitrate remediation efficiency and microbial diversity in a containerized wetland bioreactor.

    PubMed

    Krauter, Paula; Daily, Bill; Dibley, Valerie; Pinkart, Holly; Legler, Tina

    2005-01-01

    We have developed a method to remove perchlorate (14-27 microg/L) and nitrate (48 mg/L) from contaminated groundwater using a wetland bioreactor. The bioreactor has operated continuously in a remote field location for more than 2 yr with a stable ecosystem of indigenous organisms. This study assesses the bioreactorfor long-term perchlorate and nitrate remediation by evaluating influent and effluent groundwater for oxidation-reduction conditions and nitrate and perchlorate concentrations. Total community DNA was extracted and purified from 10-g sediment samples retrieved from vertical coring of the bioreactor during winter. Analysis by denaturing gradient gel electrophoresis of short, 16S rDNA, polymerase-chainreaction products was used to identify dominant microorganisms. Bacteria genera identified were closely affiliated with bacteria widely distributed in soils, mud layers, and fresh water. Of the 17 dominant bands sequenced, most were gram negative and capable of aerobic or anaerobic respiration with nitrate as the terminal electron acceptor (Pseudomonas, Acinetobacter, Halomonas, and Nitrospira). Several identified genera (Rhizobium, Acinetobactor, and Xanthomonas) are capable of fixing atmospheric nitrogen into a combined form (ammonia) usable by host plants. Isolates were identified from the Proteobacteria class, known for the ability to reduce perchlorate. Initial bacterial assessments of sediments confirm the prevalence of facultative anaerobic bacteria capable of reducing perchlorate and nitrate in situ.

  8. Income-generating activities for family planning acceptors.

    PubMed

    1989-07-01

    The Income Generating Activities program for Family Planning Acceptors was introduced in Indonesia in 1979. Capital input by the Indonesian National Family Planning Coordination Board and the UN Fund for Population Activities was used to set up small businesses by family planning acceptors. In 2 years, when the businesses become self-sufficient, the loans are repaid, and the money is used to set up new family planning acceptors in business. The program strengthens family planning acceptance, improves the status of women, and enhances community self-reliance. The increase in household income generated by the program raises the standards of child nutrition, encourages reliance on the survival of children, and decreases the value of large families. Approximately 18,000 Family Planning-Income Generating Activities groups are now functioning all over Indonesia, with financial assistance from the central and local governments, the World Bank, the US Agency for International Development, the UN Population Fund, the Government of the Netherlands, and the Government of Australia through the Association of South East Asian Nations.

  9. Virtual screening of electron acceptor materials for organic photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Halls, Mathew D.; Djurovich, Peter J.; Giesen, David J.; Goldberg, Alexander; Sommer, Jonathan; McAnally, Eric; Thompson, Mark E.

    2013-10-01

    Virtual screening involves the generation of structure libraries, automated analysis to predict properties related to application performance and subsequent screening to identify lead systems and estimate critical structure-property limits across a targeted chemical design space. This approach holds great promise for informing experimental discovery and development efforts for next-generation materials, such as organic semiconductors. In this work, the virtual screening approach is illustrated for nitrogen-substituted pentacene molecules to identify systems for development as electron acceptor materials for use in organic photovoltaic (OPV) devices. A structure library of tetra-azapentacenes (TAPs) was generated by substituting four nitrogens for CH at 12 sites on the pentacene molecular framework. Molecular properties (e.g. ELUMO, Eg and μ) were computed for each candidate structure using hybrid DFT at the B3LYP/6-311G** level of theory. The resulting TAPs library was then analyzed with respect to intrinsic properties associated with OPV acceptor performance. Marcus reorganization energies for charge transport for the most favorable TAP candidates were then calculated to further determine suitability as OPV electron acceptors. The synthesis, characterization and OPV device testing of TAP materials is underway, guided by these results.

  10. Design directed self-assembly of donor-acceptor polymers.

    PubMed

    Marszalek, Tomasz; Li, Mengmeng; Pisula, Wojciech

    2016-09-21

    Donor-acceptor polymers with an alternating array of donor and acceptor moieties have gained particular attention during recent years as active components of organic electronics. By implementation of suitable subunits within the conjugated backbone, these polymers can be made either electron-deficient or -rich. Additionally, their band gap and light absorption can be precisely tuned for improved light-harvesting in solar cells. On the other hand, the polymer design can also be modified to encode the desired supramolecular self-assembly in the solid-state that is essential for an unhindered transport of charge carriers. This review focuses on three major factors playing a role in the assembly of donor-acceptor polymers on surfaces which are (1) nature, geometry and substitution position of solubilizing alkyl side chains, (2) shape of the conjugated polymer defined by the backbone curvature, and (3) molecular weight which determines the conjugation length of the polymer. These factors adjust the fine balance between attractive and repulsive forces and ensure a close polymer packing important for an efficient charge hopping between neighboring chains. On the microscopic scale, an appropriate domain formation with a low density of structural defects in the solution deposited thin film is crucial for the charge transport. The charge carrier transport through such thin films is characterized by field-effect transistors as basic electronic elements. PMID:27440174

  11. Fullerene derivatives as electron acceptors for organic photovoltaic cells.

    PubMed

    Mi, Dongbo; Kim, Ji-Hoon; Kim, Hee Un; Xu, Fei; Hwang, Do-Hoon

    2014-02-01

    Energy is currently one of the most important problems humankind faces. Depletion of traditional energy sources such as coal and oil results in the need to develop new ways to create, transport, and store electricity. In this regard, the sun, which can be considered as a giant nuclear fusion reactor, represents the most powerful source of energy available in our solar system. For photovoltaic cells to gain widespread acceptance as a source of clean and renewable energy, the cost per watt of solar energy must be decreased. Organic photovoltaic cells, developed in the past two decades, have potential as alternatives to traditional inorganic semiconductor photovoltaic cells, which suffer from high environmental pollution and energy consumption during production. Organic photovoltaic cells are composed of a blended film of a conjugated-polymer donor and a soluble fullerene-derivative acceptor sandwiched between a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)-coated indium tin oxide positive electrode and a low-work-function metal negative electrode. Considerable research efforts aim at designing and synthesizing novel fullerene derivatives as electron acceptors with up-raised lowest unoccupied molecular orbital energy, better light-harvesting properties, higher electron mobility, and better miscibility with the polymer donor for improving the power conversion efficiency of the organic photovoltaic cells. In this paper, we systematically review novel fullerene acceptors synthesized through chemical modification for enhancing the photovoltaic performance by increasing open-circuit voltage, short-circuit current, and fill factor, which determine the performance of organic photovoltaic cells.

  12. Nitrate enrichment alters a Daphnia-microparasite interaction through multiple pathways.

    PubMed

    Dallas, Tad; Drake, John M

    2014-02-01

    Nutrient pollution has the potential to alter many ecological interactions, including host-parasite relationships. One of the largest sources of nutrient pollution comes from anthropogenic alteration of the nitrogen (N) cycle, specifically the increased rate of nitrate (NO3-N) deposition to aquatic environments, potentially altering host-parasite relationships. This study aimed to assess the mechanisms through which nitrate may impact host-pathogen relationships using a fungal pathogen (Metschnikowia bicuspidata) parasitic to crustacean zooplankton (Daphnia dentifera) as a tractable model system. First, the influence of nitrate on host population dynamics was assessed along a gradient of nitrate concentrations. Nitrate decreased host population size and increased infection prevalence. Second, the influence of nitrate on host reproduction, mortality, and infection intensity was assessed at the individual host level by examining the relationship between pathogen dose and infection prevalence at ambient (0.4 mg NO3-N*L(-1)) and intermediate (12 mg NO3-N*L(-1)) levels of nitrate. Host fecundity and infection intensity both decreased with increasing pathogen dose, but increased nitrate levels corresponded to greater infection intensities. Nitrate had no effect on host growth rate, suggesting that hosts do not alter feeding behavior in nitrate-treated media compared with ambient conditions. This study suggests that nutrient enrichment may enhance disease through increased transmission and infection intensity, but that high levels of nitrate may result in smaller epidemics through reduced transmission caused by smaller population sizes and increased pathogen mortality.

  13. Dietary nitrate improves cardiac contractility via enhanced cellular Ca²⁺ signaling.

    PubMed

    Pironti, Gianluigi; Ivarsson, Niklas; Yang, Jiangning; Farinotti, Alex Bersellini; Jonsson, William; Zhang, Shi-Jin; Bas, Duygu; Svensson, Camilla I; Westerblad, Håkan; Weitzberg, Eddie; Lundberg, Jon O; Pernow, John; Lanner, Johanna; Andersson, Daniel C

    2016-05-01

    The inorganic anion nitrate (NO3 (-)), which is naturally enriched in certain vegetables (e.g., spinach and beetroot), has emerged as a dietary component that can regulate diverse bodily functions, including blood pressure, mitochondrial efficiency, and skeletal muscle force. It is not known if dietary nitrate improves cardiac contractility. To test this, mice were supplemented for 1-2 weeks with sodium nitrate in the drinking water at a dose similar to a green diet. The hearts from nitrate-treated mice showed increased left ventricular pressure and peak rate of pressure development as measured with the Langendorff heart technique. Cardiomyocytes from hearts of nitrate-treated and control animals were incubated with the fluorescent indicator Fluo-3 to measure cytoplasmic free [Ca(2+)] and fractional shortening. Cardiomyocytes from nitrate-treated mice displayed increased fractional shortening, which was linked to larger Ca(2+) transients. Moreover, nitrate hearts displayed increased protein expression of the L-type Ca(2+) channel/dihydropyridine receptor and peak L-type Ca(2+) channel currents. The nitrate-treated hearts displayed increased concentration of cAMP but unchanged levels of cGMP compared with controls. These findings provide the first evidence that dietary nitrate can affect the expression of important Ca(2+) handling proteins in the heart, resulting in increased cardiomyocyte Ca(2+) signaling and improved left ventricular contractile function. Our observation shows that dietary nitrate impacts cardiac function and adds understanding to inorganic nitrate as a physiological modulator. PMID:27071401

  14. Morphological study on small molecule acceptor-based organic solar cells with efficiencies beyond 7% (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Ma, Wei; Yan, He

    2015-10-01

    Despite the essential role of fullerenes in achieving best-performance organic solar cells (OSCs), fullerene acceptors have several drawbacks including poor light absorption, high-cost production and purification. For this reason, small molecule acceptor (SMA)-based OSCs have attracted much attention due to the easy tunability of electronic and optical properties of SMA materials. In this study, polymers with temperature dependent aggregation behaviors are combined with various small molecule acceptor materials, which lead to impressive power conversion efficiencies of up to 7.3%. The morphological and aggregation properties of the polymer:small molecule blends are studied in details. It is found that the temperature-dependent aggregation behavior of polymers allows for the processing of the polymer solutions at moderately elevated temperature, and more importantly, controlled aggregation and strong crystallization of the polymer during the film cooling and drying process. This results in a well-controlled and near-ideal polymer:small molecule morphology that is controlled by polymer aggregation during warm casting and thus insensitive to the choice of small molecules. As a result, several cases of highly efficient (PCE between 6-7.3%) SMA OSCs are achieved. The second part of this presentation will describe the morphology of a new small molecule acceptor with a unique 3D structure. The relationship between molecular structure and morphology is revealed.

  15. Spectrophotometric study of the charge-transfer and ion-pair complexation of methamphetamine with some acceptors

    NASA Astrophysics Data System (ADS)

    Shahdousti, Parvin; Aghamohammadi, Mohammad; Alizadeh, Naader

    2008-04-01

    The charge-transfer (CT) complexes of methamphetamine (MPA) as a n-donor with several acceptors including bromocresolgreen (BCG), bromocresolpurple (BCP), chlorophenolred (CPR), picric acid (PIC), and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) have been studied spectrophotometrically in chloroform solutions in order to obtain some information about their stoichiometry and stability of complexation. The oscillator strengths, transition dipole moments and resonance energy of the complex in the ground state for all complexes have been calculated. Vertical ionization potential of MPA and electron affinity of acceptors were determined by ab initio calculation. The acceptors were also used to utilize a simple and sensitive extraction-spectrophotometric method for the determination of MPA. The method is based on the formation of 1:1 ion-pair association complexes of MPA with BCG, BCP and PIC in chloroform medium. Beer's plots were obeyed in a general concentration range of 0.24-22 μg ml -1 for the investigated drug with different acceptors. The proposed methods were applied successfully for the determination of MAP in pure and abuse drug with good accuracy and precision.

  16. EXTRACTION OF URANYL NITRATE FROM AQUEOUS SOLUTIONS

    DOEpatents

    Furman, N.H.; Mundy, R.J.

    1957-12-10

    An improvement in the process is described for extracting aqueous uranyl nitrate solutions with an organic solvent such as ether. It has been found that the organic phase will extract a larger quantity of uranyl nitrate if the aqueous phase contains in addition to the uranyl nitrate, a quantity of some other soluble nitrate to act as a salting out agent. Mentioned as suitable are the nitrates of lithium, calcium, zinc, bivalent copper, and trivalent iron.

  17. Facultative nitrate reduction by electrode-respiring Geobacter metallireducens biofilms as a competitive reaction to electrode reduction in a bioelectrochemical system.

    PubMed

    Kashima, Hiroyuki; Regan, John M

    2015-03-01

    Alternative metabolic options of exoelectrogenic biofilms in bioelectrochemical systems (BESs) are important not only to explain the fundamental ecology and performance of these systems but also to develop reliable integrated nutrient removal strategies in BESs, which potentially involve substrates or intermediates that support/induce those alternative metabolisms. This research focused on dissimilatory nitrate reduction as an alternative metabolism to dissimilatory anode reduction. Using the exoelectrogenic nitrate reducer Geobacter metallireducens, the critical conditions controlling those alternative metabolisms were investigated in two-chamber, potentiostatically controlled BESs at various anode potentials and biofilm thicknesses and challenged over a range of nitrate concentrations. Results showed that anode-reducing biofilms facultatively reduced nitrate at all tested anode potentials (-150 to +900 mV vs Standard Hydrogen Electrode) with a rapid metabolic shift. The critical nitrate concentration that triggered a significant decrease in BES performance was a function of anode biofilm thickness but not anode potential. This indicates that these alternative metabolisms were controlled by the availability of nitrate, which is a function of nitrate concentration in bulk solution and its diffusion into an anode-reducing biofilm. Coulombic recovery decreased as a function of nitrate dose due to electron-acceptor substrate competition, and nitrate-induced suspended biomass growth decreased the effluent quality. PMID:25622928

  18. Eutectic composite explosives containing ammonium nitrate

    SciTech Connect

    Stinecipher, M.M.

    1981-01-01

    The eutectic of ammonium nitrate (AN), the ammonium salt of 3,5-dinitro-1,2,4-triazole was prepared and its sensitivity and performance were studied. It was found that this AN formulation was unusual in that it performed ideally at small diameter, which indicated that it was a monomolecular explosive. Sensitivity tests included type 12 impact, Henkin thermal and wedge tests, and performance tests included rate stick/plate dent, cylinder, and aquarium tests. Results were compared with calculations, standard explosives, and another eutectic, ethylendiamine dinitrate (EDD)/AN.

  19. Enrichment and identification of biosurfactant-producing oil field microbiota utilizing electron acceptors other than oxygen and nitrate.

    PubMed

    Kryachko, Yuriy; Semler, Diana; Vogrinetz, John; Lemke, Markus; Links, Matthew G; McCarthy, E Luke; Haug, Brenda; Hemmingsen, Sean M

    2016-08-10

    Microorganisms indigenous to an oil reservoir were grown in media containing either sucrose or proteins in four steel vessels under anoxic conditions at 30°C and 8.3MPa for 30days, to enrich biosurfactant producers. Fermentation of substrate was possible in the protein-containing medium and either fermentation or respiration through reduction of sulfate occurred in the sucrose-containing medium. Growth of microorganisms led to 3.4-5.4-fold surface tension reduction indicating production of biosurfactants in amounts sufficient for enhancement of gas-driven oil recovery. Analysis of sequenced cpn60 amplicons showed that Pseudomonas sp. highly similar to biosurfactant producing P. fluorescens and to Pseudomonas sp. strain TKP predominated, and a bacterium highly similar to biosurfactant producing Bacillus mojavensis was present in vessels. Analysis of 16S rDNA amplicons allowed only genus-level identification of these bacteria. Thus, cpn60-amplicon analysis was a more relevant tool for identification of putative biosurfactant producers than 16S rDNA-amplicon analysis.

  20. Nitrate transport is independent of NADH and NAD(P)H nitrate reductases in barley seedlings

    NASA Technical Reports Server (NTRS)

    Warner, R. L.; Huffaker, R. C.

    1989-01-01

    Barley (Hordeum vulgare L.) has NADH-specific and NAD(P)H-bispecific nitrate reductase isozymes. Four isogenic lines with different nitrate reductase isozyme combinations were used to determine the role of NADH and NAD(P)H nitrate reductases on nitrate transport and assimilation in barley seedlings. Both nitrate reductase isozymes were induced by nitrate and were required for maximum nitrate assimilation in barley seedlings. Genotypes lacking the NADH isozyme (Az12) or the NAD(P)H isozyme (Az70) assimilated 65 or 85%, respectively, as much nitrate as the wild type. Nitrate assimilation by genotype (Az12;Az70) which is deficient in both nitrate reductases, was only 13% of the wild type indicating that the NADH and NAD(P)H nitrate reductase isozymes are responsible for most of the nitrate reduction in barley seedlings. For all genotypes, nitrate assimilation rates in the dark were about 55% of the rates in light. Hypotheses that nitrate reductase has direct or indirect roles in nitrate uptake were not supported by this study. Induction of nitrate transporters and the kinetics of net nitrate uptake were the same for all four genotypes indicating that neither nitrate reductase isozyme has a direct role in nitrate uptake in barley seedlings.

  1. Nitrogen and Oxygen Isotopes of Low-Level Nitrate in Groundwater For Environmental Forensics

    NASA Astrophysics Data System (ADS)

    Wang, Y.

    2009-05-01

    Sources of nitrate in water from human activities include fertilizers, animal feedlots, septic systems, wastewater treatment lagoons, animal wastes, industrial wastes and food processing wastes. Nitrogen and Oxygen isotopic analysis of nitrate in groundwater is essential to source identification and environmental forensics as nitrate from different sources carry distinctly different N and O isotopic compositions. Nitrate is extracted from groundwater samples and converted into AgNO3 using ion exchange techniques. The purified AgNO3 is then broken down into N2 and CO for N and O isotopic measurement. Since nitrate concentrations in natural ground waters are usually less than 2 mg/L, however, such method has been limited by minimum sample size it requires, in liters, which is highly nitrate concentration dependent. Here we report a TurboVap- Denitrifier method for N and O isotopic measurement of low-level dissolved nitrate, based on sample evaporation and isotopic analysis of nitrous oxide generated from nitrate by denitrifying bacteria that lack N2O- reductase activity. For most groundwater samples with mg/L-level of nitrate direct injection of water samples in mLs is applied. The volume of sample is adjusted according to its nitrate concentration to achieve a final sample size optimal for the system. For water samples with ug/L-level of nitrate, nitrate is highly concentrated using a TurboVap evaporator, followed by isotopic measurement with Denitrifier method. Benefits of TurboVap- Denitrifier method include high sensitivity and better precision in both isotopic data. This method applies to both freshwater and seawater. The analyses of isotopic reference materials in nitrate-free de-ionized water and seawater are included as method controls to correct for any blank effects. The isotopic data from groundwater and ocean profiles demonstrate the consistency of the data produced by the TurboVap-Denitrifier method.

  2. Method for producing and regenerating a synthetic CO.sub.2 acceptor

    DOEpatents

    Lancet, Michael S [Pittsburgh, PA; Curran, George P [Pittsburgh, PA; Gorin, Everett [San Rafael, CA

    1982-01-01

    A method for producing a synthetic CO.sub.2 acceptor by feeding a mixture of finely divided silica and at least one finely divided calcium compound selected from the group consisting of calcium oxide and calcium carbonate to a fluidized bed; operating the fluidized bed at suitable conditions to produce pellets of synthetic CO.sub.2 acceptor and recovering the pellets of synthetic CO.sub.2 acceptor from the fluidized bed. Optionally, spent synthetic CO.sub.2 acceptor can be charged to the fluidized bed to produce regenerated pellets of synthetic CO.sub.2 acceptor.

  3. Method for producing and regenerating a synthetic CO[sub 2] acceptor

    DOEpatents

    Lancet, M. S.; Curran, G. P.; Gorin, E.

    1982-05-18

    A method is described for producing a synthetic CO[sub 2] acceptor by feeding a mixture of finely divided silica and at least one finely divided calcium compound selected from the group consisting of calcium oxide and calcium carbonate to a fluidized bed; operating the fluidized bed at suitable conditions to produce pellets of synthetic CO[sub 2] acceptor and recovering the pellets of synthetic CO[sub 2] acceptor from the fluidized bed. Optionally, spent synthetic CO[sub 2] acceptor can be charged to the fluidized bed to produce regenerated pellets of synthetic CO[sub 2] acceptor. 1 fig.

  4. Insights on Alterations to the Rumen Ecosystem by Nitrate and Nitrocompounds.

    PubMed

    Latham, Elizabeth A; Anderson, Robin C; Pinchak, William E; Nisbet, David J

    2016-01-01

    Nitrate and certain short chain nitrocompounds and nitro-oxy compounds are being investigated as dietary supplements to reduce economic and environmental costs associated with ruminal methane emissions. Thermodynamically, nitrate is a preferred electron acceptor in the rumen that consumes electrons at the expense of methanogenesis during dissimilatory reduction to an intermediate, nitrite, which is primarily reduced to ammonia although small quantities of nitrous oxide may also be produced. Short chain nitrocompounds act as direct inhibitors of methanogenic bacteria although certain of these compounds may also consume electrons at the expense of methanogenesis and are effective inhibitors of important foodborne pathogens. Microbial and nutritional consequences of incorporating nitrate into ruminant diets typically results in increased acetate production. Unlike most other methane-inhibiting supplements, nitrate decreases or has no effect on propionate production. The type of nitrate salt added influences rates of nitrate reduction, rates of nitrite accumulation and efficacy of methane reduction, with sodium and potassium salts being more potent than calcium nitrate salts. Digestive consequences of adding nitrocompounds to ruminant diets are more variable and may in some cases increase propionate production. Concerns about the toxicity of nitrate's intermediate product, nitrite, to ruminants necessitate management, as animal poisoning may occur via methemoglobinemia. Certain of the naturally occurring nitrocompounds, such as 3-nitro-1-propionate or 3-nitro-1-propanol also cause poisoning but via inhibition of succinate dehydrogenase. Typical risk management procedures to avoid nitrite toxicity involve gradually adapting the animals to higher concentrations of nitrate and nitrite, which could possibly be used with the nitrocompounds as well. A number of organisms responsible for nitrate metabolism in the rumen have been characterized. To date a single rumen bacterium

  5. Concurrent microbial reduction of high concentrations of nitrate and perchlorate in an ion exchange membrane bioreactor.

    PubMed

    Fox, Shalom; Bruner, Tali; Oren, Yoram; Gilron, Jack; Ronen, Zeev

    2016-09-01

    acceptors. Such a mechanism has important implications for controlling the bio-reduction reaction in the IEMB when using glycerol as a carbon source and allowing treating a complex contamination of high concentrations of perchlorate and nitrating in groundwater and successfully biodegrading them to non-hazardous components. Biotechnol. Bioeng. 2016;113: 1881-1891. © 2016 Wiley Periodicals, Inc. PMID:26913813

  6. Insights on Alterations to the Rumen Ecosystem by Nitrate and Nitrocompounds

    PubMed Central

    Latham, Elizabeth A.; Anderson, Robin C.; Pinchak, William E.; Nisbet, David J.

    2016-01-01

    Nitrate and certain short chain nitrocompounds and nitro-oxy compounds are being investigated as dietary supplements to reduce economic and environmental costs associated with ruminal methane emissions. Thermodynamically, nitrate is a preferred electron acceptor in the rumen that consumes electrons at the expense of methanogenesis during dissimilatory reduction to an intermediate, nitrite, which is primarily reduced to ammonia although small quantities of nitrous oxide may also be produced. Short chain nitrocompounds act as direct inhibitors of methanogenic bacteria although certain of these compounds may also consume electrons at the expense of methanogenesis and are effective inhibitors of important foodborne pathogens. Microbial and nutritional consequences of incorporating nitrate into ruminant diets typically results in increased acetate production. Unlike most other methane-inhibiting supplements, nitrate decreases or has no effect on propionate production. The type of nitrate salt added influences rates of nitrate reduction, rates of nitrite accumulation and efficacy of methane reduction, with sodium and potassium salts being more potent than calcium nitrate salts. Digestive consequences of adding nitrocompounds to ruminant diets are more variable and may in some cases increase propionate production. Concerns about the toxicity of nitrate's intermediate product, nitrite, to ruminants necessitate management, as animal poisoning may occur via methemoglobinemia. Certain of the naturally occurring nitrocompounds, such as 3-nitro-1-propionate or 3-nitro-1-propanol also cause poisoning but via inhibition of succinate dehydrogenase. Typical risk management procedures to avoid nitrite toxicity involve gradually adapting the animals to higher concentrations of nitrate and nitrite, which could possibly be used with the nitrocompounds as well. A number of organisms responsible for nitrate metabolism in the rumen have been characterized. To date a single rumen bacterium

  7. Concurrent microbial reduction of high concentrations of nitrate and perchlorate in an ion exchange membrane bioreactor.

    PubMed

    Fox, Shalom; Bruner, Tali; Oren, Yoram; Gilron, Jack; Ronen, Zeev

    2016-09-01

    acceptors. Such a mechanism has important implications for controlling the bio-reduction reaction in the IEMB when using glycerol as a carbon source and allowing treating a complex contamination of high concentrations of perchlorate and nitrating in groundwater and successfully biodegrading them to non-hazardous components. Biotechnol. Bioeng. 2016;113: 1881-1891. © 2016 Wiley Periodicals, Inc.

  8. Insights on Alterations to the Rumen Ecosystem by Nitrate and Nitrocompounds.

    PubMed

    Latham, Elizabeth A; Anderson, Robin C; Pinchak, William E; Nisbet, David J

    2016-01-01

    Nitrate and certain short chain nitrocompounds and nitro-oxy compounds are being investigated as dietary supplements to reduce economic and environmental costs associated with ruminal methane emissions. Thermodynamically, nitrate is a preferred electron acceptor in the rumen that consumes electrons at the expense of methanogenesis during dissimilatory reduction to an intermediate, nitrite, which is primarily reduced to ammonia although small quantities of nitrous oxide may also be produced. Short chain nitrocompounds act as direct inhibitors of methanogenic bacteria although certain of these compounds may also consume electrons at the expense of methanogenesis and are effective inhibitors of important foodborne pathogens. Microbial and nutritional consequences of incorporating nitrate into ruminant diets typically results in increased acetate production. Unlike most other methane-inhibiting supplements, nitrate decreases or has no effect on propionate production. The type of nitrate salt added influences rates of nitrate reduction, rates of nitrite accumulation and efficacy of methane reduction, with sodium and potassium salts being more potent than calcium nitrate salts. Digestive consequences of adding nitrocompounds to ruminant diets are more variable and may in some cases increase propionate production. Concerns about the toxicity of nitrate's intermediate product, nitrite, to ruminants necessitate management, as animal poisoning may occur via methemoglobinemia. Certain of the naturally occurring nitrocompounds, such as 3-nitro-1-propionate or 3-nitro-1-propanol also cause poisoning but via inhibition of succinate dehydrogenase. Typical risk management procedures to avoid nitrite toxicity involve gradually adapting the animals to higher concentrations of nitrate and nitrite, which could possibly be used with the nitrocompounds as well. A number of organisms responsible for nitrate metabolism in the rumen have been characterized. To date a single rumen bacterium

  9. Thermophilic nitrate-reducing microorganisms prevent sulfate reduction in cold marine sediments incubated at high temperature

    NASA Astrophysics Data System (ADS)

    Nepomnyashchaya, Yana; Rezende, Julia; Hubert, Casey

    2014-05-01

    Hydrogen sulphide produced during metabolism of sulphate-reducing microorganisms (SRM) is toxic, corrosive and causes detrimental oil reservoir souring. During secondary oil recovery, injecting oil reservoirs with seawater that is rich in sulphate and that also cools high temperature formations provides favourable growth conditions for SRM. Nitrate addition can prevent metabolism of SRM by stimulating nitrate-reducing microorganisms (NRM). The investigations of thermophilic NRM are needed to develop mechanisms to control the metabolism of SRM in high temperature oil field ecosystems. We therefore established a model system consisting of enrichment cultures of cold surface marine sediments from the Baltic Sea (Aarhus Bay) that were incubated at 60°C. Enrichments contained 25 mM nitrate and 40 mM sulphate as potential electron acceptors, and a mixture of the organic substrates acetate, lactate, propionate, butyrate (5 mM each) and yeast extract (0.01%) as potential carbon sources and electron donors. Slurries were incubated at 60°C both with and without initial pasteurization at 80°C for 2 hours. In the enrichments containing both nitrate and sulphate, the concentration of nitrate decreased indicating metabolic activity of NRM. After a four-hour lag phase the rate of nitrate reduction increased and the concentration of nitrate dropped to zero after 10 hours of incubation. The concentration of nitrite increased as the reduction of nitrate progressed and reached 16.3 mM after 12 hours, before being consumed and falling to 4.4 mM after 19-day of incubation. No evidence for sulphate reduction was observed in these cultures during the 19-day incubation period. In contrast, the concentration of sulphate decreased up to 50% after one week incubation in controls containing only sulphate but no nitrate. Similar sulfate reduction rates were seen in the pasteurized controls suggesting the presence of heat resistant SRM, whereas nitrate reduction rates were lower in the

  10. Reduction of nitrate in Shewanella

    SciTech Connect

    Gao, Haichun; Yang, Zamin Koo; Barua, Sumitra; Reed, SB; Nealson, Kenneth H.; Fredrikson, JK; Tiedje, James; Zhou, Jizhong

    2009-01-01

    In the genome of Shewanella oneidensis, a napDAGHB gene cluster encoding periplasmic nitrate reductase (NapA) and accessory proteins and an nrfA gene encoding periplasmic nitrite reductase (NrfA) have been identified. These two systems seem to be atypical because the genome lacks genes encoding cytoplasmic membrane electron transport proteins, NapC for NAP and NrfBCD/NrfH for NRF, respectively. Here, we present evidence that reduction of nitrate to ammonium in S. oneidensis is carried out by these atypical systems in a two-step manner. Transcriptional and mutational analyses suggest that CymA, a cytoplasmic membrane electron transport protein, is likely to be the functional replacement of both NapC and NrfH in S. oneidensis. Surprisingly, a strain devoid of napB encoding the small subunit of nitrate reductase exhibited the maximum cell density sooner than the wild type. Further characterization of this strain showed that nitrite was not detected as a free intermediate in its culture and NapB provides a fitness gain for S. oneidensis to compete for nitrate in the environments. On the basis results from mutational analyses of napA, napB, nrfA and napBnrfA in-frame deletion mutants, we propose that NapB is able to favor nitrate reduction by routing electrons to NapA exclusively.

  11. Fragment charge difference method for estimating donor-acceptor electronic coupling: Application to DNA π-stacks

    NASA Astrophysics Data System (ADS)

    Voityuk, Alexander A.; Rösch, Notker

    2002-09-01

    The purpose of this communication is two-fold. We introduce the fragment charge difference (FCD) method to estimate the electron transfer matrix element HDA between a donor D and an acceptor A, and we apply this method to several aspects of hole transfer electronic couplings in π-stacks of DNA, including systems with several donor-acceptor sites. Within the two-state model, our scheme can be simplified to recover a convenient estimate of the electron transfer matrix element HDA=(1-Δq2)1/2(E2-E1)/2 based on the vertical excitation energy E2-E1 and the charge difference Δq between donor and acceptor. For systems with strong charge separation, Δq≳0.95, one should resort to the FCD method. As favorable feature, we demonstrate the stability of the FCD approach for systems which require an approach beyond the two-state model. On the basis of ab initio calculations of various DNA related systems, we compared three approaches for estimating the electronic coupling: the minimum splitting method, the generalized Mulliken-Hush (GMH) scheme, and the FCD approach. We studied the sensitivity of FCD and GMH couplings to the donor-acceptor energy gap and found both schemes to be quite robust; they are applicable also in cases where donor and acceptor states are off resonance. In the application to π-stacks of DNA, we demonstrated for the Watson-Crick pair dimer [(GC),(GC)] how structural changes considerably affect the coupling strength of electron hole transfer. For models of three Watson-Crick pairs, we showed that the two-state model significantly overestimates the hole transfer coupling whereas simultaneous treatment of several states leads to satisfactory results.

  12. REMEDIATION OF NITRATE-CONTAMINATED GROUNDWATER USING A BIOBARRIER

    SciTech Connect

    B. STRIETELMEIR; ET AL

    2000-12-01

    A biobarrier system has been developed for use in remediating shallow alluvial groundwater. This barrier is made from highly porous materials that are relatively long-lasting, carbon-based (to supply a limiting nutrient in nitrate destruction, in most cases), and extremely inexpensive and easy to emplace. In a series of laboratory studies, we have determined the effectiveness of this barrier at destroying nitrate and perchlorate in groundwater from Mortandad Canyon at Los Alamos National Laboratory (LANL). This groundwater was obtained from a monitoring well, MCO-5, which is located in the flowpath of the discharge waters from the LANL Radioactive Liquid Waste Treatment Facility (RLWTF). Water with elevated nitrate levels has been discharged from this plant for many years, until recently when the nitrate levels have been brought under the discharge limits. However, the historical discharge has resulted in a nitrate plume in the alluvial groundwater in this canyon. The LANL Multi-Barrier project was initiated this past year to develop a system of barriers that would prevent the transport of radionuclides, metals, colloids and other contaminants, including nitrate and perchlorate, further down the canyon in order to protect populations down-gradient. The biobarrier. will be part of this Multi-Barrier system. We have demonstrated the destruction of nitrate at levels up to 6.5-9.7 mhl nitrate (400-600 mg/L), and that of perchlorate at levels of about 4.3 {micro}M perchlorate (350 ppb). We have quantified the populations of microorganisms present in the biofilm that develops on the biobarrier. The results of this research will be discussed along with other potential applications of this system.

  13. Occurrence of nitrate in Tanzanian groundwater aquifers: A review

    NASA Astrophysics Data System (ADS)

    Elisante, Eliapenda; Muzuka, Alfred N. N.

    2015-03-01

    More than 25 % of Tanzanian depends on groundwater as the main source of water for drinking, irrigation and industrial activities. The current trend of land use may lead to groundwater contamination and thus increasing risks associated with the usage of contaminated water. Nitrate is one of the contaminants resulting largely from anthropogenic activities that may find its way to the aquifers and thus threatening the quality of groundwater. Elevated levels of nitrate in groundwater may lead to human health and environmental problems. The current trend of land use in Tanzania associated with high population growth, poor sanitation facilities and fertilizer usage may lead to nitrate contamination of groundwater. This paper therefore aimed at providing an overview of to what extent human activities have altered the concentration of nitrate in groundwater aquifers in Tanzania. The concentration of nitrate in Tanzanian groundwater is variable with highest values observable in Dar es Salaam (up to 477.6 mg/l), Dodoma (up to 441.1 mg/l), Tanga (above 100 mg/l) and Manyara (180 mg/l). Such high values can be attributed to various human activities including onsite sanitation in urban centres and agricultural activities in rural areas. Furthermore, there are some signs of increasing concentration of nitrate in groundwater with time in some areas in response to increased human activities. However, reports on levels and trends of nitrate in groundwater in many regions of the country are lacking. For Tanzania to appropriately address the issue of groundwater contamination, a deliberate move to determine nitrate concentration in groundwater is required, as well as protection of recharge basins and improvement of onsite sanitation systems.

  14. REMEDIATION OF NITRATE-CONTAMINATED GROUNDWATER USING A BIOBARRIER

    SciTech Connect

    B. STRIETELMEIER; M. ESPINOSA

    2001-01-01

    A biobarrier system has been developed for use in remediating shallow alluvial groundwater. This barrier is made from highly porous materials that are relatively long-lasting, carbon-based (to supply a limiting nutrient in nitrate destruction, in most cases), extremely inexpensive, and easy to replace. In a series of laboratory studies, we have determined the effectiveness of this barrier at destroying nitrate and perchlorate in groundwater from Mortandad Canyon at Los Alamos National Laboratory (LANL). This groundwater was obtained from a monitoring well, MCO-5, which is located in the flowpath of the discharge waters from the LANL Radioactive Liquid Waste Treatment Facility (RLWTF). Water with elevated nitrate levels was discharged from this plant for many years. Recently, the nitrate levels have been brought under the discharge limits. However, the historical discharge has resulted in a nitrate plume in the alluvial groundwater in this canyon. The LANL Multi-Barrier project was initiated in 1999 to develop a system of barriers that would prevent the transport of radionuclides, metals, colloids and other contaminants, including nitrate and perchlorate, further down the canyon in order to protect populations down-gradient. The biobarrier will be part of this Multi-Barrier system. We have demonstrated the destruction of nitrate at levels up to 6.5-9.7 mM nitrate (400-600 mg/L), and that of perchlorate at levels of about 4.3 {micro}M perchlorate (350 ppb). We have quantified the populations of microorganisms present in the biofilm that develops on the biobarrier. The results of this research will be discussed along with other potential applications of this system.

  15. Real-time continuous nitrate monitoring in Illinois in 2013

    USGS Publications Warehouse

    Warner, Kelly L.; Terrio, Paul J.; Straub, Timothy D.; Roseboom, Donald; Johnson, Gary P.

    2013-01-01

    Many sources contribute to the nitrogen found in surface water in Illinois. Illinois is located in the most productive agricultural area in the country, and nitrogen fertilizer is commonly used to maximize corn production in this area. Additionally, septic/wastewater systems, industrial emissions, and lawn fertilizer are common sources of nitrogen in urban areas of Illinois. In agricultural areas, the use of fertilizer has increased grain production to meet the needs of a growing population, but also has resulted in increases in nitrogen concentrations in many streams and aquifers (Dubrovsky and others, 2010). The urban sources can increase nitrogen concentrations, too. The Federal limit for nitrate nitrogen in water that is safe to drink is 10 milligrams per liter (mg/L) (http://water.epa.gov/drink/contaminants/basicinformation/nitrate.cfm, accessed on May 24, 2013). In addition to the concern with nitrate nitrogen in drinking water, nitrogen, along with phosphorus, is an aquatic concern because it feeds the intensive growth of algae that are responsible for the hypoxic zone in the Gulf of Mexico. The largest nitrogen flux to the waters feeding the Gulf of Mexico is from Illinois (Alexander and others, 2008). Most studies of nitrogen in surface water and groundwater include samples for nitrate nitrogen collected weekly or monthly, but nitrate concentrations can change rapidly and these discrete samples may not capture rapid changes in nitrate concentrations that can affect human and aquatic health. Continuous monitoring for nitrate could inform scientists and water-resource managers of these changes and provide information on the transport of nitrate in surface water and groundwater.

  16. Nitrate removal with lateral flow sulphur autotrophic denitrification reactor.

    PubMed

    Lv, Xiaomei; Shao, Mingfei; Li, Ji; Xie, Chuanbo

    2014-01-01

    An innovative lateral flow sulphur autotrophic denitrification (LFSAD) reactor was developed in this study; the treatment performance was evaluated and compared with traditional sulphur/limestone autotrophic denitrification (SLAD) reactor. Results showed that nitrite accumulation in the LFSAD reactor was less than 1.0 mg/L during the whole operation. Denitrification rate increased with the increased initial alkalinity and was approaching saturation when initial alkalinity exceeded 2.5 times the theoretical value. Higher influent nitrate concentration could facilitate nitrate removal capacity. In addition, denitrification efficiency could be promoted under an appropriate reflux ratio, and the highest nitrate removal percentage was achieved under reflux ratio of 200%, increased by 23.8% than that without reflux. Running resistance was only about 1/9 of that in SLAD reactor with equal amount of nitrate removed, which was the prominent excellence of the new reactor. In short, this study indicated that the developed reactor was feasible for nitrate removal from waters with lower concentrations, including contaminated surface water, groundwater or secondary effluent of municipal wastewater treatment with fairly low running resistance. The innovation in reactor design in this study may bring forth new ideas of reactor development of sulphur autotrophic denitrification for nitrate-contaminated water treatment.

  17. Tidal pumping facilitates dissimilatory nitrate reduction in intertidal marshes

    PubMed Central

    Zheng, Yanling; Hou, Lijun; Liu, Min; Liu, Zhanfei; Li, Xiaofei; Lin, Xianbiao; Yin, Guoyu; Gao, Juan; Yu, Chendi; Wang, Rong; Jiang, Xiaofen

    2016-01-01

    Intertidal marshes are alternately exposed and submerged due to periodic ebb and flood tides. The tidal cycle is important in controlling the biogeochemical processes of these ecosystems. Intertidal sediments are important hotspots of dissimilatory nitrate reduction and interacting nitrogen cycling microorganisms, but the effect of tides on dissimilatory nitrate reduction, including denitrification, anaerobic ammonium oxidation and dissimilatory nitrate reduction to ammonium, remains unexplored in these habitats. Here, we use isotope-tracing and molecular approaches simultaneously to show that both nitrate-reduction activities and associated functional bacterial abundances are enhanced at the sediment-tidal water interface and at the tide-induced groundwater fluctuating layer. This pattern suggests that tidal pumping may sustain dissimilatory nitrate reduction in intertidal zones. The tidal effect is supported further by nutrient profiles, fluctuations in nitrogen components over flood-ebb tidal cycles, and tidal simulation experiments. This study demonstrates the importance of tides in regulating the dynamics of dissimilatory nitrate-reducing pathways and thus provides new insights into the biogeochemical cycles of nitrogen and other elements in intertidal marshes. PMID:26883983

  18. Modulation of Lysozyme Function and Degradation after Nitration with Peroxynitrite

    PubMed Central

    Curry-McCoy, Tiana V.; Osna, Natalia A.; Donohue, Terrence M.

    2009-01-01

    Background Peroxynitrite (PN) is formed from superoxide and nitric oxide, both of which are increased during hepatic ethanol metabolism. Peroxynitrite forms adducts with proteins, causing structural and functional alterations. Here, we investigated PN-induced alterations in lysozyme structure and function, and whether they altered the protein’s susceptibility to proteasome-catalyzed degradation. Methods Hen egg lysozyme was nitrated using varying amounts of either PN or the PN donor, 3-morpholinosynonimine (SIN-1). The activity, nitration status and the susceptibility of lysozyme to proteasome-catalyzed degradation were assessed. Results Lysozyme nitration by PN or SIN-1 caused dose-dependent formation of 3-nitrotyrosine-lysozyme adducts, causing decreased catalytic activity, and enhanced susceptibility to degradation by the 20S proteasome. Kinetic analyses revealed an increased affinity by the 20S proteasome toward nitrated lysozyme compared with the native protein. Conclusion Lysozyme nitration enhances the affinity of the modified enzyme for degradation by the proteasome, thereby increasing its susceptibility to proteolysis. General Significance Increased levels of peroxynitrite have been detected in tissues of ethanol-fed animals. The damaging effects from excessive peroxynitrite in the cell increase hepatotoxicity and cellular death by protein modification due to nitration. Cellular defenses against such changes include enhanced proteolysis by the proteasome in order to maintain protein quality control. PMID:19376194

  19. Tidal pumping facilitates dissimilatory nitrate reduction in intertidal marshes.

    PubMed

    Zheng, Yanling; Hou, Lijun; Liu, Min; Liu, Zhanfei; Li, Xiaofei; Lin, Xianbiao; Yin, Guoyu; Gao, Juan; Yu, Chendi; Wang, Rong; Jiang, Xiaofen

    2016-02-17

    Intertidal marshes are alternately exposed and submerged due to periodic ebb and flood tides. The tidal cycle is important in controlling the biogeochemical processes of these ecosystems. Intertidal sediments are important hotspots of dissimilatory nitrate reduction and interacting nitrogen cycling microorganisms, but the effect of tides on dissimilatory nitrate reduction, including denitrification, anaerobic ammonium oxidation and dissimilatory nitrate reduction to ammonium, remains unexplored in these habitats. Here, we use isotope-tracing and molecular approaches simultaneously to show that both nitrate-reduction activities and associated functional bacterial abundances are enhanced at the sediment-tidal water interface and at the tide-induced groundwater fluctuating layer. This pattern suggests that tidal pumping may sustain dissimilatory nitrate reduction in intertidal zones. The tidal effect is supported further by nutrient profiles, fluctuations in nitrogen components over flood-ebb tidal cycles, and tidal simulation experiments. This study demonstrates the importance of tides in regulating the dynamics of dissimilatory nitrate-reducing pathways and thus provides new insights into the biogeochemical cycles of nitrogen and other elements in intertidal marshes.

  20. Tidal pumping facilitates dissimilatory nitrate reduction in intertidal marshes

    NASA Astrophysics Data System (ADS)

    Zheng, Yanling; Hou, Lijun; Liu, Min; Liu, Zhanfei; Li, Xiaofei; Lin, Xianbiao; Yin, Guoyu; Gao, Juan; Yu, Chendi; Wang, Rong; Jiang, Xiaofen

    2016-02-01

    Intertidal marshes are alternately exposed and submerged due to periodic ebb and flood tides. The tidal cycle is important in controlling the biogeochemical processes of these ecosystems. Intertidal sediments are important hotspots of dissimilatory nitrate reduction and interacting nitrogen cycling microorganisms, but the effect of tides on dissimilatory nitrate reduction, including denitrification, anaerobic ammonium oxidation and dissimilatory nitrate reduction to ammonium, remains unexplored in these habitats. Here, we use isotope-tracing and molecular approaches simultaneously to show that both nitrate-reduction activities and associated functional bacterial abundances are enhanced at the sediment-tidal water interface and at the tide-induced groundwater fluctuating layer. This pattern suggests that tidal pumping may sustain dissimilatory nitrate reduction in intertidal zones. The tidal effect is supported further by nutrient profiles, fluctuations in nitrogen components over flood-ebb tidal cycles, and tidal simulation experiments. This study demonstrates the importance of tides in regulating the dynamics of dissimilatory nitrate-reducing pathways and thus provides new insights into the biogeochemical cycles of nitrogen and other elements in intertidal marshes.

  1. Tidal pumping facilitates dissimilatory nitrate reduction in intertidal marshes.

    PubMed

    Zheng, Yanling; Hou, Lijun; Liu, Min; Liu, Zhanfei; Li, Xiaofei; Lin, Xianbiao; Yin, Guoyu; Gao, Juan; Yu, Chendi; Wang, Rong; Jiang, Xiaofen

    2016-01-01

    Intertidal marshes are alternately exposed and submerged due to periodic ebb and flood tides. The tidal cycle is important in controlling the biogeochemical processes of these ecosystems. Intertidal sediments are important hotspots of dissimilatory nitrate reduction and interacting nitrogen cycling microorganisms, but the effect of tides on dissimilatory nitrate reduction, including denitrification, anaerobic ammonium oxidation and dissimilatory nitrate reduction to ammonium, remains unexplored in these habitats. Here, we use isotope-tracing and molecular approaches simultaneously to show that both nitrate-reduction activities and associated functional bacterial abundances are enhanced at the sediment-tidal water interface and at the tide-induced groundwater fluctuating layer. This pattern suggests that tidal pumping may sustain dissimilatory nitrate reduction in intertidal zones. The tidal effect is supported further by nutrient profiles, fluctuations in nitrogen components over flood-ebb tidal cycles, and tidal simulation experiments. This study demonstrates the importance of tides in regulating the dynamics of dissimilatory nitrate-reducing pathways and thus provides new insights into the biogeochemical cycles of nitrogen and other elements in intertidal marshes. PMID:26883983

  2. Nitrate Trends in Minnesota Rivers

    USGS Publications Warehouse

    Wall, Dave; Christopherson, Dave; Lorenz, Dave; Martin, Gary

    2013-01-01

    The objective of this study was to assess long-term trends (30 to 35 years) of flow-adjusted concentrations of nitrite+nitrate-N (hereinafter referred to as nitrate) in a way that would allow us to discern changing trends. Recognizing that these trends are commonly different from one river to another river and from one part of the state to another, our objective was to examine as many river monitoring sites across the state as possible for which sufficient long term streamflow and concentration data were available.

  3. (Per)Chlorate-Reducing Bacteria Can Utilize Aerobic and Anaerobic Pathways of Aromatic Degradation with (Per)Chlorate as an Electron Acceptor

    PubMed Central

    Carlström, Charlotte I.; Loutey, Dana; Bauer, Stefan; Clark, Iain C.; Rohde, Robert A.; Iavarone, Anthony T.; Lucas, Lauren

    2015-01-01

    ABSTRACT The pathways involved in aromatic compound oxidation under perchlorate and chlorate [collectively known as (per)chlorate]-reducing conditions are poorly understood. Previous studies suggest that these are oxygenase-dependent pathways involving O2 biogenically produced during (per)chlorate respiration. Recently, we described Sedimenticola selenatireducens CUZ and Dechloromarinus chlorophilus NSS, which oxidized phenylacetate and benzoate, two key intermediates in aromatic compound catabolism, coupled to the reduction of perchlorate or chlorate, respectively, and nitrate. While strain CUZ also oxidized benzoate and phenylacetate with oxygen as an electron acceptor, strain NSS oxidized only the latter, even at a very low oxygen concentration (1%, vol/vol). Strains CUZ and NSS contain similar genes for both the anaerobic and aerobic-hybrid pathways of benzoate and phenylacetate degradation; however, the key genes (paaABCD) encoding the epoxidase of the aerobic-hybrid phenylacetate pathway were not found in either genome. By using transcriptomics and proteomics, as well as by monitoring metabolic intermediates, we investigated the utilization of the anaerobic and aerobic-hybrid pathways on different electron acceptors. For strain CUZ, the results indicated utilization of the anaerobic pathways with perchlorate and nitrate as electron acceptors and of the aerobic-hybrid pathways in the presence of oxygen. In contrast, proteomic results suggest that strain NSS may use a combination of the anaerobic and aerobic-hybrid pathways when growing on phenylacetate with chlorate. Though microbial (per)chlorate reduction produces molecular oxygen through the dismutation of chlorite (ClO2−), this study demonstrates that anaerobic pathways for the degradation of aromatics can still be utilized by these novel organisms. PMID:25805732

  4. Chemopreventive Agents from Physalis minima Function as Michael Reaction Acceptors

    PubMed Central

    Men, Ruizhi; Li, Ning; Ding, Chihong; Tang, Yingzhan; Xing, Yachao; Ding, Wanjing; Ma, Zhongjun

    2016-01-01

    Background: The fruits of some varieties of genus Physalis have been used as delicious fruits and functional food in the Northeast of China. Materials and Methods: To reveal the functional material basis, we performed bioactivity-guided phytochemical research and chemopreventive effect assay of the constituents from Physalis minima. Results: It was demonstrated that the ethyl acetate extract of P. minima L. (EEPM) had potential quinone reductase (QR) inducing activity with induction ratio (IR, QR induction activity) value of 1.47 ± 0.24, and glutathione binding property as potential Michael reaction acceptors (with an α, β-unsaturated ketone moiety). Furthermore, bioactivity-guided phytochemical research led eight compounds (1–8), which were elucidated as 3-isopropyl-5-acetoxycyclohexene-2-one-1 (1), isophysalin B (2), physalin G (3), physalin D (4), physalin I (5), physordinose B (6), stigmasterol-3-O-β-D-glucopyranoside (7) and 5α-6β-dihydroxyphysalin R (8) on the basis of nuclear magnetic resonance spectroscopy analyses and HRESIMS. Then, isophysalin B (2) and physordinose B (6) showed significant QR inducing activity with IR value of 2.80 ± 0.19 and 2.38 ± 0.46, respectively. SUMMARY An ultra-performance liquid chromatographic method with glutathione as the substrate was used to detect the Michael reaction acceptors in extracts of Physalis minima (EPM)We investigated the chemical constituents of EPM guided by biological activity methodIsophysalin B (1) and physordinose B (6) showed strong quinone reductase inducing activity with induction ratio values of 2.80 ± 0.19 and 2.38 ± 0.46This study generated useful information for consumers and many encourage researchers to utilize edible fruits from Physalis as a source of phytochemicals Abbreviations used: EPM: Extracts of Physalis minima, EEPM: Ethyl acetate extract of Physalis minima L., GSH: Glutathione, MRAs: Michael reaction acceptors, QR: Quinone reductase. PMID:27279713

  5. Nanostructured donor-acceptor self assembly with improved photoconductivity.

    PubMed

    Saibal, B; Ashar, A Z; Devi, R Nandini; Narayan, K S; Asha, S K

    2014-11-12

    Nanostructured supramolecular donor-acceptor assemblies were formed when an unsymmetrical N-substituted pyridine functionalized perylenebisimide (UPBI-Py) was complexed with oligo(p-phenylenevinylene) (OPVM-OH) complementarily functionalized with hydroxyl unit and polymerizable methacrylamide unit at the two termini. The resulting supramolecular complex [UPBI-Py (OPVM-OH)]1.0 upon polymerization by irradiation in the presence of photoinitiator formed well-defined supramolecular polymeric nanostructures. Self-assembly studies using fluorescence emission from thin film samples showed that subtle structural changes occurred on the OPV donor moiety following polymerization. The 1:1 supramolecular complex showed red-shifted aggregate emission from both OPV (∼500 nm) and PBI (∼640 nm) units, whereas the OPV aggregate emission was replaced by intense monomeric emission (∼430 nm) upon polymerizing the methacrylamide units on the OPVM-OH. The bulk structure was studied using wide-angle X-ray diffraction (WXRD). Complex formation resulted in distinct changes in the cell parameters of OPVM-OH. In contrast, a physical mixture of 1 mol each of OPVM-OH and UPBI-Py prepared by mixing the powdered solid samples together showed only a combination of reflections from both parent molecules. Thin film morphology of the 1:1 molecular complex as well as the supramolecular polymer complex showed uniform lamellar structures in the domain range <10 nm. The donor-acceptor supramolecular complex [UPBI-Py (OPVM-OH)]1.0 exhibited space charge limited current (SCLC) with a bulk mobility estimate of an order of magnitude higher accompanied by a higher photoconductivity yield compared to the pristine UPBI-Py. This is a very versatile method to obtain spatially defined organization of n and p-type semiconductor materials based on suitably functionalized donor and acceptor molecules resulting in improved photocurrent response using self-assembly.

  6. Nanostructured donor-acceptor self assembly with improved photoconductivity.

    PubMed

    Saibal, B; Ashar, A Z; Devi, R Nandini; Narayan, K S; Asha, S K

    2014-11-12

    Nanostructured supramolecular donor-acceptor assemblies were formed when an unsymmetrical N-substituted pyridine functionalized perylenebisimide (UPBI-Py) was complexed with oligo(p-phenylenevinylene) (OPVM-OH) complementarily functionalized with hydroxyl unit and polymerizable methacrylamide unit at the two termini. The resulting supramolecular complex [UPBI-Py (OPVM-OH)]1.0 upon polymerization by irradiation in the presence of photoinitiator formed well-defined supramolecular polymeric nanostructures. Self-assembly studies using fluorescence emission from thin film samples showed that subtle structural changes occurred on the OPV donor moiety following polymerization. The 1:1 supramolecular complex showed red-shifted aggregate emission from both OPV (∼500 nm) and PBI (∼640 nm) units, whereas the OPV aggregate emission was replaced by intense monomeric emission (∼430 nm) upon polymerizing the methacrylamide units on the OPVM-OH. The bulk structure was studied using wide-angle X-ray diffraction (WXRD). Complex formation resulted in distinct changes in the cell parameters of OPVM-OH. In contrast, a physical mixture of 1 mol each of OPVM-OH and UPBI-Py prepared by mixing the powdered solid samples together showed only a combination of reflections from both parent molecules. Thin film morphology of the 1:1 molecular complex as well as the supramolecular polymer complex showed uniform lamellar structures in the domain range <10 nm. The donor-acceptor supramolecular complex [UPBI-Py (OPVM-OH)]1.0 exhibited space charge limited current (SCLC) with a bulk mobility estimate of an order of magnitude higher accompanied by a higher photoconductivity yield compared to the pristine UPBI-Py. This is a very versatile method to obtain spatially defined organization of n and p-type semiconductor materials based on suitably functionalized donor and acceptor molecules resulting in improved photocurrent response using self-assembly. PMID:25283356

  7. Systematic evaluation of nitrate and perchlorate bioreduction kinetics in groundwater using a hydrogen-based membrane biofilm reactor.

    PubMed

    Ziv-El, Michal C; Rittmann, Bruce E

    2009-01-01

    To evaluate the simultaneous reduction kinetics of the oxidized compounds, we treated nitrate-contaminated groundwater (approximately 9.4 mg-N/L) containing low concentrations of perchlorate (approximately 12.5 microg/L) and saturated with dissolved oxygen (approximately 8 mg/L) in a hydrogen-based membrane biofilm reactor (MBfR). We systematically increased the hydrogen availability and simultaneously varied the surface loading of the oxidized compounds on the biofilm in order to provide a comprehensive, quantitative data set with which to evaluate the relationship between electron donor (H(2)) availability, surface loading of the electron acceptors (oxidized compounds), and simultaneous bioreduction of the electron acceptors. Increasing the H(2) pressure delivered more H(2) gas, and the total H(2) flux increased linearly from approximately 0.04 mg/cm(2)-d for 0.5 psig (0.034 atm) to 0.13 mg/cm(2)-d for 9.5 psig (0.65 atm). This increased rate of H(2) delivery allowed for continued reduction of the acceptors as their surface loading increased. The electron acceptors had a clear hydrogen-utilization order when the availability of hydrogen was limited: oxygen, nitrate, nitrite, and then perchlorate. Spiking the influent with perchlorate or nitrate allowed us to identify the maximum surface loadings that still achieved more than 99.5% reduction of both oxidized contaminants: 0.21 mg NO(3)-N/cm(2)-d and 3.4 microg ClO(4)/cm(2)-d. Both maximum values appear to be controlled by factors other than hydrogen availability.

  8. Investigating nitrate-dependent humic substance oxidation and in-service K-12 teachers' understanding of microbiology

    NASA Astrophysics Data System (ADS)

    Jones, Nastassia N.

    2011-12-01

    Humic substances (HS) are the humified portions of totally decomposed soil organic matter that are ubiquitous in nature. Although these substances have been studied for more than 200 years, neither their metabolic capabilities nor a specific chemical structure has yet to be determined. HS have been studied as a carbon source in many environments where they are degraded; however, previous studies have shown that some microorganisms are capable of utilizing humic substances as electron acceptors and electron donors in anaerobic respiration. Even though there have been humic-reducing and humic-oxidizing microorganisms isolated and studied in recent years, the mechanism of humics metabolism and its interaction in the natural environment are not well understood. However, it is known that the continuous change in the redox state of HS is important to the cycling of iron, stability of nitrogen and carbon, and the mobility and bioavailability of inorganic and organic environmental pollutants. In this study, microbial communities were examined to evaluate the community dynamics of nitrate-dependent HS-oxidizing populations and to provide a snapshot of the phylogenetic diversity of these microorganisms. Column studies were performed using nitrate as the sole electron acceptor and the following as the electron donors in different columns: reduced humic acids, oxidized humic acids, and acetate as the control. Liquid buffered media was added to a separate column to serve as an additional control. Polymerase chain reactions of the 16S rRNA genes using DNA from the column studies were performed and analyzed by constructing 16S rDNA clone libraries and by performing denaturing gradient gel electrophoresis (DGGE). Clones from the library have been sequenced and analyzed to paint a phylogenetic picture of the microbial community under the various conditions. Results indicate that the majority of the clones were assigned to four well-characterized divisions, the Acidobacteria, the

  9. Anaerobic taurine oxidation: a novel reaction by a nitrate-reducing Alcaligenes sp.

    PubMed

    Denger, K; Laue, H; Cook, A M

    1997-06-01

    Enrichment cultures were prepared under strictly anoxic conditions in medium representing fresh water and containing an organosulfonate as electron donor and carbon source, and nitrate as electron acceptor. The inoculum was from the anaerobic digestor of two communal sewage works. The natural organosulfonates 2-aminoethanesulfonate (taurine), DL-2-amino-3-sulfopropionate (cysteate) and 2-hydroxyethanesulfonate (isethionate) all gave positive enrichments, whereas unsubstituted alkanesulfonates, such as methanesulfonate and arenesulfonates, gave no enrichment. Two representative enrichments were used to obtain pure cultures, and strains NKNTAU (utilizing taurine) and NKNIS (utilizing isethionate) were isolated. Strain NKNTAU was examined in detail. Out of 18 tested organosulfonates, it utilized only one, taurine, and was identified as a novel Alcaligenes sp., a facultatively anaerobic bacterium. Carbon from taurine was converted to cell material and carbon dioxide. The amino group was released as ammonium ion and the sulfonate moiety was recovered as sulfate. Nitrate was reduced to nitrogen gas.

  10. Incorporation of Cu Acceptors in ZnO Nanocrystals

    SciTech Connect

    Oo, W.M.H.; Mccluskey, Matthew D.; Huso, Jesse; Morrison, J.; Bergman, Leah; Engelhard, Mark H.; Saraf, Laxmikant V.

    2010-09-16

    Doping of semiconductor nanocrystals is an important problem in nanomaterials research. Using infrared (IR) and x-ray photoelectron spectroscopy (XPS), we have observed Cu acceptor dopants that were intentionally introduced into ZnO nanocrystals. The incorporation of Cu2+ dopants increased as the diameter of the nanocrystals was increased from ~3 to 5 nm. Etching the nanocrystals with acetic acid revealed a core-shell structure, where a 2-nm lightly doped core is surrounded by a heavily doped shell. These observations are consistent with the trapped dopant model, in which dopant atoms stick to the surface of the core and are overgrown by the nanocrystal material.

  11. A Review of Nitrates in Drinking Water: Maternal Exposure and Adverse Reproductive and Developmental Outcomes

    PubMed Central

    Manassaram, Deana M.; Backer, Lorraine C.; Moll, Deborah M.

    2006-01-01

    In this review we present an update on maternal exposure to nitrates in drinking water in relation to possible adverse reproductive and developmental effects, and also discuss nitrates in drinking water in the United States. The current standard for nitrates in drinking water is based on retrospective studies and approximates a level that protects infants from methemoglobinemia, but no safety factor is built into the standard. The current standard applies only to public water systems. Drinking water source was related to nitrate exposure (i.e., private systems water was more likely than community system water to have nitrate levels above the maximum contaminant limit). Animal studies have found adverse reproductive effects resulting from higher doses of nitrate or nitrite. The epidemiologic evidence of a direct exposure–response relationship between drinking water nitrate level and adverse reproductive effect is still not clear. However, some reports have suggested an association between exposure to nitrates in drinking water and spontaneous abortions, intrauterine growth restriction, and various birth defects. Uncertainties in epidemiologic studies include the lack of individual exposure assessment that would rule out confounding of the exposure with some other cause. Nitrates may be just one of the contaminants in drinking water contributing to adverse outcomes. We conclude that the current literature does not provide sufficient evidence of a causal relationship between exposure to nitrates in drinking water and adverse reproductive effects. Future studies incorporating individual exposure assessment about users of private wells—the population most at risk—should be considered. PMID:16507452

  12. Electrospun cellulose nitrate and polycaprolactone blended nanofibers

    NASA Astrophysics Data System (ADS)

    Nartker, Steven; Hassan, Mohamed; Stogsdill, Michael

    2015-03-01

    Pure cellulose nitrate (CN) and blends of CN and polycaprolactone were electrospun to form nonwoven mats. Polymers were dissolved in a mixed solvent system of tetrahydrofuran and N,N-dimethylformamide. The concentrations were varied to obtain sub-micron and nanoscale fiber mats. Fiber mats were analyzed using scanning electron microscopy, contact angle analysis, Fourier transform infrared spectroscopy and thermal gravimetric analysis. The fiber morphology, surface chemistry and contact angle data show that these electrospun materials are suitable for applications including biosensing, biomedical and tissue engineering.

  13. The preservation of long-range transported nitrate in snow at Summit, Greenland (Invited)

    NASA Astrophysics Data System (ADS)

    Hastings, M. G.

    2013-12-01

    Nitrate is one of the major anions found in polar and alpine snow, both today and in the past. Deposition of nitrate to snow surfaces results from reactions of nitrogen oxides (NOx) with oxidants in the atmosphere, resulting in the production of HNO3 that is incorporated into precipitation or reacts on the surface of particles. Several factors motivate studying nitrate concentration in ice cores including reconstructing past levels of NOx, tropospheric oxidant concentrations and natural variability in NOx sources. The link between the atmospheric concentration of NOx and nitrate concentration in ice core records is problematic because post-depositional processing, such as photolysis and evaporation, can impact the concentration of nitrate in snow. Recent work has shown that the isotopic ratios of nitrate (15N/14N, 18O/16O, 17O/16O) can be a powerful tool for tracing post-depositional loss of nitrate from surface snow. The isotopic composition of nitrate has been shown to contain information about the source of the nitrate (i.e, NOx sources) and the oxidation processes that convert NOx to nitrate in the atmosphere prior to deposition. Results from a number of studies at Summit, Greenland reveal limited loss of nitrate from surface snow during highly photoactive periods, and the oxygen isotopic signatures in snow nitrate appear to be representative of atmospheric deposition of nitrate from outside of Summit. Higher than expected oxygen isotope ratios (18O/16O, 17O/16O) found in Summit summertime nitrate were expected to be dependent upon local photochemistry in which nitrate in the snow is photolyzed to NOx that is then oxidized above the snow by BrO to reform nitrate (i.e., BrONO2). However, the oxygen isotopic composition of nitrate collected at high time resolution in surface snow does not show any link to local gas phase concentrations of a number of species, including BrO. Furthermore, the combination of nitrogen and oxygen isotope data reveals interesting

  14. Iron Corrosion Induced by Nonhydrogenotrophic Nitrate-Reducing Prolixibacter sp. Strain MIC1-1

    PubMed Central

    Ito, Kimio; Wakai, Satoshi; Tsurumaru, Hirohito; Ohkuma, Moriya; Harayama, Shigeaki

    2014-01-01

    Microbiologically influenced corrosion (MIC) of metallic materials imposes a heavy economic burden. The mechanism of MIC of metallic iron (Fe0) under anaerobic conditions is usually explained as the consumption of cathodic hydrogen by hydrogenotrophic microorganisms that accelerates anodic Fe0 oxidation. In this study, we describe Fe0 corrosion induced by a nonhydrogenotrophic nitrate-reducing bacterium called MIC1-1, which was isolated from a crude-oil sample collected at an oil well in Akita, Japan. This strain requires specific electron donor-acceptor combinations and an organic carbon source to grow. For example, the strain grew anaerobically on nitrate as a sole electron acceptor with pyruvate as a carbon source and Fe0 as the sole electron donor. In addition, ferrous ion and l-cysteine served as electron donors, whereas molecular hydrogen did not. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain MIC1-1 was a member of the genus Prolixibacter in the order Bacteroidales. Thus, Prolixibacter sp. strain MIC1-1 is the first Fe0-corroding representative belonging to the phylum Bacteroidetes. Under anaerobic conditions, Prolixibacter sp. MIC1-1 corroded Fe0 concomitantly with nitrate reduction, and the amount of iron dissolved by the strain was six times higher than that in an aseptic control. Scanning electron microscopy analyses revealed that microscopic crystals of FePO4 developed on the surface of the Fe0 foils, and a layer of FeCO3 covered the FePO4 crystals. We propose that cells of Prolixibacter sp. MIC1-1 accept electrons directly from Fe0 to reduce nitrate. PMID:25548048

  15. Iron corrosion induced by nonhydrogenotrophic nitrate-reducing Prolixibacter sp. strain MIC1-1.

    PubMed

    Iino, Takao; Ito, Kimio; Wakai, Satoshi; Tsurumaru, Hirohito; Ohkuma, Moriya; Harayama, Shigeaki

    2015-03-01

    Microbiologically influenced corrosion (MIC) of metallic materials imposes a heavy economic burden. The mechanism of MIC of metallic iron (Fe(0)) under anaerobic conditions is usually explained as the consumption of cathodic hydrogen by hydrogenotrophic microorganisms that accelerates anodic Fe(0) oxidation. In this study, we describe Fe(0) corrosion induced by a nonhydrogenotrophic nitrate-reducing bacterium called MIC1-1, which was isolated from a crude-oil sample collected at an oil well in Akita, Japan. This strain requires specific electron donor-acceptor combinations and an organic carbon source to grow. For example, the strain grew anaerobically on nitrate as a sole electron acceptor with pyruvate as a carbon source and Fe(0) as the sole electron donor. In addition, ferrous ion and l-cysteine served as electron donors, whereas molecular hydrogen did not. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain MIC1-1 was a member of the genus Prolixibacter in the order Bacteroidales. Thus, Prolixibacter sp. strain MIC1-1 is the first Fe(0)-corroding representative belonging to the phylum Bacteroidetes. Under anaerobic conditions, Prolixibacter sp. MIC1-1 corroded Fe(0) concomitantly with nitrate reduction, and the amount of iron dissolved by the strain was six times higher than that in an aseptic control. Scanning electron microscopy analyses revealed that microscopic crystals of FePO4 developed on the surface of the Fe(0) foils, and a layer of FeCO3 covered the FePO4 crystals. We propose that cells of Prolixibacter sp. MIC1-1 accept electrons directly from Fe(0) to reduce nitrate.

  16. Biological denitrification of high concentration nitrate waste

    DOEpatents

    Francis, Chester W.; Brinkley, Frank S.

    1977-01-01

    Biological denitrification of nitrate solutions at concentrations of greater than one kilogram nitrate per cubic meter is accomplished anaerobically in an upflow column having as a packing material a support for denitrifying bacteria.

  17. Exploring the transferase activity of Ffase from Schwanniomyces occidentalis, a β-fructofuranosidase showing high fructosyl-acceptor promiscuity.

    PubMed

    Piedrabuena, David; Míguez, Noa; Poveda, Ana; Plou, Francisco J; Fernández-Lobato, María

    2016-10-01

    The β-fructofuranosidase from the yeast Schwanniomyces occidentalis (Ffase) produces the prebiotic sugars 6-kestose and 1-kestose by transfructosylation of sucrose, which makes it of biotechnological interest. In this study, the hydrolase and transferase activity of this enzyme was kinetically characterized and its potential to synthesize new fructosylated products explored. A total of 40 hydroxylated compounds were used as potential fructosyl-acceptor alternatives to sucrose. Only 17 of them, including some monosaccharides, disaccharides, and oligosaccharides as well as alditols and glycosides were fructosylated. The best alternative acceptors were the alditols. The major transfer product of the reaction including mannitol was purified and characterized as 1-O-β-D-fructofuranosyl-D-mannitol, whose maximum concentration reached 44 g/L, representing about 7.3 % of total compounds in the mixture and 89 % of all products generated by transfructosylation. The reactions including erythritol produced 35 g/L of an isomer mixture comprising 1- and 4-O-β-D-fructofuranosyl-D-erythritol. In addition, Ffase produced 24 g/L of the disaccharide blastose by direct fructosylation of glucose, which makes it the first enzyme characterized from yeast showing this ability. Thus, novel fructosylated compounds with potential applications in food and pharmaceutical industries can be obtained due to the Ffase fructosyl-acceptor promiscuity.

  18. Exploring the transferase activity of Ffase from Schwanniomyces occidentalis, a β-fructofuranosidase showing high fructosyl-acceptor promiscuity.

    PubMed

    Piedrabuena, David; Míguez, Noa; Poveda, Ana; Plou, Francisco J; Fernández-Lobato, María

    2016-10-01

    The β-fructofuranosidase from the yeast Schwanniomyces occidentalis (Ffase) produces the prebiotic sugars 6-kestose and 1-kestose by transfructosylation of sucrose, which makes it of biotechnological interest. In this study, the hydrolase and transferase activity of this enzyme was kinetically characterized and its potential to synthesize new fructosylated products explored. A total of 40 hydroxylated compounds were used as potential fructosyl-acceptor alternatives to sucrose. Only 17 of them, including some monosaccharides, disaccharides, and oligosaccharides as well as alditols and glycosides were fructosylated. The best alternative acceptors were the alditols. The major transfer product of the reaction including mannitol was purified and characterized as 1-O-β-D-fructofuranosyl-D-mannitol, whose maximum concentration reached 44 g/L, representing about 7.3 % of total compounds in the mixture and 89 % of all products generated by transfructosylation. The reactions including erythritol produced 35 g/L of an isomer mixture comprising 1- and 4-O-β-D-fructofuranosyl-D-erythritol. In addition, Ffase produced 24 g/L of the disaccharide blastose by direct fructosylation of glucose, which makes it the first enzyme characterized from yeast showing this ability. Thus, novel fructosylated compounds with potential applications in food and pharmaceutical industries can be obtained due to the Ffase fructosyl-acceptor promiscuity. PMID:27229725

  19. Controlling charge separation and recombination by chemical design in donor-acceptor dyads.

    PubMed

    Liu, Li; Eisenbrandt, Pierre; Roland, Thomas; Polkehn, Matthias; Schwartz, Pierre-Olivier; Bruchlos, Kirsten; Omiecienski, Beatrice; Ludwigs, Sabine; Leclerc, Nicolas; Zaborova, Elena; Léonard, Jérémie; Méry, Stéphane; Burghardt, Irene; Haacke, Stefan

    2016-07-21

    Conjugated donor-acceptor block co-oligomers that self-organize into D-A mesomorphic arrays have raised increasing interest due to their potential applications in organic solar cells. We report here a combined experimental and computational study of charge transfer (CT) state formation and recombination in isolated donor-spacer-acceptor oligomers based on bisthiophene-fluorene (D) and perylene diimide (A), which have recently shown to self-organize to give a mesomorphic lamellar structure at room temperature. Using femtosecond transient absorption spectroscopy and Time-Dependent Density Functional Theory in combination with the Marcus-Jortner formalism, the observed increase of the CT lifetimes is rationalized in terms of a reduced electronic coupling between D and A brought about by the chemical design of the donor moiety. A marked dependence of the CT lifetime on solvent polarity is observed, underscoring the importance of electrostatic effects and those of the environment at large. The present investigation therefore calls for a more comprehensive design approach including the effects of molecular packing. PMID:27341086

  20. Dissimilatory reduction of extracellular electron acceptors in anaerobic respiration.

    PubMed

    Richter, Katrin; Schicklberger, Marcus; Gescher, Johannes

    2012-02-01

    An extension of the respiratory chain to the cell surface is necessary to reduce extracellular electron acceptors like ferric iron or manganese oxides. In the past few years, more and more compounds were revealed to be reduced at the surface of the outer membrane of Gram-negative bacteria, and the list does not seem to have an end so far. Shewanella as well as Geobacter strains are model organisms to discover the biochemistry that enables the dissimilatory reduction of extracellular electron acceptors. In both cases, c-type cytochromes are essential electron-transferring proteins. They make the journey of respiratory electrons from the cytoplasmic membrane through periplasm and over the outer membrane possible. Outer membrane cytochromes have the ability to catalyze the last step of the respiratory chains. Still, recent discoveries provided evidence that they are accompanied by further factors that allow or at least facilitate extracellular reduction. This review gives a condensed overview of our current knowledge of extracellular respiration, highlights recent discoveries, and discusses critically the influence of different strategies for terminal electron transfer reactions.

  1. Functional analysis of a C. elegans trans-splice acceptor.

    PubMed Central

    Conrad, R; Liou, R F; Blumenthal, T

    1993-01-01

    The rol-6 gene is trans-spliced to the 22 nt leader, SL1, 173 nt downstream of the transcription start. We have analyzed splicing in transformants carrying extrachromosomal arrays of rol-6 with mutations in the trans-splice acceptor site. This site is a close match to the consensus, UUUCAG, that is highly conserved in both trans-splice and intron acceptor sites in C. elegans. When the trans-splice site was inactivated by mutating the perfectly-conserved AG, trans-splicing still occurred, but at a cryptic site 20 nt upstream. We tested the frequency with which splicing switched from the normal site to the cryptic site when the pyrimidines at this site were changed to A's. Since most C. elegans 3' splice sites lack an obvious polypyrimidine tract, we hypothesized that these four pyrimidines might play this role, and indeed mutation of these bases caused splicing to switch to the cryptic site. We also demonstrated that a major reason the downstream site is normally favored is because it occurs at a boundary between A+U rich and non-A+U rich RNA. When the RNA between the two splice sites was made less A+U rich, splicing occurred preferentially at the upstream site. Images PMID:8451190

  2. Dissimilatory Reduction of Extracellular Electron Acceptors in Anaerobic Respiration

    PubMed Central

    Richter, Katrin; Schicklberger, Marcus

    2012-01-01

    An extension of the respiratory chain to the cell surface is necessary to reduce extracellular electron acceptors like ferric iron or manganese oxides. In the past few years, more and more compounds were revealed to be reduced at the surface of the outer membrane of Gram-negative bacteria, and the list does not seem to have an end so far. Shewanella as well as Geobacter strains are model organisms to discover the biochemistry that enables the dissimilatory reduction of extracellular electron acceptors. In both cases, c-type cytochromes are essential electron-transferring proteins. They make the journey of respiratory electrons from the cytoplasmic membrane through periplasm and over the outer membrane possible. Outer membrane cytochromes have the ability to catalyze the last step of the respiratory chains. Still, recent discoveries provided evidence that they are accompanied by further factors that allow or at least facilitate extracellular reduction. This review gives a condensed overview of our current knowledge of extracellular respiration, highlights recent discoveries, and discusses critically the influence of different strategies for terminal electron transfer reactions. PMID:22179232

  3. Donor-acceptor complexation and dehydrogenation chemistry of aminoboranes.

    PubMed

    Malcolm, Adam C; Sabourin, Kyle J; McDonald, Robert; Ferguson, Michael J; Rivard, Eric

    2012-12-01

    A series of formal donor-acceptor adducts of aminoborane (H(2)BNH(2)) and its N-substituted analogues (H(2)BNRR') were prepared: LB-H(2)BNRR'(2)-BH(3) (LB = DMAP, IPr, IPrCH(2) and PCy(3); R and R' = H, Me or tBu; IPr = [(HCNDipp)(2)C:] and Dipp = 2,6-iPr(2)C(6)H(3)). To potentially access complexes of molecular boron nitride, LB-BN-LA (LA = Lewis acid), preliminary dehydrogenation chemistry involving the parent aminoborane adducts LB-H(2)BNH(2)-BH(3) was investigated using [Rh(COD)Cl](2), CuBr, and NiBr(2) as dehydrogenation catalysts. In place of isolating the intended dehydrogenated BN donor-acceptor complexes, the formation of borazine was noted as a major product. Attempts to prepare the fluoroarylborane-capped aminoborane complexes, LB-H(2)BNH(2)-B(C(6)F(5))(3), are also described. PMID:23153209

  4. 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

  5. A Novel Chemical Nitrate Destruction Process

    SciTech Connect

    Dziewinski, J.; Marczak, S.

    1999-03-01

    Nitrates represent one of the most significant pollutant discharged to the Baltic Sea by the Sliiamae hydrometallurgical plant. This article contains a brief overview of the existing nitrate destruction technologies followed by the description of a new process developed by the authors. The new chemical process for nitrate destruction is cost effective and simple to operate. It converts the nitrate to nitrogen gas which goes to the atmosphere.

  6. Nitrate removal by nitrate-dependent Fe(II) oxidation in an upflow denitrifying biofilm reactor.

    PubMed

    Zhou, Jun; Wang, Hongyu; Yang, Kai; Sun, Yuchong; Tian, Jun

    2015-01-01

    A continuous upflow biofilm reactor packed with ceramsite was constructed for nitrate removal under an anaerobic atmosphere without an organic carbon source. Denitrifying bacteria, Pseudomonas sp. W1, Pseudomonas sp. W2 and Microbacterium sp. W5, were added to the bioreactor as inocula. Nitrate concentration, nitrite accumulation and nitrogen removal efficiency in the effluent were investigated under various conditions set by several parameters including pH, hydraulic retention time (HRT), ratios of carbon to nitrogen (C/N) and temperature. The results illustrated that the maximum removal efficiency of nitrogen was 85.39%, under optimum reaction parameters, approximately pH 6.5-7, HRT = 48 hours and C/N = 13.1:1 at temperature of 30 °C, which were determined by experiment. PMID:26204069

  7. Nitrate reductase assay using sodium nitrate for rapid detection of multidrug resistant tuberculosis

    PubMed Central

    Macedo, Maíra Bidart; Groll, Andrea Von; Fissette, Krista; Palomino, Juan Carlos; da Silva, Pedro Eduardo Almeida; Martin, Anandi

    2012-01-01

    We validated the nitrate reductase assay (NRA) for the detection of multidrug-resistant Mycobacterium tuberculosis (MDR-TB) using sodium nitrate (NaNO3) in replacement of potassium nitrate (KNO3) as nitrate source. NaNO3 is cheaper than KNO3 and has no restriction on use which facilitates the implementation of NRA to detect MDR-TB. PMID:24031916

  8. 49 CFR 176.410 - Division 1.5 materials, ammonium nitrate and ammonium nitrate mixtures.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 2 2012-10-01 2012-10-01 false Division 1.5 materials, ammonium nitrate and ammonium nitrate mixtures. 176.410 Section 176.410 Transportation Other Regulations Relating to... nitrate and ammonium nitrate mixtures. (a) This section prescribes requirements to be observed...

  9. 49 CFR 176.410 - Division 1.5 materials, ammonium nitrate and ammonium nitrate mixtures.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 2 2011-10-01 2011-10-01 false Division 1.5 materials, ammonium nitrate and ammonium nitrate mixtures. 176.410 Section 176.410 Transportation Other Regulations Relating to... nitrate and ammonium nitrate mixtures. (a) This section prescribes requirements to be observed...

  10. 49 CFR 176.410 - Division 1.5 materials, ammonium nitrate and ammonium nitrate mixtures.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 2 2014-10-01 2014-10-01 false Division 1.5 materials, ammonium nitrate and ammonium nitrate mixtures. 176.410 Section 176.410 Transportation Other Regulations Relating to... nitrate and ammonium nitrate mixtures. (a) This section prescribes requirements to be observed...

  11. 49 CFR 176.410 - Division 1.5 materials, ammonium nitrate and ammonium nitrate mixtures.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 2 2010-10-01 2010-10-01 false Division 1.5 materials, ammonium nitrate and ammonium nitrate mixtures. 176.410 Section 176.410 Transportation Other Regulations Relating to... nitrate and ammonium nitrate mixtures. (a) This section prescribes requirements to be observed...

  12. 49 CFR 176.410 - Division 1.5 materials, ammonium nitrate and ammonium nitrate mixtures.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 2 2013-10-01 2013-10-01 false Division 1.5 materials, ammonium nitrate and ammonium nitrate mixtures. 176.410 Section 176.410 Transportation Other Regulations Relating to... nitrate and ammonium nitrate mixtures. (a) This section prescribes requirements to be observed...

  13. Nitration of Naphthol: A Laboratory Experiment.

    ERIC Educational Resources Information Center

    Mowery, Dwight F.

    1982-01-01

    Products of nitrations, upon distillation or steam distillation, may produce dermatitis in some students. A procedure for nitration of beta-naphthol producing a relatively non-volatile product not purified by steam distillation is described. Nitration of alpha-naphthol by the same procedure yields Martius Yellow dye which dyes wool yellow or…

  14. Modeling nitrate removal in a denitrification bed

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Denitrification beds are being promoted to reduce nitrate concentrations in agricultural drainage water to alleviate the adverse environmental effects associated with nitrate pollution in surface water. In this system, water flows through a trench filled with a carbon media where nitrate is transfor...

  15. Method of producing thin cellulose nitrate film

    DOEpatents

    Lupica, S.B.

    1975-12-23

    An improved method for forming a thin nitrocellulose film of reproducible thickness is described. The film is a cellulose nitrate film, 10 to 20 microns in thickness, cast from a solution of cellulose nitrate in tetrahydrofuran, said solution containing from 7 to 15 percent, by weight, of dioctyl phthalate, said cellulose nitrate having a nitrogen content of from 10 to 13 percent.

  16. 21 CFR 172.160 - Potassium nitrate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Potassium nitrate. 172.160 Section 172.160 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN... Preservatives § 172.160 Potassium nitrate. The food additive potassium nitrate may be safely used as a...

  17. Post-translational Regulation of Nitrate Reductase

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Nitrate reductase (NR) catalyzes the reduction of nitrate to nitrite, which is the first step in the nitrate assimilation pathway, but can also reduce nitrite to nitric oxide (NO), an important signaling molecule that is thought to mediate a wide array of of developmental and physiological processes...

  18. 21 CFR 172.160 - Potassium nitrate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Potassium nitrate. 172.160 Section 172.160 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD... nitrate. The food additive potassium nitrate may be safely used as a curing agent in the processing of...

  19. 21 CFR 172.160 - Potassium nitrate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Potassium nitrate. 172.160 Section 172.160 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Food Preservatives § 172.160 Potassium nitrate. The food additive potassium nitrate may be safely...

  20. 21 CFR 172.160 - Potassium nitrate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Potassium nitrate. 172.160 Section 172.160 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Food Preservatives § 172.160 Potassium nitrate. The food additive potassium nitrate may be safely...

  1. Efflux Of Nitrate From Hydroponically Grown Wheat

    NASA Technical Reports Server (NTRS)

    Huffaker, R. C.; Aslam, M.; Ward, M. R.

    1992-01-01

    Report describes experiments to measure influx, and efflux of nitrate from hydroponically grown wheat seedlings. Ratio between efflux and influx greater in darkness than in light; increased with concentration of nitrate in nutrient solution. On basis of experiments, authors suggest nutrient solution optimized at lowest possible concentration of nitrate.

  2. 21 CFR 172.170 - Sodium nitrate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Sodium nitrate. 172.170 Section 172.170 Food and... PERMITTED FOR DIRECT ADDITION TO FOOD FOR HUMAN CONSUMPTION Food Preservatives § 172.170 Sodium nitrate. The food additive sodium nitrate may be safely used in or on specified foods in accordance with...

  3. 21 CFR 172.160 - Potassium nitrate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Potassium nitrate. 172.160 Section 172.160 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Food Preservatives § 172.160 Potassium nitrate. The food additive potassium nitrate may be safely...

  4. Theory of Triplet Excitation Transfer in the Donor-Oxygen-Acceptor System: Application to Cytochrome b6f.

    PubMed

    Petrov, Elmar G; Robert, Bruno; Lin, Sheng Hsien; Valkunas, Leonas

    2015-10-20

    Theoretical consideration is presented of the triplet excitation dynamics in donor-acceptor systems in conditions where the transfer is mediated by an oxygen molecule. It is demonstrated that oxygen may be involved in both real and virtual intramolecular triplet-singlet conversions in the course of the process under consideration. Expressions describing a superexchange donor-acceptor coupling owing to a participation of the bridging twofold degenerate oxygen's virtual singlet state are derived and the transfer kinetics including the sequential (hopping) and coherent (distant) routes are analyzed. Applicability of this theoretical description to the pigment-protein complex cytochrome b6f, by considering the triplet excitation transfer from the chlorophyll a molecule to distant β-carotene, is discussed. PMID:26488665

  5. Binding characteristics of homogeneous molecularly imprinted polymers for acyclovir using an (acceptor-donor-donor)-(donor-acceptor-acceptor) hydrogen-bond strategy, and analytical applications for serum samples.

    PubMed

    Wu, Suqin; Tan, Lei; Wang, Ganquan; Peng, Guiming; Kang, Chengcheng; Tang, Youwen

    2013-04-12

    This paper demonstrates a novel approach to assembling homogeneous molecularly imprinted polymers (MIPs) based on mimicking multiple hydrogen bonds between nucleotide bases by preparing acyclovir (ACV) as a template and using coatings grafted on silica supports. (1)H NMR studies confirmed the AAD-DDA (A for acceptor, D for donor) hydrogen-bond array between template and functional monomer, while the resultant monodisperse molecularly imprinted microspheres (MIMs) were evaluated using a binding experiment, high performance liquid chromatography (HPLC), and solid phase extraction. The Langmuir isothermal model and the Langmuir-Freundlich isothermal model suggest that ACV-MIMs have more homogeneous binding sites than MIPs prepared through normal imprinting. In contrast to previous MIP-HPLC columns, there were no apparent tailings for the ACV peaks, and ACV-MIMs had excellent specific binding properties with a Ka peak of 3.44 × 10(5)M(-1). A complete baseline separation is obtained for ACV and structurally similar compounds. This work also successfully used MIMs as a specific sorbent for capturing ACV from serum samples. The detection limit and mean recovery of ACV was 1.8 ng/mL(-1) and 95.6%, respectively, for molecularly imprinted solid phase extraction coupled with HPLC. To our knowledge, this was the first example of MIPs using AAD-DDA hydrogen bonds.

  6. Donor-Acceptor-Type Semiconducting Polymers Consisting of Benzothiadiazole Derivatives as Electron-Acceptor Units for Organic Photovoltaic Cells.

    PubMed

    Kim, Hee Su; Park, Jong Baek; Kim, Ji-Hoon; Hwang, Do-Hoon

    2015-11-01

    We synthesized two fused pentacyclic donor-acceptor structures, where the two different outer electron rich thiophene (DTPBT) and electron poor benzene (ICTh) moieties are covalently bonded to the central electron-deficient benzothiadiazole core by two nitrogen bridges. These new electron-acceptor DTPBT and ICTh building blocks were copolymerized with fluorene, as the electron donor group, via Suzuki coupling polymerization, to produce two new alternating copolymers, PFDTPBT and PFICTh, respectively. The average molecular weights of the synthesized polymers were determined by GPC. The number-average molecular weights of PFDTPBT and PFICTh were 19,000 (PDI = 2.5) and 20,000 (PDI = 4.0), respectively. The optical bandgap energies of the polymers were measured from their absorption onsets to be 2.15 and 2.55 eV, depending on the polymer structure. The HOMO energy levels of the polymers were determined, by measuring the oxidation onsets of the polymer films by cyclic voltammetry. The measured HOMO energy levels of PFDTPBT and PFICTh were -5.10 and -5.57 eV, respectively. When the polymers were blended with PC71BM, as the active layer for bulk-heterojunction photovoltaic devices, power conversion efficiencies were 2.08% and 0.34%, respectively, under AM 1.5 G (100 mW cm(-2)) conditions.

  7. 'Low-acid' sulfide oxidation using nitrate-enriched groundwater

    NASA Astrophysics Data System (ADS)

    Donn, Michael; Boxall, Naomi; Reid, Nathan; Meakin, Rebecca; Gray, David; Kaksonen, Anna; Robson, Thomas; Shiers, Denis

    2016-04-01

    where pH remains neutral. The "low-acid" oxidation of sulfides with nitrate as an electron acceptor has been demonstrated at the laboratory scale. In 90-day microcosm respirometry experiments, we exposed a mixture of pulverized quartz and pyrite -rich ore to natural, high-nitrate groundwater and inoculated the microcosms with a culture of aerobic and anaerobic nitrate-dependent iron and sulfur-oxidising microorganisms, which were enriched from ore, groundwater and activated waste water. Incubations were performed under both oxic and anoxic conditions, in addition to abiotic controls. Initial results show that oxidation of the sulfides under nitrate-rich and microbially enhanced conditions does produce less acid than the same material under oxic conditions, and to some degree can match the models as long as oxygen ingress can be controlled. These results are the focus of further research into how this process can be enhanced and whether it can be applied in the field. Nitrate-driven oxidation of sulfides could potentially be used as a new approach to reduce acid generation and leaching of contaminants from waste dumps, in a passive or actively managed process designed to deplete and/or ameliorate (i.e. through surface passivation) the mineralogical hazard. Developing our understanding of biological aspects of these processes may also allow testing of longer-term "bio-caps" for various tailings and dump materials.

  8. Continuous flow nitration in miniaturized devices

    PubMed Central

    2014-01-01

    Summary This review highlights the state of the art in the field of continuous flow nitration with miniaturized devices. Although nitration has been one of the oldest and most important unit reactions, the advent of miniaturized devices has paved the way for new opportunities to reconsider the conventional approach for exothermic and selectivity sensitive nitration reactions. Four different approaches to flow nitration with microreactors are presented herein and discussed in view of their advantages, limitations and applicability of the information towards scale-up. Selected recent patents that disclose scale-up methodologies for continuous flow nitration are also briefly reviewed. PMID:24605161

  9. Generation of Nitrogen Acceptors in ZnO using Pulse Thermal Processing

    SciTech Connect

    Xu, Jun; Ott, Ronald D; Sabau, Adrian S; Pan, Zhengwei; Xiu, Faxian; Liu, Jilin; Erie, Jean-Marie; Norton, David P

    2008-01-01

    Bipolar doping in wide bandgap semiconductors is difficult to achieve under equilibrium conditions because of the spontaneous formation of compensating defects and unfavorable energetics for dopant substitution. In this work, we explored the use of rapid pulse thermal processing for activating nitrogen dopants into acceptor states in ZnO. Low-temperature photoluminescence spectra revealed both acceptor-bound exciton (A{sup 0}X) and donor-acceptor pair emissions, which present direct evidence for acceptors generated after pulse thermal processing of nitrogen-doped ZnO. This work suggests that pulse thermal processing is potentially an effective method for p-type doping of ZnO.

  10. Synthesis of charged bis-heteroaryl donor-acceptor (D-A+) NLO-phores coupling (π-deficient-π-excessive) heteroaromatic rings.

    PubMed

    Ramirez, Marco Antonio; Custodio, Raul; Cuadro, Ana M; Alvarez-Builla, Julio; Clays, Koen; Asselberghs, Inge; Mendicuti, Francisco; Castaño, Obis; Andrés, José L; Vaquero, Juan J

    2013-11-01

    Charged chromophores based on heteroaromatic cations were prepared by reaction of alkylazinium salts with N-heteroarylstannanes under Stille conditions. This approach provides easy access to potential single donor D-A(+) chromophores in which the acceptor moiety A(+) is the pyridinium cation and the donors are different π-excessive N-heterocycles. The β hyperpolarizabilities were measured in hyper-Rayleigh scattering experiments and the experimental data are supported by a theoretical analysis that combines a variety of computational procedures, including density functional theory and correlated Hartree-Fock-based methods. In some chromophores, the absence of a bridge between donor and acceptor fragments increases the NLO properties.

  11. Phase diagram of ammonium nitrate

    NASA Astrophysics Data System (ADS)

    Dunuwille, M.; Yoo, C. S.

    2014-05-01

    Ammonium Nitrate (AN) has often subjected to uses in improvised explosive devices, due to its wide availability as a fertilizer and its capability of becoming explosive with slight additions of organic and inorganic compounds. Yet, the origin of enhanced energetic properties of impure AN (or AN mixtures) is neither chemically unique nor well understood -resulting in rather catastrophic disasters in the past1 and thereby a significant burden on safety in using ammonium nitrates even today. To remedy this situation, we have carried out an extensive study to investigate the phase stability of AN at high pressure and temperature, using diamond anvil cells and micro-Raman spectroscopy. The present results confirm the recently proposed phase IV-to-IV' transition above 17 GPa2 and provide new constraints for the melting and phase diagram of AN to 40 GPa and 400 °C.

  12. Purification and Characterization of the Nitrate Reductase from the Diatom Thalassiosira pseudonana1

    PubMed Central

    Amy, Nancy K.; Garrett, Reginald H.

    1974-01-01

    The assimilatory nitrate reductase (NADH: nitrate oxidoreductase, E.C. 1.6.6.2.) from the marine diatom Thalassiosira pseudonana, Hasle and Heimdal, has been purified 200-fold and characterized. The regulation of nitrate reductase in response to various conditions of nitrogen nutrition has been investigated. Nitrate reductase activity is repressed by the presence of ammonium in vivo, and its synthesis is derepressed when ammonium is absent. The derepression process is sensitive to cycloheximide and apparently requires protein synthesis. Repression of enzyme activity by ammonium is neither inhibited nor delayed by the presence of cycloheximide. In vitro, ammonium does not inhibit enzyme activity. NADH is the physiological electron donor for the enzyme in a flavin-dependent reaction. Spectral studies have indicated the presence of a b-type cytochrome associated with the enzyme. It is possible to observe enzymatic oxidation-reduction reactions which represent partial functions of the over-all electron transport capacity of this enzyme. Nitrate reductase will accept electrons from artificial electron donors such as reduced methyl viologen in a flavin-independent reaction. Further, dithionitereduced flavin adenine dinucleotide can donate electrons to the enzyme to reduce nitrate to nitrite. Finally, the nitrate reductase will exhibit a diaphorase activity and reduce the artificial electron acceptor mammalian cytochrome c in flavin-adeninedinucleotide-dependent reaction. Inhibition studies with potassium cyanide, sodium azide, and o-phenanthroline have yielded indirect evidence for metal component (s) of the enzyme. The inhibition of the NADH-requiring enzyme activities by p-hydroxymercuribenzoate has shown that an essential sulfhydryl group is involved in the initial portion of the electron transport. Heat treatment exerts an effect similar to the p-hydroxymercuribenzoate inhibition; namely, the NADH-requiring activities are rapidly inactivated, whereas the terminal

  13. Deconstructing nitrate isotope dynamics in aquifers

    NASA Astrophysics Data System (ADS)

    Granger, J.

    2012-12-01

    The natural abundance N and O stable isotope ratios of nitrate provide an invaluable tool to differentiate N sources to the environment, track their dispersal, and monitor their attenuation by biological transformations. The interpretation of patterns in isotope abundances relies on knowledge of the isotope ratios of the source end-members, as well as on constraints on the isotope discrimination imposed on nitrate by respective biological processes. Emergent observations from mono-culture experiments of denitrifying bacteria reveal nitrate fractionation trends that appear at odds with trends ascribed to denitrification in soils and aquifers. This discrepancy raises the possibility that additional biological N transformations may be acting in tandem with denitrification. Here, the N and O isotope enrichments associated with nitrate removal by denitrification in aquifers are posited to bear evidence of coincident biological nitrate production - from nitrification and/or from anammox. Simulations are presented from a simple time-dependent one-box model of a groundwater mass ageing that is subject to net nitrate loss by denitrification with coincident nitrate production by nitrification or anammox. Within boundary conditions characteristic of freshwater aquifers, the apparent slope of the parallel enrichments in nitrate N and O isotopes associated with net N loss to denitrification can vary in proportion to the nitrate added simultaneous by oxidative processes. Pertinent observations from nitrate plumes in suboxic to anoxic aquifers are examined to validate this premise. In this perspective, nitrate isotope distributions suggest that we may be missing important N fluxes inherent to most aquifers.

  14. Sensitive Immunoassays of Nitrated Fibrinogen in Human Biofluids

    SciTech Connect

    Tang, Zhiwen; Wu, Hong; Du, Dan; Wang, Jun; Wang, Hua; Qian, Weijun; Bigelow, Diana J.; Pounds, Joel G.; Smith, Richard D.; Lin, Yuehe

    2010-05-05

    Three new sandwich immunoassays for detection of nitrated biomarker have been established with potential applications in biomedical studies and clinical practice. In this study, nitrated human fibrinogen, a potential oxidative stress biomarker for several pathologies, was chosen as the target. To improve the sensitivity and overcome the interference caused by the complexity of human biofluids, we developed three sandwich strategies using various combinations of primary antibody and secondary antibody. All three strategies demonstrated high sensitivity and selectivity towards nitrated forms of fibrinogen in buffer, but their performances were dramatically reduced when tested with human plasma and serum samples. Systematically optimizations were carried out to investigate the effects of numerous factors, including sampling, coating, blocking, and immunoreactions. Our final optimization results indicate that two of these strategies retain sufficient sensitivity and selectivity for use as assays in human physiological samples. Specifically, detection limits reached the pM level and the linear response ranges were up to nM level with a correlation coefficient > 0.99. To our best knowledge, this is the first example of using an electrochemical immunoassay for a nitrated biomarker in a physiological fluid. This novel approach provides a rapid, sensitive, selective, cost efficient and robust bioassay for detection of oxidative stress in pathology and for clinical applications. Moreover, the sandwich strategies developed in this paper can be readily used to establish effective methods targeting other nitration biomarkers.

  15. Nitrate Utilization by the Diatom Skeletonema costatum

    PubMed Central

    Serra, Juan L.; Llama, Maria J.; Cadenas, Eduardo

    1978-01-01

    Nitrate uptake has been studied in nitrogen-deficient cells of the marine diatom Skeletonema costatum. When these cells are incubated in the presence of nitrate, this ion is quickly taken up from the medium, and nitrite is excreted by the cells. Nitrite is excreted following classical saturation kinetics, its rate being independent of nitrate concentration in the incubation medium for nitrate concentration values higher than 3 micromolar. Nitrate uptake shows mixed-transfer kinetics, which can be attributed to the simultaneous contributions of mediated and diffusion transfer. Cycloheximide and p-hydroxymercuribenzoate inhibit the carrier-mediated contribution to nitrate uptake, without affecting the diffusion component. When cells are preincubated with nitrate, the net nitrogen uptake is increased. PMID:16660652

  16. Pollution of drinking water with nitrate

    SciTech Connect

    Cabel, B.; Kozicki, R.; Lahl, U.; Podbielshi, A.; Stachel, B.; Struss, S.

    1982-01-01

    The main sources of nitrate in man are food and drinking water. The legislature in West Germany intends to lower the permitted level of nitrate in drinking water from the present 90 mg/l to 50 mg/l in 1982. The European Community has issued a directive that recommends a level of only 25 mg/l, and for babies 10 mg/l nitrate should not be exceeded. At present, nitrate cannot be removed from raw water at an acceptable cost. The problem of high nitrate content is mainly one of drinking water generation from ground water. Several analyses indicate rising concentrations of nitrate in ground water in different regions of West Germany, especially in the last few years. The following sources of nitrate-contamination of ground water aquifers in West are discussed: natural sources; over-manuring of agricultural areas with natural organic fertilizers; over-manuring of agricultural areas with synthetic fertilizers.

  17. Quantum information processing using acceptors in silicon and phonon entanglement

    NASA Astrophysics Data System (ADS)

    Clark, Susan; Reinke, Charles; McGuinness, Hayden; El-Kady, Ihab

    2014-03-01

    Quantum computing with large numbers of qubits remains challenging due to the decoherence and complexity that arise as more qubits are added to a system. Here I propose a new platform for semiconductor quantum computing which may be robust to common sources of decoherence and may not be difficult to fabricate repeatedly. This system consists of a hole bound to an acceptor in silicon which has been implanted in the center of a mechanical cavity (similar to a photonic crystal cavity) and connected to other cavities by a system of waveguides. I will outline a basic entangling gate and calculations showing the promise of this platform as the ideal qubit. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U. S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  18. Ground-water discharge and nitrate loadings to the coastal bays of Maryland

    USGS Publications Warehouse

    Dillow, Jonathan J.A.; Greene, Earl A.

    1999-01-01

    Nitrate in ground water discharged to the Atlantic coastal bays of Maryland enhances the growth of phytoplankton and algae in the bays, which in turn contributes to the process of eutrophication (changes in a body of water as nutrients and sediments accumulate), which is one of the principal environmental problems in the bays. Information on nitrate loading to the bays has been identified as a major data gap by State and Federal resource managers. This report presents results of a study to estimate ground-water discharge and potential nitrate loads to the coastal bays of Maryland, which include Chincoteague, Newport, Sinepuxent, Isle of Wight, and Assawoman Bays. The nitrate load from the discharge of ground water to the coastal bays is dependent on the concentration of nitrate in the water and the volume of ground water being discharged. Data from 388 wells completed in the surficial aquifer that discharges to the bays were used to construct a map of the distribution of nitrate concentration in the ground water. On the basis of those data, and on several simplifying assumptions, the potential nitrate load to the coastal bays from direct discharge of ground water was estimated to be 272,000 pounds of nitrate per year, distributed throughout the 108-square-mile surface area of the bays. Nitrate from ground water can also enter the coastal bays by way of base flow to streams that discharge to the bays. The potential nitrate load to the bays from the base flow of streams was estimated to be 862,000 pounds per year, assuming that the concentration of nitrate in stream base flow is 3.2 milligrams per liter, which is the median concentration of nitrate in ground water in the study area.

  19. Post-translational Tyrosine Nitration of Eosinophil Granule Toxins Mediated by Eosinophil Peroxidase*

    PubMed Central

    Ulrich, Martina; Petre, Alina; Youhnovski, Nikolay; Prömm, Franziska; Schirle, Markus; Schumm, Michael; Pero, Ralph S.; Doyle, Alfred; Checkel, James; Kita, Hirohito; Thiyagarajan, Nethaji; Acharya, K. Ravi; Schmid-Grendelmeier, Peter; Simon, Hans-Uwe; Schwarz, Heinz; Tsutsui, Masato; Shimokawa, Hiroaki; Bellon, Gabriel; Lee, James J.; Przybylski, Michael; Döring, Gerd

    2008-01-01

    Nitration of tyrosine residues has been observed during various acute and chronic inflammatory diseases. However, the mechanism of tyrosine nitration and the nature of the proteins that become tyrosine nitrated during inflammation remain unclear. Here we show that eosinophils but not other cell types including neutrophils contain nitrotyrosine-positive proteins in specific granules. Furthermore, we demonstrate that the human eosinophil toxins, eosinophil peroxidase (EPO), major basic protein, eosinophil-derived neurotoxin (EDN) and eosinophil cationic protein (ECP), and the respective murine toxins, are post-translationally modified by nitration at tyrosine residues during cell maturation. High resolution affinity-mass spectrometry identified specific single nitration sites at Tyr349 in EPO and Tyr33 in both ECP and EDN. ECP and EDN crystal structures revealed and EPO structure modeling suggested that the nitrated tyrosine residues in the toxins are surface exposed. Studies in EPO-/-, gp91phox-/-, and NOS-/- mice revealed that tyrosine nitration of these toxins is mediated by EPO in the presence of hydrogen peroxide and minute amounts of NOx. Tyrosine nitration of eosinophil granule toxins occurs during maturation of eosinophils, independent of inflammation. These results provide evidence that post-translational tyrosine nitration is unique to eosinophils. PMID:18694936

  20. Assessment of nitrate-nitrogen distribution in Kansas groundwater, 1990-1998

    USGS Publications Warehouse

    Townsend, M.A.; Young, D.P.

    2000-01-01

    Nitrate-nitrogen (nitrate-N) in groundwater is a potential problem in many parts of Kansas. From 1990 to 1998, 747 water samples were collected from domestic, irrigation, monitoring, and public water supply wells primarily from the western two-thirds of the state, and analyzed for nitrate-N by the Kansas Geological Survey. Nitrate-N concentrations of the 747 samples analyzed range from 29% with less than or equal to 3 mg/L, 51% between 3 and 10 mg/L, and 20% greater than or equal to 10 mg/L. Factors that show a statistically significant relationship with the occurrence of nitrate-N in Kansas groundwater in this assessment include geographic area of the state, depth of well, and age of well. Nitrate-N levels of wells screened in the High Plains aquifer in south-central Kansas showed a statistically higher concentration than samples collected from the High Plains aquifer in the western portion of the state. Comparison of nitrate-N with depth of well indicated that shallower wells throughout the state generally have higher nitrate-N values than deeper wells. Irrigation wells older than 1975 showed statistically higher nitrate-N concentration than wells installed during and since 1975, possibly related to changes in well-construction practices and regulations that occurred in 1975. ?? 2000 International Association for Mathematical Geology.

  1. Photochemical reduction of uranyl nitrate

    SciTech Connect

    Duerksen, W.K.

    1993-10-20

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

  2. Beyond fullerenes: design of nonfullerene acceptors for efficient organic photovoltaics.

    PubMed

    Li, Haiyan; Earmme, Taeshik; Ren, Guoqiang; Saeki, Akinori; Yoshikawa, Saya; Murari, Nishit M; Subramaniyan, Selvam; Crane, Matthew J; Seki, Shu; Jenekhe, Samson A

    2014-10-15

    New electron-acceptor materials are long sought to overcome the small photovoltage, high-cost, poor photochemical stability, and other limitations of fullerene-based organic photovoltaics. However, all known nonfullerene acceptors have so far shown inferior photovoltaic properties compared to fullerene benchmark [6,6]-phenyl-C60-butyric acid methyl ester (PC60BM), and there are as yet no established design principles for realizing improved materials. Herein we report a design strategy that has produced a novel multichromophoric, large size, nonplanar three-dimensional (3D) organic molecule, DBFI-T, whose π-conjugated framework occupies space comparable to an aggregate of 9 [C60]-fullerene molecules. Comparative studies of DBFI-T with its planar monomeric analogue (BFI-P2) and PC60BM in bulk heterojunction (BHJ) solar cells, by using a common thiazolothiazole-dithienosilole copolymer donor (PSEHTT), showed that DBFI-T has superior charge photogeneration and photovoltaic properties; PSEHTT:DBFI-T solar cells combined a high short-circuit current (10.14 mA/cm(2)) with a high open-circuit voltage (0.86 V) to give a power conversion efficiency of 5.0%. The external quantum efficiency spectrum of PSEHTT:DBFI-T devices had peaks of 60-65% in the 380-620 nm range, demonstrating that both hole transfer from photoexcited DBFI-T to PSEHTT and electron transfer from photoexcited PSEHTT to DBFI-T contribute substantially to charge photogeneration. The superior charge photogeneration and electron-accepting properties of DBFI-T were further confirmed by independent Xenon-flash time-resolved microwave conductivity measurements, which correctly predict the relative magnitudes of the conversion efficiencies of the BHJ solar cells: PSEHTT:DBFI-T > PSEHTT:PC60BM > PSEHTT:BFI-P2. The results demonstrate that the large size, multichromophoric, nonplanar 3D molecular design is a promising approach to more efficient organic photovoltaic materials.

  3. Recent advances in photoinduced donor/acceptor copolymerization

    NASA Astrophysics Data System (ADS)

    Jönsson, S.; Viswanathan, K.; Hoyle, C. E.; Clark, S. C.; Miller, C.; Morel, F.; Decker, C.

    1999-05-01

    Photoinitiated free radical polymerization of donor (D)/acceptor (A) type monomers has gained considerable interest due to the possibility to efficiently photopolymerize non-acrylate based systems. Furthermore, this photoinduced alternating copolymerization can be accomplished without the presence of a conventional free radical generating photoinitiator. In the past, we have shown that the structural influences in the direct photolysis of N-Alkyl and N-Arylmaleimides as well as their corresponding ground state charge transfer complexes (CTC) with suitable donors have carefully been investigated. For certain combinations of A and D type monomers, a direct photolysis of the ground state complex or the excitation of the acceptor, followed by the formation of an exciplex, has been shown to initiate the copolymerization. Herein, we show that the main route of initiation is based on inter or intra molecular H-abstraction from an excited state maleimide, whereby no exciplex formation takes place. H-abstraction will predominantly take place in systems where easily abstractable hydrogens are present. Our laser flash photolysis investigation, ESR [1] (A. Hiroshi, I. Takasi, T. Nosi, Macromol. Chem. 190 (1989) 2821) and phosphorescence emissions [2,3] (K.S. Chen, T. Foster, J.K.S. Wan, J. Phys. Chem. 84 (1980) 2473; C.J. Seliskar, S.P. McGlynn, J. Chem. Phys. 55 (1971) 4337) studies show that triplet excited states of N-alkyl substituted maleimides (RMI), which are well known strong precursors for direct H-abstractions from aliphatic ethers and secondary alcohols, are formed upon excitation. Rates of copolymerization and degrees of conversion for copolymerization of maleimide/vinyl ether pairs in air and nitrogen have been measured as a function of hydrogen abstractability of the excited triplet state MI as well as the influence of concentration and hydrogen donating effect of the hydrogen donor.

  4. Uranyl Nitrate Flow Loop

    SciTech Connect

    Ladd-Lively, Jennifer L

    2008-10-01

    The objectives of the work discussed in this report were to: (1) develop a flow loop that would simulate the purified uranium-bearing aqueous stream exiting the solvent extraction process in a natural uranium conversion plant (NUCP); (2) develop a test plan that would simulate normal operation and disturbances that could be anticipated in an NUCP; (3) use the flow loop to test commercially available flowmeters for use as safeguards monitors; and (4) recommend a flowmeter for production-scale testing at an NUCP. There has been interest in safeguarding conversion plants because the intermediate products [uranium dioxide (UO{sub 2}), uranium tetrafluoride (UF{sub 4}), and uranium hexafluoride (UF{sub 6})] are all suitable uranium feedstocks for producing special nuclear materials. Furthermore, if safeguards are not applied virtually any nuclear weapons program can obtain these feedstocks without detection by the International Atomic Energy Agency (IAEA). Historically, IAEA had not implemented safeguards until the purified UF{sub 6} product was declared as feedstock for enrichment plants. H. A. Elayat et al. provide a basic definition of a safeguards system: 'The function of a safeguards system on a chemical conversion plant is in general terms to verify that no useful nuclear material is being diverted to use in a nuclear weapons program'. The IAEA now considers all highly purified uranium compounds as candidates for safeguarding. DOE is currently interested in 'developing instruments, tools, strategies, and methods that could be of use to the IAEA in the application of safeguards' for materials found in the front end of the nuclear fuel cycle-prior to the production of the uranium hexafluoride or oxides that have been the traditional starting point for IAEA safeguards. Several national laboratories, including Oak Ridge, Los Alamos, Lawrence Livermore, and Brookhaven, have been involved in developing tools or techniques for safeguarding conversion plants. This study

  5. Electrochemical reduction of nitrate in the presence of an amide

    DOEpatents

    Dziewinski, Jacek J.; Marczak, Stanislaw

    2002-01-01

    The electrochemical reduction of nitrates in aqueous solutions thereof in the presence of amides to gaseous nitrogen (N.sub.2) is described. Generally, electrochemical reduction of NO.sub.3 proceeds stepwise, from NO.sub.3 to N.sub.2, and subsequently in several consecutive steps to ammonia (NH.sub.3) as a final product. Addition of at least one amide to the solution being electrolyzed suppresses ammonia generation, since suitable amides react with NO.sub.2 to generate N.sub.2. This permits nitrate reduction to gaseous nitrogen to proceed by electrolysis. Suitable amides include urea, sulfamic acid, formamide, and acetamide.

  6. A field diagnostic test for the improvised explosive urea nitrate.

    PubMed

    Almog, Joseph; Klein, Asne; Tamiri, Tsippy; Shloosh, Yael; Abramovich-Bar, Sara

    2005-05-01

    A sensitive, specific and simple color test for the improvised explosive urea nitrate is described. It is based on the formation of a red pigment upon the reaction between urea nitrate and p-dimethylaminocinnamaldehyde (p-DMAC) under neutral conditions. Urea itself, which is the starting material for urea nitrate, does not react with p-DMAC under the same conditions. Other potential sources of false positive response e.g., common fertilizers, medications containing the urea moiety and various amines, do not produce the red pigment with p-DMAC. Exhibits collected from 10 terrorist cases have been tested with p-DMAC. The results were in full agreement with those obtained by instrumental techniques including GC/MS, XRD and IR.

  7. 49 CFR 176.415 - Permit requirements for Division 1.5, ammonium nitrates, and certain ammonium nitrate fertilizers.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... nitrates, and certain ammonium nitrate fertilizers. 176.415 Section 176.415 Transportation Other... requirements for Division 1.5, ammonium nitrates, and certain ammonium nitrate fertilizers. (a) Except as... Captain of the Port (COTP). (1) Ammonium nitrate UN1942, ammonium nitrate fertilizers containing more...

  8. 49 CFR 176.415 - Permit requirements for Division 1.5, ammonium nitrates, and certain ammonium nitrate fertilizers.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... nitrates, and certain ammonium nitrate fertilizers. 176.415 Section 176.415 Transportation Other... requirements for Division 1.5, ammonium nitrates, and certain ammonium nitrate fertilizers. (a) Except as... Captain of the Port (COTP). (1) Ammonium nitrate UN1942, ammonium nitrate fertilizers containing more...

  9. 49 CFR 176.415 - Permit requirements for Division 1.5, ammonium nitrates, and certain ammonium nitrate fertilizers.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... nitrates, and certain ammonium nitrate fertilizers. 176.415 Section 176.415 Transportation Other... requirements for Division 1.5, ammonium nitrates, and certain ammonium nitrate fertilizers. (a) Except as... Captain of the Port (COTP). (1) Ammonium nitrate UN1942, ammonium nitrate fertilizers containing more...

  10. 49 CFR 176.415 - Permit requirements for Division 1.5, ammonium nitrates, and certain ammonium nitrate fertilizers.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... nitrates, and certain ammonium nitrate fertilizers. 176.415 Section 176.415 Transportation Other... requirements for Division 1.5, ammonium nitrates, and certain ammonium nitrate fertilizers. (a) Except as... Captain of the Port (COTP). (1) Ammonium nitrate UN1942, ammonium nitrate fertilizers containing more...

  11. 49 CFR 176.415 - Permit requirements for Division 1.5, ammonium nitrates, and certain ammonium nitrate fertilizers.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... nitrates, and certain ammonium nitrate fertilizers. 176.415 Section 176.415 Transportation Other... requirements for Division 1.5, ammonium nitrates, and certain ammonium nitrate fertilizers. (a) Except as... Captain of the Port (COTP). (1) Ammonium nitrate UN1942, ammonium nitrate fertilizers containing more...

  12. Ultrafast photoinduced charge transport in Pt(II) donor-acceptor assembly bearing naphthalimide electron acceptor and phenothiazine electron donor.

    PubMed

    Sazanovich, Igor V; Best, Jonathan; Scattergood, Paul A; Towrie, Michael; Tikhomirov, Sergei A; Bouganov, Oleg V; Meijer, Anthony J H M; Weinstein, Julia A

    2014-12-21

    Visible light-induced charge transfer dynamics were investigated in a novel transition metal triad acceptor-chromophore-donor, (NDI-phen)Pt(II)(-C≡C-Ph-CH2-PTZ)2 (1), designed for photoinduced charge separation using a combination of time-resolved infrared (TRIR) and femtosecond electronic transient absorption (TA) spectroscopy. In 1, the electron acceptor is 1,4,5,8-naphthalene diimide (NDI), and the electron donor is phenothiazine (PTZ), and [(phen)Pt(-C≡C-Ph-)], where phen is 1,10-phenanthroline, represents the chromophoric core. The first excited state observed in 1 is a (3)MLCT/LL'CT, with {Pt(II)-acetylide}-to-phen character. Following that, charge transfer from the phen-anion onto the NDI subunit to form NDI(-)-phen-[Pt-(C≡C)2](+)-PTZ2 occurs with a time constant of 2.3 ps. This transition is characterised by appearance of the prominent NDI-anion features in both TRIR and TA spectra. The final step of the charge separation in 1 proceeds with a time constant of ∼15 ps during which the hole migrates from the [Pt-(C≡C)2] subunit to one of the PTZ groups. Charge recombination in 1 then occurs with two distinct time constants of 36 ns and 107 ns, corresponding to the back electron transfer to each of the two donor groups; a rather rare occurrence which manifests that the hole in the final charge-separated state is localised on one of the two donor PTZ groups. The assignment of the nature of the excited states and dynamics in 1 was assisted by TRIR investigations of the analogous previously reported ((COOEt)2bpy)Pt(C≡C-Ph-CH2-PTZ)2 (2), (J. E. McGarrah and R. Eisenberg, Inorg. Chem., 2003, 42, 4355; J. E. McGarrah, J. T. Hupp and S. N. Smirnov, J. Phys. Chem. A, 2009, 113, 6430) as well as (bpy)Pt(C≡C-Ph-C7H15)2, which represent the acceptor-free dyad, and the chromophoric core, respectively. Thus, the step-wise formation of the full charge-separated state on the picosecond time scale and charge recombination via tunnelling have been established; and

  13. Sensitivity of nitrate aerosols to ammonia emissions and to nitrate chemistry: implications for present and future nitrate optical depth

    NASA Astrophysics Data System (ADS)

    Paulot, F.; Ginoux, P.; Cooke, W. F.; Donner, L. J.; Fan, S.; Lin, M.-Y.; Mao, J.; Naik, V.; Horowitz, L. W.

    2016-02-01

    We update and evaluate the treatment of nitrate aerosols in the Geophysical Fluid Dynamics Laboratory (GFDL) atmospheric model (AM3). Accounting for the radiative effects of nitrate aerosols generally improves the simulated aerosol optical depth, although nitrate concentrations at the surface are biased high. This bias can be reduced by increasing the deposition of nitrate to account for the near-surface volatilization of ammonium nitrate or by neglecting the heterogeneous production of nitric acid to account for the inhibition of N2O5 reactive uptake at high nitrate concentrations. Globally, uncertainties in these processes can impact the simulated nitrate optical depth by up to 25 %, much more than the impact of uncertainties in the seasonality of ammonia emissions (6 %) or in the uptake of nitric acid on dust (13 %). Our best estimate for fine nitrate optical depth at 550 nm in 2010 is 0.006 (0.005-0.008). In wintertime, nitrate aerosols are simulated to account for over 30 % of the aerosol optical depth over western Europe and North America. Simulated nitrate optical depth increases by less than 30 % (0.0061-0.010) in response to projected changes in anthropogenic emissions from 2010 to 2050 (e.g., -40 % for SO2 and +38 % for ammonia). This increase is primarily driven by greater concentrations of nitrate in the free troposphere, while surface nitrate concentrations decrease in the midlatitudes following lower concentrations of nitric acid. With the projected increase of ammonia emissions, we show that better constraints on the vertical distribution of ammonia (e.g., convective transport and biomass burning injection) and on the sources and sinks of nitric acid (e.g., heterogeneous reaction on dust) are needed to improve estimates of future nitrate optical depth.

  14. Therapeutic effects of inorganic nitrate and nitrite in cardiovascular and metabolic diseases.

    PubMed

    Omar, S A; Webb, A J; Lundberg, J O; Weitzberg, E

    2016-04-01

    Nitric oxide (NO) is generated endogenously by NO synthases to regulate a number of physiological processes including cardiovascular and metabolic functions. A decrease in the production and bioavailability of NO is a hallmark of many major chronic diseases including hypertension, ischaemia-reperfusion injury, atherosclerosis and diabetes. This NO deficiency is mainly caused by dysfunctional NO synthases and increased scavenging of NO by the formation of reactive oxygen species. Inorganic nitrate and nitrite are emerging as substrates for in vivo NO synthase-independent formation of NO bioactivity. These anions are oxidation products of endogenous NO generation and are also present in the diet, with green leafy vegetables having a high nitrate content. The effects of nitrate and nitrite are diverse and include vasodilatation, improved endothelial function, enhanced mitochondrial efficiency and reduced generation of reactive oxygen species. Administration of nitrate or nitrite in animal models of cardiovascular disease shows promising results, and clinical trials are currently ongoing to investigate the therapeutic potential of nitrate and nitrite in hypertension, pulmonary hypertension, peripheral artery disease and myocardial infarction. In addition, the nutritional aspects of the nitrate-nitrite-NO pathway are interesting as diets suggested to protect against cardiovascular disease, such as the Mediterranean diet, are especially high in nitrate. Here, we discuss the potential therapeutic opportunities for nitrate and nitrite in prevention and treatment of cardiovascular and metabolic diseases.

  15. Efficiency improvement of new Tetrathienoacene-based dyes by enhancing donor, acceptor and bridge units, a theoretical study

    NASA Astrophysics Data System (ADS)

    Tavangar, Zahra; Zareie, Nazanin

    2016-10-01

    A series of metal free Tetrathienoacene-based (TTA-based) organic dyes are designed and investigated as sensitizers for application in dye sensitized solar cells (DSSCs). Density function theory and time dependent density function theory calculations were performed on these dyes at vacuum and orthodichlorobenzene as the solvent. Effects of changing π-conjugation bridges and different functional groups in acceptor and donor units were investigated. UV-Vis absorption spectra were simulated to show the wavelength shifting and absorption properties. Inserting nitro and acyl chloride functional groups in acceptor and NH2 in donor units leads to the reduction of HOMO-LUMO gap by lowering the lowest unoccupied molecular orbital (LUMO) energy level and raising the highest occupied molecular orbital (HOMO) energy level and the increase in effective parameters in DSSC' efficiency. The results show that changing spacer units from thiophene to furan has a great effect on electronic structure and absorption spectra. Investigation of the electron distributions of frontier orbitals shows the HOMO and LUMO localization in donor and acceptor, respectively. Some key parameters that were studied here include light harvesting efficiency, free energy of electron injection and open circuit photo-voltage.

  16. Shared-intermediates in the biosynthesis of thio-cofactors: Mechanism and functions of cysteine desulfurases and sulfur acceptors.

    PubMed

    Black, Katherine A; Dos Santos, Patricia C

    2015-06-01

    Cysteine desulfurases utilize a PLP-dependent mechanism to catalyze the first step of sulfur mobilization in the biosynthesis of sulfur-containing cofactors. Sulfur activation and integration into thiocofactors involve complex mechanisms and intricate biosynthetic schemes. Cysteine desulfurases catalyze sulfur-transfer reactions from l-cysteine to sulfur acceptor molecules participating in the biosynthesis of thio-cofactors, including Fe-S clusters, thionucleosides, thiamin, biotin, and molybdenum cofactor. The proposed mechanism of cysteine desulfurases involves the PLP-dependent cleavage of the C-S bond from l-cysteine via the formation of a persulfide enzyme intermediate, which is considered the hallmark step in sulfur mobilization. The subsequent sulfur transfer reaction varies with the class of cysteine desulfurase and sulfur acceptor. IscS serves as a mecca for sulfur incorporation into a network of intertwined pathways for the biosynthesis of thio-cofactors. The involvement of a single enzyme interacting with multiple acceptors, the recruitment of shared-intermediates partaking roles in multiple pathways, and the participation of Fe-S enzymes denote the interconnectivity of pathways involving sulfur trafficking. In Bacillus subtilis, the occurrence of multiple cysteine desulfurases partnering with dedicated sulfur acceptors partially deconvolutes the routes of sulfur trafficking and assigns specific roles for these enzymes. Understanding the roles of promiscuous vs. dedicated cysteine desulfurases and their partnership with shared-intermediates in the biosynthesis of thio-cofactors will help to map sulfur transfer events across interconnected pathways and to provide insight into the hierarchy of sulfur incorporation into biomolecules. This article is part of a Special Issue entitled: Fe/S proteins: Analysis, structure, function, biogenesis and diseases.

  17. Crystallization of sodium nitrate from radioactive waste

    SciTech Connect

    Krapukhin, V.B.; Krasavina, E.P. Pikaev, A.K.

    1997-07-01

    From the 1940s to the 1980s, the Institute of Physical Chemistry of the Russian Academy of Sciences (IPC/RAS) conducted research and development on processes to separate acetate and nitrate salts and acetic acid from radioactive wastes by crystallization. The research objective was to decrease waste volumes and produce the separated decontaminated materials for recycle. This report presents an account of the IPC/RAS experience in this field. Details on operating conditions, waste and product compositions, decontamination factors, and process equipment are described. The research and development was generally related to the management of intermediate-level radioactive wastes. The waste solutions resulted from recovery and processing of uranium, plutonium, and other products from irradiated nuclear fuel, neutralization of nuclear process solutions after extractant recovery, regeneration of process nitric acid, equipment decontamination, and other radiochemical processes. Waste components include nitric acid, metal nitrate and acetate salts, organic impurities, and surfactants. Waste management operations generally consist of two stages: volume reduction and processing of the concentrates for storage, solidification, and disposal. Filtration, coprecipitation, coagulation, evaporation, and sorption were used to reduce waste volume. 28 figs., 40 tabs.

  18. Optimization of a uranyl nitrate passive neutron counter

    SciTech Connect

    Rauch, Eric Benton; Bracken, David; West, James; Freeman, Corey; Newell, Matthew R; Bourret, Steven C; Rothrock, Richard B; Ladd - Lively, Jennifer L; Schuh, Denise

    2010-01-01

    Safeguarding natural uranium as it enters the fuel cycle has become a priority for the safeguards community in recent years. Uranyl nitrate is a material of interest in this endeavor because it is normally a step in the process from converting uranium ores to more concentrated forms like UO{sub 2} and U{sub 3}O{sub 8}. This paper will detail the improvements and design optimizations made for a uranyl nitrate neutron detector. The original design of the detector was based on standard neutron counter designs and featured 2 rings of He-3 tubes fully moderated and shielded from background. Several areas for enhancement were identified after months of testing in three different locations. An operating uranyl nitrate facility was included as one of the test locations. Three significant upgrades to the counter addressed in the redesign were: real time background detection, counter reliability improvements, and optimization of the detector design for the detection of neutrons emitted by the uranyl nitrate flowing through the monitored process pipe. The optimized detector design includes significant electronics upgrades, the ability to detect neutrons (background and signal) with 36 degree spatial resolution around the process pipe for signal and 45 degree spatial resolution for background, inner and outer rings of He-3 tubes for real time background corrections, and notably more reliable cabling. Monte Carlo N-Particle (MCNP) modeling was used to optimize the signal (neutrons from uranyl nitrate in the monitored process pipe) to noise (background neutrons from all sources) ratio of the inner ring of He-3 tubes. Additionally, MCNP modeling maximized noise to signal on the outer ring of He-3 tubes. Details of the detector optimization as well as all the additional detector enhancements will be discussed. The neutron counter will be field tested on the Uranyl Nitrate Calibration Loop Equipment (UNCLE) facility at Oak Ridge National Laboratory (ORNL).

  19. Mesophilic, Circumneutral Anaerobic Iron Oxidation as a Remediation Mechanism for Radionuclides, Nitrate and Perchlorate

    NASA Astrophysics Data System (ADS)

    Bose, S.; Thrash, J. C.; Coates, J. D.

    2008-12-01

    Iron oxidation is a novel anaerobic metabolism where microorganisms obtain reducing equivalents from the oxidization of Fe(II) and assimilate carbon from organic carbon compounds or CO2. Recent evidence indicates that in combination with the activity of dissimilatory Fe(III)-reducing bacteria, anaerobic microbial Fe(II) oxidation can also contribute to the global iron redox cycle. Studies have also proved that Fe(II)- oxidation is ubiquitous in diverse environments and produce a broad range of insoluble iron forms as end products. These biogenic Fe(III)-oxides and mixed valence Fe minerals have a very high adsorption capacity of heavy metals and radionuclides. Adsorption and immobilization by these biogenic Fe phases produced at circumneutral pH, is now considered a very effective mode of remediation of radionuclides like Uranium, especially under variable redox conditions. By coupling soluble and insoluble Fe(II) oxidation with nitrate and perchlorate as terminal electron acceptors in-situ, anaerobic Fe-oxidation can also be used for environmental cleanup of Fe through Fe-mineral precipitation, as well as nitrate and perchlorate through reduction. Coupling of Fe as the sole electron and energy source to the reduction of perchlorate or nitrate boosts the metabolism without building up biomass hence also taking care of biofouling. To understand the mechanisms by which microorganisms can grow at circumneutral pH by mesophilic, anaerobic iron oxidation and the ability of microorganisms to reduce nitrate and perchlorate coupled to iron oxidation recent work in our lab involved the physiological characterization of Dechlorospirillum strain VDY which was capable of anaerobic iron-oxidation with either nitrate or perchlorate serving as terminal electron acceptor. Under non-growth conditions, VDY oxidized 3mM Fe(II) coupled to nitrate reduction, and 2mM Fe(II) coupled to perchlorate reduction, in 24 hours. It contained a copy of the RuBisCO cbbM subunit gene which was

  20. Contrasting performance of donor-acceptor copolymer pairs in ternary blend solar cells and two-acceptor copolymers in binary blend solar cells.

    PubMed

    Khlyabich, Petr P; Rudenko, Andrey E; Burkhart, Beate; Thompson, Barry C

    2015-02-01

    Here two contrasting approaches to polymer-fullerene solar cells are compared. In the first approach, two distinct semi-random donor-acceptor copolymers are blended with phenyl-C61-butyric acid methyl ester (PC61BM) to form ternary blend solar cells. The two poly(3-hexylthiophene)-based polymers contain either the acceptor thienopyrroledione (TPD) or diketopyrrolopyrrole (DPP). In the second approach, semi-random donor-acceptor copolymers containing both TPD and DPP acceptors in the same polymer backbone, termed two-acceptor polymers, are blended with PC61BM to give binary blend solar cells. The two approaches result in bulk heterojunction solar cells that have the same molecular active-layer components but differ in the manner in which these molecular components are mixed, either by physical mixing (ternary blend) or chemical "mixing" in the two-acceptor (binary blend) case. Optical properties and photon-to-electron conversion efficiencies of the binary and ternary blends were found to have similar features and were described as a linear combination of the individual components. At the same time, significant differences were observed in the open-circuit voltage (Voc) behaviors of binary and ternary blend solar cells. While in case of two-acceptor polymers, the Voc was found to be in the range of 0.495-0.552 V, ternary blend solar cells showed behavior inherent to organic alloy formation, displaying an intermediate, composition-dependent and tunable Voc in the range from 0.582 to 0.684 V, significantly exceeding the values achieved in the two-acceptor containing binary blend solar cells. Despite the differences between the physical and chemical mixing approaches, both pathways provided solar cells with similar power conversion efficiencies, highlighting the advantages of both pathways toward highly efficient organic solar cells.

  1. Rovibronic Variational Calculations of the Nitrate Radical

    NASA Astrophysics Data System (ADS)

    Changala, Bryan; Baraban, Joshua H.; Stanton, John F.

    2015-06-01

    In recent years, sophisticated diabatic Hamiltonians have been developed in order to understand the low-energy vibronic level structure of the nitrate radical (NO_3), which exhibits strong coupling between the ~X and doubly degenerate ~B states. Previous studies have reproduced the observed vibronic level positions up to 2000 wn~above the zero-point level, yet the rotational structure has remained uninvestigated with ab initio methods. In this talk, we present calculations of the N≥0 rovibronic structure of low-lying vibronic states of NO_3, in which complicated rovibrational and Coriolis interactions have been observed. Our results include calculations using both adiabatic and diabatic Hamiltonians, enabling a direct comparison between the two. We discuss extensions of our treatment to include spin-orbit and spin-rotation effects.

  2. Photoaffinity labelling of methyltransferase enzymes with S-adenosylmethionine: effects of methyl acceptor substrates.

    PubMed

    Hurst, J H; Billingsley, M L; Lovenberg, W

    1984-07-31

    Radioactivity from 3H-[methyl]-S-adenosyl-L-methionine (AdoMet) was covalently bound to protein-O-carboxylmethyltransferase and phenylethanolamine N-methyltransferase following 10-15 min irradiation by short-wave ultraviolet light. This photoaffinity binding of 3H-[methyl]-AdoMet was blocked by S-adenosylhomocysteine and sinefungin, but was not affected by 5 mM dithiothreitol. The binding was also inhibited by including methyl acceptors such as calmodulin (protein-O-carboxylmethyltransferase) or phenylethanolamine (phenylethanolamine N-methyltransferase) in the photoaffinity incubation. Staphlococcus V8 protease digests of 3H-[methyl]-AdoMet/enzyme complexes revealed that the primary structure around the AdoMet binding site is different in these two enzymes. Thus, protein-O-carboxylmethyltransferase, a large molecule methyltransferase, can covalently bind 3H-[methyl]-AdoMet in a manner similar to that of phenylethanolamine-N-methyltransferase.

  3. Physical and reactive extraction equilibria of penicillin G in a hydrogen-bond acceptor solvent system.

    PubMed

    Lee, Sang Cheol

    2006-01-01

    Physical and reactive extraction equilibria of penicillin G were investigated experimentally and theoretically in the existence of n-butyl acetate as a hydrogen-bond acceptor solvent. Physical extraction equilibrium experiments were carried out varying the pH of aqueous phase and overall penicillin concentration. We compared the experimental data with the calculated results from four physical extraction equilibrium models suggested here and obtained the most reasonable model. Also, penicillin G was reactively extracted using Amberlite LA-2 in n-butyl acetate. The experimental variables were pH of the aqueous phase, overall amine concentration, and overall penicillin concentration. A combined equilibrium model including our physical extraction equilibrium expression and the reactive extraction equilibrium expression suggested by Reschke and Schügerl was used so as to analyze the current reactive extraction equilibrium system. The calculated results from the reactive extraction equilibrium model were in good agreement with the experimental data.

  4. Ultrafast electron transfer in all-carbon-based SWCNT-C60 donor-acceptor nanoensembles connected by poly(phenylene-ethynylene) spacers

    NASA Astrophysics Data System (ADS)

    Barrejón, Myriam; Gobeze, Habtom B.; Gómez-Escalonilla, María J.; Fierro, José Luis G.; Zhang, Minfang; Yudasaka, Masako; Iijima, Sumio; D'Souza, Francis; Langa, Fernando

    2016-08-01

    Building all-carbon based functional materials for light energy harvesting applications could be a solution to tackle and reduce environmental carbon output. However, development of such all-carbon based donor-acceptor hybrids and demonstration of photoinduced charge separation in such nanohybrids is a challenge since in these hybrids part of the carbon material should act as an electron donating or accepting photosensitizer while the second part should fulfil the role of an electron acceptor or donor. In the present work, we have successfully addressed this issue by synthesizing covalently linked all-carbon-based donor-acceptor nanoensembles using single-walled carbon nanotubes (SWCNTs) as the donor and C60 as the acceptor. The donor-acceptor entities in the nanoensembles were connected by phenylene-ethynylene spacer units to achieve better electronic communication and to vary the distance between the components. These novel SWCNT-C60 nanoensembles have been characterized by a number of techniques, including TGA, FT-IR, Raman, AFM, absorbance and electrochemical methods. The moderate number of fullerene addends present on the side-walls of the nanotubes largely preserved the electronic structure of the nanotubes. The thermodynamic feasibility of charge separation in these nanoensembles was established using spectral and electrochemical data. Finally, occurrence of ultrafast electron transfer from the excited nanotubes in these donor-acceptor nanohybrids has been established by femtosecond transient absorption studies, signifying their utility in building light energy harvesting devices.Building all-carbon based functional materials for light energy harvesting applications could be a solution to tackle and reduce environmental carbon output. However, development of such all-carbon based donor-acceptor hybrids and demonstration of photoinduced charge separation in such nanohybrids is a challenge since in these hybrids part of the carbon material should act as an

  5. Fresh look at electron-transfer mechanisms via the donor/acceptor bindings in the critical encounter complex.

    PubMed

    Rosokha, Sergiy V; Kochi, Jay K

    2008-05-01

    . First, Q < 1 identifies one extreme mechanism owing to slow electron-transfer rates that result from the dominance of the intrinsic activation barrier (lambdaT) between the encounter and successor complexes. At the other extreme of Q > or = 1, the overwhelming dominance of the resonance stabilization (H(DA)) predicts the odd-electron mobility between the donor and acceptor to occur without an activation barrier such that bimolecular electron transfer is coincident with their diffusional encounter. In between lies a potentially infinite set of states, 0 < Q < 1 with opposing attractive and destabilizing forces that determine the location of the bound transition states along the reaction coordinate. Three prototypical potential-energy surfaces evolve as a result of progressively increasing the donor/acceptor bindings (H(DA)) extant in the precursor complex (at constant lambdaT). In these cases, the "outer-sphere" mechanism is limited by the weak donor/acceptor coupling that characterizes the now classical Marcus outer-sphere mechanism. Next, the "inner-sphere" mechanism derives from moderate (localized) donor/acceptor bindings and includes the mechanistic concept of the bridged-activated complex introduced by Taube for a wide variety of ligand-based redox dyads. Finally, the "interior" mechanism is also another subclass of the Taube (inner-sphere) classification, and it lies at the other extreme of very fast electron-transfer rate processes (heretofore unrecognized), arising from the spontaneous annihilation of the donor/acceptor dyad to the delocalized (electron-transfer) complex as it descends barrierlessly into the chemical "black hole" that is rate-limited solely by diffusion. PMID:18380446

  6. Nitrate deposition and impact on Adirondack streams

    SciTech Connect

    Simonin, H.A.; Kretser, W.A.

    1997-12-31

    Acidic deposition has a great impact on water chemistry and fish populations in the Adirondack region. Although the Clean Air Act Amendments of 1990 have resulted in some reductions of sulfate deposition, nitrate deposition has not yet been well controlled, and continues to impact aquatic resources. As part of the USEPA funded Episodic Response Project four Adirondack headwater streams were intensively monitored over an 18 month period. Atmospheric deposition was also monitored at a centrally located station. The quantity of nitrate being deposited on the study watersheds was calculated based on monthly net deposition data which ranged from 0.6 kg/ha/month to 3.6 kg/ha/month. These data were then compared to the monthly export of nitrate from the watershed in these streams. Nitrate concentrations were highest in the streamwater during the spring snowmelt period prior to the time when forest vegetation actively utilizes nitrate. On an annual basis the amount of nitrate which left the watershed via stream water exceeded the amount which fell as nitrate deposition. These data are important in documenting the impact of nitrate in the acidification of Adirondack streams during the spring, which coincides with brook trout hatching. Control programs for nitrous oxide emissions are presently aimed at reducing ozone levels during the May-September period. These emissions control programs need to be expanded to also reduce nitrate deposition in the sensitive Adirondack region during the winter and spring periods when nitrate deposition has its greatest impact on aquatic resources.

  7. Isolation and preliminary characterization of a respiratory nitrate reductase from hydrocarbon-degrading bacterium Gordonia alkanivorans S7.

    PubMed

    Romanowska, Irena; Kwapisz, Ewa; Mitka, Magdalena; Bielecki, Stanisław

    2010-06-01

    Gordonia alkanivorans S7 is an efficient degrader of fuel oil hydrocarbons that can simultaneously utilize oxygen and nitrate as electron acceptors. The respiratory nitrate reductase (Nar) from this organism has been isolated using ion exchange chromatography and gel filtration, and then preliminarily characterized. PAGE, SDS-PAGE and gel filtration chromatography revealed that Nar consisted of three subunits of 103, 53 and 25 kDa. The enzyme was optimally active at pH 7.9 and 40 degrees C. K(m) values for NO(3)(-) (110 microM) and for ClO(3)(-) (138 microM) were determined for a reduced viologen as an electron donor. The purified Nar did not use NADH as the electron donor to reduce nitrate or chlorate. Azide was a strong inhibitor of its activity. Our results imply that enzyme isolated from G. alkanivorans S7 is a respiratory membrane-bound nitrate reductase. This is the first report of purification of a nitrate reductase from Gordonia species.

  8. Tracking sources of unsaturated zone and groundwater nitrate contamination using nitrogen and oxygen stable isotopes at the Hanford site, Washington.

    PubMed

    Singleton, Michael J; Woods, Katharine N; Conrad, Mark E; Depaolo, Donald J; Dresel, P Evan

    2005-05-15

    The nitrogen and oxygen isotopic compositions of nitrate in pore water extracts from unsaturated zone (UZ) core samples and groundwater samples indicate at least four potential sources of nitrate in groundwaters at the U.S. DOE Hanford Site in south-central Washington. Natural sources of nitrate identified include microbially produced nitrate from the soil column (delta15N of 4 - 8 per thousand, delta18O of -9 to 2 per thousand) and nitrate in buried caliche layers (delta15N of 0-8 per thousand, delta 18O of -6to 42 per thousand). Isotopically distinctindustrial sources of nitrate include nitric acid in low-level disposal waters (delta15N approximately per thousand, delta 18O approximately 23%o) per thousandnd co-contaminant nitrate in high-level radioactive waste from plutonium processing (6'5delta1of 8-33 % o, per thousand18delta oO -9 to 7%0). per thousandThe isotopic compositions of nitrate from 97 groundwater wells with concentrations up to 1290 mg/L NO3- have been analyzed. Stable isotope analyses from this study site, which has natural and industrial nitrate sources, provide a tool to distinguish nitrate sources in an unconfined aquiferwhere concentrations alone do not. These data indicate that the most common sources of high nitrate concentrations in groundwater at Hanford are nitric acid and natural nitrate flushed out of the UZ during disposal of low-level wastewater. Nitrate associated with high-level radioactive UZ contamination does not appear to be a major source of groundwater nitrate at this time.

  9. Induction of the Nitrate Assimilation nirA Operon and Protein-Protein Interactions in the Maturation of Nitrate and Nitrite Reductases in the Cyanobacterium Anabaena sp. Strain PCC 7120

    PubMed Central

    Frías, José E.

    2015-01-01

    ABSTRACT Nitrate is widely used as a nitrogen source by cyanobacteria, in which the nitrate assimilation structural genes frequently constitute the so-called nirA operon. This operon contains the genes encoding nitrite reductase (nirA), a nitrate/nitrite transporter (frequently an ABC-type transporter; nrtABCD), and nitrate reductase (narB). In the model filamentous cyanobacterium Anabaena sp. strain PCC 7120, which can fix N2 in specialized cells termed heterocysts, the nirA operon is expressed at high levels only in media containing nitrate or nitrite and lacking ammonium, a preferred nitrogen source. Here we examined the genes downstream of the nirA operon in Anabaena and found that a small open reading frame of unknown function, alr0613, can be cotranscribed with the operon. The next gene in the genome, alr0614 (narM), showed an expression pattern similar to that of the nirA operon, implying correlated expression of narM and the operon. A mutant of narM with an insertion mutation failed to produce nitrate reductase activity, consistent with the idea that NarM is required for the maturation of NarB. Both narM and narB mutants were impaired in the nitrate-dependent induction of the nirA operon, suggesting that nitrite is an inducer of the operon in Anabaena. It has previously been shown that the nitrite reductase protein NirA requires NirB, a protein likely involved in protein-protein interactions, to attain maximum activity. Bacterial two-hybrid analysis confirmed possible NirA-NirB and NarB-NarM interactions, suggesting that the development of both nitrite reductase and nitrate reductase activities in cyanobacteria involves physical interaction of the corresponding enzymes with their cognate partners, NirB and NarM, respectively. IMPORTANCE Nitrate is an important source of nitrogen for many microorganisms that is utilized through the nitrate assimilation system, which includes nitrate/nitrite membrane transporters and the nitrate and nitrite reductases. Many

  10. Formate Metabolism in Shewanella oneidensis Generates Proton Motive Force and Prevents Growth without an Electron Acceptor

    PubMed Central

    Kane, Aunica L.; Brutinel, Evan D.; Joo, Heena; Maysonet, Rebecca; VanDrisse, Chelsey M.; Kotloski, Nicholas J.

    2016-01-01

    ABSTRACT Shewanella oneidensis strain MR-1 is a facultative anaerobe that thrives in redox-stratified environments due to its ability to utilize a wide array of terminal electron acceptors. Conversely, the electron donors utilized by S. oneidensis are more limited and include products of primary fermentation such as lactate, pyruvate, formate, and hydrogen. Lactate, pyruvate, and hydrogen metabolisms in S. oneidensis have been described previously, but little is known about the role of formate oxidation in the ecophysiology of these bacteria. Formate is produced by S. oneidensis through pyruvate formate lyase during anaerobic growth on carbon sources that enter metabolism at or above the level of pyruvate, and the genome contains three gene clusters predicted to encode three complete formate dehydrogenase complexes. To determine the contribution of each complex to formate metabolism, strains lacking one, two, or all three annotated formate dehydrogenase gene clusters were generated and examined for growth rates and yields on a variety of carbon sources. Here, we report that formate oxidation contributes to both the growth rate and yield of S. oneidensis through the generation of proton motive force. Exogenous formate also greatly accelerated growth on N-acetylglucosamine, a carbon source normally utilized very slowly by S. oneidensis under anaerobic conditions. Surprisingly, deletion of all three formate dehydrogenase gene clusters enabled growth of S. oneidensis using pyruvate in the absence of a terminal electron acceptor, a mode of growth never before observed in these bacteria. Our results demonstrate that formate oxidation is a fundamental strategy under anaerobic conditions for energy conservation in S. oneidensis. IMPORTANCE Shewanella species have garnered interest in biotechnology applications for their ability to respire extracellular terminal electron acceptors, such as insoluble iron oxides and electrodes. While much effort has gone into studying the

  11. Nitrates

    MedlinePlus

    ... or interactions with other medicines and vitamin or herbal supplements. This information should not be used as medical ... your doctor about every medicine and vitamin or herbal supplement that you are taking, so he or she ...

  12. The effect of intermolecular donor?acceptor energy transfer on emission anisotropy in uniaxially oriented polymer films

    NASA Astrophysics Data System (ADS)

    Sadownik, M.; Bojarski, Piotr

    2004-10-01

    Excitation energy transport between donors and acceptors is studied for uniaxially stretched and unstretched poly(vinyl) alcohol films. Donor emission anisotropy courses versus acceptor concentration as well as donor-acceptor emission anisotropy spectra occurred quite different in stretched and unstretched films. Upon donor excitation the total emission anisotropy rapidly decreases when passing from the donor to the acceptor fluorescence band in disordered systems. However, such a pronounced effect has not been found in partly ordered films. Donors and acceptors exhibit highly preferential mutual orientation in strongly ordered films resulting in the preservation of acceptor emission anisotropy.

  13. Excitation energy transfer in partly ordered polymer films differing in donor and acceptor transition moments orientation

    NASA Astrophysics Data System (ADS)

    Synak, A.; Bojarski, P.; Sadownik, M.; Kułak, L.; Gryczynski, I.; Grobelna, B.; Rangełowa-Jankowska, S.; Jankowski, D.; Kubicki, A.

    2016-09-01

    Based on spectroscopic measurements selected properties of nonradiative Förster energy transport are studied in uniaxially stretched polyvinyl alcohol thin films for three systems differing in donor and acceptor transition moments orientation relative to the axis of stretching. In particular, donor - acceptor emission anisotropy spectra yield completely different regularities for these systems in uniaxially stretched films, whereas they are similar in unstretched films. In particular it is shown that acceptor fluorescence can be either strongly polarized after nonradiative energy transfer in stretched films or depolarized depending on the angular distribution of acceptor transition moments in the matrix. Donor and acceptor emission anisotropy decays exhibit similar regularities to those of steady-state measurements. The obtained results are analyzed with the help of Monte Carlo simulations.

  14. Ultrasound-modulated fluorescence based on donor-acceptor-labeled microbubbles

    PubMed Central

    Liu, Yuan; Feshitan, Jameel A.; Wei, Ming-Yuan; Borden, Mark A.; Yuan, Baohong

    2015-01-01

    Abstract. A fluorescence resonance energy transfer (FRET)-based microbubble contrast agent system was designed to experimentally demonstrate the concept of ultrasound-modulated fluorescence (UMF). Microbubbles were simultaneously labeled with donor and acceptor fluorophores on the surface to minimize self-quenching and maximize FRET. In response to ultrasound, the quenching efficiency was greatly modulated by changing the distance between the donor and acceptor molecules through microbubble size oscillations. Both donors and acceptors exhibited UMF on individual microbubbles. The UMF strength of the donor was more significant compared to that of the acceptor. Furthermore, the UMF of the donor was observed from a microbubble solution in a turbid media. This study exploits the feasibility of donor–acceptor labeled microbubbles as UMF contrast agents. PMID:25789423

  15. Regulation of human dihydrodiol dehydrogenase by Michael acceptor xenobiotics.

    PubMed

    Ciaccio, P J; Jaiswal, A K; Tew, K D

    1994-06-01

    A human oxidoreductase (H-37) that is overexpressed in ethacrynic acid-resistant HT29 colon cells (Ciaccio, P. J., Stuart, J.E., and Tew, K.D. (1993) Mol. Pharmacol. 43, 845-853) has been identified as a dihydrodiol dehydrogenase. Translated protein from a dihydrodiol dehydrogenase cDNA isolated from a library prepared from ethacrynic acid-resistant HT29 cell poly(A+) RNA was recognized by anti-H-37 IgG and was identical in molecular weight with H-37. The isolated cDNA was identical in both nucleotide and amino acid sequences with the recently cloned liver dihydrodiol dehydrogenase (Stolz, A., Hammond, L., Lou, H., Takikawa, H., Ronk, M., and Shively, J.E. (1993) J. Biol. Chem. 268, 10448-10457). Using this cDNA as probe, we have examined its induction by Michael acceptors. The steady state dihydrodiol dehydrogenase mRNA level in the ethacrynic acid-resistant line was increased 30-fold relative to that of wild-type cells. Twenty-four hour treatment of wild-type cells with ethacrynic acid or dimethyl maleate increased mRNA 10-fold and 5-fold, respectively. These changes are accompanied by both increased protein expression and increased NADP-dependent 1-acenaphthenol oxidative activity in cell cytosol. In gel shift assays, compared to wild type controls, increased binding of NAD(P)H quinone oxidoreductase human antioxidant response element (hARE) DNA to redox labile protein complexes present in treated and resistant cell nuclear extract was observed. Ethacrynic acid induced CAT activity 2-fold in Hepa1 cells stably transfected with NAD(P)H quinone oxidoreductase hARE-tk-CAT chimeric gene construct. Thus, dihydrodiol dehydrogenase protein is inducible by de novo synthesis from mRNA by structurally related monofunctional inducer Michael acceptors. Altered in vitro binding of nuclear protein to the hARE is indirect evidence for the involvement of an element similar to hARE in the regulation of dihydrodiol dehydrogenase by these agents. PMID:7515059

  16. The Abundance and Activity of Nitrate-Reducing Microbial Populations in Estuarine Sediments

    NASA Astrophysics Data System (ADS)

    Cardarelli, E.; Francis, C. A.

    2014-12-01

    Estuaries are productive ecosystems that ameliorate nutrient and metal contaminants from surficial water supplies. At the intersection of terrestrial and aquatic environments, estuarine sediments host major microbially-mediated geochemical transformations. These include denitrification (the conversion of nitrate to nitrous oxide and/or dinitrogen) and dissimilatory nitrate reduction to ammonium (DNRA). Denitrification has historically been seen as the predominant nitrate attenuation process and functions as an effective sink for nitrate. DNRA has previously been believed to be a minor nitrate reduction process and transforms nitrate within the ecosystem to ammonium, a more biologically available N species. Recent studies have compared the two processes in coastal environments and determined fluctuating environmental conditions may suppress denitrification, supporting an increased role for DNRA in the N cycle. Nitrate availability and salinity are factors thought to influence the membership of the microbial communities present, and the nitrate reduction process that predominates. The aim of this study is to investigate how nitrate concentration and salinity alter the transcript abundances of N cycling functional gene markers for denitrification (nirK, nirS) and DNRA (nrfA) in estuarine sediments at the mouth of the hypernutrified Old Salinas River, CA. Short-term whole core incubations amended with artificial freshwater/artificial seawater (2 psu, 35 psu) and with varying NO3- concentrations (200mM, 2000mM) were conducted to assess the activity as well as the abundance of the nitrate-reducing microbial populations present. Gene expression of nirK, nirS, and nrfA at the conclusion of the incubations was quantified using reverse transcription quantitative polymerase chain reaction (RT-qPCR). High abundances of nirK, nirS, and nrfA under particular conditions coupled with the resulting geochemical data ultimately provides insight onto how the aforementioned factors

  17. Effects of Atmospheric Nitrate on an Upland Stream of the Northeastern USA

    NASA Astrophysics Data System (ADS)

    Sebestyen, S. D.; Shanley, J. B.; Boyer, E. W.; Kendall, C.

    2009-05-01

    Excess nitrogen cascades through terrestrial biogeochemical cycles and affects stream nitrate concentrations in upland forests where atmospheric deposition is an important source of anthropogenic nitrogen. We will discuss approaches including high-frequency sampling, isotopic tracers, and end-member mixing analysis that can be used to decipher the sources, transformations, and hydrological processes that affect nitrate transport through forested upland catchments to streams. We present results of studies at the Sleepers River Research Watershed in Vermont, USA, a site where we have intensively measured stream nitrate concentrations during baseflow and stormflow. Stream nitrate concentrations are typically low and nearly 75% of annual inorganic N inputs from atmospheric deposition are retained within the catchment. However, high concentrations and stream loadings of nitrate occur during storm events due to source variation and hydrological flushing of nitrate from catchment soils. Using isotopic tracers and end-member mixing analysis, we have quantified source inputs of unprocessed atmospheric nitrate and show that this stream is directly affected by nitrogen pollution. Using a long-term record of stream hydrochemistry and our findings on event- scale nitrate flushing dynamics, we then explore how stream nitrate loading may respond to anthropogenic climate forcing during the next century. Results suggest that stream runoff and nitrate loadings will change during future emission scenarios (i.e. longer growing seasons and higher winter precipitation rates). Understanding the timing and magnitude of hydrological and hydrochemical responses is important because climate change effects on catchment hydrology may alter how nitrate is retained, produced, and hydrologically flushed in headwater ecosystems with implications for aquatic metabolism, nutrient export from catchments, and downstream eutrophication.

  18. Past and future direct radiative forcing of nitrate aerosol in East Asia

    NASA Astrophysics Data System (ADS)

    Li, Jiandong; Wang, Wei-Chyung; Liao, Hong; Chang, Wenyuan

    2015-08-01

    Nitrate as a rapidly increasing aerosol species in recent years affects the present climate and potentially has large implications on the future climate. In this study, the long-term direct radiative forcing (DRF) of nitrate aerosol is investigated using State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG) atmospheric general circulation model (AGCM) and the aerosol dataset simulated by a chemical transport model with focus on East Asia. The DRF due to other aerosols, especially sulfate, is also evaluated for comparisons. Although the chemical transport model underestimates the magnitudes of nitrate and sulfate aerosols when compared with Chinese site observations, some insights into the significances of nitrate climate effects still emerge. The present-day global annual mean all-sky DRF of nitrate is calculated to be -0.025 W m-2 relative to the preindustrial era, which is much weaker than -0.37 W m-2 for sulfate. However, nitrate DRF may become increasingly important in the future especially over East Asia, given the expectation that decreasing trend in global sulfate continues while the projected nitrate maintains at the present level for a mid-range forcing scenario and even be a factor of two larger by the end of the 21st century for high emission scenarios. For example, the anthropogenic nitrate DRF of -2.0 W m-2 over eastern China could persist until the 2050s, and nitrate is projected to account for over 60 % of total anthropogenic aerosol DRF over East Asia by 2100. In addition, we illustrate that the regional nitrate DRF and its seasonal variation are sensitive to meteorological parameters, in particular the relative humidity and cloud amount. It thus remains a need for climate models to include more realistically nitrate aerosol in projecting future climate changes.

  19. Potential importance of physiologically diverse benthic foraminifera in sedimentary nitrate storage and respiration

    NASA Astrophysics Data System (ADS)

    Bernhard, Joan M.; Casciotti, Karen L.; McIlvin, Matthew R.; Beaudoin, David J.; Visscher, Pieter T.; Edgcomb, Virginia P.

    2012-09-01

    Until recently, the process of denitrification (conversion of nitrate or nitrite to gaseous products) was thought to be performed exclusively by prokaryotes and fungi. The finding that foraminifera perform complete denitrification could impact our understanding of nitrate removal in sediments as well as our understanding of eukaryotic respiration, especially if it is widespread. However, details of this process and the subcellular location of these reactions in foraminifera remain uncertain. For example, prokaryotic endobionts, rather than the foraminifer proper, could perform denitrification, as has been shown recently in an allogromiid foraminifer. Here, intracellular nitrate concentrations and isotope ratios (δ15NNO3 and δ18ONO3) were measured to assess the nitrate dynamics in four benthic foraminiferal species (Bolivina argentea, Buliminella tenuata, Fursenkoina cornuta, Nonionella stella) with differing cellular architecture and associations with microbial endobionts, recovered from Santa Barbara Basin, California. Cellular nitrate concentrations were high (12-217 mM) in each species, and intracellular nitrate often had elevated δ15NNO3 and δ18ONO3 values. Experiments including suboxic and anoxic incubations of B. argentea revealed a decrease in intracellular nitrate concentration and an increase in δ15NNO3 and δ18ONO3over time, indicating nitrate respiration and/or denitrification within the foraminifera. Results illustrate that nitrate reduction occurs in a range of foraminiferal species, including some possessing endobionts (including a chloroplast-sequestering species) and others lacking endobionts, implying that microbial associates may not solely be responsible for this process in foraminifera. Furthermore, we show that benthic foraminifera may represent important reservoirs of nitrate storage in sediments, as well as mediators of its removal.

  20. Oxidation and mobilization of selenium by nitrate in irrigation drainage

    USGS Publications Warehouse

    Wright, W.G.

    1999-01-01

    Selenium (Se) can be oxidized by nitrate (NO3-) from irrigation on Cretaceous marine shale in western Colorado. Dissolved Se concentrations are positively correlated with dissolved NO3- concentrations in surface water and ground water samples from irrigated areas. Redox conditions dominate in the mobilization of Se in marine shale hydrogeologic settings; dissolved Se concentrations increase with increasing platinum-electrode potentials. Theoretical calculations for the oxidation of Se by NO3- and oxygen show favorable Gibbs free energies for the oxidation of Se by NO3-, indicating NO3- can act as an electron acceptor for the oxidation of Se. Laboratory batch experiments were performed by adding Mancos Shale samples to zero- dissolved-oxygen water containing 0, 5, 50, and 100 mg/L NO3- as N (mg N/L). Samples were incubated in airtight bottles at 25??C for 188 d; samples collected from the batch experiment bottles show increased Se concentrations over time with increased NO3- concentrations. Pseudo first-order rate constants for NO3- oxidation of Se ranged from 0.0007 to 0.0048/d for 0 to 100 mg N/L NO3- concentrations, respectively. Management of N fertilizer applications in Cretaceous shale settings might help to control the oxidation and mobilization of Se and other trace constituents into the environment.

  1. Nitrate removal in deep sediments of a nitrogen-rich river network: A test of a conceptual model

    USGS Publications Warehouse

    Stelzer, Robert S.; Bartsch, Lynn

    2012-01-01

    Many estimates of nitrogen removal in streams and watersheds do not include or account for nitrate removal in deep sediments, particularly in gaining streams. We developed and tested a conceptual model for nitrate removal in deep sediments in a nitrogen-rich river network. The model predicts that oxic, nitrate-rich groundwater will become depleted in nitrate as groundwater upwelling through sediments encounters a zone that contains buried particulate organic carbon, which promotes redox conditions favorable for nitrate removal. We tested the model at eight sites in upwelling reaches of lotic ecosystems in the Waupaca River Watershed that varied by three orders of magnitude in groundwater nitrate concentration. We measured denitrification potential in sediment core sections to 30 cm and developed vertical nitrate profiles to a depth of about 1 m with peepers and piezometer nests. Denitrification potential was higher, on average, in shallower core sections. However, core sections deeper than 5 cm accounted for 70%, on average, of the depth-integrated denitrification potential. Denitrification potential increased linearly with groundwater nitrate concentration up to 2 mg NO3-N/L but the relationship broke down at higher concentrations (> 5 mg NO3-N/L), a pattern that suggests nitrate saturation. At most sites groundwater nitrate declined from high concentrations at depth to much lower concentrations prior to discharge into the surface water. The profiles suggested that nitrate removal occurred at sediment depths between 20 and 40 cm. Dissolved oxygen concentrations were much higher in deep sediments than in pore water at 5 cm sediment depth at most locations. The substantial denitrification potential in deep sediments coupled with the declines in nitrate and dissolved oxygen concentrations in upwelling groundwater suggest that our conceptual model for nitrate removal in deep sediments is applicable to this river network. Our results suggest that nitrate removal rates

  2. Trend Analyses of Nitrate in Danish Groundwater

    NASA Astrophysics Data System (ADS)

    Hansen, B.; Thorling, L.; Dalgaard, T.; Erlandsen, M.

    2012-04-01

    This presentation assesses the long-term development in the oxic groundwater nitrate concentration and nitrogen (N) loss due to intensive farming in Denmark. Firstly, up to 20-year time-series from the national groundwater monitoring network enable a statistically systematic analysis of distribution, trends and trend reversals in the groundwater nitrate concentration. Secondly, knowledge about the N surplus in Danish agriculture since 1950 is used as an indicator of the potential loss of N. Thirdly, groundwater recharge CFC (Chlorofluorocarbon) age determination allows linking of the first two dataset. The development in the nitrate concentration of oxic groundwater clearly mirrors the development in the national agricultural N surplus, and a corresponding trend reversal is found in groundwater. Regulation and technical improvements in the intensive farming in Denmark have succeeded in decreasing the N surplus by 40% since the mid 1980s while at the same time maintaining crop yields and increasing the animal production of especially pigs. Trend analyses prove that the youngest (0-15 years old) oxic groundwater shows more pronounced significant downward nitrate trends (44%) than the oldest (25-50 years old) oxic groundwater (9%). This amounts to clear evidence of the effect of reduced nitrate leaching on groundwater nitrate concentrations in Denmark. Are the Danish groundwater monitoring strategy obtimal for detection of nitrate trends? Will the nitrate concentrations in Danish groundwater continue to decrease or are the Danish nitrate concentration levels now appropriate according to the Water Framework Directive?

  3. Measurement of isoprene nitrates by GCMS

    NASA Astrophysics Data System (ADS)

    Mills, Graham P.; Hiatt-Gipson, Glyn D.; Bew, Sean P.; Reeves, Claire E.

    2016-09-01

    According to atmospheric chemistry models, isoprene nitrates play an important role in determining the ozone production efficiency of isoprene; however this is very poorly constrained through observations as isoprene nitrates have not been widely measured. Measurements have been severely restricted largely due to a limited ability to measure individual isoprene nitrate isomers. An instrument based on gas chromatography/mass spectrometry (GCMS) and the associated calibration methods are described for the speciated measurements of individual isoprene nitrate isomers. Five of the primary isoprene nitrates which formed in the presence of NOx by reaction of isoprene with the hydroxyl radical (OH) in the Master Chemical Mechanism are identified using known isomers on two column phases and are fully separated on the Rtx-200 column. Three primary isoprene nitrates from the reaction of isoprene with the nitrate radical (NO3) are identified after synthesis from the already identified analogous hydroxy nitrate. A Tenax adsorbent-based trapping system allows the analysis of the majority of the known hydroxy and carbonyl primary isoprene nitrates, although not the (1,2)-IN isomer, under field-like levels of humidity and showed no impact from typical ambient concentrations of NOx and ozone.

  4. Groundwater nitrate contamination: factors and indicators.

    PubMed

    Wick, Katharina; Heumesser, Christine; Schmid, Erwin

    2012-11-30

    Identifying significant determinants of groundwater nitrate contamination is critical in order to define sensible agri-environmental indicators that support the design, enforcement, and monitoring of regulatory policies. We use data from approximately 1200 Austrian municipalities to provide a detailed statistical analysis of (1) the factors influencing groundwater nitrate contamination and (2) the predictive capacity of the Gross Nitrogen Balance, one of the most commonly used agri-environmental indicators. We find that the percentage of cropland in a given region correlates positively with nitrate concentration in groundwater. Additionally, environmental characteristics such as temperature and precipitation are important co-factors. Higher average temperatures result in lower nitrate contamination of groundwater, possibly due to increased evapotranspiration. Higher average precipitation dilutes nitrates in the soil, further reducing groundwater nitrate concentration. Finally, we assess whether the Gross Nitrogen Balance is a valid predictor of groundwater nitrate contamination. Our regression analysis reveals that the Gross Nitrogen Balance is a statistically significant predictor for nitrate contamination. We also show that its predictive power can be improved if we account for average regional precipitation. The Gross Nitrogen Balance predicts nitrate contamination in groundwater more precisely in regions with higher average precipitation.

  5. Groundwater nitrate contamination: Factors and indicators

    PubMed Central

    Wick, Katharina; Heumesser, Christine; Schmid, Erwin

    2012-01-01

    Identifying significant determinants of groundwater nitrate contamination is critical in order to define sensible agri-environmental indicators that support the design, enforcement, and monitoring of regulatory policies. We use data from approximately 1200 Austrian municipalities to provide a detailed statistical analysis of (1) the factors influencing groundwater nitrate contamination and (2) the predictive capacity of the Gross Nitrogen Balance, one of the most commonly used agri-environmental indicators. We find that the percentage of cropland in a given region correlates positively with nitrate concentration in groundwater. Additionally, environmental characteristics such as temperature and precipitation are important co-factors. Higher average temperatures result in lower nitrate contamination of groundwater, possibly due to increased evapotranspiration. Higher average precipitation dilutes nitrates in the soil, further reducing groundwater nitrate concentration. Finally, we assess whether the Gross Nitrogen Balance is a valid predictor of groundwater nitrate contamination. Our regression analysis reveals that the Gross Nitrogen Balance is a statistically significant predictor for nitrate contamination. We also show that its predictive power can be improved if we account for average regional precipitation. The Gross Nitrogen Balance predicts nitrate contamination in groundwater more precisely in regions with higher average precipitation. PMID:22906701

  6. Nitrogen-isotope ratios of nitrate in ground water under fertilized fields, Long Island, New York

    USGS Publications Warehouse

    Flipse, W.J.; Bonner, F.T.

    1985-01-01

    Ground-water samples from two heavily fertilized sites in Suffolk County, New York, were collected through the 1978 growing season and analyzed for nitrate-N concentrations and nitrogen-isotope ratios. Six wells were at a potato farm; six were on a golf course. The purpose of this study was to determine whether the 15N/14N ratios (??15N values) of fertilizer are increased during transit from land surface to ground water to an extent which would preclude use of this ratio to distinguish agricultural from animal sources of nitrate in ground water. Ground water at both sites contained a greater proportion of 15N than the fertilizers being applied. At the potato farm, the average ??15N value of the fertilizers was 0.2???; the average ??15N value of the ground-water nitrate was 6.2???. At the golf course, the average ??15N value of the fertilizers was -5.9???, and that of ground-water nitrate was 6.5???. The higher ??15N values of ground-water nitrate are probably caused by isotopic fractionation during the volatile loss of ammonia from nitrogen applied in reduced forms (NH4+ and organic-N). The ??15N values of most ground-water samples from both areas were less than 10???, the upper limit of the range characteristic of agricultural sources of nitrate; these sources include both fertilizer nitrate and nitrate derived from increased mineralization of soil nitrogen through cultivation. Previous studies have shown that the ??15N values of nitrate derived from human or animal waste generally exceed 10???. The nitrogen-isotope ratios of fertilizer-derived nitrate were not altered to an extent that would make them indistinguishable from animal-waste-derived nitrates in ground water.Ground-water samples from two heavily fertilized sites in Suffolk County, New York, were collected through the 1978 growing season and analyzed for nitrate-N concentrations and nitrogen-isotope ratios. Six wells were at a potato farm; six were on a golf course. The purpose of this study was to

  7. The distribution and modeling of nitrate transport in the Carson Valley alluvial aquifer, Douglas County, Nevada

    USGS Publications Warehouse

    Naranjo, Ramon C.; Welborn, Toby L.; Rosen, Michael R.

    2013-01-01

    The distribution of nitrate as nitrogen (referred to herein as nitrate-N) concentrations in groundwater was determined by collecting more than 200 samples from 8 land-use categories: single family residential, multifamily residential, rural (including land use for agriculture), vacant land, commercial, industrial, utilities, and unclassified. Nitrate-N concentrations ranged from below detection (less than 0.05 milligrams per liter) to 18 milligrams per liter. The results of nitrate-N concentrations that were sampled from three wells equalled or exceeded the maximum contaminant level of 10 milligrams per liter set by the U.S. Environmental Protection Agency. Nitrate-N concentrations in sampled wells showed a positive correlation between elevated nitrate-N concentrations and the percentage of single-family land use and septic-system density. Wells sampled in other land-use categories did not have any correlation to nitrate-N concentrations. In areas with greater than 50-percent single-family land use, nitrate-N concentrations were two times greater than in areas with less than 50 percent single-family land use. Nitrate-N concentrations in groundwater near septic systems that had been used more than 20 years were more than two times greater than in areas where septic systems had been used less than 20 years. Lower nitrate-N concentrations in the areas where septic systems were less than 20 years old probably result from temporary storage of nitrogen leaching from septic systems into the unsaturated zone. In areas where septic systems are abundant, nitrate-N concentrations were predicted to 2059 by using numerical models within the Ruhenstroth and Johnson Lane subdivisions in the Carson Valley. Model results indicated that nitrate-N concentrations will continue to increase and could exceed the maximum contaminant level over extended areas inside and outside the subdivisions. Two modeling scenarios were used to simulate future transport as a result of removal of septic

  8. Peroxynitrite: an endogenous oxidizing and nitrating agent.

    PubMed

    Ducrocq, C; Blanchard, B; Pignatelli, B; Ohshima, H

    1999-07-01

    Peroxynitrite, the reaction product between nitric oxide (.NO) and superoxide, has been presumed to be a mediator of cellular and tissue injury in various pathological situations. It is formed at the convergence of two independent radical-generating metabolic pathways. Its biological effects are due to its reactivity towards a large range of molecules including amino acids such as cysteine, methionine, tyrosine and tryptophan, nucleic bases and antioxidants (e.g. phenolics, selenium- and metal-containing compounds, ascorbate and urate). Peroxynitrite reactions involve oxidation and nitration. The chemical properties depend on the presence of CO2 and metallic compounds as well as the concentrations of reagents and kinetic laws. This complex chemistry can be explained by the formation of several structural forms and active intermediates released from peroxynitrite. PMID:10442088

  9. Removal of gadolinium nitrate from heavy water

    SciTech Connect

    Wilde, E.W.

    2000-03-22

    Work was conducted to develop a cost-effective process to purify 181 55-gallon drums containing spent heavy water moderator (D2O) contaminated with high concentrations of gadolinium nitrate, a chemical used as a neutron poison during former nuclear reactor operations at the Savannah River Site (SRS). These drums also contain low level radioactive contamination, including tritium, which complicates treatment options. Presently, the drums of degraded moderator are being stored on site. It was suggested that a process utilizing biological mechanisms could potentially lower the total cost of heavy water purification by allowing the use of smaller equipment with less product loss and a reduction in the quantity of secondary waste materials produced by the current baseline process (ion exchange).

  10. Risk assessment of nitrated polycyclic aromatic hydrocarbons

    SciTech Connect

    Moeller, L. ); Lax, I. ); Torndal, U.B.; Eriksson, L.C. )

    1993-06-01

    Nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) constitute a group of substances formed during incomplete combustion. Sources include diesel vehicles, heating, smoking, certain types of food-processing, and incomplete combustion in general. 2-Nitrofluorene (NF) represents a model substance for the nitro-PAHs. An attempt has been made to estimate the lifetime human cancer risk due to background exposure to nitro-PAHs by two different models. The first model is based on genotoxic lesions produced by gamma-irradiation and the second model is based on an earlier published mega study (24,000 animals) on the carcinogenicity of the major metabolite of NF. Both models agreed well -- representing a yearly human cancer risk in the range of 0.15--49 [times] 10[sup [minus]6] for an urban citizen. The weaknesses and strengths of the models are discussed. 55 refs., 3 figs.

  11. Potassium acceptor doping of ZnO crystals

    SciTech Connect

    Parmar, Narendra S. Lynn, K. G.; Corolewski, Caleb D.; McCluskey, Matthew D.

    2015-05-15

    ZnO bulk single crystals were doped with potassium by diffusion at 950°C. Positron annihilation spectroscopy confirms the filling of zinc vacancies and a different trapping center for positrons. Secondary ion mass spectroscopy measurements show the diffusion of potassium up to 10 μm with concentration ∼1 × 10{sup 16} cm{sup −3}. IR measurements show a local vibrational mode (LVM) at 3226 cm{sup −1}, at a temperature of 9 K, in a potassium doped sample that was subsequently hydrogenated. The LVM is attributed to an O–H bond-stretching mode adjacent to a potassium acceptor. When deuterium substitutes for hydrogen, a peak is observed at 2378 cm{sup −1}. The O-H peak is much broader than the O-D peak, perhaps due to an unusually low vibrational lifetime. The isotopic frequency ratio is similar to values found in other hydrogen complexes. Potassium doping increases the resistivity up to 3 orders of magnitude at room temperature. The doped sample has a donor level at 0.30 eV.

  12. Molecular insights into the terminal energy acceptor in cyanobacterial phycobilisome.

    PubMed

    Gao, Xiang; Wei, Tian-Di; Zhang, Nan; Xie, Bin-Bin; Su, Hai-Nan; Zhang, Xi-Ying; Chen, Xiu-Lan; Zhou, Bai-Cheng; Wang, Zhi-Xin; Wu, Jia-Wei; Zhang, Yu-Zhong

    2012-09-01

    The linker protein L(CM) (ApcE) is postulated as the major component of the phycobilisome terminal energy acceptor (TEA) transferring excitation energy from the phycobilisome to photosystem II. L(CM) is the only phycobilin-attached linker protein in the cyanobacterial phycobilisome through auto-chromophorylation. However, the underlying mechanism for the auto-chromophorylation of L(CM) and the detailed molecular architecture of TEA is still unclear. Here, we demonstrate that the N-terminal phycobiliprotein-like domain of L(CM) (Pfam00502, LP502) can specifically recognize phycocyanobilin (PCB) by itself. Biochemical assays indicated that PCB binds into the same pocket in LP502 as that in the allophycocyanin α-subunit and that Ser152 and Asp155 play a vital role in LP502 auto-chromophorylation. By carefully conducting computational simulations, we arrived at a rational model of the PCB-LP502 complex structure that was supported by extensive mutational studies. In the PCB-LP502 complex, PCB binds into a deep pocket of LP502 with a distorted conformation, and Ser152 and Asp155 form several hydrogen bonds to PCB fixing the PCB Ring A and Ring D. Finally, based on our results, the dipoles and dipole-dipole interactions in TEA are analysed and a molecular structure for TEA is proposed, which gives new insights into the energy transformation mechanism of cyanobacterial phycobilisome. PMID:22758351

  13. Swift Electrofluorochromism of Donor-Acceptor Conjugated Polytriphenylamines.

    PubMed

    Sun, Jingwei; Liang, Ziqi

    2016-07-20

    Electrofluorochromic (EFC) materials, which exhibit electrochemically controllable fluorescence, hold great promise in optoelectronic devices and biological analysis. Here we design such donor-acceptor (D-A) conjugated polymers-P(TPACO) and P(TCEC)-that contain the same electron-rich and oxidizable polytriphenylamine (PTPA) as π-backbone, yet with different electron-deficient ketone and cyano units as pendant groups, respectively. They both exhibit solvatochromic effects due to intrinsic characteristics of intramolecular charge transfer (ICT). Compared to P(TPACO), P(TCEC) shows stronger ICT, which leads to higher electrochemical oxidation potential and lower ion diffusion coefficient. Moreover, both polymers present simultaneous electrochromic (EC) and EFC behaviors with multistate display and remarkably rapid fluorescence response. The response time of P(TPACO) is as short as 0.19 s, nearly 4-fold faster than that of P(TCEC) (0.92 s). Such rapid response is found to be determined by the ion diffusion coefficient which is associated with the ICT nature. Finally, the EFC display device based on P(TPACO) is successfully demonstrated, which shows green fluorescence ON/OFF switching upon applied potentials. This work has successfully demonstrated that swift EFCs can be achieved by rational modulation of the ICT effect in such D-A conjugated polymers. PMID:27347724

  14. Poly(trifluoromethyl)azulenes: structures and acceptor properties

    SciTech Connect

    Clikeman, Tyler T.; Bukovsky, Eric V.; Kuvychko, Igor V.; San, Long K.; Deng, Shihu; Wang, Xue B.; Chen, Yu-Sheng; Strauss, Steven H.; Boltalina, Olga V.

    2014-07-10

    Azulene is a non-alternant, non-benzenoid aromatic hydrocarbon with an intense blue colour, a dipole moment of 1.0 D,1 positive electron affinity, and an “anomalous” emission from the second excited state in violation of Kasha’s rule.2,3 Azulene’s unique properties have potential uses in molecular switches,4,5 molecular diodes,6 organic photovoltaics,7 and charge transfer complexes.8-12 Introduction of electron-withdrawing groups to the azulenic core, such as CN,8,13,14 halogens,15-19 and CF3,20,21 can enhance certain electrical and photophysical properties. In this work, we report six new trifluoromethyl derivatives of azulene (AZUL), three isomers of AZUL(CF3)3 and three isomers of AZUL(CF3)4, and the first X-ray structure of a π-stacked donor-acceptor complex of a trifluoromethyl azulene with donor pyrene.

  15. Phase Diagram of Ammonium Nitrate

    NASA Astrophysics Data System (ADS)

    Dunuwille, Mihindra; Yoo, Choong-Shik

    2013-06-01

    Ammonium Nitrate (AN) has often been subjected to uses in improvised explosive devices, due to its wide availability as a fertilizer and its capability of becoming explosive with slight additions of organic and inorganic compounds. Yet, the origin of enhanced energetic properties of impure AN (or AN mixtures) is neither chemically unique nor well understood - resulting in rather catastrophic disasters in the past1 and thereby a significant burden on safety, in using ammonium nitrates even today. To remedy this situation, we have carried out an extensive study to investigate the phase stability of AN, in different chemical environments, at high pressure and temperature, using diamond anvil cells and micro-Raman spectroscopy. The present results confirm the recently proposed phase IV-to-IV' transition above 15 GPa2 and provide new constraints for the melting and phase diagram of AN to 40 GPa and 673 K. The present study has been supported by the U.S. DHS under Award Number 2008-ST-061-ED0001.

  16. Modeling the Current and Future Roles of Particulate Organic Nitrates in the Southeastern United States.

    PubMed

    Pye, Havala O T; Luecken, Deborah J; Xu, Lu; Boyd, Christopher M; Ng, Nga L; Baker, Kirk R; Ayres, Benjamin R; Bash, Jesse O; Baumann, Karsten; Carter, William P L; Edgerton, Eric; Fry, Juliane L; Hutzell, William T; Schwede, Donna B; Shepson, Paul B

    2015-12-15

    Organic nitrates are an important aerosol constituent in locations where biogenic hydrocarbon emissions mix with anthropogenic NOx sources. While regional and global chemical transport models may include a representation of organic aerosol from monoterpene reactions with nitrate radicals (the primary source of particle-phase organic nitrates in the Southeast United States), secondary organic aerosol (SOA) models can underestimate yields. Furthermore, SOA parametrizations do not explicitly take into account organic nitrate compounds produced in the gas phase. In this work, we developed a coupled gas and aerosol system to describe the formation and subsequent aerosol-phase partitioning of organic nitrates from isoprene and monoterpenes with a focus on the Southeast United States. The concentrations of organic aerosol and gas-phase organic nitrates were improved when particulate organic nitrates were assumed to undergo rapid (τ = 3 h) pseudohydrolysis resulting in nitric acid and nonvolatile secondary organic aerosol. In addition, up to 60% of less oxidized-oxygenated organic aerosol (LO-OOA) could be accounted for via organic nitrate mediated chemistry during the Southern Oxidants and Aerosol Study (SOAS). A 25% reduction in nitrogen oxide (NO + NO2) emissions was predicted to cause a 9% reduction in organic aerosol for June 2013 SOAS conditions at Centreville, Alabama.

  17. Modeling nitrate-nitrogen load reduction strategies for the des moines river, iowa using SWAT

    USGS Publications Warehouse

    Schilling, K.E.; Wolter, C.F.

    2009-01-01

    The Des Moines River that drains a watershed of 16,175 km2 in portions of Iowa and Minnesota is impaired for nitrate-nitrogen (nitrate) due to concentrations that exceed regulatory limits for public water supplies. The Soil Water Assessment Tool (SWAT) model was used to model streamflow and nitrate loads and evaluate a suite of basin-wide changes and targeting configurations to potentially reduce nitrate loads in the river. The SWAT model comprised 173 subbasins and 2,516 hydrologic response units and included point and nonpoint nitrogen sources. The model was calibrated for an 11-year period and three basin-wide and four targeting strategies were evaluated. Results indicated that nonpoint sources accounted for 95% of the total nitrate export. Reduction in fertilizer applications from 170 to 50 kg/ha achieved the 38% reduction in nitrate loads, exceeding the 34% reduction required. In terms of targeting, the most efficient load reductions occurred when fertilizer applications were reduced in subbasins nearest the watershed outlet. The greatest load reduction for the area of land treated was associated with reducing loads from 55 subbasins with the highest nitrate loads, achieving a 14% reduction in nitrate loads achieved by reducing applications on 30% of the land area. SWAT model results provide much needed guidance on how to begin implementing load reduction strategies most efficiently in the Des Moines River watershed. ?? 2009 Springer Science+Business Media, LLC.

  18. Application of classification-tree methods to identify nitrate sources in ground water

    USGS Publications Warehouse

    Spruill, T.B.; Showers, W.J.; Howe, S.S.

    2002-01-01

    A study was conducted to determine if nitrate sources in ground water (fertilizer on crops, fertilizer on golf courses, irrigation spray from hog (Sus scrofa) wastes, and leachate from poultry litter and septic systems) could be classified with 80% or greater success. Two statistical classification-tree models were devised from 48 water samples containing nitrate from five source categories. Model I was constructed by evaluating 32 variables and selecting four primary predictor variables (??15N, nitrate to ammonia ratio, sodium to potassium ratio, and zinc) to identify nitrate sources. A ??15N value of nitrate plus potassium 18.2 indicated inorganic or soil organic N. A nitrate to ammonia ratio 575 indicated nitrate from golf courses. A sodium to potassium ratio 3.2 indicated spray or poultry wastes. A value for zinc 2.8 indicated poultry wastes. Model 2 was devised by using all variables except ??15N. This model also included four variables (sodium plus potassium, nitrate to ammonia ratio, calcium to magnesium ratio, and sodium to potassium ratio) to distinguish categories. Both models were able to distinguish all five source categories with better than 80% overall success and with 71 to 100% success in individual categories using the learning samples. Seventeen water samples that were not used in model development were tested using Model 2 for three categories, and all were correctly classified. Classification-tree models show great potential in identifying sources of contamination and variables important in the source-identification process.

  19. Modeling nonpoint source nitrate contamination and associated uncertainty in groundwater of U.S. regional aquifers

    NASA Astrophysics Data System (ADS)

    Gurdak, J. J.; Lujan, C.

    2009-12-01

    Nonpoint source nitrate contamination in groundwater is spatially variable and can result in elevated nitrate concentrations that threaten drinking-water quality in many aquifers of the United States. Improved modeling approaches are needed to quantify the spatial controls on nonpoint source nitrate contamination and the associated uncertainty of predictive models. As part of the U.S. Geological Survey National Water Quality Assessment Program, logistic regression models were developed to predict nitrate concentrations greater than background in recently recharged (less than 50 years) groundwater in selected regional aquifer systems of the United States; including the Central Valley, California Coastal Basins, Basin and Range, Floridan, Glacial, Coastal Lowlands, Denver Basin, High Plains, North Atlantic Coastal Plain, and Piedmont aquifer systems. The models were used to evaluate the spatial controls of climate, soils, land use, hydrogeology, geochemistry, and water-quality conditions on nitrate contamination. The novel model Raster Error Propagation Tool (REPTool) was used to estimate error propagation and prediction uncertainty in the predictive nitrate models and to determine an approach to reduce uncertainty in future model development. REPTool consists of public-domain, Python-based packages that implement Latin Hypercube sampling within a probabilistic framework to track error propagation in geospatial models and quantitatively estimate the prediction uncertainty of the model output. The presented nitrate models, maps, and uncertainty analysis provide important tools for water-resource managers of regional groundwater systems to identify likely areas and the spatial controls on nonpoint source nitrate contamination in groundwater.

  20. Photolysis of Nitric Acid and Nitrate on Natural and Artificial Surfaces.

    PubMed

    Ye, Chunxiang; Gao, Honglian; Zhang, Ning; Zhou, Xianliang

    2016-04-01

    Photolysis of nitric acid and nitrate (HNO3/nitrate) was investigated on the surfaces of natural and artificial materials, including plant leaves, metal sheets, and construction materials. The surfaces were conditioned in the outdoor air prior to experiments to receive natural depositions of ambient HNO3/nitrate and other atmospheric constituents. The photolysis rate constant (JHNO3(s)) of the surface HNO3/nitrate was measured based on the production rates of nitrous acid (HONO) and nitrogen oxides (NOx). The JHNO3(s) values, from 6.0 × 10(-6) s(-1) to 3.7 × 10(-4) s(-1), are 1 to 3 orders of magnitude higher than that of gaseous HNO3. The HONO was the major product from photolysis of HNO3/nitrate on most plant leaves, whereas NOx was the major product on most artificial surfaces. The JHNO3(s) values decreased with HNO3/nitrate surface density and could be described by a simple analytical equation. Within a typical range of HNO3/nitrate surface density in the low-NOx forested areas, photolysis of HNO3/nitrate on the forest canopy can be a significant source for HONO and NOx for the overlying atmosphere. PMID:26936001

  1. Challenges with nitrate therapy and nitrate tolerance: prevalence, prevention, and clinical relevance.

    PubMed

    Thadani, Udho

    2014-08-01

    Nitrate therapy has been an effective treatment for ischemic heart disease for over 100 years. The anti-ischemic and exercise-promoting benefits of sublingually administered nitrates are well established. Nitroglycerin is indicated for the relief of an established attack of angina and for prophylactic use, but its effects are short lived. In an effort to increase the duration of beneficial effects, long-acting orally administered and topical applications of nitrates have been developed; however, following their continued or frequent daily use, patients soon develop tolerance to these long-acting nitrate preparations. Once tolerance develops, patients begin losing the protective effects of the long-acting nitrate therapy. By providing a nitrate-free interval, or declining nitrate levels at night, one can overcome or reduce the development of tolerance, but cannot provide 24-h anti-anginal and anti-ischemic protection. In addition, patients may be vulnerable to occurrence of rebound angina and myocardial ischemia during periods of absent nitrate levels at night and early hours of the morning, and worsening of exercise capacity prior to the morning dose of the medication. This has been a concern with nitroglycerin patches but not with oral formulations of isosorbide-5 mononitrates, and has not been adequately studied with isosorbide dinitrate. This paper describes problems associated with nitrate tolerance, reviews mechanisms by which nitrate tolerance and loss of efficacy develop, and presents strategies to avoid nitrate tolerance and maintain efficacy when using long-acting nitrate formulations.

  2. Arabidopsis Nitrate Transporter NRT1.9 Is Important in Phloem Nitrate Transport[W][OA

    PubMed Central

    Wang, Ya-Yun; Tsay, Yi-Fang

    2011-01-01

    This study of the Arabidopsis thaliana nitrate transporter NRT1.9 reveals an important function for a NRT1 family member in phloem nitrate transport. Functional analysis in Xenopus laevis oocytes showed that NRT1.9 is a low-affinity nitrate transporter. Green fluorescent protein and β-glucuronidase reporter analyses indicated that NRT1.9 is a plasma membrane transporter expressed in the companion cells of root phloem. In nrt1.9 mutants, nitrate content in root phloem exudates was decreased, and downward nitrate transport was reduced, suggesting that NRT1.9 may facilitate loading of nitrate into the root phloem and enhance downward nitrate transport in roots. Under high nitrate conditions, the nrt1.9 mutant showed enhanced root-to-shoot nitrate transport and plant growth. We conclude that phloem nitrate transport is facilitated by expression of NRT1.9 in root companion cells. In addition, enhanced root-to-shoot xylem transport of nitrate in nrt1.9 mutants points to a negative correlation between xylem and phloem nitrate transport. PMID:21571952

  3. REDUCTION OF NITRATE THROUGH THE USE OF NITRATE REDUCTASE FOR THE SMARTCHEM AUTOANALYZER

    EPA Science Inventory

    The standard method for the determination of nitrate in drinking water, USEPA Method 353.2 “Determination of Nitrate-Nitrite by Automated Colorimetry,” employs cadmium as the reductant for the conversion of nitrate to nitrite. The nitrite is then analyzed colorimetrically by way ...

  4. Removal of Nitrate from Groundwater by Cyanobacteria: Quantitative Assessment of Factors Influencing Nitrate Uptake

    PubMed Central

    Hu, Qiang; Westerhoff, Paul; Vermaas, Wim

    2000-01-01

    The feasibility of biologically removing nitrate from groundwater was tested by using cyanobacterial cultures in batch mode under laboratory conditions. Results demonstrated that nitrate-contaminated groundwater, when supplemented with phosphate and some trace elements, can be used as growth medium supporting vigorous growth of several strains of cyanobacteria. As cyanobacteria grew, nitrate was removed from the water. Of three species tested, Synechococcus sp. strain PCC 7942 displayed the highest nitrate uptake rate, but all species showed rapid removal of nitrate from groundwater. The nitrate uptake rate increased proportionally with increasing light intensity up to 100 μmol of photons m−2 s−1, which parallels photosynthetic activity. The nitrate uptake rate was affected by inoculum size (i.e., cell density), fixed-nitrogen level in the cells in the inoculum, and aeration rate, with vigorously aerated, nitrate-sufficient cells in mid-logarithmic phase having the highest long-term nitrate uptake rate. Average nitrate uptake rates up to 0.05 mM NO3− h−1 could be achieved at a culture optical density at 730 nm of 0.5 to 1.0 over a 2-day culture period. This result compares favorably with those reported for nitrate removal by other cyanobacteria and algae, and therefore effective nitrate removal from groundwater using this organism could be anticipated on large-scale operations. PMID:10618214

  5. Rates of primary electron transfer reactions in the photosystem I reaction center reconstituted with different quinones as the secondary acceptor

    SciTech Connect

    Kumazaki, Shigeichi; Kandori, Hideki; Yoshihara, Keitaro ); Iwaki, Masayo; Itoh, Shigeru ); Ikegamu, Isamu )

    1994-10-27

    Rates of sequential electron transfer reactions from the primary electron donor chlorophyll dimer (P700) to the electron acceptor chlorophyll a-686 (A[sub 0]) and to the secondary acceptor quinone (Q[sub [phi

  6. Removal of multiple electron acceptors by pilot-scale, two-stage membrane biofilm reactors.

    PubMed

    Zhao, He-Ping; Ontiveros-Valencia, Aura; Tang, Youneng; Kim, Bi-O; Vanginkel, Steven; Friese, David; Overstreet, Ryan; Smith, Jennifer; Evans, Patrick; Krajmalnik-Brown, Rosa; Rittmann, Bruce

    2014-05-01

    We studied the performance of a pilot-scale membrane biofilm reactor (MBfR) treating groundwater containing four electron acceptors: nitrate (NO3(-)), perchlorate (ClO4(-)), sulfate (SO4(2-)), and oxygen (O2). The treatment goal was to remove ClO4(-) from ∼200 μg/L to less than 6 μg/L. The pilot system was operated as two MBfRs in series, and the positions of the lead and lag MBfRs were switched regularly. The lead MBfR removed at least 99% of the O2 and 63-88% of NO3(-), depending on loading conditions. The lag MBfR was where most of the ClO4(-) reduction occurred, and the effluent ClO4(-) concentration was driven to as low as 4 μg/L, with most concentrations ≤10 μg/L. However, SO4(2-) reduction occurred in the lag MBfR when its NO3(-) + O2 flux was smaller than ∼0.18 g H2/m(2)-d, and this was accompanied by a lower ClO4(-) flux. We were able to suppress SO4(2-) reduction by lowering the H2 pressure and increasing the NO3(-) + O2 flux. We also monitored the microbial community using the quantitative polymerase chain reaction targeting characteristic reductase genes. Due to regular position switching, the lead and lag MBfRs had similar microbial communities. Denitrifying bacteria dominated the biofilm when the NO3(-) + O2 fluxes were highest, but sulfate-reducing bacteria became more important when SO4(2-) reduction was enhanced in the lag MBfR due to low NO3(-) + O2 flux. The practical two-stage strategy to achieve complete ClO4(-) and NO3(-) reduction while suppressing SO4(2-) reduction involved controlling the NO3(-) + O2 surface loading between 0.18 and 0.34 g H2/m(2)-d and using a low H2 pressure in the lag MBfR.

  7. Alkyl Nitrates and Oxidized Volatile Organic Compounds during NACHTT: Influence on Reactive Chlorine Activation

    NASA Astrophysics Data System (ADS)

    Swarthout, R.; Sive, B. C.; Russo, R. S.; Zhou, Y.

    2011-12-01

    Recent studies have suggested that reactive chlorine species can contribute substantially to the oxidative capacity of the atmosphere and also influence tropospheric ozone chemistry in areas far from dominant marine sources. The photochemical processing of polluted air masses containing can potentially affect the formation of chlorine radical (Cl) through various processes involving hydrocarbons and NOx (NO + NO2). Organic peroxy radicals can react with nitric oxide (NO) to form alkyl nitrates or to produce nitrogen dioxide (NO2) and oxygenated volatile organic compounds (OVOCs), including alcohols, aldehydes and ketones. Aldehydes can further react with NO2 to form peroxyacyl nitrates (PAN). Alkyl nitrates and PAN can serve as reservoirs for long range transport of NOx and can influence Cl production in remote areas. In order to further elucidate the influence of OVOCs and alkyl nitrates on chlorine activation processes, whole air samples were collected hourly during the Nitrogen, Aerosol Composition and Halogens on a Tall Tower (NACHTT) campaign at the Boulder Atmospheric Observatory in Erie, Colorado from February 18 through March 11, 2011. Profile samples up to 250 m were also collected throughout the campaign. Samples were analyzed for a comprehensive suite of volatile organic compounds, including OVOCs and C1 to C5 alkyl nitrates, using a five channel gas chromatographic analytical system. Alkyl nitrates and OVOCs were abundant throughout the campaign. Total alkyl nitrate mixing ratios ranged from 13 to 227 pptv with 2-butyl nitrate and 2-propyl nitrate accounting for over half of this total. Ethanol was the most abundant OVOC followed by methanol with median mixing ratios of 8.5 ppbv and 5.6 ppbv, respectively. This presentation will focus on the influence the observed alkyl nitrate and OVOC mixing ratios and air mass photochemical processing on Cl cycling.

  8. Heat transfer behavior of molten nitrate salt

    NASA Astrophysics Data System (ADS)

    Das, Apurba K.; Clark, Michael M.; Teigen, Bard C.; Fiveland, Woodrow A.; Anderson, Mark H.

    2016-05-01

    The usage of molten nitrate salt as heat transfer fluid and thermal storage medium decouples the generation of electricity from the variable nature of the solar resource, allowing CSP plants to avoid curtailment and match production with demand. This however brings some unique challenges for the design of the molten salt central receiver (MSCR). An aspect critical to the use of molten nitrate (60wt%/40wt% - NaNO3/KNO3) salt as heat transfer fluid in the MSCR is to understand its heat transfer behavior. Alstom collaborated with the University of Wisconsin to conduct a series of experiments and experimentally determined the heat transfer coefficients of molten nitrate salt up to high Reynolds number (Re > 2.0E5) and heat flux (q″ > 1000 kW/m2), conditions heretofore not reported in the literature. A cartridge heater instrumented with thermocouples was installed inside a stainless steel pipe to form an annular test section. The test section was installed in the molten salt flow loop at the University of Wisconsin facility, and operated over a range of test conditions to determine heat transfer data that covered the expected operating regime of a practical molten salt receiver. Heat transfer data were compared to widely accepted correlations found in heat transfer literature, including that of Gnielinski. At lower Reynolds number conditions, the results from this work concurred with the molten salt heat transfer data reported in literature and followed the aforementioned correlations. However, in the region of interest for practical receiver design, the correlations did not accurately model the experimentally determined heat transfer data. Two major effects were observed: (i) all other factors remaining constant, the Nusselt numbers gradually plateaued at higher Reynolds number; and (ii) at higher Reynolds number a positive interaction of heat flux on Nusselt number was noted. These effects are definitely not modeled by the existing correlations. In this paper a new

  9. Safety in the Chemical Laboratory: Nitric Acid, Nitrates, and Nitro Compounds.

    ERIC Educational Resources Information Center

    Bretherick, Leslie

    1989-01-01

    Discussed are the potential hazards associated with nitric acid, inorganic and organic nitrate salts, alkyl nitrates, acyl nitrates, aliphatic nitro compounds, aromatic nitro compounds, and nitration reactions. (CW)

  10. Fluorinated arene, imide and unsaturated pyrrolidinone based donor acceptor conjugated polymers: Synthesis, structure-property and device studies

    NASA Astrophysics Data System (ADS)

    Liyanage, Arawwawala Don Thilanga

    After the discovery of doped polyacetylene, organic semiconductor materials are widely studied as high impending active components in consumer electronics. They have received substantial consideration due to their potential for structural tailoring, low cost, large area and mechanically flexible alternatives to common inorganic semiconductors. To acquire maximum use of these materials, it is essential to get a strong idea about their chemical and physical nature. Material chemist has an enormous role to play in this novel area, including development of efficient synthetic methodologies and control the molecular self-assembly and (opto)-electronic properties. The body of this thesis mainly focuses on the substituent effects: how different substituents affect the (opto)-electronic properties of the donor-acceptor (D-A) conjugated polymers. The main priority goes to understand, how different alkyl substituent effect to the polymer solubility, crystallinity, thermal properties (e.g.: glass transition temperature) and morphological order. Three classes of D-A systems were extensively studied in this work. The second chapter mainly focuses on the synthesis and structure-property study of fluorinated arene (TFB) base polymers. Here we used commercially available 1,4-dibromo-2,3,5,6-tetrafluorobenzene (TFB) as the acceptor material and prepare several polymers using 3,3'-dialkyl(3,3'-R2T2) or 3,3'-dialkoxy bithiophene (3,3'-RO2T2) units as electron donors. A detail study was done using 3,3'-bithiophene donor units incorporating branched alkoxy-functionalities by systematic variation of branching position and chain length. The study allowed disentangling the branching effects on (i) aggregation tendency, intermolecular arrangement, (iii) solid state optical energy gaps, and (iv) electronic properties in an overall consistent picture, which might guide future polymer synthesis towards optimized materials for opto-electronic applications. The third chapter mainly focused on

  11. Gene and protein expression profiles of Shewanella oneidensis during anaerobic growth with different electron acceptors.

    SciTech Connect

    Beliaev, A. S.; Thompson, D. K.; Khare, T.; Lim, H.; Brandt, C. C.; Li, G.; Murray, A. E.; Heidelberg, J. F.; Giometti, C. S.; Yates, J., III; Nealson, K. H.; Tiedje, J. M.; Zhou, J.; Biosciences Division; ORNL; Scripps Research Inst.; Michigan State Univ.; The Inst. for Genomic Research; Jet Propulsion Laboratory; California Inst. of Tech.

    2002-01-01

    Changes in mRNA and protein expression profiles of Shewanella oneidenesis MR-1 during switch from aerobic to fumarate-, Fe(III)-, or nitrate-reducing conditions were examined using DNA microarrays and two-dimensional polyacrylamide gel electrophoresis (2-D PAGE). In response to changes in growth conditions, 121 of the 691 arrayed genes displayed at least a two-fold difference in transcript abundance as determined by microarray analysis. Genes involved in aerobic respiration encoding cytochrome c and d oxidases and TCA cycle enzymes were repressed under anaerobic conditions. Genes induced during anaerobic respiration included those involved in cofactor biosynthesis and assembly (moaACE, ccmHF, nosD, cysG), substrate transport (cysUP, cysTWA, dcuB), and anaerobic energy metabolism (dmsAB, psrC, pshA, hyaABC, hydA). Transcription of genes encoding a periplasmic nitrate reductase (napBHGA), cytochrome c{sub 552}, and prismane was elevated 8- to 56-fold in response to the presence of nitrate, while cymA, ifcA, and frdA were specifically induced three- to eightfold under fumarate-reducing conditions. The mRNA levels for two oxidoreductase-like genes of unknown function and several cell envelope genes involved in multidrug resistance increased two- to fivefold specifically under Fe(III)-reducing conditions. Analysis of protein expression profiles under aerobic and anaerobic conditions revealed 14 protein spots that showed significant differences in abundance on 2-D gels. Protein identification by mass spectrometry indicated that the expression of prismane, dihydrolipoamide succinyltransferase, and alcaligin siderophore biosynthesis protein correlated with the microarray data.

  12. Gene and protein expression profiles of Shewanella oneidensis during anaerobic growth with different electron acceptors.

    PubMed

    Beliaev, Alex S; Thompson, Dorothea K; Khare, Tripti; Lim, Hanjo; Brandt, Craig C; Li, Guangshan; Murray, Alison E; Heidelberg, John F; Giometti, Carol S; Yates, John; Nealson, Kenneth H; Tiedje, James M; Zhoui, Jizhong

    2002-01-01

    Changes in mRNA and protein expression profiles of Shewanella oneidenesis MR-1 during switch from aerobic to fumarate-, Fe(III)-, or nitrate-reducing conditions were examined using DNA microarrays and two-dimensional polyacrylamide gel electrophoresis (2-D PAGE). In response to changes in growth conditions, 121 of the 691 arrayed genes displayed at least a two-fold difference in transcript abundance as determined by microarray analysis. Genes involved in aerobic respiration encoding cytochrome c and d oxidases and TCA cycle enzymes were repressed under anaerobic conditions. Genes induced during anaerobic respiration included those involved in cofactor biosynthesis and assembly (moaACE, ccmHF, nosD, cysG), substrate transport (cysUP, cysTWA, dcuB), and anaerobic energy metabolism (dmsAB, psrC, pshA, hyaABC, hydA). Transcription of genes encoding a periplasmic nitrate reductase (napBHGA), cytochrome c552, and prismane was elevated 8- to 56-fold in response to the presence of nitrate, while cymA, ifcA, and frdA were specifically induced three- to eightfold under fumarate-reducing conditions. The mRNA levels for two oxidoreductase-like genes of unknown function and several cell envelope genes involved in multidrug resistance increased two- to fivefold specifically under Fe(III)-reducing conditions. Analysis of protein expression profiles under aerobic and anaerobic conditions revealed 14 protein spots that showed significant differences in abundance on 2-D gels. Protein identification by mass spectrometry indicated that the expression of prismane, dihydrolipoamide succinyltransferase, and alcaligin siderophore biosynthesis protein correlated with the microarray data. PMID:11881834

  13. Different responses to nitrate and nitrite by the model organism Escherichia coli and the human pathogen Neisseria gonorrhoeae.

    PubMed

    Whitehead, R N; Cole, J A

    2006-02-01

    The ability of Escherichia coli to use both nitrate and nitrite as terminal electron acceptors during anaerobic growth is mediated by the dual-acting two-component regulatory systems NarX-NarL and NarQ-NarP. In contrast, Neisseria gonorrhoeae responds only to nitrite: it expresses only NarQ-NarP. We have shown that although N. gonorrhoeae NarQ can phosphorylate E. coli NarL and NarP, the N. gonorrhoeae NarP is unable to regulate gene expression in E. coli. Mutagenesis experiments have revealed residues in E. coli NarQ that are essential for nitrate and nitrite sensing. Chimaeric proteins revealed domains of NarQ that are important for ligand sensing.

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

    PubMed Central

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

    2014-01-01

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

  15. Temporal patterns of tyrosine nitration in embryo heart development

    PubMed Central

    Viera, Liliana; Radmilovich, Milka; Vargas, Marcelo R.; Dennys, Cassandra N.; Wilson, Landon; Barnes, Stephen; Franco, Maria Clara; Beckman, Joseph S.; Estévez, Alvaro G.

    2012-01-01

    Tyrosine nitration is a biomarker for the production of peroxynitrite and other reactive nitrogen species. Nitrotyrosine immunoreactivity is present in many pathological conditions including several cardiac diseases. Because the events observed during heart failure may recapitulate some aspects of development, we tested whether nitrotyrosine is present during normal development of the rat embryo heart and its potential relationship in cardiac remodeling through apoptosis. Nitric oxide (NO) production is highly dynamic during development, but whether peroxynitrite and nitrotyrosine are formed during normal embryonic development has received little attention. Rat embryo hearts exhibited strong nitrotyrosine immunoreactivity in endocardial and myocardial cells of the atria and ventricles from E12 to E18. After E18, nitrotyrosine staining faded and disappeared entirely by birth. Tyrosine nitration in the myocardial tissue coincided with elevated protein expression of nitric oxide synthases (eNOS and iNOS). The immunoreactivity for these NOS isoforms remained elevated even after nitrotyrosine had disappeared. Tyrosine nitration did not correlate with cell death or proliferation of cardiac cells. Analysis of tryptic peptides by MALDI-TOF shows that nitration occurs in actin, myosin, and the mitochondrial ATP synthase alpha chain. These results suggest that reactive nitrogen species are not restricted to pathological conditions but may play a role during normal embryonic development. PMID:23195686

  16. Desferrioxamine Inhibits Protein Tyrosine Nitration: Mechanisms and Implications

    PubMed Central

    Adgent, Margaret A.; Squadrito, Giuseppe L.; Ballinger, Carol A.; Krzywanski, David M.; Lancaster, Jack R.; Postlethwait, Edward M.

    2012-01-01

    Tissues are exposed to exogenous and endogenous nitrogen dioxide (•NO2), which is the terminal agent in protein tyrosine nitration. Besides iron chelation, the hydroxamic acid (HA) desferrioxamine (DFO) shows multiple functionalities including nitration inhibition. To investigate mechanisms whereby DFO affects 3-nitrotyrosine (3-NT) formation, we utilized gas phase •NO2 exposures, to limit introduction of other reactive species, and a lung surface model wherein red cell membranes (RCM) were immobilized under a defined aqueous film. When RCM were exposed to •NO2 covered by +/− DFO: (i) DFO inhibited 3-NT formation more effectively than other HA and non-HA chelators; (ii) 3-NT inhibition occurred at very low [DFO] for prolonged times; and (iii) 3-NT formation was iron independent but inhibition required DFO present. DFO poorly reacted with •NO2 compared to ascorbate, assessed via •NO2 reactive absorption and aqueous phase oxidation rates, yet limited 3-NT formation at far lower concentrations. DFO also inhibited nitration under aqueous bulk phase conditions, and inhibited 3-NT generated by active myeloperoxidase “bound” to RCM. Per the above and kinetic analyses suggesting preferential DFO versus •NO2 reaction within membranes, we conclude that DFO inhibits 3-NT formation predominantly by facile repair of the tyrosyl radical intermediate, which prevents •NO2 addition, and thus nitration, and potentially influences biochemical functionalities. PMID:22705369

  17. 76 FR 46907 - Ammonium Nitrate Security Program

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-03

    ... Federal Bureau of Investigation FR Federal Register HMR Hazardous Materials Regulations HMT Hazardous... ``Secure Handling of Ammonium Nitrate Program'' on October 29, 2008. See 73 FR 64280. The ANPRM solicited... interacting with state and local governments regarding ammonium nitrate security. ] See 73 FR 64280,...

  18. Dietary Nitrate, Nitric Oxide, and Cardiovascular Health.

    PubMed

    Bondonno, Catherine P; Croft, Kevin D; Hodgson, Jonathan M

    2016-09-01

    Emerging evidence strongly suggests that dietary nitrate, derived in the diet primarily from vegetables, could contribute to cardiovascular health via effects on nitric oxide (NO) status. NO plays an essential role in cardiovascular health. It is produced via the classical L-arginine-NO-synthase pathway and the recently discovered enterosalivary nitrate-nitrite-NO pathway. The discovery of this alternate pathway has highlighted dietary nitrate as a candidate for the cardioprotective effect of a diet rich in fruit and vegetables. Clinical trials with dietary nitrate have observed improvements in blood pressure, endothelial function, ischemia-reperfusion injury, arterial stiffness, platelet function, and exercise performance with a concomitant augmentation of markers of NO status. While these results are indicative of cardiovascular benefits with dietary nitrate intake, there is still a lingering concern about nitrate in relation to methemoglobinemia, cancer, and cardiovascular disease. It is the purpose of this review to present an overview of NO and its critical role in cardiovascular health; to detail the observed vascular benefits of dietary nitrate intake through effects on NO status as well as to discuss the controversy surrounding the possible toxic effects of nitrate.

  19. Intravesical silver nitrate for refractory hemorrhagic cystitis

    PubMed Central

    Montgomery, Brian D.; Boorjian, Stephen A.; Ziegelmann, Matthew J.; Joyce, Daniel D.; Linder, Brian J.

    2016-01-01

    Objective Hemorrhagic cystitis is a challenging clinical entity with limited evidence available to guide treatment. The use of intravesical silver nitrate has been reported, though supporting literature is sparse. Here, we sought to assess outcomes of patients treated with intravesical silver nitrate for refractory hemorrhagic cystitis. Material and methods We identified nine patients with refractory hemorrhagic cystitis treated at our institution with intravesical silver nitrate between 2000–2015. All patients had failed previous continuous bladder irrigation with normal saline and clot evacuation. Treatment success was defined as requiring no additional therapy beyond normal saline irrigation after silver nitrate instillation prior to hospital discharge. Results Median patient age was 80 years (IQR 73, 82). Radiation was the most common etiology for hemorrhagic cystitis 89% (8/9). Two patients underwent high dose (0.1%–0.4%) silver nitrate under anesthesia, while the remaining seven were treated with doses from 0.01% to 0.1% via continuous bladder irrigation for a median of 3 days (range 2–4). All nine patients (100%) had persistent hematuria despite intravesical silver nitrate therapy, requiring additional interventions and red blood cell transfusion during the hospitalization. There were no identified complications related to intravesical silver nitrate instillation. Conclusion Although well tolerated, we found that intravesical silver nitrate was ineffective for bleeding control, suggesting a limited role for this agent in the management of patients with hemorrhagic cystitis.

  20. COMPARTMENTAL MODEL OF NITRATE RETENTION IN STREAMS

    EPA Science Inventory

    A compartmental modeling approach is presented to route nitrate retention along a cascade of stream reach sections. A process transfer function is used for transient storage equations with first order reaction terms to represent nitrate uptake in the free stream, and denitrifica...

  1. Intravesical silver nitrate for refractory hemorrhagic cystitis

    PubMed Central

    Montgomery, Brian D.; Boorjian, Stephen A.; Ziegelmann, Matthew J.; Joyce, Daniel D.; Linder, Brian J.

    2016-01-01

    Objective Hemorrhagic cystitis is a challenging clinical entity with limited evidence available to guide treatment. The use of intravesical silver nitrate has been reported, though supporting literature is sparse. Here, we sought to assess outcomes of patients treated with intravesical silver nitrate for refractory hemorrhagic cystitis. Material and methods We identified nine patients with refractory hemorrhagic cystitis treated at our institution with intravesical silver nitrate between 2000–2015. All patients had failed previous continuous bladder irrigation with normal saline and clot evacuation. Treatment success was defined as requiring no additional therapy beyond normal saline irrigation after silver nitrate instillation prior to hospital discharge. Results Median patient age was 80 years (IQR 73, 82). Radiation was the most common etiology for hemorrhagic cystitis 89% (8/9). Two patients underwent high dose (0.1%–0.4%) silver nitrate under anesthesia, while the remaining seven were treated with doses from 0.01% to 0.1% via continuous bladder irrigation for a median of 3 days (range 2–4). All nine patients (100%) had persistent hematuria despite intravesical silver nitrate therapy, requiring additional interventions and red blood cell transfusion during the hospitalization. There were no identified complications related to intravesical silver nitrate instillation. Conclusion Although well tolerated, we found that intravesical silver nitrate was ineffective for bleeding control, suggesting a limited role for this agent in the management of patients with hemorrhagic cystitis. PMID:27635296

  2. NITRATE CONTAMINATION OF GROUND WATER (GW-761)

    EPA Science Inventory

    The occurrence of nitrate and related compounds in ground water is discussed from the perspectives of its natural as well as anthropogenic origins. A brief explanation of the nitrogen cycle touches on the production as well as utilization of ammonia, nitrite, nitrate, and nitrog...

  3. Pyrimidone-based series of glucokinase activators with alternative donor-acceptor motif.

    PubMed

    Filipski, Kevin J; Guzman-Perez, Angel; Bian, Jianwei; Perreault, Christian; Aspnes, Gary E; Didiuk, Mary T; Dow, Robert L; Hank, Richard F; Jones, Christopher S; Maguire, Robert J; Tu, Meihua; Zeng, Dongxiang; Liu, Shenping; Knafels, John D; Litchfield, John; Atkinson, Karen; Derksen, David R; Bourbonais, Francis; Gajiwala, Ketan S; Hickey, Michael; Johnson, Theodore O; Humphries, Paul S; Pfefferkorn, Jeffrey A

    2013-08-15

    Glucokinase activators are a class of experimental agents under investigation as a therapy for Type 2 diabetes mellitus. An X-ray crystal structure of a modestly potent agent revealed the potential to substitute the common heterocyclic amide donor-acceptor motif for a pyridone moiety. We have successfully demonstrated that both pyridone and pyrimidone heterocycles can be used as a potent donor-acceptor substituent. Several sub-micromolar analogs that possess the desired partial activator profile were synthesized and characterized. Unfortunately, the most potent activators suffered from sub-optimal pharmacokinetic properties. Nonetheless, these donor-acceptor motifs may find utility in other glucokinase activator series or beyond.

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

    NASA Technical Reports Server (NTRS)

    Myers, Charles R.; Nealson, Kenneth H.

    1988-01-01

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

  5. The contributions of nitrate uptake and efflux to isotope fractionation during algal nitrate assimilation

    NASA Astrophysics Data System (ADS)

    Karsh, K. L.; Trull, T. W.; Sigman, D. M.; Thompson, P. A.; Granger, J.

    2014-05-01

    In order to strengthen environmental application of nitrate N and O isotopes, we measured the N and O isotopic fractionation associated with cellular nitrate uptake and efflux in the nitrate-assimilating marine diatom Thalassiosira weissflogii. We isolated nitrate uptake and efflux from nitrate reduction by growing the cells in the presence of tungsten, which substitutes for molybdenum in assimilatory nitrate reductase, yielding an inactive enzyme. After growth on ammonium and then N starvation, cells were exposed to nitrate. Numerical models fit to the evolution of intracellular nitrate concentration and N and O isotopic composition yielded distinct N isotope effects (15ɛ) for nitrate uptake and nitrate efflux (2.0 ± 0.3‰ and 1.2 ± 0.4‰, respectively). The O isotope effects (18ɛ) for nitrate uptake and nitrate efflux were indistinguishable (2.8 ± 0.6‰), yielding a ratio of O to N isotopic fractionation for uptake of 1.4 ± 0.4 and for efflux of 2.3 ± 0.9. The 15ɛ for nitrate uptake can account for at most 40% of the organism-level N isotope effect (15ɛorg) measured in laboratory studies of T. weissflogii and in the open ocean (typically 5‰ or greater). This observation supports previous evidence that most isotope fractionation during nitrate assimilation is due to intracellular nitrate reduction, with nitrate efflux allowing the signal to be communicated to the environment. An O to N fractionation ratio (18ɛorg:15ɛorg) of ˜1 has been measured for nitrate assimilation in algal cultures and linked to the N and O isotope effects of nitrate reductase. Our results suggest that the ratios of O to N fractionation for both nitrate uptake and efflux may be distinct from a ratio of 1, to a degree that could cause the net 18ɛorg:15ɛorg to rise appreciably above 1 when 15ɛorg is low (e.g., yielding a ratio of 1.1 when 15ɛorg is 5‰). However, field and culture studies have consistently measured nearly equivalent fractionation of N and O isotopes in

  6. A KAP study on MTP acceptors and their contraceptive practice.

    PubMed

    Roy, M; Lahiri, B C; Ghosh, B N

    1978-01-01

    From the point of view of the family planning program, it is necessary to determine whether a medical termination of pregnancy has a learning effect on a woman's subsequent fertility control behavior. In order to determine the knowledge and attitude of medical termination of pregnancy (MTP) acceptors towards abortion and their pre and post abortion contraceptive practices, a study was conducted during January to December 1975 in a family planning clinic in North Calcutta. 300 consecutive cases admitted to the hospital for abortions were the study subjects - the MTP group. They were subjected to repeated interviews in the ward before and after the abortion and were followed up at home within 6-10 months after the discharge from the hospital. 300 women who attended the antenatal clinic of the same hospital during the same period were selected for comparison by systematic sampling. There is no statistically significant difference in the social characteristics of the 2 groups except that the MTP group was from a comparatively poorer economic class. 13.3% of the MTP group had "good" knowledge of physiology of reproduction in contrast to only 5.0% in the comparison group. Only 52% of the MTP group and 63% in the comparison group failed to have even an "average" knowledge of this area. Nearly 55% of the MTP group and 65% of the comparison group had never practiced family planning. Over 55% of the MTP group had poor knowledge about abortion; the most important soruce of their knowledge was their neighbors. 78.7% of the cases considered MTP to be a sinful act. The primary reason for deciding to have an abortion was socioeconomic. Over 27.6% of the cases were using contraceptives to avoid the present pregnancy. The difference is statistically significant suggesting a positive learning effect of MTP on contraceptive behavior of women seeking abortions.

  7. PREPARATION OF DIBASIC ALUMINUM NITRATE

    DOEpatents

    Gresky, A.T.; Nurmi, E.O.; Foster, D.L.; Wischow, R.P.; Savolainen, J.E.

    1960-04-01

    A method is given for the preparation and recovery of basic aluminum nltrates having an OH: Al ratio of at least two, comprising two steps. First, metallic aluminum is dissolved in aqueous Al(NO/sub 3/)/sub 3/, in the presence of a small quantity of elemental or ionic mercury, to increase its Al: NO/sub 3/ ratio into the range 1 to 1.2. The resulting aqueous solution is then added to an excess of a special organic solvent, typically a mixture of five parts methanol and six parts diethyl ether, whereupon the basic aluminum nitrate, e.g. Al/sub 6/(OH)/sub 13/-(NO/sub 3/)/sub 5/, recoverably precipitates.

  8. Phase diagram of ammonium nitrate.

    PubMed

    Dunuwille, Mihindra; Yoo, Choong-Shik

    2013-12-01

    Ammonium Nitrate (AN) is a fertilizer, yet becomes an explosive upon a small addition of chemical impurities. The origin of enhanced chemical sensitivity in impure AN (or AN mixtures) is not well understood, posing significant safety issues in using AN even today. To remedy the situation, we have carried out an extensive study to investigate the phase stability of AN and its mixtures with hexane (ANFO-AN mixed with fuel oil) and Aluminum (Ammonal) at high pressures and temperatures, using diamond anvil cells (DAC) and micro-Raman spectroscopy. The results indicate that pure AN decomposes to N2, N2O, and H2O at the onset of the melt, whereas the mixtures, ANFO and Ammonal, decompose at substantially lower temperatures. The present results also confirm the recently proposed phase IV-IV' transition above 17 GPa and provide new constraints for the melting and phase diagram of AN to 40 GPa and 400°C.

  9. Phase diagram of ammonium nitrate

    NASA Astrophysics Data System (ADS)

    Dunuwille, Mihindra; Yoo, Choong-Shik

    2013-12-01

    Ammonium Nitrate (AN) is a fertilizer, yet becomes an explosive upon a small addition of chemical impurities. The origin of enhanced chemical sensitivity in impure AN (or AN mixtures) is not well understood, posing significant safety issues in using AN even today. To remedy the situation, we have carried out an extensive study to investigate the phase stability of AN and its mixtures with hexane (ANFO-AN mixed with fuel oil) and Aluminum (Ammonal) at high pressures and temperatures, using diamond anvil cells (DAC) and micro-Raman spectroscopy. The results indicate that pure AN decomposes to N2, N2O, and H2O at the onset of the melt, whereas the mixtures, ANFO and Ammonal, decompose at substantially lower temperatures. The present results also confirm the recently proposed phase IV-IV' transition above 17 GPa and provide new constraints for the melting and phase diagram of AN to 40 GPa and 400°C.

  10. Use of nitrates in ischemic heart disease.

    PubMed

    Giuseppe, Cocco; Paul, Jerie; Hans-Ulrich, Iselin

    2015-01-01

    Short-acting nitrates are beneficial in acute myocardial ischemia. However, many unresolved questions remain about the use of long-acting nitrates in stable ischemic heart disease. The use of long-acting nitrates is weakened by the development of endothelial dysfunction and tolerance. Also, we currently ignore whether lower doses of transdermal nitroglycerin would be better than those presently used. Multivariate analysis data from large nonrandomized studies suggested that long-acting nitrates increase the incidence of acute coronary syndromes, while data from another multivariate study indicate that they have positive effects. Because of methodological differences and open questions, the two studies cannot be compared. A study in Japanese patients with vasospastic angina has shown that, when compared with calcium antagonists, long-acting nitrates do not improve long-term prognosis and that the risk for cardiac adverse events increases with the combined therapy. We have many unanswered questions.

  11. Additive methane-mitigating effect between linseed oil and nitrate fed to cattle.

    PubMed

    Guyader, J; Eugène, M; Meunier, B; Doreau, M; Morgavi, D P; Silberberg, M; Rochette, Y; Gerard, C; Loncke, C; Martin, C

    2015-07-01

    The objective of this study was to test the effect of linseed oil and nitrate fed alone or in combination on methane (CH4) emissions and diet digestibility in cows. The experiment was conducted as a 2 × 2 factorial design using 4 multiparous nonlactating Holstein cows (initial BW 656 ± 31 kg). Each experimental period lasted 5 wk, with measures performed in the final 3 wk (wk 3 to 5). Diets given on a DM basis were 1) control (CON; 50% natural grassland hay and 50% concentrate), 2) CON with 4% linseed oil (LIN), 3) CON with 3% calcium nitrate (NIT), and 4) CON with 4% linseed oil plus 3% calcium nitrate (LIN+NIT). Diets were offered twice daily and were formulated to deliver similar amounts (DM basis) of CP (12.2%), starch (25.5%), and NDF (39.5%). Feed offer was restricted to 90% of voluntary intake (12.4 kg DMI/d). Total tract digestibility and N balance were determined from total feces and urine collected separately for 6 d during wk 4. Daily CH4 emissions were quantified using open chambers for 4 d during wk 5. Rumen fermentation and microbial parameters were analyzed from samples taken before and 3 h after the morning feeding. Rumen concentrations of dissolved hydrogen (H2) were measured continuously up to 6 h after feeding using a H2 sensor. Compared with the CON diet linseed oil and nitrate decreased (P < 0.01) CH4 emissions (g/kg DMI) by 17 and 22%, respectively, when fed alone and by 32% when combined. The LIN diet reduced CH4 production throughout the day, increased (P = 0.02) propionate proportion, and decreased (P = 0.03) ruminal protozoa concentration compared with CON diet. The NIT diet strongly reduced CH4 production 3 h after feeding, with a simultaneous increase in rumen dissolved H2 concentration, suggesting that nitrate does not act only as an electron acceptor. As a combined effect, linseed plus nitrate also increased H2 concentrations in the rumen. Diets had no effect (P > 0.05) on total tract digestibility of nutrients, except linseed oil

  12. Efficient syntheses of climate relevant isoprene nitrates and (1R,5S)-(-)-myrtenol nitrate.

    PubMed

    Bew, Sean P; Hiatt-Gipson, Glyn D; Mills, Graham P; Reeves, Claire E

    2016-01-01

    Here we report the chemoselective synthesis of several important, climate relevant isoprene nitrates using silver nitrate to mediate a 'halide for nitrate' substitution. Employing readily available starting materials, reagents and Horner-Wadsworth-Emmons chemistry the synthesis of easily separable, synthetically versatile 'key building blocks' (E)- and (Z)-3-methyl-4-chlorobut-2-en-1-ol as well as (E)- and (Z)-1-((2-methyl-4-bromobut-2-enyloxy)methyl)-4-methoxybenzene has been achieved using cheap, 'off the shelf' materials. Exploiting their reactivity we have studied their ability to undergo an 'allylic halide for allylic nitrate' substitution reaction which we demonstrate generates (E)- and (Z)-3-methyl-4-hydroxybut-2-enyl nitrate, and (E)- and (Z)-2-methyl-4-hydroxybut-2-enyl nitrates ('isoprene nitrates') in 66-80% overall yields. Using NOESY experiments the elucidation of the carbon-carbon double bond configuration within the purified isoprene nitrates has been established. Further exemplifying our 'halide for nitrate' substitution chemistry we outline the straightforward transformation of (1R,2S)-(-)-myrtenol bromide into the previously unknown monoterpene nitrate (1R,2S)-(-)-myrtenol nitrate. PMID:27340495

  13. Efficient syntheses of climate relevant isoprene nitrates and (1R,5S)-(-)-myrtenol nitrate.

    PubMed

    Bew, Sean P; Hiatt-Gipson, Glyn D; Mills, Graham P; Reeves, Claire E

    2016-01-01

    Here we report the chemoselective synthesis of several important, climate relevant isoprene nitrates using silver nitrate to mediate a 'halide for nitrate' substitution. Employing readily available starting materials, reagents and Horner-Wadsworth-Emmons chemistry the synthesis of easily separable, synthetically versatile 'key building blocks' (E)- and (Z)-3-methyl-4-chlorobut-2-en-1-ol as well as (E)- and (Z)-1-((2-methyl-4-bromobut-2-enyloxy)methyl)-4-methoxybenzene has been achieved using cheap, 'off the shelf' materials. Exploiting their reactivity we have studied their ability to undergo an 'allylic halide for allylic nitrate' substitution reaction which we demonstrate generates (E)- and (Z)-3-methyl-4-hydroxybut-2-enyl nitrate, and (E)- and (Z)-2-methyl-4-hydroxybut-2-enyl nitrates ('isoprene nitrates') in 66-80% overall yields. Using NOESY experiments the elucidation of the carbon-carbon double bond configuration within the purified isoprene nitrates has been established. Further exemplifying our 'halide for nitrate' substitution chemistry we outline the straightforward transformation of (1R,2S)-(-)-myrtenol bromide into the previously unknown monoterpene nitrate (1R,2S)-(-)-myrtenol nitrate.

  14. 70. INTERIOR VIEW OF AMMONIUM NITRATE HOUSE, LOOKING AT AMMONIUM ...

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

    70. INTERIOR VIEW OF AMMONIUM NITRATE HOUSE, LOOKING AT AMMONIUM NITRATE IN STORAGE. APRIL 18, 1919. - United States Nitrate Plant No. 2, Reservation Road, Muscle Shoals, Muscle Shoals, Colbert County, AL

  15. Nitrate Transport, Sensing, and Responses in Plants.

    PubMed

    O'Brien, José A; Vega, Andrea; Bouguyon, Eléonore; Krouk, Gabriel; Gojon, Alain; Coruzzi, Gloria; Gutiérrez, Rodrigo A

    2016-06-01

    Nitrogen (N) is an essential macronutrient that affects plant growth and development. N is an important component of chlorophyll, amino acids, nucleic acids, and secondary metabolites. Nitrate is one of the most abundant N sources in the soil. Because nitrate and other N nutrients are often limiting, plants have developed sophisticated mechanisms to ensure adequate supply of nutrients in a variable environment. Nitrate is absorbed in the root and mobilized to other organs by nitrate transporters. Nitrate sensing activates signaling pathways that impinge upon molecular, metabolic, physiological, and developmental responses locally and at the whole plant level. With the advent of genomics technologies and genetic tools, important advances in our understanding of nitrate and other N nutrient responses have been achieved in the past decade. Furthermore, techniques that take advantage of natural polymorphisms present in divergent individuals from a single species have been essential in uncovering new components. However, there are still gaps in our understanding of how nitrate signaling affects biological processes in plants. Moreover, we still lack an integrated view of how all the regulatory factors identified interact or crosstalk to orchestrate the myriad N responses plants typically exhibit. In this review, we provide an updated overview of mechanisms by which nitrate is sensed and transported throughout the plant. We discuss signaling components and how nitrate sensing crosstalks with hormonal pathways for developmental responses locally and globally in the plant. Understanding how nitrate impacts on plant metabolism, physiology, and growth and development in plants is key to improving crops for sustainable agriculture. PMID:27212387

  16. Nitrate Transport, Sensing, and Responses in Plants.

    PubMed

    O'Brien, José A; Vega, Andrea; Bouguyon, Eléonore; Krouk, Gabriel; Gojon, Alain; Coruzzi, Gloria; Gutiérrez, Rodrigo A

    2016-06-01

    Nitrogen (N) is an essential macronutrient that affects plant growth and development. N is an important component of chlorophyll, amino acids, nucleic acids, and secondary metabolites. Nitrate is one of the most abundant N sources in the soil. Because nitrate and other N nutrients are often limiting, plants have developed sophisticated mechanisms to ensure adequate supply of nutrients in a variable environment. Nitrate is absorbed in the root and mobilized to other organs by nitrate transporters. Nitrate sensing activates signaling pathways that impinge upon molecular, metabolic, physiological, and developmental responses locally and at the whole plant level. With the advent of genomics technologies and genetic tools, important advances in our understanding of nitrate and other N nutrient responses have been achieved in the past decade. Furthermore, techniques that take advantage of natural polymorphisms present in divergent individuals from a single species have been essential in uncovering new components. However, there are still gaps in our understanding of how nitrate signaling affects biological processes in plants. Moreover, we still lack an integrated view of how all the regulatory factors identified interact or crosstalk to orchestrate the myriad N responses plants typically exhibit. In this review, we provide an updated overview of mechanisms by which nitrate is sensed and transported throughout the plant. We discuss signaling components and how nitrate sensing crosstalks with hormonal pathways for developmental responses locally and globally in the plant. Understanding how nitrate impacts on plant metabolism, physiology, and growth and development in plants is key to improving crops for sustainable agriculture.

  17. California GAMA Special Study: An isotopic and dissolved gas investigation of nitrate source and transport to a public supply well in California's Central Valley

    SciTech Connect

    Singleton, M J; Moran, J E; Esser, B K; Roberts, S K; Hillegonds, D J

    2010-04-14

    This study investigates nitrate contamination of a deep municipal drinking water production well in Ripon, CA to demonstrate the utility of natural groundwater tracers in constraining the sources and transport of nitrate to deep aquifers in the Central Valley. The goal of the study was to investigate the origin (source) of elevated nitrate and the potential for the deep aquifer to attenuate anthropogenic nitrate. The site is ideal for such an investigation. The production well is screened from 165-325 feet below ground surface and a number of nearby shallow and deep monitoring wells were available for sampling. Furthermore, potential sources of nitrate contamination to the well had been identified, including a fertilizer supply plant located approximately 1000 feet to the east and local almond groves. A variety of natural isotopic and dissolved gas tracers including {sup 3}H-{sup 3}He groundwater age and the isotopic composition of nitrate are applied to identify nitrate sources and to characterize nitrate transport. An advanced method for sampling production wells is employed to help identify contaminant contributions from specific screen intervals. Nitrate transport: Groundwater nitrate at this field site is not being actively denitrified. Groundwater parameters indicate oxic conditions, the dissolved gas data shows no evidence for excess nitrogen as the result of denitrification, and nitrate-N and -O isotope compositions do not display patterns typical of denitrification. Contaminant nitrate source: The ambient nitrate concentration in shallow groundwater at the Ripon site ({approx}12 mg/L as nitrate) is typical of shallow groundwaters affected by recharge from agricultural and urban areas. Nitrate concentrations in Ripon City Well 12 (50-58 mg/L as nitrate) are significantly higher than these ambient concentrations, indicating an additional source of anthropogenic nitrate is affecting groundwater in the capture zone of this municipal drinking water well. This

  18. Structural basis for dynamic mechanism of nitrate/nitrite antiport by NarK

    NASA Astrophysics Data System (ADS)

    Fukuda, Masahiro; Takeda, Hironori; Kato, Hideaki E.; Doki, Shintaro; Ito, Koichi; Maturana, Andrés D.; Ishitani, Ryuichiro; Nureki, Osamu

    2015-05-01

    NarK belongs to the nitrate/nitrite porter (NNP) family in the major facilitator superfamily (MFS) and plays a central role in nitrate uptake across the membrane in diverse organisms, including archaea, bacteria, fungi and plants. Although previous studies provided insight into the overall structure and the substrate recognition of NarK, its molecular mechanism, including the driving force for nitrate transport, remained elusive. Here we demonstrate that NarK is a nitrate/nitrite antiporter, using an in vitro reconstituted system. Furthermore, we present the high-resolution crystal structures of NarK from Escherichia coli in the nitrate-bound occluded, nitrate-bound inward-open and apo inward-open states. The integrated structural, functional and computational analyses reveal the nitrate/nitrite antiport mechanism of NarK, in which substrate recognition is coupled to the transport cycle by the concomitant movement of the transmembrane helices and the key tyrosine and arginine residues in the substrate-binding site.

  19. Structural basis for dynamic mechanism of nitrate/nitrite antiport by NarK

    PubMed Central

    Fukuda, Masahiro; Takeda, Hironori; Kato, Hideaki E.; Doki, Shintaro; Ito, Koichi; Maturana, Andrés D.; Ishitani, Ryuichiro; Nureki, Osamu

    2015-01-01

    NarK belongs to the nitrate/nitrite porter (NNP) family in the major facilitator superfamily (MFS) and plays a central role in nitrate uptake across the membrane in diverse organisms, including archaea, bacteria, fungi and plants. Although previous studies provided insight into the overall structure and the substrate recognition of NarK, its molecular mechanism, including the driving force for nitrate transport, remained elusive. Here we demonstrate that NarK is a nitrate/nitrite antiporter, using an in vitro reconstituted system. Furthermore, we present the high-resolution crystal structures of NarK from Escherichia coli in the nitrate-bound occluded, nitrate-bound inward-open and apo inward-open states. The integrated structural, functional and computational analyses reveal the nitrate/nitrite antiport mechanism of NarK, in which substrate recognition is coupled to the transport cycle by the concomitant movement of the transmembrane helices and the key tyrosine and arginine residues in the substrate-binding site. PMID:25959928

  20. Molecular Signals Controlling the Inhibition of Nodulation by Nitrate in Medicago truncatula

    PubMed Central

    van Noorden, Giel E.; Verbeek, Rob; Dinh, Quy Dung; Jin, Jian; Green, Alexandra; Ng, Jason Liang Pin; Mathesius, Ulrike

    2016-01-01

    The presence of nitrogen inhibits legume nodule formation, but the mechanism of this inhibition is poorly understood. We found that 2.5 mM nitrate and above significantly inhibited nodule initiation but not root hair curling in Medicago trunatula. We analyzed protein abundance in M. truncatula roots after treatment with either 0 or 2.5 mM nitrate in the presence or absence of its symbiont Sinorhizobium meliloti after 1, 2 and 5 days following inoculation. Two-dimensional gel electrophoresis combined with mass spectrometry was used to identify 106 differentially accumulated proteins responding to nitrate addition, inoculation or time point. While flavonoid-related proteins were less abundant in the presence of nitrate, addition of Nod gene-inducing flavonoids to the Sinorhizobium culture did not rescue nodulation. Accumulation of auxin in response to rhizobia, which is also controlled by flavonoids, still occurred in the presence of nitrate, but did not localize to a nodule initiation site. Several of the changes included defense- and redox-related proteins, and visualization of reactive oxygen species indicated that their induction in root hairs following Sinorhizobium inoculation was inhibited by nitrate. In summary, the presence of nitrate appears to inhibit nodulation via multiple pathways, including changes to flavonoid metabolism, defense responses and redox changes. PMID:27384556

  1. Ignition requirements for organic-nitrate propagating reactions

    SciTech Connect

    Meacham, J.E.

    1997-09-25

    As part of the Organic Safety Project at the Hanford Site, theoretical and experimental investigations were performed at Fauske and Associates, Inc. to assess the ignition energy requirements for organic-nitrate propagating reactions. Theoretical considerations suggest that a minimum ignition energy requirement in excess of 1 J is required to produce sustained condensed-phase combustion with a stoichiometric organic-nitrate mixture in the absence of moisture and other diluents. This value is three to four orders of magnitude larger than that required to initiate combustion with flammable gas mixtures. It also is consistent with the finding that organic-nitrate mixtures are generally insensitive to spark, impact, shock, or friction. The necessary large ignition energy also is consistent with the extremely low burn velocities, 10 3 to 10 4 meters per second (m/s), characteristic of condensed-phase organic-nitrate propagating reactions. Experimental evaluations were made of the following ignition sources: hot metal spheres, electrically heated Nichrome wire coils, Watlow heaters, electric matches, and an arc welder. Results indicate that hot metal pieces are the most effective ignition source where the energy approaches the theoretical estimate of the minimum ignition energy requirement. However, the energy requirements increase rapidly with all ignition sources tested as deviations from dry stoichiometric conditions increase including lower fuel concentrations and increasing water concentrations. At the lower combustion limit and in the absence of water, the ignition energy requirement is well above 1000 J. For a stoichiometric organic-nitrate mixture with 10 weight percent (wt%) moisture, using hot metal spheres, the lowest ignition requirement also is measured to be above 1000 J. The use of electrically heated wire coils or Watlow heaters increases the value to above 10,000 J.

  2. Nitrate in watersheds: straight from soils to streams?

    USGS Publications Warehouse

    Sudduth, Elizabeth B.; Perakis, Steven S.; Bernhardt, Emily S.

    2013-01-01

    Human activities are rapidly increasing the global supply of reactive N and substantially altering the structure and hydrologic connectivity of managed ecosystems. There is long-standing recognition that N must be removed along hydrologic flowpaths from uplands to streams, yet it has proven difficult to assess the generality of this removal across ecosystem types, and whether these patterns are influenced by land-use change. To assess how well upland nitrate (NO3-) loss is reflected in stream export, we gathered information from >50 watershed biogeochemical studies that reported nitrate concentrations ([NO3-]) for stream water and for either upslope soil solution or groundwater NO3- to examine whether stream export of NO3- accurately reflects upland NO3- losses. In this dataset, soil solution and streamwater [NO3-] were correlated across 40 undisturbed forest watersheds, with streamwater [NO3-] typically half (median = 50%) soil solution [NO3-]. A similar relationship was seen in 10 disturbed forest watersheds. However, for 12 watersheds with significant agricultural or urban development, the intercept and slope were both significantly higher than the relationship seen in forest watersheds. Differences in concentration between soil solution or groundwater and stream water may be attributed to biological uptake, microbial processes including denitrification, and/or preferential flow routing. The results of this synthesis are consistent with the hypotheses that undisturbed watersheds have a significant capacity to remove nitrate after it passes below the rooting zone and that land use changes tend to alter the efficiency or the length of watershed flowpaths, leading to reductions in nitrate removal and increased stream nitrate concentrations.

  3. Observation of nitrate coatings on atmospheric mineral dust particles

    NASA Astrophysics Data System (ADS)

    Li, W. J.; Shao, L. Y.

    2009-03-01

    Nitrate compounds have received much attention because of their ability to alter the hygroscopic properties and cloud condensation nuclei (CCN) activity of mineral dust particles in the atmosphere. However, very little is known about specific characteristics of ambient nitrate-coated mineral particles on an individual particle scale. In this study, sample collection was conducted during brown haze and dust episodes between 24 May and 21 June 2007 in Beijing, northern China. Sizes, morphologies, and compositions of 332 mineral dust particles together with their coatings were analyzed using transmission electron microscopy (TEM) coupled with energy-dispersive X-ray (EDX) microanalyses. Structures of some mineral particles were verified using selected-area electron diffraction (SAED). TEM observation indicates that approximately 90% of the collected mineral particles are covered by visible coatings in haze samples whereas only 5% are coated in the dust sample. 92% of the analyzed mineral particles are covered with Ca-, Mg-, and Na-rich coatings, and 8% are associated with K- and S-rich coatings. The majority of coatings contain Ca, Mg, O, and N with minor amounts of S and Cl, suggesting that they are possibly nitrates mixed with small amounts of sulfates and chlorides. These nitrate coatings are strongly correlated with the presence of alkaline mineral components (e.g., calcite and dolomite). CaSO4 particles with diameters from 10 to 500 nm were also detected in the coatings including Ca(NO3)2 and Mg(NO3)2. Our results indicate that mineral particles in brown haze episodes were involved in atmospheric heterogeneous reactions with two or more acidic gases (e.g., SO2, NO2, HCl, and HNO3). Mineral particles that acquire hygroscopic nitrate coatings tend to be more spherical and larger, enhancing their light scattering and CCN activity, both of which have cooling effects on the climate.

  4. Fluorescence quenching in an organic donor-acceptor dyad: a first principles study.

    PubMed

    Körzdörfer, T; Tretiak, S; Kümmel, S

    2009-07-21

    Perylene bisimide and triphenyl diamine are prototypical organic dyes frequently used in organic solar cells and light emitting devices. Recent Forster-resonant-energy-transfer experiments on a bridged organic dyad consisting of triphenyl diamine as an energy-donor and perylene bisimide as an energy-acceptor revealed a strong fluorescence quenching on the perylene bisimide. This quenching is absent in a solution of free donors and acceptors and thus attributed to the presence of the saturated CH(2)O(CH(2))(12)-bridge. We investigate the cause of the fluorescence quenching as well as the special role of the covalently bound bridge by means of time dependent density functional theory and molecular dynamics. The conformational dynamics of the bridged system leads to a charge transfer process between donor and acceptor that causes the acceptor fluorescence quenching. PMID:19624200

  5. Interface-induced heavy-hole/light-hole splitting of acceptors in silicon

    SciTech Connect

    Mol, J. A.; Salfi, J.; Simmons, M. Y.; Rogge, S.; Rahman, R.; Hsueh, Y.; Klimeck, G.; Miwa, J. A.

    2015-05-18

    The energy spectrum of spin-orbit coupled states of individual sub-surface boron acceptor dopants in silicon have been investigated using scanning tunneling spectroscopy at cryogenic temperatures. The spatially resolved tunnel spectra show two resonances, which we ascribe to the heavy- and light-hole Kramers doublets. This type of broken degeneracy has recently been argued to be advantageous for the lifetime of acceptor-based qubits [R. Ruskov and C. Tahan, Phys. Rev. B 88, 064308 (2013)]. The depth dependent energy splitting between the heavy- and light-hole Kramers doublets is consistent with tight binding calculations, and is in excess of 1 meV for all acceptors within the experimentally accessible depth range (<2 nm from the surface). These results will aid the development of tunable acceptor-based qubits in silicon with long coherence times and the possibility for electrical manipulation.

  6. Dinitrogen extrusion from enoldiazo compounds under thermal conditions: synthesis of donor-acceptor cyclopropenes.

    PubMed

    Deng, Yongming; Jing, Changcheng; Doyle, Michael P

    2015-08-21

    Donor-acceptor cyclopropenes are formed quantitatively or in high yield from enoldiazoacetates and enoldiazoacetamides under moderate thermal conditions. They are more versatile than their corresponding enoldiazocarbonyl compounds as carbene precursors.

  7. Preparation and spectroscopic studies on charge-transfer complexes of 2-hydroxypyridine with electron acceptors

    NASA Astrophysics Data System (ADS)

    Gaballa, Akmal S.

    2013-07-01

    The CT-interactions of electron acceptors such as iodine (I2), chloranilic acid (H2CA) and 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) with 2-hydroxypyridine (HPyO) have been investigated in the defined solvent. The data indicate the formation of CT-complexes with the general formula [(HPyO)(acceptor)]. The 1:1 stoichiometry of the (HPyO)-acceptors were based on elemental analysis, IR spectra and thermogravimetric analysis of the solid CT-complexes along with the photometric titration measurements for the reactions. The formation constants (KCT) for the CT-complexes are shown to be strongly dependent on the type and structure of the electron acceptors. Factors affecting the CT-processes are discussed.

  8. Preparation and spectroscopic studies on charge-transfer complexes of famciclovir drug with different electron acceptors

    NASA Astrophysics Data System (ADS)

    Gaballa, Akmal S.; Teleb, Said M.; Nour, El-Metwally

    2012-09-01

    The CT-interaction of electron acceptors such as chloranilic acid (H2CA), 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) and and 7,7',8,8'-tetracyano-p-quinodimethane (TCNQ) with the antiviral drug famciclovir (FCV) have been investigated spectrophotometrically in the defined solvent. The data indicate the formation of CT-complexes with the general formula [(FCV)(acceptor)]. The 1:1 stoichiometry of the (FCV)-acceptors were based on elemental analysis, IR spectra and thermogravimetric analysis of the solid CT-complexes along with the photometric titration measurements for the reactions. The formation constants (KCT) for the CT-complexes are shown to be strongly dependent on the type and structure of the electron acceptor. Factors affecting the CT-processes such as redox potentials and steric hinderance of reactants are discussed.

  9. Computational design of donor-bridge-acceptor systems exhibiting pronounced quantum interference effects.

    PubMed

    Gorczak, Natalie; Renaud, Nicolas; Galan, Elena; Eelkema, Rienk; Siebbeles, Laurens D A; Grozema, Ferdinand C

    2016-03-01

    Quantum interference is a well-known phenomenon that dictates charge transport properties of single molecule junctions. However, reports on quantum interference in donor-bridge-acceptor molecules are scarce. This might be due to the difficulties in meeting the conditions for the presence of quantum interference in a donor-bridge-acceptor system. The electronic coupling between the donor, bridge, and acceptor moieties must be weak in order to ensure localised initial and final states for charge transfer. Yet, it must be strong enough to allow all bridge orbitals to mediate charge transfer. We present the computational route to the design of a donor-bridge-acceptor molecule that features the right balance between these contradicting requirements and exhibits pronounced interference effects.

  10. 34 CFR 303.15 - Include; including.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 34 Education 2 2010-07-01 2010-07-01 false Include; including. 303.15 Section 303.15 Education Regulations of the Offices of the Department of Education (Continued) OFFICE OF SPECIAL EDUCATION AND REHABILITATIVE SERVICES, DEPARTMENT OF EDUCATION EARLY INTERVENTION PROGRAM FOR INFANTS AND TODDLERS...

  11. Co-Occurrence of Nitrate Reduction and Anaerobic Oxidation of Methane in Gulf of Mexico Cold Seep Habitats

    NASA Astrophysics Data System (ADS)

    Fields, L.; Joye, S. B.

    2014-12-01

    Cold seeps are abundant in the Gulf of Mexico; they are fuelled by methane gas and hydrocarbon seepage at the seafloor and support diverse chemosynthetic microbial communities. Microorganisms form the base of the food chain at cold seeps, and high rates of anaerobic oxidation of methane (AOM) are characteristic of these methane-rich environments. While sulfate is often the electron acceptor for AOM in cold seep environments, recent evidence suggests that AOM can also be coupled to nitrate reduction. Little is known about nitrogen cycling in these habitats, though recent work indicates that denitrification is an important process in oily and gassy seep sediments. The co-occurrence of nitrate reduction and AOM suggests a potential coupling between the two processes in our study area. We used stable isotope (15N) tracer techniques to measure the capacity of Northern Gulf of Mexico cold seep sediments to reduce nitrate by denitrification and anammox. These measurements were made in surface and sub-surface sediments in conjunction with measurements of AOM, and with quantification of various geochemical and molecular characteristics. Here, we present our measurements of denitrification and anammox capacity in the context of environmental characteristics. Additionally, we examine spatial trends in the co-occurrence of AOM and nitrate reduction in these sediments.

  12. Effect of nitrates on biotransformation of phosphogypsum and phenol uptake in cultures of autochthonous sludge microflora from petroleum refining wastewaters.

    PubMed

    Kowalski, Włodzimierz; Przytocka-Jusiak, Magdalena; Błaszczyk, Mieczysław; Hołub, Wojciech; Wolicka, Dorota; Wesołowska, Iwona

    2002-01-01

    The effect of nitrates on the biotransformation of phosphogypsum at 30 degrees C in stationary cultures of anaerobic, heterogeneous microflora growing in medium with phenol (250-1,000 mg/L) as sole carbon source was studied. The microorganisms used in this study were isolated from sludge in biological petroleum-refining wastewater treatment plant. Phosphogypsum (a waste product in the chemical industry that contains approximately 95% CaSO4) was added in amount of 5 g/L, the source of nitrates was KNO3 in concentration equivalent to that of phenol (250-1,000 mg N-NO3/L). The presence of nitrates in heterogeneous cultures has an inhibitory effect on the process of phosphogypsum biotransformation and stimulates the uptake of phenol. We have found that in cultures in medium containing phenol, phosphogypsum and nitrates at least three physiological groups of microorganisms were present. These were phenol-biodegrading microorganisms not requiring an external electron acceptor, sulfate-reducing bacteria biodegrading phenol or intermediate products of its breakdown and denitrifying bacteria not utilising phenol as a carbon source. On solid medium these bacteria together formed heterogeneous single colonies. In spite of repeated attempts we were unable to isolate pure strains and the only result of these measures was loss of denitrification ability in medium with phenol.

  13. Arsenic, nitrate, iron, and hardness in ground water, Chena Ridge vicinity, Fairbanks, Alaska

    USGS Publications Warehouse

    Krumhardt, Andrea P.

    1979-01-01

    The report presents all data on hardness, iron, nitrate and arsenic in well water in the Chena Ridge area of Fairbanks, Alaska, through June 1979. Concentrations range as follows: arsenic - 0 to 28 micrograms per liter; nitrate - 0 to 20 milligrams per liter; iron - 0 to 18 milligrams per liter and hardness - 72 to 1,400 milligrams per liter. Values at the upper ends of the ranges for iron and nitrate exceed limits recommended by the Environmental Protection Agency for public water supplies. A map of the area showing the location of sampled wells and a table of chemical analysis are included. (Kosco-USGS)

  14. Simulating nitrate leaching under winter wheat grown on a structured clay soil considering bypass flow

    NASA Astrophysics Data System (ADS)

    Ragab, R.; Coopers, D. M.; Harris, G. L.; Catt, J. A.

    1996-07-01

    Nitrate leaching from drained plots of structured clay soil under winter wheat is simulated for one growing season using the SOILN model. Results are compared with field measurements from two replicate plots. Soil water movement is simulated both with and without a bypass flow component using the SOIL model. Flow to field drains and soil water content in the root zone are simulated better when bypass flow is included. The results emphasise the importance of considering bypass flow in modelling leaching from structured clay soils. Simulations of nitrate leaching using the SOILN model show that the model captures the main features of the cumulative loss of nitrate over the year.

  15. Curved Oligophenylenes as Donors in Shape-Persistent Donor-Acceptor Macrocycles with Solvatofluorochromic Properties.

    PubMed

    Kuwabara, Takuya; Orii, Jun; Segawa, Yasutomo; Itami, Kenichiro

    2015-08-10

    Many optoelectronic organic materials are based on donor-acceptor (D-A) systems with heteroatom-containing electron donors. Herein, we introduce a new molecular design for all-carbon curved oligoparaphenylenes as donors, which results in the generation of unique shape-persistent D-A macrocycles. Two types of acceptor-inserted cycloparaphenylenes were synthesized. These macrocycles display positive solvatofluorochromic properties owing to their D-A characteristics, which were confirmed by theoretical and electrochemical studies. PMID:26140706

  16. Experiments probing the viability of donor-acceptor norbornenes for (5 + 2)-annulation.

    PubMed

    Walker, Morgan M; Goodman, C Guy; Johnson, Jeffrey S

    2014-10-01

    This Note details experiments that probe the mechanism by which donor-acceptor norbornene systems epimerize. A number of mechanistic studies indicate that epimerization in these systems occurs via a Lewis acid catalyzed retro-Diels-Alder/Diels-Alder sequence, rather than bond rotation in an intimate ion pair. These results suggest that, under the reaction conditions examined, the ring strain present in norbornene is inadequate to induce zwitterion formation analogous to that observed with donor-acceptor cyclopropanes.

  17. New acceptor centers of the background impurities in p-CdZnTe

    SciTech Connect

    Plyatsko, S. V. Rashkovetskyi, L. V.

    2013-07-15

    Low-temperature photoluminescence data are used to study the redistribution of the background impurities and host components of p-CdZnTe single crystals with a resistivity of 1-50 {Omega} cm upon their interaction with infrared laser radiation. The effect of widening of the band gap and the formation of new acceptor centers in response to laser-stimulated changes in the system of intrinsic defects are established. The activation energy of the new acceptor centers is determined.

  18. Process for gasification using a synthetic CO.sub.2 acceptor

    DOEpatents

    Lancet, Michael S.; Curran, George P.

    1980-01-01

    A gasification process is disclosed using a synthetic CO.sub.2 acceptor consisting essentially of at least one compound selected from the group consisting of calcium oxide and calcium carbonate supported in a refractory carrier matrix, the carrier having the general formula Ca.sub.5 (SiO.sub.4).sub.2 CO.sub.3. A method for producing the synthetic CO.sub.2 acceptor is also disclosed.

  19. Fast Carrier Formation from Acceptor Exciton in Low-Gap Organic Photovotalic

    NASA Astrophysics Data System (ADS)

    Yonezawa, Kouhei; Kamioka, Hayato; Yasuda, Takeshi; Han, Liyuan; Moritomo, Yutaka

    2012-04-01

    Bulk heterojunction (BHJ) based on a donor (D) polymer and an acceptor (A) fullerene derivative is a promising organic photovoltaic. Here, we investigated the femtosecond charge dynamics after acceptor excitation in poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b '] dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b] thiophenediyl

  20. Effects of size restriction on donor-acceptor recombination in AgBr

    NASA Astrophysics Data System (ADS)

    Rodney, Paul J.; Marchetti, Alfred P.; Fauchet, Philippe M.

    2000-08-01

    The behavior of donor-acceptor (DA) recombination luminescence in quantum confined AgBr has been investigated. The DA luminescence decay, after pulsed excitation, became longer lived as the nanocluster size decreased. This result differs from theoretical expectations and from observations with AgI nanoclusters. The DA lifetime increase with decreasing size is due to an increase in yield and lifetime of ``free'' excitons that slowly dissociate into ``close'' donor-acceptor pairs, giving rise to an ``exciton dribbling'' effect.

  1. Benzodipyrrole-based Donor-Acceptor-type Boron Complexes as Tunable Near-infrared-Absorbing Materials.

    PubMed

    Nakamura, Tomoya; Furukawa, Shunsuke; Nakamura, Eiichi

    2016-07-20

    Benzodipyrrole-based donor-acceptor boron complexes were designed and synthesized as near-infrared-absorbing materials. The electron-rich organic framework combined with the Lewis acidic boron co-ordination enabled us to tune the LUMO energy level and the HOMO-LUMO gap (i.e.,the absorption wavelength) by changing the organic acceptor units, the number of boron atoms, and the substituents on the boron atoms.

  2. Nanosecond intersystem crossing times in fullerene acceptors: implications for organic photovoltaic diodes.

    PubMed

    Chow, Philip C Y; Albert-Seifried, Sebastian; Gélinas, Simon; Friend, Richard H

    2014-07-23

    Triplet-exciton formation through intersystem crossing of photogenerated singlet excitons in fullerene acceptors can compete with charge generation in organic photovoltaic diodes. This article reports the intersystem crossing timescale (τISC ) of the most commonly used fullerene acceptors, PC60 BM and PC70 BM, in solutions and in spin-coated films. These times are on the nanosecond timescale, and are longer than the characteristic times for charge generation (τd ).

  3. Study of characteristics of condom-acceptors using condom as first choice and alternative method of contraception in 1981-1987 at the NPFDB, GHKL.

    PubMed

    Low Boon Song

    1990-06-01

    Factors influencing condom acceptance were studied and compared in 2 groups of condom-acceptors--those using condoms as a 1st method of contraception and those using condoms as an alternative method of contraception. Data was obtained by reviewing the condom-acceptor cards during 1981-1987 at the General Hospital in Kuala Lumpur, Malaysia; 208 cards for the 1st group and 230 for the 2nd group were included in the study. Statistical analysis was conducted to determine characteristics influencing condom-use. AGe of wife, duration of marriage, number of living children, wife's level of education and socioeconomic status were identified as factors influencing condom acceptance. No significant difference was observed between the 2 group concerning their purpose of contraception. Age of wife had a significant influence on the use of condoms as contraception. Age of wife had a significant influence on the use of condoms as contraception; 74.5% of group 1 users were 31 years and 56.5% of group 2 users were 30 years. A very significant relationship also exist between condom use and duration of marriage and number of living children; condom-acceptors using condoms as the 1st method of contraception did so within 9 years of marriage (85.6%) and practiced condom use when they had 2 of children (73.6%) while those who used condoms subsequently were married 10 years (46.5%) and did so after having 3 or children (57.8%). Significant differences were observed between groups in higher socioeconomic status and higher level of education. With 7 or more years of education, a significant proportion of condom-acceptors used condoms as a 1st method of contraception as compared with those who used it as a subsequent method of contraception. For the higher socioeconomic, a significant number of acceptors used condoms as a 1st method of contraception.

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

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

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

  5. Modeling nitrate removal in a denitrification bed.

    PubMed

    Ghane, Ehsan; Fausey, Norman R; Brown, Larry C

    2015-03-15

    Denitrification beds are promoted to reduce nitrate load in agricultural subsurface drainage water to alleviate the adverse environmental effects associated with nitrate pollution of surface water. In this system, drainage water flows through a trench filled with a carbon media where nitrate is transformed into nitrogen gas under anaerobic conditions. The main objectives of this study were to model a denitrification bed treating drainage water and evaluate its adverse greenhouse gas emissions. Field experiments were conducted at an existing denitrification bed. Evaluations showed very low greenhouse gas emissions (mean N2O emission of 0.12 μg N m(-2) min(-1)) from the denitrification bed surface. Field experiments indicated that nitrate removal rate was described by Michaelis-Menten kinetics with the Michaelis-Menten constant of 7.2 mg N L(-1). We developed a novel denitrification bed model based on the governing equations for water flow and nitrate removal kinetics. The model evaluation statistics showed satisfactory prediction of bed outflow nitrate concentration during subsurface drainage flow. The model can be used to design denitrification beds with efficient nitrate removal which in turn leads to enhanced drainage water quality. PMID:25638338

  6. Synthesis of Nitrate Reductase in Chlorella

    PubMed Central

    Funkhouser, Edward A.; Shen, Teh-Chien; Ackermann, Renate

    1980-01-01

    Synthesis of nitrate reductase (EC 1.6.6.1) in Chlorella vulgaris was studied under inducing conditions, i.e. with cells grown on ammonia and then transferred to nitrate medium. Cycloheximide (but not chloramphenicol) completely inhibited synthesis of the enzyme, but only if it was added at the start (i.e. at the time of nitrate addition) of the induction period. Cycloheximide inhibition became less effective as induction by nitrate proceeded. Enzyme from small quantities of culture (1 to 3 milliliters of packed cells) was purified to homogeneity with the aid of blue dextran-Sepharose chromatography. Incorporation of radioactivity from labeled arginine into nitrate reductase was measured in the presence and absence of cycloheximide. Conditions were found under which the inhibitor completely blocked the incorporation of labeled amino acid, but only slightly decreased the increase in nitrate reductase activity. The results indicate that synthesis of nitrate reductase from amino acids proceeds by way of a protein precursor which is inactive enzymically. PMID:16661310

  7. The use of chlorate, nitrate, and perchlorate to promote crude oil mineralization in salt marsh sediments.

    PubMed

    Brundrett, Maeghan; Horita, Juske; Anderson, Todd; Pardue, John; Reible, Danny; Jackson, W Andrew

    2015-10-01

    Due to the high volume of crude oil released by the Deepwater Horizon oil spill, the salt marshes along the gulf coast were contaminated with crude oil. Biodegradation of crude oil in salt marshes is primarily limited by oxygen availability due to the high organic carbon content of the soil, high flux rate of S(2-), and saturated conditions. Chlorate, nitrate, and perchlorate were evaluated for use as electron acceptors in comparison to oxygen by comparing oil transformation and mineralization in mesocosms consisting of oiled salt marsh sediment from an area impacted by the BP Horizon oil spill. Mineralization rates were determined by measuring CO2 production and δ (13)C of the produced CO2 and compared to transformation evaluated by measuring the alkane/hopane ratios over a 4-month period. Total alkane/hopane ratios decreased (~55-70 %) for all treatments in the following relative order: aerated ≈ chlorate > nitrate > perchlorate. Total CO2 produced was similar between treatments ranging from 550-700 mg CO2-C. The δ (13)C-CO2 values generally ranged between the indigenous carbon and oil values (-17 and -27‰, respectively). Oil mineralization was greatest for the aerated treatments and least for the perchlorate amended. Our results indicate that chlorate has a similar potential as oxygen to support oil mineralization in contaminated salt marshes, but nitrate and perchlorate were less effective. The use of chlorate as a means to promote oil mineralization in situ may be a promising means to remediate contaminated salt marshes while preventing unwanted secondary impacts related to nutrient management as in the case of nitrate amendments. PMID:25854211

  8. The use of chlorate, nitrate, and perchlorate to promote crude oil mineralization in salt marsh sediments.

    PubMed

    Brundrett, Maeghan; Horita, Juske; Anderson, Todd; Pardue, John; Reible, Danny; Jackson, W Andrew

    2015-10-01

    Due to the high volume of crude oil released by the Deepwater Horizon oil spill, the salt marshes along the gulf coast were contaminated with crude oil. Biodegradation of crude oil in salt marshes is primarily limited by oxygen availability due to the high organic carbon content of the soil, high flux rate of S(2-), and saturated conditions. Chlorate, nitrate, and perchlorate were evaluated for use as electron acceptors in comparison to oxygen by comparing oil transformation and mineralization in mesocosms consisting of oiled salt marsh sediment from an area impacted by the BP Horizon oil spill. Mineralization rates were determined by measuring CO2 production and δ (13)C of the produced CO2 and compared to transformation evaluated by measuring the alkane/hopane ratios over a 4-month period. Total alkane/hopane ratios decreased (~55-70 %) for all treatments in the following relative order: aerated ≈ chlorate > nitrate > perchlorate. Total CO2 produced was similar between treatments ranging from 550-700 mg CO2-C. The δ (13)C-CO2 values generally ranged between the indigenous carbon and oil values (-17 and -27‰, respectively). Oil mineralization was greatest for the aerated treatments and least for the perchlorate amended. Our results indicate that chlorate has a similar potential as oxygen to support oil mineralization in contaminated salt marshes, but nitrate and perchlorate were less effective. The use of chlorate as a means to promote oil mineralization in situ may be a promising means to remediate contaminated salt marshes while preventing unwanted secondary impacts related to nutrient management as in the case of nitrate amendments.

  9. Influence of nitrate and sulfate reduction in the bioelectrochemically assisted dechlorination of cis-DCE.

    PubMed

    Lai, Agnese; Verdini, Roberta; Aulenta, Federico; Majone, Mauro

    2015-04-01

    This paper investigated the reductive dechlorination (RD) of cis-dichloroethylene (cis-DCE) (average influent 14.2±0.7 μM) by a bioelectrochemical system (BES), in the presence of real contaminated groundwater containing high levels of nitrate and sulfate. The BES enhanced both the RD and competing reactions, such as nitrate and sulfate reductions, which occurred with neither an external organic carbon source nor any inoculum other than the indigenous microbial consortia in the real groundwater. In preliminary batch tests, RD and full nitrate removal occurred after a short lag phase, whereas sulfate reduction occurred slowly and alongside the RD. Under continuous flow conditions (hydraulic retention time, HRT, 1.4 d), the competition of different electron acceptors was strongly affected by the cathodic potential in the range -550 to -750 mV vs. standard hydrogen electrode (SHE). Nitrate reduction was driven to completion at all tested cathodic potentials, whereas sulfate reduction and the RD rate increased as the cathodic potential became more negative. At -750 mV vs. SHE, strong methanogenesis was also observed and became the most important sink of electrons. The overall coulombic efficiency decreased while the potential became more negative. The RD contribution was always less than 1%. Hence, greater energy consumption was required to obtain higher RD rate and better conversion. Anodic oxidation was only observed at -750 mV vs. SHE where almost 39% of residual vinyl chloride (VC) was oxidized and the sulfate was formed back from sulfide (further contributing to electric waste).

  10. Molecular helices as electron acceptors in high-performance bulk heterojunction solar cells

    PubMed Central

    Zhong, Yu; Trinh, M. Tuan; Chen, Rongsheng; Purdum, Geoffrey E.; Khlyabich, Petr P.; Sezen, Melda; Oh, Seokjoon; Zhu, Haiming; Fowler, Brandon; Zhang, Boyuan; Wang, Wei; Nam, Chang-Yong; Sfeir, Matthew Y.; Black, Charles T.; Steigerwald, Michael L.; Loo, Yueh-Lin; Ng, Fay; Zhu, X.-Y.; Nuckolls, Colin

    2015-01-01

    Despite numerous organic semiconducting materials synthesized for organic photovoltaics in the past decade, fullerenes are widely used as electron acceptors in highly efficient bulk-heterojunction solar cells. None of the non-fullerene bulk heterojunction solar cells have achieved efficiencies as high as fullerene-based solar cells. Design principles for fullerene-free acceptors remain unclear in the field. Here we report examples of helical molecular semiconductors as electron acceptors that are on par with fullerene derivatives in efficient solar cells. We achieved an 8.3% power conversion efficiency in a solar cell, which is a record high for non-fullerene bulk heterojunctions. Femtosecond transient absorption spectroscopy revealed both electron and hole transfer processes at the donor−acceptor interfaces. Atomic force microscopy reveals a mesh-like network of acceptors with pores that are tens of nanometres in diameter for efficient exciton separation and charge transport. This study describes a new motif for designing highly efficient acceptors for organic solar cells. PMID:26382113

  11. Beyond Fullerenes: Designing Alternative Molecular Electron Acceptors for Solution-Processable Bulk Heterojunction Organic Photovoltaics.

    PubMed

    Sauvé, Geneviève; Fernando, Roshan

    2015-09-17

    Organic photovoltaics (OPVs) are promising candidates for providing a low cost, widespread energy source by converting sunlight into electricity. Solution-processable active layers have predominantly consisted of a conjugated polymer donor blended with a fullerene derivative as the acceptor. Although fullerene derivatives have been the acceptor of choice, they have drawbacks such as weak visible light absorption and poor energy tuning that limit overall efficiencies. This has recently fueled new research to explore alternative acceptors that would overcome those limitations. During this exploration, one question arises: what are the important design principles for developing nonfullerene acceptors? It is generally accepted that acceptors should have high electron affinity, electron mobility, and absorption coefficient in the visible and near-IR region of the spectra. In this Perspective, we argue that alternative molecular acceptors, when blended with a conjugated polymer donor, should also have large nonplanar structures to promote nanoscale phase separation, charge separation and charge transport in blend films. Additionally, new material design should address the low dielectric constant of organic semiconductors that have so far limited their widespread application.

  12. Molecular helices as electron acceptors in high-performance bulk heterojunction solar cells

    DOE PAGES

    Yu M. Zhong; Nam, Chang -Yong; Trinh, M. Tuan; Chen, Rongsheng; Purdum, Geoffrey E.; Khlyabich, Petr P.; Sezen, Melda; Oh, Seokjoon; Zhu, Haiming; Fowler, Brandon; et al

    2015-09-18

    Despite numerous organic semiconducting materials synthesized for organic photovoltaics in the past decade, fullerenes are widely used as electron acceptors in highly efficient bulk-heterojunction solar cells. None of the non-fullerene bulk heterojunction solar cells have achieved efficiencies as high as fullerene-based solar cells. Design principles for fullerene-free acceptors remain unclear in the field. Here we report examples of helical molecular semiconductors as electron acceptors that are on par with fullerene derivatives in efficient solar cells. We achieved an 8.3% power conversion efficiency in a solar cell, which is a record high for non-fullerene bulk heterojunctions. Femtosecond transient absorption spectroscopy revealedmore » both electron and hole transfer processes at the donor–acceptor interfaces. Atomic force microscopy reveals a mesh-like network of acceptors with pores that are tens of nanometres in diameter for efficient exciton separation and charge transport. As a result, this study describes a new motif for designing highly efficient acceptors for organic solar cells.« less

  13. Differences in gene expression of human xylosyltransferases and determination of acceptor specificities for various proteoglycans

    SciTech Connect

    Roch, Christina; Kuhn, Joachim; Kleesiek, Knut; Goetting, Christian

    2010-01-01

    The xylosyltransferase (XT) isoforms XT-I and XT-II initiate the posttranslational glycosaminoglycan (GAG) synthesis. Here, we determined the relative expression of both isoforms in 33 human cell lines. The majority of tested cell lines showed dominant XYLT2 gene expression, while only in 23132/87, JAR, NCI-H510A and THP-1 was the XT-I mRNA expression higher. Nearly equal expression levels were detected in six cell lines. Additionally, to shed light on putative differences in acceptor specificities the acceptor properties of potential acceptor sequences were determined. Peptides were expressed as glutathione-S-transferase fusion proteins containing putative or known GAG attachment sites of in vivo proteoglycans. Kinetic analysis showed that K{sub m} and V{sub max} values for XT-I mediated xylosylation were slightly higher than those for XT-II, and that XT-I showed a lesser stringency concerning the acceptor sequence. Mutagenesis of the bikunin peptide sequence in the G-S-G attachment site and flanking regions generated potential acceptor molecules. Here, mutations on the N-terminal side and the attachment site were found to be more susceptible to a loss of acceptor function than mutations in the C-terminus. Altogether the known consensus sequence a-a-a-a-G-S-G-a-a/G-a ('a' representing Asp or Glu) for XT-I mediated xylosylation could be approved and additionally extended to apply to XT-II as well.

  14. A new classification of the amino acid side chains based on doublet acceptor energy levels.

    PubMed Central

    Sneddon, S F; Morgan, R S; Brooks, C L

    1988-01-01

    We describe a new classification of the amino acid side chains based on the potential energy level at which each will accept an extra (doublet) electron. The doublet acceptor energy level, and the doublet acceptor orbital were calculated using semiempirical INDO/2-UHF molecular orbital theory. The results of these calculations show that the side chains fall into four groups. We have termed these groups repulsive, insulating, semiconducting, and attractive in accordance with where each lies on the relative energy scale. We use this classification to examine the role of residues between the donor and acceptor in modulating the rate and mechanism of electron transfer in proteins. With the calculated acceptor levels, we construct a potential barrier for those residues between the donor and acceptor. It is the area beneath this barrier that determines the decay of electronic coupling between donor and acceptor, and thus the transfer rate. We have used this schematic approach to characterize the four electron transfer pathways in myoglobin recently studied by Mayo et al. (Mayo, S.L., W.R. Ellis, R.J. Crutchley, and H.B. Gray. 1986. Science [Wash. DC]. 233:948-952). PMID:3342271

  15. Molecular helices as electron acceptors in high-performance bulk heterojunction solar cells

    SciTech Connect

    Yu M. Zhong; Nam, Chang -Yong; Trinh, M. Tuan; Chen, Rongsheng; Purdum, Geoffrey E.; Khlyabich, Petr P.; Sezen, Melda; Oh, Seokjoon; Zhu, Haiming; Fowler, Brandon; Zhang, Boyuan; Wang, Wei; Sfeir, Matthew Y.; Black, Charles T.; Steigerwald, Michael L.; Loo, Yueh -Lin; Ng, Fay; Zhu, X. -Y.; Nuckolls, Colin

    2015-09-18

    Despite numerous organic semiconducting materials synthesized for organic photovoltaics in the past decade, fullerenes are widely used as electron acceptors in highly efficient bulk-heterojunction solar cells. None of the non-fullerene bulk heterojunction solar cells have achieved efficiencies as high as fullerene-based solar cells. Design principles for fullerene-free acceptors remain unclear in the field. Here we report examples of helical molecular semiconductors as electron acceptors that are on par with fullerene derivatives in efficient solar cells. We achieved an 8.3% power conversion efficiency in a solar cell, which is a record high for non-fullerene bulk heterojunctions. Femtosecond transient absorption spectroscopy revealed both electron and hole transfer processes at the donor–acceptor interfaces. Atomic force microscopy reveals a mesh-like network of acceptors with pores that are tens of nanometres in diameter for efficient exciton separation and charge transport. As a result, this study describes a new motif for designing highly efficient acceptors for organic solar cells.

  16. Molecular helices as electron acceptors in high-performance bulk heterojunction solar cells.

    PubMed

    Zhong, Yu; Trinh, M Tuan; Chen, Rongsheng; Purdum, Geoffrey E; Khlyabich, Petr P; Sezen, Melda; Oh, Seokjoon; Zhu, Haiming; Fowler, Brandon; Zhang, Boyuan; Wang, Wei; Nam, Chang-Yong; Sfeir, Matthew Y; Black, Charles T; Steigerwald, Michael L; Loo, Yueh-Lin; Ng, Fay; Zhu, X-Y; Nuckolls, Colin

    2015-09-18

    Despite numerous organic semiconducting materials synthesized for organic photovoltaics in the past decade, fullerenes are widely used as electron acceptors in highly efficient bulk-heterojunction solar cells. None of the non-fullerene bulk heterojunction solar cells have achieved efficiencies as high as fullerene-based solar cells. Design principles for fullerene-free acceptors remain unclear in the field. Here we report examples of helical molecular semiconductors as electron acceptors that are on par with fullerene derivatives in efficient solar cells. We achieved an 8.3% power conversion efficiency in a solar cell, which is a record high for non-fullerene bulk heterojunctions. Femtosecond transient absorption spectroscopy revealed both electron and hole transfer processes at the donor-acceptor interfaces. Atomic force microscopy reveals a mesh-like network of acceptors with pores that are tens of nanometres in diameter for efficient exciton separation and charge transport. This study describes a new motif for designing highly efficient acceptors for organic solar cells.

  17. Molecular helices as electron acceptors in high-performance bulk heterojunction solar cells.

    PubMed

    Zhong, Yu; Trinh, M Tuan; Chen, Rongsheng; Purdum, Geoffrey E; Khlyabich, Petr P; Sezen, Melda; Oh, Seokjoon; Zhu, Haiming; Fowler, Brandon; Zhang, Boyuan; Wang, Wei; Nam, Chang-Yong; Sfeir, Matthew Y; Black, Charles T; Steigerwald, Michael L; Loo, Yueh-Lin; Ng, Fay; Zhu, X-Y; Nuckolls, Colin

    2015-01-01

    Despite numerous organic semiconducting materials synthesized for organic photovoltaics in the past decade, fullerenes are widely used as electron acceptors in highly efficient bulk-heterojunction solar cells. None of the non-fullerene bulk heterojunction solar cells have achieved efficiencies as high as fullerene-based solar cells. Design principles for fullerene-free acceptors remain unclear in the field. Here we report examples of helical molecular semiconductors as electron acceptors that are on par with fullerene derivatives in efficient solar cells. We achieved an 8.3% power conversion efficiency in a solar cell, which is a record high for non-fullerene bulk heterojunctions. Femtosecond transient absorption spectroscopy revealed both electron and hole transfer processes at the donor-acceptor interfaces. Atomic force microscopy reveals a mesh-like network of acceptors with pores that are tens of nanometres in diameter for efficient exciton separation and charge transport. This study describes a new motif for designing highly efficient acceptors for organic solar cells. PMID:26382113

  18. Acceptor sites for retroviral integrations map near DNase I-hypersensitive sites in chromatin.

    PubMed Central

    Vijaya, S; Steffen, D L; Robinson, H L

    1986-01-01

    Seven cellular loci with acceptor sites for retroviral integrations have been mapped for the presence of DNase I-hypersensitive sites in chromatin. Integrations in three of these loci, chicken c-erbB, rat c-myc, and a rat locus, dsi-1, had been selected for in retrovirus-induced tumors. Of the remaining four, two, designated dsi-3 and dsi-4, harbored acceptor sites for apparently unselected integrations of Moloney murine leukemia virus in a Moloney murine leukemia virus-induced thymoma, and two, designated C and F, harbored unselected acceptor sites for Moloney murine leukemia virus integrations in a rat fibroblast cell line. Each acceptor site mapped to within 500 base pairs of a DNase I-hypersensitive site. In the analyses of the unselected integrations, six hypersensitive sites were observed in 39 kilobases of DNA. The four acceptor sites in this DNA were localized between 0.05 and 0.43 kilobases of a hypersensitive site. The probability of this close association occurring by chance was calculated to be extremely low. Hypersensitive sites were mapped in cells representing the lineage in which integration had occurred as well as in an unrelated lineage. In six of the seven acceptor loci hypersensitive sites could not be detected in the unrelated lineage. Our results indicate that retroviruses preferentially integrate close to DNase I-hypersensitive sites and that many of these sites are expressed in some but not all cells. Images PMID:3490582

  19. Evaluation of Nitrate Concentrations and Sources in the Elk Creek Watershed, Southwestern Ohio, 2003-2004

    USGS Publications Warehouse

    Schumann, Thomas L.; Pletsch, Bruce A.

    2006-01-01

    Nitrate concentrations exceeding the U.S. Environmental Protection Agency maximum contaminant level of 10 milligrams per liter have been reported in ground water near the City of Trenton, Ohio, in the southern part of the Elk Creek watershed. A study of nitrate concentrations and sources in surface and ground water within the Elk Creek watershed was conducted during 2003 and 2004. Nitrate concentrations in the Elk Creek watershed range from less than 0.06 to 11 milligrams per liter. The likely sources of elevated nitrate in the ground water near the City of Trenton appear to be soil organic matter and ammonia fertilizer. Land use is predominantly (93 percent) agricultural, with no identified point sources of nitrate. Likely sources of nitrate in the surface water appear to be manure and septic system effluent, soil organic matter, and ammonia fertilizer. Water-quality constituents, including nitrate, were sampled in water from 38 wells and at 6 surface-water sites. The wells were all shallow (less than 105 feet deep), with open intervals in aquifers of glacial origin, that include tills, outwash, and alluvium. Nitrate concentrations (median of 0.06 milligrams per liter) in the ground water of the upper section of the watershed were lower than those in the lower section of the watershed (median of 4.2 milligrams per liter). Nitrate was analyzed for nitrogen and oxygen isotope values. The d15N and d18O range from -22.36 to +32.29 per mil, and -6.27 to +17.72 per mil, respectively. A positive correlation of d15N and d18O enrichment indicates that denitrification is a prevalent process within the watershed.

  20. Evidence on Anaerobic Methane Oxidation (AOM) in a boreal cultivated peatland with natural and added electron acceptors

    NASA Astrophysics Data System (ADS)

    Dorodnikov, Maxim; Silvennoinen, Hanna; Martikainen, Pertti; Dörsch, Peter

    2015-04-01

    Anaerobic oxidation of methane (AOM) is a process of methane (CH4) consumption under anoxic conditions driven by microorganisms, which oxidize CH4 with various alternate electron acceptors (AEA): sulfate, nitrate, nitrite, metals-(Fe, Mn, Cu), organic compounds. AOM is common in marine ecosystems, where microbial sulfate reduction (SR) consumes most of the CH4 produced in sediments. Despite the global significance of AOM, the exact mechanisms and relevance of the process in terrestrial ecosystems are almost unknown. In the current study the occurrence of AOM was tested for two organic soil horizons (30 and 40 cm depth) and one mineral sub-soil (sand, 50 cm depth) of a cultivated boreal peatland (Linnansuo, Eastern Finland, energy crop Phalaris arundinacea - reed canarygrass) under controlled conditions with the addition of 13C-labeled CH4 and two common AEAs - SO4-2 and Fe+3. Concentrations of CH4, CO2 and O2 were continuously measured during 10 days of incubation and CO2 was sampled periodically under anaerobic conditions for stable 13C analysis. Oxygen dynamics revealed negligible O2 contamination during incubation and its trace amounts (0.05-0.8% from the atmospheric) were accounted in the net CH4 uptake. Application of 13C-enriched CH4 (4.9 atom%) allowed to track the label in CO2 as the end-product of AOM. The highest 13CO2 enrichment (up to 60‰) was observed in mineral sub-soil, however AOM was quantitatively more pronounced in the upper 30 cm horizon (2.1 vs. 0.2 μg CO2 g soil DW-1 in the 50 cm sub-soil). The highest AOM rate of 8.9 ng CO2 g soil DW-1 h-1 was estimated for the control treatment where no AEAs were added indicating sufficient amount of naturally available AEAs, likely organic compounds. This rate was 50 times more intensive (on the C basis) than the CH4 production potential of the same soil. In contrast, external AEAs decreased AOM rates but added Fe+3 stimulated decomposition of native SOM (as seen from the most depleted 13CO2 signatures

  1. Effect of nitrate-based bioremediation on contaminant distribution and sediment toxicity-column study

    SciTech Connect

    Hutchins, S.R.; Bantle, J.A.; Schrock, E.J.

    1998-03-01

    A laboratory column study was set up to evaluate changes in contaminant distribution and sediment toxicity following nitrate-based bioremediation and to correlate toxicity reduction with loss of fuel components. Glass columns were packed with sediment from an aquifer that had been contaminated with JP-4 jet fuel and were remediated using feed solution containing 20 mg/L NO{sub 3}-N. Column influents and effluents were monitored for BTEXTMB (benzene, toluene, ethylbenzene, xylenes, trimethylbenzenes), electron acceptors, nutrients, and dissolved gases. Duplicate columns were sacrificed after 1, 4, and 7 months, and core material was analyzed for chemical constituents. In addition, core material was evaluated for toxicity using FETAX, a developmental toxicity test employing frog embryos.

  2. Quantifying the influence of halogens on nitrate photochemistry at Summit, Greenland

    NASA Astrophysics Data System (ADS)

    Fibiger, D.; Hastings, M. G.; Dibb, J. E.; Corr, C. A.; Huey, L. G.

    2011-12-01

    Concentrations of bromine oxide (BrO) >0.5 pptv have been detected regularly above the snowpack at Summit, Greenland [72°35'N, 38°25'W] during the spring and early summer. BrO often shows a diurnal cycle, with concentrations reaching as high as 10 pptv shortly after solar noon, although more typically found to be between 0.5 - 3.0 pptv. Our goal is to investigate the influence of BrO on the formation of nitrate (i.e. via BrONO2) based upon the oxygen isotopic composition of atmospheric and snow nitrate. Increased understanding of local nitrate post-depositional processing compared to transported nitrate will improve our ability to interpret nitrate in snow and ice core records. Deposition of nitrate results from reactions of NOx (NO and NO2) with oxidants in the atmosphere. The major oxidants in tropospheric nitrate formation, e.g. ozone (O3) and hydroxyl radical (OH), have distinctive isotopic compositions such that their relative contribution to NOx oxidation can be quantified based on Δ17O (Δ17O = δ17O - .52δ18O) of nitrate. In particular, O3 has a unique "mass independent fractionation" signature with Δ17O = 25-35% (per mil); BrO, formed from Br reacting with O3, is expected to carry a Δ17O = 30-42% (Morin et al., ACP, 2007); while OH has a Δ17O of 0%. Models of local photochemical post-depositional processing of NO3- utilizing the Δ17O of nitrate at Summit, Greenland cannot fully explain observed values (Kunasek et al., JGR, 2008; Jarvis et al., GRL, 2008). These O-D models do not include bromine chemistry. In a campaign consisting of two springtime (May-June) field seasons at Summit, Greenland, atmospheric and surface snow measurements were made to quantify the effect of bromine on the formation of atmospheric nitrate. Further, we look to use Δ17O of NO3- to investigate the influence of BrO on locally processed nitrate versus nitrate transported to Summit. Gas phase BrO, NO, NOy and soluble Br, NO3-, and NO2- were measured concurrently. In addition

  3. The Occurrence of Nitrate Reductase in Leaves of Prunus Species 1

    PubMed Central

    Leece, D. R.; Dilley, David R.; Kenworthy, A. L.

    1972-01-01

    Nitrate reductase was found in leaves of apricot Prunus armeniaca, sour cherry P. cerasus, sweet cherry P. avium, and plum P. domestica, but not in peach P. persica, from trees grown in sand culture receiving a nitrate containing nutrient solution. Nitrate was found in the leaves of all species. Nitrate and nitrate reductase were found in leaves of field-grown apricot, sour cherry, and plum trees. The enzyme-extracting medium contained insoluble polyvinylpyrrolidone, and including dithiothreitol or mercaptobenzothiazole did not improve enzyme recovery. Inclusion of cherry leaf extract diminished, and peach leaf extract abolished, recovery of nitrate reductase from oat tissue. Low molecular weight phenols liberated during extraction were probably responsible for inactivation of the enzyme. The enzyme from apricot was two to three times as active as from the other species. Both nicotine adenine diphosphopyridine nucleotide and flavin mononucleotide were effective electron donors. The enzyme was readily induced in apricot leaves by 10 mm nitrate supplied through the leaf petiole. PMID:16658037

  4. Compost product optimization for surface water nitrate treatment in biofiltration applications.

    PubMed

    Alcala, Martin; Jones, Kim D; Ren, Jianhong; Andreassen, Thomas E

    2009-09-01

    Compost based material has been proposed for use as media for biofiltration for environmental restoration in many areas to remediate contaminated water and soil. The objective of this project was to develop techniques to produce compost products for nitrate removal in storm water biofiltration applications, from typical solid waste materials. Compost products were manufactured from different feedstocks and evaluated for their nitrate removal efficiencies. Three different compost products manufactured from varying feedstock amounts of wood chips and grass clippings, along with some dry compost material from the City of Brownsville Municipal Landfill Facility (BMLF), were evaluated using column studies. Indicators of the compost product's quality included moisture % content, pH, and conductivity measurements. The columns were loaded with water containing at least 13.5mg/L nitrate-nitrogen and effluent water from the columns was tested to determine the nitrate reduction for the different products. All of the manufactured compost products and the BMLF material removed some nitrate. The project demonstrated that compost product materials can be effectively used for some nitrate removal for surface water quality improvement and that compost product feedstocks and blends can influence the materials capability for nitrate removal. PMID:19375308

  5. Influence of Acidity on Uranyl Nitrate Association in Aqueous Solutions: A Molecular Dynamics Simulation Study

    SciTech Connect

    de Almeida, Valmor F; Cui, Shengting; Khomami, Bamin; Ye, Xianggui; Smith, Rodney Bryan

    2010-01-01

    Uranyl ion complexation with water and nitrate is a key aspect of the uranium/plutonium extraction process. We have carried out a molecular dynamics simulation study to investigate this complexation process, including the molecular composition of the various complex species, the corresponding structure, and the equilibrium distribution of the complexes. The observed structures of the complexes suggest that in aqueous solution, uranyls are generally hydrated by 5 water molecules in the equatorial plane. When associating with nitrate ions, a water molecule is replaced by a nitrate ion, preserving the five-fold coordination and planar symmetry. Analysis of the pair correlation function between uranyl and nitrate suggests that nitrates bind to uranyl in aqueous solution mainly in a monodentate mode, although a small portion of bidentates occur. Dynamic association and dissociation between uranyls and nitrates take place in aqueous solution with a substantial amount of fluctuation in the number of various uranyl nitrate species. The average number of the uranyl mononitrate complexes shows a dependence on acid concentration consistent with equilibrium-constant analysis, namely, the concentration of [UO2NO3]+ increases with nitric acid concentration.

  6. On the mechanism by which dietary nitrate improves human skeletal muscle function

    PubMed Central

    Affourtit, Charles; Bailey, Stephen J.; Jones, Andrew M.; Smallwood, Miranda J.; Winyard, Paul G.

    2015-01-01

    Inorganic nitrate is present at high levels in beetroot and celery, and in green leafy vegetables such as spinach and lettuce. Though long believed inert, nitrate can be reduced to nitrite in the human mouth and, further, under hypoxia and/or low pH, to nitric oxide. Dietary nitrate has thus been associated favorably with nitric-oxide-regulated processes including blood flow and energy metabolism. Indeed, the therapeutic potential of dietary nitrate in cardiovascular disease and metabolic syndrome—both aging-related medical disorders—has attracted considerable recent research interest. We and others have shown that dietary nitrate supplementation lowers the oxygen cost of human exercise, as less respiratory activity appears to be required for a set rate of skeletal muscle work. This striking observation predicts that nitrate benefits the energy metabolism of human muscle, increasing the efficiency of either mitochondrial ATP synthesis and/or of cellular ATP-consuming processes. In this mini-review, we evaluate experimental support for the dietary nitrate effects on muscle bioenergetics and we critically discuss the likelihood of nitric oxide as the molecular mediator of such effects. PMID:26283970

  7. Nitrogen sources and cycling in the San Francisco Bay estuary: A nitrate dual isotopic composition approach

    USGS Publications Warehouse

    Wankel, Scott D.; Kendall, C.; Francis, C.A.; Paytan, A.

    2006-01-01

    We used the dual isotopic composition of nitrate (??15N and ??18O) within the estuarine system of San Francisco (SF) Bay, California, to explore the utility of this approach for tracing sources and cycling of nitrate (NO3-). Surface water samples from 49 sites within the estuary were sampled during July-August 2004. Spatial variability in the isotopic composition suggests that there are multiple sources of nitrate to the bay ecosystem including seawater, several rivers and creeks, and sewage effluent. The spatial distribution of nitrate from these sources is heavily modulated by the hydrodynamics of the estuary. Mixing along the estuarine salinity gradient is the main control on the spatial variations in isotopic composition of nitrate within the northern arm of SF Bay. However, the nitrate isotopic composition in the southern arm of SF Bay exhibited a combination of source mixing and phytoplankton drawdown due mostly to the long residence time during the summer study period. Very low ?? 18ONO3 values (as low as -5.0???) at the Sacramento-San Joaquin River delta region give rise to a wide range of ??18ONO3 values in the SF Bay system. The range in ??18ONO3 values is more than twice that of (??15NNO3, suggesting that ??18O NO3 is an even more sensitive tool for tracing nitrate sources and cycling than ??15NNO3. ?? 2006, by the American Society of Limnology and Oceanography, Inc.

  8. On the mechanism by which dietary nitrate improves human skeletal muscle function.

    PubMed

    Affourtit, Charles; Bailey, Stephen J; Jones, Andrew M; Smallwood, Miranda J; Winyard, Paul G

    2015-01-01

    Inorganic nitrate is present at high levels in beetroot and celery, and in green leafy vegetables such as spinach and lettuce. Though long believed inert, nitrate can be reduced to nitrite in the human mouth and, further, under hypoxia and/or low pH, to nitric oxide. Dietary nitrate has thus been associated favorably with nitric-oxide-regulated processes including blood flow and energy metabolism. Indeed, the therapeutic potential of dietary nitrate in cardiovascular disease and metabolic syndrome-both aging-related medical disorders-has attracted considerable recent research interest. We and others have shown that dietary nitrate supplementation lowers the oxygen cost of human exercise, as less respiratory activity appears to be required for a set rate of skeletal muscle work. This striking observation predicts that nitrate benefits the energy metabolism of human muscle, increasing the efficiency of either mitochondrial ATP synthesis and/or of cellular ATP-consuming processes. In this mini-review, we evaluate experimental support for the dietary nitrate effects on muscle bioenergetics and we critically discuss the likelihood of nitric oxide as the molecular mediator of such effects. PMID:26283970

  9. Compost product optimization for surface water nitrate treatment in biofiltration applications.

    PubMed

    Alcala, Martin; Jones, Kim D; Ren, Jianhong; Andreassen, Thomas E

    2009-09-01

    Compost based material has been proposed for use as media for biofiltration for environmental restoration in many areas to remediate contaminated water and soil. The objective of this project was to develop techniques to produce compost products for nitrate removal in storm water biofiltration applications, from typical solid waste materials. Compost products were manufactured from different feedstocks and evaluated for their nitrate removal efficiencies. Three different compost products manufactured from varying feedstock amounts of wood chips and grass clippings, along with some dry compost material from the City of Brownsville Municipal Landfill Facility (BMLF), were evaluated using column studies. Indicators of the compost product's quality included moisture % content, pH, and conductivity measurements. The columns were loaded with water containing at least 13.5mg/L nitrate-nitrogen and effluent water from the columns was tested to determine the nitrate reduction for the different products. All of the manufactured compost products and the BMLF material removed some nitrate. The project demonstrated that compost product materials can be effectively used for some nitrate removal for surface water quality improvement and that compost product feedstocks and blends can influence the materials capability for nitrate removal.

  10. Soil nitrate reducing processes – drivers, mechanisms for spatial variation, and significance for nitrous oxide production

    PubMed Central

    Giles, Madeline; Morley, Nicholas; Baggs, Elizabeth M.; Daniell, Tim J.

    2012-01-01

    The microbial processes of denitrification and dissimilatory nitrate reduction to ammonium (DNRA) are two important nitrate reducing mechanisms in soil, which are responsible for the loss of nitrate (NO3−) and production of the potent greenhouse gas, nitrous oxide (N2O). A number of factors are known to control these processes, including O2 concentrations and moisture content, N, C, pH, and the size and community structure of nitrate reducing organisms responsible for the processes. There is an increasing understanding associated with many of these controls on flux through the nitrogen cycle in soil systems. However, there remains uncertainty about how the nitrate reducing communities are linked to environmental variables and the flux of products from these processes. The high spatial variability of environmental controls and microbial communities across small sub centimeter areas of soil may prove to be critical in determining why an understanding of the links between biotic and abiotic controls has proved elusive. This spatial effect is often overlooked as a driver of nitrate reducing processes. An increased knowledge of the effects of spatial heterogeneity in soil on nitrate reduction processes will be fundamental in understanding the drivers, location, and potential for N2O production from soils. PMID:23264770

  11. Inhibition of respiration and nitrate assimilation enhances photohydrogen evolution under low oxygen concentrations in Synechocystis sp. PCC 6803.

    PubMed

    Gutthann, Franziska; Egert, Melanie; Marques, Alexandra; Appel, Jens

    2007-02-01

    In cyanobacterial membranes photosynthetic light reaction and respiration are intertwined. It was shown that the single hydrogenase of Synechocystis sp. PCC 6803 is connected to the light reaction. We conducted measurements of hydrogenase activity, fermentative hydrogen evolution and photohydrogen production of deletion mutants of respiratory electron transport complexes. All single, double and triple mutants of the three terminal respiratory oxidases and the ndhB-mutant without a functional complex I were studied. After activating the hydrogenase by applying anaerobic conditions in the dark hydrogen production was measured at the onset of light. Under these conditions respiratory capacity and amount of photohydrogen produced were found to be inversely correlated. Especially the absence of the quinol oxidase induced an increased hydrogenase activity and an increased production of hydrogen in the light compared to wild type cells. Our results support that the hydrogenase as well as the quinol oxidase function as electron valves under low oxygen concentrations. When the activities of photosystem II and I (PSII and PSI) are not in equilibrium or in case that the light reaction is working at a higher pace than the dark reaction, the hydrogenase is necessary to prevent an acceptor side limitation of PSI, and the quinol oxidase to prevent an overreduction of the plastoquinone pool (acceptor side of PSII). Besides oxygen, nitrate assimilation was found to be an important electron sink. Inhibition of nitrate reductase resulted in an increased fermentative hydrogen production as well as higher amounts of photohydrogen.

  12. Phase diagram of ammonium nitrate

    SciTech Connect

    Dunuwille, Mihindra; Yoo, Choong-Shik

    2013-12-07

    Ammonium Nitrate (AN) is a fertilizer, yet becomes an explosive upon a small addition of chemical impurities. The origin of enhanced chemical sensitivity in impure AN (or AN mixtures) is not well understood, posing significant safety issues in using AN even today. To remedy the situation, we have carried out an extensive study to investigate the phase stability of AN and its mixtures with hexane (ANFO–AN mixed with fuel oil) and Aluminum (Ammonal) at high pressures and temperatures, using diamond anvil cells (DAC) and micro-Raman spectroscopy. The results indicate that pure AN decomposes to N{sub 2}, N{sub 2}O, and H{sub 2}O at the onset of the melt, whereas the mixtures, ANFO and Ammonal, decompose at substantially lower temperatures. The present results also confirm the recently proposed phase IV-IV{sup ′} transition above 17 GPa and provide new constraints for the melting and phase diagram of AN to 40 GPa and 400°C.

  13. Peroxyacetyl nitrate in eastern Scotland.

    PubMed

    McFadyen, G G; Cape, J N

    2005-01-20

    Peroxyacetyl nitrate (PAN) concentrations in air were sampled hourly from 1994 to 1998 at a rural site 15 km south-west of Edinburgh, in eastern Scotland. Annual average concentrations were between 0.1 and 0.15 nl l(-1), with episodes up to 3 nl l(-1) in long-range transported polluted air. PAN concentrations were approximately log-normally distributed. The concentrations measured are the result of a balance between photochemical production rates and removal by thermal decomposition and dry deposition. In general, there was a poor correlation between PAN and ozone concentrations at this rural site except during episodes of photochemical pollution, when the PAN/O(3) volume ratio exceeded 0.01. The PAN/NO(x) volume ratio had a median value of 0.015 but ranged up to 0.25. There was a pronounced seasonal maximum in PAN concentrations in late spring, and a strong diurnal cycle only in April-June, with a maximum at 1700 h. Individual episodes, with concentrations up to 3 nl l(-1), could be traced over distances of ca. 1000 km, with rapid changes in concentration as the prevailing winds advected polluted air masses across the site.

  14. Conduction electrons in acceptor-doped GaAs/GaAlAs heterostructures: a review

    NASA Astrophysics Data System (ADS)

    Zawadzki, Wlodek; Raymond, Andre; Kubisa, Maciej

    2016-05-01

    We review magneto-optical and magneto-transport effects in GaAs/GaAlAs heterostructures doped in GaAlAs barriers with donors, providing two-dimensional (2D) electron gas (2DEG) in GaAs quantum wells (QWS), and additionally doped with smaller amounts of acceptors (mostly Be atoms) in the vicinity of 2DEG. One may also deal with residual acceptors (mostly C atoms). The behavior of such systems in the presence of a magnetic field differs appreciably from those doped in the vicinity of 2DEG with donors. Three subjects related to the acceptor-doped heterostructures are considered. First is the problem of bound states of conduction electrons confined to the vicinity of negatively charged acceptors by the joint effect of a QW and an external magnetic field parallel to the growth direction. A variational theory of such states is presented, demonstrating that an electron turning around a repulsive center has discrete energies above the corresponding Landau levels. Experimental evidence for the discrete electron energies comes from the work on interband photo-magneto-luminescence, intraband cyclotron resonance and quantum magneto-transport (the Quantum Hall and Shubnikov-de Haas effects). An electron rain-down effect at weak electric fields and a boil-off effect at strong electric fields are introduced. It is demonstrated, both theoretically and experimentally, that a negatively charged acceptor can localize more than one electron. The second subject describes experiment and theory of asymmetric quantized Hall and Shubnikov-de Haas plateaus in acceptor-doped GaAs/GaAlAs heterostructures. It is shown that the main features of the plateau asymmetry can be attributed to asymmetric density of Landau states in the presence of acceptors. However, at high magnetic fields, the rain-down effect is also at work. The third subject deals with the so-called disorder modes (DMs) in the cyclotron resonance of conduction electrons. The DMs originate from random distributions of negatively

  15. Impact of donor-acceptor geometry and metal chelation on photophysical properties and applications of triarylboranes.

    PubMed

    Hudson, Zachary M; Wang, Suning

    2009-10-20

    Three-coordinate organoboron compounds have recently found a wide range of applications in materials chemistry as nonlinear optical materials, chemical sensors, and emitters for organic light-emitting diodes (OLEDs). These compounds are excellent electron acceptors due to the empty p(pi) orbital on the boron center. When accompanied by electron donors such as amines, these molecules possess large electronic dipoles, which promote donor-acceptor charge-transfer upon excitation with light. Because of this, donor-acceptor triarylboranes are often highly luminescent both in the solid state and in solution. In this Account, we describe our research to develop donor-acceptor triarylboranes as efficient blue emitters for OLEDs. Through the use of hole-transporting donor groups such as 1-napthylphenylamines, we have prepared multifunctional triarylboranes that can act as the emissive, electron transport, or hole transport layers in OLEDs. We have also examined donor-acceptor compounds based on 2,2'-dipyridylamine or 7-azaindolyl donors, several of which have fluorescent quantum efficiencies approaching 100%. We are also investigating the chemistry of metal-containing triarylboranes. Our studies show that the electron-deficient boryl group can greatly facilitate metal-to-ligand charge-transfer transitions and phosphorescence. In addition, electronegative linker groups such as 2,2'-bipyridine can act in synergy with metal chelation to greatly improve the electron-accepting ability and Lewis acidity of triarylboranes. Donor-acceptor triarylboranes developed in our laboratory can also serve as a series of "switch-on" sensors for fluoride ions. When the donor and acceptor are linked by rigid naphthyl or nonrigid silane linkers, donor-acceptor conjugation is disrupted and charge transfer occurs primarily through space. The binding of fluoride ions to the boron center disrupts this charge transfer, activating alternative pi --> pi* transitions in the molecule and changing the

  16. Reactions Between Water Soluble Organic Acids and Nitrates in Atmospheric Aerosols: Recycling of Nitric Acid and Formation of Organic Salts

    SciTech Connect

    Wang, Bingbing; Laskin, Alexander

    2014-03-25

    Atmospheric particles often include a complex mixture of nitrate and secondary organic materials accumulated within the same individual particles. Nitrate as an important inorganic component can be chemically formed in the atmosphere. For instance, formation of sodium nitrate (NaNO3) and calcium nitrate Ca(NO3)2 when nitrogen oxide and nitric acid (HNO3) species react with sea salt and calcite, respectively. Organic acids contribute a significant fraction of photochemically formed secondary organics that can condense on the preexisting nitrate-containing particles. Here, we present a systematic microanalysis study on chemical composition of laboratory generated particles composed of water soluble organic acids and nitrates (i.e. NaNO3 and Ca(NO3)2) investigated using computer controlled scanning electron microscopy with energy dispersive analysis of X-rays (CCSEM/EDX) and Fourier transform infrared micro-spectroscopy (micro-FTIR). The results show that water-soluble organic acids can react with nitrates releasing gaseous HNO3 during dehydration process. These reactions are attributed to acid displacement of nitrate with weak organic acids driven by the evaporation of HNO3 into gas phase due to its relatively high volatility. The reactions result in significant nitrate depletion and formation of organic salts in mixed organic acids/nitrate particles that in turn may affect their physical and chemical properties relevant to atmospheric environment and climate. Airborne nitrate concentrations are estimated by thermodynamic calculations corresponding to various nitrate depletions in selected organic acids of atmospheric relevance. The results indicate a potential mechanism of HNO3 recycling, which may further affect concentrations of gas- and aerosol-phase species in the atmosphere and the heterogeneous reaction chemistry between them.

  17. Health implications of nitrate and nitrite in drinking water: an update on methemoglobinemia occurrence and reproductive and developmental toxicity.

    PubMed

    Fan, A M; Steinberg, V E

    1996-02-01

    In 1987, an evaluation of the nitrate drinking water standard was performed with a primary focus on the effects of nitrate on methemoglobinemia and reproductive/developmental effects (Fan et al. (1987). Regul. Toxicol. Pharmacol. 7, 135-148). The present review presents an updated overview and evaluation of the available information on the same health effects of nitrate and nitrite with an emphasis on data not included in the previous review, which should be used as a compendium to this report. Recent epidemiologic data have suggested an association between developmental effects in offspring and the maternal ingestion of nitrate from drinking water, but a definite conclusion on the cause and effect relationship cannot be drawn. Animal experimental data have shown reproductive toxicity associated with high exposure levels to nitrate or nitrite, which are not likely to be encountered in drinking water. No teratogenic effects were observed in rats, mice, rabbits, and hamsters tested. Several cases of methemoglobinemia have been reported in infants in the United States using water containing nitrate at levels higher than the current maximum contaminant level (MCL) of 45 ppm (mg/liter) nitrate (NO3) or 10 ppm nitrate-nitrogen (nitrate-N), but none at or lower than the MCL. The uncertainties in the data base are discussed, noting that no uncertainty factor was applied in deriving the MCL in order to account for the uncertainties that exist in the data base.

  18. A multi-tracer approach to assess fingerprints of nitrate in an aquifer under agriculturally used land

    NASA Astrophysics Data System (ADS)

    Pasten-Zapata, Ernesto; Ledesma-Ruiz, Rogelio; Ramirez, Aldo; Harter, Thomas; Mahlknecht, Jürgen

    2014-05-01

    To effectively manage groundwater quality it is essential to understand sources of contamination and underground processes. The objective of the study was to identify sources and fate of nitrate pollution occurring in an aquifer underneath a sub-humid to humid region in NE Mexico which provides 10% of national citrus production. Nitrate isotopes and halide ratios were applied to understand nitrate sources and transformations in relation to land use/land cover. It was found that the study area is subject to diverse nitrate sources including organic waste and wastewater, synthetic fertilizers and soil processes. Animal manure and sewage from septic tanks were the causes of groundwater nitrate pollution within orchards and vegetable agriculture. Dairy activities within a radius of 1,000m from a sampling point increased nitrate pollution. Leachates from septic tanks incited nitrate pollution in residential areas. Soil nitrogen and animal waste were the sources of nitrate in groundwater under shrubland and grassland. Partial denitrification processes were evidenced. The denitrification process helped to attenuate nitrate concentration in the agricultural lands and grassland particularly during summer months.

  19. Qualitative Determination of Nitrate with Triphenylbenzylphosphonium Chloride.

    ERIC Educational Resources Information Center

    Berry, Donna A.; Cole, Jerry J.

    1984-01-01

    Discusses two procedures for the identification of nitrate, the standard test ("Brown Ring" test) and a new procedure using triphenylbenzylphosphonium chloride (TPBPC). Effectiveness of both procedures is compared, with the TPBPC test proving to be more sensitive and accurate. (JM)

  20. Production and consumption of nitrous oxide in nitrate-ammonifying Wolinella succinogenes cells.

    PubMed

    Luckmann, Monique; Mania, Daniel; Kern, Melanie; Bakken, Lars R; Frostegård, Asa; Simon, Jörg

    2014-08-01

    Global warming is moving more and more into the public consciousness. Besides the commonly mentioned carbon dioxide and methane, nitrous oxide (N2O) is a powerful greenhouse gas in addition to its contribution to depletion of stratospheric ozone. The increasing concern about N2O emission has focused interest on underlying microbial energy-converting processes and organisms harbouring N2O reductase (NosZ), such as denitrifiers and ammonifiers of nitrate and nitrite. Here, the epsilonproteobacterial model organism Wolinella succinogenes is investigated with regard to its capacity to produce and consume N2O during growth by anaerobic nitrate ammonification. This organism synthesizes an unconventional cytochrome c nitrous oxide reductase (cNosZ), which is encoded by the first gene of an atypical nos gene cluster. However, W. succinogenes lacks a nitric oxide (NO)-producing nitrite reductase of the NirS- or NirK-type as well as an NO reductase of the Nor-type. Using a robotized incubation system, the wild-type strain and suitable mutants of W. succinogenes that either produced or lacked cNosZ were analysed as to their production of NO, N2O and N2 in both nitrate-sufficient and nitrate-limited growth medium using formate as electron donor. It was found that cells growing in nitrate-sufficient medium produced small amounts of N2O, which derived from nitrite and, most likely, from the presence of NO. Furthermore, cells employing cNosZ were able to reduce N2O to N2. This reaction, which was fully inhibited by acetylene, was also observed after adding N2O to the culture headspace. The results indicate that W. succinogenes cells are competent in N2O and N2 production despite being correctly grouped as respiratory nitrate ammonifiers. N2O production is assumed to result from NO detoxification and nitrosative stress defence, while N2O serves as a terminal electron acceptor in anaerobic respiration. The ecological implications of these findings are discussed. PMID:24781903