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Sample records for acceptors including nitrate

  1. Nitrite and nitrate as electron acceptors for biological sulphide oxidation.

    PubMed

    Munz, G; Mannucci, A; Arreola-Vargas, J; Alatriste-Mondragon, F; Giaccherini, F; Mori, G

    2015-01-01

    Autotrophic denitrification with sulphide using nitrate (R1) and nitrite (R2) as electron acceptor was investigated at bench scale. Different solids retention times (SRT) (5 and 20 d) have been tested in R1 while R2 was operated at SRT=13 d. The results indicated that the process allows complete sulphide removal to be achieved in all tested conditions. Tested sulphide loads were estimated from the H2S produced in a pilot-scale anaerobic digester treating vegetable tannery primary sludge; nitrogen loads originated from the nitrification of the supernatant. Average nitrogen removal efficiencies higher than 80% were observed in all the tested conditions once steady state was reached. A maximum specific nitrate removal rate equal to 0.35 g N-NO3- g VSS(-1) d(-1) was reached in R1. Due to sulphide limitation, incomplete denitrification was observed and nitrite and thiosulphate tend to accumulate especially in the presence of variable environmental conditions in both R1 and R2. Lower SRT caused higher NO2accumulated/NO3reduced ratios (0.22 and 0.24, with SRT of 5 d and 20 d, respectively) using nitrate as electron acceptor in steady-state condition. Temperature decrease caused sudden NO2accumulated/NO3reduced ratio increase in R1 and NO2- removal decrease in R2. PMID:26247758

  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. 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. PMID:24873702

  4. Steady state protein levels in Geobacter metallireducens grown with Iron (III) citrate or nitrate as terminal electron acceptor.

    SciTech Connect

    Ahrendt, A. J.; Tollaksen, S. L.; Lindberg, C.; Zhu, W.; Yates, J. R., III; Nevin, K. P.; Lovley, D.; Giometti, C. S.; Biosciences Division; The Scripps Research Inst.; Univ. of Massachusetts

    2007-01-01

    Geobacter species predominate in aquatic sediments and submerged soils where organic carbon sources are oxidized with the reduction of Fe(III). The natural occurrence of Geobacter in some waste sites suggests this microorganism could be useful for bioremediation if growth and metabolic activity can be regulated. 2-DE was used to monitor the steady state protein levels of Geobacter metallireducens grown with either Fe(III) citrate or nitrate to elucidate metabolic differences in response to different terminal electron acceptors present in natural environments populated by Geobacter. Forty-six protein spots varied significantly in abundance (p<0.05) between the two growth conditions; proteins were identified by tryptic peptide mass and peptide sequence determined by MS/MS. Enzymes involved in pyruvate metabolism and the tricarboxylic acid (TCA) cycle were more abundant in cells grown with Fe(III) citrate, while proteins associated with nitrate metabolism and sensing cellular redox status along with several proteins of unknown function were more abundant in cells grown with nitrate. These results indicate a higher level of flux through the TCA cycle in the presence of Fe(III) compared to nitrate. The oxidative stress response observed in previous studies of Geobacter sulfurreducens grown with Fe(III) citrate was not seen in G. metallireducens.

  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.

    PubMed Central

    Hutchins, S R

    1991-01-01

    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 micrograms/liter within 7 days under aerobic conditions, whereas only the alkylbenzenes were degraded when either nitrate or nitrous oxide was used. With limited oxygen, monoaromatic hydrocarbons were degraded but removal ceased once oxygen was consumed. However, when nitrate was also present, biodegradation of the alkylbenzenes continued with no apparent lag. Although benzene was still recalcitrant, levels were reduced compared with levels after treatment with nitrate or limited oxygen alone. PMID:1768110

  7. 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...

  8. Spectral, thermal, XRD and SEM studies of charge-transfer complexation of hexamethylenediamine and three types of acceptors: π-, σ- and vacant orbital acceptors that include quinol, picric acid, bromine, iodine, SnCl4 and ZnCl2 acceptors

    NASA Astrophysics Data System (ADS)

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

    2013-11-01

    In this work, structural, thermal, morphological and pharmacological characterization was performed on the interactions between a hexamethylenediamine (HMDA) donor and three types of acceptors to understand the complexation behavior of diamines. The three types of acceptors include π-acceptors (i.e., quinol (QL) and picric acid (PA)), σ-acceptors (i.e., bromine and iodine) and vacant orbital acceptors (i.e., tin(IV) tetrachloride (SnCl4) and zinc chloride (ZnCl2)). The characterization of the obtained CT complexes was performed using elemental analysis, infrared (IR), Raman, 1H NMR and electronic absorption spectroscopy, powder X-ray diffraction (XRD) and thermogravimetric (TG) analysis. Their morphologies were studied using scanning electron microscopy with energy-dispersive X-ray analysis (SEM-EDX). The biological activities of the obtained CT complexes were tested for their antibacterial activities. The complex containing the QL acceptor exhibited a remarkable electronic spectrum with a strong, broad absorption band, which had an observed λmax that was at a much longer wavelength than those of the free reactants. In addition, this complex exhibited strong antimicrobial activities against various bacterial and fungal strains compared to standard drugs. The complexes containing the PA, iodine, Sn(IV) and Zn(II) acceptors exhibited good thermal stability up to 240, 330, 275 and 295 °C, respectively. The complexes containing bromine, Sn(IV) and Zn(II) acceptors exhibited good crystallinity. In addition to its good crystallinity properties, the complex containing the bromine acceptor exhibits a remarkable morphology feature.

  9. Importance of including small-scale drain discharge data in the calibration of a catchment scale nitrate model

    NASA Astrophysics Data System (ADS)

    Hansen, A.; Refsgaard, J.; Christensen, B. S.; Jensen, K. H.

    2011-12-01

    Nitrate leaching from agricultural areas and the resulting pollution of groundwater and surface waters is one of the largest challenges in water resources management in Denmark. Nitrate can however be naturally degraded under anaerobic conditions and several studies have shown that degradation in the saturated zone removes more than 50% of the nitrate leaching in Danish catchments. For degradation of nitrate to occur in the saturated zone, nitrate must be transported under the redox interface and a correct simulation of the small-scale flow patterns within a catchment is therefore important in nitrate models. The general findings in Danish nitrate modeling studies are that the models perform well at catchment scale, but the predictability of the models decreases at smaller scale. Thus the model predictions are highly uncertain at small scale and the models cannot at present predict areas within a catchment, where the majority of the nitrate is brought under the interface and thus degraded, and areas, where nitrate is transported directly to streams and lakes without any significant reduction. The objective of this study is to test if the small scale performance of a catchment scale nitrate model can be improved by including small scale observation data in the calibration procedure. The study area is the clayey catchment to Lillebæk stream (4.7 km2), located on the island of Funen in Denmark. Due to the presence of clayey top soils subsurface drains are installed and in consequence the stream discharge is highly dominated by drain flow. An integrated transient hydrological model based on the MIKE SHE code has been developed for the study area. The model has been calibrated against hydraulic head measurements and stream discharge measurements from two stations, one covering most of the catchment and the other station approximately half, using the parameter estimator code PEST. Acceptable model performance has been achieved at catchment scale calibrating the model

  10. 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

  11. Phylogenomics of Mycobacterium Nitrate Reductase Operon.

    PubMed

    Huang, Qinqin; Abdalla, Abualgasim Elgaili; Xie, Jianping

    2015-07-01

    NarGHJI operon encodes a nitrate reductase that can reduce nitrate to nitrite. This process enhances bacterial survival by nitrate respiration under anaerobic conditions. NarGHJI operon exists in many bacteria, especially saprophytic bacteria living in soil which play a key role in the nitrogen cycle. Most actinomycetes, including Mycobacterium tuberculosis, possess NarGHJI operons. M. tuberculosis is a facultative intracellular pathogen that expands in macrophages and has the ability to persist in a non-replicative form in granuloma lifelong. Nitrogen and nitrogen compounds play crucial roles in the struggle between M. tuberculosis and host. M. tuberculosis can use nitrate as a final electron acceptor under anaerobic conditions to enhance its survival. In this article, we reviewed the mechanisms regulating nitrate reductase expression and affecting its activity. Potential genes involved in regulating the nitrate reductase expression in M. tuberculosis were identified. The conserved NarG might be an alternative mycobacterium taxonomic marker. PMID:25980349

  12. 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.

  13. Alternansucrase acceptor products

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The regioselectivity of alternansucrase (EC 2.4.1.140) differs from dextransucrase (EC 2.4.1.5) in ways that can be useful for the synthesis of novel oligosaccharide structures. For example, it has been recently shown that the major oligosaccharides produced when maltose is the acceptor include one...

  14. 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.

  15. 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,…

  16. 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.

  17. COMPARISON OF MUTAGENIC ACTIVITIES OF SEVERAL PEROXYACL NITRATES

    EPA Science Inventory

    Salmonella typhimurium, strain TA100 was exposed to a series of peroxyacyl nitrates including peroxyacetyl nitrate (PAN), peroxypropionyl nitrate (PPN), peroxybutyryl nitrate (PBN), peroxybenzoyl nitrate (PBzN), and chloroperoxyacetyl nitrate (CPAN). as-phase concentrations for t...

  18. COMPARISON OF MUTAGENIC ACTIVITIES OF SEVERAL PEROXYACYL NITRATES

    EPA Science Inventory

    Salmonella typhimurium strain TA100 was exposed to a series of peroxyacyl nitrates including peroxyacetyl nitrate (PAN), peroxypropionyl nitrate peroxybutyryl nitrate (PBN), peroxybenzoyl nitrate (PBzN), and chlororoxyacetyl nitrate (CPAN). as phase concentrations for the individ...

  19. 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. PMID:27364687

  20. 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. PMID:17686028

  1. INFLUENCE OF ALTERNATIVE ELECTRON ACCEPTORS ON THE ANAEROBIC BIODEGRADABILITY OF CHLORINATED PHENOLS AND BENZOIC ACIDS

    EPA Science Inventory

    Nitrate, sulfate, and carbonate were used as electron acceptors to examine the anaerobic biodegradability of chlorinated aromatic compounds in estuarine and freshwater sediments. he respective denitrifying, sulfidogenic, and methanogenic enrichment cultures were established on ea...

  2. 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.

  3. 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

  4. 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. PMID:24862003

  5. 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

  6. 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.

  7. 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

  8. 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

  9. Effects of nitrate injection on microbial enhanced oil recovery and oilfield reservoir souring.

    PubMed

    da Silva, Marcio Luis Busi; Soares, Hugo Moreira; Furigo, Agenor; Schmidell, Willibaldo; Corseuil, Henry Xavier

    2014-11-01

    Column experiments were utilized to investigate the effects of nitrate injection on sulfate-reducing bacteria (SRB) inhibition and microbial enhanced oil recovery (MEOR). An indigenous microbial consortium collected from the produced water of a Brazilian offshore field was used as inoculum. The presence of 150 mg/L volatile fatty acids (VFA´s) in the injection water contributed to a high biological electron acceptors demand and the establishment of anaerobic sulfate-reducing conditions. Continuous injection of nitrate (up to 25 mg/L) for 90 days did not inhibit souring. Contrariwise, in nitrogen-limiting conditions, the addition of nitrate stimulated the proliferation of δ-Proteobacteria (including SRB) and the associated sulfide concentration. Denitrification-specific nirK or nirS genes were not detected. A sharp decrease in water interfacial tension (from 20.8 to 14.5 mN/m) observed concomitantly with nitrate consumption and increased oil recovery (4.3 % v/v) demonstrated the benefits of nitrate injection on MEOR. Overall, the results support the notion that the addition of nitrate, at this particular oil reservoir, can benefit MEOR by stimulating the proliferation of fortuitous biosurfactant-producing bacteria. Higher nitrate concentrations exceeding the stoichiometric volatile fatty acid (VFA) biodegradation demands and/or the use of alternative biogenic souring control strategies may be necessary to warrant effective SRB inhibition down gradient from the injection wells. PMID:25149457

  10. 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.

  11. Influence of various nitrogenous electron acceptors on the anaerobic sulfide oxidation.

    PubMed

    Jing, Cai; Ping, Zheng; Mahmood, Qaisar

    2010-05-01

    The effect of nitrate and nitrite as electron acceptors on the performance of anaerobic sulfide oxidizing process (ASO process) was investigated. For nitrate-ASO process, the maximum influent nitrogen concentration was lower than that in nitrite-ASO process, but the maximum influent sulfur concentration was higher than that of nitrite-ASO process. The half saturation values for nitrogen and sulfur in both processes were similar. The minimum reaction time taken for nitrite and sulfide was relatively shorter than in nitrite-ASO reactor. As indicated by sensitivity ratio, activated sludge was more tolerant to sulfide, which had no significant differences between two processes; while it was relatively more sensitive to nitrite over nitrate. PCR-DGGE fingerprints, Dice and Shannon similarity indices and sequencing results all suggested that the microbial communities in both reactors were similar. The use of nitrate as an electron acceptor may be preferable over nitrite to treat sulfide-rich wastewaters. PMID:20047830

  12. 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.

  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. PMID:26783836

  14. 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.

  15. 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.

  16. [Effect of C/N ratio on nitrous oxide production during denitrification with different electron acceptors].

    PubMed

    Shang, Hui-Lai; Peng, Yong-Zhen; Zhang, Jing-Rong; Wang, Shu-Ying

    2009-07-15

    The experiment investigated the nitrous oxide production under different C/N ratios during denitrification, taking nitrate and nitrite as electron acceptor respectively. Ethanol was selected as carbon source. The C/N ratios were 0, 1.2, 2.4, 3.5, 5.0 and 20 when nitrate was taken as electron acceptor and C/N ratios 0, 1.8, 2.4, 3.0, 4.3, 5.2, 6.6, 20.6 when electron acceptor was nitrite. The results indicated that: the optimum C/N ratio was 3.0 taking nitrite as electron acceptor and the N2O production was 0.044 mg x L(-1); the optimum C/N ratio was 5.0 taking nitrate as electron acceptor and the N2O production was 0.135 mg x L(-1) which was 3 times higher than that of nitrite as electron acceptor. Though the electron acceptor changed, the trend of N2O production was similar: when carbon source was badly insufficient, the production of N2O and denitrification rate were both quite small; the N2O production increased with the increasing of the quantity of carbon source; when the carbon source was excessive, the N2O production sharply raised. Consequently, compared to complete nitrification and denitrification, short-cut nitrification and denitrification could save 40% carbon source. Moreover, controlling C/N = 3 could reduce the production of N2O in short-cut nitrification. PMID:19775000

  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. The outer membrane protein Omp35 affects the reduction of Fe(III), nitrate, and fumarate by Shewanella oneidensis MR-1

    PubMed Central

    Maier, Tamara M; Myers, Charles R

    2004-01-01

    Background Shewanella oneidensis MR-1 uses several electron acceptors to support anaerobic respiration including insoluble species such as iron(III) and manganese(IV) oxides, and soluble species such as nitrate, fumarate, dimethylsulfoxide and many others. MR-1 has complex branched electron transport chains that include components in the cytoplasmic membrane, periplasm, and outer membrane (OM). Previous studies have implicated a role for anaerobically upregulated OM electron transport components in the use of insoluble electron acceptors, and have suggested that other OM components may also contribute to insoluble electron acceptor use. In this study, the role for an anaerobically upregulated 35-kDa OM protein (Omp35) in the use of anaerobic electron acceptors was explored. Results Omp35 was purified from the OM of anaerobically grown cells, the gene encoding Omp35 was identified, and an omp35 null mutant (OMP35-1) was isolated and characterized. Although OMP35-1 grew on all electron acceptors tested, a significant lag was seen when grown on fumarate, nitrate, and Fe(III). Complementation studies confirmed that the phenotype of OMP35-1 was due to the loss of Omp35. Despite its requirement for wild-type rates of electron acceptor use, analysis of Omp35 protein and predicted sequence did not identify any electron transport moieties or predicted motifs. OMP35-1 had normal levels and distribution of known electron transport components including quinones, cytochromes, and fumarate reductase. Omp35 is related to putative porins from MR-1 and S. frigidimarina as well as to the PorA porin from Neisseria meningitidis. Subcellular fraction analysis confirmed that Omp35 is an OM protein. The seven-fold anaerobic upregulation of Omp35 is mediated post-transcriptionally. Conclusion Omp35 is a putative porin in the OM of MR-1 that is markedly upregulated anaerobically by a post-transcriptional mechanism. Omp35 is required for normal rates of growth on Fe(III), fumarate, and

  19. 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.

  20. 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

  1. 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

  2. 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.

    PubMed

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

    2015-04-15

    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, (1)H 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. PMID:25677533

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. 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

  8. 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...

  9. NITRATE FOR BIORESTORATION OF AN AQUIFER CONTAMINATED WITH JET FUEL

    EPA Science Inventory

    There is little information available in the open literature on the performance of bioremediation at field scale. The report documents the rate and extent of treatment of a spill of JP-4 in a drinking-water aquifer, using nitrate as the primary electron acceptor for microbial res...

  10. Problems Caused by Microbes and Treatment Strategies The Effect of Nitrate Injection in Oil Reservoirs - Experience with Nitrate Injection in the Halfdan Oilfield

    NASA Astrophysics Data System (ADS)

    Larsen, Jan; Skovhus, Torben Lund

    This chapter deals with the use of nitrate injection for reservoir souring mitigation in an oilfield with seawater injection in the Danish sector of the North Sea. Nitrate impacts on the activity of sulphate-reducing bacteria (SRB) and biofilm redox potential (Larsen et al., 2007), as a result of which corrosion due to SRB activity will be reduced, souring inhibited and previously formed sulphide removed (Larsen, 2002). One important aspect is that the microbiological reduction of nitrate provides approximately three times more energy to SRB than the reduction of sulphate. Therefore, when both nitrate and sulphate are present, nitrate becomes the preferred electron acceptor and SRB capable of growing on nitrate will dominate. Nitrate provides a competitive advantage to nitrate-utilising bacteria (indicated by the general acronym NUB) during competition for available carbon sources as the NUB are capable of much faster growth than SRB.

  11. 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.

  12. DONOR-ACCEPTOR INTERACTIONS OF NITROGEN*

    PubMed Central

    Kimura, J. E.; Szent-Györgyi, A.

    1969-01-01

    The nitrogen atoms of organic molecules readily enter into donor-acceptor interactions, giving off an electron from their lone pair. Under favorable conditions the acceptor can form free radicals. S and O atoms behave likewise but less intensely. PMID:4306047

  13. Glucansucrase acceptor reactions with D-mannose

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The main acceptor product of glucansucrases with D-mannose has not previously been identified. We used glucansucrases that form water-insoluble a-D-glucans to produce increased yields of acceptor products from D-mannose, and identified the major product as 6-O-a-D-glucopyranosyl-D-mannose. Glucansuc...

  14. 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.)

  15. 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

  16. 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

  17. 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

    2016-02-01

    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. PMID:26822564

  18. Optical activation behavior of ion implanted acceptor species in GaN

    SciTech Connect

    Skromme, B.J.; Martinez, G.L.

    2000-07-01

    Ion implantation is used to investigate the spectroscopic properties of Mg, Be, and C acceptors in GaN. Activation of these species is studied using low temperature photoluminescence (PL). Low dose implants into high quality undoped hydride vapor phase epitaxial (HVPE) material are used in conjunction with high temperature (1300 C) rapid thermal anneals to obtain high quality spectra. Dramatic, dose-dependent evidence of Mg acceptor activation is observed without any co-implants, including a strong, sharp neutral Mg acceptor-bound exciton and strong donor-acceptor pair peaks. Variable temperature measurements reveal a band-to-acceptor transition, whose energy yields an optical binding energy of 224 meV. Be and C implants yield only slight evidence of shallow acceptor-related features and produce dose-correlated 2.2 eV PL, attributed to residual implantation damage. Their poor optical activation is tentatively attributed to insufficient vacancy production by these lighter ions. Clear evidence is obtained for donor-Zn acceptor pair and acceptor-bound exciton peaks in Zn-doped HVPE material.

  19. Acceptor Products of Alternansucrase with Gentiobiose

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In the presence of suitable acceptor molecules, dextransucrase makes a homologous series of oligosaccharides in which the isomers differ by a single glucosyl unit, whereas alternansucrase synthesizes one trisaccharide, two tetrasaccharides, etc. Previously, we showed that alternansucrase only forms...

  20. 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.

  1. 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. PMID:25784903

  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. 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

  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. 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

  7. Mechanisms of electron acceptor utilization: implications for simulating anaerobic biodegradation.

    PubMed

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

    2004-09-01

    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

  8. Skeletal muscle as an endogenous nitrate reservoir

    PubMed Central

    Piknova, Barbora; Park, Ji Won; Swanson, Kathryn M.; Dey, Soumyadeep; Noguchi, Constance Tom; Schechter, Alan N

    2015-01-01

    The nitric oxide synthase (NOS) family of enzymes form nitric oxide (NO) from arginine in the presence of oxygen. At reduced oxygen availability NO is also generated from nitrate in a two step process by bacterial and mammalian molybdopterin proteins, and also directly from nitrite by a variety of five-coordinated ferrous hemoproteins. The mammalian NO cycle also involves direct oxidation of NO to nitrite, and both NO and nitrite to nitrate by oxy-ferrous hemoproteins. The liver and blood are considered the sites of active mammalian NO metabolism and nitrite and nitrate concentrations in the liver and blood of several mammalian species, including human, have been determined. However, the large tissue mass of skeletal muscle had not been generally considered in the analysis of the NO cycle, in spite of its long-known presence of significant levels of active neuronal NOS (nNOS or NOS1). We hypothesized that skeletal muscle participates in the NO cycle and, due to its NO oxidizing heme protein, oxymyoglobin, has high concentrations of nitrate ions. We measured nitrite and nitrate concentrations in rat and mouse leg skeletal muscle and found unusually high concentrations of nitrate but similar levels of nitrite, when compared to the liver. The nitrate reservoir in muscle is easily accessible via the bloodstream and therefore nitrate is available for transport to internal organs where it can be reduced to nitrite and NO. Nitrate levels in skeletal muscle and blood in nNOS−/− mice were dramatically lower when compared with controls, which support further our hypothesis. Although the nitrate reductase activity of xanthine oxidoreductase in muscle is less than that of liver, the residual activity in muscle could be very important in view of its total mass and the high basal level of nitrate. We suggest that skeletal muscle participates in overall NO metabolism, serving as a nitrate reservoir, for direct formation of nitrite and NO, and for determining levels of nitrate

  9. 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

  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. PMID:26031087

  11. 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... nitrate and potassium nitrate. Sodium nitrate and potassium nitrate are subject to prior sanctions issued... potassium nitrite, in the production of cured red meat products and cured poultry products....

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

    PubMed

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

    2014-08-01

    Filamentous bacteria of the Desulfobulbaceae family can conduct electrons over centimeter-long distances thereby coupling oxygen reduction at the surface of marine sediment to sulfide oxidation in deeper anoxic layers. The ability of these cable bacteria to use alternative electron acceptors is currently unknown. Here we show that these organisms can use also nitrate or nitrite as an electron acceptor thereby coupling the reduction of nitrate to distant oxidation of sulfide. Sulfidic marine sediment was incubated with overlying nitrate-amended anoxic seawater. Within 2 months, electric coupling of spatially segregated nitrate reduction and sulfide oxidation was evident from: (1) the formation of a 4-6-mm-deep zone separating sulfide oxidation from the associated nitrate reduction, and (2) the presence of pH signatures consistent with proton consumption by cathodic nitrate reduction, and proton production by anodic sulfide oxidation. Filamentous Desulfobulbaceae with the longitudinal structures characteristic of cable bacteria were detected in anoxic, nitrate-amended incubations but not in anoxic, nitrate-free controls. Nitrate reduction by cable bacteria using long-distance electron transport to get privileged access to distant electron donors is a hitherto unknown mechanism in nitrogen and sulfur transformations, and the quantitative importance for elements cycling remains to be addressed. PMID:24577351

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

    PubMed Central

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

    2014-01-01

    Filamentous bacteria of the Desulfobulbaceae family can conduct electrons over centimeter-long distances thereby coupling oxygen reduction at the surface of marine sediment to sulfide oxidation in deeper anoxic layers. The ability of these cable bacteria to use alternative electron acceptors is currently unknown. Here we show that these organisms can use also nitrate or nitrite as an electron acceptor thereby coupling the reduction of nitrate to distant oxidation of sulfide. Sulfidic marine sediment was incubated with overlying nitrate-amended anoxic seawater. Within 2 months, electric coupling of spatially segregated nitrate reduction and sulfide oxidation was evident from: (1) the formation of a 4–6-mm-deep zone separating sulfide oxidation from the associated nitrate reduction, and (2) the presence of pH signatures consistent with proton consumption by cathodic nitrate reduction, and proton production by anodic sulfide oxidation. Filamentous Desulfobulbaceae with the longitudinal structures characteristic of cable bacteria were detected in anoxic, nitrate-amended incubations but not in anoxic, nitrate-free controls. Nitrate reduction by cable bacteria using long-distance electron transport to get privileged access to distant electron donors is a hitherto unknown mechanism in nitrogen and sulfur transformations, and the quantitative importance for elements cycling remains to be addressed. PMID:24577351

  14. 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.

  15. 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.

  16. Engineered oligosaccharyltransferases with greatly relaxed acceptor site specificity

    PubMed Central

    Ollis, Anne A.; Zhang, Sheng; Fisher, Adam C.; DeLisa, Matthew P.

    2015-01-01

    The Campylobacter jejuni protein glycosylation locus (pgl) encodes machinery for asparagine-linked (N-linked) glycosylation and serves as the archetype for bacterial N-glycosylation. This machinery has been functionally transferred into Escherichia coli, thereby enabling convenient mechanistic dissection of the N-glycosylation process in this genetically tractable host. Here, we sought to identify sequence determinants in the oligosaccharyltransferase PglB that restrict its specificity to only those glycan acceptor sites containing a negatively charged residue at the −2 position relative to asparagine. This involved creation of a genetic assay named glycoSNAP (glycosylation of secreted N-linked acceptor proteins) that facilitates high-throughput screening of glycophenotypes in E. coli. Using this assay, we isolated several C. jejuni PglB variants that were capable of glycosylating an array of noncanonical acceptor sequences including one in a eukaryotic N-glycoprotein. Collectively, these results underscore the utility of glycoSNAP for shedding light on poorly understood aspects of N-glycosylation and for engineering designer N-glycosylation biocatalysts. PMID:25129029

  17. Engineered oligosaccharyltransferases with greatly relaxed acceptor-site specificity.

    PubMed

    Ollis, Anne A; Zhang, Sheng; Fisher, Adam C; DeLisa, Matthew P

    2014-10-01

    The Campylobacter jejuni protein glycosylation locus (pgl) encodes machinery for asparagine-linked (N-linked) glycosylation and serves as the archetype for bacterial N-linked glycosylation. This machinery has been functionally transferred into Escherichia coli, enabling convenient mechanistic dissection of the N-linked glycosylation process in this genetically tractable host. Here we sought to identify sequence determinants in the oligosaccharyltransferase PglB that restrict its specificity to only those glycan acceptor sites containing a negatively charged residue at the -2 position relative to asparagine. This involved creation of a genetic assay, glycosylation of secreted N-linked acceptor proteins (glycoSNAP), that facilitates high-throughput screening of glycophenotypes in E. coli. Using this assay, we isolated several C. jejuni PglB variants that could glycosylate an array of noncanonical acceptor sequences, including one in a eukaryotic N-glycoprotein. These results underscore the utility of glycoSNAP for shedding light on poorly understood aspects of N-linked glycosylation and for engineering designer N-linked glycosylation biocatalysts. PMID:25129029

  18. 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.

  19. 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.

  20. Photochemistry of Nitrate Adsorbed on Mineral Dust

    NASA Astrophysics Data System (ADS)

    Gankanda, A.; Grassian, V. H.

    2013-12-01

    Mineral dust particles in the atmosphere are often associated with adsorbed nitrate from heterogeneous reactions with nitrogen oxides including HNO3 and NO2. Although nitrate ion is a well-studied chromophore in natural waters, the photochemistry of adsorbed nitrate on mineral dust particles is yet to be fully explored. In this study, wavelength dependence of the photochemistry of adsorbed nitrate on different model components of mineral dust aerosol has been investigated using transmission FTIR spectroscopy. Al2O3, TiO2 and NaY zeolite were used as model systems to represent non-photoactive oxides, photoactive semiconductor oxides and porous materials respectively, present in mineral dust aerosol. In this study, adsorbed nitrate is irradiated with 254 nm, 310 nm and 350 nm narrow band light. In the irradiation with narrow band light, NO2 is the only detectable gas-phase product formed from nitrate adsorbed on Al2O3 and TiO2. The NO2 yield is highest at 310 nm for both Al2O3 and TiO2. Unlike Al2O3 and TiO2, in zeolite, adsorbed nitrate photolysis to nitrite is observed only at 310 nm during narrow band irradiation. Moreover gas phase products were not detected during nitrate photolysis in zeolite at all three wavelengths. The significance of these differences as related to nitrate photochemistry on different mineral dust components will be highlighted.

  1. 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.

  2. Non-fullerene acceptors: exciton dissociation with PTCDA versus C60.

    PubMed

    Dutton, Gregory J; Robey, Steven W

    2015-06-28

    Extensive development of new polymer and small molecule donors has helped produce a steady increase in the efficiency of organic photovoltaic (OPV) devices. However, OPV technology would also benefit from the introduction of non-fullerene acceptors. Unfortunately, efforts to replace fullerenes have typically led to significantly reduced efficiencies. A number of possible explanations for reduced efficiencies with non-fullerene acceptors compared to fullerene acceptors have been suggested, including the formation of unfavorable morphologies in non-fullerene systems and/or favorable excitation/carrier delocalization in fullerenes. In addition, enhanced exciton dissociation associated with fundamental characteristics of the fullerene molecular electronic states has also been suggested. We used time-resolved two-photon photoemission (TR-2PPE) to directly compare exciton dissociation at interfaces between zinc phthalocyanine (ZnPc) interfaces and the non-fullerene acceptor, perylene tetracarboxylic dianhydride (PTCDA) versus dissociation measured at the analogous interface with C60, and thus help discriminate between these potential explanations. Exciton dissociation rates are comparable for phthalocyanine interfaces with both acceptors, allowing us to suggest a hierarchy for the importance of various effects producing higher efficiencies with fullerene acceptors. PMID:26027544

  3. Compensatory periplasmic nitrate reductase activity supports anaerobic growth of Pseudomonas aeruginosa PAO1 in the absence of membrane nitrate reductase.

    PubMed

    Van Alst, Nadine E; Sherrill, Lani A; Iglewski, Barbara H; Haidaris, Constantine G

    2009-10-01

    Nitrate serves as a terminal electron acceptor under anaerobic conditions in Pseudomonas aeruginosa. Reduction of nitrate to nitrite generates a transmembrane proton motive force allowing ATP synthesis and anaerobic growth. The inner membrane-bound nitrate reductase NarGHI is encoded within the narK1K2GHJI operon, and the periplasmic nitrate reductase NapAB is encoded within the napEFDABC operon. The roles of the 2 dissimilatory nitrate reductases in anaerobic growth, and the regulation of their expressions, were examined by use of a set of deletion mutants in P. aeruginosa PAO1. NarGHI mutants were unable to grow anaerobically, but plate cultures remained viable up to 120 h. In contrast, the nitrate sensor-response regulator mutant DeltanarXL displayed growth arrest initially, but resumed growth after 72 h and reached the early stationary phase in liquid culture after 120 h. Genetic, transcriptional, and biochemical studies demonstrated that anaerobic growth recovery by the NarXL mutant was the result of NapAB periplasmic nitrate reductase expression. A novel transcriptional start site for napEFDABC expression was identified in the NarXL mutant grown anaerobically. Furthermore, mutagenesis of a consensus NarL-binding site monomer upstream of the novel transcriptional start site restored anaerobic growth recovery in the NarXL mutant. The data suggest that during anaerobic growth of wild-type P. aeruginosa PAO1, the nitrate response regulator NarL directly represses expression of periplasmic nitrate reductase, while inducing maximal expression of membrane nitrate reductase. PMID:19935885

  4. 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...

  5. 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... nitrite, with or without sodium or potassium nitrite, in the production of cured red meat products...

  6. 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... nitrite, with or without sodium or potassium nitrite, in the production of cured red meat products...

  7. 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... nitrite, with or without sodium or potassium nitrite, in the production of cured red meat products...

  8. 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.

  9. 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.

  10. 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.

  11. Field determination of nitrate using nitrate reductase

    SciTech Connect

    Campbell, E.R.; Corrigan, J.S.; Campbell, W.H.

    1997-12-31

    Nitrate is routinely measured in a variety of substrates - water, tissues, soils, and foods - both in the field and in laboratory settings. The most commonly used nitrate test methods involve the reduction of nitrate to nitrite via a copper-cadmium reagent, followed by reaction of the nitrite with the Griess dye reagents. The resulting color is translated into a nitrate concentration by comparison with a calibrated color chart or comparator, or by reading the absorbance in a spectrophotometer. This basic method is reliable and sufficiently sensitive for many applications. However, the cadmium reagent is quite toxic. The trend today is for continued increase in concern for worker health and safety; in addition, there are increasing costs and logistical problems associated with regulatory constraints on transport and disposal of hazardous materials. Some suppliers have substituted a zinc-based reagent powder for the cadmium in an effort to reduce toxicity. We describe here an enzyme-based nitrate detection method as an improvement on the basic Griess method that demonstrates equal or superior sensitivity, superior selectivity, and is more environmentally benign. Comparisons between the enzyme-based method and some standard field test kits being used today are made.

  12. Intermittent nitrate therapy in angina pectoris.

    PubMed

    Reichek, N

    1989-05-01

    The rationale for intermittent nitrate therapy is based on the pathophysiology of nitroglycerin tolerance and the diurnal pattern of symptoms encountered in patients with chronic stable angina. Nitrate tolerance was first observed as tolerance to headache in industrial toxicology. When long-acting nitrates for chronic stable angina became available, similar tolerance was observed but not thought to indicate tolerance to a haemodynamic or therapeutic effect. Subsequently, Needleman and coworkers (J Pharmacol Exp Ther 1973; 187: 324) defined in vitro the phenomenology of vascular smooth muscle tolerance to nitroglycerin-induced relaxation and reversibility was demonstrated. More recently, a potential molecular explanation for nitrate tolerance has been proposed: sulfhydryl group depletion in smooth muscle cells resulting in reduced formation of S-nitrosothiols on nitrate exposure with resultant reduced activation of cyclic GMP. In vivo, other mechanisms, including fluid retention and neurohumoral responses to vasodilation may also be important. The first demonstration that nitrate tolerance affected the therapeutic efficacy of long-acting nitrates was reported by Parker and coworkers in 1982 (Circulation 1987; 76: 572-6). This landmark study was not given much credence at the time because it appeared to be in conflict with earlier reports. However, in the past 6 years development of tolerance has been demonstrated with a variety of oral nitrates, transdermal nitroglycerin and intravenous nitroglycerin. When plasma concentrations are held constant, tolerance to antianginal effects is demonstrable within 24h, but varies markedly in severity from individual to individual.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2501096

  13. 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.

  14. The Arabidopsis NRG2 Protein Mediates Nitrate Signaling and Interacts with and Regulates Key Nitrate Regulators[OPEN

    PubMed Central

    Zhao, Lufei; Zhang, Chengfei; Li, Zehui; Lei, Zhao; Liu, Fei; Guan, Peizhu; Crawford, Nigel M.

    2016-01-01

    We show that NITRATE REGULATORY GENE2 (NRG2), which we identified using forward genetics, mediates nitrate signaling in Arabidopsis thaliana. A mutation in NRG2 disrupted the induction of nitrate-responsive genes after nitrate treatment by an ammonium-independent mechanism. The nitrate content in roots was lower in the mutants than in the wild type, which may have resulted from reduced expression of NRT1.1 (also called NPF6.3, encoding a nitrate transporter/receptor) and upregulation of NRT1.8 (also called NPF7.2, encoding a xylem nitrate transporter). Genetic and molecular data suggest that NRG2 functions upstream of NRT1.1 in nitrate signaling. Furthermore, NRG2 directly interacts with the nitrate regulator NLP7 in the nucleus, but nuclear retention of NLP7 in response to nitrate is not dependent on NRG2. Transcriptomic analysis revealed that genes involved in four nitrogen-related clusters including nitrate transport and response to nitrate were differentially expressed in the nrg2 mutants. A nitrogen compound transport cluster containing some members of the NRT/PTR family was regulated by both NRG2 and NRT1.1, while no nitrogen-related clusters showed regulation by both NRG2 and NLP7. Thus, NRG2 plays a key role in nitrate regulation in part through modulating NRT1.1 expression and may function with NLP7 via their physical interaction. PMID:26744214

  15. 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.

  16. Photodegradation of Paracetamol in Nitrate Solution

    NASA Astrophysics Data System (ADS)

    Meng, Cui; Qu, Ruijuan; Liang, Jinyan; Yang, Xi

    2010-11-01

    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.

  17. 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

  18. 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.

  19. 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

  20. 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.

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

    DOE PAGESBeta

    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

  2. Spatial sequencing of microbial reduction of chromate and nitrate in membrane bioreactor.

    PubMed

    Konovalova, V; Nigmatullin, R; Dmytrenko, G; Pobigay, G

    2008-10-01

    Sequential reduction of chromate and nitrate, two competitive electron acceptors, has been demonstrated for strains of Pseudomonas genus for both planktonic cells and cells immobilised in agar layers on the surface of synthetic membrane. Denitrification occurs practically after chromate depletion. This order of reduction process is consistent with redox potentials of the respective reactions. In a membrane bioreactor, competitive inhibition results in nitrate transfer through the membrane without transformation. Thus the receiving phase is contaminated with nitrate. To address this problem, a membrane has been used for spatial sequencing of chromate and nitrate reduction. Bacterial cells were immobilised in two layers with each layer placed on opposing sides of the membrane. By this means, chromate reduction is localised into the layer contacting the feed phase while nitrate reduction occurs in the layer facing the receiving phase. As a result, only traces of the pollutants are detected in the receiving phase. PMID:18379828

  3. 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.

  4. 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.

  5. Glycosylation of closely spaced acceptor sites in human glycoproteins

    PubMed Central

    Shrimal, Shiteshu; Gilmore, Reid

    2013-01-01

    Summary Asparagine-linked glycosylation of proteins by the oligosaccharyltransferase (OST) occurs when acceptor sites or sequons (N-x≠P-T/S) on nascent polypeptides enter the lumen of the rough endoplasmic reticulum. Metazoan organisms assemble two isoforms of the OST that have different catalytic subunits (STT3A or STT3B) and partially non-overlapping cellular roles. Potential glycosylation sites move past the STT3A complex, which is associated with the translocation channel, at the protein synthesis elongation rate. Here, we investigated whether close spacing between acceptor sites in a nascent protein promotes site skipping by the STT3A complex. Biosynthetic analysis of four human glycoproteins revealed that closely spaced sites are efficiently glycosylated by an STT3B-independent process unless the sequons contain non-optimal sequence features, including extreme close spacing between sequons (e.g. NxTNxT) or the presence of paired NxS sequons (e.g. NxSANxS). Many, but not all, glycosylation sites that are skipped by the STT3A complex can be glycosylated by the STT3B complex. Analysis of a murine glycoprotein database revealed that closely spaced sequons are surprisingly common, and are enriched for paired NxT sites when the gap between sequons is less than three residues. PMID:24105266

  6. Donor and acceptor concentrations in degenerate InN

    SciTech Connect

    Look, D.C.; Lu, H.; Schaff, W.J.; Jasinski, J.; Liliental-Weber, Z.

    2002-01-28

    A formalism is presented to determine donor (N{sub D}) and acceptor (N{sub A}) concentrations in wurtzitic InN characterized by degenerate carrier concentration (n) and mobility ({mu}). The theory includes scattering not only by charged point defects and impurities, but also by charged threading dislocations, of concentration N{sub dis}. For an 0.45-{micro}m-thick InN layer grown on Al{sub 2}O{sub 3} by molecular beam epitaxy, having N{sub dis} = 5 x 10{sup 10} cm{sup -2}, determined by transmission electron microscopy, n(20 K) = 3.5 x 10{sup 18} cm{sup -3}, and {mu}(20 K) = 1055 cm{sup 2}/V-s, determined by Hall-effect measurements, the fitted values are N{sub D} = 4.7 x 10{sup 18} cm{sup -3} and N{sub A} = 1.2 x 10{sup 18} cm{sup -3}. The identities of the donors and acceptors are not known, although a comparison of N{sub D} with analytical data, and also with calculations of defect formation energies, suggests that a potential candidate for the dominant donor is H.

  7. 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.

  8. The Chilean nitrate deposits.

    USGS Publications Warehouse

    Ericksen, G.E.

    1983-01-01

    The nitrate deposits in the arid Atacama desert of northern Chile consist of saline-cemented surficial material, apparently formed in and near a playa lake that formerly covered the area. Many features of their distribution and chemical composition are unique. The author believes the principal sources of the saline constituents were the volcanic rocks of late Tertiary and Quaternary age in the Andes and that the nitrate is of organic origin. Possible sources of the nitrate, iodate, perchlorate and chromate are discussed. -J.J.Robertson

  9. 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

  10. 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

  11. 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

  12. 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

  13. 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

  14. Nitration of naphthalene and remarks on the mechanism of electrophilic aromatic nitration.

    PubMed

    Olah, G A; Narang, S C; Olah, J A

    1981-06-01

    Naphthalene was nitrated with a variety of nitrating agents. Comparison of data with Perrin's electrochemical nitration [Perrin, C. L. (1977) J. Am. Chem. Soc. 99, 5516-5518] shows that nitration of naphthalene gives an alpha-nitronaphthalene to beta-nitronaphthalene ratio that varies between 9 and 29 and is thus not constant. Perrin's data, therefore, are considered to be inconclusive evidence for the proposed one-electron transfer mechanism for the nitration of naphthalene and other reactive aromatics. Moodie and Schoefield [Hoggett, J. G., Moodie, R. B., Penton, J. R. & Schoefield, K. (1971) Nitration and Aromatic Reactivity (Cambridge Univ. Press, London)], as well as Perrin, independently concluded that, in the general scheme of nitration of reactive aromatics, there is the necessity to introduce into the classical Ingold mechanism an additional step involving a distinct intermediate preceding the formation of the Wheland intermediate (sigma complexes). This view coincides with our two-step mechanistic picture [Kuhn, S. J. & Olah, G. A. (1961) J. Am. Chem. Soc. 83, 4564-4571] of the nitronium salt nitration of aromatic hydrocarbons (including benzene and toluene), in which low substrate selectivity but high positional selectivity was found, indicating the independence of substrate from positional selectivity. PMID:16593026

  15. Nitration of naphthalene and remarks on the mechanism of electrophilic aromatic nitration*

    PubMed Central

    Olah, George A.; Narang, Subhash C.; Olah, Judith A.

    1981-01-01

    Naphthalene was nitrated with a variety of nitrating agents. Comparison of data with Perrin's electrochemical nitration [Perrin, C. L. (1977) J. Am. Chem. Soc. 99, 5516-5518] shows that nitration of naphthalene gives an α-nitronaphthalene to β-nitronaphthalene ratio that varies between 9 and 29 and is thus not constant. Perrin's data, therefore, are considered to be inconclusive evidence for the proposed one-electron transfer mechanism for the nitration of naphthalene and other reactive aromatics. Moodie and Schoefield [Hoggett, J. G., Moodie, R. B., Penton, J. R. & Schoefield, K. (1971) Nitration and Aromatic Reactivity (Cambridge Univ. Press, London)], as well as Perrin, independently concluded that, in the general scheme of nitration of reactive aromatics, there is the necessity to introduce into the classical Ingold mechanism an additional step involving a distinct intermediate preceding the formation of the Wheland intermediate (σ complexes). This view coincides with our two-step mechanistic picture [Kuhn, S. J. & Olah, G. A. (1961) J. Am. Chem. Soc. 83, 4564-4571] of the nitronium salt nitration of aromatic hydrocarbons (including benzene and toluene), in which low substrate selectivity but high positional selectivity was found, indicating the independence of substrate from positional selectivity. PMID:16593026

  16. 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.

  17. 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

  18. The effect of nitrate and sulfate on mediator-less microbial fuel cells with high internal resistance.

    PubMed

    Yi, Taewoo; Harper, Willie F

    2009-11-01

    Microbial fuel cells (MFCs) simultaneously provide waste treatment while capturing energy in the form of electricity. Although these devices are being used in engineered and natural environments where nitrate or sulfate may inhibit power production, the effects of these electron acceptors have not been fully explored. This research investigated the effect of nitrate and sulfate on MFC power production when these chemicals are present at the anode. Nitrate decreased the maximum current and power density by 15 and 17%, respectively, when present at 20 mg/L, and sulfate caused the maximum current and power density to decrease by 4 and 7%, respectively (also at 20 mg/L). Stronger inhibition was observed at higher nitrate and sulfate concentrations, but power production persisted. Coulombic efficiency decreased as nitrate and sulfate levels increased, although this was not primarily due to the biochemical reduction of nitrate or sulfate; rather, it was probably because of the inhibition of exoelectrogens. PMID:19957763

  19. 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.

  20. 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

  1. 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

  2. Organic Nitrates: A Complex Family of Atmospheric Trace Constituents

    NASA Astrophysics Data System (ADS)

    Ballschmiter, K.; Fischer, R. G.; Grünert, A.; Kastler, J.; Schneider, M.; Woidich, S.

    2003-04-01

    Biogenic and geogenic hydrocarbons are the precursors of organic nitrates that are formed as tropospheric photo-oxidation products in the presence of NOx. Air chemistry leads to a very complex pattern of nitric acid esters: alkyl nitrates, aryl-alkyl nitrates, and bifunctional nitrates like alkyl dinitrates, hydroxy alkyl nitrates and carbonyl alkyl nitrates. We have analyzed the pattern of organic nitrates in air samples after adsorption/thermal desorption (low volume sampling-LVS) or adsorption/solvent desorption (high volume sampling-HVS) by capillary gas chromatography with electron capture (ECD) and mass spectrometric detection (MSD) using air aliquotes of 100 up to 3000 liters on column. The complexity of the organic nitrates found in air requires a group pre-separation by normal phase liquid chromatography. A detection limit per compound of 0.005 ppt(v) is achieved by our approach. We have synthesized a broad spectrum of organic nitrates as reference compounds. Air samples were taken from central Europe, the US West (Utah, Nevada, California), and the North- and South Atlantic including Antarctica. Levels and patterns of the regional and global occurrence of the various groups of C1-C12 organic nitrates including dinitrates and hydroxy nitrates and nitrates of isoprene (2-methylbutadiene) are presented. Werner G., J. Kastler, R. Looser, K. Ballschmiter: "Organic nitrates of isoprene as atmospheric trace compounds" Angewandte Chemie - International Edition (1999) 38: 1634-1637. Woidich S., O. Froescheis, O. Luxenhofer, K. Ballschmiter: "EI- and NCI-mass spectrometry of arylalkyl nitrates and their occurrence in urban air" Fresenius J. Anal. Chem. (1999) 364 : 91-99. Kastler, J; Jarman, W; Ballschmiter, K.: "Multifunctional organic nitrates as constituents in European and US urban photo-smog" Fresenius J. Anal. Chem. (2000) 368:244-249. Schneider M., K. Ballschmiter: "C3-C14 alkyl nitrates in remote South Atlantic air" Chemosphere (1999) 38: 233-244. Fischer

  3. Verification of the structural alerts for Michael acceptors.

    PubMed

    Schultz, T Wayne; Yarbrough, Jason W; Hunter, Robert S; Aptula, Aynur O

    2007-09-01

    A diverse series of polarized alpha,beta-unsaturated and related compounds were evaluated for reactivity with a spectrophotometric assay using the sulfhydryl group in the form of the cysteine residue of the tripeptide GSH as a model nucleophile. The reactive end point (RC 50) calculations were compared to previously described structural alerts based on conventional organic chemistry. This comparison focused on polarized alpha,beta-unsaturates, including ones containing an aldehyde, ketone, ester, sulfoxide, sulfone, sulfonate, nitro, or cyano moiety as well as ortho- and para-pyridino compounds and ortho- and para-quinones. The alerts were coded by substructure and are available in open-source software ( http://sourceforge.net/projects/chemeval). Comparisons of reactivity between selected analogues revealed that only the polarized alpha,beta-unsaturates were reactive. These results verified the coded structural alerts that define the applicability domain for Michael acceptor electrophiles. PMID:17672510

  4. 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

  5. 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

  6. 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.

  7. 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

  8. Characterization of Atmospheric Organic Nitrates in Particles

    NASA Astrophysics Data System (ADS)

    Bruns, E. A.; Alexander, M. L.; Perraud, V.; Yu, Y.; Ezell, M.; Johnson, S. N.; Zellenyuk, A.; Imre, D.; Finlayson-Pitts, B. J.

    2008-12-01

    Aerosols in the atmosphere significantly affect climate, human health and visibility. Knowledge of aerosol composition is necessary to understand and then predict the specific impacts of aerosols in the atmosphere. It is known that organic nitrates are present in particles, but there is limited knowledge of the individual compounds and quantity. This is in part due to the lack of a wide variety of proven analytical techniques for particulate organic nitrates. In this study, several known organic nitrates, as well as those present in complex mixtures formed from oxidation of "Ñ-pinene, were studied using a variety of techniques. These include Fourier Transform infrared spectroscopy (FTIR) of samples collected by impaction on ZnSe discs. Samples were also collected on quartz fiber filters and the extracts analyzed by electrospray mass spectrometry (ESI- MS), atmospheric pressure chemical ionization mass spectrometry (APCI-MS), HPLC-UV, LC-MS and GC-MS. In addition, real-time analysis was provided by SPLAT-II and aerosol mass spectrometry (AMS). FTIR analysis of particles collected on ZnSe discs provides information on the ratio of organic nitrate to total organic content, while the analysis of filter extracts allows identification of specific organic nitrates. These are compared to the particle mass spectrometry data and the implications for detecting and measuring particulate organic nitrate in air is discussed.

  9. 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.

  10. 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

  11. Electrochromism of a fused acceptor-donor-acceptor triad covering entire UV-vis and near-infrared regions.

    PubMed

    Yao, Bin; Ye, Xichong; Zhang, Jie; Wan, Xinhua

    2014-10-17

    A novel fused acceptor-donor-acceptor (A-D-A) type panchromatically electrochromic compound was synthesized. It exhibited intensive absorption bands covering entire UV-vis and near-infrared regions upon reduction to the radical anionic state, owing to the simultaneous presence of π*-π* transitions and intervalence charge transfer. PMID:25268224

  12. Acceptor and Excitation Density Dependence of the Ultrafast Polaron Absorption Signal in Donor-Acceptor Organic Solar Cell Blends.

    PubMed

    Zarrabi, Nasim; Burn, Paul L; Meredith, Paul; Shaw, Paul E

    2016-07-21

    Transient absorption spectroscopy on organic semiconductor blends for solar cells typically shows efficient charge generation within ∼100 fs, accounting for the majority of the charge carriers. In this Letter, we show using transient absorption spectroscopy on blends containing a broad range of acceptor content (0.01-50% by weight) that the rise of the polaron signal is dependent on the acceptor concentration. For low acceptor content (<10% by weight), the polaron signal rises gradually over ∼1 ps with most polarons generated after 200 fs, while for higher acceptor concentrations (>10%) most polarons are generated within 200 fs. The rise time in blends with low acceptor content was also found to be sensitive to the pump fluence, decreasing with increasing excitation density. These results indicate that the sub-100 fs rise of the polaron signal is a natural consequence of both the high acceptor concentrations in many donor-acceptor blends and the high excitation densities needed for transient absorption spectroscopy, which results in a short average distance between the exciton and the donor-acceptor interface. PMID:27355877

  13. Transition metal-free generation of the acceptor/acceptor-carbene viaα-elimination: synthesis of fluoroacetyl cyclopropanes.

    PubMed

    Wang, Yongdong; Han, Jing; Chen, Jie; Cao, Weiguo

    2016-05-21

    An efficient transition metal-free approach for the generation of acceptor/acceptor-carbene followed by trapping with alkenes to provide fluoroacetyl cyclopropanes has been described. The resulting cyclopropanes could be further converted into the fluoromethyl dihydrofurans or fluorodihydropyrroles through ring-expansion processes. PMID:27125517

  14. 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.

  15. 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.

  16. The Cinnamon-derived Michael Acceptor Cinnamic Aldehyde Impairs Melanoma Cell Proliferation, Invasiveness, and Tumor Growth

    PubMed Central

    Cabello, Christopher M.; Bair, Warner B.; Lamore, Sarah D.; Ley, Stephanie; Bause, Alexandra S.; Azimian, Sara; Wondrak, Georg T.

    2009-01-01

    Redox dysregulation in cancer cells represents a chemical vulnerability that can be targeted by prooxidant redox intervention. Dietary constituents that contain an electrophilic Michael acceptor pharmacophore may therefore display promising chemopreventive and chemotherapeutic anti-cancer activity. Here, we demonstrate that the cinnamon-derived dietary Michael acceptor trans-cinnamic aldehyde (CA) impairs melanoma cell proliferation and tumor growth. Feasibility of therapeutic intervention using high doses of CA (120 mg/kg, p.o., q.d., 10 days) was demonstrated in a human A375 melanoma SCID-mouse xenograft model. Low micromolar concentrations (IC50 < 10 μM) of CA, but not closely related CA-derivatives devoid of Michael acceptor activity, suppressed proliferation of human metastatic melanoma cell lines (A375, G361, LOX) with G1 cell cycle arrest, elevated intracellular ROS, and impaired invasiveness. Expression array analysis revealed that CA induced an oxidative stress response in A375 cells, up-regulating heme oxygenase-1 (HMOX1), sulfiredoxin 1 homolog (SRXN1), thioredoxin reductase 1 (TXNRD1), and other genes including the cell cycle regulator and stress-responsive tumor suppressor gene cyclin-dependent kinase inhibitor 1A (CDKN1A), a key mediator of G1 phase arrest. CA, but not Michael-inactive derivatives, inhibited NFκB transcriptional activity and TNFα-induced IL-8 production in A375 cells. These findings support a previously unrecognized role of CA as a dietary Michael acceptor with potential anticancer activity. PMID:19000754

  17. 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.

  18. Intramolecular charge transfer in donor-acceptor molecules

    SciTech Connect

    Slama-Schwok, A.; Blanchard-Desce, M.; Lehn, J.M. )

    1990-05-17

    The photophysical properties of donor-acceptor molecules, push-pull polyenes and carotenoids, have been studied by absorption and fluorescence spectroscopy. The compounds bear various acceptor and donor groups, linked together by chains of different length and structure. The position of the absorption and fluorescence maxima and their variation in solvents of increasing polarity are in agreement with long-distance intramolecular charge-transfer processes, the linker acting as a molecular wire. The effects of the linker length and structure and of the nature of acceptor and donor are presented.

  19. CONCENTRATIONS AND LOADS OF NITRATE IN THE ATCHAFALAYA RIVER, LOUISIANA, USING CONTINUOUS MONITORING

    EPA Science Inventory

    Specific Results/Outcomes Expected: Deliverables of each Tasks include: Task 1. Several field studies by USGS personnel have shown that iono-selective nitrate probes currently marketed do not meet performance minimum criteria for accurately measuring nitrate concentrations. The...

  20. Recent aspects of nitration: New preparative methods and mechanistic studies (A Review)

    PubMed Central

    Olah, George A.; Narang, Subhash C.; Olah, Judith A.; Lammertsma, Koop

    1982-01-01

    New preparative methods of electrophilic nitration and transfer nitration are reviewed, including reactions relating to the ambident reactivity of the nitronium ion. Recent aspects of the mechanism of electrophilic aromatic substitution are discussed.

  1. 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 ...

  2. 33 CFR 126.28 - Ammonium nitrate, ammonium nitrate fertilizers, fertilizer mixtures, or nitro carbo nitrate...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ..., described and defined as an oxidizer by the regulations of 49 CFR part 173 is handled, stored, stowed...) must be eliminated or plugged. Note: See 49 CFR 176.415 for permit requirements for nitro carbo nitrate... nitrate fertilizers, fertilizer mixtures, or nitro carbo nitrate; general provisions. 126.28 Section...

  3. 33 CFR 126.28 - Ammonium nitrate, ammonium nitrate fertilizers, fertilizer mixtures, or nitro carbo nitrate...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ..., described and defined as an oxidizer by the regulations of 49 CFR part 173 is handled, stored, stowed...) must be eliminated or plugged. Note: See 49 CFR 176.415 for permit requirements for nitro carbo nitrate... nitrate fertilizers, fertilizer mixtures, or nitro carbo nitrate; general provisions. 126.28 Section...

  4. 33 CFR 126.28 - Ammonium nitrate, ammonium nitrate fertilizers, fertilizer mixtures, or nitro carbo nitrate...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ..., described and defined as an oxidizer by the regulations of 49 CFR part 173 is handled, stored, stowed...) must be eliminated or plugged. Note: See 49 CFR 176.415 for permit requirements for nitro carbo nitrate... nitrate fertilizers, fertilizer mixtures, or nitro carbo nitrate; general provisions. 126.28 Section...

  5. 33 CFR 126.28 - Ammonium nitrate, ammonium nitrate fertilizers, fertilizer mixtures, or nitro carbo nitrate...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ..., described and defined as an oxidizer by the regulations of 49 CFR part 173 is handled, stored, stowed...) must be eliminated or plugged. Note: See 49 CFR 176.415 for permit requirements for nitro carbo nitrate... nitrate fertilizers, fertilizer mixtures, or nitro carbo nitrate; general provisions. 126.28 Section...

  6. 33 CFR 126.28 - Ammonium nitrate, ammonium nitrate fertilizers, fertilizer mixtures, or nitro carbo nitrate...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ..., described and defined as an oxidizer by the regulations of 49 CFR part 173 is handled, stored, stowed...) must be eliminated or plugged. Note: See 49 CFR 176.415 for permit requirements for nitro carbo nitrate... nitrate fertilizers, fertilizer mixtures, or nitro carbo nitrate; general provisions. 126.28 Section...

  7. 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.

  8. Nitrogen is a deep acceptor in ZnO

    DOE PAGESBeta

    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

  9. 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.

  10. Donor-acceptor electron transport mediated by solitons.

    PubMed

    Brizhik, L S; Piette, B M A G; Zakrzewski, W J

    2014-11-01

    We study the long-range electron and energy transfer mediated by solitons in a quasi-one-dimensional molecular chain (conjugated polymer, alpha-helical macromolecule, etc.) weakly bound to a donor and an acceptor. We show that for certain sets of parameter values in such systems an electron, initially located at the donor molecule, can tunnel to the molecular chain, where it becomes self-trapped in a soliton state, and propagates to the opposite end of the chain practically without energy dissipation. Upon reaching the end, the electron can either bounce back and move in the opposite direction or, for suitable parameter values of the system, tunnel to the acceptor. We estimate the energy efficiency of the donor-acceptor electron transport depending on the parameter values. Our calculations show that the soliton mechanism works for the parameter values of polypeptide macromolecules and conjugated polymers. We also investigate the donor-acceptor electron transport in thermalized molecular chains. PMID:25493866

  11. Donor-acceptor electron transport mediated by solitons

    NASA Astrophysics Data System (ADS)

    Brizhik, L. S.; Piette, B. M. A. G.; Zakrzewski, W. J.

    2014-11-01

    We study the long-range electron and energy transfer mediated by solitons in a quasi-one-dimensional molecular chain (conjugated polymer, alpha-helical macromolecule, etc.) weakly bound to a donor and an acceptor. We show that for certain sets of parameter values in such systems an electron, initially located at the donor molecule, can tunnel to the molecular chain, where it becomes self-trapped in a soliton state, and propagates to the opposite end of the chain practically without energy dissipation. Upon reaching the end, the electron can either bounce back and move in the opposite direction or, for suitable parameter values of the system, tunnel to the acceptor. We estimate the energy efficiency of the donor-acceptor electron transport depending on the parameter values. Our calculations show that the soliton mechanism works for the parameter values of polypeptide macromolecules and conjugated polymers. We also investigate the donor-acceptor electron transport in thermalized molecular chains.

  12. 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.

  13. 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

  14. 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.

  15. Denitrifying Bioreactors for Nitrate Removal: A Meta-Analysis.

    PubMed

    Addy, Kelly; Gold, Arthur J; Christianson, Laura E; David, Mark B; Schipper, Louis A; Ratigan, Nicole A

    2016-05-01

    Meta-analysis approaches were used in this first quantitative synthesis of denitrifying woodchip bioreactors. Nitrate removal across environmental and design conditions was assessed from 26 published studies, representing 57 separate bioreactor units (i.e., walls, beds, and laboratory columns). Effect size calculations weighted the data based on variance and number of measurements for each bioreactor unit. Nitrate removal rates in bed and column studies were not significantly different, but both were significantly higher than wall studies. In denitrifying beds, wood source did not significantly affect nitrate removal rates. Nitrate removal (mass per volume) was significantly lower in beds with <6-h hydraulic retention times, which argues for ensuring that bed designs incorporate sufficient time for nitrate removal. Rates significantly declined after the first year of bed operation but then stabilized. Nitrogen limitation significantly affected bed nitrate removal. Categorical and linear assessments found significant nitrate removal effects with bed temperature; a of 2.15 was quite similar to other studies. Lessons from this meta-analysis can be incorporated into bed designs, especially extending hydraulic retention times to increase nitrate removal under low temperature and high flow conditions. Additional column studies are warranted for comparative assessments, as are field-based studies for assessing in situ conditions, especially in aging beds, with careful collection and reporting of design and environmental data. Future assessment of these systems might take a holistic view, reviewing nitrate removal in conjunction with other processes, including greenhouse gas and other unfavorable by-product production. PMID:27136153

  16. 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

  17. 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.

  18. Ammonium nitrate explosive systems

    SciTech Connect

    Coburn, M.D.; Stinecipher, M.M.

    1981-11-17

    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.

  19. 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.

  20. 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

  1. 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

  2. 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

  3. Functional anaerobic electron transport linked to the reduction of nitrate and fumarate in membranes from Escherichia coli as demonstrated by quenching of atebrin fluorescence.

    PubMed Central

    Haddock, B A; Kendall-Tobias, M W

    1975-01-01

    Measurements were made of energy-dependent quenching of atebrin fluorescence in membrane particles prepared from Escherichia coli grown anaerobically with glycerol as carbon source in the presence of either nitrate or fumarate. It is concluded that this technique can be used to study the functional organization of the anaerobic proton-translocating electron-transport chains that use nitrate or fumarate as terminal electron acceptor. PMID:776172

  4. 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. PMID:27192208

  5. 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

  6. Tuning the Electron Acceptor in Phthalocyanine-Based Electron Donor-Acceptor Conjugates.

    PubMed

    Sekita, Michael; Jiménez, Ángel J; Marcos, M Luisa; Caballero, Esmeralda; Rodríguez-Morgade, M Salomé; Guldi, Dirk M; Torres, Tomás

    2015-12-21

    Zinc phthalocyanines (ZnPc) have been attached to the peri-position of a perylenemonoimide (PMI) and a perylenemonoanhydride (PMA), affording electron donor-acceptor conjugates 1 and 2, respectively. In addition, a perylene-monoimide-monoanhydride (PMIMA) has been connected to a ZnPc through its imido position to yield the ZnPc-PMIMA conjugate 10. The three conjugates have been studied for photoinduced electron transfer. For ZnPc-PMIMA 10, electron transfer occurs upon both ZnPc and PMIMA excitation, giving rise to a long-lived (340 ps) charge-separated state. For ZnPc-PMI 1 and ZnPc-PMA 2, stabilization of the radical ion pair states by using polar media is necessary. In THF, photoexcitation of either ZnPc or PMI/PMA produces charge-separated states with lifetimes of 375 and 163 ps, respectively. PMID:26593778

  7. The Impact of Heterogeneity and Dark Acceptor States on FRET: Implications for Using Fluorescent Protein Donors and Acceptors

    PubMed Central

    Vogel, Steven S.; Nguyen, Tuan A.; van der Meer, B. Wieb; Blank, Paul S.

    2012-01-01

    Förster resonance energy transfer (FRET) microscopy is widely used to study protein interactions in living cells. Typically, spectral variants of the Green Fluorescent Protein (FPs) are incorporated into proteins expressed in cells, and FRET between donor and acceptor FPs is assayed. As appreciable FRET occurs only when donors and acceptors are within 10 nm of each other, the presence of FRET can be indicative of aggregation that may denote association of interacting species. By monitoring the excited-state (fluorescence) decay of the donor in the presence and absence of acceptors, dual-component decay analysis has been used to reveal the fraction of donors that are FRET positive (i.e., in aggregates)._However, control experiments using constructs containing both a donor and an acceptor FP on the same protein repeatedly indicate that a large fraction of these donors are FRET negative, thus rendering the interpretation of dual-component analysis for aggregates between separately donor-containing and acceptor-containing proteins problematic. Using Monte-Carlo simulations and analytical expressions, two possible sources for such anomalous behavior are explored: 1) conformational heterogeneity of the proteins, such that variations in the distance separating donor and acceptor FPs and/or their relative orientations persist on time-scales long in comparison with the excited-state lifetime, and 2) FP dark states. PMID:23152925

  8. 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

  9. Nitrate biosensors and biological methods for nitrate determination.

    PubMed

    Sohail, Manzar; Adeloju, Samuel B

    2016-06-01

    The inorganic nitrate (NO3‾) anion is present under a variety of both natural and artificial environmental conditions. Nitrate is ubiquitous within the environment, food, industrial and physiological systems and is mostly present as hydrated anion of a corresponding dissolved salt. Due to the significant environmental and toxicological effects of nitrate, its determination and monitoring in environmental and industrial waters are often necessary. A wide range of analytical techniques are available for nitrate determination in various sample matrices. This review discusses biosensors available for nitrate determination using the enzyme nitrate reductase (NaR). We conclude that nitrate determination using biosensors is an excellent non-toxic alternative to all other available analytical methods. Over the last fifteen years biosensing technology for nitrate analysis has progressed very well, however, there is a need to expedite the development of nitrate biosensors as a suitable alternative to non-enzymatic techniques through the use of different polymers, nanostructures, mediators and strategies to overcome oxygen interference. PMID:27130094

  10. 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.

  11. 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.

  12. Nitrate therapy in the elderly.

    PubMed

    Alpert, J S

    1990-06-01

    Changes in the heart and blood vessels with age alter the response of the cardiovascular system to pharmacologic agents. Nitrate plasma half-life is longer and volume of distribution is larger in older persons. Apparently, these pharmacokinetic differences in older persons lead to increased venous smooth muscle responsivity to nitrates which, in turn, leads to greater reductions in central venous and pulmonary arterial pressures after nitrate administration. This is probably the explanation for the greater frequency of nitrate-induced severe hypotension and bradycardia in elderly patients with myocardial infarction compared with younger patients. Clinicians should be cognizant of the changes in the cardiovascular system which occur with age that sensitize the elderly patient to the action of organic nitrates. Initial dosages of nitrates should accordingly be less than in younger patients. PMID:2112335

  13. 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

  14. 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. PMID:25495895

  15. Photooxidation of cellulose nitrate: new insights into degradation mechanisms.

    PubMed

    Berthumeyrie, Sebastien; Collin, Steeve; Bussiere, Pierre-Olivier; Therias, Sandrine

    2014-05-15

    Cellulose nitrate (or nitrocellulose) has received considerable interest due to its uses in various applications, such as paints, photographic films and propellants. However, it is considered as one of the primary pollutants in the energetic material industries because it can be degraded to form polluting chemical species. In this work, the UV light degradation of cellulose nitrate films was studied under conditions of artificially accelerated photooxidation. To eliminate the reactivity of nitro groups, the degradation of ethylcellulose was also investigated. Infrared spectroscopy analyses of the chemical modifications caused by the photooxidation of cellulose nitrate films and the resulting formation of volatile products revealed the occurrence of de-nitration and the formation of oxidation photoproducts exhibiting lactone and anhydride functions. The impact of these chemical modifications on the mechanical and thermal properties of cellulose nitrate films includes embrittlement and lower temperatures of ignition when used as a propellant. PMID:24685530

  16. Secondary preventive potential of nitrates in ischaemic heart disease.

    PubMed

    Thadani, U

    1996-12-01

    Nitrates exert their anti-anginal activity by a number of mechanisms. By reducing venous return and left ventricular end-diastolic pressure they lower myocardial oxygen demand and at the same time enhance blood flow to the sub-endocardium. They also directly increase myocardial oxygen supply by dilating the coronary artery stenoses and increasing collateral blood flow. These pharmacodynamic attributes are clinically efficacious in all the ischaemic myocardial syndromes. In stable angina pectoris, nitrates reduce myocardial ischaemia and ischaemic pain and increase exercise tolerance. In unstable angina, nitrates similarly reduce electrocardiographic evidence of myocardial ischaemia and relieve anginal pain. Following acute myocardial infarction, nitrates reduce ventricular dilatation and by so doing reduce pulmonary congestion and mitral regurgitation. The weak anti-aggregatory effect of nitrates on platelets may also play an adjuvant role in their anti-ischaemic activity. Early small-scale studies with both intravenous and oral nitrates demonstrated a trend to reduced mortality and reinfarction in survivors of acute myocardial infarction. However, the later and larger ISIS-4 and GISSI-3 trials have not confirmed this trend possibly due to the smaller doses of nitrates used and the diluting effect of the widespread use of open-label nitrates in the placebo group. In patients with congestive heart failure, including those of ischaemic aetiology, nitrates together with hydralazine have clearly demonstrated a significant reduction in the medium term mortality risk. Nitrates have the undoubted ability, probably greater than any other single anti-anginal drug, to rapidly and often completely relieve the pain and breathlessness associated with myocardial ischaemia. They are haemodynamically efficacious in reducing dilatation of the ischaemic left ventricle and enhancing coronary blood flow to ischaemic areas. Although their preventative impact in survivors of acute

  17. 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

  18. 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.

  19. Theory of Primary Photoexcitations in Donor-Acceptor Copolymers.

    PubMed

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

    2015-12-31

    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. PMID:26765027

  20. An overview of molecular acceptors for organic solar cells

    NASA Astrophysics Data System (ADS)

    Hudhomme, Piétrick

    2013-07-01

    Organic solar cells (OSCs) have gained serious attention during the last decade and are now considered as one of the future photovoltaic technologies for low-cost power production. The first dream of attaining 10% of power coefficient efficiency has now become a reality thanks to the development of new materials and an impressive work achieved to understand, control and optimize structure and morphology of the device. But most of the effort devoted to the development of new materials concerned the optimization of the donor material, with less attention for acceptors which to date remain dominated by fullerenes and their derivatives. This short review presents the progress in the use of non-fullerene small molecules and fullerene-based acceptors with the aim of evaluating the challenge for the next generation of acceptors in organic photovoltaics.

  1. 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

  2. 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

  3. 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

  4. 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.

  5. Sodium acceptor doping of ZnO crystals

    NASA Astrophysics Data System (ADS)

    Parmar, Narendra S.; Joni, I. Made; Lynn, Kelvin G.

    2016-02-01

    ZnO bulk single crystals were doped with sodium by thermal diffusion using sodium dispensers. Secondary-ion mass spectrometry measurement shows the diffusion of sodium with concentration ˜1×1018 cm-3 in near surface region. Photoluminescence (PL) measurements show donor acceptor pair (DAP) emission at 408 nm at room temperature which exhibits a blue-shift to 404 nm at 9 K. DC Hall measurements show the mixed conduction due to low Hall voltage in these samples. PL measurements and variable temperature resistivity measurements suggest that the sodium acceptor activation energy is ˜0.300 eV.

  6. Nitrated phenols in the atmosphere: a review

    NASA Astrophysics Data System (ADS)

    Harrison, Mark A. J.; Barra, Silvia; Borghesi, Daniele; Vione, Davide; Arsene, Cecilia; Iulian Olariu, Romeo

    2005-01-01

    This paper reviews the data concerning the atmospheric occurrence of nitrophenols, both in the gas and in the condensed phase (rainwater, cloud, fog and snow). Data obtained from field campaigns are reported, together with a description of the analytical techniques employed for the identification and quantification of nitrophenols. Analysis is usually performed using techniques such as High Performance Liquid Chromatography (HPLC) or Gas Chromatography-Mass Spectrometry (GC-MS), with the sampling method largely determined according to the matrix under investigation. The sources of atmospheric nitrophenols include direct emissions resulting from combustion processes, hydrolysis of pesticides (e.g. parathion) and the secondary formation of nitrophenols in the atmosphere. Atmospheric nitration of phenol can take place both in the gas and liquid phases, but the relative importance of these processes is still under discussion. The gas-phase nitration involves reaction between phenol and radOH+radNO2 during the day or radNO3+radNO2 during the night. Gas-phase nitration during the day yields only 2-nitrophenol (2-NP); while during the night it is thought that both 2-NP and 4-nitrophenol (4-NP) may be formed. Because of many gaps in the experimental evidence it is apparent that more research is required to indicate whether the 4-NP present in the environment can be accounted for by this nighttime process. Nitration in the condensed phase can be initiated by electrophilic nitration agents such as N2O5 and ClNO2. Other liquid-phase processes can also take place, in the presence of radNO3, nitrate and nitrite, in the dark and under irradiation. Condensed-phase processes have been shown to yield 2- and 4-NP in similar amounts. It is also important to consider the atmospheric sinks of nitrophenols. The rate constant for the reaction between 2-NP and radOH in the gas phase is rather low (9.0×10-13 cm3 molecule-1 s-1), while incomplete data are available for the reaction with

  7. 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.

  8. Nitrate ammonification by Nautilia profundicola AmH: experimental evidence consistent with a free hydroxylamine intermediate

    PubMed Central

    Hanson, Thomas E.; Campbell, Barbara J.; Kalis, Katie M.; Campbell, Mark A.; Klotz, Martin G.

    2013-01-01

    The process of nitrate reduction via nitrite controls the fate and bioavailability of mineral nitrogen within ecosystems; i.e., whether it is retained as ammonium (ammonification) or lost as nitrous oxide or dinitrogen (denitrification). Here, we present experimental evidence for a novel pathway of microbial nitrate reduction, the reverse hydroxylamine:ubiquinone reductase module (reverse-HURM) pathway. Instead of a classical ammonia-forming nitrite reductase that performs a 6 electron-transfer process, the pathway is thought to employ two catalytic redox modules operating in sequence: the reverse-HURM reducing nitrite to hydroxylamine followed by a hydroxylamine reductase that converts hydroxylamine to ammonium. Experiments were performed on Nautilia profundicola strain AmH, whose genome sequence led to the reverse-HURM pathway proposal. N. profundicola produced ammonium from nitrate, which was assimilated into biomass. Furthermore, genes encoding the catalysts of the reverse-HURM pathway were preferentially expressed during growth of N. profundicola on nitrate as an electron acceptor relative to cultures grown on polysulfide as an electron acceptor. Finally, nitrate-grown cells of N. profundicola were able to rapidly and stoichiometrically convert high concentrations of hydroxylamine to ammonium in resting cell assays. These experiments are consistent with the reverse-HURM pathway and a free hydroxylamine intermediate, but could not definitively exclude direct nitrite reduction to ammonium by the reverse-HURM with hydroxylamine as an off-pathway product. N. profundicola and related organisms are models for a new pathway of nitrate ammonification that may have global impact due to the wide distribution of these organisms in hypoxic environments and symbiotic or pathogenic associations with animal hosts. PMID:23847604

  9. Anaerobic Nitrate-Dependent Metal Bio-Oxidation

    NASA Astrophysics Data System (ADS)

    Weber, K.; Knox, T.; Achenbach, L. A.; Coates, J. D.

    2007-12-01

    Direct biological oxidation of reduced metals (Fe(II) and U(IV)) coupled to nitrate reduction at circumneutral pH under anaerobic conditions has been recognized in several environments as well as pure culture. Several phylogentically diverse mesophilic bacteria have been described as capable of anaerobic, nitrate-dependent Fe(II) oxidation (NFOx). Our recent identification of a freshwater mesophilic, lithoautotroph, Ferrutens nitratireducens strain 2002, capable of growth through NFOx presents an opportunity to further study metal bio- oxidation. Continuing physiological studies revealed that in addition to Fe(II) oxidation, strain 2002 is capable of oxidizing U(IV) (4 μM) in washed cell suspensions with nitrate serving as the electron acceptor. Pasteurized cultures exhibited abiotic oxidation of 2 μM U(IV). Under growth conditions, strain 2002 catalyzed the oxidation of 12 μM U(IV) within a two week period. Cultures amended with sodium azide, an electron transport inhibitor, demonstrated limited oxidation (7 μM) similar to pasteurized cultures, supporting the direct role of electron transport in U(IV) bio-oxidation. The oxidation of U(IV) coupled denitrification at circumneutral pH would yield enough energy to support anaerobic microbial growth (ΔG°'= -460.36 kJ/mole). It is currently unknown whether or not strain 2002 can couple this metabolism to growth. The growth of F. nitratireducens strain 2002 utilizing Fe(II) as the sole electron donor was previously demonstrated. The amount of U(IV) (~12 μM) that strain 2002 oxidized under similar autotrophic growth conditions yields 0.0019 kJ, enough energy for the generation of ATP (5.3 x 10-20 kJ ATP-1), but not enough energy for cell replication as calculated for nitrate-dependent Fe(II) oxidizing conditions (0.096 kJ) assuming a similar metabolism. In addition to F. nitratireducens strain 2002, a nitrate-dependent Fe(II) oxidizing bacterium isolated from U contaminated groundwater, Diaphorobacter sp. strain

  10. Simultaneous removal of nitrate and arsenic from drinking water sources utilizing a fixed-bed bioreactor system.

    PubMed

    Upadhyaya, Giridhar; Jackson, Jeff; Clancy, Tara M; Hyun, Sung Pil; Brown, Jess; Hayes, Kim F; Raskin, Lutgarde

    2010-09-01

    A novel bioreactor system, consisting of two biologically active carbon (BAC) reactors in series, was developed for the simultaneous removal of nitrate and arsenic from a synthetic groundwater supplemented with acetic acid. A mixed biofilm microbial community that developed on the BAC was capable of utilizing dissolved oxygen, nitrate, arsenate, and sulfate as the electron acceptors. Nitrate was removed from a concentration of approximately 50 mg/L in the influent to below the detection limit of 0.2 mg/L. Biologically generated sulfides resulted in the precipitation of the iron sulfides mackinawite and greigite, which concomitantly removed arsenic from an influent concentration of approximately 200 ug/L to below 20 ug/L through arsenic sulfide precipitation and surface precipitation on iron sulfides. This study showed for the first time that arsenic and nitrate can be simultaneously removed from drinking water sources utilizing a bioreactor system. PMID:20732708

  11. 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. PMID:23177766

  12. 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}.

  13. 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.

  14. 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.

  15. 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.

  16. His166 Is the Schiff Base Proton Acceptor in Attractant Phototaxis Receptor Sensory Rhodopsin I

    PubMed Central

    2015-01-01

    Photoactivation of attractant phototaxis receptor sensory rhodopsin I (SRI) in Halobacterium salinarum entails transfer of a proton from the retinylidene chromophore’s Schiff base (SB) to an unidentified acceptor residue on the cytoplasmic half-channel, in sharp contrast to other microbial rhodopsins, including the closely related repellent phototaxis receptor SRII and the outward proton pump bacteriorhodopsin, in which the SB proton acceptor is an aspartate residue salt-bridged to the SB in the extracellular (EC) half-channel. His166 on the cytoplasmic side of the SB in SRI has been implicated in the SB proton transfer reaction by mutation studies, and mutants of His166 result in an inverted SB proton release to the EC as well as inversion of the protein’s normally attractant phototaxis signal to repellent. Here we found by difference Fourier transform infrared spectroscopy the appearance of Fermi-resonant X–H stretch modes in light-minus-dark difference spectra; their assignment with 15N labeling and site-directed mutagenesis demonstrates that His166 is the SB proton acceptor during the photochemical reaction cycle of the wild-type SRI–HtrI complex. PMID:25162914

  17. 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

  18. 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

  19. 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. PMID:27231856

  20. 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.

  1. 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

  2. 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.

  3. Impact of the herbicide (RS)-MCPP on an anaerobic membrane bioreactor performance under different COD/nitrate ratios.

    PubMed

    Yuzir, Ali; Chelliapan, Shreeshivadasan; Sallis, Paul J

    2012-04-01

    The degradation of (RS)-MCPP was investigated in an anaerobic membrane bioreactor (AnMBR) using nitrate as an available electron acceptor under different COD/NO(3)(-)-N ratios. Results showed high soluble COD removal efficiency (80-93%) when the reactor was operated at high COD/NO(3)(-)-N ratios. However, the COD removal started to decline (average 15%) at high nitrate concentrations coinciding with a drop in nitrate removal efficiency to 37%, suggesting that the denitrification activity dropped and affected the AnMBR performance when nitrate was the predominant electron acceptor. Additionally, the removal efficiency of (RS)-MCPP increased from 2% to 47% with reducing COD/NO(3)(-)-N ratios, whilst the (RS)-MCPP specific utilisation rate (SUR) was inversely proportional to the COD/NO(3)(-)-N ratio, suggesting that a lower COD/NO(3)(-)-N ratios had a positive influence on the (RS)-MCPP SUR. Although nitrate had a major impact on methane production rates, the methane composition was stable (approximately 80%) for COD/NO(3)(-)-N ratios of 23 or more. PMID:22318083

  4. 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.

  5. 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

  6. 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.

  7. Observations of fine and coarse particle nitrate at several rural locations in the United States

    NASA Astrophysics Data System (ADS)

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

    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 PM 2.5 nitrate in these environments should not automatically be assumed to contain only ammonium nitrate.

  8. 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.

  9. 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.

  10. Analysis of High Enriched Uranyl Nitrate Solution Containing Cadmium

    SciTech Connect

    S. S. Kim

    2006-09-01

    A benchmark evaluation has been performed for a set of twenty-one critical experiments involving high enriched uranyl nitrate solution with and without cadmium nitrate as a soluble neutron absorber. The critical experiments analyzed include two types of cylindrical vessels with 24.18 and 29.16 cm in diameters. The vessels were reflected with water and in some cases with water containing dissolved cadmium nitrate. The uranium concentration ranged from 482 to 529 g/l, and cadmium concentration in the uranyl nitrate solution ranged from 0.0 to 11.31 g/l. The cadmium concentration in the reflector solution ranged from 0.0 to 15.16 g/l. Using MCNP and KENO-V.a, complete three-dimensional models were created for the two vessels filled with the uranyl nitrate solution and reflector solution. A series of criticality calculations were performed with KENO-V.a, MCNP4b, and MCNP5. In general, good agreement between KENO-V.a and MCNP4b was observed. However, MCNP5 results show consistently lower values compared with MCNP4b results with the maximum difference of 1.2 %. This ICSBEP supported evaluation provides valuable data for the effect of soluble neutron absorber (cadmium nitrate) on the criticality safety of high-enriched uranyl nitrate solution. These data can also be used in determining critical controls and for validation of the calculation methods.

  11. 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

  12. 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?

  13. 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.

  14. 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. PMID:23892715

  15. Nitrates in Wisconsin ground water.

    PubMed

    Schuknecht, B; Lawton, G W; Steinka, P; Delfino, J J

    1975-01-01

    Nitrate analyses were performed on ground water well samples originating from sources throughout Wisconsin. The data ranged from below the analytical detection limit up to 140 mg NO3-N/1. Over nine percent of all wells sampled has nitrate concentrations in excess of 10 mg NO3-N/1. Six individual counties had more than 10 mg NO3-N/1 in at least twenty percent of the wells covered in this survey. However, data reported for over eight thousand new wells driven in 1971-1972 showed only slightly more than two percent with nitrate levels above 10 mg NO3-N/1. This reflected the trend toward drilling deeper wells which are influenced less by nitrate seepage as well as adherence to new and stricter well construction codes. PMID:1183417

  16. Thermal decomposition of isooctyl nitrate

    SciTech Connect

    Pritchard, H.O.

    1989-03-01

    The diesel ignition improver DII-3, made by Ethyl Corporation, also known as isooctyl nitrate, is a mixture whose principal constituent (about 95%) is 2-ethyl hexyl nitrate. This note describes an investigation of the thermal decomposition that is not exhaustive, but that is intended to provide sufficient information on the rate and the mechanism so as to make possible the educated guesses needed for modeling the effect of isooctyl nitrate on the diesel ignition process. As is the case with other alkyl nitrates, the decomposition of the neat material is a complex one giving a complicated pressure versus time curve, unsuitable for a quick derivation of the rate constant. However, in the presence of toluene, whose intended purpose is to trap reactive free radicals and thereby simplify the overall mechanism, the pressure rises approximately exponentially to a limit; thus, on the assumption that the reaction is homogeneous and of first order, the rate constants can be determined from the half-life.

  17. 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.

  18. 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

  19. 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

  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. Rigid Conjugated Twisted Truxene Dimers and Trimers as Electron Acceptors.

    PubMed

    Zhang, Gang; Lami, Vincent; Rominger, Frank; Vaynzof, Yana; Mastalerz, Michael

    2016-03-14

    A new class of rigid twisted truxenone oligomers with an enlarged π backbone has been established by oxidative dimerization reactions. The resulting extended conjugated systems have large extinction coefficients and low-lying LUMO levels and show good solubility in common organic solvents, thus making them attractive compounds as new electron acceptors in organic electronics. Their suitability as electron acceptors has been demonstrated in bulk-heterojunction organic solar cells with 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}) (PTB7) as the donor material. PMID:26891096

  2. Probing the spin states of a single acceptor atom.

    PubMed

    van der Heijden, Joost; Salfi, Joe; Mol, Jan A; Verduijn, Jan; Tettamanzi, Giuseppe C; Hamilton, Alex R; Collaert, Nadine; Rogge, Sven

    2014-03-12

    We demonstrate a single-hole transistor using an individual acceptor dopant embedded in a silicon channel. Magneto-transport spectroscopy reveals that the ground state splits as a function of magnetic field into four states, which is unique for a single hole bound to an acceptor in a bulk semiconductor. The two lowest spin states are heavy (|m(j)| = 3/2) and light (|m(j)| = 1/2) hole-like, a two-level system that can be electrically driven and is characterized by a magnetic field dependent and long relaxation time, which are properties of interest for qubits. Although the bulklike spin splitting of a boron atom is preserved in our nanotransistor, the measured Landé g-factors, |g(hh)| = 0.81 ± 0.06 and |g(lh)| = 0.85 ± 0.21 for heavy and light holes respectively, are lower than the bulk value. PMID:24571637

  3. 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

  4. Defect Donor and Acceptor in GaN

    SciTech Connect

    Look, D.C.; Reynolds, D.C.; Hemsky, J.W.; Sizelove, J.R.; Jones, R.L.

    1997-09-01

    High-energy (0.7{endash}1MeV) electron irradiation in GaN grown on sapphire produces shallow donors and deep or shallow acceptors at equal rates, 1{plus_minus}0.2 cm{sup {minus}1}. The data, in conjunction with theory, are consistent only with the shallow donor being the N vacancy, and the acceptor the N interstitial. The N-vacancy donor energy is 64{plus_minus}10 meV, much larger than the value of 18meV found for the residual donor (probably Si) in this material. The Hall-effect measurements also reveal a degenerate n -type layer at the GaN/sapphire interface which must be accounted for to get the proper donor activation energy. {copyright} {ital 1997} {ital The American Physical Society}

  5. 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.

  6. 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.

  7. 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

  8. 46 CFR 148.205 - Ammonium nitrate and ammonium nitrate fertilizers.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 5 2011-10-01 2011-10-01 false Ammonium nitrate and ammonium nitrate fertilizers. 148... Materials § 148.205 Ammonium nitrate and ammonium nitrate fertilizers. (a) This section applies to the stowage and transportation in bulk of ammonium nitrate and the following fertilizers composed of...

  9. 46 CFR 148.205 - Ammonium nitrate and ammonium nitrate fertilizers.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 5 2014-10-01 2014-10-01 false Ammonium nitrate and ammonium nitrate fertilizers. 148... Materials § 148.205 Ammonium nitrate and ammonium nitrate fertilizers. (a) This section applies to the stowage and transportation in bulk of ammonium nitrate and the following fertilizers composed of...

  10. 46 CFR 148.205 - Ammonium nitrate and ammonium nitrate fertilizers.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 5 2013-10-01 2013-10-01 false Ammonium nitrate and ammonium nitrate fertilizers. 148... Materials § 148.205 Ammonium nitrate and ammonium nitrate fertilizers. (a) This section applies to the stowage and transportation in bulk of ammonium nitrate and the following fertilizers composed of...

  11. 46 CFR 148.205 - Ammonium nitrate and ammonium nitrate fertilizers.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 5 2012-10-01 2012-10-01 false Ammonium nitrate and ammonium nitrate fertilizers. 148... Materials § 148.205 Ammonium nitrate and ammonium nitrate fertilizers. (a) This section applies to the stowage and transportation in bulk of ammonium nitrate and the following fertilizers composed of...

  12. 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.

  13. 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

  14. 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.

  15. Photochemistry of adsorbed nitrate on aluminum oxide particle surfaces.

    PubMed

    Rubasinghege, Gayan; Grassian, Vicki H

    2009-07-01

    Nitrogen oxides, including nitrogen dioxide and nitric acid, react with mineral dust particles in the atmosphere to yield adsorbed nitrate. Although nitrate ion is a well-known chromophore in natural waters, little is known about the surface photochemistry of nitrate adsorbed on mineral particles. In this study, nitrate adsorbed on aluminum oxide, a model system for mineral dust aerosol, is irradiated with broadband light (lambda > 300 nm) as a function of relative humidity (RH) in the presence of molecular oxygen. Upon irradiation, the nitrate ion readily undergoes photolysis to yield nitrogen-containing gas-phase products including NO(2), NO, and N(2)O, with NO being the major product. The relative ratio and product yields of these gas-phase products change with RH, with N(2)O production being highest at the higher relative humidities. Furthermore, an efficient dark reaction readily converts the major NO product into NO(2) during post-irradiation. Photochemical processes on mineral dust aerosol surfaces have the potential to impact the chemical balance of the atmosphere, yet little is known about these processes. In this study, the impact that adsorbed nitrate photochemistry may have on the renoxification of the atmosphere is discussed. PMID:19534452

  16. 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.

  17. EXAFS study of dopant ions with different charges in nanocrystalline anatase: evidence for space-charge segregation of acceptor ions.

    PubMed

    Knauth, Philippe; Chadwick, Alan V; Lippens, Pierre E; Auer, Gerhard

    2009-06-01

    Nanocrystalline TiO(2) (anatase) is an essential oxide for environment and energy applications. A combination of EXAFS spectroscopy and DFT calculations on a series of dopants with quite similar ion radius, but increasing ion charge, show boundary space charge segregation of acceptor cations. The picture illustrates the Fourier-transformed EXAFS spectrum for Sn(4+)-doped TiO(2).A series of dopants, including acceptor ions (Zn(2+), Y(3+)), isovalent ions (Zr(4+), Sn(4+)) as well as a donor ion (Nb(5+)), were studied by EXAFS spectroscopy in nanocrystalline TiO(2) anatase powders and nanoceramics. Similar results were found for nanocrystalline powders and nanocrystalline ceramics, made by hot-pressing the powders. Boundary segregation was observed for the acceptor ions yttrium and zinc, whereas tin, zirconium and niobium ions were placed on substitutional bulk sites and did not segregate, whatever their concentration. These results can be interpreted based on defect thermodynamics, in the framework of a space charge segregation model with positive boundary core, due to excess oxide ion vacancies, and negative space charge regions, where ionized acceptors are segregated. PMID:19425035

  18. 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.

  19. 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.

  20. 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

  1. 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.

  2. 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. PMID:24749413

  3. The nasB operon and nasA gene are required for nitrate/nitrite assimilation in Bacillus subtilis.

    PubMed Central

    Ogawa, K; Akagawa, E; Yamane, K; Sun, Z W; LaCelle, M; Zuber, P; Nakano, M M

    1995-01-01

    Bacillus subtilis can use either nitrate or nitrite as a sole source of nitrogen. The isolation of the nasABCDEF genes of B. subtilis, which are required for nitrate/nitrite assimilation, is reported. The probable gene products include subunits of nitrate/nitrite reductases and an enzyme involved in the synthesis of siroheme, a cofactor for nitrite reductase. PMID:7868621

  4. Reductive activation of E. coli respiratory nitrate reductase.

    PubMed

    Ceccaldi, Pierre; Rendon, Julia; Léger, Christophe; Toci, René; Guigliarelli, Bruno; Magalon, Axel; Grimaldi, Stéphane; Fourmond, Vincent

    2015-10-01

    Over the past decades, a number of authors have reported the presence of inactive species in as-prepared samples of members of the Mo/W-bisPGD enzyme family. This greatly complicated the spectroscopic studies of these enzymes, since it is impossible to discriminate between active and inactive species on the basis of the spectroscopic signatures alone. Escherichia coli nitrate reductase A (NarGHI) is a member of the Mo/W-bisPGD family that allows anaerobic respiration using nitrate as terminal electron acceptor. Here, using protein film voltammetry on NarGH films, we show that the enzyme is purified in a functionally heterogeneous form that contains between 20 and 40% of inactive species that activate the first time they are reduced. This activation proceeds in two steps: a non-redox reversible reaction followed by an irreversible reduction. By carefully correlating electrochemical and EPR spectroscopic data, we show that neither the two major Mo(V) signals nor those of the two FeS clusters that are the closest to the Mo center are associated with the two inactive species. We also conclusively exclude the possibility that the major "low-pH" and "high-pH" Mo(V) EPR signatures correspond to species in acid-base equilibrium. PMID:26073890

  5. 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.

  6. 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.

  7. 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

  8. Emerging Technologies for Enhanced In Situ Biodenitrification of Nitrate Contaminated Ground Water

    NASA Astrophysics Data System (ADS)

    Faris, B.; Faris, B.

    2001-05-01

    One of the most pervasive ground water contaminants in the U.S. is nitrate. Traditional technologies for the remediation of nitrate-contaminated ground water are generally costly, lengthy, and often only partly effective. Enhanced in situ biodenitrification (EISBD) is a developing technology for remediating nitrate contaminated ground water and protecting public and domestic supply wells through in situ reduction. Natural denitrification processes have been well understood for some time. However, managing these processes to effectively remediated contaminated ground water in a timely fashion is innovative. EISBD is a remediation technology through which a carbon source (electron donor) is introduced to a nitrate-contaminated aquifer. Since many aquifers are aerobic, indigenous aerobic bacteria utilize the introduced carbon as a food source and oxygen serves as an electron acceptor. Oxygen in the aquifer becomes depleted, forming an anaerobic aquifer. When this occurs and an abundant carbon source is present, indigenous denitrifying bacteria proliferate and reduce nitrate to nitrogen gas through anaerobic respiration. EISBD technology deployments are currently underway for either remediation of sizable nitrate plumes in ground water systems or the reduction of nitrate contaminated ground water around public and/or domestic well fields dedicated to the production of drinking water. Regulatory enforcement of nitrate plumes has been limited. Pollution prevention programs are in place to limit further nitrate contamination, however, once a site becomes contaminated with nitrates above standards, the deployment of remediation technologies is lacking. With the development and further deployment of EISBD technologies, a cost-effective short-term tool is available for nitrate remediation. A multi-disciplinary team of the Interstate Technology Regulatory Cooperation published a Technology Overview guidance document on the emerging technology of EISBD. ITRC is a state

  9. 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

  10. 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

  11. 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

  12. 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. PMID:27212608

  13. 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.

  14. 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.

  15. Chemolithotrophic nitrate-dependent Fe(II)-oxidizing nature of actinobacterial subdivision lineage TM3

    PubMed Central

    Kanaparthi, Dheeraj; Pommerenke, Bianca; Casper, Peter; Dumont, Marc G

    2013-01-01

    Anaerobic nitrate-dependent Fe(II) oxidation is widespread in various environments and is known to be performed by both heterotrophic and autotrophic microorganisms. Although Fe(II) oxidation is predominantly biological under acidic conditions, to date most of the studies on nitrate-dependent Fe(II) oxidation were from environments of circumneutral pH. The present study was conducted in Lake Grosse Fuchskuhle, a moderately acidic ecosystem receiving humic acids from an adjacent bog, with the objective of identifying, characterizing and enumerating the microorganisms responsible for this process. The incubations of sediment under chemolithotrophic nitrate-dependent Fe(II)-oxidizing conditions have shown the enrichment of TM3 group of uncultured Actinobacteria. A time-course experiment done on these Actinobacteria showed a consumption of Fe(II) and nitrate in accordance with the expected stoichiometry (1:0.2) required for nitrate-dependent Fe(II) oxidation. Quantifications done by most probable number showed the presence of 1 × 104 autotrophic and 1 × 107 heterotrophic nitrate-dependent Fe(II) oxidizers per gram fresh weight of sediment. The analysis of microbial community by 16S rRNA gene amplicon pyrosequencing showed that these actinobacterial sequences correspond to ∼0.6% of bacterial 16S rRNA gene sequences. Stable isotope probing using 13CO2 was performed with the lake sediment and showed labeling of these Actinobacteria. This indicated that they might be important autotrophs in this environment. Although these Actinobacteria are not dominant members of the sediment microbial community, they could be of functional significance due to their contribution to the regeneration of Fe(III), which has a critical role as an electron acceptor for anaerobic microorganisms mineralizing sediment organic matter. To the best of our knowledge this is the first study to show the autotrophic nitrate-dependent Fe(II)-oxidizing nature of TM3 group of uncultured Actinobacteria

  16. 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.

  17. Human GC-AG alternative intron isoforms with weak donor sites show enhanced consensus at acceptor exon positions

    PubMed Central

    Thanaraj, T. A.; Clark, Francis

    2001-01-01

    It has been previously observed that the intrinsically weak variant GC donor sites, in order to be recognized by the U2-type spliceosome, possess strong consensus sequences maximized for base pair formation with U1 and U5/U6 snRNAs. However, variability in signal strength is a fundamental mechanism for splice site selection in alternative splicing. Here we report human alternative GC-AG introns (for the first time from any species), and show that while constitutive GC-AG introns do possess strong signals at their donor sites, a large subset of alternative GC-AG introns possess weak consensus sequences at their donor sites. Surprisingly, this subset of alternative isoforms shows strong consensus at acceptor exon positions 1 and 2. The improved consensus at the acceptor exon can facilitate a strong interaction with U5 snRNA, which tethers the two exons for ligation during the second step of splicing. Further, these isoforms nearly always possess alternative acceptor sites and exhibit particularly weak polypyrimidine tracts characteristic of AG-dependent introns. The acceptor exon nucleotides are part of the consensus required for the U2AF35-mediated recognition of AG in such introns. Such improved consensus at acceptor exons is not found in either normal or alternative GT-AG introns having weak donor sites or weak polypyrimidine tracts. The changes probably reflect mechanisms that allow GC-AG alternative intron isoforms to cope with two conflicting requirements, namely an apparent need for differential splice strength to direct the choice of alternative sites and a need for improved donor signals to compensate for the central mismatch base pair (C-A) in the RNA duplex of U1 snRNA and the pre-mRNA. The other important findings include (i) one in every twenty alternative introns is a GC-AG intron, and (ii) three of every five observed GC-AG introns are alternative isoforms. PMID:11410667

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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

  3. 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

  4. 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.

  5. Urea and urea nitrate decomposition pathways: a quantum chemistry study.

    PubMed

    Tokmakov, Igor V; Alavi, Saman; Thompson, Donald L

    2006-03-01

    Electronic structure calculations have been performed to investigate the initial steps in the gas-phase decomposition of urea and urea nitrate. The most favorable decomposition pathway for an isolated urea molecule leads to HNCO and NH3. Gaseous urea nitrate formed by the association of urea and HNO3 has two isomeric forms, both of which are acid-base complexes stabilized by the hydrogen-bonding interactions involving the acidic proton of HNO3 and either the O or N atoms of urea, with binding energies (D0(o), calculated at the G2M level with BSSE correction) of 13.7 and 8.3 kcal/mol, respectively, and with estimated standard enthalpies of formation (delta(f)H298(o) of -102.3 and -97.1 kcal/mol, respectively. Both isomers can undergo relatively facile double proton transfer within cyclic hydrogen-bonded structures. In both cases, HNO3 plays a catalytic role for the (1,3) H-shifts in urea by acting as a donor of the first and an acceptor of the second protons transferred in a relay fashion. The double proton transfer in the carbonyl/hydrogen bond complex mediates the keto-enol tautomerization of urea, and in the other complex the result is the breakdown of the urea part to the HNCO and NH3 fragments. The enolic form of urea is not expected to accumulate in significant quantities due to its very fast conversion back to H2NC(O)NH2 which is barrierless in the presence of HNO3. The HNO3-catalyzed breakdown of urea to HNCO and NH3 is predicted to be the most favorable decomposition pathway for gaseous urea nitrate. Thus, HNCO + NH3 + HNO3 and their association products (e.g., ammonium nitrate and isocyanate) are expected to be the major initial products of the urea nitrate decomposition. This prediction is consistent with the experimental T-jump/FTIR data [Hiyoshi et al. 12th Int. Detonation Symp., Aug 11-16, San Diego, CA, 2002]. PMID:16494387

  6. Lithium related deep and shallow acceptors in Li-doped ZnO nanocrystals

    NASA Astrophysics Data System (ADS)

    Rauch, C.; Gehlhoff, W.; Wagner, M. R.; Malguth, E.; Callsen, G.; Kirste, R.; Salameh, B.; Hoffmann, A.; Polarz, S.; Aksu, Y.; Driess, M.

    2010-01-01

    We study the existence of Li-related shallow and deep acceptor levels in Li-doped ZnO nanocrystals using electron paramagnetic resonance (EPR) and photoluminescence (PL) spectroscopy. ZnO nanocrystals with adjustable Li concentrations between 0% and 12% have been prepared using organometallic precursors and show a significant lowering of the Fermi energy upon doping. The deep Li acceptor with an acceptor energy of 800 meV could be identified in both EPR and PL measurements and is responsible for the yellow luminescence at 2.2 eV. Additionally, a shallow acceptor state at 150 meV above the valence band maximum is made responsible for the observed donor-acceptor pair and free electron-acceptor transitions at 3.235 and 3.301 eV, possibly stemming from the formation of Li-related defect complexes acting as acceptors.

  7. The Tetrathiafulvalene-based Donor-acceptor Diads for Molecular Electronics

    NASA Astrophysics Data System (ADS)

    Perepichka, Dmitrii F.; Bryce, Martin R.; Ho, Gregory; Heath, James R.; Pearson, Christopher; Petty, Michael C.

    2004-03-01

    The challenge of covalent linking a strong electron donor (as tetrathiafulvalene, TTF) to a strong acceptor (as tetracyanoquinodimethane, TCNQ) was laid down by Aviram and Ratner, who proposed that a single donor-sigma-acceptor molecule could rectify an electric current. Although numerous organic compounds have been tested in metal-molecule-metal junctions, they had substantially higher HOMO-LUMO gap (Eg >0.5 eV) and, in most cases, high dipole moment due to conjugated character of the linker. Those molecules re-orient in the electric field limiting the device stability. Recently, we have pioneered the synthesis of DsigmaA molecules with the HOMO-LUMO gap 0.17-0.3 eV, including the original TTF-TCNQ.* We will present the intriguing electronic properties of these compounds, including the conformational control of the Eg and the thermoexcited electron transfer. The compounds form high-quality LB films, suitable for molecular electronics applications. In Si-molecule-Ti junctions, the rectification ratio increases as molecules align perpendicularly to the surface, and the device stability override significantly the related system based on D-pi-A molecules. * Perepichka, et al., Angew. Chem. Int. Ed. 2003, 42, 4635.

  8. (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

  9. 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

  10. Electron-Donor-Acceptor (EDA) Complexes Of Aromatic Hydrocarbons With Organic Acceptors In Solution And In The Solid State. A Quantitative FT-IR Investigation.

    NASA Astrophysics Data System (ADS)

    Bruni, Paolo; Giorgini, Elisabetta; Tosi, Giorgio; Zampini, Angela

    1989-12-01

    Liquid phase FT-IR investigation on π-π Electron-Donor-Acceptor (EDA) complexes between arenes and organic acceptors leads to values of formation constants that are in good agreement with the ones from other techniques (UV-Vis and NMR). In addition solid state FT-IR and UV-Vis determinations on the complexes are also reported and discussed.

  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. Effect of dissolved oxygen on elemental sulfur generation in sulfide and nitrate removal process: characterization, pathway, and microbial community analysis.

    PubMed

    Wang, Xiaowei; Zhang, Yu; Zhang, Tingting; Zhou, Jiti

    2016-03-01

    Microaerobic bioreactor treatment for enriched sulfide and nitrate has been demonstrated as an effective strategy to improve the efficiencies of elemental sulfur (S(0)) generation, sulfide oxidation, and nitrate reduction. However, there is little detailed information for the effect and mechanism of dissolved oxygen (DO) on the variations of microbial community in sulfur generation, sulfide oxidation, and nitrate reduction systems. Polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE) was employed to evaluate the variations of microbial community structures in a sulfide oxidation and nitrate reduction reactor under different DO conditions (DO 0-0.7 mg · L(-1)). Experimental results revealed that the activity of sulfide-oxidizing bacteria (SOB) and nitrate-reducing bacteria (NRB) could be greatly stimulated in 0.1-0.3 mg-DO · L(-1). However, when the DO concentration was further elevated to more than 0.5 mg · L(-1), the abundance of NRB was markedly decreased, while the heterotrophic microorganisms, especially carbon degradation species, were enriched. The reaction pathways for sulfide and nitrate removal under microaerobic conditions were also deduced by combining batch experiments with functional species analysis. It was likely that the oxidation of sulfide to sulfur could be performed by both aerobic heterotrophic SOB and sulfur-based autotrophic denitrification bacteria with oxygen and nitrate as terminal electron acceptor, respectively. The nitrate could be reduced to nitrite by both autotrophic and heterotrophic denitrification, and then the generated nitrite could be completely converted to nitrogen gas via heterotrophic denitrification. This study provides new insights into the impacts of microaerobic conditions on the microbial community functional structures of sulfide-oxidizing, nitrate-reducing, and sulfur-producing bioreactors, which revealing the potential linkage between functional microbial communities and

  13. 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

  14. 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

  15. Carbon and group II acceptor coimplantation in GaAs

    SciTech Connect

    Morton, R.; Lau, S.S.; Poker, D.B.; Chu, P.K.; Fung, K.K.; Wang, N.

    1998-11-01

    Coimplantations of carbon and one of the group II acceptors, Mg, Zn, or Cd, were performed and compared to implantations involving only a single element (Mg, Zn, or Cd) or Ga and C coimplanted into GaAs substrates. The group II and C (II/C) coimplantations act to balance the crystal stoichiometry since group II atoms prefer to reside in the Ga sublattice and C prefers to reside in the As sublattice. The electrical characteristics of the various implantations were obtained from sheet and differential Hall measurements. Rutherford backscattering spectrometry was employed to determine the amount of implantation-induced damage which was then correlated to the amount of C activation in the group II/C coimplanted samples. It was found that coimplantation of the heavier group II acceptors, Zn and Cd, resulted in layers with larger peak hole concentrations. This is a result of the large amount of lattice damage created by these elements which is thought to provide the necessary abundance of As vacancies for C activation. Secondary ion mass spectroscopy measurements of the samples after implant activation indicate that C coimplantation significantly reduces the diffusivity of the group II acceptors. Cross-sectional transmission electron microscopy indicated a unique defect structure (extrinsic dislocation loops) for the cases of group II/C coimplantation. These dislocation loops are located at the diffusion front of the group II element in the samples and therefore have a rather profound influence on the diffusion of the group II elements. A rationalization of the defect structure and the effect it has on the diffusion of group II elements is given. {copyright} {ital 1998 American Institute of Physics.}

  16. Assembly and Comparison of Plasma Membrane SNARE Acceptor Complexes.

    PubMed

    Kreutzberger, Alex J B; Liang, Binyong; Kiessling, Volker; Tamm, Lukas K

    2016-05-24

    Neuronal exocytotic membrane fusion occurs on a fast timescale and is dependent on interactions between the vesicle SNARE synaptobrevin-2 and the plasma membrane SNAREs syntaxin-1a and SNAP-25 with a 1:1:1 stoichiometry. Reproducing fast fusion rates as observed in cells by reconstitution in vitro has been hindered by the spontaneous assembly of a 2:1 syntaxin-1a:SNAP-25 complex on target membranes that kinetically alters the binding of synaptobrevin-2. Previously, an artificial SNARE acceptor complex consisting of 1:1:1 syntaxin-1a(residues 183-288):SNAP-25:syb(residues 49-96) was found to greatly accelerate the rates of lipid mixing of reconstituted target and vesicle SNARE proteoliposomes. Here we present two (to our knowledge) new procedures to assemble membrane-bound 1:1 SNARE acceptor complexes that produce fast and efficient fusion without the need of the syb(49-96) peptide. In the first procedure, syntaxin-1a is purified in a strictly monomeric form and subsequently assembled with SNAP-25 in detergent with the correct 1:1 stoichiometry. In the second procedure, monomeric syntaxin-1a and dodecylated (d-)SNAP-25 are separately reconstituted into proteoliposomes and subsequently assembled in the plane of merged target lipid bilayers. Examining single particle fusion between synaptobrevin-2 proteoliposomes and planar-supported bilayers containing the two different SNARE acceptor complexes revealed similar fast rates of fusion. Changing the stoichiometry of syntaxin-1a and d-SNAP-25 in the target bilayer had significant effects on docking, but little effect on the rates of synaptobrevin-2 proteoliposome fusion. PMID:27178662

  17. 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

  18. A biological source of oceanic alkyl nitrates

    NASA Astrophysics Data System (ADS)

    Dahl, E. E.; Lewis, C. B.; Velasco, F. L.; Escobar, C.; Kellogg, D.; Velcamp, M.

    2013-12-01

    Alkyl nitrates are an important component of reactive nitrogen in the troposphere. The oceans are a source of alkyl nitrates to the atmosphere, however the source of alkyl nitrates in the oceans is unknown. It has been demonstrated that the reaction of alkyl peroxy radicals (ROO) with nitric oxide (NO) produces alkyl nitrates in the aqueous phase. We hypothesize that alkyl nitrates may be formed by organisms through the same reaction and therefore biological production could be a source of alkyl nitrates to the troposphere. This work focuses on the production of alkyl nitrates by the diatoms Chaetoceros muelleri and Thalassiosira weisfloggi. Using chemostats, we measure alkyl nitrates formed under nitrate limited conditions. We also use triggers and inhibitors of nitric oxide formation to determine if alkyl nitrate formation is affected by changes in NO production. To date, the rates of production of alkyl nitrates in our cultures, lead us to estimate a production rate on the order of femtomolar/day for C1-C3 alkyl nitrates by diatom species in the equatorial Pacific Ocean. This suggests that diatoms may contribute to the overall ocean source of alkyl nitrates; however, it is possible that other types of phytoplankton, such as cyanobacteria, that are more abundant in the open ocean, may contribute to a greater extent.

  19. Unraveling the Photoswitching Mechanism in Donor-Acceptor Stenhouse Adducts.

    PubMed

    Lerch, Michael M; Wezenberg, Sander J; Szymanski, Wiktor; Feringa, Ben L

    2016-05-25

    Molecular photoswitches have opened up a myriad of opportunities in applications ranging from responsive materials and control of biological function to molecular logics. Here, we show that the photoswitching mechanism of donor-acceptor Stenhouse adducts (DASA), a recently reported class of photoswitches, proceeds by photoinduced Z-E isomerization, followed by a thermal, conrotatory 4π-electrocyclization. The photogenerated intermediate is manifested by a bathochromically shifted band in the visible absorption spectrum of the DASA. The identification of the role of this intermediate reveals a key step in the photoswitching mechanism that is essential to the rational design of switching properties via structural modification. PMID:27152878

  20. 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.

  1. Application of nitrate to enhance biodegradation of gasoline components in soil by indigenous microorganisms under anoxic condition.

    PubMed

    Yang, Su-Cai; Song, Yun; Wang, Dong; Wei, Wen-Xia; Yang, Yan; Men, Bin; Li, Jia-Bin

    2016-01-01

    Anaerobic/anoxic biodegradation of hydrocarbons offers an attractive approach to the removal of these compounds from polluted environments such as aquifers, aquatic sediments, submerged soils and subsurface soils. The application of nitrate was investigated to accelerate the degradation of gasoline components such as mono-aromatic hydrocarbons and total petroleum hydrocarbons (TPH) in soil by indigenous microorganisms under anoxic condition. The addition of nitrate had little effect on the degradation of mono-aromatic hydrocarbons m- & p-xylene, o-xylene, sec-butylbenzene and 1,2,4-trimethylbenzene, but facilitated the degradation of TPH (C6-C12) and mono-aromatic hydrocarbons toluene and ethylbenzene markedly. Furthermore, the more nitrate added, the higher the percentage of toluene, ethylbenzene and TPH (C6-C12) degraded after 180 days of anoxic incubation. Microorganisms capable of degrading toluene, ethylbenzene and TPH (C6-C12) with nitrate as the electron acceptor under anaerobic/anoxic condition are composed predominantly of Alpha-, Beta-, Gamma- or Delta-proteobacteria. Beta- and Gamma-proteobacteria were the main components of indigenous microorganisms, and accounted for 83-100% of the total amount of indigenous microorganisms in soil used in this study. Furthermore, the total amount of indigenous microorganisms increased with nitrate added. The addition of nitrate stimulated the growth of indigenous microorganisms, and therefore facilitated the degradation of toluene, ethylbenzene and TPH (C6-C12). PMID:26508265

  2. 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

  3. 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.

  4. Short-Term Effects of a High Nitrate Diet on Nitrate Metabolism in Healthy Individuals

    PubMed Central

    Bondonno, Catherine P.; Liu, Alex H.; Croft, Kevin D.; Ward, Natalie C.; Puddey, Ian B.; Woodman, Richard J.; Hodgson, Jonathan M.

    2015-01-01

    Dietary nitrate, through the enterosalivary nitrate-nitrite-NO pathway, can improve blood pressure and arterial stiffness. How long systemic nitrate and nitrite remain elevated following cessation of high nitrate intake is unknown. In 19 healthy men and women, the time for salivary and plasma nitrate and nitrite to return to baseline after 7 days increased nitrate intake from green leafy vegetables was determined. Salivary and plasma nitrate and nitrite was measured at baseline [D0], end of high nitrate diet [D7], day 9 [+2D], day 14 [+7D] and day 21 [+14D]. Urinary nitrite and nitrate was assessed at D7 and +14D. Increased dietary nitrate for 7 days resulted in a more than fourfold increase in saliva and plasma nitrate and nitrite (p < 0.001) measured at [D7]. At [+2D] plasma nitrite and nitrate had returned to baseline while saliva nitrate and nitrite were more than 1.5 times higher than at baseline levels. By [+7D] all metabolites had returned to baseline levels. The pattern of response was similar between men and women. Urinary nitrate and nitrate was sevenfold higher at D7 compared to +14D. These results suggest that daily ingestion of nitrate may be required to maintain the physiological changes associated with high nitrate intake. PMID:25774606

  5. 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

  6. A novel perchlorate- and nitrate-reducing bacterium, Azospira sp. PMJ.

    PubMed

    Nam, Ji-Hyun; Ventura, Jey-R S; Yeom, Ick Tae; Lee, Yongwoo; Jahng, Deokjin

    2016-07-01

    A novel perchlorate-reducing bacterium (PCRB), PMJ, was isolated from the mixed liquor suspended solids in the aerobic tank of a wastewater treatment plant. The 16S ribosomal RNA (rRNA), perchlorate reductase, and chlorite dismutase gene sequences revealed that PMJ belonged to the genus Azospira. PMJ was removed high-strength (700 mg/L) perchlorate and also removed low-strength (≤50 mg/L) perchlorate below the detection limit (2 μg/L) when acetate was used as a sole and carbon source. The maximum specific perchlorate utilization rate, q max, was 0.96 mg ClO4 (-)/mg dry cell weight day, and the half-saturation constant, K S , was lower than 0.002 mg ClO4 (-)/L. PMJ also utilized inorganic electron donors [(H2, S(0), and Fe(II)] with perchlorate as an electron acceptor. Perchlorate reduction by PMJ was completely inhibited by oxygen and chlorate but was not inhibited by nitrate. In the presence of similar concentrations (100∼140 mg/L) of nitrate and perchlorate, PMJ simultaneously removed both electron acceptors. Therefore, it was concluded that the strains PMJ might possess separate pathways for perchlorate and nitrate reduction. These results indicated that Azospira sp. PMJ could be efficiently used for treating perchlorate-contaminated groundwater and wastewater because many of these water bodies are known to contain both perchlorate and nitrate. In addition, low K S value and autotrophic perchlorate reduction of PMJ might be useful to design the biological treatment systems. PMID:26971497

  7. 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.

  8. Tuning of Stepwise Neutral-Ionic Transitions by Acceptor Site Doping in Alternating Donor/Acceptor Chains.

    PubMed

    Nakabayashi, Keita; Nishio, Masaki; Miyasaka, Hitoshi

    2016-03-01

    The stepwise neutral-ionic (N-I) phase transition found in the alternating donor/acceptor (DA) chain [Ru2(2,3,5,6-F4PhCO2)4(DMDCNQI)]·2(p-xylene) (0; 2,3,5,6-F4PhCO2(-) = 2,3,5,6-tetrafluorobenzoate; DMDCNQI = 2,5-dimethyl-N,N'-dicyanoquinonediimine) was tuned by partly substituting the acceptor DMDCNQI with 2,5-dimethoxy-N,N'-dicyanoquinonediimine (DMeODCNQI), which displays a poorer electron affinity in an isostructural series. The site-doped series comprised [Ru2(2,3,5,6-F4PhCO2)4(DMDCNQI)1-x(DMeODCNQI)x]·2(p-xylene) for doping rates (x) = 0.05 (0.05-MeO), 0.10 (0.10-MeO), 0.15 (0.15-MeO), and 0.20 (0.20-MeO). The neutral chain [Ru2(2,3,5,6-F4PhCO2)4(DMeODCNQI)]·4(p-xylene) (1), which only contained DMeODCNQI, was also characterized. All site-doped compounds were isostructural to 0 except 1 despite their identical DA chain motif. Except at an x value of 0.20, they displayed a two-step N-I transition involving an intermediate phase. This transition occurred at high temperatures in 0 but shifted to lower temperatures in a parallel manner with increasing doping rate. Simultaneously, each transition broadened with increasing doping rate, leading to a convergence of two transitions at an x value approximating 0.2. Donor/acceptor-site-doping techniques present somewhat different impacts in terms of interchain Coulomb effects. PMID:26878151

  9. Photophysics and charge transfer in donor-acceptor triblock copolymer photovoltaic materials

    NASA Astrophysics Data System (ADS)

    Schwarz, Kyra N.; Jones, David J.; Smith, Trevor A.; Ghiggino, Kenneth P.

    2014-10-01

    Efficient conversion of solar energy to electricity in low-cost organic photovoltaic (OPV) devices requires the complex interplay between multiple processes and components over various length and time scales. Optimizing device morphology to ensure efficient exciton diffusion and charge transport as well as ensuring efficient charge photogeneration is necessary to achieve optimum performance in new materials. The conjugated polymer electron donor PFM (poly(9,9-diocetyluorene-co-bis-N,N-(4-methylphenyl)-bis-N,N-phenyl-1,4-phenylenediamine)) and electron acceptor F8BT (poly[(9,9-di-n-octyluorenyl-2,7-diyl)-alt-(benzo[2,1,3]thiadiazol-4,8-diyl)), comprise the novel triblock copolymer PFM-F8BT-PFM. This copolymer is designed to phase separate on the 20-30 nm scale, a domain size ideal for maximizing exciton collection at the donor-acceptor interface. Using steady-state and ultrafast spectroscopic characterization including high repetition rate transient absorption spectroscopy, the dynamics of charge and energy transfer of the component polymers and the triblock co-polymer have been investigated. The results demonstrate that for the homopolymers solvent dependent exciton transport processes dominate, while in the triblock copolymer solutions transient spectroscopy provides evidence for interfacial charge separation.

  10. Effect of Oligomer Length on Photophysical Properties of Platinum Acetylide Donor-Acceptor-Donor Oligomers.

    PubMed

    Cekli, Seda; Winkel, Russell W; Schanze, Kirk S

    2016-07-21

    We report a systematic study that explores how the triplet excited state is influenced by conjugation length in a series of benzothiadiazole units containing donor-acceptor-donor (DAD)-type platinum acetylide oligomers and polymer. The singlet and triplet excited states for the series were characterized by an array of photophysical methods including steady-state luminescence spectroscopy and femtosecond-nanosecond transient absorption spectroscopy. In addition to the experimental work, a computational study using density functional theory was conducted to gain more information about the structure, composition, and energies of the frontier molecular orbitals. It is observed that both the singlet and triplet excited states are mainly localized on a single donor-acceptor-donor unit in the oligomers. Interestingly, it is discovered that the intersystem crossing efficiency increases dramatically in the longer oligomers. The effect is attributed to an enhanced contribution of the heavy metal platinum in the frontier orbitals (HOMO and LUMO), an effect that leads to enhanced spin-orbit coupling. PMID:27291712

  11. 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

  12. 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.

  13. 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

  14. Aerosol nitrate from lightning - from sources to impacts

    NASA Astrophysics Data System (ADS)

    Tost, Holger

    2016-04-01

    Particulate nitrate is a key component on the inorganic atmospheric aerosol composition. Due to its semi-volatility, an accurate description of the budget and the impacts of nitrate aerosol are still somewhat uncertain. To address some of the impacts of nitrate, in this study we explicitly analyse the impact of aerosol nitrate from a natural source, namely lightning. As the lightning NOx emissions are only a contribution to the total NOx emissions, this example does not resemble a typical annihilation scenario, which might substantially misjudge the effect of aerosol nitrate due to the high non-linearity in the nitrate budget, but also other directly connected compounds, but tries to shed light onto the sensitivity of aerosol nitrate and its effects. On the other hand, lightning represents an emission source of NOx, which is partly injected directly in the upper troposphere, where due to its longer lifetime and the temperature dependent stability of NH4NO3 aerosol nitrate can form much easier and has a longer lifetime against decomposition. This study uses a comprehensive chemistry climate model to track the evolution of aerosol nitrate from the lightning NOx emission, via chemical processing and gas-aerosol partitioning, aerosol microphyiscal processes down to the climatic impacts of the nitrate aerosol particles via direct aerosol-radiation and aerosol-cloud interactions. All of these processes are explicitly considered with the help of state-of-the-art (parameterisation) schemes, including a comprehensive multi-phase chemistry configuration, a microphysical and chemical composition aerosol model, aerosol optical properties and a two-moment cloud microphysical scheme with explicit activation of aerosol particles into cloud droplets and the consideration of aerosol particles in ice formation processes. Furthermore, some uncertainty with respect to cloud droplet formation has been considered by using two different aerosol activation schemes. To estimate the

  15. Mercury removal from waste gases by manganese oxide acceptors

    SciTech Connect

    Cavallaro, S.; Bertuccio, N.; Antonucci, P.; Giordano, N.

    1982-02-01

    Removal of mercury vapor from a waste gas has been investigated at atmospheric pressure and at ambient temperature using a series of manganese-based reagents supported on an inert medium. The effect of catalyst composition on activity and the influence of relative humidity of the air stream have been studied. Whereas ..gamma..-Al/sub 2/O/sub 3/ has a very low mercury sorption capacity, sorption occurs copiously on impregnated silver- and copper-doped MnO/sub 2/ acceptors but the much higher activity is reduced by the presence of water vapour in the carrier gas. The morphological and microstructural characterization of the (MnO/sub 2/, AgNO/sub 3/) ..gamma..-Al/sub 2/O/sub 3/ reagents has shown selective deposition of AgNO/sub 3/ particles on ..beta..-MnO/sub 2/ crystallites which are dispersed on the ..gamma..-Al/sub 2/O/sub 3/ matrix. As the adsorption is associated with a sequence of specific colour changes a chemical oxidation mechanism is proposed. Acceptor deactivation is discussed. 9 figures, 3 tables.

  16. 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

  17. Plasma nitrate and nitrite are increased by a high nitrate supplement, but not by high nitrate foods in older adults

    PubMed Central

    Miller, Gary D.; Marsh, Anthony P.; Dove, Robin W.; Beavers, Daniel; Presley, Tennille; Helms, Christine; Bechtold, Erika; King, S. Bruce; Kim-Shapiro, Daniel

    2012-01-01

    Little is known about the effect of dietary nitrate on the nitrate/nitrite/NO (nitric oxide) cycle in older adults. We examined the effect of a 3-day control diet vs. high nitrate diet, with and without a high nitrate supplement (beetroot juice), on plasma nitrate and nitrite kinetics, and blood pressure using a randomized four period cross-over controlled design. We hypothesized that the high nitrate diet would show higher levels of plasma nitrate/nitrite and blood pressure compared to the control diet, which would be potentiated by the supplement. Participants were eight normotensive older men and women (5 female, 3 male, 72.5±4.7 yrs) with no overt disease or medications that affect NO metabolism. Plasma nitrate and nitrite levels and blood pressure were measured prior to and hourly for 3 hours after each meal. The mean daily changes in plasma nitrate and nitrite were significantly different from baseline for both control diet+supplement (p<0.001 and =0.017 for nitrate and nitrite, respectively) and high nitrate diet+supplement (p=0.001 and 0.002), but not for control diet (p=0.713 and 0.741) or high nitrate diet (p=0.852 and 0.500). Blood pressure decreased from the morning baseline measure to the three 2 hr post-meal follow-up time-points for all treatments, but there was no main effect for treatment. In healthy older adults, a high nitrate supplement consumed at breakfast elevated plasma nitrate and nitrite levels throughout the day. This observation may have practical utility for the timing of intake of a nitrate supplement with physical activity for older adults with vascular dysfunction. PMID:22464802

  18. 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...

  19. 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...

  20. 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...

  1. 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...

  2. 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...

  3. 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...

  4. 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.

  5. 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...

  6. 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…

  7. 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...

  8. 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... ADDITIVES PERMITTED FOR DIRECT ADDITION TO FOOD FOR HUMAN CONSUMPTION Food Preservatives § 172.160 Potassium nitrate. The food additive potassium nitrate may be safely used as a curing agent in the processing of...

  9. 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...

  10. 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...

  11. 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...

  12. 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.

  13. 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... follows: (1) As a preservative and color fixative, with or without sodium nitrite, in smoked,...

  14. 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... follows: (1) As a preservative and color fixative, with or without sodium nitrite, in smoked,...

  15. 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...

  16. 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... follows: (1) As a preservative and color fixative, with or without sodium nitrite, in smoked,...

  17. 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... follows: (1) As a preservative and color fixative, with or without sodium nitrite, in smoked,...

  18. Synthesis of dithienosilole-based highly photoluminescent donor-acceptor type compounds.

    PubMed

    Ohshita, Joji; Tominaga, Yuta; Tanaka, Daiki; Ooyama, Yousuke; Mizumo, Tomonobu; Kobayashi, Norifumi; Higashimura, Hideyuki

    2013-03-14

    Highly photoluminescent acceptor-donor-acceptor (A-D-A) and donor-acceptor (D-A) type compounds with a dithienosilole unit as the donor and perfluorotolyl or dimesitylboryl group(s) as the acceptor were prepared by the reaction of lithiated dithienosilole derivatives with perfluorotoluene or fluorodimesitylborane, respectively. The resulting A-D-A and D-A type compounds showed red-shifted UV absorption and PL bands compared to those of simple dithienosiloles having no acceptor units, reported previously, and were highly photoluminescent in the solid state as well as in solution. Solvatochromic behaviour that would arise from the intramolecular donor-acceptor interaction were observed for the D-A type compounds with respect to the UV absorption and PL spectra. In addition, it was found that bis(dimesitylboryl)dithienosilole and (dimesitylboryl)(methylthio)dithienosilole responded to coexisting fluoride anions, leading to clear UV absorption and PL spectral changes in solutions. PMID:23295388

  19. Charge carrier dynamics in organic semiconductors and their donor-acceptor composites: Numerical modeling of time-resolved photocurrent

    NASA Astrophysics Data System (ADS)

    Johnson, Brian; Kendrick, Mark J.; Ostroverkhova, Oksana

    2013-09-01

    We present a model that describes nanosecond (ns) time-scale photocurrent dynamics in functionalized anthradithiophene (ADT) films and ADT-based donor-acceptor (D/A) composites. By fitting numerically simulated photocurrents to experimental data, we quantify contributions of multiple pathways of charge carrier photogeneration to the photocurrent, as well as extract parameters that characterize charge transport (CT) in organic films including charge carrier mobilities, trap densities, hole trap depth, and trapping and recombination rates. In pristine ADT films, simulations revealed two competing charge photogeneration pathways: fast, occurring on picosecond (ps) or sub-ps time scales with efficiencies below 10%, and slow, which proceeds at the time scale of tens of nanoseconds, with efficiencies of about 11%-12%, at the applied electric fields of 40-80 kV/cm. The relative contribution of these pathways to the photocurrent was electric field dependent, with the contribution of the fast process increasing with applied electric field. However, the total charge photogeneration efficiency was weakly electric field dependent exhibiting values of 14%-20% of the absorbed photons. The remaining 80%-86% of the photoexcitation did not contribute to charge carrier generation at these time scales. In ADT-based D/A composites with 2 wt.% acceptor concentration, an additional pathway of charge photogeneration that proceeds via CT exciton dissociation contributed to the total charge photogeneration. In the composite with the functionalized pentacene (Pn) acceptor, which exhibits strong exciplex emission from a tightly bound D/A CT exciton, the contribution of the CT state to charge generation was small, ˜8%-12% of the total number of photogenerated charge carriers, dependent on the electric field. In contrast, in the composite with PCBM acceptor, the CT state contributed about a half of all photogenerated charge carriers. In both D/A composites, the charge carrier mobilities were

  20. Stepwise charge transfer complexation of some pyrimidines with σ-acceptor iodine involving a new unconventional acceptor

    NASA Astrophysics Data System (ADS)

    Rabie, Usama. M.; Mohamed, Ramadan. A.; Abou-El-Wafa, Moustafa. H.

    2007-11-01

    Interactions of some pyrimidine derivatives, 4-amino-2,6-dimethylpyrimidine, kyanmethin, (4AP), 2-amino-4,6-dimethylpyrimidine (2AP), 2-aminopyrimidine (AP), 2-amino-4-methylpyrimidine (AMP), 2-amino-4-methoxy-6-methylpyrimidine (AMMP), and 4-amino-5-chloro-2,6-dimethylpyrimidine (ACDP) as electron donors, with iodine (I 2), as a typical σ-electron acceptor, have been studied. Electronic absorption spectra of these interactions in several organic solvents of different polarities have performed instant appearance of clear charge transfer (CT) bands. Formation constants ( KCT), molar absorption coefficients ( ɛCT) and thermodynamic properties, Δ H, Δ S, and Δ G, of these interactions have been determined and discussed. Electronic absorption spectra of the solutions of the synthesized pyrimidines-iodine, P-I 2, CT complexes have shown the characteristic bands of the triiodide ion, I 3-. UV/vis spectral tracking of these interactions have shown that by lapse of time the first formed CT complex, P-I 2, is transformed to the corresponding triiodide complex, P +I.I 3-, then, the later interacts as a new unconventional acceptor and it forms a CT complex of the form (P).(P +I.I 3-). Elemental analyses of these solid complexes have indicated the stoichiometric ratio 2:2, or formally 1:1, P:I 2.

  1. Stepwise charge transfer complexation of some pyrimidines with sigma-acceptor iodine involving a new unconventional acceptor.

    PubMed

    Rabie, Usama M; Mohamed, Ramadan A; Abou-El-Wafa, Moustafa H

    2007-11-01

    Interactions of some pyrimidine derivatives, 4-amino-2,6-dimethylpyrimidine, kyanmethin, (4AP), 2-amino-4,6-dimethylpyrimidine (2AP), 2-aminopyrimidine (AP), 2-amino-4-methylpyrimidine (AMP), 2-amino-4-methoxy-6-methylpyrimidine (AMMP), and 4-amino-5-chloro-2,6-dimethylpyrimidine (ACDP) as electron donors, with iodine (I(2)), as a typical sigma-electron acceptor, have been studied. Electronic absorption spectra of these interactions in several organic solvents of different polarities have performed instant appearance of clear charge transfer (CT) bands. Formation constants (KCT), molar absorption coefficients (epsilonCT) and thermodynamic properties, DeltaH, DeltaS, and DeltaG, of these interactions have been determined and discussed. Electronic absorption spectra of the solutions of the synthesized pyrimidines-iodine, P-I2, CT complexes have shown the characteristic bands of the triiodide ion, I3*. UV/vis spectral tracking of these interactions have shown that by lapse of time the first formed CT complex, P-I2, is transformed to the corresponding triiodide complex, P(+)I.I3*, then, the later interacts as a new unconventional acceptor and it forms a CT complex of the form (P).(P+I.I3*). Elemental analyses of these solid complexes have indicated the stoichiometric ratio 2:2, or formally 1:1, P:I2. PMID:17317281

  2. 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. PMID:26726610

  3. '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.

  4. Nitrated fatty acids: Synthesis and measurement

    PubMed Central

    Woodcock, Steven R.; Bonacci, Gustavo; Gelhaus, Stacy L.; Schopfer, Francisco J.

    2012-01-01

    Nitrated fatty acids are the product of nitrogen dioxide reaction with unsaturated fatty acids. The discovery of peroxynitrite and peroxidase-induced nitration of biomolecules led to the initial reports of endogenous nitrated fatty acids. These species increase during ischemia reperfusion, but concentrations are often at or near the limits of detection. Here, we describe multiple methods for nitrated fatty acid synthesis, sample extraction from complex biological matrices, and a rigorous method of qualitative and quantitative detection of nitrated fatty acids by LC-MS. In addition, optimized instrument conditions and caveats regarding data interpretation are discussed. PMID:23200809

  5. 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

  6. 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.

  7. 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.

  8. 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.

  9. A new class of organic nitrates: investigations on bioactivation, tolerance and cross-tolerance phenomena

    PubMed Central

    Schuhmacher, S; Schulz, E; Oelze, M; König, A; Roegler, C; Lange, K; Sydow, L; Kawamoto, T; Wenzel, P; Münzel, T; Lehmann, J; Daiber, A

    2009-01-01

    Background and purpose: The chronic use of organic nitrates is limited by serious side effects including oxidative stress, nitrate tolerance and/or endothelial dysfunction. The side effects and potency of nitroglycerine depend on mitochondrial aldehyde dehydrogenase (ALDH-2). We sought to determine whether this concept can be extended to a new class of organic nitrates with amino moieties (aminoalkyl nitrates). Experimental approach: Vasodilator potency of the organic nitrates, in vitro tolerance and in vivo tolerance (after continuous infusion for 3 days) were assessed in wild-type and ALDH-2 knockout mice by isometric tension studies. Mitochondrial oxidative stress was analysed by L-012-dependent chemiluminescence and protein tyrosine nitration. Key results: Aminoethyl nitrate (AEN) showed an almost similar potency to glyceryl trinitrate (GTN), even though it is only a mononitrate. AEN-dependent vasodilatation was mediated by cGMP and nitric oxide. In contrast to triethanolamine trinitrate (TEAN) and GTN, AEN bioactivation did not depend on ALDH-2 and caused no in vitro tolerance. In vivo treatment with TEAN and GTN, but not with AEN, induced cross-tolerance to acetylcholine (ACh)-dependent and GTN-dependent relaxation. Although all nitrates tested induced tolerance to themselves, only TEAN and GTN significantly increased mitochondrial oxidative stress in vitro and in vivo. Conclusions and implications: The present results demonstrate that not all high potency nitrates are bioactivated by ALDH-2 and that high potency of a given nitrate is not necessarily associated with induction of oxidative stress or nitrate tolerance. Obviously, there are distinct pathways for bioactivation of organic nitrates, which for AEN may involve xanthine oxidoreductase rather than P450 enzymes. PMID:19563531

  10. 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.

  11. Robust protein nitration contributes to acetaminophen-induced mitochondrial dysfunction and acute liver injury

    PubMed Central

    Abdelmegeed, Mohamed A.; Jang, Sehwan; Banerjee, Atrayee; Hardwick, James P.; Song, Byoung-Joon

    2013-01-01

    Acetaminophen (APAP), a widely-used analgesic agent, can cause liver injury through increased nitrative stress, leading to protein nitration. However, the identities of nitrated proteins and their roles in hepatotoxicity are poorly understood. Thus, we aimed at studying the mechanism of APAP-induced hepatotoxicity by systematic identification and characterization of nitrated proteins in the absence or presence of an anti-oxidant N-acetylcysteine (NAC). The levels of nitrated proteins markedly increased at 2 h in mice exposed to a single APAP dose (350 mg/kg ip), which caused severe liver necrosis at 24 h. Protein nitration and liver necrosis were minimal in mice exposed to nontoxic 3-hydroxyacetanilide or animals co-treated with APAP and NAC. Mass-spectral analysis of the affinity-purified nitrated proteins identified numerous mitochondrial and cytosolic proteins including mitochondrial aldehyde dehydrogenase, Mn-superoxide dismutase, glutathione peroxidase, ATP synthase, and 3-ketoacyl-CoA thiolase involved in anti-oxidant defense, energy supply, and fatty acid metabolism, respectively. Immunoprecipitation followed by immunoblot with anti-3-NT antibody confirmed that the aforementioned proteins were nitrated in APAP-exposed mice but not in NAC-co-treated mice. Consistently, NAC co-treatment significantly restored the suppressed activities of these enzymes. Thus, we demonstrate a new mechanism by which many nitrated proteins with concomitantly suppressed activities promotes APAP-induced mitochondrial dysfunction and hepatotoxicity. PMID:23454065

  12. 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.

  13. Distinct Signaling Pathways and Transcriptome Response Signatures Differentiate Ammonium- and Nitrate-supplied Plants

    PubMed Central

    Patterson, Kurt; Cakmak, Turgay; Cooper, Andrew; Lager, Ida; Rasmusson, Allan G.; Escobar, Matthew A.

    2010-01-01

    Nitrogen is the only macronutrient that is commonly available to plants in both oxidized and reduced forms, mainly nitrate and ammonium. The physiological and molecular effects of nitrate supply have been well studied, but comparatively little is known about ammonium nutrition and its differential effects on cell function and gene expression. We have used a physiologically realistic hydroponic growth system to compare the transcriptomes and redox status of the roots of ammonium- and nitrate-supplied Arabidopsis thaliana plants. While ~60% of nitrogen-regulated genes displayed common responses to both ammonium and nitrate, significant “nitrate-specific” and “ammonium-specific” gene sets were identified. Pathways involved in cytokinin response and reductant generation/distribution were specifically altered by nitrate, while a complex biotic stress response and changes in nodulin gene expression were characteristic of ammonium-supplied plants. Nitrate supply was associated with a rapid decrease in H2O2 production, potentially due to an increased export of reductant from the mitochondrial matrix. The underlying basis of the nitrate- and ammonium-specific patterns of gene expression appears to be different signals elaborated from each nitrogen source, including alterations in extracellular pH that are associated with ammonium uptake, downstream metabolites in the ammonium assimilation pathway, and the presence or absence of the nitrate ion. PMID:20444219

  14. Mutational Analysis of the Respiratory Nitrate Transporter NarK2 of Mycobacterium tuberculosis

    PubMed Central

    Giffin, Michelle M.; Raab, Ronald W.; Morganstern, Melissa; Sohaskey, Charles D.

    2012-01-01

    Mycobacterium tuberculosis induces nitrate reductase activity in response to decreasing oxygen levels. This is due to regulation of both the transcription and the activity of the nitrate transporter NarK2. A model of NarK2 structure is proposed containing 12 membrane spanning regions consistent with other members of the major facilitator superfamily. The role of the proton gradient was determined by exposing M. tuberculosis to uncouplers. Nitrite production decreased indicating that the importation of nitrate involved an H+/nitrate symporter. The addition of nitrite before nitrate had no effect, suggesting no role for a nitrate/nitrite antiporter. In addition the NarK2 knockout mutant showed no defect in nitrite export. NarK2 is proposed to be a Type I H+/nitrate symporter. Site directed mutagenesis was performed changing 23 amino acids of NarK2. This allowed the identification of important regions and amino acids of this transporter. Five of these mutants were inactive for nitrate transport, seven produced reduced activity and eleven mutants retained wild type activity. NarK2 is inactivated in the presence of oxygen by an unknown mechanism. However none of the mutants, including those with mutated cysteines, were altered in their response to oxygen levels. The assimilatory nitrate transporter NasA of Bacillus subtilis was expressed in the M. tuberculosis NarK2 mutant. It remained active during aerobic incubation showing that the point of oxygen control is NarK2. PMID:23029022

  15. 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.

  16. Dietary nitrate supplementation and exercise performance.

    PubMed

    Jones, Andrew M

    2014-05-01

    Dietary nitrate is growing in popularity as a sports nutrition supplement. This article reviews the evidence base for the potential of inorganic nitrate to enhance sports and exercise performance. Inorganic nitrate is present in numerous foodstuffs and is abundant in green leafy vegetables and beetroot. Following ingestion, nitrate is converted in the body to nitrite and stored and circulated in the blood. In conditions of low oxygen availability, nitrite can be converted into nitric oxide, which is known to play a number of important roles in vascular and metabolic control. Dietary nitrate supplementation increases plasma nitrite concentration and reduces resting blood pressure. Intriguingly, nitrate supplementation also reduces the oxygen cost of submaximal exercise and can, in some circumstances, enhance exercise tolerance and performance. The mechanisms that may be responsible for these effects are reviewed and practical guidelines for safe and efficacious dietary nitrate supplementation are provided. PMID:24791915

  17. 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.

  18. Nitration of sym-trichlorobenzene

    SciTech Connect

    Quinlin, W.T.

    1981-02-01

    Basic thermal and kinetic data were obtained for the nitration of 1,3,5-trichlorobenzene to trichlorotrinitrobenzene in the presence of oleum/nitric acid. A limiting specific production rate of 5.4 kg/l/hr was determined for the addition of the first two nitro groups at 130 C and a rate of 0.16 kg/l/hr was obtained at 150 C for the addition of the third nitro group.

  19. Fermi Surface of Donor and Acceptor Graphite Intercalation Compounds.

    NASA Astrophysics Data System (ADS)

    Wang, Guonan

    The Fermi surfaces and the electronic properties of the donor-type stage-1 C_8K and stage-2 C_{24}K, as well as the acceptor-type stage-2 BiCl_3, stage-3 HgCl_2 and stage-3 SbF _5 graphite intercalation compounds were investigated by means of the de Haas-van Alphen effect. The dHvA spectra of the stage-1 C_8 K exhibit two dHvA frequencies, 3126 T and 4250 T. The corresponding effective masses were 0.86 m _0 and 0.92 m_0, respectively. The angular dependence of the dHvA frequencies for a direction within +/-18^circ of the c-axis showed that there are both three-dimensional and two dimensional parts of the Fermi surfaces in C _8K. The three-dimensional Fermi surface has a cross-sectional area corresponding to the dHvA frequency of 3126 T. The charge transfer per potassium atom measured from the dHvA effect is 0.97. This implies that the potassium is ionized completely. These dHvA experimental results support both the Tatar and Rabii model and the revised Ohno, Nakao and Kamimura model for C_8K. Two dominant dHvA frequencies were obtained in stage-2 C_{24}K. They are 286 T and 2570 T, respectively. The predictions of Blinowski's model are in agreement with the experimental data. The charge transfer per potassium is found to be 0.88. This suggests that the potassium s-band is above the Fermi level in C_{24}K. The dHvA measurements for the acceptor compounds show that the stage-2 BiCl_3 GIC had two dHvA frequencies, 327T and 1012T, and each stage -3 compound had three dominant frequencies. They are 121T, 523T and 664T for HgCl_2, and 172T, 656T and 852T for SbF_5. The cyclotron masses corresponding to the dHvA frequencies for these compounds were measured from the temperature dependence of the dHvA amplitudes. The theoretical predictions of the dHvA frequencies and the cyclotron masses from the Blinowski's band models for stage-2 and stage-3 compounds are in agreement with the experimental results. The angular dependence of the dHvA frequencies show that the Fermi

  20. 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...

  1. 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...

  2. 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...

  3. 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...

  4. 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...

  5. 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.

  6. Catalyzed reduction of nitrate in aqueous solutions

    SciTech Connect

    Haas, P.A.

    1994-08-01

    Sodium nitrate and other nitrate salts in wastes is a major source of difficulty for permanent disposal. Reduction of nitrate using aluminum metal has been demonstrated, but NH{sub 3}, hydrazine, or organic compounds containing oxygen would be advantageous for reduction of nitrate in sodium nitrate solutions. Objective of this seed money study was to determine minimum conditions for reduction. Proposed procedure was batchwise heating of aqueous solutions in closed vessels with monitoring of temperatures and pressures. A simple, convenient apparatus and procedure were demonstrated for observing formation of gaseous products and collecting samples for analyses. The test conditions were 250{degree}C and 1000 psi max. Any useful reduction of sodium nitrate to sodium hydroxide as the primary product was not found. The nitrate present at pHs < 4 as HNO{sub 3} or NH{sub 4}NO{sub 3} is easily decomposed, and the effect of nitromethane at these low pHs was confirmed. When acetic acid or formic acid was added, 21 to 56% of the nitrate in sodium nitrate solutions was reduced by methanol or formaldehyde. With hydrazine and acetic acid, 73 % of the nitrate was decomposed to convert NaNO{sub 3} to sodium acetate. With hydrazine and formic acid, 36% of the nitrate was decomposed. If these products are more acceptable for final disposal than sodium nitrate, the reagents are cheap and the conversion conditions would be practical for easy use. Ammonium acetate or formate salts did not significantly reduce nitrate in sodium nitrate solutions.

  7. Mass transfer of electron acceptor aross the capillary fringe

    NASA Astrophysics Data System (ADS)

    Liu, S.; Piepenbrink, M.; Grathwohl, P.

    2005-12-01

    Transverse dispersion has been identified as a potentially limiting parameter controlling the mixing of electron donors and electron acceptors for natural attenuation of plumes originating from continuously emitting sources, however determining reactive transverse dispersion coefficients is not a simple task. The objective of this work is to elaborate the mass transfer of electron acceptor across the capillary fringe. A two-dimensional numerical reactive transport model and a fully controlled tank experiment are set up to investigate the mass transfer across the capillary and reactive fringe, where the oxygen supply is the limiting factor. The tank (77.9 times 14 times 0.8 cm) is made from acrylic-glass and filled with glass beads (0.5-0.75mm). Sodium dithionite, an easily oxidizable compound, is used as a surrogate for contaminants and is continuously injected from the inlets of the tank and reaches a steady state flow. Air circulates on the top of the glass beads. The oxygen concentrations as well as the reactive products (sulfate) are measured at the outlets of the tank with an oxygen sensor and via IC. In addition to that, resazurine, a redox indicator, is added to visualize the redox zones. These two-dimensional experimental results show quantitatively and qualitatively how the oxygen concentrations decrease at the plume fringe. Two dimensional numerical simulations with Min3P predicted oxygen distributions are compared with the experimental results. Acknowledgements: This work was funded by Helmholtz Association and Helmholtz Research Center UFZ; Project: `Virtual Institute for isotope biogeochemistry-biologically mediated processes at geochemical gradients and interfaces in soil - aquifer systems', Contract VH-VI-155.

  8. 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. PMID:26522443

  9. 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.; Mao, J.; Naik, V.; Horowitz, L. W.

    2015-09-01

    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 present-day fine nitrate optical depth at 550 nm is 0.006 (0.005-0.008). We only find a modest increase of nitrate optical depth (< 30 %) in response to the projected changes in the emissions of SO2 (-40 %) and ammonia (+38 %) from 2010 to 2050. Nitrate burden is projected to increase in the tropics and in the free troposphere, but to decrease at the surface in the midlatitudes because of lower nitric acid concentrations. Our results suggest that better constraints on the heterogeneous chemistry of nitric acid on dust, on tropical ammonia emissions, and on the transport of ammonia to the free troposphere are needed to improve projections of aerosol optical depth.

  10. 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

  11. 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.

  12. 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).

  13. Efficiency improvement of new Tetrathienoacene-based dyes by enhancing donor, acceptor and bridge units, a theoretical study.

    PubMed

    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. PMID:27258685

  14. 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. PMID:25447671

  15. Acceptor-donor-acceptor-based small molecules with varied crystallinity: processing additive-induced nanofibril in blend film for photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Li, Chao; Chen, Yujin; Zhao, Yue; Wang, Huifang; Zhang, Wei; Li, Yaowen; Yang, Xiaoming; Ma, Changqi; Chen, Liwei; Zhu, Xiulin; Tu, Yingfeng

    2013-09-01

    A series of acceptor-donor-acceptor-based small molecules (SMs) with varied crystallinity were successfully synthesized. The processing additive can induce the SMs to self-organize as nanofibrils with higher crystallinity and controlled scales of nanofibrils, which have significant influence on the photovoltaic performance.A series of acceptor-donor-acceptor-based small molecules (SMs) with varied crystallinity were successfully synthesized. The processing additive can induce the SMs to self-organize as nanofibrils with higher crystallinity and controlled scales of nanofibrils, which have significant influence on the photovoltaic performance. Electronic supplementary information (ESI) available: Synthetic process and characterizations of SMs; TGA, electrochemical properties, molecular orbital surfaces of SMs; AFM images of SM:PC71BM blend films; EQE curves; optical, electrochemical properties and photovoltaic parameters. See DOI: 10.1039/c3nr03048b

  16. 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.

  17. 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

  18. Probing the donor and acceptor substrate specificity of the γ-glutamyl transpeptidase.

    PubMed

    Hu, Xin; Legler, Patricia M; Khavrutskii, Ilja; Scorpio, Angelo; Compton, Jaimee R; Robertson, Kelly L; Friedlander, Arthur M; Wallqvist, Anders

    2012-02-14

    γ-Glutamyl transpeptidase (GGT) is a two-substrate enzyme that plays a central role in glutathione metabolism and is a potential target for drug design. GGT catalyzes the cleavage of γ-glutamyl donor substrates and the transfer of the γ-glutamyl moiety to an amine of an acceptor substrate or water. Although structures of bacterial GGT have revealed details of the protein-ligand interactions at the donor site, the acceptor substrate site is relatively undefined. The recent identification of a species-specific acceptor site inhibitor, OU749, suggests that these inhibitors may be less toxic than glutamine analogues. Here we investigated the donor and acceptor substrate preferences of Bacillus anthracis GGT (CapD) and applied computational approaches in combination with kinetics to probe the structural basis of the enzyme's substrate and inhibitor binding specificities and compare them with human GGT. Site-directed mutagenesis studies showed that the R432A and R520S variants exhibited 6- and 95-fold decreases in hydrolase activity, respectively, and that their activity was not stimulated by the addition of the l-Cys acceptor substrate, suggesting an additional role in acceptor binding and/or catalysis of transpeptidation. Rat GGT (and presumably HuGGT) has strict stereospecificity for L-amino acid acceptor substrates, while CapD can utilize both L- and D-acceptor substrates comparably. Modeling and kinetic analysis suggest that R520 and R432 allow two alternate acceptor substrate binding modes for L- and D-acceptors. R432 is conserved in Francisella tularensis, Yersinia pestis, Burkholderia mallei, Helicobacter pylori and Escherichia coli, but not in human GGT. Docking and MD simulations point toward key residues that contribute to inhibitor and acceptor substrate binding, providing a guide to designing novel and specific GGT inhibitors. PMID:22257032

  19. 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.

  20. 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

  1. Photovoltaic and Spectral Properties of Conjugated Polymer Poly(3-octylthiophene) Doped with Various Acceptor Materials

    NASA Astrophysics Data System (ADS)

    Lee, Tsung-Hsien; Chen, Wei-Hsin; Su, Mu-Ting; Lai, Tzay-Shing; Lee, Wei

    2010-08-01

    We propose a novel approach for enhancement of efficiency of polymer-based photovoltaic devices by means of a low-molar-mass liquid crystal as a dopent. The active layers of the photovoltaic cells are primarily fabricated from the conjugated polymer poly(3-octylthiophene) as well as various acceptor substances including single-wall carbon nanotubes, buckminsterfullerene and the nematic liquid crystal E7 for comparison. The current-voltage characteristics are measured in dark and under green light illumination at wavelength of 514.5 nm. The power conversion efficiency for the active layer doped with E7 is the best among all cells in the simplest monolayer cell structure. Owing to the superior miscibility and orientational order of the nematic liquid crystal, E7 molecules may have promoted a composite film with fewer defects and locally helped the macromolecules align more orderly and consequently improved the charge-carrier transport, leading to the higher photocurrent and power conversion efficiency.

  2. 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. PMID:15952359

  3. 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

  4. Fast photolysis of carbonyl nitrates from isoprene

    NASA Astrophysics Data System (ADS)

    Müller, Jean-Francois; Peeters, Jozef; Stavrakou, Trisevgeni

    2014-05-01

    We show that photolysis is, by far, the major atmospheric sink of isoprene-derived carbonyl nitrates. Empirical evidence from published laboratory studies on the absorption cross sections and photolysis rates of α-nitrooxy ketones suggests that the presence of the nitrate group (i) greatly enhances the absorption cross sections, and (ii) facilitates dissociation to a point that the photolysis quantum yield is close to unity, with O-NO2 dissociation as the likely major channel. On this basis, we provide new recommendations for estimating the cross sections and photolysis rates of carbonyl nitrates. The newly estimated photorates are validated using a chemical box model against measured temporal profiles of carbonyl nitrates in an isoprene oxidation experiment by Paulot et al. (2009). The comparisons for ethanal nitrate and for the sum of methacrolein- and methylvinylketone nitrates strongly supports our assumptions of large cross section enhancements and a near-unit quantum yield for these compounds. These findings have significant atmospheric implications, as carbonyl nitrates constitute an important component of the total organic nitrate pool over vegetated areas: the photorates of key carbonyl nitrates from isoprene are estimated to be typically between ~3 and 20 times higher than their sink due to reaction with OH in relevant atmospheric conditions. Moreover, since the reaction is expected to release NO2, photolysis is especially effective in depleting the total organic nitrate pool.

  5. 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

  6. Isolation and characterization of Alicycliphilus denitrificans strain BC, which grows on benzene with chlorate as the electron acceptor.

    PubMed

    Weelink, Sander A B; Tan, Nico C G; ten Broeke, Harm; van den Kieboom, Corné; van Doesburg, Wim; Langenhoff, Alette A M; Gerritse, Jan; Junca, Howard; Stams, Alfons J M

    2008-11-01

    A bacterium, strain BC, was isolated from a benzene-degrading chlorate-reducing enrichment culture. Strain BC degrades benzene in conjunction with chlorate reduction. Cells of strain BC are short rods that are 0.6 microm wide and 1 to 2 microm long, are motile, and stain gram negative. Strain BC grows on benzene and some other aromatic compounds with oxygen or in the absence of oxygen with chlorate as the electron acceptor. Strain BC is a denitrifying bacterium, but it is not able to grow on benzene with nitrate. The closest cultured relative is Alicycliphilus denitrificans type strain K601, a cyclohexanol-degrading nitrate-reducing betaproteobacterium. Chlorate reductase (0.4 U/mg protein) and chlorite dismutase (5.7 U/mg protein) activities in cell extracts of strain BC were determined. Gene sequences encoding a known chlorite dismutase (cld) were not detected in strain BC by using the PCR primers described in previous studies. As physiological and biochemical data indicated that there was oxygenation of benzene during growth with chlorate, a strategy was developed to detect genes encoding monooxygenase and dioxygenase enzymes potentially involved in benzene degradation in strain BC. Using primer sets designed to amplify members of distinct evolutionary branches in the catabolic families involved in benzene biodegradation, two oxygenase genes putatively encoding the enzymes performing the initial successive monooxygenations (BC-BMOa) and the cleavage of catechol (BC-C23O) were detected. Our findings suggest that oxygen formed by dismutation of chlorite can be used to attack organic molecules by means of oxygenases, as exemplified with benzene. Thus, aerobic pathways can be employed under conditions in which no external oxygen is supplied. PMID:18791031

  7. Dichotomous Role of Exciting the Donor or the Acceptor on Charge Generation in Organic Solar Cells.

    PubMed

    Hendriks, Koen H; Wijpkema, Alexandra S G; van Franeker, Jacobus J; Wienk, Martijn M; Janssen, René A J

    2016-08-10

    In organic solar cells, photoexcitation of the donor or acceptor phase can result in different efficiencies for charge generation. We investigate this difference for four different 2-pyridyl diketopyrrolopyrrole (DPP) polymer-fullerene solar cells. By comparing the external quantum efficiency spectra of the polymer solar cells fabricated with either [60]PCBM or [70]PCBM fullerene derivatives as acceptor, the efficiency of charge generation via donor excitation and acceptor excitation can both be quantified. Surprisingly, we find that to make charge transfer efficient, the offset in energy between the HOMO levels of donor and acceptor that govern charge transfer after excitation of the acceptor must be larger by ∼0.3 eV than the offset between the corresponding two LUMO levels when the donor is excited. As a consequence, the driving force required for efficient charge generation is significantly higher for excitation of the acceptor than for excitation of the donor. By comparing charge generation for a total of 16 different DPP polymers, we confirm that the minimal driving force, expressed as the photon energy loss, differs by about 0.3 eV for exciting the donor and exciting the acceptor. Marcus theory may explain the dichotomous role of exciting the donor or the acceptor on charge generation in these solar cells. PMID:27452683

  8. Oxygen and Nitrate Respiration in Streptomyces coelicolor A3(2).

    PubMed

    Sawers, R G; Falke, D; Fischer, M

    2016-01-01

    Streptomyces species belong to the phylum Actinobacteria and can only grow with oxygen as a terminal electron acceptor. Like other members of this phylum, such as corynebacteria and mycobacteria, the aerobic respiratory chain lacks a soluble cytochrome c. It is therefore implicit that direct electron transfer between the cytochrome bc1 and the cytochrome aa3 oxidase complexes occurs. The complex developmental cycle of streptomycetes manifests itself in the production of spores, which germinate in the presence of oxygen into a substrate mycelium that greatly facilitates acquisition of nutrients necessary to support their saprophytic lifestyle in soils. Due to the highly variable oxygen levels in soils, streptomycetes have developed means of surviving long periods of hypoxia or even anaerobiosis but they fail to grow under these conditions. Little to nothing is understood about how they maintain viability under conditions of oxygen limitation. It is assumed that they can utilise a number of different electron acceptors to help them maintain a membrane potential, one of which is nitrate. The model streptomycete remains Streptomyces coelicolor A3(2), and it synthesises three nonredundant respiratory nitrate reductases (Nar). These Nar enzymes are synthesised during different phases of the developmental cycle and they are functional only under oxygen-limiting (<5% oxygen in air) conditions. Nevertheless, the regulation of their synthesis does not appear to be responsive to nitrate and in the case of Nar1, it appears to be developmentally regulated. This review highlights some of the novel aspects of our current, but somewhat limited, knowledge of respiration in these fascinating bacteria. PMID:27134020

  9. 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 ...

  10. Identification of acceptor states in Li-doped p-type ZnO thin films

    NASA Astrophysics Data System (ADS)

    Zeng, Y. J.; Ye, Z. Z.; Lu, J. G.; Xu, W. Z.; Zhu, L. P.; Zhao, B. H.; Limpijumnong, Sukit

    2006-07-01

    We investigate photoluminescence from reproducible Li-doped p-type ZnO thin films prepared by dc reactive magnetron sputtering. The LiZn acceptor state, with an energy level located at 150meV above the valence band maximum, is identified from free-to-neutral-acceptor transitions. Another deeper acceptor state located at 250meV emerges with the increased Li concentration. A broad emission centered at 2.96eV is attributed to a donor-acceptor pair recombination involving zinc vacancy. In addition, two chemical bonding states of Li, evident in x-ray photoelectron spectroscopy, are probably associated with the two acceptor states observed.

  11. Purification and characterization of a carbohydrate: acceptor oxidoreductase from Paraconiothyrium sp. that produces lactobionic acid efficiently.

    PubMed

    Kiryu, Takaaki; Nakano, Hirofumi; Kiso, Taro; Murakami, Hiromi

    2008-03-01

    A carbohydrate:acceptor oxidoreductase from Paraconiothyrium sp. was purified and characterized. The enzyme efficiently oxidized beta-(1-->4) linked sugars, such as lactose, xylobiose, and cellooligosaccharides. The enzyme also oxidized maltooligosaccharides, D-glucose, D-xylose, D-galactose, L-arabinose, and 6-deoxy-D-glucose. It specifically oxidized the beta-anomer of lactose. Molecular oxygen and 2,6-dichlorophenol indophenol were reduced by the enzyme as electron acceptors. The Paraconiothyrium enzyme was identified as a carbohydrate:acceptor oxidoreductase according to its specificity for electron donors and acceptors, and its molecular properties, as well as the N-terminal amino acid sequence. Further comparison of the amino acid sequences of lactose oxidizing enzymes indicated that carbohydrate:acceptor oxidoreductases belong to the same group as glucooligosaccharide oxidase, while they differ from cellobiose dehydrogenases and cellobiose:quinone oxidoreductases. PMID:18323642

  12. 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.

  13. 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.

  14. 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

  15. 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.

  16. 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

  17. Nitrate removal in deep sediments of a nitrogen-rich river network: A test of a conceptual model

    NASA Astrophysics Data System (ADS)

    Stelzer, Robert S.; Bartsch, Lynn A.

    2012-06-01

    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 can

  18. Photochemistry of nitrate ion in acetonitrile

    NASA Astrophysics Data System (ADS)

    Meera, N.; Ramamurthy, P.

    1988-12-01

    The photochemistry of cobalt(II) nitrate in acetonitrile is investigated using steady-state and flash photolysis techniques. Formation of NO 3• radical has been observed as an intermediate by direct photolysis of nitrate ion and the reaction of the nitrate radical with the solvent is observed as a transient absorption around 600 nm in air-equilibrated acetonitrile. Nitrite ion forms as a product through a collision electron transfer complex intermediate.

  19. Nitrogen-isotope ratios of nitrate in ground water under fertilized fields, Long Island, New York

    USGS Publications Warehouse

    Flipse, W.J., Jr.; 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

  20. Isotopic Identification of Nitrate Sources and Cycling in Arctic Tundra Active Layer Soils and Permafrost

    NASA Astrophysics Data System (ADS)

    Heikoop, J. M.; Throckmorton, H.; Newman, B. D.; Perkins, G.; Gard, M.; Iversen, C. M.; Wilson, C. J.; Wullschleger, S. D.

    2014-12-01

    The effect of nitrogen cycling on release of carbon from tundra ecosystems is being studied as part of the US Department of Energy Next Generation Ecosystem Experiment - Arctic project. Sampling and analysis of active layer soil water at the Barrow Environmental Observatory (Alaska, USA) was performed in ancient drained thaw lake basins (DTLBs), drainages, and in polygonal terrain associated with inter-DTLB tundra. Within active layer soils, nitrate was most commonly found above analytical limits of detection in pore water from the unsaturated centers of high-centered polygons. Nitrate has also been detected, though less frequently, in soil water immediately above the frost table of an ancient (14C age of 2000 - 5500 BP) DTLB and in a small drainage adjacent to high-centered polygonal terrain. Nitrate from high-centered polygons had δ15N ranging from -9.2 to +8.5 ‰ and δ18O ranging from -8.4 to +1.4 ‰. The δ15N isotopic range is consistent with microbial mineralization and nitrification of reduced nitrogen sources including ammonium, dissolved organic nitrogen, and soil organic nitrogen. The range in δ18O of nitrate is also consistent with nitrification based on the δ18O of site waters. No evidence for an atmospheric nitrate signal, as defined by δ15N and δ18O of nitrate in snow and snowmelt, is seen. In contrast, nitrate in permafrost appears to be a mixture of pre-industrial atmospheric nitrate (with higher δ15N than modern atmospheric nitrate) and nitrate that is microbial in origin. Massive ice wedges appear to contain larger proportions of snowmelt (based on δ18O of ice) and atmospheric nitrate, whereas textural ice appears to contain a greater proportion of summer precipitation and microbially-derived nitrate. Nitrate from the ancient DTLB and drainage samples also has isotopic signatures that appear to represent a mixture of pre-industrial atmospheric nitrate and nitrate from microbial nitrification, and may, at least in part, be derived from

  1. 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.

  2. Too much of a good thing? Nitrate from nitrogen fertilizers and cancer.

    PubMed

    Ward, Mary H

    2009-01-01

    Nitrate levels in water supplies have been increasing in many areas of the world; therefore, additional studies of populations with well-characterized exposures are urgently needed to further our understanding of cancer risk associated with nitrate ingestion. Future studies should assess exposure for individuals (e.g., case-control, cohort studies) in a time frame relevant to disease development, and evaluate factors affecting nitrosation. Estimating N-nitroso compounds formation via nitrate ingestion requires information on dietary and drinking water sources of nitrate, inhibitors of nitrosation (e.g., vitamin C), nitrosation precursors (e.g., red meat, nitrosatable drugs), and medical conditions that may increase nitrosation (e.g., inflammatory bowel disease). Studies should account for the potentially different effects of dietary and water sources of nitrate and should include the population using private wells for whom exposure levels are often higher than public supplies. PMID:20384045

  3. Optimization of enhanced bioelectrical reactor with electricity from microbial fuel cells for groundwater nitrate removal.

    PubMed

    Liu, Ye; Zhang, Baogang; Tian, Caixing; Feng, Chuanping; Wang, Zhijun; Cheng, Ming; Hu, Weiwu

    2016-04-01

    Factors influencing the performance of a continual-flow bioelectrical reactor (BER) intensified by microbial fuel cells for groundwater nitrate removal, including nitrate load, carbon source and hydraulic retention time (HRT), were investigated and optimized by response surface methodology (RSM). With the target of maximum nitrate removal and minimum intermediates accumulation, nitrate load (for nitrogen) of 60.70 mg/L, chemical oxygen demand (COD) of 849.55 mg/L and HRT of 3.92 h for the BER were performed. COD was the dominant factor influencing performance of the system. Experimental results indicated the undistorted simulation and reliable optimized values. These demonstrate that RSM is an effective method to evaluate and optimize the nitrate-reducing performance of the present system and can guide mathematical models development to further promote its practical applications. PMID:26402418

  4. 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?

  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. Fast photolysis of carbonyl nitrates from isoprene

    NASA Astrophysics Data System (ADS)

    Müller, J.-F.; Peeters, J.; Stavrakou, T.

    2014-03-01

    Photolysis is shown to be a major sink for isoprene-derived carbonyl nitrates, which constitute an important component of the total organic nitrate pool over vegetated areas. Empirical evidence from published laboratory studies on the absorption cross sections and photolysis rates of α-nitrooxy ketones suggests that the presence of the nitrate group (i) greatly enhances the absorption cross sections and (ii) facilitates dissociation to a point that the photolysis quantum yield is close to unity, with O-NO2 dissociation as a likely major channel. On this basis, we provide new recommendations for estimating the cross sections and photolysis rates of carbonyl nitrates. The newly estimated photo rates are validated using a chemical box model against measured temporal profiles of carbonyl nitrates in an isoprene oxidation experiment by Paulot et al. (2009). The comparisons for ethanal nitrate and for the sum of methacrolein- and methyl vinyl ketone nitrates strongly supports our assumptions of large cross-section enhancements and a near-unit quantum yield for these compounds. These findings have significant atmospheric implications: the photorates of key carbonyl nitrates from isoprene are estimated to be typically between ~ 3 and 20 times higher than their sink due to reaction with OH in relevant atmospheric conditions. Moreover, since the reaction is expected to release NO2, photolysis is especially effective in depleting the total organic nitrate pool.

  7. Fast photolysis of carbonyl nitrates from isoprene

    NASA Astrophysics Data System (ADS)

    Müller, J.-F.; Peeters, J.; Stavrakou, T.

    2013-11-01

    Photolysis is shown to be a major sink for isoprene-derived carbonyl nitrates, which constitute an important component of the total organic nitrate pool over vegetated areas. Empirical evidence from published laboratory studies on the absorption cross sections and photolysis rates of α-nitrooxy ketones suggests that the presence of the nitrate group (i) greatly enhances the absorption cross sections, and (ii) facilitates dissociation to a point that the photolysis quantum yield is close to unity, with O-NO2 dissociation as the likely major channel. On this basis, we provide new recommendations for estimating the cross sections and photolysis rates of carbonyl nitrates. The newly estimated photorates are validated using a chemical box model against measured temporal profiles of carbonyl nitrates in an isoprene oxidation experiment by Paulot et al. (2009). The comparisons for ethanal nitrate and for the sum of methacrolein- and methylvinylketone nitrates strongly supports our assumptions of large cross section enhancements and a near-unit quantum yield for these compounds. These findings have significant atmospheric implications: the photorates of key carbonyl nitrates from isoprene are estimated to be typically between ~3 and 20 times higher than their sink due to reaction with OH in relevant atmospheric conditions. Moreover, since the reaction is expected to release NO2, photolysis is especially effective in depleting the total organic nitrate pool.

  8. Sampling of nitrates in ambient air

    NASA Astrophysics Data System (ADS)

    Appel, B. R.; Tokiwa, Y.; Haik, M.

    Methods for the measurement of nitric acid, particulate nitrate and total inorganic nitrate (i.e. HNO 3 plus particulate nitrate) are compared using atmospheric samples from the Los Angeles Basin. Nitric acid was measured by (1) the nitrate collected on nylon or NaCl-impregnated cellulose filters after removal of particulate matter with Teflon prefilters, (2) long-path Fourier transform infrared spectroscopy (FTIR) performed by a collaborating investigator, and (3) the difference between total inorganic nitrate (TIN) and particulate nitrate (PN). TIN was measured by the sum of the nitrate collected with a Teflon prefilter and nylon or NaCl-impregnated after-filter. PN was measured by the nitrate able to penetrate a diffusion dénuder coated to remove acidic gases (e.g. HNO 3). Losses of nitrate from Teflon prefilters were determined by comparing the nitrate retained by these filters to the nitrate penetrating the acid gas denuder. TIN and the nitrate collected with glass fiber filters were compared to assess the origin of the artifact particulate nitrate on the latter. Nitric acid measurements using nylon or NaCl-impregnated after-filters were substantially higher than those by the difference technique. This correlated with losses of nitrate from the Teflon prefilters, which exceeded 50 % at high ambient temperature and low relative humidity. Nitric acid by the difference method exceeded that by FTIR by, on average, 20 %. Thus errors inferred in HNO 3 measurements by comparison to the difference measurements are considered minimum values. The high values for HNO 3 by the difference method are consistent with the partial loss of PN in the acid gas denuder. However, no loss of 0.1 μm to 3 μm diameter NH 4NO 3 particles was observed. Thus, if significant, such loss is restricted to coarse particulate nitrate. Heating the filter samplers was shown to increase sampling errors. Nitrate results obtained in short-term, low volume sampling with Gelman A glass fiber

  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. Nitrate-Dependent Regulation of Acetate Biosynthesis and Nitrate Respiration by Clostridium thermoaceticum

    PubMed Central

    Arendsen, Alexander F.; Soliman, Mohsin Q.; Ragsdale, Stephen W.

    1999-01-01

    Nitrate has been shown to shunt the electron flow in Clostridium thermoaceticum from CO2 to nitrate, but it did not influence the levels of enzymes involved in the Wood-Ljungdahl pathway (J. M. Fröstl, C. Seifritz, and H. L. Drake, J. Bacteriol. 178:4597–4603, 1996). Here we show that under some growth conditions, nitrate does in fact repress proteins involved in the Wood-Ljungdahl pathway. The CO oxidation activity in crude extracts of nitrate (30 mM)–supplemented cultures was fivefold less than that of nitrate-free cultures, while the H2 oxidation activity was six- to sevenfold lower. The decrease in CO oxidation activity paralleled a decrease in CO dehydrogenase (CODH) protein level, as confirmed by Western blot analysis. Protein levels of CODH in nitrate-supplemented cultures were 50% lower than those in nitrate-free cultures. Western blots analyses showed that nitrate also decreased the levels of the corrinoid iron-sulfur protein (60%) and methyltransferase (70%). Surprisingly, the decrease in activity and protein levels upon nitrate supplementation was observed only when cultures were continuously sparged. Northern blot analysis indicates that the regulation of the proteins involved in the Wood-Ljungdahl pathway by nitrate is at the transcriptional level. At least a 10-fold decrease in levels of cytochrome b was observed with nitrate supplementation whether the cultures were sparged or stoppered. We also detected nitrate-inducible nitrate reductase activity (2 to 39 nmol min−1 mg−1) in crude extracts of C. thermoaceticum. Our results indicate that nitrate coordinately represses genes encoding enzymes and electron transport proteins in the Wood-Ljungdahl pathway and activates transcription of nitrate respiratory proteins. CO2 also appears to induce expression of the Wood-Ljungdahl pathway genes and repress nitrate reductase activity. PMID:10049380

  11. Chronic nitrate enrichment decreases severity and induces protection against an infectious disease.

    PubMed

    Smallbone, Willow; Cable, Jo; Maceda-Veiga, Alberto

    2016-05-01

    Excessive fertilisation is one of the most pernicious forms of global change resulting in eutrophication. It has major implications for disease control and the conservation of biodiversity. Yet, the direct link between nutrient enrichment and disease remains largely unexplored. Here, we present the first experimental evidence that chronic nitrate enrichment decreases severity and induces protection against an infectious disease. Specifically, this study shows that nitrate concentrations ranging between 50 and 250mgNO3(-)/l reduce Gyrodactylus turnbulli infection intensity in two populations of Trinidadian guppies Poecilia reticulata, and that the highest nitrate concentration can even clean the parasites from the fish. This added to the fact that host nitrate pre-exposure altered the fish epidermal structure and reduced parasite intensity, suggests that nitrate protected the host against the disease. Nitrate treatments also caused fish mortality. As we used ecologically-relevant nitrate concentrations, and guppies are top-consumers widely used for mosquito bio-control in tropical and often nutrient-enriched waters, our results can have major ecological and social implications. In conclusion, this study advocates reducing nitrate level including the legislative threshold to protect the aquatic biota, even though this may control an ectoparasitic disease. PMID:26995268

  12. The origin of high-nitrate ground waters in the Australian arid zone

    NASA Astrophysics Data System (ADS)

    Barnes, C. J.; Jacobson, G.; Smith, G. D.

    1992-08-01

    Nitrate concentrations beyond the drinking-water limit of 10 mg1 -1 NO 3-N, are common in Australian arid-zone ground waters and are often associated with otherwise potable waters. In some aquifers nitrate-N concentrations of up to 80 mg1 -1 have been found, and this is a severe constraint on water supply development for small settlements. Water-bore data indicate a correlation of high-nitrate ground waters with shallow unconfined aquifers. Aguifer hydrochemistry indicats that these ground waters were emplaced by episodic Holocene recharge events in an otherwise arid climate regime. Nitrate has been flushed through the unsaturated zone which apparently lacks denitrification activity. The nitrate originates by near-surface biological fixation and contributing organisms include cyanobacteria in soil crusts and bacteria in termite mounds with the highest soil nitrate concentrations found in the outer skin of termite mounds. Bacteria associated with the termites appear to fix nitrogen, which eventually appears in an inorganic form, principally as ammonia. Nitrate is produced by bacterial oxidation of the ammonia, and is leached to the outside of the termite mound by capillary action. Diffuse recharge from extreme rainfall events then flushes this nitrate to the water table.

  13. 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.

  14. 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. PMID:26544021

  15. 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.

  16. 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

  17. Interaction of nitrate and folate on the risk of breast cancer among postmenopausal women

    PubMed Central

    Inoue-Choi, Maki; Ward, Mary H.; Cerhan, James R.; Weyer, Peter J.; Anderson, Kristin E.; Robien, Kim

    2012-01-01

    Ingested nitrate can be endogenously reduced to nitrite, which may form N-nitroso compounds, known potent carcinogens. However, some studies have reported no or inverse associations between dietary nitrate intake and cancer risk. These associations may be confounded by a protective effect of folate, which plays a vital role in DNA repair. We evaluated the interaction of dietary and water nitrate intake with total folate intake on breast cancer risk in the Iowa Women’s Health Study. Dietary intake was assessed at study baseline. Nitrate intake from public water was assessed using a historical database on Iowa municipal water supplies. After baseline exclusions, 34,388 postmenopausal women and 2,875 incident breast cancers were included. Overall, neither dietary nor water nitrate was associated with breast cancer risk. Among those with folate intake ≥400 μg/d, breast cancer risk was significantly increased in public water users with the highest nitrate quintile (HR=1.40, 95%CI=1.05–1.87) and private well users (HR=1.38, 95%CI=1.05–1.82) compared to public water users with the lowest nitrate quintile; in contrast, there was no association among those with lower folate intake. Our findings do not support a previous report of increased risk of breast cancer among individuals with high dietary nitrate but low folate intake. PMID:22642949

  18. 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

  19. Ultrafast Energy Transfer in Ultrathin Organic Donor/Acceptor Blend

    PubMed Central

    Kandada, Ajay Ram Srimath; Grancini, Giulia; Petrozza, Annamaria; Perissinotto, Stefano; Fazzi, Daniele; Raavi, Sai Santosh Kumar; Lanzani, Guglielmo

    2013-01-01

    It is common knowledge that poly(3-hexylthiophene) (P3HT)/[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) blend, a prototype system for bulk heterojunction (BHJ) solar cells, consists of a network of tens of nanometers-large donor-rich and acceptor-rich phases separated by extended finely intermixed border regions where PCBM diffuse into P3HT. Here we specifically address the photo-induced dynamics in a 10 nm thin P3HT/PCBM blend that consists of the intermixed region only. Using the multi-pass transient absorption technique (TrAMP) that enables us to perform ultra high sensitive measurements, we find that the primary process upon photoexcitation is ultrafast energy transfer from P3HT to PCBM. The expected charge separation due to hole transfer from PCBM to P3HT occurs in the 100 ps timescale. The derived picture is much different from the accepted view of ultra-fast electron transfer at the polymer/PCBM interface and provides new directions for the development of efficient devices. PMID:23797845

  20. 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.

  1. 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.

  2. 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

  3. Potassium acceptor doping of ZnO crystals

    NASA Astrophysics Data System (ADS)

    Parmar, Narendra S.; Corolewski, Caleb D.; McCluskey, Matthew D.; Lynn, K. G.

    2015-05-01

    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 × 1016 cm-3. IR measurements show a local vibrational mode (LVM) at 3226 cm-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-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.

  4. Ultrafast Energy Transfer in Ultrathin Organic Donor/Acceptor Blend

    NASA Astrophysics Data System (ADS)

    Kandada, Ajay Ram Srimath; Grancini, Giulia; Petrozza, Annamaria; Perissinotto, Stefano; Fazzi, Daniele; Raavi, Sai Santosh Kumar; Lanzani, Guglielmo

    2013-06-01

    It is common knowledge that poly(3-hexylthiophene) (P3HT)/[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) blend, a prototype system for bulk heterojunction (BHJ) solar cells, consists of a network of tens of nanometers-large donor-rich and acceptor-rich phases separated by extended finely intermixed border regions where PCBM diffuse into P3HT. Here we specifically address the photo-induced dynamics in a 10 nm thin P3HT/PCBM blend that consists of the intermixed region only. Using the multi-pass transient absorption technique (TrAMP) that enables us to perform ultra high sensitive measurements, we find that the primary process upon photoexcitation is ultrafast energy transfer from P3HT to PCBM. The expected charge separation due to hole transfer from PCBM to P3HT occurs in the 100 ps timescale. The derived picture is much different from the accepted view of ultra-fast electron transfer at the polymer/PCBM interface and provides new directions for the development of efficient devices.

  5. 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.

  6. 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

  7. 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 ...

  8. 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

  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. 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

  11. New organic donor-acceptor-π-acceptor sensitizers for efficient dye-sensitized solar cells and photocatalytic hydrogen evolution under visible-light irradiation.

    PubMed

    Li, Xing; Cui, Shicong; Wang, Dan; Zhou, Ying; Zhou, Hao; Hu, Yue; Liu, Jin-Gang; Long, Yitao; Wu, Wenjun; Hua, Jianli; Tian, He

    2014-10-01

    Two organic donor-acceptor-π-acceptor (D-A-π-A) sensitizers (AQ and AP), containing quinoxaline/pyrido[3,4-b]pyrazine as the auxiliary acceptor, have been. Through fine-tuning of the auxiliary acceptor, a higher designed and synthesized photoelectric conversion efficiency of 6.02% for the AQ-based dye-sensitized solar cells under standard global AM1.5 solar conditions was achieved. Also, it was found that AQ-Pt/TiO2 photocatalysts displayed a better rate of H2 evolution under visible-light irradiation (420 nm<λ<780 nm) because of the stability of the oxidized states and the lower rates of electron recombination. Importantly, sensitizers AQ and AP-Pt/TiO2 showed strong photocatalytic activity during continuous light soaking for 10 h with methanol as the sacrificial electron donor. Additionally, the processes of their intermolecular electron transfer were further investigated theoretically by using time-dependent DFT. The calculated results indicate that the auxiliary acceptor plays the role of an electron trap and results in broad spectral responses. PMID:25154958

  12. Diversity of sugar acceptor of glycosyltransferase 1 from Bacillus cereus and its application for glucoside synthesis.

    PubMed

    Chiu, Hsi-Ho; Shen, Mo-Yuan; Liu, Yuan-Ting; Fu, Yu-Lieh; Chiu, Yu-An; Chen, Ya-Huei; Huang, Chin-Ping; Li, Yaw-Kuen

    2016-05-01

    Glycosyltransferase 1 from Bacillus cereus (BcGT1) catalyzes the transfer of a glucosyl moiety from uridine diphosphate glucose (UDP-glucose) to various acceptors; it was expressed and characterized. The specificity of acceptors was found to be broad: more than 20 compounds classified into O-, S-, and N-linkage glucosides can be prepared with BcGT1 catalysis. Based on this work, we conclude that the corresponding acceptors of these compounds must possess the following features: (1) the acceptors must contain at least one aromatic or fused-aromatic or heteroaromatic ring; (2) the reactive hydroxyl or sulfhydryl or amino group can attach either on the aromatic ring or on its aliphatic side chain; and (3) the acceptors can be a primary, secondary, or even a tertiary amine. Four representative acceptors-fluorescein methyl ester, 17-β-estradiol, 7-mercapto-4-methylcoumarin, and 6-benzylaminopurine-were chosen as a candidate acceptor for O-, S-, and N-glucosidation, respectively. These enzymatic products were purified and the structures were confirmed with mass and NMR spectra. As all isolated glucosides are β-anomers, BcGT1 is confirmed to be an inverting enzyme. This study not only demonstrates the substrate promiscuity of BcGT1 but also showed the great application prospect of this enzyme in bioconversion of valuable bioactive molecules. PMID:26795959

  13. 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

  14. Anaerobic biodegradation of nonylphenol in river sediment under nitrate- or sulfate-reducing conditions and associated bacterial community.

    PubMed

    Wang, Zhao; Yang, Yuyin; Dai, Yu; Xie, Shuguang

    2015-04-01

    Nonylphenol (NP) is a commonly detected pollutant in aquatic ecosystem and can be harmful to aquatic organisms. Anaerobic degradation is of great importance for the clean-up of NP in sediment. However, information on anaerobic NP biodegradation in the environment is still very limited. The present study investigated the shift in bacterial community structure associated with NP degradation in river sediment microcosms under nitrate- or sulfate-reducing conditions. Nearly 80% of NP (100 mg kg(-1)) could be removed under these two anaerobic conditions after 90 or 110 days' incubation. Illumina MiSeq sequencing analysis indicated that Proteobacteria, Firmicutes, Bacteroidetes and Chloroflexi became the dominant phylum groups with NP biodegradation. The proportion of Gammaproteobacteria, Deltaproteobacteria and Choloroflexi showed a marked increase in nitrate-reducing microcosm, while Gammaproteobacteria and Firmicutes in sulfate-reducing microcosm. Moreover, sediment bacterial diversity changed with NP biodegradation, which was dependent on type of electron acceptor. PMID:25590825

  15. 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.

  16. Nitrate uptake, nitrate reductase distribution and their relation to proton release in five nodulated grain legumes.

    PubMed

    Fan, X H; Tang, C; Rengel, Z

    2002-09-01

    Nitrate uptake, nitrate reductase activity (NRA) and net proton release were compared in five grain legumes grown at 0.2 and 2 mM nitrate in nutrient solution. Nitrate treatments, imposed on 22-d-old, fully nodulated plants, lasted for 21 d. Increasing nitrate supply did not significantly influence the growth of any of the species during the treatment, but yellow lupin (Lupinus luteus) had a higher growth rate than the other species examined. At 0.2 mM nitrate supply, nitrate uptake rates ranged from 0.6 to 1.5 mg N g(-1) d(-1) in the order: yellow lupin > field pea (Pisum sativum) > chickpea (Cicer arietinum) > narrow-leafed lupin (L angustifolius) > white lupin (L albus). At 2 mM nitrate supply, nitrate uptake ranged from 1.7 to 8.2 mg N g(-1) d(-1) in the order: field pea > chickpea > white lupin > yellow lupin > narrow-leafed lupin. Nitrate reductase activity increased with increased nitrate supply, with the majority of NRA being present in shoots. Field pea and chickpea had much higher shoot NRA than the three lupin species. When 0.2 mM nitrate was supplied, narrow-leafed lupinreleased the most H+ per unit root biomass per day, followed by yellow lupin, white lupin, field pea and chickpea. At 2 mM nitrate, narrow-leafed lupin and yellow lupin showed net proton release, whereas the other species, especially field pea, showed net OH- release. Irrespective of legume species and nitrate supply, proton release was negatively correlated with nitrate uptake and NRA in shoots, but not with NRA in roots. PMID:12234143

  17. 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

  18. HEALTH EFFECTS OF NITRATES IN WATER

    EPA Science Inventory

    A multi faceted study of the health effects of nitrate in drinking water using epidemiological and toxicological techniques is reported. The results of the epidemiological studies indicate that infants consuming appreciable amounts of water high in nitrates in the form of powdere...

  19. 76 FR 46907 - Ammonium Nitrate Security Program

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-03

    ...This proposed rule would implement anti-terrorism measures to better secure the homeland. The Department of Homeland Security would regulate the sale and transfer of ammonium nitrate pursuant to section 563 of the Fiscal Year 2008 Department of Homeland Security Appropriations Act with the purpose of preventing the use of ammonium nitrate in an act of terrorism. This proposed rule seeks......

  20. 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.

  1. 76 FR 62311 - Ammonium Nitrate Security Program

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-07

    ... FR 64280 (advance notice of proposed rulemaking); 76 FR 46908 (notice of proposed rulemaking... Program Web site in mid-October at http://www.dhs.gov/ files/ ] programs/ammonium-nitrate-security-program...; ] DEPARTMENT OF HOMELAND SECURITY Office of the Secretary 6 CFR Part 31 RIN 1601-AA52 Ammonium Nitrate...

  2. 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. PMID:25976309

  3. 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...

  4. 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

  5. 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.

  6. Determination of Na acceptor level in Na+ ion-implanted ZnO single crystal

    NASA Astrophysics Data System (ADS)

    Wang, Zheng; Liu, Huibin; He, Haiping; Huang, Jingyun; Chen, Lingxiang; Ye, Zhizhen

    2015-03-01

    Ion implantation was used to dope Na acceptor into ZnO single crystals. With three mixed implantation energies, uniform depth distribution of Na ion in the surface region (~300 nm) of ZnO bulk crystals is achieved. Via post-implantation annealing, a donor-acceptor pair recombination band is identified in the low-temperature photoluminescence spectra, from which the energy level of Na-related acceptor in single crystalline ZnO is estimated to be 300 meV. A p-n junction based on this ZnO-Na layer shows rectifying characteristics, confirming the p-type conductivity.

  7. 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

  8. High performance weak donor-acceptor polymers in thin film transistors: effect of the acceptor on electronic properties, ambipolar conductivity, mobility, and thermal stability.

    PubMed

    Yuen, Jonathan D; Fan, Jian; Seifter, Jason; Lim, Bogyu; Hufschmid, Ryan; Heeger, Alan J; Wudl, Fred

    2011-12-28

    We have studied the electronic, physical, and transistor properties of a family of donor-acceptor polymers consisting of diketopyrrolopyrrole (DPP) coupled with different accepting companion units in order to determine the effects of donor-acceptor interaction. Using the electronically neutral benzene (B), the weakly accepting benzothiadiazole (BT), and the strongly accepting benzobisthiadiazole (BBT), the accepting strength of the companion unit was systematically modulated. All polymers exhibited excellent transistor performance, with mobilities above 0.1 cm(2)V(-1)s(-1), even exceeding 1 cm(2)V(-1)s(-1) for one of the BBT-containing polymers. We find that the BBT is the strongest acceptor, enabling the BBT-containing polymers to be strongly ambipolar. The BBT moiety also strengthens interchain interactions, which provides higher thermal stability and performance for transistors with BBT-containing polymers as the active layer. PMID:22043809

  9. Nitrate dynamics within a stream-lake network through time and space

    NASA Astrophysics Data System (ADS)

    Loken, L. C.; Crawford, J. T.; Childress, E. S.; Casson, N. J.; Stanley, E. H.

    2014-12-01

    Nitrate dynamics in streams are governed by biology, hydrology, and geomorphology, and the ability to parse these drivers apart has improved with the development of accurate high-frequency sensors. By combining a stationary Eulerian and a quasi-Lagrangian sensor platform, we investigated the timing of nitrate flushing and identified locations of elevated biogeochemical cycling along a stream-lake network in Northern Wisconsin, USA. Two years of continuous oxygen, carbon dioxide, and discharge measurements were used to compute gross primary production (GPP) and ecosystem respiration (ER) downstream of a wetland reach of Allequash Creek. Metabolic rates and flow patterns were compared with nitrate concentrations measured every 30 minutes using an optical sensor. Additionally, we floated a sensor array from the headwater spring ponds through a heterogeneous stream reach consisting of wetlands, beaver ponds, forested segments, and two lakes. Two distinct temporal patterns of stream nitrate concentrations were observed. During high flow events such as spring snowmelt and summer rain events, nitrate concentrations increased from ~5 μM (baseflow) to 12 μM, suggesting flushing from catchment sources. During baseflow conditions, nitrate followed a diel cycle with a 0.3-1.0 μM daytime draw down. Daily nitrate reduction was positively correlated with GPP calculated from oxygen and carbon dioxide records. Lastly, spatial analyses revealed lowest nitrate concentrations in the wetland reach, approximately 2-3 μM lower than the upstream spring ponds, and downstream lakes and forested reaches. This snapshot implies greater nitrate removal potential in the wetland reach likely driven by denitrification in organic rich sediments and macrophyte uptake in the open canopy stream segment. Taken together the temporal and spatial results show the dynamics of hydrology, geomorphology, and biology to influence nitrate delivery and variability in ecosystem processing through a stream

  10. 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

  11. 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.

  12. 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

  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. PMID:27340495

  14. Molecular Engineering of Pyrido[3,4-b]pyrazine-Based Donor-Acceptor-π-Acceptor Organic Sensitizers: Effect of Auxiliary Acceptor in Cobalt- and Iodine-Based Electrolytes.

    PubMed

    Liu, Bo; Giordano, Fabrizio; Pei, Kai; Decoppet, Jean-David; Zhu, Wei-Hong; Zakeeruddin, Shaik M; Grätzel, Michael

    2015-12-14

    Due to the ease of tuning its redox potential, the cobalt-based redox couple has been extensively applied for highly efficient dye-sensitized solar cells (DSSCs) with extraordinarily high photovoltages. However, a cobalt electrolyte needs particular structural changes in the organic dye components to obtain such high photovoltages. To achieve high device performance, specific requirements in the molecular tailoring of organic sensitizers still need to be met. Besides the need for large electron donors, studies of the auxiliary acceptor segment of donor-acceptor-π-acceptor (D-A-π-A) organic sensitizers are still rare in molecular optimization in the context of cobalt electrolytes. In this work, two novel organic D-A-π-A-type sensitizers (IQ13 and IQ17) have been developed and exploited in cobalt- and iodine-based redox electrolyte DSSCs, specifically to provide insight into the effect of π-bridge modification in different electrolytes. The investigation has been focused on the additional electron-withdrawing acceptor capability with grafted long alkoxy chains. Optoelectronic transient measurements have indicated that IQ17 containing a pyrido[3,4-b]pyrazine moiety bearing long alkoxyphenyl chains is more suitable for application in cobalt-based DSSCs. PMID:26548926

  15. 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

  16. 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

  17. Molecular Signals Controlling the Inhibition of Nodulation by Nitrate in Medicago truncatula.

    PubMed

    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

  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. 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

  20. Pseudo-constitutivity of nitrate-responsive genes in nitrate reductase mutants

    PubMed Central

    Schinko, Thorsten; Gallmetzer, Andreas; Amillis, Sotiris; Strauss, Joseph

    2013-01-01

    In fungi, transcriptional activation of genes involved in NO3- assimilation requires the presence of an inducer (nitrate or nitrite) and low intracellular concentrations of the pathway products ammonium or glutamine. In Aspergillus nidulans, the two transcription factors NirA and AreA act synergistically to mediate nitrate/nitrite induction and nitrogen metabolite derepression, respectively. In all studied fungi and in plants, mutants lacking nitrate reductase (NR) activity express nitrate-metabolizing enzymes constitutively without the addition of inducer molecules. Based on their work in A. nidulans, Cove and Pateman proposed an “autoregulation control” model for the synthesis of nitrate metabolizing enzymes in which the functional nitrate reductase molecule would act as co-repressor in the absence and as co-inducer in the presence of nitrate. However, NR mutants could simply show “pseudo-constitutivity” due to induction by nitrate which accumulates over time in NR-deficient strains. Here we examined this possibility using strains which lack flavohemoglobins (fhbs), and are thus unable to generate nitrate internally, in combination with nitrate transporter mutations (nrtA, nrtB) and a GFP-labeled NirA protein. Using different combinations of genotypes we demonstrate that nitrate transporters are functional also in NR null mutants and show that the constitutive phenotype of NR mutants is not due to nitrate accumulation from intracellular sources but depends on the activity of nitrate transporters. However, these transporters are not required for nitrate signaling because addition of external nitrate (10 mM) leads to standard induction of nitrate assimilatory genes in the nitrate transporter double mutants. We finally show that NR does not regulate NirA localization and activity, and thus the autoregulation model, in which NR would act as a co-repressor of NirA in the absence of nitrate, is unlikely to be correct. Results from this study instead suggest

  1. Enhanced Surface Photochemistry in Chloride-Nitrate Ion Aerosol Mixtures

    NASA Astrophysics Data System (ADS)

    Wingen, L. M.; Moskun, A. C.; Thomas, J. L.; Roeselova, M.; Tobias, D. J.; Finlayson-Pitts, B. J.

    2007-12-01

    Heterogeneous reactions of sea salt aerosol with various oxides of nitrogen often lead to replacement of chloride ion by nitrate ion. Photolysis of aqueous nitrate at wavelengths > 290 nm leads to the production of nitrogen dioxide, hydroxyl radicals and other oxidants. The photochemistry of aerosols containing NO3- and Cl-, however, has not been investigated. Aerosols containing mixtures of NaCl and NaNO3 were used as a model system for processed sea salt aerosol. Photolysis experiments (λmax = 306 nm) were performed in 55 L Teflon chambers that contained deliquesced aerosols and production of gas phase NO2 was measured as a function of time using chemiluminescence detection. Simple alkanes were added in some experiments to probe OH radical and Cl atom production. Molecular dynamics simulations were also carried out on mixed aqueous NaCl and NaNO3 slabs to help understand ion solvation in these mixed salt systems. The simulations showed that as the Cl- to NO3- ratio increases, nitrate ions are drawn toward the interface due to the large double layer of interfacial Cl- and subsurface Na+. The systems explored both experimentally and computationally included pure NaNO3 and mixtures of Cl- and NO3- in molar ratios of 1:9, 1:1, and 9:1. The photolysis experiments showed an enhanced yield of gas phase NO2 as the chloride to nitrate ratio increased. We attribute the observed enhanced NO2 yields to an increased interfacial concentration of under-coordinated nitrate ion as the ratio of Cl- to NO3- increases. The implications of these enhanced NO2 yields as sea salt aerosols become processed in the atmosphere will also be discussed.

  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. 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.

  4. Tracing the Atmospheric Source of Desert Nitrates Using Δ 17O

    NASA Astrophysics Data System (ADS)

    Michalski, G. M.; Holve, M.; Feldmeier, J.; Bao, H.; Reheis, M.; Bockheim, J. G.; Thiemens, M. H.

    2001-05-01

    Mineral, caliche, and soil nitrates are found throughout the worlds deserts, including the cold dry Wright Valley of Antarctica, the Atacama desert in Chile and the Mojave desert in the southwest United States. Several authors have suggested biologic sources of these nitrates while others have postulated atmospheric deposition. A recent study utilizing 18O indicated that 30%, and perhaps 100%, of nitrates found in the Atacama and Mojave were of atmospheric origin [1]. A more quantitative assessment of the source strength of atmospheric nitrates was impossible because of the high variability of δ 18 18O of atmospheric nitrates and uncertainties in conditions of biologic production. Mass independently fractionated (MIF) processes are defined and quantified by the equation Δ 17O = δ 17O - .52x δ 18O. MIF processes are associated with the photochemistry of trace gases in the atmosphere and have been found in O3, N2O, CO, and sulfate aerosols . A large MIF (Δ 17O ~ 28 ‰ ) in nitrate aerosols collected in polluted regions was recently reported [2]. Here we extend measurements of MIF in nitrate to the dry deposition of nitrate in less polluted areas (Mojave desert). In addition we trace the MIF signal as it accumulates in the regolith as nitrate salts and minerals and is mixed with biologically produced nitrate (nitrification). Also examined were the isotopic composition of soil nitrates from Antarctic dry valleys. Dust samples were collected as part of the NADP program and soils were collected throughout the Mojave and Death Valley regions of California. Isotope analysis was done in addition to soluble ion content (Cl, NO3, SO4). Dust samples collected by dry deposition samplers showed a large MIF > 20‰ approaching values measured in urban nitrate aerosol. Soils collected throughout the region showed large variations in Δ 17O from ~ 0 to 18 ‰ . The low Δ 17O values are nitrates dominated by biologic nitrification and higher values are nitrates derived by

  5. 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.

  6. 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)

  7. 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.

  8. 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...

  9. TIO2 ADVANCED PHOTO-OXIDATION TECHNOLOGY: EFFECT OF ELECTRON ACCEPTORS

    EPA Science Inventory

    The effects of electron acceptors (additives) such as hydrogen peroxide, ammonium persulphate, potassium bromate and potassium peroxymonosulphate (ozone) on the TiO2 photocatalytic degradation of various organic pollutants were examined at various conditions. he individual and th...

  10. Interface-induced heavy-hole/light-hole splitting of acceptors in silicon

    NASA Astrophysics Data System (ADS)

    Mol, J. A.; Salfi, J.; Rahman, R.; Hsueh, Y.; Miwa, J. A.; Klimeck, G.; Simmons, M. Y.; Rogge, S.

    2015-05-01

    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.

  11. Photoinduced electron tunneling between randomly dispersed donors and acceptors in frozen glasses and other rigid matrices.

    PubMed

    Wenger, Oliver S

    2013-07-14

    In fluid solution un-tethered donors and acceptors can diffuse freely, and consequently the donor-acceptor distance is usually not fixed on the timescale of an electron transfer event. When attempting to investigate the influence of driving-force changes or donor-acceptor distance variations on electron transfer rates this can be a problem. In rigid matrices diffusion is suppressed, and it becomes possible to investigate fixed-distance electron transfer. This method represents an attractive alternative to investigate rigid rod-like donor-bridge-acceptor molecules which have to be made in elaborate syntheses. This perspective focuses specifically on the distance dependence of photoinduced electron transfer which occurs via tunneling of charge carriers through rigid matrices over distances between 1 and 33 Å. Some key aspects of the theoretical models commonly used for analyzing kinetic data of electron tunneling through rigid matrices are recapitulated. New findings from this rather mature field of research are emphasized. PMID:23722299

  12. 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.

  13. 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. PMID:26878200

  14. Photoelectric covalent organic frameworks: converting open lattices into ordered donor-acceptor heterojunctions.

    PubMed

    Chen, Long; Furukawa, Ko; Gao, Jia; Nagai, Atsushi; Nakamura, Toshikazu; Dong, Yuping; Jiang, Donglin

    2014-07-16

    Ordered one-dimensional open channels represent the typical porous structure of two-dimensional covalent organic frameworks (COFs). Here we report a general synthetic strategy for converting these open lattice structures into ordered donor-acceptor heterojunctions. A three-component topological design scheme was explored to prepare electron-donating intermediate COFs, which upon click reaction were transformed to photoelectric COFs with segregated donor-acceptor alignments, whereas electron-accepting buckyballs were spatially confined within the nanochannels via covalent anchoring on the channel walls. The donor-acceptor heterojunctions trigger photoinduced electron transfer and allow charge separation with radical species delocalized in the π-arrays, whereas the charge separation efficiency was dependent on the buckyball content. This new donor-acceptor strategy explores both skeletons and pores of COFs for charge separation and photoenergy conversion. PMID:24963896

  15. Microbial degradation of phenols and aromatic hydrocarbons in creosote-contaminated groundwater under nitrate-reducing conditions

    NASA Astrophysics Data System (ADS)

    Flyvbjerg, John; Arvin, Erik; Jensen, Bjørn K.; Olsen, Susan K.

    1993-02-01

    Batch experiments were carried out to investigate the biodegradation of phenols and aromatic hydrocarbons under anaerobic, nitrate-reducing conditions in groundwater from a creosote-contaminated site at Fredensborg, Denmark. The bacteria in the creosote-contaminated groundwater degraded a mixture of toluene, phenol, the cresols ( o-, m- and p-cresol) and the dimethylphenols 2,4-DMP and 3,4-DMP at both 10° and 20°C. Benzene, the xylenes, napthalene, 2,3-DMP, 2,5-DMP, 2,6-DMP and 3,5-DMP were resistant to biodegradation during 7-12 months of incubation. It was demonstrated that the degradation of toluene, 2,4-DMP, 3,4-DMP and p-cresol depended on nitrate or nitrite as electron acceptors. 40-80% of the nitrate consumed during degradation of the aromatic compounds was recovered as nitrite, and the consumption of nitrate was accompanied by a production of ATP. Stoichiometric calculations indicated that in addition to the phenols are toluene other carbon sources present in the groundwater contributed to the consumption of nitrate. If the groundwater was incubated under anaerobic conditions without nitrate, sulphate-reducing conditions evolved after ˜ 1 month at 20°C and ˜2 months at 10°C. In the sulphate-reducing batches disappearance of toluene, phenol, o-cresol and o-cresol was observed, whereas no removal of benzene, the xylenes, naphthalane, 2,3-DMP, 2,4-DMP, 2,5-DMP and 3,5-DMP was detected during 7 months of incubation.

  16. 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. PMID:27311060

  17. 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.

  18. 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

  19. 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

  20. 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

  1. 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.

  2. Molecular helices as electron acceptors in high-performance bulk heterojunction solar cells

    DOE PAGESBeta

    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

  3. Interface-split Kramers doublets for acceptor-based qubits in silicon

    NASA Astrophysics Data System (ADS)

    Mol, Jan; Salfi, Joseph; Rahman, Rajib; Rogge, Sven

    2013-03-01

    Single dopants in silicon form a particular attractive platform for hosting spin quantum bits (qubits). The effective spin-3/2 states of acceptor-bound holes in silicon can be used to store bits of quantum information for several μs. Strong coupling of spin and momentum in the silicon valence band allows for rapid electrical manipulation of the hole spin. Acceptors in silicon have a four-fold degenerate ground-state, reflecting character of the top of the valence band. Symmetry breaking, by an electric field, strain or confinement, lifts this degeneracy, resulting in two Kramers doublets. The states within these isolated Kramers doublets are protected against decoherence by time reversal symmetry and form the working levels of a hole spin qubit. Here we investigate the effect of the presence of an interface on the ground-state energy splitting of individual sub-surface acceptors, as a function of dopant depth, by means of low temperature scanning tunneling spectroscopy. The depth of individual acceptors is determined by probing the Coulomb potential of the ionized acceptor nuclei. Resonant tunneling through the localized acceptor states provides a direct measure of the excited state spectrum of single dopants.

  4. 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

  5. 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.

  6. 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

  7. 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

  8. 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.

  9. 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

  10. 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

  11. 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

  12. 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.

  13. Assessing Contamination Potential of Nitrate-N in Groundwater of Lanyang Plain

    NASA Astrophysics Data System (ADS)

    Liang, Ching-Ping; Tu, Yu-Lin; Lin, Chien-Wen; Jang, Cheng-Shin

    2013-04-01

    Nitrate-N pollution is often relevant to agricultural activities such as the fertilization of crops. Significant increases in the nitrate-N pollution of groundwater are found in natural recharging zones of Taiwan. The increasing nitrate-N contamination seriously threatens public drinking water supply and human health. Constructing a correct map of aquifer contamination potential is an effective and feasible way to protect groundwater for quality assessment and management. Therefore, in this study, we use DRASTIC model with the help of geographic information system (GIS) to assess and predict the contamination potential of nitrate-N in the aquifer of Lanyang Plain, Taiwan. Seven factors of hydrogeology and hydrology, which includes seven parameters - Depth to groundwater, net Recharge, Aquifer media, Soil media, Topography, Impact of vadose zone, and hydraulic Conductivity, are considered to carry out this assessment. The validity of the presented model is established by comparing the results with the measured nitrate concentration in wells within the study area. Adjusting factor weightings via the discriminant analysis is performed to improve the assessment and prediction. The analyzed results can provide residents with suggestive strategies against nitrate-N pollution in agricultural regions and government administrators with explicit information of Nitrate-N pollution extents when plans of water resources are considered.

  14. A simple model of stream nitrate concentrations in forested and deforested catchments in Mid-Wales

    NASA Astrophysics Data System (ADS)

    Sloan, William T.; Jenkins, Alan; Eatherall, Andrew

    1994-06-01

    A model is developed specifically for simulating the nitrate concentrations in a stream at approximately weekly intervals in an upland forested and a moorland catchment. It is constructed on the basis of observed nitrate concentrations in rain water and in two streams, the Hafren and the Hore, at Plynlimon, Mid-Wales, where long data records exist. The Hore catchment has recently undergone extensive deforestation. A simple regression model relating temperature to stream nitrate concentrations was capable of simulating the seasonal fluctuations in nitrate concentration observed in the Hafren. However, this ignores the influx of nitrate through wet deposition and is incapable of simulating land-use change. The regression model was developed into a simple dynamic model which includes a deposition term and a biomass indicator. The extended Kalman filter algorithm was used to estimate the optimum values of the parameters and to assess the model structure. The model was applied to both catchments, and the fit between observed and simulated nitrate concentrations at the Hafren was good. At the Hore, the model was able to capture the major changes in nitrate concentration through the deforestation and replanting phases although detailed short-term dynamics were not well represented. Finally, the model is related, speculatively, to processes which are known to occur in most catchments. This simple model is intended as a step towards the development of similar but more comprehensive catchment models of stream nitrogen dynamics.

  15. 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

  16. 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.

  17. Central action of dendrotoxin: selective reduction of a transient K conductance in hippocampus and binding to localized acceptors

    SciTech Connect

    Halliwell, J.V.; Othman, I.B.; Pelchen-Matthews, A.; Dolly, J.O.

    1986-01-01

    Dendrotoxin, a small single-chain protein from the venom of Dendroaspis angusticeps, is highly toxic following intracerebroventricular injection into rats. Voltage-clamp analysis of CA/sub 1/ neurons in hippocampal slices, treated with tetrodotoxin, revealed that nanomolar concentrations of dendrotoxin reduce selectively a transient, voltage-dependent K conductance. Epileptiform activity known to be induced by dendrotoxin can be attributed to such an action. Membrane currents not affected directly by the toxin include (i) Ca-activated K conductance; (ii) noninactivating voltage-dependent K conductance; (iii) inactivating the noninactivating Ca conductances; (iv) persistent inward (anomalous) rectifier current. Persistence of the effects of the toxin when Cd was included to suppress spontaneous transmitter release indicates a direct action on the neuronal membrane. Using biologically active, /sup 125/I-labeled dendrotoxin, protein acceptor sites of high affinity were detected on cerebrocortical synapotosomal membranes and sections of rat brain. In hippocampus, toxin binding was shown autoradiographically to reside in synapse-rich and white matter regions, with lower levels in cell body layers. This acceptor is implicated in the action of toxin because its affinities for dendrotoxin congeners are proportional to their central neurotoxicities and potencies in reducing the transient, voltage-dependent K conductance.

  18. 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.

  19. 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.

  20. 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.

  1. Part I. The fire properties of polymer clay nanocomposites. Part II. Thermal rearrangement of donor-acceptor substituted cyclopropanes

    NASA Astrophysics Data System (ADS)

    Su, Shengpei

    2003-08-01

    This work consists of two parts. Part I, which includes chapter 1--5, is focused on the fire properties of nanocomposites while part II deals with thermal rearrangement of the donor-acceptor cyclopropanes. In chapter 1 of the first part an introduction to the preparation of polymer-clay nanocomposites is provided along with their application to fire retardancy. Chapter 2 details the exfoliation process of clay using in situ polymerization; the results show that the exfoliation process is related to the monomer, the modified clay and the initiator. Chapter 3 concentrates on the preparation of nanocomposites by melt blending with polymer modified clays. Three different polymer modified clays (PS, PMMA and PBD modified clay) and six polymers (PS, HIPS, ABS, PMMA, PP and PE) are reported. The morphology, thermal stability, fire behavior and mechanical properties were studied. This research shows that the exfoliation process by melt blending is controlled by the types of interactions between the various polymers, the silicate surfaces and the organic modifier. The combination of polar polymer matrix and non-polar polymer modified clay with large d-spacing will be more likely to give the exfoliated nanocomposites. TGA-FTIR results show that the mechanism of degradation of polystyrene is changed in the presence of the clay. In order to better understand the effects of the organic modifier, PS surfactants with five different pendant groups, dimethylhexadecylamine, trimethylamine, dimethylbenzylamine, 1,2-dimethylimidizole and triphenylphosphine, were used and the results show that the degradation depends upon the pendant. Chapter 5 provides some suggestions for future work based upon this work. The synthesis of several new and previously reported donor-acceptor cyclopropanes is reported in part II. The study shows that the facility of the donor-acceptor cyclopropane ring cleavage is strongly influenced by the kind of activating substitutes on the cyclopropane ring, and the

  2. Electrophilic and free radical nitration of benzene and toluene with various nitrating agents*

    PubMed Central

    Olah, George A.; Lin, Henry C.; Olah, Judith A.; Narang, Subhash C.

    1978-01-01

    Electrophilic nitration of toluene and benzene was studied under various conditions with several nitrating systems. It was found that high orthopara regioselectivity is prevalent in all reactions and is independent of the reactivity of the nitrating agent. The methyl group of toluene is predominantly ortho-para directing under all reaction conditions. Steric factors are considered to be important but not the sole reason for the variation in the ortho/para ratio. The results reinforce our earlier views that, in electrophilic aromatic nitrations with reactive nitrating agents, substrate and positional selectivities are determined in two separate steps. The first step involves a π-aromatic-NO2+ ion complex or encounter pair, whereas the subsequent step is of arenium ion nature (separate for the ortho, meta, and para positions). The former determines substrate selectivity, whereas the latter determines regioselectivity. Thermal free radical nitration of benzene and toluene with tetranitromethane in sharp contrast gave nearly statistical product distributions. PMID:16592503

  3. 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

  4. Protein tyrosine nitration of mitochondrial carbamoyl phosphate synthetase 1 and its functional consequences.

    PubMed

    Takakusa, Hideo; Mohar, Isaac; Kavanagh, Terrance J; Kelly, Edward J; Kaspera, Rüdiger; Nelson, Sidney D

    2012-03-30

    Mitochondria are the primary locus for the generation of reactive nitrogen species including peroxynitrite and subsequent protein tyrosine nitration. Protein tyrosine nitration may have important functional and biological consequences such as alteration of enzyme catalytic activity. In the present study, mouse liver mitochondria were incubated with peroxynitrite, and the mitochondrial proteins were separated by 1D and 2D gel electrophoresis. Nitrotyrosinylated proteins were detected with an anti-nitrotyrosine antibody. One of the major proteins nitrated by peroxynitrite was carbamoyl phosphate synthetase 1 (CPS1) as identified by LC-MS protein analysis and Western blotting. The band intensity of nitration normalized to CPS1 was increased in a peroxynitrite concentration-dependent manner. In addition, CPS1 activity was decreased by treatment with peroxynitrite in a peroxynitrite concentration- and time-dependent manner. The decreased CPS1 activity was not recovered by treatment with reduced glutathione, suggesting that the decrease of the CPS1 activity is due to tyrosine nitration rather than cysteine oxidation. LC-MS analysis of in-gel digested samples, and a Popitam-based modification search located 5 out of 36 tyrosine residues in CPS1 that were nitrated. Taken together with previous findings regarding CPS1 structure and function, homology modeling of mouse CPS1 suggested that nitration at Y1450 in an α-helix of allosteric domain prevents activation of CPS1 by its activator, N-acetyl-l-glutamate. In conclusion, this study demonstrated the tyrosine nitration of CPS1 by peroxynitrite and its functional consequence. Since CPS1 is responsible for ammonia removal in the urea cycle, nitration of CPS1 with attenuated function might be involved in some diseases and drug-induced toxicities associated with mitochondrial dysfunction. PMID:22402285

  5. Tyrosine Nitration within the Proline-Rich Region of Tau in Alzheimer's Disease

    PubMed Central

    Reyes, Juan F.; Fu, Yifan; Vana, Laurel; Kanaan, Nicholas M.; Binder, Lester I.

    2011-01-01

    A substantial body of evidence suggests that nitrative injury contributes to neurodegeneration in Alzheimer's disease (AD) and other neurodegenerative disorders. Previously, we showed in vitro that within the tau protein the N-terminal tyrosine residues (Y18 and Y29) are more susceptible to nitrative modifications than other tyrosine sites (Y197 and Y394). Using site-specific antibodies to nitrated tau at Y18 and Y29, we identified tau nitrated in both glial (Y18) and neuronal (Y29) tau pathologies. In this study, we report the characterization of two novel monoclonal antibodies, Tau-nY197 and Tau-nY394, recognizing tau nitrated at Y197 and Y394, respectively. By Western blot analysis, Tau-nY197 labeled soluble tau and insoluble paired helical filament proteins (PHF-tau) nitrated at Y197 from control and AD brain samples. Tau-nY394 failed to label soluble tau isolated from control or severe AD samples, but labeled insoluble PHF-tau to a limited extent. Immunohistochemical analysis using Tau-nY197 revealed the hallmark tau pathology associated with AD; Tau-nY394 did not detect any pathological lesions characteristic of the disorder. These data suggest that a subset of the hallmark pathological inclusions of AD contain tau nitrated at Y197. However, nitration at Y197 was also identified in soluble tau from all control samples, including those at Braak stage 0, suggesting that nitration at this site in the proline-rich region of tau may have normal biological functions in the human brain. PMID:21514440

  6. 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

  7. Functional Roles of Protein Nitration in Acute and Chronic Liver Diseases

    PubMed Central

    Abdelmegeed, Mohamed A.; Song, Byoung-Joon

    2014-01-01

    Nitric oxide, when combined with superoxide, produces peroxynitrite, which is known to be an important mediator for a number of diseases including various liver diseases. Peroxynitrite can modify tyrosine residue(s) of many proteins resulting in protein nitration, which may alter structure and function of each target protein. Various proteomics and immunological methods including mass spectrometry combined with both high pressure liquid chromatography and 2D PAGE have been employed to identify and characterize nitrated proteins from pathological tissue samples to determine their roles. However, these methods contain a few technical problems such as low efficiencies with the detection of a limited number of nitrated proteins and labor intensiveness. Therefore, a systematic approach to efficiently identify nitrated proteins and characterize their functional roles is likely to shed new insights into understanding of the mechanisms of hepatic disease pathophysiology and subsequent development of new therapeutics. The aims of this review are to briefly describe the mechanisms of hepatic diseases. In addition, we specifically describe a systematic approach to efficiently identify nitrated proteins to study their causal roles or functional consequences in promoting acute and chronic liver diseases including alcoholic and nonalcoholic fatty liver diseases. We finally discuss translational research applications by analyzing nitrated proteins in evaluating the efficacies of potentially beneficial agents to prevent or treat various diseases in the liver and other tissues. PMID:24876909

  8. Does thiosemicarbazide lead nitrate crystal exist?

    NASA Astrophysics Data System (ADS)

    Fernandes, Royle; Srinivasan, Bikshandarkoil R.

    2016-06-01

    The authors of a recent paper (Optik 125 (2014) 2022-2025) claim to have grown a so called thiosemicarbazide lead nitrate (TSLN) crystal by the slow evaporation method. In this comment we prove that TSLN is actually thiosemicarbazide.

  9. 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)

  10. The Measurement of Hot-Spots in Granulated Ammonium Nitrate

    NASA Astrophysics Data System (ADS)

    Proud, W. G.

    2002-07-01

    Ammonium Nitrate (AN) is one of the components of the most widely used explosive in the world namely, ammonium nitrate: fuel oil mixtures (ANFO). By itself, it is an oxygen positive explosive with a large critical diameter. Hot-spots are produced in explosives by various means including gas space collapse, localised shear or friction. If these hot-spots reach critical conditions of size, temperature and duration reaction can grow. This deflagration stage may eventually transition to detonation. This paper describes high-speed image-intensified photography study in which the number and growth of hot spots in granular AN are monitored for a range of different impact pressures. The results can be used in detonation codes to provide a more accurate and realistic description of the initiation process.

  11. The Measurement of Hot-spots in Granulated Ammonium Nitrate

    NASA Astrophysics Data System (ADS)

    Proud, William; Field, John

    2001-06-01

    Ammonium Nitrate (AN) is one of the components of the most widely used explosive in the world ammonium nitrate: fuel oil mixtures (ANFO). By itself, it is an oxygen negative explosive with a large critical diameter. Hot-spots are produced in explosives by various means including gas space collapse, localised shear or friction. If these hot-spots reach critical conditions of size, temperature and duration size reaction can grow. This deflagration stage may eventually transition to detonation. This paper describes a system and presents results where high-speed image intensified photography is used to monitor the number and growth of hot spots in granular AN under a range of different impact pressures. The results can be used in detonation codes to provide a more accurate and realistic description of the initiation process.

  12. Hydroxylamine nitrate self-catalytic kinetics study with adiabatic calorimetry.

    PubMed

    Liu, Lijun; Wei, Chunyang; Guo, Yuyan; Rogers, William J; Sam Mannan, M

    2009-03-15

    Hydroxylamine nitrate (HAN) is an important member of the hydroxylamine compound family with applications that include equipment decontamination in the nuclear industry and aqueous or solid propellants. Due to its instability and autocatalytic behavior, HAN has been involved in several incidents at the Hanford and Savannah River Site (SRS) [Technical Report on Hydroxylamine Nitrate, US Department of Energy, 1998]. Much research has been conducted on HAN in different areas, such as combustion mechanism, decomposition mechanism, and runaway behavior. However, the autocatalytic decomposition behavior of HAN at runaway stage has not been fully addressed due to its highly exothermic and rapid decomposition behavior. This work is focused on extracting HAN autocatalytic kinetics and analyzing HAN critical behavior from adiabatic calorimetry measurements. A lumped autocatalytic kinetic model for HAN and associated model parameters are determined. Also the storage and handling critical conditions of diluted HAN solution without metal presence are quantified. PMID:18639378

  13. Engineering Options Assessment Report: Nitrate Salt Waste Stream Processing

    SciTech Connect

    Anast, Kurt Roy

    2015-11-18

    This report examines and assesses the available systems and facilities considered for carrying out remediation activities on remediated nitrate salt (RNS) and unremediated nitrate salt (UNS) waste containers at Los Alamos National Laboratory (LANL). The assessment includes a review of the waste streams consisting of 60 RNS, 29 aboveground UNS, and 79 candidate belowground UNS containers that may need remediation. The waste stream characteristics were examined along with the proposed treatment options identified in the Options Assessment Report . Two primary approaches were identified in the five candidate treatment options discussed in the Options Assessment Report: zeolite blending and cementation. Systems that could be used at LANL were examined for housing processing operations to remediate the RNS and UNS containers and for their viability to provide repackaging support for remaining LANL legacy waste.

  14. Engineering Options Assessment Report. Nitrate Salt Waste Stream Processing

    SciTech Connect

    Anast, Kurt Roy

    2015-11-13

    This report examines and assesses the available systems and facilities considered for carrying out remediation activities on remediated nitrate salt (RNS) and unremediated nitrate salt (UNS) waste containers at Los Alamos National Laboratory (LANL). The assessment includes a review of the waste streams consisting of 60 RNS, 29 above-ground UNS, and 79 candidate below-ground UNS containers that may need remediation. The waste stream characteristics were examined along with the proposed treatment options identified in the Options Assessment Report . Two primary approaches were identified in the five candidate treatment options discussed in the Options Assessment Report: zeolite blending and cementation. Systems that could be used at LANL were examined for housing processing operations to remediate the RNS and UNS containers and for their viability to provide repackaging support for remaining LANL legacy waste.

  15. Using solvent extraction to process nitrate anion exchange column effluents

    SciTech Connect

    Yarbro, S.L.

    1987-10-01

    Octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO), a new organophosphorous extractant, and a new centrifugal mixer-settler both recently developed at Argonne were evaluated for their potential use in the recovery of actinides from nitrate anion exchange column effluents. The performance of the extractant was evaluated by measuring the extraction coefficient values as a function of acid and salt concentration. Additional performance parameters include extraction coefficient behavior as a function of the total metal concentration in the organic phase, and comparison of different stripping and organic scrubbing techniques. A simulated effluent stream was used to evaluate the performance of the centrifugal mixer-settlers by comparing experimental and calculated interstage concentration profiles. Both the CMPO extractant and the centrifugal mixer-settlers have potential for processing nitrate column effluents, particularly if the stripping behavior can be improved. Details of the proposed process are presented in the flowsheet and contactor design analyses.

  16. The UK Nitrate Time Bomb (Invited)

    NASA Astrophysics Data System (ADS)

    Ward, R.; Wang, L.; Stuart, M.; Bloomfield, J.; Gooddy, D.; Lewis, M.; McKenzie, A.

    2013-12-01

    The developed world has benefitted enormously from the intensification of agriculture and the increased availability and use of synthetic fertilizers during the last century. However there has also been unintended adverse impact on the natural environment (water and ecosystems) with nitrate the most significant cause of water pollution and ecosystem damage . Many countries have introduced controls on nitrate, e.g. the European Union's Water Framework and Nitrate Directives, but despite this are continuing to see a serious decline in water quality. The purpose of our research is to investigate and quantify the importance of the unsaturated (vadose) zone pathway and groundwater in contributing to the decline. Understanding nutrient behaviour in the sub-surface environment and, in particular, the time lag between action and improvement is critical to effective management and remediation of nutrient pollution. A readily-transferable process-based model has been used to predict temporal loading of nitrate at the water table across the UK. A time-varying nitrate input function has been developed based on nitrate usage since 1925. Depth to the water table has been calculated from groundwater levels based on regional-scale observations in-filled by interpolated river base levels and vertical unsaturated zone velocities estimated from hydrogeological properties and mapping. The model has been validated using the results of more than 300 unsaturated zone nitrate profiles. Results show that for about 60% of the Chalk - the principal aquifer in the UK - peak nitrate input has yet to reach the water table and concentrations will continue to rise over the next 60 years. The implications are hugely significant especially where environmental objectives must be achieved in much shorter timescales. Current environmental and regulatory management strategies rarely take lag times into account and as a result will be poorly informed, leading to inappropriate controls and conflicts

  17. Synthesis of a new energetic nitrate ester

    SciTech Connect

    Chavez, David E

    2008-01-01

    Nitrate esters have been known as useful energetic materials since the discovery of nitroglycerin by Ascanio Sobrero in 1846. The development of methods to increase the safety and utility of nitroglycerin by Alfred Nobel led to the revolutionary improvement in the utility of nitroglycerin in explosive applications in the form of dynamite. Since then, many nitrate esters have been prepared and incorporated into military applications such as double-based propellants, detonators and as energetic plasticizers. Nitrate esters have also been shown to have vasodilatory effects in humans and thus have been studied and used for treatments of ailments such as angina. The mechanism of the biological response towards nitrate esters has been elucidated recently. Interestingly, many of the nitrate esters used for military purposes are liquids (ethylene glycol dinitrate, propylene glycol dinitrate, etc). Pentaerythritol tetranitrate (PETN) is one of the only solid nitrate esters, besides nitrocellulose, that is used in any application. Unfortunately, PETN melting point is above 100 {sup o}C, and thus must be pressed as a solid for detonator applications. A more practical material would be a melt-castable explosive, for potential simplification of manufacturing processes. Herein we describe the synthesis of a new energetic nitrate ester (1) that is a solid at ambient temperatures, has a melting point of 85-86 {sup o}C and has the highest density of any known nitrate ester composed only of carbon, hydrogen, nitrogen and oxygen. We also describe the chemical, thermal and sensitivity properties of 1 as well as some preliminary explosive performance data.

  18. Nitrate distribution in Mojave Desert soils

    SciTech Connect

    Hunter, R.B.; Romney, E.M.; Wallace, A.

    1982-07-01

    Extensive sampling shows high variability in nitrate concentration within profiles of Mojave Desert soils. This high variability greatly complicates studies of desert soil N and its ecological role. Patterns in nitrate distribution suggest effects of litter decomposition under shrubs, surface leaching in bare areas, and plant uptake in the root zone. Two mechanisms proposed to explain high concentrations found at seemingly random depths are concentration at drying fronts and distribution along water potential gradients.

  19. Preformed Nitrate in the Glacial North Atlantic

    NASA Astrophysics Data System (ADS)

    Homola, K.; Spivack, A. J.; D'Hondt, S.; Estes, E. R.; Insua, T. L.; McKinley, C. C.; Murray, R. W.; Pockalny, R. A.; Robinson, R. S.; Sauvage, J.

    2015-12-01

    Atmospheric CO2 abundances are highly correlated with global temperature variations over the past 800,000 years. Consequently, understanding the feedbacks between climate and CO2 is important for predictions of future climate. Leading hypotheses to explain this feedback invoke changes in ocean biology, circulation, chemistry, and/or gas exchange rates to trap CO2 in the deep ocean, thereby reducing the greenhouse effect of CO2 in the atmosphere. To test these hypotheses, we use sediment pore water profiles of dissolved nitrate and oxygen to reconstruct paleo-preformed nitrate concentrations at two deep-water sites in the western North Atlantic (23°N 57°W, 5557 m water depth; 30°N 58°W, 5367 m water depth). Preformed nitrate increases down-core to 22.7 μM (25.6 m core depth) at the northern site, and to 28.5 μM (27.8 m core depth) at the southern site. The large preformed nitrate gradient between these sites reveals a paleo-boundary between a southern water source high in preformed nitrate and a northern water source with lower concentrations, similar to today's ocean. However, the boundary between these water masses occurs north of where their modern counterparts meet, indicating that Antarctic Bottom Water (AABW) extended farther north during the Last Glacial Maximum (LGM). In addition, the southern source had a higher preformed nitrate concentration than today's AABW (25 μM), contradicting hypotheses that nutrient utilization was more efficient in the Southern Ocean deep-water formation regions during the LGM. Comparison to our previous Pacific data reveals that the average preformed nitrate concentration of the deep ocean was slightly higher during the LGM than today. This result implies that the CO2-climate feedback was not principally due to more efficient nitrate utilization.

  20. Is beetroot juice more effective than sodium nitrate? The effects of equimolar nitrate dosages of nitrate-rich beetroot juice and sodium nitrate on oxygen consumption during exercise.

    PubMed

    Flueck, Joelle Leonie; Bogdanova, Anna; Mettler, Samuel; Perret, Claudio

    2016-04-01

    Dietary nitrate has been reported to lower oxygen consumption in moderate- and severe-intensity exercise. To date, it is unproven that sodium nitrate (NaNO3(-); NIT) and nitrate-rich beetroot juice (BR) have the same effects on oxygen consumption, blood pressure, and plasma nitrate and nitrite concentrations or not. The aim of this study was to compare the effects of different dosages of NIT and BR on oxygen consumption in male athletes. Twelve healthy, well-trained men (median [minimum; maximum]; peak oxygen consumption: 59.4 mL·min(-1)·kg(-1) [40.5; 67.0]) performed 7 trials on different days, ingesting different nitrate dosages and placebo (PLC). Dosages were 3, 6, and 12 mmol nitrate as concentrated BR or NIT dissolved in plain water. Plasma nitrate and nitrite concentrations were measured before, 3 h after ingestion, and postexercise. Participants cycled for 5 min at moderate intensity and further 8 min at severe intensity. End-exercise oxygen consumption at moderate intensity was not significantly different between the 7 trials (p = 0.08). At severe-intensity exercise, end-exercise oxygen consumption was ~4% lower in the 6-mmol BR trial compared with the 6-mmol NIT (p = 0.003) trial as well as compared with PLC (p = 0.010). Plasma nitrite and nitrate concentrations were significantly increased after the ingestion of BR and NIT with the highest concentrations in the 12-mmol trials. Plasma nitrite concentration between NIT and BR did not significantly differ in the 6-mmol (p = 0.27) and in the 12-mmol (p = 0.75) trials. In conclusion, BR might reduce oxygen consumption to a greater extent compared with NIT. PMID:26988767