Sample records for n2o isotopomer ratios

  1. Characterization and production and consumption processes of N2O emitted from temperate agricultural soils determined via isotopomer ratio analysis

    NASA Astrophysics Data System (ADS)

    Toyoda, Sakae; Yano, Midori; Nishimura, Sei-Ichi; Akiyama, Hiroko; Hayakawa, Atsushi; Koba, Keisuke; Sudo, Shigeto; Yagi, Kazuyuki; Makabe, Akiko; Tobari, Yoshifumi; Ogawa, Nanako O.; Ohkouchi, Naohiko; Yamada, Keita; Yoshida, Naohiro

    2011-06-01

    Isotopomer ratios of N2O (bulk nitrogen and oxygen isotope ratios, δ15Nbulk and δ18O, and intramolecular 15N site preference, SP) are useful parameters that characterize sources of this greenhouse gas and also provide insight into production and consumption mechanisms. We measured isotopomer ratios of N2O emitted from typical Japanese agricultural soils (Fluvisols and Andisols) planted with rice, wheat, soybean, and vegetables, and treated with synthetic (urea or ammonium) and organic (poultry manure) fertilizers. The results were analyzed using a previously reported isotopomeric N2O signature produced by nitrifying/denitrifying bacteria and a characteristic relationship between δ15Nbulk and SP during N2O reduction by denitrifying bacteria. Relative contributions from nitrification (hydroxylamine oxidation) and denitrification (nitrite reduction) to gross N2O production deduced from the analysis depended on soil type and fertilizer. The contribution from nitrification was relatively high (40%-70%) in Andisols amended with synthetic ammonium fertilizer, while denitrification was dominant (50%-90%) in the same soils amended with poultry manure during the period when N2O production occurred in the surface layer. This information on production processes is in accordance with that obtained from flux/concentration analysis of N2O and soil inorganic nitrogen. However, isotopomer analysis further revealed that partial reduction of N2O was pronounced in high-bulk density, alluvial soil (Fluvisol) compared to low-bulk density, volcanic ash soil (Andisol), and that the observed difference in N2O flux between normal and pelleted manure could have resulted from a similar mechanism with different rates of gross production and gross consumption. The isotopomeric analysis is based on data from pure culture bacteria and would be improved by further studies on in situ biological processes in soils including those by fungi. When flux/concentration-weighted average isotopomer

  2. Development of atmospheric N2O isotopomers model based on a chemistry-coupled atmospheric general circulation model

    NASA Astrophysics Data System (ADS)

    Ishijima, K.; Toyoda, S.; Sudo, K.; Yoshikawa, C.; Nanbu, S.; Aoki, S.; Nakazawa, T.; Yoshida, N.

    2009-12-01

    almost underestimated, relative to the balloon observations, although the concentration is well simulated. The tendency has been somewhat improved by incorporating another photolysis scheme with slightly higher wave-length resolution into the model. From another point of view, these facts indicate that N2O isotopomers can be used for validation of the stratospheric photochemical calculations in model, because of very high sensitivity of the isotopomer ratio values to some settings such as the wave-length resolution in the photochemical scheme.Therefore, N2O isotopomers modeling seems to be not only useful for validation of the fractionation coefficients and of isotopic characterization of sources, but also have the possibility to be an index especially for precision in the stratospheric photolysis in model.

  3. Isotopomer analysis of production and consumption mechanisms of N2O and CH4 in an advanced wastewater treatment system.

    PubMed

    Toyoda, Sakae; Suzuki, Yuuri; Hattori, Shohei; Yamada, Keita; Fujii, Ayako; Yoshida, Naohiro; Kouno, Rina; Murayama, Kouki; Shiomi, Hiroshi

    2011-02-01

    Wastewater treatment processes are believed to be anthropogenic sources of nitrous oxide (N(2)O) and methane (CH(4)). However, few studies have examined the mechanisms and controlling factors in production of these greenhouse gases in complex bacterial systems. To elucidate production and consumption mechanisms of N(2)O and CH(4) in microbial consortia during wastewater treatment and to characterize human waste sources, we measured their concentrations and isotopomer ratios (elemental isotope ratios and site-specific N isotope ratios in asymmetric molecules of NNO) in water and gas samples collected by an advanced treatment system in Tokyo. Although the estimated emissions of N(2)O and CH(4) from the system were found to be lower than those from the typical treatment systems reported before, water in biological reaction tanks was supersaturated with both gases. The concentration of N(2)O, produced mainly by nitrifier-denitrification as indicated by isotopomer ratios, was highest in the oxic tank (ca. 4000% saturation). The dissolved CH(4) concentration was highest in in-flow water (ca. 3000% saturation). It decreased gradually during treatment. Its carbon isotope ratio indicated that the decrease resulted from bacterial CH(4) oxidation and that microbial CH(4) production can occur in anaerobic and settling tanks.

  4. Characterization of the N2O isotopic composition (15N, 18O and N2O isotopomers) emitted from incubated Amazon forest soils. Implications for the global N2O isotope budget

    NASA Astrophysics Data System (ADS)

    Pérez, T.; García, D.; Trumbore, S.; Tyler, S.; de Camargo, P.; Moreira, M.; Piccolo, M.; Park, S.; Boering, K.; Cerri, C.

    2003-04-01

    Tropical rain forest soils are the largest natural source of N2O to the atmosphere. Uncertainty in the signature of this source limits the utility of isotopes in constraining the global N2O budget. Differentiating the relative contribution of nitrification and denitrification to the emitted N2O using stable isotopes has been difficult due to the lack of enrichment factors values for each process measured in situ. We have devised a method for measuring enrichment factors using soil incubation experiments. We selected three Amazon rain forest soils: (1) Clay and (2) Sandy from Santarem, Pará State, and (3) Sandy from Nova Vida Farm, Rondonia State, Brazil. The enrichment factor values for nitrification and denitrification are: -97.8±4.2 and -9.9±3.8 per mil for clay Santarem soil, -86.8±4.3 and -45.2±4.5 per mil for sandy Santarem soil and-112.6±3.8 and -10.4±3.5 per mil for Nova Vida Farm soils, respectively. Our results show that enrichment factors for both processes differ with soil texture and location. The enrichment factors for nitrification are significantly smaller than the range reported in the literature (-66 to -42 per mil). Also, the enrichment factors for the Santarem soils (clay and sandy) differ significantly implying that soil texture (which will affect the soil air filled pore space at a given water content) is influencing the bacteria isotopic discrimination. However, the enrichment factors for the Santarem clay sand Nova Vida sandy soils do not differ by much. This suggests that the enrichment factors not only can be affected by texture but also by the microbial fauna present in these soils. We also determined the measurement of the N2O positional dependence. N2O is a linear molecule with two nitrogen atoms. The 15N isotope can be located in either the central nitrogen (alpha position) or in the terminal nitrogen (beta position). The isotopomer site preference (15N alpha - 15N beta) can be used to differentiate processes of production and

  5. Isotopomeric characterization of N2O produced, consumed, and emitted by automobiles.

    PubMed

    Toyoda, Sakae; Yamamoto, Sei-ichiro; Arai, Shinji; Nara, Hideki; Yoshida, Naohiro; Kashiwakura, Kiriko; Akiyama, Ken-ichi

    2008-01-01

    Fossil fuel combustion is the second largest anthropogenic source of nitrous oxide (N2O) after agriculture. The estimated global N2O flux from combustion sources, as well as from other sources, still has a large uncertainty. Herein, we characterize automobile sources using N2O isotopomer ratios (nitrogen and oxygen isotope ratios and intramolecular site preference of 15N, SP) to assess their contributions to total global sources and to deconvolute complex production/consumption processes during combustion and subsequent catalytic treatments of exhaust. Car exhaust gases were sampled under running and idling state, and N2O isotopomer ratios were measured by mass spectrometry. The N2O directly emitted from an engine of a vehicle running at constant velocity had almost constant isotopomer ratios (delta15Nbulk = -28.7 +/- 1.2 per thousand, delta18O = 28.6 +/- 3.3 per thousand, and SP = 4.2 +/- 0.8 per thousand) irrespective of the velocity. After passing through catalytic converters, the isotopomer ratios showed an increase which varied with the temperature and the aging of the catalysts. The increase suggests that both production and consumption of N2O occur on the catalyst and that their rates can be comparable. It was noticed that in the idling state, the N2O emitted from a brand new car has higher isotopomer ratios than that from used cars, which indicate that technical improvements in catalytic converters can reduce the N2O from mobile combustion sources. On average, the isotopomeric signatures of N2O finally emitted from automobiles are not sensitive to running/idling states or to aging of the catalysts. Characteristic average isotopomer ratios of N2O from automobile sources are estimated at -4.9 +/- 8.2 per thousand, 43.5 +/- 13.9 per thousand, and 12.2 +/- 9.1 per thousand for delta15Nbulk, delta18O, and SP, respectively.

  6. Spatial Variations in N2O Concentration and Isotopomer Composition off the Peru Coast

    NASA Astrophysics Data System (ADS)

    Bourbonnais, A.; Letscher, R. T.; Kock, A.; Bange, H. W.; Altabet, M. A.

    2016-02-01

    Nitrous oxide (N2O) is a potent greenhouse gas and stratospheric ozone depleting substance. The ocean is an important source of N2O to the atmosphere, accounting for up to about 30% of total emissions. However, the factors controlling N2O production and consumption in oceanic environments are still not understood nor constrained. N2O is a by-product of aerobic nitrification, and is formed by two different pathways: 1) the decomposition of hydroxylamine, an intermediate during ammonium oxidation to nitrite, or 2) the reduction of nitrite to N2O (nitrifier-denitrification). N2O is also an intermediate during denitrification under anoxic conditions. In this study, we measured N2O concentrations and isotopomer ratios, as well as O2, nutrient and biogenic N2 concentrations and the isotopic compositions of nitrate, nitrite and biogenic N2 at several coastal stations during two cruises off the Peru coast (6-14°S, 75-81°W) in December 2012 and January 2013. [N2O] varied from below equilibrium values in the OMZ to up to 238 nmol L-1 at 11 m depth at one of the shallowest stations. The isotopic composition of N2O (bulk δ15N: -5 to 30‰, δ18O: 41 to 95‰, and Site Preference: -3 to 65‰) also varied widely, with important differences between stations. Our results show a strong spatial heterogeneity in the mechanisms controlling N2O production and consumption in coastal upwelling regions, which should be taken into account in oceanic N2O models. We will discuss the contributions from different N2O production processes responsible for the observed extreme N2O accumulations.

  7. Isotopomer and isotopologue signatures of N2O produced in alpine ecosystems on the Qinghai-Tibetan Plateau.

    PubMed

    Kato, Tomomichi; Toyoda, Sakae; Yoshida, Naohiro; Tang, Yanhong; Wada, Eitaro

    2013-07-15

    Static-chamber flux measurements have suggested that one of the world's largest grasslands, the Qinghai-Tibetan Plateau (QTP), is a potential source of nitrous oxide (N2O), a major greenhouse gas. However, production and consumption pathways of N2O have not been identified by in situ field measurements. Ratios of N2O isotopomers ((14)N(15)N(16)O and (15)N(14)N(16)O) and an isotopologue ((14)N(14)N(18)O) with respect to (14)N(14)N(16)O in the atmosphere, static chambers, and soils were measured by gas chromatography and mass spectrometry in the summer of 2005 and the following winter of 2006 at three typical alpine ecosystems: alpine meadow, alpine shrub, and alpine wetland, on the QTP, China. Site preference (SP) values of soil-emitted N2 O were estimated as 33.7‰ and 30.1‰ for alpine meadow and shrub, respectively, suggesting larger contributions by fungal denitrification, than by bacterial denitrification and nitrifier-denitrification, to N2 O production. Statistical analysis of the relationship between SP and δ(15)N(bulk) values indicated that in alpine meadow, shrub, and wetland sites fungal denitrification contributed 40.7%, 40.0%, and 23.2% to gross N2O production and the produced N2O was reduced by 87.6%, 82.9%, and 92.7%, respectively. The combined measurements of N2O concentration, flux, and isotopomeric signatures provide a robust estimation of N2O circulation dynamics in alpine ecosystems on the QTP, which would contribute to the development of ecosystem nitrogen cycle model. Copyright © 2013 John Wiley & Sons, Ltd.

  8. Isotopomer fractionation during N2O consumption within soil mesocosms as a function of water filled pore space

    NASA Astrophysics Data System (ADS)

    Jinuntuya, M.; Ostrom, N. E.; Ostrom, P.; Sutka, R.

    2005-12-01

    Our prior research has demonstrated that the intramolecular distribution of 15N within the N2O molecule can be used to distinguish N2O derived from nitrification and denitrification. For this approach to be successful, however, the affect of fractionation during consumption of N2O by denitrification must be understood. Stable isotope and isotopomer analysis of soil mesocosm experiments were used to investigate fractionation of N2O during consumption at four different levels of water filled pores space (WFPS) 60, 80, 100 and 110% Uncultivated soil from the Long Term Ecological Research Site at Kellogg Biological Station was used to establish that the fractionation factors for δ15N, δ18O-N2O, δ15Nα and δ15Nβ ranged from -4.2 to -7.8 ‰, -12.5 to -19.1 ‰,-5.3 to -9.7‰ and -2.0 to -6.0 ‰, respectively. Lower fractionation factors were observed at higher WFPS demonstrating the importance of diffusion in limiting the expression of fractionation. The small degree of fractionation for δ15Nα and δ15Nβ indicates that consumption must be marked (e.g. >50%) before a significant isotope effect is observed. Our characterization of fractionation factors as a function of WFPS provides a basis to apportion the origins of N2O even when consumption is evident.

  9. Continuous measurements of nitrous oxide isotopomers during incubation experiments

    NASA Astrophysics Data System (ADS)

    Winther, Malte; Balslev-Harder, David; Christensen, Søren; Priemé, Anders; Elberling, Bo; Crosson, Eric; Blunier, Thomas

    2018-02-01

    Nitrous oxide (N2O) is an important and strong greenhouse gas in the atmosphere. It is produced by microbes during nitrification and denitrification in terrestrial and aquatic ecosystems. The main sinks for N2O are turnover by denitrification and photolysis and photo-oxidation in the stratosphere. In the linear N = N = O molecule 15N substitution is possible in two distinct positions: central and terminal. The respective molecules, 14N15N16O and 15N14N16O, are called isotopomers. It has been demonstrated that N2O produced by nitrifying or denitrifying microbes exhibits a different relative abundance of the isotopomers. Therefore, measurements of the site preference (difference in the abundance of the two isotopomers) in N2O can be used to determine the source of N2O, i.e., nitrification or denitrification. Recent instrument development allows for continuous position-dependent δ15N measurements at N2O concentrations relevant for studies of atmospheric chemistry. We present results from continuous incubation experiments with denitrifying bacteria, Pseudomonas fluorescens (producing and reducing N2O) and Pseudomonas chlororaphis (only producing N2O). The continuous measurements of N2O isotopomers reveals the transient isotope exchange among KNO3, N2O, and N2. We find bulk isotopic fractionation of -5.01 ‰ ± 1.20 for P. chlororaphis, in line with previous results for production from denitrification. For P. fluorescens, the bulk isotopic fractionation during production of N2O is -52.21 ‰ ± 9.28 and 8.77 ‰ ± 4.49 during N2O reduction.The site preference (SP) isotopic fractionation for P. chlororaphis is -3.42 ‰ ± 1.69. For P. fluorescens, the calculations result in SP isotopic fractionation values of 5.73 ‰ ± 5.26 during production of N2O and 2.41 ‰ ± 3.04 during reduction of N2O. In summary, we implemented continuous measurements of N2O isotopomers during incubation of denitrifying bacteria and believe that similar experiments will lead to a better

  10. Mass Isotopomer Analysis of Metabolically Labeled Nucleotide Sugars and N- and O-Glycans for Tracing Nucleotide Sugar Metabolisms*

    PubMed Central

    Nakajima, Kazuki; Ito, Emi; Ohtsubo, Kazuaki; Shirato, Ken; Takamiya, Rina; Kitazume, Shinobu; Angata, Takashi; Taniguchi, Naoyuki

    2013-01-01

    Nucleotide sugars are the donor substrates of various glycosyltransferases, and an important building block in N- and O-glycan biosynthesis. Their intercellular concentrations are regulated by cellular metabolic states including diseases such as cancer and diabetes. To investigate the fate of UDP-GlcNAc, we developed a tracing method for UDP-GlcNAc synthesis and use, and GlcNAc utilization using 13C6-glucose and 13C2-glucosamine, respectively, followed by the analysis of mass isotopomers using LC-MS. Metabolic labeling of cultured cells with 13C6-glucose and the analysis of isotopomers of UDP-HexNAc (UDP-GlcNAc plus UDP-GalNAc) and CMP-NeuAc revealed the relative contributions of metabolic pathways leading to UDP-GlcNAc synthesis and use. In pancreatic insulinoma cells, the labeling efficiency of a 13C6-glucose motif in CMP-NeuAc was lower compared with that in hepatoma cells. Using 13C2-glucosamine, the diversity of the labeling efficiency was observed in each sugar residue of N- and O-glycans on the basis of isotopomer analysis. In the insulinoma cells, the low labeling efficiencies were found for sialic acids as well as tri- and tetra-sialo N-glycans, whereas asialo N-glycans were found to be abundant. Essentially no significant difference in secreted hyaluronic acids was found among hepatoma and insulinoma cell lines. This indicates that metabolic flows are responsible for the low sialylation in the insulinoma cells. Our strategy should be useful for systematically tracing each stage of cellular GlcNAc metabolism. PMID:23720760

  11. Are dual isotope and isotopomer ratios of N2O useful indicators for N2O turnover during denitrification in nitrate-contaminated aquifers?

    NASA Astrophysics Data System (ADS)

    Well, Reinhard; Eschenbach, Wolfram; Flessa, Heinz; von der Heide, Carolin; Weymann, Daniel

    2012-08-01

    Denitrifying aquifers are sources of the greenhouse gas N2O. Isotopic signatures reflect processes of production and reduction of N2O, but it is not clear to which extent these can be used to quantify those processes. We investigated the spatial distribution of isotopologue values of N2O (δ18O, average δ15N, and 15N site preference, SP) in two denitrifying sandy aquifers to study N2O production and reduction and associated isotope effects in groundwater. For the first time, we combined this approach with direct estimation of N2O reduction from excess-N2 analysis. Groundwater samples were collected from 15 monitoring wells and four multilevel sampling wells and analysed for NO3-, dissolved N2O, dissolved O2, excess N2 from denitrification and isotopic signatures of NO3- and N2O. Both aquifers exhibited high NO3- concentrations with average concentrations of 22 and 15 mg N L-1, respectively. Evidence of intense denitrification with associated N2O formation was obtained from mean excess-N2 of 3.5 and 4.3 mg N L-1, respectively. Isotopic signatures of N2O were highly variable with ranges of 17.6-113.2‰ (δ18O), -55.4 to 89.4‰ (δ15Nbulk) and 1.8-97.9‰ (SP). δ15N and δ18O of NO3- ranged from -2.1‰ to 65.5‰ and from -5‰ to 33.5‰, respectively. The relationships between δ15N of NO3-, δ15Nbulk and SP were not in good agreement with the distribution predicted by a Rayleigh-model of isotope fractionation. The large ranges of δ18O and SP of N2O as well as the close correlation between these values could be explained by the fact that N2O reduction to N2 was strongly progressed but variable. We confirm and explain that a large range in SP and δ18O is typical for N2O from denitrifying aquifers, showing that this source signature can be distinguished from the isotopic fingerprint of N2O emitted from soils without water-logging. We conclude that isotopologue values of N2O in our sites were not suitable to quantify production or reduction of N2O or the

  12. Subfemtosecond quantum nuclear dynamics in water isotopomers.

    PubMed

    Rao, B Jayachander; Varandas, A J C

    2015-05-21

    Subfemtosecond quantum dynamics studies of all water isotopomers in the X̃ (2)B1 and à (2)A1 electronic states of the cation formed by Franck-Condon ionization of the neutral ground electronic state are reported. Using the ratio of the autocorrelation functions for the isotopomers as obtained from the solution of the time-dependent Schrödinger equation in a grid representation, high-order harmonic generation signals are calculated as a function of time. The results are found to be in agreement with the available experimental findings and with our earlier study for D2O(+)/H2O(+). Maxima are predicted in the autocorrelation function ratio at various times. Their origin and occurrence is explained by calculating expectation values of the bond lengths and bond angle of the water isotopomers as a function of time. The values so calculated for the (2)B1 and (2)A1 electronic states of the cation show quasiperiodic oscillations that can be associated with the time at which the nuclear wave packet reaches the minima of the potential energy surface, there being responsible for the peaks in the HHG signals.

  13. Modeling Non-Steady Isotopologue and Isotopomer Speciation and Fractionation during Denitrification in Soils

    NASA Astrophysics Data System (ADS)

    Maggi, F.; Riley, W. J.

    2009-12-01

    The composition and location of 15N atoms on N2O isotopomers and isotopologues during isotope speciation has been used to characterize soil biological N cycling and N2O surface emissions. Although there exist few experimental observations, no attempt has been made to model N2O isotopomer speciation. The mathematical treatment of biological kinetic reactions in isotopic applications normally makes use of first-order and quasi steady-state complexation assumptions without taking into account changes in enzyme concentration, reaction stoichiometry, and isotopologue and isotopomer speciation. When multiatomic isotopically-labeled reactants are used in a multi-molecurar reaction, these assumptions may fail since they always lead to a constant fractionation factor and cannot describe speciation of isotopologues and isotopomers. We have developed a mathematical framework that is capable of describing isotopologue and isotopmer speciation and fractionation under the assumption of non-steady complexation during biological kinetic reactions that overcome the limitations mentioned above. This framework was applied to a case study of non-steady (variable and inverse) isotopic effects observed during N2O production and consumption in soils. Our mathematical treatment has led to generalized kinetic equations which replicate experimental observations with high accuracy and help interpret non-steady isotopic effects and isotopologue and isotopomer speciation. The kinetic equations introduced and applied here have general validity in describing isotopic effects in any biochemical reactions by considering: changing enzyme concentrations, mass and isotope conservation, and reaction stoichiometry. The equations also describe speciation of any isotopologue and isotopomer product from any isotopologue and isotopmer reactant.

  14. Isotope signatures of N2O emitted from vegetable soil: Ammonia oxidation drives N2O production in NH4(+)-fertilized soil of North China.

    PubMed

    Zhang, Wei; Li, Yuzhong; Xu, Chunying; Li, Qiaozhen; Lin, Wei

    2016-07-08

    Nitrous oxide (N2O) is a potent greenhouse gas. In North China, vegetable fields are amended with high levels of N fertilizer and irrigation water, which causes massive N2O flux. The aim of this study was to determine the contribution of microbial processes to N2O production and characterize isotopic signature effects on N2O source partitioning. We conducted a microcosm study that combined naturally abundant isotopologues and gas inhibitor techniques to analyze N2O flux and its isotopomer signatures [δ(15)N(bulk), δ(18)O, and SP (intramolecular (15)N site preference)] that emitted from vegetable soil after the addition of NH4(+) fertilizers. The results show that ammonia oxidation is the predominant process under high water content (70% water-filled pore space), and nitrifier denitrification contribution increases with increasing N content. δ(15)N(bulk) and δ(18)O of N2O may not provide information about microbial processes due to great shifts in precursor signatures and atom exchange, especially for soil treated with NH4(+) fertilizer. SP and associated two end-member mixing model are useful to distinguish N2O source and contribution. Further work is needed to explore isotopomer signature stability to improve N2O microbial process identification.

  15. Isotope signatures of N2O emitted from vegetable soil: Ammonia oxidation drives N2O production in NH4+-fertilized soil of North China

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Li, Yuzhong; Xu, Chunying; Li, Qiaozhen; Lin, Wei

    2016-07-01

    Nitrous oxide (N2O) is a potent greenhouse gas. In North China, vegetable fields are amended with high levels of N fertilizer and irrigation water, which causes massive N2O flux. The aim of this study was to determine the contribution of microbial processes to N2O production and characterize isotopic signature effects on N2O source partitioning. We conducted a microcosm study that combined naturally abundant isotopologues and gas inhibitor techniques to analyze N2O flux and its isotopomer signatures [δ15Nbulk, δ18O, and SP (intramolecular 15N site preference)] that emitted from vegetable soil after the addition of NH4+ fertilizers. The results show that ammonia oxidation is the predominant process under high water content (70% water-filled pore space), and nitrifier denitrification contribution increases with increasing N content. δ15Nbulk and δ18O of N2O may not provide information about microbial processes due to great shifts in precursor signatures and atom exchange, especially for soil treated with NH4+ fertilizer. SP and associated two end-member mixing model are useful to distinguish N2O source and contribution. Further work is needed to explore isotopomer signature stability to improve N2O microbial process identification.

  16. Insight into nitrous oxide production processes in the western North Pacific based on a marine ecosystem isotopomer model

    NASA Astrophysics Data System (ADS)

    Yoshikawa, C.; Sasai, Y.; Wakita, M.; Honda, M. C.; Fujiki, T.; Harada, N.; Makabe, A.; Matsushima, S.; Toyoda, S.; Yoshida, N.; Ogawa, N. O.; Suga, H.; Ohkouchi, N.

    2016-02-01

    Based on the observed inverse relationship between the dissolved oxygen and N2O concentrations in the ocean, previous models have indirectly predicted marine N2O emissions from the apparent oxygen utilization (AOU), In this study, a marine ecosystem model that incorporates nitrous oxide (N2O) production processes (i.e., ammonium oxidation during nitrification and nitrite reduction during nitrifier denitrification) was newly developed to estimate the sea-air N2O flux and to quantify N2O production processes. Site preference of 15N (SP) in N2O isotopomers (14N15N16O and 15N14N16O) and the average nitrogen isotope ratio (δ15N) were added to the model because they are useful tracers to distinguish between ammonium oxidation and nitrite reduction. This model was applied to two contrasting time series sites, a subarctic station (K2) and a subtropical station (S1) in the western North Pacific. The model was validated with observed nitrogen concentration and nitrogen isotopomer datasets, and successfully simulated the higher N2O concentrations, higher δ15N values, and higher site preference values for N2O at K2 compared with S1. The annual mean N2O emissions were estimated to be 34 mg N m-2 yr-1 at K2 and 2 mg N m-2 yr-1 at S1. Using this model, we conducted three case studies: 1) estimating the ratio of in-situ biological N2O production to nitrate (NO3-) production during nitrification, 2) estimating the ratio of N2O production by ammonium oxidation to that by nitrite reduction, and 3) estimating the ratio of AOA ammonium oxidation to AOB ammonium oxidation. The results of case studies estimated the ratios of in situ biological N2O production to nitrate production during nitrification to be 0.22% at K2 and 0.06% at S1. It is also suggested that N2O was mainly produced via ammonium oxidation at K2 but was produced via both ammonium oxidation and nitrite reduction at S1. It is also revealed that 80% of the ammonium oxidation at K2 was caused by archaea in the subsurface

  17. The Rotational Spectrum of Ketene Isotopomers with 18O and 13C Revisited

    NASA Astrophysics Data System (ADS)

    Guarnieri, A.; Huckaufa, A.

    2003-06-01

    The pure rotational spectra of [18O]ketene, H2C=C18O, [1-13C]ketene, H2C=13CO, and [2-13C]ketene, H213C=CO, have been revisited in the frequency region 200 - 350 GHz in the ground vibrational state. From more than 100 R-branch transitions for each isotopomer a set of rotational and centrifugal distortion constants could be derived using the Watson S-reduction formalism. The values obtained for the rotational constants B and C agree very well with results of former investigations. The agreement is worse with respect to the A constants, but our newly determined A values agree well with the corresponding values of the main species and the 17O isotopomer.

  18. Microcosm N2O emissions wth calibration

    EPA Pesticide Factsheets

    The dataset consists of measurements of soil nitrous oxide emissions from soils under three different amendments: glucose, cellulose, and manure. Data includes the four isotopomers of nitrous oxide (14N15N16O, 15N14N16O, 14N14N18O, 14N14N16O), and the site preference.This dataset is associated with the following publication:Chen , H., D. Williams , P. Deshmukh , F. Birgand, B. Maxwell, and J. Walker. Probing the Biological Sources of Soil N2O Emissions by Quantum Cascade Laser-Based 15N Isotopocule Analysis. SOIL SCIENCE SOCIETY OF AMERICA JOURNAL. Soil Science Society of America, Madison, WI, USA, 100(0): 175-181, (2016).

  19. Detecting plant-climate interactions over decades-millennia using NMR isotopomer analysis

    NASA Astrophysics Data System (ADS)

    Ehlers, Ina; Augusti, Angela; Köhler, Iris; Wieloch, Thomas; Zuidema, Pieter; Robertson, Iain; Nilsson, Mats; Marshall, John; Schleucher, Jürgen

    2016-04-01

    . The smaller suppression of photorespiration in trees may be explained by increases in leaf temperature, suggesting that increasing temperatures may already be reducing the CO2 fertilization effect on the global scale. These results may explain the discrepancy between strong CO2 fertilization inferred from 13C measurements yet lack of biomass increases. Finally, we will stress advantages of isotopomers for studies of plant metabolism on millennial time scales: First, isotopomers multiply the information content, because glucose contains seven deuterium and six 13C isotopomers. Second, RATIOS of isotopomers are independent of the isotope compositions of a plant's substrates H2O and CO2, which often are poorly constrained over paleo time scales. Third, because isotopomer abundances are set by specific biochemical reactions, very strong correlations between isotopomers and environmental variables are observed. Forth, parallel reconstructions of physiological and climate signals from the same samples may inform analyses of plant-climate interactions (Augusti et al., Chem. Geol 2008).

  20. Isotopomer-selective spectra of a single intact H2O molecule in the Cs+(D2O)5H2O isotopologue: Going beyond pattern recognition to harvest the structural information encoded in vibrational spectra

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wolke, Conrad T.; Fournier, Joseph A.; Miliordos, Evangelos

    We report the vibrational signatures of a single H2O water molecule occupying distinct sites of the hydration network in the Cs+(H2O)6 cluster. This is accomplished using isotopomer selective IR-IR hole-burning on the Cs+(D2O)5(H2O) clusters formed by gas-phase exchange of a single, intact H2O molecule for D2O in the Cs+(D2O)6 ion. The OH stretching pattern of the Cs+(H2O)6 isotopologue is accurately recovered by superposition of the isotopomer spectra, thus establishing that the H2O incorporation is random and that the OH stretching manifold is largely due to contributions from decoupled water molecules. This behavior enables a powerful new way to extract structuralmore » information from vibrational spectra of size-selected clusters by explicitly identifying the local environments responsible for specific infrared features. The Cs+(H2O)6 structure was unambiguously assigned to the 4.1.1 isomer (a homodromic water tetramer with two additional flanking water molecules) from the fact that its computed IR spectrum matches the observed overall pattern and recovers the embedded correlations in the two OH stretching bands of the water molecule in the Cs+(D2O)5(H2O) isotopomers. The 4.1.1 isomer is the lowest in energy among other candidate networks at advanced (e.g., CCSD(T)) levels of theoretical treatment after corrections for (anharmonic) zero-point energy (ZPE). With the structure in hand, we then explore the mechanical origin of the various band locations using a local electric field formalism. This approach promises to provide a transferrable scheme for the prediction of the OH stretching fundamentals displayed by water networks in close proximity to solute ions.« less

  1. Infrared spectra of N2O-(ortho-D2)N and N2O-(HD)N clusters trapped in bulk solid parahydrogen.

    PubMed

    Lorenz, Britney D; Anderson, David T

    2007-05-14

    High-resolution infrared spectra of the clusters N2O-(ortho-D2)N and N2O-(HD)N, N=1-4, isolated in bulk solid parahydrogen at liquid helium temperatures are studied in the 2225 cm-1 region of the nu3 antisymmetric stretch of N2O. The clusters form during vapor deposition of separate gas streams of a precooled hydrogen mixture (ortho-D2para-H2 or HDpara-H2) and N2O onto a BaF2 optical substrate held at approximately 2.5 K in a sample-in-vacuum liquid helium cryostat. The cluster spectra reveal the N2O nu3 vibrational frequency shifts to higher energy as a function of N, and the shifts are larger for ortho-D2 compared to HD. These vibrational shifts result from the reduced translational zero-point energy for N2O solvated by the heavier hydrogen isotopomers. These spectra allow the N=0 peak at 2221.634 cm-1, corresponding to the nu3 vibrational frequency of N2O isolated in pure solid parahydrogen, to be assigned. The intensity of the N=0 absorption feature displays a strong temperature dependence, suggesting that significant structural changes occur in the parahydrogen solvation environment of N2O in the 1.8-4.9 K temperature range studied.

  2. N2O production and consumption from stable isotopic and concentration data in the Peruvian coastal upwelling system

    NASA Astrophysics Data System (ADS)

    Bourbonnais, Annie; Letscher, Robert T.; Bange, Hermann W.; Échevin, Vincent; Larkum, Jennifer; Mohn, Joachim; Yoshida, Naohiro; Altabet, Mark A.

    2017-04-01

    The ocean is an important source of nitrous oxide (N2O) to the atmosphere, yet the factors controlling N2O production and consumption in oceanic environments are still not understood nor constrained. We measured N2O concentrations and isotopomer ratios, as well as O2, nutrient and biogenic N2 concentrations, and the isotopic compositions of nitrate and nitrite at several coastal stations during two cruises off the Peru coast ( 5-16°S, 75-81°W) in December 2012 and January 2013. N2O concentrations varied from below equilibrium values in the oxygen deficient zone (ODZ) to up to 190 nmol L-1 in surface waters. We used a 3-D-reaction-advection-diffusion model to evaluate the rates and modes of N2O production in oxic waters and rates of N2O consumption versus production by denitrification in the ODZ. Intramolecular site preference in N2O isotopomer was relatively low in surface waters (generally -3 to 14‰) and together with modeling results, confirmed the dominance of nitrifier-denitrification or incomplete denitrifier-denitrification, corresponding to an efflux of up to 0.6 Tg N yr-1 off the Peru coast. Other evidence, e.g., the absence of a relationship between ΔN2O and apparent O2 utilization and significant relationships between nitrate, a substrate during denitrification, and N2O isotopes, suggest that N2O production by incomplete denitrification or nitrifier-denitrification decoupled from aerobic organic matter remineralization are likely pathways for extreme N2O accumulation in newly upwelled surface waters. We observed imbalances between N2O production and consumption in the ODZ, with the modeled proportion of N2O consumption relative to production generally increasing with biogenic N2. However, N2O production appeared to occur even where there was high N loss at the shallowest stations.

  3. Site-selective nitrogen isotopic ratio measurement of nitrous oxide using 2 microm diode lasers.

    PubMed

    Uehara, K; Yamamoto, K; Kikugawa, T; Yoshida, N

    2003-03-15

    We demonstrate a high-precision measurement of the isotopomer abundance ratio 14N(15)N(16)O/15N(14)N(16)O/14N(14)N(16)O (approximately 0.37/0.37/100) using three wavelength-modulated 2 microm diode lasers combined with a multipass cell which provides different optical pathlengths of 100 and 1 m to compensate the large abundance difference. A set of absorption lines for which the absorbances have almost the same temperature dependence are selected so that the effect of a change in gas temperature is minimized. The test experiment using pure nearly natural-abundance N(2)O samples showed that the site-selective 15N/14N ratios can be measured relative to a reference material with a precision of +/-3 x 10(-4) (+/-0.3 per thousand) in approximately 2 h. Copyright 2002 Elsevier Science B.V.

  4. Excessive use of nitrogen in Chinese agriculture results in high N2O/(N2O+N2) product ratio of denitrification, primarily due to acidification of the soils

    PubMed Central

    Qu, Zhi; Wang, Jingguo; Almøy, Trygve; Bakken, Lars R

    2014-01-01

    China is the world's largest producer and consumer of fertilizer N, and decades of overuse has caused nitrate leaching and possibly soil acidification. We hypothesized that this would enhance the soils' propensity to emit N2O from denitrification by reducing the expression of the enzyme N2O reductase. We investigated this by standardized oxic/anoxic incubations of soils from five long-term fertilization experiments in different regions of China. After adjusting the nitrate concentration to 2 mM, we measured oxic respiration (R), potential denitrification (D), substrate-induced denitrification, and the denitrification product stoichiometry (NO, N2O, N2). Soils with a history of high fertilizer N levels had high N2O/(N2O+N2) ratios, but only in those field experiments where soil pH had been lowered by N fertilization. By comparing all soils, we found a strong negative correlation between pH and the N2O/(N2O+N2) product ratio (r2 = 0.759, P < 0.001). In contrast, the potential denitrification (D) was found to be a linear function of oxic respiration (R), and the ratio D/R was largely unaffected by soil pH. The immediate effect of liming acidified soils was lowered N2O/(N2O+N2) ratios. The results provide evidence that soil pH has a marginal direct effect on potential denitrification, but that it is the master variable controlling the percentage of denitrified N emitted as N2O. It has been known for long that low pH may result in high N2O/(N2O+N2) product ratios of denitrification, but our documentation of a pervasive pH-control of this ratio across soil types and management practices is new. The results are in good agreement with new understanding of how pH may interfere with the expression of N2O reductase. We argue that the management of soil pH should be high on the agenda for mitigating N2O emissions in the future, particularly for countries where ongoing intensification of plant production is likely to acidify the soils. PMID:24249526

  5. N(2)O emissions and source processes in snow-covered soils in the Swiss Alps.

    PubMed

    Mohn, Joachim; Steinlin, Christine; Merbold, Lutz; Emmenegger, Lukas; Hagedorn, Frank

    2013-01-01

    Nitrous oxide (N2O) emissions from snow-covered soils represent a significant fraction of the annual flux from alpine, subalpine or cold-temperate regions. In winter 2010-2011, we investigated the temporal variability of N2O emissions and source processes from a subalpine valley in the Swiss Alps. The study included regular measurements of N2O snow profiles at a fixed location and an intensive sampling campaign along a transversal cut through the valley with grassland at the bottom and coniferous forest at the slopes. During the intensive campaign, recently developed laser spectroscopy was employed for high-precision N2O isotopomer analysis. Maximum N2O fluxes (0.77±0.64 nmol m(-2) h(-1)) were found for periods with elevated air temperature and, in contrast to our expectations, were higher from forest than from grassland in mid-February. At maximum snow height (63 cm) the main N2O source processes were heterotrophic denitrification and nitrifier denitrification. The reduction of N2O by heterotrophic denitrifiers was much more pronounced for the grassland compared with the forest soil, as indicated by the (15)N site preferences of 16.4±11.5 ‰ (grassland) and-1.6±2.1 ‰ (forest). This illustrates the potential of laser spectroscopic N2O isotopomer analysis for the identification of source processes even at low emission rates in nutrient poor ecosystems.

  6. The Millimeterwave Spectrum of Four Rare Ketene Isotopomers

    NASA Astrophysics Data System (ADS)

    Guarnieri, Antonio

    2005-09-01

    The pure rotational spectra in the ground vibrational state of (1,2-13C)ketene, H213C=13CO, (D2,1-13C)ketene, D2C=13CO, (D2,2-13C)ketene, D213C=CO, and (D2,18O)ketene, D2C=C18O, have been observed in the frequency region 200 - 350 GHz. All the spectral lines have been measured in natural abundances with a source modulated millimeterwave spectrometer. From the measured R-branch transitions a set of rotational and centrifugal distortion constants for each isotopomer could be derived, using the Watson S-reduction formalism. Further, the rotational spectra of the two isotopomers (4,5-D)ketene, D2CCO, and (4-D)ketene, DHCCO, which were already measured several years ago, have been extended to higher J-values and higher frequencies, as it is the case for all investigated isotopomers of this work. As a result of these studies a calculation of a mass-dependent structure will be the topic of a next paper.

  7. Progress in the analysis and interpretation of N2O isotopes: Potential and future challenges

    NASA Astrophysics Data System (ADS)

    Mohn, Joachim; Tuzson, Béla; Zellweger, Christoph; Harris, Eliza; Ibraim, Erkan; Yu, Longfei; Emmenegger, Lukas

    2017-04-01

    will be addressed in the upcoming European Metrology Programme for Innovation and Research (EMPIR) project "Metrology for Stable Isotope Reference Standards (SIRS)" starting in June 2017. Acknowledgement Part of this work has been carried out within the European Metrology Research Programme (EMRP) ENV52 project-HIGHGAS. The EMRP is jointly funded by the EMRP participating countries within EURAMET and the European Union. References [1] S. Toyoda et al., Isotopocule analysis of biologically produced nitrous oxide in various environments, Mass Spectrom. Rev., Doi 10.1002/mas.21459 (2015). [2] J. Mohn et al., Site selective real-time measurements of atmospheric N2O isotopomers by laser spectroscopy, Atmos. Meas. Tech. 5(7), 1601-1609 (2012). [3] B. Wolf et al., First on-line isotopic characterization of N2O above intensively managed grassland, Biogeosci. 12, 2517-2531, (2015). [4] E. Harris et al., Tracking nitrous oxide emission processes at a suburban site with semi-continuous, in-situ measurements of isotopic composition, J. Geophys. Res. Atmos., accepted (2016). [5] J. Mohn et al., Interlaboratory assessment of nitrous oxide isotopomer analysis by isotope ratio mass spectrometry and laser spectroscopy: current status and perspectives, Rapid Commun. Mass Spectrom. 28, 1995-2007 (2014). [6] J. Mohn et al. Reassessment of the NH4NO3 thermal decomposition technique for calibration of the N2O isotopic composition, Rapid Commun. Mass Spectrom. 30, 2487-2496 (2016).

  8. The diversity of the N2O reducers matters for the N2O:N2 denitrification end-product ratio across an annual and a perennial cropping system.

    PubMed

    Domeignoz-Horta, Luiz A; Spor, Aymé; Bru, David; Breuil, Marie-Christine; Bizouard, Florian; Léonard, Joël; Philippot, Laurent

    2015-01-01

    Agriculture is the main source of terrestrial emissions of N2O, a potent greenhouse gas and the main cause of ozone layer depletion. The reduction of N2O into N2 by microorganisms carrying the nitrous oxide reductase gene (nosZ) is the only biological process known to eliminate this greenhouse gas. Recent studies showed that a previously unknown clade of N2O-reducers was related to the capacity of the soil to act as an N2O sink, opening the way for new strategies to mitigate emissions. Here, we investigated whether the agricultural practices could differently influence the two N2O reducer clades with consequences for denitrification end-products. The abundance of N2O-reducers and producers was quantified by real-time PCR, and the diversity of both nosZ clades was determined by 454 pyrosequencing. Potential N2O production and potential denitrification activity were used to calculate the denitrification gaseous end-product ratio. Overall, the results showed limited differences between management practices but there were significant differences between cropping systems in both the abundance and structure of the nosZII community, as well as in the [rN2O/r(N2O+N2)] ratio. More limited differences were observed in the nosZI community, suggesting that the newly identified nosZII clade is more sensitive than nosZI to environmental changes. Potential denitrification activity and potential N2O production were explained mainly by the soil properties while the diversity of the nosZII clade on its own explained 26% of the denitrification end-product ratio, which highlights the importance of understanding the ecology of this newly identified clade of N2O reducers for mitigation strategies.

  9. Improved measurement of protein synthesis in human subjects using 2H-phenylalanine isotopomers and gas chromatography/mass spectrometry.

    PubMed

    Preston, Tom; Small, Alexandra C

    2010-03-15

    Sensitive methods to measure protein synthetic rate in vivo are required to assess changes in protein expression, especially when comparing healthy with infirm subjects. We have previously applied a 'flooding dose' procedure using (2)H(5)-phenylalanine ((2)H(5)-phe) and (2)H(8)-phe isotopomers as tracers, which has proven successful in measuring albumin and fibrinogen synthesis in response to feeding in cancer patients. Using tert-butyldimethylsilyl derivatives, we have observed that (2)H(7)-phe is formed with time in vivo from (2)H(8)-phe, probably during transamination. This increases errors when estimating the fractional synthetic rate (FSR) using the (2)H(8)-phe isotopomer compared with the (2)H(5)-phe isotopomer. We sought to improve this situation by use of an alternative derivative that overcomes this problem whilst also streamlining sample preparation. When using N-ethoxycarbonyltrifluoroethyl (ECTFE) amino acid esters, (2)H(8)-phe is effectively converted into (2)H(7)-phe through fragmentation under electron ionisation (EI), allowing both (2)H(8)-phe and (2)H(7)-phe isotopomers to be measured as a single intense C(7)(2)H(7)(+) fragment at 98 Th. To illustrate the improved situation, the mean RMS residual was calculated for all albumin data, for each isotopomer and for each derivative. Albumin-bound Phe was analysed as ECTFE-phe with improved precision, independent of the isotopomer used, confirming that the new derivative is superior. Copyright 2010 John Wiley & Sons, Ltd.

  10. Effect of COD/N ratio on N2O production during nitrogen removal by aerobic granular sludge.

    PubMed

    Velho, V F; Magnus, B S; Daudt, G C; Xavier, J A; Guimarães, L B; Costa, R H R

    2017-12-01

    N 2 O-production was investigated during nitrogen removal using aerobic granular sludge (AGS) technology. A pilot sequencing batch reactor (SBR) with AGS achieved an effluent in accordance with national discharge limits, although presented a nitrite accumulation rate of 95.79% with no simultaneous nitrification-denitrification. N 2 O production was 2.06 mg L -1 during the anoxic phase, with N 2 O emission during air pulses and the aeration phase of 1.6% of the nitrogen loading rate. Batch tests with AGS from the pilot reactor verified that at the greatest COD/N ratio (1.55), the N 2 O production (1.08 mgN 2 O-N L -1 ) and consumption (up to 0.05 mgN 2 O-N L -1 ), resulted in the lowest remaining dissolved N 2 O (0.03 mgN 2 O-N L -1 ), stripping the minimum N 2 O gas (0.018 mgN 2 O-N L -1 ). Conversely, the carbon supply shortage, under low C/N ratios, increased N 2 O emission (0.040 mgN 2 O-N L -1 ), due to incomplete denitrification. High abundance of ammonia-oxidizing and low abundance of nitrite-oxidizing bacteria were found, corroborating the fact of partial nitrification. A denitrifying heterotrophic community, represented mainly by Pseudoxanthomonas, was predominant in the AGS. Overall, the AGS showed stable partial nitrification ability representing capital and operating cost savings. The SBR operation flexibility could be advantageous for controlling N 2 O emissions, and extending the anoxic phase would benefit complete denitrification in cases of low C/N influents.

  11. Grasland Stable Isotope Flux Measurements: Three Isotopomers of Carbon Dioxide Measured by QCL Spectroscopy

    NASA Astrophysics Data System (ADS)

    Zeeman, M. J.; Tuzson, B.; Eugster, W.; Werner, R. A.; Buchmann, N.; Emmenegger, L.

    2007-12-01

    To improve our understanding of greenhouse gas dynamics of managed ecosystems such as grasslands, we not only need to investigate the effects of management (e.g., grass cuts) and weather events (e.g., rainy days) on carbon dioxide fluxes, but also need to increase the time resolution of our measurements. Thus, for the first time, we assessed respiration and assimilation fluxes with high time resolution (5Hz) stable isotope measurements at an intensively managed farmland in Switzerland (Chamau, 400m ASL). Two different methods were used to quantify fluxes of carbon dioxide and associated fluxes of stable carbon isotopes: (1) the flux gradient method, and (2) the eddy covariance method. During a week long intensive measurement campaign, we (1) measured mixing ratios of carbon dioxide isotopomers (12C16O2, 12C16O18O, 13C16O2) with a Quantum Cascade Laser (QCL, Aerodyne Inc.) spectroscope and (2) collected air samples for isotope analyses (13C/12C) and (18O/16O) of carbon dioxide by Isotope Ratio Mass Spectrometry (IRMS, Finnigan) every two hours, concurrently along a height profile (z = 0.05; 0.10; 0.31; 2.15m). In the following week, the QCL setup was used for closed-path eddy covariance flux measurement of the carbon dioxide isotopomers, with the air inlet located next to an open-path Infra Red Gas Analyzers (IRGA, LiCor 7500) used simultaneously for carbon dioxide measurements. During this second week, an area of grass inside the footprint was cut and harvested after several days. The first results of in-field continuous QCL measurements of carbon dioxide mixing ratios and their stable isotopic ratios show good agreement with IRGA measurements and isotope analysis of flask samples by IRMS. Thus, QCL spectroscopy is a very promising tool for stable isotope flux investigations.

  12. Near-Continuous Isotopic Characterization of Soil N2O Fluxes from Maize Production

    NASA Astrophysics Data System (ADS)

    Anex, R. P.; Francis Clar, J.

    2015-12-01

    Isotopomer ratios of N2O and especially intramolecular 15N site preference (SP) have been proposed as indicators of the sources of N2O and for providing insight into the contributions of different microbial processes. Current knowledge, however, is mainly based on pure culture studies and laboratory flask studies using mass spectrometric analysis. Recent development of laser spectroscopic methods has made possible high-precision, in situ measurements. We present results from a maize production field in Columbia County, Wisconsin, USA. Data were collected from the fertilized maize phase of a maize-soybean rotation. N2O mole fractions and isotopic composition were determined using an automatic gas flux measurement system comprising a set of custom-designed automatic chambers, circulating gas paths and an OA-ICOS N2O Isotope Analyzer (Los Gatos Research, Inc., Model 914-0027). The instrument system allows for up to 15 user programmable soil gas chambers. Wide dynamic range and parts-per-billion precision of OA-ICOS laser absorption instrument allows for extremely rapid estimation of N2O fluxes. Current operational settings provide measurements of N2O and its isotopes every 20 seconds with a precision of 0.1 ± 0.050 PPB. Comparison of measurements from four chambers (two between row and two in-row) show very different aggregate N2O flux, but SP values suggest similar sources from nitrifier denitrification and incomplete bacterial denitrification. SP values reported are being measured throughout the current growing season. To date, the majority of values are consistent with an origin from bacterial denitrification and coincide with periods of high water filled pore space.

  13. Nitrification and N2O production processes in soil incubations after ammonium fertilizer application at high concentrations

    NASA Astrophysics Data System (ADS)

    Deppe, Marianna; Well, Reinhard; Giesemann, Anette; Flessa, Heinz

    2016-04-01

    High concentrations of ammonium as they occur, e.g., after point-injection of ammonium fertilizer solution according to the CULTAN fertilization technique may retard nitrification. Potential advantages in comparison to conventional fertilization include a higher N efficiency of crops, reduced nitrate leaching, and lower N2O and N2 emissions. Dynamics of nitrification due to plant uptake and dilution processes, leading to decreasing ammonium concentrations in fertilizer depots, has only poorly been studied before. Furthermore, there is little information about the relative contribution of different N2O production processes under these conditions. To elucidate the process dynamics a laboratory incubation study was conducted. After fertilization with ammonium sulfate at 5 levels (from 0 to 5000 mg NH4+-N kg-1; 20mg NO3--N kg-1 each), sandy loam soil was incubated in dynamic soil microcosms for 21 days. N2O, CH4 and CO2 fluxes as well as isotope signatures of N2O and, at three dates, NO3- and NH4+ were measured. To identify N2O production processes, acetylene inhibition (0.01 vol.%), 15N tracer approaches, and isotopomer data (15N site preference and δ18O) were used. N2O emissions were highest at 450mg NH4+-N kg-1 and declined with further increasing concentrations. At 5000 mg NH4+-N kg-1 nitrification was completely inhibited. However, approximately 90% of N2O production was inhibited by acetylene application, and there was no change in the relative contribution of nitrification and denitrification to N2O production with N level. Applying the non-equilibrium technique to our 15N tracer data revealed heterogeneous distribution of denitrification in soil, with at least two distinct NO3- pools, and spatial separation of NO3- formation and consumption. In comparison with the acetylene inhibition and 15N tracer approaches the results of the isotopomer approach were reasonable and indicated substantial contribution of nitrifier-denitrification (10-40%) to total N2O

  14. Closed-loop 15N measurement of N2O and its isotopomers for real-time greenhouse gas tracing

    NASA Astrophysics Data System (ADS)

    Slaets, Johanna; Mayr, Leopold; Heiling, Maria; Zaman, Mohammad; Resch, Christian; Weltin, Georg; Gruber, Roman; Dercon, Gerd

    2016-04-01

    Quantifying sources of nitrous oxide is essential to improve understanding of the global N cycle and to develop climate-smart agriculture, as N2O has a global warming potential 300 times higher than CO2. The isotopic signature and the intramolecular distribution (site preference) of 15N are powerful tools to trace N2O, but the application of these methods is limited as conventional methods cannot provide continuous and in situ data. Here we present a method for closed-loop, real time monitoring of the N2O flux, the isotopic signature and the intramolecular distribution of 15N by using off-axis integrated cavity output spectroscopy (ICOS, Los Gatos Research). The developed method was applied to a fertilizer inhibitor experiment, in which N2O emissions were measured on undisturbed soil cores for three weeks. The treatments consisted of enriched urea-N (100 kg urea-N/ha), the same fertilizer combined with the nitrification inhibitor nitrapyrin (375 g/100 kg urea), and control cores. Monitoring the isotopic signature makes it possible to distinguish emissions from soil and fertilizer. Characterization of site preference could additionally provide a tool to identify different microbial processes leading to N2O emissions. Furthermore, the closed-loop approach enables direct measurement on site and does not require removal of CO2 and H2O. Results showed that 75% of total N2O emissions (total=11 346 μg N2O-N/m2) in the fertilized cores originated from fertilizer, while only 55% of total emissions (total=2 450 μg N2ON/m2) stemmed from fertilizer for the cores treated with nitrapyrin. In the controls, N2O derived from soil was only 40% of the size of the corresponding pool from the fertilized cores, pointing towards a priming effect on the microbial community from the fertilizer and demonstrating the bias that could be introduced by relying on non-treated cores to estimate soil emission rates, rather than using the isotopic signature. The site preference increased linearly

  15. Annual mean mixing ratios of N2, Ar, O2, and CO in the martian atmosphere

    NASA Astrophysics Data System (ADS)

    Krasnopolsky, Vladimir A.

    2017-09-01

    The precise mixing ratios of N2, Ar, O2, and CO measured by the MSL Curiosity quadrupole mass spectrometer must be corrected for the seasonal variations of the atmospheric pressure to reproduce annual mean mixing ratios on Mars. The corrections are made using measurements for the first year of the Viking Landers 1 and 2 and the Mars Climate Database data. The mean correction factor is 0.899 ± 0.006 resulting in annual mean mixing ratios of (1.83 ± 0.03)% for N2, (1.86 ± 0.02)% for Ar, (1.56 ± 0.06) × 10-3 for O2, and 673 ± 2.6 ppm for CO. The O2 mixing ratio agrees with the Herschel value within its uncertainty, the ground-based observations corrected for the dust extinction, and photochemical models by Nair et al. (1994) and Krasnopolsky (2010). The CO mixing ratio is in excellent agreement with the MRO/CRISM value of 700 ppm and with 667, 693, and 684 ppm recently observed at LS = 60, 89, and 110° and corrected to the annual mean conditions. Lifetimes of N2 and Ar are very long in the martian atmosphere, and differences between the MSL and Viking data on these species cannot be attributed to their variations.

  16. Annual mean mixing ratios of N2, Ar, O2, and CO in the martian atmosphere

    NASA Astrophysics Data System (ADS)

    Krasnopolsky, V.

    2017-09-01

    The precise mixing ratios of N2, Ar, O2, and CO measured by the MSL Curiosity quadrupole mass spectrometer must be corrected for the seasonal variations of the atmospheric pressure to reproduce annual mean mixing ratios on Mars. The corrections are made using measurements the Viking Landers and the Mars Climate Database data. The mean correction factor is 0.899 ± 0.006 resulting in annual mean mixing ratios of (1.83 ± 0.03)% for N2, (1.86 ± 0.02)% for Ar, (1.56 ± 0.06)×10-3 for O2, and 673 ± 2.6 ppm for CO. The O2 mixing ratio agrees with the Herschel value within its uncertainty, the ground-based observations corrected for the dust extinction, and photochemical models by Nair et al. (1994) and Krasnopolsky (2010). The CO mixing ratio is in excellent agreement with the MRO/CRISM value of 700 ppm and with 667, 693, and 684 ppm recently observed at LS = 60, 89, and 110° and corrected to the annual mean conditions. Lifetimes of N2 and Ar are very long in the martian atmosphere, and differences between the MSL and Viking data on these species cannot be attributed to their variations.

  17. Difluorophosphoryl nitrene F2P(O)N: matrix isolation and unexpected rearrangement to F2PNO.

    PubMed

    Zeng, Xiaoqing; Beckers, Helmut; Willner, Helge; Neuhaus, Patrik; Grote, Dirk; Sander, Wolfram

    2009-12-14

    Triplet difluorophosphoryl nitrene F(2)P(O)N (X(3)A'') was generated on ArF excimer laser irradiation (lambda=193 nm) of F(2)P(O)N(3) in solid argon matrix at 16 K, and characterized by its matrix IR, UV/Vis, and EPR spectra, in combination with DFT and CBS-QB3 calculations. On visible light irradiation (lambda>420 nm) at 16 K F(2)P(O)N reacts with molecular nitrogen and some of the azide is regenerated. UV irradiation (lambda=255 nm) of F(2)P(O)N (X(3)A'') induced a Curtius-type rearrangement, but instead of a 1,3-fluorine shift, nitrogen migration to give F(2)PON is proposed to be the first step of the photoisomerization of F(2)P(O)N into F(2)PNO (difluoronitrosophosphine). Formation of novel F(2)PNO was confirmed with (15)N- and (18)O-enriched isotopomers by IR spectroscopy and DFT calculations. Theoretical calculations predict a rather long P-N bond of 1.922 A [B3LYP/6-311+G(3df)] and low bond-dissociation energy of 76.3 kJ mol(-1) (CBS-QB3) for F(2)PNO.

  18. Method for measuring changes in the atmospheric O2/N2 ratio by a gas chromatograph equipped with a thermal conductivity detector

    NASA Astrophysics Data System (ADS)

    Tohjima, Yasunori

    2000-06-01

    We present a method for measuring changes in the atmospheric O2/N2 ratio based on data from a gas chromatograph (GC) equipped with a thermal conductivity detector (TCD). In this method, O2 and N2 in an air sample are separated on a column filled with molecular sieve 5A with H2 carrier gas. Since the separated O2 includes Ar, which has a retention time similar to that of O2, the (O2+Ar)/N2 ratio is actually measured. The change in the measured (O2+Ar)/N2 ratio can be easily converted to that in the O2/N2 ratio with a very small error based on the fact that the atmospheric Ar/N2 ratio is almost constant. The improvements to achieve the high-precision measurement include stabilization of the pressure at the GC column head and at the outlets of the TCD and the sample loop. Additionally, the precision is improved statistically by repeating alternate analyses of sample and a reference gas. The standard deviation of the replicate cycles of reference and sample analyses is about 18 per meg (corresponding to 3.8 parts per million (ppm) O2 in air). This means that the standard error is about 7 per meg (1.5 ppm O2 in air) for seven cycles of alternate analyses, which takes about 70 min. The response of this method is likely to have a 2% nonlinearity. Ambient air samples are collected under pressure in glass flasks equipped with two stopcocks sealed by Viton O-rings at both ends. Pressure depletion in the flask during the O2/N2 measurement does not cause any detectable change in the O2/N2 ratio, but the O2/N2 ratio in the flask was found to gradually decrease during the storage period. We also present preliminary results from air samples collected at Hateruma Island (latitude 24°03'N, longitude 123°49') from July 1997 through March 1999. The observed O2/N2 ratios clearly show a seasonal variation, increasing in spring and summer and decreasing in autumn and winter.

  19. Software LS-MIDA for efficient mass isotopomer distribution analysis in metabolic modelling.

    PubMed

    Ahmed, Zeeshan; Zeeshan, Saman; Huber, Claudia; Hensel, Michael; Schomburg, Dietmar; Münch, Richard; Eisenreich, Wolfgang; Dandekar, Thomas

    2013-07-09

    The knowledge of metabolic pathways and fluxes is important to understand the adaptation of organisms to their biotic and abiotic environment. The specific distribution of stable isotope labelled precursors into metabolic products can be taken as fingerprints of the metabolic events and dynamics through the metabolic networks. An open-source software is required that easily and rapidly calculates from mass spectra of labelled metabolites, derivatives and their fragments global isotope excess and isotopomer distribution. The open-source software "Least Square Mass Isotopomer Analyzer" (LS-MIDA) is presented that processes experimental mass spectrometry (MS) data on the basis of metabolite information such as the number of atoms in the compound, mass to charge ratio (m/e or m/z) values of the compounds and fragments under study, and the experimental relative MS intensities reflecting the enrichments of isotopomers in 13C- or 15 N-labelled compounds, in comparison to the natural abundances in the unlabelled molecules. The software uses Brauman's least square method of linear regression. As a result, global isotope enrichments of the metabolite or fragment under study and the molar abundances of each isotopomer are obtained and displayed. The new software provides an open-source platform that easily and rapidly converts experimental MS patterns of labelled metabolites into isotopomer enrichments that are the basis for subsequent observation-driven analysis of pathways and fluxes, as well as for model-driven metabolic flux calculations.

  20. Linking Annual N2O Emission in Organic Soils to Mineral Nitrogen Input as Estimated by Heterotrophic Respiration and Soil C/N Ratio

    PubMed Central

    Mu, Zhijian; Huang, Aiying; Ni, Jiupai; Xie, Deti

    2014-01-01

    Organic soils are an important source of N2O, but global estimates of these fluxes remain uncertain because measurements are sparse. We tested the hypothesis that N2O fluxes can be predicted from estimates of mineral nitrogen input, calculated from readily-available measurements of CO2 flux and soil C/N ratio. From studies of organic soils throughout the world, we compiled a data set of annual CO2 and N2O fluxes which were measured concurrently. The input of soil mineral nitrogen in these studies was estimated from applied fertilizer nitrogen and organic nitrogen mineralization. The latter was calculated by dividing the rate of soil heterotrophic respiration by soil C/N ratio. This index of mineral nitrogen input explained up to 69% of the overall variability of N2O fluxes, whereas CO2 flux or soil C/N ratio alone explained only 49% and 36% of the variability, respectively. Including water table level in the model, along with mineral nitrogen input, further improved the model with the explanatory proportion of variability in N2O flux increasing to 75%. Unlike grassland or cropland soils, forest soils were evidently nitrogen-limited, so water table level had no significant effect on N2O flux. Our proposed approach, which uses the product of soil-derived CO2 flux and the inverse of soil C/N ratio as a proxy for nitrogen mineralization, shows promise for estimating regional or global N2O fluxes from organic soils, although some further enhancements may be warranted. PMID:24798347

  1. Linking annual N2O emission in organic soils to mineral nitrogen input as estimated by heterotrophic respiration and soil C/N ratio.

    PubMed

    Mu, Zhijian; Huang, Aiying; Ni, Jiupai; Xie, Deti

    2014-01-01

    Organic soils are an important source of N2O, but global estimates of these fluxes remain uncertain because measurements are sparse. We tested the hypothesis that N2O fluxes can be predicted from estimates of mineral nitrogen input, calculated from readily-available measurements of CO2 flux and soil C/N ratio. From studies of organic soils throughout the world, we compiled a data set of annual CO2 and N2O fluxes which were measured concurrently. The input of soil mineral nitrogen in these studies was estimated from applied fertilizer nitrogen and organic nitrogen mineralization. The latter was calculated by dividing the rate of soil heterotrophic respiration by soil C/N ratio. This index of mineral nitrogen input explained up to 69% of the overall variability of N2O fluxes, whereas CO2 flux or soil C/N ratio alone explained only 49% and 36% of the variability, respectively. Including water table level in the model, along with mineral nitrogen input, further improved the model with the explanatory proportion of variability in N2O flux increasing to 75%. Unlike grassland or cropland soils, forest soils were evidently nitrogen-limited, so water table level had no significant effect on N2O flux. Our proposed approach, which uses the product of soil-derived CO2 flux and the inverse of soil C/N ratio as a proxy for nitrogen mineralization, shows promise for estimating regional or global N2O fluxes from organic soils, although some further enhancements may be warranted.

  2. Using stable isotopes to follow excreta N dynamics and N2O emissions in animal production systems.

    PubMed

    Clough, T J; Müller, C; Laughlin, R J

    2013-06-01

    Nitrous oxide (N2O) is a potent greenhouse gas and the dominant anthropogenic stratospheric ozone-depleting emission. The tropospheric concentration of N2O continues to increase, with animal production systems constituting the largest anthropogenic source. Stable isotopes of nitrogen (N) provide tools for constraining emission sources and, following the temporal dynamics of N2O, providing additional insight and unequivocal proof of N2O source, production pathways and consumption. The potential for using stable isotopes of N is underutilised. The intent of this article is to provide an overview of what these tools are and demonstrate where and how these tools could be applied to advance the mitigation of N2O emissions from animal production systems. Nitrogen inputs and outputs are dominated by fertiliser and excreta, respectively, both of which are substrates for N2O production. These substrates can be labelled with 15N to enable the substrate-N to be traced and linked to N2O emissions. Thus, the effects of changes to animal production systems to reduce feed-N wastage by animals and fertiliser wastage, aimed at N2O mitigation and/or improved animal or economic performance, can be traced. Further 15N-tracer studies are required to fully understand the dynamics and N2O fluxes associated with excreta, and the biological contribution to these fluxes. These data are also essential for the new generation of 15N models. Recent technique developments in isotopomer science along with stable isotope probing using multiple isotopes also offer exciting capability for addressing the N2O mitigation quest.

  3. Understanding N2O sources and sinks with laser based isotopic analysis

    NASA Astrophysics Data System (ADS)

    Mohn, Joachim; Harris, Eliza; Tuzson, Béla; Emmenegger, Lukas

    2015-04-01

    Nitrous oxide (N2O) is a potent greenhouse gas and the strongest ozone-destroying substance. The main emissions of N2O are linked to different microbial processes, therefore the sources are disperse and highly variable, complicating the development of effective mitigation strategies. Isotopic measurements have great potential to unravel spatial and temporal variations in sources, sinks and chemistry of N2O. Recent developments in quantum cascade laser spectroscopy (QCLAS) [1] allow both the intermolecular distribution of 15N substitutions ('site preference'; 15N14N16O versus 14N15N16O) and the oxygen isotopic composition (d18O) of N2O to be measured in real-time and at high precision of <0.2 ‰ [2]. Additionally, N2O isotopic analysis by QCLAS has demonstrated excellent compatibility to the standard technique isotope-ratio mass-spectrometry [3]. In a number of laboratory and pilot plant studies we investigated the isotopic signature of distinct microbial and abiotic N2O production and consumption pathways in soil and aqueous solution [e.g. 4]. Specific pathways were favoured by selection of the nitrogen substrates and process conditions and their isotopic signatures identified by real-time laser spectroscopic analysis. Results from our laboratory studies are in accordance with pure culture experiments and can therefore be applied to other ecosystems. Recently, high precision isotopic analysis at ambient N2O is also feasible by combining laser spectroscopy with automated preconcentration [5]. The field deployment was demonstrated by real-time monitoring isotopic composition of N2O emissions from an intensively managed grassland in central Switzerland for three months. The responses of the N2O isotopic signatures were analysed with respect to management events and weather influences [2]. In a follow-up project we intend to combine real-time N2O isotopic analysis at a tall tower in central Switzerland with atmospheric transport simulations and a biogeochemical model

  4. Isolation of site-specific anharmonicities of individual water molecules in the I-·(H2O)2 complex using tag-free, isotopomer selective IR-IR double resonance

    NASA Astrophysics Data System (ADS)

    Yang, Nan; Duong, Chinh H.; Kelleher, Patrick J.; Johnson, Mark A.; McCoy, Anne B.

    2017-12-01

    We reveal the microscopic mechanics of iodide ion microhydration by recording the isotopomer-selective vibrational spectra of the I-·(H2O)·(D2O), I-·(HOD)·(D2O), and I-·(DOH)·(H2O) isotopologues using a new class of ion spectrometer that is optimized to carry out two-color, IR-IR photodissociation in a variety of pump-probe schemes. Using one of these, we record the linear absorption spectrum of a cryogenically cooled cluster without the use of a messenger ;tag;. In another protocol, we reveal the spectra of individual H2O and D2O molecules embedded in each of the two possible binding sites in the iodide dihydrate, as well as the bands due to individual OH and OD groups in each of the four local binding environments. Finally, we demonstrate how temperature dependent isotopic scrambling among the spectral features can be used to monitor the onset of large amplitude motion, heretofore inferred from changes in the envelope of the OH stretching vibrational manifold.

  5. Source of nitrous oxide emissions during the cow manure composting process as revealed by isotopomer analysis of and amoA abundance in betaproteobacterial ammonia-oxidizing bacteria.

    PubMed

    Maeda, Koki; Toyoda, Sakae; Shimojima, Ryosuke; Osada, Takashi; Hanajima, Dai; Morioka, Riki; Yoshida, Naohiro

    2010-03-01

    A molecular analysis of betaproteobacterial ammonia oxidizers and a N(2)O isotopomer analysis were conducted to study the sources of N(2)O emissions during the cow manure composting process. Much NO(2)(-)-N and NO(3)(-)-N and the Nitrosomonas europaea-like amoA gene were detected at the surface, especially at the top of the composting pile, suggesting that these ammonia-oxidizing bacteria (AOB) significantly contribute to the nitrification which occurs at the surface layer of compost piles. However, the (15)N site preference within the asymmetric N(2)O molecule (SP = delta(15)N(alpha) - delta(15)N(beta), where (15)N(alpha) and (15)N(beta) represent the (15)N/(14)N ratios at the center and end sites of the nitrogen atoms, respectively) indicated that the source of N(2)O emissions just after the compost was turned originated mainly from the denitrification process. Based on these results, the reduction of accumulated NO(2)(-)-N or NO(3)(-)-N after turning was identified as the main source of N(2)O emissions. The site preference and bulk delta(15)N results also indicate that the rate of N(2)O reduction was relatively low, and an increased value for the site preference indicates that the nitrification which occurred mainly in the surface layer of the pile partially contributed to N(2)O emissions between the turnings.

  6. Effects of carbon sources and COD/N ratio on N2O emissions in subsurface flow constructed wetlands.

    PubMed

    Lyu, Wanlin; Huang, Lei; Xiao, Guangquan; Chen, Yucheng

    2017-12-01

    A set of constructed wetlands under two different carbon sources, namely, glucose (CW) and sodium acetate (YW), was established at a laboratory scale with influent COD/N ratios of 20:1, 10:1, 7:1, 4:1, and 0 to analyze the influence of carbon supply on nitrous oxide emissions. Results showed that the glucose systems generated higher N 2 O emissions than those of the sodium acetate systems. The higher amount of N 2 O-releasing fluxes in the CWs than in the YWs was consistent with the higher NO 2 - -N accumulation in the former than in the latter. Moreover, electron competition was tighter in the CWs and contributed to the incomplete denitrification with poor N 2 O production performance. Illumina MiSeq sequencing demonstrated that some denitrifying bacteria, such as Denitratisoma, Bacillus, and Zoogloea, were higher in the YWs than in the CWs. This result indicated that the carbon source is important in controlling N 2 O emissions in microbial communities. Copyright © 2017. Published by Elsevier Ltd.

  7. First real-time measurements of N2O isotopic signatures above intensively managed grassland: analytical performance, validation and illustrative examples

    NASA Astrophysics Data System (ADS)

    Wolf, Benjamin; Tuzson, Béla; Merbold, Lutz; Decock, Charlotte; Emmenegger, Lukas; Mohn, Joachim

    2014-05-01

    Measurement of the four main N2O isotopic species (14N15N16O / 15N14N16O / 14N14N18O / 14N14N16O) has been suggested as a powerful tool to trace the biogeochemical cycle of N2O and to allocate its emission sources. Studies carried out with microbial pure cultures and mixed population systems (Wunderlin et al. 2012) allowed the determination of characteristic isotopic signatures for the most important production processes. These characteristic signatures have been applied to identify relevant sources at different scales (Park et al. 2012). However, current studies suffer from limited spatial and temporal resolution due to the combination of discrete flask sampling in conjunction with laboratory-based mass spectrometric analysis. We recently demonstrated that a quantum cascade laser (QCL) based absorption spectrometer is capable of simultaneously measuring the three main N2O isotopomers at trace levels (Waechter et al. 2008). Furthermore, its potential for in-situ measurements in conjunction with a liquid nitrogen-free preconcentration unit has been proven (Mohn et al. 2012). Here we present results from the first long-term field measurement campaign conducted on intensively managed grassland in central Switzerland during three months. A modified state-of-the-art laser spectrometer (Aerodyne Research, Inc.) employing a mid-infrared cw-QCL (4.54 μm) and a novel astigmatic multipass cell with 204 m optical path-length was connected to a N2O preconcentration unit. High analytical performance in combination with the applied calibration strategy resulted in excellent long-term precision of 0.20, 0.12 and 0.11o for δ15Nα, δ15Nβ and δ18O which was determined from repeated preconcentration and measurement of target gas from a compressed air tank. This instrumental setup allowed investigating responses of isotopic composition in soil-emitted N2O to management events and weather influences. The accompanying measurements of soil temperature, soil water content, ammonia

  8. Source of Nitrous Oxide Emissions during the Cow Manure Composting Process as Revealed by Isotopomer Analysis of and amoA Abundance in Betaproteobacterial Ammonia-Oxidizing Bacteria▿ †

    PubMed Central

    Maeda, Koki; Toyoda, Sakae; Shimojima, Ryosuke; Osada, Takashi; Hanajima, Dai; Morioka, Riki; Yoshida, Naohiro

    2010-01-01

    A molecular analysis of betaproteobacterial ammonia oxidizers and a N2O isotopomer analysis were conducted to study the sources of N2O emissions during the cow manure composting process. Much NO2−-N and NO3−-N and the Nitrosomonas europaea-like amoA gene were detected at the surface, especially at the top of the composting pile, suggesting that these ammonia-oxidizing bacteria (AOB) significantly contribute to the nitrification which occurs at the surface layer of compost piles. However, the 15N site preference within the asymmetric N2O molecule (SP = δ15Nα − δ15Nβ, where 15Nα and 15Nβ represent the 15N/14N ratios at the center and end sites of the nitrogen atoms, respectively) indicated that the source of N2O emissions just after the compost was turned originated mainly from the denitrification process. Based on these results, the reduction of accumulated NO2−-N or NO3−-N after turning was identified as the main source of N2O emissions. The site preference and bulk δ15N results also indicate that the rate of N2O reduction was relatively low, and an increased value for the site preference indicates that the nitrification which occurred mainly in the surface layer of the pile partially contributed to N2O emissions between the turnings. PMID:20048060

  9. Experimental and ab initio structure of BrNO2

    NASA Astrophysics Data System (ADS)

    Kwabia Tchana, F.; Orphal, J.; Kleiner, I.; Rudolph, H. D.; Willner, H.; Garcia, P.; Bouba, O.; Demaison, J.; Redlich, B.

    The ν2 fundamental bands of different isotopomers of BrNO2 (79Br15N16O2, 81Br15N16O2, 79Br14N18O2 and 79Br14N16O18O) located around 13 µm were recorded using high-resolution Fourier transform infrared spectrometry. More than 8000 lines of all these isotopomers were reproduced using a Watson-type A-reduced Hamiltonian with a root-mean-square deviation of better than 7 × 10-4 cm-1 for the four isotopomers. Rotational and centrifugal distortion constants for the ν2 = 1 states as well as for the vibrational ground states of these isotopomers were determined. For the first time, an analysis of the ground-state rotational constants obtained in this study combined with the constants obtained in our previous work on the ν2 bands of 79Br14N16O2 and 81Br14N16O2 has allowed us to calculate the rm structure of nitryl bromide. The structural parameters obtained were rm(Br-N) = 2.0118(16) Å, rm(N-O) = 1.1956(12) Å and α(O-N-O) = 131.02(12) Å. A new ab initio structure of nitryl bromide calculated at the CCSD(T)/SDB-aug-cc-pVQZ level of theory is presented and was found to be in fair agreement with the experimental structure.

  10. Lateral variation of H2O/K2O ratios in Quaternary Magma of the Northeastern Japan arc

    NASA Astrophysics Data System (ADS)

    Miyagi, I.

    2012-12-01

    Water plays a fundamental role in the magma genesis beneath subduction zones. In order to estimate a spatial distribution of the density of water flux in the wedge mantle of the Northeastern Japan arc, this study examines a lateral variation of pre-eruptive bulk rock H2O/K2O contents among volcanoes located both in the frontal and in back arc settings. The analytical targets are the frontal volcanoes Nigorikawa (N42.12 E140.45), Zenikame (N41.74 E140.85), Adachi (N38.22 E140.65), and Nanashigure (N40.07 E141.11), and the back arc ones Hijiori (N38.61 E140.17) and Kanpu (N39.93 E139.88). The bulk magmatic H2O content (TH2O) is calculated from a mass balance of hydrogen isotopic ratios among three phases in a batch of magma; dissolved water in melt, excess H2O vapor, and hydrous phenocrysts such as amphiboles (Miyagi and Matsubaya, 2003). Since the amount of H2O in hydrous phenocryst is negligible, the bulk magmatic H2O content can be written as TH2O = (30 XD CD) / (15 - dT + dMW), where dMW is the measured hydrogen isotopic ratio of hydrous phenocrysts, XD is a melt fraction of magma, CD is a water concentration of the melt, and dT is hydrogen isotopic ratios of a bulk magma (assumed to be -50 per-mil). Both XD and CD are estimated from bulk rock chemistry of the sample using the MELTS program (Ghiorso and Sack, 1995). Hydrogen isotopic fractionation factors are assumed to be -15 and -30 per-mil for vapor and hydrous mineral, and vapor and silicate melt, respectively. There observed a clear difference among the H2O/K2O ratios of bulk magmas from the frontal and back arc volcanoes. For instance higher H2O/K2O wt ratios was observed in the frontal volcanoes (Nigorikawa 5.3, Zenikame 11-12, Adachi 8-10, and Nanashigure 4-18), while lower H2O/K2O wt ratios was observed in the back arc ones (Kanpu 0-2.5 and Hijiori 1.4). The lateral variation of H2O/K2O ratios infer the higher water flux through the frontal side of wedge mantle, which can be a potential cause of the

  11. Site-selective nitrogen isotopic ratio measurement of nitrous oxide using a TE-cooled CW-RT-QCL based spectrometer.

    PubMed

    Li, Jingsong; Zhang, Lizhu; Yu, Benli

    2014-12-10

    The feasibility of laser spectroscopic isotopic composition measurements of atmospheric N2O was demonstrated, although making them useful will require further improvements. The system relies on a thermoelectrically (TE) cooled continuous-wave (CW) room temperature (RT) quantum cascade laser source emitting wavelength of around 4.6μm, where strong fundamental absorption bands occur for the considered specie and its isotopomers. The analysis technique is based on wavelength modulation spectroscopy with second-harmonic detection and the combination of long-path absorption cell. Primary laboratory tests have been performed to estimate the achievable detection limits and the signal reproducibility levels in view of possible measurements of (15)N/(14)N and (18)O/(16)O isotope ratios. The experiment results showed that the site-selective (15)N/(14)N ratio can be measured with a precision of 3‰ with 90s averaging time using natural-abundance N2O sample of 12.7ppm. Copyright © 2014 Elsevier B.V. All rights reserved.

  12. Detection of interstellar N2O: A new molecule containing an N-O bond

    NASA Technical Reports Server (NTRS)

    Ziurys, L. M.; Apponi, A. J.; Hollis, J. M.; Snyder, L. E.

    1994-01-01

    A new interstellar molecule, N2O, known as nitrous oxide or 'laughing gas,' has been detected using the NRAO 12 m telescope. The J = 3 - 2, 4 - 3, 5 - 4, and 6 - 5 rotational transitions of this species at 75, 100, 125, and 150 GHz, respectively, were observed toward Sgr B2(M). The column density derived for N2O in this source is N(sub tot) approx. 10(exp 15)/sq. cm, which corresponds to a fractional abundance of approx. 10(exp -9), relative to H2. This value implies abundance ratios of N2O/NO approx. 0.1 and N2O/HNO approx. 3 in the Galactic center. Such ratios are in excellent agreement with predictions of ion-molecule models of interstellar chemistry using early-time calculations and primarily neutral-neutral reactions. N2O is the third interstellar molecule detected thus far containing an N-O bond. Such bonds cannot be so rare as previously thought.

  13. Detection of interstellar N2O: A new molecule containing an N-O bond

    NASA Astrophysics Data System (ADS)

    Ziurys, L. M.; Apponi, A. J.; Hollis, J. M.; Snyder, L. E.

    1994-12-01

    A new interstellar molecule, N2O, known as nitrous oxide or 'laughing gas,' has been detected using the NRAO 12 m telescope. The J = 3 - 2, 4 - 3, 5 - 4, and 6 - 5 rotational transitions of this species at 75, 100, 125, and 150 GHz, respectively, were observed toward Sgr B2(M). The column density derived for N2O in this source is Ntot approx. 1015/sq. cm, which corresponds to a fractional abundance of approx. 10-9, relative to H2. This value implies abundance ratios of N2O/NO approx. 0.1 and N2O/HNO approx. 3 in the Galactic center. Such ratios are in excellent agreement with predictions of ion-molecule models of interstellar chemistry using early-time calculations and primarily neutral-neutral reactions. N2O is the third interstellar molecule detected thus far containing an N-O bond. Such bonds cannot be so rare as previously thought.

  14. Isotopomers as a method for differentiating between bacterial and fungal production of nitrous oxide

    NASA Astrophysics Data System (ADS)

    Sutka, R. L.; Adams, G.; Ostrom, N.; Ostrom, P.

    2007-12-01

    In order to study the importance of fungi to nitrous oxide (N2O) production in the environment it is critical to have a non-intrusive method for differentiating between fungal and bacterial N2O production. Site preference (SP), the difference in d15N between the central and outer N atoms in N2O, has been used to differentiate between bacterial nitrification and denitrification. In this study we compare the SP, d15N and d18O of N2O produced by the two best-studied fungal denitrifiers, Fusarium oxysporum and Cylindrocarpon tonkinense, to data from our previous bacterial studies. Both d18O and SP values remained fairly constant during the course of nitrite reduction which likely reflects isotopic exchange with water in the case of d18O and conservative behavior in SP that has been observed previously (Sutka et al., 2006). We observed a wide range of fractionation factors for fungal denitrification, -74.7 to -6.6 ‰, and non-linear behavior indicating that fractionation was controlled by more than one step. We interpret the small degree of fractionation as reflecting fractionation during diffusion and the more negative values as being controlled by enzymatic fractionation. Data from this and our previous study of bacterial production (Sutka et al., 2006) reveals that N2O produced via nitrification by fungi can be differentiated from N2O produced by bacterial denitrification primarily on the basis of d18O. The site preference of N2O produced by F. oxysporum and C. tonkinense was 37.1 ± 2.5 ‰ and 36.9 ± 2.8 ‰, respectively. These results indicate that isotopomers can be used as a basis for differentiating bacterial and fungal denitrification. Our work further reveals the role that fungal and bacterial nitric oxide reductases have in determining site preference during N2O production.

  15. The ratio of N(C18O) and AV in Chamaeleon I and III-B. Using 2MASS and SEST

    NASA Astrophysics Data System (ADS)

    Kainulainen, J.; Lehtinen, K.; Harju, J.

    2006-02-01

    We investigate the relationship between the C18O column density and the visual extinction in Chamaeleon I and in a part of the Chamaeleon III molecular cloud. The C18O column densities, N(C18O), are calculated from J=1{-}0 rotational line data observed with the SEST telescope. The visual extinctions, A_V, are derived using {JHK} photometry from the 2MASS survey and the NICER color excess technique. In contrast with the previous results of Hayakawa et al. (2001, PASJ, 53, 1109), we find that the average N(C18O)/AV ratios are similar in Cha I and Cha III, and lie close to values derived for other clouds, i.e. N(C18O) ≈ 2 × 1014 cm-2 ( AV - 2 ). We find, however, clear deviations from this average relationship towards individual clumps. Larger than average N(C18O)/AV ratios can be found in clumps associated with the active star forming region in the northern part of Cha I. On the other hand, some regions in the relatively quiescent southern part of Cha I show smaller than average N(C18O)/AV ratios and also very shallow proportionality between N(C18O) and A_V. The shallow proportionality suggests that C18O is heavily depleted in these regions. As the degree of depletion is proportional to the gas density, these regions probably contain very dense, cold cores, which do not stand out in CO mappings. A comparison with the dust temperature map derived from the ISO data shows that the most prominent of the potentially depleted cores indeed coincides with a dust temperature minimum. It seems therefore feasible to use N(C18O) and AV data together for identifying cold, dense cores in large scale mappings.

  16. Photocatalytic decomposition of N2O over TiO2/g-C3N4 photocatalysts heterojunction

    NASA Astrophysics Data System (ADS)

    Kočí, K.; Reli, M.; Troppová, I.; Šihor, M.; Kupková, J.; Kustrowski, P.; Praus, P.

    2017-02-01

    TiO2/g-C3N4 photocatalysts with the various TiO2/g-C3N4 weight ratios from 1:2 to 1:6 were fabricated by mechanical mixing in water suspension followed by calcination. Pure TiO2 was prepared by thermal hydrolysis and pure g-C3N4 was prepared from commercial melamine by thermal annealing at 620 °C. All the nanocomposites were characterized by X-ray powder diffraction, UV-vis diffuse reflectance spectroscopy, Raman spectroscopy, infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, photoelectrochemical measurements and nitrogen physisorption. The prepared mixtures along with pure TiO2 and g-C3N4 were tested for the photocatalytic decomposition of nitrous oxide under UVC (λ = 254 nm), UVA (λ = 365 nm) and Vis (λ > 400 nm) irradiation. The TiO2/g-C3N4 nanocomposites showed moderate improvement compared to pure g-C3N4 but pure TiO2 proved to be a better photocatalyst under UVC irradiation. However, under UVA irradiation conditions, the photocatalytic activity of TiO2/g-C3N4 (1:2) nanocomposite exhibited an increase compared to pure TiO2. Nevertheless, further increase of g-C3N4 amount leads/led to a decrease in reactivity. These results are suggesting the nanocomposite with the optimal weight ratio of TiO2 and g-C3N4 have shifted absorption edge energy towards longer wavelengths and decreased the recombination rate of charge carriers compared to pure g-C3N4. This is probably due to the generation of heterojunction on the TiO2/g-C3N4 interface.

  17. Distinguishing nitrous oxide production from nitrification and denitrification on the basis of isotopomer abundances.

    PubMed

    Sutka, R L; Ostrom, N E; Ostrom, P H; Breznak, J A; Gandhi, H; Pitt, A J; Li, F

    2006-01-01

    The intramolecular distribution of nitrogen isotopes in N2O is an emerging tool for defining the relative importance of microbial sources of this greenhouse gas. The application of intramolecular isotopic distributions to evaluate the origins of N2O, however, requires a foundation in laboratory experiments in which individual production pathways can be isolated. Here we evaluate the site preferences of N2O produced during hydroxylamine oxidation by ammonia oxidizers and by a methanotroph, ammonia oxidation by a nitrifier, nitrite reduction during nitrifier denitrification, and nitrate and nitrite reduction by denitrifiers. The site preferences produced during hydroxylamine oxidation were 33.5 +/- 1.2 per thousand, 32.5 +/- 0.6 per thousand, and 35.6 +/- 1.4 per thousand for Nitrosomonas europaea, Nitrosospira multiformis, and Methylosinus trichosporium, respectively, indicating similar site preferences for methane and ammonia oxidizers. The site preference of N2O from ammonia oxidation by N. europaea (31.4 +/- 4.2 per thousand) was similar to that produced during hydroxylamine oxidation (33.5 +/- 1.2 per thousand) and distinct from that produced during nitrifier denitrification by N. multiformis (0.1 +/- 1.7 per thousand), indicating that isotopomers differentiate between nitrification and nitrifier denitrification. The site preferences of N2O produced during nitrite reduction by the denitrifiers Pseudomonas chlororaphis and Pseudomonas aureofaciens (-0.6 +/- 1.9 per thousand and -0.5 +/- 1.9 per thousand, respectively) were similar to those during nitrate reduction (-0.5 +/- 1.9 per thousand and -0.5 +/- 0.6 per thousand, respectively), indicating no influence of either substrate on site preference. Site preferences of approximately 33 per thousand and approximately 0 per thousand are characteristic of nitrification and denitrification, respectively, and provide a basis to quantitatively apportion N2O.

  18. Stable δ15N and δ13C isotope ratios in aquatic ecosystems

    PubMed Central

    Wada, Eitaro

    2009-01-01

    In the past 20 years, rapid progress in stable isotope (SI) studies has allowed scientists to observe natural ecosystems from entirely new perspectives. This report addresses the fundamental concepts underlying the use of the SI ratio. The unique characteristics of the SI ratio make it an interdisciplinary parameter that acts as a chemical fingerprint of biogenic substances and provides a key to the world of isotopomers. Variations in SI ratios of biogenic substances depend on the isotopic compositions of reactants, the pathways and kinetic modes of reaction dynamics, and the physicochemical conditions. In fact, every biogenic material has its own isotopic composition, its “dynamic SI fingerprint”, which is governed by its function and position in the material flow. For example, the relative SI ratio in biota is determined by dietary lifestyle, e.g., the modes of drinking, eating, and excreting, and appears highly regular due to the physicochemical differences of isotopomers. Our primary goal here is to elucidate the general principals of isotope partitioning in major biophilic elements in molecules, biogenic materials, and ecosystems (Wada, E. et al., 1995). To this end, the nitrogen and carbon SI distribution ratios (δ15N and δ13C, respectively) are used to examine materials cycling, food web structures, and their variability in various kinds of watershed-including aquatic ecosystems to elucidate an “isotopically ordered world”. PMID:19282646

  19. Stratospheric N2O5, CH4, and N2O profiles from IR solar occultation spectra

    NASA Technical Reports Server (NTRS)

    Camy-Peyret, C.; Flaud, J.-M.; Perrin, A.; Rinsland, C. P.; Goldman, A.; Murcray, F. J.

    1993-01-01

    Stratospheric volume mixing ratio profiles of N2O5, CH4, and N2O have been retrieved from a set of 0.052/cm resolution (FWHM) solar occultation spectra recorded at sunrise during a balloon flight from Aire sur l'Adour, France (44 N latitude) on 12 October 1990. The N2O5 results have been derived from measurements of the integrated absorption by the 1246/cm band. Assuming a total intensity of 4.32 x 10 exp -17 cm/molecule/sq cm independent of temperature, the retrieved N2O5 volume mixing ratios in ppbv, interpolated to 2 km height spacings, are 1.64 +/- 0.49 at 37.5 km, 1.92 +/- 0.56 at 35.5 km, 2.06 +/- 0.47 at 33.5 km, 1.95 +/- 0.42 at 31.5 km, 1.60 +/- 0.33 at 29.5 km, 1.26 +/- 0.28 at 27.5 km, and 0.85 +/- 0.20 at 25.5 km. Error bars indicate the estimated 1-sigma uncertainty including the error in the total band intensity. The retrieved profiles are compared with previous measurements and photochemical model results.

  20. Evolution of N/O ratios in galaxies from cosmological hydrodynamical simulations

    NASA Astrophysics Data System (ADS)

    Vincenzo, Fiorenzo; Kobayashi, Chiaki

    2018-04-01

    We study the redshift evolution of the gas-phase O/H and N/O abundances, both (i) for individual ISM regions within single spatially-resolved galaxies and (ii) when dealing with average abundances in the whole ISM of many unresolved galaxies. We make use of a cosmological hydrodynamical simulation including detailed chemical enrichment, which properly takes into account the variety of different stellar nucleosynthetic sources of O and N in galaxies. We identify 33 galaxies in the simulation, lying within dark matter halos with virial mass in the range 1011 ≤ MDM ≤ 1013 M⊙ and reconstruct how they evolved with redshift. For the local and global measurements, the observed increasing trend of N/O at high O/H can be explained, respectively, (i) as the consequence of metallicity gradients which have settled in the galaxy interstellar medium, where the innermost galactic regions have the highest O/H abundances and the highest N/O ratios, and (ii) as the consequence of an underlying average mass-metallicity relation that galaxies obey as they evolve across cosmic epochs, where - at any redshift - less massive galaxies have lower average O/H and N/O ratios than the more massive ones. We do not find a strong dependence on the environment. For both local and global relations, the predicted N/O-O/H relation is due to the mostly secondary origin of N in stars. We also predict that the O/H and N/O gradients in the galaxy interstellar medium gradually flatten as functions of redshift, with the average N/O ratios being strictly coupled with the galaxy star formation history. Because N production strongly depends on O abundances, we obtain a universal relation for the N/O-O/H abundance diagram whether we consider average abundances of many unresolved galaxies put together or many abundance measurements within a single spatially-resolved galaxy.

  1. Evolution of N/O ratios in galaxies from cosmological hydrodynamical simulations

    NASA Astrophysics Data System (ADS)

    Vincenzo, Fiorenzo; Kobayashi, Chiaki

    2018-07-01

    We study the redshift evolution of the gas-phase O/H and N/O abundances, both (i) for individual interstellar medium (ISM) regions within single spatially resolved galaxies and (ii) when dealing with average abundances in the whole ISM of many unresolved galaxies. We make use of a cosmological hydrodynamical simulation including detailed chemical enrichment, which properly takes into account the variety of different stellar nucleosynthetic sources of O and N in galaxies. We identify 33 galaxies in the simulation, lying within dark matter haloes with virial mass in the range 1011 ≤ MDM ≤ 1013 M⊙ and reconstruct how they evolved with redshift. For the local and global measurements, the observed increasing trend of N/O at high O/H can be explained, respectively, (i) as the consequence of metallicity gradients that have settled in the galaxy ISM, where the innermost galactic regions have the highest O/H abundances and the highest N/O ratios, and (ii) as the consequence of an underlying average mass-metallicity relation that galaxies obey as they evolve across cosmic epochs, where - at any redshift - less massive galaxies have lower average O/H and N/O ratios than the more massive ones. We do not find a strong dependence on the environment. For both local and global relations, the predicted N/O-O/H relation is due to the mostly secondary origin of N in stars. We also predict that the O/H and N/O gradients in the galaxy ISM gradually flatten as functions of redshift, with the average N/O ratios being strictly coupled with the galaxy star formation history. Because N production strongly depends on O abundances, we obtain a universal relation for the N/O-O/H abundance diagram whether we consider average abundances of many unresolved galaxies put together or many abundance measurements within a single spatially resolved galaxy.

  2. Stratospheric N2O5, CH4, and N2O Profiles from IR Solar Occultation Spectra

    NASA Technical Reports Server (NTRS)

    Peyeret, C. Camy; Flaud, J.-M.; Perrin, A.; Rinsland, C. P.; Goldman, A.; Murcray, F. J.

    1993-01-01

    Stratospheric volume mixing ratio profiles of N2O5, CH4, and N2O have been retrieved from a set of 0.052/ cm resolution (FWHM) solar occultation spectra recorded at sunrise during a balloon flight from Aire sur I'Adour, France (44 deg N latitude) on 12 October 1990. The N2O5 results have been derived from measurements of the integrated absorption by the 1246/ cm band. Assuming a total intensity of 4.32 x 10(exp 17)cm(exp -1) molecule sq cm(exp -2) independent of temperature, the retrieved N2O5 volume mixing ratios in ppbv (parts per billion by volume, 10(exp -9)), interpolated to 2 km height spacings, are 1.64 +/- 0.49 at 37.5 km, 1.92 +/- 0.56 at 35.5 km, 2.06 +/- 0.47 at 33.5 km, 1.95 +/- 0.42 at 31.5 km, 1.60 +/- 0.33 at 29.5 km, 1.26 +/- 0.28 at 27.5 km, and 0.85 +/- 0.20 at 25.5 km. Error bars indicate the estimated I-sigma uncertainty including the error in the total band intensity (+/- 20% has been assumed). The retrieved profiles are compared with previous measurements and photochemical model results.

  3. N2/O2/H2 Dual-Pump Cars: Validation Experiments

    NASA Technical Reports Server (NTRS)

    OByrne, S.; Danehy, P. M.; Cutler, A. D.

    2003-01-01

    The dual-pump coherent anti-Stokes Raman spectroscopy (CARS) method is used to measure temperature and the relative species densities of N2, O2 and H2 in two experiments. Average values and root-mean-square (RMS) deviations are determined. Mean temperature measurements in a furnace containing air between 300 and 1800 K agreed with thermocouple measurements within 26 K on average, while mean mole fractions agree to within 1.6 % of the expected value. The temperature measurement standard deviation averaged 64 K while the standard deviation of the species mole fractions averaged 7.8% for O2 and 3.8% for N2, based on 200 single-shot measurements. Preliminary measurements have also been performed in a flat-flame burner for fuel-lean and fuel-rich flames. Temperature standard deviations of 77 K were measured, and the ratios of H2 to N2 and O2 to N2 respectively had standard deviations from the mean value of 12.3% and 10% of the measured ratio.

  4. The calibration of the intramolecular nitrogen isotope distribution in nitrous oxide measured by isotope ratio mass spectrometry.

    PubMed

    Westley, Marian B; Popp, Brian N; Rust, Terri M

    2007-01-01

    Two alternative approaches for the calibration of the intramolecular nitrogen isotope distribution in nitrous oxide using isotope ratio mass spectrometry have yielded a difference in the 15N site preference (defined as the difference between the delta15N of the central and end position nitrogen in NNO) of tropospheric N2O of almost 30 per thousand. One approach is based on adding small amounts of labeled 15N2O to the N2O reference gas and tracking the subsequent changes in m/z 30, 31, 44, 45 and 46, and this yields a 15N site preference of 46.3 +/- 1.4 per thousand for tropospheric N2O. The other involves the synthesis of N2O by thermal decomposition of isotopically characterized ammonium nitrate and yields a 15N site preference of 18.7 +/- 2.2 per thousand for tropospheric N2O. Both approaches neglect to fully account for isotope effects associated with the formation of NO+ fragment ions from the different isotopic species of N2O in the ion source of a mass spectrometer. These effects vary with conditions in the ion source and make it impossible to reproduce a calibration based on the addition of isotopically enriched N2O on mass spectrometers with different ion source configurations. These effects have a much smaller impact on the comparison of a laboratory reference gas with N2O synthesized from isotopically characterized ammonium nitrate. This second approach was successfully replicated and leads us to advocate the acceptance of the site preference value 18.7 +/- 2.2 per thousand for tropospheric N2O as the provisional community standard until further independent calibrations are developed and validated. We present a technique for evaluating the isotope effects associated with fragment ion formation and revised equations for converting ion signal ratios into isotopomer ratios. Copyright 2007 John Wiley & Sons, Ltd.

  5. Decreased N2O reduction by low soil pH causes high N2O emissions in a riparian ecosystem.

    PubMed

    Van den Heuvel, R N; Bakker, S E; Jetten, M S M; Hefting, M M

    2011-05-01

    Quantification of harmful nitrous oxide (N(2)O) emissions from soils is essential for mitigation measures. An important N(2)O producing and reducing process in soils is denitrification, which shows deceased rates at low pH. No clear relationship between N(2)O emissions and soil pH has yet been established because also the relative contribution of N(2)O as the denitrification end product decreases with pH. Our aim was to show the net effect of soil pH on N(2)O production and emission. Therefore, experiments were designed to investigate the effects of pH on NO(3)(-) reduction, N(2)O production and reduction and N(2) production in incubations with pH values set between 4 and 7. Furthermore, field measurements of soil pH and N(2)O emissions were carried out. In incubations, NO(3)(-) reduction and N(2) production rates increased with pH and net N(2)O production rate was highest at pH 5. N(2)O reduction to N(2) was halted until NO(3)(-) was depleted at low pH values, resulting in a built up of N(2)O. As a consequence, N(2)O:N(2) production ratio decreased exponentially with pH. N(2)O reduction appeared therefore more important than N(2)O production in explaining net N(2)O production rates. In the field, a negative exponential relationship for soil pH against N(2)O emissions was observed. Soil pH could therefore be used as a predictive tool for average N(2)O emissions in the studied ecosystem. The occurrence of low pH spots may explain N(2)O emission hotspot occurrence. Future studies should focus on the mechanism behind small scale soil pH variability and the effect of manipulating the pH of soils. © 2011 Blackwell Publishing Ltd.

  6. Gas entrapment and microbial N2O reduction reduce N2O emissions from a biochar-amended sandy clay loam soil

    PubMed Central

    Harter, Johannes; Guzman-Bustamante, Ivan; Kuehfuss, Stefanie; Ruser, Reiner; Well, Reinhard; Spott, Oliver; Kappler, Andreas; Behrens, Sebastian

    2016-01-01

    Nitrous oxide (N2O) is a potent greenhouse gas that is produced during microbial nitrogen transformation processes such as nitrification and denitrification. Soils represent the largest sources of N2O emissions with nitrogen fertilizer application being the main driver of rising atmospheric N2O concentrations. Soil biochar amendment has been proposed as a promising tool to mitigate N2O emissions from soils. However, the underlying processes that cause N2O emission suppression in biochar-amended soils are still poorly understood. We set up microcosm experiments with fertilized, wet soil in which we used 15N tracing techniques and quantitative polymerase chain reaction (qPCR) to investigate the impact of biochar on mineral and gaseous nitrogen dynamics and denitrification-specific functional marker gene abundance and expression. In accordance with previous studies our results showed that biochar addition can lead to a significant decrease in N2O emissions. Furthermore, we determined significantly higher quantities of soil-entrapped N2O and N2 in biochar microcosms and a biochar-induced increase in typical and atypical nosZ transcript copy numbers. Our findings suggest that biochar-induced N2O emission mitigation is based on the entrapment of N2O in water-saturated pores of the soil matrix and concurrent stimulation of microbial N2O reduction resulting in an overall decrease of the N2O/(N2O + N2) ratio. PMID:28008997

  7. Electron density diagnositc line ratios from the n = 3 lines of O v

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Widing, K.G.; Doyle, J.G.; Dufton, P.L.

    New atomic physic calculations are presented for electron excitation rates for transitions between the n = 2 and n = 3 levels of O v. These are used to calculate theoretical line intensity ratios for the 192 A, 215 A, 220 A and 248 A lines of O v. These line intensity ratios are electron density sensitive and provide valuable diagnostics at T/sub e/approx.2 x 10/sup 5/ K for samll impulsive flare events in which the transition zone ions are enhanced relative to the coronal ions. Two flares observed by NRL spectroheliograph on Skylab, on 1973 December 22 and 1974more » January 21, are studied, with electron densities of approximately 3 x 10/sup 11/ cm/sup -3/ being deduced.« less

  8. Uptake properties of Ni2+ by nCaO.Al2O3.2SiO2 (n=1-4) prepared from solid-state reaction of kaolinite and calcite.

    PubMed

    Jha, Vinay Kumar; Kameshima, Yoshikazu; Nakajima, Akira; Okada, Kiyoshi; MacKenzie, Kenneth J D

    2005-08-31

    A series of nCaO.Al2O3.2SiO2 samples (n=1-4) were prepared by solid-state reaction of mechanochemically treated mixtures of kaolinite and calcite fired at 600-1000 degrees C for 24 h. All the samples were X-ray amorphous after firing at 600-800 degrees C but had crystallized by 900 degrees C. The main crystalline phases were anorthite (n=1), gehlenite (n=2 and 3) and larnite (n=4). The uptake of Ni2+ by nCaO.Al2O3.2SiO2 samples fired at 800 and 900 degrees C was investigated at room temperature using solutions with initial Ni2+ concentrations of 0.1-50 mmol/l. Amorphous samples (fired at 800 degrees C) showed a higher Ni2+ uptake capacity than crystalline samples (fired at 900 degrees C). Ni2+ uptake was found to increase with increasing of CaO content. Amorphous 4CaO.Al2O3.2SiO2 showed the highest Ni2+ uptake capacity (about 9 mmol/g). The Ni2+ uptake abilities of the present samples are higher than those of other materials reported in the literature. Since the sorbed Ni2+/released Ca2+ ratios of these samples are close to unity, ion replacement of Ni2+ for Ca2+ is thought to be the principal mechanism of Ni2+ uptake by the present samples.

  9. Correlation between nitrous oxide (N2O) emission and carbon to nitrogen (COD/N) ratio in denitrification process: a mitigation strategy to decrease greenhouse gas emission and cost of operation.

    PubMed

    Andalib, Mehran; Taher, Edris; Donohue, Joseph; Ledwell, Sam; Andersen, Mikkel H; Sangrey, Karla

    2018-01-01

    The reliability and accuracy of in-situ ion selective electrode and ultraviolet (NO x ) probes have been investigated at four different treatment plants with different operational conditions. This study shows that the mentioned probes tend to compromise their accuracy and trending stability at lower NO x of <1.0 mg N/L, which if used as a measuring variable for PI feedback controller for denitrification (biological reduction of nitrate to nitrogen gas), would cause overfeeding the external carbon source. In-situ Clark-type N 2 O sensors, recently introduced for industrial scale use (Unisense Environment) could potentially open a new horizon in the automation of biological processes and particularly denitrification. To demonstrate the applicability of such probes for automation, two in-situ N 2 O probes were used in two treatment plants in parallel with NO x -N probes. The effects of operational conditions such as COD/N ratios and the correlation between NO x and N 2 O were investigated at those plants. N 2 O production at non-detect dissolved oxygen concentrations and pH of 7-7.2 were found to be a function of influent nitrogen load or the ratio of COD/N INFLUENT . Finally, using an N 2 O probe as a proxy sensor for nitrates is proposed as a measured variable in the PI feedback in the automation of the denitrification process with a NO x set point of <1.2 mg N/L).

  10. The denitrification paradox: The role of O2 in sediment N2O production

    NASA Astrophysics Data System (ADS)

    Barnes, Jonathan; Upstill-Goddard, Robert C.

    2018-01-01

    We designed a novel laboratory sediment flux chamber in which we maintained the headspace O2 partial pressure at preselected values, allowing us to experimentally regulate "in-situ" O2 to evaluate its role in net N2O production by an intertidal estuarine sediment (Tyne, UK). In short-term (30 h) incubations with 10 L of overlying estuarine water (∼3 cm depth) and headspace O2 regulation (headspace: sediment/water ratio ∼9:1), net N2O production was highest at 1.2% O2 (sub-oxic; 32.3 nmol N2O m-2 d-1), an order of magnitude higher than at either 0.0% (anoxic; 2.5 N2O nmol m-2 d-1) or 20.85% (ambient; 2.3 nmol N2O m-2 d-1) O2. In a longer-term sealed incubation (∼490 h) without O2 control, time-dependent behaviour of N2O in the tank headspace was highly non-linear with time, showing distinct phases: (i) an initial period of no or little change in O2 or N2O up to ∼ 100 h; (ii) a quasi-linear, inverse correlation between O2 and N2O to ∼360 h, in which O2 declined to ∼2.1% and N2O rose to ∼7800 natm; (iii) over the following 50 h a slower O2 decline, to ∼1.1%, and a more rapid N2O increase, to ∼12000 natm; (iv) over the next 24 h a slowed O2 decline towards undetectable levels and a sharp fall in N2O to ∼4600 natm; (iv) a continued N2O decrease at zero O2, to ∼3000 natm by ∼ 490 h. These results show clearly that rapid N2O consumption (∼115 nmol m-2 d-1), presumably via heterotrophic denitrification (HD), occurs under fully anoxic conditions and therefore that N2O production, which was optimal for sub-oxic O2, results from other nitrogen transformation processes. In experiments in which we amended sediment overlying water to either 1 mM NH4+ or 1 mM NO3-, N2O production rates were 2-134 nmol N2O m-2 d-1 (NH4+ addition) and 0.4-2.2 nmol N2O m-2 d-1 (NO3- addition). We conclude that processes involving NH4+ oxidation (nitrifier nitrification; nitrifier denitrification; nitrification-coupled denitrification) are principally responsible for N2O

  11. Production of N2O/+/ by reaction of metastable O2/+/ ions with N2

    NASA Technical Reports Server (NTRS)

    Ajello, J. M.; Rayermann, P.

    1975-01-01

    Photoionization mass spectrometry examination of the production of N2O(+) was undertaken to determine whether N2(+) or O2(+) ions are responsible for onset of N2O(+). It appears that the N2(+) ion does not contribute significantly to the production of N2O(+) in this experiment. Therefore, it is clear that excited O2(+) is responsible for the formation of N2O(+) near the appearance potential of these ions.

  12. Interactive effects of MnO2, organic matter and pH on abiotic formation of N2O from hydroxylamine in artificial soil mixtures.

    PubMed

    Liu, Shurong; Berns, Anne E; Vereecken, Harry; Wu, Di; Brüggemann, Nicolas

    2017-02-01

    Abiotic conversion of the reactive nitrification intermediate hydroxylamine (NH 2 OH) to nitrous oxide (N 2 O) is a possible mechanism of N 2 O formation during nitrification. Previous research has demonstrated that manganese dioxide (MnO 2 ) and organic matter (OM) content of soil as well as soil pH are important control variables of N 2 O formation in the soil. But until now, their combined effect on abiotic N 2 O formation from NH 2 OH has not been quantified. Here, we present results from a full-factorial experiment with artificial soil mixtures at five different levels of pH, MnO 2 and OM, respectively, and quantified the interactive effects of the three variables on the NH 2 OH-to-N 2 O conversion ratio (R NH2OH-to-N2O ). Furthermore, the effect of OM quality on R NH2OH-to-N2O was determined by the addition of four different organic materials with different C/N ratios to the artificial soil mixtures. The experiments revealed a strong interactive effect of soil pH, MnO 2 and OM on R NH2OH-to-N2O . In general, increasing MnO 2 and decreasing pH increased R NH2OH-to-N2O , while increasing OM content was associated with a decrease in R NH2OH-to-N2O . Organic matter quality also affected R NH2OH-to-N2O . However, this effect was not a function of C/N ratio, but was rather related to differences in the dominating functional groups between the different organic materials.

  13. Interactive effects of MnO2, organic matter and pH on abiotic formation of N2O from hydroxylamine in artificial soil mixtures

    NASA Astrophysics Data System (ADS)

    Liu, Shurong; Berns, Anne E.; Vereecken, Harry; Wu, Di; Brüggemann, Nicolas

    2017-02-01

    Abiotic conversion of the reactive nitrification intermediate hydroxylamine (NH2OH) to nitrous oxide (N2O) is a possible mechanism of N2O formation during nitrification. Previous research has demonstrated that manganese dioxide (MnO2) and organic matter (OM) content of soil as well as soil pH are important control variables of N2O formation in the soil. But until now, their combined effect on abiotic N2O formation from NH2OH has not been quantified. Here, we present results from a full-factorial experiment with artificial soil mixtures at five different levels of pH, MnO2 and OM, respectively, and quantified the interactive effects of the three variables on the NH2OH-to-N2O conversion ratio (RNH2OH-to-N2O). Furthermore, the effect of OM quality on RNH2OH-to-N2O was determined by the addition of four different organic materials with different C/N ratios to the artificial soil mixtures. The experiments revealed a strong interactive effect of soil pH, MnO2 and OM on RNH2OH-to-N2O. In general, increasing MnO2 and decreasing pH increased RNH2OH-to-N2O, while increasing OM content was associated with a decrease in RNH2OH-to-N2O. Organic matter quality also affected RNH2OH-to-N2O. However, this effect was not a function of C/N ratio, but was rather related to differences in the dominating functional groups between the different organic materials.

  14. Effect of SiO2/Al2O3 Ratio on Micro-Mesopore Formation for Pt/Beta-MCM-41 via NaOH Treatment and the Catalytic Performance in N-heptane Hydro isomerization

    NASA Astrophysics Data System (ADS)

    Gao, Li; Shi, Zhiyuan; Liu, Yingming; Zhao, Yuanshou; Liu, Qinghua; Xu, Chengguo; Bai, Peng; Yan, Zifeng

    2018-01-01

    Micro-mesoporous composite material Beta-MCM-41(BM) were hydrothermally synthesized by treating parent beta with molar SiO2/Al2O3 ratios of 12.5, 20 and 30 as precursors. The influence of SiO2/Al2O3 ratio of zeolite beta on effective micro-mesoporous composite formation was studied by investigating the crystallinity, morphology, chemical composition, acidity and textural property of Beta-MCM-41 through XRD, nitrogen adsorption, SEM, TEM, NH3-TPD, FTIR and Pyridine-FTIR. The catalytic performance was evaluated in terms of n-heptane hydro isomerization. The results demonstrated that Beta-MCM-41 supported Pt catalysts showed higher selectivity to isoheptanes than Pt/Beta. It was attributed to the superiorities of the pore structure and mesoporous accelerated the diffusion of larger molecules of isoheptanes.

  15. Determination of the thermal rate coefficient, products, and branching ratios for the reaction of O/+/ /D-2/ with N2

    NASA Technical Reports Server (NTRS)

    Torr, D. G.; Torr, M. R.

    1980-01-01

    Atmosphere Explorer-C satellite measurements are used to determine rate coefficients (RCs) for the following reactions: O(+)(D-2) + N2 yields N2(+) + O (reaction 1), O(+)(D-2) + N2 yields O(+)(S-4) + N2 (reaction 2), and O(+)(D-2) + N2 yields NO(+) + N (reaction 3). Results show the RC for reaction 1 to be 1 (plus 1 or minus 0.5) x 10 to the -10th cu cm per sec, for reaction 2 to be 3 (plus 1 or minus 2) x 10 to the -11th cu cm per sec, and 3 to be less than 5.5 x 10 to the -11th cu cm per sec. It is also found that the reaction of O(+)(D-2) with N2 does not constitute a detectable source of NO(+) ions in the thermosphere.

  16. Large Enhancements in the O/N2 Ratio in the Evening Sector of the Winter Hemisphere During Geomagnetic Storms

    NASA Technical Reports Server (NTRS)

    Burns, A. G.; Killeen, T. L.; Carignan, G. R.; Roble, R. G.

    1995-01-01

    In this paper, we have looked for enhancements of the O/N2 ratio in data measured by the Dynamics Explorer 2 (DE 2) satellite in the middle latitudes of the winter hemisphere, based on a prediction that was made by the National Center for Atmospheric Research thermosphere/tonosphere general circulation model (NCAR-TIGCM) that such increases occur. The NCAR-TIGCM predicts that these enhancements should be seen throughout the low latitude region and in many middle latitude locations, but that the enhancements in O/N2 are particularly strong in the middle-latitude, evening-to-midnight sector of the winter hemisphere. When this prediction was used to look for these effects in DE 2 NACS (neutral atmosphere composition spectrometer) data, large enhancements in the O/N2 ratio (approx. 50 to 90%) were seen. These enhancements were observed during the main phase of a storm that occurred on November 24, 1982, and were seen in the same region of the winter hemisphere predicted by the NCAR-TIGCM. They are partially the result of the depletion of N2 and, as electron loss is dependent on dissociative recombination at F(sub 2) altitudes, they have implications for electron densities in this area. Parcel trajectories, which have been followed through the NCAR-TIGCM history file for this event, show that large O/N2 enhancements occur in this limited region in the winter hemisphere for two reasons. First, these parcels of air are decelerated by the antisunward edge of the ion convection pattern; individual parcels converge and subsidence occurs. Thus molecular-nitrogen-poor air is brought from higher to lower heights. Because neutral parcels that are found a little poleward of the equatorial edge of the eveningside convection pattern are swept inward toward the center of the auroral oval, the enhancements occur only in a very limited range of latitudes. Second, nitrogen-poor air is transported from regions close to the magnetic pole in the winter hemisphere. During geomagnetic

  17. Detecting climate-change responses of plants and soil organic matter using isotopomers

    NASA Astrophysics Data System (ADS)

    Schleucher, Jürgen; Ehlers, Ina; Segura, Javier; Haei, Mahsa; Augusti, Angela; Köhler, Iris; Zuidema, Pieter; Nilsson, Mats; Öquist, Mats

    2015-04-01

    Responses of vegetation and soils to environmental changes will strongly influence future climate, and responses on century time scales are most important for feedbacks on the carbon cycle, climate models, prediction of crop productivity, and for adaptation to climate change. That plants respond to increasing CO2 on century time scales has been proven by changes in stomatal index, but very little is known beyond this. In soil, the complexity of soil organic matter (SOM) has hampered a sufficient understanding of the temperature sensitivity of SOM turnover. Here we present new stable isotope methodology that allows detecting shifts in metabolism on long time scales, and elucidating SOM turnover on the molecular level. Compound-specific isotope analysis measures isotope ratios of defined metabolites, but as average of the entire molecule. Here we demonstrate how much more detailed information can be obtained from analyses of intramolecular distributions of stable isotopes, so-called isotopomer abundances. As key tool, we use nuclear magnetic resonance (NMR) spectroscopy, which allows detecting isotope abundance with intramolecular resolution and without risk for isotope fractionation during analysis. Enzyme isotope fractionations create non-random isotopomer patterns in biochemical metabolites. At natural isotope abundance, these patterns continuously store metabolic information. We present a strategy how these patterns can be used as to extract signals on plant physiology, climate variables, and their interactions. Applied in retrospective analyses to herbarium samples and tree-ring series, we detect century-time-scale metabolic changes in response to increasing atmospheric CO2, with no evidence for acclimatory reactions by the plants. In trees, the increase in photosynthesis expected from increasing CO2 ("CO2 fertilization) was diminished by increasing temperatures, which resolves the discrepancy between expected increases in photosynthesis and commonly observed

  18. Organic-Free, ZnO-Assisted Synthesis of Zeolite FAU with Tunable SiO2 /Al2 O3 Molar Ratio.

    PubMed

    Guo, Ya; Sun, Tianjun; Gu, Yiming; Liu, Xiaowei; Ke, Quanli; Wang, Shudong

    2018-05-04

    Zeolite FAU with tunable SiO 2 /Al 2 O 3 molar ratio has been successfully synthesized in the absence of organic structure-directing agents (OSDA). Specifically, the addition of zinc species contributes to the feasible and effective adjustment of the framework SiO 2 /Al 2 O 3 molar ratio between about 4 and 6 depending on the amount of zinc species added in the batch composition. In contrast, a typical OSDA such as tetramethylammonium hydroxide (TMAOH) has a limited effect on the SiO 2 /Al 2 O 3 molar ratio of the zeolite. The role of zinc species is essential for the crystallization of zeolite FAU with a higher SiO 2 /Al 2 O 3 molar ratio under the particular synthesis conditions. It is speculated that zinc species may suppress the incorporation of aluminum into the aluminosilicate framework, which is due to the Coulombic repulsive interaction. A higher SiO 2 /Al 2 O 3 molar ratio is also found to be accompanied by a lower CO 2 adsorption heat for CO 2 /CH 4 separation. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. New observations of stratospheric N2O5

    NASA Technical Reports Server (NTRS)

    Rinsland, C. P.; Toon, G. C.; Farmer, C. B.; Norton, R. H.; Namkung, J. S.

    1989-01-01

    The unequivocal detection of N2O5 in the stratosphere was reported by Toon et al. based on measurements of the absorption by the N2O5 bands at 1246 and 1720/cm in solar occulation spectra recorded at sunrise near 47 S latitude by the Atmospheric Trace Molecule Spectroscopy (ATMOS) experiment during the Spacelab 3 (SL3) shuttle mission. Additional measurements and analysis of stratospheric N2O5 derived from the ATMOS/SL3 spectra are reported. The primary results are the detection and measurement of N2O5 absorption at sunset in the lower stratosphere, the inversion of a precise (approximately 10 percent) N2O5 sunrise vertical distribution between 25.5 and 37.5 km altitude, and the identification and measurement of absorption by the N2O5 743/cm band at sunrise. Assuming 4.32 x 10(sup -17) and 4.36 x 10(sup -17)/cm/molecule/sq cm respectively for the integrated intensities of the 1246 and 743/cm bands at stratospheric temperatures, retrieved volume mixing ratios in parts per billion by volume (ppbv) at sunrise (47 S latitude) are 1.32 + or - 0.34 at 37.5 km, 1.53 + or - 0.35 at 35.5 km, 1.63 + or - 0.36 at 33.5 km, 1.60 + or - 0.34 at 31.5 km, 1.43 + or - 0.30 at 29.5 km, 1.15 + or - 0.24 at 27.5 km, and 0.73 + or - 0.15 at 25.5 km. Retrieved VMRs in ppbv at sunset (30 N latitude) are 0.13 + or - 0.05 at 29.5 km, 0.14 + or - 0.05 at 27.5 km, and 0.10 + or - 0.04 at 25.5 km. Quoted error limits (1 sigma) include the error in the assumed band intensities (approximately 20 percent). Within the error limits of the measurements, the inferred mixing ratios at sunrise agree with diurnal photochemical model predictions obtained by two groups using current photochemical data. The measured mixing ratios at sunset are lower than the model predictions with differences of about a factor of 2 at 25 km altitude.

  20. Effect of CaO on the selectivity of N2O decomposition products: A combined experimental and DFT study

    NASA Astrophysics Data System (ADS)

    Wu, Lingnan; Hu, Xiaoying; Qin, Wu; Gao, Pan; Dong, Changqing; Yang, Yongping

    2016-09-01

    The effect of CaO on N2O decomposition and the selectivity of its decomposition products (NO and N2) was investigated using a fixed-bed flow reactor with varying temperatures from 317 °C to 947 °C. The selectivity of NO from CaO-catalyzed N2O decomposition is much lower than the N2 selectivity with the N2/NO products ratio greater than 12.1. Compared to N2O homogeneous decomposition with the minimum N2/NO products ratio of 6.2 at 718 °C, CaO also decreases the NO selectivity from 718 °C to 947 °C. Density functional theory calculations provide possible N2O decomposition routes on the CaO (1 0 0) surface considering both N2 and NO as N2O decomposition products. The N2 formation route is more favorable than the NO formation route in terms of energy barrier and reaction energy, and NO formation on the CaO (1 0 0) surface is likely to proceed via N2O + Osurf2- → N2 + O2 , surf2- and N2O + O2 , surf2- → 2NO + Osurf2-.

  1. Phylogenetic and functional potential links pH and N2O emissions in pasture soils.

    PubMed

    Samad, Md Sainur; Biswas, Ambarish; Bakken, Lars R; Clough, Timothy J; de Klein, Cecile A M; Richards, Karl G; Lanigan, Gary J; Morales, Sergio E

    2016-10-26

    Denitrification is mediated by microbial, and physicochemical, processes leading to nitrogen loss via N 2 O and N 2 emissions. Soil pH regulates the reduction of N 2 O to N 2 , however, it can also affect microbial community composition and functional potential. Here we simultaneously test the link between pH, community composition, and the N 2 O emission ratio (N 2 O/(NO + N 2 O + N 2 )) in 13 temperate pasture soils. Physicochemical analysis, gas kinetics, 16S rRNA amplicon sequencing, metagenomic and quantitative PCR (of denitrifier genes: nirS, nirK, nosZI and nosZII) analysis were carried out to characterize each soil. We found strong evidence linking pH to both N 2 O emission ratio and community changes. Soil pH was negatively associated with N 2 O emission ratio, while being positively associated with both community diversity and total denitrification gene (nir &nos) abundance. Abundance of nosZII was positively linked to pH, and negatively linked to N 2 O emissions. Our results confirm that pH imposes a general selective pressure on the entire community and that this results in changes in emission potential. Our data also support the general model that with increased microbial diversity efficiency increases, demonstrated in this study with lowered N 2 O emission ratio through more efficient conversion of N 2 O to N 2 .

  2. Phylogenetic and functional potential links pH and N2O emissions in pasture soils

    NASA Astrophysics Data System (ADS)

    Samad, M. D. Sainur; Biswas, Ambarish; Bakken, Lars R.; Clough, Timothy J.; de Klein, Cecile A. M.; Richards, Karl G.; Lanigan, Gary J.; Morales, Sergio E.

    2016-10-01

    Denitrification is mediated by microbial, and physicochemical, processes leading to nitrogen loss via N2O and N2 emissions. Soil pH regulates the reduction of N2O to N2, however, it can also affect microbial community composition and functional potential. Here we simultaneously test the link between pH, community composition, and the N2O emission ratio (N2O/(NO + N2O + N2)) in 13 temperate pasture soils. Physicochemical analysis, gas kinetics, 16S rRNA amplicon sequencing, metagenomic and quantitative PCR (of denitrifier genes: nirS, nirK, nosZI and nosZII) analysis were carried out to characterize each soil. We found strong evidence linking pH to both N2O emission ratio and community changes. Soil pH was negatively associated with N2O emission ratio, while being positively associated with both community diversity and total denitrification gene (nir & nos) abundance. Abundance of nosZII was positively linked to pH, and negatively linked to N2O emissions. Our results confirm that pH imposes a general selective pressure on the entire community and that this results in changes in emission potential. Our data also support the general model that with increased microbial diversity efficiency increases, demonstrated in this study with lowered N2O emission ratio through more efficient conversion of N2O to N2.

  3. Phylogenetic and functional potential links pH and N2O emissions in pasture soils

    PubMed Central

    Samad, M. d. Sainur; Biswas, Ambarish; Bakken, Lars R.; Clough, Timothy J.; de Klein, Cecile A. M.; Richards, Karl G.; Lanigan, Gary J.; Morales, Sergio E.

    2016-01-01

    Denitrification is mediated by microbial, and physicochemical, processes leading to nitrogen loss via N2O and N2 emissions. Soil pH regulates the reduction of N2O to N2, however, it can also affect microbial community composition and functional potential. Here we simultaneously test the link between pH, community composition, and the N2O emission ratio (N2O/(NO + N2O + N2)) in 13 temperate pasture soils. Physicochemical analysis, gas kinetics, 16S rRNA amplicon sequencing, metagenomic and quantitative PCR (of denitrifier genes: nirS, nirK, nosZI and nosZII) analysis were carried out to characterize each soil. We found strong evidence linking pH to both N2O emission ratio and community changes. Soil pH was negatively associated with N2O emission ratio, while being positively associated with both community diversity and total denitrification gene (nir & nos) abundance. Abundance of nosZII was positively linked to pH, and negatively linked to N2O emissions. Our results confirm that pH imposes a general selective pressure on the entire community and that this results in changes in emission potential. Our data also support the general model that with increased microbial diversity efficiency increases, demonstrated in this study with lowered N2O emission ratio through more efficient conversion of N2O to N2. PMID:27782174

  4. High/variable mixture ratio O2/H2 engine

    NASA Technical Reports Server (NTRS)

    Adams, A.; Parsley, R. C.

    1988-01-01

    Vehicle/engine analysis studies have identified the High/Dual Mixture Ratio O2/H2 Engine cycle as a leading candidate for an advanced Single Stage to Orbit (SSTO) propulsion system. This cycle is designed to allow operation at a higher than normal O/F ratio of 12 during liftoff and then transition to a more optimum O/F ratio of 6 at altitude. While operation at high mixture ratios lowers specific impulse, the resultant high propellant bulk density and high power density combine to minimize the influence of atmospheric drag and low altitude gravitational forces. Transition to a lower mixture ratio at altitude then provides improved specific impulse relative to a single mixture ratio engine that must select a mixture ratio that is balanced for both low and high altitude operation. This combination of increased altitude specific impulse and high propellant bulk density more than offsets the compromised low altitude performance and results in an overall mission benefit. Two areas of technical concern relative to the execution of this dual mixture ratio cycle concept are addressed. First, actions required to transition from high to low mixture ratio are examined, including an assessment of the main chamber environment as the main chamber mixture ratio passes through stoichiometric. Secondly, two approaches to meet a requirement for high turbine power at high mixture ratio condition are examined. One approach uses high turbine temperature to produce the power and requires cooled turbines. The other approach incorporates an oxidizer-rich preburner to increase turbine work capability via increased turbine mass flow.

  5. Determination of the ortho to para ratio of H2Cl+ and H2O+ from submillimeter observations.

    PubMed

    Gerin, Maryvonne; de Luca, Massimo; Lis, Dariusz C; Kramer, Carsten; Navarro, Santiago; Neufeld, David; Indriolo, Nick; Godard, Benjamin; Le Petit, Franck; Peng, Ruisheng; Phillips, Thomas G; Roueff, Evelyne

    2013-10-03

    The opening of the submillimeter sky with the Herschel Space Observatory has led to the detection of new interstellar molecular ions, H2O(+), H2Cl(+), and HCl(+), which are important intermediates in the synthesis of water vapor and hydrogen chloride. In this paper, we report new observations of H2O(+) and H2Cl(+) performed with both Herschel and ground-based telescopes, to determine the abundances of their ortho and para forms separately and derive the ortho-to-para ratio. At the achieved signal-to-noise ratio, the observations are consistent with an ortho-to-para ratios of 3 for both H2O(+) and H2Cl(+), in all velocity components detected along the lines-of-sight to the massive star-forming regions W31C and W49N. We discuss the mechanisms that contribute to establishing the observed ortho-to-para ratio and point to the need for a better understanding of chemical reactions, which are important for establishing the H2O(+) and H2Cl(+) ortho-to-para ratios.

  6. Investigation of the N2O emission strength in the U. S. Corn Belt

    NASA Astrophysics Data System (ADS)

    Fu, Congsheng; Lee, Xuhui; Griffis, Timothy J.; Dlugokencky, Edward J.; Andrews, Arlyn E.

    2017-09-01

    Nitrous oxide (N2O) has a high global warming potential and depletes stratospheric ozone. The U. S. Corn Belt plays an important role in the global anthropogenic N2O budget. To date, studies on local surface N2O emissions and the atmospheric N2O budget have commonly used Lagrangian models. In the present study, we used an Eulerian model - Weather Research and Forecasting Chemistry (WRF-Chem) model to investigate the relationships between N2O emissions in the Corn Belt and observed atmospheric N2O mixing ratios. We derived a simple equation to relate the emission strengths to atmospheric N2O mixing ratios, and used the derived equation and hourly atmospheric N2O measurements at the KCMP tall tower in Minnesota to constrain agricultural N2O emissions. The modeled spatial patterns of atmospheric N2O were evaluated against discrete observations at multiple tall towers in the NOAA flask network. After optimization of the surface flux, the model reproduced reasonably well the hourly N2O mixing ratios monitored at the KCMP tower. Agricultural N2O emissions in the EDGAR42 database needed to be scaled up by 19.0 to 28.1 fold to represent the true emissions in the Corn Belt for June 1-20, 2010 - a peak emission period. Optimized mean N2O emissions were 3.00-4.38, 1.52-2.08, 0.61-0.81 and 0.56-0.75 nmol m- 2 s- 1 for June 1-20, August 1-20, October 1-20 and December 1-20, 2010, respectively. The simulated spatial patterns of atmospheric N2O mixing ratios after optimization were in good agreement with the NOAA discrete observations during the strong emission peak in June. Such spatial patterns suggest that the underestimate of emissions using IPCC (Inter-governmental Panel on Climate Change) inventory methodology is not dependent on tower measurement location.

  7. Selective Encaging of N2O in N2O-N2 Binary Gas Hydrates via Hydrate-Based Gas Separation.

    PubMed

    Yang, Youjeong; Shin, Donghoon; Choi, Seunghyun; Woo, Yesol; Lee, Jong-Won; Kim, Dongseon; Shin, Hee-Young; Cha, Minjun; Yoon, Ji-Ho

    2017-03-21

    The crystal structure and guest inclusion behaviors of nitrous oxide-nitrogen (N 2 O-N 2 ) binary gas hydrates formed from N 2 O/N 2 gas mixtures are determined through spectroscopic analysis. Powder X-ray diffraction results indicate that the crystal structure of all the N 2 O-N 2 binary gas hydrates is identified as the structure I (sI) hydrate. Raman spectra for the N 2 O-N 2 binary gas hydrate formed from N 2 O/N 2 (80/20, 60/40, 40/60 mol %) gas mixtures reveal that N 2 O molecules occupy both large and small cages of the sI hydrate. In contrast, there is a single Raman band of N 2 O molecules for the N 2 O-N 2 binary gas hydrate formed from the N 2 O/N 2 (20/80 mol %) gas mixture, indicating that N 2 O molecules are trapped in only large cages of the sI hydrate. From temperature-dependent Raman spectra and the Predictive Soave-Redlich-Kwong (PSRK) model calculation, we confirm the self-preservation of N 2 O-N 2 binary gas hydrates in the temperature range of 210-270 K. Both the experimental measurements and the PSRK model calculations demonstrate the preferential occupation of N 2 O molecules rather than N 2 molecules in the hydrate cages, leading to a possible process for separating N 2 O from gas mixtures via hydrate formation. The phase equilibrium conditions, pseudo-pressure-composition (P-x) diagram, and gas storage capacity of N 2 O-N 2 binary gas hydrates are discussed in detail.

  8. Wetlands and Agriculture in Africa: Major Sources of N2O?

    NASA Astrophysics Data System (ADS)

    Gettel, G. M.

    2015-12-01

    Papyrus wetlands in East Africa are rapidly being converted to agricultural production in an effort to increase food security. This conversion is often seasonal, with wetlands being used for grazing and crop production of maize, sugarcane, and rice during dry seasons, and flooding occurring during wet seasons. An important question with respect to greenhouse gas production is whether wetland conversion to agriculture increases N2O fluxes. This trend has been shown in temperate regions where increased N2O fluxes are positively related to low soil C:N ratios, especially when soil moisture content remains high. In order to examine whether denitrification contributes to N2O flux, we measured potential denitrification rates (PDR by acetylene block method) in intact papyrus wetlands and agricultural converted wetlands in Kenya, Tanzania, Uganda, and Rwanda, and also performed multivariate analysis to relate soil characteristics to PDR. Agricultural land-cover types included maize, sugarcane, rice, and grazing. Results showed that intact wetlands are potentially important sources of N2O, as PDR in papyrus vegetation were consistently the highest (p<0.05; 128 - 601 μg N2O g DW-1 hour-1) while grazing sites showed the lowest (0.1 - 0.5 μg N2O g DW-1 hour-1). Rates were second highest in rice fields (2.3 - 303 μg N2O g DW-1 hour-1), and intermediate in maize and sugarcane (6.5 - 75 μmg N2O g DW-1 hour-1 and 5 - 30 μg N2O g DW-1 hour-1 respectively). PDR across all sites was inversely related to soil C:N ratio, with nitrate consistently limiting PDR in the wetland sites while soil carbon limited PDR in agricultural sites. This is seemingly in contrast with other findings that show that lower C:N ratios result in high N2O fluxes from drained wetland sites. However, flux measurements along with more realistic process-based measurements of denitrification are urgently needed to more fully understand the effect of agricultural conversion of wetlands in East Africa.

  9. Synthesis of Nanoscale CaO-Al2O3-SiO2-H2O and Na2O-Al2O3-SiO2-H2O Using the Hydrothermal Method and Their Characterization

    PubMed Central

    Yang, Jingbin; Li, Dongxu; Fang, Yuan

    2017-01-01

    C-A-S-H (CaO-Al2O3-SiO2-H2O) and N-A-S-H (Na2O-Al2O3-SiO2-H2O) have a wide range of chemical compositions and structures and are difficult to separate from alkali-activated materials. Therefore, it is difficult to analyze their microscopic properties directly. This paper reports research on the synthesis of C-A-S-H and N-A-S-H particles with an average particle size smaller than 300 nm by applying the hydrothermal method. The composition and microstructure of the products with different CaO(Na2O)/SiO2 ratios and curing conditions were characterized using XRD, the RIR method, FTIR, SEM, TEM, and laser particle size analysis. The results showed that the C-A-S-H system products with a low CaO/SiO2 ratio were mainly amorphous C-A-S-H gels. With an increase in the CaO/SiO2 ratio, an excess of Ca(OH)2 was observed at room temperature, while in a high-temperature reaction system, katoite, C4AcH11, and other crystallized products were observed. The katoite content was related to the curing temperature and the content of Ca(OH)2 and it tended to form at a high-temperature and high-calcium environment, and an increase in the temperature renders the C-A-S-H gels more compact. The main products of the N-A-S-H system at room temperature were amorphous N-A-S-H gels and a small amount of sodalite. An increase in the curing temperature promoted the formation of the crystalline products faujasite and zeolite-P. The crystallization products consisted of only zeolite-P in the high-temperature N-A-S-H system and its content were stable above 70%. An increase in the Na2O/SiO2 ratio resulted in more non-bridging oxygen and the TO4 was more isolated in the N-A-S-H structure. The composition and microstructure of the C-A-S-H and N-A-S-H system products synthesized by the hydrothermal method were closely related to the ratio of the raw materials and the curing conditions. The results of this study increase our understanding of the hydration products of alkali-activated materials. PMID

  10. O2 Herzberg State Reaction with N2: A Possible Source of Stratospheric N2O

    NASA Technical Reports Server (NTRS)

    Slanger, Tom G.; Copeland, Richard A.

    1997-01-01

    The goal of this one-year investigation was to determine whether N2O is formed in atmospherically significant quantities by the reaction of vibrationally excited levels of the O2((A3 Sigma(sub u)(sup +)) state with nitrogen. O2(A3 Sigma(sub u)(sup +)) is made throughout the upper stratosphere in considerable amounts by solar photoabsorption, and only a very small reactive yield is necessary for this mechanism to be a major N2O source. By long-term 245-252 nm irradiation of O2/N2 mixtures on- and off-resonance with absorption lines in the O2(A3 Sigma(sub u)(sup +) - X3 Sigma(sub g)(sup -)) transition, followed by N2O analysis by frequency-modulated diode laser absorption spectroscopy, we determined an upper limit for the N2O yield of the candidate reaction. This limit, 3 x 10(exp -5), eliminates O2(A3 Sigma(sub u)(sup +)) + N2 as a significant channel for the generation of stratospheric N2O. In further measurements, we established that N2O is stable under our photolysis conditions, showing that the small amounts of ozone generated from the reaction of O2(A) and O2 do not indirectly lead to destruction of N2O.

  11. N and O isotope (δ15 Nα , δ15 Nβ , δ18 O, δ17 O) analyses of dissolved NO3- and NO2- by the Cd-azide reduction method and N2 O laser spectrometry.

    PubMed

    Wassenaar, Leonard I; Douence, Cedric; Altabet, Mark A; Aggarwal, Pradeep K

    2018-02-15

    The nitrogen and oxygen (δ 15 N, δ 18 O, δ 17 O) isotopic compositions of NO 3 - and NO 2 - are important tracers of nutrient dynamics in soil, rain, groundwater and oceans. The Cd-azide method was used to convert NO 3 - or NO 2 - to N 2 O for N and triple-O isotopic analyses by N 2 O laser spectrometry. A protocol for laser-based headspace isotope analyses was compared with isotope ratio mass spectrometry. Lasers provide the ability to directly measure 17 O anomalies which can help discern atmospheric N sources. δ 15 N, δ 18 O and δ 17 O values were measured on N/O stable isotopic reference materials (IAEA, USGS) by conversion to N 2 O using the Cd-azide method and headspace N 2 O laser spectrometry. A 15 N tracer test assessed the position-specific routing of N to the α or β positions in the N 2 O molecule. A data processing algorithm was used to correct for isotopic dependencies on N 2 O concentration, cavity pressure and water content. NO 3 - /NO 2 - nitrogen is routed to the 15 N α position of N 2 O in the azide reaction; hence the δ 15 N α value should be used for N 2 O laser spectrometry results. With corrections for cavity pressure, N 2 O concentration and water content, the δ 15 N α AIR , δ 18 O VSMOW and δ 17 O VSMOW values (‰) of international reference materials were +4.8 ± 0.1, +25.9 ± 0.3, +12.7 ± 0.2 (IAEA NO 3 ), -1.7 ± 0.1, -26.8 ± 0.8, -14.4 ± 1.1 (USGS34) and +2.6 ± 0.1, +57.6 ± 1.2, +51.2 ± 2.0 (USGS35), in agreement with their values and with the isotope ratio mass spectrometry results. The 17 O excess for USGS35 was +21.2 ± 9‰, in good agreement with previous results. The Cd-azide method yielded excellent results for routine determination of δ 15 N, δ 18 O and δ 17 O values (and the 17 O excess) of nitrate or nitrite by laser spectrometry. Disadvantages are the toxicity of Cd-azide chemicals and the lack of automated sampling devices for N 2 O laser spectrometers. The 15 N-enriched tracer test revealed potential

  12. Phase Equilibria in the System "FeO"-CaO-SiO2-Al2O3-MgO at Different CaO/SiO2 Ratios

    NASA Astrophysics Data System (ADS)

    Jang, Kyoung-oh; Ma, Xiaodong; Zhu, Jinming; Xu, Haifa; Wang, Geoff; Zhao, Baojun

    2017-06-01

    The "FeO"-containing slags play an important role in the operation of an ironmaking blast furnace (BF), in particular the primary slags such as the system "FeO"-CaO-SiO2-Al2O3-2 mass pct MgO with CaO/SiO2 weight ratios of 1.3, 1.5, and 1.8 saturated with metallic iron. To investigate the characteristics of such a slag system and its behavior in BF, the phase equilibria and liquidus temperatures in the slag system have been experimentally determined using the high-temperature equilibration and quenching technique followed by an electron probe X-ray microanalysis (EPMA). Isotherms between 1553 K and 1603 K (1280 °C and 1330 °C) were determined in the primary phase fields of dicalcium silicate, melilite, spinel, and monoxide [(Mg,Fe2+)O]. Pseudo-ternary phase diagrams of (CaO + SiO2)-Al2O3-"FeO" with a fixed MgO concentration at 2 mass pct and at CaO/SiO2 ratios of 1.3, 1.5, and 1.8 have been discussed, respectively, simplifying the complexity of the slag system for easy understanding and applying in BF operation. It was found that the liquidus temperatures increase in melilite and spinel primary phase fields, but decrease in dicalcium silicate and monoxide primary phase fields with increasing Al2O3/(CaO + SiO2) ratio. In addition, the liquidus temperatures decrease with increasing "FeO" concentration in dicalcium silicate and melilite primary phase fields, while showing an increasing trend in the spinel and monoxide primary phase fields. The data resulted from this study can be used to improve and optimize currently available database of thermodynamic models used in FactSage.

  13. Detection of stratospheric N2O5 by infrared remote sounding

    NASA Technical Reports Server (NTRS)

    Toon, G. C.; Farmer, C. B.; Norton, R. H.

    1986-01-01

    Measurements of N2O5 absorption (1230 and 1260 per cm) in infrared spectra were carried out using the Atmospheric Trace Molecule Spectroscopy (ATMOS) instruments on board Spacelab 3. The detection of stratospheric N2O5, a temporary reservoir species whose photolysis products catalyze ozone destruction, was confirmed. Preliminary analysis of spectra recorded at sunrise on 1 May 1985 indicates a peak volume mixing ratio of 1.6 x 10 the -9th at 35 km an altitude of 35 km, or a broad concentration peak pf 4 x 10 to the 8th molecules per cu cm between 21 and 35 km. Absorption was not detected in spectra measured at sunset due to the depletion of N2O5 by photolysis during the day. The volume mixing ratio profile of N2O5 between 0 and 75 km altitude is reproduced in graphic form.

  14. Effects of Carbon and Cover Crop Residues on N2O and N2 Emissions

    NASA Astrophysics Data System (ADS)

    Burger, M.; Cooperman, Y.; Horwath, W. R.

    2016-12-01

    In Mediterranean climate, nitrous oxide emissions occurring with the first rainfall after the dry summer season can contribute up to 50% of agricultural systems' total annual emissions, but the drivers of these emissions have not been clearly identified, and there are only few measurements of atmospheric nitrogen (N2) production (denitrification) during these events. In lab incubations, we investigated N2O and N2 production, gross ammonification and nitrification, and microbial N immobilization with wet-up in soil from a vineyard that was previously fallow or where cover crop residue had been incorporated the previous spring. Before the first rainfall, we measured 120 mg dissolved organic carbon (DOC-C) kg-1 soil in the 0-5 cm layer of this vineyard, and after the rain 10 mg DOC-C kg-1, while nitrate levels before the rain were <5 mg N kg-1 in fallow and <10 mg N kg-1 in previously cover cropped soil. The N2O/N2 production was 2, 7, 9, and 86% in fallow, legume-grass mixture, rye, and legume cover cropped soil. The N2O/N2 ratio tended to increase with lower DOC (post-rain) levels in the soil. The results suggest that accumulated carbon in dry surface soil is the main driving factor of N2O and N2 emissions through denitrification with the first rainfall after prolonged dry periods.

  15. Vibrational spectroscopy of NO + (H2O)n: Evidence for the intracluster reaction NO + (H2O)n --> H3O + (H2O)n - 2 (HONO) at n => 4

    NASA Astrophysics Data System (ADS)

    Choi, Jong-Ho; Kuwata, Keith T.; Haas, Bernd-Michael; Cao, Yibin; Johnson, Matthew S.; Okumura, Mitchio

    1994-05-01

    Infrared spectra of mass-selected clusters NO+(H2O)n for n=1 to 5 were recorded from 2700 to 3800 cm-1 by vibrational predissociation spectroscopy. Vibrational frequencies and intensities were also calculated for n=1 and 2 at the second-order Møller-Plesset (MP2) level, to aid in the interpretation of the spectra, and at the singles and doubles coupled cluster (CCSD) level energies of n=1 isomers were computed at the MP2 geometries. The smaller clusters (n=1 to 3) were complexes of H2O ligands bound to a nitrosonium ion NO+ core. They possessed perturbed H2O stretch bands and dissociated by loss of H2O. The H2O antisymmetric stretch was absent in n=1 and gradually increased in intensity with n. In the n=4 clusters, we found evidence for the beginning of a second solvation shell as well as the onset of an intracluster reaction that formed HONO. These clusters exhibited additional weak, broad bands between 3200 and 3400 cm-1 and two new minor photodissociation channels, loss of HONO and loss of two H2O molecules. The reaction appeared to go to completion within the n=5 clusters. The primary dissociation channel was loss of HONO, and seven vibrational bands were observed. From an analysis of the spectrum, we concluded that the n=5 cluster rearranged to form H3O+(H2O)3(HONO), i.e., an adduct of the reaction products.

  16. A study of Pd/SO4/ZrO2/Al2O3 catalysts in n-hexane isomerization

    NASA Astrophysics Data System (ADS)

    Dzhikiya, O. V.; Smolikov, M. D.; Kazantsev, K. V.; Yablokova, S. S.; Kireeva, T. V.; Paukshtis, E. A.; Gulyaeva, T. I.; Belyi, A. S.

    2017-08-01

    The effect of palladium concentration in a range from 0.02 to 1.6 wt.% on characteristics of n-hexane isomerization was studied. The (O2-Hchem) titration and O2 chemisorption study revealed that palladium in Pd/SO4/ZrO2/Al2O3 systems adsorbs hydrogen in a ratio H/Pds = 1.13-1.65 at./at. Investigation of the charge state of the metal by IR spectroscopy of adsorbed CO showed the presence of both the metallic (Pd0) and charged palladium species. Pd/SO4/ZrO2/Al2O3 catalysts with charged palladium atoms exhibit high activity and selectivity in n-hexane isomerization.

  17. A novel fuzzy-logic control strategy minimizing N2O emissions.

    PubMed

    Boiocchi, Riccardo; Gernaey, Krist V; Sin, Gürkan

    2017-10-15

    A novel control strategy for achieving low N 2 O emissions and low effluent NH 4 + concentration is here proposed. The control strategy uses the measurements of ammonium and nitrate concentrations in inlet and outlet of the aerobic zone of a wastewater treatment plant to calculate a ratio indicating the balance among the microbial groups. More specifically, the ratio will indicate if there is a complete nitrification. In case nitrification is not complete, the controller will adjust the aeration level of the plant in order to inhibit the production of N 2 O from AOB and HB denitrification. The controller was implemented using the fuzzy logic approach. It was comprehensively tested for different model structures and different sets of model parameters with regards to its ability of mitigating N 2 O emissions for future applications in real wastewater treatment plants. It is concluded that the control strategy is useful for those plants having AOB denitrification as the main N 2 O producing process. However, in treatment plants having incomplete NH 2 OH oxidation as the main N 2 O producing pathway, a cascade controller configuration adapting the oxygen supply to respect only the effluent ammonium concentration limits was found to be more effective to ensure low N 2 O emissions. Copyright © 2017 Elsevier Ltd. All rights reserved.

  18. Studies of CW lasing action in CO2-CO, N2O-CO, CO2-H2O, and N2O-H2O mixtures pumped by blackbody radiation

    NASA Technical Reports Server (NTRS)

    Abel, Robert W.; Christiansen, Walter H.; Li, Jian-Guo

    1988-01-01

    A proof of principle experiment to evaluate the efficacy of CO and H2O in increasing the power output for N2O and CO2 lasing mixtures has been conducted and theoretically analyzed for a blackbody radiation-pumped laser. The results for N2O-CO, CO2-CO, N2O-H2O and CO2-H2O mixtures are presented. Additions of CO to the N2O lasant increased power up to 28 percent for N2O laser mixtures, whereas additions of CO to the CO2 lasant, and the addition of H2O to both the CO2 and N2O lasants, resulted in decreased output power.

  19. Isotopic Ratios of H, C, N, O, and S in Comets C2012 F6 (lemmon) and C2014 Q2 (lovejoy) * ** ***

    NASA Technical Reports Server (NTRS)

    Biver, N.; Moreno, R.; Sandqvist, Aa.; Bockelee-Morvan, D.; Colom, P.; Crovisier, J.; Lis, D. C.; Bossier, J.; Debout, V.; Paubert, G.; hide

    2016-01-01

    The apparition of bright comets C/2012 F6 (Lemmon) and C/2014 Q2 (Lovejoy) in March-April 2013 and January 2015, combined with the improved observational capabilities of submillimeter facilities, offered an opportunity to carry out sensitive compositional and isotopic studies of the volatiles in their coma. We observed comet Lovejoy with the IRAM 30 meter telescope between 13 and 26 January 2015, and with the Odin submillimeter space observatory on 29 January - 3 February 2015. We detected 22 molecules and several isotopologues. The H2 O-16 and H2 O-18 production rates measured with Odin follow a periodic pattern with a period of 0.94 days and an amplitude of approximately 25 percent. The inferred isotope ratios in comet Lovejoy are O-16/O-18 = 499 +/- 24 and D/H equals 1.4 +/- 0.4 x 10(exp -4) in water, S-32/S-34 = equals 24.7 +/- 3.5 in CS, all compatible with terrestrial values. The ratio C-12/C-13 equals 109 +/- 14 in HCN is marginally higher than terrestrial and 14 N/ 15/N equals 145 +/- 12 in HCN is half the Earth ratio. Several upper limits for D/H or C-12/ C-13 in other molecules are reported. From our observation of HDO in comet C/2014 Q2 (Lovejoy), we report the first D/H ratio in an Oort Cloud comet that is not larger than the terrestrial value. On the other hand, the observation of the same HDO line in the other Oort-cloud comet, C/2012 F6 (Lemmon), suggests a D/H value four times higher. Given the previous measurements of D/H in cometary water, this illustrates that a diversity in the D/H ratio and in the chemical composition, is present even within the same dynamical group of comets, suggesting that current dynamical groups contain comets formed at very different places or times in the early solar system.

  20. Technical Note: Simultaneous measurement of sedimentary N2 and N2O production and a modified 15N isotope pairing technique

    NASA Astrophysics Data System (ADS)

    Hsu, T.-C.; Kao, S.-J.

    2013-12-01

    Dinitrogen (N2) and/or nitrous oxide (N2O) are produced through denitrification, anaerobic ammonium oxidation (anammox) or nitrification in sediments, of which entangled processes complicate the absolute rate estimations of gaseous nitrogen production from individual pathways. The classical isotope pairing technique (IPT), the most common 15N nitrate enrichment method to quantify denitrification, has recently been modified by different researchers to (1) discriminate between the N2 produced by denitrification and anammox or to (2) provide a more accurate denitrification rate under considering production of both N2O and N2. In case 1, the revised IPT focused on N2 production being suitable for the environments of a low N2O-to-N2 production ratio, while in case 2, anammox was neglected. This paper develops a modified method to refine previous versions of IPT. Cryogenic traps were installed to separately preconcentrate N2 and N2O, thus allowing for subsequent measurement of the two gases generated in one sample vial. The precision is better than 2% for N2 (m/z 28, m/z 29 and m/z 30), and 1.5% for N2O (m/z 44, m/z 45 and m/z 46). Based on the six m/z peaks of the two gases, the 15N nitrate traceable processes including N2 and N2O from denitrification and N2 from anammox were estimated. Meanwhile, N2O produced by nitrification was estimated via the production rate of unlabeled 44N2O. To validate the applicability of our modified method, incubation experiments were conducted using sediment cores taken from the Danshuei Estuary in Taiwan. Rates of the aforementioned nitrogen removal processes were successfully determined. Moreover, N2O yield was as high as 66%, which would significantly bias previous IPT approaches if N2O was not considered. Our modified method not only complements previous versions of IPT but also provides more comprehensive information to advance our understanding of nitrogen dynamics of the water-sediment interface.

  1. The vibration-rotation-tunneling levels of N2-H2O and N2-D2O.

    PubMed

    Wang, Xiao-Gang; Carrington, Tucker

    2015-07-14

    In this paper, we report vibration-rotation-tunneling levels of the van der Waals clusters N2-H2O and N2-D2O computed from an ab initio potential energy surface. The only dynamical approximation is that the monomers are rigid. We use a symmetry adapted Lanczos algorithm and an uncoupled product basis set. The pattern of the cluster's levels is complicated by splittings caused by H-H exchange tunneling (larger splitting) and N-N exchange tunneling (smaller splitting). An interesting result that emerges from our calculation is that whereas in N2-H2O, the symmetric H-H tunnelling state is below the anti-symmetric H-H tunnelling state for both K = 0 and K = 1, the order is reversed in N2-D2O for K = 1. The only experimental splitting measurements are the D-D exchange tunneling splittings reported by Zhu et al. [J. Chem. Phys. 139, 214309 (2013)] for N2-D2O in the v2 = 1 region of D2O. Due to the inverted order of the split levels, they measure the sum of the K = 0 and K = 1 tunneling splittings, which is in excellent agreement with our calculated result. Other splittings we predict, in particular those of N2-H2O, may guide future experiments.

  2. The vibration-rotation-tunneling levels of N2-H2O and N2-D2O

    NASA Astrophysics Data System (ADS)

    Wang, Xiao-Gang; Carrington, Tucker

    2015-07-01

    In this paper, we report vibration-rotation-tunneling levels of the van der Waals clusters N2-H2O and N2-D2O computed from an ab initio potential energy surface. The only dynamical approximation is that the monomers are rigid. We use a symmetry adapted Lanczos algorithm and an uncoupled product basis set. The pattern of the cluster's levels is complicated by splittings caused by H-H exchange tunneling (larger splitting) and N-N exchange tunneling (smaller splitting). An interesting result that emerges from our calculation is that whereas in N2-H2O, the symmetric H-H tunnelling state is below the anti-symmetric H-H tunnelling state for both K = 0 and K = 1, the order is reversed in N2-D2O for K = 1. The only experimental splitting measurements are the D-D exchange tunneling splittings reported by Zhu et al. [J. Chem. Phys. 139, 214309 (2013)] for N2-D2O in the v2 = 1 region of D2O. Due to the inverted order of the split levels, they measure the sum of the K = 0 and K = 1 tunneling splittings, which is in excellent agreement with our calculated result. Other splittings we predict, in particular those of N2-H2O, may guide future experiments.

  3. The effect of Cu/Zn molar ratio on CO{sub 2} hydrogenation over Cu/ZnO/ZrO{sub 2}/Al{sub 2}O{sub 3} catalyst

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Shaharun, Salina, E-mail: salinashaharun@gmail.com, E-mail: maizats@petronas.com.my; Shaharun, Maizatul S., E-mail: salinashaharun@gmail.com, E-mail: maizats@petronas.com.my; Taha, Mohd F., E-mail: faisalt@petronas.com.my

    2014-10-24

    Catalytic hydrogenation of carbon dioxide (CO{sub 2}) to methanol is an attractive way to recycle and utilize CO{sub 2}. A series of Cu/ZnO/Al{sub 2}O{sub 3}/ZrO{sub 2} catalysts (CZAZ) containing different molar ratios of Cu/Zn were prepared by the co-precipitation method and investigated in a stirred slurry autoclave system. The catalysts were characterized by temperature-programmed reduction (TPR), field emission scanning electron microscopy-energy dispersive analysis (FESEM-EDX), X-ray diffraction (XRD) and N{sub 2} adsorption-desorption. Higher surface area, SA{sub BET} values (42.6–59.9 m{sup 2}/g) are recorded at low (1) and high (5) Cu/Zn ratios with the minimum value of 35.71 m{sup 2}/g found formore » a Cu/Zn of 3. The reducibility of the metal oxides formed after calcination of catalyst samples was also affected due to change in metal-support interaction. At a low reaction temperature of 443 K, total gas pressure of 3.0 MPa and 0.1 g/mL of the CZAZ catalyst, the selectivity to methanol decreased as the Cu/Zn molar ratio increased, and the maximum selectivity of 67.73 was achieved at Cu/Zn molar ratio of 1. With a reaction time of 3h, the best performing catalyst was CZAZ75 with Cu/Zn molar ratio of 5 giving methanol yield of 79.30%.« less

  4. Quantifying N2O reduction to N2 based on N2O isotopocules - validation with independent methods (helium incubation and 15N gas flux method)

    NASA Astrophysics Data System (ADS)

    Lewicka-Szczebak, Dominika; Augustin, Jürgen; Giesemann, Anette; Well, Reinhard

    2017-02-01

    Stable isotopic analyses of soil-emitted N2O (δ15Nbulk, δ18O and δ15Nsp = 15N site preference within the linear N2O molecule) may help to quantify N2O reduction to N2, an important but rarely quantified process in the soil nitrogen cycle. The N2O residual fraction (remaining unreduced N2O, rN2O) can be theoretically calculated from the measured isotopic enrichment of the residual N2O. However, various N2O-producing pathways may also influence the N2O isotopic signatures, and hence complicate the application of this isotopic fractionation approach. Here this approach was tested based on laboratory soil incubations with two different soil types, applying two reference methods for quantification of rN2O: helium incubation with direct measurement of N2 flux and the 15N gas flux method. This allowed a comparison of the measured rN2O values with the ones calculated based on isotopic enrichment of residual N2O. The results indicate that the performance of the N2O isotopic fractionation approach is related to the accompanying N2O and N2 source processes and the most critical is the determination of the initial isotopic signature of N2O before reduction (δ0). We show that δ0 can be well determined experimentally if stable in time and then successfully applied for determination of rN2O based on δ15Nsp values. Much more problematic to deal with are temporal changes of δ0 values leading to failure of the approach based on δ15Nsp values only. For this case, we propose here a dual N2O isotopocule mapping approach, where calculations are based on the relation between δ18O and δ15Nsp values. This allows for the simultaneous estimation of the N2O-producing pathways' contribution and the rN2O value.

  5. On the electron-induced isotope fractionation in low temperature (32)O(2)/(36)O(2) ices--ozone as a case study.

    PubMed

    Sivaraman, B; Mebel, A M; Mason, N J; Babikov, D; Kaiser, R I

    2011-01-14

    The formation of six ozone isotopomers and isotopologues, (16)O(16)O(16)O, (18)O(18)O(18)O, (16)O(16)O(18)O, (18)O(18)O(16)O, (16)O(18)O(16)O, and (18)O(16)O(18)O, has been studied in electron-irradiated solid oxygen (16)O(2) and (18)O(2) (1 ∶ 1) ices at 11 K. Significant isotope effects were found to exist which involved enrichment of (18)O-bearing ozone molecules. The heavy (18)O(18)O(18)O species is formed with a factor of about six higher than the corresponding (16)O(16)O(16)O isotopologue. Likewise, the heavy (18)O(18)O(16)O species is formed with abundances of a factor of three higher than the lighter (16)O(16)O(18)O counterpart. No isotope effect was observed in the production of (16)O(18)O(16)O versus(18)O(16)O(18)O. Such studies on the formation of distinct ozone isotopomers and isotopologues involving non-thermal, non-equilibrium chemistry by irradiation of oxygen ices with high energy electrons, as present in the magnetosphere of the giant planets Jupiter and Saturn, may suggest that similar mechanisms may contribute to the (18)O enrichment on the icy satellites of Jupiter and Saturn such as Ganymede, Rhea, and Dione. In such a Solar System environment, energetic particles from the magnetospheres of the giant planets may induce non-equilibrium reactions of suprathermal and/or electronically excited atoms under conditions, which are quite distinct from isotopic enrichments found in classical, thermal gas phase reactions.

  6. Detection of HC5N and HC7N Isotopologues in TMC-1 with the Green Bank Telescope

    NASA Astrophysics Data System (ADS)

    Burkhardt, A. M.; Herbst, E.; Kalenskii, S. V.; McCarthy, M. C.; Remijan, A. J.; McGuire, B. A.

    2018-03-01

    We report the first interstellar detection of DC7N and six 13C-bearing isotopologues of HC7N towards the dark cloud TMC-1 through observations with the Green Bank Telescope, and confirm the recent detection of HC515N. For the average of the 13C isotopomers, DC7N, and HC515N, we derive column densities of 1.9(2) × 1011, 2.5(9) × 1011, and 1.5(4) × 1011 cm-2, respectively. The resulting isotopic ratios are consistent with previous values derived from similar species in the source, and we discuss the implications for the formation chemistry of the observed cyanopolyynes. Within our uncertainties, no significant 13C isotopomer variation is found for HC7N, limiting the significance CN could have in its production. The results further show that, for all observed isotopes, HC5N may be isotopically depleted relative to HC3N and HC7N, suggesting that reactions starting from smaller cyanopolyynes may not be efficient to form HCnN. This leads to the conclusion that the dominant production route may be the reaction between hydrocarbon ions and nitrogen atoms.

  7. Soil invertebrate fauna affect N2 O emissions from soil.

    PubMed

    Kuiper, Imke; de Deyn, Gerlinde B; Thakur, Madhav P; van Groenigen, Jan Willem

    2013-09-01

    Nitrous oxide (N2 O) emissions from soils contribute significantly to global warming. Mitigation of N2 O emissions is severely hampered by a lack of understanding of its main controls. Fluxes can only partly be predicted from soil abiotic factors and microbial analyses - a possible role for soil fauna has until now largely been overlooked. We studied the effect of six groups of soil invertebrate fauna and tested the hypothesis that all of them increase N2 O emissions, although to different extents. We conducted three microcosm experiments with sandy soil and hay residue. Faunal groups included in our experiments were as follows: fungal-feeding nematodes, mites, springtails, potworms, earthworms and isopods. In experiment I, involving all six faunal groups, N2 O emissions declined with earthworms and potworms from 78.4 (control) to 37.0 (earthworms) or 53.5 (potworms) mg N2 O-N m(-2) . In experiment II, with a higher soil-to-hay ratio and mites, springtails and potworms as faunal treatments, N2 O emissions increased with potworms from 51.9 (control) to 123.5 mg N2 O-N m(-2) . Experiment III studied the effect of potworm density; we found that higher densities of potworms accelerated the peak of the N2 O emissions by 5 days (P < 0.001), but the cumulative N2 O emissions remained unaffected. We propose that increased soil aeration by the soil fauna reduced N2 O emissions in experiment I, whereas in experiment II N2 O emissions were driven by increased nitrogen and carbon availability. In experiment III, higher densities of potworms accelerated nitrogen and carbon availability and N2 O emissions, but did not increase them. Overall, our data show that soil fauna can suppress, increase, delay or accelerate N2 O emissions from soil and should therefore be an integral part of future N2 O studies. © 2013 John Wiley & Sons Ltd.

  8. Direct gas injection method: A simple modification to an elemental analyzer/isotope ratio mass spectrometer for stable isotope analysis of N and C from N2O and CO2 gases in nanomolar concentrations

    EPA Science Inventory

    A simple modification to the Elemental Analyzer coupled to Isotope Ratio Mass-Spectrometer (EA-IRMS) setup is described. This modification allows the users to measure nitrous oxide (N2O) and carbon dioxide (CO2) by injecting the gases directly into an online injector placed befor...

  9. Kinetic study of the reaction of the hydroxyl radical (OH) with methyl ethyl ketone (2-butanone) and its deuterated isotopomers at low pressure

    NASA Astrophysics Data System (ADS)

    Liljegren, J. A.; Stevens, P. S.

    2012-12-01

    Methyl ethyl ketone (2-butanone) in the atmosphere comes from a variety of sources. It is produced commercially as an industrial ketone. It can be formed as a result of the OH or Cl-initiated oxidation of C4-C6 alkanes, primarily n-butane, or from the reaction of some alkenes with OH or O3. Biogenic sources include direct emissions from certain plants as well as emissions from decaying plant matter. Methyl ethyl ketone is removed from the atmosphere primarily by its reaction with OH. A product of this reaction includes acetaldehyde, which is a hazardous air pollutant, can further react to produce peroxy acetyl nitrate (PAN), and can be a significant source of free radicals to the atmosphere. The absolute rate constant for the reaction of OH with methyl ethyl ketone has been measured as a function of temperature at low pressure using discharge-flow techniques coupled with laser induced fluorescence (LIF) detection of OH. In addition, measurements of the rate constants for the reactions of OH with two deuterated isotopomers of methyl ethyl ketone, including CD3C(O)CH2CH3 and CH3C(O)CD2CD3, will be presented to gain a better understanding of the mechanism for this reaction. Theoretical studies of the potential energy surface for this reaction suggest that the reaction proceeds through the formation of a hydrogen-bonded pre-reactive complex, similar to that of several other atmospherically relevant oxygenated VOCs such as acetone, acetic acid, and hydroxyacetone.

  10. Investigation of N2O Production from 266 and 532 nm Laser Flash Photolysis of O3/N2/O2 Mixtures

    NASA Technical Reports Server (NTRS)

    Estupinan, E. G.; Nicovich, J. M.; Li, J.; Cunnold, D. M.; Wine, P. H.

    2002-01-01

    Tunable diode laser absorption spectroscopy has been employed to measure the amount of N2O produced from laser flash photolysis of O3/N2/O2 mixtures at 266 and 532 nm. In the 532 nm photolysis experiments very little N2O is observed, thus allowing an upper limit yield of 7 x 10(exp -8) to be established for the process O3 + N2 yield N2O + O2, where O3 is nascent O3 that is newly formed via O(3P(sub J)) + O2 recombination (with vibrational excitation near the dissociation energy of O3). The measured upper limit yield is a factor of approx. 600 smaller than a previous literature value and is approximately a factor of 10 below the threshold for atmospheric importance. In the 266 nm photolysis experiments, significant N2O production is observed and the N2O quantum yield is found to increase linearly with pressure over the range 100 - 900 Torr in air bath gas. The source of N2O in the 266 nm photolysis experiments is believed to be the addition reaction O(1D(sub 2)) + N2 + M yields (k(sub sigma)) N2O + M, although reaction of (very short-lived) electronically excited O3 with N2 cannot be ruled out by the available data. Assuming that all observed N2O comes from the O(1D(sub 2)) + N2 + M reaction, the following expression describes the temperature dependence of k(sub sigma) (in its third-order low-pressure limit) that is consistent with the N2O yield data: k(sub sigma) = (2.8 +/- 0.1) x 10(exp -36)(T/300)(sup -(0-88+0.36)) cm(sup 6) molecule(sup -2)/s, where the uncertainties are 2(sigma) and represent precision only. The accuracy of the reported rate coefficients at the 95% confidence level is estimated to be 30 - 40% depending on the temperature. Model calculations suggest that gas phase processes initiated by ozone absorption of a UV photon represent about 1.4% of the currently estimated global source strength of atmospheric N2O. However, these processes could account for a significant fraction of the oxygen mass-independent enrichment observed in atmospheric N2O, and

  11. The Child-Langmuir laws and cathode sheath in the N2O

    NASA Astrophysics Data System (ADS)

    Lisovskiy, Valeriy; Artushenko, Ekaterina; Yegorenkov, Vladimir

    2013-09-01

    It is established which of the Child-Langmuir collisional laws are most appropriate for describing the cathode sheath in the N2O. At low pressure p < 0 . 3 Torr the Child-Langmuir law version relating to the constant ion mobility. At p > 0 . 75 Torr one has to employ the law version for which it is assumed that ion mean free path within the cathode sheath is constant. In the intermediate pressure range 0 . 3 < p < 0 . 75 Torr neither of the Child-Langmuir law versions gives a correct description of the cathode sheath in the N2O. The ratio of the normal current density to the gas pressure squared J /p2 , the normal voltage drop and the cathode sheath thickness are determined. For the stainless steel cathode they equals to U = 364 V and pd = 2 . 5 Torr .mm. At large N2O pressure the above ratio remains constant and it amounts to J /p2 = 0.44 mA/(cm .Torr)2 for any inter-electrode gap value we studied. On decreasing the N2O pressure the ratio J /p2 increases and for narrow gaps between electrodes it may approach several or even several tens mA/(cm .Torr)2. and Scientific Center of Physical Technologies, Svobody Sq.6, Kharkov, 61022, Ukraine.

  12. Isotopomer enrichment assay for very short chain fatty acids and its metabolic applications.

    PubMed

    Tomcik, Kristyen; Ibarra, Rafael A; Sadhukhan, Sushabhan; Han, Yong; Tochtrop, Gregory P; Zhang, Guo-Fang

    2011-03-01

    The present work illustrated an accurate GC/MS measurement for the low isotopomer enrichment assay of formic acid, acetic acid, propionic aicd, butyric acid, and pentanoic acid. The pentafluorobenzyl bromide derivatives of these very short chain fatty acids have high sensitivity of isotopoic enrichment due to their low natural isotopomer distribution in negative chemical ionization mass spectrometric mode. Pentafluorobenzyl bromide derivatization reaction was optimized in terms of pH, temperature, reaction time, and the amount of pentafluorobenzyl bromide versus sample. The precision, stability, and accuracy of this method for the isotopomer analysis were validated. This method was applied to measure the enrichments of formic acid, acetic acid, and propionic acid in the perfusate from rat liver exposed to Krebs-Ringer bicarbonate buffer only, 0-1mM [3,4-(13)C(2)]-4-hydroxynonanoate, and 0-2mM [5,6,7-(13)C(3)]heptanoate. The enrichments of acetic acid and propionic acid in the perfusate are comparable to the labeling pattern of acetyl-CoA and propionyl-CoA in the rat liver tissues. The enrichment of the acetic acid assay is much more sensitive and precise than the enrichment of acetyl-CoA by LC-MS/MS. The reversibility of propionyl-CoA from succinyl-CoA was confirmed by the low labeling of M1 and M2 of propionic acid from [5,6,7-(13)C(3)]heptanoate perfusates. 2010 Elsevier Inc. All rights reserved.

  13. Effect of the CaO/SiO2 mass ratio and FeO content on the viscosity of CaO-SiO2-"FeO"-12wt%ZnO-3wt%Al2O3 slags

    NASA Astrophysics Data System (ADS)

    Lü, Jian-fang; Jin, Zhe-nan; Yang, Hong-ying; Tong, Lin-lin; Chen, Guo-bao; Xiao, Fa-xin

    2017-07-01

    An effective process for recycling lead from hazardous waste cathode ray tubes (CRTs) funnel glass through traditional lead smelting has been presented previously. The viscous behavior of the molten high lead slag, which is affected by the addition of funnel glass, plays a critical role in determining the production efficiency. Therefore, the viscosities of the CaO-SiO2-"FeO"-12wt%ZnO-3wt%Al2O3 slags were measured in the current study using the rotating spindle method. The slag viscosity decreases as the CaO/SiO2 mass ratio is increased from 0.8 to 1.2 and also as the FeO content is increased from 8wt% to 20wt%. The breaking temperature of the slag is lowered substantially by the addition of FeO, whereas the influence of the CaO/SiO2 mass ratio on the breaking temperature is complex. The structural analysis of quenched slags using Fourier transform infrared (FTIR) spectroscopy and Raman spectroscopy reveals that the silicate network structure is depolymerized with increasing CaO/SiO2 mass ratio or increasing FeO content. The [FeO6]-octahedra in the slag melt increase as the CaO/SiO2 mass ratio or the FeO content increases. This increase can further decrease the degree of polymerization (DOP) of the slag. Furthermore, the activation energy for viscous flow decreases both with increasing CaO/SiO2 mass ratio and increasing FeO content.

  14. Analysis of SAW properties in ZnO/AlxGa1-xN/c-Al2O3 structures.

    PubMed

    Chen, Ying; Emanetoglu, Nuri William; Saraf, Gaurav; Wu, Pan; Lu, Yicheng; Parekh, Aniruddh; Merai, Vinod; Udovich, Eric; Lu, Dong; Lee, Dong S; Armour, Eric A; Pophristic, Milan

    2005-07-01

    Piezoelectric thin films on high acoustic velocity nonpiezoelectric substrates, such as ZnO, AlN, or GaN deposited on diamond or sapphire substrates, are attractive for high frequency and low-loss surface acoustic wave devices. In this work, ZnO films are deposited on AlxGa1-xN/c-Al2O3 (0 < or = chi < or = 1) substrates using the radio frequency (RF) sputtering technique. In comparison with a single AlxGa1-xN layer deposited on c-Al2O3 with the same total film thickness, a ZnO/AlxGa1-xN/c-Al2O3 multilayer structure provides several advantages, including higher order wave modes with higher velocity and larger electromechanical coupling coefficient (K2). The surface acoustic wave (SAW) velocities and coupling coefficients of the ZnO/AlxGa1-xN/c-Al2O3 structure are tailored as a function of the Al mole percentage in AlxGa1-xN films, and as a function of the ZnO (h1) to AlxGa1-xN (h2) thickness ratio. It is found that a wide thickness-frequency product (hf) region in which coupling is close to its maximum value, K(2)max, can be obtained. The K(2)max of the second order wave mode (h1 = h2) is estimated to be 4.3% for ZnO/GaN/c-Al2O3, and 3.8% for ZnO/AlN/c-Al2O3. The bandwidth of second and third order wave modes, in which the coupling coefficient is within +/- 0.3% of K(2)max, is calculated to be 820 hf for ZnO/GaN/c-Al2O3, and 3620 hf for ZnO/AlN/c-Al2O3. Thus, the hf region in which the coupling coefficient is close to the maximum value broadens with increasing Al content, while K(2)max decreases slightly. When the thickness ratio of AlN to ZnO increases, the K(2)max and hf bandwidth of the second and third higher wave modes increases. The SAW test devices are fabricated and tested. The theoretical and experimental results of velocity dispersion in the ZnO/AlxGa1-xN/c-Al2O3 structures are found to be well matched.

  15. Effects of Al2O3 and CaO/SiO2 Ratio on Phase Equilbria in the ZnO-"FeO"-Al2O3-CaO-SiO2 System in Equilibrium with Metallic Iron

    NASA Astrophysics Data System (ADS)

    Zhao, Baojun; Hayes, Peter C.; Jak, Evgueni

    2011-02-01

    The phase equilibria and liquidus temperatures in the ZnO-"FeO"-Al2O3-CaO-SiO2 system in equilibrium with metallic iron have been determined experimentally in the temperature range 1383 K to 1573 K (1150 °C to 1300 °C). The experimental conditions were selected to characterize lead blast furnace and imperial smelting furnace slags. The results are presented in a form of pseudoternary sections ZnO-"FeO"-(Al2O3 + CaO + SiO2) with fixed CaO/SiO2 and (CaO + SiO2)/Al2O3 ratios. It was found that wustite and spinel are the major primary phases in the composition range investigated. Effects of Al2O3 concentration as well as the CaO/SiO2 ratio on the primary phase field, the liquidus temperature, and the partitioning of ZnO between liquid and solid phases have been discussed for zinc-containing slags.

  16. N2O emissions from an intermittently aerated semi-aerobic aged refuse bioreactor: Combined effect of COD and NH4+-N in influent leachate.

    PubMed

    Li, Weihua; Sun, Yingjie; Bian, Rongxing; Wang, Huawei; Zhang, Dalei

    2017-11-01

    The carbon-nitrogen ratio (COD/NH 4 + -N) is an important factor affecting nitrification and denitrification in wastewater treatment; this factor also influences nitrous oxide (N 2 O) emissions. This study investigated two simulated intermittently aerated semi-aerobic aged refuse bioreactors (SAARB) filled with 8-year old aged refuse (AR). The research analyzed how differences in and the combination of influent COD and NH 4 + -N impact N 2 O emissions in leachate treatment. Experimental results showed that N 2 O emissions increased as the influent COD/NH 4 + -N decreased. The influent COD had a greater effect on N 2 O emissions than NH 4 + -N at the same influent ratios of COD/NH 4 + -N (2.7 and 8.0, respectively). The maximum N 2 O emission accounted for 8.82±2.65% of the total nitrogen removed from the influent leachate; the maximum level occurred when the COD was 2000mg/L. An analysis of differences in influent carbon sources at the same COD/NH 4 + -N ratios concluded that the availability of biodegradable carbon substrates (i.e. glucose) is an important factor affecting N 2 O emissions. At a low influent COD/NH 4 + -N ratio (2.7), the N 2 O conversion rate was greater when there were more biodegradable carbon substrates. Although the SAARB included the N 2 O generation and reduction processes, N 2 O reduction mainly occurred later in the process, after leachate recirculation. The maximum N 2 O emission rate occurred in the first hour of single-period (24h) experiments, as leachate contacted the surface AR. In practical SAARB applications, N 2 O emissions may be reduced by measures such as reducing the initial recirculation loading of NH 4 + -N substrates, adding a later supplement of biodegradable carbon substrates, and/or prolonging hydraulic retention time (HRT) of influent leachate. Copyright © 2017 Elsevier Ltd. All rights reserved.

  17. Fundamental Insulation Characteristics of Air, N2, CO2, N2/O2 and SF6/N2 Mixed Gases

    NASA Astrophysics Data System (ADS)

    Rokunohe, Toshiaki; Yagihashi, Yoshitaka; Endo, Fumihiro; Oomori, Takashi

    SF6 gas has excellent dielectric strength and interruption performance. For these reasons, it has been widely used for gas insulated switchgear (GIS). However, use of SF6 gas has become regulated under agreements set at the 1997 COP3. Presently, development of a gas circuit breaker (GCB) using CO2 gas and development of a high voltage vacuum circuit breaker (VCB) are being pursued. GIS consists of disconnectors (DS), earthing switches (ES) and buses in addition to GCB. Since the interruption performance is not an important requirement for DS, ES and BUS, use of a gas with high dielectric strength is better than use of a gas with good interruption performance. Air and N2 are not greenhouse gases, and their dielectric strengths are higher than those of other SF6 alternative gases, but only about one-third of the dielectric strength of SF6 gas. This paper deals with a suitable insulation gas which has no greenhouse effect as an SF6 alternative gas. The N2/O2 mixed gas was investigated by changing the ratio of O2. Moreover, the effect of an insulation coating was investigated and compared with the dielectric strength of SF6/N2 mixed gas. The dielectric strength of air under the coating condition was equal to that of 10%SF6/N2 mixed gas.

  18. On the production of N2O from the reaction of O/1D/with N2.

    NASA Technical Reports Server (NTRS)

    Simonaitis, R.; Lissi, E.; Heicklen, J.

    1972-01-01

    Ozone was photolyzed at 2537 A and at 25 C in the presence of 42-115 torr of O2 and about 880 torr of N2 to test the relative importance of the two reactions O(1D) + N2 + M leading to N2O + M and O(1D) + N2 leading to O(3P) + N2. In this study N2O was not found as a product. Thus from our detectability limit for N2O an upper limit to the efficiency of the first reaction relative to the second of 2.5 times 10 to the -6 power at 1000-torr total pressure was computed.

  19. On the production of N2O from the reaction of O(1 D) with N2

    NASA Technical Reports Server (NTRS)

    Simonaitis, R.; Lissi, E.; Heicklen, J.

    1972-01-01

    Ozone was photolyzed at 2537 A and 25 C in the presence of 42-115 torr of O2 and about 880 torr of N2 to test the relative importance of the two reactions: (1) O(1D) + N2 + M yields N2O + M, and (2) O(1D) + N2 yields O(3P) + N2. N2O was not found as a product. Thus from our detectability limit for N2O (0.3 micron), an upper limit to the efficiency of the first reaction relative to the second of 0.0000025 at 1000 torr total pressure was computed. This corresponds to k1/k2 smaller than 0.8 x 10 to the minus 25 power cu cm/particle.

  20. A novel 15N tracer approach for the quantification of N2 and N2O emissions from soil incubations in a completely automated laboratory set up

    NASA Astrophysics Data System (ADS)

    Scheer, Clemens; Dannenmann, Michael; Meier, Rudolf

    2015-04-01

    The microbial mediated production of nitrous oxide (N2O) and its reduction to dinitrogen (N2) via denitrification represents a loss of nitrogen (N) from fertilised agro-ecosystems to the atmosphere. Although denitrification has received great interest by biogeochemists in the last decades, the magnitude of N2lossesand related N2:N2O ratios from soils still are largely unknown due to methodical constraints. We present a novel 15N tracer approach, based on a previous developed tracer method to study denitrification in pure bacterial cultures which was modified for the use on soil incubations in a completely automated laboratory set up. The method uses a background air in the incubation vessels that is replaced with a helium-oxygen gas mixture with a 50-fold reduced N2 background (2 % v/v). This method allows for a direct and sensitive quantification of the N2 and N2O emissions from the soil with isotope-ratio mass spectrometry after 15N labelling of denitrification N substrates and minimises the sensitivity to the intrusion of atmospheric N2 at the same time. The incubation set up was used to determine the influence of different soil moisture levels on N2 and N2O emissions from a sub-tropical pasture soil in Queensland/Australia. The soil was labelled with an equivalent of 50 μg-N per gram dry soil by broadcast application of KNO3solution (4 at.% 15N) and incubated for 3 days at 80% and 100% water filled pore space (WFPS), respectively. The headspace of the incubation vessel was sampled automatically over 12hrs each day and 3 samples (0, 6, and 12 hrs after incubation start) of headspace gas analysed for N2 and N2O with an isotope-ratio mass spectrometer (DELTA V Plus, Thermo Fisher Scientific, Bremen, Germany(. In addition, the soil was analysed for 15N NO3- and NH4+ using the 15N diffusion method, which enabled us to obtain a complete N balance. The method proved to be highly sensitive for N2 and N2O emissions detecting N2O emissions ranging from 20 to 627 μN kg

  1. Partial nitrogen loss in SrTaO2N and LaTiO2N oxynitride perovskites

    NASA Astrophysics Data System (ADS)

    Chen, Daixi; Habu, Daiki; Masubuchi, Yuji; Torii, Shuki; Kamiyama, Takashi; Kikkawa, Shinichi

    2016-04-01

    SrTaO2N heated in a helium atmosphere began to release nitrogen of approximately 30 at% at 950 °C while maintaining the perovskite structure and its color changed from orange to dark green. Then it decomposed above 1200 °C to a black mixture of Sr1.4Ta0.6O2.73, Ta2N, and Sr5Ta4O15. The second decomposition was not clearly observed when SrTaO2N was heated in a nitrogen atmosphere below 1550 °C. After heating at 1500 °C for 3 h under a 0.2 MPa nitrogen atmosphere, the perovskite product became dark green and conductive. Structure refinement results suggested that the product was a mixture of tetragonal and cubic perovskites with a decreased ordering of N3-/O2-. The sintered body was changed to an n-type semiconductor after a partial loss of nitrogen to be reduced from the originally insulating SrTaO2N perovskite lattice. LaTiO2N was confirmed to have a similar cis-configuration of the TiO4N2 octahedron as that of TaO4N2 in SrTaO2N. It also released some of its nitrogen at 800 °C changing its color from brown to black and then decomposed to a mixture of LaTiO3, La2O3, and TiN at 1100 °C. These temperatures are lower than those in SrTaO2N.

  2. ALLocator: an interactive web platform for the analysis of metabolomic LC-ESI-MS datasets, enabling semi-automated, user-revised compound annotation and mass isotopomer ratio analysis.

    PubMed

    Kessler, Nikolas; Walter, Frederik; Persicke, Marcus; Albaum, Stefan P; Kalinowski, Jörn; Goesmann, Alexander; Niehaus, Karsten; Nattkemper, Tim W

    2014-01-01

    Adduct formation, fragmentation events and matrix effects impose special challenges to the identification and quantitation of metabolites in LC-ESI-MS datasets. An important step in compound identification is the deconvolution of mass signals. During this processing step, peaks representing adducts, fragments, and isotopologues of the same analyte are allocated to a distinct group, in order to separate peaks from coeluting compounds. From these peak groups, neutral masses and pseudo spectra are derived and used for metabolite identification via mass decomposition and database matching. Quantitation of metabolites is hampered by matrix effects and nonlinear responses in LC-ESI-MS measurements. A common approach to correct for these effects is the addition of a U-13C-labeled internal standard and the calculation of mass isotopomer ratios for each metabolite. Here we present a new web-platform for the analysis of LC-ESI-MS experiments. ALLocator covers the workflow from raw data processing to metabolite identification and mass isotopomer ratio analysis. The integrated processing pipeline for spectra deconvolution "ALLocatorSD" generates pseudo spectra and automatically identifies peaks emerging from the U-13C-labeled internal standard. Information from the latter improves mass decomposition and annotation of neutral losses. ALLocator provides an interactive and dynamic interface to explore and enhance the results in depth. Pseudo spectra of identified metabolites can be stored in user- and method-specific reference lists that can be applied on succeeding datasets. The potential of the software is exemplified in an experiment, in which abundance fold-changes of metabolites of the l-arginine biosynthesis in C. glutamicum type strain ATCC 13032 and l-arginine producing strain ATCC 21831 are compared. Furthermore, the capability for detection and annotation of uncommon large neutral losses is shown by the identification of (γ-)glutamyl dipeptides in the same strains

  3. Quenching of I(2P1/2) by NO2, N2O4, and N2O.

    PubMed

    Kabir, Md Humayun; Azyazov, Valeriy N; Heaven, Michael C

    2007-10-11

    Quenching of excited iodine atoms (I(5p5, 2P1/2)) by nitrogen oxides are processes of relevance to discharge-driven oxygen iodine lasers. Rate constants at ambient and elevated temperatures (293-380 K) for quenching of I(2P1/2) atoms by NO2, N2O4, and N2O have been measured using time-resolved I(2P1/2) --> I(2P3/2) 1315 nm emission. The excited atoms were generated by pulsed laser photodissociation of CF3I at 248 nm. The rate constants for I(2P1/2) quenching by NO2 and N2O were found to be independent of temperature over the range examined with average values of (2.9 +/- 0.3) x 10(-15) and (1.4 +/- 0.1) x 10(-15) cm3 s(-1), respectively. The rate constant for quenching of I(2P1/2) by N2O4 was found to be (3.5 +/- 0.5) x 10(-13) cm3 s(-1) at ambient temperature.

  4. Molecular dynamic simulations of selective self-diffusion of CH4/CO2/H2O/N2 in coal

    NASA Astrophysics Data System (ADS)

    Song, Y.; Jiang, B.; Li, F. L.

    2017-06-01

    The self-diffusion coefficients (D) of CH4/CO2/H2O/N2 at a relatively broad range of temperatures(298.15∼ 458.15K)and pressures (1∼6MPa) under the NPT, NPH, NVE, and NVT ensembles were obtained after the calculations of molecular mechanics(MM), annealing kinetics(AK), giant canonical Monte Carlo(GCMC), and molecular dynamics (MD) based on Wiser bituminous coal model (WM). The Ds of the adsorbates at the saturated adsorption configurations are D CH422ON2(NPT, 298.15K, 0.1MPa). The diffusion activation energy (E) is E H2O (1.07kJ/mol)N2(1.82kJ/mol)2 (2.94kJ/mol)N2 and H2O to the lowest. The order of different ensembles is D N2 (NVE)< D N2 (NVT)≈D N2 (NPH)≈D N2 (NPT) (T<418K) and D N2 (NVE) is remarkable higher than other ensembles when T>418K. The average swelling ratios manifest as H2O (14.7∼35.18%)>CO2 (13.38∼32.25%)>CH4 (15.35∼23.71%)> N2 (11.47∼22.14%) (NPH, 1∼6MPa). There exits differences in D, swelling ratios and E among various ensembles, indicating that the selection of ensembles has an important influence on the MD calculations for self-diffusion coefficients.

  5. Active nitrogen partitioning and the nighttime formation of N sub 2 O sub 5 in the stratosphere: Simultaneous in situ measurements of NO, NO sub 2 , HNO sub 3 , O sub 3 , and N sub 2 O using the BLISS diode laser spectrometer

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Webster, C.R.; May, R.D.; Toumi, R.

    1990-08-20

    Simultaneous in situ measurements of NO, NO{sub 2}, HNO{sub 3}, O{sub 3}, N{sub 2}O, pressure, and temperature at 30 km have been made from Palestine. Texas (32{degree}N) on September 13, 1988, using the Jet Propulsion Laboratory Balloon-Borne Laser In-Situ Sensor (BLISS) instrument, with the NOAA dual-channel balloon UV ozone spectrometer on the same gondola. Using tunable diode laser absorption spectroscopy over a long path length, measurements were made during a 24-hour flight of the daytime concentrations of NO, NO{sub 2}, and O{sub 3} and of the diurnal variation in the concentration of NO{sub 2}. Postsunset measurements of NO{sub 2}, mademore » every half minutes throughout much of the night, show the NO{sub 2} mixing ratio falling from a sunset value of 10.5 ppbv to 5.2 ppbv at nights end. From the sunset/sunrise difference din the volume mixing ratio of NO{sub 2} is derived a value of 2.7 {plus minus} 0.4 ppbv for the sunrise N{sub 2}O{sub 5} mixing ratio, in excellent agreement with the model predictions of 2.9 ppbv at this latitude. The measured daytime NO{sub 2}/NO ratio was found to be in good agreement with model predictions at 30 km. The measured presunset sum NO + NO{sub 2} of 10.1 {plus minus} 0.8 ppbv agreed well with the measured postsunset NO{sub 2} amount of 10.5 {plus minus} 0.8 ppbv. Simultaneous measurements of the mixing ratios of HNO{sub 3} and postsunset NO{sub 2} allow an estimate of total reactive nitrogen, approximated at this time by NO{sub 2} + HNO{sub 3} + 2(N{sub 2}O{sub 5}) + ClONO{sub 2}, of 16.4 {plus minus} 1.2 ppbv at 30 km, and (from an earlier flight) of 13.7 {plus minus} 1.7 ppbv at 37 km. Using model predictions incorporating corrections for non-steady state and for diurnal chemistry, an OH mixing ratio of 8 {plus minus} 4 pptv is derived from the measured HNO{sub 3}/NO{sub 2} ratio of 0.72 {plus minus} 0.17 at 30 km.« less

  6. Crystal structure of aqua-1κO-{μ-2-[(2-hydroxy-ethyl)methylamino]ethanolato-2:1κ(4) O (1),N,O (2):O (1)}[μ-2,2'-(methylimino)diethanolato-1:2κ(4) O,N,O':O]dithiocyanato-1κN,2κN-chromium(III)copper(II).

    PubMed

    Rusanova, Julia A; Semenaka, Valentina V; Dyakonenko, Viktoriya V; Shishkin, Oleg V

    2015-09-01

    The title compound, [CrCu(C5H11NO2)(C5H12NO2)(NCS)2(H2O)] or [Cr(μ-mdea)Cu(μ-Hmdea)(NCS)2H2O], (where mdeaH2 is N-methylethanolamine, C5H13NO2) is formed as a neutral heterometal Cu(II)/Cr(III) complex. The mol-ecular structure of the complex is based on a binuclear {CuCr(μ-O)2} core. The coordination environment of each metal atom involves the N,O,O atoms of the tridentate ligand, one bridging O atom of the ligand and the N atom of the thio-cyanato ligands. The Cu(II) ion adopts a distorted square-pyramidal coordination while the Cr(III) ion has a distorted octa-hedral coordination geometry completed by the aqua ligand. In the crystal, the binuclear complexes are linked via two pairs of O-H⋯O hydrogen bonds to form inversion dimers, which are arranged in columns parallel to the a axis. In the μ-mdea ligand two -CH2 groups and the methyl group were refined as disordered over two sets of sites with equal occupancies. The structure was refined as a two-component twin with a twin scale factor of 0.242 (1).

  7. {μ-2-[(3-Amino-2,2-dimethyl-prop-yl)imino-meth-yl]-6-meth-oxy-phenolato-1:2κ(5)O(1),O(6):N,N',O(1)}{2-[(3-amino-2,2-dimethyl-prop-yl)imino-meth-yl]-6-meth-oxy-phenolato-1κ(3)N,N',O(1)}-μ-azido-1:2κ(2)N:N-azido-2κN-methanol-2κO-dinickel(II).

    PubMed

    Ghaemi, Akbar; Rayati, Saeed; Fayyazi, Kazem; Ng, Seik Weng; Tiekink, Edward R T

    2012-08-01

    Two distinct coordination geometries are found in the binuclear title complex, [Ni(2)(C(13)H(19)N(2)O(2))(2)(N(3))(2)(CH(3)OH)], as one Schiff base ligand is penta-dentate, coordinating via the anti-cipated oxide O, imine N and amine N atoms (as for the second, tridentate, ligand) but the oxide O is bridging and coordination also occurs through the meth-oxy O atom. The Ni(II) atoms are linked by a μ(2)-oxide atom and one end of a μ(2)-azide ligand, forming an Ni(2)ON core. The coordination geometry for the Ni(II) atom coordinated by the tridentate ligand is completed by the meth-oxy O atom derived from the penta-dentate ligand, with the resulting N(3)O(3) donor set defining a fac octa-hedron. The second Ni(II) atom has its cis-octa-hedral N(4)O(2) coordination geometry completed by the imine N and amine N atoms of the penta-dentate Schiff base ligand, a terminally coordinated azide N and a methanol O atom. The arrangement is stabilized by an intra-molecular hydrogen bond between the methanol H and the oxide O atom. Linear supra-molecular chains along the a axis are formed in the crystal packing whereby two amine H atoms from different amine atoms hydrogen bond to the terminal N atom of the monodentate azide ligand.

  8. Reconstructing the history of water ice formation from HDO/H2O and D2O/HDO ratios in protostellar cores

    NASA Astrophysics Data System (ADS)

    Furuya, K.; van Dishoeck, E. F.; Aikawa, Y.

    2016-02-01

    Recent interferometer observations have found that the D2O/HDO abundance ratio is higher than that of HDO/H2O by about one order of magnitude in the vicinity of low-mass protostar NGC 1333-IRAS 2A, where water ice has sublimated. Previous laboratory and theoretical studies show that the D2O/HDO ice ratio should be lower than the HDO/H2O ice ratio, if HDO and D2O ices are formed simultaneously with H2O ice. In this work, we propose that the observed feature, D2O/HDO > HDO/H2O, is a natural consequence of chemical evolution in the early cold stages of low-mass star formation as follows: 1) majority of oxygen is locked up in water ice and other molecules in molecular clouds, where water deuteration is not efficient; and 2) water ice formation continues with much reduced efficiency in cold prestellar/protostellar cores, where deuteration processes are highly enhanced as a result of the drop of the ortho-para ratio of H2, the weaker UV radiation field, etc. Using a simple analytical model and gas-ice astrochemical simulations, which traces the evolution from the formation of molecular clouds to protostellar cores, we show that the proposed scenario can quantitatively explain the observed HDO/H2O and D2O/HDO ratios. We also find that the majority of HDO and D2O ices are likely formed in cold prestellar/protostellar cores rather than in molecular clouds, where the majority of H2O ice is formed. This work demonstrates the power of the combination of the HDO/H2O and D2O/HDO ratios as a tool to reveal the past history of water ice formation in the early cold stages of star formation, and when the enrichment of deuterium in the bulk of water occurred. Further observations are needed to explore if the relation, D2O/HDO > HDO/H2O, is common in low-mass protostellar sources.

  9. Biological N2 fixation mainly controlled by Sphagnum tissue N:P ratio in ombrotrophic bogs

    NASA Astrophysics Data System (ADS)

    Zivkovic, Tatjana; Moore, Tim R.

    2017-04-01

    Most of the 18 Pg nitrogen (N) accumulated in northern nutrient-poor and Sphagnum-dominated peatlands (bogs and fens) can be attributed to N2-fixation by diazotrophs either associated with the live Sphagnum or non-symbiotically in the deeper peat such as through methane consumption close to the water table. Where atmospheric N deposition is low (< 0.2 g m-2 y-1), ombrotrophic bogs rely on N2-fixation as the primary source of N that sustains primary production. Due to high energetic requirements, N2-fixation depends on the available phosphorus (P). Anthropogenic impacts in the last 200 years increased atmospheric N deposition, resulting in a switch from N to P limitation in Sphagnum, suggested by the increase in tissue N:P to >16. It is unclear how Sphagnum-hosted diazotrophic activity may be affected by N deposition and thus changes in N:P ratio. First, we investigated the effects of long-term addition of different sources of nitrogen (0, 1.6, 3.2 and 6.4 g N m-2 y-1as NH4Cl and NaNO3), and phosphorus (5 g P m-2 y-1as KH2PO4) on Sphagnum nutrient status (N, P and N:P ratio), net primary productivity (NPP) and Sphagnum-associated N2fixation at Mer Bleue, a temperate ombrotrophic bog. We show that N concentration in Sphagnum tissue increased with larger rates of N addition, with a stronger effect on Sphagnum from NH4 than NO3. The addition of P created a 3.5 fold increase in Sphagnum P content compared to controls. Sphagnum NPP decreased linearly with the rise in N:P ratio, while linear growth declined exponentially with increase in Sphagnum N content. Rates of N2-fixation determined in the laboratory significantly decreased in response to even the smallest addition of both N species. In contrast, the addition of P increased N2 fixation by up to 100 times compared to N treatments and up to 5-30 times compared to controls. The change in N2-fixation was best modeled by the N:P ratio, across all experimental treatments. Secondly, to test the role of N:P ratio on N2

  10. An Experimental Study on What Controls the Ratios of 18O/16O and 17O/16O of O2 During Microbial Respiration

    NASA Astrophysics Data System (ADS)

    Stolper, D. A.; Ward, B. B.; Fischer, W. W.; Bender, M. L.

    2015-12-01

    18O/16O and 17O/16O ratios of atmospheric and dissolved oceanic O2 are key biogeochemical tracers of total photosynthesis and respiration on global to local length scales and glacial/interglacial time scales (Luz et al., 1999). Critical to the use of these ratios as biogeochemical tracers is knowledge of how they are affected by production, consumption, and transport of O2. We present new measurements of O2 respiration by E. coli and N. oceanus, an ammonia oxidizing bacterium, to test three assumptions of isotopically enabled models of the O2 cycle: (i) laboratory-measured respiratory 18O/16O isotope effects (18α) of microorganisms are constant under all experimental and natural conditions (e.g., temperature and growth rate); (ii) the respiratory 'mass law' relationship between 18O/16O and 17O/16O [17α = (18α)β] is universal; and (iii) 18α and β for aerobic ammonia and organic carbon oxidation are identical. For E. coli, we find that both 18α and β are variable. From 37°C to 15°C, 18α varies linearly with temperature from 17 to 14‰, and β varies linearly from 0.513 to 0.508. 18α and β do not appear to vary with growth rate (as tested using different carbon sources). Both 18α and β are lower than previous observations for bacteria: 18α = 17-20‰ (Kiddon et al., 1993) and β = 0.515 (Luz and Barkan, 2005). We were able to simulate the observed temperature dependence of 18α and β using a model of respiration with two isotopically discriminating steps: O2 binding to cytochrome bo oxidase (the respiratory enzyme) and reduction of O2 to H2O. Finally, initial results on N. oceanus suggest it has similar values for 18α and β as previously studied aerobic bacteria that consume organic carbon, providing the first support for assumption (iii). Based on these results, isotopically constrained biogeochemical models of O2 cycling may need to consider a temperature dependence for 18α and β for microbial respiration. For example, these results may

  11. Effect of dolomite and biochar addition on N2O and CO2 emissions from acidic tea field soil

    PubMed Central

    Win, Khin Thuzar; Shibata, Akira; Yamamoto, Akinori; Sano, Tomohito; Hirono, Yuhei

    2018-01-01

    A laboratory study was conducted to study the effects of liming and different biochar amendments on N2O and CO2 emissions from acidic tea field soil. The first experiment was done with three different rates of N treatment; N 300 (300 kg N ha-1), N 600 (600 kg N ha-1) and N 900 (900 kg N ha-1) and four different rates of bamboo biochar amendment; 0%, 0.5%, 1% and 2% biochar. The second experiment was done with three different biochars at a rate of 2% (rice husk, sawdust, and bamboo) and a control and lime treatment (dolomite) and control at two moisture levels (50% and 90% water filled pore space (WFPS)). The results showed that dolomite and biochar amendment significantly increased soil pH. However, only biochar amendment showed a significant increase in total carbon (C), C/N (the ratio of total carbon and total nitrogen), and C/IN ratio (the ratio of total carbon and inorganic nitrogen) at the end of incubation. Reduction in soil NO3--N concentration was observed under different biochar amendments. Bamboo biochar with the rates of 0.5, 1 and 2% reduced cumulative N2O emission by 38%, 48% and 61%, respectively, compare to the control soil in experiment 1. Dolomite and biochar, either alone or combined significantly reduced cumulative N2O emission by 4.6% to 32.7% in experiment 2. Reduction in N2O production under biochar amendment was due to increases in soil pH and decreases in the magnitude of mineral-N in soil. Although, both dolomite and biochar increased cumulative CO2 emission, only biochar amendment had a significant effect. The present study suggests that application of dolomite and biochar to acidic tea field soil can mitigate N2O emissions. PMID:29394272

  12. Effect of dolomite and biochar addition on N2O and CO2 emissions from acidic tea field soil.

    PubMed

    Oo, Aung Zaw; Sudo, Shigeto; Akiyama, Hiroko; Win, Khin Thuzar; Shibata, Akira; Yamamoto, Akinori; Sano, Tomohito; Hirono, Yuhei

    2018-01-01

    A laboratory study was conducted to study the effects of liming and different biochar amendments on N2O and CO2 emissions from acidic tea field soil. The first experiment was done with three different rates of N treatment; N 300 (300 kg N ha-1), N 600 (600 kg N ha-1) and N 900 (900 kg N ha-1) and four different rates of bamboo biochar amendment; 0%, 0.5%, 1% and 2% biochar. The second experiment was done with three different biochars at a rate of 2% (rice husk, sawdust, and bamboo) and a control and lime treatment (dolomite) and control at two moisture levels (50% and 90% water filled pore space (WFPS)). The results showed that dolomite and biochar amendment significantly increased soil pH. However, only biochar amendment showed a significant increase in total carbon (C), C/N (the ratio of total carbon and total nitrogen), and C/IN ratio (the ratio of total carbon and inorganic nitrogen) at the end of incubation. Reduction in soil NO3--N concentration was observed under different biochar amendments. Bamboo biochar with the rates of 0.5, 1 and 2% reduced cumulative N2O emission by 38%, 48% and 61%, respectively, compare to the control soil in experiment 1. Dolomite and biochar, either alone or combined significantly reduced cumulative N2O emission by 4.6% to 32.7% in experiment 2. Reduction in N2O production under biochar amendment was due to increases in soil pH and decreases in the magnitude of mineral-N in soil. Although, both dolomite and biochar increased cumulative CO2 emission, only biochar amendment had a significant effect. The present study suggests that application of dolomite and biochar to acidic tea field soil can mitigate N2O emissions.

  13. Preparation of p-type GaN-doped SnO2 thin films by e-beam evaporation and their applications in p-n junction

    NASA Astrophysics Data System (ADS)

    Lv, Shuliang; Zhou, Yawei; Xu, Wenwu; Mao, Wenfeng; Wang, Lingtao; Liu, Yong; He, Chunqing

    2018-01-01

    Various transparent GaN-doped SnO2 thin films were deposited on glass substrates by e-beam evaporation using GaN:SnO2 targets of different GaN weight ratios. It is interesting to find that carrier polarity of the thin films was converted from n-type to p-type with increasing GaN ratio higher than 15 wt.%. The n-p transition in GaN-doped SnO2 thin films was explained for the formation of GaSn and NO with increasing GaN doping level in the films, which was identified by Hall measurement and XPS analysis. A transparent thin film p-n junction was successfully fabricated by depositing p-type GaN:SnO2 thin film on SnO2 thin film, and a low leakage current (6.2 × 10-5 A at -4 V) and a low turn-on voltage of 1.69 V were obtained for the p-n junction.

  14. The behavior of N2 and O2 in pure, mixed or layered CO ices

    NASA Astrophysics Data System (ADS)

    Bisschop, Suzanne E.; Fraser, Helen J.; Fuchs, Guido; Öberg, Karin I.; Acharyya, Kinsuk; van Broekhuizen, Fleur; Schlemmer, Stephan; van Dishoeck, Ewine F.

    N2 and O2 are molecules that are predicted to be abundant in dense molecular clouds. Both molecules are difficult to detect as neither has a dipole moment. The chemical abundance of N2 is mostly inferred from its daughter species N2H+, but was recently detected in the ISM for the first time, with an abundance of 3.3 × 10-7 (Knauth et al 2004). Searches for the submillimeter lines of O2 have given upper limits for the abundance of ≤ 2.6 10-7 for star forming clouds and ≤ 3 10-6 for cold dark clouds (Goldsmith et al. 2000). Pontoppidan et al. (2003) deduced from the CO line profile that CO is present in both H2O poor and H2O rich ice layers, so it follows that N2 is likely to be present in a H2O poor ice layer. In many cold and protostellar cores N2H+ is found to anti-correlate with HCO+ and CO (Bergin et al. 2001; Jørgensen et al. 2004). Models by, for example Bergin & Langer (1997), assume this is due to the balance between freeze-out and evaporation, where ratios for the binding energy for N2 compared to CO of 0.50-0.70 are used. To model these processes, and reproduce the observed abundances of each species it is important to determine empirically the binding energies, sticking probabilities and desorption kinetics of model ice systems containing CO, N2 and O2. It seems that these quantities depend on the degree to which N2 and O2 mix with CO. Therefore, CO and N2 ices were studied extensively in a Ultra High Vacuum (UHV) experiment (P ~ 1 × 10-10 Torr) (Oberg et al. 2005; Bisschop et al submitted)). Ice samples were deposited at 14 K on a polycrystalline gold sample, mounted in the UHV chamber, covering morphologies from pure CO and N2, and 1:1 mixtures, to 1/1 layers of both CO over N2 and N2 over CO, and layers of 40 L of CO (1 L ≈ 1 monolayer) covered with 5 to 50 L of N2. The ices were studied using a combination of Reflection Absorption Infrared Spectroscopy (RAIRS) and Temperature Programmed Desorption (TPD), at a ramp-rate of 0.1 K min-1. The TPD

  15. Evaluation of the PaO2/FiO2 ratio after cardiac surgery as a predictor of outcome during hospital stay.

    PubMed

    Esteve, Francisco; Lopez-Delgado, Juan C; Javierre, Casimiro; Skaltsa, Konstantina; Carrio, Maria Ll; Rodríguez-Castro, David; Torrado, Herminia; Farrero, Elisabet; Diaz-Prieto, Antonio; Ventura, Josep Ll; Mañez, Rafael

    2014-09-26

    The arterial partial pressure of O2 and the fraction of inspired oxygen (PaO2/FiO2) ratio is widely used in ICUs as an indicator of oxygenation status. Although cardiac surgery and ICU scores can predict mortality, during the first hours after cardiac surgery few instruments are available to assess outcome. The aim of this study was to evaluate the usefulness of PaO2/FIO2 ratio to predict mortality in patients immediately after cardiac surgery. We prospectively studied 2725 consecutive cardiac surgery patients between 2004 and 2009. PaO2/FiO2 ratio was measured on admission and at 3 h, 6 h, 12 h and 24 h after ICU admission, together with clinical data and outcomes. All PaO2/FIO2 ratio measurements differed between survivors and non-survivors (p < 0.001). The PaO2/FIO2 at 3 h after ICU admission was the best predictor of mortality based on area under the curve (p < 0.001) and the optimum threshold estimation gave an optimal cut-off of 222 (95% Confidence interval (CI): 202-242), yielding three groups of patients: Group 1, with PaO2/FIO2 > 242; Group 2, with PaO2/FIO2 from 202 to 242; and Group 3, with PaO2/FIO2 < 202. Group 3 showed higher in-ICU mortality and ICU length of stay and Groups 2 and 3 also showed higher respiratory complication rates. The presence of a PaO2/FIO2 ratio < 202 at 3 h after admission was shown to be a predictor of in-ICU mortality (OR:1.364; 95% CI:1.212-1.625, p < 0.001) and of worse long-term survival (88.8% vs. 95.8%; Log rank p = 0.002. Adjusted Hazard ratio: 1.48; 95% CI:1.293-1.786; p = 0.004). A simple determination of PaO2/FIO2 at 3 h after ICU admission may be useful to identify patients at risk immediately after cardiac surgery.

  16. O2-O2 and O2-N2 collision-induced absorption mechanisms unravelled

    NASA Astrophysics Data System (ADS)

    Karman, Tijs; Koenis, Mark A. J.; Banerjee, Agniva; Parker, David H.; Gordon, Iouli E.; van der Avoird, Ad; van der Zande, Wim J.; Groenenboom, Gerrit C.

    2018-05-01

    Collision-induced absorption is the phenomenon in which interactions between colliding molecules lead to absorption of light, even for transitions that are forbidden for the isolated molecules. Collision-induced absorption contributes to the atmospheric heat balance and is important for the electronic excitations of O2 that are used for remote sensing. Here, we present a theoretical study of five vibronic transitions in O2-O2 and O2-N2, using analytical models and numerical quantum scattering calculations. We unambiguously identify the underlying absorption mechanism, which is shown to depend explicitly on the collision partner—contrary to textbook knowledge. This explains experimentally observed qualitative differences between O2-O2 and O2-N2 collisions in the overall intensity, line shape and vibrational dependence of the absorption spectrum. It is shown that these results can be used to discriminate between conflicting experimental data and even to identify unphysical results, thus impacting future experimental studies and atmospheric applications.

  17. N-[2-(2,2-Di-methyl-propanamido)-pyrimidin-4-yl]-2,2-di-methyl-propanamide n-hexane 0.25-solvate hemihydrate.

    PubMed

    Ośmiałowski, Borys; Valkonen, Arto; Chęcińska, Lilianna

    2013-10-05

    The asymmetric unit of the title compound, C14H22N4O2·0.25C6H14·0.5H2O, contains two independent mol-ecules of 2,4-bis-(pivaloyl-amino)-pyrimidine (M) with similar conformations, one water mol-ecule and one-half n-hexane solvent mol-ecule situated on an inversion center. In one independent M mol-ecule, one of the two tert-butyl groups is rotationally disordered between two orientations in a 3:2 ratio. The n-hexane solvent mol-ecule is disordered between two conformations in the same ratio. The water mol-ecule bridges two independent M mol-ecules via O-H⋯O, N-H⋯O and O-H⋯N hydrogen bonds into a 2M·H2O unit, and these units are further linked by N-H⋯N hydrogen bonds into chains running in the [010] direction. Weak C-H⋯O inter-actions are observed between the adjacent chains.

  18. Isotopologue signatures of nitrous oxide produced by nitrate-ammonifying bacteria isolated from soil

    NASA Astrophysics Data System (ADS)

    Behrendt, Undine; Well, Reinhard; Giesemann, Anette; Ulrich, Andreas; Augustin, Jürgen

    2015-04-01

    Agricultural soils are the largest single source of anthropogenic N2O to the atmosphere, primarily driven by microbiological processes such as denitrification and dissimilatory nitrate reduction to ammonium (DNRA). Both processes occur under similar conditions of low oxygen concentration and therefore, source partitioning of emitted N2O is difficult. Understanding what controls the dynamics and reaction equilibrium of denitrification and DNRA is important and may allow the development of more effective mitigation strategies. 15N site preference (SP), i.e. the difference between 15N of the central and peripheral N-position of the asymmetric N2O molecule, differs depending on processes involved in N2O formation. Hence investigation of the isotopomer ratios of formed N2O potentially presents a reliable mean to identify its source. In this study, bacterial isolates obtained from organic soils were screened for their ability to reduce nitrate/nitrite to ammonium and to release N2O to the atmosphere. Taxonomic characterisation of the strains revealed that N2O formation was only detected in ammonifying strains affiliated to several genera of the family Enterobacteriaceae and strains belonging to the genus Bacillus and Paenibacillus. Sampling of N2O was conducted by incubation of strains under oxic and anoxic conditions. Investigation of the 15N site preference showed SP values in the range of 39 to 57 o . Incubation conditions had no influence on the SP. The lowest values were achieved by a strain of the species Escherichia coli which was included in this study as a DNRA reference bacterium harbouring the NrfA gene that is coding the nitrite reductase, associated with respiratory nitrite ammonification. Soil isolates showed SP-values higher than 40 o . Comparison of these results with SP-values of N2O produced by denitrifying bacteria in pure cultures (-5 to 0 o )^[1, 2]revealedsignificantdifferences.Incontrast,N_2OproducedbydenitrifyingfungidisplayedSP - valuesinarangeof

  19. Complete Measurement of Stable Isotopes in N2O (δ15N, δ15Nα, δ15Nβ, δ18O, δ17O) Using Off-Axis Integrated Cavity Output Spectroscopy (OA-ICOS)

    NASA Astrophysics Data System (ADS)

    Leen, J. B.; Gupta, M.

    2014-12-01

    Nitrate contamination in water is a worldwide environmental problem and source apportionment is critical to managing nitrate pollution. Fractionation caused by physical, chemical and biological processes alters the isotope ratios of nitrates (15N/14N, 18O/16O and 17O/16O) and biochemical nitrification and denitrification impart different intramolecular site preference (15N14NO vs. 14N15NO). Additionally, atmospheric nitrate is anomalously enriched in 17O compared to other nitrate sources. The anomaly (Δ17O) is conserved during fractionation processes, providing a tracer of atmospheric nitrate. All of these effects can be used to apportion nitrate in soil. Current technology for measuring nitrate isotopes is complicated and costly - it involves conversion of nitrate to nitrous oxide (N2O), purification, preconcentration and measurement by isotope ratio mass spectrometer (IRMS). Site specific measurements require a custom IRMS. There is a pressing need to make this measurement simpler and more accessible. Los Gatos Research has developed a next generation mid-infrared Off-Axis Integrated Cavity Output Spectroscopy (OA-ICOS) analyzer to quantify all stable isotope ratios of N2O (δ15N, δ15Nα, δ15Nβ, δ18O, δ17O). We present the latest performance data demonstrating the precision and accuracy of the OA-ICOS based measurement. At an N2O concentration of 322 ppb, the analyzer quantifies [N2O], δ15N, δ15Na, δ15Nb, and δ18O with a precision of ±0.05 ppb, ±0.4 ‰, ±0.45 ‰, and ±0.6 ‰, and ±0.8 ‰ respectively (1σ, 100s; 1σ, 1000s for δ18O). Measurements of gas standards demonstrate accuracy better than ±1 ‰ for isotope ratios over a wide dynamic range (200 - 100,000 ppb). The measurement of δ17O requires a higher concentration (1 - 50 ppm), easily obtainable through conversion of nitrates in water. For 10 ppm of N2O, the instrument achieves a δ17O precision of ±0.05 ‰ (1σ, 1000s). This performance is sufficient to quantify atmospheric

  20. Unconventionally prepared TiO2/g-C3N4 photocatalysts for photocatalytic decomposition of nitrous oxide

    NASA Astrophysics Data System (ADS)

    Troppová, Ivana; Šihor, Marcel; Reli, Martin; Ritz, Michal; Praus, Petr; Kočí, Kamila

    2018-02-01

    The TiO2/g-C3N4 nanocomposites with the various TiO2:g-C3N4 weight ratios from 1:1 to 1:3 were prepared unconventionally by pressurized hot water processing in a flow regime. The parent TiO2 and g-C3N4 was prepared by thermal hydrolysis and thermal annealing, respectively. The nanocomposites as well as parent TiO2 and g-C3N4 were characterized using several complementary characterization methods and investigated in the photocatalytic decomposition of N2O under UVA (λ = 365 nm) irradiation. All the prepared TiO2/g-C3N4 nanocomposites showed higher photocatalytic activity in comparison with the pure g-C3N4 and chiefly pure TiO2. The photocatalytic activity of TiO2/g-C3N4 nanocomposites was decreasing in the following sequence: TiO2/g-C3N4 (1:3) > TiO2/g-C3N4 (1:2) > TiO2/g-C3N4 (1:1). In comparison with the parent TiO2 or g-C3N4, the TiO2/g-C3N4 nanocomposites' photocatalytic capability was significantly enhanced by coupling TiO2 with g-C3N4. The generation of TiO2/g-C3N4 Z-scheme photocatalyst mainly benefited from the effective separation of photoinduced electron-hole pairs and the extended optical absorption range. The TiO2/g-C3N4 (1:3) nanocomposite showed the best photocatalytic behavior in a consequence of the optimal weight ratio of TiO2:g-C3N4 and the lowest band gap energy from all nanocomposites. The N2O conversion in its presence was 70.6% after 20 h of UVA irradiation.

  1. Direct Detection of Hardly Detectable Hidden Chirality of Hydrocarbons and Deuterated Isotopomers by a Helical Polyacetylene through Chiral Amplification and Memory.

    PubMed

    Maeda, Katsuhiro; Hirose, Daisuke; Okoshi, Natsuki; Shimomura, Kouhei; Wada, Yuya; Ikai, Tomoyuki; Kanoh, Shigeyoshi; Yashima, Eiji

    2018-03-07

    We report the first direct chirality sensing of a series of chiral hydrocarbons and isotopically chiral compounds (deuterated isotopomers), which are almost impossible to detect by conventional optical spectroscopic methods, by a stereoregular polyacetylene bearing 2,2'-biphenol-derived pendants. The polyacetylene showed a circular dichroism due to a preferred-handed helix formation in response to the hardly detectable hidden chirality of saturated tertiary or chiroptical quaternary hydrocarbons, and deuterated isotopomers. In sharp contrast to the previously reported sensory systems, the chirality detection by the polyacetylene relies on an excess one-handed helix formation induced by the chiral hydrocarbons and deuterated isotopomers via significant amplification of the chirality followed by its static memory, through which chiral information on the minute and hidden chirality can be stored as an excess of a single-handed helix memory for a long time.

  2. N2O molecular tagging velocimetry

    NASA Astrophysics Data System (ADS)

    ElBaz, A. M.; Pitz, R. W.

    2012-03-01

    A new seeded velocity measurement technique, N2O molecular tagging velocimetry (MTV), is developed to measure velocity in wind tunnels by photochemically creating an NO tag line. Nitrous oxide "laughing gas" is seeded into the air flow. A 193 nm ArF excimer laser dissociates the N2O to O(1D) that subsequently reacts with N2O to form NO. O2 fluorescence induced by the ArF laser "writes" the original position of the NO line. After a time delay, the shifted NO line is "read" by a 226-nm laser sheet and the velocity is determined by time-of-flight. At standard atmospheric conditions with 4% N2O in air, ˜1000 ppm of NO is photochemically created in an air jet based on experiment and simulation. Chemical kinetic simulations predict 800-1200 ppm of NO for 190-750 K at 1 atm and 850-1000 ppm of NO for 0.25-1 atm at 190 K. Decreasing the gas pressure (or increasing the temperature) increases the NO ppm level. The presence of humid air has no significant effect on NO formation. The very short NO formation time (<10 ns) makes the N2O MTV method amenable to low- and high-speed air flow measurements. The N2O MTV technique is demonstrated in air jet to measure its velocity profile. The N2O MTV method should work in other gas flows as well (e.g., helium) since the NO tag line is created by chemical reaction of N2O with O(1D) from N2O photodissociation and thus does not depend on the bulk gas composition.

  3. Potassium (2,2'-bipyridine-κN,N')bis-(carbonato-κO,O')cobaltate(III) dihydrate.

    PubMed

    Wang, Jian-Fei; Lin, Jian-Li

    2010-09-30

    In the title compound, K[Co(CO(3))(2)(C(10)H(8)N(2))]·2H(2)O, the Co(III) atom is coordinated by two bipyridine N atoms and four O atoms from two bidentate chelating carbonate anions, and thus adopts a distorted octa-hedral N(2)O(4) environment. The [Co(bipy)(CO(3))(2)](-) (bipy is 2,2'-bipyridine) -units are stacked along [100] via π-π stacking inter-actions, with inter-planar distances between the bipyridine rings of 3.36 (4) and 3.44 (6) Å, forming chains. Classical O-H⋯O hydrogen-bonding inter-actions link the chains, forming channels along (100) in which the K(+) ions reside and leading to a three-dimensional supra-molecular architecture.

  4. The earthworm gut: an ideal habitat for ingested N2O-producing microorganisms.

    PubMed

    Horn, Marcus A; Schramm, Andreas; Drake, Harold L

    2003-03-01

    The in vivo production of nitrous oxide (N(2)O) by earthworms is due to their gut microbiota, and it is hypothesized that the microenvironment of the gut activates ingested N(2)O-producing soil bacteria. In situ measurement of N(2)O and O(2) with microsensors demonstrated that the earthworm gut is anoxic and the site of N(2)O production. The gut had a pH of 6.9 and an average water content of approximately 50%. The water content within the gut decreased from the anterior end to the posterior end. In contrast, the concentration of N(2)O increased from the anterior end to the mid-gut region and then decreased along the posterior part of the gut. Compared to the soil in which worms lived and fed, the gut of the earthworm was highly enriched in total carbon, organic carbon, and total nitrogen and had a C/N ratio of 7 (compared to a C/N ratio of 12 in soil). The aqueous phase of gut contents contained up to 80 mM glucose and numerous compounds that were indicative of anaerobic metabolism, including up to 9 mM formate, 8 mM acetate, 3 mM lactate, and 2 mM succinate. Compared to the soil contents, nitrite and ammonium were enriched in the gut up to 10- and 100-fold, respectively. The production of N(2)O by soil was induced when the gut environment was simulated in anoxic microcosms for 24 h (the approximate time for passage of soil through the earthworm). Anoxia, high osmolarity, nitrite, and nitrate were the dominant factors that stimulated the production of N(2)O. Supplemental organic carbon had a very minimal stimulatory effect on the production of N(2)O, and addition of buffer or ammonium had essentially no effect on the initial N(2)O production rates. However, a combination of supplements yielded rates greater than that obtained mathematically for single supplements, suggesting that the maximum rates observed were due to synergistic effects of supplements. Collectively, these results indicate that the special microenvironment of the earthworm gut is ideally suited

  5. Conversion of nitrogen oxides in N2:O2:CO2 and N2:O2:CO2:NO2 mixtures subjected to a dc corona discharge

    NASA Astrophysics Data System (ADS)

    Dors, Mirosław; Mizeraczyk, Jerzy

    1996-10-01

    This paper concerns the influence of a direct current (dc) corona discharge on production and reduction of NO, NO2 and N2O in N2:O2:CO2 and N2:O2:CO2:NO2 mixtures. The corona discharge was generated in a needle-to-plate reactor. The positively polarized electrode consisted of 7 needles. The grounded electrode was a stainless steel plate. The gas flow rate through the reactor was varied from 28 to 110 cm3/s. The time-averaged discharge current ranged from 0 to 6 mA. It was found that in the N2:O2:CO2 mixture the corona discharge produced NO, NO2 and N2O. In the N2:O2:CO2:NO2 mixture the reduction of NO2 was between 6-56%, depending on the concentration of O2, gas flow rate and corona discharge current. The NO2 reduction was accompanied by production of NO and N2O. The results show that efficient reduction of nitrogen oxides by a corona discharge cannot be expected in the mixtures containing N2 and O2 if reducing additives are not employed.

  6. Infrared spectra of seeded hydrogen clusters: (para-H2)N-N2O and (ortho-H2)N-N2O, N = 2-13.

    PubMed

    Tang, Jian; McKellar, A R W

    2005-09-15

    High-resolution infrared spectra of clusters containing para-H2 and/or ortho-H2 and a single nitrous oxide molecule are studied in the 2225-cm(-1) region of the upsilon1 fundamental band of N2O. The clusters are formed in pulsed supersonic jet expansions from a cooled nozzle and probed using a tunable infrared diode laser spectrometer. The simple symmetric rotor-type spectra generally show no resolved K structure, with prominent Q-branch features for ortho-H2 but not para-H2 clusters. The observed vibrational shifts and rotational constants are reported. There is no obvious indication of superfluid effects for para-H2 clusters up to N=13. Sharp transitions due to even larger clusters are observed, but no definite assignments are possible. Mixed (para-H2)N-(ortho-H2)M-N2O cluster line positions can be well predicted by linear interpolation between the corresponding transitions of the pure clusters.

  7. Estimating N2O processes during grassland renewal and grassland conversion to maize cropping using N2O isotopocules

    NASA Astrophysics Data System (ADS)

    Buchen, Caroline; Well, Reinhard; Flessa, Heinz; Fuß, Roland; Helfrich, Mirjam; Lewicka-Szczebak, Dominika

    2017-04-01

    Grassland break-up due to grassland renewal and grassland conversion to cropland can lead to a flush of mineral nitrogen from decomposition of the old grass sward and the decomposition of soil organic matter. Moreover, increased carbon and nitrogen mineralisation can result in enhanced nitrous oxide (N2O) emissions. As N2O is known to be an important greenhouse gas and a major precursor for ozone depletion, its emissions need to be mitigated by adjusting agricultural management practices. Therefore, it is necessary to understand the N2O processes involved, as well as the contribution of N2O reduction to N2. Apart from the widely used 15N gas flux method, natural abundance isotopic analysis of the four most abundant isotopocules of N2O species is a promising alternative to assess N2O production pathways. We used stable isotope analyses of soil-emitted N2O (δ18ON2O, δ15NN2Obulk and δ15NN2OSP= intramolecular distribution of 15N within the linear N2O molecule) with an isotopocule mapping approach to simultaneously estimate the magnitude of N2O reduction to N2 and the fraction of N2O originating from the bacterial denitrification pathway or fungal denitrification and/or nitrification. This approach is based on endmember areas of isotopic values for the N2O produced from different sources reported in the literature. For this purpose, we calculated two main scenarios with different assumptions for N2O produced: N2O is reduced to N2 before residual N2O is mixed with N2O of various sources (Scenario a) and vice versa (Scenario b). Based on this, we applied seven different scenario variations, where we evaluated the range of possible values for the potential N2O production pathways (heterotrophic bacterial denitrification and/or nitrifier denitrification and fungal denitrification and/or nitrification). This was done by using a range of isotopic endmember values and assuming different fractionation factors of N2O reduction in order to find the most reliable scenario

  8. Regional N2O fluxes in Amazonia derived from aircraft vertical profiles

    NASA Astrophysics Data System (ADS)

    D'Amelio, M. T. S.; Gatti, L. V.; Miller, J. B.; Tans, P.

    2009-11-01

    Nitrous oxide (N2O) is the third most important anthropogenic greenhouse gas. Globally, the main sources of N2O are nitrification and denitrification in soils. About two thirds of the soil emissions occur in the tropics and approximately 20% originate in wet rainforest ecosystems, like the Amazon forest. The work presented here involves aircraft vertical profiles of N2O from the surface to 4 km over two sites in the Eastern and Central Amazon: Tapajós National Forest (SAN) and Cuieiras Biologic Reserve (MAN), and the estimation of N2O fluxes for regions upwind of these sites. To our knowledge, these regional scale N2O measurements in Amazonia are unique and represent a new approach to looking regional scale emissions. The fluxes upwind of MAN exhibited little seasonality, and the annual mean was 2.1±1.0 mg N2O m-2 day-1, higher than that for fluxes upwind of SAN, which averaged 1.5±1.6 mg N2O m-2 day-1. The higher rainfall around the MAN site could explain the higher N2O emissions, as a result of increased soil moisture accelerating microbial nitrification and denitrification processes. For fluxes from the coast to SAN seasonality is present for all years, with high fluxes in the months of March through May, and in November through December. The first peak of N2O flux is strongly associated with the wet season. The second peak of high N2O flux recorded at SAN occurs during the dry season and can not be easily explained. However, about half of the dry season profiles exhibit significant correlations with CO, indicating a larger than expected source of N2O from biomass burning. The average CO:N2O ratio for all profiles sampled during the dry season is 94±77 mol CO:mol N2O and suggests a larger biomass burning contribution to the global N2O budget than previously reported.

  9. Regional N2O fluxes in Amazonia derived from aircraft vertical profiles

    NASA Astrophysics Data System (ADS)

    D'Amelio, M. T. S.; Gatti, L. V.; Miller, J. B.; Tans, P.

    2009-08-01

    Nitrous oxide (N2O) is the third most important anthropogenic greenhouse gas. Globally, the main sources of N2O are nitrification and denitrification in soils. About two thirds of the soil emissions occur in the tropics and approximately 20% originate in wet rainforest ecosystems, like the Amazon forest. The work presented here involves aircraft vertical profiles of N2O from the surface to 4 km over two sites in the Eastern and Central Amazon: Tapajós National Forest (SAN) and Cuieiras Biologic Reserve (MAN), and the estimation of N2O fluxes for regions upwind of these sites. To our knowledge, these regional scale N2O measurements in Amazonia are unique and represent a new approach to looking regional scale emissions. The fluxes upwind of MAN exhibited little seasonality, and the annual mean was 2.1±1.0 mg N2O m-2 day-1, higher than that for fluxes upwind of SAN, which averaged 1.5±1.6 mg N2O m-2 day-1. The higher rainfall around the MAN site could explain the higher N2O emissions. For fluxes from the coast to SAN seasonality is present for all years, with high fluxes in the months of March through May, and in November through December. The first peak of N2O flux is strongly associated with the wet season. The second peak of high N2O flux recorded at SAN occurs during the dry season and can not be easily explained. However, about half of the dry season profiles exhibit significant correlations with CO, indicating a larger than expected source of N2O from biomass burning. The average CO:N2O ratio for all profiles sampled during the dry season is 94±77 mol CO:mol N2O and suggests a larger biomass burning contribution to the global N2O budget than previously reported.

  10. Life on N2O: deciphering the ecophysiology of N2O respiring bacterial communities in a continuous culture.

    PubMed

    Conthe, Monica; Wittorf, Lea; Kuenen, J Gijs; Kleerebezem, Robbert; van Loosdrecht, Mark C M; Hallin, Sara

    2018-04-01

    Reduction of the greenhouse gas N 2 O to N 2 is a trait among denitrifying and non-denitrifying microorganisms having an N 2 O reductase, encoded by nosZ. The nosZ phylogeny has two major clades, I and II, and physiological differences among organisms within the clades may affect N 2 O emissions from ecosystems. To increase our understanding of the ecophysiology of N 2 O reducers, we determined the thermodynamic growth efficiency of N 2 O reduction and the selection of N 2 O reducers under N 2 O- or acetate-limiting conditions in a continuous culture enriched from a natural community with N 2 O as electron acceptor and acetate as electron donor. The biomass yields were higher during N 2 O limitation, irrespective of dilution rate and community composition. The former was corroborated in a continuous culture of Pseudomonas stutzeri and was potentially due to cytotoxic effects of surplus N 2 O. Denitrifiers were favored over non-denitrifying N 2 O reducers under all conditions and Proteobacteria harboring clade I nosZ dominated. The abundance of nosZ clade II increased when allowing for lower growth rates, but bacteria with nosZ clade I had a higher affinity for N 2 O, as defined by μ max /K s . Thus, the specific growth rate is likely a key factor determining the composition of communities living on N 2 O respiration under growth-limited conditions.

  11. Effect of Initial FeO Content and CaO:SiO2 Ratio on the Reduction Smelting Kinetics of the CaO-SiO2-MgOsatd.-FeO Slag System

    NASA Astrophysics Data System (ADS)

    Kim, Jong Bae; Sohn, Il

    2018-02-01

    The effect of the initial FeO content and CaO:SiO2 ratio (CaO mass pct/SiO2 mass pct) on the reduction smelting of FeO with carbon flake addition is investigated in the CaO-MgOsatd.-SiO2-FeO slag system at 1823 K (1550 °C). Carbon rapidly reacted with FeO in the molten slag, causing both foaming and compositional changes in the slag. As FeO is reduced, the MgO saturation is modified, and solid precipitants, including MgO and other complex oxides, were observed, which significantly affected the slag properties, including the viscosity and foaming behavior. The solid-phase fraction and viscosity were estimated from changes in the measured FeO content over time using the thermochemical software FactSage. The iron recovery, which is distinguished from the amount of reduced Fe droplets, showed opposite behavior to the measured maximum foaming height and modified foaming index. According to the FeO mass transfer coefficient considering slag foaming at various initial FeO contents and CaO:SiO2 ratios, the reduction rate was optimal at higher initial FeO contents and a CaO:SiO2 ratio of 2.0, which did not correspond to the optimal iron recovery at an initial FeO content of 44 mass pct and above and a CaO:SiO2 ratio of 1.2. The results showed that slag foaming may increase the reduction kinetics, but the slag composition needs to be optimized for greater iron recovery.

  12. Automated system measuring triple oxygen and nitrogen isotope ratios in nitrate using the bacterial method and N2 O decomposition by microwave discharge.

    PubMed

    Hattori, Shohei; Savarino, Joel; Kamezaki, Kazuki; Ishino, Sakiko; Dyckmans, Jens; Fujinawa, Tamaki; Caillon, Nicolas; Barbero, Albane; Mukotaka, Arata; Toyoda, Sakae; Well, Reinhard; Yoshida, Naohiro

    2016-12-30

    Triple oxygen and nitrogen isotope ratios in nitrate are powerful tools for assessing atmospheric nitrate formation pathways and their contribution to ecosystems. N 2 O decomposition using microwave-induced plasma (MIP) has been used only for measurements of oxygen isotopes to date, but it is also possible to measure nitrogen isotopes during the same analytical run. The main improvements to a previous system are (i) an automated distribution system of nitrate to the bacterial medium, (ii) N 2 O separation by gas chromatography before N 2 O decomposition using the MIP, (iii) use of a corundum tube for microwave discharge, and (iv) development of an automated system for isotopic measurements. Three nitrate standards with sample sizes of 60, 80, 100, and 120 nmol were measured to investigate the sample size dependence of the isotope measurements. The δ 17 O, δ 18 O, and Δ 17 O values increased with increasing sample size, although the δ 15 N value showed no significant size dependency. Different calibration slopes and intercepts were obtained with different sample amounts. The slopes and intercepts for the regression lines in different sample amounts were dependent on sample size, indicating that the extent of oxygen exchange is also dependent on sample size. The sample-size-dependent slopes and intercepts were fitted using natural log (ln) regression curves, and the slopes and intercepts can be estimated to apply to any sample size corrections. When using 100 nmol samples, the standard deviations of residuals from the regression lines for this system were 0.5‰, 0.3‰, and 0.1‰, respectively, for the δ 18 O, Δ 17 O, and δ 15 N values, results that are not inferior to those from other systems using gold tube or gold wire. An automated system was developed to measure triple oxygen and nitrogen isotopes in nitrate using N 2 O decomposition by MIP. This system enables us to measure both triple oxygen and nitrogen isotopes in nitrate with comparable precision

  13. Influence of Lumbricus terrestris and Folsomia candida on N2 O formation pathways in two different soils - with particular focus on N2 emissions.

    PubMed

    Schorpp, Quentin; Riggers, Catharina; Lewicka-Szczebak, Dominika; Giesemann, Anette; Well, Reinhard; Schrader, Stefan

    2016-11-15

    The gaseous N losses mediated by soil denitrifiers are generally inferred by measuring N 2 O fluxes, but should include associated N 2 emissions, which may be affected by abiotic soil characteristics and biotic interactions. Soil fauna, particularly anecic earthworms and euedaphic collembola, alter the activity of denitrifiers, creating hotspots for denitrification. These soil fauna are abundant in perennial agroecosystems intended to contribute to more sustainable production of bioenergy. Two microcosm experiments were designed to evaluate gaseous N emissions from a silty loam and a sandy soil, both provided with litter from the bioenergy crop Silphium perfoliatum (cup-plant) and inoculated with an anecic earthworm (Lumbricus terrestris), which was added alone or together with an euedaphic collembola (Folsomia candida). In experiment 1, litter-derived N flux was determined by adding 15 N-labelled litter, followed by mass spectrometric analysis of N 2 and N 2 O isotopologues. In experiment 2, the δ 18 O values and 15 N site preference of N 2 O were determined by isotope ratio mass spectrometry to reveal underlying N 2 O formation pathways. Lumbricus terrestris significantly increased litter-derived N 2 emissions in the loamy soil, from 174.5 to 1019.3 μg N 2 -N kg -1 soil, but not in the sandy soil (non-significant change from 944.7 to 1054.7 μg N 2 -N kg -1 soil). Earthworm feeding on plant litter resulted in elevated N 2 O emissions in both soils, derived mainly from turnover of the soil mineral N pool during denitrification. Folsomia candida did not affect N losses but showed a tendency to redirect N 2 O formation pathways from fungal to bacterial denitrification. The N 2 O/(N 2  + N 2 O) product ratio was predominantly affected by abiotic soil characteristics (loamy soil: 0.14, sandy soil: 0.26). When feeding on S. perfoliatum litter, the anecic L. terrestris, but not the euedaphic F. candida, has the potential to cause substantial N losses. Biotic

  14. Octa-akis(4-amino-pyridine)-1κN,2κN-aqua-2κO-μ-carbonato-1:2κO,O':O''-dinickel(II) dichloride penta-hydrate.

    PubMed

    Fun, Hoong-Kun; Sinthiya, A; Jebas, Samuel Robinson; Ravindran Durai Nayagam, B; Alfred Cecil Raj, S

    2008-10-18

    In the title compound, [Ni(2)(CO(3))(C(5)H(6)N(2))(8)(H(2)O)]Cl(2)·5H(2)O, one of the the Ni(II) ions is six-coordinated in a distorted octa-hedral geometry, with the equatorial plane defined by four pyridine N atoms from four amino-pyridine ligands, the axial positions being occupied by one water O and a carbonate O atom. The other Ni(II) ion is also six-coordinated, by four other pyridine N atoms from four other amino-pyridine ligands and two carbonate O atoms to complete a distorted octa-hedral geometry. In the crystal structure, mol-ecules are linked into an infinite three-dimensional network by O-H⋯O, N-H⋯Cl, N-H⋯O, O-H⋯N, C-H⋯O, C-H⋯N and C/N-H⋯π inter-actions involving the pyridine rings.

  15. Fabricated and investigated the structure and super conductivity properties of Bi2Sr2Can-1CunO2n+4+δ compound

    NASA Astrophysics Data System (ADS)

    Mahdi, Shatha H.; Salim, Faiza M.; Jasim, Kareem Ail; Ali, Mohammed Abdulmuhsin; Ahmed, Saja Amer; Fadhel, Noor Q.

    2018-05-01

    This paper investigated the influence of Cu-O and Ca-O layers change on the superconductivity properties and crystal structure of Bi2Sr2Can-1CunO2n+4+δ superconductor fabricated via conventional solid state reaction method. X-ray diffraction technique was utilized to study the structure of the specimens. The results showed that a change in the lattice parameters a, b, and c, and lattice ratio c/a appeared as a function of Cu-O and Ca-O layers change, while c/a ratio increased with the increasing of n(of Cu-O and Ca-O layers). However, the electrical resistivity as a function of temperature was used to calculate critical temperature of transition Tc, Tc (offset) = 137k,138k and 139k and Tc(onset)=144k, 160k,161k for n=1,2 and 3 specimens respectively. The study was came to conclusion that the increase in critical temperature was established due to the increase in n (Ca-O and Cu-O layers) of specimens. Atomic force microscopy showed that the Roughness average and root mean square change with the change of n of all specimens.

  16. Superconductivity at 33-37 K in A L n2Fe4As4O2 (A =Kand Cs;L n =lanthanides)

    NASA Astrophysics Data System (ADS)

    Wu, Si-Qi; Wang, Zhi-Cheng; He, Chao-Yang; Tang, Zhang-Tu; Liu, Yi; Cao, Guang-Han

    2017-09-01

    We have synthesized ten iron oxyarsenides, K L n2Fe4As4O2 (L n =Gd,Tb,Dy, and Ho) and Cs L n2Fe4As4O2 (L n =Nd,Sm,Gd,Tb,Dy, and Ho) , with the aid of the lattice-match approach. The resultant compounds possess hole-doped conducting double FeAs layers [AFe4As4] 2 - that are separated by the insulating [Ln2O2] 2 + slabs. Measurements of electrical resistivity and dc magnetic susceptibility demonstrate bulk superconductivity at Tc=33 -37 K. We find that Tc correlates with the axial ratio c /a for all 12442-type superconductors discovered. Also, Tc tends to increase with the lattice mismatch, implying that lattice instability plays a role in the enhancement of superconductivity.

  17. Isotope signatures of N₂O in a mixed microbial population system: constraints on N₂O producing pathways in wastewater treatment.

    PubMed

    Wunderlin, Pascal; Lehmann, Moritz F; Siegrist, Hansruedi; Tuzson, Béla; Joss, Adriano; Emmenegger, Lukas; Mohn, Joachim

    2013-02-05

    We present measurements of site preference (SP) and bulk (15)N/(14)N ratios (δ(15)N(bulk)(N2O)) of nitrous oxide (N(2)O) by quantum cascade laser absorption spectroscopy (QCLAS) as a powerful tool to investigate N(2)O production pathways in biological wastewater treatment. QCLAS enables high-precision N(2)O isotopomer analysis in real time. This allowed us to trace short-term fluctuations in SP and δ(15)N(bulk)(N2O) and, hence, microbial transformation pathways during individual batch experiments with activated sludge from a pilot-scale facility treating municipal wastewater. On the basis of previous work with microbial pure cultures, we demonstrate that N(2)O emitted during ammonia (NH(4)(+)) oxidation with a SP of -5.8 to 5.6 ‰ derives mostly from nitrite (NO(2)(-)) reduction (e.g., nitrifier denitrification), with a minor contribution from hydroxylamine (NH(2)OH) oxidation at the beginning of the experiments. SP of N(2)O produced under anoxic conditions was always positive (1.2 to 26.1 ‰), and SP values at the high end of this spectrum (24.9 to 26.1 ‰) are indicative of N(2)O reductase activity. The measured δ(15)N(bulk)(N2O) at the initiation of the NH(4)(+) oxidation experiments ranged between -42.3 and -57.6 ‰ (corresponding to a nitrogen isotope effect Δδ(15)N = δ(15)N(substrate) - δ(15)N(bulk)(N2O) of 43.5 to 58.8 ‰), which is considerably higher than under denitrifying conditions (δ(15)N(bulk)(N2O) 2.4 to -17 ‰; Δδ(15)N = 0.1 to 19.5 ‰). During the course of all NH(4)(+) oxidation and nitrate (NO(3)(-)) reduction experiments, δ(15)N(bulk)(N2O) increased significantly, indicating net (15)N enrichment in the dissolved inorganic nitrogen substrates (NH(4)(+), NO(3)(-)) and transfer into the N(2)O pool. The decrease in δ(15)N(bulk)(N2O) during NO(2)(-) and NH(2)OH oxidation experiments is best explained by inverse fractionation during the oxidation of NO(2)(-) to NO(3)(-).

  18. Photoelectron spectroscopic study of the hydrated nucleoside anions: Uridine(-)(H(2)O)(n=0-2), cytidine(-)(H(2)O)(n=0-2), and thymidine(-)(H(2)O)(n=0,1).

    PubMed

    Li, Xiang; Wang, Haopeng; Bowen, Kit H

    2010-10-14

    The hydrated nucleoside anions, uridine(-)(H(2)O)(n=0-2), cytidine(-)(H(2)O)(n=0-2), and thymidine(-)(H(2)O)(n=0,1), have been prepared in beams and studied by anion photoelectron spectroscopy in order to investigate the effects of a microhydrated environment on parent nucleoside anions. Vertical detachment energies (VDEs) were measured for all eight anions, and from these, estimates were made for five sequential anion hydration energies. Excellent agreement was found between our measured VDE value for thymidine(-)(H(2)O)(1) and its calculated value in the companion article by S. Kim and H. F. Schaefer III.

  19. Photoelectron spectroscopic study of the hydrated nucleoside anions: Uridine-(H2O)n=0-2, cytidine-(H2O)n=0-2, and thymidine-(H2O)n=0,1

    NASA Astrophysics Data System (ADS)

    Li, Xiang; Wang, Haopeng; Bowen, Kit H.

    2010-10-01

    The hydrated nucleoside anions, uridine-(H2O)n=0-2, cytidine-(H2O)n=0-2, and thymidine-(H2O)n=0,1, have been prepared in beams and studied by anion photoelectron spectroscopy in order to investigate the effects of a microhydrated environment on parent nucleoside anions. Vertical detachment energies (VDEs) were measured for all eight anions, and from these, estimates were made for five sequential anion hydration energies. Excellent agreement was found between our measured VDE value for thymidine-(H2O)1 and its calculated value in the companion article by S. Kim and H. F. Schaefer III.

  20. The structure, stability, and infrared spectrum of B 2N, B 2N +, B 2N -, BO, B 2O and B 2N 2.

    NASA Astrophysics Data System (ADS)

    Martin, J. M. L.; François, J. P.; Gijbels, R.

    1992-05-01

    The structure, infrared spectrum, and heat of formation of B 2N, B 2N -, BO, and B 2O have been studied ab initio. B 2N is very stable; B 2O even more so. B 2N, B 2N -, B 2O, and probably B 2N + have symmetric linear ground-state structures; for B 2O, an asymmetric linear structure lies about 12 kcal/mol above the ground state. B 2N +, B 2N - and B 2O have intense asymmetric stretching frequencies, predicted near 870, 1590 and 1400 cm -1, respectively. Our predicted harmonic frequencies and isotopic shifts for B 2O confirm the recent experimental identification by Andrews and Burkholder. Absorptions at 1889.5 and 1998.5 cm -1 in noble-gas trapped boron nitride vapor belong the BNB and BNBN ( 3Π), respectively; a tentative assignment of 882.5 cm -1 to BNB + is proposed. Total atomization energies Σ De (Σ D0) are computed (accuracy ±2 kcal/mol) as: BO 193.1 (190.4), B 2O 292.5 (288.7), B 2N 225.0 (250.3) kcal/mol. The ionization potential and electron affinity of B 2N are predicted to be 8.62±0.1 and 3.34±0.1 eV. The MP4-level additivity approximations involved in G1 theory results in errors on the order of 1 kcal/mol in the Σ De values.

  1. 'Isotopo' a database application for facile analysis and management of mass isotopomer data.

    PubMed

    Ahmed, Zeeshan; Zeeshan, Saman; Huber, Claudia; Hensel, Michael; Schomburg, Dietmar; Münch, Richard; Eylert, Eva; Eisenreich, Wolfgang; Dandekar, Thomas

    2014-01-01

    The composition of stable-isotope labelled isotopologues/isotopomers in metabolic products can be measured by mass spectrometry and supports the analysis of pathways and fluxes. As a prerequisite, the original mass spectra have to be processed, managed and stored to rapidly calculate, analyse and compare isotopomer enrichments to study, for instance, bacterial metabolism in infection. For such applications, we provide here the database application 'Isotopo'. This software package includes (i) a database to store and process isotopomer data, (ii) a parser to upload and translate different data formats for such data and (iii) an improved application to process and convert signal intensities from mass spectra of (13)C-labelled metabolites such as tertbutyldimethylsilyl-derivatives of amino acids. Relative mass intensities and isotopomer distributions are calculated applying a partial least square method with iterative refinement for high precision data. The data output includes formats such as graphs for overall enrichments in amino acids. The package is user-friendly for easy and robust data management of multiple experiments. The 'Isotopo' software is available at the following web link (section Download): http://spp1316.uni-wuerzburg.de/bioinformatics/isotopo/. The package contains three additional files: software executable setup (installer), one data set file (discussed in this article) and one excel file (which can be used to convert data from excel to '.iso' format). The 'Isotopo' software is compatible only with the Microsoft Windows operating system. http://spp1316.uni-wuerzburg.de/bioinformatics/isotopo/. © The Author(s) 2014. Published by Oxford University Press.

  2. Fabrication and electrical properties of p-CuAlO2/(n-, p-)Si heterojunctions

    NASA Astrophysics Data System (ADS)

    Suzhen, Wu; Zanhong, Deng; Weiwei, Dong; Jingzhen, Shao; Xiaodong, Fang

    2014-04-01

    CuAlO2 thin films have been prepared by the chemical solution deposition method on both n-Si and p-Si substrates. X-ray diffraction analysis indicates that the obtained CuAlO2 films have a single delafossite structure. The current transport properties of the resultant p-CuAlO2/n-Si and p-CuAlO2/p-Si heterojunctions are investigated by current-voltage measurements. The p-CuAlO2/n-Si has a rectifying ratio of ~35 within the applied voltages of -3.0 to +3.0 V, while the p-CuAlO2/p-Si shows Schottky diode-like characteristics, dominated in forward bias by the flow of space-charge-limited current.

  3. Full-Dimensional Quantum Calculations of Vibrational Levels of NH4(+) and Isotopomers on An Accurate Ab Initio Potential Energy Surface.

    PubMed

    Yu, Hua-Gen; Han, Huixian; Guo, Hua

    2016-04-14

    Vibrational energy levels of the ammonium cation (NH4(+)) and its deuterated isotopomers are calculated using a numerically exact kinetic energy operator on a recently developed nine-dimensional permutation invariant semiglobal potential energy surface fitted to a large number of high-level ab initio points. Like CH4, the vibrational levels of NH4(+) and ND4(+) exhibit a polyad structure, characterized by a collective quantum number P = 2(v1 + v3) + v2 + v4. The low-lying vibrational levels of all isotopomers are assigned and the agreement with available experimental data is better than 1 cm(-1).

  4. New metallicity calibration for Seyfert 2 galaxies based on the N2O2 index

    NASA Astrophysics Data System (ADS)

    Castro, C. S.; Dors, O. L.; Cardaci, M. V.; Hägele, G. F.

    2017-05-01

    We derive a new relation between the metallicity of Seyfert 2 active galactic nuclei (AGNs) and the intensity of the narrow emission-lines ratio N2O2 = log([N II] λ6584/[O II] λ3727). The calibration of this relation was performed by determining the metallicity (Z) of a sample of 58 AGNs through a diagram containing the observational data and the results of a grid of photoionization models obtained with the cloudy code. We find the new Z/Z⊙-N2O2 relation using the obtained metallicity values and the corresponding observational emission-line intensities for each object of the sample. Estimations derived through the use of this new calibration indicate that the narrow-line regions of Seyfert 2 galaxies exhibit a large range of metallicities (0.3 ≲ Z/Z⊙ ≲ 2.0), with a median value Z ≈ Z⊙. Regarding the possible existence of correlations between the luminosity L(Hβ), the electron density and the colour excess E(B - V) with the metallicity in this kind of objects, we do not find correlations between them.

  5. Effects of C/N ratio on nitrous oxide production from nitrification in a laboratory-scale biological aerated filter reactor.

    PubMed

    He, Qiang; Zhu, Yinying; Fan, Leilei; Ai, Hainan; Huangfu, Xiaoliu; Chen, Mei

    2017-03-01

    Emission of nitrous oxide (N 2 O) during biological wastewater treatment is of growing concern. This paper reports findings of the effects of carbon/nitrogen (C/N) ratio on N 2 O production rates in a laboratory-scale biological aerated filter (BAF) reactor, focusing on the biofilm during nitrification. Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and microelectrode technology were utilized to evaluate the mechanisms associated with N 2 O production during wastewater treatment using BAF. Results indicated that the ability of N 2 O emission in biofilm at C/N ratio of 2 was much stronger than at C/N ratios of 5 and 8. PCR-DGGE analysis showed that the microbial community structures differed completely after the acclimatization at tested C/N ratios (i.e., 2, 5, and 8). Measurements of critical parameters including dissolved oxygen, oxidation reduction potential, NH 4 + -N, NO 3 - -N, and NO 2 - -N also demonstrated that the internal micro-environment of the biofilm benefit N 2 O production. DNA analysis showed that Proteobacteria comprised the majority of the bacteria, which might mainly result in N 2 O emission. Based on these results, C/N ratio is one of the parameters that play an important role in the N 2 O emission from the BAF reactors during nitrification.

  6. Rapid synthesis of Fe-doped CuO-Ce0.8Zr0.2O2 catalysts for CO preferential oxidation in H2-rich streams: Effect of iron source and the ratio of Fe/Cu

    NASA Astrophysics Data System (ADS)

    Wang, Jing; Han, Caiyun; Gao, Xiaoya; Lu, Jichang; Wan, Gengpin; He, Dedong; Chen, Ran; Chen, Kezhen; He, Sufang; Luo, Yongming

    2017-03-01

    A facile route (urea grind combustion method) is described for the rapid synthesis of Fe-doped Cu-Ce-Zr catalysts within 30 min through simple grinding and combustion. The effects of iron source and Fe/Cu mass ratio on the performances of the catalysts for CO preferential oxidation (CO-PROX) are evaluated. The influences of H2O, CO2, and their mixture on the activity as well as stability of the catalysts are also investigated. The samples are characterized by XRD, N2 adsorption-desorption, H2-TPR, TEM, Raman and XPS. Fe(NO3)3 is found to be superior to FeCl3 and Fe2(SO4)3 as the iron source for Fe-CuCZ catalyst. Among the different synthesized catalysts, 1/10Fe(N)-CuCZ is found to be the most active catalyst, indicating that the optimal Fe/Cu mass ratio is 1/10. The influences of H2O, CO2, and H2O + CO2 on the catalytic performance of 1/10Fe(N)-CuCZ are in the order of CO2 < CO2 + H2O < H2O. 1/10Fe(N)-CuCZ exhibits excellent stability during a 228 h time-on-stream test. 1/10Fe(N)-CuCZ shows the highest catalytic activity and excellent stability even in the presence of H2O and CO2. The excellent catalytic performance can be attributed to the synergy between the highly dispersed copper species and ceria, as well as the formation of more oxygen vacancies and reduced copper species.

  7. Isotope ratios of H, C, and O in CO2 and H2O of the martian atmosphere.

    PubMed

    Webster, Chris R; Mahaffy, Paul R; Flesch, Gregory J; Niles, Paul B; Jones, John H; Leshin, Laurie A; Atreya, Sushil K; Stern, Jennifer C; Christensen, Lance E; Owen, Tobias; Franz, Heather; Pepin, Robert O; Steele, Andrew; Achilles, Cherie; Agard, Christophe; Alves Verdasca, José Alexandre; Anderson, Robert; Anderson, Ryan; Archer, Doug; Armiens-Aparicio, Carlos; Arvidson, Ray; Atlaskin, Evgeny; Aubrey, Andrew; Baker, Burt; Baker, Michael; Balic-Zunic, Tonci; Baratoux, David; Baroukh, Julien; Barraclough, Bruce; Bean, Keri; Beegle, Luther; Behar, Alberto; Bell, James; Bender, Steve; Benna, Mehdi; Bentz, Jennifer; Berger, Gilles; Berger, Jeff; Berman, Daniel; Bish, David; Blake, David F; Blanco Avalos, Juan J; Blaney, Diana; Blank, Jen; Blau, Hannah; Bleacher, Lora; Boehm, Eckart; Botta, Oliver; Böttcher, Stephan; Boucher, Thomas; Bower, Hannah; Boyd, Nick; Boynton, Bill; Breves, Elly; Bridges, John; Bridges, Nathan; Brinckerhoff, William; Brinza, David; Bristow, Thomas; Brunet, Claude; Brunner, Anna; Brunner, Will; Buch, Arnaud; Bullock, Mark; Burmeister, Sönke; Cabane, Michel; Calef, Fred; Cameron, James; Campbell, John; Cantor, Bruce; Caplinger, Michael; Caride Rodríguez, Javier; Carmosino, Marco; Carrasco Blázquez, Isaías; Charpentier, Antoine; Chipera, Steve; Choi, David; Clark, Benton; Clegg, Sam; Cleghorn, Timothy; Cloutis, Ed; Cody, George; Coll, Patrice; Conrad, Pamela; Coscia, David; Cousin, Agnès; Cremers, David; Crisp, Joy; Cros, Alain; Cucinotta, Frank; d'Uston, Claude; Davis, Scott; Day, Mackenzie; de la Torre Juarez, Manuel; DeFlores, Lauren; DeLapp, Dorothea; DeMarines, Julia; DesMarais, David; Dietrich, William; Dingler, Robert; Donny, Christophe; Downs, Bob; Drake, Darrell; Dromart, Gilles; Dupont, Audrey; Duston, Brian; Dworkin, Jason; Dyar, M Darby; Edgar, Lauren; Edgett, Kenneth; Edwards, Christopher; Edwards, Laurence; Ehlmann, Bethany; Ehresmann, Bent; Eigenbrode, Jen; Elliott, Beverley; Elliott, Harvey; Ewing, Ryan; Fabre, Cécile; Fairén, Alberto; Farley, Ken; Farmer, Jack; Fassett, Caleb; Favot, Laurent; Fay, Donald; Fedosov, Fedor; Feldman, Jason; Feldman, Sabrina; Fisk, Marty; Fitzgibbon, Mike; Floyd, Melissa; Flückiger, Lorenzo; Forni, Olivier; Fraeman, Abby; Francis, Raymond; François, Pascaline; Freissinet, Caroline; French, Katherine Louise; Frydenvang, Jens; Gaboriaud, Alain; Gailhanou, Marc; Garvin, James; Gasnault, Olivier; Geffroy, Claude; Gellert, Ralf; Genzer, Maria; Glavin, Daniel; Godber, Austin; Goesmann, Fred; Goetz, Walter; Golovin, Dmitry; Gómez Gómez, Felipe; Gómez-Elvira, Javier; Gondet, Brigitte; Gordon, Suzanne; Gorevan, Stephen; Grant, John; Griffes, Jennifer; Grinspoon, David; Grotzinger, John; Guillemot, Philippe; Guo, Jingnan; Gupta, Sanjeev; Guzewich, Scott; Haberle, Robert; Halleaux, Douglas; Hallet, Bernard; Hamilton, Vicky; Hardgrove, Craig; Harker, David; Harpold, Daniel; Harri, Ari-Matti; Harshman, Karl; Hassler, Donald; Haukka, Harri; Hayes, Alex; Herkenhoff, Ken; Herrera, Paul; Hettrich, Sebastian; Heydari, Ezat; Hipkin, Victoria; Hoehler, Tori; Hollingsworth, Jeff; Hudgins, Judy; Huntress, Wesley; Hurowitz, Joel; Hviid, Stubbe; Iagnemma, Karl; Indyk, Steve; Israël, Guy; Jackson, Ryan; Jacob, Samantha; Jakosky, Bruce; Jensen, Elsa; Jensen, Jaqueline Kløvgaard; Johnson, Jeffrey; Johnson, Micah; Johnstone, Steve; Jones, Andrea; Joseph, Jonathan; Jun, Insoo; Kah, Linda; Kahanpää, Henrik; Kahre, Melinda; Karpushkina, Natalya; Kasprzak, Wayne; Kauhanen, Janne; Keely, Leslie; Kemppinen, Osku; Keymeulen, Didier; Kim, Myung-Hee; Kinch, Kjartan; King, Penny; Kirkland, Laurel; Kocurek, Gary; Koefoed, Asmus; Köhler, Jan; Kortmann, Onno; Kozyrev, Alexander; Krezoski, Jill; Krysak, Daniel; Kuzmin, Ruslan; Lacour, Jean Luc; Lafaille, Vivian; Langevin, Yves; Lanza, Nina; Lasue, Jeremie; Le Mouélic, Stéphane; Lee, Ella Mae; Lee, Qiu-Mei; Lees, David; Lefavor, Matthew; Lemmon, Mark; Lepinette Malvitte, Alain; Léveillé, Richard; Lewin-Carpintier, Éric; Lewis, Kevin; Li, Shuai; Lipkaman, Leslie; Little, Cynthia; Litvak, Maxim; Lorigny, Eric; Lugmair, Guenter; Lundberg, Angela; Lyness, Eric; Madsen, Morten; Maki, Justin; Malakhov, Alexey; Malespin, Charles; Malin, Michael; Mangold, Nicolas; Manhes, Gérard; Manning, Heidi; Marchand, Geneviève; Marín Jiménez, Mercedes; Martín García, César; Martin, Dave; Martin, Mildred; Martínez-Frías, Jesús; Martín-Soler, Javier; Martín-Torres, F Javier; Mauchien, Patrick; Maurice, Sylvestre; McAdam, Amy; McCartney, Elaina; McConnochie, Timothy; McCullough, Emily; McEwan, Ian; McKay, Christopher; McLennan, Scott; McNair, Sean; Melikechi, Noureddine; Meslin, Pierre-Yves; Meyer, Michael; Mezzacappa, Alissa; Miller, Hayden; Miller, Kristen; Milliken, Ralph; Ming, Douglas; Minitti, Michelle; Mischna, Michael; Mitrofanov, Igor; Moersch, Jeff; Mokrousov, Maxim; Molina Jurado, Antonio; Moores, John; Mora-Sotomayor, Luis; Morookian, John Michael; Morris, Richard; Morrison, Shaunna; Mueller-Mellin, Reinhold; Muller, Jan-Peter; Muñoz Caro, Guillermo; Nachon, Marion; Navarro López, Sara; Navarro-González, Rafael; Nealson, Kenneth; Nefian, Ara; Nelson, Tony; Newcombe, Megan; Newman, Claire; Newsom, Horton; Nikiforov, Sergey; Nixon, Brian; Noe Dobrea, Eldar; Nolan, Thomas; Oehler, Dorothy; Ollila, Ann; Olson, Timothy; de Pablo Hernández, Miguel Ángel; Paillet, Alexis; Pallier, Etienne; Palucis, Marisa; Parker, Timothy; Parot, Yann; Patel, Kiran; Paton, Mark; Paulsen, Gale; Pavlov, Alex; Pavri, Betina; Peinado-González, Verónica; Peret, Laurent; Perez, Rene; Perrett, Glynis; Peterson, Joe; Pilorget, Cedric; Pinet, Patrick; Pla-García, Jorge; Plante, Ianik; Poitrasson, Franck; Polkko, Jouni; Popa, Radu; Posiolova, Liliya; Posner, Arik; Pradler, Irina; Prats, Benito; Prokhorov, Vasily; Purdy, Sharon Wilson; Raaen, Eric; Radziemski, Leon; Rafkin, Scot; Ramos, Miguel; Rampe, Elizabeth; Raulin, François; Ravine, Michael; Reitz, Günther; Rennó, Nilton; Rice, Melissa; Richardson, Mark; Robert, François; Robertson, Kevin; Rodriguez Manfredi, José Antonio; Romeral-Planelló, Julio J; Rowland, Scott; Rubin, David; Saccoccio, Muriel; Salamon, Andrew; Sandoval, Jennifer; Sanin, Anton; Sans Fuentes, Sara Alejandra; Saper, Lee; Sarrazin, Philippe; Sautter, Violaine; Savijärvi, Hannu; Schieber, Juergen; Schmidt, Mariek; Schmidt, Walter; Scholes, Daniel; Schoppers, Marcel; Schröder, Susanne; Schwenzer, Susanne; Sebastian Martinez, Eduardo; Sengstacken, Aaron; Shterts, Ruslan; Siebach, Kirsten; Siili, Tero; Simmonds, Jeff; Sirven, Jean-Baptiste; Slavney, Susie; Sletten, Ronald; Smith, Michael; Sobrón Sánchez, Pablo; Spanovich, Nicole; Spray, John; Squyres, Steven; Stack, Katie; Stalport, Fabien; Stein, Thomas; Stewart, Noel; Stipp, Susan Louise Svane; Stoiber, Kevin; Stolper, Ed; Sucharski, Bob; Sullivan, Rob; Summons, Roger; Sumner, Dawn; Sun, Vivian; Supulver, Kimberley; Sutter, Brad; Szopa, Cyril; Tan, Florence; Tate, Christopher; Teinturier, Samuel; ten Kate, Inge; Thomas, Peter; Thompson, Lucy; Tokar, Robert; Toplis, Mike; Torres Redondo, Josefina; Trainer, Melissa; Treiman, Allan; Tretyakov, Vladislav; Urqui-O'Callaghan, Roser; Van Beek, Jason; Van Beek, Tessa; VanBommel, Scott; Vaniman, David; Varenikov, Alexey; Vasavada, Ashwin; Vasconcelos, Paulo; Vicenzi, Edward; Vostrukhin, Andrey; Voytek, Mary; Wadhwa, Meenakshi; Ward, Jennifer; Weigle, Eddie; Wellington, Danika; Westall, Frances; Wiens, Roger Craig; Wilhelm, Mary Beth; Williams, Amy; Williams, Joshua; Williams, Rebecca; Williams, Richard B; Wilson, Mike; Wimmer-Schweingruber, Robert; Wolff, Mike; Wong, Mike; Wray, James; Wu, Megan; Yana, Charles; Yen, Albert; Yingst, Aileen; Zeitlin, Cary; Zimdar, Robert; Zorzano Mier, María-Paz

    2013-07-19

    Stable isotope ratios of H, C, and O are powerful indicators of a wide variety of planetary geophysical processes, and for Mars they reveal the record of loss of its atmosphere and subsequent interactions with its surface such as carbonate formation. We report in situ measurements of the isotopic ratios of D/H and (18)O/(16)O in water and (13)C/(12)C, (18)O/(16)O, (17)O/(16)O, and (13)C(18)O/(12)C(16)O in carbon dioxide, made in the martian atmosphere at Gale Crater from the Curiosity rover using the Sample Analysis at Mars (SAM)'s tunable laser spectrometer (TLS). Comparison between our measurements in the modern atmosphere and those of martian meteorites such as ALH 84001 implies that the martian reservoirs of CO2 and H2O were largely established ~4 billion years ago, but that atmospheric loss or surface interaction may be still ongoing.

  8. Introducing the Precision Isotope Ratio Mass Spectrometer: Novel Innovations in Multi-Collector Arrays for Isotopologues and Isotopomers in Organic Molecule Gas Analysis

    NASA Astrophysics Data System (ADS)

    Kasson, A.

    2016-12-01

    In January 2016, elementar Analysensysteme, GmbH (Germany), in conjunction with their daughter company, Isoprime Ltd. (United Kingdom) released the Precision isotope ratio mass spectrometer. The Precision is the newest light element IRMS on the market and adds some unique hardware and software functionalities to the basic core of stable isotopic research previously unseen. Although this system is designed to make the typical bulk and compound specific measurements that functioning stable isotope laboratories have been accustomed to, it has been designed to make complicated measurements of isotopologues, isotopomers and clumped isotopes much more turnkey and user friendly. Here we focus on some datasets that have been collected from three different beta test sites and highlight the functional use of the new hardware in conjunction with ionOS operating software. As part of those highlights, the improved precision, accuracy and ion optics of the Precision IRMS will be demonstrated. In addition, we intend to show that the reprocessing functions on the ionOS software package are not only beneficial to users of just the Precision IRMS, but to the entire stable isotope community as a whole.

  9. Antimicrobial activity of ZnO-TiO2 nanomaterials synthesized from three different precursors of ZnO: influence of ZnO/TiO2 weight ratio.

    PubMed

    Daou, Ikram; Moukrad, Najia; Zegaoui, Omar; Rhazi Filali, Fouzia

    2018-03-01

    In this study, ZnO-TiO 2 nanoparticles were synthesized from three different precursors for ZnO (zinc acetate di-hydrate, zinc nitrate hexahydrate and zinc sulfate heptahydrate) and titanium (IV) isopropoxide for TiO 2 . The prepared nanomaterials were calcined at 500 °C for 3 h and characterized by various physicochemical techniques such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and transmission electron microscopy, combined with energy dispersive X-ray spectroscopy (TEM-EDS). The obtained results showed that the crystalline structure, size and morphology of the ZnO-TiO 2 nanoparticles are strongly influenced by the nature of the precursor of ZnO, as well as the ZnO/TiO 2 weight ratio. The antibacterial and antifungal activities of the synthesized nanomaterials were evaluated, in the dark, against five multi-resistant of Gram positive (Staphylococcus aureus) and Gram negative (Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa and Salmonella Paratyphi A) bacteria and a fungus (Candida albicans), which are pathogenic for humans. The obtained results showed that pure TiO 2 anatase is inactive against the tested strains, while the addition of ZnO to TiO 2 improves noticeably the effectiveness of TiO 2 nanoparticles, depending on the nature of the precursor of ZnO and the ZnO/TiO 2 weight ratio.

  10. Partitioning N2O emissions within the US Corn Belt using an inverse modeling approach

    USDA-ARS?s Scientific Manuscript database

    Nitrous oxide (N2O) emissions within the US Corn Belt have been estimated to be 2- to 9-11 fold larger than predictions from emission inventories, implying that one or more source 12 categories in bottom-up approaches are underestimated. Here we interpret hourly N2O 13 mixing ratios measured during ...

  11. Study on adsorption of rhodamine B onto Beta zeolites by tuning SiO2/Al2O3 ratio.

    PubMed

    Cheng, Zhi-Lin; Li, Yan-Xiang; Liu, Zan

    2018-02-01

    The exploration of the relationship between zeolite composition and adsorption performance favored to facilitate its better application in removal of the hazardous substances from water. The adsorption capacity of rhodamine B (RB) onto Beta zeolite from aqueous solution was reported. The relationship between SiO 2 /Al 2 O 3 ratio and adsorption capacity of Beta zeolite for RB was explored. The structure and physical properties of Beta zeolites with various SiO 2 /Al 2 O 3 ratios were determined by XRD, FTIR, TEM, BET, UV-vis and so on characterizations. The adsorption behavior of rhodamine B onto Beta zeolite matched to Langmuir adsorption isotherm and more suitable description for the adsorption kinetics was a pseudo-second-order reaction model. The maximum adsorption capacity of the as-prepared Beta zeolite with SiO 2 /Al 2 O 3 = 18.4 was up to 27.97mg/g. Copyright © 2017 Elsevier Inc. All rights reserved.

  12. Stratospheric CFCl3, CF2Cl2, and N2O height profile measurements at several latitudes

    NASA Astrophysics Data System (ADS)

    Goldan, P. D.; Kuster, W. C.; Albritton, D. L.; Schmeltekopf, A. L.

    1980-01-01

    The mixing ratios of CFCl3, CF2Cl2, and N2O have been measured as a function of altitude from 6 to 37 km above sea level by using a balloon-borne grab-sampling system. The 24 flights were made during the period July 1976 to March 1979 from Wyoming, Panama, Brazil, and Antarctica. These data are reported here both numerically and graphically, the latter being examined for latitudinal and temporal trends. A mean tropopause height for each location and date was used as the reference for the height profiles. The resulting set of CF2Cl2 and N2O profiles show a discernible dependence on latitude; the lapse rate of these mixing ratios is greater for the mid-latitudes when compared to the equatorial latitudes. The upper tropospheric portion of the CFCl3 and CF2Cl2 data show annual increases of 10.4±3.9 and 10.7±1.9%/yr, respectively, in the northern hemisphere for the middle of the measurement period (end of 1977). Furthermore, the limited number of southern hemispheric data for these constituents are about 8% lower than the northern hemispheric values but have a comparable annual increase. The corresponding N2O data show no interhemispheric differences and the possibility of only a slight increase (less than 2%/yr).

  13. Troposphere-to-Stratosphere Transport in the Lowermost Stratosphere from Measurements of H2O, CO2, N2O and O3

    NASA Technical Reports Server (NTRS)

    Hintsa, E. J.; Boering, K. A.; Weinstock, E. M.; Anderson, J. G.; Gary, B. L.; Pfister, L.; Daube, B. C.; Wofsy, S. C.; Loewenstein, M.; Podolske, J.R.; hide

    1998-01-01

    The origin of air in the lowermost stratosphere is investigated with measurements from the NASA ER-2 aircraft. Air with high water vapor mixing ratios was observed in the stratosphere at theta-330-380 K near 40 N in May 1995, indicating the influence of intrusions of tropospheric air. Assuming that observed tracer-tracer relationships reflect mixing lines between tropospheric and stratospheric air masses, we calculate mixing ratios of H2O (12-24 ppmv) and CO2 for the admixed tropospheric air at theta=352-364 K. Temperatures on the 355 K surface at 20-40 N were low enough to dehydrate air to these values. While most ER-2 CO2 data in both hemispheres are consistent with tropical or subtropical air entering the lowermost stratosphere, measurements from May 1995 for theta<362 K suggest that entry of air from the midlatitude upper troposphere can occur in conjunction with mixing processes near the tropopause.

  14. Troposphere-to-Stratosphere Transport in the Lowermost Stratosphere from Measurements of H2O, CO2, N2O and O3

    NASA Technical Reports Server (NTRS)

    Hintsa, E. J.; Boering, K. A.; Weinstock, E. M.; Anderson, J. G.; Gary, B. L.; Pfister, L.; Daube, B. C.; Wofsy, S. C.; Loewenstein, M.; Podolske, J. R.

    1998-01-01

    The origin of air in the lowermost stratosphere is investigated with measurements from the NASA ER-2 aircraft. Air with high water vapor mixing ratios was observed in the stratosphere at theta = 330-380 K near 40 N in May 1995, indicating the influence of intrusions of tropospheric air. Assuming that observed tracer-tracer relationships reflect mixing lines between tropospheric and stratospheric air masses, we calculate mixing ratios of H2O (12-24 ppmv) and CO2 for the admixed tropospheric air at theta = 352-364 K. Temperatures on the 355 K surface at 20-40 N were low enough to dehydrate air to these values. While most ER-2 CO2 data in both hemispheres are consistent with tropical or subtropical air entering the lowermost stratosphere, measurements from May 1995 for theta < 362 K suggest that entry of air from the midlatitude upper troposphere can occur in conjunction with mixing processes near the tropopause.

  15. Troposphere-to-Stratosphere Transport in the Lowermost Stratosphere from Measurements of H2O, CO2, N2O, and O3

    NASA Technical Reports Server (NTRS)

    Hintsa, E. J.; Boering, K. A.; Weinstock, E. M.; Anderson, J. G.; Gary, B. L.; Pfister, L.; Daube, B. C.; Wofsy, S. C.; Loewenstein, M.; Podolske, J. R.; hide

    1998-01-01

    The origin of air in the lowermost stratosphere is investigated with measurements from the NASA ER-2 aircraft. Air with high water vapor mixing ratios was observed in the stratosphere at theta approximately 330-380 K near 40 N in May 1995, indicating the influence of intrusions of tropospheric air. Assuming that observed tracer-tracer relationships reflect mixing lines between tropospheric and stratospheric air masses, we calculate mixing ratios of H2O (12-24 ppmv) and CO2 for the admixed tropospheric air at theta = 352-364 K. Temperatures on the 355 K surface 20-40 N were low enough to dehydrate air to these values. While most ER-2 CO2 data in both hemispheres are consistent with tropical or subtropical air entering the lowermost stratosphere, measurements from May 1995 for theta < 362 K suggest that entry of air from the midlatitude upper troposphere can occur in conjunction with mixing processes near the tropopause.

  16. Troposphere-to-Stratosphere Transport in the Lowermost Stratosphere from Measurements of H2O, CO2, N2O and O3

    NASA Technical Reports Server (NTRS)

    Hintsa, E. J.; Boering, K. A.; Weinstock, E. M.; Anderson, J. G.; Gary, B. L.; Pfister, L.; Daube, B. C.; Wofsy, S. C.; Loewenstein, M.; Podolske, J. R.; hide

    1998-01-01

    The origin of air in the lowermost stratosphere is investigated with measurements from the NASA ER-2 aircraft. Air with high water vapor mixing ratios was observed in the stratosphere at theta about 330-380 K near 40N in May 1995, indicating the influence of intrusions of tropospheric air. Assuming that observed tracer-tracer relationships reflect mixing lines between tropospheric and stratospheric air masses, we calculate mixing ratios of H2O (12-24 ppmv) and CO2 for the admixed tropospheric air at theta =352-364 K. Temperatures on the 355 K surface at 20-40 N were low enough to dehydrate air to these values. while most ER-2 CO2 data in both hemispheres are consistent with tropical or subtropical air entering the lowermost stratosphere, measurements from May 1995 for theta <362 K suggest that entry of air from the midlatitude upper troposphere can occur in conjunction with mixing processes near the tropopause.

  17. Potential short-term losses of N2O and N2 from high concentrations of biogas digestate in arable soils

    NASA Astrophysics Data System (ADS)

    Fiedler, Sebastian Rainer; Augustin, Jürgen; Wrage-Mönnig, Nicole; Jurasinski, Gerald; Gusovius, Bertram; Glatzel, Stephan

    2017-09-01

    Biogas digestate (BD) is increasingly used as organic fertilizer, but has a high potential for NH3 losses. Its proposed injection into soils as a countermeasure has been suggested to promote the generation of N2O, leading to a potential trade-off. Furthermore, the effect of high nutrient concentrations on N2 losses as they may appear after injection of BD into soil has not yet been evaluated. Hence, we performed an incubation experiment with soil cores in a helium-oxygen atmosphere to examine the influence of soil substrate (loamy sand, clayey silt), water-filled pore space (WFPS; 35, 55, 75 %) and application rate (0, 17.6 and 35.2 mL BD per soil core, 250 cm3) on the emission of N2O, N2 and CO2 after the usage of high loads of BD. To determine the potential capacity for gaseous losses, we applied anaerobic conditions by purging with helium for the last 24 h of incubation. Immediate N2O and N2 emissions as well as the N2 / (N2O+N2) product ratio depended on soil type and increased with WFPS, indicating a crucial role of soil gas diffusivity for the formation and emission of nitrogenous gases in agricultural soils. However, emissions did not increase with the application rate of BD. This is probably due to an inhibitory effect of the high NH4+ content of BD on nitrification. Our results suggest a larger potential for N2O formation immediately following BD injection in the fine-textured clayey silt compared to the coarse loamy sand. By contrast, the loamy sand showed a higher potential for N2 production under anaerobic conditions. Our results suggest that short-term N losses of N2O and N2 after injection may be higher than probable losses of NH3 following surface application of BD.

  18. Effect of SiO2/B2O3 Ratio on the Crystallization Behavior and Dielectric Properties of Barium Strontium Titanate Glass-Ceramics Prepared by Sol-Gel Process

    NASA Astrophysics Data System (ADS)

    Chen, Yongzhou; Zhang, Yong; Song, Xiaozhen; Shen, Ziqin; Zhang, Tianyuan

    2018-05-01

    Ferroelectric glass-ceramics, with a basic composition 90 wt.% (Ba0.65Sr0.35)TiO3-10 wt.% (B2O3-nSiO2) (n = 0.5, 1, 3, 5) were synthesized by the sol-gel method and their phase development and dielectric properties were investigated by differential thermal analysis, x-ray diffraction, field emission scanning electron microscopy, dielectric temperature curves and impedance spectroscopy. From the differential thermal analysis, glass transition and crystallization behavior can be observed. From the x-ray diffraction study, two crystalline phases (Ba,Sr)TiO3 and Ba2TiSi2O8 were formed over the entire composition range of the glass-ceramics. In addition, the main crystal phase has undergone a transformation from (Ba,Sr)TiO3 to Ba2TiSi2O8 with the increase of n. A typical structure in which the crystal phase was surrounded by a glassy matrix has been observed in the scanning electron microscope images. As a result of temperature dependent dielectric property measurements, the dielectric constant increased obviously with the increase of n from 0.5 to 1. Further increasing n led to a reduction of the dielectric constant, which is in coincidence with the variation of the intensity of (Ba,Sr)TiO3 phase with n. According to the impedance spectroscopy analysis and the activation energy calculation, the relaxation peak in both Z″ and M″ data should be attributed to the crystal-glass interface, and the change of conduction mechanism with the increase of SiO2/B2O3 ratio may be attributed to the corresponding transition of the main crystal phase.

  19. Influence of the Organic Species and Oxoanion in the Synthesis of two Uranyl Sulfate Hydrates, (H 3 O) 2 [(UO 2 ) 2 (SO 4 ) 3 ­(H 2 O)]·7H 2 O and (H 3 O) 2 [(UO 2 ) 2 (SO 4 ) 3 (H 2 O)]·4H 2 O, and a Uranyl Selenate-Selenite [C 5 H 6 N][(UO 2 )(SeO 4 )(HSeO 3 )

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Jouffret, Laurent J.; Wylie, Ernest M.; Burns, Peter C.

    2012-08-08

    Two uranyl sulfate hydrates, (H3O)2[(UO2)2(SO4)3(H2O)]·7H2O (NDUS) and (H3O)2[(UO2)2(SO4)3(H2O)]·4H2O (NDUS1), and one uranyl selenate-selenite [C5H6N][(UO2)(SeO4)(HSeO3)] (NDUSe), were obtained and their crystal structures solved. NDUS and NDUSe result from reactions in highly acidic media in the presence of L-cystine at 373 K. NDUS crystallized in a closed vial at 278 K after 5 days and NDUSe in an open beaker at 278 K after 2 weeks. NDUS1 was synthesized from aqueous solution at room temperature over the course of a month. NDUS, NDUS1, and NDUSe crystallize in the monoclinic space group P21/n, a = 15.0249(4) Å,b = 9.9320(2) Å, c = 15.6518(4)more » Å, β = 112.778(1)°, V = 2153.52(9) Å3,Z = 4, the tetragonal space group P43212, a = 10.6111(2) Å,c = 31.644(1) Å, V = 3563.0(2) Å3, Z = 8, and in the monoclinic space group P21/n, a = 8.993(3) Å, b = 13.399(5) Å, c = 10.640(4) Å,β = 108.230(4)°, V = 1217.7(8) Å3, Z = 4, respectively.The structural units of NDUS and NDUS1 are two-dimensional uranyl sulfate sheets with a U/S ratio of 2/3. The structural unit of NDUSe is a two-dimensional uranyl selenate-selenite sheets with a U/Se ratio of 1/2. In-situ reaction of the L-cystine ligands gives two distinct products for the different acids used here. Where sulfuric acid is used, only H3O+ cations are located in the interlayer space, where they balance the charge of the sheets, whereas where selenic acid is used, interlayer C5H6N+ cations result from the cyclization of the carboxyl groups of L-cystine, balancing the charge of the sheets.« less

  20. Nitrous oxide nitrification and denitrification 15N enrichment factors from Amazon forest soils.

    PubMed

    Pérez, Tibisay; Garcia-Montiel, Diana; Trumbore, Susan; Tyler, Stanley; de Camargo, Plínio; Moreira, Marcelo; Piccolo, Marisa; Cerri, Carlos

    2006-12-01

    The isotopic signatures of 15N and 18O in N2O emitted from tropical soils vary both spatially and temporally, leading to large uncertainty in the overall tropical source signature and thereby limiting the utility of isotopes in constraining the global N2O budget. Determining the reasons for spatial and temporal variations in isotope signatures requires that we know the isotope enrichment factors for nitrification and denitrification, the two processes that produce N2O in soils. We have devised a method for measuring these enrichment factors using soil incubation experiments and report results from this method for three rain forest soils collected in the Brazilian Amazon: soil with differing sand and clay content from the Tapajos National Forest (TNF) near Santarém, Pará, and Nova Vida Farm, Rondônia. The 15N enrichment factors for nitrification and denitrification differ with soil texture and site: -111 per thousand +/- 12 per thousand and -31 per thousand +/- 11 per thousand for a clay-rich Oxisol (TNF), -102 per thousand +/- 5 per thousand and -45 per thousand +/- 5 per thousand for a sandier Ultisol (TNF), and -10.4 per thousand +/- 3.5 per thousand (enrichment factor for denitrification) for another Ultisol (Nova Vida) soil, respectively. We also show that the isotopomer site preference (delta15Nalpha - delta15Nbeta, where alpha indicates the central nitrogen atom and beta the terminal nitrogen atom in N2O) may allow differentiation between processes of production and consumption of N2O and can potentially be used to determine the contributions of nitrification and denitrification. The site preferences for nitrification and denitrification from the TNF-Ultisol incubated soils are: 4.2 per thousand +/- 8.4 per thousand and 31.6 per thousand +/- 8.1 per thousand, respectively. Thus, nitrifying and denitrifying bacteria populations under the conditions of our study exhibit significantly different 15N site preference fingerprints. Our data set strongly suggests

  1. Frontiers of QC Laser spectroscopy for high precision isotope ratio analysis of greenhouse gases

    NASA Astrophysics Data System (ADS)

    Emmenegger, Lukas; Mohn, Joachim; Harris, Eliza; Eyer, Simon; Ibraim, Erkan; Tuzson, Béla

    2016-04-01

    An important milestone for laser spectroscopy was achieved when isotope ratios of greenhouse gases were reported at precision levels that allow addressing research questions in environmental sciences. Real-time data with high temporal resolution at moderate cost and instrument size make the optical approach highly attractive, complementary to the well-established isotope-ratio mass-spectrometry (IRMS) method. Especially appealing, in comparison to IRMS, is the inherent specificity to structural isomers having the same molecular mass. Direct absorption in the MIR in single or dual QCL configuration has proven highly reliable for the sta-ble isotopes of CO2, N2O and CH4. The longest time series of real-time measurements is currently available for δ13C and δ18O in CO2 at the high-alpine station Jung-fraujoch. At this well-equipped site, QCL based direct absorption spectroscopy (QCLAS) measurements are ongoing since 2008 1,2. Applications of QCLAS for N2O and CH4 stable isotopes are considerably more challenging because of the lower atmospheric mixing ratios, especially for the less abundant species, such as N218O and CH3D. For high precision (< 0.1 ‰) measurements in ambient air, QCLAS may be combined with a fully automated preconcentration unit yielding an up to 500 times concentration increase and the capability to separate the target gas from spectral interferants by se-quential desorption 3. Here, we review our recent developments on high precision isotope ratio analysis of greenhouse gases, with special focus on the isotopic species of N2O and CH4. Furthermore, we show environ-mental applications illustrating the highly valuable information that isotope ratios of atmospheric trace gases can carry. For example, the intramolecular distribution of 15N in N2O gives important information on the geochemical cycle of N2O4-6, while the analysis of δ13C and δ D in CH4 may be applied to disentangle microbial, fossil and landfill sources 7. 1 Sturm, P., Tuzson, B

  2. Reactions of CH3SH and CH3SSCH3 with gas-phase hydrated radical anions (H2O)n(•-), CO2(•-)(H2O)n, and O2(•-)(H2O)n.

    PubMed

    Höckendorf, Robert F; Hao, Qiang; Sun, Zheng; Fox-Beyer, Brigitte S; Cao, Yali; Balaj, O Petru; Bondybey, Vladimir E; Siu, Chi-Kit; Beyer, Martin K

    2012-04-19

    The chemistry of (H(2)O)(n)(•-), CO(2)(•-)(H(2)O)(n), and O(2)(•-)(H(2)O)(n) with small sulfur-containing molecules was studied in the gas phase by Fourier transform ion cyclotron resonance mass spectrometry. With hydrated electrons and hydrated carbon dioxide radical anions, two reactions with relevance for biological radiation damage were observed, cleavage of the disulfide bond of CH(3)SSCH(3) and activation of the thiol group of CH(3)SH. No reactions were observed with CH(3)SCH(3). The hydrated superoxide radical anion, usually viewed as major source of oxidative stress, did not react with any of the compounds. Nanocalorimetry and quantum chemical calculations give a consistent picture of the reaction mechanism. The results indicate that the conversion of e(-) and CO(2)(•-) to O(2)(•-) deactivates highly reactive species and may actually reduce oxidative stress. For reactions of (H(2)O)(n)(•-) with CH(3)SH as well as CO(2)(•-)(H(2)O)(n) with CH(3)SSCH(3), the reaction products in the gas phase are different from those reported in the literature from pulse radiolysis studies. This observation is rationalized with the reduced cage effect in reactions of gas-phase clusters. © 2012 American Chemical Society

  3. Effects of variation in background mixing ratios of N2, O2, and Ar on the measurement of δ18O-H2O and δ2H-H2O values by cavity ring-down spectroscopy

    NASA Astrophysics Data System (ADS)

    Johnson, Jennifer E.; Rella, Chris W.

    2017-08-01

    Cavity ring-down spectrometers have generally been designed to operate under conditions in which the background gas has a constant composition. However, there are a number of observational and experimental situations of interest in which the background gas has a variable composition. In this study, we examine the effect of background gas composition on a cavity ring-down spectrometer that measures δ18O-H2O and δ2H-H2O values based on the amplitude of water isotopologue absorption features around 7184 cm-1 (L2120-i, Picarro, Inc.). For background mixtures balanced with N2, the apparent δ18O values deviate from true values by -0.50 ± 0.001 ‰ O2 %-1 and -0.57 ± 0.001 ‰ Ar %-1, and apparent δ2H values deviate from true values by 0.26 ± 0.004 ‰ O2 %-1 and 0.42 ± 0.004 ‰ Ar %-1. The artifacts are the result of broadening, narrowing, and shifting of both the target absorption lines and strong neighboring lines. While the background-induced isotopic artifacts can largely be corrected with simple empirical or semi-mechanistic models, neither type of model is capable of completely correcting the isotopic artifacts to within the inherent instrument precision. The development of strategies for dynamically detecting and accommodating background variation in N2, O2, and/or Ar would facilitate the application of cavity ring-down spectrometers to a new class of observations and experiments.

  4. Site-specific 15N isotopic signatures of abiotically produced N2O

    NASA Astrophysics Data System (ADS)

    Heil, Jannis; Wolf, Benjamin; Brüggemann, Nicolas; Emmenegger, Lukas; Tuzson, Béla; Vereecken, Harry; Mohn, Joachim

    2014-08-01

    Efficient nitrous oxide (N2O) mitigation strategies require the identification of the main source and sink processes and their contribution to total soil N2O production. Several abiotic reactions of nitrification intermediates leading to N2O production are known, but their contribution to total N2O production in soils is uncertain. As the site preference (SP) of 15N in N2O is a promising tool to give more insight into N2O production processes, we investigated the SP of N2O produced by different abiotic reactions in a laboratory study. All reactions involved the nitrification intermediate hydroxylamine (NH2OH) in combination with nitrite (NO2-), Fe3+, Fe2+ and Cu2+, reactants commonly or potentially found in soils, at different concentrations and pH values. N2O production and its four main isotopic species (14N14N16O, 15N14N16O, 14N15N16O, and 14N14N18O) were quantified simultaneously and online at high temporal resolution using quantum cascade laser absorption spectroscopy. Thereby, our study presents the first continuous analysis of δ18O in N2O. The experiments revealed the possibility of purely abiotic reactions over a wide range of acidity (pH 3-8) by different mechanisms. All studied abiotic pathways produced N2O with a characteristic SP in the range of 34-35‰, unaffected by process conditions and remaining constant over the course of the experiments. These findings reflect the benefit of continuous N2O isotopic analysis by laser spectroscopy, contribute new information to the challenging source partitioning of N2O emissions from soils, and emphasize the potentially significant role of coupled biotic-abiotic reactions in soils.

  5. Microwave dielectric properties of BaO-2CeO{sub 2}-nTiO{sub 2} ceramics

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sreemoolanadhan, H.; Sebastian, M.T.; Ratheesh, R.

    2004-11-01

    The BaO-2CeO{sub 2}-nTiO{sub 2} ceramics with n=3, 4 and 5 have been prepared with CeO{sub 2} as starting material. The ceramics have been characterized using scanning electron microscopy, X-ray diffraction, Raman and X-ray photoelectron spectroscopy techniques. The microwave dielectric properties have been measured using standard dielectric resonator techniques. BaO-2CeO{sub 2}-3TiO{sub 2} (123), BaO-2CeO{sub 2}-4TiO{sub 2} (124) and BaO-2CeO{sub 2}-5TiO{sub 2} (125) ceramics showed dielectric constants of 38, 27 and 32, respectively. All the ceramics showed fairly good unloaded Q-factors. 124 and 125 compounds exhibited low {tau}f values, while 123 showed a high {tau}f value.

  6. Isotopic Monitoring of N2O Emissions from Wastewater Treatment: Evidence for N2O Production Associated with Anammox Metabolism?

    NASA Astrophysics Data System (ADS)

    Harris, E. J.; Wunderlin, P.; Joss, A.; Emmenegger, L.; Kipf, M.; Wolf, B.; Mohn, J.

    2015-12-01

    Microbial production is the major source of N2O, the strongest greenhouse gas produced within the nitrogen cycle, and the most important stratospheric ozone destructant released in the 21st century. Wastewater treatment is an important and growing source of N2O, with best estimates predicting N2O emissions from this sector will have increased by >25% by 2020. Novel treatment employing partial nitritation-anammox, rather than traditional nitrification-denitrification, has the potential to achieve a neutral carbon footprint due to increased biogas production - if N2O production accounts for <0.5-1% of total nitrogen turnover. As a further motivation for this research, microbial pathways identified from wastewater treatment can be applied to our understanding of N cycling in the natural environment. This study presents the first online isotopic measurements of offgas N2O from a partial-nitritation anammox reactor 1. The measured N2O isotopic composition - in particular the N2O isotopic site preference (SP = δ15Nα - δ15Nβ) - was used to understand N2O production pathways in the reactor. When N2O emissions peaked due to high dissolved oxygen concentrations, low SP showed that N2O was produced primarily via nitrifier denitrification by ammonia oxidizing bacteria (AOBs). N2O production by AOBs via NH2OH oxidation, in contrast, did not appear to be important under any conditions. Over the majority of the one-month measurement period, the measured SP was much higher than expected following our current understanding of N2O production pathways 2. SP reached 41‰ during normal operating conditions and achieved a maximum of 45‰ when nitrite was added under anoxic conditions. These results could be explained by unexpectedly strong heterotrophic N2O reduction despite low dissolved organic matter concentrations, or by an incomplete understanding of isotopic fractionation during N2O production from NH2OH oxidation by AOBs - however the explanation most consistent with all

  7. Crystal structure of aqua-1κO-{μ-2-[(2-hydroxy­ethyl)methylamino]ethanolato-2:1κ4 O 1,N,O 2:O 1}[μ-2,2′-(methylimino)diethanolato-1:2κ4 O,N,O′:O]dithiocyanato-1κN,2κN-chromium(III)copper(II)

    PubMed Central

    Rusanova, Julia A.; Semenaka, Valentina V.; Dyakonenko, Viktoriya V.; Shishkin, Oleg V.

    2015-01-01

    The title compound, [CrCu(C5H11NO2)(C5H12NO2)(NCS)2(H2O)] or [Cr(μ-mdea)Cu(μ-Hmdea)(NCS)2H2O], (where mdeaH2 is N-methylethanolamine, C5H13NO2) is formed as a neutral heterometal CuII/CrIII complex. The mol­ecular structure of the complex is based on a binuclear {CuCr(μ-O)2} core. The coordination environment of each metal atom involves the N,O,O atoms of the tridentate ligand, one bridging O atom of the ligand and the N atom of the thio­cyanato ligands. The CuII ion adopts a distorted square-pyramidal coordination while the CrIII ion has a distorted octa­hedral coordination geometry completed by the aqua ligand. In the crystal, the binuclear complexes are linked via two pairs of O—H⋯O hydrogen bonds to form inversion dimers, which are arranged in columns parallel to the a axis. In the μ-mdea ligand two –CH2 groups and the methyl group were refined as disordered over two sets of sites with equal occupancies. The structure was refined as a two-component twin with a twin scale factor of 0.242 (1). PMID:26396853

  8. Excited State Intramolecular Proton Transfer of 2,5-bis(5-ethyl-2-benzoxazolyl)-hydroquinone and its OH/OD-isotopomers studied in supersonic jets

    NASA Astrophysics Data System (ADS)

    Peukert, Sebastian; Gil, Michał; Kijak, Michał; Sepioł, Jerzy

    2015-11-01

    The Excited State Intramolecular Proton Transfer (ESIPT) reactions of dually fluorescent 2,5-bis(5-ethyl-2-benzoxazolyl)-hydroquinone (DE-BBHQ) and its isotopomers have been studied in the supersonic jet applying laser induced fluorescence (LIF) and fluorescence-depletion (F-D) spectroscopy. LIF-spectra measured at photo-tautomeric (red) fluorescence exhibit a characteristic triplet pattern of vibronic bands, which gradually collapses upon successive deuteration. Complementary TDDFT calculations indicate the possibility of 2 consecutive ESIPT reactions yielding an excited state diketo-tautomer. However, concerning this matter the present experimental results are not unambiguous and could be also rationalized without assuming the formation of an additional photo-tautomer.

  9. Full-dimensional quantum calculations of vibrational levels of NH 4 + and isotopomers on an accurate ab initio potential energy surface

    DOE PAGES

    Hua -Gen Yu; Han, Huixian; Guo, Hua

    2016-03-29

    Vibrational energy levels of the ammonium cation (NH 4 +) and its deuterated isotopomers are calculated using a numerically exact kinetic energy operator on a recently developed nine-dimensional permutation invariant semiglobal potential energy surface fitted to a large number of high-level ab initio points. Like CH4, the vibrational levels of NH 4 + and ND 4 + exhibit a polyad structure, characterized by a collective quantum number P = 2(v 1 + v 3) + v 2 + v 4. As a result, the low-lying vibrational levels of all isotopomers are assigned and the agreement with available experimental data ismore » better than 1 cm –1.« less

  10. Net Community and Gross Photosynthetic Production Rates in the Eastern Tropical South Pacific, as Determined from O2/AR Ratios and Triple Oxygen Isotopic Composition of Dissolved O2

    NASA Astrophysics Data System (ADS)

    Prokopenko, M. G.; Yeung, L. Y.; Berelson, W.; Fleming, J.; Rollins, N.; Young, E. D.; Haskell, W. Z.; Hammond, D. E.; Capone, D. G.

    2010-12-01

    This study assesses the rates of ocean carbon production and its fate with respect to recycling or export in the Eastern Tropical South Pacific (ETSP). ETSP has been previously identified as a region where N2 fixation and denitrification may be spatially coupled; this is also a region of localized CO2 outgassing. Using an Equilibrated Inlet Mass Spectrometer (EIMS) system, we obtained continuous measurements of the biological O2 supersaturation in the mixed layer along the ship track encompassing a region bounded by 10-20° S and 80-100° W in January - March, 2010. Vertical profiles were also taken at selected stations and analyzed for dissolved O2/Ar ratios on EIMS and triple oxygen isotope composition (17O excess) on a multi-collector IRMS (Isotope Ratio Mass Spectrometer) at UCLA. Gas exchange rates were estimated using two approaches: the Rn-222 deficit method and the wind parameterization method, which utilized wind speeds extracted from ASCAT satellite database. Oxygen Net Community Production (O-NCP) rates calculated based on biological O2 supersaturation ranged from slightly negative to ~ 0.3 - 15 mmol/m2d, with higher rates along the northern part of the transect. Oxygen Gross Community Production (O-GPP) rates calculated from 17O excess were between 50 ± 20 and 200 ± 40 mmol/m2d, with higher rates observed along the northern cruise transect as well. Notably, the NCP/GPP ratios along the northern transect were higher by the factor of 2 to 3 than their southern counterparts. The O2/Ar-based NCP rates were comparable to POC flux measured with floating traps deployed at the southern stations, but exceeded by a factor of 5-10 the trap POC fluxes obtained at the northern stations. A one-dimensional box model has been constructed to quantify the magnitude of oxygen primary production below the mixed layer. The results of this work will be integrated with measurements of 15-N2 uptake that are in progress, to constrain the potential contribution of N2 fixation

  11. Alterations in airway microbiota in patients with PaO2/FiO2 ratio ≤ 300 after burn and inhalation injury.

    PubMed

    Walsh, Dana M; McCullough, Shaun D; Yourstone, Scott; Jones, Samuel W; Cairns, Bruce A; Jones, Corbin D; Jaspers, Ilona; Diaz-Sanchez, David

    2017-01-01

    Injury to the airways after smoke inhalation is a major mortality risk factor in victims of burn injuries, resulting in a 15-45% increase in patient deaths. Damage to the airways by smoke may induce acute respiratory distress syndrome (ARDS), which is partly characterized by hypoxemia in the airways. While ARDS has been associated with bacterial infection, the impact of hypoxemia on airway microbiota is unknown. Our objective was to identify differences in microbiota within the airways of burn patients who develop hypoxemia early after inhalation injury and those that do not using next-generation sequencing of bacterial 16S rRNA genes. DNA was extracted from therapeutic bronchial washings of 48 patients performed within 72 hours of hospitalization for burn and inhalation injury at the North Carolina Jaycee Burn Center. DNA was prepared for sequencing using a novel molecule tagging method and sequenced on the Illumina MiSeq platform. Bacterial species were identified using the MTToolbox pipeline. Patients with hypoxemia, as indicated by a PaO2/FiO2 ratio ≤ 300, had a 30% increase in abundance of Streptococcaceae and Enterobacteriaceae and 84% increase in Staphylococcaceae as compared to patients with a PaO2/FiO2 ratio > 300. Wilcoxon rank-sum test identified significant enrichment in abundance of OTUs identified as Prevotella melaninogenica (p = 0.042), Corynebacterium (p = 0.037) and Mogibacterium (p = 0.048). Linear discriminant effect size analysis (LefSe) confirmed significant enrichment of Prevotella melaninognica among patients with a PaO2/FiO2 ratio ≤ 300 (p<0.05). These results could not be explained by differences in antibiotic treatment. The airway microbiota following burn and inhalation injury is altered in patients with a PaO2/FiO2 ratio ≤ 300 early after injury. Enrichment of specific taxa in patients with a PaO2/FiO2 ratio ≤ 300 may indicate airway environment and patient changes that favor these microbes. Longitudinal studies are necessary to

  12. Characterization of Water Coordination to Ferrous Nitrosyl Complexes with fac-N2O, cis-N2O2, and N2O3 Donor Ligands.

    PubMed

    McCracken, John; Cappillino, Patrick J; McNally, Joshua S; Krzyaniak, Matthew D; Howart, Michael; Tarves, Paul C; Caradonna, John P

    2015-07-06

    Electron paramagnetic resonance (EPR) experiments were done on a series of S = (3)/2 ferrous nitrosyl model complexes prepared with chelating ligands that mimic the 2-His-1-carboxylate facial triad iron binding motif of the mononuclear nonheme iron oxidases. These complexes formed a comparative family, {FeNO}(7)(N2Ox)(H2O)3-x with x = 1-3, where the labile coordination sites for the binding of NO and solvent water were fac for x = 1 and cis for x = 2. The continuous-wave EPR spectra of these three complexes were typical of high-spin S = (3)/2 transition-metal ions with resonances near g = 4 and 2. Orientation-selective hyperfine sublevel correlation (HYSCORE) spectra revealed cross peaks arising from the protons of coordinated water in a clean spectral window from g = 3.0 to 2.3. These cross peaks were absent for the {FeNO}(7)(N2O3) complex. HYSCORE spectra were analyzed using a straightforward model for defining the spin Hamiltonian parameters of bound water and showed that, for the {FeNO}(7)(N2O2)(H2O) complex, a single water conformer with an isotropic hyperfine coupling, Aiso = 0.0 ± 0.3 MHz, and a dipolar coupling of T = 4.8 ± 0.2 MHz could account for the data. For the {FeNO}(7)(N2O)(H2O)2 complex, the HYSCORE cross peaks assigned to coordinated water showed more frequency dispersion and were analyzed with discrete orientations and hyperfine couplings for the two water molecules that accounted for the observed orientation-selective contour shapes. The use of three-pulse electron spin echo envelope modulation (ESEEM) data to quantify the number of water ligands coordinated to the {FeNO}(7) centers was explored. For this aspect of the study, HYSCORE spectra were important for defining a spectral window where empirical integration of ESEEM spectra would be the most accurate.

  13. Effect of fertilizer application on NO and N2O fluxes from agricultural fields

    NASA Astrophysics Data System (ADS)

    Harrison, Roy M.; Yamulki, Sirwan; Goulding, K. W. T.; Webster, C. P.

    1995-12-01

    Losses of fertilizer as NO and N2O were studied at Broadbalk field, Rothamsted Experimental Station in England, on which subplots have been subject to differing constant levels of fertilizer application for many years. Fluxes of NO and N2O were measured using open- and closed-chamber techniques, respectively. Fluxes from unfertilized soil ranged from 0.3 to 4.8 ng N m-2 s-1 for NO and 0.23 to 3.0 ng N m-2 s-1 for N2O. The corresponding fluxes from the plot with the highest fertilizer application (92 kg N ha-1 yr-1 as NH4NO3) ranged from 0.5 to 64 ng N m-2 s-1 for NO and 0.4 to 240 ng N m-2 s-1 for N2O. Application of increasing amounts of fertilizer substantially enhanced emission rates of both NO and N2O. However, the amount of increase was controlled by competition between the crop and the microorganisms for the available soil nutrients, and loss of N2O to the atmosphere increased sharply at superoptimal levels of fertilizer application. The fertilizer-derived NO and N2O emissions represented approximately 90% of the total emission of these gases during the 25-day sampling period after fertilizer application. The results suggest that while increasing the amount of fertilizer increases both NO and N2O fluxes simultaneously, the NO/N2O emission ratio decreases. Results from laboratory experiments showed that the magnitude of the fertilizer loss as N2O was strongly affected by the form of the applied fertilizer.

  14. Tracing changes in soil N transformations to explain the doubling of N2O emissions under elevated CO2 in the Giessen FACE

    NASA Astrophysics Data System (ADS)

    Moser, Gerald; Brenzinger, Kristof; Gorenflo, Andre; Clough, Tim; Braker, Gesche; Müller, Christoph

    2017-04-01

    To reduce the emissions of greenhouse gases (CO2, CH4 & N2O) it is important to quantify main sources and identify the respective ecosystem processes. While the main sources of N2O emissions in agro-ecosystems under current conditions are well known, the influence of a projected higher level of CO2 on the main ecosystem processes responsible for N2O emissions has not been investigated in detail. A major result of the Giessen FACE in a managed temperate grassland was that a +20% CO2 level caused a positive feedback due to increased emissions of N2O to 221% related to control condition. To be able to trace the sources of additional N2O emissions a 15N tracing study was conducted. We measured the N2O emission and its 15N signature, together with the 15N signature of soil and plant samples. The results were analyzed using a 15N tracing model which quantified the main changes in N transformation rates under elevated CO2. Directly after 15N fertilizer application a much higher dynamic of N transformations was observed than in the long run. Absolute mineralisation and DNRA rates were lower under elevated CO2 in the short term but higher in the long term. During the one year study period beginning with the 15N labelling a 1.8-fold increase of N2O emissions occurred under elevated CO2. The source of increased N2O was associated with NO3- in the first weeks after 15N application. Elevated CO2 affected denitrification rates, which resulted in increased N2O emissions due to a change of gene transcription rates (nosZ/(nirK+nirS)) and resulting enzyme activity (see: Brenzinger et al.). Here we show that the reported enhanced N2O emissions for the first 8 FACE years do prevail even in the long-term (> 15 years). The effect of elevated CO2 on N2O production/emission can be explained by altered activity ratios within a stable microbial community.

  15. Enhanced photosynthetic efficiency in trees world-wide by rising atmospheric CO2 levels

    NASA Astrophysics Data System (ADS)

    Ehlers, Ina; Wieloch, Thomas; Groenendijk, Peter; Vlam, Mart; van der Sleen, Peter; Zuidema, Pieter A.; Robertson, Iain; Schleucher, Jürgen

    2014-05-01

    The atmospheric CO2 concentration is increasing rapidly due to anthropogenic emissions but the effect on the Earth's biosphere is poorly understood. The ability of the biosphere to fix CO2 through photosynthesis will determine future atmospheric CO2 concentrations as well as future productivity of crops and forests. Manipulative CO2 enrichment experiments (e.g. FACE) are limited to (i) short time spans, (ii) few locations and (iii) large step increases in [CO2]. Here, we apply new stable isotope methodology to tree-ring archives, to study the effect of increasing CO2 concentrations retrospectively during the past centuries. We cover the whole [CO2] increase since industrialization, and sample trees with global distribution. Instead of isotope ratios of whole molecules, we use intramolecular isotope distributions, a new tool for tree-ring analysis with decisive advantages. In experiments on annual plants, we have found that the intramolecular distribution of deuterium (equivalent to ratios of isotopomer abundances) in photosynthetic glucose depends on growth [CO2] and reflects the metabolic flux ratio of photosynthesis to photorespiration. By applying this isotopomer methodology to trees from Oak Ridge FACE experiment, we show that this CO2 response is present in trees on the leaf level. This CO2 dependence constitutes a physiological signal, which is transferred to the wood of the tree rings. In trees from 13 locations on all continents the isotopomer ratio of tree-ring cellulose is correlated to atmospheric [CO2] during the past 200 years. The shift of the isotopomer ratio is universal for all 12 species analyzed, including both broad-leafed trees and conifers. Because the trees originate from sites with widely differing D/H ratios of precipitation, the generality of the response demonstrates that the signal is independent of the source isotope ratio, because it is encoded in an isotopomer abundance ratio. This decoupling of climate signals and physiological

  16. Bis(2,2'-bipyridyl-κN,N')(carbonato-κO,O')cobalt(III) bromide trihydrate.

    PubMed

    Ma, Peng-Tao; Wang, Yu-Xia; Zhang, Guo-Qian; Li, Ming-Xue

    2007-12-06

    The title complex, [Co(CO(3))(C(10)H(8)N(2))(2)]Br·3H(2)O, is isostructural with the chloride analogue. The six-coordinated octahedral [Co(2,2'-bipy)(2)CO(3)](+) cation (2,2'-bipy is 2,2'-bipyrid-yl), bromide ion and water mol-ecules are linked together via O-H⋯Br and O-H⋯O hydrogen bonds, generating a one-dimensional chain.

  17. Optimizing rice plant photosynthate allocation reduces N2O emissions from paddy fields

    NASA Astrophysics Data System (ADS)

    Jiang, Yu; Huang, Xiaomin; Zhang, Xin; Zhang, Xingyue; Zhang, Yi; Zheng, Chengyan; Deng, Aixing; Zhang, Jun; Wu, Lianhai; Hu, Shuijin; Zhang, Weijian

    2016-07-01

    Rice paddies are a major source of anthropogenic nitrous oxide (N2O) emissions, especially under alternate wetting-drying irrigation and high N input. Increasing photosynthate allocation to the grain in rice (Oryza sativa L.) has been identified as an effective strategy of genetic and agronomic innovation for yield enhancement; however, its impacts on N2O emissions are still unknown. We conducted three independent but complementary experiments (variety, mutant study, and spikelet clipping) to examine the impacts of rice plant photosynthate allocation on paddy N2O emissions. The three experiments showed that N2O fluxes were significantly and negatively correlated with the ratio of grain yield to total aboveground biomass, known as the harvest index (HI) in agronomy (P < 0.01). Biomass accumulation and N uptake after anthesis were significantly and positively correlated with HI (P < 0.05). Reducing photosynthate allocation to the grain by spikelet clipping significantly increased white root biomass and soil dissolved organic C and reduced plant N uptake, resulting in high soil denitrification potential (P < 0.05). Our findings demonstrate that optimizing photosynthate allocation to the grain can reduce paddy N2O emissions through decreasing belowground C input and increasing plant N uptake, suggesting the potential for genetic and agronomic efforts to produce more rice with less N2O emissions.

  18. Systematic Variations in CO2/H2O Ice Abundance Ratios in Nearby Galaxies Found with AKARI Near-infrared Spectroscopy

    NASA Astrophysics Data System (ADS)

    Yamagishi, M.; Kaneda, H.; Ishihara, D.; Oyabu, S.; Onaka, T.; Shimonishi, T.; Suzuki, T.

    2015-07-01

    We report CO2/H2O ice abundance ratios in seven nearby star-forming galaxies based on the AKARI near-infrared (2.5-5.0 μm) spectra. The CO2/H2O ice abundance ratios show clear variations between 0.05 and 0.2 with the averaged value of 0.14 ± 0.01. The previous study on M82 revealed that the CO2/H2O ice abundance ratios strongly correlate with the intensity ratios of the hydrogen recombination Brα line to the polycyclic aromatic hydrocarbon (PAH) 3.3 μm feature. In the present study, however, we find no correlation for the seven galaxies as a whole due to systematic differences in the relation between CO2/H2O ice abundance and Brα/PAH 3.3 μm intensity ratios from galaxy to galaxy. This result suggests that there is another parameter that determines the CO2/H2O ice abundance ratios in a galaxy in addition to the Brα/PAH 3.3 μm ratios. We find that the CO2/H2O ice abundance ratios positively correlate with the specific star formation rates of the galaxies. From these results, we conclude that CO2/H2O ice abundance ratios tend to be high in young star-forming galaxies.

  19. Effect of natural and laboratory diet on O : N ratio in juvenile lobsters (Homarus americanus).

    PubMed

    Brown, Anne Christine

    2006-05-01

    Oxygen consumption and ammonia excretion rates of juvenile lobsters spanning the size range from shelter-restricted to vagile (7-60 mm CL, carapace length) were measured. There are no significant size-dependent break points in the slope of oxygen consumption or nitrogen excretion rates versus weight in freshly caught wild or laboratory fed lobsters. This suggests that there are no inherent changes in energy metabolism in juvenile lobster in the 7-60 mm CL range (stage V to adolescent lobsters), despite major behavioral shifts related to foraging and shelter use. In addition, the O : N ratio of freshly caught wild lobsters (15.7+/-7.4, mean+/-S.D.) is not significantly different from that of lobsters fed brown algae (13.4+/-4.9) or a mixed carbohydrate/protein diet (13.7+/-6.8) in lab. The O : N ratio of wild lobsters is significantly higher than lobsters fed a high protein diet (7.5+/-2.5) in the lab. This suggests that carbohydrates, particularly algal-derived carbohydrates, make up a significant portion of the metabolic fuel of wild juvenile lobsters from settlement through adolescence.

  20. An improved CeO2 method for high-precision measurements of 17O/16O ratios for atmospheric carbon dioxide.

    PubMed

    Mahata, Sasadhar; Bhattacharya, Sourandra K; Wang, Chung-Ho; Liang, Mao-Chang

    2012-09-15

    The oxygen isotopic composition of carbon dioxide originating at the Earth's surface is modified in the stratosphere by interaction with ozone which has anomalous oxygen isotope ratio (Δ(17)O = 1000 * ln(1 + δ(17)O/1000) - 0.522 * 1000 * ln (1 + δ(18)O/1000) >0). The inherited anomaly provides a powerful tracer for studying biogeochemical cycles involving CO(2). However, the existing methods are either too imprecise or have difficulty in determining the small Δ(17)O variations found in the tropospheric CO(2). In this study an earlier published CeO(2) and CO(2) exchange method has been modified and improved for measuring the Δ(17)O values of atmospheric carbon dioxide with high precision. The CO(2) fraction from air samples was separated by cryogenic means and purified using gas chromatography. This CO(2) was first analyzed in an isotope ratio mass spectrometer, then artificially equilibrated with hot CeO(2) to alter its oxygen isotopes mass-dependently and re-analyzed. From these data the (17)O/(16)O and (18)O/(16)O ratios were calculated and the Δ(17)O value was determined. The validity of the method was established in several tests by using artificially prepared CO(2) with zero and non-zero Δ(17)O values. The published value of the CO(2)-H(2) O equilibrium slope was also reproduced. The CO(2)-CeO(2) equilibration method has been improved to measure the oxygen isotope anomaly (Δ(17)O value) of atmospheric CO(2) with an analytical precision of ±0.12‰ (2σ). Copyright © 2012 John Wiley & Sons, Ltd.

  1. [(Nitrato-κ2 O,O′)(nitrito-κ2 O,O′)(0.25/1.75)]bis­(1,10-phenanthroline-κ2 N,N′)cadmium(II)

    PubMed Central

    Najafi, Ezzatollah; Amini, Mostafa M.; Ng, Seik Weng

    2011-01-01

    The reaction of cadmium nitrate and sodium nitrite in the presence of 1,10-phenanthroline yields the mixed nitrate–nitrite title complex, [Cd(NO2)1.75(NO3)0.25(C12H8N2)2]. The metal ion is bis-chelated by two N-heterocycles as well as by the nitrate/nitrite ions in a distorted dodeca­hedral CdN4O4 coordination environment. One nitrite group is ordered; the other is disordered with respect to a nitrate group (ratio 0.75:0.25) concerning the O atom that is not involved in bonding to the metal ion. PMID:21522904

  2. Binding energies from diffusion Monte Carlo for the MB-pol H{sub 2}O and D{sub 2}O dimer: A comparison to experimental values

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Mallory, Joel D.; Mandelshtam, Vladimir A.

    2015-10-14

    The diffusion Monte Carlo (DMC) method is applied to compute the ground state energies of the water monomer and dimer and their D{sub 2}O isotopomers using MB-pol; the most recent and most accurate ab inito-based potential energy surface (PES). MB-pol has already demonstrated excellent agreement with high level electronic structure data, as well as agreement with some experimental, spectroscopic, and thermodynamic data. Here, the DMC binding energies of (H{sub 2}O){sub 2} and (D{sub 2}O){sub 2} agree with the corresponding values obtained from velocity map imaging within, respectively, 0.01 and 0.02 kcal/mol. This work adds two more valuable data points thatmore » highlight the accuracy of the MB-pol PES.« less

  3. Effect of the Molar Ratio of B2O3 to Bi2O3 in Al Paste with Bi2O3-B2O3-ZnO Glass on Screen Printed Contact Formation and Si Solar Cell Performance

    NASA Astrophysics Data System (ADS)

    Kim, Bit-Na; Kim, Hyeong Jun; Chang, Hyo Sik; Hong, Hyun Seon; Ryu, Sung-Soo; Lee, Heon

    2013-10-01

    In this study, eco-friendly Pb-free Bi2O3-B2O3-ZnO glass frits were chosen as an inorganic additive for the Al paste used in Si solar cells. The effects of the molar ratio of Bi2O3 to B2O3 in the glass composition on the electrical resistance of the Al electrode and on the cell performance were investigated. The results showed that as the molar ratio of Bi2O3 to B2O3 increased, the glass transition temperature and softening temperature decreased because of the reduced glass viscosity. In Al screen-printed Si solar cells, as the molar ratio of Bi2O3 to B2O3 increased, the sheet electrical resistance of the Al electrode decreased and the cell efficiency increased. The uniformity and thickness of the back-surface field was significantly influenced by the glass composition.

  4. Expansion of antimonato polyoxovanadates with transition metal complexes: (Co(N3C5H15)2)2[{Co(N3C5H15)2}V15Sb6O42(H2O)]·5H2O and (Ni(N3C5H15)2)2[{Ni(N3C5H15)2}V15Sb6O42(H2O)]·8H2O.

    PubMed

    Antonova, Elena; Näther, Christian; Kögerler, Paul; Bensch, Wolfgang

    2012-02-20

    Two new polyoxovanadates (Co(N(3)C(5)H(15))(2))(2)[{Co(N(3)C(5)H(15))(2)}V(15)Sb(6)O(42)(H(2)O)]·5H(2)O (1) and (Ni(N(3)C(5)H(15))(2))(2)[{Ni(N(3)C(5)H(15))(2)}V(15)Sb(6)O(42)(H(2)O)]·8H(2)O (2) (N(3)C(5)H(15) = N-(2-aminoethyl)-1,3-propanediamine) were synthesized under solvothermal conditions and structurally characterized. In both structures the [V(15)Sb(6)O(42)(H(2)O)](6-) shell displays the main structural motif, which is strongly related to the {V(18)O(42)} archetype cluster. Both compounds crystallize in the triclinic space group P1 with a = 14.3438(4), b = 16.6471(6), c = 18.9186(6) Å, α = 87.291(3)°, β = 83.340(3)°, γ = 78.890(3)°, and V = 4401.4(2) Å(3) (1) and a = 14.5697(13), b = 15.8523(16), c = 20.2411(18) Å, α = 86.702(11)°, β = 84.957(11)°, γ = 76.941(11)°, and V = 4533.0(7) Å(3) (2). In the structure of 1 the [V(15)Sb(6)O(42)(H(2)O)](6-) cluster anion is bound to a [Co(N(3)C(5)H(15))(2)](2+) complex via a terminal oxygen atom. In the Co(2+)-centered complex, one of the amine ligands coordinates in tridentate mode and the second one in bidentate mode to form a strongly distorted CoN(5)O octahedron. Similarly, in compound 2 an analogous NiN(5)O complex is joined to the [V(15)Sb(6)O(42)(H(2)O)](6-) anion via the same attachment mode. A remarkable difference between the two compounds is the orientation of the noncoordinated propylamine group leading to intermolecular Sb···O contacts in 1 and to Sb···N interactions in 2. In the solid-state lattices of 1 and 2, two additional [M(N(3)C(5)H(15))(2)](2+) complexes act as countercations and are located between the [{M(N(3)C(5)H(15))(2)}V(15)Sb(6)O(42)(H(2)O)](4-) anions. Between the anions and cations strong N-H···O hydrogen bonds are observed. In both compounds the clusters are stacked along the b axis in an ABAB fashion with cations and water molecules occupying the space between the clusters. Magnetic characterization demonstrates that the Ni(2+) and Co(2+) cations do not

  5. Limits and possibilities in the geolocation of humans using multiple isotope ratios (H, O, N, C) of hair from east coast cities of the USA.

    PubMed

    Reynard, Linda M; Burt, Nicole; Koon, Hannah E C; Tuross, Noreen

    2016-01-01

    We examined multiple natural abundance isotope ratios of human hair to assess biological variability within and between geographic locations and, further, to determine how well these isotope values predict location of origin. Sampling locations feature differing seasonality and mobile populations as a robust test of the method. Serially-sampled hair from Cambridge, MA, USA, shows lower δ(2)H and δ(18)O variability over a one-year time course than model-predicted precipitation isotope ratios, but exhibits considerable differences between individuals. Along a ∼13° north-south transect in the eastern USA (Brookline, MA, 42.3 ° N, College Park, MD, 39.0 ° N, and Gainesville, FL, 29.7 ° N) δ(18)O in human hair shows relatively greater differences and tracks changes in drinking water isotope ratios more sensitively than δ(2)H. Determining the domicile of humans using isotope ratios of hair can be confounded by differing variability in hair δ(18)O and δ(2)H between locations, differential incorporation of H and O into this protein and, in some cases, by tap water δ(18)O and δ(2)H that differ significantly from predicted precipitation values. With these caveats, randomly chosen people in Florida are separated from those in the two more northerly sites on the basis of the natural abundance isotopes of carbon, nitrogen, hydrogen, and oxygen.

  6. Plasma sterilization of Geobacillus Stearothermophilus by O{mathsf2}:N{mathsf2} RF inductively coupled plasma

    NASA Astrophysics Data System (ADS)

    Kylián, O.; Sasaki, T.; Rossi, F.

    2006-05-01

    The aim of this work is to identify the main process responsible for sterilization of Geobacillus Stearothermophilus spores in O{2}:N{2} RF inductively coupled plasma. In order to meet this objective the sterilization efficiencies of discharges in mixtures differing in the initial O{2}/N{2} ratios are compared with plasma properties and with scanning electron microscopy images of treated spores. According to the obtained results it can be concluded that under our experimental conditions the time needed to reach complete sterilization is more related to O atom density than UV radiation intensity, i.e. complete sterilization is not related only to DNA damage as in UV sterilization but more likely to the etching of the spore.

  7. Statistical modeling of the reactions Fe(+) + N2O → FeO(+) + N2 and FeO(+) + CO → Fe(+) + CO2.

    PubMed

    Ushakov, Vladimir G; Troe, Jürgen; Johnson, Ryan S; Guo, Hua; Ard, Shaun G; Melko, Joshua J; Shuman, Nicholas S; Viggiano, Albert A

    2015-08-14

    The rates of the reactions Fe(+) + N2O → FeO(+) + N2 and FeO(+) + CO → Fe(+) + CO2 are modeled by statistical rate theory accounting for energy- and angular momentum-specific rate constants for formation of the primary and secondary cationic adducts and their backward and forward reactions. The reactions are both suggested to proceed on sextet and quartet potential energy surfaces with efficient, but probably not complete, equilibration by spin-inversion of the populations of the sextet and quartet adducts. The influence of spin-inversion on the overall reaction rate is investigated. The differences of the two reaction rates mostly are due to different numbers of entrance states (atom + linear rotor or linear rotor + linear rotor, respectively). The reaction Fe(+) + N2O was studied either with (6)Fe(+) or with (4)Fe(+) reactants. Differences in the rate constants of (6)Fe(+) and (4)Fe(+) reacting with N2O are attributed to different contributions from electronically excited potential energy surfaces, such as they originate from the open-electronic shell reactants.

  8. Theoretical characterization of stable eta1-N2O-, eta2-N2O-, eta1-N2-, and eta2-N2-bound species: intermediates in the addition reactions of nitrogen hydrides with the pentacyanonitrosylferrate(II) ion.

    PubMed

    Olabe, José A; Estiú, Guillermina L

    2003-08-11

    The addition of nitrogen hydrides (hydrazine, hydroxylamine, ammonia, azide) to the pentacyanonitrosylferrate(II) ion has been analyzed by means of density functional calculations, focusing on the identification of stable intermediates along the reaction paths. Initial reversible adduct formation and further decomposition lead to the eta(1)- and eta(2)-linkage isomers of N(2)O and N(2), depending on the nucleophile. The intermediates (adducts and gas-releasing precursors) have been characterized at the B3LYP/6-31G level of theory through the calculation of their structural and spectroscopic properties, modeling the solvent by means of a continuous approach. The eta(2)-N(2)O isomer is formed at an initial stage of adduct decompositions with the hydrazine and azide adducts. Further conversion to the eta(1)-N(2)O isomer is followed by Fe-N(2)O dissociation. Only the eta(1)-N(2)O isomer is predicted for the reaction with hydroxylamine, revealing a kinetically controlled N(2)O formation. eta(1)-N(2) and eta(2)-N(2) isomers are also predicted as stable species.

  9. Spatial variability in groundwater N2 and N2O in the San Joaquin River

    NASA Astrophysics Data System (ADS)

    Hinshaw, S.; Dahlgren, R. A.

    2010-12-01

    The San Joaquin River is surrounded by nearly 2 million acres of irrigated agricultural land. Groundwater inputs from agricultural areas can have severe negative effects on water quality with high nitrate concentrations being a major concern. Riparian zones are important ecological habitats that mitigate nitrogen loading from groundwater discharging into rivers primarily by denitrification. Denitrification is a permanent removal of nitrate by anaerobic microbial communities via the reduction to NO, N2O and N2. However, previous studies have shown that these areas can be source of N2O emissions. Although removal of nitrate through denitrification is advantageous from a water quality perspective, N2O is a harmful greenhouse gas. This study aimed to investigate nitrogen dynamics and dissolved N gases in surface and groundwater of the riparian zones of the San Joaquin River. Excess N2 and N2O concentrations were measured in surface and groundwater at 4 locations along a 33 km reach of the river. Samples were collected within bank sediments and 5 transect points across the river at depth intervals between 2-3 cm and 150 cm. Dissolved N2 and Ar were measured by membrane inlet mass spectrometry and used to estimate excess dissolved N2 concentrations. Dissolved N2O concentrations were measured using the headspace equilibrium technique and analyzed with a gas chromatograph. Both N2 uptake and excess N2 were present, ranging from -3.40 to 8.65 N2 mg/L with a median concentration of 1.20 N2 mg/L. Significantly lower concentrations of N2O were present ranging from 0.0 to 0.12 N2O mg/L. Deeper groundwater sites had significantly higher N2 and N2O concentrations coinciding with decreased O2. The presence of excess N2 and low N2O concentrations documents the importance of denitrification in removing nitrate from groundwater. Further investigation will examine N2O emissions from riparian soils and benthic sediments using static chambers and focus on nitrogen pathways that

  10. Co-composting of municipal solid waste mixed with matured sewage sludge: The relationship between N2O emissions and denitrifying gene abundance.

    PubMed

    Bian, Rongxing; Sun, Yingjie; Li, Weihua; Ma, Qiang; Chai, Xiaoli

    2017-12-01

    Aerobic composting is an alternative measure to the disposal of municipal solid waste (MSW). However, it produces nitrous oxide (N 2 O), a highly potent greenhouse via microbial nitrification and denitrification. In this study, the effects of matured sewage sludge (MSS) amendment on N 2 O emissions and the inter-relationships between N 2 O emissions and the abundance of denitrifying bacteria were investigated during aerobic composting of MSW. The results demonstrated that MSW composting with MSS amendments (C1, and C2, with a MSW to MSS ratio of 2:1 and 4:1, (v/v), respectively) significantly increased N 2 O emissions during the initial stage, yet contributed to the mitigation of N 2 O emissions during the cooling and maturation stage. MSS amended composting emitted a total of 18.4%-25.7% less N 2 O than the control treatment without MSS amendment (CK). Matured sewage sludge amendment also significantly altered the abundance of denitrifying bacteria. The quantification of denitrifying functional genes revealed that the N 2 O emission rate had a significant positive correlation with the abundance of the nirS, nirK genes in both treatments with MSS amendment. The nosZ/(nirS + nirK) ratio could be a good indicator for predicting N 2 O emissions. The higher N 2 O emission rate during the initial stage of composting mixed with MSS was characterized by lower nosZ/(nirS + nirK) ratios, compared to CK treatment. Higher ratios of nosZ/(nirS + nirK) were measured during the cooling and maturation stage in treatments with MSS which resulted in a reduction of the N 2 O emissions. These results demonstrated that MSS amendment could be a valid strategy for mitigating N 2 O emissions during MSW composting. Copyright © 2017 Elsevier Ltd. All rights reserved.

  11. Atmospheric test of the J(BrONO2)/kBrO+NO2 ratio: implications for total stratospheric Bry and bromine-mediated ozone loss

    NASA Astrophysics Data System (ADS)

    Kreycy, S.; Camy-Peyret, C.; Chipperfield, M. P.; Dorf, M.; Feng, W.; Hossaini, R.; Kritten, L.; Werner, B.; Pfeilsticker, K.

    2013-07-01

    We report on time-dependent O3, NO2 and BrO profiles measured by limb observations of scattered skylight in the stratosphere over Kiruna (67.9° N, 22.1° E) on 7 and 8 September 2009 during the autumn circulation turn-over. The observations are complemented by simultaneous direct solar occultation measurements around sunset and sunrise performed aboard the same stratospheric balloon payload. Supporting radiative transfer and photochemical modelling indicate that the measurements can be used to constrain the ratio J(BrONO2)/kBrO+NO2, for which at T = 220 ± 5 K an overall 1.7 (+0.4 -0.2) larger ratio is found than recommended by the most recent Jet Propulsion Laboratory (JPL) compilation (Sander et al., 2011). Sensitivity studies reveal the major reasons are likely to be (1) a larger BrONO2 absorption cross-section σBrONO2, primarily for wavelengths larger than 300 nm, and (2) a smaller kBrO+NO2 at 220 K than given by Sander et al. (2011). Other factors, e.g. the actinic flux and quantum yield for the dissociation of BrONO2, can be ruled out. The observations also have consequences for total inorganic stratospheric bromine (Bry) estimated from stratospheric BrO measurements at high NOx loadings, since the ratio J(BrONO2)/kBrO+NO2 largely determines the stratospheric BrO/Bry ratio during daylight. Using the revised J(BrONO2)/kBrO+NO2 ratio, total stratospheric Bry is likely to be 1.4 ppt smaller than previously estimated from BrO profile measurements at high NOx loadings. This would bring estimates of Bry inferred from organic source gas measurements (e.g. CH3Br, the halons, CH2Br2, CHBr3, etc.) into closer agreement with estimates based on BrO observations (inorganic method). The consequences for stratospheric ozone due to the revised J(BrONO2)/kBrO+NO2 ratio are small (maximum -0.8%), since at high NOx (for which most Bry assessments are made) the enhanced ozone loss by overestimating Bry is compensated for by the suppressed ozone loss due to the underestimation

  12. Theoretical study of the interaction of N/sub 2/ with water molecules. (H/sub 2/O)/sub n/:N/sub 2/, n = 1--8

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Curtiss, L.A.; Eisgruber, C.L.

    1984-03-01

    Ab initio molecular orbital calculations including correlation energy have been carried out on the interaction of a single H/sub 2/O molecule with N/sub 2/. The potential energy surface for H/sub 2/O:N/sub 2/ is found to have a minimum corresponding to a HOH xxx N/sub 2/ structure with a weak (<2 kcal mol/sup -1/) hydrogen bond. A second, less stable, configuration corresponding to a H/sub 2/O xxx N/sub 2/ structure with N/sub 2/ bonded side on to the oxygen of H/sub 2/O was found to be either a minimum or a saddle point in the potential energy surface depending on themore » level of calculation. The minimal STO-3G basis set was used to investigate the interaction of up to eight H/sub 2/O molecules with N/sub 2/. Two types of clusters, one containing only HOH xxx N/sub 2/ interactions and the other containing both HOH xxxN/sub 2/ and H/sub 2/O xxx N/sub 2/ interactions, were investigated for (N/sub 2/:(H/sub 2/O)/sub n/, n = 2--8).« less

  13. Reassessment of the NH4 NO3 thermal decomposition technique for calibration of the N2 O isotopic composition.

    PubMed

    Mohn, Joachim; Gutjahr, Wilhelm; Toyoda, Sakae; Harris, Eliza; Ibraim, Erkan; Geilmann, Heike; Schleppi, Patrick; Kuhn, Thomas; Lehmann, Moritz F; Decock, Charlotte; Werner, Roland A; Yoshida, Naohiro; Brand, Willi A

    2016-09-08

    In the last few years, the study of N 2 O site-specific nitrogen isotope composition has been established as a powerful technique to disentangle N 2 O emission pathways. This trend has been accelerated by significant analytical progress in the field of isotope-ratio mass-spectrometry (IRMS) and more recently quantum cascade laser absorption spectroscopy (QCLAS). Methods The ammonium nitrate (NH 4 NO 3 ) decomposition technique provides a strategy to scale the 15 N site-specific (SP ≡ δ 15 N α - δ 15 N β ) and bulk (δ 15 N bulk  = (δ 15 N α  + δ 15 N β )/2) isotopic composition of N 2 O against the international standard for the 15 N/ 14 N isotope ratio (AIR-N 2 ). Within the current project 15 N fractionation effects during thermal decomposition of NH 4 NO 3 on the N 2 O site preference were studied using static and dynamic decomposition techniques. The validity of the NH 4 NO 3 decomposition technique to link NH 4 + and NO 3 - moiety-specific δ 15 N analysis by IRMS to the site-specific nitrogen isotopic composition of N 2 O was confirmed. However, the accuracy of this approach for the calibration of δ 15 N α and δ 15 N β values was found to be limited by non-quantitative NH 4 NO 3 decomposition in combination with substantially different isotope enrichment factors for the conversion of the NO 3 - or NH 4 + nitrogen atom into the α or β position of the N 2 O molecule. The study reveals that the completeness and reproducibility of the NH 4 NO 3 decomposition reaction currently confine the anchoring of N 2 O site-specific isotopic composition to the international isotope ratio scale AIR-N 2 . The authors suggest establishing a set of N 2 O isotope reference materials with appropriate site-specific isotopic composition, as community standards, to improve inter-laboratory compatibility. This article is protected by copyright. All rights reserved.

  14. Measuring the ratio of CO2 efflux to O2 influx in tree stem respiration.

    PubMed

    Hilman, Boaz; Angert, Alon

    2016-11-01

    In recent studies, the ratio of tree stem CO 2 efflux to O 2 influx has been defined as the apparent respiratory quotient (ARQ). The metabolism of carbohydrates, the putative respiratory substrate in trees, is expected to yield an ARQ of 1.0. However, previous studies have reported ARQ values ranging between 0.23 and 0.90. These interesting results may indicate internal transport of respired CO 2 within stems; yet no simple field applicable methods for ARQ measurement have been available. Here, we report on the assembly of a closed circulating system called 'Hampadah', which uses CO 2 and O 2 analyzers to measure air samples from stem chambers. We tested the performance of the Hampadah with samples from 36 trees (Tetragastris panamensis (Engl.) Kuntze). Additionally, we showed the feasibility of measuring ARQ directly from stem chambers, using portable CO 2 and O 2 sensors, in both discrete and continuous modes of operation. The Hampadah measurement proved to be consistent with CO 2 gas standards (R 2 = 0.999) and with O 2 determined by O 2 /Ar measurements with a mass spectrometer (R 2 = 0.998). The Hampadah gave highly reproducible results for ARQ determination of field samples (±0.01 for duplicates). The portable sensors measurement showed good correlation with the Hampadah in measuring CO 2 , O 2 and ARQ (n = 5, R 2 = 0.97, 0.98 and 0.91, respectively). We have demonstrated here that the Hampadah and the sensors' methods enable accurate ARQ measurements for both laboratory and field research. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  15. Preparation of (Fe, N)-doped TiO2 powders and their antibacterial activities under visible light irradiation.

    PubMed

    He, Rong-Liang; Wei, Yi; Cao, Wen-Bin

    2009-02-01

    Yellowish (Fe, N)-doped nanocrystalline TiO2 powders have been prepared using TiOSO4, CO(NH2)2, Fe(NO3)3.9H2O and CN3H5.HCl as precursors by hydrothermal method. The as-synthesized powders were anatase in phase and the grain size was about 10 nm according to the TEM photos. The ratio of Fe/Ti is 2.2 at% and N/O is 0.8 at% respectively. TiO2 powders were mixed with organic silicon and acrylic syrup to test their antibacterial performance by the colony counting method. The results show that the sterilization ratio of E. coli by the heat-treated (Fe, N)-doped nanocrystalline TiO2 powders is reached up to 94.5% while that of the powders without any heat treatment is 91.1% by 8 hours-400 lux-Visible-light irradiation with humidity of 55% RH.

  16. Absorption of solar radiation by O2 - Implications for O3 and lifetimes of N2O, CFCl3, and CF2Cl2

    NASA Technical Reports Server (NTRS)

    Minschwaner, K.; Salawitch, R. J.; Mcelroy, M. B.

    1993-01-01

    An accurate line-by-line model is used to evaluate effects of absorption in the Schumann-Runge bands of O2 on transmission of UV radiation. The model is used to evaluate rates of photolysis for N2O, CFCl3, and CF2Cl2, and to infer global loss rates and instantaneous lifetimes appropriate for 1980. A parameterized version of the line-by-line model enabling rapid evaluation of transmission in the Schumann-Runge region is described. Photochemical calculations employing the parameterization and constrained by data from the Atmospheric Trace Molecule Spectroscopy experiment are used to examine the budget of odd oxygen. Consistent with previous studies, it is shown that photochemical loss of odd oxygen exceeds production by photolysis of O2 for altitudes above 40 km. The imbalance between production and loss is shown to be consistent with a source of odd oxygen proportional to the product of the mixing ratio and photolysis rate of ozone, which suggests that processes involving vibrationally excited O2 may play an important role in production of odd oxygen.

  17. Bis(O-n-butyl dithio­carbonato-κ2 S,S′)bis­(pyridine-κN)manganese(II)

    PubMed Central

    Alam, Naveed; Ehsan, Muhammad Ali; Zeller, Matthias; Mazhar, Muhammad; Arifin, Zainudin

    2011-01-01

    The structure of the title manganese complex, [Mn(C5H9OS2)2(C5H5N)2] or [Mn(S2CO-n-Bu)2(C5H5N)2], consists of discrete monomeric entities with Mn2+ ions located on centres of inversion. The metal atom is coordinated by a six-coordinate trans-N2S4 donor set with the pyridyl N atoms located in the apical positions. The observed slight deviations from octa­hedral geometry are caused by the bite angle of the bidentate κ2-S2CO-n-Bu ligands [69.48 (1)°]. The O(CH2)3(CH3) chains of the O-n-butyl dithio­carbonate units are disordered over two sets of sites with an occupancy ratio of 0.589 (2):0.411 (2). PMID:22090847

  18. Alterations in airway microbiota in patients with PaO2/FiO2 ratio ≤ 300 after burn and inhalation injury

    PubMed Central

    McCullough, Shaun D.; Yourstone, Scott; Jones, Samuel W.; Cairns, Bruce A.; Jones, Corbin D.; Jaspers, Ilona; Diaz-Sanchez, David

    2017-01-01

    Background Injury to the airways after smoke inhalation is a major mortality risk factor in victims of burn injuries, resulting in a 15–45% increase in patient deaths. Damage to the airways by smoke may induce acute respiratory distress syndrome (ARDS), which is partly characterized by hypoxemia in the airways. While ARDS has been associated with bacterial infection, the impact of hypoxemia on airway microbiota is unknown. Our objective was to identify differences in microbiota within the airways of burn patients who develop hypoxemia early after inhalation injury and those that do not using next-generation sequencing of bacterial 16S rRNA genes. Results DNA was extracted from therapeutic bronchial washings of 48 patients performed within 72 hours of hospitalization for burn and inhalation injury at the North Carolina Jaycee Burn Center. DNA was prepared for sequencing using a novel molecule tagging method and sequenced on the Illumina MiSeq platform. Bacterial species were identified using the MTToolbox pipeline. Patients with hypoxemia, as indicated by a PaO2/FiO2 ratio ≤ 300, had a 30% increase in abundance of Streptococcaceae and Enterobacteriaceae and 84% increase in Staphylococcaceae as compared to patients with a PaO2/FiO2 ratio > 300. Wilcoxon rank-sum test identified significant enrichment in abundance of OTUs identified as Prevotella melaninogenica (p = 0.042), Corynebacterium (p = 0.037) and Mogibacterium (p = 0.048). Linear discriminant effect size analysis (LefSe) confirmed significant enrichment of Prevotella melaninognica among patients with a PaO2/FiO2 ratio ≤ 300 (p<0.05). These results could not be explained by differences in antibiotic treatment. Conclusions The airway microbiota following burn and inhalation injury is altered in patients with a PaO2/FiO2 ratio ≤ 300 early after injury. Enrichment of specific taxa in patients with a PaO2/FiO2 ratio ≤ 300 may indicate airway environment and patient changes that favor these microbes

  19. Daytime O/N2 Retrieval Algorithm for the Ionospheric Connection Explorer (ICON)

    NASA Astrophysics Data System (ADS)

    Stephan, Andrew W.; Meier, R. R.; England, Scott L.; Mende, Stephen B.; Frey, Harald U.; Immel, Thomas J.

    2018-02-01

    The NASA Ionospheric Connection Explorer Far-Ultraviolet spectrometer, ICON FUV, will measure altitude profiles of the daytime far-ultraviolet (FUV) OI 135.6 nm and N2 Lyman-Birge-Hopfield (LBH) band emissions that are used to determine thermospheric density profiles and state parameters related to thermospheric composition; specifically the thermospheric column O/N2 ratio (symbolized as ΣO/N2). This paper describes the algorithm concept that has been adapted and updated from one previously applied with success to limb data from the Global Ultraviolet Imager (GUVI) on the NASA Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) mission. We also describe the requirements that are imposed on the ICON FUV to measure ΣO/N2 over any 500-km sample in daytime with a precision of better than 8.7%. We present results from orbit-simulation testing that demonstrates that the ICON FUV and our thermospheric composition retrieval algorithm can meet these requirements and provide the measurements necessary to address ICON science objectives.

  20. Hydrogen production by tailoring the brookite and Cu2O ratio of sol-gel Cu-TiO2 photocatalysts.

    PubMed

    Hinojosa-Reyes, Mariana; Camposeco-Solís, Roberto; Zanella, Rodolfo; Rodríguez González, Vicente

    2017-10-01

    Cu-TiO 2 photocatalysts were prepared by the sol-gel method. Copper loadings from, 1.0 to 5.0 wt % were used. The materials were annealed at different temperatures (from 400 to 600 °C) to study the formation of brookite and copper ionic species. The photocatalysts were characterized by X-ray diffraction, UV-vis, Raman and XPS spectroscopies, H 2 -temperature programmed reduction (TPR), N 2 physisorption, and SEM-EDS to quantify the actual copper loadings and characterize morphology. The photocatalysts were evaluated during the hydrogen photocatalytic production using an ethanolic solution (50% v/v) under UV and visible radiation. The best hydrogen production was performed by Ti-Cu 1.0 with an overall hydrogen production that was five times higher than that obtained with photolysis. This sample had an optimal thermal treatment at 500 °C, and at this temperature, the Cu 2 O and brookite/anatase ratio boosted the photocatalytic production of hydrogen. In addition, a deactivation test was carried out for the most active sample (TiO 2 -Cu 1.0), showing unchanged H 2 production for three cycles with negligible Cu lixiviation. The activity of hydrogen-through-copper production reported in this research work is comparable with the one featured by noble metals and that reported in the literature for doped TiO 2 materials. Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. In situ stratospheric measurements of CH4, (C-13)H4, N2O, and OC(O-18) using the BLISS tunable diode laser spectrometer

    NASA Technical Reports Server (NTRS)

    Webster, Christopher R.; May, Randy D.

    1992-01-01

    Simultaneous in situ measurements of stratospheric CH4, (C-13)H4, N2O, OC(O-18), pressure, and temperature have been made from Palestine, Texas (32 deg N) in September 1988 with the JPL Balloon-borne Laser In Situ Sensor. Measurements of CH4 and N2O in the altitude range 30-35 km agree well with other measurements, except for an anomalously high value for the N2O at 31 km. Measurements of CH4 support earlier observations of fold in the vertical profile. A ratio for stratospheric (C-13)H4/CH4 of 0.0105 +/- 0.0010 implies an enrichment of delta(C-13) = -45 +/- 92 parts per thousand over the PDB value, in agreement with previous measurements in the troposphere. A large mixing ratio of 1.9 +/- 0.2 ppmv for OC(O-18) is measured, corresponding to an enrichment of delta(O-18) = 280 +/- 50 parts per thousand for the (O-18) isotopic species over the SMOW value.

  2. Partitioning Residue-derived and Residue-induced Emissions of N2O Using 15N-labelled Crop Residues

    NASA Astrophysics Data System (ADS)

    Farrell, R. E.; Carverhill, J.; Lemke, R.; Knight, J. D.

    2014-12-01

    Estimates of N2O emissions in Canada indicate that 17% of all agriculture-based emissions are associated with the decomposition of crop residues. However, research specific to the western Canadian prairies (including Saskatchewan) has shown that the N2O emission factor for N sources in this region typically ranges between 0.2 and 0.6%, which is well below the current IPCC default emission factor of 1.0%. Thus, it stands to reason that emissions from crop residues should also be lower than those calculated using the current IPCC emission factor. Current data indicates that residue decomposition, N mineralization and N2O production are affected by a number of factors such as C:N ratio and chemical composition of the residue, soil type, and soil water content; thus, a bench-scale incubation study was conducted to examine the effects of soil type and water content on N2O emissions associated with the decomposition of different crop residues. The study was carried out using soils from the Black, Dark Brown, Brown, and Gray soil zones and was conducted at both 50% and 70% water-filled pore space (WFPS); the soils were amended with 15N-labeled residues of wheat, pea, canola, and flax, or with an equivalent amount of 15N-labeled urea; 15N2O production was monitored using a Picarro G5101-i isotopic N2O analyzer. Crop residue additions to the soils resulted in both direct and indirect emissions of N2O, with residue derived emissions (RDE; measured as 15N2O) generally exceeding residue-induced emissions (RIE) at 50% WFPS—with RDEs ranging from 42% to 88% (mean = 58%) of the total N2O. Conversely, at 70% WFPS, RDEs were generally lower than RIEs—ranging from 21% to 83% (mean = 48%). Whereas both water content and soil type had an impact on N2O production, there was a clear and consistent trend in the emission factors for the residues; i.e., emissions were always greatest for the canola residue and lowest for the wheat residue and urea fertilizer; and intermediate for pea

  3. Enhancement of photocatalytic activity of combustion-synthesized CeO2/C3N4 nanoparticles

    NASA Astrophysics Data System (ADS)

    Li, Dong-Feng; Yang, Ke; Wang, Xiao-qin; Ma, Ya-Li; Huang, Gui-Fang; Huang, Wei-Qing

    2015-09-01

    Nanocrystalline CeO2/C3N4 was synthesized via a one-step solution combustion method using urea as fuel for the first time. The effects of the molar ratio of urea to cerium chloride on the photocatalytic activity of the synthesized samples were investigated. The synthesized nanocrystalline CeO2/C3N4 shows small size and large surface exposure area. Photocatalytic degradation of methylene blue demonstrates that the synthesized nanocrystalline CeO2/C3N4 possesses enhanced photocatalytic activity. It is proposed that the enhanced photocatalytic activity might be related to the favorable morphology and structure, and the effective charge separation between C3N4 and CeO2 in the photocatalytic process.

  4. (Carbonato-κ(2)O,O')bis-(5,5'-dimethyl-2,2'-bipyridyl-κ(2)N,N')cobalt(III) bromide trihydrate.

    PubMed

    Arun Kumar, Kannan; Meera, Parthsarathi; Amutha Selvi, Madhavan; Dayalan, Arunachalam

    2012-04-01

    In the title complex, [Co(CO(3))(C(12)H(12)N(2))(2)]Br·3H(2)O, the Co(III) cation has a distorted octa-hedral coordination environment. It is chelated by four N atoms of two different 5,5'-dimethyl-2,2'-bipyridyl (dmbpy) ligands in axial and equatorial positions, and by two O atoms of a carbonate anion completing the equatorial positions. Although the water mol-ecules are disordered and their H atoms were not located, there are typical O⋯O distances between 2.8 and 3.0 Å, indicating O-H⋯O hydrogen bonding. The crystal packing is consolidated by C-H⋯O and C-H⋯Br hydrogen bonds, as well as π-π stacking inter-actions between adjacent pyridine rings of the dmbpy ligands, with centroid-centroid distances of 3.694 (3) and 3.7053 (3) Å.

  5. Uncertainties in United States agricultural N2O emissions: comparing forward model simulations to atmospheric N2O data.

    NASA Astrophysics Data System (ADS)

    Nevison, C. D.; Saikawa, E.; Dlugokencky, E. J.; Andrews, A. E.; Sweeney, C.

    2014-12-01

    Atmospheric N2O concentrations have increased from 275 ppb in the preindustrial to about 325 ppb in recent years, a ~20% increase with important implications for both anthropogenic greenhouse forcing and stratospheric ozone recovery. This increase has been driven largely by synthetic fertilizer production and other perturbations to the global nitrogen cycle associated with human agriculture. Several recent regional atmospheric inversion studies have quantified North American agricultural N2O emissions using top-down constraints based on atmospheric N2O data from the National Oceanic and Atmospheric Administration (NOAA) Global Greenhouse Gas Reference Network, including surface, aircraft and tall tower platforms. These studies have concluded that global N2O inventories such as EDGAR may be underestimating the true U.S. anthropogenic N2O source by a factor of 3 or more. However, simple back-of-the-envelope calculations show that emissions of this magnitude are difficult to reconcile with the basic constraints of the global N2O budget. Here, we explore some possible reasons why regional atmospheric inversions might overestimate the U.S. agricultural N2O source. First, the seasonality of N2O agricultural sources is not well known, but can have an important influence on inversion results, particularly when the inversions are based on data that are concentrated in the spring/summer growing season. Second, boundary conditions can strongly influence regional inversions but the boundary conditions used may not adequately account for remote influences on surface data such as the seasonal stratospheric influx of N2O-depleted air. We will present a set of forward model simulations, using the Community Land Model (CLM) and two atmospheric chemistry tracer transport models, MOZART and the Whole Atmosphere Community Climate Model (WACCM), that examine the influence of terrestrial emissions and atmospheric chemistry and dynamics on atmospheric variability in N2O at U.S. and

  6. N2O emissions from a nitrogen-enriched river

    USGS Publications Warehouse

    McMahon, P.B.; Dennehy, K.F.

    1999-01-01

    Nitrous oxide (N2O) emissions from the South Platte River in Colorado were measured using closed chambers in the fall, winter, and summer of 1994- 1995. The South Platte River was enriched in inorganic N (9-800 ??M) derived from municipal wastewater effluent and groundwater return flows from irrigated agricultural fields. River water was as much as 2500% supersaturated with N2O, and median N2O emission rates from the river surface ranged from less than 90 to 32 600 ??g-N m-2 d-1. Seventy-nine percent of the variance in N2O emission rates was explained by concentrations of total inorganic N in river water and by water temperature. The estimated total annual N2O emissions from the South Platte River were 2 x 1013-6 x 1013 ??g-N yr-1. This amount of annual N2O emissions was similar to the estimated annual N2O emissions from all primary municipal wastewater treatment processes in the United States (1). Results from this study indicate that N-enriched rivers could be important anthropogenic sources of N2O to the atmosphere. However, N2O emission measurements from other N-enriched rivers are needed to better quantify this source.Nitrous oxide (N2O) emissions from the South Platte River in Colorado were measured using closed chambers in the fall, winter, and summer of 1994-1995. The South Platte River was enriched in inorganic N (9-800 ??M) derived from municipal wastewater effluent and groundwater return flows from irrigated agricultural fields. River water was as much as 2500% supersaturated with N2O, and median N2O emission rates from the river surface ranged from less than 90 to 32 600 ??g-N m-2 d-1. Seventy-nine percent of the variance in N2O emission rates was explained by concentrations of total inorganic N in river water and by water temperature. The estimated total annual N2O emissions from the South Platte River were 2??1013-6??1013 ??g-N yr-1. This amount of annual N2O emissions was similar to the estimated annual N2O emissions from all primary municipal

  7. Observations of a stratospheric depletion and annual mean interhemispheric gradient in the atmospheric Ar/N2 ratio from the HIPPO Global campaign

    NASA Astrophysics Data System (ADS)

    Bent, J. D.; Keeling, R. F.; Stephens, B. B.; Wofsy, S. C.; Daube, B. C.; Kort, E. A.; Pittman, J. V.; Jimenez-Pizarro, R.; Santoni, G.

    2014-12-01

    The atmospheric Ar/N2 ratio varies on a seasonal basis due to temperature-dependent solubility changes in the surface ocean. Low signal:noise ratios, limited vertical coverage, and sampler-sampler offsets have historically hampered characterization of vertical and inter-hemispheric gradients. We present data from the HIPPO Global campaign (2009-11) showing that Ar/N2 and interannually-detrended N2O correlate well in the lower stratosphere, suggesting that, as stratospheric air ages and loses N2O to photolysis and photo-oxidation, it also gradually loses argon to gravity as the heavier atom preferentially "rains out" of the air parcel. The HIPPO Ar/N2 data from the lower troposphere also resolve seasonal cycles in each hemisphere, as well as a gradient in the annual mean between hemispheres, with higher values in the southern hemisphere. The HIPPO cycles and inter-hemispheric gradient are in good agreement with data from surface stations.

  8. A reevaluation of spectral ratios for lunar mare TiO2 mapping

    NASA Technical Reports Server (NTRS)

    Johnson, Jeffrey R.; Larson, Stephen M.; Singer, Robert B.

    1991-01-01

    The empirical relation established by Charette et al. (1974) between the 400/560-nm spectral ratio of mature mare soils and weight percent TiO2 has been used extensively to map titanium content in the lunar maria. Relative reflectance spectra of mare regions show that a reference wavelength further into the near-IR, e.g., above 700 nm, could be used in place of the 560-nm band to provide greater contrast (a greater range of ratio values) and hence a more sensitive indicator of titanium content. An analysis of 400/730-nm ratio values derived from both laboratory and telescopic relative reflectance spectra suggests that this ratio provides greater sensitivity to TiO2 content than the 400/560-nm ratio. The increased range of ratio values is manifested in higher contrast 400/730-nm ratio images compared to 400/560-nm ratio images. This potential improvement in sensivity encourages a reevaluation of the original Charette et al. (1974) relation using the 400/730-nm ratio.

  9. The effect of CaO/SiO2 molar ratio of CaO-Al2O3-SiO2 glasses on their structure and reactivity in alkali activated system

    NASA Astrophysics Data System (ADS)

    Kucharczyk, Sylwia; Sitarz, Maciej; Zajac, Maciej; Deja, Jan

    2018-04-01

    The influence of CaO/SiO2 molar ratio of calcium aluminosilicate glasses on resulting structure and reactivity was investigated. Chemical compositions of glasses were chosen to mimic the composition of the fly ash and slag amorphous phase. Understanding the reactivity of these materials is of high importance allowing further development of the composite cements to limit the environmental footprint of cement industry. Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy were employed to examine the structure of glasses. Reactivity of the glasses was analyzed on paste samples after 1, 2, 7, 28 and 90 days of curing by means of thermogravimetry (TGA), X-ray diffraction (XRD) and FTIR. Spectroscopic results emphasize dependence of the structure on the chemical composition of the glasses. The higher CaO/SiO2 the more depolymerized the glass network is, though there is no direct correlation with the reactivity. Significant differences in reactivity is observed primarily between the glasses of peraluminous (CaO/Al2O3 < 1) and percalcic region (CaO/Al2O3 > 1). Amongst the pastes made of glasses of percalcic region a higher degree of reaction at later ages is observed for the paste containing glass of lower CaO/SiO2 molar ratio. This is due to both degree of depolimerization and the nature of these glasses (pozzolanic and hydraulic materials). No difference of degree of reaction has been observed within the glasses of CaO/SiO2 lower than 1.

  10. The effect of CaO/SiO2 molar ratio of CaO-Al2O3-SiO2 glasses on their structure and reactivity in alkali activated system.

    PubMed

    Kucharczyk, Sylwia; Sitarz, Maciej; Zajac, Maciej; Deja, Jan

    2018-04-05

    The influence of CaO/SiO 2 molar ratio of calcium aluminosilicate glasses on resulting structure and reactivity was investigated. Chemical compositions of glasses were chosen to mimic the composition of the fly ash and slag amorphous phase. Understanding the reactivity of these materials is of high importance allowing further development of the composite cements to limit the environmental footprint of cement industry. Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy were employed to examine the structure of glasses. Reactivity of the glasses was analyzed on paste samples after 1, 2, 7, 28 and 90days of curing by means of thermogravimetry (TGA), X-ray diffraction (XRD) and FTIR. Spectroscopic results emphasize dependence of the structure on the chemical composition of the glasses. The higher CaO/SiO 2 the more depolymerized the glass network is, though there is no direct correlation with the reactivity. Significant differences in reactivity is observed primarily between the glasses of peraluminous (CaO/Al 2 O 3 <1) and percalcic region (CaO/Al 2 O 3 >1). Amongst the pastes made of glasses of percalcic region a higher degree of reaction at later ages is observed for the paste containing glass of lower CaO/SiO 2 molar ratio. This is due to both degree of depolimerization and the nature of these glasses (pozzolanic and hydraulic materials). No difference of degree of reaction has been observed within the glasses of CaO/SiO 2 lower than 1. Copyright © 2018 Elsevier B.V. All rights reserved.

  11. Isotopic analysis of N and O in nitrite and nitrate by sequential selective bacterial reduction to N2O

    USGS Publications Warehouse

    Böhlke, J.K.; Smith, R.L.; Hannon, J.E.

    2007-01-01

    Nitrite is an important intermediate species in the biogeochemical cycling of nitrogen, but its role in natural aquatic systems is poorly understood. Isotopic data can be used to study the sources and transformations of NO2- in the environment, but methods for independent isotopic analyses of NO2- in the presence of other N species are still new and evolving. This study demonstrates that isotopic analyses of N and O in NO2- can be done by treating whole freshwater or saltwater samples with the denitrifying bacterium Stenotrophomonas nitritireducens, which selectively reduces NO2- to N2O for isotope ratio mass spectrometry. When calibrated with solutions containing NO2- with known isotopic compositions determined independently, reproducible δ15N and δ18O values were obtained at both natural-abundance levels (±0.2−0.5‰ for δ15N and ±0.4−1.0‰ for δ18O) and moderately enriched 15N tracer levels (±20−50‰ for δ15N near 5000‰) for 5−20 nmol of NO2- (1−20 μmol/L in 1−5 mL aliquots). This method is highly selective for NO2-and was used for mixed samples containing both NO2- and NO3- with little or no measurable cross-contamination. In addition, mixed samples that were analyzed with S. nitritireducens were treated subsequently with Pseudomonas aureofaciens to reduce the NO3- in the absence of NO2-, providing isotopic analyses of NO2- and NO3- separately in the same aliquot. Sequential bacterial reduction methods like this one should be useful for a variety of isotopic studies aimed at understanding nitrogen cycling in aquatic environments. A test of these methods in an agricultural watershed in Indiana provides isotopic evidence for both nitrification and denitrification as sources of NO2- in a small stream.

  12. Nitrogen removal and nitrous oxide emission in surface flow constructed wetlands for treating sewage treatment plant effluent: Effect of C/N ratios.

    PubMed

    Li, Ming; Wu, Haiming; Zhang, Jian; Ngo, Huu Hao; Guo, Wenshan; Kong, Qiang

    2017-09-01

    In order to design treatment wetlands with maximal nitrogen removal and minimal nitrous oxide (N 2 O) emission, the effect of influent C/N ratios on nitrogen removal and N 2 O emission in surface flow constructed wetlands (SF CWs) for sewage treatment plant effluent treatment was investigated in this study. The results showed that nitrogen removal and N 2 O emission in CWs were significantly affected by C/N ratio of influent. Much higher removal efficiency of NH 4 + -N (98%) and TN (90%) was obtained simultaneously in SF CWs at C/N ratios of 12:1, and low N 2 O emission (8.2mg/m 2 /d) and the percentage of N 2 O-N emission in TN removal (1.44%) were also observed. These results obtained in this study would be utilized to determine how N 2 O fluxes respond to variations in C/N ratios and to improve the sustainability of CWs for wastewater treatment. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. Molecular approaches to understand the regulation of N2O emission from denitrifying bacteria - model strains and soil communities (Invited)

    NASA Astrophysics Data System (ADS)

    Frostegard, A.; Bakken, L. R.

    2010-12-01

    Emissions of N2O from agricultural soils are largely caused by denitrifying bacteria. Field measurements of N2O fluxes show large variations and depend on several environmental factors, and possibly also on the composition of the denitrifying microbial community. The temporal and spatial variation of fluxes are not adequately captured by biogeochemical models, and few options for mitigations have been invented, which underscores the need to understand the mechanisms underlying the emissions of N2O. Analyses of denitrification genes and transcripts extracted from soils are important for describing the system, but may have limited value for prediction of N2O emissions. In contrast, phenotypic analyses are direct measures of the organisms’ responses to changing environmental conditions. Our approach is to combine phenotypic characterizations using high-resolution gas kinetics, with gene transcription analyses to study denitrification regulatory phenotypes (DRP) of bacterial strains or complex microbial communities. The rich data sets obtained provide a basis for refinement of biochemical and physiological research on this key process in the nitrogen cycle. The strength of this combined approach is illustrated by a series of experiments investigating effects of soil pH on denitrification. Soil pH emerges as a master variable determining the microbial community composition as well as its denitrification product ratio (N2O/N2), with higher ratio in acid than in alkaline soil. It is therefore likely that emissions of N2O from agro-ecosystems will increase in large parts of the world where soil pH is decreasing due to intensified management and increased use of chemical fertilizers. Considering its immense implications, surprisingly few attempts have been made to unravel the mechanisms involved in the pH-control of the product stoichiometry of denitrification. We investigated the kinetics of gas transformations (O2, NO, N2O and N2) and transcription of functional genes

  14. Reaction of N2O5 with H2O on carbonaceous surfaces

    NASA Technical Reports Server (NTRS)

    Brouwer, L.; Rossi, M. J.; Golden, D. M.

    1986-01-01

    The heterogeneous reaction of N2O5 with commercially available ground charcoal in the absence of H2O revealed a physisorption process (gamma = 0.003), together with a redox reaction generating mostly NO. Slow HNO3 formation was the result of the interaction of N2O5 with H2O that was still adsorbed after prolonged pumping at 0.0001 torr. In the presence of H2O, the same processes with gamma = 0.005 are observed. The redox reaction dominates in the early stages of the reaction, whereas the hydrolysis gains importance later at the expense of the redox reaction. The rate law for HNO3 generation was found to be d(HNO3)/dt = k(bi)(H2O)(N2O5) with k(bi), the effective bimolecular rate constants, for 10 mg of carbon being (1.6 + or - 0.3) x 10 to the -13th cu cm/s.

  15. Tempe Waste Water Degradation Using TiO2-N/Bentonite alginate Granule Photocatalyst with Ultraviolet Light Irradiation

    NASA Astrophysics Data System (ADS)

    Khoirun Nisaa', Aldila; Wardhani, Sri; Purwonugroho, Danar; Darjito

    2018-01-01

    Tempe waste water stew has high ammonia concentration which causes odor due to polluting by anaerobic decay. Free ammonia in the waste has exceeded the limit, thus endangering the aquatic environment. This research aims to determine the activity of photocatalyst granule TiO2-N/bentonite-alginate as decomposers of compounds in the photodegradation process. Photodegradation is the decomposition process of compounds by semiconductors with light. Results expected includes the photocatalyst activity of TiO2-N/bentonite-alginate granule produced by ultraviolet rays is known based on the effect of dopant N concentration on the catalyst and the effect of photocatalytic ratio toward tempe waste water. Methods proposed in this research are activation of bentonite using H2SO4 0.8 M, TiO2-N synthesize by sonication method with urea as the source of N, then TiO2-N impregnation into bentonite. Photocatalyst in granule form synthesized with alginate was then dripped with syringe pump into 3% (w/v) CaCl2. The photocatalyst characterization will be performed using XRD. The optimum tempe waste water degradation at the concentration of TiO2-N 0.4 (g/g) bentonite is 53.66%. The ratio of photocatalyst and tempe waste water, optimum at 150 mg of photocatalyst with 25 mL of waste equal to 53.66%.

  16. Diffusion Monte Carlo studies of MB-pol (H2O)2-6 and (D2O)2-6 clusters: Structures and binding energies

    NASA Astrophysics Data System (ADS)

    Mallory, Joel D.; Mandelshtam, Vladimir A.

    2016-08-01

    We employ the diffusion Monte Carlo (DMC) method in conjunction with the recently developed, ab initio-based MB-pol potential energy surface to characterize the ground states of small (H2O)2-6 clusters and their deuterated isotopomers. Observables, other than the ground state energies, are computed using the descendant weighting approach. Among those are various spatial correlation functions and relative isomer fractions. Interestingly, the ground states of all clusters considered in this study, except for the dimer, are delocalized over at least two conformations that differ by the orientation of one or more water monomers with the relative isomer populations being sensitive to the isotope substitution. Most remarkably, the ground state of the (H2O)6 hexamer is represented by four distinct cage structures, while that of (D2O)6 is dominated by the prism, i.e., the global minimum geometry, with a very small contribution from a prism-book geometry. In addition, for (H2O)6 and (D2O)6, we performed DMC calculations to compute the ground states constrained to the cage and prism geometries. These calculations compared results for three different potentials, MB-pol, TTM3/F, and q-TIP4P/F.

  17. Isotopomeric characterization of nitrous oxide produced by reaction of enzymes extracted from nitrifying and denitrifying bacteria

    NASA Astrophysics Data System (ADS)

    Yamazaki, T.; Hozuki, T.; Arai, K.; Toyoda, S.; Koba, K.; Fujiwara, T.; Yoshida, N.

    2014-05-01

    Nitrous oxide (N2O) is a potent greenhouse gas and produced in denitrification and nitrification by various microorganisms. Site preference (SP) of 15N in N2O, which is defined as the difference in the natural abundance of isotopomers 14N15NO and 15N14NO relative to 14N14NO, has been reported to be a useful tool to quantitatively distinguish N2O production pathways. To determine representative SP values for each microbial process, we firstly measured SP of N2O produced in the enzyme reaction of hydroxylamine oxidoreductase (HAO) purified from two species of ammonia oxidizing bacteria (AOB), Nitrosomonas europaea and Nitrosococcus oceani, and that of nitric oxide reductase (NOR) from Paracoccus denitrificans. The SP value for NOR reaction (-5.9 ± 2.1‰) showed nearly the same value as that reported for N2O produced by P. denitrificans in pure culture. In contrast, SP value for HAO reaction (36.3 ± 2.3‰) was a little higher than the values reported for N2O produced by AOB in aerobic pure culture. Using the SP values obtained by HAO and NOR reactions, we calculated relative contribution of the nitrite (NO2-) reduction (which is followed by NO reduction) to N2O production by N. oceani incubated under different O2 availability. Our calculations revealed that previous in vivo studies might have underestimated the SP value for the NH2OH oxidation pathway possibly due to a small contribution of NO2- reduction pathway. Further evaluation of isotopomer signatures of N2O using common enzymes of other processes related to N2O would improve the isotopomer analysis of N2O in various environments.

  18. Isotopomeric characterization of nitrous oxide produced by reaction of enzymes extracted from nitrifying and denitrifying bacteria

    NASA Astrophysics Data System (ADS)

    Yamazaki, T.; Hozuki, T.; Arai, K.; Toyoda, S.; Koba, K.; Fujiwara, T.; Yoshida, N.

    2013-10-01

    Nitrous oxide (N2O) is a potent greenhouse gas and produced in denitrification and nitrification in environmental nitrogen cycle by various microorganism. Site preference (SP) of 15N in N2O, which is defined as the difference in the natural abundance of isotopomers 14N15NO and 15N14NO relative to 14N14NO, has been reported to be a useful tool to quantitatively distinguish N2O production pathway. To determine representative SP value for each microbial process, we firstly measured SP of N2O produced in the enzyme reaction of hydroxylamine oxidoreductase (HAO) purified from two species of ammonia oxidizing bacteria (AOB), Nitrosomonas europaea and Nitrosococcus oceani, and that of nitric oxide reductase (NOR) from Paracoccus denitrificans, respectively. The SP value for NOR reaction (-5.9 ± 2.1‰) showed nearly the same value as that reported for N2O produced by P. denitrificans in pure culture. In contrast, SP value for HAO reaction (36.3 ± 2.3‰) was a little higher than the values reported for N2O produced by AOB in aerobic pure culture. Using the SP values obtained by HAO and NOR reactions, we calculated relative contribution of the nitrite (NO2-) reduction (which is followed by NO reduction) to N2O production by N. oceani incubated under different O2 availability. Our calculations revealed that previous in vivo studies might have underestimated the SP value for NH2OH oxidation pathway possibly due to a small contribution of NO2- reduction pathway. Further evaluation of isotopomer signatures of N2O using common enzymes of other processes related to N2O would improve the isotopomer analysis of N2O in various environments.

  19. The Infrared Spectrum of Isotopomers of the TeH Radical, Observed by CO Laser Magnetic Resonance

    NASA Astrophysics Data System (ADS)

    Gillett, D. A.; Towle, J. P.; Islam, M.; Brown, J. M.

    1994-02-01

    The infrared spectrum of the TeH radical in its X2Π state has been recorded using an intracavity CO laser magnetic resonance (LMR) spectrometer. Seven of the eight naturally occurring Te isotopomers were observed, with resonances originating from the first three vibrational levels; many were recorded as Lamb-dips. These observations have been combined with existing data for TeH and TeD in the X2Π state and used to determine the parameters of an N 2 Hamiltonian, including isotopic scaling and nonadiabatic corrections. The data are well described by the parameters. The different isotopic dependences of the effects of the parameters A D and γ has allowed their separation and the extent to which TeH shows Hund's case (c) coupling is discussed. Trends displayed by the chalcogen monohydrides are considered.

  20. Far infrared VRT spectroscopy of two water trimer isotopomers vibrationally averaged structures and rearrangement dynamics

    NASA Astrophysics Data System (ADS)

    Liu, K.; Brown, M. G.; Viant, M. R.; Cruzan, J. D.; Saykally, R. J.

    We report the measurement of far infrared vibration rotation tunnelling parallel bands of two partially deuterated water trimer isotopomers D O DOH and H O DOH at 97 2607 cm and 86 cm respectively The hydrogen bond rearrangement dynamics of the two mixed trimers can be described by the simplified molecular symmetry G which accounts for both the flipping and bifurcation tunnelling motions previously established for H O and D O The observed donor tunnelling quartet rather than triplet splitting indicates that the two homogeneous monomers D O or H O in each mixed trimer experience slightly different environments Vibrationally averaged structures of H O D O and D O DOH were examined in a Monte Carlo simulation of the out of plane flipping motions of the free atoms The simulation addresses both the symmetric top behaviour and the negative zero point inertial defect for H O and D O which were insufficiently counted in all previous structure models The average ground state O O separations which are correlated to other angular coordinates were determined to be 2 84 0 01 A for all three species The simulated difference in hydrogen bond nonlinearity also supports the inequivalency of the two homogeneous mono mers The structural simulation shows that the unique H in D O DOH is free while a torsional analysis suggests the unique D in H O DOH is bound within the cyclic ring Both bands can be assigned to the pseudorotational transitions which correlate to those found in the pure trimers

  1. N2O fluxes at the soil-atmosphere interface in various ecosystems and the global N2O budget

    NASA Technical Reports Server (NTRS)

    Banin, Amos

    1987-01-01

    The overall purpose of this research task is to study the effects of soil properties and ecosystem variables on N2O exchanges at the soil-atmosphere interface, and to assess their effects on the globle N2O budget. Experimental procedures are implemented in various sites to measure the source/sink relations of N2O at the soil-atmosphere interface over prolonged periods of time as part of the research of biogeochemical cycling in terrestrial ecosystems. A data-base for establishing quantitative correlations between N2O fluxes and soil and environmental parameters that are of potential use for remote sensing, is being developed.

  2. Formation of hydroxyl radicals and kinetic study of 2-chlorophenol photocatalytic oxidation using C-doped TiO2, N-doped TiO2, and C,N Co-doped TiO2 under visible light.

    PubMed

    Ananpattarachai, Jirapat; Seraphin, Supapan; Kajitvichyanukul, Puangrat

    2016-02-01

    This work reports on synthesis, characterization, adsorption ability, formation rate of hydroxyl radicals (OH(•)), photocatalytic oxidation kinetics, and mineralization ability of C-doped titanium dioxide (TiO2), N-doped TiO2, and C,N co-doped TiO2 prepared by the sol-gel method. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and UV-visible spectroscopy were used to analyze the titania. The rate of formation of OH(•) for each type of titania was determined, and the OH-index was calculated. The kinetics of as-synthesized TiO2 catalysts in photocatalytic oxidation of 2-chlorophenol (2-CP) under visible light irradiation were evaluated. Results revealed that nitrogen was incorporated into the lattice of titania with the structure of O-Ti-N linkages in N-doped TiO2 and C,N co-doped TiO2. Carbon was joined to the Ti-O-C bond in the C-doped TiO2 and C,N co-doped TiO2. The 2-CP adsorption ability of C,N co-doped TiO2 and C-doped TiO2 originated from a layer composed of a complex carbonaceous mixture at the surface of TiO2. C,N co-doped TiO2 had highest formation rate of OH(•) and photocatalytic activity due to a synergistic effect of carbon and nitrogen co-doping. The order of photocatalytic activity per unit surface area was the same as that of the formation rate of OH(•) unit surface area in the following order: C,N co-doped TiO2 > C-doped TiO2 > N-doped TiO2 > undoped TiO2.

  3. Interfacial RhO{sub x}/CeO{sub 2} sites as locations for low temperature N{sub 2}O dissociation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Cunningham, J.; Hickey, J.N.; Soria, J.

    Temperatures required for extensive N{sub 2}O dissociation to N{sub 2}, or to N{sub 2} plus O{sub 2}, over 0.5% RhO{sub x}/CeO{sub 2} materials, and over polycrystalline Rh{sub 2}O{sub 3} or CeO{sub 2}, are compared for preoxidised and for prereduced samples on the basis of conversions achieved in pulsed-reactant, continuous-flow and recirculatory microcatalytic reactors. Influences of sample prereduction or preoxidation upon those measurements and upon results from parallel ESR and FTIR studies of N{sub 2}O interactions with such materials are presented and compared. Over partially reduced 0.5% RhO{sub x}/CeO{sub 2} materials complete dissociation of N{sub 2}O pulses to N{sub 2} plusmore » O{sub 2} is obtained at temperatures 50-100{degrees} lower than those required for extensive dissociation over prereduced Rh{sub 2}O{sub 3}. Furthermore, N{sub 2} was the sole product from the latter. Higher ongoing N{sub 2}O conversions to N{sub 2} plus O{sub 2} at 623 K over 0.5% Rh/CeO{sub 2} in pulsed-reactant than in continuous-flow mode point to regeneration of active sites under helium flushing between pulses. The TPD profile for dioxygen release from Rhodia containing samples at temperatures 350-550 K is presented. ESR measurements reveal complementary effects of outgassings at temperatures, T{sub v}, {ge} 573 K upon the availability at RhO{sub x}/CeO{sub 2} surfaces of electron-excess sites reactive towards N{sub 2}O. Differences from observations over Rh{sub 2}O{sub 3} and CeO{sub 2} can be understood by attributing the low-temperature activity of RhO{sub x}/CeO{sub 2} to electron excess sites at microinterfaces between the dispersed Rhodia component and the Ceria support.« less

  4. Formation mechanisms of Si3N4 and Si2N2O in silicon powder nitridation

    NASA Astrophysics Data System (ADS)

    Yao, Guisheng; Li, Yong; Jiang, Peng; Jin, Xiuming; Long, Menglong; Qin, Haixia; Kumar, R. Vasant

    2017-04-01

    Commercial silicon powders are nitrided at constant temperatures (1453 K; 1513 K; 1633 K; 1693 K). The X-ray diffraction results show that small amounts of Si3N4 and Si2N2O are formed as the nitridation products in the samples. Fibroid and short columnar Si3N4 are detected in the samples. The formation mechanisms of Si3N4 and Si2N2O are analyzed. During the initial stage of silicon powder nitridation, Si on the outside of sample captures slight amount of O2 in N2 atmosphere, forming a thin film of SiO2 on the surface which seals the residual silicon inside. And the oxygen partial pressure between the SiO2 film and free silicon is decreasing gradually, so passive oxidation transforms to active oxidation and metastable SiO(g) is produced. When the SiO(g) partial pressure is high enough, the SiO2 film will crack, and N2 is infiltrated into the central section of the sample through cracks, generating Si2N2O and short columnar Si3N4 in situ. At the same time, metastable SiO(g) reacts with N2 and form fibroid Si3N4. In the regions where the oxygen partial pressure is high, Si3N4 is oxidized into Si2N2O.

  5. Biochar and denitrification in soils: when, how much and why does biochar reduce N2O emissions?

    PubMed Central

    Cayuela, Maria Luz; Sánchez-Monedero, Miguel Angel; Roig, Asunción; Hanley, Kelly; Enders, Akio; Lehmann, Johannes

    2013-01-01

    Agricultural soils represent the main source of anthropogenic N2O emissions. Recently, interactions of black carbon with the nitrogen cycle have been recognized and the use of biochar is being investigated as a means to reduce N2O emissions. However, the mechanisms of reduction remain unclear. Here we demonstrate the significant impact of biochar on denitrification, with a consistent decrease in N2O emissions by 10–90% in 14 different agricultural soils. Using the 15N gas-flux method we observed a consistent reduction of the N2O/(N2 + N2O) ratio, which demonstrates that biochar facilitates the last step of denitrification. Biochar acid buffer capacity was identified as an important aspect for mitigation that was not primarily caused by a pH shift in soil. We propose the function of biochar as an “electron shuttle” that facilitates the transfer of electrons to soil denitrifying microorganisms, which together with its liming effect would promote the reduction of N2O to N2. PMID:23615819

  6. The Influence of Layer Thickness-Ratio on Magnetoresistance in La2/3Ca1/3MnO3/La1/3Ca2/3MnO3 Exchange Biased System

    NASA Astrophysics Data System (ADS)

    Gomez, Maria Elena; Milena Diez, Sandra; Cuartas, Lina Maria; Marin, Lorena; Prieto, Pedro

    2012-02-01

    Isothermal magnetic field dependence of the resistance in La2/3Ca1/3MnO3 (F-LCMO)/ La1/3Ca2/3MnO3(AF-LCMO) bilayer and AF-LCMO/F-LCMO/AF-LCMO trilayer at temperatures below N'eel temperature of the antiferromagnetic layer were carried out to study the thickness layers influence on magneto transport properties. We grew multilayers using a high oxygen pressure sputtering technique. We systematically varied the thickness of the F-LCMO layer, tF, maintaining constant the thickness of the AF-LCMO layer, tAF. We studied the influence of the thickness ratio tF/tAF on the ZFC and FC magnetoresistance (MR) loops. HFC was varied from 100 Oe to 400 Oe. We found that MR has hysteretic behavior as observed in [La2/3Ca1/3MnO3/La1/3Ca2/3MnO3]N superlattices, where MR increases with the increasing field from H=0 to a maximum and then it decreases continuously. The position and magnitude of the maximum is not symmetric with respect to the axis H=0 for both FC and ZFC loops. We found that magnetoresistance behavior of the bilayer and trilayer is thickness-ratio dependent for both ZFC and FC loops.

  7. Ab initio studies on Al(+)(H(2)O)(n), HAlOH(+)(H(2)O)(n-1), and the size-dependent H(2) elimination reaction.

    PubMed

    Siu, Chi-Kit; Liu, Zhi-Feng; Tse, John S

    2002-09-11

    We report computational studies on Al(+)(H(2)O)(n), and HAlOH(+)(H(2)O)(n-1), n = 6-14, by the density functional theory based ab initio molecular dynamics method, employing a planewave basis set with pseudopotentials, and also by conventional methods with Gaussian basis sets. The mechanism for the intracluster H(2) elimination reaction is explored. First, a new size-dependent insertion reaction for the transformation of Al(+)(H(2)O)(n), into HAlOH(+)(H(2)O)(n-1) is discovered for n > or = 8. This is because of the presence of a fairly stable six-water-ring structure in Al(+)(H(2)O)(n) with 12 members, including the Al(+). This structure promotes acidic dissociation and, for n > or = 8, leads to the insertion reaction. Gaussian based BPW91 and MP2 calculations with 6-31G* and 6-31G** basis sets confirmed the existence of such structures and located the transition structures for the insertion reaction. The calculated transition barrier is 10.0 kcal/mol for n = 9 and 7.1 kcal/mol for n = 8 at the MP2/6-31G** level, with zero-point energy corrections. Second, the experimentally observed size-dependent H(2) elimination reaction is related to the conformation of HAlOH(+)(H(2)O)(n-1), instead of Al(+)(H(2)O)(n). As n increases from 6 to 14, the structure of the HAlOH(+)(H(2)O)(n-1) cluster changes into a caged structure, with the Al-H bond buried inside, and protons produced in acidic dissociation could then travel through the H(2)O network to the vicinity of the Al-H bond and react with the hydride H to produce H(2). The structural transformation is completed at n = 13, coincident approximately with the onset of the H(2) elimination reaction. From constrained ab initio MD simulations, we estimated the free energy barrier for the H(2) elimination reaction to be 0.7 eV (16 kcal/mol) at n = 13, 1.5 eV (35 kcal/mol) at n = 12, and 4.5 eV (100 kcal/mol) at n = 8. The existence of transition structures for the H(2) elimination has also been verified by ab initio calculations

  8. Temperature Measurements in the Solar Transition Region Using N III Line Intensity Ratios

    NASA Technical Reports Server (NTRS)

    Doron, R.; Doschek, G. A.; Laming, J. M.; Feldman, U.; Bhatia, A. K.

    2003-01-01

    UV emission from B-like N and O ions a rather rare opportunity for recording spectral lines in a narrow wavelength range that can potentially be used to derive temperatures relevant to the solar transition region. In these ions, the line intensity ratios of the type (2s2p(sup 2) - 2p(sup 3)) / (2s(sup 2)2p - 2s2p(sup 2)) are very sensitive to the electron temperature. Additionally, the lines involving the ratios fall within a range of only - 12 A; in N III the lines fall in the 980 - 992 A range and in O IV in the 780 - 791 A range. In this work, we explore the use of these atomic systems, primarily in N III, for temperature diagnostics of the transition region by analyzing UV spectra obtained by the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer flown on the Solar and Heliospheric Observatory (SOHO). The N III temperature-sensitive line ratios are measured in more than 60 observations. Most of the measured ratios correspond to temperatures in the range 5.7x10(exp 4) - 6.7x10(exp 4) K. This range is considerably lower than the calculated temperature of maximum abundance of N III, which is approx. 7.6x10(exp 4) K. Detailed analysis of the spectra further indicates that the measured ratios are probably somewhat overestimated due to resonant scattering effects in the 2s(sup 2)2p - 2s2p(sup 2) lines and small blends in the 2s2p(sup 2) - 2p3 lines. Actual lower ratios would only increase the disagreement between the ionization balance calculations and present temperature measurements based on a collisional excitation model. In the case of the O IV spectra, we determined that due to the close proximity in wavelength of the weak line (2s2p(sup 2)-2p3 transitions) to a strong Ne VIII line, sufficiently accurate ratio measurements cannot be obtained. Subject headings: atomic data --- atomic processes --- Sun: transition region --- Sun: U V radiation --- techniques: spectroscopic

  9. Sonocatalytic degradation of humic acid by N-doped TiO2 nano-particle in aqueous solution.

    PubMed

    Kamani, Hossein; Nasseri, Simin; Khoobi, Mehdi; Nabizadeh Nodehi, Ramin; Mahvi, Amir Hossein

    2016-01-01

    Un-doped and N-doped TiO2 nano-particles with different nitrogen contents were successfully synthesized by a simple sol-gel method, and were characterized by X-ray diffraction, field emission scanning electron microscopy, Energy dispersive X-ray analysis and UV-visible diffuse reflectance spectra techniques. Then enhancement of sonocatalytic degradation of humic acid by un-doped and N-doped TiO2 nano-particles in aqueous environment was investigated. The effects of various parameters such as initial concentration of humic acid, N-doping, and the degradation kinetics were investigated. The results of characterization techniques affirmed that the synthesis of un-doped and N-doped TiO2 nano-particles was successful. Degradation of humic acid by using different nano-particles obeyed the first-order kinetic. Among various nano-particles, N-doped TiO2 with molar doping ratio of 6 % and band gap of 2.92 eV, exhibited the highest sonocatalytic degradation with an apparent-first-order rate constant of 1.56 × 10(-2) min(-1). The high degradation rate was associated with the lower band gap energy and well-formed anatase phase. The addition of nano-catalysts could enhance the degradation efficiency of humic acid as well as N-doped TiO2 with a molar ratio of 6 %N/Ti was found the best nano-catalyst among the investigated catalysts. The sonocatalytic degradation with nitrogen doped semiconductors could be a suitable oxidation process for removal of refractory pollutants such as humic acid from aqueous solution.

  10. Alkali injection system with controlled CO.sub.2 /O.sub.2 ratios for combustion of coal

    DOEpatents

    Berry, Gregory F.

    1988-01-01

    A high temperature combustion process for an organic fuel containing sulfur n which the nitrogen of air is replaced by carbon dioxide for combination with oxygen with the ratio of CO.sub.2 /O.sub.2 being controlled to generate combustion temperatures above 2000 K. for a gas-gas reaction with SO.sub.2 and an alkali metal compound to produce a sulfate and in which a portion of the carbon-dioxide rich gas is recycled for mixing with oxygen and/or for injection as a cooling gas upstream from heating exchangers to limit fouling of the exchangers, with the remaining carbon-dioxide rich gas being available as a source of CO.sub.2 for oil recovery and other purposes.

  11. NO(y) Correlation with N2O and CH4 in the Midlatitude Stratosphere

    NASA Technical Reports Server (NTRS)

    Kondo, Y.; Schmidt, U.; Sugita, T.; Engel, A.; Koike, M.; Aimedieu, P.; Gunson, M. R.; Rodriguez, J.

    1996-01-01

    Total reactive nitrogen (NO(y)), nitrous oxide (NO2), methane (CH4), and ozone (03) were measured on board a balloon launched from Aire sur l'Adour (44 deg N, 0 deg W), France on October 12, 1994. Generally, NO(y) was highly anti-correlated with N2O and CH4 at altitudes between 15 and 32 km. The linear NO(y) - N2O and NO(y) - CH4 relationships obtained by the present observations are very similar to those obtained on board ER-2 and DC-8 aircraft previously at altitude below 20 km in the northern hemisphere. They also agree well with the data obtained by the Atmospheric Trace Molecule Spectroscopy (ATMOS) instrument at 41 deg N in November 1994. Slight departures from linear correlations occurred around 29 km, where N2O and CH4 mixing ratios were larger than typical midlatitude values, suggesting horizontal transport of tropical airmasses to northern midlatitudes in a confined altitude region.

  12. Measurements and Modeling of Nitric Oxide Formation in Counterflow, Premixed CH4/O2/N2 Flames

    NASA Technical Reports Server (NTRS)

    Thomsen, D. Douglas; Laurendeau, Normand M.

    2000-01-01

    Laser-induced fluorescence (LIF) measurements of NO concentration in a variety of CH4/O2/N2 flames are used to evaluate the chemical kinetics of NO formation. The analysis begins with previous measurements in flat, laminar, premixed CH4/O2/N2 flames stabilized on a water-cooled McKenna burner at pressures ranging from 1 to 14.6 atm, equivalence ratios from 0.5 to 1.6, and volumetric nitrogen/oxygen dilution ratios of 2.2, 3.1 and 3.76. These measured results are compared to predictions to determine the capabilities and limitations of the comprehensive kinetic mechanism developed by the Gas Research Institute (GRI), version 2.11. The model is shown to predict well the qualitative trends of NO formation in lean-premixed flames, while quantitatively underpredicting NO concentration by 30-50%. For rich flames, the model is unable to even qualitatively match the experimental results. These flames were found to be limited by low temperatures and an inability to separate the flame from the burner surface. In response to these limitations, a counterflow burner was designed for use in opposed premixed flame studies. A new LIF calibration technique was developed and applied to obtain quantitative measurements of NO concentration in laminar, counterflow premixed, CH4/O2/N2 flames at pressures ranging from 1 to 5.1 atm, equivalence ratios of 0.6 to 1.5, and an N2/O2 dilution ratio of 3.76. The counterflow premixed flame measurements are combined with measurements in burner-stabilized premixed flames and counterflow diffusion flames to build a comprehensive database for analysis of the GRI kinetic mechanism. Pathways, quantitative reaction path and sensitivity analyses are applied to the GRI mechanism for these flame conditions. The prompt NO mechanism is found to severely underpredict the amount of NO formed in rich premixed and nitrogen-diluted diffusion flames. This underprediction is traced to uncertainties in the CH kinetics as well as in the nitrogen oxidation chemistry

  13. Photoeletrocatalytic activity of an n-ZnO/p-Cu2O/n-TNA ternary heterojunction electrode for tetracycline degradation.

    PubMed

    Li, Jinhua; Lv, Shubin; Liu, Yanbiao; Bai, Jing; Zhou, Baoxue; Hu, Xiaofang

    2013-11-15

    In this study, a novel ternary heterojunction n-ZnO/p-Cu2O/n-TiO2 nanotube arrays (n-ZnO/p-Cu2O/n-TNA) nanophotocatalyst with a sandwich-like nanostructure was constructed and applied for the photoelectrocatalytic (PEC) degradation of typical PPCPs, tetracycline (TC). The ternary heterojunction n-ZnO/p-Cu2O/n-TNA was obtained by depositing Cu2O on the surface of TNA via sonoelectrochemical deposition (SED) and subsequently building a layer of ZnO onto the p-Cu2O/n-TNA surface through hydrothermal synthesis. After being deposited by the Cu2O, the absorption-band edge of the p-Cu2O/n-TNA was obviously red-shifted to the visible region (to 505 nm), and the band gap was reduced from its original 3.20 eV to 2.46 eV. The band gap absorption edge of the ternary n-ZnO/p-Cu2O/n-TNA is similar to that of p-Cu2O/n-TN and extends the visible spectrum absorption to 510 nm, corresponding to an Eg value of about 2.43 eV. Under illumination of visible light, the photocurrent density of the ternary heterojunction n-ZnO/p-Cu2O/n-TNA electrode at 0.5 V (vs. Ag/AgCl) was more than 106 times as high as that of the pure TNAs electrode, 3.6 times as high as that of the binary heterojunction p-Cu2O/n-TNA electrode. The degradation of TC indicated that the ternary heterojunction n-ZnO/p-Cu2O/n-TNA electrode maintained a very high photoelectrocatalytic activity and excellent stability and reliability. Such kind of ternary heterojunction electrode material has a broad application prospect not only in pollution control but also in many other fields. Copyright © 2013 Elsevier B.V. All rights reserved.

  14. SYSTEMATIC VARIATIONS IN CO{sub 2}/H{sub 2}O ICE ABUNDANCE RATIOS IN NEARBY GALAXIES FOUND WITH AKARI NEAR-INFRARED SPECTROSCOPY

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Yamagishi, M.; Kaneda, H.; Ishihara, D.

    2015-07-01

    We report CO{sub 2}/H{sub 2}O ice abundance ratios in seven nearby star-forming galaxies based on the AKARI near-infrared (2.5–5.0 μm) spectra. The CO{sub 2}/H{sub 2}O ice abundance ratios show clear variations between 0.05 and 0.2 with the averaged value of 0.14 ± 0.01. The previous study on M82 revealed that the CO{sub 2}/H{sub 2}O ice abundance ratios strongly correlate with the intensity ratios of the hydrogen recombination Brα line to the polycyclic aromatic hydrocarbon (PAH) 3.3 μm feature. In the present study, however, we find no correlation for the seven galaxies as a whole due to systematic differences in themore » relation between CO{sub 2}/H{sub 2}O ice abundance and Brα/PAH 3.3 μm intensity ratios from galaxy to galaxy. This result suggests that there is another parameter that determines the CO{sub 2}/H{sub 2}O ice abundance ratios in a galaxy in addition to the Brα/PAH 3.3 μm ratios. We find that the CO{sub 2}/H{sub 2}O ice abundance ratios positively correlate with the specific star formation rates of the galaxies. From these results, we conclude that CO{sub 2}/H{sub 2}O ice abundance ratios tend to be high in young star-forming galaxies.« less

  15. Diode laser-based cavity ring-down instrument for NO3, N2O5, NO, NO2 and O3 from aircraft

    NASA Astrophysics Data System (ADS)

    Wagner, N. L.; Dubé, W. P.; Washenfelder, R. A.; Young, C. J.; Pollack, I. B.; Ryerson, T. B.; Brown, S. S.

    2011-03-01

    This article presents a diode laser based, cavity ring-down spectrometer for simultaneous in situ measurements of four nitrogen oxide species, NO3, N2O5, NO, NO2, as well as O3, designed for deployment on aircraft. The instrument measures NO3 and NO2 by optical extinction at 662 nm and 405 nm, respectively; N2O5 is measured by thermal conversion to NO3, while NO and O3 are measured by chemical conversion to NO2. The instrument has several advantages over previous instruments developed by our group for measurement of NO2, NO3 and N2O5 alone, based on a pulsed Nd:YAG and dye laser. First, the use of continuous wave diode lasers reduces the requirements for power and weight and eliminates hazardous materials. Second, detection of NO2 at 405 nm is more sensitive than our previously reported 532 nm instrument, and does not have a measurable interference from O3. Third, the instrument includes chemical conversion of NO and O3 to NO2 to provide measurements of total NOx (= NO + NO2) and Ox (= NO2 + O3) on two separate channels; mixing ratios of NO and O3 are determined by subtraction of NO2. Finally, all five species are calibrated against a single standard based on 254 nm O3 absorption to provide high accuracy. Disadvantages include an increased sensitivity to water vapor on the 662 nm NO3 and N2O5 channels and a modest reduction in sensitivity for these species compared to the pulsed laser instrument. The measurement precision for both NO3 and N2O5 is below 1 pptv (2σ, 1 s) and for NO, NO2 and O3 is 170, 46, and 56 pptv (2σ, 1 s) respectively. The NO and NO2 measurements are less precise than research-grade chemiluminescence instruments. However, the combination of these five species in a single instrument, calibrated to a single analytical standard, provides a complete and accurate picture of nighttime nitrogen oxide chemistry. The instrument performance is demonstrated using data acquired during a recent field campaign in California.

  16. Surveying N2O-producing pathways in bacteria.

    PubMed

    Stein, Lisa Y

    2011-01-01

    Nitrous oxide (N(2)O) is produced by bacteria as an intermediate of both dissimilatory and detoxification pathways under a range of oxygen levels, although the majority of N(2)O is released in suboxic to anoxic environments. N(2)O production under physiologically relevant conditions appears to require the reduction of nitric oxide (NO) produced from the oxidation of hydroxylamine (nitrification), reduction of nitrite (denitrification), or by host cells of pathogenic bacteria. In a single bacterial isolate, N(2)O-producing pathways can be complex, overlapping, involve multiple enzymes with the same function, and require multiple layers of regulatory machinery. This overview discusses how to identify known N(2)O-producing inventory and regulatory sequences within bacterial genome sequences and basic physiological approaches for investigating the function of that inventory. A multitude of review articles have been published on individual enzymes, pathways, regulation, and environmental significance of N(2)O-production encompassing a large diversity of bacterial isolates. The combination of next-generation deep sequencing platforms, emerging proteomics technologies, and basic microbial physiology can be used to expand what is known about N(2)O-producing pathways in individual bacterial species to discover novel inventory and unifying features of pathways. A combination of approaches is required to understand and generalize the function and control of N(2)O production across a range of temporal and spatial scales within natural and host environments. Copyright © 2011 Elsevier Inc. All rights reserved.

  17. Activation cross section and isomeric cross-section ratio for the 151Eu(n,2n)150m,gEu process

    NASA Astrophysics Data System (ADS)

    Luo, Junhua; Li, Suyuan; Jiang, Li

    2018-07-01

    The cross sections of 151Eu(n,2n)150m,gEu reactions and their isomeric cross section ratios σm/σt have been measured experimentally. Cross sections are measured, relative to a reference 93Nb(n,2n)92mNb reaction cross section, by means of the activation technique at three neutron energies 13.5, 14.1, and 14.8 MeV. Monoenergetic neutron beams were formed via the 3H(d,n)4He reaction and both Eu2O3 samples and Nb monitor foils were activated together to determine the reaction cross section and the incident neutron flux. The activities induced in the reaction products were measured using high-resolution gamma ray spectroscopy. Cross sections were also evaluated theoretically using the numerical nuclear model code, TALYS-1.8 with different level density options at neutron energies varying from the reaction threshold to 20 MeV. Results are discussed and compared with the corresponding literature.

  18. [(Nitrato-κO,O')(nitrito-κO,O')(0.25/1.75)]bis-(1,10-phenanthroline-κN,N')cadmium(II).

    PubMed

    Najafi, Ezzatollah; Amini, Mostafa M; Ng, Seik Weng

    2011-01-22

    The reaction of cadmium nitrate and sodium nitrite in the presence of 1,10-phenanthroline yields the mixed nitrate-nitrite title complex, [Cd(NO(2))(1.75)(NO(3))(0.25)(C(12)H(8)N(2))(2)]. The metal ion is bis-chelated by two N-heterocycles as well as by the nitrate/nitrite ions in a distorted dodeca-hedral CdN(4)O(4) coordination environment. One nitrite group is ordered; the other is disordered with respect to a nitrate group (ratio 0.75:0.25) concerning the O atom that is not involved in bonding to the metal ion.

  19. Cross section data sets for electron collisions with H2, O2, CO, CO2, N2O and H2O

    NASA Astrophysics Data System (ADS)

    Anzai, K.; Kato, H.; Hoshino, M.; Tanaka, H.; Itikawa, Y.; Campbell, L.; Brunger, M. J.; Buckman, S. J.; Cho, H.; Blanco, F.; Garcia, G.; Limão-Vieira, P.; Ingólfsson, O.

    2012-02-01

    We review earlier cross section data sets for electron-collisions with H2, O2, CO, CO2, H2O and N2O, updated here by experimental results for their electronic states. Based on our recent measurements of differential cross sections for the electronic states of those molecules, integral cross sections (ICSs) are derived by applying a generalized oscillator strength analysis and then assessed against theory (BE f-scaling [Y.-K. Kim, J. Chem. Phys. 126, 064305 (2007)]). As they now represent benchmark electronic state cross sections, those ICSs for the above molecules are added into the original cross section sets taken from the data reviews for H2, O2, CO2 and H2O (the Itikawa group), and for CO and N2O (the Zecca group).

  20. Measurements of CH4, N2O, CO, H2O and O3 in the middle atmosphere by the ATMOS experiment on Spacelab 3

    NASA Technical Reports Server (NTRS)

    Gunson, M. R.; Farmer, C. B.; Norton, R. H.; Zander, R.; Rinsland, C. P.; Shaw, J. H.; Gao, Bo-Cai

    1989-01-01

    The volume mixing ratios of five minor gases (CH4, N2O, CO, H2O, and O3) were retrieved through the middle atmosphere from the analysis of 0.01/cm resolution infrared solar occultation spectra recorded near 28 N and 48 S latitudes with the ATMOS (Atmospheric Trace Molecule Spectroscopy) instrument, flown on board Spacelab 3. The results, which constitute the first simultaneous observations of continuous profiles through the middle atmosphere for these gases, are in general agreement with reported measurements from ground, balloon and satellite-based instruments for the same seasons. In detail, the vertical profiles of these gases show the effects of the upper and middle atmospheric transport patterns dominant during the season of these observations. The profiles inferred at different longitudes around 28 N suggest a near-uniform zonal distribution of these gases. Although based on fewer observations, the sunrise occultation measurements point to a larger variability in the vertical distribution of these gases at 48 S.

  1. Enhancement of Perovskite Solar Cells Efficiency using N-Doped TiO2 Nanorod Arrays as Electron Transfer Layer.

    PubMed

    Zhang, Zhen-Long; Li, Jun-Feng; Wang, Xiao-Li; Qin, Jian-Qiang; Shi, Wen-Jia; Liu, Yue-Feng; Gao, Hui-Ping; Mao, Yan-Li

    2017-12-01

    In this paper, N-doped TiO 2 (N-TiO 2 ) nanorod arrays were synthesized with hydrothermal method, and perovskite solar cells were fabricated using them as electron transfer layer. The solar cell performance was optimized by changing the N doping contents. The power conversion efficiency of solar cells based on N-TiO 2 with the N doping content of 1% (N/Ti, atomic ratio) has been achieved 11.1%, which was 14.7% higher than that of solar cells based on un-doped TiO 2 . To get an insight into the improvement, some investigations were performed. The structure was examined with X-ray powder diffraction (XRD), and morphology was examined by scanning electron microscopy (SEM). Energy dispersive spectrometer (EDS) and Tauc plot spectra indicated the incorporation of N in TiO 2 nanorods. Absorption spectra showed higher absorption of visible light for N-TiO 2 than un-doped TiO 2 . The N doping reduced the energy band gap from 3.03 to 2.74 eV. The photoluminescence (PL) and time-resolved photoluminescence (TRPL) spectra displayed the faster electron transfer from perovskite layer to N-TiO 2 than to un-doped TiO 2 . Electrochemical impedance spectroscopy (EIS) showed the smaller resistance of device based on N-TiO 2 than that on un-doped TiO 2 .

  2. Accelerated Rates of Nitrogen Cycling and N2O Production in Salt Marsh Sediments due to Long-Term Fertilization

    NASA Astrophysics Data System (ADS)

    Peng, X.; Ji, Q.; Angell, J.; Kearns, P.; Bowen, J. L.; Ward, B. B.

    2014-12-01

    Intensified sedimentary production of nitrous oxide (N2O), one of the most potent greenhouse gases, is one of the many possible environmental consequences of elevated nitrogen (N) loading into estuarine ecosystems. This study investigates the response to over 40 years of fertilization of nitrogen removal processes in the sediments of the Great Sippewissett Marsh in Falmouth, MA. Sediment slurries were incubated (1.5 hr) with trace amounts (< 10% of ambient concentration) of 15NH4+ + 14NO3- or 15NO3- + 14NH4+. An additional parallel incubation with 15NH4+ + 14NO3- and 1 mM of allylthiourea (ATU) was included to measure rates of anaerobic ammonia oxidation (anammox). Well-homogenized slurries filled about 10% of the volume in the gas-tight incubation vials, and the rest of the volume was replaced with an O2/He (20%/80%) mixture. The production of 29N2, 44N2O and 45N2O were determined using isotope ratio mass spectrometry. The rate of total N2O production in fertilized sediments (0.89 nmol hr-1 g-1 wet weight) was 30-fold higher than in unfertilized sediments. The ratio of N2O to N2 production was also significantly higher in fertilized sediments (2.9%) than in unfertilized sediments (1.2%). This highlights the disproportionally large effect of long-term fertilization on N2O production in salt marsh sediments. The reduced oxygen level and higher ammonium concentrations in situ probably contributed to the significant rise in N2O production as a result of long-term fertilization. When detected, anammox and coupled nitrification-denitrification accounted for 10% and 14% of the total N2 production in fertilized sediments (30.5 nmol hr-1 g-1 wet weight), respectively, whereas neither was detected in unfertilized sediments. Thus these experiments indicate that N loading has important effects on multiple N cycle processes that result in N loss and N2O production.

  3. Development of AlN and TiB2 Composites with Nb2O5, Y2O3 and ZrO2 as Sintering Aids

    PubMed Central

    González, José C.; Rodríguez, Miguel Á.; Figueroa, Ignacio A.; Villafuerte-Castrejón, María-Elena; Díaz, Gerardo C.

    2017-01-01

    The synthesis of AlN and TiB2 by spark plasma sintering (SPS) and the effect of Nb2O5, Y2O3 and ZrO2 additions on the mechanical properties and densification of the produced composites is reported and discussed. After the SPS process, dense AlN and TiB2 composites with Nb2O5, Y2O3 and ZrO2 were successfully prepared. X-ray diffraction analysis showed that in the AlN composites, the addition of Nb2O5 gives rise to Nb4N3 during sintering. The compound Y3Al5O12 (YAG) was observed as precipitate in the sample with Y2O3. X-ray diffraction analysis of the TiB2 composites showed TiB2 as a single phase in these materials. The maximum Vickers and toughness values were 14.19 ± 1.43 GPa and 27.52 ± 1.75 GPa for the AlN and TiB2 composites, respectively. PMID:28772681

  4. N2O production, a widespread trait in fungi

    NASA Astrophysics Data System (ADS)

    Maeda, Koki; Spor, Aymé; Edel-Hermann, Véronique; Heraud, Cécile; Breuil, Marie-Christine; Bizouard, Florian; Toyoda, Sakae; Yoshida, Naohiro; Steinberg, Christian; Philippot, Laurent

    2015-04-01

    N2O is a powerful greenhouse gas contributing both to global warming and ozone depletion. While fungi have been identified as a putative source of N2O, little is known about their production of this greenhouse gas. Here we investigated the N2O-producing ability of a collection of 207 fungal isolates. Seventy strains producing N2O in pure culture were identified. They were mostly species from the order Hypocreales order--particularly Fusarium oxysporum and Trichoderma spp.--and to a lesser extent species from the orders Eurotiales, Sordariales, and Chaetosphaeriales. The N2O 15N site preference (SP) values of the fungal strains ranged from 15.8‰ to 36.7‰, and we observed a significant taxa effect, with Penicillium strains displaying lower SP values than the other fungal genera. Inoculation of 15 N2O-producing strains into pre-sterilized arable, forest and grassland soils confirmed the ability of the strains to produce N2O in soil with a significant strain-by-soil effect. The copper-containing nitrite reductase gene (nirK) was amplified from 45 N2O-producing strains, and its genetic variability showed a strong congruence with the ITS phylogeny, indicating vertical inheritance of this trait. Taken together, this comprehensive set of findings should enhance our knowledge of fungi as a source of N2O in the environment.

  5. N2O production, a widespread trait in fungi.

    PubMed

    Maeda, Koki; Spor, Aymé; Edel-Hermann, Véronique; Heraud, Cécile; Breuil, Marie-Christine; Bizouard, Florian; Toyoda, Sakae; Yoshida, Naohiro; Steinberg, Christian; Philippot, Laurent

    2015-04-20

    N2O is a powerful greenhouse gas contributing both to global warming and ozone depletion. While fungi have been identified as a putative source of N2O, little is known about their production of this greenhouse gas. Here we investigated the N2O-producing ability of a collection of 207 fungal isolates. Seventy strains producing N2O in pure culture were identified. They were mostly species from the order Hypocreales order-particularly Fusarium oxysporum and Trichoderma spp.-and to a lesser extent species from the orders Eurotiales, Sordariales, and Chaetosphaeriales. The N2O (15)N site preference (SP) values of the fungal strains ranged from 15.8‰ to 36.7‰, and we observed a significant taxa effect, with Penicillium strains displaying lower SP values than the other fungal genera. Inoculation of 15 N2O-producing strains into pre-sterilized arable, forest and grassland soils confirmed the ability of the strains to produce N2O in soil with a significant strain-by-soil effect. The copper-containing nitrite reductase gene (nirK) was amplified from 45 N2O-producing strains, and its genetic variability showed a strong congruence with the ITS phylogeny, indicating vertical inheritance of this trait. Taken together, this comprehensive set of findings should enhance our knowledge of fungi as a source of N2O in the environment.

  6. Ammonium sorption and ammonia inhibition of nitrite-oxidizing bacteria explain contrasting soil N2O production

    NASA Astrophysics Data System (ADS)

    Venterea, R. T.; Sadowsky, M.; Breuillin-Sessoms, F.; Wang, P.; Clough, T. J.; Coulter, J. A.

    2015-12-01

    Better understanding of process controls over nitrous oxide (N2O) production in urine-impacted 'hot spots' and fertilizer bands is needed to improve mitigation strategies and emission models. Following amendment with bovine (Bos taurus) urine (Bu) or urea (Ur), we measured inorganic N, pH, N2O, and genes associated with nitrification in two soils ('L' and 'W') having similar texture, pH, C, and C/N ratio. Solution-phase ammonia (slNH3) was also calculated accounting for non-linear ammonium (NH4+) sorption capacities (ASC). Soil W displayed greater nitrification rates and nitrate (NO3-) levels than soil L, but was more resistant to nitrite (NO2-) accumulation and produced two to ten times less N2O than soil L. Genes associated with NO2- oxidation (nxrA) increased substantially in soil W but remained static in soil L. Soil NO2- was strongly correlated with N2O production, and cumulative (c-) slNH3 explained 87% of the variance in c-NO2-. Differences between soils were explained by greater slNH3 in soil L which inhibited NO2- oxidization leading to greater NO2- levels and N2O production. This is the first study to correlate the dynamics of soil slNH3, NO2-, N2O and nitrifier genes, and the first to show how ASC can regulate NO2- levels and N2O production.

  7. Ammonium sorption and ammonia inhibition of nitrite-oxidizing bacteria explain contrasting soil N2O production.

    PubMed

    Venterea, Rodney T; Clough, Timothy J; Coulter, Jeffrey A; Breuillin-Sessoms, Florence; Wang, Ping; Sadowsky, Michael J

    2015-07-16

    Better understanding of process controls over nitrous oxide (N2O) production in urine-impacted 'hot spots' and fertilizer bands is needed to improve mitigation strategies and emission models. Following amendment with bovine (Bos taurus) urine (Bu) or urea (Ur), we measured inorganic N, pH, N2O, and genes associated with nitrification in two soils ('L' and 'W') having similar texture, pH, C, and C/N ratio. Solution-phase ammonia (slNH3) was also calculated accounting for non-linear ammonium (NH4(+)) sorption capacities (ASC). Soil W displayed greater nitrification rates and nitrate (NO3(-)) levels than soil L, but was more resistant to nitrite (NO2(-)) accumulation and produced two to ten times less N2O than soil L. Genes associated with NO2(-) oxidation (nxrA) increased substantially in soil W but remained static in soil L. Soil NO2(-) was strongly correlated with N2O production, and cumulative (c-) slNH3 explained 87% of the variance in c-NO2(-). Differences between soils were explained by greater slNH3 in soil L which inhibited NO2(-) oxidization leading to greater NO2(-) levels and N2O production. This is the first study to correlate the dynamics of soil slNH3, NO2(-), N2O and nitrifier genes, and the first to show how ASC can regulate NO2(-) levels and N2O production.

  8. Ammonium sorption and ammonia inhibition of nitrite-oxidizing bacteria explain contrasting soil N2O production

    NASA Astrophysics Data System (ADS)

    Venterea, Rodney T.; Clough, Timothy J.; Coulter, Jeffrey A.; Breuillin-Sessoms, Florence

    2015-07-01

    Better understanding of process controls over nitrous oxide (N2O) production in urine-impacted ‘hot spots’ and fertilizer bands is needed to improve mitigation strategies and emission models. Following amendment with bovine (Bos taurus) urine (Bu) or urea (Ur), we measured inorganic N, pH, N2O, and genes associated with nitrification in two soils (‘L’ and ‘W’) having similar texture, pH, C, and C/N ratio. Solution-phase ammonia (slNH3) was also calculated accounting for non-linear ammonium (NH4+) sorption capacities (ASC). Soil W displayed greater nitrification rates and nitrate (NO3-) levels than soil L, but was more resistant to nitrite (NO2-) accumulation and produced two to ten times less N2O than soil L. Genes associated with NO2- oxidation (nxrA) increased substantially in soil W but remained static in soil L. Soil NO2- was strongly correlated with N2O production, and cumulative (c-) slNH3 explained 87% of the variance in c-NO2-. Differences between soils were explained by greater slNH3 in soil L which inhibited NO2- oxidization leading to greater NO2- levels and N2O production. This is the first study to correlate the dynamics of soil slNH3, NO2-, N2O and nitrifier genes, and the first to show how ASC can regulate NO2- levels and N2O production.

  9. The effects of preparation conditions for a BaNbO2 N photocatalyst on its physical properties.

    PubMed

    Hisatomi, Takashi; Katayama, Chisato; Teramura, Kentaro; Takata, Tsuyoshi; Moriya, Yosuke; Minegishi, Tsutomu; Katayama, Masao; Nishiyama, Hiroshi; Yamada, Taro; Domen, Kazunari

    2014-07-01

    BaNbO2 N is a semiconductor photocatalyst active for water oxidation under visible-light irradiation up to λ=740 nm. It is important to understand the nitridation processes of precursor materials to form BaNbO2 N to tune the physical properties and improve the photocatalytic activity. Comprehensive experiments and analyses of temperatures, durations, ammonia flow rates, and barium/niobium ratios in the precursor during the nitridation process reveals that faster ammonia flow rates and higher barium/niobium ratios in the precursors help to suppress reduction of pentavalent niobium ions in the nitridation products and that the use of a precursor prepared by a soft-chemistry route allows the production of BaNbO2 N at lower temperatures in shorter times than the use of physical mixtures of BaCO3 and Nb2 O5 because the niobium species is dispersed among the barium species. BaNbO2 N prepared by the soft-chemistry route exhibits comparatively higher activity than that prepared from physical mixtures of BaCO3 and Nb2 O5 , probably because of lower nitridation temperatures, which suppress excessive dissociation of ammonia, and thereby reduce pentavalent niobium ions, and intimate interaction of niobium and barium sources, which lowers the densities of mid-gap states associated with defects. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Down-regulation of tissue N:P ratios in terrestrial plants by elevated CO2.

    PubMed

    Deng, Qi; Hui, Dafeng; Luo, Yiqi; Elser, James; Wang, Ying-ping; Loladze, Irakli; Zhang, Quanfa; Dennis, Sam

    2015-12-01

    Increasing atmospheric CO2 concentrations generally alter element stoichiometry in plants. However, a comprehensive evaluation of the elevated CO2 impact on plant nitrogen: phosphorus (N:P) ratios and the underlying mechanism has not been conducted. We synthesized the results from 112 previously published studies using meta-analysis to evaluate the effects of elevated CO2 on the N:P ratio of terrestrial plants and to explore the underlying mechanism based on plant growth and soil P dynamics. Our results show that terrestrial plants grown under elevated CO2 had lower N:P ratios in both above- and belowground biomass across different ecosystem types. The response ratio for plant N:P was negatively correlated with the response ratio for plant growth in croplands and grasslands, and showed a stronger relationship for P than for N. In addition, the CO2-induced down-regulation of plant N:P was accompanied by 19.3% and 4.2% increases in soil phosphatase activity and labile P, respectively, and a 10.1% decrease in total soil P. Our results show that down-regulation of plant N:P under elevated CO2 corresponds with accelerated soil P cycling. These findings should be useful for better understanding of terrestrial plant stoichiometry in response to elevated CO2 and of the underlying mechanisms affecting nutrient dynamics under climate change.

  11. Collisional Removal of OH (X (sup 2)Pi, nu=7) by O2, N2, CO2, and N2O

    NASA Technical Reports Server (NTRS)

    Knutsen, Karen; Dyer, Mark J.; Copeland, Richard A.

    1996-01-01

    Collisional removal rate constants for the OH (X 2PI, nu = 7) radical are measured for the colliders O2, CO2, and N2O, and an upper limit is established for N2. OH(nu = 4) molecules, generated in a microwave discharge flow cell by the reaction of hydrogen atoms with ozone, are excited to v = 7 by the output of a pulsed infrared laser via direct vibrational overtone excitation. The temporal evolution of the P = 7 population is probed as a function of the collider gas partial pressure by a time-delayed pulsed ultraviolet laser. Fluorescence from the B 21 + state is detected in the visible spectral region.

  12. Post-harvest N2O emissions were not affected by various types of oilseed straw incorporated into soil

    NASA Astrophysics Data System (ADS)

    Köbke, Sarah; Senbayram, Mehmet; Hegewald, Hannes; Christen, Olaf; Dittert, Klaus

    2015-04-01

    Oilseed rape post-harvest N2O emissions are seen highly critical as so far they are considered as one of the most crucial drawbacks in climate-saving bioenergy production systems. N2O emissions may substantially counterbalance the intended savings in CO2 emissions. Carbon-rich crop residues in conjunction with residual soil nitrate are seen as a key driver since they may serve as energy source for denitrification and, they may alter soil-borne N2O emissions. As oilseed rape straw is known to have high N/C ratio compared to other crop residues, its soil incorporation may specifically trigger post-harvest N2O emissions. Therefore, the aim of the present study was to determine post-harvest N2O emissions in soils amended with various types of oilseed rape straw (with different N/C ratio) and barley straw in field and incubation experiments. In the incubation experiment, oilseed rape or 15N labelled barley straw were mixed with soil at a rate of 1.3 t DM ha-1 and studied for 43 days. Treatments consisted of non-treated control soil (CK), 15N labelled barley straw (BST), oilseed rape straw (RST), 15N labelled barley straw + N (BST+N), or oilseed rape straw + N (RST+N). N fertilizer was applied to the soil surface as ammonium-nitrate at a rate of 100 kg N ha-1 and soil moisture was adjusted to 80% water-holding capacity. In the field experiment, during the vegetation period 15N labelled fertilizer (15NH415NO3) was used to generate 15N labelled oilseed rape straw (up to 5 at%). Here, the three fertilizer treatments consisted of 5 kg N ha-1 (RST-5), 150 kg N ha-1 (RST-150) and 180 kg N ha-1 (RST-180). Post-harvest N2O emissions were determined during the period of August 2013 to February 2014 by using static flux chambers. In the incubation trial, cumulative N2O emissions were 5, 29, 40 g N2O-N ha-1 148 days-1 in non-fertilized control, BST and RST treatments, respectively. Here, emissions were slightly higher in RST than BST (p

  13. SpO2/FiO2 ratio on hospital admission is an indicator of early acute respiratory distress syndrome development among patients at risk.

    PubMed

    Festic, Emir; Bansal, Vikas; Kor, Daryl J; Gajic, Ognjen

    2015-05-01

    Oxygen saturation to fraction of inspired oxygen ratio (SpO(2)/FiO(2)) has been validated as a surrogate marker for partial pressure of oxygen to fraction of inspired oxygen ratio among mechanically ventilated patients with acute respiratory distress syndrome (ARDS). The validity of SpO(2)/FiO(2) measurements in predicting ARDS has not been studied. Recently, a Lung Injury Prediction Score (LIPS) has been developed to help identify patients at risk of developing ARDS. This was a secondary analysis of the LIPS-1 cohort. A multivariate logistic regression included all established variables for LIPS, Acute Physiology and Chronic Health Evaluation 2, age, and comorbid conditions that could affect SpO(2)/FiO(2). The primary outcome was development of ARDS in the hospital. The secondary outcomes included hospital mortality, hospital day of ARDS development, and hospital day of death. Of the 5584 patients, we evaluated all 4646 with recorded SpO(2)/FiO(2) values. Median SpO(2)/FiO(2) in those who did and did not develop ARDS was 254 (100, 438) and 452 (329, 467), respectively. There was a significant association between SpO(2)/FiO(2) and ARDS (P ≤ .001). The SpO(2)/FiO(2) was found to be an independent predictor of ARDS in a "dose-dependent" manner; for SpO(2)/FiO(2) < 100--odds ratios (OR) 2.49 (1.69-3.64, P < .001), for SpO(2)/FiO(2) 100 < 200--OR 1.75 (1.16-2.58, P = .007), and for SpO(2)/FiO(2) 200 < 300--OR 1.62 (1.06-2.42, P = .025). The discriminatory characteristics of the multivariable model and SpO2/FiO2 as a single variable demonstrated area under the curve (AUC) of 0.81 and AUC of 0.74, respectively. The SpO2/FiO2, measured within the first 6 hours after hospital admission, is an independent indicator of ARDS development among patients at risk. © The Author(s) 2013.

  14. Reducing fertilizer-derived N2O emission: Point injection vs. surface application of ammonium-N fertilizer at a loamy sand site

    NASA Astrophysics Data System (ADS)

    Deppe, Marianna; Well, Reinhard; Giesemann, Anette; Kücke, Martin; Flessa, Heinz

    2013-04-01

    N2O emitted from soil originates either from denitrification of nitrate and/or nitrification of ammonium. N fertilization can have an important impact on N2O emission rates. Injection of nitrate-free ammonium-N fertilizer, in Germany also known as CULTAN (Controlled Uptake Long-Term Ammonium Nutrition), results in fertilizer depots with ammonium concentrations of up to 10 mg N g-1 soil-1. High concentrations of ammonium are known to inhibit nitrification. However, it has not yet been clarified how N2O fluxes are affected by CULTAN. In a field experiment, two application methods of nitrogen fertilizer were used at a loamy sand site: Ammonium sulphate was applied either by point injection or by surface application. 15N-ammonium sulphate was used to distinguish between N2O originating from either fertilizer-N or soil-N. Unfertilized plots and plots fertilized with unlabeled ammonium sulphate served as control. N2O emissions were measured using static chambers, nitrate and ammonium concentrations were determined in soil extracts. Stable isotope analysis of 15N in N2O, nitrate and ammonium was used to calculate the contribution of fertilizer N to N2O emissions and the fertilizer turnover in soil. 15N analysis clearly indicated that fertilizer derived N2O fluxes were higher from surface application plots. For the period of the growing season, about 24% of the flux measured in surface application treatment and less than 10% from injection treatment plots originated from the fertilizer. In addition, a lab experiment was conducted to gain insight into processes leading to N2O emission from fertilizer depots. One aim was to examine whether the ratio of N2O to nitrate formation differs depending on the ammonium concentration. Loamy sand soil was incubated in microcosms continuously flushed with air under conditions favouring nitrification. 15N-labeled nitrate was used to differentiate between nitrification and denitrification. Stable isotope analyses of 15N were performed on

  15. Direct impacts of biochar on N2O production during denitrification by a soil microbial community

    NASA Astrophysics Data System (ADS)

    Mishra, Akanksha; Harter, Johannes; Hagemann, Nikolas; Kappler, Andreas

    2017-04-01

    Biochar, i.e. biomass heated under O2 limitation to 350-1000°C (pyrolysis), is suggested as a beneficial soil amendment to mitigate climate change and to maintain and restore the fertility of agro-ecosystems. Its stability enables long-term carbon sequestration and biochar effectively reduces soil-borne N2O emissions. Biochar's ability to reduce N2O emissions is well recognized through field and laboratory experiments as well as meta-analyses. However, the underlying mechanisms remain widely debated. Microbial nitrogen transformations, especially denitrification, the stepwise reduction of nitrate/nitrite via NO and N2O to N2, are considered to be a major source of N2O emissions. Soil microcosm experiments showed lower N2O emissions in the presence of biochar often correlate with a higher abundance and/or activity of N2O reducing bacteria in the presence of biochar. However, it is still unknown whether these shifts in the microbial community and/or activity is cause or effect of reduced N2O production. Biochar has the potential to change the physico-chemical environment towards conditions that favor complete denitrification, i.e. decrease the N2O/(N2O+N2) product ratio. Specifically, biochar can increase soil pH, reduce the availability of nitrate and increase the entrapment of gases, including N2O. These effects are known to decrease the N2O/(N2O+N2) ratio. In addition to the observed effects in the physio-chemical environment, we hypothesized that biochar has a direct impact on the soil microbial community. For instance, it has been shown to provide a suitable habitat to microorganisms, or facilitate electron transfer between microbe and substrates by acting as an electron shuttle or as a temporary acceptor/donor of electrons. To test this hypothesis, our experiment consisted of a microbial community extracted from soil and cultivated under anoxic conditions. It was introduced as an inoculum into three different treatments: biochar, quartz (control with a solid

  16. TROSY of side-chain amides in large proteins

    PubMed Central

    Liu, Aizhuo; Yao, Lishan; Li, Yue; Yan, Honggao

    2012-01-01

    By using the mixed solvent of 50% H2O/50% D2O and employing deuterium decoupling, TROSY experiments exclusively detect NMR signals from semideuterated isotopomers of carboxamide groups with high sensitivities for proteins with molecular weights up to 80 kDa. This isotopomer-selective strategy extends TROSY experiments from exclusively detecting backbone to both backbone and side-chain amides, particularly in large proteins. Because of differences in both TROSY effect and dynamics between 15N–HE{DZ} and 15N–HZ{DE} isotopomers of the same carboxamide, the 15N transverse magnetization of the latter relaxes significantly faster than that of the former, which provides a direct and reliable stereospecific distinction between the two configurations. The TROSY effects on the 15N–HE{DZ} isotopomers of side-chain amides are as significant as on backbone amides. PMID:17347000

  17. Syntheses and structures of [UO2( L)5](ClO4)2 and [U( L')4(H2O)4](ClO4)4 ( L is dimethylformamide, L' is N,N-dimethylcarbamide)

    NASA Astrophysics Data System (ADS)

    Serezhkin, V. N.; Vologzhanina, A. V.; Pushkin, D. V.; Astashkina, D. A.; Savchenkov, A. V.; Serezhkina, L. B.

    2017-09-01

    The reaction of aqueous solutions of uranyl perchlorate with selected organic amides was studied in the dark and under the sunlight. The complexes [UVIO2(C3H7NO)5](ClO4)2 ( I) and [UIV(C3H8N2O)4(H2O)4](ClO4)4 ( II), where C3H7NO is N,N-dimethylformamide ( Dmfa) and C3H8N2O is N,N-dimethylcarbamide ( a-Dmur), were studied by X-ray diffraction. Complex II and the complex UIV( s-Dmur)4(H2O)4(ClO4)4 ( III), where s-Dmur is N,N'-dimethylcarbamide, were studied by IR spectroscopy. Crystals I and II are composed of mononuclear [UO2( Dmfa)5]2+ and [U( Dmur)4(H2O)4]4+ groups as uranium-containing structural units belonging to the crystal-chemical groups AM 7 1 ( A = UVI, M 1 = O2- and Dmfa) and AM 8 1 ( A = UIV, M 1 = Dmur and H2O) of uranium complexes, respectively. The mononuclear uranium- containing complexes in the crystals of U(IV) and U(VI) perchlorates were found to obey the 14 neighbors rule.

  18. Comparative analysis of the effects of tantalum doping and annealing on atomic layer deposited (Ta2O5)x(Al2O3)1-x as potential gate dielectrics for GaN/AlxGa1-xN/GaN high electron mobility transistors

    NASA Astrophysics Data System (ADS)

    Partida-Manzanera, T.; Roberts, J. W.; Bhat, T. N.; Zhang, Z.; Tan, H. R.; Dolmanan, S. B.; Sedghi, N.; Tripathy, S.; Potter, R. J.

    2016-01-01

    This paper describes a method to optimally combine wide band gap Al2O3 with high dielectric constant (high-κ) Ta2O5 for gate dielectric applications. (Ta2O5)x(Al2O3)1-x thin films deposited by thermal atomic layer deposition (ALD) on GaN-capped AlxGa1-xN/GaN high electron mobility transistor (HEMT) structures have been studied as a function of the Ta2O5 molar fraction. X-ray photoelectron spectroscopy shows that the bandgap of the oxide films linearly decreases from 6.5 eV for pure Al2O3 to 4.6 eV for pure Ta2O5. The dielectric constant calculated from capacitance-voltage measurements also increases linearly from 7.8 for Al2O3 up to 25.6 for Ta2O5. The effect of post-deposition annealing in N2 at 600 °C on the interfacial properties of undoped Al2O3 and Ta-doped (Ta2O5)0.12(Al2O3)0.88 films grown on GaN-HEMTs has been investigated. These conditions are analogous to the conditions used for source/drain contact formation in gate-first HEMT technology. A reduction of the Ga-O to Ga-N bond ratios at the oxide/HEMT interfaces is observed after annealing, which is attributed to a reduction of interstitial oxygen-related defects. As a result, the conduction band offsets (CBOs) of the Al2O3/GaN-HEMT and (Ta2O5)0.16(Al2O3)0.84/GaN-HEMT samples increased by ˜1.1 eV to 2.8 eV and 2.6 eV, respectively, which is advantageous for n-type HEMTs. The results demonstrate that ALD of Ta-doped Al2O3 can be used to control the properties of the gate dielectric, allowing the κ-value to be increased, while still maintaining a sufficient CBO to the GaN-HEMT structure for low leakage currents.

  19. A universal definition of ARDS: the PaO2/FiO2 ratio under a standard ventilatory setting--a prospective, multicenter validation study.

    PubMed

    Villar, Jesús; Pérez-Méndez, Lina; Blanco, Jesús; Añón, José Manuel; Blanch, Lluís; Belda, Javier; Santos-Bouza, Antonio; Fernández, Rosa Lidia; Kacmarek, Robert M

    2013-04-01

    The PaO2/FiO2 is an integral part of the assessment of patients with acute respiratory distress syndrome (ARDS). The American-European Consensus Conference definition does not mandate any standardization procedure. We hypothesized that the use of PaO2/FiO2 calculated under a standard ventilatory setting within 24 h of ARDS diagnosis allows a more clinically relevant ARDS classification. We studied 452 ARDS patients enrolled prospectively in two independent, multicenter cohorts treated with protective mechanical ventilation. At the time of ARDS diagnosis, patients had a PaO2/FiO2 ≤ 200. In the derivation cohort (n = 170), we measured PaO2/FiO2 with two levels of positive end-expiratory pressure (PEEP) (≥ 5 and ≥ 10 cmH2O) and two levels of FiO2 (≥ 0.5 and 1.0) at ARDS onset and 24 h later. Dependent upon PaO2 response, patients were reclassified into three groups: mild (PaO2/FiO2 > 200), moderate (PaO2/FiO2 101-200), and severe (PaO2/FiO2 ≤ 100) ARDS. The primary outcome measure was ICU mortality. The standard ventilatory setting that reached the highest significance difference in mortality among these categories was tested in a separate cohort (n = 282). The only standard ventilatory setting that identified the three PaO2/FiO2 risk categories in the derivation cohort was PEEP ≥ 10 cmH2O and FiO2 ≥ 0.5 at 24 h after ARDS onset (p = 0.0001). Using this ventilatory setting, patients in the validation cohort were reclassified as having mild ARDS (n = 47, mortality 17 %), moderate ARDS (n = 149, mortality 40.9 %), and severe ARDS (n = 86, mortality 58.1 %) (p = 0.00001). Our method for assessing PaO2/FiO2 greatly improved risk stratification of ARDS and could be used for enrolling appropriate ARDS patients into therapeutic clinical trials.

  20. Development of an atmospheric N2O isotopocule model and optimization procedure, and application to source estimation

    NASA Astrophysics Data System (ADS)

    Ishijima, K.; Takigawa, M.; Sudo, K.; Toyoda, S.; Yoshida, N.; Röckmann, T.; Kaiser, J.; Aoki, S.; Morimoto, S.; Sugawara, S.; Nakazawa, T.

    2015-07-01

    This paper presents the development of an atmospheric N2O isotopocule model based on a chemistry-coupled atmospheric general circulation model (ACTM). We also describe a simple method to optimize the model and present its use in estimating the isotopic signatures of surface sources at the hemispheric scale. Data obtained from ground-based observations, measurements of firn air, and balloon and aircraft flights were used to optimize the long-term trends, interhemispheric gradients, and photolytic fractionation, respectively, in the model. This optimization successfully reproduced realistic spatial and temporal variations of atmospheric N2O isotopocules throughout the atmosphere from the surface to the stratosphere. The very small gradients associated with vertical profiles through the troposphere and the latitudinal and vertical distributions within each hemisphere were also reasonably simulated. The results of the isotopic characterization of the global total sources were generally consistent with previous one-box model estimates, indicating that the observed atmospheric trend is the dominant factor controlling the source isotopic signature. However, hemispheric estimates were different from those generated by a previous two-box model study, mainly due to the model accounting for the interhemispheric transport and latitudinal and vertical distributions of tropospheric N2O isotopocules. Comparisons of time series of atmospheric N2O isotopocule ratios between our model and observational data from several laboratories revealed the need for a more systematic and elaborate intercalibration of the standard scales used in N2O isotopic measurements in order to capture a more complete and precise picture of the temporal and spatial variations in atmospheric N2O isotopocule ratios. This study highlights the possibility that inverse estimation of surface N2O fluxes, including the isotopic information as additional constraints, could be realized.

  1. Development of an atmospheric N2O isotopocule model and optimization procedure, and application to source estimation

    NASA Astrophysics Data System (ADS)

    Ishijima, K.; Takigawa, M.; Sudo, K.; Toyoda, S.; Yoshida, N.; Röckmann, T.; Kaiser, J.; Aoki, S.; Morimoto, S.; Sugawara, S.; Nakazawa, T.

    2015-12-01

    This work presents the development of an atmospheric N2O isotopocule model based on a chemistry-coupled atmospheric general circulation model (ACTM). We also describe a simple method to optimize the model and present its use in estimating the isotopic signatures of surface sources at the hemispheric scale. Data obtained from ground-based observations, measurements of firn air, and balloon and aircraft flights were used to optimize the long-term trends, interhemispheric gradients, and photolytic fractionation, respectively, in the model. This optimization successfully reproduced realistic spatial and temporal variations of atmospheric N2O isotopocules throughout the atmosphere from the surface to the stratosphere. The very small gradients associated with vertical profiles through the troposphere and the latitudinal and vertical distributions within each hemisphere were also reasonably simulated. The results of the isotopic characterization of the global total sources were generally consistent with previous one-box model estimates, indicating that the observed atmospheric trend is the dominant factor controlling the source isotopic signature. However, hemispheric estimates were different from those generated by a previous two-box model study, mainly due to the model accounting for the interhemispheric transport and latitudinal and vertical distributions of tropospheric N2O isotopocules. Comparisons of time series of atmospheric N2O isotopocule ratios between our model and observational data from several laboratories revealed the need for a more systematic and elaborate intercalibration of the standard scales used in N2O isotopic measurements in order to capture a more complete and precise picture of the temporal and spatial variations in atmospheric N2O isotopocule ratios. This study highlights the possibility that inverse estimation of surface N2O fluxes, including the isotopic information as additional constraints, could be realized.

  2. Ti n O2n-1-Coated Li4Ti5O12 Composite Anode Material for Lithium-Ion Batteries

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaoyan; Xu, Wen; Liu, Wanying; Li, Xing; Zhong, Xiaoxi; Lin, Yuanhua

    2018-01-01

    In an effort to enhance the rate capability of Li4Ti5O12, the Ti n O2n-1-coated Li4Ti5O12 (Li4Ti5O12-Ti n O2n-1, 3 < n < 10) composite has been synthesized through a sol-gel process followed by heat treatment in H2 atmosphere. Compared with pure Li4Ti5O12, Li4Ti5O12-Ti n O2n-1 composite shows higher specific capacity, better rate capability and cycle stability. The initial discharge capacity of the Li4Ti5O12-Ti n O2n-1 composite electrode is 171.2 mAh g-1 at 0.2°C, and 103.8 mAh g-1 at 20°C. Moreover, the discharge capacity remains 79.5 mAh g-1 after 100 cycles at 20°C with a capacity loss of 23.4%. The improved rate capacity and cycling stability clarify the positive effects of Ti n O2n-1 coating layer in Li4Ti5O12-Ti n O2n-1 composite as an anode material for lithium ion batteries.

  3. Diode laser-based cavity ring-down instrument for NO3, N2O5, NO, NO2 and O3 from aircraft

    NASA Astrophysics Data System (ADS)

    Wagner, N. L.; Dubé, W. P.; Washenfelder, R. A.; Young, C. J.; Pollack, I. B.; Ryerson, T. B.; Brown, S. S.

    2011-06-01

    This article presents a diode laser-based, cavity ring-down spectrometer for simultaneous in situ measurements of four nitrogen oxide species, NO3, N2O5, NO, NO2, as well as O3, designed for deployment on aircraft. The instrument measures NO3 and NO2 by optical extinction at 662 nm and 405 nm, respectively; N2O5 is measured by thermal conversion to NO3, while NO and O3 are measured by chemical conversion to NO2. The instrument has several advantages over previous instruments developed by our group for measurement of NO2, NO3 and N2O5 alone, based on a pulsed Nd:YAG and dye laser. First, the use of continuous wave diode lasers reduces the requirements for power and weight and eliminates hazardous materials. Second, detection of NO2 at 405 nm is more sensitive than our previously reported 532 nm instrument, and does not have a measurable interference from O3. Third, the instrument includes chemical conversion of NO and O3 to NO2 to provide measurements of total NOx (= NO + NO2) and Ox (= NO2 + O3) on two separate channels; mixing ratios of NO and O3 are determined by subtraction of NO2. Finally, all five species are calibrated against a single standard based on 254 nm O3 absorption to provide high accuracy. Disadvantages include an increased sensitivity to water vapor on the 662 nm NO3 and N2O5 channels and a modest reduction in sensitivity for these species compared to the pulsed laser instrument. The in-flight detection limit for both NO3 and N2O5 is 3 pptv (2 σ, 1 s) and for NO, NO2 and O3 is 140, 90, and 120 pptv (2 σ, 1 s) respectively. Demonstrated performance of the instrument in a laboratory/ground based environment is better by approximately a factor of 2-3. The NO and NO2 measurements are less precise than research-grade chemiluminescence instruments. However, the combination of these five species in a single instrument, calibrated to a single analytical standard, provides a complete and accurate picture of nighttime nitrogen oxide chemistry. The

  4. Heterojunction p-Cu2O/n-Ga2O3 diode with high breakdown voltage

    NASA Astrophysics Data System (ADS)

    Watahiki, Tatsuro; Yuda, Yohei; Furukawa, Akihiko; Yamamuka, Mikio; Takiguchi, Yuki; Miyajima, Shinsuke

    2017-11-01

    Heterojunction p-Cu2O/n-β-Ga2O3 diodes were fabricated on an epitaxially grown β-Ga2O3(001) layer. The reverse breakdown voltage of these p-n diodes reached 1.49 kV with a specific on-resistance of 8.2 mΩ cm2. The leakage current of the p-n diodes was lower than that of the Schottky barrier diode due to the higher barrier height against the electron. The ideality factor of the p-n diode was 1.31. It indicated that some portion of the recombination current at the interface contributed to the forward current, but the diffusion current was the dominant. The forward current more than 100 A/cm2 indicated the lower conduction band offset at the hetero-interface between Cu2O and Ga2O3 layers than that predicted from the bulk properties, resulting in such a high forward current without limitation. These results open the possibility of advanced device structures for wide bandgap Ga2O3 to achieve higher breakdown voltage and lower on-resistance.

  5. trans-Bis(azido-kappaN)bis(pyridine-2-carboxamide-kappa2N1,O2)nickel(II).

    PubMed

    Daković, Marijana; Popović, Zora

    2007-11-01

    In the title compound, [Ni(N(3))(2)(C(6)H(6)N(2)O)(2)], the Ni(II) atom lies on an inversion centre. The distorted octahedral nickel(II) coordination environment contains two planar trans-related N,O-chelating picolinamide ligands in one plane and two monodentate azide ligands perpendicular to this plane. Molecules are linked into a three-dimensional framework by N-H...N hydrogen bonds.

  6. Nitrous oxide (N2O) emission from aquaculture: a review.

    PubMed

    Hu, Zhen; Lee, Jae Woo; Chandran, Kartik; Kim, Sungpyo; Khanal, Samir Kumar

    2012-06-19

    Nitrous oxide (N(2)O) is an important greenhouse gas (GHG) which has a global warming potential 310 times that of carbon dioxide (CO(2)) over a hundred year lifespan. N(2)O is generated during microbial nitrification and denitrification, which are common in aquaculture systems. To date, few studies have been conducted to quantify N(2)O emission from aquaculture. Additionally, very little is known with respect to the microbial pathways through which N(2)O is formed in aquaculture systems. This review suggests that aquaculture can be an important anthropogenic source of N(2)O emission. The global N(2)O-N emission from aquaculture in 2009 is estimated to be 9.30 × 10(10) g, and will increase to 3.83 × 10(11)g which could account for 5.72% of anthropogenic N(2)O-N emission by 2030 if the aquaculture industry continues to increase at the present annual growth rate (about 7.10%). The possible mechanisms and various factors affecting N(2)O production are summarized, and two possible methods to minimize N(2)O emission, namely aquaponic and biofloc technology aquaculture, are also discussed. The paper concludes with future research directions.

  7. KCd2[N(CN)2]5(H2O)4: an enmeshed honeycomb grid.

    PubMed

    Schlueter, John A; Geiser, Urs; Funk, Kylee A

    2008-02-01

    The title compound, poly[potassium [diaquapenta-micro(2)-dicyanamido-dicadmium(II)] dihydrate], {K[Cd(2)(C(2)N(3))(5)(H(2)O)(2)].2H(2)O}(n), contains two-dimensional anionic sheets of {[Cd(2){N(CN)(2)}(H(2)O)(2)](-)}(n) with a modified (6,3)-net (layer group cm2m, No. 35). Two sets of equivalent sheets interpenetrate orthogonally to form a tetragonal enmeshed grid.

  8. Influence of ZnO seed layer precursor molar ratio on the density of interface defects in low temperature aqueous chemically synthesized ZnO nanorods/GaN light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Alnoor, Hatim; Pozina, Galia; Khranovskyy, Volodymyr; Liu, Xianjie; Iandolo, Donata; Willander, Magnus; Nur, Omer

    2016-04-01

    Low temperature aqueous chemical synthesis (LT-ACS) of zinc oxide (ZnO) nanorods (NRs) has been attracting considerable research interest due to its great potential in the development of light-emitting diodes (LEDs). The influence of the molar ratio of the zinc acetate (ZnAc): KOH as a ZnO seed layer precursor on the density of interface defects and hence the presence of non-radiative recombination centers in LT-ACS of ZnO NRs/GaN LEDs has been systematically investigated. The material quality of the as-prepared seed layer as quantitatively deduced by the X-ray photoelectron spectroscopy is found to be influenced by the molar ratio. It is revealed by spatially resolved cathodoluminescence that the seed layer molar ratio plays a significant role in the formation and the density of defects at the n-ZnO NRs/p-GaN heterostructure interface. Consequently, LED devices processed using ZnO NRs synthesized with molar ratio of 1:5 M exhibit stronger yellow emission (˜575 nm) compared to those based on 1:1 and 1:3 M ratios as measured by the electroluminescence. Furthermore, seed layer molar ratio shows a quantitative dependence of the non-radiative defect densities as deduced from light-output current characteristics analysis. These results have implications on the development of high-efficiency ZnO-based LEDs and may also be helpful in understanding the effects of the ZnO seed layer on defect-related non-radiative recombination.

  9. Ammonium sorption and ammonia inhibition of nitrite-oxidizing bacteria explain contrasting soil N2O production

    PubMed Central

    Venterea, Rodney T.; Clough, Timothy J.; Coulter, Jeffrey A.; Breuillin-Sessoms, Florence

    2015-01-01

    Better understanding of process controls over nitrous oxide (N2O) production in urine-impacted ‘hot spots’ and fertilizer bands is needed to improve mitigation strategies and emission models. Following amendment with bovine (Bos taurus) urine (Bu) or urea (Ur), we measured inorganic N, pH, N2O, and genes associated with nitrification in two soils (‘L’ and ‘W’) having similar texture, pH, C, and C/N ratio. Solution-phase ammonia (slNH3) was also calculated accounting for non-linear ammonium (NH4+) sorption capacities (ASC). Soil W displayed greater nitrification rates and nitrate (NO3−) levels than soil L, but was more resistant to nitrite (NO2−) accumulation and produced two to ten times less N2O than soil L. Genes associated with NO2− oxidation (nxrA) increased substantially in soil W but remained static in soil L. Soil NO2− was strongly correlated with N2O production, and cumulative (c-) slNH3 explained 87% of the variance in c-NO2−. Differences between soils were explained by greater slNH3 in soil L which inhibited NO2− oxidization leading to greater NO2− levels and N2O production. This is the first study to correlate the dynamics of soil slNH3, NO2−, N2O and nitrifier genes, and the first to show how ASC can regulate NO2− levels and N2O production. PMID:26179972

  10. Amplified spontaneous emission from ZnO in n-ZnO/ZnO nanodots-SiO(2) composite/p-AlGaN heterojunction light-emitting diodes.

    PubMed

    Shih, Ying Tsang; Wu, Mong Kai; Li, Wei Chih; Kuan, Hon; Yang, Jer Ren; Shiojiri, Makoto; Chen, Miin Jang

    2009-04-22

    This study demonstrates amplified spontaneous emission (ASE) of the ultraviolet (UV) electroluminescence (EL) from ZnO at lambda~380 nm in the n-ZnO/ZnO nanodots-SiO(2) composite/p- Al(0.12)Ga(0.88)N heterojunction light-emitting diode. A SiO(2) layer embedded with ZnO nanodots was prepared on the p-type Al(0.12)Ga(0.88)N using spin-on coating of SiO(2) nanoparticles followed by atomic layer deposition (ALD) of ZnO. An n-type Al-doped ZnO layer was deposited upon the ZnO nanodots-SiO(2) composite layer also by the ALD technique. High-resolution transmission electron microscopy (HRTEM) reveals that the ZnO nanodots embedded in the SiO(2) matrix have diameters of 3-8 nm and the wurtzite crystal structure, which allows the transport of carriers through the thick ZnO nanodots-SiO(2) composite layer. The high quality of the n-ZnO layer was manifested by the well crystallized lattice image in the HRTEM picture and the low-threshold optically pumped stimulated emission. The low refractive index of the ZnO nanodots-SiO(2) composite layer results in the increase in the light extraction efficiency from n-ZnO and the internal optical feedback of UV EL into n-ZnO layer. Consequently, significant enhancement of the UV EL intensity and super-linear increase in the EL intensity, as well as the spectral narrowing, with injection current were observed owing to ASE in the n-ZnO layer.

  11. Nano ZSM-5 type ferrisilicates as novel catalysts for ethylbenzene dehydrogenation in the presence of N 2O

    NASA Astrophysics Data System (ADS)

    Khatamian, M.; Khandar, A. A.; Haghighi, M.; Ghadiri, M.

    2011-11-01

    Nanosized ZSM-5 type ferrisilicates were successfully prepared using hydrothermal process. Several parameters including gel initiative compositions (Na+ or K+ alkali system), SiO2/Fe2O3 molar ratios and hydrothermal temperature were systematically investigated. The samples were characterized by XRD, TEM, SEM-EDS, BET surface area and ICP techniques. It was found that surface areas and the total pore volume increase with increasing in the SiO2/Fe2O3 molar ratio at Na-FZ ferrisilicates. The catalytic performance of the synthesized catalysts was evaluated in ethylbenzene dehydrogenation to styrene in the presence of N2O or steam at temperatures ranging from 400 °C to 660 °C under atmospheric pressure. The effects of gel initiative compositions, SiO2/Fe2O3 molar ratio as well as the hydrothermal synthesis temperature on the catalytic performance of these catalysts have been addressed. It was shown that styrene yield significantly influenced by altering in the SiO2/Fe2O3 ratio but was not greatly influenced by changes in hydrothermal synthesis temperatures. The comparison between performance of potassium and sodium containing catalysts was shown that the one with potassium has higher yield and selectivity toward styrene production at an optimum temperature of 610 °C.

  12. Temperature dependent electrical characterisation of Pt/HfO{sub 2}/n-GaN metal-insulator-semiconductor (MIS) Schottky diodes

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Shetty, Arjun, E-mail: arjun@ece.iisc.ernet.in; Vinoy, K. J.; Roul, Basanta

    2015-09-15

    This paper reports an improvement in Pt/n-GaN metal-semiconductor (MS) Schottky diode characteristics by the introduction of a layer of HfO{sub 2} (5 nm) between the metal and semiconductor interface. The resulting Pt/HfO{sub 2}/n-GaN metal-insulator-semiconductor (MIS) Schottky diode showed an increase in rectification ratio from 35.9 to 98.9(@ 2V), increase in barrier height (0.52 eV to 0.63eV) and a reduction in ideality factor (2.1 to 1.3) as compared to the MS Schottky. Epitaxial n-type GaN films of thickness 300nm were grown using plasma assisted molecular beam epitaxy (PAMBE). The crystalline and optical qualities of the films were confirmed using high resolutionmore » X-ray diffraction and photoluminescence measurements. Metal-semiconductor (Pt/n-GaN) and metal-insulator-semiconductor (Pt/HfO{sub 2}/n-GaN) Schottky diodes were fabricated. To gain further understanding of the Pt/HfO{sub 2}/GaN interface, I-V characterisation was carried out on the MIS Schottky diode over a temperature range of 150 K to 370 K. The barrier height was found to increase (0.3 eV to 0.79 eV) and the ideality factor decreased (3.6 to 1.2) with increase in temperature from 150 K to 370 K. This temperature dependence was attributed to the inhomogeneous nature of the contact and the explanation was validated by fitting the experimental data into a Gaussian distribution of barrier heights.« less

  13. Characterization of remote O2-plasma-enhanced CVD SiO2/GaN(0001) structure using photoemission measurements

    NASA Astrophysics Data System (ADS)

    Truyen, Nguyen Xuan; Ohta, Akio; Makihara, Katsunori; Ikeda, Mitsuhisa; Miyazaki, Seiichi

    2018-01-01

    The control of chemical composition and bonding features at a SiO2/GaN interface is a key to realizing high-performance GaN power devices. In this study, an ∼5.2-nm-thick SiO2 film has been deposited on an epitaxial GaN(0001) surface by remote O2-plasma-enhanced chemical vapor deposition (O2-RPCVD) using SiH4 and Ar/O2 mixture gases at a substrate temperature of 500 °C. The depth profile of chemical structures and electronic defects of the O2-RPCVD SiO2/GaN structures has been evaluated from a combination of SiO2 thinning examined by X-ray photoelectron spectroscopy (XPS) and the total photoelectron yield spectroscopy (PYS) measurements. As a highlight, we found that O2-RPCVD is effective for fabricating an abrupt SiO2/GaN interface.

  14. Elucidating Turnover Pathways of Bioactive Small Molecules by Isotopomer Analysis: The Persistent Organic Pollutant DDT

    PubMed Central

    Ehlers, Ina; Betson, Tatiana R.; Vetter, Walter; Schleucher, Jürgen

    2014-01-01

    The persistent organic pollutant DDT (1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane) is still indispensable in the fight against malaria, although DDT and related compounds pose toxicological hazards. Technical DDT contains the dichloro congener DDD (1-chloro-4-[2,2-dichloro-1-(4-chlorophenyl)ethyl]benzene) as by-product, but DDD is also formed by reductive degradation of DDT in the environment. To differentiate between DDD formation pathways, we applied deuterium NMR spectroscopy to measure intramolecular deuterium distributions (2H isotopomer abundances) of DDT and DDD. DDD formed in the technical DDT synthesis was strongly deuterium-enriched at one intramolecular position, which we traced back to 2H/1H fractionation of a chlorination step in the technical synthesis. In contrast, DDD formed by reductive degradation was strongly depleted at the same position, which was due to the incorporation of 2H-depleted hydride equivalents during reductive degradation. Thus, intramolecular isotope distributions give mechanistic information on reaction pathways, and explain a puzzling difference in the whole-molecule 2H/1H ratio between DDT and DDD. In general, our results highlight that intramolecular isotope distributions are essential to interpret whole-molecule isotope ratios. Intramolecular isotope information allows distinguishing pathways of DDD formation, which is important to identify polluters or to assess DDT turnover in the environment. Because intramolecular isotope data directly reflect isotope fractionation of individual chemical reactions, they are broadly applicable to elucidate transformation pathways of small bioactive molecules in chemistry, physiology and environmental science. PMID:25350380

  15. The influence of ionic strength and organic compounds on nanoparticle TiO2 (n-TiO2) aggregation.

    PubMed

    Lee, Jaewoong; Bartelt-Hunt, Shannon L; Li, Yusong; Gilrein, Erica Jeanne

    2016-07-01

    This study investigated the aggregation of n-TiO2 in the presence of humic acid (HA) and/or 17β-estradiol (E2) under high ionic strength conditions simulating levels detected in landfill leachate. Aggregation of n-TiO2 was strongly influenced by ionic strength as well as ionic valence in that divalent cations (Ca(2+)) were more effective than monovalent (Na(+)) at the surface modification. HA or E2 enhanced aggregation of n-TiO2 in 20 mM CaCl2, however little aggregation was observed in 100 mM NaCl. Similarly, we observed only the increased aggregation of n-TiO2 in the presence of HA/E2. These results showed the critical role of particles' surface charges on the aggregation behaviors of n-TiO2 that HA plays more significantly than E2. However, the slightly increased zeta potential and aggregation of n-TiO2 in the combination of HA and E2 at both 20 mM CaCl2 and 100 mM NaCl means that E2 has influenced on the surface modification of n-TiO2 by adsorption. Based on the aggregation of n-TiO2 under high ionic strength with HA and/or E2, we simulated the mobility of aggregated n-TiO2 in porous media. As a result, we observed that the mobility distance of aggregated n-TiO2 was dramatically influenced by the surface modification with both HA and/or E2 between particles and media. Furthermore, larger mobility distance was observed with larger aggregation of n-TiO2 particles that can be explained by clean bed filtration (CFT) theory. Copyright © 2016 Elsevier Ltd. All rights reserved.

  16. First Measurement of the 14N/15N Ratio in the Analog of the Sun Progenitor OMC-2 FIR4

    NASA Astrophysics Data System (ADS)

    Kahane, Claudine; Jaber Al-Edhari, Ali; Ceccarelli, Cecilia; López-Sepulcre, Ana; Fontani, Francesco; Kama, Mihkel

    2018-01-01

    We present a complete census of the 14N/15N isotopic ratio in the most abundant N-bearing molecules toward the cold envelope of the protocluster OMC-2 FIR4, the best known Sun progenitor. To this scope, we analyzed the unbiased spectral survey obtained with the IRAM 30 m telescope at 3, 2, and 1 mm. We detected several lines of CN, HCN, HNC, HC3N, N2H+, and their respective 13C and 15N isotopologues. The lines’ relative fluxes are compatible with LTE conditions, and moderate line opacities have been corrected via a population diagram method or theoretical relative intensity ratios of the hyperfine structures. The five species lead to very similar 14N/15N isotopic ratios, without any systematic difference between amine- and nitrile-bearing species as previously found in other protostellar sources. The weighted average of the 14N/15N isotopic ratio is 270 ± 30. This 14N/15N value is remarkably consistent with the [250–350] range measured for the local galactic ratio but significantly differs from the ratio measured in comets (around 140). High-angular resolution observations are needed to examine whether this discrepancy is maintained at smaller scales. In addition, using the CN, HCN, and HC3N lines, we derived a 12C/13C isotopic ratio of 50 ± 5.

  17. Reactions of hydrated electrons (H2O)n- with carbon dioxide and molecular oxygen: hydration of the CO2- and O2- ions.

    PubMed

    Balaj, O Petru; Siu, Chi-Kit; Balteanu, Iulia; Beyer, Martin K; Bondybey, Vladimir E

    2004-10-04

    The gas-phase reactions of hydrated electrons with carbon dioxide and molecular oxygen were studied by Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry. Both CO2 and O2 react efficiently with (H2O)n- because they possess low-lying empty pi* orbitals. The molecular CO2- and O2- anions are concurrently solvated and stabilized by the water ligands to form CO2(-)(H2O)n and O2(-)(H2O)n. Core exchange reactions are also observed, in which CO2(-)(H2O)n is transformed into O2(-)(H2O)n upon collision with O2. This is in agreement with the prediction based on density functional theory calculations that O2(-)(H2O)n clusters are thermodynamically favored with respect to CO2(-)(H2O)n. Electron detachment from the product species is only observed for CO2(-)(H2O)2, in agreement with the calculated electron affinities and solvation energies.

  18. The ratio of the nucleon structure functions F2N for iron and deuterium

    NASA Astrophysics Data System (ADS)

    Aubert, J. J.; Bassompierre, G.; Becks, K. H.; Best, C.; Böhm, E.; de Bouard, X.; Brasse, F. W.; Broll, C.; Brown, S.; Carr, J.; Clifft, R. W.; Cobb, J. H.; Coignet, G.; Combley, F.; Court, G. R.; D'Agostini, G.; Dau, W. D.; Davies, J. K.; Déclais, Y.; Dobinson, R. W.; Dosselli, U.; Drees, J.; Edwards, A. W.; Edwards, M.; Favier, J.; Ferrero, M. I.; Flauger, W.; Gabathuler, E.; Gamet, R.; Gayler, J.; Gerhardt, V.; Gössling, C.; Haas, J.; Hamacher, K.; Hayman, P.; Henckes, M.; Korbel, V.; Landgraf, U.; Leenen, M.; Maire, M.; Minssieux, H.; Mohr, W.; Montgomery, H. E.; Moser, K.; Mount, R. P.; Norton, P. R.; McNicholas, J.; Osborne, A. M.; Payre, P.; Peroni, C.; Pessard, H.; Pietrzyk, U.; Rith, K.; Schneegans, M.; Sloan, T.; Stier, H. E.; Stockhausen, W.; Thénard, J. M.; Thompson, J. C.; Urban, L.; Villers, M.; Wahlen, H.; Whalley, M.; Williams, D.; Williams, W. S. C.; Williamson, J.; Wimpenny, S. J.

    1983-03-01

    Using the data on deep inelastic muon scattering on iron and deuterium the ratio of the nucleon structure functions F2N(Fe)/F2N(D) is presented. The observed x-dependence of this ratio is in disagreement with existing theoretical predictions.

  19. Glacial-Interglacial and Holocene N2O Stable Isotope Changes Constrain Terrestrial N Cycling

    NASA Astrophysics Data System (ADS)

    Schmitt, J.; Spahni, R.; Bock, M.; Seth, B.; Stocker, B. D.; Ri, X.; Schilt, A.; Brook, E.; Otto-Bliesner, B. L.; Liu, Z.; Prentice, I. C.; Fischer, H.; Joos, F.

    2015-12-01

    The land biosphere contributes most to the natural source of the long-lived greenhouse gas nitrous oxide (N2O), with N2O emissions being dependent on the turnover rate of both the terrestrial nitrogen (N) and carbon (C) cycle. The C:N stoichiometry of vegetation and soil organic matter links the cycles intimately. Sustained plant productivity increase must be supported by biological N fixation. Intensified N cycling in turn enhances N loss and thereby N2O emissions. The temporal and spatial dynamics of terrestrial N and C cycles and related terrestrial N2O emissions are poorly constrained over the glacial-interglacial transition and the Holocene. Here we reconstruct increased terrestrial N2O emissions since the Last Glacial Maximum based on N2O concentration and isotope measurements on several ice cores and show that this N2O increase can be explained by N cycle modelling - provided N fixation is allowed to respond dynamically to increasing N demand and turnover. The Ice core reconstructions suggest a deglacial increase of 1.1 ± 0.4 Tg N/yr in terrestrial and 0.6 ± 0.4 Tg/yr in oceanic N2O emissions, but relatively constant terrestrial emissions over the Holocene. Transient simulations with a Dynamic Global Vegetation Model are shown to represent the climate and CO2 induced changes in terrestrial N2O emission, and suggest a deglacial increase in biological N fixation by 20%, independently of its absolute magnitude. Deciphering the response of biological N fixation during climatic changes is an important factor for our understanding of plant growth and the land carbon sink, alongside anthropogenic greenhouse gas emissions.

  20. Structural and spectral analyses of N,N'-(2,2'-dithiodi-o-phenylene)bis-(furan-2-carboxamide)

    NASA Astrophysics Data System (ADS)

    Yıldırım, Sema Öztürk; Büyükmumcu, Zeki; Pekdur, Özlem Savaş; Butcher, Ray J.; Doǧan, Şengül Dilem

    2018-02-01

    In this study we report structure determination of N,N'-(2,2'-dithiodi-o-phenylene)bis-(furan-2-carboxamide). 2,2'-Dithiobis(benzamide) derivatives have been reported to possess important biological properties such as antibacterial, antifungal activities and inhibition of blood platelet aggregation and redeterrmined at 100(2)K from the data published by Raftery, Lallbeeharry, Bhowon, Laulloo & Joulea [Acta Cryst. 2009, E65, o16]. 2,2'-Dithiobis(N-butyl-benzamide) has been reported to be useful as an antiseptic for cosmetics. The structural properties of the compound have been characterized by using 1H NMR and the structure were determined by single-crystal X-ray diffraction. Molecular structure crystallizes in triclinic form, space group with a = 9.6396(7) Å, b = 9.9115(7) Å, c = 12.0026(8) Å, α = 109.743(6)°, β = 103.653(6)°, γ = 104.633(6)° and V = 977.15(13) Å3. In the solid state of the molecular structure N-H…S, N-H…O and C-H…O, type interactions provide for stabilization. The geometries of the title compound have been optimized using density functional theory (DFT) method. The calculated values were found to be in agreement with the experimental data.

  1. 2,4-Dinitrophenylhydrazine, redetermined at 120 K: a three-dimensional framework built from N-H...O, N-H...(O)2, N-H...pi(arene) and C-H...O hydrogen bonds.

    PubMed

    Wardell, James L; Low, John N; Glidewell, Christopher

    2006-06-01

    In the title compound, C6H6N4O4, the bond distances indicate significant bond fixation, consistent with charge-separated polar forms. The molecules are almost planar and there is an intramolecular N-H...O hydrogen bond. The molecules are linked into a complex three-dimensional framework structure by a combination of N-H...O, N-H...(O)2, N-H...pi(arene) and C-H...O hydrogen bonds.

  2. Crystal structure and optical property of complex perovskite oxynitrides ALi0.2Nb0.8O2.8N0.2, ANa0.2Nb0.8O2.8N0.2, and AMg0.2Nb0.8O2.6N0.4 (A = Sr, Ba)

    NASA Astrophysics Data System (ADS)

    Moon, Keon Ho; Avdeev, Maxim; Kim, Young-Il

    2017-10-01

    Oxynitride type complex perovskites AM0.2Nb0.8O3-xNx (A = Sr, Ba; M = Li, Na, Mg) were newly synthesized by the solid state diffusion of Li+, Na+, or Mg2+ into the layered oxide, A5Nb4O15, with concurrent O/N substitution. Neutron and synchrotron X-ray Rietveld refinement showed that SrLi0.2Nb0.8O2.8N0.2, SrNa0.2Nb0.8O2.8N0.2, and SrMg0.2Nb0.8O2.6N0.4 had body-centered tetragonal symmetry (I4/mcm), while those with A = Ba had simple cubic symmetry (Pm 3 ̅ m). In the tetragonal Sr-compounds, the nitrogen atoms were localized on the c-axial 4a site. However, the octahedral cations, M/Nb (M = Li, Na, Mg) were distributed randomly in all six compounds. The lattice volume of AM0.2Nb0.8O3-xNx was dependent on various factors including the type of A and the electronegativity of M. Compared to the simple perovskites, ANbO2N (A = Sr, Ba), AM0.2Nb0.8O3-xNx had wider band gaps (1.76-2.15 eV for A = Sr and 1.65-2.10 eV for A = Ba), but significantly lower sub-gap absorption.

  3. Effect of EtOH/MgCl(2) molar ratios on the catalytic properties of MgCl(2)-SiO(2)/TiCl(4) Ziegler-Natta catalyst for ethylene polymerization.

    PubMed

    Patthamasang, Supanan; Jongsomjit, Bunjerd; Praserthdam, Piyasan

    2011-09-29

    MgCl(2)-SiO(2)/TiCl(4) Ziegler-Natta catalysts for ethylene polymerization were prepared by impregnation of MgCl(2) on SiO(2) in heptane and further treatment with TiCl(4). MgCl(2nEtOH adduct solutions were prepared with various EtOH/MgCl(2) molar ratios for preparation of the MgCl(2)-supported and MgCl(2)-SiO(2)-supported catalysts in order to investigate the effect on polymerization performance of both catalyst systems. The catalytic activities for ethylene polymerization decreased markedly with increased molar ratios of [EtOH]/[MgCl(2)] for the MgCl(2)-supported catalysts, while for the bi-supported catalysts, the activities only decreased slightly. The MgCl(2)-SiO(2)-supported catalyst had relatively constant activity, independent of the [EtOH]/[MgCl(2)] ratio. The lower [EtOH]/[MgCl(2)] in MgCl(2)-supported catalyst exhibited better catalytic activity. However, for the MgCl(2)-SiO(2)-supported catalyst, MgCl(2) can agglomerate on the SiO(2) surface at low [EtOH]/[MgCl(2)] thus not being not suitable for TiCl(4) loading. It was found that the optimized [EtOH]/[MgCl(2)] value for preparation of bi-supported catalysts having high activity and good spherical morphology with little agglomerated MgCl(2) was 7. Morphological studies indicated that MgCl(2)-SiO(2)-supported catalysts have good morphology with spherical shapes that retain the morphology of SiO(2). The BET measurement revealed that pore size is the key parameter dictating polymerization activity. The TGA profiles of the bi-supported catalyst also confirmed that it was more stable than the mono-supported catalyst, especially in the ethanol removal region.

  4. The Molybdenum(V) and Tungsten(VI) Oxoazides [MoO(N3 )3 ], [MoO(N3 )3 ⋅2 CH3 CN], [(bipy)MoO(N3 )3 ], [MoO(N3 )5 ](2-) , [WO(N3 )4 ], and [WO(N3 )4 ⋅CH3 CN].

    PubMed

    Haiges, Ralf; Skotnitzki, Juri; Fang, Zongtang; Dixon, David A; Christe, Karl O

    2015-12-14

    A series of novel molybdenum(V) and tungsten(VI) oxoazides was prepared starting from [MOF4 ] (M=Mo, W) and Me3 SiN3 . While [WO(N3 )4 ] was formed through fluoride-azide exchange in the reaction of Me3 SiN3 with WOF4 in SO2 solution, the reaction with MoOF4 resulted in a reduction of Mo(VI) to Mo(V) and formation of [MoO(N3 )3 ]. Carried out in acetonitrile solution, these reactions resulted in the isolation of the corresponding adducts [MoO(N3 )3 ⋅2 CH3 CN] and [WO(N3 )4 ⋅CH3 CN]. Subsequent reactions of [MoO(N3 )3 ] with 2,2'-bipyridine and [PPh4 ][N3 ] resulted in the formation and isolation of [(bipy)MoO(N3 )3 ] and [PPh4 ]2 [MoO(N3 )5 ], respectively. Most molybdenum(V) and tungsten(VI) oxoazides were fully characterized by their vibrational spectra, impact, friction and thermal sensitivity data and, in the case of [WO(N3 )4 ⋅CH3 CN], [(bipy)MoO(N3 )3 ], and [PPh4 ]2 [MoO(N3 )5 ], by their X-ray crystal structures. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Influence of ZnO seed layer precursor molar ratio on the density of interface defects in low temperature aqueous chemically synthesized ZnO nanorods/GaN light-emitting diodes

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Alnoor, Hatim, E-mail: hatim.alnoor@liu.se; Iandolo, Donata; Willander, Magnus

    Low temperature aqueous chemical synthesis (LT-ACS) of zinc oxide (ZnO) nanorods (NRs) has been attracting considerable research interest due to its great potential in the development of light-emitting diodes (LEDs). The influence of the molar ratio of the zinc acetate (ZnAc): KOH as a ZnO seed layer precursor on the density of interface defects and hence the presence of non-radiative recombination centers in LT-ACS of ZnO NRs/GaN LEDs has been systematically investigated. The material quality of the as-prepared seed layer as quantitatively deduced by the X-ray photoelectron spectroscopy is found to be influenced by the molar ratio. It is revealedmore » by spatially resolved cathodoluminescence that the seed layer molar ratio plays a significant role in the formation and the density of defects at the n-ZnO NRs/p-GaN heterostructure interface. Consequently, LED devices processed using ZnO NRs synthesized with molar ratio of 1:5 M exhibit stronger yellow emission (∼575 nm) compared to those based on 1:1 and 1:3 M ratios as measured by the electroluminescence. Furthermore, seed layer molar ratio shows a quantitative dependence of the non-radiative defect densities as deduced from light-output current characteristics analysis. These results have implications on the development of high-efficiency ZnO-based LEDs and may also be helpful in understanding the effects of the ZnO seed layer on defect-related non-radiative recombination.« less

  6. Effect of C/N ratio, aeration rate and moisture content on ammonia and greenhouse gas emission during the composting.

    PubMed

    Jiang, Tao; Schuchardt, Frank; Li, Guoxue; Guo, Rui; Zhao, Yuanqiu

    2011-01-01

    Gaseous emission (N2O, CH4 and NH3) from composting can be an important source of anthropogenic greenhouse gas and air pollution. A laboratory scale orthogonal experiment was conducted to estimate the effects of C/N ratio, aeration rate and initial moisture content on gaseous emission during the composting of pig faeces from Chinese Ganqinfen system. The results showed that about 23.9% to 45.6% of total organic carbon (TOC) was lost in the form of CO2 and 0.8% to 7.5% of TOC emitted as CH4. Most of the nitrogen was lost in the form of NH3, which account for 9.6% to 32.4% of initial nitrogen. N2O was also an important way of nitrogen losses and 1.5% to 7.3% of initial total nitrogen was lost as it. Statistic analysis showed that the aeration rate is the most important factor which could affect the NH3 (p = 0.0189), CH4 (p = 0.0113) and N2O (p = 0.0493) emissions significantly. Higher aeration rates reduce the CH4 emission but increase the NH3 and N2O losses. C/N ratio could affect the NH3 (p = 0.0442) and CH4 (p = 0.0246) emissions significantly, but not the N2O. Lower C/N ratio caused higher NH3 and CH4 emissions. The initial moisture content can not influence the gaseous emission significantly. Most treatments were matured after 37 days, except a trial with high moisture content and a low C/N ratio.

  7. Effect of Si3N4 powder reactivity on the preparation of the Si2N2O-Al2O3 silicon aluminum oxynitride solid solution

    NASA Technical Reports Server (NTRS)

    Sekercioglu, I.; Wills, R. R.

    1979-01-01

    Dense high-purity silicon aluminum oxynitride was prepared by reactive hot-pressing of an Si3N4-Al2O3-SiO2 mixture. The formation of a single-phase material was found to be critically dependent on the Si3N4 powder in the starting mixture. It is suggested that evolution of a chlorine- and nitrogen-containing species may enhance the reactivity of Si3N4 in this reaction. Densities of O prime sialons are very similar to that of Si2N2O, the widely quoted value in the ceramics literature of 3.1 g/cu cm for the density of Si2N2O being incorrect.

  8. Infrared spectra and tunneling dynamics of the N2-D2O and OC-D2O complexes in the v2 bend region of D2O.

    PubMed

    Zhu, Yu; Zheng, Rui; Li, Song; Yang, Yu; Duan, Chuanxi

    2013-12-07

    The rovibrational spectra of the N2-D2O and OC-D2O complexes in the v2 bend region of D2O have been measured in a supersonic slit jet expansion using a rapid-scan tunable diode laser spectrometer. Both a-type and b-type transitions were observed for these two complexes. All transitions are doubled, due to the heavy water tunneling within the complexes. Assuming the tunneling splittings are the same in K(a) = 0 and K(a) = 1, the band origins, all three rotational and several distortion constants of each tunneling state were determined for N2-D2O in the ground and excited vibrational states, and for OC-D2O in the excited vibrational state, respectively. The averaged band origin of OC-D2O is blueshifted by 2.241 cm(-1) from that of the v2 band of the D2O monomer, compared with 1.247 cm(-1) for N2-D2O. The tunneling splitting of N2-D2O in the ground state is 0.16359(28) cm(-1), which is about five times that of OC-D2O. The tunneling splittings decrease by about 26% for N2-D2O and 23% for OC-D2O, respectively, upon excitation of the D2O bending vibration, indicating an increase of the tunneling barrier in the excited vibrational state. The tunneling splittings are found to have a strong dependence on intramolecular vibrational excitation as well as a weak dependence on quantum number K(a).

  9. Collision cross sections and transport coefficients of O-, O2 -, O3 - and O4 - negative ions in O2, N2 and dry air for non-thermal plasmas modelling

    NASA Astrophysics Data System (ADS)

    Hennad, Ali; Yousfi, Mohammed

    2018-02-01

    The ions interaction data such as interaction potential parameters, elastic and inelastic collision cross sections and the transport coefficients (reduced mobility and diffusion coefficients) have been determined and analyzed in the case of the main negative oxygen ions (O-, O2 -, O3 - and O4 -) present in low temperature plasma at atmospheric pressure when colliding O2, N2 and dry air. The ion transport has been determined from an optimized Monte Carlo simulation using calculated elastic and experimentally fitted inelastic collision cross sections. The elastic momentum transfer collision cross sections have been calculated from a semi-classical JWKB approximation based on a ( n-4) rigid core interaction potential model. The cross sections sets involving elastic and inelastic processes were then validated using measured reduced mobility data and also diffusion coefficient whenever available in the literature. From the sets of elastic and inelastic collision cross sections thus obtained for the first time for O3-/O2, O2 -/N2, O3 -/N2, and O4 -/N2 systems, the ion transport coefficients were calculated in pure gases and dry air over a wide range of the density reduced electric field E/N.

  10. Comparisons of switching characteristics between Ti/Al2O3/Pt and TiN/Al2O3/Pt RRAM devices with various compliance currents

    NASA Astrophysics Data System (ADS)

    Qi, Yanfei; Zhao, Ce Zhou; Liu, Chenguang; Fang, Yuxiao; He, Jiahuan; Luo, Tian; Yang, Li; Zhao, Chun

    2018-04-01

    In this study, the influence of the Ti and TiN top electrodes on the switching behaviors of the Al2O3/Pt resistive random access memory devices with various compliance currents (CCs, 1-15 mA) has been compared. Based on the similar statistical results of the resistive switching (RS) parameters such as V set/V reset, R HRS/R LRS (measured at 0.10 V) and resistance ratio with various CCs for both devices, the Ti/Al2O3/Pt device differs from the TiN/Al2O3/Pt device mainly in the forming process rather than in the following switching cycles. Apart from the initial isolated state, the Ti/Al2O3/Pt device has the initial intermediate state as well. In addition, its forming voltage is relatively lower. The conduction mechanisms of the ON and OFF state for both devices are demonstrated as ohmic conduction and Frenkel-Poole emission, respectively. Therefore, with the combined modulations of the CCs and the stop voltages, the TiN/Al2O3/Pt device is more stable for nonvolatile memory applications to further improve the RS performance.

  11. Microwave spectrum of o-benzyne produced in a discharge nozzle

    NASA Astrophysics Data System (ADS)

    Kukolich, S. G.; Tanjaroon, C.; McCarthy, M. C.; Thaddeus, P.

    2003-08-01

    The microwave spectrum for o-benzyne was obtained by passing a dilute (<1%) mixture of benzene in neon through a pulsed-DC discharge nozzle source into a pulsed-beam, Fourier transform spectrometer. Rotational transitions were measured for the normal isotopomer, the two unique single-D isotopomers, and the 13C isotopomer and one of the 13C isotopomers. Benzynes have been known as reactive intermediates in organic reactions for many years, and have recently been implicated in gasoline combustion reactions and antitumor activity of enediynes. Twenty-seven b-type transitions for the normal isotopomer were fit to obtain A=6989.7292(6), B=5706.8062(6), and C=3140.3708(4) MHz, and five centrifugal distortion constants. The inertial defect is Δ=0.069 4 amu Å2, consistent with a planar structure. Hyperfine structure for the D1 (closest to the CtrpbndC bond) and D2 (furthest from the CtrpbndC bond), was analyzed to obtain deuterium quadrupole coupling strengths eQqaa(D1)=185(3) kHz, eQqbb(D1)=-85(2) kHz, eQqaa(D2)=5(13), and eQqbb(D2)=86(13) kHz. The C-D, bond axis quadrupole coupling strengths are compared with values for benzene. Spectra for the 13C6 and one of the 13C1 isotopomers were analyzed to obtain rotational constants. Kraitchman analysis and least-squares fitting provided nearly all of the structural parameters. The preliminary structural analysis yields an acetylenic C≡C bond length of 1.24 Å, in agreement with a recent NMR value. Density functional theory (DFT) calculations were used to obtain structural parameters, and values obtained are in very good agreement with present experimental results.

  12. O2(b1Σg+) Quenching by O2, CO2, H2O, and N2 at Temperatures of 300-800 K.

    PubMed

    Zagidullin, M V; Khvatov, N A; Medvedkov, I A; Tolstov, G I; Mebel, A M; Heaven, M C; Azyazov, V N

    2017-10-05

    Rate constants for the removal of O 2 (b 1 Σ g + ) by collisions with O 2 , N 2 , CO 2 , and H 2 O have been determined over the temperature range from 297 to 800 K. O 2 (b 1 Σ g + ) was excited by pulses from a tunable dye laser, and the deactivation kinetics were followed by observing the temporal behavior of the b 1 Σ g + -X 3 Σ g - fluorescence. The removal rate constants for CO 2 , N 2 , and H 2 O were not strongly dependent on temperature and could be represented by the expressions k CO2 = (1.18 ± 0.05) × 10 -17 × T 1.5 × exp[Formula: see text], k N2 = (8 ± 0.3) × 10 -20 × T 1.5 × exp[Formula: see text], and k H2O = (1.27 ± 0.08) × 10 -16 × T 1.5 × exp[Formula: see text] cm 3 molecule -1 s -1 . Rate constants for O 2 (b 1 Σ g + ) removal by O 2 (X), being orders of magnitude lower, demonstrated a sharp increase with temperature, represented by the fitted expression k O2 = (7.4 ± 0.8) × 10 -17 × T 0.5 × exp[Formula: see text] cm 3 molecule -1 s -1 . All of the rate constants measured at room temperature were found to be in good agreement with previously reported values.

  13. Factors Controlling Fluxes of Nitrous Oxide (N-N2O) in AN Upland Tropical Forest (atlantic Forest) - Brazil, Rio de Janeiro

    NASA Astrophysics Data System (ADS)

    Perry, I.; de Mello, W. Z.; McDowell, W. H.

    2010-12-01

    fluxes occurred with a C:N ratio below 16, and also increased with WFPS, soil temperature and phosphorus. Nitrogen availability had little influence on N-N2O fluxes, while phosphorus might be a limiting nutrient for N-N2O production in SONP. *Presenting authot (E-mail: igperry@yahoo.com.br)

  14. (Carbonato-κO,O')bis-(di-2-pyridyl-amine-κN,N')cobalt(III) bromide.

    PubMed

    Czapik, Agnieszka; Papadopoulos, Christos; Lalia-Kantouri, Maria; Gdaniec, Maria

    2011-04-01

    In the title compound, [Co(CO(3))(C(10)H(9)N(3))(2)]Br, a distorted octa-hedral coordination of the Co(III) atom is completed by four N atoms of the two chelating di-2-pyridyl-amine ligands and two O atoms of the chelating carbonate anion. The di-2-pyridyl-amine ligands are nonplanar and the dihedral angles between the 2-pyridyl groups are 29.11 (9) and 37.15 (12)°. The coordination cation, which has approximate C(2) symmetry, is connected to the bromide ion via an N-H⋯Br(-) hydrogen bond. The ionic pair thus formed is further assembled into a dimer via N-H⋯O inter-actions about an inversion centre. A set of weaker C-H⋯O and C-H⋯Br(-) inter-actions connect the dimers into a three-dimensional network.

  15. Quantitatively probing water and its isotopomers: from theory to experiments; the contribution of a chemical and astrophysical European network 'Our Astrochemical History'

    NASA Astrophysics Data System (ADS)

    Wiesenfeld, Laurent

    2015-08-01

    In order to retrieve actual molecular abundances from astrophysical observations of molecular spectral lines, knowledge of the rotational levels excitation schemes is essential to go beyond Local Thermodynamical Equilibrium. These rates are almost always obtained from theoretical investigations, by computing classical or quantum dynamics of the interaction of molecules with these colliders (roueff2013).Our laboratories have recently calculated a set of collision coefficients characterizing the efficiency of energy transfer between molecular hydrogen of helium and a large variety of interstellar molecules. One of the main goal has been water and its isotopomers, computingrates for H2O, HDO and D2O in collision with H2 (valiron2008,faure2012,daniel2011).We felt it necessary to have a multidisciplinary approach: theoretical on the one hand, experimental on the second. Indeed, excitation coefficient computation is a process involving many codes and approximations. Hence we compared our theoretical results to several experiments: spectroscopy of the H2O-H2 van der Waals complex (vanderavoird 2012), differential cross sections (yang 2010, 2011), pressure broadening (drouin 2012).Thanks to these precise determinations, many water abundances could be quantitatively measured, like the HDO/H2O ratio (coutens 2012).While the excitation of water is by now well understood, much remains to be done for heavier molecules, paving the way to quantitative measures of complex organic molecules . A multi disciplinary approach is necessary, that keeps in mind the necessities of actual astrophysical observations. To do so, we describe the European COST network ‘Our Astrochemical History’ (http://prague2015astrohistory.vscht.cz/) , which brings together specialists of many areas of chemistry together with astronomy, in order to address this kind of problem. It focussses on the molecular evolution towards higher complexity and aim sat delivering new schemes for physical chemistry at

  16. Organically treated biochar increases plant production and reduces N2O emissions: mechanistic insights by 15N tracing

    NASA Astrophysics Data System (ADS)

    Kammann, Claudia; Messerschmidt, Nicole; Clough, Tim; Schmidt, Hans-Peter; Marhan, Sven; Koyro, Hans-Werner; Steffens, Diedrich; Müller, Christoph

    2014-05-01

    Pyrogenic carbon (biochar) offers considerable potential for carbon capture and soil storage (CCSS) compared to other, less recalcitrant soil-C additives. Recent meta-analysis demonstrated that it can significantly reduce agricultural N2O emissions. Freshly produced biochars, however, do not always have yield-improving effects, i.e. there is no immediate economic incentive for using it. Hence, combining biochar with organic nutrient-rich amendments may be a promising agricultural strategy to accelerate CCSS, but it is unclear if biochar still reduces N2O emissions, in particular when it may act as nutrient carrier. We explored the potential of biochar to improve the GHG-cost/yield ratio and thereby its socio-economic value as soil amendment in two subsequent studies under controlled conditions: (1) A proof-of-concept study where the effects of untreated biochar were compared to those of co-composted biochar combined with stepwise improved nutritional regimes (+/- compost; +/- mineral-N application), and (2) a 15N-labeling-tracing study to unravel N exchange on biochar particles and N2O production and reduction mechanisms. Both studies were carried out in nutrient-poor sandy soils, the most likely initial target soils for biochar-CCSS strategies. While the untreated biochar reduced plant growth under N-limiting conditions, or at best did not reduce it, the co-composted biochar always significantly stimulated plant growth. The relative stimulation was largest with the lowest nutrient additions (305% versus 61% of control with untreated biochar). Electro-ultra-filtration analyses revealed that the co-composted but not the untreated biochar carried considerable amounts of easily extractable as well as more strongly sorbed plant nutrients, in particular nitrate and phosphorus. The subsequent 15N labelling-tracing study revealed that the co-composted biochar still (i) acted as a mineral-N exchange site for nitrate and ammonium despite its N-preloading, (ii) reduced N2O

  17. C/O Ratios in Exoplanetary Atmospheres

    NASA Astrophysics Data System (ADS)

    Madhusudhan, N.

    2012-04-01

    Recent observations are allowing unprecedented constraints on the carbon-to-oxygen (C/O) ratios of giant exoplanetary atmospheres. Elemental abundance ratios, such as the C/O ratio, of planetary atmospheres provide important constraints on planetary interior compositions and formation conditions, and on the chemical and dynamical processes in the atmospheres. In addition, for super-Earths, the potential availability of water and oxygen, and hence the notion of `habitability', is contingent on the C/O ratio. Typically, an oxygen-rich composition, motivated by the solar nebula C/O of 0.5, is assumed in models of exoplanetary formation, interiors, and atmospheres. However, recent observations of exoplanetary atmospheres are suggesting the possibility of C/O ratios of 1.0 or higher, motivating the new class of Carbon-rich Planets (CRPs). In this talk, we will present observational constraints on atmospheric C/O ratios for an ensemble of transiting exoplanets and discuss their implications on the various aspects of exoplanetary characterization described above. Motivated by these results, we propose a two-dimensional classification scheme for irradiated giant exoplanets in which the incident irradiation and the atmospheric C/O ratio are the two dimensions. We demonstrate that some of the extreme anomalies reported in the literature for hot Jupiter atmospheres can be explained based on this 2-D scheme. An overview of new theoretical avenues and observational efforts underway for chemical characterization of extrasolar planets, from hot Jupiters to super-Earths, will be presented.

  18. Mitigation of nitrous oxide (N2O) emissions from denitrifying fluidized bed bioreactors (DFBBRs) using calcium.

    PubMed

    Eldyasti, Ahmed; Nakhla, George; Zhu, Jesse

    2014-12-01

    Nitrous oxide (N2O) is a significant anthropogenic greenhouse gases (AnGHGs) emitted from biological nutrient removal (BNR) processes. In this study, N2O production from denitrifying fluidized bed bioreactors (DFBBR) was reduced using calcium (Ca2+) dosage. The DFBBRs were operated on a synthetic municipal wastewater at four different calcium concentrations ranging from the typical municipal wastewater Ca2+ concentration (60 mg Ca2+/L) to 240 mg Ca2+/L at two different COD/N ratios. N2O emission rates, extracellular polymeric substances (EPS), water quality parameters, and microscopic images were monitored regularly in both phases. Calcium concentrations played a significant role in biofilm morphology with the detachment rates for R120Ca, R180Ca, and R240Ca 75% lower than for R60Ca, respectively. The N2O conversion rate at the typical municipal wastewater Ca2+ concentration (R60Ca) was about 0.53% of the influent nitrogen loading as compared with 0.34%, 0.42%, and 0.41% for R120Ca, R180Ca, and R240Ca, respectively corresponding to 21-36% reduction. Copyright © 2014 Elsevier Ltd. All rights reserved.

  19. Oxygen vibrations in the series Bi2Sr2Ca{_{n-1}}Cu{n}O{_{4+2 n+y}}

    NASA Astrophysics Data System (ADS)

    Faulques, E.; Dupouy, P.; Lefrant, S.

    1991-06-01

    We present a discussion of the oxygen vibrations in the Bi{2}Sr{2}Ca{n-1}Cu{n}O{4+2 n+y} high T_c superconductors with the aim of interpreting Raman spectra in the case of the non-symmorphic Amaa structure. Group theory shows that the oxygen atoms belonging to the central CuO{2} plane generate a Raman activity for the n=1,3 phases. Consequently, we propose a novel assignment for the lines of weak intensity at 297, 316 and 333 cm^{-1}. It is shown that the two components of the 460 cm^{-1} band may be consistent with the Amma structure. Spectra recorded in crossed polarization exhibit weak lines which could be assigned to B {1g} modes expected for the three phases. Nous présentons une discussion sur les vibrations des atomes d'oxygène dans la série des supraconducteurs Bi{2}Sr{2}Ca{n-1}Cu{n}O{4+2 n+y} dans le but d'interpréter les spectres Raman. L'analyse des modes normaux de vibration de la structure Amaa pour les phases n=1 ou 3 montre que les atomes d'oxygène du plan CuO{2} contenant les centres d'inversion donnent lieu à une activité Raman. En conséquence, nous proposons une nouvelle attribution pour les raies de faible intensité à 297, 316 et 333 cm^{-1}. Nous montrons que le dédoublement de la bande à 460 cm^{-1} pourrait être dû à la structure Amaa. Les spectres enregistrés en polarization croisée montrent de faibles bandes qui peuvent être attribuées aux modes B {1g} attendus pour les trois phases.

  20. Surface Nitrification: A Major Uncertainty in Marine N2O Emissions

    NASA Technical Reports Server (NTRS)

    Zamora, Lauren M.; Oschlies, Andreas

    2014-01-01

    The ocean is responsible for up to a third of total global nitrous oxide (N2O) emissions, but uncertainties in emission rates of this potent greenhouse gas are high (approaching 100%). Here we use a marine biogeochemical model to assess six major uncertainties in estimates of N2O production, thereby providing guidance in how future studies may most effectively reduce uncertainties in current and future marine N2O emissions. Potential surface N2O production from nitrification causes the largest uncertainty in N2O emissions (estimated up to approximately 1.6 Tg N/yr (sup -1) or 48% of modeled values), followed by the unknown oxygen concentration at which N2O production switches to N2O consumption (0.8 Tg N/yr (sup -1)or 24% of modeled values). Other uncertainties are minor, cumulatively changing regional emissions by less than 15%. If production of N2O by surface nitrification could be ruled out in future studies, uncertainties in marine N2O emissions would be halved.

  1. A kinetic study of the reactions FeO+ + O, Fe+.N2 + O, Fe+.O2 + O and FeO+ + CO: implications for sporadic E layers in the upper atmosphere.

    PubMed

    Woodcock, K R S; Vondrak, T; Meech, S R; Plane, J M C

    2006-04-21

    These gas-phase reactions were studied by pulsed laser ablation of an iron target to produce Fe(+) in a fast flow tube, with detection of the ions by quadrupole mass spectrometry. Fe(+).N(2) and Fe(+).O(2) were produced by injecting N(2) and O(2), respectively, into the flow tube. FeO(+) was produced from Fe(+) by addition of N(2)O, or by ligand-switching from Fe(+).N(2) following the addition of atomic O. The following rate coefficients were measured: k(FeO(+) + O --> Fe(+) + O(2), 186-294 K) = (3.2 +/- 1.5) x 10(-11); k(Fe(+).N(2) + O --> FeO(+)+ N(2), 294 K) = (4.6 +/- 2.5) x 10(-10); k(Fe(+).O(2) + O --> FeO(+) + O(2), 294 K) = (6.3 +/- 2.7) x 10(-11); and k(FeO(+) + CO --> Fe(+) + CO(2), 294 K) = (1.59 +/- 0.34) x 10(-10) cm(3) molecule(-1) s(-1), where the quoted uncertainties are a combination of the 1sigma standard errors in the kinetic data and the systematic experimental errors. The surprisingly slow reaction between FeO(+) and O is examined using ab initio quantum calculations of the relevant potential energy surfaces. The importance of this reaction for controlling the lifetime of sporadic E layers is then demonstrated using a model of the upper mesosphere and lower thermosphere.

  2. High-performance ultraviolet detection and visible-blind photodetector based on Cu{sub 2}O/ZnO nanorods with poly-(N-vinylcarbazole) intermediate layer

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Perng, Dung-Ching, E-mail: dcperng@ee.ncku.edu.tw; Center for Micro/Nano Science and Technology, National Cheng Kung University, One University Road, Tainan 701, Taiwan; Lin, Hsueh-Pin

    This study reports a high-performance hybrid ultraviolet (UV) photodetector with visible-blind sensitivity fabricated by inserting a poly-(N-vinylcarbazole) (PVK) intermediate layer between low-cost processed Cu{sub 2}O film and ZnO nanorods (NRs). The PVK layer acts as an electron-blocking/hole-transporting layer between the n-ZnO and p-Cu{sub 2}O films. The Cu{sub 2}O/PVK/ZnO NR photodetector exhibited a responsivity of 13.28 A/W at 360 nm, a high detectivity of 1.03 × 10{sup 13} Jones at a low bias of −0.1 V under a low UV light intensity of 24.9 μW/cm{sup 2}. The photo-to-dark current ratios of the photodetector with and without the PVK intermediate layer at a bias of −0.5 V are 1.34 × 10{supmore » 2} and 3.99, respectively. The UV-to-visible rejection ratios (R{sub 360 nm}/R{sub 450 nm}) are 350 and 1.735, respectively. Several features are demonstrated: (a) UV photo-generated holes at the ZnO NRs can effectively be transported through the PVK layer to the p-Cu{sub 2}O layer; (b) the insertion of a PVK buffer layer significantly minimizes the reverse-bias leakage current, which leads to a larger amplification of the photocurrent; and (c) the PVK buffer layer greatly improves the UV-to-visible responsivity ratio, allowing the device to achieve high UV detection sensitivity at a low bias voltage using a very low light intensity.« less

  3. Influence of immersion cycles during n-β-Bi2O3 sensitization on the photoelectrochemical behaviour of N-F-codoped TiO2 nanotubes

    NASA Astrophysics Data System (ADS)

    Hoyos, Lina J.; Rivera, Diego F.; Gualdrón-Reyes, Andrés F.; Ospina, Rogelio; Rodríguez-Pereira, Jhonatan; Ropero-Vega, Jose L.; Niño-Gómez, Martha E.

    2017-11-01

    Sensitization of TiO2 nanotube (TNT)-based photoanodes with narrow-band gap semiconductors is an important alternative to improving the photoelectrochemical properties of the material. However, the interaction between the sensitizer and TNT is not understood deeply enough to relate charge carrier transport into the composite photoanode with its photoactivity. In this contribution, we studied the photoelectrochemical behaviour of N-F-self codoped TiO2 nanotubes (N-F-TNTs) that were grown by anodization of titanium plates and sensitized with β-Bi2O3 by immersing the TNTs into a Bi2O3 sol solution by dip-coating. The number of immersion cycles was varied. The as-fabricated photoanodes were characterized by FESEM, GIXRD, DRS and XPS, while their photoelectrochemical and semiconducting properties were investigated by photovoltammetry, electrochemical impedance spectroscopy and Mott-Schottky analysis in 0.1 M HClO4. The photoelectrocatalytic activity of the composite photoanodes was evaluated for glycerol oxidation under acidic and alkaline conditions. The N-F-TNTs exhibit a well-oriented structure after β-Bi2O3 deposition. The presence of substitutions of both N and F, identified by XPS, indicates the self-doping of the TNTs during anodization. The visible-light harvesting of the N-F-TNT photoanode was enhanced after three -immersion cycles during β-Bi2O3 sensitization, establishing an adequate n-n heterojunction at the N-F-TNT/Bi2O3 interface. In addition, bismuth migration from the sensitizer to the TNT lattice was promoted during thermal treatment, forming Bi-N-F-tridoping of TNT (Bi-N-F-TNT). The suitable band alignment between TNT and β-Bi2O3 and incorporation of the Bi3+ energy levels into TiO2 facilitate charge carrier separation and electron transport throughout the cell. Nevertheless, increasing the number of immersion cycles over three creates an excess of Bi3+ species at the N-F-TNT/β-Bi2O3 interface, producing an energetic barrier that hinders electron

  4. Triaqua-1κO,2κ2 O-bis­(2,2′-bipyridine)-1κ2 N,N′;2κ2 N,N′-chlorido-1κCl-μ-terephthalato-1:2κ2 O 1:O 4-dicopper(II) nitrate monohydrate

    PubMed Central

    Liu, Yang; Feng, Yong-Lan; Kuang, Dai-Zhi

    2012-01-01

    In the binuclear title compound, [Cu2(C8H4O4)Cl(C10H8N2)2(H2O)3]NO3·H2O, the two crystallographically independent CuII ions have similar coordination environments. One of the CuII ions has a square-pyramidal arrangement, which is defined by a water mol­ecule occupying the apical position, with the equatorial ligators consisting of two N atoms from a 2,2′-bipyridine mol­ecule, one carboxyl­ate O atom from a terephthalate ligand and one O atom from a water mol­ecule. The other CuII ion has a similar coordination environment, except that the apical position is occupied by a chloride ligand instead of a water mol­ecule. An O—H⋯O and O—H⋯Cl hydrogen-bonded three-dimensional network is formed between the components. PMID:22719307

  5. Photooxidative desulfurization for diesel using Fe / N - TiO2 photocatalyst

    NASA Astrophysics Data System (ADS)

    Khan, Muhammad Saqib; Kait, Chong Fai; Mutalib, Mohd Ibrahim Abdul

    2014-10-01

    A series of N - TiO2 with different mol% N was synthesized via sol-gel method and characterized using thermal gravimetric analyzer and raman spectroscopy. 0.2 wt% Fe was incorporated onto the calcined (200°C) N - TiO2 followed by calcination at 200°C, 250°C and 300°C. Photooxidative desulfurization was conducted in the presence of 0.2wt% Fe / N - TiO2 with different mol% N with and without oxidant (H2O2). Oxidative desulfurization was only achieved when H2O2 was used while without H2O2 no major effect on the sulfur removal. 0.2Fe -30N - H2O2 photocatalysts showed best performance at all calcination temperatures as compared to other mol% N - H2O2 photocatalysts. 16.45% sulfur removal was achieved using photocatalysts calcined at 300 °C.

  6. The source of stratospheric NO and N2O

    NASA Technical Reports Server (NTRS)

    Slanger, T. G.

    1984-01-01

    The photodissociation of O3 was investigated as a possible sources of N2O production in the stratosphere. Photolysis was conducted at 1576 A to generate the excited O2 states that react with N2 to form N2O. At this wavelength, there is a quantum yield of two for prompt production of oygen atoms, which is a consequence of the existence of two photodissociative channels giving comparable yields. One of these channels gives O(D1) and O2(b1sigma(+)subg), with a quantum yield of 0.6, whereas the other results in fragmentation of the O3, with production of three ground state oxygen atoms. The O2(b) is generated with vibrational excitation, and there are comparable populations in levels O to 3. These observations are the first to show O2(b) production from any photodissociative process, and were made under conditions in which the kinetics of vibrationally excited O2(b) can be studied. It appears that O3 photodissociation at 1576 A is not a good system for generating the higher electronic states of O2; it is likely that better results will be obtained at 1930 A.

  7. (CaO)nIrO2 (n = 1, 2, 4) family: Chemical scissors effects of CaO on structural characteristics correlated to physical properties. Ab initio study

    NASA Astrophysics Data System (ADS)

    Matar, Samir F.; Etourneau, Jean

    2017-11-01

    Based on crystal chemistry analysis within Ca-Ir-O ternary, the generic (CaO)nIrO2 formula leading to CaIrO3 for n = 1, Ca2IrO4 for n = 2 and Ca4IrO6 for n = 4 actual chemical compounds show significant structural changes regarding the spatial arrangement of IrO6 octahedra whereby increasing amounts of CaO act as 'chemical scissor' decreasing the dimensionality of stacking octahedra from 3D (IrO2) to 0D (Ca4IrO6). This is accompanied by changes in the electronic structure investigated within density functional theory. Such changes are particularly exhibited by linear increase of Ir density of states at the Fermi level revealing increasing localization of d states with crystal field effects. Eventually only for Ca4IrO6 a magnetic instability occurs in non magnetic configuration. Spin polarized calculations lead to development of small magnitude but finite magnetization on Ir with M 0.50 μB totally polarized along minority spin channel ↓.

  8. Evolution of resistive switching mechanism through H2O2 sensing by using TaOx-based material in W/Al2O3/TaOx/TiN structure

    NASA Astrophysics Data System (ADS)

    Chakrabarti, Somsubhra; Panja, Rajeswar; Roy, Sourav; Roy, Anisha; Samanta, Subhranu; Dutta, Mrinmoy; Ginnaram, Sreekanth; Maikap, Siddheswar; Cheng, Hsin-Ming; Tsai, Ling-Na; Chang, Ya-Ling; Mahapatra, Rajat; Jana, Debanjan; Qiu, Jian-Tai; Yang, Jer-Ren

    2018-03-01

    Understanding of resistive switching mechanism through H2O2 sensing and improvement of switching characteristics by using TaOx-based material in W/Al2O3/TaOx/TiN structure have been reported for the first time. Existence of amorphous Al2O3/TaOx layer in the RRAM devices has been confirmed by transmission electron microscopy. By analyzing the oxidation states of Ta2+/Ta5+ for TaOx switching material and W0/W6+ for WOx layer at the W/TaOx interface through X-ray photoelectron spectroscopy and H2O2 sensing, the reduction-oxidation mechanism under Set/Reset occurs only in the TaOx layer for the W/Al2O3/TaOx/TiN structures. This leads to higher Schottky barrier height at the W/Al2O3 interface (0.54 eV vs. 0.46 eV), higher resistance ratio, and long program/erase endurance of >108 cycles with 100 ns pulse width at a low operation current of 30 μA. Stable retention of more than 104 s at 85 °C is also obtained. Using conduction mechanism and reduction-oxidation reaction, current-voltage characteristic has been simulated. Both TaOx and WOx membranes have high pH sensitivity values of 47.65 mV/pH and 49.25 mV/pH, respectively. Those membranes can also sense H2O2 with a low concentration of 1 nM in an electrolyte-insulator-semiconductor structure because of catalytic activity, while the Al2O3 membrane does not show sensing. The TaOx material in W/Al2O3/TaOx/TiN structure does not show only a path towards high dense, small size memory application with understanding of switching mechanism but also can be used for H2O2 sensors.

  9. Generating Breathable Air Through Dissociation of N2O

    NASA Technical Reports Server (NTRS)

    Zubrin, Robert; Frankie, Brian

    2006-01-01

    A nitrous oxide-based oxygen-supply system (NOBOSS) is an apparatus in which a breathable mixture comprising 2/3 volume parts of N2 and 1/3 volume part of O2 is generated through dissociation of N2O. The NOBOSS concept can be adapted to a variety of applications in which there are requirements for relatively compact, lightweight systems to supply breathable air. These could include air-supply systems for firefighters, divers, astronauts, and workers who must be protected against biological and chemical hazards. A NOBOSS stands in contrast to compressed-gas and cryogenic air-supply systems. Compressed-gas systems necessarily include massive tanks that can hold only relatively small amounts of gases. Alternatively, gases can be stored compactly in greater quantities and at low pressures when they are liquefied, but then cryogenic equipment is needed to maintain them in liquid form. Overcoming the disadvantages of both compressed-gas and cryogenic systems, the NOBOSS exploits the fact that N2O can be stored in liquid form at room temperature and moderate pressure. The mass of N2O that can be stored in a tank of a given mass is about 20 times the mass of compressed air that can be stored in a tank of equal mass. In a NOBOSS, N2O is exothermically dissociated to N2 and O2 in a main catalytic reactor. In order to ensure the dissociation of N2O to the maximum possible extent, the temperature of the reactor must be kept above 400 C. At the same time, to minimize concentrations of nitrogen oxides (which are toxic), it is necessary to keep the reactor temperature at or below 540 C. To keep the temperature within the required range throughout the reactor and, in particular, to prevent the formation of hot spots that would be generated by local concentrations of the exothermic dissociation reaction, the N2O is introduced into the reactor through an injector tube that features carefully spaced holes to distribute the input flow of N2O widely throughout the reactor. A NOBOSS

  10. Optimization of photoelectrochemical performance in Pt-modified p-Cu2O/n-Cu2O nanocomposite

    NASA Astrophysics Data System (ADS)

    Wang, Yichen; Lou, Zirui; Niu, Wenzhe; Ye, Zhizhen; Zhu, Liping

    2018-04-01

    As it is expected to be one of the most promising materials for utilizing solar energy, Cu2O has attracted considerable attention with respect to the achievement of solar energy conversion. Until now, the photocurrent densities of all planar structure of the Cu2O photocathode have not even come close to the theoretical value of -14.7 mA cm-2 due to the incompatible light absorption and charge carrier diffusion lengths. Here, we have fabricated p-n Cu2O homojunction nanocomposite by multiple steps of electrochemical deposition processing with the optimization of deposition periods. The p-Cu2O/n-Cu2O nanocomposite fabricated by optimized pH (4.9) and deposition time (4 min) exhibited double the photocurrent density of that of the bare p-Cu2O photocathode. And the highest photocurrent density of nanostructured p-n Cu2O nanorod homojunction photocathode with a p-Cu2O blocking layer reached -10.0 mA cm-2 at 0 V versus the reversible hydrogen electrode under simulated AM 1.5G illumination (100 mW cm-2).

  11. A weak-light-responsive TiO2/g-C3N4 composite film: photocatalytic activity under low-intensity light irradiation.

    PubMed

    Wang, Peifang; Guo, Xiang; Rao, Lei; Wang, Chao; Guo, Yong; Zhang, Lixin

    2018-05-10

    A TiO 2 /g-C 3 N 4 composite photocatalytic film was prepared by in situ synthesis method and its photocatalytic capability under weak-visible-light condition was studied. The co-precursor with different ratio of melamine and TiO 2 sol-gel precursor were treated using ultrasonic mixing, physical deposition, and co-sintering method to form the smooth, white-yellow, and compact TiO 2 /g-C 3 N 4 composite films. The prepared TiO 2 /g-C 3 N 4 materials were characterized by SEM, TEM, EDS, XRD, BET, VBXPS, and UV-vis diffuse reflectance spectra. The results of composite showed that TiO 2 and g-C 3 N 4 have close interfacial connections which are favorable to charge transfer between these two semiconductors with suitable band structure, g-C 3 N 4 retard the anatase-to-rutile phase transition of TiO 2 significantly, the specific surface area were increased with g-C 3 N 4 ratio raised. Under weak-light irradiation, composite films photocatalytic experiments exhibited RhB removal efficiency approaching 90% after three recycles. Powders suspension degradation experiments revealed the removal efficiency of TiO 2 /g-C 3 N 4 (90.8%) was higher than pure TiO 2 (52.1%) and slightly lower than pure g-C 3 N 4 (96.6%). By control experiment, the enhanced photocatalysis is ascribed to the combination of TiO 2 and g-C 3 N 4 , which not only produced thin films with greater stability but also formed heterojunctions that can be favorable to charge transfer between these two semiconductors with suitable band structure. This study presents the potential application of photocatalytic film in the wastewater treatment under weak-light situation.

  12. Soil Nitrification and N2O Production: the connection with N concentration and Soil Water Content

    NASA Astrophysics Data System (ADS)

    Zhu-Barker, X.; Horwath, W. R.

    2016-12-01

    The development of mitigation strategies to reduce nitrous oxide (N2O) emission from soils is dependent on explicating the biophysical factors affecting different N2O production pathways. Ammonia oxidation and heterotrophic denitrification are the main pathways of N2O production, depending on soil conditions such as soil moisture content, oxygen (O2) content and N substrate. Many researchers have reported that N2O production increased as substrate concentration and soil moisture content increased. However, less understood is how N fertilizer concentration and moisture content interact to affect N2O production pathways. To investigate interaction and its effect on O2 consumption, we incubated three agricultural soils (clay, sandy loam, and peat) with different concentrations of (NH4)2SO4 (0-1000 µg N g-1) under 50 %, 75%, and 100% of water holding capacity. All treatments received 15N -KNO3 to bring the concentrations of NO3-_N in soils to 50 mg kg-1 soil and the NO3- pool to an enrichment of 10 atom% 15N. In all soils, the total amount of O2 consumption and N2O production increased as soil ammonical N concentration increased. The increased soil moisture significantly promoted N2O production in sandy loam and clay loam soils, compared to the peat soil. These results indicate that N2O production increased as substrate concentration increased likely due to the onset of O2 limitation caused by ammonia oxidation.

  13. OH-LIF measurement of H2/O2/N2 flames in a micro flow reactor with a controlled temperature profile

    NASA Astrophysics Data System (ADS)

    Shimizu, T.; Nakamura, H.; Tezuka, T.; Hasegawa, S.; Maruta, K.

    2014-11-01

    This paper presents combustion and ignition characteristic of H2/O2/N2 flames in a micro flow reactor with a controlled temperature profile. OH-LIF measurement was conducted to capture flame images. Flame responses were investigated for variable inlet flow velocity, U, and equivalence ratio, phi. Three kinds of flame responses were experimentally observed for the inlet flow velocities: stable flat flames (normal flames) in the high inlet flow velocity regime; unstable flames called Flames with Repetitive Extinction and Ignition (FREI) in the intermediate flow velocity regime; and stable weak flames in the low flow velocity regime, at phi = 0.6, 1.0 and 1.2. On the other hand, weak flame was not observed at phi = 3.0 by OH-LIF measurement. Computational OH mole fractions showed lower level at the rich conditions than those at stoichiometric and lean conditions. To examine this response of OH signal to equivalence ratio, rate of production analysis was conducted and four kinds of major contributed reaction for OH production: R3(O + H2 <=> H + OH); R38(H + O2 <=> O + OH); R46(H + HO2 <=> 2OH); and R86(2OH <=> O + H2O), were found. Three reactions among them, R3, R38 and R46, did not showed significant difference in rate of OH production for different equivalence ratios. On the other hand, rate of OH production from R86 at phi = 3.0 was extremely lower than those at phi = 0.6 and 1.0. Therefore, R86 was considered to be a key reaction for the reduction of the OH production at phi = 3.0.

  14. Method for synthesizing N.sub.2 O.sub.5

    DOEpatents

    McGuire, Raymond R.; Coon, Clifford L.; Harrar, Jackson E.; Pearson, Richard K.

    1985-01-01

    A method and apparatus for electrochemically synthesizing N.sub.2 O.sub.5 includes oxidizing a solution of N.sub.2 O.sub.4 /HNO.sub.3 at an anode, while maintaining a controlled potential between the N.sub.2 O.sub.4 /HNO.sub.3 solution and the anode. A potential of about 1.35 to 2.0 V vs. SCE is preferred, while a potential of about 1.80 V vs. SCE is most preferred. Thereafter, the N.sub.2 O.sub.5 is reacted with either 1.5-diacetyl-3,7-dinitro-1,3,5,7-tetraazacyclooctane (DADN) or 1,3,5,7-tetraacetyl-1,3,5,7-tetraazacyclooctane (TAT) to form cyclotetramethylenetetraamine (HMX).

  15. Aqua[bis(pyrimidin-2-yl-kappa N)amine](carbonato-kappa 2O,O')copper(II) dihydrate.

    PubMed

    van Albada, Gerard A; Mutikainen, Ilpo; Turpeinen, Urho; Reedijk, Jan

    2002-03-01

    The title mononuclear complex, [Cu(CO(3))(C(8)H(7)N(5))(H(2)O)] x 2H(2)O, was obtained by fixation of CO(2) by a mixture of copper(II) tetrafluoroborate and the ligand bis(pyrimidin-2-yl)amine in ethanol/water. The Cu(II) ion of the complex has a distorted square-pyramidal environment, with a basal plane formed by two N atoms of the ligand and two chelating O atoms of the carbonate group, while the apical position is occupied by the O atom of the coordinating water molecule. In the solid state, hydrogen-bonding interactions are dominant, the most unusual being the Watson-Crick-type coplanar ligand pairing through two N--H...N bonds. Lattice water molecules also participate in hydrogen bonding.

  16. Oceanic N2O emissions in the 21st century

    NASA Astrophysics Data System (ADS)

    Martinez-Rey, J.; Bopp, L.; Gehlen, M.; Tagliabue, A.; Gruber, N.

    2014-12-01

    The ocean is a substantial source of nitrous oxide (N2O) to the atmosphere, but little is known on how this flux might change in the future. Here, we investigate the potential evolution of marine N2O emissions in the 21st century in response to anthropogenic climate change using the global ocean biogeochemical model NEMO-PISCES. We implemented two different parameterizations of N2O production, which differ primarily at low oxygen (O2) conditions. When forced with output from a climate model simulation run under the business-as-usual high CO2 concentration scenario (RCP8.5), our simulations suggest a decrease of 4 to 12% in N2O emissions from 2005 to 2100, i.e., a reduction from 4.03/3.71 to 3.54/3.56 Tg N yr-1 depending on the parameterization. The emissions decrease strongly in the western basins of the Pacific and Atlantic oceans, while they tend to increase above the Oxygen Minimum Zones (OMZs), i.e., in the Eastern Tropical Pacific and in the northern Indian Ocean. The reduction in N2O emissions is caused on the one hand by weakened nitrification as a consequence of reduced primary and export production, and on the other hand by stronger vertical stratification, which reduces the transport of N2O from the ocean interior to the ocean surface. The higher emissions over the OMZ are linked to an expansion of these zones under global warming, which leads to increased N2O production associated primarily with denitrification. From the perspective of a global climate system, the averaged feedback strength associated with the projected decrease in oceanic N2O emissions amounts to around -0.009 W m-2 K-1, which is comparable to the potential increase from terrestrial N2O sources. However, the assesment for a compensation between the terrestrial and marine feedbacks calls for an improved representation of N2O production terms in fully coupled next generation of Earth System Models.

  17. Retrievals of heavy ozone with MIPAS

    NASA Astrophysics Data System (ADS)

    Jonkheid, Bastiaan; Röckmann, Thomas; Glatthor, Norbert; Janssen, Christof; Stiller, Gabriele; von Clarmann, Thomas

    2016-12-01

    A method for retrieval of 18O-substituted isotopomers of O3 in the stratosphere with the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) is presented. Using a smoothing regularisation constraint, volume mixing ratio profiles are retrieved for the main isotopologue and the symmetric and asymmetric isotopomers of singly substituted O3. For the retrieval of the heavy isotopologues, two microwindows in the MIPAS A band (685-970 cm-1) and six in the AB band (1020-1170 cm-1) are used. As the retrievals are performed as perturbations on the previously retrieved a priori profiles, the vertical resolution of the individual isotopomer profiles is very similar, which is important when calculating the ratio between two isotopomers. The performance of the method is evaluated using 1044 vertical profiles recorded with MIPAS on 1 July 2003. The mean values are separated by latitude bands, along with estimates of their uncertainties. The asymmetric isotopomer shows a mean enrichment of ˜ 8 %, with a vertical profile that increases up to 33 km and decreases at higher altitudes. This decrease with altitude is a robust result that does not depend on retrieval settings, and it has not been reported clearly in previously published datasets. The symmetric isotopomer is considerably less enriched, with mean values around 3 % and with a large spread. In individual retrievals the uncertainty of the enrichment is dominated by the measurement noise (2-4 %), which can be reduced by averaging multiple retrievals; systematic uncertainties linked to the retrieval are generally small at ˜ 0.5 %, but this is likely underestimated because the uncertainties in key spectroscopic parameters are unknown. The variabilities in the retrieval results are largest for the Southern Hemisphere.

  18. New insights into the column CH2O/NO2 ratio as an indicator of near-surface ozone sensitivity

    NASA Astrophysics Data System (ADS)

    Schroeder, Jason R.; Crawford, James H.; Fried, Alan; Walega, James; Weinheimer, Andrew; Wisthaler, Armin; Müller, Markus; Mikoviny, Tomas; Chen, Gao; Shook, Michael; Blake, Donald R.; Tonnesen, Gail S.

    2017-08-01

    Satellite-based measurements of the column CH2O/NO2 ratio have previously been used to estimate near-surface ozone (O3) sensitivity (i.e., NOx or VOC limited), and the forthcoming launch of air quality-focused geostationary satellites provides a catalyst for reevaluating the ability of satellite-measured CH2O/NO2 to be used in this manner. In this study, we use a 0-D photochemical box model to evaluate O3 sensitivity and find that the relative rate of radical termination from radical-radical interactions to radical-NOx interactions (referred to as LROx/LNOx) provides a good indicator of maximum O3 production along NOx ridgelines. Using airborne measurements from NASA's Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relative to Air Quality (DISCOVER-AQ) deployments in Colorado, Maryland, and Houston, we show that in situ measurements of CH2O/NO2 can be used to indicate O3 sensitivity, but there is an important "transition/ambiguous" range whereby CH2O/NO2 fails to categorize O3 sensitivity, and the range and span of this transition/ambiguous range varies regionally. Then, we apply these findings to aircraft-derived column density measurements from DISCOVER-AQ and find that inhomogeneities in vertical mixing in the lower troposphere further degrades the ability of column CH2O/NO2 to indicate near-surface O3 sensitivity (i.e., the transition/ambiguous range is much larger than indicated by in situ data alone), and we hypothesize that the global transition/ambiguous range is sufficiently large to make the column CH2O/NO2 ratio unuseful for classifying near-surface O3 sensitivity. Lastly, we present a case study from DISCOVER-AQ-Houston that suggests that O3 sensitivity on exceedance days may be substantially different than on nonexceedance days (which may be observable from space) and explore the diurnal evolution of O3 sensitivity, O3 production, and the column CH2O/NO2 ratio. The results of these studies suggest that

  19. Effects of N2-O2 and CO2-O2 tensions on growth of fungi isolated from damaged flue-cured tobacco.

    PubMed

    Yang, H; Lucas, G B

    1970-02-01

    Ten fungi, Aspergillus niger, A. flavus, A. ochraceus, A. ruber, A. repens, A. amstelodami, Alternaria tenuis, Penicillium brevi-compactum, Cladosporium herbarum, and Chaetomium dolicotrichum, were isolated from moldy flue-cured tobacco and grown in various mixtures of N(2)-O(2) or CO(2)-O(2). A 1 to 5% concentration of O(2) in an N(2) atmosphere caused the greatest change in growth of the nine species, and a 10 to 20% concentration of O(2) for A. flavus. All species, except A. amstelodami and A. ruber, grew faster in air than in mixtures containing 10% O(2). High O(2) concentrations generally inhibited furrow production in the mycelial mats. In an atmosphere of 5 to 40% O(2) in the N(2) atmosphere, furrows formed in mycelial mats between 5 and 40% O(2) in the species except for A. ruber, A. repens, and A. amstelodami, which produced none in any concentration. As O(2) decreased below 20%, spore production was progressively decreased, colony color faded to white, and cleistothecia formation was suppressed. In CO(2)-O(2) mixtures radial growth of all species increased with each quantitative decrease of CO(2). All species except A. niger grew faster in air than in 10% CO(2). In contrast to N(2)-O(2) mixtures, the fungi formed furrows, sporulation and cleistothecial formation were suppressed, and colony color changed to white in higher O(2) concentrations.

  20. Infrared spectroscopic and theoretical study of the HC2n+1O+ (n = 2-5) cations

    NASA Astrophysics Data System (ADS)

    Jin, Jiaye; Li, Wei; Liu, Yuhong; Wang, Guanjun; Zhou, Mingfei

    2017-06-01

    The carbon chain cations, HC2n+1O+ (n = 2-5), are produced via pulsed laser vaporization of a graphite target in supersonic expansions containing carbon monoxide and hydrogen. The infrared spectra are measured via mass-selected infrared photodissociation spectroscopy of the CO "tagged" [HC2n+1O.CO]+ cation complexes in the 1600-3500 cm-1 region. The geometries and electronic ground states of these cation complexes are determined by their infrared spectra compared to the predications of theoretical calculations. All of the HC2n+1O+ (n = 2-5) core cations are characterized to be linear carbon chain derivatives terminated by hydrogen and oxygen, which have the closed-shell singlet ground states with polyyne-like carbon chain structures.

  1. 2'-O-[2-[2-(N,N-Dimethylamino)ethoxy]ethyl] Modified Antisense Oligonucleotides: Symbiosis of Charge Interaction Factors and Stereoelectronic Effects

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Prhavc, M.; Prakash, T.P.; Minasov, G.

    Oligonucleotides with a novel, 2'-O-[2-[2-(N,N-dimethylamino)ethoxy]ethyl] (2'-O-DMAEOE) modification have been synthesized. This modification, a cationic analogue of the 2'-O-(2-methoxyethyl) (2'-O-MOE) modification, exhibits high binding affinity to target RNA (but not to DNA) and exceptional resistance to nuclease degradation. Analysis of the crystal structure of a self-complementary oligonucleotide containing a single 2'-O-DMAEOE modification explains the importance of charge factors and gauche effects on the observed antisense properties. 2'-O-DMAEOE modified oligonucleotides are ideal candidates for antisense drugs.

  2. Toxic effect of Cr(VI) in presence of n-TiO2 and n-Al2O3 particles towards freshwater microalgae.

    PubMed

    Dalai, Swayamprava; Pakrashi, Sunandan; Bhuvaneshwari, M; Iswarya, V; Chandrasekaran, N; Mukherjee, Amitava

    2014-01-01

    The reactivity and toxicity of the soluble toxicants in the presence of the engineered nanomaterials is not well explored. In this study, the probable effects of TiO2 and Al2O3 nanoparticles (n-TiO2, n-Al2O3) on the toxicity of Cr(VI) were assessed with the dominant freshwater algae, Scenedesmus obliquus, in a low range of exposure concentrations (0.05, 0.5 and 1μg/mL). In the presence of 0.05μg/mL n-TiO2, the toxicity of Cr(VI) decreased considerably, which was presumably due to the Cr(VI) adsorption on the nanoparticle surface leading to its aggregation and precipitation. The elevated n-TiO2 concentrations (0.5 and 1μg/mL) did not significantly influence Cr(VI) bio-availability, and a dose dependent toxicity of Cr(VI) was observed. On the other hand, n-Al2O3 did not have any significant effect on the Cr(VI) toxicity. The microscopic observations presented additional information on the morphological changes of the algal cells in the presence of the binary toxicants. The generation of reactive oxygen species (ROS) suggested contribution of oxidative stress on toxicity and LDH release confirmed membrane permeability of algal cells upon stress. Copyright © 2013 Elsevier B.V. All rights reserved.

  3. Removal of NO in NO/N2, NO/N2/O2, NO/CH4/N2, and NO/CH4/O2/N2 systems by flowing microwave discharges.

    PubMed

    Hueso, José L; Gonzalez-Elipe, Agustín R; Cotrino, José; Caballero, Alfonso

    2007-02-15

    In this paper, continuing previous work, we report on experiments carried out to investigate the removal of NO from simulated flue gas in nonthermal plasmas. The plasma-induced decomposition of small concentrations of NO in N2 used as the carrier gas and O2 and CH4 as minority components has been studied in a surface wave discharge induced with a surfatron launcher. The reaction products and efficiency have been monitored by mass spectrometry as a function of the composition of the mixture. NO is effectively decomposed into N2 and O2 even in the presence of O2, provided always that enough CH4 is also present in the mixture. Other majority products of the plasma reactions under these conditions are NH3, CO, and H2. In the absence of O2, decomposition of NO also occurs, although in that case HCN accompanies the other reaction products as a majority component. The plasma for the different reaction mixtures has been characterized by optical emission spectroscopy. Intermediate excited species of NO*, C*, CN*, NH*, and CH* have been monitored depending on the gas mixture. The type of species detected and their evolution with the gas composition are in agreement with the reaction products detected in each case. The observations by mass spectrometry and optical emission spectroscopy are in agreement with the kinetic reaction models available in literature for simple plasma reactions in simple reaction mixtures.

  4. Threshold voltage tuning in AlGaN/GaN HFETs with p-type Cu2O gate synthesized by magnetron reactive sputtering

    NASA Astrophysics Data System (ADS)

    Wang, Lei; Li, Liuan; Xie, Tian; Wang, Xinzhi; Liu, Xinke; Ao, Jin-Ping

    2018-04-01

    In present study, copper oxide films were prepared at different sputtering powers (10-100 W) using magnetron reactive sputtering. The crystalline structure, surface morphologies, composition, and optical band gap of the as-grown films are dependent on sputtering power. As the sputtering power decreasing from 100 to 10 W, the composition of films changed from CuO to quasi Cu2O domination. Moreover, when the sputtering power is 10 W, a relative high hole carrier density and high-surface-quality quasi Cu2O thin film can be achieved. AlGaN/GaN HFETs were fabricated with the optimized p-type quasi Cu2O film as gate electrode, the threshold voltage of the device shows a 0.55 V positive shift, meanwhile, a lower gate leakage current, a higher ON/OFF drain current ratio of ∼108, a higher electron mobility (1465 cm2/Vs), and a lower subthreshold slope of 74 mV/dec are also achieved, compared with the typical Ni/Au-gated HFETs. Therefore, Cu2O have a great potential to develop high performance p-type gate AlGaN/GaN HFETs.

  5. Diagnosing ozone recovery using the O3-N2O relationship

    NASA Astrophysics Data System (ADS)

    Butler, A. H.; Gao, R. S.; Maycock, A.; Portmann, R. W.; Thornberry, T. D.; Rosenlof, K. H.; Fahey, D. W.

    2016-12-01

    The ubiquitous compact correlation between collocated values of stratospheric ozone (O3) and the tracer nitrous oxide (N2O) results from the stratospheric photochemical processes that produce ozone and destroy N2O combined with common transport and mixing processes. Changes in the correlation slope under certain circumstances reflect changes in the production and loss balance of ozone. This approach has been used extensively to diagnose and quantify ozone loss in polar spring. Using a coupled atmosphere-ocean model with interactive chemistry (CESM/WACCM), we show that this relationship can be used to diagnose ozone recovery in the lower extratropical stratosphere. We then consider in situ measurements of O3 and N2O from ATTREX, GloPac, and HIPPO as well as satellite measurements from ACE and Aura MLS to consider whether ozone recovery can be detected in observations during the period 2004-2016.

  6. Catalytic performance of V2O5-MoO3/γ-Al2O3 catalysts for partial oxidation of n-hexane1

    NASA Astrophysics Data System (ADS)

    Mahmoudian, R.; Khodadadi, Z.; Mahdavi, Vahid; Salehi, Mohammed

    2016-01-01

    In the current study, a series of V2O5-MoO3 catalyst supported on γ-Al2O3 with various V2O5 and MoO3 loadings was prepared by wet impregnation technique. The characterization of prepared catalysts includes BET surface area, powder X-ray diffraction (XRD), and oxygen chemisorptions. The partial oxidation of n-hexane by air over V2O5-MoO3/γ-Al2O3 catalysts was carried out under flow condition in a fixed bed glass reactor. The effect of V2O5 loading, temperature, MoO3 loading, and n-hexane LHSV on the n-hexane conversion and the product selectivity were investigated. The partial oxygenated products of n-hexane oxidation were ethanol, acetic anhydride, acetic acid, and acetaldehyde. The 10% V2O5-1%MoO3/γ-Al2O3 was found in most active and selective catalyst during partial oxidation of n-hexane. The results indicated that by increasing the temperature, the n-hexane conversion increases as well, although the selectivity of the products passes through a maximum by increasing the temperature.

  7. Measurements of the O+ plus N2 and O+ plus O2 reaction rates from 300 to 900 K

    NASA Technical Reports Server (NTRS)

    Chen, A.; Johnsen, R.; Biondi, M. A.

    1977-01-01

    Rate coefficients for the O(+) + N2 atom transfer and O(+) + O2 charge transfer reactions are determined at thermal energies between 300 K and 900 K difference in a heated drift tube mass spectrometer apparatus. At 300 K the values K(O(+) + N2) = (1.2 plus or minus 0.1) x 10 to the negative 12 power cubic cm/sec and k(O(+) + O2) = (2.1 plus or minus 0.2) x 10 to the negative 11 power cubic cm/sec were obtained, with a 50% difference decrease in the reaction rates upon heating to 700 K. These results are in good agreement with heated flowing afterglow results, but the O(+) + O2 thermal rate coefficients are systematically lower than equivalent Maxwellian rates inferred by conversion of nonthermal drift tube and flow drift data.

  8. A simplified calculation procedure for mass isotopomer distribution analysis (MIDA) based on multiple linear regression.

    PubMed

    Fernández-Fernández, Mario; Rodríguez-González, Pablo; García Alonso, J Ignacio

    2016-10-01

    We have developed a novel, rapid and easy calculation procedure for Mass Isotopomer Distribution Analysis based on multiple linear regression which allows the simultaneous calculation of the precursor pool enrichment and the fraction of newly synthesized labelled proteins (fractional synthesis) using linear algebra. To test this approach, we used the peptide RGGGLK as a model tryptic peptide containing three subunits of glycine. We selected glycine labelled in two 13 C atoms ( 13 C 2 -glycine) as labelled amino acid to demonstrate that spectral overlap is not a problem in the proposed methodology. The developed methodology was tested first in vitro by changing the precursor pool enrichment from 10 to 40% of 13 C 2 -glycine. Secondly, a simulated in vivo synthesis of proteins was designed by combining the natural abundance RGGGLK peptide and 10 or 20% 13 C 2 -glycine at 1 : 1, 1 : 3 and 3 : 1 ratios. Precursor pool enrichments and fractional synthesis values were calculated with satisfactory precision and accuracy using a simple spreadsheet. This novel approach can provide a relatively rapid and easy means to measure protein turnover based on stable isotope tracers. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

  9. Fabrication of high aspect ratio TiO{sub 2} and Al{sub 2}O{sub 3} nanogratings by atomic layer deposition

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Shkondin, Evgeniy, E-mail: eves@fotonik.dtu.dk; Takayama, Osamu; Lavrinenko, Andrei V.

    The authors report on the fabrication of TiO{sub 2} and Al{sub 2}O{sub 3} nanostructured gratings with an aspect ratio of up to 50. The gratings were made by a combination of atomic layer deposition (ALD) and dry etch techniques. The workflow included fabrication of a Si template using deep reactive ion etching followed by ALD of TiO{sub 2} or Al{sub 2}O{sub 3}. Then, the template was etched away using SF{sub 6} in an inductively coupled plasma tool, which resulted in the formation of isolated ALD coatings, thereby achieving high aspect ratio grating structures. SF{sub 6} plasma removes silicon selectively withoutmore » any observable influence on TiO{sub 2} or Al{sub 2}O{sub 3}, thus revealing high selectivity throughout the fabrication. Scanning electron microscopy was used to analyze every fabrication step. Due to nonreleased stress in the ALD coatings, the top parts of the gratings were observed to bend inward as the Si template was removed, thus resulting in a gradual change in the pitch value of the structures. The pitch on top of the gratings is 400 nm, and it gradually reduces to 200 nm at the bottom. The form of the bending can be reshaped by Ar{sup +} ion beam etching. The chemical purity of the ALD grown materials was analyzed by x-ray photoelectron spectroscopy. The approach presented opens the possibility to fabricate high quality optical metamaterials and functional nanostructures.« less

  10. Nitrogen removal from wastewater and bacterial diversity in activated sludge at different COD/N ratios and dissolved oxygen concentrations.

    PubMed

    Zielińska, Magdalena; Bernat, Katarzyna; Cydzik-Kwiatkowska, Agnieszka; Sobolewska, Joanna; Wojnowska-Baryła, Irena

    2012-01-01

    The impact of the organic carbon to nitrogen ratio (chemical oxygen demand (COD)/N) in wastewater and dissolved oxygen (DO) concentration on carbon and nitrogen removal efficiency, and total bacteria and ammonia-oxidizing bacteria (AOB) communities in activated sludge in constantly aerated sequencing batch reactors (SBRs) was determined. At DO of 0.5 and 1.5 mg O2/L during the aeration phase, the efficiency of ammonia oxidation exceeded 90%, with nitrates as the main product. Nitrification and denitrification achieved under the same operating conditions suggested the simultaneous course of these processes. The most effective nitrogen elimination (above 50%) was obtained at the COD/N ratio of 6.8 and DO of 0.5 mg O2/L. Total bacterial diversity was similar in all experimental series, however, for both COD/N ratios of 6.8 and 0.7, higher values were observed at DO of 0.5 mg O2/L. The diversity and abundance of AOB were higher in the reactors with the COD/N ratio of 0.7 in comparison with the reactors with the COD/N of 6.8. For both COD/N ratios applied, the AOB population was not affected by oxygen concentration. Amplicons with sequences indicating membership of the genus Nitrosospira were the determinants of variable technological conditions.

  11. When the Sun's Away, N2O5 Comes Out to Play: An Updated Analysis of Ambient N2O5 Heterogeneous Chemistry

    NASA Astrophysics Data System (ADS)

    McDuffie, E. E.; Brown, S. S.

    2017-12-01

    The heterogeneous chemistry of N2O5 impacts the budget of tropospheric oxidants, which directly controls air quality at Earth's surface. The reaction between gas-phase N2O5 and aerosol particles occurs largely at night, and is therefore more important during the less-intensively-studied winter season. Though N2O5-aerosol interactions are vital for the accurate understanding and simulation of tropospheric chemistry and air quality, many uncertainties persist in our understanding of how various environmental factors influence the reaction rate and probability. Quantitative and accurate evaluation of these factors directly improves the predictive capabilities of atmospheric models, used to inform mitigation strategies for wintertime air pollution. In an update to last year's presentation, The Wintertime Fate of N2O5: Observations and Box Model Analysis for the 2015 WINTER Aircraft Campaign, this presentation will focus on recent field results regarding new information about N2O5 heterogeneous chemistry and future research directions.

  12. Bis(2,3,5,6-tetra-2-pyridylpyrazine-κ3 N 2,N 1,N 6)iron(II) bis­(dicyanamidate) 4.5-hydrate

    PubMed Central

    Callejo, L.; De la Pinta, N.; Madariaga, G.; Fidalgo, M.L.; Cortés, R.

    2010-01-01

    In the title compound, [Fe(C24H16N6)2][N(CN)2]2·4.5H2O, the central iron(II) ion is hexa­coordinated by six N atoms of two tridentate 2,3,5,6-tetra-2-pyridylpyrazine (tppz) ligands. Two dicyanamide anions [dca or N(CN)2 −] act as counter-ions, and 4.5 water mol­ecules act as solvation agents. The structure contains isolated cationic iron(II)–tppz complexes and the final neutrality is obtained with the two dicyanamide anions. One of the dicyanamide anions and a water mol­ecule are disordered with an occupancy ratio of 0.614 (8):0.386 (8). O—H⋯O, O—H⋯N and C—H⋯O hydrogen bonds involving dca, water and tppz mol­ecules are observed. PMID:21580205

  13. Biochar reduces efficiency of nitrification inhibitor 3,4-dymethylpyrazole phospate (DMPP) mitigating N2O emissions.

    NASA Astrophysics Data System (ADS)

    Fuertes-Mendizábal, Teresa; Huérfano, Ximena; Menéndez, Sergio; González-Murua, Carmen; Begoña González-Moro, Mª; Ippolito, James; Kamann, Claudia; Wrage-Mönnig, Nicole; Borchard, Nils; Cayuela, Maria Luz; Spokas, Kurt; Sigua, Gilbert; Novak, Jeff; Estavillo, José Mª

    2017-04-01

    Nitrous oxide (N2O) is the strongest greenhouse gas associated with agricultural soils. Current agricultural practices, based on the use of N fertilizers, can lead to environmental N losses, with some losses occurring as N2O emissions. Among the strategies suggested by the Intergovernmental Panel on Climate Change to decrease N losses through agriculture is the utilization of nitrification inhibitors, such as DMPP (3,4-dimethylpyrazole phosphate). This compound inhibits nitrification, thus reducing N2O emissions. However, the efficiency of DMPP might be affected by soil amendments. One soil amendment is biochar, which typically increases soil C, can reduce N2O emissions, affect the retention of water, and alter the C and N cycle. Nevertheless, these effects are not uniformly observed across varying soil types, N fertilization schemes and biochar properties. Assuming that both DMPP and biochars with C/N > 30 ratios are presumably able to reduce soil N2O emissions, the aim of this study was to evaluate the synergic effect of a woody biochar applied in combination with DMPP on N2O emissions. For this purpose, a laboratory incubation study was conducted with a silt loam grassland soil and a biochar obtained from Pinus taeda at 500°C. The experimental design consisted of an arrangement including two biochar levels (0 and 2% (w/w)), three fertilization levels (unfertilized, fertilized and fertilized+DMPP) and two soil water content levels (40% and 80% of water filled pore space, WFPS), giving rise to 12 different individual treatments with four replications of each treatment. Soil N2O emissions were monitored over the incubation period (163 days). Results showed that DMPP reduced N2O emissions to levels comparable to the unfertilized controls. Biochar showed ability to mitigate N2O emissions only at the low soil water content (40% WFPS). However, when DMPP was applied to the biochar amended soil, a counteracting effect was observed, since the reduction in N2O emissions

  14. The natural greenhouse effect of atmospheric oxygen (O2) and nitrogen (N2)

    NASA Astrophysics Data System (ADS)

    Höpfner, M.; Milz, M.; Buehler, S.; Orphal, J.; Stiller, G.

    2012-05-01

    The effect of collision-induced absorption by molecular oxygen (O2) and nitrogen (N2) on the outgoing longwave radiation (OLR) of the Earth's atmosphere has been quantified. We have found that on global average under clear-sky conditions the OLR is reduced due to O2 by 0.11 Wm-2 and due to N2 by 0.17 Wm-2. Together this amounts to 15% of the OLR-reduction caused by CH4 at present atmospheric concentrations. Over Antarctica the combined effect of O2 and N2 increases on average to about 38% of CH4 with single values reaching up to 80%. This is explained by less interference of H2O spectral bands on the absorption features of O2 and N2 for dry atmospheric conditions.

  15. Combining two complementary micrometeorological methods to measure CH4 and N2O fluxes over pasture

    NASA Astrophysics Data System (ADS)

    Laubach, J.; Barthel, M.; Fraser, A.; Hunt, J. E.; Griffith, D. W. T.

    2015-09-01

    New Zealand's largest industrial sector is pastoral agriculture, giving rise to a large fraction of the country's emissions of methane (CH4) and nitrous oxide (N2O). We designed a system to continuously measure CH4 and N2O fluxes at the field scale on two adjacent pastures that differed with respect to management. At the core of this system was a closed-cell Fourier-transform infrared spectrometer (FTIR), measuring the mole fractions of CH4, N2O and carbon dioxide (CO2) at two heights at each site. In parallel, CO2 fluxes were measured using eddy-covariance instrumentation. We applied two different micrometeorological ratio methods to infer the CH4 and N2O fluxes from their respective mole fractions and the CO2 fluxes. The first is a variant of the flux-gradient method, where it is assumed that the turbulent diffusivities of CH4 and N2O equal that of CO2. This method was reliable when the CO2 mole-fraction difference between heights was at least 4 times greater than the FTIR's resolution of differences. For the second method, the temporal increases of mole fractions in the stable nocturnal boundary layer, which are correlated for concurrently-emitted gases, are used to infer the unknown fluxes of CH4 and N2O from the known flux of CO2. This method was sensitive to "contamination" from trace gas sources other than the pasture of interest and therefore required careful filtering. With both methods combined, estimates of mean daily CH4 and N2O fluxes were obtained for 60 % of days at one site and 77 % at the other. Both methods indicated both sites as net sources of CH4 and N2O. Mean emission rates for one year at the unfertilised, winter-grazed site were 8.2 (± 0.91) nmol CH4 m-2 s-1 and 0.40 (± 0.018) nmol N2O m-2 s-1. During the same year, mean emission rates at the irrigated, fertilised and rotationally-grazed site were 7.0 (± 0.89) nmol CH4 m-2 s-1 and 0.57 (± 0.019) nmol N2O m-2 s-1. At this site, the N2O emissions amounted to 1.19 (± 0.15) % of the

  16. Modulation of Protein Metabolism to Mitigate Nitrous Oxide (N2O) Emission from Excreta of Livestock.

    PubMed

    Zhao, Guangyong

    2017-01-01

    Dietary protein is the main source of the body needed protein for animals. A great number of domestic animals including cattle, sheep, goats, pigs and chicken and other species are raised in the world to supply meat, milk and eggs that contain high quality of protein for human consumption. Domestic animals consume a great amount of feeds and water and excrete a large amount of faeces and urine. The conversion rate of dietary nitrogen (N, mainly dietary protein) to product N in livestock is low and the amount of N excretion is high and the nitrogenous compounds in excreta can be used as materials for nitrous oxide (N2O) formation in the processes of nitrification and denitrification in storage of excreta. Hence livestock farms and grazing pastures are important sources of N2O. N2O is a potent greenhouse gas and the key factor that damages the ozonosphere of the earth. Therefore, it is urgent to reveal the dietary protein metabolism processes and the regulation mechanism, which will help to reduce N2O emission. The nutritional options to reduce N excretion from livestock and consequently N2O emission include feeding low N rations and supplementing essential amino acid (AA) such as lysine and methionine to balance the AA profile of rations for pigs and ruminants. Other options include regulating partition of N excretion from urine to faeces and urinary nitrogenous constituents by decreasing urea N and increasing hippuric acid in ruminants. Supplementing tannic acid in the ration of ruminants has the potential to decrease the ratio of urinary N/faecal N and regulate the urinary nitrogenous components of ruminants and possibly reduce N2O emission in storage of excreta. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

  17. Evaluation of new flux attribution methods for mapping N2O emissions at the landscape scale from EC measurements

    NASA Astrophysics Data System (ADS)

    Grossel, Agnes; Bureau, Jordan; Loubet, Benjamin; Laville, Patricia; Massad, Raia; Haas, Edwin; Butterbach-Bahl, Klaus; Guimbaud, Christophe; Hénault, Catherine

    2017-04-01

    The objective of this study was to develop and evaluate an attribution method based on a combination of Eddy Covariance (EC) and chamber measurements to map N2O emissions over a 3-km2 area of croplands and forests in France. During 2 months of spring 2015, N2O fluxes were measured (i) by EC at 15 m height and (ii) punctually with a mobile chamber at 16 places within 1-km of EC mast. The attribution method was based on coupling the EC measurements, information on footprints (Loubet et al., 20101) and emission ratios based on crops and fertilizations, calculated based on chamber measurements. The results were evaluated against an independent flux dataset measured by automatic chambers in a wheat field within the area. At the landscape scale, the method estimated a total emission of 114-271 kg N-N2O during the campaign. This new approach allowed estimating continuously N2O emission and better accounting for the spatial variability of N2O emission at the landscape scale.

  18. Combining two complementary micrometeorological methods to measure CH4 and N2O fluxes over pasture

    NASA Astrophysics Data System (ADS)

    Laubach, Johannes; Barthel, Matti; Fraser, Anitra; Hunt, John E.; Griffith, David W. T.

    2016-03-01

    New Zealand's largest industrial sector is pastoral agriculture, giving rise to a large fraction of the country's emissions of methane (CH4) and nitrous oxide (N2O). We designed a system to continuously measure CH4 and N2O fluxes at the field scale on two adjacent pastures that differed with respect to management. At the core of this system was a closed-cell Fourier transform infrared (FTIR) spectrometer, which measured the mole fractions of CH4, N2O and carbon dioxide (CO2) at two heights at each site. In parallel, CO2 fluxes were measured using eddy-covariance instrumentation. We applied two different micrometeorological ratio methods to infer the CH4 and N2O fluxes from their respective mole fractions and the CO2 fluxes. The first is a variant of the flux-gradient method, where it is assumed that the turbulent diffusivities of CH4 and N2O equal that of CO2. This method was reliable when the CO2 mole-fraction difference between heights was at least 4 times greater than the FTIR's resolution of differences. For the second method, the temporal increases of mole fractions in the stable nocturnal boundary layer, which are correlated for concurrently emitted gases, are used to infer the unknown fluxes of CH4 and N2O from the known flux of CO2. This method was sensitive to "contamination" from trace gas sources other than the pasture of interest and therefore required careful filtering. With both methods combined, estimates of mean daily CH4 and N2O fluxes were obtained for 56 % of days at one site and 73 % at the other. Both methods indicated both sites as net sources of CH4 and N2O. Mean emission rates for 1 year at the unfertilised, winter-grazed site were 8.9 (±0.79) nmol CH4 m-2 s-1 and 0.38 (±0.018) nmol N2O m-2 s-1. During the same year, mean emission rates at the irrigated, fertilised and rotationally grazed site were 8.9 (±0.79) nmol CH4 m-2 s-1 and 0.58 (±0.020) nmol N2O m-2 s-1. At this site, the N2O emissions amounted to 1.21 (±0.15) % of the nitrogen

  19. Structure of (Ga2O3)2(ZnO)13 and a unified description of the homologous series (Ga2O3)2(ZnO)(2n + 1).

    PubMed

    Michiue, Yuichi; Kimizuka, Noboru; Kanke, Yasushi; Mori, Takao

    2012-06-01

    The structure of (Ga(2)O(3))(2)(ZnO)(13) has been determined by a single-crystal X-ray diffraction technique. In the monoclinic structure of the space group C2/m with cell parameters a = 19.66 (4), b = 3.2487 (5), c = 27.31 (2) Å, and β = 105.9 (1)°, a unit cell is constructed by combining the halves of the unit cell of Ga(2)O(3)(ZnO)(6) and Ga(2)O(3)(ZnO)(7) in the homologous series Ga(2)O(3)(ZnO)(m). The homologous series (Ga(2)O(3))(2)(ZnO)(2n + 1) is derived and a unified description for structures in the series is presented using the (3+1)-dimensional superspace formalism. The phases are treated as compositely modulated structures consisting of two subsystems. One is constructed by metal ions and another is by O ions. In the (3 + 1)-dimensional model, displacive modulations of ions are described by the asymmetric zigzag function with large amplitudes, which was replaced by a combination of the sawtooth function in refinements. Similarities and differences between the two homologous series (Ga(2)O(3))(2)(ZnO)(2n + 1) and Ga(2)O(3)(ZnO)(m) are clarified in (3 + 1)-dimensional superspace. The validity of the (3 + 1)-dimensional model is confirmed by the refinements of (Ga(2)O(3))(2)(ZnO)(13), while a few complex phenomena in the real structure are taken into account by modifying the model.

  20. Isotopologue fractionation during N(2)O production by fungal denitrification.

    PubMed

    Sutka, Robin L; Adams, Gerard C; Ostrom, Nathaniel E; Ostrom, Peggy H

    2008-12-01

    Identifying the importance of fungi to nitrous oxide (N2O) production requires a non-intrusive method for differentiating between fungal and bacterial N2O production such as natural abundance stable isotopes. We compare the isotopologue composition of N2O produced during nitrite reduction by the fungal denitrifiers Fusarium oxysporum and Cylindrocarpon tonkinense with published data for N2O production during bacterial nitrification and denitrification. The fractionation factors for bulk nitrogen isotope values for fungal denitrification were in the range -74.7 to -6.6 per thousand. There was an inverse relationship between the absolute value of the fractionation factors and the reaction rate constant. We interpret this in terms of variation in the relative importance of the rate constants for diffusion and enzymatic reduction in controlling the net isotope effect for N2O production during fungal denitrification. Over the course of nitrite reduction, the delta(18)O values for N2O remained constant and did not exhibit a relationship with the concentration characteristic of an isotope effect. This probably reflects isotopic exchange with water. Similar to the delta(18)O data, the site preference (SP; the difference in delta(15)N between the central and outer N atoms in N2O) was unrelated to concentration during nitrite reduction and, therefore, has the potential to act as a conservative tracer of production from fungal denitrification. The SP values of N2O produced by F. oxysporum and C. tonkinense were 37.1 +/- 2.5 per thousand and 36.9 +/- 2.8 per thousand, respectively. These SP values are similar to those obtained in pure culture studies of bacterial nitrification but quite distinct from SP values for bacterial denitrification. The large magnitude of the bulk nitrogen isotope fractionation and the delta(18)O values associated with fungal denitrification are distinct from bacterial production pathways; thus multiple isotopologue data holds much promise for

  1. Quantification of nitrous oxide (N2O) emissions and soluble microbial product (SMP) production by a modified AOB-NOB-N2O-SMP model.

    PubMed

    Kim, MinJeong; Wu, Guangxue; Yoo, ChangKyoo

    2017-03-01

    A modified AOB-NOB-N 2 O-SMP model able to quantify nitrous oxide (N 2 O) emissions and soluble microbial product (SMP) production during wastewater treatment is proposed. The modified AOB-NOB-N 2 O-SMP model takes into account: (1) two-step nitrification by ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB), (2) N 2 O production by AOB denitrification under oxygen-limited conditions and (3) SMP production by microbial growth and endogenous respiration. Validity of the modified model is demonstrated by comparing the simulation results with experimental data from lab-scale sequencing batch reactors (SBRs). To reliably implement the modified model, a model calibration that adjusts model parameters to fit the model outputs to the experimental data is conducted. The results of this study showed that the modeling accuracy of the modified AOB-NOB-N 2 O-SMP model increases by 19.7% (NH 4 ), 51.0% (NO 2 ), 57.8% (N 2 O) and 16.7% (SMP) compared to the conventional model which does not consider the two-step nitrification and SMP production by microbial endogenous respiration. Copyright © 2016 Elsevier Ltd. All rights reserved.

  2. Acidic Peptizing Agent Effect on Anatase-Rutile Ratio and Photocatalytic Performance of TiO2 Nanoparticles

    NASA Astrophysics Data System (ADS)

    Mahmoud, Hatem A.; Narasimharao, Katabathini; Ali, Tarek T.; Khalil, Kamal M. S.

    2018-02-01

    TiO2 nanoparticles were synthesized from titanium isopropoxide by a simple peptization method using sulfuric, nitric, and acetic acids. The effect of peptizing acid on physicochemical and photocatalytic properties of TiO2 powders was studied. The structural properties of synthesized TiO2 powders were analyzed by using XRD, TEM, N2-physisorption, Raman, DR UV- vis, FTIR, and X-ray photoelectron spectroscopy techniques. The characterization results showed that acetic acid peptization facilitated the formation of pure anatase phase after thermal treatment at 500 °C; in contrast, nitric acid peptization led to a major rutile phase formation (67%). Interestingly, the sample peptized using sulfuric acid yielded 95% anatase and 5% rutile phases. The photocatalytic activity of synthesized TiO2 nanoparticles was evaluated for degradation of selected organic dyes (crystal violet, methylene blue, and p-nitrophenol) in aqueous solution. The results confirmed that the TiO2 sample peptized using nitric acid (with rutile and anatase phases in 3:1 ratio) offered the highest activity for degradation of organic dyes, although, TiO2 samples peptized using sulfuric acid and acetic acid possessed smaller particle size, higher band gap energy, and high surface area. Interestingly, TiO2 sample peptized with nitric acid possessed relatively high theoretical photocurrent density (0.545 mAcm-2) and pore diameter (150 Å), which are responsible for high electron-hole separation efficiency and diffusion and mass transportation of organic reactants during the photochemical degradation process. The superior activity of TiO2 sample peptized with nitric acid is due to the effective transfer of photogenerated electrons between rutile and anatase phases.

  3. N2O production by nitrifier denitrification in the Benguela Upwelling System

    NASA Astrophysics Data System (ADS)

    Frame, C. H.; Hou, L.; Lehmann, M. F.

    2014-12-01

    The Benguela upwelling system off the coast of southwestern Africa is an important zone of marine N2O production whose upwelling rates vary seasonally. Here we present N2O stable isotopic and isotopomeric data collected during a period of high upwelling (September 2013) and low upwelling (January 2014). During both periods, 15N-nitrite and 15N-ammonium tracer inucbation experiments were used to investigate N2O production by ammonia oxidizing microorganisms in the top 150m of the water column. N2O production from 15N-ammonium was not measurable during these incubations. However, we detected N2O production from 15N-nitrite, suggesting that nitrifier denitrification is a source of shallow N2O in this region. Furthermore, decreasing the pH of the incubation water enhanced the amount of N2O produced, suggesting that upwelling of CO2-rich/low-pH deep water may enhance N2O production in this region. Finally, we present our incubation data in the larger context of the N2O and nitrite isotopic and concentration profiles, with an eye toward comparing incubation-based N2O production rates with profile-based estimates.

  4. A novel amido-pyrophosphate Mn(II) chelate complex with the synthetic ligand O{P(O)[NHC(CH3)3]2}2 (L): [Mn(L)2{OC(H)N(CH3)2}2]Cl2·2H2O.

    PubMed

    Tarahhomi, Atekeh; Pourayoubi, Mehrdad; Fejfarová, Karla; Dušek, Michal

    2013-03-01

    The title complex, trans-bis(dimethylformamide-κO)bis{N,N'-N'',N'''-tetra-tert-butyl[oxybis(phosphonic diamide-κO)]}manganese(II) dichloride dihydrate, [Mn(C16H40N4O3P2)2(C3H7NO)2]Cl2·2H2O, is the first example of a bis-chelate amido-pyrophosphate (pyrophosphoramide) complex containing an O[P(O)(NH)2]2 fragment. Its asymmetric unit contains half of the complex dication, one chloride anion and one water molecule. The Mn(II) atom, located on an inversion centre, is octahedrally coordinated, with a slight elongation towards the monodentate dimethylformamide ligand. Structural features of the title complex, such as the P=O bond lengths and the planarity of the chelate ring, are compared with those of previously reported complexes with six-membered chelates involving the fragments C(O)NHP(O), (X)NP(O) [X = C(O), C(S), S(O)2 and P(O)] and O[P(O)(N)2]2. This analysis shows that the six-membered chelate rings are less puckered in pyrophosphoramide complexes containing a P(O)OP(O) skeleton, such as the title compound. The extended structure of the title complex involves a linear aggregate mediated by N-H...O and N-H...Cl hydrogen bonds, in which the chloride anion is an acceptor in two additional O-H...Cl hydrogen bonds.

  5. Diffusion Monte Carlo studies of MB-pol (H{sub 2}O){sub 2−6} and (D{sub 2}O){sub 2−6} clusters: Structures and binding energies

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Mallory, Joel D.; Mandelshtam, Vladimir A.

    2016-08-14

    We employ the diffusion Monte Carlo (DMC) method in conjunction with the recently developed, ab initio-based MB-pol potential energy surface to characterize the ground states of small (H{sub 2}O){sub 2−6} clusters and their deuterated isotopomers. Observables, other than the ground state energies, are computed using the descendant weighting approach. Among those are various spatial correlation functions and relative isomer fractions. Interestingly, the ground states of all clusters considered in this study, except for the dimer, are delocalized over at least two conformations that differ by the orientation of one or more water monomers with the relative isomer populations being sensitivemore » to the isotope substitution. Most remarkably, the ground state of the (H{sub 2}O){sub 6} hexamer is represented by four distinct cage structures, while that of (D{sub 2}O){sub 6} is dominated by the prism, i.e., the global minimum geometry, with a very small contribution from a prism-book geometry. In addition, for (H{sub 2}O){sub 6} and (D{sub 2}O){sub 6}, we performed DMC calculations to compute the ground states constrained to the cage and prism geometries. These calculations compared results for three different potentials, MB-pol, TTM3/F, and q-TIP4P/F.« less

  6. Ground-based remote sensing of HDO/H2O ratio profiles: introduction and validation of an innovative retrieval approach

    NASA Astrophysics Data System (ADS)

    Schneider, M.; Hase, F.; Blumenstock, T.

    2006-10-01

    We propose an innovative approach for analysing ground-based FTIR spectra which allows us to detect variabilities of lower and middle/upper tropospheric HDO/H2O ratios. We show that the proposed method is superior to common approaches. We estimate that lower tropospheric HDO/H2O ratios can be detected with a noise to signal ratio of 15% and middle/upper tropospheric ratios with a noise to signal ratio of 50%. The method requires the inversion to be performed on a logarithmic scale and to introduce an inter-species constraint. While common methods calculate the isotope ratio posterior to an independent, optimal estimation of the HDO and H2O profile, the proposed approach is an optimal estimator for the ratio itself. We apply the innovative approach to spectra measured continuously during 15 months and present, for the first time, an annual cycle of tropospheric HDO/H2O ratio profiles as detected by ground-based measurements. Outliers in the detected middle/upper tropospheric ratios are interpreted by backward trajectories.

  7. Ground-based remote sensing of HDO/H2O ratio profiles: introduction and validation of an innovative retrieval approach

    NASA Astrophysics Data System (ADS)

    Schneider, M.; Hase, F.; Blumenstock, T.

    2006-06-01

    We propose an innovative approach for analysing ground-based FTIR spectra which allows us to detect variabilities of lower and middle/upper tropospheric HDO/H2O ratios. We show that the proposed method is superior to common approaches. We estimate that lower tropospheric HDO/H2O ratios can be detected with a noise to signal ratio of 15% and middle/upper tropospheric ratios with a noise to signal ratio of 50%. The method requires the inversion to be performed on a logarithmic scale and to introduce an inter-species constraint. While common methods calculate the isotope ratio posterior to an independent, optimal estimation of the HDO and H2O profile, the proposed approach is an optimal estimator for the ratio itself. We apply the innovative approach to spectra measured continuously during 15 months and present, for the first time, an annual cycle of tropospheric HDO/H2O ratio profiles as detected by ground-based measurements. Outliers in the detected middle/upper tropospheric ratios are interpreted by backward trajectories.

  8. Effects of N2-O2 and CO2-O2 Tensions on Growth of Fungi Isolated from Damaged Flue-Cured Tobacco 1

    PubMed Central

    Yang, H.; Lucas, G. B.

    1970-01-01

    Ten fungi, Aspergillus niger, A. flavus, A. ochraceus, A. ruber, A. repens, A. amstelodami, Alternaria tenuis, Penicillium brevi-compactum, Cladosporium herbarum, and Chaetomium dolicotrichum, were isolated from moldy flue-cured tobacco and grown in various mixtures of N2-O2 or CO2-O2. A 1 to 5% concentration of O2 in an N2 atmosphere caused the greatest change in growth of the nine species, and a 10 to 20% concentration of O2 for A. flavus. All species, except A. amstelodami and A. ruber, grew faster in air than in mixtures containing 10% O2. High O2 concentrations generally inhibited furrow production in the mycelial mats. In an atmosphere of 5 to 40% O2 in the N2 atmosphere, furrows formed in mycelial mats between 5 and 40% O2 in the species except for A. ruber, A. repens, and A. amstelodami, which produced none in any concentration. As O2 decreased below 20%, spore production was progressively decreased, colony color faded to white, and cleistothecia formation was suppressed. In CO2-O2 mixtures radial growth of all species increased with each quantitative decrease of CO2. All species except A. niger grew faster in air than in 10% CO2. In contrast to N2-O2 mixtures, the fungi formed furrows, sporulation and cleistothecial formation were suppressed, and colony color changed to white in higher O2 concentrations. PMID:5461786

  9. A pure inorganic 1D chain based on {Mo8O28} clusters and Mn(II) ions: [Mn(H2O)2Mo8O28 ] n 6 n -

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaofen; Yan, Yonghong; Wu, Lizhou; Yu, Chengxin; Dong, Xinbo; Hu, Huaiming; Xue, Ganglin

    2016-01-01

    A new pure inorganic polymer, (NH4)6n[Mn(H2O)2Mo8O28)]n(H2O)2n(1), has been synthesized and characterized by elemental analyses, IR spectrum, UV-vis absorption spectra, TG-DSC and electrochemical studies. In 1, [Mo8O28]8- anions act as tetradentate ligands and are alternately linked by Mn(H2O)2 2 + ions into a one-dimensional chain structure. It is interesting that 1 represents the first example of pure inorganic-inorganic hybrid based on octamolybdate and transition metal ions. Moreover, it was indicated that 1 had definite catalytic activities on the probe reaction of benzyl alcohol oxidation to benzaldehyde with H2O2.

  10. Designed Synthesis of CeO2 Nanorods and Nanowires for Studying Toxicological Effects of High Aspect Ratio Nanomaterials

    PubMed Central

    Ji, Zhaoxia; Wang, Xiang; Zhang, Haiyuan; Lin, Sijie; Meng, Huan; Sun, Bingbing; George, Saji; Xia, Tian; Nel, André E.; Zink, Jeffrey I.

    2012-01-01

    While it has been shown that high aspect ratio nanomaterials like carbon nanotubes and TiO2 nanowires can induce toxicity by acting as fiber-like substances that damage the lysosome, it is not clear what the critical lengths and aspect ratios are that induce this type of toxicity. To answer this question, we synthesized a series of cerium oxide (CeO2) nanorods and nanowires with precisely controlled lengths and aspect ratios. Both phosphate and chloride ions were shown to play critical roles in obtaining these high aspect ratio nanostructures. High resolution TEM analysis shows that single crystalline CeO2 nanorods/nanowires were formed along the [211] direction by an “oriented attachment” mechanism, followed by Ostwald ripening. The successful creation of a comprehensive CeO2 nanorod/nanowire combinatorial library allows, for the first time, the systematic study of the effect of aspect ratio on lysosomal damage, cytoxicity and IL-1β production by the human myeloid cell line (THP-1). This in vitro toxicity study demonstrated that at lengths ≥200 nm and aspect ratios ≥ 22, CeO2 nanorods induced progressive cytotoxicity and pro-inflammatory effects. The relatively low “critical” length and aspect ratio were associated with small nanorod/nanowire diameters (6–10 nm), which facilitates the formation of stacking bundles due to strong van der Waals and dipole-dipole attractions. Our results suggest that both length and diameter components of aspect ratio should be considered when addressing the cytotoxic effects of long aspect ratio materials. PMID:22564147

  11. Overlap corrections for emissivity calculations of H2O-CO2-CO-N2 mixtures

    NASA Astrophysics Data System (ADS)

    Alberti, Michael; Weber, Roman; Mancini, Marco

    2018-01-01

    Calculations of total gas emissivities of gas mixtures containing several radiatively active species require corrections for band overlapping. In this paper, we generate such overlap correction charts for H2O-CO2-N2, H2O-CO-N2, and CO2-CO-N2 mixtures. These charts are applicable in the 0.1-40 bar total pressure range and in the 500 K-2500 K temperature range. For H2O-CO2-N2 mixtures, differences between our charts and Hottel's graphs as well as models of Leckner and Modak are highlighted and analyzed.

  12. Influence of aerosol chemical composition on N2O5 uptake: airborne regional measurements in northwestern Europe

    NASA Astrophysics Data System (ADS)

    Morgan, W. T.; Ouyang, B.; Allan, J. D.; Aruffo, E.; Di Carlo, P.; Kennedy, O. J.; Lowe, D.; Flynn, M. J.; Rosenberg, P. D.; Williams, P. I.; Jones, R.; McFiggans, G. B.; Coe, H.

    2015-01-01

    Aerosol chemical composition was found to influence nighttime atmospheric chemistry during a series of airborne measurements in northwestern Europe in summer conditions, which has implications for regional air quality and climate. The uptake of dinitrogen pentoxide, γ (N2O5), to particle surfaces was found to be modulated by the amount of water content and ammonium nitrate present in the aerosol. The conditions prevalent in this study suggest that the net uptake rate of N2O5 to atmospheric aerosols was relatively efficient compared to previous studies, with γ (N2O5) values in the range 0.01-0.03. This is likely a consequence of the elevated relative humidity in the region, which promotes greater aerosol water content. Increased nitrate concentrations relative to particulate water were found to suppress N2O5 uptake. The results presented here contrast with previous ambient studies of N2O5 uptake, which have generally taken place in low-nitrate environments in the USA. Comparison of the N2O5 uptake derived from the measurements with a parameterised scheme that is based on the ratio of particulate water to nitrate yielded reasonably good agreement in terms of the magnitude and variation in uptake, provided the effect of chloride was neglected. An additional suppression of the parameterised uptake is likely required to fully capture the variation in N2O5 uptake, which could be achieved via the known suppression by organic aerosol. However, existing parameterisations representing the suppression by organic aerosol were unable to fully represent the variation in N2O5 uptake. These results provide important ambient measurement constraint on our ability to predict N2O5 uptake in regional and global aerosol models. N2O5 uptake is a potentially important source of nitrate aerosol and a sink of the nitrate radical, which is the main nocturnal oxidant in the atmosphere. The results further highlight the importance of ammonium nitrate in northwestern Europe as a key component

  13. The series Bi2Sr2Ca(n-1) Cu(n)O(2n+4) (1 less than or equal to n less than or equal to 5): Phase stability and superconducting properties

    NASA Technical Reports Server (NTRS)

    Deguire, Mark R.; Bansal, Narottam P.; Farrell, David E.; Finan, Valerie; Kim, Cheol J.; Hills, Bethanie J.; Allen, Christopher J.

    1989-01-01

    Phase relations at 850 and 870 C, melting transitions in air, oxygen, and helium were studied for Bi(2.1)Sr(1.9) CuO6 and for the Bi2Sr2Ca(n-1) Cu(n)O(2n+4) for n = 1, 2, 3, 4, 5, and infinity (CaCuO2). Up to 870 C, the n = 2 composition resides in the compatibility tetrahedron bounded by Bi(2+x)(Sr,Ca)(3-y) Cu2O8, (Sr,Ca)14 Cu24O41, Ca2CuO3, and a Bi-Sr-Ca-O phase. The n is greater than or equal to 3 compositions reside in the compatibility tetrahedron Bi(2+x)(Sr,Ca)(3-y) Cu2O8 - (Sr,Ca)14 Cu24O41 - Ca2CuO3 - CuO up to 850 C. However, Bi(2+x)Sr(4-y) Cu3O10 forms for n is greater than or equal to 3 after extended heating at 870 C. Bi(2+x)Sr(2-y) CuO6 and Bi(2+x)(Sr,Ca)(3-y) Cu2O8 melt in air at 914 C and 895 C respectively. During melting, all of the compositions studied lose 1 to 2 percent by weight of oxygen from the reduction of copper. Bi(2+x)Sr(2-y) CuO6, Bi(2+n)(Sr,Ca)(3-y) Cu2O8, and Bi(2+x)(Sr,Ca)(4-y) Cu3O10 exhibit crystallographic alignment in a magnetic field, with the c-axes orienting parallel to the field.

  14. Influence of CYP2D6 and CYP2C19 genotypes on venlafaxine metabolic ratios and stereoselective metabolism in forensic autopsy cases.

    PubMed

    Karlsson, L; Zackrisson, A-L; Josefsson, M; Carlsson, B; Green, H; Kugelberg, F C

    2015-04-01

    We investigated whether polymorphisms in the CYP2D6 and CYP2C19 genes influence the metabolic ratios and enantiomeric S/R ratios of venlafaxine (VEN) and its metabolites O-desmethylvenlafaxine (ODV), N-desmethylvenlafaxine (NDV) and N,O-didesmethylvenlafaxine (DDV) in blood from forensic autopsy cases. In all, 94 postmortem cases found positive for VEN during toxicological screening were included. The CYP2D6 genotype was shown to significantly influence the ODV/VEN (P=0.003), DDV/NDV (P=0.010) and DDV/ODV (P=0.034) ratios. The DDV/ODV (P=0.013) and DDV/VEN (P=0.021) ratios were significantly influenced by the CYP2C19 genotype. The S/R ratios of VEN were significantly influenced by both CYP2D6 and CYP2C19 genotypes. CYP2D6 poor metabolizers (PMs) had lower S/R VEN ratios and CYP2C19 PMs had high S/R ratios of VEN in comparison. Our results show that the CYP2D6 genotype influences the O-demethylation whereas CYP2C19 influences the N-demethylation of VEN and its metabolites. In addition, we show a stereoselective metabolism where CYP2D6 favours the R-enantiomer whereas CYP2C19 favours the S-enantiomer.

  15. Evaluation of N-ratio in selecting patients for adjuvant chemoradiotherapy after d2-gastrectomy.

    PubMed

    Costa Junior, Wilson Luiz da; Coimbra, Felipe José Fernández; Batista, Thales Paulo; Ribeiro, Héber Salvador de Castro; Diniz, Alessandro Landskron

    2013-01-01

    Whether adjuvant chemoradiotherapy may contribute to improve survival outcomes after D2-gastrectomy remains controversial. To explore the clinical utility of N-Ratio in selecting gastric cancer patients for adjuvant chemoradiotherapy after D2-gastrectomy. A retrospective cohort study was carried out on gastric cancer patients who underwent D2-gastrectomy alone or D2-gastrectomy plus adjuvant chemoradiotherapy (INT-0116 protocol) at the Hospital A. C. Camargo from September 1998 to December 2008. Statistical analysis were performed using multiple conventional methods, such as c-statistic, adjusted Cox's regression and stratified survival analysis. Our analysis involved 128 patients. According to c-statistic, the N-Ratio (i.e., as a continuous variable) presented "area under ROC curve" (AUC) of 0.713, while the number of metastatic nodes presented AUC of 0.705. After categorization, the cut-offs provide by Marchet et al. displayed the highest discriminating power - AUC value of 0.702. This N-Ratio categorization was confirmed as an independent predictor of survival using multivariate analyses. There also was a trend of better survival by adding of adjuvant chemoradiotherapy only for patients with milder degrees of lymphatic spread - 5-year survival of 23.1% vs 66.9%, respectively (HR = 0.426, 95% CI 0.150-1.202; P = 0.092). This study confirms the N-Ratio as a tool to improve the lymph node metastasis staging in gastric cancer and suggests the cut-offs provided by Marchet et al. as the best way for its categorization after a D2-gastrectomy. In these settings, the N-Ratio appears a useful tool to select patients for adjuvant chemoradiotherapy, and the benefit of adding this type of adjuvancy to D2-gastrectomy is suggested to be limited to patients with milder degrees of lymphatic spread (i.e., NR2, 10%-25%).

  16. Increasing the availability of l-arginine and nitric oxide increases sensitivity of nitrous oxide (N2O)-insensitive inbred mice to N2O-induced antinociception.

    PubMed

    Chung, Eunhee; Ohgami, Yusuke; Quock, Raymond M

    2016-07-01

    Nitrous oxide (N2O)-induced antinociception in mice is dependent on the neuromodulator nitric oxide (NO). In contrast to C57BL/6J (B6) mice, DBA/2J (D2) mice fail to respond to N2O with a robust antinociceptive response or with an increase in brain nitric oxide synthase (NOS) enzyme activity, suggesting that failure of D2 mice to respond to N2O might result from a deficit of NO function. Therefore, it was of interest to determine whether increasing the availability of NO might increase sensitivity of D2 mice to N2O. Male D2 mice were pretreated with sub-antinociceptive intracerebroventricular doses of the NO donor 3-morpholinosydnoimine or the NO precursor l-arginine then assessed for responsiveness to N2O-induced antinociception using the acetic acid abdominal constriction test. Both pretreatments increased the antinociceptive responsiveness of D2 mice to N2O. These results indicate that the NOS enzyme in D2 mice is functional and that the deficit in NO function that obstructs sensitivity to N2O-induced antinociception may lie in availability or utilization of l-arginine. Copyright © 2016 Elsevier Inc. All rights reserved.

  17. In-Situ Denitrification and N2O Emission from Natural and Semi-natural Land Use Types in two UK Catchments

    NASA Astrophysics Data System (ADS)

    Sgouridis, F.; Ullah, S.

    2014-12-01

    Whilst data and understanding of the controls of denitrification process and the subsequent emission of N2O at microbial and plot scale exist, quantification of in situ annual denitrification rates at catchment scales is scarce due to methodological constraints in measuring in situ denitrification in large temporal and spatial scales. In situ denitrification (DNT) was measured monthly (April 2013 - October 2014) in organic (peat bog, heathland, acid grassland), forest (mixed and deciduous), and grassland (improved and semi-improved) land use types in the Ribble-Wyre and Conwy River catchments in the UK. A static chamber technique according to the 15N-Gas Flux method1 was employed for quantifying the fluxes of 15N-N2 and 15N-N2O gases after labelling the soil with 98 at% K15NO3- at tracer level amounts (10% of the ambient nitrate concentration) and sampling the chamber headspace at 0, 1, 2 and 20 hour intervals. The DNT rates ranged between 0 and 2.3 mg N m-2 h-1 and were significantly influenced by land use type (p<0.05). The annual denitrification rate of organic and forest soils (4 kg N ha-1 y-1) was 3 and 6 times less than that of semi-improved (12 kg N ha-1 y-1) and improved (23 kg N ha-1 y-1) grassland soils, respectively. The N2O emission, due to denitrification, followed a similar trend with lower fluxes from organic and higher from improved grassland soils (range: 0 - 0.04 mg N m-2 h-1), whilst the N2O:N2 ratio ranged between 0.2 and 4%. The relative contribution of denitrification to net N2O flux varied temporally and across the different land use types and ranged from 0.2 to 75%. The 15N-Gas Flux method can be successfully applied in a variety of land use types for relatively high temporal and spatial resolution measurement of in situ denitrification and the simultaneous quantification of N2 and N2O fluxes due to denitrification. Therefore the ratio of N2O:N2 and also the source apportionment for N2O can be estimated more accurately. The results suggested

  18. Abiotic controls on N2O emissions from soils and wetlands

    NASA Astrophysics Data System (ADS)

    Horwath, W. R.

    2016-12-01

    The increase in atmospheric nitrous oxide (N2O) is a critical climate change issue contributing to global warming. Most studies on N2O production attribute microbial processes and their associated enzymatic reactions to be the main driver affecting emissions. The role of redox capable iron, manganese and organic compounds that can react with intermediates in the nitrogen cycle has also been shown to produce N2O abiotically. The importance of the abiotic pathways, however, is highly debated. The abiotic production of N2O is related to biophysiochemical controls and unique isotopic signatures of nitrogen cycle intermediates (hydroxylamine, nitric oxide, and nitrite), redox-active metals (iron and manganese) and organic matter (humic and fulvic acids). In a range of soils, we find that the iron directly associated with organic compounds is the strongest variable relating to N2O emissions. In addition to these factors, management is also assumed to affect abiotic N2O production through its impact on nitrogen cycle intermediates, but the environmental and physiochemical conditions that are changed by management are rarely considered in the abiotic production of N2O. We find that the amount and quality of organic compounds in soils directly determines the fate of soil N2O production (i.e. be emitted or consumed). Water depth in rice paddies and wetlands also plays a significant role in partitioning production and consumption of N2O. What is evident from studies on N2O emission is that abiotic reactions are coupled to biotic processes and they cannot be easily separated. The biotic/abiotic interactions have important ecological outcomes that influence abiotic production mechanisms and should be recognized as important controllers of N2O production and consumption processes in soils and sediments.

  19. Monoclinic modification of bis­(μ2-pyridine-2,6-dicarboxyl­ato)-κ4 O 2,N,O 6:O 6;κ4 O 2:O 2,N,O 6-bis­[aqua­dibutyl­tin(IV)

    PubMed Central

    Ng, Seik Weng

    2011-01-01

    The SnIV atom in the centrosymmetric dinuclear title compound, [Sn2(C4H9)4(C7H3NO4)2(H2O)2], exists in a trans-C2SnNO4 penta­gonal–bipyramidal geometry. There are two half-mol­ecules in the asymmetric unit that are completed by inversion symmetry. The crystal studied was a non-merohedral twin with a ratio of 47.3 (1)% for the minor twin component. Bond dimensions are similar to those found in the tetra­gonal polymorph [Huber et al. (1989 ▶). Acta Cryst. C45, 51–54]. O—H⋯O hydrogen-bonding interactions stabilize the crystal packing. PMID:21522924

  20. Effect of sulfation on the surface activity of CaO for N2O decomposition

    NASA Astrophysics Data System (ADS)

    Wu, Lingnan; Hu, Xiaoying; Qin, Wu; Dong, Changqing; Yang, Yongping

    2015-12-01

    Limestone addition to circulating fluidized bed boilers for sulfur removal affects nitrous oxide (N2O) emission at the same time, but mechanism of how sulfation process influences the surface activity of CaO for N2O decomposition remains unclear. In this paper, we investigated the effect of sulfation on the surface properties and catalytic activity of CaO for N2O decomposition using density functional theory calculations. Sulfation of CaO (1 0 0) surface by the adsorption of a single gaseous SO2 or SO3 molecule forms stable local CaSO3 or CaSO4 on the CaO (1 0 0) surface with strong hybridization between the S atom of SOx and the surface O anion. The formed local CaSO3 increases the barrier energy of N2O decomposition from 0.989 eV (on the CaO (1 0 0) surface) to 1.340 eV, and further sulfation into local CaSO4 remarkably increases the barrier energy to 2.967 eV. Sulfation from CaSO3 into CaSO4 is therefore the crucial step for deactivating the surface activity for N2O decomposition. Completely sulfated CaSO4 (0 0 1) and (0 1 0) surfaces further validate the negligible catalytic ability of CaSO4 for N2O decomposition.

  1. Controllable synthesis of high aspect ratio Mg2B2O5 nanowires and their applications in reinforced polyhydroxyalkanoate composites

    NASA Astrophysics Data System (ADS)

    Mo, Zhao-Jun; Chen, Jin-Peng; Lin, Jing; Fan, Ying; Liang, Chun-Yong; Wang, Hong-Shui; Xu, Xue-Wen; Hu, Long; Tang, Cheng-Chun

    2014-05-01

    Highly pure magnesium borate (Mg2B2O5) nanowires with an average diameter of ~ 30 nm, an average length of ~ 15 μm, and a high aspect ratio of ~ 500 have been synthesized on a large scale via a two-step method. MgBO2(OH) nanowires with high aspect ratios were first prepared via a PVP-assisted hydrothermal technique. Using these nanowires as precursors, single crystalline Mg2B2O5 nanowires were synthesized by post-annealing treatment at a relatively low temperature of 700 °C. The important effect of the MgBO2(OH)—Mg2B2O5 conversion process on the morphology of the Mg2B2O5 nanowires was investigated and it was indicated that the recrystallization process plays an important role in the protection of the one-dimensional (1D) nanostructure. Moreover, the rigidity and the toughness of the Mg2B2O5 nanowire-reinforced PHA composites were tremendously improved compared to those of the pure PHA. Our results demonstrate the effectiveness of Mg2B2O5 nanowires for reinforcement applications in polymer composites.

  2. Facile fabrication and electrical investigations of nanostructured p-Si/n-TiO2 hetero-junction diode

    NASA Astrophysics Data System (ADS)

    Kumar, Arvind; Mondal, Sandip; Rao, K. S. R. Koteswara

    2018-05-01

    In this work, we have fabricated the nanostructured p-Si/n-TiO2 hetero-junction diode by using a facile spin-coating method. The XRD analysis suggests the presence of well crystalline anatase TiO2 film on Si with small grain size (˜16 nm). We have drawn the band alignment using Anderson model to understand the electrical transport across the junction. The current-voltage (J-V) characteristics analysis reveals the good rectification ratio (103 at ± 3 V) and slightly higher ideality factor (4.7) of our device. The interface states are responsible for the large ideality factor as Si/TiO2 form a dissimilar interface and possess a large number of dangling bonds. The study reveals the promises to be used Si/TiO2 diode as an alternative to the traditional p-n homo-junction diode, which typically require high budget.

  3. Measurement of the D/H, 18O/16O, and 17O/16O Isotope Ratios in Water by Laser Absorption Spectroscopy at 2.73 μm

    PubMed Central

    Wu, Tao; Chen, Weidong; Fertein, Eric; Masselin, Pascal; Gao, Xiaoming; Zhang, Weijun; Wang, Yingjian; Koeth, Johannes; Brückner, Daniela; He, Xingdao

    2014-01-01

    A compact isotope ratio laser spectrometry (IRLS) instrument was developed for simultaneous measurements of the D/H, 18O/16O and 17O/16O isotope ratios in water by laser absorption spectroscopy at 2.73 μm. Special attention is paid to the spectral data processing and implementation of a Kalman adaptive filtering to improve the measurement precision. Reduction of up to 3-fold in standard deviation in isotope ratio determination was obtained by the use of a Fourier filtering to remove undulation structure from spectrum baseline. Application of Kalman filtering enables isotope ratio measurement at 1 s time intervals with a precision (<1‰) better than that obtained by conventional 30 s averaging, while maintaining a fast system response. The implementation of the filter is described in detail and its effects on the accuracy and the precision of the isotope ratio measurements are investigated. PMID:24854363

  4. Ignition and Combustion of Pulverized Coal and Biomass under Different Oxy-fuel O2/N2 and O2/CO2 Environments

    NASA Astrophysics Data System (ADS)

    Khatami Firoozabadi, Seyed Reza

    This work studied the ignition and combustion of burning pulverized coals and biomasses particles under either conventional combustion in air or oxy-fuel combustion conditions. Oxy-fuel combustion is a 'clean-coal' process that takes place in O2/CO2 environments, which are achieved by removing nitrogen from the intake gases and recirculating large amounts of flue gases to the boiler. Removal of nitrogen from the combustion gases generates a high CO2-content, sequestration-ready gas at the boiler effluent. Flue gas recirculation moderates the high temperatures caused by the elevated oxygen partial pressure in the boiler. In this study, combustion of the fuels took place in a laboratory laminar-flow drop-tube furnace (DTF), electrically-heated to 1400 K, in environments containing various mole fractions of oxygen in either nitrogen or carbon-dioxide background gases. The experiments were conducted at two different gas conditions inside the furnace: (a) quiescent gas condition (i.e., no flow or inactive flow) and, (b) an active gas flow condition in both the injector and furnace. Eight coals from different ranks (anthracite, semi-snthracite, three bituminous, subbituminous and two lignites) and four biomasses from different sources were utilized in this work to study the ignition and combustion characteristics of solid fuels in O2/N2 or O2/CO2 environments. The main objective is to study the effect of replacing background N2 with CO2, increasing O2 mole fraction and fuel type and rank on a number of qualitative and quantitative parameters such as ignition/combustion mode, ignition temperature, ignition delay time, combustion temperatures, burnout times and envelope flame soot volume fractions. Regarding ignition, in the quiescent gas condition, bituminous and sub-bituminous coal particles experienced homogeneous ignition in both O2/N 2 and O2/CO2 atmospheres, while in the active gas flow condition, heterogeneous ignition was evident in O2/CO 2. Anthracite, semi

  5. Crystal structure, chemical composition, and extended defects of the high-Tc (Bi,Pb)2Sr2Ca(n)-1CunO4 + 2n + delta compounds.

    PubMed

    Eibl, O

    1995-02-15

    This paper summarizes results obtained by high-resolution transmission electron microscopy on the crystal structure and microstructure of the (Bi,Pb)2Sr2Ca(n)-1CunO4 + 2n + delta high-Tc superconducting oxides. The experimental basis for the work presented here are high-resolution structure images obtained at ultra-thin (3 nm) areas of carefully prepared transmission electron microscope (TEM) samples. The analysis was carried out on a 400 kV TEM equipped with a pole piece yielding 0.17 nm point-to-point resolution. From the images obtained the projected crystal potential of the cations can be extracted directly, as confirmed by detailed image simulation. Structural analysis of the oxygen sublattice remains an unsolved problem by high-resolution TEM (HRTEM), mainly because of the small scattering factors, and thus the contribution of the oxygen sublattice to the image contrast is small. The (BiPb)2Sr2Ca(n)-1CunO4 + 2n + delta phases are modulated structures that can be understood as an average structure plus a superimposed displacement field. The crystal structure consists of BiO double layers and perovskite-type cuboids (containing Sr, Ca, Cu, and O), which are sandwiched between the BiO double layers. The displacement field can be directly analyzed by HRTEM, and the largest displacement amplitudes of 70 pm were determined for the Bi atoms in the n = 1 compound. The chemical composition of the n = 2 and n = 3 compounds was determined by EDX in the TEM for the cation sublattice. A significant (Ca + Sr) deficiency (approximately 10%) with respect to Cu was found. The (Sr + Ca)/Cu mole fraction ratio was 1.31 for the Bi-2212 phase and 1.14 for the Bi(Pb)-2223 phase. The oxygen content cannot be determined by EDX in the TEM with the accuracy necessary for a correlation with electrical and superconducting properties. The defect structure present in these materials, that is, intergrown lamellae with different crystal structures and equal or different chemical

  6. Estimation of nocturnal CO2 and N2O soil emissions from changes in surface boundary layer mass storage

    NASA Astrophysics Data System (ADS)

    Grant, Richard H.; Omonode, Rex A.

    2018-04-01

    Annual budgets of greenhouse and other trace gases require knowledge of the emissions throughout the year. Unfortunately, emissions into the surface boundary layer during stable, calm nocturnal periods are not measurable using most micrometeorological methods due to non-stationarity and uncoupled flow. However, during nocturnal periods with very light winds, carbon dioxide (CO2) and nitrous oxide (N2O) frequently accumulate near the surface and this mass accumulation can be used to determine emissions. Gas concentrations were measured at four heights (one within and three above canopy) and turbulence was measured at three heights above a mature 2.5 m maize canopy from 23 July to 10 September 2015. Nocturnal CO2 and N2O fluxes from the canopy were determined using the accumulation of mass within a 6.3 m control volume and out the top of the control volume within the nocturnal surface boundary layer. Diffusive fluxes were estimated by flux gradient method. The total accumulative and diffusive fluxes during near-calm nights (friction velocities < 0.05 ms-1) averaged 1.16 µmol m-2 s-1 CO2 and 0.53 nmol m-2 s-1 N2O. Fluxes were also measured using chambers. Daily mean CO2 fluxes determined by the accumulation method were 90 to 130 % of those determined using soil chambers. Daily mean N2O fluxes determined by the accumulation method were 60 to 80 % of that determined using soil chambers. The better signal-to-noise ratios of the chamber method for CO2 over N2O, non-stationary flow, assumed Schmidt numbers, and anemometer tilt were likely contributing reasons for the differences in chambers versus accumulated nocturnal mass flux estimates. Near-surface N2O accumulative flux measurements in more homogeneous regions and with greater depth are needed to confirm the conclusion that mass accumulation can be effectively used to estimate soil emissions during nearly calm nights.

  7. Chirality in distorted square planar Pd(O,N)2 compounds.

    PubMed

    Brunner, Henri; Bodensteiner, Michael; Tsuno, Takashi

    2013-10-01

    Salicylidenimine palladium(II) complexes trans-Pd(O,N)2 adopt step and bowl arrangements. A stereochemical analysis subdivides 52 compounds into 41 step and 11 bowl types. Step complexes with chiral N-substituents and all the bowl complexes induce chiral distortions in the square planar system, resulting in Δ/Λ configuration of the Pd(O,N)2 unit. In complexes with enantiomerically pure N-substituents ligand chirality entails a specific square chirality and only one diastereomer assembles in the lattice. Dimeric Pd(O,N)2 complexes with bridging N-substituents in trans-arrangement are inherently chiral. For dimers different chirality patterns for the Pd(O,N)2 square are observed. The crystals contain racemates of enantiomers. In complex two independent molecules form a tight pair. The (RC) configuration of the ligand induces the same Δ chirality in the Pd(O,N)2 units of both molecules with varying square chirality due to the different crystallographic location of the independent molecules. In complexes and atrop isomerism induces specific configurations in the Pd(O,N)2 bowl systems. The square chirality is largest for complex [(Diop)Rh(PPh3 )Cl)], a catalyst for enantioselective hydrogenation. In the lattice of two diastereomers with the same (RC ,RC) configuration in the ligand Diop but opposite Δ and Λ square configurations co-crystallize, a rare phenomenon in stereochemistry. © 2013 Wiley Periodicals, Inc.

  8. Comparison and mechanism of photocatalytic activities of N-ZnO and N-ZrO2 for the degradation of rhodamine 6G.

    PubMed

    Sudrajat, Hanggara; Babel, Sandhya

    2016-05-01

    N-doped ZnO (N-ZnO) and N-doped ZrO2 (N-ZrO2) are synthesized by novel, simple thermal decomposition methods. The catalysts are evaluated for the degradation of rhodamine 6G (R6G) under visible and UV light. N-ZnO exhibits higher dye degradation under both visible and UV light compared to N-ZrO2 due to possessing higher specific surface area, lower crystalline size, and lower band gap. However, it is less reusable than N-ZrO2 and its photocatalytic activity is also deteriorated at low pH. At the same intensity of 3.5 W/m(2), UVC light is shown to be a better UV source for N-ZnO, while UVA light is more suitable for N-ZrO2. At pH 7 with initial dye concentration of 10 mg/L, catalyst concentration of 1 g/L, and UVC light, 94.3 % of R6G is degraded by N-ZnO within 2 h. Using UVA light under identical experimental conditions, 93.5 % degradation of R6G is obtained by N-ZrO2. Moreover, the type of light source is found to determine the reactive species produced in the R6G degradation by N-ZnO and N-ZrO2. Less oxidative reactive species such as superoxide radical and singlet oxygen play a major role in the degradation of R6G under visible light. On the contrary, highly oxidative hydroxyl radicals are predominant under UVC light. Based on the kinetic study, the adsorption of R6G on the catalyst surface is found to be the controlling step.

  9. Wavelength-dependent UV photodesorption of pure N2 and O2 ices

    NASA Astrophysics Data System (ADS)

    Fayolle, E. C.; Bertin, M.; Romanzin, C.; Poderoso, H. A. M.; Philippe, L.; Michaut, X.; Jeseck, P.; Linnartz, H.; Öberg, K. I.; Fillion, J.-H.

    2013-08-01

    Context. Ultraviolet photodesorption of molecules from icy interstellar grains can explain observations of cold gas in regions where thermal desorption is negligible. This non-thermal desorption mechanism should be especially important where UV fluxes are high. Aims: N2 and O2 are expected to play key roles in astrochemical reaction networks, both in the solid state and in the gas phase. Measurements of the wavelength-dependent photodesorption rates of these two infrared-inactive molecules provide astronomical and physical-chemical insights into the conditions required for their photodesorption. Methods: Tunable radiation from the DESIRS beamline at the SOLEIL synchrotron in the astrophysically relevant 7 to 13.6 eV range is used to irradiate pure N2 and O2 thin ice films. Photodesorption of molecules is monitored through quadrupole mass spectrometry. Absolute rates are calculated by using the well-calibrated CO photodesorption rates. Strategic N2 and O2 isotopolog mixtures are used to investigate the importance of dissociation upon irradiation. Results: N2 photodesorption mainly occurs through excitation of the b1Πu state and subsequent desorption of surface molecules. The observed vibronic structure in the N2 photodesorption spectrum, together with the absence of N3 formation, supports that the photodesorption mechanism of N2 is similar to CO, i.e., an indirect DIET (Desorption Induced by Electronic Transition) process without dissociation of the desorbing molecule. In contrast, O2 photodesorption in the 7-13.6 eV range occurs through dissociation and presents no vibrational structure. Conclusions: Photodesorption rates of N2 and O2 integrated over the far-UV field from various star-forming environments are lower than for CO. Rates vary between 10-3 and 10-2 photodesorbed molecules per incoming photon.

  10. The K 2S 2O 8-KOH photoetching system for GaN

    NASA Astrophysics Data System (ADS)

    Weyher, J. L.; Tichelaar, F. D.; van Dorp, D. H.; Kelly, J. J.; Khachapuridze, A.

    2010-09-01

    A recently developed photoetching system for n-type GaN, a KOH solution containing the strong oxidizing agent potassium peroxydisulphate (K 2S 2O 8), was studied in detail. By careful selection of the etching parameters, such as the ratio of components and the hydrodynamics, two distinct modes were defined: defect-selective etching (denoted by KSO-D) and polishing (KSO-P). Both photoetching methods can be used under open-circuit (electroless) conditions. Well-defined dislocation-related etch whiskers are formed during KSO-D etching. All types of dislocations are revealed, and this was confirmed by cross-sectional TEM examination of the etched samples. Extended electrically active defects are also clearly revealed. The known relationship between etch rate and carrier concentration for photoetching of GaN in KOH solutions was confirmed for KSO-D etch using Raman measurements. It is shown that during KSO-P etching diffusion is the rate-limiting step, i.e. this etch is suitable for polishing of GaN. Some constraints of the KSO etching system for GaN are discussed and peculiar etch features, so far not understood, are described.

  11. A study of nitrogen behavior in the formation of Ta/TaN and Ti/TaN alloyed metal electrodes on SiO2 and HfO2 dielectrics

    NASA Astrophysics Data System (ADS)

    Gassilloud, R.; Maunoury, C.; Leroux, C.; Piallat, F.; Saidi, B.; Martin, F.; Maitrejean, S.

    2014-04-01

    We studied Ta, TaN, and sub-stoichiometric TaNx electrodes (obtained by nitrogen redistribution in Ta/TaN or Ti/TaN bilayers) deposited on thermal SiO2 and HfO2/IL (0.8 nm SiO2 IL, i.e., interlayer) stacks. Effective work-functions (WF) were extracted on MOS capacitor structures on SiO2 bevelled insulator of 4.2 eV for pure Ta, 4.6 eV for TaN, and 4.3 eV for sub-stoichiometric TaNx. This intermediate WF value is explained by TaN nitrogen redistribution with reactive Ta or Ti elements shifting the gate work-function toward the Si conduction band. The same electrodes deposited on an HfO2/IL dielectric showed different behavior: First, the Ta/HfO2/IL stack shows a +200 meV WF increase (towards the Si valence band) compared to the SiO2 dielectric stack. This increase is explained by the well-known HfO2/IL dipole formation. Second, in contrast to electrodes deposited on SiO2, sub-stoichiometric TaNx/HfO2 is found to have a lower WF (4.3 eV), than pure Ta on HfO2 (4.4 eV). This inversion in work-function behavior measured on SiO2 vs. HfO2 is explained by the nitrogen redistribution in Ta/TaN bilayer together with diffusion of nitrogen through the HfO2 layer, leading to Si-N formation which prevents dipole formation at the HfO2/IL interface.

  12. Molecular and Dissociative Adsorption of Water on (TiO 2 ) n Clusters, n = 1–4

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chen, Mingyang; Straatsma, Tjerk P.; Dixon, David A.

    In the low energy structures of the (TiO 2) n(H 2O) m (n ≤ 4, m ≤ 2n) and (TiO 2) 8(H 2O) m (m = 3, 7, 8) clusters were predicted using a global geometry optimization approach, with a number of new lowest energy isomers being found. Water can molecularly or dissociatively adsorb on pure and hydrated TiO 2 clusters. Dissociative adsorption is the dominant reaction for the first two H 2O adsorption reactions for n = 1, 2, and 4, for the first three H 2O adsorption reactions for n = 3, and for the first four Hmore » 2O adsorption reactions for n = 8. As more H 2O’s are added to the hydrated (TiO 2)n cluster, dissociative adsorption becomes less exothermic as all the Ti centers become 4-coordinate. Furthermore two types of bonds can be formed between the molecularly adsorbed water and TiO 2 clusters: a Lewis acid–base Ti–O(H 2) bond or an O···H hydrogen bond. The coupled cluster CCSD(T) results show that at 0 K the H 2O adsorption energy at a 4-coordinate Ti center is ~15 kcal/mol for the Lewis acid–base molecular adsorption and ~7 kcal/mol for the H-bond molecular adsorption, in comparison to that of 8–10 kcal/mol for the dissociative adsorption. The cluster size and geometry independent dehydration reaction energy, ED, for the general reaction 2(-TiOH) → -TiOTi– + H 2O at 4-coordinate Ti centers was estimated from the aggregation reaction of nTi(OH) 4 to form the monocyclic ring cluster (TiO 3H 2) n + nH 2O. E D is estimated to be -8 kcal/mol, showing that intramolecular and intermolecular dehydration reactions are intrinsically thermodynamically allowed for the hydrated (TiO 2) n clusters with all of the Ti centers 4-coordinate, which can be hindered by cluster geometry changes caused by such processes. Finally by bending force constants for the TiOTi and OTiO bonds are determined to be 7.4 and 56.0 kcal/(mol·rad 2). Infrared vibrational spectra were calculated using density functional theory, and the new bands appearing upon water adsorption

  13. Molecular and Dissociative Adsorption of Water on (TiO 2 ) n Clusters, n = 1–4

    DOE PAGES

    Chen, Mingyang; Straatsma, Tjerk P.; Dixon, David A.

    2015-10-20

    In the low energy structures of the (TiO 2) n(H 2O) m (n ≤ 4, m ≤ 2n) and (TiO 2) 8(H 2O) m (m = 3, 7, 8) clusters were predicted using a global geometry optimization approach, with a number of new lowest energy isomers being found. Water can molecularly or dissociatively adsorb on pure and hydrated TiO 2 clusters. Dissociative adsorption is the dominant reaction for the first two H 2O adsorption reactions for n = 1, 2, and 4, for the first three H 2O adsorption reactions for n = 3, and for the first four Hmore » 2O adsorption reactions for n = 8. As more H 2O’s are added to the hydrated (TiO 2)n cluster, dissociative adsorption becomes less exothermic as all the Ti centers become 4-coordinate. Furthermore two types of bonds can be formed between the molecularly adsorbed water and TiO 2 clusters: a Lewis acid–base Ti–O(H 2) bond or an O···H hydrogen bond. The coupled cluster CCSD(T) results show that at 0 K the H 2O adsorption energy at a 4-coordinate Ti center is ~15 kcal/mol for the Lewis acid–base molecular adsorption and ~7 kcal/mol for the H-bond molecular adsorption, in comparison to that of 8–10 kcal/mol for the dissociative adsorption. The cluster size and geometry independent dehydration reaction energy, ED, for the general reaction 2(-TiOH) → -TiOTi– + H 2O at 4-coordinate Ti centers was estimated from the aggregation reaction of nTi(OH) 4 to form the monocyclic ring cluster (TiO 3H 2) n + nH 2O. E D is estimated to be -8 kcal/mol, showing that intramolecular and intermolecular dehydration reactions are intrinsically thermodynamically allowed for the hydrated (TiO 2) n clusters with all of the Ti centers 4-coordinate, which can be hindered by cluster geometry changes caused by such processes. Finally by bending force constants for the TiOTi and OTiO bonds are determined to be 7.4 and 56.0 kcal/(mol·rad 2). Infrared vibrational spectra were calculated using density functional theory, and the new bands appearing upon water adsorption

  14. Controlled nitric oxide production via O(1D) + N2O reactions for use in oxidation flow reactor studies

    NASA Astrophysics Data System (ADS)

    Lambe, Andrew; Massoli, Paola; Zhang, Xuan; Canagaratna, Manjula; Nowak, John; Daube, Conner; Yan, Chao; Nie, Wei; Onasch, Timothy; Jayne, John; Kolb, Charles; Davidovits, Paul; Worsnop, Douglas; Brune, William

    2017-06-01

    Oxidation flow reactors that use low-pressure mercury lamps to produce hydroxyl (OH) radicals are an emerging technique for studying the oxidative aging of organic aerosols. Here, ozone (O3) is photolyzed at 254 nm to produce O(1D) radicals, which react with water vapor to produce OH. However, the need to use parts-per-million levels of O3 hinders the ability of oxidation flow reactors to simulate NOx-dependent secondary organic aerosol (SOA) formation pathways. Simple addition of nitric oxide (NO) results in fast conversion of NOx (NO + NO2) to nitric acid (HNO3), making it impossible to sustain NOx at levels that are sufficient to compete with hydroperoxy (HO2) radicals as a sink for organic peroxy (RO2) radicals. We developed a new method that is well suited to the characterization of NOx-dependent SOA formation pathways in oxidation flow reactors. NO and NO2 are produced via the reaction O(1D) + N2O2NO, followed by the reaction NO + O3 → NO2 + O2. Laboratory measurements coupled with photochemical model simulations suggest that O(1D) + N2O reactions can be used to systematically vary the relative branching ratio of RO2 + NO reactions relative to RO2 + HO2 and/or RO2 + RO2 reactions over a range of conditions relevant to atmospheric SOA formation. We demonstrate proof of concept using high-resolution time-of-flight chemical ionization mass spectrometer (HR-ToF-CIMS) measurements with nitrate (NO3-) reagent ion to detect gas-phase oxidation products of isoprene and α-pinene previously observed in NOx-influenced environments and in laboratory chamber experiments.

  15. Controlled Nitric Oxide Production via O(1D) + N2O Reactions for Use in Oxidation Flow Reactor Studies

    NASA Technical Reports Server (NTRS)

    Lambe, Andrew; Massoli, Paola; Zhang, Xuan; Canagaratna, Manjula; Nowak, John; Daube, Conner; Yan, Chao; Nie, Wei; Onasch, Timothy; Jayne, John; hide

    2017-01-01

    Oxidation flow reactors that use low-pressure mercury lamps to produce hydroxyl (OH) radicals are an emerging technique for studying the oxidative aging of organic aerosols. Here, ozone (O3) is photolyzed at 254 nm to produce O(1D) radicals, which react with water vapor to produce OH. However, the need to use parts-per-million levels of O3 hinders the ability of oxidation flow reactors to simulate NOx-dependent secondary organic aerosol (SOA) formation pathways. Simple addition of nitric oxide (NO) results in fast conversion of NOx (NO+NO2) to nitric acid (HNO3), making it impossible to sustain NOx at levels that are sufficient to compete with hydroperoxy (HO2) radicals as a sink for organic peroxy (RO2) radicals. We developed a new method that is well suited to the characterization of NOx-dependent SOA formation pathways in oxidation flow reactors. NO and NO2 are produced via the reaction O(1D)+N2O->2NO, followed by the reaction NO+O3->NO2+O2. Laboratory measurements coupled with photochemical model simulations suggest that O(1D)+N2O reactions can be used to systematically vary the relative branching ratio of RO2 +NO reactions relative to RO2 +HO2 and/or RO2+RO2 reactions over a range of conditions relevant to atmospheric SOA formation. We demonstrate proof of concept using high-resolution time-of-flight chemical ionization mass spectrometer (HR-ToF-CIMS) measurements with nitrate (NO-3 ) reagent ion to detect gas-phase oxidation products of isoprene and -pinene previously observed in NOx-influenced environments and in laboratory chamber experiments.

  16. Aqua­(dicyanamido-κN 1)(nitrato-κ2 O,O′)(2,3,5,6-tetra-2-pyridylpyrazine-κ3 N 2,N 1,N 6)manganese(II)

    PubMed Central

    Callejo, Lorena; De la Pinta, Noelia; Vitoria, Pablo; Cortés, Roberto

    2009-01-01

    In the title compound, [Mn(C2N3)(NO3)(C24H16N6)(H2O)], the central manganese(II) ion is hepta­coordinated to a tridentate 2,3,5,6-tetra-2-pyridylpyrazine ligand (tppz), a bidentate nitrate ligand, a terminal monodentate dicyanamide ligand (dca) and a water mol­ecule. The structure contains isolated neutral complexes, which are linked by O(water)—H⋯N hydrogen bonds generating chains along [010]. PMID:21581535

  17. Preparation and visible light photocatalytic activity of Bi2O3/Bi2WO6 heterojunction photocatalysts

    NASA Astrophysics Data System (ADS)

    Yan, C. Y.; Yi, W. T.; Xiong, J.; Ma, J.

    2018-03-01

    The Bi2O3 nanorods, flower-like Bi2WO6 and Bi2O3/Bi2WO6 heterojunction composites with the molar ratio of nBi:nW from 2:1, 2.5:1, to 3:1 have been synthesized via one-step hydrothermal method and two-step hydrothermal method, respectively. The products are characterized by powder X-ray diffraction (XRD), UV–vis diffuse reflectance spectroscopy (UV-vis DRS), and scanning electron microscopy (SEM). Photocatalytic experiments indicate that such Bi2O3/Bi2WO6 composite possesses higher photocatalytic activity for RhB degradation under visible-light irradiation in comparison with pure Bi2O3 and Bi2WO6. The enhancement of the photocatalytic activity of the Bi2O3/Bi2WO6 heterojunction catalysts can be ascribed to the reduced recombination of the photoexcited electrons and holes during the photocatalytic reaction. The effect of the molar ratio of nBi:nW on the catalytic performance of the heterojunction catalysts was also investigated. And the optimal molar ratio of nBi:nW is 2.5:1 which was synthesized by one-step hydrothermal method.

  18. N2O FIELD STUDY

    EPA Science Inventory

    The report gives results of measurements of nitrous oxide (N2O) emissions from coal-fired utility boilers at three electric power generating stations. Six units were tested, two at each site, including sizes ranging from 165 to 700 MW. Several manufacturers and boiler firing type...

  19. Constraints on global oceanic emissions of N2O from observations and models

    NASA Astrophysics Data System (ADS)

    Buitenhuis, Erik T.; Suntharalingam, Parvadha; Le Quéré, Corinne

    2018-04-01

    We estimate the global ocean N2O flux to the atmosphere and its confidence interval using a statistical method based on model perturbation simulations and their fit to a database of ΔpN2O (n = 6136). We evaluate two submodels of N2O production. The first submodel splits N2O production into oxic and hypoxic pathways following previous publications. The second submodel explicitly represents the redox transformations of N that lead to N2O production (nitrification and hypoxic denitrification) and N2O consumption (suboxic denitrification), and is presented here for the first time. We perturb both submodels by modifying the key parameters of the N2O cycling pathways (nitrification rates; NH4+ uptake; N2O yields under oxic, hypoxic and suboxic conditions) and determine a set of optimal model parameters by minimisation of a cost function against four databases of N cycle observations. Our estimate of the global oceanic N2O flux resulting from this cost function minimisation derived from observed and model ΔpN2O concentrations is 2.4 ± 0.8 and 2.5 ± 0.8 Tg N yr-1 for the two N2O submodels. These estimates suggest that the currently available observational data of surface ΔpN2O constrain the global N2O flux to a narrower range relative to the large range of results presented in the latest IPCC report.

  20. Two mixed-ligand lanthanide–hydrazone complexes: [Pr(NCS)3(pbh)2]·H2O and [Nd(NCS)(NO3)(pbh)2(H2O)]NO3·2.33H2O [pbh is N′-(pyridin-2-ylmethylidene)benzo­hydrazide, C13H11N3O

    PubMed Central

    Paschalidis, Damianos G.; Harrison, William T. A.

    2016-01-01

    The gel-mediated syntheses and crystal structures of [N′-(pyridin-2-ylmethylidene-κN)benzohydrazide-κ2 N′,O]tris(thiocyanato-κN)praseodymium(III) mono­hydrate, [Pr(NCS)3(C13H11N3O)2]·H2O, (I), and aqua(nitrato-κ2 O,O′)[N′-(pyri­din-2-ylmethylidene-κN)benzohydrazide-κ2 N′,O](thiocyanato-κN)neo­dym­ium(III) nitrate 2.33-hydrate, [Nd(NCS)(NO3)(C13H11N3O)2(H2O)]NO3·2.33H2O, (II), are reported. The Pr3+ ion in (I) is coordinated by two N,N,O-tridentate N′-(pyridin-2-ylmethylidene)benzohydrazide (pbh) ligands and three N-bonded thio­cyanate ions to generate an irregular PrN7O2 coordination polyhedron. The Nd3+ ion in (II) is coordinated by two N,N,O-tridentate pbh ligands, an N-bonded thio­cyanate ion, a bidentate nitrate ion and a water mol­ecule to generate a distorted NdN5O5 bicapped square anti­prism. The crystal structures of (I) and (II) feature numerous hydrogen bonds, which lead to the formation of three-dimensional networks in each case. PMID:26958385

  1. Arbuscular mycorrhizal fungi reduce nitrous oxide emissions from N2 O hotspots.

    PubMed

    Storer, Kate; Coggan, Aisha; Ineson, Phil; Hodge, Angela

    2017-12-05

    Nitrous oxide (N 2 O) is a potent, globally important, greenhouse gas, predominantly released from agricultural soils during nitrogen (N) cycling. Arbuscular mycorrhizal fungi (AMF) form a mutualistic symbiosis with two-thirds of land plants, providing phosphorus and/or N in exchange for carbon. As AMF acquire N, it was hypothesized that AMF hyphae may reduce N 2 O production. AMF hyphae were either allowed (AMF) or prevented (nonAMF) access to a compartment containing an organic matter and soil patch in two independent microcosm experiments. Compartment and patch N 2 O production was measured both before and after addition of ammonium and nitrate. In both experiments, N 2 O production decreased when AMF hyphae were present before inorganic N addition. In the presence of AMF hyphae, N 2 O production remained low following ammonium application, but increased in the nonAMF controls. By contrast, negligible N 2 O was produced following nitrate application to either AMF treatment. Thus, the main N 2 O source in this system appeared to be via nitrification, and the production of N 2 O was reduced in the presence of AMF hyphae. It is hypothesized that AMF hyphae may be outcompeting slow-growing nitrifiers for ammonium. This has significant global implications for our understanding of soil N cycling pathways and N 2 O production. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.

  2. Lower stratosphere measurements of variation with latitude of CF2Cl2, CFCl3, CCl4, and N2O profiles in the northern hemisphere

    NASA Technical Reports Server (NTRS)

    Vedder, J. F.; Tyson, B. J.; Brewer, R. B.; Inn, E. C. Y.; Boitnott, C. A.

    1978-01-01

    Measurements were made from a U-2 aircraft of profiles of CF2Cl2, CFCl3, CCl4 and N2O in the lower stratosphere in a meridional survey at a longitude of 159 deg W during the period October 1 to November 14, 1976. The latitude distributions obtained show a marked decrease in mixing ratio with increasing latitude from about 7 deg N in the Intertropical Convergence Zone to about 79 deg N. The results suggest the importance of meridional transport and mixing in the stratosphere in accounting, at least in part, for the observed profile variation with latitude. The contaminants C2F4Cl2, C2F3Cl3, CHCCl3 and SF6 were also detected but their mixing ratios were small and no accurate standards were prepared for them.

  3. Heterogeneous reaction of N2O5 with airborne TiO2 particles and its implication for stratospheric particle injection

    NASA Astrophysics Data System (ADS)

    Tang, M. J.; Telford, P. J.; Pope, F. D.; Rkiouak, L.; Abraham, N. L.; Archibald, A. T.; Braesicke, P.; Pyle, J. A.; McGregor, J.; Watson, I. M.; Cox, R. A.; Kalberer, M.

    2014-06-01

    Injection of aerosol particles (or their precursors) into the stratosphere to scatter solar radiation back into space has been suggested as a solar-radiation management scheme for the mitigation of global warming. TiO2 has recently been highlighted as a possible candidate particle because of its high refractive index, but its impact on stratospheric chemistry via heterogeneous reactions is as yet unknown. In this work the heterogeneous reaction of airborne sub-micrometre TiO2 particles with N2O5 has been investigated for the first time, at room temperature and different relative humidities (RH), using an atmospheric pressure aerosol flow tube. The uptake coefficient of N2O5 onto TiO2, γ(N2O5), was determined to be ~1.0 × 10-3 at low RH, increasing to ~3 × 10-3 at 60% RH. The uptake of N2O5 onto TiO2 is then included in the UKCA chemistry-climate model to assess the impact of this reaction on stratospheric chemistry. While the impact of TiO2 on the scattering of solar radiation is chosen to be similar to the aerosol from the Mt Pinatubo eruption, the impact of TiO2 injection on stratospheric N2O5 is much smaller.

  4. Slowdown of N2O emissions from China's croplands

    NASA Astrophysics Data System (ADS)

    Zhou, F.; Shang, Z.; Ciais, P.; Piao, S.; Tian, H.; Saikawa, E.; Zaehle, S.; Del Grosso, S. J.; Galloway, J. N.

    2016-12-01

    To feed the increasing population, China has experienced a rapid agricultural development over past decades, accompanied by increased fertilizer consumptions in croplands, but the magnitude, trend, and causes of the associated nitrous oxide (N2O) emissions has remain unclear. The primary sources of this uncertainty are conflicting estimates of fertilizer consumption and emission factors, the latter being uncertain because of very few regional representativeness of the Nrate-flux relationships in China. Here we re-estimate China's N2O emissions from croplands using three different methods: flux upscaling technique, process-based models and atmospheric inversion, and also analyze the corresponding drivers using an attribution approach. The three methods produce similar estimates of N2O emissions in the range of 0.67 ± 0.08 to 0.62± 0.11 Tg nitrogen per year, which is 29% larger than the estimates by the Emission Database for Global Atmospheric Research (EDGAR) that is adopted by Intergovernmental Panel on Climate Change (IPCC) as the emission baseline and twofold larger than the latest Chinese national report submitted to the United Nations Framework Convention on Climate Change, but the revised trend slows down after 2005. Fertilizer N application per area is the dominant factor driving the increase in N2O emissions across most cropping regions from 1990 to 2004, but climate-induced change of emission factors has also controlled N2O flux from 2005 onwards. Our findings suggest that, as precipitation would increase in North China but decline in the South in future, EF will increasingly control China's agri. soil emissions of N2O, unless offset by larger reductions of fertilizer consumptions.

  5. Hydrazinium lanthanide oxalates: synthesis, structure and thermal reactivity of N2H5[Ln2(C2O4)4(N2H5)]·4H2O, Ln = Ce, Nd.

    PubMed

    De Almeida, Lucie; Grandjean, Stéphane; Rivenet, Murielle; Patisson, Fabrice; Abraham, Francis

    2014-03-28

    New hydrazinium lanthanide oxalates N2H5[Ln2(C2O4)4(N2H5)]·4H2O, Ln = Ce (Ce-HyOx) and Nd (Nd-HyOx), were synthesized by hydrothermal reaction at 150 °C between lanthanide nitrate, oxalic acid and hydrazine solutions. The structure of the Nd compound was determined from single-crystal X-ray diffraction data, space group P2₁/c with a = 16.315(4), b = 12.127(3), c = 11.430(2) Å, β = 116.638(4)°, V = 2021.4(7) Å(3), Z = 4, and R1 = 0.0313 for 4231 independent reflections. Two distinct neodymium polyhedra are formed, NdO9 and NdO8N, an oxygen of one monodentate oxalate in the former being replaced by a nitrogen atom of a coordinated hydrazinium ion in the latter. The infrared absorption band at 1005 cm(-1) confirms the coordination of N2H5(+) to the metal. These polyhedra are connected through μ2 and μ3 oxalate ions to form an anionic three-dimensional neodymium-oxalate arrangement. A non-coordinated charge-compensating hydrazinium ion occupies, with water molecules, the resulting tunnels. The N-N stretching frequencies of the infrared spectra demonstrate the existence of the two types of hydrazine ions. Thermal reactivity of these hydrazinium oxalates and of the mixed isotypic Ce/Nd (CeNd-HyOx) oxalate were studied by using thermogravimetric and differential thermal analyses coupled with gas analyzers, and high temperature X-ray diffraction. Under air, fine particles of CeO2 and Ce(0.5)Nd(0.5)O(1.75) are formed at low temperature from Ce-HyOx and CeNd-HyOx, respectively, thanks to a decomposition/oxidation process. Under argon flow, dioxymonocyanamides Ln2O2CN2 are formed.

  6. Controlled carrier screening in p-n NiO/GaN piezoelectric generators by an Al2O3 insertion layer

    NASA Astrophysics Data System (ADS)

    Johar, Muhammad Ali; Jeong, Dae Kyung; Afifi Hassan, Mostafa; Kang, Jin-Ho; Ha, Jun-Seok; Key Lee, June; Ryu, Sang-Wan

    2017-12-01

    The performance of a piezoelectric generator (PG) depends significantly on the internal screening process inside the device. As piezoelectric charges appear on both ends of the piezoelectric crystal, internal screening starts to decrease the piezoelectric bias. Therefore, the piezoelectric energy generated by external stress is not fully utilized by external circuit, which is the most challenging aspect of high-efficiency PGs. In this work, the internal screening effect of a NiO/GaN p-n PG was analyzed and controlled with an Al2O3 insertion layer. Internal screening in the p-n diode PG was categorized into free-carrier screening in neutral regions and junction screening due to charge drift across the junction. It was observed that junction screening could be significantly suppressed by inserting an Al2O3 layer and that effect was dominant in a leaky diode PG. With this implementation, the piezoelectric bias of the NiO/GaN PG was improved by a factor of ~100 for high-leakage diodes and a factor of ~1.6 for low-leakage diodes. Consequently, NiO/Al2O3/GaN PGs under a stress of 5 MPa provided a piezoelectric bias of 12.1 V and a current density of 2.25 µA cm-2. The incorporation of a highly resistive Al2O3 layer between p-NiO and n-GaN layers in NiO/GaN heterojunctions provides an efficient means of improving the piezoelectric performance by controlling the internal screening of the piezoelectric field.

  7. IDENTIFICATION OF NOVEL TOXICITY-ASSOCIATED METABOLITES BY METABOLOMICS AND MASS ISOTOPOMER ANALYSIS OF ACETAMINOPHEN METABOLISM IN WILD-TYPE AND CYP2E1-NULL MICE

    PubMed Central

    Chen, Chi; Krausz, Kristopher W.; Idle, Jeffrey R.; Gonzalez, Frank J.

    2008-01-01

    CYP2E1 is recognized as the most important enzyme for initiation of acetaminophen (APAP)-induced toxicity. In this study, the resistance of Cyp2e1-null mice to APAP treatment was confirmed by comparing serum aminotransferase activities and blood urea nitrogen levels in wild-type and Cyp2e1-null mice. However, unexpectedly, profiling of major known APAP metabolites in urine and serum revealed that the contribution of CYP2E1 to APAP metabolism decreased with increasing APAP doses administered. Measurement of hepatic glutathione and hydrogen peroxide levels exposed the importance of oxidative stress in determining the consequence of APAP overdose. Subsequent metabolomic analysis was capable of constructing a principal components analysis (PCA) model that delineated a relationship between urinary metabolomes and the responses to APAP treatment. Urinary ions high in wild-type mice treated with 400 mg/kg APAP were elucidated as 3-methoxy-APAP glucuronide (VII) and three novel APAP metabolites, including S-(5-acetylamino-2-hydroxyphenyl)mercaptopyruvic acid (VI, formed by a Cys-APAP transamination reaction in kidney), 3,3′-biacetaminophen (VIII, an APAP dimer) and a benzothiazine compound (IX, originated from deacetylated APAP), through mass isotopomer analysis, accurate mass measurement, tandem MS fragmentation, in vitro reactions and chemical treatments. Dose-, time- and genotype-dependent appearance of these minor APAP metabolites implied their association with the APAP-induced toxicity and potential biomarker application. Overall, the oxidative stress elicited by CYP2E1-mediated APAP metabolism might significantly contribute to APAP-induced toxicity. The combination of genetically-modified animal models, mass isotopomer analysis and metabolomics provides a powerful and efficient technical platform to characterize APAP-induced toxicity through identifying novel biomarkers and unravelling novel mechanisms. PMID:18093979

  8. Mixed Matrix Membranes for O2/N2 Separation: The Influence of Temperature

    PubMed Central

    Fernández-Barquín, Ana; Casado-Coterillo, Clara; Valencia, Susana; Irabien, Angel

    2016-01-01

    In this work, mixed matrix membranes (MMMs) composed of small-pore zeolites with various topologies (CHA (Si/Al = 5), LTA (Si/Al = 1 and 5), and Rho (Si/Al = 5)) as dispersed phase, and the hugely permeable poly(1-trimethylsilyl-1-propyne) (PTMSP) as continuous phase, have been synthesized via solution casting, in order to obtain membranes that could be attractive for oxygen-enriched air production. The O2/N2 gas separation performance of the MMMs has been analyzed in terms of permeability, diffusivity, and solubility in the temperature range of 298–333 K. The higher the temperature of the oxygen-enriched stream, the lower the energy required for the combustion process. The effect of temperature on the gas permeability, diffusivity, and solubility of these MMMs is described in terms of the Arrhenius and Van’t Hoff relationships with acceptable accuracy. Moreover, the O2/N2 permselectivity of the MMMs increases with temperature, the O2/N2 selectivities being considerably higher than those of the pure PTMSP. In consequence, most of the MMMs prepared in this work exceeded the Robeson’s upper bound for the O2/N2 gas pair in the temperature range under study, with not much decrease in the O2 permeabilities, reaching O2/N2 selectivities of up to 8.43 and O2 permeabilities up to 4,800 Barrer at 333 K. PMID:27196937

  9. Effects of interfacial layer on characteristics of TiN/ZrO2 structures.

    PubMed

    Kim, Younsoo; Kang, Sang Yeol; Choi, Jae Hyoung; Lim, Jae Soon; Park, Min Young; Chung, Suk-Jin; Chung, Jaegwan; Lee, Hyung Ik; Kim, Ki Hong; Kyoung, Yong Koo; Heo, Sung; Yoo, Cha Young; Kang, Ho-Kyu

    2011-09-01

    To minimize the formation of unwanted interfacial layers, thin interfacial layer (ZrCN layer) was deposited between TiN bottom electrode and ZrO2 dielectric in TiN/ZrO2/TiN capacitor. Carbon and nitrogen were also involved in the layer because ZrCN layer was thermally deposited using TEMAZ without any reactant. Electrical characteristics of TiN/ZrO2/TiN capacitor were improved by insertion of ZrCN layer. The oxidation of TiN bottom electrode was largely inhibited at TiN/ZrCN/ZrO2 structure compared to TiN/ZrO2 structure. While the sheet resistance of TiN/ZrCN/ZrO2 structure was constantly sustained with increasing ZrO2 thickness, the large increase of sheet resistance was observed in TiN/ZrO2 structure after 6 nm ZrO2 deposition. When ZrO2 films were deposited on ZrCN layer, the deposition rate of ZrO2 also increased. It is believed that ZrCN layer acted both as a protection layer of TiN oxidation and a seed layer of ZrO2 growth.

  10. Can Isotopic Substitution Change a Bright State into a Dark State? The Case of the v3= 1 State of FClO 3

    NASA Astrophysics Data System (ADS)

    Meguellati, F.; Graner, G.; Burczyk, K.; Bürger, H.

    1997-10-01

    High-resolution infrared spectra of monoisotopic samples of F35Cl18O3and F37Cl18O3have been recorded with the purpose of analyzing the ν3fundamental at 535 cm-1. However, this band could not be observed whereas it had been seen and studied earlier in F35Cl16O3. To determine the parameters of thev3= 1 state, indirect methods were used. Hot bands νn+ ν3- ν3(n= 1 or 2) were first analyzed and their LSCD (Lower State Combination Differences) yielded rotational parameters of ν3. Then, with the help of ν1+ ν3, all rovibrational parameters of ν3were obtained. Similar methods were applied to spectra of F35Cl16O3and F37Cl16O3to prove that the parameters of ν3obtained in this fashion are identical to those determined directly for these isotopomers and are even more comprehensive. It is shown that the different character of ν3in the two18O and in the two16O isotopomers is due to the fact that the former are much closer to a spherical top molecule ((A0- B0)/A0= 0.015). This is not only reflected in intensities different by two orders of magnitude but also in the very different values of α3Bin these two pairs.

  11. CO2-induced pH reduction increases physiological toxicity of nano-TiO2 in the mussel Mytilus coruscus

    PubMed Central

    Hu, Menghong; Lin, Daohui; Shang, Yueyong; Hu, Yi; Lu, Weiqun; Huang, Xizhi; Ning, Ke; Chen, Yimin; Wang, Youji

    2017-01-01

    The increasing usage of nanoparticles has caused their considerable release into the aquatic environment. Meanwhile, anthropogenic CO2 emissions have caused a reduction of seawater pH. However, their combined effects on marine species have not been experimentally evaluated. This study estimated the physiological toxicity of nano-TiO2 in the mussel Mytilus coruscus under high pCO2 (2500–2600 μatm). We found that respiration rate (RR), food absorption efficiency (AE), clearance rate (CR), scope for growth (SFG) and O:N ratio were significantly reduced by nano-TiO2, whereas faecal organic weight rate and ammonia excretion rate (ER) were increased under nano-TiO2 conditions. High pCO2 exerted lower effects on CR, RR, ER and O:N ratio than nano-TiO2. Despite this, significant interactions of CO2-induced pH change and nano-TiO2 were found in RR, ER and O:N ratio. PCA showed close relationships among most test parameters, i.e., RR, CR, AE, SFG and O:N ratio. The normal physiological responses were strongly correlated to a positive SFG with normal pH and no/low nano-TiO2 conditions. Our results indicate that physiological functions of M. coruscus are more severely impaired by the combination of nano-TiO2 and high pCO2. PMID:28054631

  12. CO2-induced pH reduction increases physiological toxicity of nano-TiO2 in the mussel Mytilus coruscus

    NASA Astrophysics Data System (ADS)

    Hu, Menghong; Lin, Daohui; Shang, Yueyong; Hu, Yi; Lu, Weiqun; Huang, Xizhi; Ning, Ke; Chen, Yimin; Wang, Youji

    2017-01-01

    The increasing usage of nanoparticles has caused their considerable release into the aquatic environment. Meanwhile, anthropogenic CO2 emissions have caused a reduction of seawater pH. However, their combined effects on marine species have not been experimentally evaluated. This study estimated the physiological toxicity of nano-TiO2 in the mussel Mytilus coruscus under high pCO2 (2500-2600 μatm). We found that respiration rate (RR), food absorption efficiency (AE), clearance rate (CR), scope for growth (SFG) and O:N ratio were significantly reduced by nano-TiO2, whereas faecal organic weight rate and ammonia excretion rate (ER) were increased under nano-TiO2 conditions. High pCO2 exerted lower effects on CR, RR, ER and O:N ratio than nano-TiO2. Despite this, significant interactions of CO2-induced pH change and nano-TiO2 were found in RR, ER and O:N ratio. PCA showed close relationships among most test parameters, i.e., RR, CR, AE, SFG and O:N ratio. The normal physiological responses were strongly correlated to a positive SFG with normal pH and no/low nano-TiO2 conditions. Our results indicate that physiological functions of M. coruscus are more severely impaired by the combination of nano-TiO2 and high pCO2.

  13. (Cu 0.5Tl 0.5)Ba 2Ca n-1 Cu n- yGe yO 2 n+4- δ ( n = 3, 4 and y = 0.5, 0.75, 1.0); superconductors with GeO 2 planes

    NASA Astrophysics Data System (ADS)

    Khan, Nawazish A.; Irfan, M.

    2008-12-01

    We have successfully synthesized germanium doped (Cu 0.5Tl 0.5)Ba 2Ca n-1 Cu n- yGe yO 2 n+4- δ ( n = 3, 4 and y = 0, 0.5, 0.75, 1.0) superconductors and investigated the effect of Ge doping on the superconducting properties of these compounds. The solubility of Ge till y = 1 in the CuO 2 planes of (Cu 0.5Tl 0.5)Ba 2Ca 2Cu 3- yGe yO 10- δ, have been found to give superconductivity above 77 K. To our surprise an enhanced superconductivity is observed with the doping of semiconductor germanium in some samples. The enhanced superconductivity associated with mixed CuO 2/GeO 2 planes can be extremely useful for the understanding of mechanism of superconductivity; since we very well know the properties of germanium based semiconductors.

  14. Single photon ionization of van der Waals clusters with a soft x-ray laser: (CO2)n and (CO2)n(H2O)m.

    PubMed

    Heinbuch, S; Dong, F; Rocca, J J; Bernstein, E R

    2006-10-21

    Pure neutral (CO2)n clusters and mixed (CO2)n(H2O)m clusters are investigated employing time of flight mass spectroscopy and single photon ionization at 26.5 eV. The distribution of pure (CO2)n clusters decreases roughly exponentially with increasing cluster size. During the ionization process, neutral clusters suffer little fragmentation because almost all excess cluster energy above the vertical ionization energy is taken away by the photoelectron and only a small part of the photon energy is deposited into the (CO2)n cluster. Metastable dissociation rate constants of (CO2)n+ are measured in the range of (0.2-1.5) x 10(4) s(-1) for cluster sizes of 5< or =n< or =16. Mixed CO2-H2O clusters are studied under different generation conditions (5% and 20% CO2 partial pressures and high and low expansion pressures). At high CO2 concentration, predominant signals in the mass spectrum are the (CO2)n+ cluster ions. The unprotonated cluster ion series (CO2)nH2O+ and (CO2)n(H2O)2+ are also observed under these conditions. At low CO2 concentration, protonated cluster ions (H2O)nH+ are the dominant signals, and the protonated CO2(H2O)nH+ and unprotonated (H2O)n+ and (CO2)(H2O)n+ cluster ion series are also observed. The mechanisms and dynamics of the formation of these neutral and ionic clusters are discussed.

  15. Photoluminescence Probing of Complex H2O Adsorption on InGaN/GaN Nanowires.

    PubMed

    Maier, Konrad; Helwig, Andreas; Müller, Gerhard; Hille, Pascal; Teubert, Jörg; Eickhoff, Martin

    2017-02-08

    We demonstrate that the complex adsorption behavior of H 2 O on InGaN/GaN nanowire arrays is directly revealed by their ambient-dependent photoluminescence properties. Under low-humidity, ambient-temperature, and low-excitation-light conditions, H 2 O adsorbates cause a quenching of the photoluminescence. In contrast, for high humidity levels, elevated temperature, and high excitation intensity, H 2 O adsorbates act as efficient photoluminescence enhancers. We show that this behavior, which can only be detected due to the low operation temperature of the InGaN/GaN nanowires, can be explained on the basis of single H 2 O adsorbates forming surface recombination centers and multiple H 2 O adsorbates forming surface passivation layers. Reversible creation of such passivation layers is induced by the photoelectrochemical splitting of adsorbed water molecules and by the interaction of reactive H 3 O + and OH - ions with photoactivated InGaN surfaces. Due to electronic coupling of adsorbing molecules with photoactivated surfaces, InGaN/GaN nanowires act as sensitive nanooptical probes for the analysis of photoelectrochemical surface processes.

  16. Equation of state for Eu-doped SrSi2O2N2

    NASA Astrophysics Data System (ADS)

    Ermakova, Olga; Paszkowicz, Wojciech; Kaminska, Agata; Barzowska, Justyna; Szczodrowski, Karol; Grinberg, Marek; Minikayev, Roman; Nowakowska, Małgorzata; Carlson, Stefan; Li, Guogang; Liu, Ru-Shi; Suchocki, Andrzej

    2014-07-01

    α-SrSi2O2N2 is one of the recently studied oxonitridosilicates applicable in optoelectronics, in particular in white LEDs. Its elastic properties remain unknown. A survey of literature shows that, up to now, nine oxonitridosilicate materials have been identified. For most of these compounds, doped with rare earths and manganese, a luminescence has been reported at a wavelength characteristic for the given material; all together cover a broad spectral range. The present study focuses on the elastic properties of one of these oxonitridosilicates, the Eu-doped triclinic α-SrSi2O2N2. High-pressure powder diffraction experiments are used in order to experimentally determine, for the first time, the equation of state of this compound. The in situ experiment was performed for pressures ranging up to 9.65 GPa, for Eu-doped α-SrSi2O2N2 sample mounted in a diamond anvil cell ascertaining the hydrostatic compression conditions. The obtained experimental variation of volume of the triclinic unit cell of α-SrSi2O2N2:Eu with rising pressure served for determination of the Birch-Murnaghan equation of state. The determined above quoted bulk modulus is 103(5) GPa, its first derivative is 4.5(1.1). The above quoted bulk modulus value is found to be comparable to that of earlier reported oxynitrides of different composition.

  17. Influence of aerosol chemical composition on N2O5 uptake: airborne regional measurements in North-Western Europe

    NASA Astrophysics Data System (ADS)

    Morgan, W. T.; Ouyang, B.; Allan, J. D.; Aruffo, E.; Di Carlo, P.; Kennedy, O. J.; Lowe, D.; Flynn, M. J.; Rosenberg, P. D.; Williams, P. I.; Jones, R.; McFiggans, G. B.; Coe, H.

    2014-07-01

    Aerosol chemical composition was found to influence nighttime atmospheric chemistry during a series of airborne measurements in North-Western Europe in summer conditions, which has implications for regional air quality and climate. The uptake of dinitrogen pentoxide, γ (N2O5), to particle surfaces was found to be modulated by the amount of water content and ammonium nitrate present in the aerosol. The conditions prevalent in this study suggest that the net uptake rate of N2O5 to atmospheric aerosols was relatively efficient compared to previous studies, with γ (N2O5) values in the range 0.01-0.03. This is likely a consequence of the elevated relative humidity in the region, which promotes greater aerosol water content. Increased nitrate concentrations relative to particulate water were found to suppress N2O5 uptake. The results presented here contrast with previous ambient studies of N2O5 uptake, which have generally taken place in low-nitrate environments in the USA. Comparison of the N2O5 uptake derived from the measurements with a parameterised scheme that is based on the ratio of particulate water to nitrate yielded reasonably good agreement in terms of the magnitude and variation in uptake, provided the effect of chloride was neglected. An additional suppression of the parameterised uptake is likely required to fully capture the variation in N2O5 uptake, which could be achieved via the known suppression by organic aerosol. However, existing parameterisations representing the suppression by organic aerosol were unable to fully represent the variation in N2O5 uptake. These results provide important ambient measurement constraint on our ability to predict N2O5 uptake in regional and global aerosol models. N2O5 uptake is a potentially important source of nitrate aerosol and a sink of the nitrate radical, which is the main nocturnal oxidant in the atmosphere. The results further highlight the importance of ammonium nitrate in North-Western Europe as a key

  18. Low-Temperature Desorption of N2O from NO on Rutile TiO2(110)-1x1

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kim, Boseong; Li, Zhenjun; Kay, Bruce D.

    2014-05-08

    We find that NO dosed on rutile TiO2(110)-1×1 at substrate temperatures as low as 50 K readily reacts to produce N2O which desorbs promptly from the surface leaving an oxygen adatom behind. The desorption rate of N2O reaches a maximum value after 1 – 2 sec at an NO flux of 1.2 ×1014 NO/cm2∙sec and then decreases rapidly as the initially clean, reduced TiO2(110) surface with ~5% oxygen vacancies (VO’s) becomes covered with oxygen adatoms and unreacted NO. The maximum desorption rate is also found to increase as the substrate temperature is raised up to about 100 K. Interestingly, themore » N2O desorption during the low-temperature (LT) NO dose is strongly suppressed when molecular oxygen is predosed, whereas it persists on the surface with VO’s passivated by surface hydroxyls. Our results show that the surface charge, not the VO sites, plays a dominant role in the LT N2O desorption induced by a facile NO reduction at such low temperatures.« less

  19. SnO2-gated AlGaN/GaN high electron mobility transistors based oxygen sensors

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hung, S.T.; Chung, Chi-Jung; Chen, Chin Ching

    2012-01-01

    Hydrothermally grown SnO2 was integrated with AlGaN/GaN high electron mobility transistor (HEMT) sensor as the gate electrode for oxygen detection. The crystalline of the SnO2 was improved after annealing at 400 C. The grain growth kinetics of the SnO2 nanomaterials, together with the O2 gas sensing properties and sensing mechanism of the SnO2 gated HEMT sensors were investigated. Detection of 1% oxygen in nitrogen at 100 C was possible. A low operation temperature and low power consumption oxygen sensor can be achieved by combining the SnO2 films with the AlGaN/GaN HEMT structure

  20. C/O Ratio as a Dimension for Characterizing Exoplanetary Atmospheres

    NASA Astrophysics Data System (ADS)

    Madhusudhan, Nikku

    2012-10-01

    Until recently, infrared observations of exoplanetary atmospheres have typically been interpreted using models that assumed solar elemental abundances. With the chemical composition fixed, attempts have been made to classify hot Jupiter atmospheres on the basis of stellar irradiation. However, recent observations have revealed deviations from predictions based on such classification schemes, and chemical compositions retrieved from some data sets have also indicated non-solar abundances. The data require a two-dimensional (2D) characterization scheme with dependence on both irradiation and chemistry. In this work, we suggest the carbon-to-oxygen (C/O) ratio as an important second dimension for characterizing exoplanetary atmospheres. In hot-hydrogen-dominated atmospheres, the C/O ratio critically influences the relative concentrations of several spectroscopically dominant species. Between a C/O of 0.5 (solar value) and 2, the H2O and CH4 abundances can vary by several orders of magnitude in the observable atmosphere, and new hydrocarbon species such as HCN and C2H2 become prominent for C/O >= 1, while the CO abundance remains almost unchanged. Furthermore, a C/O >= 1 can preclude a strong thermal inversion due to TiO and VO in a hot Jupiter atmosphere, since TiO and VO are naturally underabundant for C/O >= 1. We, therefore, suggest a new 2D classification scheme for hydrogen-dominated exoplanetary atmospheres with irradiation (or temperature) and C/O ratio as the two dimensions. We define four classes in this 2D space (O1, O2, C1, and C2) with distinct chemical, thermal, and spectral properties. Based on the most recent observations, we characterize the thermal structure and C/O ratios of six hot Jupiters (XO-1b, CoRoT-2b, WASP-14b, WASP-19b, WASP-33b, and WASP-12b) in the framework of our proposed 2D classification scheme. While the data for several systems in our sample are consistent with C-rich atmospheres, new observations are required to conclusively

  1. Hierarchical Honeycomb Br-, N-Codoped TiO2 with Enhanced Visible-Light Photocatalytic H2 Production.

    PubMed

    Zhang, Chao; Zhou, Yuming; Bao, Jiehua; Sheng, Xiaoli; Fang, Jiasheng; Zhao, Shuo; Zhang, Yiwei; Chen, Wenxia

    2018-06-06

    The halogen elements modification strategy of TiO 2 encounters a bottleneck in visible-light H 2 production. Herein, we have for the first time reported a hierarchical honeycomb Br-, N-codoped anatase TiO 2 catalyst (HM-Br,N/TiO 2 ) with enhanced visible-light photocatalytic H 2 production. During the synthesizing process, large amounts of meso-macroporous channels and TiO 2 nanosheets were fabricated in massive TiO 2 automatically, constructing the hierarchical honeycomb structure with large specific surface area (464 m 2 g -1 ). cetyl trimethylammonium bromide and melamine played a key role in constructing the meso-macroporous channels. Additionally, HM-Br,N/TiO 2 showed a high visible-light H 2 production rate of 2247 μmol h -1 g -1 , which is far more higher than single Br- or N-doped TiO 2 (0 or 63 μmol h -1 g -1 , respectively), thereby demonstrating the excellent synergistic effects of Br and N elements in H 2 evolution. In HM-Br,N/TiO 2 catalytic system, the codoped Br-N atoms could reduce the band gap of TiO 2 to 2.88 eV and the holes on acceptor levels (N acceptor) can passivate the electrons on donor levels (Br donor), thereby preventing charge carriers recombination significantly. Furthermore, the proposed HM-Br,N/TiO 2 fabrication strategy had a wide range of choices for N source (e.g., melamine, urea, and dicyandiamide) and it can be applied to other TiO 2 materials (e.g., P25) as well, thereby implying its great potential application in visible-light H 2 production. Finally, on the basis of experimental results, a possible photocatalytic H 2 production mechanism for HM-Br,N/TiO 2 was proposed.

  2. Coupling of N2O and CO2 fluxes from agriculture in Michigan

    NASA Astrophysics Data System (ADS)

    Cui, M.; Tang, J.; Hastings, M. G.; Gelfand, I.; Tao, L.; Sun, K.

    2012-12-01

    CO2 has been known to cause global warming, and N2O is the largest contributor to the greenhouse gas burden of cropping systems in the United States due to application of fertilizer. In our study, fluxes of N2O and CO2 were measured at two maize fields and one reference grassland from Kellogg Biological Station in Southwest Michigan. Here we compared two measuring systems, traditional GC method and LGR/Li-Cor system. Our initial results show that the two measuring systems are consistent (N2O slope=0.96, R2=0.96; and CO2 slope= 1.03, R2=0.86 measuring from the same chamber). Measurements done in pairs of chambers suggest great spatial variations, despite that the chambers were only 0.5 meter apart. The two systems are still comparable by averaging 8 pairs of chambers distributed within one site. Increase of CO2 fluxes were observed the second day after fertilization, but no significant change of N2O fluxes was shown. After artificial rainfall, boosting N2O fluxes and further increase in CO2 fluxes were demonstrated. Our result indicates that precipitation is necessary before a prominent N2O peak. In our LGR/Li-Cor system, CO was also measured from chambers. Interesting CO fluxes were shown in our experiment. Soil, which is usually considered as a CO sink, emits CO in some chambers during our measurement, which is probably related to the nationwide forest fires and lack of precipitation during the period.

  3. The δ15N and δ18O values of N2O produced during the co-oxidation of ammonia by methanotrophic bacteria

    USGS Publications Warehouse

    Mandernack, Kevin W.; Mills, Christopher T.; Johnson, Craig A.; Rahn, Thomas; Kinney, Chad

    2009-01-01

    In order to determine if the δ15N and δ18O values of N2O produced during co-oxidation of NH4+ by methanotrophic (methane oxidizing) bacteria can be isotopically distinguished from N2O produced either by autotrophic nitrifying or denitrifying bacteria, we conducted laboratory incubation experiments with pure cultures of methanotrophic bacteria that were provided NH4Cl as an oxidation substrate. The N2O produced during NH4+ oxidation by methanotrophic bacteria showed nitrogen isotope fractionation between NH4+ and N2ON2O–NH4+) of − 48 and − 55‰ for Methylomonas methanica and Methylosinus trichosporium, OB3b respectively. These large fractionations are similar to those previously measured for autotrophic nitrifying bacteria and consistent with N2O formation by multiple rate limiting steps that include NH4+oxidation by the methane monooxygenase enzyme and reduction of NO2− to N2O. Consequently, N2O formed by NH4+ oxidation via methanotrophic or autotrophic nitrifying bacteria might generally be characterized by lower δ15NN2O values than that formed by denitrificaiton, although this also depends on the variability of δ15N of available nitrogen sources (e.g., NH4+, NO3−, NO2−). Additional incubations with M. trichosporium OB3b at high and low CH4 conditions in waters of different δ18O values revealed that 19–27% of the oxygen in N2O was derived from O2 with the remainder from water. The biochemical mechanisms that could explain this amount of O2 incorporation are discussed. The δ18O of N2O formed under high CH4 conditions was ~ + 15‰ more positive than that formed under lower CH4 conditions. This enrichment resulted in part from the incorporation of O2 into N2O that was enriched in 18O due to an isotope fractionation effect of − 16.1 ± 2.0‰ and − 17.5 ± 5.4‰ associated with O2 consumption during the high and low methane concentration incubations, respectively. Therefore, N2O formed by NH4+

  4. Quantifying Uncertainties in N2O Emission Due to N Fertilizer Application in Cultivated Areas

    PubMed Central

    Philibert, Aurore; Loyce, Chantal; Makowski, David

    2012-01-01

    Nitrous oxide (N2O) is a greenhouse gas with a global warming potential approximately 298 times greater than that of CO2. In 2006, the Intergovernmental Panel on Climate Change (IPCC) estimated N2O emission due to synthetic and organic nitrogen (N) fertilization at 1% of applied N. We investigated the uncertainty on this estimated value, by fitting 13 different models to a published dataset including 985 N2O measurements. These models were characterized by (i) the presence or absence of the explanatory variable “applied N”, (ii) the function relating N2O emission to applied N (exponential or linear function), (iii) fixed or random background (i.e. in the absence of N application) N2O emission and (iv) fixed or random applied N effect. We calculated ranges of uncertainty on N2O emissions from a subset of these models, and compared them with the uncertainty ranges currently used in the IPCC-Tier 1 method. The exponential models outperformed the linear models, and models including one or two random effects outperformed those including fixed effects only. The use of an exponential function rather than a linear function has an important practical consequence: the emission factor is not constant and increases as a function of applied N. Emission factors estimated using the exponential function were lower than 1% when the amount of N applied was below 160 kg N ha−1. Our uncertainty analysis shows that the uncertainty range currently used by the IPCC-Tier 1 method could be reduced. PMID:23226430

  5. Controlled nitric oxide production via O( 1D)+N 2O reactions for use in oxidation flow reactor studies

    DOE PAGES

    Lambe, Andrew; Massoli, Paola; Zhang, Xuan; ...

    2017-06-22

    Oxidation flow reactors that use low-pressure mercury lamps to produce hydroxyl (OH) radicals are an emerging technique for studying the oxidative aging of organic aerosols. Here, ozone (O 3) is photolyzed at 254 nm to produce O( 1D) radicals, which react with water vapor to produce OH. However, the need to use parts-per-million levels of O 3 hinders the ability of oxidation flow reactors to simulate NO x-dependent secondary organic aerosol (SOA) formation pathways. Simple addition of nitric oxide (NO) results in fast conversion of NO x (NO+NO 2) to nitric acid (HNO 3), making it impossible to sustain NOmore » x at levels that are sufficient to compete with hydroperoxy (HO 2) radicals as a sink for organic peroxy (RO 2) radicals. We developed a new method that is well suited to the characterization of NO x-dependent SOA formation pathways in oxidation flow reactors. NO and NO 2 are produced via the reaction O( 1D) + N 2O2NO, followed by the reaction NO + O 3 → NO 2+O 2. Laboratory measurements coupled with photochemical model simulations suggest that O( 1D) + N 2O reactions can be used to systematically vary the relative branching ratio of RO 2 + NO reactions relative to RO 2 + HO 2 and/or RO 2 + RO 2 reactions over a range of conditions relevant to atmospheric SOA formation. We demonstrate proof of concept using high-resolution time-of-flight chemical ionization mass spectrometer (HR-ToF-CIMS) measurements with nitrate (NO 3 -) reagent ion to detect gas-phase oxidation products of isoprene and α-pinene previously observed in NO x-influenced environments and in laboratory chamber experiments.« less

  6. Controlled nitric oxide production via O( 1D)+N 2O reactions for use in oxidation flow reactor studies

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lambe, Andrew; Massoli, Paola; Zhang, Xuan

    Oxidation flow reactors that use low-pressure mercury lamps to produce hydroxyl (OH) radicals are an emerging technique for studying the oxidative aging of organic aerosols. Here, ozone (O 3) is photolyzed at 254 nm to produce O( 1D) radicals, which react with water vapor to produce OH. However, the need to use parts-per-million levels of O 3 hinders the ability of oxidation flow reactors to simulate NO x-dependent secondary organic aerosol (SOA) formation pathways. Simple addition of nitric oxide (NO) results in fast conversion of NO x (NO+NO 2) to nitric acid (HNO 3), making it impossible to sustain NOmore » x at levels that are sufficient to compete with hydroperoxy (HO 2) radicals as a sink for organic peroxy (RO 2) radicals. We developed a new method that is well suited to the characterization of NO x-dependent SOA formation pathways in oxidation flow reactors. NO and NO 2 are produced via the reaction O( 1D) + N 2O2NO, followed by the reaction NO + O 3 → NO 2+O 2. Laboratory measurements coupled with photochemical model simulations suggest that O( 1D) + N 2O reactions can be used to systematically vary the relative branching ratio of RO 2 + NO reactions relative to RO 2 + HO 2 and/or RO 2 + RO 2 reactions over a range of conditions relevant to atmospheric SOA formation. We demonstrate proof of concept using high-resolution time-of-flight chemical ionization mass spectrometer (HR-ToF-CIMS) measurements with nitrate (NO 3 -) reagent ion to detect gas-phase oxidation products of isoprene and α-pinene previously observed in NO x-influenced environments and in laboratory chamber experiments.« less

  7. N2O and NO2 Emissions from Heavy-Duty Diesel Trucks with Advanced Emission Controls

    NASA Astrophysics Data System (ADS)

    Preble, C.; Harley, R.; Kirchstetter, T.

    2014-12-01

    Diesel engines are the largest source of nitrogen oxides (NOx) emissions nationally, and also a major contributor to the black carbon (BC) fraction of fine particulate matter (PM). Recently, diesel particle filter (DPF) and selective catalytic reduction (SCR) emission control systems that target exhaust PM and NOx have become standard equipment on new heavy-duty diesel trucks. However, the deliberate catalytic oxidation of engine-out nitric oxide (NO) to nitrogen dioxide (NO2) in continuously regenerating DPFs leads to increased tailpipe emission of NO2. This is of potential concern due to the toxicity of NO2 and the resulting increases in atmospheric formation of other air pollutants such as ozone, nitric acid, and fine PM. While use of SCR reduces emissions of both NO and NO2, it may lead to increased emissions of nitrous oxide (N2O), a potent greenhouse gas. Here we report results from on-road measurements of heavy-duty diesel truck emissions conducted at the Port of Oakland and the Caldecott Tunnel in the San Francisco Bay Area. Emission factors (g pollutant per kg of diesel) were linked via recorded license plates to individual truck attributes, including engine model year and installed emission control equipment. Between 2009 and 2013, the fraction of DPF-equipped trucks at the Port of Oakland increased from 2 to 99%, and median engine age decreased from 11 to 6 years. Over the same period, fleet-average emission factors for black carbon and NOx decreased by 76 ± 22% and 53 ± 8%, respectively. However, direct emissions of NO2 increased, and consequently the NO2/NOx emission ratio increased from 0.03 ± 0.02 to 0.18 ± 0.03. Older trucks retrofitted with DPFs emitted approximately 3.5 times more NO2 than newer trucks equipped with both DPF and SCR. Preliminary data from summer 2014 measurements at the Caldecott Tunnel suggest that some older trucks have negative emission factors for N2O, and that for newer trucks, N2O emission factors have changed sign and

  8. TES/Aura L2 Ozone (O3) Nadir V6 (TL2O3N)

    Atmospheric Science Data Center

    2018-01-18

    TES/Aura L2 Ozone (O3) Nadir (TL2O3N) News:  TES News Join ... Project Title:  TES Discipline:  Tropospheric Composition Version:  V6 Level:  L2 Platform:  TES/Aura L2 Ozone Spatial Coverage:  5.3 x 8.5 km nadir ...

  9. Sensitivity of terrestrial N2O emission to atmospheric nitrogen deposition

    NASA Astrophysics Data System (ADS)

    Ito, A.; Sudo, K.; Nishina, K.; Ishijima, K.; Inatomi, M. I.

    2015-12-01

    Terrestrial N2O emission is generated from several nitrogen sources including biological fixation, agricultural fertilizer, and atmospheric deposition. There remain large uncertainties how much N2O is produced from atmospheric deposition. This is a crosscutting issue between global warming and atmospheric pollution. In this study, we assessed the sensitivity of global terrestrial N2O emission to atmospheric deposition, using a process-based model VISIT. In the model, N2O emission is estimated separately for nitrification and denitrfication with the NGAS parameterization. The global simulations were conducted from 1901 to 2014 at spatial resolution of 0.5 degree. Atmospheric deposition of ammonium, NOy, and organic nitrogen simulated by the atmospheric chemistry model CHASER from the pre-industrial time to the present was used. Annual total nitrogen deposition was estimated to increase from 27 Tg N in 1901 to 77 Tg N in 2014. The total N2O emission was also estimated to increase in the period, but it was largely attributable to the increased emission from croplands. We need further investigations for the N2O emission from natural soils, which may be nitrogen-limited.

  10. Modeling global annual N2O and NO emissions from fertilized fields

    NASA Astrophysics Data System (ADS)

    Bouwman, A. F.; Boumans, L. J. M.; Batjes, N. H.

    2002-12-01

    Information from 846 N2O emission measurements in agricultural fields and 99 measurements for NO emissions was used to describe the influence of various factors regulating emissions from mineral soils in models for calculating global N2O and NO emissions. Only those factors having a significant influence on N2O and NO emissions were included in the models. For N2O these were (1) environmental factors (climate, soil organic C content, soil texture, drainage and soil pH); (2) management-related factors (N application rate per fertilizer type, type of crop, with major differences between grass, legumes and other annual crops); and (3) factors related to the measurements (length of measurement period and frequency of measurements). The most important controls on NO emission include the N application rate per fertilizer type, soil organic-C content and soil drainage. Calculated global annual N2O-N and NO-N emissions from fertilized agricultural fields amount to 2.8 and 1.6 Mtonne, respectively. The global mean fertilizer-induced emissions for N2O and NO amount to 0.9% and 0.7%, respectively, of the N applied. These overall results account for the spatial variability of the main N2O and NO emission controls on the landscape scale.

  11. MOCVD of HfO2 and ZrO2 high-k gate dielectrics for InAlN/AlN/GaN MOS-HEMTs

    NASA Astrophysics Data System (ADS)

    Abermann, S.; Pozzovivo, G.; Kuzmik, J.; Strasser, G.; Pogany, D.; Carlin, J.-F.; Grandjean, N.; Bertagnolli, E.

    2007-12-01

    We apply metal organic chemical vapour deposition (MOCVD) of HfO2 and of ZrO2 from β-diketonate precursors to grow high-k gate dielectrics for InAlN/AlN/GaN metal oxide semiconductor (MOS)-high electron mobility transistors (HEMTs). High-k oxides of about 12 nm-14 nm are deposited for the MOS-HEMTs incorporating Ni/Au gates, whereas as a reference, Ni-contact-based 'conventional' Schottky-barrier (SB)-HEMTs are processed. The processed dielectrics decrease the gate current leakage of the HEMTs by about four orders of magnitude if compared with the SB-gated HEMTs and show superior device characteristics in terms of IDS and breakdown.

  12. Acidification Enhances Hybrid N2O Production Associated with Aquatic Ammonia-Oxidizing Microorganisms

    PubMed Central

    Frame, Caitlin H.; Lau, Evan; Nolan, E. Joseph; Goepfert, Tyler J.; Lehmann, Moritz F.

    2017-01-01

    Ammonia-oxidizing microorganisms are an important source of the greenhouse gas nitrous oxide (N2O) in aquatic environments. Identifying the impact of pH on N2O production by ammonia oxidizers is key to understanding how aquatic greenhouse gas fluxes will respond to naturally occurring pH changes, as well as acidification driven by anthropogenic CO2. We assessed N2O production rates and formation mechanisms by communities of ammonia-oxidizing bacteria (AOB) and archaea (AOA) in a lake and a marine environment, using incubation-based nitrogen (N) stable isotope tracer methods with 15N-labeled ammonium (15NH4+) and nitrite (15NO2−), and also measurements of the natural abundance N and O isotopic composition of dissolved N2O. N2O production during incubations of water from the shallow hypolimnion of Lake Lugano (Switzerland) was significantly higher when the pH was reduced from 7.54 (untreated pH) to 7.20 (reduced pH), while ammonia oxidation rates were similar between treatments. In all incubations, added NH4+ was the source of most of the N incorporated into N2O, suggesting that the main N2O production pathway involved hydroxylamine (NH2OH) and/or NO2− produced by ammonia oxidation during the incubation period. A small but significant amount of N derived from exogenous/added 15NO2− was also incorporated into N2O, but only during the reduced-pH incubations. Mass spectra of this N2O revealed that NH4+ and 15NO2− each contributed N equally to N2O by a “hybrid-N2O” mechanism consistent with a reaction between NH2OH and NO2−, or compounds derived from these two molecules. Nitrifier denitrification was not an important source of N2O. Isotopomeric N2O analyses in Lake Lugano were consistent with incubation results, as 15N enrichment of the internal N vs. external N atoms produced site preferences (25.0–34.4‰) consistent with NH2OH-dependent hybrid-N2O production. Hybrid-N2O formation was also observed during incubations of seawater from coastal Namibia

  13. Preparation of single-crystal spherical γ-Mo2N by temperature-programmed reaction between β-MoO3 and NH3

    NASA Astrophysics Data System (ADS)

    Wang, Lu; Zhang, Guo-Hua; Chou, Kuo-Chih

    2017-10-01

    In the present wok, single-crystalline spherical γ-Mo2N powders was successfully prepared by the temperature-programmed reaction of single-crystal spherical β-MoO3 with NH3 in the temperature ranges of 1013-1073 K. Herein, the Mo source used was monoclinic system, β-MoO3, a metastable phase of MoO3. It is found that the characterizations of the as-prepared γ-Mo2N powders are strongly depended on the selection of the MoO3 precursor. In other words, the as-prepared γ-Mo2N powders inherited the shape, size and structure of the used β-MoO3 precursors upon reaction with NH3. In order to make a comparison, β-MoO3 was also reduced by the mixed gases of N2 and H2 with the flow rate ratio of 1:3 at the identical conditions. It was found that pure β-Mo2N polycrystalline can be obtained when the temperature was 1013 K; while further increasing the reaction temperature, metal Mo powder will be turned up.

  14. Kinetics of nitrous oxide (N2O) formation and reduction by Paracoccus pantotrophus.

    PubMed

    Read-Daily, B L; Sabba, F; Pavissich, J P; Nerenberg, R

    2016-12-01

    Nitrous oxide (N 2 O) is a powerful greenhouse gas emitted from wastewater treatment, as well as natural systems, as a result of biological nitrification and denitrification. While denitrifying bacteria can be a significant source of N 2 O, they can also reduce N 2 O to N 2 . More information on the kinetics of N 2 O formation and reduction by denitrifying bacteria is needed to predict and quantify their impact on N 2 O emissions. In this study, kinetic parameters were determined for Paracoccus pantotrophus, a common denitrifying bacterium. Parameters included the maximum specific reduction rates, [Formula: see text], growth rates, [Formula: see text], and yields, Y, for reduction of NO 3 - (nitrate) to nitrite (NO 2 - ), NO 2 - to N 2 O, and N 2 O to N 2 , with acetate as the electron donor. The [Formula: see text] values were 2.9 gN gCOD -1 d -1 for NO 3 - to NO 2 - , 1.4 gN gCOD -1  d -1 for NO 2 - to N 2 O, and 5.3 gN gCOD -1  d -1 for N 2 O to N 2 . The [Formula: see text] values were 2.7, 0.93, and 1.5 d -1 , respectively. When N 2 O and NO 3 - were added concurrently, the apparent (extant) kinetics, [Formula: see text], assuming reduction to N 2 , were 6.3 gCOD gCOD -1  d -1 , compared to 5.4 gCOD gCOD -1  d -1 for NO 3 - as the sole added acceptor. The [Formula: see text] was 1.6 d -1 , compared to 2.5 d -1 for NO 3 - alone. These results suggest that NO 3 - and N 2 O were reduced concurrently. Based on this research, denitrifying bacteria like P. pantotrophus may serve as a significant sink for N 2 O. With careful design and operation, treatment plants can use denitrifying bacteria to minimize N 2 O emissions.

  15. Enhancement by O6-benzyl-N2-acetylguanosine of N'-[2-chloroethyl]-N-[2-(methylsulphonyl)ethyl]-N'-nitrosourea therapeutic index on nude mice bearing resistant human melanoma.

    PubMed Central

    Debiton, E.; Cussac-Buchdhal, C.; Mounetou, E.; Rapp, M.; Dupuy, J. M.; Maurizis, J. C.; Veyre, A.; Madelmont, J. C.

    1997-01-01

    The exposure of cells to O6-benzyl-N2-acetylguanosine (BNAG) and several guanine derivatives is known to reduce the activity of O6-alkylguanine-DNA alkyltransferase (MGMT) and to enhance the sensitivity of Mer+ (methyl enzyme repair positive) tumour cells to chloroethylnitrosoureas (CENUs) in vitro and in vivo. High water solubility and the pharmacokinetic properties of BNAG make it a candidate for simultaneous administration with CENUs by the i.v. route in human clinical use. In vivo we have shown previously that BNAG significantly increases the efficiency of N'-[2-chloroethyl]-N-[2-(methylsulphonyl)ethyl]-N'-nitrosourea (cystemustine) against M4Beu melanoma cells (Mer+) through its cytostatic activity by the i.p. route, but also increases its toxicity. To investigate the toxicity of BNAG and cystemustine when administered simultaneously in mice, we compared the maximum tolerated dose and LD50 doses of cystemustine alone or in combination with 40 mg kg(-1) BNAG by the i.p. route. The toxicity of cystemustine was enhanced by a factor of almost 1.44 when combined with BNAG. To compare the therapeutic index of cystemustine alone and the cystemustine/BNAG combination, pharmacological tests were carried out in nude mice bearing Mer+ M4Beu human melanoma cells. Isotoxic doses were calculated using the 1.44 ratio. The treatments were administered three times by the i.v. route on days 1, 5 and 9 after s.c. inoculation of tumour cells. Although the toxicities of the treatments were equal, BNAG strongly enhanced tumour growth inhibition. These results demonstrate the increase of the therapeutic index of cystemustine by BNAG and justify the use of BNAG to enhance nitrosourea efficiency in vivo by i.v. co-injection. PMID:9365163

  16. Self-terminated etching of GaN with a high selectivity over AlGaN under inductively coupled Cl2/N2/O2 plasma with a low-energy ion bombardment

    NASA Astrophysics Data System (ADS)

    Zhong, Yaozong; Zhou, Yu; Gao, Hongwei; Dai, Shujun; He, Junlei; Feng, Meixin; Sun, Qian; Zhang, Jijun; Zhao, Yanfei; DingSun, An; Yang, Hui

    2017-10-01

    Etching of GaN/AlGaN heterostructure by O-containing inductively coupled Cl2/N2 plasma with a low-energy ion bombardment can be self-terminated at the surface of the AlGaN layer. The estimated etching rates of GaN and AlGaN were 42 and 0.6 nm/min, respectively, giving a selective etching ratio of 70:1. To study the mechanism of the etching self-termination, detailed characterization and analyses were carried out, including X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectroscopy (TOF-SIMS). It was found that in the presence of oxygen, the top surface of the AlGaN layer was converted into a thin film of (Al,Ga)Ox with a high bonding energy, which effectively prevented the underlying atoms from a further etching, resulting in a nearly self-terminated etching. This technique enables a uniform and reproducible fabrication process for enhancement-mode high electron mobility transistors with a p-GaN gate.

  17. Mathematical treatment of isotopologue and isotopomer speciation and fractionation in biochemical kinetics

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Maggi, F.M.; Riley, W.J.

    2009-11-01

    We present a mathematical treatment of the kinetic equations that describe isotopologue and isotopomer speciation and fractionation during enzyme-catalyzed biochemical reactions. These equations, presented here with the name GEBIK (general equations for biochemical isotope kinetics) and GEBIF (general equations for biochemical isotope fractionation), take into account microbial biomass and enzyme dynamics, reaction stoichiometry, isotope substitution number, and isotope location within each isotopologue and isotopomer. In addition to solving the complete GEBIK and GEBIF, we also present and discuss two approximations to the full solutions under the assumption of biomass-free and enzyme steady-state, and under the quasi-steady-state assumption as applied tomore » the complexation rate. The complete and approximate approaches are applied to observations of biological denitrification in soils. Our analysis highlights that the full GEBIK and GEBIF provide a more accurate description of concentrations and isotopic compositions of substrates and products throughout the reaction than do the approximate forms. We demonstrate that the isotopic effects of a biochemical reaction depend, in the most general case, on substrate and complex concentrations and, therefore, the fractionation factor is a function of time. We also demonstrate that inverse isotopic effects can occur for values of the fractionation factor smaller than 1, and that reactions that do not discriminate isotopes do not necessarily imply a fractionation factor equal to 1.« less

  18. First on-line isotopic characterization of N2O above intensively managed grassland

    NASA Astrophysics Data System (ADS)

    Wolf, B.; Merbold, L.; Decock, C.; Tuzson, B.; Harris, E.; Six, J.; Emmenegger, L.; Mohn, J.

    2015-04-01

    The analysis of the four main isotopic N2O species (14N14N16O, 14N15N16O, 15N14N16O, 14N14N18O) and especially the intramolecular distribution of 15N ("site preference", SP) has been suggested as a tool to distinguish source processes and to help constrain the global N2O budget. However, current studies suffer from limited spatial and temporal resolution capabilities due to the combination of discrete flask sampling with subsequent laboratory-based mass-spectrometric analysis. Quantum cascade laser absorption spectroscopy (QCLAS) allows the selective high-precision analysis of N2O isotopic species at trace levels and is suitable for in situ measurements. Here, we present results from the first field campaign, conducted on an intensively managed grassland site in central Switzerland. N2O mole fractions and isotopic composition were determined in the atmospheric surface layer (at 2.2 m height) at a high temporal resolution with a modified state-of-the-art laser spectrometer connected to an automated N2O preconcentration unit. The analytical performance was determined from repeated measurements of a compressed air tank and resulted in measurement repeatability of 0.20, 0.12 and 0.11‰ for δ15Nα, δ15Nβ and δ18O, respectively. Simultaneous eddy-covariance N2O flux measurements were used to determine the flux-averaged isotopic signature of soil-emitted N2O. Our measurements indicate that, in general, nitrifier-denitrification and denitrification were the prevalent sources of N2O during the campaign and that variations in isotopic composition were due to alterations in the extent to which N2O was reduced to N2 rather than to other pathways, such as hydroxylamine oxidation. Management and rewetting events were characterized by low values of the intramolecular 15N site preference (SP), δ15Nbulk and δ18O, suggesting that nitrifier-denitrification and incomplete heterotrophic bacterial denitrification responded most strongly to the induced disturbances. The flux

  19. Improving estimates of N2O emissions for western and central Europe using a Bayesian inversion approach

    NASA Astrophysics Data System (ADS)

    Thompson, R. L.; Gerbig, C.; Roedenbeck, C.; Heimann, M.

    2009-04-01

    The nitrous oxide (N2O) mixing ratio has been increasing in the atmosphere since the industrial revolution, from 270 ppb in 1750 to 320 ppb in 2007 with a steady growth rate of around 0.26% since the early 1980's. The increase in N2O is worrisome for two main reasons. First, it is a greenhouse gas; this means that its atmospheric increase translates to an enhancement in radiative forcing of 0.16 ± 0.02 Wm-2 making it currently the fourth most important long-lived greenhouse gas and is predicted to soon overtake CFC's to become the third most important. Second, it plays an important role in stratospheric ozone chemistry. Human activities are the primary cause of the atmospheric N2O increase. The largest anthropogenic source of N2O is from the use of N-fertilizers in agriculture but fossil fuel combustion and industrial processes, such as adipic and nitric acid production, are also important. We present a Bayesian inversion approach for estimating N2O fluxes over central and western Europe using high frequency in-situ concentration data from the Ochsenkopf tall tower (50 °01′N, 11 °48′, 1022 masl). For the inversion, we employ a Lagrangian-type transport model, STILT, which provides source-receptor relationships at 10 km using ECMWF meteorological data. The a priori flux estimates used were from IER, for anthropogenic, and GEIA, for natural fluxes. N2O fluxes were retrieved monthly at 2 x 2 degree spatial resolution for 2007. The retrieved N2O fluxes showed significantly more spatial heterogeneity than in the a priori field and considerable seasonal variability. The timing of peak emissions was different for different regions but in general the months with the strongest emissions were May and August. Overall, the retrieved flux (anthropogenic and natural) was lower than in the a priori field.

  20. Hydrothermal synthesis and enhanced photocatalytic activity of mixed-phase TiO2 powders with controllable anatase/rutile ratio

    NASA Astrophysics Data System (ADS)

    Wang, Qi; Qiao, Zhi; Jiang, Peng; Kuang, Jianlei; Liu, Wenxiu; Cao, Wenbin

    2018-03-01

    In this study, mixed-phase TiO2 powders were novelly synthesized via a facile and mild hydrothermal method without any post-heat treatment. TiOSO4 and peroxide titanic acid (PTA) were used as inorganic titanium sources, while no special solvent or additive were introduced. The XRD and TEM results showed the mixed-phase TiO2 powders were composed of anatase and rutile phases, and the PTA sol played an important role on forming the rutile nucleus. The proportion of rutile in the mixed-phase TiO2 could be easily controlled in the range of 0%-70.5% by changing the amount of PTA sol used in the synthesis process. The UV-Visible absorption spectra indicated the prepared mixed-phase TiO2 showed enhanced visible light absorption with the increase of rutile ratio. The photodegradation experiments revealed the mixed-phase TiO2 exhibited the best photocatalytic activity at the rutile ratio of 41.5%, while a higher or lower rutile ratio both resulted in the decrease of photocatalytic activity.

  1. Leachate treatment in landfills is a significant N2O source.

    PubMed

    Wang, Xiaojun; Jia, Mingsheng; Zhang, Chengliang; Chen, Shaohua; Cai, Zucong

    2017-10-15

    The importance of methane (CH 4 ) emissions from landfills has been extensively documented, while the nitrous oxide (N 2 O) emissions from landfills are considered negligible. In this study, three landfills were selected to measure CH 4 and N 2 O emissions using the static chamber method. Dongbu (DB) and Dongfu (DF) landfills, both located in Xiamen city, Fujian Province, were classified as sanitary. The former started to receive solid waste from Xiamen city in 2009, and the latter was closed in 2009. Nanjing (NJ) landfill, located in Nanjing county, Fujian Province, was classified as managed. Results showed that for the landfill reservoirs, CH 4 emissions were significant, while N 2 O emissions occurred mainly in operating areas (on average, 16.3 and 19.0mgN 2 Om -2 h -1 for DB and NJ landfills, respectively) and made a negligible contribution to the total greenhouse gas emissions in term of CO 2 equivalent. However, significant N 2 O emissions were observed in the leachate treatment systems of sanitary landfills and contributed 72.8% and 45.6% of total emissions in term of CO 2 equivalent in DB and DF landfills, respectively. The N 2 O emission factor (EF) of the leachate treatment systems was in the range of 8.9-11.9% of the removed nitrogen. The total N 2 O emissions from the leachate treatment systems of landfills in Xiamen city were estimated to be as high as 8.55gN 2 O-Ncapita -1 yr -1 . These results indicated that N 2 O emissions from leachate treatment systems of sanitary landfills were not negligible and should be included in national and/or local inventories of greenhouse gas emissions. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. N2O and CO2 emissions following repeated application of organic and mineral N fertiliser from a vegetable crop rotation.

    PubMed

    De Rosa, Daniele; Rowlings, David W; Biala, Johannes; Scheer, Clemens; Basso, Bruno; Grace, Peter R

    2018-05-11

    Accounting for nitrogen (N) release from organic amendments (OA) can reduce the use of synthetic N-fertiliser, sustain crop production, and potentially reduce soil borne greenhouse gases (GHG) emissions. However, it is difficult to assess the GHG mitigation potential for OA as a substitute of N-fertiliser over the long term due to only part of the organic N added to soil is being released in the first year after application. High-resolution nitrous oxide (N 2 O) and carbon dioxide (CO 2 ) emissions monitored from a horticultural crop rotation over 2.5 years from conventional urea application rates were compared to treatments receiving an annual application of raw and composted chicken manure combined with conventional and reduced N-fertiliser rates. The repeated application of composted manure did not increase annual N 2 O emissions while the application of raw manure resulted in N 2 O emissions up to 35.2 times higher than the zero N fertiliser treatment and up to 4.7 times higher than conventional N-fertiliser rate due to an increase in C and N availability following the repeated application of raw OA. The main factor driving N 2 O emissions was the incorporation of organic material accompanied by high soil moisture while the application of synthetic N-fertiliser induced only short-term N 2 O emission pulse. The average annual N 2 O emission factor calculated accounting for the total N applied including OA was equal to 0.27 ± 0.17%, 3.7 times lower than the IPCC default value. Accounting for the estimated N release from OA only enabled a more realistic N 2 O emission factor to be defined for organically amended field that was equal to 0.48 ± 0.3%. This study demonstrated that accounting for the N released from repeated application of composted rather than raw manure can be a viable pathway to reduce N 2 O emissions and maintain soil fertility. Copyright © 2017. Published by Elsevier B.V.

  3. Simple radiosensitizing of hypoxic tumor tissues by N2O/Br(-) mixture.

    PubMed

    Billik, P

    2015-07-01

    The radiosensitization model of hypoxic tumor tissues based on the N2O/Br(-) mixture is described. The well-documented radiolysis of water in the presence of N2O and Br(-) ions at a low concentration supports this model. An aqueous solution saturated with N2O gas during the radiolysis generates OH radicals in a large extent. In N2O/Br- media at pH<9, Br2 is formed. Br2 hydrolyzes in an aqueous solution to form a very reactive hypobromous (HOBr) acid. Such process is described by the following chemical reaction: H2O + Br(-) + N2O + ionizing radiation (IR) --> HOBr + OH(-). In vivo formed HOBr as a long-lived product with a high biological activity induces the hypoxic tumor cell damage via many unique mechanisms. A local application or inhalation of an N2O-O2 mixture before or during the radiotherapy to enhance the saturation of tissues with N2O is a key prerequisite. Since the extracellular concentration of Br(-) ions is very low (0.02-0.05 mM), an oral or local application of NaBr should be used to shift the extracellular concentration of Br(-) ions to the mM region. Copyright © 2015 Elsevier Ltd. All rights reserved.

  4. TiO2-based (Fe3O4, SiO2, reduced graphene oxide) magnetically recoverable photocatalysts for imazalil degradation in a synthetic wastewater.

    PubMed

    Santiago, Dunia E; Pastrana-Martínez, Luisa M; Pulido-Melián, Elisenda; Araña, Javier; Faria, Joaquim L; Silva, Adrián M T; González-Díaz, Óscar; Doña-Rodríguez, José M

    2018-03-02

    Magnetite (Fe 3 O 4 ), a core-shell material (SiO 2 @Fe 3 O 4 ), and reduced graphene oxide-Fe 3 O 4 (referred as rGO-MN) were used as supports of a specific highly active TiO 2 photocatalyst. Thermal treatments at 200 or 450 °C, different atmospheres (air or N 2 ), and TiO 2 :support weight ratios (1.0, 1.5, or 2.0) were investigated. X-ray diffractograms revealed that magnetite is not oxidized to hematite when the core-shell SiO 2 @Fe 3 O 4 material-or a N 2 atmosphere (instead of air) in the thermal treatment-was employed to prepare the TiO 2 -based catalysts (the magnetic properties being preserved). The materials treated with N 2 were first tested for degradation of imazalil (a well-known fungicide) in deionized water. The best compromise between the photocatalytic activity, magnetic separation, and Fe leached (1.61 mg L -1 , i.e., below the threshold for water reuse in irrigation) was found for the magnetic catalyst prepared with SiO 2 @Fe 3 O 4 , an intermediate TiO 2 :support ratio (1.5), and treated at 200 °C under N 2 atmosphere (i.e., SiO 2 @Fe 3 O 4 -EST-1.5-200-N 2 ). This material was then tested for the treatment of imazalil in a synthetic wastewater, SW (with a chemical composition simulating an effluent resulting from fruit postharvest activity). This SW has a pH of 4.2 and the experiments were carried out at this natural pH 0 and at neutral conditions (keeping pH at 7 along the reaction). The magnetic catalyst was more active than bare TiO 2 for the treatment of imazalil in SW at natural pH. Since Fe leaching was observed (3.53 mg L -1 ), added H 2 O 2 enhanced both imazalil degradation and mineralization. Conveniently, these catalysts can be readily recovered by using a conventional magnetic field, as demonstrated over three consecutive recycling runs. Graphical abstract % Imazalil conversion using different magnetic catalysts and comparison with bare TiO 2 .

  5. The N2O activation by Rh5 clusters. A quantum chemistry study.

    PubMed

    Olvera-Neria, Oscar; Avilés, Roberto; Francisco-Rodríguez, Héctor; Bertin, Virineya; García-Cruz, Raúl; González-Torres, Julio César; Poulain, Enrique

    2015-04-01

    Nitrous oxide (N2O) is a by-product of exhaust pipe gases treatment produced by motor vehicles. Therefore, the N2O reduction to N2 is necessary to meet the actual environmental legislation. The N2O adsorption and dissociation assisted by the square-based pyramidal Rh5 cluster was investigated using the density functional theory and the zero-order regular approximation (ZORA). The Rh5 sextet ground state is the most active in N2O dissociation, though the quartet and octet states are also active because they are degenerate. The Rh5 cluster spontaneously activates the N2O cleavage, and the reaction is highly exothermic ca. -75 kcal mol(-1). The N2O breaking is obtained for the geometrical arrangement that maximizes the overlap and electron transfers between the N2O and Rh5 frontier orbitals. The Rh5 high activity is due to the Rh 3d orbitals are located between the N2O HOMO and LUMO orbitals, which makes possible the interactions between them. In particular, the O 2p states strongly interact with Rh 3d orbitals, which finally weaken the N2O bond. The electron transfer is from the Rh5 HOMO orbital to the N2O antibonding orbital.

  6. Optimization of Al2O3/TiO2 nanolaminate thin films prepared with different oxide ratios, for use in organic light-emitting diode encapsulation, via plasma-enhanced atomic layer deposition.

    PubMed

    Kim, Lae Ho; Jeong, Yong Jin; An, Tae Kyu; Park, Seonuk; Jang, Jin Hyuk; Nam, Sooji; Jang, Jaeyoung; Kim, Se Hyun; Park, Chan Eon

    2016-01-14

    Encapsulation is essential for protecting the air-sensitive components of organic light-emitting diodes (OLEDs), such as the active layers and cathode electrodes. Thin film encapsulation approaches based on an oxide layer are suitable for flexible electronics, including OLEDs, because they provide mechanical flexibility, the layers are thin, and they are easy to prepare. This study examined the effects of the oxide ratio on the water permeation barrier properties of Al2O3/TiO2 nanolaminate films prepared by plasma-enhanced atomic layer deposition. We found that the Al2O3/TiO2 nanolaminate film exhibited optimal properties for a 1 : 1 atomic ratio of Al2O3/TiO2 with the lowest water vapor transmission rate of 9.16 × 10(-5) g m(-2) day(-1) at 60 °C and 90% RH. OLED devices that incorporated Al2O3/TiO2 nanolaminate films prepared with a 1 : 1 atomic ratio showed the longest shelf-life, in excess of 2000 hours under 60 °C and 90% RH conditions, without forming dark spots or displaying edge shrinkage.

  7. Microhabitat Effects on N2O Emissions from Floodplain Soils under Controlled Conditions

    NASA Astrophysics Data System (ADS)

    Ley, Martin; Lehmann, Moritz F.; Niklaus, Pascal A.; Kuhn, Thomas; Luster, Jörg

    2016-04-01

    Semi-terrestrial soils such as floodplain soils are considered to be potential hotspots of nitrous oxide (N2O) emissions. The quantitative assessment of N2O release from these hotspots under field conditions, and of the microbial pathways that underlie net N2O production (ammonium oxidation, nitrifier-denitrification, and denitrification) is challenging because of their high spatial and temporal variability. The production and consumption of N2O appears to be linked to the presence or absence of micro-niches, providing specific conditions that may be favorable to either of the relevant microbial pathways. Flood events have been shown to trigger moments of enhanced N2O emission through a close coupling of niches with high and low oxygen availabilities. This coupling might be modulated by microhabitat effects related to soil aggregate formation, root soil interactions and the degradation of organic matter accumulations. In order to assess how these factors can modulate N2O production and consumption under simulated flooding/drying conditions, we have set up a mesocosm experiment with N-rich floodplain soils comprising different combinations of soil aggregate size classes and inert matrix material. These model soils were either planted with basket willow (Salix viminalis L.), mixed with leaf litter, or left untreated. Throughout a simulated flood event, we repeatedly measured the net N2O production rate. In addition, soil water content, redox potential, as well as C and N substrate availability were monitored. In order to gain insight into the sources of, and biogeochemical controls on N2O production, we also measured the bulk δ15N signature of the produced N2O, as well as its intramolecular 15N site preference (SP). In this presentation we focus on a period of enhanced N2O emission during the drying phase after 48 hrs of flooding. We will discuss the observed emission patterns in the context of possible treatment effects. Soils with large aggregates showed a

  8. Ocean N2O Emissions : Recent Global Estimates and Anthropogenically Influenced Changes

    NASA Astrophysics Data System (ADS)

    Suntharalingam, P.; Buithenuis, E.; Andrews, O.; Le Quere, C.

    2016-12-01

    Oceanic N2O is produced by microbial activity during organic matter cycling in the subsurface ocean; its production mechanisms display sensitivity to ambient oxygen level. In the oxic ocean, N2O is produced as a byproduct during the oxidation of ammonia to nitrate, mediated by ammonia oxidizing bacteria and archea. N2O is also produced and consumed in sub-oxic and anoxic waters through the action of marine denitrifiers during the multi-step reduction of nitrate to gaseous nitrogen. The oceanic N2O distribution therefore displays significant heterogeneity with background levels of 10-20 nmol/l in the well-oxygenated ocean basins, high concentrations (> 40 nmol/l) in hypoxic waters, and N2O depletion in the core of ocean oxygen minimum zones (OMZs). Oceanic N2O emissions are estimated to account for up to a third of the pre-industrial N2O fluxes to the atmosphere, however the natural cycle of ocean N2O has been perturbed in recent decades by inputs of anthropogenically derived nutrient, and by the impacts of climate change. Anthropogenic nitrogen inputs (e.g., NOx and NHy from fossil fuel combustion and agricultural fertilizer) enter the ocean via atmospheric deposition and riverine fluxes, influencing oceanic N2O production via their impact on the marine organic matter cycle. In addition, climate variations associated with surface ocean warming affect oceanic circulation and nutrient transport pathways, influencing marine productivity and the ventilation of oxygen minimum zones. Recent studies have suggested that possible expansion of oceanic OMZs in a warming climate could lead to significant changes in N2O production and fluxes from these regions. We will summarise the current state of knowledge on the ocean N2O budget and net flux to the atmosphere. Recently reported estimates have been based on (i) empirical relationships derived from ocean tracer data (e.g., involving excess N2O and Apparent Oxygen Utilization (AOU) correlations), (ii) ocean biogeochemical

  9. Air content and O2/N2 tuned chronologies on local insolation signatures in the Vostok ice core are similar

    NASA Astrophysics Data System (ADS)

    Lipenkov, V.; Raynaud, D.; Loutre, M.-F.; Duval, P.; Lemieux-Dudon, B.

    2009-04-01

    An accurate chronology of ice cores is needed for interpreting the paleoclimatic record and understanding the relation between insolation and climate. A new domain of research in this area has been initially stimulated by the work of M. Bender (2002) linking the record of O2/N2 ratio in the air trapped in the Vostok ice with the local insolation. More recently, it has been proposed that the long-term changes in air content, V, recorded in ice from the high Antarctic plateau is also dominantly imprinted by the local summer insolation (Raynaud et al., 2007). The present paper presents a new V record from Vostok, which is compared with the published Vostok O2/N2 record for the same period of time (150-400 ka BP) by using the same spectral analysis methods. The spectral differences between the two properties and the possible mechanisms linking them with insolation through the surface snow structure and the close-off processes are discussed. The main result of our study is that the two experimentally independent local insolation proxies lead to absolute (orbital) time scales, which agree together within a standard deviation of 0.6 ka. This result strongly adds credibility to the air content of ice and the O2 to N2 ratio of the air trapped in ice as equally reliable and complementary tools for accurate dating of existing and future deep ice cores. References: M. Bender, Orbital tuning chronology for the Vostok climate record supported by trapped gas composition, Earth and Planetary Science Letters 204(2002) 275-289. D. Raynaud, V. Lipenkov, B. Lemieux-Dudon, P. Duval, M.F. Loutre, N. Lhomme, The local insolation signature of air content in Antarctic ice: a new step toward an absolute dating of ice records, Earth and Planetary Science Letters 261(2007) 337-349.

  10. Managed grassland alters soil N dynamics and N2O emissions in temperate steppe.

    PubMed

    Xu, Lijun; Xu, Xingliang; Tang, Xuejuan; Xin, Xiaoping; Ye, Liming; Yang, Guixia; Tang, Huajun; Lv, Shijie; Xu, Dawei; Zhang, Zhao

    2018-04-01

    Reclamation of degraded grasslands as managed grasslands has been increasingly accelerated in recent years in China. Land use change affects soil nitrogen (N) dynamics and nitrous oxide (N 2 O) emissions. However, it remains unclear how large-scale grassland reclamation will impact the grassland ecosystem as a whole. Here, we investigated the effects of the conversion from native to managed grasslands on soil N dynamics and N2O emissions by field experiments in Hulunber in northern China. Soil (0-10cm), nitrate (NO 3 - ), ammonium (NH 4 + ), and microbial N were measured in plots in a temperate steppe (Leymus chinensis grassland) and two managed grasslands (Medicago sativa and Bromus inermis grasslands) in 2011 and 2012. The results showed conversion of L. chinensis grassland to M. sativa or B. inermis grasslands decreased concentrations of NO 3 - -N, but did not change NH 4 + -N. Soil microbial N was slightly decreased by the conversion of L. chinensis grassland to M. sativa, but increased by the conversion to B. inermis. The conversion of L. chinensis grassland to M. sativa (i.e., a legume grass) increased N 2 O emissions by 26.2%, while the conversion to the B. inermis (i.e., a non-legume grass) reduced N 2 O emissions by 33.1%. The conversion from native to managed grasslands caused large created variations in soil NO 3 - -N and NH 4 + -N concentrations. Net N mineralization rates did not change significantly in growing season or vegetation type, but to net nitrification rate. These results provide evidence on how reclamation may impact the grassland ecosystem in terms of N dynamics and N 2 O emissions. Copyright © 2017. Published by Elsevier B.V.

  11. Effect of chitosan, O-carboxymethyl chitosan, and N-[(2-hydroxy-3-N,N-dimethylhexadecyl ammonium)propyl] chitosan chloride on overweight and insulin resistance in a murine diet-induced obesity.

    PubMed

    Liu, Xiaofei; Zhi, Xiaona; Liu, Yunfei; Wu, Bo; Sun, Zhong; Shen, Jun

    2012-04-04

    Two water-soluble chitosan derivatives, O-carboxymethyl chitosan (O-CM-chitosan) and N-[(2-hydroxy-3-N,N-dimethylhexadecyl ammonium)propyl] chitosan chloride (N-CQ-chitosan), were prepared, and the therapeutic effects of chitosan, O-CM-chitosan, and N-CQ-chitosan on insulin resistance were simultaneously evaluated by rats fed on a high-fat diet. The parameters of high-fat diet-induced rats indicated that chitosan and its two derivatives not only have low cytotoxicity but can control overnutrition by fat and achieve insulin resistance therapy. However, the results in experiment in vivo showed that the therapeutic degree varied by the molecular weight and surface charge of chitosan, O-CM-chitosan, and N-CQ-chitosan. N-CQ-chitosan with a MW of 5 × 10(4) decreased body weight, the ratio of fat to body weight, triglyceride, fasting plasma glucose, fasting plasma insulin, free fatty acid, and leptin by 11, 17, 44, 46, 44, 87, and 64% and increased fecal lipid by 95%, respectively.

  12. Theoretical prediction of a self-forming gallium oxide layer at an n-type GaN/SiO2 interface

    NASA Astrophysics Data System (ADS)

    Chokawa, Kenta; Narita, Tetsuo; Kikuta, Daigo; Kachi, Tetsu; Shiozaki, Koji; Shiraishi, Kenji

    2018-03-01

    We examine the energy band diagram at the n-type GaN (n-GaN)/SiO2 interface and show that electron transfer from n-GaN to SiO2 leads to the formation of negatively charged oxygen vacancies in the SiO2, resulting in the self-formation of an n-GaN/Ga2O3/SiO2 structure. On the other hand, it is difficult to automatically form Ga2O3 at a p-type GaN (p-GaN)/SiO2 interface. This electron-transfer-induced self-formation of Ga2O3 causes an interface dipole, which leads to band bending, resulting in an increase in the conduction band offset between GaN and SiO2. Accordingly, by using this self-forming phenomenon, GaN MOSFETs with lower leakage current can be realized.

  13. Identification and isolation of active N2O reducers in rice paddy soil

    PubMed Central

    Ishii, Satoshi; Ohno, Hiroki; Tsuboi, Masahiro; Otsuka, Shigeto; Senoo, Keishi

    2011-01-01

    Dissolved N2O is occasionally detected in surface and ground water in rice paddy fields, whereas little or no N2O is emitted to the atmosphere above these fields. This indicates the occurrence of N2O reduction in rice paddy fields; however, identity of the N2O reducers is largely unknown. In this study, we employed both culture-dependent and culture-independent approaches to identify N2O reducers in rice paddy soil. In a soil microcosm, N2O and succinate were added as the electron acceptor and donor, respectively, for N2O reduction. For the stable isotope probing (SIP) experiment, 13C-labeled succinate was used to identify succinate-assimilating microbes under N2O-reducing conditions. DNA was extracted 24 h after incubation, and heavy and light DNA fractions were separated by density gradient ultracentrifugation. Denaturing gradient gel electrophoresis and clone library analysis targeting the 16S rRNA and the N2O reductase gene were performed. For culture-dependent analysis, the microbes that elongated under N2O-reducing conditions in the presence of cell-division inhibitors were individually captured by a micromanipulator and transferred to a low-nutrient medium. The N2O-reducing ability of these strains was examined by gas chromatography/mass spectrometry. Results of the SIP analysis suggested that Burkholderiales and Rhodospirillales bacteria dominated the population under N2O-reducing conditions, in contrast to the control sample (soil incubated with only 13C-succinate). Results of the single-cell isolation technique also indicated that the majority of the N2O-reducing strains belonged to the genera Herbaspirillum (Burkholderiales) and Azospirillum (Rhodospirillales). In addition, Herbaspirillum strains reduced N2O faster than Azospirillum strains. These results suggest that Herbaspirillum spp. may have an important role in N2O reduction in rice paddy soils. PMID:21677691

  14. Production of NO2/-/ and N2O by nitrifying bacteria at reduced concentrations of oxygen

    NASA Technical Reports Server (NTRS)

    Goreau, T. J.; Kaplan, W. A.; Wofsy, S. C.; Mcelroy, M. B.; Valois, F. W.; Watson, S. W.

    1980-01-01

    The influence of oxygen concentration on the production of NO2(-) and N2O by nitrifying marine bacteria of the genus Nitrosomonas is investigated. Pure cultures of the ammonium-oxiding bacteria isolated from the Western Tropical Atlantic Ocean were grown at oxygen partial pressures from 0.005 to 0.2 atm, and concentrations of N2O in the air above the growth medium and dissolved NO2(-) were determined. Decreasing oxygen concentrations are observed to induce a marked decrease in NO2(-) production rates and increase in N2O evolution, leading to an increase of the relative yield of N2O with respect to NO2(-) from 0.3% to nearly 10%. Similar yields of N2O at atmospheric oxygen levels are found for nitrifying bacteria of the genera Nitrosomonas, Nitrosolobus, Nitrosospira and Nitrosococcus, while nitrite-oxydizing bacteria and a dinoflagellate did not produce detectable quantities of N2O. Results support the view that nitrification is a major source of N2O in the environment.

  15. Nitrous Oxide (N2O) Emissions by Termites: Does the Feeding Guild Matter?

    PubMed

    Brauman, Alain; Majeed, Muhammad Zeeshan; Buatois, Bruno; Robert, Alain; Pablo, Anne-Laure; Miambi, Edouard

    2015-01-01

    In the tropics, termites are major players in the mineralization of organic matter leading to the production of greenhouse gases including nitrous oxide (N2O). Termites have a wide trophic diversity and their N-metabolism depends on the feeding guild. This study assessed the extent to which N2O emission levels were determined by termite feeding guild and tested the hypothesis that termite species feeding on a diet rich in N emit higher levels of N2O than those feeding on a diet low in N. An in-vitro incubation approach was used to determine the levels of N2O production in 14 termite species belonging to different feeding guilds, collected from a wide range of biomes. Fungus-growing and soil-feeding termites emit N2O. The N2O production levels varied considerably, ranging from 13.14 to 117.62 ng N2O-N d(-1) (g dry wt.)(-1) for soil-feeding species, with Cubitermes spp. having the highest production levels, and from 39.61 to 65.61 ng N2O-N d(-1) (g dry wt.)(-1) for fungus-growing species. Wood-feeding termites were net N2O consumers rather than N2O producers with a consumption ranging from 16.09 to 45.22 ng N2O-N d(-1) (g dry wt.)(-1). Incubating live termites together with their mound increased the levels of N2O production by between 6 and 13 fold for soil-feeders, with the highest increase in Capritermes capricornis, and between 14 and 34 fold for fungus-growers, with the highest increase in Macrotermes muelleri. Ammonia-oxidizing (amoA-AOB and amoA-AOA) and denitrifying (nirK, nirS, nosZ) gene markers were detected in the guts of all termite species studied. No correlation was found between the abundance of these marker genes and the levels of N2O production from different feeding guilds. Overall, these results support the hypothesis that N2O production rates were higher in termites feeding on substrates with higher N content, such as soil and fungi, compared to those feeding on N-poor wood.

  16. Adsorption of H2O, H2, O2, CO, NO, and CO2 on graphene/g-C3N4 nanocomposite investigated by density functional theory

    NASA Astrophysics Data System (ADS)

    Wu, Hong-Zhang; Bandaru, Sateesh; Liu, Jin; Li, Li-Li; Wang, Zhenling

    2018-02-01

    Motivated by the photocatalytic reactions of small molecules on g-C3N4 by these insights, we sought to explore the adsorption of H2O and CO2 molecules on the graphene side and H2O, H2, O2, CO, NO, and CO2 molecules on the g-C3N4 side of hybrid g-C3N4/graphene nanocomposite using first-principles calculations. The atomic structure and electronic properties of hybrid g-C3N4/graphene nanocomposite is explored. The adsorption of small molecules on graphene/g-C3N4 nanocomposite is thoroughly investigated. The computational studies revels that all small molecules on graphene/g-C3N4 nanocomposite are the physisorption. The adsorption characteristics of H2O and CO2 molecules on the graphene side are similar to that on graphene. The adsorption of H2O, H2, O2, CO, NO, and CO2 molecules on the g-C3N4 side always leads to a buckle structure of graphene/g-C3N4 nanocomposite. Graphene as a substrate can significantly relax the buckle degree of g-C3N4 in g-C3N4/graphene nanocomposite.

  17. Detection mechanism and characteristics of ZnO-based N2O sensors operating with photons

    NASA Astrophysics Data System (ADS)

    Jeong, T. S.; Yu, J. H.; Mo, H. S.; Kim, T. S.; Youn, C. J.; Hong, K. J.

    2013-11-01

    N2O sensors made with ZnO-based ZnCdO films were grown on Pyrex substrates by using the RF co-sputtering method. The structure of the N2O sensor was electrode/sensor/glass/illuminant. The mechanism of the photo-assisted oxidation and reduction process on the surface of the N2O sensors was investigated using light from a UV lamp and violet light emitting diode (LED). For photon exposure wavelengths of 365 and 405 nm, the sensitivity of the ZnO-based ZnCdO sensors was measured. From these measurements, the values of the sensitivity of the sensors with x = 0, 0.01, and 0.05 were found to be S = 1.44, 1.39, and 1.33 under LED light with a wavelength of 405 nm, respectively. These sensitivities were compared to those of SnO2 and WO3 materials measured at operating temperatures of 300-600 °C. Also, under exposure with UV light, the response times were observed to be 130 to 270 sec. These response times were slightly slower than that for the traditional method of thermal heating. However, they indicate that the described photon exposure method for N2O detection can replace the conventional heating mode. Consequently, we demonstrated that portable N2O sensors for room-temperature operation could be fabricated without thermal heating.

  18. Highly Efficient Low-Temperature N-Doped TiO2 Catalysts for Visible Light Photocatalytic Applications

    PubMed Central

    Mahy, Julien G.; Cerfontaine, Vincent; Devred, François; Gaigneaux, Eric M.; Heinrichs, Benoît; Lambert, Stéphanie D.

    2018-01-01

    In this paper, TiO2 prepared with an aqueous sol-gel synthesis by peptization process is doped with nitrogen precursor to extend its activity towards the visible region. Three N-precursors are used: urea, ethylenediamine and triethylamine. Different molar N/Ti ratios are tested and the synthesis is adapted for each dopant. For urea- and trimethylamine-doped samples, anatase-brookite TiO2 nanoparticles of 6–8 nm are formed, with a specific surface area between 200 and 275 m2·g−1. In ethylenediamine-doped samples, the formation of rutile phase is observed, and TiO2 nanoparticles of 6–8 nm with a specific surface area between 185 and 240 m2·g−1 are obtained. X-ray photoelectron spectroscopy (XPS) and diffuse reflectance measurements show the incorporation of nitrogen in TiO2 materials through Ti–O–N bonds allowing light absorption in the visible region. Photocatalytic tests on the remediation of water polluted with p-nitrophenol show a marked improvement for all doped catalysts under visible light. The optimum doping, taking into account cost, activity and ease of synthesis, is up-scaled to a volume of 5 L and compared to commercial Degussa P25 material. This up-scaled sample shows similar properties compared to the lab-scale sample, i.e., a photoactivity 4 times higher than commercial P25. PMID:29642626

  19. Atmospheric O2, CO2 and delta13C measurements from aircraft sampling over Griffin Forest, Perthshire, UK.

    PubMed

    Sturm, Patrick; Leuenberger, Markus; Moncrieff, John; Ramonet, Michel

    2005-01-01

    Regular vertical aircraft sampling has been performed in the lower troposphere above Griffin Forest, near Aberfeldy, Perthshire, UK (56 degrees 37'N, 3 degrees 47'W), between February 2003 and May 2004, for analysis of O2/N2, CO2 and delta13C of CO2. We sampled flasks between 800 and 3100 m above sea level. The peak-to-peak amplitude of the seasonal cycle of O2/N2 decreases from 171 per meg at 800 m to 113 per meg at 3100 m. Furthermore, the seasonal cycle is shifted from low to high altitudes with a lag of about 1 month. The same features are observed for CO2 with a decrease in the peak-to-peak amplitude of the seasonal cycle from 17.6 ppm at 800 m to 11.4 ppm at 3100 m. The vertical profiles show decreasing O2/N2 ratios in summer and increasing O2/N2 ratios in wintertime with increasing sampling height, due to surface exchange of oxygen with the land biosphere and the ocean. The O2:CO2 exchange ratios of the vertical profiles vary between -1.5 and -2.4 mol O2/mol CO2. Copyright (c) 2005 John Wiley & Sons, Ltd.

  20. Densities of Active species in N2/H2 RF and HF afterglows: application to surface nitriding of TiO2 nanocrystals

    NASA Astrophysics Data System (ADS)

    Ricard, André; Sarrette, Jean-Philippe; Wang, Yunfei; Kim, Yu-Kwon

    2017-10-01

    N2/0-5% H2 flowing afterglows from Radio Frequency (RF) and High Frequency (HF) sources have been analyzed by optical emission spectroscopy. In similar conditions (pressure 5-6 Torr, flow rate 0.5 slm and power 100 W), it is found in pure N2 a nearly constant N-atom density from the pink to the late afterglow, which is higher in HF than in RF: (1-2) and 0.4 × 1015 cm-3, respectively. With a N2/2% H2 gas mixture, the early afterglows is changed to a late afterglow with about the same N-atom density for both RF and HF cases: (8-9) × 1014 cm-3. Anatase TiO2 nanocrystals and Atomic Layer Deposition-grown films were exposed to the RF afterglows at room temperature. XPS analysis of the samples has shown that the highest N/Ti ratio of 0.24 can be achieved with the pure N2 late afterglow. In the HF pure N2 late afterglow, however, the N/Ti coverage was limited to 0.04 in spite of higher N-atom density. Such differences in the N content between the two RF and HF cases are attributed to the presence of a high O-atom impurity of 2 × 1013 cm-3 in HF as compared to that (8 × 1011 cm-3) in RF. Contribution to the topical issue "Plasma Sources and Plasma Processes (PSPP)", edited by Luis Lemos Alves, Thierry Belmonte and Tiberiu Minea

  1. Photo degradation of methyl orange by attapulgite-SnO2-TiO2 nanocomposites.

    PubMed

    Zhang, Lili; Lv, Fujian; Zhang, Weiguang; Li, Rongqing; Zhong, Hui; Zhao, Yijiang; Zhang, Yu; Wang, Xin

    2009-11-15

    Photocatalytic removal of methyl orange under ultraviolet radiation has been studied using attapulgite (ATT) composites, which were synthesized by depositing SnO(2)-TiO(2) hybrid oxides on the surface of ATT to form a composite photocatalyst (denoted ATT-SnO(2)-TiO(2)) using an in situ sol-gel technique. Results showed that SnO(2)-TiO(2) nanocomposite particles with average size of about 10nm were loaded successfully on to the surface of ATT fibers and were widely dispersed. Correspondingly, the photocatalytic activity of ATT was improved significantly by loading SnO(2)-TiO(2). The photoactivity of the composite photocatalyst decreased in the sequence ATT-SnO(2)-TiO(2)>ATT-SnO(2)>ATT-TiO(2)>ATT. In order to achieve the best photocatalyst, the molar ratio of SnO(2) and TiO(2) in the ATT-SnO(2)-TiO(2) composites was adjusted to give a series with proportions r=n(Ti)/(n(Ti)+n(Sn))=0.0, 0.25, 0.33, 0.50, 0.67, 0.75, 0.80, 0.82, 0.86, 1.0. Results indicated that the proportion of SnO(2) and TiO(2) had a critical effect on the photocatalytic activity, which increased as the content of TiO(2) increased to r0.82. The highest degradation rate of methyl orange was 99% within 30 min obtained by using ATT-SnO(2)-TiO(2) with r=0.82. The repeated use of the composite photocatalyst was also confirmed.

  2. Temperature dependence of the reaction N2(A3Σu+)+O in the terrestrial thermosphere

    NASA Astrophysics Data System (ADS)

    Hill, Steven M.; Solomon, Stanley C.; Cleary, David D.; Broadfoot, A. Lyle

    2000-05-01

    Previous models for dayglow and auroral emissions of the N2(A3Σu+->X1Σg+) Vegard-Kaplan (VK) bands and O(1S) lines, when based on laboratory rate coefficients, disagree with observations. The problem has two parts: the overall rate of N2(A)+O and the state-specific yield of O(1S). Resolving these discrepancies should yield more accurate determinations of atomic oxygen density by remote sensing of the 2972 and 5577 Å lines. To solve the problem, the sources and sinks of O(1S) are considered using dayglow observations from 105 to 315 km and a numerical model. Line and band intensities are extracted from the data using a multiple regression fit to synthetic spectra. A photoelectron and photochemical model is used to analyze the resulting vertical emission profiles. N2 Second Positive (2P) altitude profiles indicate that photoelectron excitation of the N2 triplet system is modeled with an absolute uncertainty of +/-23%. The VK/2P intensity ratio suggests that laboratory rate coefficients for the reaction N2(Aν'=0,1,2)+O should be increased by a factor of 1.74 to 2.34. However, the laboratory rates were measured at room temperature. When the effect of high thermospheric temperatures on collision frequency is accounted for the rate coefficients for ν'=0, 1, and 2 are found to be (3.4+/-0.8)×10-11(T/298)1/2, (5.6+/-1.3)×10-11(T/298)1/2, and (4.8+/-1.2)×10-11(T/298)1/2cm3s-1. At 298 K, the ν'=0 and 2 values are within 5% of the laboratory values, but for ν'=1 the value is 40% larger than the laboratory value. The effective quantum yield of O(1S) by N2(A)+O is found to be 0.47+/-0.17. The observations support a photoelectron cross section for O(1S) that is consistent with laboratory measurements, but about 2.0 times larger than theoretical calculations.

  3. Pseudomonas stutzeri N2O reductase contains CuA-type sites.

    PubMed Central

    Scott, R A; Zumft, W G; Coyle, C L; Dooley, D M

    1989-01-01

    N2O reductase (N2O----N2) is the terminal enzyme in the energy-conserving denitrification pathway of soil and marine denitrifying bacteria. The protein is composed of two identical subunits and contains eight copper ions per enzyme molecule. The magnetic circular dichroism spectrum of resting (oxidized) N2O reductase is strikingly similar to the magnetic circular dichroism spectrum of the CuA site in mammalian cytochrome c oxidase [Greenwood, C., Hull, B. C., Barber, D., Eglinton, D. G. & Thomson, A. J. (1983) Biochem. J. 215, 303-316] and is unlike the magnetic circular dichroism spectra of all other biological copper chromophores obtained to date. Sulfur (or chlorine) scatterers are required to fit the copper extended x-ray absorption fine structure data of both the oxidized and reduced forms of N2O reductase. Satisfactory fits require a Cu-N or Cu-O [denoted Cu-(N, O)] interaction at 2.0 A, a Cu-(S, Cl) interaction at 2.3 A and an additional Cu(S, Cl) interaction at approximately 2.6 A (oxidized) or approximately 2.7 A (reduced). Approximately eight sulfur ions (per eight copper ions) at approximately 2.3 A are required to fit the extended x-ray absorption fine structure data for both the oxidized and reduced N2O reductase. The 2.3-A Cu-(S, Cl) distance is nearly identical to that previously determined for the CuA site in cytochrome c oxidase. A 2.6-2.7 A Cu-(S, Cl) interaction is also present in resting and fully reduced cytochrome c oxidase. Comparison of the N2O reductase sequence, determined by translating the structural NosZ gene, with cytochrome c oxidase subunit II sequences from several sources indicates that a Gly-Xaa-Xaa-Xaa-Xaa-Xaa-Cys-Ser-Xaa-Xaa-Cys-Xaa-Xaa-Xaa-His stretch is highly conserved. This sequence contains three of the probable ligands (two cysteines and one histidine) in a CuA-type site. Collectively these data establish that Pseudomonas stutzeri N2O reductase contains CuA-type sites. PMID:2542963

  4. C/O RATIO AS A DIMENSION FOR CHARACTERIZING EXOPLANETARY ATMOSPHERES

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Madhusudhan, Nikku, E-mail: Nikku.Madhusudhan@yale.edu; Department of Astronomy, Yale University, New Haven, CT 06511

    2012-10-10

    Until recently, infrared observations of exoplanetary atmospheres have typically been interpreted using models that assumed solar elemental abundances. With the chemical composition fixed, attempts have been made to classify hot Jupiter atmospheres on the basis of stellar irradiation. However, recent observations have revealed deviations from predictions based on such classification schemes, and chemical compositions retrieved from some data sets have also indicated non-solar abundances. The data require a two-dimensional (2D) characterization scheme with dependence on both irradiation and chemistry. In this work, we suggest the carbon-to-oxygen (C/O) ratio as an important second dimension for characterizing exoplanetary atmospheres. In hot-hydrogen-dominated atmospheres,more » the C/O ratio critically influences the relative concentrations of several spectroscopically dominant species. Between a C/O of 0.5 (solar value) and 2, the H{sub 2}O and CH{sub 4} abundances can vary by several orders of magnitude in the observable atmosphere, and new hydrocarbon species such as HCN and C{sub 2}H{sub 2} become prominent for C/O {>=} 1, while the CO abundance remains almost unchanged. Furthermore, a C/O {>=} 1 can preclude a strong thermal inversion due to TiO and VO in a hot Jupiter atmosphere, since TiO and VO are naturally underabundant for C/O {>=} 1. We, therefore, suggest a new 2D classification scheme for hydrogen-dominated exoplanetary atmospheres with irradiation (or temperature) and C/O ratio as the two dimensions. We define four classes in this 2D space (O1, O2, C1, and C2) with distinct chemical, thermal, and spectral properties. Based on the most recent observations, we characterize the thermal structure and C/O ratios of six hot Jupiters (XO-1b, CoRoT-2b, WASP-14b, WASP-19b, WASP-33b, and WASP-12b) in the framework of our proposed 2D classification scheme. While the data for several systems in our sample are consistent with C-rich atmospheres, new

  5. The combined effect of dissolved oxygen and nitrite on N2O production by ammonia oxidizing bacteria in an enriched nitrifying sludge.

    PubMed

    Peng, Lai; Ni, Bing-Jie; Ye, Liu; Yuan, Zhiguo

    2015-04-15

    Both nitrite [Formula: see text] and dissolved oxygen (DO) play important roles in nitrous oxide (N2O) production by ammonia oxidizing bacteria (AOB). However, few studies focused on the combined effect of them on N2O production by AOB as well as the corresponding mechanisms. In this study, N2O production by an enriched nitrifying sludge, consisting of both AOB and nitrite-oxidizing bacteria (NOB), was investigated under various [Formula: see text] and DO concentrations. At each investigated DO level, both the biomass specific N2O production rate and the N2O emission factor (the ratio between N2O nitrogen emitted and the ammonium nitrogen converted) increased as [Formula: see text] concentration increased from 3 mg N/L to 50 mg N/L. However, at each investigated [Formula: see text] level, the maximum biomass specific N2O production rate occurred at DO of 0.85 mg O2/L, while the N2O emission factor decreased as DO increased from 0.35 to 3.5 mg O2/L. The analysis of the process data using a mathematical N2O model incorporating both the AOB denitrification and hydroxylamine (NH2OH) oxidation pathways indicated that the contribution of AOB denitrification pathway increased as [Formula: see text] concentration increased, but decreased as DO concentration increased, accompanied by a corresponding change in the contribution of NH2OH oxidation pathway to N2O production. The AOB denitrification pathway was predominant in most cases, with the NH2OH oxidation pathway making a comparable contribution only at high DO level (e.g. 3.5 mg O2/L). Copyright © 2015 Elsevier Ltd. All rights reserved.

  6. Model simulation of NO3, N2O5 and ClNO2 at a rural site in Beijing during CAREBeijing-2006

    NASA Astrophysics Data System (ADS)

    Wang, Haichao; Lu, Keding; Tan, Zhaofeng; Sun, Kang; Li, Xin; Hu, Min; Shao, Min; Zeng, Limin; Zhu, Tong; Zhang, Yuanhang

    2017-11-01

    A chemical box model was used to study nitrate radical (NO3), dinitrogen pentoxide (N2O5) and nitryl chloride (ClNO2) in a rural site during the Campaign of Air Quality Research in Beijing 2006 (CAREBeijing-2006). The model was based on regional atmospheric chemistry mechanism version 2 (RACM2) with the heterogeneous uptake of N2O5 and the simplified chloride radical (Cl) chemistry mechanism. A high production rate of NO3 with a mean value of 0.8 ppbv/h and low mixing ratios of NO3 and N2O5 (peak values of 17 pptv and 480 pptv, respectively) existed in this site. Budget analysis showed that NO emission suppressed the NO3 chemistry at the surface layer, the reaction of NO3 with VOCs made a similar contribution to NO3 loss as N2O5 heterogeneous uptake. The NO3 chemistry was predominantly controlled by isoprene, and NO3 oxidation produced organic nitrate with a mean value of 0.06 ppbv/h during nighttime. The organic nitrate production initiated by NO3 was equal to that initiated by OH, implying the importance of nighttime chemistry for secondary organic aerosol (SOA) formation. We confirmed that the N2O5 heterogeneous reaction accounted for nighttime particle NO3- enhancement, with a large day to day variability, and made less of a contribution to NOx loss compared to that of OH reacting with NO2. Additionally, abundant ClNO2, up to 5.0 ppbv, was formed by N2O5 heterogeneous uptake. ClNO2 was sustained at a high level until noon in spite of the gradually increasing photolysis of ClNO2 after sunrise. Chlorine activation caused by N2O5 heterogeneous uptake increased primary ROx formation by 5% and accounted for 8% of the net ozone production enhancement in the morning.

  7. The Nitrous Oxide (N2O) Budget: Constraints from Atmospheric Observations and Models

    NASA Astrophysics Data System (ADS)

    Tian, H.; Thompson, R.; Canadell, J.; Winiwarter, W.; Tian, H.; Thompson, R.; Prather, M. J.

    2017-12-01

    The increasing global abundance of N2O poses a threat to human health and society over this coming century through both climate change and ozone depletion. In the sense of greenhouse gases, N2O ranks third behind CO2 and CH4. In the sense of ozone depletion, N2O stands alone. In order to identify the cause of these increases and hopefully reverse them, we need to have a thorough understanding of the sources and sinks (a.k.a. the budget) of N2O and how they can be altered. A bottom-up approach to the budget evaluates individual biogeochemical sources of N2O from the land and ocean; whereas, a top-down approach uses atmospheric observations of the variability, combined with modeling of the atmospheric chemistry and transport, to infer the magnitude of sources and sinks throughout the Earth system. This paper reviews top-down approaches using atmospheric data; a similar top-down approach can be taken with oceanic measurements of N2O, but is not covered here. Stratospheric chemistry is the predominant loss of N2O, and here we review how a merging of new measurements with stratospheric chemistry models is able to provide a constrained budget for the global N2O sink. N2O surface sources are transported and mixed throughout the atmosphere, providing positive anomalies in the N2O abundance (mole fraction of N2O with respect to dry air); while N2O-depleted air from the stratosphere provides negative anomalies. With accurate atmospheric transport models, including for stratosphere-troposphere exchange, the observed tropospheric variability in N2O is effectively a fingerprint of the location and magnitude of sources. This inverse modeling of sources is part of the top-down constraints and is reviewed here.

  8. The correlation between HCN/H2O flux ratios and disk mass: evidence for protoplanet formation

    NASA Astrophysics Data System (ADS)

    Rose, Caitlin; Salyk, Colette

    2017-01-01

    We analyze hydrogen cyanide (HCN) and water vapor flux ratios in protoplanetary disks as a way to trace planet formation. Analyzing only disks in the Taurus molecular cloud, Najita et al. (2013) found a tentative correlation between protoplanetary disk mass and the HCN/H2O line flux ratio in Spitzer-IRS emission spectra. They interpret this correlation to be a consequence of more massive disks forming planetesimals more efficiently than smaller disks, as the formation of large planetesimals may lock up water ice in the cool outer disk region and prevent it from migrating, drying out the inner disk. The sequestering of water (and therefore oxygen) in the outer disk may also increase the carbon-to- oxygen ratio in the inner disk, leading to enhanced organic molecule (e.g. HCN) emission. To confirm this trend, we expand the Najita et al. sample by calculating HCN/H2O line flux ratios for 8 more sources with known disk masses from clusters besides Taurus. We find agreement with the Najita et al. trend, suggesting that this is a widespread phenomenon. In addition, we find HCN/H2O line flux ratios for 17 more sources that await disk mass measurements, which should become commonplace in the ALMA era. Finally, we investigate linear fits and outliers to this trend, and discuss possible causes.

  9. N2O and N2 emissions from contrasting soil environments - interactive effects of soil nitrogen, hydrology and microbial communities

    NASA Astrophysics Data System (ADS)

    Christiansen, Jesper; Elberling, Bo; Ribbons, Relena; Hedo, Javier; José Fernández Alonso, Maria; Krych, Lukasz; Sandris Nielsen, Dennis; Kitzler, Barbara

    2016-04-01

    Reactive nitrogen (N) in the environment has doubled relative to the natural global N cycle with consequences for biogeochemical cycling of soil N. Also, climate change is expected to alter precipitation patterns and increase soil temperatures which in Arctic environments may accelerate permafrost thawing. The combination of changes in the soil N cycle and hydrological regimes may alter microbial transformations of soil N with unknown impacts on N2O and N2 emissions from temperate and Arctic soils. We present the first results of soil N2O and N2 emissions, chemistry and microbial communities over soil hydrological gradients (upslope, intermediate and wet) across a global N deposition gradient. The global gradient covered an N-limited high Arctic tundra (Zackenberg-ZA), a pacific temperate rain forest (Vancouver Island-VI) and an N saturated forest in Austria (Klausenleopoldsdorf-KL). The N2O and N2 emissions were measured from intact cores at field moisture in a He-atmosphere system. Extractable NH4+ and NO3-, organic and microbial C and N and potential enzyme-activities were determined on soil samples. Soil genomic DNA was subjected to MiSeq-based tag-encoded 16S rRNA and ITS gene amplicon sequencing for the bacterial and fungal community structure. Similar soil moisture levels were observed for the upslope, intermediate and wet locations at ZA, VI and KL, respectively. Extractable NO3- was highest at the N rich KL and lowest at ZA and showed no trend with soil moisture similar to NH4+. At ZA and VI soil NH4+ was higher than NO3- indicating a tighter N cycling. N2O emissions increased with soil moisture at all sites. The N2O emissions for the wet locations ranked similarly to NO3- with the largest response to soil moisture at KL. N2 emissions were remarkably similar across the sites and increased with soil wetness. Microbial C and N also increased with soil moisture and were overall lowest at the N rich KL site. The potential activity of protease enzyme was site

  10. Selective Adsorption Resonances in the Scattering of n-H2 p-H2 n-D2 and o-D2 from Ag(111)

    NASA Astrophysics Data System (ADS)

    Yu, Chien-Fan; Whaley, K. Birgitta; Hogg, Charles S.; Sibener, Steven J.

    1983-12-01

    Diffractive and rotationally mediated selective adsorption scattering resonances are reported for n-H2 p-H2 n-D2 and o-D2 on Ag(111). Small resonance shifts and line-width differences are observed between n-H2 and p-H2 indicating a weak orientation dependence of the laterally averaged H2/Ag(111) potential. The p-H2 and o-D2 levels were used to determine the isotropic component of this potential, yielding a well depth of ~ 32 meV.

  11. N2O, NO, N2 and CO2 emissions from tropical savanna and grassland of northern Australia: an incubation experiment with intact soil cores

    NASA Astrophysics Data System (ADS)

    Werner, C.; Reiser, K.; Dannenmann, M.; Hutley, L. B.; Jacobeit, J.; Butterbach-Bahl, K.

    2014-11-01

    Strong seasonal variability of hygric and thermal soil conditions are a defining environmental feature in northern Australia. However, how such changes affect the soil-atmosphere exchange of nitrous oxide (N2O), nitric oxide (NO) and dinitrogen (N2) is still not well explored. By incubating intact soil cores from four sites (three savanna, one pasture) under controlled soil temperatures (ST) and soil moisture (SM) we investigated the release of the trace gas fluxes of N2O, NO and carbon dioxide (CO2). Furthermore, the release of N2 due to denitrification was measured using the helium gas flow soil core technique. Under dry pre-incubation conditions NO and N2O emissions were very low (<7.0 ± 5.0 μg NO-N m-2 h-1; <0.0 ± 1.4 μg N2O-N m-2 h-1) or in the case of N2O, even a net soil uptake was observed. Substantial NO (max: 306.5 μg N m-2 h-1) and relatively small N2O pulse emissions (max: 5.8 ± 5.0 μg N m-2 h-1) were recorded following soil wetting, but these pulses were short lived, lasting only up to 3 days. The total atmospheric loss of nitrogen was generally dominated by N2 emissions (82.4-99.3% of total N lost), although NO emissions contributed almost 43.2% to the total atmospheric nitrogen loss at 50% SM and 30 °C ST incubation settings (the contribution of N2 at these soil conditions was only 53.2%). N2O emissions were systematically higher for 3 of 12 sample locations, which indicates substantial spatial variability at site level, but on average soils acted as weak N2O sources or even sinks. By using a conservative upscale approach we estimate total annual emissions from savanna soils to average 0.12 kg N ha-1 yr-1 (N2O), 0.68 kg N ha-1 yr-1 (NO) and 6.65 kg N ha-1 yr-1 (N2). The analysis of long-term SM and ST records makes it clear that extreme soil saturation that can lead to high N2O and N2 emissions only occurs a few days per year and thus has little impact on the annual total. The potential contribution of nitrogen released due to pulse events

  12. P-type ZnO:N Films Prepared by Thermal Oxidation of Zn3N2

    NASA Astrophysics Data System (ADS)

    Zhang, Bin; Li, Min; Wang, Jian-Zhong; Shi, Li-Qun

    2013-02-01

    We prepare p-type ZnO:N films by annealing Zn3N2 films in oxygen over a range of temperatures. The prepared films are characterized by various techniques, such as Rutherford backscattering spectroscopy, x-ray diffraction, x-ray photoemission spectroscopy, the Hall effect and photoluminescence spectra. The results show that the Zn3N2 films start to transform to ZnO at 300°C and the N content decreases with an increase in annealing temperature. N has two local chemical states: zinc oxynitride (ZnO1-xNx) and substitutional NO in O-rich local environments (α -NO). The conduction type changes from n-type to p-type upon oxidation at 400-600°C, indicating that N is an effective acceptor in the ZnO film. The photoluminescence spectra show the UV emission and defect-related emissions of ZnO:N films. The mechanism and efficiency of p-type doping are briefly discussed.

  13. Effects of cover crops incorporation and nitrogen fertilization on N2O and CO2 emissions

    NASA Astrophysics Data System (ADS)

    Kandel, T. P.; Gowda, P. H.; Northup, B. K.; DuPont, J.; Somenahally, A. C.; Rocateli, A.

    2017-12-01

    In this study, we measured N2O and CO2 fluxes from plots planted to hairy vetch (winter cover crop) and broadleaf vetch (spring cover crop) as N sources for the following crabgrass (summer forage crop) in El Reno, Oklahoma, USA. Comparisons also included 0 and 60 kg ha-1 mineral N fertilizer supplied as dry urea. No significant N2O fluxes were observed during rapid growing periods of cover crops (March-April, 2017), however, large fluxes were observed after hairy vetch incorporation. Immediately after the hairy vetch biomass incorporation, large rainfall events were recorded. The fluxes subsided gradually with drying soil condition but were enhanced after every consecutive rainfall events. A rainfall induced flux measuring up to 8.2 kg N2O ha-1 day-1 was observed after 26 days of biomass incorporation. In total, 29 kg N2O ha-1 (18 kg N ha-1) was emitted within a month after biomass incorporation from hairy vetch plots. Growth of broadleaf vetch was poor and N2O fluxes were also lower. Similarly, plots fertilized with 60 kg N ha-1 had significant fluxes of N2O but the magnitude was much lower than the hairy vetch plots. Dynamics of N2O and CO fluxes correlated strongly. The results thus indicated that although cover crops may provide many environmental/agronomic benefits such as N fixation, soil carbon built-up, weed suppression and erosion control, high N2O emissions may dwarf these benefits.

  14. Time-dependent one-dimensional simulation of atmospheric dielectric barrier discharge in N2/O2/H2O using COMSOL Multiphysics

    NASA Astrophysics Data System (ADS)

    Sohbatzadeh, F.; Soltani, H.

    2018-04-01

    The results of time-dependent one-dimensional modelling of a dielectric barrier discharge (DBD) in a nitrogen-oxygen-water vapor mixture at atmospheric pressure are presented. The voltage-current characteristics curves and the production of active species are studied. The discharge is driven by a sinusoidal alternating high voltage-power supply at 30 kV with frequency of 27 kHz. The electrodes and the dielectric are assumed to be copper and quartz, respectively. The current discharge consists of an electrical breakdown that occurs in each half-period. A detailed description of the electron attachment and detachment processes, surface charge accumulation, charged species recombination, conversion of negative and positive ions, ion production and losses, excitations and dissociations of molecules are taken into account. Time-dependent one-dimensional electron density, electric field, electric potential, electron temperature, densities of reactive oxygen species (ROS) and reactive nitrogen species (RNS) such as: O, O-, O+, {O}2^{ - } , {O}2^{ + } , O3, {N}, {N}2^{ + } , N2s and {N}2^{ - } are simulated versus time across the gas gap. The results of this work could be used in plasma-based pollutant degradation devices.

  15. Experimental Study on the Behavior of TiN and Ti2O3 Inclusions in Contact with CaO‐Al2O3‐SiO2‐MgO Slags

    PubMed Central

    Bernhard, C.

    2017-01-01

    TiN and Ti2O3 are the predominant inclusion types in Ti-alloyed ferritic chromium stainless steels. In order to ensure the required steel cleanness level, an effective removal of such inclusions in the slag during secondary metallurgy is essential. This inclusion removal predominantly takes place via dissolution of the inclusion in the slag. The dissolution behavior of TiN and Ti2O3 in CaO-SiO2-Al2O3-MgO slags as well as their agglomeration behavior in the liquid steel is investigated using High Temperature Laser Scanning Confocal Microscopy and Tammann Furnace experiments. Thermodynamic calculations are performed using FactSage 7.0. The behavior of TiN is observed to be completely different to that of oxides. Ti2O3 dissolves quickly in slags, and its dissolution behavior is comparable to that of other already well examined oxides. In contrast, TiN shows a very intense gas reaction which is attributed to the release of nitrogen during contact with slag. Slags with higher SiO2 content show a significantly higher ability for the dissolution of TiN as compared to Al2O3-rich slags. The gas reaction is found to also significantly influence the final steel cleanness. Despite the easy absorption of TiN in the slag, the formed nitrogen supports the formation of pinholes in the steel. PMID:29109805

  16. Upland Trees Contribute to Exchange of Nitrous Oxide (N2O) in Forest Ecosystems

    NASA Astrophysics Data System (ADS)

    Tian, H.; Thompson, R.; Canadell, J.; Winiwarter, W.; Machacova, K.; Maier, M.; Halmeenmäki, E.; Svobodova, K.; Lang, F.; Pihlatie, M.; Urban, O.

    2017-12-01

    The increase in atmospheric nitrous oxide (N2O) concentration contributes to the acceleration of the greenhouse effect. However, the role of trees in the N2O exchange of forest ecosystems is still an open question. While the soils of temperate and boreal forests were shown to be a natural source of N2O, trees have been so far overlooked in the forest N2O inventories. We determined N2O fluxes in common tree species of boreal and temperate forests: Scots pine (Pinus sylvestris), Norway spruce (Picea abies), downy and silver birch (Betula pubescens, B. pendula), and European beech (Fagus sylvatica). We investigated (1) whether these tree species exchange N2O with the atmosphere under natural field conditions, (2) how the tree N2O fluxes contribute to the forest N2O balance, and (3) whether these fluxes show seasonal dynamics. The studies were performed in a boreal forest (SMEAR II station, Finland; June 2014 - May 2015) and two temperate mountain forests (White Carpathians, Czech Republic; Black Forest, Germany; June and July 2015). Fluxes of N2O in mature tree stems and forest floor were measured using static chamber systems followed by chromatographic and photo-acoustic analyses of N2O concentration changes. Pine, spruce and birch trees were identified as net annual N2O sources. Spruce was found the strongest emitter (0.27 mg ha-1 h-1) amounting thus up to 2.5% of forest floor N2O emissions. All tree species showed a substantial seasonality in stem N2O flux that was related to their physiological activity and climatic variables. In contrast, stems of beech trees growing at soils consuming N2O may act as a substantial sink of N2O from the atmosphere. Consistent N2O consumption by tree stems ranging between -12.1 and -35.2 mg ha-1 h-1 and contributing by up to 3.4% to the forest floor N2O uptake is a novel finding in contrast to current studies presenting trees as N2O emitters. To understand these fluxes, N2O exchange of photoautotrophic organisms associated with

  17. Raman study of HgBa 2Ca n-1 Cu nO 2 n+2+ δ ( n=1,2,3,4 and 5) superconductors

    NASA Astrophysics Data System (ADS)

    Zhou, Xingjiang; Cardona, M.; Chu, C. W.; Lin, Q. M.; Loureiro, S. M.; Marezio, M.

    1996-02-01

    Polarized micro-Raman scattering measurements have been performed on the five members of the HgBa 2Ca n-1 Cu nO 2 n+2+ δ ( n=1,2,3,4 and 5) high- Tc superconductor family using different laser frequencies. Local laser annealing measurements were carried out to investigate the variation of the Raman spectra with the excess oxygen content, δ. A systematic evolution of the spectra, which display mainly peaks near 590, 570, 540 and 470 cm -1, with increasing number of CuO 2 layers has been observed; its origin has been shown to lie in the variation of the interstitial oxygen content. In addition to confirming that the 590 cm -1 mode represents vibration of apical oxygens in the absence of neighboring excess oxygen, the 570 cm -1 mode, which may be composed of some finer structures, has been assigned to the vibration of the apical oxygen modified by the presence of the neighboring excess oxygens. The 540 and 470 cm -1 modes may represent the direct vibration of excess oxygens. The implication of possible different distribution sites of excess oxygens is discussed. All other observed lower-frequency modes are also assigned.

  18. Tris(5,6-dimethyl-1H-benzimidazole-κN(3))(pyridine-2,6-dicarboxyl-ato-κ(3)O(2),N,O(6))nickel(II).

    PubMed

    Li, Yue-Hua; Li, Feng-Feng; Liu, Xin-Hua; Zhao, Ling-Yan

    2012-06-01

    The title mononuclear complex, [Ni(C(7)H(3)NO(4))(C(9)H(10)N(2))(3)], shows a central Ni(II) atom which is coordinated by two carboxyl-ate O atoms and the N atom from a pyridine-2,6-dicarboxyl-ate ligand and by three N atoms from different 5,6-dimethyl-1H--benzimidazole ligands in a distorted octa-hedral geometry. The crystal structure shows intermolecular N-H⋯O hydrogen bonds.

  19. Spin dynamics and magnetoelectric coupling mechanism of C o4N b2O9

    NASA Astrophysics Data System (ADS)

    Deng, Guochu; Cao, Yiming; Ren, Wei; Cao, Shixun; Studer, Andrew J.; Gauthier, Nicolas; Kenzelmann, Michel; Davidson, Gene; Rule, Kirrily C.; Gardner, Jason S.; Imperia, Paolo; Ulrich, Clemens; McIntyre, Garry J.

    2018-02-01

    Neutron powder diffraction experiments reveal that C o4N b2O9 forms a noncollinear in-plane magnetic structure with C o2 + moments lying in the a b plane. The spin-wave excitations of this magnet were measured by using inelastic neutron scattering and soundly simulated by a dynamic model involving nearest- and next-nearest-neighbor exchange interactions, in-plane anisotropy, and the Dzyaloshinskii-Moriya interaction. The in-plane magnetic structure of C o4N b2O9 is attributed to the large in-plane anisotropy, while the noncollinearity of the spin configuration is attributed to the Dzyaloshinskii-Moriya interaction. The high magnetoelectric coupling effect of C o4N b2O9 in fields can be explained by its special in-plane magnetic structure.

  20. Aspects of Supercritical Turbulence: Direct Numerical Simulation of O2/H2 and C7H16/N2 Temporal Mixing Layers

    NASA Technical Reports Server (NTRS)

    Bellan, J.; Okongo, N. A.; Harstad, K. G.; Hutt, John (Technical Monitor)

    2002-01-01

    Results from Direct Numerical Simulations of temporal, supercritical mixing layers for two species systems are analyzed to elucidate species-specific turbulence aspects. The two species systems, O2/H2 and C7HG16/N2, have different thermodynamic characteristics; thus, although the simulations are performed at similar reduced pressure (ratio of the pressure to the critical pressure), the former system is dose to mixture ideality and has a relatively high solubility with respect to the latter, which exhibits strong departures from mixture ideality Due to the specified, smaller initial density stratification, the C7H16/N2 layers display higher growth and increased global molecular mixing as well as larger turbulence levels. However, smaller density gradients at the transitional state for the O2/H2 system indicate that on a local basis, the layer exhibits an enhanced mixing, this being attributed to the increased solubility and to mixture ideality. These thermodynamic features are shown to affect the irreversible entropy production (i.e. the dissipation), which is larger for the O2/H2 layer and is primarily concentrated in high density-gradient magnitude regions that are distortions of the initial density stratification boundary. In contrast, the regions of largest dissipation in the C7H16/N2 layer are located in high density-gradient magnitude regions resulting from the mixing of the two fluids.

  1. Comparing N2O emissions at varying N rates from irrigated and rainfed corn in the US Midwest

    NASA Astrophysics Data System (ADS)

    Millar, N.; Kahmark, K.; Basso, B.; Robertson, G. P.

    2011-12-01

    Global N2O emissions from agriculture are estimated to be ~2.8 Pg CO2e yr-1 accounting for 60% of total anthropogenic emissions. N2O is the largest contributor to the GHG burden of cropping systems in the US, with annual estimated emissions of ~0.5 Tg primarily due to N fertilizer inputs and other soil management activities. Currently 23 million acres of corn, soybean and wheat are irrigated annually in the US with increased N2O emissions due to the practice likely under-reported in GHG inventories. Here we compare N2O emissions and yield from irrigated and rainfed corn at varying N rates between 0 and 246 kg N ha-1 from the Kellogg Biological Station in SW Michigan. Initial results show that N2O emissions increase with increasing N rate and are significantly higher from irrigated corn compared to rainfed corn at the same N rate. At increasing N rates daily emissions following an irrigation event were between 2.4 - 77.5 g N2O-N ha-1 from irrigated corn and 1.6 - 13.0 g N2O-N ha-1 from rainfed corn. Emissions data from automated and static chambers will be presented and trade-offs between N2O emissions, N fertilizer rate, crop yield and irrigation practice will be evaluated from an environmental and economic standpoint.

  2. Mechanisms of nitrous oxide (N2 O) formation and reduction in denitrifying biofilms.

    PubMed

    Sabba, Fabrizio; Picioreanu, Cristian; Nerenberg, Robert

    2017-12-01

    Nitrous oxide (N 2 O) is a potent greenhouse gas that can be formed in wastewater treatment processes by ammonium oxidizing and denitrifying microorganisms. While N 2 O emissions from suspended growth systems have been extensively studied, and some recent studies have addressed emissions from nitrifying biofilms, much less is known about N 2 O emissions from denitrifying biofilm processes. This research used modeling to evaluate the mechanisms of N 2 O formation and reduction in denitrifying biofilms. The kinetic model included formation and consumption of key denitrification species, including nitrate (NO3-), nitrite (NO2-), nitric oxide (NO), and N 2 O. The model showed that, in presence of excess of electron donor, denitrifying biofilms have two distinct layers of activity: an outer layer where there is net production of N 2 O and an inner layer where there is net consumption. The presence of oxygen (O 2 ) had an important effect on N 2 O emission from suspended growth systems, but a smaller effect on biofilm systems. The effects of NO3- and O 2 differed significantly based on the biofilm thickness. Overall, the effects of biofilm thickness and bulk substrate concentrations on N 2 O emissions are complex and not always intuitive. A key mechanism for denitrifying biofilms is the diffusion of N 2 O and other intermediates from one zone of the biofilm to another. This leads to zones of N 2 O formation or consumption transformations that would not exist in suspended growth systems. © 2017 Wiley Periodicals, Inc.

  3. Multivariate regulation of soil CO2 and N2 O pulse emissions from agricultural soils.

    PubMed

    Liang, Liyin L; Grantz, David A; Jenerette, G Darrel

    2016-03-01

    Climate and land-use models project increasing occurrence of high temperature and water deficit in both agricultural production systems and terrestrial ecosystems. Episodic soil wetting and subsequent drying may increase the occurrence and magnitude of pulsed biogeochemical activity, affecting carbon (C) and nitrogen (N) cycles and influencing greenhouse gas (GHG) emissions. In this study, we provide the first data to explore the responses of carbon dioxide (CO2 ) and nitrous oxide (N2 O) fluxes to (i) temperature, (ii) soil water content as percent water holding capacity (%WHC), (iii) substrate availability throughout, and (iv) multiple soil drying and rewetting (DW) events. Each of these factors and their interactions exerted effects on GHG emissions over a range of four (CO2 ) and six (N2 O) orders of magnitude. Maximal CO2 and N2 O fluxes were observed in environments combining intermediate %WHC, elevated temperature, and sufficient substrate availability. Amendments of C and N and their interactions significantly affected CO2 and N2 O fluxes and altered their temperature sensitivities (Q10 ) over successive DW cycles. C amendments significantly enhanced CO2 flux, reduced N2 O flux, and decreased the Q10 of both. N amendments had no effect on CO2 flux and increased N2 O flux, while significantly depressing the Q10 for CO2 , and having no effect on the Q10 for N2 O. The dynamics across DW cycles could be attributed to changes in soil microbial communities as the different responses to wetting events in specific group of microorganisms, to the altered substrate availabilities, or to both. The complex interactions among parameters influencing trace gas fluxes should be incorporated into next generation earth system models to improve estimation of GHG emissions. © 2015 John Wiley & Sons Ltd.

  4. Ab initio electron correlated studies on the intracluster reaction of NO+ (H2O)(n) → H3O+ (H2O)(n-2) (HONO) (n = 4 and 5).

    PubMed

    Asada, Toshio; Nagaoka, Masataka; Koseki, Shiro

    2011-01-28

    Hydrated nitrosonium ion clusters NO(+)(H(2)O)(n) (n = 4 and 5) were investigated by using MP2/aug-cc-pVTZ level of theory to clarify isomeric reaction pathways for formation of HONO and fully hydrated hydride ions. We found some new isomers and transition state structures in each hydration number, whose lowest activation energies of the intracluster reactions were found to be 4.1 and 3.4 kcal mol(-1) for n = 4 and n = 5, respectively. These thermodynamic properties and full quantum mechanical molecular dynamics simulation suggest that product isomers with HONO and fully hydrated hydride ions can be obtained at n = 4 and n = 5 in terms of excess hydration binding energies which can overcome these activation barriers.

  5. The kinetic friction of ZnO nanowires on amorphous SiO2 and SiN substrates

    NASA Astrophysics Data System (ADS)

    Roy, Aditi; Xie, Hongtao; Wang, Shiliang; Huang, Han

    2016-12-01

    ZnO nanowires were bent on amorphous SiO2 and SiN substrates in an ambient atmosphere using optical nanomanipulation. The kinetic friction between the nanowires and substrate was determined from the bent shape of the nanowires. The kinetic friction force per unit area, i.e. frictional shear stress, for the ZnO/SiO2 and ZnO/SiN nanowire/substrate systems being measured were 1.05 ± 0.28 and 2.08 ± 0.33 MPa, respectively. The surface roughness and the Hamaker constant of SiO2 and SiN substrates had significant effect on the frictional stresses.

  6. The pH dependency of N-converting enzymatic processes, pathways and microbes: effect on net N2 O production.

    PubMed

    Blum, Jan-Michael; Su, Qingxian; Ma, Yunjie; Valverde-Pérez, Borja; Domingo-Félez, Carlos; Jensen, Marlene Mark; Smets, Barth F

    2018-05-01

    Nitrous oxide (N 2 O) is emitted during microbiological nitrogen (N) conversion processes, when N 2 O production exceeds N 2 O consumption. The magnitude of N 2 O production vs. consumption varies with pH and controlling net N 2 O production might be feasible by choice of system pH. This article reviews how pH affects enzymes, pathways and microorganisms that are involved in N-conversions in water engineering applications. At a molecular level, pH affects activity of cofactors and structural elements of relevant enzymes by protonation or deprotonation of amino acid residues or solvent ligands, thus causing steric changes in catalytic sites or proton/electron transfer routes that alter the enzymes' overall activity. Augmenting molecular information with, e.g., nitritation or denitrification rates yields explanations of changes in net N 2 O production with pH. Ammonia oxidizing bacteria are of highest relevance for N 2 O production, while heterotrophic denitrifiers are relevant for N 2 O consumption at pH > 7.5. Net N 2 O production in N-cycling water engineering systems is predicted to display a 'bell-shaped' curve in the range of pH 6.0-9.0 with a maximum at pH 7.0-7.5. Net N 2 O production at acidic pH is dominated by N 2 O production, whereas N 2 O consumption can outweigh production at alkaline pH. Thus, pH 8.0 may be a favourable pH set-point for water treatment applications regarding net N 2 O production. © 2018 Society for Applied Microbiology and John Wiley & Sons Ltd.

  7. Deep ultraviolet photodetectors based on p-Si/ i-SiC/ n-Ga2O3 heterojunction by inserting thin SiC barrier layer

    NASA Astrophysics Data System (ADS)

    An, Yuehua; Zhi, Yusong; Wu, Zhenping; Cui, Wei; Zhao, Xiaolong; Guo, Daoyou; Li, Peigang; Tang, Weihua

    2016-12-01

    Deep ultraviolet photodetectors based on p-Si/ n-Ga2O3 and p-Si/ i-SiC/ n-Ga2O3 heterojunctions were fabricated by laser molecular beam epitaxial (L-MBE), respectively. In compare with p-Si/ n-Ga2O3 heterostructure-based photodetector, the dark current of p-Si/ i-SiC/ n-Ga2O3-based photodetector decreased by three orders of magnitude, and the rectifying behavior was tuned from reverse to forward. In order to improve the quality of the photodetector, we reduced the oxygen vacancies of p-Si/ i-SiC/ n-Ga2O3 heterostructures by changing the oxygen pressure during annealing. As a result, the rectification ratio ( I F/ I R) of the fabricated photodetectors was 36 at 4.5 V and the photosensitivity was 5.4 × 105% under the 254 nm light illumination at -4.5 V. The energy band structure of p-Si/ n-Ga2O3 and p-Si/ i-SiC/ n-Ga2O3 heterostructures was schematic drawn to explain the physic mechanism of enhancement of the performance of p-Si/ i-SiC/ n-Ga2O3 heterostructure-based deep UV photodetector by introduction of SiC layer.

  8. Visible spectrum photofragmentation of O{sub 3}{sup −}(H{sub 2}O){sub n}, n ≤ 16

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lehman, Julia H.; Lineberger, W. Carl, E-mail: wcl@jila.colorado.edu

    2014-10-21

    Photofragmentation of ozonide solvated in water clusters, O{sub 3}{sup −}(H{sub 2}O){sub n}, n ≤ 16, has been studied as a function of photon energy as well as the degree of solvation. Using mass selection, the effect of the presence of the solvent molecule on the O{sub 3}{sup −} photodissociation process is assessed one solvent molecule at a time. The O{sub 3}{sup −} acts as a visible light chromophore within the water cluster, namely the O{sub 3}{sup −}(H{sub 2}O) total photodissociation cross-section exhibits generally the same photon energy dependence as isolated O{sub 3}{sup −} throughout the visible wavelength range studied (430–620more » nm). With the addition of a single solvent molecule, new photodissociation pathways are opened, including the production of recombined O{sub 3}{sup −}. As the degree of solvation of the parent anion increases, recombination to O{sub 3}{sup −}-based products accounts for close to 40% of photoproducts by n = 16. The remainder of the photoproducts exist as O{sup −}-based; no O{sub 2}{sup −}-based products are observed. Upper bounds on the O{sub 3}{sup −} solvation energy (530 meV) and the O{sup −}-OO bond dissociation energy in the cluster (1.06 eV) are derived.« less

  9. Heterogeneous interaction of SiO2 with N2O5: aerosol flow tube and single particle optical levitation-Raman spectroscopy studies.

    PubMed

    Tang, M J; Camp, J C J; Rkiouak, L; McGregor, J; Watson, I M; Cox, R A; Kalberer, M; Ward, A D; Pope, F D

    2014-09-25

    Silica (SiO2) is an important mineral present in atmospheric mineral dust particles, and the heterogeneous reaction of N2O5 on atmospheric aerosol is one of the major pathways to remove nitrogen oxides from the atmosphere. The heterogeneous reaction of N2O5 with SiO2 has only been investigated by two studies previously, and the reported uptake coefficients differ by a factor of >10. In this work two complementary laboratory techniques were used to study the heterogeneous reaction of SiO2 particles with N2O5 at room temperature and at different relative humidities (RHs). The uptake coefficients of N2O5, γ(N2O5), were determined to be (7.2 ± 0.6) × 10(-3) (1σ) at 7% RH and (5.3 ± 0.8) × 10(-3) (1σ) at 40% RH for SiO2 particles, using the aerosol flow tube technique. We show that γ(N2O5) determined in this work can be reconciled with the two previous studies by accounting for the difference in geometric and BET derived aerosol surface areas. To probe the particle phase chemistry, individual micrometer sized SiO2 particles were optically levitated and exposed to a continuous flow of N2O5 at different RHs, and the composition of levitated particles was monitored online using Raman spectroscopy. This study represents the first investigation into the heterogeneous reactions of levitated individual SiO2 particles as a surrogate for mineral dust. Relative humidity was found to play a critical role: while no significant change of particle composition was observed by Raman spectroscopy during exposure to N2O5 at RH of <2%, increasing the RH led to the formation of nitrate species on the particle surface which could be completely removed after decreasing the RH back to <2%. This can be explained by the partitioning of HNO3 between the gas and adsorbed phases. The atmospheric implications of this work are discussed.

  10. Matrix isolation infrared spectra of O2 and N2 insertion reactions with atomic uranium

    NASA Astrophysics Data System (ADS)

    Hunt, Rodney D.; Toth, L. Mac; Yustein, Jason T.; Andrews, Lester

    1993-10-01

    Laser ablation of refractory metals can be an effective source of vapor for matrix isolation IR studies. This combination of techniques was used for the first time to study the mechanisms of U vapor reactions with atmospheric components. U atoms and O2 were codeposited with excess Ar at 12 K. The dominant codeposition products were UO2 and UO3. In contrast, the UO yield was always small because UO2 is formed by an insertion mechanism. This mechanism was verified in the 16O2/18O2 experiments which failed to produce 16OU18O. The effects of UV photolysis and matrix annealings were also examined. The U atoms and O2 reaction requires little or no activation energy since UO2 was formed from cold reagents. New charge-transfer species, (UO2+2)(O2-2) and (UO+2)(O-2), and a weak complex, UO3-O2, were primarily produced under conditions which favored further O2 reactions. Similar U atom and N2 experiments produced only linear NUN which is also produced by an insertion mechanism. This U reaction represents the first time that atom was observed breaking and inserting into the triple bond of N2. Photolysis dramatically increased the NUN yield by 3-fold. Matrix annealings produced weak UN2-N2 and UN2-2N2 complexes.

  11. Seasonal effect on N2O formation in nitrification in constructed wetlands.

    PubMed

    Inamori, Ryuhei; Wang, Yanhua; Yamamoto, Tomoko; Zhang, Jixiang; Kong, Hainan; Xu, Kaiqin; Inamori, Yuhei

    2008-10-01

    Constructed wetlands are considered to be important sources of nitrous oxide (N(2)O). In order to investigate the contribution of nitrification in N(2)O formation, some environmental factors, plant species and ammonia-oxidizing bacteria (AOB) in active layers have been compared. Vegetation cells indicated remarkable effect of seasons and different plant species on N(2)O emission and AOB amount. Nitrous oxide data showed large temporal and spatial fluctuations ranging 0-52.8 mg N(2)O m(-2)d(-1). Higher AOB amount and N(2)O flux rate were observed in the Zizania latifolia cell, reflecting high potential of global warming. Roles of plants as ecosystem engineers are summarized with rhizosphere oxygen release and organic matter transportation to affect nitrogen transformation. The Phragmites australis cell contributed to keeping high T-N removal performance and lower N(2)O emission. The distribution of AOB also supported this result. Statistical analysis showed several environmental parameters affecting the strength of observed greenhouse gases emission, such as water temperature, water level, TOC, plant species and plant cover.

  12. The effect of bulk/surface defects ratio change on the photocatalysis of TiO2 nanosheet film

    NASA Astrophysics Data System (ADS)

    Wang, Fangfang; Ge, Wenna; Shen, Tong; Ye, Bangjiao; Fu, Zhengping; Lu, Yalin

    2017-07-01

    The photocatalysis behavior of TiO2 nanosheet array films was studied, in which the ratio of bulk/surface defects were adjusted by annealing at different temperature. Combining positron annihilation spectroscopy, EPR and XPS, we concluded that the bulk defects belonged to Ti3+ related vacancy defects. The results show that the separation efficiency of photogenerated electrons and holes could be significantly improved by optimizing the bulk/surface defects ratio of TiO2 nanosheet films, and in turn enhancing the photocatalysis behaviors.

  13. Heterojunction solar cell with 6% efficiency based on an n-type aluminum-gallium-oxide thin film and p-type sodium-doped Cu2O sheet

    NASA Astrophysics Data System (ADS)

    Minami, Tadatsugu; Nishi, Yuki; Miyata, Toshihiro

    2015-02-01

    In this paper, we describe efforts to enhance the efficiency of Cu2O-based heterojunction solar cells fabricated with an aluminum-gallium-oxide (Al-Ga-O) thin film as the n-type layer and a p-type sodium (Na)-doped Cu2O (Cu2O:Na) sheet prepared by thermally oxidizing copper sheets. The optimal Al content [X; Al/(Ga + Al) atomic ratio] of an AlX-Ga1-X-O thin-film n-type layer was found to be approximately 2.5 at. %. The optimized resistivity was approximately 15 Ω cm for n-type AlX-Ga1-X-O/p-type Cu2O:Na heterojunction solar cells. A MgF2/AZO/Al0.025-Ga0.975-O/Cu2O:Na heterojunction solar cell with 6.1% efficiency was fabricated using a 60-nm-thick n-type oxide thin-film layer and a 0.2-mm-thick Cu2O:Na sheet with the optimized resistivity.

  14. Observations of D/H ratios in H2O, HCl, and HF on Venus and new DCl and DF line strengths

    NASA Astrophysics Data System (ADS)

    Krasnopolsky, V. A.; Belyaev, D. A.; Gordon, I. E.; Li, G.; Rothman, L. S.

    2013-05-01

    Intensities of the spectral lines in the fundamental bands of D35Cl and DF were calculated using the semi-empirical dipole moment functions derived from the most accurate and precise measurements of intensities of the ro-vibrational lines of H35Cl and HF. Values obtained in this way for the deuterated species are superior to any available measured or calculated data to date. Our study of the D/H ratios in H2O, HCl, and HF on Venus is based on spatially-resolved high-resolution spectroscopy using the CSHELL spectrograph at NASA IRTF. Search for DF on Venus using its R5 (1-0) line at 3024.054 cm-1 results in a DF mixing ratio of 0.23 ± 0.11 ppb that corresponds to (D/H)HF = 420 ± 200 times that in the Standard Mean Ocean Water (SMOW). H2O abundances on Venus were retrieved using lines at 3022.366 and 3025.761 cm-1 that were observed at an exceptionally low overhead telluric water abundance of 0.3 pr. mm. The measured H2O mixing ratios at 74 km vary insignificantly between 55°S and 55°N with a mean value of 3.2 ppm. When compared with simultaneous observations of HDO near 2722 cm-1, this results in (D/H)H2O = 95 ± 15 times SMOW. Reanalysis of the observation of the D35Cl R4 (1-0) line at 2141.540 cm-1 (Krasnopolsky, V.A. [2012b]. Icarus 219, 244-249) using the improved line strength and more thorough averaging of the spectra gives (D/H)HCl = 190 ± 50 times SMOW. The similarity of the measured (D/H)H2O = 95 ± 15 at 74 km with 120 ± 40 observed by De Bergh et al. (De Bergh, C., Bezard, B., Owen, T., Crisp, D., Maillard, J.P., Lutz, B.L. [1991]. Science 251, 547-549) below the clouds favors the constant (D/H)H2O from the surface to the mesosphere, in accord with the prediction by theory. D/H ≈ 100 removes a difference of a factor of 2 between H2O abundances in the observations by Krasnopolsky (Krasnopolsky, V.A. [2010b]. Icarus 209, 314-322) and the Venus Express nadir observations (Cottini, V., Ignatiev, N.I., Piccioni, G., Drossart, P., Grassi, D., Markiewicz

  15. NbN/MgO/NbN edge-geometry tunnel junctions

    NASA Technical Reports Server (NTRS)

    Hunt, B. D.; Leduc, H. G.; Cypher, S. R.; Stern, J. A.; Judas, A.

    1989-01-01

    The fabrication and low-frequency testing of the first edge-geometry NbN/MgO/NbN superconducting tunnel junctions are reported. The use of an edge geometry allows very small junction areas to be obtained, while the all-NbN electrodes permit operation at 8-10 K with a potential maximum operating frequency above 1 THz. Edge definition in the base NbN film was accomplished utilizing Ar ion milling with an Al2O3 milling mask, followed by a lower energy ion cleaning step. This process has produced all-refractory-material tunnel junctions with areas as small as 0.1 sq micron, resistance-area products less than 21 ohm sq micron, and subgap to normal state resistance ratios larger than 18.

  16. Riverine N2O concentrations, exports to estuary and emissions to atmosphere from the Changjiang River in response to increasing nitrogen loads

    NASA Astrophysics Data System (ADS)

    Yan, Weijin; Yang, Libiao; Wang, Fang; Wang, Jianing; Ma, Pei

    2012-12-01

    This study investigated the variations of dissolved N2O and emissions over diurnal and seasonal temporal scales in 2009, as well as the time series of riverine N2O export to estuary and emission to atmosphere in response to increasing anthropogenic nitrogen loads in the Changjiang River. For the diurnal study, N2O concentrations ranged from 0.26 to 0.34 and from 0.44 to 0.52 μg N-N2O L-1 in August and October 2009, respectively. The dissolved N2O was supersaturated with a mean value of 197%. Studies on N2O emissions, also taken in August and October, ranged from 2.67 to 11.6 and from 6.72 to 15.2 μg N-N2O m-2 h-1, respectively. For the seasonal study (June through December 2009), N2O concentrations ranged from 0.34 to 0.72 μg N-N2O L-1 and were supersaturated in all the samples (average 212%). N2O emissions ranged from 1.87 to 40.8 μg N-N2O m-2 h-1. Our study found no significant differences in diurnal patterns of N2O saturation but detected significant difference in seasonal patterns of N2O saturation: higher during summer while lower during autumn and winter. We found a significant relationship between dissolved N2O and river nitrate, which can predict the variation of N2O concentrations in the River. The net production of N2 ranged from 0.01 to 0.47 mg N-N2 L-1. These excess N2 values were significantly correlated to the N2O production and are suggestive of denitrification in the river. Applying the Global News model to the river system using measures taken during the 1970 to 2002 period, we estimated N2O emissions to atmosphere increased from 330 to 3650 ton N-N2O yr-1. During that same 1970-2002 period, N2O exports to estuary increased from 91 to 470 ton N-N2O yr-1. Taken together, the findings reported here suggest that both the river N2O concentrations and emissions would increase in response to rising anthropogenic nitrogen loads. Our study showed that the mean emission factor based on the ratio of the total N2O flux to NO3- flux is four times greater

  17. Electrical Conducting and Mechanism of Oxygen-Deficient Tin Oxide Films Deposited by RF Magnetron Sputtering at Various O2/Ar Ratios

    NASA Astrophysics Data System (ADS)

    Wang, Qi; Wang, Chengbiao; Lv, Changchun; Wang, Yang; Peng, Zhijian; Fu, Xiuli

    Oxygen-deficient tin oxide thin films were prepared by radiofrequency magnetron sputtering with a sintered non-stoichiometric tin oxide ceramic target under an atmosphere of various ratios of O2/Ar from pure Ar to 1:1. X-ray diffraction analysis showed that the thin films were polycrystalline with relatively strong (1 1 0), (1 0 1) and (2 1 1) diffraction peaks. Scanning electron microscopy observation revealed that the thin films prepared at different O2/Ar ratios were all of relatively dense and homogeneous structure. With increasing O2/Ar ratio, the grain size of the films decreased slightly, and their chemical composition became close to the stoichiometric SnO2; but the deposition rate as well as film thickness increased first and then decreased sharply. It was revealed that the main defect in obtained films was oxygen vacancy (VO), and as the O2/Ar ratio increased, the concentration of VO fell down monotonously, which would lead to an increased electrical resistivity.

  18. First on-line isotopic characterization of N2O emitted from intensively managed grassland

    NASA Astrophysics Data System (ADS)

    Wolf, B.; Merbold, L.; Decock, C.; Tuzson, B.; Harris, E.; Six, J.; Emmenegger, L.; Mohn, J.

    2015-01-01

    The analysis of the four main isotopic N2O species (14N14N16O, 14N15N16O, 15N14N16O, 14N14N18O) and especially the intramolecular distribution of 15N (site preference, SP) has been suggested as a tool to distinguish source processes and to help constrain the global N2O budget. However, current studies suffer from limited spatial and temporal resolution capabilities due to the combination of discrete flask sampling with subsequent laboratory-based mass spectrometric analysis. Quantum cascade laser absorption spectroscopy (QCLAS) allows selective high-precision analysis of N2O isotopic species at trace levels and is suitable for in situ measurements. Here, we present results from the first field campaign, conducted on an intensively managed grassland in central Switzerland. N2O mole fractions and isotopic composition were determined in the atmospheric surface layer (2 m height) at high temporal resolution with a modified state-of-the-art laser spectrometer connected to an automated N2O preconcentration unit. The analytical performance was determined from repeated measurements of a compressed air tank and resulted in measurement repeatability of 0.20, 0.12 and 0.11‰ for δ15Nα, δ15Nβ and δ18O, respectively. Simultaneous eddy-covariance N2O flux measurements were used to determine the flux-averaged isotopic signature of soil-emitted N2O. Our measurements indicate that in general, nitrifier-denitrification and denitrification were the prevalent sources of N2O during the campaign, and that variations in isotopic composition were rather due to alterations in the extent to which N2O was reduced to N2, than other pathways such as hydroxylamine oxidation. Management and rewetting events were characterized by low values of the intra-molecular 15N site preference (SP), δ15Nbulk and δ18O, suggesting nitrifier denitrification and incomplete heterotrophic bacterial denitrification responded most strongly to the induced disturbances. Flux-averaged isotopic composition of N

  19. Self-encapsulation of [MII(phen)2(H2O)2]2+ (M=Co, Zn) in one-dimensional nanochannels of [MII(H2O)6(BTC)2]4- (M=Co, Cu, Mn): a high HQ/CAT ratio catalyst for hydroxylation of phenols.

    PubMed

    Bi, Jianhong; Kong, Lingtao; Huang, Zixiang; Liu, Jinhuai

    2008-06-02

    Four novel three-dimensional (3D) microporous supramolecular compounds containing nanosized channels, namely, [Co(phen)2(H2O)2]2[Co(H2O)6].2BTC.21.5H2O (1), [Co(phen)2(H2O)2]2[Cu(H2O)6].2BTC.21.5H2O (2), [Co(phen)2(H2O)2]2[Mn(H2O)6].2BTC.18H2O (3), and [Zn(phen)2(H2O)2]2[Mn(H2O)6].2BTC.22.5H2O (4), were synthesized from 1,3,5-benzenetricarboxylate (BTC), 1,10-phenanthroline (phen), and the transition-metal salt(s) by self-assembly. Single-crystal X-ray structural analysis showed that the resulting 3D microporous supramolecular frameworks consist of a two-dimensional (2D) hydrogen-bonded host framework of [MII(H2O)6(BTC)2]4- (M=Co for 1, Cu for 2, Mn for 3, 4) with rectangular-shaped cavities containing [MII(phen)2(H2O)2]2+ (M=Co for 1-3, Zn for 4) guests. The guest complex is encapsulated in the 2D hydrogen-bonded host framework by hydrogen bonding and aromatic pi-pi stacking interactions, forming the 3D hydrogen-bonded framework. The catalytic activities of 1, 2, 3, and 4 were studied using hydroxylation of phenols with 30% aqueous H2O2 as a test reaction. The compounds displayed a good phenol conversion ratio and excellent channel selectivity in the hydroxylation reaction, with a maximum hydroquinone (HQ)/catechol (CAT) ratio of 3.9.

  20. Fe-N co-doped SiO2@TiO2 yolk-shell hollow nanospheres with enhanced visible light photocatalytic degradation

    NASA Astrophysics Data System (ADS)

    Wan, Hengcheng; Yao, Weitang; Zhu, Wenkun; Tang, Yi; Ge, Huilin; Shi, Xiaozhong; Duan, Tao

    2018-06-01

    SiO2@TiO2 yolk@shell hollow nanospheres (STNSs) is considered as an outstanding photocatalyst due to its tunable structure and composition. Based on this point, we present an unprecedentedly excellent photocatalytic property of STNSs toward tannic acid via a Fe-N co-doped strategy. Their morphologies, compositions, structure and properties are characterized. The Fe-N co-doped STNSs formed good hollow yolk@shell structure. The results show that the energy gap of the composites can be downgraded to 2.82 eV (pure TiO2 = 3.2 eV). Photocatalytic degradation of tannic acid (TA, 30 mg L-1) under visible light (380 nm < λ < 780 nm) irradiation is used to evaluate the photocatalytic activity of the composites. Compared with pure TiO2 nanospheres, non-doped STNSs and N-doped STNSs, the Fe-N co-doped STNSs exhibits the highest activity, which can degrade 99.5% TA into CO2 and H2O in 80 min. The probable degradation mechanism of the composites is simultaneously proposed, the band gap of STNSs becomes narrow by co-doping Fe-N, so that the TiO2 shell can stimulate electrons under visible light exposure, generate the ions of radOH and radO2- with a strong oxidizing property. Therefore this approach works is much desired for radioactive organic wastewater photocatalytic degradation.