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Sample records for air o2 n2

  1. Orbital tuning of deep ice cores using O2/N2 of trapped air

    NASA Astrophysics Data System (ADS)

    Kawamura, K.; Aoki, S.; Nakazawa, T.

    2014-12-01

    The chronology of the first Dome Fuji deep ice core (80,000-340,000 yr BP) was established by orbital tuning of measured O2/N2 ratios in trapped air to the past local summer insolation at the drill site (Kawamura et al., 2007). The O2/N2 ratios found in ice cores are generally lower than atmospheric ratio because of size-dependent molecular fractionation during bubble close-off. The magnitude of this gas fractionation appears to be influenced by snow metamorphism when the layer was originally at the surface, which in turn is controlled by local summer insolation (Fujita et al., 2009). The O2/N2 record has little 100,000-yr periodicity (strongest in climatic records), suggesting insignificant climatic influence in the orbital tuning. Agreement of the O2/N2 chronology with U-Th radiometric chronology of speleothems (within ~2000 yr) suggests that O2/N2 and summer insolation are indeed in phase. However, it may not be common to all ice cores that O2/N2 signal only records local summer insolation. For example, the GISP2 ice core (Greenland) has clear imprint of abrupt climate changes in the O2/N2 record, indicating climatic (non-insolation) signal in the record and the possibility of phase variability of O2/N2 relative to the past insolation (Suwa and Bender, 2008). Here we present new O2/N2 record from the second Dome Fuji ice core with significant improvements in ice core storage practice and mass spectrometry. In particular, the ice core had been stored at about -50 ˚C until the air extraction except during transportations, which prevent fractionation due to gas loss during the core storage. The precision of the new O2/N2 data set is improved by a factor of 3 over the previous data, and we do not observe outliers (there were 15% outliers in the previous data). Clear imprint of local insolation is recognizable in the new O2/N2, which would enable us to generate a chronology with accuracy of ~2000 yr towards older periods. Samples from the first core after long

  2. A systematic study of Rayleigh-Brillouin scattering in air, N2, and O2 gases

    NASA Astrophysics Data System (ADS)

    Gu, Ziyu; Ubachs, Wim

    2014-09-01

    Spontaneous Rayleigh-Brillouin scattering experiments in air, N2, and O2 have been performed for a wide range of temperatures and pressures at a wavelength of 403 nm and at a 90° scattering angle. Measurements of the Rayleigh-Brillouin spectral scattering profile were conducted at high signal-to-noise ratio for all three species, yielding high-quality spectra unambiguously showing the small differences between scattering in air, and its constituents N2 and O2. Comparison of the experimental spectra with calculations using the Tenti S6 model, developed in the 1970s based on linearized kinetic equations for molecular gases, demonstrates that this model is valid to high accuracy for N2 and O2, as well as for air. After previous measurements performed at 366 nm, the Tenti S6 model is here verified for a second wavelength of 403 nm, and for the pressure-temperature parameter space covered in the present study (250-340 K and 0.6-3 bars). In the application of the Tenti S6 model, based on the transport coefficients of the gases, such as thermal conductivity κ, internal specific heat capacity cint and shear viscosity η, as well as their temperature dependencies taken as inputs, values for the more elusive bulk viscosity ηb for the gases are derived by optimizing the model to the measurements. It is verified that the bulk viscosity parameters obtained from previous experiments at 366 nm are valid for wavelengths of 403 nm. Also for air, which is treated as a single-component gas with effective gas transport coefficients, the Tenti S6 treatment is validated for 403 nm as for the previously used wavelength of 366 nm, yielding an accurate model description of the scattering profiles for a range of temperatures and pressures, including those of relevance for atmospheric studies. It is concluded that the Tenti S6 model, further verified in the present study, is applicable to LIDAR applications for exploring the wind velocity and the temperature profile distributions of the

  3. Ion swarm data of N{4}+ in N2, O2 and dry air for streamer dynamics simulation

    NASA Astrophysics Data System (ADS)

    Bekstein, A.; Benhenni, M.; Yousfi, M.; Ducasse, O.; Eichwald, O.

    2008-04-01

    The ion swarm data such as reduced mobilities, diffusion coefficients and reaction rates of N{4}+ in N{2}, O{2} and dry air (80% N{2}, 20% O{2}) have been determined from a Monte Carlo simulation using calculated and measured elastic and inelastic cross sections. The elastic cross sections used have been determined from a semi-classical JWKB approximation based on a rigid core potential model. The inelastic cross section of N{4}+ in N{2} has been deduced from the measured experimental rates whereas for N{4}+ in O{2} the measured inelastic cross sections have been extended to low and high energies by appropriate approximations. Then the cross sections sets have been validated from comparison of calculated and measured ion swarm data. From the cross sections sets obtained in pure N{2} and O{2}, the ion swarm data for N{4}+ in dry air are then calculated for a large E/N range [ 1 104] Td. Finally, the influence of N{4}+ ions on the streamer development was analyzed with a 2D fluid model in the case of dry air at atmospheric pressure for a point-to-plane electrode configuration.

  4. Accurate age scale of the Dome Fuji ice core, Antarctica from O2/N2 ratio of trapped air

    NASA Astrophysics Data System (ADS)

    Kawamura, K.; Aoki, S.; Nakazawa, T.; Suzuki, K.; Parrenin, F.

    2012-04-01

    Chronology of the first Dome Fuji deep ice core (core length: 2,500 m, ice thickness: 3,035 m) for the age range from 80 kyr to 340 kyr ago was established by orbital tuning of measured O2/N2 ratios in trapped air to local summer insolation, with precision better than about 2,000 years (Kawamura et al., 2007). The O2/N2 ratios found in polar ice cores are slightly lower than the atmospheric ratio because of size-dependent molecular fractionation during bubble close-off. The magnitude of this gas fractionation is believed to be governed by the magnitude of snow metamorphism when the layer was originally at the surface, which in turn is controlled by local summer insolation (Fujita et al., 2009). A strong advantage of the O2/N2 chronology is that there is no need to assume a lag between climatic records in the ice core and orbital forcings, becacuse O2/N2 ratios record local insolation through physical processes. Accuracy of the chronology was validated by comparing the O2/N2 chronology with U-Th radiometric chronology of speleothem records (Cheng et al., 2009) for the ends of Terminations II, III and IV, as well as several large climatic events, for which both ice-core CH4 and speleothem δ18O (a proxy for precipitation) show abrupt shifts as seen in the last glacial period. All ages from O2/N2 and U-Th chronology agreed with each other within ~2,000 yr. The O2/N2 chronology permits comparisons between Antarctic climate, greenhouse gases, astronomically calculated orbital parameters, and radiometrically-dated sea level and monsoon records. Here, we completed the measurements of O2/N2 ratios of the second Dome Fuji ice core, which reached bedrock, for the range from 2,400 to 3,028 m (320 - 700 kyr ago) at approximately 2,000-year time resolution. We made significant improvements in ice core storage practices and mass spectrometry. In particular, the ice core samples were stored at about -50 ° C until the air extraction, except during short periods of transportation

  5. Inactivation of Escherichia coli Cells in Aqueous Solution by Atmospheric-Pressure N2, He, Air, and O2 Microplasmas

    PubMed Central

    Zhou, Renwu; Zhang, Xianhui; Bi, Zhenhua; Zong, Zichao; Niu, Jinhai; Song, Ying; Yang, Size

    2015-01-01

    Atmospheric-pressure N2, He, air, and O2 microplasma arrays have been used to inactivate Escherichia coli cells suspended in aqueous solution. Measurements show that the efficiency of inactivation of E. coli cells is strongly dependent on the feed gases used, the plasma treatment time, and the discharge power. Compared to atmospheric-pressure N2 and He microplasma arrays, air and O2 microplasma arrays may be utilized to more efficiently kill E. coli cells in aqueous solution. The efficiencies of inactivation of E. coli cells in water can be well described by using the chemical reaction rate model, where reactive oxygen species play a crucial role in the inactivation process. Analysis indicates that plasma-generated reactive species can react with E. coli cells in water by direct or indirect interactions. PMID:26025895

  6. Inactivation of Escherichia coli Cells in Aqueous Solution by Atmospheric-Pressure N2, He, Air, and O2 Microplasmas.

    PubMed

    Zhou, Renwu; Zhang, Xianhui; Bi, Zhenhua; Zong, Zichao; Niu, Jinhai; Song, Ying; Liu, Dongping; Yang, Size

    2015-08-01

    Atmospheric-pressure N2, He, air, and O2 microplasma arrays have been used to inactivate Escherichia coli cells suspended in aqueous solution. Measurements show that the efficiency of inactivation of E. coli cells is strongly dependent on the feed gases used, the plasma treatment time, and the discharge power. Compared to atmospheric-pressure N2 and He microplasma arrays, air and O2 microplasma arrays may be utilized to more efficiently kill E. coli cells in aqueous solution. The efficiencies of inactivation of E. coli cells in water can be well described by using the chemical reaction rate model, where reactive oxygen species play a crucial role in the inactivation process. Analysis indicates that plasma-generated reactive species can react with E. coli cells in water by direct or indirect interactions.

  7. Characteristics of surface-wave plasma with air-simulated N2 O2 gas mixture for low-temperature sterilization

    NASA Astrophysics Data System (ADS)

    Xu, L.; Nonaka, H.; Zhou, H. Y.; Ogino, A.; Nagata, T.; Koide, Y.; Nanko, S.; Kurawaki, I.; Nagatsu, M.

    2007-02-01

    Sterilization experiments using low-pressure air discharge plasma sustained by the 2.45 GHz surface-wave have been carried out. Geobacillus stearothermoplilus spores having a population of 3.0 × 106 were sterilized for only 3 min using air-simulated N2-O2 mixture gas discharge plasma, faster than the cases of pure O2 or pure N2 discharge plasmas. From the SEM analysis of plasma-irradiated spores and optical emission spectroscopy measurements of the plasmas, it has been found that the possible sterilization mechanisms of air-simulated plasma are the chemical etching effect due to the oxygen radicals and UV emission from the N2 molecules and NO radicals in the wavelength range 200-400 nm. Experiment suggested that UV emission in the wavelength range less than 200 nm might not be significant in the sterilization. The UV intensity at 237.0 nm originated from the NO γ system (A 2Σ+ → X 2Π) in N2-O2 plasma as a function of the O2 percentage added to N2-O2 mixture gas has been investigated. It achieved its maximum value when the O2 percentage was roughly 10-20%. This result suggests that air can be used as a discharge gas for sterilization, and indeed we have confirmed a rapid sterilization with the actual air discharge at a sample temperature of less than 65 °C.

  8. Electrical analysis of positive corona discharge in air and N2, O2, and CO2 mixtures

    NASA Astrophysics Data System (ADS)

    Dubois, D.; Merbahi, N.; Eichwald, O.; Yousfi, M.; Benhenni, M.

    2007-03-01

    This paper presents an experimental analysis of the electrical behavior of positive point-plane corona discharges. The corona current, streamer velocity, mean discharge frequency, and current-voltage characteristic are studied, firstly in synthetic air as a function of experimental parameters such as gap distance and tip radius. Different electrical diagnostics are used in order to better understand the streamer development as well as the dependence of its characteristics on the previous listed parameters. Then the influence of gas mixture (several proportions of N2 and O2 with or without CO2) is analyzed. When the gas concentration is varied the shape and amplitude of the corona current are significantly affected due to the variation of the gas electronegativity following its composition and concentration. The ionization and attachment coefficients are calculated from the electron energy distribution function in the case of these different gas mixtures in order to quantify the critical electric field value enabling the streamer development for a given gas mixture.

  9. Effects of Atmospheric-Pressure N2, He, Air, and O2 Microplasmas on Mung Bean Seed Germination and Seedling Growth

    NASA Astrophysics Data System (ADS)

    Zhou, Renwu; Zhou, Rusen; Zhang, Xianhui; Zhuang, Jinxing; Yang, Size; Bazaka, Kateryna; (Ken) Ostrikov, Kostya

    2016-09-01

    Atmospheric-pressure N2, He, air, and O2 microplasma arrays have been used to investigate the effects of plasma treatment on seed germination and seedling growth of mung bean in aqueous solution. Seed germination and growth of mung bean were found to strongly depend on the feed gases used to generate plasma and plasma treatment time. Compared to the treatment with atmospheric-pressure O2, N2 and He microplasma arrays, treatment with air microplasma arrays was shown to be more efficient in improving both the seed germination rate and seedling growth, the effect attributed to solution acidification and interactions with plasma-generated reactive oxygen and nitrogen species. Acidic environment caused by air discharge in water may promote leathering of seed chaps, thus enhancing the germination rate of mung bean, and stimulating the growth of hypocotyl and radicle. The interactions between plasma-generated reactive species, such as hydrogen peroxide (H2O2) and nitrogen compounds, and seeds led to a significant acceleration of seed germination and an increase in seedling length of mung bean. Electrolyte leakage rate of mung bean seeds soaked in solution activated using air microplasma was the lowest, while the catalase activity of thus-treated mung bean seeds was the highest compared to other types of microplasma.

  10. Effects of Atmospheric-Pressure N2, He, Air, and O2 Microplasmas on Mung Bean Seed Germination and Seedling Growth

    PubMed Central

    Zhou, Renwu; Zhou, Rusen; Zhang, Xianhui; Zhuang, Jinxing; Yang, Size; Bazaka, Kateryna; (Ken) Ostrikov, Kostya

    2016-01-01

    Atmospheric-pressure N2, He, air, and O2 microplasma arrays have been used to investigate the effects of plasma treatment on seed germination and seedling growth of mung bean in aqueous solution. Seed germination and growth of mung bean were found to strongly depend on the feed gases used to generate plasma and plasma treatment time. Compared to the treatment with atmospheric-pressure O2, N2 and He microplasma arrays, treatment with air microplasma arrays was shown to be more efficient in improving both the seed germination rate and seedling growth, the effect attributed to solution acidification and interactions with plasma-generated reactive oxygen and nitrogen species. Acidic environment caused by air discharge in water may promote leathering of seed chaps, thus enhancing the germination rate of mung bean, and stimulating the growth of hypocotyl and radicle. The interactions between plasma-generated reactive species, such as hydrogen peroxide (H2O2) and nitrogen compounds, and seeds led to a significant acceleration of seed germination and an increase in seedling length of mung bean. Electrolyte leakage rate of mung bean seeds soaked in solution activated using air microplasma was the lowest, while the catalase activity of thus-treated mung bean seeds was the highest compared to other types of microplasma. PMID:27584560

  11. Effects of Atmospheric-Pressure N2, He, Air, and O2 Microplasmas on Mung Bean Seed Germination and Seedling Growth.

    PubMed

    Zhou, Renwu; Zhou, Rusen; Zhang, Xianhui; Zhuang, Jinxing; Yang, Size; Bazaka, Kateryna; Ken Ostrikov, Kostya

    2016-09-01

    Atmospheric-pressure N2, He, air, and O2 microplasma arrays have been used to investigate the effects of plasma treatment on seed germination and seedling growth of mung bean in aqueous solution. Seed germination and growth of mung bean were found to strongly depend on the feed gases used to generate plasma and plasma treatment time. Compared to the treatment with atmospheric-pressure O2, N2 and He microplasma arrays, treatment with air microplasma arrays was shown to be more efficient in improving both the seed germination rate and seedling growth, the effect attributed to solution acidification and interactions with plasma-generated reactive oxygen and nitrogen species. Acidic environment caused by air discharge in water may promote leathering of seed chaps, thus enhancing the germination rate of mung bean, and stimulating the growth of hypocotyl and radicle. The interactions between plasma-generated reactive species, such as hydrogen peroxide (H2O2) and nitrogen compounds, and seeds led to a significant acceleration of seed germination and an increase in seedling length of mung bean. Electrolyte leakage rate of mung bean seeds soaked in solution activated using air microplasma was the lowest, while the catalase activity of thus-treated mung bean seeds was the highest compared to other types of microplasma.

  12. Effects of Atmospheric-Pressure N2, He, Air, and O2 Microplasmas on Mung Bean Seed Germination and Seedling Growth.

    PubMed

    Zhou, Renwu; Zhou, Rusen; Zhang, Xianhui; Zhuang, Jinxing; Yang, Size; Bazaka, Kateryna; Ken Ostrikov, Kostya

    2016-01-01

    Atmospheric-pressure N2, He, air, and O2 microplasma arrays have been used to investigate the effects of plasma treatment on seed germination and seedling growth of mung bean in aqueous solution. Seed germination and growth of mung bean were found to strongly depend on the feed gases used to generate plasma and plasma treatment time. Compared to the treatment with atmospheric-pressure O2, N2 and He microplasma arrays, treatment with air microplasma arrays was shown to be more efficient in improving both the seed germination rate and seedling growth, the effect attributed to solution acidification and interactions with plasma-generated reactive oxygen and nitrogen species. Acidic environment caused by air discharge in water may promote leathering of seed chaps, thus enhancing the germination rate of mung bean, and stimulating the growth of hypocotyl and radicle. The interactions between plasma-generated reactive species, such as hydrogen peroxide (H2O2) and nitrogen compounds, and seeds led to a significant acceleration of seed germination and an increase in seedling length of mung bean. Electrolyte leakage rate of mung bean seeds soaked in solution activated using air microplasma was the lowest, while the catalase activity of thus-treated mung bean seeds was the highest compared to other types of microplasma. PMID:27584560

  13. Comparison of the effects of room air and N2O + O2 used for ProSeal LMA cuff inflation on cuff pressure and oropharyngeal structure.

    PubMed

    Tekin, Murat; Kati, Ismail; Tomak, Yakup; Yuca, Koksal

    2008-01-01

    This study aimed to evaluate the effects of different inflating gases used for ProSeal LMA (PLMA) cuff inflation on cuff pressure, oropharyngeal structure, and the incidence of sore throat. Eighty patients (American Society of Anesthesiologists; ASA I-II) were randomly divided into two groups. PLMA cuff inflation was achieved with appropriate volumes of 50% N2O + 50% O2 in group I and room air in group II, respectively. When the PLMA was removed, oropharyngeal examination was carried out immediately, using a rigid optical telescope. Patients were asked about sore throat symptoms postoperatively. Cuff pressures were significantly lower in group I, except at the initial pressure measurement. Cuff pressure was positively correlated with the length of the operation in group II, and negatively correlated in group I. PLMA cuff inflation with room air led to increased cuff pressure during the operation, possibly due to the diffusion of N2O into the cuff. We consider that a PLMA cuff inflated with an N2O-O2 mixture is convenient, especially in operations in which N2O has been used.

  14. 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.

  15. Strain-induced extinction of hydrogen-air counterflow diffusion flames - Effects of steam, CO2, N2, and O2 additives to air

    NASA Technical Reports Server (NTRS)

    Pellett, G. L.; Northam, G. B.; Wilson, L. G.

    1992-01-01

    A fundamental study was performed using axisymmetric nozzle and tubular opposed jet burners to measure the effects of laminar plug flow and parabolic input velocity profiles on the extinction limits of H2-air counterflow diffusion flames. Extinction limits were quantified by 'flame strength', (average axial air jet velocity) at blowoff of the central flame. The effects of key air contaminants, on the extinction limits, are characterized and analyzed relative to utilization of combustion contaminated vitiated air in high enthalpy supersonic test facilities.

  16. Collision cross sections and swarm coefficients of water vapour ion clusters (H2O) n H+ with n = 1, 2 and 3 in N2, O2 and air

    NASA Astrophysics Data System (ADS)

    Bekstein, A.; Benhenni, M.; Yousfi, M.

    2011-01-01

    The ion swarm transport coefficients such as reduced mobility, diffusion coefficients and reaction rates of three water vapour ion clusters (H2O) n H+ (with n = 1, 2 and 3) in N2 and O2 have been determined from a Monte Carlo simulation using calculated and measured elastic and inelastic collision cross sections. The elastic momentum transfer cross sections have been determined from a semi-classical JWKB approximation based on a rigid core interaction potential model. The inelastic cross sections have been deduced from the measured ones in the case of similar ion cluster. Then, the cross sections sets are fitted using either the measured reduced mobility at low electric field in the case of (H2O) n H+ in N2 or the zero-field mobility calculated from the Satoh's relation and the measured ones in N2. From the sets of elastic and inelastic collision cross sections thus obtained in pure N2 and O2, the ion transport and reaction coefficients for (H2O) n H+ are then calculated in dry air and also extended over a wide range of reduced electric field in N2 and O2. These ion data are very useful for modelling and simulation of non-equilibrium electrical discharges more particularly in humid gases at atmospheric pressure.

  17. 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.

  18. Air- and N2-Broadening Coefficients and Pressure-Shift Coefficients in the C-12(O2-16) Laser Bands

    NASA Technical Reports Server (NTRS)

    Devi, V. Malathy; Benner, D. Chris; Smith, Mary Ann H.; Rinsland, Curtis P.

    1998-01-01

    In this paper we report the pressure broadening and the pressure-induced line shift coefficients for 46 individual rovibrational lines in both the (12)C(16)O2, 00(sup 0)1-(10(sup 0)0-02(sup 0)0)I, and 00(sup 0)1-(10(sup 0)0-02(sup 0)0)II, laser bands (laser band I centered at 960.959/cm and laser band II centered at 1063.735/cm) determined from spectra recorded with the McMath-Pierce Fourier transform spectrometer. The results were obtained from analysis of 10 long-path laboratory absorption spectra recorded at room temperature using a multispectrum nonlinear least-squares technique. Pressure effects caused by both air and nitrogen have been investigated. The air-broadening coefficients determined in this study agree well with the values in the 1996 HITRAN database; ratios and standard deviations of the ratios of the present air-broadening measurements to the 1996 HITRAN values for the two laser bands are: 1.005(15) for laser band I and 1.005(14) for laser band II. Broadening by nitrogen is 3 to 4% larger than that of air. The pressure-induced line shift coefficients are found to be transition dependent and different for the P- and R-branch lines with same J" value. No noticeable differences in the shift coefficients caused by air and nitrogen were found. The results obtained are compared with available values previously reported in the literature.

  19. 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

  20. Active species in N2 and N2-O2 afterglows for surface treatments

    NASA Astrophysics Data System (ADS)

    Ricard, A.; Pointu, A. M.; Villeger, S.; Canal, C.

    2010-01-01

    Production of active species is studied in N2 and in N2-O2 afterglows of electrical discharges at low and atmospheric gas pressures. They are produced in microwave discharges in a large range of gas pressures from a few Torr to 100 Torr and in corona discharges at atmospheric gas pressure. The active species in N2 afterglows are the N-atoms which are in the range of a few percents in the afterglows. The effect of O2 molecules in low percentages in low pressure N2microwave plasmas and as impurity in corona N2 discharges is specially analysed. The interaction of N and O-atoms with surfaces is studied for bacteria decontamination and for transmission of N-atoms though porous membranes. The processes of bacteria decontamination in N2-O2 afterglows are described for low pressure microwave and atmospheric pressure corona discharges. Transmission of N-atoms through porous membranes is studied at medium pressure (10-100 Torr) microwave afterglows.

  1. Potential energy surface of triplet N2O2

    NASA Astrophysics Data System (ADS)

    Varga, Zoltan; Meana-Pañeda, Rubén; Song, Guoliang; Paukku, Yuliya; Truhlar, Donald G.

    2016-01-01

    We present a global ground-state triplet potential energy surface for the N2O2 system that is suitable for treating high-energy vibrational-rotational energy transfer and collision-induced dissociation. The surface is based on multi-state complete-active-space second-order perturbation theory/minimally augmented correlation-consistent polarized valence triple-zeta electronic structure calculations plus dynamically scaled external correlation. In the multireference calculations, the active space has 14 electrons in 12 orbitals. The calculations cover nine arrangements corresponding to dissociative diatom-diatom collisions of N2, O2, and nitric oxide (NO), the interaction of a triatomic molecule (N2O and NO2) with the fourth atom, and the interaction of a diatomic molecule with a single atom (i.e., the triatomic subsystems). The global ground-state potential energy surface was obtained by fitting the many-body interaction to 54 889 electronic structure data points with a fitting function that is a permutationally invariant polynomial in terms of bond-order functions of the six interatomic distances.

  2. Potential energy surface of triplet N2O2.

    PubMed

    Varga, Zoltan; Meana-Pañeda, Rubén; Song, Guoliang; Paukku, Yuliya; Truhlar, Donald G

    2016-01-14

    We present a global ground-state triplet potential energy surface for the N2O2 system that is suitable for treating high-energy vibrational-rotational energy transfer and collision-induced dissociation. The surface is based on multi-state complete-active-space second-order perturbation theory/minimally augmented correlation-consistent polarized valence triple-zeta electronic structure calculations plus dynamically scaled external correlation. In the multireference calculations, the active space has 14 electrons in 12 orbitals. The calculations cover nine arrangements corresponding to dissociative diatom-diatom collisions of N2, O2, and nitric oxide (NO), the interaction of a triatomic molecule (N2O and NO2) with the fourth atom, and the interaction of a diatomic molecule with a single atom (i.e., the triatomic subsystems). The global ground-state potential energy surface was obtained by fitting the many-body interaction to 54 889 electronic structure data points with a fitting function that is a permutationally invariant polynomial in terms of bond-order functions of the six interatomic distances.

  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. Rate constant and thermochemistry for K + O2 + N2 = KO2 + N2.

    PubMed

    Sorvajärvi, Tapio; Viljanen, Jan; Toivonen, Juha; Marshall, Paul; Glarborg, Peter

    2015-04-01

    The addition reaction of potassium atoms with oxygen has been studied using the collinear photofragmentation and atomic absorption spectroscopy (CPFAAS) method. KCl vapor was photolyzed with 266 nm pulses and the absorbance by K atoms at 766.5 nm was measured at various delay times with a narrow line width diode laser. Experiments were carried out with O2/N2 mixtures at a total pressure of 1 bar, over 748-1323 K. At the lower temperatures single exponential decays of [K] yielded the third-order rate constant for addition, kR1, whereas at higher temperatures equilibration was observed in the form of double exponential decays of [K], which yielded both kR1 and the equilibrium constant for KO2 formation. kR1 can be summarized as 1.07 × 10(-30)(T/1000 K)(-0.733) cm(6) molecule(-2) s(-1). Combination with literature values leads to a recommended kR1 of 5.5 × 10(-26)T(-1.55) exp(-10/T) cm(6) molecule(-2) s(-1) over 250-1320 K, with an error limit of a factor of 1.5. A van't Hoff analysis constrained to fit the computed ΔS298 yields a K-O2 bond dissociation enthalpy of 184.2 ± 4.0 kJ mol(-1) at 298 K and ΔfH298(KO2) = -95.2 ± 4.1 kJ mol(-1). The corresponding D0 is 181.5 ± 4.0 kJ mol(-1). This value compares well with a CCSD(T) extrapolation to the complete basis set limit, with all electrons correlated, of 177.9 kJ mol(-1). PMID:25775408

  5. Biological and physical controls on N2, O2, and CO2 distributions in contrasting Southern Ocean surface waters

    NASA Astrophysics Data System (ADS)

    Tortell, Philippe D.; Bittig, Henry C.; Körtzinger, Arne; Jones, Elizabeth M.; Hoppema, Mario

    2015-07-01

    We present measurements of pCO2, O2 concentration, biological oxygen saturation (ΔO2/Ar), and N2 saturation (ΔN2) in Southern Ocean surface waters during austral summer, 2010-2011. Phytoplankton biomass varied strongly across distinct hydrographic zones, with high chlorophyll a (Chl a) concentrations in regions of frontal mixing and sea ice melt. pCO2 and ΔO2/Ar exhibited large spatial gradients (range 90 to 450 µatm and -10 to 60%, respectively) and covaried strongly with Chl a. However, the ratio of biological O2 accumulation to dissolved inorganic carbon (DIC) drawdown was significantly lower than expected from photosynthetic stoichiometry, reflecting the differential time scales of O2 and CO2 air-sea equilibration. We measured significant oceanic CO2 uptake, with a mean air-sea flux (~ -10 mmol m-2 d-1) that significantly exceeded regional climatological values. N2 was mostly supersaturated in surface waters (mean ΔN2 of +2.5%), while physical processes resulted in both supersaturation and undersaturation of mixed layer O2 (mean ΔO2phys = 2.1%). Box model calculations were able to reproduce much of the spatial variability of ΔN2 and ΔO2phys along the cruise track, demonstrating significant effects of air-sea exchange processes (e.g., atmospheric pressure changes and bubble injection) and mixed layer entrainment on surface gas disequilibria. Net community production (NCP) derived from entrainment-corrected surface ΔO2/Ar data, ranged from ~ -40 to > 300 mmol O2 m-2 d-1 and showed good coherence with independent NCP estimates based on seasonal mixed layer DIC deficits. Elevated NCP was observed in hydrographic frontal zones and stratified regions of sea ice melt, reflecting physical controls on surface water light fields and nutrient availability.

  6. 15N2 Fixation by Bacteria Associated with Maize Roots at a Low Partial O2 Pressure

    PubMed Central

    Alexander, David B.; Zuberer, David A.

    1989-01-01

    Nitrogen fixation by bacteria associated with roots of intact maize plants was measured by exposing the roots to 15N2 at a partial O2 pressure (pO2) of 2 or 10 kPa. The plants were grown in a mixture of Weswood soil and sand and then transferred to plastic cylinders containing an N-free plant nutrient solution. The solution was sparged continuously with a mixture of air and N2 at a pO2 of 2 or 10 kPa. Acetylene reduction was measured after the roots were exposed to the low pO2 overnight. The air-N2 atmosphere in the cylinders was then replaced with an O2-He atmosphere at the same pO2, and the roots were exposed to 20 kPa of 15N2 for 20 to 22 h. Incorporation of 15N into the roots was 200 times greater at 2 kPa of O2 than at 10 kPa of O2. Adding l-malate (1 g of C liter−1) to the nutrient solution increased root-associated nitrogenase activity, producing a strong 15N label which could be traced into the shoots. Fixed 15N was detected in the shoots within 5 days after the plants were returned to unfertilized soil. In a similar experiment with undisturbed plants grown in fritted clay, movement of fixed 15N into the shoots was evident within 4 days after the roots were exposed to 15N2 at 2 kPa of O2. Inoculation with Azospirillum lipoferum yielded no significant differences in shoot dry weight, total nitrogen content, percent nitrogen, or 15N enrichment of plant tissues. Inoculated plants did exhibit greater root dry weight than uninoculated plants, however. PMID:16347968

  7. The Effects of Flame Structure on Extinction of CH4-O2-N2 Diffusion Flames

    NASA Technical Reports Server (NTRS)

    Du, J.; Axelbaum, R. L.; Gokoglu, S. (Technical Monitor)

    1996-01-01

    The effects of flame structure on the extinction limits of CH4-O2-N2 counterflow diffusion flames were investigated experimentally and numerically by varying the stoichiometric mixture fraction Z(sub st), Z(sub st) was varied by varying free-stream concentrations, while the adiabatic flame temperature T(sub ad) was held fixed by maintaining a fixed amount of nitrogen at the flame. Z(sub st) was varied between 0.055 (methane-air flame) and 0.78 (diluted- methane-oxygen flame). The experimental results yielded an extinction strain rate K(sub ext) of 375/s for the methane-air flame, increasing monotonically to 1042/s for the diluted-methane-oxygen flame. Numerical results with a 58-step Cl mechanism yielded 494/s and 1488/s, respectively. The increase in K(sub ext) with Z(sub st) for a fixed T(sub ad) is explained by the shift in the O2 profile toward the region of maximum temperature and the subsequent increase in rates for chain-branching reactions. The flame temperature at extinction reached a minimum at Z(sub st) = 0.65, where it was 200 C lower than that of the methane-air flame. This significant increase in resistance to extinction is seen to correspond to the condition in which the OH and O production zones are centered on the location of maximum temperature.

  8. 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

  9. Towards orbital dating of the EPICA Dome C ice core using δO2/N2

    NASA Astrophysics Data System (ADS)

    Landais, A.; Dreyfus, G.; Capron, E.; Pol, K.; Loutre, M. F.; Raynaud, D.; Lipenkov, V. Y.; Arnaud, L.; Masson-Delmotte, V.; Paillard, D.; Jouzel, J.; Leuenberger, M.

    2012-01-01

    Based on a composite of several measurement series performed on ice samples stored at -25 °C or -50 °C, we present and discuss the first δO2/N2 record of trapped air from the EPICA Dome C (EDC) ice core covering the period between 300 and 800 ka (thousands of years before present). The samples stored at -25 °C show clear gas loss affecting the precision and mean level of the δO2/N2 record. Two different gas loss corrections are proposed to account for this effect, without altering the spectral properties of the original datasets. Although processes at play remain to be fully understood, previous studies have proposed a link between surface insolation, ice grain properties at close-off, and δO2/N2 in air bubbles, from which orbitally tuned chronologies of the Vostok and Dome Fuji ice core records have been derived over the last four climatic cycles. Here, we show that limitations caused by data quality and resolution, data filtering, and uncertainties in the orbital tuning target limit the precision of this tuning method for EDC. Moreover, our extended record includes two periods of low eccentricity. During these intervals (around 400 ka and 750 ka), the matching between δO2/N2 and the different insolation curves is ambiguous because some local insolation maxima cannot be identified in the δO2/N2 record (and vice versa). Recognizing these limitations, we restrict the use of our δO2/N2 record to show that the EDC3 age scale is generally correct within its published uncertainty (6 kyr) over the 300-800 ka period.

  10. Estimates of N2 narcosis and O2 toxicity during submarine escapes from 600 to 1,000 fsw.

    PubMed

    Connor, Christopher W; Ferrigno, Massimo

    2009-01-01

    The U.S. Navy recommends submarine escape for depths down to 600 fsw, with deeper escapes entailing the risks of decompression sickness, nitrogen (N2) narcosis and CNS oxygen (O2) toxicity. However, the escape equipment, including the submarine escape and immersion equipment and the escape trunk, could probably function even at 1,000 fsw. Here we report a theoretical analysis of the risks of both N2 narcosis and CNS O2 toxicity for different escape profiles from 600 to 1,000 fsw. The effect of N2 narcosis, calculated as a function of N2 pressure in the brain using Gas Man software, was expressed as equivalent narcosis depth (END), corresponding to the depth at which the same pressure of N2 would be produced in the brain after five minutes of scuba diving with air. The risk of O2-induced convulsions was estimated using the model developed by Arieli et al. Different dwell times (DTs) at maximal pressure in the escape trunk (from 0 to 60 s) and lungs-to-brain circulation times (10 to 30 s) were included in our analysis. When DT in the escape trunk is very short (e.g., 10 s), the risk of either incapacitating N2 narcosis and/or O2-induced convulsions occurring in the trunk is low, even during escapes from 1,000 fsw.

  11. Conversion of N2O to N? on TiO2 (110)

    SciTech Connect

    Henderson, Michael A.; Szanyi, Janos; Peden, Charles HF.

    2003-10-15

    In this study we examine the interaction of TiO2 with TiO2 (110) in an effort to better understand the conversion of NOx species to N2 over TiO2-based catalysts. The TiO2 (110) surface was used as a model system because this material is commonly used as a support and because oxygen vacancies on this surface are perhaps the best available models for the role of electronic defects in catalysis. Annealing TiO2 (110) in vacuum at high temperature (above 800 K) generates oxygen vacancy sites that are associated with reduced surface cations (Ti3?sites) and that are easily quantified using temperature programmed desorption (TPD) of water. Using TPD, x-ray photoelectron spectroscopy (XPS) and electron energy loss spectroscopy (EELS), we found that the majority of N2O molecules adsorbed at 90 K on TiO2 (110) are weakly held, and desorb from the surface at 130 K. However, a small fraction of the N2O molecules exposed to TiO2 (110) at 90 K decompose to N2 via one of two channels, both of which a re vacancy-mediated. One channel occurs at 90 K, and results in N2 ejection from the surface and vacancy oxidation. We propose that this channel involves N2O molecules bound at vacancies with the O-end of the molecule. The second channel results from an adsorbed state of N2O that decomposes at 170 K to liberate N2 in the gas phase and deposit oxygen adatoms at non-defect Ti4? sites. The presence of these O adatoms is clearly evident in subsequent water TPD measurements. We propose that this channel involves N2O molecules that are bound at vacancies with the N-end of the molecule, which permits the O-end of the molecule to interact with an adjacent Ti4? site. The partitioning between these two channels is roughly 1:1 for adsorption at 90 K, but neither is observed to occur for moderate N2O exposures at temperatures above 200 K. EELS data indicate that vacancies readily transfer charge to N2O at 90 K, and this charge transfer facilitates N2O decomposition. Based on this result, it

  12. Dielectric breakdown properties of N2-O2 mixtures by considering electron detachments from negative ions

    NASA Astrophysics Data System (ADS)

    Zhao, Hu; Lin, Hui

    2016-07-01

    The paper analyzes the dielectric breakdown properties of N2-O2 mixtures at different O2 concentrations and gas pressures, taking into account electron detachments from negative ions. The reduced effective ionization coefficients α(eff)/N in N2-O2 mixtures at different O2 concentrations and gas pressures were calculated and analyzed, by considering electron detachments. The critical reduced electric fields (E/N)cr and the critical electron temperature Tb were then determined. The result indicates a clear enhancement of α(eff)/N by collisional detachments, which causes a reduction in the (E/N)cr. In addition, a synergistic effect in the N2-O2 mixture was also observed in both (E/N)cr and Tb. The value of Tb was decreased by the increase of pd product, however, Tb tended to be constant at relatively high pd products.

  13. On the long-term stability of reference gases for atmospheric O2/N2 and CO2 measurements

    NASA Astrophysics Data System (ADS)

    Keeling, Ralph F.; Manning, Andrew C.; Paplawsky, William J.; Cox, Adam C.

    2007-02-01

    Measurements of changes in the atmospheric O2/N2 ratio have typically relied on compressed air derived from high-pressure tanks as the reference material against which atmospheric changes are assessed. The validity of this procedure is examined here in the context of the history of 18 O2/N2 reference tanks compared over a 12-yr time-frame. By considering differences in tank sizes, material types, and by performing additional tests, the long-term stability of the delivered gas is evaluated with respect to surface reactions, leakage, regulator effects, and thermal diffusion and gravimetric fractionation. Results are also reported for the stability of CO2 in these tanks. The results emphasize the importance of orienting tanks horizontally within a thermally insulated enclosure to reduce thermal and gravimetric fractionation of both O2/N2 and CO2 concentrations, and they emphasize the importance of avoiding elastomeric O-rings at the head-valve base. With the procedures documented here, the long-term drift in O2/N2 appears to be zero to within approximately +/-0.4 per meg yr-1, which projects to an uncertainty of +/-0.16 Pg C yr-1 (1σ) in O2-based global carbon budgets.

  14. Electron transport coefficients in the mixtures of H2O with N2, O2, CO2 and dry air for the optimization of non-thermal atmospheric pressure plasmas

    NASA Astrophysics Data System (ADS)

    Ruíz-Vargas, G.; Yousfi, M.; de Urquijo, J.

    2010-11-01

    This paper presents the simultaneous measurement and calculation of the electron drift velocity in binary and ternary mixtures of N2, O2, CO2 with H2O. The main aim of this study has been the generation of a self-consistent set of validated collision cross sections that explain thoroughly the dependence of the electron drift velocity in the above pure gases and their mixtures. In doing this, changes to the collision cross section set for H2O had to be made, while all other cross section sets remained unchanged. It is worth mentioning that only a few experiments had been performed before dealing with water mixtures. The electron drift velocities in the binary and ternary mixtures under study show the effects of negative differential conductivity, and this has been explained thoroughly in terms of the collision cross sections and electron distribution functions through a multi-term Boltzmann code. It is important to note that two-term codes fail to predict the dependence of the drift velocity at low water concentrations and low E/N values. Calculated values of longitudinal and transverse diffusion coefficients, mean energies and distribution functions are also given over the E/N range 0.1 Td-2 kTd (1 Td = 10-17 V cm2).

  15. 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

  16. Laboratory measurements of the O+/2D/ + N2 and O+/2D/ + O2 reaction rate coefficients and their ionospheric implications

    NASA Technical Reports Server (NTRS)

    Johnsen, R.; Biondi, M. A.

    1980-01-01

    Rate coefficients which have been measured at thermal energies for the charge transfer reactions of metastable O+/2D/ ions with N2 and O2 are reported. It is found that at an effective temperature of about 550 K, k(n2) = (8 + or - 2) x 10 to the -10 cu cm/sec and k(O2) = (7 + or - 2) x 10 to the -10 cu cm/sec. Drift tube-mass spectrometer measurements employ the reaction He(+) + O2 as the source of metastable O+ ions, showing that the ions produced in this manner are in the 2D state rather than the 2P state, a possible alternative identification. Finally, consideration is given to the ionospheric implications of the laboratory measurements.

  17. Fiber-Optic Determination of N2, O2, and Fuel Vapor in the Ullage of Liquid-Fuel Tanks

    NASA Technical Reports Server (NTRS)

    Nguyen, Quang-Viet

    2008-01-01

    A fiber-optic sensor system has been developed that can remotely measure the concentration of molecular oxygen (O2), nitrogen (N2), hydrocarbon vapor, and other gases (CO2, CO, H2O, chlorofluorocarbons, etc.) in the ullage of a liquid-fuel tank. The system provides an accurate and quantitative identification of the above gases with an accuracy of better than 1 percent by volume (for O2 or N2) in real-time (5 seconds). In an effort to prevent aircraft fuel tank fires or explosions similar to the tragic TWA Flight 800 explosion in 1996, OBIGGS are currently being developed for large commercial aircraft to prevent dangerous conditions from forming inside fuel tanks by providing an inerting gas blanket that is low in oxygen, thus preventing the ignition of the fuel/air mixture in the ullage. OBIGGS have been used in military aircraft for many years and are now standard equipment on some newer large commercial aircraft (such as the Boeing 787). Currently, OBIGGS are being developed for retrofitting to existing commercial aircraft fleets in response to pending mandates from the FAA. Most OBIGGS use an air separation module (ASM) that separates O2 from N2 to make nitrogen-enriched air from compressed air flow diverted from the engine (bleed air). Current OBIGGS systems do not have a closed-loop feedback control, in part, due to the lack of suitable process sensors that can reliably measure N2 or O2 and at the same time, do not constitute an inherent source of ignition. Thus, current OBIGGS operate with a high factor-of-safety dictated by process protocol to ensure adequate fuel-tank inerting. This approach is inherently inefficient as it consumes more engine bleed air than is necessary compared to a closed-loop controlled approach. The reduction of bleed air usage is important as it reduces fuel consumption, which translates to both increased flight range and lower operational costs. Numerous approaches to developing OBIGGS feedback-control sensors have been under

  18. Numerical simulations of turbulent premixed H2/O2/N2 flames with complex chemistry

    NASA Technical Reports Server (NTRS)

    Baum, M.; Poinsot, T. J.; Haworth, D. C.

    1992-01-01

    Premixed stoichiometric H2/O2/N2 flames propagating in two-dimensional turbulence were studied using direct numerical simulation (simulations in which all fluid and thermochemical scales are fully resolved) including realistic chemical kinetics and molecular transport. Results are compared with earlier zero-chemistry (flame sheet) and one-step chemistry simulations. Consistent with the simpler models, the turbulent flame with realistic chemistry aligns preferentially with extensive strain rates in the tangent plane and flame curvature probability density functions are close to symmetric with near-zero means. By contrast to simple-chemistry results with non-unity Lewis numbers (ratio of thermal to species diffusivity), local flame structure does not correlate with curvature but rather with tangential strain rate. Turbulent straining results in substantial thinning of the flame relative to the steady unstrained laminar case. Heat release and H2O2 contours remain thin and connected ('flamelet-like') while species including H-atom and OH are more diffuse. Peak OH concentration occurs well behind the peak heat-release zone. The feasibility of incorporating realistic chemistry into full turbulence simulations to address issues such as pollutant formation in hydrocarbon-air flames is suggested.

  19. Towards orbital dating of the EPICA Dome C ice core using δO2/N2

    NASA Astrophysics Data System (ADS)

    Landais, A.; Dreyfus, G.; Capron, E.; Pol, K.; Loutre, M. F.; Raynaud, D.; Lipenkov, V. Y.; Arnaud, L.; Masson-Delmotte, V.; Paillard, D.; Jouzel, J.; Leuenberger, M.

    2011-06-01

    Based on a composite of several measurement series performed on ice samples stored at -25 °C or -50 °C, we present and discuss the first δO2/N2 record of trapped air from the EPICA Dome C (EDC) ice core covering the period between 300 and 800 ka (thousands of years before present). The samples stored at -25 °C show clear gas loss affecting the precision and mean level of the δO2/N2 record. Two different gas loss corrections are proposed to account for this effect, without altering the spectral properties of the original datasets. Although processes at play remain to be fully understood, previous studies have proposed a link between surface insolation, ice grain properties at close-off and δO2/N2 in air bubbles, from which an orbitally tuned chronologies of the Vostok and Dome Fuji ice core records have been derived over the last four climatic cycles. Here, we show that limitations caused by data quality and resolution, data filtering and uncertainties in the orbital tuning target limit the precision of this tuning method for EDC to at least 2.5 kyrs (thousands of years). Moreover, our extended record includes two periods of low eccentricity. During these intervals (around 400 ka and 750 ka), the matching between δO2/N2 and the different insolation curves is ambiguous because some local insolation maxima cannot be identified in the δO2/N2 record (and vice versa). Recognizing these limitations, we restrict the use of our δO2/N2 record to show that the EDC3 age scale is generally correct within its published uncertainty (6 kyrs) over the 300-800 ka period. We illustrate the uncertainties associated with data quality, filtering and tuning target for periods of low eccentricity by highlighting the difficulty to constrain the duration of Marine Isotopic Stage 11 based on the EDC δO2/N2 information.

  20. Regional differences in the δO2/N2 records from East Antarctica over the last interglacial

    NASA Astrophysics Data System (ADS)

    Bazin, L.; Landais, A.; Masson-Delmotte, V.; Kageyama, M.; Paillard, D.; Bopp, L.; Ritz, C.; Leuenberger, M.

    2013-12-01

    Ice cores are the only climate archives offering samples of past atmosphere. The air is trapped at around 100 m under the surface, where the snow is compacted into ice. During this process, multiple influences may modify the air composition as the quantity of insolation received at the surface impacts snow metamorphism and hence air trapping conditions at the basis of the firn (top ~100m of the ice sheet). Analyses of trapped air in ice cores thus give us information on both local and global scales. In this study, we focus on temporal variations of elemental and isotopic composition of oxygen from East Antarctic ice cores. On the one hand, the δ18Oatm, uniformly distributed in the atmosphere, is known to be related to the hydrological cycle and the vegetation cover (Landais et al., 2010), and can be linked to the precession variations. The δO2/N2, on the other hand, appears to be influenced by the local insolation, probably because of modification of the snow structure affecting pore close-off. These two quantities have largely been used as orbital tuning tools for dating purposes in several ice cores from Antarctica (Bender 2002, Suwa et Bender 2008, Kawamura et al., 2007, Dreyfus et al., 2007,Landais et al., 2012, Bazin et al., 2013). Still, gaps in our understanding of the exact mechanisms explaining the δ18Oatm and δO2/N2 variations lead to quite large uncertainties when using these proxies as tie-points for dating purposes. In this study, we use several ice core records in low accumulation rate sites of East Antarctica to decipher global and local effects on the δO2/N2 records. First, we present a compilation of δO2/N2 measurements of the Dome F, Vostok and Dome C ice cores over the last interglacial period. While Dome F and Vostok data were corrected for gas loss during several years of storage at -25°C, new measurements of the air isotopic composition on the Dome C ice core were performed on well-conserved ice (-50°C). Different δO2/N2 mean levels

  1. Investigation of charge loss characteristics of HfO2 annealed in N2 or O2 ambient

    NASA Astrophysics Data System (ADS)

    Yuqiong, Chu; Zongliang, Huo; Yulong, Han; Guoxing, Chen; Dong, Zhang; Xinkai, Li; Ming, Liu

    2014-08-01

    The retention characteristics of electrons and holes in hafnium oxide with post-deposition annealing in a N2 or O2 ambient were investigated by Kelvin probe force microscopy. The KFM results show that compared with the N2 PDA process, the O2 PDA process can lead to a significant retention improvement. Vertical charge leakage and lateral charge spreading both played an important role in the charge loss mechanisms. The retention improvement is attributed to the deeper trap energy. For electrons, the trap energy of the HOS structure annealed in a N2 or O2 ambient were determined to be about 0.44 and 0.49 eV, respectively. For holes, these are about 0.34 and 0.36 eV, respectively. Finally, the electrical characteristics of the memory devices are demonstrated from the experiment, which agreed with our characterization results. The qualitative and quantitative determination of the charge retention properties, the possible charge decay mechanism and trap energy reported in this work can be very useful for the characterization of hafnium charge storage devices.

  2. 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.

  3. Ozone production and losses in N2/O2 mixtures in an ozone generator

    NASA Astrophysics Data System (ADS)

    Mankelevich, Yu. A.; Poroykov, A. Yu.; Rakhimova, T. V.; Voloshin, D. G.; Chukalovskii, A. A.; Zosimov, A. V.; Lunin, V. V.; Samoilovich, V. G.

    2016-09-01

    Nonunique ozone concentrations at the output of an ozone generator under identical external conditions of barrier discharge activation of N2/O2 mixtures but with different prehistories of operating practice and employed gas mixtures are investigated theoretically. An analytical approach is developed to determine the ozone yield with regard for its heterogeneous loss. Plasma-chemical and electron kinetics in the N2/O2-mixtures are calculated numerically. The results of numerical calculations are compared to experimental data obtained by the authors. It is noted that the heterogeneous loss of ozone is the probable reason for the observed variety of behavior of O3 concentrations, depending on prehistory of ozone generator operation, along with the N2 and O2 gas flow rates and the specific active power.

  4. 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.

  5. 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

  6. Nanosecond repetitively pulsed discharges in N2-O2 mixtures: inception cloud and streamer emergence

    NASA Astrophysics Data System (ADS)

    Chen, She; Heijmans, L. C. J.; Zeng, Rong; Nijdam, S.; Ebert, U.

    2015-05-01

    We evaluate the nanosecond temporal evolution of tens of thousands of positive discharges in a 16 cm point-plane gap in high purity nitrogen 6.0 and in N2-O2 gas mixtures with oxygen contents of 100 ppm, 0.2%, 2% and 20%, for pressures between 66.7 and 200 mbar. The voltage pulses have amplitudes of 20 to 40 kV with rise times of 20 or 60 ns and repetition frequencies of 0.1 to 10 Hz. The discharges first rapidly form a growing cloud around the tip, then they expand much more slowly like a shell and finally after a stagnation stage they can break up into rapid streamers. The radius of cloud and shell in artificial air is about 10% below the theoretically predicted value and scales with pressure p as theoretically expected, while the observed scaling of time scales with p raises questions. We find characteristic dependences on the oxygen content. No cloud and shell stage can be seen in nitrogen 6.0, and streamers emerge immediately. The radius of cloud and shell increases with oxygen concentration. On the other hand, the stagnation time after the shell phase is maximal for the intermediate oxygen concentration of 0.1% and the number of streamers formed is minimal; here the cloud and shell phase seem to be particularly stable against destabilization into streamers.

  7. Absolute intensity and polarization of rotational Raman scattering from N2, O2, and CO2

    NASA Technical Reports Server (NTRS)

    Penney, C. M.; St.peters, R. L.; Lapp, M.

    1973-01-01

    An experimental examination of the absolute intensity, polarization, and relative line intensities of rotational Raman scattering (RRS) from N2, O2, and CO2 is reported. The absolute scattering intensity for N2 is characterized by its differential cross section for backscattering of incident light at 647.1 nm, which is calculated from basic measured values. The ratio of the corresponding cross section for O2 to that for N2 is 2.50 plus or minus 5 percent. The intensity recent for N2, O2, and CO2 are shown to compare favorably to values calculated from recent measurements of the depolarization of Rayleigh scattering plus RRS. Measured depolarizations of various RRS lines agree to within a few percent with the theoretical value of 3/4. Detailed error analyses are presented for intensity and depolarization measurements. Finally, extensive RRS spectra at nominal gas temperatures of 23 C, 75 C, and 125 C are presented and shown to compare favorably to theoretical predictions.

  8. Fast gas heating in N2/O2 mixtures under nanosecond surface dielectric barrier discharge: the effects of gas pressure and composition.

    PubMed

    Nudnova, M M; Kindysheva, S V; Aleksandrov, N L; Starikovskii, A Yu

    2015-08-13

    The fractional electron power quickly transferred to heat in non-equilibrium plasmas was studied experimentally and theoretically in N(2)/O(2) mixtures subjected to high electric fields. Measurements were performed in and after a nanosecond surface dielectric barrier discharge at various (300-750 Torr) gas pressures and (50-100%) N(2) percentages. Observations showed that the efficiency of fast gas heating is almost independent of pressure and becomes more profound when the fraction of O(2) in N(2)/O(2) mixtures increases. The processes that contribute towards the fast transfer of electron energy to thermal energy were numerically simulated under the conditions considered. Calculations were compared with measurements and the main channels of fast gas heating were analysed at the gas pressures, compositions and electric fields under study. It was shown that efficient fast gas heating in the mixtures with high fraction of O(2) is due to a notable contribution of heat release during quenching of electronically excited N(2) states in collisions with O(2) molecules and to ion-ion recombination. The effect of hydrocarbon addition to air on fast gas heating was numerically estimated. It was concluded that the fractional electron power transferred to heat in air, as a first approximation, could be used to estimate this effect in lean and stoichiometric hydrocarbon-air mixtures.

  9. Fast gas heating in N2/O2 mixtures under nanosecond surface dielectric barrier discharge: the effects of gas pressure and composition

    PubMed Central

    Nudnova, M. M; Kindysheva, S. V; Aleksandrov, N. L; Starikovskii, A. Yu

    2015-01-01

    The fractional electron power quickly transferred to heat in non-equilibrium plasmas was studied experimentally and theoretically in N2/O2 mixtures subjected to high electric fields. Measurements were performed in and after a nanosecond surface dielectric barrier discharge at various (300–750 Torr) gas pressures and (50–100%) N2 percentages. Observations showed that the efficiency of fast gas heating is almost independent of pressure and becomes more profound when the fraction of O2 in N2/O2 mixtures increases. The processes that contribute towards the fast transfer of electron energy to thermal energy were numerically simulated under the conditions considered. Calculations were compared with measurements and the main channels of fast gas heating were analysed at the gas pressures, compositions and electric fields under study. It was shown that efficient fast gas heating in the mixtures with high fraction of O2 is due to a notable contribution of heat release during quenching of electronically excited N2 states in collisions with O2 molecules and to ion–ion recombination. The effect of hydrocarbon addition to air on fast gas heating was numerically estimated. It was concluded that the fractional electron power transferred to heat in air, as a first approximation, could be used to estimate this effect in lean and stoichiometric hydrocarbon–air mixtures. PMID:26170431

  10. Enhanced O2 selectivity versus N2 by partial metal substitution in Cu-BTC

    DOE PAGES

    Sava Gallis, Dorina F.; Parkes, Marie V.; Greathouse, Jeffery A.; Zhang, Xiaoyi; Nenoff, Tina M.

    2015-03-05

    Here we describe the homogeneous substitution of Mn, Fe and Co at various levels into a prototypical metal-organic framework (MOF), namely Cu-BTC (HKUST-1), and the effect of that substitution on preferential gas sorption. Using a combination of density functional theory (DFT) calculations, postsynthetic metal substitutions, materials characterization, and gas sorption testing, we demonstrate that the identity of the metal ion has a quantifiable effect on their oxygen and nitrogen sorption properties at cryogenic temperatures. An excellent correlation is found between O2/N2 selectivities determined experimentally at 77 K and the difference in O2 and N2 binding energies calculated from DFT modelingmore » data: Mn > Fe > Co > Cu. Room temperature gas sorption studies were also performed and correlated with metal substitution. The Fe-exchanged sample shows a significantly higher nitrogen isosteric heat of adsorption at temperatures close to ambient conditions (273 K - 298 K) as compared to all other metals studied, indicative of favorable interactions between N2 and coordinatively unsaturated Fe metal centers. Furthermore, differences in gas adsorption results at cryogenic and room temperatures are evident; they are explained by comparing experimental results with DFT binding energies (0 K) and room temperature Grand Canonical Monte Carlo simulations.« less

  11. Enhanced O-2 Selectivity versus N-2 by Partial Metal Substitution in Cu-BTC

    SciTech Connect

    Sava Gallis, Dorina F.; Parkes, Marie V.; Greathouse, Jeffery A.; Zhang, Xiaoyi; Nenoff, Tina M.

    2015-03-24

    Here, we describe the homogeneous substitution of Mn, Fe, and Co at various levels into a prototypical metal organic framework (MOP), namely Cu-BTC (HKUST-1), and the effect of that substitution on preferential gas sorption. Using a combination of density functional theory (DFT) calculations, postsynthetic metal substitutions, materials characterization, and gas sorption testing, we demonstrate that the identity of the metal ion has a quantifiable effect on their oxygen and nitrogen sorption properties at cryogenic temperatures. An excellent correlation is found between O-2/N-2 selectivities determined experimentally at 77 K and the difference in O-2 and N-2 binding energies calculated from DFT modeling data: Mn > Fe Co >> Cu. Room temperature gas sorption studies were also performed and correlated with metal substitution. The Fe-exchanged sample shows a significantly higher nitrogen isosteric heat of adsorption at temperatures close to ambient conditions (273-298 K) as compared to all other metals studied, indicative of favorable interactions between N-2 and coordinatively unsaturated Fe metal centers. Interestingly, differences in gas adsorption results at cryogenic and room temperatures are evident; they are explained by comparing experimental results with DFT binding energies (0 K) and room temperature Grand Canonical Monte Carlo simulations.

  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

    2015-07-01

    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. 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

    2015-07-01

    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. PMID:26090963

  14. Polarizability-based equation of state: Application to CO, N 2 and O 2

    NASA Astrophysics Data System (ADS)

    de Visser, Sam P.

    2011-10-01

    The description of dense gases and liquids still remains a challenge in thermodynamics. Recently, our group developed a new equation of state that is described by an attractive exponential contribution and a repulsive component that both are a function of polarizability volume and macroscopic volume. In this Letter, we apply this equation of state to moderately dense gases of CO, N 2 and O 2 over a broad temperature range. Literature data is excellently reproduced with the new equation of state and in comparison to the Ideal Gas Law or the original van der Waals equation of state gives substantial improvement.

  15. N2-, O2- and He-collision-induced broadening of sulfur dioxide ro-vibrational lines in the 9.2 μm atmospheric window.

    PubMed

    Tasinato, Nicola; Pietropolli Charmet, Andrea; Stoppa, Paolo; Giorgianni, Santi; Buffa, Giovanni

    2014-01-24

    Sulfur dioxide (SO2) is a molecule of considerable interest for both atmospheric chemistry and astrophysics. In the Earth's atmosphere, it enters in the sulfur cycle and it is ubiquitous present in polluted atmospheres, where it is responsible for acid rains. It is also of astrophysical and planetological importance, being present on Venus and in interstellar clouds. In this work the collisional broadening of a number of ν1 ro-vibrational lines of SO2 perturbed by N2, O2 and He are investigated at room temperature in the 9 μm atmospheric region by means of high resolution tunable diode laser (TDL) infrared spectroscopy. From N2- and O2-broadening coefficients, the broadening parameters of sulfur dioxide in air, useful for atmospheric applications, are derived as well. From the present measurements some conclusions on the quantum number dependence of the N2-, O2- and He-broadening coefficients are drawn. While the J dependence is weak for all the perturbers investigated, different trends with Ka are reported. N2-broadening coefficients show a slight decrease with increasing values of Ka, whereas O2 and He broadening cross sections first increase up to Ka(″)≈6 and then they keep a nearly constant value. A comparison and a brief discussion on the efficiency of self-, N2-, O2- and He-collisional dynamics are given. The data obtained represent a significant analysis on foreign broadening of SO2 useful for atmospheric remote sensing and astrophysical applications.

  16. N2-, O2- and He-collision-induced broadening of sulfur dioxide ro-vibrational lines in the 9.2 μm atmospheric window

    NASA Astrophysics Data System (ADS)

    Tasinato, Nicola; Pietropolli Charmet, Andrea; Stoppa, Paolo; Giorgianni, Santi; Buffa, Giovanni

    2014-01-01

    Sulfur dioxide (SO2) is a molecule of considerable interest for both atmospheric chemistry and astrophysics. In the Earth's atmosphere, it enters in the sulfur cycle and it is ubiquitous present in polluted atmospheres, where it is responsible for acid rains. It is also of astrophysical and planetological importance, being present on Venus and in interstellar clouds. In this work the collisional broadening of a number of ν1 ro-vibrational lines of SO2 perturbed by N2, O2 and He are investigated at room temperature in the 9 μm atmospheric region by means of high resolution tunable diode laser (TDL) infrared spectroscopy. From N2- and O2-broadening coefficients, the broadening parameters of sulfur dioxide in air, useful for atmospheric applications, are derived as well. From the present measurements some conclusions on the quantum number dependence of the N2-, O2- and He-broadening coefficients are drawn. While the J dependence is weak for all the perturbers investigated, different trends with Ka are reported. N2-broadening coefficients show a slight decrease with increasing values of Ka, whereas O2 and He broadening cross sections first increase up to Ka″≈6 and then they keep a nearly constant value. A comparison and a brief discussion on the efficiency of self-, N2-, O2- and He-collisional dynamics are given. The data obtained represent a significant analysis on foreign broadening of SO2 useful for atmospheric remote sensing and astrophysical applications.

  17. Modeling and basic data for streamer dynamics in N2 and O2 discharges

    NASA Astrophysics Data System (ADS)

    Kanzari, Z.; Yousfi, M.; Hamani, A.

    1998-10-01

    A second order hydrodynamics model of streamer dynamics is developed without using the classical restrictive approximations concerning the source term of the conservation equation of electron energy. The first three moments of the Boltzmann equation coupled to the Poisson equation for the space charge electric field are closed using the local energy approximation. The basic data needed for the present second order model for electrons and the first order model for ions are obtained from the solution of the steady state Boltzmann equation and the Monte Carlo simulation, respectively. The electron data associated with the source term of the electron energy conservation equation and which correspond to the different electron-molecule processes considered in our N2 and O2 discharges (ionization, attachment, excitation, elastic, and superelastic collisions) are explicitly given. Then, we give the results obtained with the present second order hydrodynamics model and concerning N2 and O2 gases at atmospheric pressure between parallel plate electrodes under overvoltage conditions. Comparisons are also performed with the results obtained from the classical first order model generally used in the literature.

  18. Destruction of N/2D/ by O2 - A major source of 6300 A dayglow emission

    NASA Technical Reports Server (NTRS)

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

    1980-01-01

    The paper discusses the N(2D) + O2 yields NO + O(1D), for k1 reaction, and examines under different geophysical conditions, the effect of this source of 6300 A surface brightness on the dayglow redline. In calculating the 6300 A volume emission rate, a computer code is used which provides the thermal electron density, photoelectron flux, ion concentrations, electron and ion temperatures and odd nitrogen densities required to evaluate the O(1D) sources and sinks. It is found that under most conditions this source is the dominant mechanism responsible for the production of the 6300 A dayglow above 150 km. The volume emission rate of this source in summer is 2.5 times larger than the sum of all other sources at 180 km, and 1.5 times as large in winter. In addition, when the N(2D) source of O(1D) is taken into account, the rate coefficient for quenching of O(1D) by N2 is estimated to be 4 plus or minus 1 x 10 to the -11th cu cm per sec.

  19. CO oxidation at nickel centres by N2O or O2 to yield a novel hexanuclear carbonate.

    PubMed

    Horn, Bettina; Limberg, Christian; Herwig, Christian; Feist, Michael; Mebs, Stefan

    2012-08-25

    Reaction of a nickel(0) carbonyl complex, K(2)[L(tBu)NiCO](2), with N(2)O generates a cyclic carbonate compound composed of six [Ni(II)(CO(3))K](+) units. The same product can also be obtained using O(2) as the oxidant in a solid-state/gas reaction. These conversions represent unique examples of a nickel-bound CO oxidation by N(2)O and O(2), respectively. PMID:22785444

  20. Etch Properties of Amorphous Carbon Material Using RF Pulsing in the O2/N2/CHF3 Plasma.

    PubMed

    Jeon, Min Hwan; Park, Jin Woo; Yun, Deok Hyun; Kim, Kyong Nam; Yeom, Geun Young

    2015-11-01

    The amorphous carbon layer (ACL), used as the hardmask for the etching of nanoscale semi-conductor materials, was etched using O2/CHF3 in addition to O2/N2 using pulsed dual-frequency capacitively coupled plasmas, and the effects of source power pulsing for different gas combinations on the characteristics of the plasmas and ACL etching were investigated. As the etch mask for ACL, a patterned SiON layer was used. The etch rates of ACL were decreased with the decrease of pulse duty percentage for both O2/N2 and O2/CHF3 due to decrease of the reactive radicals, such as F and O, with decreasing pulse duty percentage. In addition, at the same pulse duty percentage, the etch selectivity of ACL/SiON with O2/CHF3 was also significantly lower than that with O2/N2. However, the etch profiles of ACL with O2/CHF3 was more anisotropic and the etch profiles were further improved with decreasing the pulse duty percentage than those of ACL with O2/N2. The improved anisotropic etch profiles of ACL with decreasing pulse duty percentage for O2/CHF3 were believed to be related to the formation of a more effective passivation layer, such as a thick fluorocarbon layer, on the sidewall of the ACL during the etching with O2/CHF3, compared to the weak C-N passivation layer formed on the sidewall of ACL when using O2/N2. PMID:26726555

  1. Positive DC Corona Discharge in N2-NO-CO2-O2 Mixtures

    NASA Astrophysics Data System (ADS)

    Hensel, Karol; Hayashi, Nobuya; Yamabe, Chobei; Morvová, Marcela

    2002-01-01

    Positive DC corona discharge in a hemicylindrical discharge reactor was applied to mixtures containing N2, NO, O2, CO2 and H2O, while an NOx chemiluminescence analyzer and an IR spectrometer were used to evaluate the concentration changes and analyze the products of the process in the discharge chamber. The removal efficiency of 89% for NO and the energy cost of 350 eV/molecule were achieved. Special attention was paid to the influence of CO2 on discharge, its character, performance and products of the process. In addition to the main components of the gas mixture (NO, NO2, CO2, CO etc.), other compounds and functional groups (e.g., amides I-III, imides, NCO) have been identified among the products of the process.

  2. Electron ionization dynamics of N2 and O2 molecules: Velocity-map imaging

    NASA Astrophysics Data System (ADS)

    Bull, James N.; Lee, Jason W. L.; Vallance, Claire

    2015-02-01

    This paper reports a crossed-beam velocity-map imaging study into the electron ionization dynamics of jet-cooled N2 and O2 molecules at electron collision energies from 35 to 100 eV. The use of velocity-map imaging detection provides insight into the detailed ionization dynamics through the dimension of the product ion kinetic energy associated with impulsive dissociation. In particular, "mesoscopic" cross sections corresponding to ionization from manifolds of energetically close states converging to the same dissociation asymptote are reported for a number of single-ionization channels. In addition, a range of double-ionization cross sections have been characterized, including those yielding X2 2 + dications. These are found to be in excellent agreement with other cross sections determined in coincidence measurements. This agreement supports a meaningful and accurate determination of the single-ionization channels.

  3. Direct N2H4/H2O2 Fuel Cells Powered by Nanoporous Gold Leaves

    PubMed Central

    Yan, Xiuling; Meng, Fanhui; Xie, Yun; Liu, Jianguo; Ding, Yi

    2012-01-01

    Dealloyed nanoporous gold leaves (NPGLs) are found to exhibit high electrocatalytic properties toward both hydrazine (N2H4) oxidation and hydrogen peroxide (H2O2) reduction. This observation allows the implementation of a direct hydrazine-hydrogen peroxide fuel cell (DHHPFC) based on these novel porous membrane catalysts. The effects of fuel and oxidizer flow rate, concentration and cell temperature on the performance of DHHPFC are systematically investigated. With a loading of ~0.1 mg cm−2 Au on each side, an open circuit voltage (OCV) of 1.2 V is obtained at 80°C with a maximum power density 195 mW cm−2, which is 22 times higher than that of commercial Pt/C electrocatalyst at the same noble metal loading. NPGLs thus hold great potential as effective and stable electrocatalysts for DHHPFCs. PMID:23230507

  4. Nonstationary effects in ozone generation by barrier discharges in N2/O2 mixtures

    NASA Astrophysics Data System (ADS)

    Zosimov, A. V.; Lunin, V. V.; Samoilovich, V. G.; Abramovskaya, E. A.; Mankelevich, Yu. A.; Poroykov, A. Yu.; Rakhimova, T. V.; Voloshin, D. G.

    2016-08-01

    The yield of ozone in barrier discharges in oxygen-nitrogen mixtures containing 0.001 to 40% of nitrogen is investigated experimentally. Phenomena of the nonstationarity of processes of ozone generation that differ from the known ozone-zero phenomenon (OZP) apparent in the reduced efficiency of ozone generation in very high purity oxygen at long periods (from hours to tens of hours) of ozonator operation are found. It is established that the characteristic times (from minutes to tens of minutes) of ozone attaining stationary values after changes in the discharge parameters indicate slow adjustment of the surface condition of insulators and thus the heterogeneous decay of ozone to more rapidly changing flows of neutral and charged particles from gas discharge plasma on the surfaces of dielectrics. The possibility of such a scenario is confirmed using a new analytical approach and numerical calculations of the plasma-chemical kinetics of N2/O2 mixtures presented in the accompanying theoretical study.

  5. The calculation of high-temperature equilibrium and nonequilibrium specific heat data for N2, O2 and NO

    NASA Technical Reports Server (NTRS)

    Jaffe, Richard L.

    1987-01-01

    Specific heat data for high-temperature air species are needed to compute the temperature and enthalpy of gas mixtures in aerothermodynamics flowfield calculations. Accurate data are known only for temperatures under 6000 K, but are required for temperatures exceeding 25,000 K. In the present study, CP data are computed for N2, O2 and NO. The calculations are based on summations over all the vibration-rotation energy levels for all known bound electronic states. Estimates are made for the error introduced by the neglect of possible additional high-lying electronic states. In addition, a scheme for the partitioning of the internal energy into vibrational, rotational and electronic contributions is presented which consistently accounts for the nonseparable nature of the various energy modes. The multitemperature specific heat data are recommended for use in nonequilibrium flowfield models.

  6. Optical and electrical analyses of DC positive corona discharge in N2/O2/CO2 gas mixtures

    NASA Astrophysics Data System (ADS)

    Merbahi, N.; Abahazem, A.; Dubois, D.; Eichwald, O.; Yousfi, M.

    2008-04-01

    This paper presents an experimental analysis of the electrical and optical behaviour of positive point-plane corona discharges. The measurements of the instantaneous corona current and the current-voltage characteristics are used with the imagery analyses (CCD and streak camera) to determine the streamer properties such as the streamer morphology and velocity with the primary and secondary streamer developments. These analyses are performed first in synthetic air as a function of operating parameters such the applied voltage. Then the effect of gas mixtures (several proportions of N{2}, O{2} with or without CO{2}) is analysed. When the gas concentration is varied the discharge morphology, the shape and amplitude of the corona current are significantly affected due to the variation of the gas electronegativity following its composition and concentration.

  7. Suppressed N2O formation during NH3 selective catalytic reduction using vanadium on zeolitic microporous TiO2

    PubMed Central

    Lee, Seung Gwan; Lee, Hyun Jeong; Song, Inhak; Youn, Seunghee; Kim, Do Heui; Cho, Sung June

    2015-01-01

    Emission of N2O from mobile and off-road engine is now being currently regulated because of its high impact compared to that of CO2, thereby implying that N2O formation from the exhaust gas after-treatment system should be suppressed. Selective catalytic reduction using vanadium supported TiO2 catalyst in mobile and off-road engine has been considered to be major source for N2O emission in the system. Here we have demonstrated that vanadium catalyst supported on zeolitic microporous TiO2 obtained from the hydrothermal reaction of bulk TiO2 at 400 K in the presence of LiOH suppresses significantly the N2O emission compared to conventional VOx/TiO2 catalyst, while maintaining the excellent NOx reduction, which was ascribed to the location of VOx domain in the micropore of TiO2, resulting in the strong metal support interaction. The use of zeolitic microporous TiO2 provides a new way of preparing SCR catalyst with a high thermal stability and superior catalytic performance. It can be also extended further to the other catalytic system employing TiO2-based substrate. PMID:26235671

  8. Suppressed N2O formation during NH3 selective catalytic reduction using vanadium on zeolitic microporous TiO2.

    PubMed

    Lee, Seung Gwan; Lee, Hyun Jeong; Song, Inhak; Youn, Seunghee; Kim, Do Heui; Cho, Sung June

    2015-08-03

    Emission of N2O from mobile and off-road engine is now being currently regulated because of its high impact compared to that of CO2, thereby implying that N2O formation from the exhaust gas after-treatment system should be suppressed. Selective catalytic reduction using vanadium supported TiO2 catalyst in mobile and off-road engine has been considered to be major source for N2O emission in the system. Here we have demonstrated that vanadium catalyst supported on zeolitic microporous TiO2 obtained from the hydrothermal reaction of bulk TiO2 at 400 K in the presence of LiOH suppresses significantly the N2O emission compared to conventional VOx/TiO2 catalyst, while maintaining the excellent NOx reduction, which was ascribed to the location of VOx domain in the micropore of TiO2, resulting in the strong metal support interaction. The use of zeolitic microporous TiO2 provides a new way of preparing SCR catalyst with a high thermal stability and superior catalytic performance. It can be also extended further to the other catalytic system employing TiO2-based substrate.

  9. Suppressed N2O formation during NH3 selective catalytic reduction using vanadium on zeolitic microporous TiO2

    NASA Astrophysics Data System (ADS)

    Lee, Seung Gwan; Lee, Hyun Jeong; Song, Inhak; Youn, Seunghee; Kim, Do Heui; Cho, Sung June

    2015-08-01

    Emission of N2O from mobile and off-road engine is now being currently regulated because of its high impact compared to that of CO2, thereby implying that N2O formation from the exhaust gas after-treatment system should be suppressed. Selective catalytic reduction using vanadium supported TiO2 catalyst in mobile and off-road engine has been considered to be major source for N2O emission in the system. Here we have demonstrated that vanadium catalyst supported on zeolitic microporous TiO2 obtained from the hydrothermal reaction of bulk TiO2 at 400 K in the presence of LiOH suppresses significantly the N2O emission compared to conventional VOx/TiO2 catalyst, while maintaining the excellent NOx reduction, which was ascribed to the location of VOx domain in the micropore of TiO2, resulting in the strong metal support interaction. The use of zeolitic microporous TiO2 provides a new way of preparing SCR catalyst with a high thermal stability and superior catalytic performance. It can be also extended further to the other catalytic system employing TiO2-based substrate.

  10. H2, N2, and O2 metabolism by isolated heterocysts from Anabaena sp. strain CA.

    PubMed Central

    Smith, R L; Kumar, D; Zhang, X K; Tabita, F R; Van Baalen, C

    1985-01-01

    Metabolically active heterocysts isolated from wild-type Anabaena sp. strain CA showed high rates of light-dependent acetylene reduction and hydrogen evolution. These rates were similar to those previously reported in heterocysts isolated from the mutant Anabaena sp. strain CA-V possessing fragile vegetative cell walls. Hydrogen production was observed with isolated heterocysts. The ratio of C2H4 to H2 produced ranged from 0.9 to 1.2, and H2 production exhibited unique biphasic kinetics consisting of a 1 to 2-min burst of hydrogen evolution followed by a lower, steady-state rate of hydrogen production. This burst was found to be dependent upon the length of the dark period immediately preceding illumination and may be related to dark-to-light ATP transients. The presence of 100 nM NiCl2 in the growth medium exerted an effect on both acetylene reduction and hydrogen evolution in the isolated heterocysts from strain CA. H2-stimulated acetylene reduction was increased from 2.0 to 3.2 mumol of C2H4 per mg (dry weight) per h, and net hydrogen production was abolished. A phenotypic Hup- mutant (N9AR) of Anabaena sp. strain CA was isolated which did not respond to nickel. In isolated heterocysts from N9AR, ethylene production rates were the same under both 10% C2H2-90% Ar and 10% C2H2-90% H2 with or without added nickel, and net hydrogen evolution was not affected by the presence of 100 nM Ni2+. Isolated heterocysts from strain CA were shown to have a persistent oxygen uptake of 0.7 mumol of O2 per mg (dry weight) per h, 35% of the rate of whole filaments, at air saturating O2 levels, indicating that O2 impermeability is not a requirement for active heterocysts. PMID:3921524

  11. In Situ Multi-Species (O2, N2, Fuel, Other) Fiber Optic Sensor for Fuel Tank Ullage

    NASA Technical Reports Server (NTRS)

    Nguyen, Quang-Viet

    2007-01-01

    A rugged and compact fiber optic sensor system for in situ real-time measurement of nitrogen (N2), oxygen (O2), hydrocarbon (HC) fuel vapors, and other gases has been developed over the past several years at Glenn Research Center. The intrinsically-safe, solid-state fiber optic sensor system provides a 1% precision measurement (by volume) of multiple gases in a 5-sec time window. The sensor has no consumable parts to wear out and requires less than 25 W of electrical power to operate. The sensor head is rugged and compact and is ideal for use in harsh environments such as inside an aircraft fuel tank, or as a feedback sensor in the vent-box of an on-board inert gas generation system (OBIGGS). Multiple sensor heads can be monitored with a single optical detection unit for a cost-effective multi-point sensor system. The present sensor technology is unique in its ability to measure N2 concentration directly, and in its ability to differentiate different types of HC fuels. The present sensor system provides value-added aircraft safety information by simultaneously and directly measuring the nitrogen-oxygen-fuel triplet, which provides the following advantages: (1) information regarding the extent of inerting by N2, (2) information regarding the chemical equivalence ratio, (3) information regarding the composition of the aircraft fuel, and (4) by providing a self-consistent calibration by utilizing a singular sensor for all species. Using the extra information made available by this sensor permits the ignitability of a fuel-oxidizer mixture to be more accurately characterized, which may permit a reduction in the amount of inerting required on a real-time basis, and yet still maintain a fire-safe fuel tank. This translates to an increase in fuel tank fire-safety through a better understanding of the physics of fuel ignition, and at the same time, a reduction in compressed bleed air usage and concomitant aircraft operational costs over the long-run. The present fiber

  12. Quantum Cascade Laser Measurements of Line Intensities, N2-, O2- and Ar- Collisional Broadening Coefficients of N2O in the ν3 Band Near 4.5 µm.

    PubMed

    Es-Sebbar, Et-Touhami; Deli, Meriem; Farooq, Aamir

    2016-06-01

    This study deals with precise measurements of absolute line intensities, N2-, O2- and Ar- collisional broadening coefficients of N2O in the P-branch of the ν3 vibrational band near 4.5 µm. Collisional broadening coefficients of N2O-air are derived from the N2- and O2- broadening contributions by considering an ideal atmospheric composition. Studies are performed at room temperature for 10 rotational transitions over 2190-2202 cm(-1) spectral range using a distributed-feedback quantum cascade laser. To retrieve spectroscopic parameters for each individual transition, measured absorption line shape is simulated within Voigt and Galatry profiles. The obtained results compare well with previous experimental data available in the literature: the discrepancies being less than 4% for most of the probed transitions. The spectroscopic data reported here are very useful for the design of sensors used to monitor the abundance of N2O in earth's atmosphere.

  13. Thermogravimetric study of the combustion of Tetraselmis suecica microalgae and its blend with a Victorian brown coal in O2/N2 and O2/CO2 atmospheres.

    PubMed

    Tahmasebi, Arash; Kassim, Mohd Asyraf; Yu, Jianglong; Bhattacharya, Sankar

    2013-12-01

    The combustion characteristics of microalgae, brown coal and their blends under O2/N2 and O2/CO2 atmospheres were studied using thermogravimetry. In microalgae combustion, two peaks at 265 and 485°C were attributable to combustion of protein and carbohydrate with lipid, respectively. The DTG profile of coal showed one peak with maximum mass loss rate at 360°C. Replacement of N2 by CO2 delayed the combustion of coal and microalgae. The increase in O2 concentration did not show any effect on combustion of protein at the first stage of microalgae combustion. However, between 400 and 600°C, with the increase of O2 partial pressure the mass loss rate of microalgae increased and TG and DTG curves of brown coal combustion shifted to lower temperature zone. The lowest and highest activation energy values were obtained for coal and microalgae, respectively. With increased microalgae/coal ratio in the blends, the activation energy increased due to synergy effect.

  14. 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.

  15. Opposed jet burner studies of hydrogen combustion with pure and N2, NO-contaminated air

    NASA Technical Reports Server (NTRS)

    Guerra, Rosemary; Pellett, Gerald L.; Northam, G. Burton; Wilson, Lloyd G.

    1987-01-01

    A counterflow diffusion flame formed by an argon-bathed tubular-opposed jet burner (OJB) was used to determine the 'blowoff' and 'restore' combustion characteristics for jets of various H2/N2 mixtures and for jets of air contaminated by NO (which normally occurs in high-enthalpy airflows supplied to hypersonic test facilities for scramjet combustors). Substantial divergence of 'blowoff' and 'restore' limits occurred as H2 mass flux, M(H)2, increased, the H2 jet became richer, and the M(air)/M(H2 + N2) ratio increased from 1 to 3 (molar H2/O2 from 1 to 16). Both OJB limits were sensitive to reactant composition. One to six percent NO in air led to significant N2-corrected decreases in the M(H2) values for 'blowoff' (2-8 percent) and 'restore' (6-12 percent) for mole fractions of H2 ranging from 0.5 to 0.95. However, when H2/O2 was held constant, all N2-corrected changes in M(H2) were negligible.

  16. Synthesis and characterization of different MnO2 morphologies for lithium-air batteries

    NASA Astrophysics Data System (ADS)

    Choi, Hyun-A.; Jang, Hyuk; Hwang, Hyein; Choi, Mincheol; Lim, Dongwook; Shim, Sang Eun; Baeck, Sung-Hyeon

    2014-09-01

    Manganese dioxide (MnO2) was synthesized in the forms of nanorods, nanoparticles, and mesoporous structures and the characteristics of these materials were investigated. Crystallinities were studied by x-ray diffraction and morphologies by scanning and transmission electron microscopy. Average pore sizes and specific surface areas were analyzed using the Barret-Joyner-Halenda and Brunauer-Emmett-Teller methods, respectively. Samples were also studied by cyclic voltammetry using 1M aqueous KOH solution saturated with either O2 or N2 as electrolytes to investigate their ORR (oxygen reduction reaction) and OER (oxygen evolution reaction) activities. Of the samples produced, mesoporous MnO2 exhibited the highest ORR and OER catalytic activities. Mesoporous MnO2 supported on a gas diffusion layer was also used as a catalyst on the air electrode (cathode) of a lithium-air battery in organic electrolyte. The charge-discharge behavior of mesoporous MnO2 was investigated at a current density 0.2 mAcm-2 in a pure oxygen environment. Mesoporous MnO2 electrodes showed stable cycleability up to 65 cycles at a cell capacity of 700 mAhg-1.

  17. Kinetic modeling of the formation and growth of inorganic nano-particles during pulverized coal char combustion in O2/N2 and O2/CO2 atmospheres

    DOE PAGES

    Shaddix, Christopher R.; Niu, Yanqing; Hui, Shi'en; Wang, Shuai

    2016-08-01

    In this formation of nano-particles during coal char combustion, the vaporization of inorganic components in char and the subsequent homogeneous particle nucleation, heterogeneous condensation, coagulation, and coalescence play decisive roles. Furthermore, conventional measurements cannot provide detailed information on the dynamics of nano-particle formation and evolution, In this study, a sophisticated intrinsic char kinetics model that considers ash effects (including ash film formation, ash dilution, and ash vaporization acting in tandem), both oxidation and gasification by CO2 and H2O, homogeneous particle nucleation, heterogeneous vapor condensation, coagulation, and and coalescence mechanisms is developed and used to compare the temporal evolution of themore » number and size of nano-particles during coal char particle combustion as a function of char particle size, ash content, and oxygen content in O2/N2 and O2/CO2 atmospheres .« less

  18. Pressure broadening of the 2.5 THz H(Cl-35) rotational line by N2 and O2

    NASA Technical Reports Server (NTRS)

    Park, K.; Chance, K. V.; Nolt, I. G.; Radostitz, J. V.; Vanek, M. D.; Jennings, D. A.; Evenson, K. M.

    1991-01-01

    The pressure broadening coefficients of the 2.5 THz rotation line of H(Cl-35) by N2 and O2, for application to the analysis of far infrared spectra obtained in the stratosphere, are reported. The broadening coefficients were measured in absorption at 296 and 201 L using a tunable far infrared spectrometer. Results show that at room temperature the N2 pressure broadening coefficient is 0.0669 +/-0.0021/cm/atm (2sigma), with a temperature coefficient B of 0.58 +/-0.02.

  19. Unraveling the importance of surface association to the formation of molecules in a recombining N_2 / O_2 plasma

    NASA Astrophysics Data System (ADS)

    Zijlmans, R.; Welzel, S.; Gabriel, O.; van Helden, J. H.; Ropcke, J.; Schram, D. C.; Engeln, R.

    2008-07-01

    mainly on the gas phase formation of NO, but recognize the importance of the surfaces of the plasma reactor. Also Castillo et al. (2005) conclude in their studies that mainly heterogeneous processes are responsible for the formation of NO. To unravel the contribution of surface related processes to the total kinetics in a low pressure recombining plasma created from mixtures of N_2 and O_2, we measured the abundance of the stable molecules NO, N_2O and NO_2 in the plasma by means of IRMA, which is an IR tunable diode laser absorption system (Ropcke et al. 2000), and mass spectrometry (N_2 and O_2). A simulation, developed in CHEMKIN (2004), is used to investigate the effect of radical-surface interactions on the conversion of the feedstock gases. 2. RESULTS A plasma expansion is created from a flow of 3000 standard cubic centimeters per minute (sccm) argon through a cascaded arc plasma source. A total power of 5 kW (I = 75 A) is used to create the Ar plasma in the arc channel of the source. This plasma expands from the exit of the arc channel into the reactor, which is kept at a pressure of p = 20 Pa or p =100 Pa. A total flow of 1800 sccm of mixtures of N_2 and O_2 is injected directly into the reactor. The molecular abundances of the species formed in the plasma vessel are investigated as function of the ratio of admixed O_2 flow over the total flow of O_2 and N_2. In Figure 1 the symbols denote the measured mole fractions of Ar, N_2, O_2, NO, N_2O and NO_2, which are plotted on a semi-logarithmic scale. All the species are measured with the quadrupole mass spectrometer, while NO and N_2O are also measured by infrared absorption spectroscopy, using the IRMA system (Ropcke et al. 2000). The results of both the mass spectrometry measurements and tunable diode laser absorption spectroscopy measurements showed good agreement (within 10 %). For both pressures the molecules N_2 and O_2 are dominantly present. The abundance of the other types of molecules (NO, NO_2 and N_2O

  20. Low-energy proton stopping power of N2, O2 and water vapor and deviations from Bragg's rule

    NASA Technical Reports Server (NTRS)

    Xu, Y. J.; Khandelwal, G. S.; Wilson, J. W.

    1984-01-01

    A modified local plasma model, based on the works of Lindhard and Winther; and Bethe, Brown, and Walske, is established. The Gordon-Kim model for molecular electron density is used to calculate stopping power of N2, O2, and water vapor for protons of energy ranging from 40 keV to 2.5 MeV, resulting in good agreement with experimental data. Deviations from Bragg's rule are evaluated and are discussed under the present theoretical model.

  1. Vibration-dissociation coupling in CO, N2 and O2 - An evaluation of analytic transition rate expressions

    NASA Technical Reports Server (NTRS)

    Gonzales, David A.; Varghese, Philip L.

    1993-01-01

    Closed form expressions for inelastic state-to-state and state-specific dissociative rate coefficients for utilization in vibrational master equation studies of shock heated CO, N2, and O2 highly dilute in Ar are considered. The master equation is linearized by neglecting diatom-diatom collisions and recombination. Master equation results indicate that the most significant contribution to dissociation comes from low and mid lying vibrational levels.

  2. N2O seasonal distributions and air-sea exchange in UK estuaries: Implications for the tropospheric N2O source from European coastal waters

    NASA Astrophysics Data System (ADS)

    Barnes, J.; Upstill-Goddard, R. C.

    2011-03-01

    We report measurements of dissolved nitrous oxide (N2O), dissolved inorganic nitrogen, and turbidity in surveys of six UK inner estuaries between February 2000 and October 2002: the Humber, Forth, Tamar, Tyne, Tees, and Tay. We also present dissolved N2O data for the Wash outer estuary from May 1995 and dissolved O2 data for the Forth estuary from June 2001. N2O was always supersaturated relative to air and was highest in the Humber (range 140-6500%) and generally higher at all sites during summer. In estuaries with well defined turbidity maximum zones (TMZs) at low salinity, N2O was maximal in the TMZ, coincident with high NH4+ and/or NO3-. Inspection of the broad relationships between N2O, NH4+, NO3-, NO2-, and O2 revealed a predominantly nitrification source for the N2O in the estuaries studied; denitrification-derived N2O was apparently unimportant and denitrification did not constitute a significant NO3- sink. In the anthropogenically impacted Tees estuary N2O (saturation 140-2000%) was attributed to high NH4+ in sewage and industrial effluent. N2O emissions were thus primarily a function of NH4+ derived from internal resuspension and/or ammonification, or external inputs and were independent of river-borne NO3-. We reevaluated total UK and European estuarine N2O emissions using these and published data, based on an aerially weighted approach that separately identified inner and outer estuaries, and a downward revision of the total European estuarine area used in a recent synthesis. Our revised estimates, ˜1.9 ± 1.2 × 109 g N2O yr-1 for the UK and 6.8 ± 13.2 × 109 g N2O yr-1 for Europe (including UK) are dominated by large (area ˜200-500 km2) anthropogenically impacted macrotidal inner estuaries. By contrast large pristine macrotidal systems, small inner estuaries, and large outer estuaries appear to be comparatively minor N2O sources. The UK estuarine N2O source is <2% of the UK N2O budget. Our revised European estuarine N2O emission is around 2 orders

  3. Thymidine decomposition induced by low-energy electrons and soft X rays under N2 and O2 atmospheres.

    PubMed

    Alizadeh, Elahe; Sanz, Ana G; Madugundu, Guru S; García, Gustavo; Wagner, J Richard; Sanche, Léon

    2014-06-01

    A novel technique has been employed to investigate the simultaneous damage to DNA components induced by soft X rays (1.5 keV) and low-energy electrons (0-30 eV) in thin films of thymidine deposited on glass and tantalum substrates and irradiated under atmospheric pressure and temperature. The films were surrounded by either an N2 or O2 environment. The formation of four radiation-induced products is reported in this article: base release, 5-hydroxymethyl-2'-deoxyuridine (5-HMdUrd), 5-formyl-2'-deoxyuridine (5-FordUrd) and 5,6-dihydrothymidine (5,6-DHThd). Analysis with LC-MS/MS shows larger damage yields in the samples deposited on tantalum than in those deposited on glass, which is attributed to the interaction of the additional low-energy electrons that are photoemitted from the metal surface. From a comparison of the results obtained from N2 and O2 environment, we report a dramatic effect from 6 O2: an approximately threefold increase in the yield of products, attributed to the reaction of O2 with initial carbon-centered thymidine radicals generated in the film during irradiation.

  4. Absence of diuresis during a 7-day saturation dive at 2.5 ATA N2-O2.

    PubMed

    Niu, A K; Hong, S K; Claybaugh, J R; Goldinger, J M; Kwon, O; Li, M; Randall, E; Lundgren, C E

    1990-05-01

    Three male divers were studied for 2 days during each of the predive and postdive 1 ATA air control periods and for 7 days at 2.5 ATA (2.3 ATA N2 and 0.2 ATA O2). The chamber temperature was always maintained at a comfort level. Average urine flow remained at 1500 ml.day-1 during both predive and 2.5 ATA periods; urine osmolality also remained constant at around 700 mOSM/kg. On the other hand, daily excretion of Na increased significantly from 139 mEq during the predive period to 178 mEq at 2.5 ATA (P less than 0.05) but returned to the predive level during the postdive period. In contrast, daily K excretion decreased progressively with a significant decrease during the postdive period (P less than 0.05). Plasma osmolality, Na, and K remained unchanged, whereas a 6% reduction of total protein concentration at 2.5 ATA (P less than 0.05) was observed. A quantitatively similar decrease (8%) was observed for hematocrit during the 2.5 ATA period, which did not recover at postdive. These changes were accompanied by a significant increase in urinary excretion of antidiuretic hormone (P less than 0.05) and by decreases in both plasma renin and aldosterone (P less than 0.05) level and urinary excretion of aldosterone (P less than 0.05). Plasma atrial natriuretic factor remained unchanged throughout the entire dive period.

  5. Premixed CH4/O2-enriched air combustion: Identification of thermal, chemical and aerodynamic effects

    NASA Astrophysics Data System (ADS)

    Most, J.-M.; Dahikar, S.; Pal, S.; Claverie, A.; Denis, D.; Pillier, L.; de Persis, S.

    2012-11-01

    This work contributes to the evaluation of a new innovative process focused on the reduction of the cost of a post-combustion capture of CO2 in a Carbon Capture and Storage system (CCS). The process based on the separation of dried fumes composed mainly by CO2 and N2 by using membranes, which should lead to a lower energetic separation cost than amines. But the membranes become efficient if the upstream CO2 concentration is higher than 30% at their entrance that requires enriching the oxidizer flow by O2. To maintain the exhaust temperature compatible with materials thermal resistance, the reactants are diluted by a recirculation of a part of the flue gases (like N2/O2/CO2). But, the chemical kinetic, the energetic efficiencies, the radiation transfer, the transport and thermal properties of the flow can be affected by CO2. The objective of this work will be to identify the behaviour of the combustion of premixed CH4/O2-enriched air, both diluted in N2 and CO2 and to determine the combustion parameters. This allows to recover the CH4/air conditions in terms of CO2 concentration in reactants, O2 excess, dilution rate, temperature of the reactants, etc. Experiments are performed on the laminar premixed flame using counterflow burner. To characterize the combustion behaviour, the flammability limits are determined and flame thickness and position are measured from PLIF-OH diagnostic. Further, CHEMKIN simulations are performed to check the validity of the GRI3.0 chemical kinetic mechanism for premixed CH4/air synthetic combustion and identify the leading phenomena.

  6. The Benthic Exchange of O2, N2 and Dissolved Nutrients Using Small Core Incubations.

    PubMed

    Owens, Michael S; Cornwell, Jeffrey C

    2016-08-03

    The measurement of sediment-water exchange of gases and solutes in aquatic sediments provides data valuable for understanding the role of sediments in nutrient and gas cycles. After cores with intact sediment-water interfaces are collected, they are submerged in incubation tanks and kept under aerobic conditions at in situ temperatures. To initiate a time course of overlying water chemistry, cores are sealed without bubbles using a top cap with a suspended stirrer. Time courses of 4-7 sample points are used to determine the rate of sediment water exchange. Artificial illumination simulates day-time conditions for shallow photosynthetic sediments, and in conjunction with dark incubations can provide net exchanges on a daily basis. The net measurement of N2 is made possible by sampling a time course of dissolved gas concentrations, with high precision mass spectrometric analysis of N2:Ar ratios providing a means to measure N2 concentrations. We have successfully applied this approach to lakes, reservoirs, estuaries, wetlands and storm water ponds, and with care, this approach provides valuable information on biogeochemical balances in aquatic ecosystems.

  7. The Benthic Exchange of O2, N2 and Dissolved Nutrients Using Small Core Incubations.

    PubMed

    Owens, Michael S; Cornwell, Jeffrey C

    2016-01-01

    The measurement of sediment-water exchange of gases and solutes in aquatic sediments provides data valuable for understanding the role of sediments in nutrient and gas cycles. After cores with intact sediment-water interfaces are collected, they are submerged in incubation tanks and kept under aerobic conditions at in situ temperatures. To initiate a time course of overlying water chemistry, cores are sealed without bubbles using a top cap with a suspended stirrer. Time courses of 4-7 sample points are used to determine the rate of sediment water exchange. Artificial illumination simulates day-time conditions for shallow photosynthetic sediments, and in conjunction with dark incubations can provide net exchanges on a daily basis. The net measurement of N2 is made possible by sampling a time course of dissolved gas concentrations, with high precision mass spectrometric analysis of N2:Ar ratios providing a means to measure N2 concentrations. We have successfully applied this approach to lakes, reservoirs, estuaries, wetlands and storm water ponds, and with care, this approach provides valuable information on biogeochemical balances in aquatic ecosystems. PMID:27583833

  8. Synthesis, crystal structure and spectroscopic properties of a supramolecular zinc(II) complex with N2O2 coordination sphere.

    PubMed

    Dong, Wen-Kui; Zhang, Li-Sha; Sun, Yin-Xia; Zhao, Meng-Meng; Li, Gang; Dong, Xiu-Yan

    2014-01-01

    A new hexa-coordinated zinc(II) complex, namely [ZnL(H2O)2]n, with N2O2 coordination sphere (H2L=4,4'-dibromo-6,6'-dichloro-2,2'-[ethylenedioxybis(nitrilomethylidyne)]diphenol) has been synthesized and structurally characterized by elemental analyses, IR, UV-vis spectra and TG-DTA analyses, etc. Crystallographic data are monoclinic, space group P2(1)/c, a=24.634(2)Å, b=10.144(1)Å, c=7.9351(6)Å, β=91.371(2)°, V=1982.4(3)Å(3), Dc=2.099 g/cm(3), Z=4. The zinc(II) complex exhibits a slightly distorted octahedral geometry with halogen-substituted Salen-type bisoxime forming the basal N2O2 coordination sphere and two oxygen atoms from two coordinated water molecules in the axial position. The hydrogen-bonding and π-π stacking interactions have stabilized the zinc(II) complex molecules to form a self-assembling infinite dual metal-water chain-like structure with the nearest Zn⋯Zn distance of 4.954(4)Å.

  9. A kinetic study of the reactions of Fe+ with N2O, N2, O2, CO2 and H2O, and the ligand-switching reactions Fe+.X + Y --> Fe+.Y + X (X = N2, O2, CO2; Y = O2, H2O).

    PubMed

    Vondrak, T; Woodcock, K R I; Plane, J M C

    2006-01-28

    A series of reactions involving Fe(+) ions were studied by the pulsed laser ablation of an iron target, with detection of ions by quadrupole mass spectrometry at the downstream end of a fast flow tube. The reactions of Fe(+) with N(2)O, N(2) and O(2) were studied in order to benchmark this new technique. Extending measurements of the rate coefficient for Fe(+) + N(2)O from 773 K to 185 K shows that the reaction exhibits marked non-Arrhenius behaviour, which appears to be explained by excitation of the N(2)O bending vibrational modes. The recombination of Fe(+) with CO(2) and H(2)O in He was then studied over a range of pressure and temperature. The data were fitted by RRKM theory combined with ab initio quantum calculations on Fe(+).CO(2) and Fe(+).H(2)O, yielding the following results (120-400 K and 0-10(3) Torr). For Fe(+) + CO(2): k(rec,0) = 1.0 x 10(-29) (T/300 K)(-2.31) cm(6) molecule(-2) s(-1); k(rec,infinity) = 8.1 x 10(-10) cm(3) molecule(-1) s(-1). For Fe(+) + H(2)O: k(rec,0) = 5.3 x 10(-29) (T/300 K)(-2.02) cm(6) molecule(-2) s(-1); k(rec,infinity) = 2.1 x 10(-9) (T/300 K)(-0.41) cm(3) molecule(-1) s(-1). The uncertainty in these rate coefficients is determined using a Monte Carlo procedure. A series of exothermic ligand-switching reactions were also studied at 294 K: k(Fe(+).N(2) + O(2)) = (3.17 +/- 0.41) x 10(-10), k(Fe(+).CO(2) + O(2)) = (2.16 +/- 0.35) x 10(-10), k(Fe(+).N(2) + H(2)O) = (1.25 +/- 0.14) x 10(-9) and k(Fe(+).O(2) + H(2)O) = (8.79 +/- 1.30) x 10(-10) cm(3) molecule(-1) s(-1), which are all between 36 and 52% of their theoretical upper limits calculated from long-range capture theory. Finally, the role of these reactions in the chemistry of meteor-ablated iron in the upper atmosphere is discussed. The removal rates of Fe(+) by N(2), O(2), CO(2) and H(2)O at 90 km altitude are approximately 0.1, 0.07, 3 x 10(-4) and 1 x 10(-6) s(-1), respectively. The initially formed Fe(+).N(2) and Fe(+).O(2) are converted into the H(2)O complex at

  10. 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

  11. Cryogenically formed prestressed composite fiber-metal structures for O2/N2 high pressure gas tanks.

    NASA Technical Reports Server (NTRS)

    Gleich, D.

    1971-01-01

    Demonstration of high-structural-performance ARDEFORM cryoformed 301 stainless-steel glass-fiber-reinforced (GFR) vessels by room temperature tests of 13 1/2-in. diam spheres. Tests verified that the structural performance of ARDEFORM spherical GFR vessels not only exceeded that of all metal construction, but also bettered previous GFR experimental results by 50%. Achievement of essentially the full strength of fiberglass in a spherical wrap pattern was again verified. Significant weight advantages for this construction are projected for O2/N2 high-pressure gas tanks for Space Shuttle environmental control/life support system missions.

  12. Full CI benchmark calculations on N2, NO, and O2 - A comparison of methods for describing multiple bonds

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Langhoff, Stephen R.

    1987-01-01

    Full configuration interaction (CI) calculations on the ground states of N2, NO, and O2 using a DZP Gaussian basis are compared with single-reference SDCI and coupled pair approaches (CPF), as well as with CASSCF multireference CI approaches. The CASSCF/MRCI technique is found to describe multiple bonds as well as single bonds. Although the coupled pair functional approach gave chemical accuracy (1 kcal/mol) for bonds involving hydrogen, larger errors occur in the CPF approach for the multiple bonded systems considered here. CI studies on the 1Sigma(g +) state of N2, including all single, double, triple, and quadruple excitations show that triple excitations are very important for the multiple bond case, and accounts for most of the deficiency in the coupled pair functional methods.

  13. Calculated potential surfaces for the reactions: O + N2 yields NO + N and N + O2 yields NO + O

    NASA Technical Reports Server (NTRS)

    Walch, Stephen P.; Jaffe, Richard J.

    1986-01-01

    Complete Active Space SCF/Contracted CI (CASSCF/CCI) calculations, using large Gaussian basis sets, are presented for selected portions of the potential surfaces for the reactions in the Zeldovich mechanism for the conversion of N2 to NO. The N + O2 reaction is exoergic by 32 kcal/mole and is computed to have an early barrier of 10.2 kcal/mole for the (sup 2)A(sup prime) surface and 18.0 kcal/mole for the (sup 4)A(sup prime) surface. The O + N2 reaction is endoergic by 75 kcal/mole. The (sup 3)A(sup double prime) surface is calculated to have a late barrier of 0.5 kcal/mole, while the (sup 3)A(sup prime) surface is calculated to have a late barrier of 14.4 kcal/mole.

  14. EUV studies of N2 and O2 produced by low energy electron impact

    NASA Technical Reports Server (NTRS)

    Morgan, H. D.; Mentall, J. E.

    1983-01-01

    The emission spectra resulting from electron impact excitation on molecular nitrogen and oxygen in the 500-1200 A spectral region are investigated. Electron energies are from 0 to 300 eV. Numerous bands of N2 are found between 800 and 1000 A. Excitation functions are measured for the NII 916 A, the OI 879 A, and the OII 834 multiplets, and nitrogen band emission. Cross sections were measured at 200 eV for several of the band emissions plus the NI 1135 A, NI 1164 A, NI 1177 A, NII 776 A, NII 1084 A, OI 1152 A, OI 1041 A, OI 999 A, OI 989 A, OI 879 A, OII 834 A, OII 616 A, OII 555 A, OII 539 A, and OII 718 A multiplets.

  15. Atomic layer deposition of ZnO on thermal SiO2 and Si surfaces using N2-diluted diethylzinc and H2O2 precursors

    NASA Astrophysics Data System (ADS)

    Qian, Ke-Jia; Chen, Sun; Zhu, Bao; Chen, Lin; Ding, Shi-Jin; Lu, Hong-Liang; Sun, Qing-Qing; Zhang, David Wei; Chen, Zhenyi

    2012-03-01

    ZnO nanodots are attracting more and more attention in various photoelectrical applications due to multiple excition generation. In this article, atomic layer deposition (ALD) growth of ZnO nanodots has been realized for the first time on both thermal SiO2 and Si surfaces using N2-diluted gaseous DEZn and H2O2 precursors. The experimental results indicate that the ALD ZnO exhibits a nano-crystalline film with corrugated surfaces in the case of the deposition temperature of 200 °C, likely due to concrescence among ZnO nanodots. When the deposition temperature is increased up to 300 °C, ZnO is grown in the form of well-discrete nanodots. This is due to increased desorption of the reacting molecules and a reduction of nucleation sites on the growing surfaces at 300 °C, thus leading to the reaction between DEZn and sbnd OH groups only on some favorable sites from thermodynamic and energy points of view. In terms of the thermal SiO2 surface, ZnO nanodots with a density of around 5 × 1010 cm-2 are obtained for 100 cycles. As for the Si surface, ZnO nanodots with a density as high as ˜1 × 1011 cm-2 are achieved for 50 cycles. Finally, the X-ray photoelectron spectroscopy and X-ray diffraction analyses reveal that the ALD ZnO at 300 °C is dominated by Znsbnd O bonds together with a small quantity of Znsbnd OH bonds, and the deposition temperature of 300 °C can result in preferential growth of ZnO (0 0 2) orientation and a bigger crystallite size.

  16. Spectroscopic studies of MW plasmas containing HMDSO, O2 and N2

    NASA Astrophysics Data System (ADS)

    Nave, Andy; Roepcke, Juergen; Mitschker, Felix; Awakowicz, Peter

    2015-09-01

    The deposition of SiOx layers based on organosilicon plasmas is used to implement advantageous mechanical, electrical, and/or optical properties on various substrates. The development of such coating processes resulting in a wide range of chemical and physical film properties, using hexamethyldisiloxane (HMDSO) as a precursor, has been in the center of interest of various studies. In plasma, the dissociation of HMDSO into a large amount of fragments is a complex chemical phenomenon. The monitoring of the precursor and of formed species is very valuable to understand the plasma chemistry. Infrared absorption spectroscopy based on lead salt lasers and EC Quantum Cascade Laser have been used to monitor the concentrations of HMDSO, and of the reaction products CH4, C2H2, C2H4,C2H6, CO, CO2 and CH3 as a function of the HMDSO/O2 mixture ratio, and the power at various pressures in a MW plasma deposition reactor. Optical emission spectroscopy has been applied as complementary diagnostics to evaluate electron density and electron temperature. Supported by the German Research Foundation within SFB-TR24 and SFB-TR87.

  17. Effect of excited nitrogen atoms on inactivation of spore-forming microorganisms in low pressure N2/O2 surface-wave plasma

    NASA Astrophysics Data System (ADS)

    Yang, Xiaoli; Chang, Xijiang; Tei, Reitou; Nagatsu, Masaaki

    2016-06-01

    Using a vacuum ultraviolet (VUV) absorption spectroscopy with a compact low pressure plasma light source, the absolute nitrogen atom density was measured to study its role in the spore inactivation with low pressure N2/O2 gas mixture surface-wave plasmas (SWPs). Self-absorption effect of the resonance emission lines of nitrogen atoms near 120 nm was minimized by optimizing its discharge conditions of the plasma light source. Experimental results showed that excited nitrogen atom densities monotonically decreased with the decrease of N2 gas percentage in N2/O2 gas mixture SWPs, concomitantly with similar decrease of VUV/UV emission intensities of nitrogen atoms and molecules. In the pure N2 gas SWPs, it was confirmed that a dominant lethal factor was VUV/UV emission generated by N2 plasma, while spore etching occurred via physical and chemical interactions with nitrogen species. With an addition of O2 gas, significant spore etching by excited oxygen atoms made it much easier for the VUV/UV photons emitted by nitrogen atoms, N2 and NO molecules to penetrate through the etched spore coats to the core and cause the fatal DNA damage of the microorganisms. As a result, more rapid inactivation was achieved in the middle region of N2/O2 gas mixture ratio, such as 30–80% O2 gas addition, in the present N2/O2 gas mixture SWPs.

  18. Picosecond-TALIF and VUV absorption measurements of absolute atomic nitrogen densities from an RF atmospheric pressure plasma jet with He/O2/N2 gas mixtures

    NASA Astrophysics Data System (ADS)

    West, Andrew; Niemi, Kari; Schröter, Sandra; Bredin, Jerome; Gans, Timo; Wagenaars, Erik

    2015-09-01

    Reactive Oxygen and Nitrogen species (RONS) from RF atmospheric pressure plasma jets (APPJs) are important in biomedical applications as well as industrial plasma processing such as surface modification. Atomic oxygen has been well studied, whereas, despite its importance in the plasma chemistry, atomic nitrogen has been somewhat neglected due to its difficulty of measurement. We present absolute densities of atomic nitrogen in APPJs operating with He/O2/N2 gas mixtures in open air, using picosecond Two-photon Absorption Laser Induced Fluorescence (ps-TALIF) and vacuum ultra-violet (VUV) absorption spectroscopy. In order to apply the TALIF technique in complex, He/O2/N2 mixtures, we needed to directly measure the collisional quenching effects using picosecond pulse widths (32ps). Traditional calculated quenching corrections, used in nanosecond TALIF, are inadequate due to a lack of quenching data for complex mixtures. Absolute values for the densities were found by calibrating against a known density of Krypton. The VUV absorption experiments were conducted on the DESIRS synchrotron beamline using a unique VUV Fourier-transform spectrometer. Atomic nitrogen densities were on the order of 1020 m-3 with good agreement between TALIF and VUV absorption. UK EPSRC grant EP/K018388/1.

  19. Effects of H2O, CO2, and N2 Air Contaminants on Critical Airside Strain Rates for Extinction of Hydrogen-Air Counterflow Diffusion Flames

    NASA Technical Reports Server (NTRS)

    Pellett, G. L.; Wilson, L. G.; Northam, G. B.; Guerra, Rosemary

    1989-01-01

    Coaxial tubular opposed jet burners (OJB) were used to form dish shaped counterflow diffusion flames (CFDF), centered by opposing laminar jets of H2, N2 and both clean and contaminated air (O2/N2 mixtures) in an argon bath at 1 atm. Jet velocities for flame extinction and restoration limits are shown versus wide ranges of contaminant and O2 concentrations in the air jet, and also input H2 concentration. Blowoff, a sudden breaking of CFDF to a stable ring shape, occurs in highly stretched stagnation flows and is generally believed to measure kinetically limited flame reactivity. Restore, a sudden restoration of central flame, is a relatively new phenomenon which exhibits a H2 dependent hysteresis from Blowoff. For 25 percent O2 air mixtures, mole for mole replacement of 25 percent N2 contaminant by steam increased U(air) or flame strength at Blowoff by about 5 percent. This result is consistent with laminar burning velocity results from analogous substitution of steam for N2 in a premixed stoichiometric H2-O2-N2 (or steam) flame, shown by Koroll and Mulpuru to promote a 10 percent increase in experimental and calculated laminar burning velocity, due to enhanced third body efficiency of water in: H + O2 + M yields HO2 + M. When the OJB results were compared with Liu and MacFarlane's experimental laminar burning velocity of premixed stoichiometric H2 + air + steam, a crossover occurred, i.e., steam enhanced OJB flame strength at extinction relative to laminar burning velocity.

  20. Effect of oxygen on the conversion of acetaldehyde in homogeneous plasmas of N2/O2/CH3CHO mixtures

    NASA Astrophysics Data System (ADS)

    Faider, W.; Pasquiers, S.; Blin-Simiand, N.; Magne, L.

    2013-12-01

    A photo-triggered discharge producing a homogeneous plasma was used to investigate, experimentally and with the help of a self-consistent 0D model, the decomposition processes of acetaldehyde (concentration up to 0.5%) in N2/O2/CH3CHO mixtures containing up to 20% oxygen, at a total pressure of 460 mbar. This work follows a previous one about N2/CH3CHO, having provided the necessary data about the quenching of the N2 metastable states by the acetaldehyde molecule. For the condition of the experiment, it was shown that oxygen has a weak influence on the acetaldehyde removal. Nevertheless, the kinetic reactions involved drastically change when the oxygen percentage is increased. Quenching reactions gradually give way to oxidation reactions by O(3P) and OH. Oxidation by OH dominates for a high acetaldehyde concentration or a high oxygen percentage. Moreover, CH3 is an important primary compound for the formation of CH4 and C2H6. Ethane is less populated than methane in the whole range of oxygen percentage values studied, and there are still hydrocarbon molecules in the gas mixture at 20% oxygen. This is well explained by the adopted kinetic scheme.

  1. Enhancement of Photoluminescence in BaSi2O2N2:Eu2+ by Partial Ge4+ Substitution for Si4+.

    PubMed

    Wang, Baochen; Chen, Jian; Xia, Yufei; Liu, Yangai

    2016-04-01

    Ge4+-doped BaSi2O2N2: Eu2+ phosphors were prepared by a high temperature solid-state reaction method. The phase structure, photoluminescence (PL) properties and PL thermal stability of the as-synthesized samples were investigated. The emission intensity of the Ba(Si0.99Ge0.01)2O2N2: 0.05Eu2+ phosphor was 41.7% greater than that of BaSi2O2N2:0.05Eu2+. When the temperature increased to 150 °C, the emission intensity of Ba(Si0.99Ge0.01)2O2N2:0.05Eu2+ phosphor was 67.0% of the initial value at room temperature. This value was 22.9% greater than that of BaSi2O2N2:0.05Eu2+. The related mechanism has also been explained through the crystal field theory. All these results indicated that the Ge4+-doped BaSi2O2N2:0.05Eu2+ phosphor is a promising material for application in white light emitting diodes. PMID:27451674

  2. Feature Scale Simulation of PECVD of SiO2 in SiH4/N2O Mixture

    NASA Astrophysics Data System (ADS)

    Liu, Xuan; Ge, Jie; Yang, Yi; Song, Yixu; Ren, Tianling

    2014-04-01

    In this paper, to simulate the process of PECVD (plasma enhanced chemical vapor deposition) of SiO2, the plasma chemistry and plasma density of SiH4/N2O mixture have been studied with an inductive coupled plasma model, and the level set methodology has been used to obtain the feature scale variation during the process. In this simulation, the goal is to fill a trench. We studied how ion sputtering and chamber pressure affect the feature scale model. After the simulation, we found that the trench will close up at the top after a few steps, and if we add the ion sputtering into the surface reactions, the trench top will close up a little later. When the chamber pressure is improved, the plasma density will increase, so the trench top will close up earlier. In semiconductor device manufacture, people can control the trench's feature scale through adjusting these two parameters.

  3. Enhanced Flexibility of the O2 + N2 Interaction and Its Effect on Collisional Vibrational Energy Exchange.

    PubMed

    Garcia, E; Laganà, A; Pirani, F; Bartolomei, M; Cacciatore, M; Kurnosov, A

    2016-07-14

    Prompted by a comparison of measured and computed rate coefficients of Vibration-to-Vibration and Vibration-to-Translation energy transfer in O2 + N2 non-reactive collisions, extended semiclassical calculations of the related cross sections were performed to rationalize the role played by attractive and repulsive components of the interaction on two different potential energy surfaces. By exploiting the distributed concurrent scheme of the Grid Empowered Molecular Simulator we extended the computational work to quasiclassical techniques, investigated in this way more in detail the underlying microscopic mechanisms, singled out the interaction components facilitating the energy transfer, improved the formulation of the potential, and performed additional calculations that confirmed the effectiveness of the improvement introduced. PMID:26982814

  4. Studies of iron(II) and iron(III) complexes with fac-N2O, cis-N2O2 and N2O3 donor ligands: models for the 2-His 1-carboxylate motif of non-heme iron monooxygenases.

    PubMed

    Cappillino, Patrick J; Miecznikowski, John R; Tyler, Laurie A; Tarves, Paul C; McNally, Joshua S; Lo, Wayne; Kasibhatla, Bala Sundari T; Krzyaniak, Matthew D; McCracken, John; Wang, Feng; Armstrong, William H; Caradonna, John P

    2012-05-14

    Enzymes in the oxygen-activating class of mononuclear non-heme iron oxygenases (MNOs) contain a highly conserved iron center facially ligated by two histidine nitrogen atoms and one carboxylate oxygen atom that leave one face of the metal center (three binding sites) open for coordination to cofactor, substrate, and/or dioxygen. A comparative family of [Fe(II/III)(N(2)O(n))(L)(4-n))](±x), n = 1-3, L = solvent or Cl(-), model complexes, based on a ligand series that supports a facially ligated N,N,O core that is then modified to contain either one or two additional carboxylate chelate arms, has been structurally and spectroscopically characterized. EPR studies demonstrate that the high-spin d(5) Fe(III)g = 4.3 signal becomes more symmetrical as the number of carboxylate ligands decreases across the series Fe(N(2)O(3)), Fe(N(2)O(2)), and Fe(N(2)O(1)), reflecting an increase in the E/D strain of these complexes as the number of exchangeable/solvent coordination sites increases, paralleling the enhanced distribution of electronic structures that contribute to the spectral line shape. The observed systematic variations in the Fe(II)-Fe(III) oxidation-reduction potentials illustrate the fundamental influence of differential carboxylate ligation. The trend towards lower reduction potential for the iron center across the [Fe(III)(N(2)O(1))Cl(3)](-), [Fe(III)(N(2)O(2))Cl(2)](-) and [Fe(III)(N(2)O(3))Cl](-) series is consistent with replacement of the chloride anions with the more strongly donating anionic O-donor carboxylate ligands that are expected to stabilize the oxidized ferric state. This electrochemical trend parallels the observed dioxygen sensitivity of the three ferrous complexes (Fe(II)(N(2)O(1)) < Fe(II)(N(2)O(2)) < Fe(II)(N(2)O(3))), which form μ-oxo bridged ferric species upon exposure to air or oxygen atom donor (OAD) molecules. The observed oxygen sensitivity is particularly interesting and discussed in the context of α-ketoglutarate-dependent MNO enzyme

  5. Studies of iron(II) and iron(III) complexes with fac-N2O, cis-N2O2 and N2O3 donor ligands: models for the 2-His 1-carboxylate motif of non-heme iron monooxygenases.

    PubMed

    Cappillino, Patrick J; Miecznikowski, John R; Tyler, Laurie A; Tarves, Paul C; McNally, Joshua S; Lo, Wayne; Kasibhatla, Bala Sundari T; Krzyaniak, Matthew D; McCracken, John; Wang, Feng; Armstrong, William H; Caradonna, John P

    2012-05-14

    Enzymes in the oxygen-activating class of mononuclear non-heme iron oxygenases (MNOs) contain a highly conserved iron center facially ligated by two histidine nitrogen atoms and one carboxylate oxygen atom that leave one face of the metal center (three binding sites) open for coordination to cofactor, substrate, and/or dioxygen. A comparative family of [Fe(II/III)(N(2)O(n))(L)(4-n))](±x), n = 1-3, L = solvent or Cl(-), model complexes, based on a ligand series that supports a facially ligated N,N,O core that is then modified to contain either one or two additional carboxylate chelate arms, has been structurally and spectroscopically characterized. EPR studies demonstrate that the high-spin d(5) Fe(III)g = 4.3 signal becomes more symmetrical as the number of carboxylate ligands decreases across the series Fe(N(2)O(3)), Fe(N(2)O(2)), and Fe(N(2)O(1)), reflecting an increase in the E/D strain of these complexes as the number of exchangeable/solvent coordination sites increases, paralleling the enhanced distribution of electronic structures that contribute to the spectral line shape. The observed systematic variations in the Fe(II)-Fe(III) oxidation-reduction potentials illustrate the fundamental influence of differential carboxylate ligation. The trend towards lower reduction potential for the iron center across the [Fe(III)(N(2)O(1))Cl(3)](-), [Fe(III)(N(2)O(2))Cl(2)](-) and [Fe(III)(N(2)O(3))Cl](-) series is consistent with replacement of the chloride anions with the more strongly donating anionic O-donor carboxylate ligands that are expected to stabilize the oxidized ferric state. This electrochemical trend parallels the observed dioxygen sensitivity of the three ferrous complexes (Fe(II)(N(2)O(1)) < Fe(II)(N(2)O(2)) < Fe(II)(N(2)O(3))), which form μ-oxo bridged ferric species upon exposure to air or oxygen atom donor (OAD) molecules. The observed oxygen sensitivity is particularly interesting and discussed in the context of α-ketoglutarate-dependent MNO enzyme

  6. Technique to retrieve solar EUV flux and neutral thermospheric O, O2, N2, and temperature from airglow measurements

    NASA Technical Reports Server (NTRS)

    Fennelly, J. A.; Germany, G. A.; Torr, D. G.; Richards, P. G.; Torr, M. R.

    1994-01-01

    We describe a method for retrieving neutral thermospheric composition and solar EUV flux from optical measurements of the O(+)(P-2) 732 nm and O(D-1) 630 nm airglow emissions. The parameters retrieved are the neutral temperature, the O, L2, and N2 density profiles, and a scaling factor for the solar EUV flux spectrum. The temperature, solar EUV flux scaling factor, and atomic oxygen density are first retrieved from the 732 nm emission, which are then used with the 630 nm emission to retrieve the O2 and N2 densities. Between the altitudes of 200 and 400 km the retrieval technique is able to statistically retrieve values to within 3.1% for thermospheric temperature, 3.3% for atomic oxygen, 2.3% for molecular oxygen, and 2.4% for molecular nitrogen. The solar EUV flux scaling factor has a retrieval error of 5.1%. We also present the results of retrievals using existing data taken from both groundbased and spacebased instruments. These include airglow data taken by the Visible Airglow Experiment on the Atmospheric Explorer spacecraft and the Imaging Spectrometric Observatory flown on the ATLAS 1 shuttle mission in 1992.

  7. Tricrystalline TiO2 with enhanced photocatalytic activity and durability for removing volatile organic compounds from indoor air.

    PubMed

    Chen, Kunyang; Zhu, Lizhong; Yang, Kun

    2015-06-01

    It is important to develop efficient and economic techniques for removing volatile organic compounds (VOCs) in indoor air. Heterogeneous TiO2-based semiconductors are a promising technology for achieving this goal. Anatase/brookite/rutile tricrystalline TiO2 with mesoporous structure was synthesized by a low-temperature hydrothermal route in the presence of HNO3. The obtained samples were characterized by X-ray diffraction and N2 adsorption-desorption isotherm. The photocatalytic activity was evaluated by photocatalytic decomposition of toluene in air under UV light illumination. The results show that tricrystalline TiO2 exhibited higher photocatalytic activity and durability toward gaseous toluene than bicrystalline TiO2, due to the synergistic effects of high surface area, uniform mesoporous structure and junctions among mixed phases. The tricrystalline TiO2 prepared at RHNO3=0.8, containing 80.7% anatase, 15.6% brookite and 3.7% rutile, exhibited the highest photocatalytic activity, about 3.85-fold higher than that of P25. The high activity did not significantly degrade even after five reuse cycles. In conclusion, it is expected that our study regarding gas-phase degradation of toluene over tricrystalline TiO2 will enrich the chemistry of the TiO2-based materials as photocatalysts for environmental remediation and stimulate further research interest on this intriguing topic.

  8. Tricrystalline TiO2 with enhanced photocatalytic activity and durability for removing volatile organic compounds from indoor air.

    PubMed

    Chen, Kunyang; Zhu, Lizhong; Yang, Kun

    2015-06-01

    It is important to develop efficient and economic techniques for removing volatile organic compounds (VOCs) in indoor air. Heterogeneous TiO2-based semiconductors are a promising technology for achieving this goal. Anatase/brookite/rutile tricrystalline TiO2 with mesoporous structure was synthesized by a low-temperature hydrothermal route in the presence of HNO3. The obtained samples were characterized by X-ray diffraction and N2 adsorption-desorption isotherm. The photocatalytic activity was evaluated by photocatalytic decomposition of toluene in air under UV light illumination. The results show that tricrystalline TiO2 exhibited higher photocatalytic activity and durability toward gaseous toluene than bicrystalline TiO2, due to the synergistic effects of high surface area, uniform mesoporous structure and junctions among mixed phases. The tricrystalline TiO2 prepared at RHNO3=0.8, containing 80.7% anatase, 15.6% brookite and 3.7% rutile, exhibited the highest photocatalytic activity, about 3.85-fold higher than that of P25. The high activity did not significantly degrade even after five reuse cycles. In conclusion, it is expected that our study regarding gas-phase degradation of toluene over tricrystalline TiO2 will enrich the chemistry of the TiO2-based materials as photocatalysts for environmental remediation and stimulate further research interest on this intriguing topic. PMID:26040745

  9. Chlorine mobility during annealing in N2 in ZrO2 and HfO2 films grown by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Ferrari, S.; Scarel, G.; Wiemer, C.; Fanciulli, M.

    2002-12-01

    Atomic layer deposition (ALD) growth of high-κ dielectric films (ZrO2 and HfO2) was performed using ZrCl4, HfCl4, and H2O as precursors. In this work, we use time of flight secondary ion mass spectrometry to investigate the chlorine distribution in ALD grown ZrO2 and HfO2 films, and its evolution during rapid thermal processes in nitrogen atmosphere. Chlorine outdiffusion is found to depend strongly upon annealing temperature and weakly upon the annealing time. While in ZrO2 chlorine concentration is significantly decreased already at 900 °C, in HfO2 it is extremely stable, even at temperatures as high as 1050 °C.

  10. Self-, N2-, O2-broadening coefficients and line parameters of HFC-32 for ν7 band and ground state transitions from infrared and microwave spectroscopy

    NASA Astrophysics Data System (ADS)

    Tasinato, Nicola; Turchetto, Arianna; Puzzarini, Cristina; Stoppa, Paolo; Pietropolli Charmet, Andrea; Giorgianni, Santi

    2014-09-01

    Hydrofluorocarbons have been used as replacement gases of chlorofluorocarbons, since the latter have been phased out by the Montreal Protocol due to their environmental hazardous ozone-depleting effects. This is also the case of difluoromethane (CH2F2, HFC-32), which nowadays is widely used in refrigerant mixtures together with CF3CH3, CF3CH2F, and CF3CHF2. Due to its commercial use, in the last years, the atmospheric concentration of HFC-32 has increased significantly. However, this molecule presents strong absorptions within the 8-12 μm atmospheric window, and hence it is a greenhouse gas which contributes to global warming. Although over the years several experimental and theoretical investigations dealt with the spectroscopic properties of CH2F2, up to now pressure broadening coefficients have never been determined. In the present work, the line-by-line parameters of CH2F2 are retrieved for either ground state or ν7 band transitions by means of microwave (MW) and infrared (IR) absorption spectroscopy, respectively. In particular, laboratory experiments are carried out on 9 pure rotational transitions of the ground state and 26 ro-vibrational transitions belonging to the ν7 band lying around 8.2 μm within the atmospheric region. Measurements are carried out at room temperature on self-perturbed CH2F2 as well as on CH2F2 perturbed by N2 and O2. The line shape analysis leads to the first determination of self-, N2-, O2-, and air-broadening coefficients, and also of line intensities (IR). Upon comparison, broadening coefficients of ground state transitions are larger than those of the ν7 band, and no clear dependence on the rotational quantum numbers can be reported. The obtained results represent basic information for the atmospheric modelling of this compound as well as for remote sensing applications.

  11. Synthesis, spectral characterization, molecular modeling and antimicrobial activity of new potentially N2O2 Schiff base complexes

    NASA Astrophysics Data System (ADS)

    Adly, Omima M. I.; Taha, Ali; Fahmy, Shery A.

    2013-12-01

    Metal complexes of a new potentially tetradentate symmetrical Schiff base ligand (H2L) with Cu(II), Ni(II), Co(II), VO(IV), Zn(II), Cd(II), Ce(III), Fe(III) and UO2(VI) metal ions have been synthesized and characterized based on their elemental analyses, spectral (IR, UV-Vis, 1H NMR and mass spectra), magnetic and molar conductance studies as well as thermal gravimetric analysis (TGA). The synthesized complexes have the general formula [MHxL(H2O)yXn]: x = 0-1, y = 0-4 and n = 0-1; where: L = dianion of 6-hydroxy-5-[N-(2-{[(1E)-1-(6-hydroxy-2,4-dioxo-3,4-dihydro-2H-1,3-thiazin-5-yl)ethylidene]amino}ethyl) ethanimidoyl]-2H-1,3-thiazine-2,4(3H)-dione and X = nitrate or sulphate anion. The ligand behaves as diabasic tetradentate N2O2 sites, except in cases of Co(II), VO(IV) and UO2(VI) metal ions, it behaves as monobasic tetradentate Schiff base ligand. The metal complexes exhibited square planar, square-pyramidal and octahedral geometrical arrangements except for Ce(III) and UO2(VI) complexes, they are octa-coordinated. The Coats-Redfern equation was used to calculate the kinetic and thermodynamic parameters for the different thermal decomposition stages of some complexes. Structural parameters of the ligand and its metal complexes have been theoretically computed on the basis of semiemperical PM3 level, and the results were correlated with their experimental data. The antimicrobial activities of the ligand and its metal complexes were tested against some Gram-positive and Gram-negative bacteria; and fungus strain and the results were discussed.

  12. Transport properties of SF_{6}^{-} in SF6-Ne, SF6-N2 and SF6-O2 mixtures

    NASA Astrophysics Data System (ADS)

    Benhenni, M.; Yousfi, M.; de Urquijo, J.; Hennad, A.

    2009-06-01

    The mobility of SF_{6}^{-} has been calculated for the gas mixtures SF6-Ne, SF6-N2 and SF6-O2 using an optimized Monte Carlo code for the ion transport simulation in a drift tube. The elastic momentum transfer collision cross sections needed for the calculation were determined from a semi-classical JWKB approximation, while the inelastic ones (detachment, dissociative charge transfer and SF_{6}^{-} conversion to SF_{5}^{-} and F-) were taken from the literature for the case of the SF_{6}^{-}/Ne collision system. The resulting sets of collision cross sections were validated by comparing the SF_{6}^{-} calculated mobilities with those measured in the above mixtures with a time-resolved pulsed Townsend technique. The SF_{6}^{-} longitudinal and transverse density-normalized diffusion coefficients were calculated for these mixtures for the case where the share of SF6 in the mixture was 50%. Finally, the validity of Blanc's law was discussed at low and high electric fields, whereby we show that it fails at high fields, where inelastic processes are dominant.

  13. Structural and functional mimic of galactose oxidase by a copper complex of a sterically demanding [N2O2] ligand.

    PubMed

    John, Alex; Shaikh, Mobin M; Ghosh, Prasenjit

    2008-06-01

    A structural and functional mimic of the galactose oxidase (GOase) enzyme active-site by a copper complex supported over a sterically demanding ligand having [N2O2] donor sites is reported. Specifically, the binding of the histidine (496 and 581) and tyrosine (272 and 495) residues to the copper center in a square-pyramidal fashion in the active-site of galactose oxidase (GOase) enzyme has been modeled in a copper complex, ([(3-tert-butyl-5-methyl-2-hydoxybenzyl)(3'-tert-butyl-5'-methyl-2'-oxobenzyl)(2-pyridylmethyl)]amine)Cu(OAc)) (1b), stabilized over a sterically demanding ligand in which the two phenolate-O atoms mimicked the tyrosine binding while an amine-N and pyridyl-N atoms emulated the histidine binding to the metal center, similar to that in the enzyme active-site. Furthermore, the copper complex 1b is found to be an effective functional model of the enzyme as it efficiently catalyzed the chemoselective oxidation of primary alcohols to aldehydes in high turnover numbers under ambient conditions. An insight into the nature of the active-species was obtained by EPR and CV studies, which in conjunction with the DFT studies, revealed that the active-species is an anti-ferromagnetically coupled diamagnetic radical cation, (1)1b+, obtained by one electron oxidation at the equatorial phenolate-O atom of the ligand in the 1b complex.

  14. Effects of H2O, CO2, and N2 air contaminants on critical airside strain rates for extinction of hydrogen-air counterflow diffusion flames

    NASA Technical Reports Server (NTRS)

    Pellett, G. L.; Northam, G. B.; Wilson, L. G.; Guerra, Rosemary

    1989-01-01

    Dish-shaped counterflow diffusion flames centered by opposing laminar jets of H2 and clean and contaminant O2/N2 mixtures in an argon bath at 1 atm were used to study the effects of contaminants on critical airside strain. The jet velocities for both flame extinction and restoration are found for a wide range of contaminant and O2 concentrations in the air jet. The tests are also conducted for a variety of input H2 concentrations. The results are compared with those from several other studies.

  15. Novel chemical vapor deposition process of ZnO films using nonequilibrium N2 plasma generated near atmospheric pressure with small amount of O2 below 1%

    NASA Astrophysics Data System (ADS)

    Nose, Yukinori; Yoshimura, Takeshi; Ashida, Atsushi; Uehara, Tsuyoshi; Fujimura, Norifumi

    2016-05-01

    We propose a novel chemical vapor deposition (CVD) process of ZnO films involving a nonequilibrium N2 plasma generated near atmospheric pressure with small O2 concentration (O2%) below 1%. In the optical emission (OE) spectra of the plasma, OE lines corresponding to the NO-γ system ( A 2 Σ + → X 2 Πγ + ) were observed, despite the only introduced gases being N2 and O2; these vanish at an O2% of more than 1%. ZnO films were grown on a glass substrate placed in the plasma at a growth temperature of as low as 200 °C and at an O2% of below 1% in the presence of the NO-γ system. This plasma yielded almost the same growth rate for ZnO films as O2 plasma including atomic O radicals that are often observed in low-pressure O2 plasma, suggesting that some highly reactive oxidant was sufficiently generated in such a small O2%. ZnO films synthesized using this plasma exhibited excellent ( 0001 ) preferred orientation without other diffractions such as 10 1 ¯ 1 diffraction, and with an optical bandgap of 3.30 eV. Based on the analyses of the plasma and the exhaust gases, the coexistence state of NO-γ and O3 should be essential and useful for the decomposition and oxidation of Zn source material in the proposed CVD process.

  16. A SnO2-Based Cathode Catalyst for Lithium-Air Batteries.

    PubMed

    Mei, Delong; Yuan, Xianxia; Ma, Zhong; Wei, Ping; Yu, Xuebin; Yang, Jun; Ma, Zi-Feng

    2016-05-25

    SnO2 and SnO2@C have been successfully synthesized with a simple hydrothermal procedure combined with heat treatment, and their performance as cathode catalysts of Li-air batteries has been comparatively evaluated and discussed. The results show that both SnO2 and SnO2@C are capable of catalyzing oxygen reduction reactions (ORR) and oxygen evolution reactions (OER) at the cathode of Li-air batteries, but the battery with SnO2@C displays better performance due to its unique higher conductivity, larger surface area, complex pore distribution, and huge internal space. PMID:27152996

  17. Heterogeneous interaction of SiO2 with N2O5: single particle optical levitation-Raman spectroscopy and aerosol flow tube studies

    NASA Astrophysics Data System (ADS)

    Tang, Mingjin; Camp, Jules; Cox, Tony; Kalberer, Markus; McGregor, James; Rkiouak, Laylla; Ward, Andy; Watson, Matt; Pope, Francis

    2014-05-01

    The heterogeneous reaction of SiO2 with N2O5 was investigated at room temperature and different relative humidities (RH). The uptake coefficient of N2O5 onto airborne sub-micrometre SiO2 particles, γ(N2O5), was measured using an atmospheric-pressure aerosol flow tube. γ(N2O5) was measured to be (4.8±0.4)×10-3 at 7% RH and (3.5±0.5)×10-3 at 40%, probably suggesting a slightly negative dependence on RH. In contrast, Raman spectroscopy measurements of the singles particles during the exposure to N2O5 show that the amount of nitrate formed on the particles increases with RH, and that nitrate formed on the particles can be entirely removed when the RH is reduced to 0%. The results suggest that nitric acid formed in the heterogeneous hydrolysis of N2O5 on the SiO2 surface can partition in both the gas phase and particulate phase, and the RH determines the partitioning. The atmospheric implications for photochemistry and aerosol aging processes will also be discussed.

  18. Carbon-based air electrodes carrying MnO 2 in zinc-air batteries

    NASA Astrophysics Data System (ADS)

    Wei, Zidong; Huang, Wenzhang; Zhang, Shengtao; Tan, Jun

    Catalysts prepared from the carbon black impregnated with manganous nitrate solution and then heated at temperature from 270°C to 450°C were investigated. It was found that the impregnated catalysts heated at temperature of 340°C exhibited the best catalytic activity for oxygen reduction in alkaline electrolyte. It was also found that the XRD spectra of pyrolytic MnO 2 from manganous nitrate over 340°C were different from those below 340°C. The enhanced catalysis of air electrodes was ascribed to the formation of MnO 2 crystal with d-value of 2.72 Å as the impregnated-catalysts was heated at temperature of 340°C. The other factors in preparation of air electrodes were also discussed.

  19. Opposed jet burner studies of effects of CO, CO2, and N2 air-contaminants on hydrogen-air diffusion flames

    NASA Technical Reports Server (NTRS)

    Guerra, Rosemary; Pellett, Gerald L.; Northam, G. Burton; Wilson, Lloyd G.

    1987-01-01

    The blowoff/restore characteristics for jets of various H2/N2 mixtures opposed to jets of air contaminated by N2, CO, and CO2 have been determined using a counterflow diffusion flame formed by a tubular opposed jet burner. Both blowoff and restore limits are found to be sensitive to fuel and air composition. Empirically derived variations in the limits of the average mass flux of incoming H2 with percent contaminant, at fixed incoming fuel and H2/O2 inputs, are used to quantify the effects of oxygen dilution, flame augmentation, and flame retardation by N2, CO, and CO2 contaminants. The implications of the results are discussed.

  20. Heterogeneous reaction of N2O5 with airborne TiO2 particles and the implication for stratospheric particle injection

    NASA Astrophysics Data System (ADS)

    Tang, Mingjin; Abraham, Luke; Braesicke, Peter; Cox, Tony; McGregor, James; Pope, Francis; Pyle, John; Rkiouak, Laylla; Telford, Paul; Watson, Matt; Kalberer, Markus

    2014-05-01

    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 (SRM) scheme for the mitigation for global warming. TiO2 has recently been highlighted as a possible candidate aerosol because of its high light scattering ability with a refractive index of 2.5 (Pope et al. 2012). The impact of particles injection on stratospheric ozone requires systematical assessment via laboratory and modelling studies. In this work, the heterogeneous reaction of airborne sub-micrometre TiO2 particles with N2O5 has been investigated 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, and increase to ~3×10-3 at 60% RH. The dependence of γ(N2O5) on RH can be explained by the water adsorption isotherm of TiO2 particles. In addition, the uptake of N2O5 onto TiO2 aerosol particles has been included in the UKCA chemistry-climate model to assess the effect of N2O5 uptake onto TiO2 particles on the stratospheric composition. We construct a case study based on the eruption of Mt. Pinatubo, comparing the effects of TiO2 to those from the volcanic sulfate and to the situation with only background amount of aerosol. The changes in reactive nitrogen species and ozone due to the heterogeneous reaction of TiO2 with N2O5 are assessed relative to sulfate aerosol impacts. Pope, F. D., Braesicke, P., Grainger, R. G., Kalberer, M., Watson, I. M., Davidson, P. J., and Cox, R. A.: Stratospheric aerosol particles and solar-radiation management, Nature Clim. Change, 2, 713-719, 2012

  1. Synthesis and Characterization of Bimetallic Ni50Pt50 Catalyst Supported on SiO2 for N2O Decomposition.

    PubMed

    Angeles-Pascual, A; Esparza, R; Tellez-Vazquez, O; Velumani, S; Pérez, R

    2015-12-01

    Nanometallic and bimetallic catalyst of Ni, Pt and Ni50Pt50 were studied by the decompositions of N2O. The catalyst were prepared by incipient wetness impregnation of the silica with low superficial area of 50 m2/g supported with aqueous solution of the metal precursors, for Pt H2Pt Cl6 x 6H2O was used and for Ni, Ni(NO3)2 was used to a total metal loading of 1% wt. Catalyst were oxidized for 2 hours at 400 degrees C with O2, then the samples were reduced for 30 minutes with N2 and 2 hours with H2, all at the same temperature. The catalyst was characterized by Transmission Electron Microscopy (TEM), High Angular Annular Dark Field (HAADF), High Resolution Transmission Electron Microscopy (HR-TEM) and Termoprogramed Reduction (TPR). The mean particle sizes obtained by TEM and HAADF were about 12.5 nm for Ni/SiO2, 2.8 nm for Pt/SiO2 and 3.5 nm Ni50Pt50/SiO2 catalysts respectability. HR-TEM and HAADF analysis showed differences between Ni and Pt catalysts displaying mainly cuboctahedral shapes. Stepped surface defects were found in the Ni50Pt50/SiO2 catalyst. Finally Ni50Pt50/SiO2 was more active than Pt/SiO2 and Ni/SiO2 catalysts for the decomposition of N2O. PMID:26682368

  2. Rat calvaria osteoblast behavior and antibacterial properties of O(2) and N(2) plasma-implanted biodegradable poly(butylene succinate).

    PubMed

    Wang, Huaiyu; Ji, Junhui; Zhang, Wei; Wang, Wei; Zhang, Yihe; Wu, Zhengwei; Zhang, Yumei; Chu, Paul K

    2010-01-01

    Poly(butylene succinate), a novel biodegradable aliphatic polyester with excellent processability and mechanical properties, was modified by O(2) or N(2) plasma immersion ion implantation (PIII). X-ray photoelectron spectroscopy and contact angle measurements were carried out to reveal the surface characteristics of the treated and control specimens. The in vitro effects of the materials on seeded osteoblasts were detected by cell viability assay, alkaline phosphatase activity test, and real-time polymerase chain reaction analysis. Plate counting was performed to investigate the antibacterial properties. Our results show that both PIII treatments significantly improve the hydrophilicity of PBSu, and CO and nitrogen groups (CNH and CNH(2)) can be detected on the PBSu after O(2) and N(2) PIII, respectively. The modified samples exhibit similar compatibility to osteoblasts, which is better than that of the control, but O(2) PIII and N(2) PIII produce different effects according to the osteogenic gene expressions of seeded osteoblasts on the materials. Moreover, the N(2) plasma-modified PBSu exhibits anti-infection effects against Staphylococcus aureus and Escherichia coli but no such effects can be achieved after O(2) PIII.

  3. Sediment-water fluxes of dissolved inorganic carbon, O2,nutrients, and N2 from the hypoxic region of the Louisianacontinental shelf

    EPA Science Inventory

    Sediment fluxes of dissolved inorganic carbon (DIC), O2, nutrients, and N2 (denitrification) were measured on the Louisiana Continental Shelf during six cruises from 2005 to 2007. On each cruise, three to seven stations were occupied in regions of the shelf that experience summer...

  4. Simultaneous and time-resolved temperature and relative CO2-N2 and O2-CO2-N2 concentration measurements with pure rotational coherent anti-Stokes Raman scattering for pressures as great as 5 MPa

    SciTech Connect

    Schenk, Martin; Seeger, Thomas; Leipertz, Alfred

    2005-09-10

    Pure rotational coherent anti-Stokes Raman-scattering (CARS) measurements have been performed in binary CO2-N2 and ternary CO2-O2-N2 mixtures in a temperature range between 300 and 773 K and pressures from 0.1 to 5 MPa to prove its potential for simultaneous single-shot thermometry and multispecies concentration measurements. In pressurized systems the CO2 component has a strong spectral influence on the pure rotational CARS spectra. Because of this dominance, pure rotational CARS proves to be a sensitive tool to measure in high-pressure combustion systems and the relative CO2-N2 concentration in the lower temperature range simultaneously with the temperature and the relative O2-N2 concentration. The evaluation of the spectra utilized a least-sum-squared differences fit of the spectral shape, weighted either constantly or inversely with respect to the normalized signal intensity. The results of the simultaneous temperature and relative CO2-N2 and O2-CO2-N2 concentration measurements provided a good accuracy and precision both in temperature and in concentrations. Because of the strong increase in the relative spectral contribution of CO2 with rising pressure, the precision of the CO2 concentration determination is in general significantly improved toward higher pressures, thus also clearly enhancing the CO2 detectability. The influence of temperature, O2 and CO2 concentration, pressure, and the evaluation techniques employed on both the accuracy and the precision is explained as well as their cross dependencies. The influence and limitations of the approximations used to model the CO2 molecule are discussed.

  5. 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. PMID:25188692

  6. 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.

  7. CO 2 and O 2/N 2 variations in and just below the bubble-clathrate transformation zone of Antarctic ice cores

    NASA Astrophysics Data System (ADS)

    Lüthi, Dieter; Bereiter, Bernhard; Stauffer, Bernhard; Winkler, Renato; Schwander, Jakob; Kindler, Philippe; Leuenberger, Markus; Kipfstuhl, Sepp; Capron, Emilie; Landais, Amaelle; Fischer, Hubertus; Stocker, Thomas F.

    2010-08-01

    CO 2 measurements on the EPICA (European Project for Ice Coring in Antarctica) DML ice core in depth levels just below the bubble ice-clathrate ice transformation zone (1230-2240 m depth) were performed. In the youngest part (1230-1600 m), they reveal variations of up to 25 ppmv around the mean atmospheric concentration within centimetres, corresponding to a snow deposition interval of a few years. Similar results are found at corresponding depth regions of the Dome C and the Talos Dome ice cores. Since we can exclude all hitherto known processes altering the concentration of CO 2 in ice cores, we present a hypothesis about spatial fractionation of air components related to episodically increasing clathrate formation followed by diffusion processes from bubbles to clathrates. This hypothesis is supported by optical line-scan observations and by O 2/N 2 measurements at the same depth where strong CO 2 variations are detected. Below the clathrate formation zone, this small-scale fractionation process is slowly smoothed out, most likely by diffusion, regaining the initial mean atmospheric concentration. Although this process compromises the representativeness of a single CO 2 measurement on small ice samples in the clathrate formation zone of an ice core, it does not affect the mean atmospheric CO 2 concentration if CO 2 values are averaged over a sufficiently long depth scale (> 10 cm in case of the EPICA DML ice core).

  8. Oxygen Selective Membranes for Li-Air (O2) Batteries

    PubMed Central

    Crowther, Owen; Salomon, Mark

    2012-01-01

    Lithium-air (Li-air) batteries have a much higher theoretical energy density than conventional lithium batteries and other metal air batteries, so they are being developed for applications that require long life. Water vapor from air must be prevented from corroding the lithium (Li) metal negative electrode during discharge under ambient conditions, i.e., in humid air. One method of protecting the Li metal from corrosion is to use an oxygen selective membrane (OSM) that allows oxygen into the cell while stopping or slowing the ingress of water vapor. The desired properties and some potential materials for OSMs for Li-air batteries are discussed and the literature is reviewed. PMID:24958173

  9. Collisional Removal of O2 (c(sup 1) Sigma(sup-)(sub u), nu=9) by O2, N2, and He

    NASA Technical Reports Server (NTRS)

    Copeland, Richard A.; Knutsen, Karen; Onishi, Marc E.; Yalcin, Talat

    1996-01-01

    The collisional removal Of 02 molecules in selected vibrational levels of the c state is studied using a two-laser double-resonance technique. The output of the first laser excites the 02 to nu = 9 or 10 of the c Sigma - state, and the ultraviolet output of the second laser monitors specific rovibrational levels via resonance-enhanced ionization. The temporal evolution of the c Sigma u state vibrational level is observed by scanning the time delay between the two pulsed lasers. As the rate constants for 02 and N2 are similar in magnitude, N2 collisions dominate the removal rate in the earth's atmosphere. For v= 10 colliding with 02, we find a removal rate constant that is 2-5 times that for v=9 and that single quantum collision cascade is an important pathway for removal.

  10. Inactivation factors of spore-forming bacteria using low-pressure microwave plasmas in an N2 and O2 gas mixture

    NASA Astrophysics Data System (ADS)

    Singh, M. K.; Ogino, A.; Nagatsu, M.

    2009-11-01

    In this study, we investigated the inactivation characteristics of Geobacillus stearothermophilus spores under different plasma exposure conditions using low-pressure microwave plasma in nitrogen, oxygen and an air-simulated (N2:O2=4:1) gas mixture. The microwave-excited surface-wave plasma discharges were produced at low pressure by a large volume device. The directly plasma-exposed spores, up to 106 populations, were successfully inactivated within 15, 10 and 5 min of surface-wave plasma treatment using nitrogen, oxygen and an air-simulated gas mixture, respectively, as working gases within the temperature of 75 °C. The contribution of different inactivation factors was evaluated by placing different filters (e.g. a LiF plate, a quartz plate and a Tyvek® sheet) as indirect exposure of spores to the plasma. It was observed that optical emissions (including vacuum UV (VUV)/UV) play an important role in the inactivation process. To further evaluate the effect of VUV/UV photons, we placed an evacuated isolated chamber, inside which spores were set, into the main plasma chamber. The experimental results show that the inactivation time by VUV/UV photons alone, without working gas in the immediate vicinity of the spores, is longer than that with working gas. This suggests that the VUV/UV emission is responsible not only for direct UV inactivation of spores but also for generation of reactive neutral species by photoexcitation. The scanning electron microscopy images revealed significant changes in the morphology of directly plasma-exposed spores but no change in the spores irradiated by VUV/UV photons only.

  11. Phase stability and magnetic behavior of hexagonal phase of N2-O2 system with kagome lattice under high pressure and low temperature

    NASA Astrophysics Data System (ADS)

    Akahama, Y.; Ishihara, D.; Yamashita, H.; Fujihisa, H.; Hirao, N.; Ohishi, Y.

    2016-08-01

    The pressure-temperature (P -T ) phase diagram of N2-O2 mixture with a composition of N2-48 mol % O2 has been investigated using x-ray diffraction and the phase stability of a hexagonal phase (space group: P 6 /mmm), with the kagome lattice examined under high-pressure and low-temperature conditions. While the phase appears as a low-temperature phase of the cubic phase (P m 3 n ) with the structure of γ -O2 or δ -N2 and is stable in a wide range of pressures and temperatures, it transforms to lower symmetry monoclinic or orthorhombic phases at lower temperature, accompanied with a distortion of the kagome lattice. Based on Rietveld refinements, the monoclinic and orthorhombic phases are found to be in the P 21/a and Cmmm space groups, respectively. In magnetization measurements, a magnetic transition is observed with a relatively large drop of magnetization, corresponding to the cubic-to-hexagonal phase transition. This suggests that the hexagonal phase has a certain magnetic ordered state that arises from the molecular magnetic moment of O2.

  12. The 2140 cm-1 (4.673 microns) solid CO band: the case for interstellar O2 and N2 and the photochemistry of nonpolar interstellar ice analogs.

    PubMed

    Elsila, J; Allamandola, L J; Sandford, S A

    1997-04-20

    The infrared spectra of CO frozen in nonpolar ices containing N2, CO2, O2, and H2O and the UV photochemistry of these interstellar/precometary ice analogs are reported. The spectra are used to test the hypothesis that the narrow 2140 cm-1 (4.673 microns) interstellar absorption feature attributed to solid CO might be produced by CO frozen in ices containing nonpolar species such as N2 and O2. It is shown that mixed molecular ices containing CO, N2, O2, and CO2 provide a good match to the interstellar band at all temperatures between 12 and 30 K both before and after photolysis. The optical constants (real and imaginary parts of the index of refraction) in the region of the solid CO feature are reported for several of these ices. The N2 and O2 absorptions at 2328 cm-1 (4.296 microns) and 1549 cm-1 (6.456 microns), respectively, are also shown. The best matches between the narrow interstellar band and the feature in the laboratory spectra of nonpolar ices are for samples which contain comparable amounts of N2, O2, CO2, and CO. Co-adding the CO band from an N2:O2:CO2:CO = 1:5:1/2:1 ice with that of an H2O:CO = 20:1 ice provides an excellent fit across the entire interstellar CO feature. The four-component, nonpolar ice accounts for the narrow 2140 cm-1 portion of the feature which is associated with quiescent regions of dense molecular clouds. Using this mixture, and applying the most recent cosmic abundance values, we derive that between 15% and 70% of the available interstellar N is in the form of frozen N2 along several lines of sight toward background stars. This is reduced to a range of 1%-30% for embedded objects with lines of sight more dominated by warmer grains. The cosmic abundance of O tied up in frozen O2 lies in the 10%-45% range toward background sources, and it is between 1% and 20% toward embedded objects. The amount of oxygen tied up in CO and CO2 frozen in nonpolar ices can be as much as 2%-10% toward background sources and on the order of 0

  13. The 2140 cm-1 (4.673 microns) solid CO band: the case for interstellar O2 and N2 and the photochemistry of nonpolar interstellar ice analogs

    NASA Technical Reports Server (NTRS)

    Elsila, J.; Allamandola, L. J.; Sandford, S. A.

    1997-01-01

    The infrared spectra of CO frozen in nonpolar ices containing N2, CO2, O2, and H2O and the UV photochemistry of these interstellar/precometary ice analogs are reported. The spectra are used to test the hypothesis that the narrow 2140 cm-1 (4.673 microns) interstellar absorption feature attributed to solid CO might be produced by CO frozen in ices containing nonpolar species such as N2 and O2. It is shown that mixed molecular ices containing CO, N2, O2, and CO2 provide a good match to the interstellar band at all temperatures between 12 and 30 K both before and after photolysis. The optical constants (real and imaginary parts of the index of refraction) in the region of the solid CO feature are reported for several of these ices. The N2 and O2 absorptions at 2328 cm-1 (4.296 microns) and 1549 cm-1 (6.456 microns), respectively, are also shown. The best matches between the narrow interstellar band and the feature in the laboratory spectra of nonpolar ices are for samples which contain comparable amounts of N2, O2, CO2, and CO. Co-adding the CO band from an N2:O2:CO2:CO = 1:5:1/2:1 ice with that of an H2O:CO = 20:1 ice provides an excellent fit across the entire interstellar CO feature. The four-component, nonpolar ice accounts for the narrow 2140 cm-1 portion of the feature which is associated with quiescent regions of dense molecular clouds. Using this mixture, and applying the most recent cosmic abundance values, we derive that between 15% and 70% of the available interstellar N is in the form of frozen N2 along several lines of sight toward background stars. This is reduced to a range of 1%-30% for embedded objects with lines of sight more dominated by warmer grains. The cosmic abundance of O tied up in frozen O2 lies in the 10%-45% range toward background sources, and it is between 1% and 20% toward embedded objects. The amount of oxygen tied up in CO and CO2 frozen in nonpolar ices can be as much as 2%-10% toward background sources and on the order of 0

  14. Inactivation of Gram-Negative Bacteria by Low-Pressure RF Remote Plasma Excited in N2-O2 Mixture and SF6 Gases

    PubMed Central

    Al-Mariri, Ayman; Saloum, Saker; Mrad, Omar; Swied, Ghayath; Alkhaled, Bashar

    2013-01-01

    The role of low-pressure RF plasma in the inactivation of Escherichia coli O157, Klebsiella pneumoniae, Proteus mirabilis, and Enterobacter sakazakii using N2-O2 and SF6 gases was assessed. 1×109 colony-forming units (CFUs) of each bacterial isolate were placed on three polymer foils. The effects of pressure, power, distance from the source, and exposure time to plasma gases were optimized. The best conditions to inactivate the four bacteria were a 91%N2-9%O2 mixture and a 30-minute exposure time. SF6 gas was more efficient for all the tested isolates in as much as the treatment time was reduced to only three minutes. Therefore, low-pressure plasma could be used to sterilize heat and/or moisture-sensitive medical instruments. PMID:24293788

  15. Variable temperature pressure broadening of the 4(1,4)-3(2,1) transition of H2O by O2 and N2

    NASA Technical Reports Server (NTRS)

    Goyette, Thomas M.; Delucia, Frank C.; Dutta, J. M.; Jones, C. R.

    1993-01-01

    The O2 and N2 pressure-broadening parameters of the 4(1,4)-3(2,1) rotational transition in the ground vibrational state of H2O have been measured in the temperature range between 100 and 520 K. Above 250 K the measurements were made in an equilibrium cell. Below 250 K a cell, which uses collisional cooling to circumvent the temperature limits imposed by the vapor pressure of the sample gas, was used. The data were fitted to an exponential temperature-dependence for data above 150 K with resultant n values of 0.81(3) for O2 and 0.70(3) for N2, where the entries in parentheses represent the error in the last significant figure of the parameter. Below 150 K the measured pressure-broadening parameters are smaller than those calculated using these values of n.

  16. Theoretical study of CO and O2 adsorption and CO oxidation on linear-shape gold molecules (LGMn) (n=2, 4, 8, 16, and 24)

    NASA Astrophysics Data System (ADS)

    Ohkawa, Tetsuya; Kuramoto, Kei

    2016-09-01

    Density functional theory is used to study the effect of increase of the number of Au atom in the adsorption of CO and O2 as well as CO oxidation on anionic, neutral, and cationic Linear-shape Gold Molecules (LGMn) (n=2, 4, 8, 16, and 24). The more the number of Au atom increases, the more the adsorption energies of CO lower and larger in the cationic and anionic LGMnCO complexes, respectively. In contrast, the adsorption energies of both CO and O2 on neutral LGMn exhibit approximately constant values. There are little differences of both adsorption energies and net charge of CO and O2 on the number of Au atom in LGM regardless of each charge state. This indicates that the charge state of LGM plays a less important role for the adsorption of CO and O2 with increase of the number of Au atom in LGM. The trend of the overall activation energies of reaction pathway is switched between LGM-14 and LGM-18 with increase of the number of Au atom in LGM, and OC-OO intermediate of the initial state in n-1LGM (n=8, 16, and 24) are unstable compared to the separated reactants (LGMn, CO, O2). These are caused by the values of charge of O2 of OC-OO intermediate.

  17. Tuning the afterglow plasma composition in Ar/N2/O2 mixtures: characteristics of a flowing surface-wave microwave discharge system

    NASA Astrophysics Data System (ADS)

    Kutasi, Kinga; Noël, Cédric; Belmonte, Thierry; Guerra, Vasco

    2016-10-01

    A self-consistent kinetic model is used to study the possibility of tuning the plasma composition in the afterglow of a flowing surface-wave microwave discharge by the different discharge and system parameters in the case of 90%Ar-10%(N2-O2) and N2-O2 mixtures. The afterglow system consists of a 0.5 cm diameter quartz tube of 50 cm in length—where the discharge is generated and the early-afterglow develops—and an afterglow reactor. The plasma composition is studied at the end of the discharge plasma column and at the reactor inlet as a function of the N2:O2 ratio for selected conditions, which are set with the system parameters and are illustrated in the experimental set-up. The validity of the model used is proven by the agreement of the calculated atomic densities with those measured by mass spectrometry. Due to the pressure drop along the tube, the position of the discharge (which also defines the lengths of the early-afterglow, t aft) and the discharge pressure (p dis) can be set with the position of the wave coupler—surfatron—along the tube at a constant gas flow rate (which defines the pressure in the reactor, p reac). It is shown that the relative densities of species at the end of plasma column, which constitute the initial condition for the afterglow, depend on the discharge pressure. Therefore, at a constant gas flow rate with the position of the surfatron the plasma composition in the reactor is changing due to the variation of both the p dis and t aft. The evolution of the plasma composition is also studied when both the surfatron’s position and the gas flow rate are changed, realizing conditions (i) with the same p dis, and different t aft and p reac, and (ii) with the same t aft, and different p dis and p reac. Comparing the N2-O2 binary and the ternary mixtures, it is shown that the atomic densities obtained in the binary mixtures can be reproduced in ternary mixtures with different N2:O2 ratios. Furthermore, according to the spectra

  18. Differential cross sections for scattering of 0.5-, 1.5-, and 5.0 keV oxygen atoms by He, N2, and O2

    NASA Technical Reports Server (NTRS)

    Schafer, D. A.; Newman, J. H.; Smith, K. A.; Stebbings, R. F.

    1987-01-01

    This paper reports measurements of absolute scattering cross sections, differential in angle, for collisions of ground-state oxygen atoms with He, N2, and O2. Data are presented for scattering of 0.5-, 1.5-, and 5.0-keV oxygen-atom projectiles in the range of laboratory frame angles between 0.06 and 5 deg. These measurements provide information relevant to calculations of the aeronomic consequences of O(+) precipitation in the earth's upper atmosphere.

  19. Performance of MnO2 Crystallographic Phases in Rechargeable Lithium-Air Oxygen Cathode

    NASA Astrophysics Data System (ADS)

    Oloniyo, Olubukun; Kumar, Senthil; Scott, Keith

    2012-05-01

    Manganese dioxide (MnO2) has been shown to be effective for improving the efficiency of cathodes in lithium-air cells. Different crystallographic phases including α-, β-, and γ-MnO2 nanowires, α-MnO2 nanospheres, and α-MnO2 nanowires on carbon ( α-MnO2/C) were synthesized using the hydrothermal method. Their physical properties were examined using x-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area measurements, and scanning electron microscopy (SEM) and found to be in agreement with the literature. Electrochemical properties of the synthesized catalyst particles were investigated by fabricating cathodes and testing them in a lithium-air cell with lithium hexafluorophosphate in propylene carbonate (LiPF6/PC) and tetra(ethylene glycol)dimethyl ether (LiTFSi/TEGDME) electrolytes. α-MnO2 had the highest discharge capacity in the LiTFSi/TEGDME electrolyte (2500 mAh/g), whilst α-MnO2/C in LiPF6/PC showed a significantly higher discharge capacity of 11,000 mAh/g based on total mass of the catalytic cathode. However, the latter showed poor capacity retention compared with γ-MnO2 nanowires, which was stable for up to 30 cycles. The reported discharge capacity is higher than recorded in previous studies on lithium-air cells.

  20. Electron Transport Coefficients and Effective Ionization Coefficients in SF6-O2 and SF6-Air Mixtures Using Boltzmann Analysis

    NASA Astrophysics Data System (ADS)

    Wei, Linsheng; Xu, Min; Yuan, Dingkun; Zhang, Yafang; Hu, Zhaoji; Tan, Zhihong

    2014-10-01

    The electron drift velocity, electron energy distribution function (EEDF), density-normalized effective ionization coefficient and density-normalized longitudinal diffusion velocity are calculated in SF6-O2 and SF6-Air mixtures. The experimental results from a pulsed Townsend discharge are plotted for comparison with the numerical results. The reduced field strength varies from 40 Td to 500 Td (1 Townsend=10-17 V·cm2) and the SF6 concentration ranges from 10% to 100%. A Boltzmann equation associated with the two-term spherical harmonic expansion approximation is utilized to gain the swarm parameters in steady-state Townsend. Results show that the accuracy of the Boltzmann solution with a two-term expansion in calculating the electron drift velocity, electron energy distribution function, and density-normalized effective ionization coefficient is acceptable. The effective ionization coefficient presents a distinct relationship with the SF6 content in the mixtures. Moreover, the E/Ncr values in SF6-Air mixtures are higher than those in SF6-O2 mixtures and the calculated value E/Ncr in SF6-O2 and SF6-Air mixtures is lower than the measured value in SF6-N2. Parametric studies conducted on these parameters using the Boltzmann analysis offer substantial insight into the plasma physics, as well as a basis to explore the ozone generation process.

  1. Low-Temperature Desorption of N2O from NO on Rutile TiO2(110)-1x1

    SciTech Connect

    Kim, Boseong; Li, Zhenjun; Kay, Bruce D.; Dohnalek, Zdenek; Kim, Yu Kwon

    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, the 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.

  2. Photoinduced interaction studies on N-(2-methylthiophenyl)-2-hydroxy-1-naphthadiamine with TiO2 nanoparticles: A combined experimental and theoretical (DFT and spectroscopic) approach

    NASA Astrophysics Data System (ADS)

    Pushpam, S.; Gayathri, S.; Ramakrishnan, V.

    2014-12-01

    Schiff base derivative synthesized by the reaction of 2-(methylthio) aniline and 2-hydroxy-1-naphthaldehyde exhibits keto-amine tautomerism in methanol solvent. The fluorescence quenching of N-(2-methyl thiophenyl)-2-hydroxy-1-naphthadiamine (NMTHN) by TiO2 nanoparticles in methanol has been studied. The excitation and emission peaks have been observed at 439 and 509 nm respectively. The apparent association constant has been deduced from the absorption spectral changes of NMTHN-TiO2 nanoparticles using Bensi-Hildebrand equation. The number of binding sites and the binding constant have been calculated from the relevant fluorescence data. Quenching of fluorescence of NMTHN by TiO2 could be due to a dynamic mode. Density Functional Theory (DFT) calculations also have been performed to study the charge distribution of NMTHN-TiO2 both in ground and excited states. The HOMO-LUMO analysis of NMTHN-TiO2 in the ground state has been made.

  3. Prevalence of Bimolecular Routes in the Activation of Diatomic Molecules with Strong Chemical Bonds (O2, NO, CO, N2) on Catalytic Surfaces.

    PubMed

    Hibbitts, David; Iglesia, Enrique

    2015-05-19

    Dissociation of the strong bonds in O2, NO, CO, and N2 often involves large activation barriers on low-index planes of metal particles used as catalysts. These kinetic hurdles reflect the noble nature of some metals (O2 activation on Au), the high coverages of co-reactants (O2 activation during CO oxidation on Pt), or the strength of the chemical bonds (NO on Pt, CO and N2 on Ru). High barriers for direct dissociations from density functional theory (DFT) have led to a consensus that "defects", consisting of low-coordination exposed atoms, are required to cleave such bonds, as calculated by theory and experiments for model surfaces at low coverages. Such sites, however, bind intermediates strongly, rendering them unreactive at the high coverages prevalent during catalysis. Such site requirements are also at odds with turnover rates that often depend weakly on cluster size or are actually higher on larger clusters, even though defects, such as corners and edges, are most abundant on small clusters. This Account illustrates how these apparent inconsistencies are resolved through activations of strong bonds assisted by co-adsorbates on crowded low-index surfaces. Catalytic oxidations occur on Au clusters at low temperatures in spite of large activation barriers for O2 dissociation on Au(111) surfaces, leading to proposals that O2 activation requires low-coordination Au atoms or Au-support interfaces. When H2O is present, however, O2 dissociation proceeds with low barriers on Au(111) because chemisorbed peroxides (*OOH* and *HOOH*) form and weaken O-O bonds before cleavage, thus allowing activation on low-index planes. DFT-derived O2 dissociation barriers are much lower on bare Pt surfaces, but such surfaces are nearly saturated with CO* during CO oxidation. A dearth of vacant sites causes O2* to react with CO* to form *OOCO* intermediates that undergo O-O cleavage. NO-H2 reactions occur on Pt clusters saturated with NO* and H*; direct NO* dissociation requires vacant

  4. Islisberg-2011 - measurements of vehicle emissions in a highway tunnel: CO2, CO, H2, N2O, O2/N2; stable isotopes of CO2, CO and H2

    NASA Astrophysics Data System (ADS)

    Popa, M. E.; Vollmer, M. K.; Brand, W.; Jordan, A.; Rothe, M.; Batenburg, A. M.; Pathirana, S.; Röckmann, T.

    2012-04-01

    A measurement campaign of vehicle emissions took place in the summer of 2011 in the Islisberg highway tunnel in Switzerland. The purpose was to characterize the present vehicle fleet in terms of emission rates of H2, CO, CO2 and N2O; emission ratios O2:CO2, CO:CO2 and H2:CO, and isotopic signatures in CO2, CO and H2. The tunnel has a separate bore for each traffic direction, and no active ventilation, thus offering an ideal setting for measuring large traffic signals without significant interference of other sources or sinks. Two RGA analyzers were installed at the entrance and at the exit of the tunnel for continuous, in-situ measurements of H2 and CO. This in-situ dataset allows to determine the CO and H2 emission rates and the H2:CO emission ratios for different traffic conditions and vehicle types (traffic count data are also available). Additionally, a large number of flask samples were filled at both entrance and exit and were distributed for various measurements at three institutes. Some of the flasks were analyzed at MPI-BGC (Jena, Germany) for CO2, CO, N2O, H2, O2/N2 and 13C and 18O in CO2. A second flask batch was analyzed at EMPA (Switzerland) for H2 and CO, and at IMAU (Utrecht, Netherlands) for the corresponding H2 and CO isotopes. A third flask batch travelled to all three institutes for a complete set of measurements, serving also as a consistency check. We will present the initial results, discussing the following points: - H2 and CO emission rates, and H2:CO ratios of vehicle emissions; - H2 and CO isotopic composition; - CO:CO2 ratios; - O2:CO2 ratios; - 13C and 18O in CO2.

  5. RF discharge modelling in a N2O/SiH4 mixture for SiO2 deposition and comparison with experiment

    NASA Astrophysics Data System (ADS)

    Radouane, K.; Date, L.; Yousfi, M.; Despax, B.; Caquineau, H.

    2000-06-01

    The present work concerns the experimental and theoretical analysis of the electrical behaviour and N2O/SiH4 dissociation of a classical RF discharge used for SiO2 thin-film deposition. Electric and deposition rate measurements are undertaken at 0.5 and 1 Torr gas pressures. The reactor modelling involves electrical, hydrodynamic and mass transfer models. The electrical model enables the calculation of the electron impact dissociation rates required for the mass transfer model, while the gas velocities are determined by the hydrodynamic model. Only an electrical discharge model accounting for the negative-ion conversion reactions O-/SiH4 and NO-/SiH4 allows good agreement between the measured and calculated power densities particularly at 1 Torr. Furthermore, a simplified chemical scheme which includes 16 species (N2O, N2, O2, NO, NO2, N, O(3P), O(1D), SiH4, SiH3, SiH3O, H2SiO, H, H2, OH and H2O) is used in the mass transfer model. The corresponding results (deposition rates) are quite consistent with the measurements.

  6. Electron localizability indicators ELI-D and ELIA for highly correlated wavefunctions of homonuclear dimers. II. N2, O2, F2, and Ne2.

    PubMed

    Bezugly, Viktor; Wielgus, Pawel; Kohout, Miroslav; Wagner, Frank R

    2010-09-01

    Electron localizability indicators based on the electron pair density ELI-D and ELIA Electron localizability indicators ELI-D and ELIA based on the electron pair density are studied for the correlated ground-state wavefunctions of N(2), O(2), F(2), and Ne(2) diatomics. Different basis sets and reference spaces are used for the multireference configuration interaction method following the complete active space calculations to investigate the local effect of electron correlation on the extent of electron localizability in position space determined by the two indicators. The results are complemented by calculations of effective bond order, vibrational frequency, and Laplacian of the electron density at the bond midpoint. It turns out that for O(2) and F(2), the reliable topology of ELI-D is obtained only at the correlated level of theory.

  7. 15N2 formation and fast oxygen isotope exchange during pulsed 15N18O exposure of MnOx/CeO2

    SciTech Connect

    Kwak, Ja Hun; Szanyi, Janos

    2014-12-23

    Pulsing 15N18O onto an annealed 1% Mn16Ox/Ce16O2 catalyst resulted in very fast oxygen isotope exchange and 15N2 formation at 295 K. In the 1st 15N18O pulse, due to the presence of large number of surface oxygen defects, extensive 15N218O and 15N2 formations were observed. In subsequent pulses oxygen isotope exchange dominated as a result of highly labile oxygen in the oxide. We gratefully acknowledge the US Department of Energy (DOE), Office of Energy Efficiency and Renewable Energy/Vehicle Technologies Program for the support of this work. The research described in this paper was performed at the Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory (PNNL). PNNL is operated for the US DOE by Battelle.

  8. Effect of N2O to C4F8/O2 on Global Warming during Silicon Nitride Plasma Enhanced Chemical Vapor Deposition (PECVD) Chamber Cleaning Using a Remote Inductively Coupled Plasma Source

    NASA Astrophysics Data System (ADS)

    Kim, Ji Hwang; Oh, Chang Hyun; Lee, Nae Eung; Yeom, Geun Young

    2002-12-01

    For the silicon nitride plasma enhanced chemical vapor deposition (PECVD) chamber cleaning, a remote inductively coupled plasma (ICP) source was used with C4F8/O2/N2O and the effects of N2O on the silicon nitride cleaning rates and global warming were investigated. By adding 5% of N2O to C4F8/O2, the cleaning rate comparable to that of optimized Ar/NF3 could be obtained. At the exhaust line, CF4, C4F8, NF3, etc. were detected and the significant decrease of million metric tons of carbon equivalent (MMTCE) observed by the addition of N2O to C4F8/O2 was due to the decrease of emitted CF4. The MMTCE for the optimized C4F8/O2/N2O was also similar to that for Ar/NF3 at the highest cleaning condition.

  9. Mechanistic Evaluation of LixOy Formation on δ-MnO2 in Nonaqueous Li-Air Batteries.

    PubMed

    Liu, Zhixiao; De Jesus, Luis R; Banerjee, Sarbajit; Mukherjee, Partha P

    2016-09-01

    Transition metal oxides are usually used as catalysts in the air cathode of lithium-air (Li-air) batteries. This study elucidates the mechanistic origin of the oxygen reduction reaction catalyzed by δ-MnO2 monolayers and maps the conditions for Li2O2 growth using a combination of first-principles calculations and mesoscale modeling. The MnO2 monolayer, in the absence of an applied potential, preferentially reacts with a Li atom instead of an O2 molecule to initiate the formation of LiO2. The oxygen reduction products (LiO2, Li2O2, and Li2O molecules) strongly interact with the MnO2 monolayer via the stabilization of Li-O chemical bonds with lattice oxygen atoms. As compared to the disproportionation reaction, direct lithiation reactions are the primary contributors to the stabilization of Li2O2 on the MnO2 monolayer. The energy profiles of (Li2O2)2 and (Li2O)2 nucleation on δ-MnO2 monolayer during the discharge process demonstrate that Li2O2 is the predominant discharge product and that further reduction to Li2O is inhibited by the high overpotential of 1.21 V. Interface structures have been examined to study the interaction between the Li2O2 and MnO2 layers. This study demonstrates that a Li2O2 film can be homogeneously deposited onto δ-MnO2 and that the Li2O2/MnO2 interface acts as an electrical conductor. A mesoscale model, developed based on findings from the first-principles calculations, further shows that Li2O2 is the primary product of electrochemical reactions when the applied potential is smaller than 2.4 V. PMID:27532334

  10. Sterilization/disinfection of medical devices using plasma: the flowing afterglow of the reduced-pressure N2-O2 discharge as the inactivating medium

    NASA Astrophysics Data System (ADS)

    Moisan, Michel; Boudam, Karim; Carignan, Denis; Kéroack, Danielle; Levif, Pierre; Barbeau, Jean; Séguin, Jacynthe; Kutasi, Kinga; Elmoualij, Benaïssa; Thellin, Olivier; Zorzi, Willy

    2013-07-01

    Potential sterilization/disinfection of medical devices (MDs) is investigated using a specific plasma process developed at the Université de Montréal over the last decade. The inactivating medium of the microorganisms is the flowing afterglow of a reduced-pressure N2-O2 discharge, which provides, as the main biocidal agent, photons over a broad ultraviolet (UV) wavelength range. The flowing afterglow is considered less damaging to MDs than the discharge itself. Working at gas pressures in the 400—700 Pa range (a few torr) ensures, through species diffusion, the uniform filling of large volume chambers with the species outflowing from the discharge, possibly allowing batch processing within them. As a rule, bacterial endospores are used as bio-indicators (BI) to validate sterilization processes. Under the present operating conditions, Bacillus atrophaeus is found to be the most resistant one and is therefore utilized as BI. The current paper reviews the main experimental results concerning the operation and characterization of this sterilizer/disinfector, updating and completing some of our previously published papers. It uses modeling results as guidelines, which are particularly useful when the corresponding experimental data are not (yet) available, hopefully leading to more insight into this plasma afterglow system. The species flowing out of the N2-O2 discharge can be divided into two groups, depending on the time elapsed after they left the discharge zone as they move toward the chamber, namely the early afterglow and the late afterglow. The early flowing afterglow from a pure N2 discharge (also called pink afterglow) is known to be comprised of N2+ and N4+ ions. In the present N2-O2 mixture discharge, NO+ ions are additionally generated, with a lifetime that extends over a longer period than that of the nitrogen molecular ions. We shall suppose that the disappearance of the NO+ ions marks the end of the early afterglow regime, thereby stressing our intent

  11. Effects of pressure and disorder on superconductivity in Tl2Ba2Can-1CunO2 n + 4 + δ (n =2,3)

    NASA Astrophysics Data System (ADS)

    Zhang, Jian-Bo; Chen, Xiao-Jia; Struzhkin, Viktor; Yang, Wenge; Mao, Ho-Kwang; Lin, Hai-Qing; Ma, Yong-Chang; Wang, Nan-Lin

    The structural, vibrational, and superconducting properties of nearly optimally doped Tl2Ba2Can-1CunO2 n + 4 + δ (n =2,3) single crystals are studied at high pressures. While the superconducting transition temperature Tc of the bilayer system exhibits a parabolic behavior with a maximum around an optimal pressure level, its increased path has a kink in the trilayer compound, indicating a joint effect from the inner CuO2 plane. The latter is further supported by the appearance of the two additional Raman modes. At higher pressures, we observe the sudden increase of the full width at half maximum of some lattice modes as well as the anomaly of the lattice parameters at certain pressure. These together contribute the enhanced disorder and the Tc reduction accordingly. We thus are able to distinguish the contribution to Tc from the intrinsic pressure variables, disorder, and the CuO2 plane number and type in this layered family.

  12. Investigation on the Charging Process of Li2O2-Based Air Electrodes in Li-O2 Batteries with Organic Carbonate Electrolytes

    SciTech Connect

    Xu, Wu; Viswanathan, Vilayanur V.; Wang, Deyu; Towne, Silas A.; Xiao, Jie; Nie, Zimin; Hu, Dehong; Zhang, Jiguang

    2011-04-15

    The charge processes of Li-O2 batteries were investigated by analyzing the gas evolution by in situ gas chromatography-mass spectroscopy (GC/MS) technique. The mixture of Li2O2/Fe3O4/Super P carbon/polyvinylidene fluoride (PVDF) was used as the starting air electrode material and 1M LiTFSI in carbonate-based solvents was used as electrolyte. It was found that Li2O2 is reactive to 1-methyl-2-pyrrolidinone and PVDF binder used in the electrode preparation. During the 1st charge (up to 4.6 V), O2 was the main component in the gases released. The amount of O2 measured by GC/MS was consistent with the amount of Li2O2 decomposed in the electrochemical process as measured by the charge capacity, indicative of the good chargeability of Li2O2. However, after the cell was discharged to 2.0 V in O2 atmosphere and re-charged to ~ 4.6 V in the second cycle, CO2 was dominant in the released gases. Further analysis of the discharged air electrode by X-ray diffraction and Fourier transform infrared spectroscopy indicated that lithium-containing carbonate species (lithium alkyl carbonate and/or Li2CO3) were the main reaction products. Therefore, compatible electrolyte and electrodes as well as the electrode preparation procedures need to be developed for long term operation of rechargeable Li-O2 or Li-air batteries.

  13. Vibrational relaxation of H2O(|04> ) in collisions with H2O, Ar, H2, N2 and O2: dynamical and atmospheric implications

    NASA Astrophysics Data System (ADS)

    Barnes, P. W.; Sims, I. R.; Smith, I. W.

    2003-04-01

    It has been suggested that sequential two-photon dissociation of water might provide a mechanism for the atmospheric production of OH radical. ^1 This mechanism requires that photodissociation of vibrationally excited molecules must occur at a rate competitive with their relaxation by collisions with atmospheric gases. In this paper, we shall describe new experiments on the collisional relaxation of H_2O molecules from the highly excited mid04>± vibrational state in collisions with H_2O, Ar, H_2, N_2 and O_2. In our experiments, the mid04>^- state is populated by direct absorption of radiation from a pulsed dye laser tuned to ca. 719 nm. Evolution of the population in the (mid04>±) levels is observed using the combination of a frequency-quadrupled Nd:YAG laser, which selectively photolyses H_2O(mid04>±), and a frequency-doubled dye laser, which observes the OH(v = 0) produced via laser-induced fluorescence (LIF). The delay between the pulse from the pump laser and those from the photolysis and probe lasers was systematically varied to generate kinetic decays. The rate coefficients for relaxation obtained from these experiments, in units of cm^3 molecule-1 s-1, are: k(H_2O) = (4.1 ± 1.2) x 10-10, k(Ar) = (4.9 ± 1.1) x 10-12, k(H_2) = (6.8 ± 1.1) x 10-12, k(N_2) = (7.7 ± 1.5) x 10-12, k(O_2) = (6.7 ± 1.4) x 10-12. The results will be discussed in two contexts. First, we shall consider the implications of our new results for the interpretation of our previous experiments on the reactions of vibrationally excited H_2O with H atoms.^2 Second, we shall consider the proposal of Goss et al.1 in the light of our finding that the collisional relaxation of H_2O(mid04>±) by N_2 and O_2 is rather rapid. ^1 L. M Goss, V. Vaida, J. W. Brault and R. T. Skodje, J. Phys. Chem. A, 05, 70 (2001). ^2 (a) G. Hawthorne, P. Sharkey and I. W. M. Smith, J. Chem. Phys., 108, 4693(1998); (b) P. W. Barnes, P. Sharkey, I. R. Sims and I. W. M. Smith, Faraday Discuss. Chem. Soc., 13, 167

  14. Stabilizing MoS2 Nanosheets through SnO2 Nanocrystal Decoration for High-Performance Gas Sensing in Air.

    PubMed

    Cui, Shumao; Wen, Zhenhai; Huang, Xingkang; Chang, Jingbo; Chen, Junhong

    2015-05-20

    The unique properties of MoS(2) nanosheets make them a promising candidate for high-performance room temperature sensing. However, the properties of pristine MoS(2) nanosheets are strongly influenced by the significant adsorption of oxygen in an air environment, which leads to instability of the MoS(2) sensing device, and all sensing results on MoS(2) reported to date were exclusively obtained in an inert atmosphere. This significantly limits the practical sensor application of MoS(2) in an air environment. Herein, a novel nanohybrid of SnO(2) nanocrystal (NC)-decorated crumpled MoS(2) nanosheet (MoS(2)/SnO(2)) and its exciting air-stable property for room temperature sensing of NO(2) are reported. Interestingly, the SnO(2) NCs serve as strong p-type dopants for MoS(2), leading to p-type channels in the MoS(2) nanosheets. The SnO(2) NCs also significantly enhance the stability of MoS(2) nanosheets in dry air. As a result, unlike other MoS(2) sensors operated in an inert gas (e.g. N(2)), the nanohybrids exhibit high sensitivity, excellent selectivity, and repeatability to NO(2) under a practical dry air environment. This work suggests that NC decoration significantly tunes the properties of MoS(2) nanosheets for various applications.

  15. Pt-TiO2/MWCNTs Hybrid Composites for Monitoring Low Hydrogen Concentrations in Air

    PubMed Central

    Trocino, Stefano; Donato, Andrea; Latino, Mariangela; Donato, Nicola; Leonardi, Salvatore Gianluca; Neri, Giovanni

    2012-01-01

    Hydrogen is a valuable fuel for the next energy scenario. Unfortunately, hydrogen is highly flammable at concentrations higher than 4% in air. This aspect makes the monitoring of H2 leaks an essential issue for safety reasons, especially in the transportation field. In this paper, nanocomposites based on Pt-doped TiO2/multiwalled carbon nanotubes (MWCNTs) have been introduced as sensitive materials for H2 at low temperatures. Pt-TiO2/MWNTs nanocomposites with different composition have been prepared by a simple wet chemical procedure and their morphological, microstructural and electrical properties were investigated. Resistive thick-film devices have been fabricated printing the hybrid nanocomposites on alumina substrates provided with Pt interdigitated electrodes. Electrical tests in air have shown that embedding MWCNTs in the TiO2 matrix modify markedly the electrical conductivity, providing a means to decrease the resistance of the sensing layer. Pt acts as a catalytic additive. Pt-TiO2/MWNTs-based sensors were found to be sensitive to hydrogen at concentrations between 0.5 and 3% in air, satisfying the requisites for practical applications in hydrogen leak detection devices.

  16. Transferable force-field for modelling of CO2, N2, O2 and Ar in all silica and Na+ exchanged zeolites

    NASA Astrophysics Data System (ADS)

    Vujić, Bojan; Lyubartsev, Alexander P.

    2016-05-01

    In this work we propose a new force field for modelling of adsorption of CO2, N2, O2 and Ar in all silica and Na+ exchanged Si-Al zeolites. The force field has a standard molecular-mechanical functional form with electrostatic and Lennard-Jones interactions satisfying Lorentz-Berthelot mixing rules and thus has a potential for further extension in terms of new molecular types. The parameters for the zeolite framework atom types are optimized by an iterative procedure minimizing the difference with experimental adsorption data for a number of different zeolite structures and Si:Al ratios. The new force field shows a good agreement with available experimental data including those not used in the optimization procedure, and which also shows a reasonable transferability within different zeolite topologies. We suggest a potential usage in screening of different zeolite structures for carbon capture and storage process, and more generally, for separation of other gases.

  17. Solvatochromism, spectral properties and antimicrobial activities of new azo-azomethine dyes with N2S2O2 donor set of atoms

    NASA Astrophysics Data System (ADS)

    Khanmohammadi, Hamid; Pass, Maryam; Rezaeian, Khatereh; Talei, Gholamreza

    2014-08-01

    Six new azo-azomethine dyes, H2Ln (n = 1-6), with N2S2O2 donor set of atoms have been prepared via condensation reaction of 1,10-diaza-4,7-dithiadecane, I, with substituted azo-coupled salicylaldehyde. The dyes were characterized by IR, UV-Vis and 1H NMR spectroscopic methods as well as elemental analysis. The solvatochromic behavior of the dyes was also probed by studying their UV-Vis spectra in four pure organic solvents of different polarities and a meaningful correlation was observed. Furthermore, all prepared dyes were assayed for their antibacterial and antifungal activities by disc diffusion method. The results indicated that all prepared dyes show good inhibition against Staphylococcus epidermidis and Bacillus cereus and did not show any antibacterial activity against Escherichia coli as compared to standard drugs.

  18. Radiation chemistry of 2'-deoxycytidylyl-(3'-5')-2'-deoxyguanosine and its sequence isomer in N2O- and O2-saturated solutions.

    PubMed

    Paul, C R; Arakali, A V; Wallace, J C; McReynolds, J; Box, H C

    1987-12-01

    The radiation chemistry of the dinucleoside monophosphate d(CpG) and its sequence isomer, d(GpC), has been examined in aqueous solutions saturated with either N2O or O2. The products were isolated using HPLC, and the major products were identified using proton NMR spectroscopy and mass spectrometry. The major products include 5,6-dihydroxy-5,6-dihydrouracil (glycol) derivatives, 5- and 6-hydroxycytosine substitution products, 1-carbamoyl-2-oxo-4,5-dihydroxyimidazolidine products, and the 8-hydroxyguanine substitution product. Both trans stereoisomers of the imidazolidine derivatives are obtained from d(CpG) as well as from its sequence isomer. These are prominent products when the irradiation is carried out in the presence of oxygen, but they are not observed in the absence of oxygen.

  19. Parity-Dependent Rotational Energy Transfer in CN(A2Π, ν = 4, jF1ε) + N2, O2, and CO2 Collisions

    PubMed Central

    2015-01-01

    We report state-resolved total removal cross sections and state-to-state rotational energy transfer (RET) cross sections for collisions of CN(A2Π, ν = 4, jF1ε) with N2, O2, and CO2. CN(X2Σ+) was produced by 266 nm photolysis of ICN in a thermal bath (296 K) of the collider gas. A circularly polarized pulse from a dye laser prepared CN(A2Π, ν = 4) in a range of F1e rotational states, j = 2.5, 3.5, 6.5, 11.5, 13.5, and 18.5. These prepared states were monitored using the circularly polarized output of an external cavity diode laser by frequency-modulated (FM) spectroscopy on the CN(A–X)(4,2) band. The FM Doppler profiles were analyzed as a function of pump–probe delay to determine the time dependence of the population of the initially prepared states. Kinetic analysis of the resulting time dependences was used to determine total removal cross sections from the initially prepared levels. In addition, a range of j′ F1e and j′ F2f product states resulting from rotational energy transfer out of the j = 6.5 F1e initial state were probed, from which state-to-state RET cross sections were measured. The total removal cross sections lie in the order CO2 > N2 > O2, with evidence for substantial cross sections for electronic and/or reactive quenching of CN(A, ν = 4) to unobserved products with CO2 and O2. This is supported by the magnitude of the state-to-state RET cross sections, where a deficit of transferred population is apparent for CO2 and O2. A strong propensity for conservation of rotational parity in RET is observed for all three colliders. Spin–orbit-changing cross sections are approximately half of those of the respective conserving cross sections. These results are in marked disagreement with previous experimental observations with N2 as a collider but are in good agreement with quantum scattering calculations from the same study (Khachatrian et al. J. Phys. Chem. A2009, 113, 392219215110). Our results with CO2 as a collider are similarly in strong

  20. Studies on DNA binding behaviour of biologically active transition metal complexes of new tetradentate N2O2 donor Schiff bases: Inhibitory activity against bacteria

    NASA Astrophysics Data System (ADS)

    Sobha, S.; Mahalakshmi, R.; Raman, N.

    A series of Cu(II), Ni(II) and Zn(II) complexes of the type ML have been synthesized with Schiff bases derived from o-acetoacetotoluidide, 2-hydroxybenzaldehyde and o-phenylenediamine/1,4-diaminobutane. The complexes are insoluble in common organic solvents but soluble in DMF and DMSO. The measured molar conductance values in DMSO indicate that the complexes are non-electrolytic in nature. All the six metal complexes have been fully characterized with the help of elemental analyses, molecular weights, molar conductance values, magnetic moments and spectroscopic data. The analytical data helped to elucidate the structure of the metal complexes. The Schiff bases are found to act as tetradentate ligands using N2O2 donor set of atoms leading to a square-planar geometry for the complexes around all the metal ions. The binding properties of metal complexes with DNA were investigated by absorption spectra, viscosity measurements and cyclic voltammetry. Detailed analysis reveals that the metal complexes intercalate into the DNA base stack as intercalators. All the metal complexes cleave the pUC19 DNA in presence of H2O2. The Schiff bases and their complexes have been screened for their antibacterial activity against five bacterial strains (Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Staphylococcus epidermidis, Klebsiella pneumoniae) by disk diffusion method. All the metal complexes have potent biocidal activity than the free ligands.

  1. Review of the absorption spectra of solid O2 and N2 as they relate to contamination of a cooled infrared telescope

    NASA Technical Reports Server (NTRS)

    Smith, S. M.

    1977-01-01

    During contamination studies for the liquid helium cooled shuttle infrared telescope facility, a literature search was conducted to determine the absorption spectra of the solid state of homonuclear molecules of O2 and N2, and ascertain what laboratory measurements of the solid have been made in the infrared. With the inclusion of one unpublished spectrum, the absorption spectrum of the solid oxygen molecule has been thoroughly studied from visible to millimeter wavelengths. Only two lines appear in the solid that do not also appear in the gas or liquid. A similar result is implied for the solid nitrogen molecule because it also is homonuclear. The observed infrared absorption lines result from lattice modes of the alpha phase of the solid, and disappear at the warmer temperatures of the beta, gamma, and liquid phases. They are not observed from polycrystalline forms of O2, while strong scattering is. Scattering, rather than absorption, is considered to be the principal natural contamination problem for cooled infrared telescopes in low earth orbit.

  2. CH3CO + O2 + M (M = He, N2) Reaction Rate Coefficient Measurements and Implications for the OH Radical Product Yield.

    PubMed

    Papadimitriou, Vassileios C; Karafas, Emmanuel S; Gierczak, Tomasz; Burkholder, James B

    2015-07-16

    The gas-phase CH3CO + O2 reaction is known to proceed via a chemical activation mechanism leading to the formation of OH and CH3C(O)OO radicals via bimolecular and termolecular reactive channels, respectively. In this work, rate coefficients, k, for the CH3CO + O2 reaction were measured over a range of temperature (241-373 K) and pressure (0.009-600 Torr) with He and N2 as the bath gas and used to characterize the bi- and ter-molecular reaction channels. Three independent experimental methods (pulsed laser photolysis-laser-induced fluorescence (PLP-LIF), pulsed laser photolysis-cavity ring-down spectroscopy (PLP-CRDS), and a very low-pressure reactor (VLPR)) were used to characterize k(T,M). PLP-LIF was the primary method used to measure k(T,M) in the high-pressure regime under pseudo-first-order conditions. CH3CO was produced by PLP, and LIF was used to monitor the OH radical bimolecular channel reaction product. CRDS, a complementary high-pressure method, measured k(295 K,M) over the pressure range 25-600 Torr (He) by monitoring the temporal CH3CO radical absorption following its production via PLP in the presence of excess O2. The VLPR technique was used in a relative rate mode to measure k(296 K,M) in the low-pressure regime (9-32 mTorr) with CH3CO + Cl2 used as the reference reaction. A kinetic mechanism analysis of the combined kinetic data set yielded a zero pressure limit rate coefficient, kint(T), of (6.4 ± 4) × 10(-14) exp((820 ± 150)/T) cm(3) molecule(-1) s(-1) (with kint(296 K) measured to be (9.94 ± 1.3) × 10(-13) cm(3) molecule(-1) s(-1)), k0(T) = (7.39 ± 0.3) × 10(-30) (T/300)(-2.2±0.3) cm(6) molecule(-2) s(-1), and k∞(T) = (4.88 ± 0.05) × 10(-12) (T/300)(-0.85±0.07) cm(3) molecule(-1) s(-1) with Fc = 0.8 and M = N2. A He/N2 collision efficiency ratio of 0.60 ± 0.05 was determined. The phenomenological kinetic results were used to define the pressure and temperature dependence of the OH radical yield in the CH3CO + O2 reaction. The

  3. Laser-induced fluorescence from N2(+) ions generated by a corona discharge in ambient air.

    PubMed

    Konthasinghe, Kumarasiri; Fitzmorris, Kristin; Peiris, Manoj; Hopkins, Adam J; Petrak, Benjamin; Killinger, Dennis K; Muller, Andreas

    2015-09-01

    In this work, we present the measurement of laser-induced fluorescence from N2(+) ions via the B(2)Σu(+)-X(2)Σg(+) band system in the near-ultraviolet. The ions were generated continuously by a plasma glow discharge in low pressure N2 and by a corona discharge in ambient air. The fluorescence decay time was found to rapidly decrease with increasing pressure leading to an extrapolated decay rate of ≍10(10) s(-1) at atmospheric pressure. In spite of this quenching, we were able to observe laser induced fluorescence in ambient air by means of a time-gated spectral measurement. In the process of comparing the emission signal with that of N2 spontaneous Raman scattering, ion concentrations in ambient air of order 10(8-)10(10) cm(-3) were determined. With moderate increases in laser power and collection efficiency, ion concentrations of less than 10(6) cm(-3) may be measurable, potentially enabling applications in atmospheric standoff detection of ionizing radiation from hazardous radioactive sources. PMID:26414524

  4. Treatment of aniline by catalytic wet air oxidation: comparative study over CuO/CeO2 and NiO/Al2O3.

    PubMed

    Ersöz, Gülin; Atalay, Süheyda

    2012-12-30

    The treatment of aniline by catalytic wet air oxidation (CWAO) was studied in a bubble reactor. The experiments were performed to investigate the effects of catalyst loading, temperature, reaction time, air flow rate, and pressure on aniline removal. The catalytic effects of the prepared nanostructured catalysts, CuO/CeO(2) (10% wt) and NiO/Al(2)O(3) (10% wt), on the CWAO treatment efficiency were also examined and compared. The prepared catalysts seem to be active having an aniline removal of 45.7% with CuO/CeO(2) and 41.9% with NiO/Al(2)O(3). The amount of N(2) formed was approximately the same for both of the catalysts.

  5. Treatment of aniline by catalytic wet air oxidation: comparative study over CuO/CeO2 and NiO/Al2O3.

    PubMed

    Ersöz, Gülin; Atalay, Süheyda

    2012-12-30

    The treatment of aniline by catalytic wet air oxidation (CWAO) was studied in a bubble reactor. The experiments were performed to investigate the effects of catalyst loading, temperature, reaction time, air flow rate, and pressure on aniline removal. The catalytic effects of the prepared nanostructured catalysts, CuO/CeO(2) (10% wt) and NiO/Al(2)O(3) (10% wt), on the CWAO treatment efficiency were also examined and compared. The prepared catalysts seem to be active having an aniline removal of 45.7% with CuO/CeO(2) and 41.9% with NiO/Al(2)O(3). The amount of N(2) formed was approximately the same for both of the catalysts. PMID:23041516

  6. Synergy effect of heat and UV photons on bacterial-spore inactivation in an N2-O2 plasma-afterglow sterilizer

    NASA Astrophysics Data System (ADS)

    Boudam, M. K.; Moisan, M.

    2010-07-01

    As a rule, medical devices (MDs) made entirely from metals and ceramics can withstand, for sterilization purposes, elevated temperatures such as those encountered in autoclaves (moist heat >=120 °C) or Poupinel (Pasteur) ovens (dry heat >=160 °C). This not the case with MDs containing polymers: 70 °C seems to be a limit beyond which their structural and functional integrity will be compromised. Nonetheless, all the so-called low-temperature sterilization techniques, relying essentially on some biocidal chemistry (e.g. ethylene oxide, H2O2, O3), are operated at temperatures close to 65 °C, essentially to enhance the chemical reactivity of the biocidal agent. Based on this fact, we have examined the influence of increasing the temperature of the polystyrene Petri dish containing B. atrophaeus bacterial spores when exposing them to UV radiation coming from an N2-O2 flowing plasma afterglow. We have observed that, for a given UV radiation intensity, the inactivation rate increases with the temperature of the Petri dish, provided heat and UV photons are applied simultaneously, a clear case of synergistic effect. More specifically, it means that (i) simply heating the spores at temperatures below 65 °C without irradiating them with UV photons does not induce mortality; (ii) there is no additional increase in the inactivation rate when the Petri has been pre-heated and then brought back to ambient temperature before the spores are UV irradiated; (iii) no additional inactivation results from post-heating spores previously inactivated with UV radiation. Undoubtedly, the synergistic effect shows up only when the physico-chemical agents (UV photons and temperature) are simultaneously in action.

  7. Synthesis and spectroscopic studies of binuclear metal complexes of a tetradentate N 2O 2 Schiff base ligand derived from 4,6-diacetylresorcinol and benzylamine

    NASA Astrophysics Data System (ADS)

    Shebl, Magdy

    2008-09-01

    A tetradentate N 2O 2 donor Schiff base ligand, H 2L, was synthesized by the condensation of 4,6-diacetylresorcinol with benzylamine. The structure of the ligand was elucidated by elemental analyses, IR, 1H NMR, electronic and mass spectra. Reaction of the Schiff base ligand with nickel(II), cobalt(II), iron(III), cerium(III), vanadyl(IV) and uranyl(VI) ions in 1:2 molar ratio afforded binuclear metal complexes. Also, reaction of the ligand with several copper(II) salts, including Cl -, NO 3-, AcO -, ClO 4- and SO 42- afforded different metal complexes that reflect the non-coordinating or weakly coordinating power of the ClO 4- anion as compared to the strongly coordinating power of SO 42- and Cl - anions. Characterization and structure elucidation of the prepared complexes were achieved by elemental and thermal analyses, IR, 1H NMR, electronic, mass and ESR spectra as well as magnetic susceptibility measurements. The metal complexes exhibited different geometrical arrangements such as square planar, octahedral, square pyramidal and pentagonal bipyramidal arrangements. The variety in the geometrical arrangements depends on the nature of both the anion and the metal ion.

  8. Effects of O 2 and N 2/H 2 plasma treatments on the neuronal cell growth on single-walled carbon nanotube paper scaffolds

    NASA Astrophysics Data System (ADS)

    Yoon, Ok Ja; Lee, Hyun Jung; Jang, Yeong Mi; Kim, Hyun Woo; Lee, Won Bok; Kim, Sung Su; Lee, Nae-Eung

    2011-08-01

    The O 2 and N 2/H 2 plasma treatments of single-walled carbon nanotube (SWCNT) papers as scaffolds for enhanced neuronal cell growth were conducted to functionalize their surfaces with different functional groups and to roughen their surfaces. To evaluate the effects of the surface roughness and functionalization modifications of the SWCNT papers, we investigated the neuronal morphology, mitochondrial membrane potential, and acetylcholine/acetylcholinesterase levels of human neuroblastoma during SH-SY5Y cell growth on the treated SWCNT papers. Our results demonstrated that the plasma-chemical functionalization caused changes in the surface charge states with functional groups with negative and positive charges and then the increased surface roughness enhanced neuronal cell adhesion, mitochondrial membrane potential, and the level of neurotransmitter in vitro. The cell adhesion and mitochondrial membrane potential on the negatively charged SWCNT papers were improved more than on the positively charged SWCNT papers. Also, measurements of the neurotransmitter level showed an enhanced acetylcholine level on the negatively charged SWCNT papers compared to the positively charged SWCNT papers.

  9. Low Temperature Heat Capacities and Standard Molar Enthalpy of Formation of 2-Pyrazinecarboxylic Acid (C5H4N2O2)(s).

    PubMed

    Kong, Yu-Xia; Di, You-Ying; Yang, Wei-Wei; Gao, Sheng-Li; Tan, Zhi-Cheng

    2010-06-01

    Low-temperature heat capacities of 2-pyrazinecarboxylic acid (C5H4N2O2)(s) were measured by a precision automated adiabatic calorimeter over the temperature range from 78 to 400 K. A polynomial equation of heat capacities as a function of temperature was fitted by least squares method. Based on the fitted polynomial, the smoothed heat capacities and thermodynamic functions of the compound relative to the standard reference temperature 298.15 K were calculated and tabulated at 10 K intervals. The constant-volume energy of combustion of the compound at T = 298.15 K was measured by a precision rotating-bomb combustion calorimeter to be ΔcU = -(17839.40 ± 7.40) J g-1. The standard molar enthalpy of combustion of the compound was determined to be ΔcH0m = -(2211.39 ± 0.92) KJ mol-1, according to the definition of combustion enthalpy. Finally, the standard molar enthalpy of formation of the compound was calculated to be ΔfH0m = -(327.82 ± 1.13) kJ mol-1 in accordance with Hess law. PMID:24061733

  10. Ru(II) complexes of N 4 and N 2O 2 macrocyclic Schiff base ligands: Their antibacterial and antifungal studies

    NASA Astrophysics Data System (ADS)

    Shanker, Kanne; Rohini, Rondla; Ravinder, Vadde; Reddy, P. Muralidhar; Ho, Yen-Peng

    2009-07-01

    Reactions of [RuCl 2(DMSO) 4] with some of the biologically active macrocyclic Schiff base ligands containing N 4 and N 2O 2 donor group yielded a number of stable complexes, effecting complete displacement of DMSO groups from the complex. The interaction of tetradentate ligand with [RuCl 2(DMSO) 4] gave neutral complexes of the type [RuCl 2(L)] [where L = tetradentate macrocyclic ligand]. These complexes were characterized by elemental, IR, 1H, 13C NMR, mass, electronic, thermal, molar conductance and magnetic susceptibility measurements. An octahedral geometry has been proposed for all complexes. All the macrocycles and macrocyclic Ru(II) complexes along with existing antibacterial drugs were screened for antibacterial activity against Gram +ve ( Bacillus subtilis, Staphylococcus aureus) and Gram -ve ( Escherichia coli, Klebsiella pneumonia) bacteria. All these compounds were found to be more active when compared to streptomycin and ampicillin. The representative macrocyclic Schiff bases and their complexes were also tested in vitro to evaluate their activity against fungi, namely, Aspergillus flavus and Fusarium species.

  11. Modeling disequilibrium in gas ensembles: How quantum state populations evolve under multicollision conditions; CO*+Ar, CO, O2, and N2

    NASA Astrophysics Data System (ADS)

    McCaffery, Anthony J.; Marsh, Richard J.

    2010-02-01

    The method of Marsh and McCaffery [J. Chem. Phys. 117, 503 (2002)] is used to quantify how rovibrational populations and mode temperatures change as an ensemble of CO molecules, initially excited to (v;j)=(8;12), evolves to thermal equilibrium in a bath gas. The bath gases considered are Ar, N2, O2, and CO all at 300 K with the diatomics in their (0;8) rovibrational states. Ensembles generally contain 1000 molecules, 10% of which are excited CO (CO∗) molecules. State (v;j) populations and mode temperatures of CO∗ and bath molecules are calculated for successive collisions to 1000 or more. We find that relaxation to local thermodynamic equilibrium occurs in distinct phases that vary widely in rate of cooling. There is especially fast vibration-vibration (VV) exchange in CO∗-CO mixtures that is largely decoupled from rotation and translation. Several aspects of ensemble behavior may be rationalized using concepts established in quantum state resolved single collision studies. We demonstrate the existence of a simultaneous energy quasiresonant, angular momentum conserving, low Δj VV process that can cause either ultrafast relaxation or up pumping of the kind seen in a number of experiments.

  12. Bio-relevant complexes of novel N2O2 type heterocyclic ligand: Synthesis, structural elucidation, biological evaluation and docking studies.

    PubMed

    Arun, T; Packianathan, S; Malarvizhi, M; Antony, R; Raman, N

    2015-08-01

    Organic and inorganic entities [Cu(II), Co(II), Ni(II) and Zn(II)] have been bridged by N2O2 type heterocyclic imine (CN) ligand for the synthesis of novel organic-inorganic bridged complexes of the type [M(H2L)]. The synthesized complexes were characterized by spectral techniques such as FT-IR, UV-visible, (1)H NMR, (13)C NMR, EPR, ESI-Mass, elemental analysis, magnetic susceptibility and molar conductivity measurements. The metal complexes adopt square planar geometrical arrangement around the metal ions. DNA binding ability of these complexes has been explored by different techniques viz. electronic absorption, fluorescence, cyclic voltammetry, differential pulse voltammetry and viscosity measurements. These studies prove that CT DNA interaction of the complexes follows intercalation mode. The oxidative cleavage of the complexes with pUC19 DNA has been investigated by gel electrophoresis. Molecular docking calculations have been performed to understand the nature of binding of the complexes with DNA. Moreover, the anti-pathogenic actions of the complexes were tested in vitro against few bacteria and fungi by disk diffusion method. The data reveal that the complexes have higher anti-pathogenic activity than the ligand.

  13. The 2140 cm(exp -1) (4.673 Microns) Solid CO Band: The Case for Interstellar O2 and N2 and the Photochemistry of Non-Polar Interstellar Ice Analogs

    NASA Technical Reports Server (NTRS)

    Elsila, Jamie; Allamandola, Louis J.; Sandford, Scott A.; Witteborn, Fred C. (Technical Monitor)

    1996-01-01

    The infrared spectra of CO frozen in non-polar ices containing N2, CO2, O2, and H2O, and the ultraviolet photochemistry of these interstellar/precometary ice analogs are reported. The spectra are used to test the hypothesis that the narrow 2140/cm (4.673 micrometer) interstellar absorption feature attributed to solid CO might be produced by CO frozen in ices containing non-polar species such as N2 and O2. It is shown that mixed molecular ices containing CO, N2, O2, and CO2 provide a very good match to the interstellar band at all temperatures between 12 and 30 K both before and after photolysis. The optical constants (real and imaginary parts of the index of refraction) in the region of the solid CO feature are reported for several of these ices.

  14. Feasibility of measuring temperature and density fluctuations in air using laser-induced O2 fluorescence

    NASA Technical Reports Server (NTRS)

    Massey, G. A.; Lemon, C. J.

    1984-01-01

    A tunable line-narrowed ArF laser can selectively excite several rotation al lines of the Schumann-Runge band system of O2 in air. The resulting ultraviolet fluorescence can be monitored at 90 deg to the laser beam axis, permitting space and time resolved observation of density and temperature fluctuations in turbulence. Experiments and calculations show that + or - 1 K, + or - 1 percent density, 1 cu mm spatial, and 1 microsecond temporal resolution can be achieved simultaneously under some conditions.

  15. In situ and air index measurements: influence of the deposition parameters on the shift of TiO2/SiO2 Fabry-Perot filters.

    PubMed

    Schmitt, B; Borgogno, J P; Albrand, G; Pelletier, E

    1986-11-01

    We measure the refractive index of thin films of TiO2 and SiO2 for given deposition parameters. Two complementary methods are used. The first is a postdeposition technique which uses the measurements of reflectance and transmittance in air. The second, in contrast, makes use of in situ measurements (under vacuum and during the actual deposition of the layer). The differences between the values deduced from the two methods can be explained by the amount of atmospheric moisture adsorbed by films. One tries to minimize these shifts for the two materials by choosing deposition parameters. The difficulties come from the absorption losses which must be as small as possible. We use the measured refractive indices of individual layers to give good numerical prediction of the wavelength shift (observed during the admittance of air after deposition in the vacuum chamber) of the transmittance peak of multidielectric Fabry-Perot filters.

  16. Rhodium-Catalyzed Regioselective Hydroxylation of Cage B-H Bonds of o-Carboranes with O2 or Air.

    PubMed

    Lyu, Hairong; Quan, Yangjian; Xie, Zuowei

    2016-09-19

    A rhodium-catalyzed hydroxylation of a cage B4-H bond in o-carboranes with either O2 or air as the oxygen source is described, and serves as a new methodology for the regioselective generation of a series of 4-OH-o-carboranes in a one-pot process. The use of either O2 or air as both the oxidant and the oxygen source makes this protocol very environmentally friendly and practical. PMID:27599774

  17. Synthesis and spectroscopic characterization of some transition metal complexes of a new hexadentate N(2)S(2)O(2) Schiff base ligand.

    PubMed

    Sarkar, Saikat; Dey, Kamalendu

    2005-11-01

    A novel interesting hexadentate dibasic N(2)S(2)O(2) donor Schiff base ligand, H(4)dcsalpte, was synthesized by the condensation of 3-formylsalicylic acid and 1,2-di(o-aminophenylthio)ethane and characterized. The reactions of the ligand with different metal(II/III)salts under varied reaction conditions afforded a series of metal complexes. The ligand, H(4)dcsalpte, behaves either as a dibasic or neutral hexadentate one, depending on the reaction conditions. Structural investigations on the ligand and their complexes have been made based on elemental analyses, molar conductance values, magnetic moment values, cryomagnetic and spectral (UV-vis, IR, (1)H NMR, and Mössbauer) data. Based on magnetic susceptibility, Mössbauer and electronic spectral data the iron(III) complex [Fe(III)(H(2)dcsalpte)]ClO(4) (8), isolated in the present investigation, it is inferred that the spin states 5/2 and 1/2 are in equilibrium. Similarly a tri-iron(III) complex [Fe(III)(3)(H(2)dcsalpte)(H(3)dcsalpte)Cl(3)]Cl(3) (7), isolated in this study, has been inferred to contain two iron(III) sites in tetrahedral environment and one in the octahedral environment. The aerial oxidation of an equimolar mixture of H(4)dcsalpte and Co(CH(3)COO)(2).4H(2)O in ethanol under reflux gave two products, [Co(H(2)dcsalpte)]CH(3)COO (10) and [(Hbtcsaldm)Co(Hbvcsaldm)] (11), a cobalt(III) complex bound to two dissimilar tridentate NSO donor ligands formed as a result of the oxidative cleavage of the CS bond. In the complex 11, Hbtcsaldm stands for the dianion of the tridentate Schiff base ligand N-(2'-benzenethiol)-3-carboxysalicylaldimine and Hbvcsaldm stands for the mono anion of the tridentate Schiff base ligand N-(benzene-2'-S-vinyl)-3-carboxysalicylaldimine, both being formed as a result of the oxidative cleavage of H(4)dcsalpte. PMID:16257739

  18. Synthesis and spectroscopic characterization of some transition metal complexes of a new hexadentate N 2S 2O 2 Schiff base ligand

    NASA Astrophysics Data System (ADS)

    Sarkar, Saikat; Dey, Kamalendu

    2005-11-01

    A novel interesting hexadentate dibasic N 2S 2O 2 donor Schiff base ligand, H4dcsalpte, was synthesized by the condensation of 3-formylsalicylic acid and 1,2-di( o-aminophenylthio)ethane and characterized. The reactions of the ligand with different metal(II/III)salts under varied reaction conditions afforded a series of metal complexes. The ligand, H4dcsalpte, behaves either as a dibasic or neutral hexadentate one, depending on the reaction conditions. Structural investigations on the ligand and their complexes have been made based on elemental analyses, molar conductance values, magnetic moment values, cryomagnetic and spectral (UV-vis, IR, 1H NMR, and Mössbauer) data. Based on magnetic susceptibility, Mössbauer and electronic spectral data the iron(III) complex [Fe III( H2dcsalpte)]ClO 4 ( 8), isolated in the present investigation, it is inferred that the spin states 5/2 and 1/2 are in equilibrium. Similarly a tri-iron(III) complex [Fe III3( H2dcsalpte)( H3dcsalpte)Cl 3]Cl 3 ( 7), isolated in this study, has been inferred to contain two iron(III) sites in tetrahedral environment and one in the octahedral environment. The aerial oxidation of an equimolar mixture of H4dcsalpte and Co(CH 3COO) 2·4H 2O in ethanol under reflux gave two products, [Co( H2dcsalpte)]CH 3COO ( 10) and [( Hbtcsaldm)Co( Hbvcsaldm)] ( 11), a cobalt(III) complex bound to two dissimilar tridentate NSO donor ligands formed as a result of the oxidative cleavage of the C sbnd S bond. In the complex 11, Hbtcsaldm stands for the dianion of the tridentate Schiff base ligand N-(2'-benzenethiol)-3-carboxysalicylaldimine and Hbvcsaldm stands for the mono anion of the tridentate Schiff base ligand N-(benzene-2'-S-vinyl)-3-carboxysalicylaldimine, both being formed as a result of the oxidative cleavage of H4dcsalpte.

  19. Synthesis, spectroscopic characterization, thermal studies, catalytic epoxidation and biological activity of chromium and molybdenum hexacarbonyl bound to a novel N 2O 2 Schiff base

    NASA Astrophysics Data System (ADS)

    Abdel Aziz, Ayman A.

    2010-08-01

    Complexes of M(CO) 6 (M = Cr and Mo) with novel Schiff base N,N'-bis(salicylidene)4,5-dichloro-1,2-phenylenediamine (H 2L) were prepared in benzene in two different conditions: (i) under reduced pressure resulting the dicarbonyl precursors [Cr(CO) 2(H 2L)] and [Mo(CO) 2(L)] and (ii) in air resulting the oxo complex [Cr(O)(L)] and the dioxo complex [Mo(O) 2(L)]. The complexes were characterized by elemental analysis, IR, 1H NMR, mass spectrometry, and magnetic measurement. Thermal behaviors of the complexes were also studied by using thermogravimetric analysis (TGA). The catalytic activity of the novel complexes in the epoxidation of cyclooctene, cyclohexene, 1-octene and 1-hexene with tert-butyl-hydroperoxide (TBHP) in methylene chloride was investigated. The antimicrobial activities of the ligand and their complexes have been screened against various strains of bacteria and fungi and the results have been compared with some known antibiotics.

  20. Evaluation of clay-TiO2 nanocomposite efficiency on the photocatalytic elimination of a model hydrophobic air pollutant.

    NASA Astrophysics Data System (ADS)

    Cervini-Silva, J.; Kibanova, D.; Destaillats, H.

    2008-12-01

    Clay-supported TiO2 photocatalysts can potentially improve the performance of air treatment technologies due to enhanced adsorption and reactivity of volatile organic compounds (VOCs). In this study, a bench-top photocatalytic flow reactor was used to evaluate hectorite-TiO2 and kaolinite-TiO2, two novel composite materials synthesized in our laboratory. Toluene, a model hydrophobic VOC and a common indoor air pollutant, was introduced in the air stream at realistic concentrations and reacted under UVA (?max = 365 nm) or UVC (?max = 254 nm) irradiation. The UVC lamp presented secondary emission at 185 nm, leading to the formation of ozone and other short-lived reactive species. Performance of clay-TiO2 composites was compared with that of pure TiO2 (Degussa P25) and with UV irradiation in the absence of photocatalyst under identical conditions. Films of clay-TiO2 composites and of P25 were prepared by a dip- coating method on the surface of Raschig rings placed inside the flow reactor. An upstream toluene concentration of 150 ppbv was generated by diluting a constant vapor flow with dry air, or with humid air at 10, 33, and 66 % relative humidity (RH). Toluene concentrations downstream were determined by collecting Tenax-TA ® sorbent tubes and subsequent thermal desorption/gas chromatography/mass spectrometry (TD/GC/MS) analysis. The fraction of toluene removed, %R, and the reaction rate, Tr, were calculated for each experimental condition from the concentration changes registered with and without UV irradiation. Use of UVC light (UV/TiO2/O3) led to overall higher reactivity, which can be partially attributed to contribution of gas phase reactions by O3 and other short-lived species. When the reaction rate was normalized by the light irradiance, Tr/Iλ, the UV/TiO2 reaction under UVA irradiation was more efficient for samples with a higher content of TiO2 (P25 and Hecto-TiO2), but not for Kao-TiO2. Considering the effect of relative humidity, in all cases reaction

  1. Highly efficient indoor air purification using adsorption-enhanced-photocatalysis-based microporous TiO2 at short residence time.

    PubMed

    Lv, Jinze; Zhu, Lizhong

    2013-01-01

    A short residence time is a key design parameter for the removal of organic pollutants in catalyst-based indoor air purification systems. In this study, we synthesized a series of TiO2 with different micropore volumes and studied their removal efficiency of indoor carbonyl pollutants at a short residence time. Our results indicated that the superior adsorption capability of TiO2 with micropores improved its performance in the photocatalytic degradation of cyclohexanone, while the photocatalytic removal of the pollutant successfully kept porous TiO2 from becoming saturated. When treated with 1 mg m(-3) cyclohexanone at a relatively humidity of 18%, the adsorption amount on microporous TiO2 was 5.4-7.9 times higher than that on P25. Removal efficiency via photocatalysis followed'the same order as the adsorption amount: TiO2-5 > TiO2-20 > TiO2-60 > TiO2-180 > P25. The advantage of microporous TiO2 over P25 became more pronounced when the residence time declined from 0.072 to 0.036 s. Moreover, as the concentration of cyclohexanone deceased from 1000 ppb to 500 ppb, removal efficiency by microporous TiO2 increased more rapidly than P25.

  2. Characterization of the flowing afterglows of an N2 O2 reduced-pressure discharge: setting the operating conditions to achieve a dominant late afterglow and correlating the NOβ UV intensity variation with the N and O atom densities

    NASA Astrophysics Data System (ADS)

    Boudam, M. K.; Saoudi, B.; Moisan, M.; Ricard, A.

    2007-03-01

    The flowing afterglow of an N2-O2 discharge in the 0.6-10 Torr range is examined in the perspective of achieving sterilization of medical devices (MDs) under conditions ensuring maximum UV intensity with minimum damage to polymer-based MDs. The early afterglow is shown to be responsible for creating strong erosion damage, requiring that the sterilizer be operated in a dominant late-afterglow mode. These two types of afterglow can be characterized by optical emission spectroscopy: the early afterglow is distinguished by an intense emission from the N_{2}^{+} 1st negative system (band head at 391.4 nm) while the late afterglow yields an overpopulation of the v' = 11 ro-vibrational level of the N2(B) state, indicating a reduced contribution from the early afterglow N2 metastable species. We have studied the influence of operating conditions (pressure, O2 content in the N2-O2 mixture, distance of the discharge from the entrance to the afterglow (sterilizer) chamber) in order to achieve a dominant late afterglow that also ensures maximum and almost uniform UV intensity in the sterilization chamber. As far as operating conditions are concerned, moving the plasma source sufficiently far from the chamber entrance is shown to be a practical means for significantly reducing the density of the characteristic species of the early afterglow. Using the NO titration method, we obtain the (absolute) densities of N and O atoms in the afterglow at the NO injection inlet, a few cm before the chamber entrance: the N atom density goes through a maximum at approximately 0.3-0.5% O2 and then decreases, while the O atom density increases regularly with the O2 percentage. The spatial variation of the N atom (relative) density in the chamber is obtained by recording the emission intensity from the 1st positive system at 580 nm: in the 2-5 Torr range, this density is quite uniform everywhere in the chamber. The (relative) densities of N and O atoms in the discharge are determined by using

  3. Vehicle emissions of greenhouse gases and related tracers from a tunnel study: CO : CO2, N2O : CO2, CH4 : CO2, O2 : CO2 ratios, and the stable isotopes 13C and 18O in CO2 and CO

    NASA Astrophysics Data System (ADS)

    Popa, M. E.; Vollmer, M. K.; Jordan, A.; Brand, W. A.; Pathirana, S. L.; Rothe, M.; Röckmann, T.

    2014-02-01

    Measurements of CO2, CO, N2O and CH4 mole fractions, O2 / N2 ratios and the stable isotopes 13C and 18O in CO2 and CO have been performed in air samples from the Islisberg highway tunnel (Switzerland). The molar CO : CO2 ratios, with an average of (4.15 ± 0.34) ppb:ppm, are lower than reported in previous studies, pointing to a reduction in CO emissions from traffic. The 13C in CO2 reflects the isotopic composition of the fuel. 18O in CO2 is slightly depleted compared to the 18O in atmospheric O2, and shows significant variability. In contrast, the δ13C values of CO show that significant fractionation takes place during CO destruction in the catalytic converter. 13C in CO is enriched by 3‰ compared to the 13C in the fuel burnt, while the 18O content is similar to that of atmospheric O2. We compute a fractionation constant of (-2.7 ± 0.7)‰ for 13C during CO destruction. The N2O : CO2 average ratio of (1.8 ± 0.2) × 10-2 ppb:ppm is significantly lower than in past studies, showing a reduction in N2O emissions likely related to improvements in the catalytic converter technology. We also observed small CH4 emissions, with an average CH4 : CO2 ratio of (4.6 ± 0.2) × 10-2 ppb:ppm. The O2 : CO2 ratios of (-1.47 ± 0.01) ppm:ppm are very close to the expected, theoretically calculated values of O2 depletion per CO2 enhancement.

  4. A new Raman-N2 lidar dedicated to air quality survey

    NASA Astrophysics Data System (ADS)

    Royer, P.; Chazette, P.; Lardier, M.; Raut, J.-C.; Sauvage, L.

    2010-05-01

    The Commissariat à l'Energie Atomique (CEA) and the Centre National de la Recherche Scientifique (CNRS) have developed the Lidar Aérosols UltraViolet Aéroporté (LAUVA). The new version of this prototype is now commercialized with success under license by the LEOSPHERE Company with the name EZ LIDAR®. This eye-safe lidar is based on a Nd:YAG laser giving pulses of 16 mJ at 355 nm with a frequency of 20 Hz. The CEA and LEOSPHERE have recently upgraded this instrument into a three detection channels lidar measuring the two elastic cross-polarizations and the Raman-N2 backscatter signal at 387 nm. It is able to retrieve aerosol optical properties (extinction, backscatter coefficients and depolarization ratio) and atmospheric structures (boundary layer height and clouds) with a resolution of 1.5 m along the line-of-sight in analog mode and 15 m in photon-counting mode. This new lidar is particularly well-adapted to air quality survey thanks to a full overlap reached at ~150 m. This compact (90x50x20 cm) and light (less than50 kg) instrument has been integrated into the Mobile Aerosol Station (MAS) onboard a small truck and enables mobile measurements. We will here present and analyze some results obtained around Paris area with this Raman-N2 lidar.

  5. Etching characteristics of SiC, SiO2, and Si in CF4/CH2F2/N2/Ar inductively coupled plasma: Effect of CF4/CH2F2 mixing ratio

    NASA Astrophysics Data System (ADS)

    Lee, Jongchan; Efremov, Alexander; Kim, Kwangsoo; Kwon, Kwang-Ho

    2016-10-01

    This study investigated the etching characteristics and mechanisms of SiC, Si, and SiO2 in CF4/CH2F2/N2/Ar inductively-coupled plasmas. The investigation showed that a change in the CF4/CH2F2 mixing ratio at fixed N2 and Ar fractions in a feed gas causes a decrease in the etching rates of SiC and Si, but results in an almost constant SiO2 etching rate. Plasma chemistry was analyzed using Langmuir probe diagnostics and optical emission spectroscopy. The good agreement between the behaviors of both the SiC and the Si etching rates with a change in F atom density suggested a neutral-flux-limited etching regime for these materials. On the contrary, the SiO2 etching process appeared in the transitional regime of the ion-assisted chemical reaction and was influenced by both neutral and ion fluxes.

  6. The Performance Improvement of N2 Plasma Treatment on ZrO2 Gate Dielectric Thin-Film Transistors with Atmospheric Pressure Plasma-Enhanced Chemical Vapor Deposition IGZO Channel.

    PubMed

    Wu, Chien-Hung; Huang, Bo-Wen; Chang, Kow-Ming; Wang, Shui-Jinn; Lin, Jian-Hong; Hsu, Jui-Mei

    2016-06-01

    The aim of this paper is to illustrate the N2 plasma treatment for high-κ ZrO2 gate dielectric stack (30 nm) with indium-gallium-zinc-oxide (IGZO) thin-film transistors (TFTs). Experimental results reveal that a suitable incorporation of nitrogen atoms could enhance the device performance by eliminating the oxygen vacancies and provide an amorphous surface with better surface roughness. With N2 plasma treated ZrO2 gate, IGZO channel is fabricated by atmospheric pressure plasma-enhanced chemical vapor deposition (AP-PECVD) technique. The best performance of the AP-PECVD IGZO TFTs are obtained with 20 W-90 sec N2 plasma treatment with field-effect mobility (μ(FET)) of 22.5 cm2/V-s, subthreshold swing (SS) of 155 mV/dec, and on/off current ratio (I(on)/I(off)) of 1.49 x 10(7). PMID:27427669

  7. Functionalization of graphene by atmospheric pressure plasma jet in air or H2O2 environments

    NASA Astrophysics Data System (ADS)

    Huang, Weixin; Ptasinska, Sylwia

    2016-03-01

    The functionalization of graphene, which deforms its band structure, can result in a metal-semiconductor transition. In this work, we report a facile strategy to oxidize single-layer graphene using an atmospheric pressure plasma jet (APPJ) that generates a variety of reactive plasma species at close to ambient temperature. We systematically characterized the oxygen content and chemical structure of the graphene films after plasma treatment under different oxidative conditions (ambient air atmosphere or hydrogen peroxide solution) by X-ray Photoelectron Spectroscopy (XPS). Plasma-treated graphene films containing more than 40% oxygen were obtained in both oxidative environments. Interestingly, prolonged irradiation led to the reduction of graphene oxides. N-doping of graphene also occurred during the APPJ treatment in H2O2 solution; the nitrogen content of the doped graphene was dependent on the duration of irradiation and reached up to 8.1% within 40 min. Moreover, the H2O2 solution served as a buffer layer that prevented damage to the graphene during plasma irradiation. Four-point probe measurement revealed an increase in sheet resistance of the plasma-treated graphene, indicating the transition of the material property from semi-metallic to semiconducting.

  8. The rate constant of the reaction NCN + H2 and its role in NCN and NO modeling in low pressure CH4/O2/N2-flames.

    PubMed

    Faßheber, Nancy; Lamoureux, Nathalie; Friedrichs, Gernot

    2015-06-28

    Bimolecular reactions of the NCN radical play a key role in modeling prompt-NO formation in hydrocarbon flames. The rate constant of the so-far neglected reaction NCN + H2 has been experimentally determined behind shock waves under pseudo-first order conditions with H2 as the excess component. NCN3 thermal decomposition has been used as a quantitative high temperature source of NCN radicals, which have been sensitively detected by difference UV laser absorption spectroscopy at [small nu, Greek, tilde] = 30383.11 cm(-1). The experiments were performed at two different total densities of ρ≈ 4.1 × 10(-6) mol cm(-3) and ρ≈ 7.4 × 10(-6) mol cm(-3) (corresponding to pressures between p = 324 mbar and p = 1665 mbar) and revealed a pressure independent reaction. In the temperature range 1057 K < T < 2475 K, the overall rate constant can be represented by the Arrhenius expression k/(cm(3) mol(-1) s(-1)) = 4.1 × 10(13) exp(-101 kJ mol(-1)/RT) (Δlog k = ±0.11). The pressure independent reaction as well as the measured activation energy is consistent with a dominating H abstracting reaction channel yielding the products HNCN + H. The reaction NCN + H2 has been implemented together with a set of reactions for subsequent HNCN and HNC chemistry into the detailed GDFkin3.0_NCN mechanism for NOx flame modeling. Two fuel-rich low-pressure CH4/O2/N2-flames served as examples to quantify the impact of the additional chemical pathways. Although the overall NCN consumption by H2 remains small, significant differences have been observed for NO yields with the updated mechanism. A detailed flux analysis revealed that HNC, mainly arising from HCN/HNC isomerization, plays a decisive role and enhances NO formation through a new HNC → HNCO → NH2→ NH → NO pathway.

  9. The rate constant of the reaction NCN + H2 and its role in NCN and NO modeling in low pressure CH4/O2/N2-flames.

    PubMed

    Faßheber, Nancy; Lamoureux, Nathalie; Friedrichs, Gernot

    2015-06-28

    Bimolecular reactions of the NCN radical play a key role in modeling prompt-NO formation in hydrocarbon flames. The rate constant of the so-far neglected reaction NCN + H2 has been experimentally determined behind shock waves under pseudo-first order conditions with H2 as the excess component. NCN3 thermal decomposition has been used as a quantitative high temperature source of NCN radicals, which have been sensitively detected by difference UV laser absorption spectroscopy at [small nu, Greek, tilde] = 30383.11 cm(-1). The experiments were performed at two different total densities of ρ≈ 4.1 × 10(-6) mol cm(-3) and ρ≈ 7.4 × 10(-6) mol cm(-3) (corresponding to pressures between p = 324 mbar and p = 1665 mbar) and revealed a pressure independent reaction. In the temperature range 1057 K < T < 2475 K, the overall rate constant can be represented by the Arrhenius expression k/(cm(3) mol(-1) s(-1)) = 4.1 × 10(13) exp(-101 kJ mol(-1)/RT) (Δlog k = ±0.11). The pressure independent reaction as well as the measured activation energy is consistent with a dominating H abstracting reaction channel yielding the products HNCN + H. The reaction NCN + H2 has been implemented together with a set of reactions for subsequent HNCN and HNC chemistry into the detailed GDFkin3.0_NCN mechanism for NOx flame modeling. Two fuel-rich low-pressure CH4/O2/N2-flames served as examples to quantify the impact of the additional chemical pathways. Although the overall NCN consumption by H2 remains small, significant differences have been observed for NO yields with the updated mechanism. A detailed flux analysis revealed that HNC, mainly arising from HCN/HNC isomerization, plays a decisive role and enhances NO formation through a new HNC → HNCO → NH2→ NH → NO pathway. PMID:26017854

  10. Feasibility of Silver Doped TiO2/Glass Fiber Photocatalyst under Visible Irradiation as an Indoor Air Germicide

    PubMed Central

    Pham, Thanh-Dong; Lee, Byeong-Kyu

    2014-01-01

    This study investigated the feasibility of using Ag-TiO2 photocatalyst supported on glass fiber (Ag-TiO2/GF) prepared by a sol-gel method as an indoor air germicide. An experimental model was designed to investigate the bacterial disinfection efficiency of Staphylococcus (Staph), the most popular bacterium in hospitals in Korea, by the Ag-TiO2/GF photocatalyst. The silver content in Ag/TiO2 was altered from 1 to 10% to investigate the optimal ratio of Ag doped on TiO2/glass fiber (TiO2/GF) for photocatalytic disinfection of Staph. This study confirmed that Ag in Ag-TiO2/GF could work as an electron sink or donor to increase photocatalytic activity and promote the charge separation of electron-hole pairs generated from TiO2 after photon absorption. Ag also acts as an intermediate agent for the transfer of photo-generated electrons from the valence band of TiO2 to an acceptor (O2 gas) to promote photo-oxidation processes. The photocatalytic disinfection activity of Ag-TiO2/GF under visible light increased with the increase in silver content up to 7.5% and then slightly decreased with further increasing silver content. The highest disinfection efficiency and disinfection capacity of Staph using 7.5% Ag-TiO2/GF were 75.23% and 20 (CFU∙s−1∙cm−2) respectively. The medium level of humidity of 60% ± 5% showed better photocatalytic disinfection than the lower (40% ± 5%) or higher (80% ± 5%) levels. PMID:24658408

  11. Microstructure of Suspension Plasma Spray and Air Plasma Spray Al2O3-ZrO2 Composite Coatings

    NASA Astrophysics Data System (ADS)

    Chen, Dianying; Jordan, Eric H.; Gell, Maurice

    2009-09-01

    Al2O3-ZrO2 coatings were deposited by the suspension plasma spray (SPS) molecularly mixed amorphous powder and the conventional air plasma spray (APS) Al2O3-ZrO2 crystalline powder. The amorphous powder was produced by heat treatment of molecularly mixed chemical solution precursors below their crystallization temperatures. Phase composition and microstructure of the as-synthesized and heat-treated SPS and APS coatings were characterized by XRD and SEM. XRD analysis shows that the as-sprayed SPS coating is composed of α-Al2O3 and tetragonal ZrO2 phases, while the as-sprayed APS coating consists of tetragonal ZrO2, α-Al2O3, and γ-Al2O3 phases. Microstructure characterization revealed that the Al2O3 and ZrO2 phase distribution in SPS coatings is much more homogeneous than that of APS coatings.

  12. Experimental and modeling study on effects of N2 and CO2 on ignition characteristics of methane/air mixture

    PubMed Central

    Zeng, Wen; Ma, Hongan; Liang, Yuntao; Hu, Erjiang

    2014-01-01

    The ignition delay times of methane/air mixture diluted by N2 and CO2 were experimentally measured in a chemical shock tube. The experiments were performed over the temperature range of 1300–2100 K, pressure range of 0.1–1.0 MPa, equivalence ratio range of 0.5–2.0 and for the dilution coefficients of 0%, 20% and 50%. The results suggest that a linear relationship exists between the reciprocal of temperature and the logarithm of the ignition delay times. Meanwhile, with ignition temperature and pressure increasing, the measured ignition delay times of methane/air mixture are decreasing. Furthermore, an increase in the dilution coefficient of N2 or CO2 results in increasing ignition delays and the inhibition effect of CO2 on methane/air mixture ignition is stronger than that of N2. Simulated ignition delays of methane/air mixture using three kinetic models were compared to the experimental data. Results show that GRI_3.0 mechanism gives the best prediction on ignition delays of methane/air mixture and it was selected to identify the effects of N2 and CO2 on ignition delays and the key elementary reactions in the ignition chemistry of methane/air mixture. Comparisons of the calculated ignition delays with the experimental data of methane/air mixture diluted by N2 and CO2 show excellent agreement, and sensitivity coefficients of chain branching reactions which promote mixture ignition decrease with increasing dilution coefficient of N2 or CO2. PMID:25750753

  13. Experimental and modeling study on effects of N2 and CO2 on ignition characteristics of methane/air mixture.

    PubMed

    Zeng, Wen; Ma, Hongan; Liang, Yuntao; Hu, Erjiang

    2015-03-01

    The ignition delay times of methane/air mixture diluted by N2 and CO2 were experimentally measured in a chemical shock tube. The experiments were performed over the temperature range of 1300-2100 K, pressure range of 0.1-1.0 MPa, equivalence ratio range of 0.5-2.0 and for the dilution coefficients of 0%, 20% and 50%. The results suggest that a linear relationship exists between the reciprocal of temperature and the logarithm of the ignition delay times. Meanwhile, with ignition temperature and pressure increasing, the measured ignition delay times of methane/air mixture are decreasing. Furthermore, an increase in the dilution coefficient of N2 or CO2 results in increasing ignition delays and the inhibition effect of CO2 on methane/air mixture ignition is stronger than that of N2. Simulated ignition delays of methane/air mixture using three kinetic models were compared to the experimental data. Results show that GRI_3.0 mechanism gives the best prediction on ignition delays of methane/air mixture and it was selected to identify the effects of N2 and CO2 on ignition delays and the key elementary reactions in the ignition chemistry of methane/air mixture. Comparisons of the calculated ignition delays with the experimental data of methane/air mixture diluted by N2 and CO2 show excellent agreement, and sensitivity coefficients of chain branching reactions which promote mixture ignition decrease with increasing dilution coefficient of N2 or CO2. PMID:25750753

  14. Experimental and modeling study on effects of N2 and CO2 on ignition characteristics of methane/air mixture.

    PubMed

    Zeng, Wen; Ma, Hongan; Liang, Yuntao; Hu, Erjiang

    2015-03-01

    The ignition delay times of methane/air mixture diluted by N2 and CO2 were experimentally measured in a chemical shock tube. The experiments were performed over the temperature range of 1300-2100 K, pressure range of 0.1-1.0 MPa, equivalence ratio range of 0.5-2.0 and for the dilution coefficients of 0%, 20% and 50%. The results suggest that a linear relationship exists between the reciprocal of temperature and the logarithm of the ignition delay times. Meanwhile, with ignition temperature and pressure increasing, the measured ignition delay times of methane/air mixture are decreasing. Furthermore, an increase in the dilution coefficient of N2 or CO2 results in increasing ignition delays and the inhibition effect of CO2 on methane/air mixture ignition is stronger than that of N2. Simulated ignition delays of methane/air mixture using three kinetic models were compared to the experimental data. Results show that GRI_3.0 mechanism gives the best prediction on ignition delays of methane/air mixture and it was selected to identify the effects of N2 and CO2 on ignition delays and the key elementary reactions in the ignition chemistry of methane/air mixture. Comparisons of the calculated ignition delays with the experimental data of methane/air mixture diluted by N2 and CO2 show excellent agreement, and sensitivity coefficients of chain branching reactions which promote mixture ignition decrease with increasing dilution coefficient of N2 or CO2.

  15. Constraining N2O emissions over the last century by firn air isotope measurements in both hemispheres

    NASA Astrophysics Data System (ADS)

    Prokopiou, Markella; Sapart, Celia; Martinerie, Patricia; Witrant, Emmanuel; Ishijima, Kentaro; Magand, Sophie; Kaiser, Jan; van de Wal, Roderik; Röckmann, Thomas

    2014-05-01

    N2O is a greenhouse gas that it is responsible for increased radiative forcing of the climate system. In addition to this, it is primarily destroyed in the stratosphere providing an important source of NOx, which in turn plays an important role in ozone depletion. Large uncertainties remain as to the actual strength of the individual sources of N2O. Knowledge of the historical record, of the temporal evolution of N2O emissions, can provide insight on how its sources and sinks altered during the industrial period. Data from air trapped in firn enables us to better determine the source/sink strength emissions over time. In this study we analyze firn measurements on 15N, 18O and position dependent 15N isotopic composition of N2O, from both hemispheres, combining new and previously published data, in order to constrain the N2O budget. From the Northern Hemisphere we use data from North Greenland Ice core Project (NGRIP) and North Eemian Ice core Project (NEEM) and for the Southern Hemisphere we use data from Berkner Island (BI), Dronning Maud Land (DML) and Dome Concordia (DOME C). Results show that the isotopic composition of 15N, 18O of N2O is presently more depleted which indicates a strong depleting source contribution probably originating from agricultural activities. The LGGE-GIPSA firn air diffusion model allows single site reconstructions, as well as using all data together in a multi-site inversion, in order to reconstruct the temporal evolution of N2O and its isotopic composition. We investigate the consistency between the different datasets and present a best-guess isotope history based on the firn air data. A simple two-box atmospheric model is applied in order to simulate the N2O atmospheric contribution from different sources and sinks.

  16. Decomposition of benzene and toluene in air streams in fixed-film photoreactors coated with TiO2 catalyst.

    PubMed

    Ku, Young; Chen, Juan-Shiang; Chen, Hua-Wei

    2007-03-01

    The decomposition of benzene and toluene in air streams by UV/TiO2 process was studied in different annular photoreactors under various operating conditions. The shells of reactors used in this research are made of stainless steel, Pyrex glass, or titanium. The TiO2 film was coated to the inner surface of the reactors by either rotating coating or sol-gel techniques. The TiO2 films coated by sol-gel technique were found to be smoother and more uniform than those coated by rotating coating. However, experimental results indicated that the photocatalysis of benzene or toluene in a glass reactor with rotating-coated TiO2 film delivered higher decompositions in air streams than that with sol-gel coated reactors. Benzene and toluene were decomposed more effectively in a coated glass reactor than in a coated stainless steel reactor under the same operating conditions. The presence of water vapor in air-stream plays an important role in the decomposition of benzene and toluene, and a relative humidity of approximately 5-6% was found to be adequate. The presence of excessive amounts of humidity retarded the decomposition to certain extents possibly results from the competitive adsorption of water molecules on the active sites of TiO2.

  17. AES, EELS and XPS characterization of Ti(C, N, O) films prepared by PLD using a Ti target in N 2, CH 4, O 2 and CO as reactive gases

    NASA Astrophysics Data System (ADS)

    Soto, G.

    2004-06-01

    Titanium-based films were grown on (1 0 0)-Si substrates by the pulsed laser deposition (PLD) method using a Ti target in reactive atmospheres. The films were grown in vacuum (Ti-film), O 2 (TiO x), N 2 (TiN x), CH 4 (TiC x), CO (TiC xO y), N 2+CH 4 (TiC xN y) and CO+N 2 (TiC xN yO z). After depositions, every film is characterized in situ by Auger, electron-energy loss and X-ray photoelectron (XPS) spectroscopies. For the binary compounds the stoichiometry is regulated without difficulty by gas pressure during ablation. However, for ternary and quaternary compounds there is a tendency to produce chemically inhomogeneous films. For example, the ablation of Ti in a N 2+CH 4 environment results in a TiNC:C composite. In this case, the overabundance of nitrogen influences the segregation of carbon. In the other hand, the O 2+CH 4 mixture was ineffectively to produce TiC xO y films, yielding mostly TiO 2 with traces of embedded carbon. By using CO as reactive gas the TiC xO y films were completed. Also, a mixture of CO with N 2 was tested to produce quaternary TiC xN yO z compounds. Based on these results, it is recommended that better control on film stoichiometry and chemical homogeneity can be achieved by using reactive gases with predetermined C:N:O ratios.

  18. Efficiency of clay-TiO2 nanocomposites on the photocatalytic eliminationof a model hydrophobic air pollutant

    SciTech Connect

    Kibanova, Daria; Cervini-Silva, Javiera; Destaillats, Hugo

    2009-01-01

    Clay-supported TiO2 photocatalysts can potentially improve the performance of air treatment technologies via enhanced adsorption and reactivity of target volatile organic compounds (VOCs). In this study, a bench-top photocatalytic flow reactor was used to evaluate the efficiency of hectorite-TiO2 and kaolinite-TiO2, two novel composite materials synthesized in our laboratory. Toluene, a model hydrophobic VOC and a common indoor air pollutant, was introduced in the air stream at realistic concentrations, and reacted under UVA (gamma max = 365 nm) or UVC (gamma max = 254 nm) irradiation. The UVC lamp generated secondary emission at 185 nm, leading to the formation of ozone and other short-lived reactive species. Performance of clay-TiO2 composites was compared with that of pure TiO2 (Degussa P25), and with UV irradiation in the absence of photocatalyst under identical conditions. Films of clay-TiO2 composites and of P25 were prepared by a dip-coating method on the surface of Raschig rings, which were placed inside the flow reactor. An upstream toluene concentration of ~;;170 ppbv was generated by diluting a constant flow of toluene vapor from a diffusion source with dry air, or with humid air at 10, 33 and 66percent relative humidity (RH). Toluene concentrations were determined by collecting Tenax-TA (R) sorbent tubes downstream of the reactor, with subsequent thermal desorption -- GC/MS analysis. The fraction of toluene removed, percentR, and the reaction rate, Tr, were calculated for each experimental condition from the concentration changes measured with and without UV irradiation. Use of UVC light (UV/TiO2/O3) led to overall higher reactivity, which can be partially attributed to the contribution of gas phase reactions by short-lived radical species. When the reaction rate was normalized to the light irradiance, Tr/I gamma, the UV/TiO2 reaction under UVA irradiation was more efficient for samples with a higher content of TiO2 (P25 and Hecto-TiO2), but not for Kao-TiO

  19. Comparison of Benzene & Toluene removal from synthetic polluted air with use of Nano photocatalyticTiO2/ ZNO process

    PubMed Central

    2014-01-01

    Background Mono aromatic hydrocarbons (BTEX) are a group of hazardous pollutants which originate from sources such as refineries, gas, and oil extraction fields, petrochemicals and paint and glue industries. Conventional methods, including incineration, condensation, adsorption and absorption have been used for removal of VOCs. None of these methods is economical for removal of pollutants of polluted air with low to moderate concentrations. The heterogeneous photocatalytic processes involve the chemical reactions to convert pollutant to carbon dioxide and water. The aim of this paper is a comparison of Benzene & Toluene removal from synthetic polluted air using a Nano photocatalytic TiO2/ ZNO process. Results The X-ray diffraction (XRD) patterns showed that Nano crystals of TiO2 and ZNO were in anatase and rutile phases. Toluene & benzene were decomposed by TiO2/ ZNO Nano photocatalyst and UV radiation. Kruskal-wallis Test demonstrated that there are significant differences (pvalue < 0.05) between pollutant concentrations in different operational conditions. Conclusions Degradation of toluene & benzene increases with increasing UV intensity and decreasing initial concentrations. Effect of TiO2/ZNO Nano photocatalyst on benzene is less than that on toluene. In this research, Toluene & benzene removal by TiO2/ZNO and UV followed first-order reactions. PMID:24499601

  20. Synthesis of Cu/TiO2/organo-attapulgite fiber nanocomposite and its photocatalytic activity for degradation of acetone in air

    NASA Astrophysics Data System (ADS)

    Zhang, Gaoke; Wang, He; Guo, Sheng; Wang, Junting; Liu, Jin

    2016-01-01

    The Cu/TiO2/organo-attapulgite fiber (CTOA) nanocomposite was synthesized by a facile method and was used for photocatalytic degradation of acetone in air under UV light irradiation. The as-prepared samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscope (SEM), transmission electron microscopy (TEM), UV-vis diffuse reflectance spectrum (UV-vis DRS), inductively coupled plasma (ICP) spectrometry and N2 adsorption-desorption measurement. The results showed that the structure of organo-attapulgite (OAT) had no obvious change as compared to unmodified attapulgite (AT) and the attapulgite fibers in the OAT were well-dispersed. Both micropores and mesopores exist in the CTOA catalyst. The CTOA catalysts prepared at the Cu/TiO2 molar ratio of 0.003 shows an excellent photocatalytic activity for the degradation of acetone in air. The synergistic effect of Cu species and cetyltrimethylammonium bromide modification can be responsible for the enhanced photocatalytic activity of the CTOA catalyst. The mechanism of the photocatalytic degradation of acetone by the CTOA catalyst was discussed.

  1. Fractal analysis methods for solid alkane monolayer domains at SiO2/air interfaces.

    PubMed

    Knüfing, Lydia; Schollmeyer, Hauke; Riegler, Hans; Mecke, Klaus

    2005-02-01

    A systematic evaluation of various fractal analysis methods is essential for studying morphologies of finite and noisy experimental patterns such as domains of long chain alkanes at SiO(2)/air interfaces. The derivation of trustworthy fractal dimensions crucially relies on the definition of confidence intervals for the assumed scaling range. We demonstrate that the determination of the intervals can be improved largely by comparing the scaling behavior of different morphological measures (area, boundary, curvature). We show that the combination of area and boundary data from coarse-grained structures obtained with the box-counting method reveals clear confidence limits and thus credible morphological data. This also holds for the Minkowski density method. It also reveals the confidence range. Its main drawback, the larger swing-in period at the lower cutoff compared to the box-counting method, is compensated by more details on the scaling behavior of area, boundary, and curvature. The sandbox method is less recommendable. It essentially delivers the same data as box-counting, but it is more susceptible to finite size effects at the lower cutoff. It is found that the domain morphology depends on the surface coverage of alkanes. The individual domains at low surface coverage have a fractal dimension of approximately 1.7, whereas at coverages well above 50% the scaling dimension is 2 with a large margin of uncertainty at approximately 50% coverage. This change in morphology is attributed to a crossover from a growth regime dominated by diffusion-limited aggregation of individual domains to a regime where the growth is increasingly affected by annealing and the interaction of solid growth fronts which approach each other and thus compete for the alkane supply.

  2. A novel thermally stable hydroperoxo-copper(II) complex in a Cu(N2O2) chromophore of a potential N4O2 donor Schiff base ligand: synthesis, structure and catalytic studies.

    PubMed

    Biswas, Surajit; Dutta, Arpan; Debnath, Mainak; Dolai, Malay; Das, Kalyan K; Ali, Mahammad

    2013-09-28

    The generation and study of metal-hydroperoxo/metal-peroxo (LCu(II)-OOH or LCu(II)-OO˙) complexes is a fascinating area of research of many chemical and biochemical researchers, because of their involvement as active intermediates in many biological and industrial catalytic oxidation processes. For this purpose we have designed a bulky hexa-coordinating ligand with potential N4O2 donor atoms which could provide an opportunity to synthesize a mononuclear Cu(II) complex with an aim to utilize it in the catalytic oxidation of aromatic hydrocarbons by an environmentally benign oxidant, H2O2. The Cu(II) complex (1) was structurally characterized and found to have square-planar geometry with the two pyrazolyl groups remaining in dangling mode. A novel mononuclear complex [Et3NH][LCu(II)-OOH] (2) was found to form in the reaction between 1 and H2O2 in the presence of Et3N. The presence of this dangling groups favours the stability of hydroperoxo species, [LCu-OOH](-) (2) through H-bonding with the coordinated phenoxo oxygen atom, which was confirmed by ESI-MS(+) and MS(-) (m/z) mass analysis and DFT calculations. This complex was found to be thermally stable at room temperature [k(d) = (5.67 ± 0.03) × 10(-5) s(-1) at 25 °C] and may be due to the formation of O-O-H···O(phenoxo) H-bonding as delineated by the DFT calculations. Complex 1 was found to be an efficient catalyst for the oxidation of aromatic hydrocarbons to the corresponding aldehyde and alcohol in 2:1 mole ratio with TON ~300. PMID:23884097

  3. Effect of air annealing on structure and magnetic properties of Sn1-xFexO2 thin films

    NASA Astrophysics Data System (ADS)

    Kuppan, M.; Begam, M. Regana; Babu, S. Harinath; Kaleemulla, S.; Rao, N. Madhusudhana; Krishnamoorthi, C.

    2016-05-01

    Sn1-xFexO2 (x = 0.07) thin films were prepared on to glass substrates using flash evaporation technique and annealed in air at different temperatures. The X-ray diffraction study showsed that all the thin films annealed at different temperatures were in tetragonal rutile structure of SnO2. The Elemental analysis confirms the presence of Fe and Sn and O in the films. The magnetic measurements were carried out using vibrating sample magnetometer and found that the strength of magnetization decreased with increase of annealing temperature.

  4. Structural, elastic, and electronic properties of icosahedral boron subcarbides (B12C3, B13C2), subnitride B12N2, and suboxide B12O2 from data of SCC-DFTB calculations

    NASA Astrophysics Data System (ADS)

    Enyashin, A. N.; Ivanovskii, A. L.

    2011-08-01

    The structural, elastic, and electronic properties of a series of icosahedral phases, such as boron subcarbides B12C3 and B13C2, subnitride B12N2, and suboxide B12O2, have been studied in the framework of the SCC-DFTB method. It has been found that the B12C2 and B13C2 phases manifest metal-like properties, while B12C3 and B12O2 are semiconductors. The estimates have shown that the insertion of 2 p atoms (C, N, or O) into intericosahedral pores of elemental boron can cause both a decrease in its elastic modulus (an increase in the compressibility of B12N2) and a sharp increase in the modulus B (in subcarbides B12C3 and B12BCC). On the other hand, the insertion of 2 p atoms into α-B12 will favor an increase in its hardness (suboxide B12O2 will have a maximum hardness).

  5. Effect of CuO2 planes on the structural and superconducting transport properties of [CuTl - 12(n - 1)n;n = 2,3,4] superconductor family

    NASA Astrophysics Data System (ADS)

    Muzaffar, M. Usman; Khan, Nawazish A.

    2016-06-01

    Cu0.5Tl0.5Ba2Can-1CunO2n+4-δ (n = 2, 3, 4) superconducting bulk samples have been synthesized by using two-step solid state reaction method. We investigated the effects of CuO2 planes on the structural and superconducting transport properties of [CuTl - 12(n - 1)n; n = 2, 3, 4] superconducting family. These samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) absorption spectroscopy and DC-resistivity (ρ) measurements. These samples are c-axis length oriented and have shown orthorhombic crystal structure. All the samples have shown metallic variations of resistivity from room temperature down to onset of superconductivity. The zero resistivity critical temperature Tc(R = 0) increases with the increase in superconducting planes and normal state resistivity systematically decreases, which show the density of inadvertent defects decreases in the final compound. The apical oxygen phonon modes are hardened as observed in the FTIR absorption measurements. The intrinsic microscopic superconducting parameters, such as the cross-over temperatures, coherence length along c-axis (ξc(0)) at 0 K, inter-layer coupling (J), inter-grain coupling (α) and fermi velocity (VF), were extracted from the fluctuation-induced conductivity (FIC) analysis. FIC analysis also showed the improvement in superconductivity with the increase in CuO2 planes.

  6. Effect of CuO2 planes on the structural and superconducting transport properties of [CuTl ‑ 12(n ‑ 1)n;n = 2,3,4] superconductor family

    NASA Astrophysics Data System (ADS)

    Muzaffar, M. Usman; Khan, Nawazish A.

    2016-06-01

    Cu0.5Tl0.5Ba2Can‑1CunO2n+4‑δ (n = 2, 3, 4) superconducting bulk samples have been synthesized by using two-step solid state reaction method. We investigated the effects of CuO2 planes on the structural and superconducting transport properties of [CuTl ‑ 12(n ‑ 1)n; n = 2, 3, 4] superconducting family. These samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) absorption spectroscopy and DC-resistivity (ρ) measurements. These samples are c-axis length oriented and have shown orthorhombic crystal structure. All the samples have shown metallic variations of resistivity from room temperature down to onset of superconductivity. The zero resistivity critical temperature Tc(R = 0) increases with the increase in superconducting planes and normal state resistivity systematically decreases, which show the density of inadvertent defects decreases in the final compound. The apical oxygen phonon modes are hardened as observed in the FTIR absorption measurements. The intrinsic microscopic superconducting parameters, such as the cross-over temperatures, coherence length along c-axis (ξc(0)) at 0 K, inter-layer coupling (J), inter-grain coupling (α) and fermi velocity (VF), were extracted from the fluctuation-induced conductivity (FIC) analysis. FIC analysis also showed the improvement in superconductivity with the increase in CuO2 planes.

  7. Effect of small admixtures of N2, H2 or O2 on the electron drift velocity in argon: experimental measurements and calculations

    NASA Astrophysics Data System (ADS)

    Stano, M.; Pinhão, N.; Loffhagen, D.; Kučera, M.; Donkó, Z.; Matejčík, Š.

    2011-12-01

    The electron drift velocity in argon with admixtures of up to 2% of nitrogen, hydrogen or oxygen is measured in a pulsed Townsend system for reduced electric fields ranging from 0.1 Td to 2.5 Td. The results are compared with those obtained by Monte Carlo simulations and from the solution of the electron Boltzmann equation using two different solution techniques: a multiterm method based on Legendre polynomial expansion of the angular dependence of the velocity distribution function and the S n method applied to a density gradient expansion representation of the distribution function. An almost perfect agreement between the results of the three numerical methods and, in general, very good agreement between the experimental and the calculated results is obtained. Measurements in Ar-O2 mixtures were limited by electron attachment to oxygen molecules, which contributes to the measured drift velocity. As a result of this attachment contribution, the bulk drift velocity becomes larger than the flux drift velocity if attachment is more probable for electrons with energy below the mean value and smaller in the opposite case. Attachment also contributes to the negative differential conductivity observed in Ar-O2 mixtures.

  8. Development of automated preparation system for isotopocule analysis of N2O in various air samples

    NASA Astrophysics Data System (ADS)

    Toyoda, Sakae; Yoshida, Naohiro

    2016-05-01

    Nitrous oxide (N2O), an increasingly abundant greenhouse gas in the atmosphere, is the most important stratospheric ozone-depleting gas of this century. Natural abundance ratios of isotopocules of N2O, NNO molecules substituted with stable isotopes of nitrogen and oxygen, are a promising index of various sources or production pathways of N2O and of its sink or decomposition pathways. Several automated methods have been reported to improve the analytical precision for the isotopocule ratio of atmospheric N2O and to reduce the labor necessary for complicated sample preparation procedures related to mass spectrometric analysis. However, no method accommodates flask samples with limited volume or pressure. Here we present an automated preconcentration system which offers flexibility with respect to the available gas volume, pressure, and N2O concentration. The shortest processing time for a single analysis of typical atmospheric sample is 40 min. Precision values of isotopocule ratio analysis are < 0.1 ‰ for δ15Nbulk (average abundances of 14N15N16O and 15N14N16O relative to 14N14N16O), < 0.2 ‰ for δ18O (relative abundance of 14N14N18O), and < 0.5 ‰ for site preference (SP; difference between relative abundance of 14N15N16O and 15N14N16O). This precision is comparable to that of other automated systems, but better than that of our previously reported manual measurement system.

  9. Differential cross sections for scattering of 0.5-, 1.5-, and 5.0-keV hydrogen atoms by He, H2, N2, and O2

    NASA Technical Reports Server (NTRS)

    Newman, J. H.; Chen, Y. S.; Smith, K. A.; Stebbings, R. F.

    1986-01-01

    This paper reports measurements of absolute cross sections, differential in angle, for scattering of 0.5-, 1.5-, and 5.0-keV hydrogen atoms by He, H2, N2, and O2 at laboratory scattering angles between 0.1 and 5 deg. The measured cross sections are the sums of those for elastic and inelastic collisions having a fast H atom product and are needed for calculating energy transfer to the upper atmosphere from precipitating ring current particles.

  10. Guided ion beam studies of the reactions of Vn+ (n=2-17) with O2: Bond energies and dissociation pathways

    NASA Astrophysics Data System (ADS)

    Xu, J.; Rodgers, M. T.; Griffin, J. B.; Armentrout, P. B.

    1998-06-01

    The kinetic energy dependence of the reactions of Vn+ (n=2-17) with oxygen is studied using a guided ion beam mass spectrometer. In all but the smallest clusters, the primary reaction process at low energies is the formation of a vanadium cluster dioxide ion which then loses one or two vanadium atoms or a vanadium oxide diatom (VO). Vanadium atom loss is the preferred reaction pathway for large clusters (n⩾5), whereas loss of VO is more favorable for the smallest reactant clusters (n⩽4). As the collision energy is increased, these primary products dissociate further by loss of additional vanadium atoms. Bond dissociation energies of the vanadium cluster oxides are determined by analysis of the kinetic energy dependence of several different products. The effect of oxygen atoms on the stabilities of vanadium cluster ions is discussed and compared with bulk phase thermochemistry.

  11. Palladium(II) and zinc(II) complexes of neutral [N2O2] donor Schiff bases derived from furfuraldehyde: Synthesis, characterization, fluorescence and corrosion inhibitors of ligands

    NASA Astrophysics Data System (ADS)

    Ali, Omyma A. M.

    2014-11-01

    Metal complexes of Schiff bases derived from furfuraldehyde and 4,5-dimethyl-1,2-phenylendiamine (L1) or 4,5-dichloro-1,2-phenylendiamine (L2) have been reported and characterized based on elemental analyses, IR, 1H NMR, UV-Vis, magnetic moment, molar conductance and thermal analysis. The complexes are found to have the formulae [PdL1-2]Cl2 and [ZnL1-2](AcO)2·H2O. The molar conductance data reveal that Pd(II) and Zn(II) chelates are ionic in nature and are of the type 2:1 electrolytes. The spectral data are consistent with a square planar and tetrahedral geometry around Pd(II) and Zn(II), respectively, in which the ligands act as tetradentate ligands. The thermal behavior of some chelates is studied and the activation thermodynamic parameters are calculated using Coats-Redfern method. The corrosion inhibition of stainless steel types 410 and 304 in 1 M HCl using the synthesized Schiff bases as inhibitors have been studied by weight loss method. The obtained data considered these ligands as efficient corrosion inhibitors. The ligands and their metal complexes exhibited considerable antibacterial activity against Staphylococcusaureus, and Escherichiacoli and antifungal activity against Candida albicans.

  12. Palladium(II) and zinc(II) complexes of neutral [N2O2] donor Schiff bases derived from furfuraldehyde: synthesis, characterization, fluorescence and corrosion inhibitors of ligands.

    PubMed

    Ali, Omyma A M

    2014-11-11

    Metal complexes of Schiff bases derived from furfuraldehyde and 4,5-dimethyl-1,2-phenylendiamine (L1) or 4,5-dichloro-1,2-phenylendiamine (L2) have been reported and characterized based on elemental analyses, IR, 1H NMR, UV-Vis, magnetic moment, molar conductance and thermal analysis. The complexes are found to have the formulae [PdL1-2]Cl2 and [ZnL1-2](AcO)2·H2O. The molar conductance data reveal that Pd(II) and Zn(II) chelates are ionic in nature and are of the type 2:1 electrolytes. The spectral data are consistent with a square planar and tetrahedral geometry around Pd(II) and Zn(II), respectively, in which the ligands act as tetradentate ligands. The thermal behavior of some chelates is studied and the activation thermodynamic parameters are calculated using Coats-Redfern method. The corrosion inhibition of stainless steel types 410 and 304 in 1 M HCl using the synthesized Schiff bases as inhibitors have been studied by weight loss method. The obtained data considered these ligands as efficient corrosion inhibitors. The ligands and their metal complexes exhibited considerable antibacterial activity against Staphylococcusaureus, and Escherichiacoli and antifungal activity against Candida albicans. PMID:24858346

  13. Palladium(II) and zinc(II) complexes of neutral [N2O2] donor Schiff bases derived from furfuraldehyde: synthesis, characterization, fluorescence and corrosion inhibitors of ligands.

    PubMed

    Ali, Omyma A M

    2014-11-11

    Metal complexes of Schiff bases derived from furfuraldehyde and 4,5-dimethyl-1,2-phenylendiamine (L1) or 4,5-dichloro-1,2-phenylendiamine (L2) have been reported and characterized based on elemental analyses, IR, 1H NMR, UV-Vis, magnetic moment, molar conductance and thermal analysis. The complexes are found to have the formulae [PdL1-2]Cl2 and [ZnL1-2](AcO)2·H2O. The molar conductance data reveal that Pd(II) and Zn(II) chelates are ionic in nature and are of the type 2:1 electrolytes. The spectral data are consistent with a square planar and tetrahedral geometry around Pd(II) and Zn(II), respectively, in which the ligands act as tetradentate ligands. The thermal behavior of some chelates is studied and the activation thermodynamic parameters are calculated using Coats-Redfern method. The corrosion inhibition of stainless steel types 410 and 304 in 1 M HCl using the synthesized Schiff bases as inhibitors have been studied by weight loss method. The obtained data considered these ligands as efficient corrosion inhibitors. The ligands and their metal complexes exhibited considerable antibacterial activity against Staphylococcusaureus, and Escherichiacoli and antifungal activity against Candida albicans.

  14. Effect of fuel to air ratio on Mach 0.3 burner rig hot corrosion of ZrO2-Y2O3 thermal barrier coatings

    NASA Technical Reports Server (NTRS)

    Hodge, P. E.

    1982-01-01

    A Mach 0.3 burner rig test program was conducted to determine how the fuel to air mass ratio affects the durability of ZrO2-Y2O3/Ni-16Cr-6Al-0.31Y thermal barrier coating systems in combustion products containing 5 ppm Na and 2 ppm V. As the fuel to air mass ratio was increased from 0.039 to 0.049, the durability of ZrO2-6Y2O3, ZrO2-8Y2O3 and ZrO2-12Y2O3 coatings decreased. ZrO2-8Y2O3 coatings were approximately 2X and 1.3X more durable than ZrO2-12Y2O3 and ZrO2-6Y2O3 coatings respectively at the fuel to air mass ratio of 0.039. The number of one hour cycles endured by ZrO2-8Y2O3 coatings varied from averages of 53 to 200 for the fuel to air mass ratios of 0.049 and 0.039, respectively. At the fuel to air mass ratio of 0.049, all ZrO2-Y2O3 coated specimens failed in 40 to 60 one hour cycles

  15. Long-term measurements of atmospheric trace gases (CO2, CH4, N2O, SF6, CO, H2), O2, and δ13CH4 isotopes at Weybourne Atmospheric Observatory, UK: past, present and future

    NASA Astrophysics Data System (ADS)

    Manning, Andrew C.; Forster, Grant L.; Oram, David E.; Reeves, Claire E.; Pickers, Penelope A.; Barningham, S. Thomas; Sturges, William T.; Bandy, Brian; Nisbet, Euan G.; Lowry, David; Fisher, Rebecca; Fleming, Zoe

    2016-04-01

    The Weybourne Atmospheric Observatory (WAO) is situated on the north Norfolk Coast (52.95°N, 1.13°E) in the United Kingdom and is run by the University of East Anglia (UEA), with support from the UK National Centre for Atmospheric Science (NCAS). In 2016, the WAO became a UK-ICOS (Integrated Carbon Observing System) monitoring station. Since 2008, we have been collecting high-precision long-term in situ measurements of atmospheric carbon dioxide (CO2), oxygen (O2), carbon monoxide (CO) and molecular hydrogen (H2), as well as regular bag sampling for δ13CH4. In early 2013, the measurement of atmospheric methane (CH4) commenced, and nitrous oxide (N2O) and sulphur hexafluoride (SF6) began in 2014. We summarise the CO2, O2, CH4, N2O, SF6, CO, H2 and δ13CH4 measurements made to date and highlight some key features observed (e.g. seasonal cycles, long-term trends, pollution events and deposition events). We summarise how the long-term measurements fit into other broader projects which have helped to support the long term time-series at WAO over the years, and highlight how we contribute to broader global atmospheric observation networks.

  16. Vibrational and thermodynamic properties of Ar, N2, O2, H2 and CO adsorbed and condensed into (H,Na)-Y zeolite cages as studied by variable temperature IR spectroscopy.

    PubMed

    Gribov, Evgueni N; Cocina, Donato; Spoto, Giuseppe; Bordiga, Silvia; Ricchiardi, Gabriele; Zecchina, Adriano

    2006-03-14

    The adsorption of Ar, H2, O2, N2 and CO on (H,Na)-Y zeolite (Si/Al = 2.9, H+/Na+ approximately 5) has been studied at variable-temperature (90-20 K) and sub-atmospheric pressure (0-40 mbar) by FTIR spectroscopy. Unprecedented filling conditions of the zeolite cavities were attained, which allowed the investigation of very weakly adsorbed species and of condensed, liquid-like or solid-like, phases. Two pressure regimes were singled out, characterized by: (i) specific interaction at low pressure of the probe molecules (P) with the internal Brønsted and Lewis sites, and (ii) multilayer adsorption at higher pressure. In the case of CO the perturbation of the protonic sites located inside the sodalite cages was also observed. As the molecule is too large to penetrate the sodalite cage, the perturbation is thought to involve a proton jump tunneling mechanism. The adsorption energy for the (HF)OH...P (P = Ar, H2, O2, N2 and CO) specific interaction involving the high frequency Brønsted acid sites exposed in the supercages was derived following the VTIR (variable temperature infrared spectroscopy) method described by E. Garrone and C. Otero Areán (Chem. Soc. Rev., 2005, 34, 846).

  17. TOPICAL REVIEW: High-pressure synthesis, crystal growth, phase diagrams, structural and magnetic properties of Y2Ba4CunO2n+x, HgBa2Can- 1CunO2n+2+delta and quasi-one-dimensional cuprates

    NASA Astrophysics Data System (ADS)

    Karpinski, J.; Meijer, G. I.; Schwer, H.; Molinski, R.; Kopnin, E.; Conder, K.; Angst, M.; Jun, J.; Kazakov, S.; Wisniewski, A.; Puzniak, R.; Hofer, J.; Alyoshin, V.; Sin, A.

    1999-09-01

    In this paper we present a review of high-gas-pressure single crystal growth studies of YBa2Cu4O8 and Y2Ba4Cu7O15-x performed in oxygen pressure up to 3000 bar and Hg1-xMxBa2Can- 1CunO2n+2+icons/Journals/Common/delta" ALT="delta" ALIGN="MIDDLE"/> (M = Pb, Re; n = 1-7) compounds in argon pressure up 11 000 bar at temperature up to 1200 °C. Chain compounds A1-xCuO2 (A = Sr, Ca, Ba) have been synthesized at high oxygen pressure up to 2000 bar. High-pressure phase diagram studies of the investigated systems are also discussed. Structure analyses of Y2Ba4CunO2n+x (n = 6-8), Hg1-xMxBa2Can- 1CunO2n+2+icons/Journals/Common/delta" ALT="delta" ALIGN="MIDDLE"/> (M = Pb, Re; n = 1-8), Sr0.73CuO2 and (Sr,Ca)4Cu6O10 single crystals have been performed. The effects of substitutions and trends in bondlengths are discussed. The vortex state properties of HgBa2Ca2Cu3O8+icons/Journals/Common/delta" ALT="delta" ALIGN="MIDDLE"/> and YBa2Cu4O8 single crystals are compared. For Hg-based compounds, the influence of oxygen content, chemical substitutions and radiation defects on vortex pinning were determined. The quasi-one-dimensional cuprates Ca0.83CuO2 and Sr0.73CuO2 show an antiferromagnetically ordered state of long-range 3D character at T < 10 K. The spin dynamics of Sr0.73CuO2, measured by inelastic neutron scattering, indicate that this ordered state coexists with a dimerized singlet ground state.

  18. Highly efficient photocatalytic TiO2 coatings deposited by open air atmospheric pressure plasma jet with aerosolized TTIP precursor

    NASA Astrophysics Data System (ADS)

    Fakhouri, H.; Ben Salem, D.; Carton, O.; Pulpytel, J.; Arefi-Khonsari, F.

    2014-07-01

    A simple method to deposit photocatalytic TiO2 coatings, at a high rate (20-40 µm s-1), and with a high porosity, is reported in this paper. This method, which allows the treatment of membranes (with an 800 nm pore size), is based on the introduction of a liquid precursor sprayed into an open-air atmospheric pressure plasma jet (APPJ). The photocatalytic activity of the TiO2 thin films prepared by APPJ have been compared with our best N-doped TiO2 thin films, deposited by reactive radio frequency (RF) magnetron sputtering, previously reported in the literature. The morphology, chemical composition, photoelectrochemical, and photocatalytic properties of the coatings have been studied in this paper. Significant control of the porosity and crystallinity was achieved by varying the deposition parameters and the annealing temperature. Under optimized conditions, the TiO2 coatings deposited by APPJ are characterized by a higher photocatalytic activity as compared to the optimized thin films deposited by RF sputtering. This difference can be explained by the higher specific surface of the APPJ coatings. Finally, the most interesting characteristic of this APPJ-liquid spray process is its capacity to treat membranes without blocking the pores, and to produce photocatalytic membranes which can efficiently combine filtration and photocatalysis for water treatment.

  19. Graphene oxide electrocatalyst on MnO2 air cathode as an efficient electron pump for enhanced oxygen reduction in alkaline solution

    NASA Astrophysics Data System (ADS)

    Basirun, Wan Jeffrey; Sookhakian, Mehran; Baradaran, Saeid; Endut, Zulkarnain; Mahmoudian, Mohammad Reza; Ebadi, Mehdi; Yousefi, Ramin; Ghadimi, Hanieh; Ahmed, Sohail

    2015-03-01

    Graphene oxide (GO) was deposited on the surface of a MnO2 air cathode by thermal evaporation at 50°C from a GO colloidal suspension. Fourier transformed infrared spectroscopy and field emission scanning electron microscopy confirmed the presence of GO on the MnO2 air cathode (GO-MnO2). Voltammetry and chrono-amperometry showed increased currents for the oxygen reduction reaction (ORR) in 6 M KOH solution for GO-MnO2 compared to the MnO2 cathode. The GO-MnO2 was used as an air cathode in an alkaline tin-air cell and produced a maximum power density of 13 mW cm-2, in contrast to MnO2, which produced a maximum power density of 9.2 mW cm-2. The electrochemical impedance spectroscopy results suggest that the chemical step for the ORR is the rate determining step, as proposed earlier by different researchers. It is suggested that the presence of GO and electrochemically reduced graphene oxide (ERGO) on the MnO2 surface are responsible for the increased rate of this step, whereby GO and ERGO accelerate the process of electron donation to the MnO2 and to adsorbed oxygen atoms.

  20. Graphene oxide electrocatalyst on MnO2 air cathode as an efficient electron pump for enhanced oxygen reduction in alkaline solution

    PubMed Central

    Basirun, Wan Jeffrey; Sookhakian, Mehran; Baradaran, Saeid; Endut, Zulkarnain; Mahmoudian, Mohammad Reza; Ebadi, Mehdi; Yousefi, Ramin; Ghadimi, Hanieh; Ahmed, Sohail

    2015-01-01

    Graphene oxide (GO) was deposited on the surface of a MnO2 air cathode by thermal evaporation at 50°C from a GO colloidal suspension. Fourier transformed infrared spectroscopy and field emission scanning electron microscopy confirmed the presence of GO on the MnO2 air cathode (GO-MnO2). Voltammetry and chrono-amperometry showed increased currents for the oxygen reduction reaction (ORR) in 6 M KOH solution for GO-MnO2 compared to the MnO2 cathode. The GO-MnO2 was used as an air cathode in an alkaline tin-air cell and produced a maximum power density of 13 mW cm−2, in contrast to MnO2, which produced a maximum power density of 9.2 mW cm−2. The electrochemical impedance spectroscopy results suggest that the chemical step for the ORR is the rate determining step, as proposed earlier by different researchers. It is suggested that the presence of GO and electrochemically reduced graphene oxide (ERGO) on the MnO2 surface are responsible for the increased rate of this step, whereby GO and ERGO accelerate the process of electron donation to the MnO2 and to adsorbed oxygen atoms. PMID:25765731

  1. Using elastin protein to develop highly efficient air cathodes for lithium-O2 batteries

    NASA Astrophysics Data System (ADS)

    Guo, Guilue; Yao, Xin; Ang, Huixiang; Tan, Huiteng; Zhang, Yu; Guo, Yuanyuan; Fong, Eileen; Yan, Qingyu

    2016-01-01

    Transition metal-nitrogen/carbon (M-N/C, M = Fe, Co) catalysts are synthesized using environmentally friendly histidine-tag-rich elastin protein beads, metal sulfate and water soluble carbon nanotubes followed by post-annealing and acid leaching processes. The obtained catalysts are used as cathode materials in lithium-O2 batteries. It has been discovered that during discharge, Li2O2 nanoparticles first nucleate and grow around the bead-decorated CNT regions (M-N/C centres) and coat on the catalysts at a high degree of discharge. The Fe-N/C catalyst-based cathodes deliver a capacity of 12 441 mAh g-1 at a current density of 100 mA g-1. When they were cycled at a limited capacity of 800 mAh g-1 at current densities of 200 or 400 mA g-1, these cathodes showed stable charge voltages of ˜3.65 or 3.90 V, corresponding to energy efficiencies of ˜71.2 or 65.1%, respectively. These results are considerably superior to those of the cathodes based on bare annealed CNTs, which prove that the Fe-N/C catalysts developed here are promising for use in non-aqueous lithium-O2 battery cathodes.

  2. Using elastin protein to develop highly efficient air cathodes for lithium-O2 batteries.

    PubMed

    Guo, Guilue; Yao, Xin; Ang, Huixiang; Tan, Huiteng; Zhang, Yu; Guo, Yuanyuan; Fong, Eileen; Yan, Qingyu

    2016-01-29

    Transition metal-nitrogen/carbon (M-N/C, M = Fe, Co) catalysts are synthesized using environmentally friendly histidine-tag-rich elastin protein beads, metal sulfate and water soluble carbon nanotubes followed by post-annealing and acid leaching processes. The obtained catalysts are used as cathode materials in lithium-O2 batteries. It has been discovered that during discharge, Li2O2 nanoparticles first nucleate and grow around the bead-decorated CNT regions (M-N/C centres) and coat on the catalysts at a high degree of discharge. The Fe-N/C catalyst-based cathodes deliver a capacity of 12,441 mAh g(-1) at a current density of 100 mA g(-1). When they were cycled at a limited capacity of 800 mAh g(-1) at current densities of 200 or 400 mA g(-1), these cathodes showed stable charge voltages of ∼3.65 or 3.90 V, corresponding to energy efficiencies of ∼71.2 or 65.1%, respectively. These results are considerably superior to those of the cathodes based on bare annealed CNTs, which prove that the Fe-N/C catalysts developed here are promising for use in non-aqueous lithium-O2 battery cathodes.

  3. Tunable diode laser measurements of air-broadened linewidths in the nu6 band of H2O2

    NASA Technical Reports Server (NTRS)

    Malathy Devi, V.; Benner, D. C.; Rinsland, C. P.; Smith, M. A. H.; Fridovich, B.

    1986-01-01

    Air-broadened half-widths of 18 transitions in the nu6 band of H2O2 between 1252/cm and 1291/cm have been determined from spectra recorded at room temperature using a tunable diode laser spectrometer. The preparation of the H2O2 gas samples for the measurements is described, and the data analysis is discussed, including the derivation of Lorentz broadening coefficients and the contribution of molecular collisions to the measured Lorentz half-widths. For the 18 transitions, the half-widths varied from 0.0923/cm/atm to 0.1155/cm/atm at 296 K, with a mean value of 0.1020/cm/atm. An error of less than 10 percent is estimated for these results.

  4. Effect of metal in M3(btc)2 and M2(dobdc) MOFs for O2/N2 separations: A combined density functional theory and experimental study

    DOE PAGES

    Parkes, Marie V.; Sava Gallis, Dorina F.; Greathouse, Jeffery A.; Nenoff, Tina M.

    2015-03-02

    Computational screening of metal-organic framework (MOF) materials for selective oxygen adsorption from air could lead to new sorbents for the oxyfuel combustion process feedstock streams. A comprehensive study on the effect of MOF metal chemistry on gas binding energies in two common but structurally disparate metal-organic frameworks has been undertaken. Dispersion-corrected density functional theory methods were used to calculate the oxygen and nitrogen binding energies with each of fourteen metals, respectively, substituted into two MOF series, M2(dobdc) and M3(btc)2. The accuracy of DFT methods was validated by comparing trends in binding energy with experimental gas sorption measurements. A periodic trendmore » in oxygen binding energies was found, with greater oxygen binding energies for early transition-metal-substituted MOFs compared to late transition metal MOFs; this was independent of MOF structural type. The larger binding energies were associated with oxygen binding in a side-on configuration to the metal, with concomitant lengthening of the O-O bond. In contrast, nitrogen binding energies were similar across the transition metal series, regardless of both MOF structural type and metal identity. Altogether, these findings suggest that early transition metal MOFs are best suited to separating oxygen from nitrogen, and that the MOF structural type is less important than the metal identity.« less

  5. Mean Ages of Stratospheric Air Derived From in Situ Observations of CO2, CH4, and N2O

    NASA Technical Reports Server (NTRS)

    Andrews, A. E.; Boering, K. A.; Daube, B. C.; Wofsy, S. C.; Loewenstein, M.; Jost, H.; Podolske, J. R.; Webster, C. R.; Herman, R. L.; Scott, D. C.; Einaudi, Franco (Technical Monitor)

    2001-01-01

    Accurate mean ages for stratospheric air have been derived from a spatially and temporally comprehensive set of in situ observations of CO2, CH4, and N2O obtained from 1992 to 1998 from the NASA ER-2 aircraft and balloon flights. Errors associated with the tropospheric CO2 seasonal cycle and interannual variations in the CO2 growth rate are less than 0.5 year throughout the stratosphere and less than 0.3 year for air older than 2 years (N2O less than 275 ppbv), indicating that the age spectra are broad enough to attenuate these influences over the time period covered by these observations. The distribution of mean age with latitude and altitude provides detailed, quantitative information about the general circulation of the stratosphere. At 20 km, sharp meridional gradients in the mean age are observed across the subtropics. Between 20 and 30 km, the average difference in mean age between the tropics and midlatitudes is approximately 2 years, with slightly smaller differences at higher and lower altitudes. The mean age in the midlatitude middle stratosphere (approx. 25-32 km) is relatively constant with respect to altitude at 5 plus or minus 0.5 years. Comparison with earlier balloon observations of CO2 dating back to the 1970s indicates that the mean age of air in this region has remained within 11 year of its current value over the last 25 years. A climatology of mean age is derived from the observed compact relationship between mean age and N2O. These characteristics of the distribution of mean age in the stratosphere will serve as critically needed diagnostics for models of stratospheric transport.

  6. Visible-Light Responsive Catalysts Using Quantum Dot-Modified TiO2 for Air and Water Purification

    NASA Technical Reports Server (NTRS)

    Coutts, Janelle L.; Hintze, Paul E.; Clausen, Christian A.; Richards, Jeffrey T.

    2014-01-01

    Photocatalysis, the oxidation or reduction of contaminants by light-activated catalysts, utilizing titanium dioxide (TiO2) as the catalytic substrate has been widely studied for trace contaminant control in both air and water applications. The interest in this process is due primarily to its low energy consumption and capacity for catalyst regeneration. Titanium dioxide requires ultraviolet light for activation due to its relatively large band gap energy of 3.2 eV. Traditionally, Hg-vapor fluorescent light sources are used in PCO reactors; however, the use of mercury precludes the use of this PCO technology in a spaceflight environment due to concerns over crew Hg exposure.

  7. Tribology of Si/SiO2 in humid air: transition from severe chemical wear to wearless behavior at nanoscale.

    PubMed

    Chen, Lei; He, Hongtu; Wang, Xiaodong; Kim, Seong H; Qian, Linmao

    2015-01-13

    Wear at sliding interfaces of silicon is a main cause for material loss in nanomanufacturing and device failure in microelectromechanical system (MEMS) applications. However, a comprehensive understanding of the nanoscale wear mechanisms of silicon in ambient conditions is still lacking. Here, we report the chemical wear of single crystalline silicon, a material used for micro/nanoscale devices, in humid air under the contact pressure lower than the material hardness. A transmission electron microscopy (TEM) analysis of the wear track confirmed that the wear of silicon in humid conditions originates from surface reactions without significant subsurface damages such as plastic deformation or fracture. When rubbed with a SiO2 ball, the single crystalline silicon surface exhibited transitions from severe wear in intermediate humidity to nearly wearless states at two opposite extremes: (a) low humidity and high sliding speed conditions and (b) high humidity and low speed conditions. These transitions suggested that at the sliding interfaces of Si/SiO2 at least two different tribochemical reactions play important roles. One would be the formation of a strong "hydrogen bonding bridge" between hydroxyl groups of two sliding interfaces and the other the removal of hydroxyl groups from the SiO2 surface. The experimental data indicated that the dominance of each reaction varies with the ambient humidity and sliding speed.

  8. Differential scattering cross sections for collisions of 0.5-, 1.5-, and 5.0-keV helium atoms with He, H2, N2, and O2. [for atmospheric processes modeling

    NASA Technical Reports Server (NTRS)

    Newman, J. H.; Smith, K. A.; Stebbings, R. F.; Chen, Y. S.

    1985-01-01

    This paper reports the first results of an experimental program established to provide cross section data for use in modeling various atmospheric processes. Absolute cross sections, differential in the scattering angle, have been measured for collisions of 0.5-, 1.5-, and 5.0-keV helium atoms with He, H2, N2, and O2 at laboratory scattering angles between 0.1 deg and 5 deg. The results are the sums of cross sections for elastic and inelastic scattering of helium atoms; charged collision products are not detected. Integration of the differential cross section data yields integral cross sections consistent with measurements by other workers. The apparatus employs a position-sensitive detector for both primary and scattered particles and uses a short target cell with a large exit aperture to ensure a simple and well-defined apparatus geometry.

  9. Impulsive rotational Raman scattering of N2 by a remote "air laser" in femtosecond laser filament.

    PubMed

    Ni, Jielei; Chu, Wei; Zhang, Haisu; Zeng, Bin; Yao, Jinping; Qiao, Lingling; Li, Guihua; Jing, Chenrui; Xie, Hongqiang; Xu, Huailiang; Cheng, Ya; Xu, Zhizhan

    2014-04-15

    We report on experimental realization of impulsive rotational Raman scattering from neutral nitrogen molecules in a femtosecond laser filament using an intense self-induced white-light seeding "air laser" generated during the filamentation of an 800 nm Ti:sapphire laser in nitrogen gas. The impulsive rotational Raman fingerprint signals are observed with a maximum conversion efficiency of ∼0.8%. Our observation provides a promising way of remote identification and location of chemical species in the atmosphere by a rotational Raman scattering of molecules. PMID:24978965

  10. 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.

  11. Co3O4 nanoparticle-modified MnO2 nanotube bifunctional oxygen cathode catalysts for rechargeable zinc-air batteries

    NASA Astrophysics Data System (ADS)

    Du, Guojun; Liu, Xiaogang; Zong, Yun; Hor, T. S. Andy; Yu, Aishui; Liu, Zhaolin

    2013-05-01

    We report the preparation of MnO2 nanotubes functionalized with Co3O4 nanoparticles and their use as bifunctional air cathode catalysts for oxygen reduction reaction and oxygen evolution reaction in rechargeable zinc-air batteries. These hybrid MnO2/Co3O4 nanomaterials exhibit enhanced catalytic reactivity toward oxygen evolution reaction under alkaline conditions compared with that in the presence of MnO2 nanotubes or Co3O4 nanoparticles alone.We report the preparation of MnO2 nanotubes functionalized with Co3O4 nanoparticles and their use as bifunctional air cathode catalysts for oxygen reduction reaction and oxygen evolution reaction in rechargeable zinc-air batteries. These hybrid MnO2/Co3O4 nanomaterials exhibit enhanced catalytic reactivity toward oxygen evolution reaction under alkaline conditions compared with that in the presence of MnO2 nanotubes or Co3O4 nanoparticles alone. Electronic supplementary information (ESI) available: Zinc-air cell device, XPS survey scan and power density of the cell. See DOI: 10.1039/c3nr00300k

  12. Temperature measurements in hypersonic air flows using laser-induced O2 fluorescence

    NASA Technical Reports Server (NTRS)

    Laufer, Gabriel; Mckenzie, Robert L.

    1988-01-01

    An investigation is reported of the use of laser-induced fluorescence on oxygen for the measurement of air temperature and its fluctuations owing to turbulence in hypersonic wind tunnel flows. The results show that for temperatures higher than 60 K and densities higher than 0.01 amagat, the uncertainty in the temperature measurement can be less than 2 percent if it is limited by photon-statistical noise. The measurement is unaffected by collisional quenching and, if the laser fluence is kept below 1.5 J/sq cm, it is also unaffected by nonlinear effects which are associated with depletion of the absorbing states.

  13. Zn/gelled 6 M KOH/O 2 zinc-air battery

    NASA Astrophysics Data System (ADS)

    Mohamad, A. A.

    The gel electrolyte for the zinc-air cell was prepared by mixing hydroponics gel with a 6 M potassium hydroxide aqueous solution. The self-discharge of cells was characterized by measuring the open-circuit voltage. The effect of a discharge rate of 50 mA constant current on cell voltage and plateau hour, as well as the voltage-current and current density-power density were measured and analysed. The electrode degradation after discharge cycling was characterized by structural and surface methods. The oxidation of the electrode surface further blocked the utilization of the Zn anode and was identified as a cause for the failure of the cell.

  14. Formation of oxygen vacancies and Ti(3+) state in TiO2 thin film and enhanced optical properties by air plasma treatment.

    PubMed

    Bharti, Bandna; Kumar, Santosh; Lee, Heung-No; Kumar, Rajesh

    2016-01-01

    This is the first time we report that simply air plasma treatment can also enhances the optical absorbance and absorption region of titanium oxide (TiO2) films, while keeping them transparent. TiO2 thin films having moderate doping of Fe and Co exhibit significant enhancement in the aforementioned optical properties upon air plasma treatment. The moderate doping could facilitate the formation of charge trap centers or avoid the formation of charge recombination centers. Variation in surface species viz. Ti(3+), Ti(4+), O(2-), oxygen vacancies, OH group and optical properties was studied using X-ray photon spectroscopy (XPS) and UV-Vis spectroscopy. The air plasma treatment caused enhanced optical absorbance and optical absorption region as revealed by the formation of Ti(3+) and oxygen vacancies in the band gap of TiO2 films. The samples were treated in plasma with varying treatment time from 0 to 60 seconds. With the increasing treatment time, Ti(3+) and oxygen vacancies increased in the Fe and Co doped TiO2 films leading to increased absorbance; however, the increase in optical absorption region/red shift (from 3.22 to 3.00 eV) was observed in Fe doped TiO2 films, on the contrary Co doped TiO2 films exhibited blue shift (from 3.36 to 3.62 eV) due to Burstein Moss shift. PMID:27572095

  15. Formation of oxygen vacancies and Ti3+ state in TiO2 thin film and enhanced optical properties by air plasma treatment

    NASA Astrophysics Data System (ADS)

    Bharti, Bandna; Kumar, Santosh; Lee, Heung-No; Kumar, Rajesh

    2016-08-01

    This is the first time we report that simply air plasma treatment can also enhances the optical absorbance and absorption region of titanium oxide (TiO2) films, while keeping them transparent. TiO2 thin films having moderate doping of Fe and Co exhibit significant enhancement in the aforementioned optical properties upon air plasma treatment. The moderate doping could facilitate the formation of charge trap centers or avoid the formation of charge recombination centers. Variation in surface species viz. Ti3+, Ti4+, O2‑, oxygen vacancies, OH group and optical properties was studied using X-ray photon spectroscopy (XPS) and UV-Vis spectroscopy. The air plasma treatment caused enhanced optical absorbance and optical absorption region as revealed by the formation of Ti3+ and oxygen vacancies in the band gap of TiO2 films. The samples were treated in plasma with varying treatment time from 0 to 60 seconds. With the increasing treatment time, Ti3+ and oxygen vacancies increased in the Fe and Co doped TiO2 films leading to increased absorbance; however, the increase in optical absorption region/red shift (from 3.22 to 3.00 eV) was observed in Fe doped TiO2 films, on the contrary Co doped TiO2 films exhibited blue shift (from 3.36 to 3.62 eV) due to Burstein Moss shift.

  16. RuO2 nanoparticles decorated MnOOH/C as effective bifunctional electrocatalysts for lithium-air battery cathodes with long-cycling stability

    NASA Astrophysics Data System (ADS)

    Kim, Gil-Pyo; Lim, Dongwook; Park, Inyeong; Park, Hyelee; Shim, Sang Eun; Baeck, Sung-Hyeon

    2016-08-01

    Manganite (MnOOH) is one of the most effective electrocatalysts for oxygen reduction reaction (ORR), and RuO2 nanoparticles exhibit high activity for oxygen evolution reaction (OER). We herein report a facile means of producing well dispersed RuO2/MnOOH on Ketjen black (RuO2/MnOOH/C) as a bifunctional catalyst for lithium-air (Li-air) batteries. RuO2/MnOOH/C was simply synthesized using a hydrothermal/precipitation based method, and was used as a cathode for a Li-air battery using a Swagelok-type cell. The importance of dispersing active catalysts on a carbon support was clearly demonstrated by textural, charge-discharge voltammetric, and electrochemical impedance spectroscopic (EIS) analyses, comparing results with a catalyst produced by physically mixing RuO2/MnOOH with carbon (RuO2/MnOOH + C). RuO2/MnOOH/C showed low overpotential and stable cycleability up to 170th cycles with 1000 mAh g-1 of charge-discharge capacity, which was attributed to its enhanced active surface area and low charge-transfer resistance. The results obtained suggest that this strategy can be widely applied to bifunctional electrocatalysis, such as secondary batteries and regenerative fuel cell (RFC).

  17. RuO2 nanoparticles decorated MnOOH/C as effective bifunctional electrocatalysts for lithium-air battery cathodes with long-cycling stability

    NASA Astrophysics Data System (ADS)

    Kim, Gil-Pyo; Lim, Dongwook; Park, Inyeong; Park, Hyelee; Shim, Sang Eun; Baeck, Sung-Hyeon

    2016-08-01

    Manganite (MnOOH) is one of the most effective electrocatalysts for oxygen reduction reaction (ORR), and RuO2 nanoparticles exhibit high activity for oxygen evolution reaction (OER). We herein report a facile means of producing well dispersed RuO2/MnOOH on Ketjen black (RuO2/MnOOH/C) as a bifunctional catalyst for lithium-air (Li-air) batteries. RuO2/MnOOH/C was simply synthesized using a hydrothermal/precipitation based method, and was used as a cathode for a Li-air battery using a Swagelok-type cell. The importance of dispersing active catalysts on a carbon support was clearly demonstrated by textural, charge-discharge voltammetric, and electrochemical impedance spectroscopic (EIS) analyses, comparing results with a catalyst produced by physically mixing RuO2/MnOOH with carbon (RuO2/MnOOH + C). RuO2/MnOOH/C showed low overpotential and stable cycleability up to 170th cycles with 1000 mAh g-1 of charge-discharge capacity, which was attributed to its enhanced active surface area and low charge-transfer resistance. The results obtained suggest that this strategy can be widely applied to bifunctional electrocatalysis, such as secondary batteries and regenerative fuel cell (RFC).

  18. Formation of oxygen vacancies and Ti3+ state in TiO2 thin film and enhanced optical properties by air plasma treatment

    PubMed Central

    Bharti, Bandna; Kumar, Santosh; Lee, Heung-No; Kumar, Rajesh

    2016-01-01

    This is the first time we report that simply air plasma treatment can also enhances the optical absorbance and absorption region of titanium oxide (TiO2) films, while keeping them transparent. TiO2 thin films having moderate doping of Fe and Co exhibit significant enhancement in the aforementioned optical properties upon air plasma treatment. The moderate doping could facilitate the formation of charge trap centers or avoid the formation of charge recombination centers. Variation in surface species viz. Ti3+, Ti4+, O2−, oxygen vacancies, OH group and optical properties was studied using X-ray photon spectroscopy (XPS) and UV-Vis spectroscopy. The air plasma treatment caused enhanced optical absorbance and optical absorption region as revealed by the formation of Ti3+ and oxygen vacancies in the band gap of TiO2 films. The samples were treated in plasma with varying treatment time from 0 to 60 seconds. With the increasing treatment time, Ti3+ and oxygen vacancies increased in the Fe and Co doped TiO2 films leading to increased absorbance; however, the increase in optical absorption region/red shift (from 3.22 to 3.00 eV) was observed in Fe doped TiO2 films, on the contrary Co doped TiO2 films exhibited blue shift (from 3.36 to 3.62 eV) due to Burstein Moss shift. PMID:27572095

  19. Formation of oxygen vacancies and Ti(3+) state in TiO2 thin film and enhanced optical properties by air plasma treatment.

    PubMed

    Bharti, Bandna; Kumar, Santosh; Lee, Heung-No; Kumar, Rajesh

    2016-08-30

    This is the first time we report that simply air plasma treatment can also enhances the optical absorbance and absorption region of titanium oxide (TiO2) films, while keeping them transparent. TiO2 thin films having moderate doping of Fe and Co exhibit significant enhancement in the aforementioned optical properties upon air plasma treatment. The moderate doping could facilitate the formation of charge trap centers or avoid the formation of charge recombination centers. Variation in surface species viz. Ti(3+), Ti(4+), O(2-), oxygen vacancies, OH group and optical properties was studied using X-ray photon spectroscopy (XPS) and UV-Vis spectroscopy. The air plasma treatment caused enhanced optical absorbance and optical absorption region as revealed by the formation of Ti(3+) and oxygen vacancies in the band gap of TiO2 films. The samples were treated in plasma with varying treatment time from 0 to 60 seconds. With the increasing treatment time, Ti(3+) and oxygen vacancies increased in the Fe and Co doped TiO2 films leading to increased absorbance; however, the increase in optical absorption region/red shift (from 3.22 to 3.00 eV) was observed in Fe doped TiO2 films, on the contrary Co doped TiO2 films exhibited blue shift (from 3.36 to 3.62 eV) due to Burstein Moss shift.

  20. Continuous Distributions of Ventilation-Perfusion Ratios in Normal Subjects Breathing Air and 100% O2

    PubMed Central

    Wagner, Peter D.; Laravuso, Raymond B.; Uhi, Richard R.; West, John B.

    1974-01-01

    A new method has been developed for measuring virtually continuous distributions of ventilation-perfusion ratios (V̇A/Q̇) based on the steadystate elimination of six gases of different solubilities. The method is applied here to 12 normal subjects, aged 21—60. In nine, the distributions were compared breathing air and 100% oxygen, while in the remaining three, effects of changes in posture were examined. In four young semirecumbent subjects (ages 21—24) the distributions of blood flow and ventilation with respect to V̇A/Q̇ were virtually log-normal with little dispersion (mean log standard deviations 0.43 and 0.35, respectively). The 95.5% range of both blood flow and ventilation was from V̇A/Q̇ ratios of 0.3—2.1, and there was no intrapulmonary shunt (V̇A/Q̇ of 0). On breathing oxygen, a shunt developed in three of these subjects, the mean value being 0.5% of the cardiac output. The five older subjects (ages 39—60) had broader distributions (mean log standard deviations, 0.76 and 0.44) containing areas with V̇A/Q ratios in the range 0.01—0.1 in three subjects. As for the young subjects, there was no shunt breathing air, but all five developed a shunt breathing oxygen (mean value 3.2%), and in one the value was 10.7%. Postural changes were generally those expected from the known effects of gravity, with more ventilation to high VA/Q areas when the subjects were erect than supine. Measurements of the shunt while breathing oxygen, the Bohr CO2 dead space, and the alveolar-arterial oxygen difference were all consistent with the observed distributions. Since the method involves only a short infusion of dissolved inert gases, sampling of arterial blood and expired gas, and measurement of cardiac output and minute ventilation, we conclude that it is well suited to the investigation of pulmonary gas exchange in man. PMID:4601004

  1. Air-sea gas transfer for two gases of different solubility (CO2 and O2)

    NASA Astrophysics Data System (ADS)

    Rutgersson, A.; Andersson, A.; Sahlée, E.

    2016-05-01

    At the land-based marine measuring site Östergarnsholm in the Baltic Sea, the eddy covariance technique was used to measure air-sea fluxes of carbon dioxide and oxygen. High- frequency measurements of oxygen were taken with a Microx TX3 optode using the luminescence lifetime technique. The system gives reasonable oxygen fluxes after the limited frequency response of the sensor was corrected for. For fluxes of carbon dioxide the LICOR-7500 instrument was used. Using flux data to estimate transfer velocities indicates higher transfer velocity for oxygen compared to carbon dioxide for winds above 5 m/s. There are too few data for any extensive conclusions, but a least-square fit of the data gives a cubic wind speed dependence of oxygen corresponding to k 660 = 0.074U 3 10. The more effective transfer for oxygen compared to carbon dioxide above 5 m/s is most likely due to enhanced efficiency of oxygen exchange across the surface. Oxygen has lower solubility compared with carbon dioxide and might be more influenced by near surface processes such as microscale wave breaking or sea spray.

  2. Microemulsion-assisted synthesis of hierarchical porous Ni(OH)2/SiO2 composites toward efficient removal of formaldehyde in air.

    PubMed

    Xu, Zhihua; Yu, Jiaguo; Liu, Gang; Cheng, Bei; Zhou, Peng; Li, Xinyang

    2013-07-28

    Ni(OH)2/SiO2 composites with hierarchical flake-like nanostructures were synthesized using water-in-oil microemulsion and characterized by X-ray diffraction, thermogravimetry, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, nitrogen adsorption, and X-ray photoelectron spectroscopy. The as-prepared hierarchical porous Ni(OH)2/SiO2 composites show an excellent performance for formaldehyde (HCHO) removal in air at an ambient temperature. It was found that the aging time had a significant impact on the pore structure, surface area and HCHO adsorption. The Ni(OH)2/SiO2 composite aged for 4 h in the presence of tetraethyl orthosilicate (TEOS) exhibited a relatively high HCHO adsorption capacity as well as good recyclability compared with Ni(OH)2, attributed to a relatively large BET surface area, an optimal pore size, a suitable proportion between Ni(OH)2 and SiO2, and a synergistic effect between Ni(OH)2 and SiO2. The results from this work not only demonstrate that hierarchical porous Ni(OH)2/SiO2 composites can act as an efficient adsorbent toward HCHO in air, but suggest a new route for the rational design of cost-effective, high-performance and environmentally benign adsorbents for indoor air cleanup.

  3. The use of radiative transition rates to study the changes in the excitation of Cu ions in a Ne glow discharge caused by small additions of H2, O2 and N2

    NASA Astrophysics Data System (ADS)

    Weiss, Z.; Steers, E. B. M.; Mushtaq, S.; Hoffmann, V.; Pickering, J. C.

    2016-04-01

    The excitation of Cu+ ions in a Ne glow discharge with small additions of H2, O2 and N2 was studied. Ratios of radiative transition rates between different Cu II levels in a discharge in neon, with and without the molecular gas added, were calculated, and the formalism of transition rate ratio (TRR) diagrams was developed and used to study the changing excitation conditions. Virtually no changes in the excitation of Cu+ ions occur in a neon discharge if nitrogen is added. Additions of hydrogen and oxygen to neon as the discharge gas affect excitation of the 4d, 5s and some other Cu II levels in the vicinity of the ionization energy of neon (21.56 eV). Also some lower Cu II levels, excited by radiative decay of those higher energy levels, are affected. The 4p 3P2 level at 15.96 eV is enhanced by additions of hydrogen. It was suggested that this enhancement is caused by the asymmetric charge transfer reaction between neutral copper atoms and the H2+ molecular ions.

  4. Elevated α-methyl-γ-hydroxy-1,N2-propano-2'-deoxyguanosine levels in urinary samples from individuals exposed to urban air pollution.

    PubMed

    Garcia, Camila C M; Freitas, Florêncio P; Sanchez, Angélica B; Di Mascio, Paolo; Medeiros, Marisa H G

    2013-11-18

    Acetaldehyde and crotonaldehyde are genotoxic aldehydes present in tobacco smoke and vehicle exhaust. The reaction of these aldehydes with 2'-deoxyguanosine in DNA produces α-methyl-γ-hydroxy-1,N(2)-propano-2'-deoxyguanosine (1,N(2)-propanodGuo). Online HPLC-tandem mass spectrometry was utilized to accurately quantify 1,N(2)-propanodGuo in human urinary samples from 47 residents of São Paulo City (SP) and 35 residents of the rural municipality of São João da Boa Vista (SJBV) in the state of São Paulo. Significantly higher 1,N(2)-propanodGuo levels were found in the samples from SP donors than in samples from SJBV donors. Our results provide the first evidence that elevated levels of 1,N(2)-propanodGuo in urinary samples may be correlated with urban air pollution.

  5. Satellite retrieval of cloud properties from the O2 A-band for air quality and climate applications

    NASA Astrophysics Data System (ADS)

    Wang, P.; Stammes, P.; van der A, R.

    2009-04-01

    The FRESCO (Fast Retrieval Scheme for Clouds from the Oxygen A-band) algorithm has been used to retrieve cloud information from measurements of the O2 A-band around 760 nm by GOME, SCIAMACHY and GOME-2. The cloud parameters retrieved by FRESCO are the effective cloud fraction and cloud pressure, which are used for cloud correction in the retrieval of trace gases like O3 and NO2. To improve the cloud pressure retrieval for partly cloudy scenes, single Rayleigh scattering has been included in an improved version of the algorithm, called FRESCO+. FRESCO+ gives more reliable cloud pressures over partly cloudy pixels. Simulations and comparisons with ground-based radar measurements of clouds shows that the FRESCO+ cloud pressure is about the optical midlevel of the cloud. Globally averaged, the FRESCO+ cloud pressure is about 50 hPa higher than the FRESCO cloud pressure, while the FRESCO+ effective cloud fraction is about 0.01 larger. From ground-based validation (P. Wang et al., Atmos. Chem. Phys., 8, 6565-6576, 2008) it appears that the FRESCO+ cloud retrievals improve the retrieval of tropospheric NO2 as compared to FRESCO. So FRESCO+ contributes to better monitoring of air quality from space. The FRESCO+ cloud algorithm has been applied to GOME and SCIAMACHY measurements since the beginning of the missions. Monthly averaged SCIAMACHY FRESCO+ effective cloud fraction and cloud pressure maps show similar patterns as the ISCCP cloud maps, although there are some differences, due to the different meaning of the cloud products and due to the fact that photons in the O2 A-band penetrate into clouds. The 6-year averaged seasonal cloud maps from SCIAMACHY data have good agreement with the global circulation patterns. Therefore, the FRESCO+ products are not only efficient for cloud correction of trace gas retrievals but also contribute additional information for climate research.

  6. Visible-Light-Responsive Catalysts Using Quantum Dot-Modified TiO2 for Air and Water Purification

    NASA Technical Reports Server (NTRS)

    Coutts, Janelle L.; Hintze, Paul E.; Clausen, Christian; Richards, Jeffrey Todd

    2014-01-01

    Photocatalysis, the oxidation or reduction of contaminants by light-activated catalysts, utilizing titanium dioxide (TiO2) as the catalytic substrate has been widely studied for trace contaminant control in both air and water applications. The interest in this process is due primarily to its low energy consumption and capacity for catalyst regeneration. Titanium dioxide requires ultraviolet light for activation due to its relatively large band gap energy of 3.2 eV. Traditionally, Hg-vapor fluorescent light sources are used in PCO reactors; however, the use of mercury precludes the use of this PCO technology in a spaceflight environment due to concerns over crew Hg exposure. The development of a visible-light responsive (VLR) TiO2-based catalyst would eliminate the concerns over mercury contamination. Further, VLR development would allow for the use of ambient visible solar radiation or highly efficient LEDs, both of which would make PCO approaches more efficient, flexible, economical, and safe. Though VLR catalyst development has been an active area of research for the past two decades, there are few commercially available VLR catalysts. Those VLR catalysts that are commercially available do not have adequate catalytic activity, in the visible region, to make them competitive with those operating under UV irradiation. This study was initiated to develop more effective VLR catalysts through a novel method in which quantum dots (QD) consisting of narrow band gap semiconductors (e.g., CdS, CdSe, PbS, ZnSe, etc.) are coupled to TiO2 via two preparation methods: 1) photodeposition and 2) mechanical alloying using a high-speed ball mill. A library of catalysts was developed and screened for gas and aqueous phase applications using ethanol and 4-chlorophenol as the target contaminants, respectively. Both target compounds are well studied in photocatalytic systems and served as model contaminants for this research. Synthesized catalysts were compared in terms of

  7. Catalytic wet air oxidation of phenol using CeO2 as the catalyst. Kinetic study and mechanism development.

    PubMed

    Chang, Dong-Jang; Lin, Shiow-Shyung; Chen, Chun-Liang; Wang, Shu-Pin; Ho, Wei-Lun

    2002-08-01

    Using a CeO2 catalyst prepared from CeCl3.7H2O under high thermal impact, the catalytic wet air oxidation (CWAO) of phenol was effectively implemented. With initial phenol concentrations of between (400 and 2500) mg/L, and at a temperature of 160 degrees C, the rate of phenol conversion increased with increased catalyst loading (0.2g/L-1.0g/L) and oxygen pressure (0.5 MPa-1.5 MPa). Even at an initial concentration of 2500 mg/L, conversion of phenol was as high as 95% after 3 h reaction. The effect of phenol concentration, catalyst loading, and oxygen pressure on the initial rate of phenol conversion was evaluated in a kinetic study. The initial rate equation derived from kinetic study is: Ro=k1 x [Ph]1.3-1.4 x W0.5-0.6 x PO2(0.9-1.1), where k1 is a rate constant, and [Ph], W and PO2 refer to phenol concentration, catalyst loading and oxygen pressure, respectively. A free-radical involved reaction mechanism was proposed and an initial rate expression based on this mechanism was derived: Ro = k2 x [Ph]1.5 x W0.5, where k2 is also a rate constant. Fitting of experimental data with the theoretically derived initial rate equation resulted in good correlation: the coefficient is greater than 0.99.

  8. Synthesis and Characterization of New Iron Phosphatooxalates: [( - 5H 14N 2] [Fe 4(C 2O 4) 3(HPO 4) 2(H 2O) 2] and [( - 5H 14N 2] [Fe 4(C 2O 4) 3(HPO 4) 2

    NASA Astrophysics Data System (ADS)

    Chang, Wen-Jung; Lin, Hsiu-Mei; Lii, Kwang-Hwa

    2001-02-01

    Two new organically templated iron(II) phosphatooxalates, [(S)-C5H14N2] [Fe4(C2O4)3(HPO4)2(H2O)2] (1) and [(S)-C5H14 N2] [Fe4(C2O4)3(HPO4)2] (2), have been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction and Mössbauer spectroscopy. Crystal data are as follows: compound 1, triclinic, P1 (No. 1), a=7.6999(4) Å, b=7.9542(4) Å, c=9.8262(5) Å, α=74.8444(7)°, β=81.7716(8)°, γ=85.4075(8)°, V=574.34(8) Å3, Z=1, and R1=0.0255; compound 2, monoclinic, P21 (No. 4), a=7.5943(8) Å, b=7.8172(8) Å, c=18.318(2) Å, β=99.111(2)°, V=1073.8(3) Å3, Z=2, and R1=0.0281. The structure of 1 consists of dimers of edge-sharing FeO6 octahedra that are linked by phosphate and oxalate groups to generate a three-dimensional framework with intersecting tunnels parallel to the [100] and [010] directions. Diprotonated (S)-2-methylpiperazinium cations are located at the intersections of these tunnels. Compound 1 crystallizes as a minor product when a racemic mixture of 2-methylpiperazine is used in the synthesis, and can be prepared as a major product with a small amount of 2 if optically pure (S)-2-methylpiperzine is used. The structure of 2 is similar to that of 1 except that the coordination around the iron centers in the dimer are square pyramidal and octahedral. The two compounds are the first 3-dimensional phosphatooxalates containing a chiral amine.

  9. Direct Measurement of Air-Sea Exchange of N2O5 and ClNO2 at a Polluted Coastal Site (Invited)

    NASA Astrophysics Data System (ADS)

    Bertram, T. H.; Kim, M.; Ryder, O. S.; Farmer, D.

    2013-12-01

    The reactive uptake of N2O5 at aqueous interfaces can serve as both an efficient NOx removal mechanism and regionally significant halogen activation process through the production of photo-labile ClNO2 molecules. Both the reaction rate and ClNO2 product yield are a complex function of the chemical composition and chloride molarity of the reactive surface. To date, analysis of the impact of N2O5 chemistry on oxidant loadings in the marine boundary layer has been limited to reactions occurring on aerosol particles, with little attention paid to reactions occurring at the air-sea interface. Here, we report the first direct measurements of the air-sea flux of N2O5 and ClNO2 made via eddy covariance in the polluted marine boundary layer in La Jolla, CA. We observe rapid N2O5 deposition to the ocean surface, while ClNO2 deposition rates were significantly lower and fastest during the first three hours following sunset. The results are interpreted using a time-dependent box-model, suggesting that under conditions characterized by shallow marine boundary layer heights (< 100 m) and representative aerosol reactive uptake coefficients (< 0.01), N2O5 deposition to the ocean surface can account for over 50% of the total N2O5 loss rate.

  10. Ozone generation in a kHz-pulsed He-O2 capillary dielectric barrier discharge operated in ambient air

    NASA Astrophysics Data System (ADS)

    Sands, Brian L.; Ganguly, Biswa N.

    2013-12-01

    The generation of reactive oxygen species using nonequilibrium atmospheric pressure plasma jet devices has been a subject of recent interest due to their ability to generate localized concentrations from a compact source. To date, such studies with plasma jet devices have primarily utilized radio-frequency excitation. In this work, we characterize ozone generation in a kHz-pulsed capillary dielectric barrier discharge configuration comprised of an active discharge plasma jet operating in ambient air that is externally grounded. The plasma jet flow gas was composed of helium with an admixture of up to 5% oxygen. A unipolar voltage pulse train with a 20 ns pulse risetime was used to drive the discharge at repetition rates between 2-25 kHz. Using UVLED absorption spectroscopy centered at 255 nm near the Hartley-band absorption peak, ozone was detected over 1 cm from the capillary axis. We observed roughly linear scaling of ozone production with increasing pulse repetition rate up to a "turnover frequency," beyond which ozone production steadily dropped and discharge current and 777 nm O(5P→5S°) emission sharply increased. The turnover in ozone production occurred at higher pulse frequencies with increasing flow rate and decreasing applied voltage with a common energy density of 55 mJ/cm3 supplied to the discharge. The limiting energy density and peak ozone production both increased with increasing O2 admixture. The power dissipated in the discharge was obtained from circuit current and voltage measurements using a modified parallel plate dielectric barrier discharge circuit model and the volume-averaged ozone concentration was derived from a 2D ozone absorption measurement. From these measurements, the volume-averaged efficiency of ozone production was calculated to be 23 g/kWh at conditions for peak ozone production of 41 mg/h at 11 kV applied voltage, 3% O2, 2 l/min flow rate, and 13 kHz pulse repetition rate, with 1.79 W dissipated in the discharge.

  11. Selective adsorption of thiophenic compounds from fuel over TiO2/SiO2 under UV-irradiation.

    PubMed

    Miao, Guang; Ye, Feiyan; Wu, Luoming; Ren, Xiaoling; Xiao, Jing; Li, Zhong; Wang, Haihui

    2015-12-30

    This study investigates selective adsorption of thiophenic compounds from fuel over TiO2/SiO2 under UV-irradiation. The TiO2/SiO2 adsorbents were prepared and then characterized by N2 adsorption, X-ray diffraction and X-ray photoelectron spectroscopy. Adsorption isotherms, selectivity and kinetics of TiO2/SiO2 were measured in a UV built-in batch reactor. It was concluded that (a) with the employment of UV-irradiation, high organosulfur uptake of 5.12 mg/g was achieved on the optimized 0.3TiO2/0.7SiO2 adsorbent at low sulfur concentration of 15 ppmw-S, and its adsorption selectivity over naphthalene was up to 325.5; (b) highly dispersed TiO2 served as the photocatalytic sites for DBT oxidation, while SiO2 acted as the selective adsorption sites for the corresponding oxidized DBT using TiO2 as a promoter, the two types of active sites worked cooperatively to achieve the high adsorption selectivity of TiO2/SiO2; (c) The kinetic rate-determining step for the UV photocatalysis-assisted adsorptive desulfurization (PADS) over TiO2/SiO2 was DBT oxidation; (d) consecutive adsorption-regeneration cycles suggested that the 0.3TiO2/0.7SiO2 adsorbent can be regenerated by acetonitrile washing followed with oxidative air treatment. This work demonstrated an effective PADS approach to greatly enhance adsorption capacity and selectivity of thiophenic compounds at low concentrations for deep desulfurization under ambient conditions.

  12. Reactive uptake coefficients for N2O5 determined from aircraft measurements during the Second Texas Air Quality Study: Comparison to current model parameterizations

    NASA Astrophysics Data System (ADS)

    Brown, Steven S.; Dubé, William P.; Fuchs, Hendrik; Ryerson, Thomas B.; Wollny, Adam G.; Brock, Charles A.; Bahreini, Roya; Middlebrook, Ann M.; Neuman, J. Andrew; Atlas, Elliot; Roberts, James M.; Osthoff, Hans D.; Trainer, Michael; Fehsenfeld, Frederick C.; Ravishankara, A. R.

    2009-04-01

    This paper presents determinations of reactive uptake coefficients for N2O5, γ(N2O5), on aerosols from nighttime aircraft measurements of ozone, nitrogen oxides, and aerosol surface area on the NOAA P-3 during Second Texas Air Quality Study (TexAQS II). Determinations based on both the steady state approximation for NO3 and N2O5 and a plume modeling approach yielded γ(N2O5) substantially smaller than current parameterizations used for atmospheric modeling and generally in the range 0.5-6 × 10-3. Dependence of γ(N2O5) on variables such as relative humidity and aerosol composition was not apparent in the determinations, although there was considerable scatter in the data. Determinations were also inconsistent with current parameterizations of the rate coefficient for homogenous hydrolysis of N2O5 by water vapor, which may be as much as a factor of 10 too large. Nocturnal halogen activation via conversion of N2O5 to ClNO2 on chloride aerosol was not determinable from these data, although limits based on laboratory parameterizations and maximum nonrefractory aerosol chloride content showed that this chemistry could have been comparable to direct production of HNO3 in some cases.

  13. Synthesis of hectorite-TiO2 and kaolinite-TiO2 nanocomposites with photocatalytic activity for the degradation of model air pollutants

    SciTech Connect

    Destaillats, Hugo; Kibanova, D.; Trejo, M.; Destaillats, H.; Cervini-Silva, J.

    2008-03-01

    We studied the synthesis and photocatalytic activity of small-sized TiO{sub 2} supported on hectorite and kaolinite. Deposition of TiO{sub 2} on the clay mineral surface was conducted by using a sol-gel method with titanium isopropoxide as precursor. Anatase TiO{sub 2} particles formation was achieved by hydrothermal treatment at 180 C. Material characterization was conducted using XRD, SEM, XPS, ICP-OES, BET and porosimetry analysis. Efficiency in synthesizing clay-TiO{sub 2} composites depended strongly on the clay mineral structure. Incorporation of anatase in hectorite, an expandable clay mineral, was found to be very significant (> 36 wt.% Ti) and to be followed by important structural changes at the clay mineral surface. Instead, no major structural modifications of the clay were observed for kaolinite-TiO{sub 2}, as compared with the untreated material. Photocatalytic performance of clay-TiO{sub 2} composites was evaluated with ATR-FTIR following the oxidation of adsorbed toluene and d-limonene, two model air pollutants. In either case, the photocatalytic removal efficiency of these hydrophobic substrates by the synthesized clay-TiO{sub 2} composites was comparable to that observed using pure commercial TiO{sub 2} (Degussa P25).

  14. Semi-rechargeable Aluminum-Air Battery with a TiO2 Internal Layer with Plain Salt Water as an Electrolyte

    NASA Astrophysics Data System (ADS)

    Mori, Ryohei

    2016-07-01

    To develop a semi-rechargeable aluminum-air battery, we attempted to insert various kinds of ceramic oxides between an aqueous NaCl electrolyte and an aluminum anode. From cyclic voltammetry experiments, we found that some of the ceramic oxide materials underwent an oxidation-reduction reaction, which indicates the occurrence of a faradaic electrochemical reaction. Using a TiO2 film as an internal layer, we successfully prepared an aluminum-air battery with secondary battery behavior. However, cell impedance increased as the charge/discharge reactions proceeded probably because of accumulation of byproducts in the cell components and the air cathode. Results of quantum calculations and x-ray photoelectron spectroscopy suggest the possibility of developing an aluminum rechargeable battery using TiO2 as an internal layer.

  15. Comparative study on the reactivity of Fe/Cu bimetallic particles and zero valent iron (ZVI) under different conditions of N2, air or without aeration.

    PubMed

    Xiong, Zhaokun; Lai, Bo; Yang, Ping; Zhou, Yuexi; Wang, Juling; Fang, Shuping

    2015-10-30

    In order to further compare the degradation capacity of Fe(0) and Fe/Cu bimetallic system under different aeration conditions, the mineralization of PNP under different aeration conditions has been investigated thoroughly. The results show that the removal of PNP by Fe(0) or Fe/Cu system followed the pseudo-first-order reaction kinetics. Under the optimal conditions, the COD removal efficiencies obtained through Fe(0) or Fe/Cu system under different aeration conditions followed the trend that Fe/Cu (air)>Fe/Cu (N2: 0-30 min, air: 30-120 min)>control-Fe (air)>Fe/Cu (without aeration)>Fe/Cu (N2)>control-Fe (N2). It revealed that dissolved oxygen (DO) could improve the mineralization of PNP, and Cu could enhance the reactivity of Fe(0). In addition, the degradation of PNP was further analyzed by using UV-vis, FTIR and GC/MS, and the results suggest that Fe/Cu bimetallic system with air aeration could completely break the benzene ring and NO2 structure of PNP and could generate the nontoxic and biodegradable intermediate products. Meanwhile, most of these intermediate products were further mineralized into CO2 and H2O, which brought about a high COD removal efficiency (83.8%). Therefore, Fe/Cu bimetallic system with air aeration would be a promising process for toxic refractory industry wastewater.

  16. ABA induces H2O2 production in guard cells, but does not close the stomata on Vicia faba leaves developed at high air humidity.

    PubMed

    Arve, Louise E; Carvalho, Dália R A; Olsen, Jorunn E; Torre, Sissel

    2014-01-01

    Plants developed under constant high (> 85%) relative air humidity (RH) have larger stomata that are unable to close completely. One of the hypotheses for the less responsive stomata is that the plants have reduced sensitivity to abscisic acid (ABA). Both ABA and darkness are signals for stomatal closure and induce the production of the secondary messenger hydrogen peroxide (H2O2). In this study, the ability of Vicia faba plants developed in moderate or high RH to close the stomata in response to darkness, ABA and H2O2 was investigated. Moreover, the ability of the plants to produce H2O2 when treated with ABA or transferred to darkness was also assessed. Our results show that the ABA concentration in moderate RH is not increased during darkness even though the stomata are closing. This indicates that stomatal closure in V. faba during darkness is independent of ABA production. ABA induced both H2O2 production and stomatal closure in stomata formed at moderate RH. H2O2 production, as a result of treatment with ABA, was also observed in stomata formed at high RH, though the closing response was considerably smaller as compared with moderate RH. In either RH, leaf ABA concentration was not affected by darkness. Similarly to ABA treatment, darkness elicited both H2O2 production and stomatal closure following plant cultivation at moderate RH. Contrary to this, neither H2O2 production nor stomatal closure took place when stomata were formed at high RH. These results suggest that the reduced stomatal response in plants developed in continuous high RH is caused by one or more factors downstream of H2O2 in the signaling pathway toward stomatal closure. PMID:25763494

  17. The Use of Small-Particle Sized TiO2 Supported on Clays as Photocatalytic Materials: A Low- Cost Alternative Technology for the Degradation of Air Pollutants

    NASA Astrophysics Data System (ADS)

    Kibanova, D.; Trejo, M.; Destaillats, H.; Cervini-Silva, J.

    2007-05-01

    Assisted photocatalysis by TiO2 is an advanced oxidation process that has been employed for air and water remediation. Clays are natural porous materials bearing high surface areas and interlayer spacing that allows entrapment of small-sized particles. Pillared clays exchanged with small-sized TiO2 can constitute materials with interesting photocatalytic properties because high surface area values and large contents of mesospores, which enables analyte trapping. Furthermore, intercalation at the clay interlayer enables TiO2 to become more resistant to aggregation when in solution. Just recently it has been reported that clays can lead to increases in the photocatalytic activity of TiO2 when the mesopores size is adequate to host organic solutes and ensure their effective interaction with the TiO2 particles. In this paper we study the photocatalytic properties of small-sized TiO2 supported on the following clay samples: Montmorillonite [SWy-2, Na0.2Ca0.1Al2Si4O10(OH)2(H2O)10 ] from Crook Country, Wyoming, USA; Hectorite [SHCa-1, Na0.4Mg2.7Li0.3Si4O10(OH)2 ] from San Bernardino. Country, California, USA; Kaolinite [KGa-1b, Al2Si2O5(OH)4 ] from Washington Country, Georgia, USA. Deposition of TiO2 on the clay surface was conducted by using a sol-gel synthetic method. Anatase TiO2 particles transformation at the clay interlayer was achieved by thermic treatment at 180 °C. Material characterization was conducted using FTIR microspectroscopy, Scanning Electron Microscopy (SEM), and XRD analysis. The organic compound used as probe was ethanol

  18. ABA induces H2O2 production in guard cells, but does not close the stomata on Vicia faba leaves developed at high air humidity.

    PubMed

    Arve, Louise E; Carvalho, Dália R A; Olsen, Jorunn E; Torre, Sissel

    2014-01-01

    Plants developed under constant high (> 85%) relative air humidity (RH) have larger stomata that are unable to close completely. One of the hypotheses for the less responsive stomata is that the plants have reduced sensitivity to abscisic acid (ABA). Both ABA and darkness are signals for stomatal closure and induce the production of the secondary messenger hydrogen peroxide (H2O2). In this study, the ability of Vicia faba plants developed in moderate or high RH to close the stomata in response to darkness, ABA and H2O2 was investigated. Moreover, the ability of the plants to produce H2O2 when treated with ABA or transferred to darkness was also assessed. Our results show that the ABA concentration in moderate RH is not increased during darkness even though the stomata are closing. This indicates that stomatal closure in V. faba during darkness is independent of ABA production. ABA induced both H2O2 production and stomatal closure in stomata formed at moderate RH. H2O2 production, as a result of treatment with ABA, was also observed in stomata formed at high RH, though the closing response was considerably smaller as compared with moderate RH. In either RH, leaf ABA concentration was not affected by darkness. Similarly to ABA treatment, darkness elicited both H2O2 production and stomatal closure following plant cultivation at moderate RH. Contrary to this, neither H2O2 production nor stomatal closure took place when stomata were formed at high RH. These results suggest that the reduced stomatal response in plants developed in continuous high RH is caused by one or more factors downstream of H2O2 in the signaling pathway toward stomatal closure.

  19. ABA induces H2O2 production in guard cells, but does not close the stomata on Vicia faba leaves developed at high air humidity

    PubMed Central

    Arve, Louise E; Carvalho, Dália RA; Olsen, Jorunn E; Torre, Sissel

    2014-01-01

    Plants developed under constant high (> 85%) relative air humidity (RH) have larger stomata that are unable to close completely. One of the hypotheses for the less responsive stomata is that the plants have reduced sensitivity to abscisic acid (ABA). Both ABA and darkness are signals for stomatal closure and induce the production of the secondary messenger hydrogen peroxide (H2O2). In this study, the ability of Vicia faba plants developed in moderate or high RH to close the stomata in response to darkness, ABA and H2O2 was investigated. Moreover, the ability of the plants to produce H2O2 when treated with ABA or transferred to darkness was also assessed. Our results show that the ABA concentration in moderate RH is not increased during darkness even though the stomata are closing. This indicates that stomatal closure in V. faba during darkness is independent of ABA production. ABA induced both H2O2 production and stomatal closure in stomata formed at moderate RH. H2O2 production, as a result of treatment with ABA, was also observed in stomata formed at high RH, though the closing response was considerably smaller as compared with moderate RH. In either RH, leaf ABA concentration was not affected by darkness. Similarly to ABA treatment, darkness elicited both H2O2 production and stomatal closure following plant cultivation at moderate RH. Contrary to this, neither H2O2 production nor stomatal closure took place when stomata were formed at high RH. These results suggest that the reduced stomatal response in plants developed in continuous high RH is caused by one or more factors downstream of H2O2 in the signaling pathway toward stomatal closure. PMID:25763494

  20. Measurements of N2O and SF6 mole fraction between 1977 and 1998 in archived air samples from Cape Meares, Oregon

    NASA Astrophysics Data System (ADS)

    Rolfe, T.; Rice, A. L.; Radda, J.

    2015-12-01

    The quantification of greenhouse gas concentrations in the atmosphere is important for monitoring imbalances in their global budgets between sources and sinks and their changes in time. Nitrous oxide (N2O) is a strong radiative trace gas with a GWP of ~300 times CO2 over a 100 year period and an atmospheric lifetime of ~100 years. The preindustrial revolution background concentration of N2O was ~270 ppb. Today, the concentration is ~330 ppb. Sulfur hexafluoride (SF6) is another potent greenhouse gas with a long lifetime (800 to 3200 years) and very large GWP (~23000 times CO2 over a 100 year period). Its current atmospheric concentration is low (~8 ppt today). Direct measurements of N2O and SF6 in air prior to the mid-1990s are few. Over 200 archived atmospheric gas samples collected at Cape Meares, Oregon between 1977 and 1998 were analyzed for their N2O and SF6 concentrations using an Agilent (model 6890 N) gas chromatograph fitted with an electron capture detector using a two column "heart-cut" technique. Precision of measurement of N2O and SF6 is calculated at 0.13% (1σ) and 1.35% (1σ) respectively. N2O concentrations in the late 1970s and early 1980s average around 303 ppb, rising to 309 ppb in the early 1990s. Between 1980 and 1990, the increase in N2O concentrations is found to be ~0.5 ppb/yr. SF6 concentrations during the late 1970s and early 1980s average around 0.9 ppt and rise slowly, reaching 1.6 ppt in the 1990s. We find that the increase in SF6 between 1980 and 1990 to be ~0.07 ppt/yr. We also discuss sample integrity in storage and observed temporal trends of N2O and SF6.

  1. Performance enhancement of an experimental air conditioning system by using TiO2/methanol nanofluid in heat pipe heat exchangers

    NASA Astrophysics Data System (ADS)

    Monirimanesh, Negin; Nowee, S. Mostafa; Khayyami, Shideh; Abrishamchi, Iman

    2016-05-01

    The effect of using nanofluid in thermosyphon-type heat pipe heat exchangers on energy conservation of an air-conditioning system was sought in this study. Innovatively, two heat exchangers in-series were deployed using TiO2/methanol nanofluids with 0-4 wt% concentrations as working fluids. The impacts of temperature and relative humidity on the effectiveness of 2 and 4-row heat exchangers were analyzed experimentally and more that 40 % energy saving was obtained.

  2. High-Precision Measurement of The Oxygen Isotopic Composition of Tropospheric O2: Implications for Δ17O of air as a Biosignature

    NASA Astrophysics Data System (ADS)

    Young, E. D.; Ziegler, K.

    2006-05-01

    Here we present high-precision measurements of 18O/16O and 17O/16O in samples of tropospheric O2 using a standard calibrated with measurements of terrestrial and extraterrestrial rock samples. These new data provide a measure of Δ17O on an absolute scale that aids in the interpretation of the cause of the disparity in Δ17O between O2 in the troposphere and terrestrial rocks. We measured the isotopic composition of four separate aliquotes of ground-level air O2. Oxygen was isolated from air cryogenically using molecular sieve substrates. Correction was made for the influence of Ar scattered across the Faraday collectors (~0.06 per mil in δ17O) of the gas- source mass spectrometer. The reference gas used as an internal standard was calibrated against terrestrial rock samples and meteorites analyzed using infrared laser heating fluorination. All results are reported as linearized delta values (signified with a prime superscript symbol). With a mean terrestrial rock Δ17O'of 0.00 ‰ ± 0.02 we obtain Δ17O values of -0.25 ‰ ± 0.04 1σ, -0.22 ‰ ± 0.03, and -0.23 ‰ ± 0.05 for 5 mesosiderite meteorites, 7 pallasites, and 12 HED meteorites, respectively. The latter meteorite data are consistent with results from three other laboratories and serve to establish the absolute scale for the air O2 measurements. Our results for the O2 samples give a mean linearized δ18O' of 23.237 ‰ ± 0.008 1 std err (corresponding to a normal, non-linearized δ18O SMOW value of 23.509 ‰), a mean δ17O' of 11.922 ‰ ± 0.018, and a mean linearized Δ17O' of -0.347 ‰ ± 0.018 based on a rock-water terrestrial fractionation reference line with a slope (β) of 0.528. The latter is the exponent in a normal fractionation law described by the relation α17=(α18)β. This result can be reconciled with the suggestion by Young et al (2002) that the whole of the departure in Δ17O' of tropospheric O2 relative to terrestrial rocks can be attributed to respiration (a Δ17O Dole effect

  3. Phase Equilibria Study in the TeO2-Na2O-SiO2 System in Air Between 723 K (500 °C) and 1473 K (1200 °C)

    NASA Astrophysics Data System (ADS)

    Santoso, Imam; Taskinen, Pekka

    2016-08-01

    Knowledge of phase equilibria in the TeO2-Na2O-SiO2 system at elevated temperatures is important for ceramic and glass industries and for improving the operation of the smelting process of tellurium-containing materials. A review of previous investigations has indicated, however, that there are omissions in the available datasets on the liquidus temperatures of the molten TeO2-Na2O-SiO2 mixtures. The employed experimental method included equilibration of mixtures made from high purity oxides, rapid quenching of the equilibrated samples in water and followed by compositional analysis of the phases using an electron probe X-ray microanalyzer. The liquidus and phase equilibria in the TeO2-SiO2, TeO2-Na2O, and SiO2-TeO2-Na2O systems have been studied for a wide range of compositions between 723 K (500 °C) and 1473 K (1200 °C) at TeO2, SiO2, and Na2SiO3 saturations. New data have been generated in the SiO2-TeO2-Na2O system at SiO2 saturation. The liquidus compositions in the TeO2-Na2O system at TeO2 saturation have been compared with the previous data and an assessed phase diagram.

  4. Performance of air plasma spraying parameters in the fabrication of ZrO2-10%Y2O3-18% TiO2 thermal barrier coatings

    NASA Astrophysics Data System (ADS)

    Liscano, S.; Gil, L.

    2013-11-01

    In this research, ZrO2-10%Y2O3-18% TiO2 thermal barrier coatings (TBCs) were sprayed by employing an air plasma thermal spray (APS) technique following a 23 factorial design experiment in order to obtain the best favorable spraying conditions able to enhance their properties. The effect of the spraying parameters on the porosity, microhardness, microstructure and morphology were determined by using different techniques such as optical microscopy (OP), image analysis, Vickers indentation and scanning electron microscopy (SEM) technique, this latter coupled with X-Ray microanalysis (EDS). It was found that both the arc voltage and the powder feed rate, as well as their interaction had a significant effect on the values of the reported hardness and these results were related to the existing level of porosity in the coatings. It was concluded that the best coatings properties, for the level of the variables studied in this work, could be obtained if the arc voltage is maintained at 36 V, the arc current at 900 A and the powder feed rate to 24 g/min.

  5. A selected ion flow tube study of the reactions of NO + and O + 2 ions with some organic molecules: The potential for trace gas analysis of air

    NASA Astrophysics Data System (ADS)

    Španěl, Patrik; Smith, David

    1996-02-01

    A study has been carried out using our selected ion flow tube apparatus of the reactions of NO+ and O+2 ions in their vibronic ground states with ten organic species: the hydrocarbons, benzene, toluene, isoprene, cyclopropane, and n-pentane; the oxygen-containing organics, methanol, ethanol, acetaldehyde, acetone, and diethyl ether. The major objectives of this work are, on the one hand, to fully understand the processes involved in these reactions and, on the other hand, to explore the potential of NO+ and O+2 as chemical ionization agents for the analysis of trace gases in air and on human breath. Amongst the NO+ reactions, charge transfer, hydride-ion transfer, and termolecular association occur, and the measured rate coefficients, k, for the reactions vary from immeasurably small to the maximum value, collisional rate coefficient, kc. The O+2 reactions are all fast, in each case the k being equal to or an appreciable fraction of kc, and charge transfer producing the parent organic ion or dissociative charge transfer resulting in two or three fragments of the parent ion are the reaction processes that occur. We conclude from these studies, and from previous studies, that NO+ ions and O+2 ions can be used to great effect as chemical ionization agents for trace gas analysis, especially in combination with H3O+ ions which we now routinely use for this purpose.

  6. Determination of the rate coefficients for the reactions IO + NO2 + M (air) --> IONO2 + M and O(3P) + NO2 --> O2 + NO using laser-induced fluorescence spectroscopy.

    PubMed

    Dillon, Terry J; Blitz, Mark A; Heard, Dwayne E

    2006-06-01

    Laser-induced fluorescence spectroscopy via excitation of the A2pi(3/2) <-- X2pi(3/2) (2,0) band at 445 nm was used to monitor IO in the presence of NO2 following its generation in the reactions O(3P) + CF3I and O(3P) + I2. Both photolysis of O3 (248 nm) and NO2 (351 nm) were used to initiate the production of IO. The rate coefficients for the thermolecular reaction IO + NO2 + M --> IONO2 + M were measured in air, N2, and O2 over the range P = 18-760 Torr, covering typical tropospheric conditions, and were found to be in the falloff region. No dependence of k1 upon bath gas identity was observed, and in general, the results are in good agreement with recent determinations. Using a Troe broadening factor of F(B) = 0.4, the falloff parameters k0(1) = (9.5 +/- 1.6) x 10(-31) cm6 molecule(-2) s(-1) and k(infinity)(1) = (1.7 +/- 0.3) x 10(-11) cm3 molecule(-1) s(-1) were determined at 294 K. The temporal profile of IO at elevated temperatures was used to investigate the thermal stability of the product, IONO2, but no evidence was observed for the regeneration of IO, consistent with recent calculations for the IO-NO2 bond strength being approximately 100 kJ mol(-1). Previous modeling studies of iodine chemistry in the marine boundary layer that utilize values of k1 measured in N2 are hence validated by these results conducted in air. The rate coefficient for the reaction O(3P) + NO2 --> O2 + NO at 294 K and in 100 Torr of air was determined to be k2 = (9.3 +/- 0.9) x 10(-12) cm3 molecule(-1) s(-1), in good agreement with recommended values. All uncertainties are quoted at the 95% confidence limit.

  7. Determination of Phosphorescence Quantum Yield of Singlet Oxygen O 2( 1Δ g) Photosensitized by Phenalenone in Air-Saturated Carbon Tetrachloride

    NASA Astrophysics Data System (ADS)

    Shimizu, Okiyasu; Watanabe, Jun; Imakubo, Keiichi; Naito, Shizuo

    1998-11-01

    The phosphorescence quantum yield Φ P (=einsteins emitted/einsteins absorbed by sensitizer) of singlet oxygen (1O2) was measured for an air-saturated CCl4 solution of phenalenone (PH) used as a photosensitizer, by means of a photon-counting technique based on the use of a near-IR-sensitive photomultiplier. Employment of steady-state excitation allowed for the determination of the absolute quantum yield of Φ P=(1.38±0.05)×10-3 in CCl4. The result was obtained by direct comparison of the areas under the corrected emission spectra of 1O2 and of quinine bisulfate (QBS) in 1N H2SO4 as a luminescence standard.

  8. Benefits and technological challenges in the implementation of TiO2-based ultraviolet photocatalytic oxidation (UVPCO) air cleaners

    SciTech Connect

    Hodgson, Al; Destaillats, Hugo; Hotchi, Toshifumi; Fisk, William J.

    2008-10-01

    Heating, ventilating, and cooling classrooms in California consume substantial electrical energy. Indoor air quality (IAQ) in classrooms affects student health and performance. In addition to airborne pollutants that are emitted directly by indoor sources and those generated outdoors, secondary pollutants can be formed indoors by chemical reaction of ozone with other chemicals and materials. Filters are used in nearly all classroom heating, ventilation and air-conditioning (HVAC) systems to maintain energy-efficient HVAC performance and improve indoor air quality; however, recent evidence indicates that ozone reactions with filters may, in fact, be a source of secondary pollutants. This project quantitatively evaluated ozone deposition in HVAC filters and byproduct formation, and provided a preliminary assessment of the extent to which filter systems are degrading indoor air quality. The preliminary information obtained will contribute to the design of subsequent research efforts and the identification of energy efficient solutions that improve indoor air quality in classrooms and the health and performance of students.

  9. Electrochemical properties of graphene flakes as an air cathode material for Li-O2 batteries in an ether-based electrolyte.

    PubMed

    Kim, Se Young; Lee, Ho-Taek; Kim, Kwang-Bum

    2013-12-14

    We employed graphene flakes as an air-cathode material for Li-O2 batteries and investigated their electrochemical properties in the dimethyl ether electrolyte. Graphene flakes were prepared by microwave-assisted reduction of graphene oxide, and their electrochemical properties were compared with those of Ketjen Black and carbon nanotubes. The catalytic effect of the prepared graphene flake-air cathode was demonstrated using cyclic voltammetry and discharge-charge testing performed under a limited discharge capacity. The catalytic effect of graphene flakes was also supported by morphological and spectroscopic analysis of the discharge-charge products formed on the graphene surface. Scanning electron microscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy revealed that Li2O2, Li2O, and Li2CO3 were the main discharge products on all carbon-air cathode surfaces. Raman spectroscopy revealed that LiRCO3 was additionally formed on Ketjen Black and carbon nanotubes during the first discharge; however, its formation was not observed on the graphene flakes. The catalytic effect of the graphene flakes and the absence of LiRCO3 in the discharge product could explain the higher Coulombic efficiency in the discharge-charge tests.

  10. Electrochemical properties of graphene flakes as an air cathode material for Li-O2 batteries in an ether-based electrolyte.

    PubMed

    Kim, Se Young; Lee, Ho-Taek; Kim, Kwang-Bum

    2013-12-14

    We employed graphene flakes as an air-cathode material for Li-O2 batteries and investigated their electrochemical properties in the dimethyl ether electrolyte. Graphene flakes were prepared by microwave-assisted reduction of graphene oxide, and their electrochemical properties were compared with those of Ketjen Black and carbon nanotubes. The catalytic effect of the prepared graphene flake-air cathode was demonstrated using cyclic voltammetry and discharge-charge testing performed under a limited discharge capacity. The catalytic effect of graphene flakes was also supported by morphological and spectroscopic analysis of the discharge-charge products formed on the graphene surface. Scanning electron microscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy revealed that Li2O2, Li2O, and Li2CO3 were the main discharge products on all carbon-air cathode surfaces. Raman spectroscopy revealed that LiRCO3 was additionally formed on Ketjen Black and carbon nanotubes during the first discharge; however, its formation was not observed on the graphene flakes. The catalytic effect of the graphene flakes and the absence of LiRCO3 in the discharge product could explain the higher Coulombic efficiency in the discharge-charge tests. PMID:24166701

  11. Bi ˜3.785Cd ˜3.575Cu ˜1.5(PO 4) 3.5O 5.5, a new arrangement of double ( n=2) and triple ( n=3) [ M4Bi 2n-2O 2n] x+ polycationic ribbons in the bismuth-transition metal oxy-phosphate series

    NASA Astrophysics Data System (ADS)

    Colmont, Marie; Huvé, Marielle; Abraham, Francis; Mentré, Olivier

    2004-11-01

    This work is dedicated to investigation of new disordered bismuth-containing oxy-phosphates compounds with an original structure type. As previously observed in this series, they are formed of [M 4Bi 2n-2O 2n] x+ polycationic ribbons of width n O(Bi,M) 4 tetrahedra, surrounded by PO 4 groups. In the new crystal structure type, double (= D), triple (= T) and tunnels (= t) alternate along a common axis obeying the TtDtTtDt/TTtTTt sequence in respect to a nomenclature previously described and recalled in this work. The existence this new polymorph has first been detected by electron diffraction in a multi-phased sample. Then, the crystal structure type, i.e., the TtDtTtDt/TTtTTt sequence, has been deduced from HREM images help to a contrast-interpreting code available for these series of polycations-formed compounds. The subsequent compounds formulation leads to a number of new materials that verify the general formula: [Bi 2(Bi, M) 4O 4] 2 [Bi 4(Bi, M) 4O 6] 6 (PO 4) 28M x, with x⩽12 and M=Cu 2+, Cd 2+ cations. Single crystals of the nominal [O6Bi 4.57Cd 3.43] 4+8.57 [O 6Bi 4Cd 4] 2+8 [O 4Bi 2Cd 3.56Cu 0.44] 2+6 (PO 4) 28 Cu 10.86 have been prepared in a further stage and confirms the predicted crystal structure, Bi ˜3.785Cd ˜3.575Cu ˜1.5(PO 4) 3.5O 5.5, a=11.506(8) Å, b=5.416(4) Å, c=53.94 (4) Å, β=90.10(1)°, R=0.0835, R=0.0993, SG= A2/m, Z=8. As already observed for other elements of this family such as Bi ˜1.2M˜1.2O 1.5(PO 4), Bi ˜6.2Cu ˜6.2O 8(PO 4) 5 or Bi ˜3Cd ˜3.72M˜1.28O 5(PO 4) 3 ( M=Cu, Co, Zn), this compound shows an additional example of PO 4 disorder due to the presence of mixed Bi 3+/M 2+ sites at the edges of ribbons. The origin and consequence of this so-called disorder mostly occurring on PO 4 configurations is intensively discussed and has been characterized by infrared spectroscopy and by neutron diffraction on similar compounds. It is noticeable that the great number of antagonist PO 4 configurations may order along the b

  12. N2 fixation and cycling in Alnus glutinosa, Betula pendula and Fagus sylvatica woodland exposed to free air CO2 enrichment.

    PubMed

    Millett, Jonathan; Godbold, Douglas; Smith, Andrew R; Grant, Helen

    2012-06-01

    We measured the effect of elevated atmospheric CO(2) on atmospheric nitrogen (N(2)) fixation in the tree species Alnus glutinosa growing in monoculture or in mixture with the non-N(2)-fixing tree species Betula pendula and Fagus sylvatica. We addressed the hypotheses that (1) N(2) fixation in A. glutinosa will increase in response to increased atmospheric CO(2) concentrations, when growing in monoculture, (2) the impact of elevated CO(2) on N(2) fixation in A. glutinosa is the same in mixture and in monoculture and (3) the impacts of elevated CO(2) on N cycling will be evident by a decrease in leaf δ(15)N and by the soil-leaf enrichment factor (EF), and that these impacts will not differ between mixed and single species stands. Trees were grown in a forest plantation on former agricultural fields for four growing seasons, after which the trees were on average 3.8 m tall and canopy closure had occurred. Atmospheric CO(2) concentrations were maintained at either ambient or elevated (by 200 ppm) concentrations using a free-air CO(2) enrichment (FACE) system. Leaf δ(15)N was measured and used to estimate the amount (N(dfa)) and proportion (%N(dfa)) of N derived from atmospheric fixation. On average, 62% of the N in A. glutinosa leaves was from fixation. The %N(dfa) and N(dfa) for A. glutinosa trees in monoculture did not increase under elevated CO(2), despite higher growth rates. However, N(2) fixation did increase for trees growing in mixture, despite the absence of significant growth stimulation. There was evidence that fixed N(2) was transferred from A. glutinosa to F. sylvatica and B. pendula, but no evidence that this affected their CO(2) response. The results of this study show that N(2) fixation in A. glutinosa may be higher in a future elevated CO(2) world, but that this effect will only occur where the trees are growing in mixed species stands.

  13. Nonhomogeneous surface properties of parylene-C film etched by an atmospheric pressure He/O2 micro-plasma jet in ambient air

    NASA Astrophysics Data System (ADS)

    Wang, Tao; Yang, Bin; Chen, Xiang; Wang, Xiaolin; Yang, Chunsheng; Liu, Jingquan

    2016-10-01

    Surface properties of parylene-C film etched by an atmospheric pressure He/O2 micro-plasma jet in ambient air were investigated. The morphologies and chemical compositions of the etched surface were analyzed by optical microscopy, SEM, EDS, XPS and ATR-FTIR. The microscopy and SEM images showed the etched surface was nonhomogeneous with six discernable ring patterns from the center to the outside domain, which were composed of (I) a central region; (II) an effective etching region, where almost all of the parylene-C film was removed by the plasma jet with only a little residual parylene-C being functionalized with carboxyl groups (Cdbnd O, Osbnd Cdbnd O-); (III) an inner etching boundary; (IV) a middle etching region, where the film surface was smooth and partially removed; (V) an outer etching boundary, where the surface was decorated with clusters of debris, and (VI) a pristine parylene-C film region. The analysis of the different morphologies and chemical compositions illustrated the different localized etching process in the distinct regions. Besides, the influence of O2 flow rate on the surface properties of the etched parylene-C film was also investigated. Higher volume of O2 tended to weaken the nonhomogeneous characteristics of the etched surface and improve the etched surface quality.

  14. Heat-transfer distributions on biconics at incidence in hypersonic-hypervelocity He, N2, air, and CO2 flows

    NASA Technical Reports Server (NTRS)

    Miller, C. G.; Micol, J. R.; Gnoffo, P. A.; Wilder, S.E.

    1983-01-01

    Laminar heat-transfer rates were measured on spherically blunted, 13 degrees/F degrees on-axis and bent biconics (fore cone bent 7 degrees upward relative to aft cone) at hypersonic-hypervelocity flow conditions in the Langley Expansion Tube. Freestream velocities from 4.5 to 6.9 km/sec and Mach numbers from 6 to 9 were generated using helium, nitrogen, air, and carbon dioxide test gases, resulting in normal shock density ratios from 4 to 19. Angle of attack, referenced to the axis of the aft cone, was varied from zero to 20 degrees in 4 degree increments. The effect of nose bend, angle of attack, and real-gas phenomena on heating distributions are presented along with comparisons of measurement to prediction from a code which solves the three-dimensional 'parabolized Navier-Stokes' equations.

  15. Heat-transfer distributions on biconics at incidence in hypersonic-hypervelocity He, N2, air, and CO2 flows

    NASA Technical Reports Server (NTRS)

    Miller, C. G.; Micol, J. R.; Gnoffo, P. A.; Wilder, S. E.

    1983-01-01

    Laminar heat transfer rates were measured on spherically blunted, 13 deg/7 deg on axis and bent biconics (fore cone bent 7 deg upward relative to aft cone) at hypersonic hypervelocity flow conditions in the Langley Expansion Tube. Freestream velocities from 4.5 to 6.9 km/sec and Mach numbers from 6 to 9 were generated using helium, nitrogen, air, and carbon dioxide test gases, resulting in normal shock density ratios from 4 to 19. Angle of attack, referenced to the axis of the aft cone, was varied from 0 to 20 deg in 4 deg increments. The effect of nose bend, angle of attack, and real gas phenomena on heating distributions are presented along with comparisons of measurement to prediction from a code which solves the three dimensional parabolized Navier-Stokes equations.

  16. Fundamental understanding of the thermal degradation mechanisms of waste tires and their air pollutant generation in a N2 atmosphere.

    PubMed

    Kwon, Eilhann; Castaldi, Marco J

    2009-08-01

    The thermal decomposition of waste tires has been characterized via thermo-gravimetric analysis (TGA) tests, and significant mass loss has been observed between 300 and 500 degrees C. A series of gas chromatography-mass spectrometer (GC-MS) measurements, in which the instrument was coupled to a TGA unit, have been carried out to investigate the thermal degradation mechanisms as well as the air pollutant generation including volatile organic carbons (VOCs) and polycyclic aromatic hydrocarbons (PAHs) in a nitrogen atmosphere. In order to understand fundamental information on the thermal degradation mechanisms of waste tires, the main constituents of tires, poly-isoprene rubber (IR) and styrene butadiene rubber (SBR), have been studied under the same conditions. All of the experimental work indicated that the bond scission on each monomer of the main constituents of tires was followed by hydrogenation and gas phase reactions. This helped to clarify the independent pathways and species attributable to IR and SBR during the pyrolysis process. To extend that understanding to a more practical level, a flow-through reactor was used to test waste tire, SBR and IR samples in the temperature range of 500-800 degrees C at a heating rate of approximately 200 degrees C. Lastly, the formation of VOCs (approximately 1-50 PPMV/10 mg of sample) and PAHs (approximately 0.2-7 PPMV/10 mg of sample) was observed at relatively low temperatures compared to conventional fuels, and its quantified concentration was significantly high due to the chemical structure of SBR and IR. The measurement of chemicals released during pyrolysis suggests not only a methodology for reducing the air pollutants but also the feasibility of petrochemical recovery during thermal treatment.

  17. Nitrogen metastable (N2(A3 Σu + )) in a cold argon atmospheric pressure plasma jet: Shielding and gas composition

    NASA Astrophysics Data System (ADS)

    Iseni, Sylvain; Bruggeman, Peter J.; Weltmann, Klaus-Dieter; Reuter, Stephan

    2016-05-01

    N 2 ( A 3 Σu + ) metastable species are detected and measured in a non-equilibrium atmospheric pressure plasma jet by laser induced fluorescence. A shielding device is used to change the ambient conditions additionally to the feeding gas composition. Varying the amount of N2 and air admixed to the feeding gas as well as changing the shielding gas from N2 to air reveals that the highest N 2 ( A 3 Σu + ) is achieved in the case of air admixtures in spite of the enhanced collisional quenching due to the presence of O2. The reasons for these observations are discussed in detail.

  18. 193Ir Mössbauer spectroscopy of Pt-IrO 2 nanoparticle catalysts developed for detection and removal of carbon monoxide from air

    NASA Astrophysics Data System (ADS)

    Sawicki, J. A.; Marcinkowska, K.; Wagner, F. E.

    2010-08-01

    Mössbauer spectroscopy of 73.0 keV gamma-ray transition in 193Ir and supplementary analytical techniques were used to study the microstructure and chemical form of polymer-supported hydrophobic bimetallic Pt-Ir catalysts for detection and removal of CO from humid air at ambient conditions. The catalysts, typically with a composition of 9 wt.% Pt and 1 wt.% Ir, were prepared by incipient wetness impregnation of polystyrene-divinylbenzene (SDB) granules with ethanol solutions of hexachloroplatinic and hexachloroiridic acids. This procedure, followed by reduction in H 2 or CO at only 200 °C or 250 °C, resulted in formation of highly-dispersed Pt-Ir particles usually smaller than 20 nm and having high catalytic activity and selectivity. Mössbauer spectra of 73.0 keV gamma-ray transition in 193Ir were taken after consecutive steps of preparation and exposure of catalysts to better understand and further improve the fabrication processes. In the as-impregnated state, iridium was found mostly as Ir(III) in [IrCl 6] 3- ions, with only a small fraction of Ir(IV) in [IrCl 6] 2- ions. The iridium in bimetallic clusters formed by reduction in hydrogen showed a strong tendency towards oxidation on exposure to air at room temperature, while Pt remained mostly metallic. In the most active and stable catalysts, the Ir and Pt in metallic regions of the clusters did not tend to segregate, unlike in Pt-Ir/silica-supported catalysts studied by us earlier. Further, this study shows that the IrO 2-like regions in the clusters exhibit stronger deviations from local symmetry and stoichiometry of crystalline IrO 2 than observed previously in Pt-Ir/silica catalysts. Our study also indicates that in the examined Pt-IrO 2 nanoparticles iridium largely provides the dissociative O 2 adsorption sites, while the CO adsorption occurs primarily at metallic Pt sites.

  19. The Effect of O2, H2O, and N2 on the Fatigue Crack Growth Behavior of an Alpha + Beta Titanium Alloy at 24 C and 177 C

    NASA Technical Reports Server (NTRS)

    Smith, Stephen W.; Piascik, Robert S.

    2001-01-01

    To study the effects of atmospheric species on the fatigue crack growth behavior of an a+B titanium alloy (Ti 6-2-2-2-2) at room temperature and 177 C, fatigue tests were performed in laboratory air, ultrahigh vacuum, and high purity water vapor, oxygen, nitrogen and helium at various partial pressures. Accelerated fatigue crack growth rates in laboratory air compared to ultrahigh vacuum are linked to the damaging effects of both water vapor and oxygen. Observations of the fatigue crack growth behavior in ultrahigh purity environments, along with surface film analysis using X-ray photoelectron spectroscopy (XPS), suggest that multiple crack-tip processes govern the damaging effects of air. Three possible mechanisms are proposed: 1) at low pressure (less than 10(exp -1) Pa), accelerated da/dN is likely due to monolayer adsorption on crack-tip surfaces presumably resulting in decreased bond strengths at the fatigue crack tip, 2) for pressures greater than 10(exp -1) Pa, accelerated da/dN in oxygen may result from oxidation at the crack tip limiting reversible slip, and 3) in water vapor, absorption of atomic hydrogen at the reactive crack tip resulting in process zone embrittlement.

  20. Electrical Behavior of SnO2 Polycrystalline Ceramic Pieces Formed by Slip Casting: Effect of Surrounding Atmosphere (Air and CO)

    NASA Astrophysics Data System (ADS)

    Aguilar-Paz, C. J.; Ochoa-Muñoz, Y.; Ponce, M. A.; Rodríguez-Páez, J. E.

    2016-01-01

    Pieces of porous polycrystalline SnO2 with and without cobalt have been formed by the slip-casting method, using ceramic powders synthesized by the controlled precipitation method. A suitable methodology was developed for forming and sintering the pieces to enable controlled modification of their microstructure, principally grain size, porosity, and type of intergranular contacts. Better control of the microstructure was obtained in the samples containing cobalt. In these, predominance of open necks and intergranular contacts was observed, which can represent Schottky barriers. Because of its good structural homogeneity, porosity, and small grain size (of the order of 1 μm), the sample with 2 mol.% Co sintered at 1250°C for 2 h was selected for electrical characterization by complex impedance spectroscopy, varying the operating temperature, concentration and nature of the surrounding gas (air or CO), and bias voltage. The resulting R p and C p curves were very sensitive to variation in these parameters, being most obvious for the C p curves, which showed a phenomenon of low-frequency dispersion when bias voltages other than zero were used, in the presence of O2, and at operating temperature of 280°C. The electrical behavior of the SnO2 with 2 mol.% Co sample sintered at 1250°C was consistent with the nature and microstructural characteristics of the active material and was justified based on the presence of shallow- and deep-type defects, and variations in barrier height and width, caused by adsorption of gas molecules.

  1. Graphene supported heterogeneous catalysts for Li-O2 batteries

    NASA Astrophysics Data System (ADS)

    Alaf, M.; Tocoglu, U.; Kartal, M.; Akbulut, H.

    2016-09-01

    In this study production and characterization of free-standing and flexible (i) graphene, (ii) α-MnO2/graphene, (iii) Pt/graphene (iv) α-MnO2/Pt/graphene composite cathodes for Li-air batteries were reported. Graphene supported heterogeneous catalysts were produced by a facile method. In order to prevent aggregation of graphene sheets and increase not only interlayer distance but also surface area, a trace amount multi-wall carbon nano tube (MWCNT) was introduced to the composite structure. The obtained composite catalysts were characterized by SEM, X-ray diffraction, N2 adsorption-desorption analyze and Raman spectroscopy. The electrochemical characterization tests including galvanostatic charge/discharge and electrochemical impedance spectroscopy (EIS) measurement of catalyst were carried out by using an ECC-Air test cell. These highly active graphene supported heterogeneous composite catalysts provide competitive properties relative to other catalyst materials for Li-air batteries.

  2. Air purification equipment combining a filter coated by silver nanoparticles with a nano-TiO2 photocatalyst for use in hospitals

    NASA Astrophysics Data System (ADS)

    Son Le, Thanh; Hien Dao, Trong; Nguyen, Dinh Cuong; Chau Nguyen, Hoai; Balikhin, I. L.

    2015-03-01

    X-ray diffraction, scanning electron microscopy and transmission electron microscopy showed that TiO2 particles synthesized by a sol-gel procedure exhibited uniform size about 16-20 nm. This nanopowder was deposited on a porous quartz tube (D = 74 mm, L = 418 mm, deposit density ˜16.4 mg cm-2) through an intermediate adhesive polymethylmethacrylate layer to manufacture a photocatalytic filter tube. A polypropylene pre-filter was coated with a nanosilver layer (particle size ˜20 nm) prepared by aqueous molecular solution method. An air cleaner of 250 m3 h-1 capacity equipped with this pre-filter, an electrostatic air filter, 4 photocatalytic filter tubes and 4 UV-A lamps (36 W) presented the high degradation ability for certain volatile organic compounds (VOCs), bacteria and fungi. The VOCs degradation performances of the equipment with respect to divers compounds are different: in a 10 m3 box, 91.6% of butanol was removed within 55 min, 80% of acetone within 100 min, 70.1% of diethyl ether within 120 min and only 43% of benzene was oxidized within 150 min. Over 99% of bacteria and fungi were killed after the air passage through the equipment. For application, it was placed in the intensive care room (volume of 125 m3) of E hospital in Hanoi; 69% of bacteria and 63% of fungi were killed within 6 h.

  3. Method for measuring temperatures and densities in hypersonic wind tunnel air flows using laser-induced O2 fluorescence

    NASA Technical Reports Server (NTRS)

    Laufer, Gabriel; Mckenzie, Robert L.; Fletcher, Douglas G.

    1990-01-01

    Laser-induced fluorescence in oxygen, in combination with Raman scattering, is shown to be an accurate means by which temperature, density, and their fluctuations owing to turbulence can be measured in air flows associated with high-speed wind tunnels. For temperatures above 60 K and densities above 0.01 amagat, the uncertainties in the temperature and density measurements can be less than 2 percent, if the signal uncertainties are dominated by photon statistical noise. The measurements are unaffected by collisional quenching and can be achieved with laser fluences for which nonlinear effects are insignificant. Temperature measurements using laser-induced fluorescence alone have been demonstrated at known densities in the range of low temperatures and densities which are expected in a hypersonic wind tunnel.

  4. A method for measuring temperatures and densities in hypersonic wind tunnel air flows using laser-induced O2 fluorescence

    NASA Technical Reports Server (NTRS)

    Laufer, Gabriel; Fletcher, Douglas G.; Mckenzie, Robert L.

    1990-01-01

    Laser-induced fluorescence in oxygen, in combination with Raman scattering, is shown to be an accurate means by which temperature, density, and their fluctuations due to turbulence can be measured in air flows associated with high-speed wind tunnels. For temperatures above 60 K and densities above 0.01 amagat, the uncertainty in the temperature and density measurements can be less than 2 and 3 percent, respectively, if the signal uncertainties are dominated by photon-statistical noise. The measurements are unaffected by collisional quenching and can be achieved with laser fluences for which nonlinear effects are insignificant. Temperature measurements using laser-induced fluorescence alone have been demonstrated at known densities in the range of low temperatures and densities which are expected in a hypersonic wind tunnel.

  5. Method for measuring temperatures and densities in hypersonic wind tunnel air flows using laser-induced O(2) fluorescence.

    PubMed

    Laufer, G; McKenzie, R L; Fletcher, D G

    1990-11-20

    Laser-induced fluorescence in oxygen, in combination with Raman scattering, is shown to be an accurate means by which temperature, density, and their fluctuations owing to turbulence can be measured in air flows associated with high speed wind tunnels. For temperatures above 60 K and densities above 0.01 amagat, the uncertainties in the temperature and density measurements can be <2%, if the signal uncertainties are dominated by photon statistical noise. The measurements are unaffected by collisional quenching and can be achieved with laser fluences for which nonlinear effects are insignificant. Temperature measurements using laser-induced fluorescence alone have been demonstrated at known densities in the range of low temperatures and densities which are expected in a hypersonic wind tunnel.

  6. Discussion on "field study of air purification paving elements containing TiO2" by Folli et al. (2015)

    NASA Astrophysics Data System (ADS)

    Kleffmann, Jörg

    2016-03-01

    In the study by Folli et al. (2015) photocatalytic pavement blocks were used on both sidewalks of a street canyon in Copenhagen (Denmark) for the purpose of air remediation of nitrogen oxides (NOx). Outstanding nitrogen monoxide (NO) degradation was observed with an average (day and night) reduction of 22% during summer months reaching values >45% at noontime. In contrast, for nitrogen dioxide (NO2) no significant improvement was obtained. Although these results would be of significant importance for many European urban environments usually suffering from high NOx levels, the results are highly unrealistic. Two simple back-to-the-envelope calculations show that the upper limit photocatalytic reduction of NO will be <1% for the investigated street canyon conditions. In addition, an alternative explanation of the experimental observations by the gas phase titration of NO by ozone (O3) is discussed.

  7. A Study of a QCM Sensor Based on TiO2 Nanostructures for the Detection of NO2 and Explosives Vapours in Air

    PubMed Central

    Procek, Marcin; Stolarczyk, Agnieszka; Pustelny, Tadeusz; Maciak, Erwin

    2015-01-01

    The paper deals with investigations concerning the construction of sensors based on a quartz crystal microbalance (QCM) containing a TiO2 nanostructures sensor layer. A chemical method of synthesizing these nanostructures is presented. The prepared prototype of the QCM sensing system, as well as the results of tests for detecting low NO2 concentrations in an atmosphere of synthetic air have been described. The constructed NO2 sensors operate at room temperature, which is a great advantage, because resistance sensors based on wide gap semiconductors often require much higher operation temperatures, sometimes as high as 500 °C. The sensors constructed by the authors can be used, among other applications, in medical and chemical diagnostics, and also for the purpose of detecting explosive vapours. Reactions of the sensor to nitroglycerine vapours are presented as an example of its application. The influence of humidity on the operation of the sensor was studied. PMID:25912352

  8. Increased cardiac output, not pulmonary artery systolic pressure, increases intrapulmonary shunt in healthy humans breathing room air and 40% O2

    PubMed Central

    Elliott, Jonathan E; Duke, Joseph W; Hawn, Jerold A; Halliwill, John R; Lovering, Andrew T

    2014-01-01

    Blood flow through intrapulmonary arteriovenous anastomoses (IPAVAs) has been demonstrated to increase in healthy humans during a variety of conditions; however, whether or not this blood flow represents a source of venous admixture (/) that impairs pulmonary gas exchange efficiency (i.e. increases the alveolar-to-arterial difference (A–aDO2)) remains controversial and unknown. We hypothesized that blood flow through IPAVAs does provide a source of /. To test this, blood flow through IPAVAs was increased in healthy humans at rest breathing room air and 40% O2: (1) during intravenous adrenaline (epinephrine) infusion at 320 ng kg−1 min−1 (320 ADR), and (2) with vagal blockade (2 mg atropine), before and during intravenous adrenaline infusion at 80 ng kg−1 min−1 (ATR + 80 ADR). When breathing room air the A–aDO2 increased by 6 ± 2 mmHg during 320 ADR and by 5 ± 2 mmHg during ATR + 80 ADR, and the change in calculated / was +2% in both conditions. When breathing 40% O2, which minimizes contributions from diffusion limitation and alveolar ventilation-to-perfusion inequality, the A–aDO2 increased by 12 ± 7 mmHg during 320 ADR, and by 9 ± 6 mmHg during ATR + 80 ADR, and the change in calculated / was +2% in both conditions. During 320 ADR cardiac output () and pulmonary artery systolic pressure (PASP) were significantly increased; however, during ATR + 80 ADR only was significantly increased, yet blood flow through IPAVAs as detected with saline contrast echocardiography was not different between conditions. Accordingly, we suggest that blood flow through IPAVAs provides a source of intrapulmonary shunt, and is mediated primarily by increases in rather than PASP. PMID:25085889

  9. Continuous distributions of ventilation-perfusion ratios in normal subjects breathing air and 100 per cent O2.

    PubMed

    Wagner, P D; Laravuso, R B; Uhl, R R; West, J B

    1974-07-01

    A new method has been developed for measuring virtually continuous distributions of ventilation-perfusion ratios (V(A)/Q) based on the steadystate elimination of six gases of different solubilities. The method is applied here to 12 normal subjects, aged 21-60. In nine, the distributions were compared breathing air and 100% oxygen, while in the remaining three, effects of changes in posture were examined. In four young semirecumbent subjects (ages 21-24) the distributions of blood flow and ventilation with respect to V(A)/Q were virtually log-normal with little dispersion (mean log standard deviations 0.43 and 0.35, respectively). The 95.5% range of both blood flow and ventilation was from V(A)/Q ratios of 0.3-2.1, and there was no intrapulmonary shunt (V(A)/Q of 0). On breathing oxygen, a shunt developed in three of these subjects, the mean value being 0.5% of the cardiac output. The five older subjects (ages 39-60) had broader distributions (mean log standard deviations, 0.76 and 0.44) containing areas with V(A)/Q ratios in the range 0.01-0.1 in three subjects. As for the young subjects, there was no shunt breathing air, but all five developed a shunt breathing oxygen (mean value 3.2%), and in one the value was 10.7%. Postural changes were generally those expected from the known effects of gravity, with more ventilation to high V(A)/Q areas when the subjects were erect than supine. Measurements of the shunt while breathing oxygen, the Bohr CO(2) dead space, and the alveolar-arterial oxygen difference were all consistent with the observed distributions. Since the method involves only a short infusion of dissolved inert gases, sampling of arterial blood and expired gas, and measurement of cardiac output and minute ventilation, we conclude that it is well suited to the investigation of pulmonary gas exchange in man.

  10. Line parameters including temperature dependences of self- and air-broadened line shapes of 12C16O2: 1.6-μm region

    NASA Astrophysics Data System (ADS)

    Devi, V. Malathy; Benner, D. Chris; Sung, Keeyoon; Brown, Linda R.; Crawford, Timothy J.; Miller, Charles E.; Drouin, Brian J.; Payne, Vivienne H.; Yu, Shanshan; Smith, Mary Ann H.; Mantz, Arlan W.; Gamache, Robert R.

    2016-07-01

    Pressure-broadened line shapes in the 30013←00001 (ν1+4 ν20 +ν3) band of 12C16O2 at 6228 cm-1 are reanalyzed using new spectra recorded with sample temperatures down to 170 K. High resolution, high signal-to-noise (S/N) laboratory measurements of line shapes (Lorentz air- and self-broadened half-width coefficients, pressure-shift coefficients and off-diagonal relaxation matrix element coefficients) as a function of gas sample temperatures for various pressures and volume mixing ratios are presented. The spectra were recorded using two different Fourier transform spectrometers (FTS): (1) the McMath-Pierce FTS located at the National Solar Observatory on Kitt Peak, Arizona (and reported in Devi et al., J Mol Spectrosc 2007;245:52-80) and, (2) the Bruker IFS-125HR FTS at the Jet Propulsion Laboratory in Pasadena, California. The 19 spectra taken at Kitt Peak were all recorded near room temperature while the 27 Bruker spectra were acquired both at room temperature and colder temperatures (170-296 K). Various spectral resolutions (0.004-0.011 cm-1), absorption path lengths (2.46-121 m) and CO2 samples (natural and 12C-enriched) were included in the dataset. To maximize the accuracies of the various retrieved line parameters, a multispectrum nonlinear least squares spectrum fitting software program was used to adjust the ro-vibrational constants (G,B,D etc.) and intensity parameters (including Herman-Wallis terms) instead of directly measuring the individual line positions and intensities. To minimize systematic residuals, line mixing (via off-diagonal relaxation matrix elements) and quadratic speed dependence parameters were included in the analysis. Contributions from other weakly absorbing bands: the 30013←00001 and 30012←00001 bands of 13C16O2, the 30013←00001 band of 12C16O18O, hot bands 31113←01101 and 32212←02201 of 12C16O2, as well as the 40013←10001 and the 40014←10002 bands of 12C16O2, present within the fitted interval were also measured

  11. MWCNT-supported phthalocyanine cobalt as air-breathing cathodic catalyst in glucose/O2 fuel cells

    NASA Astrophysics Data System (ADS)

    Elouarzaki, Kamal; Haddad, Raoudha; Holzinger, Michael; Le Goff, Alan; Thery, Jessica; Cosnier, Serge

    2014-06-01

    Simple and highly efficient glucose fuel cells using abiotic catalysts and different ion exchange membranes were designed. The glucose fuel cells are based on a multi-walled carbon nanotube (MWCNT)-supported cobalt phthalocyanine (CoPc) cathode and a carbon black/platinum (C/Pt) anode. The electrocatalytic activity of the MWCNT/CoPc electrode for oxygen reduction was investigated by cyclic and linear sweep voltammetry. The electrochemical experiments show that CoPc exhibits promising catalytic properties for oxygen reduction due to its high overpotential and efficiency at reduced metal load. The MWCNT/CoPc electrodes were applied to the oxygen reduction reaction as air-breathing cathode in a single-chambered glucose fuel cell. This cathode was associated with a C/Pt anode in fuel cell configurations using either an anion (Nafion®) or a cation (Tokuyama) exchange membrane. The best fuel cell configuration delivered a maximum power density of 2.3 mW cm-2 and a cell voltage of 0.8 V in 0.5 M KOH solution containing 0.5 M glucose using the Tokuyama membrane at ambient conditions. Beside the highest power density per cathodic catalyst mass (383 W g-1), these glucose fuel cells exhibit a high operational stability, delivering 0.3 mW cm-2 after 50 days.

  12. Characteristics of a laser triggered spark gap using air, Ar, CH4, H2, He, N2, SF6, and Xe

    NASA Astrophysics Data System (ADS)

    Kimura, W. D.; Kushner, M. J.; Seamans, J. F.

    1988-03-01

    A KrF discharge laser (248 nm) has been used to laser trigger, by volume preionization, a spark gap switch (38-65 kV, >10 kA, 100 ns pulse duration) filled with 20 different gas mixtures using various combinations of air, Ar, CH4, H2, He, N2 SF6, and Xe. A pulsed laser interferometer is used to probe the spark column. Characteristics studied include the internal structure of the column, the arc expansion rate, and evidence of any photoionization precursor effect. Our results show that the rate of arc expansion varies depending on the average molecular weight of the mixtures. In this experiment, pure H2 has the highest rate (≊9.5×105 cm/s) and air has one of the lowest (≊7×105 cm/s) for the same hold-off voltage. A computer model of the spark column formation is able to predict most of the structure observed in the arcs, including the effect of mixing gases with widely different molecular weights. The work suggests that, under proper circumstances, the spark gap switch performance may be improved by using gases lighter than conventional switch gases such as SF6.

  13. A Pleistocene ice core record of atmospheric O2 concentrations

    NASA Astrophysics Data System (ADS)

    Stolper, D. A.; Bender, M. L.; Dreyfus, G. B.; Yan, Y.; Higgins, J. A.

    2016-09-01

    The history of atmospheric O2 partial pressures (PO2) is inextricably linked to the coevolution of life and Earth’s biogeochemical cycles. Reconstructions of past PO2 rely on models and proxies but often markedly disagree. We present a record of PO2 reconstructed using O2/N2 ratios from ancient air trapped in ice. This record indicates that PO2 declined by 7 per mil (0.7%) over the past 800,000 years, requiring that O2 sinks were ~2% larger than sources. This decline is consistent with changes in burial and weathering fluxes of organic carbon and pyrite driven by either Neogene cooling or increasing Pleistocene erosion rates. The 800,000-year record of steady average carbon dioxide partial pressures (PCO2) but declining PO2 provides distinctive evidence that a silicate weathering feedback stabilizes PCO2 on million-year time scales.

  14. Discharge performance of solid-state oxygen shuttle metal-air battery using Ca-stabilized ZrO2 electrolyte.

    PubMed

    Inoishi, Atsushi; Kim, Hack-Ho; Sakai, Takaaki; Ju, Young-Wan; Ida, Shintaro; Ishihara, Tatsumi

    2015-04-13

    The effects of metal choice on the electrochemical performance of oxygen-shuttle metal-air batteries with Ca-stabilized ZrO2 (CSZ) as the electrolyte and various metals as the anodes were studied at 1073 K. The equilibrium oxygen partial pressure (P O 2) in the anode chamber was governed by the metal used in the anode chamber. A lower-P O 2 environment in the anode decreased the polarization resistance of the anode. The oxidation of oxide ions to oxygen in the anode is drastically enhanced by the n-type conduction generated in the CSZ electrolyte when it is exposed to a reducing atmosphere. A high discharge potential and high capacity can be achieved in an oxygen-shuttle battery with a Li or Mg anode because of the fast anode reaction compared to that of cells with a Zn, Fe, or Sn anode. However, only the mildly reducing metals (Zn, Si, Fe, and Sn) can potentially be used in rechargeable metal-air batteries because the transport number of the CSZ electrolyte must be unity during charge and discharge. Oxygen shuttle rechargeable batteries with Fe, and Sn electrodes are demonstrated.

  15. Discharge performance of solid-state oxygen shuttle metal-air battery using Ca-stabilized ZrO2 electrolyte.

    PubMed

    Inoishi, Atsushi; Kim, Hack-Ho; Sakai, Takaaki; Ju, Young-Wan; Ida, Shintaro; Ishihara, Tatsumi

    2015-04-13

    The effects of metal choice on the electrochemical performance of oxygen-shuttle metal-air batteries with Ca-stabilized ZrO2 (CSZ) as the electrolyte and various metals as the anodes were studied at 1073 K. The equilibrium oxygen partial pressure (P O 2) in the anode chamber was governed by the metal used in the anode chamber. A lower-P O 2 environment in the anode decreased the polarization resistance of the anode. The oxidation of oxide ions to oxygen in the anode is drastically enhanced by the n-type conduction generated in the CSZ electrolyte when it is exposed to a reducing atmosphere. A high discharge potential and high capacity can be achieved in an oxygen-shuttle battery with a Li or Mg anode because of the fast anode reaction compared to that of cells with a Zn, Fe, or Sn anode. However, only the mildly reducing metals (Zn, Si, Fe, and Sn) can potentially be used in rechargeable metal-air batteries because the transport number of the CSZ electrolyte must be unity during charge and discharge. Oxygen shuttle rechargeable batteries with Fe, and Sn electrodes are demonstrated. PMID:25727525

  16. Air-gating and chemical-gating in transistors and sensing devices made from hollow TiO2 semiconductor nanotubes.

    PubMed

    Alivov, Yahya; Funke, Hans; Nagpal, Prashant

    2015-07-24

    Rapid miniaturization of electronic devices down to the nanoscale, according to Moore's law, has led to some undesirable effects like high leakage current in transistors, which can offset additional benefits from scaling down. Development of three-dimensional transistors, by spatial extension in the third dimension, has allowed higher contact area with a gate electrode and better control over conductivity in the semiconductor channel. However, these devices do not utilize the large surface area and interfaces for new electronic functionality. Here, we demonstrate air gating and chemical gating in hollow semiconductor nanotube devices and highlight the potential for development of novel transistors that can be modulated using channel bias, gate voltage, chemical composition, and concentration. Using chemical gating, we reversibly altered the conductivity of nanoscaled semiconductor nanotubes (10-500 nm TiO2 nanotubes) by six orders of magnitude, with a tunable rectification factor (ON/OFF ratio) ranging from 1-10(6). While demonstrated air- and chemical-gating speeds were slow here (∼seconds) due to the mechanical-evacuation rate and size of our chamber, the small nanoscale volume of these hollow semiconductors can enable much higher switching speeds, limited by the rate of adsorption/desorption of molecules at semiconductor interfaces. These chemical-gating effects are completely reversible, additive between different chemical compositions, and can enable semiconductor nanoelectronic devices for 'chemical transistors', 'chemical diodes', and very high-efficiency sensing applications.

  17. Air-gating and chemical-gating in transistors and sensing devices made from hollow TiO2 semiconductor nanotubes

    NASA Astrophysics Data System (ADS)

    Alivov, Yahya; Funke, Hans; Nagpal, Prashant

    2015-07-01

    Rapid miniaturization of electronic devices down to the nanoscale, according to Moore’s law, has led to some undesirable effects like high leakage current in transistors, which can offset additional benefits from scaling down. Development of three-dimensional transistors, by spatial extension in the third dimension, has allowed higher contact area with a gate electrode and better control over conductivity in the semiconductor channel. However, these devices do not utilize the large surface area and interfaces for new electronic functionality. Here, we demonstrate air gating and chemical gating in hollow semiconductor nanotube devices and highlight the potential for development of novel transistors that can be modulated using channel bias, gate voltage, chemical composition, and concentration. Using chemical gating, we reversibly altered the conductivity of nanoscaled semiconductor nanotubes (10-500 nm TiO2 nanotubes) by six orders of magnitude, with a tunable rectification factor (ON/OFF ratio) ranging from 1-106. While demonstrated air- and chemical-gating speeds were slow here (˜seconds) due to the mechanical-evacuation rate and size of our chamber, the small nanoscale volume of these hollow semiconductors can enable much higher switching speeds, limited by the rate of adsorption/desorption of molecules at semiconductor interfaces. These chemical-gating effects are completely reversible, additive between different chemical compositions, and can enable semiconductor nanoelectronic devices for ‘chemical transistors’, ‘chemical diodes’, and very high-efficiency sensing applications.

  18. [Regulation of geochemical activity of microorganisms in a petroleum reservoir by injection of H2O2 or water-air mixture].

    PubMed

    Nazina, T N; Pavlova, N K; Ni, F; Shestakova, N M; Ivoĭlov, V S; Feng, Q; Dongyun, Z; Prusakova, T S; Beliaev, S S; Ivanov, M V

    2008-01-01

    In the course of pilot trials of biotechnologies for the enhancement of oil recovery in the Gangxi bed of the Dagang oil field (China), microbiological processes were investigated. The biotechnologies were based on injection into the petroleum reservoir of different oxygen sources (H2O2 solution or a water-air mixture) with nitrogen and phosphorus salts. The injection of water-air mixture with nitrogen and phosphorus salts resulted in an increase in the number of aerobic and anaerobic organotrophic bacteria, rates of sulfate reduction and methanogenesis in formation water and also the content of CO2 (from 4.8-12 to 15-23.2%) and methane (from 86-88 to 91.8%) in the gas. The preferential consumption of isotopically light bicarbonate by methanogens resulted in a higher content of the light 12C in methane; the delta13C/CH4 value changed from -45.1...-48.3 to -50.7...-59.3 per thousand). At the same time, mineral carbonates of the formation water became isotopically heavier; the delta13C/Sigmacarbonates value increased from 3.4...4.0 to 5.4...9.6 per thousand. Growth of hydrocarbon-oxidizing bacteria was accompanied by production of biosurfactants and decreased interfacial tension of formation water. Injection of H2O2 solution resulted in the activation of aerobic processes and in suppression of both sulfate reduction and methanogenesis. Methane content in the gas decreased from 86-88 to 75.4-79.8%, probably due to its consumption by methanotrophs. Due to consumption of isotopically light methane, the residual methane carbon became heavier, with the delta13C/CH4 values from -39.0 to -44.3 per thousand. At the same time, mineral carbonates of the formation water became isotopically considerably lighter; the delta13C/Sigmacarbonates value decreased from 5.4... 9.6 to -1.4...2.7 per thousand). The additional amount of oil recovered during the trial of both variants of biotechnological treatment was 3819 t.

  19. Atomic Layer Deposition of TiO2 for a High-Efficiency Hole-Blocking Layer in Hole-Conductor-Free Perovskite Solar Cells Processed in Ambient Air.

    PubMed

    Hu, Hang; Dong, Binghai; Hu, Huating; Chen, Fengxiang; Kong, Mengqin; Zhang, Qiuping; Luo, Tianyue; Zhao, Li; Guo, Zhiguang; Li, Jing; Xu, Zuxun; Wang, Shimin; Eder, Dominik; Wan, Li

    2016-07-20

    In this study we design and construct high-efficiency, low-cost, highly stable, hole-conductor-free, solid-state perovskite solar cells, with TiO2 as the electron transport layer (ETL) and carbon as the hole collection layer, in ambient air. First, uniform, pinhole-free TiO2 films of various thicknesses were deposited on fluorine-doped tin oxide (FTO) electrodes by atomic layer deposition (ALD) technology. Based on these TiO2 films, a series of hole-conductor-free perovskite solar cells (PSCs) with carbon as the counter electrode were fabricated in ambient air, and the effect of thickness of TiO2 compact film on the device performance was investigated in detail. It was found that the performance of PSCs depends on the thickness of the compact layer due to the difference in surface roughness, transmittance, charge transport resistance, electron-hole recombination rate, and the charge lifetime. The best-performance devices based on optimized TiO2 compact film (by 2000 cycles ALD) can achieve power conversion efficiencies (PCEs) of as high as 7.82%. Furthermore, they can maintain over 96% of their initial PCE after 651 h (about 1 month) storage in ambient air, thus exhibiting excellent long-term stability.

  20. Atomic Layer Deposition of TiO2 for a High-Efficiency Hole-Blocking Layer in Hole-Conductor-Free Perovskite Solar Cells Processed in Ambient Air.

    PubMed

    Hu, Hang; Dong, Binghai; Hu, Huating; Chen, Fengxiang; Kong, Mengqin; Zhang, Qiuping; Luo, Tianyue; Zhao, Li; Guo, Zhiguang; Li, Jing; Xu, Zuxun; Wang, Shimin; Eder, Dominik; Wan, Li

    2016-07-20

    In this study we design and construct high-efficiency, low-cost, highly stable, hole-conductor-free, solid-state perovskite solar cells, with TiO2 as the electron transport layer (ETL) and carbon as the hole collection layer, in ambient air. First, uniform, pinhole-free TiO2 films of various thicknesses were deposited on fluorine-doped tin oxide (FTO) electrodes by atomic layer deposition (ALD) technology. Based on these TiO2 films, a series of hole-conductor-free perovskite solar cells (PSCs) with carbon as the counter electrode were fabricated in ambient air, and the effect of thickness of TiO2 compact film on the device performance was investigated in detail. It was found that the performance of PSCs depends on the thickness of the compact layer due to the difference in surface roughness, transmittance, charge transport resistance, electron-hole recombination rate, and the charge lifetime. The best-performance devices based on optimized TiO2 compact film (by 2000 cycles ALD) can achieve power conversion efficiencies (PCEs) of as high as 7.82%. Furthermore, they can maintain over 96% of their initial PCE after 651 h (about 1 month) storage in ambient air, thus exhibiting excellent long-term stability. PMID:27340730

  1. Effects of CO 2 in air on Li deintercalation from LiNi 1- x- yCo xAl yO 2

    NASA Astrophysics Data System (ADS)

    Matsumoto, Kazutoshi; Kuzuo, Ryuichi; Takeya, Kaname; Yamanaka, Atsushi

    The reaction of CO 2 and practical high-performance cathode materials LiNi 1- x- yCo xAl yO 2 was examined with XRD at RT and high temperature, TGA, IR, and chemical analysis. Even at room temperature, Li deintercalation took place and formed Li 2CO 3 on the mother surface. The conversion to Li 2CO 3 in air at 55% RH at 25°C was in proportion to the square root of exposure time. It was 8% after being left for 500 h. Using high-temperature XRD at 25-800°C, the Li 2CO 3 phase formation was confirmed from about 500°C, and the conversion exceeded 70% under atmospheric CO 2 at 675°C. The activation energy of the reaction of deintercalated Li and CO 2 was estimated by Ozawa's method. The activation energy obtained using Ozawa's method was 130 kJ/mol for CO 2 diffusing through the Li 2CO 3 layer which formed on the surface during the reaction.

  2. Binder-Free and Carbon-Free 3D Porous Air Electrode for Li-O2 Batteries with High Efficiency, High Capacity, and Long Life.

    PubMed

    Luo, Wen-Bin; Gao, Xuan-Wen; Shi, Dong-Qi; Chou, Shu-Lei; Wang, Jia-Zhao; Liu, Hua-Kun

    2016-06-01

    Pt-Gd alloy polycrystalline thin film is deposited on 3D nickel foam by pulsed laser deposition method serving as a whole binder/carbon-free air electrode, showing great catalytic activity enhancement as an efficient bifunctional catalyst for the oxygen reduction and evolution reactions in lithium oxygen batteries. The porous structure can facilitate rapid O2 and electrolyte diffusion, as well as forming a continuous conductive network throughout the whole energy conversion process. It shows a favorable cycle performance in the full discharge/charge model, owing to the high catalytic activity of the Pt-Gd alloy composite and 3D porous nickel foam structure. Specially, excellent cycling performance under capacity limited mode is also demonstrated, in which the terminal discharge voltage is higher than 2.5 V and the terminal charge voltage is lower than 3.7 V after 100 cycles at a current density of 0.1 mA cm(-2) . Therefore, this electrocatalyst is a promising bifunctional electrocatalyst for lithium oxygen batteries and this depositing high-efficient electrocatalyst on porous substrate with polycrystalline thin film by pulsed laser deposition is also a promising technique in the future lithium oxygen batteries research.

  3. Dissociative recombination of O2(+), NO(+) and N2(+)

    NASA Technical Reports Server (NTRS)

    Guberman, S. L.

    1983-01-01

    A new L(2) approach for the calculation of the threshold molecular capture width needed for the determination of DR cross sections was developed. The widths are calculated with Fermi's golden rule by substituting Rydberg orbitals for the free electron continuum coulomb orbital. It is shown that the calculated width converges exponentially as the effective principal quantum number of the Rydberg orbital increases. The threshold capture width is then easily obtained. Since atmospheric recombination involves very low energy electrons, the threshold capture widths are essential to the calculation of DR cross sections for the atmospheric species studied here. The approach described makes use of bound state computer codes already in use. A program that collects width matrix elements over CI wavefunctions for the initial and final states is described.

  4. Effects of elevated ozone concentration on CH4 and N2O emission from paddy soil under fully open-air field conditions.

    PubMed

    Tang, Haoye; Liu, Gang; Zhu, Jianguo; Kobayashi, Kazuhiko

    2015-04-01

    We investigated the effects of elevated ozone concentration (E-O3) on CH4 and N2O emission from paddies with two rice cultivars: an inbred Indica cultivar Yangdao 6 (YD6) and a hybrid one II-you 084 (IIY084), under fully open-air field conditions in China. A mean 26.7% enhancement of ozone concentration above the ambient level (A-O3) significantly reduced CH4 emission at tillering and flowering stages leading to a reduction of seasonal integral CH4 emission by 29.6% on average across the two cultivars. The reduced CH4 emission is associated with O3-induced reduction in the whole-plant biomass (-13.2%), root biomass (-34.7%), and maximum tiller number (-10.3%), all of which curbed the carbon supply for belowground CH4 production and its release from submerged soil to atmosphere. Although no significant difference was detected between the cultivars in the CH4 emission response to E-O3, a larger decrease in CH4 emission with IIY084 (-33.2%) than that with YD6 (-7.0%) was observed at tillering stage, which may be due to the larger reduction in tiller number in IIY084 by E-O3. Additionally, E-O3 reduced seasonal mean NOx flux by 5.7% and 11.8% with IIY084 and YD6, respectively, but the effects were not significant statistically. We found that the relative response of CH4 emission to E-O3 was not significantly different from those reported in open-top chamber experiments. This study has thus confirmed that increasing ozone concentration would mitigate the global warming potential of CH4 and suggested consideration of the feedback mechanism between ozone and its precursor emission into the projection of future ozone effects on terrestrial ecosystem.

  5. Effects of elevated ozone concentration on CH4 and N2O emission from paddy soil under fully open-air field conditions.

    PubMed

    Tang, Haoye; Liu, Gang; Zhu, Jianguo; Kobayashi, Kazuhiko

    2015-04-01

    We investigated the effects of elevated ozone concentration (E-O3) on CH4 and N2O emission from paddies with two rice cultivars: an inbred Indica cultivar Yangdao 6 (YD6) and a hybrid one II-you 084 (IIY084), under fully open-air field conditions in China. A mean 26.7% enhancement of ozone concentration above the ambient level (A-O3) significantly reduced CH4 emission at tillering and flowering stages leading to a reduction of seasonal integral CH4 emission by 29.6% on average across the two cultivars. The reduced CH4 emission is associated with O3-induced reduction in the whole-plant biomass (-13.2%), root biomass (-34.7%), and maximum tiller number (-10.3%), all of which curbed the carbon supply for belowground CH4 production and its release from submerged soil to atmosphere. Although no significant difference was detected between the cultivars in the CH4 emission response to E-O3, a larger decrease in CH4 emission with IIY084 (-33.2%) than that with YD6 (-7.0%) was observed at tillering stage, which may be due to the larger reduction in tiller number in IIY084 by E-O3. Additionally, E-O3 reduced seasonal mean NOx flux by 5.7% and 11.8% with IIY084 and YD6, respectively, but the effects were not significant statistically. We found that the relative response of CH4 emission to E-O3 was not significantly different from those reported in open-top chamber experiments. This study has thus confirmed that increasing ozone concentration would mitigate the global warming potential of CH4 and suggested consideration of the feedback mechanism between ozone and its precursor emission into the projection of future ozone effects on terrestrial ecosystem. PMID:25403809

  6. Perennial N2 supersaturation in an Antarctic lake. [biological processes in thin martian atmosphere

    NASA Technical Reports Server (NTRS)

    Wharton, Robert A., Jr.; Mckay, Christopher P.; Mancinelli, Rocco L.; Simmons, George M., Jr.

    1987-01-01

    The results of a study are reported which, for the first time, documents the supersaturation of N2 in a lake. Dissolved N2 levels of 145 percent and 163 percent were determined for Antarctica's Lake Hoare from samples taken just below the ice cover and at a depth of 12 m, respectively. The relative importance of biological and abiological sources is reflected in the ratio of N2 concentration to O2 concentration. In Lake Hoare this ratio was 1.20 at the ice/water interface and 1.05 at 12 m, considerably different from the ratio in equilibrium with air (about 1.8). Based on these results, it is determined that about half of the net O2 production in the lake is the result of biological processes. The significance of these results for the putative ice-covered paleolakes in the canyon regions of Mars is discussed.

  7. Self-assembly formation of Bi-functional Co3O4/MnO2-CNTs hybrid catalysts for achieving both high energy/power density and cyclic ability of rechargeable zinc-air battery

    NASA Astrophysics Data System (ADS)

    Xu, Nengneng; Liu, Yuyu; Zhang, Xia; Li, Xuemei; Li, Aijun; Qiao, Jinli; Zhang, Jiujun

    2016-09-01

    α-MnO2 nanotubes-supported Co3O4 (Co3O4/MnO2) and its carbon nanotubes (CNTs)-hybrids (Co3O4/MnO2-CNTs) have been successfully developed through a facile two-pot precipitation reaction and hydrothermal process, which exhibit the superior bi-functional catalytic activity for both ORR and OER. The high performance is believed to be induced by the hybrid effect among MnO2 nanotubes, hollow Co3O4 and CNTs, which can produce a synergetic enhancement. When integrated into the practical primary and electrochemically rechargeable Zn-air batteries, such a hybrid catalyst can give a discharge peak power density as high as 450 mW cm‑2. At 1.0 V of cell voltage, a current density of 324 mA cm‑2 is achieved. This performance is superior to all reported non-precious metal catalysts in literature for zinc-air batteries and significantly outperforms the state-of-the-art platinum-based catalyst. Particularly, the rechargeable Zn-air battery can be fabricated into all-solid-state one through a simple solid-state approach, which exhibits an excellent peak power density of 62 mW cm‑2, and the charge and discharge potentials remain virtually unchanged during the overall cycles, which is comparable to the one with liquid electrolyte.

  8. Self-assembly formation of Bi-functional Co3O4/MnO2-CNTs hybrid catalysts for achieving both high energy/power density and cyclic ability of rechargeable zinc-air battery.

    PubMed

    Xu, Nengneng; Liu, Yuyu; Zhang, Xia; Li, Xuemei; Li, Aijun; Qiao, Jinli; Zhang, Jiujun

    2016-09-20

    α-MnO2 nanotubes-supported Co3O4 (Co3O4/MnO2) and its carbon nanotubes (CNTs)-hybrids (Co3O4/MnO2-CNTs) have been successfully developed through a facile two-pot precipitation reaction and hydrothermal process, which exhibit the superior bi-functional catalytic activity for both ORR and OER. The high performance is believed to be induced by the hybrid effect among MnO2 nanotubes, hollow Co3O4 and CNTs, which can produce a synergetic enhancement. When integrated into the practical primary and electrochemically rechargeable Zn-air batteries, such a hybrid catalyst can give a discharge peak power density as high as 450 mW cm(-2). At 1.0 V of cell voltage, a current density of 324 mA cm(-2) is achieved. This performance is superior to all reported non-precious metal catalysts in literature for zinc-air batteries and significantly outperforms the state-of-the-art platinum-based catalyst. Particularly, the rechargeable Zn-air battery can be fabricated into all-solid-state one through a simple solid-state approach, which exhibits an excellent peak power density of 62 mW cm(-2), and the charge and discharge potentials remain virtually unchanged during the overall cycles, which is comparable to the one with liquid electrolyte.

  9. Self-assembly formation of Bi-functional Co3O4/MnO2-CNTs hybrid catalysts for achieving both high energy/power density and cyclic ability of rechargeable zinc-air battery

    PubMed Central

    Xu, Nengneng; Liu, Yuyu; Zhang, Xia; Li, Xuemei; Li, Aijun; Qiao, Jinli; Zhang, Jiujun

    2016-01-01

    α-MnO2 nanotubes-supported Co3O4 (Co3O4/MnO2) and its carbon nanotubes (CNTs)-hybrids (Co3O4/MnO2-CNTs) have been successfully developed through a facile two-pot precipitation reaction and hydrothermal process, which exhibit the superior bi-functional catalytic activity for both ORR and OER. The high performance is believed to be induced by the hybrid effect among MnO2 nanotubes, hollow Co3O4 and CNTs, which can produce a synergetic enhancement. When integrated into the practical primary and electrochemically rechargeable Zn-air batteries, such a hybrid catalyst can give a discharge peak power density as high as 450 mW cm−2. At 1.0 V of cell voltage, a current density of 324 mA cm−2 is achieved. This performance is superior to all reported non-precious metal catalysts in literature for zinc-air batteries and significantly outperforms the state-of-the-art platinum-based catalyst. Particularly, the rechargeable Zn-air battery can be fabricated into all-solid-state one through a simple solid-state approach, which exhibits an excellent peak power density of 62 mW cm−2, and the charge and discharge potentials remain virtually unchanged during the overall cycles, which is comparable to the one with liquid electrolyte. PMID:27646032

  10. Self-assembly formation of Bi-functional Co3O4/MnO2-CNTs hybrid catalysts for achieving both high energy/power density and cyclic ability of rechargeable zinc-air battery.

    PubMed

    Xu, Nengneng; Liu, Yuyu; Zhang, Xia; Li, Xuemei; Li, Aijun; Qiao, Jinli; Zhang, Jiujun

    2016-01-01

    α-MnO2 nanotubes-supported Co3O4 (Co3O4/MnO2) and its carbon nanotubes (CNTs)-hybrids (Co3O4/MnO2-CNTs) have been successfully developed through a facile two-pot precipitation reaction and hydrothermal process, which exhibit the superior bi-functional catalytic activity for both ORR and OER. The high performance is believed to be induced by the hybrid effect among MnO2 nanotubes, hollow Co3O4 and CNTs, which can produce a synergetic enhancement. When integrated into the practical primary and electrochemically rechargeable Zn-air batteries, such a hybrid catalyst can give a discharge peak power density as high as 450 mW cm(-2). At 1.0 V of cell voltage, a current density of 324 mA cm(-2) is achieved. This performance is superior to all reported non-precious metal catalysts in literature for zinc-air batteries and significantly outperforms the state-of-the-art platinum-based catalyst. Particularly, the rechargeable Zn-air battery can be fabricated into all-solid-state one through a simple solid-state approach, which exhibits an excellent peak power density of 62 mW cm(-2), and the charge and discharge potentials remain virtually unchanged during the overall cycles, which is comparable to the one with liquid electrolyte. PMID:27646032

  11. Impacts on Air Quality due to Photosensitized Production of Excited State O2 (1Δg) by PAHs and Oxy-PAHs in the Lower Atmosphere: An Experimental and Computational Modeling Approach

    NASA Astrophysics Data System (ADS)

    Montoya, G. A.; Carreras-Sospedra, M.; Montoya, J.; Dabdub, D.; Foster, K. L.

    2014-12-01

    Complex reactions between hydroxyl radicals (OH) and volatile organic compounds (VOCs) in the lower atmosphere have a high impact on the formation/fates of airborne toxic chemicals, polycyclic aromatic hydrocarbons (PAHs), and particulate matter.1 Recently, air quality models have been implemented to identify OH sources, but have underpredicted OH concentrations. Studies suggest that O2 (1Δg) is produced via an energy transfer (ET) mechanism initiated by the electronic excitation of PAH and oxygenated-PAH. Energy transfer involves the formation of triplet excited state PAH which is then quenched by the surrounding ground state O2 (3∑g) resulting in excited state O2 (1Δg) formation. Excited state O2 (1Δg) is known to readily react with mono-olefins to produce organic hydroperoxides.2,3 Furthermore, the organic hydroperoxide can photodegrade to yield OH. In this study, a Nd:YAG laser coupled to a time-resolved near infrared detector was used to obtain quantum yields of O2 (1Δg) production by irradiating PAHs and oxy-PAHs at both 355 nm and 532 nm in different solvents. Select PAHs, primarily emitted by combustion engines (e.g. pyrene and benzo[a]pyrene), and their oxygenated forms (oxy-PAHs) have been identified as highly efficient O2 (1Δg) photosensitizers. For example, the measured quantum yield for pyrene in toluene was 0.90 ± 0.02. The measured quantum yields were used to calculate the photochemical rate constants for O2 (1Δg) production via ET from electronically excited PAHs and oxy-PAHs. These results were incorporated into the University of California, Irvine-California Institute of Technology (UCI-CIT) model to assess the impact on OH concentrations and the overall air quality of the South Coast Air Basin of California. References 1 Finlayson-Pitts, B.J., and J. N. Pitts (1997), Science, 276(5315),1045-1052. 2 Foote, C. S. (1968), Accts. Chem. Res., 1, 104-110; Gollnick, K. (1968), Adv. Photochem., 6, 1-112; Kearns, D. R. (1971), Chem. Rev., 71, 395

  12. (Anilino{(Z)-2-[(E)-5-bromo-3-meth-oxy-2-oxidobenzyl-idene]hydrazin-1-yl-idene-κ(2)O(2),N(2)}methane-thiol-ato-κS)(4,4'-di-methyl-2,2'-bipyridine-κ(2)N,N')zinc N,N-dimethyl-formamide monosolvate.

    PubMed

    Jacob, Jinsa Mary; Prathapachandra Kurup, M R; Ng, Seik Weng

    2012-08-01

    The asymmetric unit of the title compound, [Zn(C(15)H(12)BrN(3)O(2)S)(C(12)H(12)N(2))]·C(3)H(7)NO, contains two independent mol-ecules with a similar structure. The doubly deprotonated Schiff base ligand O,N,S-chelates to the metal atom, and the three coordinating atoms along with one N atom of the substituted 2,2'-bipyridine ligand constitute the square plane of the distorted square pyramid surrounding the metal atom. The apical site is occupied by the second N atom of the substituted 2,2'-bipyridine. The secondary amine group of the Schiff base dianion forms a hydrogen bond to the O atom of the dimethyl-formamide solvent. In the crystal, the phenyl ring of one of the two Schiff base anions is disordered over two positions in a 1:1 ratio. The crystal studied is a racemic twin. PMID:22904750

  13. Absolute intensities and self-, N2-, and air-broadened Lorentz halfwidths for selected lines in the nu3 band of (C-12)H3D from measurements with a tunable diode laser spectrometer

    NASA Technical Reports Server (NTRS)

    Malathy Devi, V.; Benner, D. C.; Rinsland, C. P.; Smith, M. A. H.; Thakur, K. B.

    1986-01-01

    Absolute intensities and self-, air- and N2-broadened half-widths have been determined for the first time for individual lines in the nu3(A1) band of (C-12)H3D near 7.6 microns from measurements of individual vibration-rotation lines using a tunable diode laser spectrometer. The intensity measurements are believed to be accurate to within three percent. Within experimental uncertainties, equal broadening efficiencies are found for both air and nitrogen. Self-broadened half-widths determined for three transitions yield an average half-width value of 0.803 + or -0.0010/cm/atm at 296 K.

  14. N2-Fixation by Freshly Isolated Nostoc from Coralloid Roots of the Cycad Macrozamia riedlei (Fisch. ex Gaud.) Gardn. 1

    PubMed Central

    Lindblad, Peter; Atkins, Craig A.; Pate, John S.

    1991-01-01

    Nitrogenase (EC 1.7.99.2) activity (acetylene reduction) and nitrogen fixation (15N2 fixation) were measured in cyanobacteria freshly isolated from the coralloid roots of Macrozamia riedlei (Fisch. ex Gaud.) Gardn. Light and gas phase oxygen concentration had marked interactive effects on activity, with higher (up to 100-fold) rates of acetylene reduction and 15N2 fixation in light. The relationship between ethylene formation and N2-fixation varied in the freshly isolated cyanobacteria from 4 to 7 nanomoles of C2H4 per nanomole 15N2. Intact coralloid roots, incubated in darkness and ambient air, showed a value of 4.3. Maximum rates of nitrogenase activity occurred at about 0.6% O2 in light, while in darkness there was a broad optimum around 5 to 8% O2. Inhibition of nitrogenase, in light, by pO2 above 0.6% was irreversible. Measurements of light-dependent O2 evolution and 14CO2 fixation indicated negligible photosynthetic electron transport involving photosystem II and, on the basis of inhibitor studies, the stimulatory effect of light was attributed to cyclic photophos-phorylation. Nitrogenase activity of free-living culture of an isolate from Macrozamia (Nostoc PCC 73102) was only slightly inhibited by O2 levels above 6% O2 and the inhibition was reversible. These cells showed rates of light-dependent O2 evolution and 14CO2 fixation which were 100- to 200-fold higher than those by the freshly isolated symbiont. Furthermore, nitrogenase activity was dependent on both photosynthetic electron transport and photophosphorylation. These data indicate that cyanobacteria within cycad coralloid roots are differentiated specifically for symbiotic functioning in a microaerobic environment. Specializations include a high heterocyst frequency, enhanced permeability to O2, and a direct dependence on the cycad for substrates to support nitrogenase activity. PMID:16668050

  15. Enhanced Photoelectrochemical Performance of TiO2 Nanorod Arrays by a 500°C Annealing in Air: Insights into the Mechanism

    NASA Astrophysics Data System (ADS)

    Zhang, Shuang; Gu, Xiuquan; Zhao, Yulong; Qiang, Yinghuai

    2016-01-01

    Oriented, single-crystal TiO2 nanorod arrays (NRAs) were synthesized for photoelectrochemical (PEC) water-splitting by a facile hydrothermal route. It was observed that a 500°C annealing process facilitated enhancing the PEC activity of TiO2 NRAs, in agreement with our previous reports on NRA-related solar cells. Further, electrochemical impedance measurements were employed to investigate the underlying mechanism. Compared with pristine TiO2 NRAs, the 500°C sintered samples showed a positive flat-band shifting of ˜0.12 V as well as a suppression of the donor density. Thus, suggesting that the enhanced PEC performance might be attributed to the widening of depletion layer regions due to the reduction of crystal defects after sintering. The mechanism was also expanded to explain why the dye-sensitized solar cells made with sintered TiO2 NRAs exhibited an 11-times higher power conversion efficiency than those consisting of pristine arrays.

  16. Global distribution of N2O and the ΔN2O-AOU yield in the subsurface ocean

    NASA Astrophysics Data System (ADS)

    Nevison, Cynthia; Butler, James H.; Elkins, J. W.

    2003-12-01

    We present and analyze a data set of subsurface N2O from a range of oceanic regions. Observed N2O concentrations are highest in the eastern tropical Pacific (ETP), intermediate in the northern Pacific and Indian Oceans, and relatively low in the Southern and Atlantic Oceans. Tongues of high N2O, which propagate along sigma surfaces, provide evidence that N2O from the ETP is exported widely. Correlation slopes of ΔN2O (the level above atmospheric equilibrium) versus apparent oxygen utilization (AOU) are found to be an unreliable gauge of the biological N2O yield per mole O2 consumed because the slopes are strongly influenced by mixing gradients. Most features of the subsurface data set are consistent with an N2O source dominated by nitrification, including the widespread, robust ΔN2O-AOU correlation and the lack of a widespread anticorrelation between ΔN2O and N*. In addition, ΔN2O/NO3- ratios tend to increase with decreasing O2 in a manner consistent with laboratory studies of nitrifying bacteria. The sensitivity of the nitrifier N2O/NO3- yield to O2 can explain much of the variability in ΔN2O/AOU observed in the ocean. A parameterization is derived for the instantaneous production of N2O per mole O2 consumed as a nonlinear function of O2 and depth. The parameterization is based on laboratory and oceanic data and is designed for use in ocean biogeochemistry models. It is coupled to a global dissolved O2 climatology and ocean carbon model output to estimate a total oceanic N2O inventory of 610-840 Tg N and a global production rate of ˜5.8 ± 2 Tg N/y.

  17. Novel MoO2/carbon hierarchical nano/microcomposites: synthesis, characterization, solid state transformations and thiophene HDS activity.

    PubMed

    Avendaño, Carlos; Briceño, Alexander; Méndez, Franklin J; Brito, Joaquín L; González, Gema; Cañizales, Edgar; Atencio, Reinaldo; Dieudonné, Philippe

    2013-02-28

    Novel MoO(2)/C nano/microcomposites were prepared via a bottom-up approach by hydrothermal carbonization of a solution of glucose as a carbon precursor in the presence of polyoxometalates (POMs: phosphomolybdic acid [H(3)PMo(12)O(40)] and ammonium heptamolybdate tetrahydrate [(NH(4))(6)Mo(7)O(24)]·4H(2)O). The structural characterization by FT-IR, XRPD, SEM and TEM analyses revealed the controlled formation of hierarchical MoO(2)/C composites with different morphologies: strawberry-like, based on carbon microspheres decorated with MoO(2) nanoparticles; MoO(2)/C core-shell composites; and irregular aggregates in combination with ring-like microstructures bearing amorphous Mo species. These composites can be fine-tuned by varying reaction time, glucose/POM ratio and type of POM precursor. Subsequent transformations in the solid state through calcinations of MoO(2)/C core-shell composites in air lead to hollow nanostructured molybdenum trioxide microspheres together with nanorods and plate microcrystals or cauliflower-like composites (MoO(2)/C). In addition, the MoO(2)/C composite undergoes a morphology evolution to urchin-like composites when it is calcined under nitrogen atmosphere (MoO(2)/C-N(2)). The MoO(2)/C strawberry-like and MoO(2)/C-N(2) composites were transformed into Mo carbide and nitride supported on carbon microspheres (Mo(2)C/C, MoN/C, and MoN/C-N(2)). These phases were tested as precursors in thiophene hydrodesulphurization (HDS) at 400 °C, observing the following trend in relation to the thiophene steady-state conversion: MoN/C-N(2) > MoN/C > Mo(2)C/C > MoO(2)/C-N(2) > MoO(2)/C. According to these conversion values, a direct correlation was observed between higher HDS activity and decreasing crystal size as estimated from the Scherrer equation. These results suggest that such composites represent interesting and promising precursors for HDS catalysts, where the activity and stability can be modified either by chemical or structural changes of the

  18. Fractional Distillation of Air and Other Demonstrations with Condensed Gases

    ERIC Educational Resources Information Center

    Oliver-Hoyo, Maria; Switzer, William L., III; Eierman, Robert

    2005-01-01

    The learning objectives of the fractional distillation of air and other demonstrations includes observing N2, O2, CO2 and H2O in air, studying the fractional separation of components based on boiling point differences and so on. The materials, reagent and equipment preparation, experimental procedures, hazards of the demonstration are also…

  19. Isolation of H5N6, H7N9 and H9N2 avian influenza A viruses from air sampled at live poultry markets in China, 2014 and 2015.

    PubMed

    Zhou, Jie; Wu, Jie; Zeng, Xianqiao; Huang, Guofeng; Zou, Lirong; Song, Yingchao; Gopinath, Divya; Zhang, Xin; Kang, Min; Lin, Jinyan; Cowling, Benjamin J; Lindsley, William G; Ke, Changwen; Peiris, Joseph Sriyal Malik; Yen, Hui-Ling

    2016-09-01

    Zoonotic infections by avian influenza viruses occur at the human-poultry interface, but the modes of transmission have not been fully investigated. We assessed the potential for airborne and fomite transmission at live poultry markets in Guangzhou city and in Hong Kong Special Administrative Region (SAR), China, during 2014 and 2015. Viral genome and infectious avian influenza A viruses of H5N6, H7N9, and H9N2 subtypes were detected predominantly from particles larger or equal to 1 μm in diameter in the air sampled with cyclone-based bioaerosol samplers at the live poultry markets in Guangzhou. Influenza A(H9N2) viruses were ubiquitously isolated every month during the study period from air and environmental swabs, and different lineages of H9N2 virus were isolated from markets where chickens and minor land-based poultry were sold. The use of de-feathering devices increased the quantity of virus-laden airborne particles while market closure reduced the amount of such particles. The results highlight the possibility of airborne transmission of avian influenza viruses among poultry or from poultry to humans within such settings. This may explain epidemiological observations in which some patients with H7N9 infection reported being in markets but no direct contact with live poultry or poultry stalls.

  20. Isolation of H5N6, H7N9 and H9N2 avian influenza A viruses from air sampled at live poultry markets in China, 2014 and 2015.

    PubMed

    Zhou, Jie; Wu, Jie; Zeng, Xianqiao; Huang, Guofeng; Zou, Lirong; Song, Yingchao; Gopinath, Divya; Zhang, Xin; Kang, Min; Lin, Jinyan; Cowling, Benjamin J; Lindsley, William G; Ke, Changwen; Peiris, Joseph Sriyal Malik; Yen, Hui-Ling

    2016-09-01

    Zoonotic infections by avian influenza viruses occur at the human-poultry interface, but the modes of transmission have not been fully investigated. We assessed the potential for airborne and fomite transmission at live poultry markets in Guangzhou city and in Hong Kong Special Administrative Region (SAR), China, during 2014 and 2015. Viral genome and infectious avian influenza A viruses of H5N6, H7N9, and H9N2 subtypes were detected predominantly from particles larger or equal to 1 μm in diameter in the air sampled with cyclone-based bioaerosol samplers at the live poultry markets in Guangzhou. Influenza A(H9N2) viruses were ubiquitously isolated every month during the study period from air and environmental swabs, and different lineages of H9N2 virus were isolated from markets where chickens and minor land-based poultry were sold. The use of de-feathering devices increased the quantity of virus-laden airborne particles while market closure reduced the amount of such particles. The results highlight the possibility of airborne transmission of avian influenza viruses among poultry or from poultry to humans within such settings. This may explain epidemiological observations in which some patients with H7N9 infection reported being in markets but no direct contact with live poultry or poultry stalls. PMID:27608369

  1. Isolation of H5N6, H7N9 and H9N2 avian influenza A viruses from air sampled at live poultry markets in China, 2014 and 2015

    PubMed Central

    Zhou, Jie; Wu, Jie; Zeng, Xianqiao; Huang, Guofeng; Zou, Lirong; Song, Yingchao; Gopinath, Divya; Zhang, Xin; Kang, Min; Lin, Jinyan; Cowling, Benjamin J; Lindsley, William G.; Ke, Changwen; Peiris, Joseph Sriyal Malik; Yen, Hui-Ling

    2016-01-01

    Zoonotic infections by avian influenza viruses occur at the human–poultry interface, but the modes of transmission have not been fully investigated. We assessed the potential for airborne and fomite transmission at live poultry markets in Guangzhou city and in Hong Kong Special Administrative Region (SAR), China, during 2014 and 2015. Viral genome and infectious avian influenza A viruses of H5N6, H7N9, and H9N2 subtypes were detected predominantly from particles larger or equal to 1 μm in diameter in the air sampled with cyclone-based bioaerosol samplers at the live poultry markets in Guangzhou. Influenza A(H9N2) viruses were ubiquitously isolated every month during the study period from air and environmental swabs, and different lineages of H9N2 virus were isolated from markets where chickens and minor land-based poultry were sold. The use of de-feathering devices increased the quantity of virus-laden airborne particles while market closure reduced the amount of such particles. The results highlight the possibility of airborne transmission of avian influenza viruses among poultry or from poultry to humans within such settings. This may explain epidemiological observations in which some patients with H7N9 infection reported being in markets but no direct contact with live poultry or poultry stalls. PMID:27608369

  2. Daytime ion chemistry of N2+.

    NASA Technical Reports Server (NTRS)

    Feldman, P. D.

    1973-01-01

    Rocket measurements of the emission of the (0, 0) first negative band of N2+ at 3914 A in the day airglow have been made between 120 and 300 km. The solar zenith angle at the time of the flight was 60 deg, and the zenith intensity above 120 km was 1.6 kR averaged over both legs of the flight. The data are compared with a model in which charge exchange of N2 with metastable O+(2D) ions is included as an additional source of N2 ionization. Above 240 km this mechanism is dominant over the photoionization of N2 by solar extreme ultraviolet radiation. The derived N2+ density is consistent with the results of rocket-borne mass spectrometric observations.

  3. A novel dual-isotope labelling method for distinguishing between soil sources of N2O.

    PubMed

    Wrage, N; van Groenigen, J W; Oenema, O; Baggs, E M

    2005-01-01

    We present a novel 18O-15N-enrichment method for the distinction between nitrous oxide (N2O) from nitrification, nitrifier denitrification and denitrification based on a method with single- and double-15N-labelled ammonium nitrate. We added a new treatment with 18O-labelled water to quantify N2O from nitrifier denitrification. The theory behind this is that ammonia oxidisers use oxygen (O2) from soil air for the oxidation of ammonia (NH3), but use H2O for the oxidation of the resulting hydroxylamine (NH2OH) to nitrite (NO2-). Thus, N2O from nitrification would therefore be expected to reflect the 18O signature of soil O2, whereas the 18O signature of N2O from nitrifier denitrification would reflect that of both soil O2 and H2O. It was assumed that (a) there would be no preferential removal of 18O or 16O during nitrifier denitrification or denitrification, (b) the 18O signature of the applied 18O-labelled water would remain constant over the experimental period, and (c) any O exchange between H(2)18O and NO3- would be negligible under the chosen experimental conditions. These assumptions were tested and validated for a silt loam soil at 50% water-filled pore space (WFPS) following application of 400 mg N kg-1 dry soil. We compared the results of our new method with those of a conventional inhibition method using 0.02% v/v acetylene (C2H2) and 80% v/v O2 in helium. Both the 18O-15N-enrichment and inhibitor methods identified nitrifier denitrification to be a major source of N2O, accounting for 44 and 40%, respectively, of N2O production over 24 h. However, compared to our 18O-15N-method, the inhibitor method overestimated the contribution from nitrification at the expense of denitrification, probably due to incomplete inhibition of nitrifier denitrification and denitrification by large concentrations of O2 and a negative effect of C2H2 on denitrification. We consider our new 18O-15N-enrichment method to be more reliable than the use of inhibitors; it enables the

  4. Membraneless enzymatic ethanol/O2 fuel cell: Transitioning from an air-breathing Pt-based cathode to a bilirubin oxidase-based biocathode

    NASA Astrophysics Data System (ADS)

    Aquino Neto, Sidney; Milton, Ross D.; Hickey, David P.; De Andrade, Adalgisa R.; Minteer, Shelley D.

    2016-08-01

    The bioelectrooxidation of ethanol was investigated in a fully enzymatic membraneless ethanol/O2 biofuel cell assembly using hybrid bioanodes containing multi-walled carbon nanotube (MWCNT)-decorated gold metallic nanoparticles with either a pyrroloquinoline quinone (PQQ)-dependent alcohol dehydrogenase (ADH) enzyme or a nicotinamide adenine dinucleotide (NAD+)-dependent ADH enzyme. The biofuel cell anode was prepared with the PQQ-dependent enzyme and designed using either a direct electron transfer (DET) architecture or via a mediated electron transfer (MET) configuration through a redox polymer, 1,1‧-dimethylferrocene-modified linear polyethyleneimine (FcMe2-C3-LPEI). In the case of the bioanode containing the NAD+-dependent enzyme, only the mediated electron transfer mechanism was employed using an electropolymerized methylene green film to regenerate the NAD+ cofactor. Regardless of the enzyme being employed at the anode, a bilirubin oxidase-based biocathode prepared within a DET architecture afforded efficient electrocatalytic oxygen reduction in an ethanol/O2 biofuel cell. The power curves showed that DET-based bioanodes via the PQQ-dependent ADH still lack high current densities, whereas the MET architecture furnished maximum power density values as high as 226 ± 21 μW cm-2. Considering the complete membraneless enzymatic biofuel cell with the NAD+-dependent ADH-based bioanode, power densities as high as 111 ± 14 μW cm-2 were obtained. This shows the advantage of PQQ-dependent ADH for membraneless ethanol/O2 biofuel cell applications.

  5. Membraneless enzymatic ethanol/O2 fuel cell: Transitioning from an air-breathing Pt-based cathode to a bilirubin oxidase-based biocathode

    NASA Astrophysics Data System (ADS)

    Aquino Neto, Sidney; Milton, Ross D.; Hickey, David P.; De Andrade, Adalgisa R.; Minteer, Shelley D.

    2016-08-01

    The bioelectrooxidation of ethanol was investigated in a fully enzymatic membraneless ethanol/O2 biofuel cell assembly using hybrid bioanodes containing multi-walled carbon nanotube (MWCNT)-decorated gold metallic nanoparticles with either a pyrroloquinoline quinone (PQQ)-dependent alcohol dehydrogenase (ADH) enzyme or a nicotinamide adenine dinucleotide (NAD+)-dependent ADH enzyme. The biofuel cell anode was prepared with the PQQ-dependent enzyme and designed using either a direct electron transfer (DET) architecture or via a mediated electron transfer (MET) configuration through a redox polymer, 1,1‧-dimethylferrocene-modified linear polyethyleneimine (FcMe2-C3-LPEI). In the case of the bioanode containing the NAD+-dependent enzyme, only the mediated electron transfer mechanism was employed using an electropolymerized methylene green film to regenerate the NAD+ cofactor. Regardless of the enzyme being employed at the anode, a bilirubin oxidase-based biocathode prepared within a DET architecture afforded efficient electrocatalytic oxygen reduction in an ethanol/O2 biofuel cell. The power curves showed that DET-based bioanodes via the PQQ-dependent ADH still lack high current densities, whereas the MET architecture furnished maximum power density values as high as 226 ± 21 μW cm-2. Considering the complete membraneless enzymatic biofuel cell with the NAD+-dependent ADH-based bioanode, power densities as high as 111 ± 14 μW cm-2 were obtained. This shows the advantage of PQQ-dependent ADH for membraneless ethanol/O2 biofuel cell applications.

  6. Interaction of surface laser treatment upon ZrO2-Y2O3 ceramic coating structure obtained by means of air plasma spraying

    NASA Astrophysics Data System (ADS)

    Kobylanska-Szkaradek, Krystyna

    2003-10-01

    The subject of the analysis and examination is the structure and utilitarian properties of thin ceramic layers placed on the nickel base heat-resistant alloy by plasma spraying method, which later on underwent laser remelting. Examined materials consisting of outer coating ZrO2+8%wt.Y2O3 and NiCrAlY laser are to be used as thermal barriers and protection against high temperature corrosion of heating-resisting alloy on nickel base, applied in internal combustion turbine blades and other construction elements working under stress in high temperature conditions.

  7. Benzoisothiazolone Organo/Copper-Cocatalyzed Redox Dehydrative Construction of Amides and Peptides from Carboxylic Acids using (EtO)3P as the Reductant and O2 in Air as the Terminal Oxidant.

    PubMed

    Liebeskind, Lanny S; Gangireddy, Pavankumar; Lindale, Matthew G

    2016-06-01

    Carboxylic acids and amine/amino acid reactants can be converted to amides and peptides at neutral pH within 5-36 h at 50 °C using catalytic quantities of a redox-active benzoisothiazolone and a copper complex. These catalytic "oxidation-reduction condensation" reactions are carried out open to dry air using O2 as the terminal oxidant and a slight excess of triethyl phosphite as the reductant. Triethyl phosphate is the easily removed byproduct. These simple-to-run catalytic reactions provide practical and economical procedures for the acylative construction of C-N bonds. PMID:27175892

  8. Control of Lactate Dehydrogenase, Lactate Glycolysis, and α-Amylase by O2 Deficit in Barley Aleurone Layers 1

    PubMed Central

    Hanson, Andrew D.; Jacobsen, John V.

    1984-01-01

    After 4 days in an atmosphere of N2, aleurone layers of barley (Hordeum vulgare L. cv Himalaya) remained viable as judged by their ability to produce near normal amounts of α-amylases when incubated with gibberellic acid (GA3) in air. However, layers did not produce α-amylase when GA3 was supplied under N2, apparently because α-amylase mRNA failed to accumulate. When an 8-hour pulse of [U-14C]glucose was supplied under N2 to freshly prepared aleurone layers, both [14C]lactate and [14C]ethanol accumulated; the [14C]lactate/[14C]ethanol ratio was about 0.3. Prior incubation of layers for 1 day under N2 changed this ratio to about 0.8, indicating an increase in the relative importance of the lactate branch of glycolysis. l(+)Lactate dehydrogenase (LDH) activity was low in freshly prepared aleurone layers and increased 10-fold during 2 days under N2, whereas alcohol dehydrogenase activity (ADH) was high initially and rose by 60%. The responses of LDH and ADH activities to O2 tension were dissimilar; when layers were incubated in various O2/N2 mixtures, LDH activity peaked at 2 to 5% O2 whereas ADH activity was highest at 0% O2. The LDH activity was resolved into several enzymically active bands by native polyacrylamide gel electrophoresis. We conclude that barley aleurone layers are highly adapted to O2 deficiency, that they possess an inducible LDH system as well as an ADH system, and we infer that the LDH and ADH systems are independently regulated. Images Fig. 2 Fig. 5 PMID:16663667

  9. Synthesis cathode material LiNi0.80Co0.15Al0.05O2 with two step solid-state method under air stream

    NASA Astrophysics Data System (ADS)

    Xia, Shubiao; Zhang, Yingjie; Dong, Peng; Zhang, Yannan

    2014-01-01

    A facile generic strategy of solid-state reaction under air atmosphere is employed to prepare LiNi0.8Co0.15Al0.05O2 layer structure micro-sphere as cathodes for Li-ion batteries. The impurity phase has been eliminated wholly without changing the R-3m space group of LiNi0.8Co0.15Al0.05O2. The electrochemical performance of LiNi0.8Co0.15Al0.05O2 cathodes depend on the sintering step, temperature, particle size and uniformity. The sample pre-sintered at 540 °C for 12 h and then sintered at 720 °C for 28 h exhibits the best electrochemical performance, which delivers a reversible capacity of 180.4, 165.8, 154.7 and 135.6 mAhg-1 at 0.2 C, 1 C, 2 C and 5 C, respectively. The capacity retention keeps over 87% after 76 cycles at 1 C. This method is simple, cheap and mass-productive, and thus suitable to large scale production of NCA cathodes directly used for lithium ion batteries.

  10. Towards high efficiency air-processed near-infrared responsive photovoltaics: bulk heterojunction solar cells based on PbS/CdS core-shell quantum dots and TiO2 nanorod arrays.

    PubMed

    Gonfa, Belete Atomsa; Kim, Mee Rahn; Delegan, Nazar; Tavares, Ana C; Izquierdo, Ricardo; Wu, Nianqiang; El Khakani, My Ali; Ma, Dongling

    2015-06-14

    Near infrared (NIR) PbS quantum dots (QDs) have attracted significant research interest in solar cell applications as they offer several advantages, such as tunable band gaps, capability of absorbing NIR photons, low cost solution processability and high potential for multiple exciton generation. Nonetheless, reports on solar cells based on NIR PbS/CdS core-shell QDs, which are in general more stable and better passivated than PbS QDs and thus more promising for solar cell applications, remain very rare. Herein we report high efficiency bulk heterojunction QD solar cells involving hydrothermally grown TiO2 nanorod arrays and PbS/CdS core-shell QDs processed in air (except for a device thermal annealing step) with a photoresponse extended to wavelengths >1200 nm and with a power conversion efficiency (PCE) as high as 4.43%. This efficiency was achieved by introducing a thin, sputter-deposited, uniform TiO2 seed layer to improve the interface between the TiO2 nanorod arrays and the front electrode, by optimizing TiO2 nanorod length and by conducting QD annealing treatment to enhance charge carrier transport. It was found that the effect of the seed layer became more obvious when the TiO2 nanorods were longer. Although photocurrent did not change much, both open circuit voltage and fill factor clearly changed with TiO2 nanorod length. This was mainly attributed to the variation of charge transport and recombination processes, as evidenced by series and shunt resistance studies. The optimal PCE was obtained at the nanorod length of ∼450 nm. Annealing is shown to further increase the PCE by ∼18%, because of the improvement of charge carrier transport in the devices as evidenced by considerably increased photocurrent. Our results clearly demonstrate the potential of the PbS/CdS core-shell QDs for the achievement of high PCE, solution processable and NIR responsive QD solar cells.

  11. Enhancement of photocatalytic properties of TiO2 nanoparticles doped with CeO2 and supported on SiO2 for phenol degradation

    NASA Astrophysics Data System (ADS)

    Hao, Chunjing; Li, Jing; Zhang, Zailei; Ji, Yongjun; Zhan, Hanhui; Xiao, Fangxing; Wang, Dan; Liu, Bin; Su, Fabing

    2015-03-01

    A series of CeO2-TiO2 and CeO2-TiO2/SiO2 composites were prepared with TiCl4 and Ce (NO3)3·6H2O as precursors via a facile co-precipitation method. The obtained samples were characterized by various techniques such as X-ray diffraction (XRD), nitrogen adsorption (N2-BET), Fourier transformation infrared spectrum (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV-Vis spectroscopy measurements. The results indicated that TiO2 doped with CeO2 and supported on SiO2 could reduce the crystallite size, inhibit the phase transformation, enhance the thermal stability, and effectively extend the spectral response from UV to visible range. When applied to the phenol photodegradation on a homemade batch reactor with an external cooling jacket, the CeO2-TiO2/SiO2 catalysts exhibited significantly enhanced photodegradation efficiency in comparison with commercial Degussa P25 and CeO2-TiO2. The unique catalytic properties of CeO2-TiO2/SiO2 were ascribed to improved electron-hole pairs separation efficiency and formation of more reactive oxygen species owing to the presence of Ce3+/Ce4+, as well as high dispersion of active component of CeO2-TiO2 as a result of the introduction of SiO2 support. Furthermore, the catalysts can be easily recovered from the reaction solution by centrifugation and reused for four cycles without significant loss of activity.

  12. Aqueous-phase chemistry and bactericidal effects from an air discharge plasma in contact with water: evidence for the formation of peroxynitrite through a pseudo-second-order post-discharge reaction of H2O2 and HNO2

    NASA Astrophysics Data System (ADS)

    Lukes, P.; Dolezalova, E.; Sisrova, I.; Clupek, M.

    2014-02-01

    The formation of transient species (OH·, NO2·, NO radicals) and long-lived chemical products (O3, H2O2, NO_{3}^{-} , NO_{2}^{-} ) produced by a gas discharge plasma at the gas-liquid interface and directly in the liquid was measured in dependence on the gas atmosphere (20% oxygen mixtures with nitrogen or with argon) and pH of plasma-treated water (controlled by buffers at pH 3.3, 6.9 or 10.1). The aqueous-phase chemistry and specific contributions of these species to the chemical and biocidal effects of air discharge plasma in water were evaluated using phenol as a chemical probe and bacteria Escherichia coli. The nitrated and nitrosylated products of phenol (4-nitrophenol, 2-nitrophenol, 4-nitrocatechol, 4-nitrosophenol) in addition to the hydroxylated products (catechol, hydroquinone, 1,4-benzoquinone, hydroxy-1,4-benzoquinone) evidenced formation of NO2·, NO· and OH· radicals and NO+ ions directly by the air plasma at the gas-liquid interface and through post-discharge processes in plasma-activated water (PAW) mediated by peroxynitrite (ONOOH). Kinetic study of post-discharge evolution of H2O2 and NO_{2}^{-} in PAW has demonstrated excellent fit with the pseudo-second-order reaction between H2O2 and NO_{2}^{-} . The third-order rate constant k = 1.1 × 103 M-2 s-1 for the reaction NO_{2}^{-} +H_{2}O_{2}+H^{+}\\to ONOOH+H_{2}O was determined in PAW at pH 3.3 with the rate of ONOOH formation in the range 10-8-10-9 M s-1. Peroxynitrite chemistry was shown to significantly participate in the antibacterial properties of PAW. Ozone presence in PAW was proved indirectly by pH-dependent degradation of phenol and detection of cis,cis-muconic acid, but contribution of ozone to the inactivation of bacteria by the air plasma was negligible.

  13. Thermal and sonochemical synthesis of porous (Ce,Zr)O2 mixed oxides from metal β-diketonate precursors and their catalytic activity in wet air oxidation process of formic acid.

    PubMed

    Cau, Camille; Guari, Yannick; Chave, Tony; Larionova, Joulia; Nikitenko, Sergey I

    2014-07-01

    Porous (Ce0.5Zr0.5)O2 solid solutions were prepared by thermolysis (T=285 °C) or sonolysis (20 kHz, I=32 W cm(-2), Pac=0.46 W mL(-1), T=200 °C) of Ce(III) and Zr(IV) acetylacetonates in oleylamine or hexadecylamine under argon followed by heat treatment of the precipitates obtained in air at 450 °C. Transmission Electron Microscopy images of the samples show nanoparticles of ca. 4-6 nm for the two synthetic approaches. The powder X-ray diffraction, scanning electron microscopy, energy dispersive X-ray and μ-Raman spectroscopy of solids obtained after heat treatment indicate the formation of (Ce0.5Zr0.5)O2 solid solutions with a metastable tetragonal crystal structure for the two synthetic routes. The specific surface area of the samples varies between 78 and 149 m(2) g(-1) depending on synthesis conditions. The use of Barrett-Joyner-Halenda and t-plot methods reveal the formation of mixed oxides with a hybrid morphology that combines mesoporosity and microporosity regardless of the method of preparation. Platinum nanoparticles were deposited on the surface of the mixed oxides by sonochemical reduction of Pt(IV). It was found that the materials prepared by sonochemistry exhibit better resistance to dissolution during the deposition process of platinum. X-ray photoelectron spectroscopy analysis shows the presence of Pt(0) and Pt(II) on the surface of mixed oxides. Porous (Ce0.5Zr0.5)O2 mixed oxides loaded with 1.5%wt. platinum exhibit high activity in catalytic wet air oxidation of formic acid at 40 °C.

  14. Pulmonary NO and C18O2 uptake during pressure-induced lung expansion in rabbits.

    PubMed

    Heller, Hartmut; Schuster, Klaus-Dieter

    2007-01-01

    In artificially ventilated animals we investigated the dependence of the pulmonary diffusing capacities of nitric oxide (NO) and doubly 18O-labeled carbon dioxide (DLNO, DLC18O2) on lung expansion with respect to ventilator-driven increases in intrapulmonary pressure. For this purpose we applied computerized single-breath experiments to 11 anesthetized paralyzed rabbits (weight 2.8-3.8 kg) at various alveolar volumes (45-72 ml) by studying the almost entire inspiratory limb of the respective pressure/volume curves (intrapulmonary pressure: 6-27 cmH2O). The animals were ventilated with room air, employing a computerized ventilatory servo-system that we designed to maintain mechanical ventilation and to execute the particular lung function tests automatically. Each single-breath maneuver was started from residual volume (13.5+/-2 ml, mean+/-SD) by inflating the rabbit lungs with 35-55 ml indicator gas mixture containing 0.05% NO in N2 or 0.9% C18O2 in N2. Alveolar partial pressures of NO and C18O2 were measured by respiratory mass spectrometry. Values of DLNO and DLC18O2 ranged between 1.55 and 2.49 ml/(mmHg min) and 11.7 and 16.6 ml/(mmHg min), respectively. Linear regression analyses yielded a significant increase in DLNO with simultaneous increase in alveolar volume (P<0.005) and intrapulmonary pressure (P<0.023) whereas DLC18O2 was not improved. Our results suggest that the ventilator-driven lung expansion impaired the C18O2 blood uptake conductance, finally compensating for the beneficial effect of the increase in alveolar volume on DLC18O2 values.

  15. N = 2 string amplitudes

    SciTech Connect

    Ooguri, H.

    1995-08-01

    In physics, solvable models have played very important roles. Understanding a simple model in detail teaches us a lot about more complicated models in generic situations. Five years ago, C. Vafa and I found that the closed N = 2 string theory, that is a string theory with the N = 2 local supersymmetry on the worldsheet, is classically equivalent to the self-dual Einstein gravity in four spacetime dimensions. Thus this string theory is solvable at the classical level. More recently, we have examined the N = 2 string partition function for spacial compactifications, and computed it to all order in the string perturbation expansion. The fact that such computation is possible at all suggests that the N = 2 string theory is solvable even quantum mechanically.

  16. Line parameters including temperature dependences of air- and self-broadened line shapes of 12C16O2: 2.06-μm region

    NASA Astrophysics Data System (ADS)

    Benner, D. Chris; Devi, V. Malathy; Sung, Keeyoon; Brown, Linda R.; Miller, Charles E.; Payne, Vivienne H.; Drouin, Brian J.; Yu, Shanshan; Crawford, Timothy J.; Mantz, Arlan W.; Smith, Mary Ann H.; Gamache, Robert R.

    2016-08-01

    This study reports the results from analyzing a number of high resolution, high signal-to-noise ratio (S/N) spectra in the 2.06-μm spectral region for pure CO2 and mixtures of CO2 in dry air. A multispectrum nonlinear least squares curve fitting technique has been used to retrieve the various spectral line parameters. The dataset includes 27 spectra: ten pure CO2, two 99% 13C-enriched CO2 and fifteen spectra of mixtures of 12C-enriched CO2 in dry air. The spectra were recorded at various gas sample temperatures between 170 and 297 K. The absorption path lengths range from 0.347 to 49 m. The sample pressures for the pure CO2 spectra varied from 1.1 to 594 Torr; for the two 13CO2 spectra the pressures were ∼10 and 146 Torr. For the air-broadened spectra, the pressures of the gas mixtures varied between 200 and 711 Torr with CO2 volume mixing ratios ranging from 0.014% to 0.203%. The multispectrum fitting technique was applied to fit simultaneously all these spectra to retrieve consistent set of line positions, intensities, and line shape parameters including their temperature dependences; for this, the Voigt line shape was modified to include line mixing (via the relaxation matrix formalism) and quadratic speed dependence. The new results are compared to select published values, including recent ab initio calculations. These results are required to retrieve the column averaged dry air mole fraction (XCO2) from space-based observations, such as the Orbiting Carbon Observatory-2 (OCO-2) satellite mission that NASA launched in July 2014.

  17. Legumes, N2 fixation and the H2 cycle

    NASA Astrophysics Data System (ADS)

    Layzell, D. B.

    2004-12-01

    Legume plants such as soybean or pea can form symbiotic, N2 fixing associations with bacteria that exist in root nodules. For every N2 fixed, 1 to 3 H2 are produced as a by-product of the nitrogenase reaction. Therefore, a typical N2 fixing legume crop produces about 200,000 L H2 gas (at STP) per hectare per crop season. This paper will summarize our current understanding of the processes leading to H2 production in legumes, the magnitude of H2 production associated with global cropping systems, and the implications for its production and oxidation on both the legumes and the soils in which they grow. Specific points may include: ˜ In symbioses lacking uptake hydrogenase (HUP) activity (thought to be the majority of crop legumes), the H2 diffuses into the soil where it is oxidized by soil microbes that grow up around the legume nodules. The kinetic properties of these microbes are very different (higher Km and Vmax) from that of microbes in soils exposed to normal air (ca. 0.5 ppm H2); ˜ Laboratory studies indicate that 60% of the reducing power from H2 is coupled to O2 uptake, whereas 40% is coupled to autotrophic CO2 fixation. The latter process should increase soil carbon stocks by about 25 kg C/ha/yr; ˜ At the site of the nitrogenase enzyme, H2 production is autocatalytic such that the higher the H2 concentration, the more H2 is produced and the less N2 fixed. The variable O2 diffusion barrier in legumes can act to restrict H2 diffusion from the nodule, thereby increasing the relative magnitude of H2 production versus N2 fixation; ˜ Studies to understand why legume symbioses make such an energy investment in H2 production have led to the discovery that H2 treated soils have improved fertility, supporting the growth and yield of legume and non-legume crops. This observation may account for the benefits of legumes when used in rotation with cereal crops, a phenomenon that has been used by farmers for over 2000 years, but which has remained unexplained. An

  18. Promotion effects of SiO2 or/and Al2O3 doped CeO2/TiO2 catalysts for selective catalytic reduction of NO by NH3.

    PubMed

    Zhao, Wenru; Tang, Yu; Wan, Yaping; Li, Liang; Yao, Si; Li, Xiaowei; Gu, Jinlou; Li, Yongsheng; Shi, Jianlin

    2014-08-15

    A series of the CeO2-based catalysts loaded on TiO2, TiO2-SiO2, TiO2-Al2O3, and TiO2-SiO2-Al2O3 supports were prepared by incipient impregnation method for the selective catalytic reduction (SCR) of NO by NH3 in the presence of oxygen. The SCR activities of the catalysts with different supports increases in the order of Ce/TiO2 < Ce/TiO2-20SiO2 ≈ Ce/TiO2-3.5Al2O3 < Ce/TiO2-20SiO2-3.5Al2O3. The Ce/TiO2-20SiO2-3.5Al2O3 catalyst showed 100% NO conversion in the temperature range of 250-425°C and 100% N2 selectivity in the whole temperature range. The catalytic activity of Ce/TiO2-20SiO2-3.5Al2O3 exhibited good stability and strong resistance to SO2 and H2O poisoning. The co-introduction of SiO2 and Al2O3 into TiO2 could increase the amount of chemisorbed oxygen and Lewis acid sites on the surface of catalyst, which should be responsible for the excellent SCR activity.

  19. Effects of lung volume and O2 and CO2 content on cutaneous gas exchange in frogs.

    PubMed

    Malvin, G M; Hlastala, M P

    1986-11-01

    The effects of lung O2 and CO2 content and volume on cutaneous gas exchange and perfusion were investigated in the frog, Rana pipiens. (Ha)-anesthetized frogs were equilibrated with 9.5% Freon-22 (Fr, chlorodifluoromethane) and 1.1% Ha. Cutaneous elimination of Fr, Ha, and CO2 into a small sample chamber on the abdomen was measured with a mass spectrometer. Introducing an air mixture into the lung decreased cutaneous Fr, Ha, and CO2 elimination. Lung inflation with an O2 mixture decreased cutaneous gas elimination more than with the air mixture. Inflation with a N2 mixture had no effect. The response to lung inflation with the air mixture was not affected by adding 4.8% CO2 to the air mixture or by atropine. Voluntary lung ventilation decreased CO2 and Fr elimination. The results indicate that intrapulmonary O2 is a factor regulating skin breathing. If a change in lung volume is also a factor, it requires a concomitant change in lung O2. Intrapulmonary CO2 and cholinergic nerves are not involved in cutaneous respiration across the abdomen.

  20. Air

    MedlinePlus

    ... do to protect yourself from dirty air . Indoor air pollution and outdoor air pollution Air can be polluted indoors and it can ... this chart to see what things cause indoor air pollution and what things cause outdoor air pollution! Indoor ...

  1. N2O Decomposed by Discharge Plasma with Catalysts

    NASA Astrophysics Data System (ADS)

    Hu, Hui; Huang, Hao; Xu, Jie; Yang, Qi; Tao, Gongkai

    2015-12-01

    A great deal of attention has been focused on discharge plasma as it can rapidly decompose N2O without additives, which is not only a kind of greenhouse gas but also a kind of damages to the ozone layer. The thermal equilibrium plasma is chosen to combine with catalysts to decompose N2O, and its characteristics are analyzed in the present paper. The results indicate that NO and NO2 were formed besides N2 and O2 during N2O decomposition when N2O was treated merely by discharge plasma. Concentration of NO declined greatly when the discharge plasma was combined with catalysts. Results of Raman spectra analysis on CeO2, Ce0.75Zr0.25O2 and Ce0.5Zr0.5O2 imply that the products selectivity has been obviously improved in discharge plasma decomposing N2O because of the existence of massive oxygen vacancies over the composite oxide catalysts. supported by National Natural Science Foundation of China (No. 50677026) and the Applied Basic Research Program of Wuhan, China (No. 2015060101010068)

  2. Comparative Study of Two Different TiO2 Film Sensors on Response to H2 under UV Light and Room Temperature

    PubMed Central

    Peng, Xiaoying; Wang, Zhongming; Huang, Pan; Chen, Xun; Fu, Xianzhi; Dai, Wenxin

    2016-01-01

    An anatase TiO2 film sensor was prepared by a facile in-situ method on the interdigitated Au electrode deposited on the alumina substrate. The structure, morphology and the optical properties of the in-situ TiO2 film sensor were characterized by X-ray diffraction, Scanning Electron Microscopy, and UV-vis diffuse reflectance spectra. The photo-assisted gas sensitivities of the prepared film towards H2 gas were evaluated at room temperature in N2 and synthetic air atmospheres. As compared to TiO2 film sensor prepared by drop-coating method, this in-situ TiO2 film sensor exhibited a more compact structure composed of uniform TiO2 microspheres as well as a better gas sensitivity towards H2 under UV irradiation, especially in synthetic air. The photo-electrochemical measurements suggest that these improvements may be associated with the efficient charge transfer in the TiO2 interface induced by the TiO2 microsphere structure. This study might offer a feasible approach to develop photo-assisted gas sensors at ambient temperature. PMID:27509502

  3. Mn3O4-CeO2 nano-catalysts: Synthesis, characterization and application

    NASA Astrophysics Data System (ADS)

    Anushree, Sharma, C.; Kumar, S.

    2016-05-01

    Nano-sized Mn3O4-CeO2 catalysts were synthesized by a cost effective co-precipitation method, and were studied as a heterogeneous catalyst for wet air oxidation of paper industry wastewater at mild operating conditions of 90 °C and 1 atm. The structural, micro-structural and textural properties of synthesized catalysts were studied through various characterization techniques, i.e. XRD, TEM, N2-sorption and EDS. The catalytic activity of Mn3O4-CeO2 was interestingly found to be higher than the corresponding single-metal oxides, and the Ce50Mn50 nano-catalyst with small crystallite size (4.5 nm), high specific surface area (75 m2g-1) and high porosity (0.24 ccg-1) was found to be most efficient with 69% color, 60% COD, 59% TOC, 48% AOX removal.

  4. High Thermal Stability of La2O3- and CeO2-Stabilized Tetragonal ZrO2.

    PubMed

    Wang, Shichao; Xie, Hong; Lin, Yuyuan; Poeppelmeier, Kenneth R; Li, Tao; Winans, Randall E; Cui, Yanran; Ribeiro, Fabio H; Canlas, Christian P; Elam, Jeffrey W; Zhang, Hongbo; Marshall, Christopher L

    2016-03-01

    Catalyst support materials of tetragonal ZrO2, stabilized by either La2O3 (La2O3-ZrO2) or CeO2 (CeO2-ZrO2), were synthesized under hydrothermal conditions at 200 °C with NH4OH or tetramethylammonium hydroxide as the mineralizer. From in situ synchrotron powder X-ray diffraction and small-angle X-ray scattering measurements, the calcined La2O3-ZrO2 and CeO2-ZrO2 supports were nonporous nanocrystallites that exhibited rectangular shapes with a thermal stability of up to 1000 °C in air. These supports had an average size of ∼ 10 nm and a surface area of 59-97 m(2)/g. The catalysts Pt/La2O3-ZrO2 and Pt/CeO2-ZrO2 were prepared by using atomic layer deposition with varying Pt loadings from 6.3 to 12.4 wt %. Monodispersed Pt nanoparticles of ∼ 3 nm were obtained for these catalysts. The incorporation of La2O3 and CeO2 into the t-ZrO2 structure did not affect the nature of the active sites for the Pt/ZrO2 catalysts for the water-gas shift reaction.

  5. High thermal stability of La2O3 and CeO2-stabilized tetragonal ZrO2

    DOE PAGES

    Wang, Shichao; Xie, Hong; Lin, Yuyuan; Poeppelmeier, Kenneth R.; Li, Tao; Winans, Randall E.; Cui, Yanran; Ribeiro, Fabio H.; Canlas, Christian P.; Elam, Jeffrey W.; et al

    2016-02-15

    Catalyst support materials of tetragonal ZrO2, stabilized by either La2O3 (La2O3-ZrO2) or CeO2 (CeO2-ZrO2), were synthesized under hydrothermal conditions at 200 °C with NH4OH or tetramethylammonium hydroxide as the mineralizer. From In Situ synchrotron powder X-ray diffraction and small-angle X-ray scattering measurements, the calcined La2O3-ZrO2 and CeO2-ZrO2 supports were nonporous nanocrystallites that exhibited rectangular shapes with thermal stability up to 1000 °C in air. These supports had an average size of ~10 nm and a surface area of 59-97 m2/g. The catalysts Pt/La2O3-ZrO2 and Pt/CeO2-ZrO2 were prepared by using atomic layer deposition with varying Pt loadings from 6.3-12.4 wt %.more » Mono-dispersed Pt nanoparticles of ~3 nm were obtained for these catalysts. As a result, the incorporation of La2O3 and CeO2 into the t-ZrO2 structure did not affect the nature of the active sites for the Pt/ZrO2 catalysts for the water-gas-shift (WGS) reaction.« less

  6. Nanostructured porous RuO2/MnO2 as a highly efficient catalyst for high-rate Li-O2 batteries.

    PubMed

    Wang, Guoqing; Huang, Liliang; Huang, Wei; Xie, Jian; Du, Gaohui; Zhang, Shichao; Zhu, Peiyi; Cao, Gaoshao; Zhao, Xinbing

    2015-12-28

    Despite the recent advancements in Li-O(2) (or Li-air) batteries, great challenges still remain to realize high-rate, long-term cycling. In this work, a binder-free, nanostructured RuO(2)/MnO(2) catalytic cathode was designed to realize the operation of Li-O(2) batteries at high rates. At a current density as high as 3200 mA g(-1) (or ∼1.3 mA cm(-2)), the RuO(2)/MnO(2) catalyzed Li-O(2) batteries with LiI can sustain stable cycling of 170 and 800 times at limited capacities of 1000 and 500 mA h g(-1), respectively, with low charge cutoff potentials of ∼4.0 and <3.8 V, respectively. The underlying mechanism of the high catalytic performance of MnO(2)/RuO(2) was also clarified in this work. It was found that with the catalytic effect of RuO(2), Li(2)O(2) can crystallize into a thin-sheet form and realize a conformal growth on sheet-like δ-MnO(2) at a current density up to 3200 mA g(-1), constructing a sheet-on-sheet structure. This crystallization behavior of Li(2)O(2) not only defers the electrode passivation upon discharge but also renders easy decomposition of Li(2)O(2) upon charge, leading to low polarizations and reduced side reactions. This work provides a unique design of catalytic cathodes capable of controlling Li(2)O(2) growth and sheds light on the design of high-rate, long-life Li-O(2) batteries with potential applications in electric vehicles. PMID:26592423

  7. The effect of soil pH on N2O/(N2O+N2) product ratio of denitrification depends on soil NO3- concentration

    NASA Astrophysics Data System (ADS)

    Senbayram, Mehmet; Dittert, Klaus; Well, Reinhard; Lewicka-Szczebak, Dominika; Lammel, Joachim; Bakken, Lars

    2015-04-01

    Globally, agricultural soils account for about 60% of the atmospheric N2O emissions and denitrification in soil is the major source of atmospheric N2O, which contributes to global warming and destruction of stratospheric ozone. Denitrification is the microbially mediated process of dissimilatory nitrate reduction that may produce not only N2O but also nitric oxide (NO), and molecular nitrogen (N2). The major controls on denitrification rates are soil NO3, O2, and labile C levels. Typically, when soils become more anoxic, larger proportions of N2O produced in denitrification are further reduced to N2 before leaving the soil. Microbial ecology may possibly find solutions to this major environmental problem of agricultural systems once mechanisms controlling the product ratio of denitrification (N2O/N2O+N2) are better understood. Recent investigations of these gaseous microbial products provided the evidence for a negative effect of soil acidity on the N2O/N2O+N2 product ratio. However, in an earlier study, we showed that, regardless of soil type, higher NO3- concentrations in soil may also retard the reduction of N2O to N2. In this context, the positive effect of higher soil pH on the N2O/(N2O+N2) product ratio in soils with high NO3- content is still poorly understood. Therefore, we set up a number of incubation experiments in order to test short-term and long-term effects of soil pH and NO3- concentration on denitrification rates and the product stoichiometry of denitrification. We measured N2O, NO as well as elemental N2 in soils with pH levels ranging 4.1 to pH 6.9 collected from a long-term liming experiment. In a continuous flow incubation system we evacuated and flushed all vessels with He. Then, fresh He was directed through an inlet in the lid at a flow rate of 15-30 ml min-1. Gas samples were analyzed twice a day for N2O by ECD and for N2 by TCD detectors. Denitrification rates increased significantly with increasing soil pH, however, during the initial

  8. Isotopologue signatures of N2O from denitrification in soil

    NASA Astrophysics Data System (ADS)

    Well, R.; Flessa, H.

    2009-04-01

    There is few information on N2 fluxes from denitrification in the field, because this process is difficult to measure in situ. Isotopologue signatures of N2O such as δ18O, average δ15N (δ15Nbulk) and 15N site preference (SP = difference in δ15N between the central and peripheral N positions of the asymmetric N2O molecule) can be used to constrain the atmospheric N2O budget and to characterize N2O turnover processes including N2O reduction to N2. However, the use of this approach to study N2O dynamics in soils requires knowledge of isotopologue fractionation factors (ɛ) for the various partial processes involved, e.g. N2O production by nitrification or denitrification, N2O reduction by denitrification and diffusive transport. The aim of our study was to investigate whether isotopologue signatures of soil-emitted N2O can be used to estimate N2O reduction, and accordingly N2 formation. Two arable soils were incubated in the laboratory under varying conditions in order to manipulate the partial processes of N2O turnover. ɛ of δ18O, δ15Nbulk and SP was determined in experiments, where only one of the partial processes was governing the isotopic signature of N2O in the incubation system of the respective treatment. ɛ of N2O reduction to N2 was derived by (i) comparing treatments with and without inhibition of N2O reduction (indirect approach) or (ii) by monitoring the time course of isotopic signatures of N2O applied to the headspace of NO3--depleted anaerobic soil (direct approach). Moreover, we incubated the soils under conditions favoring denitrification (high moisture, low O2 level, NO3- fertilization) and monitored isotopic signatures of emitted N2O. In parallel experiments with 15N-labeled NO3- pool we measured N2 fluxes directly. Isotopologue signatures were compared with 15N2 flux data in order to check their relationship with N2 production. References Well R, Kurganova, I., Lopes, V., Flessa H. (2006), Isotopomer signatures of N2O emitted from an arable

  9. 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.

  10. Effect of TiO2, ZrO2, and TiO2-ZrO2 on the performance of CuO-ZnO catalyst for CO2 hydrogenation to methanol

    NASA Astrophysics Data System (ADS)

    Xiao, Jie; Mao, Dongsen; Guo, Xiaoming; Yu, Jun

    2015-05-01

    The influence of TiO2, ZrO2, and TiO2-ZrO2 mixed oxide on the catalytic performance of CuO-ZnO catalyst in the methanol synthesis from CO2 hydrogenation was studied. The catalysts were prepared by oxalate co-precipitation method and characterized by TGA, N2 adsorption, XRD, reactive N2O adsorption, XPS, H2-TPR, H2-TPD, and CO2-TPD techniques. Characterization results reveal that all the additives improve the CuO dispersion in the catalyst body and increase the Cu surface area and adsorption capacities of CO2 and H2. The results of catalytic test reveal that the additives increase both the CO2 conversion and methanol selectivity, and TiO2-ZrO2 mixed oxide is more effective than single components of TiO2 or ZrO2. Moreover, the activity of methanol synthesis is correlated directly with CO2 adsorption capacity over the catalysts.

  11. Synthesis of superamphiphobic breathable membranes utilizing SiO2 nanoparticles decorated fluorinated polyurethane nanofibers.

    PubMed

    Wang, Jialin; Raza, Aikifa; Si, Yang; Cui, Lingxiao; Ge, Jianfeng; Ding, Bin; Yu, Jianyong

    2012-12-01

    Superamphiphobic nanofibrous membranes exhibiting robust water/oil proof and breathable performances were prepared by the combination of a novel synthesized fluorinated polyurethane (FPU) containing a terminal perfluoroalkane segment and incorporated SiO(2) nanoparticles (SiO(2) NPs). By employing the FPU/SiO(2) NPs incorporation, the hybrid membranes possess superhydrophobicity with a water contact angle of 165° and superoleophobicity with an oil contact angle of 151°. Surface morphological studies have indicated that the wettability of resultant membranes could be manipulated by tuning the surface composition as well as the hierarchical structures. The quantitative hierarchical roughness analysis using N(2) adsorption method has confirmed a major contribution of SiO(2) NPs on enhancing the porous structure, and a detailed correlation between the fractal dimension and amphiphobicity is proposed. Furthermore, a designed concept test shows that the as-prepared membranes could load 1.5 kg water or oil at the same time maintained an extremely high air permeability of 2 L min(-1), suggesting their use as promising materials for a variety of potential applications in protective clothing, bioseparation, water purification, tissue engineering, microfluidic systems, etc., and also provided new insight into the design and development of functional hybrid membranes based on FPU. PMID:23108344

  12. Synthesis of superamphiphobic breathable membranes utilizing SiO2 nanoparticles decorated fluorinated polyurethane nanofibers.

    PubMed

    Wang, Jialin; Raza, Aikifa; Si, Yang; Cui, Lingxiao; Ge, Jianfeng; Ding, Bin; Yu, Jianyong

    2012-12-01

    Superamphiphobic nanofibrous membranes exhibiting robust water/oil proof and breathable performances were prepared by the combination of a novel synthesized fluorinated polyurethane (FPU) containing a terminal perfluoroalkane segment and incorporated SiO(2) nanoparticles (SiO(2) NPs). By employing the FPU/SiO(2) NPs incorporation, the hybrid membranes possess superhydrophobicity with a water contact angle of 165° and superoleophobicity with an oil contact angle of 151°. Surface morphological studies have indicated that the wettability of resultant membranes could be manipulated by tuning the surface composition as well as the hierarchical structures. The quantitative hierarchical roughness analysis using N(2) adsorption method has confirmed a major contribution of SiO(2) NPs on enhancing the porous structure, and a detailed correlation between the fractal dimension and amphiphobicity is proposed. Furthermore, a designed concept test shows that the as-prepared membranes could load 1.5 kg water or oil at the same time maintained an extremely high air permeability of 2 L min(-1), suggesting their use as promising materials for a variety of potential applications in protective clothing, bioseparation, water purification, tissue engineering, microfluidic systems, etc., and also provided new insight into the design and development of functional hybrid membranes based on FPU.

  13. Evaluating Soil Oxygen as a Control on N2O Emissions from Ruminant Urine Patches under Different Irrigation Frequencies

    NASA Astrophysics Data System (ADS)

    Owens, J.; Clough, T. J.; Laubach, J.; Hunt, J.; Venterea, R. T.; Phillips, R. L.

    2015-12-01

    Urine patches from grazing ruminant animals are a significant source of nitrous oxide (N2O) emissions, and irrigation is increasingly used to improve forage quality and yield for grazing cattle. The objective of this study was to test whether irrigation frequency influenced N2O emissions from urine patches on a free-draining grazed pasture soil. It was hypothesized that greater irrigation frequency would increase soil moisture thereby lowering soil oxygen (O2), and that these O2-limited conditions would increase the potential for N2O to be reduced to nitrogen gas (N2), resulting in lower N2O emissions. A field trial tested the effects of two irrigation frequencies and urine deposition on N2O fluxes measured daily for 35 days. Denitrification potential measurements using the acetylene inhibition technique were completed to infer N2O/(N2O+N2) ratios, and soil O2 concentrations were measured continuously at three depths within the soil profile. While a more frequent irrigation treatment resulted in a lower N2O/(N2O+N2) ratio, this did not give rise to lower N2O emissions. Nitrous oxide fluxes were not influenced by irrigation frequency, and approximately 0.09% of the nitrogen applied as urine was emitted as N2O from both irrigation treatments. Neither N2O nor soil O2 varied with individual irrigation events. Soil O2 ranged from 17 to 20% expect following urine deposition, where it temporarily decreased to 13%. Soil O2 measurements failed to explain N2O emissions, but a relationship was derived between N2O fluxes and estimates of soil gas diffusivity (Dp/Do). This work is the first to show how soil O2 concentrations vary under a urine patch and under different irrigation treatments, and supports Dp/Do as robust predictor of N2O emissions in situ.

  14. Combining Accurate O2 and Li2O2 Assays to Separate Discharge and Charge Stability Limitations in Nonaqueous Li-O2 Batteries.

    PubMed

    McCloskey, Bryan D; Valery, Alexia; Luntz, Alan C; Gowda, Sanketh R; Wallraff, Gregory M; Garcia, Jeannette M; Mori, Takashi; Krupp, Leslie E

    2013-09-01

    Li-air batteries have generated enormous interest as potential high specific energy alternatives to existing energy storage devices. However, Li-air batteries suffer from poor rechargeability caused by the instability of organic electrolytes and carbon cathodes. To understand and address this poor rechargeability, it is essential to elucidate the efficiency in which O2 is converted to Li2O2 (the desired discharge product) during discharge and the efficiency in which Li2O2 is oxidized back to O2 during charge. In this Letter, we combine many quantitative techniques, including a newly developed peroxide titration, to assign and quantify decomposition pathways occurring in cells employing a variety of solvents and cathodes. We find that Li2O2-induced electrolyte solvent and salt instabilities account for nearly all efficiency losses upon discharge, whereas both cathode and electrolyte instabilities are observed upon charge at high potentials.

  15. Effects of water-contaminated air on blowoff limits of opposed jet hydrogen-air diffusion flames

    NASA Technical Reports Server (NTRS)

    Pellett, Gerald L.; Jentzen, Marilyn E.; Wilson, Lloyd G.; Northam, G. Burton

    1988-01-01

    The effects of water-contaminated air on the extinction and flame restoration of the central portion of N2-diluted H2 versus air counterflow diffusion flames are investigated using a coaxial tubular opposed jet burner. The results show that the replacement of N2 contaminant in air by water on a mole for mole basis decreases the maximum sustainable H2 mass flow, just prior to extinction, of the flame. This result contrasts strongly with the analogous substitution of water for N2 in a relatively hot premixed H2-O2-N2 flame, which was shown by Koroll and Mulpuru (1986) to lead to a significant, kinetically controlled increase in laminar burning velocity.

  16. Pt and Pd catalyzed oxidation of Li2O2 and DMSO during Li–O2 battery charging

    DOE PAGES

    Gittleson, Forrest S.; Ryu, Won-Hee; Schwab, Mark; Tong, Xiao; Taylor, André D.

    2016-01-01

    Rechargeable Li-O2 and Li-air batteries require electrode and electrolyte materials that synergistcally promote long-term cell operation. We investigate the role of noble metals Pt and Pd as catalysts for the Li-O2 oxidation process and their compatibility with a dimethyl sulfoxide (DMSO) based electrolyte. Lastly, we identify a basis for low potential Li2O2 evolution followed by oxidative decomposition of the electrolyte to form carbonate side products.

  17. Pt and Pd catalyzed oxidation of Li2O2 and DMSO during Li-O2 battery charging.

    PubMed

    Gittleson, Forrest S; Ryu, Won-Hee; Schwab, Mark; Tong, Xiao; Taylor, André D

    2016-05-01

    Rechargeable Li-O2 and Li-air batteries require electrode and electrolyte materials that synergistically promote long-term cell operation. In this study, we investigate the role of noble metals Pt and Pd as catalysts in the Li-O2 oxidation process and their compatibility with dimethyl sulfoxide (DMSO) based electrolytes. We identify a basis for low potential Li2O2 evolution followed by oxidative decomposition of the electrolyte to form carbonate side products. PMID:27111589

  18. TiO2-TiO2 composite resistive humidity sensor: ethanol crosssensitivity

    NASA Astrophysics Data System (ADS)

    Ghalamboran, Milad; Saedi, Yasin

    2016-03-01

    The fabrication method and characterization results of a TiO2-TiO2 composite bead used for humidity sensing along with its negative cross-sensitivity to ethanol vapor are reported. The bead shaped resistive sample sensors are fabricated by the drop-casting of a TiO2 slurry on two Pt wire segments. The dried bead is pre-fired at 750°C and subsequently impregnated with a Ti-based sol. The sample is ready for characterization after a thermal annealing at 600°C in air. Structurally, the bead is a composite of the micron-sized TiO2 crystallites embedded in a matrix of nanometric TiO2 particle aggregates. The performance of the beads as resistive humidity sensors is recorded at room temperature in standard humidity level chambers. Results evince the wide dynamic range of the sensors fabricated in the low relative humidity range. While the sensor conductance is not sensitive to ethanol vapor in dry air, in humid air, sensor's responses are negatively affected by the contaminant.

  19. Enhanced oxygen evolution activity of IrO2 and RuO2 (100) surfaces

    SciTech Connect

    Stoerzinger, Kelsey; Qiao, Liang; Biegalski, Michael D; Christen, Hans M; Shao-Horn, Yang

    2014-01-01

    The activities of the oxygen evolution reaction (OER) on IrO2 and RuO2 catalysts are among the highest known to date. However, the intrinsic OER activities of surfaces with defined crystallographic orientations are not well established experimentally. Here we report that the (100) surface of IrO2 and RuO2 is more active than the (110) surface that has been traditionally explored by density functional theory studies. The relation between the OER activity and density of coordinatively undersaturated metal sites exposed on each rutile crystallographic facet is discussed. The surface-orientation dependent activities can guide the design of high-surface-area catalysts with increased activity for electrolyzers, metal-air batteries, and photoelectrochemical water splitting applications.

  20. A fundamental study on biological removal of N2O in the presence of oxygen.

    PubMed

    Figueroa-González, Ivonne; Quijano, Guillermo; Laguna, Inés; Muñoz, Raúl; García-Encina, Pedro A

    2016-09-01

    The biodegradation of N2O by a non-acclimated secondary activated sludge in the presence of O2 was studied. Batch tests with a headspace containing an initial N2O concentration of ∼400 mg m(-3) (∼200 ppmv) and initial O2 gas concentrations of 0%, 1%, 2%, 5% and 21% were investigated. The effect of O2 on the biokinetic parameters qmax (maximum specific N2O uptake rate) and KS (half-saturation constant), as well as on the bacterial population structure, was evaluated. A complete N2O removal was recorded in the presence of up to 2% O2, while O2 at 5% and 21% mediated inhibitions of 37% and 95% in the removal of N2O compared with the control without O2. The elemental analysis of the biomass obtained at the end of the batch tests strongly suggested that NN2O was not used as a nitrogen source. The presence of O2 mediated decreases of up to 12.6- and 4.8-fold in qmax and KS, respectively, compared to the control without O2. Likewise, the presence of O2 induced changes in the structure of the bacterial population. The predominant microorganisms in the presence of O2 belonged to the phyla Proteobacteria, Firmicutes and Chlamydiae. Bacteria belonging to the Proteobacteria phylum, particularly the Dokdonella genus, were predominant at 2% O2, which was the highest O2 concentration without inhibitory effects on N2O biodegradation. PMID:27236493

  1. Optimization of 1D ZnO@TiO2 core-shell nanostructures for enhanced photoelectrochemical water splitting under solar light illumination.

    PubMed

    Hernández, Simelys; Cauda, Valentina; Chiodoni, Angelica; Dallorto, Stefano; Sacco, Adriano; Hidalgo, Diana; Celasco, Edvige; Pirri, Candido Fabrizio

    2014-08-13

    A fast and low-cost sol-gel synthesis used to deposit a shell of TiO2 anatase onto an array of vertically aligned ZnO nanowires (NWs) is reported in this paper. The influence of the annealing atmosphere (air or N2) and of the NWs preannealing process, before TiO2 deposition, on both the physicochemical characteristics and photoelectrochemical (PEC) performance of the resulting heterostructure, was studied. The efficient application of the ZnO@TiO2 core-shells for the PEC water-splitting reaction, under simulated solar light illumination (AM 1.5G) solar light illumination in basic media, is here reported for the first time. This application has had a dual function: to enhance the photoactivity of pristine ZnO NWs and to increase the photodegradation stability, because of the protective role of the TiO2 shell. It was found that an air treatment induces a better charge separation and a lower carrier recombination, which in turn are responsible for an improvement in the PEC performance with respect to N2-treated core-shell materials. Finally, a photocurrent of 0.40 mA/cm(2) at 1.23 V versus RHE (2.2 times with respect to the pristine ZnO NWs) was obtained. This achievement can be regarded as a valuable result, considering similar nanostructured electrodes reported in the literature for this application.

  2. Photocatalytic degradation of dyestuff wastewater with Zn(2+)-TiO2-SiO2 nanocomposite.

    PubMed

    Sui, Guozhe; Liu, Tao; Li, Jinlong; Jia, Lihua; Lv, Jun

    2013-06-01

    A novel photocatalyst of Zn(2+)-TiO2-SiO2 nanocomposite has been prepared by a sol-gel method, which is used for the degradation of Rhodamine B (RhB) and Congo red (CR) as the probe dyestuff that are notorious organic compounds present in dyes wastewater. The prepared samples are characterized by low temperature N2 adsorption (BET), X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-vis diffuse reflectance spectroscopy (DRS) and Fourier transformed infrared spectroscopy (FT-IR). It is found that the nanocomposite of Zn(2+)-TiO2-SiO2 exhibits much higher photocatalytic activity under both UV light and visible light irradiation as compared with Degussa P25, Zn(2+)-TiO2 and SiO2-TiO2. The photodegradation efficiencies of RhB (5 mg/L) and CR (10 mg/L) can reach above 90% and 83% for 1.5 h visible light irradiation, respectively. Synergetic effect between Zn(2+)-SiO2-doping not only inhibit the crystal growth and anatase-to-rutile transformation of TiO2 nanocatalyst, but also extend the light response to the visible region, which provides a good way and material in the degradation field of dyes wastewater.

  3. Preparation of SnO2 -TiO2 /Fly Ash Cenospheres and its Application in Phenol Degradation.

    PubMed

    Liu, Shaomin; Zhu, Jinglin; Yang, Qing; Xu, Pengpeng; Ge, Jianhua; Guo, Xuetao

    2015-11-01

    SnO2 -TiO2 /fly ash cenospheres (FAC) were prepared via hydrothermal method and used as an active photocatalyst in a photocatalytic system. Scanning electron microscopy, X-ray diffraction analysis, UV-Vis diffuse reflectance spectroscopy, Fourier transform infrared spectroscopy and N2 adsorption-desorption measurements were used to determine the structure and optical property of SnO2 -TiO2 /FAC. Phenol was selected as the model substance for photocatalytic reactions to evaluate catalytic ability. Results showed that the degradation efficiency of phenol by SnO2 -TiO2 /FAC was 90.7% higher than that decomposed by TiO2 /FAC. Increased efficiency could be due to the enhanced synergistic effect of semiconductors and FAC could provide more adsorption sites for the pollutant in the photocatalytic reaction. Furthermore, SnO2 -TiO2 /FAC composites exhibited excellent photocatalytic stability in four reuse cycles. Radical-trapping experiments further revealed the dominating functions of holes in the photocatalytic reaction. PMID:26342185

  4. Synthesis of Radioisotope Mn-56@SiO2, Sm-153@SiO2, and Dy-165@SiO2 Hybrid Nanoparticles for Use as Radiotracer.

    PubMed

    Seo, Sang-Ei; Kang, Yun Ok; Jung, Sung-Hee; Choi, Seong-Ho

    2015-09-01

    Radioisotope hybrid nanoparticles (NPs) of Mn-56@SiO2, Sm-153@SiO2, and Dy-165@SiO2 were synthesized by neutron irradiation of Mn-55@SiO2, Sm-150@SiO2, and Dy-163@SiO2 NPs respectively using the HANARO research reactor. The Mn-55@SiO2, Sm-150@SiO2, and Dy-163@SiO2 NPs were synthesized by calcination in air flow at 500 degrees C for 8 h of the hybrid NPs that has been prepared by the sol-gel reaction of tetraethyl silicate in the presence of the complex precursors. Mn-55, Sm-150, and Dy-163 were selected for use as radiotracers were selected because these elements can be easily gamma-activated by neutrons (activation limits: 1 picogram (Dy), 1-10 picogram (Mn), 10-100 picogram (Sm)). The successful synthesis of the radioisotope hybrid NPs was confirmed by Transmission Electron Microscopy (TEM), Energy Dispersive X-ray Spectrometry (EDS), Scanning Electron Microscopy (SEM), and Gamma Spectroscopy analysis. The synthesized the radioisotope hybrid NPs could be used as radiotracers in the scientific, environmental, engineering, and industrial fields.

  5. Nitrogen-plasma treatment of parallel-aligned SnO2-nanowire field-effect transistors

    NASA Astrophysics Data System (ADS)

    Choi, Yong-Hee; Na, Junhong; Kim, Jae-Sung; Joo, Min-Kyu; Kim, Gyu Tae; Kang, Pil Soo

    2014-08-01

    Nitrogen (N2)-plasma treatment and polymethylmethacrylate (PMMA) passivation were carried out to stabilize the electrical properties of parallel-aligned tin-dioxide (SnO2)-nanowire field-effect transistors. Treatment led to a positive shift in the threshold voltage, V th , with a reduction in the hysteresis in the transfer curves of more than 30% compared to the case without treatment. Passivation was carried using a PMMA coating to prevent changes in the electrical properties over time. X-ray photoelectron spectroscopy and Auger electron spectroscopy were employed to determine the chemical mechanisms that resulted in the changes in the electrical properties over time, those changes being attributed to the recombination of oxygen vacancies and carbon contaminants on the surface of the SnO2 nanowires with oxygen in the ambient air.

  6. 40 CFR 1065.280 - Paramagnetic and magnetopneumatic O2 detection analyzers.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Measurement Instruments O2 Measurements § 1065... diluted exhaust for batch or continuous sampling. You may use O2 measurements with intake air or fuel flow.... 15, 2011] Air-to-Fuel Ratio Measurements...

  7. 40 CFR 1065.280 - Paramagnetic and magnetopneumatic O2 detection analyzers.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Measurement Instruments O2 Measurements § 1065... diluted exhaust for batch or continuous sampling. You may use O2 measurements with intake air or fuel flow...), regardless of the uncompensated signal's bias. Air-to-Fuel Ratio Measurements...

  8. 40 CFR 1065.280 - Paramagnetic and magnetopneumatic O2 detection analyzers.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Measurement Instruments O2 Measurements § 1065... diluted exhaust for batch or continuous sampling. You may use O2 measurements with intake air or fuel flow... must meet the linearity verification in § 1065.307. Air-to-Fuel Ratio Measurements...

  9. 40 CFR 1065.280 - Paramagnetic and magnetopneumatic O2 detection analyzers.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Measurement Instruments O2 Measurements § 1065... diluted exhaust for batch or continuous sampling. You may use O2 measurements with intake air or fuel flow...), regardless of the uncompensated signal's bias. Air-to-Fuel Ratio Measurements...

  10. 40 CFR 1065.280 - Paramagnetic and magnetopneumatic O2 detection analyzers.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Measurement Instruments O2 Measurements § 1065... diluted exhaust for batch or continuous sampling. You may use O2 measurements with intake air or fuel flow...), regardless of the uncompensated signal's bias. Air-to-Fuel Ratio Measurements...

  11. Nanostructured porous RuO2/MnO2 as a highly efficient catalyst for high-rate Li-O2 batteries

    NASA Astrophysics Data System (ADS)

    Wang, Guoqing; Huang, Liliang; Huang, Wei; Xie, Jian; Du, Gaohui; Zhang, Shichao; Zhu, Peiyi; Cao, Gaoshao; Zhao, Xinbing

    2015-12-01

    Despite the recent advancements in Li-O2 (or Li-air) batteries, great challenges still remain to realize high-rate, long-term cycling. In this work, a binder-free, nanostructured RuO2/MnO2 catalytic cathode was designed to realize the operation of Li-O2 batteries at high rates. At a current density as high as 3200 mA g-1 (or ~1.3 mA cm-2), the RuO2/MnO2 catalyzed Li-O2 batteries with LiI can sustain stable cycling of 170 and 800 times at limited capacities of 1000 and 500 mA h g-1, respectively, with low charge cutoff potentials of ~4.0 and <3.8 V, respectively. The underlying mechanism of the high catalytic performance of MnO2/RuO2 was also clarified in this work. It was found that with the catalytic effect of RuO2, Li2O2 can crystallize into a thin-sheet form and realize a conformal growth on sheet-like δ-MnO2 at a current density up to 3200 mA g-1, constructing a sheet-on-sheet structure. This crystallization behavior of Li2O2 not only defers the electrode passivation upon discharge but also renders easy decomposition of Li2O2 upon charge, leading to low polarizations and reduced side reactions. This work provides a unique design of catalytic cathodes capable of controlling Li2O2 growth and sheds light on the design of high-rate, long-life Li-O2 batteries with potential applications in electric vehicles.Despite the recent advancements in Li-O2 (or Li-air) batteries, great challenges still remain to realize high-rate, long-term cycling. In this work, a binder-free, nanostructured RuO2/MnO2 catalytic cathode was designed to realize the operation of Li-O2 batteries at high rates. At a current density as high as 3200 mA g-1 (or ~1.3 mA cm-2), the RuO2/MnO2 catalyzed Li-O2 batteries with LiI can sustain stable cycling of 170 and 800 times at limited capacities of 1000 and 500 mA h g-1, respectively, with low charge cutoff potentials of ~4.0 and <3.8 V, respectively. The underlying mechanism of the high catalytic performance of MnO2/RuO2 was also clarified in this

  12. Nonthermal metabolic response of rats to He-O2, N2-O2, and Ar-O2 at 1 atm.

    NASA Technical Reports Server (NTRS)

    Schatte, C. L.; Jordan, J. P.; Phillips, R. W.; Clarkson, D. P.; Simmons, J. B., II

    1973-01-01

    Experiments were performed to describe qualitatively and quantitatively the nonthermal metabolic response of rats to normoxic mixtures of helium, nitrogen, or argon at 1 atm ambient pressure. Hypoxic mixtures were similarly tested to determine any differences in hypoxic response as a function of the diluent gas. Rats exposed to argon for 5 days had a reduced metabolic rate relative to nitrogen, as evidenced by oxygen and food consumption, CO2 production, and the catabolism of radiosubstrates. While some parameters indicated that helium increased metabolic rate, oxygen consumption did not significantly differ from that in nitrogen. The physiologic and metabolic response to an imposed hypoxia varied among the different environments. Certain indices suggested that the hypoxic effects were less severe in helium and more pronounced in argon than in nitrogen. The mechanisms by which the diluent gases produced the observed changes could not be identified, but some possibilities are discussed.

  13. Experimental and kinetic modeling of oxygen-enriched air combustion of municipal solid waste.

    PubMed

    Liu, Guo Hui; Ma, Xiao Qian; Yu, Zhaosheng

    2009-02-01

    The characteristics of oxygen-enriched air combustion of raw municipal solid waste (MSW) were studied by thermogravimetric analysis. Experiments on oxidative pyrolysis of MSW were carried out under different atmospheres (N(2), N(2):O(2)=7:3, N(2):O(2)=5:5, N(2):O(2)=4:6, and N(2):O(2)=2:8) at 30 degrees C/min. Two distinct peaks of weight loss were obtained according to the derivative thermogravimetric curves; one of them is centered on 305 degrees C with about 40% weight loss, and the second is centered on 420 degrees C with about 20% weight loss. Effects of oxygen concentration on the decomposition process and char combustion were analyzed, and then the process of oxygen-enriched air combustion of MSW was divided into four steps. Kinetic parameters were observed by direct non-linear regressions. According to the obtained data, the apparent activation energy and reaction order decreases along with the combustion process, while that of char combustion increases as oxygen concentration increases. PMID:18691862

  14. Chlorine Gas Sensing Performance of On-Chip Grown ZnO, WO3, and SnO2 Nanowire Sensors.

    PubMed

    Tran, Van Dang; Nguyen, Duc Hoa; Nguyen, Van Duy; Nguyen, Van Hieu

    2016-02-01

    Monitoring toxic chlorine (Cl2) at the parts-per-billion (ppb) level is crucial for safe usage of this gas. Herein, ZnO, WO3, and SnO2 nanowire sensors were fabricated using an on-chip growth technique with chemical vapor deposition. The Cl2 gas-sensing characteristics of the fabricated sensors were systematically investigated. Results demonstrated that SnO2 nanowires exhibited higher sensitivity to Cl2 gas than ZnO and WO3 nanowires. The response (RCl2/Rair) of the SnO2 nanowire sensor to 50 ppb Cl2 at 50 °C was about 57. Hence, SnO2 nanowires can be an excellent sensing material for detecting Cl2 gas at the ppb level under low temperatures. Abnormal sensing characteristics were observed in the WO3 and SnO2 nanowire sensors at certain temperatures; in particular, the response level of these sensors to 5 ppm of Cl2 was lower than that to 2.5 ppm of Cl2. The sensing mechanism of the SnO2 nanowire sensor was also elucidated by determining Cl2 responses under N2 and dry air as carrier gases. We proved that the Cl2 molecule was first directly adsorbed on the metal oxide surface and was then substituted for pre-adsorbed oxygen, followed by lattice oxygen.

  15. N2O and δ15N-N2O and δ18O-N2O from polar ice cores: interpretable data for interglacials

    NASA Astrophysics Data System (ADS)

    Bock, Michael; Schmitt, Jochen; Seth, Barbara; Beck, Jonas; Fischer, Hubertus

    2014-05-01

    Ice cores provide a wealth of information on climate change. For instance, the history of the atmospheric greenhouse gas N2O can be reconstructed using air entrapped in polar ice cores. N2O has several sources in both terrestrial and marine ecosystems, predominantly wetland soils and oxygen minimum zones in the ocean. N2O records generally follow the climatic changes during the glacial-interglacial cycles with higher N2O mixing ratios during warmer climate stages. However, the underlying processes driving these changes are difficult to identify from N2O mixing ratios alone. Additional information on the individual sources and sinks are provided by stable isotope measurements. The emission fluxes of the dominant N2O sources are ascribed to several pathways (nitrification, denitrification), with characteristic fractionation factors for the nitrogen and oxygen isotope signatures of the generated N2O (δ15N-N2O and δ18O-N2O). In the end, the individual proportions of pathways are responsible for distinct δ15N-N2O and δ18O-N2O for the average terrestrial and marine sources. Here, we present new ice core measurements of δ15N-N2O and δ18O-N2O covering the Holocene, MIS 5 and MIS 11. For the past 15 kyrs the δ15N-N2O record shows a continuous decrease starting at 15 kyrs to about 6 kyrs; during the past 6 kyrs δ15N-N2O remains rather constant. The resemblance with a recently published global reconstruction of bulk δ15N is remarkable (McLauchlan et al. 2013, Nature). Taken at face value this could mean that mainly the terrestrial source signature changed rather than a shift in the relative proportions of the terrestrial and marine source. The integrity of N2O ice core records relies on the assumption that the measurements truly represent the past atmosphere. However, comparative analyses of different ice cores from the same age intervals show offsets in the N2O mixing ratios among the records. One likely assumption is that higher mixing ratios are due to in

  16. Design and Preparation of MnO2/CeO2-MnO2 Double-Shelled Binary Oxide Hollow Spheres and Their Application in CO Oxidation.

    PubMed

    Zhang, Jian; Cao, Yidan; Wang, Chang-An; Ran, Rui

    2016-04-01

    Herein, we designed an extremely facile method to prepare well-defined MnO2@CeO2-MnO2 ball-in-ball binary oxide hollow spheres by employing carbon spheres (CSs) as sacrificial templates. The synthesis process involves a novel self-assembled approach to prepare core-shell CSs@CeO2 precursor, which would directly react with KMnO4 aqueous solution to form yolk-shell CSs@MnO2/CeO2-MnO2 precursor in the following step. Well-dispersed Ce-Mn binary oxide with double-shelled hollow sphere structure could be achieved after annealing the precursor in air. The evolution process and formation mechanism of this novel structure were thoroughly studied in this paper. Especially the as-prepared double-shell MnO2/CeO2-MnO2 hollow spheres exhibited enhanced catalytic activity for CO oxidation compared with the pure MnO2 hollow spheres and pure CeO2 hollow spheres. We believe the high surface area, hierarchical porous structures, and strong synergistic interaction between CeO2 and MnO2 contribute to the excellent catalytic activity. Most importantly, this method could be extended to prepare other transition metal oxides. As an example, triple-shelled Co-Mn composite hollow spheres assembled by ultrathin nanoplates were successfully prepared.

  17. Selective, Tunable O2 Binding in Cobalt(II)–Triazolate/Pyrazolate Metal–Organic Frameworks

    PubMed Central

    2016-01-01

    The air-free reaction of CoCl2 with 1,3,5-tri(1H-1,2,3-triazol-5-yl)benzene (H3BTTri) in N,N-dimethylformamide (DMF) and methanol leads to the formation of Co-BTTri (Co3[(Co4Cl)3(BTTri)8]2·DMF), a sodalite-type metal–organic framework. Desolvation of this material generates coordinatively unsaturated low-spin cobalt(II) centers that exhibit a strong preference for binding O2 over N2, with isosteric heats of adsorption (Qst) of −34(1) and −12(1) kJ/mol, respectively. The low-spin (S = 1/2) electronic configuration of the metal centers in the desolvated framework is supported by structural, magnetic susceptibility, and computational studies. A single-crystal X-ray structure determination reveals that O2 binds end-on to each framework cobalt center in a 1:1 ratio with a Co–O2 bond distance of 1.973(6) Å. Replacement of one of the triazolate linkers with a more electron-donating pyrazolate group leads to the isostructural framework Co-BDTriP (Co3[(Co4Cl)3(BDTriP)8]2·DMF; H3BDTriP = 5,5′-(5-(1H-pyrazol-4-yl)-1,3-phenylene)bis(1H-1,2,3-triazole)), which demonstrates markedly higher yet still fully reversible O2 affinities (Qst = −47(1) kJ/mol at low loadings). Electronic structure calculations suggest that the O2 adducts in Co-BTTri are best described as cobalt(II)–dioxygen species with partial electron transfer, while the stronger binding sites in Co-BDTriP form cobalt(III)–superoxo moieties. The stability, selectivity, and high O2 adsorption capacity of these materials render them promising new adsorbents for air separation processes. PMID:27180991

  18. 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.

  19. Highly active Ce 1- xCu xO 2 nanocomposite catalysts for the low temperature oxidation of CO

    NASA Astrophysics Data System (ADS)

    Mai, Hailing; Zhang, Dengsong; Shi, Liyi; Yan, Tingting; Li, Hongrui

    2011-06-01

    A series of Ce 1- xCu xO 2 nanocomposite catalysts with various copper contents were synthesized by a simple hydrothermal method at low temperature without any surfactants, using mixed solutions of Cu(II) and Ce(III) nitrates as metal sources. These bimetal oxide nanocomposites were characterized by means of XRD, TEM, HRTEM, EDS, N 2 adsorption, H 2-TPR and XPS. The influence of Cu loading (5-25 mol%) and calcination temperature on the surface area, particle size and catalytic behavior of the nanocomposites have been discussed. The catalytic activity of Ce 1- xCu xO 2 nanocomposites was investigated using the test of CO oxidation reaction. The optimized performance was achieved for the Ce 0.80Cu 0.20O 2 nanocomposite catalyst, which exhibited superior reaction rate of 11.2 × 10 -4 mmol g -1 s -1 and high turnover frequency of 7.53 × 10 -2 s -1 (1% CO balanced with air at a rate of 40 mL min -1, at 90 °C). No obvious deactivation was observed after six times of catalytic reactions for Ce 0.80Cu 0.20O 2 nanocomposite catalyst.

  20. Insight into unusual impurity absorbability of GeO(2) in GeO(2)∕Ge stacks.

    PubMed

    Ogawa, Shingo; Suda, Taichi; Yamamoto, Takashi; Kutsuki, Katsuhiro; Hideshima, Iori; Hosoi, Takuji; Shimura, Takayoshi; Watanabe, Heiji

    2011-10-01

    Adsorbed species and its diffusion behaviors in GeO(2)∕Ge stacks, which are future alternative metal-oxide-semiconductor (MOS) materials, have been investigated using various physical analyses. We clarified that GeO(2) rapidly absorbs moisture in air just after its exposure. After the absorbed moisture in GeO(2) reaches a certain limit, the GeO(2) starts to absorb some organic molecules, which is accompanied by a structural change in GeO(2) to form a partial carbonate or hydroxide. We also found that the hydrogen distribution in GeO(2) shows intrinsic characteristics, indicative of different diffusion behaviors at the surface and at the GeO(2)∕Ge interface. Because the impurity absorbability of GeO(2) has a great influence on the electrical properties in Ge-MOS devices, these results provide valuable information in realizing high quality GeO(2)∕Ge stacks for the actual use of Ge-MOS technologies.

  1. Stability of polymer binders in Li-O2 batteries

    SciTech Connect

    Nasybulin, Eduard N.; Xu, Wu; Engelhard, Mark H.; Nie, Zimin; Li, Xiaohong S.; Zhang, Jiguang

    2013-06-24

    A number of polymers with various chemical structures were studied as binders for air electrodes in Li-O2 batteries. The nature of the polymer significantly affects the binding properties in the carbon electrodes thus altering the discharge performance of Li-O2 batteries. Stability of polymers to the aggressive reduced oxygen species generated during discharge was tested by ball milling them with KO2 and Li2O2, respectively. Most of the polymers decomposed under these conditions and mechanisms of the decompositions are proposed for some of the polymers. Polyethylene was found to have excellent stability and is suggested as robust binder for air electrodes in Li-O2 batteries.

  2. Ventilatory response to transient hypoxia in O2 divers.

    PubMed

    Melamed, Y; Kerem, D

    1988-05-01

    This study addresses the question of whether repeated acute exposure to hyperbaric oxygen, such as encountered in O2 diving, affects the peripheral oxygen chemosensors. Groups of nondivers, active O2 divers, and ex-O2 divers, as well as active air scuba divers, were given 1 or both of 2 tests that measure the ventilatory response to transient hypoxia. Results showed that all groups of divers have a mean response similar to or higher than that of nondivers as well as that of normal subjects, as reported in the literature. A repeat test on 10 diving candidates before and after 200 h of accrued O2 diving also did not show an impairment in the hypoxic ventilatory response. Oxygen diving within the established depth and time limits does not seem to cause cumulative damage to the peripheral O2 chemosensors.

  3. PECVD grown SiO2 film process optimization

    NASA Astrophysics Data System (ADS)

    Ping, Song; Jie, Lian; Gao, Shang; Li, Ping; Wang, Xiao; Wu, Shiliang; Ma, Zheng

    2011-02-01

    SiO2 films have been widely applied in the production of electronic devices, integrated devices, optical thin film devices, sensors because of their desirable properties, such as good insulation, high light transmittance, strong corrosion resistance, good dielectric properties, etc. Amorphous silicon dioxide was fabricated by plasma enhanced chemical deposition on GaAs substrate. The thickness and refractive index are obtained by optical transmittance of the film, which are measured by ellipsometer. The deposition rate of the film and the refractive index are studied at different time, pressure, and the ratio of SiH4/N2O. The SiO2 thin film growth rate remained basically unchanged versus time. The reaction chamber pressure, which make the SiO2 thin film growth rate getting the peak, should be about 105Pa. But the SiO2 thin film growth rate and the refractive index are anti-related. The enormous changes of the gas flow rate do not have huge impact to the response rate. However, the refractive index of SiO2 thin film changed greatly when the SiH4flow increased the refractive index of the thin films is highest when the ratio of SiH4/N2O is 200:20

  4. CARS Temperature and Species Measurements For Air Vehicle Propulsion Systems

    NASA Technical Reports Server (NTRS)

    Danehy, Paul M.; Gord, James R.; Grisch, Frederic; Klimenko, Dmitry; Clauss, Walter

    2005-01-01

    The coherent anti-Stokes Raman spectroscopy (CARS) method has recently been used in the United States and Europe to probe several different types of propulsion systems for air vehicles. At NASA Langley Research Center in the United States, CARS has been used to simultaneously measure temperature and the mole fractions of N2, O2 and H2 in a supersonic combustor, representative of a scramjet engine. At Wright- Patterson Air Force Base in the United States, CARS has been used to simultaneously measure temperature and mole fractions of N2, O2 and CO2, in the exhaust stream of a liquid-fueled, gas-turbine combustor. At ONERA in France and the DLR in Germany researchers have used CARS to measure temperature and species concentrations in cryogenic LOX-H2 rocket combustion chambers. The primary aim of these measurements has been to provide detailed flowfield information for computational fluid dynamics (CFD) code validation.

  5. CFD Simulation of the distribution of ClO2 in fresh produce to improve safety

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The shelf life of fresh-cut produce may be prolonged with the injection of bactericide gases like chlorine dioxide (ClO2). A comparative study has been conducted by modeling the injection of three different gases, CO2, ClO2 and N2 inside a PET clamshell containers commonly use to package fresh produ...

  6. Synthesis of superamphiphobic breathable membranes utilizing SiO2 nanoparticles decorated fluorinated polyurethane nanofibers

    NASA Astrophysics Data System (ADS)

    Wang, Jialin; Raza, Aikifa; Si, Yang; Cui, Lingxiao; Ge, Jianfeng; Ding, Bin; Yu, Jianyong

    2012-11-01

    Superamphiphobic nanofibrous membranes exhibiting robust water/oil proof and breathable performances were prepared by the combination of a novel synthesized fluorinated polyurethane (FPU) containing a terminal perfluoroalkane segment and incorporated SiO2 nanoparticles (SiO2 NPs). By employing the FPU/SiO2 NPs incorporation, the hybrid membranes possess superhydrophobicity with a water contact angle of 165° and superoleophobicity with an oil contact angle of 151°. Surface morphological studies have indicated that the wettability of resultant membranes could be manipulated by tuning the surface composition as well as the hierarchical structures. The quantitative hierarchical roughness analysis using N2 adsorption method has confirmed a major contribution of SiO2 NPs on enhancing the porous structure, and a detailed correlation between the fractal dimension and amphiphobicity is proposed. Furthermore, a designed concept test shows that the as-prepared membranes could load 1.5 kg water or oil at the same time maintained an extremely high air permeability of 2 L min-1, suggesting their use as promising materials for a variety of potential applications in protective clothing, bioseparation, water purification, tissue engineering, microfluidic systems, etc., and also provided new insight into the design and development of functional hybrid membranes based on FPU.Superamphiphobic nanofibrous membranes exhibiting robust water/oil proof and breathable performances were prepared by the combination of a novel synthesized fluorinated polyurethane (FPU) containing a terminal perfluoroalkane segment and incorporated SiO2 nanoparticles (SiO2 NPs). By employing the FPU/SiO2 NPs incorporation, the hybrid membranes possess superhydrophobicity with a water contact angle of 165° and superoleophobicity with an oil contact angle of 151°. Surface morphological studies have indicated that the wettability of resultant membranes could be manipulated by tuning the surface composition as

  7. TiO2-graphene nanocomposites for gas-phase photocatalytic degradation of volatile aromatic pollutant: is TiO2-graphene truly different from other TiO2-carbon composite materials?

    PubMed

    Zhang, Yanhui; Tang, Zi-Rong; Fu, Xianzhi; Xu, Yi-Jun

    2010-12-28

    The nanocomposites of TiO(2)-graphene (TiO(2)-GR) have been prepared via a facile hydrothermal reaction of graphene oxide and TiO(2) in an ethanol-water solvent. We show that such a TiO(2)-GR nanocomposite exhibits much higher photocatalytic activity and stability than bare TiO(2) toward the gas-phase degradation of benzene, a volatile aromatic pollutant in air. By investigating the effect of different addition ratios of graphene on the photocatalytic activity of TiO(2)-GR systematically, we find that the higher weight ratio in TiO(2)-GR will decrease the photocatalytic activity. Analogous phenomenon is also observed for the liquid-phase degradation of dyes over TiO(2)-GR. In addition, the key features for TiO(2)-GR including enhancement of adsorptivity of pollutants, light absorption intensity, electron-hole pairs lifetime, and extended light absorption range have also been found in the composite of TiO(2) and carbon nanotubes (TiO(2)-CNT). These strongly manifest that TiO(2)-GR is in essence the same as other TiO(2)-carbon (carbon nanotubes, fullerenes, and activated carbon) composite materials on enhancement of photocatalytic activity of TiO(2), although graphene by itself has unique structural and electronic properties. Notably, this key fundamental question remains completely unaddressed in a recent report ( ACS Nano 2010 , 4 , 380 ) regarding liquid-phase degradation of dyes over the TiO(2)-GR photocatalyst. Thus, we propose that TiO(2)-GR cannot provide truly new insights into the fabrication of TiO(2)-carbon composite as high-performance photocatalysts. It is hoped that our work could avert the misleading message to the readership, hence offering a valuable source of reference on fabricating TiO(2)-carbon composites for their application as a photocatalyst in the environment cleanup. PMID:21117654

  8. Ag-TiO2 nanoparticle codoped SiO2 films on ZrO2 barrier-coated glass substrates with antibacterial activity in ambient condition.

    PubMed

    Mukhopadhyay, Anindita; Basak, Sujit; Das, Jugal Kishore; Medda, Samar Kumar; Chattopadhyay, Krishnananda; De, Goutam

    2010-09-01

    Anatase TiO2 and Ag nanoparticles (NPs) codoped SiO2 films were prepared by the sol-gel method. Proportionate amounts of 3-(glycidoxypropyl)trimethoxysilane (GLYMO), tetraethylorthosilicate (TEOS) and 3-(methacryloxypropyl)trimethoxysilane (MEMO) derived inorganic-organic silica sol, commercially available dispersed anatase TiO2 NPs, and AgNO3 were used to prepare the sols. The films were prepared on ZrO2 (cubic) precoated soda-lime glass substrates by a single-dipping technique and heat-treated at 450 °C in air and H2/Ar atmosphere to obtain hard, relatively porous, and transparent coatings of thickness>600 nm. The ZrO2 barrier layer was previously applied on soda-lime glass to restrict the diffusion of Ag into the substrate. The Ag-TiO2 NPs incorporated SiO2 films were intense yellow in color and found to be fairly stable at ambient condition for several days under fluorescent light. These films show a considerable growth inhibition on contact with the gram negative bacteria E. coli.

  9. Charge exchange of metastable 2D oxygen ions with molecular oxygen - A new source of thermospheric O2/+/ ions

    NASA Technical Reports Server (NTRS)

    Torr, D. G.; Torr, M. R.; Rusch, D. W.; Nier, A. O.; Kayser, D.; Hanson, W. B.; Hoffman, J. H.; Donahue, K.

    1979-01-01

    Reactions involving metastable ions are difficult to study in the laboratory. Much new information on these reactions has been derived from satellite measurements of aeronomic parameters. In this paper, Atmosphere Explorer D data are used to study charge exchange of metastable O(+)(2D) ions with O2. Using direct measurements of the O2 at 200 km to compute O2 densities at 300 km and supporting ionic concentrations and temperature observations, we find the rate coefficient for this reaction to be 1 + or - 0.6 times 10 to the minus 9th cu cm/sec. The process constitutes a significant source of O2(+) ions in the F2 layer at times when the N2 and O2 densities are enhanced. This finding leads to the conclusion that charge exchange with O2 must be a major sink for O(+)(2D) and an important source of O2(+) ions in the E region, because of the increase in the O2 concentration/N2 concentration ratio with decreasing altitude. The results imply that 80% of all O(+) ions formed in the E region are converted to O2(+) and that only about 20% of the metastable O(+) ions are converted into N2(+) through charge exchange with N2.

  10. Lan+1NinO3n+1 (n = 2 and 3) phases and composites for solid oxide fuel cell cathodes: Facile synthesis and electrochemical properties

    NASA Astrophysics Data System (ADS)

    Sharma, Rakesh K.; Burriel, Mónica; Dessemond, Laurent; Bassat, Jean-Marc; Djurado, Elisabeth

    2016-09-01

    In this work we present a modified citrate-nitrate route using citric acid as a chelating agent as an effective and facile strategy to obtain nanocrystalline La3Ni2O7+δ (L3N2) and La4Ni3O10-δ (L4N3) powders for the preparation of solid oxide fuel cell cathodes. Both samples crystallize in a Fmmm orthorhombic layered Lan+1NinO3n+1 Ruddlesden-Popper structure, with n = 2 and 3, respectively. The oxygen non-stoichiometry, determined by TGA is equal to 0.05 and 0.06 for L3N2 and L4N3, respectively. The thermal expansion coefficient values of L3N2 and L4N3 are 11.0 × 10-6 K-1 and 11.5 × 10-6 K-1, respectively. This study focused on L3N2, L4N3 and on novel composite electrodes with CGO (Ce0.9Gd0.1O2-δ): L3N2-CGO and L4N3-CGO with a view to taking advantage of their complimentary properties, i.e. high ionic conductivity of CGO and high electronic conductivity of Lan+1NinO3n+1 (n = 2 and 3). A significant improvement of the polarization resistance, from 1.0 to 0.03 Ω cm2 and from 1.5 to 0.52 Ω cm2 at 700 °C, is obtained when 50 wt% CGO is added to L3N2 and L4N3, respectively. In addition, the L3N2-CGO composite shows good long-term stability at 900 °C for 2 weeks in air, confirming its suitability as a SOFC cathode.

  11. Direct sun and airborne MAX-DOAS measurements of the collision induced oxygen complex, O2O2 absorption with significant pressure and temperature differences

    NASA Astrophysics Data System (ADS)

    Spinei, E.; Cede, A.; Herman, J.; Mount, G. H.; Eloranta, E.; Morley, B.; Baidar, S.; Dix, B.; Ortega, I.; Koenig, T.; Volkamer, R.

    2014-09-01

    The collision induced O2 complex, O2O2, is a very important trace gas in remote sensing measurements of aerosol and cloud properties. Some ground based MAX-DOAS measurements of O2O2 slant column density require correction factors of 0.75 ± 0.1 to reproduce radiative transfer modeling (RTM) results for a near pure Rayleigh atmosphere. One of the potential causes of this discrepancy is believed to be uncertainty in laboratory measured O2O2 absorption cross section temperature and pressure dependence, due to difficulties in replicating atmospheric conditions in the laboratory environment. This paper presents direct-sun (DS) and airborne multi-axis (AMAX) DOAS measurements of O2O2 absorption optical depths under actual Earth atmospheric conditions in two wavelength regions (335-390 nm and 435-490 nm). DS irradiance measurements were made by the research grade MFDOAS instrument from 2007-2014 at seven sites with significant pressure (778-1013 hPa) and O2O2 profile weighted temperature (247-275 K) differences. Aircraft MAX-DOAS measurements were conducted by the University of Colorado AMAX-DOAS instrument on 29 January 2012 over the Southern Hemisphere subtropical Pacific Ocean. Scattered solar radiance spectra were collected at altitudes between 9 and 13.2 km, with O2O2 profile weighted temperatures of 231-244 K, and near pure Rayleigh scattering conditions. Due to the well defined DS air mass factors and extensively characterized atmospheric conditions during the AMAX-DOAS measurements, O2O2"pseudo" absorption cross sections, σ, are derived from the observed optical depths and estimated O2O2column densities. Vertical O2O2 columns are calculated from the atmospheric sounding temperature, pressure and specific humidity profiles. Based on the atmospheric DS observations, there is no pressure dependence of the O2O2 σ, within the measurement errors (3%). The two data sets are combined to derive peak σ temperature dependence of 360 and 477 nm absorption bands from 231

  12. Extreme Emission of N2O from Tropical Wetland Soil (Pantanal, South America)

    PubMed Central

    Liengaard, Lars; Nielsen, Lars Peter; Revsbech, Niels Peter; Priemé, Anders; Elberling, Bo; Enrich-Prast, Alex; Kühl, Michael

    2013-01-01

    Nitrous oxide (N2O) is an important greenhouse gas and ozone depleter, but the global budget of N2O remains unbalanced. Currently, ∼25% of the global N2O emission is ascribed to uncultivated tropical soils, but the exact locations and controlling mechanisms are not clear. Here we present the first study of soil N2O emission from the Pantanal indicating that this South American wetland may be a significant natural source of N2O. At three sites, we repeatedly measured in situ fluxes of N2O and sampled porewater nitrate (NO3-) during the low water season in 2008 and 2009. In 2010, 10 sites were screened for in situ fluxes of N2O and soil NO3- content. The in situ fluxes of N2O were comparable to fluxes from heavily fertilized forests or agricultural soils. An important parameter affecting N2O emission rate was precipitation, inducing peak emissions of >3 mmol N2O m−2 day−1, while the mean daily flux was 0.43 ± 0.03 mmol N2O m−2 day−1. Over 170 days of the drained period, we estimated non-wetted drained soil to contribute 70.0 mmol N2O m−2, while rain-induced peak events contributed 9.2 mmol N2O m−2, resulting in a total N2O emission of 79.2 mmol N2O m−2. At the sites of repeated sampling, the pool of porewater nitrate varied (0.002-7.1μmolNO3-gdW-1) with higher concentrations of NO3- (p < 0.05) found in drained soil than in water-logged soil, indicating dynamic shifts between nitrification and denitrification. In the field, O2 penetrated the upper 60 cm of drained soil, but was depleted in response to precipitation. Upon experimental wetting the soil showed rapid O2 depletion followed by N2O accumulation and a peak emission of N2O (2.5 - 3.0mmolN2Om-2day-1). Assuming that the observed emission of N2O from these wetland soils is generally representative to the Pantanal, we suggest that this undisturbed tropical wetland potentially contributes ∼1.7% to the global N2O emission budget, a significant

  13. NOAA's Global Network of N2O Observations

    NASA Astrophysics Data System (ADS)

    Dlugokencky, E. J.; Crotwell, A. M.; Crotwell, M.; Masarie, K. A.; Lang, P. M.; Dutton, G. S.; Hall, B. D.

    2014-12-01

    Nitrous oxide has surpassed CFC-12 to become the third largest contributor to radiative forcing. When climate impacts for equal emitted masses of N2O and CO2 are integrated over 100 years, N2O impacts are about 300 times greater than those of CO2. Increasing the atmospheric burden of N2O also decreases the abundance of O3 in the stratosphere. With reductions in emissions of ODSs as a result of the Montreal Protocol, N2O now has the largest ODP-weighted emissions of all gases. Given its long lifetime of about 130 years, today's emissions will impact climate and stratospheric O3 for a long time. Because emission rates are very small and spread over enormous areas, the detailed N2O budget has large uncertainties. It also means measurement requirements on precision and accuracy are stringent, especially for the background atmosphere. The Carbon Cycle Group of NOAA ESRL's Global Monitoring Division began measuring N2O in discrete air samples collected as part of its global cooperative air sampling network in 1998. Data from about 60 air sampling sites provide important constraints on the large-scale budget of N2O and provide boundary conditions for continental and regional-scale studies. This presentation will briefly describe the procedures used to ensure the data are of sufficient quality to meet scientific demands, and describe remaining limitations. Although sampling is infrequent (weekly), the data are quite useful in N2O budget studies. Examples will be given of large scale constraints on N2O's budget, including the global burden, trends in the burden, global emissions, spatial distributions, vertical gradients, and seasonal patterns.

  14. Diurnality of soil nitrous oxide (N2O) emissions

    NASA Astrophysics Data System (ADS)

    Gelfand, I.; Moyer, R.; Poe, A.; Pan, D.; Abraha, M.; Chen, J.; Zondlo, M. A.; Robertson, P.

    2015-12-01

    Soil emissions of nitrous oxide (N2O) are important contributors to the greenhouse gas balance of the atmosphere. Agricultural soils contribute ~65% of anthropogenic N2O emissions. Understanding temporal and spatial variability of N2O emissions from agricultural soils is vital for closure of the global N2O budget and the development of mitigation opportunities. Recent studies have observed higher N2O fluxes during the day and lower at night. Understanding the mechanisms of such diurnality may have important consequences for our understanding of the N cycle. We tested the hypothesis that diurnal cycles are driven by root carbon exudes that stimulate denitrification and therefore N2O production. Alternatively, we considered that the cycle could result from higher afternoon temperatures that accelerate soil microbial activity. We removed all plants from a corn field plot and left another plot untouched. We measured soil N2O emissions in each plot using a standard static chamber technique throughout the corn growing season. And also compared static chamber results to ecosystem level N2O emissions as measured by eddy covariance tower equipped with an open-path N2O sensor. We also measured soil and air temperatures and soil water and inorganic N contents. Soil N2O emissions followed soil inorganic N concentrations and in control plot chambers ranged from 10 μg N m-2 hr-1 before fertilization to 13×103 after fertilization. We found strong diurnal cycles measured by both techniques with emissions low during night and morning hours and high during the afternoon. Corn removal had no effect on diurnality, but had a strong effect on the magnitude of soil N2O emissions. Soil temperature exhibited a weak correlation with soil N2O emissions and could not explain diurnal patterns. Further studies are underway to explore additional mechanisms that might contribute to this potentially important phenomena.

  15. On the Global Oxygen Anomaly and Air-Sea Flux

    NASA Technical Reports Server (NTRS)

    Garcia, Hernan E.; Keeling, Ralph F.

    2001-01-01

    A new climatology of monthly air-sea oxygen fluxes throughout the ice-free surface global ocean is presented. The climatology is based on weighted linear least squares regressions using heat flux monthly anomalies for spatial and temporal interpolation of historical O2 data. The seasonal oceanic variations show that the tropical belt (20 S - 20 N) is characterized by relatively small air-sea fluxes when compared to the middle to high latitudes (40 deg - 70 deg). The largest and lowest seasonal fluxes occur during summer and winter in both hemispheres. By means of an atmospheric transport model we show that our climatology is in better agreement with the observed amplitude and phasing of the variations in atmospheric O2/N2 ratios because of seasonal air-sea exchanges at baseline stations in the Pacific Ocean than with previous air-sea O2 climatologies. Our study indicates that the component of the air-sea O2 flux that correlates with heat flux dominates the large-scale air-sea O2 exchange on seasonal timescales. The contribution of each major oceanic basin to the atmospheric observations is described. The seasonal net thermal (SNO(sub T)) and biological (SNO(sub B)) outgassing components of the flux are examined in relation to latitudinal bands, basin-wide, and hemispheric contributions. The Southern Hemisphere's SNO(sub B) (approximately 0.26 Pmol) and SNO(sub T) (approximately 0.29 Pmol) values are larger than the Northern Hemisphere's SNO(sub B) (approximately 0.15 Pmol) and SNO(sub T) (approximately 0.16 Pmol) values (1 Pmol = 10(exp 15) mol). We estimate a global extratropical carbon new production during the outgassing season of 3.7 Pg C (1 Pg = 10(exp 15) g), lower than previous estimates with air-sea O2 climatologies.

  16. The simultaneous measurement of low rates of CO2 and O2 exchange in biological systems.

    PubMed

    Willms, J R; Dowling, A N; Dong, Z M; Hunt, S; Shelp, B J; Layzell, D B

    1997-12-15

    An instrument for measuring low rates of biological O2 exchange using an open-flow gas analysis system is described. A novel differential O2 sensor that is capable of measuring as little as 0.4 Pa O2 against a back-ground of ambient air (20,900 Pa O2), yet has a dynamic range of +/- 2000 Pa O2 (i.e., +/- ca. 2% O2) is described. Baseline drift was typically less than 0.025 Pa min-1. The differential O2 sensor was incorporated into a respiratory quotient/photosynthetic quotient analyzer that contained other environmental sensors for atmospheric pressure, absolute O2 and CO2 concentration, temperature of the differential O2 sensor block, and differential pressure between reference and sample streams. Protocols for how these sensors can be used to calibrate the differential O2 sensor and to improve its stability with time are described. Together, the differential O2 sensor, the environmental sensors, and the simple calibration techniques allow for simultaneous, noninvasive, and accurate measurements of O2 and CO2 exchange in tissues with metabolic rates as low as about 0.1 mumol O2 or CO2 h-1. Example data are provided in which O2 differentials of 3 to 41 Pa O2 were measured in an open-flow system. PMID:9417789

  17. 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...

  18. Continuous Remote Measurements of Atmospheric O2 Concentrations in Relation to Interannual Variations in Biological Production and Carbon Cycling in the Oceans

    NASA Technical Reports Server (NTRS)

    Keeling, Ralph F.; Campbell, J. A. (Technical Monitor)

    2002-01-01

    We successfully initiated a program to obtain continuous time series of atmospheric O2 concentrations at a semi-remote coastal site, in Trinidad, California. The installation, which was completed in September 1999, consists of a commercially-available O2 and CO2 analyzers interfaced to a custom gas handling system and housed in a dedicated building at the Trinidad site. Ultimately, the data from this site are expected to provide constraints, complementing satellite data, on variations in ocean productivity and carbon exchange on annual and interannual time scales, in the context of human-induced changes in global climate and other perturbations. The existing time-series, of limited duration, have been used in support of studies of the O2/CO2 exchange from a wild fire (which fortuitously occurred nearby in October 1999) and to quantify air-sea N2O and O2 exchanges related to coastal upwelling events. More generally, the project demonstrates the feasibility of obtaining semi-continuous O2 time series at moderate cost from strategic locations globally.

  19. Alumina decorated TiO2 nanotubes with ordered mesoporous walls as high sensitivity NO(x) gas sensors at room temperature.

    PubMed

    Lü, Renjiang; Zhou, Wei; Shi, Keying; Yang, Ying; Wang, Lei; Pan, Kai; Tian, Chungui; Ren, Zhiyu; Fu, Honggang

    2013-09-21

    Alumina (Al2O3) decorated anatase TiO2 nanotubes with ordered mesoporous pore walls (Al2O3/meso-TiO2 nanotubes) are successfully synthesized through vacuum pressure induction technology, and then combined with the thermal decomposition of a mesoporous TiO2 sol precursor, inside the cylindrical nanochannels of an anodic aluminium oxide (AAO) template. The decorated Al2O3 was formed by in situ deposition via direct reaction of the strong acid sol precursor and the nanochannel wall of the AAO template. The resultant Al2O3/meso-TiO2 nanotubes are characterized in detail by transmission electron microscopy, scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and N2 adsorption-desorption. The experimental results reveal that the Al2O3/meso-TiO2 nanotubes have a tubular structure with an average diameter of ∼200 nm and highly ordered mesopores in the tubular walls. The Al2O3 is distributed evenly on the anatase TiO2 nanotubes. Moreover, the Al2O3/meso-TiO2 nanotubes possess a large specific surface area (136 m(2) g(-1)) and narrow mesopore size distribution (∼10 nm). By using NO(x) as a probe molecule, the Al2O3/meso-TiO2 nanotube films exhibit better sensing performance than that of mesoporous TiO2 nanotubes, in terms of their high sensitivity, fast response-recovery time, and good stability in air at room temperature. The outstanding performance in the gas sensing ability of Al2O3/meso-TiO2 nanotubes is a result of their one-dimensional tubular and mesoporous nanostructures, advantageous for the adsorption and diffusion of NO(x) gas. In addition, the sensing response is greatly improved by virtue of the decorated Al2O3 on the surfaces of the TiO2 nanotubes, which acts as an energy barrier to suppress charge recombination. The structural properties of the Al2O3/meso-TiO2 nanotubes makes them a viable novel gas sensor material at room temperature.

  20. Activated Carbon Composites for Air Separation

    SciTech Connect

    Baker, Frederick S; Contescu, Cristian I; Tsouris, Costas; Burchell, Timothy D

    2011-09-01

    Coal-derived synthesis gas is a potential major source of hydrogen for fuel cells. Oxygen-blown coal gasification is an efficient approach to achieving the goal of producing hydrogen from coal, but a cost-effective means of enriching O2 concentration in air is required. A key objective of this project is to assess the utility of a system that exploits porous carbon materials and electrical swing adsorption to produce an O2-enriched air stream for coal gasification. As a complement to O2 and N2 adsorption measurements, CO2 was used as a more sensitive probe molecule for the characterization of molecular sieving effects. To further enhance the potential of activated carbon composite materials for air separation, work was implemented on incorporating a novel twist into the system; namely the addition of a magnetic field to influence O2 adsorption, which is accompanied by a transition between the paramagnetic and diamagnetic states. The preliminary findings in this respect are discussed.

  1. Detection of room air contamination of angiographic CO2 with use of a gas analyzer.

    PubMed

    Culp, William C; Culp, William C

    2002-07-01

    The purpose of this study was to describe a practical method to detect room air contamination in CO2 used for angiography. Samples of CO2 with known room air contamination levels were used in a "bag system" of CO2 delivery and sampled by a gas analyzer commonly used in anesthesia. Nitrogen levels were reliably detected indicating contamination with as little as 2% air. Oxygen levels were reliably detected, indicating contamination with as little as 5% air. Measured CO2 values were unreliable with higher-than-true values at all levels except 100%. All clinically important amounts of N2 and O2 contamination were readily detected by this practical method.

  2. Plasmonic properties of Ag nanoparticles embedded in GeO2-SiO2 matrix by atom beam sputtering.

    PubMed

    Mohapatra, Satyabrata

    2016-02-01

    Nanocomposite thin films containing Ag nanoparticles embedded in the GeO2-SiO2 matrix were synthesized by the atom beam co-sputtering technique. The structural, optical and plasmonic properties and the chemical composition of the nanocomposite thin films were studied by transmission electron microscopy (TEM) with energy dispersive X-ray spectroscopy (EDX), UV-visible absorption spectroscopy and X-ray photoelectron spectroscopy (XPS). UV-visible absorption studies on Ag-SiO2 nanocomposites revealed the presence of a strong localized surface plasmon resonance (LSPR) peak characteristic of Ag nanoparticles at 413 nm, which showed a blue shift of 26 nm (413 to 387 nm) along with a significant broadening and drastic decrease in intensity with the incorporation of 16 at% of Ge into the SiO2 matrix. TEM studies on Ag-GeO2-SiO2 nanocomposite thin films confirmed the presence of Ag nanoparticles with an average size of 3.8 nm in addition to their aggregates with an average size of 16.2 nm. Thermal annealing in air resulted in strong enhancement in the intensity of the LSPR peak, which showed a regular red shift of 51 nm (from 387 to 438 nm) with the increase in annealing temperature up to 500 °C. XPS studies showed that annealing in air resulted in oxidation of excess Ge atoms in the nanocomposite into GeO2. Our work demonstrates the possibility of controllably tuning the LSPR of Ag nanoparticles embedded in the GeO2-SiO2 matrix by single-step thermal annealing, which is interesting for optical applications.

  3. Coherent Anti-Stokes Raman Scattering (CARS) as a Probe for Supersonic Hydrogen-Fuel/Air Mixing

    NASA Technical Reports Server (NTRS)

    Danehy, P. M.; O'Byrne, S.; Cutler, A. D.; Rodriguez, C. G.

    2003-01-01

    The dual-pump coherent anti-Stokes Raman spectroscopy (CARS) method was used to measure temperature and the absolute mole fractions of N2, O2 and H2 in a supersonic non-reacting fuel-air mixing experiment. Experiments were conducted in NASA Langley Research Center s Direct Connect Supersonic Combustion Test Facility. Under normal operation of this facility, hydrogen and air burn to increase the enthalpy of the test gas and O2 is added to simulate air. This gas is expanded through a Mach 2 nozzle and into a combustor model where fuel is then injected, mixes and burns. In the present experiment the O2 of the test gas is replaced by N2. The lack of oxidizer inhibited combustion of the injected H2 fuel jet allowing the fuel/air mixing process to be studied. CARS measurements were performed 427 mm downstream of the nozzle exit and 260 mm downstream of the fuel injector. Maps were obtained of the mean temperature, as well as the N2, O2 and H2 mean mole fraction fields. A map of mean H2O vapor mole fraction was also inferred from these measurements. Correlations between different measured parameters and their fluctuations are presented. The CARS measurements are compared with a preliminary computational prediction of the flow.

  4. Marine hypoxia/anoxia as a source of CH4 and N2O

    NASA Astrophysics Data System (ADS)

    Naqvi, S. W. A.; Bange, H. W.; Farías, L.; Monteiro, P. M. S.; Scranton, M. I.; Zhang, J.

    2010-07-01

    We review here the available information on methane (CH4) and nitrous oxide (N2O) from major marine, mostly coastal, oxygen (O2)-deficient zones formed both naturally and as a result of human activities (mainly eutrophication). Concentrations of both gases in subsurface waters are affected by ambient O2 levels to varying degrees. Organic matter supply to seafloor appears to be the primary factor controlling CH4 production in sediments and its supply to (and concentration in) overlying waters, with bottom-water O2-deficiency exerting only a modulating effect. High (micromolar level) CH4 accumulation occurs in anoxic (sulphidic) waters of silled basins, such as the Black Sea and Cariaco Basin, and over the highly productive Namibian shelf. In other regions experiencing various degrees of O2-deficiency (hypoxia to anoxia), CH4 concentrations vary from a few to hundreds of nanomolar levels. Since coastal O2-deficient zones are generally very productive and are sometimes located close to river mouths and submarine hydrocarbon seeps, it is difficult to differentiate any O2-deficiency-induced enhancement from in situ production of CH4 in the water column and its inputs through freshwater runoff or seepage from sediments. While the role of bottom-water O2-deficiency in CH4 formation appears to be secondary, even when CH4 accumulates in O2-deficient subsurface waters, methanotrophic activity severely restricts its diffusive efflux to the atmosphere. As a result, an intensification or expansion of coastal O2-deficient zones will probably not drastically change the present status where emission from the ocean as a whole forms an insignificant term in the atmospheric CH4 budget. The situation is different for N2O, the production of which is greatly enhanced in low-O2 waters, and although it is lost through denitrification in most suboxic and anoxic environments, the peripheries of such environments offer most suitable conditions for its production, with the exception of

  5. Bootstrapping N=2 chiral correlators

    NASA Astrophysics Data System (ADS)

    Lemos, Madalena; Liendo, Pedro

    2016-01-01

    We apply the numerical bootstrap program to chiral operators in four-dimensional N=2 SCFTs. In the first part of this work we study four-point functions in which all fields have the same conformal dimension. We give special emphasis to bootstrapping a specific theory: the simplest Argyres-Douglas fixed point with no flavor symmetry. In the second part we generalize our setup and consider correlators of fields with unequal dimension. This is an example of a mixed correlator and allows us to probe new regions in the parameter space of N=2 SCFTs. In particular, our results put constraints on relations in the Coulomb branch chiral ring and on the curvature of the Zamolodchikov metric.

  6. Photocatalytic Performance of a Nd-SiO2-TiO2 Nanocomposite for Degradation of Rhodamine B Dye Wastewater.

    PubMed

    Li, Jinlong; Liu, Tao; Sui, Guozhe; Zhen, Deshuai

    2015-02-01

    The photocatalytic performance of a novel Nd-SiO2-TiO2 nanocomposite catalyst prepared by a sol-gel method was examined in the degradation of Rhodamine B (RhB), a notorious organic compound present in dye wastewaters. The prepared samples were characterized by low-temperature N2 adsorption, X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV-vis diffuse reflectance spectroscopy (DRS). Fourier-transform infrared (FT-IR) spectroscopic analysis indicated the enhanced chemical bonding of O--Ti and O--Ti--O with introduction of Nd and SiO2 dopant species into TiO2. The Nd-SiO2-TiO2 nanocomposite was found to exhibit a much higher photo- catalytic activity toward the decomposition of RhB under both UV and visible light irradiation as compared to a commercial TiO2 photocatalyst. The photodegradation efficiency of RhB (5 mg/L) was greater than 93% under visible light irradiation after 90 min. Addition of SiO2 was shown to not only inhibit crystal growth and TiO2 anatase-to-rutile phase transformation, but also enhance the adsorption of organic compounds. Nd doping has been suggested for slowing down the radiative recombination of photo-generated electrons and holes in TiO2, extending the photocatalyst light response to the visible region. The synergetic effects between Nd-SiO2 and TiO2 are described; the prepared Nd-SiO2-TiO2 represents a noteworthy contribution to the study of pollutant degradation in dye wastewaters.

  7. The Impact of Iron on Soil N2O Production Depends on Oxygen Availability

    NASA Astrophysics Data System (ADS)

    Zhu, X.; Doane, T. A.; Burger, M.; Horwath, W. R.

    2014-12-01

    The continuous increase of nitrous oxide (N2O) abundance in the atmosphere is a global concern. Soils are both an important source and sink of N2O, which is produced and consumed through biological processes including ammonia oxidation, heterotrophic denitrification, codenitrification, and through abiotic processes such as chemodenitrification. Iron is the most abundant element in the earth and is also the most prevalent redox-active metal in the biosphere. Its role in both chemical and biochemical reactions in N biogeochemistry cycling is well recognized. However, iron's significance to N2O production is poorly understood, especially under varying O2 concentration. We examined N2O production under different O2 concentrations following amorphous iron (III) oxyhydroxide and ammonical N fertilizer additions in four soil slurries and two static soils (soil moisture was 50% of water holding capacity). Under 21% O2, the addition of iron (III) significantly decreased N2O production in all the soil slurries and static soils, while the opposite phenomenon was observed once the O2 concentration became limited (≤3% in the soil slurry and ≤0.5% in the static soil). Our results show that the influence of iron on soil N2O production depends on O2 availability, which is the dominant controller of N2O production pathways. We hypothesize that under ambient O2 conditions, iron can react with nitrite produced during ammonia oxidation, thus reducing the probability of NO2- being used by nitrifiers as electron acceptor in nitrifier denitrification. In contrast, under anaerobic conditions (O2<0.5%), less nitrite was detected in the presence of the iron addition. Under these conditions, iron may have inhibited N2O reductase, or reduced iron (II) reacted with nitrite, both of which would lead to greater release of N2O.These findings imply that management practices which focus on mitigating N2O emission should avoid the application of iron-rich materials such as biosolids when

  8. Well-organized meso-macroporous TiO2/SiO2 film derived from amphiphilic rubbery comb copolymer.

    PubMed

    Jeon, Harim; Lee, Chang Soo; Patel, Rajkumar; Kim, Jong Hak

    2015-04-15

    We report the facile synthesis of a well-organized meso-macroporous TiO2/SiO2 thin film with high porosity and good interconnectivity from a binary mixture (i.e., titania precursor and polymer template). Our process is based on self-assembly of the amphiphilic rubbery comb copolymer, poly(dimethylsiloxane)-g-poly(oxyethylene methacrylate) (PDMS-g-POEM) with titanium tetraisopropoxide (TTIP). SiO2 is self-provided by thermal oxidation of PDMS chains during calcination under air. The selective, preferential interaction between TTIP and the hydrophilic POEM chains was responsible for the formation of well-organized TiO2/SiO2 films, as supported by transmission electron microscopy, scanning electron microscopy, X-ray photospectroscopy, and X-ray diffraction analyses. We investigated in detail the effect of precursor content, solvent type, and polymer concentration on thin film morphology. Photodegradation of methyl orange by the well-organized meso-macroporous TiO2/SiO2 film was greater than that of a dense TiO2 film prepared without PDMS-g-POEM as well as a SiO2-etched TiO2 film. These results indicate that the well-organized structure and SiO2 doping of the TiO2 film play a pivotal role in enhancing its photocatalytic properties. PMID:25805232

  9. On the Δ17O budget of atmospheric O2

    NASA Astrophysics Data System (ADS)

    Young, Edward D.; Yeung, Laurence Y.; Kohl, Issaku E.

    2014-06-01

    We modeled the Δ17O of atmospheric O2 using 27 ordinary differential equations comprising a box model composed of the stratosphere, troposphere, geosphere, hydrosphere and biosphere. Results show that 57% of the deficit in 17O in O2 relative to a reference water fractionation line is the result of kinetic isotope fractionation attending the Dole effect, 33% balances the positive Δ17O of O(1D) in the stratosphere, and 10% is from evapotranspiration. The predicted Δ‧17O O2 relative to waters is -0.410‰ as measured at the δ18O of air. The value for Δ‧17O O2 varies at fixed δ18O with the concentration of atmospheric CO2, gross primary production, and net primary production as well as with reaction rates in the stratosphere. Our model prediction is consistent with our measurements of the oxygen isotopic composition of air O2 compared with rocks if rocks define a fractionation line with an intercept in δ‧17O = 103ln(δ17O/103 + 1) vs. δ‧18O = 103ln(δ18O/103 + 1) space less than SMOW but more positive than some recent measurements imply. The predicted Δ17O is less negative than that obtained from recent measurements of O2 directly against SMOW. Underestimation of Δ‧17O O2 can only be ameliorated if the integrated (bulk) Δ‧17O for stratospheric CO2 is significantly greater than measurements currently allow. Our results underscore the need for high-precision comparisons of the 17O/16O and 18O/16O ratios of atmospheric O2, VSMOW, and rocks.

  10. Effect of hydrolysis ratio on structural, optical and electrical properties of SnO2 nanoparticles synthesized by polyol method

    NASA Astrophysics Data System (ADS)

    Soltan, Wissem Ben; Mbarki, Mourad; Bargougui, Radhouane; Ammar, Salah; Babot, Odile; Toupance, Thierry

    2016-08-01

    Using the polyol method and a thermal post-treatment, nanoporous tin dioxide (SnO2) were prepared at different hydrolysis ratio (h = n (H2O)/n (Sn)). The influence of the hydrolysis ratio on the structural, textural, optical and electrical properties of SnO2 nanopowders was investigated by employing a set of various techniques including Fourier Transform Infra-Red spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), Energy Dispersive X-ray spectroscopy (EDX), Scanning Electron Microscopy (SEM), Nitrogen Sorption Porosimetry and Impedance Spectroscopy. FTIR and EDX studies revealed that SnO2 species were obtained. Nanocrystallites of cassiterite, i.e. rutile-like tetragonal SnO2 structure, were formed after annealing in air at 700 °C and the average crystallite size increased from 12.8 to 29.1 when the hydrolysis ratio rose from 17 to 24. Moreover, TEM, SEM, and N2 sorption porosimetry investigations indicated that the sample prepared for h = 17 was composed of an aggregated network of almost spherical nanoparticles, the morphology and sizes of which changed with the increase in the hydrolysis ratio to h = 24 and the mesoporosity of which was found to be linked to the interparticle space. Moreover, this increase in mean nanoparticle size was accompanied by a decrease in the band gap value from 3.4 eV (h = 17) to 3.16 eV (h = 24). Finally, bulk conductivity dependence with temperature was found to follow an Arrhenius law for samples annealed at 700 °C with an activation energy of 0.65 eV for h = 17, 0.69 eV for h = 20 and 0.71 eV for h = 24 that is typical of SnO2 nanopowders.

  11. Comparative study of Laser induce damage of HfO2/SiO2 and TiO2/SiO2 mirrors at 1064 nm.

    PubMed

    Jiao, Hongfei; Ding, Tao; Zhang, Qian

    2011-02-28

    A comparative study of laser induced damage of HfO2/SiO2 and TiO2/SiO2 mirrors at 1064 nm has been carried out. One TiO2/SiO2 mirror with absorption of 300 ppm and two HfO2/SiO2 mirrors with absorption of 40 and 4.5 ppm were fabricated using electron beam evaporation method. For r-on-1 test, all HfO2/SiO2 mirrors with low average absorption are above 150 J/cm2 at 10 ns. However, the TiO2/SiO2 mirrors with high average absorption are just 9.5 J/cm2, which are probably due to the rather high absorption and rather low band gap energy. Meanwhile, all the samples were irradiated from front and back side respectively using the raster scan test mode. In case of front side irradiation, it is found that: for TiO2/SiO2 high reflectors, the representative damage morphologies are shallow pits that were probably caused by absorbing centers. However, for HfO2/SiO2 high reflectors, the dominant damage morphologies are micrometer-sized nodules ejected pits and the delamination initiating from the pits. The absorption of HfO2/SiO2 coatings is low enough to have minor influence on the laser damage resistance. In case of backside irradiation, the morphology of TiO2/SiO2 mirrors is mainly center melted pits that are thermal melting induced damage. Meanwhile, HfO2/SiO2 mirrors with isometrical fracture rings damage morphology are thermal induced stress damage.

  12. 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-.

  13. TiO2-BASED Composite Films for the Photodegradation of Oxytetracycline

    NASA Astrophysics Data System (ADS)

    Li, Hui; Guan, Ling-Xiao; Feng, Ji-Jun; Li, Fang; Yao, Ming-Ming

    2015-02-01

    The spread of the antibiotic oxytetracycline (OTC) has been thought as a threat to the safety of drinking water. In this paper, the photocatalytic activity of the nanocrystalline Fe/Ca co-doped TiO2-SiO2 composite film for the degradation of OTC was studied. The films were characterized by field emission scanning electron microscopy (FE-SEM) equipped with energy-dispersive spectroscopy (EDS), N2 adsorption/desorption isotherms, photoluminescence (PL) spectra, and UV-Vis diffraction reflectance absorption spectra (DRS). The FE-SEM results indicated that the Fe/Ca co-doped TiO2-SiO2 film was composed of smaller nanoparticles compared to pure TiO2 or TiO2-SiO2 film. The BET surface area results showed that the specific surface area of the pure TiO2, TiO2-SiO2 and Ca2+/Fe3+ co-doped TiO2-SiO2 is 118.3 m2g-1, 294.3 m2g-1 and 393.7 m2g-1, respectively. The DRS and PL spectra revealed that the Fe/Ca co-doped TiO2-SiO2 film had strong visible light adsorption and diminished electrons/holes recombination. Experimental results showed that the Fe/Ca co-doped TiO2-SiO2 film is effective in the degradation of OTC under both UV and visible light irradiation.

  14. Orientation-Dependent Oxygen Evolution Activities of Rutile IrO2 and RuO2.

    PubMed

    Stoerzinger, Kelsey A; Qiao, Liang; Biegalski, Michael D; Shao-Horn, Yang

    2014-05-15

    The activities of the oxygen evolution reaction (OER) on IrO2 and RuO2 catalysts are among the highest known to date. However, the intrinsic OER activities of surfaces with defined crystallographic orientations are not well-established experimentally. Here we report that the (100) surface of IrO2 and RuO2 is more active in alkaline environments (pH 13) than the most thermodynamically stable (110) surface. The OER activity was correlated with the density of coordinatively undersaturated metal sites of each crystallographic facet. The surface-orientation-dependent activities can guide the design of nanoscale catalysts with increased activity for electrolyzers, metal-air batteries, and photoelectrochemical water splitting applications. PMID:26270358

  15. Laser induced fluorescence studies of iodine oxide chemistry. Part II. The reactions of IO with CH3O2, CF3O2 and O3.

    PubMed

    Dillon, Terry J; Tucceri, María E; Crowley, John N

    2006-11-28

    The technique of pulsed laser photolysis was coupled to laser induced fluorescence detection of iodine oxide (IO) to measure rate coefficients, k for the reactions IO + CH(3)O(2)--> products (R1, 30-318 Torr N(2)), IO + CF(3)O(2)--> products (R2, 70-80 Torr N(2)), and IO + O(3)--> OIO + O(2) (R3a). Values of k(1) = (2 +/- 1) x 10(-12) cm(3) molecule(-1) s(-1), k(2) = (3.6 +/- 0.8) x 10(-11) cm(3) molecule(-1) s(-1), and k(3a) <5 x 10(-16) cm(3) molecule(-1) s(-1) were obtained at T = 298 K. In the course of this work, the product yield of IO from the reaction of CH(3)O(2) with I was determined to be close to zero, whereas CH(3)OOI was formed efficiently at 70 Torr N(2). Similarly, no evidence was found for IO formation in the CF(3)O(2) + I reaction. An estimate of the rate coefficients k(CH(3)O(2) + I) = 2 x 10(-11) cm(3) molecule(-1) s(-1) and k(CH(3)OOI + I) = 1.5 x 10(-10) cm(3) molecule(-1) s(-1) was also obtained. The results on k(1)-k(3) are compared to the limited number of previous investigations and the implications for the chemistry of the marine boundary layer are briefly discussed.

  16. NO reduction by CO over CuO supported on CeO2-doped TiO2: the effect of the amount of a few CeO2.

    PubMed

    Deng, Changshun; Li, Bin; Dong, Lihui; Zhang, Feiyue; Fan, Minguang; Jin, Guangzhou; Gao, Junbin; Gao, Liwen; Zhang, Fei; Zhou, Xinpeng

    2015-06-28

    This work is mainly focused on the investigation of the influence of the amount of a few CeO2 on the physicochemical and catalytic properties of CeO2-doped TiO2 catalysts for NO reduction by a CO model reaction. The obtained samples were characterized by means of XRD, N2-physisorption (BET), LRS, UV-vis DRS, XPS, (O2, CO, and NO)-TPD, H2-TPR, in situ FT-IR, and a NO + CO model reaction. These results indicate that a small quantity of CeO2 doping into the TiO2 support will cause an obvious change in the properties of the catalyst and the TC-60 : 1 (the TiO2/CeO2 molar ratio is 60 : 1) support exhibits the most extent of lattice expansion, which indicates that the band lengths of Ce-O-Ti are longer than other TC (the solid solution of TiO2 and CeO2) samples, probably contributing to larger structural distortion and disorder, more defects and oxygen vacancies. Copper oxide species supported on TC supports are much easier to be reduced than those supported on the pure TiO2 and CeO2 surface-modified TiO2 supports. Furthermore, the Cu/TC-60 : 1 catalyst shows the highest activity and selectivity due to more oxygen vacancies, higher mobility of surface and lattice oxygen at lower temperature (which contributes to the regeneration of oxygen vacancies, and the best reducing ability), the most content of Cu(+), and the strongest synergistic effect between Ti(3+), Ce(3+) and Cu(+). On the other hand, the CeO2 doping into TiO2 promotes the formation of a Cu(+)/Cu(0) redox cycle at high temperatures, which has a crucial effect on N2O reduction. Finally, in order to further understand the nature of the catalytic performances of these samples, taking the Cu/TC-60 : 1 catalyst as an example, a possible reaction mechanism is tentatively proposed.

  17. Trapped Air in Glacial Ice from the base of Penny, Agassiz, and Devon Ice Caps, Canada

    NASA Astrophysics Data System (ADS)

    Yau, A. M.; Fisher, D.

    2013-12-01

    Basal ice from the Canadian Arctic ice caps, Penny, Agassiz, and Devon, has long been suggested to date back into the last interglacial, or Stage 5e. Cores from all three ice caps contain long Holocene sections with heavy δ18Oice values, overlaying condensed glacial sections with light δ18Oice values, which are underlain by ~1-7 m of ice with δ18Oice values similar to that of the Holocene, suggesting accumulation during the last interglacial. However, the origin of the ice, whether the ice is regelation/segregated or pristine glacial ice has been debated, with important implications as to whether or not ice caps in the Canadian arctic persisted through the last interglacial. Here we present analyses of the trapped air from the bottom portions of Penny, Agassiz, and Devon ice caps to provide context about the nature of the basal ice. Geochemical analyses of N2/Ar, O2/Ar, O2/N2, δ15N2, δ18OATM, and total air content (TAC) indicate a spectrum of ice conditions in basal ice. Low N2/Ar ratios and low TAC indicate partial melting in some of the samples from all three ice caps. High δ15N2, high TAC, and N2/Ar ratios close to air indicate that clean glacial ice is also present in the basal section of each ice cap. Low O2/Ar and high δ18OATM indicates microbial respiration in most samples. The lowest δ18OATM values, near 0‰, indicate trapped air ages >80 ka for the Devon and Agassiz ice caps.

  18. Drift and reactions of positive tetratomic ions in dry, atmospheric air: Their effects on the dynamics of primary and secondary streamers

    NASA Astrophysics Data System (ADS)

    Bekstein, A.; Yousfi, M.; Benhenni, M.; Ducasse, O.; Eichwald, O.

    2010-05-01

    The ion swarm data, namely, the reduced mobility, diffusion, and reaction rates of the positive tetratomic ions O4+ and N2O2+ in N2 and O2 have been determined from a Monte Carlo simulation using calculated and fitted elastic and inelastic cross sections. The elastic momentum transfer cross sections have been determined from a semiclassical Jeffreys-Wentzell-Kramers-Brilouin (JWKB) approximation based on a rigid core potential model well adapted for polyatomic ions. The inelastic cross sections have been approximated from considerations based on the N4+/O2 and N4+/N2 systems. The validated cross section sets in pure N2 and O2 have been used to determine the O4+ and N2O2+ swarm data in dry air over a large E/N range up to 1000 Td. However, due to the lack of experimental ion transport coefficients necessary for a more rigorous cross section validation, the present data, validated only at low E/N, should be regarded as a first approximation, susceptible to improvements as soon as measurements of ion transport coefficients become available in the literature. Then, the present data are used in a two-dimensional discharge dynamics fluid model for the simulation of the primary and secondary streamers for the case of a positive point-to-plane corona discharge in dry air. Relevant characteristics such as discharge current, charged particle densities, space charge electric field and the variation in active species like N and O radicals (very useful in many nonthermal plasma applications) are analyzed and discussed with and without the consideration of three positive tetratomic ions (N4+, O4+, and N2O2+). More particularly, the non-negligible effect of O4+, in the dynamics of the primary and secondary streamers during the discharge propagation and relaxation stages is highlighted with an emphasis on the role of the related kinetic reactions occurring between the different charged particles.

  19. Analysis of the N2O dissociation in a RF discharge reactor

    NASA Astrophysics Data System (ADS)

    Date, L.; Radouane, K.; Despax, B.; Yousfi, M.; Caquineau, H.; Hennad, A.

    1999-07-01

    In situ diagnostic measurements and reactor modelling are used to study the N2O dissociation by radio frequency (RF) discharges. Measurements are undertaken at 0.5 and 1 Torr gas pressure with a RF power density varying from 4.2 to 35.7 mW cm-2. The reactor modelling involves an electrical discharge model coupled to hydrodynamic and mass transfer models. Only an electrical discharge model accounting for the negative ion conversion from O- to NO- and the subsequent electron detachment allow a good coherence between the measured and predicted power densities. The electron-N2O dissociation cross sections are first fitted in the present work and then the corresponding dissociation rates, obtained from the electrical model, are used in the mass transfer model which includes eight species (N2O, N2, O2, NO, NO2, N, O(3P) and O(1D)). The corresponding results are in good agreement with the experimental ones related to the production of N2 and O2 and the consumption of N2O. Furthermore, the reactor model results show that N2 and O2 are the most abundant products (>1014 molecules/cm3) at 1 Torr.

  20. Effect of sintering procedures in development of LiCoO 2-cathodes for the molten carbonate fuel cell

    NASA Astrophysics Data System (ADS)

    Lundblad, Anders; Schwartz, Stephan; Bergman, Bill

    LiCoO 2-powder was synthesized from carbonate precursors by calcination in air. Greentapes were tape-cast using a non-aqueous slurry and 10 μm plastic spheres as pore formers. Sintering was carried out in air at 850-950°C and in argon/air at 500/750°C. The two sintering procedures led to very different sub-micron morphologies, with the primary particles being much smaller in the latter case. The electrochemical performance at 650°C, in terms of overpotential at 160 mA/cm 2, for the air- and argon/air-sintered electrodes was 57 and 81 mV, respectively. The potential drop due to contact resistance between electrode and current collector was estimated to be 100 and 70 mV, respectively. The electrode materials were characterized by scanning electron microscopy (SEM), Hg-porosimetry, the BET-method (N 2-adsorption), X-ray diffractometry (XRD), flame atomic absorption spectrometry (F-AAS), carbon analysis and a van der Pauw conductivity measurement set-up.

  1. Ion swarm data for electrical discharge modeling in air and flue gas mixtures

    NASA Astrophysics Data System (ADS)

    Nelson, D.; Benhenni, M.; Eichwald, O.; Yousfi, M.

    2003-07-01

    The first step of this work is the determination of the elastic and inelastic ion-molecule collision cross sections for the main ions (N2+, O2+, CO2+, H2O+ and O-) usually present either in the air or flue gas discharges. The obtained cross section sets, given for ion kinetic energies not exceeding 100 eV, correspond to the interactions of each ion with its parent molecule (symmetric case) or nonparent molecule (asymmetric case). Then by using these different cross section sets, it is possible to obtain the ion swarm data for the different gas mixtures involving N2, CO2, H2O and O2 molecules whatever their relative proportions. These ion swarm data are obtained from an optimized Monte Carlo method well adapted for the ion transport in gas mixtures. This also allows us to clearly show that the classical linear approximations usually applied for the ion swarm data in mixtures such as Blanc's law are far to be valid. Then, the ion swarm data are given in three cases of gas mixtures: a dry air (80% N2, 20% O2), a ternary gas mixture (82% N2, 12% CO2, 6% O2) and a typical flue gas (76% N2, 12% CO2, 6% O2, 6% H2O). From these reliable ion swarm data, electrical discharge modeling for a wire to plane electrode configuration has been carried out in these three mixtures at the atmospheric pressure for different applied voltages. Under the same discharge conditions, large discrepancies in the streamer formation and propagation have been observed in these three mixture cases. They are due to the deviations existing not only between the different effective electron-molecule ionization rates but also between the ion transport properties mainly because of the presence of a highly polar molecule such as H2O. This emphasizes the necessity to properly consider the ion transport in the discharge modeling.

  2. PAMAM-grafted TiO2 nanotubes as novel versatile materials for drug delivery applications.

    PubMed

    Torres, Cecilia C; Campos, Cristian H; Diáz, Carola; Jiménez, Verónica A; Vidal, Felipe; Guzmán, Leonardo; Alderete, Joel B

    2016-08-01

    PAMAM-grafted TiO2 nanotubes (PAMAM-TiO2NT) have been synthesized and evaluated as new drug nanocarriers, using curcumin (CUR), methotrexate (MTX), and silibinin (SIL) as model therapeutic compounds. TiO2NT were surface-modified using a silane coupling agent and subsequently conjugated with PAMAM dendrimer of the third generation. The characterization of PAMAM-TiO2NT nanomaterials was performed by FTIR, TEM, N2 adsorption-desorption isotherms, XRD, and TGA techniques, which accounted for a 2.6wt.% of PAMAM grafting in the prepared materials. The drug loading capacity, drug release properties, and cytotoxicity of PAMAM-TiO2NT showed a significant improvement compared to pristine TiO2NT, thus revealing the promising properties of these new materials for drug delivery purposes. PMID:27157739

  3. Growth of TiO2 with thermal and plasma enhanced atomic layer deposition.

    PubMed

    Tallarida, Massimo; Friedrich, Daniel; Städter, Matthias; Michling, Marcel; Schmeisser, Dieter

    2011-09-01

    We show a comparative study of the TiO2 ALD with TTIP and either O2 or O2-plasma on Si/SiO2 substrates. In particular we compare the surface morphology and crystalline phase by means of Atomic Force Microscopy (AFM), X-ray Photoelectron Spectroscopy (XPS) and X-ray Absorption Spectroscopy (XAS) for different O2-plasma procedures upon changing the time between cycles and the N2-purging pressure. The AFM images show that already these parameters may induce structural changes in the TiO2 films grown by ALD, with the formation of crystallites with average lateral width varying between 15 and 80 nm. By means of XAS we also found that the crystallites have mixed anatase and rutile crystalline phases and that smaller crystallites have a greater rutile component than the larger ones. PMID:22097528

  4. An integrated regenerative air revitalization system for spacecraft

    NASA Technical Reports Server (NTRS)

    Noyes, G. P.; Heppner, D. B.; Schubert, F. H.; Quattrone, P. D.

    1982-01-01

    Progress towards development of an air revitalization system (ARS) for spacecraft breathable atmosphere regeneration is assessed, and a preliminary design for a one-person ARS is described. The ARS is considered a necessary component of any permanently manned orbital station, and studies have demonstrated that penalties for expendable air supplies justify an ARS for missions longer than 40 days. CO2 must be removed and O2 returned along with N2, which can be extracted from hydrazine, with the H2 component returning to the operation of the CO2 reduction subsystem. An experimental ARS (ARX-1) features a cabin humidity control unit, a CO2 concentrator, an air-cooled CO2 reduction reactor, an oxygen generator (electrolysis), the hydrazine N2 generator, and a water handling unit. A 120-day test demonstrated one-button startup and 480 hr operation in a normal mode.

  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. Oxygen adsorption at noble metal/TiO2 junctions

    NASA Astrophysics Data System (ADS)

    Hossein-Babaei, F.; Alaei-Sheini, Navid; Lajvardi, Mehdi M.

    2016-03-01

    Electric conduction in titanium dioxide is known to be oxygen sensitive and the conductivity of a TiO2 ceramic body is determined mainly by the concentration of its naturally occurring oxygen vacancy. Recently, fabrications and electronic features of a number of noble metal/TiO2-based electronic devices, such as solar cells, UV detectors, gas sensors and memristive devices have been demonstrated. Here, we investigate the effect of oxygen adsorption at the noble metal/TiO2 junction in such devices, and show the potentials of these junctions in chemical sensor fabrication. The polycrystalline, poly-phase TiO2 layers are grown by the selective and controlled oxidation of titanium thin films vacuum deposited on silica substrates. Noble metal thin films are deposited on the oxide layers by physical vapor deposition. Current-voltage (I-V) diagrams of the fabricated devices are studied for Ag/, Au/, and Pt/TiO2 samples. The raw samples show no junction energy barrier. After a thermal annealing in air at 250° C, I-V diagrams change drastically. The annealed samples demonstrate highly non-linear I-V indicating the formation of high Schottky energy barriers at the noble metal/TiO2 junctions. The phenomenon is described based on the effect of the oxygen atoms adsorbed at the junction.

  7. Chemical aspects in thermal treatment of ZrO 2CeO 2Y 2O 3 alloy

    NASA Astrophysics Data System (ADS)

    Ingo, G. M.; Righini, G.; Scoppio, L.

    By means of X-ray photoelectron spectroscopy (XPS), simultaneous differential thermal analysis (DTA) and thermogravimetric analysis (TGA), changes of valence state and surface chemical composition of a 25.5CeO 22.5Y 2O 372ZrO 2 (percentages by weight) fine powder, suitable for producing sintered components, have been studied as a function of temperature (up to 1550°C) and atmosphere (flowing N 2(90%)-H 2(10%) and static air). XPS results lead to the evaluation of the valence state of cerium, zirconium and yttrium both in the starting powder and in thermal-treated powders. In particular, the analysis of the characteristic satellite structure, binding energy and peak lineshape in the Ce3d spectra show that cerium in the starting powder is confirmed to be Ce(IV) with a small amount of Ce(III) and that after the thermal treatments cerium is either unaffected, partially or fully reduced to Ce(III). DTA and TGA thermograms confirm this redox behaviour and show, for static-air treatment, the presence of a strong and sharp exothermic peak at about 410°C, which is interpreted as being due to the oxidation of a small amount of Ce 2O 3. On the contrary, under reducing conditions in the range 630 to 730°C, the powder is affected by a remarkable weight loss owing to the Ce(IV) reduction to Ce(III) oxide. The change of valence state of zirconium, due to the reduction of ZrO 2 to Zr 2O 3, under reducing condition at 1050°C has been also monitored by XPS. Furthermore, starting from ≥ 900°C. XPS results show the occurennce of segregation phenomena of both bulk-dissolved impurities, such as silicon, sodium, iron and aluminium as well as of yttrium-stabilizing oxide. The Wagner two-dimensional chemical state plots for silicon and aluminium indicate that the chemical nature of the segregated phase is ascribable to an infinite chain silicate of sodium and yttrium with the presence of aluminium at higher temperatures. The effect of the aforecited chemical aspects on the

  8. Temperature Dependence of O2(b1Σ ^+g, v = 0 and 1) Relative Yield in O(1D) + O2 Energy Transfer

    NASA Astrophysics Data System (ADS)

    Kostko, O.; Raj, S.; Campbell, K.; Pejakovic, D. A.; Kalogerakis, K.

    2011-12-01

    Energy transfer from excited O(1D) atoms to ground-state O2(X3Σ ^-g) leads to production of O2 in the first two vibrational levels of the O2 (b1Σ ^+g) state: O(1D) + O2 -> O(3P) + O2(b1Σ ^+g, v = 0, 1). Subsequent radiative decay of O2(b1Σ ^+g, v = 0, 1) to the ground state results in the Atmospheric Band emission, a prominent feature of the terrestrial airglow. The relative yield for production of O2(b1Σ ^+g, v = 0 and 1) in the above process, k1/k0, is an important parameter in modeling of the observed Atmospheric Band emission intensities. Recent measurements at room temperature have shown that production of O2(b1Σ ^+g, v = 1) dominates that of O2(b1Σ ^+g, v = 0), with k1/k0 having a value of approximately 3.5 [1]. In the laboratory experiments, the output of a pulsed fluorine laser at 157 nm is used to photodissociate molecular oxygen in an O2/N2 mixture flowing through a heated gas cell. Photodissociation of O2 produces a ground-state O(3P) atom and an excited O(1D) atom. O(1D) rapidly transfers energy to the remaining O2 to produce O2(b1Σ ^+g, v = 0, 1). The populations of O2(b1Σ ^+g, v = 0 and 1) are monitored by observing emissions in the O2(b--X) 0--0 and 1--0 bands at 762 and 688 nm, respectively. The value of k1/k0 is extracted from the time-dependent O2(b1Σ ^+g, v = 0 and 1) fluorescence signals using computer simulations. We will present measurements on the temperature dependence of k1/k0 and discuss their atmospheric significance. This work was supported by the US National Science Foundation (NSF) Aeronomy Program under grant AGS-0937317. The fluorine laser was purchased under grant ATM-0216583 from the NSF Major Research Instrumentation Program. S. Raj and K. M. Campbell participated in a Research Experiences for Undergraduates (REU) site, co-funded by the Division of Physics of the NSF and the Department of Defense in partnership with the NSF REU program under grant PHY-1002892. [1] K. S. Kalogerakis, D. A. Pejaković, R. A. Copeland, T. G

  9. Temporal and latitudinal distributions of stratospheric N2O isotopomers

    NASA Astrophysics Data System (ADS)

    Toyoda, Sakae; Yoshida, Naohiro; Urabe, Taichiro; Nakayama, Yusuke; Suzuki, Takeshi; Tsuji, Kazuhide; Shibuya, Kazuhiko; Aoki, Shuji; Nakazawa, Takakiyo; Ishidoya, Shigeyuki; Ishijima, Kentaro; Sugawara, Satoshi; Machida, Toshinobu; Hashida, Gen; Morimoto, Shinji; Honda, Hideyuki

    2004-04-01

    Temporal and latitudinal variations of vertical profiles of N2O isotopomers were observed in the stratosphere over Japan (39°N, 142°E), Sweden (68°N, 20°E), and Antarctica (69°N, 40°E) during the period between 1990 and 2001. Samples were collected with a balloon-borne cryogenic sampler and analyzed by mass spectrometry in the laboratory. Observed enrichment factors for heavier isotopomers (15N14N16O, 14N15N16O, and 14N14N18O) relative to 14N14N16O were nearly constant in the lower stratosphere (less than ˜22 km) but increased at higher altitudes (˜22-35 km) while showing seasonal and latitudinal differences. Enrichment factors during the photolysis and photo-oxidation of N2O were also obtained in laboratory experiments and compared with those observed. We found that in the higher-altitude region (1) fractionation of the isotopomers is mainly determined by photolysis, but is also affected by physical processes, (2) subsidence of air masses in the winter polar vortex induces the intrusion of an upper stratospheric air mass depleted in N2O, and (3) decay of the vortex in the local spring leads to rapid horizontal advection of midlatitude air masses. At lower altitudes, isotopomer ratios are determined by photolysis, photo-oxidation, and the mixing of air masses within the stratosphere or between the stratosphere and the troposphere. Secular trend of isotopomer profiles was not detectable over Japan during 11 years. Assuming that the lower stratospheric air over midlatitudes is exchanged with the troposphere, isotopomer ratios of the N2O "back-flux" from the stratosphere were estimated. These values can be used in the isotopomeric mass balance model to constrain the global N2O budget.

  10. 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.

  11. Highly branched RuO2 Nanorods on Electrospun TiO2 Nanofibers toward Electrochemical Catalysts

    NASA Astrophysics Data System (ADS)

    Cho, Yukyung; Kim, Su-Jin; Lee, Nam-Suk; Kim, Myung Hwa; Lee, Youngmi

    2014-03-01

    We report a facile growth route to synthesize hierarchically grown single crystalline metallic RuO2 nanorods on electrospun TiO2 nanofibers via a combination of a simple vapour phase transport process with an electrospinning process. This synthetic strategy could be very useful to design a variety of highly branched network architectures of the functional hetero-nanostructures for electrochemical applications. Particularly, Ruthenium oxide (RuO2) 1-dimensional nanostructures can be used as the effective catalysts or electrochemical electrode materials. Thus, we first synthesize TiO2 nanofibers from mixture of titanium isopropoxide precursor and polymer and then ruthenium hydroxide precursor on TiO2 nanofibers are transformed into RuO2 nanorods by thermal treatment at 250oC in air. The crystalline structures of products are confirmed using scanning electron microscopy (FE-SEM), X-ray diffraction (XRD) spectrum, Raman spectroscopy, and high resolution electron microscopy (HRTEM). The fundamental electrochemical performances are examined using cyclic voltammetry (CV).

  12. Nanocomposite of Cu-TiO2-SiO2 with high photoactive performance for degradation of rhodamine B dye in aqueous wastewater.

    PubMed

    Li, Jinlong; Zhen, Deshuai; Sui, Guozhe; Zhang, Chunming; Deng, Qigang; Jia, Lihua

    2012-08-01

    The nanocomposite of Cu-TiO2-SiO2 photocatalyst have been prepared by a sol-gel method, which is used for the degradation of Rhodamine B (RB) as a probe that is notorious organic compound present in dyes wastewater. Morphological and structural characteristics of the Cu-TiO2-SiO2 nanocomposite were studied with low temperature N2 adsorption (BET), X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-vis diffuse reflectance spectroscopy (DRS). The Fourier transformed infrared spectroscopy (FT-IR) analysis shows the enhanced chemical bonding of O-Ti and O-Ti-O after the composition of Cu and SiO2 species into TiO2. It is found that the Cu-TiO2-SiO2 nanocomposite exhibits much higher photocatalytic activity under both UV light and visible light irradiation as compared with that over commercial titania (Degussa P25) toward the dyes wastewater containing RB. The photodegradation rate of RB (5 mg/L) can reach above 95.0% under sunlight after 3 h. The addition of SiO2 not only inhibites the crystal growth and anatase-to-rutile transformation of TiO2 nanocatalyst, but also enhances the adsorption of organic compounds. Cu-doping extends the light response to the visible region. Synergetic effects between Cu-SiO2 and TiO2 have been investigated, which provides a good way and material in the degradation field of dyes wastewater.

  13. Low-temperature activation and deactivation of high-Curie-temperature ferromagnetism in a new diluted magnetic semiconductor: Ni2+-Doped SnO2

    SciTech Connect

    Archer, Paul I.; Radovanovic, Pavle; Heald, Steve M.; Gamelin, Daniel R.

    2005-10-19

    We report the synthesis of colloidal Ni2+-doped SnO2 (Ni2+:SnO2) nanocrystals and their characterization by electronic absorption, magnetic circular dichroism, X-ray absorption, magnetic susceptibility, scanning electron microscopy, and X-ray diffraction measurements. The Ni2+ dopants are found to occupy pseudo-octahedral Sn4+ cation sites of rutile SnO2 without local charge compensation. The paramagnetic nanocrystals exhibit robust high-TC ferromagnetism (Ms (300 K) = 0.8 μB/Ni2+) when spin-coated into films, attributed to the formation of interfacial fusion defects. Facile reversibility of the paramagnetic-to-ferromagnetic phase transition is also observed. This magnetic phase transition is studied as a function of temperature, time, and atmospheric composition, from which the barrier to ferromagnetic activation is estimated to be Ea = 1200 cm-1. This energy is associated with ligand mobility on the surfaces of the Ni2+:SnO2 nanocrystals. The phase transition is reversed under air but not under N2, from which the microscopic identity of the activating defect is proposed to be interfacial oxygen vacancies.

  14. Mechanism investigation of visible light-induced degradation in a heterogeneous TiO2/eosin Y/rhodamine B system.

    PubMed

    Yin, Mingcai; Li, Zhaosheng; Kou, Jiahui; Zou, Zhigang

    2009-11-01

    Visible light-induced degradation of rhodamine B (RhB) and eosin Y (EO) in a heterogeneous TiO(2) P-25/EO/RhB system was investigated in the present work. The results showed that the photodegradation of RhB is enhanced significantly when EO is introduced into the P-25/RhB system. Under optimal conditions (50 mg P-25, 20 mg L(-1) EO), RhB (4 mg L(-1)) almost decomposed completely after 35 min of visible light irradiation, though EO was photodegraded simultaneously. The possible photodegradation mechanism was studied by the examination of active species HO*, O(2)(*-) anions, or dye radical cations through adding their scavengers such as methanol, t-butanol, benzoquinone, EDTA, and the I(-) anion. In addition, the electron paramagnetic resonance (EPR) spin trapping technique was also used to monitor the active oxygen species formed in the photocatalytic process. Combined with the contrastive experiments under different atmospheres (N(2)-purged or air) and in different systems, it can be deduced that dissolved O(2) plays a crucial role in dye photodegradation and the O(2)(*-) anion is possibly the major active oxygen species. The low degradation rate with the introduction of EDTA or I(-) indicated that dye radical cations also play a part in photodegradation. Furthermore, except for the dye-sensitized photodegradation on the P-25 surface, reaction in bulk solution also occurs in this system, leading to effective photodegradation of RhB.

  15. Photocatalytic TiO2 coating-to reduce ammonia and greenhouse gases concentration and emission from animal husbandries.

    PubMed

    Guarino, Marcella; Costa, Annamaria; Porro, Marco

    2008-05-01

    Animal production is a main source of NH3 emission into the environment and a significant producer of other polluting gases. Most of the best available techniques (BAT) that could be used today are not very widely applied in the field because of costs, especially in existing livestock buildings. Industrial applications show that TiO2 catalytic paint can be used to transform NH3 into N2, N2O or NO and water. Field experiments aimed at determining effects on indoor air quality and NH3 and polluting gas emissions into the environment of coating pig house walls with TiO2 catalytic paint and to assess the potential efficiency of this simple painting technique as a low cost BAT technique for animal farmers. The trial was performed in two identical mechanical ventilated farrowing rooms in a swine farm in Northern Italy. Environmental parameters, ventilation rate and gas concentrations were continuously monitored in the two units throughout a 28 day production cycle. NH3, N2O, CO2, CH4 average concentrations of 5.41, 1.18, 6.28 and 2109.38 mg m(-3) (reference unit without treatment) and 3.76, 1.13, 5.32 and 1881.64 mg m(-3) (experimental unit) were, respectively, recorded during a full farrowing cycle. Pollutant emissions, expressed on a Livestock Unit (LU, i.e., 500 kg live weight) basis, were 16.33, 3.57, 18.96 and 6365.01 kg y(-1)LU(-1) (reference unit) and 11.37, 3.43, 16.11 and 5695.58 kg y(-1) LU(-1) (experimental unit), respectively. Significantly higher pollutant concentrations and emissions were found in the untreated reference unit, under similar environmental conditions and with identical numbers of sows and piglets per unit.

  16. The Change in Oceanic O2 Inventory Associated with Recent Global Warming

    NASA Technical Reports Server (NTRS)

    Keeling, Ralph; Garcia, Hernan

    2002-01-01

    Oceans general circulation models predict that global warming may cause a decrease in the oceanic O2 inventory and an associated O2 outgassing. An independent argument is presented here in support of this prediction based on observational evidence of the ocean's biogeochemical response to natural warming. On time scales from seasonal to centennial, natural O2 flux/heat flux ratios are shown to occur in a range of 2 to 10 nmol O2 per Joule of warming, with larger ratios typically occurring at higher latitudes and over longer time scales. The ratios are several times larger than would be expected solely from the effect of heating on the O2 solubility, indicating that most of the O2 exchange is biologic