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

NASA Technical Reports Server (NTRS)

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

1998-01-01

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

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

NASA Technical Reports Server (NTRS)

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

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

NASA Technical Reports Server (NTRS)

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

Retrieval of constituent mixing ratios from limb thermal emission spectra

NASA Technical Reports Server (NTRS)

Shaffer, William A.; Kunde, Virgil G.; Conrath, Barney J.

1988-01-01

An onion-peeling iterative, least-squares relaxation method to retrieve mixing ratio profiles from limb thermal emission spectra is presented. The method has been tested on synthetic data, containing various amounts of added random noise for O3, HNO3, and N2O. The retrieval method is used to obtain O3 and HNO3 mixing ratio profiles from high-resolution thermal emission spectra. Results of the retrievals compare favorably with those obtained previously.

Effect of solvents on the extraction of natural pigments and adsorption onto TiO2 for dye-sensitized solar cell applications

NASA Astrophysics Data System (ADS)

Al-Alwani, Mahmoud A. M.; Mohamad, Abu Bakar; Kadhum, Abd. Amir H.; Ludin, Norasikin A.

2015-03-01

Nine solvents, namely, n-hexane, ethanol, acetonitrile, chloroform, ethyl-ether, ethyl-acetate, petroleum ether, n-butyl alcohol, and methanol were used to extract natural dyes from Cordyline fruticosa, Pandannus amaryllifolius and Hylocereus polyrhizus. To improve the adsorption of dyes onto the TiO2 particles, betalain and chlorophyll dyes were mixed with methanol or ethanol and water at various ratios. The adsorption of the dyes mixed with titanium dioxide (TiO2) was also observed. The highest adsorption of the C.fruticosa dye mixed with TiO2 was achieved at ratio 3:1 of methanol: water. The highest adsorption of P.amaryllifolius dye mixed with TiO2 was observed at 2:1 of ethanol: water. H.polyrhizus dye extracted by water and mixed with TiO2 demonstrated the highest adsorption among the solvents. All extracted dye was adsorbed onto the surface of TiO2 based on Fourier Transform Infrared Spectroscopy (FTIR) analysis. The inhibition of crystallinity of TiO2 was likewise investigated by X-ray analysis. The morphological properties and composition of dyes were analyzed via SEM and EDX.

Day and night profiles of tropospheric nitrous oxide

NASA Technical Reports Server (NTRS)

Cofer, Wesley R., III; Connors, Vickie S.; Levine, Joel S.; Edahl, Robert A., Jr.

1986-01-01

Daytime and nighttime vertical profiles of the tropospheric trace gas N2O were determined from grab sample collections off the Atlantic and Gulf coasts of Florida. The grab samples were collected during the week of October 7-13, 1984, from a Lear jet during descent spirals over an altitude range of 12.5-0.3 km in approximately 1.2-km intervals. During this period there were two distinct airflow regimes sampled: (1) the surface boundary layer (less than 2 km), in which the wind direction was typically easterly; and (2) the regime above the boundary layer, which was predominantly characterized by westerly flow. N2O mixing ratios, normalized to dry air, were determined from 148 daytime and nighttime samplings. N2O was found to be uniformly mixed at all altitudes at 301.9 + or - 2.4 parts per billion by volume.

WRF-Chem model predictions of the regional impacts of N2O5 heterogeneous processes on night-time chemistry over north-western Europe

NASA Astrophysics Data System (ADS)

Lowe, D.; Archer-Nicholls, S.; Morgan, W.; Allan, J.; Utembe, S.; Ouyang, B.; Aruffo, E.; Le Breton, M.; Zaveri, R. A.; Di Carlo, P.; Percival, C.; Coe, H.; Jones, R.; McFiggans, G.

2015-02-01

Chemical modelling studies have been conducted over north-western Europe in summer conditions, showing that night-time dinitrogen pentoxide (N2O5) heterogeneous reactive uptake is important regionally in modulating particulate nitrate and has a~modest influence on oxidative chemistry. Results from Weather Research and Forecasting model with Chemistry (WRF-Chem) model simulations, run with a detailed volatile organic compound (VOC) gas-phase chemistry scheme and the Model for Simulating Aerosol Interactions and Chemistry (MOSAIC) sectional aerosol scheme, were compared with a series of airborne gas and particulate measurements made over the UK in July 2010. Modelled mixing ratios of key gas-phase species were reasonably accurate (correlations with measurements of 0.7-0.9 for NO2 and O3). However modelled loadings of particulate species were less accurate (correlation with measurements for particulate sulfate and ammonium were between 0.0 and 0.6). Sulfate mass loadings were particularly low (modelled means of 0.5-0.7 μg kg-1air, compared with measurements of 1.0-1.5 μg kg-1air). Two flights from the campaign were used as test cases - one with low relative humidity (RH) (60-70%), the other with high RH (80-90%). N2O5 heterogeneous chemistry was found to not be important in the low-RH test case; but in the high-RH test case it had a strong effect and significantly improved the agreement between modelled and measured NO3 and N2O5. When the model failed to capture atmospheric RH correctly, the modelled NO3 and N2O5 mixing ratios for these flights differed significantly from the measurements. This demonstrates that, for regional modelling which involves heterogeneous processes, it is essential to capture the ambient temperature and water vapour profiles. The night-time NO3 oxidation of VOCs across the whole region was found to be 100-300 times slower than the daytime OH oxidation of these compounds. The difference in contribution was less for alkenes (× 80) and comparable for dimethylsulfide (DMS). However the suppression of NO3 mixing ratios across the domain by N2O5 heterogeneous chemistry has only a very slight, negative, influence on this oxidative capacity. The influence on regional particulate nitrate mass loadings is stronger. Night-time N2O5 heterogeneous chemistry maintains the production of particulate nitrate within polluted regions: when this process is taken into consideration, the daytime peak (for the 95th percentile) of PM10 nitrate mass loadings remains around 5.6 μg kg-1air, but the night-time minimum increases from 3.5 to 4.6 μg kg-1air. The sustaining of higher particulate mass loadings through the night by this process improves model skill at matching measured aerosol nitrate diurnal cycles and will negatively impact on regional air quality, requiring this process to be included in regional models.

WRF-Chem model predictions of the regional impacts of N 2O 5 heterogeneous processes on night-time chemistry over north-western Europe

DOE PAGES

Lowe, Douglas; Archer-Nicholls, Scott; Morgan, Will; ...

2015-02-09

Chemical modelling studies have been conducted over north-western Europe in summer conditions, showing that night-time dinitrogen pentoxide (N 2O 5) heterogeneous reactive uptake is important regionally in modulating particulate nitrate and has a~modest influence on oxidative chemistry. Results from Weather Research and Forecasting model with Chemistry (WRF-Chem) model simulations, run with a detailed volatile organic compound (VOC) gas-phase chemistry scheme and the Model for Simulating Aerosol Interactions and Chemistry (MOSAIC) sectional aerosol scheme, were compared with a series of airborne gas and particulate measurements made over the UK in July 2010. Modelled mixing ratios of key gas-phase species were reasonablymore » accurate (correlations with measurements of 0.7–0.9 for NO 2 and O 3). However modelled loadings of particulate species were less accurate (correlation with measurements for particulate sulfate and ammonium were between 0.0 and 0.6). Sulfate mass loadings were particularly low (modelled means of 0.5–0.7 μg kg −1 air, compared with measurements of 1.0–1.5 μg kg −1 air). Two flights from the campaign were used as test cases – one with low relative humidity (RH) (60–70%), the other with high RH (80–90%). N 2O 5 heterogeneous chemistry was found to not be important in the low-RH test case; but in the high-RH test case it had a strong effect and significantly improved the agreement between modelled and measured NO 3 and N 2O 5. When the model failed to capture atmospheric RH correctly, the modelled NO 3 and N 2O 5 mixing ratios for these flights differed significantly from the measurements. This demonstrates that, for regional modelling which involves heterogeneous processes, it is essential to capture the ambient temperature and water vapour profiles. The night-time NO 3 oxidation of VOCs across the whole region was found to be 100–300 times slower than the daytime OH oxidation of these compounds. The difference in contribution was less for alkenes (× 80) and comparable for dimethylsulfide (DMS). However the suppression of NO 3 mixing ratios across the domain by N 2O 5 heterogeneous chemistry has only a very slight, negative, influence on this oxidative capacity. The influence on regional particulate nitrate mass loadings is stronger. Night-time N 2O 5 heterogeneous chemistry maintains the production of particulate nitrate within polluted regions: when this process is taken into consideration, the daytime peak (for the 95th percentile) of PM 10 nitrate mass loadings remains around 5.6 μg kg −1 air, but the night-time minimum increases from 3.5 to 4.6 μg kg −1 air. The sustaining of higher particulate mass loadings through the night by this process improves model skill at matching measured aerosol nitrate diurnal cycles and will negatively impact on regional air quality, requiring this process to be included in regional models.« less

WRF-Chem model predictions of the regional impacts of N 2O 5 heterogeneous processes on night-time chemistry over north-western Europe

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

Lowe, Douglas; Archer-Nicholls, Scott; Morgan, Will

Chemical modelling studies have been conducted over north-western Europe in summer conditions, showing that night-time dinitrogen pentoxide (N 2O 5) heterogeneous reactive uptake is important regionally in modulating particulate nitrate and has a~modest influence on oxidative chemistry. Results from Weather Research and Forecasting model with Chemistry (WRF-Chem) model simulations, run with a detailed volatile organic compound (VOC) gas-phase chemistry scheme and the Model for Simulating Aerosol Interactions and Chemistry (MOSAIC) sectional aerosol scheme, were compared with a series of airborne gas and particulate measurements made over the UK in July 2010. Modelled mixing ratios of key gas-phase species were reasonablymore » accurate (correlations with measurements of 0.7–0.9 for NO 2 and O 3). However modelled loadings of particulate species were less accurate (correlation with measurements for particulate sulfate and ammonium were between 0.0 and 0.6). Sulfate mass loadings were particularly low (modelled means of 0.5–0.7 μg kg −1 air, compared with measurements of 1.0–1.5 μg kg −1 air). Two flights from the campaign were used as test cases – one with low relative humidity (RH) (60–70%), the other with high RH (80–90%). N 2O 5 heterogeneous chemistry was found to not be important in the low-RH test case; but in the high-RH test case it had a strong effect and significantly improved the agreement between modelled and measured NO 3 and N 2O 5. When the model failed to capture atmospheric RH correctly, the modelled NO 3 and N 2O 5 mixing ratios for these flights differed significantly from the measurements. This demonstrates that, for regional modelling which involves heterogeneous processes, it is essential to capture the ambient temperature and water vapour profiles. The night-time NO 3 oxidation of VOCs across the whole region was found to be 100–300 times slower than the daytime OH oxidation of these compounds. The difference in contribution was less for alkenes (× 80) and comparable for dimethylsulfide (DMS). However the suppression of NO 3 mixing ratios across the domain by N 2O 5 heterogeneous chemistry has only a very slight, negative, influence on this oxidative capacity. The influence on regional particulate nitrate mass loadings is stronger. Night-time N 2O 5 heterogeneous chemistry maintains the production of particulate nitrate within polluted regions: when this process is taken into consideration, the daytime peak (for the 95th percentile) of PM 10 nitrate mass loadings remains around 5.6 μg kg −1 air, but the night-time minimum increases from 3.5 to 4.6 μg kg −1 air. The sustaining of higher particulate mass loadings through the night by this process improves model skill at matching measured aerosol nitrate diurnal cycles and will negatively impact on regional air quality, requiring this process to be included in regional models.« less

Aircraft Observation of CO2, CO, O3 and H2 over the North Pacific during the PACE-7 Campaign

NASA Astrophysics Data System (ADS)

Sawa, Y.; Matsueda, H.; Makino, Y.; Inoue, H. Y.; Murayama, S.; Hirota, M.; Tsutsumi, Y.; Zaizen, Y.; Ikegami, M.; Okada, K.

2004-02-01

Aircraft observation under the Pacific Atmospheric Chemistry Experiment (PACE) program was performed from February 13 to 21, 2000 to examine in detail the distributions of CO2 in the free troposphere between 5 and 11 km. Continuous measurements of CO2 mixing ratios were made using an on-board measuring system over the northern North Pacific between Nagoya, Japan and Anchorage, Alaska, and the western North Pacific between Nagoya and Saipan. Other trace gases, such as CO and O3, were also observed using continuous measuring systems at the same time. CO2 over the northern Pacific (35°N and higher) showed highly variable mixing ratios, ranging from 374 ppm in the upper troposphere to 366 ppm in the lowermost stratosphere. This highly variable distribution of CO2 was quite similar to that of CO, but the relationship between CO2 and O3 showed a strong negative correlation. These results indicated that the exchange process between the stratosphere and the troposphere significantly influences the large CO2 variation. On the other hand, the CO2 over the western North Pacific to the south of Japan showed no significant variation in the upper troposphere at 11 km but a relatively larger variability at 5 km. The CO2 enhancement at lower altitudes coincided with the CO elevation due to the intrusion of a polluted air mass. Trajectory analysis indicated that the Asian continental outflow perturbed the CO2 distributions over the western Pacific. Very low mixing ratios of O3 of less than 20 ppb were distributed in the latitude band of 15 30°N at 11 km, reflecting the effects of transport from the equatorial region.

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

PubMed

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

2017-12-01

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

The extent of mixing in stellar interiors: the open clusters Collinder 261 and Melotte 66

NASA Astrophysics Data System (ADS)

Drazdauskas, Arnas; Tautvaišienė, Gražina; Randich, Sofia; Bragaglia, Angela; Mikolaitis, Šarūnas; Janulis, Rimvydas

2016-05-01

Context. Determining carbon and nitrogen abundances in red giants provides useful diagnostics to test mixing processes in stellar atmospheres. Aims: Our main aim is to determine carbon-to-nitrogen and carbon isotope ratios for evolved giants in the open clusters Collinder 261 and Melotte 66 and to compare the results with predictions of theoretical models. Methods: High-resolution spectra were analysed using a differential model atmosphere method. Abundances of carbon were derived using the C2 Swan (0, 1) band head at 5635.5 Å. The wavelength interval 7940-8130 Å, which contains CN features, was analysed to determine nitrogen abundances and carbon isotope ratios. The oxygen abundances were determined from the [O I] line at 6300 Å. Results: The mean values of the elemental abundances in Collinder 261, as determined from seven stars, are: [ C/Fe ] = -0.23 ± 0.02 (s.d.), [ N/Fe ] = 0.18 ± 0.09, [ O/Fe ] = -0.03 ± 0.07. The mean 12C /13C ratio is 11 ± 2, considering four red clump stars and 18 for one star above the clump. The mean C/N ratios are 1.60 ± 0.30 and 1.74, respectively. For the five stars in Melotte 66 we obtained: [ C/Fe ] = -0.21 ± 0.07 (s.d.), [ N/Fe ] = 0.17 ± 0.07, [ O/Fe ] = 0.16 ± 0.04. The 12C /13C and C/N ratios are 8 ± 2 and 1.67 ± 0.21, respectively. Conclusions: The 12C /13C and C/N ratios of stars in the investigated open clusters were compared with the ratios predicted by stellar evolution models. The mean values of 12C /13C ratios in Collinder 261 and Melotte 66 agree well with models of thermohaline-induced extra-mixing for the corresponding stellar turn-off masses of about 1.1-1.2 M⊙. The mean C/N ratios are not decreased as much as predicted by the model in which the thermohaline- and rotation-induced extra-mixing act together. Based on observations collected at ESO telescopes under Guaranteed Time Observation programmes 071.D-0065, 072.D-0019, and 076.D-0220.

Measurements of HNO3 and N2O5 using Ion drift - Chemical Ionization Mass Spectrometry during the MCMA - 2006 Campaign

NASA Astrophysics Data System (ADS)

Zheng, J.; Zhang, R.; Fortner, E. C.; Molina, L.; Aiken, A. C.; Jimenez, J. L.; Gäggeler, K.; Dommen, J.; Dusanter, S.; Stevens, P. S.; Tie, X.

2008-03-01

An ion drift - chemical ionization mass spectrometry (ID-CIMS) was deployed in Mexico City between 5 and 31 March to measure HNO3 and N2O5 during the 2006 Mexico City Metropolitan Area (MCMA) field campaign. The observation site, T0, was located at the Instituto Mexicano del Petróleo at the center of the Mexico City Basin with major emissions of pollutants from both domestic and industrial sources. Diurnally, HNO3 was less than 200 parts per trillion (ppt) during the night and in the early morning, increased steadily from around 09:00 a.m. central standard time (CST), reached a peak value of 0.5 to 3 parts per billion (ppb) in the early afternoon, and declined sharply to less than half of the peak value near 05:00 p.m. CST. An inter-comparison between the ID-CIMS and an ion chromatograph/mass spectrometer (ICMS) showed a good correlation in the HNO3 measurements (R2=0.75). The HNO3 mixing ratio was found to anti-correlate with aerosol nitrate, suggesting that the gaseous HNO3 concentration was controlled by the gas-particle partitioning process. During most times of the MCMA 2006 field campaign, N2O5 was found to be under the detection limit (about 20 ppt for a 10 s integration time) of the ID-CIMS, because of high NO mixing ratio (>100 ppb) during the night. With one exception on 26 March 2006, about 40 ppt N2O5 was observed during the late afternoon and early evening hours under a cloudy condition, before NO built up at the surface site. The results revealed that during the 2006 MCMA field campaign HNO3 was primarily produced by the reaction of OH with NO2 and regulated by gas/particle partitioning, and HNO3 production from N2O5 hydrolysis during the nighttime was small because of high NO and low O3 concentrations near the surface.

Lower stratosphere measurements of variation with latitude of CF2Cl2, CFCl3, CCl4, and N2O profiles in the northern hemisphere

NASA Technical Reports Server (NTRS)

Vedder, J. F.; Tyson, B. J.; Brewer, R. B.; Inn, E. C. Y.; Boitnott, C. A.

1978-01-01

Measurements were made from a U-2 aircraft of profiles of CF2Cl2, CFCl3, CCl4 and N2O in the lower stratosphere in a meridional survey at a longitude of 159 deg W during the period October 1 to November 14, 1976. The latitude distributions obtained show a marked decrease in mixing ratio with increasing latitude from about 7 deg N in the Intertropical Convergence Zone to about 79 deg N. The results suggest the importance of meridional transport and mixing in the stratosphere in accounting, at least in part, for the observed profile variation with latitude. The contaminants C2F4Cl2, C2F3Cl3, CHCCl3 and SF6 were also detected but their mixing ratios were small and no accurate standards were prepared for them.

Measurement and Modeling of Site-specific Nitrogen and Oxygen Isotopic Composition of Atmospheric Nitrous Oxide at Mace Head, Ireland

NASA Astrophysics Data System (ADS)

McClellan, M. J.; Saikawa, E.; Prinn, R. G.; Ono, S.

2015-12-01

Global mixing ratios of atmospheric nitrous oxide (N2O), a potent greenhouse gas, have increased nearly linearly from the beginning of the modern industrial period to today, with the current global average in excess of 325 ppb. This increase can be largely attributed to anthropogenic activity above the level of N2O emissions from natural biotic sources. The effect of N2O on Earth's climate is twofold: in the troposphere, N2O is radiatively active and chemically inert, while it serves as a reactive source of ozone-destroying nitrogen oxides in the stratosphere. The marked altitudinal divide in its reactivity means that all stages in the N2O life cycle—emission, transport, and destruction—must be examined to understand the overall effect of N2O on Earth's climate. However, the understanding of the total impact of N2O is incomplete, as there remain significant uncertainties in the global budget of this gas. Due to unique isotopic substitutions (15N and 18O) made by different N2O sources and stratospheric chemical reactions, the measurement of N2O isotopic ratios in ambient air can help identify the distribution and magnitude of distinct source types. We present the first year of site-specific nitrogen and oxygen isotopic composition data from the MIT Stheno-tunable infrared direct absorption spectroscopy (TILDAS) instrument at Mace Head, Ireland. Aided by the Stheno preconcentration system, Stheno-TILDAS can achieve measurement precisions of 0.10‰ or greater for all isotopic ratios (δ15N and δ18O) in ambient N2O. We further compare these data to the results from Model for Ozone and Related Tracers version 4 (MOZART-4) simulations, including N2O isotopic fractionation processes and MERRA/GEOS-5 reanalysis meteorological fields. These results will form the basis of future Bayesian inverse modeling simulations that will constrain global N2O source, circulation, and sink dynamics better.

Heterogeneous formation of nitryl chloride and its role as a nocturnal NOx reservoir species during CalNex-LA 2010

NASA Astrophysics Data System (ADS)

Mielke, L. H.; Stutz, J.; Tsai, C.; Hurlock, S. C.; Roberts, J. M.; Veres, P. R.; Froyd, K. D.; Hayes, P. L.; Cubison, M. J.; Jimenez, J. L.; Washenfelder, R. A.; Young, C. J.; Gilman, J. B.; de Gouw, J. A.; Flynn, J. H.; Grossberg, N.; Lefer, B. L.; Liu, J.; Weber, R. J.; Osthoff, H. D.

2013-09-01

nocturnal conversion of dinitrogen pentoxide (N2O5) to nitryl chloride (ClNO2) on chloride-containing aerosol can be a regionally important NOx (= NO + NO2) recycling and halogen activation pathway that affects oxidant photochemistry the following day. Here we present a comprehensive measurement data set acquired at Pasadena, California, during the CalNex-LA campaign 2010 that included measurements of odd nitrogen and its major components (NOy = NOx + NO3 + 2N2O5 + ClNO2 + HNO3 + HONO + peroxyacyl, alkyl, and aerosol nitrates) and aerosol size distribution and composition. Nitryl chloride was present during every night of the study (median mixing ratio at sunrise 800 pptv) and was usually a more significant nocturnal NOx and odd oxygen (Ox = O3 + NO2 + 3N2O5 + ClNO2) reservoir species than N2O5 (whose concentrations were calculated from its equilibrium with NO2 and NO3). At sunrise, ClNO2 accounted for 21% of NOz (=NOy - NOx), 4% of NOy, and 2.5% of Ox, respectively (median values). Kinetic parameters for the N2O5 to ClNO2 conversion were estimated by relating ClNO2 concentrations to their time-integrated heterogeneous production from N2O5 and were highly variable between nights. Production of ClNO2 required conversion of N2O5 on submicron aerosol with average yield (φ) and N2O5 reactive uptake probability (γ) of γφ = 0.008 (maximum 0.04), scaled with submicron aerosol chloride content, and was suppressed by aerosol organic matter and liquid water content. Not all of the observed variability of ClNO2 production efficiency could be rationalized using current literature parameterizations.

A three-dimensional model simulation of atmospheric nitrous oxide

NASA Technical Reports Server (NTRS)

Turner, R. E.; Blackshear, W. T.; Grose, W. L.; Eckman, R. S.; Pierce, R. B.; Fairlie, T. D. A.

1992-01-01

The NASA Langley 3D GCM chemical transport model is used to investigate the distribution of atmospheric N2O up to 60 km altitude. The transport characteristics of the model is evaluated without the complications of a detailed chemical formulation for all of the relevant stratospheric minor constituents. Interpretation of the yearly average zonal mean N2O distribution in terms of transport by the yearly averaged meridional circulation and stratospheric photochemical loss indicates large regions in the Northern Hemisphere stratosphere where dynamical mixing apparently plays a large role in maintaining the N2O distribution. In these regions, slopes of the N2O mixing ratio isopleths are maintained by competition between advection by the meridional circulation acting to steepen and dynamical mixing acting to flatten the slopes.

Stratospheric Horizontal Wavenumber Spectra of Winds, Potential Temperature, and Atmospheric Tracers Observed by High-Altitude Aircraft

NASA Technical Reports Server (NTRS)

Bacmeister, Julio T.; Eckermann, Stephen D.; Newman, Paul A.; Lait, Leslie; Chan, K. R.; Loewenstein, Max; Proffitt, Michael H.; Gary, Bruce L.

1996-01-01

Horizontal wavenumber power spectra of vertical and horizontal wind velocities, potential temperatures, and ozone and N(2)O mixing ratios, as measured in the mid-stratosphere during 73 ER-2 flights (altitude approx. 20km) are presented. The velocity and potential temperature spectra in the 100 to 1-km wavelength range deviate significantly from the uniform -5/3 power law expected for the inverse energy-cascade regime of two-dimensional turbulence and also for inertial-range, three-dimensional turbulence. Instead, steeper spectra approximately consistent with a -3 power law are observed at horizontal scales smaller than 3 km for all velocity components as well as potential temperature. Shallower spectra are observed at scales longer than 6 km. For horizontal velocity and potential temperature the spectral indices at longer scales are between -1.5 and -2.0. For vertical velocity the spectrum at longer scales become flat. It is argued that the observed velocity and potential temperature spectra are consistent with gravity waves. At smaller scales, the shapes are also superficially consistent with a Lumley-Shur-Weinstock buoyant subrange of turbulence and/or nonlinear gravity waves. Contemporaneous spectra of ozone and N(sub 2)O mixing ratio in the 100 to 1-km wavelength range do conform to an approximately uniform -5/3 power law. It is argued that this may reflect interactions between gravity wave air-parcel displacements and laminar or filamentary structures in the trace gas mixing ratio field produced by enstropy-cascading two-dimensional turbulence.

Effect of organic loading on nitrification and denitrification in a marine sediment microcosm

USGS Publications Warehouse

Caffrey, J.M.; Sloth, N.P.; Kaspar, H.F.; Blackburn, T.H.

1993-01-01

The effects of organic additions on nitrification and denitrification were examined in sediment microcosms. The organic material, heat killed yeast, had a C/N ratio of 7.5 and was added to sieved, homogenized sediments. Four treatments were compared: no addition (control, 30 g dry weight (dw) m-2 mixed throughout the 10 cm sediment column (30 M), 100 g dw m-2 mixed throughout sediments (100M), and 100 g dw m-2 mixed into top 1 cm (100S). After the microcosms had been established for 7-11 days, depth of O2 penetration, sediment-water fluxes and nitrification rates were measured. Nitrification rates were measured using three different techniques: N-serve and acetylene inhibition in intact cores, and nitrification potentials in slurries. Increased organic additions decreased O2 penetration from 2.7 to 0.2 mm while increasing both O2 consumption, from 30 to 70 mmol O2 m-2 d-1, and NO3- flux into sediments. Nitrification rates in intact cores were similar for the two methods. Highest rates occurred in the 30 M treatment, while the lowest rate was measured in the 100S treatment. Total denitrification rates (estimated from nitrification and nitrate fluxes) increased with increased organic addition, because of the high concentrations of NO3- (40 ??M) in the overlying water. The ratio of nitrification: denitrification was used as an indication of the importance of nitrification as the NO3- supply for denitrification. This ratio decreased from 1.55 to 0.05 with increased organic addition.

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

NASA Astrophysics Data System (ADS)

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

N2 and O2 are molecules that are predicted to be abundant in dense molecular clouds. Both molecules are difficult to detect as neither has a dipole moment. The chemical abundance of N2 is mostly inferred from its daughter species N2H+, but was recently detected in the ISM for the first time, with an abundance of 3.3 × 10-7 (Knauth et al 2004). Searches for the submillimeter lines of O2 have given upper limits for the abundance of ≤ 2.6 10-7 for star forming clouds and ≤ 3 10-6 for cold dark clouds (Goldsmith et al. 2000). Pontoppidan et al. (2003) deduced from the CO line profile that CO is present in both H2O poor and H2O rich ice layers, so it follows that N2 is likely to be present in a H2O poor ice layer. In many cold and protostellar cores N2H+ is found to anti-correlate with HCO+ and CO (Bergin et al. 2001; Jørgensen et al. 2004). Models by, for example Bergin & Langer (1997), assume this is due to the balance between freeze-out and evaporation, where ratios for the binding energy for N2 compared to CO of 0.50-0.70 are used. To model these processes, and reproduce the observed abundances of each species it is important to determine empirically the binding energies, sticking probabilities and desorption kinetics of model ice systems containing CO, N2 and O2. It seems that these quantities depend on the degree to which N2 and O2 mix with CO. Therefore, CO and N2 ices were studied extensively in a Ultra High Vacuum (UHV) experiment (P ~ 1 × 10-10 Torr) (Oberg et al. 2005; Bisschop et al submitted)). Ice samples were deposited at 14 K on a polycrystalline gold sample, mounted in the UHV chamber, covering morphologies from pure CO and N2, and 1:1 mixtures, to 1/1 layers of both CO over N2 and N2 over CO, and layers of 40 L of CO (1 L ≈ 1 monolayer) covered with 5 to 50 L of N2. The ices were studied using a combination of Reflection Absorption Infrared Spectroscopy (RAIRS) and Temperature Programmed Desorption (TPD), at a ramp-rate of 0.1 K min-1. The TPD data were modeled to accurately determine the binding energies and desorption kinetics o each system, using information from the RAIR spectra to develop the model. Sticking probabilities were calculated from a comparison between the molecular load at the mass spectrometer during dosing onto a hot and cold sample surface. The experiments show that N2 desorption from pure N2 ice gives a slightly lower binding energy for N2-N2 than CO-CO, 790 ± 25 K and 855 ± 25 K respectively, resulting in a ratio RBE = 0.923 ± 0.003. The TPD data for the mixtures and layers (see Figure 1) show that N2 can also completely mix in with the CO ice. A fraction of the N2 molecules that have mixed into the CO-ice, desorb with CO, giving them an effective binding energy of 855 ± 25 K (RBE=1). In either case, this ratio is much closer to unity than that used in models by (for example) Bergin & Langer (1997).

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

USDA-ARS?s Scientific Manuscript database

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

Anode-supported single-chamber solid oxide fuel cell based on cobalt-free composite cathode of Nd0.5Sr0.5Fe0.8Cu0.2O3-δ-Sm0.2Ce0.8O1.9 at intermediate temperatures

NASA Astrophysics Data System (ADS)

Yin, Jie-Wei; Zhang, Chunming; Yin, Yi-Mei; Shi, Huangang; Lin, Ye; Lu, Jun; Ma, Zi-Feng

2015-07-01

As a candidate of cathode material of single-chamber solid oxide fuel cell (SC-SOFC), cobalt-free mixed ionic electronic conductor (MIEC) Nd0.5Sr0.5Fe0.8Cu0.2O3-δ (NSFCu) is synthesized by sol-gel method with ethylene diamine tetraacetic acid and citric acid as co-complexing agents. The XRD shows NSFCu is stable after CO2 treatment and chemical compatible with SDC at high temperatures. CO2-TPD (CO2-temperature programmed desorption) demonstrates both CO2 adsorption and desorption phenomenon on NSFCu surface. However, the polarization resistances (Rp) of NSFCu and SDC (10:4 in weight) composite electrodes showed no decay in 5% CO2. Single cell using N2-O2-CH4 mixed gas (CH4 to O2 ratio = 1.5) as fuel shows maximum power density of 635 mW cm-2 at 700 °C. These results suggest that NSFCu-SDC is a promising composite cathode material for application in single-chamber solid oxide fuel cell.

Determining thermal inactivation of Escherichia coli O157:H7 in fresh compost by simulating early phases of the composting process.

PubMed

Singh, Randhir; Kim, Jinkyung; Shepherd, Marion W; Luo, Feng; Jiang, Xiuping

2011-06-01

A three-strain mixture of Escherichia coli O157:H7 was inoculated into fresh dairy compost (ca. 10(7) CFU/g) with 40 or 50% moisture and was placed in an environmental chamber (ca. 70% humidity) that was programmed to ramp from room temperature to selected composting temperatures in 2 and 5 days to simulate the early composting phase. The surviving E. coli O157:H7 population was analyzed by direct plating and enrichment. Optimal and suboptimal compost mixes, with carbon/nitrogen (C/N) ratios of 25:1 and 16:1, respectively, were compared in this study. In the optimal compost mix, E. coli O157:H7 survived for 72, 48, and 24 h in compost with 40% moisture and for 72, 24, and 24 h with 50% moisture at 50, 55, and 60°C, respectively, following 2 days of come-up time (rate of heating up). However, in the suboptimal compost mix, the pathogen survived for 288, 72, and 48 h in compost with 40% moisture and for 240, 72, 24 h in compost with 50% moisture at the same temperatures, respectively. Pathogen survival was longer, with 5 days of come-up time compared with 2 days of come-up. Overall, E. coli O157:H7 was inactivated faster in the compost with 50% moisture than in the compost with 40% at 55 and 60°C. Both moisture and come-up time were significant factors affecting Weibull model parameters. Our results suggest that slow come-up time at the beginning of composting can extend pathogen survival during composting. Additionally, both the C/N ratio and the initial moisture level in the compost mix affect the rate of pathogen inactivation as well.

Determining Thermal Inactivation of Escherichia coli O157:H7 in Fresh Compost by Simulating Early Phases of the Composting Process ▿

PubMed Central

Singh, Randhir; Kim, Jinkyung; Shepherd, Marion W.; Luo, Feng; Jiang, Xiuping

2011-01-01

A three-strain mixture of Escherichia coli O157:H7 was inoculated into fresh dairy compost (ca. 107 CFU/g) with 40 or 50% moisture and was placed in an environmental chamber (ca. 70% humidity) that was programmed to ramp from room temperature to selected composting temperatures in 2 and 5 days to simulate the early composting phase. The surviving E. coli O157:H7 population was analyzed by direct plating and enrichment. Optimal and suboptimal compost mixes, with carbon/nitrogen (C/N) ratios of 25:1 and 16:1, respectively, were compared in this study. In the optimal compost mix, E. coli O157:H7 survived for 72, 48, and 24 h in compost with 40% moisture and for 72, 24, and 24 h with 50% moisture at 50, 55, and 60°C, respectively, following 2 days of come-up time (rate of heating up). However, in the suboptimal compost mix, the pathogen survived for 288, 72, and 48 h in compost with 40% moisture and for 240, 72, 24 h in compost with 50% moisture at the same temperatures, respectively. Pathogen survival was longer, with 5 days of come-up time compared with 2 days of come-up. Overall, E. coli O157:H7 was inactivated faster in the compost with 50% moisture than in the compost with 40% at 55 and 60°C. Both moisture and come-up time were significant factors affecting Weibull model parameters. Our results suggest that slow come-up time at the beginning of composting can extend pathogen survival during composting. Additionally, both the C/N ratio and the initial moisture level in the compost mix affect the rate of pathogen inactivation as well. PMID:21498743

Effects of incorporation of 2.5 and 5 wt% TiO2 nanotubes on fracture toughness, flexural strength, and microhardness of denture base poly methyl methacrylate (PMMA).

PubMed

Abdulrazzaq Naji, Sahar; Behroozibakhsh, Marjan; Jafarzadeh Kashi, Tahereh Sadat; Eslami, Hossein; Masaeli, Reza; Mahgoli, Hosseinali; Tahriri, Mohammadreza; Ghavvami Lahiji, Mehrsima; Rakhshan, Vahid

2018-04-01

The aim of this preliminary study was to investigate, for the first time, the effects of addition of titania nanotubes (n-TiO 2 ) to poly methyl methacrylate (PMMA) on mechanical properties of PMMA denture base. TiO 2 nanotubes were prepared using alkaline hydrothermal process. Obtained nanotubes were assessed using FESEM-EDX, XRD, and FT-IR. For 3 experiments of this study (fracture toughness, three-point bending flexural strength, and Vickers microhardness), 135 specimens were prepared according to ISO 20795-1:2013 (n of each experiment=45). For each experiment, PMMA was mixed with 0% (control), 2.5 wt%, and 5 wt% nanotubes. From each TiO 2 :PMMA ratio, 15 specimens were fabricated for each experiment. Effects of n-TiO 2 addition on 3 mechanical properties were assessed using Pearson, ANOVA, and Tukey tests. SEM images of n-TiO 2 exhibited the presence of elongated tubular structures. The XRD pattern of synthesized n-TiO 2 represented the anatase crystal phase of TiO 2 . Moderate to very strong significant positive correlations were observed between the concentration of n-TiO 2 and each of the 3 physicomechanical properties of PMMA (Pearson's P value ≤.001, correlation coefficient ranging between 0.5 and 0.9). Flexural strength and hardness values of specimens modified with both 2.5 and 5 wt% n-TiO 2 were significantly higher than those of control ( P ≤.001). Fracture toughness of samples reinforced with 5 wt% n-TiO 2 (but not those of 2.5% n-TiO 2 ) was higher than control ( P =.002). Titania nanotubes were successfully introduced for the first time as a means of enhancing the hardness, flexural strength, and fracture toughness of denture base PMMA.

Mixed Metal Oxides of the Type CoxZn1-xFe2O4 as Photocatalysts for Malachite Green Degradation Under UV Light Irradiation.

PubMed

Tzvetkov, Martin; Milanova, Maria; Cherkezova-Zheleva, Zara; Spassova, Ivanka; Valcheva, Evgenia; Zaharieva, Joana; Ivan, Mitov

2017-06-01

A combination of thermal and mechanical (high energy ball milling) treatment was applied in an attempt to obtain polycrystalline mixed metal binary and ternary oxides of the type CoxZn1-xFe2O4 (x = 0; 0.25; 0.5; 0.75; 1). The synthetic procedure used successfully produced single-phased, homogeneous ZnFe2O4, CoFe2O4, and Co0.75Zn0.25Fe2O4, as well as mixed oxides, whose composition depended both on the duration of the high energy ball milling and the ratio Zn(II)/Co(II). The formation of spinel-like structures was proved by XRD, Mössbauer spectroscopy and Raman spectroscopy. For the characterization of the samples low-temperature N2 adsorption, UV/Vis spectroscopy and transmission electron microscopy were applied. The energy band gap of the samples was calculated, suggesting they are promising photocatalysts. The decomposition of the Malachite Green in model water solutions under UV-light irradiation was successfully achieved in the presence of the samples as photocatalysts. The highest rate constant was obtained for the sample synthesized at longer milling time in combination with higher Zn(II)/Co(II) ratio. The photocatalytic activity of the ternary mixed oxides was compared with the pure hematite, α-Fe2O3, and the binary ZnFe2O4 and CoFe2O4 ferrites with spinel structure that were treated in the same way. A synergetic effect of α-Fe2O3 and the spinel-like structure on the photocatalytic properties of ternary mixed metal oxides was detected.

Infrared Measurements of Atmospheric Gases Above Mauna Loa, Hawaii, in February 1987

NASA Technical Reports Server (NTRS)

Rinsland, C. P.; Goldman, A.; Murcray, F. J.; Murcray, F. H.; Blatherwick, R. D.; Murcray, D. G.

1988-01-01

Infrared solar absorption spectra recorded at 0.02/ cm resolution from the National Oceanic and Atmospheric Administration (NOAA) Geophysical Monitoring for Climate Change (GMCC) program station at Mauna Loa, Hawaii (latitude 19.5 deg N, longitude 155.6 deg W, elevation 3.40 km), in February 1997 have been analyzed to determine simultaneous total vertical column amounts for 13 atmospheric gases. Average tropospheric concentrations of CO2, N2O, CH4, and CHCIF2 and the daytime diurnal variations or the total columns of NO and NO2 have also been inferred. The retrieved total columns (in molecules /sq cm) of the nondiurnally varying gases are 1.6 +/- 0.2 x 10(exp 15) for HCl, 5.9 +/- 1.2 x 10(exp 15) for HNO3, 2.0 +/- 0.2 x 10(exp 21) for H2O16, 4.4 +/- 0.7 x 10(exp 18) for H2O18, 2.7 +/- 0.1 x 10(exp 17) for HDO, 2.3 +/- 0.2 x 10(exp 19) for CH4, 5.0 +/- 0.5 x 10(exp 21) for CO2, 6.7 +/- 0.8 x 10(exp 18) for O3, 4.3 +/- 0.4 x 10(exp 18) for N2O, 1.0 +/- 0.2 x 10(exp 16) for C2H6, and 9.7 +/- 2.5 x 10(exp 14) for CHClF2. We compare the total column measurements of HCl and HNO3 with previously reported ground-based, aircraft, and satellite measurements. The results for HCl are or particular interest because of the expected temporal increase in the concentration of this gas in the stratosphere. However, systematic differences among stratospheric HCl total column measurements from 1978 to 1980 and the absence of observations of free tropospheric HCl above Mauna Loa make it impossible to obtain a reliable estimate of the trend in the total burden of HCl. The measured HNO3 total column is consistent with aircraft measurements from approx. 12 km altitude. The O3 total column deduced from the IR spectra agrees with correlative Mauna Loa Umkehr measurements within the estimated error limits. The column-averaged D/H ratio of water vapor is (68 +/- 9) x- 10(exp -6), which is 0.44 +/- 0.06 times the reference value of 155.76 x 10(exp -6) for standard mean ocean water (SMOW). This large depletion in the D content of water vapor is similar to published measurements of the upper troposphere and lower stratosphere. Average tropospheric concentrations deduced for CO2, N2O, and CH4 are in good agreement with correlative NOAA GMCC surface data, indicating consistency between the measurement techniques for determining tropospheric volume mixing ratios. Results of the present study indicate that Mauna Loa is a favorable site for infrared monitoring of atmospheric gases. The site is particularly favorable for monitoring the tropospheric volume mixing ratios of long-lived gases, since the high altitude of the tropopause reduces corrections required to account for the decrease in volume mixing ratio in the stratosphere.

Sensitive detection of n-alkanes using a mixed ionization mode proton-transfer-reaction mass spectrometer

NASA Astrophysics Data System (ADS)

Amador-Muñoz, Omar; Misztal, Pawel K.; Weber, Robin; Worton, David R.; Zhang, Haofei; Drozd, Greg; Goldstein, Allen H.

2016-11-01

Proton-transfer-reaction mass spectrometry (PTR-MS) is a technique that is widely used to detect volatile organic compounds (VOCs) with proton affinities higher than water. However, n-alkanes generally have a lower proton affinity than water and therefore proton transfer (PT) by reaction with H3O+ is not an effective mechanism for their detection. In this study, we developed a method using a conventional PTR-MS to detect n-alkanes by optimizing ion source and drift tube conditions to vary the relative amounts of different primary ions (H3O+, O2+, NO+) in the reaction chamber (drift tube). There are very few studies on O2+ detection of alkanes and the mixed mode has never been proposed before. We determined the optimum conditions and the resulting reaction mechanisms, allowing detection of n-alkanes from n-pentane to n-tridecane. These compounds are mostly emitted by evaporative/combustion process from fossil fuel use. The charge transfer (CT) mechanism observed with O2+ was the main reaction channel for n-heptane and longer n-alkanes, while for n-pentane and n-hexane the main reaction channel was hydride abstraction (HA). Maximum sensitivities were obtained at low E / N ratios (83 Td), low water flow (2 sccm) and high O2+ / NO+ ratios (Uso = 180 V). Isotopic 13C contribution was taken into account by subtracting fractions of the preceding 12C ion signal based on the number of carbon atoms and the natural abundance of 13C (i.e., 5.6 % for n-pentane and 14.5 % for n-tridecane). After accounting for isotopic distributions, we found that PT cannot be observed for n-alkanes smaller than n-decane. Instead, protonated water clusters of n-alkanes (M ṡ H3O+) species were observed with higher abundance using lower O2+ and higher water cluster fractions. M ṡ H3O+ species are probably the source for the M + H+ species observed from n-decane to n-tridecane. Normalized sensitivities to O2+ or to the sum of O2++ NO+ were determined to be a good metric with which to compare sensitivities for n-alkane detection between experiments. Double hydride abstraction was observed from the reaction with O2+. Sensitivity to CT increased with carbon chain length from n-pentane to n-dodecane, sensitivity to HA increased from n-heptane to n-dodecane and sensitivity to PT increased from n-decane to n-tridecane. Sensitivity to CT exponentially decreased with molecular ionization energy, which is inversely related to the carbon chain length. We introduce a calibrated fragmentation algorithm as a method to determine the concentrations of n-alkanes and demonstrate its effectiveness using a custom n-alkane mixture and a much more complex oil example representing perhaps the most difficult mixture available for application of the method. We define optimum conditions for using the mixed ionization mode to measure n-alkanes in conventional PTR-MS instruments regardless of whether they are equipped with switchable reagent ion (SRI) capabilities.

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

USGS Publications Warehouse

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

2007-01-01

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

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

NASA Astrophysics Data System (ADS)

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

2015-04-01

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

Nimbus-7 Stratospheric and Mesospheric Sounder (SAMS) experiment data user's guide

NASA Technical Reports Server (NTRS)

Taylor, F. W.; Rodgers, C. D.; Nutter, S. T.; Oslik, N.

1989-01-01

The Stratospheric and Mesospheric Sounder (SAMS) aboard Nimbus-7 observes infrared radiation from the atmospheric limb. Global upper atmosphere temperature profiles and vertical concentrations of H2O, NO, N2O, CH4 and CO2 are derived from these measurements. The status of all channels was carefully monitored. Temperature and composition were retrieved from the measurements by linearizing the direct equation about an a priori profile and using an optimum statistical estimator to find the most likely solution. The derived temperature and composition profiles are archived on two tape products whose file structure and record formats are described in detail. The gridded retrieved temperature tape (GRID-T) contains daily day and night average temperatures at 62 pressure levels in a 2.5 degree latitude by 10 degree longitude grid extending from 67.5 degrees N to 50 degrees S. The zonal mean methane and nitrous oxide composition tape (ZMT-G) contains zonal mean day and night average CH4 and N2O mixing ratios at 31 pressure levels for 2.5 degrees latitude zones extending from 67.5 degrees N to 50 degrees S.

Effect of Oxygen Gas on the Decomposition of Dye by Pulsed Discharge in Water Droplet Spray

NASA Astrophysics Data System (ADS)

Nose, Taisuke; Yokoyama, Yuzo; Nakamura, Akira; Minamitani, Yasushi

Effect of O2 on the decolorization of indigo carmine and on the production of dissolved species such as NO2-, NO3-, O3 and H2O2 in the treatment water by pulsed discharge in water droplet spray was investigated by controlling the O2/N2 ratios as carrier gases in the reactor. The decolorization rate gradually increased with rise in O2 ratio, which reached a constant value in the range of 50% to 90% O2 ratio and decreased in pure O2. The maximum value was about 2 times as high as that of 20% O2 ratio. The decolorization efficiency was not affected by gas flow rate in the range of 4 L/min to 50 L/min. NO2- in the treatment water was only detected in pure N2, but NO3- was produced in O2/N2. NO2- added to the treatment water was not oxidized in pure N2, but was perfectly converted to NO3- in O2/N2. These results implied that hydroxyl radical produced in gas phase does not directly contribute to the oxidation of substances in water. O3 concentration gradually increased with rise in O2 ratio, whereas H2O2 concentration decreased. In the range of 50 to 80% O2 ratio, O3 and H2O2 concentrations were approximately constant value, similar to the trend of decolorization rate. Moreover rate constants on various gas mixing ratio of O2/N2 were determined from the kinetics study. These results suggested that hydroxyl radical produced in the treatment water by the chain reactions of O3 and hydroperoxy radical (HO2·) plays an important role of the decomposition of molecules in water.

Measurements of HNO3 and N2O5 using ion drift-chemical ionization mass spectrometry during the MILAGRO/MCMA-2006 campaign

NASA Astrophysics Data System (ADS)

Zheng, J.; Zhang, R.; Fortner, E. C.; Volkamer, R. M.; Molina, L.; Aiken, A. C.; Jimenez, J. L.; Gaeggeler, K.; Dommen, J.; Dusanter, S.; Stevens, P. S.; Tie, X.

2008-11-01

An ion drift-chemical ionization mass spectrometer (ID-CIMS) was deployed in Mexico City between 7 and 31 March to measure gas-phase nitric acid (HNO3) and dinitrogen pentoxide (N2O5 during the Mexico City Metropolitan Area (MCMA)-2006 field campaign. The observation site was located at the Instituto Mexicano del Petróleo in the northern part of Mexico City urban area with major emissions of pollutants from residential, vehicular and industrial sources. Diurnally, HNO3 was less than 200 parts per trillion (ppt) during the night and early morning. The concentration of HNO3 increased steadily from around 09:00 a.m. central standard time (CST), reached a peak value of 0.5 to 3 parts per billion (ppb) in the early afternoon, and then declined sharply to less than half of the peak value near 05:00 p.m. CST. An inter-comparison between the ID-CIMS and an ion chromatograph/mass spectrometer (ICMS) showed a good agreement between the two HNO3 measurements (R2=0.75). The HNO3 mixing ratio was found to anti-correlate with submicron-sized aerosol nitrate, suggesting that the gas-particle partitioning process was a major factor in determining the gaseous HNO3 concentration. Losses by irreversible reactions with mineral dust and via dry deposition also could be important at this site. Most of the times during the MCMA 2006 field campaign, N2O5 was found to be below the detection limit (about 30 ppt for a 10 s integration time) of the ID-CIMS, because of high NO mixing ratio at the surface (>100 ppb) during the night. An exception occurred on 26 March 2006, when about 40 ppt N2O5 was observed during the late afternoon and early evening hours under cloudy conditions before the build-up of NO at the surface site. The results revealed that during the MCMA-2006 field campaign HNO3 was primarily produced from the reaction of OH with NO2 and regulated by gas/particle transfer and dry deposition. The production of HNO3 from N2O5 hydrolysis during the nighttime was small because of high NO and low O3 concentrations near the surface.

Effects of Zr/Ce molar ratio and water content on thermal stability and structure of ZrO{sub 2}–CeO{sub 2} mixed oxides prepared via sol–gel process

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

Huang, Wenzhi; Yang, Jili; Wang, Chunjie

2012-09-15

Highlights: ► Tetragonal t″ phase was stabilized in Zr{sub 0.5}Ce{sub 0.5}O{sub 2} solid solution at temperature as high as 1000 °C. ► Specific surface area of powders decreased with the increase of water addition and the Ce content. ► The single stable phase was controlled by adjusting the volume ratio of water and ethanol. ► Tetragonal (t″) phase dissociated into cubic and tetragonal (t′) phases at 1200 °C. -- Abstract: ZrO{sub 2}–CeO{sub 2} mixed oxides were synthesized via sol–gel process. Thermal stability, structure and morphology of samples were investigated by powder X-ray diffraction, FT-Raman spectroscopy, X-ray photoelectron spectroscopy and scanningmore » electron microscopy. In this approach, the solvent composition and Zr/Ce molar ratio have great influences on the structure and morphology of final products. With decreasing water content in the mixed solvent, specific surface area of powders increased and the single tetragonal phase was obtained. Only when the volume ratio of water and ethanol and the Zr/Ce molar ratio were 1:1, tetragonal t″-Zr{sub 0.5}Ce{sub 0.5}O{sub 2} could be stabilized in powders at temperature as high as 1000 °C. Meanwhile, tetragonal (t′) and (t″) phases coexisted in Zr{sub 0.5}Ce{sub 0.5}O{sub 2} solid solution without peak splitting after calcination at 1100 °C, further transforming into cubic and tetragonal (t′) phases at 1200 °C. The effective activation energy for Zr{sub 0.5}Ce{sub 0.5}O{sub 2} nanocrystallite growth during annealing is about 5.24 ± 0.15 kJ/mol.« less

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

PubMed

Brown, Anne Christine

2006-05-01

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

Model simulation of NO3, N2O5 and ClNO2 at a rural site in Beijing during CAREBeijing-2006

NASA Astrophysics Data System (ADS)

Wang, Haichao; Lu, Keding; Tan, Zhaofeng; Sun, Kang; Li, Xin; Hu, Min; Shao, Min; Zeng, Limin; Zhu, Tong; Zhang, Yuanhang

2017-11-01

A chemical box model was used to study nitrate radical (NO3), dinitrogen pentoxide (N2O5) and nitryl chloride (ClNO2) in a rural site during the Campaign of Air Quality Research in Beijing 2006 (CAREBeijing-2006). The model was based on regional atmospheric chemistry mechanism version 2 (RACM2) with the heterogeneous uptake of N2O5 and the simplified chloride radical (Cl) chemistry mechanism. A high production rate of NO3 with a mean value of 0.8 ppbv/h and low mixing ratios of NO3 and N2O5 (peak values of 17 pptv and 480 pptv, respectively) existed in this site. Budget analysis showed that NO emission suppressed the NO3 chemistry at the surface layer, the reaction of NO3 with VOCs made a similar contribution to NO3 loss as N2O5 heterogeneous uptake. The NO3 chemistry was predominantly controlled by isoprene, and NO3 oxidation produced organic nitrate with a mean value of 0.06 ppbv/h during nighttime. The organic nitrate production initiated by NO3 was equal to that initiated by OH, implying the importance of nighttime chemistry for secondary organic aerosol (SOA) formation. We confirmed that the N2O5 heterogeneous reaction accounted for nighttime particle NO3- enhancement, with a large day to day variability, and made less of a contribution to NOx loss compared to that of OH reacting with NO2. Additionally, abundant ClNO2, up to 5.0 ppbv, was formed by N2O5 heterogeneous uptake. ClNO2 was sustained at a high level until noon in spite of the gradually increasing photolysis of ClNO2 after sunrise. Chlorine activation caused by N2O5 heterogeneous uptake increased primary ROx formation by 5% and accounted for 8% of the net ozone production enhancement in the morning.

Surface gas pollutants in Lhasa, a highland city of Tibet - current levels and pollution implications

NASA Astrophysics Data System (ADS)

Ran, L.; Lin, W. L.; Deji, Y. Z.; La, B.; Tsering, P. M.; Xu, X. B.; Wang, W.

2014-10-01

Through several years of development, the city of Lhasa has become one of the most populated and urbanized areas on the highest plateau in the world. In the process of urbanization, current and potential air quality issues have been gradually concerned. To investigate the current status of air pollution in Lhasa, various gas pollutants including NOx, CO, SO2, and O3, were continuously measured from June 2012 to May 2013 at an urban site (29.40° N, 91.08° E, 3650 m a.s.l.). The seasonal variations of primary gas pollutants exhibited a peak from November to January with a large variability. High mixing ratios of primary trace gases almost exclusively occurred under low wind speed and showed no distinct dependence on wind direction, implying local urban emissions to be predominant. A comparison of NO2, CO, and SO2 mixing ratios in summer between 1998 and 2012 indicated a significant increase in emissions of these gas pollutants and a change in their intercorrelations, as a result of a substantial growth in the demand of energy consumption using fossil fuels instead of previously widely used biomass. The pronounced diurnal double peaks of primary trace gases in all seasons suggested automobile exhaust to be a major emission source in Lhasa. The secondary gas pollutant O3 displayed an average diurnal cycle of a shallow flat peak for about 4-5 h in the afternoon and a minimum in the early morning. Nighttime O3 was sometimes completely consumed by the high level of NOx. Seasonally, the variations of O3 mixing ratios displayed a low valley in winter and a peak in spring. In autumn and winter, transport largely contributed to the observed O3 mixing ratios, given its dependence on wind speed and wind direction, while in spring and summer photochemistry played an important role. A more efficient buildup of O3 mixing ratios in the morning and a higher peak in the afternoon was found in summer 2012 than in 1998. An enhancement in O3 mixing ratios would be expected in the future and more attention should be given to O3 photochemistry in response to increasing precursor emissions in this area.

The retrieval of atmospheric constituent mixing-ratio profiles from solar absorption spectra. Ph.D. Thesis. Interim Technical Report

NASA Technical Reports Server (NTRS)

Shaffer, W. A.

1983-01-01

Methods used to determine various atmospheric gas distributions are summarized. The experimentally determined mixing ratio profiles (the mixing ratio of a gas is the ratio of the number of gas molecules to the number of air molecules) of some atmospheric gases are shown. In most in situ experiments stratospheric gas samples are collected at several altitudes by balloon, aircraft, or rocket. These samples are then analyzed by various methods. Mixing ratio profiles of Ci, ClO, and OH were determined by laser induced fluorescence of samples. Others have analyzed gas samples by gas chromatography in order to determine the molecular abundances of CCl2F2, CCl4, CCl3F, CFCl3, CF2Cl2, CHClF2, CH3CCl3, CH4, CO, C2Cl3F3, C2Cl4, C2HCl3, C2H2, C2H4, C2H6, C3H8, C6H6, C7H8, H2, and N2O.

Novel synthesis of manganese and vanadium mixed oxide (V{sub 2}O{sub 5}/OMS-2) as an efficient and selective catalyst for the oxidation of alcohols in liquid phase

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

Mahdavi, Vahid, E-mail: v-mahdavi@araku.ac.ir; Soleimani, Shima

2014-03-01

Graphical abstract: Oxidation of various alcohols is studied in the liquid phase over new composite mixed oxide (V{sub 2}O{sub 5}/OMS-2) catalyst using tert-butyl hydroperoxide (TBHP). The activity of V{sub 2}O{sub 5}/OMS-2 samples was considerably increased with respect to OMS-2 catalyst and these samples are found to be suitable for the selective oxidation of alcohols. - Highlights: • V{sub 2}O{sub 5}/K-OMS-2 with different V/Mn molar ratios prepared by the impregnation method. • Oxidation of alcohols was studied in the liquid phase over V{sub 2}O{sub 5}/K-OMS-2 catalyst. • V{sub 2}O{sub 5}/K-OMS-2 catalyst had excellent activity for alcohol oxidation. • Benzyl alcohol oxidationmore » using excess TBHP followed a pseudo-first order kinetic. • The selected catalyst was reused without significant loss of activity. - Abstract: This work reports the synthesis and characterization of mixed oxide vanadium–manganese V{sub 2}O{sub 5}/K-OMS-2 at various V/Mn molar ratios and prepared by the impregnation method. Characterization of these new composite materials was made by elemental analysis, BET, XRD, FT-IR, SEM and TEM techniques. Results of these analyses showed that vanadium impregnated samples contained mixed phases of cryptomelane and crystalline V{sub 2}O{sub 5} species. Oxidation of various alcohols was studied in the liquid phase over the V{sub 2}O{sub 5}/K-OMS-2 catalyst using tert-butyl hydroperoxide (TBHP) and H{sub 2}O{sub 2} as the oxidant. Activity of the V{sub 2}O{sub 5}/K-OMS-2 samples was increased considerably with respect to K-OMS-2 catalyst due to the interaction of manganese oxide and V{sub 2}O{sub 5}. The kinetic of benzyl alcohol oxidation using excess TBHP over V{sub 2}O{sub 5}/K-OMS-2 catalyst was investigated at different temperatures and a pseudo-first order reaction was determined with respect to benzyl alcohol. The effects of reaction time, oxidant/alcohol molar ratio, reaction temperature, solvents, catalyst recycling potential and leaching were investigated.« less

Effects of Sludge Retention Times on Nutrient Removal and Nitrous Oxide Emission in Biological Nutrient Removal Processes

PubMed Central

Li, Bo; Wu, Guangxue

2014-01-01

Sludge retention time (SRT) is an important factor affecting not only the performance of the nutrient removal and sludge characteristics, but also the production of secondary pollutants such as nitrous oxide (N2O) in biological nutrient removal (BNR) processes. Four laboratory-scale sequencing batch reactors (SBRs), namely, SBR5, SBR10, SBR20 and SBR40 with the SRT of 5 d, 10 d, 20 d and 40 d, respectively, were operated to examine effects of SRT on nutrient removal, activated sludge characteristics and N2O emissions. The removal of chemical oxygen demand or total phosphorus was similar under SRTs of 5–40 d, SRT mainly affected the nitrogen removal and the optimal SRT for BNR was 20 d. The molecular weight distribution of the effluent organic matters was in the range of 500–3,000 Da under SRTs of 5–40 d. The lowest concentration of the effluent soluble microbial products concentration was obtained at the SRT of 5 d. Nitrifier growth was limited at a short SRT and nitrite existed in the effluent of SBR5. With increasing SRTs, mixed liquor suspended solids concentration increased while the excess sludge production was reduced due to the high endogenous decay rate at high SRTs. Endogenous decay coefficients were 0.020 d−1, 0.036 d−1, 0.037 d−1 and 0.039 d−1 under SRTs of 5–40 d, respectively. In BNR, the N2O emission occurred mainly during the aerobic phase and its emission ratio decreased with increasing SRTs. The ratio between the N2O-N emission and the removed ammonium nitrogen in the aerobic phase was 5%, 3%, 1.8% and 0.8% at the SRT of 5 d, 10 d, 20 d and 40 d, respectively. With low concentrations of dissolved oxygen and high concentrations of oxidized nitrogen, the N2O emission was significantly accelerated due to heterotrophic denitrification activities. PMID:24681555

Ternary mixed metal Fe-doped NiCo2O4 nanowires as efficient electrocatalysts for oxygen evolution reaction

NASA Astrophysics Data System (ADS)

Yan, Kai-Li; Shang, Xiao; Li, Zhen; Dong, Bin; Li, Xiao; Gao, Wen-Kun; Chi, Jing-Qi; Chai, Yong-Ming; Liu, Chen-Guang

2017-09-01

Designing mixed metal oxides with unique nanostructures as efficient electrocatalysts for water electrolysis has been an attractive approach for the storage of renewable energies. The ternary mixed metal spinel oxides FexNi1-xCo2O4 (x = 0, 0.1, 0.25, 0.5, 0.75, 0.9, 1) have been synthesized by a facile hydrothermal approach and calcination treatment using nickel foam as substrate. Fe/Ni ratios have been proved to affect the nanostructures of FexNi1-xCo2O, which imply different intrinsic activity for oxygen evolution reaction (OER). SEM images show that Fe0.5Ni0.5Co2O4 has the uniform nanowires morphology with about 30 nm of the diameter and 200-300 nm of the length. The OER measurements show that Fe0.5Ni0.5Co2O4 exhibits the better electrocatalytic performances with lower overpotential of 350 mV at J = 10 mA cm-2. In addition, the smaller Tafel slope of 27 mV dec-1 than other samples with different Fe/Ni ratios for Fe0.5Ni0.5Co2O4 is obtained. The improved OER activity of Fe0.5Ni0.5Co2O4 may be attributed to the synergistic effects from ternary mixed metals especially Fe-doping and the uniform nanowires supported on NF. Therefore, synthesizing Fe-doped multi-metal oxides with novel nanostructures may be a promising strategy for excellent OER electrocatalysts and it also provides a facile way for the fabrication of high-activity ternary mixed metal oxides electrocatalysts.

Surface ozone scenario and air quality in the north-central part of India.

PubMed

Saini, Renuka; Taneja, Ajay; Singh, Pradyumn

2017-09-01

Tropospheric pollutants including surface ozone (O 3 ), nitrogen dioxide (NO 2 ), carbon monoxide (CO) and meteorological parameters were measured at a traffic junction (78°2' E and 27°11' N) in Agra, India from January 2012 to December 2012. Temporal analysis of pollutants suggests that annual average mixing ratios of tropospheric pollutants were: O 3 - 22.97±23.36ppbV, NO 2 - 19.84±16.71ppbV and CO - 0.91±0.86ppmV, with seasonal variations of O 3 having maximum mixing ratio during summer season (32.41±19.31ppbV), whereas lowest was found in post-monsoon season (8.74±3.8ppbV). O 3 precursors: NO 2 and CO, showed inverse relationship with O 3 . Seasonal variation and high O 3 episodes during summer are associated with meteorological parameters such as high solar radiation, atmospheric temperature and transboundary transport. The interdependence of these variables showed a link between the daytime mixing ratios of O 3 with the nighttime level of NO 2 . The mixing ratios of CO and NO 2 showed tight correlations, which confirms the influence of vehicular emissions combined with other anthropogenic activities due to office/working hours, shallowing, and widening of boundary layer. FLEXTRA backward trajectories for the O 3 episode days clearly indicate the transport from the NW and W to S/SE and SW direction at Agra in different seasons. Copyright © 2017. Published by Elsevier B.V.

Oxidative desulfurization of dibenzothiophene from model oil using ionic liquids as extracting agent

NASA Astrophysics Data System (ADS)

Taha, Mohd F.; Atikah, N.; Chong, F. K.; Shaharun, Maizatul S.

2012-09-01

The oxidative desulfurization of dibenzothiophene (DBT) from model oil (in n-dodecane) was carried out using ionic liquid as the extractant and catalyst, and hydrogen peroxide (H2O2) in combination with acetic acid (CH3COOH) and sulphuric acid (H2SO4) as the oxidant. The ionic liquids used were 1-butyl-3-methylimidazolium octyl sulphate ([Bmim][OcSO4]) and 1-butyl-3-methylimidazolium acetate ([Bmim][Ac]). The effect of the amounts of H2O2 on oxidative desulphurization of model oil was first investigated without the usage of ionic liquids at room temperature. The results indicate that greater amount of H2O2 give higher desulfurization and the maximum desulfurization in this study, i.e. 34 %, was occurred when the molar ratio of H2O2 to sulfur was 5:1. With the usage of ionic liquid and the molar ratio of 5:1 (H2O2:sulfur), the efficiency of DBT removal from model oil was increased significantly in terms of percent removal and removal time. Ionic liquid of [Bmim][OcSO4] performed better than [Bmim][Ac] with 72 % DBT removal. When molar ratio of H2O2 to sulphur was 5:1, volume ratio of ionic liquid to model oil was 1:1 and mixing time was 60 min at room temperature. The results indicate the potential of ionic liquids as the extractant and catalyst for oxidative desulfurization of hydrocarbon fuels.

Isotopes of nitrogen on Mars: Atmospheric measurements by Curiosity's mass spectrometer

PubMed Central

Wong, Michael H; Atreya, Sushil K; Mahaffy, Paul N; Franz, Heather B; Malespin, Charles; Trainer, Melissa G; Stern, Jennifer C; Conrad, Pamela G; Manning, Heidi L K; Pepin, Robert O; Becker, Richard H; McKay, Christopher P; Owen, Tobias C; Navarro-González, Rafael; Jones, John H; Jakosky, Bruce M; Steele, Andrew

2013-01-01

[1] The Sample Analysis at Mars (SAM) instrument suite on the Mars Science Laboratory (MSL) measured a Mars atmospheric14N/15N ratio of 173 ± 11 on sol 341 of the mission, agreeing with Viking's measurement of 168 ± 17. The MSL/SAM value was based on Quadrupole Mass Spectrometer measurements of an enriched atmospheric sample, with CO2 and H2O removed. Doubly ionized nitrogen data at m/z 14 and 14.5 had the highest signal/background ratio, with results confirmed by m/z 28 and 29 data. Gases in SNC meteorite glasses have been interpreted as mixtures containing a Martian atmospheric component, based partly on distinctive14N/15N and40Ar/14N ratios. Recent MSL/SAM measurements of the40Ar/14N ratio (0.51 ± 0.01) are incompatible with the Viking ratio (0.35 ± 0.08). The meteorite mixing line is more consistent with the atmospheric composition measured by Viking than by MSL. PMID:26074632

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

PubMed

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

2013-02-05

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

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

NASA Astrophysics Data System (ADS)

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

2010-12-01

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

The chemistry of bromine in the stratosphere: Influence of a new rate constant for the reaction BrO + HO2

NASA Technical Reports Server (NTRS)

Pirre, Michel; Marceau, Francois J.; Lebras, Georges; Maguin, Francoise; Poulet, Gille; Ramaroson, Radiela

1994-01-01

The impact of new laboratory data for the reaction BrO + HO2 yields HOBr + O2 in the depletion of global stratospheric ozone has been estimated using a one-dimensional photochemical model taking into account the heterogeneous reaction on sulphate aerosols which converts N2O5 into HNO3. Assuring an aerosol loading 2 times as large as the 'background' and a reaction probability of 0.1 for the above heterogeneous reaction, the 6 fold increase in the measured rate constant for the reaction of BrO with HO2 increases the computed depletion of global ozone produced by 20 ppt of total bromine from 2.01 percent to 2.36 percent. The use of the higher rate constant increases the HOBr mixing ratio and makes the bromine partitioning and the ozone depletion very sensitive to the branching ratio of the potential channel forming HBr in the BrO + HO2 reaction.

The puzzle of the CNO isotope ratios in asymptotic giant branch carbon stars

NASA Astrophysics Data System (ADS)

Abia, C.; Hedrosa, R. P.; Domínguez, I.; Straniero, O.

2017-03-01

Context. The abundance ratios of the main isotopes of carbon, nitrogen and oxygen are modified by the CNO-cycle in the stellar interiors. When the different dredge-up events mix the burning material with the envelope, valuable information on the nucleosynthesis and mixing processes can be extracted by measuring these isotope ratios. Aims: Previous determinations of the oxygen isotopic ratios in asymptotic giant branch (AGB) carbon stars were at odds with the existing theoretical predictions. We aim to redetermine the oxygen ratios in these stars using new spectral analysis tools and further develop discussions on the carbon and nitrogen isotopic ratios in order to elucidate this problem. Methods: Oxygen isotopic ratios were derived from spectra in the K-band in a sample of galactic AGB carbon stars of different spectral types and near solar metallicity. Synthetic spectra calculated in local thermodynamic equillibrium (LTE) with spherical carbon-rich atmosphere models and updated molecular line lists were used. The CNO isotope ratios derived in a homogeneous way, were compared with theoretical predictions for low-mass (1.5-3 M⊙) AGB stars computed with the FUNS code assuming extra mixing both during the RGB and AGB phases. Results: For most of the stars the 16O/17O/18O ratios derived are in good agreement with theoretical predictions confirming that, for AGB stars, are established using the values reached after the first dredge-up (FDU) according to the initial stellar mass. This fact, as far as the oxygen isotopic ratios are concerned, leaves little space for the operation of any extra mixing mechanism during the AGB phase. Nevertheless, for a few stars with large 16O/17O/18O, the operation of such a mechanism might be required, although their observed 12C/13C and 14N/15N ratios would be difficult to reconcile within this scenario. Furthermore, J-type stars tend to have lower 16O/17O ratios than the normal carbon stars, as already indicated in previous studies. Excluding these peculiar stars, AGB carbon stars occupy the same region as pre-solar type I oxide grains in a 17O/16O vs. 18O/16O diagram, showing little spread. This reinforces the idea that these grains were probably formed in low-mass stars during the previous O-rich phases.

Peroxyacetyl nitrate measurements during CITE 2 - Atmospheric distribution and precursor relationships

NASA Technical Reports Server (NTRS)

Singh, H. B.; Condon, E.; Vedder, J.; O'Hara, D.; Ridley, B. A.; Gandrud, B. W.; Shetter, J. D.; Beck, S. M.; Gregory, G. L.; Lebel, P. J.

1990-01-01

Results are reported from airborne PAN measurements obtained at altitudes 0-6 km over the continental U.S. and the eastern Pacific during the NASA Global Tropospheric Experiment Chemical Instrumentation Test and Evaluation 2 (CITE 2) in summer 1986. The CITE 2 flights and instrumentation are described, and the results are presented in extensive graphs and characterized in detail. It is shown that PAN is an important reactive N-containing species in the troposphere. Although the PAN mixing ratios were highly variable, in general high mixing ratios of 100-300 parts per trillion by volume (pptv) were found at 4-6 km, and very low ratios (5-20 pptv) were detected in the marine boundary layer. Good correlation was seen between the CITE 2 PAN values and those for O3, NO(y), NO(x), HNO3, C2H6, CO, and CFCl3.

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

PubMed

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

2017-03-01

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

Novel mixed ligand technetium complexes as 5-HT1A receptor imaging agents.

PubMed

León, A; Rey, A; Mallo, L; Pirmettis, I; Papadopoulos, M; León, E; Pagano, M; Manta, E; Incerti, M; Raptopoulou, C; Terzis, A; Chiotellis, E

2002-02-01

The synthesis, characterization and biological evaluation of two novel 3 + 1 mixed ligand 99mTc-complexes, bearing the 1-(2-methoxyphenylpiperazine) moiety, a fragment of the true 5-HT1A antagonist WAY 100635, is reported. Complexes at tracer level 99mTcO[(CH3CH2)2NCH2CH2N(CH2CH2S)2][o-CH3OC6H4N(CH2CH2)2NCH2CH2S], 99mTc-1, and 99mTcO[((CH3)2CH)2NCH2CH2N(CH2CH2S)2][o-CH3OC6H4N (CH2CH2)2NCH2CH2S], 99mTc-2, were prepared using 99mTc-glucoheptonate as precursor. For structural characterization, the analogous oxorhenium complexes, Re-1 and Re-2, were prepared by ligand exchange reaction using ReOCl3(PPh3)2 as precursor, and characterized by elemental analysis and spectroscopic methods. Complex Re-1 was further characterized by crystallographic analysis. Labeling was performed with high yield (>85%) and radiochemical purity (>90%) using very low ligand concentration. The structure of 99mTc complexes was established by comparative HPLC using the well-characterized oxorhenium analogues as references. In vitro binding assays demonstrated the affinity of these complexes for 5-HT1A receptors (IC50 : 67 and 45 nM for Re-1 and Re-2 respectively). Biological studies in mice showed the ability of 99mTc-1 and 99mTc-2 complexes to cross the intact blood-brain barrier (1.4 and 0.9% dose/g, respectively at 1 min post-inj.). The distribution of these complexes in various regions in rat brain is inhomogeneous. The highest ratio between areas reach and poor in 5-HT1A receptors was calculated for complex Tc-1 at 60 min p.i. (hippocampus/cerebellum = 1.7).

Permian magmatic sequences of the Bilihe gold deposit in central Inner Mongolia, China: Petrogenesis and tectonic significance

NASA Astrophysics Data System (ADS)

Liu, Chunhua; Nie, Fengjun

2015-08-01

The Bilihe gold deposit is located in the eastern section of the Ondor Sum-Yanji Suture at the southern margin of the Xing'an-Mongolian Orogenic Belt (XMOB) and the northern margin of the North China Craton (NCC), central Inner Mongolia. The magmatic rocks in the ore district are generally high-K calc-alkaline, enriched in LREE, Zr, and Hf, and depleted in HREE, Nb, Ta, and P. The magmatic evolution sequences are norite gabbro → granodiorite porphyry → granite or norite gabbro → andesite → dacite porphyry → granodiorite, which show a trend of decreasing TiO2, FeO, MgO, CaO, and P2O5 with increasing SiO2. In the Bilihe ore district, hydrothermal processes were coeval with granitic magmatism for a period of ~ 17 Myr (272-255 Ma). The ages of the granite, granodiorite porphyry, granodiorite, and dacite porphyry are 271.5-264.1 Ma, 269.8-255.8 Ma, 268.3 Ma, and 268.6-259.4 Ma, respectively. The magmatic rocks contain magmatic, hydrothermal, and magmatic-hydrothermal zircons. The magmatic zircons have δCe > 4, La < 3 ppm, and SmN/LaN > 2.5; the hydrothermal zircons have δCe < 4, La > 3 ppm, and SmN/LaN < 2.5. The Nb/Ta and Zr/Hf ratios of granodiorite are 12.7-14.99 and 40.2-46.56, respectively. The Zr/Hf ratios successively increase in the sequence of granite (27.4-29.02) → granodiorite porphyry (29.19-32.18) → dacite porphyry (33.54-38.5) → norite gabbro (36.75-38.37), and their Nb/Ta ratios are 9.09-12.38. Zircons in granodiorite yield ε Hf (t) values of - 0.29 to - 56 (n = 13) and 2.07-7.62 (n = 5), and they give a Hf two-stage model age (tDM2) of 807-4765 Ma. The ε Hf (t) values of the zircons in granite, granodiorite porphyry, and dacite porphyry are - 0.46 to 8.03, 3.17 to 10.32, and - 0.78 to 6.58, respectively, and their Hf tDM2 ages are 787-1324 Ma, 638-1091 Ma, and 868-1343 Ma, respectively. Dehydration partial melting of subducted oceanic crust resulted in the formation of dacite porphyry; partial melting of depleted mantle resulted in the formation of norite gabbro; mixing of depleted mantle and lower crust resulted in the formation of granodiorite porphyry; partial melting of lower crust resulted in the formation of granite; and mixing of lower crust and old upper crust resulted in the formation of granodiorite. Magmatic rocks in the ore district with ages of 272-255 Ma were formed during the late stages of closure of the Paleoasian Ocean; i.e., during the transformation from a collisional to extensional setting.

Heterotrophs are key contributors to nitrous oxide production in activated sludge under low C-to-N ratios during nitrification-Batch experiments and modeling.

PubMed

Domingo-Félez, Carlos; Pellicer-Nàcher, Carles; Petersen, Morten S; Jensen, Marlene M; Plósz, Benedek G; Smets, Barth F

2017-01-01

Nitrous oxide (N 2 O), a by-product of biological nitrogen removal during wastewater treatment, is produced by ammonia-oxidizing bacteria (AOB) and heterotrophic denitrifying bacteria (HB). Mathematical models are used to predict N 2 O emissions, often including AOB as the main N 2 O producer. Several model structures have been proposed without consensus calibration procedures. Here, we present a new experimental design that was used to calibrate AOB-driven N 2 O dynamics of a mixed culture. Even though AOB activity was favoured with respect to HB, oxygen uptake rates indicated HB activity. Hence, rigorous experimental design for calibration of autotrophic N 2 O production from mixed cultures is essential. The proposed N 2 O production pathways were examined using five alternative process models confronted with experimental data inferred. Individually, the autotrophic and heterotrophic denitrification pathway could describe the observed data. In the best-fit model, which combined two denitrification pathways, the heterotrophic was stronger than the autotrophic contribution to N 2 O production. Importantly, the individual contribution of autotrophic and heterotrophic to the total N 2 O pool could not be unambiguously elucidated solely based on bulk N 2 O measurements. Data on NO would increase the practical identifiability of N 2 O production pathways. Biotechnol. Bioeng. 2017;114: 132-140. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

An extraction process to recover vanadium from low-grade vanadium-bearing titanomagnetite.

PubMed

Chen, Desheng; Zhao, Hongxin; Hu, Guoping; Qi, Tao; Yu, Hongdong; Zhang, Guozhi; Wang, Lina; Wang, Weijing

2015-08-30

An extraction process to recover vanadium from low-grade vanadium-bearing titanomagnetite was developed. In this study, a mixed solvent system of di(2-ethylhexyl) phosphate (D2EHPA) and tri-n-butyl phosphate (TBP) diluted with kerosene was used for the selective extraction of vanadium from a hydrochloric acid leaching solution that contained low vanadium concentration with high concentrations of iron and impurities of Ca, Mg, and Al. In the extraction process, the initial solution pH and the phase ratio had considerable functions in the extraction of vanadium from the hydrochloric acid leaching solution. Under optimal extraction conditions (i.e., 30-40°C for 10min, 1:3 phase ratio (O/A), 20% D2EHPA concentration (v/v), and 0-0.8 initial solution pH), 99.4% vanadium and only 4.2% iron were extracted by the three-stage counter-current extraction process. In the stripping process with H2SO4 as the stripping agent and under optimal stripping conditions (i.e., 20% H2SO4 concentration, 5:1 phase ratio (O/A), 20min stripping time, and 40°C stripping temperature), 99.6% vanadium and only 5.4% iron were stripped by the three-stage counter-current stripping process. The stripping solution contained 40.16g/LV2O5,0.691g/L Fe, 0.007g/L TiO2, 0.006g/L SiO2 and 0.247g/L CaO. A V2O5 product with a purity of 99.12% V2O5 and only 0.026% Fe was obtained after the oxidation, precipitation, and calcination processes. The total vanadium recovered from the hydrochloric acid leaching solution was 85.5%. Copyright © 2015 Elsevier B.V. All rights reserved.

Single photon ionization of van der Waals clusters with a soft x-ray laser: (CO2)n and (CO2)n(H2O)m.

PubMed

Heinbuch, S; Dong, F; Rocca, J J; Bernstein, E R

2006-10-21

Pure neutral (CO2)n clusters and mixed (CO2)n(H2O)m clusters are investigated employing time of flight mass spectroscopy and single photon ionization at 26.5 eV. The distribution of pure (CO2)n clusters decreases roughly exponentially with increasing cluster size. During the ionization process, neutral clusters suffer little fragmentation because almost all excess cluster energy above the vertical ionization energy is taken away by the photoelectron and only a small part of the photon energy is deposited into the (CO2)n cluster. Metastable dissociation rate constants of (CO2)n+ are measured in the range of (0.2-1.5) x 10(4) s(-1) for cluster sizes of 5< or =n< or =16. Mixed CO2-H2O clusters are studied under different generation conditions (5% and 20% CO2 partial pressures and high and low expansion pressures). At high CO2 concentration, predominant signals in the mass spectrum are the (CO2)n+ cluster ions. The unprotonated cluster ion series (CO2)nH2O+ and (CO2)n(H2O)2+ are also observed under these conditions. At low CO2 concentration, protonated cluster ions (H2O)nH+ are the dominant signals, and the protonated CO2(H2O)nH+ and unprotonated (H2O)n+ and (CO2)(H2O)n+ cluster ion series are also observed. The mechanisms and dynamics of the formation of these neutral and ionic clusters are discussed.

Tequila authenticity assessment by headspace SPME-HRGC-IRMS analysis of 13C/12C and 18O/16O ratios of ethanol.

PubMed

Aguilar-Cisneros, Blanca O; López, Mercedes G; Richling, Elke; Heckel, Frank; Schreier, Peter

2002-12-18

By use of headspace SPME sampling and a PLOT column, on-line capillary gas chromatography-isotope ratio mass spectrometry was employed in the combustion (C) and the pyrolysis (P) modes (HRGC-C/P-IRMS) to determine the delta(13)C(VPDB) and delta(18)O(VSMOW) values of ethanol in authentic (n = 14) and commercial tequila samples (n = 15) as well as a number of other spirits (n = 23). Whereas with delta(13)C(VPDB) values ranging from -12.1 to -13.2 per thousand and from -12.5 to -14.8 per thousand similar variations were found for 100% agave and mixed tequilas, respectively, the delta(18)O(VSMOW) data differed slightly within these categories: ranges from +22.1 to +22.8 per thousand and +20.8 to +21.7 per thousand were determined for both the authentic 100% agave and mixed products, respectively. The data recorded for commercial tequilas were less homogeneous; delta(13)C(VPDB) data from -10.6 to -13.9 per thousand and delta(18)O(VSMOW) values from +15.5 to +22.7 per thousand were determined in tequilas of both categories. Owing to overlapping data, attempts to differentiate between white, rested, and aged tequilas within each of the two categories failed. In addition, discrimination of tequila samples from other spirits by means of delta(13)C(VPDB) and delta(18)O(VSMOW) data of ethanol was restricted to the products originating from C(3) as well as C(4)/CAM raw materials.

Abundance and Isotopic Composition of Gases in the Martian Atmosphere: First Results from the Mars Curiosity Rover

NASA Technical Reports Server (NTRS)

Mahaffy, Paul; Webster, Chris R.; Atreya, Sushil K.; Franz, Heather; Wong, Michael; Conrad, Pamela G.; Harpold, Dan; Jones, John J.; Leshin, Laurie, A.; Manning, Heidi;

Nano-glass ceramic cathodes for Li+/Na+ mixed-ion batteries

NASA Astrophysics Data System (ADS)

He, Wen; Zhang, Xudong; Jin, Chao; Wang, Yaoyao; Mossin, Susanne; Yue, Yuanzheng

2017-02-01

Electrode materials can display superior electrochemical performances and behavior via the nanoscale design. Here, the low-temperature synthesis of nano-glass ceramics (NGCs) is based on inheriting the network structure of yeast polyphosphate metabolism. The NGCs-3 sample synthesized with a molar ratio of Fe/V = 7:6 is composed of nano-domains of semiconducting oxide glass (Li2O-Na2O-Fe2O3-V2O5-P2O5, LNFVP), nanocrystalline particles (Li9Fe3P8O29, Li0.6V1.67O3.67 and VOPO4), and nanopores connected by interfaces. We have clarified the mixing ion transport mechanism and the electrochemical reactions, and the influences of molar ratio of Fe/V on the structure and electrochemical properties of NGCs. This nanoscale design offers a new possibility improved the electrochemical performances of Li+/Na+ mixed-ion batteries (LNMIBs). The NGCs-3 electrode exhibits a higher discharge capacity (145 mAh g-1) and energy storage density (525 Whkg-1) at 5C, and the capacity retention reaches 70% after 1000 cycles. More importantly, we have established a direct relationship between the electrochemical kinetics and nanostructure of NGC electrode materials.

Effects of aeration and internal recycle flow on nitrous oxide emissions from a modified Ludzak-Ettinger process fed with glycerol.

PubMed

Song, Kang; Suenaga, Toshikazu; Harper, Willie F; Hori, Tomoyuki; Riya, Shohei; Hosomi, Masaaki; Terada, Akihiko

2015-12-01

Nitrous oxide (N2O) is emitted from a modified Ludzak-Ettinger (MLE) process, as a primary activated sludge system, which requires mitigation. The effects of aeration rates and internal recycle flow (IRF) ratios on N2O emission were investigated in an MLE process fed with glycerol. Reducing the aeration rate from 1.5 to 0.5 L/min increased gaseous the N2O concentration from the aerobic tank and the dissolved N2O concentration in the anoxic tank by 54.4 and 53.4 %, respectively. During the period of higher aeration, the N2O-N conversion ratio was 0.9 % and the potential N2O reducers were predominantly Rhodobacter, which accounted for 21.8 % of the total population. Increasing the IRF ratio from 3.6 to 7.2 decreased the N2O emission rate from the aerobic tank and the dissolved N2O concentration in the anoxic tank by 56 and 48 %, respectively. This study suggests effective N2O mitigation strategies for MLE systems.

Triple-activated blast furnace slag

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

Clarke, W.J.

1995-12-31

The current shortage of portland cement in the world will require the use of Ground Granulated Blast Furnace Slag (GGBFS) to fill demands in many industrialized countries. Therefore, an extensive series of triple-activated slag experiments have been undertaken to optimize an economical combination of mechanical properties for alkali-activated slags. Na{sub 2}OSiO{sub 2} (N Grade), Ca(OH){sub 2}, H{sub 2}O and Na{sub 2}CO{sub 3} have been added as activators in 5 to 10, 0 to 5 and 0 to 5 weight percentages of water and slag in a mix with a water:cement ratio of 1:1. Silica Fume and Sika 10 superplasticizer havemore » been added as 1 and 10 weight percent of slag. Set times, initial hardening times and compressive strengths at percentages of the mix to identify more refined formulations. Finally, the resulting aggregate to develop a triple-activated slag formulation with the ultimate objective of contributing toward satisfying the world shortage of high performance concrete.« less

Crystal structure study of dielectric oxynitride perovskites La{sub 1−x}Sr{sub x}TiO{sub 2+x}N{sub 1−x} (x=0, 0.2)

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

Habu, Daiki; Masubuchi, Yuji; Torii, Shuki

As is the case with SrTaO{sub 2}N, both cis-ordering of nitride anions and octahedral titling are also preferable in La{sub 1−x}Sr{sub x}TiO{sub 2+x}N{sub 1−x} (x=0, 0.2) oxynitride perovskites. A larger dielectric constant of ε{sub r}≈5.0×10{sup 3} was estimated for the pure oxynitride with x=0.2, compared with ε{sub r}≈750 for the product with x=0, by extrapolating the ε{sub r} values obtained from powders mixed with paraffin at various mixing ratios. The crystal structure of x=0.2 with larger tolerance factor than x=0 increased the octahedral tilting, which contributes to the increased dielectric constant. The increased dielectric constant supports the exchange mechanism formore » the dielectric property between two kinds of –Ti–N– helical coils (clockwise and anticlockwise) derived from the above cis-ordering of nitride anions. - Graphical abstract: Very large dielectric constant values were estimated for La{sub 1−x}Sr{sub x}TiO{sub 2+x}N{sub 1−x}; ε{sub r}≈5.0×10{sup 3} in x=0.2 and ε{sub r}≈750 in x=0. - Highlights: • Cis-configuration of nitride anions was confirmed in La{sub 1−x}Sr{sub x}TiO{sub 2+x}N{sub 1−x} (x=0, 0.2). • Dielectric constant values were estimated to be 750 for x=0 and 5.0×10{sup 3} for x=0.2, respectively. • The large dielectric property is to the exchange mechanism between clockwise and anticlockwise –Ti–N– coil motifs.« less

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

PubMed

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

2011-01-22

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

Synthesis, Structure, White-Light Emission, and Temperature Recognition Properties of Eu/Tb Mixed Coordination Polymers.

PubMed

An, Ran; Zhao, Hui; Hu, Huai-Ming; Wang, Xiaofang; Yang, Meng-Lin; Xue, Ganglin

2016-01-19

Two series of Eu(III)/Tb(III) coordination polymers, [LnL(glu)]n·2nH2O (Ln = Eu (1), Tb (2)) and [LnL(glu)(H2O)]n (Ln = Eu (3), Tb (4)) [HL = (2-(2-sulfophenyl)imidazo(4,5-f)(1,10)-phenanthroline, H2glu = glutaric acid] have been hydrothermally synthesized by controlling the pH values and characterized by elemental analysis, infrared spectra, and single-crystal X-ray diffraction. Isomorphic compounds 1 and 2 exhibit 6-connected 3D network with the pcu topological net, containing left- and right-handed helical chains. Isomorphic compounds 3 and 4 show 3,4-connected 2D new topology with the point symbol of (4(2)·6(3)·8)(4(2)·6). Multicolor luminescence can be tailored from red to green regions by singly varying the mixing molar ratio of Eu(III)/Tb(III) cations. The mixing component of 1Eu/2Tb = 4:6 not only achieves white-light emission with the CIE coordinate of (0.323, 0.339) upon excitation at 405 nm but also presents a temperature recognition property with the significantly high sensitivity of 0.68% per K in the 50-225 K temperature range upon excitation at 370 nm.

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

NASA Technical Reports Server (NTRS)

Webster, Christopher R.; May, Randy D.

1992-01-01

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

Nitrous oxide measurements in the eastern tropical Pacific Ocean

NASA Technical Reports Server (NTRS)

Pierotti, D.; Rasmussen, R. A.

1980-01-01

The paper considers nitrous oxide measurements in the eastern tropical Pacific Ocean. The concentration of N2O in the marine air showed a direct relationship to the N2O in the surface sea water, with the highest N2O mixing ratios over highly supersaturated regions; water samples were also collected down to depths of 300 m at seven hydrocast stations. The stations showed two distribution patterns for N2O concentration vs depth for the region between the surface and 300 m; two stations in the oxygen deficient region off the coast of Peru showed considerable N2O super-saturation at all depths, and results indicate that the role of N2O in the nitrogen cycle of the ocean may be more complex than previously suggested.

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.

On the production of He, C, and N by low- and intermediate-mass stars: a comparison of observed and model-predicted planetary nebula abundances

NASA Astrophysics Data System (ADS)

Henry, R. B. C.; Stephenson, B. G.; Miller Bertolami, M. M.; Kwitter, K. B.; Balick, B.

2018-01-01

The primary goal of this paper is to make a direct comparison between the measured and model-predicted abundances of He, C, and N in a sample of 35 well-observed Galactic planetary nebulae (PNe). All observations, data reductions, and abundance determinations were performed in house to ensure maximum homogeneity. Progenitor star masses (M ≤ 4 M⊙) were inferred using two published sets of post-asymptotic giant branch model tracks and L and Teff values. We conclude the following: (1) the mean values of N/O across the progenitor mass range exceeds the solar value, indicating significant N enrichment in the majority of our objects; (2) the onset of hot bottom burning appears to begin around 2 M⊙, i.e. lower than ∼5 M⊙ implied by theory; (3) most of our objects show a clear He enrichment, as expected from dredge-up episodes; (4) the average sample C/O value is 1.23, consistent with the effects of third dredge up; and (5) model grids used to compare to observations successfully span the distribution over metallicity space of all C/O and many He/H data points but mostly fail to do so in the case of N/O. The evident enrichment of N in PN and the general discrepancy between the observed and model-predicted N/O abundance ratios signal the need for extra mixing as an effect of rotation and/or thermohaline mixing in the models. The unexpectedly high N enrichment that is implied here for low-mass stars, if confirmed, will likely impact our conclusions about the source of N in the Universe.

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

NASA Astrophysics Data System (ADS)

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

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

Greenhouse gas emissions from home composting in practice.

PubMed

Ermolaev, Evgheni; Sundberg, Cecilia; Pell, Mikael; Jönsson, Håkan

2014-01-01

In Sweden, 16% of all biologically treated food waste is home composted. Emissions of the greenhouse gases CH4 and N2O and emissions of NH3 from home composts were measured and factors affecting these emissions were examined. Gas and substrate in the compost bins were sampled and the composting conditions assessed 13 times during a 1-year period in 18 home composts managed by the home owners. The influence of process parameters and management factors was evaluated by regression analysis. The mean CH4 and N2O concentration was 28.1 and 5.46 ppm (v/v), respectively, above the ambient level and the CH4:CO2 and N2O:CO2 ratio was 0.38% and 0.15%, respectively (median values 0.04% and 0.07%, respectively). The home composts emitted less CH4 than large-scale composts, but similar amounts of N2O. Overall NH3 concentrations were low. Increasing the temperature, moisture content, mixing frequency and amount of added waste all increased CH4 emissions. Copyright © 2013 Elsevier Ltd. All rights reserved.

Mixed-valent [FeIV(mu-O)(mu-carboxylato)2FeIII]3+ core.

PubMed

Slep, Leonardo D; Mijovilovich, Ana; Meyer-Klaucke, Wolfram; Weyhermüller, Thomas; Bill, Eckhard; Bothe, Eberhard; Neese, Frank; Wieghardt, Karl

2003-12-17

The symmetrically ligated complexes 1, 2, and 3 with a (mu-oxo)bis(mu-acetato)diferric core can be one-electron oxidized electrochemically or chemically with aminyl radical cations [*NR3][SbCl6] in acetonitrile yielding complexes which contain the mixed-valent [(mu-oxo)bis(mu-acetato)iron(IV)iron(III)]3+ core: [([9]aneN3)(2FeIII2)(mu-O)(mu-CH3CO2)2](ClO4)2 (1(ClO4)2), [(Me3[9]aneN3)(2FeIII2)(mu-O)(mu-CH3CO2)2](PF6)2 (2(PF6)(2)), and [(tpb)(2FeIII2)(mu-O)(mu-CH3CO2)2] (3) where ([9]aneN3) is the neutral triamine 1,4,7-triazacyclononane and (Me3[9]aneN3) is its tris-N-methylated derivative, and (tpb)(-) is the monoanion trispyrazolylborate. The asymmetrically ligated complex [(Me3[9]aneN3)FeIII(mu-O)(mu-CH3CO2)2FeIII(tpb)](PF6) (4(PF6)) and its one-electron oxidized form [4ox]2+ have also been prepared. Finally, the known heterodinuclear species [(Me3[9]aneN3)CrIII(mu-O)(mu-CH3CO2)2Fe([9]aneN3)](PF6)2 (5(PF6)(2)) can also be one-electron oxidized yielding [5ox]3+ containing an iron(IV) ion. The structure of 4(PF6).0.5CH3CN.0.25(C2H5)2O has been determined by X-ray crystallography and that of [5ox]2+ by Fe K-edge EXAFS-spectroscopy (Fe(IV)-O(oxo): 1.69(1) A; Fe(IV)-O(carboxylato) 1.93(3) A, Fe(IV)-N 2.00(2) A) contrasting the data for 5 (Fe(III)-O(oxo) 1.80 A; Fe(III)-O(carboxylato) 2.05 A, Fe-N 2.20 A). [5ox]2+ has an St = 1/2 ground state whereas all complexes containing the mixed-valent [FeIV(mu-O)(mu-CH3CO2)2FeIII]3+ core have an St = 3/2 ground state. Mössbauer spectra of the oxidized forms of complexes clearly show the presence of low spin FeIV ions (isomer shift approximately 0.02 mm s(-1), quadrupole splitting approximately 1.4 mm s(-1) at 80 K), whereas the high spin FeIII ion exhibits delta approximately 0.46 mm s(-1) and DeltaE(Q) approximately 0.5 mm s(-1). Mössbauer, EPR spectral and structural parameters have been calculated by density functional theoretical methods at the BP86 and B3LYP levels. The exchange coupling constant, J, for diiron complexes with the mixed-valent FeIV-FeIII core (H = -2J S1.S2; S(1) = 5/2; S2 = 1) has been calculated to be -88 cm(-1) (intramolecular antiferromagnetic coupling) and for the reduced diferric form of -75 cm(-1) in reasonable agreement with experiment (J = -120 cm(-1)).

Biological Productivity from an Oxygen Mass Balance in the subarctic North Pacific

NASA Astrophysics Data System (ADS)

Giesbrecht, K. E.; Hamme, R. C.

2008-12-01

Biological productivity is an important process controlling the export of carbon into the deep ocean and thus influencing the earth's climate. An O2 mass balance of the upper ocean can estimate this export of organic carbon if the physical processes affecting the O2 concentrations are accounted for. This can be accomplished by measuring the dissolved O2/Ar ratio, because their similar physical properties allow us to consider Ar an 'abiotic' O2 analogue. Here we present a two-year data set of O2/N2/Ar ratio measurements collected at Station Papa and along Line P in 2007/08. Line P, situated in the subarctic North Pacific, is a series of oceanographic stations running from the southwest tip of Vancouver Island to Station Papa (50°N, 145°W), one of the oldest deep-ocean time series in existence which is located in the High-Nutrient/Low-Chlorophyll (HNLC) region of the subarctic gyre. Current cruises along Line P run three times per year, typically in February, June and August. The dissolved gas ratios are measured using a stable isotope mass spectrometer and oxygen concentrations by titration. In a simple steady state, we equate biological O2 production to diffusive gas exchange, using the O2/Ar ratio to normalize the physical component of the oxygen signal and calculate the net biological oxygen production. Diffusive gas exchange is calculated using a wind speed parameterization. Preliminary estimates of the net biological production in the mixed layer at Station Papa for 2007 are calculated at 30.9 and 14.0 mmol C m-2 d- 1 for June and August respectively, both exhibiting mixed layer O2/Ar supersaturations. The O2/Ar undersaturation in the mixed layer for February 2007 suggests net respiration at that time. The wind speed parameterization of diffusive gas exchange is the major source of error for this method. We plan to refine our productivity calculation to account for vertical mixing and also by measuring rates of production using a number of different methods, so that we may determine if the values obtained converge on a result. Future investigations to obtain a better-constrained estimate of the biological carbon export in this region by measuring Nitrogen and Carbon uptake rates in the euphotic zone using dual, stable isotope tracer 15N/13C incubations in addition to the oxygen mass balance will be discussed.

Investigation of luminescence and laser transition of Dy3+ ion in P2O5sbnd PbOsbnd Bi2O3sbnd R2O3 (R = Al, Ga, In) glasses

NASA Astrophysics Data System (ADS)

Ram, G. Chinna; Narendrudu, T.; Suresh, S.; Kumar, A. Suneel; Rao, M. V. Sambasiva; Kumar, V. Ravi; Rao, D. Krishna

2017-04-01

P2O5sbnd PbOsbnd Bi2O3sbnd R2O3 (R = Al, Ga, In) glasses doped with Dy2O3 were prepared by melt quenching technique. The prepared glasses were characterized by XRD, optical absorption, FTIR, luminescence studies. Judd-Ofelt parameters have been evaluated for three glass systems from optical absorption spectra and in turn radiative parameters for excited luminescent levels of Dy3+ ion are also calculated. Emission cross section and branching ratio values are observed to high for 6H13/2 level for Dy3+ ion. The yellow to blue intensity ratios and CIE chromaticity coordinates were calculated. Decay curves exhibit non exponential behavior. Quantum efficiency of prepared glasses was measured by using radiative and calculated life times. IR studies, J-O parameters and Y/B ratio values indicate that more asymmetry around Dy3+ ions in Ga2O3 mixed glass was observed. Chromaticity coordinates lie near ideal white light region. These coordinates and CCT values have revealed that all the prepared glasses emit quality white light especially the glasses mixed with Ga2O3 are suitable for development of white LEDs.

Aspects of Supercritical Turbulence: Direct Numerical Simulation of O2/H2 and C7H16/N2 Temporal Mixing Layers

NASA Technical Reports Server (NTRS)

Bellan, J.; Okongo, N. A.; Harstad, K. G.; Hutt, John (Technical Monitor)

2002-01-01

Results from Direct Numerical Simulations of temporal, supercritical mixing layers for two species systems are analyzed to elucidate species-specific turbulence aspects. The two species systems, O2/H2 and C7HG16/N2, have different thermodynamic characteristics; thus, although the simulations are performed at similar reduced pressure (ratio of the pressure to the critical pressure), the former system is dose to mixture ideality and has a relatively high solubility with respect to the latter, which exhibits strong departures from mixture ideality Due to the specified, smaller initial density stratification, the C7H16/N2 layers display higher growth and increased global molecular mixing as well as larger turbulence levels. However, smaller density gradients at the transitional state for the O2/H2 system indicate that on a local basis, the layer exhibits an enhanced mixing, this being attributed to the increased solubility and to mixture ideality. These thermodynamic features are shown to affect the irreversible entropy production (i.e. the dissipation), which is larger for the O2/H2 layer and is primarily concentrated in high density-gradient magnitude regions that are distortions of the initial density stratification boundary. In contrast, the regions of largest dissipation in the C7H16/N2 layer are located in high density-gradient magnitude regions resulting from the mixing of the two fluids.

Nitrous oxide emissions are enhanced in a warmer and wetter world

NASA Astrophysics Data System (ADS)

Griffis, Timothy J.; Chen, Zichong; Baker, John M.; Wood, Jeffrey D.; Millet, Dylan B.; Lee, Xuhui; Venterea, Rodney T.; Turner, Peter A.

2017-11-01

Nitrous oxide (N2O) has a global warming potential that is 300 times that of carbon dioxide on a 100-y timescale, and is of major importance for stratospheric ozone depletion. The climate sensitivity of N2O emissions is poorly known, which makes it difficult to project how changing fertilizer use and climate will impact radiative forcing and the ozone layer. Analysis of 6 y of hourly N2O mixing ratios from a very tall tower within the US Corn Belt—one of the most intensive agricultural regions of the world—combined with inverse modeling, shows large interannual variability in N2O emissions (316 Gg N2O-Nṡy‑1 to 585 Gg N2O-Nṡy‑1). This implies that the regional emission factor is highly sensitive to climate. In the warmest year and spring (2012) of the observational period, the emission factor was 7.5%, nearly double that of previous reports. Indirect emissions associated with runoff and leaching dominated the interannual variability of total emissions. Under current trends in climate and anthropogenic N use, we project a strong positive feedback to warmer and wetter conditions and unabated growth of regional N2O emissions that will exceed 600 Gg N2O-Nṡy‑1, on average, by 2050. This increasing emission trend in the US Corn Belt may represent a harbinger of intensifying N2O emissions from other agricultural regions. Such feedbacks will pose a major challenge to the Paris Agreement, which requires large N2O emission mitigation efforts to achieve its goals.

Roasting and leaching behaviors of vanadium and chromium in calcification roasting-acid leaching of high-chromium vanadium slag

NASA Astrophysics Data System (ADS)

Wen, Jing; Jiang, Tao; Zhou, Mi; Gao, Hui-yang; Liu, Jia-yi; Xue, Xiang-xin

2018-05-01

Calcification roasting-acid leaching of high-chromium vanadium slag (HCVS) was conducted to elucidate the roasting and leaching behaviors of vanadium and chromium. The effects of the purity of CaO, molar ratio between CaO and V2O5 ( n(CaO)/ n(V2O5)), roasting temperature, holding time, and the heating rate used in the oxidation-calcification processes were investigated. The roasting process and mechanism were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetry-differential scanning calorimetry (TG-DSC). The results show that most of vanadium reacted with CaO to generate calcium vanadates and transferred into the leaching liquid, whereas almost all of the chromium remained in the leaching residue in the form of (Fe0.6Cr0.4)2O3. Variation trends of the vanadium and chromium leaching ratios were always opposite because of the competitive reactions of oxidation and calcification between vanadium and chromium with CaO. Moreover, CaO was more likely to combine with vanadium, as further confirmed by thermodynamic analysis. When the HCVS with CaO added in an n(CaO)/ n(V2O5) ratio of 0.5 was roasted in an air atmosphere at a heating rate of 10°C/min from room temperature to 950°C and maintained at this temperature for 60 min, the leaching ratios of vanadium and chromium reached 91.14% and 0.49%, respectively; thus, efficient extraction of vanadium from HCVS was achieved and the leaching residue could be used as a new raw material for the extraction of chromium. Furthermore, the oxidation and calcification reactions of the spinel phases occurred at 592 and 630°C for n(CaO)/ n(V2O5) ratios of 0.5 and 5, respectively.

Investigation of Heterogeneous N2O5 Uptake and ClNO2 Yield at a Rural and a Mountain-top Site in Northern China

NASA Astrophysics Data System (ADS)

Wang, Z.; Tham, Y. J.; Wang, W.; LI, Q.; Yun, H.; Wang, X.; Xue, L.; Wang, T.

2017-12-01

Dinitrogen pentoxide (N2O5) is a reactive intermediate in the atmospheric oxidation of nitrogen oxides (NOx), and its heterogeneous reaction plays key roles in the chemical transformation and removal of NOx, as well as the production of nitrate and nitryl chloride (ClNO2) that affects the radical budget and photochemical ozone formation. Ambient measurements at a rural site and a mountain top site in northern China in the summer of 2014 revealed significant ClNO2 mixing ratios (up to 2.1 ppbv) produced by fast heterogeneous N2O5 uptake on atmospheric aerosols. Frequently intercepted ClNO2-laden plumes at the mountain site indicate significant ClNO2 production occurred in the nocturnal residual layer, and could help explain the sustained ClNO2 peaks after sunrise observed in the ground site in the region. The meteorological and chemical analysis suggested that elevated ClNO2 plumes were mostly associated with nocturnal buoyant emission from point combustion sources, such as power and industry plants. The uptake coefficients (γ) of N2O5 and yields (ϕ) of ClNO2 were then derived for different plumes observed at the ground and mountain sites, and the factors affecting the variability of γ and ϕ under different conditions were also investigated. The uptake coefficients and yields obtained in this study in northern China will be compared with other observations in the world, and also compared to the existing parameterizations based on aerosol compositions. The contribution of fast N2O5 heterogeneous reaction to the nocturnal NOx processing and nitrate aerosol formation will be further examined, to better understand the impacts of heterogeneous reactive nitrogen chemistry on air quality in northern China.

Tracing troposphere-to-stratosphere transport above a mid-latitude deep convective system

NASA Astrophysics Data System (ADS)

Hegglin, M. I.; Brunner, D.; Wernli, H.; Schwierz, C.; Martius, O.; Hoor, P.; Fischer, H.; Spelten, N.; Schiller, C.; Krebsbach, M.; Parchatka, U.; Weers, U.; Staehelin, J.; Peter, Th.

2004-01-01

Within the project SPURT (trace gas measurements in the tropopause region) a variety of trace gases have been measured in situ in order to investigate the role of dynamical and chemical processes in the extra-tropical tropopause region. In this paper we report on a flight on 10 November 2001 leading from Hohn, Germany (52° N) to Faro, Portugal (37° N) through a strongly developed deep stratospheric intrusion. This streamer was associated with a large convective system over the western Mediterranean with potentially significant troposphere-to-stratosphere transport. Along major parts of the flight we measured unexpectedly high NOy mixing ratios. Also H2O mixing ratios were significantly higher than stratospheric background levels confirming the extraordinary chemical signature of the probed air masses in the interior of the streamer. Backward trajectories encompassing the streamer enable to analyze the origin and physical characteristics of the air masses and to trace troposphere-to-stratosphere transport. Near the western flank of the intrusion features caused by long range transport, such as tropospheric filaments characterized by sudden drops in the O3 and NOy mixing ratios and enhanced CO and H2O can be reconstructed in great detail using the reverse domain filling technique. These filaments indicate a high potential for subsequent mixing with the stratospheric air. At the south-western edge of the streamer a strong gradient in the NOy and the O3 mixing ratios coincides very well with a sharp gradient in potential vorticity in the ECMWF fields. In contrast, in the interior of the streamer the observed highly elevated NOy and H2O mixing ratios up to a potential temperature level of 365 K and potential vorticity values of maximum 10 PVU cannot be explained in terms of resolved troposphere-to-stratosphere transport along the backward trajectories. Also mesoscale simulations with a High Resolution Model reveal no direct evidence for convective H2O injection up to this level. Elevated H2O mixing ratios in the ECMWF and HRM model are seen only up to about tropopause height at 340 hPa and 270hPa, respectively, well below flight altitude of about 200 hPa. However, forward tracing of the convective influence as identified by satellite brightness temperature measurements and counts of lightning strokes shows that during this part of the flight the aircraft was closely following the border of an air mass which was heavily impacted by convective activity over Spain and Algeria. This is evidence that deep convection at mid-latitudes may have a large impact on the tracer distribution of the lowermost stratosphere reaching well above the thunderstorms anvils as claimed by recent studies using cloud-resolving models.

Tracing troposphere-to-stratosphere transport above a mid-latitude deep convective system

NASA Astrophysics Data System (ADS)

Hegglin, M. I.; Brunner, D.; Wernli, H.; Schwierz, C.; Martius, O.; Hoor, P.; Fischer, H.; Parchatka, U.; Spelten, N.; Schiller, C.; Krebsbach, M.; Weers, U.; Staehelin, J.; Peter, Th.

2004-05-01

Within the project SPURT (trace gas measurements in the tropopause region) a variety of trace gases have been measured in situ in order to investigate the role of dynamical and chemical processes in the extra-tropical tropopause region. In this paper we report on a flight on 10 November 2001 leading from Hohn, Germany (52ºN) to Faro, Portugal (37ºN) through a strongly developed deep stratospheric intrusion. This streamer was associated with a large convective system over the western Mediterranean with potentially significant troposphere-to-stratosphere transport. Along major parts of the flight we measured unexpectedly high NOy mixing ratios. Also H2O mixing ratios were significantly higher than stratospheric background levels confirming the extraordinary chemical signature of the probed air masses in the interior of the streamer. Backward trajectories encompassing the streamer enable to analyze the origin and physical characteristics of the air masses and to trace troposphere-to-stratosphere transport. Near the western flank of the intrusion features caused by long range transport, such as tropospheric filaments characterized by sudden drops in the O3 and NOy mixing ratios and enhanced CO and H2O can be reconstructed in great detail using the reverse domain filling technique. These filaments indicate a high potential for subsequent mixing with the stratospheric air. At the south-western edge of the streamer a strong gradient in the NOy and the O3 mixing ratios coincides very well with a sharp gradient in potential vorticity in the ECMWF fields. In contrast, in the interior of the streamer the observed highly elevated NOy and H2O mixing ratios up to a potential temperature level of 365 K and potential vorticity values of maximum 10 PVU cannot be explained in terms of resolved troposphere-to-stratosphere transport along the backward trajectories. Also mesoscale simulations with a High Resolution Model reveal no direct evidence for convective H2O injection up to this level. Elevated H2O mixing ratios in the ECMWF and HRM model are seen only up to about tropopause height at 340 hPa and 270hPa, respectively, well below flight altitude of about 200 hPa. However, forward tracing of the convective influence as identified by satellite brightness temperature measurements and counts of lightning strokes shows that during this part of the flight the aircraft was closely following the border of an air mass which was heavily impacted by convective activity over Spain and Algeria. This is evidence that deep convection at mid-latitudes may have a large impact on the tracer distribution of the lowermost stratosphere reaching well above the thunderstorms anvils as claimed by recent studies using cloud-resolving models.

Curiosity and the Four Seasons: In Situ Measurements of the Atmospheric Composition over Three Mars Years

NASA Astrophysics Data System (ADS)

Trainer, M. G.; Franz, H. B.; Mahaffy, P. R.; Malespin, C.; Wong, M. H.; Atreya, S. K.; Becker, R. H.; Conrad, P. G.; Lefèvre, F.; Manning, H. L. K.; Martin-Torres, F. J.; McConnochie, T.; McKay, C.; Navarro-Gonzalez, R.; Pepin, R. O.; Webster, C. R.; Zorzano, M. P.

2017-12-01

The Sample Analysis at Mars (SAM) instrument onboard the Mars Science Laboratory Curiosity rover measures the chemical composition of major atmospheric species in the vicinity of the rover through a dedicated atmospheric inlet. We report here on measurements of atmospheric volume mixing ratios in Gale Crater using the SAM quadrupole mass spectrometer (QMS), over a period of nearly three Mars years (5 Earth years) from landing. The observation period spans the southern winter of MY 31, solar longitude (Ls) of 175° through southern fall of MY 34, Ls = 12°. The initial mixing ratios measured by the SAM QMS were reported for the first 105 sols of the mission [1], and were updated to account for newly developed calibration factors [2]. The SAM QMS atmospheric measurements were continued, periodically interspersed between solid sample measurements and other rover activities, with a cumulative coverage of 4 or 5 experiments per season. The three major volatiles - CO2, N2, and 40Ar - are compatible with the annual pressure cycle but with a repeatable lag that indicates incomplete mixing and the influences of seasonal circulation patterns. The mixing ratios for the two inert, non-condensable species are qualitatively consistent with what is predicted from annual cycle of CO2 deposition and sublimation at the poles, which is manifested in a large enhancement of Ar mixing ratio at the winter poles (and assumed for N2) [3]. The mixing ratio for the minor species O2 appears to follow a distinct seasonal trend and may be indicative of possible deviations from known atmospheric chemistry or a surface flux of oxygen from an unknown source, or both. This unprecedented seasonal coverage and precision in mixing ratio determination provides valuable data for understanding the seasonal chemical and dynamics cycles. Further, this measurement campaign supplies useful ground-truth data for global climate model simulations, which can study atmospheric effects for other locations on Mars as well as long-term evolution of Mars climate. References:[1] Mahaffy, P. R., et al. (2013), Science, doi:10.1126/science.1237966. [2] Franz, H. B., et al. (2017), Planet. Space Sci., doi:10.1016/j.pss.2017.01.014. [3] Sprague, A. L., et al. (2012), J. Geophys. Res., doi:10.1029/2011JE003873.

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

NASA Astrophysics Data System (ADS)

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

1980-01-01

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

Assembly of bicyclic or monocyclic clusters from [(η5-C5Me5)2Mo2(μ3-S)4(CuMeCN)2]2+ with tetraphosphine or N,P mixed ligands: syntheses, structures and enhanced third-order NLO performances.

PubMed

Ren, Zhi-Gang; Sun, Sha; Dai, Min; Wang, Hui-Fang; Lü, Chun-Ning; Lang, Jian-Ping; Sun, Zhen-Rong

2011-09-07

Reactions of the preformed cluster [(η(5)-C(5)Me(5))(2)Mo(2)(μ(3)-S)(4)Cu(2)(MeCN)(2)](ClO(4))(2) (1) with two tetraphosphine ligands, 1,4-N,N,N',N'-tetra(diphenylphosphanylmethyl)benzene diamine (dpppda) and N,N,N',N'-tetra(diphenylphosphanylmethyl)ethylene diamine (dppeda), produced two bicyclic clusters {[(η(5)-C(5)Me(5))(2)Mo(2)(μ(3)-S)(4)Cu(2)](2)(L)}(ClO(4))(4) (3: L = dpppda; 4: L = dppeda). Analogous reactions of 1 or [(η(5)-C(5)Me(5))(2)Mo(2)(μ(3)-S)(4)Cu(2)(MeCN)(2)](PF(6))(2) (2) with two N,P mixed ligands, N,N-bi(diphenylphosphanylmethyl)-2-aminopyridine (bdppmapy) and N-diphenylphosphanylmethyl-4-aminopyridine (dppmapy), afforded two monocyclic clusters {[(η(5)-C(5)Me(5))(2)Mo(2)(μ(3)-S)(4)Cu(2)](2)(L)(2)}X(4) (5: L = bdppmapy, X = ClO(4); 6: L = dppmapy, X = PF(6)). Compounds 3-6 were fully characterized by elemental analysis, IR spectra, UV-vis spectra, (1)H and (31)P{(1)H} NMR spectra, ESI-MS and single-crystal X-ray crystallography. In the tetracations of 3-6, two cubane-like [Mo(2)(μ(3)-S)(4)Cu(2)] cores are linked either by one dpppda or dppeda bridge to form a bicyclic structure or by a pair of bdppmapy or dppmapy bridges to afford a monocyclic structure. The third-order nonlinear optical (NLO) properties of 1 and 3-6 in MeCN were also investigated by femtosecond degenerate four-wave mixing (DFWM) technique with a 50 fs pulse width at 800 nm. Compounds 3-6 exhibited enhanced third-order NLO performances relative to that of 1. This journal is © The Royal Society of Chemistry 2011

The structural influence of aluminium ions on emission characteristics of Sm{sup 3+} ions in lead aluminium silicate glass system

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

Bhargavi, K.; Srinivasa Reddy, M.; Raghava Rao, P.

Graphical abstract: The optical absorption and photoluminescence spectra of Sm ions in PbO-Al{sub 2}O{sub 3}-SiO{sub 2} glasses mixed with different concentrations of Al{sub 2}O{sub 3} have been investigated. From these spectra, the emission probabilities and also fluorescence lifetime principal transition viz., {sup 4}G{sub 5/2} {yields} {sup 6}H{sub 7/2} of Sm{sup 3+} ions of has been evaluated. The analysis of results of these studies has indicated that there is a less radiative trapping and enhanced fluorescence lifetime and high quantum efficiency in the glasses mixed with 8.0 mol% of Al{sub 2}O{sub 3}. Highlights: Black-Right-Pointing-Pointer Glasses of the composition (40 - x)PbO-(5more » + x)Al{sub 2}O{sub 3}-54SiO{sub 2}:1.0Sm{sub 2}O{sub 3} with x = 5-10 mol% were prepared. Black-Right-Pointing-Pointer Spectroscopic properties (OA, PL and IR) were investigated. Black-Right-Pointing-Pointer Emission probability, lifetime, branching ratio of {sup 4}G{sub 5/2} {yields} {sup 6}H{sub 7/2} transition of Sm{sup 3+} have been evaluated. Black-Right-Pointing-Pointer Analysis of the results indicated that glass mixed with 8.0 mol% exhibits high luminescence efficiency. -- Abstract: Optical absorption and photoluminescence characteristics of Sm{sup 3+} ions in lead silicate glasses mixed with different concentrations of Al{sub 2}O{sub 3} (5-10 mol%) have been investigated. From these studies, the radiative properties viz., spontaneous emission probability A, the total emission probability, the radiative lifetime {tau}{sub R}, the fluorescent branching ratio {beta} of emission transition of {sup 4}G{sub 5/2} {yields} {sup 6}H{sub 7/2} along with other transitions for Sm{sup 3+} have been evaluated and found to be the highest for the glass mixed with 8.0 mol% of Al{sub 2}O{sub 3}.The IR spectral studies have indicated that Al{sup 3+} ions do participate in the glass network with AlO{sub 4} and AlO{sub 6} structural units and further revealed that the concentration of octahedral aluminium ions induce bonding defects in the glass network. Such bonding defects are assumed to be responsible for low phonon losses in these glasses and lead to higher values of radiative parameters for the glass mixed with 8.0 mol% of Al{sub 2}O{sub 3}.« less

Hot-pressed silicon nitride with various lanthanide oxides as sintering additives

NASA Technical Reports Server (NTRS)

Ueno, K.; Toibana, Y.

1984-01-01

The effects of addition of various lanthanide oxides and their mixture with Y2O3 on the sintering of Si3N4 were investigated. The addition of simple and mixed lanthanide oxides promoted the densification of Si3N4 in hot-pressing at 1800 C under 300-400kg/ centimeters squared for 60 min. The crystallization of yttrium and lanthanide-silicon oxynitrides which was observed inn the sintered body containing yttrium-lanthanide mixed oxides as additives led to the formation of a highly refractory Si3N4 ceramic having a bending strength of 82 and 84 kg/millimeters squared at room temperature and 1300 C respectively. In a Y2O3+La2O3 system, a higher molar ratio of La2O3 to Y2O3 gave a higher hardness and strength at high temperatures. It was found that 90 min was an optimum sintering time for the highest strength.

Episodic nitrous oxide soil emissions in Brazilian savanna (cerrado) fire-scars

NASA Technical Reports Server (NTRS)

Nobre, A. D.; Crill, P. M.; Harriss, R. C.

1994-01-01

The seasonally burned cerrados of Brazil are the largest savanna-type ecosystem of South America and their contribution to the global atmospheric nitrous oxide (N20) budget is unknown. Four types of fire-scarred cerrado along a vegetation gradient from grassland to forest were investigated during the wet season of 1992/93. The effect of fire and subsequent water additions on epiodic emissions of N2O and the associated profile dynamic of soil/gas phase N2O concentrations were studied for several months. Additionally, the effect on episodic emissions of N2O of nitrate and glucose additions to a cerrado soil after fire and the associated profile dynamic of soil/gas phase N2O mixing ratios were determined. Finally, N2O episodic emissions in cerrado converted to corn, soybean, and pasture fields were investigated during one growing/wet season. Results showed N2O consumption/emission for the four fire-scared savanna ecosystems, for nitrogen and carbon fertilization, and for agriculture/pasture ranging from -0.3 to +0.7, 1.8 to 9.1, and 0.5 to 3.7 g N2O-N ha(exp -1) d(exp -1), respectively. During the wet season the cerrado biome does not appear to be a major source of N2O to the troposphere, even following fire events. However, the results of this study suggest that conversion of the cerrado to high input agriculture, with liming and fertilization, can increase N2O emissions more than ten fold.

Comparative study of structural, optical and impedance measurements on V{sub 2}O{sub 5} and V-Ce mixed oxide thin films

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

Malini, D. Rachel; Sanjeeviraja, C., E-mail: sanjeeviraja@rediffmail.com

Vanadium pentoxide (V{sub 2}O{sub 5}) and Vanadium-Cerium mixed oxide thin films at different molar ratios of V{sub 2}O{sub 5} and CeO{sub 2} have been deposited at 200 W rf power by rf planar magnetron sputtering in pure argon atmosphere. The structural and optical properties were studied by taking X-ray diffraction and transmittance and absorption spectra respectively. The amorphous thin films show an increase in transmittance and optical bandgap with increase in CeO{sub 2} content in as-prepared thin films. The impedance measurements for as-deposited thin films show an increase in electrical conductivity with increase in CeO{sub 2} material.

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

NASA Astrophysics Data System (ADS)

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

2011-06-01

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

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

NASA Astrophysics Data System (ADS)

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

2011-03-01

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

Trace gas emissions from chaparral and boreal forest fires

NASA Technical Reports Server (NTRS)

Cofer, Wesley R., III; Levine, Joel S.; Sebacher, Daniel I.; Winstead, Edward L.; Riggan, Philip J.; Stocks, Brian J.; Brass, James A.; Ambrosia, Vincent G.

1989-01-01

Using smoke samples collected during low-level helicopter flights, the mixing ratios of CO2, CO, CH4, total nonmethane hydrocarbons, H2, and N2O over burning chaparral in southern California and over a burning boreal forest site in northern Ontario, Canada, were determined. Carbon dioxide-normalized emission ratios were determined for each trace gas for conditions of flaming, mixed, and smoldering combustion. The emission ratios for these trace gases were found to be highest for the smoldering combustion, generally thought to be the least efficient combustion stage. However, high emission ratios for these gases could be also produced during very vigorous flaming combustion.

ATMOS/ATLAS-3 Measurements of Stratospheric Chlorine and Reactive Nitrogen Partitioning Inside and Outside the November 1994 Antarctic Vortex

NASA Technical Reports Server (NTRS)

Rinsland, C. P.; Gunson, M. R.; Salawitch, R. J.; Michelsen, H. A.; Zander, R.; Newchurch, M. J.; Abbas, M. M.; Abrams, M. C.; Manney, G. L.; Chang, A. Y.;

Isotope Fractionation in the Stratospheric Nitrous Oxide Sinks: Photolysis and "Photooxidation"

NASA Astrophysics Data System (ADS)

Chen, N.; Bianchi, T. S.; McKee, B. A.; Bland, J. M.; Kaiser, J.; Rockmann, T.; Bruhl, C.; Brenninkmeijer, C. A.

2002-05-01

N2O is an important greenhouse gas and a key factor in the ozone cycle, being the major source of stratospheric NOx. It is produced mainly at Earth's surface by microbial N conversion processes. Despite the atmospheric significance of N2O, its global budget is relatively ill-constrained: Recent estimates of the total nitrogen source flux span a range from 6.7-36.6 Tg/a as opposed to the better-quantified stratospheric losses of 9-16 Tg/a and the observed increase in the global atmospheric N2O load by 3.9 Tg/a [IPCC, 2001]. Isotope measurements have been used tentatively to improve these estimates, but without immediate success. However, spawned by the development of new spectrometric techniques which can distinguish between the isotope ratios of the terminal and central nitrogen sites in N2O, it is hoped that the global budget can now be constrained better. Detailed knowledge about the factors determining the stratospheric N2O isotope ratios is required to incorporate them into chemistry and transport models. To this end, we will present measurements of fractionation constants for N2O photolysis at different wavelengths and temperatures as well as a complete kinetic characterization of the second N2O loss reaction, N2O+O(1D), at all stratospherically relevant conditions. The intramolecular distribution of 15N is always accounted for. The laboratory measurements are interpreted in the context of stratospheric air samples which revealed strong altitude-dependent enrichments of heavy N2O isotopomers (15N14NO, 14N15NO, N218O) in the lower and middle stratosphere. Taken as a whole, these observations can be interpreted by a Rayleigh fractionation pattern in the decrease of N2O mixing ratios due to photolysis (90 % of total sink) and oxidation by O(1D) (10 % of total sink). The apparent fractionation constants are depleted in the lower stratosphere (<200 nmol/mol N2O), caused by chemistry or transport. However, even the ratio of 14N15NO and 15N14NO decreases towards the tropopause, but is influenced only negligibly by transport. Differences in photochemistry must be responsible for this discrepancy. Particularly interesting is the reaction N2O+O(1D) with remarkably lower fractionation constants than for photolysis. Moreover, the enrichment of 15N at the two non-equivalent positions of the N2O molecule is in diametrical opposition to the enrichment during photolysis. It will be shown to what extent the incorporation of these laboratory measurements into a global atmospheric model can explain the observed stratospheric isotope ratios in N2O.

Flame thermometry using laser-induced-grating spectroscopy of nitric oxide

NASA Astrophysics Data System (ADS)

Luers, Andrew; Salhlberg, Anna-Lena; Hochgreb, Simone; Ewart, Paul

2018-03-01

A systematic study of laser-induced thermal-grating scattering (LITGS) using nitric oxide as an absorbing species is presented as a means of thermometry in air-fed combustion. The relative contributions to the scattered signal from degenerate four-wave mixing, DFWM, and from laser-induced thermal-grating scattering, LITGS, are studied in the time domain for NO in N2 buffer gas up to 4 bar, using a pulsed laser system to excite the (0,0) γ-bands of NO at 226.21 nm. LITGS signals from combustion-generated NO in a laminar, pre-mixed CH4/O2/N2 flame on an in-house constructed slot burner were used to derive temperature values as a function of O2 concentration and position in the flame at 1 and 2.5 bar total pressure. Temperature values consistent with the calculated adiabatic flame temperature were derived from averaged LITGS signals over 50-100 single shots at 10 Hz repetition rate in the range 1600-2400 K with a pressure-dependent uncertainty of ± 1.8% at 1 bar to ± 1.4% at 2.5 bar. Based on observed signal-to-noise ratios, the minimum detectable concentration of NO in the flame is estimated to be 80 ppm for a 5 s measurement time at 10 Hz repetition rate.

Gas discharges from the Kueishantao hydrothermal vents, offshore northeast Taiwan: Implications for drastic variations of magmatic/hydrothermal activities

NASA Astrophysics Data System (ADS)

Chen, Xue-Gang; Lyu, Shuang-Shuang; Zhang, Ping-Ping; Yu, Ming-Zhen; Chen, Chen-Tung Arthur; Chen, Yun-Jie; Li, Xiaohu; Jin, Aimin; Zhang, Hai-Yan; Duan, Wei; Ye, Ying

2018-03-01

The chemical compositions of gas discharges from the Kueishantao (KST) hydrothermal field changed dramatically from 2000 to 2014. In this study, we established a gas mixing model for the KST gases. The N2, Ar, and CO2 contents were mixed from a magmatic endmember with CO2 of about 990 mmol/mol, a hydrothermal and an atmospheric endmember enriched in N2 and Ar. More than 71% KST gas components were mantle-derived/magmatic. The calculated endmember N2/Ar ratio and Ar contents of the hydrothermal endmember (percolated fluid) are about 140 and 5.28-5.52 mmol/mol, respectively. This relatively elevated N2/Ar ratio was probably caused by the thermogenic addition of N2. The log(CH4/CO2) values of the KST gas samples correlate well with the mixing temperature that estimated from the mixing ratio between the percolated fluid and the magmatic endmember. It is indicated that the KST CH4 and CO2 may have attained chemical equilibrium. The temporal variations of the KST gas compositions are determined by the mixing ratio, which is dependent on the magmatic activity underneath the KST field. With the decreasing of magmatic activity since 2005, the proportion of the hydrothermal endmember increased, along with the increasing of N2, Ar, and CH4 contents. This study proposed an effective model to quantitatively assess the sources of gas components discharged from submarine hydrothermal vents. In addition, it is suggested that the mixing between a magmatic and a hydrothermal endmember may play an important role in the concentrations of CO2 and CH4 in hydrothermal gas discharges.

Overview of Global/Regional Models Used to Evaluate Tropospheric Ozone in North America

NASA Technical Reports Server (NTRS)

Johnson, Matthew S.

2015-01-01

Ozone (O3) is an important greenhouse gas, toxic pollutant, and plays a major role in atmospheric chemistry. Tropospheric O3 which resides in the planetary boundary layer (PBL) is highly reactive and has a lifetime on the order of days, however, O3 in the free troposphere and stratosphere has a lifetime on the order of weeks or months. Modeling O3 mixing ratios at and above the surface is difficult due to the multiple formation/destruction processes and transport pathways that cause large spatio-temporal variability in O3 mixing ratios. This talk will summarize in detail the global/regional models that are commonly used to simulate/predict O3 mixing ratios in the United States. The major models which will be focused on are the: 1) Community Multi-scale Air Quality Model (CMAQ), 2) Comprehensive Air Quality Model with Extensions (CAMx), 3) Goddard Earth Observing System with Chemistry (GEOS-Chem), 4) Real Time Air Quality Modeling System (RAQMS), 5) Weather Research and Forecasting/Chemistry (WRF-Chem) model, National Center for Atmospheric Research (NCAR)'s Model for OZone And Related chemical Tracers (MOZART), and 7) Geophysical Fluid Dynamics Laboratory (GFDL) AM3 model. I will discuss the major modeling components which impact O3 mixing ratio calculations in each model and the similarities/differences between these models. This presentation is vital to the 2nd Annual Tropospheric Ozone Lidar Network (TOLNet) Conference as it will provide an overview of tools, which can be used in conjunction with TOLNet data, to evaluate the complex chemistry and transport pathways controlling tropospheric O3 mixing ratios.

Mass spectrometry for water vapor measurements in the UT/LS

NASA Astrophysics Data System (ADS)

Kaufmann, S.; Voigt, C.; Schäuble, D.; Schäfler, A.; Schlager, H.; Thornberry, T. D.; Fahey, D. W.

2012-12-01

Water vapor in the lower stratosphere plays a crucial role for the atmospheric radiation budget (Solomon et al., 2011). However, large uncertainties remain in measuring atmospheric water vapor mixing ratios below 10 ppmv typical for the lower stratosphere. To this end, we have developed the Atmospheric Ionization Mass Spectrometer (AIMS) for the accurate and fast detection of water vapor in the UT/LS from aircraft. In the AIMS instrument atmospheric air is directly ionized in a discharge ion source and the resulting water vapor clusters H3O+(H2O)n (n = 0..3) are detected with a linear quadrupole mass spectrometer as a direct measure of the atmospheric water vapor mixing ratio. AIMS is calibrated in-flight with a H2O calibration source using the catalytic reaction of H2 and O2 on a heated platinum surface to form gaseous H2O. This calibration setup combined with the water vapor mass spectrometry offers a powerful technical development in atmospheric hygrometry, enriching existing H2O measurement techniques by a new independent method. Here, we present AIMS water vapor measurements performed during the CONCERT2011 campaign (Contrail and Cirrus Experiment) with the DLR research aircraft Falcon. In September 2011 a deep stratospheric intrusion was probed over northern Europe with a dynamical tropopause lowered down to 6 km. We found sharp humidity gradients between tropospheric and stratospheric air at the edge of the tropopause fold, which we crossed 4 times at altitudes between 6 and 11 km. In the center of the tropopause fold, we measured water vapor mixing ratios down to 4 ppmv. The observed water vapor distribution is compared to water vapor analysis fields of the ECMWF's Integrated Forecast System (IFS) to evaluate the representation water vapor in this specific meteorological situation.

(Cu 0.5Tl 0.5)Ba 2Ca n-1 Cu n- yGe yO 2 n+4- δ ( n = 3, 4 and y = 0.5, 0.75, 1.0); superconductors with GeO 2 planes

NASA Astrophysics Data System (ADS)

Khan, Nawazish A.; Irfan, M.

2008-12-01

We have successfully synthesized germanium doped (Cu 0.5Tl 0.5)Ba 2Ca n-1 Cu n- yGe yO 2 n+4- δ ( n = 3, 4 and y = 0, 0.5, 0.75, 1.0) superconductors and investigated the effect of Ge doping on the superconducting properties of these compounds. The solubility of Ge till y = 1 in the CuO 2 planes of (Cu 0.5Tl 0.5)Ba 2Ca 2Cu 3- yGe yO 10- δ, have been found to give superconductivity above 77 K. To our surprise an enhanced superconductivity is observed with the doping of semiconductor germanium in some samples. The enhanced superconductivity associated with mixed CuO 2/GeO 2 planes can be extremely useful for the understanding of mechanism of superconductivity; since we very well know the properties of germanium based semiconductors.

Fast heterogeneous N2O5 uptake and ClNO2 production in power plant and industrial plumes observed in the nocturnal residual layer over the North China Plain

NASA Astrophysics Data System (ADS)

Wang, Zhe; Wang, Weihao; Tham, Yee Jun; Li, Qinyi; Wang, Hao; Wen, Liang; Wang, Xinfeng; Wang, Tao

2017-10-01

Dinitrogen pentoxide (N2O5) and nitryl chloride (ClNO2) are key species in nocturnal tropospheric chemistry and have significant effects on particulate nitrate formation and the following day's photochemistry through chlorine radical production and NOx recycling upon photolysis of ClNO2. To better understand the roles of N2O5 and ClNO2 in the high-aerosol-loading environment of northern China, an intensive field study was carried out at a high-altitude site (Mt. Tai, 1465 m a.s.l.) in the North China Plain (NCP) during the summer of 2014. Elevated ClNO2 plumes were frequently observed in the nocturnal residual layer with a maximum mixing ratio of 2.1 ppbv (1 min), whilst N2O5 was typically present at very low levels (< 30 pptv), indicating fast heterogeneous N2O5 hydrolysis. Combined analyses of chemical characteristics and backward trajectories indicated that the ClNO2-laden air was caused by the transport of NOx-rich plumes from the coal-fired industry and power plants in the NCP. The heterogeneous N2O5 uptake coefficient (γ) and ClNO2 yield (ϕ) were estimated from steady-state analysis and observed growth rate of ClNO2. The derived γ and ϕ exhibited high variability, with means of 0.061 ± 0.025 and 0.28 ± 0.24, respectively. These values are higher than those derived from previous laboratory and field studies in other regions and cannot be well characterized by model parameterizations. Fast heterogeneous N2O5 reactions dominated the nocturnal NOx loss in the residual layer over this region and contributed to substantial nitrate formation of up to 17 µg m-3. The estimated nocturnal nitrate formation rates ranged from 0.2 to 4.8 µg m-3 h-1 in various plumes, with a mean of 2.2 ± 1.4 µg m-3 h-1. The results demonstrate the significance of heterogeneous N2O5 reactivity and chlorine activation in the NCP, and their unique and universal roles in fine aerosol formation and NOx transformation, and thus their potential impacts on regional haze pollution in northern China.

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

NASA Technical Reports Server (NTRS)

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

1994-01-01

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

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

PubMed Central

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

2011-01-01

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

Distribution, physical state and mixing of materials at the surface of Pluto from New Horizons

NASA Astrophysics Data System (ADS)

Schmitt, Bernard; Philippe, Sylvain; Grundy, Will; Reuter, D. C.; Quirico, Eric; Protopapa, Silvia; Côte, Rémi; Young, Leslie; Binzel, Richard; Cook, Jason C.; Cruikshank, Dale P.; Dalle Ore, Cristina M.; Earle, Alissa M.; Ennico, Kimberly; Howett, Carly; Jennings, Donald; Linscott, Ivan; Lunsford, A. W.; Olkin, Catherine B.; Parker, Joel Wm.; Parker, Alex; Singer, Kelsi N.; Spencer, John R.; Stansberry, John A.; Stern, S. Alan; Tsang, Constantine; Verbiscer, Anne J.; Weaver, Harold A.; New Horizons Science Team

2016-10-01

In July 2015 the New Horizons spacecraft recorded a large set of data on Pluto, in particular with the LEISA spectro-imager dedicated to the study of the surface composition.In this talk we report a study of the distribution and physical state of the ices and non-ice materials on Pluto's surface and their mode and degree of mixing. Principal Component analysis as well as specific spectral indicators and correlation plots are used on high resolution LEISA spectro-images covering the whole illuminated face of Pluto. Qualitative distribution maps have been obtained for the 4 main condensed molecules, N2, CH4, CO, H2O as well as for the visible-dark red material. These maps indicate the presence of 3 different types of ices: N2-rich:CH4:CO ices, CH4-rich:(CO:N2?) ices and H2O ice. Their mixing lines and with the dark reddish material are studied. CH4 is mixed at the molecular level with N2 and CO, thus forming a ternary molecular mixture that follows its phase diagram with low solubility limits. The occurrence of a N2-rich - CH4-rich ices mixing line associated with a decrease of the CO/CH4 ratio tell us that a fractionation sublimation sequence transforms N2-rich ice into either a N2-rich - CH4-rich binary mixture at the surface or an upper CH4-rich(:CO:N2) ice crust that may hide the N2-rich ice below. The CH4-rich - H2O mixing line witnesses the subsequent sublimation of CH4 ice left behind by the N2:CO sublimation (N spring-summer), or a direct condensation of CH4 ice on cold H2O ice (S autumn). The very sharp spatial transitions between CH4-containing ices and the dark red material are probably due to thermal incompatibility. Finally there is some spatial mixing of the reddish material covering H2O ice. H2O ice appears to be the substratum on which other ices condense or non-volatile organic material is deposited from the atmosphere. The spatial distribution of these materials is very complex.The high spatial definition of all these composition maps will allow us to compare them with Pluto's geologic features observed by LORRI panchromatic and MVIC multispectral imagers to better understand the geophysical processes in action at the surface of this astonishingly active cold world.

Conversion of Syngas-Derived C2+ Mixed Oxygenates to C3-C5 Olefins over ZnxZryOz Mixed Oxides Catalysts

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

Smith, Colin D.; Lebarbier, Vanessa M.; Flake, Matthew D.

2016-04-01

In this study we report on a ZnxZryOz mixed oxide type catalyst capable of converting a syngas-derived C2+ mixed oxygenate feedstock to isobutene-rich olefins. Aqueous model feed comprising of ethanol, acetaldehyde, acetic acid, ethyl acetate, methanol, and propanol was used as representative liquid product derived from a Rh-based mixed oxygenate synthesis catalyst. Greater than 50% carbon yield to C3-C5 mixed olefins was demonstrated when operating at 400-450oC and 1 atm. In order to rationalize formation of the products observed feed components were individually evaluated. Major constituents of the feed mixture (ethanol, acetaldehyde, acetic acid, and ethyl acetate) were found tomore » produce isobutene-rich olefins. C-C coupling was also demonstrated for propanol feedstock - a minor constituent of the mixed oxygenate feed - producing branched C6 olefins, revealing scalability to alcohols higher than ethanol following an analogous reaction pathway. Using ethanol and propanol feed mixtures, cross-coupling reactions produced mixtures of C4, C5, and C6 branched olefins. The presence of H2 in the feed was found to facilitate hydrogenation of the ketone intermediates, thus producing straight chain olefins as byproducts. While activity loss from coking is observed complete catalyst regeneration is achieved by employing mild oxidation. For conversion of the mixed oxygenate feed a Zr/Zn ratio of 2.5 and a reaction temperature of 450oC provides the best balance of stability, activity, and selectivity. X-ray diffraction and scanning transmission electron microscopy analysis reveals the presence of primarily cubic phase ZrO2 and a minor amount of the monoclinic phase, with ZnO being highly dispersed in the lattice. The presence of ZnO appears to stabilize the cubic phase resulting in less monoclinic phase as the ZnO concentration increases. Infrared spectroscopy shows the mixed oxide acid sites are characterized as primarily Lewis type acidity. The direct relationship between isobutene production and the ratio of basic/acidic sites was demonstrated. An optimized balance of active sites for isobutene production from acetone was obtained with a basic/acidic site ratio of ~2. This technology for the conversion of aqueous mixtures of C2+ mixed oxygenates provides significant advantages over other presently studied catalysts in that its unique properties permit the utilization of a variety of feeds in a consistently selective manner.« less

Investigation into the disparate origin of CO 2 and H 2O outgassing for comet 67P

NASA Astrophysics Data System (ADS)

Fink, Uwe; Doose, Lyn; Rinaldi, Giovanna; Capaccioni, Fabrizio; Bockelee-Morvan, Dominique; VIRTIS Team

2016-10-01

We present an investigation of the emission intensity of CO2 and H2O and their distribution in the coma of 67P/ Churyumov-Gerasimenko obtained by the VIRTIS-M imaging spectrometer on the Rosetta mission. We analyze 4 data cubes from Feb. 28, and 7 data cubes from April 27, 2015. For both data sets the spacecraft was at a sufficiently large distance from the comet to allow images of the whole nucleus and the surrounding coma.We find that unlike water which has a reasonably predictable behavior and correlates well with the solar illumination, CO2 outgasses mostly in local regions or spots. Furthermore for the data on April 27, the CO2 evolves almost exclusively from the southern hemisphere, a region of the comet that has not received solar illumination since the comet's last perihelion passage. Because CO2 and H2O have such disparate origins, deriving mixing ratios from local column density measurements cannot provide a meaningful measurement of the CO2/H2O ratio in the coma of the comet. We obtain total production rates of H2O and CO2 by integrating the band intensity in an annulus surrounding the nucleus and obtain pro-forma production rate CO2/H2O mixing ratios of ~5.0% and ~2.5% for Feb. 28 and April 27 respectively. Because of the highly variable nature of the CO2 evolution we do not believe that these numbers are diagnostic of the comets bulk CO2/H2O composition. We believe that our investigation provides an explanation for the large observed variations reported in the literature for the CO2/H2O production rate ratios. Our mixing ratio maps indicate that, besides the difference in vapor pressure of the two gases, this ratio depends on the comet's geometric shape, illumination and past orbital history.Our annulus measurement for the total water production for Feb. 28 at 2.21AU from the sun is 2.5x1026 molecules/s while for April 27 at 1.76 AU it is 4.65x1026. We find that about 83% of the H2O resides in the illuminated portion of our annulus and about 17% on the night side. A rough estimate of the water surface evaporation rate of the illuminated nucleus for April 27 yields about 5x1019 molecules/s m2.

Line Shape Parameters of Water Vapor Transitions in the 3645-3975 cm^{-1} Region

NASA Astrophysics Data System (ADS)

Devi, V. Malathy; Benner, D. Chris; Gamache, Robert R.; Vispoel, Bastien; Renaud, Candice L.; Smith, Mary Ann H.; Sams, Robert L.; Blake, Thomas A.

2017-06-01

A Bruker IFS 120HR Fourier transform spectrometer (FTS) at the Pacific Northwest National Laboratory (PNNL) in Richland, Washington was used to record a series of spectra in the regions of the ν_1 and ν_3 bands of H_2O. The samples included low pressures of pure H_2O as well as H_2O broadened by air at different pressures, temperatures and volume mixing ratios. We fit simultaneously 16 high-resolution (0.008 cm^{-1}), high S/N ratio absorption spectra recorded at 268, 296 and 353 K (L=19.95 cm), employing a multispectrum fitting technique to retrieve accurate line positions, relative intensities, Lorentz air-broadened half-width and pressure-shift coefficients and their temperature dependences for more than 220 H_2O transitions. Self-broadened half-width and self-shift coefficients were measured for over 100 transitions. For select sets of transition pairs for the H_2O-air system we determined collisional line mixing coefficients via the off-diagonal relaxation matrix element formalism, and we also measured speed dependence parameters for 85 transitions. Modified Complex Robert Bonamy (MCRB) calculations of the half-widths, line shifts, and temperature dependences were made for self-, N_2-, O_2-, and air-broadening. The measurements and calculations are compared with each other and with similar parameters reported in the literature. D. C. Benner, C. P. Rinsland, V. Malathy Devi, M. A. H. Smith, D. Atkins, JQSRT 53 (1995) 705-721. A. Levy, N. Lacome, C. Chackerian, Collisional line mixing, in Spectroscopy of the Earth's Atmosphere and Interstellar Medium, Academic Press, Inc., Boston (1992) 261-337.

Nitrous oxide emissions are enhanced in a warmer and wetter world.

PubMed

Griffis, Timothy J; Chen, Zichong; Baker, John M; Wood, Jeffrey D; Millet, Dylan B; Lee, Xuhui; Venterea, Rodney T; Turner, Peter A

2017-11-07

Nitrous oxide (N 2 O) has a global warming potential that is 300 times that of carbon dioxide on a 100-y timescale, and is of major importance for stratospheric ozone depletion. The climate sensitivity of N 2 O emissions is poorly known, which makes it difficult to project how changing fertilizer use and climate will impact radiative forcing and the ozone layer. Analysis of 6 y of hourly N 2 O mixing ratios from a very tall tower within the US Corn Belt-one of the most intensive agricultural regions of the world-combined with inverse modeling, shows large interannual variability in N 2 O emissions (316 Gg N 2 O-N⋅y -1 to 585 Gg N 2 O-N⋅y -1 ). This implies that the regional emission factor is highly sensitive to climate. In the warmest year and spring (2012) of the observational period, the emission factor was 7.5%, nearly double that of previous reports. Indirect emissions associated with runoff and leaching dominated the interannual variability of total emissions. Under current trends in climate and anthropogenic N use, we project a strong positive feedback to warmer and wetter conditions and unabated growth of regional N 2 O emissions that will exceed 600 Gg N 2 O-N⋅y -1 , on average, by 2050. This increasing emission trend in the US Corn Belt may represent a harbinger of intensifying N 2 O emissions from other agricultural regions. Such feedbacks will pose a major challenge to the Paris Agreement, which requires large N 2 O emission mitigation efforts to achieve its goals. Published under the PNAS license.

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

NASA Astrophysics Data System (ADS)

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

1994-12-01

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

Tropospheric ozone enhancement during post-harvest crop-residue fires at two downwind sites of the Indo-Gangetic Plain.

PubMed

Kumari, Sonal; Verma, Nidhi; Lakhani, Anita; Tiwari, Suresh; Kandikonda, Maharaj Kumari

2018-05-01

In the present study, surface ozone (O 3 ), nitrogen oxides (NO x ), and carbon monoxide (CO) levels were measured at two sites downwind of fire active region in the Indo-Gangetic Plain (IGP): Agra (27.16° N, 78.08° E) and Delhi (28.37° N, 77.12° E) to study the impact of post-harvest crop-residue fires. The study period was classified into two groups: Pre-harvest period and Post-harvest period. During the post-harvest period, an enhancement of 17.3 and 31.7 ppb in hourly averaged O 3 mixing ratios was observed at Agra and Delhi, respectively, under similar meteorological conditions. The rate of change of O 3 was also higher in the post-harvest period by 56.2% in Agra and 39.5% in Delhi. Relatively higher O 3 episodic days were observed in the post-harvest period. Fire hotspots detected by Moderate Resolution Imaging Spectroradiometer (MODIS) along with backward air-mass trajectory analysis suggested that the enhanced O 3 and CO levels at the study sites during the post-harvest period could be attributed to crop-residue burning over the North-West IGP (NW-IGP). Satellite observations of surface CO mixing ratios and tropospheric formaldehyde (HCHO) column also showed higher levels during the post-harvest period. Graphical abstract.

The Formation of Haze During the Rise of Oxygen in the Atmosphere of the Early Earth

NASA Astrophysics Data System (ADS)

Horst, S. M.; Jellinek, M.; Pierrehumbert, R.; Tolbert, M. A.

2013-12-01

Atmospheric aerosols play an important role in determining the radiation budget of an atmosphere and can also provide a wealth of organic material to the surface. Photochemical hazes are abundant in reducing atmospheres, such as the N2/CH4 atmosphere of Titan, but are unlikely to form in oxidizing atmospheres, such as the N2/O2 atmosphere of present day Earth. However, information about haze formation in mildly oxidizing atmospheres is lacking. Understanding haze formation in mildly oxidizing atmospheres is necessary for models that wish to investigate the atmosphere of the Early Earth as O2 first appeared and then increased in abundance. Previous studies of the atmosphere of the Early Earth have focused on haze formation in N2/CO2/CH4 atmospheres. In this work, we experimentally investigate the effect of the addition of O2 on the formation and composition of aerosols. Using a High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS) (see e.g. [1]) we have obtained in situ composition measurements of aerosol particles produced in N2/CO2/CH4/O2 gas mixtures subjected to FUV radiation (deuterium lamp, 115-400 nm) for a range of initial CO2/CH4/O2 mixing ratios. In particular, we studied the effect of O2 ranging from 2 ppm to 2%. The particles were also investigated using a Scanning Mobility Particle Sizer (SMPS), which measures particle size, number density and mass loading. A comparison of the composition of the aerosols will be presented. The effect of variation of O2 mixing ratio on aerosol production, size, and composition will also be discussed. [1] Trainer, M.G., et al. (2012) Astrobiology, 12, 315-326.

The Formation of Haze During the Rise of Oxygen in the Atmosphere of the Early Earth

NASA Astrophysics Data System (ADS)

Horst, S. M.; Jellinek, M.; Pierrehumbert, R.; Tolbert, M. A.

2014-12-01

also provide a wealth of organic material to the surface. Photochemical hazes are abundant in reducing atmospheres, such as the N2/CH4 atmosphere of Titan, but are unlikely to form in oxidizing atmospheres, such as the N2/O2 atmosphere of present day Earth. However, information about haze formation in mildly oxidizing atmospheres is lacking. Understanding haze formation in mildly oxidizing atmospheres is necessary for models that wish to investigate the atmosphere of the Early Earth as O2 first appeared and then increased in abundance. Previous studies of the atmosphere of the Early Earth have focused on haze formation in N2/CO2/CH4 atmospheres. In this work, we experimentally investigate the effect of the addition of O2 on the formation and composition of aerosols. Using a High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS) (see e.g. [1]) we have obtained in situ composition measurements of aerosol particles produced in N2/CO2/CH4/O2 gas mixtures subjected to FUV radiation (deuterium lamp, 115-400 nm) for a range of initial CO2/CH4/O2 mixing ratios. In particular, we studied the effect of O2 ranging from 2 ppm to 2%. The particles were also investigated using a Scanning Mobility Particle Sizer (SMPS), which measures particle size, number density and mass loading. A comparison of the composition of the aerosols will be presented. The effect of variation of O2 mixing ratio on aerosol production, size, and composition will also be discussed. [1] Trainer, M.G., et al. (2012) Astrobiology, 12, 315-326.

Photochemical control of the distribution of Venusian water

NASA Astrophysics Data System (ADS)

Parkinson, Christopher D.; Gao, Peter; Esposito, Larry; Yung, Yuk; Bougher, Stephen; Hirtzig, Mathieu

2015-08-01

We use the JPL/Caltech 1-D photochemical model to solve continuity diffusion equation for atmospheric constituent abundances and total number density as a function of radial distance from the planet Venus. Photochemistry of the Venus atmosphere from 58 to 112 km is modeled using an updated and expanded chemical scheme (Zhang et al., 2010, 2012), guided by the results of recent observations and we mainly follow these references in our choice of boundary conditions for 40 species. We model water between 10 and 35 ppm at our 58 km lower boundary using an SO2 mixing ratio of 25 ppm as our nominal reference value. We then vary the SO2 mixing ratio at the lower boundary between 5 and 75 ppm holding water mixing ratio of 18 ppm at the lower boundary and finding that it can control the water distribution at higher altitudes. SO2 and H2O can regulate each other via formation of H2SO4. In regions of high mixing ratios of SO2 there exists a "runaway effect" such that SO2 gets oxidized to SO3, which quickly soaks up H2O causing a major depletion of water between 70 and 100 km. Eddy diffusion sensitivity studies performed characterizing variability due to mixing that show less of an effect than varying the lower boundary mixing ratio value. However, calculations using our nominal eddy diffusion profile multiplied and divided by a factor of four can give an order of magnitude maximum difference in the SO2 mixing ratio and a factor of a few difference in the H2O mixing ratio when compared with the respective nominal mixing ratio for these two species. In addition to explaining some of the observed variability in SO2 and H2O on Venus, our work also sheds light on the observations of dark and bright contrasts at the Venus cloud tops observed in an ultraviolet spectrum. Our calculations produce results in agreement with the SOIR Venus Express results of 1 ppm at 70-90 km (Bertaux et al., 2007) by using an SO2 mixing ratio of 25 ppm SO2 and 18 ppm water as our nominal reference values. Timescales for a chemical bifurcation causing a collapse of water concentrations above the cloud tops (>64 km) are relatively short and on the order of a less than a few months, decreasing with altitude to less than a few days.

Non-invasive cerebral oxygenation reflects mixed venous oxygen saturation during the varying haemodynamic conditions in patients undergoing transapical transcatheter aortic valve implantation.

PubMed

Paarmann, Hauke; Heringlake, Matthias; Heinze, Hermann; Hanke, Thorsten; Sier, Holger; Karsten, Jan; Schön, Julika

2012-03-01

Transapical transcatheter aortic valve implantation (TA-TAVI) is increasingly used to treat aortic valve stenosis in high-risk patients. Mixed venous oxygen saturation (SvO(2)) is still the 'gold standard' for the determination of the systemic oxygen delivery to consumption ratio in cardiac surgery patients. Recent data suggest that regional cerebral oxygen saturation (rScO(2)) determined by near-infrared spectroscopy is closely related to SvO(2). The present study compares rScO(2) and SvO(2) in patients undergoing TA-TAVI. n = 20 cardiac surgery patients scheduled for TA-TAVI were enrolled in this prospective observational study. SvO(2) and rScO(2) were determined at predefined time points during the procedure. Correlation and Bland-Altman analysis of the complete data set showed a correlation coefficient of r(2 )= 0.7 between rScO(2) and SvO(2) (P < 0.0001), a mean difference (bias) of 5.8 with limits of agreement (1.96 SD) of -6.8 to 18.3% and a percentage error of 17.5%. At all predefined time points correlation was moderate (r(2 )= 0.50) to close (r = 0.84), and the percentage error was <24%. RScO(2) determined by near-infrared spectroscopy is correlated to SvO(2) during varying haemodynamic conditions in patients undergoing TA-TAVI. This suggests that rScO(2) is reflective not only of the cerebral, but also of the systemic oxygen balance.

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

NASA Astrophysics Data System (ADS)

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

2017-02-01

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

Atmospheric emissivity with clear sky computed by E-Trans/HITRAN

NASA Astrophysics Data System (ADS)

Mendoza, Víctor M.; Villanueva, Elba E.; Garduño, René; Sánchez-Meneses, Oscar

2017-04-01

The vertical profiles of temperature and pressure from the International Standard Atmosphere, together with the mixing ratio profiles of the main greenhouse effect gases (GG), namely water vapour, CO2 , CH4 , N2 O and stratospheric O3 , are used to determine the downward emissivity of long wave radiation by cloudless atmosphere, by means of the spectral calculator E-Trans with the HITRAN (high-resolution transmission) database. We make a review of emissivity parameterizations, reported by several authors, in terms of the surface vapour pressure and surface air temperature. We compute vertically weighted averages of temperature and pressure, also parameterize the CH4 , N2 O and O3 mixing ratio profiles, in order to adapt these variables as required by the E-Trans/HITRAN. Our results of emissivity for the corresponding vapour pressures agree well with those obtained by the reviewed authors. With this method, the emissivity can be computed at a regional scale and towards the future global warming, according to the IPCC temperature projections that will also increase the atmospheric humidity, from the emission scenarios of GG.

Mixed alkali effect on the spectroscopic properties of alkali-alkaline earth oxide borate glasses

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

Srinivas, G., E-mail: srinu123g@gmail.com; Ramesh, B.; Shareefuddin, Md.

2016-05-06

The mixed alkali and alkaline earth oxide borate glass with the composition xK{sub 2}O - (25-x) Li{sub 2}O-12.5BaO-12.5MgO-50B{sub 2}O{sub 3} (x = 0, 5, 10, 15, 20 and 25mol %) and doped with 1mol% CuO were prepared by the melt quenching technique. From the optical absorption spectra the optical band gap, electronic polarizability(α{sub 0}2-), interaction parameter (A), theoretical and experimental optical basicity (Λ) values were evaluated. From the Electron Paramagnetic Resonance (EPR) spectral data the number of spins (N) and susceptibility (χ) were evaluated. The values of (α{sub 0}2-), and (Λ) increases with increasing of K{sub 2}O content and electronicmore » polarizability and interaction parameter show opposite behaviuor which may be due to the creation of non-bridging oxygens and expansion of borate network. The reciprocal of susceptibility (1/χ) and spin concentration (N) as a function of K{sub 2}O content, varied nonlinearly which may be due to creation of non-bridging oxygens in the present glass system. This may be attributed to mixed alkali effect (MAE).« less

Tolerability of an equimolar mix of nitrous oxide and oxygen during painful procedures in very elderly patients.

PubMed

Bauer, Carole; Lahjibi-Paulet, Hayat; Somme, Dominique; Onody, Peter; Saint Jean, Olivier; Gisselbrecht, Mathilde

2007-01-01

Although an equimolar mix of nitrous oxide-oxygen (N(2)O/O(2)) [Kalinox] is widely used as an analgesic, there have been few specific studies of this product in the elderly. In this article, we investigate the tolerability of this equimolar mix in very elderly patients undergoing painful procedures. This was a prospective, observational study of patients hospitalised in the geriatric short-stay unit of a teaching hospital between July 2001 and September 2003. All patients aged >/=80 years who were scheduled for invasive care procedures were eligible for inclusion. Sixty-two patients were recruited and underwent a total of 68 procedures. The procedures were divided into four classes based on the degree of pain they were expected to cause and their duration. Patients received the equimolar N(2)O/O(2) mix (Kalinox) for 5 minutes before the beginning of the procedure and throughout its duration. The inhaled treatment was administered via a high-concentration mask. Assessments were carried out during the inhalation and over the 15 minute period following inhalation. The primary endpoint of the study was tolerability of the equimolar N(2)O/O(2) mix, and all adverse events were recorded. Secondary endpoints were the efficacy of the product (assessed on a verbal rating scale and/or the Doloplus scale), its ease of use and its acceptability to patients and staff. Fourteen patients (22.6%) each reported at least one adverse event: impaired hearing (n = 1), altered perception of the environment (n = 8), anxiety (n = 1), headache (n = 3) and drowsiness at the end of the procedure (n = 2). All these disorders subsided rapidly after treatment was completed. This study shows the favourable tolerability of the equimolar N(2)O/O(2) mix in very elderly subjects, which makes this product a valuable tool for the management of acute pain in this age group.

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

Bauer, R.; Engel, A.; Franken, H.

This paper describes balloon borne air samples taken above Kiruna (67.9[degrees]N; 21.1[degrees]E) during EASOE, which monitored the N[sub 2]O density, as the polar vortex shifted, between altitudes of 10 and 31 km. Different air samplers were used to collect samples. The results show vertical profiles, outside, in the edge of, and inside the vertex, which reveal variation in mixing ratios as airmasses mix both vertically and horizontally near the vortex.

O3 and CO in New England: Temporal variations and relationships

NASA Astrophysics Data System (ADS)

Mao, Huiting; Talbot, Robert

2004-11-01

We examined seasonal and interannual variability in the mixing ratios of ozone (O3) and carbon monoxide (CO) and their relationships at a rural low-elevation site (24 m, 43.11°N, 70.95°W) and higher-elevation site (406 m, 43.75°N, 71.35°W) in New Hampshire, United States. The data were obtained over 2 years (2001-2003) by the Atmospheric Investigation, Regional Modeling, Analysis, and Prediction (AIRMAP) program at the University of New Hampshire. An analysis of the frequency distributions of O3 and CO grouped by wind speed and direction and over four time periods of the day showed that the most polluted air masses arrived from the southeasterly and westerly wind sectors during the local afternoon hours (1800-2300 UT, -5 hours for U.S. eastern standard time (EST)). In summer within this time window a well-defined positive O3-CO correlation with a slope ˜0.37 existed in these air masses. Applying this relationship together with the CO emission inventory and its temporal profile from the emission model SMOKE, we estimate that 370 Mmol d-1 of O3 are exported from the northeastern United States within this time window during summer. However, over 70% of the data were obtained under weak wind conditions (<2 m s-1) when CO and O3 exhibited a dispersed relationship. An analysis using the ratio NO/NOy and the mixing ratios of NOy revealed a dominance of photochemically aged air masses with significant NOy removal accompanying high levels of O3. This result implies that elevated O3 in southern New Hampshire can largely be attributed to long-range transport of air masses from outside the region. Furthermore, the O3-CO relationship in each season produced a smooth lower CO boundary, which appears to represent air masses with a composition reflecting the evolutionary stages of photochemical aging and progressive phases of transport.

Photochemical production of ozone in Beijing during the 2008 Olympic Games

NASA Astrophysics Data System (ADS)

Chou, C. C.-K.; Tsai, C.-Y.; Chang, C.-C.; Lin, P.-H.; Liu, S. C.; Zhu, T.

2011-09-01

As a part of the CAREBeijing-2008 campaign, observations of O3, oxides of nitrogen (NOx and NOy), CO, and hydrocarbons (NMHCs) were carried out at the air quality observatory of the Peking University in Beijing, China during August 2008, including the period of the 29th Summer Olympic Games. The measurements were compared with those of the CAREBeijing-2006 campaign to evaluate the effectiveness of the air pollution control measures, which were conducted for improving the air quality in Beijing during the Olympics. The results indicate that significant reduction in the emissions of primary air pollutants had been achieved; the monthly averaged mixing ratios of NOx, NOy, CO, and NMHCs decreased by 42.2, 56.5, 27.8, and 49.7 %, respectively. In contrast to the primary pollutants, the averaged mixing ratio of O3 increased by 42.2 %. Nevertheless, it was revealed that the ambient levels of total oxidant (Ox = O3+NO2+1.5 NOz) and NOz were reduced by 21.3 and 77.4 %, respectively. The contradictions between O3 and Ox were further examined in two case studies. Ozone production rates of 30-70 ppbv h-1 and OPEx of ~8 mole mole-1 were observed on a clear-sky day in spite of the reduced levels of precursors. In that case, it was found that the mixing ratio of O3 increased with the increasing NO2/NO ratio, whereas the NOz mixing ratio leveled off when NO2/NO>8. Consequently, the ratio of O3 to NOz increased to above 10, indicating the shift from VOC-sensitive regime to NOx-sensitive regime. However, in the other case, it was found that the O3 production was inhibited significantly due to substantial reduction in the NMHCs. According to the observations, it was suggested that the O3 and/or Ox production rates in Beijing should have been reduced as a result of the reduction in the emissions of precursors during the Olympic period. However, the nighttime O3 levels increased due to a decline in the NO-O3 titration, and the midday O3 peak levels were elevated because of the shift in the photochemical regime and the inhibition of NOz formation.

Performance of diesel engine using diesel B3 mixed with crude palm oil.

PubMed

Namliwan, Nattapong; Wongwuttanasatian, Tanakorn

2014-01-01

The objective of this study was to test the performance of diesel engine using diesel B3 mixed with crude palm oil in ratios of 95 : 5, 90 : 10, and 85 : 15, respectively, and to compare the results with diesel B3. According to the tests, they showed that the physical properties of the mixed fuel in the ratio of 95 : 5 were closest to those of diesel B3. The performance of the diesel engine that used mixed fuels had 5-17% lower torque and power than that of diesel B3. The specific fuel consumption of mixed fuels was 7-33% higher than using diesel B3. The components of gas emissions by using mixed fuel had 1.6-52% fewer amount of carbon monoxide (CO), carbon dioxide (CO2), sulfur dioxide (SO2), and oxygen (O2) than those of diesel B3. On the other hand, nitric oxide (NO) and nitrogen oxides (NO X ) emissions when using mixed fuels were 10-39% higher than diesel B3. By comparing the physical properties, the performance of the engine, and the amount of gas emissions of mixed fuel, we found out that the 95 : 5 ratio by volume was a suitable ratio for agricultural diesel engine (low-speed diesel engine).

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

PubMed

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

2008-01-01

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

The combined effects of carbon/nitrogen ratio, suspended biomass, hydraulic retention time and dissolved oxygen on nutrient removal in a laboratory-scale anaerobic-anoxic-oxic activated sludge biofilm reactor.

PubMed

Manu, D S; Kumar Thalla, Arun

2018-01-01

The current trend in sustainable development deals mainly with environmental management. There is a need for economically affordable, advanced treatment methods for the proper treatment and management of domestic wastewater containing excess nutrients (such as nitrogen and phosphorus) which can cause eutrophication. The reduction of the excess nutrient content of wastewater by appropriate technology is of much concern to the environmentalist. In the current study, a novel integrated anaerobic-anoxic-oxic activated sludge biofilm (A 2 O-AS-biofilm) reactor was designed and operated to improve the biological nutrient removal by varying reactor operating conditions such as carbon to nitrogen (C/N) ratio, suspended biomass, hydraulic retention time (HRT) and dissolved oxygen (DO). Based on various trials, it was seen that the A 2 O-AS-biofilm reactor achieved good removal efficiencies with regard to chemical oxygen demand (95.5%), total phosphorus (93.1%), ammonia nitrogen concentration (NH 4 + -N) (98%) and total nitrogen (80%) when the reactor was maintained at C/N ratio of 4, suspended biomass of 3 to 3.5 g/L, HRT of 10 h, and DO of 1.5 to 2.5 mg/L. Scanning electron microscopy (SEM) of suspended and attached biofilm showed a dense structure of coccus and bacillus bacteria with the diameter ranging from 0.3 to 1.2 μm. The Fourier transform infrared (FTIR) spectroscopy results indicated phosphorylated macromolecules and carbohydrates mix or bind with extracellular proteins in exopolysaccharides.

Effect of mixing ratio of food waste and rice husk co-digestion and substrate to inoculum ratio on biogas production.

PubMed

Haider, Muhammad Rizwan; Zeshan; Yousaf, Sohail; Malik, Riffat Naseem; Visvanathan, Chettiyappan

2015-08-01

Aim of this study was to find out suitable mixing ratio of food waste and rice husk for their co-digestion in order to overcome VFA accumulation in digestion of food waste alone. Four mixing ratios of food waste and rice husk with C/N ratios of 20, 25, 30 and 35 were subjected to a lab scale anaerobic batch experiment under mesophilic conditions. Highest specific biogas yield of 584L/kgVS was obtained from feedstock with C/N ratio of 20. Biogas yield decreased with decrease in food waste proportion. Further, fresh cow dung was used as inoculum to investigate optimum S/I ratio with the selected feedstock. In experiment 2, feedstock with C/N ratio 20 was subjected to anaerobic digestion at five S/I ratios of 0.25, 0.5, 1.0, 1.5 and 2.0. Specific biogas yield of 557L/kgVS was obtained at S/I ratio of 0.25. However, VFA accumulation occurred at higher S/I ratios due to higher organic loadings. Copyright © 2015 Elsevier Ltd. All rights reserved.

Topological ferrimagnetic behaviours of coordination polymers containing manganese(II) chains with mixed azide and carboxylate bridges and alternating F/AF/AF'/AF'/AF interactions.

PubMed

Wang, Yan-Qin; Liu, Hou-Ting; Qi, Yan; Gao, En-Qing

2014-08-21

Two Mn(ii) complexes with azide and a new zwitterionic tetracarboxylate ligand 1,2,4,5-tetrakis(4-carboxylatopyridinium-1-methylene)benzene (L(1)), {[Mn5(L(1))2(N3)8(OH)2]·12H2O}n () and {[Mn5(L(1))2(N3)8(H2O)2](ClO4)2·6H2O}n (), have been synthesized and characterized crystallographically and magnetically. and contain similar alternating chains constructed by azide and carboxylate bridges. The independent sets of bridges alternate in an ABCCB sequence between adjacent Mn(ii) ions: (EO-N3)2 double bridges (EO = end-on) (denoted as A), [(EO-N3)(OCO)2] triple bridges (denoted as B) and [(EO-N3)(OCO)] double bridges (denoted as C). The alternating chains are interlinked into 2D coordination networks by the tetrapyridinium spacers. Magnetic studies demonstrate that the magnetic coupling through the double EO azide bridges is ferromagnetic and that through mixed azide/carboxylate bridges is antiferromagnetic. The unprecedented F/AF/AF'/AF'/AF coupling sequence along the chain dictates an uncompensated ground spin state (S = 5/2 per Mn5 unit) and leads to one-dimensional topological ferrimagnetism, which features a minimum in the χT versus T plot.

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

Calculation of thermodynamic properties and transport coefficients of C5F10O-CO2 thermal plasmas

NASA Astrophysics Data System (ADS)

Li, Xingwen; Guo, Xiaoxue; Murphy, Anthony B.; Zhao, Hu; Wu, Jian; Guo, Ze

2017-10-01

The thermodynamic properties and transport coefficients of C5F10O-CO2 gas mixtures, which are being considered as substitutes for SF6 in circuit breaker applications, are calculated for the temperature range from 300 K to 30 000 K and the pressure range from 0.05 MPa to 1.6 MPa. Special attention is paid on investigating the evolution of thermophysical properties of C5F10O-CO2 mixtures with different mixing ratios and with different pressures; both the mixing ratio and pressure significantly affect the properties. This is explained mainly in terms of the changes in the temperatures at which the dissociation and ionization reactions take place. Comparisons of different thermophysical properties of C5F10O-CO2 mixtures with those of SF6 are also carried out. It is found that most of the thermophysical properties of the C5F10O-CO2 mixtures, such as thermal conductivity, viscosity, and electrical conductivity, become closer to those of SF6 as the C5F10O concentration increases. The composition and thermophysical properties of pure C5F10O in the temperature range from 300 K to 2000 K based on the decomposition pathway are also given. The calculation results provide a basis for further study of the insulation and arc-quenching capability of C5F10O-CO2 gas mixtures as substitutes for SF6.

Preparation and visible light photocatalytic activity of Bi2O3/Bi2WO6 heterojunction photocatalysts

NASA Astrophysics Data System (ADS)

Yan, C. Y.; Yi, W. T.; Xiong, J.; Ma, J.

2018-03-01

The Bi2O3 nanorods, flower-like Bi2WO6 and Bi2O3/Bi2WO6 heterojunction composites with the molar ratio of nBi:nW from 2:1, 2.5:1, to 3:1 have been synthesized via one-step hydrothermal method and two-step hydrothermal method, respectively. The products are characterized by powder X-ray diffraction (XRD), UV–vis diffuse reflectance spectroscopy (UV-vis DRS), and scanning electron microscopy (SEM). Photocatalytic experiments indicate that such Bi2O3/Bi2WO6 composite possesses higher photocatalytic activity for RhB degradation under visible-light irradiation in comparison with pure Bi2O3 and Bi2WO6. The enhancement of the photocatalytic activity of the Bi2O3/Bi2WO6 heterojunction catalysts can be ascribed to the reduced recombination of the photoexcited electrons and holes during the photocatalytic reaction. The effect of the molar ratio of nBi:nW on the catalytic performance of the heterojunction catalysts was also investigated. And the optimal molar ratio of nBi:nW is 2.5:1 which was synthesized by one-step hydrothermal method.

Synthesis, characterization and photocatalysis enhancement of Eu2O3-ZnO mixed oxide nanoparticles

NASA Astrophysics Data System (ADS)

Mohamed, W. S.; Abu-Dief, Ahmed M.

2018-05-01

Pure ZnO nanoparticles (NPs) and mixed Eu2O3 and ZnO NPs with different Eu2O3 ratios (5%, 10%, and 15%) were synthesized by a precipitation method under optimum conditions. The synthesized samples were characterized by means of X-ray diffraction, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy, transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, and UV-vis diffuse reflectance spectroscopy. The as-synthesized ZnO NPs exhibit high phase purity and a highly crystalline wurtzite ZnO structure. The mixed Eu2O3 and ZnO NPs exhibit a Eu2O3 zinc blend phase in addition to the wurtzite phase of pure ZnO, confirming the high purity and good crystallinity of the as-synthesized samples. The high-purity formation of ZnO and Eu2O3 phases was confirmed by FTIR and Raman spectra. Microstructural analysis by SEM and TEM confirmed the sphere-like morphology with different particle sizes (29-40 nm) of the as-synthesized samples. The photocatalytic activities of pure ZnO NPs and mixed Eu2O3 and ZnO NPs for the degradation of methylene blue were evaluated under ultraviolet (UV) irradiation. The results show that Eu2O3 plays an important role in the enhancement of the photocatalytic properties of ZnO NPs. We found that mixed 5% Eu2O3 and ZnO NPs exhibit the highest photocatalytic activity (degradation efficiency of 96.5% after 180 min of UV irradiation) as compared with pure ZnO NPs (degradation efficiency of 80.3% after 180 min of UV irradiation). The increased photocatalytic activity of the optimum mixed Eu2O3 and ZnO NPs is due to the high crystallinity, high surface area with small particle size, and narrow energy gap.

Optical properties of white organic light-emitting devices fabricated utilizing a mixed CaAl12O19:Mn4+ and Y3Al5O12:Ce3+ color conversion layer.

PubMed

Jeong, H S; Kim, S H; Lee, K S; Jeong, J M; Yoo, T W; Kwon, M S; Yoo, K H; Kim, T W

2013-06-01

White organic light-emitting devices (OLEDs) were fabricated by combining a blue OLED with a color conversion layer made of mixed Y3Al5O12:Ce3+ green and Ca2AlO19:Mn4+ red phosphors. The X-ray diffraction patterns showed that Ce3+ ions in the Y3Al5O12:Ce3+ phosphors completely substituted for the Y3+ ions and the Mn4+ ions in the CaAl12O19:Mn4+ phosphors completely substituted for the Ca2+ ions. Electroluminescence spectra at 11 V for the OLEDs fabricated utilizing a color conversion layer showed that the Commission Internationale de l'Eclairage coordinates for the Y3Al5O12:Ce3+ and CaAl12O19:Mn4+ phosphors mixed at the ratio of 1:5 and 1:10 were (0.31, 0.34) and (0.32, 0.37), respectively, indicative of a good white color.

Optical absorption and photoluminescence properties of Er3+ doped mixed alkali borate glasses.

PubMed

Ratnakaram, Y C; Kumar, A Vijaya; Naidu, D Tirupathi; Rao, J L

2005-07-01

An investigations of the optical absorption and fluorescence spectra of 0.2 mol% Er2O3 in mixed alkali borate glasses of the type 67.8B2O3 x xLi2O(32-x)Na2O, 67.8B2O3 x xLi2O(32-x)K2O and 67.8B2O3 x xNa2O(32-x)K2O (where x = 8, 12, 16, 20 and 24) are presented. The glasses were obtained by quenching melts consisting of H3BO3, Li2CO3, Na2CO3, K2CO3 and Er2O3 (950-1100 degrees C, 1.5-2 h) between two brass plates. Spectroscopic parameters like Racah (E1, E2 and E3), spin-orbit (xi(4f)) and configuration interaction (alpha) parameters are deduced as function of x. Using Judd-Ofelt theory, Judd-Ofelt intensity parameters (omega2, omega4 and omega6) are obtained. Radiative and non-radiative transition rates (A(T) and W(MPR)), radiative lifetimes (tauR), branching ratios (beta) and integrated absorption cross-sections (sigma) have been computed for certain excited states of Er3+ in these mixed alkali borate glasses. Emission spectra have been studied for all the three Er3+ doped mixed alkali borate glasses. The present paper throws light on the trends observed in the intensity parameters, radiative lifetimes, branching ratios and emission cross-sections as a function of x in these borate glasses, keeping in view the effect of mixed alkalies in borate glasses.

Quantitative fluid inclusion gas analysis of airburst, nuclear, impact and fulgurite glasses.

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

Parnell, John; Newsom, Horton E.; Blamey, Nigel J. F.

We present quantitative fluid inclusion gas analysis on a suite of violently-formed glasses. We used the incremental crush mass spectrometry method (Norman & Blamey, 2001) to analyze eight pieces of Libyan Desert Glass (LDG). As potential analogues we also analyzed trinitite, three impact crater glasses, and three fulgurites. The 'clear' LDG has the lowest CO{sub 2} content and O{sub 2}/Ar ratios are two orders of magnitude lower than atmospheric. The 'foamy' glass samples have heterogeneous CO{sub 2} contents and O{sub 2}/Ar ratios. N{sub 2}/Ar ratios are similar to atmospheric (83.6). H{sub 2} and He are elevated but it is difficultmore » to confirm whether they are of terrestrial or meteoritic origin. Combustion cannot account for oxygen depletion that matches the amount of CO{sub 2} produced. An alternative mechanism is required that removes oxygen without producing CO{sub 2}. Trinitite has exceedingly high CO{sub 2} which we attribute to carbonate breakdown of the caliche at ground zero. The O{sub 2}/Ar ratio for trinitite is lower than atmospheric but higher than all LDG samples. N{sub 2}/Ar ratios closely match atmospheric. Samples from Lonar, Henbury and Aouelloul impact craters have atmospheric N{sub 2}/Ar ratios. O{sub 2}/Ar ratios at Lonar and Henbury are 9.5 to 9.9 whereas the O{sub 2}/Ar ratio is 0.1 for the Aouelloul sample. In most fulgurites the N{sub 2}/Ar ratio is higher than atmospheric, possibly due to interference from CO. Oxygen ranges from 1.3 to 19.3%. Gas signatures of LDG inclusions neither match those from the craters, trinitite nor fulgurites. It is difficult to explain both the observed depletion of oxygen in the LDG and a CO{sub 2} level that is lower than it would be if the CO{sub 2} were simply a product of hydrocarbon combustion in air. One possible mechanism for oxygen depletion is that as air turbulently mixed with a hot jet of vaporized asteroid from an airburst and expanded, the atmospheric oxygen reacted with the metal vapor to form metal oxides that condensed. This observation is compatible with the model of Boslough & Crawford (2008) who suggest that an airburst incinerates organic materials over a large area, melting surface materials that then quench to form glass. Bubbles would contain a mixture of pre-existing atmosphere with combustion products from organic material and products of the reaction between vaporized cosmic materials (including metals) and terrestrial surface and atmosphere.« less

ATMOS/ATLAS-3 Observations of Long-Lived Tracers and Descent in the Antarctic Vortex in November 1994

NASA Technical Reports Server (NTRS)

Abrams, M. C.; Manney, G. L.; Gunson, M. R.; Abbas, M. M.; Chang, A. Y.; Goldman, A.; Irion, F. W.; Michelsen, H. A.; Newchurch, M. J.; Rinsland, C. P.;

Perrhenate incorporation into binary mixed sodalites: The role of anion size and implications for technetium-99 sequestration

DOE PAGES

Dickson, Johnbull O.; Harsh, James B.; Lukens, Wayne W.; ...

2014-12-20

Perrhenate (ReO 4 -), as a TcO 4 - analogue, was incorporated into mixed-anion sodalites from binary solutions containing ReO 4 - and a competing anion X n- (Cl -, CO 3 2-, SO 4 2-, MnO 4 -, or WO 4 2-). For this study, our objective was to determine the extent of solid solution formation and the dependence of competing ion selectivity on ion size. Using equivalent aqueous concentrations of the anions (ReO 4 -/X n- molar ratio = 1:1), we synthesized mixed-anion sodalites from zeolite and NaOH at 90 °C for 96 h. The resulting solids weremore » characterized by bulk chemical analysis, powder X-ray diffraction, scanning electron microscopy, and X-ray absorption near edge structure (XANES) spectroscopy to determine crystal structure, chemical composition, morphology, and rhenium (Re) oxidation state. Rhenium in the solid phase occurred predominately as Re(VII)O 4 - in the sodalites, which have a primitive cubic pattern in the space group P43n. The refined unit-cell parameters of the mixed sodalites ranged from 8.88 to 9.15 Å and showed a linear dependence on the size and mole fraction of the incorporated anion(s). The ReO 4 - selectivity, represented by its distribution coefficient (K d), increased in the following order: Cl - < NO 3 - < MnO 4 - and CO 3 2- < SO 4 2- < WO 4 2- for the monovalent and divalent anions, respectively. The relationship between the ReO 4 - distribution coefficient and competing anion size was nonlinear. When the difference in ionic radius (DIR) between ReO 4 - and X n - (n = 1 or 2) was greater than ~ 12%, then ReO 4 - incorporation into sodalite was insignificant. The results imply that anion size is the major factor that determines sodalite anion compositions. Given the similarity in chemical behavior and anion size, ReO 4 - serves as a suitable analogue for TcO 4 - under oxidizing conditions where both elements are expected to remain as oxyanions in the + 7 oxidation state.« less

Actinide Oxidation State and O/M Ratio in Hypostoichiometric Uranium-Plutonium-Americium U0.750Pu0.246Am0.004O2-x Mixed Oxides.

PubMed

Vauchy, Romain; Belin, Renaud C; Robisson, Anne-Charlotte; Lebreton, Florent; Aufore, Laurence; Scheinost, Andreas C; Martin, Philippe M

2016-03-07

Innovative americium-bearing uranium-plutonium mixed oxides U1-yPuyO2-x are envisioned as nuclear fuel for sodium-cooled fast neutron reactors (SFRs). The oxygen-to-metal (O/M) ratio, directly related to the oxidation state of cations, affects many of the fuel properties. Thus, a thorough knowledge of its variation with the sintering conditions is essential. The aim of this work is to follow the oxidation state of uranium, plutonium, and americium, and so the O/M ratio, in U0.750Pu0.246Am0.004O2-x samples sintered for 4 h at 2023 K in various Ar + 5% H2 + z vpm H2O (z = ∼ 15, ∼ 90, and ∼ 200) gas mixtures. The O/M ratios were determined by gravimetry, XAS, and XRD and evidenced a partial oxidation of the samples at room temperature. Finally, by comparing XANES and EXAFS results to that of a previous study, we demonstrate that the presence of uranium does not influence the interactions between americium and plutonium and that the differences in the O/M ratio between the investigated conditions is controlled by the reduction of plutonium. We also discuss the role of the homogeneity of cation distribution, as determined by EPMA, on the mechanisms involved in the reduction process.

Structural phases, magnetic properties and Maxwell-Wagner type relaxation of CoFe2O4/Sr2Co2Fe12O22 ferrite composites

NASA Astrophysics Data System (ADS)

Patel, Chirag K.; Solanki, Neha P.; Singh, Charanjeet; Jotania, Rajshree B.; Chauhan, Chetna C.; Kulkarni, Shailja D.; Shirsath, Sagar E.

2017-07-01

CoFe2O4 (S:Y-1:0) and Sr2Co2Fe12O22 (S:Y-0:1) ferrites were synthesized separately by using chemical coprecipitation technique and calcined at 1000 °C for 5 h. The mixed ferrite composites (S:Y-3:7, 4:6, 5:5, 6:4 and 7:3) were prepared by physical mixing of individual ferrite powders in required weight proportions. The prepared composites were heated at 1150 °C for 5 h in a muffle furnace and then slowly cooled to room temperature. The prepared ferrites were characterized using various instrumental techniques like FTIR, XRD, SEM, VSM and dielectric measurements. The x-ray diffraction studies of pure Sr2Co2Fe12O22 ferrite sample show the presence of M and Y-type hexagonal phases, while the composites consist of spinel and Y-type phases. FTIR spectra of all samples show two bands of Fe-O stretching vibrations. VSM results of composites reveal that the values of the saturation magnetization (M s) vary from 50.44 emu g-1 to 31.21 emu g-1, while remanent magnetization values found from 11.18 emu g-1 to 3.70 emu g-1. A higher value of coercivity (H c  =  562 emu g-1) is observed in the composite S:Y-3:7 but M r/M s ratio of pure and composites is found to be less than 0.5. The dielectric behavior is explained using Maxwell-Wegner type interfacial polarization and N. Rezlescu’s model.

Eddy covariance fluxes of the NO-NO2-O3 triad above a spruce forest canopy in south-eastern Germany.

NASA Astrophysics Data System (ADS)

Tsokankunku, A.; Zhu, Z.; Meixner, F. X.; Foken, T.; Andreae, M. O.

2009-04-01

We investigated the diel variability of the eddy covariance fluxes of the NO-NO2-O3 triad above a spruce forest canopy at the "Weidenbrunnen" research site (Fichtelgebirge, Germany). Measurements were part of the EGER project (ExchanGE processes in mountainous Regions), which focuses on the role of process interactions among the different scales of soil, in-canopy and atmospheric exchange processes of reactive and non-reactive trace gases and energy. The eddy covariance platform was at the top of a 32 m high tower (50˚ 08'31" N, 11˚ 52'1"E, elevation 755 m.a.s.l). The eddy covariance system consisted of a CSAT3 sonic anemometer and a high speed, high resolution NO-NO2two channel chemiluminescence analyzer (Ecophysics CLD 790 SR2). A solid-state blue-light photolytic converter was connected to the NO2 channel of the analyzer just behind the sample inlet. Ambient NO and NO2 mixing ratios were sampled via 52 m long tubes with the instrument itself located in a temperature-controlled container at the ground. The NO-NO2 analyzer was operated at 5 Hz. Additionally we measured eddy covariance fluxes of CO2 and H2O. An infrared absorption-based analyzer (LI-7000) was used to sample CO2 and H2O mixing ratios, and a fast solid-phase chemiluminescence ozone analyzer (GFAS) was deployed to measure O3 mixing ratios. All trace gas inlets were situated at 32.5 m, 20 cm below the path of the sonic anemometer. The 32m inlet of an independent NO, NO2, and O3 concentration profile measuring system was used as the calibration source for the fast ozone analyzer and the two channel NO-NO2chemiluminescence analyzer. Preliminary results show that NO and NO2advection plays a big role in the magnitude and direction of the fluxes at the site. The main source of the advection is a busy country road situated about 2 km west of the site. CO2 fluxes were also influenced by advection. Extended periods of stationarity usually occurred on Sundays when the amount of traffic was significantly lower. During the "golden days period" (29 June - 3 July 2008), there was mainly downward directed NO fluxes (within the margin of error). However there is also evidence of NO leaving the canopy in some instances. NO and NO2 fluxes ranged between +1.5 and -1.5 nmol m-2 s-1 (±45 ngNO m-2 s-1 and ±70 ngNO2 m-2 s-1).

Wintertime Overnight NOx Removal in a Southeastern United States Coal-Fired Power Plant Plume: A Model for Understanding Winter NOx Processing and Its Implications

NASA Technical Reports Server (NTRS)

Fibiger, Dorothy L.; McDuffie, Erin E.; Dube, William P.; Aikin, Kenneth C.; Lopez-Hilifiker, Felipe D.; Lee, Ben H.; Green, Jaime R.; Fiddler, Marc N.; Holloway, John S.; Ebben, Carlena;

Wintertime Overnight NOx Removal in a Southeastern United States Coal-fired Power Plant Plume: A Model for Understanding Winter NOx Processing and its Implications

NASA Astrophysics Data System (ADS)

Fibiger, Dorothy L.; McDuffie, Erin E.; Dubé, William P.; Aikin, Kenneth C.; Lopez-Hilfiker, Felipe D.; Lee, Ben H.; Green, Jaime R.; Fiddler, Marc N.; Holloway, John S.; Ebben, Carlena; Sparks, Tamara L.; Wooldridge, Paul; Weinheimer, Andrew J.; Montzka, Denise D.; Apel, Eric C.; Hornbrook, Rebecca S.; Hills, Alan J.; Blake, Nicola J.; DiGangi, Josh P.; Wolfe, Glenn M.; Bililign, Solomon; Cohen, Ronald C.; Thornton, Joel A.; Brown, Steven S.

2018-01-01

Nitric oxide (NO) is emitted in large quantities from coal-burning power plants. During the day, the plumes from these sources are efficiently mixed into the boundary layer, while at night, they may remain concentrated due to limited vertical mixing during which they undergo horizontal fanning. At night, the degree to which NO is converted to HNO3 and therefore unable to participate in next-day ozone (O3) formation depends on the mixing rate of the plume, the composition of power plant emissions, and the composition of the background atmosphere. In this study, we use observed plume intercepts from the Wintertime INvestigation of Transport, Emissions and Reactivity campaign to test sensitivity of overnight NOx removal to the N2O5 loss rate constant, plume mixing rate, background O3, and background levels of volatile organic compounds using a 2-D box model of power plant plume transport and chemistry. The factor that exerted the greatest control over NOx removal was the loss rate constant of N2O5. At the lowest observed N2O5 loss rate constant, no other combination of conditions converts more than 10% of the initial NOx to HNO3. The other factors did not influence NOx removal to the same degree.

Mimicking floodplain reconnection and disconnection using 15N mesocosm incubations

NASA Astrophysics Data System (ADS)

Welti, N.; Bondar-Kunze, E.; Mair, M.; Bonin, P.; Wanek, W.; Pinay, G.; Hein, T.

2012-11-01

Floodplain restoration changes the nitrate delivery pattern and dissolved organic matter pool in backwaters, though the effects these changes have are not yet well known. We performed two mesocosm experiments on floodplain sediments to quantify the nitrate metabolism in two types of floodplains. Rates of denitrification, dissimilatory nitrate reduction to ammonium (DNRA) and anammox were measured using 15N-NO3 tracer additions in mesocosms of undisturbed floodplain sediments originating from (1) restored and (2) disconnected sites in the Alluvial Zone National Park on the Danube River downstream of Vienna, Austria. DNRA rates were an order of magnitude lower than denitrification and neither rate was affected by changes in nitrate delivery pattern or organic matter quality. Anammox was not detected at any of the sites. Denitrification was out-competed by assimilation, which was estimated to use up to 70% of the available nitrate. Overall, denitrification was higher in the restored sites, with mean rates of 5.7 ± 2.8 mmol N m-2 h-1 compared to the disconnected site (0.6 ± 0.5 mmol N m-2 h-1). In addition, ratios of N2O : N2 were lower in the restored site indicating a more complete denitrification. Nitrate addition had neither an effect on denitrification, nor on the N2O : N2 ratio. However, DOM (dissolved organic matter) quality significantly changed the N2O : N2 ratio in both sites. Addition of riverine-derived organic matter lowered the N2O : N2 ratio in the disconnected site, whereas addition of floodplain-derived organic matter increased the N2O : N2 ratio in the restored site. These results demonstrate that increasing floodplains hydrological connection to the main river channel increases nitrogen retention and decreases nitrous oxide emissions.

Reactive Nitrogen and its Correlation with O3 and CO Over the Pacific in Winter and Early Spring

NASA Technical Reports Server (NTRS)

Koike, M.; Kondo,Y.; Kawakami, S.; Nakajima, H.; Sachse, G. W.; Singh, H. B.; Browell, E. V.; Merrill, J. T.; Newell, R. E.

1997-01-01

Measurements of NO, NO(y), O3, and CO were made during NASA's Global Tropospheric Experiment/Pacific Exploratory Mission-West B (GTE/PEM-West B) carried out over the western Pacific in February and March 1994. NO(x) was calculated from NO using a photostationary state model ((NO(x)(sub mc)). Correlations between these species are presented, and some insights into the sources of NO(x) and NO(y) are described. The boundaries between the lower, middle, and upper troposphere have been defined at potential temperatures of 311 K and 328 K, which correspond to the geometric altitudes of about 5 and 9 km at 30degN. Enhancements in the mixing ratios of NO(y) and CO were observed in the lower and middle troposphere. A positive correlation was found between these two species suggesting that the high NO(y) values were due to anthropogenic emissions over the continental surface. On the other hand, O3 increased little with increase in CO. As a result, NO(y)/O3 ratios were higher in air more influenced by pollution. NO(y), values in 55 and 28% of the air masses sampled in the lower and middle troposphere, respectively, were higher than the clean free tropospheric NO(y)-O3 range when O3 values simultaneously observed were used. High (NOx)mc/NOy ratios between 0.15 and 0.3 were found in the boundary layer with relatively low mixing ratios of CO and NOy during the three flights. These air masses were transported from a higher altitude (approximately 5 km) and a higher latitude (approximately 50degN) within a few days. The peroxyacetyl nitrate (PAN)/NO(y) ratios were generally high (approximately 0.4) in these air masses, and the thermal decomposition of PAN was a probable source of NO(x). In the middle troposphere the (NO(x))mc mixing ratio did not generally increase with NO(y) or CO, suggesting that the transport of air masses affected by anthropogenic emissions did not increase the NO(x) level significantly. In the upper troposphere, very minor effects from the continental surface sources were seen in the CO mixing ratio. By contrast, NO(y) values in 33% of the air masses were higher than those expected when stratospheric air intrusion is assumed to be a single source of NO(y) based on NO(y)-O3 correlation analyses. This result suggests significant free tropospheric NO(y) sources, namely exhaust from the aircraft and NO production by lightning activity. In fact, spikes in the (NO(x))(sub m)c mixing ratios were observed near the aircraft corridor south of Tokyo at an altitude of 10 km. These two free tropospheric NO(x) sources were considered to be important in determining the levels of the upper tropospheric NO(x) and NO(y) during PEM-West B.

A weak-light-responsive TiO2/g-C3N4 composite film: photocatalytic activity under low-intensity light irradiation.

PubMed

Wang, Peifang; Guo, Xiang; Rao, Lei; Wang, Chao; Guo, Yong; Zhang, Lixin

2018-05-10

A TiO 2 /g-C 3 N 4 composite photocatalytic film was prepared by in situ synthesis method and its photocatalytic capability under weak-visible-light condition was studied. The co-precursor with different ratio of melamine and TiO 2 sol-gel precursor were treated using ultrasonic mixing, physical deposition, and co-sintering method to form the smooth, white-yellow, and compact TiO 2 /g-C 3 N 4 composite films. The prepared TiO 2 /g-C 3 N 4 materials were characterized by SEM, TEM, EDS, XRD, BET, VBXPS, and UV-vis diffuse reflectance spectra. The results of composite showed that TiO 2 and g-C 3 N 4 have close interfacial connections which are favorable to charge transfer between these two semiconductors with suitable band structure, g-C 3 N 4 retard the anatase-to-rutile phase transition of TiO 2 significantly, the specific surface area were increased with g-C 3 N 4 ratio raised. Under weak-light irradiation, composite films photocatalytic experiments exhibited RhB removal efficiency approaching 90% after three recycles. Powders suspension degradation experiments revealed the removal efficiency of TiO 2 /g-C 3 N 4 (90.8%) was higher than pure TiO 2 (52.1%) and slightly lower than pure g-C 3 N 4 (96.6%). By control experiment, the enhanced photocatalysis is ascribed to the combination of TiO 2 and g-C 3 N 4 , which not only produced thin films with greater stability but also formed heterojunctions that can be favorable to charge transfer between these two semiconductors with suitable band structure. This study presents the potential application of photocatalytic film in the wastewater treatment under weak-light situation.

Performance of Diesel Engine Using Diesel B3 Mixed with Crude Palm Oil

PubMed Central

Namliwan, Nattapong; Wongwuttanasatian, Tanakorn

2014-01-01

The objective of this study was to test the performance of diesel engine using diesel B3 mixed with crude palm oil in ratios of 95 : 5, 90 : 10, and 85 : 15, respectively, and to compare the results with diesel B3. According to the tests, they showed that the physical properties of the mixed fuel in the ratio of 95 : 5 were closest to those of diesel B3. The performance of the diesel engine that used mixed fuels had 5–17% lower torque and power than that of diesel B3. The specific fuel consumption of mixed fuels was 7–33% higher than using diesel B3. The components of gas emissions by using mixed fuel had 1.6–52% fewer amount of carbon monoxide (CO), carbon dioxide (CO2), sulfur dioxide (SO2), and oxygen (O2) than those of diesel B3. On the other hand, nitric oxide (NO) and nitrogen oxides (NOX) emissions when using mixed fuels were 10–39% higher than diesel B3. By comparing the physical properties, the performance of the engine, and the amount of gas emissions of mixed fuel, we found out that the 95 : 5 ratio by volume was a suitable ratio for agricultural diesel engine (low-speed diesel engine). PMID:24688402

Measurements of condensation nuclei in the Airborne Arctic Stratospheric Expedition - Observations of particle production in the polar vortex

NASA Technical Reports Server (NTRS)

Wilson, J. C.; Stolzenburg, M. R.; Clark, W. E.; Loewenstein, M.; Ferry, G. V.; Chan, K. R.

1990-01-01

The ER-2 Condensation Nucleus Counter (ER-2 CNC) was operated in the Airborne Arctic Stratospheric Expedition (AASE) in January and February 1989. The ER-2 CNC measures the mixing ratio of particles, CN, with diameters from approximately 0.02 to approximately 1 micron. The spatial distribution of CN in the Arctic polar vortex was found to resemble that measured in the Antarctic in the Spring of 1987. The vertical profile of CN in the vortex was lowered by subsidence. At altitudes above the minimum in the CN mixing ratio profile, CN mixing ratios correlated negatively with that of N2O, demonstrating new particle production. CN serve as nuclei in the formation of Polar Stratospheric Clouds (PSCs) and the concentration of CN can affect PSC properties.

Chemical Composition of Atmospheric Aerosols From High and Low Altitude Sites in Northern and Western India

NASA Astrophysics Data System (ADS)

Rastogi, N.; Athiyarath, S.; Sarin, M.; R, R.

2006-12-01

The chemical composition of ambient aerosols, collected during wintertime from four designated sites: Ahmedabad (23.0oN, 72.6oE, 49 m asl), Mt Abu (24.6oN, 72.7oE, 1680 m asl), Hisar (29.2oN, 75.7oE, 216m asl) and Nainital (29.4oN, 79.5oE, 1940 m asl), has been studied to understand the potential role of regional emission sources as well as the long-range transport of chemical constituents through free troposphere. The two high altitude sites, Mt Abu and Nainital, exhibit free tropospheric characteristics during wintertime; whereas the urban sites (Ahmedabad and Hisar) are within boundary layer. The ratios of major ionic species, measured in water extracts of aerosols, are considered to be advantageous in order to remove the effect of aerosol mass loading on the atmospheric concentrations of species at different sites. At low-altitude-urban sites (Ahmedabad and Hisar), geometric mean of Ca2+/Na+ ratios (4.3 and 4.5) and HCO3-/ Ca2+ ratios (1.7 and 1.5) are comparable; whereas significant differences are observed in Cl-/Na+ (1.1 and 0.6), SO42-/Ca2+ (1.5 and 3.5) and SO42-/NO3- (2.1 and 1.0). These differences are attributed to relative dominance of anthropogenic emissions over the northern site (Hisar). In contrast, major differences arise over Mt Abu and Nainital with respect to Cl-/Na+ (1.0 and 0.2), Ca2+/Na+ (9.0 and 4.4) and HCO3-/ Ca2+ (1.8 and 0.9) ratios; whereas SO42-/Ca2+ (2.3 and 3.1) and SO42-/NO3- (5.3 and 5.9) ratios are comparable. Such regional differences for a high altitude site could arise due to semi-arid climate and high abundance of mineral dust at Mt Abu. Higher SO42-/NO3- ratios over high altitude sites than those over low altitude sites are attributed to the relative difference in the size distribution of SO42- (fine mode) and NO3- (coarse mode) aerosols.

Performance characteristics of MM5-SMOKE-CMAQ for a summer photochemical episode in southeast England, United Kingdom

NASA Astrophysics Data System (ADS)

Yu, Y.; Sokhi, R. S.; Kitwiroon, N.; Middleton, D. R.; Fisher, B.

In this study a modelling system consisting of Mesoscale Model (MM5), Sparse Matrix Operator Kernel Emissions (SMOKE) and Community Multiscale Air Quality (CMAQ) model has been applied to a summer photochemical period in southeast England, UK. Ozone (O 3), nitrogen dioxide (NO 2) and particulate matter (PM 2.5) concentrations modelled with different horizontal grid resolutions (9 and 3 km) were evaluated against available ground-level observations from the UK Automatic Urban and Rural Network (AURN) and London Air Quality Network (LAQN) for the period of 24-28 June 2001 with a focus on O 3 predictions. This effort, which represents the first comprehensive performance evaluation of the modelling system over a UK domain, reveals that CMAQ's ability to reproduce surface O 3 observations varies with O 3 concentrations. It underpredicts O 3 mixing ratios on high-O 3 days and overpredicts the maximum and minimum hourly O 3 values for most low-O 3 days. Model sensitivity analysis with doubled anthropogenic NO x or volatile organic compounds (VOC) emissions and analysis of the daylight-averaged levels of OX (sum of O 3 and NO 2) as a function of NO x revealed that the undereprediction of peak O 3 concentrations on high-O 3 days is caused by the underprediction of regional contribution and to a lesser extent local production, which might be related to the underestimation of European emissions in EMEP inventory and the lacked reactivity of the modelled atmosphere. CMAQ systematically underpredicts hourly NO 2 mixing ratios but captures the temporal variations. The normalized mean bias for hourly NO 2, although much larger than that for O 3, falls well within the generally accepted range of -20% to -50%. CMAQ with both resolutions (9 and 3 km) significantly underpredicts PM 2.5 mass concentrations and fails to reproduce its temporal variations. While model performance for O 3 and PM 2.5 are not very sensitive to model grid resolutions, a better agreement between modelled and measured hourly NO 2 mixing ratios was achieved with higher resolution. Further investigation into the uncertainties in meteorological input, uncertainties in emissions, as well as representation of physical and chemical processes (e.g. chemical mechanism) in the model is needed to identify the causes for the discrepancies between observations and predictions.

Multiscale structural characterizations of mixed U(iv)-An(iii) oxalates (An(iii) = Pu or Am) combining XAS and XRD measurements.

PubMed

Arab-Chapelet, B; Martin, P M; Costenoble, S; Delahaye, T; Scheinost, A C; Grandjean, S; Abraham, F

2016-04-28

Mixed actinide(III,IV) oxalates of the general formula M2.2UAn(C2O4)5·nH2O (An = Pu or Am and M = H3O(+) and N2H5(+)) have been quantitatively precipitated by oxalic precipitation in nitric acid medium (yield >99%). Thorough multiscale structural characterization using XRD and XAS measurements confirmed the existence of mixed actinide oxalate solid solutions. The XANES analysis confirmed that the oxidation states of the metallic cations, tetravalent for uranium and trivalent for plutonium and americium, are maintained during the precipitation step. EXAFS measurements show that the local environments around U(+IV), Pu(+III) and Am(+III) are comparable, and the actinides are surrounded by ten oxygen atoms from five bidentate oxalate anions. The mean metal-oxygen distances obtained by XAS measurements are in agreement with those calculated from XRD lattice parameters.

Diurnal variations of BrONO2 observed by MIPAS-B at midlatitudes and in the Arctic

NASA Astrophysics Data System (ADS)

Wetzel, Gerald; Oelhaf, Hermann; Höpfner, Michael; Friedl-Vallon, Felix; Ebersoldt, Andreas; Gulde, Thomas; Kazarski, Sebastian; Kirner, Oliver; Kleinert, Anne; Maucher, Guido; Nordmeyer, Hans; Orphal, Johannes; Ruhnke, Roland; Sinnhuber, Björn-Martin

2017-12-01

The first stratospheric measurements of the diurnal variation in the inorganic bromine (Bry) reservoir species BrONO2 around sunrise and sunset are reported. Arctic flights of the balloon-borne Michelson Interferometer for Passive Atmospheric Sounding (MIPAS-B) were carried out from Kiruna (68° N, Sweden) in January 2010 and March 2011 inside the stratospheric polar vortices where diurnal variations of BrONO2 around sunrise have been observed. High nighttime BrONO2 volume mixing ratios of up to 21 pptv (parts per trillion by volume) were detected in late winter 2011 in the absence of polar stratospheric clouds (PSCs). In contrast, the amount of measured BrONO2 was significantly lower in January 2010 due to low available NO2 amounts (for the build-up of BrONO2), the heterogeneous destruction of BrONO2 on PSC particles, and the gas-phase interaction of BrO (the source to form BrONO2) with ClO. A further balloon flight took place at midlatitudes from Timmins (49° N, Canada) in September 2014. Mean BrONO2 mixing ratios of 22 pptv were observed after sunset in the altitude region between 21 and 29 km. Measurements are compared and discussed with the results of a multi-year simulation performed with the chemistry climate model ECHAM5/MESSy Atmospheric Chemistry (EMAC). The calculated temporal variation in BrONO2 largely reproduces the balloon-borne observations. Using the nighttime simulated ratio between BrONO2 and Bry, the amount of Bry observed by MIPAS-B was estimated to be about 21-25 pptv in the lower stratosphere.

Line Mixing in Water Vapor and Methane

NASA Technical Reports Server (NTRS)

Smith, M. A. H.; Brown, L. R.; Toth, R. A.; Devi, V. Malathy; Benner, Chris

2006-01-01

A multispectrum fitting algorithm has been used to identify line mixing and determine mixing parameters for infrared transitions of H2O and CH4 in the 5-9 micrometer region. Line mixing parameters at room temperature were determined for two pairs of transitions in the v2 fundamental band of H2O-16, for self-broadening and for broadening by H2, He, CO2, N2, O2 and air. Line mixing parameters have been determined from air-broadened CH4 spectra, recorded at temperatures between 210 K and 314 K, in selected R-branch manifolds of the v4 band. For both H2O and CH4, the inclusion of line mixing was seen to have a greater effect on the retrieved values of the line shifts than on the retrieved values of other parameters

Laser Spectroscopy Monitoring of 13C18O16O and 12C17O16O of Atmospheric Carbon Dioxide

NASA Astrophysics Data System (ADS)

Shorter, J. H.; Nelson, D. D.; Ono, S.; McManus, J. B.; Zahniser, M. S.

2017-12-01

One of the main challenges to making accurate predictions of future changes in CO2 concentration is the capability to determine what fraction of human produced CO2 remains in the atmosphere. We present our progress in the application of Tunable Infrared Laser Direct Absorption Spectroscopy (TILDAS) to the measurement of the primary clumped (13C18O16O) as well as 17O (12C17O16O) isotopologues of atmospheric CO2, as a tracer of its sources and sinks. We expect unique isotopologue signals in CO2 from high-temperature combustion sources, plants, soils, and air-sea exchange processes. High sampling frequency (a few minutes for each sample vs. reference cycle) achieved by a TILDAS instrument is expected to enable us to document local heterogeneous sources and temporal variations. The TILDAS is equipped with a newly developed 400-meter absorption cell. We designed a dual pressure measurement technique in which the clumped isotopologue, 13C18O16O, and 13C16O16O are first measured at 30 torr cell pressure. This is followed by measurement of 12C17O16O, 12C18O16O and 12C16O16O at lower ( 5 torr) cell pressure. Isotopologue ratios are compared between reference and sample gases. Preliminary tests demonstrated a precision approaching 0.03 ‰ for the ratio 13C18O16O/13C16O16O and 0.08‰ for Δ13C18O16O value (1σ repeatability for 4 min sample vs. reference cycle). Sample size for a single analysis is approximately 100 mL of air (1.6μmol of CO2). Given the previously observed range of variations for Δ13C18O16O and Δ17O values as large as 0.6 to 0.3 ‰, respectively, TILDAS offers a novel approach for real time monitoring of atmospheric CO2 isotopologues. It was found that achieving better than 0.1‰ requires careful matching of CO2 mixing ratios between reference and sample air. A primary cause of pressure and mixing ratio dependence is inaccurate baseline fitting (analogous to abundance sensitivity or pressure baseline for IRMS). Given that mixing ratios of atmospheric CO2 can vary as much as 50% or more, a dynamic dilution scheme, where sample air is diluted by CO2 free air to match the reference mixing ratio, is being developed. An in-line calibration source of hot, equilibrated CO2 isotopologues is also being tested. We will discuss the current instrument performance, areas for improvement, and project future applications.

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

NASA Technical Reports Server (NTRS)

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

1980-01-01

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

The Impact of the Afternoon Planetary Boundary-Layer Height on the Diurnal Cycle of CO and CO2 Mixing Ratios at a Low-Altitude Mountaintop

NASA Astrophysics Data System (ADS)

Lee, Temple R.; De Wekker, Stephan F. J.; Pal, Sandip

2018-02-01

Mountaintop trace-gas mixing ratios are often assumed to represent free atmospheric values, but are affected by valley planetary boundary-layer (PBL) air at certain times. We hypothesize that the afternoon valley-PBL height relative to the ridgetop is important in the diurnal cycle of mountaintop trace-gas mixing ratios. To investigate this, we use, (1) 4-years (1 January 2009-31 December 2012) of CO and CO2 mixing-ratio measurements and supporting meteorological observations from Pinnacles (38.61°N , 78.35°W , 1017 m a.s.l.), which is a monitoring site in the Appalachian Mountains, (2) regional O3 mixing-ratio measurements, and (3) PBL heights determined from a nearby sounding station. Results reveal that the amplitudes of the diurnal cycles of CO and CO2 mixing ratios vary as a function of the daytime maximum valley-PBL height relative to the ridgetop. The mean diurnal cycle for the subset of days when the afternoon valley-PBL height is at least 400 m below the ridgetop shows a daytime CO mixing-ratio increase, implying the transport of PBL air from the valley to the mountaintop. During the daytime, on days when the PBL heights exceed the mountaintop, PBL dilution and entrainment cause CO mixing ratios to decrease. This decrease in CO mixing ratio, especially on days when PBL heights are at least 400 m above the ridgetop, suggests that measurements from these days can be used as with afternoon measurements from flat terrain in applications requiring regionally-representative measurements.

Nitrogen oxides and ozone fluxes from an oilseed-rape management cycle: the influence of cattle slurry application

NASA Astrophysics Data System (ADS)

Vuolo, Raffaella M.; Loubet, Benjamin; Mascher, Nicolas; Gueudet, Jean-Christophe; Durand, Brigitte; Laville, Patricia; Zurfluh, Olivier; Ciuraru, Raluca; Stella, Patrick; Trebs, Ivonne

2017-05-01

This study reports NO, NO2 and O3 mixing ratios and flux measurements using the eddy covariance method during a 7-month period over an oilseed-rape field, spanning an organic and a mineral fertilisation event. Cumulated NO emissions during the whole period were in agreement with previous studies and showed quite low emissions of 0.26 kg N ha-1 with an emission factor of 0.27 %, estimated as the ratio between total N emitted in the form of NO and total N input. The NO emissions were higher following organic fertilisation in August due to conditions favouring nitrification (soil water content around 20 % and high temperatures), while mineral fertilisation in February did not result in high emissions. The ozone deposition velocity increased significantly after organic fertilisation. The analysis of the chemical and turbulent transport times showed that reactions between NO, NO2 and O3 below the measurement height occurred constantly throughout the 7-month period. Following organic fertilisation, the NO ground fluxes were 30 % larger than the NO fluxes at the measurement height (3.2 m), while the NO2 fluxes switched from deposition to emission during certain periods, being negative at the surface and positive at the measurement height. This phenomenon of apparent NO2 emissions appears to be significant during strong NO emissions and high O3 ambient mixing ratios, even on a bare soil during August.

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

PubMed

Ośmiałowski, Borys; Valkonen, Arto; Chęcińska, Lilianna

2013-10-05

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

Trace gas measurements from whole air samples collected over the Antarctic continent

NASA Technical Reports Server (NTRS)

Heidt, L. E.; Vedder, J. F.; Pollock, Walter H.; Henry, Bruce E.; Lueb, Richard A.

1988-01-01

Whole air samples collected aboard the NASA DC-8 and ER-2 aircraft as part of the Airborne Antarctic Ozone Experiment (AAOE) were analyzed in a field laboratory set up at Punta Arenas, Chile, in August and September, 1987. Mixing ratios obtained from gas chromatographic analyses of these samples are presented for N2O, CFCl3, CFCl2, C2F3Cl3, CH3CCl3, CH4, and CO. Variations in the mixing ratios of these gases along the individual flight paths of the aircraft are used as tracers to indicate the history of air masses over and near the Antarctic continent.

Photochemically deposited nano-Ag/sol-gel TiO2-In2O3 mixed oxide mesoporous-assembled nanocrystals for photocatalytic dye degradation.

PubMed

Sreethawong, Thammanoon; Ngamsinlapasathian, Supachai; Yoshikawa, Susumu

2014-05-01

This work focused on the improvement of the photocatalytic activity for Congo Red (CR) azo dye degradation of mesoporous-assembled 0.95 TiO2-0.05 In2O3 mixed oxide photocatalyst (with a TiO2-to-In2O3 molar ratio of 0.95:0.05) by loading with Ag nanoparticles. The mesoporous-assembled 0.95TiO2-0.05In2O3 mixed oxide photocatalyst was synthesized by a hydrolytic sol-gel method with the aid of a structure-directing surfactant, prior to loading with various Ag contents (0.5-2 wt.%) by a photochemical deposition method. The optimum Ag loading content was found to be 1.5 wt.%, exhibiting a great increase in photocatalytic CR dye degradation activity. The 1.5 wt.% Ag-loaded 0.95TiO2-0.05In2O3 mixed oxide photocatalyst was further applied for the CR dye degradation in the presence of water hardness. Different types (Ca2+ and Ca2+ -Mg2+ mixture) and concentrations (200 and 500 mg/l) of water hardness were investigated. The results showed that the water hardness reduced the photocatalytic CR dye degradation activity, particularly for the extremely hard water with 500 mg/l of Ca2+ -Mg2+ mixture. The adjustment of initial solution pH of the CR dye-containing hard water to an appropriate value was found to improve the photocatalytic CR dye degradation activity under the identical reaction conditions. Copyright © 2014 Elsevier Inc. All rights reserved.

Dielectric relaxation of selenium-tellurium mixed former glasses

NASA Astrophysics Data System (ADS)

Palui, A.; Ghosh, A.

2017-05-01

We report the study of dielectric properties of mixed network former glasses of composition 0.3Ag2O-0.7(xSeO2-(1-x)TeO2); x=0, 0.1, 0.3, 0.4, 0.5 and 0.6 in a wide frequency 10 Hz - 2 MHz and temperature range 223 K - 403 K. The experimental data have been analyzed in the framework of complex dielectric permittivity. The dielectric permittivity data have been analyzed using the Cole-Cole function. The inverse temperature dependence of relaxation time obtained from real part of dielectric permittivity data follows the Arrhenius relation. The activation energy shows mixed glass former effect with variation of mixed former ratio. A non-zero value of shape parameters is observed and it is almost independent of temperature and composition.

Nitrous oxide emissions from yellow brown soil as affected by incorporation of crop residues with different carbon-to-nitrogen ratios: a case study in central China.

PubMed

Lin, Shan; Iqbal, Javed; Hu, Ronggui; Shaaban, Muhammad; Cai, Jianbo; Chen, Xi

2013-08-01

To investigate the influence of crop residues decomposition on nitrous oxide (N2O) emission, a field study was performed with application of crop residues with different C:N ratios in a bare yellow brown soil at the experimental station of Zhangjiachong at Zigui, China. We set up six experimental treatments: no crop residue (CK), rapeseed cake (RC), potato stalk (PS), rice straw (RS), wheat straw (WS), and corn straw (CS). The carbon (C) to nitrogen (N) ratios of these crop residues were 7.5, 32.9, 40.4, 65.7, and 90.9, respectively. Nitrous oxide fluxes were measured using a static closed chamber method. N2O emissions were significantly enhanced by incorporation of crop residues. Cumulative N2O emissions negatively correlated with C:N ratio (R (2) = 0.9821) of the crop residue, but they were positively correlated with average concentrations of dissolved organic carbon and microbial biomass carbon. Nitrogen emission fraction, calculated as N2O-N emissions originated from the crop residues N, positively correlated with C:N ratio of the residues (P < 0.05). Soil temperature did, whereas soil moisture did not, control the residue's induced N2O emissions because a significant correlation (P < 0.01) existed between soil temperature and N2O emissions in all treatments except the control. In contrast, a significant relationship between soil moisture and N2O emissions was found in the control only. Furthermore, N2O emission significantly correlated (P < 0.05) with NO3 (-)-N, and NH4 (+)-N contents from all residue treatments. These results indicate that (1) crop residues with distinct carbon and nitrogen contents can significantly alter soil N2O flux rates; and (2) soil biotic as well as abiotic variables are critical in determining soil-atmospheric N2O emissions after crop residue incorporation into soil.

Heterogeneous reactions in a stratospheric box model: A sensitivity study

NASA Astrophysics Data System (ADS)

Danilin, Michael Y.; McConnell, John C.

1994-12-01

Recent laboratory data concerning the reactions of HCl and HOx on/in sulfuric acid aerosol (Hanson et al., 1994), N2O5 and ClONO2 hydrolysis on the frozen aerosol (Hanson and Ravishankara, 1993a) and the temperature dependence of the HNO3 absorption cross section (Burkholder et al., 1993) indicate that a reevaluation of the role of heterogeneous reactions in the chemical balance of the stratosphere is required. A chemical module prepared for a three-dimensional (3-D) global chemistry transport model (CTM) and a general circulation model (GCM) has been used to carry out a sensitivity study of the effects of heterogeneous reactions on/in the sulfate aerosol and on the polar stratospheric cloud (PSC) particles. We present here results for the latitudes 60°S, 70°S and 75°S at the 50-mbar level. Our findings indicate that (1) the new values of the HNO3 cross sections result in lower mixing ratios for NOx and make ozone more vulnerable to catalytic destruction by ClOx; (2) the effect of the heterogeneous reactions OH + HNO3(a) → H2O + NO3 and HO2 +HO2(a) → H2O2 + O2 are small in comparison with the same gas phase reactions and play a negligible role for the ozone balance; (3) the HCl reactions in the sulfuric acid aerosol at 60°S and 70°S increase the chlorine activation up to 0.53 parts per billion by volume (ppbv) and 0.72 ppbv, respectively, for liquid aerosol and up to 0.87 ppbv for frozen aerosol at 70°S for volcanic conditions and this results in considerable ozone depletion at these latitudes; (4) studying the ozone "hole" phenomenon, we have considered the different initial ratios of ClONO2/HCl, of N2O5, galactic cosmic rays (GCRs), and longer lifetimes for the PSC. We have speculated an existence of the reaction N2O5 + HCl(a) → ClNO2 + HNO3.

A chemical perspective of day and night tropical (10°N-15°N) mesospheric inversion layers

NASA Astrophysics Data System (ADS)

Ramesh, K.; Sridharan, S.; Raghunath, K.; Rao, S. Vijaya Bhaskara

2017-03-01

The various occurrence characteristics of day and night tropical (10°N-15°N, 60°E-90°E) mesospheric inversion layers (MILs) are studied by using TIMED Sounding of the Atmosphere using Broadband Emission Radiometry satellite data products of kinetic temperature; volume mixing ratios of O, H, and O3; volume emission rates of O2 (1Δ) and OH (1.6 µm channel), and chemical heating rates due to seven dominant exothermic reactions among H, O, O2, O3, OH, HO2, and CO2 cooling rates for the year 2011. Although both dynamics and chemistry play important roles, the present study mainly focuses on the chemical processes involved in the formation of day and night MILs. It is found that the upper level height of daytime (nighttime) MIL descends (ascends) from 88 km ( 80 km) in winter to 72 km ( 90 km) in summer. The day and night inversion amplitudes are correlated with total chemical heating rates and CO2 cooling rates, and they show semi annual variation with larger (smaller) values during equinoxes (solstices). The daytime (nighttime) inversion layers are predominantly due to the exothermic reaction, R5: O + O + M → O2 + M and R6: O + O2 + M → O3 + M (R3: H + O3 → OH + O2). In addition, the CO2 causes large cooling at the top and small heating at the bottom levels of both day and night MILs. In the absence of dynamical effects, the chemical heating and CO2 cooling jointly contribute for the occurrence of day and night MILs.

Nitrogen removal from wastewater and bacterial diversity in activated sludge at different COD/N ratios and dissolved oxygen concentrations.

PubMed

Zielińska, Magdalena; Bernat, Katarzyna; Cydzik-Kwiatkowska, Agnieszka; Sobolewska, Joanna; Wojnowska-Baryła, Irena

2012-01-01

The impact of the organic carbon to nitrogen ratio (chemical oxygen demand (COD)/N) in wastewater and dissolved oxygen (DO) concentration on carbon and nitrogen removal efficiency, and total bacteria and ammonia-oxidizing bacteria (AOB) communities in activated sludge in constantly aerated sequencing batch reactors (SBRs) was determined. At DO of 0.5 and 1.5 mg O2/L during the aeration phase, the efficiency of ammonia oxidation exceeded 90%, with nitrates as the main product. Nitrification and denitrification achieved under the same operating conditions suggested the simultaneous course of these processes. The most effective nitrogen elimination (above 50%) was obtained at the COD/N ratio of 6.8 and DO of 0.5 mg O2/L. Total bacterial diversity was similar in all experimental series, however, for both COD/N ratios of 6.8 and 0.7, higher values were observed at DO of 0.5 mg O2/L. The diversity and abundance of AOB were higher in the reactors with the COD/N ratio of 0.7 in comparison with the reactors with the COD/N of 6.8. For both COD/N ratios applied, the AOB population was not affected by oxygen concentration. Amplicons with sequences indicating membership of the genus Nitrosospira were the determinants of variable technological conditions.

Effects of ZnO Nanoparticle on the Gas Separation Performance of Polyurethane Mixed Matrix Membrane

PubMed Central

Soltani, Banafsheh

2017-01-01

Polyurethane (PU)-ZnO mixed matrix membranes (MMM) were fabricated and characterized for gas separation. A thermogravimetric analysis (TGA), a scanning electron microscope (SEM) test and an atomic-force microscopy (AFM) revealed that the physical properties and thermal stability of the membranes were improved through filler loading. Hydrogen Bonding Index, obtained from the Fourier transform infrared spectroscopy (FTIR), demonstrate that the degree of phase separation in PU-ZnO 0.5 wt % MMM was more than the neat PU, while in PU-ZnO 1.0 wt % MMM, the phase mixing had increased. Compared to the neat membrane, the CO2 permeability of the MMMs increased by 31% for PU-ZnO 0.5 wt % MMM and decreased by 34% for 1.0 wt % ZnO MMM. The CO2/CH4 and CO2/N2 selectivities of PU-ZnO 0.5 wt % were 18.75 and 64.75, respectively. PMID:28800109

Preparation and reactivity of mixed-ligand ruthenium(II) hydride complexes with phosphites and polypyridyls.

PubMed

Albertin, Gabriele; Antoniutti, Stefano; Bacchi, Alessia; D'Este, Claudia; Pelizzi, Giancarlo

2004-02-23

Chloro complexes [RuCl(N-N)P3]BPh4 (1-3) [N-N = 2,2'-bipyridine, bpy; 1,10-phenanthroline, phen; 5,5'-dimethyl-2,2'-bipyridine, 5,5'-Me2bpy; P = P(OEt)3, PPh(OEt)2 and PPh2OEt] were prepared by allowing the [RuCl4(N-N)].H2O compounds to react with an excess of phosphite in ethanol. The bis(bipyridine) [RuCl(bpy)2[P(OEt)3

DEEP MIXING IN EVOLVED STARS. II. INTERPRETING Li ABUNDANCES IN RED GIANT BRANCH AND ASYMPTOTIC GIANT BRANCH STARS

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

Palmerini, S.; Busso, M.; Maiorca, E.

2011-11-01

We reanalyze the problem of Li abundances in red giants of nearly solar metallicity. After outlining the problems affecting our knowledge of the Li content in low-mass stars (M {<=} 3 M{sub sun}), we discuss deep-mixing models for the red giant branch stages suitable to account for the observed trends and for the correlated variations of the carbon isotope ratio; we find that Li destruction in these phases is limited to masses below about 2.3 M{sub sun}. Subsequently, we concentrate on the final stages of evolution for both O-rich and C-rich asymptotic giant branch (AGB) stars. Here, the constraints onmore » extra-mixing phenomena previously derived from heavier nuclei (from C to Al), coupled to recent updates in stellar structure models (including both the input physics and the set of reaction rates used), are suitable to account for the observations of Li abundances below A(Li) {identical_to} log {epsilon}(Li) {approx_equal} 1.5 (and sometimes more). Also, their relations with other nucleosynthesis signatures of AGB phases (like the abundance of F, and the C/O and {sup 12}C/{sup 13}C ratios) can be explained. This requires generally moderate efficiencies (M-dot < or approx. 0.3-0.5 x 10{sup -6} M{sub sun} yr{sup -1}) for non-convective mass transport. At such rates, slow extra mixing does not remarkably modify Li abundances in early AGB phases; on the other hand, faster mixing encounters a physical limit in destroying Li, set by the mixing velocity. Beyond this limit, Li starts to be produced; therefore, its destruction on the AGB is modest. Li is then significantly produced by the third dredge up. We also show that effective circulation episodes, while not destroying Li, would easily bring the {sup 12}C/{sup 13}C ratios to equilibrium, contrary to the evidence in most AGB stars, and would burn F beyond the limits shown by C(N) giants. Hence, we do not confirm the common idea that efficient extra mixing drastically reduces the Li content of C stars with respect to K-M giants. This misleading appearance is induced by biases in the data, namely: (1) the difficulty of measuring very low Li abundances in O-rich AGB stars due to the presence of TiO bands and (2) the fact that many, relatively massive (M > 3 M{sub sun}) K- and M-type giants may remain Li-rich, not evolving to the C-rich stages. Efficient extra mixing on the AGB is instead typical of very low masses (M {approx}< 1.5 M{sub sun}). It also characterizes CJ stars, where it produces Li and reduces F and the carbon isotope ratio, as observed in these peculiar objects.« less

Asian Dust Storm Events of 2001 and Associated Pollution Observed in New England by the AIRMAP Monitoring Network

NASA Astrophysics Data System (ADS)

Debell, L. J.; Vozzella, M. E.; Talbot, R. W.; Dibb, J. E.

2002-12-01

The Atmospheric Investigation, Regional Modeling, Analysis and Prediction (AIRMAP) program is operating 4 monitoring sites in New Hampshire, located at Fort Constitution (FC)(43.07oN, 70.71oW, 5m elevation), Thompson Farm (TF) (43.11oN, 70.95oW, 21m elevation), Castle Springs (CS) (43.75oN,71.35oW, 406m elevation) and Mount Washington (MW)(44.267oN, 71.30oW, 1909m elevation). Three chemically distinct, statistically extreme, regional scale dust aerosol events were observed at all four AIRMAP monitoring stations in NH between 4/18/01 and 5/13/01 (UTC). All three events, at all four sites, had days where the 24 hr bulk aerosol samples had Ca2+ concentrations that exceeded at least the 95th percentile of the site-specific, multi-year datasets. NO3- and SO42- were also enhanced above typical levels, ranging from above the 75th to above the 99th percentile. During all three events, mixing ratios of the gas phase pollutants O3 and CO were compared to mixing ratios on either side of the events. During event 1,enhancements above background levels were approximately 130 ppbv for CO and 30 ppbv for O3, very similar to the CO values in apparent Asian dust plumes sampled over Colorado at 6-7 km by aircraft measurements (http://www.cmdl.noaa.gov/info/asiandust.html); enhancements during events 2 and 3 were similar to event 1. The maximum elemental carbon value ever observed at TF, 0.97 μg/m3, occurred during the peak day of event 1. Elemental carbon was not substantially elevated during event 2 and no data were collected during event 3. Elemental ratios, determined by PIXE, on filters from events 1 and 3 were compared pairwise to each other and to published samples attributed to Asian dust storms. The AIRMAP samples collected on the same date at different sites showed good statistical agreement whereas samples collected at the same site on different dates show only moderate correlation. Of 17 published samples of Asian dust storm aerosol, collected well outside of the major desert and loess source regions, 15 showed good statistical agreement with at least 2 of our samples. In addition, at least 2 of our samples have good agreement with 1 published aerosol sample collected in the Gobi desert and for 1 published soil sample collected in the Takla Makan desert; indicating that the Asian dust storms are a possible source for our events. We also compared elemental ratios in our dust impacted samples to the IMPROVE dataset from Acadia, ME. Acadia was chosen for the longevity and completeness of its record and downwind location from the AIRMAP stations. Out of the over 1400 IMPROVE aerosol samples collected between 1988 and 2001, 476 have both Al, Fe and Ca above detection limit, and 120 show good agreement with at least 1 AIRMAP sample. The 120 samples selected above occurred primarily in spring: 52 samples from 3/1-5/15, 37 samples from 2/15-3/1 or 5/15-6/31. All three events are clearly discernible in the Acadia dataset both in timing and chemical similarity with the AIRMAP samples. A U.S. source cannot be ruled out chemically, but there are no reports in the National Climatic Data Centers Storm Publication that indicated large-scale dust storms in the period 4/10/01-5/10/01. TOMS images and the NRL-NAAPS model results also support an Asian source for the 3 events.

Wetlands and Agriculture in Africa: Major Sources of N2O?

NASA Astrophysics Data System (ADS)

Gettel, G. M.

2015-12-01

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

The crystal structure of the mixed-layer Aurivillius phase Bi 5Ti 1.5W 1.5O 15

NASA Astrophysics Data System (ADS)

Tellier, J.; Boullay, Ph.; Créon, N.; Mercurio, D.

2005-09-01

The crystal structure of the 1+2 mixed-layer Aurivillius phase Bi 5Ti 1.5W 1.5O 15 (SG I2cm n o 46: -cba, Z=4, a=5.4092(3) Å, b=5.3843(3) Å and c=41.529(3) Å) consisting of the ordered intergrowth of one and two octahedra thick perovskite-type blocks separated by [Bi 2O 2] 2+ slabs is reported. Supported by an electron diffraction investigation and, using the Rietveld analysis, it is shown that this compound should be described using a I-centering lattice in agreement with the generalised structural model of the Aurivillius type compounds recently presented by the authors. The structure of this Bi 5Ti 1.5W 1.5O 15 phase is analyzed in comparison with the related simple members (Bi 2WO 6 and Bi 3Ti 1.5W 0.5O 9). The crystal structure of Bi 3Ti 1.5W 0.5O 9 is also reported.

Hg⁰ removal from flue gas by ionic liquid/H₂O₂.

PubMed

Cheng, Guangwen; Bai, Bofeng; Zhang, Qiang; Cai, Ming

2014-09-15

1-Alkyl-3-methylimidazolium chloride ionic liquids ([Cnmim] Cl, n=4, 6, 8) were prepared. The ionic liquid was then mixed with hydrogen peroxide (H2O2) to form an absorbent. The Hg(0) removal performance of the absorbent was investigated in a gas/liquid scrubber using simulated flue gas. It was found that the ionic liquid/H2O2 mixture was an excellent absorbent and could be used to remove Hg(0) from flue gas. When the mass ratio of H2O2 to ionic liquid was 0.5, the absorbent showed high Hg(0) removal efficiency (up to 98%). The Hg(0) removal efficiency usually increased with the absorption temperature, while decreased with the increase of alkyl chain length in ionic liquid molecule. The Hg(0) removal mechanism involved with Hg(0) oxidation by H2O2 and Hg(2+) transfer from aqueous phase to ionic liquid phase. Copyright © 2014 Elsevier B.V. All rights reserved.

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

NASA Astrophysics Data System (ADS)

Leen, J. B.; Gupta, M.

2014-12-01

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

Structural identification of Zn xZr yO z catalysts for Cascade aldolization and self-deoxygenation reactions

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

Baylon, Rebecca A. L.; Sun, Junming; Kovarik, Libor

Complementary characterizations, such as nitrogen sorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), visible Raman, scanning transmission electron microscopy (STEM) coupled with elemental mapping, NH3/CO2 temperature programmed desorption (NH3/CO2-TPD), infrared spectroscopic analysis of adsorbed pyridine (Py-IR), and CO2-IR, have been employed to identify the structure and surface chemistry (i.e., acid-base) of mixed Zn xZr yO z oxide catalysts of varied ratios of Zn/Zr. Atomically dispersed Zn2+ species are present in the framework within a thin surface shell (1.5-2.0 nm) of ZrO2 particles when the Zn/Zr ratio is smaller than 1/10; when the ratio is above this, both atomically dispersed Zn2+more » and ZnO clusters coexist in mixed Zn xZr yO z oxide catalysts. The presence of ZnO clusters shows no significant side effect but only a slight increase of selectivity to CO2, caused by steam reforming. The incorporation of atomic Zn2+ into the ZrO2 framework was found to not only passivate strong Lewis acid sites (i.e., Zr-O-Zr) on ZrO2, but to also generate new Lewis acid-base site pairs with enhanced Lewis basicity on the bridged O (i.e., ). In the mixed ketone (i.e., acetone and methyl ethyl ketone (MEK)) reactions, while the passivation of strong acid sites can be correlated to the inhibition of side reactions, such as ketone decomposition and coking, the new Lewis acid-base pairs introduced enhance the cascade aldolization and self-deoxygenation reactions involved in olefin (C3=-C6=) production. More importantly, the surface acid-base properties change with varying Zn/Zr ratios, which in turn affect the cross- and self-condensation reactivity and subsequent distribution of olefins.« less

Structural Identification of Zn xZr yO z Catalysts for Cascade Aldolization and Self-Deoxygenation Reactions

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

Baylon, Rebecca A. L.; Sun, Junming; Kovarik, Libor

Here, complementary characterizations, such as nitrogen sorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), visible Raman, scanning transmission electron microscopy (STEM) coupled with elemental mapping, NH 3/CO 2 temperature programmed desorption (NH 3/CO 2-TPD), infrared spectroscopic analysis of adsorbed pyridine (Py-IR), and CO 2-IR, have been employed to identify the structure and surface chemistry (i.e., acid-base) of mixed Zn xZr yO z oxide catalysts of varied ratios of Zn/Zr. Atomically dispersed Zn 2+ species are present in the framework within a thin surface shell (1.5-2.0 nm) of ZrO 2 particles when the Zn/Zr ratio is smaller than 1/10; when the ratio is above this, both atomically dispersed Zn 2+ and ZnO clusters coexist in mixed Zn xZr yO z oxide catalysts. The presence of ZnO clusters shows no significant side effect but only a slight increase of selectivity to CO 2, caused by steam reforming. The incorporation of atomic Zn 2+ into the ZrO 2 framework was found to not only passivate strong Lewis acid sites (i.e., Zr-O-Zr) on ZrO 2, but to also generate new Lewis acid-base site pairs with enhanced Lewis basicity on the bridged O (i.e., Zr—omore » $$\\curvearrowleft\\atop{e\\atop—}$$Zn). In the mixed ketone (i.e., acetone and methyl ethyl ketone (MEK)) reactions, while the passivation of strong acid sites can be correlated to the inhibition of side reactions, such as ketone decomposition and coking, the new Lewis acid-base pairs introduced enhance the cascade aldolization and self-deoxygenation reactions involved in olefin (C 3 =-C 6 =) production. More importantly, the surface acid-base properties change with varying Zn/Zr ratios, which in turn affect the cross- and self-condensation reactivity and subsequent distribution of olefins.« less

Structural Identification of Zn xZr yO z Catalysts for Cascade Aldolization and Self-Deoxygenation Reactions

DOE PAGES

Baylon, Rebecca A. L.; Sun, Junming; Kovarik, Libor; ...

2018-04-22

Here, complementary characterizations, such as nitrogen sorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), visible Raman, scanning transmission electron microscopy (STEM) coupled with elemental mapping, NH 3/CO 2 temperature programmed desorption (NH 3/CO 2-TPD), infrared spectroscopic analysis of adsorbed pyridine (Py-IR), and CO 2-IR, have been employed to identify the structure and surface chemistry (i.e., acid-base) of mixed Zn xZr yO z oxide catalysts of varied ratios of Zn/Zr. Atomically dispersed Zn 2+ species are present in the framework within a thin surface shell (1.5-2.0 nm) of ZrO 2 particles when the Zn/Zr ratio is smaller than 1/10; when the ratio is above this, both atomically dispersed Zn 2+ and ZnO clusters coexist in mixed Zn xZr yO z oxide catalysts. The presence of ZnO clusters shows no significant side effect but only a slight increase of selectivity to CO 2, caused by steam reforming. The incorporation of atomic Zn 2+ into the ZrO 2 framework was found to not only passivate strong Lewis acid sites (i.e., Zr-O-Zr) on ZrO 2, but to also generate new Lewis acid-base site pairs with enhanced Lewis basicity on the bridged O (i.e., Zr—omore » $$\\curvearrowleft\\atop{e\\atop—}$$Zn). In the mixed ketone (i.e., acetone and methyl ethyl ketone (MEK)) reactions, while the passivation of strong acid sites can be correlated to the inhibition of side reactions, such as ketone decomposition and coking, the new Lewis acid-base pairs introduced enhance the cascade aldolization and self-deoxygenation reactions involved in olefin (C 3 =-C 6 =) production. More importantly, the surface acid-base properties change with varying Zn/Zr ratios, which in turn affect the cross- and self-condensation reactivity and subsequent distribution of olefins.« less

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

NASA Astrophysics Data System (ADS)

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

2018-01-01

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

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

NASA Technical Reports Server (NTRS)

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

1996-01-01

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

Oxygen transport pathways in Ruddlesden–Popper structured oxides revealed via in situ neutron diffraction

DOE PAGES

Tomkiewicz, Alex C.; Tamimi, Mazin; Huq, Ashfia; ...

2015-09-21

Ruddlesden-Popper structured oxides, general form A n+1B nO 3n+1, consist of n-layers of the perovskite structure stacked in between rock-salt layers, and have potential application in solid oxide electrochemical cells and ion transport membrane reactors. Three materials with constant Co/Fe ratio, LaSrCo 0.5Fe 0.5O 4-δ (n = 1), La 0.3Sr 2.7CoFeO 7-δ (n = 2), and LaSr 3Co 1.5Fe 1.5O 10-δ (n = 3) were synthesized and studied via in situ neutron powder diffraction between 765 K and 1070 K at a pO 2 of 10 -1 atm. Then, the structures were fit to a tetragonal I4/mmm space group, andmore » were found to have increased total oxygen vacancy concentration in the order La 0.3Sr 2.7CoFeO 7-δ > LaSr 3Co 1.5Fe 1.5O 10-δ > LaSrCo 0.5Fe 0.5O 4-δ, following the trend predicted for charge compensation upon increasing Sr 2+/La 3+ ratio. The oxygen vacancies within the material were almost exclusively located within the perovskite layers for all of the crystal structures with only minimal vacancy formation in the rock-salt layer. Finally, analysis of the concentration of these vacancies at each distinct crystallographic site and the anisotropic atomic displacement parameters for the oxygen sites reveals potential preferred oxygen transport pathways through the perovskite layers.« less

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

NASA Astrophysics Data System (ADS)

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

2016-04-01

An important milestone for laser spectroscopy was achieved when isotope ratios of greenhouse gases were reported at precision levels that allow addressing research questions in environmental sciences. Real-time data with high temporal resolution at moderate cost and instrument size make the optical approach highly attractive, complementary to the well-established isotope-ratio mass-spectrometry (IRMS) method. Especially appealing, in comparison to IRMS, is the inherent specificity to structural isomers having the same molecular mass. Direct absorption in the MIR in single or dual QCL configuration has proven highly reliable for the sta-ble isotopes of CO2, N2O and CH4. The longest time series of real-time measurements is currently available for δ13C and δ18O in CO2 at the high-alpine station Jung-fraujoch. At this well-equipped site, QCL based direct absorption spectroscopy (QCLAS) measurements are ongoing since 2008 1,2. Applications of QCLAS for N2O and CH4 stable isotopes are considerably more challenging because of the lower atmospheric mixing ratios, especially for the less abundant species, such as N218O and CH3D. For high precision (< 0.1 ‰) measurements in ambient air, QCLAS may be combined with a fully automated preconcentration unit yielding an up to 500 times concentration increase and the capability to separate the target gas from spectral interferants by se-quential desorption 3. Here, we review our recent developments on high precision isotope ratio analysis of greenhouse gases, with special focus on the isotopic species of N2O and CH4. Furthermore, we show environ-mental applications illustrating the highly valuable information that isotope ratios of atmospheric trace gases can carry. For example, the intramolecular distribution of 15N in N2O gives important information on the geochemical cycle of N2O4-6, while the analysis of δ13C and δ D in CH4 may be applied to disentangle microbial, fossil and landfill sources 7. 1 Sturm, P., Tuzson, B., Henne, S. & Emmenegger, L. Tracking isotopic signatures of CO2 at the high altitude site Jungfraujoch with laser spectroscopy: Analytical improvements and representative re-sults. Atmospheric Measurement Techniques 6, 1659-1671 (2013). 2 Tuzson, B. et al. Continuous isotopic composition measurements of tropospheric CO2 at Jungfraujoch (3580 m a.s.l.), Switzerland: real-time observation of regional pollution events. Atmospheric Chemistry and Physics 11, 1685-1696 (2011). 3 Mohn, J. et al. A liquid nitrogen-free preconcentration unit for measurements of ambient N2O isotopomers by QCLAS. Atmospheric Measurement Techniques 3, 609-618 (2010). 4 Wolf, B. et al. First on-line isotopic characterization of N2O above intensively managed grassland. Biogeosciences 12, 2517-1960 (2015). 5 Harris, E. et al. Nitrous oxide and methane emissions and nitrous oxide isotopic composition from waste incineration in Switzerland. Waste Management 35, 135-140 (2015). 6 Harris, E. et al. Isotopic evidence for nitrous oxide production pathways in a partial nitritation-anammox reactor. Water Research 83, 258-270 (2015). 7 Eyer, S. et al. Real-time analysis of δ13C- and δ D-CH4 in ambient air with laser spectroscopy: method development and first intercomparison results. Atmos. Meas. Tech. Discuss. 8, 8925-8970 (2015).

Impacts of updated spectroscopy on thermal infrared retrievals of methane evaluated with HIPPO data

NASA Astrophysics Data System (ADS)

Alvarado, M. J.; Payne, V. H.; Cady-Pereira, K. E.; Hegarty, J. D.; Kulawik, S. S.; Wecht, K. J.; Worden, J. R.; Pittman, J. V.; Wofsy, S. C.

2014-09-01

Errors in the spectroscopic parameters used in the forward radiative transfer model can introduce altitude-, spatially-, and temporally-dependent biases in trace gas retrievals. For well-mixed trace gases such as methane, where the variability of tropospheric mixing ratios is relatively small, reducing such biases is particularly important. We use aircraft observations from all five missions of the HIAPER Pole-to-Pole Observations (HIPPO) of the Carbon Cycle and Greenhouse Gases Study to evaluate the impact of updates to spectroscopic parameters for methane (CH4), water vapor (H2O), and nitrous oxide (N2O) on thermal infrared retrievals of methane from the NASA Aura Tropospheric Emission Spectrometer (TES). We find that updates to the spectroscopic parameters for CH4 result in a substantially smaller mean bias in the retrieved CH4 when compared with HIPPO observations. After an N2O-based correction, the bias in TES methane upper tropospheric representative values for measurements between 50° S and 50° N decreases from 56.9 to 25.7 ppbv, while the bias in the lower tropospheric representative value increases only slightly (from 27.3 to 28.4 ppbv). For retrievals with less than 1.6 DOFS, the bias is reduced from 26.8 to 4.8 ppbv. We also find that updates to the spectroscopic parameters for N2O reduce the errors in the retrieved N2O profile.

A fast sampling device for the mass spectrometric analysis of liquid rocket engine exhaust

NASA Technical Reports Server (NTRS)

Ryason, P. R.

1975-01-01

The design of a device to obtain compositional data on rocket exhaust by direct sampling of reactive flow exhausts into a mass spectrometer is presented. Sampling at three stages differing in pressure and orifice angle and diameter is possible. Results of calibration with pure gases and gas mixtures are erratic and of unknown accuracy for H2, limiting the usefulness of the apparatus for determining oxidizer/fuel ratios from combustion product analysis. Deposition effects are discussed, and data obtained from rocket exhaust spectra are analyzed to give O/F ratios and mixture ratio distribution. The O/F ratio determined spectrometrically is insufficiently accurate for quantitative comparison with cold flow data. However, a criterion for operating conditions with improved mixing of fuel and oxidizer which is consistent with cold flow results may be obtained by inspection of contour plots. A chemical inefficiency in the combustion process when oxidizer is in excess is observed from reactive flow measurements. Present results were obtained with N2O4/N2H4 propellants.

Decoupling peroxyacetyl nitrate from ozone in Chinese outflows observed at Gosan Climate Observatory

NASA Astrophysics Data System (ADS)

Han, Jihyun; Lee, Meehye; Shang, Xiaona; Lee, Gangwoong; Emmons, Louisa K.

2017-09-01

We measured peroxyacetyl nitrate (PAN) and other reactive species such as O3, NO2, CO, and SO2 with aerosols including mass, organic carbon (OC), and elemental carbon (EC) in PM2. 5 and K+ in PM1. 0 at Gosan Climate Observatory in Korea (33.17° N, 126.10° E) during 19 October-6 November 2010. PAN was determined through fast gas chromatography with luminol chemiluminescence detection at 425 nm every 2 min. The PAN mixing ratios ranged from 0.1 (detection limit) to 2.4 ppbv with a mean of 0.6 ppbv. For all measurements, PAN was unusually better correlated with PM2. 5 (Pearson correlation coefficient, γ = 0.79) than with O3 (γ = 0.67). In particular, the O3 level was highly elevated with SO2 at midnight, along with a typical midday peak when air was transported rapidly from the Beijing areas. The PAN enhancement was most noticeable during the occurrence of haze under stagnant conditions. In Chinese outflows slowly transported over the Yellow Sea, PAN gradually increased up to 2.4 ppbv at night, in excellent correlation with a concentration increase in PM2. 5 OC and EC, PM2. 5 mass, and PM1. 0 K+. The high K+ concentration and OC / EC ratio indicated that the air mass was impacted by biomass combustion. This study highlights PAN decoupling with O3 in Chinese outflows and suggests PAN as a useful indicator for diagnosing continental outflows and assessing their perturbation of regional air quality in northeast Asia.

Physical State and Distribution of Materials at the Surface of Pluto from New Horizons LEISA Imaging Spectrometer

NASA Technical Reports Server (NTRS)

Schmitt, B.; Philippe, S.; Grundy, W. M.; Reuter, D. C.; Cote, R.; Quirico, E.; Protopappa, S.; Young, L. A.; Binzel, R. P.; Cook, J. C.;

Physical state and distribution of materials at the surface of Pluto from New Horizons LEISA imaging spectrometer

NASA Astrophysics Data System (ADS)

Schmitt, B.; Philippe, S.; Grundy, W. M.; Reuter, D. C.; Côte, R.; Quirico, E.; Protopapa, S.; Young, L. A.; Binzel, R. P.; Cook, J. C.; Cruikshank, D. P.; Dalle Ore, C. M.; Earle, A. M.; Ennico, K.; Howett, C. J. A.; Jennings, D. E.; Linscott, I. R.; Lunsford, A. W.; Olkin, C. B.; Parker, A. H.; Parker, J. Wm.; Singer, K. N.; Spencer, J. R.; Stansberry, J. A.; Stern, S. A.; Tsang, C. C. C.; Verbiscer, A. J.; Weaver, H. A.; New Horizons Science Team

2017-05-01

From Earth based observations Pluto is known to be the host of N2, CH4 and CO ices and also a dark red material. Very limited spatial distribution information is available from rotational visible and near-infrared spectral curves obtained from hemispheric measurements. In July 2015 the New Horizons spacecraft reached Pluto and its satellite system and recorded a large set of data. The LEISA spectro-imager of the RALPH instruments are dedicated to the study of the composition and physical state of the materials composing the surface. In this paper we report a study of the distribution and physical state of the ices and non-ice materials on Pluto's illuminated surface and their mode and degree of mixing. Principal Component analysis as well as various specific spectral indicators and correlation plots are used on the first set of 2 high resolution spectro-images from the LEISA instrument covering the whole illuminated face of Pluto at the time of the New Horizons encounter. Qualitative distribution maps have been obtained for the 4 main condensed molecules, N2, CH4, CO, H2O as well as for the visible-dark red material. Based on specific spectral indicators, using either the strength or the position of absorption bands, these 4 molecules are found to indicate the presence of 3 different types of ices: N2-rich:CH4:CO ices, CH4-rich(:CO:N2?) ices and H2O ice. The mixing lines between these ices and with the dark red material are studied using scatter plots between the various spectral indicators. CH4 is mixed at the molecular level with N2, most probably also with CO, thus forming a ternary molecular mixture that follows its phase diagram with low solubility limits. The occurrence of a N2-rich - CH4-rich ices mixing line associated with a progressive decrease of the CO/CH4 ratio tells us that a fractionation sublimation sequence transforms one type of ice to the other forming either a N2-rich - CH4-rich binary mixture at the surface or an upper CH4-rich ice crust that may hide the N2-rich ice below. The strong CH4-rich - H2O mixing line witnesses the subsequent sublimation of the CH4-rich ice lag left behind by the N2:CO sublimation (N spring-summer), or a direct condensation of CH4 ice on the cold H2O ice (S autumn). The weak mixing line between CH4-containing ices and the dark red material and the very sharp spatial transitions between these ices and this non-volatile material are probably due to thermal incompatibility. Finally the occurrence of a H2O ice - red material mixing line advocates for a spatial mixing of the red material covering H2O ice, with possibly a small amount intimately mixed in water ice. From this analysis of the different materials distribution and their relative mixing lines, H2O ice appears to be the substratum on which other ices condense or non-volatile organic material is deposited from the atmosphere. N2-rich ices seem to evolve to CH4-dominated ices, possibly still containing traces of CO and N2, as N2 and CO sublimate away. The spatial distribution of these materials is very complex. The high spatial definition of all these composition maps, as well as those at even higher resolution that will be soon available, will allow us to compare them with Pluto's geologic features observed by LORRI panchromatic and MVIC multispectral imagers to better understand the geophysical processes in action at the surface of this astonishingly active frozen world.

Denitrification nitrogen gas formation and gene expression in alpine grassland soil as affected by climate change conditions

NASA Astrophysics Data System (ADS)

Chen, Zhe; Wang, Changhui; Gschwendtner, Silvia; Schloter, Michael; Butterbach-Bahl, Klaus; Dannenmann, Michael

2013-04-01

Due to methodological problems, reliable data on soil dinitrogen (N2) emission by denitrification are extremely scarce, and the impacts of climate change on nitrogen (N) gas formation by denitrification and N gas product ratios as well as the underlying microbial drivers remain unclear. We combined the helium-gas-flow-soil-core technique for simultaneously quantification of nitrous oxide (N2O) and N2 emission with the reverse transcript qPCR technology. Our goals were to characterize denitrification dynamics and N gas product ratios in alpine grassland soil as affected by climate change conditions and to evaluate relationships between denitrification gene expression and N gas emission. We used soils from the pre-alpine grassland Terrestrial Environmental Observatory (TERENO), exposed to ambient temperature and precipitation (control treatment), or three years of simulated climate change conditions (increased temperature, reduction of summer precipitation and reduced snow cover). Soils were amended with glucose and nitrate and incubated subsequently at 1) 5°C and 20% oxygen; 2) 5°C and 0% oxygen; 3) 20°C and 0% oxygen until stabilization of N gas emissions in each incubation step. After switching incubation conditions to 0% oxygen and 20°C, N2O emission peaked immediately and declined again, followed by a delayed peak in N2 emission. The dynamics of cnorB gene expression, encoding the reduction of nitric oxide (NO) to N2O, followed the N2O emission pattern, while nosZ gene expression, encoding N2O reduction to N2 followed the course of N2 emission. The mean N2O:N2 ratios were 1.31 + 0.10 and 1.56 + 0.16 for control and climate change treatment respectively, but the denitrification potential was overall lower in climate change treatment. Hence, simulated climate change promoted N2O but lessened N2 emission. This stimulation of N2O was in accordance with increased cnorB gene expression in soil of the climate change treatment. N mass balance calculations revealed that denitrification N gas formation accounted for 21%, dissimilatory nitrate reduction to ammonium for 8%, and microbial immobilization for 73% of nitrate consumption. Overall, our study shows that changes in climate exert feedback on denitrification N gas formation and N gas product ratios via changes in microbial activity at the level of single denitrification steps. The close relationships found between denitrification N gas formation, N gas product ratios and denitrification gene expression suggests a large potential of molecular methods to predict denitrification dynamics in soil.

Detecting and Constraining N2 Abundances in Planetary Atmospheres Using Collisional Pairs

NASA Astrophysics Data System (ADS)

Schwieterman, Edward W.; Robinson, Tyler D.; Meadows, Victoria S.; Misra, Amit; Domagal-Goldman, Shawn

2015-09-01

Characterizing the bulk atmosphere of a terrestrial planet is important for determining surface pressure and potential habitability. Molecular nitrogen (N2) constitutes the largest fraction of Earth's atmosphere and is likely to be a major constituent of many terrestrial exoplanet atmospheres. Due to its lack of significant absorption features, N2 is extremely difficult to remotely detect. However, N2 produces an N2-N2 collisional pair, (N2)2, which is spectrally active. Here we report the detection of (N2)2 in Earth's disk-integrated spectrum. By comparing spectra from NASA's EPOXI mission to synthetic spectra from the NASA Astrobiology Institute's Virtual Planetary Laboratory three-dimensional spectral Earth model, we find that (N2)2 absorption produces a ˜35% decrease in flux at 4.15 μm. Quantifying N2 could provide a means of determining bulk atmospheric composition for terrestrial exoplanets and could rule out abiotic O2 generation, which is possible in rarefied atmospheres. To explore the potential effects of (N2)2 in exoplanet spectra, we used radiative transfer models to generate synthetic emission and transit transmission spectra of self-consistent N2-CO2-H2O atmospheres, and analytic N2-H2 and N2-H2-CO2 atmospheres. We show that (N2)2 absorption in the wings of the 4.3 μm CO2 band is strongly dependent on N2 partial pressures above 0.5 bar and can significantly widen this band in thick N2 atmospheres. The (N2)2 transit transmission signal is up to 10 ppm for an Earth-size planet with an N2-dominated atmosphere orbiting within the habitable zone of an M5V star and could be substantially larger for planets with significant H2 mixing ratios.

Effect of C/N ratio, aeration rate and moisture content on ammonia and greenhouse gas emission during the composting.

PubMed

Jiang, Tao; Schuchardt, Frank; Li, Guoxue; Guo, Rui; Zhao, Yuanqiu

2011-01-01

Gaseous emission (N2O, CH4 and NH3) from composting can be an important source of anthropogenic greenhouse gas and air pollution. A laboratory scale orthogonal experiment was conducted to estimate the effects of C/N ratio, aeration rate and initial moisture content on gaseous emission during the composting of pig faeces from Chinese Ganqinfen system. The results showed that about 23.9% to 45.6% of total organic carbon (TOC) was lost in the form of CO2 and 0.8% to 7.5% of TOC emitted as CH4. Most of the nitrogen was lost in the form of NH3, which account for 9.6% to 32.4% of initial nitrogen. N2O was also an important way of nitrogen losses and 1.5% to 7.3% of initial total nitrogen was lost as it. Statistic analysis showed that the aeration rate is the most important factor which could affect the NH3 (p = 0.0189), CH4 (p = 0.0113) and N2O (p = 0.0493) emissions significantly. Higher aeration rates reduce the CH4 emission but increase the NH3 and N2O losses. C/N ratio could affect the NH3 (p = 0.0442) and CH4 (p = 0.0246) emissions significantly, but not the N2O. Lower C/N ratio caused higher NH3 and CH4 emissions. The initial moisture content can not influence the gaseous emission significantly. Most treatments were matured after 37 days, except a trial with high moisture content and a low C/N ratio.

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

NASA Astrophysics Data System (ADS)

Miyagi, I.

2012-12-01

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

Novel types of tetra-, hexa-, octa-, and dodecanuclear silver clusters containing (2,7-Di-tert-butylfluoren-9-ylidene)methanedithiolate.

PubMed

Vicente, José; González-Herrero, Pablo; García-Sánchez, Yolanda; Jones, Peter G

2009-03-02

The reaction of AgClO(4) with piperidinium 2,7-di-tert-butyl-9H-fluorene-9-carbodithioate (pipH)[S(2)C(t-Bu-Hfy)] (1) (t-Bu-Hfy = 2,7-di-tert-butylfluoren-9-yl) afforded [Ag(n){S(2)C(t-Bu-Hfy)}(n)] (2), which reacted with phosphines to give [Ag{S(2)C(t-Bu-Hfy)}L(2)] [L = PPh(3) (3a); L(2) = bis(diphenylphosphino)ethane (dppe, 3b), 1,1'-bis(diphenylphosphino)ferrocene (dppf, 3c). By reacting complex 2 with AgClO(4) and piperidine in a 1:1:1 molar ratio, the dodecanuclear cluster [Ag(12){S(2)C(t-Bu-fy)}(6)] (4) (t-Bu-fy = 2,7-di-tert-butylfluoren-9-ylidene) was obtained. Compound 4 can also be directly prepared from the reaction of 1 with AgClO(4) and piperidine in a 1:2:1 molar ratio. The reactions of 1 with AgClO(4), phosphines, and piperidine afforded the compounds [Ag(6){S(2)C(t-Bu-fy)}(3)L(5)] [1:2:2:1 molar ratio; L = PPh(3) (5a), P(p-To)(3) (5b)], [Ag(4){S(2)C(t-Bu-fy)}(2)(dppf)(2)] (6) (1:2:1:1 molar ratio), [Ag(n){S(2)C(t-Bu-fy)}(n/2){P(i-Pr)(3)}(n)] (7) (1:2:2:1 molar ratio), or [Ag(8){S(2)C(t-Bu-fy)}(4){P(i-Pr)(3)}(4)] (8) (1:2:1:1 molar ratio). Complexes 5a,b, 6, 7, and 8 can be also obtained by reacting 4 with the corresponding phosphine in the appropriate molar ratio. The crystal structures of 4, 5b, and 8 have been determined by X-ray diffraction studies. The nuclearity of complex 6 was established from its (31)P{(1)H} NMR data, which reveal a very fast dynamic process leading to an average coupling of each of the P atoms of the dppf ligands with four Ag atoms.

Zirconia-hydroxyapatite composite material with micro porous structure.

PubMed

Matsumoto, Takuya Junior; An, Sang-Hyun; Ishimoto, Takuya; Nakano, Takayoshi; Matsumoto, Takuya; Imazato, Satoshi

2011-11-01

Titanium plates and apatite blocks are commonly used for restoring large osseous defects in dental and orthopedic surgery. However, several cases of allergies against titanium have been recently reported. Also, sintered apatite block does not possess sufficient mechanical strength. In this study, we attempted to fabricate a composite material that has mechanical properties similar to biocortical bone and high bioaffinity by compounding hydroxyapatite (HAp) with the base material zirconia (ZrO(2)), which possesses high mechanical properties and low toxicity toward living organisms. After mixing the raw material powders at several different ZrO(2)/HAp mixing ratios, the material was compressed in a metal mold (8 mm in diameter) at 5 MPa. Subsequently, it was sintered for 5 h at 1500°C to obtain the ZrO(2)/HAp composite. The mechanical property and biocompatibility of materials were investigated. Furthermore, osteoconductivity of materials was investigated by animal studies. A composite material with a minute porous structure was successfully created using ZrO(2)/HAp powders, having different particle sizes, as the starting material. The material also showed high protein adsorption and a favorable cellular affinity. When the mixing ratio was ZrO(2)/HAp=70/30, the strength was equal to cortical bone. Furthermore, in vivo experiments confirmed its high osteoconductivity. The composite material had strength similar to biocortical bones with high cell and tissue affinities by compounding ZrO(2) and HAp. The ZrO(2)/HAp composite material having micro porous structure would be a promising bone restorative material. Copyright © 2011 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Estimation of indoor and outdoor ratios of selected volatile organic compounds in Canada

NASA Astrophysics Data System (ADS)

Xu, Jing; Szyszkowicz, Mieczyslaw; Jovic, Branka; Cakmak, Sabit; Austin, Claire C.; Zhu, Jiping

2016-09-01

Indoor air and outdoor air concentration (I/O) ratio can be used to identify the origins of volatile organic compounds (VOCs). I/O ratios of 25 VOCs in Canada were estimated based on the data collected in various areas in Canada between September 2009 and December 2011. The indoor VOC data were extracted from the Canadian Health Measures Survey (CHMS). Outdoor VOC data were obtained from Canada's National Air Pollution Surveillance (NAPS) Network. The sampling locations covered nine areas in six provinces in Canada. Indoor air concentrations were found higher than outdoor air for all studied VOCs, except for carbon tetrachloride. Two different approaches were employed to estimate the I/O ratios; both approaches produced similar I/O values. The I/O ratios obtained from this study were similar to two other Canadian studies where indoor air and outdoor air of individual dwellings were measured. However, the I/O ratios found in Canada were higher than those in European cities and in two large USA cities, possibly due to the fact that the outdoor air concentrations recorded in the Canadian studies were lower. Possible source origins identified for the studied VOCs based on their I/O ratios were similar to those reported by others. In general, chlorinated hydrocarbons, short-chain (C5, C6) n-alkanes and benzene had significant outdoor sources, while long-chain (C10sbnd C12) n-alkanes, terpenes, naphthalene and styrene had significant indoor sources. The remaining VOCs had mixed indoor and outdoor sources.

Electrical and optical characteristics of n-Zno/p-GaN hetero-junction diode fabricated by ultra-high vacuum sputter.

PubMed

Cho, Seong Gook; Lee, Dong Uk; Kim, Eun Kyu

2013-09-01

We investigated the electrical and optical properties of n-ZnO/p-GaN hetero-junction diode fabricated by an ultra-high vacuum radio frequency magnetron sputter. A physical relationship between the rotation rate during deposition process and post annealing conditions after deposited ZnO layer on p-GaN layer was discussed. When the rotation rates during deposition process of n-ZnO layer were 5 rpm and 15 rpm, the full width at half maximum of photoluminescence spectra of ZnO layer on the p-GaN layer was about 106 and 133 meV, respectively. Also, the ratio of deep level emission to near band edge emission was dramatically increased as increasing the rotation rate from 5 to 15 rpm. The n-ZnO/p-GaN hetero-junction diode grown at 5 rpm has a higher ratio of forward to reverse currents than the diode grown at 15 rpm. Also, the 600 degrees C-annealed diodes with 5 rpm showed good rectifying behavior with the barrier height of 0.74 eV, the ideality factor of 12.2, and the forward to reverse current ratio of 614 at +/- 8 V.

Trace gas emissions from a mid-latitude prescribed chaparral fire

NASA Technical Reports Server (NTRS)

Cofer, Wesley R., III; Levine, Joel S.; Sebacher, Daniel I.; Riggan, Philip J.; Winstead, Edward L.; Shaw, Edwin F., Jr.; Brass, James A.; Ambrosia, Vincent G.

1988-01-01

Smoke-plume gas samples were collected at altitudes from 35-670 m above the ground over the San Dimas Experimental Forest during a 400-acre prescribed chaparral fire. Mean emission ratios relative to CO2 for CO, H2, CH4, and total nonmethane hydrocarbons were lower than previous values obtained for large biomass-burning field experiments. Comparison of samples from vigorously flaming and mixed stages of combustion revealed little differences in CO2 normalized emission ratios for these gases (except for N2O).

Preparation of single-crystal spherical γ-Mo2N by temperature-programmed reaction between β-MoO3 and NH3

NASA Astrophysics Data System (ADS)

Wang, Lu; Zhang, Guo-Hua; Chou, Kuo-Chih

2017-10-01

In the present wok, single-crystalline spherical γ-Mo2N powders was successfully prepared by the temperature-programmed reaction of single-crystal spherical β-MoO3 with NH3 in the temperature ranges of 1013-1073 K. Herein, the Mo source used was monoclinic system, β-MoO3, a metastable phase of MoO3. It is found that the characterizations of the as-prepared γ-Mo2N powders are strongly depended on the selection of the MoO3 precursor. In other words, the as-prepared γ-Mo2N powders inherited the shape, size and structure of the used β-MoO3 precursors upon reaction with NH3. In order to make a comparison, β-MoO3 was also reduced by the mixed gases of N2 and H2 with the flow rate ratio of 1:3 at the identical conditions. It was found that pure β-Mo2N polycrystalline can be obtained when the temperature was 1013 K; while further increasing the reaction temperature, metal Mo powder will be turned up.

Observations of nitryl chloride and modeling its source and effect on ozone in the planetary boundary layer of southern China

NASA Astrophysics Data System (ADS)

Wang, Tao; Tham, Yee Jun; Xue, Likun; Li, Qinyi; Zha, Qiaozhi; Wang, Zhe; Poon, Steven C. N.; Dubé, William P.; Blake, Donald R.; Louie, Peter K. K.; Luk, Connie W. Y.; Tsui, Wilson; Brown, Steven S.

2016-03-01

Nitryl chloride (ClNO2) plays potentially important roles in atmospheric chemistry, but its abundance and effect are not fully understood due to the small number of ambient observations of ClNO2 to date. In late autumn 2013, ClNO2 was measured with a chemical ionization mass spectrometer (CIMS) at a mountain top (957 m above sea level) in Hong Kong. During 12 nights with continuous CIMS data, elevated mixing ratios of ClNO2 (>400 parts per trillion by volume) or its precursor N2O5 (>1000 pptv) were observed on six nights, with the highest ever reported ClNO2 (4.7 ppbv, 1 min average) and N2O5 (7.7 ppbv, 1 min average) in one case. Backward particle dispersion calculations driven by winds simulated with a mesoscale meteorological model show that the ClNO2/N2O5-laden air at the high-elevation site was due to transport of urban/industrial pollution north of the site. The highest ClNO2/N2O5 case was observed in a later period of the night and was characterized with extensively processed air and with the presence of nonoceanic chloride. A chemical box model with detailed chlorine chemistry was used to assess the possible impact of the ClNO2 in the well-processed regional plume on next day ozone, as the air mass continued to downwind locations. The results show that the ClNO2 could enhance ozone by 5-16% at the ozone peak or 11-41% daytime ozone production in the following day. This study highlights varying importance of the ClNO2 chemistry in polluted environments and the need to consider this process in photochemical models for prediction of ground-level ozone and haze.

Spring dehydration in the Antarctic stratospheric vortex observed by HALOE

NASA Technical Reports Server (NTRS)

Pierce, R. Bradley; Grose, William L.; Russell, James M., III; Tuck, Adrian F.; Swinbank, Richard; O'Neill, Alan

1994-01-01

The distribution of dehydrated air in the middle and lower stratosphere during the 1992 Southern Hemisphere spring is investigated using Halogen Occultation Experiment (HALOE) observations and trajectory techniques. Comparisons between previously published Version 9 and the improved Version 16 retrievals on the 700-K isentropic surface show very slight (0.05 ppmv) increases in Version 16 CH4 relative to Version 9 within the polar vortex. Version 16 H2O mixing ratios show a reduction of 0.5 ppmv relative to Version 9 within the polar night jet and a reduction of nearly 1.0 ppmv in middle latitudes when compared to Version 9. The version 16 HALOE retrievals show low mixing ratios of total hydrogen (2CH4 + H2O) within the polar vortex on both 700 and 425 K isentropic surfaces relative to typical middle-stratospheric 2CH4 + H2O mixing ratios. The low 2CH4 + H2O mixing ratios are associated with dehydration. Slight reductions in total hydrogen, relative to typical middle-stratospheric values, are found at these levels throughout the Southern Hemisphere during this period. Trajectory calculations show that middle-latitude air masses are composed of a mixture of air from within the polar night jet and air from middle latitudes. A strong kinematic barrier to large-scale exchange is found on the poleward flank of the polar night jet at 700 K. A much weaker kinematic barrier is found at 425 K. The impact of the finite tangent pathlength of the HALOE measurements is investigated using an idealized tracer distribution. This experiment suggests that HALOE should be able to resolve the kinematic barrier, if it exists.

Global lower mesospheric water vapor revealed by LIMS observations

NASA Technical Reports Server (NTRS)

Gordley, L. L.; Russell, J. M., III; Remsberg, E. E.

1985-01-01

The Limb Infrared Monitor of the Stratospheric water vapor channel data analysis has been extended from the 1. mb level (about 48 km) to the .3 mb level (about 60 km) through a radiance averaging procedure and better understanding of systematic errors. The data show H2O mixing ratio peaks near the .5 mb level varying from 4 to 7 ppmv with latitude and season. Above this level the mixing ratio drops off quickly with altitude, but, due to experimental uncertainties, at an uncertain rate. The stratospheric results are virtually the same as determined from the archived LIMS results with a tropical hygropause and enhanced H2O concentration in the lower levels at high winter latitudes.

A Comparison of Measurements from ATMOS and Instruments Aboard the ER-2 Aircraft: Tracers of Atmospheric Transport

NASA Technical Reports Server (NTRS)

Chang, A. Y.; Salawitch, R. J.; Michelsen, H. A.; Gunson, M. R.; Abrams, M. C.; Zander, R.; Rinsland, C. P.; Loewenstein, M.; Podolske, J. R.; Proffitt, M. H.;

Photocatalytic degradation of diclofenac using TiO2-SnO2 mixed oxide catalysts.

PubMed

Mugunthan, E; Saidutta, M B; Jagadeeshbabu, P E

2017-12-26

The complex nature of diclofenac limits its biological degradation, posing a serious threat to aquatic organisms. Our present work aims to eliminate diclofenac from wastewater through photocatalytic degradation using TiO 2 -SnO 2 mixed-oxide catalysts under various operating conditions such as catalyst loading, initial diclofenac concentration and initial pH. Different molar ratios of Ti-Sn (1:1, 5:1, 10:1, 20:1 and 30:1) were prepared by the hydrothermal method and were characterized. The results indicated that addition of Sn in small quantity enhances the catalytic activity of TiO 2 . Energy Band gap of the TiO 2 -SnO 2 catalysts was found to increase with an increase in Tin content. TiO 2 -SnO 2 catalyst with a molar ratio of 20:1 was found to be the most effective when compared to other catalysts. The results suggested that initial drug concentration of 20 mg/L, catalyst loading of 0.8 g/L and pH 5 were the optimum operating conditions for complete degradation of diclofenac. Also, the TiO 2 -SnO 2 catalyst was effective in complete mineralization of diclofenac with a maximum total organic carbon removal of 90% achieved under ultraviolet irradiation. The repeatability and stability results showed that the TiO 2 -SnO 2 catalyst exhibited an excellent repeatability and better stability over the repeated reaction cycles. The photocatalytic degradation of diclofenac resulted in several photoproducts, which were identified through LC-MS.

The influence of south foehn on the ozone mixing ratios at the high alpine site Arosa

NASA Astrophysics Data System (ADS)

Campana, Mike; Li, Yingshi; Staehelin, Johannes; Prevot, Andre S. H.; Bonasoni, Paolo; Loetscher, Hanspeter; Peter, Thomas

Within 2 years of trace gas measurements performed at Arosa (Switzerland, 2030 m above sea level), enhanced ozone mixing ratios were observed during south foehn events during summer and spring (5-10 ppb above the median value). The enhancements can be traced back to ozone produced in the strongly industrialized Po basin as confirmed by various analyses. Backward trajectories clearly show advection from this region during foehn. NO y versus O 3 correlation and comparison of O 3 mixing ratios between Arosa and Mt. Cimone (Italy, 2165 m asl) suggest that ozone is the result of recent photochemical production (+5.6 ppb on average), either directly formed during the transport or via mixing of air processed in the Po basin boundary layer. The absence of a correlation between air parcel residence times over Europe and ozone mixing ratios at Arosa during foehn events is in contrast to a previous analysis, which suggested such correlation without reference to the origin of the air. In the case of south foehn, the continental scale influence of pollutants emission on ozone at Arosa appears to be far less important than the direct influence of the Po basin emissions. In contrast, winter time displays a different situation, with mean ozone reductions of about 4 ppb for air parcels passing the Po basin, probably caused by mixing with ozone-poor air from the Po basin boundary layer.

Four years of ozone measurements in the Central Amazon - Effects of increasing deforestation rates and different meteorological conditions on near surface concentrations

NASA Astrophysics Data System (ADS)

Wolff, Stefan; Tsokankunku, Anywhere; Pöhlker, Christopher; Saturno, Jorge; Walter, David; Ditas, Florian; Könemann, Tobias; Ganzeveld, Laurens; Yañez-Serrano, Ana Maria; Souza, Rodrigo; Trebs, Ivonne; Sörgel, Matthias

2017-04-01

The ATTO (Amazon Tall Tower Observatory) site (02°08'38.8''S, 58°59'59.5''W) is located in the remote Amazon rainforest, allowing atmospheric and forest studies away from nearby anthropogenic emission sources. Starting with continuous measurements of vertical mixing ratio profiles of H2O, CO2 and O3 in April 2012 at 8 heights between 0.05 m and 80 m above ground, the longest continuous record of near surface O3 in the Amazon rainforest was established. Black carbon (BC), CO and micrometeorological measurements are available for the same period. During intensive campaigns, NOx was measured as well using the same profile system, and, therefore several month of simultaneous NOx measurements are available. During a period of about four months also direct flux measurements of O3 are available. Here, we analyze the long term and seasonal variability of near surface O3 mixing ratios with respect to air pollution, deposition and transport. The Central Amazon is characterized by a clear seasonal precipitation pattern (ca. 350 mm around March and ca. 80 mm around September), correlating strongly with ozone mixing ratios. Since 2012 deforestation rates have increased again in the Amazon, leading to higher air pollution especially during the drier season in the last years. For several strong pollution events we compared the effects of long and short distance biomass burning on O3 and NOx mixing ratios using back trajectories and satellite data. By comparing O3 mixing ratios with solar radiation, Bowen ratio, several trace gases and aerosol loads (Volatile Organic Compounds, CO and BC), different correlation patterns throughout the year that are linked to the sources (transport of O3 and precursors) and sinks (stomatal uptake and chemical reactions) are investigated. For example, the last months of 2015 were strongly influenced by an extraordinary El Niño phenomenon, leading to much drier conditions and enhanced biomass burning in the Amazon, which prolonged the period of increased O3 values. These exceptional dry conditions and a slight La Niña in 2016 have influenced the water availability, which in turn may have affected the O3 deposition.

2-(3-Cyano-4-{3-[1-(2-hy-droxy-eth-yl)-3,3-dimethyl-1,3-di-hydro-indol-2-yl-idene]prop-2-en-yl}-5,5-dimethyl-5H-furan-2-yl-idene)malono-nitrile.

PubMed

Gainsford, Graeme J; Bhuiyan, M Delower H; Kay, Andrew J

2014-01-01

The title compound, C25H24N4O2, adopts a cisoid configuration and has twofold orientational disorder of the 2-hy-droxy-ethyl group. The mol-ecule is twisted from planarity so that the dihedral angle between the terminating indol-2-yl-idene and the furan-2-yl-idene moiety mean planes is 12.75 (7)°. Conformational disorder occurs at the indol-2-yl-idene N atom, which results in two orientations for the hy-droxy-ethyl group [occupancy ratio = 0.896 (2):0.104 (2)], and the hy-droxy O atom of the 2-hy-droxy-ethyl group is located over three sites [occupancy ratio = 0.548 (2):0.348 (2):0.104 (2)]. An intra-molecular C-H⋯O hydrogen bond involving the lowest occupancy hy-droxy O atom is observed. In the crystal, the mol-ecules pack in parallel dimeric sheets about centres of symmetry, utilizing O-H⋯N(cyano), C-H⋯N(cyano) and O-H⋯O hydrogen bonds, in two sets parallel to (02-1) and (021) planes.

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

PubMed Central

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

2011-01-01

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

Stratospheric constituent distributions from balloon-based limb thermal emission measurements

NASA Technical Reports Server (NTRS)

Abbas, Mian M.; Kunde, Vigil G.

1990-01-01

This research task deals with an analysis of infrared thermal emission observations of the Earth's atmosphere for determination of trace constituent distributions. Infrared limb thermal emission spectra in the 700-2000 cm(exp -1) region were obtained with a liquid nitrogen cooled Michelson interferometer-spectrometer (SIRIS) on a balloon flight launched from Palestine, Texas, at nighttime on September 15-16, 1986. An important objective of this work is to obtain simultaneously measured vertical mixing ratio profiles of O3, H2O, N2O, NO2, N2O5, HNO3 and ClONO2 and compare with measurements made with a variety of techniques by other groups as well as with photochemical model calculations. A portion of the observed spectra obtained by SIRIS from the balloon flight on September 15-16, 1986, has been analyzed with a focus on calculation of the total nighttime odd nitrogen budget from the simultaneously measured profiles of important members of the NO(sub x) family. The measurements permit first direct determination of the nighttime total odd nitrogen concentrations NO(sub y) and the partitioning of the important elements of the NO(sub x) family.

Investigations of the local distortions and EPR parameters for Cu2+ in xNa2 O-(30-x)K2 O-70B2 O3 (5 ≤ x ≤ 25 mol%) glasses.

PubMed

Zhang, Zhen-Ya; Wu, Shao-Yi; Zhang, Fu; Zhang, Cheng-Xi; Qin, Rui-Jie; Gao, Han

2018-03-01

The local distortions and electron paramagnetic resonance parameters for Cu 2+ in the mixed alkali borate glasses xNa 2 O-(30-x)K 2 O-70B 2 O 3 (5 ≤ x ≤ 25 mol%) are theoretically studied with distinct modifier Na 2 O compositions x. Owing to the Jahn-Teller effect, the octahedral [CuO 6 ] 10- clusters show significant tetragonal elongation ratios p ~19% along the C 4 axis. With the increase of composition x, the cubic field parameter Dq and the orbital reduction factor k exhibit linearly and quasi-linearly decreasing tendencies, respectively, whereas the relative tetragonal elongation ratio p has quasi-linearly increasing rule with some fluctuations, leading to the minima of g factors at x = 10 mol%. The composition dependences of the optical spectra and the electron paramagnetic resonance parameters are suitably reproduced by the linear or quasi-linear relationships of the relevant quantities (i.e., Dq, k, and p) with x. The above composition dependences are analyzed from mixed alkali effect, which brings forward the modifications of the local crystal-fields and the electronic cloud distribution around Cu 2+ with the variation of the composition of Na 2 O. Copyright © 2017 John Wiley & Sons, Ltd.

Observations of Gas Emissions from Cascade Range Volcanoes (USA) using a Portable Real-Time Sensor Package and Evacuated Flasks

NASA Astrophysics Data System (ADS)

Kelly, P. J.; Werner, C. A.; Evans, W.; Ingebritsen, S.; Tucker, D.

2012-12-01

Degassing from most Cascade Range Volcanoes, USA, is characterized by low-temperature hydrothermal emissions. It is important to monitor these emissions as part of a comprehensive monitoring strategy yet access is often difficult and most features are sampled by the USGS only once per year at best. In an effort to increase the sampling frequency of major gas species and in preparation for building permanent, autonomous units, we built a portable sensor package capable of measuring H2O, CO2, SO2, and H2S in volcanic gas plumes. Here we compare results from the portable sensor package with gas analyses from direct samples obtained using a titanium tube and evacuated glass flasks collected at the same time. The sensor package is housed in a small, rugged case, weighs 5 kg, and includes sensors for measuring H2O (0-16 parts per thousand), CO2 (0-5000 ppmv), SO2 (0-100 ppm), and H2S (0-20 ppm) gases. Additional temperature and pressure sensors, a micro air pump, datalogger, and an internal battery are also incorporated. H2O and CO2 are measured using an infrared spectrometer (Licor 840) and sulfur-containing gases are measured using electrochemical sensors equipped with filters to mitigate cross-sensitivities. Data are collected at a 1 Hz sampling rate and can be recorded and displayed in real-time using a netbook computer or can be saved to the onboard datalogger. The data display includes timeseries of H2O, CO2, SO2, and H2S mixing ratios, the four-component bulk composition of the plume, and automated calculation of gas ratios commonly used in volcanic gas monitoring, such as H2O/CO2, CO2/SO2, and CO2/H2S . In the Cascade Range, the sensor package has been tested at Mt. Baker, Mt. St. Helens, Mt. Hood, and in Lassen Volcanic National Park. In each case, the instrument was placed 5 to 30 meters from the fumarole or fumarole field and emissions were sampled for 5 to 30 minutes. No SO2 was detected at any location. At Mt. Hood the sensor package yielded average CO2/H2S ratios from 10 to 16 in fumarole plumes versus flask CO2/H2S ratios (n = 2) of 13 and 16 on 9 July 2011, and on 28 July 2012 the sensor package yielded an average CO2/H2S ratio of 12 versus flask ratios (n = 2) of 13 (both sets of flask samples obtained in the Crater Rock area). At Mt. Baker, the sensor package yielded average CO2/H2S ratios from 19 to 22 whereas flask ratios (n = 3) were higher, from 25 to 32 (both fumarole-plume and flask samples obtained in the Sherman Crater area) on 22 July 2011. The mismatch falls slightly outside expected analytical uncertainty for the sensor package (about 20% relative for CO2/H2S ratios). However, flask samples collected in Sherman Crater in 2006 and 2007 (n = 5) yielded CO2/H2S ratios from 18 to 29, which nearly spans the range of observations in 2011. Therefore, one explanation for the small mismatch between the results of the sensor package and direct samples is that the sensor package measures bulk plume compositions that may integrate emissions from several chemically distinct fumaroles and the direct samples better represent the composition of discrete vents. Overall, the sensor package and evacuated flask data show good agreement and demonstrate that the real-time technique is a viable means for monitoring major volcanic gas species.

Bis(O-n-butyl dithio-carbonato-κS,S')bis-(pyridine-κN)manganese(II).

PubMed

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

2011-08-01

The structure of the title manganese complex, [Mn(C(5)H(9)OS(2))(2)(C(5)H(5)N)(2)] or [Mn(S(2)CO-n-Bu)(2)(C(5)H(5)N)(2)], consists of discrete monomeric entities with Mn(2+) ions located on centres of inversion. The metal atom is coordinated by a six-coordinate trans-N(2)S(4) donor set with the pyridyl N atoms located in the apical positions. The observed slight deviations from octa-hedral geometry are caused by the bite angle of the bidentate κ(2)-S(2)CO-n-Bu ligands [69.48 (1)°]. The O(CH(2))(3)(CH(3)) chains of the O-n-butyl dithio-carbonate units are disordered over two sets of sites with an occupancy ratio of 0.589 (2):0.411 (2).

Effect of heterogeneous aqueous reactions on the secondary formation of inorganic aerosols during haze events

DOE PAGES

Quan, Jiannong; Liu, Yangang; Liu, Quan; ...

2015-09-30

In this study, the effect of heterogeneous aqueous reactions on the secondary formation of inorganic aerosols during haze events was investigated by analysis of comprehensive measurements of aerosol composition and concentrations [e.g., particular matters (PM 2.5), nitrate (NO 3), sulfate (SO 4), ammonium (NH 4)], gas-phase precursors [e.g., nitrogen oxides (NOx), sulfur dioxide (SO 2), and ozone (O 3)], and relevant meteorological parameters [e.g., visibility and relative humidity (RH)]. The measurements were conducted in Beijing, China from Sep. 07, 2012 to Jan. 16, 2013. The results show that the conversion ratios of N from NOx to nitrate (N ratio) andmore » S from SO 2 to sulfate (S ratio) both significantly increased in haze events, suggesting enhanced conversions from NOx and SO 2 to their corresponding particle phases in the late haze period. Further analysis shows that N ratio and S ratio increased with increasing RH, with N ratio and S ratio being only 0.04 and 0.03, respectively, when RH < 40%, and increasing up to 0.16 and 0.12 when RH reached 60–80%, respectively. The enhanced conversion ratios of N and S in the late haze period is likely due to heterogeneous aqueous reactions, because solar radiation and thus the photochemical capacity are reduced by the increases in aerosols and RH. This point was further affirmed by the relationships of N ratio and S ratio to O 3: the conversion ratios increase with decreasing O 3 concentration when O 3 concentration is lower than <15 ppb but increased with increasing O 3 when O 3 concentration is higher than 15 ppb. The results suggest that heterogeneous aqueous reactions likely changed aerosols and their precursors during the haze events: in the beginning of haze events, the precursor gases accumulated quickly due to high emission and low reaction rate; the occurrence of heterogeneous aqueous reactions in the late haze period, together with the accumulated high concentrations of precursor gases such as SO 2 and NOx, accelerated the formation of secondary inorganic aerosols, and led to rapid increase of the PM 2.5 concentration.« less

Investigation into the disparate origin of CO2 and H2O outgassing for Comet 67/P

NASA Astrophysics Data System (ADS)

Fink, Uwe; Doose, Lyn; Rinaldi, Giovanna; Bieler, André; Capaccioni, Fabrizio; Bockelée-Morvan, Dominique; Filacchione, Gianrico; Erard, Stephane; Leyrat, Cedric; Blecka, Maria; Capria, Maria Teresa; Combi, Michael; Crovisier, Jacques; De Sanctis, Maria Cristina; Fougere, Nicolas; Taylor, Fred; Migliorini, Alessandra; Piccioni, Giuseppe

2016-10-01

We present an investigation of the emission intensity of CO2 and H2O and their distribution in the coma of 67P/ Churyumov-Gerasimenko obtained by the VIRTIS-M imaging spectrometer on the Rosetta mission. We analyze 4 data cubes from Feb. 28, and 7 data cubes from April 27, 2015. For both data sets the spacecraft was at a sufficiently large distance from the comet to allow images of the whole nucleus and the surrounding coma. We find that unlike water which has a reasonably predictable behavior and correlates well with the solar illumination, CO2 outgasses mostly in local regions or spots. Furthermore for the data on April 27, the CO2 evolves almost exclusively from the southern hemisphere, a region of the comet that has not received solar illumination since the comet's last perihelion passage. Because CO2 and H2O have such disparate origins, deriving mixing ratios from local column density measurements cannot provide a meaningful measurement of the CO2/H2O ratio in the coma of the comet. We obtain total production rates of H2O and CO2 by integrating the band intensity in an annulus surrounding the nucleus and obtain pro-forma production rate CO2/H2O mixing ratios of ∼5.0% and ∼2.5% for Feb. 28 and April 27, respectively. Because of the highly variable nature of the CO2 evolution from the surface we do not believe that these numbers are diagnostic of the comet's bulk CO2/H2O composition. We believe that our investigation provides an explanation for the large observed variations reported in the literature for the CO2/H2O production rate ratios. Our mixing ratio maps indicate that, besides the difference in vapor pressure of the two gases, this ratio depends on the comet's rotational orientation combined with its complex geometric shape which can result in quite variable rates of erosion for different surface areas such as the northern and southern hemisphere. Our annulus measurement for the total water production for Feb. 28 at 2.21AU from the Sun is 2.5 × 1026 molecules/s while for April 27 at 1.76 AU it is 4.65 × 1026. We find that about 83% of the H2O resides in the illuminated portion of our annulus and about 17% on the night side. We also make an attempt to obtain the fraction of the H2O production coming from the highly active neck of the comet versus the rest of the illuminated surface from the pole-on view of Feb. 28 and estimate that about 60% of the H2O derives from the neck area. A rough estimate of the water surface evaporation rate of the illuminated nucleus for April 27 yields about 5 × 1019 molecules/s/m2. Spatial radial profiles of H2O on April 27 on the illuminated side of the comet, extending from 1.78 to 6.47 km from the nucleus center, show that water follows model predictions quite well, with the gas accelerating as it expands into the coma. Our dayside radial profile allows us to make an empirical determination of the expansion velocity of water. On the night side the spatial profile of water follows 1/ρ. The CO2 profiles do not exhibit any acceleration into the coma but are closely matched by a 1/ρ profile.

Effect of TiO2 addition on surface microstructure and bioactivity of fluorapatite coatings deposited using Nd:YAG laser.

PubMed

Chien, Chi-Sheng; Ko, Yu-Sheng; Kuo, Tsung-Yuan; Liao, Tze-Yuan; Lee, Tzer-Min; Hong, Ting-Fu

2014-04-01

To study the effect of titania (TiO2) addition on the surface microstructure and bioactivity of fluorapatite coatings, fluorapatite was mixed with TiO2 in 1:0.5 (FA + 0.5TiO2), 1:0.8 (FA + 0.8TiO2), and 1:1 (FA + TiO2) ratios (wt%) and clad on Ti-6Al-4V substrates using an Nd:YAG laser system. The experimental results show that the penetration depth of the weld decreases with increasing TiO2 content. Moreover, the subgrain structure of the coating layer changes from a fine cellular-like structure to a cellular-dendrite-like structure as the amount of TiO2 increases. Consequently, as the proportion of TiO2 decreases (increase in fluorapatite content), the Ca/P ratio of the coating layer also decreases. The immersion of specimens into simulated body fluid resulted in the formation of individual apatite. With a lower Ca/P ratio before immersion, the growth of the apatite was faster and then the coating layer provided a better bioactivity. X-ray diffraction analysis results show that prior to simulated body fluid immersion, the coating layer in all three specimens was composed mainly of fluorapatite, CaTiO3, and Al2O3 phases. Following simulated body fluid immersion, a peak corresponding to hydroxycarbonated apatite appeared after 2 days in the FA + 0.5TiO2 and FA + 0.8TiO2 specimens and after 7 days in the FA + TiO2 specimen. Overall, the results show that although the bioactivity of the coating layer tended to decrease with increasing TiO2 content, in accordance with the above-mentioned ratios, the bioactivity of all three specimens remained generally good.

Determination of nitrogen monoxide in high purity nitrogen gas with an atmospheric pressure ionization mass spectrometer

NASA Technical Reports Server (NTRS)

Kato, K.

1985-01-01

An atmospheric pressure ionization mass spectrometric (API-MS) method was studied for the determination of residual NO in high purity N2 gas. The API-MS is very sensitive to NO, but the presence of O2 interferes with the NO measurement. Nitrogen gas in cylinders as sample gas was mixed with NO standard gas and/or O2 standard gas, and then introduced into the API-MS. The calibration curves of NO and O2 has linearity in the region of 0 - 2 ppm, but the slopes changed with every cylinder. The effect of O2 on NO+ peak was additive and proportional to O2 concentration in the range of 0 - 0.5 ppm. The increase in NO+ intensity due to O2 was (0.07 - 0.13)%/O2, 1 ppm. Determination of NO and O2 was carried out by the standard addition method to eliminate the influence of variation of slopes. The interference due to O2 was estimated from the product of the O2 concentration and the ratio of slope A to Slope B. Slope A is the change in the NO+ intensity with the O2 concentration. Slope B is the intensity with O2 concentration.

Synthesis of fatty acid methyl ester from the transesterification of high- and low-acid-content crude palm oil (Elaeis guineensis) and karanj oil (Pongamia pinnata) over a calcium-lanthanum-aluminum mixed-oxides catalyst.

PubMed

Syamsuddin, Y; Murat, M N; Hameed, B H

2016-08-01

The synthesis of fatty acid methyl ester (FAME) from the high- and low-acid-content feedstock of crude palm oil (CPO) and karanj oil (KO) was conducted over CaO-La2O3-Al2O3 mixed-oxide catalyst. Various reaction parameters were investigated using a batch reactor to identify the best reaction condition that results in the highest FAME yield for each type of oil. The transesterification of CPO resulted in a 97.81% FAME yield with the process conditions of 170°C reaction temperature, 15:1 DMC-to-CPO molar ratio, 180min reaction time, and 10wt.% catalyst loading. The transesterification of KO resulted in a 96.77% FAME yield with the conditions of 150°C reaction temperature, 9:1 DMC-to-KO molar ratio, 180min reaction time, and 5wt.% catalyst loading. The properties of both products met the ASTM D6751 and EN 14214 standard requirements. The above results showed that the CaO-La2O3-Al2O3 mixed-oxide catalyst was suitable for high- and low-acid-content vegetable oil. Copyright © 2016 Elsevier Ltd. All rights reserved.

Fe3O4 and metal-organic framework MIL-101(Fe) composites catalyze luminol chemiluminescence for sensitively sensing hydrogen peroxide and glucose.

PubMed

Qian Tang, Xue; Dan Zhang, Yi; Wei Jiang, Zhong; Mei Wang, Dong; Zhi Huang, Cheng; Fang Li, Yuan

2018-03-01

In this work, Fe 3 O 4 and metal-organic framework MIL-101(Fe) composites (Fe 3 O 4 /MIL-101(Fe)) was demonstrated to possess excellent catalytic property to directly catalyze luminol chemiluminescence without extra oxidants. We utilized Fe 3 O 4 /MIL-101(Fe) to develop a ultra-sensitive quantitative analytical method for H 2 O 2 and glucose. The possible mechanism of the chemiluminescence reaction had been investigated. Under optimal conditions, the relative chemiluminescence intensity was linearly proportional to the logarithm of H 2 O 2 concentration in the range of 5-150nM with a limit of detection of 3.7nM (signal-to-noise ratio = 3), and glucose could be linearly detected in the range from 5 to 100nM and the detection limit was 4.9nM (signal-to-noise ratio = 3). Furthermore, the present approach was successfully applied to quantitative determination of H 2 O 2 in medical disinfectant and glucose in human serum samples. Copyright © 2017 Elsevier B.V. All rights reserved.

A compact QCL based methane and nitrous oxide sensor for environmental and medical applications.

PubMed

Jahjah, Mohammad; Ren, Wei; Stefański, Przemysław; Lewicki, Rafał; Zhang, Jiawei; Jiang, Wenzhe; Tarka, Jan; Tittel, Frank K

2014-05-07

A methane (CH4) and nitrous oxide (N2O) sensor based on a sensitive, selective and well established technique of quartz enhanced photoacoustic spectroscopy (QEPAS) was developed for environmental and biomedical measurements. A thermoelectrically cooled (TEC) distributed feedback quantum cascade laser (DFB-QCL), capable of continuous wave (CW) mode hop free emission in the 7.83 μm wavelength range, was used as an excitation source. For the targeted CH4 and N2O absorption lines located at 1275.04 cm(-1) and 1275.49 cm(-1) detection limits (1σ) of 13 ppbv and 6 ppbv were achieved with a 1 second data acquisition time, respectively. Environmental data of CH4 and N2O mixing ratios acquired using the QEPAS sensor system are also reported.

Stabilities of protonated water-ammonia clusters

NASA Astrophysics Data System (ADS)

Sundén, A. E. K.; Støchkel, K.; Hvelplund, P.; Brøndsted Nielsen, S.; Dynefors, B.; Hansen, K.

2018-05-01

Branching ratios of water and ammonia evaporation have been measured for spontaneous evaporation from protonated mixed clusters H+(H2O)n(NH3)m in the size range 0 ≤ n ≤ 11 and 0 ≤ m ≤ 7. Mixed clusters evaporate water except for clusters containing six or more ammonia molecules, indicating the formation of a stable core of one ammonium ion surrounded by four ammonia molecules and a second shell consisting predominantly of water. We relate evaporative branching ratios to free energy differences between the products of competing channels and determine the free energy differences for clusters with up to seven ammonia molecules. Clusters containing up to five ammonia molecules show a very strong scaling of these free energy differences.

Exploring the possibility to store the mixed oxygen-hydrogen cluster in clathrate hydrate in molar ratio 1:2 (O2+2H2).

PubMed

Qin, Yan; Du, Qi-Shi; Xie, Neng-Zhong; Li, Jian-Xiu; Huang, Ri-Bo

2017-05-01

An interesting possibility is explored: storing the mixture of oxygen and hydrogen in clathrate hydrate in molar ratio 1:2. The interaction energies between oxygen, hydrogen, and clathrate hydrate are calculated using high level quantum chemical methods. The useful conclusion points from this study are summarized as follows. (1) The interaction energies of oxygen-hydrogen mixed cluster are larger than the energies of pure hydrogen molecular cluster. (2) The affinity of oxygen molecules with water molecules is larger than that of the hydrogen molecules with water molecules. (3) The dimension of O 2 -2H 2 interaction structure is smaller than the dimension of CO 2 -2H 2 interaction structure. (4) The escaping energy of oxygen molecules from the hydrate cell is larger than that of the hydrogen molecules. (5) The high affinity of the oxygen molecules with both the water molecules and the hydrogen molecules may promote the stability of oxygen-hydrogen mixture in the clathrate hydrate. Therefore it is possible to store the mixed (O 2 +2H 2 ) cluster in clathrate hydrate. Copyright © 2017 Elsevier Inc. All rights reserved.

Chemical Signature of Biomass Burning Emitted PM2.5 as Revealed by a C/N/S Multi- Elemental Scanning Thermal Analysis (MESTA) Technique

NASA Astrophysics Data System (ADS)

Hsieh, Y.; Bugna, G.

2006-12-01

Uncertainty of black carbon (BC) research is often plagued by the analytical difficulty associated with separating carbon components in solid samples. A rapid and sensitive multi-elemental scanning thermal analysis (MESTA), originally developed for organic matter analysis in solid samples, was applied to this study. The objective was to identify the chemical signature of biomass burning emitted PM2.5 (aerosols less than 2.5 micron) for tracing purposes. We collected PM2.5 from the burning of various biomass of a pine forest and from the ambient air of an urban campus using a PM sampler. The MESTA provides simultaneous C, N and S thermograms of the PM2.5 samples that can be used for characterization and identification purposes. This study showed that the PM2.5 samples produced from the burning of forest biomass can be characterized by a high temperature (greater than 350 oC) volatile organic component with high C/N ratio and no S content while those produced from the ambient air can be characterized by a low temperature (less than 350 oC) volatile organic component with low C/N ratio and high S content. Burning of the soaked woody debris, however, produced significant amount of the low-temperature volatile organic component similar to that of the ambient air in C/N ratio but different in S content. Most PM2.5 samples have a very low temperature (less than 110 oC) volatile N component that is identified as absorbed ammonia. The absorbed ammonia is most significant in the PM2.5 of the ambient air and the burning of soaked woody debris. All PM2.5 samples have significant amount of BC which volatilized above 500 oC with very high C/N ratio. This study also shows that MESTA can provide an objective means to present the chemical signature of the whole spectrum of OC/BC in the PM2.5 samples.

Two mixed-ligand lanthanide–hydrazone complexes: [Pr(NCS)3(pbh)2]·H2O and [Nd(NCS)(NO3)(pbh)2(H2O)]NO3·2.33H2O [pbh is N′-(pyridin-2-ylmethylidene)benzo­hydrazide, C13H11N3O

PubMed Central

Paschalidis, Damianos G.; Harrison, William T. A.

2016-01-01

The gel-mediated syntheses and crystal structures of [N′-(pyridin-2-ylmethylidene-κN)benzohydrazide-κ2 N′,O]tris(thiocyanato-κN)praseodymium(III) mono­hydrate, [Pr(NCS)3(C13H11N3O)2]·H2O, (I), and aqua(nitrato-κ2 O,O′)[N′-(pyri­din-2-ylmethylidene-κN)benzohydrazide-κ2 N′,O](thiocyanato-κN)neo­dym­ium(III) nitrate 2.33-hydrate, [Nd(NCS)(NO3)(C13H11N3O)2(H2O)]NO3·2.33H2O, (II), are reported. The Pr3+ ion in (I) is coordinated by two N,N,O-tridentate N′-(pyridin-2-ylmethylidene)benzohydrazide (pbh) ligands and three N-bonded thio­cyanate ions to generate an irregular PrN7O2 coordination polyhedron. The Nd3+ ion in (II) is coordinated by two N,N,O-tridentate pbh ligands, an N-bonded thio­cyanate ion, a bidentate nitrate ion and a water mol­ecule to generate a distorted NdN5O5 bicapped square anti­prism. The crystal structures of (I) and (II) feature numerous hydrogen bonds, which lead to the formation of three-dimensional networks in each case. PMID:26958385

Synthesis and electrochemical assessment of Ce{sub 0.5}Yb{sub 0.5}O{sub 1.75} ceramics and derived composite electrolytes

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

Martins, Natércia C.T.; Rajesh, Surendran; Marques, Fernando M.B.

2015-10-15

Highlights: • Ce{sub 0.5}Yb{sub 0.5}O{sub 1.75} prepared for the first time through solid state reaction. • High energy milling needed to assist the ceramic route. • Ce{sub 0.5}Yb{sub 0.5}O{sub 1.75} is oxide-ion conductor in air and n-type conductor at low pO{sub 2}. • Ce{sub 0.5}Yb{sub 0.5}O{sub 1.75} decomposes slightly when exposed to alkaline carbonates. • Composites based on Ce{sub 0.5}Yb{sub 0.5}O{sub 1.75} show standard electrical performance. - Abstract: Ce{sub 0.5}Yb{sub 0.5}O{sub 1.75} was prepared for the first time through high temperature (1600 °C for 5 h) solid state reaction, after high energy milling to enhance the mechano-chemical interaction of precursormore » oxides (CeO{sub 2} and Yb{sub 2}O{sub 3}). Single phase formation was confirmed by powder X-ray diffraction. Impedance spectroscopy data obtained under wide temperature (300–800 °C) and oxygen partial pressure (0.21 to about 10{sup −25} atm) ranges indicates that this material exhibits predominant oxide-ion conductivity under oxidizing conditions while n-type electronic conductivity prevails at low oxygen partial pressure. The mixed oxide shows modest ionic conductivity (1.1 × 10{sup −3} S cm{sup −1} at 800 °C) with activation energy of 1.3 eV in the 600–800 °C temperature range. When combined with molten carbonates (Li{sub 2}CO{sub 3} + Na{sub 2}CO{sub 3}, 1:1 molar ratio) to produce composite electrolytes, Ce{sub 0.5}Yb{sub 0.5}O{sub 1.75} slightly decomposed. However, the composite electrical performance is still acceptable and closely matches the conductivity of similar materials (>0.1 S cm{sup −1} immediately above 500 °C)« less

Two Zinc(II) metal-organic frameworks with mixed ligands of 5-amino-tetrazolate and l,2,4,5-benzenetetracarboxylate: Synthesis, structural diversity and photoluminescent properties

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

Wang, Xiao-Bing; Lu, Wen-Guan, E-mail: lwg@sgu.edu.cn; Zhong, Di-Chang

The reactions of Zn(NO{sub 3}){sub 2}·6H{sub 2}O with mixed ligands of 5-amino-tetrazole (Hatz) and l,2,4,5-benzenetetracarboxylic acid (H{sub 4}btec) under hydro(solvo)thermal conditions, gave two three-dimensional (3D) porous metal-organic frameworks (MOFs) of ([Zn{sub 3}(atz){sub 2}(btec)(DMF){sub 2}]·DMF·2H{sub 2}O){sub n} (1) and [Zn{sub 2}(Hprz)(atz)(btec)(H{sub 2}O)]{sub n} (2) in the absence and presence of piperazine (prz), respectively. 1 and 2 were characterized by infrared spectra (IR), elemental analyses (EA) and single-crystal/powder X-ray diffraction. In 1, the adjacent 1D [Zn{sub 3}(btec)]{sub n}{sup 2n+} chains are linked together by atz{sup −} ligands to form a 3D porous MOF with 1D tetragonal channels filled with coordinated and guestmore » DMF, and lattice water molecules. In 2, the adjacent 2D [Zn{sub 2}(btec)]{sub n} wavelike sheets are pillared through atz{sup −} ligands to generate a 3D layered-pillared porous MOF with 1D open channels, which are occupied by coordinated Hprz{sup +} cations and coordinated water molecules. Additionally, thermal stabilities and photoluminescent properties of both compounds in the solid-state at room temperature have been investigated and discussed in detail. - Graphical abstract: Two new MOFs constructed from Zn(II) salts with mixed ligands of 5-amino-tetrazole and l,2,4,5-benzenetetracarboxylic acid were synthesized under different reaction conditions. Structural diversities indicate that the reaction solvent system or the presence of organic base play crucial roles in modulating structures of these compounds. And more, their thermal stability and luminescence are also discussed. - Highlights: • Two new Zn(II) MOFs based on mixed ligands were synthesized. • The two Zn(II) MOFs exhibit different structural motifs. • The two Zn(II) MOFs are photoluminscent in the solid state at room temperature.« less

Bis(2,3,5,6-tetra-2-pyridylpyrazine-κ3 N 2,N 1,N 6)iron(II) bis­(dicyanamidate) 4.5-hydrate

PubMed Central

Callejo, L.; De la Pinta, N.; Madariaga, G.; Fidalgo, M.L.; Cortés, R.

2010-01-01

In the title compound, [Fe(C24H16N6)2][N(CN)2]2·4.5H2O, the central iron(II) ion is hexa­coordinated by six N atoms of two tridentate 2,3,5,6-tetra-2-pyridylpyrazine (tppz) ligands. Two dicyanamide anions [dca or N(CN)2 −] act as counter-ions, and 4.5 water mol­ecules act as solvation agents. The structure contains isolated cationic iron(II)–tppz complexes and the final neutrality is obtained with the two dicyanamide anions. One of the dicyanamide anions and a water mol­ecule are disordered with an occupancy ratio of 0.614 (8):0.386 (8). O—H⋯O, O—H⋯N and C—H⋯O hydrogen bonds involving dca, water and tppz mol­ecules are observed. PMID:21580205

One-Step Condensation and Hydrogenation of Furfural-Acetone Using Mixed and Single Catalyst Based on Ni/M-Oxide [M=Al; Mg

NASA Astrophysics Data System (ADS)

Ulfa, S. M.; Pramesti, I. N.; Mustafidah, H.

2018-01-01

Modification of furfural by condensation and hydrogenation reaction is a promising approach to produce higher alkane derivatives (C8-C13) as diesel fraction. This research investigated the catalytic activity of Ni/MgO as bifunctional catalyst compared with MgO-Ni/Al2O3 mixed catalyst for condensation-hydrogenation reaction. The Ni/MgO and Ni/Al2O3 with 20% Ni loading were prepared by wet impregnation methods using Ni(NO3)2.6H2O salt, calcined and reduced at 500°C. The catalyst performance was tested for one-step condensation-hydrogenation reaction using autoclave oil batch reactor. The reaction was conducted by reacting furfural and acetone in 1:1 ratio using water as solvent. Condensation reaction was performed at 100°C for 8 hours, followed by hydrogenation at 120°C during 7 hours. Analysis by gas chromatography showed that C=C double bond of furfurylidene acetone were successfully hydrogenated. Using Ni/MgO catalyst at 120°C, the products were identified as 1,5-bis-(2-furanyl)-1,4-penta-1-ene-3-one (2.68%) and 1,5-bis-(2-furanyl)-1,4-pentan-3-one (trace amount). On the other hand, reaction using mixed catalyst, MgO-Ni/Al2O3 showed better activity over bifunctional Ni/MgO at the same reaction temperature. The products were identified as 4-(2-furanyl)-3-butan-2-one (27.30%); 1,5-bis-(2-furanyl)-1,4-penta-1-ene-3-one (3.82%) and 1,5-bis-(2-furanyl)-1,4-pentan-3-one (1.11%). The impregnation of Ni on MgO decrease the physical properties of catalyst, confirmed by surface area analysis (SAA).

Influence of extensive compressed natural gas (CNG) usage on air quality

NASA Astrophysics Data System (ADS)

Suthawaree, Jeeranut; Sikder, Helena Akhter; Jones, Charlotte Emily; Kato, Shungo; Kunimi, Hitoshi; Mohammed Hamidul Kabir, Abu Naser; Kajii, Yoshizumi

2012-07-01

Compressed Natural Gas (CNG) is an inexpensive, indigenous energy resource which currently accounts for the majority of automobile and domestic energy consumption in Bangladesh. This extensive CNG usage, particularly within the capital city, Dhaka, heavily influences the atmospheric composition (and hence air quality), yet to date measurements of trace gases in regions dominated by CNG emissions are relatively limited. Here we report continuous observations of the atmospherically important trace gases O3, CO, SO2, NOx and volatile organic compounds (VOC), in ambient air in Dhaka City, Bangladesh, during May 2011. The average mixing ratios of O3, CO, SO2, and NOx for the measurement period were 18.9, 520.9, 7.6 and 21.5 ppbv, respectively. The ratios of CO to NO reveal that emissions from gasoline and CNG-fuelled vehicles were dominant during the daytime (slope of ˜26), while in contrast, owing to restrictions imposed on diesel fuelled vehicles entering Dhaka City, emissions from these vehicles only became significant during the night (slope of ˜10). The total VOC mixing ratio in Dhaka was ˜5-10 times higher than the levels reported in more developed Asian cities such as Tokyo and Bangkok, which consequently gives rise to a higher ozone formation potential (OFP). However, the most abundant VOC in Dhaka were the relatively long-lived ethane and propane (with mean mixing ratios of ˜115 and ˜30 ppbv, respectively), and as a consequence, the ozone formation potential per ppb carbon (ppbC) was lower in Dhaka than in Tokyo and Bangkok. Thus the atmospheric composition of air influenced by extensive CNG combustion may be characterized by high VOC mixing ratios, yet mixing ratios of the photochemical pollutant ozone do not drastically exceed the levels typical of Asian cities with considerably lower VOC levels.

Impacts of updated spectroscopy on thermal infrared retrievals of methane evaluated with HIPPO data

NASA Astrophysics Data System (ADS)

Alvarado, M. J.; Payne, V. H.; Cady-Pereira, K. E.; Hegarty, J. D.; Kulawik, S. S.; Wecht, K. J.; Worden, J. R.; Pittman, J. V.; Wofsy, S. C.

2015-02-01

Errors in the spectroscopic parameters used in the forward radiative transfer model can introduce spatially, temporally, and altitude-dependent biases in trace gas retrievals. For well-mixed trace gases such as methane, where the variability of tropospheric mixing ratios is relatively small, reducing such biases is particularly important. We use aircraft observations from all five missions of the HIAPER Pole-to-Pole Observations (HIPPO) of the Carbon Cycle and Greenhouse Gases Study to evaluate the impact of updates to spectroscopic parameters for methane (CH4), water vapor (H2O), and nitrous oxide (N2O) on thermal infrared retrievals of methane from the NASA Aura Tropospheric Emission Spectrometer (TES). We find that updates to the spectroscopic parameters for CH4 result in a substantially smaller mean bias in the retrieved CH4 when compared with HIPPO observations. After an N2O-based correction, the bias in TES methane upper tropospheric representative values for measurements between 50° S and 50° N decreases from 56.9 to 25.7 ppbv, while the bias in the lower tropospheric representative value increases only slightly (from 27.3 to 28.4 ppbv). For retrievals with less than 1.6 degrees of freedom for signal (DOFS), the bias is reduced from 26.8 to 4.8 ppbv. We also find that updates to the spectroscopic parameters for N2O reduce the errors in the retrieved N2O profile.

Observational characteristics of the tropopause inversion layer derived from CHAMP/GRACE radio occultations and MOZAIC aircraft data

NASA Astrophysics Data System (ADS)

Schmidt, Torsten; Cammas, Jean-Pierre; Heise, Stefan; Wickert, Jens; Haser, Antonia

2010-05-01

In this study we discuss characteristics of the tropopause inversion layer (TIL) based on two datasets. Temperature measurements from GPS radio occultation (RO) data (CHAMP and GRACE) for the time interval 2001-2009 are used to exhibit seasonal properties of the TIL on a global scale. In agreement with previous studies the vertical structure of the TIL is investigated using the square of the buoyancy frequency N. For the extratropics on both hemispheres N2 has an universal distribution independent from season: a local minimum about 2 km below the lapse rate tropopause height (LRTH), an absolute maximum about 1 km above the LRTH, and a local minimum about 4 km above the LRTH. In the tropics (15°N-15°S) the N2 maximum above the tropopause is 200-300 m higher compared with the extratropics and the local minimum of N2 below the tropopause appears about 4 km below the LRTH. Trace gas measurements onboard commercial aircrafts from 2001-2007 are used as a complementary dataset (MOZAIC program). We demonstrate that the mixing ratio gradients of ozone, carbon monoxide and water vapor are suitable parameters for characterizing the TIL reproducing most of the vertical structure of N2. We also show that the LRTH is strongly correlated with the absolute maxima of ozone and carbon monoxide mixing ratio gradients. Mean deviations of the heights of the absolute maxima of mixing ratio gradients from O3 and CO to the LRTH are (-0.02±1.51) km and (-0.35±1.28) km, respectively.

From Ba{sub 3}Ta{sub 5}O{sub 14}N to LaBa{sub 2}Ta{sub 5}O{sub 13}N{sub 2}: Decreasing the optical band gap of a photocatalyst

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

Anke, B.; Bredow, T.; Pilarski, M.

Yellow LaBa{sub 2}Ta{sub 5}O{sub 13}N{sub 2} was successfully synthesized as phase-pure material crystallizing isostructurally to previously reported Ba{sub 3}Ta{sub 5}O{sub 14}N and mixed-valence Ba{sub 3}Ta{sup V}{sub 4}Ta{sup IV}O{sub 15}. The electronic structure of LaBa{sub 2}Ta{sub 5}O{sub 13}N{sub 2} was studied theoretically with the range-separated hybrid method HSE06. The most stable structure was obtained when lanthanum was placed on 2a and nitrogen on 4h sites confirming Pauling's second rule. By incorporating nitrogen, the measured band gap decreases from ∼3.8 eV for the oxide via 2.74 eV for Ba{sub 3}Ta{sub 5}O{sub 14}N to 2.63 eV for the new oxide nitride, giving risemore » to an absorption band well in the visible-light region. Calculated fundamental band gaps confirm the experimental trend. The atom-projected density of states has large contributions from N2p orbitals close to the valence band edge. These are responsible for the observed band gap reduction. Photocatalytic hydrogen formation was investigated and compared with that of Ba{sub 3}Ta{sub 5}O{sub 14}N revealing significantly higher activity for LaBa{sub 2}Ta{sub 5}O{sub 13}N{sub 2} under UV-light. - Graphical abstract: X-ray powder diffraction pattern of LaBa{sub 2}Ta{sub 5}O{sub 13}N{sub 2} with the results of the Rietveld refinements. Inset: Unit cell of LaBa{sub 2}Ta{sub 5}O{sub 13}N{sub 2} and polyhedral representation of the crystal structure. - Highlights: • Synthesis of a new oxide nitride LaBa{sub 2}Ta{sub 5}O{sub 13}N{sub 2}. • Refinement of the crystal structure. • Quantum chemical calculations provided band gap close to the measured value. • New phase shows a higher photocatalytic H{sub 2} evolution rate compared to prior tested Ba{sub 3}Ta{sub 5}O{sub 14}N.« less

Unexpected autumnal halogen activity in the lower troposphere at Neumayer III/Antarctica

NASA Astrophysics Data System (ADS)

Nasse, Jan-Marcus; Frieß, Udo; Pöhler, Denis; Schmitt, Stefan; Weller, Rolf; Schaefer, Thomas; Platt, Ulrich

2017-04-01

The influence of Reactive Halogen Species (RHS, like IO, BrO, ClO, etc.) on the lower polar troposphere has been subject of intense research for several decades. Ozone Depletion Events (ODEs) caused by the catalytic reaction of tropospheric ozone with inorganic halogen species or the oxidation of gaseous elemental mercury are well observed phenomena that occur during the respective springtime in both Arctic and Antarctica. Chlorine atoms also react more efficiently with hydrocarbons than e.g. OH radicals and all reactive halogen species can furthermore influence the atmospheric sulphur or nitrate cycles. While an autocatalytic release mechanism from salty surfaces, the so called bromine explosion, has been identified to rapidly increase inorganic bromine mixing ratios many aspects of atmospheric halogen chemistry in polar regions remains unclear. Since January 2016, we are operating an active Long Path DOAS instrument at Neumayer III on the Antarctic Ekström shelf ice designed for autonomous measurements. This instrument is able to detect a wide range of trace gases absorbing in the UV/Vis including ClO, BrO, OClO, IO, I2, OIO, ozone, NO2, H2O, O4, and SO2 at a temporal resolution of 5-30 minutes. The analysis of the first year of observations shows several surprising findings which give new insights into polar halogen chemistry. E.g. we observe surprisingly strong bromine activity in late summer and autumn (in addition to well-known springtime events) with mixing ratios often higher than 20 pptv. We could even observe peak mixing ratios of 110 pptv. The observed BrO levels could be the result of local/regional chemistry rather than long-range transport and modulated by the stability of the boundary layer. Also, there are hints for NOx - driven halogen activation. Furthermore, chlorine monoxide (ClO) and OClO mixing ratios of several ten pptv could be detected on a number of days, however the source mechanism for reactive chlorine remains unclear. We will give an overview of the entire time series and discuss interesting case studies with regard to chemistry, atmospheric conditions and transport.

Characterisation of methane isotope composition over the Silesian Coal Basin, Poland.

NASA Astrophysics Data System (ADS)

Necki, Jaroslaw; Zimnoch, Miroslaw; Jasek, Alina; Chmura, Lukasz; Galkowski, Michal; Wolkowicz, Wojciech

2017-04-01

Methane emissions from Silesian Coal Basin (SCB), one of European regions associated with coal excavation industry constitute an important component of the continental anthropogenic flux of this gas into the atmosphere. It is estimated by different methodology that SCB is responsible for between 450 - 1350 Gg CH4 of atmospheric methane releases annually, making it one of the most significant sources of this gas in Europe. In this region, active or restructuring coal mining methane emissions may lead to elevated concentrations of this gas in near-ground atmosphere. Observed methane mixing ratio in pbl during nighttime over the specific areas of SCB is elevated by up to 50ppm with carbon isotope source ratio -46‰ to -52‰ with occasionally lighter methane (-58) form particular coal beds. Numbers were derived from direct measurement of samples taken from ventilation shafts (concentration 1.5% to 4% of CH4, subsequently diluted to 2ppm with zero air and measured by Picarro CRDS analyzer). Measurements of CH4 mixing ratios and isotopic composition were performed along latitudinal transects (ca. 50oN), typically extending from ca. 15oE to 20oE, covering the Upper Silesia and bordering regions on the public roads in vicinity of the mine ventilation shafts. Apart from CH4 emissions associated with coal production, other sources of anthropogenic methane are also active over SCB. These include city gas networks leakages that enrich the air by up to 5ppm (in the city centers, carbon isotope ratio on average -52). Most of the numerous landfills, not yet equipped with appropriate CH4 uptake installations, also contribute to substantial anthropogenic flux of this gas to the atmosphere. Values of methane mixing ratio recorded during the in-situ measurements close to the landfill sites reached 15ppm (with carbon isotope ratio -56‰ to -60). The transects of methane concentration over Silesian area, assisted by analysis of its stable isotopic composition has been performed in all of the locations where active and closed mining shafts are positioned, and most of the landfills and cities under the different meteorological and synoptic conditions to provide a base for efficient future verification of methane inventory over SCB. Project will be continued with MEMO2 ITN H2020.

Synthesis and characterization of a mixed phase of anatase TiO2 and TiO2(B) by low pressure chemical vapour deposition (LPCVD) for high photocatalytic activity

NASA Astrophysics Data System (ADS)

Chimupala, Y.; Hyett, G.; Simpson, R.; Brydson, R.

2014-06-01

This project is concerned with enhancing photocatalytic activity by preparing a mixed phase of nano-sized TiO2. TiO2 thin films were synthesized by using Low Pressure Chemical Vapour Deposition (LPCVD). Titanium isopropoxide and N2 gas were used as the precursor and carrier gas respectively. The effects of reaction temperature, carrier gas flow rate and deposited area were studied. TiO2 thin films with nano-sized TiO2 particles were obtained under suitable conditions and SEM, TEM, powder XRD and Raman spectroscopy were employed to characterize the phase and physical appearance of synthesized materials. Preliminary results show that a dual phase (TiO2(B) and anatase) thin film nanopowder was successfully prepared by LPCVD with needle- and polygonal plate-shape crystallites respectively. This thin film deposit produced a preferred orientation of TiO2(B) needles in the [001] direction of average crystallite size 50-80 nm in length and 5-10 nm in width, whilst the crystallite size of anatase polygonal-plates was around 200 nm. The optimal LPCVD condition for preparing this mixed phase of TiO2 was 600°C with a 1 mL/s N2 flow rate.

Abundances of O3 and O2 in the Martian Atmosphere Retrieved from MAVEN/IUVS Stellar Occultations

NASA Astrophysics Data System (ADS)

Gröller, H.; Lefèvre, F.; Gonzalez-Galindo, F.; Yelle, R. V.; Koskinen, T.; Montmessin, F.; Schneider, N.; Deighan, J.; Jain, S.

2017-12-01

We present O3 and O2 abundances retrieved from stellar occultations taken with the Imaging UltraViolet Spectrometer (IUVS) on MAVEN. The IUVS instrument has two separate spectral channels, the FUV and the MUV channel from 110 to 190 nm and from 180 to 340 nm, respectively. The O3 absorption feature is present in the MUV channel, whereas the O2 absorption features are in the FUV channel. So far, 15 stellar occultation campaigns have been executed on average every two to three months; covering more than one Martian year. During these campaigns, more than 900 stellar occultations were recorded. From those 900 stellar occultations, around 50 % can be used for O2 detection and around 25 % for O3. We detect O3 in almost 40 % of the occultations that can be used for O3 retrievals. The obtained O3 profiles are between 20 and 60 km and show a maximum number density around 30 to 40 km. The peak O3 number density varies almost one order of magnitude; between a few times 108 cm-3 and 2 x 109 cm-3. Our measurements show that the most O3 is present during the first half of the Martian year (up to a solar longitude of around 140°, end of northern summer) with a maximum around 60° solar longitude (close to aphelion). In most of the cases, the retrieved O3 profiles are in agreement with the LMD-MGCM predicted values. However, in some cases a difference in altitude and pressure space can be seen. Furthermore, during the northern early spring season, higher number densities at altitudes above 40 km can be seen in the data. The retrieved density profiles of O2 cover an altitude range from around 90 km up to 150 km. The corresponding O2 mixing ratios range from 1 to 9 x 10-3, also in agreement with previous observations. Even though the O2 mixing ratio shows high variability, the mean value seems to be constant with solar longitude. The obtained O2 profiles agree with previous measurements obtained by the Mars Express SPICAM instrument and by the Viking mass spectrometer. Furthermore, the retrieved O2mixing ratios are in agreement with the LMD-MGCM ratios for solar longitudes greater than around 65° (close to aphelion). However, the O2 mixing ratios predicted with the LMD-MGCM are up to a factor of 10 higher than the mixing ratios derived from stellar occultations during the northern spring season.

Atmospheric O2, CO2 and delta13C measurements from aircraft sampling over Griffin Forest, Perthshire, UK.

PubMed

Sturm, Patrick; Leuenberger, Markus; Moncrieff, John; Ramonet, Michel

2005-01-01

Regular vertical aircraft sampling has been performed in the lower troposphere above Griffin Forest, near Aberfeldy, Perthshire, UK (56 degrees 37'N, 3 degrees 47'W), between February 2003 and May 2004, for analysis of O2/N2, CO2 and delta13C of CO2. We sampled flasks between 800 and 3100 m above sea level. The peak-to-peak amplitude of the seasonal cycle of O2/N2 decreases from 171 per meg at 800 m to 113 per meg at 3100 m. Furthermore, the seasonal cycle is shifted from low to high altitudes with a lag of about 1 month. The same features are observed for CO2 with a decrease in the peak-to-peak amplitude of the seasonal cycle from 17.6 ppm at 800 m to 11.4 ppm at 3100 m. The vertical profiles show decreasing O2/N2 ratios in summer and increasing O2/N2 ratios in wintertime with increasing sampling height, due to surface exchange of oxygen with the land biosphere and the ocean. The O2:CO2 exchange ratios of the vertical profiles vary between -1.5 and -2.4 mol O2/mol CO2. Copyright (c) 2005 John Wiley & Sons, Ltd.

Electronic structure of a laterally graded ZrO2-TiO2 film on Si(100) prepared by metal-organic chemical vapor deposition in ultrahigh vacuum

NASA Astrophysics Data System (ADS)

Richter, J. H.; Karlsson, P. G.; Sandell, A.

2008-05-01

A TiO2-ZrO2 film with laterally graded stoichiometry has been prepared by metal-organic chemical vapor deposition in ultrahigh vacuum. The film was characterized in situ using synchrotron radiation photoelectron spectroscopy (PES) and x-ray absorption spectroscopy. PES depth profiling clearly shows that Ti ions segregate toward the surface region when mixed with ZrO2. The binding energy of the ZrO2 electronic levels is constant with respect to the local vacuum level. The binding energy of the TiO2 electronic levels is aligned to the Fermi level down to a Ti /Zr ratio of about 0.5. At a Ti /Zr ratio between 0.1 and 0.5, the TiO2 related electronic levels become aligned to the local vacuum level. The addition of small amounts of TiO2 to ZrO2 results in a ZrO2 band alignment relative to the Fermi level that is less asymmetric than for pure ZrO2. The band edge positions shift by -0.6eV for a Ti /Zr ratio of 0.03. This is explained in terms of an increase in the work function when adding TiO2, an effect that becomes emphasized by Ti surface segregation.

Description and evaluation of the Community Multiscale Air ...

EPA Pesticide Factsheets

The Community Multiscale Air Quality (CMAQ) model is a comprehensive multipollutant air quality modeling system developed and maintained by the US Environmental Protection Agency's (EPA) Office of Research and Development (ORD). Recently, version 5.1 of the CMAQ model (v5.1) was released to the public, incorporating a large number of science updates and extended capabilities over the previous release version of the model (v5.0.2). These updates include the following: improvements in the meteorological calculations in both CMAQ and the Weather Research and Forecast (WRF) model used to provide meteorological fields to CMAQ, updates to the gas and aerosol chemistry, revisions to the calculations of clouds and photolysis, and improvements to the dry and wet deposition in the model. Sensitivity simulations isolating several of the major updates to the modeling system show that changes to the meteorological calculations result in enhanced afternoon and early evening mixing in the model, periods when the model historically underestimates mixing. This enhanced mixing results in higher ozone (O3) mixing ratios on average due to reduced NO titration, and lower fine particulate matter (PM2. 5) concentrations due to greater dilution of primary pollutants (e.g., elemental and organic carbon). Updates to the clouds and photolysis calculations greatly improve consistency between the WRF and CMAQ models and result in generally higher O3 mixing ratios, primarily due to reduced

Stratospheric ozone depletion from future nitrous oxide increases

NASA Astrophysics Data System (ADS)

Wang, W.; Tian, W.; Dhomse, S.; Xie, F.; Shu, J.; Austin, J.

2014-12-01

We have investigated the impact of the assumed nitrous oxide (N2O) increases on stratospheric chemistry and dynamics using a series of idealized simulations with a coupled chemistry-climate model (CCM). In a future cooler stratosphere the net yield of NOy from N2O is shown to decrease in a reference run following the IPCC A1B scenario, but NOy can still be significantly increased by extra increases of N2O over 2001-2050. Over the last decade of simulations, 50% increases in N2O result in a maximal 6% reduction in ozone mixing ratios in the middle stratosphere at around 10 hPa and an average 2% decrease in the total ozone column (TCO) compared with the control run. This enhanced destruction could cause an ozone decline in the first half of this century in the middle stratosphere around 10 hPa, while global TCO still shows an increase at the same time. The results from a multiple linear regression analysis and sensitivity simulations with different forcings show that the chemical effect of N2O increases dominates the N2O-induced ozone depletion in the stratosphere, while the dynamical and radiative effects of N2O increases are overall insignificant. The analysis of the results reveals that the ozone depleting potential of N2O varies with the time period and is influenced by the environmental conditions. For example, carbon dioxide (CO2) increases can strongly offset the ozone depletion effect of N2O.

Water vapour in the middle atmosphere of Venus:. An improved treatment of the Venera 15 ir spectra

NASA Astrophysics Data System (ADS)

Ignatiev, N. i.; Moroz, V. i.; Zasova, L. V.; Khatuntsev, I. v.

1999-08-01

In 1983, spectra of Venus in the region of 6-40 μm were measured by means of the Fourier Spectrometer aboard the Venera 15 orbiter. It covered local solar times from 4 am to 10 am and from 4 pm to 10 pm in the latitude range from 65°S up to 87°N. The results of an extended processing and analysis of these data are presented. Time and spatial variations of the water vapour were found. Most of the measurements fall in the range of 5-15 ppm, which is close to earlier results. The effective altitude of sounding is approximately equal to the altitude where the optical depth τ = 1. In the northern hemisphere, which was mainly covered by the measurements, two latitude regions can be distinguished; (A) 20° < φ < 50° and (B) φ > 60°, which are characterised by different altitudes of the level of τ = 1, 62 and 55 km respectively. Mean mixing ratios near this level in the two regions are almost the same, but the partial pressures and mass densities in the region (B) are 2-4 times greater than those in region (A). In region (A) a weak maximum was detected near 10 am local solar time (17 ppm at φ = 35°) and a minimum-near 10 pm (2ppm at φ = 30°). Region (B) is of inhomogeneous structure, and the retrieved mixing ratio has greater uncertainty and may probably change from the low values up to 30 ppm. In region (A) the water vapour mass density at the level of τ = 1 is 2-4 times greater than the mean density of the water contained in aerosol particles, while in region (B) this ratio may vary in the limits 0.5-5. Although the retrieval of H2O mixing ratio altitude profile from the Venera 15 data appeared to be impossible, indirect indications were found that at least in region (A) the mixing ratio decreases with altitude.

AASE-2 in-situ tracer correlations of methane, nitrous oxide, and ozone as observed aboard the DC-8

NASA Technical Reports Server (NTRS)

Collins, J. E., Jr.; Sachse, G. W.; Anderson, B. E.; Weinheimer, A. J.; Walega, J. G.; Ridley, B. A.

1993-01-01

We report in situ stratospheric measurements of CH4, N2O, and O3 obtained aboard the NASA DC-8 during the January-March 1992 Airborne Arctic Stratospheric Expedition 2 field campaign. These data demonstrate a strong linear correlation between N2O and CH4 in the lower stratosphere thus indicating that both species are effective tracers of stratospheric air motion. Measurements of both species on constant geometric height surfaces indicate that significant subsidence of the arctic stratospheric air mass occurred at DC-8 altitudes over the course of the AASE-2 expedition. In addition, a widespread reduction in O3 mixing ratios (up to 20%) relative to these conserved tracers was also observed in the lower stratosphere in March as compared to January and February results.

Photophysical studies of europium coordination polymers based on a tetracarboxylate ligand.

PubMed

Gai, Yan-Li; Jiang, Fei-Long; Chen, Lian; Bu, Yang; Su, Kong-Zhao; Al-Thabaiti, Shaeel A; Hong, Mao-Chun

2013-07-01

Reaction of europium sulfate octahydrate with p-terphenyl-3,3″,5,5″-tetracarboxylic acid (H4ptptc) in a mixed solvent system has afforded three new coordination polymers formulated as {[Eu(ptptc)0.75(H2O)2]·0.5DMF·1.5H2O}n (1), {[Me2H2N]2 [Eu2(ptptc)2(H2O)(DMF)]·1.5DMF·7H2O}n (2), and {[Eu(Hptptc)(H2O)4]·0.5DMF·H2O}n (3). Complex 1 exhibits a three-dimensional (3D) metal-organic framework based on {Eu2(μ2-COO)2(COO)4}n chains, complex 2 shows a 3D metal-organic framework constructed by [Eu2(μ2-COO)2(COO)6](2-) dimetallic subunits, and complex 3 features a 2D layer architecture assembling to 3D framework through π···π interactions. All complexes exhibit the characteristic red luminescence of Eu(III) ion. The triplet state of ligand H4ptptc matches well with the emission level of Eu(III) ion, which allows the preparation of new optical materials with enhanced luminescence properties. The luminescence properties of these complexes are further studied in terms of their emission quantum yields, emission lifetimes, and the radiative/nonradiative rates.

Variation of photoautotrophic fatty acid production from a highly CO2 tolerant alga, Chlorococcum littorale, with inorganic carbon over narrow ranges of pH.

PubMed

Ota, Masaki; Takenaka, Motohiro; Sato, Yoshiyuki; Smith, Richard L; Inomata, Hiroshi

2015-01-01

Photoautotrophic fatty acid production of a highly CO2 -tolerant green alga Chlorococcum littorale in the presence of inorganic carbon at 295 K and light intensity of 170 µmol-photon m(-2) s(-1) was investigated. CO2 concentration in the bubbling gas was adjusted by mixing pure gas components of CO2 and N2 to avoid photorespiration and β-oxidation of fatty acids under O2 surrounding conditions. Maximum content of total fatty acid showed pH-dependence after nitrate depletion of the culture media and increased with the corresponding inorganic carbon ratio. Namely, [HCO3 (-) ]/([CO2 ]+n[ CO32-]) ratio in the culture media was found to be a controlling factor for photoautotrophic fatty acid production after the nitrate limitation. At a CO2 concentration of 5% (vol/vol) and a pH of 6.7, the fatty acid content was 47.8 wt % (dry basis) at its maximum that is comparable with land plant seed oils. © 2015 American Institute of Chemical Engineers.

Nano ZSM-5 type ferrisilicates as novel catalysts for ethylbenzene dehydrogenation in the presence of N 2O

NASA Astrophysics Data System (ADS)

Khatamian, M.; Khandar, A. A.; Haghighi, M.; Ghadiri, M.

2011-11-01

Nanosized ZSM-5 type ferrisilicates were successfully prepared using hydrothermal process. Several parameters including gel initiative compositions (Na+ or K+ alkali system), SiO2/Fe2O3 molar ratios and hydrothermal temperature were systematically investigated. The samples were characterized by XRD, TEM, SEM-EDS, BET surface area and ICP techniques. It was found that surface areas and the total pore volume increase with increasing in the SiO2/Fe2O3 molar ratio at Na-FZ ferrisilicates. The catalytic performance of the synthesized catalysts was evaluated in ethylbenzene dehydrogenation to styrene in the presence of N2O or steam at temperatures ranging from 400 °C to 660 °C under atmospheric pressure. The effects of gel initiative compositions, SiO2/Fe2O3 molar ratio as well as the hydrothermal synthesis temperature on the catalytic performance of these catalysts have been addressed. It was shown that styrene yield significantly influenced by altering in the SiO2/Fe2O3 ratio but was not greatly influenced by changes in hydrothermal synthesis temperatures. The comparison between performance of potassium and sodium containing catalysts was shown that the one with potassium has higher yield and selectivity toward styrene production at an optimum temperature of 610 °C.

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

NASA Astrophysics Data System (ADS)

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

2018-05-01

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

Halogen speciation in volcanic plumes - Development of compact denuder sampling techniques with in-situ derivatization followed by gas chromatography-mass spectrometry and their application at Mt. Etna, Mt. Nyiragongo and Mt. Nyamulagira in 2015.

NASA Astrophysics Data System (ADS)

Rüdiger, Julian; Bobrowski, Nicole; Hoffmann, Thorsten

2016-04-01

Volcanoes are a large source for several reactive atmospheric trace gases including sulfur and halogen containing species. The detailed knowledge of volcanic plume chemistry can give insights into subsurface processes and can be considered as a useful geochemical tool for monitoring of volcanic activity, especially halogen to sulfur ratios (e.g. Bobrowski and Giuffrida, 2012; Donovan et al., 2014). The reactive bromine species bromine monoxide (BrO) is of particular interest, because BrO as well as SO2 are readily measurable by UV spectrometer at a safe distance. Furthermore it is formed in the plume by a multiphase reaction mechanism under depletion of ozone in the plume. The abundance of BrO changes as a function of the reaction time and therefore distance from the vent as well as the spatial position in the plume. The precursor substance for the formation of BrO is HBr with Br2as an intermediate product. The reaction of HBr to BrO involves heterogeneous reactions involving aerosol particles, while Br2 reacts directly with O3 to form BrO in a UV radiation induced mechanism. Due to the lack of analytical approaches for the species analysis of halogens (HBr, Br2, Br, BrCl, HOBr) there are still uncertainties about the magnitude of volcanic halogen emissions and in particular their speciation and therefore also in the understanding of the bromine chemistry in volcanic plumes (Bobrowski et al., 2007). In this study a gas diffusion denuder sampling method using a 1,3,5-trimethoxybenzene (1,3,5-TMB) coating for the derivatization of reactive halogen species (Rüdiger et al., 2015) was characterized by reaction chamber experiments. The coating proved to be suitable to collect selectively gaseous bromine species with oxidation states of +1 or 0 (such as Br2, BrCl, BrO(H) and BrONO2), while being ignorant to HBr (OS -1). The reaction of 1,3,5-TMB with reactive bromine species gives 1-bromo-2,4,6-trimethoxybenzene (1-bromo-2,4,6-TMB) - other halogens give corresponding products. The diffusion denuder technique allows sampling of gaseous compounds exclusively without collecting particulate matter. Solvent elution of the derivatized analytes and subsequent analysis with gas chromatography-mass spectrometry gives a limit of detection below 1 ng of bromine. The method was applied in 2015 on volcanic gas plumes at Mt. Etna (Italy), Mt. Nyiragongo and Mt. Nyamulagira (DR Congo) giving reactive bromine mixing ratios from 0.3 ppb (Nyiragongo) up to 22 ppb (Etna, NEC). Compared with total halogen data derived by alkaline trap sampling (Raschig-tube) and ion-chromatography analysis the reactive bromine mixing ratios allow the investigation of the conversion of HBr into reactive species due to plume chemistry with progressing plume age. The new method will be described in detail and the first results on the reactive halogen to total halogen output will be discussed (for bromine and chlorine) and compared to earlier volcanic plume chemistry model studies. References Bobrowski, N. and G. Giuffrida: Bromine monoxide / sulphur dioxide ratios in relation to volcanological observations at Mt. Etna 2006-2009. Solid Earth, 3, 433-445, 2012 Bobrowski, N., R. von Glasow, A. Aiuppa, S. Inguaggiato, I. Louban, O. W. Ibrahim and U. Platt: Reactive halogen chemistry in volcanic plumes. J. Geophys. Res., 112, 2007 Donovan A., V. Tsanev, C. Oppenheimer and M. Edmonds: Reactive halogens (BrO and OClO) detected in the plume of Soufrière Hills Volcano during an eruption hiatus. Geochem. Geophys. Geosyst., 15, 3346-3363, 2014 Rüdiger, J., N. Bobrowski, T. Hoffmann (2015), Development and application of compact denuder sampling techniques with in situ derivatization followed by gas chromatography-mass spectrometry for halogen speciation in volcanic plumes (EGU2015-2392-2), EGU General Assembly 2015

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

PubMed Central

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

2018-01-01

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

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

PubMed

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

2018-01-01

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

Characteristic of nitrous oxide production in partial denitrification process with high nitrite accumulation.

PubMed

Du, Rui; Peng, Yongzhen; Cao, Shenbin; Wang, Shuying; Niu, Meng

2016-03-01

Nitrous oxide (N2O) production during the partial denitrification process with nitrate (NO3(-)-N) to nitrite (NO2(-)-N) transformation ratio of 80% was investigated in this study. Results showed that N2O was seldom observed before complete depletion of NO3(-)-N, but it was closely related to the reduction of NO2(-)-N rather than NO3(-)-N. High COD/NO3(-)-N was in favor of N2O production in partial denitrification with high NO2(-)-N accumulation. It was seriously enhanced at constant acidic pH due to the free nitrous acid (FNA) inhibition. However, the N2O production was much lower at initial pH of 5.5 and 6.5 due to the pH increase during denitrification process. Significantly, the pH turning point could be chosen as a controlled parameter to denote the end of NO3(-)-N reduction, which could not only achieve high NO2(-)-N accumulation but also decrease the N2O production significantly for practical application. Copyright © 2015 Elsevier Ltd. All rights reserved.

Jet Mixing in a Reacting Cylindrical Crossflow

NASA Technical Reports Server (NTRS)

Leong, M. Y.; Samuelsen, G. S.; Holdeman, J. D.

1995-01-01

This paper addresses the mixing of air jets into the hot, fuel-rich products of a gas turbine primary zone. The mixing, as a result, occurs in a reacting environment with chemical conversion and substantial heat release. The geometry is a crossflow confined in a cylindrical duct with side-wall injection of jets issuing from round orifices. A specially designed reactor, operating on propane, presents a uniform mixture without swirl to mixing modules consisting of 8, 9, 10, and 12 holes at a momentum-flux ratio of 57 and a jet-to-mainstream mass-flow ratio of 2.5. Concentrations of O2, CO2, CO, and HC are obtained upstream, downstream, and within the orifice plane. O2 profiles indicate jet penetration while CO2, CO, and HC profiles depict the extent of reaction. Jet penetration is observed to be a function of the number of orifices and is found to affect the mixing in the reacting system. The results demonstrate that one module (the 12-hole) produces near-optimal penetration defined here as a jet penetration closest to the module half-radius, and hence the best uniform mixture at a plane one duct radius from the orifice leading edge.

Nanocrystalline CeO2-δ coated β-MnO2 nanorods with enhanced oxygen transfer property

NASA Astrophysics Data System (ADS)

Huang, Xiubing; Zhao, Guixia; Chang, Yueqi; Wang, Ge; Irvine, John T. S.

2018-05-01

In this research, β-MnO2 nanorods were synthesized by a hydrothermal method, followed by a facile precipitation method to obtain nanocrystalline CeO2-δ coated β-MnO2 nanorods. The as-prepared samples were characterized by XRD, HRTEM, FESEM, XPS and in-situ high-temperature XRD. The HRTEM results show that well dispersed CeO2-δ nanocrystals sized about 5 nm were coated on the surface of β-MnO2 nanorods. The oxygen storage and transfer property of as-synthesized materials were evaluated using TGA under various atmospheres (air, pure N2, and 5%H2/95%Ar). The TGA results indicate that CeO2-δ modification could favour the reduction of Mn4+ to Mn3+ and/or Mn2+ at lower temperature as compared with pure β-MnO2 nanorods and the physically mixed CeO2-δ-β-MnO2 under low oxygen partial pressure conditions (i.e., pure N2, 5%H2/95%Ar). Specifically, CeO2-δ@β-MnO2 sample can exhibit 7.5 wt% weight loss between 100 and 400 °C under flowing N2 and 11.4 wt% weight loss between 100 and 350 °C under flowing 5%H2/95%Ar. During the reduction process under pure N2 or 5%H2/95%Ar condition, the oxygen ions in β-MnO2 nanorods are expected to be released to the surroundings in the form of O2 or H2O with the coated CeO2-δ nanocrystals acting as mediator as inferred from the synergistic effect between the well-interacted CeO2-δ nanocrystals and β-MnO2 nanorods.

Fractionation of stable isotopes in perchlorate and nitrate during in situ biodegradation in a sandy aquifer

USGS Publications Warehouse

Hatzinger, P.B.; Böhlke, J.K.; Sturchio, N.C.; Gu, B.; Heraty, L.J.; Borden, R.C.

2009-01-01

Environmental context. Perchlorate (ClO4-) and nitrate (NO3-) are common co-contaminants in groundwater, with both natural and anthropogenic sources. Each of these compounds is biodegradable, so in situ enhanced bioremediation is one alternative for treating them in groundwater. Because bacteria typically fractionate isotopes during biodegradation, stable isotope analysis is increasingly used to distinguish this process from transport or mixing-related decreases in contaminant concentrations. However, for this technique to be useful in the field to monitor bioremediation progress, isotope fractionation must be quantified under relevant environmental conditions. In the present study, we quantify the apparent in situ fractionation effects for stable isotopes in ClO4- (Cl and O) and NO3- (N and O) resulting from biodegradation in an aquifer. Abstract. An in situ experiment was performed in a shallow alluvial aquifer in Maryland to quantify the fractionation of stable isotopes in perchlorate (Cl and O) and nitrate (N and O) during biodegradation. An emulsified soybean oil substrate that was previously injected into this aquifer provided the electron donor necessary for biological perchlorate reduction and denitrification. During the field experiment, groundwater extracted from an upgradient well was pumped into an injection well located within the in situ oil barrier, and then groundwater samples were withdrawn for the next 30 h. After correction for dilution (using Br- as a conservative tracer of the injectate), perchlorate concentrations decreased by 78% and nitrate concentrations decreased by 82% during the initial 8.6 h after the injection. The observed ratio of fractionation effects of O and Cl isotopes in perchlorate (18O/37Cl) was 2.6, which is similar to that observed in the laboratory using pure cultures (2.5). Denitrification by indigenous bacteria fractionated O and N isotopes in nitrate at a ratio of ???0.8 (18O/15N), which is within the range of values reported previously for denitrification. However, the magnitudes of the individual apparent in situ isotope fractionation effects for perchlorate and nitrate were appreciably smaller than those reported in homogeneous closed systems (0.2 to 0.6 times), even after adjustment for dilution. These results indicate that (1) isotope fractionation factor ratios (18O/37Cl, 18O/15N) derived from homogeneous laboratory systems (e.g. pure culture studies) can be used qualitatively to confirm the occurrence of in situ biodegradation of both perchlorate and nitrate, but (2) the magnitudes of the individual apparent values cannot be used quantitatively to estimate the in situ extent of biodegradation of either anion. ?? CSIRO 2009.

Survival of endospores of Bacillus subtilis on spacecraft surfaces under simulated martian environments: implications for the forward contamination of Mars

NASA Technical Reports Server (NTRS)

Schuerger, Andrew C.; Mancinelli, Rocco L.; Kern, Roger G.; Rothschild, Lynn J.; McKay, Christopher P.

2003-01-01

Experiments were conducted in a Mars simulation chamber (MSC) to characterize the survival of endospores of Bacillus subtilis under high UV irradiation and simulated martian conditions. The MSC was used to create Mars surface environments in which pressure (8.5 mb), temperature (-80, -40, -10, or +23 degrees C), gas composition (Earth-normal N2/O2 mix, pure N2, pure CO2, or a Mars gas mix), and UV-VIS-NIR fluence rates (200-1200 nm) were maintained within tight limits. The Mars gas mix was composed of CO2 (95.3%), N2 (2.7%), Ar (1.7%), O2 (0.2%), and water vapor (0.03%). Experiments were conducted to measure the effects of pressure, gas composition, and temperature alone or in combination with Mars-normal UV-VIS-NIR light environments. Endospores of B. subtilis, were deposited on aluminum coupons as monolayers in which the average density applied to coupons was 2.47 x 10(6) bacteria per sample. Populations of B. subtilis placed on aluminum coupons and subjected to an Earth-normal temperature (23 degrees C), pressure (1013 mb), and gas mix (normal N2/O2 ratio) but illuminated with a Mars-normal UV-VIS-NIR spectrum were reduced by over 99.9% after 30 sec exposure to Mars-normal UV fluence rates. However, it required at least 15 min of Mars-normal UV exposure to reduce bacterial populations on aluminum coupons to non-recoverable levels. These results were duplicated when bacteria were exposed to Mars-normal environments of temperature (-10 degrees C), pressure (8.5 mb), gas composition (pure CO2), and UV fluence rates. In other experiments, results indicated that the gas composition of the atmosphere and the temperature of the bacterial monolayers at the time of Mars UV exposure had no effects on the survival of bacterial endospores. But Mars-normal pressures (8.5 mb) were found to reduce survival by approximately 20-35% compared to Earth-normal pressures (1013 mb). The primary implications of these results are (a) that greater than 99.9% of bacterial populations on sun-exposed surfaces of spacecraft are likely to be inactivated within a few tens of seconds to a few minutes on the surface of Mars, and (b) that within a single Mars day under clear-sky conditions bacterial populations on sun-exposed surfaces of spacecraft will be sterilized. Furthermore, these results suggest that the high UV fluence rates on the martian surface can be an important resource in minimizing the forward contamination of Mars. c2003 Elsevier Inc. All rights reserved.

Probing the Influence of Acidity and Temperature to Th(IV) on Hydrolysis, Nucleation, and Structural Topology.

PubMed

Lin, Jian; Qie, Meiying; Zhang, Linjuan; Wang, Xiaomei; Lin, Yuejian; Liu, Wei; Bao, Hongliang; Wang, Jianqiang

2017-11-20

Systematic control of the molar ratio between thorium hydroxides and selenic acid and their reaction temperature under hydrothermal conditions results in four novel thorium-based selenate complexes, namely, [Th 8 O 4 (OH) 8 (SeO 4 ) 6 (H 2 O) 16 ]·(SeO 4 ) 2 ·13H 2 O (Th-1), [Th 8 O 4 (OH) 8 (SeO 4 ) 8 (H 2 O) 13 ]·7H 2 O (Th-2), Th(OH) 2 (SeO 4 )H 2 O (Th-3), and Th 3 (SeO 4 ) 6 (H 2 O) 6 ·2.5H 2 O (Th-4), as well as the thorium mixed selenite selenate compound Th(SeO 3 )(SeO 4 ) (Th-5). Smaller [H 2 SeO 4 ]/[Th(IV)] ratio or lower temperature give rise to the formation of octameric [Th 8 (μ 3 -O) 4 (μ 2 -OH) 8 ] 16+ cores in Th-1/Th-2 and infinite [Th(μ 2 -OH) 2 H 2 O] 2+ chains in Th-3, respectively. Increasing the [H 2 SeO 4 ]/[Th(IV)] ratio or elevating the temperature generates a microporous (11.3 Å voids) open-framework Th-4, a monomeric thorium species without oxo/hydroxyl ligands, and a three-dimensional thorium structure Th-5. Formation of these compounds suggests that variables including acidity and temperature play a critical role in the hydrolysis and oligomerization of Th IV ions. Increasing acidity limits the deprotonation of water molecules and formation of nucleophilic hydroxo/oxo-aquo Th species, and high temperature appears to suppress the olation/oxolation hydrolysis reactions, which in both ways limit the formation of the thorium oligomers.

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

NASA Technical Reports Server (NTRS)

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

1989-01-01

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

Ozone Formation Induced by the Impact of Reactive Bromine and Iodine Species on Photochemistry in a Polluted Marine Environment.

PubMed

Shechner, M; Tas, E

2017-12-19

Reactive iodine and bromine species (RIS and RBS, respectively) are known for altering atmospheric chemistry and causing sharp tropospheric ozone (O 3 ) depletion in polar regions and significant O 3 reduction in the marine boundary layer (MBL). Here we use measurement-based modeling to show that, unexpectedly, both RIS and RBS can lead to enhanced O 3 formation in a polluted marine environment under volatile organic compound (VOC)-limited conditions associated with high nitrogen oxide (NO X = [NO] + [NO 2 ]) concentrations. Under these conditions, the daily average O 3 mixing ratio increased to ∼44 and ∼28% for BrO and IO mixing ratios of up to ∼6.8 and 4.7 ppt, respectively. The increase in the level of O 3 was partially induced by enhanced ClNO 3 formation for higher Br 2 and I 2 emission flux. The increase in the level of O 3 was associated with an increased mixing ratio of hydroperoxyl radical to hydroxyl radical ([HO 2 ]/[OH]) and increased [NO 2 ]/[NO] with higher levels of RBS and/or RIS. NO X -rich conditions are typical of the polluted MBL, near coastlines and ship plumes. Considering that O 3 is toxic to humans, plants, and animals and is a greenhouse gas, our findings call for adequate updating of local and regional air-quality models with the effects of activities of RBS and RIS on O 3 mixing ratios in the polluted MBL.

Effect of methanol on the biofiltration of n-hexane.

PubMed

Zehraoui, Abderrahman; Hassan, Ashraf Aly; Sorial, George A

2012-06-15

This study investigated the removal of recalcitrant compounds in the presence of a hydrophilic compound. n-Hexane is used as a model compound to represent hydrophobic compounds. Methanol has been introduced in mixture with n-hexane in order to increase the bioavailability of n-hexane in trickle-bed-air-biofilters (TBABs). The mixing ratios investigated were: 70% methanol:30% n-hexane, and 80% methanol:20% n-hexane by volume. n-Hexane loading rates (LRs) ranged from 0.9 to 13.2 g m(-3) h(-1). Methanol LRs varied from 4.6 to 64.5 g m(-3) h(-1) and from 2.3 to 45.2 g m(-3) h(-1) depending upon the mixing ratio used. Biofilter performance, effect of mixing ratios of methanol to n-hexane, removal profile along biofilter depth, COD/nitrogen consumption and CO(2) production were studied under continuous loading operation conditions. Results have shown that the degradation of n-hexane is significantly enhanced by the presence of methanol for n-hexane LRs less than 13.2 g m(-3) h(-1). For n-hexane LR greater than 13.2 g m(-3) h(-1), even though methanol had impacted n-hexane biodegradation, its removal efficiency was higher than our previous study for biodegradation of n-hexane alone, in presence of surfactant, or in presence of benzene. On the other hand, the degradation of methanol was not impacted by the presence of n-hexane. Copyright © 2012 Elsevier B.V. All rights reserved.

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

NASA Astrophysics Data System (ADS)

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

2017-04-01

In recent years, research on nitrous oxide (N2O) stable isotopes has significantly advanced, addressing an increasing number of research questions in biogeochemical and atmospheric sciences [1]. An important milestone was the development of quantum cascade laser based spectroscopic devices [2], which are inherently specific for structural isomers (15N14N16O vs. 14N15N16O) and capable to collect real-time data with high temporal resolution, complementary to the well-established isotope-ratio mass-spectrometry (IRMS) method. In combination with automated preconcentration, optical isotope ratio spectroscopy (OIRS) has been applied to disentangle source processes in suburban, rural and pristine environments [e.g. 3, 4]. Within the European Metrology Research Programme (EMRP) ENV52 project "Metrology for high-impact greenhouse gases (HIGHGAS)", the quality of N2O stable isotope analysis by OIRS, the comparability between laboratories, and the traceability to the international isotope ratio scales have been addressed. An inter-laboratory comparison between eleven IRMS and OIRS laboratories, organised within HIGHGAS, indicated limited comparability for 15N site preference, i.e. the difference between 15N abundance in central (N*NO) and end (*NNO) position [5]. In addition, the accuracy of the NH4NO3 decomposition reaction, which provides the link between 15N site preference and the international 15N/14N scale, was found to be limited by non-quantitative NH4NO3 decomposition in combination with substantially different isotope enrichment factors for both nitrogen atoms [6]. Results of the HIGHGAS project indicate that the following research tasks have to be completed to foster research on N2O isotopes: 1) develop improved techniques to link the 15N and 18O abundance and the 15N site preference in N2O to the international stable isotope ratio scales; 2) provide N2O reference materials, pure and diluted in an air matrix, to improve inter-laboratory compatibility. These tasks will be addressed in the upcoming European Metrology Programme for Innovation and Research (EMPIR) project "Metrology for Stable Isotope Reference Standards (SIRS)" starting in June 2017. Acknowledgement Part of this work has been carried out within the European Metrology Research Programme (EMRP) ENV52 project-HIGHGAS. The EMRP is jointly funded by the EMRP participating countries within EURAMET and the European Union. References [1] S. Toyoda et al., Isotopocule analysis of biologically produced nitrous oxide in various environments, Mass Spectrom. Rev., Doi 10.1002/mas.21459 (2015). [2] J. Mohn et al., Site selective real-time measurements of atmospheric N2O isotopomers by laser spectroscopy, Atmos. Meas. Tech. 5(7), 1601-1609 (2012). [3] B. Wolf et al., First on-line isotopic characterization of N2O above intensively managed grassland, Biogeosci. 12, 2517-2531, (2015). [4] E. Harris et al., Tracking nitrous oxide emission processes at a suburban site with semi-continuous, in-situ measurements of isotopic composition, J. Geophys. Res. Atmos., accepted (2016). [5] J. Mohn et al., Interlaboratory assessment of nitrous oxide isotopomer analysis by isotope ratio mass spectrometry and laser spectroscopy: current status and perspectives, Rapid Commun. Mass Spectrom. 28, 1995-2007 (2014). [6] J. Mohn et al. Reassessment of the NH4NO3 thermal decomposition technique for calibration of the N2O isotopic composition, Rapid Commun. Mass Spectrom. 30, 2487-2496 (2016).

Synthesis of Mixed Cu/Ce Oxide Nanoparticles by the Oil-in-Water Microemulsion Reaction Method

PubMed Central

Pemartin-Biernath, Kelly; Vela-González, Andrea V.; Moreno-Trejo, Maira B.; Leyva-Porras, César; Castañeda-Reyna, Iván E.; Juárez-Ramírez, Isaías; Solans, Conxita; Sánchez-Domínguez, Margarita

2016-01-01

Cerium oxide and mixed Cu/Ce oxide nanoparticles were prepared by the oil-in-water (O/W) microemulsion reaction method in mild conditions. The Cu/Ce molar ratio was varied between 0/100 and 50/50. According to X-ray diffraction (XRD), below 30/70 Cu/Ce molar ratio, the materials presented a single phase consistent with cubic fluorite CeO2. However, above Cu/Ce molar ratio 30/70, an excess monoclinic CuO phase in coexistence with the predominant Cu/Ce mixed oxide was detected by XRD and High-Resolution Transmission Electron Microscopy (HRTEM). Raman spectroscopy showed that oxygen vacancies increased significantly as the Cu content was increased. Band gap (Eg) was investigated as a function of the Cu/Ce molar ratio, resulting in values from 2.91 eV for CeO2 to 2.32 eV for the mixed oxide with 30/70 Cu/Ce molar ratio. These results indicate that below 30/70 Cu/Ce molar ratio, Cu2+ is at least partially incorporated into the ceria lattice and very well dispersed in general. In addition, the photodegradation of Indigo Carmine dye under visible light irradiation was explored for selected samples; it was shown that these materials can remove such contaminants, either by adsorption and/or photodegradation. The results obtained will encourage investigation into the optical and photocatalytic properties of these mixed oxides, for widening their potential applications. PMID:28773602

Series of mixed uranyl-lanthanide (Ce, Nd) organic coordination polymers with aromatic polycarboxylates linkers.

PubMed

Mihalcea, Ionut; Volkringer, Christophe; Henry, Natacha; Loiseau, Thierry

2012-09-17

Three series of mixed uranyl-lanthanide (Ce or Nd) carboxylate coordination polymers have been successfully synthesized by means of a hydrothermal route using either conventional or microwave heating methods. These compounds have been prepared from mixtures of uranyl nitrate, lanthanide nitrate together with phthalic acid (1,2), pyromellitic acid (3,4), or mellitic acid (5,6) in aqueous solution. The X-ray diffraction (XRD) single-crystal revealed that the phthalate complex (UO(2))(4)O(2)Ln(H(2)O)(7)(1,2-bdc)(4)·NH(4)·xH(2)O (Ln = Ce(1), Nd(2); x = 1 for 1, x = 0 for 2), is based on the connection of tetranuclear uranyl-centered building blocks linked to discrete monomeric units LnO(2)(H(2)O)(7) via the organic species to generate infinite chains, intercalated by free ammonium cations. The pyromellitate phase (UO(2))(3)Ln(2)(H(2)O)(12)(btec)(3)·5H(2)O (Ce(3), Nd(4)) contains layers of monomeric uranyl-centered hexagonal and pentagonal bipyramids linked via the carboxylate arms of the organic molecules. The three-dimensionality of the structure is ensured by the connection of remaining free carboxylate groups with isolated monomeric units LnO(2)(H(2)O)(7). The network of the third series (UO(2))(2)(OH)Ln(H(2)O)(7)(mel)·5H(2)O (Ce(5), Nd(6)) is built up from dinuclear uranyl units forming layers through connection with the mellitate ligands, which are further linked to each other through discrete monomers LnO(3)(H(2)O)(6). The thermal decomposition of the various coordination complexes led to the formation of mixed uranium-lanthanide oxide, with the fluorite-type structure at 1500 °C (for 1, 2) or 1400 °C for 3-6. Expected U/Ln ratio from the crystal structures were observed for compounds 1-6.

Magnetoelectric behavior of carbonyl iron mixed Mn oxide-coated ferrite nanoparticles

NASA Astrophysics Data System (ADS)

Ahad, Faris B. Abdul; Lee, Shang-Fan; Hung, Dung-Shing; Yao, Yeong-Der; Yang, Ruey-Bin; Lin, Chung-Kwei; Tsay, Chien-Yie

2010-05-01

The dielectric and magnetic properties of manganese oxide-coated Fe3O4 nanoparticles (NPs) were measured by the cavity perturbation method at x-band microwave frequencies ranging from 7-12.5 GHz with controlled external magnetic field up to 2.2 kOe at room temperature. Different ratios (5%, 10%, and 20% by weight) of coated NPs were prepared by sol-gel method then mixed with carbonyl iron powder in epoxy matrix. The saturation magnetization is inversely proportional to the NPs ratio in the mixture between 150 and 180 emu/g. The real part of the permittivity decreased with increasing NPs concentration, but the permittivity change by magnetic field increased. The tunability behavior is explained by insulator-ferromagnetic interface magnetoelectricity and the large surface volume ratio for the NPs.

A Comparison of Measurements from ATMOS and Instruments Aboard the ER-2 Aircraft: Tracers of Atmospheric Transport and Halogenated Gases

NASA Technical Reports Server (NTRS)

Chang, A. Y.; Salawitch, R. J.; Michelsen, H. A.; Gunson, M. R.; Abrams, M. C.; Zander, R.; Rinsland, C. P.; Loewenstein, M.; Podolske, J. R.; Proffitt, M. H.;

Spectroscopic Study of HD 179821 (IRAS 19114+0002): Proto-Planetary Nebula or Supergiant?

NASA Technical Reports Server (NTRS)

Reddy, B. E.; Hrivnak, Bruce J.

1999-01-01

A detailed chemical composition analysis of the bright post-AGB candidate HD 179821 (IRAS 19114 + 0002) is presented. The LTE analysis, based on high-resolution (R approximately equal 50,000) and high-quality (S/N approximately equal 300) spectra, yields atmospheric parameters T(sub eff) = 6750 K, log g = 0.5, and xi(sub t) = 5.25 km/s. The elemental abundance results of HD 179821 are found to be [Fe/H] = -0.1, [C/Fe] = +0.2, [N/Fe] = +1.3, [O/Fe] = +0.2, [alpha-process/Fe] = +0.5, and [s-process/Fe] = +0.4. These values clearly differ from the elemental abundances of Population I F supergiants. The C, N, and O abundances and the total CNO abundance value relative to Fe, [C+N+O/Fe] = +0.5, indicate that the photosphere of HD 179821 is contaminated with both the H- and He-burning products of the AGB phase. The evidence for He burning through the 3.alpha process and deep AGB mixing also comes from the observed overabundances of s-process elements. Remarkably, the abundance of the element Na is found to be very large, [Na/Fe] = +0.9. The ratio O/C = 2.6 indicates that the atmosphere is oxygen rich. The results of this abundance study support the argument that HD 179821 is a proto-planetary nebula,. probably with an intermediate-mass progenitor. However, the strength of the O I triplet lines at 7774 A and the distance derived from the interstellar Na I D1 and D2 components imply that the star is a luminous object (M(sub bol) approximately -8.9 +/- 1) and thus a massive supergiant. Thus, while this study contributes important new observational results for this star, an unambiguous determination of its evolutionary status has yet to be achieved.

Source apportionment of methane and nitrous oxide in California's San Joaquin Valley at CalNex 2010 via positive matrix factorization

NASA Astrophysics Data System (ADS)

Guha, A.; Gentner, D. R.; Weber, R. J.; Provencal, R.; Goldstein, A. H.

2015-03-01

Sources of methane (CH4) and nitrous oxide (N2O) were investigated using measurements from a site in southeast Bakersfield as part of the CalNex (California at the Nexus of Air Quality and Climate Change) experiment from 15 May to 30 June 2010. Typical daily minimum mixing ratios of CH4 and N2O were higher than daily averages that were simultaneously observed at a similar latitude background station (NOAA, Mauna Loa) by approximately 70 and 0.5 ppb, respectively. Substantial enhancements of CH4 and N2O (hourly averages > 500 ppb and > 7 ppb, respectively) were routinely observed suggesting the presence of large regional sources. Collocated measurements of carbon monoxide (CO) and a range of volatile organic compounds (VOCs) (e.g. straight-chain and branched alkanes, cycloalkanes, chlorinated alkanes, aromatics, alcohols, isoprene, terpenes and ketones) were used with a Positive Matrix Factorization (PMF) source apportionment method to estimate the contribution of regional sources to observed enhancements of CH4 and N2O. The PMF technique provided a "top-down" deconstruction of ambient gas-phase observations into broad source categories, yielding a 7-factor solution. We identified these source factors as emissions from evaporative and fugitive; motor vehicles; livestock and dairy; agricultural and soil management; daytime light and temperature driven; non-vehicular urban; and nighttime terpene biogenics and anthropogenics. The dairy and livestock factor accounted for a majority of the CH4 (70-90%) enhancements during the duration of the experiments. Propagation of uncertainties in the PMF-derived factor profiles and time series from bootstrapping analysis resulted in a 29% uncertainty in the CH4 apportionment to this factor. The dairy and livestock factor was also a principal contributor to the daily enhancements of N2O (60-70%) with an uncertainty of 33%. Agriculture and soil management accounted for ~20-25% of N2O enhancements over the course of a day, not surprisingly given that organic and synthetic fertilizers are known to be a major source of N2O. The evaporative/fugitive source profile resembles a mix of petroleum operation and non-tailpipe evaporative gasoline sources, but was not responsible for any observed PMF resolved-CH4 enhancements. The vehicle emission source factor broadly matches VOC profiles of on-road exhaust sources and had no detected contribution to the N2O signals and negligible CH4 in the presence of a dominant dairy and livestock factor. The CalNex PMF study provides a measurement-based assessment of the state CH4 and N2O inventories for the southern San Joaquin valley. The state inventory attributes ~18% of the total N2O emissions to the transportation sector. Our PMF analysis directly contradicts the state inventory and demonstrates there were no discernible N2O emissions from the transportation sector.

Photoionized Mixing Layer Models of the Diffuse Ionized Gas

NASA Astrophysics Data System (ADS)

Binette, Luc; Flores-Fajardo, Nahiely; Raga, Alejandro C.; Drissen, Laurent; Morisset, Christophe

2009-04-01

It is generally believed that O stars, confined near the galactic midplane, are somehow able to photoionize a significant fraction of what is termed the "diffuse ionized gas" (DIG) of spiral galaxies, which can extend up to 1-2 kpc above the galactic midplane. The heating of the DIG remains poorly understood, however, as simple photoionization models do not reproduce the observed line ratio correlations well or the DIG temperature. We present turbulent mixing layer (TML) models in which warm photoionized condensations are immersed in a hot supersonic wind. Turbulent dissipation and mixing generate an intermediate region where the gas is accelerated, heated, and mixed. The emission spectrum of such layers is compared with observations of Rand of the DIG in the edge-on spiral NGC 891. We generate two sequence of models that fit the line ratio correlations between [S II]/Hα, [O I]/Hα, [N II]/[S II], and [O III]/Hβ reasonably well. In one sequence of models, the hot wind velocity increases, while in the other, the ionization parameter and layer opacity increase. Despite the success of the mixing layer models, the overall efficiency in reprocessing the stellar UV is much too low, much less than 1%, which compels us to reject the TML model in its present form.

Enhanced tunability of the composition in silicon oxynitride thin films by the reactive gas pulsing process

NASA Astrophysics Data System (ADS)

Aubry, Eric; Weber, Sylvain; Billard, Alain; Martin, Nicolas

2014-01-01

Silicon oxynitride thin films were sputter deposited by the reactive gas pulsing process. Pure silicon target was sputtered in Ar, N2 and O2 mixture atmosphere. Oxygen gas was periodically and solely introduced using exponential signals. In order to vary the injected O2 quantity in the deposition chamber during one pulse at constant injection time (TON), the tau mounting time τmou of the exponential signals was systematically changed for each deposition. Taking into account the real-time measurements of the discharge voltage and the I(O*)/I(Ar*) emission lines ratio, it is shown that the oscillations of the discharge voltage during the TON and TOFF times (injection of O2 stopped) are attributed to the preferential adsorption of the oxygen compared to that of the nitrogen. The sputtering mode alternates from a fully nitrided mode (TOFF time) to a mixed mode (nitrided and oxidized mode) during the TON time. For the highest injected O2 quantities, the mixed mode tends toward a fully oxidized mode due to an increase of the trapped oxygen on the target. The oxygen (nitrogen) concentration in the SiOxNy films similarly (inversely) varies as the oxygen is trapped. Moreover, measurements of the contamination speed of the Si target surface are connected to different behaviors of the process. At low injected O2 quantities, the nitrided mode predominates over the oxidized one during the TON time. It leads to the formation of Si3N4-yOy-like films. Inversely, the mixed mode takes place for high injected O2 quantities and the oxidized mode prevails against the nitrided one producing SiO2-xNx-like films.

CARBON AND OXYGEN ISOTOPIC RATIOS FOR NEARBY MIRAS

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

Hinkle, Kenneth H.; Lebzelter, Thomas; Straniero, Oscar, E-mail: khinkle@noao.edu, E-mail: thomas.lebzelter@univie.ac.at, E-mail: straniero@oa-teramo.inaf.it

2016-07-01

Carbon and oxygen isotopic ratios are reported for a sample of 46 Mira and SRa-type variable asymptotic giant branch (AGB) stars. Vibration–rotation first and second-overtone CO lines in 1.5–2.5 μ m spectra were measured to derive isotopic ratios for {sup 12}C/{sup 13}C, {sup 16}O/{sup 17}O, and {sup 16}O/{sup 18}O. Comparisons with previous measurements for individual stars and with various samples of evolved stars, as available in the extant literature, are discussed. Models for solar composition AGB stars of different initial masses are used to interpret our results. We find that the majority of M-stars have main sequence masses ≤2 Mmore » {sub ⊙} and have not experienced sizable third dredge-up (TDU) episodes. The progenitors of the four S-type stars in our sample are slightly more massive. Of the six C-stars in the sample three have clear evidence relating their origin to the occurrence of TDU. Comparisons with O-rich presolar grains from AGB stars that lived before the formation of the solar system reveal variations in the interstellar medium chemical composition. The present generation of low-mass AGB stars, as represented by our sample of long period variables (LPVs), shows a large spread of {sup 16}O/{sup 17}O ratios, similar to that of group 1 presolar grains and in agreement with theoretical expectations for the composition of mass 1.2–2 M {sub ⊙} stars after the first dredge-up. In contrast, the {sup 16}O/{sup 18}O ratios of present-day LPVs are definitely smaller than those of group 1 grains. This is most probably a consequence of the the decrease with time of the {sup 16}O/{sup 18}O ratio in the interstellar medium due to the chemical evolution of the Milky Way. One star in our sample has an O composition similar to that of group 2 presolar grains originating in an AGB star undergoing extra-mixing. This may indicate that the extra-mixing process is hampered at high metallicity, or, equivalently, favored at low metallicity. Similarly to O-rich grains, no star in our sample shows evidence of hot bottom burning, which is expected for massive AGB stars.« less

A new cavity ring-down instrument for airborne monitoring of N2O5, NO3, NO2 and O3 in the upper troposphere lower stratosphere

NASA Astrophysics Data System (ADS)

Ruth, Albert A.; Brown, Steven S.; Dinesan, Hemanth; Dubé, William P.; Goulette, Marc; Hübler, Gerhard; Orphal, Johannes; Zahn, Andreas

2016-04-01

The chemistry of NO3 and N2O5 is important to the regulation of both tropospheric and stratospheric ozone. In situ detection of NO3 and N2O5 in the upper troposphere lower stratosphere (UTLS) represents a new scientific direction as the only previous measurements of these species in this region of the atmosphere has been via remote sensing techniques. Because both the sources and the sinks for NO3 and N2O5 are potentially stratified spatially, their mixing ratios, and their influence on nitrogen oxide and ozone transport and loss at night can show large variability as a function of altitude. Aircraft-based measurements of heterogeneous N2O5 uptake in the lower troposphere have uncovered a surprising degree of variability in the uptake coefficient [1], but there are no corresponding high altitude measurements.The UTLS is routinely sampled by the IAGOS-CARIBIC program (Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container, www.caribic-atmospheric.com), a European infrastructural program with the aim of studying the chemistry and transport across this part of the atmosphere. An airfreight container with 15 different automated instruments from 8 European research partners is utilized on board a commercial Lufthansa airbus 340-600 to monitor ~ 100 atmospheric species (trace gases and aerosol parameters) in the UTLS. The instrumentation in the CARIBIC container is now to be supplemented by a new cavity ring-down device for monitoring nitrogen oxides, jointly developed by researchers from Cork (Ireland), Boulder (USA) and Karlsruhe (Germany). The compact and light-weight instrument is designed to monitor not only NO3 and N2O5, but also NO2 and O3. The detection is based on 4 high-finesse optical cavities (cavity length ~ 44 cm). Two cavities are operated at 662 nm (maximum absorption of NO3), the other two at 405 nm (maximum absorption of NO2). The inlet to one of the (662)-cavities is heated in order to thermally decompose N2O5 entirely to provide the sum of NO3 and N2O5, with N2O5 provided by difference to a direct NO3 measurement in a separate, unheated channel. One of the (405)-cavities is flushed continuously with NO in order to measure O3 concentrations via quantitative conversion to NO2. The air sampled underneath the cargo bay of the aircraft is distributed inside the instrument through a dedicated inlet system distributing the flow over all four cavities. Flow control, data collection, analysis, and zeroing procedures are fully automated and controlled by dedicated electronics and software within the device. On the poster the new instrument, its design and application within the CARIBIC program, will be outlined. [1] S.S. Brown, T.B. Ryerson, A.G. Wollny, C.A. Brock, R. Peltier, A.P. Sullivan, R.J. Weber, J.S. Holloway, W.P. Dubé, M. Trainer, J.F. Meagher, F.C. Fehsenfeld, A. R. Ravishankara, Variability in nocturnal nitrogen oxide processing and its role in regional air quality, Science, 311 (2006) 67-70.

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

PubMed Central

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

2014-01-01

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

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

NASA Astrophysics Data System (ADS)

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

2018-01-01

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

Fast microwave-assisted catalytic co-pyrolysis of corn stover and scum for bio-oil production with CaO and HZSM-5 as the catalyst.

PubMed

Liu, Shiyu; Xie, Qinglong; Zhang, Bo; Cheng, Yanling; Liu, Yuhuan; Chen, Paul; Ruan, Roger

2016-03-01

This study investigated fast microwave-assisted catalytic co-pyrolysis of corn stover and scum for bio-oil production with CaO and HZSM-5 as the catalyst. Effects of reaction temperature, CaO/HZSM-5 ratio, and corn stover/scum ratio on co-pyrolysis product fractional yields and selectivity were investigated. Results showed that co-pyrolysis temperature was selected as 550°C, which provides the maximum bio-oil and aromatic yields. Mixed CaO and HZSM-5 catalyst with the weight ratio of 1:4 increased the aromatic yield to 35.77 wt.% of feedstock, which was 17% higher than that with HZSM-5 alone. Scum as the hydrogen donor, had a significant synergistic effect with corn stover to promote the production of bio-oil and aromatic hydrocarbons when the H/C(eff) value exceeded 1. The maximum yield of aromatic hydrocarbons (29.3 wt.%) were obtained when the optimal corn stover to scum ratio was 1:2. Copyright © 2016 Elsevier Ltd. All rights reserved.

Effect of counter-ion on packing and crystal density of 5,5'-(3,3'-bi[1,2,4-oxadiazole]-5,5'-diyl)bis(1 H -tetrazol-1-olate) with five different cations

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

Giles, Ian D.; DeHope, Alan J.; Zuckerman, Nathaniel B.

In energetic materials, the crystal density is an important parameter that affects the performance of the material. When making ionic energetic materials, the choice of counter-ion can have detrimental or beneficial effects on the packing, and therefore the density, of the resulting energetic crystal. Presented herein are a series of five ionic energetic crystals, all containing the dianion 5,5′-(3,3′-bi[1,2,4-oxadiazole]-5,5′-diyl)bis(1 H -tetrazol-1-olate), with the following cations: hydrazinium ( 1 ) (2N 2 H 5 + ·C 6 N 12 O 4 2− ), hydroxylammonium ( 2 ) 2NH 4 O + ·C 6 N 12 O 4 2− [Pagoria et al..more » (2017). Chem. Heterocycl. Compd , 53 , 760–778; included for comparison], dimethylammonium ( 3 ) (2C 2 H 8 N + ·C 6 N 12 O 4 2− ), 5-amino-1 H -tetrazol-4-ium ( 4 ) (2CH 4 N 5 + ·C 6 N 12 O 4 2− ·4H 2 O), and aminoguanidinium ( 5 ) (2CH 7 N 4 + ·C 6 N 12 O 4 2− ). Both the supramolecular interactions and the sterics of the cation play a role in the density of the resulting crystals, which range from 1.544 to 1.873 Mg m −1 . In 5 , the tetrazolate ring is disordered over two positions [occupancy ratio 0.907 (5):0.093 (5)] due to a 180° rotation in the terminal tetrazole rings.« less

Effect of counter-ion on packing and crystal density of 5,5'-(3,3'-bi[1,2,4-oxadiazole]-5,5'-diyl)bis(1 H -tetrazol-1-olate) with five different cations

DOE PAGES

Giles, Ian D.; DeHope, Alan J.; Zuckerman, Nathaniel B.; ...

2018-03-09

In energetic materials, the crystal density is an important parameter that affects the performance of the material. When making ionic energetic materials, the choice of counter-ion can have detrimental or beneficial effects on the packing, and therefore the density, of the resulting energetic crystal. Presented herein are a series of five ionic energetic crystals, all containing the dianion 5,5′-(3,3′-bi[1,2,4-oxadiazole]-5,5′-diyl)bis(1 H -tetrazol-1-olate), with the following cations: hydrazinium ( 1 ) (2N 2 H 5 + ·C 6 N 12 O 4 2− ), hydroxylammonium ( 2 ) 2NH 4 O + ·C 6 N 12 O 4 2− [Pagoria et al..more » (2017). Chem. Heterocycl. Compd , 53 , 760–778; included for comparison], dimethylammonium ( 3 ) (2C 2 H 8 N + ·C 6 N 12 O 4 2− ), 5-amino-1 H -tetrazol-4-ium ( 4 ) (2CH 4 N 5 + ·C 6 N 12 O 4 2− ·4H 2 O), and aminoguanidinium ( 5 ) (2CH 7 N 4 + ·C 6 N 12 O 4 2− ). Both the supramolecular interactions and the sterics of the cation play a role in the density of the resulting crystals, which range from 1.544 to 1.873 Mg m −1 . In 5 , the tetrazolate ring is disordered over two positions [occupancy ratio 0.907 (5):0.093 (5)] due to a 180° rotation in the terminal tetrazole rings.« less

Laser-Induced Dynamics of Peroxodicopper(II) Complexes Vary with the Ligand Architecture. One-Photon Two-Electron O2 Ejection and Formation of Mixed-Valent Cu(I)Cu(II)-Superoxide Intermediates.

PubMed

Saracini, Claudio; Ohkubo, Kei; Suenobu, Tomoyoshi; Meyer, Gerald J; Karlin, Kenneth D; Fukuzumi, Shunichi

2015-12-23

Photoexcitation of end-on trans-μ-1,2-peroxodicopper(II) complex [(tmpa)2Cu(II)2(O2)](2+) (1) (λmax = 525 and 600 nm) and side-on μ-η(2):η(2)-peroxodicopper(II) complexes [(N5)Cu(II)2(O2)](2+) (2) and [(N3)Cu(II)2(O2)](2+) (3) at -80 °C in acetone led to one-photon two-electron peroxide-to-dioxygen oxidation chemistry (O2(2-) + hν → O2 + 2e(-)). Interestingly, light excitation of 2 and 3 (having side-on μ-η(2):η(2)-peroxo ligation) led to release of dioxygen, while photoexcitation of 1 (having an end-on trans-1,2-peroxo geometry) did not, even though spectroscopic studies revealed that both reactions proceeded through previously unknown mixed-valent superoxide species: [Cu(II)(O2(•-))Cu(I)](2+) (λmax = 685-740 nm). For 1, this intermediate underwent further fast intramolecular electron transfer to yield an "O2-caged" dicopper(I) adduct, Cu(I)2-O2, and a barrierless stepwise back electron transfer to regenerate 1 occurred. Femtosecond laser excitation of 2 and 3 under the same conditions still led to [Cu(II)(O2(•-))Cu(I)](2+) intermediates that, instead, underwent O2 release with a quantum yield of 0.14 ± 0.1 for 3. Such remarkable differences in reaction pathways likely result from the well-known ligand-derived stability of 2 and 3 vs 1 indicated by ligand-Cu(II/I) redox potentials; (N5)Cu(I) and (N3)Cu(I) complexes are far more stable than (tmpa)Cu(I) species. The fast Cu(I)2/O2 rebinding kinetics was also measured after photoexcitation of 2 and 3, with the results closely tracking those known for the dicopper proteins hemocyanin and tyrosinase, for which the synthetic dicopper(I) precursors [(N5)Cu(I)2](2+) and [(N3)Cu(I)2](2+) and their dioxygen adducts serve as models. The biological relevance of the present findings is discussed, including the potential impact on the solar water splitting process.

Combining single source chemical vapour deposition precursors to explore the phase space of titanium oxynitride thin films.

PubMed

Rees, Kelly; Lorusso, Emanuela; Cosham, Samuel D; Kulak, Alexander N; Hyett, Geoffrey

2018-02-14

In this paper we report on a novel chemical vapour deposition approach to the formation and control of composition of mixed anion materials, as applied to titanium oxynitride thin films. The method used is the aerosol assisted chemical vapour deposition (AACVD) of a mixture of single source precursors. To explore the titanium-oxygen-nitrogen system the single source precursors selected were tetrakis(dimethylamido) titanium and titanium tetraisopropoxide which individually are precursors to thin films of titanium nitride and titanium dioxide respectively. However, by combining these precursors in specific ratios in a series of AACVD reactions at 400 °C, we are able to deposit thin films of titanium oxynitride with three different structure types and a wide range of compositions. Using this precursor system we can observe films of nitrogen doped anatase, with 25% anion doping of nitrogen; a new composition of pseudobrookite titanium oxynitride with a composition of Ti 3 O 3.5 N 1.5 , identified as being a UV photocatalyst; and rock-salt titanium oxynitride in the range TiO 0.41 N 0.59 to TiO 0.05 N 0.95 . The films were characterised using GIXRD, WDX and UV-vis spectroscopy, and in the case of the pseudobrookite films, assessed for photocatalytic activity. This work shows that a so-called dual single-source CVD approach is an effective method for the deposition of ternary mixed anion ceramic films through simple control of the ratio of the precursors, while keeping all other experimental parameters constant.

Water Vapor in the Middle Atmosphere of Venus from the Data of the Venera-15 IR Fourier Spectrometer

NASA Astrophysics Data System (ADS)

Ignat'ev, N. I.; Moroz, V. I.; Zasova, L. V.; Khatuntsev, I. V.

In 1983, the Fourier spectrometer experiment onboard Venera-15 returned spectra of IR radiation (6-50 micron) of the Venusian atmosphere which contained information about temperature, aerosols, and minor constituents, including water vapor. The currently available techniques of radiation-transfer modeling and the H2O-abundance reconstruction allowed us to reanalyze these data, and the most recent results of this analysis are presented here. Most of the measurements are in the range 5-15 ppm. Temporal and spatial variations of the water-vapor abundance were measured. The estimates of H2O abundance calculated from the spectra refer to a certain altitude approximately determined by the level where the optical depth tau in the aerosol continuum near the H2O bands region is close to unity. This altitude varies from 62.5 +/- 2 km at low latitudes to 56 +/- 2 km at high altitudes, but the mean measured water-vapor abundance is found to be roughly the same for both areas, about 10 ppm. At low and middle latitudes, the H2O mixing ratio is maximum on the dayside of the planet and minimum on the nightside. Although the direct reconstruction of the H2O vertical profile from the spectra failed, its indirect estimates confirming the decrease of the mixing ratio with altitude were obtained.

Impact of water mass mixing on the biogeochemistry and microbiology of the Northeast Atlantic Deep Water

NASA Astrophysics Data System (ADS)

Reinthaler, Thomas; Álvarez Salgado, Xosé Antón; Álvarez, Marta; van Aken, Hendrik M.; Herndl, Gerhard J.

2013-12-01

The extent to which water mass mixing contributes to the biological activity of the dark ocean is essentially unknown. Using a multiparameter water mass analysis, we examined the impact of water mass mixing on the nutrient distribution and microbial activity of the Northeast Atlantic Deep Water (NEADW) along an 8000 km long transect extending from 62°N to 5°S. Mixing of four water types (WT) and basin scale mineralization from the site where the WT where defined to the study area explained up to 95% of the variability in the distribution of inorganic nutrients and apparent oxygen utilization. Mixing-corrected average O2:N:P mineralization ratios of 127(±11):13.0(±0.7):1 in the core of the NEADW suggested preferential utilization of phosphorus compounds while dissolved organic carbon mineralization contributed a maximum of 20% to the oxygen demand of the NEADW. In conjunction with the calculated average mineralization ratios, our results indicate a major contribution of particulate organic matter to the biological activity in the NEADW. The variability in prokaryotic abundance, high nucleic acid containing cells, and prokaryotic heterotrophic production in the NEADW was explained by large scale (64-79%) and local mineralization processes (21-36%), consistent with the idea that deep-water prokaryotic communities are controlled by substrate supply. Overall, our results suggest a major impact of mixing on the distribution of inorganic nutrients and a weaker influence on the dissolved organic matter pool supporting prokaryotic activity in the NEADW.

High Static Stability in the Mixed Layer Above the Extratropical Tropopause

NASA Astrophysics Data System (ADS)

Kunz, A.; Konopka, P.; Müller, R.; Pan, L. L.; Schiller, C.

2009-04-01

A strong relationship between the static stability N2 in the tropopause inversion layer (TIL) and the intensity of mixing is evident from in-situ observations during SPURT. With a new simple measure of mixing intensity based on O3/CO tracer correlations, a very high mixing intensity connected to a high N2 is found in the extratropical mixing layer. Using radiative transfer calculations we simulate the influence of trace gases such as O3 and H2O on the temperature gradient and thus on the static stability above the tropopause in an idealized (L-shaped) non-mixed and reference mixed atmosphere. N2 enhances due to an intensifying mixing in the LS. At the same time the temperature decreases together with a development of an inversion and the TIL. Hereby H2O plays the dominant role in maintenance the temperature inversion and the TIL structure. In case of non mixed profiles the TIL vanishes. The results motivate a link between the mixing layer and the TIL. The mixing layer contains on the one hand older air masses, with high values of N2 due to radiative adjustment. This part of the mixing layer is spatial identically to the TIL. On the other hand, there are younger air masses with somehow lower N2 values within the mixing layer, because of fast intrusion processes from the troposphere due to the permeability or so-called mid-latitude-breaks associated with the jet.

Is the surface oxygen exchange rate linked to bulk ion diffusivity in mixed conducting Ruddlesden–Popper phases?

DOE PAGES

Tomkiewicz, Alex C.; Tamimi, Mazin A.; Huq, Ashfia; ...

2015-03-02

There is a possible link between oxygen surface exchange rate and bulk oxygen anion diffusivity in mixed ionic and electronic conducting oxides; it is a topic of great interest and debate. While a large body of experimental evidence and theoretical analyses support a link, observed differences between bulk and surface composition of these materials are hard to reconcile with this observation. This is further compounded by potential problems with simultaneous measurement of both parameters. Here we utilize separate techniques, in situ neutron diffraction and pulsed isotopic surface exchange, to examine bulk ion mobility and surface oxygen exchange rates of threemore » Ruddlesden-Popper phases, general form A n-1A 2'BnO 3n+1, A n-1A 2'BnX 3n+1; LaSrCo 0.5Fe 0.5O 4-δ (n = 1), La 0.3Sr 2.7CoFeO 7-δ (n = 2) and LaSr 3Co 1.5Fe 1.5O 10-δ (n = 3). These measurements are complemented by surface composition determination via high sensitivity-low energy ion scattering. We observe a correlation between bulk ion mobility and surface exchange rate between materials. The surface exchange rates vary by more than one order of magnitude with high anion mobility in the bulk of an oxygen vacancy-rich n = 2 Ruddlesden-Popper material correlating with rapid oxygen exchange. Furthermore this is in contrast with the similar surface exchange rates which we may expect due to similar surface compositions across all three samples. This paper conclude that experimental limitations lead to inherent convolution of surface and bulk rates, and that surface exchange steps are not likely to be rate limiting in oxygen incorporation.« less

Synthesis and characterization of homo- and heterobimetallic niobium v and tantalum v peroxo-polyaminocarboxylato complexes and their use as single or multiple molecular precursors for Nb-Ta mixed oxides

NASA Astrophysics Data System (ADS)

Bayot, Daisy; Degand, Matthieu; Devillers, Michel

2005-09-01

New water-soluble bimetallic peroxo complexes of niobium V and/or tantalum V with high-denticity polyaminocarboxylate ligands have been prepared, characterized from the spectroscopic point of view, and used as molecular precursors for Nb-Ta mixed oxides. Four new homobimetallic complexes, (gu) 3[Nb 2(O 2) 4(dtpaO 3)]·3H 2O 1, (gu) 3[Ta 2(O 2) 4(dtpaO 3)]·5H 2O 2, (gu) 3[Nb 2(O 2) 4(HtthaO 4)]·2H 2O 4 and (gu) 3[Ta 2(O 2) 4(HtthaO 4)]·3H 2O 5 and the corresponding heterometallic complexes, (gu) 3[NbTa(O 2) 4(dtpaO 3)]·2.5H 2O 3 and (gu) 3[NbTa(O 2) 4(HtthaO 4)]·2H 2O 6 have been obtained. In these compounds, the in situ oxidation of the nitrogen atoms of the PAC ligands into N-oxide groups has been evidenced by IR spectroscopy and mass spectrometry. The thermal treatment of the homonuclear complexes in air at 700 or 800 °C, depending on the Ta content, provided Nb 2O 5 or Ta 2O 5 while the heteronuclear compounds led to the solid solution TaNbO 5. BET and SEM measurements have been carried out and comparison of the morphology of the samples prepared from homo- and heterometallic precursors is discussed.

How does conversion from peat swamp forest to oil palm plantation affect emissions of nitrous oxide from the soil? A case study in Jambi, Indonesia

NASA Astrophysics Data System (ADS)

Hartill, Jodie; Hergoualc'h, Kristell; Comeau, Louis-Pierre; Jo, Smith; Lou, Verchot

2017-04-01

Half of the peatlands across Peninsular Malaysia, Borneo and Sumatra are 'managed'. Conversion of peat swamp forest to workable oil palm plantation requires a drastic, potentially irreversible, change to the landscape, to which fertilizers are then routinely applied. A combination of these factors is now widely thought to increase soil nitrous oxide (N2O) emissions, although there is high uncertainty due to gaps in the knowledge, both regionally and nationally. Despite the widespread use of fertilizers in plantations on peats, studies observing their effects remain very limited. Therefore, there is a need for in situ studies to evaluate how environmental parameters (edaphic properties, climate, soil moisture and N availability indicators) influence soil emissions. This 18 month study was located in plots local to each other, representing the start, intermediate and end of the land conversion process; namely mixed peat swamp forest, drained and logged forest and industrial oil palm plantation. Spatial variability was taken into account by differentiating the hollows and hummocks in the mixed peat swamp forest, and the fertilized zone and the zone without fertilizer addition in the oil palm plantation. Gas samples were collected each month from static chambers at the same time as key environmental parameters were measured. Intensive sampling was performed during a 35 day period following two fertilizer applications, in which urea was applied to palms at rates of 0.5 and 1 kg urea palm-1. Soil N2O emissions (kg N ha-1 y-1 ± SE) were low overall, but they were greater in the oil palm plantation (0.8 ± 0.1) than in the mixed peat swamp forest (0.3 ± 0.0) and the drained/logged forest (0.2 ± 0.0). In the mixed peat swamp forest, monthly average fluxes of N2O (g N ha-1 d-1 ± SE) were similar in the hollows (0.6 ± 0.2) and the hummocks (0.3 ± 0.1), whereas in the oil palm plantation they were consistently higher in the zone without fertilizer (2.5 ± 0.4) than in the fertilized zone (0.5 ± 0.1), even after fertilizer application. In the fertilized zones, the N2O fluxes following the two fertilizer applications were 2.4 and 4.5 times higher respectively than fluxes observed in the absence of fertilizers. No change in emissions was observed in the neighboring unfertilized zone at the time of fertilizer application. Soil N2O emissions were related to changes in air and soil temperature in the mixed peat swamp forest, air temperature and water table depth in the drained and logged forest, and rainfall on the day of measurement in the oil palm plantation. This research confirms that peat forest conversion to oil palm plantation has negative consequences on the emissions of N2O. It also corroborates an increase in emission due to fertilizer application, with a magnitude comparable to the emission factor provided by the IPCC guidelines, but this is restricted to the limited area of fertilizer application.

Dehydration in the lower Antarctic stratosphere during late winter and early spring, 1987

NASA Technical Reports Server (NTRS)

Kelly, K. K.; Tuck, A. F.; Murphy, D. M.; Fahey, D. W.; Proffitt, M. H.; Jones, R. L.; Mckenna, D. S.; Loewenstein, M.; Podolske, J. P.; Strahan, S. E.

1989-01-01

The history of minimum temperatures at 50 and 70 mb is examined from NMC, UK Met O and ECMWF analyses. MSU channel 24 data are similarly inspected. South Pole sonde data are used to calculate saturation humidity mixing ratio as a function of altitude and time throughout 1987. Saturation with respect to ice could be maintained for water mixing ratios of 3.5 ppmv for a period of about 80 days from mid-June to mid-September. Dehydration to mixing ratios of 1 ppmv or less was possible sporadically. Data from the ER-2 flights between 53 S and 72 S are used in conjunction with particle size measurements and air parcel trajectories to demonstrate the dehydration occurring over Antarctica. Water mixing ratios at the latitude of Punta Arens (53 S), in conjunction with tracer measurements and trajectory analysis, show that at potential temperatures from about 325 to 400 K, the dryness (less than 3 ppmv) had its origin over Antarctica rather than in the tropics. Water mixing ratios within the Antarctic vortex varied from 1.5 to 3.8 ppmv, with a strong isentropic gradient being evident in the region of high potential vorticity gradients.

Seasonal behavior of NO2 in the winter stratosphere - Inferred NO(x)

NASA Astrophysics Data System (ADS)

Zawodny, J. M.; Rusch, D. W.

1986-04-01

An analysis is performed of Solar Mesosphere Explorer (SME) data for the first 90 days of 1982, when a trend of increasing NO2 content in the stratosphere near the 10 mbar pressure level was detected. A photochemical-dynamical model is developed to account for the observed densities, which were also detected with ground-based instrumentation. The model calculations indicated that partitioning of the NO(x) family from N2O5 to NO2 was responsible for the trend. The new partitioning requires a lowering of the mixing ratio of NO(x), which was also observed. Finally, the SME data also confirmed that the enhanced NO2 concentrations were dependent on the solar zenith angle.

AASE-2 In-Situ Tracer Correlations of Methane Nitrous Oxide and Ozone as Observed Aboard the DC-8

NASA Technical Reports Server (NTRS)

Collins, J. E., Jr.; Sachse, G. W.; Anderson, B. E.; Weinheimer, A. J.; Walgea, J. G.; Ridley, B. A.

1993-01-01

We report in situ stratospheric measurements of CH4, N2O, and O3 obtained aboard the NASA DC-8 during the January-March 1992 Airborne Arctic Stratospheric Expedition II field campaign. These data demonstrate a strong linear correlation between N2O and CH4 in the lower stratosphere thus indicating that both species are effective tracers of stratospheric air motion. Measurements of both species on constant geometric height surfaces indicate that significant subsidence of the arctic stratospheric air mass occurred at DC-8 altitudes over the course of the AASE-II expedition. In addition, a widespread reduction in O3 mixing ratios (up to 20%) relative to these conserved tracers was also observed in the lower stratosphere in March a compared to January and February results.

Proper interpretation of dissolved nitrous oxide isotopes, production pathways, and emissions requires a modelling approach.

PubMed

Thuss, Simon J; Venkiteswaran, Jason J; Schiff, Sherry L

2014-01-01

Stable isotopes ([Formula: see text]15N and [Formula: see text]18O) of the greenhouse gas N2O provide information about the sources and processes leading to N2O production and emission from aquatic ecosystems to the atmosphere. In turn, this describes the fate of nitrogen in the aquatic environment since N2O is an obligate intermediate of denitrification and can be a by-product of nitrification. However, due to exchange with the atmosphere, the [Formula: see text] values at typical concentrations in aquatic ecosystems differ significantly from both the source of N2O and the N2O emitted to the atmosphere. A dynamic model, SIDNO, was developed to explore the relationship between the isotopic ratios of N2O, N2O source, and the emitted N2O. If the N2O production rate or isotopic ratios vary, then the N2O concentration and isotopic ratios may vary or be constant, not necessarily concomitantly, depending on the synchronicity of production rate and source isotopic ratios. Thus prima facie interpretation of patterns in dissolved N2O concentrations and isotopic ratios is difficult. The dynamic model may be used to correctly interpret diel field data and allows for the estimation of the gas exchange coefficient, N2O production rate, and the production-weighted [Formula: see text] values of the N2O source in aquatic ecosystems. Combining field data with these modelling efforts allows this critical piece of nitrogen cycling and N2O flux to the atmosphere to be assessed.

Synthesis of lithium mangan dioxide (LiMn2O4) for lithium-ion battery cathode from various lithium sources

NASA Astrophysics Data System (ADS)

Priyono, S.; Ginting, N. R.; Humaidi, S.; Subhan, A.; Prihandoko, B.

2018-03-01

LiMn2O4 as a cathode material has been synthesized via solid state reaction. The synthesis has been done by varying lithium sources such as LiOH.H2O and Li2CO3 while MnO2 was used as Mn sources. All raw materials were mixed stoichiometrically to be the precursors of LiMn2O4. The precursors were sintered using high temperature furnace at 800 °C for 4 hours in atmospheric condition to form final product. The final products were sieved to separate the finer and smoother particles from the coarse ones. The products were characterized by X-Ray Diffractometer (XRD) to identify phases and crystal structure. The peak wave number was also determined using Fourier Transform Infra Red (FTIR) to find functional group. LiMn2O4 sheets were prepared by mixing active material with polyvinylidene fluoride (PVdF) and acetylene black (AB) in mass ratio of 85:10:5 wt.% in N,N-Dimethylacetamide (DMAc) solvents to form slurry. The slurry was then coated onto Al foil with thickness of about 0.15 mm and dried in an oven. LiMn2O4 sheet was cut into circular discs and arranged with separator, metallic lithium, and electrolyte in a coin cell. Automatic battery cycler was used to measure electrochemical performance and specific capacity of the cell. XRD analysis showed that sample synthesized with Li2CO3 has higher crystallinity and more pristine than sample synthesized with LiOH.H2O. FTIR analysis revealed that both of samples have identical functional group but sample with Li2CO3 source tend to degrade. Cyclic voltammetry data gave information that sample with LiOH.H2O source has better electrochemical performance. It showed double oxidation/reduction peaks more clearly but sample with Li2CO3 source has higher specific capacity (64.78 mAh/g) than sample with LiOH.H2O (50 mAh/g).

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

NASA Astrophysics Data System (ADS)

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

2016-01-01

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

Effect of cooling rate on achieving thermodynamic equilibrium in uranium-plutonium mixed oxides

NASA Astrophysics Data System (ADS)

Vauchy, Romain; Belin, Renaud C.; Robisson, Anne-Charlotte; Hodaj, Fiqiri

2016-02-01

In situ X-ray diffraction was used to study the structural changes occurring in uranium-plutonium mixed oxides U1-yPuyO2-x with y = 0.15; 0.28 and 0.45 during cooling from 1773 K to room-temperature under He + 5% H2 atmosphere. We compare the fastest and slowest cooling rates allowed by our apparatus i.e. 2 K s-1 and 0.005 K s-1, respectively. The promptly cooled samples evidenced a phase separation whereas samples cooled slowly did not due to their complete oxidation in contact with the atmosphere during cooling. Besides the composition of the annealing gas mixture, the cooling rate plays a major role on the control of the Oxygen/Metal ratio (O/M) and then on the crystallographic properties of the U1-yPuyO2-x uranium-plutonium mixed oxides.

Hydrazinium lanthanide oxalates: synthesis, structure and thermal reactivity of N2H5[Ln2(C2O4)4(N2H5)]·4H2O, Ln = Ce, Nd.

PubMed

De Almeida, Lucie; Grandjean, Stéphane; Rivenet, Murielle; Patisson, Fabrice; Abraham, Francis

2014-03-28

New hydrazinium lanthanide oxalates N2H5[Ln2(C2O4)4(N2H5)]·4H2O, Ln = Ce (Ce-HyOx) and Nd (Nd-HyOx), were synthesized by hydrothermal reaction at 150 °C between lanthanide nitrate, oxalic acid and hydrazine solutions. The structure of the Nd compound was determined from single-crystal X-ray diffraction data, space group P2₁/c with a = 16.315(4), b = 12.127(3), c = 11.430(2) Å, β = 116.638(4)°, V = 2021.4(7) Å(3), Z = 4, and R1 = 0.0313 for 4231 independent reflections. Two distinct neodymium polyhedra are formed, NdO9 and NdO8N, an oxygen of one monodentate oxalate in the former being replaced by a nitrogen atom of a coordinated hydrazinium ion in the latter. The infrared absorption band at 1005 cm(-1) confirms the coordination of N2H5(+) to the metal. These polyhedra are connected through μ2 and μ3 oxalate ions to form an anionic three-dimensional neodymium-oxalate arrangement. A non-coordinated charge-compensating hydrazinium ion occupies, with water molecules, the resulting tunnels. The N-N stretching frequencies of the infrared spectra demonstrate the existence of the two types of hydrazine ions. Thermal reactivity of these hydrazinium oxalates and of the mixed isotypic Ce/Nd (CeNd-HyOx) oxalate were studied by using thermogravimetric and differential thermal analyses coupled with gas analyzers, and high temperature X-ray diffraction. Under air, fine particles of CeO2 and Ce(0.5)Nd(0.5)O(1.75) are formed at low temperature from Ce-HyOx and CeNd-HyOx, respectively, thanks to a decomposition/oxidation process. Under argon flow, dioxymonocyanamides Ln2O2CN2 are formed.

Paired N and O isotopic analysis of nitrate and nitrite in the Arabian Sea oxygen deficient zone

NASA Astrophysics Data System (ADS)

Martin, T. S.; Casciotti, K. L.

2017-03-01

The Arabian Sea is home to one of the three main oceanic oxygen deficient zones (ODZs). We present paired nitrogen (N) and oxygen (O) isotope measurements of nitrate (NO3-) and nitrite (NO2-) from the central Arabian Sea in order to understand the effects of N biogeochemistry on the distribution of these species in the low oxygen waters. Within the ODZ, NO2- accumulated in a secondary NO2- maximum (SNM), though the shape and magnitude of the SNM, along with the isotopic composition of NO3- and NO2-, were highly dependent on the location within the ODZ. We also explored water mass mixing within the Arabian Sea as an explanatory factor in the distribution of NO2- in the SNM. The intrusion of Persian Gulf Water at depth may influence the shape of the NO2- peak by introducing small amounts of dissolved oxygen (O2), favoring NO2- oxidation. There was also evidence that vertical mixing may play a role in shaping the top of the SNM peak. Finally, we present evidence for NO2- oxidation and NO2- reduction co-occurring within the ODZ, as has been previously suggested in the Arabian Sea, as well as in other ODZs. The decoupling of the N and O isotopes of NO3-, deviating from the expected 1:1 ratio for dissimilatory NO3- reduction, indicates that NO2- oxidation has a significant influence on the isotopic composition of NO3-. Additionally, the N isotopes of NO2- were generally fit well by Rayleigh curves for NO2- oxidation. However, the removal of dissolved inorganic nitrogen (DIN) within the domain reflects the importance of NO2- reduction to N2.

Low temperature synthesis of polyaniline-crystalline TiO2-halloysite composite nanotubes with enhanced visible light photocatalytic activity.

PubMed

Li, Cuiping; Wang, Jie; Guo, Hong; Ding, Shujiang

2015-11-15

A series of one-dimensional polyaniline-crystalline TiO2-halloysite composite nanotubes with different mass ratio of polyaniline to TiO2 are facilely prepared by employing the low-temperature synthesis of crystalline TiO2 on halloysite nanotubes. The halloysite nanotubes can adsorb TiO2/polyaniline precursors and induce TiO2 nanocrystals/polyaniline to grow on the support in situ simultaneously. By simply adjusting the acidity of reaction system, PANI-crystalline TiO2-HA composite nanotubes composed of anatase, a mixed phase TiO2 and different PANI redox state are obtained. The XRD and UV-vis results show that the surface polyaniline sensitization has no effect on the crystalline structure of halloysite and TiO2 and the light response of TiO2 is extended to visible-light regions. Photocatalysis test results reveal the photocatalytic activity will be affected by the pH value and the volume ratio of ANI to TTIP. The highest photocatalytic activity is achieved with the composite photocatalysts prepared at pH 0.5 and 1% volume ratio of ANI and TTIP owing to the sensitizing effect of polyaniline and the charge transfer from the photoexcited PANI sensitizer to TiO2. Moreover, the PANI-TiO2-HA composite nanotubes synthesized by one-step at pH 0.5 with 1% volume ratio of ANI to TTIP exhibit higher visible light photocatalytic activity than those synthesized by the two-step. Heterogeneous PANI-TiO2-HA composite nanotubes prepared at pH 0.5 exhibit a higher degradation activity than that prepared at pH 1.5. The redoped experiment proves that the PANI redox state plays the main contribution to the enhanced visible light catalytic degradation efficiency of PANI-TiO2-HA prepared at pH 0.5. Furthermore, the heterogeneous PANI-crystalline TiO2-HA nanotubes have good photocatalytic stability and can be reused four times with only gradual loss of activity under visible light irradiation. Copyright © 2015 Elsevier Inc. All rights reserved.

The role of magma mixing in the petrogenesis of mafic alkaline lavas, Rockeskyllerkopf Volcanic Complex, West Eifel, Germany

NASA Astrophysics Data System (ADS)

Shaw, Cliff S. J.; Woodland, Alan B.

2012-03-01

The quaternary Rockeskyllerkopf Volcanic Complex (RVC) comprises three spatially and temporally distinct volcanic centers that can also be distinguished on the basis of their geochemical signatures. All the volcanic products in the complex are olivine basanites whose major and trace element compositions span almost the entire range defined for the West Eifel field as a whole. The RVC lavas have lower Al2O3, Na2O and Y contents and higher TiO2, CaO, K2O, Sc, V, Co, Rb, and Ba than the Tertiary lavas in nearby Hocheifel volcanic field. Within the complex, the oldest South East Lammersdorf Center (SEL) comprises primitive lavas with an average MgO content of ˜11 wt.% and LaN/YbN of 29 ± 2. The second center, Mäuseberg, has similar MgO to SEL but is distinct in its much higher LaN/YbN of 42 ± 2. The Rockeskyllerkopf Center, which was erupted after a break in activity, comprises lavas similar in composition to the SEL Center but with distinctly higher Al2O3 and lower MgO contents. Given the lack of evidence for significant fractionation or assimilation in the RVC lavas, we attribute the compositional variations within and between the centers of the RVC to be due to variations in the composition of the source region in combination with magma mixing. Our preferred model involves 1-5% partial melting of LREE-enriched mantle in the garnet stability field, likely within the thermal boundary layer at the base of the lithospheric mantle. These melts mixed to variable degrees with 2-4% partial melts of phlogopite-spinel peridotite formed at higher levels in the modally metasomatised lithospheric mantle.

Theoretical Design and Experimental Evaluation of Molten Carbonate Modified LSM Cathode for Low Temperature Solid Oxide Fuel Cells

DTIC Science & Technology

2012-01-01

Li-K binary eutectic salts were prepared for infiltration. Li2CO3 (99%, Alfa Aesar) and K2CO3 (99%, Alfa Aesar) were mixed with a molar ratio of 62:38...99.9%, Alfa Aesar) were also prepared. For infiltration, the eutectic melt was ultrasonic dispersed in ethanol. A few drops of the salt suspension...and heated at 650 oC for 2 h to form a eutectic melt. In addition, eutectic melts containing 0.5 mol % La2O3 (99.9%, Alfa Aesar) or 0.5 mol % Gd2O3

Influence of the physico-chemical properties of CeO 2-ZrO 2 mixed oxides on the catalytic oxidation of NO to NO 2

NASA Astrophysics Data System (ADS)

Atribak, Idriss; Guillén-Hurtado, Noelia; Bueno-López, Agustín; García-García, Avelina

2010-10-01

Commercial and home-made Ce-Zr catalysts prepared by co-precipitation were characterised by XRD, Raman spectroscopy, N 2 adsorption at -196 °C and XPS, and were tested for NO oxidation to NO 2. Among the different physico-chemical properties characterised, the surface composition seems to be the most relevant one in order to explain the NO oxidation capacity of these Ce-Zr catalysts. As a general trend, Ce-Zr catalysts with a cerium-rich surface, that is, high XPS-measured Ce/Zr atomic surface ratios, are more active than those with a Zr-enriched surface. The decrease in catalytic activity of the Ce-Zr mixed oxided upon calcinations at 800 °C with regard to 500 °C is mainly attributed to the decrease in Ce/Zr surface ratio, that is, to the surface segregation of Zr. The phase composition (cubic or t'' for Ce-rich compositions) seems not to be a direct effect on the catalytic activity for NO oxidation in the range of compositions tested. However, the formation of a proper solid solution prevents important surface segregation of Zr upon calcinations at high temperature. The effect of the BET surface area in the catalytic activity for NO oxidation of Ce-Zr mixed oxides is minor in comparison with the effect of the Ce/Zr surface ratio.

Source apportionment of methane and nitrous oxide in California's San Joaquin Valley at CalNex 2010 via positive matrix factorization

NASA Astrophysics Data System (ADS)

Guha, A.; Gentner, D. R.; Weber, R. J.; Provencal, R.; Goldstein, A. H.

2015-10-01

Sources of methane (CH4) and nitrous oxide (N2O) were investigated using measurements from a site in southeast Bakersfield as part of the CalNex (California at the Nexus of Air Quality and Climate Change) experiment from mid-May to the end of June 2010. Typical daily minimum mixing ratios of CH4 and N2O were higher than daily minima that were simultaneously observed at a mid-oceanic background station (NOAA, Mauna Loa) by approximately 70 ppb and 0.5 ppb, respectively. Substantial enhancements of CH4 and N2O (hourly averages > 500 and > 7 ppb, respectively) were routinely observed, suggesting the presence of large regional sources. Collocated measurements of carbon monoxide (CO) and a range of volatile organic compounds (VOCs) (e.g., straight-chain and branched alkanes, cycloalkanes, chlorinated alkanes, aromatics, alcohols, isoprene, terpenes and ketones) were used with a positive matrix factorization (PMF) source apportionment method to estimate the contribution of regional sources to observed enhancements of CH4 and N2O. The PMF technique provided a "top-down" deconstruction of ambient gas-phase observations into broad source categories, yielding a seven-factor solution. We identified these emission source factors as follows: evaporative and fugitive; motor vehicles; livestock and dairy; agricultural and soil management; daytime light and temperature driven; non-vehicular urban; and nighttime terpene biogenics and anthropogenics. The dairy and livestock factor accounted for the majority of the CH4 (70-90 %) enhancements during the duration of experiments. The dairy and livestock factor was also a principal contributor to the daily enhancements of N2O (60-70 %). Agriculture and soil management accounted for ~ 20-25 % of N2O enhancements over a 24 h cycle, which is not surprising given that organic and synthetic fertilizers are known to be a major source of N2O. The N2O attribution to the agriculture and soil management factor had a high uncertainty in the conducted bootstrapping analysis. This is most likely due to an asynchronous pattern of soil-mediated N2O emissions from fertilizer usage and collocated biogenic emissions from crops from the surrounding agricultural operations that is difficult to apportion statistically when using PMF. The evaporative/fugitive source profile, which resembled a mix of petroleum operation and non-tailpipe evaporative gasoline sources, did not include a PMF resolved-CH4 contribution that was significant (< 2 %) compared to the uncertainty in the livestock-associated CH4 emissions. The uncertainty of the CH4 estimates in this source factor, derived from the bootstrapping analysis, is consistent with the ~ 3 % contribution of fugitive oil and gas emissions to the statewide CH4 inventory. The vehicle emission source factor broadly matched VOC profiles of on-road exhaust sources. This source factor had no statistically significant detected contribution to the N2O signals (confidence interval of 3 % of livestock N2O enhancements) and negligible CH4 (confidence interval of 4 % of livestock CH4 enhancements) in the presence of a dominant dairy and livestock factor. The CalNex PMF study provides a measurement-based assessment of the state CH4 and N2O inventories for the southern San Joaquin Valley (SJV). The state inventory attributes ~ 18 % of total N2O emissions to the transportation sector. Our PMF analysis directly contradicts the state inventory and demonstrates there were no discernible N2O emissions from the transportation sector in the southern SJV region.

Nondestructive and continuous monitoring of oxygen levels in modified atmosphere packaged ready-to-eat mixed salad products using optical oxygen sensors, and its effects on sensory and microbiological counts during storage.

PubMed

Hempel, A; O'Sullivan, M G; Papkovsky, D B; Kerry, J P

2013-07-01

The objective of this study was to determine the percentage oxygen consumption of fresh, respiring ready-to-eat (RTE) mixed leaf salad products (Iceberg salad leaf, Caesar salad leaf, and Italian salad leaf). These were held under different modified atmosphere packaging (MAP) conditions (5% O2 , 5% CO2 , 90% N2 (MAPC-commercial control), 21% O2 , 5% CO2 , 74% N2 (MAP 1), 45% O2 , 5% CO2 , 50% N2 (MAP 2), and 60% O2 , 5% CO2 , 35% N2 (MAP 3)) and 4 °C for up to 10 d. The quality and shelf-life stability of all packaged salad products were evaluated using sensory, physiochemical, and microbial assessment. Oxygen levels in all MAP packs were measured on each day of analysis using optical oxygen sensors allowing for nondestructive assessment of packs. Analysis showed that with the exception of control packs, oxygen levels for all MAP treatments decreased by approximately 10% after 7 d of storage. Oxygen levels in control packs were depleted after 7 d of storage. This appears to have had no detrimental effect on either the sensory quality or shelf-life stability of any of the salad products investigated. Additionally, the presence of higher levels of oxygen in modified atmosphere packs did not significantly improve product quality or shelf-life stability; however, these additional levels of oxygen were freely available to fresh respiring produce if required. This study shows that the application of optical sensors in MAP packs was successful in nondestructively monitoring oxygen level, or changes in oxygen level, during refrigerated storage of RTE salad products. © 2013 Institute of Food Technologists®

2,4,6-Tri-amino-1,3,5-triazin-1-ium 3-(prop-2-eno-yloxy)propano-ate acrylic acid monosolvate monohydrate.

PubMed

Sangeetha, V; Kanagathara, N; Chakkaravarthi, G; Marchewka, M K; Anbalagan, G

2013-05-01

The asymmetric unit of the title salt, C3H7N6 (+)·C6H7O4 (-)·C3H4O2·H2O, contains a 2,4,6-tri-amino-1,3,5-triazin-1-ium cation, a 3-(prop-2-eno-yloxy)propano-ate anion and acrylic acid and water solvent mol-ecules in a 1:1:1:1 ratio and with each species in a general position. In the crystal, the components are linked into a supra-molecular layer in the bc plane via a combination of O-H⋯O, N-H⋯N and N-H⋯O hydrogen bonding. The crystal studied was a non-merohedral twin, the minor component contribution being approximately 26%.

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

DOEpatents

Berry, Gregory F.

1988-01-01

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

Discrete hexamer water clusters and 2D water layer trapped in three luminescent Ag/tetramethylpyrazine/benzene-dicarboxylate hosts: 1D chain, 2D layer and 3D network

NASA Astrophysics Data System (ADS)

Mei, Hong-Xin; Zhang, Ting; Huang, Hua-Qi; Huang, Rong-Bin; Zheng, Lan-Sun

2016-03-01

Three mix-ligand Ag(I) coordination compounds, namely, {[Ag10(tpyz) 5(L1) 5(H2 O)2].(H2 O)4}n (1, tpyz = 2,3,4,5-tetramethylpyrazine, H2 L1 = phthalic acid), [Ag4(tpyz) 2(L2) 2(H2 O)].(H2 O)5}n (2, H2 L2 = isophthalic acid) {[Ag2(tpyz) 2(L3) (H2 O)4].(H2 O)8}n (3, H2 L3 = terephthalic acid), have been synthesized and characterized by elemental analysis, IR, PXRD and X-ray single-crystal diffraction. 1 exhibits a 2D layer which can be simplified as a (4,4) net. 2 is a 3D network which can be simplified as a (3,3)-connected 2-nodal net with a point symbol of {102.12}{102}. 3 consists of linear [Ag(tpyz) (H2 O)2]n chain. Of particular interest, discrete hexamer water clusters were observed in 1 and 2, while a 2D L10(6) water layer exists in 3. The results suggest that the benzene dicarboxylates play pivotal roles in the formation of the different host architectures as well as different water aggregations. Moreover, thermogravimetric analysis (TGA) and emissive behaviors of these compounds were investigated.

Novel Electronically Conducting Tellurium Oxides

NASA Astrophysics Data System (ADS)

Subramanian, Mas; Siritanon, Theerunan; Sleight, Arthur

2010-03-01

Tellurium oxides seldom show measurable electronic conductivity. Tellurium oxides that appear to have Te^5+ contain Te^4+ and Te^6+ in two distinct crystallographic sites and are electronic insulators. Here we report on the synthesis and characterization of several new tellurium rich oxides of the general formula, CsMxTe2-xO6, crystallizing in modified pyrochlore structure. Most of the compounds reported here are black in color with some exhibiting good electronic conductivities (2 S/cm) and Seebeck measurements indicate all are n-type. The observation of high electronic conductivities in compounds like CsGe0.5Te1.5O6, CsAl0.33Te1.67O6 confirms that observed conductivity is arising from doping of electrons into the empty 5s orbitals of Te^6+. This reduction is apparently accompanied with some small deviation from the ideal formula: oxygen content and/or ratio of cations on octahedral sites. This is in consistent with single-crystal X-ray as well as powder neutron diffraction structure refinements and the observed sign of the Seebeck coefficient. To our knowledge, this is a first observance of high electrical conductivity in mixed valent tellurium oxides.

Towards efficient and cost-effective inverted hybrid organic solar cells using inorganic semiconductor in the active layer

NASA Astrophysics Data System (ADS)

Imran, M.; Ikram, M.; Dilpazir, S.; Nafees, M.; Ali, S.; Geng, J.

2017-11-01

The article investigates the effects of NiO (p-type) and TiO2 (n-type) nanoparticles (NPs) on the performance of poly(3-hexylthiophene) (P3HT) and (phenyl-C61-butyric acid methylester) (PCBM) based devices with an inverse geometry. Various weight ratios of these nanoparticles were mixed in the polymer solution using 1,2-dichlorobenzene as solvent. An optimal amount of NPs-doped active layer exhibited higher power conversion efficiency (PCE) of 3.85% as compared to the reference cell, which exhibited an efficiency of 3.40% under white light illumination intensity of 100 mW/cm2. Enhanced PCE originates from increased film roughness and light harvesting due to increased absorption range upon mixing an optimal amount of NPs in the organic-based active layer. Further addition of NiO and TiO2 concentration relative to PCBM resulted in significant agglomeration of nanoparticles leading to degraded device parameters.

Ground-high altitude joint detection of ozone and nitrogen oxides in urban areas of Beijing.

PubMed

Chen, Pengfei; Zhang, Qiang; Quan, Jiannong; Gao, Yang; Zhao, Delong; Meng, Junwang

2013-04-01

Based on observational data of ozone (O3) and nitrogen oxide (NO(x)) mixing ratios on the ground and at high altitude in urban areas of Beijing during a period of six days in November 2011, the temporal and spatial characteristics of mixing ratios were analyzed. The major findings include: urban O3 mixing ratios are low and NO(x) mixing ratios are always high near the road in November. Vertical variations of the gases are significantly different in and above the planetary boundary layer. The mixing ratio of O3 is negatively correlated with that of NO(x) and they are positively correlated with air temperature, which is the main factor directly causing vertical variation of O3 and NO(x) mixing ratios at 600-2100 m altitude. The NO(x) mixing ratios elevated during the heating period, while the O3 mixing ratios decreased: these phenomena are more significant at high altitudes compared to lower altitudes. During November, air masses in the urban areas of Beijing are brought by northwesterly winds, which transport O3 and NO(x) at low mixing ratios. Due to Beijing's natural geographical location, northwest air currents are beneficial to the dilution and dispersion of pollutants, which can result in lower O3 and NO(x) background values in the Beijing urban area.

Up-converted ultraviolet luminescence of Er3+:BaGd2ZnO5 phosphors for healthy illumination

NASA Astrophysics Data System (ADS)

Zhang, Ya; Cui, Qingzhi; Wang, Zhanyong; Liu, Gan; Tian, Tian; Xu, Jiayue

2016-09-01

Moderate level of exposure to the solar irradiation containing UV component is essential for health care. To incorporate the UV-emitting phosphors into the commercial YAG-based white light-emitting diode introduces the possibilities of healthy illumination to individuals' daily lives. 1 mol.% Er3+-doped BaGd2ZnO5 (BGZ) particles were synthesized via sol-gel method and efficient up-converted luminescence peaked at 380 nm was detected under 480 nm excitation. The mixed phosphors with varied mass ratio of Er3+:BGZ and Ce3+:YAG particles were encapsulated to form LEDs. The study of the LEDs indicated that the introduction of BGZ component favored the enhancement of color-rendering index and the neutralization of the white light emitting. The WLED with the BGZ/YAG ratio of 8:2 was recommendable for its excellent overall white light luminous performances and UV intensity of 84.55 mW/cm2. The UV illumination dose of the WLEDs with mixed YAG and BGZ was controllable by adjusting the ratio, the illumination distance and the illumination time. Er3+:BGZ phosphors are promising UVemitting phosphors for healthy indoor illumination.

High Static Stability in the Mixed Layer Above the Extratropical Tropopause

NASA Astrophysics Data System (ADS)

Kunz, A.; Konopka, P.; Müller, R.; Schiller, C.

2008-12-01

A strong relationship between the static stability N2 and the strength of mixing in the mixed layer above the extratropical tropopause is evident from in-situ data observed during the SPURT aircraft campaigns. We present a method for quantifying the strength of mixing from O3/CO tracer correlations and we find that N2 is positively correlated with the strength of mixing. Age of air simulations with the CLaMS model reveal two different types of mixed regions. One type consisting of older airmasses with higher values of N2 which are created by radiative adjustment after a mixing event. These airmasses are within the TIL (Tropopause Inversion Layer), considering the TIL as part of the mixing layer. The second type comprises younger airmasses with somehow lower stratospheric N2 values within the mixing layer, because of recent intrusion processes due to the permeability or so-called mid-latitude-breaks associated with the jet stream. With the help of radiative transfer calculations we simulate the influence of trace gases such as O3 and H2O on the temperature gradient and thus on the static stability above the tropopause in the idealized case of non-mixing (L-shape) O3 and H2O profiles and in the reference case of mixed profiles. Within the altitude range of the SPURT campaigns the mean vertical SPURT profiles are used as reference, which are fitted to the HALOE climatological profiles above the UT/LS.

(E)-4-Meth-oxy-N'-(2,4,5-tri-meth-oxy-benzyl-idene)benzohydrazide hemihydrate.

PubMed

Chantrapromma, Suchada; Boonnak, Nawong; Horkaew, Jirapa; Quah, Ching Kheng; Fun, Hoong-Kun

2014-02-01

The title compound crystallizes as a hemihydrate, C18H20N2O5·0.5H2O. The mol-ecule exists in an E conformation with respect to the C=N imine bond. The 4-meth-oxy-phenyl unit is disordered over two sets of sites with a refined occupancy ratio of 0.54 (2):0.46 (2). The dihedral angles between the benzene rings are 29.20 (9) and 26.59 (9)°, respectively, for the major and minor components of the 4-meth-oxy-substituted ring. All meth-oxy substituents lie close to the plane of the attached benzene rings [the Cmeth-yl-O-C-C torsion angles range from -4.0 (12) to 3.9 (2)°]. In the crystal, the components are linked into chains propagating along [001] via N-H⋯O and O-H⋯O hydrogen bonds and weak C-H⋯O inter-actions.

Gaseous emission during the composting of pig feces from Chinese Ganqinfen system.

PubMed

Jiang, Tao; Schuchardt, Frank; Li, Guo Xue; Guo, Rui; Luo, Yi Ming

2013-01-01

The Ganqinfen system - a process of manually cleaning animal feces by means of a shovel - is a widely used manure separating method in Chinese pig farms. Ganqinfen pig feces and chopped corn stalks were mixed at the ratio of 7:1, and composted in 1.5 m(3) rotting boxes for 70 d. Evolution of CH(4), N(2)O and NH(3) during composting, and the effects of turning and covering, were studied in this research. Results showed that 20-39% and 0.5-4% of total nitrogen were lost in the form of NH(3) and N(2)O respectively, and 0.1-0.9% of initial organic carbon was emitted as CH(4). Turning enhanced air exchange in the piles, thus decreasing CH(4) emission by 83-93% and shortening the maturing period. When trials were finished, all non-turned piles were separated to three layers by moisture content. This structure caused the N(2)O losses of non-turning treatments to be 6-12.7 times higher than that of turning treatments. Covering materials reduced air exchange at the surface of the pile, thus decreasing the O(2) supply and consequently increasing CH(4) production by 33-45%. Covering also reduced NH(3) emission by 4-34%. For the composting of Ganqinfen pig feces, we suggest that a program of turning twice weekly without covering will result in compost that is sufficiently matured after 6 wk with the lowest resultant greenhouse gas emission. Copyright © 2012. Published by Elsevier Ltd.

Construction of fiber-shaped silver oxide/tantalum nitride p-n heterojunctions as highly efficient visible-light-driven photocatalysts.

PubMed

Li, Shijie; Hu, Shiwei; Xu, Kaibing; Jiang, Wei; Liu, Yu; Leng, Zhe; Liu, Jianshe

2017-10-15

Constructing novel and efficient p-n heterojunction photocatalysts has stimulated great interest. Herein, we report the design and synthesis of fiber-shaped Ag 2 O/Ta 3 N 5 p-n heterojunctions as a kind of efficient photocatalysts. Ta 3 N 5 nanofibers were prepared by an electrospinning-calcination-nitridation method, and then the in-situ anchoring of Ag 2 O on their surfaces was realized by a facile deposition method. The resulting Ag 2 O/Ta 3 N 5 heterojunctions were comprised of porous Ta 3 N 5 nanofibers (diameter: ∼150nm) and Ag 2 O nanoparticles (size: ∼12nm). The photocatalytic activity of these heterojunctions were studied by decomposing rhodamine B (RhB) dye and tetracycline (TC) antibiotic under visible light (λ>400nm). In all the samples, the heterojunction with Ag 2 O/Ta 3 N 5 molar ratio of 0.2/1 displays the best activity. It is found that a synergistic effect contributes to the effective suppression of charges recombination between Ta 3 N 5 and Ag 2 O, leading to an enhanced photocatalytic activity with good stability. The photogenerated holes (h + ) and superoxide radicals (O 2 - ) play dominant roles in the photocatalytic process. These p-n heterojunctions will have great potential for environmental remediation because of the facile preparation process and exceptional photocatalytic activity. Copyright © 2017 Elsevier Inc. All rights reserved.

Group-12 metal complexes with isomeric 1-(diphenylphosphino)-1'-[N-(pyridylmethyl)carbamoyl]ferrocenes: coordination polymers vs. finite multinuclear coordination assemblies.

PubMed

Kühnert, Janett; Císarová, Ivana; Lamac, Martin; Stepnicka, Petr

2008-05-14

The isomeric ferrocene phosphine-carboxamides, 1-(diphenylphosphino)-1'-{[N-(2-pyridyl)-methyl]carbamoyl}ferrocene (1) and 1-(diphenylphosphino)-1'-{[N-(4-pyridyl)methyl]carbamoyl}ferrocene (2) have been studied as ligands in group-12 metal bromide complexes. The reactions of 1 with CdBr2 x 4H2O and HgBr(2) at 1:1 mole ratio gave the discrete tetracadmium complex [Cd2(micro-Br)2(-1kappa2O,N2)2[micro-1kappa2O,N2:2kappaP-(C5H4N)CH2NHC(O)fcPPh2-CdBr3]2] (7; fc = ferrocene-1,1'-diyl) and the halogeno-bridged dimer [[Hg(micro-Br)Br(-kappaP)]2] (8), respectively. In the presence of acetic acid, the CdBr2-1 system furnished a zwitterionic complex featuring protonated 1 as the P-monodentate donor, [CdBr3[Ph2PfcC(O)NHCH2(C5H4NH)-kappaP

Water vapor in the middle atmosphere of Mars during the 2007 global dust storm

NASA Astrophysics Data System (ADS)

Fedorova, Anna; Bertaux, Jean-Loup; Betsis, Daria; Montmessin, Franck; Korablev, Oleg; Maltagliati, Luca; Clarke, John

2018-01-01

Recent observations of the Martian hydrogen corona in the UV H Ly-alpha emission by the Hubble Space Telescope (HST) (Clarke et al., 2014) and the SPICAM UV spectrometer on Mars Express (Chaffin et al., 2014) reported its rapid change by an order of magnitude over a short few months period in 2007 (MY28), which is inconsistent with the existing models. One proposed explanation of the observed increase of the coronal emission is that during the global dust storm water vapor from the lower atmosphere can be transported to higher altitudes, where its photodissociation rate by near-UV sunlight increases, providing an additional source of hydrogen for the upper atmosphere. In this work we study the water vapor vertical distribution in the middle atmosphere of Mars during the 2007 global dust storm based on solar occultation measurements by the SPICAM IR spectrometer onboard the Mars-Express spacecraft. The vertical profiles of H2O density and mixing ratio have been obtained for solar longitudes Ls = 255°-300° in MY28. In the Northern hemisphere from Ls = 268° to Ls = 285° the H2O density at altitudes of 60-80 km increased by an order of magnitude. During the dust storm the profiles extended up to 80 km, with an H2O density exceeding 1010 molecules/cm3 (mixing ratio ≥200 ppm). Two maxima of the H2O density were detected. The largest H2O densities observed at latitudes higher than 60°N, over Ls = 269°-275°, do not directly correlate with the aerosol loading and likely relate to the downwelling branch of the meridional circulation that was intensified during the dust storm, and transported water from the Southern hemisphere to high northern latitudes. The second smaller maximum coincides with the high dust loading at middle northern latitudes. The comparison with geographically close observations in the quiet Mars year MY32, when the H2O content in the Northern hemisphere did not exceed 2 × 1010 molecules/cm3 and 50 ppm at 60 km, showed that the global dust storm was a unique event. The situation was different in the Southern hemisphere. During the dust storm the water density at 50-80 km increased by a factor of 4-5 with a mixing ratio >100 ppm, well correlated with the aerosol vertical extension. A somewhat weaker increase of the H2O density by a factor of 2-3 with a mixing ratio > 100 ppm was also observed during MY32 starting from Ls = 260°, suggesting a seasonal repeatability. The observed amount of water at high altitudes in both hemispheres can produce a large increase in the H escape rate on a timescale of weeks, as was shown in the photochemical modeling by Chaffin et al. (2017). Future modeling would be necessary to separate the seasonal and the dust storm contributions to the hydrogen escape.

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

PubMed

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

2017-09-01

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

Syntheses, characterization and antioxidant activity studies of mixed-ligand copper(II) complexes of 2,2‧-bipyridine and glycine: The X-ray crystal structure of [Cu(BPy)(Gly)]ClO4

NASA Astrophysics Data System (ADS)

Ibrahim, Mohamed M.; Ramadan, Abd El-Motaleb M.; Shaban, Shaban Y.; Mersal, Gaber A. M.; El-Shazly, Samir A.; Al-Juaid, Salih

2017-04-01

A series of mixed-ligand complexes, viz., [CuLL'X]Y {L = bipyridine; L' = glycine; X = 0, Y = ClO4- (1); X = Cl, Y = 2H2O (2); X = H2O, Y = NO3- (3); X = CH3COO-, Y = H2O (4)} and {[Cu(Gly)(BPy)]2-μ-(SO4)}(5)} have been synthesized and characterized by means of elemental analysis, spectroscopic (FT-IR, UV-Vis and ESR), and thermal analysis, as well as magnetic moment measurements. Spectral and X-ray structural features led to the conclusion that complexes 2-5 have square-pyramidal environments around copper(II) center with coordination chromophores CuN3OCl and CuN3O2, respectively. Whereas complex 1 displays square planar geometry. The quasi-reversible CuII/CuI redox couple slightly improves its reversibility with considerable decrease in current intensity. Additionally, the antioxidant (superoxide dismutase and catalase) biomimetic catalytic activities of the obtained complexes have been tested and found to be promising candidates as dual functional mimic enzyme to serve for complete reactive oxygen species (ROS) detoxification, both with respect to the superoxide radicals and the related peroxides.

Effect of different emission inventories on modeled ozone and carbon monoxide in Southeast Asia

NASA Astrophysics Data System (ADS)

Amnuaylojaroen, T.; Barth, M. C.; Emmons, L. K.; Carmichael, G. R.; Kreasuwun, J.; Prasitwattanaseree, S.; Chantara, S.

2014-12-01

In order to improve our understanding of air quality in Southeast Asia, the anthropogenic emissions inventory must be well represented. In this work, we apply different anthropogenic emission inventories in the Weather Research and Forecasting Model with Chemistry (WRF-Chem) version 3.3 using Model for Ozone and Related Chemical Tracers (MOZART) gas-phase chemistry and Global Ozone Chemistry Aerosol Radiation and Transport (GOCART) aerosols to examine the differences in predicted carbon monoxide (CO) and ozone (O3) surface mixing ratios for Southeast Asia in March and December 2008. The anthropogenic emission inventories include the Reanalysis of the TROpospheric chemical composition (RETRO), the Intercontinental Chemical Transport Experiment-Phase B (INTEX-B), the MACCity emissions (adapted from the Monitoring Atmospheric Composition and Climate and megacity Zoom for the Environment projects), the Southeast Asia Composition, Cloud, Climate Coupling Regional Study (SEAC4RS) emissions, and a combination of MACCity and SEAC4RS emissions. Biomass-burning emissions are from the Fire Inventory from the National Center for Atmospheric Research (NCAR) (FINNv1) model. WRF-Chem reasonably predicts the 2 m temperature, 10 m wind, and precipitation. In general, surface CO is underpredicted by WRF-Chem while surface O3 is overpredicted. The NO2 tropospheric column predicted by WRF-Chem has the same magnitude as observations, but tends to underpredict the NO2 column over the equatorial ocean and near Indonesia. Simulations using different anthropogenic emissions produce only a slight variability of O3 and CO mixing ratios, while biomass-burning emissions add more variability. The different anthropogenic emissions differ by up to 30% in CO emissions, but O3 and CO mixing ratios averaged over the land areas of the model domain differ by ~4.5% and ~8%, respectively, among the simulations. Biomass-burning emissions create a substantial increase for both O3 and CO by ~29% and ~16%, respectively, when comparing the March biomass-burning period to the December period with low biomass-burning emissions. The simulations show that none of the anthropogenic emission inventories are better than the others for predicting O3 surface mixing ratios. However, the simulations with different anthropogenic emission inventories do differ in their predictions of CO surface mixing ratios producing variations of ~30% for March and 10-20% for December at Thai surface monitoring sites.

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

PubMed

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

2014-07-01

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

Construction of (CuX)2n cluster-containing (X = Br, I; n = 1, 2) coordination polymers assembled by dithioethers ArS(CH2)(m)SAr (Ar = Ph, p-Tol; m = 3, 5): effect of the spacer length, aryl group, and metal-to-ligand ratio on the dimensionality, cluster nuclearity, and the luminescence properties of the metal-organic frameworks.

PubMed

Knorr, Michael; Guyon, Fabrice; Khatyr, Abderrahim; Strohmann, Carsten; Allain, Magali; Aly, Shawkat M; Lapprand, Antony; Fortin, Daniel; Harvey, Pierre D

2012-09-17

Reaction of CuI with bis(phenylthio)propane in a 1:1 ratio yields the two-dimensional coordination polymer [{Cu(μ(2)-I)(2)Cu}{μ-PhS(CH(2))(3)SPh}(2)](n) (1). The 2D-sheet structure of 1 is built up by dimeric Cu(2)I(2) units, which are connected via four bridging 1,3-bis(phenylthio)propane ligands. In contrast, treatment of 2 equiv of CuI with 1,3-bis(phenylthio)propane in MeCN solution affords in a self-assembly reaction the strongly luminescent metal-organic 2D-coordination polymer [Cu(4)I(4){μ-PhS(CH(2))(3)Ph}(2)](n) (2), in which cubane-like Cu(4)(μ(3)-I)(4) cluster units are linked by the dithioether ligands. The crystallographically characterized one-dimensional (1D) compound [{Cu(μ(2)-Br)(2)Cu}{μ-PhS(CH(2))(3)SPh}(2)](n) (3) is obtained using CuBr. The outcome of the reaction of PhS(CH(2))(5)SPh with CuI also depends of the metal-to-ligand ratio employed. Mixing CuI and the dithioether in a 2:1 ratio results in formation of [Cu(4)I(4){μ-PhS(CH(2))(5)Ph}(2)](n) (4) in which cubane-like Cu(4)(μ(3)-I)(4) clusters are linked by the bridging dithioether ligand giving rise to a 1D necklace structure. A ribbon-like 1D-polymer with composition [{Cu(μ(2)-I)(2)Cu}{μ-PhS(CH(2))(5)SPh}(2)](n) (5), incorporating rhomboid Cu(2)I(2) units, is produced upon treatment of CuI with 1,5-bis(phenylthio)pentane in a 1:1 ratio. Reaction of CuBr with PhS(CH(2))(5)SPh produces the isomorphous 1D-compound [{Cu(μ(2)-Br)(2)Cu}{μ-PhS(CH(2))(5)SPh}(2)](n) (6). Strongly luminescent [Cu(4)I(4){μ-p-TolS(CH(2))(5)STol-p}(2)](n) (7) is obtained after mixing 1,5-bis(p-tolylthio)pentane with CuI in a 1:2 ratio, and the 2D-polymer [{Cu(μ(2)-I)(2)Cu}(2){μ-p-TolS(CH(2))(5)STol-p}(2)](n) (8) results from reaction in a 1:1 metal-to-ligand ratio. Under the same reaction conditions, 1D-polymeric [{Cu(μ(2)-Br)(2)Cu}{μ-p-TolS(CH(2))(5)STol-p}(2)](n) (9) is formed using CuBr. This study reveals that the structure of the self-assembly process between CuX and ArS(CH(2))(m)SAr ligands is hard to predict. The solid-state luminescence spectra at 298 and 77 K of 2 and 4 exhibit very strong emissions around 535 and 560 nm, respectively, whereas those for 1 and 5 display weaker ones at about 450 nm. The emission lifetimes are longer for the longer wavelength emissions (>1.0 μs arising from the cubane species) and shorter for the shorter wavelength ones (<1.4 μs arising from the rhomboid units). The Br-containing species are found to be weakly fluorescent.

High static stability in the mixing layer above the extratropical tropopause

NASA Astrophysics Data System (ADS)

Kunz, A.; Konopka, P.; Müller, R.; Pan, L. L.; Schiller, C.; Rohrer, F.

2009-08-01

The relationship between the static stability N2 and the mixing in the tropopause inversion layer (TIL) is investigated using in situ aircraft observations during SPURT (trace gas transport in the tropopause region). With a new simple measure of mixing degree based on O3-CO tracer correlations, high N2 related to an enhanced mixing in the extratropical mixing layer is found. This relation becomes even more pronounced if fresh mixing events are excluded, indicating that mixing within the TIL occurs on a larger than synoptic timescale. A temporal variance analysis of N2 suggests that processes responsible for the composition of the TIL take place on seasonal timescales. Using radiative transfer calculations, we simulate the influence of a change in O3 and H2O vertical gradients on the temperature gradient and thus on the static stability above the tropopause, which are contrasted in an idealized nonmixed atmosphere and in a reference mixed atmosphere. The results show that N2 increases with enhanced mixing degree near the tropopause. At the same time, the temperature above the tropopause decreases together with the development of an inversion and the TIL. In the idealized case of nonmixed profiles the TIL vanishes. Furthermore, the results suggest that H2O plays a major role in maintaining the temperature inversion and the TIL structure compared to O3. The results substantiate the link between the extratropical mixing layer and the TIL.

Monitoring gas and heat emissions at Norris Geyser Basin, Yellowstone National Park, USA based on a combined eddy covariance and Multi-GAS approach

NASA Astrophysics Data System (ADS)

Lewicki, J. L.; Kelly, P. J.; Bergfeld, D.; Vaughan, R. G.; Lowenstern, J. B.

2017-11-01

We quantified gas and heat emissions in an acid-sulfate, vapor-dominated area (0.04-km2) of Norris Geyser Basin, located just north of the 0.63 Ma Yellowstone Caldera and near an area of anomalous uplift. From 14 May to 3 October 2016, an eddy covariance system measured half-hourly CO2, H2O and sensible (H) and latent (LE) heat fluxes and a Multi-GAS instrument measured (1 Hz frequency) atmospheric H2O, CO2 and H2S volumetric mixing ratios. We also measured soil CO2 fluxes using the accumulation chamber method and temperature profiles on a grid and collected fumarole gas samples for geochemical analysis. Eddy covariance CO2 fluxes ranged from - 56 to 885 g m- 2 d- 1. Using wavelet analysis, average daily eddy covariance CO2 fluxes were locally correlated with average daily environmental parameters on several-day to monthly time scales. Estimates of CO2 emission rate from the study area ranged from 8.6 t d- 1 based on eddy covariance measurements to 9.8 t d- 1 based on accumulation chamber measurements. Eddy covariance water vapor fluxes ranged from 1178 to 24,600 g m- 2 d- 1. Nighttime H and LE were considered representative of hydrothermal heat fluxes and ranged from 4 to 183 and 38 to 504 W m- 2, respectively. The total hydrothermal heat emission rate (H + LE + radiant) estimated for the study area was 11.6 MW and LE contributed 69% of the output. The mean ± standard deviation of H2O, CO2 and H2S mixing ratios measured by the Multi-GAS system were 9.3 ± 3.1 parts per thousand, 467 ± 61 ppmv, and 0.5 ± 0.6 ppmv, respectively, and variations in the gas compositions were strongly correlated with diurnal variations in environmental parameters (wind speed and direction, atmospheric temperature). After removing ambient H2O and CO2, the observed variations in the Multi-GAS data could be explained by the mixing of relatively H2O-CO2-H2S-rich fumarole gases with CO2-rich and H2O-H2S-poor soil gases. The fumarole H2O/CO2 and CO2/H2S end member ratios (101.7 and 27.1, respectively, on average) were invariant during the measurement period and fell within the range of values measured in direct fumarole gas samples. The soil gas H2O/CO2 end member ratios ( 15-30) were variable and low relative to the fumarole end member, likely resulting from water vapor loss during cooling and condensation in the shallow subsurface, whereas the CO2/H2S end member ratio was high ( 160), presumably related to transport of CO2-dominated soil gas emissions mixed with trace fumarolic emissions to the Multi-GAS station. Nighttime eddy covariance ratios of H2O to CO2 flux were typically between the soil gas and fumarole end member H2O/CO2 ratios defined by Multi-GAS measurements. Overall, the combined eddy covariance and Multi-GAS approach provides a powerful tool for quasi-continuous measurements of gas and heat emissions for improved volcano-hydrothermal monitoring.

Synthesis and structural characterization of a novel Sillén - Aurivillius bismuth oxyhalide, PbBi3VO7.5Cl, and its derivatives

NASA Astrophysics Data System (ADS)

Charkin, Dmitri O.; Plokhikh, Igor V.; Kazakov, Sergey M.; Kalmykov, Stepan N.; Akinfiev, Victor S.; Gorbachev, Anatoly V.; Batuk, Maria; Abakumov, Artem M.; Teterin, Yury A.; Maslakov, Konstantin I.; Teterin, Anton Yu; Ivanov, Kirill E.

2018-01-01

A new Sillén - Aurivillius family of layered bismuth oxyhalides has been designed and successfully constructed on the basis of PbBiO2X (X = halogen) synthetic perites and γ-form of Bi2VO5.5 solid electrolyte. This demonstrates, for the first time, the ability of the latter to serve as a building block in construction of mixed-layer structures. The parent compound PbBi3VO7.5-δCl (δ ≤ 0.05) has been investigated by powder XRD, TEM, XPS methods and magnetic susceptibility measurements. An unexpected but important condition for the formation of the mixed-layer structure is partial (ca. 5%) reduction of VV into VIV which probably suppresses competitive formation of apatite-like Pb - Bi vanadates. This reduction also stabilizes the γ polymorphic form of Bi2VO5.5 not only in the intergrowth structure, but in Bi2V1-xMxO5.5-y (M = Nb, Sb) solid solutions.

Ag2O:SiO2:V2O5 Glass System:. a Novel Reference Electrode for SO2 Gas Sensor

NASA Astrophysics Data System (ADS)

Singh, K.; Lad, A.; Bhoga, S. S.

2002-12-01

Ag2O:SiO2:V2O5 glass system with 0.5≤ y ≥ 0.66 for fixed n = 9 is synthesized, structurally and electrically characterized with a view to have high glass transition temperature (Tg ≈ 500°C) which can be used as solid reference electrode in electrochemical SOx gas sensor application. 10Ag2O:40SiO2:50V2O5 glass having Tg ≈ 502°C exhibits maximum bulk and electronic conductivity 3.67*10-3 and 4.47*10-2 S/cm, respectively at 450°C. The increase in conductivity is understood to be due to a mixed former effect. A few galvanic SOx sensors fabricated utilizing optimized glass as reference and Ag+ conducting solid electrolyte responds to change in PSOx according to 2 electron cell reaction.

Abundance of nitrogen in QSOs

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

Shields, G.A.

1976-03-01

Models of photoionized QSO emission-line regions show that measurements of O iii/N iv/C iv or N iii/C iii can yield the C/N/O ratios to an accuracy of a factor 2 or better. The N iii/C iii intensity ratios observed for the QSO PKS 1756+237 (z=1.72) implies a N/C abundance ratio 5 times larger than the solar value. This is comparable with the nitrogen overabundance in the nuclei of nearby galaxies, and it points to advanced chemical evolution in this QSO, with Zapproximately-greater-thanZ/sub sun/. Such a large abundance of nitrogen appears to be exceptional; composite spectra indicate that most QSOs havemore » (N/O) approximately one-fourth to one-half the solar value. (AIP)« less

Analysis of Non-Methane Hydrocarbon Data from 2004-2016 in a Subtropical Area close to the Gulf of Mexico

NASA Astrophysics Data System (ADS)

Rappenglueck, B.

2017-12-01

Speciated C2-C11 non-methane hydrocarbons (NMHC) have been measured online on an hourly basis at Lake Jackson/TX close to the Gulf of Mexico. Altogether 48 NMHCs along with NO, NO2, NOx, O3 have been collected continuously from January 2004-December 2016 under the auspices of the Texas Commission on Environmental Quality. Data was screened for background conditions representing marine wind sectors. The data set represents a combination of marine air masses mixed with local biogenic emissions. The data analysis addresses photochemical processing of air masses as reflected in the relationship of ln(n-butane/ethane) vs. ln(propane/ethane) and ln(i-butane/ethane) vs. ln(n-butane/ethane). In addition, key NMHC relationships for radical chemistry, e.g. i-butane vs n-butane for OH and Cl chemistry and i-pentane vs. n-pentane for NO3 chemistry, are discussed. Seasonal analysis revealed a clear trend with maximum NMHC mixing ratios in winter time and lowest mixing ratios in summer reflecting the impact of photochemical processes in summer. Propene equivalents were highest during summertime, with significant contributions from alkenes, including isoprene. The relation of propane/ethane vs ethane indicates seasonal variation with lowest values (i.e. most aged air masses) in winter.

δ(15)N and δ(18)O Reveal the Sources of Nitrate-Nitrogen in Urban Residential Stormwater Runoff.

PubMed

Yang, Yun-Ya; Toor, Gurpal S

2016-03-15

Nitrogen (N) sources are widely distributed in the complex urban environment. High-resolution data elucidating N sources in the residential catchments are not available. We used stable isotopes of N and oxygen (O) of nitrate (δ(18)O-NO3(-) and δ(15)N-NO3(-)) along with δ(18)O and hydrogen (δD) of water (H2O) to understand the sources and transformations of N in residential stormwater runoff. Stormwater runoff samples were collected over 25 stormwater events at 5 min intervals using an autosampler installed at the residential catchment outlet pipe that drained 31 low-density homes with a total drainage area of 0.11 km(2). Bayesian mixing model results indicated that atmospheric deposition (range 43-71%) and chemical N fertilizers (range <1-49%) were the dominant NO3-N sources in the stormwater runoff and that there was a continuum of source changes during the stormwater events. Further, the NO3-N transport in the stormwater runoff from the residential catchment was driven by mixing of multiple sources and biotic (i.e., nitrification) processes. This work suggests that a better understanding of N transport and sources is needed to reduce N export and improve water quality in urban water systems.

Deep ultraviolet photodetectors based on p-Si/ i-SiC/ n-Ga2O3 heterojunction by inserting thin SiC barrier layer

NASA Astrophysics Data System (ADS)

An, Yuehua; Zhi, Yusong; Wu, Zhenping; Cui, Wei; Zhao, Xiaolong; Guo, Daoyou; Li, Peigang; Tang, Weihua

2016-12-01

Deep ultraviolet photodetectors based on p-Si/ n-Ga2O3 and p-Si/ i-SiC/ n-Ga2O3 heterojunctions were fabricated by laser molecular beam epitaxial (L-MBE), respectively. In compare with p-Si/ n-Ga2O3 heterostructure-based photodetector, the dark current of p-Si/ i-SiC/ n-Ga2O3-based photodetector decreased by three orders of magnitude, and the rectifying behavior was tuned from reverse to forward. In order to improve the quality of the photodetector, we reduced the oxygen vacancies of p-Si/ i-SiC/ n-Ga2O3 heterostructures by changing the oxygen pressure during annealing. As a result, the rectification ratio ( I F/ I R) of the fabricated photodetectors was 36 at 4.5 V and the photosensitivity was 5.4 × 105% under the 254 nm light illumination at -4.5 V. The energy band structure of p-Si/ n-Ga2O3 and p-Si/ i-SiC/ n-Ga2O3 heterostructures was schematic drawn to explain the physic mechanism of enhancement of the performance of p-Si/ i-SiC/ n-Ga2O3 heterostructure-based deep UV photodetector by introduction of SiC layer.

Line shape parameters of air-broadened water vapor transitions in the ν 1 and ν 3 spectral region

DOE PAGES

Malathy Devi, V.; Gamache, Robert R.; Vispoel, Bastien; ...

2017-11-26

A Bruker IFS-120HR Fourier transform spectrometer located at the Pacific Northwest National Laboratory (PNNL) in Richland, Washington was used to record a series of spectra of pure H 2O and air-broadened H 2O in the regions of the ν 1 and ν 3 bands (3450–4000 cm -1) at different pressures, temperatures and volume mixing ratios of H 2O in air. Eighteen high-resolution, high signal-to-noise (S/N) ratio absorption spectra were recorded at T = 268, 296 and 353 K using two temperature-controlled absorption cells with path lengths of 9.906(1) and 19.95(1) cm. Furthermore, the resolution of the spectra recorded with themore » 9.906 cm and 19.95 cm absorption cells was 0.006 and 0.008 cm -1, respectively. A multispectrum nonlinear least squares fitting technique was employed to fit all the eighteen spectra simultaneously to retrieve 313 accurate line positions, 315 intensities, 229 Lorentz air-broadened half-width and 213 air-shift coefficients and their temperature dependences (136 for air-broadened width and 128 for air-shift coefficients, respectively). Room temperature self-broadened half-width coefficients for 209 transitions and self-shift coefficients for 106 transitions were also measured. Line mixing coefficients were experimentally determined for isolated sets of 10 transition pairs for H 2O-air and 8 transition pairs for H 2O-H 2O using the off-diagonal relaxation matrix element formalism, and 85 quadratic speed dependence parameters were measured. Modified Complex Robert-Bonamy (MCRB) calculations of self-, and air-broadened (from N 2- and O 2-broadening) half-width and air-shift coefficients, and temperature dependence exponents of air-broadened half-width coefficients are made. Finally, the measurements and calculations are compared with each other and with similar parameters reported in the literature.« less

Line shape parameters of air-broadened water vapor transitions in the ν1 and ν3 spectral region

NASA Astrophysics Data System (ADS)

Malathy Devi, V.; Gamache, Robert R.; Vispoel, Bastien; Renaud, Candice L.; Chris Benner, D.; Smith, Mary Ann H.; Blake, Thomas A.; Sams, Robert L.

2018-06-01

A Bruker IFS-120HR Fourier transform spectrometer located at the Pacific Northwest National Laboratory (PNNL) in Richland, Washington was used to record a series of spectra of pure H2O and air-broadened H2O in the regions of the ν1 and ν3 bands (3450-4000 cm-1) at different pressures, temperatures and volume mixing ratios of H2O in air. Eighteen high-resolution, high signal-to-noise (S/N) ratio absorption spectra were recorded at T = 268, 296 and 353 K using two temperature-controlled absorption cells with path lengths of 9.906(1) and 19.95(1) cm. The resolution of the spectra recorded with the 9.906 cm and 19.95 cm absorption cells was 0.006 and 0.008 cm-1, respectively. A multispectrum nonlinear least squares fitting technique was employed to fit all the eighteen spectra simultaneously to retrieve 313 accurate line positions, 315 intensities, 229 Lorentz air-broadened half-width and 213 air-shift coefficients and their temperature dependences (136 for air-broadened width and 128 for air-shift coefficients, respectively). Room temperature self-broadened half-width coefficients for 209 transitions and self-shift coefficients for 106 transitions were also measured. Line mixing coefficients were experimentally determined for isolated sets of 10 transition pairs for H2O-air and 8 transition pairs for H2O-H2O using the off-diagonal relaxation matrix element formalism, and 85 quadratic speed dependence parameters were measured. Modified Complex Robert-Bonamy (MCRB) calculations of self-, and air-broadened (from N2- and O2-broadening) half-width and air-shift coefficients, and temperature dependence exponents of air-broadened half-width coefficients are made. The measurements and calculations are compared with each other and with similar parameters reported in the literature.

Line shape parameters of air-broadened water vapor transitions in the ν 1 and ν 3 spectral region

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

Malathy Devi, V.; Gamache, Robert R.; Vispoel, Bastien

A Bruker IFS-120HR Fourier transform spectrometer located at the Pacific Northwest National Laboratory (PNNL) in Richland, Washington was used to record a series of spectra of pure H 2O and air-broadened H 2O in the regions of the ν 1 and ν 3 bands (3450–4000 cm -1) at different pressures, temperatures and volume mixing ratios of H 2O in air. Eighteen high-resolution, high signal-to-noise (S/N) ratio absorption spectra were recorded at T = 268, 296 and 353 K using two temperature-controlled absorption cells with path lengths of 9.906(1) and 19.95(1) cm. Furthermore, the resolution of the spectra recorded with themore » 9.906 cm and 19.95 cm absorption cells was 0.006 and 0.008 cm -1, respectively. A multispectrum nonlinear least squares fitting technique was employed to fit all the eighteen spectra simultaneously to retrieve 313 accurate line positions, 315 intensities, 229 Lorentz air-broadened half-width and 213 air-shift coefficients and their temperature dependences (136 for air-broadened width and 128 for air-shift coefficients, respectively). Room temperature self-broadened half-width coefficients for 209 transitions and self-shift coefficients for 106 transitions were also measured. Line mixing coefficients were experimentally determined for isolated sets of 10 transition pairs for H 2O-air and 8 transition pairs for H 2O-H 2O using the off-diagonal relaxation matrix element formalism, and 85 quadratic speed dependence parameters were measured. Modified Complex Robert-Bonamy (MCRB) calculations of self-, and air-broadened (from N 2- and O 2-broadening) half-width and air-shift coefficients, and temperature dependence exponents of air-broadened half-width coefficients are made. Finally, the measurements and calculations are compared with each other and with similar parameters reported in the literature.« less

Intercontinental transport of pollution from North America to Europe: Airborne trace gas measurements over Central and Northern Europe during CONTRACE

NASA Astrophysics Data System (ADS)

Huntrieser, H.; Schlager, H.; Heland, J.; Forster, C.; Stohl, A.; Lawrence, M.; Arnold, F.; Aufmhoff, H.; Cooper, O.

2003-04-01

The CONTRACE project investigates the uplift of pollution in frontal systems (warm conveyor belts) over North America and the transport of these air masses to Europe. The first airborne field experiment was carried out from Southern Germany in fall 2001. The DLR research aircraft Falcon was equipped with a complex instrumentation to measure NO, NOy, CO, CO2, O3, J(NO2), acetone, SO2, ions, H2O2, formaldehyde, NMHC, J(O1D) and particles. An extensive set of chemical and meteorological forecast products, including trajectory calculations, was developed and used in combination with satellite images to plan the flights. A passive tracer for surface emissions (CO) was included in the forecast models to separate the regional and intercontinental transport of polluted air masses. For the first time it succeeded to guide the Falcon aircraft into pollution plumes transported all the way from North America (NA). On 22nd November a complex chemical weather situation was predicted for Central Europe with lifting of European emissions into the lower troposphere ahead of an approaching cold front and simultaneously, the advection of a pollution plume from Eastern NA in mid tropospheric layers. Similar CO mixing ratios were observed in both plumes making it difficult to distinguish the two plumes without additional trace gas information. The European pollution plume was characterized by large enhancements in the CO (150 ppbv) and NOy (6 ppbv) mixing ratios. The NOy/CO ratio was 0.135 (typical value for fresh emissions). In comparison the estimated NOy/CO ratio for the NA pollution plume was 0.010 which indicate a tracer age of 4 days. The observed CO and NOy mixing ratios in this plume were 160 ppbv and 1 ppbv. The two plumes were also characterized by very different O3/CO relationships. In the plume from NA a positive O3/CO slope was observed indicating photochemical ozone production (O3 mixing ratios up to 50 ppbv were observed). Most likely O3 was produced photochemically in the polluted boundary layer over Southeastern North America and not in transit over the North Atlantic. The European plume showed a strong negative O3/CO relationship with O3 mixing ratios dropping down to 20 ppbv (due to titration by NO emissions in winter in northern latitudes).

In situ observations of midlatitude stratospheric ClO and BrO

NASA Technical Reports Server (NTRS)

Brune, William H.; Anderson, James C.

1986-01-01

A balloon-borne experiment to measure midlatitude stratospheric BrO and ClO concentrations by NO chemical conversion/atomic resonance fluorescence was flown from Palestine, Texas, on May 20 1986. In this first study of BrO, no signal attributable to BrO was detected, and upper limits (2 sigma uncertainty) between 35 and 24 km altitude give BrO mixing ratios less than 15 pptv. Current models predict mixing ratios that are 1.7 times larger. Measurements of ClO were obtained at less than 0.2-km altitude resolution from 41 to 22 km. The smoothly varying altitude profile lies within the range of two-dimensional model calculations.

Immobilization of Mn and NH4 (+)-N from electrolytic manganese residue waste.

PubMed

Chen, Hongliang; Liu, Renlong; Liu, Zuohua; Shu, Jiancheng; Tao, Changyuan

2016-06-01

The objective of this work was the immobilization of soluble manganese (Mn) and ammonium nitrogen (NH4 (+)-N) leached from electrolytic manganese residue (EMR). Immobilization of Mn was investigated via carbonation using carbon dioxide (CO2) and alkaline additives. NH4 (+)-N immobilization was evaluated via struvite precipitation using magnesium and phosphate sources. Results indicated that the immobilization efficiency of Mn using CO2 and quicklime (CaO) was higher than using CO2 and sodium hydroxide (NaOH). This higher efficiency was likely due to the slower release of OH(-) during CaO hydrolysis. The immobilization efficiency of Mn was >99.99 % at the CaO:EMR mass ratio of 0.05:1 for 20-min reaction time. The struvite precipitation of NH4 (+)-N was conducted in the carbonated EMR slurry and the immobilization efficiency was 89 % using MgCl2 · 6H2O + Na3PO4 · 12H2O at the Mg:P:N molar ratio of 1.5:1.5:1 for 90-min reaction time. A leaching test showed that the concentrations of Mn and NH4 (+)-N in the filtrate of the treated EMR were 0.2 and 9 mg/L, respectively. The combined immobilization of Mn and NH4 (+)-N was an effective pretreatment method in the harmless treatment of the EMR.

Analysis of the Atmospheric Distribution, Sources, and Sinks of Oxygenated Volatile Organic Chemicals Based on Measurements over the Pacific during TRACE-P

NASA Technical Reports Server (NTRS)

Singh, H. B.; Salas, L. J.; Chatfield, r. B.; Czech, E.; Fried, A.; Walega, J.; Evans, M. J.; Field, B. D.; Jacob, D. J.; Blake, D.;

Dynamics and Fragmentation of Hydrogen Bonded and van der Waal Clusters upon 26.5 eV Soft X-ray Laser Ionization

NASA Astrophysics Data System (ADS)

Dong, Feng; Heinbuch, Scott; Bernstein, Elliot; Rocca, Jorge

2006-05-01

A desk-top soft x-ray laser is applied to the study of water, methanol, ammonia, sulfur dioxide, carbon dioxide, mixed sulfur dioxide-water, and mixed carbon dioxide-water clusters through single photon ionization time of flight mass spectroscopy. Almost all of the energy above the vertical ionization energy is removed by the ejected electron. Protonated water, methanol, and ammonia clusters dominate the mass spectra for the first three systems. The temperatures of the neutral water and methanol clusters can be estimated. In the case of pure SO2 and CO2, the mass spectra are dominated by (SO2)n^+ and (CO2)n^+ cluster series. When a high or low concentration of SO2/CO2 is mixed with water, we observe (SO2/CO2)nH2O^+ or SO2/CO2(H2O)nH^+ in the mass spectra, respectively. The unimolecular dissociation rate constants for reactions involving loss of one neutral molecule are calculated for the protonated water, methanol, and ammonia clusters as well as for SO2 and CO2 clusters. We find that the 26.5 eV soft x-ray laser is a nearly ideal tool for the study of hydrogen bonded and van der Waals cluster systems and we are currently exploring its usefulness for other more strongly bound systems.

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

NASA Astrophysics Data System (ADS)

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

2014-12-01

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

Microphysical and macrophysical characteristics of ice and mixed-phase clouds compared between in-situ observations from the NSF ORCAS campaign and the NCAR Community Atmospheric Model

NASA Astrophysics Data System (ADS)

Diao, M.; D'Alessandro, J.; Wu, C.; Liu, X.; Jensen, J. B.

2016-12-01

Large spatial coverage of ice and mixed-phase clouds is frequently observed in the higher latitudinal regions, especially over the Arctic and Antarctica. However, because the microphysical properties in the ice and mixed-phase clouds are highly variable in space, major challenges still remain in understanding the characteristics of ice and mixed-phase clouds on the microscale, as well as representing the sub-grid scale variabilities of relative humidity in the General Circulation Models. In this work, we use the in-situ, airborne observations from the NSF O2/N2 Ratio and CO2 Airborne Southern Ocean (ORCAS) Study (January - February 2016) to analyze the microphysical and macrophysical characteristics of ice and mixed-phase clouds over the Southern Ocean. A total of 18 flights onboard the NSF Gulfstream-V research aircraft are used to quantify the cloud properties and relative humidity distributions at various temperatures, pressures and aerosol background. New QC/QA water vapor data of the Vertical Cavity Surface Emitting Laser based on the laboratory calibration in summer 2016 will be presented. The statistical distributions of cloud microphysical properties and relative humidity with respect to ice (RHi) derived from in-situ observations will be compared with the NCAR Community Atmospheric Model Version 5 (CAM5). The horizontal extent of ice and mixed-phase clouds, and their formation and evolution will be derived based on the method of Diao et al. (2013). The occurrence frequency of ice supersaturation (i.e., RHi > 100%) will be examined in relation to various chemical tracers (i.e., O3 and CO) and total aerosol number concentrations (e.g., aerosols > 0.1 μm and > 0.5 μm) at clear-sky and in-cloud conditions. We will quantify whether these characteristics of ISS are scale-dependent from the microscale to the mesoscale. Overall, our work will evaluate the spatial variabilities of RHi inside/outside of ice and mixed-phase clouds, the frequency and magnitude of ice supersaturation, as well as the correlations between ice water content and liquid water content in the CAM5 simulations.

SDSS IV MaNGA - metallicity and nitrogen abundance gradients in local galaxies

NASA Astrophysics Data System (ADS)

Belfiore, Francesco; Maiolino, Roberto; Tremonti, Christy; Sánchez, Sebastian F.; Bundy, Kevin; Bershady, Matthew; Westfall, Kyle; Lin, Lihwai; Drory, Niv; Boquien, Médéric; Thomas, Daniel; Brinkmann, Jonathan

2017-07-01

We study the gas phase metallicity (O/H) and nitrogen abundance gradients traced by star-forming regions in a representative sample of 550 nearby galaxies in the stellar mass range 109-1011.5 M⊙ with resolved spectroscopic data from the Sloan Digital Sky Survey IV Mapping Nearby Galaxies at Apache Point Observatory survey. Using strong-line ratio diagnostics (R23 and O3N2 for metallicity and N2O2 for N/O) and referencing to the effective (half-light) radius (Re), we find that the metallicity gradient steepens with stellar mass, lying roughly flat among galaxies with log (M⋆/M⊙) = 9.0 but exhibiting slopes as steep as -0.14 dex R_e^{-1} at log (M⋆/M⊙) = 10.5 (using R23, but equivalent results are obtained using O3N2). At higher masses, these slopes remain typical in the outer regions of our sample (R > 1.5Re), but a flattening is observed in the central regions (R < 1Re). In the outer regions (R > 2.0Re), we detect a mild flattening of the metallicity gradient in stacked profiles, although with low significance. The N/O ratio gradient provides complementary constraints on the average chemical enrichment history. Unlike the oxygen abundance, the average N/O profiles do not flatten out in the central regions of massive galaxies. The metallicity and N/O profiles both depart significantly from an exponential form, suggesting a disconnect between chemical enrichment and stellar mass surface density on local scales. In the context of inside-out growth of discs, our findings suggest that central regions of massive galaxies today have evolved to an equilibrium metallicity, while the nitrogen abundance continues to increase as a consequence of delayed secondary nucleosynthetic production.

Enhanced Ga2O3-photocatalyzed and photochemical degradation of the Fipronil insecticide by UVC irradiation in mixed aqueous/organic media under an inert atmosphere.

PubMed

Hidaka, Hisao; Tsukamoto, Tohru; Mitsutsuka, Yoshihiro; Oyama, Toshiyuki; Serpone, Nick

2015-05-01

Agrochemicals such as the insecticide Fipronil that bear fluoro groups are generally fat-soluble and nearly insoluble in water, so that their photodegradation in a heterogeneous aqueous gallium oxide dispersion presents some challenges. This article examined the photodegradation of this insecticide by solubilizing it through the addition of organic solvents (EtOH, MeOH, THF, 1,4-dioxane and ethylene glycol) to an aqueous medium and then subjecting the insecticide to 254 nm UVC radiation under photocatalytically inert (Ga2O3/N2) and air-equilibrated (Ga2O3/O2) conditions, as well as photochemically in the absence of Ga2O3 but also under inert and air-equilibrated conditions. Defluorination, dechlorination, desulfonation and denitridation of Fipronil were examined in mixed aqueous/organic media (10, 25 and 50 vol% in organic solvent). After 3 h of UVC irradiation (50 vol% mixed media) defluorination with Ga2O3/N2 was ∼65% greater than in aqueous media, and ca. 80% greater than the direct photolysis of Fipronil under inert (N2) conditions; under air-equilibrated conditions both Ga2O3-photocatalyzed and photochemical defluorination were significantly lower than in aqueous media. Dechlorination of Fipronil was ∼160% (Ga2O3/N2) and 140% (photochemically, N2) greater than in aqueous media; under air-equilibrated conditions, both photocatalyzed and photochemical formation of Cl(-) ions in mixed media fell rather short relative to aqueous media. The photocatalyzed (Ga2O3/N2) and photochemical (N2) conversion of the sulfur group in Fipronil to SO4(2(-)) ions was ca. 20% and 30% greater, respectively, in mixed media, while under air-equilibrated conditions photocatalyzed desulfonation was nearly twofold less than in the aqueous phase; direct photolysis showed little variations in mixed media. Denitridation of the nitrogens in Fipronil occurred mostly through the formation of ammonia (as NH4(+)) under all conditions with negligible quantities of NO3(-); again mixed media offered enhanced denitridation, particularly under inert N2 conditions. Time-of-flight electrospray (TOF-MS/ESI(-)) mass spectrometry revealed a fairly large number of intermediates formed in the degradation of Fipronil, particularly under photocatalytic conditions. Only a couple of intermediates were identified in the photodegradation and the presence of Ga2O3 enhanced the complexity of an already cumbersome problem owing to the involvement of organic solvents.

Turbulence in Supercritical O2/H2 and C7H16/N2 Mixing Layers

NASA Technical Reports Server (NTRS)

Bellan, Josette; Harstad, Kenneth; Okong'o, Nora

2003-01-01

This report presents a study of numerical simulations of mixing layers developing between opposing flows of paired fluids under supercritical conditions, the purpose of the study being to elucidate chemical-species-specific aspects of turbulence. The simulations were performed for two different fluid pairs O2/H2 and C7H16/N2 at similar reduced initial pressures (reduced pressure is defined as pressure divided by critical pressure). Thermodynamically, O2/H2 behaves more nearly like an ideal mixture and has greater solubility, relative to C7H16/N2, which departs strongly from ideality. Because of a specified smaller initial density stratification, the C7H16/N2 layers exhibited greater levels of growth, global molecular mixing, and turbulence. However, smaller density gradients at the transitional state for the O2/H2 system were interpreted as indicating that locally, this system exhibits enhanced mixing as a consequence of its greater solubility and closer approach to ideality. These thermodynamic features were shown to affect entropy dissipation, which was found to be larger for O2/H2 and concentrated in high-density-gradient-magnitude regions that are distortions of the initial density-stratification boundary. In C7H16/N2, the regions of largest dissipation were found to lie in high-density-gradient-magnitude regions that result from mixing of the two fluids.

Cassini UVIS Observations of the Io Plasma Torus. 3; Observations of Temporal and Azimuthal Variability

NASA Technical Reports Server (NTRS)

Steffl, A. J.; Delamere, P. A.; Bagenal, F.

2006-01-01

In this third paper in a series presenting observations by the Cassini Ultraviolet Imaging Spectrometer (UVIS) of the Io plasma torus, we show remarkable, though subtle, spatio-temporal variations in torus properties. The Io torus is found to exhibit significant, near sinusoidal variations in ion composition as a functions of azimuthal position. The azimuthal variation in composition is such that the mixing ratio of S II us strongly correlated with the mixing ratio of S III and the equatorial electron density and strongly anti-correlated with the mixing ratios of both S IV and O II and the equatorial electron temperature. Surprisingly, the azimuthal variation in ion composition is observed to have a period of 10.07 h -- 1.5% longer than the System III rotation period of Jupiter, yet 1.3% shorter than the System UV period defined by [Brown, M. E., 1995. J. Geophys. Res. 100, 21683-21696]. Although the amplitude of the azimuthal variation of S III and O II remained in the range of 2-5%, the amplitude of the S II and S IV compositional variation ranged between 5 and 25% during the UVIS observations. Furthermore, the amplitude of the azimuthal variations of S II and S IV appears to be modulated by its location in System III longitude, such that when the region of maximum S II mixing ration (minimum S IV mixing ratio) is aligned with a System III longitude of 200 deg +/-, the amplitude is a factor of 4 greater than when the variation is anti-aligned. This behavior can explain numerous, often apparently contradictory, observations of variations in the properties of the Io plasma torus with the System III and System IV coordinate systems.

Influence of aerosol chemical composition on N2O5 uptake: airborne regional measurements in northwestern Europe

NASA Astrophysics Data System (ADS)

Morgan, W. T.; Ouyang, B.; Allan, J. D.; Aruffo, E.; Di Carlo, P.; Kennedy, O. J.; Lowe, D.; Flynn, M. J.; Rosenberg, P. D.; Williams, P. I.; Jones, R.; McFiggans, G. B.; Coe, H.

2015-01-01

Aerosol chemical composition was found to influence nighttime atmospheric chemistry during a series of airborne measurements in northwestern Europe in summer conditions, which has implications for regional air quality and climate. The uptake of dinitrogen pentoxide, γ (N2O5), to particle surfaces was found to be modulated by the amount of water content and ammonium nitrate present in the aerosol. The conditions prevalent in this study suggest that the net uptake rate of N2O5 to atmospheric aerosols was relatively efficient compared to previous studies, with γ (N2O5) values in the range 0.01-0.03. This is likely a consequence of the elevated relative humidity in the region, which promotes greater aerosol water content. Increased nitrate concentrations relative to particulate water were found to suppress N2O5 uptake. The results presented here contrast with previous ambient studies of N2O5 uptake, which have generally taken place in low-nitrate environments in the USA. Comparison of the N2O5 uptake derived from the measurements with a parameterised scheme that is based on the ratio of particulate water to nitrate yielded reasonably good agreement in terms of the magnitude and variation in uptake, provided the effect of chloride was neglected. An additional suppression of the parameterised uptake is likely required to fully capture the variation in N2O5 uptake, which could be achieved via the known suppression by organic aerosol. However, existing parameterisations representing the suppression by organic aerosol were unable to fully represent the variation in N2O5 uptake. These results provide important ambient measurement constraint on our ability to predict N2O5 uptake in regional and global aerosol models. N2O5 uptake is a potentially important source of nitrate aerosol and a sink of the nitrate radical, which is the main nocturnal oxidant in the atmosphere. The results further highlight the importance of ammonium nitrate in northwestern Europe as a key component of atmospheric composition in the region.

Influence of aerosol chemical composition on N2O5 uptake: airborne regional measurements in North-Western Europe

NASA Astrophysics Data System (ADS)

Morgan, W. T.; Ouyang, B.; Allan, J. D.; Aruffo, E.; Di Carlo, P.; Kennedy, O. J.; Lowe, D.; Flynn, M. J.; Rosenberg, P. D.; Williams, P. I.; Jones, R.; McFiggans, G. B.; Coe, H.

2014-07-01

Aerosol chemical composition was found to influence nighttime atmospheric chemistry during a series of airborne measurements in North-Western Europe in summer conditions, which has implications for regional air quality and climate. The uptake of dinitrogen pentoxide, γ (N2O5), to particle surfaces was found to be modulated by the amount of water content and ammonium nitrate present in the aerosol. The conditions prevalent in this study suggest that the net uptake rate of N2O5 to atmospheric aerosols was relatively efficient compared to previous studies, with γ (N2O5) values in the range 0.01-0.03. This is likely a consequence of the elevated relative humidity in the region, which promotes greater aerosol water content. Increased nitrate concentrations relative to particulate water were found to suppress N2O5 uptake. The results presented here contrast with previous ambient studies of N2O5 uptake, which have generally taken place in low-nitrate environments in the USA. Comparison of the N2O5 uptake derived from the measurements with a parameterised scheme that is based on the ratio of particulate water to nitrate yielded reasonably good agreement in terms of the magnitude and variation in uptake, provided the effect of chloride was neglected. An additional suppression of the parameterised uptake is likely required to fully capture the variation in N2O5 uptake, which could be achieved via the known suppression by organic aerosol. However, existing parameterisations representing the suppression by organic aerosol were unable to fully represent the variation in N2O5 uptake. These results provide important ambient measurement constraint on our ability to predict N2O5 uptake in regional and global aerosol models. N2O5 uptake is a potentially important source of nitrate aerosol and a sink of the nitrate radical, which is the main nocturnal oxidant in the atmosphere. The results further highlight the importance of ammonium nitrate in North-Western Europe as a key component of atmospheric composition in the region.

Nano-phase separation and structural ordering in silica-rich mixed network former glasses.

PubMed

Liu, Hao; Youngman, Randall E; Kapoor, Saurabh; Jensen, Lars R; Smedskjaer, Morten M; Yue, Yuanzheng

2018-06-13

We investigate the structure, phase separation, glass transition, and crystallization in a mixed network former glass series, i.e., B2O3-Al2O3-SiO2-P2O5 glasses with varying SiO2/B2O3 molar ratio. All the studied glasses exhibit two separate glassy phases: droplet phase (G1) with the size of 50-100 nm and matrix phase (G2), corresponding to a lower calorimetric glass transition temperature (Tg1) and a higher one (Tg2), respectively. Both Tg values decrease linearly with the substitution of B2O3 for SiO2, but the magnitude of the decrease is larger for Tg1. Based on nuclear magnetic resonance and Raman spectroscopy results, we infer that the G1 phase is rich in boroxol rings, while the G2 phase mainly involves the B-O-Si network. Both phases contain BPO4- and AlPO4-like units. Ordered domains occur in G2 upon isothermal and dynamic heating, driven by the structural heterogeneity in the as-prepared glasses. The structural ordering lowers the activation energy of crystal growth, thus promoting partial crystallization of G2. These findings are useful for understanding glass formation and phase separation in mixed network former oxide systems, and for tailoring their properties.

Nocturnal Ozone Depletion Events at the Amphitrite Point Observatory on West Vancouver Island

NASA Astrophysics Data System (ADS)

Garner, N.; Brownsey, D. K.; Tokarek, T. W.; Ye, C. Z.; Yordanov, N. R.; Osthoff, H. D.; Schiller, C. L.; Vingarzan, R.

2015-12-01

Routine monitoring stations on the West coast of North America serve to monitor baseline levels of criteria pollutants such as ozone (O3) arriving from the Pacific Ocean. In Canada, the Amphitrite Point Observatory (APO) in Ucluelet on the West coast of Vancouver Island has been added to this network to provide regional baseline measurements. Recently, McKendry and coworkers have reported frequent episodes of nocturnal O3 depletion events (ODEs) at APO (range: 5-20 ppbv) that generally correlate with alongshore winds, elevated levels of carbon dioxide (CO2), and low vertical entrainment but whose cause(s) has (have) remained unclear. In this work, results from the Ozone-depleting reactions in a coastal atmosphere (ORCA) campaign, which took place at APO from July 6 - 31, 2015, are presented. In addition to the long-term measurements that include aerosol size distribution and composition measurements, mixing ratios of speciated monoterpenes (e.g., α- and β-pinene, limonene), molecular halogens (i.e., Cl2, I2), halogen oxides (i.e., OIO), plus a full suite of nitrogen oxides (including N2O5, PAN, PPN, ΣPN, ΣAN, HNO3, HONO, and ClNO2) were quantified. Synoptic conditions at the site varied greatly between nights. During westerly flow of relatively clean marine air, O3 was generally conserved at night, indicating that deposition of O3 to the ocean surface is a minor loss pathway. When the air mass originated from other sectors, episodes of nocturnal ODEs were observed on several occasions, in which mixing ratios of biogenic VOCs were enhanced. These included air masses that originated from densely forested areas to the East, air masses polluted by marine traffic emissions from the southeast, and air masses from the NW that have traveled parallel to the coastline. In this sector, the air was likely in contact with terrestrial vegetation via land-sea breeze circulations. The results suggest that nocturnal ODEs at APO are mainly driven by local or regional processes involving near-shore vegetation.

In situ synthesis of g-C3N4/TiO2 heterojunction nanocomposites as a highly active photocatalyst for the degradation of Orange II under visible light irradiation.

PubMed

Ren, Bin; Wang, Tiecheng; Qu, Guangzhou; Deng, Fang; Liang, Dongli; Yang, Wenli; Liu, Meishan

2018-05-04

As a highly active photocatalyst, g-C 3 N 4 /TiO 2 heterojunction nanocomposites were in situ synthesized by simple ultrasonic mixing and calcination by using TiO 2 and melamine as precursors. The morphology and structure of the prepared photocatalysts were characterized by field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, UV-Vis diffuse reflectance spectroscopy, and X-ray photoelectron spectroscopy. The photocatalytic activities of g-C 3 N 4 /TiO 2 nanocomposites to degrade Orange II (AO7) under visible light irradiation were evaluated. Results showed that the photocatalytic rate of the prepared g-C 3 N 4 /TiO 2 photocatalyst to degrade AO7 was about three times than that of pristine TiO 2 and g-C 3 N 4 . The g-C 3 N 4 /TiO 2 composite with a ratio of 1:4 had the highest degradation efficiency for AO7 solution. Its degradation efficiency under acidic conditions was significantly higher than that under alkaline conditions. The enhancement of photocatalytic activity can be attributed to the formation of heterojunctions between g-C 3 N 4 and TiO 2 , which leads to rapid charge transfer and the efficient separation of photogenerated electron-hole pairs. The recycling experiment indicated that the photocatalyst of g-C 3 N 4 /TiO 2 nanocomposites still maintained good photochemical stability and recyclability after five cycles; this finding was important for its practical applications. A series of free radical trapping experiments showed that •O 2 - played a crucial role in the degradation of AO7. Graphical Abstract ᅟ.

Tuning different kinds of entangled metal-organic frameworks by modifying the spacer group of aliphatic dicarboxylate ligands and the reactant ratio.

PubMed

Yang, Jin-Xia; Zhai, Ji-Quan; Zhang, Xin; Qin, Ye-Yan; Yao, Yuan-Gen

2016-01-14

Taking advantage of the conformational flexibility of the bpp ligand and aliphatic dicarboxylic acids, six interesting entangled coordination polymers, {[Cd(fum)(bpp)(H2O)]·(H2O)}n (), {[Cd(fum)(bpp)2]·(H2O)5}n (), {[Cd2(suc)1.5(bpp)2(NO3)(H2O)2]·6H2O}n (), {[Cd(suc)(bpp)2]·(H2O)1.5}n (), {[Cd2(glu)2(bpp)3]·10H2O}n (), and {Cd(adp)(bpp)(H2O)}n () have been prepared and structurally characterized (bpp = 1,3-bi(4-pyridyl)propane, fum = fumaric, suc = succinate, glu = glutaric, adp = adipic). Compounds and are comprised of undulated 2D 4(4)-sql networks. In the structure of compound , two identical undulated layers are parallelly interpenetrated with each other to give a 2D → 2D interpenetrating framework. For , the dangling arms projected from 2D layers are intercalated into the neighboring sheets, producing a 2D → 3D polythreading framework. Compound shows a rare example of a 2D self-penetrating framework with a (3,4)-connected (4(2)·6(3)·8)(4(2)·6) topology. Compound presents an unusual 2D self-threading network with a novel 4-connected {4(2)·6(3)·8} topology. Compound displays a 3D self-penetrating system based on a 2D → 3D parallel polycatenation array. Compound exhibits an unprecedented 3D self-penetrating structure having both 1D + 1D → 1D polycatenation and 3D + 3D → 3D interpenetration characteristics. A comparison of these six compounds demonstrates that both the different spacer lengths of the aliphatic dicarboxylates and reactant ratios appear to play a significant role in the assembly of entangled frameworks. In addition, thermal stabilities and photoluminescence properties of have been examined in the solid state at room temperature.

Soil invertebrate fauna affect N2 O emissions from soil.

PubMed

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

2013-09-01

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

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

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

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

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

Measurements and Interpretation of Surface Mixing Ratios of CH4 and CO and δ 13C and δ D of CH4 in Air from Pacific Ocean Transects Between Auckland, New Zealand and Los Angeles, California

NASA Astrophysics Data System (ADS)

Ajie, H. O.; Tyler, S. C.; Gotoh, A. A.; McMillan, A. M.; Rice, A. L.; Lowe, D. C.

2003-12-01

We report on measurements of atmospheric CH4 and CO mixing ratios and δ 13C of CH4 from air samples collected every 2.5 to 5° latitude along a transect over the Pacific Ocean using container ships of P&O Nedlloyd (formerly Blue Star) shipping line. Data presented here begins in June 1996 and extends to January 2002. Scientists from the National Institute of Water and Atmospheric Research in New Zealand and from University of California, Irvine alternate sampling trips so that a transect between Auckland, New Zealand (35° S) and Los Angeles, California (35° N) can be sampled over a period of ˜15 days approximately every four months. Data sets from the two laboratories are intercalibrated through a sample exchange program. The data provide detail on the spatial and seasonal variation of CH4 and CO mixing ratios and stable isotope ratios of CH4 over the Pacific equatorial region, including the Intertropical Convergence Zone (ITCZ) and both northern and southern temperate zones to about 30° latitude, including the South Pacific Convergence Zone (SPCZ). Data from 18 transect samplings so far clearly show that δ 13C in the mid latitudes of both hemispheres are ˜6 months out of phase. In June, a minimum in δ 13C CH4 in the southern hemisphere (SH) coincides approximately with the maximum in the northern hemisphere (NH) seasonal cycle. Because the NH is less enriched in 13C than the SH this situation results in a remarkably flat gradient between 30° N and 30° S. In November the opposite situation occurs with the SH mid latitude maximum coinciding with the minimum in the NH cycle, leading to a relatively large gradient of ˜0.5‰ between the hemispheres. We discuss how CH4 and CO mixing ratios are related to the changing positions and strengths of the ITCZ and SPCZ and how this data can be used in multi-dimensional models of atmospheric chemistry and transport to better define CH4 sources and sinks both temporally and spatially.

Synthesis, characterization and photocatalytic activity of mixed oxides derived from ZnAlTi ternary layered double hydroxides

NASA Astrophysics Data System (ADS)

Sahu, R. K.; Mohanta, B. S.; Das, N. N.

2013-09-01

A new series of Ti4+ containing ZnAl-LDHs with varying Zn:Al:Ti (~3:1:0-3:0.5:0.5) ratio were prepared by coprecipitation of homogeneous solution metal salts and characterized by various physicochemical methods. Powder XRD revealed the formation of well crystallized LDH even at the highest Ti4+ content. On thermal treatment at 450 °C, the well crystallized LDH precursors yielded mixed oxides with BET surface area in the range 92-118 m2/g. UV-vis diffuse reflection spectroscopy (DRS) showed a marginal decrease of band gap energy for calcined ZnAlTi-LDHs in comparison to either ZnO or TiO2-P25. The TEM analyses of a representative sample (as-synthesized and calcined) indicated more or less uniform distribution of titanium species. The derived mixed oxides from titanium containing LDH precursors demonstrated better activity toward photodegradation of methylene blue and rhodamine B than those of a physical mixture of ZnO and TiO2. Moreover, the present work not only provided a first hand understanding about semiconductor properties of ZnAlTi-LDHs but also demonstrated their potential as photocatalysts for degradation of organic pollutants.

Newer mixed ligand Schiff base complexes from aquo-N-(2‧-hydroxy acetophenone) glycinatocopper(II) as synthon: DFT, antimicrobial activity and molecular docking study

NASA Astrophysics Data System (ADS)

Pramanik, Harun A. R.; Das, Dharitri; Paul, Pradip C.; Mondal, Paritosh; Bhattacharjee, Chira R.

2014-02-01

Synthesis of a series of newer mixed ligand copper(II) complexes of aminoacid Schiff base of the type [CuL(X)] (L = N-(2‧-hydroxy acetophenone) glycinate, X = imidazole (im) 2, benzimidazole (benz) 3, pyridine (py) 4, hydrazine (hz) 5,8-hydroxyquinoline (8-hq) 6, pyrrolidine (pyrr) 7, piperidine (pip) 8, and nicotinamide (nic) 9) have been accomplished from the interaction of an aquated Schiff base complex, [CuL(H2O)]·H2O, 1 with some selected neutral nitrogen-donor ligands. The copper(II) Schiff base complex, [CuL(H2O)]·H2O, L = N-(2‧-hydroxy acetophenone) glycinate was synthesized from the reaction of glycine and 2‧ hydroxy acetophenone and copper(II) acetate. The compounds were characterised by elemental analysis, spectral, magnetic and thermal studies. The density functional theory calculations were performed using LANL2DZ and 6-311 G(d, p) basis sets with B3LYP correlation functional to ascertain the stable electronic structure, HOMO-LUMO energy gap, chemical hardness and dipole moment of the mixed ligand complexes. A distorted square planar geometry has been conjectured for the complexes. Antibacterial activities of the ligand and its metal complexes have been tested against selected gram-positive and gram-negative strains and correlated with computational docking scores.

Synthesis, characterization and color performance of novel Co²+-doped alumina/titania nanoceramic pigments.

PubMed

Hafez, Hoda S; El-Fadaly, E

2012-09-01

Blue-green nanoceramic pigments from Co(2+)-doped alumina-titania (xCo(2+)-Al(2)O(3)/TiO(2)) have been synthesized by alkoxide sol-gel route from a mixture of titania and boehmite sols that derived from titanium isopropoxide and aluminum nitrate precursors. The composition of the alumina/titania (AT) matrix is 3:1M ratio. A series of xCo(2+):3TiO(2):1Al(2)O(3) mixed oxides with different Co(2+)-dopant ion concentration has been prepared. The molar ratio of the Co(2+)-dopant ion in the Al(2)O(3)/TiO(2) matrix is from x=0 to 0.5M ratio relative to the titania composition. Characterizations of Co(2+)-doped alumina/titania nanocomposites are carried out using reflectance spectroscopy, transmission electron microscope (TEM), scanning electron microscopy (SEM-EDS), thermo-gravimetric analysis (TGA) and X-ray diffractometer (XRD). The experimental results demonstrated that the prepared Co(2+)-doped alumina-titania nanocomposites fulfill the current technological requirements for ceramic pigment applications that exhibit a high physico-chemical and thermal stabilities at high firing temperatures. Copyright © 2012 Elsevier B.V. All rights reserved.

Synthesis, characterization and electrochemical performance of graphene decorated with 1D NiMoO4.nH2O nanorods

NASA Astrophysics Data System (ADS)

Ghosh, Debasis; Giri, Soumen; Das, Chapal Kumar

2013-10-01

One-dimensional NiMoO4.nH2O nanorods and their graphene based hybrid composite with good electrochemical properties have been synthesized by a cost effective hydrothermal procedure. The formation of the mixed metal oxide and the composite was confirmed by XRD, XPS and Raman analyses. The morphological characterizations were carried out using FESEM and TEM analyses. The materials were subjected to electrochemical characterization through cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS) studies with 6 M KOH as the supporting electrolyte. For NiMoO4.nH2O, a maximum specific capacitance of 161 F g-1 was obtained at 5 A g-1 current density, accompanied with an energy density of 4.53 W h kg-1 at a steady power delivery rate of 1125 W kg-1. The high utility of the pseudocapacitive NiMoO4.nH2O was achieved in its graphene based composite, which exhibited a high specific capacitance of 367 F g-1 at 5 A g-1 current density and a high energy density of 10.32 W h kg-1 at a power density of 1125 W kg-1 accompanied with long term cyclic stability.One-dimensional NiMoO4.nH2O nanorods and their graphene based hybrid composite with good electrochemical properties have been synthesized by a cost effective hydrothermal procedure. The formation of the mixed metal oxide and the composite was confirmed by XRD, XPS and Raman analyses. The morphological characterizations were carried out using FESEM and TEM analyses. The materials were subjected to electrochemical characterization through cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS) studies with 6 M KOH as the supporting electrolyte. For NiMoO4.nH2O, a maximum specific capacitance of 161 F g-1 was obtained at 5 A g-1 current density, accompanied with an energy density of 4.53 W h kg-1 at a steady power delivery rate of 1125 W kg-1. The high utility of the pseudocapacitive NiMoO4.nH2O was achieved in its graphene based composite, which exhibited a high specific capacitance of 367 F g-1 at 5 A g-1 current density and a high energy density of 10.32 W h kg-1 at a power density of 1125 W kg-1 accompanied with long term cyclic stability. Electronic supplementary information (ESI) available: Materials used, characterization techniques and preparation of electrode, tables containing specific capacitance, coulombic efficiency, energy density and power density values at different current densities of NiMoO4.nH2O and Gr-NiMoO4.nH2O. See DOI: 10.1039/c3nr02444j

[Control strategies of nitrogen removal process in a pilot test of the southern WWTP based on the nitrogen balance].

PubMed

Jiang, Ying-He; Liu, Pei-Ju; Wang, Lei; Tian, Zhong-Kai; Liu, Xiao-Ying

2014-04-01

By building the mass balance of nitrogen in A2/O process, the nitrogen model which raised some strategies on how to control sludge return ratio and mixed liquid return ratio to make the effluent nitrogen achieve the national standard A under different influent total nitrogen (TN) , was set up. And the presumed parameters were verified by the pilot test of the Wuhan's Longwangzui WWTP. The result showed that when the temperature and the TN were over 15 degrees C and below 30 mg x L(-1) respectively, the mixed liquid return ratio was 0. When the temperature was between 10 degrees C and 15 degrees C and TN was over 30 mg x L(-1), higher MLSS and DO elevated N removal. When the temperature was far below 10 degrees C, the mixed liquid return ratio was also at a higher level. Based on the Wuhan's Longwangzui WWTP influent water quality, measures of adjusting the return ratio were well adapted to obtain acceptable nitrogen effluent.

Deep extractive and oxidative desulfurization of dibenzothiophene with C5H9NO·SnCl2 coordinated ionic liquid.

PubMed

Li, Fa-tang; Kou, Cheng-guang; Sun, Zhi-min; Hao, Ying-juan; Liu, Rui-hong; Zhao, Di-shun

2012-02-29

A new C5H9NO·SnCl2 coordinated ionic liquid (IL) was prepared by reacting N-methyl-pyrrolidone with anhydrous SnCl2. Desulfurization of dibenzothiophene (DBT) via extraction and oxidation with C5H9NO·SnCl2 IL as extractant, H2O2 and equal mol of CH3COOH as oxidants was investigated. The Nernst partition coefficients k(N) of C5H9NO·SnCl2 IL for the DBT in n-octane was above 5.0, showing its excellent extraction ability. During the oxidative desulfurization process, the optimal molar ratio of H2O2/DBT was six. Sulfur removal of DBT in n-octane was 94.8% in 30 min at 30 °C under the conditions of H2O2/DBT molar ratio of six and V (IL):V (oil)=1:3. Moreover, the sulfur removal increased with increasing temperature because of the high reaction rate constant, low viscosity, and high solubility of dibenzothiophene-sulfone in the IL. The kinetics of oxidative desulfurization of DBT was also investigated, and the apparent activation energy was found to be 32.5 kJ/mol. The IL could be recycled six times without a significant decrease in activity. Copyright © 2011 Elsevier B.V. All rights reserved.

Effect of the Cerium Oxide (CeO2) on the Structural and Electrochemical Properties of the LaNi5Ce Metal Hydride Anode

NASA Astrophysics Data System (ADS)

Utami Hapsari, Ade; Zulfia, Anne; Raharjo, Jarot; Agustanhakri

2017-07-01

One of negative electrode, AB5-type alloy electrodes, have been extensively studied and applied in rechargeable Ni-MH batteries due to their excellent electrochemical characteristics. Some researchers have found that addition of rare earth oxides (La, Ce, Pr, Er, Tm, Yb) to AB5-type alloy (MH) electrode improves battery performance significantly. Cerium Oxide (CeO2) is a light rare earth oxide is widely obtained from the processing of tailings in mining activities. During this time, there is still little data for research applications of cerium oxide for electrode materials. In this paper, the effects of adding CeO2 on the performance metal hydride electrode were investigated. In order to study the effects of CeO2 on the performance of anode material, 1%, 2%, and 3% of weight ratio CeO2 was mixed to LaNi5 as an negative electrode. The powder mixtures were mechanically milled at a speed of rpm 240 for 2 hours using ball mill. The powder mixtures were characterized by X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM). Electrochemical characteristics were measured using electrochemical impedance spectroscopy (EIS). The powder mixing showed the presence of Ce atom substitution into LaNi5 structures that affect the electrochemical properties of the material. The addition of cerium oxide at LaNi5 increase of the value of impedance. However, the addition of the value of impedance at 1% CeO2 is not significant when compared with the addition of 2% and 3% CeO2 that actually make the electrochemical properties of LaNi5 worst. Although the addition of 1% CeO2 also slightly increases the impedance value of LaNi5, but the addition of 1% CeO2 showed increase the corrosion resistance than without the addition of CeO2 and the addition of 2% and 3% CeO2.

Performance of combined sodium persulfate/H2O2 based advanced oxidation process in stabilized landfill leachate treatment.

PubMed

Hilles, Ahmed H; Abu Amr, Salem S; Hussein, Rim A; El-Sebaie, Olfat D; Arafa, Anwaar I

2016-01-15

A combination of persulfate and hydrogen peroxide (S2O8(2-)/H2O2) was used to oxidizelandfill leachate. The reaction was performed under varying S2O8(2-)/H2O2 ratio (g/g), S2O8(2-)/H2O2 dosages (g/g), pH, and reaction time (minutes), so as to determine the optimum operational conditions. Results indicated that under optimum operational conditions (i.e. 120 min of oxidation using a S2O8(2-)/H2O2 ratio of 1 g/1.47 g at a persulfate and hydrogen peroxide dosage of 5.88 g/50 ml and8.63 g/50 ml respectively, at pH 11) removal of 81% COD and 83% NH3-N was achieved. In addition, the biodegradability (BOD5/COD ratio) of the leachate was improved from 0.09 to 0.17. The results obtained from the combined use of (S2O8(2-)/H2O2) were compared with those obtained with sodium persulfate only, hydrogen peroxide only and sodium persulfate followed by hydrogen peroxide. The combined method (S2O8(2-)/H2O2) achieved higher removal efficiencies for COD and NH3-N compared with the other methods using a single oxidizing agent. Additionally, the study has proved that the combination of S2O8(2-)/H2O2 is more efficient than the sequential use of sodium persulfate followed by hydrogen peroxide in advanced oxidation processes aiming at treatingstabilizedlandfill leachate. Copyright © 2015 Elsevier Ltd. All rights reserved.

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

PubMed

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

2016-10-26

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

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

NASA Astrophysics Data System (ADS)

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

2016-10-01

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

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

PubMed Central

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

2016-01-01

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

Deposition Velocities of C1 - C5 Alkyl Nitrates at a Northern Colorado Site

NASA Astrophysics Data System (ADS)

Abeleira, A.; Sive, B. C.; Farmer, D.; Swarthout, B.

2017-12-01

Organic nitrates (RONO2) are ubiquitous in the troposphere and are part of gas-phase oxidized nitrogen (NOy = NOx + HNO3 + HONO + N2O5 + HO2NO2 + PAN + NO3 + RONO2). RONO2 can act as both sinks and sources of HOx (RO + RO2 + OH) and NOx (NO + NO2), contributing to the nonlinearity of ozone (O3) formation. It is thus potentially important to understand sinks of RONO2, and how they change seasonally, in order to predict O3 on local, regional and global scales. We focus here on speciated C1 - C5 monofunctional alkyl nitrates (C1 - C5 ANs). In polluted continental regions the dominant source of C1 - C5 ANs is the OH-initiated oxidation of parent alkanes in the presence of NO, and thus changes seasonally with OH mixing ratios. Direct emissions of C1 - C2 ANs include oceanic sources and biomass burning. The sinks of C1 - C5 ANs include OH oxidation and photolysis, both of which release O3 precursors. Chemical transport models tend to overestimate the mixing ratios of small ANs indicating that a missing sink is not included. Wet deposition of C1 - C5 ANs is typically ignored due to the very low Henry's Law constants of these species. However, dry deposition of total organic nitrogen has been observed to be substantial. The dry deposition velocity of methyl nitrate has previously been estimated from summer observations at a rural New England site with a value of 0.13 cm s-1. Here we report deposition velocities for C1 - C5 ANs from surface observations at the Boulder Atmospheric Observatory (BAO) in Erie, Colorado during winter 2011 and spring 2015. We calculate deposition velocities from the observed decay in C1 - C5 ANs at night during periods with a stable nocturnal boundary layer height of 100 - 200 meters. Ideal meteorological conditions were observed for 5 nights during the 2011 NACHTT campaign (February - March 2011), and for 5 nights during the 2015 SONGNEX campaign (March - May 2015). Deposition velocities increased with alkyl nitrate size, ranging from 0.15 cm/s for methyl nitrate to 0.36 cm s-1 for 2-pentyl nitrate. The deposition rate impacts the lifetime of C1 - C5 ANs, and will be discussed in detail. For example, the winter lifetime of methyl nitrate from photolysis and OH oxidation at the BAO site is estimated to be 39 - 46 days while the dry deposition lifetime is estimated to be 1 - 3 days.

Green Approach To Synthesize Crystalline Nanoscale ZnII-Coordination Polymers: Cell Growth Inhibition and Immunofluorescence Study.

PubMed

Mukherjee, Somali; Ganguly, Sumi; Manna, Krishnendu; Mondal, Sanchaita; Mahapatra, Supratim; Das, Debasis

2018-04-02

Five new coordination polymers (CPs) namely, [{Zn(μ 2 -H 2 O) 0.5 (5N 3 -IPA)(2,2'-bpe)}] ∞ (1), [{Zn(μ 2 -H 2 O) 0.5 (5N 3 -IPA)(1,10-phen)}] ∞ (2), [{Zn(5N 3 -IPA)(1,2-bpe)}] ∞ (3), [{Zn(5N 3 -IPA)(1,2-bpey)}] ∞ (4), and [{Zn(H 2 O)(5N 3 -IPA)(4,4'-tme)}(H 2 O) 0.5 ] ∞ (5) (5N 3 -H 2 IPA = 5-azidoisophthalic acid, 2,2'-bpe= 2,2'-bipyridine, 1,10-phen = 1,10-phenanthroline, 1,2-bpe = 1,2-bis(4-pyridyl)ethane, 1,2-bpey = 1,2-bis(4-pyridyl)ethylene, 4,4'-tme = 4,4'-trimethylenedipyridine), have been synthesized based on a mixed ligand approach adopting a solvothermal technique. Depending upon the intrinsic structural flexibility of the bis-pyridyl coligands, interesting structural topologies have also been observed in the resulting CPs: Sra SrAl2 type topology for 3 and a 3-fold interpenetrated dmp topology for 4. A green hand grinding technique has been implemented to reduce the particle size of the CPs to generate nanoscale CPs (NCPs). SEM studies of NCPs reveal the formation of square and spherical particles for NCP 1 and 2, respectively, and nano rod for NCP 3, 4, and 5. Remarkably, when scaled down to nano range all the NCPs retain their crystalline nature. The cytotoxic activity of the NCPs (1-5) has been studied using human colorectal carcinoma cells (HCT 116). Significant cell death is observed for NCP 2, which is further corroborated by cell growth inhibition study. The observed cell death is likely to be due to mitochondrial-assisted apoptosis as is evident from immunofluorescence study.

Synthesis Of Nanosized CGYO Powders Via Glycine Nitrate Methods As Precursors For Dense Ceramic Membranes

NASA Astrophysics Data System (ADS)

Kochhar, Savinder P.; Singh, Anirudh P.

2011-12-01

Glycine nitrate combustion method was used to synthesize Ce0.8Gd0.1Y0.1O1.9 powders. Soluble metal-glycine complexes, detected by infrared spectroscopy, were formed by atomic level mixing of metal cations with glycine. The concentration of glycine has been varied in order to change the fuel to oxidant ratio i.e. of glycine to nitrate (g/n) with the purpose to study the effect of concentration of glycine on the parameters of resulting CGYO powder. The ratio of glycine to nitrate per mole is 0.5, 0.7, 0.8, 0.9, 1.0, 1.2, and 1.4. Increasing the glycine increases the temperatures reached during combustion. Powders prepared from GNP method demonstrated that combustion synthesized powders have large surface area as shown by SEM.

A Survey of Large Molecules of Biological Interest toward Selected High Mass Star Forming Regions

NASA Technical Reports Server (NTRS)

Remijan, A.; Shiao, Y.-S.; Friedel, D. N.; Meier, D. S.; Snyder, L. E.

2004-01-01

We have surveyed three high mass Galactic star forming regions for interstellar methanol (CH3OH), formic acid (HCOOH), acetic acid (CH3COOH), methyl formate (HCOOCH3), methyl cyanide (CH3CN), and ethyl cyanide (CH3CH2CN) with the BIMA Array. From our observations, we have detected two new sources of interstellar HCOOH toward the hot core regions G19.61-0.23 and W75N. We have also made the first detections of CH3CH2CN and HCOOCH3 toward G19.61-0.23. The relative HCOOH/HCOOCH3 abundance ratio toward G19.61-0.23 is 0.18 which is comparable to the abundance ratios found by Liu and colleagues toward Sgr B2(N-LMH), Orion and W51(approximately 0.10). We have made the first detection of HCOOCH3 toward W75N. The relative HCOOH/HCOOCH3 abundance ratio toward W75N is 0.26 which is more than twice as large as the abundance ratios found by Liu and colleagues. Furthermore, the hot core regions around W75N show a chemical differentiation between the O and N cores similar to what is seen toward the Orion Hot Core and Compact Ridge and W3(OH) and W3(H2O). It is also apparent from our observations that the high mass star forming region G45.47+0.05 does not contain any compact hot molecular core and as a consequence its chemistry may be similar to cold dark clouds. Finally, the formation of CH3COOH appears to favor HMCs with well mixed N and O, despite the fact that CH3COOH does not contain a N atom. If proved to be true, this is an important constraint on CH3COOH formation and possibly other structurally similar biomolecules.

Continuous field measurements of δD in water vapor by open-path Fourier transform infrared spectrometry

NASA Astrophysics Data System (ADS)

Wang, Wei; Liu, Wenqing; Zhang, Tianshu

2012-12-01

The stable isotopes in atmospheric water vapor contain rich information on the hydrologic cycles and gaseous exchange processes between biosphere and atmosphere. About one-week field experiment was conducted to continuously measure the isotope composition of water vapor in ambient air using an open-path FTIR system. Mixing ratios of H2 16O and HD16O were measured simultaneously. Analysis of water vapor isotopes revealed that the variations of H2 16O and HD16O were highly related. Mixing ratios of both isotopes varied considerably on a daily timescale or between days, with no obvious diurnal cycle, whereas the deuterium isotopic [delta]D showed clear diel cycle. The results illustrated that the correlation between [delta]D and H2O mixing ratio was relatively weak, which was also demonstrated by the Keeling plot analysis with the whole data. Yet the further Keeling analysis on a daily timescale displayed more obvious linear relationship between [delta]D and the total H2O concentration. All daily isotopic values of evapotranspiration source were obtained, with the range between -113.93±10.25‰ and -245.63±17.61‰ over the observation period.

Observations of D/H ratios in H2O, HCl, and HF on Venus and new DCl and DF line strengths

NASA Astrophysics Data System (ADS)

Krasnopolsky, V. A.; Belyaev, D. A.; Gordon, I. E.; Li, G.; Rothman, L. S.

2013-05-01

Intensities of the spectral lines in the fundamental bands of D35Cl and DF were calculated using the semi-empirical dipole moment functions derived from the most accurate and precise measurements of intensities of the ro-vibrational lines of H35Cl and HF. Values obtained in this way for the deuterated species are superior to any available measured or calculated data to date. Our study of the D/H ratios in H2O, HCl, and HF on Venus is based on spatially-resolved high-resolution spectroscopy using the CSHELL spectrograph at NASA IRTF. Search for DF on Venus using its R5 (1-0) line at 3024.054 cm-1 results in a DF mixing ratio of 0.23 ± 0.11 ppb that corresponds to (D/H)HF = 420 ± 200 times that in the Standard Mean Ocean Water (SMOW). H2O abundances on Venus were retrieved using lines at 3022.366 and 3025.761 cm-1 that were observed at an exceptionally low overhead telluric water abundance of 0.3 pr. mm. The measured H2O mixing ratios at 74 km vary insignificantly between 55°S and 55°N with a mean value of 3.2 ppm. When compared with simultaneous observations of HDO near 2722 cm-1, this results in (D/H)H2O = 95 ± 15 times SMOW. Reanalysis of the observation of the D35Cl R4 (1-0) line at 2141.540 cm-1 (Krasnopolsky, V.A. [2012b]. Icarus 219, 244-249) using the improved line strength and more thorough averaging of the spectra gives (D/H)HCl = 190 ± 50 times SMOW. The similarity of the measured (D/H)H2O = 95 ± 15 at 74 km with 120 ± 40 observed by De Bergh et al. (De Bergh, C., Bezard, B., Owen, T., Crisp, D., Maillard, J.P., Lutz, B.L. [1991]. Science 251, 547-549) below the clouds favors the constant (D/H)H2O from the surface to the mesosphere, in accord with the prediction by theory. D/H ≈ 100 removes a difference of a factor of 2 between H2O abundances in the observations by Krasnopolsky (Krasnopolsky, V.A. [2010b]. Icarus 209, 314-322) and the Venus Express nadir observations (Cottini, V., Ignatiev, N.I., Piccioni, G., Drossart, P., Grassi, D., Markiewicz, W.J. [2012]. Icarus 217, 561-569). Equivalent widths of the HDO and H2O lines are similar in our observations; therefore some errors cancel out in their ratios. Photochemistry of HCl in the mesosphere tends to enrich D in HCl and deplete it in H2O. This may be an explanation of the twofold difference between the observed D/H in HCl and H2O. An alternative explanation is based on (D/H)H2O ≈ 200 observed in the mesosphere by Bjoraker et al. (Bjoraker, G.L., Larson, H.P., Mumma, M.J., Timmermann, R., Montani, J.L. [1992]. Bull. Am. Astron. Soc. 24, 995) and Fedorova et al. (Fedorova, A. et al. J. Geophys. Res. 113, E00B22). This means an effective exchange of D between H2O and HCl and almost equal D/H in both species. However, this requires a twofold increase in D/H from the lower atmosphere to the mesosphere. This increase is not supported by theory; furthermore, condensation processes usually deplete D/H above the clouds. Photochemistry of HF has not been studied; it proceeds mostly in the lower thermosphere, and D/H in HF may be very different from that in H2O. Overall, the observational data on D/H in all hydrogen-bearing species on Venus are helpful to solve the problem of deuterium fractionation on Venus.

The Child-Langmuir laws and cathode sheath in the N2O

NASA Astrophysics Data System (ADS)

Lisovskiy, Valeriy; Artushenko, Ekaterina; Yegorenkov, Vladimir

2013-09-01

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

Mixing properties of coaxial jets with large velocity ratios and large inverse density ratios

NASA Astrophysics Data System (ADS)

Alexander Schumaker, S.; Driscoll, James F.

2012-05-01

An experimental study was conducted to better understand the mixing properties of coaxial jets as several parameters were systematically varied, including the velocity ratio, density ratio, and the Reynolds number. Diameters of the inner and outer jet were also varied. Coaxial jets are commonly used to mix fluids due to the simplicity of their geometry and the rapid mixing that they provide. A measure of the overall mixing efficiency is the stoichiometric mixing length (Ls), which is the distance along the jet centerline where the two fluids have mixed to some desired concentration, which was selected to be the stoichiometric concentration for H2/O2 and CH4/O2 in this case. For 56 cases, the profiles of mean mixture fraction, rms mixture fraction fluctuations (unmixedness), and Ls were measured using acetone planar laser induced fluorescence diagnostics. Results were compared to three mixing models. The entrainment model of Villermaux and Rehab showed good agreement with the data, indicating that the proper non-dimensional scaling parameter is the momentum flux ratio M. The work extends the existing database of coaxial jet scalar mixing properties because it considers the specific regime of large values of both the velocity ratio and the inverse density ratio, which is the regime in which rocket injectors operate. Also the work focuses on the mixing up to Ls where previous work focused on the mixing up to the end of the inner core. The Reynolds numbers achieved for a number of cases were considerably larger than previous gas mixing studies, which insures that the jet exit boundary conditions are fully turbulent.

Treatment of landfill leachate using a combined stripping, Fenton, SBR, and coagulation process.

PubMed

Guo, Jin-Song; Abbas, Abdulhussain A; Chen, You-Peng; Liu, Zhi-Ping; Fang, Fang; Chen, Peng

2010-06-15

The leachate from Changshengqiao landfill (Chongqing, China) was characterized and submitted to a combined process of air stripping, Fenton, sequencing batch reactor (SBR), and coagulation. Optimum operating conditions for each process were identified. The performance of the treatment was assessed by monitoring the removal of organic matter (COD and BOD(5)) and ammonia nitrogen (NH(3)-N). It has been confirmed that air stripping (at pH 11.0 and aeration time 18h) effectively removed 96.6% of the ammonia. The Fenton process was investigated under optimum conditions (pH 3.0, FeSO(4).7H(2)O of 20 g l(-1) and H(2)O(2) of 20 ml l(-1)), COD removal of up to 60.8% was achieved. Biodegradability (BOD(5)/COD ratio) increased from 0.18 to 0.38. Thereafter the Fenton effluent was mixed with sewage at dilutions to a ratio of 1:3 before it was subjected to the SBR reactor; under the optimum aeration time of 20 h, up to 82.8% BOD(5) removal and 83.1% COD removal were achieved. The optimum coagulant (Fe(2)(SO(4))(3)) was a dosage of 800 mg l(-1) at pH of 5.0, which reduced COD to an amount of 280 mg l(-1). These combined processes were successfully employed and very effectively decreased pollutant loading. Crown Copyright 2010. Published by Elsevier B.V. All rights reserved.

Facile synthesis of hierarchical gold nanostructures and their catalytic application

NASA Astrophysics Data System (ADS)

Ma, Ying; Siang Yi, Edward Ng

2016-08-01

We demonstrate a one-step, surfactant-free method to prepare gold (Au) nanostructures using a synthesized aniline (ANI) derivative N-(3-amidino)-aniline (NAAN) as a reducing agent. By simply mixing NAAN with a Au precursor, raspberry-like Au particles (RSPs) were formed. The presence of Ag+ resulted in the formation of Au nanoflowers (AuNFs). The size and shape of the AuNFs can be tuned by the reaction conditions such as the NAAN/HAuCl4 ratio, the temperature and the solvent composition. Under the same reaction conditions, bowling-pin-like particles (BPLPs) were reported for the first time using commercial ANI as a reducing agent. The AuNFs exhibited good ability to oxidize peroxidase substrate 3, 3‧, 5, 5‧-tetramethylbenzidine (TMB) by H2O2, allowing them as a peroxidase mimetic.

Constraints on the photolysis and the equilibrium constant of ClO-dimer from airborne and balloon-borne measurements of chlorine compounds

NASA Astrophysics Data System (ADS)

Kleinboehl, A.; Canty, T. P.; Salawitch, R. J.; Khosravi, M.; Urban, J.; Toon, G. C.; Kuellmann, H.; Notholt, J.

2011-12-01

Significant differences exist between different laboratory measurements of the photolysis cross-sections of ClO-dimer, and the rate constant controlling the thermal equilibrium between ClO-dimer and ClO. This leads to uncertainties in the calculations of stratospheric ozone loss in the winter polar regions. One way to constrain the plausibility of these parameters is the measurement of ClO across the terminator in the activated polar vortex. Here we analyze measurements of ClO taken by the airborne submillimeter radiometer ASUR in the Arctic winter of 1999/2000. We use measured ClO at low solar zenith angles (SZA) to estimate the total active chlorine (ClOx). We estimate total available inorganic chlorine (Cly) using ASUR measurements of N2O in January 2000 and a N2O-Cly correlation established by a balloon measurement of the MarkIV interferometer in December 1999. We compare the ClOx estimates based on different photolysis rates of ClO-Dimer. Our results show that cross-sections leading to fast photolysis rates like the ones by Burkholder et al. [1990] or Papanastasiou et al. [2009] give ClOx mixing ratios that overlap with our estimated range of available Cly. Slower photolysis rates like the ones by von Hobe et al. [2009] and Pope et al. [2007] lead to ClOx values that are significantly higher than the available Cly. We use the calculated ClOx from low SZA to estimate the ClO in darkness with different equilibrium constants, and compare it with ASUR ClO measurements before sunrise (SZA > 95). We find that calculations with equilibrium constants published in the JPL evaluation of the last few years all give good agreement with observed ClO mixing ratios. The equilibrium constant estimated by von Hobe et al. [2005] yields ClO values that are higher than the ones observed.

Mitigation of soil N2O emission by inoculation with a mixed culture of indigenous Bradyrhizobium diazoefficiens

NASA Astrophysics Data System (ADS)

Akiyama, Hiroko; Hoshino, Yuko Takada; Itakura, Manabu; Shimomura, Yumi; Wang, Yong; Yamamoto, Akinori; Tago, Kanako; Nakajima, Yasuhiro; Minamisawa, Kiwamu; Hayatsu, Masahito

2016-09-01

Agricultural soil is the largest source of nitrous oxide (N2O), a greenhouse gas. Soybean is an important leguminous crop worldwide. Soybean hosts symbiotic nitrogen-fixing soil bacteria (rhizobia) in root nodules. In soybean ecosystems, N2O emissions often increase during decomposition of the root nodules. Our previous study showed that N2O reductase can be used to mitigate N2O emission from soybean fields during nodule decomposition by inoculation with nosZ++ strains [mutants with increased N2O reductase (N2OR) activity] of Bradyrhizobium diazoefficiens. Here, we show that N2O emission can be reduced at the field scale by inoculation with a mixed culture of indigenous nosZ+ strains of B. diazoefficiens USDA110 group isolated from Japanese agricultural fields. Our results also suggested that nodule nitrogen is the main source of N2O production during nodule decomposition. Isolating nosZ+ strains from local soybean fields would be more applicable and feasible for many soybean-producing countries than generating mutants.

Mitigation of soil N2O emission by inoculation with a mixed culture of indigenous Bradyrhizobium diazoefficiens

PubMed Central

Akiyama, Hiroko; Hoshino, Yuko Takada; Itakura, Manabu; Shimomura, Yumi; Wang, Yong; Yamamoto, Akinori; Tago, Kanako; Nakajima, Yasuhiro; Minamisawa, Kiwamu; Hayatsu, Masahito

2016-01-01

Agricultural soil is the largest source of nitrous oxide (N2O), a greenhouse gas. Soybean is an important leguminous crop worldwide. Soybean hosts symbiotic nitrogen-fixing soil bacteria (rhizobia) in root nodules. In soybean ecosystems, N2O emissions often increase during decomposition of the root nodules. Our previous study showed that N2O reductase can be used to mitigate N2O emission from soybean fields during nodule decomposition by inoculation with nosZ++ strains [mutants with increased N2O reductase (N2OR) activity] of Bradyrhizobium diazoefficiens. Here, we show that N2O emission can be reduced at the field scale by inoculation with a mixed culture of indigenous nosZ+ strains of B. diazoefficiens USDA110 group isolated from Japanese agricultural fields. Our results also suggested that nodule nitrogen is the main source of N2O production during nodule decomposition. Isolating nosZ+ strains from local soybean fields would be more applicable and feasible for many soybean-producing countries than generating mutants. PMID:27633524

The study of new complex compounds of Ni (II) and Co (II) with N- hydroxy-succinimide and their potential applications as sensors

NASA Astrophysics Data System (ADS)

Sibiescu, Doina; Tutulea, Mihaela-Dana; Mîţă, Carmen; Stan, Corneliu; Roţca, Ioan; Vizitiu, Mihaela

2010-11-01

In this paper, the study of obtaining new coordination compounds of Ni (II) and Co(II) using as ligand, N-hydroxy-succinimide, was presented. Also, the stability constants of these compounds in aqueous medium were determined. The obtaining conditions and the stability of the new compounds were accomplished in aqueous solutions using characteristic methods for coordination compounds: pH-metry, conductometry and UV-VIS absorption spectroscopy. The combination ratios and the stability constants were determined with methods characteristic for studies in solutions. From experimental data resulted that the combination ratio of central metallic atoms with the ligand N-hydroxy-succinimide was: 1:1 and respectively 1:2. In the experiments were used salts of NiCl2.6H2O and CoCl2.6H2O. The optimal domain of pH stability of the studied compounds is limited between 5.74 - 5.86 for Co- N-hydroxy-succinimide (for molar ratio 1:1 and 1:2) and respectively 5.69 - 5.87 for Ni-N-hydroxysuccinimide( for molar ratio 1:1 and 1:2, too). It is important to mention that these compounds were used with very good results in determination of wastewaters from textile, metallurgical, chemical and food industry. Complexion reactions with this ligand are very sensitive for the cations in this paper mentioned. Therefore it is used most often with success in analytical chemistry and also it is posibil to use as sensors. The new complex compounds has electronics transitions at λ = 517 nm for both complexes Co-N-hydroxy-succinimide at molar ratio 1:1 and 1:2 and also at the same λ = 397nm for Ni-N-hydroxysuccinimide at molar ratio 1:1 and 1:2. These complexes compounds was separated and recrystallized from aqueous solution. From the spectrophotometric data it was determined the type and the nature of the electronics transitions by Dq parameters.

Reactive Nitrogen Multiphase Chemistry and Chlorine Activation on Authentic Biomass Burning Aerosol

NASA Astrophysics Data System (ADS)

Goldberger, Lexie

Biomass burning is both a major source of particulate matter and reactive nitrogen oxide radicals, yet the rate and products of the multiphase chemistry between the two has not been well studied. Nitryl chloride (ClNO2), formed by the multiphase reaction of dinitrogen pentoxide (N2O 5) on chloride-containing particles, is known to occur in polluted marine environments where it contributes significantly to the oxidant budget. Since the observation of ClNO2 levels in a moderately polluted region far from the coast, there has been motivation to determine the source of particulate chloride, postulated as the limiting ingredient to ClNO2 formation. Using a smog chamber reactor at Carnegie Mellon University coupled to a biomass combustion chamber with controlled particle and gas injection, we simulated the nocturnal evolution of N2O5 in biomass burning plumes mixed with ozone. A range of authentic fuel types, including saw grass, cut grass, and white European birch were burned in the combustion chamber and a portion of the smoke plume was then mixed into the 12 m3 chamber, where it was exposed to 70-150 ppb of ozone and relative humidity ranging from 0-60% in the dark. Gaseous N 2O5, nitric acid (HNO3), ClNO 2, Cl2, and HCl were monitored using a high resolution time of flight iodide adduct chemical ionization mass spectrometer, and particle size distributions and composition were monitored continuously with an SMPS and a Soot-Particle Aerosol Mass Spectrometer among other instruments. With chemical mechanism modeling I attempt to abstract N2O 5 uptake coefficients as well as molar yields of ClNO2 and report correlated changes in Cl2 and HCl. I analyze dependences on combustion fuel type. These results suggest a potentially important impact of chlorine atom initiated oxidation in biomass burning plumes. The uptake of N2O5 and yields of ClNO2, Cl2, and HCl determined from this study will allow for more robust parameterizations of these compounds in atmospheric models.

The Consistency of Isotopologues of Ambient Atmospheric Nitric Acid in Passively Collected Samples

NASA Astrophysics Data System (ADS)

Bell, M. D.; Sickman, J. O.; Bytnerowicz, A.; Padgett, P.; Allen, E. B.

2012-12-01

Anthropogenic sources of nitrogen oxides have previously been shown to have distinctive isotopic signatures of oxygen and nitrogen. Nylon filters are currently used in passive sampling arrays to measure ambient atmospheric nitric acid concentrations and estimate deposition rates. This experiment measured the ability of nylon filters to consistently collect isotopologues of atmospheric nitric acid in the same ratios as they are present in the atmosphere. Samplers were deployed in continuous stirred tank reactors (CSTR) and at field sites across a nitrogen deposition gradient in Southern California. Filters were exposed over a four week period with individual filters being subjected to 1-4 week exposure times. Extracted nitric acid were measured for δ18O and δ15N ratios and compared for consistency based on length of exposure and amount of HNO3 collected. Filters within the CSTRs collected HNO3 at a consistent rate in both high and low concentration chambers. After two weeks of exposure, the mean δ18O values were within 0.5‰ of the δ18O of the source HNO3 solution. The mean of all weekly exposures were within 0.5‰ of the δ15N of the source solution, but after three weeks, the mean δ15N of adsorbed HNO3 was within 0.2‰. As the length of the exposure increased, the variability of measured delta values decreased for both elements. The field samplers collected HNO3 consistent with previously measured values along a deposition gradient. The mean δ18O at high deposition sites was 52.2‰ compared to 35.7‰ at the low deposition sites. Mean δ15N values were similar at all sites across the deposition gradient. Due to precipitation events occurring during the exposure period, the δ15N and δ18O of nitric acid were highly variable at all field sites. At single sites, changes in δ15N and δ18O were negatively correlated, consistent with two-sourcing mixing dynamics, but the slope of the regressions differed between high and low deposition sites. Anthropogenic sources of atmospheric nitric acid accounted for 58% of the atmospheric nitric acid at the high deposition sites and 36.5% of the atmospheric nitric acid at the low deposition sites. The nylon filters proved to be an effective means of collecting isotopologues of HNO3 consistent with atmospheric concentrations. A length of the exposure of two weeks stabilizes isotopologue composition and minimizes the chance of variable weather events altering atmospheric values.

Fuel clad chemical interactions in fast reactor MOX fuels

NASA Astrophysics Data System (ADS)

Viswanathan, R.

2014-01-01

Clad corrosion being one of the factors limiting the life of a mixed-oxide fast reactor fuel element pin at high burn-up, some aspects known about the key elements (oxygen, cesium, tellurium, iodine) in the clad-attack are discussed and many Fuel-Clad-Chemical-Interaction (FCCI) models available in the literature are also discussed. Based on its relatively superior predictive ability, the HEDL (Hanford Engineering Development Laboratory) relation is recommended: d/μm = ({0.507 ṡ [B/(at.% fission)] ṡ (T/K-705) ṡ [(O/M)i-1.935]} + 20.5) for (O/M)i ⩽ 1.98. A new model is proposed for (O/M)i ⩾ 1.98: d/μm = [B/(at.% fission)] ṡ (T/K-800)0.5 ṡ [(O/M)i-1.94] ṡ [P/(W cm-1)]0.5. Here, d is the maximum depth of clad attack, B is the burn-up, T is the clad inner surface temperature, (O/M)i is the initial oxygen-to-(uranium + plutonium) ratio, and P is the linear power rating. For fuels with [n(Pu)/n(M = U + Pu)] > 0.25, multiplication factors f are recommended to consider the potential increase in the depth of clad-attack.

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

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

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

2012-08-08

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

Effects of pH on nitrogen transformations in media-based aquaponics.

PubMed

Zou, Yina; Hu, Zhen; Zhang, Jian; Xie, Huijun; Guimbaud, Christophe; Fang, Yingke

2016-06-01

To investigate the effects of pH on performance and nitrogen transformations in aquaponics, media-based aquaponics operated at pH 6.0, 7.5 and 9.0 were systematically examined and compared in this study. Results showed that nitrogen utilization efficiency (NUE) reached its maximum of 50.9% at pH 6.0, followed by 47.3% at pH 7.5 and 44.7% at pH 9.0. Concentrations of nitrogen compounds (i.e., TAN, NO2(-)-N and NO3(-)-N) in three pH systems were all under tolerable levels. pH had significant effect on N2O emission and N2O conversion ratio decreased from 2.0% to 0.6% when pH increased from 6.0 to 9.0, mainly because acid environment would inhibit denitrifiers and lead to higher N2O emission. 75.2-78.5% of N2O emission from aquaponics was attributed to denitrification. In general, aquaponics was suggested to maintain pH at 6.0 for high NUE, and further investigations on N2O mitigation strategy are needed. Copyright © 2016 Elsevier Ltd. All rights reserved.

3D coordination polymers with nitrilotriacetic and 4,4'-bipyridyl mixed ligands: structural variation based on dinuclear or tetranuclear subunits assisted by Na-O and/or O-H...O interactions.

PubMed

Lü, Xing-Qiang; Jiang, Ji-Jun; Chen, Chun-Long; Kang, Bei-Sheng; Su, Cheng-Yong

2005-06-27

The reactions of Cu(II) with the mixed nitrilotriacetic acid (H3NTA) and 4,4'-bipyridyl (4,4'-bpy) ligands in different metal-to-ligand ratios in the presence of NaOH and NaClO4 afforded two complexes, Na3[Cu2(NTA)2(4,4'-bpy)]ClO4 x 5H2O (1) and [Cu2(NTA) (4,4'-bpy)2]ClO4 x 4H2O (2). The two complexes have been characterized by elemental analysis, IR, XRD, and single-crystal X-ray diffraction. 1 contains a basic doubly negatively charged [Cu2(NTA)2(4,4'-bpy)]2- dinuclear unit which was further assembled via multiple Na-O and O-H...O interactions into a three-dimensional (3D) pillared-layer structure. 2 features a two-dimensional (2D) undulated brick-wall architecture containing a basic doubly positively charged [Cu4(NTA)2(4,4'-bpy)2]2+ tetranuclear unit. The 2D network possesses large cavities hosting guest molecules and was further assembled via O-H...O hydrogen bonds into a 3D structure with several channels running in different directions.

In-Situ Denitrification and N2O Emission from Natural and Semi-natural Land Use Types in two UK Catchments

NASA Astrophysics Data System (ADS)

Sgouridis, F.; Ullah, S.

2014-12-01

Whilst data and understanding of the controls of denitrification process and the subsequent emission of N2O at microbial and plot scale exist, quantification of in situ annual denitrification rates at catchment scales is scarce due to methodological constraints in measuring in situ denitrification in large temporal and spatial scales. In situ denitrification (DNT) was measured monthly (April 2013 - October 2014) in organic (peat bog, heathland, acid grassland), forest (mixed and deciduous), and grassland (improved and semi-improved) land use types in the Ribble-Wyre and Conwy River catchments in the UK. A static chamber technique according to the 15N-Gas Flux method1 was employed for quantifying the fluxes of 15N-N2 and 15N-N2O gases after labelling the soil with 98 at% K15NO3- at tracer level amounts (10% of the ambient nitrate concentration) and sampling the chamber headspace at 0, 1, 2 and 20 hour intervals. The DNT rates ranged between 0 and 2.3 mg N m-2 h-1 and were significantly influenced by land use type (p<0.05). The annual denitrification rate of organic and forest soils (4 kg N ha-1 y-1) was 3 and 6 times less than that of semi-improved (12 kg N ha-1 y-1) and improved (23 kg N ha-1 y-1) grassland soils, respectively. The N2O emission, due to denitrification, followed a similar trend with lower fluxes from organic and higher from improved grassland soils (range: 0 - 0.04 mg N m-2 h-1), whilst the N2O:N2 ratio ranged between 0.2 and 4%. The relative contribution of denitrification to net N2O flux varied temporally and across the different land use types and ranged from 0.2 to 75%. The 15N-Gas Flux method can be successfully applied in a variety of land use types for relatively high temporal and spatial resolution measurement of in situ denitrification and the simultaneous quantification of N2 and N2O fluxes due to denitrification. Therefore the ratio of N2O:N2 and also the source apportionment for N2O can be estimated more accurately. The results suggested a difference in DNT rates between unmanaged/ low nitrate content versus managed/ high nitrate content land use types, which was further supported by the significant positive correlation between DNT and soil nitrate content. 1R. Stevens and R. Laughlin, Nutr. Cycling Agroecosyst., 1998, 52, 131-139.

Long Term Monitoring Trends In The Southeastern U.S.: Changes In Atmospheric Chemistry?

NASA Astrophysics Data System (ADS)

Blanchard, C. L.; Hidy, G. M.

2013-12-01

The SOS/SEARCH network has measured air pollutant concentrations in the southeastern U.S. since 1992, providing context for the 2013 Southeastern Organic Aerosol Study (SOAS). Ambient concentrations and species ratios indicate evolution in atmospheric chemistry. Since 1999, ~50 percent decreases in anthropogenic SOx, NOx, CO, and VOC emissions reduced gas and fine particle concentrations at all SEARCH sites. Primary but not secondary pollutant concentration decreases were approximately proportional to emission declines. Mean annual ambient SO2 mixing ratios at rural SEARCH sites decreased in proportion to annual SO2 emissions, whereas mean annual PM2.5 sulfate (SO4) concentrations decreased until 2009 but then showed minimal change despite continuing SO2 emission reductions. This difference suggests a change in oxidant-SO2 relationships. Between 1999 and 2012, the mean ratios of SO2/SOx (SOx = SO2 + SO4, molar basis) decreased from 0.68 × 0.04 to 0.57 × 0.05 and from 0.73 × 0.05 to 0.59 × 0.05 at two rural sites, indicating changes in SO4 production. Mean annual mixing ratios of oxidized nitrogen species (NOy) at rural sites decreased from 5.8 × 1.9 ppbv in 1992 to 4.8 × 1.4 ppbv in 2002 and 2.4 × 0.5 ppbv in 2012, proportional to NOx emission changes. Mean annual afternoon (noon through 4 p.m.) ratios of NOz/NOy (NOz = NOy - NOx) at rural sites varied between 0.36 and 0.63 from 1997 to 2011, without showing trends. Mean afternoon O3/NOy ratios increased at both urban and non-urban sites, e.g., from 8.3 × 0.4 in 1992 to 11.5 × 0.5 in 1999 and 19.9 × 0.9 in 2011 in rural Alabama, and from 2.0 × 0.1 in 1999 to 4.9 × 0.3 in 2011 in Atlanta, suggesting increased oxidation rates. Regression of daily peak 8-hour O3 against afternoon NOz yielded slopes ranging from urban 4.02 × 0.15 to rural 11.32 × 0.42, reflecting higher O3 production efficiency (OPE) at rural compared to urban sites. The OPE exhibited year-to-year variability with increasing trends at each site, e.g., from 9.8 × 0.8 in 2002 to 16.6 × 1.0 in 2011 and increasing at 1.06 × 0.39 units per year at one rural location. Year-to-year variability of mean O3, O3/NOy, O3/NOz, and NOz/NOy was related to meteorological variability. Anthropogenic emissions of VOCs in AL, GA, and MS decreased by 39 percent from 2002 to 2011, with proportionately larger decreases in mean annual NMOC in Atlanta, GA from 1999 to 2008. Mean annual mixing ratios of total NMOC decreased from 285 × 13 ppbC in 1999 to 120 × 4 ppbC in 2008; toluene and benzene decreased respectively from 14.8 × 0.8 ppbC and 4.5 × 0.2 ppbC in 1999 to 5.7 × 0.2 ppbC and 2.0 × 0.1 ppbC in 2008. The OH reactivity of the NMOC mixtures changed negligibly. The Atlanta mean NMOC/NOy varied from 4.8 × 0.3 in 1999 to 3.6 × 0.2 in 2008 without significant trend. Peak O3 and precursor concentrations suggest a transition from VOC to NOx sensitivity of O3 occurring between urban Atlanta and its rural surroundings. Particle composition showed significant reductions of SO4 and of organic and elemental carbon at all sites from 1999 to 2011. Mean PM2.5 nitrate (NO3) concentrations ranged from 0.3 - 0.9 μg m-3 at rural and coastal sites and 0.5 - 1.1 mg m-3 at inland urban sites, declined by 0.001 - 0.05 μg m-3 y-1, and represented on average 1 - 6 percent of NOy by mass.

Transitions from functionalization to fragmentation reactions of laboratory secondary organic aerosol (SOA) generated from the OH oxidation of alkane precursors.

PubMed

Lambe, Andrew T; Onasch, Timothy B; Croasdale, David R; Wright, Justin P; Martin, Alexander T; Franklin, Jonathan P; Massoli, Paola; Kroll, Jesse H; Canagaratna, Manjula R; Brune, William H; Worsnop, Douglas R; Davidovits, Paul

2012-05-15

Functionalization (oxygen addition) and fragmentation (carbon loss) reactions governing secondary organic aerosol (SOA) formation from the OH oxidation of alkane precursors were studied in a flow reactor in the absence of NO(x). SOA precursors were n-decane (n-C10), n-pentadecane (n-C15), n-heptadecane (n-C17), tricyclo[5.2.1.0(2,6)]decane (JP-10), and vapors of diesel fuel and Southern Louisiana crude oil. Aerosol mass spectra were measured with a high-resolution time-of-flight aerosol mass spectrometer, from which normalized SOA yields, hydrogen-to-carbon (H/C) and oxygen-to-carbon (O/C) ratios, and C(x)H(y)+, C(x)H(y)O+, and C(x)H(y)O(2)+ ion abundances were extracted as a function of OH exposure. Normalized SOA yield curves exhibited an increase followed by a decrease as a function of OH exposure, with maximum yields at O/C ratios ranging from 0.29 to 0.74. The decrease in SOA yield correlates with an increase in oxygen content and decrease in carbon content, consistent with transitions from functionalization to fragmentation. For a subset of alkane precursors (n-C10, n-C15, and JP-10), maximum SOA yields were estimated to be 0.39, 0.69, and 1.1. In addition, maximum SOA yields correspond with a maximum in the C(x)H(y)O+ relative abundance. Measured correlations between OH exposure, O/C ratio, and H/C ratio may enable identification of alkane precursor contributions to ambient SOA.

Vertical and meridional distributions of the atmospheric CO2 mixing ratio between northern midlatitudes and southern subtropics

NASA Astrophysics Data System (ADS)

Machida, T.; Kita, K.; Kondo, Y.; Blake, D.; Kawakami, S.; Inoue, G.; Ogawa, T.

2003-02-01

The atmospheric CO2 mixing ratio was measured using a continuous measurement system onboard a Gulfstream-II aircraft between the northern midlatitudes and the southern subtropics during the Biomass Burning and Lightning Experiment Phase A (BIBLE A) campaign in September-October 1998. The vertical distribution of CO2 over tropical regions was almost constant from the surface to an altitude of 13 km. CO2 enhancements from biomass burning and oceanic release were observed in the tropical boundary layer. Measurements in the upper troposphere indicate interhemispheric exchange was effectively suppressed between 2°N-7°N. Interhemispheric transport of air in the upper troposphere was suppressed effectively in this region. The CO2 mixing ratios in the Northern and Southern Hemispheres were almost constant, with an average value of about 365 parts per million (ppm) and 366 ppm, respectively. The correlation between the CO2 and NOy mixing ratios observed north of 7°N was apparently different from that obtained south of 2°N. This fact strongly supports the result that the north-south boundary in the upper troposphere during BIBLE A was located around 2°N-7°N as the boundary is not necessary a permanent feature.

Vertical and meridional distributions of the atmospheric CO2 mixing ratio between northern midlatitudes and southern subtropics

NASA Astrophysics Data System (ADS)

Machida, T.; Kita, K.; Kondo, Y.; Blake, D.; Kawakami, S.; Inoue, G.; Ogawa, T.

2002-02-01

The atmospheric CO2 mixing ratio was measured using a continuous measurement system onboard a Gulfstream-II aircraft between the northern midlatitudes and the southern subtropics during the Biomass Burning and Lightning Experiment Phase A (BIBLE A) campaign in September-October 1998. The vertical distribution of CO2 over tropical regions was almost constant from the surface to an altitude of 13 km. CO2 enhancements from biomass burning and oceanic release were observed in the tropical boundary layer. Measurements in the upper troposphere indicate interhemispheric exchange was effectively suppressed between 2°N-7°N. Interhemispheric transport of air in the upper troposphere was suppressed effectively in this region. The CO2 mixing ratios in the Northern and Southern Hemispheres were almost constant, with an average value of about 365 parts per million (ppm) and 366 ppm, respectively. The correlation between the CO2 and NOy mixing ratios observed north of 7°N was apparently different from that obtained south of 2°N. This fact strongly supports the result that the north-south boundary in the upper troposphere during BIBLE A was located around 2°N-7°N as the boundary is not necessary a permanent feature.

Comparative analysis of the effects of tantalum doping and annealing on atomic layer deposited (Ta{sub 2}O{sub 5}){sub x}(Al{sub 2}O{sub 3}){sub 1−x} as potential gate dielectrics for GaN/Al{sub x}Ga{sub 1−x}N/GaN high electron mobility transistors

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

Partida-Manzanera, T., E-mail: sgtparti@liv.ac.uk; Institute of Materials Research and Engineering, A*STAR; Roberts, J. W.

2016-01-14

This paper describes a method to optimally combine wide band gap Al{sub 2}O{sub 3} with high dielectric constant (high-κ) Ta{sub 2}O{sub 5} for gate dielectric applications. (Ta{sub 2}O{sub 5}){sub x}(Al{sub 2}O{sub 3}){sub 1−x} thin films deposited by thermal atomic layer deposition (ALD) on GaN-capped Al{sub x}Ga{sub 1−x}N/GaN high electron mobility transistor (HEMT) structures have been studied as a function of the Ta{sub 2}O{sub 5} molar fraction. X-ray photoelectron spectroscopy shows that the bandgap of the oxide films linearly decreases from 6.5 eV for pure Al{sub 2}O{sub 3} to 4.6 eV for pure Ta{sub 2}O{sub 5}. The dielectric constant calculated from capacitance-voltage measurementsmore » also increases linearly from 7.8 for Al{sub 2}O{sub 3} up to 25.6 for Ta{sub 2}O{sub 5}. The effect of post-deposition annealing in N{sub 2} at 600 °C on the interfacial properties of undoped Al{sub 2}O{sub 3} and Ta-doped (Ta{sub 2}O{sub 5}){sub 0.12}(Al{sub 2}O{sub 3}){sub 0.88} films grown on GaN-HEMTs has been investigated. These conditions are analogous to the conditions used for source/drain contact formation in gate-first HEMT technology. A reduction of the Ga-O to Ga-N bond ratios at the oxide/HEMT interfaces is observed after annealing, which is attributed to a reduction of interstitial oxygen-related defects. As a result, the conduction band offsets (CBOs) of the Al{sub 2}O{sub 3}/GaN-HEMT and (Ta{sub 2}O{sub 5}){sub 0.16}(Al{sub 2}O{sub 3}){sub 0.84}/GaN-HEMT samples increased by ∼1.1 eV to 2.8 eV and 2.6 eV, respectively, which is advantageous for n-type HEMTs. The results demonstrate that ALD of Ta-doped Al{sub 2}O{sub 3} can be used to control the properties of the gate dielectric, allowing the κ-value to be increased, while still maintaining a sufficient CBO to the GaN-HEMT structure for low leakage currents.« less

Structural and electronic properties of U{sub n}O{sub m} (n=1-3,m=1-3n) clusters: A theoretical study using screened hybrid density functional theory

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

Yang, Yu; Liu, Haitao; Zhang, Ping, E-mail: zhang-ping@iapcm.ac.cn

The structural and electronic properties of small uranium oxide clusters U{sub n}O{sub m} (n=1-3, m=1-3n) are systematically studied within the screened hybrid density functional theory. It is found that the formation of U–O–U bondings and isolated U–O bonds are energetically more stable than U–U bondings. As a result, no uranium cores are observed. Through fragmentation studies, we find that the U{sub n}O{sub m} clusters with the m/n ratio between 2 and 2.5 are very stable, hinting that UO{sub 2+x} hyperoxides are energetically stable. Electronically, we find that the O-2p states always distribute in the deep energy range, and the U-5fmore » states always distribute at the two sides of the Fermi level. The U-6d states mainly hybridize with the U-5f states in U-rich clusters, while hybridizing with O-2p states in O-rich clusters. Our work is the first one on the screened hybrid density functional theory level studying the atomic and electronic properties of the actinide oxide clusters.« less

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

NASA Technical Reports Server (NTRS)

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

1993-01-01

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

Resistivity and magnetic susceptibility studies of Tl[sub m]Ca[sub n[minus]1]Ba[sub 2]Cu[sub n]O[sub y] before and after doping with LiF

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

El-Hamalawy, A.A.; El-Zaidia, M.M.; Ammar, A.A.

1993-04-01

Measurements of the superconducting resistance as a function of temperature were performed using the conventional four-probe method. The transition to complete superconductivity was recorded for samples of (Tl[sub 2]Ca[sub 2]Ba[sub 2]Cu[sub 3]O[sub 10])[sub 100[minus]x]LiF[sub x] (2223) mixed with different LiF ratios x = 0, 2, 4, 5, 6, 8, 10, and 12wt.%. It was found that the transition temperature T[sub c] was increased up to 5 wt.% of LiF. Further addition of LiF decreases T[sub c]. Therefore, 5 wt.% LiF is the optimum concentration giving a transition temperature of 130 K. Measurements of the superconducting resistance of all the samplesmore » except the (1111) compound show that the addition of 5 wt.% LiF increases T[sub c] and decreases the metastable phases. The real part of the a.c. magnetic susceptibility [chi][sub a.c.] is studied using a zero-field cooled mechanism. The temperature dependence of [chi][sub a.c.] for the prepared TlBaCaCuO having stoichiometric composition of (1111), (2223), (2234), and (3245) and that after doping with 5 wt.% LiF showed a broad feature. The transition to the complete diamagnetic state takes place in a broad transition region containing many transition steps, indicating the presence of metastable phases. The addition of LiF decreases the fluctuation in the transition region and its effect in reducing the number of multiphases. 29 refs., 10 refs.« less

On the reduced lifetime of nitrous oxide due to climate change induced acceleration of the Brewer-Dobson circulation as simulated by the MPI Earth System Model

NASA Astrophysics Data System (ADS)

Kracher, D.; Manzini, E.; Reick, C. H.; Schultz, M. G.; Stein, O.

2014-12-01

Greenhouse gas induced climate change will modify the physical conditions of the atmosphere. One of the projected changes is an acceleration of the Brewer-Dobson circulation in the stratosphere, as it has been shown in many model studies. This change in the stratospheric circulation consequently bears an effect on the transport and distribution of atmospheric components such as N2O. Since N2O is involved in ozone destruction, a modified distribution of N2O can be of importance for ozone chemistry. N2O is inert in the troposphere and decays only in the stratosphere. Thus, changes in the exchange between troposphere and stratosphere can also affect the stratospheric sink of N2O, and consequently its atmospheric lifetime. N2O is a potent greenhouse gas with a global warming potential of currently approximately 300 CO2-equivalents in a 100-year perspective. A faster decay in atmospheric N2O mixing ratios, i.e. a decreased atmospheric lifetime of N2O, will also reduce its global warming potential. In order to assess the impact of climate change on atmospheric circulation and implied effects on the distribution and lifetime of atmospheric N2O, we apply the Max Planck Institute Earth System Model, MPI-ESM. MPI-ESM consists of the atmospheric general circulation model ECHAM, the land surface model JSBACH, and MPIOM/HAMOCC representing ocean circulation and ocean biogeochemistry. Prognostic atmospheric N2O concentrations in MPI-ESM are determined by land N2O emissions, ocean-atmosphere N2O exchange and atmospheric tracer transport. As stratospheric chemistry is not explicitly represented in MPI-ESM, stratospheric decay rates of N2O are prescribed from a MACC MOZART simulation. Increasing surface temperatures and CO2 concentrations in the stratosphere impact atmospheric circulation differently. Thus, we conduct a series of transient runs with the atmospheric model of MPI-ESM to isolate different factors governing a shift in atmospheric circulation. From those transient simulations we diagnose decreasing tropospheric N2O concentrations, increased transport of N2O from the troposphere to the stratosphere, and increasing stratospheric decay of N2O leading to a reduction in atmospheric lifetime of N2O, in dependency to climate change evolution.

Photovoltaic Performance Enhancement of Silicon Solar Cells Based on Combined Ratios of Three Species of Europium-Doped Phosphors

PubMed Central

You, Bang-Jin; Liu, Jheng-Jie; Bai, Wen-Bin; Syu, Hong-Jhang; Lin, Ching-Fuh

2018-01-01

This paper presents a scheme for the enhancement of silicon solar cells in terms of luminescent emission band and photovoltaic performance. The proposed devices are coated with an luminescent down-shifting (LDS) layer comprising three species of europium (Eu)-doped phosphors mixed within a silicate film (SiO2) using a spin-on film deposition. The three species of phosphor were mixed at ratios of 0.5:1:1.5, 1:1:1, or 1.5:1:0.5 in weight percentage (wt %). The total quantity of Eu-doped phosphors in the silicate solution was fixed at 3 wt %. The emission wavelengths of the Eu-doped phosphors were as follows: 518 nm (specie-A), 551 nm (specie-B), and 609 nm (specie-C). We examined the extended luminescent emission bands via photoluminescence measurements at room temperature. Closely matching the luminescent emission band to the high responsivity band of the silicon semiconductor resulted in good photovoltaic performance. Impressive improvements in efficiency were observed in all three samples: 0.5:1:1.5 (20.43%), 1:1:1 (19.67%), 1.5:1:0.5 (16.81%), compared to the control with a layer of pure SiO2 (13.80%). PMID:29783716

Epitaxial ZnO gate dielectrics deposited by RF sputter for AlGaN/GaN metal-oxide-semiconductor high-electron-mobility transistors

NASA Astrophysics Data System (ADS)

Yoon, Seonno; Lee, Seungmin; Kim, Hyun-Seop; Cha, Ho-Young; Lee, Hi-Deok; Oh, Jungwoo

2018-01-01

Radio frequency (RF)-sputtered ZnO gate dielectrics for AlGaN/GaN metal-oxide-semiconductor high-electron-mobility transistors (MOS-HEMTs) were investigated with varying O2/Ar ratios. The ZnO deposited with a low oxygen content of 4.5% showed a high dielectric constant and low interface trap density due to the compensation of oxygen vacancies during the sputtering process. The good capacitance-voltage characteristics of ZnO-on-AlGaN/GaN capacitors resulted from the high crystallinity of oxide at the interface, as investigated by x-ray diffraction and high-resolution transmission electron microscopy. The MOS-HEMTs demonstrated comparable output electrical characteristics with conventional Ni/Au HEMTs but a lower gate leakage current. At a gate voltage of -20 V, the typical gate leakage current for a MOS-HEMT with a gate length of 6 μm and width of 100 μm was found to be as low as 8.2 × 10-7 mA mm-1, which was three orders lower than that of the Ni/Au Schottky gate HEMT. The reduction of the gate leakage current improved the on/off current ratio by three orders of magnitude. These results indicate that RF-sputtered ZnO with a low O2/Ar ratio is a good gate dielectric for high-performance AlGaN/GaN MOS-HEMTs.

Catalytic activity of calcium-based mixed metal oxides nanocatalysts in transesterification reaction of palm oil

NASA Astrophysics Data System (ADS)

Hassan, Noraakinah; Ismail, Kamariah Noor; Hamid, Ku Halim Ku; Hadi, Abdul

2017-12-01

Nowadays, biodiesel has become the forefront development as an alternative diesel fuel derived from biological sources such as oils of plant and fats. Presently, the conventional transesterification of vegetable oil to biodiesel gives rise to some technological problem. In this sense, heterogeneous nanocatalysts of calcium-based mixed metal oxides were synthesized through sol-gel method. It was found that significant increase of biodiesel yield, 91.75 % was obtained catalyzed by CaO-NbO2 from palm oil compared to pure CaO of 53.99 % under transesterification conditions (methanol/oil ratio 10:1, reaction time 3 h, catalyst concentration 4 wt%, reaction temperature 60 °C, and mixing speed of 600 rpm). The phase structure and crystallinity as well as the texture properties of the prepared catalysts were characterized by X-ray Diffraction (XRD) and the textural properties were characterized by N2 adsorption-desorption analysis. Sol-gel method has been known as versatile method in controlling the structural and chemical properties of the catalyst. Calcium-based mixed oxide synthesized from sol-gel method was found to exist as smaller crystallite size with high surface area.

Photodegradation of dioxin in contaminated soil in the presence of solvents and nanoscale TiO2 particles.

PubMed

Binh, Nguyen Duy; Oanh, Nguyen Thi Kim; Parkpian, Preeda

2014-01-01

Decomposition of 2,3,7,8-Tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) present in soil under ultraviolet (UV) illumination (350-400nm) was investigated using a combination of nontoxic solvents mixed in soil and nanoscale anatase TiO2 (nTiO2) distributed on 2mm top soil surface. Three types of UV-exposure experiments were conducted: intermittent exposure (8 h/day) for 90 days and 120 days, sequential intermittent (120 days) and continuous (24 h/day) for the next 55 days, and continuous exposure for 55 days. The influence of several factors on dioxin photodegradation efficiency was investigated, including the UV absorption by the targeted dioxin, presence of catalytic nTiO2 on soil surface, solvent evaporation rate, as well as vertical gradients of solvents added into the soil columns. Results of dioxin analysis for the soil samples collected at the end of every experiment condition show that the photodegradation enhanced by the nTiO2 presence on the soil surface considerably increased the dioxin removal. Higher removal efficiencies were found for treatments with 15%wt of nTiO2 mixed in the 2-mm surface soil as compared to the 5%wt nTiO2 treatments. The highest removal efficiency (79.6%) was for the sequential intermittent-continuous UV-exposure experiment with nTiO2. Dechlorinated products of 2,3,7,8-TCDD were generally not detected which suggests degradation of targeted dioxin by C-Cl cleavage was negligible. Further modifications to improve removal efficiencies were proposed. Large-scale engineered systems may employ this integrated treatment approach which can also incorporate the reuse of the top soil containing nTiO2 and solvent vapours. With the utilization of natural sunlight such systems would be promisingly suitable for tropical conditions.

The combined effect of dissolved oxygen and nitrite on N2O production by ammonia oxidizing bacteria in an enriched nitrifying sludge.

PubMed

Peng, Lai; Ni, Bing-Jie; Ye, Liu; Yuan, Zhiguo

2015-04-15

Both nitrite [Formula: see text] and dissolved oxygen (DO) play important roles in nitrous oxide (N2O) production by ammonia oxidizing bacteria (AOB). However, few studies focused on the combined effect of them on N2O production by AOB as well as the corresponding mechanisms. In this study, N2O production by an enriched nitrifying sludge, consisting of both AOB and nitrite-oxidizing bacteria (NOB), was investigated under various [Formula: see text] and DO concentrations. At each investigated DO level, both the biomass specific N2O production rate and the N2O emission factor (the ratio between N2O nitrogen emitted and the ammonium nitrogen converted) increased as [Formula: see text] concentration increased from 3 mg N/L to 50 mg N/L. However, at each investigated [Formula: see text] level, the maximum biomass specific N2O production rate occurred at DO of 0.85 mg O2/L, while the N2O emission factor decreased as DO increased from 0.35 to 3.5 mg O2/L. The analysis of the process data using a mathematical N2O model incorporating both the AOB denitrification and hydroxylamine (NH2OH) oxidation pathways indicated that the contribution of AOB denitrification pathway increased as [Formula: see text] concentration increased, but decreased as DO concentration increased, accompanied by a corresponding change in the contribution of NH2OH oxidation pathway to N2O production. The AOB denitrification pathway was predominant in most cases, with the NH2OH oxidation pathway making a comparable contribution only at high DO level (e.g. 3.5 mg O2/L). Copyright © 2015 Elsevier Ltd. All rights reserved.

X-ray fluorescence analysis of Cr(6+) component in mixtures of Cr(2)O(3) and K(2)CrO(4).

PubMed

Tochio, Tatsunori; Sakakura, Shusuke; Oohashi, Hirofumi; Mizota, Hirohisa; Zou, Yanhui; Ito, Yoshiaki; Fukushima, Sei; Tanuma, Shigeo; Shoji, Takashi; Fujimura, Hajime; Yamashita, Michiru

2010-01-01

X-ray fluorescence analysis using Cr K(alpha) spectra was applied to the determination of the mixing ratio of Cr(6+) to (Cr(6+) + Cr(3+)) in several mixtures of K(2)CrO(4) and Cr(2)O(3). Because the powder of K(2)CrO(4) contained large particles that were more than 50 microm in diameter, it was ground between a pestle and a mortar for about 8 h. The coarse particles still remaining were removed by using a sieve with 325-mesh (44 microm) in order to reduce the difference in absorption effects between emissions from Cr(6+) and those from Cr(3+). The mixing ratio, K(2)CrO(4)/(K(2)CrO(4) + Cr(2)O(3)), of the five mixtures investigated is 0.50, 0.40, 0.20, 0.10, and 0.05 in weight, respectively. Each spectrum obtained was analyzed by decomposing it into two reference spectra, those of the two pure materials, K(2)CrO(4) and Cr(2)O(3), with a constant background. The results for the mixtures containing K(2)CrO(4) of more than 20 wt% are that the relative deviation from the true value is less than approximately 5%. On the other hand, when the content of K(2)CrO(4) decreases to less than 10 wt%, the relative deviation gets so large as 20 - 25%. The error coming from a peak separation of spectrum involved in our results were estimated by applying our method to five sets of data for each mixture computationally generated, taking into account the uncertainty in total counts of real measurements.

Mixing Ratios of CO, CO2, CH4, and Isotope Ratios of Associated 13C, 18O, and 2H in Air Samples from Niwot Ridge, Colorado\\, and Montana de Oro, California, USA (January 2004)

DOE Data Explorer

Tyler, Stanley C. [Department of Earth System Science, University of California, Irvine, CA (USA)

2004-01-01

Air samples from Niwot Ridge, Colorado (41°N, 105°W) and Montaña de Oro, CA (35°N, 121°W) have been collected at approximately semi-monthly to monthly intervals since the mid 1990s. Such time series can provide information about: (1) seasonal cycling of CO, CO2, and CH4 sources and sinks in background air, (2) trends in atmospheric concentrations of CO2 and CH4 and their stable carbon, oxygen, and hydrogen isotopes, (3) the distribution of the hydroxyl (OH) radical in the atmosphere, and (4) the role of the terrestrial biosphere as a source or sink of atmospheric CO2.

A Monte Carlo Study of Flux Ratios of Raman Scattered O VI Features at 6825 and 7082 Å in Symbiotic Stars

NASA Astrophysics Data System (ADS)

Lee, Young-Min; Lee, Dae-Sub; Chang, Seok-Jun; Heo, Jeong-Eun; Lee, Hee-Won; Hwang, Narae; Park, Byeong-Gon; Lee, Ho-Gyu

2016-12-01

Symbiotic stars are regarded as wide binary systems consisting of a hot white dwarf and a mass losing giant. They exhibit unique spectral features at 6825 and 7082 Å, which are formed via Raman scattering of O VI λλ 1032 and 1038 with atomic hydrogen. We adopt a Monte Carlo technique to generate the same number of O VI λ1032 and λ1038 line photons and compute the flux ratio F(6825)/F(7082) of these Raman scattered O VI features formed in neutral regions with a simple geometric shape as a function of H I column density N H I . In cylindrical and spherical neutral regions with the O VI source embedded inside, the flux ratio F(6825)/F(7082) shows an overall decrease from 3 to 1 as N H I increases in the range {10}22{--24} {{cm}}-2. In cases of slab geometry and other geometries with the O VI source outside the H I region, Rayleigh escape operates to lower the flux ratio considerably. For moderate values of {N}{{H}{{I}}}˜ {10}23 {{cm}}-2 the flux ratio behaves in a complicated way to exhibit a broad bump with a peak value of 3.5 in the case of a sphere geometry. We find that the ratio of Raman conversion efficiencies of O VI λλ 1032, 1038 ranges from 0.8 to 3.5. Our high resolution spectra of “D” type HM Sge and “S” type AG Dra obtained with the Canada-France-Hawaii Telescope show that the flux ratio F(6825)/F(7082) of AG Dra is significantly smaller than that of HM Sge, implying that “S” type symbiotics are characterized by higher N H I than “D” type symbiotics.

Elevated O3 in Fresh and Aged Lightning-NOx Plumes Interacting with Biomass Burning Plumes over the Central U.S. during DC3 (Invited)

NASA Astrophysics Data System (ADS)

Huntrieser, H.; Lichtenstern, M.; Scheibe, M.; Aufmhoff, H.; Schlager, H.; Pucik, T.; Minikin, A.; Weinzierl, B.; Heimerl, K.; Fütterer, D.; Rappenglück, B.; Ackermann, L.; Pickering, K. E.; Cummings, K.; Barth, M. C.

2013-12-01

During the Deep Convective Clouds and Chemistry Experiment (DC3) in summer 2012 a variety of different thunderstorm systems were investigated over the Central U.S. by the DLR research aircraft Falcon together with the NCAR GV and NASA DC-8 aircraft. In addition, the complete DC3 field phase was characterized by a number of extended wildfires burning in the surroundings of the thunderstorms. Here we mainly focus on trace gas in situ measurements, such as NOx, CO, O3, CH4, SO2, NMHC, and a variety of aerosol measurements carried out by the Falcon in the fresh (~0-6 h) and aged (~12-24 h) anvil outflow at ~10-12 km altitude. It is well-known that thunderstorms modify the trace gas composition in the upper troposphere (UT) and may affect O3 mixing ratios, an important greenhouse gas in the UT. However, a complete picture of the different processes affecting the UT-O3 composition in vicinity of thunderstorms and its large-scale effects is still missing. From the DC3 data set we present an example of small-scale effects on the O3 composition in the anvil outflow, such as immediate O3 production by an aircraft-induced flash. But we also show how the efficient convective transport that extended over the whole updraft region may transport O3-poorer air masses from the, in general, rather unpolluted inflow region (with regard to anthropogenic emissions) over the Central U.S. directly to the UT. However, in a few cases enhanced O3 mixing ratios were observed in the anvil outflow attributed to different chemical and dynamical processes. In the two most powerful convective systems, an intense MCS over Missouri/Arkansas and a supercell over Texas, extended biomass burning (BB) plumes from New Mexico interacted with the thunderstorms. Ozone production was obvious in the BB plumes transported mainly in the lower troposphere at ~2-5 km altitude (ΔO3/ΔCO=0.1). However, if these air masses affected by BB emissions (containing high amounts of O3 precursors such as CH4 and NMHC) were ingested into the surrounding thunderstorms (with high HOx and NOx) and transported to the UT region, the ΔO3/ΔCO slope increased dramatically to values up to ~0.6-2.5. In addition to enhanced O3 production rates in thunderstorm outflows interacting with BB plumes, the pronounced downward mixing of O3-rich air mass from the stratosphere down to 8 km was observed in an aged anvil outflow from a squall line active over Colorado which was advected to Kansas the day after. Overall, from the local DC3 Falcon measurements the effect of downward mixing of O3-rich stratospheric air masses seems to cause the largest increase in O3 mixing ratios in the aged anvil outflow.

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

PubMed

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

2014-01-01

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

Stratospheric HF and HCl observations /15 June 1981/

NASA Technical Reports Server (NTRS)

Traub, W. A.; Chance, K. V.

1981-01-01

Balloon measurements of the stratospheric HF/HCl ratio are reported. Seven far-infrared rotational lines of HF and HCl were observed at elevation angles of 25, 18 and 8 deg by a far-infrared Fourier-transform spectrometer on board a balloon platform at 28.5 km. Analysis of line intensities yields an average HF/HCl ratio of 0.18 + or - 0.02 at an effective altitude of 33 km, with a water vapor mixing ratio of about 4 ppmv. Results are noted to be in reasonable agreement with the calculated profile of Sze and Ko (1981) with 4.5 ppmv H2O.

Preparation and Characterization of a Superparamagnetic Polymer Nanocomposite

NASA Astrophysics Data System (ADS)

Brenner, N.; Isseroff, R.; Rafailovich, M.; Rudomen, G.; Gambino, R.; Liang, S. S.; Sunil, D.; Si, M.; Collazo, L.; Pernodet, N.; Fang, X.

2006-03-01

Fe(CO)5 decomposition produced ferro- and superparamagnetic polymer nanocomposites. Fe(CO)5 and Cloisite 20A clay were combined in a closed vial for 12 hours, then opened to air for 2 hours. Mössbauer analysis indicated formation of Fe2O3 on clay; mass analysis indicated 12% Fe in clay. A Brabender mixed Fe2O3/clays with PMMA and EVA at ratios by mass of 9:4:36 and 1:1:4 respectively (Fe(CO)5:clay:polymer). TEM displayed Fe2O3 nanoparticles, 3.3 ^+ 0.8 nm in diameter, adsorbed on exfoliated clay platelet surfaces in polymer matrices. VSM data indicated superparamagnetism with moments of 510.3 emu/g(Fe2O3) (PMMA) and 8.46 emu/g(Fe2O3) (EVA). DMA showed 37% decreased dynamic modulus (EVA) and 11% (PMMA) due to Fe2O3. TGA indicated PMMA stability to 400^oC (9.3% mass residual) and EVA to 435^oC (11% mass residual). Cell adhesion tests showed Fe2O3/clay enhanced proliferation, promising applications in bone implants.

TiO2-based (Fe3O4, SiO2, reduced graphene oxide) magnetically recoverable photocatalysts for imazalil degradation in a synthetic wastewater.

PubMed

Santiago, Dunia E; Pastrana-Martínez, Luisa M; Pulido-Melián, Elisenda; Araña, Javier; Faria, Joaquim L; Silva, Adrián M T; González-Díaz, Óscar; Doña-Rodríguez, José M

2018-03-02

Magnetite (Fe 3 O 4 ), a core-shell material (SiO 2 @Fe 3 O 4 ), and reduced graphene oxide-Fe 3 O 4 (referred as rGO-MN) were used as supports of a specific highly active TiO 2 photocatalyst. Thermal treatments at 200 or 450 °C, different atmospheres (air or N 2 ), and TiO 2 :support weight ratios (1.0, 1.5, or 2.0) were investigated. X-ray diffractograms revealed that magnetite is not oxidized to hematite when the core-shell SiO 2 @Fe 3 O 4 material-or a N 2 atmosphere (instead of air) in the thermal treatment-was employed to prepare the TiO 2 -based catalysts (the magnetic properties being preserved). The materials treated with N 2 were first tested for degradation of imazalil (a well-known fungicide) in deionized water. The best compromise between the photocatalytic activity, magnetic separation, and Fe leached (1.61 mg L -1 , i.e., below the threshold for water reuse in irrigation) was found for the magnetic catalyst prepared with SiO 2 @Fe 3 O 4 , an intermediate TiO 2 :support ratio (1.5), and treated at 200 °C under N 2 atmosphere (i.e., SiO 2 @Fe 3 O 4 -EST-1.5-200-N 2 ). This material was then tested for the treatment of imazalil in a synthetic wastewater, SW (with a chemical composition simulating an effluent resulting from fruit postharvest activity). This SW has a pH of 4.2 and the experiments were carried out at this natural pH 0 and at neutral conditions (keeping pH at 7 along the reaction). The magnetic catalyst was more active than bare TiO 2 for the treatment of imazalil in SW at natural pH. Since Fe leaching was observed (3.53 mg L -1 ), added H 2 O 2 enhanced both imazalil degradation and mineralization. Conveniently, these catalysts can be readily recovered by using a conventional magnetic field, as demonstrated over three consecutive recycling runs. Graphical abstract % Imazalil conversion using different magnetic catalysts and comparison with bare TiO 2 .

Slags in a Large Variation Range of Oxygen Potential Based on the Ion and Molecule Coexistence Theory

NASA Astrophysics Data System (ADS)

Yang, Xue-Min; Li, Jin-Yan; Zhang, Meng; Chai, Guo-Min; Zhang, Jian

2014-12-01

A thermodynamic model for predicting sulfide capacity of CaO-FeO-Fe2O3-Al2O3-P2O5 slags in a large variation range of oxygen potential corresponding to mass percentage of FetO from 1.88 to 55.50 pct, i.e., IMCT- model, has been developed by coupling with the deduced desulfurization mechanism of the slags based on the ion and molecule coexistence theory (IMCT). The developed IMCT- model has been verified through comparing the determined sulfide capacity after Ban-ya et al.[20] with the calculated by the developed IMCT- model and the calculated by the reported sulfide capacity models such as the KTH model. Mass percentage of FetO as 6.75 pct corresponding to the mass action concentration of FetO as 0.0637 or oxygen partial as 2.27 × 10-6 Pa is the criterion for distinguishing reducing and oxidizing zones for the slags. Sulfide capacity of the slags in reducing zone is controlled by reaction ability of CaO regardless of slag oxidization ability. However, sulfide capacity of the slags in oxidizing zone shows an obvious increase tendency with the increasing of slag oxidization ability. Sulfide capacity of the slags in reducing zone keeps almost constant with variation of the simplified complex basicity (pct CaO)/((pct Al2O3) + (pct P2O5)), or optical basicity, or the mass action concentration ratios of N FeO/ N CaO, , , and . Sulfide capacity of the slags in oxidizing zone shows an obvious increase with the increasing of the simplified complex basicity (pct CaO)/((pct Al2O3) + (pct P2O5)) or optical basicity, or the aforementioned mass action concentration ratios. Thus, the aforementioned mass action concentration ratios and the corresponding mass percentage ratios of various iron oxides to basic oxide CaO are recommended to represent the comprehensive effect of various iron oxides and basic oxide CaO on sulfide capacity of the slags.

Monitoring and optimizing the co-composting of dewatered sludge: a mixture experimental design approach.

PubMed

Komilis, Dimitrios; Evangelou, Alexandros; Voudrias, Evangelos

2011-09-01

The management of dewatered wastewater sludge is a major issue worldwide. Sludge disposal to landfills is not sustainable and thus alternative treatment techniques are being sought. The objective of this work was to determine optimal mixing ratios of dewatered sludge with other organic amendments in order to maximize the degradability of the mixtures during composting. This objective was achieved using mixture experimental design principles. An additional objective was to study the impact of the initial C/N ratio and moisture contents on the co-composting process of dewatered sludge. The composting process was monitored through measurements of O(2) uptake rates, CO(2) evolution, temperature profile and solids reduction. Eight (8) runs were performed in 100 L insulated air-tight bioreactors under a dynamic air flow regime. The initial mixtures were prepared using dewatered wastewater sludge, mixed paper wastes, food wastes, tree branches and sawdust at various initial C/N ratios and moisture contents. According to empirical modeling, mixtures of sludge and food waste mixtures at 1:1 ratio (ww, wet weight) maximize degradability. Structural amendments should be maintained below 30% to reach thermophilic temperatures. The initial C/N ratio and initial moisture content of the mixture were not found to influence the decomposition process. The bio C/bio N ratio started from around 10, for all runs, decreased during the middle of the process and increased to up to 20 at the end of the process. The solid carbon reduction of the mixtures without the branches ranged from 28% to 62%, whilst solid N reductions ranged from 30% to 63%. Respiratory quotients had a decreasing trend throughout the composting process. Copyright © 2011 Elsevier Ltd. All rights reserved.

A medium range order structural connection to the configurational heat capacity of borate-silicate mixed glasses.

PubMed

Liu, Hao; Smedskjaer, Morten M; Tao, Haizheng; Jensen, Lars R; Zhao, Xiujian; Yue, Yuanzheng

2016-04-28

It has been reported that the configurational heat capacity (C(p,conf)) first increases and then becomes saturated with increasing B2O3/SiO2 ratio in borate-silicate mixed glasses. Through Raman spectroscopy measurements, we have, in this work, found an implication for the intermediate range order (IRO) structural connection to the composition dependence of the C(p,conf) of borate-silicate mixed glasses. In the silica-rich compositions, the C(p,conf) rapidly increases with increasing B2O3 content. This is attributed to the increase of the content of the B-O-Si network units ([B2Si2O8](2-)) and 6-membered borate rings with 1 or 2 B(4). In the boron-rich compositions, the C(p,conf) is almost constant, independent of the increase in the B2O3/SiO2 ratio. This is likely attributed to the counteraction between the decrease of the fraction of two types of metaborate groups and the increase of the fraction of other borate superstructural units (particularly 6-membered borate rings). The overall results suggest that the glasses containing more types of superstructural units have a larger C(p,conf).

Synergy of iron and copper oxides in the catalytic formation of PCDD/Fs from 2-monochlorophenol.

PubMed

Potter, Phillip M; Guan, Xia; Lomnicki, Slawomir M

2018-07-01

Transition metal oxides present in waste incineration systems have the ability to catalyze the formation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) through surface reactions involving organic dioxin precursors. However, studies have concentrated on the catalytic effects of individual transition metal oxides, while the complex elemental composition of fly ash introduces the possibility of synergistic or inhibiting effects between multiple, catalytically active components. In this study, we have tested fly ash surrogates containing different ratios (by weight) of iron (III) oxide and copper (II) oxide. Such Fe 2 O 3 /CuO mixed-oxide surrogates (in the Fe:Cu ratio of 3.5, 0.9 and 0.2 ) were used to study the cooperative effects between two transition metals that are present in high concentrations in most combustion systems and are known to individually catalyze the formation of PCDD/Fs. The presence of both iron and copper oxides increased the oxidative power of the fly ash surrogates in oxygen rich conditions and led to extremely high PCDD/F yields under pyrolytic conditions (up to >5% yield) from 2-monochlorophenol precursor. PCDD/F congener profiles from the mixed oxide samples are similar to results obtained from only CuO, however the total PCDD/F yield increases with increasing Fe 2 O 3 content. Careful analysis of the reaction products and changes to the oxidation states of active metals indicate the CuO surface sites are centers for reaction while the Fe 2 O 3 is affecting the bonds in CuO and increasing the ability of copper centers to form surface-bound radicals that are precursors to PCDD/Fs. Copyright © 2018 Elsevier Ltd. All rights reserved.

Prognostic value of gasometric parameters of carbon dioxide in resuscitation of septic patients. A bibliography review.

PubMed

Lamsfus-Prieto, J Á; de Castro-Fernández, R; Hernández-García, A M; Marcano-Rodriguez, G

2016-04-01

The anaerobic metabolism is the cornerstone in physiopathology of septic shock. Nowadays we have both the central or mixed venous oxygen saturation and lactate levels to monitoring the metabolism in septic patients. Some studies have shown that normalization of systemic hemodynamic and oxygen metabolism variables not prevent progression to multiorgan damage and death. Recently has been proposed the venous-to-arterial carbon dioxide difference (ΔpvaCO2) as an alternative marker of tissue hypoperfusion, like Cardiac Index. High ΔpvaCO2 predicts adverse outcomes. Also has been proposed both, the ratio between the ΔpvaCO2 and arterial-to-venous oxygen content difference (ΔCavO2): ΔpvaCO2/ΔCavO2; and, the ratio between venous-to-arterial carbon dioxide difference (ΔCvaCO2) and ΔCavO2: ΔCvaCO2/ΔCavO2, as markers of anaerobic metabolism. Both of high ratios are related to high levels of lactate and worse prognosis. Therefore in patients with sepsis the combination of markers of resuscitation could be important to improve the outcomes. Copyright © 2015 Sociedad Española de Anestesiología, Reanimación y Terapéutica del Dolor. Publicado por Elsevier España, S.L.U. All rights reserved.

Heptanuclear CoII5CoIII2 Cluster as Efficient Water Oxidation Catalyst.

PubMed

Xu, Jia-Heng; Guo, Ling-Yu; Su, Hai-Feng; Gao, Xiang; Wu, Xiao-Fan; Wang, Wen-Guang; Tung, Chen-Ho; Sun, Di

2017-02-06

Inspired by the transition-metal-oxo cubical Mn 4 CaO 5 in photosystem II, we herein report a disc-like heptanuclear mixed-valent cobalt cluster, [Co II 5 Co III 2 (mdea) 4 (N 3 ) 2 (CH 3 CN) 6 (OH) 2 (H 2 O) 2 ·4ClO 4 ] (1, H 2 mdea = N-methyldiethanolamine), for photocatalytic oxygen evolution. The topology of the Co 7 core resembles a small piece of cobaltate protected by terminal H 2 O, N 3 - , CH 3 CN, and multidentate N-methyldiethanolamine at the periphery. Under the optimal photocatalytic conditions, 1 exhibits water oxidation activity with a turnover number (TON) of 210 and a turnover frequency (TOF initial ) of 0.23 s -1 . Importantly, electrospray mass spectrometry (ESI-MS) was used to not only identify the possible main active species in the water oxidation reaction but also monitor the evolutions of oxidation states of cobalt during the photocatalytic reactions. These results shed light on the design concept of new water oxidation catalysts and mechanism-related issues such as the key active intermediate and oxidation state evolution in the oxygen evolution process. The magnetic properties of 1 were also discussed in detail.

Recovering folic acid and its identification on mixed pastes of tempeh and fermented vegetable as natural source of folic acid

NASA Astrophysics Data System (ADS)

Susilowati, Agustine; Aspiyanto, Maryati, Yati; Melanie, Hakiki; Lotulung, Puspa D.

2017-11-01

Mixing between tempeh and both fermented broccoli (Brassica oleracea) and spinach (Amaranthus sp.) were conducted to achieve mixed pastes as natural source of folic acid for 'smart food'. Mixing was performed on soy, mung bean, and kidney bean tempehs with both fermented broccoli and spinach at ratio of 1 : 1, 1 : 2, 1 : 3, 1 : 4, 1 : 5 and 1 : 6, respectively. Result of experimental activity showed that pulverizing ratio becoming more and more low will decrease total solids, soluble protein and N-Amino, but fluctuates on folic acid in mixed paste. Based on folic acid equivalent and the best fermented vegetable efficiency, optimization condition was reached in paste with combination between mung beans tempeh and fermented spinach at ratio of 1 : 2 by increasing folic acid concentration of 83.18 % (0.83 times), dissolved protein 432.29 % (4.32 times) and N-amino 55.36 % (0,55 times). While, it is occurred a lowering total solids 22.16 % (0.22 times) when compared with folic acid, soluble protein, N-amino, and total solids on initial materials of mung bean tempeh. In this condition, it is achieved folic acid monomer with molecular weight (MW) 148.14 Da. with relative intensity 100 %, and glutamic acid monomer 443.50 Da.with relative intensity 0.07 %.

Atmos/Atlas 3 Infrared Profile Measurements of Trace Gases in The November 1994 Tropical and Subtropical Upper Troposphere

NASA Technical Reports Server (NTRS)

Rinsland, C. P.; Gunson, M. R.; Wang, P.-H.; Arduini, R. F.; Baum, B. A.; Minnis, P.; Minnis, P.; Goldman, A.; Abrams, M. C.; Zander, R.;

Using Neural Networks to Describe Tracer Correlations

NASA Technical Reports Server (NTRS)

Lary, D. J.; Mueller, M. D.; Mussa, H. Y.

2003-01-01

Neural networks are ideally suited to describe the spatial and temporal dependence of tracer-tracer correlations. The neural network performs well even in regions where the correlations are less compact and normally a family of correlation curves would be required. For example, the CH4-N2O correlation can be well described using a neural network trained with the latitude, pressure, time of year, and CH4 volume mixing ratio (v.m.r.). In this study a neural network using Quickprop learning and one hidden layer with eight nodes was able to reproduce the CH4-N2O correlation with a correlation co- efficient of 0.9995. Such an accurate representation of tracer-tracer correlations allows more use to be made of long-term datasets to constrain chemical models. Such as the dataset from the Halogen Occultation Experiment (HALOE) which has continuously observed CH4, (but not N2O) from 1991 till the present. The neural network Fortran code used is available for download.

Synthesis and characterization of homo- and heterobimetallic niobium{sup v} and tantalum{sup v} peroxo-polyaminocarboxylato complexes and their use as single or multiple molecular precursors for Nb-Ta mixed oxides

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

Bayot, Daisy; Degand, Matthieu; Devillers, Michel

2005-09-15

New water-soluble bimetallic peroxo complexes of niobium{sup V} and/or tantalum{sup V} with high-denticity polyaminocarboxylate ligands have been prepared, characterized from the spectroscopic point of view, and used as molecular precursors for Nb-Ta mixed oxides. Four new homobimetallic complexes (gu){sub 3}[Nb{sub 2}(O{sub 2}){sub 4}(dtpaO{sub 3})].3H{sub 2}O 1 (gu){sub 3}[Ta{sub 2}(O{sub 2}){sub 4}(dtpaO{sub 3})].5H{sub 2}O 2 (gu){sub 3}[Nb{sub 2}(O{sub 2}){sub 4}(HtthaO{sub 4})].2H{sub 2}O 4 and (gu){sub 3}[Ta{sub 2}(O{sub 2}){sub 4}(HtthaO{sub 4})].3H{sub 2}O 5 and the corresponding heterometallic complexes (gu){sub 3}[NbTa(O{sub 2}){sub 4}(dtpaO{sub 3})].2.5H{sub 2}O 3 and (gu){sub 3}[NbTa(O{sub 2}){sub 4}(HtthaO{sub 4)}].2H{sub 2}O 6 have been obtained. In these compounds, the in situmore » oxidation of the nitrogen atoms of the PAC ligands into N-oxide groups has been evidenced by IR spectroscopy and mass spectrometry. The thermal treatment of the homonuclear complexes in air at 700 or 800 deg. C, depending on the Ta content, provided Nb{sub 2}O{sub 5} or Ta{sub 2}O{sub 5} while the heteronuclear compounds led to the solid solution TaNbO{sub 5}. BET and SEM measurements have been carried out and comparison of the morphology of the samples prepared from homo- and heterometallic precursors is discussed.« less

Influence of the Mode of Ventilation on Ketamine/Xylazine Requirements in Rabbits

DTIC Science & Technology

2007-01-01

latory continuous positive airway pressure ( CPAP ) of 7–10 cmH2O, and demand CPAP of 8– 10 cmH2O. (4) A fourth group, spontaneously ventilating (SV, n...minute)1) superimposed on 40 minute)1 low-frequency respiratory cycles, I:E ratio ¼ 1:1, oscillatory continuous positive airway pressure ( CPAP ) of 7–10...cmH2O and demand CPAP of 8–10 cmH2O, FiO2 ¼ 0.5. Rabbits from group 4 (SV; n ¼ 17) were anesthetized, the trachea intu- bated, and breathed air

Shipboard measurements and modeling of the distribution of CH4 and 13CH4 in the western Pacific

NASA Astrophysics Data System (ADS)

Bromley, T.; Allan, W.; Martin, R.; Mikaloff Fletcher, S. E.; Lowe, D. C.; Struthers, H.; Moss, R.

2012-02-01

We present observations of methane (CH4) mixing ratio and 13C/12C isotopic ratios in CH4 (δ13C) data from a collaborative shipboard project using bulk carrier ships sailing between Nelson, New Zealand, and Osaka, Japan, in the western Pacific Ocean. Measurements of the CH4 mixing ratio and δ13C in CH4were obtained from large clean-air samples collected in each 2.5° to 5° of latitude between 30°S and 30°N on eight voyages from 2004 to 2007. The data show large variations in CH4 mixing ratio in the tropical western Pacific, and data analysis suggests that these large variations are related to the positions and strengths of the South Pacific Convergence Zone and the Intertropical Convergence Zone, with variability in the sources playing a much smaller role. These measurements are compared with results from a modified version of the Unified Model (UMeth) general circulation model along two transects, one similar to the ship transects and another 18.75° to the east. Although UMeth was run to a steady state with the same sources and sinks each year, the gradient structures varied considerably from year to year, supporting our conclusion that variability in transport is a major driver for the observed variations in CH4. Simulations forced with an idealized representation of the El Niño-Southern Oscillation (ENSO) suggest that a large component of the observed variability in latitudinal gradients of CH4 and its δ13C arises from intrinsic variability in the climate system that does not occur on ENSO time scales.

Short tests to couple N₂O emission mitigation and nitrogen removal strategies for landfill leachate recirculation.

PubMed

Wu, Dong; Wang, Chao; Dolfing, Jan; Xie, Bing

2015-04-15

Landfills implemented with onsite leachate recirculation can efficiently remove pollutants, but currently they are reckoned as N2O emission hot spots. In this project, we evaluated the relationship between N2O emission and nitrogen (N) removal efficiency with different types of leachate recirculated. Nitrate supplemented leachate showed low N2O emission rates with the highest N removal efficiency (~70%), which was equivalent to ~1% nitrogen emitted as N2O. Although in nitrite containing leachates' N removal efficiencies also reached to ~60%, their emitted N2O comprised ~40% of total removed nitrogen. Increasing nitrogen load promoted N2O emission and N removal efficiency, except in ammonia type leachate. When the ratio of BOD to total nitrogen increased from 0.2 to 0.4, the N2O emission flux from nitrate supplemented leachate decreased from ~25 to <0.5 μg N/kg-soil·h. We argue prior to leachate in situ recirculation, sufficient pre-aeration is critical to mitigate N2O surges and simultaneously enhance nitrogen removal efficiency. Copyright © 2015 Elsevier B.V. All rights reserved.

Titanium-dioxide nanotube p-n homojunction diode

NASA Astrophysics Data System (ADS)

Alivov, Yahya; Ding, Yuchen; Singh, Vivek; Nagpal, Prashant

2014-12-01

Application of semiconductors in functional optoelectronic devices requires precise control over their doping and formation of junction between p- and n-doped semiconductors. While doped thin films have led to several semiconductor devices, need for high-surface area nanostructured devices for photovoltaic, photoelectrochemical, and photocatalytic applications has been hindered by lack of desired doping in nanostructures. Here, we show titanium-dioxide (TiO2) nanotubes doped with nitrogen (N) and niobium (Nb) as acceptors and donors, respectively, and formation of TiO2 nanotubes p-n homojunction. This TiO2:N/TiO2:Nb homojunction showed distinct diode-like behaviour with rectification ratio of 1115 at ±5 V and exhibited good photoresponse for ultraviolet light (λ = 365 nm) with sensitivity of 0.19 A/W at reverse bias of -5 V. These results can have important implications for development of nanostructured metal-oxide solar-cells, photodiodes, LED's, photocatalysts, and photoelectrochemical devices.

Late Pleistocene paleoproductivity patterns during the last climatic cycle in the Guyana Basin as revealed by calcareous nannoplankton

NASA Astrophysics Data System (ADS)

López-Otálvaro, G.-E.; Flores, J. A.; Sierro, F. J.; Cacho, I.; Grimalt, J.-O.; Michel, E.; Cortijo, E.; Labeyrie, L.

2008-03-01

Variations in the assemblages and abundances of calcareous nannoplankton have allowed us to interpret changes in oceanic and atmospheric dynamics in the Guyana Basin, mainly linked to the southeast trades over the last climatic cycle. Records of the paleoproductivity index of coccolithophores (N ratio) allowed us to monitor the nutri-thermocline fluctuations. Additionally, nannofossil accumulation rates vary closely with the N ratio, indicating a strong correlation between these two paleoproductivity proxies. The dominance of upper (small Noelaerhabdaceae, Emiliania huxleyi and Gephyrocapsa oceanica), over lower photic zone dwellers (Florisphaera profunda) during Termination II and interglacial substages 5.1 and 5.3 is related to eutrophic conditions due to a shoaling of the nutri-thermocline as a consequence of enhanced southeast Trade Winds. This activated an upwelling at the continental margin of the Guyana Basin. Low N ratio values and the dominance of F. profunda over the glacial substages of MIS 5 and glacial MIS 2-4 are linked to a deep nutri-thermocline (deep stratification of the mixed layer), at times of low influence of the southeast Trade Winds, and a weak upwelling. However, the N ratio during MIS 2-4 was slightly higher than those seen for the MIS 4/5 boundary and glacial substages 5.2 and 5.4. These micropaleontological proxies follow the insolation at high northern latitude (65° N): the high N ratio and NAR data from the Guyana Basin during Termination II and interglacials 5.1. and 5.3 are correlated with high insolation values, and low values of the N ratio and NAR during the MIS 4/5 boundary, glacials 5.2, 5.4 and MIS 2-4 are correlated with low insolation at the same latitudes. This situation suggests a link between the ITCZ, the southeast Trade Wind dynamics and the Northern Hemisphere climate changes during the last climatic cycle.

Enhancement of electrical and optical performance of N719 by co-sensitization

NASA Astrophysics Data System (ADS)

Shikoh, Ali Sephar; Ahmad, Zubair; Touati, Farid; Al-Muhtaseb, Shaheen A.

2018-04-01

This paper deals with the electrical, optical and electrochemical properties of a metal-free dye C78H74O8 (AS-2), which has been used to improve the photo-detection properties of C58H86N8O8RuS2 (N719) based Dye sensitized photo-sensors (DSPSs). Both dyes were mixed together in various proportions and the most promising ratio N719/AS-2 (1:0.25) was selected for staining photo-anodes for DSPS integration. The fabricated DSPSs were studied in terms of electrical parameters and photodetection properties. The N719/AS-2 (1:0.25) based DSPS were found to have a reduced leakage current, increased breakdown voltage and a closer proximity to an ideal diode, as compared to the N719 based DSPS. Further, the N719/AS-2 (1:0.25) based DSPS was also found to have better linearity at high irradiance levels, thus rendering the co-sensitized device useful as a photosensor in various applications. Electrochemical Impedance Spectroscopy (EIS) analysis was also performed to explain the interfacial charge recombination process.

The O2 A-Band in the Fluxes and Polarization of Starlight Reflected by Earth-Like Exoplanets

NASA Astrophysics Data System (ADS)

Fauchez, Thomas; Rossi, Loic; Stam, Daphne M.

2017-06-01

Earth-like, potentially habitable exoplanets are prime targets in the search for extraterrestrial life. Information about their atmospheres and surfaces can be derived by analyzing the light of the parent star reflected by the planet. We investigate the influence of the surface albedo A s, the optical thickness b cloud, the altitude of water clouds, and the mixing ratio of biosignature O2 on the strength of the O2 A-band (around 760 nm) in the flux and polarization spectra of starlight reflected by Earth-like exoplanets. Our computations for horizontally homogeneous planets show that small mixing ratios (η < 0.4) will yield moderately deep bands in flux and moderate-to-small band strengths in polarization, and that clouds will usually decrease the band depth in flux and the band strength in polarization. However, cloud influence will be strongly dependent on properties such as optical thickness, top altitude, particle phase, coverage fraction, and horizontal distribution. Depending on the surface albedo and cloud properties, different O2 mixing ratios η can give similar absorption-band depths in flux and band strengths in polarization, especially if the clouds have moderate-to-high optical thicknesses. Measuring both the flux and the polarization is essential to reduce the degeneracies, although it will not solve them, especially not for horizontally inhomogeneous planets. Observations at a wide range of phase angles and with a high temporal resolution could help to derive cloud properties and, once those are known, the mixing ratio of O2 or any other absorbing gas.

Hollow waveguides with low intrinsic photoluminescence fabricated with Ta2O5 and SiO2 films

NASA Astrophysics Data System (ADS)

Zhao, Y.; Jenkins, M.; Measor, P.; Leake, K.; Liu, S.; Schmidt, H.; Hawkins, A. R.

2011-02-01

A type of integrated hollow core waveguide with low intrinsic photoluminescence fabricated with Ta2O5 and SiO2 films is demonstrated. Hollow core waveguides made with a combination of plasma-enhanced chemical vapor deposition SiO2 and sputtered Ta2O5 provide a nearly optimal structure for optofluidic biofluorescence measurements with low optical loss, high fabrication yield, and low background photoluminescence. Compared to earlier structures made using Si3N4, the photoluminescence background of Ta2O5 based hollow core waveguides is decreased by a factor of 10 and the signal-to-noise ratio for fluorescent nanobead detection is improved by a factor of 12.

Synthesis, Magnetism, and X-ray Molecular Structure of the Mixed-Valence Vanadium(IV/V)-Oxygen Cluster [VO(4) subset(V(18)O(45))](9-).

PubMed

Suber, Lorenza; Bonamico, Mario; Fares, Vincenzo

1997-05-07

Within the transition metal oxide systems, vanadium presents a unique chemistry due to its capacity to form a great number of mixed-valence oxo clusters which often have the peculiarity to incorporate species that function, for size, shape, and charge, as templates. Prismatic, lustrous dark brown crystals of [(n-C(4)H(9))NH(3)](9)[V(19)O(49)].7H(2)O are obtained by reacting (n-C(4)H(9)NH(3))VO(3), VOSO(4), and (n-C(4)H(9))NH(2) in H(2)O. The X-ray crystal structure shows an ellipsoidal metal-oxo cluster formed by 15 VO(5) and 3 VO(4) polyhedra surrounding an almost regular VO(4) tetrahedron located on the 3-fold axis of a trigonal cell of dimensions a = 19.113(5) Å and c = 13.743(5) Å with space group P&thremacr; and Z = 2. Exponentially weighted bond valence sum calculations, manganometric titration of the V(IV) centers, and magnetic measurements are consistent with the presence of three localized and three delocalized electrons. Variable-temperature solid-state susceptibility studies indicate antiferromagnetic coupling between V(IV) centers. Cyclic voltammetry in acetonitrile shows a irreversible reduction at -1.24 V and a reversible oxidation at +0.17 V (vs Ag/AgCl). The title compound converts quantitatively to the metal oxide K(2)V(3)O(8) with an extended layered structure as soon as a potassium salt is added to a neutral aqueous solution of the polyoxoanion.

In situ stratospheric measurements of HNO3 and HCl near 30 km using the balloon-borne laser in situ sensor tunable diode laser spectrometer

NASA Technical Reports Server (NTRS)

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

1989-01-01

In situ stratospheric measurements of the concentrations of the reservoir species HNO3 and HCl made during two flights of the high-resolution (0.0005/cm) balloon-borne laser in situ sensor instrument from Palestine, Texas, are reported. A measured HNO3 volume mixing ratio of 4.3 parts per billion by volume (ppbv) at 31 km altitude is about 1 ppbv larger than previously reported measurements at 32 deg N. An HCl mixing ratio of 1.6 ppbv at 29 km is in agreement with values obtained from earlier remote sensing techniques within the experimental uncertainties. Upper limits at 31 km of 0.4 ppbv for H2O2 and 0.2 ppbv for HOCl are also derived from analyses of spectra recorded near 1252/cm.

Synthesis, characterization and solid state electrical properties of 1-D coordination polymer of the type [CuxNi1-x(dadb)·yH2O]n

NASA Astrophysics Data System (ADS)

Prasad, R. L.; Kushwaha, A.; Shrivastava, O. N.

2012-12-01

New heterobimetallic complexes [CuxNi1-x(dadb)·yH2O]n {where dadb=2,5-Diamino-3,6-dichloro-1,4-benzoquinone (1); x=1 (2), 0.5 (4), 0.25 (5), 0.125 (6), 0.0625 (7) and 0 (3); y=2; n=degree of polymerization} were synthesized and characterized. Heterobimetallic complexes show normal magnetic moments, whereas, monometallic complexes exhibit magnetic moments less than the value due to spin only. Thermo-gravimetric analysis shows that degradation of the ligand dadb moiety is being controlled by the electronic environment of the Cu(II) ions in preference over Ni(II) in heterobimetallic complexes. Existence of the mixed valency/non-integral oxidation states of copper and nickel metal ions in the complex 4 has been attributed from magnetic moment and ESR spectral results. Solid state dc electrical conductivity of all the complexes was investigated. Monometallic complexes were found to be semiconductors, whereas heterobimetallic coordination polymer 4 was found to exhibit metallic behaviour. Existence of mixed valency/ non-integral oxidation state of metal ions seems to be responsible for the metallic behaviour.

Sensitivities of winter ozone pollution events in oil and gas producing regions to VOCs, NOx and radicals (Invited)

NASA Astrophysics Data System (ADS)

Edwards, P. M.; Aikin, K.; De Gouw, J. A.; Dube, W. P.; Geiger, F.; Gilman, J.; Helmig, D.; Holloway, J.; Kercher, J. P.; Koss, A.; Lerner, B. M.; Martin, R. S.; McLaren, R.; Min, K.; Parrish, D. D.; Peischl, J.; Roberts, J. M.; Ryerson, T. B.; Thornton, J. A.; Veres, P. R.; Warneke, C.; Wild, R. J.; Williams, E. J.; Young, C.; Yuan, B.; Brown, S. S.

2013-12-01

The Uintah Basin in northeastern Utah, a region of intense oil and gas extraction, experienced ozone (O3) mixing ratios well above limits set by air quality standards for multiple days during three of the last four winters. The Uintah Basin Winter Ozone Study (UBWOS) consisted of two field intensives, in early 2012 and 2013, with the goal of addressing current uncertainties in the chemical and physical processes that drive wintertime O3 production in regions of oil and gas development. The data from these two study periods provide an excellent comparison of high and low O3 production years, as meteorological conditions during the winter of 2011-2012 resulted in no elevated O3 mixing ratios, in contrast to the winter of 2012-2013 when observed O3 mixing ratios were the highest yet recorded in the Uintah Basin. Box modeling studies, using the Master Chemical Mechanism (MCM v3.2) chemistry scheme, have been used to investigate our understanding of O3 photochemistry in this unusual emissions environment. Simulations identify O3 production in 2012 to be highly radical limited, with less conventional radical sources, such as HCHO, HONO, and ClNO2 photolysis, playing a central role. Consequently, O3 production during 2012 was highly VOC sensitive, despite the much larger mixing ratio of total non-methane hydrocarbons relative to NO¬x. Conditions during UBWOS 2013 resulted in significantly higher O3 precursor species concentrations than during 2012, including the concentrations of the radical precursors HCHO and HONO. Simulations constrained to the 2013 data show the effects of these changes in pre-cursor concentrations on the radical budget, and thus on local O3 photochemistry and its sensitivities during a wintertime O3 pollution episode.

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

PubMed

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

2017-11-01

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

The vertical distribution and origin of HCN in Neptune's atmosphere

NASA Technical Reports Server (NTRS)

Lellouch, Emmanuel; Romani, Paul N.; Rosenqvist, Jan

1994-01-01

Measurements and modeling of the (3-2) rotational line of hydrogen cyanide at 265.9 GHz in Neptune's atmosphere are presented. High signal-to-noise observations provide information on the HCN vertical distribution in Neptune's stratosphere. The HCN mixing ratio is found to be nearly uniform with height above the condensation level. Best fits occur for HCN distributions that have a slight increase with altitude. A least-squares analysis yields a mixing ratio of (3.2 +/- 0.8)10(exp -10) at 2 mbar and a mean mixing ratio scale height of 250(sup 750)(sub -110) km in the 0.1-3 mbar region. To interpret these results, we developed a photochemical model of HCN. HCN formation is initiated by the reaction between CH3 radicals, produced from methane photochemistry, and N atoms. The primary sink for HCN is condensation, with minor contributions from photolysis and chemical losses. Two possible sources of N atoms are investigated: (1) infall of N escaped from Triton's upper atmosphere, and (2) galactic cosmic ray (GCR) impact on internal N2. Given the uncertainties on (i) the transport and possible ionization of N in Neptune's magnetosphere, and the fate of N(+) reaching Neptune's upper atmosphere and (ii) the N2 mixing ratio in Neptune's deep atmosphere, we suggest that both sources of N atoms may significantly contibute to the formation of HCN.

CNO Abundances in Metal-Rich Environments: Infrared Space Observatory Spectroscopy of Ionized Gas in M51

NASA Astrophysics Data System (ADS)

Garnett, Donald R.; Edmunds, Michael G.; Henry, Richard B. C.; Pagel, Bernard E. J.; Skillman, Evan D.

2004-12-01

We present Infrared Space Observatory (ISO) Long Wavelength Spectrograph observations centered on the H II region CCM 10 in the spiral galaxy M51. We detect several emission lines in this spectrum, including [O I] 63 and 145 μm, [C II] 158 μm, [O III] 88 μm, and [N II] 122 μm, with a significant upper limit on [N III] 57 μm. We use these measurements to estimate abundances for C, N, and O in the interstellar medium in M51. We compare our [O III] 88 μm flux with the flux for [O III] λ5007 obtained from narrowband imaging. The derived 5007Å/88μm ratio yields an electron temperature Te=5300+/-300 K. This temperature agrees with estimates of T[O III] based on photoionization models of CCM 10 with logO/H=-3.2, an abundance that is about a factor of 2 smaller than earlier results for this object derived from photoionization modeling of the visible spectrum. A possible cause for the discrepancy is that the older photoionization models based on CLOUDY predict significantly larger optical emission-line strengths than the current version of CLOUDY at the same metallicity; models with the more recent version are more consistent with the observed spectra of M51 H II region with reduced O/H. Assuming N/O=N+2/O+2, the upper limit for [NIII]/[OIII] yields logN/O<-0.5, which is consistent with the trend of N/O versus O/H seen in other spiral galaxies. C/O is estimated from the [CII]/[OI] ratio using photodissociation region models constrained by published CO line ratios, [CI]/CO, and [OI]63μm/145μm. With these various constraints on ne and G0, the observed [CII]/[OI] intensity ratio is in good agreeement with that predicted by photodissociation region models with approximately solar abundances. We infer from this that C/O in M51 is consistent with the solar neighborhood value.

Benzene-contaminated groundwater remediation using calcium peroxide nanoparticles: synthesis and process optimization.

PubMed

Mosmeri, Hamid; Alaie, Ebrahim; Shavandi, Mahmoud; Dastgheib, Seyed Mohammad Mehdi; Tasharrofi, Saeideh

2017-08-14

Nano-size calcium peroxide (nCaO 2 ) is an appropriate oxygen source which can meet the needs of in situ chemical oxidation (ISCO) for contaminant remediation from groundwater. In the present study, an easy to handle procedure for synthesis of CaO 2 nanoparticles has been investigated. Modeling and optimization of synthesis process was performed by application of response surface methodology (RSM) and central composite rotatable design (CCRD) method. Synthesized nanoparticles were characterized by XRD and FESEM techniques. The optimal synthesis conditions were found to be 5:1, 570 rpm and 10 °C for H 2 O 2 :CaSO 2 ratio, mixing rate and reaction temperature, respectively. Predicted values showed to be in good agreement with experimental results (R 2 values were 0.915 and 0.965 for CaO 2 weight and nanoparticle size, respectively). To study the efficiency of synthesized nanoparticles for benzene removal from groundwater, batch experiments were applied in biotic and abiotic (chemical removal) conditions by 100, 200, 400, and 800 mg/L of nanoparticles within 70 days. Results indicated that application of 400 mg/L of CaO 2 in biotic condition was able to remediate benzene completely from groundwater after 60 days. Furthermore, comparison of biotic and abiotic experiments showed a great potential of microbial stimulation using CaO 2 nanoparticles in benzene remediation from groundwater.

Occurrence and survival of verocytotoxin-producing Escherichia coli O157 in meats obtained from retail outlets in The Netherlands.

PubMed

Heuvelink, A E; Zwartkruis-Nahuis, J T; Beumer, R R; de Boer, E

1999-10-01

In 1996 and 1997, 2,941 fresh and processed meat products obtained from supermarkets and butcher shops in The Netherlands were examined for the presence of verocytotoxin-producing Escherichia coli of serogroup O157 (O157 VTEC). Additionally, the fate of O157 VTEC in raw meat products stored at low temperatures and the effect of different additives were evaluated. O157 VTEC strains were isolated from 6 (1.1%) of 571 samples of raw minced beef, 2 (0.5%) of 402 samples of raw minced mixed beef and pork, 1 (1.3%) of 76 samples of raw minced pork, 1 (0.3%) of 393 samples of other raw pork products, and 1 (0.3%) of 328 samples of cooked or fermented ready-to-eat meats. Other raw beef products (n = 223) and meat samples originating from poultry (n = 819), sheep or lamb (n = 46), or wild animals (n = 83) were all found to be negative for O157 VTEC. For the survival experiments we used tartaar (minced beef with a fat content of less than 10%) and filet americain (tartaar mixed with a mayonnaise-based sauce [80 to 20%]). The O157 VTEC strain tested was able to survive in tartaar and filet americain stored at -20, 0, 5, or 7 degrees C for 3 days. At both 7 and at 15 degrees C, O157 VTEC counts in tartaar and filet americain remained virtually unchanged throughout a storage period of 5 days. Addition of acetic acid (to pH 4.0), sodium lactate (1 and 2% [wt/wt]), or components of the lactoperoxidase-thiocyanate-hydrogen peroxide system to filet americain did not result in a reduction of viable O157 VTEC cells during storage at 7 or 15 degrees C. It was concluded that raw meat contaminated with O157 VTEC will remain a hazard even if the meat is held at low or freezing temperatures.

Hydrothermal synthesis, crystal structures and photoluminescence properties of mixed europium-yttrium organic frameworks

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

Han Yinfeng; Department of Chemistry and Environmental Science, Taishan University, Taian 271021; Fu Lianshe

Three mixed europium-yttrium organic frameworks: Eu{sub 2-x}Y{sub x}(Mel)(H{sub 2}O){sub 6} (Mel=mellitic acid or benzene-1,2,3,4,5,6-hexacarboxylic acid, x=0.38 1, 0.74 2, and 0.86 3) have been synthesized and characterized. All the compounds contain a 3-D net with (4, 8)-flu topology. The study indicates that the photoluminescence properties are effectively affected by the different ratios of europium and yttrium ions, the quantum efficiency is increased and the Eu{sup 3+} lifetime becomes longer in these MOFs than those of the Eu analog. - Graphical abstract: Three mixed europium and yttrium organic frameworks: Eu{sub 2-x}Y{sub x}(Mel)(H{sub 2}O){sub 6} (Mel=mellitic acid) have been synthesized and characterized.more » All the compounds contain a 3-D net with (4, 8)-flu topology. The study indicates that the photoluminescence properties are effectively affected by the different ratios of europium and yttrium ions, the quantum efficiency is increased and the Eu{sup 3+} lifetime becomes longer in these MOFs than those of the Eu analog. Highlights: Black-Right-Pointing-Pointer Three (4, 8)-flu topological mixed Eu and Y MOFs were synthesized under mild conditions. Black-Right-Pointing-Pointer Metal ratios were refined by the single crystal data consistent with the EDS analysis. Black-Right-Pointing-Pointer Mixed Eu and Y MOFs show longer lifetime and higher quantum efficiency than the Eu analog. Black-Right-Pointing-Pointer Adding inert lanthanide into luminescent MOFs enlarges the field of luminescent MOFs.« less

A meta-analysis of fertilizer-induced soil NO and combined NO+N2 O emissions.

PubMed

Liu, Shuwei; Lin, Feng; Wu, Shuang; Ji, Cheng; Sun, Yi; Jin, Yaguo; Li, Shuqing; Li, Zhaofu; Zou, Jianwen

2017-06-01

Soils are among the important sources of atmospheric nitric oxide (NO) and nitrous oxide (N 2 O), acting as a critical role in atmospheric chemistry. Updated data derived from 114 peer-reviewed publications with 520 field measurements were synthesized using meta-analysis procedure to examine the N fertilizer-induced soil NO and the combined NO+N 2 O emissions across global soils. Besides factors identified in earlier reviews, additional factors responsible for NO fluxes were fertilizer type, soil C/N ratio, crop residue incorporation, tillage, atmospheric carbon dioxide concentration, drought and biomass burning. When averaged across all measurements, soil NO-N fluxes were estimated to be 4.06 kg ha -1  yr -1 , with the greatest (9.75 kg ha -1  yr -1 ) in vegetable croplands and the lowest (0.11 kg ha -1  yr -1 ) in rice paddies. Soil NO emissions were more enhanced by synthetic N fertilizer (+38%), relative to organic (+20%) or mixed N (+18%) sources. Compared with synthetic N fertilizer alone, synthetic N fertilizer combined with nitrification inhibitors substantially reduced soil NO emissions by 81%. The global mean direct emission factors of N fertilizer for NO (EF NO ) and combined NO+N 2 O (EF c ) were estimated to be 1.16% and 2.58%, with 95% confidence intervals of 0.71-1.61% and 1.81-3.35%, respectively. Forests had the greatest EF NO (2.39%). Within the croplands, the EF NO (1.71%) and EF c (4.13%) were the greatest in vegetable cropping fields. Among different chemical N fertilizer varieties, ammonium nitrate had the greatest EF NO (2.93%) and EF c (5.97%). Some options such as organic instead of synthetic N fertilizer, decreasing N fertilizer input rate, nitrification inhibitor and low irrigation frequency could be adopted to mitigate soil NO emissions. More field measurements over multiyears are highly needed to minimize the estimate uncertainties and mitigate soil NO emissions, particularly in forests and vegetable croplands. © 2016 John Wiley & Sons Ltd.

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

PubMed

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

2017-02-01

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

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

NASA Astrophysics Data System (ADS)

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

2017-02-01

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

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

NASA Astrophysics Data System (ADS)

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

2016-02-01

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

Chemical kinetic analysis of hydrogen-air ignition and reaction times

NASA Technical Reports Server (NTRS)

Rogers, R. C.; Schexnayder, C. J., Jr.

1981-01-01

An anaytical study of hydrogen air kinetics was performed. Calculations were made over a range of pressure from 0.2 to 4.0 atm, temperatures from 850 to 2000 K, and mixture equivalence ratios from 0.2 to 2.0. The finite rate chemistry model included 60 reactions in 20 species of the H2-O2-N2 system. The calculations also included an assessment of how small amounts of the chemicals H2O, NOx, H2O2, and O3 in the initial mixture affect ignition and reaction times, and how the variation of the third body efficiency of H2O relative of N2 in certain key reactions may affect reaction time. The results indicate that for mixture equivalence ratios between 0.5 and 1.7, ignition times are nearly constant; however, the presence of H2O and NO can have significant effects on ignition times, depending on the mixture temperature. Reaction time is dominantly influenced by pressure but is nearly independent of initial temperature, equivalence ratio, and the addition of chemicals. Effects of kinetics on reaction at supersonic combustor conditions are discussed.

Melt Inclusions Record Extreme Compositional Variability in Primitive Magmas at Mauna Loa Volcano, Hawaii

NASA Astrophysics Data System (ADS)

Kamenetsky, V. S.; Norman, M. D.; Garcia, M. O.

2002-12-01

Melt inclusions carry potentially unique information about magmatic processes and the compositional evolution of erupted lavas. Major element compositions of olivine-hosted melt inclusions in submarine tholeiitic picrites from the southwest rift zone of Mauna Loa volcano have been studied to examine the compositional variability of primitive magmas feeding the world's largest volcano. Approximately 600 naturally quenched inclusions were examined from 8 samples with 3-25 vol% olivine phenocrysts and 9-22 wt% MgO. Olivine compositions ranged from Fo91-Fo82. The inclusions show a continuous variation in FeO contents from near-magmatic values (9 to 11 wt%) in the most evolved olivines to extremely low values (3.5 to 7.0 wt%) in the most primitive olivines. This appears to reflect a complex magmatic history for these crystals involving extensive re-equlibration of melts trapped by early formed phenocrysts with their host olivine. Extreme compositional variability also characterizes incompatible elements that would not be affected by equilibration with the host olivine. Inclusions trapped in relatively primitive olivines (Fo88-91) show a large range of K2O contents (0.1 to 2.1 wt%), whereas inclusions in more evolved olivines converge on whole rock compositions with 0.3 to 0.4 wt% K2O. Similarly, TiO2/K2O, Na2O/K2O, and K2O/P2O5 ratios of inclusions in primitive olivines span a much larger range than do inclusions hosted by more evolved olivines, with TiO2/K2O ratios extending from enriched to depleted compositions (1.2 to 24.7) in primitive olivines, and converging on whole rock compositions (TiO2/K2O = 6-9) in more evolved host olivine. This points toward extreme compositional variability in melts feeding Mauna Loa, and effective mixing of these melt parcels in the shallower summit reservoir to produce the restricted range of whole rock compositions sampled by erupted lavas. Whole rock compositions, therefore provide an integrated view of melting and high-level mixing processes, whereas melt inclusions provide more detailed information about source characteristics.

Covalent bonding in heavy metal oxides

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

Bagus, Paul S.; Nelin, Connie J.; Hrovat, Dave A.

Novel theoretical methods were used to quantify the magnitude and the energetic contributions of 4f/5f-O2p and 5d/6d-O2p interactions to covalent bonding in lanthanide and actinide oxides. Although many analyses have neglected the involvement of the frontier d orbitals, the present study shows that f and d covalency are of comparable importance. Two trends are identified. As is expected, the covalent mixing is larger when the nominal oxidation state is higher. More subtly, the importance of the nf covalent mixing decreases sharply relative to (n+1)d as the nf occupation increases. Atomic properties of the metal cations that drive these trends aremore » identified.« less

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

PubMed

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

2015-01-01

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

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

PubMed

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

2017-12-01

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

Heavy Ozone Enrichments from ATMOS Infrared Solar Spectra

NASA Technical Reports Server (NTRS)

Irion, F. W.; Gunson, M. R.; Rinsland, C. P.; Yung, Y. L.; Abrams, M. C.; Chang, A. Y.; Goldman, A.

1996-01-01

Vertical enrichment profiles of stratospheric O-16O-16O-18 and O-16O-18O-16 (hereafter referred to as (668)O3 and (686)O3 respectively) have been derived from space-based solar occultation spectra recorded at 0.01 cm(exp-1) resolution by the ATMOS (Atmospheric Trace MOlecule Spectroscopy) Fourier transform infrared (FTIR) spectrometer. The observations, made during the Spacelab 3 and ATLAS-1, -2, and -3 shuttle missions, cover polar, mid-latitude and tropical regions between 26 to 2.6 mb inclusive (approximately 25 to 41 km). Average enrichments, weighted by molecular (48)O3 density, of (15 +/- 6)% were found for (668)O3 and (10 +/- 7)% for (686)O3. Defining the mixing ratio of (50)O3 as the sum of those for (668)O3 and (686)O3, an enrichment of (13 plus or minus 5)% was found for (50)O3 (1 sigma standard deviation). No latitudinal or vertical gradients were found outside this standard deviation. From a series of ground-based measurements by the ATMOS instrument at Table Mountain, California (34.4 deg N), an average total column (668)O3 enrichment of (17 +/- 4)% (1 sigma standard deviation) was determined, with no significant seasonal variation discernable. Possible biases in the spectral intensities that affect the determination of absolute enrichments are discussed.

Two series of reactant's ratio-dependent lanthanide organic frameworks derived from nicotinic acid N-oxide and oxalate: synthesis, crystal structures and luminescence properties.

PubMed

Yu, Yanyan; Zhang, Lijuan; Zhou, Yunshan; Zuhra, Zareen

2015-03-14

Two series of lanthanide(III)–organic frameworks with the molecular formula [Ln2(NNO)2(OX)2(H2O)4]n (Ln = Eu 1, Tb 2, Sm 3, Dy 4, Gd 5) and [Ln2(NNO)4(OX)(H2O)2]n (Ln = Eu 6, Tb 7, Sm 8, Dy 9, Gd 10) were synthesized successfully under the same hydrothermal conditions with nicotinic N-oxide (HNNO) and oxalic acid (H2OX) as the mixed ligands merely through varying the molar ratio of the reactants. The compounds were characterized by IR, elemental analysis, UV, TG-DTA and powder X-ray diffraction (XRD). X-ray single-crystal diffraction analyses of compounds 1 and 7 selected as representatives and powder XRD analysis of the compounds revealed that both the series of compounds feature three-dimensional (3-D) open frameworks, and crystallize in the triclinic P1 space group while with different unit cell parameters. In compound 1, pairs of Eu(3+) ions and pairs of NNO(−) ligands connect with each other alternately to form a 1-D infinite Eu-NNO double chain, the adjacent 1-D double-chains are then joined together through OX(2−) ligands leading to a 2D layer, the 2-D layers are further ‘pillared’ by OX(2−) ligands resulting in a 3-D framework. In compound 7, the 1-D Tb-NNO infinite chain and its 2-D layer are formed in an almost similar fashion to that in compound 1. The difference between the structures of the two compounds 1 and 7 is that the adjacent 2-D layers in compound 7 are further connected by NNO(−) ligands resulting in a 3-D framework. The photoluminescence properties and energy transfer mechanism of the compounds were studied systematically. The energy level of the lowest triplet states of the HNNO ligand (23148 cm(−1)) was determined based on the phosphorescence spectrum of compound 5 at 77 K. The (5)D0 (Eu(3+)) and (5)D4 (Tb(3+)) emission lifetimes are 0.46 ms, 0.83 ms, 0.69 ms and 0.89 ms and overall quantum yields are 1.03%, 3.29%, 2.58% and 3.78% for the compounds 1, 2, 6 and 7, respectively.

Adsorption and degradation processes of tributyltin and trimethyltin in landfill leachates treated with iron nanoparticles.

PubMed

Peeters, Kelly; Lespes, Gaëtane; Milačič, Radmila; Ščančar, Janez

2015-10-01

Biotic and abiotic degradation of toxic organotin compounds (OTCs) in landfill leachates is usually not complete. In this work adsorption and degradation processes of tributyltin (TBT) and trimethyltin (TMeT) in leachate sample treated with different iron nanoparticles (FeNPs): Fe(0) (nZVI), FeO and Fe3O4 were investigated to find conditions for their efficient removal. One sample aliquot was kept untreated (pH 8), while to the others (pH 8) FeNPs dispersed with tetramethyl ammonium hydroxide (TMAH) or by mixing were added and samples shaken under aerated conditions for 7 days. The same experiments were done in leachates in which the pH was adjusted to 3 with citric acid. Size distribution of TBT and TMeT between particles >5 µm, 0.45-5 µm, 2.5-0.45 µm, and <2.5 nm was determined by sequential filtration and their concentrations in a given fraction by gas chromatography coupled to inductively coupled plasma mass spectrometry (GC-ICP-MS). Results revealed that most of the TBT or TMeT was present in fractions with particles >2.5 or <2.5 nm, respectively. At pH 8 adsorption of TBT to FeNPs prevailed, while at pH 3, the Fenton reaction provoked degradation of TBT by hydroxyl radicals. TBT was the most effectively removed (96%) when sequential treatment of leachate with nZVI (dispersed by mixing) was applied first at pH 8, followed by nZVI treatment of the aqueous phase, previously acidified to pH 3 with citric acid. Such treatment less effectively removed TMeT (about 40%). It was proven that TMAH provoked methylation of tin, so mixing was recommended for dispersion of nZVI. Copyright © 2015 Elsevier Inc. All rights reserved.

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

PubMed Central

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

2014-01-01

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

Coupling between Chemical and Meteorological Processes under Persistent Cold-Air Pool Conditions: Evolution of Wintertime PM2.5 Pollution Events and N2O5 Observations in Utah's Salt Lake Valley.

PubMed

Baasandorj, Munkhbayar; Hoch, Sebastian W; Bares, Ryan; Lin, John C; Brown, Steven S; Millet, Dylan B; Martin, Randal; Kelly, Kerry; Zarzana, Kyle J; Whiteman, C David; Dube, William P; Tonnesen, Gail; Jaramillo, Isabel Cristina; Sohl, John

2017-06-06

The Salt Lake Valley experiences severe fine particulate matter pollution episodes in winter during persistent cold-air pools (PCAPs). We employ measurements throughout an entire winter from different elevations to examine the chemical and dynamical processes driving these episodes. Whereas primary pollutants such as NO x and CO were enhanced twofold during PCAPs, O 3 concentrations were approximately threefold lower. Atmospheric composition varies strongly with altitude within a PCAP at night with lower NO x and higher oxidants (O 3 ) and oxidized reactive nitrogen (N 2 O 5 ) aloft. We present observations of N 2 O 5 during PCAPs that provide evidence for its role in cold-pool nitrate formation. Our observations suggest that nighttime and early morning chemistry in the upper levels of a PCAP plays an important role in aerosol nitrate formation. Subsequent daytime mixing enhances surface PM 2.5 by dispersing the aerosol throughout the PCAP. As pollutants accumulate and deplete oxidants, nitrate chemistry becomes less active during the later stages of the pollution episodes. This leads to distinct stages of PM 2.5 pollution episodes, starting with a period of PM 2.5 buildup and followed by a period with plateauing concentrations. We discuss the implications of these findings for mitigation strategies.

Synthesis and structure of the first discrete dinuclear cationic aluminum complexes.

PubMed

Wang, Xingbao; Dorcet, Vincent; Luo, Yi; Carpentier, Jean-Francois; Kirillov, Evgueni

2016-08-02

The reactions of the charge neutral dinuclear aluminum tetraalkyl complexes of di-Schiff base ligands, i.e. [AlMe2{ON}-R-{ON}AlMe2] (1a, R = 1,3-propylene; 1b, R = 1,3-cyclohexylene) with B(C6F5)3 and [H(Et2O)2](+)[H2N{B(C6F5)3}2](-) were investigated. When B(C6F5)3 was used as the cationizing agent (1 or 2 equiv. vs. Al), only monocationic dinuclear complexes [2a,b]+[MeB(C6F5)3]- were obtained. In contrast, with [H(Et2O)2](+)[H2N{B(C6F5)3}2](-), both mixed-dicationic [3a,b·(OEt2)2]2+[MeB(C6F5)3]-[H2N{B(C6F5)3}2]- and homo-dicationic [3a,b·(OEt2)2]2+[H2N{B(C6F5)3}2]-2 ion-pairs were prepared. All cationic complexes were characterized by (1)H, (13)C, (19)F and (11)B NMR spectroscopy, and an X-ray diffraction study was performed for [3b·(OEt2)2]2+[H2N{B(C6F5)3}2]-2.

Crystal chemistry and thermal behavior of La doped (U, Th)O2

NASA Astrophysics Data System (ADS)

Keskar, Meera; Shelke, Geeta P.; Shafeeq, Muhammed; Krishnan, K.; Sali, S. K.; Kannan, S.

2017-12-01

X-ray diffraction, chemical and thermal studies of [(U0.2Th0.8)1-yLay]O2+x (LUTL) and [(U0.3Th0.7)1-yLay]O2+x (UTL); compounds (where y ≤ 0.4) were carried out. These compounds were synthesized by gel combustion method followed by heating in reduced atmospheres at 1673 K. To co-relate lattice parameters with metal and oxygen concentrations, reduced oxides were heated in Ar, CO2 and air atmospheres. Retention of FCC phase was confirmed in all mixed oxides with y ≤ 0.4. The cubic lattice parameters could be expressed in a linear equation of x and y as: a (Ǻ) = 5.5709 - 0.187 x + 0.032 y; [x < 0 and 0 ≤ y ≤ 0.40] for LUTL and a (Ǻ) = 5.5580 - 0.26 x + 0.015 y; [x < 0 and 0 ≤ y ≤ 0.36] for UTL. Oxidation studies and simple ionic model calculations suggested that uranium is predominantly present as a mixture of +5 and + 6 states when La/U ratio ∼2. Oxidation kinetics of mixed oxides was studied by non-isothermal method using thermogravimetry and was found to be a diffusion controlled reaction. High temperature X-ray diffraction studies of LUTL and UTL mixed oxides showed positive thermal expansion in the temperature range of 298-1273 K and % expansion increases with La concentration.

Chemical abundances of fast-rotating massive stars . II. Interpretation and comparison with evolutionary models

NASA Astrophysics Data System (ADS)

Cazorla, Constantin; Nazé, Yaël; Morel, Thierry; Georgy, Cyril; Godart, Mélanie; Langer, Norbert

2017-08-01

Aims: Past observations of fast-rotating massive stars exhibiting normal nitrogen abundances at their surface have raised questions about the rotational mixing paradigm. We revisit this question thanks to a spectroscopic analysis of a sample of bright fast-rotating OB stars, with the goal of quantifying the efficiency of rotational mixing at high rotation rates. Methods: Our sample consists of 40 fast rotators on the main sequence, with spectral types comprised between B0.5 and O4. We compare the abundances of some key element indicators of mixing (He, CNO) with the predictions of evolutionary models for single objects and for stars in interacting binary systems. Results: The properties of half of the sample stars can be reproduced by single evolutionary models, even in the case of probable or confirmed binaries that can therefore be true single stars in a pre-interaction configuration. The main problem for the rest of the sample is a mismatch for the [N/O] abundance ratio (we confirm the existence of fast rotators with a lack of nitrogen enrichment) and/or a high helium abundance that cannot be accounted for by models. Modifying the diffusion coefficient implemented in single-star models does not solve the problem as it cannot simultaneously reproduce the helium abundances and [N/O] abundance ratios of our targets. Since part of them actually are binaries, we also compared their chemical properties with predictions for post-mass transfer systems. We found that these models can explain the abundances measured for a majority of our targets, including some of the most helium-enriched, but fail to reproduce them in other cases. Our study thus reveals that some physical ingredients are still missing in current models.

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

NASA Astrophysics Data System (ADS)

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

2011-06-01

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

Effects of P/Ni ratio and Ni content on performance of γ-Al2O3-supported nickel phosphides for deoxygenation of methyl laurate to hydrocarbons

NASA Astrophysics Data System (ADS)

Zhang, Zhena; Tang, Mingxiao; Chen, Jixiang

2016-01-01

γ-Al2O3-supported nickel phosphides (mNi-Pn) were prepared by the TPR method and tested for the deoxygenation of methyl laurate to hydrocarbons. The effects of the P/Ni ratio (n = 1.0-2.5) and Ni content (m = 5-15 wt.%) in the precursors on their structure and performance were investigated. Ni/γ-Al2O3 was also studied for comparison. It was found that the formation of AlPO4 in the precursor inhibited the reduction of phosphate and so the formation of nickel phosphides. With increasing the P/Ni ratio and Ni content, the Ni, Ni3P, Ni12P5 and Ni2P phases orderly formed, accompanying with the increases of their particle size and the amount of weak acid sites (mainly due to P-OH group), while the CO uptake and the amount of medium strong acid sites (mainly related to Ni sites) reached maximum on 10%Ni-P1.5. In the deoxygenation reaction, compared with Ni/γ-Al2O3, the mNi-Pn catalysts showed much lower activities for decarbonylation, Csbnd C hydrogenolysis and methanation due to the ligand and ensemble effects of P. The conversion and the selectivity to n-C11 and n-C12 hydrocarbons achieved maximum on 10%Ni-P 2.0 for the 10%Ni-Pn catalysts and on 8%Ni-P2.0 for the mNi-P2.0 catalysts, while the turnover frequency (TOF) of methyl laurate mainly increased with the P/Ni ratio and Ni content. We propose that TOF was influenced by the nickel phosphide phases, the catalyst acidity and the particle size as well as the synergetic effect between the Ni site and acid site. Again, the hydrodeoxygenation pathway of methyl laurate was promoted with increasing P/Ni ratio and Ni content, ascribed to the phase change in the order of Ni, Ni3P, Ni12P5 and Ni2P in the prepared catalysts.

Diazido­bis(5,5′-dimethyl-2,2′-bipyridyl-κ2 N,N′)nickel(II) monohydrate

PubMed Central

Phatchimkun, Jaturong; Kongsaeree, Palangpon; Suchaichit, Nattawut; Chaichit, Narongsak

2009-01-01

In the crystal structure of the title compound, [Ni(N3)2(C12H12N2)2]·H2O, the NiII atom is situated on a twofold axis and adopts a distorted octa­hedral geometry with the two 5,5′-dimethyl-2,2′-bipyridyl (dmbpy) and the two azide ligands in a cis arrangement. The water solvent mol­ecule is disordered over two positions in a 1:1 ratio. PMID:21577389

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

NASA Astrophysics Data System (ADS)

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

2012-08-01

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

Phase behavior, rheological property, and transmutation of vesicles in fluorocarbon and hydrocarbon surfactant mixtures.

PubMed

Yuan, Zaiwu; Qin, Menghua; Chen, Xiushan; Liu, Changcheng; Li, Hongguang; Hao, Jingcheng

2012-06-26

We present a detailed study of a salt-free cationic/anionic (catanionic) surfactant system where a strongly alkaline cationic surfactant (tetradecyltrimethylammonium hydroxide, TTAOH) was mixed with a single-chain fluorocarbon acid (nonadecafluorodecanoic acid, NFDA) and a hyperbranched hydrocarbon acid [di-(2-ethylhexyl)phosphoric acid, DEHPA] in water. Typically the concentration of TTAOH is fixed while the total concentration and mixing molar ratio of NFDA and DEHPA is varied. In the absence of DEHPA and at a TTAOH concentration of 80 mmol·L(-1), an isotropic L(1) phase, an L(1)/L(α) two-phase region, and a single L(α) phase were observed successively with increasing mixing molar ratio of NFDA to TTAOH (n(NFDA)/n(TTAOH)). In the NFDA-rich region (n(NFDA)/n(TTAOH) > 1), a small amount of excess NFDA can be solubilized into the L(α) phase while a large excess of NFDA eventually leads to phase separation. When NFDA is replaced gradually by DEHPA, the mixed system of TTAOH/NFDA/DEHPA/H(2)O follows the same phase sequence as that of the TTAOH/NFDA/H(2)O system and the phase boundaries remain almost unchanged. However, the viscoelasticity of the samples in the single L(α) phase region becomes higher at the same total surfactant concentration as characterized by rheological measurements. Cryo-transmission electron microscopic (cryo-TEM) observations revealed a microstructural evolution from unilamellar vesicles to multilamellar ones and finally to gaint onions. The size of the vesicle and number of lamella can be controlled by adjusting the molar ratio of NFDA to DEHPA. The dynamic properties of the vesicular solutions have also been investigated. It is found that the yield stress and the storage modulus are time-dependent after a static mixing process between the two different types of vesicle solutions, indicating the occurrence of a dynamic fusion between the two types of vesicles. The microenvironmental changes induced by aggregate transitions were probed by (19)F NMR as well as (31)P NMR measurements. Upon replacement of NFDA by DEHPA, the signal from the (19)F atoms adjacent to the hydrophilic headgroup disappears and that from the (19)F atoms on the main chain becomes sharper. This could be interpreted as an increase of microfluidity in the mixed vesicle bilayers at higher content of DEHPA, whose alkyl chains are expected to have a lower chain melting point. Our results provide basic knowledge on vesicle formation and their structural evolution in salt-free catanionic surfactant systems containing mixed ion pairs, which may contribute to a deeper understanding of the rules governing the formation and properties of surfactant self-assembly.

Hydrothermal synthesis, crystal structures and photoluminescence properties of mixed europium-yttrium organic frameworks

NASA Astrophysics Data System (ADS)

Han, Yinfeng; Fu, Lianshe; Mafra, Luís; Shi, Fa-Nian

2012-02-01

Three mixed europium-yttrium organic frameworks: Eu2-xYx(Mel)(H2O)6 (Mel=mellitic acid or benzene-1,2,3,4,5,6-hexacarboxylic acid, x=0.38 1, 0.74 2, and 0.86 3) have been synthesized and characterized. All the compounds contain a 3-D net with (4, 8)-flu topology. The study indicates that the photoluminescence properties are effectively affected by the different ratios of europium and yttrium ions, the quantum efficiency is increased and the Eu3+ lifetime becomes longer in these MOFs than those of the Eu analog.

Characterization of Barium Borate Frameworks Using Raman Spectroscopy.

PubMed

Gharavi-Naeini, Jafar; Yoo, Kyung W; Stump, Nathan A

2018-04-01

Systematic micro-Raman scattering investigations have been carried out on Sm +2 doped 2(BaO)-n(B 2 O 3 ) matrices for n = 4, 5, 8, and 2(BaO)-(Na 2 O)-9(B 2 O 3 ) using the 364 nm excitation of an Ar + laser. The Raman results have been compared with the known structures of barium tetraborate, barium pentaborate, barium octaborate, and barium sodium nonaborate. An excellent correlation has been found between the BO 4 /BO 3 composition ratios for each product and intensity ratios of the designated BO 4 and BO 3 Raman peaks. Furthermore, the Raman frequencies of both BO 4 and BO 3 groups undergo a systematic blueshift as n increases from four to nine. The shift results from a decrease of the B-O bond lengths for both BO 4 and BO 3 groups as the samples transition from the tetraborate to nonaborate structures. Linear relations (with negative slopes) have been determined between the measured Raman frequencies and B-O bond lengths in the frameworks.

Chemistry of solutions from the 13°N East Pacific Rise hydrothermal site

NASA Astrophysics Data System (ADS)

Michard, G.; Albarède, F.; Michard, A.; Minster, J.-F.; Charlou, J.-L.; Tan, N.

1984-03-01

Ten samples were recovered by the submersible "Cyana" submersible from two groups of hydrothermal vents located 2600 m deep along the East Pacific Rise at 13°N. The maximum measured temperature was 317°C and minimum pH 3.8. A systematic determination of major and trace elements has been carried out and mixing lines between a high-temperature component (HTC) and seawater are observed. The water chemistry of the HTC slightly differs for several elements at the two sites. This HTC is deprived of SO 4 and Mg and is greatly enriched in most other species. Maximum concentrations are (in units per kg): Cl = 0.72mol; Br = 1.1mmol; Na = 0.55mol; K = 29mmol; Rb = 14 μmol; Ca = 52mmol; Sr = 170 μmol; Mn = 750 μmol; Fe = 1mmol; Al = 15 μmol; Si = 21mmol. For many elements, the magnitude of the anomaly relative to seawater does not compare with the results obtained from the Galapagos or East Pacific Rise 21°N. The enrichment of cations relative to seawater is likely related to the huge Cl excess through charge balance. The Br/Cl ratio is close to that for seawater. However, it is not clear whether the Cl excess is due to gas release or basalt hydration (formation of amphibole chlorite or epidote). P-T dependence of SiO 2 solubility suggests that water-rock interaction last occurred at a depth in excess of 1 km below the sea floor. A mixing line of 87Sr/ 86Sr vs. Mg/Sr demonstrates that the HTCs have a nearly identical 87Sr/ 86Sr ratio of 0.7041 for both sites. A water/rock ratio of about 5 is inferred, which differs from the 1.5 value obtained at 21°N.

Small gas-phase dianions produced by sputtering and gas flooding

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

Franzreb, Klaus; Williams, Peter

2005-12-08

We have extended our previous experiment [Schauer et al., Phys. Rev. Lett. 65, 625 (1990)] where we had produced small gas-phase dianion clusters of C{sub n}{sup 2-}(n{>=}7) by means of sputtering a graphite surface by Cs{sup +} ion bombardment. Our detection sensitivity for small C{sub n}{sup 2-} could now be increased by a factor of about 50 for odd n. Nevertheless, a search for the elusive pentamer dianion of C{sub 5}{sup 2-} was not successful. As an upper limit, the sputtered flux of C{sub 5}{sup 2-} must be at least a factor of 5000 lower than that of C{sub 7}{supmore » 2-}, provided that the lifetime of C{sub 5}{sup 2-} is sufficiently long to allow its detection by mass spectrometry. When oxygen gas (flooding with either O{sub 2} or with N{sub 2}O) was supplied to the Cs{sup +}-bombarded graphite surface, small dianions of OC{sub n}{sup 2-}(5{<=}n{<=}14) and O{sub 2}C{sub 7}{sup 2-} were observed in addition to C{sub n}{sup 2-}(n{>=}7). Similarly, Cs{sup +} sputtering of graphite with simultaneous SF{sub 6} gas flooding produced SC{sub n}{sup 2-}(6{<=}n{<=}18). Mixed nitrogen-carbon or fluorine-carbon dianion clusters could not be observed by these means. Attempts to detect mixed metal-fluoride dianions for SF{sub 6} gas flooding of various Cs{sup +}-bombarded metal surfaces were successful for the case of Zr, where metastable ZrF{sub 6}{sup 2-} was observed. Cs{sup +} bombardment of a silicon carbide (SiC) wafer produced SiC{sub n}{sup 2-} (n=6,8,10). When oxygen gas was supplied to the Cs{sup +}-bombarded SiC surface, small dianions of SiOC{sub n}{sup 2-} (n=4,6,8) and of SiO{sub 2}C{sub n}{sup 2-} (n=4,6) as well as a heavier unidentified dianion (at m/z=98.5) were observed. For toluene (C{sub 7}H{sub 8}) vapor flooding of a Cs{sup +}-bombarded graphite surface, several hydrocarbon dianion clusters of C{sub n}H{sub m}{sup 2-}(n{>=}7) were produced in addition to C{sub n}{sup 2-}(n{>=}7), while smaller C{sub n}H{sub m}{sup 2-} with n{<=}6 could not be observed. BeC{sub n}{sup 2-} (n=4,6,8,10), Be{sub 2}C{sub 6}{sup 2-}, as well as BeC{sub 8}H{sub m}{sup 2-} (with m=2 and/or m=1) were observed for toluene vapor flooding of a Cs{sup +}-bombarded beryllium metal foil. The metastable pentamer {sup 9}Be{sup 12}C{sub 4}{sup 2-} at m/z=28.5 was the smallest and lightest dianion molecule that we could detect. The small dianion clusters of SC{sub n}{sup 2-}, OC{sub n}{sup 2-}, BeC{sub n}{sup 2-}, and SiO{sub m}C{sub n}{sup 2-} (m=0,1,2) have different abundance patterns. A resemblance exists between the abundance patterns of BeC{sub n}{sup 2-} and SiC{sub n}{sup 2-}, even though calculated molecular structures of BeC{sub 6}{sup 2-} and SiC{sub 6}{sup 2-} are different. The abundance pattern of SC{sub n}{sup 2-} is fairly similar to that of C{sub n}{sup 2-}.« less

Equilibrium of particle nitrite with gas phase HONO: Tropospheric measurements in the high Arctic during polar sunrise

NASA Astrophysics Data System (ADS)

Li, Shao-Meng

1994-12-01

Gas phase HONO(g) and nitrite in particles of <5-μm size were measured in the troposphere during the Polar Sunrise Experiment at Alert, Northwest Territories, Canada, during January 19 to April 20, 1992, using denuder-filter pack sampling and IC-UV detection. The measurements indicated that HONO(g) existed at concentrations of up to 70 ppt before polar sunrise but gradually decreased to 5-10 ppt after sunrise. The calculated OH formation rate from HONO(g) photolysis was greater than from the photolysis of both O3 and CH2O by more than one order of magnitude during the sunlit period and led to moderately high levels of OH, e.g., 3×105 molecules cm-3 OH at noontime on April 5. Particle nitrite measurements showed a gradual increase in concentrations with increasing solar insolation, but the concentrations were generally less than 10 ppt. The pH and the sulfate molar concentrations of the particles and the water vapor mixing ratio indicate that the particles were highly acidic being approximately 70% (W/W) H2SO4 solution. In such highly concentrated H2SO4 solution, most particle nitrite should exist as hydrated nitrosonium ion H2ONO+. Taking this into consideration, the particle nitrite was in an approximate equilibrium with the measured HONO(g). This equilibrium, with HONO(g) rapidly photolyzed, was a good indication that the particles were effective sources of HONO(g) and implied rapid production of particle N(+III) during this period. Two possible pathways leading to the formation of particle N(+III) species are suggested, i.e., reduction of HNO3(aq) by SO2(g) and reduction of NO3-; (aq) by Br- (aq). However, N2O5 reaction with NaBr cannot be ruled out as the alternative HONO(g) formation mechanism which bypasses the equilibrium.

Isotopic measurements (C,N,O) of detonation soot produced from labeled and unlabeled Composition B-3 indicate source of solid carbon residues

NASA Astrophysics Data System (ADS)

Podlesak, David; Manner, Virginia; Amato, Ronald; Dattelbaum, Dana; Gusavsen, Richard; Huber, Rachel

2017-06-01

Detonation of HE is an exothermic process whereby metastable complex molecules are converted to simple stable molecules such as H2 O, N2, CO, CO2, and solid carbon. The solid carbon contains various allotropes such as detonation nanodiamonds, graphite, and amorphous carbon. It is well known that certain HE formulations such as Composition B (60% RDX, 40% TNT) produce greater amounts of solid carbon than other more oxygen-balanced formulations. To develop a greater understanding of how formulation and environment influence solid carbon formation, we synthesized TNT and RDX with 13 C and 15 N at levels slightly above natural abundance levels. Synthesized RDX and TNT were mixed at a ratio of 60:40 to form Composition B and solid carbon residues were collected from detonations of isotopically-labeled as well as un-labelled Composition B. The raw HE and detonation residues were analyzed isotopically for C, N, O isotopic compositions. We will discuss differences between treatments groups as a function of formulation and environment. LA-UR - 17-21266.

Experimental Study of Static Contact-angle on Peak-like Microstructural Surfaces Produced by PIII Technology

NASA Astrophysics Data System (ADS)

Yang, Runhua; Yang, Lixin

2018-06-01

Plasma immersion ion implantation (PIII) was used to fabricate micro/nano structures on monocrystalline Si surfaces with different ratios of mixed gases (SF6/O2). The micro/nano structures on the surfaces of the sample were characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The results showed that with increasing ratio of mixed gases (SF6/O2), the height of the micro/nano structures first increased and then decreased. Contact-angle measurements indicated that the surfaces' micro/nano structures have an obvious effect on the contact-angle, and could cause a change in surface wettability. The theoretical analysis of contact-angle showed that the Wenzel and Cassie theories cannot predict the contact-angle of a roughened surface accurately, and should be corrected for practical applications using an actual model. Moreover, the contact-angle first increased and then decreased with increasing ratio of mixed gases (SF6/O2), which is in accordance with the change of the height of micro/nano structures.

β-Ga2O3 versus ε-Ga2O3: Control of the crystal phase composition of gallium oxide thin film prepared by metal-organic chemical vapor deposition

NASA Astrophysics Data System (ADS)

Zhuo, Yi; Chen, Zimin; Tu, Wenbin; Ma, Xuejin; Pei, Yanli; Wang, Gang

2017-10-01

Gallium oxide thin films of β and ε phase were grown on c-plane sapphire using metal-organic chemical vapor deposition and the phase compositions were analyzed using X-ray diffraction. The epitaxial phase diagram was constructed as a function of the growth temperature and VI/III ratio. A low growth temperature and low VI/III ratio were beneficial for the formation of hexagonal-type ε-Ga2O3. Further structure analysis revealed that the epitaxial relationship between ε-Ga2O3 and c-plane sapphire is ε-Ga2O3 (0001) || Al2O3 (0001) and ε-Ga2O3 || Al2O3 . The structural evolution of the mixed-phase sample during film thickening was investigated. By reducing the growth rate, the film evolved from a mixed phase to the energetically favored ε phase. Based on these results, a Ga2O3 thin film with a phase-pure ε-Ga2O3 upper layer was successfully obtained.

Seasonal variability in methane and nitrous oxide fluxes from tropical peatlands in the western Amazon basin

NASA Astrophysics Data System (ADS)

Arn Teh, Yit; Murphy, Wayne A.; Berrio, Juan-Carlos; Boom, Arnoud; Page, Susan E.

2017-08-01

The Amazon plays a critical role in global atmospheric budgets of methane (CH4) and nitrous oxide (N2O). However, while we have a relatively good understanding of the continental-scale flux of these greenhouse gases (GHGs), one of the key gaps in knowledge is the specific contribution of peatland ecosystems to the regional budgets of these GHGs. Here we report CH4 and N2O fluxes from lowland tropical peatlands in the Pastaza-Marañón foreland basin (PMFB) in Peru, one of the largest peatland complexes in the Amazon basin. The goal of this research was to quantify the range and magnitude of CH4 and N2O fluxes from this region, assess seasonal trends in trace gas exchange, and determine the role of different environmental variables in driving GHG flux. Trace gas fluxes were determined from the most numerically dominant peatland vegetation types in the region: forested vegetation, forested (short pole) vegetation, Mauritia flexuosa-dominated palm swamp, and mixed palm swamp. Data were collected in both wet and dry seasons over the course of four field campaigns from 2012 to 2014. Diffusive CH4 emissions averaged 36.05 ± 3.09 mg CH4-C m-2 day-1 across the entire dataset, with diffusive CH4 flux varying significantly among vegetation types and between seasons. Net ebullition of CH4 averaged 973.3 ± 161.4 mg CH4-C m-2 day-1 and did not vary significantly among vegetation types or between seasons. Diffusive CH4 flux was greatest for mixed palm swamp (52.0 ± 16.0 mg CH4-C m-2 day-1), followed by M. flexuosa palm swamp (36.7 ± 3.9 mg CH4-C m-2 day-1), forested (short pole) vegetation (31.6 ± 6.6 mg CH4-C m-2 day-1), and forested vegetation (29.8 ± 10.0 mg CH4-C m-2 day-1). Diffusive CH4 flux also showed marked seasonality, with divergent seasonal patterns among ecosystems. Forested vegetation and mixed palm swamp showed significantly higher dry season (47.2 ± 5.4 mg CH4-C m-2 day-1 and 85.5 ± 26.4 mg CH4-C m-2 day-1, respectively) compared to wet season emissions (6.8 ± 1.0 mg CH4-C m-2 day-1 and 5.2 ± 2.7 mg CH4-C m-2 day-1, respectively). In contrast, forested (short pole) vegetation and M. flexuosa palm swamp showed the opposite trend, with dry season flux of 9.6 ± 2.6 and 25.5 ± 2.9 mg CH4-C m-2 day-1, respectively, versus wet season flux of 103.4 ± 13.6 and 53.4 ± 9.8 mg CH4-C m-2 day-1, respectively. These divergent seasonal trends may be linked to very high water tables (> 1 m) in forested vegetation and mixed palm swamp during the wet season, which may have constrained CH4 transport across the soil-atmosphere interface. Diffusive N2O flux was very low (0.70 ± 0.34 µg N2O-N m-2 day-1) and did not vary significantly among ecosystems or between seasons. We conclude that peatlands in the PMFB are large and regionally significant sources of atmospheric CH4 that need to be better accounted for in regional emissions inventories. In contrast, N2O flux was negligible, suggesting that this region does not make a significant contribution to regional atmospheric budgets of N2O. The divergent seasonal pattern in CH4 flux among vegetation types challenges our underlying assumptions of the controls on CH4 flux in tropical peatlands and emphasizes the need for more process-based measurements during periods of high water table.

Tunability of p- and n-channel TiOx thin film transistors.

PubMed

Peng, Wu-Chang; Chen, Yao-Ching; He, Ju-Liang; Ou, Sin-Liang; Horng, Ray-Hua; Wuu, Dong-Sing

2018-06-18

To acquire device-quality TiO x films usually needs high-temperature growth or additional post-thermal treatment. However, both processes make it very difficult to form the p-type TiO x even under oxygen-poor growth condition. With the aid of high energy generated by high power impulse magnetron sputtering (HIPIMS), a highly stable p-type TiO x film with good quality can be achieved. In this research, by varying the oxygen flow rate, p-type γ-TiO and n-type TiO 2 films were both prepared by HIPIMS. Furthermore, p- and n-type thin film transistors employing γ-TiO and TiO 2 as channel layers possess the field-effect carrier mobilities of 0.2 and 0.7 cm 2 /Vs, while their on/off current ratios are 1.7 × 10 4 and 2.5 × 10 5 , respectively. The first presented p-type γ-TiO TFT is a major breakthrough for fabricating the TiO x -based p-n combinational devices. Additionally, our work also confirms HIPIMS offers the possibility of growing both p- and n-type conductive oxides, significantly expanding the practical usage of this technique.

Photocatalytic Water Splitting for O2 Production under Visible Light Irradiation Using NdVO4-V2O5 Hybrid Powders

PubMed Central

Chiang, Tzu Hsuan; Chen, Tso-Ming

2017-01-01

The study investigated photocatalytic water splitting for O2 production under visible light irradiation using neodymium vanadium oxide (NdVO4) and vanadium oxide (V2O5) hybrid powders. The results in a sacrificial agent of 0.01 M AgNO3 solution were obtained, and the highest photocatalytic O2 evolution was 2.63 μmol/h, when the hybrid powders were prepared by mixing Nd and V at a volume ratio of 1:3 at a calcination temperature of 350 °C for 1 h. The hybrid powders were synthesized by neodymium nitrate and ammonium metavanadate using the glycothermal method in ethylene glycol at 120 °C for 1 h. The hybrid powders consisted of two shapes, NdVO4 nanoparticles and the cylindrical V2O5 particles, and they possessed the ability for photocatalytic oxygen (O2) evolution during irradiation with visible light. The band gaps and structures of the hybrid powders were analyzed using UV-visible spectroscopy and transmission electron microscopy. PMID:28772692

Monitoring gas and heat emissions at Norris Geyser Basin, Yellowstone National Park, USA based on a combined eddy covariance and Multi-GAS approach

USGS Publications Warehouse

Lewicki, Jennifer L.; Kelly, Peter; Bergfeld, Deborah; Vaughan, R. Greg; Lowenstern, Jacob B.

2017-01-01

We quantified gas and heat emissions in an acid-sulfate, vapor-dominated area (0.04-km2) of Norris Geyser Basin, located just north of the 0.63 Ma Yellowstone Caldera and near an area of anomalous uplift. From 14 May to 3 October 2016, an eddy covariance system measured half-hourly CO2, H2O and sensible (H) and latent (LE) heat fluxes and a Multi-GAS instrument measured (1 Hz frequency) atmospheric H2O, CO2 and H2S volumetric mixing ratios. We also measured soil CO2 fluxes using the accumulation chamber method and temperature profiles on a grid and collected fumarole gas samples for geochemical analysis. Eddy covariance CO2 fluxes ranged from − 56 to 885 g m− 2 d− 1. Using wavelet analysis, average daily eddy covariance CO2 fluxes were locally correlated with average daily environmental parameters on several-day to monthly time scales. Estimates of CO2emission rate from the study area ranged from 8.6 t d− 1 based on eddy covariance measurements to 9.8 t d− 1 based on accumulation chamber measurements. Eddy covariance water vapor fluxes ranged from 1178 to 24,600 g m− 2 d− 1. Nighttime H and LEwere considered representative of hydrothermal heat fluxes and ranged from 4 to 183 and 38 to 504 W m− 2, respectively. The total hydrothermal heat emission rate (H + LE + radiant) estimated for the study area was 11.6 MW and LE contributed 69% of the output. The mean ± standard deviation of H2O, CO2 and H2S mixing ratios measured by the Multi-GAS system were 9.3 ± 3.1 parts per thousand, 467 ± 61 ppmv, and 0.5 ± 0.6 ppmv, respectively, and variations in the gas compositions were strongly correlated with diurnal variations in environmental parameters (wind speed and direction, atmospheric temperature). After removing ambient H2O and CO2, the observed variations in the Multi-GAS data could be explained by the mixing of relatively H2O-CO2-H2S-rich fumarole gases with CO2-rich and H2O-H2S-poor soil gases. The fumarole H2O/CO2 and CO2/H2S end member ratios (101.7 and 27.1, respectively, on average) were invariant during the measurement period and fell within the range of values measured in direct fumarole gas samples. The soil gas H2O/CO2end member ratios (~ 15–30) were variable and low relative to the fumarole end member, likely resulting from water vapor loss during cooling and condensation in the shallow subsurface, whereas the CO2/H2S end member ratio was high (~ 160), presumably related to transport of CO2-dominated soil gas emissions mixed with trace fumarolic emissions to the Multi-GAS station. Nighttime eddy covariance ratios of H2O to CO2 flux were typically between the soil gas and fumarole end member H2O/CO2 ratios defined by Multi-GAS measurements. Overall, the combined eddy covariance and Multi-GAS approach provides a powerful tool for quasi-continuous measurements of gas and heat emissions for improved volcano-hydrothermal monitoring.

Dechlorination of polychlorinated biphenyls by iron and its oxides.

PubMed

Sun, Yifei; Liu, Xiaoyuan; Kainuma, Masashi; Wang, Wei; Takaoka, Masaki; Takeda, Nobuo

2015-10-01

The decomposition efficiency of polychlorinated biphenyls (PCBs) was determined using elemental iron (Fe) and three iron (hydr)oxides, i.e., α-Fe2O3, Fe3O4, and α-FeOOH, as catalysts. The experiments were performed using four distinct PCB congeners (PCB-209, PCB-153, and the coplanar PCB-167 and PCB-77) at temperatures ranging from 180 °C to 380 °C and under an inert, oxidizing or reducing atmosphere composed of N2, N2+O2, or N2+H2. From these three options N2 showed to provide the best reaction atmosphere. Among the iron compounds tested, Fe3O4 showed the highest activity for decomposing PCBs. The decomposition efficiencies of PCB-209, PCB-167, PCB-153, and PCB-77 by Fe3O4 in an N2 atmosphere at 230 °C were 88.5%, 82.5%, 69.9%, and 66.4%, respectively. Other inorganic chlorine (Cl) products which were measured by the amount of inorganic Cl ions represented 82.5% and 76.1% of the reaction products, showing that ring cleavage of PCBs was the main elimination process. Moreover, the dechlorination did not require a particular hydrogen donor. We used X-ray photoelectron spectroscopy to analyze the elemental distribution at the catalyst's surface. The O/Fe ratio influenced upon the decomposition efficiency of PCBs: the lower this ratio, the higher the decomposition efficiency. X-ray absorption near edge structure spectra showed that α-Fe2O3 effectively worked as a catalyst, while Fe3O4 and α-FeOOH were consumed as reactants, as their final state is different from their initial state. Finally, a decomposition pathway was postulated in which the Cl atoms in ortho-positions were more difficult to eliminate than those in the para- or meta-positions. Copyright © 2015 Elsevier Ltd. All rights reserved.

First detection of HDO in the atmosphere of Venus at radio wavelengths - An estimate of the H2O vertical distribution

NASA Technical Reports Server (NTRS)

Encrenaz, T.; Lellouch, E.; Paubert, G.; Gulkis, S.

1991-01-01

The 225.9 GHz line of HDO has been detected in absorption in the atmosphere of Venus, with the 30-m IRAM antenna. This measurement gives information regarding the vertical distributions of HDO, and thus H2O, in this planet. The observations are consistent with an H2O vertical distribution strongly depleted by saturation at an altitude of 95 km, and, assuming a D/H enrichment of 120 with respect to the terrestrial value, with a mixing ratio of 3.5 (+ or - 2.0) ppm in the range 65-95 km.

Testing Binary Mixing Models for Lavas Erupted Along the Reykjanes Ridge: Insights From C-He Relationships

NASA Astrophysics Data System (ADS)

de Leeuw, G. A.; Hilton, D. R.; Shaw, A. M.; Murton, B. J.; Taylor, R. N.

2002-12-01

We report new CO2 abundance and isotope data for 36 basalt glasses erupted along the Reykjanes Ridge between latitudes 57.5 and 63°N. Lavas can be divided into (a) water-rich samples (~0.4 wt.%), erupted at depths < 775m north of 61.5°N, and (b) samples with water ~ 0.2 wt.%, erupted at depths of 620 - 2060 m and located between 57.5 and 61.5°N. Based upon He-Pb isotope systematics (Hilton et al., EPSL, 2000), deeper samples (category b) lie along binary mixing trajectories between plume-like (3He/4He ~ 30RA; 206Pb/204Pb ~ 18.7) and MORB-like endmembers (3He/4He ~ 8RA; 206Pb/204Pb ~ 18.0). Shallow samples (category a) do not fall on mixing trajectories: consistent with volatile loss followed by addition of a crustal contaminant, resulting in lower 3He/4He ratios. The aim of this study is to test whether binary mixing trends are observed using C-He relationships. All samples were analyzed using incremental heating techniques which allows for resolution of vesicle-sited CO2 from CO2 dissolved within the glass matrix. Results show that samples north of 61.5 °N (category a) have low CO2 contents in both the vesicle (2-37 ppm) and dissolved (15-61 ppm) phases. The isotopic composition of the CO2 varies between -8 and -34‰ (vesicle) and -6 and -10‰ (glass). The combined effect of low CO2 concentrations and low δ13C values are consistent with extensive gas loss +/- contamination of volatile-poor magmas with an isotopically-light C component. In contrast, samples in category b have significantly higher CO2 abundances (vesicles: 7-318 ppm; glass: 9-200 ppm) and higher and less variable δ13C values (vesicles: -5 to -26‰ ; glass: -4 to -11‰ ). This suggests that category b samples have not been subjected to the same degree of degassing and/or contamination as samples in category a. By combining the vesicle-sited CO2 abundances with He-contents determined by crushing (Hilton, op. cit), CO2/3He ratios for the vesicle phase can be derived. We observe high ratios (3x109 to 2x1010) in the more degassed category a samples. Category b CO2/3He ratios show a trend from low CO2/3He values (3x108) and MORB-like 206Pb/204Pb to high CO2/3He values (up to 2x1010) and more radiogenic 206Pb/204Pb. There are two possible explanations for the observed trends: 1) degassing followed by contamination with a high CO2/3He crustal component. This process controls C-He relationships in low concentration (highly degassed) samples close to Iceland. 2) mixing between a MORB-like source (CO2/3He ~ 2x109) and an enriched source with a higher initial CO2/3He value. This process controls samples in category b.

Urchin-like CdS/ZrO2 nanocomposite prepared by microwave-assisted hydrothermal combined with ion-exchange and its multimode photocatalytic activity

NASA Astrophysics Data System (ADS)

Li, Li; Wang, Lili; Zhang, Wenzhi; Zhang, Xiuli; Chen, Xi; Dong, Xue

2014-12-01

A series of urchin-like CdS/ZrO2 nanocomposites with different mole ratios of Cd/Zr were prepared by a two-step method combining the microwave-assisted hydrothermal and ion exchange methods. The products were characterized by X-ray diffraction, ultraviolet-visible diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and N2 adsorption-desorption measurements. The results of the study revealed that the CdS/ZrO2 nanocomposites had mixed phases of tetragonal ZrO2 and hexagonal CdS. Moreover, the samples prepared by the microwave-assisted hydrothermal method possessed the urchin-like structure with a surface composed of protrude-like nanoparticles in large quantities. The absorption in the visible region changed slightly with increasing mole ratio of Cd/Zr. Moreover, compared to the nanocomposites prepared by the conventional heating, the nanocomposites prepared by the microwave-assisted hydrothermal synthesis showed significantly different Brunauer-Emmett-Teller values, and the urchin-like CdS/ZrO2 structures were obtained. The photocatalytic degradation of methyl orange under ultraviolet (UV) light irradiation indicated that the photocatalytic activity of the CdS/ZrO2 nanocomposite with CdS/ZrO2 molar ratio of 30 % was higher than those of CdS, ZrO2, and other different ratios of CdS/ZrO2 nanocomposites. Moreover, under UV light, visible light, and microwave-assisted multimode photocatalytic degradation, the urchin-like CdS/ZrO2 nanocomposites significantly affected the photodegradation of various dyes. To understand the possible reaction mechanism of the photocatalysis by the CdS/ZrO2 nanocomposites, a series of controlled experiments were performed, and the stability and reusability of the CdS/ZrO2 nanocomposites were further investigated by the photocatalytic reaction.

Energy accommodation of 5-50 eV ions within an enclosure. [for subsequent detection by satellite-borne mass spectrometers

NASA Technical Reports Server (NTRS)

Humphris, R. R.; Boring, J. W.; Nelson, C. V.

1981-01-01

Beams of 5-50 eV He(+), Ar(+), Ne(+), O(+), and N2(+) ions were directed into an aluminum sphere, and the equilibrium number density of the atom or molecules was measured inside the sphere using a quadrupole mass spectrometer and signal averaging techniques. The equilibrium number density is inversely proportional to the average speed of the atoms; thus, the results are expressed in terms of the speed ratio, R = V(i)/V(s), where V(i) is the average speed within the enclosure, and V(s) is the average speed of atoms fully accommodated to the temperature of the wall. The speed ratios vary between 1.0 and 1.8. For N2, several values of R were less than 1; this was largely due to desorbed N2. There was no detectable number density for O, which is explained by the reaction of O with the surface.

Heterojunction solar cell with 6% efficiency based on an n-type aluminum-gallium-oxide thin film and p-type sodium-doped Cu2O sheet

NASA Astrophysics Data System (ADS)

Minami, Tadatsugu; Nishi, Yuki; Miyata, Toshihiro

2015-02-01

In this paper, we describe efforts to enhance the efficiency of Cu2O-based heterojunction solar cells fabricated with an aluminum-gallium-oxide (Al-Ga-O) thin film as the n-type layer and a p-type sodium (Na)-doped Cu2O (Cu2O:Na) sheet prepared by thermally oxidizing copper sheets. The optimal Al content [X; Al/(Ga + Al) atomic ratio] of an AlX-Ga1-X-O thin-film n-type layer was found to be approximately 2.5 at. %. The optimized resistivity was approximately 15 Ω cm for n-type AlX-Ga1-X-O/p-type Cu2O:Na heterojunction solar cells. A MgF2/AZO/Al0.025-Ga0.975-O/Cu2O:Na heterojunction solar cell with 6.1% efficiency was fabricated using a 60-nm-thick n-type oxide thin-film layer and a 0.2-mm-thick Cu2O:Na sheet with the optimized resistivity.

Effect of varying Ga content in ZnO:GaN solid solution synthesized by solution combustion technique for photocatalytic applications

NASA Astrophysics Data System (ADS)

Menon, Sumithra Sivadas; Janani, R.; Baskar, K.; Gupta, Bhavana; Singh, Shubra

2017-05-01

ZnO:GaN (oxy)nitride solid solution has been established as the most efficient non-oxide photocatalyst for water splitting under visible irradiation with one step photoexcitation and also boasts a band gap tunability from 2.8 eV to 2.5 eV[1]. The solid solution of GaN in ZnO is formed by the intersubstitution of few of Zn/O ions by Ga/N ions, and this results in the introduction of new defect levels above the valence band which narrows the effective band gap enabling activity under visible region of spectra. In this work, we report the synthesis of ZnO:GaN solid solution by a solution combustion technique where metal nitrates and urea are used as precursors. The Zn/Ga ratio was varied from 16 to 1 in the precursors. The as synthesized samples were characterized as phase pure by X-ray diffraction, where the wurtzite structure was retained up to Zn/Ga ratio of 5. The Diffuse reflectance spectroscopy studies revealed that as the Ga content in the solid solution increases there is a reduction in band gap, from 2.9 eV to 2.4 eV. The reduced band gap of the samples facilitates its photocatalytic activity under visible region of the spectra as evaluated by photoelectrochemical measurements.

Aromatization of n-hexane over ZnO/H-ZSM-5 catalysts

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

Kanai, J.; Kawata, N.

The mechanism of transformation of n-hexane into aromatics over ZnO/H-ZSM-5 catalyst has been investigated. The yields of aromatics in the transformation of n-hexane over H-ZSM-5 are enhanced by mechanical mixing of ZnO as well as by ion exchange or impregnation of zinc cation. It is concluded that aromatization of n-hexane over ZnO/H-ZSM-5 is a bifunctional reaction, and that ZnO as well as H-ZSM-5 takes part both in the activation of n-hexane and in the aromatization of lower olefins. By contrasting the conversion of n-hexane with that of 1-hexane, it is found that aromatization of n-hexane over ZnO/H-ZSM-5 involves both themore » dehydrogenation of n-hexane into hexene and that of the oligomerized products into aromatics. It is proposed that ZnO catalyzes the dehydrogenation of n-hexane into hexene and of the oligomerized products into aromatics.« less

Indoor/outdoor relationships, sources and cancer risk assessment of NPAHs and OPAHs in PM2.5 at urban and suburban hotels in Jinan, China

NASA Astrophysics Data System (ADS)

Li, Yanyan; Yang, Lingxiao; Chen, Xiangfeng; Jiang, Pan; Gao, Ying; Zhang, Junmei; Yu, Hao; Wang, Wenxing

2018-06-01

Paired indoor and outdoor measurements of 16 NPAHs and 5 OPAHs in PM2.5 were conducted at urban and suburban sites during January 2016 in Jinan, China. The concentrations of both indoor and outdoor NPAHs and OPAHs were higher at the urban site compared with the suburban site. 9N-ANT (16-42%), 2+3N-FLA (15-51%), 2N-PYR (6-20%), and 1N-PYR (4-6%) were the dominant NPAHs at all sites, and 9-FO (61-81%) was the most abundant OPAHs. Solid fuel combustion, motor vehicle exhausts, and secondary generation were the main sources of the PAH derivatives in this study area. The I/O ratios of 90% of NPAHs and OPAHs at the first urban indoor site (abbreviated as URI1, Green Tree Inn) and the suburban indoor site (abbreviated as SUI, the Seven Star Hotel) were <1.00 indicating that many of the compounds measured indoors originated from outdoor sources. At the second urban indoor site (abbreviated as URI2, Shandong University Hotel), the I/O ratios of 2- and 3-ring NPAHs and OPAHs were >1.00, which was likely due to cooking activities occurring near the measurement site. Measurements of outdoor 2+3N-FLA/1N-PYR revealed mainly primary emission at the urban site and secondary sources at the suburban site, the average ratios were 3.76 and 12.22, respectively. The average ratio of 2+3N-FLA/2N-PYR at all sites was 3.3, indicating that the OH-initiated reaction was the dominant secondary formation pathway. Nighttime ratios of 2+3N-FLA/1N-PYR were significantly higher than the daytime ratios at all sites. The difference was especially pronounced during heavily polluted conditions at the suburban site, which suggests that heavy pollution and nighttime conditions promote secondary production. Additionally, the cancer risk was highest in urban outdoor (abbreviated as URO) when the population expose to the level as the outdoor air in the urban. The risk suggested that adults may be at a higher cancer risk.

Halogen and trace element geochemistry in Mid-Ocean Ridge basalts from the Australian-Antarctic Ridge (AAR)

NASA Astrophysics Data System (ADS)

Yang, Y. S.; Seo, J. H.; Park, S. H.; Kim, T.

2015-12-01

Australian-Antarctic Ridge (AAR) is an extension of easternmost SE Indian Mid-Ocean Ridge (MOR).We collected volcanic glasses from the "in-axis" of the KR1 and KR2 MOR, and the overlapping zones of the KR1 MOR and the nearby seamounts ("KR1 mixing"). We determined trace and halogen elements in the glasses. Halogen concentrations and its ratios in the glasses are important to understand the mantle metasomatism and volatile recycling. 52 of the collected glasses are "primitive" (higher than 6 wt% MgO), while 3 of them have rather "evolved" composition (MgO wt% of 1.72, 2.95 and 4.15). K2O concentrations and Th/Sc ratios in the glasses show a negative correlation with its MgO concentration. Incompatible element ratios such as La/Sm are rather immobile during a magma differentiation so the ratios are important to understand mantle composition (Hofmann et al. 2003). La/Sm ratios in the glasses are 0.95 ~ 3.28 suggesting that the AAR basalts can be classified into T-MORB and E-MORB (Schilling et al., 1983). La/Sm ratios are well-correlated with incompatible elements such as U, Ba, Nb, and negatively correlated with compatible elements such as Sc, Eu2+, Mg. The AAR glasses contain detectable halogen elements. The "KR1 mixing" glasses in halogen elements are more abundant than "in-axis" the glasses. Cl is the least variable element compared to the other halogens such as Br and I in the AAR. The "KR1 mixing" glasses have the largest variations of Br/Cl ratios compared to the "in-axis" glasses. The Cl/Br and Th/Sc ratios in the "in-axis" glasses and in the "KR1 mixing" glasses show positive and negative correlations, respectively. The Br-rich glasses in the "KR1 mixing" zone might be explained by a recycled Br-rich oceanic slab of paleo-subduction or by a hydrothermal alteration in the AAR. I composition in the glasses does not show a correlation other trace elements. The K/Cl and K/Ti ratios in the AAR glasses are similar to the basalts from the Galapagos Spreading Center (Geldmacher et al., 2010) and Pacific MORB. The AAR region closely located with Balleny hotspot (Lanyon et al., 1993) and Pacific-Antarctic Ridge. K2O/Nb and Zr/Nb ratios are very low compared with near Pacific-Antarctic Ridge and Southeast Indian Ridge. The ratios are close to the Balleny hotspot.

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-.

Improving estimates of N2O emissions for western and central Europe using a Bayesian inversion approach

NASA Astrophysics Data System (ADS)

Thompson, R. L.; Gerbig, C.; Roedenbeck, C.; Heimann, M.

2009-04-01

The nitrous oxide (N2O) mixing ratio has been increasing in the atmosphere since the industrial revolution, from 270 ppb in 1750 to 320 ppb in 2007 with a steady growth rate of around 0.26% since the early 1980's. The increase in N2O is worrisome for two main reasons. First, it is a greenhouse gas; this means that its atmospheric increase translates to an enhancement in radiative forcing of 0.16 ± 0.02 Wm-2 making it currently the fourth most important long-lived greenhouse gas and is predicted to soon overtake CFC's to become the third most important. Second, it plays an important role in stratospheric ozone chemistry. Human activities are the primary cause of the atmospheric N2O increase. The largest anthropogenic source of N2O is from the use of N-fertilizers in agriculture but fossil fuel combustion and industrial processes, such as adipic and nitric acid production, are also important. We present a Bayesian inversion approach for estimating N2O fluxes over central and western Europe using high frequency in-situ concentration data from the Ochsenkopf tall tower (50 °01′N, 11 °48′, 1022 masl). For the inversion, we employ a Lagrangian-type transport model, STILT, which provides source-receptor relationships at 10 km using ECMWF meteorological data. The a priori flux estimates used were from IER, for anthropogenic, and GEIA, for natural fluxes. N2O fluxes were retrieved monthly at 2 x 2 degree spatial resolution for 2007. The retrieved N2O fluxes showed significantly more spatial heterogeneity than in the a priori field and considerable seasonal variability. The timing of peak emissions was different for different regions but in general the months with the strongest emissions were May and August. Overall, the retrieved flux (anthropogenic and natural) was lower than in the a priori field.

Effect of the Ti/Si ratio of spin coating solutions on surface passivation of crystalline silicon by TiO x -SiO x composite films

NASA Astrophysics Data System (ADS)

Yoshiba, Shuhei; Tanitsu, Katsuya; Suda, Yoshiyuki; Kamisako, Koichi

2017-06-01

Passivation films or antireflection coatings are generally prepared using costly vacuum or high-temperature processes. Thus, we report the preparation of TiO x -SiO x composite films by novel spin coatable solutions for the synthesis of low-cost passivation coating materials. The desired films were formed by varying the mixing ratios of TiO x and SiO x , and the resulting films exhibited excellent surface passivation properties. For the p-type wafer, an optimal effective surface recombination velocity (S eff) of 93 cm/s was achieved at \\text{TiO}x:\\text{SiO}x = 6:4, while a surface recombination current density (J 0s) of 195 fA/cm2 was obtained. In contrast, for the n-type wafer, an S eff of 27 cm/s and a J 0s of 38 fA/cm2 were achieved at \\text{TiO}x:\\text{SiO}x = 8:2. This excellent surface passivation effect could be attributed to the low interface state density and high positive fixed charge density. Furthermore, the thickness of the interfacial SiO x layer was determined to be important for obtaining the desired surface passivation effect.

TiO2/water Nanofluid Heat Transfer in Heat Exchanger Equipped with Double Twisted-Tape Inserts

NASA Astrophysics Data System (ADS)

Eiamsa-ard, S.; Ketrain, R.; Chuwattanakul, V.

2018-05-01

Nowadays, heat transfer enhancement plays an important role in improving efficiency of heat transfer and thermal systems for numerous areas such as heat recovery processes, chemical reactors, air-conditioning/refrigeration system, food engineering, solar air/water heater, cooling of high power electronics etc. The present work presents the experimental results of the heat transfer enhancement of TiO2/water nanofluid in a heat exchanger tube fitted with double twisted tapes. The study covered twist ratios of twisted tapes (y/w) of 1.5, 2.0, and 2.5) while the concentration of the nanofluid was kept constant at 0.05% by volume. Observations show that heat transfer, friction loss and thermal performance increase as twist ratio (y/w) decreases. The use of the nanofluid in the tube equipped with the double twisted-tapes with the smallest twist ratio (y/w = 1.5) results in the increases of heat transfer rates and friction factor up to 224.8% and 8.98 times, respectively as compared to those of water. In addition, the experimental results performed that double twisted tapes induced dual swirling-flows which played an important role in improving fluid mixing and heat transfer enhancement. It is also observed that the TiO2/water nanofluid was responsible for low pressure loss behaviors.

Experimental ammonia-free phosphate-bonded investments using Mg(H2PO4)2.

PubMed

Zhang, Z; Tamaki, Y; Miyazaki, T

2001-12-01

In previous study, we found that Mg(H2PO4)2 instead of NH4H2PO4 was available as a binder material for phosphate-bonded investments and possibly could be used to develop the phosphate-bonded investment without ammonia gas release. The purpose of the present study was to develop the experimental ammonia-free phosphate-bonded investments by investigating suitable refractories. Mg(H2PO4)2.nH2O and MgO were prepared as a binder. Cristobalite and quartz were selected as refractories. The power ratio of MgO/Mg(H2PO4)2.nH2O was set constant at 1.2 according to our previous findings. Fundamental properties of dental investment such as strength, manipulation and expansion were evaluated. Using cristobalite as the refractory material, further investigations were performed. The refractory/binder ratio was definitely effective. The increase of this ratio led to low mold strength and large mold expansion. The present findings suggested that C5 was desirable for dental investment.

Estimation of the fossil fuel component in atmospheric CO2 based on radiocarbon measurements at the Beromünster tall tower, Switzerland

NASA Astrophysics Data System (ADS)

Berhanu, Tesfaye A.; Szidat, Sönke; Brunner, Dominik; Satar, Ece; Schanda, Rüdiger; Nyfeler, Peter; Battaglia, Michael; Steinbacher, Martin; Hammer, Samuel; Leuenberger, Markus

2017-09-01

Fossil fuel CO2 (CO2ff) is the major contributor of anthropogenic CO2 in the atmosphere, and accurate quantification is essential to better understand the carbon cycle. Since October 2012, we have been continuously measuring the mixing ratios of CO, CO2, CH4, and H2O at five different heights at the Beromünster tall tower, Switzerland. Air samples for radiocarbon (Δ14CO2) analysis have also been collected from the highest sampling inlet (212.5 m) of the tower on a biweekly basis. A correction was applied for 14CO2 emissions from nearby nuclear power plants (NPPs), which have been simulated with the Lagrangian transport model FLEXPART-COSMO. The 14CO2 emissions from NPPs offset the depletion in 14C by fossil fuel emissions, resulting in an underestimation of the fossil fuel component in atmospheric CO2 by about 16 %. An average observed ratio (RCO) of 13.4 ± 1.3 mmol mol-1 was calculated from the enhancements in CO mixing ratios relative to the clean-air reference site Jungfraujoch (ΔCO) and the radiocarbon-based fossil fuel CO2 mole fractions. The wintertime RCO estimate of 12.5 ± 3.3 is about 30 % higher than the wintertime ratio between in situ measured CO and CO2 enhancements at Beromünster over the Jungfraujoch background (8.7 mmol mol-1) corrected for non-fossil contributions due to strong biospheric contribution despite the strong correlation between ΔCO and ΔCO2 in winter. By combining the ratio derived using the radiocarbon measurements and the in situ measured CO mixing ratios, a high-resolution time series of CO2ff was calculated exhibiting a clear seasonality driven by seasonal variability in emissions and vertical mixing. By subtracting the fossil fuel component and the large-scale background, we have determined the regional biospheric CO2 component that is characterized by seasonal variations ranging between -15 and +30 ppm. A pronounced diurnal variation was observed during summer modulated by biospheric exchange and vertical mixing, while no consistent pattern was found during winter.

Ionic rotational branching ratios in resonant enhanced multiphoton ionization of NO via the A2Sigma(+)(3s sigma) and D2Sigma(+)(3p sigma) states

NASA Technical Reports Server (NTRS)

Rudolph, H.; Mckoy, V.; Dixit, S. N.; Huo, W. M.

1988-01-01

Results are presented for the rotationally resolved photoelectron spectra resulting from a (2 + 1) one-color resonant enhanced multiphoton ionization (REMPI) of NO via the rotationally clean S21(11.5) and mixed S11(15.5) + R21(15.5) branches of the 0-0 transition in the D-X band. The calculations were done in the fixed-nuclei frozen core approximation. The resulting photoionization spectra, convoluted with a Lorentzian detection function, agree qualitatively with experimental results of Viswanathan et al. (1986) and support their conclusion that the nonspherical nature of the molecular potential creates a substantial l-mixing in the continuum, which in turn leads to the intense Delta N = 0 peak. The rather strong photoelectron energy dependence of the rotational branching ratios of the D 2Sigma(+) S21(11.5) line was investigated and compared to the weak energy dependence of the A 2Sigma(+) R22(21.5) line.

Thin film integrated capacitors with sputtered-anodized niobium pentoxide dielectric for decoupling applications

NASA Astrophysics Data System (ADS)

Jacob, Susan

Electronics system miniaturization is a major driver for high-k materials. High-k materials in capacitors allow for high capacitance, enabling system miniaturization. Ta2O5 (k˜24) has been the dominant high-k material in the electronic industry for decoupling capacitors, filter capacitors, etc. In order to facilitate further system miniaturization, this project has investigated thin film integrated capacitors with Nb2O5 dielectric. Nb2O 5 has k˜41 and is a potential candidate for replacing Ta2O5. But, the presence of suboxides (NbO2 and NbO) in the dielectric deteriorates the electrical properties (leakage current, thermal instability of capacitance, etc.). Also, the high oxygen solubility of niobium results in oxygen diffusion from the dielectric to niobium metal, if any is present. The major purpose of this project was to check the ability of NbN as a diffusion barrier and fabricate thermally stable niobium capacitors. As a first step to produce niobium capacitors, the material characterizations of reactively sputtered Nb2O5 and NbN were done. Thickness and film composition, and crystal structures of the sputtered films were obtained and the deposition parameters for the desired stoichiometry were found. Also, anodized Nb2O5 was characterized for its stoichiometry and thickness. To study the effect of nitrides on capacitance and thermal stability, Ta2O5 capacitors were initially fabricated with and without TaN. The results showed that the nitride does not affect the capacitance, and that capacitors with TaN are stable up to 150°C. In the next step, niobium capacitors were first fabricated with anodized dielectric and the oxygen diffusion issues associated with capacitor processing were studied. Reactively sputtered Nb2O5 was anodized to form complete Nb2O5 (with few oxygen vacancies) and NbN was used to sandwich the dielectric. The capacitor fabrication was not successful due to the difficulties in anodizing the sputtered dielectric. Another method, anodizing reactively sputtered Nb2O5 and a thin layer of sputtered niobium metal yielded high yield (99%) capacitors. Capacitors were fabricated with and without NbN and the results showed 93% decrease in leakage for a capacitor with ˜2000 A dielectric when NbN was present in the structure. These capacitors could withstand 20 V and showed 2.7 muA leakage current at 5 V. These results were obtained after thermal storage at 100°C and 150°C in air for 168 hours at each temperature. Two set of experiments were performed using Ta2O5 dielectric: one to determine the effect of anodization end point on the thickness (capacitance) and the second to determine the effect of boiling the dielectric on functional yield. The anodization end point experiment showed that the final current of anodization along with the anodizing voltage determines the anodic oxide thickness. The lower the current, the thicker the films produced by anodization. Therefore, it was important to specify the final current along with the anodization voltage for oxide growth rate. The capacitors formed with boiled wafers showed better functional yield 3 out of 5 times compared with the unboiled wafer. Niobium anodization was studied for the Nb--->Nb 2O5 conversion ratio and the effect of anodization bath temperature on the oxide film; a color chart was prepared for thicknesses ranging from 1900 A - 5000 A. The niobium metal to oxide conversion ratio was found to change with temperature.

Desolventizing of Jatropha curcas oil from azeotropes of solvents using ceramic membranes.

PubMed

Carniel, Naira; Zabot, Giovani L; Paliga, Marshall; Mignoni, Marcelo L; Mazutti, Marcio A; Priamo, Wagner L; Oliveira, J V; Di Luccio, Marco; Tres, Marcus V

2017-12-01

The separation of Jatropha curcas oil from azeotropes of ethyl alcohol-n-hexane and isopropyl alcohol-n-hexane using ceramic membranes with different cutoffs (5, 10 and 20 kDa) is presented. The mass ratios of oil:azeotropes (O:S) studied were 1:3 for feeding pressures of 0.1, 0.2 and 0.3 MPa, and 1:1 for the feeding pressure of 0.1 MPa. Isopropyl alcohol was the best solvent for the membranes conditioning to permeate n-hexane (240 kg/m 2  h). In the separation of J. curcas oil and azeotropes of solvents, both membranes showed oil retention and total flux decreases with time. Overall, the lowest decrease in the retentions was reached in the 5 kDa membrane, while the lowest decrease in the total flux was reached in the 20 kDa. In the separation of oil and ethyl alcohol-n-hexane azeotrope, the best retention at 60 min of the process was equal to 17.3 wt% in the 20 kDa membrane at 0.3 MPa and O:S ratio equalled to 1:3. In this condition, the total permeate flux was 17.5 kg/m 2  h. Different retentions and permeabilities are provided when changing the O:S ratio, the feeding pressure and the molecular weight cutoff of membranes.

Efficient Separation and Extraction of Vanadium and Chromium in High Chromium Vanadium Slag by Selective Two-Stage Roasting-Leaching

NASA Astrophysics Data System (ADS)

Wen, Jing; Jiang, Tao; Xu, Yingzhe; Liu, Jiayi; Xue, Xiangxin

2018-06-01

Vanadium and chromium are important rare metals, leading to a focus on high chromium vanadium slag (HCVS) as a potential raw material to extract vanadium and chromium in China. In this work, a novel method based on selective two-stage roasting-leaching was proposed to separate and extract vanadium and chromium efficiently in HCVS. XRD, FT-IR, and SEM were utilized to analyze the phase evolutions and microstructure during the whole process. Calcification roasting, which can calcify vanadium selectively using thermodynamics, was carried out in the first roasting stage to transfer vanadium into acid-soluble vanadate and leave chromium in the leaching residue as (Fe0.6Cr0.4)2O3 after H2SO4 leaching. When HCVS and CaO were mixed in the molar ratio CaO/V2O3 (n(CaO)/n(V2O3)) of 0.5 to 1.25, around 90 pct vanadium and less than 1 pct chromium were extracted in the first leaching liquid, thus achieving the separation of vanadium and chromium. In the second roasting stage, sodium salt, which combines with chromium easily, was added to the first leaching residue to extract chromium and 95.16 pct chromium was extracted under the optimal conditions. The total vanadium and chromium leaching rates were above 95 pct, achieving the efficient separation and extraction of vanadium and chromium. The established method provides a new technique to separate vanadium and chromium during roasting rather than in the liquid form, which is useful for the comprehensive application of HCVS.

Efficient Separation and Extraction of Vanadium and Chromium in High Chromium Vanadium Slag by Selective Two-Stage Roasting-Leaching

NASA Astrophysics Data System (ADS)

Wen, Jing; Jiang, Tao; Xu, Yingzhe; Liu, Jiayi; Xue, Xiangxin

2018-04-01

Vanadium and chromium are important rare metals, leading to a focus on high chromium vanadium slag (HCVS) as a potential raw material to extract vanadium and chromium in China. In this work, a novel method based on selective two-stage roasting-leaching was proposed to separate and extract vanadium and chromium efficiently in HCVS. XRD, FT-IR, and SEM were utilized to analyze the phase evolutions and microstructure during the whole process. Calcification roasting, which can calcify vanadium selectively using thermodynamics, was carried out in the first roasting stage to transfer vanadium into acid-soluble vanadate and leave chromium in the leaching residue as (Fe0.6Cr0.4)2O3 after H2SO4 leaching. When HCVS and CaO were mixed in the molar ratio CaO/V2O3 (n(CaO)/n(V2O3)) of 0.5 to 1.25, around 90 pct vanadium and less than 1 pct chromium were extracted in the first leaching liquid, thus achieving the separation of vanadium and chromium. In the second roasting stage, sodium salt, which combines with chromium easily, was added to the first leaching residue to extract chromium and 95.16 pct chromium was extracted under the optimal conditions. The total vanadium and chromium leaching rates were above 95 pct, achieving the efficient separation and extraction of vanadium and chromium. The established method provides a new technique to separate vanadium and chromium during roasting rather than in the liquid form, which is useful for the comprehensive application of HCVS.

Temperature sensitivity of differential absorption lidar measurements of water vapor in the 720-nm region

NASA Technical Reports Server (NTRS)

Browell, Edward V.; Ismail, Syed; Grossmann, Benoist E.

1991-01-01

Recently measured properties of water vapor (H2O) absorption lines have been used in calculations to evalute the temperature sensitivity of differential absorption lidar (Dial) H2O measurements. This paper estimates the temperature sensitivity of H2O lines in the 717-733-nm region for both H2O mixing ratio and number density measurements, and discusses the influence of the H2O line ground state energies E-double-prime, the H2O absorption linewidths, the linewidth temperature dependence parameter, and the atmospheric temperature and pressure variations with altitude and location on the temperature sensitivity calculations. Line parameters and temperature sensitivity calculations for 67 H2O lines in the 720-nm band are given which can be directly used in field experiments. Water vapor lines with E-double-prime values in the 100-300/cm range were found to be optimum for Dial measurements of H2O number densities, while E-double-prime values in the 250-500/cm range were found to be optimum for H2O mixing ratio measurements.

The influence of narrow optical gap silver oxide on zinc oxide nanoparticles produced by microwave-assisted colloidal synthesis: photocatalytic studies

NASA Astrophysics Data System (ADS)

Prakoso, S. P.; Paramarta, V.; Tju, H.; Taufik, A.; Saleh, R.

2016-11-01

This paper reports a photocatalytic study on wide band gap zinc oxide (ZnO) incorporated by narrow band gap silver oxide (Ag2O), namely Ag2O/ZnO nanocomposites, which were prepared by colloidal synthesis with microwave supports. The Ag2O/ZnO nanocomposites were prepared with three different molar ratios (MR) of Ag2O to ZnO (MR: 0.25, 0.5 and 0.75). In order to confirm qualitatively the concentration ratio of Ag2O in ZnO, crystal phase intensity ratio was executed by peak indexing from x-ray diffraction. The Ag2O/ZnO nanocomposites properties were further investigated using diffuse reflectance spectroscopy. The nanocomposites were tested for the degradation of organic dyes solutions under visible and UV light irradiations. The photocatalytic activity of Ag2O/ZnO nanocomposites under visible light increased with increasing molar ratio of Ag2O to ZnO, while the opposite trends observed under UV light irradiation. The improvement of photoabsorption together with photocatalytic activities might be suspected due to the p-n heterojunction structure in Ag2O/ZnO nanocomposites. The corresponding mechanism will be discussed in detail.

The O{sub 2} A-Band in the Fluxes and Polarization of Starlight Reflected by Earth-Like Exoplanets

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

Fauchez, Thomas; Rossi, Loic; Stam, Daphne M.

Earth-like, potentially habitable exoplanets are prime targets in the search for extraterrestrial life. Information about their atmospheres and surfaces can be derived by analyzing the light of the parent star reflected by the planet. We investigate the influence of the surface albedo A {sub s}, the optical thickness b {sub cloud}, the altitude of water clouds, and the mixing ratio of biosignature O{sub 2} on the strength of the O{sub 2} A-band (around 760 nm) in the flux and polarization spectra of starlight reflected by Earth-like exoplanets. Our computations for horizontally homogeneous planets show that small mixing ratios ( ηmore » < 0.4) will yield moderately deep bands in flux and moderate-to-small band strengths in polarization, and that clouds will usually decrease the band depth in flux and the band strength in polarization. However, cloud influence will be strongly dependent on properties such as optical thickness, top altitude, particle phase, coverage fraction, and horizontal distribution. Depending on the surface albedo and cloud properties, different O{sub 2} mixing ratios η can give similar absorption-band depths in flux and band strengths in polarization, especially if the clouds have moderate-to-high optical thicknesses. Measuring both the flux and the polarization is essential to reduce the degeneracies, although it will not solve them, especially not for horizontally inhomogeneous planets. Observations at a wide range of phase angles and with a high temporal resolution could help to derive cloud properties and, once those are known, the mixing ratio of O{sub 2} or any other absorbing gas.« less

CSF/serum albumin ratio in dementias: a cross-sectional study on 1861 patients.

PubMed

Skillbäck, Tobias; Delsing, Louise; Synnergren, Jane; Mattsson, Niklas; Janelidze, Shorena; Nägga, Katarina; Kilander, Lena; Hicks, Ryan; Wimo, Anders; Winblad, Bengt; Hansson, Oskar; Blennow, Kaj; Eriksdotter, Maria; Zetterberg, Henrik

2017-11-01

A connection between dementias and blood-brain barrier (BBB) dysfunction has been suggested, but previous studies have yielded conflicting results. We examined cerebrospinal fluid (CSF)/serum albumin ratio in a large cohort of patients diagnosed with Alzheimer's disease (AD, early onset [EAD, n = 130], late onset AD [LAD, n = 666]), vascular dementia (VaD, n = 255), mixed AD and VaD (MIX, n = 362), Lewy body dementia (DLB, n = 50), frontotemporal dementia (FTD, n = 56), Parkinson's disease dementia (PDD, n = 23), other dementias (other, n = 48), and dementia not otherwise specified (NOS, n = 271). We compared CSF/serum albumin ratio to 2 healthy control groups (n = 292, n = 20), between dementia diagnoses, and tested biomarker associations. Patients in DLB, LAD, VaD, MIX, other, and NOS groups had higher CSF/serum albumin ratio than controls. CSF/serum albumin ratio correlated with CSF neurofilament light in LAD, MIX, VaD, and other groups but not with AD biomarkers. Our data show that BBB leakage is common in dementias. The lack of association between CSF/serum albumin ratio and AD biomarkers suggests that BBB dysfunction is not inherent to AD but might represent concomitant cerebrovascular pathology. Copyright © 2017 Elsevier Inc. All rights reserved.

Effect of preparation methods on the activity of titanium dioxide-carbon nitride composites for photocatalytic degradation of salicylic acid

NASA Astrophysics Data System (ADS)

Yuliati, L.; Salleh, A. M.; Hatta, M. H. M.; Lintang, H. O.

2018-04-01

In this study, titanium dioxide-carbon nitride (TiO2-CN) composites were prepared by three methods, which were one pot oxidation, impregnation, and physical mixing. Each series of the photocatalysts was prepared with different ratios of titanium to carbon (Ti/C), i.e., 1, 5, 10, 20, and 50 mol%. All samples were characterized by X-ray diffraction (XRD) and diffuse reflectance ultraviolet-visible (DR UV-Vis) spectroscopies. The characterization results confirmed the successful preparation of TiO2, CN, and the TiO2-CN composites. Photocatalytic activity tests were carried out for degradation of salicylic acid at room temperature for 6 h under UV and visible light irradiations. It was confirmed that all the prepared TiO2-CN composites showed better photocatalytic activities than the bare TiO2 and the bare CN. Under UV light irradiation, 90.6% of salicylic acid degradation was achieved on the best composite prepared by one pot oxidation with 5 mol% of titanium to carbon (Ti/C) ratio. On the other hand, the highest degradation under visible light irradiation was 94.3%, observed on the composite that was prepared also by one pot oxidation method with the Ti/C ratio of 10 mol%. Therefore, among the investigated methods, the best method to prepare the titanium dioxide-carbon nitride composites with high photocatalytic activity was one pot oxidation method.

Self-assembly of novel manganese (II) compounds based on bifunctional-group ligands: Synthesis, structures, and magnetic properties

NASA Astrophysics Data System (ADS)

Yan, Juan-zhi; Lu, Li-ping; Zhu, Miao-li; Feng, Si-si

2018-06-01

Four manganese (II) compounds are obtained by the reaction of manganese salts, triazole-derivatives and auxiliary reagents in aqueous solution or mix-solvents by routine or hydrothermal reactions. X-ray crystal structure analyses reveal that a neutral 0D compound [Mn(Hmctrz)2(H2O)2] (1) (H2mctrz = 1H-1,2,4-triazole-3-carboxylic acid) displays a centro-symmetric mononuclear octahedral entity with two Hmctrz- anions and two water molecules; two neutral 2D clusters [Mn(Hdctrz)(H2O)2]n (2) (H3dctrz = 1H-1,2,4-triazole-3,5-dicarboxylic acid) and [Mn2(pbtrz)(btca)]n·4nH2O (3) (pbtrz = 1,3-bis(1,2,4-triazol-1-yl)-propane&H4btca = benzene-1,2,4,5-tetracarboxylic acid) possess layer structures with Hdctrz2- linkers (2) and Mn(II)-pbtrz-Mn(II) building blocks periodically extended by μ-btca4- connectors (3); [Mn(pbtrz)]n·nOAc·nOH (4) shows a 3D diamond-shaped cationic framework with the anion void volume of 49.2%. Nitrogenous bases are used as the auxiliary ligand in compound 3 and the temple ligand in compounds 1, 2, and 4. Compounds 1-4 show antiferromagnetic coupling that has been fitted by different models with the molecular field approximate with D = - 0.129(1) cm-1 for 1, J = - 0.354(4) cm-1 for 2 and J = - 0.696(6) cm-1 for 3, respectively. The magnetic differences can be related to different superexchange interactions transmitted by the crystal lattice and/or the zero field splitting (ZFS) of the 6A1g single-ion states of 1 and the syn-anti-COO- of 2 as well as the mixed magnetic bridges of μ1-O and μ-pbtrz-μ-COO- of 3.

Study of the Solvent Extraction of V(V) from Nitrate Medium by Tri- n-Octylamine Dissolved in Kerosene

NASA Astrophysics Data System (ADS)

Biswas, Ranjit Kumar; Karmakar, Aneek Krishna; Mottakin, Mohammad

2017-10-01

The liquid-liquid extraction of V(V) from a nitrate medium by tri- n-Octylamine [( n-C8H17)3N; abbreviated as TOA] dissolved in distilled colorless kerosene has been investigated as a function of various experimental parameters. The equilibration time is less than 10 min. It is observed that the extraction ratio increases with increasing [V(V)] in the aqueous phase, which is possibly a result of the formation of V10O26(OH) 2 4- (via reaction: 10 VO2 + + 8 H2O → V10O26(OH) 2 4- + 14 H+) with increasing concentration in the aqueous phase. The nature of the species extracted into the organic phase depends on the existing aqueous species prevailing at a certain pH. At lower pH values, the extraction of VO2 + occurs via cation (H+) exchange of (C8H17)3NHNO3. On the other hand, at higher pH values, anionic V(V) species such as V10O26(OH) 2 4- , V10O27(OH)5-, V10O28 6- etc. are extracted by solvated ion-pair formation mechanism. The TOA concentration dependence varies from 2 at a lower pH region ( 2.3) to 1 at a higher pH region ( 5.7). The extraction is also found to be favored by a rise of nitrate concentration in the aqueous phase. Temperature has a pronounced effect with Δ H < -58 kJ/mol. Kerosene is demonstrated as the best diluent for this system. Increased organic to aqueous phase volume ratio (O/A) enhances extraction ratio. The extracted species can be stripped by 0.75 mol/L NH4OH solution to the extent of 72% in a single stage. But stage-wise stripping is not so effective. It is observed a very high loading, of the order of 2.3 mol V(V) per mol TOA.

A bifunctional luminescent Tb(III)-metal-organic framework by a tetracarboxylate ligand for highly selective detection of Fe3+ cation and Cr2O72- anion

NASA Astrophysics Data System (ADS)

Yu, Li; Wang, Chao; Hu, Chang-Jiang; Dong, Wen-Wen; Wu, Ya-Pan; Li, Dong-Sheng; Zhao, Jun

2018-06-01

Reaction of Tb3+ ions with p-terphenyl-3,3″,5,5″-tetracarboxylic acid (H4ptptc) in a mixed solvent system has afforded a new metal-organic framework formulated as [Tb2(ptptc)1.5(H2O)2]n (1). Compound 1 displays a 3D (5,6,8)-connected framework with fascinating one-dimensional triangle open channels. The luminescence explorations demonstrated that 1 exhibits highly selective and sensitive response to Fe3+ in DMF solution and biological system through luminescence quenching effects. In addition, 1 also shows high detection for the Cr2O72-, making it a promising dual functional materials for detecting Fe3+ cation and Cr2O72- anion with high sensitivity and selectivity.

An ion-neutral model to investigate chemical ionization mass spectrometry analysis of atmospheric molecules - application to a mixed reagent ion system for hydroperoxides and organic acids

NASA Astrophysics Data System (ADS)

Heikes, Brian G.; Treadaway, Victoria; McNeill, Ashley S.; Silwal, Indira K. C.; O'Sullivan, Daniel W.

2018-04-01

An ion-neutral chemical kinetic model is described and used to simulate the negative ion chemistry occurring within a mixed-reagent ion chemical ionization mass spectrometer (CIMS). The model objective was the establishment of a theoretical basis to understand ambient pressure (variable sample flow and reagent ion carrier gas flow rates), water vapor, ozone and oxides of nitrogen effects on ion cluster sensitivities for hydrogen peroxide (H2O2), methyl peroxide (CH3OOH), formic acid (HFo) and acetic acid (HAc). The model development started with established atmospheric ion chemistry mechanisms, thermodynamic data and reaction rate coefficients. The chemical mechanism was augmented with additional reactions and their reaction rate coefficients specific to the analytes. Some existing reaction rate coefficients were modified to enable the model to match laboratory and field campaign determinations of ion cluster sensitivities as functions of CIMS sample flow rate and ambient humidity. Relative trends in predicted and observed sensitivities are compared as instrument specific factors preclude a direct calculation of instrument sensitivity as a function of sample pressure and humidity. Predicted sensitivity trends and experimental sensitivity trends suggested the model captured the reagent ion and cluster chemistry and reproduced trends in ion cluster sensitivity with sample flow and humidity observed with a CIMS instrument developed for atmospheric peroxide measurements (PCIMSs). The model was further used to investigate the potential for isobaric compounds as interferences in the measurement of the above species. For ambient O3 mixing ratios more than 50 times those of H2O2, O3-(H2O) was predicted to be a significant isobaric interference to the measurement of H2O2 using O2-(H2O2) at m/z 66. O3 and NO give rise to species and cluster ions, CO3-(H2O) and NO3-(H2O), respectively, which interfere in the measurement of CH3OOH using O2-(CH3OOH) at m/z 80. The CO3-(H2O) interference assumed one of its O atoms was 18O and present in the cluster in proportion to its natural abundance. The model results indicated monitoring water vapor mixing ratio, m/z 78 for CO3-(H2O) and m/z 98 for isotopic CO3-(H2O)2 can be used to determine when CO3-(H2O) interference is significant. Similarly, monitoring water vapor mixing ratio, m/z 62 for NO3- and m/z 98 for NO3-(H2O)2 can be used to determine when NO3-(H2O) interference is significant.

Band Alignment-Driven Oxidative Injury to the Skin by Anatase/Rutile Mixed-Phase Titanium Dioxide Nanoparticles under Sunlight Exposure.

PubMed

Sun, Xiujuan; Chang, Yun; Cheng, Yan; Feng, Yanlin; Zhang, Haiyuan

2018-04-12

Anatase/rutile mixed-phase titanium dioxide (TiO2) nanoparticles (NPs) have been found in cosmetics and cotton textiles. Once exposed to sunlight, mixed-phase TiO2 NPs are even more toxic to cells than pure phase NPs, however, the underlying mechanism remains unclear. Considering the unique anatase/rutile heterojunction structure existing in mixed-phase NPs, the potent toxicity of mixed-phase TiO2 NPs probably originates from the high reactive oxygen species (ROS) production because the anatase/rutile heterojunction is constituted by the staggered energy bands that facilitate the electron-hole separation at the interface due to the band alignment. In the present study, a library of mixed-phase TiO2 NPs with different anatase/rutile ratios was established to investigate the potential property-activity relationship and further clarify the underlying molecular mechanism. Under sunlight exposure, these mixed-phase TiO2 NPs could produce significant abiotic ROS and induce hierarchical oxidative stress to HaCaT skin cells and mice skin. The ROS magnitude and toxicity potential of these NPs were found to be proportional to their energy band bending (BB) levels. This means that the toxicity of mixed-phase TiO2 NPs can be correlated to their heterojunction density, and the toxicity potential of mixed-phase TiO2 NPs can be weighed by their BB levels.