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Sample records for additional hono sources

  1. Effects of additional HONO sources on visibility over the North China Plain

    NASA Astrophysics Data System (ADS)

    Li, Ying; An, Junling; Gultepe, Ismail

    2014-09-01

    The objective of the present study was to better understand the impacts of the additional sources of nitrous acid (HONO) on visibility, which is an aspect not considered in current air quality models. Simulations of HONO contributions to visibility over the North China Plain (NCP) during August 2007 using the fully coupled Weather Research and Forecasting/Chemistry (WRF/Chem) model were performed, including three additional HONO sources: (1) the reaction of photo-excited nitrogen dioxide (NO * 2) with water vapor; (2) the NO2 heterogeneous reaction on aerosol surfaces; and (3) HONO emissions. The model generally reproduced the spatial patterns and diurnal variations of visibility over the NCP well. When the additional HONO sources were included in the simulations, the visibility was occasionally decreased by 20%-30% (3-4 km) in local urban areas of the NCP. Monthly-mean concentrations of NO{3/-}, NH{4/+}, SO{4/2-} and PM2.5 were increased by 20%-52% (3-11 μg m-3), 10%-38%, 6%-10%, and 6%-11% (9-17 μg m-3), respectively; and in urban areas, monthly-mean accumulationmode number concentrations (AMNC) and surface concentrations of aerosols were enhanced by 15%-20% and 10%-20%, respectively. Overall, the results suggest that increases in concentrations of PM2.5, its hydrophilic components, and AMNC, are key factors for visibility degradation. A proposed conceptual model for the impacts of additional HONO sources on visibility also suggests that visibility estimation should consider the heterogeneous reaction on aerosol surfaces and the enhanced atmospheric oxidation capacity due to additional HONO sources, especially in areas with high mass concentrations of NO x and aerosols.

  2. Impacts of Additional HONO Sources on Concentrations and Deposition of NOy in the Beijing-Tianjin-Hebei Region of China

    NASA Astrophysics Data System (ADS)

    Li, Ying; An, Junling; Kajino, Mizuo; Li, Jian; Qu, Yu

    2015-04-01

    Reactive nitrogen-containing compounds (NOy) are involved in many important chemical processes in the atmosphere, including aerosol formation as well as ozone (O3) production and destruction. As NOy deposition was increasing rapidly in China during 1980s ~ 2000s, great effort is urgently needed to reduce N deposition. HONO, an important component of NOy, is a significant precursor of the hydroxyl radical (OH) that drives the formation of O3 and fine particles (PM2.5). Nevertheless, the detailed formation mechanisms of HONO and strength of its sources remain unclear. Unknown HONO sources and their potential impacts on air quality have gained extensive interests but to our current knowledge, the impact of HONO sources on regional-scale deposition of NOy has not been quantified up to date. The goal of this work is to evaluate the effects of the additional HONO sources on concentrations and deposition of individual NOy species as well as the NOy budget in the northern Chinese regions being affected by heavy pollution. Simulations of HONO contributions over Beijing-Tianjin-Hebei region (BTH) during summer and winter periods of 2007 using the fully coupled Weather Research and Forecasting /Chemistry (WRF/Chem) model are performed by including three additional HONO sources: 1) the reaction of photo-excited nitrogen dioxide (NO2*) with water vapor, 2) NO2 heterogeneous reaction at the aerosol surfaces, and 3) HONO emissions. The model results show that the three additional HONO sources produce a 20%~40% (> 100%) increase in monthly-mean OH concentrations in many urban areas in August (February), leading to a 10%~40% (10%~100%) variation in monthly-mean concentrations of NOx, nitrate and PAN, a 5%~10% (10%~40%) increase in the total dry deposition of NOy, and an enhancement of 1.4 Gg N (1.5 Gg N) in the total of dry and wet deposition of NOy over this region in August (February). These results suggest that the additional HONO sources aggravate regional-scale acid deposition

  3. Parameterization of HONO sources in Mega-Cities

    NASA Astrophysics Data System (ADS)

    Li, G.; Zhang, R.; Tie, X.; Molina, L. T.

    2013-05-01

    Nitrous acid (HONO) plays an important role in the photochemistry of the troposphere because the photolysis of HONO is a primary source of the hydroxyl radical (OH) in the early morning. However, the formation or sources of HONO are still poorly understood in the troposphere and thence the representation of the HONO sources in chemical transport models (CTMs) is lack of comprehensive consideration. In the present study, the observed HONO, NOx, and aerosols at an urban supersite T0 during the MCMA-2006 field campaign in Mexico City are used to interpret the HONO formation in association with the suggested HONO sources from literature. The HONO source parameterizations are proposed and incorporated into the WRF-CHEM model. Homogeneous sources of HONO include the reaction of NO with OH and excited NO2 with H2O. Four HONO heterogeneous sources are considered: NO2 reaction with semivolatile organics, NO2 reaction with freshly emitted soot, NO2 reaction on aerosol and ground surfaces. Four cases are used in the present study to evaluate the proposed HONO parameterizations during four field campaigns in which HONO measurements are available, including MCMA-2003 and MCMA-2006 (Mexico City Metropolitan Area, Mexico), MIRAGE-2009 (Shanghai, China), and SHARP (Houston, USA). The WRF-CHEM model with the proposed HONO parameterizations performs moderately well in reproducing the observed diurnal variation of HONO concentrations, showing that the HONO parameterizations in the study are reasonable and potentially useful in improving the HONO simulation in CTMs.

  4. Parameterization of HONO sources in Mega-Cities

    NASA Astrophysics Data System (ADS)

    Li, Guohui; Zhang, Renyi; Tie, Xuxie; Molina, Luisa

    2013-04-01

    Nitrous acid (HONO) plays an important role in the photochemistry of the troposphere because the photolysis of HONO is a primary source of the hydroxyl radical (OH) in the early morning. However, the formation or sources of HONO are still poorly understood in the troposphere; hence the representation of the HONO sources in chemical transport models (CTMs) has lack comprehensive consideration. In the present study, the observed HONO, NOx, and aerosols at an urban supersite T0 during the MCMA-2006 field campaign in Mexico City are used to interpret the HONO formation in association with the suggested HONO sources from literature. The HONO source parameterizations are proposed and incorporated into the WRF-CHEM model. Homogeneous sources of HONO include the reaction of NO with OH and excited NO2 with H2O. Four HONO heterogeneous sources are considered: NO2 reaction with semivolatile organics, NO2 reaction with freshly emitted soot, NO2 reaction on aerosol and ground surfaces. Four cases are used in the present study to evaluate the proposed HONO parameterizations during four field campaigns in which HONO measurements are available, including MCMA-2003 and MCMA-2006 (Mexico City Metropolitan Area, Mexico), MIRAGE-2009 (Shanghai, China), and SHARP (Houston, USA). The WRF-CHEM model with the proposed HONO parameterizations performs moderately well in reproducing the observed diurnal variation of HONO concentrations, showing that the HONO parameterizations in the study are reasonable and potentially useful in improving the HONO simulation in CTMs.

  5. Missing gas-phase source of HONO inferred from Zeppelin measurements in the troposphere

    NASA Astrophysics Data System (ADS)

    Li, Xin; Rohrer, Franz; Hofzumahaus, Andreas; Brauers, Theo; Häseler, Rolf; Bohn, Birger; Broch, Sebastian; Fuchs, Hendrik; Gomm, Sebastian; Holland, Frank; Jäger, Julia; Kaiser, Jennifer; Keutsch, Frank N.; Lohse, Insa; Tillmann, Ralf; Wegener, Robert; Wolfe, Glenn M.; Mentel, Thomas F.; Kiendler-Scharr, Astrid; Wahner, Andreas

    2014-05-01

    Nitrous acid (HONO) is an important trace gas in the atmosphere due to its contribution to the cycles of nitrogen oxides (NOX) and hydrogen oxides (HOX). In the past decades, ground-based observations of HONO around the world showed much higher daytime concentrations than can be explained by the known gas-phase chemistry (i.e., HONO + hν → OH + NO, HONO + OH → NO2 + H2O, OH + NO + M → HONO + M). Different light-dependent reactions on ground surfaces have been proposed as additional daytime HONO sources. However, due to lack of measurements, little is known about the concentrations of HONO and its sources in the planetary boundary layer (PBL) at higher altitudes above the earth's surface. The airship Zeppelin NT is an ideal platform to investigate the chemistry and dynamics of the PBL. During the PEGASOS field campaigns in 2012 and 2013, HONO and its gas-phase sources and sinks were measured simultaneously on-board the airship Zeppelin NT, for the lowest 1 km of the PBL. In the upper part of the altitude range during morning hours, when the airmass is still isolated from processes at the earth's surface by the remaining nocturnal boundary layer, we find unexpectedly large concentrations of HONO which can neither be explained by heterogeneous reactions on aerosol and ground surfaces, nor by known gas-phase reactions. Our observations show evidence for an unknown gas-phase light-dependent HONO production which dominates the overall HONO formation in the lower troposphere. This new HONO source requires NOX and possibly OH or HO2 radicals. As a result, the general impact of HONO on the OH formation is likely overestimated.

  6. Impact of HONO sources on the performance of mesoscale air quality models

    NASA Astrophysics Data System (ADS)

    Gonçalves, M.; Dabdub, D.; Chang, W. L.; Jorba, O.; Baldasano, J. M.

    2012-07-01

    Nitrous acid (HONO) photolysis constitutes a primary source of OH in the early morning, which leads to changes in model gas-phase and particulate matter concentrations. However, state-of-the-art models of chemical mechanisms share a common representation of gas-phase chemistry leading to HONO that fails in reproducing the observed profiles. Hence, there is a growing interest in improving the definition of additional HONO sources within air quality models, i.e. direct emissions or heterogeneous reactions. In order to test their feasibility under atmospheric conditions, the WRF-ARW/HERMES/CMAQ modeling system is applied with high horizontal resolution (4 × 4 km2) to Spain for November 24-27, 2008. HONO modeled sources include: (1) direct emissions from on-road transport; NO2 hydrolysis on aerosol and ground surfaces, the latter with (2) kinetics depending exclusively on available surfaces for reaction and (3) refined kinetics considering also relative humidity dependence; and (4) photoenhanced NO2 reduction on ground surfaces. The DOMINO measurement campaign performed in El Arenosillo (Southern Spain) provides valuable HONO observations. Modeled HONO results are consistently below observations, even when the most effective scenario is assessed, corresponding to contributions of direct emissions and NO2 hydrolysis with the simplest kinetics parameterization. With the additional sources of HONO, PM2.5 predictions can be up to 14% larger in urban areas. Quantified impacts on secondary pollutants have to be taken as a low threshold, due to the proven underestimation of HONO levels. It is fundamental to improve HONO sources definition within air quality models, both for the scientific community and decision makers.

  7. Laboratory studies of sources of HONO in polluted urban atmospheres

    NASA Astrophysics Data System (ADS)

    Saliba, Najat A.; Mochida, Michihiro; Finlayson-Pitts, Barbara. J.

    2000-10-01

    Laboratory studies reported here and in previous work show that the reaction of NO(g) with surface adsorbed HNO3 may be a significant source of HONO in polluted urban atmospheres. If these laboratory studies can be extrapolated to ambient conditions, this heterogeneous reaction may generate HONO to about the same extent as the hydrolysis of NO2 on surfaces, which is greater than the heterogeneous reaction of NO, NO2 and water. It may also be involved in generating HONO in snowpacks, and important in reconciling the discrepancy between measured and modeled HNO3/NOx ratios in the troposphere.

  8. Near surface profiles of HONO: The vegetated surface as source and sink

    NASA Astrophysics Data System (ADS)

    Sörgel, M.; Held, A.

    2012-04-01

    The photolysis of HONO is an important primary OH radical source. The OH radical is the most important oxidizing agent, the so called "detergent" of the atmosphere. HONO formation pathways are still unclear (e.g. Sörgel et al., 2011). Nevertheless, the main pathways are believed to be heterogeneous. Thus, the surface is proposed to be a major source. Furthermore, soil emissions of HONO due to microbiological activity in soil (Su et al., 2011) have been proposed. Therefore, we measured gradients of HONO, NO, NO2 and O3 close to the surface (0.1 to 1.6 m above ground). We used an automated, programmable moving inlet to measure at 3 or 5 heights between 0.1 m and 1.6 m above the ground. HONO, O3, NO and NO2 were measured simultaneously. HONO was measured with a long path absorption photometer (LOPAP), O3 by UV absorption and NO and NO2 by chemiluminescence with photolytic conversion of NO2. The time resolution of an individual LOPAP measurement was 3 min, and a full profile was measured within 30 min. Additionally, profiles of temperature and relative humidity as well as leaf wetness and j(NO2) were measured. Measurements were conducted above a clearing at the Waldstein field site of the University of Bayreuth in the Fichtelgebirge Mountains in south-east Germany. Preliminary results are presented. For example, during the day the highest values were often measured close to the ground, indicating emission of HONO at the surface. This also indicates that the daytime formation of HONO is heterogeneous or the emissions are due to microbiological activity (Su et al., 2011). During the night, the lowest values were often measured at the surface indicating deposition. Thus, HONO emissions as well as HONO deposition have been observed. The profile data will be analyzed with respect to light intensity, NO2 availability, atmospheric stability and surface wetness in order to elucidate the driving forces behind emission and deposition, respectively. Sörgel, M; Regelin, E; Bozem

  9. Impacts of an unknown daytime HONO source on the mixing ratio and budget of HONO, and hydroxyl, hydroperoxyl, and organic peroxy radicals, in the coastal regions of China

    NASA Astrophysics Data System (ADS)

    Tang, Y.; An, J.; Wang, F.; Li, Y.; Qu, Y.; Chen, Y.; Lin, J.

    2015-08-01

    Many field experiments have found high nitrous acid (HONO) mixing ratios in both urban and rural areas during daytime, but these high daytime HONO mixing ratios cannot be explained well by gas-phase production, HONO emissions, and nighttime hydrolysis conversion of nitrogen dioxide (NO2) on aerosols, suggesting that an unknown daytime HONO source (Punknown) could exist. The formula Punknown ≈ 19.60[NO2] · J(NO2) was obtained using observed data from 13 field experiments across the globe. The three additional HONO sources (i.e., the Punknown, nighttime hydrolysis conversion of NO2 on aerosols, and HONO emissions) were coupled into the WRF-Chem model (Weather Research and Forecasting model coupled with Chemistry) to assess the Punknown impacts on the concentrations and budgets of HONO and peroxy (hydroxyl, hydroperoxyl, and organic peroxy) radicals (ROx) (= OH + HO2 + RO2) in the coastal regions of China. Results indicated that the additional HONO sources produced a significant improvement in HONO and OH simulations, particularly in the daytime. High daytime average Punknown values were found in the coastal regions of China, with a maximum of 2.5 ppb h-1 in the Beijing-Tianjin-Hebei region. The Punknown produced a 60-250 % increase of OH, HO2, and RO2 near the ground in the major cities of the coastal regions of China, and a 5-48 % increase of OH, HO2, and RO2 in the daytime meridional-mean mixing ratios within 1000 m above the ground. When the three additional HONO sources were included, the photolysis of HONO was the second most important source in the OH production rate in Beijing, Shanghai, and Guangzhou before 10:00 LST with a maximum of 3.72 ppb h-1 and a corresponding Punknown contribution of 3.06 ppb h-1 in Beijing, whereas the reaction of HO2 + NO (nitric oxide) was dominant after 10:00 LST with a maximum of 9.38 ppb h-1 and a corresponding Punknown contribution of 7.23 ppb h-1 in Beijing. The whole ROx cycle was accelerated by the three additional HONO

  10. Detailed budget analysis of HONO in central London reveals a missing daytime source

    NASA Astrophysics Data System (ADS)

    Lee, J. D.; Whalley, L. K.; Heard, D. E.; Stone, D.; Dunmore, R. E.; Hamilton, J. F.; Young, D. E.; Allan, J. D.; Laufs, S.; Kleffmann, J.

    2016-03-01

    Measurements of HONO were carried out at an urban background site near central London as part of the Clean air for London (ClearfLo) project in summer 2012. Data were collected from 22 July to 18 August 2014, with peak values of up to 1.8 ppbV at night and non-zero values of between 0.2 and 0.6 ppbV seen during the day. A wide range of other gas phase, aerosol, radiation, and meteorological measurements were made concurrently at the same site, allowing a detailed analysis of the chemistry to be carried out. The peak HONO/NOx ratio of 0.04 is seen at ˜ 02:00 UTC, with the presence of a second, daytime, peak in HONO/NOx of similar magnitude to the night-time peak, suggesting a significant secondary daytime HONO source. A photostationary state calculation of HONO involving formation from the reaction of OH and NO and loss from photolysis, reaction with OH, and dry deposition shows a significant underestimation during the day, with calculated values being close to 0, compared to the measurement average of 0.4 ppbV at midday. The addition of further HONO sources from the literature, including dark conversion of NO2 on surfaces, direct emission, photolysis of ortho-substituted nitrophenols, the postulated formation from the reaction of HO2 × H2O with NO2, photolysis of adsorbed HNO3 on ground and aerosols, and HONO produced by photosensitized conversion of NO2 on the surface increases the daytime modelled HONO to 0.1 ppbV, still leaving a significant missing daytime source. The missing HONO is plotted against a series of parameters including NO2 and OH reactivity (used as a proxy for organic material), with little correlation seen. Much better correlation is observed with the product of these species with j(NO2), in particular NO2 and the product of NO2 with OH reactivity. This suggests the missing HONO source is in some way related to NO2 and also requires sunlight. Increasing the photosensitized surface conversion rate of NO2 by a factor of 10 to a mean daytime first

  11. Nitrous acid (HONO) during polar spring in Barrow, Alaska: A net source of OH radicals?

    NASA Astrophysics Data System (ADS)

    Villena, G.; Wiesen, P.; Cantrell, C. A.; Flocke, F.; Fried, A.; Hall, S. R.; Hornbrook, R. S.; Knapp, D.; Kosciuch, E.; Mauldin, R. L., III; McGrath, J. A.; Montzka, D.; Richter, D.; Ullmann, K.; Walega, J.; Weibring, P.; Weinheimer, A.; Staebler, R. M.; Liao, J.; Huey, L. G.; Kleffmann, J.

    2011-07-01

    HONO was measured by a LOPAP instrument (LOng Path Absorption Photometer) for one month during the OASIS spring 2009 campaign in Barrow, Alaska. HONO concentrations between ≤ 0.4 pptv (DL) and ˜500 pptv were measured. The very high concentrations observed on several days were caused by local direct emissions and were highly correlated with the NOx and CO data. When only "clean days" were considered, average HONO concentrations varied between ≤ 0.4 - 10 pptv. Average HONO/NOx and HONO/NOy ratios of ˜6% and ˜1% were observed, respectively, in good agreement with other remote LOPAP measurement data, but lower than measured in most other polar regions by other methods. The strong correlation between sharp peaks of OH and HONO during daytime, which was not observed for any other measured radical precursor, suggested that HONO photolysis was a major source of OH radicals in Barrow. This was supported by calculated net OH radical production by HONO and O3 photolysis for which the contribution of O3 (2%) could be neglected compared to that of HONO (98%). A net extra HONO/OH source necessary to explain elevated HONO levels during daytime of up to 90 pptv/h was determined, which was highly correlated with the actinic flux. Accordingly, a photochemical HONO source is proposed here, in good agreement with recent studies. From the higher correlation of the net HONO source with ? and [NO2] compared to ? and [NO3-], photosensitized conversion of NO2 on humic acid containing snow surfaces may be a more likely source of HONO in the polar atmosphere of Barrow than nitrate photolysis.

  12. Missing gas-phase source of HONO inferred from Zeppelin measurements in the troposphere.

    PubMed

    Li, Xin; Rohrer, Franz; Hofzumahaus, Andreas; Brauers, Theo; Häseler, Rolf; Bohn, Birger; Broch, Sebastian; Fuchs, Hendrik; Gomm, Sebastian; Holland, Frank; Jäger, Julia; Kaiser, Jennifer; Keutsch, Frank N; Lohse, Insa; Lu, Keding; Tillmann, Ralf; Wegener, Robert; Wolfe, Glenn M; Mentel, Thomas F; Kiendler-Scharr, Astrid; Wahner, Andreas

    2014-04-18

    Gaseous nitrous acid (HONO) is an important precursor of tropospheric hydroxyl radicals (OH). OH is responsible for atmospheric self-cleansing and controls the concentrations of greenhouse gases like methane and ozone. Due to lack of measurements, vertical distributions of HONO and its sources in the troposphere remain unclear. Here, we present a set of observations of HONO and its budget made onboard a Zeppelin airship. In a sunlit layer separated from Earth's surface processes by temperature inversion, we found high HONO concentrations providing evidence for a strong gas-phase source of HONO consuming nitrogen oxides and potentially hydrogen oxide radicals. The observed properties of this production process suggest that the generally assumed impact of HONO on the abundance of OH in the troposphere is substantially overestimated. PMID:24744373

  13. Large mixing ratios of atmospheric nitrous acid (HONO) at Concordia (East Antarctic Plateau) in summer: a strong source from surface snow?

    NASA Astrophysics Data System (ADS)

    Legrand, M.; Preunkert, S.; Frey, M.; Bartels-Rausch, Th.; Kukui, A.; King, M. D.; Savarino, J.; Kerbrat, M.; Jourdain, B.

    2014-09-01

    During the austral summer 2011/2012 atmospheric nitrous acid (HONO) was investigated for the second time at the Concordia site (75°06' S, 123°33' E), located on the East Antarctic Plateau, by deploying a long-path absorption photometer (LOPAP). Hourly mixing ratios of HONO measured in December 2011/January 2012 (35 ± 5.0 pptv) were similar to those measured in December 2010/January 2011 (30.4 ± 3.5 pptv). The large value of the HONO mixing ratio at the remote Concordia site suggests a local source of HONO in addition to weak production from oxidation of NO by the OH radical. Laboratory experiments demonstrate that surface snow removed from Concordia can produce gas-phase HONO at mixing ratios half that of the NOx mixing ratio produced in the same experiment at typical temperatures encountered at Concordia in summer. Using these lab data and the emission flux of NOx from snow estimated from the vertical gradient of atmospheric concentrations measured during the campaign, a mean diurnal HONO snow emission ranging between 0.5 and 0.8 × 109 molecules cm-2 s-1 is calculated. Model calculations indicate that, in addition to around 1.2 pptv of HONO produced by the NO oxidation, these HONO snow emissions can only explain 6.5 to 10.5 pptv of HONO in the atmosphere at Concordia. To explain the difference between observed and simulated HONO mixing ratios, tests were done both in the field and at lab to explore the possibility that the presence of HNO4 had biased the measurements of HONO.

  14. Soil Nitrite as a Source of Atmospheric HONO and OH Radicals

    NASA Astrophysics Data System (ADS)

    Su, H.; Cheng, Y. F.; Oswald, R.; Behrendt, T.; Trebs, I.; Meixner, F. X.; Andreae, M. O.; Cheng, P.; Zhang, Y. H.; Pöschl, U.

    2012-04-01

    Hydroxyl radicals (OH) are a key species in atmospheric photochemistry. In the lower atmosphere, up to ~30% of the primary OH radical production is attributed to the photolysis of nitrous acid (HONO), and field observations suggest a large missing source of HONO. Photoenhanced reactions of NO2 on various surfaces (e.g., soil surfaces) have been proposed to explain the observed missing source of HONO. We show that soil nitrite can release HONO and explain the reported strength and diurnal variation of the missing source. Fertilized soils with low pH appear to be particularly strong sources of HONO and OH. Because of enhanced fertilizer use and soil acidification in developing countries, the release of HONO from soil nitrite might strongly increase in the course of global change, resulting in elevated OH concentrations and amplified oxidizing capacity of the lower troposphere. Besides fertilization and intensified agricultural use of soils in populated environments, nitrite production and HONO release may also be important in natural environments, including forests and boreal soils, because of increasing N deposition, acid deposition, and the ubiquity of (de)nitrifying microbes. In view of the potentially large impact on atmospheric chemistry and global environmental change, we recommend further studies of HONO release from soil nitrite and related processes in the biogeochemical cycling of N in both agricultural and natural environments.

  15. Soil Nitrite as a Source of Atmospheric HONO and OH Radicals

    NASA Astrophysics Data System (ADS)

    Su, Hang; Cheng, Yafang; Oswald, Robert; Behrendt, Thomas; Trebs, Ivonne; Meixner, Franz X.; Andreae, Meinrat O.; Cheng, Peng; Zhang, Yuanhang; Pöschl, Ulrich

    2011-09-01

    Hydroxyl radicals (OH) are a key species in atmospheric photochemistry. In the lower atmosphere, up to ~30% of the primary OH radical production is attributed to the photolysis of nitrous acid (HONO), and field observations suggest a large missing source of HONO. We show that soil nitrite can release HONO and explain the reported strength and diurnal variation of the missing source. Fertilized soils with low pH appear to be particularly strong sources of HONO and OH. Thus, agricultural activities and land-use changes may strongly influence the oxidizing capacity of the atmosphere. Because of the widespread occurrence of nitrite-producing microbes, the release of HONO from soil may also be important in natural environments, including forests and boreal regions.

  16. Large mixing ratios of atmospheric nitrous acid (HONO) at Concordia (East Antarctic plateau) in summer: a strong source from surface snow?

    NASA Astrophysics Data System (ADS)

    Legrand, M.; Preunkert, S.; Frey, M.; Bartels-Rausch, T.; Kukui, A.; King, M. D.; Savarino, J.; Kerbrat, M.; Jourdain, B.

    2014-05-01

    During the austral summer 2011/2012 atmospheric nitrous acid was investigated for the second time at the Concordia site (75°06' S, 123°33' E) located on the East Antarctic plateau by deploying a long path absorption photometer (LOPAP). Hourly mixing ratios of HONO measured in December 2011/January 2012 (35 ± 5.0 pptv) were similar to those measured in December 2010/January 2011 (30.4 ± 3.5 pptv). The large value of the HONO mixing ratio at the remote Concordia site suggests a local source of HONO in addition to weak production from oxidation of NO by the OH radical. Laboratory experiments demonstrate that surface snow removed from Concordia can produce gas phase HONO at mixing ratios half that of NOx mixing ratio produced in the same experiment at typical temperatures encountered at Concordia in summer. Using these lab data and the emission flux of NOx from snow estimated from the vertical gradient of atmospheric concentrations measured during the campaign, a mean diurnal HONO snow emission ranging between 0.5 and 0.8 × 109 molecules cm-2 s-1 is calculated. Model calculations indicate that, in addition to around 1.2 pptv of HONO produced by the NO oxidation, these HONO snow emissions can only explain 6.5 to 10.5 pptv of HONO in the atmosphere at Concordia. To explain the difference between observed and simulated HONO mixing ratios, tests were done both in the field and at lab to explore the possibility that the presence of HNO4 had biased the measurements of HONO.

  17. Potential sources of nitrous acid (HONO) and their impacts on ozone: A WRF-Chem study in a polluted subtropical region

    NASA Astrophysics Data System (ADS)

    Zhang, Li; Wang, Tao; Zhang, Qiang; Zheng, Junyu; Xu, Zheng; Lv, Mengyao

    2016-04-01

    Current chemical transport models commonly undersimulate the atmospheric concentration of nitrous acid (HONO), which plays an important role in atmospheric chemistry, due to the lack or inappropriate representations of some sources in the models. In the present study, we parameterized up-to-date HONO sources into a state-of-the-art three-dimensional chemical transport model (Weather Research and Forecasting model coupled with Chemistry: WRF-Chem). These sources included (1) heterogeneous reactions on ground surfaces with the photoenhanced effect on HONO production, (2) photoenhanced reactions on aerosol surfaces, (3) direct vehicle and vessel emissions, (4) potential conversion of NO2 at the ocean surface, and (5) emissions from soil bacteria. The revised WRF-Chem was applied to explore the sources of the high HONO concentrations (0.45-2.71 ppb) observed at a suburban site located within complex land types (with artificial land covers, ocean, and forests) in Hong Kong. With the addition of these sources, the revised model substantially reproduced the observed HONO levels. The heterogeneous conversions of NO2 on ground surfaces dominated HONO sources contributing about 42% to the observed HONO mixing ratios, with emissions from soil bacterial contributing around 29%, followed by the oceanic source (~9%), photochemical formation via NO and OH (~6%), conversion on aerosol surfaces (~3%), and traffic emissions (~2%). The results suggest that HONO sources in suburban areas could be more complex and diverse than those in urban or rural areas and that the bacterial and/or ocean processes need to be considered in HONO production in forested and/or coastal areas. Sensitivity tests showed that the simulated HONO was sensitive to the uptake coefficient of NO2 on the surfaces. Incorporation of the aforementioned HONO sources significantly improved the simulations of ozone, resulting in increases of ground-level ozone concentrations by 6-12% over urban areas in Hong Kong and

  18. Photoenhanced Conversion of NO2 on Solid Organic Compounds: an Important Source of HONO

    NASA Astrophysics Data System (ADS)

    George, C.; Kleffmann, J.; Stemmler, K.; Ammann, M.

    2005-12-01

    The presence of nitrous acid (HONO) in the atmosphere was first detected more than two decades ago. Since then many studies have elucidated its important role as a major photochemical precursor of the hydroxyl radical- the key oxidant in the degradation of most air pollutants and a crucial intermediate in the formation of photochemical smog in the troposphere. However, the sources of HONO in the troposphere are still poorly understood, especially since recent atmospheric measurements revealed a strongly enhanced formation of HONO during daytime via an unknown mechanism. Here we show that reduction of NO2 on light-activated organics is a major source of gaseous HONO. Under atmospherically relevant conditions, this photosensitized formation of HONO is by magnitudes faster than the previously known disproportionation of NO2 on humid glass surfaces. This is the first example showing that solid surfaces containing traces of natural occurring organic matter have to be considered as photoreactive towards atmospheric oxidants and can explain the high daytime concentrations of HONO recently observed in the boundary layer, the photolysis of which accounts for up to 60% of the integrated OH radical source strengths. Thus this new photoinduced HONO source has a considerable impact on the oxidation capacity of the lower atmosphere.

  19. Contribution of airborne dust particles to HONO sources

    NASA Astrophysics Data System (ADS)

    Saliba, N. A.; Moussa, S. G.; El Tayyar, G.

    2014-02-01

    HONO is a major precursor for OH radicals in early mornings. Its formation has been mainly attributed to the heterogeneous hydrolysis of NO2 on surfaces such as soot, glass, mineral oxides and aerosol surfaces. In particular, dust events which are loaded with mineral oxide aerosols have been associated with higher HONO concentrations in the gas phase. In order to understand the mechanism of reactions related to this process, samples during dusty and non-dusty days were collected between October 2009 and April 2011. Based on HYSPLIT backward trajectories, data were divided between wind trajectories originating from Arabian or African deserts. In this study an increase of HONO levels was observed during dusty days. The increase in the acidic gas concentrations was accompanied by an increase in the PM nitrate and sulfate ion concentrations. During high relative humidity (African dusty days), it is proposed that the mechanism of NO2 hydrolysis predominates whereas during Arabian dusty days, where the air is relatively dry, a synergistic mechanism of adsorption and reaction between NO2 and SO2 on dust particles to produce HONO and sulfate in the particle phase is suggested. This study implies that the NOx reactivity on mineral oxide surfaces leads to a higher mixing level of OH. An increase in the sulfate forming capacity could account for the underestimation of sulfates in aerosols when the reactive uptake of SO2 alone is considered.

  20. Photoenhanced uptakes of NO2 by indoor surfaces: A new HONO source

    NASA Astrophysics Data System (ADS)

    Gligorovski, S.; Bartolomei, V.; Soergel, M.; Gomez Alvarez, E.; Zetzsch, C.; Wortham, H.

    2012-12-01

    Nitrous acid (HONO) is a known household pollutant that can lead to human respiratory tract irritation. HONO acts as the nitrosating agent, e.g. by the formation of the so-called third-hand smoke after wall reactions of HONO with nicotine (1). HONO can be generated indoors directly during combustion processes or indirectly via heterogeneous NO2 reactions with adsorbed water on diverse surfaces (2). Recently a new source was identified as another path of HONO formation in the troposphere (3). Namely, the light-induced heterogeneous reaction of NO2 with adsorbed organics (known as photosensitizers) on various surfaces such as roads, buildings, rocks or plants leads to enhanced HONO production. The detected values of HONO indoors vary in the range between 2 and 25 parts per billion (ppb). However, like outdoors, the processes leading to HONO formation indoors are not completely understood (4). Indoor photolysis radiation sources include exterior sunlight (λ>350 nm) that enters typically through the windows and indoor illumination sources, i.e., rare gas/mercury fluorescent light bulbs and tungsten and tungsten/halogen light bulbs among others. The present work is showing the importance of indoor sources of HONO recently identified or postulated. We have tested a number of common household chemical agents commonly used for cleaning purposes or coatings of domestic surfaces to better identify different indoor HONO sources. We used a heterogeneous flow tube technique to test the HONO production potentials of these household chemical agents under different experimental conditions, namely with and without light and at different relative humidity levels and different NO2 concentrations. We report uptake kinetics measurements of the heterogeneous reaction of gas phase NO2 with lacquer and paint coated on the walls of the reactor. The flow tube was irradiated with four near-ultraviolet (UV) emitting lamps (range of wavelengths 300-420nm). We observed that the heterogeneous

  1. Observation of HONO in Changzhou

    NASA Astrophysics Data System (ADS)

    Hou, Yanping; Chen, Jun; Lou, Shengrong

    2016-04-01

    Gaseous nitrous acid (HONO) is one of the sources of atmospheric hydroxyl radicals, which has an important influence on the increase of atmospheric oxidation. In addition to the first emission and the homogeneous reaction of OH+NO in the gas phase, the heterogeneous reaction of NO2 on various surfaces is considered to be the source of HONO. During the period of observation in the Yangtze River Delta on June 2015, we apply the LOng Path Absorption Photometer (LOPAP) to measure the HONO concentration at Changzhou site. With the information of NOX, aerosol physics, properties and meteorological conditions obtained from the same period, we analyzed the source of HONO at night. In the case of June 4th, 5th, and 15th at night, the concentration of HONO reached the highest value during the observation period ~3.0 ppb. Except for these three days, HONO mean concentration generally in about 1-2 ppb, the HONO/NO2 range during the period of observation is 0.32%~10.9%, within the domestic and foreign observation in the clean zone values, the average of values is 4.23%, within the general scope of 0.5% ~ 5%. The results between HONO concentration and PM10 and PM2.5 at night show uncorrelated coefficient of R=0.186 and R=0.2108 respectively. The source apportionment showed high contribution from local combustion process of fossil fuels during the observation period and the heterogeneous reaction on the surface of the aerosol at night needs further study.

  2. Understanding HONO concentrations, its role as a hydroxyl radical source and the impact on summertime ozone production in London

    NASA Astrophysics Data System (ADS)

    Stone, D. J.; Whalley, L. K.; Hopkins, J. R.; Holmes, R. E.; Lee, J. D.; Hamilton, J. F.; Laufs, S.; Kleffmann, J.; Heard, D. E.

    2014-12-01

    Understanding the chemistry of free-radicals in the atmosphere is necessary to understand the lifetime of primary pollutants and production of secondary pollutants, such as ozone. In the urban environment, field observations of HONO have revealed elevated concentrations persisting throughout the day and subsequent modelling studies have identified HONO as the major OH precursor (e.g. Elshorbany et al. 2009). Attempts to reproduce the strong daytime HONO signature in models, however, have revealed that the currently known chemistry is unable to account for the levels observed. Here we present simultaneous measurements of OH, HO2, RO2 and HONO made during the Clean air for London project in the summer of 2012. HONO concentrations were observed to build up throughout the night, with concentrations exceeding 2ppbV on several nights. Daytime concentrations were lower, but ~ 300 pptv was observed to persist throughout the afternoon. Zero dimensional box modelling studies, constrained with the detailed MCM chemistry and to the measured HONO, suggest that HONO makes up ~85% of the primary OH budget and just over 50% of the total primary radical budget at noon. The model, however, greatly over-predicts the OH concentrations (and HO2 and RO2concentrations) observed. Unconstrained to HONO, the basic model is unable to reproduce the measured HONO concentrations. A source of HONO from the reaction of NO2 with HO2.H2O, as postulated by Li et al. (2014), can enhance HONO concentrations considerably and also reduces the discrepancy between modelled and measured radicals by reducing the fraction of HONO acting as a net radical source. The model still underestimates the observed HONO by ~ 80% at noon, suggesting that this portion of HONO should still be considered as a primary radical source. The net in-situ ozone production estimated from the measured peroxy radical concentrations and their reaction with NO is sufficient to account for the daily increases in ozone that were

  3. Understanding HONO concentrations in London, its role as a hydroxyl radical source and the impact on summertime ozone production

    NASA Astrophysics Data System (ADS)

    Whalley, Lisa; Lee, James; Stone, Daniel; Hamilton, Jacqueline; Holmes, Rachel; Hopkins, James; Laufs, Sebastian; Kleffmann, Jörg; Heard, Dwayne

    2015-04-01

    Understanding the chemistry of free-radicals in the atmosphere is necessary to understand the lifetime of primary pollutants and the production of secondary pollutants, such as ozone and organic aerosol. In the urban environment, field observations of HONO have revealed elevated concentrations persisting throughout the day and subsequent modelling studies have identified HONO as the major OH precursor. Attempts to reproduce the strong daytime HONO signature in models, however, have revealed that the currently known chemistry is unable to account for the levels observed. Here we present simultaneous measurements of OH, HO2, RO2, OH reactivity and HONO made during the Clean Air for London project in the summer of 2012. HONO concentrations were observed to build up throughout the night, with concentrations exceeding 2 ppbV on several nights. Daytime concentrations were lower, but ~ 300 pptv was observed to persist throughout the afternoon. Box modelling studies, using the Master Chemical Mechanism (MCM) and constrained to the measured HONO, suggest that HONO makes up ~85% of the primary OH budget and just under 50% of the total primary radical budget at noon. The model, however, significantly over-predicts the OH concentrations (and HO2 and RO2 concentrations) observed. Unconstrained to HONO, the basic model is unable to reproduce the measured HONO concentrations. A source of HONO from the reaction of NO2 with HO2.H2O, as postulated by Li et al. (Science, 344, 292, 2014), can enhance HONO concentrations considerably and also reduces the discrepancy between modelled and measured radicals by reducing the fraction of HONO acting as a net radical source. With this process included, the model still underestimates the observed HONO by ~ 69% at noon, suggesting that this portion of HONO should still be considered as a primary radical source. The net in-situ ozone production estimated from the measured peroxy radical concentrations and their reaction with NO is sufficient to

  4. HONO and its potential source particulate nitrite at an urban site in North China during the cold season.

    PubMed

    Wang, Liwei; Wen, Liang; Xu, Caihong; Chen, Jianmin; Wang, Xinfeng; Yang, Lingxiao; Wang, Wenxing; Yang, Xue; Sui, Xiao; Yao, Lan; Zhang, Qingzhu

    2015-12-15

    Characteristics and transformation of nitrous acid (HONO) and particulate nitrite were investigated with high time-resolution field measurements at an urban site in Ji'nan, China from Nov. 2013 to Jan. 2014. During the sampling period, averages of 0.35ppbv HONO and 2.08μgm(-3) fine particulate nitrite were observed. HONO and particulate nitrite exhibited similar diurnal variation patterns but differed in the time at which concentration peaks and valleys occurred. Elevated nocturnal HONO concentration peaks were mainly associated with primary emissions from vehicle exhaust and secondary formation via heterogeneous reactions of NO2. In fresh air masses dominated by vehicle emissions, the average HONO/NOx ratio was 0.58%. The nocturnal heterogeneous reactions of NO2 contributed to about half of the elevated HONO concentration peaks, with the conversion rates in the range of 0.05% to 0.96%h(-1). Meanwhile, a large amount of particulate nitrite, which greatly exceeded the concentration of the gas-phase HONO, was also produced through the heterogeneous reactions of NO2. The large yields of particulate nitrite were facilitated by abundant ammonia and particulate cations in urban Ji'nan. Notably, in the daytime, particulate nitrite acted as a potential source of HONO, especially in conditions of low humidity and acidic aerosols, which possibly has subsequent effects on photochemistry in the boundary layer. PMID:26298252

  5. The primary and recycling sources of OH during the NACHTT-2011 campaign: HONO as an important OH primary source in the wintertime

    NASA Astrophysics Data System (ADS)

    Kim, Saewung; VandenBoer, Trevor C.; Young, Cora J.; Riedel, Theran P.; Thornton, Joel A.; Swarthout, Bob; Sive, Barkley; Lerner, Brian; Gilman, Jessica B.; Warneke, Carsten; Roberts, James M.; Guenther, Alex; Wagner, Nicholas L.; Dubé, William P.; Williams, Eric; Brown, Steven S.

    2014-06-01

    We present OH observations from Nitrogen, Aerosol Composition, and Halogens on a Tall Tower 2011 (NACHTT-11) held at the Boulder Atmospheric Observatory in Weld County, Colorado. Average OH levels at noon were ~ 2.7 × 106 molecules cm-3 at 2 m above ground level. Nitrous acid (HONO) photolysis was the dominant OH source (80.4%) during this campaign, while alkene ozonolysis (4.9%) and ozone photolysis (14.7%) were smaller contributions to OH production. To evaluate recycling sources of OH from HO2 and RO2, an observationally constrained University of Washington Chemical Mechanism (UWCM) box model (version 2.1) was employed to simulate ambient OH levels over several scenarios. For the base run, not constrained by observed HONO, the model significantly underestimated OH by a factor of 5.3 in the morning (9:00-11:00) and by a factor of 3.2 in the afternoon (13:00-15:00). The results suggest that known chemistry cannot constrain HONO and, subsequently, OH during the observational period. When HONO is constrained in the model by observations (< 50 m), the discrepancy between observation and model simulation improves to a factor of 1.3 in the morning and a factor 1.1 in the afternoon, within the 35% estimated instrumental uncertainty. However, the model produces both a morning and afternoon maximum in OH, in contrast to the observations, which show strong evidence for morning OH production but no distinct morning maximum. Two additional OH sources were also considered, although they do not improve the differences in modeled and measured temporal OH profiles. First, the impact of daytime HONO gradients near the ground surface (< 20 m) was evaluated. Strong HONO gradients were observed between 06:00 and 09:00 MST (mountain standard time), especially within 20 m of the surface. When constrained to HONO observed below 20 m (rather than 50 m), the model produced an even larger morning OH maximum, in contrast to the observations. Second, Cl atoms from ClNO2 photolysis

  6. A comparison of measured HONO uptake and release with calculated source strengths in a heterogeneous forest environment

    NASA Astrophysics Data System (ADS)

    Sörgel, M.; Trebs, I.; Wu, D.; Held, A.

    2015-08-01

    Vertical mixing ratio profiles of nitrous acid (HONO) were measured in a clearing and on the forest floor in a rural forest environment. For the forest floor, HONO was found to predominantly deposit, whereas for the clearing, net deposition dominated only during nighttime and net emissions were observed during daytime. For selected days, net fluxes of HONO were calculated from the measured profiles using the aerodynamic gradient method. The emission fluxes were in the range of 0.02 to 0.07 nmol m-2 s-1 and thus were in the lower range of previous observations. These fluxes were compared to the strengths of postulated HONO sources. Laboratory measurements of different soil samples from both sites revealed an upper limit for soil biogenic HONO emission fluxes of 0.025 nmol m-2 s-1. HONO formation by light-induced NO2 conversion was calculated to be below 0.03 nmol m-2 s-1 for the investigated days, which is comparable to the potential soil fluxes. Due to light saturation at low irradiance, this reaction pathway was largely found to be independent of light intensity, i.e. it was only dependent on ambient NO2. We used three different approaches based on measured leaf nitrate loadings for calculating HONO formation from HNO3 photolysis. While the first two approaches based on empirical HONO formation rates yielded values in the same order of magnitude as the estimated fluxes, the third approach based on available kinetic data of the postulated pathway failed to produce noticeable amounts of HONO. Estimates based on reported cross sections of adsorbed HNO3 indicate that the lifetime of adsorbed HNO3 was only about 15 min, which would imply a substantial renoxification. Although the photolysis of HNO3 was significantly enhanced at the surface, the subsequent light-induced conversion of the photolysis product NO2 did not produce considerable amounts of HONO. Consequently, this reaction might occur via an alternative mechanism. By explicitly calculating HONO formation based

  7. A comparison of measured HONO uptake and release with calculated source strengths in a heterogeneous forest environment

    NASA Astrophysics Data System (ADS)

    Sörgel, M.; Trebs, I.; Wu, D.; Held, A.

    2015-01-01

    Vertical mixing ratio profiles of nitrous acid (HONO) were measured in a clearing and on the forest floor in a rural forest environment. For the forest floor, HONO was found to be predominantly deposited, whereas net deposition was dominating in the clearing only during nighttime and net emissions were observed during daytime. For selected days, net fluxes of HONO were calculated from the measured profiles using the aerodynamic gradient method. The emission fluxes were in the range of 0.02 to 0.07 nmol m-2 s-1, and, thus were in the lower range of previous observations. These fluxes were compared to the strengths of postulated HONO sources. Laboratory measurements of different soil samples from both sites revealed an upper limit for soil biogenic HONO emission fluxes of 0.025 nmol m-2 s-1. HONO formation by light induced NO2 conversion was calculated to be below 0.03 nmol m-2 s-1 for the investigated days, which is comparable to the potential soil fluxes. Due to light saturation at low irradiance, this reaction pathway was largely found to be independent of light intensity, i.e. it was only dependent on ambient NO2. We used three different approaches based on measured leaf nitrate loadings for calculating HONO formation from HNO3 photolysis. While the first two approaches based on empirical HONO formation rates yielded values in the same order of magnitude as the estimated fluxes, the third approach based on available kinetic data of the postulated pathway failed to produce noticeable amounts of HONO. Estimates based on reported cross sections of adsorbed HNO3 indicate that the lifetime of adsorbed HNO3 was only about 15 min, which would imply a substantial renoxification. Although the photolysis of HNO3 was significantly enhanced at the surface, the subsequent light induced conversion of the photolysis product NO2 did not produce considerable amounts of HONO. Consequently, this reaction might occur via an alternative mechanism.

  8. A comparison of measured HONO uptake and release with calculated source strengths in a heterogeneous forest environment

    NASA Astrophysics Data System (ADS)

    Sörgel, Matthias; Trebs, Ivonne; Wu, Dianming; Held, Andreas

    2015-04-01

    Vertical mixing ratio profiles of nitrous acid (HONO) were measured in a clearing and on the forest floor in a rural forest environment (in the south-east of Germany) by applying a lift system to move the sampling unit of the LOng Path Absorption Photometer (LOPAP) up and down. For the forest floor, HONO was found to be predominantly deposited, whereas net deposition was dominating in the clearing only during nighttime and net emissions were observed during daytime. For selected days, net fluxes of HONO were calculated from the measured profiles using the aerodynamic gradient method. The emission fluxes were in the range of 0.02 to 0.07 nmol m-2 s-1, and, thus were in the lower range of previous observations. These fluxes were compared to the strengths of postulated HONO sources and to the amount of HONO needed to sustain photolysis in the boundary layer. Laboratory measurements of different soil samples from both sites revealed an upper limit for soil biogenic HONO emission fluxes of 0.025 nmol m-2 s-1. HONO formation by light induced NO2 conversion was calculated to be below 0.03 nmol m-2 s-1 for the investigated days, which is comparable to the potential soil fluxes. Due to light saturation at low irradiance, this reaction pathway was largely found to be independent of light intensity, i.e. it was only dependent on ambient NO2. We used three different approaches based on measured leaf nitrate loadings for calculating HONO formation from HNO3 photolysis. While the first two approaches based on empirical HONO formation rates yielded values in the same order of magnitude as the estimated fluxes, the third approach based on available kinetic data of the postulated pathway failed to produce noticeable amounts of HONO. Estimates based on reported cross sections of adsorbed HNO3 indicate that the lifetime of adsorbed HNO3 was only about 15 min, which would imply a substantial renoxification. Although the photolysis of HNO3 was significantly enhanced at the surface, the

  9. HONO Vertical Gradients during the 2006 TRAMP and the 2009 SHARP experiments in Houston, TX

    NASA Astrophysics Data System (ADS)

    Wong, K.; Tsai, C.; Pikelnaya, O.; Stutz, J.; Fu, D.

    2009-12-01

    Nitrous acid (HONO) plays a significant role in tropospheric photochemistry as a precursor of the hydroxyl radical (OH). Despite the importance of HONO photolysis for the OH budget in the early morning, HONO formation mechanisms are not yet fully understood. In addition, recent observations of higher than expected daytime HONO concentrations are currently unexplained. The vertical distribution of HONO in the morning and during the day can have a considerable impact on its importance for ozone formation in the boundary layer. The observation of vertical profiles is also important to allow a better understanding of HONO formation in the atmosphere. Consequently there is an urgent need to provide observations and detailed model calculations of vertical HONO profiles. During the 2009 SHARP experiment from April 15 to May 29, 2009 in Houston, TX, we performed measurements of HONO, NO2, O3 and other trace gases in three altitude intervals (30-70m, 70 - 130m, and 130 - 300m), using UCLA’s long path DOAS instrument. Vertical gradients of all atmospheric trace gases were frequently observed during stable nights. HONO established negative gradients, with higher concentrations near the ground, indicating that the source of HONO is at or near the ground. Daytime HONO gradients were also observed during some days. Here we compare our results with observations made at the same location in 2006 and with results from a 1-D chemical transport model to elucidate the mechanisms forming HONO in urban areas.

  10. Combustion Processes Indoors: a Source of High OH Radical Concentrations Through the Photolysis of Hono

    NASA Astrophysics Data System (ADS)

    Bartolomei, V.; Gomez Alvarez, E.; Glor, M.; Gligorovski, S.; Temime-Roussel, B.; Quivet, E.; Strekowski, R.; Zetzsch, C.; Held, A. B.; Wortham, H.

    2013-12-01

    Hydroxyl radical (OH) is one of the most important oxidant species in the atmosphere controlling its self-oxidizing capacity. The main sources of OH radicals are photolysis of ozone and photolysis of nitrous acid (HONO), among the others. In the indoor air, the ozonolysis of alkenes has been suggested as the main OH formation pathway. The possibility for OH formation through photolytic pathways in the indoor environment has been, up to now, ignored (Gómez Alvarez et al., 2012). Models and indirect measurements to the present time predicted concentrations of OH radicals in the order of 104 -105 cm-3. Recently, by direct measurements we have detected high OH radical concentrations of 1.8 106 cm-3 in a classroom in Marseille and we demonstrated that its main source is the photolysis of HONO (Gómez Alvarez et al., 2013). The concentrations of HONO are quite high indoors, reaching levels in the order of a few tens of ppbV (Gómez Alvarez et al., 2013). This is mainly due to 1) direct combustion sources and 2) heterogeneous reactions of NO2 on the numerous surfaces present in the indoor environment. HONO levels of 30 ppb were measured in a previous campaign carried out in Bayreuth in July 2012 as direct emissions from the combustion of a candle. The combination between so high concentrations of HONO and higher than expected light transmissions indoors (or indoor artificial lighting) could have a significant impact on the OH concentrations indoors which could feasibly become considerably higher than we measured in our school campaign (Gomez Alvarez et al., 2013). In order to evaluate these upper limits under combustion conditions in the indoor environment, we have carried out a campaign in the LOTASC chamber (Bayreuth, Germany). For this aim, the exhaust fumes from the burning of a commonly used domestic candle have been introduced in the chamber. The chamber was irradiated under well research indoor lighting conditions. A thorough characterization of light intensities

  11. The Primary and Recycling Sources of OH During the NACHTT-2011 Campaign: HONO as an Important OH Primary Source in the Wintertime

    SciTech Connect

    Kim, S.; VandenBoer, Trevor; Young, Cora; Riedel, Theran; Thornton, Joel A.; Swarthout, Bob; Sive, B.; Lerner, Brian M.; Gilman, Jessica; Warneke, Carsten; Roberts, James M.; Guenther, Alex B.; Wagner, Nicholas; Dube, William P.; Williams, Eric; Brown, Steve

    2014-06-10

    We present OH observation results during the NACHTT-11 field campaign at the Boulder Atmospheric Observatory in Weld County, Colorado. The observed OH levels during the daytime (at noon) were ~ 2.7 × 106 molecules cm-3 at the ground level (2 m above ground level, AGL). HONO and ozone photolysis were the two dominant photochemical OH production pathways during the field campaign. However, alkene ozonolysis, found an important source for OH by two previous winter season OH observations, was a minor contribution to OH primary production (~5 %). To evaluate recycling sources of OH from HO2 and RO2, an observation constrained University of Washington Chemical Mechanism (UWCM) box model is employed to simulated ambient OH levels with different model scenarios. For the base run without constraining observed HONO, the model simulated OH significantly underestimates the observed OH level (20.8 times in the morning and 7.2 times in the daytime). This indicates that the known HONO sources incorporated in the UWCM model cannot explain the observed HONO level. Once HONO is constrained by the observation, the discrepancy between observation and model simulation improves (5.1 times in the morning and 2.1 times in the daytime) but still out of the measurement uncertainty range (35 %). We explore two possible reasons for the observed unexplainably high wintertime OH levels. First, potential roles of Cl atoms produce organic peroxy radicals from the reactions between Cl atmos and alkane compounds. However, the Cl levels during the observation period are estimated very low (~ 103 atoms cm-3) to explain the enhanced OH levels. Second, Impacts of higher HONO levels on the ground was evaluated. Strong HONO gradient towards ground was observed especially during the early morning (6 am to 8 am) was observed and the lowest level available for the HONO observation during the campaign is 5 m AGL. Once we assume the twice of the observed HONO levels averaged between 5 m to 15 m at 2 m AGL

  12. Evaluating emissions of HCHO, HONO, NO2, and SO2 from point sources using portable Imaging DOAS

    NASA Astrophysics Data System (ADS)

    Pikelnaya, O.; Tsai, C.; Herndon, S. C.; Wood, E. C.; Fu, D.; Lefer, B. L.; Flynn, J. H.; Stutz, J.

    2011-12-01

    Our ability to quantitatively describe urban air pollution to a large extent depends on an accurate understanding of anthropogenic emissions. In areas with a high density of individual point sources of pollution, such as petrochemical facilities with multiple flares or regions with active commercial ship traffic, this is particularly challenging as access to facilities and ships is often restricted. Direct formaldehyde emissions from flares may play an important role for ozone chemistry, acting as an initial radical precursor and enhancing the degradation of co-emitted hydrocarbons. HONO is also recognized as an important OH source throughout the day. However, very little is known about direct HCHO and HONO emissions. Imaging Differential Optical Absorption Spectroscopy (I-DOAS), a relatively new remote sensing technique, provides an opportunity to investigate emissions from these sources from a distance, making this technique attractive for fence-line monitoring. In this presentation, we will describe I-DOAS measurements during the FLAIR campaign in the spring/summer of 2009. We performed measurements outside of various industrial facilities in the larger Houston area as well as in the Houston Ship Channel to visualize and quantify the emissions of HCHO, NO2, HONO, and SO2 from flares of petrochemical facilities and ship smoke stacks. We will present the column density images of pollutant plumes as well as fluxes from individual flares calculated from I-DOAS observations. Fluxes from individual flares and smoke stacks determined from the I-DOAS measurements vary widely in time and by the emission sources. We will also present HONO/NOx ratios in ship smoke stacks derived from the combination of I-DOAS and in-situ measurements, and discuss other trace gas ratios in plumes derived from the I-DOAS observations. Finally, we will show images of HCHO, NO2 and SO2 plumes from control burn forest fires observed in November of 2009 at Vandenberg Air Force Base, Santa Maria

  13. Fluxes of Nitrous Acid (HONO) above an Agricultural Field Side near Paris

    NASA Astrophysics Data System (ADS)

    Laufs, S.; Cazaunau, M.; Stella, P.; Loubet, B.; Kurtenbach, R.; Cellier, P.; Mellouki, W.; Kleffmann, J.

    2012-04-01

    HONO is an important precursor of the OH radical, the detergent of the atmosphere. Field measurements show high diurnal HONO mixing ratios that cannot be explained by chemical models with known gas phase chemistry. Therefore, daytime sources of HONO are still under discussion. During the last decade many experimental investigation were performed to study heterogeneous production of HONO like the photo enhanced reduction of NO2 on humic acids or photolysis of HNO3 on surfaces. Recently, nitrite produced by bacteria, present in soil, was discussed as a source of HONO as well. In addition gas phase sources like the photolysis of nitrophenols, or the reaction of excited NO2 are discussed. Gradient measurements show high mixing ratios of HONO even above the boundary layer. However, beside intensive investigations on the sources of HONO, it is still an open question whether heterogeneous or gas phase sources are more important in the atmosphere. Flux measurements could represent a method to find the origin of missing sources of HONO. Until now instruments are not sensitive and fast enough to do Eddy correlation measurements for HONO. Alternatively, HONO fluxes are estimated by the Aerodynamic Gradient (AGM), or Relaxed Eddy Accumulation (REA) methods. Here we present HONO fluxes estimated by AGM and the LOPAP technique (Long Path Absorption Photometer) above an agricultural field in Grignon, Paris (48°51'N, 1°58'E). Fluxes during different seasons and different types of vegetations including bare soil will be presented and compared with chemical corrected fluxes of NO, NO2 and O3, or other parameters.

  14. On the interpretation of in situ HONO observations via photochemical steady state.

    PubMed

    Crilley, Leigh R; Kramer, Louisa; Pope, Francis D; Whalley, Lisa K; Cryer, Danny R; Heard, Dwayne E; Lee, James D; Reed, Christopher; Bloss, William J

    2016-07-18

    A substantial body of recent literature has shown that boundary layer HONO levels are higher than can be explained by simple, established gas-phase chemistry, to an extent that implies that additional HONO sources represent a major, or the dominant, precursor to OH radicals in such environments. This conclusion may be reached by analysis of point observations of (for example) OH, NO and HONO, alongside photochemical parameters; however both NO and HONO have non-negligible atmospheric lifetimes, so these approaches may be problematic if substantial spatial heterogeneity exists. We report a new dataset of HONO, NOx and HOx observations recorded at an urban background location, which support the existence of additional HONO sources as determined elsewhere. We qualitatively evaluate the possible impacts of local heterogeneity using a series of idealised numerical model simulations, building upon the work of Lee et al. (J. Geophys. Res., 2013, DOI: 10.1002/2013JD020341). The simulations illustrate the time required for photostationary state approaches to yield accurate results following substantial perturbations in the HOx/NOx/NOy chemistry, and the scope for bias to an inferred HONO source from NOx and VOC emissions in either a positive or negative sense, depending upon the air mass age following emission. To assess the extent to which these impacts may be present in actual measurements, we present exploratory spatially resolved measurements of HONO and NOx abundance obtained using a mobile instrumented laboratory. Measurements of the spatial variability of HONO in urban, suburban and rural environments show pronounced changes in abundance are found in proximity to major roads within urban areas, indicating that photo-stationary steady state (PSS) analyses in such areas are likely to be problematic. The measurements also show areas of very homogeneous HONO and NOx abundance in rural, and some suburban, regions, where the PSS approach is likely to be valid. Implications

  15. HONO fluxes from soil surfaces: an overview

    NASA Astrophysics Data System (ADS)

    Wu, Dianming; Sörgel, Matthias; Tamm, Alexandra; Ruckteschler, Nina; Rodriguez-Caballero, Emilio; Cheng, Yafang; Pöschl, Ulrich; Weber, Bettina

    2016-04-01

    Gaseous nitrous acid (HONO) contributes up to 80% of atmospheric hydroxyl (OH) radicals and is also linked to health risks through reactions with tobacco smoke forming carcinogens. Field and modeling results suggested a large unknown HONO source in the troposphere during daytime. By measuring near ground HONO mixing ratio, up to 30% of HONO can be released from forest, rural and urban ground as well as snow surfaces. This source has been proposed to heterogeneous reactions of nitrogen dioxide (NO2) on humic acid surfaces or nitric acid photolysis. Laboratory studies showed that HONO emissions from bulk soil samples can reach 258 ng m‑2 s‑1 (in term of nitrogen), which corresponding to 1.1 × 1012 molecules cm‑2 s‑1and ˜ 100 times higher than most of the field studies, as measured by a dynamic chamber system. The potential mechanisms for soil HONO emissions include chemical equilibrium of acid-base reaction and gas-liquid partitioning between soil nitrite and HONO, but the positive correlation of HONO fluxes with pH (largest at neutral and slightly alkaline) points to the dominance of the formation process by ammonia-oxidizing bacteria (AOB). In general soil surface acidity, nitrite concentration and abundance of ammonia-oxidizing bacteria mainly regulate the HONO release from soil. A recent study showed that biological soil crusts in drylands can also emit large quantities of HONO and NO, corresponding to ˜20% of global nitrogen oxide emissions from soils under natural vegetation. Due to large concentrations of microorganisms in biological soil crusts, particularly high HONO and NO emissions were measured after wetting events. Considering large areas of arid and arable lands as well as peatlands, up to 70% of global soils are able to emitting HONO. However, the discrepancy between large soil HONO emissions measured in lab and low contributions of HONO flux from ground surfaces in field as well as the role of microorganisms should be further investigated.

  16. Heterogeneous Photochemical Conversion of NO2 to HONO on the Humic Acid Surface under Simulated Sunlight.

    PubMed

    Han, Chong; Yang, Wangjin; Wu, Qianqian; Yang, He; Xue, Xiangxin

    2016-05-17

    The poor understanding of HONO sources in the daytime highlights the importance of the heterogeneous photochemical reaction of NO2 with aerosol or soil surfaces. The conversion of NO2 to HONO on humic acid (HA) under simulated sunlight was investigated using a flow tube reactor at ambient pressure. The uptake coefficient (γ) of NO2 linearly increased with irradiation intensity and HA mass in the range of 0-2.0 μg/cm(2), while it decreased with the NO2 concentration. The HONO yield was found to be independent of irradiation intensity, HA mass, and NO2 concentration. The temperature (278-308 K) had little influence on both γ and HONO yield. Additionally, γ increased continuously with relative humidity (RH, 7-70%), and a maximum HONO yield was observed at 40% RH. The heterogeneous photochemical reaction of NO2 with HA was explained by the Langmuir-Hinshelwood mechanism. PMID:27074517

  17. Nitrous acid (HONO) observations during the Uintah Basin Wintertime Ozone Studies (UBWOS) and the Wintertime Investigation of Transport, Emission, and Reactivity (WINTER) study: sources, measurements interferences, and implications beyond.

    NASA Astrophysics Data System (ADS)

    Veres, P. R.; Roberts, J. M.; Alvarez, S. L.; Bates, T. S.; Brown, S. S.; Edwards, P.; Flynn, J. H., III; De Gouw, J. A.; Johnson, J. E.; Lee, B. H.; Lefer, B. L.; Liggio, J.; Lopez-Hilfiker, F.; Quinn, P.; Stutz, J.; Thornton, J. A.; Tsai, J. Y.; Wentzell, J. J. B.; Wild, R. J.; Yuan, B.

    2015-12-01

    Recent work has highlighted HONO as a strong daytime source of OH radicals though a general lack of consensus exists with respect to the sources and overall impact of HONO photolysis on daytime radical budgets. Improvements in atmospheric HOx and NOx budgets, and therefore daytime HONO constraints, are necessary to improve air quality control strategies in adversely affected regions. In this presentation HONO measurements made using multiple collocated instruments during the UBWOS 2013 and 2014 field studies will be discussed. These results suggest that our ability to measure HONO is heavily dependent on our understanding of sampling artifacts, measurement interferences, and background determinations. We also present mid-latitude tropospheric observations of HO2NO2, as high as 1.5 ppbv, that coincide with the observed maxima in daytime HONO. These coinciding observations of both HONO and HO2NO2 will be presented with a particular emphasis on potential vertical gradients, surface chemistry, and daytime budgets. Results of this work may be relevant to interpretation of HONO observations in a range of environments from clean arctic to relatively polluted urban summertime regions. Measurements of HONO from the Wintertime Investigation of Transport, Emission, and Reactivity (WINTER) project in 2015 will be shown for comparison.

  18. Heterogeneous Reactivity of NO2 with Photocatalytic Paints: A Possible Source of Nitrous Acid (HONO) in the Indoor Environment

    NASA Astrophysics Data System (ADS)

    Gligorovski, S.; Bartolomei, V.; Gandolfo, A.; Gomez Alvarez, E.; Kleffmann, J.; Wortham, H.

    2014-12-01

    There is an increasing concern about the indoor air environment, where we spend most of our time. Common methods of improving indoor air quality include controlling pollution sources, increasing ventilation rates or using air purifiers. Photocatalytic remediation technology was suggested as a new possibility to eliminate indoor air pollutants instead of just diluting or disposing them. In the present study, heterogeneous reactions of NO2 were studied on photocatalytic paints containing different size and quantity of TiO2. The heterogeneous reactions were conducted in a photo reactor under simulated atmospheric conditions. The flat pyrex rectangular plates covered with the paint were inserted into the reactor. These plates have been sprayed with the photocatalytic paints at our industrial partner's (ALLIOS) facilities using a high precision procedure that allowed the application of a thin layer of a given thickness of the paint. This allows a homogeneous coverage of the surface with the paint and an accurate determination of the exact amount of paint exposed to gaseous NO2. We demonstrate that the indoor photocatalytic paints which contain TiO2 can substantially reduce the concentrations of nitrogen dioxide (NO2). We show that the efficiency of nitrogen dioxide (NO2) removal increase with the quantity of TiO2 in the range 0 - 7 %. The geometric uptake coefficients increase from 5 · 10-6 to 1.6 · 10-5 under light irradiation of the paints. On the other hand, during the reactions of NO2 with this paint (7 % of TiO2) nitric oxide (NO) and nitrous acid (HONO) are formed. Nitrous acid (HONO) is an important harmful indoor pollutant and its photolysis leads to the formation of highly reactive OH radicals (Gomez Alvarez et al., 2013). Maximum conversion efficiencies of NO2to HONO and NO of 15 % and 33 % were observed at 30 % RH, respectively. Thus, the quantity of TiO2 embedded in the paint is an important parameter regarding the nitrogen oxides (NOx = NO + NO2

  19. Daytime and Nighttime Vertical Gradients of HONO in Houston, TX.

    NASA Astrophysics Data System (ADS)

    Wong, K.; Stutz, J.; Oh, H.

    2008-12-01

    Nitrous acid (HONO) plays an important role in tropospheric photochemistry as a precursor of the hydroxyl radical (OH), the primary oxidizing agent in the atmosphere. Nevertheless, the sources of HONO have not yet been fully understood. Recently, daytime HONO concentrations higher than expected have been observed in various field experiments. The cause of these elevated HONO levels is currently unclear. The vertical distribution of HONO at night and during the day, which can have a considerable impact on the importance of HONO for ozone formation, is also currently poorly characterized by observations and models. Measurements of daytime and nighttime HONO vertical profiles were made in Houston in Summer 2006 during the TexAQS II Radical and Aerosol Measurement Project (TRAMP) using long path DOAS. HONO developed negative concentration gradients during the night, due to inefficient vertical mixing, and a combination of ground deposition of NO2 and HONO and heterogeneous conversion of NO2 to HONO on surfaces. Despite the efficient vertical mixing during the day, boundary layer HONO gradients were also observed, indicating possible unknown source of HONO near the ground. Here we present and discuss the field observations of HONO and other traces gases during TRAMP and the modeling of daytime and nighttime HONO gradients using a one dimensional (1-D) chemistry and transport model.

  20. Observation and modelling of ambient nitrous acid (HONO) at a rural site (Wangdu) in the North China Plain in summer 2014

    NASA Astrophysics Data System (ADS)

    Liu, Yuhan; Lu, Keding; Li, Xin; Dong, Huabin; Ye, Nini; Tan, Zhaofeng; Wu, Yusheng; Zeng, Liming; Bohn, Birger; Broch, Sebastian; Fuchs, Hendrik; Hofzumahaus, Andrease; Holland, Frank; Rohrer, Franz; Wahner, Andrease; Zhang, Yuanhang

    2016-04-01

    Significant missing daytime HONO sources were determined in many places worldwide from urban to rural conditions. In recent field campaigns performed in Chinese megacity regions such as Pearl River Delta, Yangtze River Delta and North China Plain, strong missing HONO sources were also determined and possible explanations including photoenhanced heterogeneous conversion of NO2, photolysis of particulate nitrate, soil emission, and emission from biomass burning. In the present work, we performed in situ measurements of ambient HONO concentration at a rural site (Wangdu) in North China Plain in summer 2014. The observed HONO concentration ranges from tens ppt to 5 ppb. The relations between observed HONO concentration and nitrogen oxide, aerosol and gas-phase chemistry are discussed with statistical methods. Moreover, we use an observational constrained box model to explore the possible roles of the state of art HONO production mechanisms. In addition, after the day of fertilization, we observed a daytime HONO peak around noon time which was distinct from other days by the HONO/NO2 ratio. We believe this peak is a strong indication of soil HONO emission since our site was located in center of a large wheat field. Compared to other days, this increased HONO concentration contributes significantly to the OH production around noontime.

  1. Comment on “Missing gas-phase source of HONO inferred from Zeppelin measurements in the troposphere”

    NASA Astrophysics Data System (ADS)

    Ye, Chunxiang; Zhou, Xianliang; Pu, Dennis; Stutz, Jochen; Festa, James; Spolaor, Max; Cantrell, Christopher; Mauldin, Roy L.; Weinheimer, Andrew; Haggerty, Julie

    2015-06-01

    Li et al. (Reports, 18 April 2014, p. 292) proposed a unity nitrous acid (HONO) yield for reaction between nitrogen dioxide and the hydroperoxyl-water complex and suggested a substantial overestimation in HONO photolysis contribution to hydroxyl radical budget. Based on airborne observations of all parameters in this chemical system, we have determined an upper-limit HONO yield of 0.03 for the reaction.

  2. ATMOSPHERIC SCIENCE. Comment on "Missing gas-phase source of HONO inferred from Zeppelin measurements in the troposphere".

    PubMed

    Ye, Chunxiang; Zhou, Xianliang; Pu, Dennis; Stutz, Jochen; Festa, James; Spolaor, Max; Cantrell, Christopher; Mauldin, Roy L; Weinheimer, Andrew; Haggerty, Julie

    2015-06-19

    Li et al. (Reports, 18 April 2014, p. 292) proposed a unity nitrous acid (HONO) yield for reaction between nitrogen dioxide and the hydroperoxyl-water complex and suggested a substantial overestimation in HONO photolysis contribution to hydroxyl radical budget. Based on airborne observations of all parameters in this chemical system, we have determined an upper-limit HONO yield of 0.03 for the reaction. PMID:26089507

  3. Intercomparison of the DOAS and LOPAP techniques for the detection of nitrous acid (HONO)

    NASA Astrophysics Data System (ADS)

    Kleffmann, J.; Lörzer, J. C.; Wiesen, P.; Kern, C.; Trick, S.; Volkamer, R.; Rodenas, M.; Wirtz, K.

    Recent studies have demonstrated that nitrous acid (HONO) is a source of hydroxyl radicals (OH) in the boundary layer not only early in the morning but also throughout the day. Despite its importance, all known instruments to detect HONO in the atmosphere suffer either from the great experimental effort necessary or from the possibility of significant interferences. In addition, only a few instruments are sensitive enough to detect low HONO concentrations during daytime. Accordingly, validated and sensitive measurements of nitrous acid are of paramount importance to describe the oxidation capacity of the atmosphere. Up to now, in intercomparisons of these chemical detectors with the well accepted DOAS technique significantly higher concentrations have been detected during the day with the chemical detectors, the discrepancy being attributed to interferences. In the present study, a recently developed HONO instrument (LOPAP) was validated against the DOAS technique, both in the field and in a large smog chamber under various conditions. Since sampling artefacts were minimised and interferences were measured and corrected for by the LOPAP instrument excellent agreement was obtained between these techniques during daytime as well as night-time. It is demonstrated that chemical instruments, which do not measure and do not correct interferences may significantly overestimate daytime concentrations of HONO caused by unknown interferences, which are particularly important during daytime, when HONO concentrations are low. For the DOAS technique, the possibility of HONO impurities in the NO 2 reference spectra used for the spectral analysis needs to be treated actively in the evaluation process, to avoid a potential negative interference at low HONO/NO 2 ratios. A simple procedure is presented that eliminates this possible error source in DOAS measurements of HONO in the atmosphere.

  4. HONO (nitrous acid) emissions from acidic northern soils

    NASA Astrophysics Data System (ADS)

    Maljanen, Marja; Yli-Pirilä, Pasi; Joutsensaari, Jorma; Martikainen, Pertti J.

    2015-04-01

    The photolysis of HONO (nitrous acid) is an important source of OH radical, the key oxidizing agent in the atmosphere, contributing also to removal of atmospheric methane (CH4), the second most important greenhouse gas after carbon dioxide (CO2). The emissions of HONO from soils have been recently reported in few studies. Soil HONO emissions are regarded as missing sources of HONO when considering the chemical reactions in the atmosphere. The soil-derived HONO has been connected to soil nitrite (NO2-) and also directly to the activity of ammonia oxidizing bacteria, which has been studied with one pure culture. Our hypothesis was that boreal acidic soils with high nitrification activity could be also sources of HONO and the emissions of HONO are connected with nitrification. We selected a range of dominant northern acidic soils and showed in microcosm experiments that soils which have the highest nitrous oxide (N2O) and nitric oxide (NO) emissions (drained peatlands) also have the highest HONO production rates. The emissions of HONO are thus linked to nitrogen cycle and also NO and N2O emissions. Natural peatlands and boreal coniferous forests on mineral soils had the lowest HONO emissions. It is known that in natural peatlands with high water table and in boreal coniferous forest soils, low nitrification activity (microbial production of nitrite and nitrate) limits their N2O production. Low availability of nitrite in these soils is the likely reason also for their low HONO production rates. We also studied the origin of HONO in one peat soil with acetylene and other nitrification inhibitors and we found that HONO production is not closely connected to ammonium oxidation (nitrification). Acetylene blocked NO emissions but did not affect HONO or N2O emissions, thus there is another source behind HONO emission from these soils than ammonium oxidation. It is still an open question if this process is microbial or chemical origin.

  5. Nocturnal Measurements of HONO by Differential Optical Absorption Spectroscopy

    NASA Astrophysics Data System (ADS)

    Wojtal, P.; McLaren, R.

    2011-12-01

    Differential optical absorption spectroscopy (DOAS) was used to quantify the concentration of HONO, NO2 and SO2 in the nocturnal urban atmosphere at York University over a period of one year. These measurements form a comprehensive HONO data set, including a large range of temperatures, relative humidity, surface conditions (snow, water, dry, etc.) and NO2 concentrations. Laboratory studies and observations within the nocturnal boundary layer reported in the literature suggest heterogeneous conversion of NO2 on surface adsorbed water as the major nighttime source of HONO. HONO formation and photolysis is believed to represent a major source term in the hydroxyl radical budget in polluted continental regions. Currently, most air quality models tend to significantly underpredict HONO, caused by the lack of understanding of HONO formation processes and the parameters that affect its concentration. Recently, we reported nocturnal pseudo steady states (PSS) of HONO in an aqueous marine environment and a conceptual model for HONO formation on aqueous surfaces was proposed. The data set collected at York University is being analyzed with a view towards further understanding the nighttime HONO formation mechanism and testing several hypotheses: 1) A HONO PSS can exist during certain times at night in an urban area in which the HONO concentration is independent of NO2, given the surface contains sufficient water coverage and is saturated with nitrogen containing precursors; 2) The concentration of HONO is positively correlated with temperature during periods where a PSS exists; 3) Different conversion efficiencies of NO2 to HONO exist on dry, wet and snow surfaces; 4) HONO formation has a NO2 order dependence between 0 and 2nd order, dependant on NO2 concentration, relative humidity, etc. The data set will be presented along with statistical analysis that sheds new light on the source of HONO in urban areas at night.

  6. HONO (nitrous acid) emissions from acidic northern soils

    NASA Astrophysics Data System (ADS)

    Maljanen, Marja; Yli-Pirilä, Pasi; Joutsensaari, Jorma; Sulassaari, Sirkka; Martikainen, Pertti J.

    2014-05-01

    The photolysis of HONO (nitrous acid) is an important source of OH radical, the key oxidizing agent in the atmosphere, contributing also to removal of atmospheric methane (CH4), the second most important greenhouse gas after carbon dioxide (CO2). There are missing sources of HONO when considering the chemical reactions in the atmosphere. Soil could be such a missing source. Emissions of HONO from soils studied in laboratory incubations have been recently reported. The soil-derived HONO has been connected to soil nitrite (NO2-) and a study with an ammonium oxidizing bacterium has shown that HONO could be produced in ammonium oxidation. Our hypothesis was that boreal acidic soils with high nitrification activity could be important sources of HONO. We selected a range of dominant northern acidic soils and showed in microcosm experiments that soils which have the highest nitrous oxide (N2O) and nitric oxide (NO) emissions (drained peatlands) also have the highest HONO production rates. The emissions of HONO are thus linked to nitrogen cycle processes. In contrast to drained peatlands, natural peatlands with high water table and boreal coniferous forests on mineral soils with low nitrification capacity had low HONO emissions. It is known that in natural peatlands with high water table and in boreal coniferous forest soils, low nitrification activity (microbial production of nitrite and nitrate) limits their N2O production. Low nitrification rate and low availability of nitrite in these soils are the likely reasons for their low HONO production rates. We studied the origin of HONO in one drained peat soil by inhibiting nitrification with acetylene. Acetylene blocked NO emissions but did not affect HONO or N2O emissions, thus ammonium oxidation is not the direct mechanism for the HONO emission in this soil. It is still an open question if HONO originates directly from some microbial process like ammonium oxidation or chemically from nitrite produced in microbial processes.

  7. Theoretical study of the hydrogen abstraction of substituted phenols by nitrogen dioxide as a source of HONO.

    PubMed

    Shenghur, Abraham; Weber, Kevin H; Nguyen, Nhan D; Sontising, Watit; Tao, Fu-Ming

    2014-11-20

    The mild yet promiscuous reactions of nitrogen dioxide (NO2) and phenolic derivatives to produce nitrous acid (HONO) have been explored with density functional theory calculations. The reaction is found to occur via four distinct pathways with both proton coupled electron transfer (PCET) and hydrogen atom transfer (HAT) mechanisms available. While the parent reaction with phenol may not be significant in the gas phase, electron donating groups in the ortho and para positions facilitate the reduction of nitrogen dioxide by electronically stabilizing the product phenoxy radical. Hydrogen bonding groups in the ortho position may additionally stabilize the nascent resonantly stabilized radical product, thus enhancing the reaction. Catechol (ortho-hydroxy phenol) has a predicted overall free energy change ΔG(0) = -0.8 kcal mol(-1) and electronic activation energy Ea = 7.0 kcal mol(-1). Free amines at the ortho and para positions have ΔG(0) = -3.8 and -1.5 kcal mol(-1); Ea = 2.3 and 2.1 kcal mol(-1), respectively. The results indicate that the hydrogen abstraction reactions of these substituted phenols by NO2 are fast and spontaneous. Hammett constants produce a linear correlation with bond dissociation energy (BDE) demonstrating that the BDE is the main parameter controlling the dark abstraction reaction. The implications for atmospheric chemistry and ground-level nitrous acid production are discussed. PMID:25325182

  8. Evidence for a snowpack biological source of NOx and HONO to the Arctic boundary layer in Svalbard

    NASA Astrophysics Data System (ADS)

    Amoroso, A.; Domine, F.; Esposito, G.; Morin, S.; Nardino, M.; Montagnoli, M.; Erbland, J.; Savarino, J.; Beine, H.

    2009-04-01

    Nitrogen oxides (NO + NO2) and HONO are among the most reactive species in the polar boundary layer. About a decade ago, the discovery of photochemical production of NOx and HONO in the polar snowpack forced us to consider the role of snowpack emissions to understand the composition of the polar boundary layer. Here we present evidence that NOx and HONO can be emitted by the snowpack to the polar boundary layer in the absence of sunlight. NOx and HONO fluxes were measured at Ny Alesund, Svalbard (79∘N) from mid February (no sunlight) to late April (24 h sunlight). Values were mostly positive (i.e. species transferred from snow to atmosphere) and up to 800 and 120 nmol m-2 h-1, respectively, with the highest values observed in the near absence of sunlight. Mineral ions in surface snow were also analyzed continuously, and snow chemistry data led us to suspect that bacteria were involved in those emissions. The measurements of nitrate isotopic data (δ15N and Δ17O) confirmed that a large fraction of nitrate in most snow layers was not of atmospheric origin, and our interpretation is that is was produced from ammonium by nitrifying bacteria. NO2- is an intermediate in nitrification, and can lead to NO emission by bacteria. NO can be rapidly oxidized to NO2 by ozone in the snowpack. Physical release of HONO from NO2- by the snow also takes place. We therefore suggest that microbial activity in cold snowpacks can lead to the release of significant amounts of reactive species, and deserves consideration in the understanding of polar boundary chemistry and of polar snow chemistry.

  9. Daytime formation of HONO measured close to the surface: Indication for a light driven process?

    NASA Astrophysics Data System (ADS)

    Sörgel, M.; Held, A. B.

    2012-12-01

    The photolysis of HONO is an important primary OH radical source. The OH radical is the most important oxidizing agent, the so called "detergent" of the atmosphere. HONO formation pathways are still unclear (e.g. Sörgel et al., 2011). Nevertheless, the main pathways are believed to be heterogeneous. Thus, the surface is proposed to be a major source. Furthermore, soil emissions of HONO due to microbiological activity in soil (Su et al., 2011) have been proposed and have to be distinguished from the proposed photochemical sources. Therefore, we measured gradients of HONO, NO, NO2 and O3 close to the surface (0.1 to 1.6 m above ground) at the forest floor and on a clearing. We used an automated, programmable moving inlet to measure at 3 or 5 heights between 0.1 m and 1.6 m above the ground. HONO, O3, NO and NO2 were measured simultaneously. HONO was measured with a long path absorption photometer (LOPAP), O3 by UV absorption and NO and NO2 by chemiluminescence with photolytic conversion of NO2. The time resolution of an individual LOPAP measurement was 3 min, and a full profile was measured within 30 min. Additionally, profiles of temperature and relative humidity as well as leaf wetness and j(NO2) were measured. Measurements were conducted at the forest floor and on a clearing at the Waldstein field site of the University of Bayreuth in the Fichtelgebirge Mountains in south-east Germany. Preliminary results are presented. For example, during the day the highest values were often measured close to the ground at the clearing, indicating emission of HONO at the surface. This also indicates that the daytime formation of HONO is heterogeneous or the emissions are due to microbiological activity (Su et al., 2011). During the night, the lowest values were often measured at the surface indicating deposition. Thus, HONO emissions as well as HONO deposition have been observed. The profile data will be analyzed with respect to light intensity, NO2 availability, atmospheric

  10. HONO Measurements in Barrow, Alaska; using LOPAP technique

    NASA Astrophysics Data System (ADS)

    Villena Tapia, G.; Wiesen, P.; Flocke, F. M.; Weinheimer, A. J.; Montzka, D. D.; Knapp, D. J.; Hall, S. R.; Ullmann, K.; Mauldin, L.; Kosciuch, E.; McGrath, J.; Beine, H. J.; Staebler, R. M.; Kleffmann, J.

    2009-12-01

    Nitrous acid (HONO) is an important precursor of the hydroxyl radical (OH) the “cleaning detergent” of the atmosphere. Recent polar studies indicate the existence of a strong surface source of HONO over snow and ice surfaces which can affect the oxidation capacity of the polar atmosphere. However, the mechanism of nitrous acid formation is still under discussion. In addition, from modeling of experimental field data it was recently proposed that high measured HONO levels may be caused, at least in part, by strong interferences of chemical instruments used in polar studies. These high interferences were recently also observed by a LOPAP instrument under simulated polar conditions on the mountain “Jungfraujoch” in the Swiss Alps. In the present study mixing ratios of HONO were measured during the OASIS campaign in Barrow, Alaska from 13th March - 14th April, 2009. The measurements were done with an optimized ultra sensitive Long Path Absorption Photometer (LOPAP), which has two channels in series, correcting for interferences. In addition, sampling artifacts in sampling lines are minimized by the use of an external sampling unit. Mixing ratios were in the range from below detection limit (DL= 0.4 pptV) to ~500 pptV with an average of 27 pptV. The very high concentrations observed were caused by strong emissions from combustion sources close to the field site (City of Barrow and the BARC research complex). For typical clean days the diurnal profile during the campaign was as expected, i.e. low mixing ratios during the night and high mixing ratios during the day which can be explained by photochemical sources.

  11. Measurements of HONO during the OASIS campaign in Barrow, Alaska

    NASA Astrophysics Data System (ADS)

    Villena Tapia, Guillermo; Wiesen, Peter; Kleffmann, Jörg

    2010-05-01

    Nitrous acid (HONO) is an important precursor of the hydroxyl radical (OH). Recent polar studies indicate the existence of a strong surface source of HONO over snow and ice surfaces which can affect the oxidation capacity of the polar atmosphere. However, the mechanism of nitrous acid formation is still under discussion. In addition, from modelling of experimental field data it was recently proposed that high measured HONO levels may be caused, at least in part, by strong interferences of chemical instruments used in polar studies. In the present study mixing ratios of HONO were measured during the OASIS campaign in Barrow, Alaska from 13th March - 14th April, 2009. The measurements were done with an optimized ultra sensitive Long Path Absorption Photometer (LOPAP), which has two channels in series, correcting for the significant chemical interferences under polar conditions, in contrast to other chemical instruments. In addition, sampling artefacts in sampling lines are minimized by the use of an external sampling unit. Mixing ratios were in the range from below detection limit (DL= 0.4 pptV) to ~500 pptV with an average of 27 pptV. The very high concentrations observed were caused by strong emissions from combustion sources close to the field site (the city of Barrow and the BARC research complex). For typical clean days the diurnal profile during the campaign was as expected, i.e. low mixing ratios close to the detection limit during the night and higher mixing ratios (ca. 10 ppt) during the day. Daytime concentrations were higher than the photo-stationary state (PSS) which can be explained by photochemical sources which were found to correlate very well with J(NO2).

  12. Measurements of HONO in a Forested Region of Alberta Impacted by Oil Sands Processing Facilities

    NASA Astrophysics Data System (ADS)

    McLaren, R.; Nikelski, K.; Lobo, A.; Davis, Z.

    2015-12-01

    During the summer of 2013, measurements of NO2, SO2 and HONO were made at a ground site in a rural forested region of Alberta known to be impacted by several oil sands processing facilities. Such sources are known to be the main sources of NOx and SOx emissions in the region. Nitrous acid (HONO) can be emitted directly from combustion sources in addition to being formed from the heterogeneous hydrolysis of NO2 on moist surfaces. The measurements were made both day and night by Differential Optical Absorption Spectroscopy (DOAS) along a 2.304 km optical return path through the forest canopy using a 30-corner cube reflector. Nitrous acid (HONO) is of particular relevance to atmospheric chemistry as it can contribute to photochemical production of the OH radical, the main daytime oxidant in the troposphere, which was estimated to exceed 2•107 molec cm-3 on several days during the study, giving rise to rapid aerosol formation. Typically in urban areas HONO mixing ratios accumulate during the night, and are lost the next morning due to photolysis (HONO + hv→ OH + NO2). During this study however, HONO mixing ratios were found to be quite low with a median nightime mixing ratio of ~ 200 ppt. This is attributed to the very low nighttime NO2 precursor levels, perhaps in combination with a high surface area for deposition on the coniferous canopy. The low nighttime mixing ratios of NO2 and SO2 were driven by limited nocturnal mixing of elevated plumes down to the surface, while high daytime levels of NO2 and SO2 were episodic and frequently driven by daytime fumigation of the elevated plumes to the surface with additional contribution from surface sources of NOx. Daytime mixing ratios of HONO persisted longer than expected with median noontime mixing ratios of >50ppt. While this can imply an additional daytime source of HONO as has been observed by many others, it may also result from reduced photolysis rates below the canopy. This issue is being pursued more

  13. Measurements of Nitrous Acid (HONO) in an Indiana Forest by Laser Photofragmentation/Laser-induced Flourescence (LP/LIF)

    NASA Astrophysics Data System (ADS)

    Bottorff, B.; Stevens, P. S.; Lew, M.; Sigler, P. S. R.; Dusanter, S.

    2015-12-01

    The hydroxyl radical (OH) is an important oxidant in the atmosphere. Reactions of OH with volatile organic compounds (VOCs) initiate a series of reactions that can lead to the production of ozone and secondary aerosols in the atmosphere. An accurate understanding of the major sources of OH is important to develop accurate models of atmospheric chemistry. Nocturnal nitrous acid (HONO) is an important radical resevoir species and releases OH upon photolysis the next morning. Recent studies have indicated higher than expected mixing ratios of HONO during the daytime, suggesting that the production mechanisms of HONO are not fully understood. Additional ambient HONO measurements are necessary to improve our knowledge of the oxidative capacity of the atmosphere. Measurements of HONO were made during summer 2015 using a Laser Photofragmentation/Laser-induced flourescence (LP/LIF) instrument as part of the Indiana Radical, Reactivity and Ozone Production Intercomparison (IRRONIC). This campaign took place in a forested area in the Indiana Research and Teaching Preserve (IURTP) near the Bloomington Campus. In LP/LIF, ambient air is drawn through a 0.035" diameter inlet and expands into a cell held at ~5 torr . HONO within the sampled air mass is photo-fragmented by laser emision at 355 nm and resulting OH fragments are subsequently detected by laser-induced fluorescence at 308 nm. In this presentation the development of the LP/LIF insturment will be discussed and preliminary measurements and model comparisons from the campaign will be presented.

  14. [Monitoring and analysis of vertical profile of atmospheric HONO, NO2 in boundary layer of Beijing].

    PubMed

    Zhu, Yan-Wu; Liu, Wen-Qing; Fang, Jing; Xie, Pin-Hua; Dou, Ke; Qin, Min; Si, Fu-Qi

    2011-04-01

    Based on the scanning differential optical absorption spectroscopy (DOAS) system, field measurement of vertical profiles of HONO and NO2 was performed continuously from Aug. 27, 2007 to Sep. 4, 2007 in Chaoyang District of Beijing, and their vertical profiles were analyzed. Based on the acquired data, the typical vertical variation characteristics of HONO, NO2 and the ratio HONO/NO2 were discussed, and the possible formation sources of HONO were studied. The results indicated that the decrease of HONO with height was faster than the decrease of NO2. The study found good correlation between NO2 and HONO, as well as between the ratio HONO/NO2 and vapor, respectively. Therefore, the authors' conclusion is that HONO was formed by heterogeneous conversion of NO2 on surfaces or near ground and then transported to higher altitudes. PMID:21714264

  15. An Atmospheric Constraint on the NO2 Dependence of Daytime Near-Surface Nitrous Acid (HONO).

    PubMed

    Pusede, Sally E; VandenBoer, Trevor C; Murphy, Jennifer G; Markovic, Milos Z; Young, Cora J; Veres, Patrick R; Roberts, James M; Washenfelder, Rebecca A; Brown, Steven S; Ren, Xinrong; Tsai, Catalina; Stutz, Jochen; Brune, William H; Browne, Eleanor C; Wooldridge, Paul J; Graham, Ashley R; Weber, Robin; Goldstein, Allen H; Dusanter, Sebastien; Griffith, Stephen M; Stevens, Philip S; Lefer, Barry L; Cohen, Ronald C

    2015-11-01

    Recent observations suggest a large and unknown daytime source of nitrous acid (HONO) to the atmosphere. Multiple mechanisms have been proposed, many of which involve chemistry that reduces nitrogen dioxide (NO2) on some time scale. To examine the NO2 dependence of the daytime HONO source, we compare weekday and weekend measurements of NO2 and HONO in two U.S. cities. We find that daytime HONO does not increase proportionally to increases in same-day NO2, i.e., the local NO2 concentration at that time and several hours earlier. We discuss various published HONO formation pathways in the context of this constraint. PMID:26436410

  16. Photoelectron Spectroscopy of cis-Nitrous Acid Anion (cis-HONO(-)).

    PubMed

    Oliveira, Allan M; Lehman, Julia H; McCoy, Anne B; Lineberger, W Carl

    2016-03-17

    We report photoelectron spectra of cis-HONO(-) formed from an association reaction of OH(-) and NO in a pulsed, plasma-entrainment ion source. The experimental data are assigned to the cis-HONO(-) isomer, which is predicted to be the global minimum on the anion potential energy surface. We do not find evidence for a significant contribution from trans-HONO(-). Electron photodetachment of cis-HONO(-) with 1613, 1064, 532, 355, and 301 nm photons accesses the ground X̃ (1)A' (S0) and excited ã (3)A″ (T1) states of neutral HONO. The photoelectron spectrum resulting from detachment forming cis-HONO (S0) exhibits a long vibrational progression, dominated by overtones and combination bands involving the central O-N stretching and ONO bending vibrations. This indicates that there is a significant change in the central O-N bond length between cis-HONO(-) and cis-HONO (S0). The electron affinity (EA) of cis-HONO is determined to be 0.356(8) eV. We also report the dissociation energy (D0) of cis-HONO(-), forming OH(-) + NO, as 0.594(9) eV, which is a factor of 4 decrease in the central O-N bond strength compared to neutral cis-HONO. The T1 state of cis-HONO is shown to be ∼2.3 eV higher in energy than cis-HONO (S0). Electron photodetachment to form cis-HONO (T1) accesses a transition state along the HO-NO bond dissociation coordinate. The resulting photoelectron spectrum exhibits broad peaks spaced by the terminal N═O stretching frequency. Electronic structure calculations and photoelectron spectrum simulations reported here show very good agreement with the experimental data. PMID:26886478

  17. Surface formation of HONO over soil and snow during UBWS 2012, 2014

    NASA Astrophysics Data System (ADS)

    Tsai, J. Y.; Colosimo, S. F.; Spolaor, M.; Cheung, R.; Pikelnaya, O.; Zamora, R. J.; Williams, E. J.; Stutz, J.

    2014-12-01

    The release of HONO from snow in remote polar regions has been known for many years. HONO in the snow is likely formed through chemical processes initiated by the photolysis of nitrate in the snowpack. This source has recently also been invoked to explain high ozone levels observed at wintertime gas-drilling locations. The release of HONO from snowpack would be enhanced in oil and gas fields, where emissions of NOx are significant, thus serving as an important OH precursor and driver of ozone formation. Here we present observations of gradients of HONO mixing ratios using the UCLA LP-DOAS instrument during the Uintah Basin Winter Ozone Studies (UBWOS) in 2012 and 2014. HONO levels were measured at about 25, 45, and 65 m above the ground level. The lack of snow during UBWS 2012 compared to the snowy 2014 conditions allows us to directly study the influence of snow cover on HONO chemistry. Preliminary results show that HONO mixing ratios were comparable during both years, with nighttime hourly averages ranging from 60 ppt to 120ppt and daytime hourly averages close to 50ppt. However, during the snow covered year, we observed a significant peak of HONO (up to 100 ppt in the lowest light path) around 13:00 local time. During this time, a strong HONO vertical gradient was also observed. We will discuss the possible daytime HONO sources responsible for these observations and investigate the role of snow in HONO formation in a polluted environment

  18. Photo-induced formation of nitrous acid (HONO) on protein surfaces

    NASA Astrophysics Data System (ADS)

    Meusel, Hannah; Elshorbany, Yasin; Bartels-Rausch, Thorsten; Selzle, Kathrin; Lelieveld, Jos; Ammann, Markus; Pöschl, Ulrich; Su, Hang; Cheng, Yafang

    2014-05-01

    The study of nitrous acid (HONO) is of great interest, as the photolysis of HONO leads to the OH radical, which is the most important oxidant in the troposphere. HONO is directly emitted by combustion of fossil fuel and from soil biogenic nitrite (Su et al., 2011), and can also be formed by gas phase reactions of NO and OH and heterogeneous reactions of NO2. Previous atmospheric measurements have shown unexpectedly high HONO concentrations during daytime. Measured mixing ratios were about one order of magnitude higher than model simulations (Kleffmann et al. 2005, Vogel et al. 2003). The additional daytime source of HONO might be attributed to the photolysis of adsorbed nitric acid or heterogeneous photochemistry of NO2 on organic substrates, such as humic acids or polyphenolic compounds (Stemmler et al., 2006), or indirectly through nitration of phenols and subsequent photolysis of nitrophenols (Sosedova et al., 2011, Bejan et al., 2006). An important reactive surface for the heterogeneous formation of HONO could involve proteins, which are ubiquitous in the environment. They are part of coarse biological aerosol particles like pollen grains, fine particles (fragments of pollen, microorganism, plant debris) and dissolved in rainwater, soil and road dust (Miguel et al. 1999). In this project a thin film of bovine serum albumin (BSA), a model protein with 67 kDa and 21 tyrosine residues per molecule, is irradiated and exposed to nitrogen dioxide in humidified nitrogen. The formation of HONO is measured with long path absorption photometry (LOPAP). The generated HONO is in the range of 100 to 1100 ppt depending on light intensity, NO2 concentration and film thickness. Light induced HONO formation on protein surfaces is stable over the 20-hours experiment of irradiation and exposure. On the other hand, light activated proteins reacting with NO2 form nitrated proteins, as detected by liquid chromatography (LC-DAD). Our experiments on tetranitromethane (TNM) nitrated

  19. Soil HONO Emissions and Its Potential Impact on the Atmospheric Chemistry and Nitrogen Cycle

    NASA Astrophysics Data System (ADS)

    Su, H.; Chen, C.; Zhang, Q.; Poeschl, U.; Cheng, Y.

    2014-12-01

    Hydroxyl radicals (OH) are a key species in atmospheric photochemistry. In the lower atmosphere, up to ~30% of the primary OH radical production is attributed to the photolysis of nitrous acid (HONO), and field observations suggest a large missing source of HONO. The dominant sources of N(III) in soil, however, are biological nitrification and denitrification processes, which produce nitrite ions from ammonium (by nitrifying microbes) as well as from nitrate (by denitrifying microbes). We show that soil nitrite can release HONO and explain the reported strength and diurnal variation of the missing source. The HONO emissions rates are estimated to be comparable to that of nitric oxide (NO) and could be an important source of atmospheric reactive nitrogen. Fertilized soils appear to be particularly strong sources of HONO. Thus, agricultural activities and land-use changes may strongly influence the oxidizing capacity of the atmosphere. A new HONO-DNDC model was developed to simulate the evolution of HONO emissions in agriculture ecosystems. Because of the widespread occurrence of nitrite-producing microbes and increasing N and acid deposition, the release of HONO from soil may also be important in natural environments, including forests and boreal regions. Reference: Su, H. et al., Soil Nitrite as a Source of Atmospheric HONO and OH Radicals, Science, 333, 1616-1618, 10.1126/science.1207687, 2011.

  20. Understanding the mechanism behind the nitrous acid (HONO) emissions from the northern soils

    NASA Astrophysics Data System (ADS)

    Bhattarai, Hem Raj; Siljanen, Henri MP; Biasi, Christina; Maljanen, Marja

    2016-04-01

    The interest of the flux of nitrous acid (HONO) from soils has recently increased. HONO is an important source of the oxidant OH- radical in the troposphere and thus results a reduction of the greenhouse gas methane (CH4) in the atmosphere. Soils have been recently found to be potential sources of HONO as these emissions are linked to other nitrogen cycle processes, especially presence of nitrite in soils. Ammonia oxidizing archaea (AOA) and ammonia oxidizing bacteria (AOB) have been suggested as possible yet substantial sources of HONO. Along with soil pH, other physical properties such as C:N, nitrogen availability, soil moisture and temperature may effect HONO emissions. Our preliminary results demonstrate that drained acidic peatlands with a low C:N produces higher NO, N2O and HONO emissions compared to those in pristine peatlands and upland forest soils. This study will identify the hotspots and the process involved in HONO emissions in northern ecosystems. Along with HONO, we will examine the emissions of NO and N2O to quantify the related N-gases emitted. These results will add a new piece of information in our knowledge of the nitrogen cycle. Soil samples will be collected from several boreal and arctic sites in Finland, Sweden and Russia. In the laboratory, soil samples will be manipulated based on previously described soil physical properties. This will be followed by labelling experiment coupled with selective nitrification inhibitor experiment in the soils. Our first hypothesis is that northern ecosystems are sources of HONO. Second, is that the soil properties (C:N ratio, moisture, N-availability, pH) regulate the magnitude of HONO emissions from northern soils. Third is that the first step of nitrification (ammonium oxidation) is the main pathway to produce HONO. This study will show that the northern ecosystems could be sources of HONO and therefore increasing the oxidizing capacity of the lower atmosphere.

  1. The Role of Iron-Bearing Minerals in NO2 to HONO Conversion on Soil Surfaces.

    PubMed

    Kebede, Mulu A; Bish, David L; Losovyj, Yaroslav; Engelhard, Mark H; Raff, Jonathan D

    2016-08-16

    Nitrous acid (HONO) accumulates in the nocturnal boundary layer where it is an important source of daytime hydroxyl radicals. Although there is clear evidence for the involvement of heterogeneous reactions of NO2 on surfaces as a source of HONO, mechanisms remain poorly understood. We used coated-wall flow tube measurements of NO2 reactivity on environmentally relevant surfaces (Fe (hydr)oxides, clay minerals, and soil from Arizona and the Saharan Desert) and detailed mineralogical characterization of substrates to show that reduction of NO2 by Fe-bearing minerals in soil can be a more important source of HONO than the putative NO2 hydrolysis mechanism. The magnitude of NO2-to-HONO conversion depends on the amount of Fe(2+) present in substrates and soil surface acidity. Studies examining the dependence of HONO flux on substrate pH revealed that HONO is formed at soil pH < 5 from the reaction between NO2 and Fe(2+)(aq) present in thin films of water coating the surface, whereas in the range of pH 5-8 HONO stems from reaction of NO2 with structural iron or surface complexed Fe(2+) followed by protonation of nitrite via surface Fe-OH2(+) groups. Reduction of NO2 on ubiquitous Fe-bearing minerals in soil may explain HONO accumulation in the nocturnal boundary layer and the enhanced [HONO]/[NO2] ratios observed during dust storms in urban areas. PMID:27409359

  2. HONO measurement by differential photolysis

    NASA Astrophysics Data System (ADS)

    Reed, Chris; Brumby, Charlotte A.; Crilley, Leigh R.; Kramer, Louisa J.; Bloss, William J.; Seakins, Paul W.; Lee, James D.; Carpenter, Lucy J.

    2016-06-01

    Nitrous acid (HONO) has been quantitatively measured in situ by differential photolysis at 385 and 395 nm, and subsequent detection as nitric oxide (NO) by the chemiluminescence reaction with ozone (O3). The technique has been evaluated by Fourier transform infrared (FT-IR) spectroscopy to provide a direct HONO measurement in a simulation chamber and compared side by side with a long absorption path optical photometer (LOPAP) in the field. The NO-O3 chemiluminescence technique is robust, well characterized, and capable of sampling at low pressure, whilst solid-state converter technology allows for unattended in situ HONO measurements in combination with fast time resolution and response.

  3. The relationship between nighttime formation of gaseous HONO and nocturnal stability in an urban environment

    NASA Astrophysics Data System (ADS)

    McLaren, Robert; Wojtal, Patryk; Taylor, Peter

    2014-05-01

    nocturnal mixing suggest that the steady-state may result from an equilibrium between a surface reservoir source of HONO, reminiscent of those observed in the polluted marine boundary layer at night (Wojtal et al., Atmos. Chem. Phys., 11, 3243-3261, 2011).

  4. Evidence for a nitrous acid (HONO) reservoir at the ground surface in Bakersfield, CA, during CalNex 2010

    NASA Astrophysics Data System (ADS)

    VandenBoer, T. C.; Markovic, M. Z.; Sanders, J. E.; Ren, X.; Pusede, S. E.; Browne, E. C.; Cohen, R. C.; Zhang, L.; Thomas, J.; Brune, W. H.; Murphy, J. G.

    2014-07-01

    Measurements of HONO(g) and particulate nitrite (NO2-(p)) were made with a modified Ambient Ion Monitor-Ion Chromatography (AIM-IC) instrument during California at the Nexus of Air Quality and Climate 2010 in Bakersfield, CA (CalNex-San Joaquin Valley (SJV)). Observations of gas and particulate matter (PM2.5) water-soluble composition showed accumulation of both species at night, followed by loss the next day. Intercomparison with a Stripping Coil-UV/Vis Absorption Photometer (SC-AP) demonstrated excellent agreement with the AIM-IC HONO(g) measurement (slope = 0.957, R2 = 0.86), and the particulate nitrite observations were validated to be free of known interferences for wet chemical instrumentation. The accumulation of nitrite into particulate matter was found to be enhanced when gaseous mixing ratios of HONO(g) were highest. Reactive uptake of HONO(g) on to lofted dust and the ground surface, forming a reservoir, is a potential mechanism to explain these observations. The AIM-IC HONO(g) measurements were parameterized in a chemical model to calculate the ground surface daytime HONO(g) source strength at 4.5 m above the surface, found to be on the order of 1.27 ppb h-1, to determine the relative importance of a surface reservoir. If all deposited nighttime HONO(g) is reemitted the following day, up to 30% of the daytime HONO(g) source at CalNex-SJV may be accounted for. The observations of HONO(g) and NO2-(p) in Bakersfield, during CalNex, suggest a surface sink and source of HONO(g). Extension of currently accepted unknown daytime HONO(g) source reactions to include a potential surface HONO(g) reservoir should therefore be sound, but quantitation of the relative contributions of each surface source toward daytime HONO(g) production remains to be resolved.

  5. Evidence of Aerosols as a Media for Rapid Daytime HONO Production over China

    SciTech Connect

    Liu, Zhen; Wang, Yuhang; Costabile, Francesa; Amoroso, Antonio; Zhao, Chun; Huey, L. G.; Stickel, Robert; Liao, Jin; Zhu, Tong

    2014-12-16

    Current knowledge of daytime HONO sources remains incomplete. A large missing daytime HONO source has been found in many places around the world, including polluted regions in China. Conventional understanding and recent studies attributed this missing source mainly to ground surface processes or gas-phase chemistry, while assuming aerosols to be an insignificant media for HONO production. We analyze in situ observations of HONO and its precursors at an urban site in Beijing, China, and report an apparent dependence of the missing HONO source strength on aerosol surface area and solar ultraviolet radiation. Based on extensive correlation analysis and process-modeling, we propose that the rapid daytime HONO production in Beijing can be explained by enhanced hydrolytic disproportionation of NO2 on aqueous aerosol surfaces due to catalysis by dicarboxylic acid anions. The combination of high abundance of NO2, aromatic hydrocarbons, and aerosols over broad regions in China likely leads to elevated HONO levels, rapid OH production, and enhanced oxidizing capacity on a regional basis. Our findings call for attention to aerosols as a media for daytime heterogeneous HONO production in polluted regions like Beijing. This study also highlights the complex and uncertain heterogeneous chemistry in China, which merits future efforts of reconciling regional modeling and laboratory experiments, in order to understand and mitigate the regional particulate and O3 pollutions over China.

  6. Urban measurements of atmospheric nitrous acid: A caveat on the interpretation of the HONO photostationary state

    NASA Astrophysics Data System (ADS)

    Lee, B. H.; Wood, E. C.; Herndon, S. C.; Lefer, B. L.; Luke, W. T.; Brune, W. H.; Nelson, D. D.; Zahniser, M. S.; Munger, J. W.

    2013-11-01

    studies infer the existence of an "unknown" daytime HONO source based on the assumption that HONO is at photostationary state (PSS). Secondary HONO production rate as high as 1.1 ppb hr-1 can be estimated from this approach, based on measurements made during the Study of Houston Atmospheric Radical Precursors campaign in May of 2009. We argue, however, that the PSS assumption might not have been valid because the transport time from nearby NOx emission sources to the measurement site was likely less than the time required for HONO in vehicle exhaust to reach PSS. Using a chemical box model, we demonstrate that there is initially net HONO formation as high levels of NO in exhaust react with ambient OH. Net production is followed by a period of net HONO loss dominated by photolysis that is sustained for several minutes to hours depending on time of day. The presence of relatively fresh exhaust in sampled air can partially, if not fully, account for the observed measurement PSS discrepancy. We also show that a large fraction of the observed nighttime increase in HONO/NOx ratio is explained by NO2 oxidation. These results do not rule out the existence of an unexplained secondary HONO source but suggest that great care must be exercised when applying the PSS method to quantify its strength.

  7. Impact of updated traffic emissions on HONO mixing ratios simulated for urban site in Houston, Texas

    NASA Astrophysics Data System (ADS)

    Czader, B. H.; Choi, Y.; Li, X.; Alvarez, S.; Lefer, B.

    2015-02-01

    Recent measurements in Houston show that HONO traffic emissions are 1.7% of NOx emissions, which is about twice the previously estimated value of 0.8% based on tunnel measurements in 2001. The 0.8% value is widely used to estimate mobile emissions of HONO for air quality modeling applications. This study applies the newly estimated HONO / NOx ratio in the WRF-SMOKE-CMAQ modeling system and estimates the impact of higher HONO traffic emissions on its mixing ratios. Since applied emission inventory resulted in overestimates of NOx mixing ratios and because HONO emissions and chemical formation depend on the magnitude of NOx, thus, before proceeding with HONO emission modifications emissions of NOx were adjusted to reflect current emission trends. The modeled mixing ratios of NOx were evaluated against measured data from a number of sites in the Houston area. Overall, the NOx mean value dropped from 11.11 ppbv in the base case to 7.59 ppbv in the NOx-adjusted case becoming much closer to the observed mean of 7.76 ppbv. The index of agreement (IOA) is improved in the reduced NOx case (0.71 vs. 0.75) and the absolute mean error (AME) is lowered from 6.76 to 4.94. The modeled mixing ratios of HONO were evaluated against the actual observed values attained at the Moody Tower in Houston. The model could not reproduce the morning HONO peaks when the low HONO / NOx ratio of 0.008 was used to estimate HONO emissions. Doubling HONO emissions from mobile sources resulted in higher mixing ratios, and the mean value increased from 0.30 to 0.41 ppbv becoming closer to the observed mean concentrations of 0.69 but still low; AME was slightly reduced from 0.46 to 0.43. IOA for simulation that used the 2001 emission values is 0.63 while for simulation with higher HONO emission it increased to 0.70. Increased HONO emissions from mobile sources resulted in a 14% increase in OH during morning time at the location of the Moody Tower and 3% when averaged over an urban area. The increase

  8. Nitrous acid formation in the urban atmosphere: Gradient measurements of NO2 and HONO over grass in Milan, Italy

    NASA Astrophysics Data System (ADS)

    Stutz, Jochen; Alicke, Björn; Neftel, Albrecht

    2002-10-01

    The source of nitrous acid, HONO, in the troposphere remains uncertain, even after two decades of research. It is currently believed that HONO is formed by heterogeneous conversion of NO2 on either the ground or the aerosol surface. While this conversion has been studied in the laboratory, few atmospheric studies have been reported. Here we present the first simultaneous determination of the vertical gradients and fluxes of HONO, its precursor NO2, and SO2 over a flat grass surface in the polluted atmosphere. The measurements were performed in Milan, Italy, during the Limitation of Oxidant Production/Pianura Padana Produzione di Ozono (LOOP/PIPAPO) study in summer 1998, using differential optical absorption spectroscopy. While deposition of NO2 onto the ground was frequently observed, heterogeneous HONO formation was much smaller than expected. We can explain our observation by a mechanism that consists of a combination of NO2 and HONO deposition, and a heterogeneous conversion of NO2 to HONO on the ground. The compensation point for deposition and formation of HONO is characterized by a HONO/NO2 ratio of ~0.03, indicating that only one HONO molecule is released into the gas phase for every 33 NO2 molecules deposited. Our measurements also show that direct emission of HONO is an important source in strongly polluted areas.

  9. Nitrous acid formation in the urban atmosphere: Gradient measurements of NO2 and HONO over grass in Milan, Italy

    NASA Astrophysics Data System (ADS)

    Stutz, Jochen; Alicke, BjöRn; Neftel, Albrecht

    2002-11-01

    The source of nitrous acid, HONO, in the troposphere remains uncertain, even after two decades of research. It is currently believed that HONO is formed by heterogeneous conversion of NO2 on either the ground or the aerosol surface. While this conversion has been studied in the laboratory, few atmospheric studies have been reported. Here we present the first simultaneous determination of the vertical gradients and fluxes of HONO, its precursor NO2, and SO2 over a flat grass surface in the polluted atmosphere. The measurements were performed in Milan, Italy, during the Limitation of Oxidant Production/Pianura Padana Produzione di Ozono (LOOP/PIPAPO) study in summer 1998, using differential optical absorption spectroscopy. While deposition of NO2 onto the ground was frequently observed, heterogeneous HONO formation was much smaller than expected. We can explain our observation by a mechanism that consists of a combination of NO2 and HONO deposition, and a heterogeneous conversion of NO2 to HONO on the ground. The compensation point for deposition and formation of HONO is characterized by a HONO/NO2 ratio of ˜0.03, indicating that only one HONO molecule is released into the gas phase for every 33 NO2 molecules deposited. Our measurements also show that direct emission of HONO is an important source in strongly polluted areas.

  10. Simultaneous measurements of HONO and NO2 at a rural site in Northern China by IBBCEAS

    NASA Astrophysics Data System (ADS)

    Qin, Min; Duan, Jun; Fang, Wu; Hu, Renzi; Lu, Xue; Shen, Lanlan; Li, Ang; Xie, Pinhua; Liu, Wenqing

    2016-04-01

    HONO arose the interests for its photolysis is an important source of OH radical. However, its source, especially the daytime source is still unclear. With high primary pollutants and aerosol concentrations, the characteristics of air pollutions in China can be expected to be sometimes quite different from the one observed in developed countries. HONO shows high level not only in urban areas but also in rural areas in China. The temporal behavior of HONO and NO2 was investigated at a rural site in Wangdu, Hebei Province, China, by using incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS) during the CAREBEIJING-NCP Campaign from June 26th to July 9th 2014. The concentrations of HONO and NO2 measured by IBBCEAS were compared with a LOPAP (Long Path Absorption Photometer) instrument and a commercial NOx analyzer (Thermo 42i), and the results showed the well correlations for the correlation coefficient (R2) of HONO and NO2 were up to 0.878 and 0.989, respectively. During the measurements, the daytime rapid variations of HONO were found. The peak values of HONO at around noon even unexpected exceed 3ppb and the unknown daytime HONO source strength (PM) reached up to 14 ppb/h, while the concentrations of NO2 were very low (< 5ppb) and the peaks of HONO/NO2 even exceed 100%, which were different from the previous field observations. The possible formations were discussed in this paper, the so high value of daytime HONO could not be explained by the known direct emissions or reactions related to NO2 and might come from soils much possible or the other unknown sources.

  11. Impact of updated traffic emissions on HONO mixing ratios simulated for urban site in Houston, Texas

    NASA Astrophysics Data System (ADS)

    Czader, B. H.; Choi, Y.; Li, X.; Alvarez, S.; Lefer, B.

    2014-08-01

    Recent measurements in Houston show that HONO traffic emissions are 1.7% of NOx emissions which is about twice the previously estimated value of 0.8% based on tunnel measurements in 2001. The 0.8% value is widely used to estimate mobile emissions of HONO for air quality modeling applications. This study applies the newly estimated HONO/NOx ratio in the WRF-SMOKE-CMAQ modeling system and estimates the impact of higher HONO traffic emissions on its mixing ratios. Since applied emission inventory resulted in overestimates of NOx mixing ratios and because HONO emissions and chemical formation depends on the magnitude of NOx, thus, before proceeding with HONO emission modifications emissions of NOx were adjusted to reflect current emission trends. The modeled mixing ratios of NOx were evaluated against measured data from a number of sites in the Houston area. Overall, the NOx mean value dropped from 11.11 ppbv in the base case to 7.59 ppbv in the NOx adjusted case becoming much closer to the observed mean of 7.76 ppbv. The Index of Agreement (IOA) is improved in the reduced NOx case (0.71 vs. 0.75) and the Absolute Mean Error (AME) is lowered from 6.76 to 4.94. The modeled mixing ratios of HONO were evaluated against the actual observed values attained at the Moody Tower in Houston. The model could not reproduce the morning HONO peaks when the low HONO/NOx ratio of 0.008 was used to estimate HONO emissions. Doubling HONO emissions from mobile sources resulted in higher mixing ratios, the mean value increased from 0.30 to 0.41 ppbv becoming closer to the observed mean concentrations of 0.69 but still low; AME was slightly reduced from 0.46 to 0.43. IOA for simulation that used the 2001 emission values is 0.63 while for simulation with higher HONO emission it increased to 0.70. Increased HONO emissions impacted OH mixing ratio, up to about 6% increase was found during morning and mid-day hours. The impact on ozone is marginal. This study results sheds light on the

  12. Quantum chemical study of the O 3-HONO complex

    NASA Astrophysics Data System (ADS)

    Roohi, Hossein; Ashuri, Masomeh

    2009-07-01

    Gas phase hydrogen-bonded isomers of the O 3-HONO complex have been investigated by means of DFT(B3LYP), MP2, MP4(SDTQ), CCSD(T) and QCISD(T) methods in conjunction with the 6-311++G(2d,2p), 6-311++G(df,pd), AUG-cc-pVDZ and AUG-cc-pVTZ basis sets. Ten isomers were found for the O 3-HONO complex. The O⋯H and O⋯O interactions are predicted that participate in the formation of non-planar ring structure of the most stable isomer. The AIM calculations reveal that the O⋯H interaction in the most stable complex is stronger than others. In addition, both O⋯H and O⋯O interactions in O 3-HONO complexes are electrostatic in nature.

  13. Tropospheric HONO Distribution and Chemistry in the Southeastern U.S.

    NASA Astrophysics Data System (ADS)

    Zhou, X.; Ye, C.; Pu, D.; Stutz, J.; Festa, J.; Spolaor, M.; Weinheimer, A. J.; Campos, T. L.; Haggerty, J. A.; Cantrell, C. A.; Mauldin, L.; Guenther, A. B.; Hornbrook, R. S.; Apel, E. C.; Jensen, J. B.

    2014-12-01

    During the NOMADSS field campaign, nitrous acid (HONO) and particulate nitrate (pNO3) was measured on NCAR C-130 research aircraft during five research flights over the Southeast U.S. Aerosol samples were also collected on Teflon filters for the determination of pNO3 photolysis rate constants in the laboratory. Daytime HONO concentrations range from low ppt in free troposphere to 10-20 ppt in the boundary layer in the background air masses, to up to 40 ppt in the industrial and urban plumes. While daytime HONO sink is well defined, dominated by its photolysis, daytime sources vary in different types of air masses: pNO3 photolysis appears to be the major HONO source in the background terrestrial air masses in both the boundary layer and the free troposphere. With an average pNO3 photolysis rate constant of (2.8±1.7)×10-4 s-1, p-NO3 photolysis becomes to be an effective pathway to recycle HNO3 to NOx in the troposphere, with HONO as a dominant intermediate product. Within the high-NOx industrial plumes encountered, HONO is predominantly produced by secondary formation processes involving NOx as the precursor. Away from ground surface, no significant nighttime HONO accumulation exists in the background terrestrial air mass.

  14. Measurements of Nitrous Acid (HONO) Using Ion Drift - Chemical Ionization Mass Spectrometry during the 2009 SHARP Field Campaign

    NASA Astrophysics Data System (ADS)

    Levy, M. E.; Zhang, R.

    2013-12-01

    During the 2009 SHARP Field Campaign in Houston, TX, measurements of HONO were continuously conducted from May 1 to June 1 at a site located on the campus of the University of Houston. We have developed a novel approach for ambient measurements of nitrous acid (HONO) using ion drift - chemical ionization mass spectrometry (ID-CIMS). In our innovative method, HONO is ionized using the sulfur hexafluoride anion, representing the first application of this reagent ion under humid tropospheric conditions. In this presentation, we will discuss the temporal trends and sources of HONO, as well as, as the involvement of HONO in the formation of key atmospheric constituents, such as ozone. Diurnally, HONO concentration accumulates in the late afternoon, reaches a nighttime maximum, and declines rapidly after sunrise; the averaged daytime and nighttime concentrations are 0.15 × 0.05 and 0.26 × 0.04, respectively. The nighttime measured HONO peaks show strong correlations with the NO2 concentration, particle surface area, and soot mass concentration, indicating that the aerosol-phase chemistry represents a significant contributor to the HONO yield. A higher nighttime HONO peak concentration consistently precedes a higher and earlier ozone peak concentration of the following day, by about 20 ppb higher and four hours earlier than those with a lower preceding HONO peak concentration do. Using a kinetic approach, we estimate an uptake coefficient in the range of 6 x 10-4 to 2 x 10-3 for the heterogeneous conversion of NO2 to HONO on aerosol surfaces, which is necessary to account for the measured nighttime HONO peaks. Our results underscore the importance of aerosol heterogeneous chemistry in HONO production and the contributions of this non-photolytic HONO source to the radical budget and the photochemical ozone production in this region. Furthermore, because of its high detection sensitivity and fast-responding time, the ID-CIMS method described in this work may greatly

  15. Atmospheric HONO and NO2 measurement based on a broadband cavity enhanced UV-LED spectrometer

    NASA Astrophysics Data System (ADS)

    Wu, Tao; Zha, Qiaozhi; Chen, Weidong; Xu, Zheng; Wang, Tao; He, Xingdao

    2015-04-01

    Nitrous acid (HONO) is a key component in tropospheric oxidant chemistry due to its contribution to the cycles of nitrogen oxides (NOx) and hydrogen oxides (HOx). Though numerous laboratory, field, and modeling studies were performed to explain the observed HONO concentrations in the atmosphere, the knowledge of atmospheric HONO chemistry is still not well understood and sometimes controversial [1]. Accurate measurements of HONO and its precursors with high precision should aid in understanding the HONO chemistry. In this paper we report on the measurements of HONO and NO2 concentrations at a suburban site of Tung Chung in Hong Kong during a field intercomparison campaign using a broadband cavity enhanced UV-LED spectrometer. 1σ detection limits of 0.3 ppbv for HONO and 1 ppbv for NO2 were achieved with an optimum acquisition time of 120 s. The measured HONO and NO2 concentrations were compared with the data from commercial HONO (LOPAP) and NO2 (NOX-analyzer) measurement instrument. Typical diurnal pattern of HONO have been observed and the potential formation sources have been analyzed [2]. Acknowledgements The supported by National Natural Science Foundation of China (No. 41265011), Educational Commission of Jiangxi Province of China (No.GJJ14548) and Environment and Conservation Fund of the Hong Kong Special Administrative Region (No. 7/2009). The support of the IRENI program of the Région Nord-Pas de Calaisn, is acknowledged. References [1] W. Chen, R. Maamary, X. Cui, T. Wu, E. Fertein, D. Dewaele, F. Cazier, Q. Zha, Z. Xu, T. Wang, Y. Wang, W. Zhang, X. Gao, W. Liu, F. Dong, 'Photonic Sensing of Environmental Gaseous Nitrous Acid (HONO): Opportunities and Challenges' in The Wonder of Nanotechnology: Quantum Optoelectronic Devices and Applications, M. Razeghi. L. Esaki, and K. von Klitzing, Eds., SPIE Press, Bellingham, WA, 2013, pp. 693-737 [2] T. Wu, Q. Zha, W. Chen, Z. XU, T. Wang, X. He, 'Development and deployment of a cavity enhanced UV

  16. The Importance of Nitrous Acid (hono) For Tropospheric Daytime Chemistry In Urban Areas

    NASA Astrophysics Data System (ADS)

    Trick, S.; Geyer, A.; Platt, U.; Bruno, P.; Febo, A.; Acker, K.; Wieprecht, W.

    Nitrous acid (HONO) has been first detected as a typical product of the polluted urban atmosphere about 20 years ago. At this time OH radicals were believed to be formed dominantly by ozone photolysis followed by the reaction with water vapor. Influences of the photolysis of nitrous acid and aldehydes as well as the ozonolysis of alkenes were suggested to be of minor importance for a long time. This was item reasoned by measurements of ozone levels reaching its maximum at noontime, when HONO was found to be below the detection limit at the same time. Here we present the data set and interpretation of an intensive field campaign in May and June 2001 in Rome, Italy during various situations (rainy and clear sky days and photochemical smog events). HONO, NO2, O3, HCHO, NO, SO2, CO, photoly- sis frequencies, aerosol amount and distribution, meteorological data and radon were reported in the city of Rome, at a background station in Rome and in the plume of Rome. During the campaign high HONO daytime levels averaging 200 ppt clear above the detection limits have been measured by three different and independent measurement techniques: Differential Optical Absorption Spectroscopy, Wetted Ef- fluent Diffusion Denuder and High Performance Liquid Chromatography. These mea- surements and first modeling studies give strong evidence that HONO is the most important OH source in urban atmosphere throughout the day. Especially early in the morning, when ozone is still around the detection limit, HONO photolysis was found to initialize photochemical smog events in Rome.

  17. Global and regional impacts of HONO on the chemical composition of clouds and aerosols

    NASA Astrophysics Data System (ADS)

    Elshorban, Y. F.; Crutzen, P. J.; Steil, B.; Pozzer, A.; Tost, H.; Lelieveld, J.

    2013-09-01

    Nitrous acid (HONO) photolysis can significantly increase HOx (OH+HO2) radical formation, enhancing organic and inorganic oxidation products in polluted regions, especially during winter. It has been reported that chemistry-transport models underestimate sulphate concentrations, mostly during winter. Here we show that HONO can significantly enhance aerosol sulphate (S(VI)), mainly due to the increased formation of H2SO4. Even though in-cloud aqueous phase oxidation of dissolved SO2 (S(IV)) is the main source of S(VI), it appears that HONO related enhancement of H2O2 does not significantly affect sulphate because of the predominantly S(IV) limited conditions, except over eastern Asia. Nitrate is also increased via enhanced gaseous HNO3 formation and N2O5 hydrolysis on aerosol particles. Ammonium nitrate is enhanced in ammonia-rich regions but not under ammonia-limited conditions. Furthermore, particle number concentrations are also higher, accompanied by the transfer from hydrophobic to hydrophilic aerosol modes. This implies a significant impact on the particle lifetime and cloud nucleating properties. The HONO induced enhancements of all species studied are relatively strong in winter though negligible in summer. Simulating realistic HONO levels is found to improve the model-measurement agreement of sulphate aerosols, most apparent over the US. Our results underscore the importance of HONO for the atmospheric oxidizing capacity and the central role of cloud chemical processing in aerosol formation.

  18. Global and Regional Impacts of HONO on the Chemical Composition of Clouds and Aerosols

    NASA Technical Reports Server (NTRS)

    Elshorbany, Y. F.; Crutzen, P. J.; Steil, B.; Pozzer, A.; Tost, H.; Lelieveld, J.

    2014-01-01

    Recently, realistic simulation of nitrous acid (HONO) based on the HONO/NO(sub x) ratio of 0.02 was found to have a significant impact on the global budgets of HO(sub x) (OH + HO2) and gas phase oxidation products in polluted regions, especially in winter when other photolytic sources are of minor importance. It has been reported that chemistry-transport models underestimate sulphate concentrations, mostly during winter. Here we show that simulating realistic HONO levels can significantly enhance aerosol sulphate (S(VI)) due to the increased formation of H2SO4. Even though in-cloud aqueous phase oxidation of dissolved SO2 (S(IV)) is the main source of S(VI), it appears that HONO related enhancement of H2O2 does not significantly affect sulphate because of the predominantly S(IV) limited conditions, except over eastern Asia. Nitrate is also increased via enhanced gaseous HNO3 formation and N2O5 hydrolysis on aerosol particles. Ammonium nitrate is enhanced in ammonia-rich regions but not under ammonia-limited conditions. Furthermore, particle number concentrations are also higher, accompanied by the transfer from hydrophobic to hydrophilic aerosol modes. This implies a significant impact on the particle lifetime and cloud nucleating properties. The HONO induced enhancements of all species studied are relatively strong in winter though negligible in summer. Simulating realistic HONO levels is found to improve the model measurement agreement of sulphate aerosols, most apparent over the US. Our results underscore the importance of HONO for the atmospheric oxidizing capacity and corroborate the central role of cloud chemical processing in S(IV) formation.

  19. Global and Regional Impacts of HONO on the Chemical Composition of Clouds and Aerosols

    NASA Technical Reports Server (NTRS)

    Elshorbany, Y. F.; Crutzen, P. J.; Steil, B.; Pozzer, A.; Tost, H.; Lelieveld, J.

    2014-01-01

    Recently, realistic simulation of nitrous acid (HONO) based on the HONO / NOx ratio of 0.02 was found to have a significant impact on the global budgets of HOx (OH + HO2) and gas phase oxidation products in polluted regions, especially in winter when other photolytic sources are of minor importance. It has been reported that chemistry-transport models underestimate sulphate concentrations, mostly during winter. Here we show that simulating realistic HONO levels can significantly enhance aerosol sulphate (S(VI)) due to the increased formation of H2SO4. Even though in-cloud aqueous phase oxidation of dissolved SO2 (S(IV)) is the main source of S(VI), it appears that HONO related enhancement of H2O2 does not significantly affect sulphate because of the predominantly S(IV) limited conditions, except over eastern Asia. Nitrate is also increased via enhanced gaseous HNO3 formation and N2O5 hydrolysis on aerosol particles. Ammonium nitrate is enhanced in ammonia-rich regions but not under ammonia-limited conditions. Furthermore, particle number concentrations are also higher, accompanied by the transfer from hydrophobic to hydrophilic aerosol modes. This implies a significant impact on the particle lifetime and cloud nucleating properties. The HONO induced enhancements of all species studied are relatively strong in winter though negligible in summer. Simulating realistic HONO levels is found to improve the model measurement agreement of sulphate aerosols, most apparent over the US. Our results underscore the importance of HONO for the atmospheric oxidizing capacity and corroborate the central role of cloud chemical processing in S(IV) formation

  20. Global and regional impacts of HONO on the chemical composition of clouds and aerosols

    NASA Astrophysics Data System (ADS)

    Elshorbany, Y. F.; Crutzen, P. J.; Steil, B.; Pozzer, A.; Tost, H.; Lelieveld, J.

    2014-02-01

    Recently, realistic simulation of nitrous acid (HONO) based on the HONO / NOx ratio of 0.02 was found to have a significant impact on the global budgets of HOx (OH + HO2) and gas phase oxidation products in polluted regions, especially in winter when other photolytic sources are of minor importance. It has been reported that chemistry-transport models underestimate sulphate concentrations, mostly during winter. Here we show that simulating realistic HONO levels can significantly enhance aerosol sulphate (S(VI)) due to the increased formation of H2SO4. Even though in-cloud aqueous phase oxidation of dissolved SO2 (S(IV)) is the main source of S(VI), it appears that HONO related enhancement of H2O2 does not significantly affect sulphate because of the predominantly S(IV) limited conditions, except over eastern Asia. Nitrate is also increased via enhanced gaseous HNO3 formation and N2O5 hydrolysis on aerosol particles. Ammonium nitrate is enhanced in ammonia-rich regions but not under ammonia-limited conditions. Furthermore, particle number concentrations are also higher, accompanied by the transfer from hydrophobic to hydrophilic aerosol modes. This implies a significant impact on the particle lifetime and cloud nucleating properties. The HONO induced enhancements of all species studied are relatively strong in winter though negligible in summer. Simulating realistic HONO levels is found to improve the model-measurement agreement of sulphate aerosols, most apparent over the US. Our results underscore the importance of HONO for the atmospheric oxidizing capacity and corroborate the central role of cloud chemical processing in S(IV) formation.

  1. Nitrous acid (HONO) in a polluted subtropical atmosphere: Seasonal variability, direct vehicle emissions and heterogeneous production at ground surface

    NASA Astrophysics Data System (ADS)

    Xu, Zheng; Wang, Tao; Wu, Jueqi; Xue, Likun; Chan, James; Zha, Qiaozhi; Zhou, Shengzhen; Louie, Peter K. K.; Luk, Connie W. Y.

    2015-04-01

    Although nitrous acid (HONO) plays an important role in the chemistry of polluted atmospheres, its atmospheric abundances and sources are still not well understood. This paper reports ambient measurements of HONO taken over four select months in different seasons at a suburban site in Hong Kong. The data were analyzed to elucidate the seasonal characteristics, emission ratios and rates of heterogeneous production. The monthly averaged HONO concentrations ranged from 0.35 ± 0.30 ppbv in late spring (May) to 0.93 ± 0.67 ppbv in late autumn (November). The similar variation patterns of HONO, NOx, and traffic flow from midnight to rush hours suggest that the HONO concentration was strongly influenced by vehicle emissions. The emission ratios (HONO/NOx) were derived from an analysis of 21 fresh plumes (NO/NOx > 0.80), with the range of 0.5-1.6%. The large variability in the emission ratios is attributed to the reaction of NO2 on black carbon (BC) emitted from vehicles, based on a strong correlation between the HONO/NOx and concurrently measured BC. The mean conversion rate of NO2 to HONO on ground surface during nighttime estimated on nine select days was 0.52 × 10-2 h-1, which is relatively low compared with other reported values. This paper highlights a large variability in vehicle emission ratios and heterogeneous conversions of NO2 at ground surface. Photochemical models must consider this variability to better simulate the primary sources of HONO and subsequent photochemistry in the lower part of the troposphere.

  2. The Reduction of HNO3 to HONO by Volatile Organic Compounds Associated with Rush Hour Traffic

    NASA Astrophysics Data System (ADS)

    Rutter, A. P.; Malloy, Q.; Scheuer, E.; Gutierrez, C.; Calzada, M.; Dibb, J. E.; Griffin, R. J.

    2012-12-01

    Nitrous acid (HONO) is an important source of OH radicals in urban environments. However, the sources of HONO are not completely understood, which makes modeling urban atmospheric chemistry difficult. During a previous field study in Houston, TX a correlation was observed between increases in HONO and organic aerosol freshly emitted by motor vehicle traffic during morning rush hours (Ziemba et al., 2010). This source of HONO could not be explained by primary HONO emissions, and the hypothesis was drawn that the HONO was being formed from the reduction of HNO3 by the organic aerosols emitted by motor vehicles. To test this hypothesis, nitric acid (HNO3) was combined in a flow tube with aerosols made from automobile engine oil, which were used as a model for the organic aerosols emitted by rush hour traffic. Reduction of the HNO3 to HONO was observed, although the reaction was found to occur with the volatile organic carbon compounds (VOCs) found in the aerosol vapor, and not the particle surfaces. To explore this further Teflon raschig rings were added to the flow tube to increase surface area but the reaction was not enhanced, confirming the reaction to be homogeneous. The HONO formation observed ranged between 0.1 and 0.5 ppb hr-1 with a mean of 0.3±0.1 ppb hr-1, for typical nitric acid concentrations of 4-5 ppb and estimated concentrations of the reactive components in the engine oil vapor of between 200 and 300 ppt. The observations in this study compared well to the cited field study which observed formation rates between 0.05 and 0.5 ppb hr-1 with an average of 0.3±0.15 ppb hr-1. Water vapor was found to decrease the HONO formation rate by 0.1 ppb hr-1 for every1% of increase in the water mixing ratio. Reference Ziemba L.D., Dibb J.E., Griffin R.J., Anderson C.H., Whitlow S.I., Lefer B.L., Rappenglueck B., and Flynn J. (2010) Heterogeneous conversion of nitric acid to nitrous acid on the surface of primary organic aerosol in an urban atmosphere. Atmospheric

  3. The Exchange of Soil Nitrite and Atmospheric HONO: a Missing Process in the Nitrogen Cycle and Atmospheric Chemistry

    NASA Astrophysics Data System (ADS)

    Cheng, Yafang; Su, Hang; Oswald, Robert; Behrendt, Thomas; Trebs, Ivonne; Meixner, Franz X.; Andreae, Meinrat O.; Pöschl, Ulrich

    2013-04-01

    Hydroxyl radicals (OH) are a key species in atmospheric photochemistry. In the lower atmosphere, up to ~30% of the primary OH radical production is attributed to the photolysis of nitrous acid (HONO), and field observations suggest a large missing source of HONO. The dominant sources of N(III) in soil, however, are biological nitrification and denitrification processes, which produce nitrite ions from ammonium (by nitrifying microbes) as well as from nitrate (by denitrifying microbes). We show that soil nitrite can release HONO and explain the reported strength and diurnal variation of the missing source. We also show that the soil-atmosphere exchange of N(III), though not considered in the N cycle, might result in significant amount of reactive nitrogen emission (comparable to soil NO emissions). Fertilized soils with low pH appear to be particularly strong sources of HONO and OH. Thus, agricultural activities and land-use changes may strongly influence the oxidizing capacity of the atmosphere. Because of the widespread occurrence of nitrite-producing microbes and increasing N and acid deposition, the release of HONO from soil may also be important in natural environments, including forests and boreal regions. In view of the potentially large impact on atmospheric chemistry and global environmental change, we recommend further studies of HONO release from soil nitrite and related processes in the biogeochemical cycling of N in both agricultural and natural environments. Reference: Su, H., Cheng, Y., et al., Soil Nitrite as a Source of Atmospheric HONO and OH Radicals, Science, 333, 1616-1618, 10.1126/science.1207687, 2011. Su, H., et al., The Exchange of Soil Nitrite and Atmospheric HONO: A Missing Process in the Nitrogen Cycle and Atmospheric Chemistry, NATO Science for Peace and Security Series C: Environmental Security, Springer Netherlands, 93-99, 2013.

  4. Uptake of gaseous nitrous acid (HONO) by several plant species

    NASA Astrophysics Data System (ADS)

    Schimang, Ralf; Folkers, Achim; Kleffmann, Jörg; Kleist, Einhard; Miebach, Marco; Wildt, Jürgen

    Uptake of gaseous nitrous acid (HONO) by sunflower ( Heliantus annuus L. var. gigantheus), tobacco ( Nicotiana tabacum L. var. Bel W3), castor ( Rhicinus communis L. var. Carmencita), and birch ( Betula pendula L.) was studied under controlled conditions in a continuously stirred tank reactor. Exposing plants to HONO at concentrations between 60 ppt and 10 ppb led to significant uptake by the plants. The uptake was proportional to HONO concentrations and linearly related to stomatal conductivity. HONO losses at the cuticle were of minor importance. Our data imply a quick metabolism of HONO and it is concluded that the uptake of HONO by plants is only limited by diffusion of HONO through the plants stomata. Comparing results from measurements with and without plants in the chamber it is furthermore concluded that a compensation point for HONO uptake is below 20 ppt if it exists at all. Heterogeneous formation of HONO by reactions of NO 2 on the plant surfaces was either not effective or compensated by the stomatal uptake of HONO. The data of the present study imply that plant surfaces represent a sink for HONO. Therefore, it was concluded that processes on plant surfaces cannot explain HONO formation on ground surfaces as observed in field studies.

  5. [Observational study of atmospheric HONO in summer of Beijing].

    PubMed

    Zhu, Yan-Wu; Liu, Wen-Qing; Xie, Pin-Hua; Dou, Ke; Liu, Shi-Sheng; Si, Fu-Qi; Li, Su-Wen; Qin, Min

    2009-06-15

    The concentration of HONO, NO2, O3 and other atmospheric pollutants were observed continuously by using differential optical absorption spectroscopy (DOAS) from 2007-08-14 to 2007-08-24 in Beijing, China. Diurnal variation characteristics of HONO and NO2 were analyzed. The HONO levels originated from the nocturnal direct emission were discussed. And the correlation between the heterogeneous formation of HONO and its related factors (BC, RH, and so on) was studied. The results showed that HONO had two peaks at about 01:00 and 06:00, respectively, while two peaks of NO2 concentrations appeared at about 01:00 and 07:00. The highest HONO(em)/HONO ratio of 31.3% was observed at about 20:00 between 19:00 to 07:00, and the average ratio was 15%. Good correlation of HONO(corr)/NO2 ratio with BC and RH at night was obtained. The correlation suggested that heterogeneous NO2 to HONO conversion processes may occur on BC surfaces by reaction with absorption water, and the average nighttime conversion frequency from NO2 into HONO (HONO/NO2) was calculated about 0.8% x h(-1). At the same time, the results showed that heterogeneous formation of HONO was increased with RH and inhibited at RH > 80%, and the hypothesis was further supported by detailed analysis of selected case. PMID:19662832

  6. Simultaneous measurements of HONO below and above a spruce forest canopy

    NASA Astrophysics Data System (ADS)

    Sörgel, M.; Trebs, I.; Moravek, A.; Hens, K.; Zetzsch, C.

    2009-04-01

    Nitrous Acid (HONO) plays an important role in atmospheric chemistry because it is easily photolyzed and contributes to OH, the most important oxidizing agent in the atmosphere. Understanding sources and sinks of HONO (especially during daytime) leads to a better estimation of OH-budget. We have performed simultaneous HONO measurements in and above a tall spruce forest canopy using two long path absorption photometers (LOPAPs) at a field site located in the Fichtelgebirge mountains in northeastern Bavaria, Germany (50°09'N, 11°52'E, 775m above sea level). The LOPAP is a wet chemical instrument actively correcting for interferences (Kleffmann et al., 2002). Measurements were made simultaneously with the devices from 13-25 Sep 2007 on a tower (z = 24.25m, above canopy) and in the trunk space (z = 0.48m close to the forest floor). To determine the instrument precisions, both instruments were operated side-by-side in the trunk space at z = 1m, enabling the validation of observed mixing ratio differences in and above the canopy. At HONO levels ranging from 30 ppt to 220 ppt, the two LOPAP instruments agreed within 10% under dry conditions. Both instruments were operating without temperature control under field conditions including rainy, foggy and dry clear sky periods with large temperature variations (5 - 20 °C). Several other micrometeorological and chemical quantities were measured aiming to investigate the coupling between soil, canopy and atmospheric boundary layer. The measured HONO mixing ratios showed typical diel cycles with higher values during nighttime, especially during dry periods. During wet conditions, mixing ratios were significantly lower. Average mixing ratios measured with the LOPAP instruments ranged from 40 ppt to 80 ppt during the day and from 80 ppt to 150 ppt during the night with a higher variability during nighttime, but were found to be independent of NO2 mixing ratios. The average HONO/NO2 ratios are 0.03 both in and above canopy, which

  7. Simultaneous measurements of atmospheric HONO and NO2 via absorption spectroscopy using tunable mid-infrared continuous-wave quantum cascade lasers

    NASA Astrophysics Data System (ADS)

    Lee, B. H.; Wood, E. C.; Zahniser, M. S.; McManus, J. B.; Nelson, D. D.; Herndon, S. C.; Santoni, G. W.; Wofsy, S. C.; Munger, J. W.

    2011-02-01

    Nitrous acid (HONO) is important as a significant source of hydroxyl radical (OH) in the troposphere and as a potent indoor air pollutant. It is thought to be generated in both environments via heterogeneous reactions involving nitrogen dioxide (NO2). In order to enable fast-response HONO detection suitable for eddy-covariance flux measurements and to provide a direct method that avoids interferences associated with derivatization, we have developed a 2-channel tunable infrared laser differential absorption spectrometer (TILDAS) capable of simultaneous high-frequency measurements of HONO and NO2. Beams from two mid-infrared continuous-wave mode quantum cascade lasers (cw-QCLs) traverse separate 210 m paths through a multi-pass astigmatic sampling cell at reduced pressure for the direct detection of HONO (1660 cm-1) and NO2 (1604 cm-1). The resulting one-second detection limits (S/N=3) are 300 and 30 ppt (pmol/mol) for HONO and NO2, respectively. Our HONO quantification is based on revised line-strengths and peak positions for cis-HONO in the 6-micron spectral region that were derived from laboratory measurements. An essential component of ambient HONO measurements is the inlet system and we demonstrate that heated surfaces and reduced pressure minimize sampling artifacts.

  8. HONO and Inorganic Fine Particle Composition in Typical Monsoon Region with Intensive Anthropogenic Emission: In-situ Observations and Source Identification.

    NASA Astrophysics Data System (ADS)

    Xie, Y.; Nie, W.; Ding, A.; Huang, X.

    2015-12-01

    Yangtze River Delta (YRD) is one of the most typical monsoon area with probably the most largest population intensity in the world. With sharply economic development and the large anthropogenic emissions, fine particle pollution have been one of the major air quality problem and may further have impact on the climate system. Though a lot of control policy (sulfur emission have been decreasing from 2007) have been conducted in the region, studies showed the sulfate in fine particles still take major fraction as the nitrate from nitrogen oxides increased significantly. In this study, the role of inorganic chemical compositions in fine particles was investigated with two years in-situ observation. Sulfate and Nitrate contribute to fine particle mass equally in general, but sulfate contributes more during summer and nitrate played more important role in winter. Using lagrangian dispersion backward modeling and source contribution clustering method, the impact of airmass coming from different source region (industrial, dust, biogenic emissions, etc) on fine particle inorganic compositions were discussed. Furthermore, we found two unique cases showing in-situ implications for sulfate formation by nitrogen dioxide oxidation mechanisms. It was showed that the mixing of anthropogenic pollutants with long-range transported mineral dust and biomass burning plume would enhance the sulfate formation by different chemistry mechanisms. This study focus on the complex aspects of fine particle formation in airmasses from different source regions: . It highlights the effect of NOx in enhancing the atmospheric oxidization capacity and indicates a potentially very important impact of increasing NOx on air pollution formation and regional climate change in East Asia.

  9. Intercomparison of Nitrous Acid (HONO) Measurement Techniques during SHARP

    NASA Astrophysics Data System (ADS)

    Pinto, J. P.; Meng, Q.; Dibb, J. E.; Lefer, B. L.; Rappenglueck, B.; Ren, X.; Stutz, J.; Zhang, R.

    2010-12-01

    HONO is regarded as a potentially important radical precursor in a number of diverse environments ranging from polar to semi-tropical. As part of the SHARP (Study of Houston Atmospheric Radical Precursors), time series of HONO were obtained by five different measurement techniques. Techniques used were long path differential optical absorption spectroscopy (DOAS), long-path absorption photometry (LoPAP), mist chamber (MC), quantum cascade laser and ionization detection-chemical ionization mass spectrometry. Various combinations of techniques were in operation during the whole period from 15 April through 31 May 2009 with a common measurement period extending from 16 to 28 May. All instruments recorded a similar diurnal pattern of HONO concentrations with higher mean values from the in-situ techniques than either the low- or mid-path DOAS. The largest differences among techniques were found during the afternoon with measurements from the in-situ techniques higher than either the low- or mid-path DOAS. Principal components analysis using measurements of trace species was used to identify possible sources of interference in the chemical measurements. Two major components were identified: one associated with primary, mainly traffic related pollutants and the other with photochemical species. The afternoon differences between DOAS and MC and the U Miami LoPAP were found to be most strongly associated with the photochemical component. The results for comparison between DOAS and MC are in accord with those found previously during August-September 2006. All instruments showed some association between measurement differences and the primary component. Further details and associations with air coming from different areas of the Houston airshed will also be presented.

  10. Direct measurements of HONO and NO2 by tunable infrared differential absorption spectroscopy; Results from two field campaigns sampling aircraft exhaust and ambient urban air

    NASA Astrophysics Data System (ADS)

    Lee, B. H.; Santoni, G.; Herndon, S. C.; Wood, E. C.; Miake-Lye, R. C.; Munger, J. W.; Wofsy, S. C.; Zahniser, M. S.; McManus, J. B.; Nelson, D. D.

    2009-12-01

    Nitrous acid (HONO) is an important source of hydroxyl radicals (OH), the main oxidizing agent in the atmosphere. However, gaseous HONO has historically proven difficult to measure accurately and to date there is no standard technique. We describe a new instrument capable of high-frequency measurements of HONO and nitrogen dioxide (NO2) mixing ratios by tunable infrared differential absorption spectrometry. Mid-infrared light from two continuous-wave mode quantum cascade lasers traverse a 210 m path through a multi-pass astigmatic cell at reduced pressures for the direct detection of HONO (1660 cm-1) and NO2 (1604 cm-1). We achieve an absorbance precision less than 3×10-6 Hz-1 in one second, which translates to detection limits (S/N=3) of 300 and 30 ppt for HONO and NO2, respectively, in one second. Both lasers and the detector are thermoelectrically cooled, facilitating long-term unattended measurements. We also report preliminary results from two field campaigns; the Alternative Aviation Fuels Experiment (AAFEX) and the Study of Houston Air Radical Precursors (SHARP). At AAFEX, HONO emission ratios relative to CO2 and NOy observed in commercial aircraft exhaust are larger than in most other combustion sources and likely to play a significant role in regional HOx chemistry. Preliminary analysis from the SHARP campaign shows good agreement in HONO and NO2 levels between various measurement techniques.

  11. Intercomparison of HONO Measurements Made Using Wet-Chemical (NITROMAC) and Spectroscopic (IBBCEAS & LP/FAGE) Techniques

    NASA Astrophysics Data System (ADS)

    Dusanter, S.; Lew, M.; Bottorff, B.; Bechara, J.; Mielke, L. H.; Berke, A.; Raff, J. D.; Stevens, P. S.; Afif, C.

    2013-12-01

    A good understanding of the oxidative capacity of the atmosphere is important to tackle fundamental issues related to climate change and air quality. The hydroxyl radical (OH) is the dominant oxidant in the daytime troposphere and an accurate description of its sources in atmospheric models is of utmost importance. Recent field studies indicate higher-than-expected concentrations of HONO during the daytime, suggesting that the photolysis of HONO may be an important underestimated source of OH. Understanding the tropospheric HONO budget requires confidence in analytical instrumentation capable of selectively measuring HONO. In this presentation, we discuss an intercomparison study of HONO measurements performed during summer 2013 at the edge of a hardwood forest in Southern Indiana. This exercise involved a wet chemical technique (NITROMAC), an Incoherent Broad-Band Cavity Enhanced Absorption Spectroscopy instrument (IBBCEAS), and a Laser-Photofragmentation/Fluorescence Assay by Gas Expansion instrument (LP/FAGE). The agreement observed between the three techniques will be discussed for both ambient measurements and cross calibration experiments.

  12. Evaluation of nitrous acid sources and sinks in urban outflow

    NASA Astrophysics Data System (ADS)

    Gall, Elliott T.; Griffin, Robert J.; Steiner, Allison L.; Dibb, Jack; Scheuer, Eric; Gong, Longwen; Rutter, Andrew P.; Cevik, Basak K.; Kim, Saewung; Lefer, Barry; Flynn, James

    2016-02-01

    Intensive air quality measurements made from June 22-25, 2011 in the outflow of the Dallas-Fort Worth (DFW) metropolitan area are used to evaluate nitrous acid (HONO) sources and sinks. A two-layer box model was developed to assess the ability of established and recently identified HONO sources and sinks to reproduce observations of HONO mixing ratios. A baseline model scenario includes sources and sinks established in the literature and is compared to scenarios including three recently identified sources: volatile organic compound-mediated conversion of nitric acid to HONO (S1), biotic emission from the ground (S2), and re-emission from a surface nitrite reservoir (S3). For all mechanisms, ranges of parametric values span lower- and upper-limit values. Model outcomes for 'likely' estimates of sources and sinks generally show under-prediction of HONO observations, implying the need to evaluate additional sources and variability in estimates of parameterizations, particularly during daylight hours. Monte Carlo simulation is applied to model scenarios constructed with sources S1-S3 added independently and in combination, generally showing improved model outcomes. Adding sources S2 and S3 (scenario S2/S3) appears to best replicate observed HONO, as determined by the model coefficient of determination and residual sum of squared errors (r2 = 0.55 ± 0.03, SSE = 4.6 × 106 ± 7.6 × 105 ppt2). In scenario S2/S3, source S2 is shown to account for 25% and 6.7% of the nighttime and daytime budget, respectively, while source S3 accounts for 19% and 11% of the nighttime and daytime budget, respectively. However, despite improved model fit, there remains significant underestimation of daytime HONO; on average, a 0.15 ppt/s unknown daytime HONO source, or 67% of the total daytime source, is needed to bring scenario S2/S3 into agreement with observation. Estimates of 'best fit' parameterizations across lower to upper-limit values results in a moderate reduction of the unknown

  13. Effect of Coatings on the Uptake Rate and HONO Yield in Heterogeneous Reaction of Soot with NO2

    NASA Astrophysics Data System (ADS)

    Cruz-Quiñones, M.; Khalizov, A. F.; Zhang, R.

    2009-12-01

    Heterogeneous reaction of nitrogen dioxide on carbon soot aerosols has been suggested as a possible source of nighttime nitrous acid (HONO) in atmosphere boundary layer. Available laboratory data show significant variability in the measured reaction probabilities and HONO yields, making it difficult to asses the atmospheric significance of this process. Moreover, little is known of how aging of soot aerosol through internal mixing with other atmospheric trace constituents will affect the heterogeneous reactivity and HONO production. In this work, the heterogeneous reaction of NO2 on fresh and aged soot films leading to HONO formation was studied through a series of kinetic uptake experiments and HONO yield measurements. Soot samples were prepared by incomplete combustion of propane and kerosene fuels under lean and rich flame conditions. Experiments were performed in a low-pressure, fast-flow reactor coupled to a chemical ionization mass spectrometer (CIMS), using atmospheric-level NO2 concentrations. Heterogeneous uptake coefficients, γ(geom) and γ(BET), were calculated using geometric and internal BET soot surface areas, respectively. The uptake coefficient and the HONO yield depend on the type of fuel and combustion regime and are the highest for soot samples prepared using rich kerosene flame. Although, the internal surface area of soot measured by BET method is a factor of 50 to 500 larger than the geometric surface area, only the top soot layers are involved in heterogeneous reaction with NO2 as follows from the observed weak dependence of γ(geom) and decrease in γ(BET) with increasing sample mass. Heating the soot samples before exposure to NO2 increases the BET surface area, the HONO yield, and the NO2 uptake coefficient due to the removal of the organic fraction from the soot backbone that unblocks active sites and makes them accessible for physical adsorption and chemical reactions. Our results support the oxidation-reduction mechanism involving

  14. Intercomparison of HONO SCDs and profiles from MAX-DOAS observations during the MAD-CAT campaign and comparison to chemical model simulations

    NASA Astrophysics Data System (ADS)

    Wang, Yang; Wagner, Thomas; Xie, Pinhua; Remmers, Julia; Li, Ang; Lampel, Johannes; Friess, Udo; Peters, Enno; Wittrock, Folkard; Richter, Andreas; Hilboll, Andreas; Volkamer, Rainer; Ortega, Ivan; Hendrick, Francois; Van Roozendael, Michel; Ma, Jianzhong; Jin, Junli; Su, Hang; Cheng, Yafang

    2015-04-01

    In order to promote the development of the passive DOAS technique and to improve the retrieval algorithms of trace gases and aerosols the Multi Axis DOAS - Comparison campaign for Aerosols and Trace gases (MAD-CAT) was held at the Max Planck Institute for Chemistry in Mainz, Germany from June to October 2013. MAX-DOAS (Multi-Axis Differential Optical Absorption Spectroscopy) instruments of various designs recorded UV-visible spectra of scattered sunlight at different elevation and azimuth angles. We present intercomparison results for slant column densities (SCDs) of nitrous acid (HONO) retrieved during this campaign by several research groups. Data analysis was performed in two steps, starting with the preferred settings of the individual groups, followed by an analysis using common retrieval settings. In general good agreement of the resulting HONO SCD sets was found. Furthermore, we performed various sensitivity analyses to improve and evaluate the uncertainties in the HONO SCD retrieval, such as the influence of the wavelength dependence of the NO2 air mass factor, the selection of the wavelength interval of the retrieval, the choice of the Fraunhofer reference spectrum, or the offset correction. Finally we compared the results from different kinds of inversion algorithms for the vertical profiles of trace gases and aerosols. The derived HONO profiles, VMR near surface and tropospheric vertical column densities are compared with each other and with the results of regional chemical model simulations. We found a high HONO VMR near surface of about 200 ppt, which is much higher than the typical daytime VMR of lower than 10 ppt at the early noon (around 9:30 local time), probably indicating a strong source of HONO. The strong vertical gradient in the profile of HONO VMR probably indicates the HONO source is close to the surface.

  15. Observations of nitrous acid (HONO) and peroxynitric acid (HO2NO2) made during the 2013 and 2014 Uintah Basin Winter Ozone Study (UBWOS)

    NASA Astrophysics Data System (ADS)

    Veres, P. R.; Roberts, J. M.; Alvarez, S. L.; Brown, S. S.; Burkholder, J. B.; De Gouw, J. A.; Edwards, P. M.; Lefer, B. L.; Liggio, J.; Min, K. E.; Stutz, J.; Tsai, J. Y.; Colosimo, S. F.; Wentzell, J. J. B.; Wild, R. J.; Yuan, B.; Flynn, J. H., III

    2014-12-01

    HONO is frequently observed to be the main OH source in the early morning, with more recent urban measurements showing significant rates of daytime production. Quantifying the impact of HONO as a source of daytime oxidant is crucial to forming a more explicit understanding of tropospheric ozone formation. In this work, ambient observations of HONO were made during the 2013 and 2014 Uintah Basin Wintertime Ozone Study (UBWOS) at a field site in Utah using various analytical techniques including chemical ionization mass spectrometry (CIMS), differential optical absorption spectroscopy (DOAS), cavity enhanced absorption spectroscopy (CEAS), and long path absorption photometry (LOPAP). Observations of HONO and HO2NO2 will be presented and compared to model results using a chemical box model applying explicit MCM chemistry to describe an ozone formation event observed during the 2013 wintertime season. Strong inversions leading to a build-up of many primary and secondary pollutants as well as low temperatures drove daytime HO2NO2 observations as high as 1.5 ppbv during the 2013 study. The potential of these high HO2NO2 concentrations as an interference to the various HONO measurements techniques will be discussed. Daytime HONO observations will be presented and analyzed with respect to coinciding vertical gradients, sampling artifacts, and potential instrumental interferences.

  16. In-Situ (MC/IC) and Remote (Long-Path DOAS) Measurements of HONO During TRAMP.

    NASA Astrophysics Data System (ADS)

    Whitlow, S. I.; Anderson, C. H.; Dibb, J. E.; Oh, H.; Stutz, J.

    2007-12-01

    Nitrous acid is an important component of night-time N-oxide chemistry, and provides a significant source of both OH and NO in polluted urban airmasses shortly after sunrise. Several recent studies have called for new sources of HONO to account for daytime levels much higher than are consistent with current understanding. However, measurement of HONO is problematic, with most in-situ techniques reporting higher values than simultaneous optical measurements by long-path DOAS, especially during daytime. The discrepancy has been attributed to: positive interference in the in-situ techniques, negative interference in DOAS retrievals, the difficulty of comparing the different airmasses sampled by the methods, or combinations of these. During August and September, 2006, HONO mixing ratios from collocated long-path DOAS and automated mistchamber-ion chromatograph (MC/IC) systems ranged from several ppbv during morning rush hour to daytime minima near 100 pptv. Agreement between the two techniques was excellent across this entire range during many days, giving us confidence that both instruments accurately measured HONO during this campaign. Discrepancies that were observed during some nights can be explained by vertical mixing of HONO. Daytime discrepancies during several days in late August/early September are more difficult to explain, but perhaps informative. It should be noted that in previous campaigns at South Pole (summertime) and central Greenland (springtime) HONO mixing ratios in the 10-30 pptv range from the MC/IC were suggested to be too high (compared to NOx and OH) due to unknown interferants. The results from Houston suggest that the polar interferants either do not scale with NOx in urban air, or are thermally labile, hence too-short lived in Houston to be significant.

  17. 17 CFR 38.801 - Additional sources for compliance.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 17 Commodity and Securities Exchanges 1 2013-04-01 2013-04-01 false Additional sources for compliance. 38.801 Section 38.801 Commodity and Securities Exchanges COMMODITY FUTURES TRADING COMMISSION DESIGNATED CONTRACT MARKETS Governance Fitness Standards § 38.801 Additional sources for...

  18. 17 CFR 38.258 - Additional sources for compliance.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 17 Commodity and Securities Exchanges 1 2013-04-01 2013-04-01 false Additional sources for compliance. 38.258 Section 38.258 Commodity and Securities Exchanges COMMODITY FUTURES TRADING COMMISSION DESIGNATED CONTRACT MARKETS Prevention of Market Disruption § 38.258 Additional sources for...

  19. Intercomparison of field measurements of nitrous acid (HONO) during the SHARP campaign

    NASA Astrophysics Data System (ADS)

    Pinto, J. P.; Dibb, J.; Lee, B. H.; Rappenglück, B.; Wood, E. C.; Levy, M.; Zhang, R.-Y.; Lefer, B.; Ren, X.-R.; Stutz, J.; Tsai, C.; Ackermann, L.; Golovko, J.; Herndon, S. C.; Oakes, M.; Meng, Q.-Y.; Munger, J. W.; Zahniser, M.; Zheng, J.

    2014-05-01

    Because of the importance of HONO as a radical reservoir, consistent and accurate measurements of its concentration are needed. As part of SHARP (Study of Houston Atmospheric Radical Precursors), time series of HONO were obtained by six different measurement techniques on the roof of the Moody Tower at the University of Houston. Techniques used were long path differential optical absorption spectroscopy (DOAS), stripping coil-visible absorption photometry (SC-AP), long path absorption photometry (LOPAP®), mist chamber/ion chromatography (MC-IC), quantum cascade-tunable infrared laser differential absorption spectroscopy (QC-TILDAS), and ion drift-chemical ionization mass spectrometry (ID-CIMS). Various combinations of techniques were in operation from 15 April through 31 May 2009. All instruments recorded a similar diurnal pattern of HONO concentrations with higher median and mean values during the night than during the day. Highest values were observed in the final 2 weeks of the campaign. Inlets for the MC-IC, SC-AP, and QC-TILDAS were collocated and agreed most closely with each other based on several measures. Largest differences between pairs of measurements were evident during the day for concentrations < ~100 parts per trillion (ppt). Above ~ 200 ppt, concentrations from the SC-AP, MC-IC, and QC-TILDAS converged to within about 20%, with slightly larger discrepancies when DOAS was considered. During the first 2 weeks, HONO measured by ID-CIMS agreed with these techniques, but ID-CIMS reported higher values during the afternoon and evening of the final 4 weeks, possibly from interference from unknown sources. A number of factors, including building related sources, likely affected measured concentrations.

  20. Nitrogen Oxides in the Nocturnal Boundary Layer: Chemistry of Nitrous Acid (HONO) and the Nitrate Radical (N03)

    SciTech Connect

    Jochen Stutz

    2005-05-24

    dependent. Measurements at one altitude, for example at the ground, where most air quality monitoring stations are located, are not representative for the rest of the NBL. Our model also revealed that radical chemistry is, in general, altitude dependent at night. We distinguish three regions: an unreactive, NO rich, ground layer; an upper, O3 and NO3 dominated layer, and a reactive mixing layer, where RO2 radicals are mixed from aloft with NO from the ground. In this reactive layer an active radical chemistry and elevated OH radical levels can be found. The downward transport of N2O5 and HO2NO2, followed by their thermal decay, was also identified as a radical source in this layer. Our observations also gave insight into the formation of HONO in the NBL. Based on our field experiments we were able to show that the NO2 to HONO conversion was relative humidity dependent. While this fact was well known, we found that it is most likely the uptake of HONO onto surfaces which is R.H. dependent, rather than the NO2 to HONO conversion. This finding led to the proposal of a new NO2 to HONO conversion mechanism, which is based on solid physical chemical principles. Noteworthy is also the observation of enhanced NO2 to HONO conversion during a dust storm event in Phoenix. The final activity in our project investigated the influence of the urban canopy, i.e. building walls and surfaces, on nocturnal chemistry. For the first time the surface area of a city was determined based on a Geographical Information System database of the city of Santa Monica. The surface to volume areas found in this study showed that, in the 2 lower part of the NBL, buildings provide a much larger surface area than the aerosol. In addition, buildings take up a considerable amount of the volume near the ground. The expansion of our model and sensitivity studies based on the Santa Monica data revealed that the surface area of buildings considerably influences HONO levels in urban areas. The volume reduction leads

  1. Impacts of an unknown daytime nitrous acid source on its daytime concentration and budget, as well as those of hydroxyl, hydroperoxyl, and organic peroxy radicals, in the coastal regions of China

    NASA Astrophysics Data System (ADS)

    Tang, Y.; An, J.; Wang, F.; Li, Y.; Qu, Y.; Chen, Y.; Lin, J.

    2015-01-01

    Many field experiments have found high nitrous acid (HONO) mixing ratios in both urban and rural areas during daytime, but these high daytime HONO mixing ratios cannot be explained well by gas-phase production, suggesting that an unknown daytime HONO source (Punknown) could exist. The formula Punknown ≈ 19.60 × NO2 × J(NO2) was obtained using observed data from 13 field experiments across the globe. The additional HONO sources (i.e. the Punknown, HONO emissions, and nighttime hydrolysis conversion of nitrogen dioxide (NO2) on aerosols) were coupled into the WRF-Chem model (Weather Research and Forecasting model coupled with Chemistry) to assess the Punknown impacts on the concentrations and budgets of HONO and peroxy (hydroxyl, hydroperoxyl, and organic peroxy) radicals (ROx) (= OH + HO2 + RO2) in the coastal regions of China. Results indicated that the additional HONO sources produced a significant improvement in HONO and OH simulations, particularly in the daytime. Elevated daytime-mean Punknown values were found in the coastal regions of China, with a maximum of 2.5 ppb h-1 in the Beijing-Tianjin-Hebei region. The Punknown produced a 60-250% increase of OH, HO2 and RO2 near the ground in the major cities of the coastal regions of China, and a 5-48% increase of OH, HO2 and RO2 in the daytime meridional-mean mixing ratios within 1000 m above the ground. When the additional HONO sources were included, the photolysis of HONO was dominated in the OH production rate in Beijing, Shanghai and Guangzhou before 10:00 LST with a maximum of 10.01 [7.26 due to the Punknown] ppb h-1 in Beijing, whereas the reaction of HO2 + NO (nitric oxide) was dominated after 10:00 LST with a maximum of 9.38 [7.23] ppb h-1 in Beijing. The whole ROx cycle was accelerated by the additional HONO sources, especially the Punknown. The OH production rate was enhanced by 0.67 [0.64] to 4.32 [3.86] ppb h-1 via the reaction of HO2 + NO, and by 0.85 [0.69] to 4.11 [3.61] ppb h-1 via the

  2. Impacts of a strong cold front on concentrations of HONO, HCHO, O 3, and NO 2 in the heavy traffic urban area of Beijing

    NASA Astrophysics Data System (ADS)

    An, Junling; Zhang, Wei; Qu, Yu

    Much rain and strong winds caused by a cold front occurred in Beijing during the period of Sep. 27 to Oct. 4, 2004 and led to sharp drops in maximum and mean concentrations of HONO, HCHO, O 3, and NO 2, i.e., the maximum concentrations were reduced by 5.9, 21.3, 45.6, and 44.4 ppb, respectively, and the mean concentrations were decreased by 4.0, 5.5, 30.3, and 32.3 ppb, respectively. For daily HO x production rates HONO photolysis was the largest contributor and over 90% contributions were from photolysis of HONO and HCHO. Large number and area percentages of soot aggregate from PM10, and high correlations between concentrations of PM10 and chemical formation of HONO suggested that heterogeneous reactions of NO 2 on surfaces of soot aggregate could be a key source of HONO in the heavy traffic areas of Beijing during the night and should be considered in air quality simulations for such areas.

  3. Characterization and Application of an Ambient Ion Monitor - Ion Chromatography (AIM-IC) System for the Detection of HONO and Nitrite in Polluted Environments

    NASA Astrophysics Data System (ADS)

    Vandenboer, T. C.; Markovic, M. Z.; Czar, M.; Murphy, J. G.

    2008-12-01

    The photolysis of the atmospheric trace gas nitrous acid (HONO) has been implicated as a major source of the OH radical, especially in early morning hours. While this rapid photolysis is expected to drive HONO concentrations to nearly zero during the day, significant concentrations have been observed in a variety of environments, indicating unknown or underestimated daytime sources. However, chemical interferences and lack of instrumental sensitivity make quantification of ambient HONO a true analytical challenge. During the Border Air Quality Study (BAQS) in 2007 near Harrow, ON observations frequently indicated low but non-zero mixing ratios of HONO and the presence of comparable amounts of particulate nitrite. Online, automated analysis of trace gases and PM2.5 constituents, was accomplished using Ambient Ion Monitor Ion Chromatography (AIM-IC) with collection by means of a parallel plate denuder and super saturated steam particle condensation chamber. The system was operated with one hour time resolution and was capable of characterizing 16 analyte ions. Subsequent method characterization yielded detection limits of 0.012 μg/m3 for particulate NO2- and 10 ppt for HONO by the isocratic elution methodology used in the Harrow field study. Laboratory experiments following this field campaign show that the collection efficiency of these species presented a source of uncertainty in observations of these trace gases. Interferences due to the presence of high NOX have also been explored. The method has since been used to characterize the effectiveness of particulate and gaseous collection between impactor and cyclone inlet assemblies. Finally, the optimized analytical system has been used to make measurements of HONO and nitrite in an urban setting in Toronto, ON.

  4. Influence of biomass burning plumes on HONO chemistry in eastern China

    NASA Astrophysics Data System (ADS)

    Nie, W.; Ding, A. J.; Xie, Y. N.; Xu, Z.; Mao, H.; Kerminen, V.; Zheng, L. F.; Qi, X. M.; Yang, X. Q.; Sun, J. N.; Herrmann, E.; Petäjä, T.; Kulmala, M.; Fu, C. B.

    2014-03-01

    Nitrous acid (HONO) plays a key role in atmospheric chemistry via influencing the budget of hydroxyl radical (OH). In this study, a two-month measurement period of HONO and related quantities were analyzed during a biomass burning season in 2012 at a suburban site in the western Yangtze River delta, eastern China. An overall high HONO concentration with the mean value of 1.1 ppbv was observed. During biomass burning (BB) periods, both HONO concentration and HONO / NO2 ratio were enhanced significantly compared with non-biomass burning periods. A correlation analysis showed that the HONO concentration was not associated potassium (a tracer of BB) in BB plumes, but showed a high correlation with the NO2 concentration, suggesting a principle role of secondary production rather than direct emissions in elevated HONO concentrations. A further analysis based on comparing the surface area at similar PM levels and HONO / NO2 ratios at similar surface area levels suggested larger specific surface areas and higher NO2 conversion efficiencies of BB aerosols. A mixed plume of BB and anthropogenic fossil fuel (FF) emissions was observed on 10 June with even higher HONO concentrations and HONO / NO2 ratios. The strong HONO production potential (high HONO / NO2 to PM2.5 ratio) was accompanied with a high sulfate concentration in this plume, suggesting a promotion of mixed aerosols to HONO formation. In summary, our study suggests an important role of BB in atmospheric oxidation capacity by affecting the HONO budget. This can be especially important in eastern China, where agricultural burning plumes are inevitably mixed with urban pollutions.

  5. [Study on contribution factor to atmospheric .OH by O3, HONO, HCHO and H2O2 in spring at Mangdang Mountain, Fujian Province].

    PubMed

    Liu, Hao; Wang, Hui-xiang

    2013-09-01

    The observation was conducted in Mangdang Mountain, Nanping, Fujian Province in the spring of 2009. Ozone, HONO, HCHO and H2O2 which are regarded as the sources of .OH and other atmospheric components were measured. Mixing ratios of O3, HCHO, HONO and H2O2 were determined to be 4.96 x 10(-8), 3.97 x 10(-10), 2. 53 x 10(-10) and 1.18 x 10(10) respectively, which were lower than the previous observation at the rural areas in Northern China. Using CMAQ, the contribution factors to the .OH of O3, HCHO, HONO, and H2O2 were calculated to be 57.0%, 7.7%, 34.9% and 0.4% respectively. The photolysis of O3 was the most important source of OH radicals in the atmosphere. The contribution factors of O3, HCHO, and H2O2 had a single peak during 12:00-13:00 local time. For HONO, the contribution factor showed fluctuations during the daytime, unlike the human living environment in which it peaked in the morning. PMID:24288975

  6. Influence of biomass burning plumes on HONO chemistry in eastern China

    NASA Astrophysics Data System (ADS)

    Nie, W.; Ding, A. J.; Xie, Y. N.; Xu, Z.; Mao, H.; Kerminen, V.-M.; Zheng, L. F.; Qi, X. M.; Huang, X.; Yang, X.-Q.; Sun, J. N.; Herrmann, E.; Petäjä, T.; Kulmala, M.; Fu, C. B.

    2015-02-01

    Nitrous acid (HONO) plays a key role in atmospheric chemistry by influencing the budget of hydroxyl radical (OH). In this study, a two-month measurement of HONO and related quantities were analyzed during a biomass burning season in 2012 at a suburban site in the western Yangtze River delta, eastern China. An overall high HONO concentration with the mean value of 0.76 ppbv (0.01 ppbv to 5.95 ppbv) was observed. During biomass burning (BB) periods, both HONO concentration and HONO/NO2 ratio were enhanced significantly (more than a factor of 2, p < 0.01) compared with non-biomass burning (non-BB) periods. A correlation analysis showed that the HONO in BB plumes was more correlated with nitrogen dioxide (NO2) than that with potassium (a tracer of BB). Estimation by the method of potassium tracing suggests a maximum contribution of 17 ± 12% from BB emission to the observed HONO concentrations, and the other over 80% of the observed nighttime HONO concentrations during BB periods were secondarily produced by the heterogeneous conversion of NO2. The NO2-to-HONO conversion rate (CHONO) in BB plumes was almost twice as that in non-BB plumes (0.0062 hr-1 vs. 0.0032 hr-1). Given that the residence time of the BB air masses was lower than that of non-BB air masses, these results suggest BB aerosols have higher NO2 conversion potentials to form HONO than non-BB aerosols. A further analysis based on comparing the surface area at similar particle mass levels and HONO/NO2 ratios at similar surface area levels suggested larger specific surface areas and higher NO2 conversion efficiencies of BB aerosols. A mixed plume of BB and anthropogenic fossil fuel (FF) emissions was observed on 10 June with even higher HONO concentrations and HONO/NO2 ratios. The strong HONO production potential (high HONO/NO2 to PM2.5 ratio) was accompanied with a high sulfate concentration in this plume, suggesting a promotion of mixed aerosols to the HONO formation. In summary, our study suggests an

  7. Percolation model with an additional source of disorder.

    PubMed

    Kundu, Sumanta; Manna, S S

    2016-06-01

    The ranges of transmission of the mobiles in a mobile ad hoc network are not uniform in reality. They are affected by the temperature fluctuation in air, obstruction due to the solid objects, even the humidity difference in the environment, etc. How the varying range of transmission of the individual active elements affects the global connectivity in the network may be an important practical question to ask. Here a model of percolation phenomena, with an additional source of disorder, is introduced for a theoretical understanding of this problem. As in ordinary percolation, sites of a square lattice are occupied randomly with probability p. Each occupied site is then assigned a circular disk of random value R for its radius. A bond is defined to be occupied if and only if the radii R_{1} and R_{2} of the disks centered at the ends satisfy a certain predefined condition. In a very general formulation, one divides the R_{1}-R_{2} plane into two regions by an arbitrary closed curve. One defines a point within one region as representing an occupied bond; otherwise it is a vacant bond. The study of three different rules under this general formulation indicates that the percolation threshold always varies continuously. This threshold has two limiting values, one is p_{c}(sq), the percolation threshold for the ordinary site percolation on the square lattice, and the other is unity. The approach of the percolation threshold to its limiting values are characterized by two exponents. In a special case, all lattice sites are occupied by disks of random radii R∈{0,R_{0}} and a percolation transition is observed with R_{0} as the control variable, similar to the site occupation probability. PMID:27415234

  8. Percolation model with an additional source of disorder

    NASA Astrophysics Data System (ADS)

    Kundu, Sumanta; Manna, S. S.

    2016-06-01

    The ranges of transmission of the mobiles in a mobile ad hoc network are not uniform in reality. They are affected by the temperature fluctuation in air, obstruction due to the solid objects, even the humidity difference in the environment, etc. How the varying range of transmission of the individual active elements affects the global connectivity in the network may be an important practical question to ask. Here a model of percolation phenomena, with an additional source of disorder, is introduced for a theoretical understanding of this problem. As in ordinary percolation, sites of a square lattice are occupied randomly with probability p . Each occupied site is then assigned a circular disk of random value R for its radius. A bond is defined to be occupied if and only if the radii R1 and R2 of the disks centered at the ends satisfy a certain predefined condition. In a very general formulation, one divides the R1-R2 plane into two regions by an arbitrary closed curve. One defines a point within one region as representing an occupied bond; otherwise it is a vacant bond. The study of three different rules under this general formulation indicates that the percolation threshold always varies continuously. This threshold has two limiting values, one is pc(sq) , the percolation threshold for the ordinary site percolation on the square lattice, and the other is unity. The approach of the percolation threshold to its limiting values are characterized by two exponents. In a special case, all lattice sites are occupied by disks of random radii R ∈{0 ,R0} and a percolation transition is observed with R0 as the control variable, similar to the site occupation probability.

  9. 10 CFR 1.3 - Sources of additional information.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    .../cfr/. Final opinions made in the adjudication of cases are published in “Nuclear Regulatory Commission... Regional Offices. In addition, NRC Functional Organization Charts, NUREG-0325, contains...

  10. Measurements of nitrous acid (HONO) in urban area of Shanghai, China.

    PubMed

    Bernard, François; Cazaunau, Mathieu; Grosselin, Benoît; Zhou, Bin; Zheng, Jun; Liang, Peng; Zhang, Yujie; Ye, Xingnan; Daële, Véronique; Mu, Yujing; Zhang, Renyi; Chen, Jianmin; Mellouki, Abdelwahid

    2016-03-01

    Nitrous acid (HONO), as a precursor of the hydroxyl radical (OH), plays an important role in the photochemistry of the troposphere, especially in the polluted urban atmosphere. A field campaign was conducted to measure atmospheric HONO concentration and that of other pollutants (such as NO2 and particle mass concentration) in the autumn of 2009 at Shanghai urban areas. HONO mixing ratios were simultaneously measured by three different techniques: long path absorption photometer (LOPAP), differential optical absorption spectroscopy (DOAS) and chemical ionization mass spectrometer (CIMS). The measurements showed that the mixing ratios of HONO were highly variable and depended strongly on meteorological parameters. The HONO levels ranged from 0.5 to 7 ppb with maximum values during early morning and minimum levels during late afternoon. The three instruments reproduced consistent diurnal pattern of HONO concentrations with higher concentration during the night compared to the daylight hours. Comparison of HONOLOPAP/HONOCIMS ratios during daytime and nighttime periods exhibited a non-systematic disagreement of 0.93 and 1.16, respectively. This would indicate different chemical compositions of sampled air for the LOPAP and the CIMS instruments during daytime and nighttime periods, which have possibly affected measurements. Mean HONO concentration reported by LOPAP was 33 % higher than by DOAS on the whole period with no significant difference between daytime and nighttime periods. This revealed a systematic deviation from both instruments. The present data provides complementary information of HONO ambient levels in the atmosphere of Shanghai urban areas. PMID:26590058

  11. Intercomparison of field measurements of nitrous acid (HONO) during the SHARP Campaign

    EPA Science Inventory

    Because of the importance of HONO as a radical reservoir, consistent and accurate measurements of its concentration are needed. As part of the SHARP (Study of Houston Atmospheric Radical Precursors), time series of HONO were obtained by five different measurement techniques on th...

  12. Biological soil crusts emit large amounts of NO and HONO affecting the nitrogen cycle in drylands

    NASA Astrophysics Data System (ADS)

    Tamm, Alexandra; Wu, Dianming; Ruckteschler, Nina; Rodríguez-Caballero, Emilio; Steinkamp, Jörg; Meusel, Hannah; Elbert, Wolfgang; Behrendt, Thomas; Sörgel, Matthias; Cheng, Yafang; Crutzen, Paul J.; Su, Hang; Pöschl, Ulrich; Weber, Bettina

    2016-04-01

    Dryland systems currently cover ˜40% of the world's land surface and are still expanding as a consequence of human impact and global change. In contrast to that, information on their role in global biochemical processes is limited, probably induced by the presumption that their sparse vegetation cover plays a negligible role in global balances. However, spaces between the sparse shrubs are not bare, but soils are mostly covered by biological soil crusts (biocrusts). These biocrust communities belong to the oldest life forms, resulting from an assembly between soil particles and cyanobacteria, lichens, bryophytes, and algae plus heterotrophic organisms in varying proportions. Depending on the dominating organism group, cyanobacteria-, lichen-, and bryophyte-dominated biocrusts are distinguished. Besides their ability to restrict soil erosion they fix atmospheric carbon and nitrogen, and by doing this they serve as a nutrient source in strongly depleted dryland ecosystems. In this study we show that a fraction of the nitrogen fixed by biocrusts is metabolized and subsequently returned to the atmosphere in the form of nitric oxide (NO) and nitrous acid (HONO). These gases affect the radical formation and oxidizing capacity within the troposphere, thus being of particular interest to atmospheric chemistry. Laboratory measurements using dynamic chamber systems showed that dark cyanobacteria-dominated crusts emitted the largest amounts of NO and HONO, being ˜20 times higher than trace gas fluxes of nearby bare soil. We showed that these nitrogen emissions have a biogenic origin, as emissions of formerly strongly emitting samples almost completely ceased after sterilization. By combining laboratory, field, and satellite measurement data we made a best estimate of global annual emissions amounting to ˜1.1 Tg of NO-N and ˜0.6 Tg of HONO-N from biocrusts. This sum of 1.7 Tg of reactive nitrogen emissions equals ˜20% of the soil release under natural vegetation according

  13. Biological soil crusts emit large amounts of NO and HONO affecting the nitrogen cycle in drylands

    NASA Astrophysics Data System (ADS)

    Tamm, Alexandra; Wu, Dianming; Ruckteschler, Nina; Rodríguez-Caballero, Emilio; Steinkamp, Jörg; Meusel, Hannah; Elbert, Wolfgang; Behrendt, Thomas; Sörgel, Matthias; Cheng, Yafang; Crutzen, Paul J.; Su, Hang; Pöschl, Ulrich; Weber, Bettina

    2016-04-01

    Dryland systems currently cover ˜40% of the worl&dacute;s land surface and are still expanding as a consequence of human impact and global change. In contrast to that, information on their role in global biochemical processes is limited, probably induced by the presumption that their sparse vegetation cover plays a negligible role in global balances. However, spaces between the sparse shrubs are not bare, but soils are mostly covered by biological soil crusts (biocrusts). These biocrust communities belong to the oldest life forms, resulting from an assembly between soil particles and cyanobacteria, lichens, bryophytes, and algae plus heterotrophic organisms in varying proportions. Depending on the dominating organism group, cyanobacteria-, lichen-, and bryophyte-dominated biocrusts are distinguished. Besides their ability to restrict soil erosion they fix atmospheric carbon and nitrogen, and by doing this they serve as a nutrient source in strongly depleted dryland ecosystems. In this study we show that a fraction of the nitrogen fixed by biocrusts is metabolized and subsequently returned to the atmosphere in the form of nitric oxide (NO) and nitrous acid (HONO). These gases affect the radical formation and oxidizing capacity within the troposphere, thus being of particular interest to atmospheric chemistry. Laboratory measurements using dynamic chamber systems showed that dark cyanobacteria-dominated crusts emitted the largest amounts of NO and HONO, being ˜20 times higher than trace gas fluxes of nearby bare soil. We showed that these nitrogen emissions have a biogenic origin, as emissions of formerly strongly emitting samples almost completely ceased after sterilization. By combining laboratory, field, and satellite measurement data we made a best estimate of global annual emissions amounting to ˜1.1 Tg of NO-N and ˜0.6 Tg of HONO-N from biocrusts. This sum of 1.7 Tg of reactive nitrogen emissions equals ˜20% of the soil release under natural vegetation

  14. 10 CFR 1.3 - Sources of additional information.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    .../cfr/. Final opinions made in the adjudication of cases are published in “Nuclear Regulatory Commission... NUCLEAR REGULATORY COMMISSION STATEMENT OF ORGANIZATION AND GENERAL INFORMATION Introduction § 1.3 Sources..., assignments of responsibility, and delegations of authority is in the Nuclear Regulatory Commission...

  15. 10 CFR 1.3 - Sources of additional information.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    .../cfr/. Final opinions made in the adjudication of cases are published in “Nuclear Regulatory Commission... NUCLEAR REGULATORY COMMISSION STATEMENT OF ORGANIZATION AND GENERAL INFORMATION Introduction § 1.3 Sources..., assignments of responsibility, and delegations of authority is in the Nuclear Regulatory Commission...

  16. 10 CFR 1.3 - Sources of additional information.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    .../cfr/. Final opinions made in the adjudication of cases are published in “Nuclear Regulatory Commission... NUCLEAR REGULATORY COMMISSION STATEMENT OF ORGANIZATION AND GENERAL INFORMATION Introduction § 1.3 Sources..., assignments of responsibility, and delegations of authority is in the Nuclear Regulatory Commission...

  17. 10 CFR 1.3 - Sources of additional information.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    .../cfr/. Final opinions made in the adjudication of cases are published in “Nuclear Regulatory Commission... NUCLEAR REGULATORY COMMISSION STATEMENT OF ORGANIZATION AND GENERAL INFORMATION Introduction § 1.3 Sources..., assignments of responsibility, and delegations of authority is in the Nuclear Regulatory Commission...

  18. Slice imaging of nitric acid photodissociation: The O({sup 1}D) + HONO channel

    SciTech Connect

    Herath, Nuradhika; Everhart, Stephanie C.; Suits, Arthur G.; Vasyuntinskii, Oleg S.

    2011-01-21

    We report an imaging study of nitric acid (HNO{sub 3}) photodissociation near 204 nm with detection of O({sup 1}D), one of the major decomposition products in this region. The images show structure reflecting the vibrational distribution of the HONO coproduct and significant angular anisotropy that varies with recoil speed. The images also show substantial alignment of the O({sup 1}D) orbital, which is analyzed using an approximate treatment that reveals that the polarization is dominated by incoherent, high order contributions. The results offer additional insight into the dynamics of the dissociation of nitric acid through the S{sub 3} (2 {sup 1}A{sup '}) excited state, resolving an inconsistency in previously reported angular distributions, and pointing the way to future studies of the angular momentum polarization.

  19. Ab initio study of the H + HONO reaction: Direct abstraction versus indirect exchange processes

    SciTech Connect

    Hsu, C.C.; Lin, M.C.; Mebel, A.M.; Melius, C.F.

    1997-01-02

    The mechanism of the H + HONO reaction (for which no experimental data are available) has been elucidated by ab initio molecular orbital calculations using modified G2 and BAC-MP4 methods. These results indicate that the reaction occurs predominantly by two indirect metathetical processes. One produces OH + HNO and H{sub 2}O + NO from the decomposition of vibrationally excited hydroxyl nitroxide, HN(O)OH, formed by H atom addition to the N atom of HONO. The other produces H{sub 2}O + NO from the decomposition of vibrationally excited dihydroxylamino radical, N(OH){sub 2}, formed by H atom addition to the terminal O atom. These indirect displacement processes are much more efficient than the commonly assumed, direct H-abstraction reaction producing H{sub 2} + NO{sub 2}. A transition-state theory calculation for the direct abstraction reaction and RRKM calculations for the two indirect displacement processes give rise to the following rate constants, in units of cm{sup 3} molecule{sup -1} s{sup -1} for the 300-3500 K temperature range under atmospheric conditions: k{sub H(2)} = 3.33 x 10{sup -16}T{sup 1.55} exp(-3328.5/T), k{sub OH} = 9.36 x 10{sup -14}T{sup 0.86} exp(-2500.8/T), k{sub H(2)O} = 1.35 x 10{sup -17}T{sup 1.89} exp-(-1935.7/T), where the rate constant for H{sub 2}O production represents the sum from both indirect displacement reactions. 32 refs., 3 figs., 7 tabs.

  20. Biological soil crusts accelerate the nitrogen cycle through large NO and HONO emissions in drylands

    PubMed Central

    Wu, Dianming; Tamm, Alexandra; Ruckteschler, Nina; Rodríguez-Caballero, Emilio; Meusel, Hannah; Elbert, Wolfgang; Behrendt, Thomas; Sörgel, Matthias; Cheng, Yafang; Crutzen, Paul J.; Su, Hang; Pöschl, Ulrich

    2015-01-01

    Reactive nitrogen species have a strong influence on atmospheric chemistry and climate, tightly coupling the Earth’s nitrogen cycle with microbial activity in the biosphere. Their sources, however, are not well constrained, especially in dryland regions accounting for a major fraction of the global land surface. Here, we show that biological soil crusts (biocrusts) are emitters of nitric oxide (NO) and nitrous acid (HONO). Largest fluxes are obtained by dark cyanobacteria-dominated biocrusts, being ∼20 times higher than those of neighboring uncrusted soils. Based on laboratory, field, and satellite measurement data, we obtain a best estimate of ∼1.7 Tg per year for the global emission of reactive nitrogen from biocrusts (1.1 Tg a−1 of NO-N and 0.6 Tg a−1 of HONO-N), corresponding to ∼20% of global nitrogen oxide emissions from soils under natural vegetation. On continental scales, emissions are highest in Africa and South America and lowest in Europe. Our results suggest that dryland emissions of reactive nitrogen are largely driven by biocrusts rather than the underlying soil. They help to explain enigmatic discrepancies between measurement and modeling approaches of global reactive nitrogen emissions. As the emissions of biocrusts strongly depend on precipitation events, climate change affecting the distribution and frequency of precipitation may have a strong impact on terrestrial emissions of reactive nitrogen and related climate feedback effects. Because biocrusts also account for a large fraction of global terrestrial biological nitrogen fixation, their impacts should be further quantified and included in regional and global models of air chemistry, biogeochemistry, and climate. PMID:26621714

  1. Biological soil crusts accelerate the nitrogen cycle through large NO and HONO emissions in drylands.

    PubMed

    Weber, Bettina; Wu, Dianming; Tamm, Alexandra; Ruckteschler, Nina; Rodríguez-Caballero, Emilio; Steinkamp, Jörg; Meusel, Hannah; Elbert, Wolfgang; Behrendt, Thomas; Sörgel, Matthias; Cheng, Yafang; Crutzen, Paul J; Su, Hang; Pöschl, Ulrich

    2015-12-15

    Reactive nitrogen species have a strong influence on atmospheric chemistry and climate, tightly coupling the Earth's nitrogen cycle with microbial activity in the biosphere. Their sources, however, are not well constrained, especially in dryland regions accounting for a major fraction of the global land surface. Here, we show that biological soil crusts (biocrusts) are emitters of nitric oxide (NO) and nitrous acid (HONO). Largest fluxes are obtained by dark cyanobacteria-dominated biocrusts, being ∼20 times higher than those of neighboring uncrusted soils. Based on laboratory, field, and satellite measurement data, we obtain a best estimate of ∼1.7 Tg per year for the global emission of reactive nitrogen from biocrusts (1.1 Tg a(-1) of NO-N and 0.6 Tg a(-1) of HONO-N), corresponding to ∼20% of global nitrogen oxide emissions from soils under natural vegetation. On continental scales, emissions are highest in Africa and South America and lowest in Europe. Our results suggest that dryland emissions of reactive nitrogen are largely driven by biocrusts rather than the underlying soil. They help to explain enigmatic discrepancies between measurement and modeling approaches of global reactive nitrogen emissions. As the emissions of biocrusts strongly depend on precipitation events, climate change affecting the distribution and frequency of precipitation may have a strong impact on terrestrial emissions of reactive nitrogen and related climate feedback effects. Because biocrusts also account for a large fraction of global terrestrial biological nitrogen fixation, their impacts should be further quantified and included in regional and global models of air chemistry, biogeochemistry, and climate. PMID:26621714

  2. Measurements of HONO, NO, NOy and SO2 in aircraft exhaust plumes at cruise

    NASA Astrophysics Data System (ADS)

    Jurkat, T.; Voigt, C.; Arnold, F.; Schlager, H.; Kleffmann, J.; Aufmhoff, H.; Schäuble, D.; Schaefer, M.; Schumann, U.

    2011-05-01

    Measurements of gaseous nitrogen and sulfur oxide emissions in young aircraft exhaust plumes give insight into chemical oxidation processes inside aircraft engines. Particularly, the OH-induced formation of nitrous acid (HONO) from nitrogen oxide (NO) and sulfuric acid (H2SO4) from sulfur dioxide (SO2) inside the turbine which is highly uncertain, need detailed analysis to address the climate impact of aviation. We report on airborne in situ measurements at cruise altitudes of HONO, NO, NOy, and SO2 in 9 wakes of 8 different types of modern jet airliners, including for the first time also an A380. Measurements of HONO and SO2 were made with an ITCIMS (Ion Trap Chemical Ionization Mass Spectrometer) using a new ion-reaction scheme involving SF5- reagent ions. The measured molar ratios HONO/NO and HONO/NOy with averages of 0.038 ± 0.010 and 0.027 ± 0.005 were found to decrease systematically with increasing NOx emission-index (EI NOx). We calculate an average EI HONO of 0.31 ± 0.12 g NO2 kg-1. Using reliable measurements of HONO and NOy, which are less adhesive than H2SO4 to the inlet walls, we derive the OH-induced conversion fraction of fuel sulfur to sulfuric acid $\\varepsilon$ with an average of 2.2 ± 0.5 %. $\\varepsilon$ also tends to decrease with increasing EI NOx, consistent with earlier model simulations. The lowest HONO/NO, HONO/NOy and $\\varepsilon$ was observed for the largest passenger aircraft A380.

  3. Additives

    NASA Technical Reports Server (NTRS)

    Smalheer, C. V.

    1973-01-01

    The chemistry of lubricant additives is discussed to show what the additives are chemically and what functions they perform in the lubrication of various kinds of equipment. Current theories regarding the mode of action of lubricant additives are presented. The additive groups discussed include the following: (1) detergents and dispersants, (2) corrosion inhibitors, (3) antioxidants, (4) viscosity index improvers, (5) pour point depressants, and (6) antifouling agents.

  4. 5 CFR 3601.103 - Additional exceptions for gifts from outside sources.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 5 Administrative Personnel 3 2013-01-01 2013-01-01 false Additional exceptions for gifts from outside sources. 3601.103 Section 3601.103 Administrative Personnel DEPARTMENT OF DEFENSE SUPPLEMENTAL STANDARDS OF ETHICAL CONDUCT FOR EMPLOYEES OF THE DEPARTMENT OF DEFENSE § 3601.103 Additional exceptions for gifts from outside sources. In addition...

  5. Light-induced nitrous acid (HONO) production from NO2 heterogeneous reactions on household chemicals

    NASA Astrophysics Data System (ADS)

    Gómez Alvarez, Elena; Sörgel, Matthias; Gligorovski, Sasho; Bassil, Sabina; Bartolomei, Vincent; Coulomb, Bruno; Zetzsch, Cornelius; Wortham, Henri

    2014-10-01

    Nitrous acid (HONO) can be generated in various indoor environments directly during combustion processes or indirectly via heterogeneous NO2 reactions with water adsorbed layers on diverse surfaces. Indoors not only the concentrations of NO2 are higher but the surface to volume (S/V) ratios are larger and therefore the potential of HONO production is significantly elevated compared to outdoors. It has been claimed that the UV solar light is largely attenuated indoors. Here, we show that solar light (λ > 340 nm) penetrates indoors and can influence the heterogeneous reactions of gas-phase NO2 with various household surfaces. The NO2 to HONO conversion mediated by light on surfaces covered with domestic chemicals has been determined at atmospherically relevant conditions i.e. 50 ppb NO2 and 50% RH. The formation rates of HONO were enhanced in presence of light for all the studied surfaces and are determined in the following order: 1.3·109 molecules cm-2 s-1 for borosilicate glass, 1.7·109 molecules cm-2 s-1 for bathroom cleaner, 1.0·1010 molecules cm-2 s-1 on alkaline detergent (floor cleaner), 1.3·1010 molecules cm-2 s-1 for white wall paint and 2.7·1010 molecules cm-2 s-1 for lacquer. These results highlight the potential of household chemicals, used for cleaning purposes to generate HONO indoors through light-enhanced NO2 heterogeneous reactions. The results obtained have been applied to predict the timely evolution of HONO in a real indoor environment using a dynamic mass balance model. A steady state mixing ratio of HONO has been estimated at 1.6 ppb assuming a contribution from glass, paint and lacquer and considering the photolysis of HONO as the most important loss process.

  6. Measurements of nitrous acid (HONO) using ion drift-chemical ionization mass spectrometry during the 2009 SHARP field campaign

    NASA Astrophysics Data System (ADS)

    Levy, Misti; Zhang, Renyi; Zheng, Jun; Zhang, Annie L.; Xu, Wen; Gomez-Hernandez, Mario; Wang, Yuan; Olaguer, Eduardo

    2014-09-01

    We have developed a novel approach for ambient measurements of nitrous acid (HONO) using ion drift-chemical ionization mass spectrometry (ID-CIMS). HONO is ionized using the sulfur hexafluoride anion, representing the first application of this reagent ion under humid tropospheric conditions. During the 2009 Study of Houston Atmospheric Radical Precursors (SHARP) Field Campaign, HONO measurements were continuously conducted from 1 May to 1 June at a site located on the campus of the University of Houston. Diurnally, HONO concentration accumulates in the late afternoon, reaches a nighttime maximum, and declines rapidly after sunrise. The nighttime HONO peaks show close correlations with the NO2 concentration, particle surface area, and soot mass concentration, indicating that the aerosol-phase chemistry likely contributes to HONO formation. A higher nighttime HONO peak concentration typically precedes a higher and earlier ozone peak concentration of the following day, by about 20 ppb higher and four hours earlier than those with a lower preceding HONO peak concentration. Because of its high detection sensitivity and fast-responding time, the ID-CIMS method described in this work may greatly facilitate HONO detection under typical tropospheric conditions.

  7. Soil nitrous acid emissions as a major source of atmospheric reactive nitrogen

    NASA Astrophysics Data System (ADS)

    Ermel, M.; Oswald, R.; Behrendt, T.; Wu, D.; Su, H.; Cheng, Y.; Breuninger, C.; Moravek, A.; Mougin, E.; Delon, C.; Loubet, B.; Pommerening-Röser, A.; Sörgel, M.; Poeschl, U.; Hoffmann, T.; Andreae, M. O.; Meixner, F. X.; Trebs, I.

    2013-12-01

    Nitrous acid (HONO) is known to be a major source of hydroxyl radicals (OH) in the planetary boundary layer. OH is the major oxidant of the atmosphere and strongly affects its oxidation capacity. However, soil was found to release HONO, which is in equilibrium with soil nitrite (NO2-). These emissions are thought to depend on soil pH and NO2- content and were suggested to be an important contributor to the missing source of atmospheric HONO and OH radicals. The role of total soil-derived HONO in the biogeochemical and atmospheric nitrogen cycles, however, has remained unknown. We investigated a wide range of different soils in laboratory experiments, and found that HONO emissions from soils with high nutrient content and neutral pH can be of the same magnitude as nitric oxide (NO) emissions. Consequently, the co-emission of HONO with NO could substantially enhance the source of atmospheric reactive nitrogen in remote regions, with extensive arable areas. Observed temperature dependencies and obtained activation energies indicate that the HONO emissions are mainly due to microbial nitrification processes. Laboratory sterilization and inhibition experiments with soil samples yield further new insights into underlying processes of soil HONO emissions.

  8. 36 CFR 1290.3 - Sources of assassination records and additional records and information.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... records and additional records and information. 1290.3 Section 1290.3 Parks, Forests, and Public Property... Sources of assassination records and additional records and information. Assassination records and additional records and information may be located at, or under the control of, without limitation:...

  9. Consistency of the Health of the Nation Outcome Scales (HoNOS) at inpatient-to-community transition

    PubMed Central

    Harvey, Richard; Phung, Dinh; Venkatesh, Svetha; Connor, Jason P

    2016-01-01

    Objectives The Health of the Nation Outcome Scales (HoNOS) are mandated outcome-measures in many mental-health jurisdictions. When HoNOS are used in different care settings, it is important to assess if setting specific bias exists. This article examines the consistency of HoNOS in a sample of psychiatric patients transitioned from acute inpatient care and community centres. Setting A regional mental health service with both acute and community facilities. Participants 111 psychiatric patients were transferred from inpatient care to community care from 2012 to 2014. Their HoNOS scores were extracted from a clinical database; Each inpatient-discharge assessment was followed by a community-intake assessment, with the median period between assessments being 4 days (range 0–14). Assessor experience and professional background were recorded. Primary and secondary outcome measures The difference of HoNOS at inpatient-discharge and community-intake were assessed with Pearson correlation, Cohen's κ and effect size. Results Inpatient-discharge HoNOS was on average lower than community-intake HoNOS. The average HoNOS was 8.05 at discharge (median 7, range 1–22), and 12.16 at intake (median 12, range 1–25), an average increase of 4.11 (SD 6.97). Pearson correlation between two total scores was 0.073 (95% CI −0.095 to 0.238) and Cohen's κ was 0.02 (95% CI −0.02 to 0.06). Differences did not appear to depend on assessor experience or professional background. Conclusions Systematic change in the HoNOS occurs at inpatient-to-community transition. Some caution should be exercised in making direct comparisons between inpatient HoNOS and community HoNOS scores. PMID:27121703

  10. 5 CFR 3601.103 - Additional exceptions for gifts from outside sources.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... gifts from outside sources. In addition to the gifts which come within the exceptions set forth in 5 CFR 2635.204, and subject to all provisions of 5 CFR 2635.201 through 2635.205, a DoD employee may accept gifts from outside sources otherwise prohibited by 5 CFR 2635.202(a) as follows: (a) Events sponsored...

  11. Known Unknowns Explained: Hono Daytime Production from the Anion-Catalyzed Uptake of NO2 on Secondary Organic Aerosol

    NASA Astrophysics Data System (ADS)

    Colussi, A. J.

    2012-12-01

    Recent evidence strongly suggests that the decay of NO2 in urban air and the related production of HONO at daytime involve unidentified multiphase reactions. Here we address these issues and analyze the results of field campaigns from the perspective of our laboratory studies on interfacial NO2 chemistry. We note that the similar (~ 4 hr) NO2 decay lifetimes inferred from satellite sightings over megacities ranging from 2° N to 40° N at all seasons are incompatible with the conventional view that NO2 is removed (as HNO3) by gas-phase OH-radicals whose concentrations depend on solar irradiance. This insight also applies to the daytime source of HONO, a non-photochemical process that reaches its maximal strength at noon. Herein, we present new laboratory experiments and quantum mechanical calculations confirming that the reactive uptake of gaseous NO2 on aqueous interfaces is generally catalyzed by anions, and show that the preceding observations can be accounted for by the disproportionation of NO2 (via 2 NO2 + H2O = H+ + NO3- + HONO) on secondary organic aerosol particles containing carboxylate ion loadings that peak at noon, as reported elsewhere.IGURE 1 - Left axis: The frequencies of O(1D) atom production from the solar photolysis of ozone, J(O1D), at zero elevation under an ozone column of 300 Dobson units at noon on (from left to right) Feb. 1st, May 1st, Aug. 1st and Nov. 1st over: (1) Singapore 1.3° N, (2) Pearl River Delta 22.5° N, (3) Riyadh 24.6° N, (4) Isfahan 32.6° N, (5) Los Angeles 34° N, (6) Tokyo 35.6° N, (7) Four Corners 36.7° N, (8) Madrid 40.4° N and (9) Moscow 55.8° N. Right axis (note the logarithmic scale): red dashes correspond to the ratios J(O1D)mid-summer/J(O1D)mid-winter (herein midsummer is Aug. 1st, midwinter is Feb. 1st).

  12. Heterogeneous Chemistry of HONO on Liquid Sulfuric Acid: A New Mechanism of Chlorine Activation on Stratospheric Sulfate Aerosols

    NASA Technical Reports Server (NTRS)

    Zhang, Renyi; Leu, Ming-Taun; Keyser, Leon F.

    1996-01-01

    Heterogeneous chemistry of nitrous acid (HONO) on liquid sulfuric acid (H2SO4) Was investigated at conditions that prevail in the stratosphere. The measured uptake coefficient (gamma) of HONO on H2SO4 increased with increasing acid content, ranging from 0.03 for 65 wt % to about 0.1 for 74 wt %. In the aqueous phase, HONO underwent irreversible reaction with H2SO4 to form nitrosylsulfuric acid (NO(+)HSO4(-). At temperatures below 230 K, NO(+)HSO4(-) was observed to be stable and accumulated in concentrated solutions (less than 70 wt % H2SO4) but was unstable and quickly regenerated HONO in dilute solutions (less than 70 wt %). HCl reacted with HONO dissolved in sulfuric acid, releasing gaseous nitrosyl chloride (ClNO). The reaction probability between HCl and HONO varied from 0.01 to 0.02 for 60-72 wt % H2SO4. In the stratosphere, ClNO photodissociates rapidly to yield atomic chlorine, which catalytically destroys ozone. Analysis of the laboratory data reveals that the reaction of HCl with HONO on sulfate aerosols can affect stratospheric ozone balance during elevated sulfuric acid loadings after volcanic eruptions or due to emissions from the projected high-speed civil transport (HSCT). The present results may have important implications on the assessment of environmental acceptability of HSCT.

  13. Resolving the HONO formation mechanism in the ionosphere via ab initio molecular dynamic simulations.

    PubMed

    He, Rongxing; Li, Lei; Zhong, Jie; Zhu, Chongqin; Francisco, Joseph S; Zeng, Xiao Cheng

    2016-04-26

    Solar emission produces copious nitrosonium ions (NO(+)) in the D layer of the ionosphere, 60 to 90 km above the Earth's surface. NO(+) is believed to transfer its charge to water clusters in that region, leading to the formation of gaseous nitrous acid (HONO) and protonated water cluster. The dynamics of this reaction at the ionospheric temperature (200-220 K) and the associated mechanistic details are largely unknown. Using ab initio molecular dynamics (AIMD) simulations and transition-state search, key structures of the water hydrates-tetrahydrate NO(+)(H2O)4 and pentahydrate NO(+)(H2O)5-are identified and shown to be responsible for HONO formation in the ionosphere. The critical tetrahydrate NO(+)(H2O)4 exhibits a chain-like structure through which all of the lowest-energy isomers must go. However, most lowest-energy isomers of pentahydrate NO(+)(H2O)5 can be converted to the HONO-containing product, encountering very low barriers, via a chain-like or a three-armed, star-like structure. Although these structures are not the global minima, at 220 K, most lowest-energy NO(+)(H2O)4 and NO(+)(H2O)5 isomers tend to channel through these highly populated isomers toward HONO formation. PMID:27071120

  14. Photolysis of nitrous acid as a primary source of OH radicals indoors

    NASA Astrophysics Data System (ADS)

    Gomez Alvarez, E.; Amedro, D.; Afif, C.; Gligorovski, S.; Schoemacker, C.; Fittschen, C. M.; Doussin, J.; Wortham, H.

    2013-12-01

    Hydroxyl radical (OH) is the most important oxidant in the atmosphere controlling its self- oxidizing capacity. The main sources of OH radicals are the photolysis of ozone and the photolysis of nitrous acid (HONO). Due to the attenuation of solar radiation in the indoor environment, the possibility of OH formation through photolytic pathways indoors has been, up to now, ignored. We present the first direct measurement of OH radicals in the indoor environment. To the present moment, only indirect measurements based on the follow-up of different tracers or model studies had been carried out. The measurements were carried out between July, 19 and July, 30, 2011 in a classroom of 170 m3 with two large windows, oriented northwest. The effect of different concentrations of NO2 and RH were tested for their effect on the generation of HONO. In order to measure the generation of OH radicals under different light intensities, the experiments were performed at three different periods during the day, corresponding to different light intensity levels: 1) (11 a.m. to 15.00 p.m.), 2) (15.00 p.m. to 19.00 p.m.) and 3) (21.00 p.m. to 00:30 a.m.). A pool of state-of-the-art analytical instrumentation was deployed to tackle the objectives set. We measured OH radical concentrations of up to 1.8 106 cm-3 in the indoor environment (Gomez Alvarez et al., 2013). We also show that photolysis is an important source of OH radicals indoors under certain conditions, i.e. direct solar irradiation inside the room. HONO was the most probable precursor, considering the different sources leading to OH formation by photolysis. Additionally, the OH concentrations were found to follow a linear dependence with J(HONO) [HONO]. This was also supported by employing a simple quasi-photostationary state model (PSS) on the OH radical budget. These findings force a change in our understanding of indoor air quality as the reactivity linked to OH would involve formation of secondary species through chemical

  15. HUMAN HEALTH DAMAGES FROM MOBILE SOURCE AIR POLLUTION: ADDITIONAL DELPHI DATA ANALYSIS. VOLUME II

    EPA Science Inventory

    The report contains the results of additional analyses of the data generated by a panel of medical experts for a study of Human Health Damages from Mobile Source Air Pollution (hereafter referred to as HHD) conducted by the California Air Resources Board in 1973-75 for the U.S. E...

  16. 5 CFR 3601.103 - Additional exceptions for gifts from outside sources.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... sponsor in accordance with 5 CFR 2635.204(g)(5); and (3) The gift of free attendance meets the definition... gifts from outside sources. In addition to the gifts which come within the exceptions set forth in 5 CFR 2635.204, and subject to all provisions of 5 CFR 2635.201 through 2635.205, a DoD employee may...

  17. RAINFALL AND RUNOFF AS A SOURCE OF ORGANIC CARBON ADDITIONS TO BAYOU TEXAR, FLORIDA

    EPA Science Inventory

    Rainfall and Runoff as a Source of Organic Carbon Additions to Bayou Texar, Florida (Abstract). To be presented at the16th Biennial Conference of the Estuarine Research Foundation, ERF 2001: An Estuarine Odyssey, 4-8 November 2001, St. Pete Beach, FL. 1 p. (ERL,GB R852).

    T...

  18. Additive effect of BPA and Gd-DTPA for application in accelerator-based neutron source.

    PubMed

    Yoshida, F; Yamamoto, T; Nakai, K; Zaboronok, A; Matsumura, A

    2015-12-01

    Because of its fast metabolism gadolinium as a commercial drug was not considered to be suitable for neutron capture therapy. We studied additive effect of gadolinium and boron co-administration using colony forming assay. As a result, the survival of tumor cells with additional 5 ppm of Gd-DTPA decreased to 1/10 compared to the cells with boron only. Using gadolinium to increase the effect of BNCT instead of additional X-ray irradiation might be beneficial, as such combination complies with the short-time irradiation regimen at the accelerator-based neutron source. PMID:26242560

  19. Addition Laws for Intensities of Radiation Emerging from Scattering Atmospheres Containing Energy Sources

    NASA Astrophysics Data System (ADS)

    Nikoghossian, A. G.; Kapanadze, N. G.

    2016-03-01

    A group theoretical approach is developed for solving astrophysical radiative transfer problems described in a previous series of papers. Addition laws for observed radiative intensities are derived for the case in which atmospheres not only absorb and scatter radiation incident on them, but radiate themselves because of energy sources contained within them. As an illustration of the application of these laws, several special radiative transfer problems which we believe are of practical interest are discussed.

  20. Exploring the nitrous acid (HONO) formation mechanism in winter Beijing: direct emissions and heterogeneous production in urban and suburban areas.

    PubMed

    Tong, Shengrui; Hou, Siqi; Zhang, Ying; Chu, Biwu; Liu, Yongchun; He, Hong; Zhao, Pusheng; Ge, Maofa

    2016-07-18

    Continuous measurements of nitrous acid (HONO) were performed from December 12 to December 22, 2015 in both urban and suburban areas of Beijing to study the formation mechanism of HONO. The measurement campaign in both sites included a clean-haze-clean transformation process. HONO concentrations showed similar variations in the two sites, while they were always higher in the urban area. Moreover, correlations of HONO with NOx, NO2, NO, PM2.5 and relative humidity (RH) were studied to explore possible HONO formation pathways, and the contributions of direct emissions, heterogeneous reactions, and homogeneous reactions were also calculated. This showed that HONO in urban and suburban areas underwent totally different formation procedures, which were affected by meteorological conditions, PM2.5 concentrations, direct emissions, homogeneous reactions and heterogeneous reactions. PM2.5 concentrations and RH would influence the NO2 conversion efficiency. Heterogeneous reactions of NO2 were more efficient in suburban areas and in clean periods while direct emissions and homogeneous reactions contributed more in urban areas and in polluted periods when the concentrations of NOx and NO were at a high level. PMID:27081740

  1. Development of a new Laser Photofragmentation/Fluorescent Assay by Gas Expansion (LP/FAGE) technique for the quantification of tropospheric nitrous acid (HONO) at low parts-per-trillion mixing ratios

    NASA Astrophysics Data System (ADS)

    Mielke, L. H.; Lew, M.; Bottorff, B.; Berke, A.; Raff, J. D.; Stevens, P. S.; Dusanter, S.

    2013-12-01

    Determining the full oxidative capacity of the atmosphere is vital to understanding the production of secondary pollutants such as ozone and secondary organic aerosols and for regulating the lifetime of pollutants leading to climate change. The hydroxyl radical is the primary oxidant of volatile organic compounds (VOCs) in the troposphere. Nocturnal nitrous acid (HONO) is an important radical reservoir species and releases OH upon photolysis the next morning. In addition, recent studies have indicated higher than expected mixing ratios of HONO in the daytime. As daytime HONO mixing ratios usually maximize at only a couple hundred part-per-trillion, it is important to have a technique that is accurate, sensitive, and precise. Here we outline an instrumental technique called Laser Photofragmention/Fluorescent Assay by Gas Expansion (LP/FAGE). Ambient air is drawn through an inlet composed of a 1' diameter metal disk with a 0.025' cylindrically bored hole where it undergoes expansion into a cell held at ~3 torr. Fiber coupled laser emission (YILF: 355 nm, 2.2 W) induces photofragmentation of HONO to OH and NO whereby the OH is quantified by the FAGE technique using a fiber coupled 308 nm (6 mW) laser emission. The 355 nm and 308 nm emission are single pass, collinear, and separated only by the time delay of the pulses. To differentiate ambient OH from HONO-generated-OH, a shutter is used to block the 355 nm laser emission for a given period of time. Fluorescence from OH vs. fluorescence from interfering species can be differentiated by scanning on and off a specific rovibronic feature in the OH absorbance spectra. In this presentation we outline the instrumental technique, including its calibration in which effluent from an HCl permeation device is humidified and passed over a bed of sodium nitrate coated glass beads. The calibrator output is varied from 1 to several tens of parts-per-billions (ppb) and is detected using a chemiluminescence NOx analyzer. The

  2. Impact of isoprene and HONO chemistry on ozone and OVOC formation in a semirural South Korean forest

    SciTech Connect

    Kim, S.; Kim, S. -Y.; Lee, M.; Shim, H.; Wolfe, G. M.; Guenther, A. B.; He, A.; Hong, Y.; Han, J.

    2015-04-29

    Rapid urbanization and economic development in East Asia in past decades has led to photochemical air pollution problems such as excess photochemical ozone and aerosol formation. Asian megacities such as Seoul, Tokyo, Shanghai, Guangzhou, and Beijing are surrounded by densely forested areas, and recent research has consistently demonstrated the importance of biogenic volatile organic compounds (VOCs) from vegetation in determining oxidation capacity in the suburban Asian megacity regions. Uncertainties in constraining tropospheric oxidation capacity, dominated by hydroxyl radical, undermine our ability to assess regional photochemical air pollution problems. We present an observational data set of CO, NOx, SO2, ozone, HONO, and VOCs (anthropogenic and biogenic) from Taehwa research forest (TRF) near the Seoul metropolitan area in early June 2012. The data show that TRF is influenced both by aged pollution and fresh biogenic volatile organic compound emissions. With the data set, we diagnose HOx (OH, HO2, and RO2) distributions calculated using the University of Washington chemical box model (UWCM v2.1) with near-explicit VOC oxidation mechanisms from MCM v3.2 (Master Chemical Mechanism). Uncertainty from unconstrained HONO sources and radical recycling processes highlighted in recent studies is examined using multiple model simulations with different model constraints. The results suggest that (1) different model simulation scenarios cause systematic differences in HOx distributions, especially OH levels (up to 2.5 times), and (2) radical destruction (HO2 + HO2 or HO2 + RO2) could be more efficient than radical recycling (RO2 + NO), especially in the afternoon. Implications of the uncertainties in radical chemistry are discussed with respect to ozone–VOC–NOx sensitivity and VOC oxidation product

  3. Impact of isoprene and HONO chemistry on ozone and OVOC formation in a semirural South Korean forest

    SciTech Connect

    Kim, Saewung; Kim, So-Young; Lee, Meehye; Shim, Heeyoun; Wolfe, Glenn; Guenther, Alex B.; He, Amy; Hong, Youdeog; Han, Jinseok

    2014-01-01

    Rapid urbanization and economic development in East Asia in past decades has led to photochemical air pollution problems such as excess photochemical ozone and aerosol formation. Asian megacities such as Seoul, Tokyo, Shanghai, Gangzhou, and Beijing are surrounded by densely forested areas and recent research has consistently demonstrated the importance of biogenic volatile organic compounds from vegetation in determining oxidation capacity in the suburban Asian megacity regions. Uncertainties in constraining tropospheric oxidation capacity, dominated by hydroxyl radical concentrations, undermine our ability to assess regional photochemical air pollution problems. We present an observational dataset of CO, NOX, SO2, ozone, HONO, and VOCs (anthropogenic and biogenic) from Taehwa Research Forest (TRF) near the Seoul Metropolitan Area (SMA) in early June 2012. The data show that TRF is influenced both by aged pollution and fresh BVOC emissions. With the dataset, we diagnose HOx (OH, HO2, and RO2) distributions calculated with the University of Washington Chemical Box Model (UWCM v 2.1). Uncertainty from unconstrained HONO sources and radical recycling processes highlighted in recent studies is examined using multiple model simulations with different model constraints. The results suggest that 1) different model simulation scenarios cause systematic differences in HOX distributions especially OH levels (up to 2.5 times) and 2) radical destruction (HO2+HO2 or HO2+RO2) could be more efficient than radical recycling (HO2+NO) especially in the afternoon. Implications of the uncertainties in radical chemistry are discussed with respect to ozone-VOC-NOX sensitivity and oxidation product formation rates. Overall, the VOC limited regime in ozone photochemistry is predicted but the degree of sensitivity can significantly vary depending on the model scenarios. The model results also suggest that RO2 levels are positively correlated with OVOCs production that is not routinely

  4. Impact of isoprene and HONO chemistry on ozone and OVOC formation in a semirural South Korean forest

    NASA Astrophysics Data System (ADS)

    Kim, S.; Kim, S.-Y.; Lee, M.; Shim, H.; Wolfe, G. M.; Guenther, A. B.; He, A.; Hong, Y.; Han, J.

    2015-04-01

    Rapid urbanization and economic development in East Asia in past decades has led to photochemical air pollution problems such as excess photochemical ozone and aerosol formation. Asian megacities such as Seoul, Tokyo, Shanghai, Guangzhou, and Beijing are surrounded by densely forested areas, and recent research has consistently demonstrated the importance of biogenic volatile organic compounds (VOCs) from vegetation in determining oxidation capacity in the suburban Asian megacity regions. Uncertainties in constraining tropospheric oxidation capacity, dominated by hydroxyl radical, undermine our ability to assess regional photochemical air pollution problems. We present an observational data set of CO, NOx, SO2, ozone, HONO, and VOCs (anthropogenic and biogenic) from Taehwa research forest (TRF) near the Seoul metropolitan area in early June 2012. The data show that TRF is influenced both by aged pollution and fresh biogenic volatile organic compound emissions. With the data set, we diagnose HOx (OH, HO2, and RO2) distributions calculated using the University of Washington chemical box model (UWCM v2.1) with near-explicit VOC oxidation mechanisms from MCM v3.2 (Master Chemical Mechanism). Uncertainty from unconstrained HONO sources and radical recycling processes highlighted in recent studies is examined using multiple model simulations with different model constraints. The results suggest that (1) different model simulation scenarios cause systematic differences in HOx distributions, especially OH levels (up to 2.5 times), and (2) radical destruction (HO2 + HO2 or HO2 + RO2) could be more efficient than radical recycling (RO2 + NO), especially in the afternoon. Implications of the uncertainties in radical chemistry are discussed with respect to ozone-VOC-NOx sensitivity and VOC oxidation product formation rates. Overall, the NOx limited regime is assessed except for the morning hours (8 a.m. to 12 p.m. local standard time), but the degree of sensitivity can

  5. Impact of isoprene and HONO chemistry on ozone and OVOC formation in a semirural South Korean forest

    DOE PAGESBeta

    Kim, S.; Kim, S. -Y.; Lee, M.; Shim, H.; Wolfe, G. M.; Guenther, A. B.; He, A.; Hong, Y.; Han, J.

    2015-04-29

    Rapid urbanization and economic development in East Asia in past decades has led to photochemical air pollution problems such as excess photochemical ozone and aerosol formation. Asian megacities such as Seoul, Tokyo, Shanghai, Guangzhou, and Beijing are surrounded by densely forested areas, and recent research has consistently demonstrated the importance of biogenic volatile organic compounds (VOCs) from vegetation in determining oxidation capacity in the suburban Asian megacity regions. Uncertainties in constraining tropospheric oxidation capacity, dominated by hydroxyl radical, undermine our ability to assess regional photochemical air pollution problems. We present an observational data set of CO, NOx, SO2, ozone, HONO,more » and VOCs (anthropogenic and biogenic) from Taehwa research forest (TRF) near the Seoul metropolitan area in early June 2012. The data show that TRF is influenced both by aged pollution and fresh biogenic volatile organic compound emissions. With the data set, we diagnose HOx (OH, HO2, and RO2) distributions calculated using the University of Washington chemical box model (UWCM v2.1) with near-explicit VOC oxidation mechanisms from MCM v3.2 (Master Chemical Mechanism). Uncertainty from unconstrained HONO sources and radical recycling processes highlighted in recent studies is examined using multiple model simulations with different model constraints. The results suggest that (1) different model simulation scenarios cause systematic differences in HOx distributions, especially OH levels (up to 2.5 times), and (2) radical destruction (HO2 + HO2 or HO2 + RO2) could be more efficient than radical recycling (RO2 + NO), especially in the afternoon. Implications of the uncertainties in radical chemistry are discussed with respect to ozone–VOC–NOx sensitivity and VOC oxidation product formation rates. Overall, the NOx limited regime is assessed except for the morning hours (8 a.m. to 12 p.m. local standard time), but the degree of sensitivity

  6. Two years of MAXDOAS measurements of NO2, HONO, SO2 and HCHO at SORPES station in Nanjing, China

    NASA Astrophysics Data System (ADS)

    Hao, Nan; Ding, Aijun; Van Roozendael, Michel; Hendrick, Francois; Shen, Yicheng; Valks, Pieter

    2015-04-01

    The Yangtze River Delta (YRD) region includes the mega-city Shanghai and the well-industrialized and urbanized areas of Zhejiang Province and Jiangsu Province, with over ten large cities, such as Hangzhou, Suzhou and Nanjing. Covering only 2% land area, this region produces over 20% of China's Gross Domestic Product (GDP) which makes it the most densely populated region and one of the most polluted regions in China. In the YRD region, knowledge gaps still exist in the understanding of the source and transport of air pollutants because only few measurement studies have been conducted. This work presents two years measurements of air pollutants including NO2, HONO, SO2, HCHO and CHOCHO at a regional back-ground site, the Station for Observing Regional Processes of the Earth System (SORPES), in the western part of the Yangtze River Delta (YRD) in eastern China. A retrieval algorithm, based on an on-line implementation of the radiative transfer code LIDORT and the optimal estimation technique, has been used to provide information on trace gases vertical profiles and vertical column densities (VCDs). The seasonal and diurnal cycles of trace gases have been studies and compared with in situ measurements. The retrieved tropospheric NO2, HCHO and SO2 VCDs were compared to satellite measurements, while the NO2 and SO2 near surface concentrations (0-200 m layer) were compared to measurements from in situ instruments at SORPES.

  7. Fast in-situ measurements of glyoxal (CHOCHO) and nitrous acid (HONO) in northern Chinese plane during CAREBEIJING - NCP2014

    NASA Astrophysics Data System (ADS)

    Min, K. E.; Dube, W. P.; Washenfelder, R. A.; Langford, A. O.; Brown, S. S.; Broch, S.; Fuchs, H.; Gomm, S.; Hofzumahaus, A.; Holland, F.; Hu, M.; Huey, L. G.; Kubik, K.; Li, X.; Liu, X.; Lu, K.; Rohrer, F.; Shao, M.; Sjostedt, S. J.; Tan, Z.; Zhu, T.; Wahner, A.; Wang, B.; Wang, M.; Wang, Y.; Zeng, L.; Zhang, Y.

    2014-12-01

    The Northern China Plain has experienced visibility degradation and detrimental health impacts due to aerosol and photochemical pollution. To examine these air quality issues, CAREBEIJING-NCP2014 (Care Beijing - Northern China Plain 2014) was held in WangDu, Hebei province, China from 6 June to 15 July 2014. We deployed our newly developed instrument, ACES (Airborne Cavity Enhanced Spectrometer), for high time resolution in-situ measurement of glyoxal (CHOCHO), nitrous acid (HONO) and other trace gases (NO2, H2O) to investigate mechanisms of oxidation processes and secondary organic aerosol (SOA) formation. The in situ measurements of CHOCHO provide observational constraints on secondary organic aerosol formation and oxidation processes, since this molecule has been proposed to play a crucial role in forming aerosol due to its high water solubility, isomerization, and abundant production from the oxidation of many different volatile organic compounds (VOCs). A box model analysis incorporating secondary glyoxal sources from VOC oxidation and sinks to OH reaction, photolysis and heterogeneous uptake will be used to determine a budget and potential for SOA formation. This work was supported by the National Natural Science Foundation of China (21190052), the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB05010500) and the U.S. National Science Foundation Atmospheric (AGS-1405805).

  8. A study of the effects of an additional sound source on RASS performance

    SciTech Connect

    Coulter, R.L.

    1998-12-31

    The Southern Great Plains (SGP) Cloud and Radiation Testbed (CART) site of the Atmospheric Radiation Measurements (ARM) Program continuously operates a nine panel 915 MHz wind profiler with Radio Acoustic Sounding System (RASS), measuring wind profiles for 50 minutes and virtual temperature profiles for the remaining 10 minutes during each hour. It is well recognized that one of the principal limits on RASS performance is high horizontal wind speed that moves the acoustic wave front sufficiently to prevent the microwave energy produced by the radar and scattered from the acoustic wave from being reflected back t the radar antenna. With this limitation in mind, the ARM program purchased an additional, portable acoustic source that could be mounted on a small trailer and placed in strategic locations to enhance the RASS performance (when it was not being used for spare parts). A test of the resulting improvement in RASS performance was performed during the period 1995--1997.

  9. Styrofoam Debris as a Source of Hazardous Additives for Marine Organisms.

    PubMed

    Jang, Mi; Shim, Won Joon; Han, Gi Myung; Rani, Manviri; Song, Young Kyoung; Hong, Sang Hee

    2016-05-17

    There is growing concern over plastic debris and their fragments as a carrier for hazardous substances in marine ecosystem. The present study was conducted to provide field evidence for the transfer of plastic-associated chemicals to marine organisms. Hexabromocyclododecanes (HBCDs), brominated flame retardants, were recently detected in expanded polystyrene (styrofoam) marine debris. We hypothesized that if styrofoam debris acts as a source of the additives in the marine environment, organisms inhabiting such debris might be directly influenced by them. Here we investigated the characteristics of HBCD accumulation by mussels inhabiting styrofoam. For comparison, mussels inhabiting different substrates, such as high-density polyethylene (HDPE), metal, and rock, were also studied. The high HBCD levels up to 5160 ng/g lipid weight and the γ-HBCD dominated isomeric profiles in mussels inhabiting styrofoam strongly supports the transfer of HBCDs from styrofoam substrate to mussels. Furthermore, microsized styrofoam particles were identified inside mussels, probably originating from their substrates. PMID:27100560

  10. Aqueous-phase story of isoprene - A mini-review and reaction with HONO

    NASA Astrophysics Data System (ADS)

    Rudziński, Krzysztof J.; Szmigielski, Rafał; Kuznietsova, Inna; Wach, Paulina; Staszek, Dorota

    2016-04-01

    Isoprene is a major biogenic hydrocarbon emitted to the atmosphere and a well-recognized player in atmospheric chemistry, formation of secondary organic aerosol and air quality. Most of the scientific work on isoprene has focused on the gas-phase and smog chamber processing while direct aqueous chemistry has escaped the major attention because physical solubility of isoprene in water is low. Therefore, this work recollects the results of genuine research carried on atmospherically relevant aqueous-phase transformations of isoprene. It clearly shows that isoprene dissolves in water and reacts in aqueous solutions with common atmospheric oxidants such as hydrogen peroxide, ozone, hydroxyl radicals, sulfate radicals and sulfite radicals. The reactions take place in the bulk of solutions or on the gas-liquid interfaces and often are acid-catalyzed and/or enhanced by light. The review is appended by an experimental study of the aqueous-phase reaction of isoprene with nitrous acid (HONO). The decay of isoprene and formation of new products are demonstrated. The tentative chemical mechanism of the reaction is suggested, which starts with slow decomposition of HONO to NO2 and NO. The aqueous chemistry of isoprene explains the formation of a few tropospheric components identified by scientists yet considered of unknown origin. The reaction of isoprene with sulfate radicals explains formation of the MW 182 organosulfate found in ambient aerosol and rainwater while the reaction of isoprene with HONO explains formation of the MW 129 and MW 229 nitroorganic compounds identified in rainwater. Thus, aqueous transformations of isoprene should not be neglected without evidence but rather considered and evaluated in modeling of atmospheric chemical processes even if alternative and apparently dominant heterogeneous pathways of isoprene transformation, dry or wet, are demonstrated.

  11. OT2_jalcolea_2: Additional Hpoint observations of large post-AGB sources from HIFIStars

    NASA Astrophysics Data System (ADS)

    Alcolea, J.

    2011-09-01

    One of the most spectacular phases in the evolution of intermediate mass stars takes place at the end of their lives. At the end of the AGB, the central star dashes across the HR diagram from the red giant to the blue dwarf region. At the same time, the spherically symmetric and slowly expanding circumstellar envelopes around AGB stars become planetary nebulae (PNe), displaying a large variety of shapes and structures far more complex. This transformation takes place at the very end of the AGB, and it is due to the interaction of fast and bipolar molecular winds with the fossil AGB circumstellar envelope. The origin of these post-AGB winds is still unclear, but we know that the resulting two-wind interactions are only active during a very short period of time, ~ 100 yr, but still they are able to strongly modify the kinematics of the nebulae and re-shape them. To better understand these processes we must study the warm molecular gas component of early post-AGB sources, both pre-planetary nebulae (pPNe) and young PNe. Herschel/HIFI is very well suited at this, because its spectral coverage, high velocity resolution, and superb sensitivity. For these reasons, 10 pPNe and young PNe were included in the KPGT HIFISTARS, were a large number of spectral lines are observed in a moderate number of frequency setups, but just at the central point. In many cases this is simply enough, since most post-AGB sources in HIFIStars are compact. However there are three cases in which the non spherically symmetric structures seen in the warm gas are larger than the telescope beam: OH231.8+4.2, NGC7027 and NGC6302. Therefore we propose to perform some additional points in these three sources in a selected sample of HIFISTARS frequency setups, were we have detected strong lines of CO, H2O, NH3 and OH. These observations are crucial to understand the kinematics and interactions traced by these warm gas probes, and gain insight in the intricate problem of the post-AGB dynamics.

  12. The CERN antiproton source: Controls aspects of the additional collector ring and fast sampling devices

    NASA Astrophysics Data System (ADS)

    Chohan, V.

    1990-08-01

    The upgrade of the CERN antiproton source, meant to gain an order of magnitude in antiproton flux, required the construction of an additional ring to complement the existing antiproton accumulator (AA) and an entire rebuild of the target zone. The AA also needed major modifications to handle the increased flux and perform purely as an accumulator, preceded by collection in the collector ring (AC). The upgrade, known as the ACOL (antiproton collector) project, was approved under strict time and budgetary constraints and the existing AA control system, based on the Proton Synchrotron (PS) Divisional norms of CAMAC and Norsk-Data computers, had to be extended in the light of this. The limited (9 months) installation period for the whole upgrade meant that substantial preparatory and planning activities had to be carried out during the normal running of the AA. Advantage was taken of the upgrade to improve and consolidate the AA. Some aspects of the control system related to this upgrade are discussed together with the integration of new applications and instrumentation. The overall machine installation and running-in was carried out within the defined milestones and the project has now achieved the physics design goals.

  13. Solar neutrinos and the influences of opacity, thermal instability, additional neutrino sources, and a central black hole on solar models

    NASA Technical Reports Server (NTRS)

    Stothers, R. B.; Ezer, D.

    1972-01-01

    Significant quantities that affect the internal structure of the sun are examined for factors that reduce the temperature near the sun's center. The four factors discussed are: opacity, central black hole, thermal instability, and additional neutrino sources.

  14. NitroMAC: An instrument for the measurement of HONO and intercomparison with a long-path absorption photometer.

    PubMed

    Afif, Charbel; Jambert, Corinne; Michoud, Vincent; Colomb, Aurélie; Eyglunent, Gregory; Borbon, Agnès; Daële, Véronique; Doussin, Jean-François; Perros, Pascal

    2016-02-01

    NitroMAC (French acronym for continuous atmospheric measurements of nitrogenous compounds) is an instrument which has been developed for the semi-continuous measurement of atmospheric nitrous acid (HONO). This instrument relies on wet chemical sampling and detection using high performance liquid chromatography (HPLC)-visible absorption at 540 nm. Sampling proceeds by dissolution of gaseous HONO in a phosphate buffer solution followed by derivatization with sulfanilamide/N-(1-naphthyl)-ethylenediamine. The performance of this instrument was found to be as follows: a detection limit of around 3 ppt with measurement uncertainty of 10% over an analysis time of 10 min. Intercomparison was made between the instrument and a long-path absorption photometer (LOPAP) during two experiments in different environments. First, air was sampled in a smog chamber with concentrations up to 18 ppb of nitrous acid. NitroMAC and LOPAP measurements showed very good agreement. Then, in a second experiment, ambient air with HONO concentrations below 250 ppt was sampled. While NitroMAC showed its capability of measuring HONO in moderate and highly polluted environments, the intercomparison results in ambient air highlighted that corrections must be made for minor interferences when low concentrations are measured. PMID:26969550

  15. Relationship Between HNO3, NO, NO2 and HONO Fluxes Above Snow Surfaces at Ny- Aalesund, Svalbard (Arctic)

    NASA Astrophysics Data System (ADS)

    Amoroso, A.; Beine, H. J.; Esposito, G.; Nardino, M.; Montagnoli, M.; Ianniello, A.

    2006-12-01

    Deposition of NO3- in and on snow surfaces is not the final sink for atmospheric N-species; nitrates can be photochemically re-activated in the snow: this leads to the release of the more reactive species NO, NO2, and HONO back into the atmosphere. Surface flux measurements of HONO, HNO3, NO and NO2 were made above the snow surface near the Italian Station "Dirigibile Italia" at the Kongsfjorden International Research Base at Ny-Aalesund, Svalbard (79 N), between February 20, 2006 and April 20, 2006 During a few defined episodes the maximum fluxes observed were 40 nmol m-2h-1 for HONO, 50 and 150 nmol m-2h-1 for NO and NO2 , respectively, and -350 nmol m-2h-1 for HNO3 . However, for the most part the fluxes were much smaller at this Arctic marine site, in accord with earlier observations. These observations help us understand the nitrogen exchange processes between snow surfaces and the atmosphere. In this work we explore the chemical and physical snow and light conditions necessary for NOx and HONO release.

  16. Meta-analysis on Methane Mitigating Properties of Saponin-rich Sources in the Rumen: Influence of Addition Levels and Plant Sources.

    PubMed

    Jayanegara, Anuraga; Wina, Elizabeth; Takahashi, Junichi

    2014-10-01

    Saponins have been considered as promising natural substances for mitigating methane emissions from ruminants. However, studies reported that addition of saponin-rich sources often arrived at contrasting results, i.e. either it decreased methane or it did not. The aim of the present study was to assess ruminal methane emissions through a meta-analytical approach of integrating related studies from published papers which described various levels of different saponin-rich sources being added to ruminant feed. A database was constructed from published literature reporting the addition of saponin-rich sources at various levels and then monitoring ruminal methane emissions in vitro. Accordingly, levels of saponin-rich source additions as well as different saponin sources were specified in the database. Apart from methane, other related rumen fermentation parameters were also included in the database, i.e. organic matter digestibility, gas production, pH, ammonia concentration, short-chain fatty acid profiles and protozoal count. A total of 23 studies comprised of 89 data points met the inclusion criteria. The data obtained were subsequently subjected to a statistical meta-analysis based on mixed model methodology. Accordingly, different studies were treated as random effects whereas levels of saponin-rich source additions or different saponin sources were considered as fixed effects. Model statistics used were p-value and root mean square error. Results showed that an addition of increasing levels of a saponin-rich source decreased methane emission per unit of substrate incubated as well as per unit of total gas produced (p<0.05). There was a decrease in acetate proportion (linear pattern; p<0.001) and an increase in propionate proportion (linear pattern; p<0.001) with increasing levels of saponin. Log protozoal count decreased (p<0.05) at higher saponin levels. Comparing between different saponin-rich sources, all saponin sources, i.e. quillaja, tea and yucca saponins

  17. Meta-analysis on Methane Mitigating Properties of Saponin-rich Sources in the Rumen: Influence of Addition Levels and Plant Sources

    PubMed Central

    Jayanegara, Anuraga; Wina, Elizabeth; Takahashi, Junichi

    2014-01-01

    Saponins have been considered as promising natural substances for mitigating methane emissions from ruminants. However, studies reported that addition of saponin-rich sources often arrived at contrasting results, i.e. either it decreased methane or it did not. The aim of the present study was to assess ruminal methane emissions through a meta-analytical approach of integrating related studies from published papers which described various levels of different saponin-rich sources being added to ruminant feed. A database was constructed from published literature reporting the addition of saponin-rich sources at various levels and then monitoring ruminal methane emissions in vitro. Accordingly, levels of saponin-rich source additions as well as different saponin sources were specified in the database. Apart from methane, other related rumen fermentation parameters were also included in the database, i.e. organic matter digestibility, gas production, pH, ammonia concentration, short-chain fatty acid profiles and protozoal count. A total of 23 studies comprised of 89 data points met the inclusion criteria. The data obtained were subsequently subjected to a statistical meta-analysis based on mixed model methodology. Accordingly, different studies were treated as random effects whereas levels of saponin-rich source additions or different saponin sources were considered as fixed effects. Model statistics used were p-value and root mean square error. Results showed that an addition of increasing levels of a saponin-rich source decreased methane emission per unit of substrate incubated as well as per unit of total gas produced (p<0.05). There was a decrease in acetate proportion (linear pattern; p<0.001) and an increase in propionate proportion (linear pattern; p<0.001) with increasing levels of saponin. Log protozoal count decreased (p<0.05) at higher saponin levels. Comparing between different saponin-rich sources, all saponin sources, i.e. quillaja, tea and yucca saponins

  18. 75 FR 74773 - Mandatory Reporting of Greenhouse Gases: Additional Sources of Fluorinated GHGs

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-12-01

    ... reporting rule on October 7, 2010, and it was not published until October 28, 2010, 75 FR 66434, three weeks... electronics, fluorinated GHG production, and electrical equipment use on April 12, 2009 (74 FR 16448) as part... October 30, 2009 (74 FR 56260). EPA deferred action on these source categories because EPA received...

  19. 75 FR 18651 - Mandatory Reporting of Greenhouse Gases: Additional Sources of Fluorinated GHGs

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-12

    ...EPA is revising and supplementing its initial proposed actions to require reporting of fluorinated greenhouse gas (fluorinated GHG) emissions from certain source categories. Specifically, EPA is revising and supplementing its initial proposal to require reporting of fluorinated GHG emissions from electronics manufacturing, production of fluorinated gases, and use of electrical transmission and......

  20. Food additives and environmental chemicals as sources of childhood behavior disorders

    SciTech Connect

    Weiss, B.

    1982-01-01

    The Feingold hypothesis postulates that many children who exhibit disturbed behavior improve on a diet devoid of certain food additives. Its validity has been examined on the basis of controlled trails. The total evidence, although not wholly consistent, nevertheless suggests that the hypothesis is, in principle, correct. Such a conclusion poses difficult problems and new issues for etiology, treatment, toxicology, and regulation.

  1. Common genetic variants, acting additively, are a major source of risk for autism

    PubMed Central

    2012-01-01

    Background Autism spectrum disorders (ASD) are early onset neurodevelopmental syndromes typified by impairments in reciprocal social interaction and communication, accompanied by restricted and repetitive behaviors. While rare and especially de novo genetic variation are known to affect liability, whether common genetic polymorphism plays a substantial role is an open question and the relative contribution of genes and environment is contentious. It is probable that the relative contributions of rare and common variation, as well as environment, differs between ASD families having only a single affected individual (simplex) versus multiplex families who have two or more affected individuals. Methods By using quantitative genetics techniques and the contrast of ASD subjects to controls, we estimate what portion of liability can be explained by additive genetic effects, known as narrow-sense heritability. We evaluate relatives of ASD subjects using the same methods to evaluate the assumptions of the additive model and partition families by simplex/multiplex status to determine how heritability changes with status. Results By analyzing common variation throughout the genome, we show that common genetic polymorphism exerts substantial additive genetic effects on ASD liability and that simplex/multiplex family status has an impact on the identified composition of that risk. As a fraction of the total variation in liability, the estimated narrow-sense heritability exceeds 60% for ASD individuals from multiplex families and is approximately 40% for simplex families. By analyzing parents, unaffected siblings and alleles not transmitted from parents to their affected children, we conclude that the data for simplex ASD families follow the expectation for additive models closely. The data from multiplex families deviate somewhat from an additive model, possibly due to parental assortative mating. Conclusions Our results, when viewed in the context of results from genome

  2. BREEDING PIERCE'S DISEASE RESISTANT TABLE AND RAISIN GRAPES AND THE DEVELOPMENT OF MARKERS FOR ADDITIONAL SOURCES OF RESISTANCE

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Fifteen BC3 and two BC2 crosses between V. arizonica source of Pierce’s disease (PD) resistance and seedless table and raisin selections were made and produced 3,396 berries, 4,459 ovules and 1,840 embryos. Two additional seedless and two seeded crosses were made. Ten 2006 BC2 families (V. arizoni...

  3. A radio/optical reference frame. 5: Additional source positions in the mid-latitude southern hemisphere

    NASA Technical Reports Server (NTRS)

    Russell, J. L.; Reynolds, J. E.; Jauncey, D. L.; De Vegt, C.; Zacharias, N.; Ma, C.; Fey, A. L.; Johnston, K. J.; Hindsley, R.; Hughes, J. A.

    1994-01-01

    We report new accurate radio position measurements for 30 sources, preliminary positions for two sources, improved radio postions for nine additional sources which had limited previous observations, and optical positions and optical-radio differences for six of the radio sources. The Very Long Baseline Interferometry (VLBI) observations are part of the continuing effort to establish a global radio reference frame of about 400 compact, flat spectrum sources, which are evenly distributed across the sky. The observations were made using Mark III data format in four separate sessions in 1988-89 with radio telescopes at Tidbinbilla, Australia, Kauai, USA, and Kashima, Japan. We observed a total of 54 sources, including ten calibrators and three which were undetected. The 32 new source positions bring the total number in the radio reference frame catalog to 319 (172 northern and 147 southern) and fill in the zone -25 deg greater than delta greater than -45 deg which, prior to this list, had the lowest source density. The VLBI positions have an average formal precision of less than 1 mas, although unknown radio structure effects of about 1-2 mas may be present. The six new optical postion measurements are part of the program to obtain positions of the optical counterparts of the radio reference frame source and to map accurately the optical on to the radio reference frames. The optical measurements were obtained from United States Naval Observatory (USNO) Black Birch astrograph plates and source plates from the AAT, and Kitt Peak National Observatory (KPNO) 4 m, and the European Southern Observatory (ESO) Schmidt. The optical positions have an average precision of 0.07 sec, mostly due to the zero point error when adjusted to the FK5 optical frame using the IRS catalog. To date we have measured optical positions for 46 sources.

  4. Human placenta and chorion: potential additional sources of hematopoietic stem cells for transplantation

    PubMed Central

    Bárcena, Alicia; Muench, Marcus O.; Kapidzic, Mirhan; Gormley, Matthew; Goldfien, Gabriel A.; Fisher, Susan J.

    2012-01-01

    Background Hematopoietic stem cell (HSC) transplantation is an essential element of medical therapy, leading to cures of previously incurable disease for hematological and non-hematological pathologies. Many patients do not find matched donors in a timely manner, which has driven efforts to find alternative pools of transplantable HSCs. The use of umbilical cord blood (UCB) as a source of transplantable HSCs began more than two decades ago. However, the use of UCB as a reliable source of HSCs for transplantation still faces crucial challenges: the number of HSCs present in a unit of UCB is usually sufficient for younger children but not for adults and the persistent delayed engraftment often seen can result in high rates of infection and mortality. Study Design and Methods We propose a new approach to a solution of these problems: a potential increase of the limited number of UCB–HSCs available by harvesting HSCs contained in the placenta and the fetal chorionic membrane available at birth. Results We investigated the presence of hematopoietic progenitors/HSC in human placenta and chorion at different gestational ages. The characterization of these cells was performed by flow cytometry and immunolocalization and their functional status was investigated by transplanting them into immunodeficient mice. Conclusion HSCs are present in extraembryonic tissues and could be banked in conjunction to the UCB-HSCs. This novel approach could have a large impact on the field of HSC banking and more crucially, on the outcome of patients undergoing this treatment by greatly improving the use of life-saving hematopoietic transplants. PMID:22074633

  5. Numerical and exact kinetic energy operator using Eckart conditions with one or several reference geometries: Application to HONO

    NASA Astrophysics Data System (ADS)

    Lauvergnat, David; Luis, Josep M.; Kirtman, Bernard; Reis, Heribert; Nauts, André

    2016-02-01

    For the computation of rovibrational levels and their spectroscopic intensities, the Eckart conditions are essential to achieve the optimal separation between rotation and vibration. Dymarsky and Kudin [J. Chem. Phys. 122, 124103 (2005)] proposed a procedure for a simplified calculation of the Eckart rotation matrix. In the present work, we have adapted their approach to obtain a kinetic energy operator in curvilinear coordinates using a numerical but exact procedure without resorting to finite differences. Furthermore, we have modified this approach for the study of molecular systems with several minima, for which several Eckart reference geometries are required. The HONO molecular system has been used to show the efficiency of our implementation. Using the Eckart conditions with multi-reference geometries allows for a calculation of the rotational levels as well as frequencies and intensities of the infrared spectra of both HONO isomers with a single calculation.

  6. Wood decomposition in Amazonian hydropower reservoirs: An additional source of greenhouse gases

    NASA Astrophysics Data System (ADS)

    Abril, Gwenaël; Parize, Marcelo; Pérez, Marcela A. P.; Filizola, Naziano

    2013-07-01

    Amazonian hydroelectric reservoirs produce abundant carbon dioxide and methane from large quantities of flooded biomass that decompose anaerobically underwater. Emissions are extreme the first years after impounding and progressively decrease with time. To date, only water-to-air fluxes have been considered in these estimates. Here, we investigate in two Amazonian reservoirs (Balbina and Petit Saut) the fate of above water standing dead trees, by combining a qualitative analysis of wood state and density through time and a quantitative analysis of the biomass initially flooded. Dead wood was much more decomposed in the Balbina reservoir 23 years after flooding than in the Petit Saut reservoir 10 years after flooding. Termites apparently played a major role in wood decomposition, occurring mainly above water, and resulting in a complete conversion of this carbon biomass into CO2 and CH4 at a timescale much shorter than reservoir operation. The analysis of pre-impounding wood biomass reveals that above-water decomposition in Amazonian reservoirs is a large, previously unrecognized source of carbon emissions to the atmosphere, representing 26-45% of the total reservoir flux integrated over 100 years. Accounting for both below- and above-water fluxes, we could estimate that each km2 of Amazonian forest converted to reservoir would emit over 140 Gg CO2-eq in 100 years. Hydropower plants in the Amazon should thus generate 0.25-0.4 MW h per km2 flooded area to produce lower greenhouse gas emissions than gas power plants. They also have the disadvantage to emit most of their greenhouse gases the earliest years of operation.

  7. Enhancement of Identifying Cancer Specialists through the Linkage of Medicare Claims to Additional Sources of Physician Specialty

    PubMed Central

    Pollack, Lori A; Adamache, Walter; Eheman, Christie R; Ryerson, A Blythe; Richardson, Lisa C

    2009-01-01

    Objective To examine the number of cancer specialists identified in three national datasets, the effect of combining these datasets, and the use of refinement rules to classify physicians as cancer specialists. Data Sources 1992–2003 linked Surveillance, Epidemiology, and End Results (SEER)-Medicare data and a cancer-free comparison population of Medicare beneficiaries, Unique Physician Identification Number (UPIN) Registry, and the American Medical Association (AMA) Masterfile. Study Design We compared differences in counts of cancer specialists identified in Medicare claims only with the number obtained by combining data sources and after using rules to refine specialty identification. Data Extraction We analyzed physician specialty variables provided on Medicare claims, along with the specialties obtained by linkage of unencrypted UPINs on Medicare claims to the UPIN Registry, the AMA Masterfile, and all sources combined. Principle Findings Medicare claims identified the fewest number of cancer specialists (n=11,721) compared with 19,753 who were identified when we combined all three datasets. The percentage increase identified by combining datasets varied by subspecialty (187 percent for surgical oncologists to 50 percent for radiation oncologists). Rules created to refine identification most affected the count of radiation oncologists. Conclusions Researchers should consider taking the additional effort and cost to refine classification by using additional data sources based on their study objectives. PMID:19207588

  8. Effect of SO2 concentration on SOA formation in a photorreactor from a mixture of anthropogenic hydrocarbons and HONO

    NASA Astrophysics Data System (ADS)

    García Vivanco, Marta; Santiago, Manuel; García Diego, Cristina; Borrás, Esther; Ródenas, Milagros; Martínez-Tarifa, Adela

    2010-05-01

    Sulfur dioxide (SO2) is an important urban atmospheric pollutant, mainly produced by the combustion of fossil fuels containing sulfur. In the atmosphere, SO2 can react with OH radicals to form sulfuric acid, which can condense to form acidic aerosol. Sulfuric acid particles act as an acid catalyst for some heterogeneous carbonyl reactions like hydration, polymerization or acetals formation, which may lead to a large increase on SOA mass. In order to evaluate the effect of the SO2 concentration on SOA formation, 3 experiments were performed during the campaign carried out by CIEMAT on the EUPHORE facility (CEAM, Valencia, Spain) during June- July 2008. The objective of the campaign was to evaluate the effect of different experimental conditions on SOA formation from the photooxidation of some anthropogenic and biogenic VOCs using HONO as oxidant. Experiment on 6/17/08 was selected as base case (no SO2 was introduced) and experiments 6/26/08 and 7/1/08 were selected as high SO2 (2600 ug/m3) and low SO2 (60 ug/m3) concentration experiments respectively. In the three experiments a mixture of toluene, 1,3,5-TMB (trimethylbenzene), o-xylene and octane was selected as the parent VOCs. Single and coupled to mass spectroscopy gas cromatography (GC and GC/MS), as well as high performance liquid chromatography (HPLC) and Fourier transform infrared spectroscopy (FTIR) were used to measure the initial VOCs and oxidant concentrations decay and the formation of gas phase oxidation products through the experiments. Aerosol size distribution and concentration were measured with SMPS (scanning mobility particle sizer) and TEOM (tapered element oscillating monitor) respectively. In addition, analysis of the organic and inorganic aerosol content was also performed via filter sampling followed by GC/MS and ionic chromatography (for organic and inrganic content respectively). Comparing the filters collected in the three experiments, clearly the largest mass aerosol formation is observed

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

    PubMed

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

    2016-02-16

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

  10. Experimental investigations of the swirling flow in the conical diffuser using flow-feedback control technique with additional energy source

    NASA Astrophysics Data System (ADS)

    Tǎnasǎ, C.; Bosioc, A. I.; Susan-Resiga, R. F.; Muntean, S.

    2012-11-01

    The previous experimental and numerical investigations of decelerated swirling flows in conical diffusers have demonstrated that water injection along to the axis mitigates the pressure fluctuations associated to the precessing vortex rope [1]. However, for swirling flows similar to Francis turbines operated at partial discharge, the water jet becomes effective when the jet discharge is larger than 10% from the turbine discharge, leading to large volumetric losses when the jet is supplied from upstream the runner. As a result, it was introduced a new approach for supplying the jet by using a fraction of the discharge collected downstream the conical diffuser [2]. This is called flow-feedback control technique (FFCT) and it was investigated experimentally in order to assess its capability [3]. The FFCT approach not requires additional energy to supply the jet. Consequently, the turbine efficiency is not diminished due to the volumetric losses injected even if around 10% of the main flow is used. However, the equivalent amplitude of the pressure pulsations associated to the vortex rope decreases with 30% if 10% jet discharge is applied [3]. Using 12% water jet discharge from upstream then the equivalent amplitude of the pressure pulsations is mitigated with 70% according to Bosioc et al. [4]. In our case, an extra 2% jet discharge is required in order to obtain similar results with FFCT. This extra discharge is provided using an additional energy source. Therefore, the paper presents experimental investigation performed with FFCT with additional energy source. The experimental results obtained with this technique are compared against FFCT and the swirling flow with vortex rope, respectively.

  11. Analytic gradients for coupled-cluster energies that include noniterative connected triple excitations - Application to cis- and trans-HONO

    NASA Technical Reports Server (NTRS)

    Lee, Timothy J.; Rendell, Alistair P.

    1991-01-01

    An efficient formulation of the analytic energy gradient for the single and double excitation coupled-cluster method that includes a perturbational estimate of the effects of connected triple excitations is presented. The formulation has a small computational cost, and the algebraic manipulations may be applied generally to the analytic gradient of Moller-Plesset perturbation theory energies. The new formulation has been implemented in an efficient set of programs that utilize highly vectorized algorithms and has been used to investigate the equilibrium structures, harmonic vibrational frequencies, IR intensities, and energy separation of cis- and trans-HONO.

  12. Radical Sources in the Uintah Basin during 2013 Winter Ozone Episodes

    NASA Astrophysics Data System (ADS)

    Roberts, J. M.; Yuan, B.; Veres, P. R.; Warneke, C.; De Gouw, J. A.; Geiger, F.; Brown, S. S.; Edwards, P. M.; Wild, R.; Min, K.; Bates, T. S.; Quinn, P.; Banta, R. M.; Zamora, R. J.; McLaren, R.; Young, C.; Kercher, J. P.; Thornton, J. A.; Williams, E. J.

    2013-12-01

    Winter time O3 in excess of the NAAQS, 75 ppbv, has been observed in several geographic basins in Wyoming and Utah that are heavily impacted by emissions from oil and gas operations. The timing and circumstances of these high O3 events imply that radical sources such as HONO, HCHO, and perhaps ClNO2 are significant relative to the traditional O3-photolysis channel. Here we present data from the 2013 Uintah Basin Winter Ozone Study (UBWOS) that show that HONO and HCHO were the major sources of radicals during O3 episodes. This result stands in contrast to the results obtained in more typical urban atmospheres, such as the CalNEx 2010 measurements in Pasadena, where O3 photolysis was found to be the major radical source. The precise contribution of each radical source during UBWOS 2013 awaits further work on the fluxes to and from snow surfaces, and verification of HONO measurement techniques. Such a coupling of radical and NOx sources complicates the traditional NOx vs.VOC paradigm in which one or the other quantity determines the best O3 control strategy. This amplifies the need for a quantitative understanding of NOx to HONO conversion mechanisms.

  13. Addition of a Worm Leachate as Source of Humic Substances in the Drinking Water of Broiler Chickens

    PubMed Central

    Gomez-Rosales, S.; de L. Angeles, M.

    2015-01-01

    The objective of this research was to evaluate the growth performance, the apparent ileal digestibility of nitrogen and energy, the retention of nutrients and the apparent metabolizable energy corrected to zero nitrogen retention (AMEn) in broiler chickens supplemented with increasing doses of a worm leachate (WL) as a source of humic substances (HS) in the drinking water. In Exp. 1, 140 male broilers were penned individually and assigned to four WL levels (0%, 10%, 20%, and 30%) mixed in the drinking water from 21 to 49 days of age. Water was offered in plastic bottles tied to the cage. In Exp. 2, 600 male broilers from 21 to 49 days of age housed in floor pens were assigned to three levels of WL (0%, 10%, and 20%) mixed in the drinking water. The WL was mixed with tap water in plastic containers connected by plastic tubing to bell drinkers. The results of both experiments were subjected to analysis of variance and polynomial contrasts. In Exp. 1, the daily water consumption was similar among treatments but the consumption of humic, fulvic, and total humic acids increased linearly (p<0.01) as the WL increased in the drinking water. The feed conversion (p<0.01) and the ileal digestibility of energy, the excretion of dry matter and energy, the retention of dry matter, ash and nitrogen and the AMEn showed quadratic responses (p<0.05) relative to the WL levels in drinking water. In Exp. 2, the increasing level of WL in the drinking water had quadratic effects on the final body weight, daily weight gain and feed conversion ratio (p<0.05). The addition of WL as a source of HS in the drinking water had beneficial effects on the growth performance, ileal digestibility of energy, the retention of nutrients as well on the AMEn in broiler chickens; the best results were observed when the WL was mixed at levels of 20% to 30% in the drinking water. PMID:25557817

  14. 77 FR 12226 - Sadex Corp.; Filing of Food Additive Petition (Animal Use); Electron Beam and X-Ray Sources for...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-02-29

    ... Petition (Animal Use); Electron Beam and X-Ray Sources for Irradiation of Poultry Feed and Poultry Feed... regulations be amended to provide for the safe use of electron beam and x-ray sources for irradiation of... use of electron beam and x- ray sources for irradiation of poultry feed and poultry feed...

  15. Field-scale investigation of enhanced petroleum hydrocarbon biodegradation in the vadose zone combining soil venting as an oxygen source with moisture and nutrient addition. Appendices. Doctoral thesis

    SciTech Connect

    Miller, R.N.

    1990-01-01

    This document contains appendices regarding a reprint on a field scale investigation of enhanced petroleum hydrocarbon biodegradation in the vadose zone combining soil venting as a oxygen source with moisture and nutrient addition.

  16. Effect of feeding organic and inorganic sources of additional zinc on growth performance and zinc balance in nursery pigs.

    PubMed

    Case, C L; Carlson, M S

    2002-07-01

    Three experiments were conducted to evaluate the effect of feeding pharmacological concentrations of zinc (Zn), from organic and inorganic sources, on growth performance, plasma and tissue Zn accumulation, and Zn excretion of nursery pigs. Blood from all pigs was collected for plasma Zn determination on d 14 in Exp. 1, d 7 and 28 in Exp. 2, and d 15 in Exp. 3. In Exp. 1, 2, and 3, 90, 100, and 15 crossbred (GenetiPorc USA, LLC, Morris, MN) pigs were weaned at 24+/-0.5, 18, and 17 d of age (6.45, 5.47, and 5.3 kg avg initial BW), respectively, and allotted to dietary treatment based on initial weight, sex, and litter. A Phase 1 nursery diet was fed as crumbles from d 0 to 14 in Exp. 1, 2, and 3, and a Phase 2 nursery diet was fed as pellets from d 15 to 28 in Exp. 1 and 2. The Phase 1 and Phase 2 basal diets were supplemented with 100 ppm Zn as ZnSO4. Both dietary phases contained the same five dietary treatments: 150 ppm additional Zn as zinc oxide (ZnO), 500 ppm added Zn as ZnO, 500 ppm added Zn as a Zn-amino acid complex (Availa-Zn 100), 500 ppm added Zn as a Zn-polysaccharide complex (SQM-Zn), and 3,000 ppm added Zn as ZnO. Overall in Exp. 1, pigs fed 500 ppm added Zn as SQM-Zn or 3,000 ppm added Zn as ZnO had greater ADG (P < 0.05) than pigs fed 150 ppm, 500 ppm added Zn as ZnO, or 500 ppm added Zn as Availa-Zn 100 (0.44 and 0.46 kg/d vs 0.35, 0.38, and 0.33 kg/d respectively). Overall in Exp. 2, pigs fed 3,000 ppm added Zn as ZnO had greater (P < 0.05) ADG and ADFI than pigs fed any other dietary treatment. On d 14 of Exp. 1 and d 28 of Exp. 2, pigs fed 3,000 ppm added Zn as ZnO had higher (P < 0.05) plasma Zn concentrations than pigs on any other treatment. In Exp. 3, fecal, urinary, and liver Zn concentrations were greatest (P < 0.05) in pigs fed 3,000 ppm added Zn as ZnO. On d 10 to 15 of Exp. 3, pigs fed 3,000 ppm added Zn as ZnO had the most negative Zn balance (P < 0.05) compared with pigs fed the other four dietary Zn treatments. In conclusion, feeding

  17. Airborne measurements of nitrous acid and its budget in the planetary boundary layer

    NASA Astrophysics Data System (ADS)

    Li, Xin; Häseler, Rolf; Brauers, Theo; Rohrer, Franz; Hofzumahaus, Andreas; Bohn, Birger; Broch, Sebastian; Fuchs, Hendrik; Gomm, Sebastian; Holland, Frank; Lohse, Insa; Tillmann, Ralf; Mentel, Thomas F.; Kiendler-Scharr, Astrid; Wahner, Andreas

    2013-04-01

    Nitrous acid (HONO) is an important trace gas in the atmosphere due to its contribution to the cycles of nitrogen oxides (NOX) and hydrogen oxides (HOX). In the past decades, most HONO observations were performed at ground level, and only a few HONO gradient measurements were reported for the lowest 100 m of the planetary boundary layer (PBL). In most field measurements, it is found that the ambient HONO concentrations cannot be explained by the known gas-phase chemistry alone. Additional HONO production is needed, and heterogeneous production at ground and on aerosol surfaces was proposed. Within the framework of PEGASOS, an instrument for ambient HONO measurement using the LOPAP technique was setup together with instruments measuring HOX radicals, NOX, photolysis frequencies, and other parameters on board the airship Zeppelin NT. During two field campaigns in the Netherlands and in Italy, HONO and its gas phase sources and sinks were measured continuously in each flight, covering the altitude range from ground to 1 km. The measured daytime HONO mixing ratios ranged from 50 ppt to 1.2 ppb with an average value of 140 ppt. While a strong HONO gradient was found in early morning hours, it was vanishing with the breakup of the nocturnal boundary layer. Elevated HONO to NOX ratios were observed at higher altitudes, indicating an enhanced HONO production. HONO simulations using a 1-D model indicate that the HONO production at higher altitudes cannot be explained by known processes, neither by gas-phase reactions nor by vertical mixing of HONO produced at ground surface. Therefore, in addition to the current knowledge of the atmospheric HONO budget, other HONO formation pathways are need to explain the field observations.

  18. 26 CFR 31.6001-5 - Additional records in connection with collection of income tax at source on wages.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... Employment Taxes (Selected Provisions of Subtitle F, Internal Revenue Code of 1954) § 31.6001-5 Additional... (Forms W-4 and W-4E) filed with the employer by the employee. (14) The agreement, if any, between...

  19. 26 CFR 31.6001-5 - Additional records in connection with collection of income tax at source on wages.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... Employment Taxes (Selected Provisions of Subtitle F, Internal Revenue Code of 1954) § 31.6001-5 Additional... (Forms W-4 and W-4E) filed with the employer by the employee. (14) The agreement, if any, between...

  20. 26 CFR 31.6001-5 - Additional records in connection with collection of income tax at source on wages.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... Employment Taxes (Selected Provisions of Subtitle F, Internal Revenue Code of 1954) § 31.6001-5 Additional... (Forms W-4 and W-4E) filed with the employer by the employee. (14) The agreement, if any, between...

  1. 26 CFR 31.6001-5 - Additional records in connection with collection of income tax at source on wages.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... Employment Taxes (Selected Provisions of Subtitle F, Internal Revenue Code of 1954) § 31.6001-5 Additional... (Forms W-4 and W-4E) filed with the employer by the employee. (14) The agreement, if any, between...

  2. Recent Additions in the Modeling Capabilities of an Open-Source Wave Energy Converter Design Tool: Preprint

    SciTech Connect

    Tom, N.; Lawson, M.; Yu, Y. H.

    2015-04-20

    WEC-Sim is a midfidelity numerical tool for modeling wave energy conversion devices. The code uses the MATLAB SimMechanics package to solve multibody dynamics and models wave interactions using hydrodynamic coefficients derived from frequency-domain boundary-element methods. This paper presents the new modeling features introduced in the latest release of WEC-Sim. The first feature discussed conversion of the fluid memory kernel to a state-space form. This enhancement offers a substantial computational benefit after the hydrodynamic body-to-body coefficients are introduced and the number of interactions increases exponentially with each additional body. Additional features include the ability to calculate the wave-excitation forces based on the instantaneous incident wave angle, allowing the device to weathervane, as well as import a user-defined wave elevation time series. A review of the hydrodynamic theory for each feature is provided and the successful implementation is verified using test cases.

  3. Kinetics and bioenergetics of Spirulina platensis cultivation by fed-batch addition of urea as nitrogen source.

    PubMed

    Sassano, Carlos E N; Carvalho, João C M; Gioielli, Luiz A; Sato, Sunao; Torre, Paolo; Converti, Attilio

    2004-03-01

    The cyanobacterium Spirulina platensis was cultivated in bench-scale miniponds on bicarbonate/carbonate solutions using urea as nitrogen source. To minimize limitation and inhibition phenomena, urea was supplied semicontinuously using exponentially increasing feeding rates. The average growth rates obtained alternately varying the total mass of urea added per unit reactor volume (275 < mT < 725 mg/L) and the total feeding time (9 < tT < 15 d) clearly evidenced nitrogen limitation for mT< 500 mg/L and excess nitrogen inhibition above this threshold. The time behavior of the specific growth rate at variable urea feeding patterns allowed estimation of the time-dependent Gibbs energy dissipation for cell growth under the actual depletion conditions of fed-batch cultivations. Comparison of the yield of growth on Gibbs energy obtained using either urea or KNO3 pointed to the preference of S. platensis for the former nitrogen source, likely owing to more favorable bioenergetic conditions. PMID:15007182

  4. In situ time-resolved X-ray diffraction of tobermorite formation in autoclaved aerated concrete: Influence of silica source reactivity and Al addition

    SciTech Connect

    Matsui, Kunio; Kikuma, Jun; Tsunashima, Masamichi; Ishikawa, Tetsuji; Matsuno, Shin-ya; Ogawa, Akihiro; Sato, Masugu

    2011-05-15

    The hydrothermal formation of tobermorite during the processing of autoclaved aerated concrete was investigated by in situ X-ray diffraction (XRD) analysis. High-energy X-rays from a synchrotron radiation source in combination with a newly developed autoclave cell and a photon-counting pixel array detector were used. To investigate the effects of the silica source, reactive quartz from chert and less-reactive quartz from quartz sand were used as starting materials. The effect of Al addition on tobermorite formation was also studied. In all cases, C-S-H, hydroxylellestadite and katoite were clearly observed as intermediates. Acceleration of tobermorite formation by Al addition was clearly observed. However, Al addition did not affect the dissolution rate of quartz. Two pathways, via C-S-H and katoite, were also observed in the Al-containing system. These results suggest that the structure of initially formed C-S-H is important for the subsequent tobermorite formation reactions.

  5. Sources of lunar magnetic anomalies and their bulk directions of magnetization - Additional evidence from Apollo orbital data

    NASA Technical Reports Server (NTRS)

    Hood, L. L.

    1982-01-01

    A relatively high-amplitude magnetic anomaly directly detected with the Apollo 15 subsatellite magnetometer and centered near the crater Gerasimovich on the southeastern lunar far side is found to correlate with the location of a conspicuous Reiner Gamma-type swirl marking visible on a Zond 8 photograph. Examinations of available direct and indirect orbital magnetics measurements demonstrate that most strong anomalies occur in areas where morphologically similar markings are concentrated. Even though photogeologic studies indicate an impact-related origin for the swirls, both the swirls and their associated strong anomalies tend to exist preferentially in or near areas that have been seismically modified. Modeling of improved vector magnetic anomaly maps is used to infer 28 independent bulk directions of magnetization for relatively strong and isolated lunar magnetic anomaly sources.

  6. Effect of cycle time on fungal morphology, broth rheology, and recombinant enzyme productivity during pulsed addition of limiting carbon source.

    PubMed

    Bhargava, Swapnil; Wenger, Kevin S; Rane, Kishore; Rising, Vanessa; Marten, Mark R

    2005-03-01

    For many years, high broth viscosity has remained a key challenge in large-scale filamentous fungal fermentations. In previous studies, we showed that broth viscosity could be reduced by pulsed addition of limiting carbon during fed-batch fermentation. The objective in this study was to determine how changing the frequency of pulsed substrate addition affects fungal morphology, broth rheology, and recombinant enzyme productivity. To accomplish this, a series of duplicate fed-batch fermentations were performed in 20-L fermentors with a recombinant glucoamylase producing strain of Aspergillus oryzae. The total cycle time for substrate pulsing was varied over a wide range (30-2,700 s), with substrate added only during the first 30% of each cycle. As a control, a fermentation was conducted with continuous substrate feeding, and in all fermentations the same total amount of substrate was added. Results show that the total biomass concentration remained relatively unaltered, while a substantial decrease in the mean projected area of fungal elements (i.e., average size) was observed with increasing cycle time. This led to reduced broth viscosity and increased oxygen uptake rate. However, high values of cycle time (i.e., 900-2,700 s) showed a significant increase in fungal conidia formation and significantly reduced recombinant enzyme productivity, suggesting that the fungi channeled substrate to storage compounds rather than to recombinant protein. In addition to explaining the effect of cycle time on fermentation performance, these results may aid in explaining the discrepancies observed on scale-up to larger fermentors. PMID:15643626

  7. Short-term nitrogen additions can shift a coastal wetland from a sink to a source of N2O

    USGS Publications Warehouse

    Moseman-Valtierra, S.; Gonzalez, R.; Kroeger, K.D.; Tang, J.; Chao, W.C.; Crusius, J.; Bratton, J.; Green, A.; Shelton, J.

    2011-01-01

    Coastal salt marshes sequester carbon at high rates relative to other ecosystems and emit relatively little methane particularly compared to freshwater wetlands. However, fluxes of all major greenhouse gases (N2O, CH4, and CO2) need to be quantified for accurate assessment of the climatic roles of these ecosystems. Anthropogenic nitrogen inputs (via run-off, atmospheric deposition, and wastewater) impact coastal marshes. To test the hypothesis that a pulse of nitrogen loading may increase greenhouse gas emissions from salt marsh sediments, we compared N2O, CH4 and respiratory CO2 fluxes from nitrate-enriched plots in a Spartina patens marsh (receiving single additions of NaNO3 equivalent to 1.4 g N m-2) to those from control plots (receiving only artificial seawater solutions) in three short-term experiments (July 2009, April 2010, and June 2010). In July 2009, we also compared N2O and CH4 fluxes in both opaque and transparent chambers to test the influence of light on gas flux measurements. Background fluxes of N2O in July 2009 averaged -33 ??mol N2O m-2 day-1. However, within 1 h of nutrient additions, N2O fluxes were significantly greater in plots receiving nitrate additions relative to controls in July 2009. Respiratory rates and CH4 fluxes were not significantly affected. N2O fluxes were significantly higher in dark than in transparent chambers, averaging 108 and 42 ??mol N2O m-2 day-1 respectively. After 2 days, when nutrient concentrations returned to background levels, none of the greenhouse gas fluxes differed from controls. In April 2010, N2O and CH4 fluxes were not significantly affected by nitrate, possibly due to higher nitrogen demands by growing S. patens plants, but in June 2010 trends of higher N2O fluxes were again found among nitrate-enriched plots, indicating that responses to nutrient pulses may be strongest during the summer. In terms of carbon equivalents, the highest average N2O and CH4 fluxes observed, exceeded half the magnitude of typical

  8. Short-term nitrogen additions can shift a coastal wetland from a sink to a source of N 2O

    NASA Astrophysics Data System (ADS)

    Moseman-Valtierra, Serena; Gonzalez, Rosalinda; Kroeger, Kevin D.; Tang, Jianwu; Chao, Wei Chun; Crusius, John; Bratton, John; Green, Adrian; Shelton, James

    2011-08-01

    Coastal salt marshes sequester carbon at high rates relative to other ecosystems and emit relatively little methane particularly compared to freshwater wetlands. However, fluxes of all major greenhouse gases (N 2O, CH 4, and CO 2) need to be quantified for accurate assessment of the climatic roles of these ecosystems. Anthropogenic nitrogen inputs (via run-off, atmospheric deposition, and wastewater) impact coastal marshes. To test the hypothesis that a pulse of nitrogen loading may increase greenhouse gas emissions from salt marsh sediments, we compared N 2O, CH 4 and respiratory CO 2 fluxes from nitrate-enriched plots in a Spartina patens marsh (receiving single additions of NaNO 3 equivalent to 1.4 g N m -2) to those from control plots (receiving only artificial seawater solutions) in three short-term experiments (July 2009, April 2010, and June 2010). In July 2009, we also compared N 2O and CH 4 fluxes in both opaque and transparent chambers to test the influence of light on gas flux measurements. Background fluxes of N 2O in July 2009 averaged -33 μmol N 2O m -2 day -1. However, within 1 h of nutrient additions, N 2O fluxes were significantly greater in plots receiving nitrate additions relative to controls in July 2009. Respiratory rates and CH 4 fluxes were not significantly affected. N 2O fluxes were significantly higher in dark than in transparent chambers, averaging 108 and 42 μmol N 2O m -2 day -1 respectively. After 2 days, when nutrient concentrations returned to background levels, none of the greenhouse gas fluxes differed from controls. In April 2010, N 2O and CH 4 fluxes were not significantly affected by nitrate, possibly due to higher nitrogen demands by growing S. patens plants, but in June 2010 trends of higher N 2O fluxes were again found among nitrate-enriched plots, indicating that responses to nutrient pulses may be strongest during the summer. In terms of carbon equivalents, the highest average N 2O and CH 4 fluxes observed, exceeded half

  9. Development of wide band gap p- a-SiOxCy:H using additional trimethylboron as carbon source gas

    NASA Astrophysics Data System (ADS)

    Kang, Dong-Won; Sichanugrist, Porponth; Janthong, Bancha; Khan, Muhammad Ajmal; Niikura, Chisato; Konagai, Makoto

    2016-07-01

    We report p-type a-SiOxCy:H thin films which were fabricated by introducing additional Trimethylboron (TMB, B(CH3)3) doping gas into conventional standard p-type a-SiOx:H films. The TMB addition into the condition of p-a-SiOx:H improved optical bandgap from 2.14 to 2.20 eV without deterioration of electrical conductivity, which is promising for p-type window layer of thin film solar cells. The suggested p-a-SiOxCy:H films were applied in amorphous silicon solar cells and we found an increase of quantum efficiency at short wavelength regions due to wide bandgap of the new p-layer, and thus efficiency improvement from 10.4 to 10.7% was demonstrated in a-Si:H solar cell by employing the p-a-SiOxCy:H film. In case of a-SiOx:H cell, high open circuit voltage of 1.01 V was confirmed by using the suggested the p-a-SiOxCy:H film as a window layer. This new p-layer can be highly promising as a wide bandgap window layer to improve the performance of thin film silicon solar cells. [Figure not available: see fulltext.

  10. Selective hydrogenation of furan-containing condensation products as a source of biomass-derived diesel additives.

    PubMed

    Balakrishnan, Madhesan; Sacia, Eric R; Bell, Alexis T

    2014-10-01

    In this study, we demonstrate that while the energy density and lubricity of the C15 and C16 products of furan condensation of biomass-derived aldehydes with 2-methylfuran are consistent with requirements for diesel, these products do not meet specifications for cetane number and pour point due to their aromatic furan rings. However, a novel class of products that fully meet or exceed most specifications for diesel can be produced by converting the furan rings in these compounds to cyclic ether moieties. Full hydrodeoxygenation of furan condensation products to alkanes would require 55-60% higher hydrogen demand, starting from biomass, compared to the products of furan ring saturation, providing an additional incentive to support the saturated products. We also report here on a tunable class of catalysts that contain Pd nanoparticles supported on ionic liquid-modified SiO2 that can achieve complete saturation of the furan rings in yields of 95% without opening these rings. PMID:25169952

  11. Nocturnal Vertical Gradients of O3, NO2, NO3, HONO, HCHO, and SO2 in Los Angeles, CA, during CalNex 2010

    NASA Astrophysics Data System (ADS)

    Tsai, J.; Pikelnaya, O.; Hurlock, S. C.; Wong, K.; Cheung, R.; Haman, C. L.; Lefer, B. L.; Stutz, J.

    2010-12-01

    Nocturnal chemistry, through the conversion and removal of air pollutants, plays an important role in determining the initial condition for photochemistry during the following day. In the stable nocturnal boundary layer (NBL) the interplay between suppressed vertical mixing and surface emissions of NOx and VOCs can result in pronounced vertical trace gas profiles. The resulting altitude dependence of nocturnal chemistry makes the interpretation of ground observations challenging. In particular, the quantification of the nocturnal loss of NOx, due to NO3 and N2O5 chemistry, requires observations throughout the entire vertical extent of the NBL. The formation of daytime radical precursors, such as HONO, is also altitude dependent. An accurate assessment of their impact on daytime chemistry requires measurements of their profiles during the night and morning. Here we present observations from the CalNex-LA experiment, which took place from May 15 to June 15, 2010 on the east side of the Los Angeles Basin, CA. A Long-Path Differential Optical Absorption Spectrometer (LP-DOAS) was set up on the roof of the Millikan library (265 m asl, 35m agl) on the campus of the California Institute of Technology. Four retroreflector arrays were mounted about 5 -7 km North-East of the instrument at 310m, 353m, 487m and 788 m asl. The vertical profiles of NO3, HONO, NO2, O3, HCHO, and SO2 were retrieved at altitude intervals of 35-78m, 78-121m, 121-255m and 255-556m above the ground. During many nights vertical gradients were observed, with elevated NO2 and HONO concentrations near the surface and larger ozone and NO3 concentrations aloft. Simultaneous ceilometer observations of the NBL structure show the impact of meteorology on the vertical trace gas distributions. We will discuss the consequences of trace gases gradients on the nocturnal NOx budget.

  12. The addition of strain in uniaxially strained transistors by both SiN contact etch stop layers and recessed SiGe sources and drains

    NASA Astrophysics Data System (ADS)

    Denneulin, Thibaud; Cooper, David; Hartmann, Jean-Michel; Rouviere, Jean-Luc

    2012-11-01

    SiN contact etch stop layers (CESL) and recessed SiGe sources/drains are two uniaxial strain techniques used to boost the charge carriers mobility in p-type metal oxide semiconductor field effect transistors (pMOSFETs). It has already been shown that the electrical performances of the devices can be increased by combining both of these techniques on the same transistor. However, there are few experimental investigations of their additivity from the strain point of view. Here, spatially resolved strain mapping was performed using dark-field electron holography (DFEH) on pMOSFETs transistors strained by SiN CESL and embedded SiGe sources/drains. The influence of both processes on the strain distribution has been investigated independently before the combination was tested. This study was first performed with non-silicided devices. The results indicated that in the channel region, the strain induced by the combination of both processes is equal to the sum of the individual components. Then, the same investigation was performed after Ni-silicidation of the devices. It was found that in spite of a slight reduction of the strain due to the silicidation, the strain additivity is approximately preserved. Finally, it was also shown that DFEH can be a useful technique to characterize the strain field around dislocations.

  13. Solid sampling determination of lithium and sodium additives in microsamples of yttrium oxyorthosilicate by high-resolution continuum source graphite furnace atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Laczai, Nikoletta; Kovács, László; Péter, Ágnes; Bencs, László

    2016-03-01

    Solid sampling high resolution continuum source graphite furnace atomic absorption spectrometry (SS-HR-CS-GFAAS) methods were developed and studied for the fast and sensitive quantitation of Li and Na additives in microsamples of cerium-doped yttrium oxyorthosilicate (Y2SiO5:Ce) scintillator materials. The methods were optimized for solid samples by studying a set of GFAAS conditions (i.e., the sample mass, sensitivity of the analytical lines, and graphite furnace heating programs). Powdered samples in the mass range of 0.099-0.422 mg were dispensed onto graphite sample insertion boats, weighed and analyzed. Pyrolysis and atomization temperatures were optimized by the use of single-element standard solutions of Li and Na (acidified with 0.144 mol/L HNO3) at the Li I 610.353 nm and Na I 285.3013 nm analytical lines. For calibration purposes, the method of standard addition with Li and Na solutions was applied. The correlation coefficients (R values) of the calibration graphs were not worse than 0.9678. The limit of detection for oxyorthosilicate samples was 20 μg/g and 80 μg/g for Li and Na, respectively. The alkaline content of the solid samples were found to be in the range of 0.89 and 8.4 mg/g, respectively. The accuracy of the results was verified by means of analyzing certified reference samples, using methods of standard (solution) addition calibration.

  14. Reliability and Validity of the HoNOS-LD and HoNOS in a Sample of Individuals with Mild to Borderline Intellectual Disability and Severe Emotional and Behavior Disorders

    ERIC Educational Resources Information Center

    Tenneij, Nienke; Didden, Robert; Veltkamp, Eline; Koot, Hans M.

    2009-01-01

    In this study, psychometric properties of the Health of the Nation Outcome scales (HoNOS) and Health of the Nation Outcome Scales for People with Learning Disabilities (HoNOS-LD) were investigated in a sample (n = 79) of (young) adults with mild to borderline intellectual disability (ID) and severe behavior and mental health problems who were…

  15. Dual-source dual-energy CT with additional tin filtration: Dose and image quality evaluation in phantoms and in-vivo

    PubMed Central

    Primak, Andrew N.; Giraldo, Juan Carlos Ramirez; Eusemann, Christian D.; Schmidt, Bernhard; Kantor, B.; Fletcher, Joel G.; McCollough, Cynthia H.

    2010-01-01

    Purpose To investigate the effect on radiation dose and image quality of the use of additional spectral filtration for dual-energy CT (DECT) imaging using dual-source CT (DSCT). Materials and Methods A commercial DSCT scanner was modified by adding tin filtration to the high-kV tube, and radiation output and noise measured in water phantoms. Dose values for equivalent image noise were compared among DE-modes with and without tin filtration and single-energy (SE) mode. To evaluate DECT material discrimination, the material-specific DEratio for calcium and iodine were determined using images of anthropomorphic phantoms. Data were additionally acquired in 38 and 87 kg pigs, and noise for the linearly mixed and virtual non-contrast (VNC) images compared between DE-modes. Finally, abdominal DECT images from two patients of similar sizes undergoing clinically-indicated CT were compared. Results Adding tin filtration to the high-kV tube improved the DE contrast between iodine and calcium as much as 290%. Pig data showed that the tin filtration had no effect on noise in the DECT mixed images, but decreased noise by as much as 30% in the VNC images. Patient VNC-images acquired using 100/140 kV with added tin filtration had improved image quality compared to those generated with 80/140 kV without tin filtration. Conclusion Tin filtration of the high-kV tube of a DSCT scanner increases the ability of DECT to discriminate between calcium and iodine, without increasing dose relative to SECT. Furthermore, use of 100/140 kV tube potentials allows improved DECT imaging of large patients. PMID:20966323

  16. Complexes of HNO₃ and NO₃¯ with NO₂ and N₂O₄, and their potential role in atmospheric HONO formation

    SciTech Connect

    Kamboures, Michael A.; Raff, Jonathan D.; Miller, Y.; Phillips, Leon F.; Finlayson-Pitts, Barbara J.; Gerber, Robert B.

    2008-08-11

    Calculations were performed to determine the structures, energetics, and spectroscopy of the atmospherically relevant complexes (HNO₃)•(NO₂), (HNO₃)•(N₂O₄), (NO₃¯)•(NO₂), and (NO₃¯)•(N₂O₄). The binding energies indicate that three of the four complexes are quite stable, with the most stable (NO₃¯)•(N₂O₄) possessing binding energy of almost -14 kcal mol¯¹. Vibrational frequencies were calculated for use in detecting the complexes by infrared and Raman spectroscopy. An ATR-FTIR experiment showed features at 1632 and 1602 cm¯¹ that are attributed to NO₂ complexed to NO₃¯ and HNO₃, respectively. The electronic states of (HNO₃)•(N₂O₄) and (NO₃¯)•( N₂O₄) were investigated using an excited state method and it was determined that both complexes possess one low-lying excited state that is accessible through absorption of visible radiation. Evidence for the existence of (NO₃¯)•( N₂O₄) was obtained from UV/vis absorption spectra of N₂O₄ in concentrated HNO₃, which show a band at 320 nm that is blue shifted by 20 nm relative to what is observed for N₂O₄ dissolved in organic solvents. Finally, hydrogen transfer reactions within the (HNO₃)•(NO₂) and (HNO₃)•( N₂O₄) complexes leading to the formation of HONO, were investigated. In both systems the calculated potential profiles rule out a thermal mechanism, but indicate the reaction could take place following the absorption of visible radiation. We propose that these complexes are potentially important in the thermal and photochemical production of HONO observed in previous laboratory and field studies.

  17. Effect of high-pressure/temperature (HP/T) treatments of in-package food on additive migration from conventional and bio-sourced materials.

    PubMed

    Mauricio-Iglesias, M; Jansana, S; Peyron, S; Gontard, N; Guillard, V

    2010-01-01

    Migration was assessed during and after two high-pressure/temperature (HP/T) treatments intended for a pasteurization (800 MPa for 5 min, from 20 to 40 degrees C) and a sterilization treatment (800 MPa for 5 min, from 90 to 115 degrees C) and were compared with conventional pasteurization and sterilization, respectively. The specific migration of actual packaging additives used as antioxidants and ultraviolet light absorbers (Irganox 1076, Uvitex OB) was investigated in a number of food-packaging systems combining one synthetic common packaging (LLDPE) and a bio-sourced one (PLA) in contact with the four food-simulating liquids defined by European Commission regulations. After standard HP/T processing, migration kinetics was followed during the service life of the packaging material using Fourier transform infrared spectrometer (FTIR) spectroscopy. LLDPE withstood the high-pressure sterilization, whereas it melted during the conventional sterilization. No difference was observed on migration from LLDPE for both treatments. In the case of PLA, migration of Uvitex OB was very low or not detectable for all the cases studied. PMID:19809898

  18. Estimating PM2.5 Concentrations in Xi'an City Using a Generalized Additive Model with Multi-Source Monitoring Data.

    PubMed

    Song, Yong-Ze; Yang, Hong-Lei; Peng, Jun-Huan; Song, Yi-Rong; Sun, Qian; Li, Yuan

    2015-01-01

    Particulate matter with an aerodynamic diameter <2.5 μm (PM2.5) represents a severe environmental problem and is of negative impact on human health. Xi'an City, with a population of 6.5 million, is among the highest concentrations of PM2.5 in China. In 2013, in total, there were 191 days in Xi'an City on which PM2.5 concentrations were greater than 100 μg/m3. Recently, a few studies have explored the potential causes of high PM2.5 concentration using remote sensing data such as the MODIS aerosol optical thickness (AOT) product. Linear regression is a commonly used method to find statistical relationships among PM2.5 concentrations and other pollutants, including CO, NO2, SO2, and O3, which can be indicative of emission sources. The relationships of these variables, however, are usually complicated and non-linear. Therefore, a generalized additive model (GAM) is used to estimate the statistical relationships between potential variables and PM2.5 concentrations. This model contains linear functions of SO2 and CO, univariate smoothing non-linear functions of NO2, O3, AOT and temperature, and bivariate smoothing non-linear functions of location and wind variables. The model can explain 69.50% of PM2.5 concentrations, with R2 = 0.691, which improves the result of a stepwise linear regression (R2 = 0.582) by 18.73%. The two most significant variables, CO concentration and AOT, represent 20.65% and 19.54% of the deviance, respectively, while the three other gas-phase concentrations, SO2, NO2, and O3 account for 10.88% of the total deviance. These results show that in Xi'an City, the traffic and other industrial emissions are the primary source of PM2.5. Temperature, location, and wind variables also non-linearly related with PM2.5. PMID:26540446

  19. Estimating PM2.5 Concentrations in Xi'an City Using a Generalized Additive Model with Multi-Source Monitoring Data

    PubMed Central

    Song, Yong-Ze; Yang, Hong-Lei; Peng, Jun-Huan; Song, Yi-Rong; Sun, Qian; Li, Yuan

    2015-01-01

    Particulate matter with an aerodynamic diameter <2.5 μm (PM2.5) represents a severe environmental problem and is of negative impact on human health. Xi'an City, with a population of 6.5 million, is among the highest concentrations of PM2.5 in China. In 2013, in total, there were 191 days in Xi’an City on which PM2.5 concentrations were greater than 100 μg/m3. Recently, a few studies have explored the potential causes of high PM2.5 concentration using remote sensing data such as the MODIS aerosol optical thickness (AOT) product. Linear regression is a commonly used method to find statistical relationships among PM2.5 concentrations and other pollutants, including CO, NO2, SO2, and O3, which can be indicative of emission sources. The relationships of these variables, however, are usually complicated and non-linear. Therefore, a generalized additive model (GAM) is used to estimate the statistical relationships between potential variables and PM2.5 concentrations. This model contains linear functions of SO2 and CO, univariate smoothing non-linear functions of NO2, O3, AOT and temperature, and bivariate smoothing non-linear functions of location and wind variables. The model can explain 69.50% of PM2.5 concentrations, with R2 = 0.691, which improves the result of a stepwise linear regression (R2 = 0.582) by 18.73%. The two most significant variables, CO concentration and AOT, represent 20.65% and 19.54% of the deviance, respectively, while the three other gas-phase concentrations, SO2, NO2, and O3 account for 10.88% of the total deviance. These results show that in Xi'an City, the traffic and other industrial emissions are the primary source of PM2.5. Temperature, location, and wind variables also non-linearly related with PM2.5. PMID:26540446

  20. Combustion Processes as a Source of High Levels of Indoor Hydroxyl Radicals through the Photolysis of Nitrous Acid.

    PubMed

    Bartolomei, V; Gomez Alvarez, E; Wittmer, J; Tlili, S; Strekowski, R; Temime-Roussel, B; Quivet, E; Wortham, H; Zetzsch, C; Kleffmann, J; Gligorovski, S

    2015-06-01

    Hydroxyl radicals (OH) are known to control the oxidative capacity of the atmosphere but their influence on reactivity within indoor environments is believed to be of little importance. Atmospheric direct sources of OH include the photolysis of ozone and nitrous acid (HONO) and the ozonolysis of alkenes. It has been argued that the ultraviolet light fraction of the solar spectrum is largely attenuated within indoor environments, thus, limiting the extent of photolytic OH sources. Conversely, the ozonolysis of alkenes has been suggested as the main pathway of OH formation within indoor settings. According to this hypothesis the indoor OH radical concentrations span in the range of only 10(4) to 10(5) cm(-3). However, recent direct OH radical measurements within a school classroom yielded OH radical peak values at moderate light intensity measured at evenings of 1.8 × 10(6) cm(-3) that were attributed to the photolysis of HONO. In this work, we report results from chamber experiments irradiated with varying light intensities in order to mimic realistic indoor lighting conditions. The exhaust of a burning candle was introduced in the chamber as a typical indoor source causing a sharp peak of HONO, but also of nitrogen oxides (NOx). The photolysis of HONO yields peak OH concentration values, that for the range of indoors lightning conditions were estimated in the range 5.7 ×· 10(6) to 1.6 × 10(7) cm(-3). Excellent agreement exists between OH levels determined by a chemical clock and those calculated by a simple PSS model. These findings suggest that significant OH reactivity takes place at our dwellings and the consequences of this reactivity-that is, formation of secondary oxidants-ought to be studied hereafter. PMID:25942056

  1. Inductively coupled plasma spectrometry: Noise characteristics of aerosols, application of generalized standard additions method, and Mach disk as an emission source

    SciTech Connect

    Shen, Luan

    1995-10-06

    This dissertation is focused on three problem areas in the performance of inductively coupled plasma (ICP) source. The noise characteristics of aerosols produced by ICP nebulizers are investigated. A laser beam is scattered by aerosol and detected by a photomultiplier tube and the noise amplitude spectrum of the scattered radiation is measured by a spectrum analyzer. Discrete frequency noise in the aerosol generated by a Meinhard nebulizer or a direct injection nebulizer is primarily caused by pulsation in the liquid flow from the pump. A Scott-type spray chamber suppresses white noise, while a conical, straight-pass spray chamber enhances white noise, relative to the noise seen from the primary aerosol. Simultaneous correction for both spectral interferences and matrix effects in ICP atomic emission spectrometry (AES) can be accomplished by using the generalized standard additions method (GSAM). Results obtained with the application of the GSAM to the Perkin-Elmer Optima 3000 ICP atomic emission spectrometer are presented. The echelle-based polychromator with segmented-array charge-coupled device detectors enables the direct, visual examination of the overlapping lines Cd (1) 228.802 nm and As (1) 228.812 nm. The slit translation capability allows a large number of data points to be sampled, therefore, the advantage of noise averaging is gained. An ICP is extracted into a small quartz vacuum chamber through a sampling orifice in a water-cooled copper plate. Optical emission from the Mach disk region is measured with a new type of echelle spectrometer equipped with two segmented-array charge-coupled-device detectors, with an effort to improve the detection limits for simultaneous multielement analysis by ICP-AES.

  2. The Multi-allelic Genetic Architecture of a Variance-Heterogeneity Locus for Molybdenum Concentration in Leaves Acts as a Source of Unexplained Additive Genetic Variance

    PubMed Central

    Forsberg, Simon K. G.; Andreatta, Matthew E.; Huang, Xin-Yuan; Danku, John; Salt, David E.; Carlborg, Örjan

    2015-01-01

    Genome-wide association (GWA) analyses have generally been used to detect individual loci contributing to the phenotypic diversity in a population by the effects of these loci on the trait mean. More rarely, loci have also been detected based on variance differences between genotypes. Several hypotheses have been proposed to explain the possible genetic mechanisms leading to such variance signals. However, little is known about what causes these signals, or whether this genetic variance-heterogeneity reflects mechanisms of importance in natural populations. Previously, we identified a variance-heterogeneity GWA (vGWA) signal for leaf molybdenum concentrations in Arabidopsis thaliana. Here, fine-mapping of this association reveals that the vGWA emerges from the effects of three independent genetic polymorphisms that all are in strong LD with the markers displaying the genetic variance-heterogeneity. By revealing the genetic architecture underlying this vGWA signal, we uncovered the molecular source of a significant amount of hidden additive genetic variation or “missing heritability”. Two of the three polymorphisms underlying the genetic variance-heterogeneity are promoter variants for Molybdate transporter 1 (MOT1), and the third a variant located ~25 kb downstream of this gene. A fourth independent association was also detected ~600 kb upstream of MOT1. Use of a T-DNA knockout allele highlights Copper Transporter 6; COPT6 (AT2G26975) as a strong candidate gene for this association. Our results show that an extended LD across a complex locus including multiple functional alleles can lead to a variance-heterogeneity between genotypes in natural populations. Further, they provide novel insights into the genetic regulation of ion homeostasis in A. thaliana, and empirically confirm that variance-heterogeneity based GWA methods are a valuable tool to detect novel associations of biological importance in natural populations. PMID:26599497

  3. The effectiveness of power-generating complexes constructed on the basis of nuclear power plants combined with additional sources of energy determined taking risk factors into account

    NASA Astrophysics Data System (ADS)

    Aminov, R. Z.; Khrustalev, V. A.; Portyankin, A. V.

    2015-02-01

    The effectiveness of combining nuclear power plants equipped with water-cooled water-moderated power-generating reactors (VVER) with other sources of energy within unified power-generating complexes is analyzed. The use of such power-generating complexes makes it possible to achieve the necessary load pickup capability and flexibility in performing the mandatory selective primary and emergency control of load, as well as participation in passing the night minimums of electric load curves while retaining high values of the capacity utilization factor of the entire power-generating complex at higher levels of the steam-turbine part efficiency. Versions involving combined use of nuclear power plants with hydrogen toppings and gas turbine units for generating electricity are considered. In view of the fact that hydrogen is an unsafe energy carrier, the use of which introduces additional elements of risk, a procedure for evaluating these risks under different conditions of implementing the fuel-and-hydrogen cycle at nuclear power plants is proposed. Risk accounting technique with the use of statistical data is considered, including the characteristics of hydrogen and gas pipelines, and the process pipelines equipment tightness loss occurrence rate. The expected intensities of fires and explosions at nuclear power plants fitted with hydrogen toppings and gas turbine units are calculated. In estimating the damage inflicted by events (fires and explosions) occurred in nuclear power plant turbine buildings, the US statistical data were used. Conservative scenarios of fires and explosions of hydrogen-air mixtures in nuclear power plant turbine buildings are presented. Results from calculations of the introduced annual risk to the attained net annual profit ratio in commensurable versions are given. This ratio can be used in selecting projects characterized by the most technically attainable and socially acceptable safety.

  4. Food additives

    MedlinePlus

    Food additives are substances that become part of a food product when they are added during the processing or making of that food. "Direct" food additives are often added during processing to: Add nutrients ...

  5. Food additives

    PubMed Central

    Spencer, Michael

    1974-01-01

    Food additives are discussed from the food technology point of view. The reasons for their use are summarized: (1) to protect food from chemical and microbiological attack; (2) to even out seasonal supplies; (3) to improve their eating quality; (4) to improve their nutritional value. The various types of food additives are considered, e.g. colours, flavours, emulsifiers, bread and flour additives, preservatives, and nutritional additives. The paper concludes with consideration of those circumstances in which the use of additives is (a) justified and (b) unjustified. PMID:4467857

  6. The contribution of soil biogenic NO and HONO emissions from a managed hyperarid ecosystem to the regional NOx emissions during growing season

    NASA Astrophysics Data System (ADS)

    Mamtimin, Buhalqem; Meixner, Franz X.; Behrendt, Thomas; Badawy, Moawad; Wagner, Thomas

    2016-08-01

    A study was carried out to understand the contributions of soil biogenic NO emissions from managed (fertilized and irrigated) hyperarid ecosystems in NW China to the regional NOx emissions during the growing season. Soil biogenic net potential NO fluxes were quantified by laboratory incubation of soil samples from the three dominating ecosystems (desert, cotton, and grape fields). Regional biogenic NO emissions were calculated bottom-up hourly for the entire growing season (April-September 2010) by considering corresponding land use, hourly data of soil temperature, gravimetric soil moisture, and fertilizer enhancement factors. The regional HONO emissions were estimated using the ratio of the optimum condition ((FN,opt(HONO) to FN,opt (NO)). Regional anthropogenic NOx emissions were calculated bottom-up from annual statistical data provided by regional and local government bureaus which have been downscaled to monthly value. Regional top-down emission estimates of NOx were derived on the monthly basis from satellite observations (OMI) of tropospheric vertical NO2 column densities and prescribed values of the tropospheric NOx lifetime. In order to compare the top-down and bottom-up emission estimates, all emission estimates were expressed in terms of mass of atomic nitrogen. Consequently, monthly top-down NOx emissions (total) were compared with monthly bottom-up NOx emissions (biogenic + anthropogenic) for the time of the satellite overpass (around 13:00 LT) with the consideration of the diurnal cycle of bottom-up estimates. Annual variation in total Tohsun Oasis NOx emissions is characterized by a strong peak in winter (December-February) and a secondary peak in summer (June-August). During summer, soil biogenic emissions were from equal to double that of related anthropogenic emissions, and grape soils were the main contributor to soil biogenic emissions, followed by cotton soils, while emissions from the desert were negligible. The top-down and bottom

  7. Surface-catalyzed chlorine and nitrogen activation: mechanisms for the heterogeneous formation of ClNO, NO, NO2, HONO, and N2O from HNO3 and HCl on aluminum oxide particle surfaces.

    PubMed

    Rubasinghege, Gayan; Grassian, Vicki H

    2012-05-31

    It is well-known that chlorine active species (e.g., Cl(2), ClONO(2), ClONO) can form from heterogeneous reactions between nitrogen oxides and hydrogen chloride on aerosol particle surfaces in the stratosphere. However, less is known about these reactions in the troposphere. In this study, a potential new heterogeneous pathway involving reaction of gaseous HCl and HNO(3) on aluminum oxide particle surfaces, a proxy for mineral dust in the troposphere, is proposed. We combine transmission Fourier transform infrared spectroscopy with X-ray photoelectron spectroscopy to investigate changes in the composition of both gas-phase and surface-bound species during the reaction under different environmental conditions of relative humidity and simulated solar radiation. Exposure of surface nitrate-coated aluminum oxide particles, from prereaction with nitric acid, to gaseous HCl yields several gas-phase products, including ClNO, NO(2), and HNO(3), under dry (RH < 1%) conditions. Under humid more conditions (RH > 20%), NO and N(2)O are the only gas products observed. The experimental data suggest that, in the presence of adsorbed water, ClNO is hydrolyzed on the particle surface to yield NO and NO(2), potentially via a HONO intermediate. NO(2) undergoes further hydrolysis via a surface-mediated process, resulting in N(2)O as an additional nitrogen-containing product. In the presence of broad-band irradiation (λ > 300 nm) gas-phase products can undergo photochemistry, e.g., ClNO photodissociates to NO and chlorine atoms. The gas-phase product distribution also depends on particle mineralogy (Al(2)O(3) vs CaCO(3)) and the presence of other coadsorbed gases (e.g., NH(3)). These newly identified reaction pathways discussed here involve continuous production of active ozone-depleting chlorine and nitrogen species from stable sinks such as gas-phase HCl and HNO(3) as a result of heterogeneous surface reactions. Given that aluminosilicates represent a major fraction of mineral dust

  8. Breeding Pierce’s disease resistant table and raisin grapes and the development of markers for additional sources of resistance 2008

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Twenty-two seedless x seedless crosses to develop additional BC2 and BC3 V. arizonica and BC1 SEUS BD5-117 families were made in 2008. Powdery mildew resistance was included in five of these crosses. These crosses produced 5,148 berries, 8,824 ovules and 1,861 embryos. Nine seeded BC1 crosses bas...

  9. Food additives.

    PubMed

    Berglund, F

    1978-01-01

    The use of additives to food fulfils many purposes, as shown by the index issued by the Codex Committee on Food Additives: Acids, bases and salts; Preservatives, Antioxidants and antioxidant synergists; Anticaking agents; Colours; Emulfifiers; Thickening agents; Flour-treatment agents; Extraction solvents; Carrier solvents; Flavours (synthetic); Flavour enhancers; Non-nutritive sweeteners; Processing aids; Enzyme preparations. Many additives occur naturally in foods, but this does not exclude toxicity at higher levels. Some food additives are nutrients, or even essential nutritents, e.g. NaCl. Examples are known of food additives causing toxicity in man even when used according to regulations, e.g. cobalt in beer. In other instances, poisoning has been due to carry-over, e.g. by nitrate in cheese whey - when used for artificial feed for infants. Poisonings also occur as the result of the permitted substance being added at too high levels, by accident or carelessness, e.g. nitrite in fish. Finally, there are examples of hypersensitivity to food additives, e.g. to tartrazine and other food colours. The toxicological evaluation, based on animal feeding studies, may be complicated by impurities, e.g. orthotoluene-sulfonamide in saccharin; by transformation or disappearance of the additive in food processing in storage, e.g. bisulfite in raisins; by reaction products with food constituents, e.g. formation of ethylurethane from diethyl pyrocarbonate; by metabolic transformation products, e.g. formation in the gut of cyclohexylamine from cyclamate. Metabolic end products may differ in experimental animals and in man: guanylic acid and inosinic acid are metabolized to allantoin in the rat but to uric acid in man. The magnitude of the safety margin in man of the Acceptable Daily Intake (ADI) is not identical to the "safety factor" used when calculating the ADI. The symptoms of Chinese Restaurant Syndrome, although not hazardous, furthermore illustrate that the whole ADI

  10. Oxidative capacity of the Mexico City atmosphere - Part 1: A radical source perspective

    NASA Astrophysics Data System (ADS)

    Volkamer, R.; Sheehy, P.; Molina, L. T.; Molina, M. J.

    2010-07-01

    A detailed analysis of OH, HO2 and RO2 radical sources is presented for the near field photochemical regime inside the Mexico City Metropolitan Area (MCMA). During spring of 2003 (MCMA-2003 field campaign) an extensive set of measurements was collected to quantify time-resolved ROx (sum of OH, HO2, RO2) radical production rates from day- and nighttime radical sources. The Master Chemical Mechanism (MCMv3.1) was constrained by measurements of (1) concentration time-profiles of photosensitive radical precursors, i.e., nitrous acid (HONO), formaldehyde (HCHO), ozone (O3), glyoxal (CHOCHO), and other oxygenated volatile organic compounds (OVOCs); (2) respective photolysis-frequencies (J-values); (3) concentration time-profiles of alkanes, alkenes, and aromatic VOCs (103 compound are treated) and oxidants, i.e., OH- and NO3 radicals, O3; and (4) NO, NO2, meteorological and other parameters. The ROx production rate was calculated directly from these observations; the MCM was used to estimate further ROx production from unconstrained sources, and express overall ROx production as OH-equivalents (i.e., taking into account the propagation efficiencies of RO2 and HO2 radicals into OH radicals). Daytime radical production is found to be about 10-25 times higher than at night; it does not track the abundance of sunlight. 12-h average daytime contributions of individual sources are: Oxygenated VOC other than HCHO about 33%; HCHO and O3 photolysis each about 20%; O3/alkene reactions and HONO photolysis each about 12%, other sources <3%. Nitryl chloride photolysis could potentially contribute ~15% additional radicals, while NO2* + water makes - if any - a very small contribution (~2%). The peak radical production of ~7.5 107 molec cm-3 s-1 is found already at 10:00 a.m., i.e., more than 2.5 h before solar noon. O3/alkene reactions are indirectly responsible for ~33% of these radicals. Our measurements and analysis comprise a database that enables testing of the representation of

  11. EFFECT OF VITAMIN C ADDITION TO GROUND BEEF FROM GRASS-FED OR GRAIN-FED SOURCES ON COLOR AND LIPID STABILITY, AND PREDICTION OF FATTY ACID COMPOSITION BY NEAR INFRARED REFLECTANCE ANALYSIS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Research was conducted to determine the effect of postmortem vitamin C addition (VITC) versus no VITC (CONTROL) to ground beef from grass-fed (GRASS) or grain-fed (GRAIN) sources on color and lipid stability during 8 d of illuminated display at 4°C. The use of near infrared reflectance (NIR) spectro...

  12. Potlining Additives

    SciTech Connect

    Rudolf Keller

    2004-08-10

    In this project, a concept to improve the performance of aluminum production cells by introducing potlining additives was examined and tested. Boron oxide was added to cathode blocks, and titanium was dissolved in the metal pool; this resulted in the formation of titanium diboride and caused the molten aluminum to wet the carbonaceous cathode surface. Such wetting reportedly leads to operational improvements and extended cell life. In addition, boron oxide suppresses cyanide formation. This final report presents and discusses the results of this project. Substantial economic benefits for the practical implementation of the technology are projected, especially for modern cells with graphitized blocks. For example, with an energy savings of about 5% and an increase in pot life from 1500 to 2500 days, a cost savings of $ 0.023 per pound of aluminum produced is projected for a 200 kA pot.

  13. Phosphazene additives

    SciTech Connect

    Harrup, Mason K; Rollins, Harry W

    2013-11-26

    An additive comprising a phosphazene compound that has at least two reactive functional groups and at least one capping functional group bonded to phosphorus atoms of the phosphazene compound. One of the at least two reactive functional groups is configured to react with cellulose and the other of the at least two reactive functional groups is configured to react with a resin, such as an amine resin of a polycarboxylic acid resin. The at least one capping functional group is selected from the group consisting of a short chain ether group, an alkoxy group, or an aryloxy group. Also disclosed are an additive-resin admixture, a method of treating a wood product, and a wood product.

  14. Decoupling of unpolluted temperate forests from rock nutrient sources revealed by natural 87Sr/86Sr and 84Sr tracer addition

    PubMed Central

    Kennedy, Martin J.; Hedin, Lars O.; Derry, Louis A.

    2002-01-01

    An experimental tracer addition of 84Sr to an unpolluted temperate forest site in southern Chile, as well as the natural variation of 87Sr/86Sr within plants and soils, indicates that mechanisms in shallow soil organic horizons are of key importance for retaining and recycling atmospheric cation inputs at scales of decades or less. The dominant tree species Nothofagus nitida feeds nearly exclusively (>90%) on cations of atmospheric origin, despite strong variations in tree size and location in the forest landscape. Our results illustrate that (i) unpolluted temperate forests can become nutritionally decoupled from deeper weathering processes, virtually functioning as atmospherically fed ecosystems, and (ii) base cation turnover times are considerably more rapid than previously recognized in the plant available pool of soil. These results challenge the prevalent paradigm that plants largely feed on rock-derived cations and have important implications for understanding sensitivity of forests to air pollution. PMID:12119394

  15. Superconducting Properties of MgB2 with Addition of Other AlB2-type Diborides and Carbon Sources, Prepared Using High Energy Ball Milling and HIP

    NASA Astrophysics Data System (ADS)

    Rodrigues, Durval; Silva, Lucas B. S. da; Metzner, Vivian C. V.; Hellstrom, Eric E.

    In the present work it is described the production of MgB2 samples by using the mixture of MgB2 with other diborides, (TaB2, VB2, and AlB2) which have the same C32 hexagonal structure as the MgB2, and simultaneous addition with the diborides and SiC, that contribute with C, to replace B in the crystalline structure of the matrix. As an important result, the critical current density (Jc) was improved at low magnetic fields when just the diborides are added. However, when SiC is added simultaneously with the diborides, the result is the improvement of Jc at high fields. The critical temperature (Tc) was maintained high.

  16. Kilogram-scale production of SnO(2) yolk-shell powders by a spray-drying process using dextrin as carbon source and drying additive.

    PubMed

    Choi, Seung Ho; Kang, Yun Chan

    2014-05-01

    A simple and general method for the large-scale production of yolk-shell powders with various compositions by a spray-drying process is reported. Metal salt/dextrin composite powders with a spherical and dense structure were obtained by spray drying and transformed into yolk-shell powders by simple combustion in air. Dextrin plays a key role in the preparation of precursor powders for fabricating yolk-shell powders by spray drying. Droplets containing metal salts and dextrin show good drying characteristics even in a severe environment of high humidity. Sucrose, glucose, and polyvinylpyrrolidone are widely used as carbon sources in the preparation of metal oxide/carbon composite powders; however, they are not appropriate for large-scale spray-drying processes because of their caramelization properties and adherence to the surface of the spray dryer. SnO2 yolk-shell powders were studied as the first target material in the spray-drying process. Combustion of tin oxalate/dextrin composite powders at 600 °C in air produced single-shelled SnO2 yolk-shell powders with the configuration SnO2 @void@SnO2 . The SnO2 yolk-shell powders prepared by the simple spray-drying process showed superior electrochemical properties, even at high current densities. The discharge capacities of the SnO2 yolk-shell powders at a current density of 2000 mA g(-1) were 645 and 570 mA h g(-1) for the second and 100th cycles, respectively; the corresponding capacity retention measured for the second cycle was 88 %. PMID:24665070

  17. Potential biofuel additive from renewable sources--Kinetic study of formation of butyl acetate by heterogeneously catalyzed transesterification of ethyl acetate with butanol.

    PubMed

    Ali, Sami H; Al-Rashed, Osama; Azeez, Fadhel A; Merchant, Sabiha Q

    2011-11-01

    Butyl acetate holds great potential as a sustainable biofuel additive. Heterogeneously catalyzed transesterification of biobutanol and bioethylacetate can produce butyl acetate. This route is eco-friendly and offers several advantages over the commonly used Fischer Esterification. The Amberlite IR 120- and Amberlyst 15-catalyzed transesterification is studied in a batch reactor over a range of catalyst loading (6-12 wt.%), alcohol to ester feed ratio (1:3 to 3:1), and temperature (303.15-333.15K). A butanol mole fraction of 0.2 in the feed is found to be optimum. Amberlite IR 120 promotes faster kinetics under these conditions. The transesterifications studied are slightly exothermic. The moles of solvent sorbed per gram of catalyst decreases (ethanol>butanol>ethyl acetate>butyl acetate) with decrease in solubility parameter. The dual site models, the Langmuir Hinshelwood and Popken models, are the most successful in correlating the kinetics over Amberlite IR 120 and Amberlyst 15, respectively. PMID:21908187

  18. NGSI student activities in open source information analysis in support of the training program of the U.S. DOE laboratories for the entry into force of the additional protocol

    SciTech Connect

    Sandoval, M Analisa; Uribe, Eva C; Sandoval, Marisa N; Boyer, Brian D; Stevens, Rebecca S

    2009-01-01

    In 2008 a joint team from Los Alamos National Laboratory (LANL) and Brookhaven National Laboratory (BNL) consisting of specialists in training of IAEA inspectors in the use of complementary access activities formulated a training program to prepare the U.S. Doe laboratories for the entry into force of the Additional Protocol. As a major part of the support of the activity, LANL summer interns provided open source information analysis to the LANL-BNL mock inspection team. They were a part of the Next Generation Safeguards Initiative's (NGSI) summer intern program aimed at producing the next generation of safeguards specialists. This paper describes how they used open source information to 'backstop' the LANL-BNL team's effort to construct meaningful Additional Protocol Complementary Access training scenarios for each of the three DOE laboratories, Lawrence Livermore National Laboratory, Idaho National Laboratory, and Oak Ridge National Laboratory.

  19. Discovery of a Plains Caldera Complex and Extinct Lava Lake in Arabia Terra, Mars: Implications for the Discovery of Additional Highland Volcanic Source Regions

    NASA Technical Reports Server (NTRS)

    Bleacher, Jacob; Michalski, Joseph

    2012-01-01

    Several irregularly shaped topographic depressions occur near the dichotomy boundary in northern Arabia Terra, Mars. The geomorphology of these features suggests that they formed by collapse, opposed to meteor impact. At least one depression (approx.55 by 85 km) displays geologic features indicating a complex, multi-stage collapse history. Features within and around the collapse structure indicate volcanic processes. The complex occurs within Hesperian ridged plains of likely volcanic origin and displays no crater rim or evidence for ejecta. Instead the depression consists of a series of circumferential graben and down-dropped blocks which also display upper surfaces similar to ridged plain lavas. Large blocks within the depression are tilted towards the crater center, and display graben that appear to have originally been linked with circumferential graben outside of the complex related to earlier collapse events. A nearly 700 m high mound exists along a graben within the complex that might be a vent. The deepest depression displays two sets of nearly continuous terraces, which we interpret as high-stands of a drained lava lake. These features appear similar to the black ledge described during the Kilauea Iki eruption in 1959. A lacustrine origin for the terraces seems unlikely because of the paucity of channels found in or around the depression that could be linked to aqueous surface processes. In addition, there is no obvious evidence for lacustrine sediments within the basin. Together with the presence of significant faulting that is indicative of collapse we conclude that this crater complex represents a large caldera formed in the Late Noachian to Early Hesperian. Other linear and irregular depressions in the region also might be linked to ancient volcanism. If that hypothesis is correct, it suggests that northern Arabia Terra could contain a large, previously unrecognized highland igneous province. Evacuation of magma via explosive and effusive activity

  20. Effects of different fibre sources and fat addition on cholesterol and cholesterol-related lipids in blood serum, bile and body tissues of growing pigs.

    PubMed

    Kreuzer, M; Hanneken, H; Wittmann, M; Gerdemann, M M; Machmuller, A

    2002-04-01

    Knowledge is limited on the efficacy of hindgut-fermentable dietary fibre to reduce blood, bile and body tissue cholesterol levels. In three experiments with growing pigs the effects of different kinds and levels of bacterially fermentable fibre (BFS) on cholesterol metabolism were examined. Various diets calculated to have similar contents of metabolizable energy were supplied for complete fattening periods. In the first experiment, a stepwise increase from 12 to 20% BFS was performed by supplementing diets with fermentable fibre from sugar beet pulp (modelling hemicelluloses and pectin). Beet pulp, rye bran (modelling cellulose) and citrus pulp (pectin) were offered either independently or in a mixture in the second experiment. These diets were opposed to rations characterized in carbohydrate type by starch either mostly non-resistant (cassava) or partly resistant (maize) to small intestinal digestion. The third experiment was planned to explore the interactions of BFS from citrus pulp with fat either through additional coconut oil/palm kernel oil blend or full-fat soybeans. In all experiments the increase of the BFS content was associated with a constant (cellulose) or decreasing (hemicelluloses, pectin) dietary proportion of non-digestible fibre. In experiment 1 an inverse dose-response relationship between BFS content and cholesterol in blood serum and adipose tissue as well as bile acid concentration in bile was noted while muscle cholesterol did not respond. In experiment 2 the ingredients characterized by cellulose and hemicelluloses/pectin reduced cholesterol-related traits relative to the low-BFS-high-starch controls whereas, except in adipose tissue cholesterol content, the pectinous ingredient had the opposite effect. However, the changes in serum cholesterol mainly affected HDL and not LDL cholesterol. Adipose tissue cholesterol also was slightly lower with partly resistant starch compared to non-resistant starch in the diet. Experiment 3 showed that

  1. Additive usage levels.

    PubMed

    Langlais, R

    1996-01-01

    With the adoption of the European Parliament and Council Directives on sweeteners, colours and miscellaneous additives the Commission is now embarking on the project of coordinating the activities of the European Union Member States in the collection of the data that are to make up the report on food additive intake requested by the European Parliament. This presentation looks at the inventory of available sources on additive use levels and concludes that for the time being national legislation is still the best source of information considering that the directives have yet to be transposed into national legislation. Furthermore, this presentation covers the correlation of the food categories as found in the additives directives with those used by national consumption surveys and finds that in a number of instances this correlation still leaves a lot to be desired. The intake of additives via food ingestion and the intake of substances which are chemically identical to additives but which occur naturally in fruits and vegetables is found in a number of cases to be higher than the intake of additives added during the manufacture of foodstuffs. While the difficulties are recognized in contributing to the compilation of food additive intake data, industry as a whole, i.e. the food manufacturing and food additive manufacturing industries, are confident that in a concerted effort, use data on food additives by industry can be made available. Lastly, the paper points out that with the transportation of the additives directives into national legislation and the time by which the food industry will be able to make use of the new food legislative environment several years will still go by; food additives use data by the food industry will thus have to be reviewed at the beginning of the next century. PMID:8792135

  2. Combined Flux Chamber and Genomics Approach Links Nitrous Acid Emissions to Ammonia Oxidizing Bacteria and Archaea in Urban and Agricultural Soil.

    PubMed

    Scharko, Nicole K; Schütte, Ursel M E; Berke, Andrew E; Banina, Lauren; Peel, Hannah R; Donaldson, Melissa A; Hemmerich, Chris; White, Jeffrey R; Raff, Jonathan D

    2015-12-01

    Nitrous acid (HONO) is a photochemical source of hydroxyl radical and nitric oxide in the atmosphere that stems from abiotic and biogenic processes, including the activity of ammonia-oxidizing soil microbes. HONO fluxes were measured from agricultural and urban soil in mesocosm studies aimed at characterizing biogenic sources and linking them to indigenous microbial consortia. Fluxes of HONO from agricultural and urban soil were suppressed by addition of a nitrification inhibitor and enhanced by amendment with ammonium (NH4(+)), with peaks at 19 and 8 ng m(-2) s(-1), respectively. In addition, both agricultural and urban soils were observed to convert (15)NH4(+) to HO(15)NO. Genomic surveys of soil samples revealed that 1.5-6% of total expressed 16S rRNA sequences detected belonged to known ammonia oxidizing bacteria and archaea. Peak fluxes of HONO were directly related to the abundance of ammonia-oxidizer sequences, which in turn depended on soil pH. Peak HONO fluxes under fertilized conditions are comparable in magnitude to fluxes reported during field campaigns. The results suggest that biogenic HONO emissions will be important in soil environments that exhibit high nitrification rates (e.g., agricultural soil) although the widespread occurrence of ammonia oxidizers implies that biogenic HONO emissions are also possible in the urban and remote environment. PMID:26248160

  3. Liquid chromatography coupled to different atmospheric pressure ionization sources-quadrupole-time-of-flight mass spectrometry and post-column addition of metal salt solutions as a powerful tool for the metabolic profiling of Fusarium oxysporum.

    PubMed

    Cirigliano, Adriana M; Rodriguez, M Alejandra; Gagliano, M Laura; Bertinetti, Brenda V; Godeas, Alicia M; Cabrera, Gabriela M

    2016-03-25

    Fusarium oxysporum L11 is a non-pathogenic soil-borne fungal strain that yielded an extract that showed antifungal activity against phytopathogens. In this study, reversed-phase high-performance liquid chromatography (RP-HPLC) coupled to different atmospheric pressure ionization sources-quadrupole-time-of-flight mass spectrometry (API-QTOF-MS) was applied for the comprehensive profiling of the metabolites from the extract. The employed sources were electrospray (ESI), atmospheric pressure chemical ionization (APCI) and atmospheric pressure photoionization (APPI). Post-column addition of metal solutions of Ca, Cu and Zn(II) was also tested using ESI. A total of 137 compounds were identified or tentatively identified by matching their accurate mass signals, suggested molecular formulae and MS/MS analysis with previously reported data. Some compounds were isolated and identified by NMR. The extract was rich in cyclic peptides like cyclosporins, diketopiperazines and sansalvamides, most of which were new, and are reported here for the first time. The use of post-column addition of metals resulted in a useful strategy for the discrimination of compound classes since specific adducts were observed for the different compound families. This technique also allowed the screening for compounds with metal binding properties. Thus, the applied methodology is a useful choice for the metabolic profiling of extracts and also for the selection of metabolites with potential biological activities related to interactions with metal ions. PMID:26655791

  4. Measurements of gas phase acids in diesel exhaust: a relevant source of HNCO?

    PubMed

    Wentzell, Jeremy J B; Liggio, John; Li, Shao-Meng; Vlasenko, A; Staebler, Ralf; Lu, Gang; Poitras, Marie-Josée; Chan, Tak; Brook, Jeffrey R

    2013-07-16

    Gas-phase acids in light duty diesel (LDD) vehicle exhaust were measured using chemical ionization mass spectrometry (CIMS). Fuel based emission factors (EF) and NOx ratios for these species were determined under differing steady state engine operating conditions. The derived HONO and HNO3 EFs agree well with literature values, with HONO being the single most important acidic emission. Of particular importance is the quantification of the EF for the toxic species, isocyanic acid (HNCO). The emission factors for HNCO ranged from 0.69 to 3.96 mg kgfuel(-1), and were significantly higher than previous biomass burning emission estimates. Further ambient urban measurements of HNCO demonstrated a clear relationship with the known traffic markers of benzene and toluene, demonstrating for the first time that urban commuter traffic is a source of HNCO. Estimates based upon the HNCO-benzene relationship indicate that upward of 23 tonnes of HNCO are released annually from commuter traffic in the Greater Toronto Area, far exceeding the amount possible from LDD alone. Nationally, 250 to 770 tonnes of HNCO may be emitted annually from on-road vehicles, likely representing the dominant source of exposure in urban areas, and with emissions comparable to that of biomass burning. PMID:23781923

  5. Screening of additives in plastics with high resolution time-of-flight mass spectrometry and different ionization sources: direct probe injection (DIP)-APCI, LC-APCI, and LC-ion booster ESI.

    PubMed

    Ballesteros-Gómez, Ana; Jonkers, Tim; Covaci, Adrian; de Boer, Jacob

    2016-04-01

    Plastics are complex mixtures consisting of a polymer and additives with different physico-chemical properties. We developed a broad screening method to elucidate the nature of compounds present in plastics used in electrical/electronic equipment commonly found at homes (e.g., electrical adaptors, computer casings, heaters). The analysis was done by (a) solvent extraction followed by liquid chromatography coupled to high accuracy/resolution time-of-flight mass spectrometry (TOFMS) with different ionization sources or (b) direct analysis of the solid by ambient mass spectrometry high accuracy/resolution TOFMS. The different ionization methods showed different selectivity and sensitivity for the different compound classes and were complementary. A variety of antioxidants, phthalates, UV filters, and flame retardants were found in most samples. Furthermore, some recently reported impurities or degradation products derived from flame retardants were identified, such as hydroxylated triphenyl phosphate and tetrabromobisphenol A monoglycidyl ether. PMID:26758596

  6. Effect of protein source and protease addition on performance, blood metabolites and nutrient digestibility of turkeys fed on low-protein diets from 28 to 55 d post hatch.

    PubMed

    Shahir, M H; Rahimi, R; Taheri, H R; Heidariniya, A; Baradaran, N; Asadi Kermani, Z

    2016-06-01

    The objective of this study was to investigate the effect of a monocomponent protease and dietary inclusion of canola meal (CM) and poultry by-product meal (PBM) on growth performance, carcass characteristics and blood metabolites of turkeys fed on low crude protein (CP) diets from 28 to 55 d post hatch. Experimental treatments included control, maize-soybean meal diet including 258.3 g/kg CP; negative control 1 (NC1), maize-soybean meal diet with reduced CP (232.4 g/kg); NC2, control diet (CP, 258.3 g/kg) including CM (80 g/kg) and PBM (80 g/kg); NC3, maize-soybean meal diet with reduced CP (232.4 g/kg) including CM (80 g/kg) and PBM (80 g/kg). Also, the NC1 + P and NC3 + P diets were created by addition of protease enzyme (30 000 units/kg of diet) to the NC1 and NC3 diets, respectively. The NC3 group had lower body weight gain (BWG) compared to those fed on the control diet, and no improvement with enzyme addition (NC3 + P) was achieved. The protease addition to the NC1 diet (NC1 + P) improved BWG to the level of the control diet. The NC1 group had higher feed conversion ratio (FCR) compared to the control and NC3 + P, but protease addition to the NC1 diet improved FCR. Protease addition to the low CP diets resulted in higher nitrogen (N) retention than in the control and NC2 groups. Also, the NC1 + P and NC3 + P diets increased apparent ileal digestibility (AID) of CP compared to the control group. It was concluded that addition of CM (up to 80 g/kg) and PBM (up to 80 g/kg) to turkey diets had no negative effect on growth performance from 28 to 55 d of age. The NC1 + P group achieved the BWG of the control group which was partially due to increases in N retention and AID of CP, but the NC3 + P group failed to recover the growth losses. This difference implies that the efficacy of the protease may depend upon the protein source in the ration. PMID:27074290

  7. Oxidative capacity of the Mexico City atmosphere - Part 1: A radical source perspective

    NASA Astrophysics Data System (ADS)

    Volkamer, R.; Sheehy, P. M.; Molina, L. T.; Molina, M. J.

    2007-04-01

    A detailed analysis of OH, HO2 and RO2 radical sources is presented for the near field photochemical regime inside the Mexico City Metropolitan Area (MCMA). During spring of 2003 (MCMA-2003 field campaign) an extensive set of measurements was collected to quantify time resolved ROx (sum of OH, HO2, RO2) radical production rates from day- and nighttime radical sources. The Master Chemical Mechanism (MCMv3.1) was constrained by measurements of (1) concentration time-profiles of photosensitive radical precursors, i.e., nitrous acid (HONO), formaldehyde (HCHO), ozone (O3), glyoxal (CHOCHO), and other oxygenated volatile organic compounds (OVOCs); (2) respective photolysis-frequencies (J-values); (3) concentration time-profiles of alkanes, alkenes, and aromatic VOCs (103 compound are treated) and oxidants, i.e., OH- and NO3 radicals, O3; and (4) NO, NO2, meteorological and other parameters. The ROx production rate was calculated directly from these observations; MCM was used to estimate further ROx production from unconstrained sources, and express overall ROx production as OH-equivalents (i.e., taking into account the propagation efficiencies of RO2 and HO2 radicals into OH radicals). Daytime radical production is found to be about 10-25 times higher than at night; it does not track the abundance of sunlight. 12-h average daytime contributions of individual sources are: HCHO and O3 photolysis, each about 20%; O3/alkene reactions and HONO photolysis, each about 15%; unmeasured sources about 30%. While the direct contribution of O3/alkene reactions appears to be moderately small, source-apportionment of ambient HCHO and HONO identifies O3/alkene reactions as being largely responsible for jump-starting photochemistry about one hour after sunrise. The peak radical production is found to be higher than in any other urban influenced environment studied to date; further, differences exist in the timing of radical production. Our measurements and analysis comprise a database

  8. Volatile organic compound conversion by ozone, hydroxyl radicals, and nitrate radicals in residential indoor air: Magnitudes and impacts of oxidant sources

    NASA Astrophysics Data System (ADS)

    Waring, Michael S.; Wells, J. Raymond

    2015-04-01

    Indoor chemistry may be initiated by reactions of ozone (O3), the hydroxyl radical (OH), or the nitrate radical (NO3) with volatile organic compounds (VOC). The principal indoor source of O3 is air exchange, while OH and NO3 formation are considered as primarily from O3 reactions with alkenes and nitrogen dioxide (NO2), respectively. Herein, we used time-averaged models for residences to predict O3, OH, and NO3 concentrations and their impacts on conversion of typical residential VOC profiles, within a Monte Carlo framework that varied inputs probabilistically. We accounted for established oxidant sources, as well as explored the importance of two newly realized indoor sources: (i) the photolysis of nitrous acid (HONO) indoors to generate OH and (ii) the reaction of stabilized Criegee intermediates (SCI) with NO2 to generate NO3. We found total VOC conversion to be dominated by reactions both with O3, which almost solely reacted with D-limonene, and also with OH, which reacted with D-limonene, other terpenes, alcohols, aldehydes, and aromatics. VOC oxidation rates increased with air exchange, outdoor O3, NO2 and D-limonene sources, and indoor photolysis rates; and they decreased with O3 deposition and nitric oxide (NO) sources. Photolysis was a strong OH formation mechanism for high NO, NO2, and HONO settings, but SCI/NO2 reactions weakly generated NO3 except for only a few cases.

  9. Volatile organic compound conversion by ozone, hydroxyl radicals, and nitrate radicals in residential indoor air: Magnitudes and impacts of oxidant sources

    PubMed Central

    Waring, Michael S.; Wells, J. Raymond

    2016-01-01

    Indoor chemistry may be initiated by reactions of ozone (O3), the hydroxyl radical (OH), or the nitrate radical (NO3) with volatile organic compounds (VOC). The principal indoor source of O3 is air exchange, while OH and NO3 formation are considered as primarily from O3 reactions with alkenes and nitrogen dioxide (NO2), respectively. Herein, we used time-averaged models for residences to predict O3, OH, and NO3 concentrations and their impacts on conversion of typical residential VOC profiles, within a Monte Carlo framework that varied inputs probabilistically. We accounted for established oxidant sources, as well as explored the importance of two newly realized indoor sources: (i) the photolysis of nitrous acid (HONO) indoors to generate OH and (ii) the reaction of stabilized Criegee intermediates (SCI) with NO2 to generate NO3. We found total VOC conversion to be dominated by reactions both with O3, which almost solely reacted with d-limonene, and also with OH, which reacted with d-limonene, other terpenes, alcohols, aldehydes, and aromatics. VOC oxidation rates increased with air exchange, outdoor O3, NO2 and d-limonene sources, and indoor photolysis rates; and they decreased with O3 deposition and nitric oxide (NO) sources. Photolysis was a strong OH formation mechanism for high NO, NO2, and HONO settings, but SCI/NO2 reactions weakly generated NO3 except for only a few cases. PMID:26855604

  10. Summertime formaldehyde observations in New York City: Ambient levels, sources and its contribution to HOx radicals

    NASA Astrophysics Data System (ADS)

    Lin, Yu Chi; Schwab, James J.; Demerjian, Kenneth L.; Bae, Min-Suk; Chen, Wei-Nai; Sun, Yele; Zhang, Qi; Hung, Hui-Ming; Perry, Jacqueline

    2012-04-01

    Measurements of ambient formaldehyde (HCHO), related gases and particulate matter were carried out from the SUNY Albany mobile platform at the Queens College site in New York City (NYC) from 15 July to 3 August 2009. Ambient HCHO was measured using a quantum cascade laser (QCL) trace gas detector. HCHO concentrations ranged from 0.4 to 7.5 ppb with a mean value of 2.2 ± 1.1 ppb. Daily HCHO peaks were nearly always found between 1100 EST (Eastern Standard Time) and noontime throughout the sampling period. HCHO correlated strongly with NOx and black carbon during the traffic rush hours, but around noontime HCHO correlated much better with total oxidants (Ox = O3 + NO2). Using the diurnal pattern of HCHO/BC ratios, we estimated that 70% of HCHO present between 1200 EST to 1500 EST was produced by photochemical reactions. Sources of photochemically produced HCHO were calculated using measured concentrations of hydrocarbons, their reaction kinetics with OH radicals, and HCHO yields. These calculations indicated that isoprene oxidation was the dominant source of HCHO for this period at this site, responsible for 44%, followed by methane (25%) and propene (18%). To assess the impact of HCHO as a radical source, the HOx production rates from HCHO, HONO, O3 photolysis, and alkenes +O3 were calculated as well. Daily averaged HOx production rates from HONO, HCHO, O3 photolysis and alkenes +O3 were 8.6 × 106, 2.3 × 106, 1.7 × 106, 2.1 × 105 molecules cm-3 s-1, respectively, contributing 67, 18, 13 and 2% to the overall daily HOx radical budget from these precursors.

  11. Photochemistry at interfaces: a source of radicals impacting on aerosol formation and properties

    NASA Astrophysics Data System (ADS)

    George, C.; D'anna, B.; Monge, M.; Dupart, Y.

    2011-12-01

    Recent findings confirm the presence of light absorbing organic material (HULIS, biomass burning particles, PAHs) in atmospheric aerosols... but also at the air/ocean interface. The presence of such light absorbing material allows photosensitised processes to occur. The latter may be sources of radicals in the troposphere that may alter its oxidation capacity (as for instance through the formation of HONO) or change the pathways leading to particle formation and ageing. We will exemplify such processes by presenting new data on the generation of radicals from dust particles or at the air/sea interface leading to particle formation in presence of SO2. These are recent findings that are questioning our current understanding of tropospheric photochemistry.

  12. Atmospheric Pollution and Emission Sources in South Asian Urban Region

    NASA Astrophysics Data System (ADS)

    Biswas, K. F.; Husain, Liaquat

    2009-04-01

    Rapid urbanization, and lack of efficient monitoring and control of pollution, along with phenomena like Asian Brown Haze or prolonged episodes of winter fog, makes the South Asian atmospheric chemistry a very complex one. The anthropogenic aerosols released from this region are projected to become the dominant component of anthropogenic aerosols worldwide in the next 25 years (Nakicenovic and Swart, 2000). The region is one of the most densely populated in the world, with present population densities of 100-500 persons km-2. There are six big cities, namely, Delhi, Dhaka, Karachi, Kolkata, Lahore, and Mumbai, each housing a population around or above 10 million. There is now a real concern about the sustainability of the region's ability to support the population due to air pollution, loss of biodiversity and soil degradation. Therefore, we conducted several extensive campaigns over last 10 years in Lahore, Karachi, and Islamabad in Pakistan to (1) chemically characterize the aerosols (PM2.5 mass, concentrations of trace elements, ions, black and organic carbon), and gaseous pollutants (concentrations of NH3, SO2, HONO, HNO3, HCl and (COOH)2, and (2) identify the major emission sources in this region. Exceedingly high concentrations of all species, relative to major urban areas of US and Europe, were observed. Concentrations of PM2.5, BC, Pb, SO42-, NH4+, HONO, NH3 respectively, up to 476, 110, 12, 66, 60, 19.6 and 50 μgm-3 were observed in these cities, which were far in excess of WHO and US EPA air quality standard (Biswas et al., 2008). We use air parcel back trajectories, intercomponent relationships and meteorological observations to explain chemistry and emission sources of aerosol constituents. Carbonaceous aerosols contributed up to 69% of the PM2.5 mass (Husain et al., 2007). Source apportionment was conducted using positive matrix factorization. The analysis has classified six emission sources of aerosol components, namely, industrial activities, wood

  13. Release of nitrous acid and nitrogen dioxide from nitrate photolysis in acidic aqueous solutions.

    PubMed

    Scharko, Nicole K; Berke, Andrew E; Raff, Jonathan D

    2014-10-21

    Nitrate (NO3(-)) is an abundant component of aerosols, boundary layer surface films, and surface water. Photolysis of NO3(-) leads to NO2 and HONO, both of which play important roles in tropospheric ozone and OH production. Field and laboratory studies suggest that NO3¯ photochemistry is a more important source of HONO than once thought, although a mechanistic understanding of the variables controlling this process is lacking. We present results of cavity-enhanced absorption spectroscopy measurements of NO2 and HONO emitted during photodegradation of aqueous NO3(-) under acidic conditions. Nitrous acid is formed in higher quantities at pH 2-4 than expected based on consideration of primary photochemical channels alone. Both experimental and modeled results indicate that the additional HONO is not due to enhanced NO3(-) absorption cross sections or effective quantum yields, but rather to secondary reactions of NO2 in solution. We find that NO2 is more efficiently hydrolyzed in solution when it is generated in situ during NO3(-) photolysis than for the heterogeneous system where mass transfer of gaseous NO2 into bulk solution is prohibitively slow. The presence of nonchromophoric OH scavengers that are naturally present in the environment increases HONO production 4-fold, and therefore play an important role in enhancing daytime HONO formation from NO3(-) photochemistry. PMID:25271384

  14. Novel tracer method to measure isotopic labeled gas-phase nitrous acid (HO15NO) in biogeochemical studies.

    PubMed

    Wu, Dianming; Kampf, Christopher J; Pöschl, Ulrich; Oswald, Robert; Cui, Junfang; Ermel, Michael; Hu, Chunsheng; Trebs, Ivonne; Sörgel, Matthias

    2014-07-15

    Gaseous nitrous acid (HONO), the protonated form of nitrite, contributes up to ∼60% to the primary formation of hydroxyl radical (OH), which is a key oxidant in the degradation of most air pollutants. Field measurements and modeling studies indicate a large unknown source of HONO during daytime. Here, we developed a new tracer method based on gas-phase stripping-derivatization coupled to liquid chromatography-mass spectrometry (LC-MS) to measure the 15N relative exceedance, ψ(15N), of HONO in the gas-phase. Gaseous HONO is quantitatively collected and transferred to an azo dye, purified by solid phase extraction (SPE), and analyzed using high performance liquid chromatography coupled to mass spectrometry (HPLC-MS). In the optimal working range of ψ(15N)=0.2-0.5, the relative standard deviation of ψ(15N) is <4%. The optimum pH and solvents for extraction by SPE and potential interferences are discussed. The method was applied to measure HO15NO emissions from soil in a dynamic chamber with and without spiking 15) labeled urea. The identification of HO15NO from soil with 15N urea addition confirmed biogenic emissions of HONO from soil. The method enables a new approach of studying the formation pathways of HONO and its role for atmospheric chemistry (e.g., ozone formation) and environmental tracer studies on the formation and conversion of gaseous HONO or aqueous NO2- as part of the biogeochemical nitrogen cycle, e.g., in the investigation of fertilization effects on soil HONO emissions and microbiological conversion of NO2- in the hydrosphere. PMID:24954648

  15. Vertical profiles of nitrous acid in the nocturnal urban atmosphere of Houston, TX

    NASA Astrophysics Data System (ADS)

    Wong, K. W.; Oh, H.-J.; Lefer, B. L.; Rappenglück, B.; Stutz, J.

    2011-04-01

    HONO conversion on the ground was the dominant source of HONO, followed by traffic emission. Aerosol did not play an important role in HONO formation. Although ground deposition was also a major removal pathway of HONO, net HONO production at the ground was the main source of HONO in our model studies. Sensitivity studies showed that in the stable NBL, net HONO production at the ground tends to increase with faster vertical mixing and stronger NOx emission. Vertical transport was found to be the dominant source of HONO aloft.

  16. Vertical profiles of nitrous acid in the nocturnal urban atmosphere of Houston, TX

    NASA Astrophysics Data System (ADS)

    Wong, K. W.; Oh, H.-J.; Lefer, B.; Rappenglück, B.; Stutz, J.

    2010-12-01

    Nitrous acid (HONO) often plays an important role in tropospheric photochemistry as a major precursor of the hydroxyl radical (OH) in early morning hours and potentially during the day. However, the processes leading to formation of HONO and its vertical distribution at night, which can have a considerable impact on daytime ozone formation, are currently poorly characterized by observations and models. Long-path differential optical absorption spectroscopy (LP-DOAS) measurements of HONO during the 2006 TexAQS II Radical and Aerosol Measurement Project (TRAMP), near downtown Houston, TX, show nocturnal vertical profiles of HONO, with mixing ratios of up to 2.2 ppb near the surface and below 100 ppt aloft. Three nighttime periods of HONO, NO2 and O3 observations during TRAMP were used to perform model simulations of vertical mixing ratio profiles. By adjusting vertical mixing and NOx emissions the modeled NO2 and O3 mixing ratios showed very good agreement with the observations. Using a simple conversion of NO2 to HONO on the ground, direct HONO emissions, as well as HONO loss at the ground and on aerosol, the observed HONO profiles were reproduced well by the model. The unobserved increase of HONO to NO2 ratio (HONO/NO2) with altitude that was simulated by the initial model runs was found to be due to HONO uptake being too small on aerosol and too large on the ground. Refined model runs, with adjusted HONO uptake coefficients, showed much better agreement of HONO and HONO/NO2 for two typical nights, except during morning rush hour, when other HONO formation pathways are most likely active. One of the nights analyzed showed increase of HONO mixing ratios together with decreasing NO2 mixing ratios that the model was unable to reproduce, most likely due to the impact of weak precipitation during this night. HONO formation and removal rates averaged over the lowest 300 m of the atmosphere showed that NO2 to HONO conversion on the ground was the dominant source of HONO

  17. [Food additives and healthiness].

    PubMed

    Heinonen, Marina

    2014-01-01

    Additives are used for improving food structure or preventing its spoilage, for example. Many substances used as additives are also naturally present in food. The safety of additives is evaluated according to commonly agreed principles. If high concentrations of an additive cause adverse health effects for humans, a limit of acceptable daily intake (ADI) is set for it. An additive is a risk only when ADI is exceeded. The healthiness of food is measured on the basis of nutrient density and scientifically proven effects. PMID:24772784

  18. Polyimide processing additives

    NASA Technical Reports Server (NTRS)

    Pratt, J. R.; St. Clair, T. L.; Burks, H. D.; Stoakley, D. M.

    1987-01-01

    A method has been found for enhancing the melt flow of thermoplastic polyimides during processing. A high molecular weight 422 copoly(amic acid) or copolyimide was fused with approximately 0.05 to 5 pct by weight of a low molecular weight amic acid or imide additive, and this melt was studied by capillary rheometry. Excellent flow and improved composite properties on graphite resulted from the addition of a PMDA-aniline additive to LARC-TPI. Solution viscosity studies imply that amic acid additives temporarily lower molecular weight and, hence, enlarge the processing window. Thus, compositions containing the additive have a lower melt viscosity for a longer time than those unmodified.

  19. Kentucky Department for Natural Resources and Environmental Protection permit application for air contaminant source: SRC-I demonstration plant, Newman, Kentucky. Supplement I. [Additional information on 38 items requested by KY/DNREP

    SciTech Connect

    Pearson, Jr., John F.

    1981-02-13

    In response to a letter from KY/DNREP, January 19, 1981, ICRC and DOE have prepared the enclosed supplement to the Kentucky Department for Natural Resources and Environmental Protection Permit Application for Air Contaminant Source for the SRC-I Demonstration Plant. Each of the 38 comments contained in the letter has been addressed in accordance with the discussions held in Frankfort on January 28, 1981, among representatives of KY/DNREP, EPA Region IV, US DOE, and ICRC. The questions raised involve requests for detailed information on the performance and reliability of proprietary equipment, back-up methods, monitoring plans for various pollutants, composition of wastes to flares, emissions estimates from particular operations, origin of baseline information, mathematical models, storage tanks, dusts, etc. (LTN)

  20. An additional middle cuneiform?

    PubMed Central

    Brookes-Fazakerley, S.D.; Jackson, G.E.; Platt, S.R.

    2015-01-01

    Additional cuneiform bones of the foot have been described in reference to the medial bipartite cuneiform or as small accessory ossicles. An additional middle cuneiform has not been previously documented. We present the case of a patient with an additional ossicle that has the appearance and location of an additional middle cuneiform. Recognizing such an anatomical anomaly is essential for ruling out second metatarsal base or middle cuneiform fractures and for the preoperative planning of arthrodesis or open reduction and internal fixation procedures in this anatomical location. PMID:26224890

  1. Carbamate deposit control additives

    SciTech Connect

    Honnen, L.R.; Lewis, R.A.

    1980-11-25

    Deposit control additives for internal combustion engines are provided which maintain cleanliness of intake systems without contributing to combustion chamber deposits. The additives are poly(oxyalkylene) carbamates comprising a hydrocarbyloxyterminated poly(Oxyalkylene) chain of 2-5 carbon oxyalkylene units bonded through an oxycarbonyl group to a nitrogen atom of ethylenediamine.

  2. Bioprocessing of “Hair Waste” by Paecilomyces lilacinus as a Source of a Bleach-Stable, Alkaline, and Thermostable Keratinase with Potential Application as a Laundry Detergent Additive: Characterization and Wash Performance Analysis

    PubMed Central

    Cavello, Ivana A.; Hours, Roque A.; Cavalitto, Sebastián F.

    2012-01-01

    Paecilomyces lilacinus (Thom) Samson LPS 876, a locally isolated fungal strain, was grown on minimal mineral medium containing “hair waste,” a residue from the hair-saving unhairing process, and produced a protease with keratinolytic activity. This enzyme was biochemically characterized. The optimum reaction conditions, determined with a response surface methodology, were 60°C and pH 6.0. It was remarkably stable in a wide range of pHs and temperatures. Addition of Ca2+, Mg2+, or sorbitol was found to be effective in increasing thermal stability of the protease. PMSF and Hg2+ inhibited the proteolytic activity indicating the presence of a thiol-dependent serine protease. It showed high stability toward surfactants, bleaching agents, and solvents. It was also compatible with commercial detergents (7 mg/mL) such as Ariel, Skip, Drive, and Ace, retaining more than 70% of its proteolytic activity in all detergents after 1 h of incubation at 40°C. Wash performance analysis revealed that this protease could effectively remove blood stains. From these properties, this enzyme may be considered as a potential candidate for future use in biotechnological processes, as well as in the formulation of laundry detergents. PMID:23365760

  3. Bioprocessing of "Hair Waste" by Paecilomyces lilacinus as a Source of a Bleach-Stable, Alkaline, and Thermostable Keratinase with Potential Application as a Laundry Detergent Additive: Characterization and Wash Performance Analysis.

    PubMed

    Cavello, Ivana A; Hours, Roque A; Cavalitto, Sebastián F

    2012-01-01

    Paecilomyces lilacinus (Thom) Samson LPS 876, a locally isolated fungal strain, was grown on minimal mineral medium containing "hair waste," a residue from the hair-saving unhairing process, and produced a protease with keratinolytic activity. This enzyme was biochemically characterized. The optimum reaction conditions, determined with a response surface methodology, were 60°C and pH 6.0. It was remarkably stable in a wide range of pHs and temperatures. Addition of Ca(2+), Mg(2+), or sorbitol was found to be effective in increasing thermal stability of the protease. PMSF and Hg(2+) inhibited the proteolytic activity indicating the presence of a thiol-dependent serine protease. It showed high stability toward surfactants, bleaching agents, and solvents. It was also compatible with commercial detergents (7 mg/mL) such as Ariel, Skip, Drive, and Ace, retaining more than 70% of its proteolytic activity in all detergents after 1 h of incubation at 40°C. Wash performance analysis revealed that this protease could effectively remove blood stains. From these properties, this enzyme may be considered as a potential candidate for future use in biotechnological processes, as well as in the formulation of laundry detergents. PMID:23365760

  4. Polyimide processing additives

    NASA Technical Reports Server (NTRS)

    Fletcher, James C. (Inventor); Pratt, J. Richard (Inventor); St.clair, Terry L. (Inventor); Stoakley, Diane M. (Inventor); Burks, Harold D. (Inventor)

    1992-01-01

    A process for preparing polyimides having enhanced melt flow properties is described. The process consists of heating a mixture of a high molecular weight poly-(amic acid) or polyimide with a low molecular weight amic acid or imide additive in the range of 0.05 to 15 percent by weight of additive. The polyimide powders so obtained show improved processability, as evidenced by lower melt viscosity by capillary rheometry. Likewise, films prepared from mixtures of polymers with additives show improved processability with earlier onset of stretching by TMA.

  5. Polyimide processing additives

    NASA Technical Reports Server (NTRS)

    Pratt, J. Richard (Inventor); St.clair, Terry L. (Inventor); Stoakley, Diane M. (Inventor); Burks, Harold D. (Inventor)

    1993-01-01

    A process for preparing polyimides having enhanced melt flow properties is described. The process consists of heating a mixture of a high molecular weight poly-(amic acid) or polyimide with a low molecular weight amic acid or imide additive in the range of 0.05 to 15 percent by weight of the additive. The polyimide powders so obtained show improved processability, as evidenced by lower melt viscosity by capillary rheometry. Likewise, films prepared from mixtures of polymers with additives show improved processability with earlier onset of stretching by TMA.

  6. Smog control fuel additives

    SciTech Connect

    Lundby, W.

    1993-06-29

    A method is described of controlling, reducing or eliminating, ozone and related smog resulting from photochemical reactions between ozone and automotive or industrial gases comprising the addition of iodine or compounds of iodine to hydrocarbon-base fuels prior to or during combustion in an amount of about 1 part iodine per 240 to 10,000,000 parts fuel, by weight, to be accomplished by: (a) the addition of these inhibitors during or after the refining or manufacturing process of liquid fuels; (b) the production of these inhibitors for addition into fuel tanks, such as automotive or industrial tanks; or (c) the addition of these inhibitors into combustion chambers of equipment utilizing solid fuels for the purpose of reducing ozone.

  7. Food Additives and Hyperkinesis

    ERIC Educational Resources Information Center

    Wender, Ester H.

    1977-01-01

    The hypothesis that food additives are causally associated with hyperkinesis and learning disabilities in children is reviewed, and available data are summarized. Available from: American Medical Association 535 North Dearborn Street Chicago, Illinois 60610. (JG)

  8. Additional Types of Neuropathy

    MedlinePlus

    ... A A Listen En Español Additional Types of Neuropathy Charcot's Joint Charcot's Joint, also called neuropathic arthropathy, ... can stop bone destruction and aid healing. Cranial Neuropathy Cranial neuropathy affects the 12 pairs of nerves ...

  9. Additive Manufacturing Infrared Inspection

    NASA Technical Reports Server (NTRS)

    Gaddy, Darrell

    2014-01-01

    Additive manufacturing is a rapid prototyping technology that allows parts to be built in a series of thin layers from plastic, ceramics, and metallics. Metallic additive manufacturing is an emerging form of rapid prototyping that allows complex structures to be built using various metallic powders. Significant time and cost savings have also been observed using the metallic additive manufacturing compared with traditional techniques. Development of the metallic additive manufacturing technology has advanced significantly over the last decade, although many of the techniques to inspect parts made from these processes have not advanced significantly or have limitations. Several external geometry inspection techniques exist such as Coordinate Measurement Machines (CMM), Laser Scanners, Structured Light Scanning Systems, or even traditional calipers and gages. All of the aforementioned techniques are limited to external geometry and contours or must use a contact probe to inspect limited internal dimensions. This presentation will document the development of a process for real-time dimensional inspection technique and digital quality record of the additive manufacturing process using Infrared camera imaging and processing techniques.

  10. 40 CFR 412.37 - Additional measures.

    Code of Federal Regulations, 2012 CFR

    2009-07-01

    ... 40 Protection of Environment 28 2009-07-01 2009-07-01 false Additional measures. 412.37 Section 412.37 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS CONCENTRATED ANIMAL FEEDING OPERATIONS (CAFO) POINT SOURCE CATEGORY Dairy Cows and Cattle Other Than Veal Calves § 412.37 Additional...

  11. Phenylethynyl Containing Reactive Additives

    NASA Technical Reports Server (NTRS)

    Connell, John W. (Inventor); Smith, Joseph G., Jr. (Inventor); Hergenrother, Paul M. (Inventor)

    2002-01-01

    Phenylethynyl containing reactive additives were prepared from aromatic diamine, containing phenylethvnvl groups and various ratios of phthalic anhydride and 4-phenylethynviphthalic anhydride in glacial acetic acid to form the imide in one step or in N-methyl-2-pvrrolidinone to form the amide acid intermediate. The reactive additives were mixed in various amounts (10% to 90%) with oligomers containing either terminal or pendent phenylethynyl groups (or both) to reduce the melt viscosity and thereby enhance processability. Upon thermal cure, the additives react and become chemically incorporated into the matrix and effect an increase in crosslink density relative to that of the host resin. This resultant increase in crosslink density has advantageous consequences on the cured resin properties such as higher glass transition temperature and higher modulus as compared to that of the host resin.

  12. Additives in plastics.

    PubMed Central

    Deanin, R D

    1975-01-01

    The polymers used in plastics are generally harmless. However, they are rarely used in pure form. In almost all commercial plastics, they are "compounded" with monomeric ingredients to improve their processing and end-use performance. In order of total volume used, these monomeric additives may be classified as follows: reinforcing fibers, fillers, and coupling agents; plasticizers; colorants; stabilizers (halogen stabilizers, antioxidants, ultraviolet absorbers, and biological preservatives); processing aids (lubricants, others, and flow controls); flame retardants, peroxides; and antistats. Some information is already available, and much more is needed, on potential toxicity and safe handling of these additives during processing and manufacture of plastics products. PMID:1175566

  13. Biobased lubricant additives

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Fully biobased lubricants are those formulated using all biobased ingredients, i.e. biobased base oils and biobased additives. Such formulations provide the maximum environmental, safety, and economic benefits expected from a biobased product. Currently, there are a number of biobased base oils that...

  14. Multifunctional fuel additives

    SciTech Connect

    Baillargeon, D.J.; Cardis, A.B.; Heck, D.B.

    1991-03-26

    This paper discusses a composition comprising a major amount of a liquid hydrocarbyl fuel and a minor low-temperature flow properties improving amount of an additive product of the reaction of a suitable diol and product of a benzophenone tetracarboxylic dianhydride and a long-chain hydrocarbyl aminoalcohol.

  15. 17 CFR 38.1201 - Additional sources for compliance.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... contract design meets the risk management needs of prospective users and promotes price discovery of the.../or price discovery functions. A designated contract market should provide a statement indicating that... submitted for the most recent three full calendar years and for as many of the current year's months...

  16. TLSpy: An Open-Source Addition to Terrestrial Lidar Workflows

    NASA Astrophysics Data System (ADS)

    Frechette, J. D.; Weissmann, G. S.; Wawrzyniec, T. F.

    2008-12-01

    Terrestrial lidar scanners (TLS) that capture three dimensional (3D) geometry with cm scale precision present many new opportunities in the Earth Sciences and related fields. However, the lack of domain specific tools impedes full and efficient utilization of the information contained in these datasets. Most processing and analysis is performed using a variety of manufacturing, surveying, airborne lidar, and GIS software. Although much overlap exists, inevitably some needs are not addressed by these applications. TLSpy provides a plugin driven framework with 3D visualization capabilities that encourages researchers to fill these gaps. The goal is to free researchers from the intellectual overhead imposed by user and data interface design, enabling rapid development of TLS specific processing and analysis algorithms. We present two plugins as examples of problems that TLSpy is being applied to. The first plugin corrects for the strong influence of target orientation on TLS measured reflectance intensities. It calculates the distribution of incidence angles and intensities in an input scan and assists the user in fitting a reflectance model to the distribution. The model is then used to normalize input intensities, minimizing the impact of surface orientation and simplifying the extraction of quantitative data from reflectance measurements. Although reasonable default models can be determined the large number of factors influencing reflectance values require that the plugin be designed for maximum flexibility, allowing the user to adjust all model parameters and define new reflectance models as needed. The second plugin helps eliminate multipath reflections from water surfaces. Characterized by a lower intensity mirror image of the subaerial bank appearing below the water surface, these reflections are a common problem in scans containing water. These erroneous reflections can be removed by manually selecting points that lie on the waterline, fitting a plane to the points, and deleting points below that plane. This plugin simplifies the process by automatically identifying waterline points using characteristic changes in geometry and intensity. Automatic identification is often faster and more reliable than manual identification, however, manual control is retained as a fallback for degenerate cases.

  17. Boron addition to alloys

    SciTech Connect

    Coad, B. C.

    1985-08-20

    A process for addition of boron to an alloy which involves forming a melt of the alloy and a reactive metal, selected from the group consisting of aluminum, titanium, zirconium and mixtures thereof to the melt, maintaining the resulting reactive mixture in the molten state and reacting the boric oxide with the reactive metal to convert at least a portion of the boric oxide to boron which dissolves in the resulting melt, and to convert at least portion of the reactive metal to the reactive metal oxide, which oxide remains with the resulting melt, and pouring the resulting melt into a gas stream to form a first atomized powder which is subsequently remelted with further addition of boric oxide, re-atomized, and thus reprocessed to convert essentially all the reactive metal to metal oxide to produce a powdered alloy containing specified amounts of boron.

  18. Tackifier for addition polyimides

    NASA Technical Reports Server (NTRS)

    Butler, J. M.; St.clair, T. L.

    1980-01-01

    A modification to the addition polyimide, LaRC-160, was prepared to improve tack and drape and increase prepeg out-time. The essentially solventless, high viscosity laminating resin is synthesized from low cost liquid monomers. The modified version takes advantage of a reactive, liquid plasticizer which is used in place of solvent and helps solve a major problem of maintaining good prepeg tack and drape, or the ability of the prepeg to adhere to adjacent plies and conform to a desired shape during the lay up process. This alternate solventless approach allows both longer life of the polymer prepeg and the processing of low void laminates. This approach appears to be applicable to all addition polyimide systems.

  19. Vinyl capped addition polyimides

    NASA Technical Reports Server (NTRS)

    Vannucci, Raymond D. (Inventor); Malarik, Diane C. (Inventor); Delvigs, Peter (Inventor)

    1991-01-01

    Polyimide resins (PMR) are generally useful where high strength and temperature capabilities are required (at temperatures up to about 700 F). Polyimide resins are particularly useful in applications such as jet engine compressor components, for example, blades, vanes, air seals, air splitters, and engine casing parts. Aromatic vinyl capped addition polyimides are obtained by reacting a diamine, an ester of tetracarboxylic acid, and an aromatic vinyl compound. Low void materials with improved oxidative stability when exposed to 700 F air may be fabricated as fiber reinforced high molecular weight capped polyimide composites. The aromatic vinyl capped polyimides are provided with a more aromatic nature and are more thermally stable than highly aliphatic, norbornenyl-type end-capped polyimides employed in PMR resins. The substitution of aromatic vinyl end-caps for norbornenyl end-caps in addition polyimides results in polymers with improved oxidative stability.

  20. [Biologically active food additives].

    PubMed

    Velichko, M A; Shevchenko, V P

    1998-07-01

    More than half out of 40 projects for the medical science development by the year of 2000 have been connected with the bio-active edible additives that are called "the food of XXI century", non-pharmacological means for many diseases. Most of these additives--nutricevtics and parapharmacevtics--are intended for the enrichment of food rations for the sick or healthy people. The ecologicaly safest and most effective are combined domestic adaptogens with immuno-modulating and antioxidating action that give anabolic and stimulating effect,--"leveton", "phytoton" and "adapton". The MKTs-229 tablets are residue discharge means. For atherosclerosis and general adiposis they recommend "tsar tablets" and "aiconol (ikhtien)"--on the base of cod-liver oil or "splat" made out of seaweed (algae). All these preparations have been clinically tested and received hygiene certificates from the Institute of Dietology of the Russian Academy of Medical Science. PMID:9752776

  1. Electrophilic addition of astatine

    SciTech Connect

    Norseev, Yu.V.; Vasaros, L.; Nhan, D.D.; Huan, N.K.

    1988-03-01

    It has been shown for the first time that astatine is capable of undergoing addition reactions to unsaturated hydrocarbons. A new compound of astatine, viz., ethylene astatohydrin, has been obtained, and its retention numbers of squalane, Apiezon, and tricresyl phosphate have been found. The influence of various factors on the formation of ethylene astatohydrin has been studied. It has been concluded on the basis of the results obtained that the univalent cations of astatine in an acidic medium is protonated hypoastatous acid.

  2. Hydrocarbon fuel additive

    SciTech Connect

    Ambrogio, S.

    1989-02-28

    This patent describes the method of fuel storage or combustion, wherein the fuel supply contains small amounts of water, the step of adding to the fuel supply an additive comprising a blend of a hydrophilic agent chosen from the group of ethylene glycol, n-butyl alcohol, and cellosolve in the range of 22-37% by weight; ethoxylated nonylphenol in the range of 26-35% by weight; nonylphenol polyethylene glycol ether in the range of 32-43% by weight.

  3. Functional Generalized Additive Models.

    PubMed

    McLean, Mathew W; Hooker, Giles; Staicu, Ana-Maria; Scheipl, Fabian; Ruppert, David

    2014-01-01

    We introduce the functional generalized additive model (FGAM), a novel regression model for association studies between a scalar response and a functional predictor. We model the link-transformed mean response as the integral with respect to t of F{X(t), t} where F(·,·) is an unknown regression function and X(t) is a functional covariate. Rather than having an additive model in a finite number of principal components as in Müller and Yao (2008), our model incorporates the functional predictor directly and thus our model can be viewed as the natural functional extension of generalized additive models. We estimate F(·,·) using tensor-product B-splines with roughness penalties. A pointwise quantile transformation of the functional predictor is also considered to ensure each tensor-product B-spline has observed data on its support. The methods are evaluated using simulated data and their predictive performance is compared with other competing scalar-on-function regression alternatives. We illustrate the usefulness of our approach through an application to brain tractography, where X(t) is a signal from diffusion tensor imaging at position, t, along a tract in the brain. In one example, the response is disease-status (case or control) and in a second example, it is the score on a cognitive test. R code for performing the simulations and fitting the FGAM can be found in supplemental materials available online. PMID:24729671

  4. Siloxane containing addition polyimides

    NASA Technical Reports Server (NTRS)

    Maudgal, S.; St. Clair, T. L.

    1984-01-01

    Addition polyimide oligomers have been synthesized from bis(gamma-aminopropyl) tetramethyldisiloxane and 3, 3', 4, 4'-benzophenonetetracarboxylic dianhydride using a variety of latent crosslinking groups as endcappers. The prepolymers were isolated and characterized for solubility (in amide, chlorinated and ether solvents), melt flow and cure properties. The most promising systems, maleimide and acetylene terminated prepolymers, were selected for detailed study. Graphite cloth reinforced composites were prepared and properties compared with those of graphite/Kerimid 601, a commercially available bismaleimide. Mixtures of the maleimide terminated system with Kerimid 601, in varying proportions, were also studied.

  5. Oil additive process

    SciTech Connect

    Bishop, H.

    1988-10-18

    This patent describes a method of making an additive comprising: (a) adding 2 parts by volume of 3% sodium hypochlorite to 45 parts by volume of diesel oil fuel to form a sulphur free fuel, (b) removing all water and foreign matter formed by the sodium hypochlorite, (c) blending 30 parts by volume of 24% lead naphthanate with 15 parts by volume of the sulphur free fuel, 15 parts by volume of light-weight material oil to form a blended mixture, and (d) heating the blended mixture slowly and uniformly to 152F.

  6. An Additive Manufacturing Test Artifact

    PubMed Central

    Moylan, Shawn; Slotwinski, John; Cooke, April; Jurrens, Kevin; Donmez, M Alkan

    2014-01-01

    A test artifact, intended for standardization, is proposed for the purpose of evaluating the performance of additive manufacturing (AM) systems. A thorough analysis of previously proposed AM test artifacts as well as experience with machining test artifacts have inspired the design of the proposed test artifact. This new artifact is designed to provide a characterization of the capabilities and limitations of an AM system, as well as to allow system improvement by linking specific errors measured in the test artifact to specific sources in the AM system. The proposed test artifact has been built in multiple materials using multiple AM technologies. The results of several of the builds are discussed, demonstrating how the measurement results can be used to characterize and improve a specific AM system. PMID:26601039

  7. An Additive Manufacturing Test Artifact.

    PubMed

    Moylan, Shawn; Slotwinski, John; Cooke, April; Jurrens, Kevin; Donmez, M Alkan

    2014-01-01

    A test artifact, intended for standardization, is proposed for the purpose of evaluating the performance of additive manufacturing (AM) systems. A thorough analysis of previously proposed AM test artifacts as well as experience with machining test artifacts have inspired the design of the proposed test artifact. This new artifact is designed to provide a characterization of the capabilities and limitations of an AM system, as well as to allow system improvement by linking specific errors measured in the test artifact to specific sources in the AM system. The proposed test artifact has been built in multiple materials using multiple AM technologies. The results of several of the builds are discussed, demonstrating how the measurement results can be used to characterize and improve a specific AM system. PMID:26601039

  8. Emission Sources and Chemical Composition of the Atmosphere of a Mega-city in South Asia

    NASA Astrophysics Data System (ADS)

    Husain, L.; Farhana, B. K.; Ghauri, B. M.

    2007-05-01

    . HONO and NH3 concentrations of up to 25 and 117 ppb were observed. A strong diurnal pattern was evident in the concentration of elemental and organic carbon which was perhaps controlled by variation in mixing heights. We used HYSPLIT4 air trajectories, intercomponent relationships and meteorological observations to explain the sources and the impacts of fog chemistry and mixing heights on atmospheric processing of the chemical constituents. Aerosols collected on this campaign were found to carry the signatures of emissions from Afghanistan, North and Central Pakistan, North India in addition to the local pollution sources. Statistical analysis suggests emissions from coal and oil combustion, industrial processes, building construction sites and biomass burning as the primary emission sources. Carbonaceous aerosols contributed about 69% of the PM2.5 mass. Findings of our study will improve the understanding of the critical roles and interactions between chemical composition and size of atmospheric particles, atmospheric boundary layer and meteorological phenomena that manipulate the chemistry of an urban atmosphere. The results should play a vital role in any strategy to regulate emissions and improve air quality in the region.

  9. Performance Boosting Additive

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Mainstream Engineering Corporation was awarded Phase I and Phase II contracts from Goddard Space Flight Center's Small Business Innovation Research (SBIR) program in early 1990. With support from the SBIR program, Mainstream Engineering Corporation has developed a unique low cost additive, QwikBoost (TM), that increases the performance of air conditioners, heat pumps, refrigerators, and freezers. Because of the energy and environmental benefits of QwikBoost, Mainstream received the Tibbetts Award at a White House Ceremony on October 16, 1997. QwikBoost was introduced at the 1998 International Air Conditioning, Heating, and Refrigeration Exposition. QwikBoost is packaged in a handy 3-ounce can (pressurized with R-134a) and will be available for automotive air conditioning systems in summer 1998.

  10. Sewage sludge additive

    NASA Technical Reports Server (NTRS)

    Kalvinskas, J. J.; Mueller, W. A.; Ingham, J. D. (Inventor)

    1980-01-01

    The additive is for a raw sewage treatment process of the type where settling tanks are used for the purpose of permitting the suspended matter in the raw sewage to be settled as well as to permit adsorption of the dissolved contaminants in the water of the sewage. The sludge, which settles down to the bottom of the settling tank is extracted, pyrolyzed and activated to form activated carbon and ash which is mixed with the sewage prior to its introduction into the settling tank. The sludge does not provide all of the activated carbon and ash required for adequate treatment of the raw sewage. It is necessary to add carbon to the process and instead of expensive commercial carbon, coal is used to provide the carbon supplement.

  11. Perspectives on Additive Manufacturing

    NASA Astrophysics Data System (ADS)

    Bourell, David L.

    2016-07-01

    Additive manufacturing (AM) has skyrocketed in visibility commercially and in the public sector. This article describes the development of this field from early layered manufacturing approaches of photosculpture, topography, and material deposition. Certain precursors to modern AM processes are also briefly described. The growth of the field over the last 30 years is presented. Included is the standard delineation of AM technologies into seven broad categories. The economics of AM part generation is considered, and the impacts of the economics on application sectors are described. On the basis of current trends, the future outlook will include a convergence of AM fabricators, mass-produced AM fabricators, enabling of topology optimization designs, and specialization in the AM legal arena. Long-term developments with huge impact are organ printing and volume-based printing.

  12. New addition curing polyimides

    NASA Technical Reports Server (NTRS)

    Frimer, Aryeh A.; Cavano, Paul

    1991-01-01

    In an attempt to improve the thermal-oxidative stability (TOS) of PMR-type polymers, the use of 1,4-phenylenebis (phenylmaleic anhydride) PPMA, was evaluated. Two series of nadic end-capped addition curing polyimides were prepared by imidizing PPMA with either 4,4'-methylene dianiline or p-phenylenediamine. The first resulted in improved solubility and increased resin flow while the latter yielded a compression molded neat resin sample with a T(sub g) of 408 C, close to 70 C higher than PME-15. The performance of these materials in long term weight loss studies was below that of PMR-15, independent of post-cure conditions. These results can be rationalized in terms of the thermal lability of the pendant phenyl groups and the incomplete imidization of the sterically congested PPMA. The preparation of model compounds as well as future research directions are discussed.

  13. The Oxidant Production over Antarctic Land and its Export (OPALE) project: An overview of data collected in summer 2011-2012 at Concordia

    NASA Astrophysics Data System (ADS)

    Kukui, Alexandre; Legrand, Michel; Frey, Markus; Preunkert, Susanne; Savarino, Joel; Gallée, Hubert; Vicars, William; Gil Roca, Jaime; Jourdain, Bruno

    2015-04-01

    inter-play between the NOx snow emission rates and boundary layer dynamics. The major radical primary sources at Concordia are represented by the photolysis of HONO, and HCHO. The main net losses of radicals are their reactions with NO2 and cross radical reactions. It is found, however, that these results are inconsistent with radical observations leading to about 2 times overestimation of RO2 and OH levels. At the same time, neglecting the OH production from HONO results in about 2 times underestimation of radical levels and to explain the radical observations in this case an additional OH source equivalent to about 20% of measured HONO photolysis is required. Assuming that HONO at Concordia originates from snow emissions whose the emission strength was evaluated from lab experiments done by irradiating surface collected at Concordia, model calculations suggest that HONO levels about 20% of measured are consistent with those calculated from radical measurements. We suggest that an explanation for the found overestimation of radical production could be an overestimation of measured HONO, which may originate from the interference from HO2NO2 affecting HONO measurements by LOPAP. Even with 5 times reduced HONO levels, the HONO photolysis represents the major primary radical source at Dome C accounting for about 40% of primary radical production. Presented in this work analysis of the OH and RO2 budget may be significantly biased by inconsistency of the mechanism based on the available observations with observed NO2/NO ratios. Further studies of NOx, HONO and radical chemistry at Antarctic Plateau are therefore strongly needed with specific efforts dedicated to increase the reliability of measurements (especially HONO) under polar conditions.

  14. 33 CFR 214.4 - Additional authority.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... DEFENSE EMERGENCY SUPPLIES OF DRINKING WATER § 214.4 Additional authority. Section 82(2), Pub. L. 93-251... of clean drinking water, on such terms as he determines to be advisable, to any locality which he finds is confronted with a source of contaminated drinking water causing or likely to cause...

  15. 40 CFR 412.47 - Additional measures.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 29 2011-07-01 2009-07-01 true Additional measures. 412.47 Section 412.47 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS CONCENTRATED ANIMAL FEEDING OPERATIONS (CAFO) POINT SOURCE CATEGORY Swine, Poultry, and...

  16. 40 CFR 412.47 - Additional measures.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 29 2014-07-01 2012-07-01 true Additional measures. 412.47 Section 412.47 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS CONCENTRATED ANIMAL FEEDING OPERATIONS (CAFO) POINT SOURCE CATEGORY Swine, Poultry, and...

  17. 40 CFR 412.47 - Additional measures.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 30 2013-07-01 2012-07-01 true Additional measures. 412.47 Section 412.47 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS CONCENTRATED ANIMAL FEEDING OPERATIONS (CAFO) POINT SOURCE CATEGORY Swine, Poultry, and...

  18. 40 CFR 412.47 - Additional measures.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 30 2012-07-01 2012-07-01 false Additional measures. 412.47 Section 412.47 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS CONCENTRATED ANIMAL FEEDING OPERATIONS (CAFO) POINT SOURCE CATEGORY Swine, Poultry, and...

  19. 40 CFR 412.47 - Additional measures.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 28 2010-07-01 2010-07-01 true Additional measures. 412.47 Section 412.47 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS CONCENTRATED ANIMAL FEEDING OPERATIONS (CAFO) POINT SOURCE CATEGORY Swine, Poultry, and...

  20. 33 CFR 214.4 - Additional authority.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... DEFENSE EMERGENCY SUPPLIES OF DRINKING WATER § 214.4 Additional authority. Section 82(2), Pub. L. 93-251... of clean drinking water, on such terms as he determines to be advisable, to any locality which he finds is confronted with a source of contaminated drinking water causing or likely to cause...

  1. 33 CFR 214.4 - Additional authority.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... DEFENSE EMERGENCY SUPPLIES OF DRINKING WATER § 214.4 Additional authority. Section 82(2), Pub. L. 93-251... of clean drinking water, on such terms as he determines to be advisable, to any locality which he finds is confronted with a source of contaminated drinking water causing or likely to cause...

  2. 33 CFR 214.4 - Additional authority.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... DEFENSE EMERGENCY SUPPLIES OF DRINKING WATER § 214.4 Additional authority. Section 82(2), Pub. L. 93-251... of clean drinking water, on such terms as he determines to be advisable, to any locality which he finds is confronted with a source of contaminated drinking water causing or likely to cause...

  3. 33 CFR 214.4 - Additional authority.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... DEFENSE EMERGENCY SUPPLIES OF DRINKING WATER § 214.4 Additional authority. Section 82(2), Pub. L. 93-251... of clean drinking water, on such terms as he determines to be advisable, to any locality which he finds is confronted with a source of contaminated drinking water causing or likely to cause...

  4. Pharmacological and Chemical Effects of Cigarette Additives

    PubMed Central

    Rabinoff, Michael; Caskey, Nicholas; Rissling, Anthony; Park, Candice

    2007-01-01

    We investigated tobacco industry documents and other sources for evidence of possible pharmacological and chemical effects of tobacco additives. Our findings indicated that more than 100 of 599 documented cigarette additives have pharmacological actions that camouflage the odor of environmental tobacco smoke emitted from cigarettes, enhance or maintain nicotine delivery, could increase the addictiveness of cigarettes, and mask symptoms and illnesses associated with smoking behaviors. Whether such uses were specifically intended for these agents is unknown. Our results provide a clear rationale for regulatory control of tobacco additives. PMID:17666709

  5. Formaldehyde Source Attribution in Houston during TexAQS II and TRAMP

    NASA Astrophysics Data System (ADS)

    Guven, B.; Olaguer, E. P.

    2010-12-01

    To determine the relative importance of primary vs secondary formaldehyde in Houston, source apportionment was performed on continuous online measurements of VOCs, formaldehyde (HCHO), CO, SO2, and HONO at one urban and two industrial sites. The results of source apportionment were used in conjunction with the meteorological, emission inventory, emission event, and back trajectory data catalogued in Air Research Information Infrastructure (ARII) to determine the dominant source regions and evaluate the accuracy of reported regular and upset emissions from industrial facilities. The contribution of industrial sources such as flares from petrochemical plants and refineries to total atmospheric formaldehyde concentrations at the urban site is estimated to be 17% compared to 23% for mobile sources, amounting to 40% for the total contribution of primary HCHO sources. The relative contribution of industrial sources to HCHO concentration at the urban site increased to about 66% on some mornings coinciding with the HCHO peak concentrations. Secondary formation of HCHO during the day and night resulted from the reactions of industrial olefins and other VOCs with OH or ozone was a significant contributor to HCHO concentrations at the urban site. An analysis of emission event, back trajectory and ambient concentration data in ARII showed that a large percentage of emission events were associated with trajectories that passed through the two industrial sites when peaks in concentrations were detected at those sites. Some peak HCHO concentrations can also be linked to emission events of other VOCs, while a significant portion remained unexplained by the reported events. It is likely, based on the results from the SHARP campaign and our analysis, that some episodic emission events containing HCHO are unreported to the TCEQ. Overlaid CPF plots for nighttime (green) and daytime (red) HCHO concentrations measured at three sites and the locations of the largest emitting point

  6. The Chandra Source Catalog

    NASA Astrophysics Data System (ADS)

    Evans, Ian N.; Primini, F. A.; Glotfelty, K. J.; Anderson, C. S.; Bonaventura, N. R.; Chen, J. C.; Davis, J. E.; Doe, S. M.; Evans, J. D.; Fabbiano, G.; Galle, E.; Gibbs, D. G.; Grier, J. D.; Hain, R.; Hall, D. M.; Harbo, P. N.; He, X.; Houck, J. C.; Karovska, M.; Lauer, J.; McCollough, M. L.; McDowell, J. C.; Miller, J. B.; Mitschang, A. W.; Morgan, D. L.; Nichols, J. S.; Nowak, M. A.; Plummer, D. A.; Refsdal, B. L.; Rots, A. H.; Siemiginowska, A. L.; Sundheim, B. A.; Tibbetts, M. S.; Van Stone, D. W.; Winkelman, S. L.; Zografou, P.

    2009-01-01

    The Chandra Source Catalog (CSC) is the definitive catalog of X-ray sources detected by the Chandra X-ray Observatory. When compared to all previous and current X-ray missions, Chandra breaks the resolution barrier with an arcsecond scale on-axis point spread function. The combination of excellent spatial resolution, a reasonable field of view, and low instrumental background translate into a high detectable-source density, with low confusion and good astrometry. The wealth of information that can be extracted from identified serendipitous sources is a powerful and valuable resource for astronomy. The aim of the CSC is to disseminate this wealth of information by characterizing the X-ray sky as seen by Chandra. The CSC provides simple access to Chandra data for individual sources or sets of sources matching user-specified search criteria. The catalog is intended to satisfy the needs of a broad-based group of scientists, including those who may be less familiar with astronomical data analysis in the X-ray regime. For each detected X-ray source, the catalog lists the source position and a detailed set of source properties, including multi-band aperture fluxes, X-ray colors and hardness ratios, spectra, temporal variability information, and source extent estimates. In addition to these traditional elements, the catalog includes file-based data products that can be manipulated interactively, including images, photon event lists, light curves, and spectra for each source individually from each observation in which a source is detected. The first release of the CSC includes information for 150,000 X-ray sources detected in a subset of public imaging observations from the first eight years of the Chandra mission. Only point sources, and compact sources with extents < 30 arcsec, are included. Highly extended sources, and sources located in selected fields containing bright, highly extended sources, are excluded from this release. This work is supported by NASA contract NAS

  7. The Chandra Source Catalog

    NASA Astrophysics Data System (ADS)

    Evans, Ian N.; Primini, Francis A.; Glotfelty, Kenny J.; Anderson, Craig S.; Bonaventura, Nina R.; Chen, Judy C.; Davis, John E.; Doe, Stephen M.; Evans, Janet D.; Fabbiano, Giuseppina; Galle, Elizabeth C.; Gibbs, Danny G., II; Grier, John D.; Hain, Roger M.; Hall, Diane M.; Harbo, Peter N.; (Helen He, Xiangqun; Houck, John C.; Karovska, Margarita; Kashyap, Vinay L.; Lauer, Jennifer; McCollough, Michael L.; McDowell, Jonathan C.; Miller, Joseph B.; Mitschang, Arik W.; Morgan, Douglas L.; Mossman, Amy E.; Nichols, Joy S.; Nowak, Michael A.; Plummer, David A.; Refsdal, Brian L.; Rots, Arnold H.; Siemiginowska, Aneta; Sundheim, Beth A.; Tibbetts, Michael S.; Van Stone, David W.; Winkelman, Sherry L.; Zografou, Panagoula

    2010-07-01

    The Chandra Source Catalog (CSC) is a general purpose virtual X-ray astrophysics facility that provides access to a carefully selected set of generally useful quantities for individual X-ray sources, and is designed to satisfy the needs of a broad-based group of scientists, including those who may be less familiar with astronomical data analysis in the X-ray regime. The first release of the CSC includes information about 94,676 distinct X-ray sources detected in a subset of public Advanced CCD Imaging Spectrometer imaging observations from roughly the first eight years of the Chandra mission. This release of the catalog includes point and compact sources with observed spatial extents lsim30''. The catalog (1) provides access to the best estimates of the X-ray source properties for detected sources, with good scientific fidelity, and directly supports scientific analysis using the individual source data; (2) facilitates analysis of a wide range of statistical properties for classes of X-ray sources; and (3) provides efficient access to calibrated observational data and ancillary data products for individual X-ray sources, so that users can perform detailed further analysis using existing tools. The catalog includes real X-ray sources detected with flux estimates that are at least 3 times their estimated 1σ uncertainties in at least one energy band, while maintaining the number of spurious sources at a level of lsim1 false source per field for a 100 ks observation. For each detected source, the CSC provides commonly tabulated quantities, including source position, extent, multi-band fluxes, hardness ratios, and variability statistics, derived from the observations in which the source is detected. In addition to these traditional catalog elements, for each X-ray source the CSC includes an extensive set of file-based data products that can be manipulated interactively, including source images, event lists, light curves, and spectra from each observation in which a

  8. Neutron Characterization for Additive Manufacturing

    NASA Technical Reports Server (NTRS)

    Watkins, Thomas; Bilheux, Hassina; An, Ke; Payzant, Andrew; DeHoff, Ryan; Duty, Chad; Peter, William; Blue, Craig; Brice, Craig A.

    2013-01-01

    Oak Ridge National Laboratory (ORNL) is leveraging decades of experience in neutron characterization of advanced materials together with resources such as the Spallation Neutron Source (SNS) and the High Flux Isotope Reactor (HFIR) shown in Fig. 1 to solve challenging problems in additive manufacturing (AM). Additive manufacturing, or three-dimensional (3-D) printing, is a rapidly maturing technology wherein components are built by selectively adding feedstock material at locations specified by a computer model. The majority of these technologies use thermally driven phase change mechanisms to convert the feedstock into functioning material. As the molten material cools and solidifies, the component is subjected to significant thermal gradients, generating significant internal stresses throughout the part (Fig. 2). As layers are added, inherent residual stresses cause warping and distortions that lead to geometrical differences between the final part and the original computer generated design. This effect also limits geometries that can be fabricated using AM, such as thin-walled, high-aspect- ratio, and overhanging structures. Distortion may be minimized by intelligent toolpath planning or strategic placement of support structures, but these approaches are not well understood and often "Edisonian" in nature. Residual stresses can also impact component performance during operation. For example, in a thermally cycled environment such as a high-pressure turbine engine, residual stresses can cause components to distort unpredictably. Different thermal treatments on as-fabricated AM components have been used to minimize residual stress, but components still retain a nonhomogeneous stress state and/or demonstrate a relaxation-derived geometric distortion. Industry, federal laboratory, and university collaboration is needed to address these challenges and enable the U.S. to compete in the global market. Work is currently being conducted on AM technologies at the ORNL

  9. COMBUSTION AREA SOURCES: DATA SOURCES

    EPA Science Inventory

    The report identifies, documents, and evaluates data sources for stationary area source emissions, including solid waste and agricultural burning. Area source emissions of particulate matter, sulfur dioxide, oxides of nitrogen, reactive volatile organic compounds, and carbon mon...

  10. COMBUSTION AREA SOURCES: DATA SOURCES

    EPA Science Inventory

    The report identifies, documents, and evaluates data sources for stationary area source emissions, including solid waste and agricultural burning. rea source emissions of particulate matter, sulfur dioxide, oxides of nitrogen, reactive volatile organic compounds, and carbon monox...

  11. The Chandra Source Catalog

    NASA Astrophysics Data System (ADS)

    Evans, Ian; Primini, Francis A.; Glotfelty, Kenny J.; Anderson, Craig S.; Bonaventura, Nina R.; Chen, Judy C.; Davis, John E.; Doe, Stephen M.; Evans, Janet D.; Fabbiano, Giuseppina; Galle, Elizabeth C.; Gibbs, Danny G., II; Grier, John D.; Hain, Roger; Hall, Diane M.; Harbo, Peter N.; He, Xiang Qun (Helen); Houck, John C.; Karovska, Margarita; Kashyap, Vinay L.; Lauer, Jennifer; McCollough, Michael L.; McDowell, Jonathan C.; Miller, Joseph B.; Mitschang, Arik W.; Morgan, Douglas L.; Mossman, Amy E.; Nichols, Joy S.; Nowak, Michael A.; Plummer, David A.; Refsdal, Brian L.; Rots, Arnold H.; Siemiginowska, Aneta L.; Sundheim, Beth A.; Tibbetts, Michael S.; van Stone, David W.; Winkelman, Sherry L.; Zografou, Panagoula

    2009-09-01

    The first release of the Chandra Source Catalog (CSC) was published in 2009 March, and includes information about 94,676 X-ray sources detected in a subset of public ACIS imaging observations from roughly the first eight years of the Chandra mission. This release of the catalog includes point and compact sources with observed spatial extents <˜30''.The CSC is a general purpose virtual X-ray astrophysics facility that provides access to a carefully selected set of generally useful quantities for individual X-ray sources, and is designed to satisfy the needs of a broad-based group of scientists, including those who may be less familiar with astronomical data analysis in the X-ray regime.The catalog (1) provides access to the best estimates of the X-ray source properties for detected sources, with good scientific fidelity, and directly supports medium sophistication scientific analysis on using the individual source data; (2) facilitates analysis of a wide range of statistical properties for classes of X-ray sources; (3) provides efficient access to calibrated observational data and ancillary data products for individual X-ray sources, so that users can perform detailed further analysis using existing tools; and (4) includes real X-ray sources detected with flux significance greater than a predefined threshold, while maintaining the number of spurious sources at an acceptable level. For each detected X-ray source, the CSC provides commonly tabulated quantities, including source position, extent, multi-band fluxes, hardness ratios, and variability statistics, derived from the observations in which the source is detected. In addition to these traditional catalog elements, for each X-ray source the CSC includes an extensive set of file-based data products that can be manipulated interactively, including source images, event lists, light curves, and spectra from each observation in which a source is detected.

  12. Observations of Radical Precursors during TexAQS II: Findings and Implications

    NASA Astrophysics Data System (ADS)

    Olaguer, E. P.; Lefer, B. L.; Rappenglueck, B.; Pinto, J. P.

    2009-12-01

    The Texas Environmental Research Consortium (TERC) sponsored and helped organize significant components of the Second Texas Air Quality Study (TexAQS II). Some of the TERC-sponsored experiments, most notably those associated with the TexAQS II Radical and Aerosol Measurement Project (TRAMP) sited on top of the Moody Tower at the University of Houston, found evidence for the importance of short-lived radical sources such as formaldehyde (HCHO) and nitrous acid (HONO) in increasing ozone productivity. During TRAMP, daytime HCHO pulses as large as 32 ppb were observed and attributed to industrial activities upwind in the Houston Ship Channel (HSC), and HCHO peaks as large as 52 ppb were detected by in-situ surface monitors in the HSC. In addition, an instrumented Piper Aztec aircraft observed plumes of apparent primary formaldehyde in flares from petrochemical facilities in the HSC. In one such combustion plume, depleted of ozone by large NOx emissions, the Piper Aztec measured an HCHO-to-CO ratio three times that of mobile sources. HCHO from uncounted primary sources or ozonolysis of underestimated olefin emissions could significantly increase ozone productivity in Houston beyond previous expectations. Simulations with the CAMx model show that additional emissions of HCHO from industrial flares can increase peak ozone in Houston by up to 30 ppb, depending on conditions in the planetary boundary layer. Other findings from TexAQS II include significant concentrations of HONO throughout the day, well in excess of current air quality model predictions, with large nocturnal vertical gradients indicating a surface or near-surface source of HONO, and large concentrations of night-time radicals (~30 ppt HO2). Additional HONO sources could increase daytime ozone by more than 10 ppb. Improving the representation of primary and secondary HCHO and HONO in air quality models could enhance the effectiveness of simulated control strategies, and thus make ozone attainment

  13. Effusion plate using additive manufacturing methods

    DOEpatents

    Johnson, Thomas Edward; Keener, Christopher Paul; Ostebee, Heath Michael; Wegerif, Daniel Gerritt

    2016-04-12

    Additive manufacturing techniques may be utilized to construct effusion plates. Such additive manufacturing techniques may include defining a configuration for an effusion plate having one or more internal cooling channels. The manufacturing techniques may further include depositing a powder into a chamber, applying an energy source to the deposited powder, and consolidating the powder into a cross-sectional shape corresponding to the defined configuration. Such methods may be implemented to construct an effusion plate having one or more channels with a curved cross-sectional geometry.

  14. The Chandra Source Catalog

    NASA Astrophysics Data System (ADS)

    Evans, Ian N.; Primini, F. A.; Glotfelty, K. J.; Anderson, C. S.; Bonaventura, N. R.; Chen, J. C.; Davis, J. E.; Doe, S. M.; Evans, J. D.; Fabbiano, G.; Galle, E. C.; Gibbs, D. G., II; Grier, J. D.; Hain, R. M.; Hall, D. M.; Harbo, P. N.; He, X.; Houck, J. C.; Karovska, M.; Kashyap, V. L.; Lauer, J.; McCollough, M. L.; McDowell, J. C.; Miller, J. B.; Mitschang, A. W.; Morgan, D. L.; Mossman, A. E.; Nichols, J. S.; Nowak, M. A.; Plummer, D. A.; Refsdal, B. L.; Rots, A. H.; Siemiginowska, A.; Sundheim, B. A.; Tibbetts, M. S.; Van Stone, D. W.; Winkelman, S. L.; Zografou, P.

    2010-03-01

    The Chandra Source Catalog (CSC) is a general purpose virtual X-ray astrophysics facility that provides access to a carefully selected set of generally useful quantities for individual X-ray sources, and is designed to satisfy the needs of a broad-based group of scientists, including those who may be less familiar with astronomical data analysis in the X-ray regime. The first release of the CSC includes information about 94,676 distinct X-ray sources detected in a subset of public ACIS imaging observations from roughly the first eight years of the Chandra mission. This release of the catalog includes point and compact sources with observed spatial extents < 30". The catalog (1) provides access to estimates of the X-ray source properties for detected sources with good scientific fidelity; (2) facilitates analysis of a wide range of statistical properties for classes of X-ray sources; and (3) provides efficient access to calibrated observational data and ancillary data products for individual X-ray sources. The catalog includes real X-ray sources detected with flux estimates that are at least 3 times their estimated 1σ uncertainties in at least one energy band, while maintaining the number of spurious sources at a level of < 1 false source per field for a 100 ks observation. For each detected source, the CSC provides commonly tabulated quantities, including source position, extent, multi-band fluxes, hardness ratios, and variability statistics. In addition, for each X-ray source the CSC includes an extensive set of file-based data products that can be manipulated interactively, including source images, event lists, light curves, and spectra. Support for development of the CSC is provided by the National Aeronautics and Space Administration through the Chandra X-ray Center, which is operated by the Smithsonian Astrophysical Observatory for and on behalf of the National Aeronautics and Space Administration under contract NAS 8-03060.

  15. Microwave ion source

    DOEpatents

    Leung, Ka-Ngo; Reijonen, Jani; Thomae, Rainer W.

    2005-07-26

    A compact microwave ion source has a permanent magnet dipole field, a microwave launcher, and an extractor parallel to the source axis. The dipole field is in the form of a ring. The microwaves are launched from the middle of the dipole ring using a coaxial waveguide. Electrons are heated using ECR in the magnetic field. The ions are extracted from the side of the source from the middle of the dipole perpendicular to the source axis. The plasma density can be increased by boosting the microwave ion source by the addition of an RF antenna. Higher charge states can be achieved by increasing the microwave frequency. A xenon source with a magnetic pinch can be used to produce intense EUV radiation.

  16. Energetic additive manufacturing process with feed wire

    SciTech Connect

    Harwell, Lane D.; Griffith, Michelle L.; Greene, Donald L.; Pressly, Gary A.

    2000-11-07

    A process for additive manufacture by energetic wire deposition is described. A source wire is fed into a energy beam generated melt-pool on a growth surface as the melt-pool moves over the growth surface. This process enables the rapid prototyping and manufacture of fully dense, near-net shape components, as well as cladding and welding processes. Alloys, graded materials, and other inhomogeneous materials can be grown using this process.

  17. Selection Sources.

    ERIC Educational Resources Information Center

    Kerby, Ramona

    2002-01-01

    Discusses library collection development by school library media specialists and describes selection sources for new books and materials; retrospective selection sources for materials published in preceding years; and an acquisition source. Provides an overview of the selection process and includes 10 suggestions for selection. (LRW)

  18. Nonpoint Sources.

    ERIC Educational Resources Information Center

    Browne, F. X.

    1978-01-01

    Presented a literature review of nonpoint source effects on water quality and pollution covering: (1) water quality effects; (2) watershed studies; (3) nonpoint source models; and nonpoint source controls. A list of 122 references published in 1976 and 1977 is also presented. (HM)

  19. Photoenhanced nitrous acid formation upon NO2 uptake on tannic and gentisic acid films

    NASA Astrophysics Data System (ADS)

    Sosedova, Yulia; Rouvière, Aurélie; Ammann, Markus

    2010-05-01

    The heterogeneous chemistry of nitrogen dioxide (NO2) is a potential source of nitrous acid (HONO). Hydroxy and methoxy substituted phenols may play a significant role in the aqueous-phase chemistry occurring on the ground or within aerosol particles in air masses affected by biomass burning. It is well established that electron transfer between phenols and NO2 in alkaline aqueous solutions is fast and could be a source of nitrite in the aqueous phase and HONO in the gas phase. However its kinetics is very slow under atmospheric conditions. The role of phenolic species as electron donors has also been suspected to be responsible for the photoenhanced transformation of NO2 to HONO over humic acids [1]. In this study we used tannic (TA) and gentisic (GA) as another proxy for atmospheric phenolic compounds. TA was shown to easily decompose under near UV light irradiation [2] resulting in oxidized products that might change the hygroscopic properties of the original material or have some potential photosensitizing effect. It was interesting to check the hypothesis that the presence of such products could lead to photoenhanced HONO formation upon NO2 uptake to aqueous surfaces containing TA. Experiments were performed in a horizontal coated wall flow tube (40 cm × 5.9 cm i.d.) circularly surrounded by 7 fluorescence lamps (UV: 300-420 nm, or visible: 400-750 nm), in an air cooled lamp housing. The inner surface coating was containing ~0.5 mg/cm-2 of either TA or GA, and was operated under RH 20-80%, 21-23 °C and ambient pressure. Concentration of HONO in the gas phase at the flow tube exit was measured with a LOPAP (Long Path Absorption Spectrometer). The uptake coefficient (γ) leading to NO2 to HONO conversion above aqueous films containing GA or TA in the dark was in the range 4×10-7 - 2×10-6. The photochemically enhanced HONO production was demonstrated by UV irradiation of the GA or TA coatings being in contact with gaseous NO2. In this case γ was 3-10 times

  20. Measuring additive interaction using odds ratios

    PubMed Central

    Kalilani, Linda; Atashili, Julius

    2006-01-01

    Interaction measured on the additive scale has been argued to be better correlated with biologic interaction than when measured on the multiplicative scale. Measures of interaction on the additive scale have been developed using risk ratios. However, in studies that use odds ratios as the sole measure of effect, the calculation of these measures of additive interaction is usually performed by directly substituting odds ratios for risk ratios. Yet assessing additive interaction based on replacing risk ratios by odds ratios in formulas that were derived using the former may be erroneous. In this paper, we evaluate the extent to which three measures of additive interaction – the interaction contrast ratio (ICR), the attributable proportion due to interaction (AP), and the synergy index (S), estimated using odds ratios versus using risk ratios differ as the incidence of the outcome of interest increases in the source population and/or as the magnitude of interaction increases. Our analysis shows that the difference between the two depends on the measure of interaction used, the type of interaction present, and the baseline incidence of the outcome. Substituting odds ratios for risk ratios, when calculating measures of additive interaction, may result in misleading conclusions. Of the three measures, AP appears to be the most robust to this direct substitution. Formulas that use stratum specific odds and odds ratios to accurately calculate measures of additive interaction are presented. PMID:16620385

  1. 26 CFR 31.3402(i)-1 - Additional withholding.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 26 Internal Revenue 15 2010-04-01 2010-04-01 false Additional withholding. 31.3402(i)-1 Section 31.3402(i)-1 Internal Revenue INTERNAL REVENUE SERVICE, DEPARTMENT OF THE TREASURY (CONTINUED) EMPLOYMENT... Collection of Income Tax at Source § 31.3402(i)-1 Additional withholding. (a) In addition to the tax...

  2. 26 CFR 31.3402(i)-1 - Additional withholding.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 26 Internal Revenue 15 2011-04-01 2011-04-01 false Additional withholding. 31.3402(i)-1 Section 31.3402(i)-1 Internal Revenue INTERNAL REVENUE SERVICE, DEPARTMENT OF THE TREASURY (CONTINUED) EMPLOYMENT... Collection of Income Tax at Source § 31.3402(i)-1 Additional withholding. (a) In addition to the tax...

  3. Nonpoint sources

    SciTech Connect

    Selzer, L.

    1994-12-31

    Nonpoint source pollution remains the most pervasive water quality issue faced today. Unlike pollution from point sources, nonpoint source pollution is diffuse both in terms of its origin and the manner in which it enters ground and surface waters. It results from a great variety of human activities that take place over a wide geographic area perhaps many hundreds or even thousands of acres. And unlike pollutants from point sources--which enter the environment at well-defined locations and in relatively even, continuous discharges--pollutants from nonpoint sources usually find their way into surface and ground waters in sudden surges associated with rainfall, thunderstorms, or snowmelt. The author discusses some of the most significant sources of nonpoint source pollution.

  4. Incorporation of additives into polymers

    DOEpatents

    McCleskey, T. Mark; Yates, Matthew Z.

    2003-07-29

    There has been invented a method for incorporating additives into polymers comprising: (a) forming an aqueous or alcohol-based colloidal system of the polymer; (b) emulsifying the colloidal system with a compressed fluid; and (c) contacting the colloidal polymer with the additive in the presence of the compressed fluid. The colloidal polymer can be contacted with the additive by having the additive in the compressed fluid used for emulsification or by adding the additive to the colloidal system before or after emulsification with the compressed fluid. The invention process can be carried out either as a batch process or as a continuous on-line process.

  5. Deciphering the roles of multiple additives in organocatalyzed Michael additions.

    PubMed

    Günler, Z Inci; Companyó, Xavier; Alfonso, Ignacio; Burés, Jordi; Jimeno, Ciril; Pericàs, Miquel A

    2016-05-21

    The synergistic effects of multiple additives (water and acetic acid) on the asymmetric Michael addition of acetone to nitrostyrene catalyzed by primary amine-thioureas (PAT) were precisely determined. Acetic acid facilitates hydrolysis of the imine intermediates, thus leading to catalytic behavior, and minimizes the formation of the double addition side product. In contrast, water slows down the reaction but minimizes catalyst deactivation, eventually leading to higher final yields. PMID:27128165

  6. Evaluation of certain food additives and contaminants.

    PubMed

    2004-01-01

    This report represents the conclusions of a Joint FAO/WHO Expert Committee convened to evaluate the safety of various food additives, with a view to recommending acceptable daily intakes (ADIs) and to prepare specifications for the identity and purity of food additives. The first part of the report contains a general discussion of the principles governing the toxicological evaluation of food additives (including flavouring agents) and contaminants, assessments of intake, and the establishment and revision of specifications for food additives. A summary follows of the Committee's evaluations of toxicological and intake data on various specific food additives (alpha-amylase from Bacillus lichenformis containing a genetically engineered alpha-amylase gene from B. licheniformis, annatto extracts, curcumin, diacetyl and fatty acid esters of glycerol, D-tagatose, laccase from Myceliophthora thermophila expressed in Aspergillus oryzae, mixed xylanase, beta-glucanase enzyme preparation produced by a strain of Humicola insolens, neotame, polyvinyl alcohol, quillaia extracts and xylanase from Thermomyces lanuginosus expressed in Fusarium venenatum), flavouring agents, a nutritional source of iron (ferrous glycinate, processed with citric acid), a disinfectant for drinking-water (sodium dichloroisocyanurate) and contaminants (cadmium and methylmercury). Annexed to the report are tables summarizing the Committee's recommendations for ADIs of the food additives, recommendations on the flavouring agents considered, and tolerable intakes of the contaminants considered, changes in the status of specifications and further information requested or desired. PMID:15354533

  7. Ion source

    DOEpatents

    Leung, Ka-Ngo; Ehlers, Kenneth W.

    1984-01-01

    A magnetic filter for an ion source reduces the production of undesired ion species and improves the ion beam quality. High-energy ionizing electrons are confined by the magnetic filter to an ion source region, where the high-energy electrons ionize gas molecules. One embodiment of the magnetic filter uses permanent magnets oriented to establish a magnetic field transverse to the direction of travel of ions from the ion source region to the ion extraction region. In another embodiment, low energy 16 eV electrons are injected into the ion source to dissociate gas molecules and undesired ion species into desired ion species.

  8. Enantioselective Michael Addition of Water

    PubMed Central

    Chen, Bi-Shuang; Resch, Verena; Otten, Linda G; Hanefeld, Ulf

    2015-01-01

    The enantioselective Michael addition using water as both nucleophile and solvent has to date proved beyond the ability of synthetic chemists. Herein, the direct, enantioselective Michael addition of water in water to prepare important β-hydroxy carbonyl compounds using whole cells of Rhodococcus strains is described. Good yields and excellent enantioselectivities were achieved with this method. Deuterium labeling studies demonstrate that a Michael hydratase catalyzes the water addition exclusively with anti-stereochemistry. PMID:25529526

  9. Nuclear electric power sources

    NASA Technical Reports Server (NTRS)

    Singh, J. J.

    1978-01-01

    Measurements on radioactive commercial p-n junction silicon cells show that these units are capable of delivering several hundred microwatts per curie of Am-241 alpha source, indicating their usefulness in such electronic devices as hearing aids, heart pacemakers, electronic watches, delay timers and nuclear dosimeter chargers. It is concluded that the Am-241 sources are superior to the beta sources used previously, because of higher alpha specific ionization and simultaneous production of low energy photons which are easily converted into photoelectrons for additional power.

  10. Photonic crystal light source

    DOEpatents

    Fleming, James G.; Lin, Shawn-Yu; Bur, James A.

    2004-07-27

    A light source is provided by a photonic crystal having an enhanced photonic density-of-states over a band of frequencies and wherein at least one of the dielectric materials of the photonic crystal has a complex dielectric constant, thereby producing enhanced light emission at the band of frequencies when the photonic crystal is heated. The dielectric material can be a metal, such as tungsten. The spectral properties of the light source can be easily tuned by modification of the photonic crystal structure and materials. The photonic crystal light source can be heated electrically or other heating means. The light source can further include additional photonic crystals that exhibit enhanced light emission at a different band of frequencies to provide for color mixing. The photonic crystal light source may have applications in optical telecommunications, information displays, energy conversion, sensors, and other optical applications.

  11. Gasoline additives, emissions, and performance

    SciTech Connect

    1995-12-31

    The papers included in this publication deal with the influence of fuel, additive, and hardware changes on a variety of vehicle performance characteristics. Advanced techniques for measuring these performance parameters are also described. Contents include: Fleet test evaluation of gasoline additives for intake valve and combustion chamber deposit clean up; A technique for evaluating octane requirement additives in modern engines on dynamometer test stands; A fleet test of two additive technologies comparing their effects on tailpipe emissions; Investigation into the vehicle exhaust emissions of high percentage ethanol blends; Variability in hydrocarbon speciation measurements at low emission (ULEV) levels; and more.

  12. Color Addition and Subtraction Apps

    ERIC Educational Resources Information Center

    Ruiz, Frances; Ruiz, Michael J.

    2015-01-01

    Color addition and subtraction apps in HTML5 have been developed for students as an online hands-on experience so that they can more easily master principles introduced through traditional classroom demonstrations. The evolution of the additive RGB color model is traced through the early IBM color adapters so that students can proceed step by step…

  13. 75 FR 27313 - Proposed Additions

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-05-14

    ... FROM PEOPLE WHO ARE BLIND OR SEVERELY DISABLED PROCUREMENT LIST Proposed Additions AGENCY: Committee for Purchase From People Who Are Blind or Severely Disabled. ACTION: Proposed additions to the... or Severely Disabled, Jefferson Plaza 2, Suite 10800, 1421 Jefferson Davis Highway,...

  14. Mechanistic investigations reveal that dibromobimane extrudes sulfur from biological sulfhydryl sources other than hydrogen sulfide† †Electronic supplementary information (ESI) available: Experimental details, pH stability data for BTE, NMR spectra. See DOI: 10.1039/c4sc01875c Click here for additional data file.

    PubMed Central

    Montoya, Leticia A.; Shen, Xinggui; McDermott, James J.

    2015-01-01

    Hydrogen sulfide (H2S) has emerged as an important biological signaling molecule in the last decade. During the growth of this field, significant controversy has arisen centered on the physiological concentrations of H2S. Recently, a monobromobimane (mBB) method has been developed for the quantification of different biologically-relevant sulfide pools. Based on the prevalence of the mBB method for sulfide quantification, we expand on this method to report the use of dibromobimane (dBB) for sulfide quantification. Reaction of H2S with dBB results in formation of highly-fluorescent bimane thioether (BTE), which is readily quantifiable by HPLC. Additionally, the reaction of sulfide with dBB to form BTE is significantly faster than the reaction of sulfide with mBB to form sulfide dibimane. Using the dBB method, BTE levels as low as 0.6 pM can be detected. Upon use of the dBB method in wild-type and CSE–/– mice, however, dBB reports significantly higher sulfide levels than those measured using mBB. Further investigation revealed that dBB is able to extract sulfur from other sulfhydryl sources including thiols. Based on mechanistic studies, we demonstrate that dBB extracts sulfur from thiols with α- or β-hydrogens, thus leading to higher BTE formation than from sulfide alone. Taken together, the dBB method is a highly sensitive method for H2S but is not compatible for use in studies in which other thiols are present. PMID:25632344

  15. ION SOURCE

    DOEpatents

    Martina, E.F.

    1958-04-22

    An improved ion source particularly adapted to provide an intense beam of ions with minimum neutral molecule egress from the source is described. The ion source structure includes means for establishing an oscillating electron discharge, including an apertured cathode at one end of the discharge. The egress of ions from the source is in a pencil like beam. This desirable form of withdrawal of the ions from the plasma created by the discharge is achieved by shaping the field at the aperture of the cathode. A tubular insulator is extended into the plasma from the aperture and in cooperation with the electric fields at the cathode end of the discharge focuses the ions from the source,

  16. 48 CFR 207.106 - Additional requirements for major systems.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...) Competitive prototyping. (ii) Dual-sourcing. (iii) Unbundling of contracts. (iv) Funding of next-generation...) Licensing of additional suppliers. (x) Periodic system or program reviews to address long-term...

  17. Color Addition and Subtraction Apps

    NASA Astrophysics Data System (ADS)

    Ruiz, Frances; Ruiz, Michael J.

    2015-10-01

    Color addition and subtraction apps in HTML5 have been developed for students as an online hands-on experience so that they can more easily master principles introduced through traditional classroom demonstrations. The evolution of the additive RGB color model is traced through the early IBM color adapters so that students can proceed step by step in understanding mathematical representations of RGB color. Finally, color addition and subtraction are presented for the X11 colors from web design to illustrate yet another real-life application of color mixing.

  18. Acoustic emission source location

    NASA Astrophysics Data System (ADS)

    Promboon, Yajai

    The objective of the research program was development of reliable source location techniques. The study comprised two phases. First, the research focused on development of source location methods for homogeneous plates. The specimens used in the program were steel railroad tank cars. Source location methods were developed and demonstrated for empty and water filled tanks. The second phase of the research was an exploratory study of source location method for fiber reinforced composites. Theoretical analysis and experimental measurement of wave propagation were carried out. This data provided the basis for development of a method using the intersection of the group velocity curves for the first three wave propagation modes. Simplex optimization was used to calculate the location of the source. Additional source location methods have been investigated and critically examined. Emphasis has been placed on evaluating different methods for determining the time of arrival of a wave. The behavior of wave in a water filled tank was studied and source location methods suitable for use in this situation have been examined through experiment and theory. Particular attention is paid to the problem caused by leaky Lamb waves. A preliminary study into the use of neural networks for source location in fiber reinforced composites was included in the research program. A preliminary neural network model and the results from training and testing data are reported.

  19. Light Source

    NASA Technical Reports Server (NTRS)

    1993-01-01

    Research on food growth for long duration spacecraft has resulted in a light source for growing plants indoors known as Qbeam, a solid state light source consisting of a control unit and lamp. The light source, manufactured by Quantum Devices, Inc., is not very hot, although it generates high intensity radiation. When Ron Ignatius, an industrial partner of WCSAR, realized that terrestrial plant research lighting was not energy efficient enough for space use, he and WCSAR began to experiment with light emitting diodes. A line of LED products was developed, and QDI was formed to market the technology. An LED-based cancer treatment device is currently under development.

  20. Calculators and Computers: Graphical Addition.

    ERIC Educational Resources Information Center

    Spero, Samuel W.

    1978-01-01

    A computer program is presented that generates problem sets involving sketching graphs of trigonometric functions using graphical addition. The students use calculators to sketch the graphs and a computer solution is used to check it. (MP)

  1. Embedding Sensors During Additive Manufacturing

    SciTech Connect

    Sbriglia, Lexey Raylene

    2015-08-10

    This PowerPoint presentation had the following headings: Fused deposition modeling (FDM); Open source 3D printing; Objectives; Vibration analysis; Equipment; Design; Material choices; Failure causes, such as tension, bubbling; Potential solutions; Simulations; Embedding the sensors; LabView programming; Alternate data acquisition; Problem and proposed solution; and, Conclusions

  2. Polyolefins as additives in plastics

    SciTech Connect

    Deanin, R.D.

    1993-12-31

    Polyolefins are not only major commodity plastics - they are also very useful as additives, both in other polyolefins and also in other types of plastics. This review covers ethylene, propylene, butylene and isobutylene polymers, in blends with each other, and as additives to natural rubber, styrene/butadiene rubber, polystyrene, polyvinyl chloride, polymethyl methacrylate, polyphenylene oxide, polycarbonate, thermoplastic polyesters, polyurethanes, polyamides, and mixed automotive plastics recycling.

  3. [Trends in the utilization of food additives].

    PubMed

    Szűcs, Viktória; Bánáti, Diána

    2013-11-17

    The frequent media reports on food additives weakened consumers' trust in food producers and food control authorities as well. Furthermore, consumers' uncertainty is also raised by the fact that they obtain their information from inadequate, mistrustful sources and, therefore, consumers might avoid the consumption of certain foodstuffs. While food producers may react by replacing artificial components by natural ones, they try to emphasize the favourable characteristics of their products. The authors describe the main trends and efforts related to food additives. On the basis of the overview it can be concluded that - besides taking into consideration consumers' needs - product development and research directions are promising. Food producers' efforts may help to restore consumer confidence and trust and they may help them to have informed choice. PMID:24212041

  4. NEUTRON SOURCES

    DOEpatents

    Richmond, J.L.; Wells, C.E.

    1963-01-15

    A neutron source is obtained without employing any separate beryllia receptacle, as was formerly required. The new method is safer and faster, and affords a source with both improved yield and symmetry of neutron emission. A Be container is used to hold and react with Pu. This container has a thin isolating layer that does not obstruct the desired Pu--Be reaction and obviates procedures previously employed to disassemble and remove a beryllia receptacle. (AEC)

  5. Soil surface acidity plays a determining role in the atmospheric-terrestrial exchange of nitrous acid

    PubMed Central

    Donaldson, Melissa A.; Bish, David L.; Raff, Jonathan D.

    2014-01-01

    Nitrous acid (HONO) is an important hydroxyl (OH) radical source that is formed on both ground and aerosol surfaces in the well-mixed boundary layer. Recent studies report the release of HONO from nonacidic soils, although it is unclear how soil that is more basic than the pKa of HONO (∼3) is capable of protonating soil nitrite to serve as an atmospheric HONO source. Here, we used a coated-wall flow tube and chemical ionization mass spectrometry (CIMS) to study the pH dependence of HONO uptake onto agricultural soil and model substrates under atmospherically relevant conditions (1 atm and 30% relative humidity). Experiments measuring the evolution of HONO from pH-adjusted surfaces treated with nitrite and potentiometric titrations of the substrates show, to our knowledge for the first time, that surface acidity rather than bulk aqueous pH determines HONO uptake and desorption efficiency on soil, in a process controlled by amphoteric aluminum and iron (hydr)oxides present. The results have important implications for predicting when soil nitrite, whether microbially derived or atmospherically deposited, will act as a net source or sink of atmospheric HONO. This process represents an unrecognized mechanism of HONO release from soil that will contribute to HONO emissions throughout the day. PMID:25512517

  6. Soil surface acidity plays a determining role in the atmospheric-terrestrial exchange of nitrous acid.

    PubMed

    Donaldson, Melissa A; Bish, David L; Raff, Jonathan D

    2014-12-30

    Nitrous acid (HONO) is an important hydroxyl (OH) radical source that is formed on both ground and aerosol surfaces in the well-mixed boundary layer. Recent studies report the release of HONO from nonacidic soils, although it is unclear how soil that is more basic than the pKa of HONO (∼ 3) is capable of protonating soil nitrite to serve as an atmospheric HONO source. Here, we used a coated-wall flow tube and chemical ionization mass spectrometry (CIMS) to study the pH dependence of HONO uptake onto agricultural soil and model substrates under atmospherically relevant conditions (1 atm and 30% relative humidity). Experiments measuring the evolution of HONO from pH-adjusted surfaces treated with nitrite and potentiometric titrations of the substrates show, to our knowledge for the first time, that surface acidity rather than bulk aqueous pH determines HONO uptake and desorption efficiency on soil, in a process controlled by amphoteric aluminum and iron (hydr)oxides present. The results have important implications for predicting when soil nitrite, whether microbially derived or atmospherically deposited, will act as a net source or sink of atmospheric HONO. This process represents an unrecognized mechanism of HONO release from soil that will contribute to HONO emissions throughout the day. PMID:25512517

  7. ADDITIVITY ASSESSMENT OF TRIHALOMETHANE MIXTURES BY PROPORTIONAL RESPONSE ADDITION

    EPA Science Inventory

    If additivity is known or assumed, the toxicity of a chemical mixture may be predicted from the dose response curves of the individual chemicals comprising the mixture. As single chemical data are abundant and mixture data sparse, mixture risk methods that utilize single chemical...

  8. [INVITED] Lasers in additive manufacturing

    NASA Astrophysics Data System (ADS)

    Pinkerton, Andrew J.

    2016-04-01

    Additive manufacturing is a topic of considerable ongoing interest, with forecasts predicting it to have major impact on industry in the future. This paper focusses on the current status and potential future development of the technology, with particular reference to the role of lasers within it. It begins by making clear the types and roles of lasers in the different categories of additive manufacturing. This is followed by concise reviews of the economic benefits and disadvantages of the technology, current state of the market and use of additive manufacturing in different industries. Details of these fields are referenced rather than expanded in detail. The paper continues, focusing on current indicators to the future of additive manufacturing. Barriers to its development, trends and opportunities in major industrial sectors, and wider opportunities for its development are covered. Evidence indicates that additive manufacturing may not become the dominant manufacturing technology in all industries, but represents an excellent opportunity for lasers to increase their influence in manufacturing as a whole.

  9. Evaluation of certain food additives.

    PubMed

    2015-01-01

    This report represents the conclusions of a Joint FAO/WHO Expert Committee convened to evaluate the safety of various food additives, including flavouring agents, and to prepare specifications for identity and purity. The first part of the report contains a general discussion of the principles governing the toxicological evaluation of and assessment of dietary exposure to food additives, including flavouring agents. A summary follows of the Committee's evaluations of technical, toxicological and dietary exposure data for eight food additives (Benzoe tonkinensis; carrageenan; citric and fatty acid esters of glycerol; gardenia yellow; lutein esters from Tagetes erecta; octenyl succinic acid-modified gum arabic; octenyl succinic acid-modified starch; paprika extract; and pectin) and eight groups of flavouring agents (aliphatic and alicyclic hydrocarbons; aliphatic and aromatic ethers; ionones and structurally related substances; miscellaneous nitrogen-containing substances; monocyclic and bicyclic secondary alcohols, ketones and related esters; phenol and phenol derivatives; phenyl-substituted aliphatic alcohols and related aldehydes and esters; and sulfur-containing heterocyclic compounds). Specifications for the following food additives were revised: citric acid; gellan gum; polyoxyethylene (20) sorbitan monostearate; potassium aluminium silicate; and Quillaia extract (Type 2). Annexed to the report are tables summarizing the Committee's recommendations for dietary exposures to and toxicological evaluations of all of the food additives and flavouring agents considered at this meeting. PMID:26118220

  10. Manipulating crystallization with molecular additives.

    PubMed

    Shtukenberg, Alexander G; Lee, Stephanie S; Kahr, Bart; Ward, Michael D

    2014-01-01

    Given the importance of organic crystals in a wide range of industrial applications, the chemistry, biology, materials science, and chemical engineering communities have focused considerable attention on developing methods to control crystal structure, size, shape, and orientation. Tailored additives have been used to control crystallization to great effect, presumably by selectively binding to particular crystallographic surfaces and sites. However, substantial knowledge gaps still exist in the fundamental mechanisms that govern the formation and growth of organic crystals in both the absence and presence of additives. In this review, we highlight research discoveries that reveal the role of additives, either introduced by design or present adventitiously, on various stages of formation and growth of organic crystals, including nucleation, dislocation spiral growth mechanisms, growth inhibition, and nonclassical crystal morphologies. The insights from these investigations and others of their kind are likely to guide the development of innovative methods to manipulate crystallization for a wide range of materials and applications. PMID:24579880

  11. Additive Manufacturing of Hybrid Circuits

    NASA Astrophysics Data System (ADS)

    Sarobol, Pylin; Cook, Adam; Clem, Paul G.; Keicher, David; Hirschfeld, Deidre; Hall, Aaron C.; Bell, Nelson S.

    2016-07-01

    There is a rising interest in developing functional electronics using additively manufactured components. Considerations in materials selection and pathways to forming hybrid circuits and devices must demonstrate useful electronic function; must enable integration; and must complement the complex shape, low cost, high volume, and high functionality of structural but generally electronically passive additively manufactured components. This article reviews several emerging technologies being used in industry and research/development to provide integration advantages of fabricating multilayer hybrid circuits or devices. First, we review a maskless, noncontact, direct write (DW) technology that excels in the deposition of metallic colloid inks for electrical interconnects. Second, we review a complementary technology, aerosol deposition (AD), which excels in the deposition of metallic and ceramic powder as consolidated, thick conformal coatings and is additionally patternable through masking. Finally, we show examples of hybrid circuits/devices integrated beyond 2-D planes, using combinations of DW or AD processes and conventional, established processes.

  12. Tougher Addition Polyimides Containing Siloxane

    NASA Technical Reports Server (NTRS)

    St. Clair, T. L.; Maudgal, S.

    1986-01-01

    Laminates show increased impact resistances and other desirable mechanical properties. Bismaleamic acid extended by reaction of diaminosiloxane with maleic anhydride in 1:1 molar ratio, followed by reaction with half this molar ratio of aromatic dianhydride. Bismaleamic acid also extended by reaction of diaminosiloxane with maleic anhydride in 1:2 molar ratio, followed by reaction with half this molar ratio of aromatic diamine (Michael-addition reaction). Impact resistances improved over those of unmodified bismaleimide, showing significant increase in toughness. Aromatic addition polyimides developed as both matrix and adhesive resins for applications on future aircraft and spacecraft.

  13. Neutron source

    DOEpatents

    Cason, J.L. Jr.; Shaw, C.B.

    1975-10-21

    A neutron source which is particularly useful for neutron radiography consists of a vessel containing a moderating media of relatively low moderating ratio, a flux trap including a moderating media of relatively high moderating ratio at the center of the vessel, a shell of depleted uranium dioxide surrounding the moderating media of relatively high moderating ratio, a plurality of guide tubes each containing a movable source of neutrons surrounding the flux trap, a neutron shield surrounding one part of each guide tube, and at least one collimator extending from the flux trap to the exterior of the neutron source. The shell of depleted uranium dioxide has a window provided with depleted uranium dioxide shutters for each collimator. Reflectors are provided above and below the flux trap and on the guide tubes away from the flux trap.

  14. ION SOURCE

    DOEpatents

    Leland, W.T.

    1960-01-01

    The ion source described essentially eliminater the problem of deposits of nonconducting materials forming on parts of the ion source by certain corrosive gases. This problem is met by removing both filament and trap from the ion chamber, spacing them apart and outside the chamber end walls, placing a focusing cylinder about the filament tip to form a thin collimated electron stream, aligning the cylinder, slits in the walls, and trap so that the electron stream does not bombard any part in the source, and heating the trap, which is bombarded by electrons, to a temperature hotter than that in the ion chamber, so that the tendency to build up a deposit caused by electron bombardment is offset by the extra heating supplied only to the trap.

  15. Crowd Sourcing.

    PubMed

    Baum, Neil

    2016-01-01

    The Internet has contributed new words and slang to our daily vernacular. A few terms, such as tweeting, texting, sexting, blogging, and googling, have become common in most vocabularies and in many languages, and are now included in the dictionary. A new buzzword making the rounds in industry is crowd sourcing, which involves outsourcing an activity, task, or problem by sending it to people or groups outside a business or a practice. Crowd sourcing allows doctors and practices to tap the wisdom of many instead of relying only on the few members of their close-knit group. This article defines "crowd sourcing," offers examples, and explains how to get started with this approach that can increase your ability to finish a task or solve problems that you don't have the time or expertise to accomplish. PMID:27039640

  16. Promoting Additive Acculturation in Schools.

    ERIC Educational Resources Information Center

    Gibson, Margaret A.

    1995-01-01

    A study focusing on 113 ninth graders of Mexican descent indicates that most students and their parents adhere to a strategy of additive acculturation (incorporating skills of the new culture and language), but that the school curriculum and general school climate devalue Mexican culture. (SLD)

  17. Individualized Additional Instruction for Calculus

    ERIC Educational Resources Information Center

    Takata, Ken

    2010-01-01

    College students enrolling in the calculus sequence have a wide variance in their preparation and abilities, yet they are usually taught from the same lecture. We describe another pedagogical model of Individualized Additional Instruction (IAI) that assesses each student frequently and prescribes further instruction and homework based on the…

  18. Out of bounds additive manufacturing

    SciTech Connect

    Holshouser, Chris; Newell, Clint; Palas, Sid; Love, Lonnie J.; Kunc, Vlastimil; Lind, Randall F.; Lloyd, Peter D.; Rowe, John C.; Blue, Craig A.; Duty, Chad E.; Peter, William H.; Dehoff, Ryan R.

    2013-03-01

    Lockheed Martin and Oak Ridge National Laboratory are working on an additive manufacturing system capable of manufacturing components measured not in terms of inches or feet, but multiple yards in all dimensions with the potential to manufacture parts that are completely unbounded in size.

  19. The Additive Property of Energy.

    ERIC Educational Resources Information Center

    Tsaoussis, Dimitris S.

    1995-01-01

    Presents exercises that analyze the additive property of energy. Concludes that if a body has more than one component of energy depending on the same physical quantity, the body's total energy will be the algebraic sum of the components if a linear relationship exists between the energy components and that physical quantity. (JRH)

  20. Tinkertoy Color-Addition Device.

    ERIC Educational Resources Information Center

    Ferguson, Joe L.

    1995-01-01

    Describes construction and use of a simple home-built device, using an overhead projector, for use in demonstrations of the addition of various combinations of red, green, and blue light. Useful in connection with discussions of color, color vision, or color television. (JRH)

  1. Silage Additives and Management Issues

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Inoculants are the most common silage additives in the United States. These products contain lactic acid bacteria to supplement the lactic acid bacteria naturally on the crop and help insure a consistent fermentation in the silo. There are three types of inoculants: homofermentative lactic acid bact...

  2. Tetrasulfide extreme pressure lubricant additives

    SciTech Connect

    Gast, L.E.; Kenney, H.E.; Schwab, A.W.

    1980-08-19

    A novel class of compounds has been prepared comprising the tetrasulfides of /sup 18/C hydrocarbons, /sup 18/C fatty acids, and /sup 18/C fatty and alkyl and triglyceride esters. These tetrasulfides are useful as extreme pressure lubricant additives and show potential as replacements for sulfurized sperm whale oil.

  3. NEUTRON SOURCE

    DOEpatents

    Reardon, W.A.; Lennox, D.H.; Nobles, R.G.

    1959-01-13

    A neutron source of the antimony--beryllium type is presented. The source is comprised of a solid mass of beryllium having a cylindrical recess extending therein and a cylinder containing antimony-124 slidably disposed within the cylindrical recess. The antimony cylinder is encased in aluminum. A berylliunn plug is removably inserted in the open end of the cylindrical recess to completely enclose the antimony cylinder in bsryllium. The plug and antimony cylinder are each provided with a stud on their upper ends to facilitate handling remotely.

  4. RADIATION SOURCES

    DOEpatents

    Brucer, M.H.

    1958-04-15

    A novel long-lived source of gamma radiation especially suitable for calibration purposes is described. The source of gamma radiation is denoted mock iodine131, which comprises a naixture of barium-133 and cesium-137. The barium and cesium are present in a barium-cesium ratio of approximately 5.7/1 to 14/1, uniformly dispersed in an ion exchange resin and a filter surrounding the resin comprised of a material of atomic number below approximately 51, and substantially 0.7 to 0.9 millimeter thick.

  5. Evaluation of certain food additives.

    PubMed

    2012-01-01

    This report represents the conclusions of a Joint FAO/WHO Expert Committee convened to evaluate the safety of various food additives, including flavouring agents, with a view to concluding as to safety concerns and to preparing specifications for identity and purity. The first part of the report contains a general discussion of the principles governing the toxicological evaluation of and assessment of dietary exposure to food additives, including flavouring agents. A summary follows of the Committee's evaluations of technical, toxicological and dietary exposure data for five food additives (magnesium dihydrogen diphosphate; mineral oil (medium and low viscosity) classes II and III; 3-phytase from Aspergillus niger expressed in Aspergillus niger; serine protease (chymotrypsin) from Nocardiopsis prasina expressed in Bacillus licheniformis; and serine protease (trypsin) from Fusarium oxysporum expressed in Fusarium venenatum) and 16 groups of flavouring agents (aliphatic and aromatic amines and amides; aliphatic and aromatic ethers; aliphatic hydrocarbons, alcohols, aldehydes, ketones, carboxylic acids and related esters, sulfides, disulfides and ethers containing furan substitution; aliphatic linear alpha,beta-unsaturated aldehydes, acids and related alcohols, acetals and esters; amino acids and related substances; epoxides; furfuryl alcohol and related substances; linear and branched-chain aliphatic, unsaturated, unconjugated alcohols, aldehydes, acids and related esters; miscellaneous nitrogen-containing substances; phenol and phenol derivatives; pyrazine derivatives; pyridine, pyrrole and quinoline derivatives; saturated aliphatic acyclic branched-chain primary alcohols, aldehydes and acids; simple aliphatic and aromatic sulfides and thiols; sulfur-containing heterocyclic compounds; and sulfur-substituted furan derivatives). Specifications for the following food additives were revised: ethyl cellulose, mineral oil (medium viscosity), modified starches and titanium

  6. Observation of atmospheric nitrous acid with DOAS in Beijing, China.

    PubMed

    Qin, Min; Xie, Pin-Hua; Liu, Wen-Qing; Li, Ang; Dou, Ke; Fang, Wu; Liu, Jian-Guo; Zhang, Wei-Jun

    2006-01-01

    Measurements of nitrous acid (HONO) and nitrogen dioxide (NO2) in Beijing City have been performed by means of a developed differential optical absorption spectroscopy (DOAS) system based on photodiode array (PDA), during the autumn of 2004. HONO and NO2 were simultaneously identified by their characteristic absorption bands in the spectral region between 337 nm and 372 nm with high sensibility and time resolution. The concentrations of HONO exhibit obviously diurnal variation with a nocturnal maximum and a daytime minimum. The highest HONO value up to 11.8 microg/m3 was observed during the night of 2/3 September. Possible sources of the observed HONO were discussed. Good correlation to NO2 indicates that NO2 is a main source component. The measurement also shows direct emission of HONO is an important source in strongly polluted urban area. PMID:20050551

  7. Food additives and contaminants. An update.

    PubMed

    Newberne, P M; Conner, M W

    1986-10-15

    Food additives continue to be a source of benefits to the consuming public but there are also perceived risks. Concern for the latter in the last decade has produced a society afflicted with cancer phobia. The intentional additives including sugars, salt, corn syrup, and dextrose make up 90% of the direct additives. These, along with a limited number of familiar items make up a large proportion of the remainder of the additives. Such common ingredients as nitrates and nitrites, solanine, cyanogenetic compounds, arsenic, etc., are unavoidably consumed in the diet and with little if any evidence for public health consequences. Major concern on the part of the public in recent years has been focused on man-made chemicals which are intentionally added to foods to enhance flavors and acceptability, nutrient value, shelf life and increased availability. These include food colors, nonnutritive and low-nutrient sweeteners, (saccharin, cyclamate, aspartame); antioxidants; and nitrites. Contaminants, sometimes incorrectly included in lists of food additives, present the greatest potential threat to public health. Such contaminants as mycotoxins, nitrosamines, polychlorinated biphenyls (PCBs), pesticides, among others, provide a continuing challenge to our regulatory agencies and to public health authorities. Evidence to date indicate that these responsible for food safety are doing an admirable job, and as a society, our food supply has never been better, or safer, and, as a population, we have never been healthier. Aside from contaminants, major concerns relate to an excess of good food and to obesity. These comments should not be taken to infer that we should relax our concern and surveillance; instead more concern and surveillance should be exerted toward those uncontrolled substances such as natural plant products and alleged natural nutrients, roots, herbs, etc., which are given much credit for positive health effects, without meeting the high standards of our

  8. Terahertz sources

    NASA Astrophysics Data System (ADS)

    Shumyatsky, Pavel; Alfano, Robert R.

    2011-03-01

    We present an overview and history of terahertz (THz) sources for readers of the biomedical and optical community for applications in physics, biology, chemistry, medicine, imaging, and spectroscopy. THz low-frequency vibrational modes are involved in many biological, chemical, and solid state physical processes.

  9. Superluminal sources.

    PubMed Central

    Vermeulen, R C

    1995-01-01

    Predictions for the apparent velocity statistics under simple beaming models are presented and compared to the observations. The potential applications for tests of unification models and for cosmology (source counts, measurements of the Hubble constant H0 and the deceleration parameter q0) are discussed. First results from a large homogeneous survey are presented. The data do not show compelling evidence for the existence of intrinsically different populations of galaxies, BL Lacertae objects, or quasars. Apparent velocities betaapp in the range 1-5 h-1, where h = H0/100 km.s-1.Mpc-1 [1 megaparsec (Mpc) = 3.09 x 10(22) m], occur with roughly equal frequency; higher values, up to betaapp = 10 h-1, are rather more scarce than appeared to be the case from earlier work, which evidently concentrated on sources that are not representative of the general population. The betaapp distribution suggests that there might be a skewed distribution of Lorentz factors over the sample, with a peak at gammab approximately 2 h-1 and a tail up to at least gammab approximately 10 h-1. There appears to be a clearly rising upper envelope to the betaapp distribution when plotted as a function of observed 5-GHz luminosity; a combination of source counts and the apparent velocity statistics in a larger sample could provide much insight into the properties of radio jet sources. PMID:11607604

  10. Decontamination formulation with sorbent additive

    DOEpatents

    Tucker; Mark D. , Comstock; Robert H.

    2007-10-16

    A decontamination formulation and method of making that neutralizes the adverse health effects of both chemical and biological compounds, especially chemical warfare (CW) and biological warfare (BW) agents, and toxic industrial chemicals. The formulation provides solubilizing compounds that serve to effectively render the chemical and biological compounds, particularly CW and BW compounds, susceptible to attack, and at least one reactive compound that serves to attack (and detoxify or kill) the compound. The formulation includes at least one solubilizing agent, a reactive compound, a bleaching activator, a sorbent additive, and water. The highly adsorbent, water-soluble sorbent additive (e.g., sorbitol or mannitol) is used to "dry out" one or more liquid ingredients, such as the liquid bleaching activator (e.g., propylene glycol diacetate or glycerol diacetate) and convert the activator into a dry, free-flowing powder that has an extended shelf life, and is more convenient to handle and mix in the field.

  11. Robust stability under additive perturbations

    NASA Technical Reports Server (NTRS)

    Bhaya, A.; Desoer, C. A.

    1985-01-01

    A MIMO linear time-invariant feedback system 1S(P,C) is considered which is assumed to be U-stable. The plant P is subjected to an additive perturbation Delta P which is proper but not necessarily stable. It is proved that the perturbed system is U-stable if and only if Delta P(I + Q x Delta P) exp -1 is U-stable.

  12. 21 CFR 640.60 - Source Plasma.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 7 2012-04-01 2012-04-01 false Source Plasma. 640.60 Section 640.60 Food and... ADDITIONAL STANDARDS FOR HUMAN BLOOD AND BLOOD PRODUCTS Source Plasma § 640.60 Source Plasma. The proper name of the product shall be Source Plasma. The product is defined as the fluid portion of human...

  13. 21 CFR 640.60 - Source Plasma.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 7 2013-04-01 2013-04-01 false Source Plasma. 640.60 Section 640.60 Food and... ADDITIONAL STANDARDS FOR HUMAN BLOOD AND BLOOD PRODUCTS Source Plasma § 640.60 Source Plasma. The proper name of the product shall be Source Plasma. The product is defined as the fluid portion of human...

  14. 21 CFR 640.60 - Source Plasma.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 7 2014-04-01 2014-04-01 false Source Plasma. 640.60 Section 640.60 Food and... ADDITIONAL STANDARDS FOR HUMAN BLOOD AND BLOOD PRODUCTS Source Plasma § 640.60 Source Plasma. The proper name of the product shall be Source Plasma. The product is defined as the fluid portion of human...

  15. 21 CFR 640.60 - Source Plasma.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 7 2010-04-01 2010-04-01 false Source Plasma. 640.60 Section 640.60 Food and... ADDITIONAL STANDARDS FOR HUMAN BLOOD AND BLOOD PRODUCTS Source Plasma § 640.60 Source Plasma. The proper name of the product shall be Source Plasma. The product is defined as the fluid portion of human...

  16. 48 CFR 13.102 - Source list.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... as their primary sources of vendor information. Offices maintaining additional vendor source files or... 48 Federal Acquisition Regulations System 1 2010-10-01 2010-10-01 false Source list. 13.102... AND CONTRACT TYPES SIMPLIFIED ACQUISITION PROCEDURES Procedures 13.102 Source list. (a)...

  17. 48 CFR 13.102 - Source list.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... as their primary sources of vendor information. Offices maintaining additional vendor source files or... 48 Federal Acquisition Regulations System 1 2011-10-01 2011-10-01 false Source list. 13.102... AND CONTRACT TYPES SIMPLIFIED ACQUISITION PROCEDURES Procedures 13.102 Source list. (a)...

  18. Additive manufacturing of hybrid circuits

    DOE PAGESBeta

    Bell, Nelson S.; Sarobol, Pylin; Cook, Adam; Clem, Paul G.; Keicher, David M.; Hirschfeld, Deidre; Hall, Aaron Christopher

    2016-03-26

    There is a rising interest in developing functional electronics using additively manufactured components. Considerations in materials selection and pathways to forming hybrid circuits and devices must demonstrate useful electronic function; must enable integration; and must complement the complex shape, low cost, high volume, and high functionality of structural but generally electronically passive additively manufactured components. This article reviews several emerging technologies being used in industry and research/development to provide integration advantages of fabricating multilayer hybrid circuits or devices. First, we review a maskless, noncontact, direct write (DW) technology that excels in the deposition of metallic colloid inks for electrical interconnects.more » Second, we review a complementary technology, aerosol deposition (AD), which excels in the deposition of metallic and ceramic powder as consolidated, thick conformal coatings and is additionally patternable through masking. As a result, we show examples of hybrid circuits/devices integrated beyond 2-D planes, using combinations of DW or AD processes and conventional, established processes.« less

  19. Evaluation of certain food additives.

    PubMed

    2009-01-01

    This report represents the conclusions of a Joint FAO/WHO Expert Committee convened to evaluate the safety of various food additives, including flavouring agents, with a view to recommending acceptable daily intakes (ADIs) and to preparing specifications for identity and purity. The first part of the report contains a general discussion of the principles governing the toxicological evaluation and assessment of intake of food additives (in particular, flavouring agents). A summary follows of the Committee's evaluations of technical, toxicological and intake data for certain food additives (asparaginase from Aspergillus niger expressed in A. niger, calcium lignosulfonate (40-65), ethyl lauroyl arginate, paprika extract, phospholipase C expressed in Pichia pastoris, phytosterols, phytostanols and their esters, polydimethylsiloxane, steviol glycosides and sulfites [assessment of dietary exposure]) and 10 groups of related flavouring agents (aliphatic branched-chain saturated and unsaturated alcohols, aldehydes, acids and related esters; aliphatic linear alpha,beta-unsaturated aldehydes, acids and related alcohols, acetals and esters; aliphatic secondary alcohols, ketones and related esters; alkoxy-substituted allylbenzenes present in foods and essential oils and used as flavouring agents; esters of aliphatic acyclic primary alcohols with aliphatic linear saturated carboxylic acids; furan-substituted aliphatic hydrocarbons, alcohols, aldehydes, ketones, carboxylic acids and related esters, sulfides, disulfides and ethers; miscellaneous nitrogen-containing substances; monocyclic and bicyclic secondary alcohols, ketones and related esters; hydroxy- and alkoxy-substituted benzyl derivatives; and substances structurally related to menthol). Specifications for the following food additives were revised: canthaxanthin; carob bean gum and carob bean gum (clarified); chlorophyllin copper complexes, sodium and potassium salts; Fast Green FCF; guar gum and guar gum (clarified

  20. Fire-Retardant Polymeric Additives

    NASA Technical Reports Server (NTRS)

    Williams, Martha K.; Smith, Trent M.

    2011-01-01

    Polyhydroxyamide (PHA) and polymethoxyamide (PMeOA) are fire-retardant (FR) thermoplastic polymers and have been found to be useful as an additive for imparting fire retardant properties to other compatible, thermoplastic polymers (including some elastomers). Examples of compatible flammable polymers include nylons, polyesters, and acrylics. Unlike most prior additives, PHA and PMeOA do not appreciably degrade the mechanical properties of the matrix polymer; indeed, in some cases, mechanical properties are enhanced. Also, unlike some prior additives, PHA and PMeOA do not decompose into large amounts of corrosive or toxic compounds during combustion and can be processed at elevated temperatures. PMeOA derivative formulations were synthesized and used as an FR additive in the fabrication of polyamide (PA) and polystyrene (PS) composites with notable reduction (>30 percent for PS) in peak heat release rates compared to the neat polymer as measured by a Cone Calorimeter (ASTM E1354). Synergistic effects were noted with nanosilica composites. These nanosilica composites had more than 50-percent reduction in peak heat release rates. In a typical application, a flammable thermoplastic, thermoplastic blend, or elastomer that one seeks to render flame-retardant is first dry-mixed with PHA or PMeOA or derivative thereof. The proportion of PHA or PMeOA or derivative in the mixture is typically chosen to lie between 1 and 20 weight percent. The dry blend can then be melt-extruded. The extruded polymer blend can further be extruded and/or molded into fibers, pipes, or any other of a variety of objects that may be required to be fire-retardant. The physical and chemical mechanisms which impart flame retardancy of the additive include inhibiting free-radical oxidation in the vapor phase, preventing vaporization of fuel (the polymer), and cooling through the formation of chemical bonds in either the vapor or the condensed phase. Under thermal stress, the cyclic hydroxyl/ methoxy

  1. ION SOURCE

    DOEpatents

    Bell, W.A. Jr.; Love, L.O.; Prater, W.K.

    1958-01-28

    An ion source is presented capable of producing ions of elements which vaporize only at exceedingly high temperatures, i.e.,--1500 degrees to 3000 deg C. The ion source utilizes beams of electrons focused into a first chamber housing the material to be ionized to heat the material and thereby cause it to vaporize. An adjacent second chamber receives the vaporized material through an interconnecting passage, and ionization of the vaporized material occurs in this chamber. The ionization action is produced by an arc discharge sustained between a second clectron emitting filament and the walls of the chamber which are at different potentials. The resultant ionized material egresses from a passageway in the second chamber. Using this device, materials which in the past could not be processed in mass spectometers may be satisfactorily ionized for such applications.

  2. ION SOURCE

    DOEpatents

    Blue, C.W.; Luce, J.S.

    1960-07-19

    An ion source is described and comprises an arc discharge parallel to the direction of and inside of a magnetic field. an accelerating electrode surrounding substantially all of the discharge except for ion exit apertures, and means for establishing an electric field between that electrode and the arc discharge. the electric field being oriented at an acute angle to the magnetic field. Ions are drawn through the exit apertures in the accelrating electrcde in a direction substantially divergent to the direction of the magnetic field and so will travel in a spiral orbit along the magnetic field such that the ions will not strike the source at any point in their orbit within the magnetic field.

  3. Ion source

    DOEpatents

    Brobeck, W. M.

    1959-04-14

    This patent deals with calutrons and more particularly to an arrangement therein whereby charged bottles in a calutron source unit may be replaced without admitting atmospheric air to the calutron vacuum chamber. As described, an ion unit is disposed within a vacuum tank and has a reservoir open toward a wall of the tank. A spike projects from the source into the reservoir. When a charge bottle is placed in the reservoir, the spike breaks a frangible seal on the bottle. After the contents of the bottle are expended the bottle may be withdrawn and replaced with another charge bottle by a vacuum lock arrangement in conjunction with an arm for manipulating the bottle.

  4. ION SOURCE

    DOEpatents

    Brobeck, W.M.

    1959-04-14

    This patent deals with calutrons and more particularly to an arrangement therein whereby charged bottles in a calutron source unit may be replaced without admitting atmospheric air to the calutron vacuum chamber. As described, an ion unit is disposed within a vacuum tank and has a reservoir open toward a wall of the tank. A spike projects from thc source into the reservoir. When a charge bottle is placed in the reservoir, the spike breaks a frangible seal on the bottle. After the contents of the bottle are expended the bottle may be withdrawn and replaced with another charge bottle by a varuum lock arrangement in conjunction with an arm for manipulating the bottle.

  5. Additional evidence of Mercurian volcanism

    USGS Publications Warehouse

    Trask, N.J.; Strom, R.G.

    1976-01-01

    Evidence concerned with (1) the character and distribution of terrain surrounding fresh basins, (2) albedo, color and temporal differences between a basin rim and smooth plains on its floor, and (3) the stratigraphic relations and local distribution of smooth plains in the hilly and lineated terrain are cited as additional evidence for an internal origin of much of the Mercurian smooth plains. Altough the question of Mercurian volcanism should be kept open, this evidence together with that presented in an earlier paper suggests that volcanism occurred on Mercury early in its history. ?? 1976.

  6. Individualized additional instruction for calculus

    NASA Astrophysics Data System (ADS)

    Takata, Ken

    2010-10-01

    College students enrolling in the calculus sequence have a wide variance in their preparation and abilities, yet they are usually taught from the same lecture. We describe another pedagogical model of Individualized Additional Instruction (IAI) that assesses each student frequently and prescribes further instruction and homework based on the student's performance. Our study compares two calculus classes, one taught with mandatory remedial IAI and the other without. The class with mandatory remedial IAI did significantly better on comprehensive multiple-choice exams, participated more frequently in classroom discussion and showed greater interest in theorem-proving and other advanced topics.

  7. Water based drilling mud additive

    SciTech Connect

    McCrary, J.L.

    1983-12-13

    A water based fluid additive useful in drilling mud used during drilling of an oil or gas well is disclosed, produced by reacting water at temperatures between 210/sup 0/-280/sup 0/ F. with a mixture comprising in percent by weight: gilsonite 25-30%, tannin 7-15%, lignite 25-35%, sulfonating compound 15-25%, water soluble base compound 5-15%, methylene-yielding compound 1-5%, and then removing substantially all of the remaining water to produce a dried product.

  8. Metal Additive Manufacturing: A Review

    NASA Astrophysics Data System (ADS)

    Frazier, William E.

    2014-06-01

    This paper reviews the state-of-the-art of an important, rapidly emerging, manufacturing technology that is alternatively called additive manufacturing (AM), direct digital manufacturing, free form fabrication, or 3D printing, etc. A broad contextual overview of metallic AM is provided. AM has the potential to revolutionize the global parts manufacturing and logistics landscape. It enables distributed manufacturing and the productions of parts-on-demand while offering the potential to reduce cost, energy consumption, and carbon footprint. This paper explores the material science, processes, and business consideration associated with achieving these performance gains. It is concluded that a paradigm shift is required in order to fully exploit AM potential.

  9. Nutrition information sources.

    PubMed

    Farrell, L

    1972-10-01

    Medical personnel and medical librarians may tend to think of nutrition in medical terms and to forget its interdisciplinary aspects. For this reason, it is desirable for medical librarians to become familiar with a variety of sources of information on the composition of foods, nutrient values, food additives, and food protection. Many of these are government publications from such agencies as the U.S. Department of Agriculture, the National Research Council, and the Food and Agriculture Organization. Less familiar sources include nutrition materials from state agricultural experiment stations and extension services and important data published in a wide range of scientific or agricultural journals, which may be located through Nutrition Abstracts and Reviews, Food Science and Technology Abstracts, and the Bibliography of Agriculture. Sources of current information on nutrition research in progress include the Department of Agriculture's Current Research Information System (CRIS) and selective listings from the Smith-sonian Information Exchange. PMID:4563540

  10. Nutrition Information Sources

    PubMed Central

    Farrell, Lois

    1972-01-01

    Medical personnel and medical librarians may tend to think of nutrition in medical terms and to forget its interdisciplinary aspects. For this reason, it is desirable for medical librarians to become familiar with a variety of sources of information on the composition of foods, nutrient values, food additives, and food protection. Many of these are government publications from such agencies as the U.S. Department of Agriculture, the National Research Council, and the Food and Agriculture Organization. Less familiar sources include nutrition materials from state agricultural experiment stations and extension services and important data published in a wide range of scientific or agricultural journals, which may be located through Nutrition Abstracts and Reviews, Food Science and Technology Abstracts, and the Bibliography of Agriculture. Sources of current information on nutrition research in progress include the Department of Agriculture's Current Research Information System (CRIS) and selective listings from the Smith-sonian Information Exchange. PMID:4563540

  11. Density functional studies of the formation of nitrous acid from the reaction of nitrogen dioxide and water vapor

    SciTech Connect

    Chou, A.; Li, Z.; Tao, F.M.

    1999-09-30

    Nitrous acid (HONO) has long been recognized as an important trace gas in the troposphere where its rapid photolysis represents a significant source of hydroxy (OH) radicals. During the night, HONO has been observed to accumulate to concentrations up to 15 ppb, and this accumulation of HONO has a profound impact on the daytime chemistry of the troposphere. Reaction mechanisms for the production of nitrous acid (HONO ) from the homogeneous gas-phase hydrolysis of nitrogen dioxide (NO{sub 2}) are examined by density functional theory calculations. The molecular structures and energies of the NO{sub 2}-(H{sub 2}O){sub n} (n = 1, 2, 3) and N{sub 2}O{sub 4}-(H{sub 2} O){sub n}(n = 1, 2) systems corresponding to the stationary points on the potential energy surface along the reaction pathways are calculated using the B3LYP method with the 6-311+G(2d,p) basis set. These reaction pathways represent the homogeneous hydrolysis of NO{sub 2} or N{sub 2}O{sub 4} with a varying number of water (H{sub 2}O) molecules. The reactions of NO{sub 2} with water produce HONO, along with the OH radical which was postulated to combine in the next step with a second NO{sub 2} to form nitric acid (HNO{sub 3}). The simple NO{sub 2} + H{sub 2}O bimolecular reaction leads to the highly unstable OH radical which reacts reversibly with HONO without an energy barrier. The introduction of single solvating H{sub 2}O molecule appears to stabilize the transition state as well as an intermediate that contains the OH radical. However, the energy barrier is found to be near 30 kcal mol{sup {minus}1} and is not affected by multiple additional H{sub 2}O molecules. On the other hand, the reaction of N{sub 2}O{sub 4} with water lead directly to HONO and HNO{sub 3}. the energy barrier for the N{sub 2}O{sub 4} reaction is above 30 kcal mol{sup {minus}1} and is also unaffected by additional H{sub 2}O molecules. The study demonstrates that the gas-phase hydrolysis of NO{sub 2} or N{sub 2}O{sub 4} is

  12. UV-visible absorption cross sections of nitrous acid

    NASA Astrophysics Data System (ADS)

    Stutz, J.; Kim, E. S.; Platt, U.; Bruno, P.; Perrino, C.; Febo, A.

    2000-06-01

    Nitrous acid, HONO, is a source of OH radicals in the polluted atmosphere. Although the atmospheric chemistry of HONO is qualitatively understood, not much quantitative information exists. The magnitude of the OH production by HONO photolysis depends on the spectrum of its absorption cross sections; therefore the knowledge of σ'HONO(λ) is essential. The spectrum of the differential cross sections σ'HONO(λ) is needed to detect HONO in the atmosphere by differential optical absorption spectroscopy (DOAS). Here we present measurements of the HONO UV-visible absorption cross sections with a spectral resolution better than 0.1 nm and a high signal-to-noise ratio. The maximum value of the absorption cross sections is σHONO (354 nm) = (5.19±0.26) × 10-19 cm2 and agrees well with literature data. Nevertheless, calculations based on data from this work and on literature data reveal that an uncertainty of ˜15% remains for the HONO photolysis rates. The new σHONO(λ) has been employed in DOAS measurements in Milan, Italy.

  13. Additive manufacturing of RF absorbers

    NASA Astrophysics Data System (ADS)

    Mills, Matthew S.

    The ability of additive manufacturing techniques to fabricate integrated electromagnetic absorbers tuned for specific radio frequency bands within structural composites allows for unique combinations of mechanical and electromagnetic properties. These composites and films can be used for RF shielding of sensitive electromagnetic components through in-plane and out-of-plane RF absorption. Structural composites are a common building block of many commercial platforms. These platforms may be placed in situations in which there is a need for embedded RF absorbing properties along with structural properties. Instead of adding radar absorbing treatments to the external surface of existing structures, which adds increased size, weight and cost; it could prove to be advantageous to integrate the microwave absorbing properties directly into the composite during the fabrication process. In this thesis, a method based on additive manufacturing techniques of composites structures with prescribed electromagnetic loss, within the frequency range 1 to 26GHz, is presented. This method utilizes screen printing and nScrypt micro dispensing to pattern a carbon based ink onto low loss substrates. The materials chosen for this study will be presented, and the fabrication technique that these materials went through to create RF absorbing structures will be described. The calibration methods used, the modeling of the RF structures, and the applications in which this technology can be utilized will also be presented.

  14. High Flow Addition Curing Polyimides

    NASA Technical Reports Server (NTRS)

    Chuang, Kathy C.; Vannucci, Raymond D.; Ansari, Irfan; Cerny, Lawrence L.; Scheiman, Daniel A.

    1994-01-01

    A new series of high flow PMR-type addition curing polyimides was developed, which employed the substitution of 2,2'-bis (trifluoromethyl) -4,4'-diaminobiphenyl (BTDB) for p-phenylenediamine (p -PDA) in a PMR-IL formulation. These thermoset polyimides, designated as 12F resins, were prepared from BTDB and the dimethyl ester of 4,4'- (hexafluo- roisopropylidene) -diphthalic acid (HFDE) with either nadic ester (NE) or p-aminostyrene (PAS) as the endcaps for addition curing. The 12F prepolymers displayed lower melting temperatures in DSC analysis, and higher melt flow in rheological studies than the cor- responding PMR-11 polyimides. Long-term isothermal aging studies showed that BTDB- based 12F resins exhibited comparable thermo-oxidative stability to P-PDA based PMR-11 polyimides. The noncoplanar 2- and 2'-disubstituted biphenyldiamine (BTDB) not only lowered the melt viscosities of 12F prepolymers, but also retained reasonable thermal sta- bility of the cured resins. The 12F polyimide resin with p-aminostyrene endcaps showed the best promise for long-term, high-temperature application at 343 C (650 F).

  15. Cherenkov Source for PMT Calibrations

    NASA Astrophysics Data System (ADS)

    Kaptanoglu, Tanner; SNO+ at UC Berkeley Collaboration

    2013-10-01

    My research is focused on building a deployable source for PMT calibrations in the SNO+ detector. I work for the SNO+ group at UC Berkeley headed by Gabriel Orebi Gann. SNO+ is an addition to the SNO project, and its main goal is to search for neutrinoless double beta decay. The detector will be monitored by over 9500 photomultiplier tubes (PMTs). In order to characterize the PMTs, several calibration sources are being constructed. One of which, the Cherenkov Source, will provide a well-understood source of non-isotropic light for calibrating the detector response. My goal is to design and construct multiple aspects of the Cherenkov Source. However, there are multiple questions that arose with its design. How do we keep the scintillation light inside the Cherenkov source so it does not contaminate calibration? How do we properly build the Cherenkov source: a hollow acrylic sphere with a neck? Can we maintain a clean source throughout these processes? These are some of the problems I have been working on, and will continue to work on, until the deployment of the source. Additionally, I have worked to accurately simulate the physics inside the source, mainly the energy deposition of alphas.

  16. Additives in fibers and fabrics.

    PubMed

    Barker, R H

    1975-06-01

    The additives and contaminants which occur in textile fibers vary widely, depending on the type of fiber and the pretreatment which it has received. Synthetic fibers such as nylon and polyester contain trace amounts of contaminants such as catalysts and catalyst deactivators which remain after the synthesis of the basic polymers. In addition, there are frequently a number of materials which are added to perform specific functions in almost all man-made fibers. Examples of these would include traces of metals or metal salts used as tracers for identification of specific lots of fiber, TiO2 or similar materials added as delustrants, and a host of organic species added for such special purposes as antistatic agents or flame retardants. There may also be considerable quantities of residual monomer or small oligomers dissolved in the polymer matrix. The situation becomes even more complex after the fibers are converted into fabric form. Numerous materials are applied at various stages of fabric preparation to act as lubricants, sizing agents, antistats, bleaches, and wetting agents to facilitate the processing, but these are normally removed before the fabric reaches the cutters of the ultimate consumers and therefore usually do not constitute potential hazards. However, there are many other chemical agents which are frequently added during the later stages of fabric preparation and which are not designed to be removed. Aside from dyes and printing pigments, the most common additive for apparel fabrics is a durable press treatment. This generally involves the use of materials capable of crosslinking cellulosics by reacting through such functions as N-methylolated amides or related compounds such as ureas and carbamates. These materials pose some potential hazards due to both the nitrogenous bases and the formaldehyde which they usually release. There is usually also some residual catalyst in fabrics which have received such treatments. Other types of chemical treatments

  17. Additives in fibers and fabrics.

    PubMed Central

    Barker, R H

    1975-01-01

    The additives and contaminants which occur in textile fibers vary widely, depending on the type of fiber and the pretreatment which it has received. Synthetic fibers such as nylon and polyester contain trace amounts of contaminants such as catalysts and catalyst deactivators which remain after the synthesis of the basic polymers. In addition, there are frequently a number of materials which are added to perform specific functions in almost all man-made fibers. Examples of these would include traces of metals or metal salts used as tracers for identification of specific lots of fiber, TiO2 or similar materials added as delustrants, and a host of organic species added for such special purposes as antistatic agents or flame retardants. There may also be considerable quantities of residual monomer or small oligomers dissolved in the polymer matrix. The situation becomes even more complex after the fibers are converted into fabric form. Numerous materials are applied at various stages of fabric preparation to act as lubricants, sizing agents, antistats, bleaches, and wetting agents to facilitate the processing, but these are normally removed before the fabric reaches the cutters of the ultimate consumers and therefore usually do not constitute potential hazards. However, there are many other chemical agents which are frequently added during the later stages of fabric preparation and which are not designed to be removed. Aside from dyes and printing pigments, the most common additive for apparel fabrics is a durable press treatment. This generally involves the use of materials capable of crosslinking cellulosics by reacting through such functions as N-methylolated amides or related compounds such as ureas and carbamates. These materials pose some potential hazards due to both the nitrogenous bases and the formaldehyde which they usually release. There is usually also some residual catalyst in fabrics which have received such treatments. Other types of chemical treatments

  18. Stereochemistry of enzymatic water addition to C=C bonds.

    PubMed

    Chen, Bi-Shuang; Otten, Linda G; Hanefeld, Ulf

    2015-01-01

    Water addition to carbon-carbon double bonds using hydratases is attracting great interest in biochemistry. Most of the known hydratases are involved in primary metabolism and to a lesser extent in secondary metabolism. New hydratases have recently been added to the toolbox, both from natural sources or artificial metalloenzymes. In order to comprehensively understand how the hydratases are able to catalyse the water addition to carbon-carbon double bonds, this review will highlight the mechanistic and stereochemical studies of the enzymatic water addition to carbon-carbon double bonds, focusing on the syn/anti-addition and stereochemistry of the reaction. PMID:25640045

  19. A novel addition polyimide adhesive

    NASA Technical Reports Server (NTRS)

    St.clair, T. L.; Progar, D. J.

    1981-01-01

    An addition polyimide adhesive, LARC 13, was developed which shows promise for bonding both titanium and composites for applications which require service temperatures in excess of 533 K. The LARC 13 is based on an oligomeric bis nadimide containing a meta linked aromatic diamine. The adhesive melts prior to polymerization due to its oligomeric nature, thereby allowing it to be processed at 344 kPa or less. Therefore, LARC 13 is ideal for the bonding of honeycomb sandwich structures. After melting, the resin thermosets during the cure of the nadic endcaps to a highly crosslinked system. Few volatiles are evolved, thus allowing large enclosed structures to be bonded. Preparation of the adhesive as well as bonding, aging, and testing of lap shear and honeycomb samples are discussed.

  20. Optics of progressive addition lenses.

    PubMed

    Sheedy, J E; Buri, M; Bailey, I L; Azus, J; Borish, I M

    1987-02-01

    The optical characteristics of the major progressive addition lenses were measured using an automated lensometer with a specially designed lens holder to simulate eye rotation. Measurements were made every 3 degrees (about 1.5 mm) and graphs of isospherical equivalent lines and isocylinder lines were developed. Generally the near zone of these lenses is narrower and lower than in bifocal or trifocal lenses. Distinct differences exist between the various progressive lenses. The width of the near zone, rate of power progression, amount of unwanted cylinder (level with the distance center), and clarity of the distance zone are compared for the various lenses. The optical measurements demonstrate an apparent trade-off between the size of the cylinder-free area of the lens and the amount of the cylinder. PMID:3826294

  1. Addition polyimide end cap study

    NASA Technical Reports Server (NTRS)

    St.clair, T. L.

    1980-01-01

    The characterization of addition polyimides with various end caps for adhesive applications at 120-250 C environments is discussed. Oligometric polyimides were prepared from 3,3',4,4'-benzophenone tetracarboxylic dianhydride and 3,3'-methylenedianiline which were end-capped with functionally reactive moities which cause crosslinking when the oligomers are heated to 200-400 C. The syntheses of the oligomers are outlined. The thermolysis of the oligomers was studied by differential scanning calorimetry and the resulting polymers were characterized by differential thermal analysis and adhesive performance. The adhesive data include lap shear strengths on titanium 6-4 adherends both before and after aging for 1000 hours at 121 C and/or 232 C.

  2. SIPSEY WILDERNESS AND ADDITIONS, ALABAMA.

    USGS Publications Warehouse

    Schweinfurth, Stanley P.; Mory, Peter C.

    1984-01-01

    On the basis of geologic, geochemical, and mineral surveys the Sipsey Wilderness and additions are deemed to have little promise for the occurrence of metallic mineral resources. Although limestone, shale, and sandstone resources that occur in the area are physically suitable for a variety of uses, similar materials are available outside the area closer to transportation routes and potential markets. A small amount of coal has been identified in the area, occurring as nonpersistent beds less than 28 in. thick. Oil and (or) natural gas resources may be present if suitable structural traps exist in the subsurface. Therefore, the area has a probable oil and gas potential. Small amounts of asphaltic sandstone and limestone, commonly referred to as tar sands, may also occur in the subsurface. 5 refs.

  3. Adverse reactions to food additives.

    PubMed

    Simon, R A

    1986-01-01

    There are thousands of agents that are intentionally added to the food that we consume. These include preservatives, stabilizers, conditioners, thickeners, colorings, flavorings, sweeteners, antioxidants, etc. etc. Yet only a surprisingly small number have been associated with hypersensitivity reactions. Amongst all the additives, FD&C dyes have been most frequently associated with adverse reactions. Tartrazine is the most notorious of them all; however, critical review of the medical literature and current Scripps Clinic studies would indicate that tartrazine has been confirmed to be at best only occasionally associated with flares of urticaria or asthma. There is no convincing evidence in the literature of reactivity to the other azo or nonazo dyes. This can also be said of BHA/BHT, nitrites/nitrates and sorbates. Parabens have been shown to elicit IgE mediated hypersensitivity reactions when used as pharmaceutical preservatives; however, as with the other additives noted above, ingested parabens have only occasionally been associated with adverse reactions. MSG, the cause of the 'Chinese restaurant syndrome' has only been linked to asthma in one report. Sulfiting agents used primarily as food fresheners and to control microbial growth in fermented beverages have been established as the cause of any where from mild to severe and even fatal reactions in at least 5% of the asthmatic population. Other reactions reported to follow sulfite ingestion include anaphylaxis, gastro intestinal complaints and dermatological eruptions. The prevalence of these non asthmatic reactions is unknown. The mechanism of sulfite sensitive asthma is also unknown but most likely involves hyperreactivity to inhale SO2 in the great majority of cases; however, there are reports of IgE mediated reactions and other sulfite sensitive asthmatics have been found with low levels of sulfite oxidase; necessary to oxidize endogenous sulfite to sulfate. PMID:3302664

  4. Impact of nitrous acid photolysis on the total hydroxyl radical budget during the Limitation of Oxidant Production/Pianura Padana Produzione di Ozono study in Milan

    NASA Astrophysics Data System (ADS)

    Alicke, B.; Platt, U.; Stutz, J.

    2002-11-01

    The photolysis of nitrous acid (HONO) in the early morning hours is believed to be a significant source of hydroxyl radicals (OH), the most important daytime oxidizing species. Although the importance of this mechanism has been recognized for many years, no accurate experimental quantification is available. Here we present measurements of HONO, NO2, SO2, O3 and HCHO by Differential Optical Absorption Spectroscopy (DOAS) during the Limitation of Oxidant Production/Pianura Padana Produzione di Ozono (LOOP/PIPAPO) study in May-June 1998 in Milan, Italy. The concentration of NO and J(NO2)/J(HONO) were simultaneously monitored by in situ monitors. The photolysis frequencies of HCHO and O3 were determined with a radiative transfer model. High nocturnal HONO mixing ratios of up to 4.4 ppb were regularly observed. Elevated daytime HONO levels during cloudy periods show that the formation of HONO proceeds after sunrise and therefore also represents a source of hydroxyl radicals throughout the day. Averaged over 24 hours, HCHO photolysis is the most important source of OH in Milan, followed by either ozone or HONO photolysis. Our observations indicate that on certain days the OH production from HONO can be even more important than that from ozone photolysis. The diurnal variation of the different OH formation mechanisms shows that HONO photolysis is by far the most important source in the early hours of the morning, and can be as large as and even surpass the total OH production at noon.

  5. Surface texture measurement for additive manufacturing

    NASA Astrophysics Data System (ADS)

    Triantaphyllou, Andrew; Giusca, Claudiu L.; Macaulay, Gavin D.; Roerig, Felix; Hoebel, Matthias; Leach, Richard K.; Tomita, Ben; Milne, Katherine A.

    2015-06-01

    The surface texture of additively manufactured metallic surfaces made by powder bed methods is affected by a number of factors, including the powder’s particle size distribution, the effect of the heat source, the thickness of the printed layers, the angle of the surface relative to the horizontal build bed and the effect of any post processing/finishing. The aim of the research reported here is to understand the way these surfaces should be measured in order to characterise them. In published research to date, the surface texture is generally reported as an Ra value, measured across the lay. The appropriateness of this method for such surfaces is investigated here. A preliminary investigation was carried out on two additive manufacturing processes—selective laser melting (SLM) and electron beam melting (EBM)—focusing on the effect of build angle and post processing. The surfaces were measured using both tactile and optical methods and a range of profile and areal parameters were reported. Test coupons were manufactured at four angles relative to the horizontal plane of the powder bed using both SLM and EBM. The effect of lay—caused by the layered nature of the manufacturing process—was investigated, as was the required sample area for optical measurements. The surfaces were also measured before and after grit blasting.

  6. Nitrous acid in Albuquerque, New Mexico, homes

    SciTech Connect

    Spengler, J.D.; Brauer, M. ); Samet, J.M.; Lambert, W.E. )

    1993-05-01

    Experimental studies have shown that nitrogen acid species, particularly nitrous acid, are formed indoors during unvented combustion and by heterogeneous reactions of nitrogen dioxide. Limited measurements support the occurrence of nitrous acid production in occupied homes. The authors report additional measurements of HONO and NO[sub 2] in homes located in Albuquerque, NM, and assess the relationship with housing variables. Indoor HONO concentrations were found to be well correlated with indoor NO[sub 2] levels; HONO concentrations ranged from 5% to 15% of the measured NO[sub 2] concentrations. Given the correlation between HONO and NO[sub 2] in indoor environments, and the plausibility of HONO respiratory toxicity, investigations of respiratory health effects of unvented combustion should consider HONO, in addition to NO[sub 2], as a potentially hazardous indoor pollutant. 38 refs., 2 figs., 2 tabs.

  7. Additively manufactured porous tantalum implants.

    PubMed

    Wauthle, Ruben; van der Stok, Johan; Amin Yavari, Saber; Van Humbeeck, Jan; Kruth, Jean-Pierre; Zadpoor, Amir Abbas; Weinans, Harrie; Mulier, Michiel; Schrooten, Jan

    2015-03-01

    The medical device industry's interest in open porous, metallic biomaterials has increased in response to additive manufacturing techniques enabling the production of complex shapes that cannot be produced with conventional techniques. Tantalum is an important metal for medical devices because of its good biocompatibility. In this study selective laser melting technology was used for the first time to manufacture highly porous pure tantalum implants with fully interconnected open pores. The architecture of the porous structure in combination with the material properties of tantalum result in mechanical properties close to those of human bone and allow for bone ingrowth. The bone regeneration performance of the porous tantalum was evaluated in vivo using an orthotopic load-bearing bone defect model in the rat femur. After 12 weeks, substantial bone ingrowth, good quality of the regenerated bone and a strong, functional implant-bone interface connection were observed. Compared to identical porous Ti-6Al-4V structures, laser-melted tantalum shows excellent osteoconductive properties, has a higher normalized fatigue strength and allows for more plastic deformation due to its high ductility. It is therefore concluded that this is a first step towards a new generation of open porous tantalum implants manufactured using selective laser melting. PMID:25500631

  8. Sustainability Characterization for Additive Manufacturing

    PubMed Central

    Mani, Mahesh; Lyons, Kevin W; Gupta, SK

    2014-01-01

    Additive manufacturing (AM) has the potential to create geometrically complex parts that require a high degree of customization, using less material and producing less waste. Recent studies have shown that AM can be an economically viable option for use by the industry, yet there are some inherent challenges associated with AM for wider acceptance. The lack of standards in AM impedes its use for parts production since industries primarily depend on established standards in processes and material selection to ensure the consistency and quality. Inability to compare AM performance against traditional manufacturing methods can be a barrier for implementing AM processes. AM process sustainability has become a driver due to growing environmental concerns for manufacturing. This has reinforced the importance to understand and characterize AM processes for sustainability. Process characterization for sustainability will help close the gaps for comparing AM performance to traditional manufacturing methods. Based on a literature review, this paper first examines the potential environmental impacts of AM. A methodology for sustainability characterization of AM is then proposed to serve as a resource for the community to benchmark AM processes for sustainability. Next, research perspectives are discussed along with relevant standardization efforts. PMID:26601038

  9. Additive Transforms Paint into Insulation

    NASA Technical Reports Server (NTRS)

    2007-01-01

    Tech Traders Inc. sought assistance developing low-cost, highly effective coatings and paints that created useful thermal reflectance and were safe and non-toxic. In cooperation with a group of engineers at Kennedy Space Center., Tech Traders created Insuladd, a powder additive made up of microscopic, inert gas-filled, ceramic microspheres that can be mixed into ordinary interior or exterior paint, allowing the paint to act like a layer of insulation. When the paint dries, this forms a radiant heat barrier, turning the ordinary house paint into heat-reflecting thermal paint. According to Tech Traders, the product works with all types of paints and coatings and will not change the coverage rate, application, or adhesion of the paint. Other useful applications include feed storage silos to help prevent feed spoilage, poultry hatcheries to reduce the summer heat and winter cold effects, and on military vehicles and ships. Tech Traders has continued its connection to the aerospace community by recently providing Lockheed Martin Corporation with one of its thermal products for use on the F-22 Raptor.

  10. Sustainability Characterization for Additive Manufacturing.

    PubMed

    Mani, Mahesh; Lyons, Kevin W; Gupta, S K

    2014-01-01

    Additive manufacturing (AM) has the potential to create geometrically complex parts that require a high degree of customization, using less material and producing less waste. Recent studies have shown that AM can be an economically viable option for use by the industry, yet there are some inherent challenges associated with AM for wider acceptance. The lack of standards in AM impedes its use for parts production since industries primarily depend on established standards in processes and material selection to ensure the consistency and quality. Inability to compare AM performance against traditional manufacturing methods can be a barrier for implementing AM processes. AM process sustainability has become a driver due to growing environmental concerns for manufacturing. This has reinforced the importance to understand and characterize AM processes for sustainability. Process characterization for sustainability will help close the gaps for comparing AM performance to traditional manufacturing methods. Based on a literature review, this paper first examines the potential environmental impacts of AM. A methodology for sustainability characterization of AM is then proposed to serve as a resource for the community to benchmark AM processes for sustainability. Next, research perspectives are discussed along with relevant standardization efforts. PMID:26601038

  11. Additive attacks on speaker recognition

    NASA Astrophysics Data System (ADS)

    Farrokh Baroughi, Alireza; Craver, Scott

    2014-02-01

    Speaker recognition is used to identify a speaker's voice from among a group of known speakers. A common method of speaker recognition is a classification based on cepstral coefficients of the speaker's voice, using a Gaussian mixture model (GMM) to model each speaker. In this paper we try to fool a speaker recognition system using additive noise such that an intruder is recognized as a target user. Our attack uses a mixture selected from a target user's GMM model, inverting the cepstral transformation to produce noise samples. In our 5 speaker data base, we achieve an attack success rate of 50% with a noise signal at 10dB SNR, and 95% by increasing noise power to 0dB SNR. The importance of this attack is its simplicity and flexibility: it can be employed in real time with no processing of an attacker's voice, and little computation is needed at the moment of detection, allowing the attack to be performed by a small portable device. For any target user, knowing that user's model or voice sample is sufficient to compute the attack signal, and it is enough that the intruder plays it while he/she is uttering to be classiffed as the victim.

  12. Femtosecond tunable light source

    NASA Astrophysics Data System (ADS)

    Miesak, Edward Jozef

    1999-09-01

    A practical source of continuously tunable coherent visible and infrared light would have an enormous impact on science, medicine and technology. While microwave and radio transmitters offer wide tunability at the ``turn of a knob,'' the best known source of coherent optical radiation, the laser, does not possess the same versatility. Dye lasers provide some degree of tunability, but many dyes are needed to cover even the visible region. Ti:sapphire lasers are tunable only over the red to near infra-red portion of the spectrum (about 65 0 nm to about 1.1μm). This presentation documents the development of a unique pulsed light source tunable across the visible and near infrared portion of the spectrum, a femtosecond optical parametric amplifier (OPA). Much work was expended in developing the system itself. But a great deal of work was also done in developing the support equipment (hardware and software) necessary to build as well as maintain and operate an OPA. Once completed, the system characteristics were measured and documented. Initially it possessed ``personality'' which had to be understood and removed as much as possible. In addition, the pump source for this OPA, a regenerative amplifier, is unique in that it uses Cr3+:LiSGaF as the gain medium. This regen was also characterized and compared to other more standard regenerative amplifiers. System verification was done by performing a standard experiment (Z-scan) on well known samples, several of which are well characterized at specific wavelengths (1.06 μm, 0.523 μm) in the nanosecond and picosecond regimes. The results were compared against previously published results. The OPA was also compared against another very similar system which became commercially available during the time of this research. The results were helpful in analyzing the light source(s) and data acquisition systems for areas that could be improved.

  13. Radiation source

    DOEpatents

    Thode, Lester E.

    1981-01-01

    A device and method for relativistic electron beam heating of a high-density plasma in a small localized region. A relativistic electron beam generator or accelerator produces a high-voltage electron beam which propagates along a vacuum drift tube and is modulated to initiate electron bunching within the beam. The beam is then directed through a low-density gas chamber which provides isolation between the vacuum modulator and the relativistic electron beam target. The relativistic beam is then applied to a high-density target plasma which typically comprises DT, DD, or similar thermonuclear gas at a density of 10.sup.17 to 10.sup.20 electrons per cubic centimeter. The target gas is ionized prior to application of the relativistic electron beam by means of a laser or other preionization source to form a plasma. Utilizing a relativistic electron beam with an individual particle energy exceeding 3 MeV, classical scattering by relativistic electrons passing through isolation foils is negligible. As a result, relativistic streaming instabilities are initiated within the high-density target plasma causing the relativistic electron beam to efficiently deposit its energy into a small localized region of the high-density plasma target.

  14. Changes in soil test phosphorus from broiler litter additions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Nutrient surpluses on the Delmarva Peninsula have lead to a continual accumulation of soil test P (STP), a potential source for transport of P to surface waters. This paper examines the effects of initial soil test P concentrations and broiler litter additions on STP accumulation. Broiler litter wa...

  15. 48 CFR 819.202-71 - Additional contracting officer responsibilities.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... OF VETERANS AFFAIRS SOCIOECONOMIC PROGRAMS SMALL BUSINESS PROGRAMS Policies 819.202-71 Additional..., contracting officers must perform the following functions in support of the small business program: (a) Make maximum use of small business source lists. (b) Assure that small business firms are identified...

  16. Benefits of additives application during combustion of phytomass

    NASA Astrophysics Data System (ADS)

    Palacka, Matej; Vician, Peter; Holubčík, Michal; Jandačka, Jozef

    2016-06-01

    Phytomass, particularly wheat straw as a source of energy has countless benefits, but it has many problems in its direct burn too. The worst problem is the ash flow temperature. The aim of study was to analyze and reduce the problems of the wheat straw combustion. The experiment was conducted under realistic conditions. In this paper was implemented analysis of ash features with and without adding additives into the wheat straw. Selected samples were laboratory processed and examined. The result of the work was the impact of additional additives for ash features.

  17. Improving electrochemical properties of porous iron substituted lithium manganese phosphate in additive addition electrolyte

    NASA Astrophysics Data System (ADS)

    Kim, Jae-Kwang; Vijaya, Rani; Zhu, Likun; Kim, Youngsik

    2015-02-01

    Porous LiMn0.6Fe0.4PO4 (LMFP) is synthesized by a modified sol-gel process. Highly conductive LMFP due to uniform dispersion of carbon throughout LMFP particles are achieved by the addition of sucrose as an additional carbon source. The LMFP obtained has a high specific surface area with a uniform, porous, and web-like nano-sized carbon layer on the surface. The initial discharge capacity and energy density of the LMFP cathode is 152 mAh g-1 and 570 Wh kg-1, respectively, at 0.1C current rate. The combined effect of high porosity and high electrical conductivity lead to fast lithium ion diffusion and enhance initial capacity compared to materials prepared by the general sol-gel method. However, with conventional electrolyte (1M LiPF6 in EC/DMC) poor cycle performance is observed due to HF attack. To improve the cycle stability we add tris (trimethylsily) phosphite (TMSP) as an additive in the electrolyte which dramatically improves cycle stability and rate-capability.

  18. Sources of tritium

    SciTech Connect

    Phillips, J.E.; Easterly, C.E.

    1980-12-01

    A review of tritium sources is presented. The tritium production and release rates are discussed for light water reactors (LWRs), heavy water reactors (HWRs), high temperature gas cooled reactors (HTGRs), liquid metal fast breeder reactors (LMFBRs), and molten salt breeder reactors (MSBRs). In addition, release rates are discussed for tritium production facilities, fuel reprocessing plants, weapons detonations, and fusion reactors. A discussion of the chemical form of the release is included. The energy producing facilities are ranked in order of increasing tritium production and release. The ranking is: HTGRs, LWRs, LMFBRs, MSBRs, and HWRs. The majority of tritium has been released in the form of tritiated water.

  19. Exposure to chemical additives from polyvinyl chloride polymer extrusion processing

    SciTech Connect

    Lamb, C.S.

    1989-12-01

    The report presents a model to predict worker inhalation exposure due to off-gassing of additives during polyvinyl chloride (PVC) extrusion processing. Data on off-gassing of additives were reviewed in the literature, the off-gassing at normal PVC processing temperatures was studied in the laboratory, process variables were estimated from an equipment manufacturer survey, and worker-activities and possible exposure sources were observed in an industrial survey. The purpose of the study was to develop a theoretical model to predict worker inhalation exposure to additives used during PVC extrusion processing. A model to estimate the generation rate of the additive from the polymer extrudate was derived from the mass transport equations governing diffusion. The mass flow rate, initial additive volatile weight fraction, off-gassing time, diffusivity, and slab thickness are required to determine the generation rate from the model.

  20. ORNL ECR multicharged ion source

    SciTech Connect

    Meyer, F.W.

    1984-01-01

    A multicharged ion source based on Electron Cyclotron Resonance (ECR) heating has been designed and built at ORNL. The ECR ion source, which is completely dedicated for atomic physics collision studies, produces higher charge states and higher beam intensities than the present ORNL PIG multicharged ion source, and will thus permit study of collision processes involving ions of higher charge states in experiments requiring higher beam intensities than could be previously obtained in our laboratory. The source has already produced up to fully stripped C and O beams, as well as up to He-like Ar beams. Measurements of the energy spread of ions extracted from the ion source operating in both single-stage and two-stage mode are described. In addition, initial results of total cross section measurements for fully stripped light ions incident on atomic hydrogen in the energy range 0.2 to 10 keV are presented. 13 references, 7 figures, 1 table.

  1. 16 CFR 1102.16 - Additional information.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... PUBLICLY AVAILABLE CONSUMER PRODUCT SAFETY INFORMATION DATABASE Content Requirements § 1102.16 Additional... in the Database any additional information it determines to be in the public interest,...

  2. 16 CFR 1102.16 - Additional information.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... PUBLICLY AVAILABLE CONSUMER PRODUCT SAFETY INFORMATION DATABASE Content Requirements § 1102.16 Additional... in the Database any additional information it determines to be in the public interest,...

  3. 16 CFR 1102.16 - Additional information.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... PUBLICLY AVAILABLE CONSUMER PRODUCT SAFETY INFORMATION DATABASE Content Requirements § 1102.16 Additional... in the Database any additional information it determines to be in the public interest,...

  4. 40 CFR 79.31 - Additives.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... OF FUELS AND FUEL ADDITIVES Designation of Fuels and Additives § 79.31 Additives. (a) All additives produced or sold for use in motor vehicle gasoline and/or motor vehicle diesel fuel are hereby designated... persons or property on a street or highway. For purposes of this registration, however,...

  5. 40 CFR 79.31 - Additives.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... OF FUELS AND FUEL ADDITIVES Designation of Fuels and Additives § 79.31 Additives. (a) All additives produced or sold for use in motor vehicle gasoline and/or motor vehicle diesel fuel are hereby designated... persons or property on a street or highway. For purposes of this registration, however,...

  6. 40 CFR 79.31 - Additives.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... OF FUELS AND FUEL ADDITIVES Designation of Fuels and Additives § 79.31 Additives. (a) All additives produced or sold for use in motor vehicle gasoline and/or motor vehicle diesel fuel are hereby designated... persons or property on a street or highway. For purposes of this registration, however,...

  7. 40 CFR 79.31 - Additives.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... OF FUELS AND FUEL ADDITIVES Designation of Fuels and Additives § 79.31 Additives. (a) All additives produced or sold for use in motor vehicle gasoline and/or motor vehicle diesel fuel are hereby designated... persons or property on a street or highway. For purposes of this registration, however,...

  8. 40 CFR 79.31 - Additives.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... OF FUELS AND FUEL ADDITIVES Designation of Fuels and Additives § 79.31 Additives. (a) All additives produced or sold for use in motor vehicle gasoline and/or motor vehicle diesel fuel are hereby designated... persons or property on a street or highway. For purposes of this registration, however,...

  9. ReviewsGCSE Book Review: Modular Science for AQA GCSE Book Review: Modular Science for Edexcel GCSE Book Review: Revise for GCSE Science (Edexcel Modular Foundation and Higher) GCSE Book Review: AQA GCSE Physics, AQA GCSE Physics Additions Book Review: Studying Maths and its Applications Book Review: Medical Physics, 2nd edition Book Review: The Physics of Hockey Book Review: Nine Crazy Ideas In Science Book Review: Light and Dark Talking Point: The Skeptical Environmentalist Places To Visit: Centre for Alternative Technology, Machynlleth, Powys Resources: Sources of Energy Web Watch: Terence, this is stupid stuff...

    NASA Astrophysics Data System (ADS)

    2003-03-01

    GCSE BOOK REVIEWS (162) Modular Science for AQA Modular Science for Edexcel Revise for GCSE Science (Edexcel Modular Foundation and Higher) AQA GCSE Physics, AQA GCSE Physics Additions BOOK REVIEWS (166) Studying Maths and its Applications Medical Physics, 2nd edition The Physics of Hockey Nine Crazy Ideas In Science Light and Dark TALKING POINT (169) The Skeptical Environmentalist PLACES TO VISIT (170) Centre for Alternative Technology, Machynlleth, Powys RESOURCES (172) Sources of Energy WEB WATCH (173) Terence, this is stupid stuff...

  10. Metal Additive Manufacturing: A Review of Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Lewandowski, John J.; Seifi, Mohsen

    2016-07-01

    This article reviews published data on the mechanical properties of additively manufactured metallic materials. The additive manufacturing techniques utilized to generate samples covered in this review include powder bed fusion (e.g., EBM, SLM, DMLS) and directed energy deposition (e.g., LENS, EBF3). Although only a limited number of metallic alloy systems are currently available for additive manufacturing (e.g., Ti-6Al-4V, TiAl, stainless steel, Inconel 625/718, and Al-Si-10Mg), the bulk of the published mechanical properties information has been generated on Ti-6Al-4V. However, summary tables for published mechanical properties and/or key figures are included for each of the alloys listed above, grouped by the additive technique used to generate the data. Published values for mechanical properties obtained from hardness, tension/compression, fracture toughness, fatigue crack growth, and high cycle fatigue are included for as-built, heat-treated, and/or HIP conditions, when available. The effects of test orientation/build direction on properties, when available, are also provided, along with discussion of the potential source(s) (e.g., texture, microstructure changes, defects) of anisotropy in properties. Recommendations for additional work are also provided.

  11. Decision-Making, Science and Gasoline Additives

    NASA Astrophysics Data System (ADS)

    Weaver, J. W.; Small, M. C.

    2001-12-01

    Methyl-tert butyl ether (MTBE) has been used as a gasoline additive to serve two major purposes. The first use was as an octane-enhancer to replace organic lead, beginning in 1979. The second use, which began about 1992, was as a oxygenated additive to meet requirements of the Clean Air Act Amendments (CAAA) of 1990. Generally, the amount of MTBE used for octane enhancement was lower than that required to meet CAAA requirements. An unintended consequence of MTBE use has been widespread groundwater contamination. The decision to use certain amounts of MTBE or other chemcials as gasoline additives is the outcome of economic, regulatory, policy, political, and scientific considerations. Decision makers ask questions such as "How do ground water impacts change with changing MTBE content? How many wells would be impacted? and What are the associated costs?" These are best answered through scientific inquiry, but many different approaches could be developed. Decision criteria include time, money, comprehensiveness, and complexity of the approach. Because results must be communicated to a non-technical audience, there is a trade off between the complexity of the approach and the ability to convince economists, lawyers and policy makers that results make sense. The question on MTBE content posed above was investigated using transport models, a release scenario and gasoline composition. Because of the inability of transport models to predict future concentrations, an approach was chosen to base comparative assessment on a calibrated model. By taking this approach, "generic" modeling with arbitrarily selected parameters was avoided and the validity of the simulation results rests upon relatively small extrapolations from the original calibrated models. A set of simulations was performed that assumed 3% (octane enhancement) and 11% (CAAA) MTBE in gasoline. The results were that ground water concentrations would be reduced in proportion to the reduction of MTBE in the fuel

  12. Additive Manufacturing of Aerospace Propulsion Components

    NASA Technical Reports Server (NTRS)

    Misra, Ajay K.; Grady, Joseph E.; Carter, Robert

    2015-01-01

    The presentation will provide an overview of ongoing activities on additive manufacturing of aerospace propulsion components, which included rocket propulsion and gas turbine engines. Future opportunities on additive manufacturing of hybrid electric propulsion components will be discussed.

  13. Compatibility of lubricant additives with HFC refrigerants and synthetic lubricants. Final report, Part 1

    SciTech Connect

    Cavestri, R.C.

    1997-07-01

    Part one of this research provides manufacturers of components of air-conditioning and refrigeration equipment with a useful list of lubricant additives, sources, functional properties and chemical species. The list in part one is comprised of domestic lubricant additive suppliers and the results of a literature search that was specifically targeted for additives reported to be useful in polyolester chemistry.

  14. Diversity employment and recruitment sources

    SciTech Connect

    Not Available

    1994-08-01

    Effective human resources management has been identified as one of four critical success factors in the Department of Energy Strategic Plan. The Plan states relative to this factor: ``The Department seeks greater alignment of resources with agency priorities and increased diversification of the workforce, including gender, ethnicity, age, and skills. This diversification will bring new thinking and perspectives that heretofore have not had a voice in departmental decision-making.`` This Guide has been developed as a key tool to assist Department of Energy management and administrative staff in achieving Goal 2 of this critical success factor, which is to ``Ensure a diverse and talented workforce.`` There are numerous sources from which to recruit minorities, women and persons with disabilities. Applying creativity and proactive effort, using traditional and non-traditional approaches, and reaching out to various professional, academic and social communities will increase the reservoir of qualified candidates from which to make selections. In addition, outreach initiatives will undoubtedly yield further benefits such as a richer cultural understanding and diversity awareness. The resource listings presented in this Guide are offered to encourage active participation in the diversity recruitment process. This Guide contains resource listings by state for organizations in the following categories: (1) African American Recruitment Sources; (2) Asian American/Pacific Islander Recruitment Sources; (3) Hispanic Recruitment Sources; (4) Native American/Alaskan Native Recruitment Sources; (5) Persons with Disabilities Recruitment Sources; and (6) Women Recruitment Sources.

  15. 47 CFR 25.111 - Additional information.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 2 2011-10-01 2011-10-01 false Additional information. 25.111 Section 25.111... Applications and Licenses General Application Filing Requirements § 25.111 Additional information. (a) The Commission may request from any party at any time additional information concerning any application, or...

  16. 20 CFR 901.72 - Additional rules.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 20 Employees' Benefits 3 2011-04-01 2011-04-01 false Additional rules. 901.72 Section 901.72... Additional rules. The Joint Board may, in notice or other guidance of general applicability, provide additional rules regarding the enrollment of actuaries. Effective Date Note: At 76 FR 17776, Mar. 31,...

  17. 17 CFR 48.10 - Additional contracts.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 17 Commodity and Securities Exchanges 1 2013-04-01 2013-04-01 false Additional contracts. 48.10... FOREIGN BOARDS OF TRADE § 48.10 Additional contracts. (a) Generally. A registered foreign board of trade that wishes to make an additional futures, option or swap contract available for trading by...

  18. 17 CFR 48.10 - Additional contracts.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 17 Commodity and Securities Exchanges 2 2014-04-01 2014-04-01 false Additional contracts. 48.10...) REGISTRATION OF FOREIGN BOARDS OF TRADE § 48.10 Additional contracts. (a) Generally. A registered foreign board of trade that wishes to make an additional futures, option or swap contract available for trading...

  19. 46 CFR 355.5 - Additional material.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 8 2011-10-01 2011-10-01 false Additional material. 355.5 Section 355.5 Shipping... STATES CITIZENSHIP § 355.5 Additional material. If additional material is determined to be essential to clarify or support the evidence of U.S. citizenship, such material shall be furnished by...

  20. 20 CFR 802.215 - Additional briefs.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 20 Employees' Benefits 3 2011-04-01 2011-04-01 false Additional briefs. 802.215 Section 802.215 Employees' Benefits BENEFITS REVIEW BOARD, DEPARTMENT OF LABOR RULES OF PRACTICE AND PROCEDURE Prereview Procedures Initial Processing § 802.215 Additional briefs. Additional briefs may be filed or ordered in...

  1. 77 FR 49783 - Procurement List; Additions

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-08-17

    ... INFORMATION: Additions On 6/15/2012 (77 FR 35942-35944) and 6/22/2012 (77 FR 37659-37660), the Committee for... PEOPLE WHO ARE BLIND OR SEVERELY DISABLED Procurement List; Additions AGENCY: Committee for Purchase From People Who Are Blind or Severely Disabled. ACTION: Additions to the Procurement List. SUMMARY:...

  2. 7 CFR 1944.545 - Additional grants.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 13 2011-01-01 2009-01-01 true Additional grants. 1944.545 Section 1944.545...) PROGRAM REGULATIONS (CONTINUED) HOUSING Technical and Supervisory Assistance Grants § 1944.545 Additional grants. An additional grant may be made to an applicant that has previously received a TSA grant and...

  3. 20 CFR 802.215 - Additional briefs.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 20 Employees' Benefits 3 2010-04-01 2010-04-01 false Additional briefs. 802.215 Section 802.215 Employees' Benefits BENEFITS REVIEW BOARD, DEPARTMENT OF LABOR RULES OF PRACTICE AND PROCEDURE Prereview Procedures Initial Processing § 802.215 Additional briefs. Additional briefs may be filed or ordered in...

  4. 14 CFR 27.927 - Additional tests.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... STANDARDS: NORMAL CATEGORY ROTORCRAFT Powerplant Rotor Drive System § 27.927 Additional tests. (a) Any additional dynamic, endurance, and operational tests, and vibratory investigations necessary to determine... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Additional tests. 27.927 Section...

  5. 78 FR 9386 - Procurement List; Addition

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-02-08

    ... INFORMATION: Addition On 11/30/2012 (77 FR 71400-71401), the Committee for Purchase From People Who Are Blind... PEOPLE WHO ARE BLIND OR SEVERELY DISABLED Procurement List; Addition AGENCY: Committee for Purchase From People Who Are Blind or Severely Disabled. ACTION: Addition to the Procurement List. SUMMARY: This...

  6. 78 FR 45183 - Procurement List Additions

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-07-26

    ... INFORMATION: Additions On 5/31/2013 (78 FR 32631-32632); 6/7/2013 (78 FR 34350-34351); and 6/14/2013 (78 FR... PEOPLE WHO ARE BLIND OR SEVERELY DISABLED Procurement List Additions AGENCY: Committee for Purchase From People Who Are Blind or Severely Disabled. ACTION: Additions to the Procurement List. SUMMARY:...

  7. 34 CFR 75.231 - Additional information.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 34 Education 1 2012-07-01 2012-07-01 false Additional information. 75.231 Section 75.231 Education... Make A Grant § 75.231 Additional information. After selecting an application for funding, the Secretary may require the applicant to submit additional information. (Authority: 20 U.S.C. 1221e-3 and 3474)...

  8. 10 CFR 810.14 - Additional information.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 10 Energy 4 2012-01-01 2012-01-01 false Additional information. 810.14 Section 810.14 Energy DEPARTMENT OF ENERGY ASSISTANCE TO FOREIGN ATOMIC ENERGY ACTIVITIES § 810.14 Additional information. The... activity to submit additional information....

  9. 10 CFR 725.13 - Additional information.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 10 Energy 4 2011-01-01 2011-01-01 false Additional information. 725.13 Section 725.13 Energy DEPARTMENT OF ENERGY PERMITS FOR ACCESS TO RESTRICTED DATA Applications § 725.13 Additional information. The... and before the termination of the permit, require additional information in order to enable the...

  10. 10 CFR 725.13 - Additional information.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 10 Energy 4 2012-01-01 2012-01-01 false Additional information. 725.13 Section 725.13 Energy DEPARTMENT OF ENERGY PERMITS FOR ACCESS TO RESTRICTED DATA Applications § 725.13 Additional information. The... and before the termination of the permit, require additional information in order to enable the...

  11. 46 CFR 355.5 - Additional material.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 8 2014-10-01 2014-10-01 false Additional material. 355.5 Section 355.5 Shipping... STATES CITIZENSHIP § 355.5 Additional material. If additional material is determined to be essential to clarify or support the evidence of U.S. citizenship, such material shall be furnished by...

  12. 46 CFR 355.5 - Additional material.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 8 2013-10-01 2013-10-01 false Additional material. 355.5 Section 355.5 Shipping... STATES CITIZENSHIP § 355.5 Additional material. If additional material is determined to be essential to clarify or support the evidence of U.S. citizenship, such material shall be furnished by...

  13. 12 CFR 1249.19 - Additional provisions.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 12 Banks and Banking 7 2011-01-01 2011-01-01 false Additional provisions. 1249.19 Section 1249.19 Banks and Banking FEDERAL HOUSING FINANCE AGENCY ENTERPRISES BOOK-ENTRY PROCEDURES § 1249.19 Additional provisions. (a) Additional requirements. In any case or any class of cases arising under this part, an Enterprise may require such...

  14. 75 FR 33269 - Procurement List; Additions

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-06-11

    ... . SUPPLEMENTARY INFORMATION: Additions On 4/9/2010 (75 FR 18164-18165), the Committee for Purchase From People Who... PEOPLE WHO ARE BLIND OR SEVERELY DISABLED Procurement List; Additions AGENCY: Committee for Purchase From People Who Are Blind or Severely Disabled. ACTION: Additions to the Procurement List. SUMMARY:...

  15. Polymeric Additives For Graphite/Epoxy Composites

    NASA Technical Reports Server (NTRS)

    Kourtides, D. A.; Nir, Z.

    1990-01-01

    Report describes experimental studies of properties of several graphite/epoxy composites containing polymeric additives as flexibilizing or toughening agents. Emphasizes effects of brominated polymeric additives (BPA's) with or without carboxy-terminated butadiene acrylonitrile rubber. Reviews effects of individual and combined additives on fracture toughnesses, environmental stabilities, hot/wet strengths, thermomechanical behaviors, and other mechanical properties of composites.

  16. 14 CFR 27.927 - Additional tests.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Additional tests. 27.927 Section 27.927... STANDARDS: NORMAL CATEGORY ROTORCRAFT Powerplant Rotor Drive System § 27.927 Additional tests. (a) Any additional dynamic, endurance, and operational tests, and vibratory investigations necessary to...

  17. 14 CFR 29.927 - Additional tests.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Additional tests. 29.927 Section 29.927... STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Powerplant Rotor Drive System § 29.927 Additional tests. (a) Any additional dynamic, endurance, and operational tests, and vibratory investigations necessary to...

  18. 7 CFR 1944.545 - Additional grants.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 13 2013-01-01 2013-01-01 false Additional grants. 1944.545 Section 1944.545...) PROGRAM REGULATIONS (CONTINUED) HOUSING Technical and Supervisory Assistance Grants § 1944.545 Additional grants. An additional grant may be made to an applicant that has previously received a TSA grant and...

  19. 76 FR 18189 - Procurement List; Additions

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-04-01

    ... INFORMATION: Additions On 1/28/2011 (76 FR 5142-5143), the Committee for Purchase From People Who Are Blind or... PEOPLE WHO ARE BLIND OR SEVERELY DISABLED Procurement List; Additions AGENCY: Committee for Purchase From People Who Are Blind or Severely Disabled. ACTION: Additions to the Procurement List. SUMMARY:...

  20. 75 FR 4784 - Procurement List; Addition

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-29

    ... INFORMATION: Addition On 11/16/2009 (74 FR 58949-58950), the Committee for Purchase From People Who Are Blind... PEOPLE WHO ARE BLIND OR SEVERELY DISABLED Procurement List; Addition AGENCY: Committee for Purchase From People Who Are Blind or Severely Disabled. ACTION: Addition to the Procurement List. SUMMARY: This...

  1. 75 FR 54114 - Procurement List Additions

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-09-03

    ... . SUPPLEMENTARY INFORMATION: Additions On 7/2/2010 (75 FR 38467-38468) and 7/9/2010 (75 FR 39497-39499), the... PEOPLE WHO ARE BLIND OR SEVERELY DISABLED Procurement List Additions AGENCY: Committee for Purchase From People Who Are Blind or Severely Disabled. ACTION: Additions to the Procurement List. SUMMARY:...

  2. 77 FR 53180 - Procurement List; Additions

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-08-31

    ... INFORMATION: Additions On 6/15/2012 (77 FR 35942-35944) and 6/29/2012 (77 FR 38775-38776), the Committee for... PEOPLE WHO ARE BLIND OR SEVERELY DISABLED Procurement List; Additions AGENCY: Committee for Purchase from People who are Blind or Severely Disabled. ACTION: Additions to the Procurement List. SUMMARY:...

  3. 76 FR 19751 - Procurement List; Addition

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-04-08

    ... INFORMATION: Addition On 1/28/2011 (76 FR 5142-5143), the Committee for Purchase From People Who Are Blind or... PEOPLE WHO ARE BLIND OR SEVERELY DISABLED Procurement List; Addition AGENCY: Committee for Purchase From People Who Are Blind or Severely Disabled. ACTION: Addition to the Procurement List. SUMMARY: This...

  4. 17 CFR 48.10 - Additional contracts.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 17 Commodity and Securities Exchanges 1 2012-04-01 2012-04-01 false Additional contracts. 48.10... FOREIGN BOARDS OF TRADE § 48.10 Additional contracts. (a) Generally. A registered foreign board of trade that wishes to make an additional futures, option or swap contract available for trading by...

  5. 10 CFR 55.7 - Additional requirements.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 10 Energy 2 2012-01-01 2012-01-01 false Additional requirements. 55.7 Section 55.7 Energy NUCLEAR REGULATORY COMMISSION (CONTINUED) OPERATORS' LICENSES General Provisions § 55.7 Additional requirements. The Commission may, by rule, regulation, or order, impose upon any licensee such requirements, in addition to those established in...

  6. 14 CFR 29.927 - Additional tests.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Additional tests. 29.927 Section 29.927... STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Powerplant Rotor Drive System § 29.927 Additional tests. (a) Any additional dynamic, endurance, and operational tests, and vibratory investigations necessary to...

  7. 14 CFR 27.927 - Additional tests.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Additional tests. 27.927 Section 27.927... STANDARDS: NORMAL CATEGORY ROTORCRAFT Powerplant Rotor Drive System § 27.927 Additional tests. (a) Any additional dynamic, endurance, and operational tests, and vibratory investigations necessary to...

  8. 14 CFR 27.927 - Additional tests.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Additional tests. 27.927 Section 27.927... STANDARDS: NORMAL CATEGORY ROTORCRAFT Powerplant Rotor Drive System § 27.927 Additional tests. (a) Any additional dynamic, endurance, and operational tests, and vibratory investigations necessary to...

  9. 14 CFR 29.927 - Additional tests.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Additional tests. 29.927 Section 29.927... STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Powerplant Rotor Drive System § 29.927 Additional tests. (a) Any additional dynamic, endurance, and operational tests, and vibratory investigations necessary to...

  10. 46 CFR 355.5 - Additional material.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 8 2012-10-01 2012-10-01 false Additional material. 355.5 Section 355.5 Shipping... STATES CITIZENSHIP § 355.5 Additional material. If additional material is determined to be essential to clarify or support the evidence of U.S. citizenship, such material shall be furnished by...

  11. 28 CFR 80.16 - Additional requests.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 28 Judicial Administration 2 2012-07-01 2012-07-01 false Additional requests. 80.16 Section 80.16 Judicial Administration DEPARTMENT OF JUSTICE (CONTINUED) FOREIGN CORRUPT PRACTICES ACT OPINION PROCEDURE § 80.16 Additional requests. Additional requests for FCPA Opinions may be filed with the...

  12. 28 CFR 80.16 - Additional requests.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 28 Judicial Administration 2 2013-07-01 2013-07-01 false Additional requests. 80.16 Section 80.16 Judicial Administration DEPARTMENT OF JUSTICE (CONTINUED) FOREIGN CORRUPT PRACTICES ACT OPINION PROCEDURE § 80.16 Additional requests. Additional requests for FCPA Opinions may be filed with the...

  13. 77 FR 17034 - Procurement List; Addition

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-23

    ... INFORMATION: Addition On 1/13/2012 (77 FR 2048), the Committee for Purchase From People Who Are Blind or... PEOPLE WHO ARE BLIND OR SEVERELY DISABLED Procurement List; Addition AGENCY: Committee for Purchase From People Who Are Blind or Severely Disabled. ACTION: Addition to the Procurement List. SUMMARY: This...

  14. 75 FR 39497 - Procurement List; Additions

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-07-09

    ... INFORMATION: Additions On 5/14/2010 (75 FR 27313), the Committee for Purchase From People Who Are Blind or... PEOPLE WHO ARE BLIND OR SEVERELY DISABLED Procurement List; Additions AGENCY: Committee for Purchase From People Who Are Blind or Severely Disabled. ACTION: Additions to the Procurement List. SUMMARY:...

  15. 78 FR 59658 - Procurement List; Additions

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-09-27

    ... INFORMATION: Additions On 7/26/2013 (78 FR 45183); 8/9/2013 (78 FR 48656-48657) and 8/16/ 2013 (78 FR 50040... PEOPLE WHO ARE BLIND OR SEVERELY DISABLED Procurement List; Additions AGENCY: Committee for Purchase From People Who Are Blind or Severely Disabled. ACTION: Additions to the Procurement List. SUMMARY:...

  16. 77 FR 12816 - Procurement List; Additions

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-02

    ... INFORMATION: Additions On 6/24/2011 (76 FR 37069-37070) and 1/6/2012 (77 FR 780), the Committee for Purchase... PEOPLE WHO ARE BLIND OR SEVERELY DISABLED Procurement List; Additions AGENCY: Committee for Purchase From People Who Are Blind or Severely Disabled. ACTION: Additions to the Procurement List. SUMMARY:...

  17. 76 FR 80345 - Procurement List; Additions

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-12-23

    ... INFORMATION: Additions On 10/14/2011 (76 FR 63905-63906) and 10/28/2011 (76 FR 66913- 66914), the Committee... PEOPLE WHO ARE BLIND OR SEVERELY DISABLED Procurement List; Additions AGENCY: Committee for Purchase From People Who Are Blind or Severely Disabled. ACTION: Additions to the Procurement List. SUMMARY:...

  18. 75 FR 21246 - Procurement List; Addition

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-23

    ... INFORMATION: Addition On 2/26/2010 (75 FR 8927), the Committee for Purchase From People Who Are Blind or... PEOPLE WHO ARE BLIND OR SEVERELY DISABLED Procurement List; Addition AGENCY: Committee for Purchase From People Who Are Blind or Severely Disabled. ACTION: Addition to the Procurement List. SUMMARY: This...

  19. 75 FR 43152 - Procurement List Additions

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-07-23

    ... . SUPPLEMENTARY INFORMATION: Additions On 5/28/2010 (75 FR 29994-29995) and 6/4/2010 (75 FR 31768-31769), the... PEOPLE WHO ARE BLIND OR SEVERELY DISABLED Procurement List Additions AGENCY: Committee for Purchase From People Who Are Blind or Severely Disabled. ACTION: Additions to the Procurement List. SUMMARY:...

  20. 75 FR 29995 - Procurement List Addition

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-05-28

    ... INFORMATION: Addition On 12/18/2009 (74 FR 67176-67177), the Committee for Purchase From People Who Are Blind... PEOPLE WHO ARE BLIND OR SEVERELY DISABLED Procurement List Addition AGENCY: Committee for Purchase From People Who Are Blind or Severely Disabled. ACTION: Addition to the Procurement List. SUMMARY: This...

  1. 78 FR 4133 - Procurement List; Addition

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-01-18

    ... . SUPPLEMENTARY INFORMATION: Addition On 11/9/2012 (77 FR 67343-67344), the Committee for Purchase From People Who... FROM PEOPLE WHO ARE BLIND OR SEVERELY DISABLED Procurement List; Addition AGENCY: Committee for Purchase From People Who Are Blind or Severely Disabled. ACTION: Addition to the Procurement List....

  2. 76 FR 23997 - Procurement List; Addition

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-04-29

    ... INFORMATION: Addition On 2/25/2011 (76 FR 10571), the Committee for Purchase From People Who Are Blind or... PEOPLE WHO ARE BLIND OR SEVERELY DISABLED Procurement List; Addition AGENCY: Committee for Purchase From People Who Are Blind or Severely Disabled. ACTION: Addition to the Procurement List. SUMMARY: This...

  3. 77 FR 59595 - Procurement List; Additions

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-09-28

    ... . SUPPLEMENTARY INFORMATION: Additions On 7/9/2012 (77 FR 40344-40345) and 7/20/2012 (77 FR 42701-42702), the... PEOPLE WHO ARE BLIND OR SEVERELY DISABLED Procurement List; Additions AGENCY: Committee for Purchase From People Who Are Blind or Severely Disabled. ACTION: Additions to the Procurement List. SUMMARY:...

  4. 76 FR 35415 - Procurement List; Addition

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-06-17

    ... INFORMATION: Additions On 4/29/2011 (76 FR 23998), the Committee for Purchase From People Who Are Blind or... PEOPLE WHO ARE BLIND OR SEVERELY DISABLED Procurement List; Addition AGENCY: Committee for Purchase From People Who Are Blind or Severely Disabled. ACTION: Addition to the Procurement List. SUMMARY: This...

  5. 78 FR 2378 - Procurement List, Addition

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-01-11

    ... INFORMATION: Addition On 11/9/2012 (77 FR 67343-67344), the Committee for Purchase From People Who Are Blind... PEOPLE WHO ARE BLIND OR SEVERELY DISABLED Procurement List, Addition AGENCY: Committee for Purchase From People Who Are Blind or Severely Disabled. ACTION: Addition to the Procurement List. SUMMARY: This...

  6. 75 FR 72815 - Procurement List Additions

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-26

    ... INFORMATION: Additions On 6/4/2010 (75 FR 31768-31769) and 10/1/2010 (75 FR 60739-60740), the Committee for... PEOPLE WHO ARE BLIND OR SEVERELY DISABLED Procurement List Additions AGENCY: Committee for Purchase From People Who Are Blind or Severely Disabled. ACTION: Additions to the Procurement List. SUMMARY:...

  7. 78 FR 16476 - Procurement List Additions

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-15

    ...: Additions On 1/18/2013 (78 FR 4133-4134), the Committee for Purchase From People Who Are Blind or Severely... PEOPLE WHO ARE BLIND OR SEVERELY DISABLED Procurement List Additions AGENCY: Committee for Purchase From People Who Are Blind or Severely Disabled. ACTION: Additions to the Procurement List. SUMMARY:...

  8. 75 FR 70908 - Procurement List; Addition

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-19

    ... INFORMATION: Addition On 9/24/2010 (75 FR 58367), the Committee for Purchase From People Who Are Blind or... PEOPLE WHO ARE BLIND OR SEVERELY DISABLED Procurement List; Addition AGENCY: Committee for Purchase From People Who Are Blind or Severely Disabled. ACTION: Addition to the Procurement List. SUMMARY: This...

  9. 75 FR 58366 - Procurement List Additions

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-09-24

    ... INFORMATION: Additions On 6/11/2010 (75 FR 33270-33271) and 7/16/2010 (75 FR 41451), the Committee for... PEOPLE WHO ARE BLIND OR SEVERELY DISABLED Procurement List Additions AGENCY: Committee for Purchase From People Who Are Blind or Severely Disabled. ACTION: Additions to the Procurement List. SUMMARY:...

  10. 75 FR 52723 - Procurement List Addition

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-27

    ... INFORMATION: Addition On 7/9/2010 (75 FR 39497-39499), the Committee for Purchase From People Who Are Blind or... PEOPLE WHO ARE BLIND OR SEVERELY DISABLED Procurement List Addition AGENCY: Committee for Purchase From People Who Are Blind or Severely Disabled. ACTION: Addition to the Procurement List. SUMMARY: This...

  11. 47 CFR 78.65 - Additional orders.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 4 2012-10-01 2012-10-01 false Additional orders. 78.65 Section 78.65... SERVICE General Operating Requirements § 78.65 Additional orders. In case the rules of this part do not... additional orders in each case as may be deemed necessary....

  12. 47 CFR 74.28 - Additional orders.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 4 2012-10-01 2012-10-01 false Additional orders. 74.28 Section 74.28... Services in Part 74 § 74.28 Additional orders. In case the rules contained in this part do not cover all... additional orders in each case as may be deemed necessary....

  13. 27 CFR 19.967 - Additional security.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Additional security. 19..., Equipment and Security § 19.967 Additional security. If the appropriate TTB officer finds that security is... diversion of spirits to unauthorized purposes, additional security measures may be required. Such...

  14. 28 CFR 80.16 - Additional requests.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 28 Judicial Administration 2 2011-07-01 2011-07-01 false Additional requests. 80.16 Section 80.16 Judicial Administration DEPARTMENT OF JUSTICE (CONTINUED) FOREIGN CORRUPT PRACTICES ACT OPINION PROCEDURE § 80.16 Additional requests. Additional requests for FCPA Opinions may be filed with the...

  15. 28 CFR 80.16 - Additional requests.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 28 Judicial Administration 2 2010-07-01 2010-07-01 false Additional requests. 80.16 Section 80.16 Judicial Administration DEPARTMENT OF JUSTICE (CONTINUED) FOREIGN CORRUPT PRACTICES ACT OPINION PROCEDURE § 80.16 Additional requests. Additional requests for FCPA Opinions may be filed with the...

  16. 28 CFR 80.16 - Additional requests.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 28 Judicial Administration 2 2014-07-01 2014-07-01 false Additional requests. 80.16 Section 80.16 Judicial Administration DEPARTMENT OF JUSTICE (CONTINUED) FOREIGN CORRUPT PRACTICES ACT OPINION PROCEDURE § 80.16 Additional requests. Additional requests for FCPA Opinions may be filed with the...

  17. 21 CFR 25.32 - Foods, food additives, and color additives.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Foods, food additives, and color additives. 25.32... ENVIRONMENTAL IMPACT CONSIDERATIONS Categorical Exclusions § 25.32 Foods, food additives, and color additives... of a color additive petition to change a provisionally listed color additive to permanent listing...

  18. Perovskite photonic sources

    NASA Astrophysics Data System (ADS)

    Sutherland, Brandon R.; Sargent, Edward H.

    2016-05-01

    The field of solution-processed semiconductors has made great strides; however, it has yet to enable electrically driven lasers. To achieve this goal, improved materials are required that combine efficient (>50% quantum yield) radiative recombination under high injection, large and balanced charge-carrier mobilities in excess of 10 cm2 V-1 s-1, free-carrier densities greater than 1017 cm-3 and gain coefficients exceeding 104 cm-1. Solid-state perovskites are -- in addition to galvanizing the field of solar electricity -- showing great promise in photonic sources, and may be the answer to realizing solution-cast laser diodes. Here, we discuss the properties of perovskites that benefit light emission, review recent progress in perovskite electroluminescent diodes and optically pumped lasers, and examine the remaining challenges in achieving continuous-wave and electrically driven lasing.

  19. Problems with packaged sources in foreign countries

    SciTech Connect

    Abeyta, Cristy L; Matzke, James L; Zarling, John; Tompkin, J. Andrew

    2010-01-01

    The Global Threat Reduction Initiative's (GTRI) Off-Site Source Recovery Project (OSRP), which is administered by the Los Alamos National Laboratory (LANL), removes excess, unwanted, abandoned, or orphan radioactive sealed sources that pose a potential threat to national security, public health, and safety. In total, GTRI/OSRP has been able to recover more than 25,000 excess and unwanted sealed sources from over 825 sites. In addition to transuranic sources, the GTRI/OSRP mission now includes recovery of beta/gamma emitting sources, which are of concern to both the U.S. government and the International Atomic Energy Agency (IAEA). This paper provides a synopsis of cooperative efforts in foreign countries to remove excess and unwanted sealed sources by discussing three topical areas: (1) The Regional Partnership with the International Atomic Energy Agency; (2) Challenges in repatriating sealed sources; and (3) Options for repatriating sealed sources.

  20. On non-radiating sources

    NASA Astrophysics Data System (ADS)

    Musafir, Ricardo E.

    2013-08-01

    .g., dipoles or quadrupoles?) If discrete sources are considered, how should the source region be decomposed? And how do each source (or source element) relate to the others (i.e., how does phase vary across a non-compact source region)? Sometimes this last issue is fully considered in algorithms, but not always. Of course, it is simpler to consider independent point monopole sources, but this is not necessarily the best option—notably in aeroacoustics, where another issue is also to be considered: Which is the Green's function relating source and field? Again, it is simpler to consider the Green's function for waves in homogeneous medium at rest, i.e., that of Eq. (1), but if the sources are, e.g., in a moving medium, this choice may lead to incorrect results.Independently on the choices made, a solution (i.e., a source distribution) will be found. In general, algorithms will provide equivalent sources where one is looking for them, and of the prescribed type. These sources constitute a solution to a given problem considering the (explicitly or implicitly) specified constraints, but not necessarily the solution to the actual physical problem: this depends on how appropriate are the constraints considered (and also on the algorithm limitations). Examples of algorithms focusing on different aspects are given, e.g., in [9,10,27-35].Also, as noted in Section 2, the existence of eventual boundaries should be incorporated into the problem; otherwise, reflection or absorption will also be treated as additional equivalent sources, which is not a problem only in the case one is expecting this to happen. A simple way to check if a field governed by the d'Alembert equation is active or reactive without computing the intensity or the local impedance is to check the gradients of the field amplitude and phase (which can be done in the frequency domain or in the time domain): a non-zero phase gradient implies in an active part while a non-zero gradient of the absolute value implies in the

  1. Source Identification and Location Techniques

    NASA Technical Reports Server (NTRS)

    Weir, Donald; Bridges, James; Agboola, Femi; Dougherty, Robert

    2001-01-01

    Mr. Weir presented source location results obtained from an engine test as part of the Engine Validation of Noise Reduction Concepts program. Two types of microphone arrays were used in this program to determine the jet noise source distribution for the exhaust from a 4.3 bypass ratio turbofan engine. One was a linear array of 16 microphones located on a 25 ft. sideline and the other was a 103 microphone 3-D "cage" array in the near field of the jet. Data were obtained from a baseline nozzle and from numerous nozzle configuration using chevrons and/or tabs to reduce the jet noise. Mr. Weir presented data from two configurations: the baseline nozzle and a nozzle configuration with chevrons on both the core and bypass nozzles. This chevron configuration had achieved a jet noise reduction of 4 EPNdB in small scale tests conducted at the Glenn Research Center. IR imaging showed that the chevrons produced significant improvements in mixing and greatly reduced the length of the jet potential core. Comparison of source location data from the 1-D phased array showed a shift of the noise sources towards the nozzle and clear reductions of the sources due to the noise reduction devices. Data from the 3-D array showed a single source at a frequency of 125 Hz. located several diameters downstream from the nozzle exit. At 250 and 400 Hz., multiple sources, periodically spaced, appeared to exist downstream of the nozzle. The trend of source location moving toward the nozzle exit with increasing frequency was also observed. The 3-D array data also showed a reduction in source strength with the addition of chevrons. The overall trend of source location with frequency was compared for the two arrays and with classical experience. Similar trends were observed. Although overall trends with frequency and addition of suppression devices were consistent between the data from the 1-D and the 3-D arrays, a comparison of the details of the inferred source locations did show differences. A

  2. Online bibliographic sources in hydrology

    USGS Publications Warehouse

    Wild, Emily C.; Havener, W. Michael

    2001-01-01

    Traditional commercial bibliographic databases and indexes provide some access to hydrology materials produced by the government; however, these sources do not provide comprehensive coverage of relevant hydrologic publications. This paper discusses bibliographic information available from the federal government and state geological surveys, water resources agencies, and depositories. In addition to information in these databases, the paper describes the scope, styles of citing, subject terminology, and the ways these information sources are currently being searched, formally and informally, by hydrologists. Information available from the federal and state agencies and from the state depositories might be missed by limiting searches to commercially distributed databases.

  3. 78 FR 77105 - Procurement List; Proposed Addition

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-12-20

    ... Defense, National Geospatial- Intelligence Agency, Arnold, MO Barry S. Lineback, Director, Business... Geospatial-Intelligence Agency, NGA Campus West, 3200 S 2nd Street, St. Louis, MO NPAs: ServiceSource,...

  4. Creative fund-raising for nursing homes. An additional revenue source in tough economic times.

    PubMed

    March, C; Kleckner, R; Schumer, M F

    1991-12-01

    Nursing home administrators and sponsors should look to fund-raising as a way to increase their facilities' revenues. The board should first appoint a development coordinator and a special board to be responsible for the fund-raising program. The nursing home can reach potential contributors by regularly sending printed material to specially selected persons from its mailing list. The staff must know the procedures to follow when someone wants to make a donation (e.g., to whom the check should be made payable). To generate interest and to motivate contributors, the fund-raising board should identify specific needs for which the contributions will be solicited. A computer program can help keep track of to whom acknowledgements must be sent. Options for a fund-raising program include memorial and honor gifts, gifts in kind, grants and special gifts, special events, deferred gifts, educational programs, and membership clubs. PMID:10115217

  5. The Linguistic Landscape as an Additional Source of Input in Second Language Acquisition

    ERIC Educational Resources Information Center

    Cenoz, Jasone; Gorter, Durk

    2008-01-01

    In this article we explore the role that the linguistic landscape, in the sense of all the written language in the public space, can have in second language acquisition (SLA). The linguistic landscape has symbolic and informative functions and it is multimodal, because it combines visual and printed texts, and multilingual, because it uses several…

  6. Additional thyroid dose factor from transportation sources in Russia after the Chernobyl disaster.

    PubMed Central

    Parshkov, E M; Chebotareva, I V; Sokolov, V A; Dallas, C E

    1997-01-01

    Beginning approximately 4 years after the Chernobyl nuclear accident a steady increase in the incidence of thyroid cancer was observed in children and adolescents of the Bryansk Oblast, which received the highest level of radionuclide contaminants in Russia. We examined the spatial relationship between the residence location of patients with identified thyroid cancer (0-18 years old at the time of the accident) and a number of geographic parameters to better account for the etiology of thyroid cancer spatial distribution. Geographic parameters analyzed included spatial distribution of 137Cs and 131I in soil, population demographics, measurements and reconstructions. of absorbed thyroid 131I doses in the population, and maps of major transportation arteries. An interesting finding is the lack of a consistent correlation between the spatial distribution of radionuclides in the soil and thyroid cancer incidence. Instead, most of the thyroid cancer cases were diagnosed in settlements situated on major railways and roads. Correlating population with thyroid cancer cases and transportation arteries reveals a much higher cancer rate on or near major roads and railways than at a distance from them, again independent of radionuclide soil concentration. There are other important factors, of course, that must be considered in future evaluations of this phenomenon. These include the influence of iodine endemic zones, genetic predisposition to thyroid cancer, and duration of residence time in contaminated areas. The feasibility of radionuclide transport on railways and roads is discussed, together with the vectors for transfer of the contaminants to the human population. Developing a model to reconstruct the radiation dose to the thyroid over time in this geographic region is proposed in light of the impact of transportation arteries. Specific studies are outlined to provide the data necessary to develop this model as well as to better characterize the feasibility and scientific validity of the contribution to human health effects of this transport factor. Transport factor refers to the transport of radionuclides on transportation arteries and the transfer of these agents to the human population residing in the vicinity of these arteries. If the impact on thyroid cancer of the transport of radionuclides on major railways and roads is indeed significant, a major reappraisal of the risk of large-scale radioactive release into the environment is necessary. PMID:9467070

  7. Addition of soluble soybean polysaccharides to dairy products as a source of dietary fiber.

    PubMed

    Chen, Wenpu; Duizer, Lisa; Corredig, Milena; Goff, H Douglas

    2010-08-01

    Increasing consumption of dietary fiber in food leads to many important health benefits: for example, reduction in blood cholesterol, reduced risk of diabetes, and improved laxation. Water soluble soybean polysaccharide (SSPS) is a dietary fiber extracted and refined from okara, a byproduct of soy manufacturing. It was incorporated into 3 categories of dairy-based products, thickened milkshake-style beverages, puddings, and low-fat ice cream, to the maximum amount without over-texturing the food. Rheological measurements and sensory tests were used to develop desirable SSPS-fortified products. From the rheological data, 4% SSPS-fortified dairy beverages and 4% SSPS -fortified puddings were in the range of commercial products. From sensory analyses, 4% SSPS-fortified dairy beverage with 0.015%kappa-carrageenan, 4% SSPS-fortified pudding with 0.1%kappa-carrageenan, and 2% SSPS-fortified low-fat ice cream gained the highest scores in consumer hedonic rating. Panelists also indicated their willingness to consume those products if they were available commercially. Practical Application: Since the dietary fiber intake of many people is below their suggested adequate intake values, strategies to successfully fortify foods with fiber may help alleviate this gap. We have developed 3 dairy products, a beverage, a pudding, and a low-fat ice cream, that have been fortified with soluble soybean polysaccharide at levels of 4%, 4%, and 2%, respectively. These products were within acceptable ranges of rheological parameters and other physical stability measurements and were judged to be acceptable by sensory analyses. PMID:20722900

  8. 36 CFR 1290.3 - Sources of assassination records and additional records and information.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... NATIONAL ARCHIVES AND RECORDS ADMINISTRATION JFK ASSASSINATION RECORDS GUIDANCE FOR INTERPRETATION AND IMPLEMENTATION OF THE PRESIDENT JOHN F. KENNEDY ASSASSINATION RECORDS COLLECTION ACT OF 1992 (JFK ACT) §...

  9. 76 FR 36339 - Mandatory Reporting of Greenhouse Gases: Additional Sources of Fluorinated GHGs: Extension of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-06-22

    ... Regulations EPA U.S. Environmental Protection Agency FR Federal Register GHG greenhouse gas mm millimeters...: Electronics Manufacturing of the Greenhouse Gas Reporting Rule on December 1, 2010 (75 FR 74774). This subpart... Order 12866 (58 FR 51735, October 4, 1993) and, therefore, not subject to review under Executive...

  10. Mobile hard substrata - An additional biodiversity source in a high latitude shallow subtidal system

    NASA Astrophysics Data System (ADS)

    Balazy, Piotr; Kuklinski, Piotr

    2013-03-01

    This study demonstrates the importance of a hard mobile substratum (hermit crab shells) for Arctic biodiversity. Based on previous observations from other geographic regions we hypothesized that this niche at high latitudes would support a higher biodiversity of epifauna than might be predicted from similar substrata. We test whether the hermit crab epifauna is specific to that substratum providing unique biodiversity components to the local community. From four study sites in Isfjorden (78°N), West Spitsbergen and two study sites in Northern Norway (69°N) we collected approximately 50 each of hermit crabs, gastropods and pebbles, of visually similar surface area using SCUBA diving. Hermit crab shells were colonized by a larger number of epifaunal species than either gastropods or pebbles, even when they were of a larger size. Among 87 taxa found on all the three substrata, 22 occurred only on hermit crab shells. Except for two study sites hermit crab shells also supported more individuals. This study shows that the contribution of shells carried by hermit crabs to high-latitude, shallow-subtidal diversity is higher than might be predicted by their surface area alone and that hermit crabs modify, maintain and create a unique habitat. This is the result of a number of factors interacting positively on the presence of epifauna including shell surface heterogeneity and the complex influence of the crab host.

  11. 5 CFR 736.102 - Notice to investigative sources.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... agency investigator will notify the source from whom information is requested, whether in person or by... contacted that all information provided, including the record source's identity, may be disclosed upon the... confidential the identity of an information source upon specific request by the source. In addition, the...

  12. 5 CFR 736.102 - Notice to investigative sources.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... agency investigator will notify the source from whom information is requested, whether in person or by... contacted that all information provided, including the record source's identity, may be disclosed upon the... confidential the identity of an information source upon specific request by the source. In addition, the...

  13. Nitrogen as a friendly addition to steel

    SciTech Connect

    Rawers, J.C.

    2006-01-01

    Interstitial alloying with nitrogen or carbon is a common means of enhancing properties of iron-based alloys. Interstitial nitrogen addition to fcc-phase Fe-Cr-Mn/Ni alloys results in improved mechanical properties, whereas addition of carbon can result in the formation of unwanted carbides. Carbon addition to low alloy, bcc-phase iron alloys significantly improves strength through the formation of carbides, whereas addition of nitrogen in bcc-phase iron alloys can result in porous casting and reduced mechanical properties. This study will show that alloying iron-based alloys with both nitrogen and carbon can produce positive results. Nitrogen addition to Fe-C and Fe-Cr-C alloys, and both nitrogen and nitrogen-carbon additions to Fe-Cr-Mn/Ni alloys altered the microstructure, improved mechanical properties, increased hardness, and reduced wear by stabilizing the fcc-phase and altering (possibly eliminating) precipitate formation.

  14. Monitoring the source monitoring.

    PubMed

    Luna, Karlos; Martín-Luengo, Beatriz

    2013-11-01

    The hypothesis that the retrieval of correct source memory cues, those leading to a correct source attribution, increases confidence, whereas the retrieval of incorrect source memory cues, those leading to a source misattribution, decreases confidence was tested. Four predictions were derived from this hypothesis: (1) confidence should be higher for correct than incorrect source attribution except; (2) when no source cues are retrieved; (3) only the source misattributions inferred from the retrieval of incorrect source cues will be rated with low confidence; and (4) the number of source cues retrieved, either correct or incorrect, will affect the confidence in the source attributions. To test these predictions, participants read two narratives from two witnesses to a bank robbery, a customer and a teller. Then, participants completed a source monitoring test with four alternatives, customer, teller, both, or neither, and rated their confidence in their source attribution. Results supported the first three predictions, but they also suggested that the number of correct source monitoring cues retrieved did not play a role in the monitoring of the accuracy of the source attributions. Attributions made from the recovery of incorrect source cues could be tagged as dubious or uncertain, thus leading to lowered confidence irrespective of the number of incorrect source cues or whether another correct source cue was also recovered. This research has potential applications for eyewitness memory because it shows that confidence can be an indicator of the accuracy of a source attribution. PMID:23553316

  15. NONPOINT SOURCES AND WATER QUALITY TRADING

    EPA Science Inventory

    Management of nonpoint sources (NPS) of nutrients may reduce discharge levels more cost effectively than can additional controls on point sources (PS); water quality trading (WQT), where a PS buys nutrient or sediment reductions from an NPS, may be an alternative means for the PS...

  16. Handbook of Reference Sources. Second Edition.

    ERIC Educational Resources Information Center

    Nichols, Margaret Irby

    Designed to serve as a selection aid for small public libraries and to list important sources available through the major resource centers of the Texas Library System, this bibliography lists 804 annotated reference sources with 126 additional works named within the annotations. The books are grouped into 18 major areas, each of which is broken…

  17. Cincinnati Big Area Additive Manufacturing (BAAM)

    SciTech Connect

    Duty, Chad E.; Love, Lonnie J.

    2015-03-04

    Oak Ridge National Laboratory (ORNL) worked with Cincinnati Incorporated (CI) to demonstrate Big Area Additive Manufacturing which increases the speed of the additive manufacturing (AM) process by over 1000X, increases the size of parts by over 10X and shows a cost reduction of over 100X. ORNL worked with CI to transition the Big Area Additive Manufacturing (BAAM) technology from a proof-of-principle (TRL 2-3) demonstration to a prototype product stage (TRL 7-8).

  18. 21 CFR 25.32 - Foods, food additives, and color additives.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 1 2011-04-01 2011-04-01 false Foods, food additives, and color additives. 25.32... ENVIRONMENTAL IMPACT CONSIDERATIONS Categorical Exclusions § 25.32 Foods, food additives, and color additives.... (b) Action on a request for exemption for investigational use of a food additive if the food...

  19. 21 CFR 25.32 - Foods, food additives, and color additives.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 1 2014-04-01 2014-04-01 false Foods, food additives, and color additives. 25.32... ENVIRONMENTAL IMPACT CONSIDERATIONS Categorical Exclusions § 25.32 Foods, food additives, and color additives.... (b) Action on a request for exemption for investigational use of a food additive if the food...

  20. 21 CFR 25.32 - Foods, food additives, and color additives.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 1 2013-04-01 2013-04-01 false Foods, food additives, and color additives. 25.32... ENVIRONMENTAL IMPACT CONSIDERATIONS Categorical Exclusions § 25.32 Foods, food additives, and color additives.... (b) Action on a request for exemption for investigational use of a food additive if the food...